JPH08191755A - Electric water boiler - Google Patents

Abstract

PURPOSE: To reserve the heat regardless of the atmospheric pressure at the heat reservation of an electric water boiler and more quickly reserve the water at a temperature closer to the boiling temperature. CONSTITUTION: After a current is carried to a heating heater 4 or a heat reserving heater 5 to boil the water according to the temperature information from a temperature sensor 6 mounted on the lower part of a vessel 2, the current- carrying to the heating heater 4 or the heat reserving heater 5 is stopped for a fixed time, and the current is then carried only to the heat reserving heater 5 for a prescribed time. The water is reserved at a temperature lower by a prescribed temperature than the temperature data of the temperature sensor 6 after the prescribed time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric water heater for heating and retaining the water contained in a container.

[0002]

2. Description of the Related Art Recently, in an electric water heater,
Generally, water is boiled and then kept at a predetermined temperature.

A conventional electric water heater will be described below. FIG. 5 is a partial cross-sectional configuration diagram of a conventional electric water heater,
FIG. 6 is a circuit configuration diagram and FIG. 7 is an explanatory diagram of boiling detection.

In FIG. 6, a container 2 having an upper surface opening is provided in a main body container 1, and a lid 3 for covering an upper portion of the container 2 is arranged. Further, a heating heater 4 which is a heating means for heating the water inside the container 2, a warming heater 5 which is a warming means for heating the water to keep it warm, and a temperature sensor 6 for detecting the water temperature inside the container 2 are arranged below. Has been done. The signal from the temperature sensor 6 is input to the temperature detecting means 7 to detect the water temperature. The heating heater 4 and the heat retaining heater 5 are energized and controlled by a heating energizing means 8 and a heat retaining energizing means 9, respectively. The boiling detection means 10 uses the temperature data from the temperature detection means 7 to output a boiling detection output when the temperature rise rate becomes a predetermined value or less than the temperature rise rate when the water temperature is low.
Go to 2. The reboil setting means 13 is for setting when boiling again in the heat retention state, and is constituted by, for example, a push switch or the like, and the heating and heat retention control means 1
You are typing in 2. The heat retention temperature setting means 14 sets the heat retention temperature and inputs it to the heating energizing means. Output from the heating energization means 12 to the display means 15 and the display means 1
5 is a boiling LED 15a indicating that water is being heated.
And high temperature insulation LE that indicates that the temperature is kept at about 95 ℃
Display that the temperature is kept at about 85 ℃ with D15b 85
It is composed of a heat retaining LED 15c and a 70 heat retaining LED 15d that indicates that the temperature is kept at about 70 ° C.

When the water in the container 2 is heated for the first time, the heating and heat retention control means 12 uses the output of the temperature detection means 7 to heat the heater 4 through the heating energization means 8 and the temperature retention energization means 9.
And the heat retention heater 5 is energized and heated. Boiling detection means 1
When the fact that the boiling is detected is input by 0, the heat retention heater 5 is energized and controlled so as to maintain the temperature at the temperature set by the heat retention setting means 14. When the reboil setting means is set,
Based on the temperature data from the temperature detecting means 7 again, the heating heater 4 and the warming heater 5 are energized by the heating energizing means 8 and the warming energizing means 9 to heat the water in the container 2 until it boils.

The entire operation of the electric water heater constructed as above will be described with reference to FIGS. 6 and 7. In FIG. 7, the microcomputer 20 controls the relay 8 and the triac 9 to determine the amount of electricity supplied to the heating heater 4 and the heat retaining heater 5. When boiling water, the microcomputer 20 operates the relay 8 and the triac 9 to energize the heating heater 4 and the heat retaining heater 5. When the water is kept warm after boiling, the microcomputer 20 operates the triac 9 to energize the warm heater 5.

