JPH10117938A - Electric water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric water heater which secures the safety and prevents a container from being damaged by quickly stopping energization to a heater, when the water quantity is reduced during heating. SOLUTION: An electric water boiler is provided with a container 3 for storing water, a heat insulating heater 5 for heating water stored in the container 3, and a temperature detection means 25 for measuring the temperature of the water. It is also provided with a heat insulation control means 26 which outputs an energization instruction or an energization stop instruction based on the water temperature measured by the temperature detection means 25 in insulating heat so as to hold the water temperature to a prescribed heat insulation temperature, an abnormal temperature detection means 29 which calculates the temperature difference between the preset prescribed standard temperature and the temperature measured by the temperature detection means 25 and outputs the energization stop holding instruction, when the temperature difference is judged to be more than the preset prescribed temperature difference, and a heater control means 27 which controls energization to the heater 5 based on the energization, an energization stop, or an energization stop holding instruction.

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 which keeps the temperature of water after boiling, for example, and more particularly to the prevention of heating by reducing the amount of water.

[0002]

2. Description of the Related Art FIG. 13 is a longitudinal sectional view of a conventional electric water heater. In the figure, 1 is the main body of the electric water heater, 2
Is an exterior body, 3 is a container for storing water made of stainless steel disposed in the main body 1, 4 is a heater for boiling water, 5 is a heater for keeping heat, 6 is a temperature detecting element for detecting the temperature of water in the container 3 made of a thermistor or the like. , 7 are display means, a boiling indicator lamp 8, a high-temperature keeping indicator lamp 9, and a low-temperature keeping indicator lamp 1.
0. The display means 7 is provided on the upper part of the main body 1. Reference numeral 61 denotes a thermal fuse for preventing emptying.
The water heater 4, the heat retaining heater 5, the temperature detecting element 6, and the temperature fuse 61 are provided at the bottom of the container 3. The temperature fuse 61 is wired in series with the water heater 4 and the heat retaining heater 5.

Next, the operation of the conventional electric water heater will be described. When a predetermined amount of water is poured into the container 3 and the power is turned on, the heater 4 starts heating, and the boiling indicator lamp 8
Lights up. When the water temperature in the container 3 rises and boils, the microcomputer (not shown) built in the main body 1 based on a detection signal from the temperature detecting element 6.
Determines the boiling state, and turns off the water heater 4. When the water heater 4 is turned off, the boiling lamp 7 is turned off, and the high-temperature keeping lamp 8 is turned on instead. When the temperature is maintained, the microcomputer controls ON and OFF of the heater 5 based on the detection signal of the temperature detecting element 6 to maintain a predetermined temperature (for example, 90 ° C.). In the case of low-temperature heat retention, when a heat-retention switch (not shown) is switched, the microcomputer controls the heat-retention heater 5 on and off based on the detection signal of the temperature detection element 6 to set the temperature to a temperature lower than the high-temperature heat retention. A predetermined temperature (for example, 65 ° C.) is maintained. This hot water is collected and the container 3
Even if the amount of hot water in the inside decreases, the above-described heat retention operation is repeated. As a result, when the water is full (for example, a capacity of 2 liters), the water temperature in the container 3 is maintained within a predetermined heat retaining temperature range.
In the case where the amount of water is reduced (for example, 1 / 20th of full water, that is, 0.1 liter), if the capacity of the heat retaining heater 5 is fixed to, for example, 100 W, the heat capacity of the water decreases, and the water temperature rises rapidly. Ascends and keeps heater 5 off
After that, the water temperature overshoots, rises beyond the range of the predetermined temperature, and then falls. When this state is repeated and the amount of water decreases or becomes empty, the temperature inside the container 3 (especially at the bottom) rapidly rises. Thus, when the temperature inside the container 3 reaches a predetermined temperature, the thermal fuse 61 is blown to cut off the power supply.

Since the thermal fuse 61 cannot be reused after being blown, it cannot be safely used unless this part is replaced. As an alternative to the thermal fuse, a thermostat is used as a safety device. When the thermostat is used, the power is not shut off.
Since the ON-OFF control is continued, if the temperature rises abnormally, the container 3 and the like will be damaged.

[0005]

In the above-described conventional electric water heater, when the amount of water is reduced or the water heater becomes empty, if the safety device is a thermal fuse, it needs to be replaced, which is inconvenient. Also ON-OF like a thermostat
The method of repeating F has a problem that parts such as the container are damaged when the temperature of the container becomes abnormally high.

The present invention has been made to solve such a problem, and when the amount of water decreases during heat insulation, the power supply to the heater is immediately stopped to ensure safety and prevent damage to the container and the like. The purpose is to obtain an electric water heater.

[0007]

An electric water heater according to the present invention comprises a container for storing water, a heater for heating the water stored in the container, temperature detecting means for measuring the temperature of the water,
Insulation control means for outputting an energization command or an energization stop command based on the temperature of the water measured by the temperature detection means so as to maintain the temperature of the water at a predetermined temperature during the heat insulation, and a predetermined reference. An abnormal temperature detection means for calculating a temperature difference between the temperature and the temperature measured by the temperature detection means and outputting an energization stop holding command when it is determined that the temperature difference is equal to or greater than a predetermined temperature difference; Heater control means for controlling power supply to the heater based on the stop command or the power supply stop holding command.

