JPS5915755A - Electric water heater - Google Patents

Abstract

PURPOSE:To obtain an electric water heater capable of keeping water in boiled state without causing spilling of boiled water, by providing a circuit for heating a heater with an intermediate electric power between its heating power and temperature keeping power for a prescribed while after the temperature of water is raised to a reference value. CONSTITUTION:When the temperature of water exceeds, for instance, 95 deg.C, voltage VX impressed to the negative terminal of a comparator 21 becomes higher than voltage impressed to the positive terminal of the comparator 21, so that the output of the comparator 21 is switched from 1 to 0. The signal 0 is inverted by an inverter 31, and current is passed from a terminal 14-1 of a resistance 14 to a capacitor 35 via a resistance 34, so that the capacitor 35 is charged. The voltage of the capacitor 35 is changed to a prescribed high level of 1 after passing of a time tauB (tauB CBXRB) corresponding to the time constant tau determined by the value RB of the resistance 34 and the capacitance CB of the capacitor 35.

Description

[Detailed description of the invention] This invention relates to an electric water heater.

Conventionally, a temperature sensor for detecting the temperature of a liquid, such as water, stored in the container is attached to a container equipped with a heater. An electric water boiler equipped with a heater power switching circuit that switches the heating power of the heater, for example 600 W, to a lower heating power of about 125 W, for example, to keep the hot water warm, and turns it on and off when the temperature rises. [Seven vessels are known.

In the above-mentioned case, the water cannot be brought to a boiling state, resulting in incomplete sterilization, deodorization, etc. of the water.

This invention was made in order to solve the problem described in item 2, and when the temperature of the water in the container rises to a predetermined reference temperature for switching to the heat retention state, the difference between the heating power and the heat retention power is To provide an electric water heater that can heat a heater for a predetermined period using electric power to boil water without causing water spill.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, I is a thermally conductive volume gg, 2 is a band-shaped heater for boiling water wrapped around the outer peripheral surface of the bottom of the container 1, and 3 is a liquid stored in the container 1, e.g. , a negative characteristic thermistor for detecting water temperature, and 4 a negative characteristic thermistor for detecting dry cooking.

Figure 2 shows an example of the electric circuit of a dual electric water heater.

In FIG. 2, the heater 2 for boiling water is, for example,
The heater 2, which is formed in the shape of a 600W band, is connected to a commercial AC power source 5. Between this heater 2 and the ground side terminal of the AC power supply 5, the heater 2
For example, a try-out 10 is connected for controlling the supply of electricity to the terminal.

Reference numeral 11 denotes a zero-crossing point detector that generates a pulse at the zero-crossing point of the output voltage of the AC power supply 5, and includes a voltage dividing resistor 8.
It is connected to the AC power supply 5 via. The output pulse of this zero cross point detector 11 is shown in FIG. 3(b).

A rectifier diode 13, a resistor 14, and a constant voltage diode 6 whose anode is grounded are connected in series to the non-grounded terminal of the AC power supply 5, and a predetermined voltage is connected to the output terminal 14-1 of the resistor 14. DC voltage saving. is now appearing.

A negative characteristic thermistor 3 for detecting the temperature of the liquid and a resistor 15 are connected in series between the terminal 4-1 of the resistor 14 and the ground, while a variable resistor 16 for setting the reference temperature is connected in series.
, ], 7, and 18 and a resistor 19 are connected in series.

20, 21, and 22 are comparators for water temperature determination using operational amplifiers. Each comparator 20°21.22
The positive input terminals of are connected to a connection point T0 between the variable resistor 18 and the resistor 19, a connection point T2 between the variable resistors 17 and 18, and a connection point T2 between the variable resistors 16 and 17 so as to receive the reference temperature signal, respectively.
The negative input terminals of these comparators are commonly connected to the connection point T3 between the thermistor 3 and the resistor 15. is connected to.

25 is a binary counter with four output terminals, 26 and 27 are two-person gates, 28, 29° and 30
is a three-man power gate, and 37 is a three-man power or gate. Binary counter 25 and these games 1-26.27
, 28, 29, 30.37 are the zero cross point detector 1
1 and the thermistor 3 and comparator 2
Based on the water temperature determination signal from 0, 21, and 22, a pulse for controlling the firing angle of the trier (3) 10 is generated.

The binary counter 25 receives the pulse train from the zero cross point detector 11 at the clock terminal CL, and outputs the pulse train from the zero cross point detector 11 to the output terminals A and B.
, C, D, the frequency of the pulse train is '/2, respectively.
, 1/4, 1/s, and '/16. Examples of signals at output terminals A, B, and C are shown in FIGS. 3(f), (g), and (I).

