JP3012953B2 - Electric water heater - Google Patents

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 that keeps water warm in ordinary households.

[0002]

2. Description of the Related Art In recent years, an electric water heater that heats water by boiling water has been required to be able to boil a large amount of water at a time in a short time and keep the temperature.

A conventional electric water heater of this type will be described with reference to FIG. In FIG. 6, a bottomed cylindrical container 1 stores water, and the water stored in the container 1 is supplied to a first heating unit 2 and a second heating unit having a smaller heating power than the first heating unit 2. Heat with 3. The temperature detecting means 4 outputs the output of the temperature sensing element 4a attached to the outer bottom of the container 1 to A /
The temperature of the water contained in the container 1 is detected by performing A / D conversion by the D converter 4b. The temperature change rate calculation means 5 receives the output of the temperature detection means 4 as input and calculates the change rate of the temperature of the water contained in the container 1. The temperature change rate comparison means 6 receives the output of the temperature change rate calculation means 5 as an input, compares the temperature change rate of water with a predetermined temperature change rate, and the heating control means 7 receives the output of the temperature change rate comparison means 6 as an input. And the first
Of the heating means 2 and the second heating means 3 are controlled. In order to shorten the time for boiling water, the heating control means 7 simultaneously supplies electricity to the first heating means 2 and the second heating means 3 when the heating is started. In addition, the output of the temperature change rate comparing means 6 keeps energizing the heating means so long as the temperature change rate of the water is smaller than the predetermined temperature change rate so that the container is not heated while being empty. When the rate becomes larger than a predetermined rate of temperature change, the power supply to the first heating means 2 and the second heating means 3 is stopped.

FIG. 5 is a diagram showing the detected temperature of the thermistor 4a and the temperature at the bottom of the container 1, wherein the horizontal axis indicates the elapsed time from the start of heating, and the vertical axis indicates the temperature at that time. It is. When the first heating means 2 and the second heating means 3 are energized from the start of water heating, the temperature at the bottom of the container 1 starts to rise immediately, but the detected temperature of the thermistor 4a passes T1 from the start of energization. After that, the temperature at the bottom of the container 1 rises to K1 (usually a high temperature of 400 ° C. or more) even if the power supply to the heating means is stopped by the output of the temperature change rate comparing means.

[0005]

In such a conventional electric water heater, although the output of the temperature sensing element 4a has a delay in thermal response, it starts with a heating means having an increased electric power in order to shorten the water heating time. , The output of the temperature sensing element 4a rises, and the output of the temperature change rate comparing means 6 determines that the temperature change rate of the water is greater than the predetermined temperature change rate. Even if the power supply to the second heating means 3 is stopped, the power supplied so far is large, so that the temperature rise of the container 1 after the power supply is stopped becomes large, and the container and the temperature-sensitive element portion are deformed, There was a problem that the bottom was discolored.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problem. Even when heating is performed without water in the container 1, the temperature rise of the container 1 is reduced to reduce the thermal deformation of the container and the temperature-sensitive element. An object of the present invention is to provide an excellent electric water heater capable of suppressing discoloration.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides, as a first invention, a container for containing water;
A first heating unit for heating the water contained in the container, a second heating unit having a lower heating power than the first heating unit, and a first heating unit and a second heating unit. Heating control means for performing control; temperature detection means for detecting the temperature of water contained in the container; and temperature for calculating the rate of change of the temperature of water contained in the container based on the output of the temperature detection means. Change rate calculating means, temperature change rate comparing means for receiving the output of the temperature change rate calculating means as an input, and comparing the temperature change rate of the contained water with a predetermined temperature change rate, and a predetermined rate after starting the water heating. A heating means for counting time, wherein the heating control means energizes only the second heating means while a predetermined time has been measured from the start of boiling water by the timing means, and the temperature change of the water during that time. Rate is greater than the specified temperature change rate When the water temperature becomes lower, the power supply to the second heating means is stopped. If the temperature change rate of the water is smaller than the predetermined temperature change rate, the power supply to only the first heating means or the first heating means is performed after a predetermined time. And both the second heating means and the second heating means.