Further, the predetermined reference temperature of the electric water heater according to the present invention is set to a predetermined heat retaining temperature.

Further, the predetermined reference temperature of the electric water heater according to the present invention is a temperature of water used as a reference when the heat retention control means outputs the power supply command or a temperature of the water used as a reference when outputting the power supply stop command. Is set to one of

[0010] The predetermined reference temperature of the electric water heater according to the present invention is set to either the maximum temperature or the minimum temperature under predetermined conditions during heat retention. The maximum temperature is a temperature set by previously measuring the temperature at a displacement point at which the power supply stop command is output, the heating is stopped, and the water temperature starts to decrease under predetermined conditions such as the amount of water at the time of keeping the temperature. In addition, the minimum temperature is a temperature set by previously measuring a temperature at a displacement point at which an energization command is output and heating is performed and the water temperature starts to rise under predetermined conditions such as a water amount at the time of keeping the temperature.

Further, the electric water heater according to the present invention further comprises a display means for displaying a heat treatment, a heat retention treatment and a state of the temperature of the water, and the abnormal temperature detection means determines that the temperature difference is not less than a predetermined temperature difference. When it is determined, the display means is caused to display a message indicating an abnormality.

Further, the electric water heater according to the present invention comprises a container for storing water, a heater for heating the water stored in the container, a temperature detecting means for measuring the temperature of the water, The heat insulation control means for outputting an energization command or an energization stop command based on the temperature of the water measured by the temperature detection means so as to maintain the temperature at the predetermined insulation temperature, Calculates the temperature difference, compares the temperature difference with the predetermined temperature difference, and outputs an abnormal signal when it is determined that the temperature difference is equal to or more than the predetermined temperature difference, and counts the abnormal signal and counts the predetermined number of times. Then, there are provided a counting means for outputting an energization stop holding command, and a heater control means for controlling energization to the heater based on the energization command, the energization stop command or the energization stop holding command.

Further, the electric water heater according to the present invention comprises a container for storing water, a heater for heating the water stored in the container, a temperature detecting means for measuring the temperature of the water, Insulation control means for outputting an energization command or an energization stop command based on the temperature of the water measured by the temperature detection means so as to maintain the predetermined heat retention temperature, and determining that the temperature of the water is equal to or higher than a preset temperature. An abnormal temperature detecting means for outputting an abnormal signal, and counting the abnormal signal,
There are provided a counting means for outputting an energization stop holding command when a predetermined number of times has been counted, and a heater control means for controlling energization to the heater based on the energization command, the energization stop command or the energization stop holding command.

Further, the electric water heater according to the present invention comprises a container for storing water, a heater for heating the water stored in the container, temperature detecting means for measuring the temperature of the water, In order to keep the temperature at a predetermined temperature, the temperature control means outputs a power supply command or a power supply stop command based on the temperature of the water measured by the temperature detection means, and the temperature detection means measures the temperature in a normal heat control state of the heat control means. Calculating means for calculating a temperature difference between the reference heat retention maximum temperature and the maximum heat retention temperature measured by the temperature detection means after measuring the heat retention reference maximum temperature, and calculating the temperature difference calculated by the calculation means and a predetermined temperature difference in advance. When the temperature difference is determined to be greater than or equal to the predetermined temperature difference, an abnormal temperature detection unit that outputs an energization stop holding command, and based on the energization command, the energization stop command, or the energization stop holding command. And a heater control means for controlling the energization of the over data. The temperature detecting means measures the reference maximum temperature of the water when the heat control is performed with the amount of water equal to or more than a predetermined value. Calculates the temperature difference between the maximum heat retention temperature measured after the reference maximum heat retention temperature measurement and the reference maximum heat retention temperature, compares it with the predetermined temperature difference, and outputs an energization stop retention command if the calculated temperature difference is greater than or equal to the predetermined temperature difference I do. The heater control means forcibly stops and holds the heater when the power supply stop holding command is input.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a block diagram showing a configuration of the electric water heater according to the first embodiment of the present invention. In the figure, 1 is an electric water heater main body, 2 is an exterior body, 3 is a main body 1
A container made of a stainless steel material disposed therein, 4 is a water heater, 5 is a warming heater, 6 is a thermistor or the like, a temperature detecting element for detecting a water temperature in the container 3, and 7 is disposed on an upper portion of the main body 1. The display means comprises a boiling indicator lamp 8, a high-temperature keeping indicator lamp 9, and a low-temperature indicator lamp 10. In addition, the water heater 4 and the heat retaining heater 5
The temperature detecting element 6 is disposed at the bottom of the container 4.

FIG. 2 is a circuit diagram of the electric water heater according to the first embodiment of the present invention. In the figure, reference numeral 11 denotes an AC power supply, and 12 denotes a transformer, which transforms the voltage of the AC power supply 11 to a predetermined voltage. A rectifier circuit 13 is provided on the secondary side of the transformer 12, and rectifies the predetermined AC voltage to a DC voltage. A microcomputer 14 is provided between the + terminal and the − terminal of the rectifier circuit 13. Further, a relay 16 is connected via a switching transistor 15. A diode 17 for protection is connected in series to the switching transistor 15.
The relay 16 opens and closes a relay contact 16 a connected in series to the water heater 4 provided on the primary side of the transformer 12. A switching transistor 18 is connected to the negative terminal of the rectifier circuit 13, and one end of the switching transistor 18 is connected to the transformer 12.
Is connected to a bidirectional switching element 19 connected in series to the warming heater 5 arranged in parallel with the water heater 4 on the primary side of the heater. The bases of the switching transistors 15 and 18 are connected to output ports a and b of the microcomputer 14, respectively.