On the other hand, the temperature sensor 6 mounted in pressure contact with the container 2 changes its resistance value depending on the temperature of the water in the container 2. Then, the resistance value ratio between the temperature sensor 6 and the resistor 7a connected in series changes and is input to the A / D converter 7d as a voltage change, and after being converted into a digital value by the A / D converter 7d, the microcomputer 20 is input as temperature data. The voltage determined by the resistors 7b and 7c is also input to the A / D converter 7d, and the temperature (about 95
℃) has been determined. Further, the voltage determined by the resistors 7e and 7f determines the temperature (about 85 ° C.) when the temperature is kept 85. The voltage determined by the resistors 7g and 7h determines the temperature (about 70 ° C.) when the temperature is 70. Further, the heat retention switch 14 which is a heat retention temperature setting means and the reboil switch 13 which is a reboil setting means are connected to the input of the microcomputer 20, and the display means 15 is connected to the output of the microcomputer 20.

A boiling detection method will be described with reference to FIG.
After energizing the heater 4 and the heater 5, the temperature sensor 6
Measure the time (Δta) when the temperature data from the unit temperature (△ θ--approx. 0.5 ° C) rises, and the time is constant when the temperature of the water is rising and the boiling point (θ1 ) As it gets closer, Δta becomes longer (Δtb). When Δtb becomes longer than Δta by a predetermined magnification or more, the microcomputer 20 detects that water has boiled.

After the boiling is detected, when the temperature is kept high, the temperature sensor 6 and the resistor 7a connected in series are compared with each other to compare the resistance ratios of the resistors 7b and 7c which determine the high temperature. The triac 9 is operated so as to keep the temperature at the temperature when the temperature is kept (about 95 ° C.).

[0010]

However, in the above-mentioned conventional configuration, since the heat retention temperature is determined by the temperature sensor and the resistor connected in series to the temperature sensor, the heat retention temperature is always set constant at the set temperature. Therefore, if it is attempted to increase the heat retention temperature at a temperature closer to the boiling point, the boiling point becomes lower when the atmospheric pressure becomes lower, such as in highlands, and the boiling continues. Therefore, there is a problem in that hot water cannot be provided because the heat retention temperature cannot be increased.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to make it possible to retain heat more quickly and at a temperature closer to the boiling point.

[0012]

In order to achieve the above object, the first means for solving the problems of the present invention is to provide a heating energizing means and a heat retaining energizing means so as to stop energizing the heating means and the heat retaining means for a predetermined time after the boiling is detected. Stop means for controlling the means, temperature fixing means for controlling the warming energizing means so as to energize the heat retaining means for a predetermined time after the stopping means, and inputting the detected temperature from the temperature detecting means after a predetermined time, and the temperature fixing means The control means controls the heat retention energizing means so that the temperature is maintained at a temperature lower than the above temperature by a predetermined temperature.

A second means for solving the problems of the present invention is a stop means for controlling the heating energizing means and the heat retaining and energizing means so as to stop energizing the heating means and the heat retaining means for a predetermined time after the boiling is detected, and a stopping means. The temperature fixing means for controlling the warming energizing means so as to energize the heat retaining means until the temperature change rate from the rear temperature detecting means becomes equal to or less than a predetermined value, and the temperature fixing means for inputting the detected temperature from the temperature detecting means at that time, and the temperature fixing means. The control means controls the heat retention energizing means so that the temperature is maintained at a temperature lower than the temperature of the means by a predetermined temperature.

A third means for solving the problems of the present invention is a stop means for controlling the heating energizing means and the heat retaining and energizing means so as to stop energizing the heating means and the heat retaining means for a predetermined time after the boiling is detected, and a stopping means. While controlling the heat retention energizing means to energize the heat retention means later, the passage time of the temperature detected by the temperature detection means per unit temperature is constant with respect to the passage time per unit temperature after the elapse of a predetermined time after boiling detection. A temperature determining means for inputting the detected temperature of the temperature detecting means when the ratio becomes less than or equal to a ratio, and a control means for controlling the heat retaining energizing means so as to maintain the temperature at a temperature lower than the temperature of the temperature determining means by a predetermined temperature. Is.

