JPH02255115A - Controller for electric water heater - Google Patents

Abstract

PURPOSE:To improve the accuracy for boiling detection irrespective of whether the water quantity is large or small by detecting the water quantity by dividing it into N stages, when heating is started, and executing the boiling detection, when the time required to rise the temperature upto the prescribed temperature range is longer than a set comparison value, and also, higher than a prescribed temperature. CONSTITUTION:A heating means 5 controls a heating element 6 by the output of a control means 4, and a time counting means 7 executes count-clear by a signal from the control means 4. A water quantity detecting means 9 detects the quantity of a liquid in a container by detecting a water level of N stages in a water level tube 16 connected to a container 15 by the upper part and the lower part, and transmits its output to a setting means 10. By such an output, the setting means 10 selects a comparison value conforming to its water quantity in a water quantity section of N stages, and outputs its value to the control means 4. The control means 4 compares this comparison value and a value of the time counting means 7, when a temperature rise detecting means 3 detects a fact that a temperature rises by prescribed temperature width, and when it is detected that the value of the time counting means 7 is large, and also, a temperature comparing means 2 detects a fact that a temperature is higher than a prescribed temperature, the heating means 5 is turned off and boiling is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for an electric water heater that heats and keeps a liquid contained in a container warm.

2. Prior Art A conventional electric water heater of this type is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-12
As in Publication No. 0816, boiling detection performed within a predetermined time after the start of heating and boiling detection performed below a predetermined temperature (warming temperature) are invalidated to prevent erroneous boiling detection. there were. In other words, the temperature rise is small for a while after the start of heating due to a delay in thermal response, and at this time there are warm and cold parts in the heated object, which may cause ripples in the temperature rise curve. Erroneous boiling detection that occurs during this period is invalidated, and if this occurs after a predetermined period of time has elapsed, the boiling detection is invalidated if the temperature at that time is below a predetermined temperature.

Problems that the invention aims to solveHowever, with this conventional structure, the worst problem is
, -7, it is possible to raise the temperature to above the heat retention temperature, but it is not possible to bring it to a boil reliably. For example, if a container filled with enough water is gradually cooled to the insulating temperature,
At this time, the hot water that has dropped in temperature first accumulates at the bottom of the container.
A temperature difference occurs in the upper layer of the hot water, and when reheating in such a state, convection continues for a while centered on the bottom heated by the heating element, and eventually changes to convection from the bottom to the upper layer. When convection occurs around the bottom, it is like heating a small volume of hot water, and the temperature curve rises very steeply, but when convection takes over the entire area, the temperature curve becomes gentler. , if a comparison value is made at a point where the temperature curve rises steeply, this value will be small and boiling will be detected when the convection changes over the whole.

Therefore, an object of the present invention is to improve the accuracy of boil detection regardless of the amount of water.

Means for Solving the Problems In order to solve the above problems, the electric water heater control device of the present invention, when heating starts, detects the amount of water divided into N stages, and adjusts the amount of water 11k in N stages in advance. A comparison value is set, and if the time it takes for the temperature to rise within a predetermined temperature range is longer than the direct temperature, and the temperature is higher than the predetermined temperature, boiling is detected.

By having the above-described structure, the present invention can prevent heating from being stopped erroneously due to unstable factors at the start of heating, and can correctly detect boiling.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a Glock diagram showing an embodiment of the electric water heater of the present invention, in which 1 is a temperature detection element that detects the temperature inside the container;
The voltage output corresponding to the temperature is transmitted to the temperature comparison means 2 and the temperature rise detection means 3. The temperature comparison means 2 compares the obtained output with a predetermined temperature (here, the heat retention temperature) and transmits the comparison result to the control means 4. Temperature detection means 3
is the predetermined temperature range (here, 0.
5 degrees) and transmits the output to the control means 4. Reference numeral 5 denotes a heating means, which controls a heating element 6 based on the output of the control means 4. Reference numeral 7 denotes a timer means for clearing the sicrant based on a signal from the control means 4. Reference numeral 9 denotes a water level detection means, which includes a water level pipe 16 connected to the container 16 at the upper and lower sides.
The amount of liquid in the container is detected by detecting the water level in the N stage, and the output is transmitted to the setting means 10. Based on this output, the setting means 10 selects a comparison value suitable for the water amount from among the N levels of water amount classifications, and outputs the comparison value to the control means 4. The control means 4 compares this comparison value with the value of the time measurement means 7 when the temperature rise detection means 3 detects that the temperature has increased by a predetermined range, and determines that the value of the time measurement means 7 is large;
When the temperature comparison means 2 detects that the temperature is higher than a predetermined temperature, it transmits an off signal to the heating means 5.

