JP2955184B2 - Electric water heater - Google Patents

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, and more particularly to an electric water heater having a reboil function without a microcomputer.

[0002]

2. Description of the Related Art Conventionally, in an electric water heater without a microcomputer, water is poured into an inner container, and
Detecting a decrease in temperature or operating the boiling start button to perform water heating with a water heater,
After boiling, let it cool naturally and keep it at a predetermined temperature with a warming heater, then, if you need boiling water,
Each time, the reboil switch is turned on to enable reboil.

[0003] By the way, in the electric water heater having such a re-boiling function, for example, 97% lower than the boiling point.
Unless the temperature drops to ℃, re-boiling is not accepted. That is, if re-boiling is received at a temperature near the boiling point higher than 97 ° C., malfunction may occur between the detection of boiling and the use of one thermistor for temperature detection.

[0004]

However, in the above-described conventional electric water heater, as described above, after boiling, the temperature becomes 97 ° C.
Reboil is not accepted until the water temperature drops to 97
There is a problem in that boiling water cannot be used for a long time (about 2 hours) until the temperature drops to ° C.

Therefore, while detecting the temperature at which re-boiling can be accepted (higher than 97 ° C. and near the boiling point) with a thermistor provided on the bottom of the inner container, the temperature of steam generated by providing a thermistor at the shoulder is detected. Although the thermistor is expensive, there is a demand that only one thermistor should be used if possible. In view of the above problems, the present invention, after boiling,
It is an object of the present invention to provide an inexpensive electric water heater that can shorten the time until re-boiling can be performed.

[0006]

According to the first aspect of the present invention, there is provided a water heater for heating an inner container in which water is contained, and a change in resistance value of a thermistor for detecting an inner container temperature. A detection voltage value that rises and falls based on
By comparing with the reference voltage value set by the reference resistance and detecting that the level of both voltage values is reversed,
Reheating means for judging whether or not the temperature of the hot water has reached a predetermined value, and after the end of the boiling, by the input signal from the reboil switch, the energization to the hot water heater is restarted to reboil. In the electric water heater provided with control means, while the reference resistance is constituted by a plurality of resistances, based on an input signal from the reboil switch, the energization state of each resistance is changed, and the reference voltage value is changed. And a reference voltage changing means for forcibly returning to a state before the hot water temperature detecting means outputs the detection signal.

In the invention according to claim 2, the reference voltage changing means is constituted by a transistor connected to the reference resistor, and the transistor is turned on / off based on an input signal from the reboil switch. The current supply state of each resistor can be changed so that the reference resistance value changes.

[0008]

According to the configuration of the first aspect of the present invention, if the reboil switch is turned on after the energization of the water heater is stopped, the reference voltage value is detected by the reference voltage changing means, and the hot water temperature detecting means is used. Forcibly returns to the state before outputting the detection signal, and re-boiling is started by supplying electricity to the water heater.

According to the second aspect of the present invention, when the reboil switch is turned on, the transistor is turned on and the total resistance value is changed. The state before outputting the detection signal is restored.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a front sectional view of the electric water heater. Inside the main body 1 of the electric kettle, an inner container 2 is accommodated, and a water pump 4 extending from the bottom of the inner container 2 to the spout 3 is provided upright.

A lid 5 is removably attached to the upper end of the main body 1 and houses a steam flow path 6 and a bellows pump 7 inside. The steam passage 6 is a passage for discharging generated steam. The bellows pump 7 can be pushed down by operating the pushing member 8. When the bellows pump 7 is pushed down, the inside of the inner container 2 is pressurized and hot water is discharged from the spout 3 through the water pump 4.

A thermistor 9 is provided at the center of the bottom surface of the inner container 2 so that the internal water temperature can be detected. A water heater 10 and a warming heater 11 are provided on the outer peripheral side of the bottom surface of the inner container 2, and generate heat by the power supplied from the AC power supply 12. It changes based on the excitation and demagnetization of the relay 13 driven by the electric circuit described below.

FIG. 2 shows a temperature detecting circuit 14, a boiling circuit 15 and a re-boiling circuit 16 for controlling the energization of the kettle heater 10. These electric circuits include an AC power supply 12 and a rectifying circuit 17. A direct current is supplied via the. In the temperature detection circuit 14, the rectifier circuit 1
7, resistors R ₁ and R ₂ are connected. In addition, both resistors R
₁ and R ₂ include resistors R ₃ and R ₄ , resistors R ₅ and R ₆ and resistors R ₇ , R ₈ and R ₉ and a first transistor T connected in parallel.
_r1 is connected. The resistance to the R ₂ the thermistor 9 and the resistor R ₁₀ are connected in parallel, the voltage applied to these plus input terminal of the first comparator 18 and second comparator 19, respectively to the negative input terminal of the third comparator 20 Has been entered.

