JPH0124496B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electric water heater such as a jar pot for boiling water and keeping it warm in general households.

Conventional technology In conventional electric water heaters of this type, the third
As shown in FIG. 4, a cylindrical container 1 with a bottom,
A heating element 2 that heats the water contained in this container 1
a first thermostat 3 attached to the bottom of the container 1 and connected in series with the heating element 2; and a first thermostat 3 attached near the heating element 2 and connected in series with the first thermostat 3. A second thermostat 4 connected to the container 1, an outer case 5 that covers the outer periphery of the container 1, and a lid 6 that covers the upper opening of the outer case 5. controls the temperature of the water with the first thermostat 3, while when there is no water in the container 1, the heating element 2
A second thermostat 4 mounted near the
It was common for the heating element 2 to stop being energized when the temperature reached a high temperature. However, with this configuration, in order to detect that there is no water in the container 1, it is necessary to energize the heating element 2 to reach a temperature at which the second thermostat 4 operates. Moreover, the second thermostat 4 is normally set at an operating temperature that does not operate when water is present, and the temperature is quite high.

Problems to be Solved by the Invention However, with such a conventional configuration, even if a user mistakenly turns on electricity without filling the container 1 with water, it takes time to detect that there is no water. However, there were problems in that various parts became high temperature, causing the container 1 to change color, and components of the heating element 2, etc., to be highly heat resistant.

The present invention solves these problems,
It is an object of the present invention to provide an electric water heater that can detect the presence or absence of water in a container immediately after the heating element is energized or when the temperature is low.

Means for Solving the Problems In order to solve the above problems, the electric water heater of the present invention includes a bottomed cylindrical container, a heating element that heats the liquid contained in the container, and a heating element that heats the liquid contained in the container. a temperature sensor in contact with the temperature sensor; a time measuring means that is reset each time the temperature sensor rises per unit temperature;
The apparatus is constructed of a comparison means for comparing the time at the moment when the time measurement means is reset with a predetermined time, and an energization stopping means for stopping energization to the heating element based on the output of the comparison means.

Effect According to this configuration, immediately after the heating element is energized, the temperature rise time per unit temperature of the temperature detector is measured, and by utilizing the fact that the time is short when there is no liquid in the container, Since the presence or absence of liquid in the container can be detected, the presence or absence of liquid in the container can be detected immediately after the heating element is energized or when the temperature is low, without using a special water level detection device. , it is possible to provide a safe and easy-to-use electric water heater with a simple configuration.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a circuit diagram of an electric water heater according to an embodiment of the present invention, which is composed of a microcomputer 7 and peripheral circuits. The microcomputer 7 shown here has a CPU.ROM.
It is a so-called one-chip microcontroller, consisting of RAM, input/output ports, etc. Reference numeral 8 denotes a temperature detector that comes into contact with the container 1 shown in FIG. 3, and this temperature detector 8 is connected to an input port of the microcomputer 7 via an A/D converter 9. As a result, the temperature signal from the temperature detector 8 is converted into a binary code and read into the microcomputer 7. Reference numeral 10 denotes a start switch, and input is input to the microcomputer 7 to determine whether or not the start switch 10 has been pressed.

11 is an AC power supply, and this AC power supply 11 is connected to a third
A series circuit of a heating element 12 that heats a liquid contained in a bottomed cylindrical container 1 shown in the figure and a relay contact 13 is connected, and a signal from an output port of a microcomputer 7 is relayed via a transistor 14. The relay contact 13 is configured to be opened and closed by passing a current through the coil 15.

Next, the operation of the electric water heater configured as described above will be explained.

FIG. 2 shows a flowchart stored in the ROM in the microcomputer 7, and the steps of the program shown in this flowchart will be explained. First, in step 1, it is determined whether or not the start switch 10 has been pressed, and the sound continues until it is pressed.When it is determined that the start switch 10 has been pressed, the heating element 12 is energized in step 2, and the time To is measured in step 3. In step 4, the temperature detector 8 determines whether or not the temperature has increased by a unit temperature. If the temperature has not increased by a unit temperature, the process proceeds to step 5. In step 5, it is determined whether or not it is boiling. If not, step 2
Proceed to. Here, the determination that it is boiling is
Program it so that it is determined that it is boiling when the time To takes more than 1 minute. If it is determined in step 5 that the water is boiling, the process proceeds to step 6, where the electricity to the heating element 12 is stopped, and the process proceeds to step 1.
Further, if it is determined in step 4 that the temperature detector 8 has increased by the unit temperature, the time To is set to 1 in step 7.
Determine whether it is less than 1 second, and if time To is 1 second or more, reset time To to zero in step 8,
Proceed to step 5. If the time To is less than 1 second in step 7, the process proceeds to step 6, and the power supply to the heating element 12 is stopped.

Effects of the Invention As described above, according to the present invention, the temperature rise time per unit temperature of the temperature detector is measured immediately after the heating element is energized, and the time is short when there is no liquid in the container. It is possible to detect the presence or absence of liquid in a container by using this technology, so it is possible to detect the presence or absence of liquid in a container immediately after the heating element is energized or when the temperature is low, without using a special water level detection device. As a result, it is possible to provide a safe and easy-to-use electric water heater with a simple configuration.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an electric water heater showing an embodiment of the present invention, Fig. 2 is a flowchart showing an example of a program of the electric water heater, and Fig. 3 is a cross section of a part of a conventional electric water heater. The side view shown in FIG. 4 is an electric circuit diagram of the electric water heater. 1... Container, 7... Microcomputer, 8
... Temperature detector, 12 ... Heating element, 13 ... Relay contact, 14 ... Transistor, 15 ... Relay coil.

Claims (1)

[Claims] 1. A cylindrical container with a bottom, a heating element that heats the liquid contained in the container, a temperature sensor that comes into contact with the container, and a time that is reset each time the temperature sensor rises per unit temperature. An electric water boiler comprising: a measuring means; a comparing means for comparing the time at the moment when the time measuring means is reset with a predetermined time; and an energization stopping means for stopping energization to the heating element based on the output of the comparing means. vessel.