A temperature detecting element 6 and a resistor 20 are connected in series between the + terminal and the − terminal of the rectifier circuit 13.
Is connected to the input port A / D control terminal d. The boiling indicator lamp 8, the high-temperature keeping lamp 9 and the low-temperature keeping lamp 10 are connected to output ports c, f or g of the microcomputer 14 via resistors 22, 23 or 24, respectively.

The microcomputer 14 determines the temperature of the water in the container 3 based on the detection signal from the temperature detecting element 6, and outputs the measured temperature TB to the heat keeping control means 26 and the abnormal temperature detecting means 29. A temperature keeping control means 26 for comparing the measured temperature TB of the temperature detecting means 25 with a preset temperature keeping heater ON temperature t3 or a preset temperature keeping heater OFF temperature t1, and a comparison decision result of the temperature keeping control means 26 and an abnormal temperature detecting means 29. A heater control means 27 for controlling ON-OFF of the heater 5 or self-holding of stopping the power supply based on the judgment result of
Display control means 28 for controlling the temperature and the heat retaining heater 5 are turned off.
Then, the temperature gradient of the measured temperature TB is calculated based on the measurement result of the temperature detecting means 25, and when the difference between the measured temperature TB and the predetermined temperature difference is higher than a predetermined temperature difference, An abnormal temperature detecting means 29 which outputs an energization stop holding instruction to the heat retaining heater control means 27 and outputs a time keeping start instruction to the time keeping means 30 and a clock means (not shown) ) Is started based on the clock signal from the controller 7), and when a predetermined time has elapsed, the display operation of the display means 7 is stopped, and the power supply OF
And a timing unit 30 for outputting an instruction to change to the F state.

FIG. 3 is a flowchart when the electric water heater according to the first embodiment is kept warm. FIG. 4 shows the first
Water Temperature Change in Container 3 and Heat Insulation Heater 5 According to Embodiment
FIG. 6 is a diagram showing a correspondence relationship between the operations of FIG. The operation of the electric water heater will be described with reference to FIGS. Container 3
When a predetermined amount of water is supplied to the inside and power is supplied from the AC power supply 11, the temperature detecting means 25 starts measuring the water temperature based on the detection signal from the temperature detecting element 6. The water heater 4 is heated to boil the water in the container 3. When boiling, the temperature detecting means 25 measures the boiling temperature (100 ° C.) based on the detection signal of the temperature detecting element 6, and based on the measurement result, the heater control means (not shown) in the microcomputer 14 sends the signal to the heater 4. OFF
I do.

When the power supply to the water heater 4 is turned off, the warming process starts (S1). When the heat keeping process starts, the display control means 29 in the microcomputer 14 turns on the high-temperature keeping lamp 9 or the low-temperature keeping lamp 10. In the present embodiment, a description will be given of an example of high-temperature keeping, and a high-temperature keeping lamp is turned on. Further, the timer time S1 of the timer means 30 is reset to S1 = 0 (S2).

The detection signal from the temperature detecting element 6 is inputted to the temperature detecting means 25. With the turning off of the water heater 4, the water temperature in the container 3 gradually decreases. Temperature detection means 2
5, when the measured temperature TB is input,
Compares and determines the measured temperature TB with a pre-set temperature-maintaining heater ON temperature t1 (90 ° C.) (S
3). If the result of the comparison is TB ≦ t1 (see elapsed time T1), the heater control unit 27 operates the switching transistor 18 to turn on the bidirectional switching element 19 to energize the heater 5 ( S
4). Here, since there is a heating delay until the heat of the heat retaining heater 5 is transferred to the water, the water temperature is once reduced to the minimum heat retaining temperature t2.
(89 ° C.) and then start to rise (elapsed time T
2).

When the power supply to the warming heater 5 is turned on, the warming control means 26 then measures the measured temperature TB from the temperature detecting means 25 and the preset warming heater OFF temperature t3.
(91 ° C.) (S5). If the comparison judgment result is not TB ≧ t3, TB is measured and the comparison judgment with t3 is repeated. If TB ≧ t3 (see elapsed time T3), the warming heater control means 27 activates the switching transistor 18, turns off the bidirectional switching element 19, and turns off the power supply to the warming heater 5 (S
6). Here, usually, even if the heat retention heater 5 is turned off, the water temperature is affected by the heat capacity of the container 3 and the water therein,
After rising to the maximum heat retention temperature t4 (92 ° C.), the temperature starts to decrease (see elapsed time T4).

When the heat retaining heater 5 is turned off, the abnormal temperature detecting means 29 calculates the inclination ΔTB of the water temperature in the container 3 based on the measured temperature TB from the temperature detecting means 25 (S
7). If ΔTB is positive, then the abnormal temperature detecting means 29
Is the temperature difference Th (3.5 ° C.) between the temperature t5 (94 ° C.) determined to be abnormal and the heat retention center temperature t0 (90.5 ° C.) and TB
-T0 is compared and determined (S8). If TB-t0 is not equal to or greater than Th, the operations of S7 and S8 are repeated. If the temperature gradient becomes 0 or less before TB-t0 becomes equal to or more than Th, it can be considered that the temperature difference does not become equal to or more than Th. The comparison with the warming heater ON temperature t1 is started.