According to a second aspect of the present invention, there is provided a container for storing water, a first heating unit and a second heating unit for heating water contained in the container.
A heating control unit that controls the first heating unit and the second heating unit; a temperature detection unit that detects a temperature of the water contained in the container; Temperature change rate calculating means for calculating a change rate; temperature change rate comparing means for receiving the output of the temperature change rate calculating means as input and comparing the temperature change rate of water with a predetermined temperature change rate; A heating means for measuring a predetermined time after the start of heating, wherein the heating control means energizes the first heating means at a predetermined duty ratio while the predetermined time is measured from the start of water heating by the time measuring means. In the meantime, if the temperature change rate of the water becomes larger than the predetermined temperature change rate, the power supply to the first and second heating means is stopped, and if the temperature change rate of the water is smaller than the predetermined temperature change rate. After a predetermined time has elapsed, the first It is obtained by a structure for energizing the heat means and the second heating means.

[0009]

According to the first aspect of the present invention, since only the heating means having a small heating power is supplied for a predetermined time after the start of water heating, the water temperature changes after the temperature of the thermosensitive element starts to rise. Even if the power supply is stopped by detecting the rate, the temperature rise of the container can be kept low, and heating can be performed with the maximum power after the lapse of a predetermined time. Can be.

According to the second aspect of the present invention, the heating means having a large heating power is energized at a predetermined duty ratio for a predetermined time after the start of water heating. Even if the temperature change rate of the water is detected after the temperature of the temperature-sensitive element starts to rise and the energization is stopped, the rise in the temperature of the container can be suppressed to a low level. Can be prevented. In addition, since the heating is performed with the maximum power after a predetermined time has elapsed, the water heater can be completed in a short time.

[0011]

【Example】

(Embodiment 1) An embodiment of the first invention will be described below with reference to FIGS. The same components as those in the conventional example are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 1, the temperature change rate comparison means 6
A comparison is made between the predetermined temperature change rate when the heating means 3 is turned on and the temperature change rate calculated by the temperature change rate calculation means 5 from the output of the temperature detection means 4. The time keeping means 8 comprises the heating control means 7
Is a time measuring means for measuring a predetermined time from the start of water heating. The heating control means 7 controls the energization of the first heating means 2 and the second heating means 3 with the outputs of the temperature change rate comparing means 6 and the time keeping means 8 as inputs. In the first embodiment, the first heating means 2 is a main heater at the time of boiling water, the second heating means 3 is an auxiliary heater for keeping the heating power smaller than that of the main heater, and a thermistor is used as the temperature-sensitive element 4a. I'm using Further, the temperature change rate calculating means 5, the temperature change rate comparing means 6, the time keeping means 8 and the heating control means 7 are realized by a one-chip microcomputer.

In the above configuration, the operation of the first embodiment will be described with reference to FIG. 2. First, when water heating is started, energization of the second heating means 3 is started in step 101a and the process proceeds to step 102. . In step 102, the clocking by the clocking means 8 is started (can be reset), and the process proceeds to step 103. In step 103, the thermistor 4a
The A / D converter 4b converts the output from the A / D converter into an A / D converter, detects the temperature θ1 of the water contained in the container 1, and proceeds to step 104.
In step 104, a new output of the temperature detecting means 4 is input to calculate the temperature change rate Δθ1 and the routine proceeds to step 105. In step 105, the temperature change rate Δθ1 obtained in step 104 by the temperature change rate comparison means 6 is compared with a predetermined temperature change rate Δθ0 (0.5 degrees / second in the first embodiment) four times. And Δθ0 are determined, and if Δθ1 <Δθ0, the process proceeds to step 106, where Δ
If θ1 ≧ Δθ0, the process proceeds to step 107. In step 106, the elapsed time t1 from the start of energization to the second heating means 3 by the time measuring means 9 is measured.
Proceed to 08. In step 107, the heating is terminated by stopping the current supply to the first heating means 2 and the second heating means 3. In step 108, a comparison is made between the time t1 measured in step 106 and a predetermined time T0 in which only the second heating means is energized after the water heater is started.
If 1 <T0, that is, the elapsed time from the start of water heating is shorter than the predetermined time T0, the process returns to step 103 and the monitoring of the temperature change rate is repeated. If t1 ≧ T0, the process proceeds to step 109. In step 109, the first heating means 2 and the second heating means 3 are energized. In addition,
The heating means may include an electric heater or an induction heating wire loop.

