JPH0554624B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a humidity sensor used for measuring or controlling humidity.

Conventional configurations and their problems In recent years, the need for humidity sensors has increased in various industrial fields including the air conditioning field, but there are many problems with their reliability. In particular, reliability in a contaminated environment where salt particles, inorganic solid particles such as dust, etc. are present is a concern.

Hereinafter, the conventional humidity sensor as described above will be explained with reference to FIGS. 5a and 5b.

The moisture sensing section 1, the cleaning heater 2, the electrode 3, the holding section 5, and the lead wire 9 have the same structure as shown in FIG. 1, so the same reference numerals are given and the details are omitted. Reference numeral 8 denotes a protector for protecting the contained moisture sensing section 1 and heater 2 from mechanical damage, and a large number of through holes 8a are provided around the protector to improve heat dissipation after heating and cleaning.

Regarding the humidity sensor configured as above,
The operation will be explained below.

In the above configuration, first, the humidity sensor is brought into contact with the measurement atmosphere. Water vapor in the atmosphere reaches the humidity sensing section 1 by diffusion or airflow and is adsorbed therein. The moisture sensing section 1 changes its electrical characteristics depending on the amount of adsorption at that time. This change can be detected electrically by applying a voltage to the electrode 3 via the lead wire 9 in advance, thereby allowing the humidity in the atmosphere to be detected electrically.

However, the above configuration has the following drawbacks. The first point is that if there are inorganic solid particles such as salt particles or dust that cannot be removed by heating cleaning in the atmosphere, the inorganic solid particles can easily pass through the through holes 8a of the protector 8 to the moisture sensitive area. This is due to the fact that it adheres to the electrodes and causes deterioration of the device, making it impossible to reproduce it. The second drawback is
During heating cleaning, the heater reaches a high temperature of 500°C or higher, so if flammable substances are present in the atmosphere, there is a risk of explosion or fire, which poses a safety problem.

Therefore, it is desired to develop a heat-cleaning type humidity sensor that is highly safe and highly reliable even in environments where inorganic solid particles such as salt particles and dust, and explosive substances are present.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention provides a heating cleaning type humidifier that is explosion-proof and fire-proof, and has high reliability in contaminated environments where inorganic solid particles such as salt particles and dust exist. It provides a sensor.

Structure of the Invention In order to achieve this object, the humidity sensor of the present invention includes a humidity sensing part, a heating part of the humidity sensing part, a holding part of the humidity sensing part and the heating part, a part that is combined with the holding part, a first casing that encloses a heating section and a heating section and has an opening, and a second casing that encapsulates the first casing and has a large number of through holes, and the first casing An opening connecting the inside and outside of the body is provided on one side of the first casing, and the opening is provided in a range where the solid angle from the humidity sensing part or the center of the casing does not exceed 1/10 steradian. It is.

This configuration protects the humidity sensing part and electrodes from adhesion of inorganic solid particles such as salt particles and dust in the atmosphere, and maintains a low surface temperature during heating, making the humidity sensor highly fire-resistant and explosion-proof. It provides:

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1a and 1b show the structure of a humidity sensor in an embodiment of the present invention. In FIG. 1, 1 is a humidity sensing section for detecting humidity, 2 is a cleaning heater for heating the humidity sensing section, and 3 is a cleaning heater for heating the humidity sensing section.
4 is an electrode for converting humidity into an electrical signal; 4 is a bottomed cylindrical first housing housing a humidity sensing section 1, a heater 2, and an electrode 3; a cylindrical holding section 5 to which the heater 2 is attached; It is closed with a lid. This first casing has a vertically slit-shaped opening 7 formed on its side surface to bring the moisture sensing section 1 into direct contact with the atmosphere. Reference numeral 6 designates a second casing in the form of a cylinder with a bottom that encloses the first casing 4, the bottom of which is closed by a holding part 5, the top of which is closed by a cap 6a, and the sides are formed of wire mesh. ing. This second casing has a large number of through holes 8 each having a width of 1 mm or less. The holding section 5 fixes the humidity sensing section 1 and the heater 2. 9 is a lead wire for voltage application and signal output, which is led out from the electrode 3;
It passes through the holding part 5.

Regarding the humidity sensor configured as above,
The operation will be explained below.

