JPS59197848A - Humidity sensor - Google Patents

Abstract

PURPOSE:To obtain a humidity sensor superior in heating efficiency by constituting the titled sensor of the hollow elliptic cylinder-shaped reflective outer circumferential wall, linear heating elements provided at the focus of the elliptic cylinder and a humidity sensitive element provided at the other focus of the elliptic cylinder. CONSTITUTION:Since the linear heating element 6 is positioned at the focus 5, a thermal radiation 8 emitted from the surface of the element 6 is reflected at the reflective inner surface of the hollow elliptic cylinder-shaped outer circumferential wall 4 and is made incident to the humidity sensitive element positioned at the other focus 7. The humidity-sensitive element is absorbable, and the radiation 8 is absorbed to the humidity sensor to heat said sensor. Since the emitted thermal radiation can be utilized efficiently by the humidity sensor for heating the humidity sensitive element, the sensor is superior in heating efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application The present invention relates to a humidity sensor having an indirect heater.

Structure of a conventional example and its problems The structure of a conventional humidity sensor is shown in FIG. A humidity sensing element is formed on the surface of the sensor ceramic 10, whose electrical resistance changes due to humidity (accordingly, the electrode films 2, 2 are formed). An indirect heater 3 is arranged. When the temperature sensing element is exposed to, for example, a cooking atmosphere, organic substances adhere to the surface of the temperature sensing element, so that the humidity sensing element no longer senses humidity. The humidity sensing element is heated to a high temperature using a thermal heater 3 to thermally remove dirt adhering to its surface. Humidity is then detected by measuring the resistance between the electrode films 2 and 2'. .

However, since the indirect heater 3 is arranged around the outer periphery of the temperature sensing element as shown in FIG. 1, the heating efficiency of the humidity sensing element by the indirect heater 3 is poor.

OBJECTS OF THE INVENTION An object of the present invention is to provide a humidity sensor with excellent heating efficiency.

Structure of the Invention The humidity sensor of the present invention comprises a reflective hollow elliptical cylindrical outer circumferential wall, a linear heating element provided at the focal point of the elliptical cylinder, and a fl-shaped humidity sensing element provided at the other focal point of the elliptical cylinder. .

A linear heating element 6 was provided at a focal point 5 of the opposite hollow elliptical cylindrical outer circumferential wall 4, and a moisture sensing element was provided at another focal point 7. The humidity sensing element was composed of a sensor ceramic 1 and an electrode film 2.2'.

When the linear heating element 6 is heated to a high temperature, heat dissipation is mainly due to thermal radiation. At this time, the linear heating element 6 is located at the focal point 5, so that the thermal radiation 8 emitted from the surface of the linear heating element 6 is reflected from the inner surface of the reflective hollow elliptical cylindrical outer circumferential wall 4 to the other focal point 7. Since the moisture sensitive element is absorbing, the thermal radiation 8 is absorbed by the moisture sensitive element and heats it.

Thermal radiation 8 is radiated not only in the direction shown in Fig. 2 but also in all directions, but since the linear heating elements are located at the focal point 5, most of the thermal radiation is reflected in the same way and is emitted elsewhere. The light enters the humidity sensing element located at the focal point 7 of the sensor and heats the humidity sensing element. As described above, the humidity sensor of the present invention has excellent heating efficiency because the thermal radiation radiated from the linear heating element 6 can be effectively used to heat the humidity sensing element.

When the reflective hollow elliptical cylindrical outer peripheral wall 4 is made of stainless steel, the power consumption of the linear heating element 6 required to heat the humidity sensing element to about 450°C is about 3 W, which is lower than the conventional power consumption. 4. Effects of the Invention: Heating efficiency is greatly improved compared to about 10 WK.The humidity sensor of the present invention provides the following effects.

(1) Most of the thermal radiation emitted from the linear heating element can be effectively used to heat the humidity sensing element, so heating efficiency is high.

(≧ In conventional humidity sensors, the indirect heater is generally constructed by closely winding heat-generating metal heating wires, so an insulator must be placed between the heating wires in order to obtain electrical insulation between the heating wires.

However, in the present invention, since a linear heating element is sufficient as the heating element, electrical insulation can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a top view showing the structure of a conventional humidity sensor, and FIG. 2 is a top view showing the structure of an embodiment of the humidity sensor of the present invention. 1...Sensor ceramic (moisture sensing element), 4...
...Reflective hollow elliptical cylindrical outer circumferential wall, 5... Focus point of the elliptical cylinder, 6... Linear heating element,
7...Other focal points of the elliptical cylinder.

Claims (1)

[Claims] A humidity sensor comprising a reflective hollow elliptical cylindrical outer circumferential wall, a linear heating element provided at a focal point of the elliptical cylinder, and a humidity sensing element provided at another focal point of the elliptical cylinder.