A fourth means for solving the problems of the present invention is a stop means for controlling the heating energizing means and the heat retaining and energizing means so as to stop energizing the heating means and the heat retaining means for a predetermined time after the boiling is detected, and a stopping means. After that, the heating energizing means is controlled to intermittently energize the heating means for a predetermined time, and the temperature fixing means for inputting the detected temperature from the temperature detecting means after a predetermined time and the temperature keeping temperature lower than the temperature of the temperature fixing means by a predetermined temperature. Therefore, the control means for controlling the heat retention energizing means is provided.

A fifth means for solving the problems of the present invention is a stop means for controlling the heating energizing means and the heat retaining and energizing means so as to stop energizing the heating means and the heat retaining means for a predetermined time after the boiling is detected, and a stopping means. Until the rate of temperature change from the post-temperature detection means becomes a predetermined value or less, the heating energization means is controlled so as to intermittently energize the heating means, and the temperature fixing means for inputting the detected temperature from the temperature detection means at that time, and the temperature The control means controls the heat retention energizing means so as to maintain the temperature at a temperature lower than the temperature of the determining means by a predetermined temperature.

A sixth means for solving the problems of the present invention is a stop means for controlling the heating energizing means and the heat retaining and energizing means so as to stop energizing the heating means and the heat retaining means for a predetermined time after the boiling is detected, and a stopping means. The heating energizing means is controlled so that the heating means is intermittently energized later, and the passage time of the temperature detected by the temperature detecting means per unit temperature is constant with respect to the passage time per unit temperature after the elapse of a predetermined time after boiling detection. A temperature determining means for inputting the detected temperature of the temperature detecting means when the ratio becomes less than or equal to a ratio, and a control means for controlling the heat retaining energizing means so as to maintain the temperature at a temperature lower than the temperature of the temperature determining means by a predetermined temperature. Is.

[0018]

According to the present invention, the temperature detected by the temperature sensor is brought close to the water temperature by stopping the energization of the heating means and the heat retaining means for a certain period of time after the water is boiled by the means for solving the above problems. By subsequently energizing, you can stably input the temperature detected by the temperature sensor when the water boils, and keep the temperature at a few degrees lower than the detected temperature to set the heat retention temperature to a predetermined constant temperature. Instead, it can be set to a temperature lower than the boiling point of water by a predetermined temperature. Therefore, it is possible to keep warm even at high altitude without continuing boiling, and close to the boiling point, for example, minus 2 boiling points.
Since a heat retention temperature of ℃ is also possible, hot water with a higher temperature can be provided.

[0019]

The first to sixth embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional configuration diagram of the first to sixth embodiments of the present invention. The circuit diagram is almost the same as the conventional example (without the resistors 7b and 7c), and only the operation of the microcomputer is different. Therefore, only the flowcharts when the high temperature keeping is selected are shown in FIGS. FIG. 5 is a graph showing the operation when the boiling is detected. In FIGS. 1 and 5, the same parts as those in FIGS. 7 and 9 described above are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, the difference between the first to sixth embodiments is the operation of the stopping means 16 and the temperature determining means 17 after the boiling is detected. In the first embodiment of the present invention, the stopping means 16 stops the energization of the heating heater 4 and the heat retaining heater 5 for a predetermined time (for example, 3 minutes in this embodiment) after the boiling is detected by the boiling detecting means 10. A signal for controlling the heating energization means 8 and the heat retention energization means 9 is output to the control means 18. After that, the temperature determining means 17 detects boiling by the boiling detecting means 10,
A signal for controlling the heat retention energizing means 9 so as to energize the heat retaining means 5 for a predetermined time (for example, 3 minutes in this embodiment) is output to the control means 18, and the temperature detecting means 10 after the predetermined time.
Enter the detected temperature from. The control means 18 performs the same operation as the conventional example when boiling water, and at the time of heat retention, the heat retention energization means that keeps the temperature lower than the temperature determined by the temperature determination means 17 by a predetermined temperature (for example, about 2 ° C. in this embodiment). To control.

