JPH01227019A - Detecting device of water level of electric water heater - Google Patents

Abstract

PURPOSE:To prevent the boilover of hot water or the strong release of steam, by a method wherein an ultrasonic vibration element is provided in the bottom part of a water indicator tube communicating with the bottom part of a vessel, and a level of water close to boiling is detected from an ultrasonic wave so as to control a heating element. CONSTITUTION:An ultrasonic vibration element 3 is provided in the bottom part of a water indicator tube 1 communicating with the bottom part of a vessel, and a water level is detected from a time required for an ultrasonic wave emitted from the element 3 to be reflected on a water surface and returned to the element 3 again. When a sharp rise of the level of water being heated and close to boiling is detected, a power of electrification of a heating element 11 is controlled through a water level detecting means 10. As the result, the boilover of hot water or the strong release of steam can be prevented in the case when the quantity of the hot water is nearly full. Thus, the danger is eliminated and safety can be improved economically.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a water level detection device for an electric water heater.

BACKGROUND OF THE INVENTION Conventional water level detection devices for electric water heaters are visually observed from the outside using a water level display tube made of a glass pipe or the like that communicates with the bottom of a bottomed cylindrical container and extends upward. The water level display tube was designed with a visual indicator.

Furthermore, in recent years, a method of measuring the water level using reflection of ultrasonic waves has been considered. In this method, an ultrasonic vibration element is provided at the bottom of a water indicator tube, and its radiation surface is exposed in the water. Ultrasonic waves emitted into the water propagate into the water, are totally reflected on the water surface, and return to the original vibrating element.

The time required for the ultrasonic waves to propagate and return is proportional to the water level because the propagation speed of the ultrasonic waves in water is approximately constant at about 1500 m/see. By measuring the time from when the ultrasonic waves are emitted until they return, the water level can be determined accurately.

In addition, conventional power control for electric water heaters involves energizing the heating element at the start of energization, and when the water in the container becomes hot water and boils, the temperature sensor installed in the lid of the main unit is rapidly heated by the release of steam. By the way, it was working, and the signal was used to stop the power supply to the heating element and control the completion of boiling the water.

Problems to be Solved by the Present Invention The conventional water level display tubes described above have the drawback that they are difficult to see unless in a bright place, and people often do not notice a drop in the water level. Although detection control is possible, another display element, such as a lamp, is required to display the water level to the user, and there are still problems in external confirmation. Furthermore, when using conventional energization control in devices that use ultrasonic vibration elements, the heating element is continuously energized until the temperature reaches 100°C, so when the temperature reaches about 98°C from 95°C, which is near boiling. The water level was rising and steam was being released violently, creating a risk of hot water splashing out if the water level was close to RRS.

Means for Solving the Problems The present invention has been made to solve the above problems, and includes a water quantity display tube communicating with the bottom of the container and extending upward;
An ultrasonic vibrating element is installed at the bottom of this water level display tube, and the water level is determined by the time it takes for the ultrasonic waves emitted from this ultrasonic vibrating element to propagate through the water in the water level display tube, reflect on the water surface, and return to the ultrasonic vibrating element again. The water level detecting means is provided with a water level detecting means for controlling the electric power applied to the heating element to be reduced when a change in the rise in the water level near boiling during heating of the water is detected.

Function With the above configuration, the water level display tube communicating with the bottom of the container and the ultrasonic vibration element provided at the bottom of the water level display tube make the water level visible and emit ultrasonic waves from the bottom. The ultrasonic waves propagate through the water, reflect on the water surface, form a propagation path, and function to receive the returned ultrasonic waves. In addition, the water level detection means detects the water level based on the time from the emission of the ultrasonic waves to the reception of the ultrasonic waves, and
When a change in the rise in the water level that is close to boiling is detected, it acts to reduce the power applied to the heating element.

Embodiment FIG. 1 is a block circuit diagram of an embodiment of the water level detection device for an electric water heater according to the present invention, FIG. It is a flow chart showing a program of the same device.

