JP2876827B2 - 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 for heating hot water in a tank by using a heating wire, wherein the electric water heater is adapted to prevent equipment damage due to emptying, which is an electric heating before water supply. It is.

[0002]

2. Description of the Related Art As shown in FIGS. 4 and 5, a conventional electric water heater of this type comprises a heating device 2 (hereinafter generally referred to as a heater) comprising a flange portion 2a and a pipe portion 2b below a heat storage tank 1. 2), and a temperature-sensitive operation type protector 3 having a power supply to the heater 2 outside the flange portion 2a.
(Hereinafter referred to collectively as Protector 3).

[0003] In particular, the operating point for stopping the energization in the protector 3 is as shown in FIG. That is, energization is stopped only when the temperature of the temperature detector of the protector 3 reaches a preset value (this set value was 95 ° C. in the conventional example). Normally, the protector 3 is attached to the outside of the flange portion 2a for attaching the heater 2, so that when the heat storage tank 1 is supplied with water, the heater 2 is continuously energized, and even when heated most, the heater 2 is 95%. C did not exceed. In other words, the protector 3 does not operate during the normal heating of the electric water heater.

On the other hand, if the heat storage tank 1 is not supplied with water due to misuse (hereinafter referred to as empty), the heater 2
When the power is supplied to the heater 2, the heater 2 generates a remarkable amount of heat, leading to breakage. However, the protector 3 is actuated beforehand and stops energizing so as to avoid damage. At this time, as shown in FIG. 6, the heater 2 generates heat immediately after the start of energization, that is, the heat generated by the internal heating wire is transferred to the pipe portion 2b, thereby increasing the surface temperature of the flange portion 2a. The temperature detector of the protector 3, which is electrically heated to this part, is also gradually heated and operates so as to stop the power supply to the heater 2 when the temperature reaches the set temperature.

[0005]

However, in the above-mentioned conventional construction, the material constituting the heater 2 is comprised of a heating wire and a pipe portion 2b containing the heating wire, and since the pipe portion 2b is made of stainless steel, the heater 2 is energized. After fever,
It takes time for the surface temperature of the flange portion 2a to rise by heat transfer via the pipe portion 2b, and therefore, it takes a considerable time for the temperature detection unit of the protector 3 to reach the set temperature. Meanwhile, the heater 2 having the heating wire therein is kept heated. Then, the surface temperature of the pipe portion 2b of the heater 2 rises remarkably, and the heating wire of the heater 2 abnormally heats, thereby deteriorating the insulation performance of the filling material inside the pipe portion 2b, and furthermore, the insulation resistance of the heater 2 However, there is a problem that this may lead to a decrease in

SUMMARY OF THE INVENTION The present invention solves the above-described conventional problem. The detection of an emptying abnormality is determined based on the temperature rise near the heater and the time energization to the heater, and the energization is immediately stopped. The purpose is to reduce the damage of the.

[0007]

In order to achieve the above object, the present invention provides a hot water storage tank for storing hot water and a hot water stored inside the hot water tank having a heating wire therein. And a heating device configured to heat the heating wire.
Current transformer as current detecting means for detecting flowing current
(CT) and the current transformer (CT) to the heating device
A time detecting device for detecting the actual time current flows, the hot water storage and temperature sensing device for detecting the temperature of the hot water that is stored in tanks, the temperature detector the time water detected temperature is inspected
A storage device for storing the integration time data detected by the output device at predetermined times at predetermined time intervals, an arithmetic device for substituting the value stored in the storage device into a preset calculation formula for calculation, And a discriminating device for comparing a value calculated in accordance with the above with a preset value. When a signal from the recognizing device causes an abnormality due to emptying, the power supply to the heating device is controlled.

[0008]

According to the present invention, the temperature rise near the preset heater and the current actually flowing through the heater are caused by the above-described structure.
Since the abnormality caused by the emptying is detected from the change amount of the power supply time to the heater obtained from the obtained time, the power supply to the heater is stopped reliably and in a short time.