When the amount of water in the container 3 is reduced, for example, when a tapping valve (not shown) is pressed to take out hot water, the heater 5 is energized as usual when TB ≦ t1 ( After falling to t2 (see elapsed time T5), it starts to rise after falling to t2. However, since the slope of the water temperature rise is steeper than usual, TB ≧ t3, so that TB ≧ t3.
The water temperature continues to rise rapidly even if the power supply to the power supply is turned off. In such a case, the abnormal temperature detecting means 29
If it is determined that h ≦ TB−t0, the warming heater control unit 27
Is inputted with the power supply stop command (S9). When the power-supply stop holding command is input, the heat-retention heater control means 27 self-holds the heat-retention heater 5 so as not to re-energize. This self-holding is such that the power plug (not shown) cannot be returned again until the power plug (not shown) is once pulled out from the outlet (not shown). The abnormal temperature detecting means 29 causes the time measuring means 30 to start measuring time (S10). The timer 30 starts the clocking and operates the display controller 28. The display control unit 28 causes the boiling lamp 8 and the high-temperature keeping lamp 9 to blink alternately (S11) (see elapsed time T8).

The measured time S1 is compared with a preset blinking time S (for example, 10 minutes) (S12), and S1 ≧ S
If not, the display control means 28 is caused to continue blinking. S1
When ≧ S, the timing unit 30 causes the display control unit 28 to stop the alternately blinking display of the boiling lamp 8 and the high-temperature keeping lamp 9 (S13), stop the timing (S14), and turn off the power.
F to end the operation of the electric water heater (S15)
(See elapsed time T9).

As described above, according to the first embodiment,
If the water temperature rises to an abnormal temperature by heating a small amount of water during the heat keeping, the abnormal temperature detecting means 29 calculates the temperature difference between the measured temperature and the reference temperature (predetermined warming temperature) and determines the temperature difference in advance. When the calculated temperature difference is determined to be equal to or greater than the predetermined temperature difference, the control unit 27 outputs an energization stop holding command to force the insulated heater control unit 27 to stop the energization of the insulated heater 5. In addition, since the time is started at the same time when the abnormality is displayed on the display means 7 and the power is turned off after a predetermined time and the operation is terminated, damage due to abnormal heating can be prevented. Further, when the power-supply stop holding command is input, the heat-retention heater control means 27 self-holds in the power-off state, and, for example, does not return again until the power plug is once pulled out from the outlet. Can be prevented.

Embodiment 2 FIG. In the second embodiment, the base temperature used as a reference when calculating the temperature difference to be compared by the abnormal temperature detecting means 29 is the warming temperature t0 (90.5 ° C.) in the first embodiment. , It's a heater heater OF
F temperature t3 (91 ° C.) or warming heater ON temperature t1 (9
0 ° C.). As in the second embodiment, the same effect as in the first embodiment can be obtained even when the base temperature is set to the warming heater OFF temperature t3 (91 ° C.) or the warming heater ON temperature t1 (90 ° C.). .

Embodiment 3 In the third embodiment, the base temperature used as a reference when calculating the temperature difference to be compared by the abnormal temperature detecting means 29 is the warming temperature t0 (90.5 ° C.) in the first embodiment. , It is usually kept at the highest temperature t4 (92 ° C.) or the lowest temperature t2 (89).
° C). This maximum heat retention temperature t4 (92
° C) or the minimum heat retention temperature t2 (89 ° C) is measured in advance under certain conditions, and is set based on the result. Even if the base temperature is set to t4 or t2, the first
The same effect as that of the embodiment can be obtained.

Embodiment 4 FIG. FIG. 5 is a block diagram of an electric water heater according to a fourth embodiment of the present invention. FIG. 6 is a circuit diagram of an electric water heater according to the fourth embodiment. In FIG. 5 or FIG. 6, the same operations as those in FIG. 1 or FIG. 5 and 6, reference numeral 31 counts the number of abnormal temperatures on the basis of the result of the comparison and judgment by the abnormal temperature detecting means 29.
This is a number-of-times counting means for stopping the energization of the heat retaining heater 5 by self-holding 7.

FIG. 7 is a flowchart at the time of keeping the temperature of the electric water heater according to the fourth embodiment. FIG. 8 shows the fourth
Water Temperature Change in Container 3 and Heat Insulation Heater 5 According to Embodiment
FIG. 6 is a diagram showing a correspondence relationship between the operations of FIG. The operation of the electric kettle according to the fourth embodiment will be described with reference to FIGS. When the warming process starts (S10
1) The display control means 29 turns on the high-temperature keeping lamp 9, resets the value of n of the number counting means 27 to n = 0, and resets the time S2 of the time counting means 30 to S2 = 0 (S10).
2).

The detection signal from the temperature detecting element 6 is inputted to the temperature detecting means 25. With the turning off of the water heater 4, the water temperature in the container 3 gradually decreases. Temperature detection means 2
5, when the measured temperature TB is input,
In step S10, the measured temperature TB is compared with a preset warm-up heater ON temperature t1 (90 ° C.).
3). If the result of the comparison is TB ≦ t1 (see elapsed time T1), the heater control unit 27 operates the switching transistor 18 to turn on the bidirectional switching element 19 to energize the heater 5 ( S1
04). Here, since there is a heating delay until the heat of the heat retaining heater 5 is transferred to the water, the water temperature is once reduced to the minimum heat retaining temperature t2.
(89 ° C.) and then start to rise (elapsed time T
2).

