JPH0779865A - Electric water heater - Google Patents

Abstract

(57) [Summary] [Purpose] In an electric water heater that heats and keeps the liquid warm, keeps the liquid in the container warm at a high temperature close to the boiling temperature. [Structure] A heating means 2 for heating a liquid in a container 1 and a heat retention means 3 for heating and keeping the temperature, an energization means 5 for controlling energization of the heating means 2 and the heat retention means 3, and a temperature detection for detecting the temperature in the container 1. The means 4 and the heating start means 6 for driving the heating means 2 when the temperature detecting means 4 detects a temperature lower than a predetermined temperature.
When the temperature rise gradient detected by the temperature detecting means 4 is equal to or lower than the first predetermined value and is equal to or higher than the predetermined temperature, the heating means 2
When the boiling detection means 7 for stopping the heating and the heating means 2 are stopped, the heat retention means 3 is driven until the temperature change amount detected by the temperature detection means 4 becomes equal to or less than the second predetermined value, and the temperature is preset from the temperature at this time. The temperature setting means 8 for determining the heat retention temperature by subtracting the determined temperature and the comparison means 9 for driving the heat retention means 3 so as to maintain the determined heat retention temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric water heater for heating and retaining the temperature of a liquid contained in a container.

[0002]

2. Description of the Related Art As shown in Japanese Patent Laid-Open No. 3-114421, there is an electric water heater which heats and keeps a liquid temperature controlled by using a temperature detecting means and a microcomputer.

The temperature control of the conventional electric water heater will be described below with reference to FIG.

Conventionally, in setting the heat retention temperature of the electric water heater, a temperature at which continuous boiling is not likely to occur is set in advance, and the heat retention control is performed so that this set temperature is reached.

This is because the liquid temperature detected by the temperature detecting means indirectly detects the temperature of the liquid through the container,
Further, since the heating means is configured so as to surround the temperature detecting means and the heat of the heating means is easily received, a difference occurs from the actual liquid temperature.

As shown in FIGS. 6 (a) and 6 (b), there is a difference in the tracking of the temperature detecting means at the time of boiling detection depending on the amount of water in the container. Therefore, when the liquid boils, the temperature detected by the temperature detecting means includes many variations. The reason is that the heat retention temperature cannot be determined based on the temperature at the time of boiling.

[0007]

However, it is not possible to reduce the difference between the temperature at the time of boiling and the heat retention temperature with such a conventional structure. That is, in order to keep the temperature at a constant temperature regardless of the boiling point, it is necessary to re-boil when hot water is desired by setting it to a lower value in advance in consideration of variations in boiling point. Also, it took a long time to boil, which was inconvenient.

The present invention is intended to solve the above problems, and firstly, to keep the temperature at a high temperature close to the temperature at the time of boiling.
The purpose of.

A second object is to keep the temperature high even when the temperature is already high when the power is turned on and the temperature can be kept immediately.

[0010]

In order to solve the above problems, the present invention provides a container for containing a liquid, a heating means for heating the liquid in the container, and a heat retaining means for heating and retaining the water in the container. An energizing means for controlling energization of the heating means and the heat retaining means, a temperature detecting means for detecting the temperature of the liquid in the container, and driving the heating means when the output of the temperature detecting means falls below a predetermined temperature. Boiling detection means for detecting a temperature rise gradient from the output of the heating start means and the temperature detection means, and stopping the heating means when the temperature rise gradient is equal to or lower than a first predetermined value and equal to or higher than the predetermined temperature; When the detecting means stops the heating means, the heat retaining means is driven, and when the temperature change amount becomes equal to or less than the second predetermined value by the output of the temperature detecting means, the heat retaining means is stopped,
The value of the temperature setting means is compared by comparing the value set by the temperature setting means and the output of the temperature detecting means with the temperature setting means for determining the heat retention temperature by subtracting a preset value from the temperature at this time. Is provided with a comparison means for driving the heat retention means.

Further, a control means is provided for driving the temperature setting means when the heating start means is not driven when the power is turned on.

[0012]

According to the present invention, in the above structure, if the temperature rising gradient disappears at a high temperature higher than the predetermined temperature while the heating means is being driven, it is considered as boiling and the driving is switched to the heat retaining means. When the drive is switched to the heat retention means, the temperature detection means does not receive the heat of the heater, and the temperature gradient becomes stable at a temperature slightly lower than the liquid temperature regardless of whether it is higher or lower than the liquid temperature at the time of boiling detection. When the temperature gradient disappears, the preset temperature can be obtained by subtracting a preset value from the temperature at this time.

