JPS5937138Y2 - electric water heater - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to an electric water heater.

Conventionally known electric water heaters have a heating element for heating water and an automatic temperature controller placed at the bottom of the water heater, and water is boiled by energizing the heating element for heating water, and the temperature sensing operation of the automatic temperature controller The system is configured so that when the water boils, the electricity to the heating element for boiling the water is automatically stopped.

The operating temperature of the automatic temperature controller in this type of electric water heater is set at a temperature slightly lower than the boiling temperature, taking into consideration that there may be slight variations in the set temperature. This is to ensure that it works.

In addition, the higher the altitude in the area where it is used, the lower the boiling point, so in order for automatic thermostats to operate reliably even in such areas, the operating point must be set much lower than the boiling point in flatlands. There is.

For this reason, it is not possible to obtain boiling water with conventional electric water heaters, and the water heated with these electric water heaters is not suitable for making milk for infants, and also makes the tea taste bad when used for tea. etc., it was impossible to boil water suitable for drinking.

In view of this point, the present invention is designed to automatically obtain a constant boiling time regardless of changes in boiling point due to differences in altitude, etc.

An example of this will be described below with reference to the drawings.

Reference numeral 1 denotes a heating element for boiling water provided at the bottom of a water boiling container (not shown), and is connected to a heater power source 3 via a switch circuit 2.

A detector 4 detects the water temperature and outputs a signal according to the water temperature, and is composed of a temperature-sensitive resistance element 11 and a fixed resistor 12.

5 is a comparator whose inputs are the signal directly led from the detector 4 and the signal delayed for a certain period of time by the delay circuit 6, and the output signal from the comparator 5 causes the switch control circuit I to The relay 14 is operated via the transistor 13 to turn the switch circuit 2 ON-OFF, thereby controlling the supply of electricity to the heating element 1 for boiling water.

15 is a DC power supply for operating the above-mentioned circuit.

The present invention is constructed as described above, and its operation will be described next.

First, fill water in a water boiling container (not shown), and
When you turn on the power, it starts boiling water.

At this time, the output signal of the detector 4 increases until it reaches a boiling state, as shown by the curve 8 in FIG. 2, and when the boiling point is reached, the temperature of the water becomes constant, so the output also becomes constant.

The signal passing through the delay circuit 6 becomes like the curve 9 in Fig. 2,
It is opened for a certain period of time and changes in the same way as the detector output signal 8.

When these two signals are input to the comparator 5, its output becomes as shown by the curve 10 in FIG.

Therefore, the switch control circuit 7 is designed to operate in such a way that the switch circuit 2 is turned ON when electricity is started, and when the water boils and the output of the comparator 5 reaches O, the switch circuit 2 is turned OFF. .

Therefore, when electricity is started, the water temperature rises and eventually reaches a boiling state, but since the output of the comparator 5 is not O, continue boiling.

Eventually, when the delay time of the delay circuit 6 elapses, since the output signal of the detector 4 remains constant, the signal from the delay circuit 6 also becomes the same magnitude, and the signal from the comparator 5 becomes O.
The switch circuit 2 is turned off by the switch control circuit 7, and the power supply to the heating element 1 for boiling water is cut off, thereby completing the boiling of water.

The present invention does not control energization based on the water temperature itself as described above, but takes advantage of the fact that the water temperature remains constant during boiling, and uses the water temperature detection signal and its delayed signal to compare the water temperature detection signal and its delayed signal. The power supply to the heating element is controlled.

Therefore, even if the boiling point changes due to water flow or altitude, if boiling is always achieved for a certain period of time, continuous boiling will no longer occur.

In addition, as mentioned above, in this invention, it is not necessary to know the absolute value of the water temperature, so the sensor for detecting the water temperature does not need to be accurate with respect to temperature, and variation is not a problem.
Another feature is that the sensor does not need to be expensive.

As described above, the present invention provides an electric water heater that can always boil water completely for a certain period of time, so the water heated with this water heater is suitable for making milk for infants, and it does not make the taste of tea bad. The water is suitable for drinking.

In addition, since the sensor for detecting the water temperature does not require a highly accurate one, the electric water heater becomes a useful electric water heater that has the effect of being inexpensive.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a circuit diagram thereof, and FIG. 2 is a diagram showing output signals of various parts. 1... Heating element for water boiler, 2... Switch circuit, 4...
- Detector, 5... Comparator, 6... Delay circuit.

Claims (1)

[Scope of utility model registration request] A heating element for a water heater connected to the power supply via a switch circuit,
A detector that outputs a signal corresponding to the temperature of the water heated by this heating element, a fixed time delay circuit for the signal from this detector, and a comparator that compares the signal from this delay circuit with the signal from the detector. An electric water heater characterized in that the switch circuit is controlled by the output signal of the comparator.