When the power supply to the heat retaining heater 5 is turned on, the temperature keeping control means 26 then measures the measured temperature TB from the temperature detecting means 25 and the preset heat keeping heater OFF temperature t3.
(91 ° C.) (S105). If the comparison judgment result is not TB ≧ t3, TB is measured and the comparison judgment with t3 is repeated. If TB ≧ t3 (the elapsed time T
3), the warming heater control means 27 operates the switching transistor 18, and the bidirectional switching element 1
The power supply to the heat retention heater 5 is turned off by turning off the power supply 9 (S106). Here, normally, even if the heat retaining heater 5 is turned off, the water temperature rises to the maximum heat retaining temperature t4 (92 ° C.) and then starts to decrease due to the heat capacity of the container 3 and the water therein (see elapsed time T4). ).

When the heat retaining heater 5 is turned off, the abnormal temperature detecting means 29 calculates the inclination ΔTB of the water temperature in the container 3 based on the measured temperature TB from the temperature detecting means 25 (S1).
07). If ΔTB is positive, then abnormal temperature detection means 2
No. 9 compares the abnormal temperature t5 (94 ° C.) with the measured temperature TB (S108).

If it is not determined in step S108 that TB ≧ t5, the process returns to step S107 and repeats the determination of ΔTB> 0. If the temperature of the measured temperature TB starts decreasing without judging that TB ≧ t5, the heat retention control unit 26 again executes S103 to S1.
The warming operation of 06 is performed (see elapsed times T5 to T8).

In S107, ΔTB is positive, and S1
If it is determined at 08 that the TB is equal to or higher than the abnormal temperature t5 (94 ° C.), the number counting means 31 increments the value of n by one (S109). The value of n counted up is 2
Is determined (S110), and if n is not 2, the normal warming operation is continued again (elapsed time T8 to T1).
1). If n = 2, the number counting means 31
An energization stop holding command is input to the warming heater control means 27 (S111). When the power-supply stop holding command is input, the heat-retention heater control means 27 self-holds the heat-retention heater 5 so as not to re-energize. As in the first embodiment, the self-holding can be resumed only after the power plug is pulled out from the outlet. Further, the abnormal temperature detecting means 29 causes the time measuring means 30 to start measuring time (S
112). The timer 30 starts the clocking and operates the display controller 28. The display control unit 28 causes the boiling lamp 8 and the high-temperature keeping lamp 9 to blink alternately (S113) (see elapsed time T12).

The measured time S2 is compared with a preset blinking time S (S114). If S2 ≧ S, the display control means 28 continues blinking. When S2 ≧ S,
The time keeping means 30 causes the display control means 28 to stop the blinking display of the boiling lamp 8 and the high-temperature keeping lamp 9 alternately (S11).
5) The timer is stopped (S116), the power is turned off, and the operation of the electric kettle is terminated (S117) (see elapsed time T13).

As described above, in the fourth embodiment, when the number-of-times counting means 31 has counted the abnormal temperature detection of the abnormal temperature detecting means 29 twice, it outputs an energization stop holding command to the heat keeping heater control means 27. So,
The stop due to a measurement error or the like is reduced, and the abnormally high temperature state in the container 3 due to the decrease in the amount of water is more accurately determined. When the power supply stop holding command is input, the heat insulation heater control unit 27 is activated.
Is self-maintained in the power-off state, for example, the power plug is only once pulled out from the outlet so that it does not return to the original state, so that baking can be reliably prevented.

Embodiment 5 FIG. FIG. 9 is a block diagram of an electric water heater according to a fifth embodiment of the present invention. FIG. 10 is a circuit diagram of an electric water heater according to the fifth embodiment. In FIG. 9 or FIG. 10, the components denoted by the same reference numerals as those in FIG. 1 or FIG. 9 and 10, 32 is 1
The arithmetic means for calculating the difference between the maximum water temperature t4 detected at the time of overshoot after turning off the heat retaining heater 5 for the second time and the maximum water temperature t6 at overshoot after turning off the heat retaining heater 5 for the second and subsequent times. is there. Reference numeral 33 denotes a storage means. When the abnormal temperature detecting means 29 detects that ΔTB has become negative, the temperature at that time (that is, the first time is the maximum water temperature t4, and the second and subsequent times is the maximum water temperature). t6) is stored.

FIG. 11 is a flowchart when the electric water heater according to the fifth embodiment is kept warm. FIG. 12 is a diagram showing a correspondence relationship between a change in water temperature in the container 3 and the operation of the heat retaining heater 5 according to the fifth embodiment. The operation of the electric kettle according to the fifth embodiment will be described with reference to FIGS. When the power supply to the water heater 4 is turned off, the warming process starts (S201).
It is assumed that the amount of water in the container 3 is at least a certain amount during the heat insulation. When the heat keeping process starts, the display control means 29 in the microcomputer 14 turns on the high-temperature keeping lamp 9 or the low-temperature keeping lamp 10. In the present embodiment, a description will be given of an example of high-temperature keeping, and a high-temperature keeping lamp is turned on. Further, the timer time of the timer means 30 is reset (S202).