In the above configuration, if the opening 7 is provided in a predetermined position with the opening 7 facing vertically downward, the moisture sensing part 1 and the electrode 3 are surrounded by the first and second casings, and are passed through the through hole 8 and the opening 7. Detects humidity by coming into contact with the atmosphere. In this way, inorganic solid particles such as salt particles and dust in the atmosphere, especially salt particles (sea salt particles) that affect life performance due to salt damage, are heavy and will mainly settle due to gravity, and will not be absorbed by diffusion like water vapor. Since it cannot be moved, it is difficult to enter through the opening 6 in windless conditions.
It is difficult to adhere to the humidity sensing part 1 and the electrode 3. Also, in the case of wind, the humidity sensing part 1 and the electrode 3 are located above the opening 7, and the solid angle of the opening 7 is 1/10 steradian or less, and only one side is provided with respect to the wind direction. Due to the structure of the casing 4 of 1 that does not allow ventilation, even if wind were to blow vertically upward, it would be difficult to adhere to the humidity sensing section 1 and the electrodes 3. In this way, the moisture sensing portion 1 and the electrode 3 are free from adhesion of the inorganic solid particles in any state. Figure 2 shows the solid angle of the opening 7 of the first housing and the deterioration of the sensor under severe conditions in which seawater was sprayed from right side to the opening 7 at a wind speed of about 0.55 m/s to the humidity sensor configured as described above. The relationship between quantities was shown. As shown in the figure, by reducing the solid angle to 1/10 or less, it is possible to significantly reduce the deterioration of the sensor due to salt particles even if a sideways wind blows. In addition,
From the viewpoint of salt removal, it can be said that the smaller the area of this opening, the more effective it is, but on the other hand, when considering the responsiveness of the humidity sensor to changes in the environment, an opening area of a certain value or more is required. In practice, assuming that the response time of a humidity sensor is about 10 seconds, the aperture size is 1/
1000 steradians. By the way, organic substances such as cigarettes and oil vapor may adhere to the humidity sensing part 1 and the electrode 3.
When the sensor deteriorates, the organic matter can be removed by heating using the heater 2 to restore the deteriorated characteristics. However, for some reason, the heater may be left energized for a long time, causing the surface temperature of the first casing 4 to overheat to 100°C or higher.
In that case, since the second housing 6 covers the first housing 4, the substantial surface temperature of the humidity sensor of this embodiment can be considered to be the surface temperature of the second housing 6.

Figure 3 shows a slit-shaped opening with a width of 1 mm and a length of 30 mm in the side of a sealed cylinder with a diameter of Dmmφ and a height of 30 mm, and a 4.5 W heater is placed inside.
Cylindrical surface saturation temperature and cylinder diameter when heated continuously in an atmosphere of 25℃ and wind speed of 0.05 m/s or less
This shows the relationship between Dφ. If Dφ=20 mm or more, it is possible to reduce the surface temperature to 70°C or less. Therefore, even if the surface temperature of the first casing is overheated to a high temperature of 100°C or higher for some reason during thermal cleaning, the second casing, which has a diameter of about 20 mmφ and has many through holes on the side surface, cannot be used. 6 covers the first housing 4, the surface temperature of the sensor can be limited to 70° C. or less.

On the other hand, water vapor in the atmosphere reaches the humidity sensing part 1 through the through hole 8 and the opening 7 by diffusion even in a windless state, and is adsorbed therein. Its electrical characteristics are changed depending on the amount of adsorption at that time. The amount of change is converted into an electrical signal by the electrode 3 to which a voltage is applied via the lead wire 9.

As described above, the humidity sensor of this embodiment is free from the adhesion of inorganic solid particles in the atmosphere, and also limits the sensor skin temperature to 70°C or less during heating cleaning, thereby maintaining the atmosphere while maintaining safety. Detects humidity.

In the above embodiment, the through hole 8 is provided in the side surface of the second casing 6, but a large number of slits 8a may be provided as shown in FIG. 4a. Alternatively, the second casing itself may be made into a net shape as a whole to form the through holes 8b, as shown in FIG. 4b.

In addition, the opening 7 and the through hole 8 of the above embodiment are
m, the first and second casings are made explosion-proof, and the sensor as a whole has a double explosion-proof structure. can be avoided from the dangers of

Effects of the Invention As described above, the present invention accommodates a humidity sensing section and an electrode in a first casing having an opening having a solid angle of 1/10 to 1/1000 from the humidity sensing section, and By providing the second casing that includes the first casing and has a large number of through holes, it is possible to prevent the sensor from deteriorating due to the adhesion of inorganic solid particles such as salt particles and dust to the moisture sensing portion and electrodes. By setting the width of the through hole in the second casing to 1 mm or less, the surface temperature of the sensor can be maintained at 70°C or less, and the casing has an explosion-proof structure, preventing fires and explosions during heated cleaning. This can be prevented and safety in use can be ensured.

[Brief explanation of the drawing]

FIG. 1a is a partially cutaway vertical cross-sectional view showing the configuration of a humidity sensor according to an embodiment of the present invention, FIG. 1b is a cross-sectional view of FIG. 1a, and FIG. 2 is a humidity sensor of the present embodiment. Figure 3 is a graph showing the relationship between the solid angle of the opening and the amount of sensor deterioration when seawater is sprayed on the sensor. Figure 3 is a graph showing the relationship between the diameter Dφ of a cylinder with slits and the surface saturation temperature when heated continuously. Figure 4 a and b are side views showing the second casing and another example of the through hole in Fig. 1, and Fig. 5 a is a partially broken longitudinal section showing the configuration of a conventional heating cleaning type humidity sensor. figure,
FIG. 5b is a cross-sectional view of FIG. 5a. 1... Moisture sensing part, 2... Heater, 3... Electrode, 4
...First case, 5...Opening, 6...Second case, 8
...through hole.

Claims (1)

[Claims] 1. A humidity sensing section having an electrode and a heating section of the humidity sensing section;
A holding section for the humidity sensing section and heating section, a first casing coupled to the holding section and containing the humidity sensing section and heating section, and an opening connecting the inside and outside of the first casing. The opening is provided on one side of the first casing, and the opening is so large that the solid angle from the moisture sensing part does not exceed 1/10 steradian, and the first casing includes a large number of transparent A humidity sensor comprising a second casing having a hole. 2. The humidity sensor according to claim 1, wherein the second humidity sensor is reticulated. 3. The humidity sensor according to claim 1, wherein the through hole of the second housing is constituted by a slit.