JP4219424B2 - Sensing element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat-driven sensing element used in a place where gas concentration is measured and controlled, such as facility horticulture, environmental sanitation, disaster prevention, industrial use, building use, and house use.
[0002]
[Prior art]
Hereinafter, the detection element will be described with reference to FIG. 9, taking a heat-driven gas sensor as an example.
[0003]
As shown in the figure, the gas sensitive part 101 is located on one side upper part of the substrate 103 provided with the heating part 102 on one side lower part, and is taken out from the lead wires 105a, 105b for taking out the outputs from the electrodes 104a, 104b and the heating part 102. It is fixed to the lower pedestal 108 via lead pins 107a, 107b, 107c, 107d connected to the lead wires 106a, 106b, respectively. The casing 109 has an opening for protecting the gas sensing unit 101, the heating unit 102, the electrodes 104a and 104b, and the lead wires 105a, 105b, 106a, and 106b contained therein from mechanical damage and improving contact with the measurement atmosphere. 110 is provided and fixed to the pedestal 108.
[0004]
In the above configuration, the gas sensitive unit 101 is heated to the measurement temperature by the heating unit 102, a constant voltage is applied between the electrodes 104a and 104b, and the gas sensitive unit 101 comes into contact with the measurement atmosphere through the opening 110 of the casing 109. In this case, the resistance value of the gas sensitive portion changes according to the concentration of the detection target gas, and the concentration of the detection target gas in the measurement atmosphere can be measured.
[0005]
[Problems to be solved by the invention]
Such a conventional sensing element has a problem that it malfunctions depending on the humidity of the measurement atmosphere because the gas sensitive part is sensitive to humidity, and it is required to prevent this malfunction.
[0006]
The present invention solves such a conventional problem, and even when the humidity of the measurement atmosphere changes, the humidity inside the casing can be prevented and malfunction due to humidity can be prevented. By using a material that absorbs and releases moisture reversibly according to the humidity, it is possible to prevent the influence of a sudden change in humidity, and the moisture absorption means absorbs moisture over the entire humidity change range of the measurement atmosphere by means of a moisture absorbent heating means. By heating to a temperature where the capacity can be obtained, malfunction due to humidity can be prevented at any humidity of the measurement atmosphere, and the heat of the heating section that heats the gas sensitive part can be used to cover the entire humidity change range of the measurement atmosphere. Heating to a temperature that provides moisture absorption capability prevents malfunctions due to humidity with low power consumption, and regenerating moisture absorption means prevents malfunctions due to long-term humidity changes. And its object is to provide a sensing device that can be prevented.
[0007]
[Means for Solving the Problems]
For sensing element of the present invention to achieve the above object, a sensitive part, the sensitive part and enclosing, in a sensing device and a today body having an opening, moisture absorption into a form covering a part or all of the openings A moisture absorbent heating means for heating the moisture absorbent to a temperature higher than the measurement atmosphere so as to prevent moisture change in the casing and prevent malfunction of the sensitive part by providing a material and improving moisture absorption characteristics with respect to relative humidity changes; By installing the hygroscopic material on the hygroscopic material and heating the hygroscopic material, the hygroscopic material is used in a relative humidity range of an atmosphere having excellent hygroscopic properties with respect to changes in relative humidity .
[0008]
According to the present invention, the hygroscopic material is heated to a temperature at which the hygroscopic capacity of the hygroscopic material is optimal within the humidity change range of the measurement atmosphere, so that it is possible to prevent humidity changes in the casing regardless of the humidity of the atmosphere. Thus, a sensing element that can prevent malfunction due to humidity change is obtained.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a sensing element that includes a sensitive part and a housing that includes the sensitive part and has an opening. A hygroscopic material heating means for heating the hygroscopic material to a temperature higher than the measurement atmosphere is installed in the hygroscopic material so as to prevent the humidity change in the housing and prevent malfunction of the sensitive part, and the hygroscopic material is heated. Thus, the hygroscopic material is used in the relative humidity range of the atmosphere having excellent moisture absorption characteristics with respect to the relative humidity change , and the operating temperature of the moisture absorption means is set to a temperature at which the hygroscopic ability can be obtained in the humidity change range of the measurement atmosphere. Has the effect of heating.
[0010]
Embodiments of the present invention will be described below with reference to the drawings.
[0011]
【Example】
(Reference Example 1)
The same parts as those in the conventional example are denoted by the same reference numerals and the description thereof is omitted.