FIG. 3 shows the thermistor 4 according to the first embodiment.
FIG. 3 is a diagram showing the detected temperature of a and the temperature at the bottom of the container 1, in which the horizontal axis represents the elapsed time from the start of heating and the vertical axis represents the temperature at that time. When there is no water, the temperature at the bottom of the container 1 starts increasing immediately after the start of heating, but the detected temperature of the thermistor 4a starts increasing after a lapse of T1 after the start of heating. Therefore, the temperature change rate Δθ1 of water obtained from the output of the temperature detection means 4 is compared with a predetermined temperature change rate Δθ0 to detect that there is no water in the container 1 and to start water heating T2 seconds after the start of water heating. When the power supply to the container 1 is stopped, the temperature at the bottom of the container 1 becomes K2 (250 in the embodiment).
° C), but the temperature rise is lower than the temperature rise K1 (for example, 400 ° C) in the conventional configuration.

As a result, during the period from the start of water heating to a predetermined time T1, heating is performed only by the second heating means 3, and the rate of temperature change at that time is detected, thereby energizing the first heating means 2. The temperature of the container 1 can be kept low even if there is no water in the container.

(Embodiment 2) An embodiment of the second invention will be described below with reference to the drawings. The same components as those in the conventional example are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 1 (because it is the same as that of the first embodiment), the temperature change rate comparing means 8 compares the temperature change rate obtained by the temperature change rate calculating means 5 from the output of the temperature detecting means 4 with a predetermined temperature. Compare with the change rate. The time measuring means 9 is a time measuring means for measuring a predetermined time from the start of water heating and the energization of the first heating means at a predetermined duty ratio. The heating control means 10 controls the energization of the first heating means 2 and the second heating means 3 with the outputs of the temperature change rate comparing means 8 and the time measuring means 9 as inputs. In the second embodiment, the first heating means 2 is a main heater when water is being boiled, the second heating means 3 is an auxiliary heater for keeping the heating power smaller than that of the main heater, and a thermistor is used as the temperature sensing element 4a. I'm using Further, the temperature change rate calculating means 5, the temperature change rate comparing means 6, the time keeping means 8 and the heating control means 7 are realized by a one-chip microcomputer.

In the above configuration, the operation of the second embodiment will be described with reference to FIG. 4. First, when water heating is started, a predetermined duty ratio (in the second embodiment, (は duty), the intermittent energization is started, and the routine proceeds to step 102. Step 1
At 02, the time counting by the time counting means 8 is started (can be reset), and the routine proceeds to step 103. In step 103, the output of the thermistor 4a is A / D converted by the A / D converter 4b, and the temperature θ1 of the water contained in the container 1 is detected.
Proceed to 4. In step 104, a new output of the temperature detecting means 4 is input to calculate the temperature change rate Δθ1 and the routine proceeds to step 105. In step 105, the temperature change rate Δ of the water obtained in step 104 by the temperature change rate comparing means 6.
A comparison between θ1 and a predetermined temperature change rate Δθ0 is performed, and Δθ
If 1 <Δθ0, the process proceeds to step 106, where Δθ1 ≧ Δ
If θ0, the process proceeds to step 107. In step 106, the elapsed time t1 from the start of energization of the second heating means 3 by the time measuring means 9 is measured, and the routine proceeds to step 108. In step 107, the heating is terminated by stopping the current supply to the first heating means 2 and the second heating means 3.

In step 108, a comparison is made between the time t1 measured in step 107 and a predetermined time T0 in which the first heating means is energized at a predetermined duty ratio after the water heater is started, and t1 <T0, that is, the water heater is heated. If the elapsed time from the start of the process is shorter than the predetermined time T0, the process returns to step 103 and the monitoring of the temperature change rate is repeated, and t1 ≧
If it is T0, the process proceeds to step 109. In step 109, the first heating means 2 and the second heating means 3 are energized.

FIG. 5 shows a thermistor 4 according to the second embodiment.
FIG. 3 is a diagram showing the detected temperature of a and the temperature at the bottom of the container 1, in which the horizontal axis represents the elapsed time from the start of heating and the vertical axis represents the temperature at that time. When there is no water, the temperature at the bottom of the container 1 starts increasing immediately after the start of heating, but the detected temperature of the thermistor 4a starts increasing after a lapse of T1 after the start of heating. Therefore, when the temperature change rate Δθ1 of the water obtained from the output of the temperature detection means 4 is compared with a predetermined temperature change rate Δθ0, it is detected that there is no water in the vessel 1, and the power supply to the heating means is stopped. The temperature at the bottom of 1 is K2
It can be seen that the temperature rise is lower than the temperature rise K1 in the conventional configuration.