[0009]

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

In FIG. 1, reference numeral 1 denotes a heat storage tank provided with a heater 2 at a lower portion thereof. Reference numeral 7 denotes a contact capable of stopping the power supply to the heater 2 (hereinafter referred to as a relay 7).
The operation of the relay 7 is controlled by a microcomputer (hereinafter, referred to as a microcomputer 4). The microcomputer 4 includes a signal from a temperature detecting device 5 (hereinafter, collectively referred to as a thermistor 5) and an integrated time sent from a time detecting device 6 (hereinafter, collectively referred to as a timer 6) for detecting the energization time to the heater 2. A storage device 4c for storing the data of a predetermined number of times at regular intervals, and a storage device 4c
The arithmetic device 4a performs an operation for determining the presence or absence of an empty space by substituting the value stored in the formula into a preset calculation formula, and the identification device 4b for comparing the calculated value with a preset numerical value. The power supply to the heater 2 is stopped based on the identification result.

The thermistor 5 is mounted on the outside of the flange 2a for mounting the heater 2, and as shown in FIG. 2, the heat is transferred to the pipe 2b and the flange 2a, and the temperature of the heater 2 is accurately determined. The rise can be detected.

The measurement of the integration time of the timer 6 is performed by detecting a current.
Using a current transformer (CT)
The time during which the current flows through the heater 2 is detected. As shown in FIG. 3, the storage device 4c and the arithmetic device 4a provided in the microcomputer 4 change the energization time T to the heater 2 and the temperature rise t, that is, the slope of the temperature rise of the heater 2 (ΔK = t /
T) is calculated and stored. By performing such an operation several times, the change in the rise of the heater 2 is stored. On the other hand, the identification device 4b stores ΔK0 based on the microcomputer setting time T0 and the microcomputer setting temperature t0 which are set in advance, and compares it with the slope ΔK of the temperature rise of the heater 2. In other words, when the inclination of the normal boiling is significantly large (the inclination at the time of emptying in an abnormal state), it is recognized that the heater 2 is energized before the water supply, and the heater 2 is immediately turned on.
That is, the relay 7 is instructed to stop supplying power to the relay 7.

The relay 7 simply turns on and off the current, and its control is performed by the microcomputer 4.

[0014]

As described above, according to the electric water heater of the present invention , the current that actually flows can be detected by the current detection means.
Detected by transformer (CT) and heater is in heating state
In some case, since detecting the abnormality due to boil-dry by the temperature rise and the amount of change in energization time of the heater near the heater, heating
If a contact failure occurs at the connection of the
No misjudgment, and can reliably detect emptying.
In addition, the power supply to the heater can be stopped in a short time, and it takes time for the temperature detection unit to reach the set temperature as in the conventional example, during which time the heater having the heating wire inside keeps heating. As a result, the surface temperature of the heater does not rise significantly, so that the insulation resistance of the heater can be reliably prevented from lowering.

[Brief description of the drawings]

FIG. 1 is a side view of an essential part of an electric water heater according to an embodiment of the present invention;

FIG. 2 is a side view of a heater portion of the electric water heater.

FIG. 3 is a diagram showing the energizing time of the electric water heater and the temperature rise of the flange portion for mounting the heater.

FIG. 4 is a side view of a main part of a conventional electric water heater with a main part cut away.

FIG. 5 is a diagram showing a relationship between the energization time of the conventional electric water heater and the temperature rise of the flange portion.

[Explanation of symbols]

 Reference Signs List 1 heat storage tank (hot water tank) 2 heater (heating device) 3 protector 4 microcomputer 5 thermistor 6 timer 7 relay

Continuation of the front page (72) Inventor Satoshi Akekawa 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-2-115655 (JP, A) JP-A-2-130343 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F24H 1/18 503

Claims (1)

(57) [Claims] 1. A hot water storage tank for storing hot water, a heating device having a heating wire therein and configured to heat the hot water stored in the hot water tank by the heat generated by the heating wire;
Current transformer as current detecting means for detecting flowing current
(CT) and the current transformer (CT) to the heating device
A time detecting device for detecting the actual time current flows, the hot water storage and temperature sensing device for detecting the temperature of the hot water that is stored in tanks, the temperature detector the time water detected temperature is inspected
A storage device for storing the integration time data detected by the output device at predetermined times at predetermined time intervals, an arithmetic device for substituting the value stored in the storage device into a preset calculation formula for calculation, An electric water heater comprising: a discriminating device for comparing a value calculated in accordance with the above with a preset value; and controlling a power supply to the heating device in the event of an abnormality due to emptying by a signal from the recognizing device.