JP3052287U - Electric water heater - Google Patents

Abstract

(57) [Summary] [Problem] Without providing a water level sensor and thermal fuse
Provided is an electric water heater that does not overheat even when there is no water or empty cooking. A non-linear resistance element having a transition temperature of 80 to 90 ° C. and having a positive characteristic is used as an overheating prevention device and a heating source heating element of an electric water heater in close contact with the bottom surface of a housing water tank.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to an electric water heater.

[0002]

[Prior art]

 In hotels, restaurants, fast foods, and other places that handle foodstuffs, for example, it is necessary to keep curries, roux, sausages, prepared foods, and the like for a long time, and provide warm foodstuffs. For this reason, an electric water heater is used as a tool for boiling hot water, immersing a food container such as a hotel pan in the hot water, and indirectly keeping the food at an appropriate temperature. Conventionally, such an electric water heater uses a seeds heater or the like as a heating element, and inserts them into a water bath or attaches them to the bottom surface of the bath.

FIG. 5 is an explanatory view of a conventional electric water heater 1. The electric water heater 1 stores water 3 to be heated in a housing water tank 2, and supplies electric power from a power source 5 to a sheath heater 21 to heat the sheath heater 21. A food material 8 to be kept warm is stored in a food material storage container 7. 6 is a lid. The water 3 is heated by the sheath heater 21 to keep the food 8 warm. In such a conventional electric water heater 1, when the supply of water is forgotten for a long time, the sheathed heater 21 becomes in an empty state, the heating element reaches an abnormal temperature, and there is a danger of fire or the like. . In order to prevent such accidents, safety devices such as a thermostat 22, a temperature fuse 23, and a float switch 24 are provided as a device to prevent drainage, empty cooking, and overheating, but these safety devices are not maintained for a long time. When used in, reliability may be lacking due to incomplete operation or a time lag until operation, and safety may not always be ensured.

[0004]

[Problems to be solved by the invention]

 The present invention has been made in view of the above circumstances, and aims to develop and provide an electric water heater that does not overheat even when there is no water or empty cooking.

[0005]

[Means for Solving the Problems]

 The present invention has been made in order to solve the above-mentioned problems.In an electric water heater, a non-linear resistance element having a positive characteristic is used as an overheating prevention device and a heating source heating element, and this is placed on the bottom of a housing water tank. An electric water heater characterized by being in close contact. A non-linear resistance element with positive characteristics is used as an alternative heating element to the nichrome wire heater or sheathed heater, and this is pressed against the bottom of the water tank to heat the water tank efficiently. Generally, the non-linear resistance element is 200 W to 300 W at 100 V, and several or several tens can be mounted according to the volume of the water tank.

In the above electric water heater, it is preferable to use a non-linear resistance element having a transition temperature of 80 to 90 ° C. Non-linear resistance elements with positive characteristics are expected to have low resistance at low temperature in the early stage of energization, and a large instantaneous current will flow, but the characteristic value of the element will increase by about 20% even at low temperature. It is a current, and the transient time for the rated value is as short as a few microseconds. Therefore, in practice, the operation of the breaker attached to the switchboard etc. is not affected at all. This was confirmed by experiments.

[0007]

[Embodiment of the invention]

 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing an electric water heater 1 according to an embodiment of the present invention. The main body of the electric water heater 1 is the same as that of the prior art. That is, the water 3 was put in the housing water tank 2 and the food material 8 to be kept warm was stored. The food material storage container 7 is immersed and heated.

In the present invention, a non-linear resistance element having a positive characteristic is used as the heater 4. Non-linear resistance elements with positive characteristics are a type of semiconductor element, and have the function of automatically increasing the temperature, increasing the electrical resistance, suppressing the current value, reducing power consumption, and automatically adjusting the temperature. Things. FIG. 2 is a graph showing an example of the resistance-temperature characteristics of such a nonlinear resistance element having a positive characteristic. As shown in FIG. 2, the relationship between resistance and temperature shows a substantially constant resistance value from room temperature to the transition temperature indicated by the point D, and when the temperature exceeds the transition temperature (point D), the electric resistance value rapidly increases. It shows a steep positive resistance-temperature characteristic. The transition temperature (point D) is defined by design as a temperature that is twice the normal temperature resistance (resistance value at a temperature of 25 ° C.), and a nonlinear resistance element having a different transition temperature every 10 ° C. It can be manufactured. In addition, the relationship between the applied voltage of the nonlinear resistance element having a positive characteristic and the current at the time of thermal equilibrium shows that the resistance shows a substantially constant resistance up to a certain voltage, and that the power becomes a substantially constant power beyond that. The relationship between current and time when a voltage is applied to the nonlinear resistance element (dynamic characteristics) is such that a relatively large current (rush current) flows immediately after the voltage is applied, and then rapidly attenuates and stabilizes.