In the second embodiment of the present invention, the stopping means 16
After the boiling is detected by the boiling detecting means 10, the control means 1 sends a signal for controlling the heating energizing means 8 and the warming energizing means 9 so as to stop energizing the heating heater 4 and the warming heater 5 for a predetermined time.
Output to 8. After that, the temperature determining means 17 controls the heat retaining energizing means 9 so that the heat retaining means 5 is energized until the rate of temperature change from the temperature detecting means 10 falls below a predetermined value after the boiling detecting means 10 detects boiling. To the control means 18, and the detected temperature from the temperature detection means 10 when the temperature change rate becomes equal to or lower than a predetermined value is input.

In the third embodiment of the present invention, the stopping means 16
After the boiling is detected by the boiling detecting means 10, the control means 1 sends a signal for controlling the heating energizing means 8 and the warming energizing means 9 so as to stop energizing the heating heater 4 and the warming heater 5 for a predetermined time.
Output to 8. After that, the temperature fixing means 17 detects the boiling by the boiling detecting means 10, and then outputs a signal for controlling the heat retaining energizing means 9 to energize the heat retaining means 5 to the control means 18, and the temperature detected by the temperature detecting means 10 is detected. When the passage time per unit temperature becomes less than a certain ratio with respect to the passage time per unit temperature after the elapse of a predetermined time after the boiling is detected, the temperature detected by the temperature detecting means 10 is input.

In the fourth embodiment of the present invention, the stopping means 16
After the boiling is detected by the boiling detecting means 10, the control means 1 sends a signal for controlling the heating energizing means 8 and the warming energizing means 9 so as to stop energizing the heating heater 4 and the warming heater 5 for a predetermined time.
Output to 8. After that, the temperature fixing means 17 detects the boiling by the boiling detecting means 10, and then outputs a signal for controlling the heating energizing means 8 so as to intermittently energize the heating means 4 for a predetermined time to the control means 18, and after a predetermined time. The detected temperature from the temperature detecting means 10 is input. The control means 18 performs the same operation as the conventional example when boiling water, and when the temperature is kept warm, the temperature determining means 1
The heat retention energizing means is controlled so that the temperature is maintained at a temperature lower than the temperature determined in 6 by a predetermined temperature.

In the fifth embodiment of the present invention, the stopping means 16
After the boiling is detected by the boiling detecting means 10, the control means 1 sends a signal for controlling the heating energizing means 8 and the warming energizing means 9 so as to stop energizing the heating heater 4 and the warming heater 5 for a predetermined time.
Output to 8. After that, the temperature determining means 17 detects the boiling by the boiling detecting means 10, and then controls the heating energizing means 8 so as to intermittently energize the heating means 4 until the temperature change rate from the temperature detecting means 10 becomes a predetermined value or less. Signal control means 1
8, and the detected temperature from the temperature detecting means 10 when the temperature change rate becomes equal to or lower than a predetermined value is input.

In the sixth embodiment of the present invention, the stopping means 16
After the boiling is detected by the boiling detecting means 10, the control means 1 sends a signal for controlling the heating energizing means 8 and the warming energizing means 9 so as to stop energizing the heating heater 4 and the warming heater 5 for a predetermined time.
Output to 8. After that, the temperature determining means 17 outputs a signal for controlling the heating energizing means 8 to perform intermittent energization of the heating means 4 to the control means 18 after the boiling detecting means 10 detects boiling, and the temperature detected by the temperature detecting means 10 is detected. When the passage time per unit temperature becomes less than a certain ratio with respect to the passage time per unit temperature after the elapse of a predetermined time after the boiling is detected, the temperature detected by the temperature detecting means 10 is input.