The AND gate 26 is connected to receive the pulse train from the zero cross point detector 11 and the pulse train from the output terminal A of the binary counter 25.

And the above AND gate 27 is ant game 1.26.
It is connected to receive the output of the binary counter 25 and the pulse train from the output terminal C of the binary counter 25.

The AND gate 28 is connected to receive the pulse train from the zero cross point detector 11, the output from the comparator 20, and an empty cooking determination signal from the comparator 40, which will be described in detail later. This AND gate 28 outputs a pulse train similar to the pulse train in FIG. 3(C).

”-Note and game-1 and 29 are “-Note and game-1-2”
6(4), the output signal from the above-mentioned comparator 40, and the output from the above-mentioned comparator 21 are connected to be received via inverters 31 and 32.

A resistor 34 having a predetermined resistance value RB is connected between the connection point 33 between the inverters 31 and 32 and the output terminal 14-1 of the resistor 14, and one electrode is connected to the resistor 34. A capacitor 35 having a capacitance CB grounded is connected to form a delay circuit 36.

From the AND gate 29 having the above-mentioned configuration, as shown in FIG.
A pulse train similar to the H/L/S train is sent out.

The AND gate 30 is connected to receive the output of the AND gate 27, the output of the comparator 22, and the output from the two comparators 40. This AND gate 30 sends out a pulse train similar to the pulse train shown in FIG. 3(e).

"2 or gate 37 is the above AND gate 28.29
, and 30 to receive the output signals therefrom. The output terminal of this OR game 1-37 is the current amplifier 38
The output terminal of the current amplifier 38 is connected to the gate 1-G of the l-liquid 10 via a key vacsitor 39 for generating an ignition pulse.

Reference numeral 40 denotes a comparator using, for example, an operational amplifier, for determining if the cooking is empty. The positive input terminal of this ratio voltage converter 40 is -1-
A variable resistor 41 for setting the dry cooking reference temperature is connected in series with the terminal 14-1 on the output side of the resistor 14, and a resistor 42 whose one end is grounded is connected to which connection point 11'14.
The negative input terminal of the comparator 40 is connected to the terminal 14-1 of the resistor 14.
It is connected to a connection point T5 between a negative characteristic thermistor 4 for dry cooking detection connected in series with a resistor 7 whose one end is grounded.

The operation of the electric water heater having the above configuration will be explained below.

By adjusting the resistance values of the variable resistors 16, 17 and 1.8, the reference temperature for the comparator 20 is set to 90C, the reference temperature for the comparator 21 is set to 95C, and the reference temperature for the comparator 22 is set to [C].
It is assumed that the reference temperature is set to 97C.

As shown in FIG. 3(b), the zero ps point detector 11 outputs a pulse with a predetermined pulse width when the output voltage of the AC power source 5 becomes zero, using a known method. Further, a predetermined DC voltage is applied from the AC power supply 5 to the terminal 14-1 on the output side of the resistor 14 via the diode 13, the resistor 14, and the voltage regulator diode 6. appears.

In this case, a thermistor 3 that detects the water temperature in the container 1 is used.
The connection point t represents the detected temperature tx.

The voltage vX of is lower than the voltage v1 of the connection point T1 representing the first reference temperature ta=90tl; vX<v, <■2
It is v3. Here, ■2 is the second reference temperature Ib =
95 C table h+t'1ffiR point 'T'2ON pressure, v
3 is a connection point T3 representing the third reference temperature tc=97t:'
voltage. It is assumed that a large amount of water is stored in the container 1 and the container 1 is not in an empty state.

Comparator 20 receives voltage v1 at its positive input terminal and voltage Vx at its negative input terminal. When the water temperature is 90C or less, as mentioned above, VX<vl, and therefore the comparator 2
0 outputs 1". Also, (7) comparators 21 and 22 similarly output "1".Furthermore, the comparator 40 connects the connection point T4 to the positive input terminal.
It receives the voltage 4 from the negative input terminal T, and receives the voltage vX' from the negative input terminal T. Since there is no dry cooking state, the voltage vX' at the connection point T, which represents the temperature tx' detected by the thermistor 4, is lower than the voltage v4 at the connection point T, which represents the reference temperature td for determining dry cooking. It is v4. Therefore, the comparator 40 outputs 1''.

On the other hand, the Antogame I 28 receives the pulse train from the zero cross point detector 11, the signal "111" from the comparator 20, and the signal "1" from the comparator 40, and receives the signal "1" from the comparator 40 as shown in FIG. As shown in FIG. 3, a pulse train synchronized with each zero-crossing point of the AC power supply 5, which is the same as the output from the zero-crossing point detector 11, is output.This pulse train is applied to the current amplifier 38 via the OR gate 37. The amplified pulse train is applied to the gate electrode G of the triac 10 via the capacitor 39.