In the figure, 1 is a water display tube made of glass pipe, 2
3 is installed at the bottom of the water level display tube 1, and receives vibration input and emits ultrasonic waves toward the water surface 2, and receives reflected waves from the water surface 2 and outputs vibrations. A sound wave vibration element, 4 is an amplifier, 5 is an ultrasonic generator that generates an ultrasonic wave of about 2 Mtlz, 6 is a timing pulse generator that generates a pulse with a constant period, 7 is a receiver that converts the output of the amplifier 4 into a pulse. A waveform shaping section 8 is a pulse input section that combines the pulses of the waveform shaping section 7 and the pulses from the timing pulse generation section 6; 9 is a microcomputer that controls the heating element 11; It is composed of a computer 9. 11 is a heating element, which is in contact with a bottomed cylindrical container 12 that stores water.

The operation of this embodiment having the above configuration will be explained.

Ultrasonic waves generated by the ultrasonic generator 5 are input to the ultrasonic vibration element 3 via the amplifier 4, and the ultrasonic waves are radiated toward the water surface 2. The emitted ultrasonic waves propagate upward through the water inside the water indicator tube 1, are totally reflected when they reach the water surface 2, and return to the ultrasonic vibration element 3, which causes the ultrasonic vibration element 3 to vibrate and generate ultrasonic waves. Generate a sound wave signal. This returned ultrasonic signal is amplified by an amplifier 4 and converted into a pulse through a waveform shaping section 7. This pulse and the pulse from the timing pulse generator 6 are synthesized by the pulse input section 8, and the resulting value is input to the microcomputer 9.

This value has information on the time difference from when the ultrasonic wave is emitted by the ultrasonic vibrating element 3 until it returns, and if the water level 2 changes, the propagation time also changes proportionally, so the water level detecting means 10 Water level can be detected.

Furthermore, as shown in FIG. 2, when the water temperature exceeds 95° C., the water level suddenly rises, and the propagation time also increases rapidly, so it is possible to know from the water level that the water is close to boiling. 1
1 memorizes the water level at the initial stage of energization, and continuously energizes the heating element 11 to boil water. The water level is constantly detected by the water level detection means 10, and when the water level rises above the - chamber, the heating element 11 is turned on to 0N10FF at a predetermined energization rate. When the water level detecting means 10 detects that the boiling point has been reached, the power supply to the heating element 11 is completely stopped. Therefore, violent discharge of hot water and dissipation of steam due to the continuous wire can be prevented.

Effects of the Invention According to the present invention, an ultrasonic vibration element is provided at the bottom of the water volume display tube that communicates with the bottom of the container and extends upward, and the water level is detected by the ultrasonic waves emitted from the ultrasonic vibration element.
A water level detection means stage is provided that detects a rise in water level that is close to boiling and controls the power applied to the heating element, which prevents boiling over of hot water and strong release of steam when the measured amount is close to full. , has the effect of improving safety economically.

[Brief explanation of the drawing]

Fig. 1 is a block circuit diagram of a water level detection device for an electric water heater showing an embodiment of the present invention, Fig. 2 is a characteristic curve diagram of changes in water level with respect to changes in water temperature, and Fig. 3 is a flowchart showing its program. . DESCRIPTION OF SYMBOLS 1...Water level display tube, 2...Water surface, 3...Ultrasonic vibration element, IO...Water level detection means, 11...
Heating element, 12... container.

Claims (1)

[Claims] A bottomed cylindrical container (12) for storing water, and this container (
12) A heating element (11) that heats and boils the water in the container, and a water quantity display tube (1) that communicates with the bottom of the container (12) and extends upward.
An ultrasonic vibration element (3) is provided at the bottom of the water display tube (1), and the ultrasonic waves emitted from the ultrasonic vibration element (3) propagate through the water of the water display tube (1). Water surface (2)
The water level is detected based on the time it takes for the water to be reflected back to the ultrasonic vibrating element (3), and when a change in the rise in the water level that is close to boiling while the water is being heated is detected, power is applied to the heating element (11). A water level detection device for an electric water heater, characterized in that it is provided with a water level detection means (10) for controlling the water level so as to reduce the water level.