JPH02255114A - Electric water heater control device - Google Patents

Abstract

PURPOSE:To prevent an erroneous boiling detection at the time of heating hot water being kept at a somewhat lukewarm temperature by inhibiting a saturation detection until a timer means counts a first prescribed time, and inhibiting an inflection point detection until a second prescribed time. CONSTITUTION:By an energizing control means 18, the energizing of a heater 11 is started, and time counting by a timer means 19 is started. Subsequently, the time counted by the timer means 19 is checked, and a first prescribed time is awaited. When a first prescribed time comes, only an output of a saturation detecting means 16 is checked until a second prescribed time comes. As a result, when there is an output of the saturation detecting means 16, it is decided to be a temperature saturation caused by a fact that hot water in a container 6 reaches a boiling point and heating is stopped, and boiling is informed by a buzzer contained in the body and flickering of a light emission diode provided on the upper part of the body. On the other hand, when a second prescribed time comes, a rise rate of a temperature is stored in a storage means 17, and thereafter, both a saturation detection and an inflection point detection of a temperature rise are executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is characterized in that when water boils, the temperature rises -! The present invention relates to a control device for an electric water heater that detects boiling by utilizing a decrease in the i″l rate.

Conventional technology Conventionally, in devices that detect boiling, such as this type of electric water heater, systems that are caused by radiant heat from the heater to the temperature detection element that occurs immediately after heating starts, or mechanical strain that occurs around the temperature detection element have been detected. Some attempts to prevent erroneous boiling detection by distinguishing only from disturbances in boiling water.

Problems to be Solved by the Invention However, conventional boil detection methods mainly focus on heating water, reheating hot water that has been kept at a temperature close to the boiling point, or heating when water is added to hot water. However, in recent years, the need for WAI has increased in electric hot water/7J.
When reheating hot water that has been kept at a lukewarm temperature of o'b, there is a problem in that boiling is incorrectly detected.

That is, as shown in Fig. 3, fluctuation 1 of the temperature curve of the temperature detection element when heating from water, fluctuation 2 when heating with additional water, and fluctuation 3 when reheating high temperature hot water. Both occur immediately after the start of heating, but 80
When you heat water that has been kept at a lukewarm temperature of ℃,
As shown in Fig. 4, in addition to the fluctuation 4 immediately after the start of heating,
Since the obvious inflection point 6 occurs after a while, this change in temperature rise rate is mistakenly detected as the boiling point.

Incidentally, according to the inventors' research, the bending point 5 occurs as follows. In other words, the temperature of boiling water is 80℃
At this time, as shown in Figure 5a, the hot water that has lowered its temperature first accumulates on the bottom 7 of the container 6 and is separated from the upper layer 8 of the hot water. Creates a temperature difference. When heating is started in this state, convection continues for a while centered around the bottom 7 heated by the heater 9, as shown in FIG. 6, and eventually changes to convection from the bottom to the top. When convection occurs centered at the bottom, it is as if a small volume of hot water is being heated, and the temperature curve rises very steeply. Then, when the convection flows through the entire hot water, a bending point 5 occurs.

Here, if boiling detection is prohibited depending on the time from the start of heating until the bending point 5 occurs, erroneous boiling detection due to the bending point 5 will be eliminated, but if reheating is performed immediately after boiling, it will take a long time. This is a problem as steam continues to come out.

Therefore, an object of the present invention is to prevent erroneous boiling detection and correctly detect boiling even when heating hot water that has been kept at a slightly lukewarm temperature.

Means for Solving the Problems In order to achieve the above object, the present invention includes a timer means for measuring the time from the start of heating, and when the timer means measures the first predetermined time, saturation detection prohibited,
The structure is such that detection of bending 5'... is prohibited until a second predetermined time.

Function: With the above configuration, boiling can be detected correctly without being affected by the bending point caused by the temperature difference between the upper layer and the bottom layer in the container.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram of the main parts of this embodiment, showing a part of the main body 10 in cross section. In the figure, an annular heater 11
is in contact with the bottom of the container 6, and a temperature detection device 13 incorporating a thermistor 12 as a temperature detection element is pressed into contact with the container 6 in the medium heat section.