Therefore, the triac 10 is turned on for all of the AC (8) waves at the timing of each zero cross point of the AC wave as shown in FIG. The entire power of the AC power source 5 is supplied to the heater 2.
generates heat at the maximum rating of approximately 600W. In this way, Yong? J? Water in Jl is heated to maximum 60 by heater 2.
Heated at 0W.

The binary counter 25 receives a pulse train synchronized with the zero-crossing point of the output voltage of the AC power supply 5 from the zero-crossing point detector 11, and outputs the signals from the output terminals A and C in FIGS. 3(f) and (), respectively. As shown in h), a pulse train with the frequency & of the zero-cross pulse divided by /2 and 1/8 is output.

On the other hand, the output signal ``1''' of the comparator 21 is
1, the capacitor 35 is inverted to °°0.
is not charged, and the output terminal of the inverter 31 and the capacitor/
The voltage at the connection point 33 with the terminal 35 is 0'°. This voltage ``0''' is inverted to 1'' via an inverter 32. In this way, at the same time that the comparator 21 outputs 1'', the signal It
I I+ is applied to one input terminal of AND gate 29 .

The AND gate 29 receives the signals from the comparator 2I, the inverter 81.32, and the AND gate 26.
The output pulse train of the zero cross point detector 11 shown in FIG. 3(1)) and the pulse train to the output terminal of the binary counter 25 shown in FIG. 3(f) are logically determined. In response to the pulse train shown in FIG. 3 and the signal +111+ from the comparator 40, a pulse train similar to the pulse train shown in FIG. 3(d) is sent out.

Also, from And Gate 30, Ant Game 1 and 27,
In addition to receiving the pulse train shown in FIG. 3(e) logically determined by the output of the AND gate 26 and the pulse train of the output terminal C of the binary counter 25,
'' and 1'' from the comparator 40. Therefore, this AND gate 30 sends out a pulse train similar to the pulse train in FIG. 3(e).

Now, in a double row, the water in container 1 is being heated to heater 2.
Assume that the water is heated at about 600 W, the water temperature rises, and the voltage vX indicating the temperature tx detected by the thermistor 3 exceeds the voltage V1 indicating the first reference temperature ta=900.

Voltage applied to the positive and negative input terminals of the comparator 20■1.
Vx becomes vx>■1, so the output of the comparator 20 changes from N1'' to 0°'C).

The output of the AND gate 28 is set to 0 by the "0" from the comparator 20, thereby blocking the passage of the pulse train shown in FIG. 8(C). , the pulse trains shown in FIGS. 3(d) and (e) are passed.

As a result, the OR gate 37 sends out a pulse train similar to the pulse train in FIG.
In the same way as in the case of , the current amplifier 38 and the capacitor 39
is applied to the gate electrode G of the triac 10 via. Therefore, the triac 10 is turned on every positive half cycle of the AC wave (and is turned on only during every positive half cycle) at the timing of the pulse train shown in FIG. Electric power equivalent to the positive half wave of the above-mentioned summer is supplied, and this electric power is about 300 W, which is half of that in the case of summer described above.

(11) In this way, when the water temperature in the container 1 reaches 90fC, which is close to the boiling point of 100°C, the power supplied from the AC power supply 5 to the heater 2 is automatically changed to the power in the water boiling state in case 1 above. Reduce by half.

Now, assume that the water temperature in the container 1 exceeds 95 U as described above. Note that, as described above, it is assumed that there is no dry cooking and the output of the comparator 40 is "1".

The voltage V2 applied to the positive and negative input terminals of the comparator 21,
Vx Ili, vx>v2, yacht, comparator 2
The output of 1 switches from N1'' to 0''.

Note that the output of the comparator 20 is "0" as in the case of "double series".
′.

When the output of the comparator 21 switches from °1''' to 0', this signal "N0" is inverted by the inverter 31, and is therefore connected to the capacitor 35 from the terminal 14-1 of the resistor 14 via the resistor 34. A current flows and the capacitor 35 is charged.The voltage of the capacitor 35 increases over a period of time τ corresponding to a time constant τ determined by the resistance value RB of the resistor 34 and the capacitance value cB of the capacitor 35.
After the elapse of CB-T during B, the predetermined... level 1
In this way, from the time when the output of the comparator 21 switches from "1" to "0", the connection point 33 is at the low level, L/ff o
Therefore, the output of the inverter 32 is "1".
The heater 2 is maintained at a double H state, and about 300 W of power is supplied to the heater 2 to maintain a medium flame state.