The detection signal from the temperature detecting element 6 is inputted to the temperature detecting means 25. With the turning off of the water heater 4, the water temperature in the container 3 gradually decreases. Temperature detection means 2
5, when the measured temperature TB is input,
Compares and determines the measured temperature TB with a preset heat-retention heater ON temperature t1 (90 ° C.) (S20).
3). If the result of the comparison is TB ≦ t1 (see elapsed time T1), the heater control unit 27 operates the switching transistor 18 to turn on the bidirectional switching element 19 to energize the heater 5 ( S2
04). Here, since there is a heating delay until the heat of the heat retaining heater 5 is transferred to the water, the water temperature is once reduced to the minimum heat retaining temperature t2.
(89 ° C.) and then start to rise (elapsed time T
2).

When the power supply to the warming heater 5 is turned on, the warming control means 26 then measures the measured temperature TB from the temperature detecting means 25 and the preset warming heater OFF temperature t3.
(91 ° C.) (S205). If the comparison judgment result is not TB ≧ t3, TB is measured and the comparison judgment with t3 is repeated. If TB ≧ t3 (the elapsed time T
3), the warming heater control means 27 operates the switching transistor 18, and the bidirectional switching element 1
9 is turned off to turn off the power supply to the heat retaining heater 5 (S206). Here, usually, even if the heat retaining heater 5 is turned off, the water temperature once rises above t3 once and then starts to decrease due to the heat capacity of the container 3 and the water therein.
Therefore, the abnormal temperature detecting means 29 determines whether or not ΔTB has started to fall (S207). When it is determined that ΔTB has started to fall, the abnormal temperature detecting means 29 determines that the measured temperature TB at that time is the maximum temperature t4 (for example, 92 ° C.). Remember (S
208) (see elapsed time T4).

After memorizing t4, the measured temperature TB becomes t1.
When the temperature falls below, the heater 5 is energized to heat water and t3
When the above is reached, the power supply to the heat retention heater 5 is stopped.
A normal heat retaining operation is performed (S209 to S212). When the power supply to the heat retaining heater 5 is stopped, the abnormal temperature detecting means 29
Determines whether ΔTB has turned downward (S21).
3) When it is determined that the temperature has started to fall, the measured temperature TB at that time is stored as the maximum temperature t6 (S21).
4). The calculating means 32 calculates the temperature difference H1 between t6 and t4 (S215). The abnormal temperature detecting means 29 compares H1 with a predetermined temperature difference T (for example, 2 ° C.) set in advance (S216). If H1 ≧ T, the normal heat retaining operation is repeated, H1 is calculated from the newly detected t6, and the comparison operation with T is repeated.

When the amount of water in the container 3 is reduced, for example, when a tapping valve (not shown) is pressed and hot water is collected,
A normal heat retaining operation is performed (elapsed time T5 to T7).
Since the inclination of the water temperature rise is steeper than usual, the water temperature overshoots and continues to rise rapidly even if the power supply to the heat retaining heater 5 is turned off. Therefore, the value of t6 increases (for example, 96 ° C.), and accordingly, the value of H1 also increases (for example, 4 ° C. in FIG. 12). In S16, if the abnormal temperature detecting means 29 determines that T ≦ H1, it outputs an energization stop holding command to the heat keeping heater control means 27 (S217). When the power-supply stop holding command is input, the heat-retention heater control means 27 self-holds the heat-retention heater 5 so as not to re-energize. This self-holding is such that the power plug (not shown) cannot be returned again until the power plug (not shown) is once pulled out from the outlet (not shown). Further, the abnormal temperature detecting means 29 causes the time measuring means 30 to start measuring time (S
218). The timer 30 starts the clocking and operates the display controller 28. The display control means 28 causes the boiling lamp 8 and the high-temperature keeping lamp 9 to blink alternately (S219) (see elapsed time T8).

The measured time S3 is compared with a preset blinking time S (S220). If S3 ≧ S, the display control means 28 continues blinking. When S3 ≧ S,
The time keeping means 30 causes the display control means 28 to stop the blinking display of the boiling lamp 8 and the high-temperature keeping lamp 9 alternately (S22).
1), the timer is stopped (S222), the power is turned off, and the operation of the electric kettle is terminated (S223) (see elapsed time T9).

As described above, according to the fifth embodiment,
The maximum temperature of the water temperature due to overshoot after the first heating heater 5 is turned off is stored, and the second and subsequent heating heaters 5 are stored.
Based on the temperature difference from the maximum water temperature at the time of the overshoot after the OFF, the temperature abnormality in the container 3 due to a decrease in the amount of water or the like can be determined. Damage can be prevented.

Embodiment 6 FIG. In the fifth embodiment, the second and subsequent warming heaters 5OF are based on the maximum water temperature due to overshoot after the first warming heater 5OFF.
Temperature difference H from the maximum water temperature during overshoot after F
1 was calculated and compared with the predetermined temperature difference T. The OFF temperature t3 of the heat retaining heater 5 at the time of keeping the temperature was a reference temperature,
Similar effects can be obtained by calculating the temperature difference H2 as shown in FIG. 12 and comparing it with a predetermined temperature difference set in advance.