[0012]
As shown in FIG. 1, the moisture absorbing means 1 is fixed inside the casing 109 by fixing means 2. The hygroscopic means 1 is made of a hygroscopic material such as zeolite or silica gel, and has a configuration in which powder and particles are fixed, and air in the atmosphere is sufficiently communicated from the opening 110 to the inside of the casing 109.
[0013]
In the above configuration, the air flowing from the opening 110 passes through the moisture absorbing means 1 and flows into the housing 109, and the gas sensitive unit 101 detects the gas concentration of the flowing air. At that time, moisture in the measurement atmosphere is absorbed by the moisture absorption means 1 and does not enter the housing 109. Therefore, the humidity inside the casing 109 is always kept low, and even if the humidity of the atmosphere changes, the humidity inside the casing 109 does not change, so that malfunction of the gas sensitive unit 101 due to moisture can be prevented.
[0014]
The hygroscopic means 1 is zeolite, silica gel or the like, but the same effect can be obtained as long as the material absorbs humidity in the atmosphere. In addition, although the form is powder or grain, any form may be used as long as it can be fixed inside the casing and there is a flow of air, and it may be sealed in a molded body, paper or cloth. Good.
[0015]
(Reference Example 2)
The same parts as those in the conventional example are denoted by the same reference numerals, and description thereof is omitted.
[0016]
In FIG. 2, the silica gel particles 3 as moisture absorbing means are fixed between the metal mesh plate 4 of 100 mesh and the opening 110 inside the casing 109 by the fixing means 2.
[0017]
In the above configuration, the silica gel particles 3 as the dehumidifying means have the moisture absorption characteristics shown in FIG. That is, when the relative humidity of the atmosphere changes from low humidity to high humidity, moisture is absorbed. Further, when the humidity is changed from high humidity to low humidity, the moisture that has been absorbed is released. Therefore, the humidity inside the casing 109 is kept constant regardless of the humidity change of the atmosphere, and malfunction of the gas sensitive unit 101 can be prevented.
[0018]
Although the silica gel particles are used as the moisture absorbing means, any material may be used as long as it absorbs and releases moisture reversibly with respect to changes in the relative humidity of the atmosphere. Moreover, although it was made into a grain, it may be fixed inside the casing and may be in any form as long as it has air circulation, and may be sealed in a molded body, paper, or cloth.
[0019]
Example 1
The same parts as those in the conventional example are denoted by the same reference numerals, and description thereof is omitted.
[0020]
In FIG. 4, a heater 5 is installed in the moisture absorbing means 1 as a heating means for heating silica gel that is a moisture absorbent material of the moisture absorbing means 1. The heater 5 is supplied with power from the power source 4.
[0021]
In the above configuration, the silica gel particles 3 as the dehumidifying means are heated by the heater 5 as the heating means, and the temperature is higher than the measurement atmosphere. The moisture absorption characteristics of the silica gel particles 3 are shown in FIG. As the moisture absorption characteristics of the silica gel particles 3 become higher, the moisture absorption characteristics with respect to the relative humidity change become worse. Therefore, when the humidity of the atmosphere changes in the range of 20% to 80%, the moisture absorption capacity is insufficient on the high humidity side. Therefore, by heating the silica gel particles 3 with the heater 5, for example, when the temperature is 30 ° C. as shown in FIG. 5, the humidity range of 20% to 80% at 20 ° C. is about 10% to 45% at 30 ° C. It can be used in a range where the moisture absorption characteristics with respect to the relative humidity change of the grains 3 are excellent. Therefore, the humidity inside the casing 109 can be kept constant regardless of the humidity change of the atmosphere, and malfunction of the gas sensitive unit 101 can be prevented.
[0022]
Note that the heater may be anything such as a nichrome wire or a sheet-like heater as long as it can heat the moisture-absorbing material as a moisture-absorbing means. Further, the heater may be installed inside or around the hygroscopic material, and there is no difference in the effect. The heating temperature is higher than the temperature of the atmosphere and can maintain the hygroscopic ability of the hygroscopic material, generally 100 ° C. or less, and there is no difference in the effect.
[0023]
( Reference Example 3 )
The same parts as those in the conventional example are denoted by the same reference numerals, and description thereof is omitted.
[0024]
In FIG. 6, the gas sensitive part 101 is heated to about 300 ° C. by the heating part 102. The capacity of the heating unit is about 250 mW. The distance between the gas sensitive part 101 and the lower surface of the silica gel particles 3 is about 3 mm, and the amount of the silica gel particles 3 is about 1 g.