FIG. 2 is a flow chart of the first embodiment of the present invention. After energizing the power source, the heating heater 4 and the heat retaining heater 5 are energized to start heating at 100. Then, the time when the unit temperature rises is measured (Δtn), and at 101, the time when the unit temperature rises last time (Δtn-1) is compared. When Δtn is smaller than Δtn-1, it is judged that the temperature has not risen and the process returns to 100. If it is the same or larger, check at 102 whether 4 measurements have been taken, 1 until 4
Return to 00. When measured four times, it is 103 from Δt2 to Δt4
Up to (ΔT = Δt2 + Δt3 + Δt4). Then, the time when the unit temperature rises is measured at 104 (△
T ′) and 105, ΔT ′ and ΔT are compared. If ΔT 'is small, the process returns to 104. When it becomes the same or larger, boiling is detected at 106. When the boiling is detected, at 107, the power supply to the heating heater and the heat retaining heater is stopped for a predetermined time. Then 10
In step 8, only the heat retaining heater is energized for a predetermined time. When the temperature data of the temperature sensor becomes stable, the temperature is input at 109 (θ4), and at 110, the temperature is kept so that the temperature becomes a few degrees lower than the temperature (θ4) (θ4-Δθ4).

The flow chart of the fourth embodiment of the present invention is different from that of FIG. 2 in that instead of energizing only the heat-retaining heater at 108, the heater is intermittently energized so that the temperature of the temperature sensor can be quickly increased with higher power. The point is to make it stable.

FIG. 3 is a flow chart of the second embodiment of the present invention. The same parts as those in FIG. 2 are denoted by the same reference numerals and the description thereof will be omitted. After the boiling detection in 106, the energization to the heating heater and the warming heater is stopped for a predetermined time in 107. Then, at 111, only the heat-retaining heater is energized, and at 112, the passage time when the predetermined temperature is raised is measured (Δtm). 1
If Δtm is larger than a predetermined value in 13 and comparison is made, if it is smaller, the process returns to 112, and if same or larger, it is judged that the temperature data of the temperature sensor is stable, and the temperature is inputted in 109 (θ4), At 110, the temperature sensor detects the temperature (θ
4) Keep the temperature a few degrees lower than (θ4−Δθ4).

The flow chart of the fifth embodiment of the present invention is different from that of FIG. 3 in that instead of energizing only the heat retaining heater at 111, the heating heater is intermittently energized so that the temperature of the temperature sensor can be quickly increased with higher power. The point is to make it stable.

FIG. 4 is a flow chart of the third embodiment of the present invention. The same parts as those in FIG. 2 are denoted by the same reference numerals and the description thereof will be omitted. After the boiling detection in 106, the energization to the heating heater and the warming heater is stopped for a predetermined time in 107. Then, at 114, the heater is energized and then 115
And wait for a predetermined time. Then, at 116, the passage time when the predetermined temperature is raised is measured (Δtm), after waiting for a certain time at 117, the passage time when the predetermined temperature is raised is further measured at 118 (Δtl). At 119, Δtl is Δt
If it is a predetermined magnification of m or more, it is judged that the temperature data of the temperature sensor is stable, and the temperature is input at 109 (θ4), and at 110, the temperature of the temperature sensor is several degrees lower than the temperature (θ4) ( Insulate so that θ4− △ θ4). If Δtl is equal to or smaller than the predetermined magnification of Δtm, the process returns to 117.

In the flow chart of the sixth embodiment of the present invention, the difference from FIG. 4 is that the heater is intermittently energized instead of energizing only the heat retaining heater at 114, and the temperature of the temperature sensor can be quickly increased with higher power. The point is to make it stable.