The automatic temperature control function of the nonlinear resistance element will be described with reference to FIG. 2 showing resistance / temperature characteristics. Now, it is assumed that the operation is performed at the point A of the resistance temperature characteristic curve in the steady state. In this state, when the applied voltage or the ambient temperature rises, the temperature of the nonlinear resistance element rises, and the operating point shifts to point B. As the temperature rises, the resistance of the nonlinear resistance element increases, and the power decreases. Therefore, it acts to return to the original point A. Also, when the applied voltage or the ambient temperature decreases, the temperature of the nonlinear resistance element decreases, and the operating point shifts to the point C. As the temperature decreases, the resistance of the nonlinear resistance element decreases, the power increases, and the function returns to the original point A. In this way, the nonlinear resistance element operates so as to always maintain a constant temperature even when the applied voltage or the ambient temperature changes.

The factors of the temperature change of the non-linear resistance element include the magnitude of the load such as a radiator plate in addition to the change of the applied voltage and the ambient temperature. There is an adjustment function. As shown in FIG. 1, the water heater 1 of the present invention may be provided with a temperature adjusting function such as a temperature sensor 11, a temperature adjusting device 12, and a drain indicator lamp (with a buzzer). As shown in FIG. 3, for example, a variable thermostat 14 such as a small resistor R having a resistance of 0.01 to 0.05Ω, such as a bimetal, a liquid expansion thermostat, an electronic thermostat, etc. It is inserted into a circuit to detect a change in the displacement signal voltage Vs. As shown in FIG. 4, the notification alarm function for running out of water or the like is performed by detecting an electric displacement such as a current decrease due to an increase in the element resistance of the non-linear resistance element heater 4 by a current detection coil (CT) 15 or the like, and displacing a displacement signal voltage. Detects a change in Vs and displays a buzzer or lamp.

[0011]

[Effect of the invention]

 The electric water heater of the present invention is configured as described above, and the non-linear resistance element having a positive characteristic increases in resistance value when the temperature rises, suppresses the current value, reduces power consumption, and automatically There is a function to adjust the temperature. Therefore, even if the water heater of the present invention runs out of water or runs out of water, the resistance of the heater rises rapidly and the power is close to OFF, and there is no danger of overheating etc. Extremely high. In addition, since the element is small, there is an advantage that a space for mounting the heating element is small.

[Brief description of the drawings]

FIG. 1 is a view showing an electric water heater of an embodiment.

FIG. 2 is a graph showing the relationship between temperature and resistance of a nonlinear resistance element having positive characteristics.

FIG. 3 is a circuit diagram illustrating an example of a temperature adjustment function.

FIG. 4 is a circuit diagram showing an example of an alarm function.

FIG. 5 is an explanatory view of a conventional electric water heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric water heater 2 Casing water tank 3 Water 4 Non-linear resistance element 5 Power plug 6 Lid 7 Foodstuff storage container 8 Foodstuff 11 Temperature sensor 12 Temperature controller 13 Out-of-water indication lamp (along with buzzer) 14 Variable thermostat 15 Current detection coil 21 Seeds Heater 22 Thermostat 23 Thermal fuse 24 Float switch

Claims (2)

[Utility model registration claims] 1. An electric water heater in which a non-linear resistance element having a positive characteristic as an overheating prevention device and a heating source heating element is closely attached to a bottom surface of a housing water tank. 2. The non-linear resistance element has a transition temperature of 80 to 80.
The electric water heater according to claim 1, wherein the temperature is 90 ° C.