As a result, the first heating means 2 is energized and heated at a predetermined duty ratio from the start of water heating to a predetermined time T1, and the rate of temperature change at that time is detected to thereby heat the first heating means 2. This determines whether or not the full energization is performed, so that the temperature of the container 1 can be kept low even if there is no water in the container.

[0022]

As is apparent from the above embodiment, according to the first aspect of the present invention, the heating electric power is kept low for a predetermined time after the start of water heating, and the container is set based on the temperature change rate. Judgment whether it is empty or not and heating with the maximum power after a predetermined time elapses, so even if the heating power becomes large to shorten the heating time, the temperature rise of the container during empty baking is kept low. Thus, heat deformation and discoloration can be prevented.

According to the second aspect of the present invention, the first heating means is energized at a predetermined duty ratio for a predetermined time after the start of water heating, so that the heating power is kept low and the temperature change rate is reduced. Judgment whether the container is empty based on, and heating with maximum power after a predetermined time,
Even when the heating power is increased to shorten the heating time, the rise in temperature of the container during baking can be suppressed to a low level, thereby preventing thermal deformation and discoloration.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electric water heater according to embodiments 1 and 2 of the present invention.

FIG. 2 is an operation flowchart of heating control means of the electric water heater according to the first embodiment of the first invention;

FIG. 3 is a temperature characteristic diagram of the electric water heater.

FIG. 4 is an operation flowchart of heating control means of the electric water heater according to the second embodiment of the second invention.

FIG. 5 is a temperature characteristic diagram of the electric water heater.

FIG. 6 is a block diagram of a conventional electric water heater.

FIG. 7 is a temperature characteristic diagram of a conventional electric water heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 2 1st heating means 3 2nd heating means 4 Temperature detection means 5 Temperature change rate calculation means 6 Temperature change rate comparison means 7 Heating control means 8 Clocking means

Continuation of the front page (56) References JP-A-2-149225 (JP, A) JP-A-60-198115 (JP, A) JP-A-4-35621 (JP, A) JP-A-63-117435 (JP, A) , U) (58) Field surveyed (Int. Cl. ⁷ , DB name) A47J 27/21 101

Claims (2)

(57) [Claims] A container for storing water; a first heating unit for heating water contained in the container; a second heating unit having a lower heating power than the first heating unit; First
Heating control means for controlling the heating means and the second heating means, temperature detecting means for detecting the temperature of water contained in the container, and the temperature contained in the container by the output of the temperature detecting means. Temperature change rate calculating means for calculating a change rate of water temperature; temperature change rate comparing means for receiving the output of the temperature change rate calculating means as input and comparing the temperature change rate of the contained water with a predetermined temperature change rate. And a timer means for measuring a predetermined time after starting the water heater, wherein the heating control means only controls the second heating means while the predetermined time has been measured from the start of the water heater by the timer means. Energize,
In the meantime, if the temperature change rate of the water becomes larger than the predetermined temperature change rate, the energization to the second heating means is stopped, and if the temperature change rate of the water is smaller than the predetermined temperature change rate, a predetermined time has elapsed. Is an electric kettle for supplying electricity to the first heating means or to both the first heating means and the second heating means. 2. A container for storing water, a first heating unit and a second heating unit for heating water contained in the container, and control of the first and second heating units. Temperature control means for detecting the temperature of the water contained in the container, and a temperature change for calculating a rate of change of the temperature of the water contained in the container based on the output of the temperature detection means. Rate calculation means, temperature change rate comparison means for comparing the temperature change rate of water with a predetermined temperature change rate by using the output of the temperature change rate calculation means as an input, and timing of a predetermined time after starting water heating And a heating control means for supplying electricity to the first heating means at a predetermined duty ratio while a predetermined time is being measured from the start of water heating by the time measurement means, during which time the temperature of the water is controlled. The rate of change is greater than the specified rate of temperature change When it becomes larger, the power supply to the first and second heating means is stopped, and when the temperature change rate of the water is smaller than the predetermined temperature change rate, the first heating means and the second heating means after a predetermined time have elapsed. To energize the electric water heater.