In FIG. 5, the temperature of the temperature sensor when the water reaches the boiling point changes variously depending on the amount of water.
After the boiling is detected, when the amount of water is large in the first to third embodiments of the present invention, the temperature detected by the temperature sensor can be brought close to the temperature of the water by stopping energization of the heating heater and the heat retaining heater. When the amount of water is small, the temperature detected by the temperature sensor does not drop because the temperature of the water approaches the temperature of the water even if the heating heater and the heat retaining heater are de-energized. After that, the warming heater is energized, and in the fourth to sixth embodiments, the heating heater is intermittently energized, so that the temperature of the temperature sensor when the water is boiling does not change depending on the amount of water, and always has a constant temperature difference (Δ).
θ 5). By controlling the temperature sensor at a temperature (Δθ4) that is several degrees lower than the temperature of the temperature sensor (θ4) when water is boiling, the hot water is kept at a temperature (Δθ4) that is several degrees lower than the boiling temperature. can do.

[0033]

As described above, the present invention brings the temperature detected by the temperature sensor close to the water temperature by stopping the energization of the heating heater and the heat retaining heater for a certain period of time after the water boils. After that, stabilize the temperature detected by the temperature sensor when the water is boiling by energizing it, and keep it warm at a few degrees lower than the stable detected temperature, so you can keep it warm without continuing boiling even in highlands, Further, since it is possible to keep the temperature close to the boiling point, for example, the boiling point minus 2 ° C., it is possible to provide hot water having a higher temperature.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional configuration diagram of an electric water heater according to first to sixth embodiments of the present invention.

FIG. 2 is a flowchart showing the operation of the electric water heater according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the electric water heater according to the second embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of the electric water heater according to the third embodiment of the present invention.

FIG. 5 is a graph showing a boiling operation of the electric water heater.

FIG. 6 is a partial sectional configuration diagram of a conventional electric water heater.

FIG. 7 is a circuit configuration diagram of the electric water heater.

FIG. 8 is a graph showing a boiling operation of the electric water heater.

[Explanation of symbols]

 2 container 4 heating heater 5 heat retention heater 6 temperature sensor 7 temperature detection means 8 heating energization means 9 heat retention energization means 10 boiling detection means 12 heating insulation control means 16 stop means 17 temperature determination means 18 control means

Claims (6)