[0025]
In the above configuration, the silica gel particles 3 are heated by the radiant heat of the heating unit 102 of the gas sensitive unit 101. FIG. 7 shows the temperature of the silica gel particles with respect to the ambient temperature. As shown in FIG. 7, when the ambient temperature is about 25 ° C., the silica gel particles 3 are heated to about 30 ° C. to 70 ° C. Therefore, even when the relative humidity of the atmosphere changes from 20% to 100%, it can be used in a region having excellent moisture absorption characteristics of the silica gel particles 3, and the humidity inside the casing 109 can be kept constant. The malfunction of the gas sensitive part 101 can be prevented.
[0026]
(Reference Example 4 )
The same parts as those in the conventional example are denoted by the same reference numerals, and description thereof is omitted.
[0027]
In FIG. 8, as a regeneration means, a heater 5 is supplied with electric power from a power source 6 and heats the moisture absorption means 1 to a temperature at which the moisture absorption capacity is regenerated. The power supply 6 receives a signal from the timer 7 and periodically supplies power to the heater 5 at regular time intervals.
[0028]
In the above configuration, the moisture absorbing means 1 absorbs moisture of the atmosphere and keeps the inside of the casing 109 at a low humidity. However, if the moisture absorption amount is saturated, the moisture absorbing ability is lost, and the humidity inside the casing 109 is kept at a low humidity. Disappear. However, the moisture absorption means 1 is heated to release the moisture absorbed, thereby regenerating the moisture absorption capacity. Although the temperature which the moisture absorption means 1 reproduces changes with materials, the range of 100 to 150 degreeC is suitable in the case of a silica gel. The time interval of the timer 7 varies depending on the amount of silica gel to be used, but when about 1 g of silica gel is used as the moisture absorption means 1, 6 hours to 12 hours are desirable. As described above, by regenerating the moisture absorbing means 1, the humidity inside the casing 109 can be kept low for a long period of time, and malfunction of the gas sensitive unit 101 can be prevented.
[0029]
【The invention's effect】
As described above, according to the present invention, the hygroscopic material is higher than the measurement atmosphere so as to improve the hygroscopic property with respect to the relative humidity change by the hygroscopic material heating means and prevent the humidity change in the casing and the malfunction of the sensitive part. By using the hygroscopic material in the relative humidity range of the atmosphere that has excellent moisture absorption characteristics against changes in relative humidity by heating to a temperature, it is possible to obtain the optimum moisture absorption capacity in the humidity range of the atmosphere used. The humidity inside the casing can be kept constant with a smaller amount of hygroscopic material, and an advantageous effect that malfunction due to the humidity of the sensitive part can be prevented can be obtained.
[Brief description of the drawings]
1 is a cross-sectional view showing the structure of a sensing element according to Reference Example 1 of the present invention. FIG. 2 is a cross-sectional view showing the structure of a sensing element according to Reference Example 2. FIG. 3 is a graph showing the moisture absorption characteristics of the moisture absorbing means. 4 is a cross-sectional view showing the structure of the sensing element according to Example 1 of the present invention. FIG. 5 is a graph showing the moisture absorption characteristics of the moisture absorbent material. FIG. 6 is a cross-sectional view showing the structure of the sensing element according to Reference Example 3 . 7] Graph showing the temperature of the hygroscopic material [FIG. 8] Cross-sectional view showing the structure of the sensing element according to Reference Example 4 [FIG. 9] Cross-sectional view showing the structure of the conventional sensing element
DESCRIPTION OF SYMBOLS 1 Moisture absorption means 3 Silica gel particle 5 Heater 6 Power supply 7 Timer 101 Gas sensitive part 102 Heating part 109 Housing 110 Opening part

Claims (1)

In a sensing element having a sensitive part and a casing having a sensitive part and having an opening, a moisture absorbing material is provided so as to cover a part or all of the opening, so that the moisture absorption characteristics with respect to changes in relative humidity are excellent. By installing a hygroscopic material heating means in the hygroscopic material to heat the hygroscopic material to a temperature higher than the measurement atmosphere so as to prevent the humidity change of the sensitive part and preventing malfunction of the sensitive part, and heating the hygroscopic material , A sensing element using the moisture absorbing material in a relative humidity range of an atmosphere having excellent moisture absorption characteristics with respect to a change in relative humidity .

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