Therefore, the heat retention temperature can be maintained at a high temperature close to the temperature at the time of boiling. Further, since the operation for setting the heat retention temperature is performed even when the heat retention temperature is not set when the power is turned on, it is possible to maintain the temperature at a high temperature close to the temperature at the time of boiling.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram of an electric water heater showing an embodiment of the present invention. In FIG. 1, 1 is a container for containing a liquid, 2 is a heating means for contacting the container 1 and heating the liquid in the container 1. Reference numeral 3 is a heat retaining means for contacting the container 1 to heat and retain the liquid in the container 1, 4 is temperature detecting means for contacting the container 1 to detect the temperature of the liquid in the container 1, and 5 is the heating means 2 And an energizing means for energizing the heat retaining means 3.

When the output of the temperature detecting means 4 detects a temperature lower than a predetermined temperature (about 92 ° C. in the present embodiment), 6 is a heating starting means for driving the heating means 2 by the energizing means 5, and 7 is the heating means. When the starting means 6 detects a temperature lower than a predetermined temperature, the amount of change in the temperature rising gradient is measured by the output of the temperature detecting means 4, and when considered as boiling, the boiling detecting means for stopping the heating means 2, 8 is the boiling When the detecting means 7 detects boiling, the heat retaining means 3 is driven until the temperature change amount of the temperature detecting means 4 disappears, and the temperature is kept at a value obtained by subtracting a preset value from the temperature when the temperature change amount disappears. A temperature setting means for determining the temperature, and 9 is a comparing means for comparing the temperature determined by the temperature setting means 8 with the output of the temperature detecting means 4 and controlling the heat retaining means 3 so as to reach the determined temperature. That.

Reference numeral 10 is a control means for driving the temperature setting means 8 to set a heat retention temperature when the temperature detecting means 4 determines that the temperature is above a predetermined temperature when the power is turned on.

Next, the temperature change from boiling to determining the set temperature will be described with reference to FIG. As shown in FIG. 2, the temperature rising gradient of the temperature detecting means 4 varies depending on the amount of water, but the gradient gradually decreases from the point where the water temperature reaches the boiling point. In this embodiment, 0.5 ° C./25 seconds is the first
When the temperature rise gradient becomes smaller than this, it is determined to be boiling. Then, after that, the heat retaining means 3 is driven. At this point, as shown in FIG. 2, the temperatures at the time of boiling detection with a small amount of water and a large amount of water are considerably different,
After that, the influence of the heat of the heating means 2 is eliminated, and the temperature of the temperature detecting means 4 approaches a value slightly lower than the water temperature. This is because the temperature detecting means 4 does not directly measure the water temperature but the temperature of the container 1.

The temperature detecting means 4 detects that the temperature change amount is the second
When it is detected that the temperature is less than a predetermined value (1 ° C./1 minute in this embodiment), the temperature is kept lower than the value set at that time (about 3 ° C. in this embodiment). To do.

FIG. 3 is a circuit diagram of an electric water heater showing an embodiment of the present invention. In FIG. 3, 11 is an AC power supply. The heating means 2 is composed of a first heating element that heats the liquid in the container, and the heat retaining means 3 is composed of a second heating element that has a smaller heating power than the heating means 2 and that heats and retains the liquid in the container 1. It The energizing means 5 includes relay contacts 5a and 5b connected in series with the heating elements of the heating means 2 and the heat retaining means 3 and the AC power supply 11, and the relay contacts 5a and 5b.
It is composed of relay coils 5c and 5d for controlling a and 5b, and a current is passed through the relay coils 5c and 5d to close the relay contacts 5a and 5b.

In the temperature detecting means 4, the temperature sensitive element 4a for converting the temperature into a resistance value, and the temperature sensitive element 4a and the resistor 4b generate a divided voltage value, which is converted into a binary code AD.
It is input to the converter 4c and the comparator 4d. The output of the comparator 4d is configured such that the output of the temperature sensitive element 4a is inverted at a predetermined temperature as a boundary. Further, the AD converter 4c is configured so as to be able to detect a range of about 70 to 120 ° C. in 0.5 ° C. increments, and it is possible to detect a temperature gradient or the like.

Reference numeral 12 realizes a control method of the heating start means 6, the boiling detection means 7, the temperature setting means 8, the comparison means 9 and the control means 10 by executing a program by a microcomputer.

FIG. 4 shows a flow chart of a program stored in the microcomputer 12 in the embodiment of the invention as set forth in claim 1, and the operation will be described by this.