[0014] The first base of the transistor Tr ₁ is connected between the resistor R ₁₀ and a thermistor 9. The first transistor Tr ₁ is normally in an ON state because a voltage is applied to the base of the first transistor Tr ₁ via the resistor R ₁₀ and the thermistor 9. However, when the thermistor 9 is disconnected or at a very low temperature (for example, (−20 ° C.), the transistor is turned off.

For example, when the thermistor 9 is disconnected, the first transistor Tr ₁ is turned off, and the input voltage to the minus input terminal of the first comparator 18 increases. As a result, the first comparator 18 outputs low,
Accordingly, the fourth comparator 21 also outputs low. Then, the seventh transistor Tr ₇ is turned on, the first 8
Transistor Tr ₈ is turned off by the voltage difference disappears between the emitter and base. Thereby, the relay 13
Is demagnetized, and the power supply to the water heater 10 is stopped. In other words, parallel connecting the thermistor 9 to the resistor R _2, and,
By connecting the first transistor Tr ₁ to the resistors R ₃ and R ₄ ,
Since the base was to be connected between the resistor R ₁₀ and a thermistor 9, if abnormality occurs in the thermistor 9 can be stopped reliably energizing the boiler heater 10. Therefore, when the thermistor 9 fails, the inner container 2
Can be prevented from being abnormally heated to cause a failure.

A second transistor Tr ₂ is connected in parallel to the resistor R ₇ . This second transistor T
The base of r ₂ is connected to a reboil circuit 16 described below. The resistors R ₁ and R _{2 are connected} between the resistors R ₃ and R ₄ , the resistors R ₅ and R _6, and the resistors R ₈ and R ₉ via capacitors C ₁ , C ₂ and C ₃ , respectively. , The resistors R ₄ , R ₆ ,
The voltage applied to R ₉ is input to the plus input terminal of the third comparator 20, the minus input terminal of the second comparator 19, and the minus input terminal of the first comparator 18, respectively.

[0017] In the Boiling circuit 15, the rectifier circuit 17, resistors R _11, parallel connected resistor R ₁₂ and diode D ₁ and capacitor C ₄ is connected to the capacitor C ₄ resistor R ₁₃ and the third transistor Tr ₃ Are connected in parallel. The output terminal of the first comparator 18, as described above, the fourth through the parallel connected diodes D ₁ and the resistor R ₁₂
It is connected to the plus input terminal of the comparator 21.

The base of the third transistor Tr ₃ is:
Base of the fourth transistor Tr _9, emitter and fifth
It is connected to the collectors of the transistor Tr _5. Base of the fifth transistor Tr ₅ is connected to the resistor R ₁₄ rectifier circuit 17 via are connected to the reboiling switch SW.

The base of the sixth transistor Tr ₆ is connected to the rectifier circuit 17, the output terminal of the fourth comparator 21 and the output terminal of the second comparator 19, and the collector is connected to the reboil switch SW.

[0020] In the reboil circuit 16, the rectifier circuit 17, a seventh transistor Tr ₇ and reboil switch SW, 8
The transistor Tr ₈ , the ninth transistor Tr ₄ and the relay 13 are connected in parallel. The base of the seventh transistor Tr ₇ is connected to the rectifier circuit 17, the output terminal of the fourth comparator 21, and the output terminal of the second comparator 19, respectively. The eighth transistor T
together with the base and emitter of r ₈ is connected to the rectifier circuit 17 via a resistor R _15, the third comparator 20
Output terminal. Further, the base of the ninth transistor Tr ₄ is connected between the collector of the eighth transistor Tr ₈ and the relay 13.

Next, control of energization of the heater 10 by the relay 13 driven based on the electric circuit will be described. In the present electric circuit, the input voltage to the minus input terminal of the first comparator 18 is determined by the voltage division of the resistors R ₇ and R ₈ and the resistor R ₉ except for the boiling detection and re-boiling described below. 18 always outputs high (in this embodiment, the resistors R ₇ and R ₈ and the resistor R ₉
Is set so that the output of the first comparator 18 switches at the detected temperature of 103 ° C. by the partial pressure. ). Therefore, the fourth comparator 21 outputs a high output, and the seventh transistor Tr ₇ maintains the off state.

