JPH0153055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electric water heater that heats water to produce hot water.

Conventional Structure and Problems Conventionally, in this type of electric water heater, a container for storing water is made of a material such as stainless steel, a heater is wrapped around the lower side of the container, and the water in the container is heated. A temperature regulator was attached to the bottom of the container, and the temperature regulator and the heater were connected in series.
Furthermore, the operating temperature of the temperature controller is set at 93 to 98°C, requiring a highly accurate one, making it expensive. Moreover, even if such a temperature controller is used, the water will not reach the boiling point, the sterilization of the water will be insufficient, and the scale, etc. in the tap water will not be completely removed, making it impossible to make delicious tea or coffee. Ta.

In addition, because electric jar pots use synthetic resin parts such as polypropylene on the upper part,
If the boiling state is allowed to continue, the steam will accelerate the deterioration of the synthetic resin parts, causing cracks to appear in a short period of time.

OBJECTS OF THE INVENTION The present invention takes into consideration the above-mentioned conventional drawbacks and provides an electric water heater that can ensure that the water in the container reaches the boiling point and can suppress deterioration of the synthetic resin parts.

Structure of the Invention In order to achieve the above object, the electric water heater of the present invention includes a heater 1 that directly or indirectly heats water, and a temperature of this water that is directly or indirectly detected, as shown in FIG. a temperature sensor 2; a first temperature detection means 3 that detects a first temperature of the temperature sensor 2 and outputs a signal; and the temperature sensor 2.
A second temperature detection means 4 detects a second temperature higher than the first temperature of the temperature and outputs a signal, and an addition time measurement is started based on a signal from the first temperature detection means 3, and the second temperature detection means 4 outputs a signal. A clock means 5 performs subtraction time counting based on a signal from the means 4, and outputs a signal when a predetermined value is reached, and the heater 1 is continuously energized until a signal is output from the second temperature detecting means 4, and then from the clock means 5. The heater 1 is configured to have an energization rate control means 6 which energizes the heater 1 intermittently until a signal is output, and stops energizing the heater 1 when a signal is output from the timer 5.

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

As shown in Figure 2, 7 is a DC power supply that drives the following electronic components, and 8 is a thermistor with negative characteristics attached to the bottom of the container to indirectly detect the water temperature. 9 is connected in series with the DC power supply 7, and outputs a corresponding voltage V _I.
Reference numeral 10 denotes a comparator, which together with resistors 11 and 12 constitutes the first temperature detection means 3, in which the output is turned ON when the water temperature exceeds 80°C. The comparator 10 used in this embodiment has an open collector output. 13 is a comparator, which together with resistors 14 and 15 constitutes the second temperature detection means 4, in which the water temperature is
The output turns ON when the temperature exceeds 90℃. 16 is a capacitor for a timer that charges and discharges, a resistor 17 is for charging and one end is connected to the output of the comparator 10, and a resistor 18 is for discharging, and when the comparator 13 is turned on, it is connected in parallel to the capacitor 16 by a transistor 19. It's becoming like that. This capacitor 1
The charging/discharging voltage V _C of No. 6 is input to the positive input of the comparator 20, and when it exceeds the voltage V _- divided between the resistors 21 and 22, the output is turned OFF. 23 is a capacitor, comparator 24 and resistors 25-2
9 and diodes 30 and 31, a triangular wave is generated across the capacitor 23. The voltage of this capacitor 23 is inputted to one side of a comparator 32, and the divided voltage of resistors 33 and 34 is inputted to the + side input. The output terminal of the comparator 32 is connected to the base of a transistor 35, and is also connected to +V _D of the DC power supply 7 via a resistor 36. 36 is a relay coil whose one end is connected to + of DC power supply 7.
V _D and the other end is connected to the collector of the transistor 35. When the transistor 35 is turned on, current flows through the relay coil 36, the contact connected in series to the heater 1 is closed, and the heater 1 is energized. It's summery. Furthermore, the output terminal of the comparator 13 is connected to the AND
The output of the comparator 20 is connected to the input of the circuit 38, and the output of the comparator 20 is connected to +V _D of the DC power supply 7 via a resistor 39, and further connected to the input of the AND circuit 38, and further connected to one side of the comparator 24 via an inverter 40 with an open collector output. connected to the input.
The output of the AND circuit 38 is connected to the base of a transistor 41 via a resistor, and the collector of the transistor 41 is connected to the base of the transistor 35.

