JPH0249085B2 - FUTSUTOKENSHUTSUSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a boiler that has the function of boiling water placed in a heating tank and automatically stopping heating or switching to keeping warm at the point of boiling, such as in an electric kettle. This invention relates to a detection device.

Conventional configuration and problems thereof Conventionally, in a water heater, as shown in FIG. Some devices were equipped with a temperature detection section 3 consisting of a thermostat. This is heating tank 1
The water 4 inside is heated by the heating element 2, and as the temperature rises, the temperature of the temperature detection part 3 also rises, and when the water temperature approaches the boiling point, the thermos constituting the temperature detection part 3 The switch is activated, and the electricity to the heating element 2 is stopped. However, with this configuration, the water may not boil due to differences in usage conditions such as the amount of water in the heating tank 1 and ambient temperature, and structural differences such as the installation state of the temperature detection unit 3 and variations in its operating temperature. Moreover, since the water temperature cannot rise above the boiling point (usually 100℃) after the water has boiled, electricity continues to be applied to the heating element 2 even after the water has boiled, and the water boils completely. It may also happen. For this reason, the structure and operating temperature of the temperature detection section 3 are usually determined so that the heating ends before the water reaches the boiling point. Therefore, with conventional water heaters, there is a problem in that water cannot be boiled before use.

OBJECTS OF THE INVENTION It is an object of the present invention to solve such conventional problems and provide a boiling detection device that reliably detects boiling of water.

Configuration of the Invention In order to achieve the above object, the boiling detection device of the present invention includes a positive resistance temperature coefficient heating element that heats water;
A power detection device that detects the power consumption of this positive resistance temperature coefficient type heating element, a power change rate measuring device that measures the rate of change in power using the power detected by this power detection device as an input signal, and this power change rate measurement device. This system is equipped with a boiling determination device that determines whether water has boiled based on a change in the rate of change in power based on the measurement signal of the device. According to this configuration, instead of detecting boiling based on the absolute value of temperature as in the past, Since boiling is detected using the relative value of the power change rate, the detection point does not change due to usage conditions or structural differences, and boiling of water can be reliably detected.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. In FIG. 2, 5 is a positive resistance temperature coefficient type heating element that heats water, 6 is a power detection device that detects the power consumption of the heating element 5, and 7 is an electric power using the power detected by the power detection device 6 as an input signal. 8 is a boiling determination device that determines boiling of water based on a change in the power change rate based on the measurement signal of the power change rate measuring device 7; 9 is a stainless steel or the like in which water is stored; This is a heating tank.

Figure 3 shows the relationship between the change in power of the positive resistance temperature coefficient type heating element 5 and the change in water temperature. This is a so-called self-control type heating element that consumes less power and suppresses its own heat generation, so that it reaches a saturated state at a specific temperature. When water is poured into the heating tank 9 and electricity is applied to the positive resistance temperature coefficient type heating element 5, its temperature is low and the resistance value is small, so the initial electric power is large and the amount of heat generated is also large, resulting in a sudden rise in temperature. In this case, the power will decrease rapidly. As the amount of heat generated decreases, the temperature change becomes gradual, and the change in power also becomes smaller, and it tends to reach a certain point, reaching saturation, but as the water temperature gradually rises, positive resistance temperature coefficient type heat generation occurs. Along with this, the temperature of the body 5 also gradually increases, and the electric power further gradually decreases. The temperature rise of the water and the power change of the positive resistance temperature coefficient type heating element 5 are in a stable state with a certain relationship due to the specific heat of the water, but when the water starts to boil, this relationship breaks down and the heat of vaporization is lost. , and the electric power of the positive resistance temperature coefficient type heating element 5 becomes large. Further, the power detection device 6 detects the power of the positive resistance temperature coefficient type heating element 5, and the power change rate measuring device 7 measures the change rate, and as described above, the water boils and the power change rate gradually increases. The boiling determination device 8 detects the point in time when the temperature decreases and then becomes large again, or the point in time when the temperature changes from negative to positive, determines this to be water boiling, and can notify the outside as soon as the electricity is turned off.

Note that power measurement may be performed by measuring current value or resistance value, and is not particularly limited.

Effects of the Invention As is clear from the above embodiments, the boiling detection device of the present invention uses a positive resistance temperature coefficient type heating element as the heating element, detects the rate of change in the electric power, and detects boiling based on the change in the rate of change. This allows boiling to be reliably detected without being affected by usage conditions, structural differences, or other initial conditions, and can improve the performance of water heaters and other heaters. It is.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a water heater using a conventional boiling detection device, Fig. 2 is a block diagram of a boiling detection device showing an embodiment of the present invention, and Fig. 3 is a water temperature and heat generation when boiling water in the same device. FIG. 3 is a characteristic diagram showing changes in power consumption of the body. 5... Positive resistance temperature coefficient heating element, 6... Power detection device, 7... Power change rate measuring device, 8... Boiling determination device, 9... Heating tank.

Claims (1)

[Claims] 1. A positive resistance temperature coefficient type heating element that heats water, a power detection device that detects the power consumption of this positive resistance temperature coefficient type heating element, and a power detection device that uses the power detected by this power detection device as an input signal to calculate the rate of change in power. A boiling detection device comprising: a power change rate measuring device for measuring a power change rate; and a boiling determination device determining water boiling based on a change in the power change rate based on a measurement signal from the power change rate measuring device.