Embodiment 7 FIG. In the fifth embodiment, the second and subsequent warming heaters 5OF are based on the maximum water temperature due to overshoot after the first warming heater 5OFF.
Temperature difference H from the maximum water temperature during overshoot after F
1 was calculated and compared with the predetermined temperature difference T. The temperature difference H3 as shown in FIG. 12 was calculated using the ON temperature t1 of the heat retaining heater 5 at the time of keeping the temperature as the reference temperature, and the predetermined temperature was set in advance. Similar effects can be obtained by comparing with the difference.

Embodiment 8 FIG. In the fifth embodiment, the second and subsequent warming heaters 5OF are based on the maximum water temperature due to overshoot after the first warming heater 5OFF.
Temperature difference H from the maximum water temperature during overshoot after F
1 was calculated and compared with the predetermined temperature difference T.
A temperature difference H4 as shown in FIG. 12 is calculated by using the minimum temperature t2 at the time of heat retention due to the heating delay at the time of ON as a reference temperature,
Similar effects can be obtained by comparing with a predetermined temperature difference set in advance.

Embodiment 9 FIG. The ninth embodiment is the first,
In the second and third embodiments, the temperature difference between the measured temperature TB and the reference temperatures t0, t1, t2, t3, and t4 is calculated, and the temperature difference Th, which is the difference between the abnormal temperature t5 and the reference temperature, is calculated.
(See S8 in FIG. 3) that the temperature of the container 3 is determined to be abnormal is changed to the abnormal temperature detecting means 29, as in the fourth embodiment. Are compared directly. If the measured temperature TB is equal to or higher than the abnormal temperature T5, the heat insulation heater control means 27 is caused to output an energization stop holding command. In the ninth embodiment, the same effects as in the first, second, and third embodiments can be obtained.

Embodiment 10 FIG. The tenth embodiment is different from the fourth embodiment in that the measured temperature TB and the abnormal temperature t5
Are directly compared with each other, and the result of the comparison is used to determine whether the temperature inside the container 3 is abnormal. In the same manner as in the first, second, or third embodiment, the reference temperature is set, and the measured temperature is set. The temperature difference between TB and the reference temperature and the temperature difference between the abnormal temperature t5 and the reference temperature are calculated. Comparing the two calculated temperature differences, if the temperature difference between the measured temperature TB and the reference temperature is equal to or greater than the temperature difference between the abnormal temperature t5 and the reference temperature, the number counting means 31 counts and a predetermined number of times. When the counting is performed, the heat-retention heater control means 27 is caused to output an energization stop holding command. In the tenth embodiment, the same effect as in the fourth embodiment can be obtained.

Embodiment 11 FIG. In the above embodiment, the processing state and the container 3 are indicated by the boiling indicator lamp 8, the high-temperature keeping indicator lamp 9, and the low-temperature keeping indicator lamp 9 of the display means 7.
Although the abnormality in the inside is displayed, teaching by sound or the like may be performed.

[0052]

As described above, according to the present invention, a temperature difference between a predetermined reference temperature and a measured temperature is compared with a predetermined temperature difference set in advance, and the heater is stopped based on the comparison result. As a result, abnormal heating and baking can be prevented, and components such as containers can be protected.

Further, according to the present invention, a temperature difference is calculated by using a predetermined warming temperature, which is a reference when maintaining the temperature of water, as a predetermined reference temperature, and the temperature difference is compared with the predetermined temperature difference. Is stopped, abnormal heating and baking can be prevented, and components such as containers can be protected.

Further, according to the present invention, the temperature difference is calculated using the temperature used as the reference when the heat retention control means outputs the power supply command or the power supply stop command as a predetermined reference temperature, and the calculated temperature difference is compared with the predetermined temperature difference. Since the heater is stopped based on the result, abnormal heating and dry burning can be prevented, and components such as containers can be protected.

Further, according to the present invention, the temperature difference is calculated as the predetermined maximum reference temperature or the maximum preservation temperature or the minimum preservation temperature under the predetermined condition during the preservation of the reference temperature, and is compared with the predetermined temperature difference. Since the heater is stopped based on this, abnormal heating and dry burning can be prevented, and components such as containers can be protected.

Further, according to the present invention, by displaying the state on the display means, it is possible to visually determine the abnormal state of the temperature in the container.

Further, according to the present invention, a temperature difference between a predetermined reference temperature and a measured temperature is calculated and compared with a predetermined temperature difference set in advance. The heater is stopped when it is counted a predetermined number of times, so that the abnormal condition can be accurately grasped to reduce the stoppage due to errors, and also to prevent abnormal heating and burning and protect parts such as containers. Can be achieved.

Further, according to the present invention, the predetermined reference temperature is compared with the measured temperature, and if the measured temperature is equal to or higher than the predetermined reference temperature, the counting means counts. Therefore, it is possible to accurately grasp the abnormal state, reduce the stoppage due to the error, and prevent the abnormal heating and the empty burning to protect the components such as the container.

Further, according to the present invention, the difference between the maximum temperature at which the heat retention control means outputs the power supply stop command a predetermined number of times and the maximum temperature at which the power supply stop command is output after the predetermined number of times is calculated. Since the heater is stopped based on the result of the comparison with the predetermined temperature difference, abnormal heating and idling can be prevented, and components such as containers can be protected.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electric water heater according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of the electric water heater according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating an operation of the first exemplary embodiment of the present invention.