The rate of increase calculation means 14 calculates the rate of temperature increase from the temperature detected by the thermistor 12, and transmits the output to the bending point detection means 15 and the saturation detection means 16. The storage means 17 temporarily stores the output of the increase rate calculation means 14. Bend point detection means 1
6 compares the stored value of the storage means 17 and the output of the increase rate calculation means 14, and when the value falls below a predetermined ratio, it is determined that the increase rate has suddenly decreased, and the bending point of the temperature increase curve is determined. is detected and the output is transmitted to the energization control means 18. On the other hand, the saturation detection means 16 determines that the temperature rise is saturated when the rate of increase is less than a predetermined value, and outputs an output to the energization control means 1.
Tell 8. The timer means 19 is connected to the energization control means 18.
measures the elapsed time after the heater 11 starts heating, prohibits the saturation detection means 16 from detecting the saturation of the temperature rise until a first predetermined time, and prohibits the saturation detection means 16 from detecting the saturation of the temperature rise during a second predetermined time. The storage means 1 is prohibited from storing the output of the increase rate calculation means 14, thereby delaying the detection of the bending point.

Next, the operation will be explained. FIG. 2 is a flowchart showing the flow of processing, in which in step 20 the energization control means 1
Step 8 starts energizing the heater 11, and step 21
Then, the timer means 19 starts counting time. In step 22, the time counted by the timer means 19 is checked, and the process waits at the first predetermined time. When the first predetermined time has elapsed, the process proceeds to step 23, and at the second predetermined time, in step 24, only the output of the saturation detection means 16 is adjusted.
・ .

Bell. If there is an output from the saturation detection means 16, the container θ
It is determined that the temperature is saturated and the water inside the tank reaches the boiling point, and the process proceeds to step 24 to stop heating. Boiling is notified by flashing diodes. On the other hand, when the second predetermined time is reached in step 23, the temperature increase rate is stored in the storage means 17 in step 2, and then both the saturation detection and the inflection point detection of the temperature rise are performed in step 28 and 29.

In this embodiment, the first predetermined time is set to (1) 1 minute when hot water is heated to a temperature below the heat retention temperature, and (2) 12 seconds when hot water is heated to a temperature higher than the heat retention temperature. ing. The second predetermined time is still set to 1 minute.

As described above, according to this embodiment, even if water that has been brought to a boil and then cooled to a slightly lukewarm temperature is heated again, the bending point that occurs during heating is mistakenly determined to be the boiling point, and the heating is continued. never stops.

Effects of the Invention As is clear from the description of the above-mentioned embodiments, according to the present invention, detection of the bending point is prohibited until a predetermined time has elapsed from the start of heating. Even when water that has been cooled to lukewarm temperature is reheated, boiling can be detected correctly.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the main parts of an electric water heater according to an embodiment of the present invention, Fig. 2 is a flowchart of the same embodiment, Fig. 3 is a characteristic diagram explaining fluctuations in the initial stage of heating, and Fig. 4 is during heating. FIG. 6 is a diagram showing water temperature distribution and convection to explain the occurrence of bending points. 11... Heater, 12... Temperature detection element, 14... Temperature increase rate calculation means, 15...
... bending point detection means, 16 ... saturation detection means, 17 ... storage means, 18 ... energization control means, 19 ... timer means. Name of agent: Patent attorney Shigetaka Awano and one other person (α) <b)

Claims (1)

[Claims] A temperature detection element for detecting the temperature of water in a container heated by a heater, a rise rate calculation means for calculating the rise rate of the temperature detected by the temperature detection element, and an output of the rise rate calculation means for storing the output. and a bending point detecting means which compares the stored value of the storage means with the output of the increase rate calculation means and detects the bending point of the temperature increase curve when the value becomes equal to or less than a predetermined ratio; saturation detection means receives the output of the rate calculation means and detects that the temperature rise is saturated when the temperature rise rate becomes equal to or less than a predetermined value; It is equipped with an energization control means for stopping heating by the heater, and a timer means for measuring the elapsed time after starting heating by the heater, and this timer means controls the saturation detection means from the start of heating until a first predetermined time. A control device for an electric water heater, which is configured to prohibit the output and also prohibit the storage means from storing the output of the increase rate calculation means from the start of heating until a second predetermined time.