FIG. 2 is a circuit diagram showing a specific configuration of an embodiment of the present invention. The temperature sensing element 1 includes a thermistor 1a and a resistor 1.
When the temperature is low, the resistance value of the thermistor 1a is large, and when the temperature is high, the resistance is small. Output to. Reference numeral 11 designates an AC power supply for supplying current to the heating element 6, and reference numeral 12 designates a DC power supply for supplying voltage to the circuits of the temperature detection element 1, temperature comparison means 2, and 9. The temperature comparing means 2 includes a comparator 2a, a resistor 2b, and a resistor 2C.
The resistors 2b and 2c configure this partial voltage as a reference potential for the comparator 2a (a potential at which the temperature comparison means reaches a predetermined temperature to determine whether it is high or low), and the Sometimes, the output voltage of the temperature sensing element 1 is low, so the comparator 2a outputs L'', and when the temperature is higher than the predetermined temperature by υ, the output voltage of the temperature sensing element 1 is high, so the comparator 2a outputs H''. . The temperature rise detection means 3 is composed of an A/D converter, and the temperature detection element 1
The output is converted into a binary code and output. The heating means 6 includes a transistor 6a, a relay contact 5b, and a relay coil)
V6c, and when the transistor 5a is turned on, a current of 'IF7, -; flows through the relay coil 5C, closing the relay contact 5b and heating the heating element 6. The water amount detection means 9 is for discriminating the amount of liquid in the container into N stages (in this case, three stages), and electrodes 9a and 9b are installed at the top and bottom heights of the container, respectively. When the water level reaches a certain position between the electrodes, the connection between the electrodes outputs a H11 signal.Reheating means 13 is composed of a switch 13a and a resistor 13b, and when the switch 13a is pressed, an NHI+ signal is output. 14 is a microcomputer (hereinafter abbreviated as microcomputer) which constitutes the control means 4, time measurement means 7, and setting means 10, and is configured to realize these functions by executing a program. Next, the flow of the process will be explained based on FIGS. 3 and 4.

If the reheating means 13 is turned on during heat retention, and the temperature drops below the heat retention temperature, the microcomputer 14 turns on the heating means 5, clears the clock means 7, and sets the comparison value shown in FIG. Assuming that the amount of water is equally divided into three stages,
In step 30, the output of the water amount detection means 9 is input, and it is determined whether the water amount is more than μ of full water (step 31). If it is less than μ, time T1 is set as a comparison value in step 34.

If it is determined in step 31 that it is more than μ, it is determined in step 32 whether it is equal to or greater than % of full water, and if it is less than %, time T2 is directly set for comparison in step 35, and if it is equal to or greater than %, time T3 is compared. Set to value.

Note that the larger the amount of water, the longer it will take for the temperature to rise.
The relationship is as follows: T1 x T2 < T3.

In FIG. 3, when a comparison value for boiling detection is set, boiling detection processing is performed, which will be explained with reference to FIG. 4. In step 41, the temperature rise detection means 3
In step 42, it is determined whether the temperature has risen within a predetermined temperature range (here, 0.6 degrees). If the temperature has not risen, the timer 7 counts the temperature in step 47. When an increase in the predetermined temperature range is detected in step 42, the value of the timer at that time is compared with the comparison value in step 43, and if the comparison value is larger, the timer is cleared in step 48 and the process starts again from the beginning. Count the time it takes for the temperature to rise within a predetermined range. If in step 43 the chain of the timer is larger, the output of the temperature comparison means 2 is input in step 44, if the temperature is below the predetermined temperature in step 45, the timer 7 is cleared in step 48, and in step 45 the temperature is higher than the predetermined temperature. If the temperature is , the heating means 5 is turned off and boiling is detected.

Effects of the Invention According to the present invention, in order to set the time period in which boiling is not detected when convection is transmitted throughout the entire body and a stable temperature curve is obtained, the stable temperature curve is Since boiling is not detected until the rise becomes more gradual, accurate boiling detection can be performed.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of an electric water heater according to an embodiment of the present invention, Figure 2 is a specific circuit diagram of the electric water heater, and Figure 3 is a comparison of the electric water heater at the start of heating. FIG. 4 is a flowchart showing the value setting process, and FIG. 4 is a flowchart showing the boiling detection process of the electric water heater. 1゜1...Temperature detection element, 2...Temperature comparison means, 3...Temperature rise detection means, 4...
- Control means, 5... Heating means, 6...
Heating element, 7...Timekeeping means, 9...Water amount detection means, 1o...Setting means. Name of agent: Patent attorney Shigetaka Awano and one other person Nη
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Claims (1)

[Claims] A temperature sensing element that comes into contact with a container containing a liquid and detects the temperature of the liquid, a temperature comparison means that compares the temperature sensing element with a predetermined temperature, and the temperature sensing element detects that the temperature increases by a predetermined range. a heating element for heating the liquid in the container; a heating means for controlling energization of the heating element; a water amount detection means for dividing the amount of water in the container into N stages; a setting means for setting comparison data for boiling detection by the means; a clock means for measuring the time for the temperature rise detection means to increase by a predetermined temperature range; and a time measurement means for measuring the time for the temperature rise detection means to increase by a predetermined range, and the temperature comparison means detects a temperature higher than a predetermined temperature, and An electric water heater comprising control means for detecting boiling and transmitting an off signal to the heating means if the value of the timer means is larger than the value of the setting means when the temperature rise detection means detects a rise in a predetermined temperature range. control device.