FIG. 4 is a graph showing the water temperature in the container 3 and the operation of the heater according to the first embodiment of the present invention.

FIG. 5 is a block diagram of an electric water heater according to a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram of an electric water heater according to a fourth embodiment of the present invention.

FIG. 7 is a flowchart showing an operation of the fourth exemplary embodiment of the present invention.

FIG. 8 is a graph showing a water temperature in a container 3 and an operation of a heater according to a fourth embodiment of the present invention.

FIG. 9 is a block diagram of an electric water heater according to a fifth embodiment of the present invention.

FIG. 10 is a circuit diagram of an electric water heater according to a fifth embodiment of the present invention.

FIG. 11 is a flowchart showing the operation of the fifth embodiment of the present invention.

FIG. 12 is a graph showing a water temperature in a container 3 and an operation of a heater according to a fifth embodiment of the present invention.

FIG. 13 is a longitudinal sectional view of a conventional electric water heater.

[Explanation of symbols]

1 body of electric water heater, 2 exterior body, 3 container, 4
Water heater, 5 warming heater, 6 temperature detecting element, 7 display means, 25 temperature detecting means, 26 warming controlling means, 27 warming heater controlling means, 28 display controlling means, 29 abnormal temperature detecting means, 30 clocking means, 31
Number counting means, 32 arithmetic means, 33 storage means.

Claims (8)

[Claims] 1. A container for storing water, a heater for heating the water stored in the container, a temperature detecting means for measuring the temperature of the water, and a method for keeping the temperature of the water at a predetermined temperature while maintaining the temperature. A heat retention control unit that outputs an energization command or an energization stop command based on the temperature of the water measured by the temperature detection unit so as to maintain the temperature, and a predetermined reference temperature determined in advance and a temperature measured by the temperature detection unit. An abnormal temperature detecting means for outputting an energization stop holding command when it is determined that the temperature difference is equal to or greater than a predetermined temperature difference, the energization command, the energization stop command or the energization stop An electric water heater comprising: heater control means for controlling energization of the heater based on a holding command. 2. The electric water heater according to claim 1, wherein the predetermined reference temperature is set to the predetermined heat retaining temperature. 3. The predetermined reference temperature is a temperature of water used as a reference when the heat retention control unit outputs the energization command,
2. The electric water heater according to claim 1, wherein the water heater is set to one of the temperatures of water used as a reference when the power supply stop command is output. 3. 4. The electric water heater according to claim 1, wherein the predetermined reference temperature is set to one of a maximum temperature and a minimum temperature under predetermined conditions when keeping the temperature. 5. An apparatus according to claim 1, further comprising display means for displaying a state of a heat treatment, a heat retention treatment, and a temperature of said water, wherein said abnormal temperature detecting means displays said display when said temperature difference is equal to or more than said predetermined temperature difference. 5. The electric water heater according to claim 1, wherein the means for displaying an abnormality is displayed on the means. 6. A container for storing water, a heater for heating the water stored in the container, a temperature detecting means for measuring the temperature of the water, and when the temperature is kept warm, the temperature of the water is kept at a predetermined temperature. A heat retention control unit that outputs an energization command or an energization stop command based on the temperature of the water measured by the temperature detection unit so as to maintain the temperature difference between a predetermined reference temperature and the temperature measured by the temperature detection unit Is calculated, and the temperature difference is compared with a predetermined temperature difference,
An abnormal temperature detecting unit that outputs an abnormal signal when it is determined that the temperature difference is equal to or more than a predetermined temperature difference; a counting unit that counts the abnormal signal and outputs an energization stop holding command when the predetermined number of times is counted; And a heater control means for controlling the power supply to the heater based on the power supply stop command or the power supply stop holding command. 7. A container for storing water, a heater for heating the water stored in the container, a temperature detecting means for measuring the temperature of the water, and when the temperature is maintained, the temperature of the water is maintained at a predetermined temperature. A heat retention control unit that outputs an energization command or an energization stop command based on the temperature of the water measured by the temperature detection unit so as to maintain the temperature; and an abnormality when the temperature of the water is determined to be equal to or higher than a preset temperature. An abnormal temperature detecting means for outputting a signal, a counting means for counting the abnormal signal and outputting an energization stop holding command when a predetermined number of times have been counted, based on the energization instruction, the energization stop instruction or the energization stop holding instruction An electric water heater, comprising: heater control means for controlling energization of the heater. 8. A container for storing water, a heater for heating the water stored in the container, a temperature detecting means for measuring the temperature of the water, and a method for keeping the temperature of the water at a predetermined temperature during the heat retention. Insulation control means for outputting an energization command or an energization stop command based on the temperature of the water measured by the temperature detection means so as to maintain the temperature, and the temperature detection means measures in a normal heat insulation control state of the heat insulation control means. Calculating means for calculating a temperature difference between a reference maximum heat retention temperature and a maximum heat retention temperature measured by the temperature detecting means after the measurement of the maximum heat retention reference temperature; and a predetermined temperature determined by the temperature difference calculated by the calculation means and a predetermined temperature Comparing the difference with the temperature difference, and determining that the calculated temperature difference is equal to or greater than the predetermined temperature difference, an abnormal temperature detecting means for outputting an energization stop holding instruction, the energization instruction, the energization stop instruction or the energization An electric water heater comprising: heater control means for controlling energization of the heater based on a stop holding command.