As mentioned above, the delay circuit 36 maintains the medium flame state with a delay time τB, so during this period the water
It reaches 0C and boils for a predetermined time.

Therefore, water can be reliably sterilized, deodorized, etc.

As mentioned above, the delay time τB has elapsed since the water temperature in the container 1 reached 95C, and the charging voltage of the capacitor 35,
Therefore, the voltage at the connection point 33 is at a predetermined high level,
When it rises to +111+, it is inverted through impark 32, and this inverted signal +101+ is applied to one input terminal of AND gate 29. Therefore, the output of the AND gate 29 becomes "0". If the water temperature exceeds 97C after the old record time τ□, V
Since x>"s, the output of the comparator 22 becomes 0", and the output of the ORG-1.

■ By stopping the power supply to the heat retention operation heater 2, the water temperature naturally drops,
When the temperature becomes 97C or less, the comparator 22 outputs 1'' as in the above-mentioned case (2), and therefore, the AND gate 30 sends out a pulse train similar to the pulse train in FIG. 3(e). .

As a result, the OR gate 37 receives "0'' and 0" from the AND gates 28 and 29, respectively, and also receives the pulse train shown in FIG. 3(C) from the AND gate 30. A pulse train similar to the pulse train in FIG. 3(C) is sent out.

This pulse train is applied to the gate electrode G of the triac 10 via a current amplifier 38 and a canister 39. Therefore, in the same manner as described above, the triac 10 turns and turns for a period corresponding to the positive half wave of two consecutive cycles of the AC wave at the timing of the pulse train shown in FIG. 3(e).
The heater 2 is turned on and then turned off for a period corresponding to two consecutive cycles, so that the heater 2 generates heat with a power of 150 W, which is approximately 1/4 of the total power in case 1. In this way, the water temperature in container 1 is 9
When the water temperature reaches 5C, after the -J double delay time τ8 has elapsed, the water temperature is automatically set to 97C and the heater 2 is set to 150C.
The hot water is kept warm at 97C by turning it on and off with W.

Note that when the amount of water in the container 1 is very small and the water is boiled, and the temperature of the container 1 rises abnormally and the resistance value of the thermistor 4 becomes small, the connection point T, which represents the detected temperature tx' of the container 1, The voltage vx' at the node T4 becomes larger than the voltage 4 representing the reference temperature td at the connection point T4. At this time, the output of the comparator 40 becomes “0゛°.This signal I
IOI+ is applied to the AND gates 28, 29.80, so the outputs of these AND gates 28, 29.80 are all (15) HOI+, and the output of the OR gate 37 is 0'', which is the triac 10. The ignition pulse is not applied, the triac 10 is cut off, and the power supply from the AC power source 5 to the heater 2 is stopped.In this way, the temperature of the container 1 rises abnormally due to the dry cooking state. Then, power supply to the heater 2 is automatically stopped, and empty cooking can be reliably prevented.

As explained above, according to the present invention, when the temperature of the water in the container rises to a predetermined reference temperature for switching to the heat retention state, an electric power of a magnitude between the heating power and the heat retention power is applied for a predetermined period. Since the heater is heated by the heater, the water in the container can be boiled for the desired time without spilling water, and the water can be sterilized, deodorized, etc. reliably, which is an excellent advantage.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an outline of the configuration of an electric water heater according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of a specific electric circuit in the water heater of FIG. 1, and FIG. 3(a) 7(h) are graphs showing the output signals of each component, with the time axes aligned, for explaining the operation (16) of the electric circuit shown in FIG. 2. 1... Container, 2... Heater for boiling water, 3.
...Negative characteristic thermistor for liquid temperature detection, 4...Negative characteristic thermistor for dry cooking detection, 5...AC power supply, 1
0... Triac, 1.11... Zero cross point detector/device, 16.17, 18.41... Variable resistor for reference temperature setting, 20, 21.22... Comparator,
25...Binary counter, 26, 27, 28, 29
．． 8.0...AND gate, 36...Delay circuit, 37...OR gate, 38...Current amplifier. Patent applicant Zojirushi Mahobin Co., Ltd. Representative Patent Attorney Sanzan Bogai 2 people

Claims (1)

[Claims] (1) In an electric water heater in which the heater power is switched from heating power to warming power when the water temperature in the container reaches a predetermined reference temperature, the heater power is switched from heating power to heat retention power when the water temperature in the container reaches a predetermined reference temperature for a predetermined period of time, An electric water heater characterized by being equipped with a circuit that heats a heater with a power that is intermediate in magnitude between heating power and heat retention power.