In this embodiment, when the power is turned on, the temperature detecting means 4 determines whether the temperature is higher than a predetermined temperature and determines whether to boil or keep the temperature (step 2).
1). When the temperature is lower than the predetermined temperature, the heating means 2 is driven until boiling is detected with the above-mentioned temperature rising gradient (steps 22 and 23). When boiling is detected, the heating means 2 is stopped, and the heat retention means 3 is driven to detect whether the temperature rises or falls (steps 24 and 25). When there is no temperature change, the heat retaining means 3 is stopped, and the set temperature is subtracted from the detected temperature at this time to set the heat retaining temperature (step 26). After the heat retention temperature is set, if the value of the temperature detecting means 4 is higher than the set value, the heat retaining means 3 is stopped, and if the value of the temperature detecting means 4 is low, the heat retaining means 3 is driven ( Step 27
~ 29). Then, the process returns to step 21.

On the other hand, if the temperature is equal to or higher than the predetermined temperature in step 21, the process goes to step 27. Here, when the power is turned on and the set temperature has not been determined yet, the driving of the heat retaining means 3 is determined based on the predetermined temperature.

In any case, when the temperature is lower than the predetermined temperature (for example, when water is added while keeping the temperature at the set temperature), the heating means 2 is driven again to reset the set temperature thereafter. It is supposed to be set.

By doing so, the heat retaining temperature can be kept high with a simple structure. FIG. 5 shows the microcomputer 12 according to the second embodiment of the invention.
The flowchart of the program stored in FIG.

In the present embodiment, the same steps as those of the embodiment of the invention described in claim 1 are designated by the same reference numerals and the description thereof will be omitted. The difference from the embodiment of the invention described in claim 1 is that the temperature detecting means 4 is operated in step 30 when the power is turned on.
When the temperature is higher than the predetermined temperature due to the temperature detected by the above, the temperature maintaining means 3 is driven to proceed to step 32 for setting the temperature maintaining temperature. When the temperature is lower than the predetermined temperature, in step 30, the heating means 2 is driven to proceed to step 31 for detecting boiling.

With the above arrangement, the heat retention temperature can always be kept high.

[0030]

As is apparent from the above description, according to the invention of claim 1, since the heat retention temperature is set on the basis of the stable sensor temperature during boiling, there is no fear of continuous boiling and the temperature is close to the boiling point. It can be kept warm, and hot water can be used immediately, making it safe and easy to use.

According to the second aspect of the present invention, it is possible to set the heat retention temperature to be high even when the heat retention temperature is suddenly set when the heat retention temperature has not yet been set, such as when the power is turned on. , Can be more convenient.

[Brief description of drawings]

FIG. 1 is a block diagram of an electric water heater according to an embodiment of the present invention.

FIG. 2 is a temperature characteristic diagram of the electric water heater when the heat retention temperature is set.

FIG. 3 is a circuit diagram of the electric water heater

FIG. 4 is a flowchart showing a process in the embodiment of the invention of claim 1 of the electric water heater.

FIG. 5 is a flowchart showing a process in the embodiment of the invention according to claim 2 of the electric water heater.

FIG. 6 (a) is a temperature characteristic diagram during heating of the electric water heater with a small amount of water, and (b) is a temperature characteristic diagram during heating of the electric water heater with a large amount of water.

[Explanation of symbols]

 1 Container 2 Heating Means 3 Insulating Means 4 Temperature Detecting Means 5 Energizing Means 6 Heating Starting Means 7 Boiling Detecting Means 8 Temperature Setting Means 9 Comparing Means 10 Control Means

Claims (2)

[Claims] 1. A container for containing a liquid, a heating means for heating the liquid in the container, a heat retaining means for heating and retaining water in the container, and an energization for controlling energization of the heating means and the heat retaining means. Means, temperature detecting means for detecting the temperature of the liquid in the container, heating starting means for driving the heating means when the output of the temperature detecting means falls below a predetermined temperature, and a temperature rise gradient from the output of the temperature detecting means. When the temperature rise gradient is equal to or lower than a first predetermined value and is equal to or higher than the predetermined temperature, the boiling detection unit that stops the heating unit, and the heat retention unit when the boiling detection unit stops the heating unit. When the temperature change amount is driven and the temperature change amount becomes equal to or less than the second predetermined value by the output of the temperature detection means, the heat retention means is stopped, and the heat retention temperature is determined by subtracting a preset value from the temperature at this time. An electric water heater equipped with a temperature setting means and a comparing means for comparing the value set by the temperature setting means with the output of the temperature detecting means and driving the heat retaining means while the value of the temperature setting means is higher. . 2. The electric water heater according to claim 1, further comprising control means for driving the temperature setting means when the heating start means is not driven when the power is turned on.