(Cold Water Detection) Immediately after cold water is stored in the inner container 2, the resistance of the thermistor 9 is high and the input voltage to the minus input terminal of the third comparator 20 is large. Output low. Thus, current is supplied to the resistor R _15, since the eighth transistor Tr ₈ is turned on by a voltage drop there, relay 1
3 is heated and the heater 10 is energized, and the heater 10 is energized.

In this case, the ninth transistor Tr ₄ is turned on, so that even if the third comparator 20 outputs a high output, the current supply to the resistor R ₁₅ is continued.
Eighth transistor Tr ₈ is kept on. Therefore, the relay 13 is not demagnetized, and the heating by the water heater 10 is continued until the output from the fourth comparator 21 is switched, as described below.

Also, the low output of the third comparator 20 turns on the second transistor Tr ₂ ,
Since no longer energized the resistor R _7, the negative input terminal of the first comparator 18 so that the voltage determined by the partial pressure of the resistor R ₈ and the resistor R ₉ is input. For this reason, if the resistance value of the thermistor 9 decreases to a predetermined value as the hot water temperature rises, the first comparator 18 switches from the high output to the low output (in this embodiment,
The hot water temperature is set to be switched at 95 ° C. by the partial pressure of the resistors R ₈ and R ₉ . ).

The high output of the fourth comparator 21 turns off the sixth transistor Tr ₆ as well as the seventh transistor Tr _7. However, in this state, the resistor R ₁₄ is not energized. , The fifth transistor Tr ₅ maintains the off state. Therefore, the fourth transistor Tr ₉ and the third transistor Tr ₃ also maintain the off state, and the resistor R ₁₃ is not energized.

(Boiling Detection) Here, when the water contained in the inner container 2 reaches a predetermined temperature (95 ° C.), the relationship of the input voltage of the first comparator 18 is reversed, and the output is switched from the high output to the low output. This starts the discharge by the capacitor C _4, the fourth comparator 21 is not switched to the low output immediately. In this case, the third transistor T
Since r ₃ is that maintains the OFF state, no current is supplied to the resistor R _13, the discharge of the capacitor C ₄ is performed only through the resistor R _12.

Therefore, regardless of the low output from the first comparator 18, the heating is continued by the water heater 10, so that the water boils, and for a predetermined time after reaching the boiling point,
This boiling state will be maintained.

Thereafter, if the input voltage to the fourth comparator 21 reverses between the plus side and the minus side due to the discharge of the capacitor C ₄ , the fourth comparator 21 outputs low, and the seventh transistor Tr ₇ is turned on. Becomes Thus, the potential difference is eliminated between the base and emitter of the eighth transistor Tr _8, the eighth transistor Tr ₈
Is turned off. Therefore, the ninth transistor Tr
₄ is turned off, the relay 13 is demagnetized, and the energization of the water heater 10 is stopped. Thus, by maintaining a predetermined time boiling state by utilizing the discharge time in the capacitor C _4, a so-called chlorine skip is performed.

(Heat preservation) After the detection of boiling, when the power supply to the water heater 10 is stopped, the heat preservation by only the heat preservation heater 11 is continued, and the hot water temperature gradually decreases by natural cooling.
Maintained at ~ 97 ° C. The fourth comparator 2
When the seventh transistor Tr ₇ is turned on at the low output of 1, the current supply to R ₁₅ is stopped, and the second transistor T ₇ is turned off.
Since r ₂ is turned off, the resistors R ₇ and R ₈ and the resistor R ₉
Is applied to the minus input terminal of the first comparator 18, and as described above, the first comparator 18
Is high output, the charging of the capacitor C ₄ is performed.

(Reboiling) In addition, when the boiling water is required during the period from the boiling to the transition to the heat retaining state or after the transition to the heat retaining state, the reboil switch SW is turned on. To cause re-boiling as follows.

First, when the reboil switch SW is turned on, the voltage applied to the base of the eighth transistor Tr ₈ drops by energizing the resistor R ₁₅ . As a result, the eighth transistor Tr ₈ is turned on, the ninth transistor Tr ₄ is turned on, and the relay 13 is energized to start water heating and energize the heater 10.

Further, the second with the energization of the resistor R ₁₅
Since the voltage applied to the base of the transistor Tr ₂ also drops, the second transistor Tr ₂ is also turned on, and the resistor R ₇ is not energized. Therefore, the input voltage to the minus input terminal of the first comparator 18 is equal to the resistance R ₈
Increases become a partial pressure of and the resistor R _9.