The operation of the above configuration will be explained based on FIG. 3. When water is poured into a container and electricity is applied, the water temperature is low and the resistance value of thermistor 8 is large, so the outputs of comparators 10 and 13 are OFF, and since the voltage V _C is high, the output of comparator 20 is also OFF, and the inverter The output of the comparator 40 is turned ON, and the output of the comparator 32 is turned OFF. Further, since the comparator 13 is OFF, the output of the inverter 37 is LOW, the output of the AND circuit 38 is LOW, and the transistor 41 is turned OFF. Therefore, the transistor 35 turns on, and the relay coil 36
A current flows through the heater 1', and the heater 1' is energized. Then, when the water temperature reaches 80℃, the output of comparator 10 becomes
ON, the capacitor 16 is charged via the resistor 17, the voltage V _C decreases, and when it becomes lower than the voltage V _- , the output of the comparator 20 is turned ON, the output of the inverter 40 is turned OFF, and the voltage across both ends of the capacitor 23 is turned ON. A triangular wave is generated. Then, the output of the comparator 32 repeats ON-OFF at a constant cycle according to the divided voltage of the resistors 33 and 34.
In response, the transistor 35 repeats OFF and ON, and the heater 1 starts to be energized intermittently at a constant cycle. Furthermore, when the water temperature reaches 90℃, the output of the comparator 13 turns ON and the transistor 19 turns ON.
At the same time that the capacitor 16 starts discharging via the resistor 18, the output of the inverter 37 becomes +V _D.
When the voltage V _C exceeds the voltage V _- , the output of the comparator 20 turns OFF, and the two inputs of the AND circuit 38 become +V _D , so the output becomes +V _D , the transistor 41 turns on, and the transistor 35 turns OFF.
OFF, current no longer flows through the relay coil 36, and power supply to the heater 1 is stopped. In this way, the boiling point of water can be detected by determining the energization time T ₁ from 90° C. depending on the time T ₀ for the water temperature to reach 90° C. from 80° C., and then stopping the energization. The time T ₀ becomes longer when the amount of water is large or the room temperature is low.
The discharge starting voltage V _CO of the capacitor 16 becomes lower,
Since T ₁ becomes correspondingly longer, it becomes easier to detect the boiling point. In addition, since intermittent current is applied from about 85°C, the boiling state can be alleviated and deterioration of the synthetic resin parts, etc. above the electric jar pot can be suppressed. Also, since it can reduce the boiling state, when used on electric stoves, etc., it can prevent boiling over from the pot.

It should be noted that although discrete parts were used here, the structure can of course be easily constructed using an arithmetic element such as a microcomputer.

Structure of the Invention As is clear from the description of the embodiments above, according to the electric water heater of the present invention, even if the water volume, room temperature, etc. change, the energization time T ₁ can be automatically changed to energize. It is possible to reliably bring the water to the boiling point, to sufficiently sterilize the water, to remove limescale from the tap water, and to make delicious tea or coffee, which has great effects.

Furthermore, since the energization is switched to intermittent energization halfway through, the boiling state can be alleviated, and deterioration of synthetic resin parts, etc. above the electric jar pot can be suppressed, making the effect even greater.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a control circuit diagram of an embodiment of the present invention, and FIG. 3 is a diagram of its operating principle. 1... Heater, 2... Temperature sensor, 3... First temperature detection means, 4... Second temperature detection means,
5... Timing means, 6... Energization rate control means.

Claims (1)

[Claims] 1. A heater that directly or indirectly heats water, a temperature sensor that directly or indirectly detects water temperature, and a first temperature that detects a first temperature of this temperature sensor and issues a signal. a detection means; a second temperature detection means that detects a second temperature higher than the first temperature of the temperature sensor and outputs a signal; and starts addition time counting by the signal from the first temperature detection means; A timer that performs subtraction timekeeping based on a signal from a second temperature detector and outputs a signal when a predetermined value is reached; and a timer that continuously energizes the heater until a signal is output from the second temperature detector, and then a signal is output from the timer. An electric water heater comprising an energization rate control means that energizes the heater intermittently until the heater is turned off, and stops energization of the heater when a signal is output from the timer.