[Claims] 1. A container for containing a liquid, a heating means for heating the liquid in the container, a heating and energizing means for energizing the heating means, and a heat retaining means for heating and retaining the temperature of the liquid in the container. A heat-retention energizing means for energizing the heat-retaining means, and a temperature detecting means for detecting the liquid temperature in the container,
Boiling detection means for detecting that the liquid in the container has boiled by the output of the temperature detection means, and after the boiling detection, the heating energization means and the heating energization means to stop energization to the heating means and the heat retaining means for a predetermined time. A stop means for controlling the heat retention energizing means, and a temperature for controlling the heat retention energizing means to energize the heat retaining means for a predetermined time after the operation of the stopping means, and inputting the detected temperature from the temperature detecting means after a predetermined time. An electric water heater equipped with a fixing means and a control means for controlling the warming energizing means so as to keep the temperature at a temperature lower by a predetermined temperature than the temperature of the temperature fixing means. 2. A container for containing a liquid, a heating means for heating the liquid in the container, a heating energizing means for energizing the heating means, and a heat retaining means for heating and retaining the temperature of the liquid in the container. A heat-retention energizing means for energizing the heat-retaining means, and a temperature detecting means for detecting the liquid temperature in the container,
Boiling detection means for detecting that the liquid in the container has boiled by the output of the temperature detection means, and after the boiling detection, the heating energization means and the heating energization means to stop energization to the heating means and the heat retaining means for a predetermined time. Stop means for controlling the heat retention energizing means, and the heat retention energizing means is controlled so as to energize the heat retaining means until the temperature change rate from the temperature detecting means becomes a predetermined value or less after the operation of the stopping means. An electric water heater comprising: a temperature determining means for inputting a detected temperature from the temperature detecting means; and a control means for controlling the warming energizing means so as to keep the temperature at a temperature lower by a predetermined temperature than the temperature of the temperature determining means. 3. A container for containing a liquid, a heating unit for heating the liquid in the container, a heating energizing unit for energizing the heating unit, and a heat retaining unit for heating and retaining the temperature of the liquid in the container. A heat-retention energizing means for energizing the heat-retaining means, and a temperature detecting means for detecting the liquid temperature in the container,
Boiling detection means for detecting that the liquid in the container has boiled by the output of the temperature detection means, and after the boiling detection, the heating energization means and the heating energization means to stop energization to the heating means and the heat retaining means for a predetermined time. Stopping means for controlling the heat retaining energizing means, and controlling the heat retaining energizing means to energize the heat retaining means after the operation of the stopping means, and the passage time per unit temperature of the temperature detected by the temperature detecting means, Temperature determining means for inputting the detected temperature of the temperature detecting means when the ratio becomes lower than a certain ratio with respect to the passage time per unit temperature after the elapse of a predetermined time after boiling detection, and the temperature is lower than the temperature of the temperature determining means by a predetermined temperature An electric water heater equipped with a control means for controlling the heat insulation energizing means so as to maintain the temperature. 4. A container for containing a liquid, a heating means for heating the liquid in the container, a heating and energizing means for energizing the heating means, and a heat retaining means for heating and retaining the temperature of the liquid in the container. A heat-retention energizing means for energizing the heat-retaining means, and a temperature detecting means for detecting the liquid temperature in the container,
Boiling detection means for detecting that the liquid in the container has boiled by the output of the temperature detection means, and after the boiling detection, the heating energization means and the heating energization means to stop energization to the heating means and the heat retaining means for a predetermined time. Stop means for controlling the heat retention energizing means and the heating energizing means for intermittently energizing the heating means for a predetermined time after the stopping means is operated, and the detected temperature from the temperature detecting means after a predetermined time is input. An electric water heater comprising a temperature determining means and a control means for controlling the heat retaining energizing means so as to keep the temperature at a temperature lower by a predetermined temperature than the temperature of the temperature determining means. 5. A container for containing a liquid, a heating unit for heating the liquid in the container, a heating energizing unit for energizing the heating unit, and a heat retaining unit for heating and retaining the temperature of the liquid in the container. A heat-retention energizing means for energizing the heat-retaining means, and a temperature detecting means for detecting the liquid temperature in the container,
Boiling detection means for detecting that the liquid in the container has boiled by the output of the temperature detection means, and after the boiling detection, the heating energization means and the heating energization means to stop energization to the heating means and the heat retaining means for a predetermined time. Stop means for controlling the heat retention energizing means, and the heating energizing means is controlled so as to intermittently energize the heating means until the temperature change rate from the temperature detecting means after the operation of the stopping means becomes equal to or less than a predetermined value, and at that time, Temperature determining means for inputting the detected temperature from the temperature detecting means,
An electric water heater equipped with a control means for controlling the warming energizing means so as to keep the temperature at a temperature lower than the temperature of the temperature determining means by a predetermined temperature. 6. A container for containing a liquid, a heating unit for heating the liquid in the container, a heating energizing unit for energizing the heating unit, and a heat retaining unit for heating and retaining the temperature of the liquid in the container. A heat-retention energizing means for energizing the heat-retaining means, and a temperature detecting means for detecting the liquid temperature in the container,
Boiling detection means for detecting that the liquid in the container has boiled by the output of the temperature detection means, and after the boiling detection, the heating energization means and the heating energization means to stop energization to the heating means and the heat retaining means for a predetermined time. Stopping means for controlling the heat retention energizing means, while controlling the heating energizing means so as to intermittently energize the heating means after the operation of the stopping means, the passing time per unit temperature of the temperature detected by the temperature detecting means, Temperature determining means for inputting the detected temperature of the temperature detecting means when the ratio becomes lower than a certain ratio with respect to the passage time per unit temperature after the elapse of a predetermined time after boiling detection, and the temperature is lower than the temperature of the temperature determining means by a predetermined temperature An electric water heater equipped with a control means for controlling the heat insulation energizing means so as to maintain the temperature.