The first comparator 18 maintains a high output when the hot water temperature is low (less than 95 ° C.), and maintains a high output when the hot water temperature is high (95 ° C.).
As described above, the output is switched from the high output to the low output. In the high output state, since the seventh transistor Tr ₇ is kept in the off state, the relay 13 continues to be excited, and the heating by the water heater 10 is continued. When the hot water temperature rises, the first comparator 18 switches from the high output to the low output.

[0034] If the first comparator 18 is low output, the discharge due to the capacitor C ₄ in the same manner as in the case of the boiling detection is started. However, in the case of re-boiling, the fifth transistor T is turned on by turning on the re-boiling switch SW.
r ₅ , the fourth transistor Tr ₉ and the third transistor Tr
Since ₃ is turned sequentially turned on, it is possible energized resistor R _13. Therefore, as described above, if the first comparator 18 by low output, the discharge of the capacitor C ₄ is also performed via the resistor R ₁₃ as well resistor R ₁₂ only, the early than in the case of the kettle 4 the input voltage to the positive input terminal of the comparator 21 is lowered (i.e., since as compared with the resistance value of the resistor R ₁₂ only the resistor R _12, towards the combined resistance value R ₁₃ is small, easy to discharge Because.) As a result, it is possible to shorten the boiling maintenance time in the re-boiling of the hot water for which the calcination has already been completed in the first boiling.

(Detection of empty heating) When the power supply to the heater 10 is started even though no water is contained in the inner container 2, the inner container temperature rises abnormally and the thermistor 9, the second comparator 19 switches from the high output to the low output, and the energization of the water heater 10 is stopped and the heating of the inner container 2 is forcibly performed as in the case of the boiling detection. Has been discontinued.

As described above, in the above embodiment, the second transistor T is turned on by turning on the reboil switch SW.
The r ₂ as ON state, and the power supply to the resistor R ₇ to be able to stop, can be reversed by the forced positive and negative input voltage to the first comparator 18. That is, if on the reboiling switch SW, the first comparator 18 is low output, the discharge due to the capacitor C ₄ is started, before going to insulation state, specifically, water temperature within 95 ° C. Even before the decline,
Power supply to the water heater 5 can be resumed.

In the above embodiment, the PNP type is used for the second transistor Tr ₂ , but it goes without saying that an NPN type may be used.

[0038]

As is apparent from the above description, according to the first aspect of the present invention, if the reboiler switch is turned on after the energization of the water heater is stopped, the reference voltage changing means is used. Since the relationship between the reference voltage value and the detected voltage value can be forcibly returned to the state before detection by the hot water temperature detection means, re-boiling can always be started, and re-boiling can be performed as in the conventional case. In addition, there is no need to wait for a long time until the temperature of the hot water drops, and there is no need to provide a new thermistor, so that the cost can be reduced.

According to the second aspect of the present invention, the electric circuit can have a simple structure by forming the reference voltage varying means with a transistor.

[Brief description of the drawings]

FIG. 1 is a front sectional view of an electric water heater according to the present embodiment.

FIG. 2 is a control circuit diagram of the electric water heater shown in FIG.

[Explanation of symbols]

9: thermistor, 10: water heater, 13: relay,
16: reboil circuit, 18: first comparator, SW: reboil switch, Tr ₂ : second transistor, R ₇ : resistor.

Claims (2)

(57) [Claims] 1. A water heater for heating an inner container in which water is stored, a detected voltage value which rises and falls based on a change in a resistance value of a thermistor for detecting an inner container temperature, and a reference voltage value set by a reference resistor Hot water temperature detecting means for determining whether the hot water temperature has reached a predetermined value by detecting that the level of the voltage value of the two has been reversed, and An electric water heater having reboil control means for re-energizing the water heater and performing reboil by an input signal, wherein the reference resistance is constituted by a plurality of resistances, Reference voltage changing means for changing the energization state of each resistor based on an input signal and forcibly returning a reference voltage value to a state before the hot water temperature detection means outputs a detection signal is provided. Features Electric water heater that. 2. The method according to claim 1, wherein the reference voltage changing means includes a transistor connected to the reference resistor, and turns on / off the transistor based on an input signal from the reboil switch.
2. The electric water heater according to claim 1, wherein the power supply state of each resistor can be changed so as to change the reference resistance value by turning off.