JP4401445B2 - Sensing element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sensing element used in a place for measuring and controlling environments such as facility horticulture, environmental hygiene, disaster prevention, industrial use, building use, and house use.
[0002]
[Prior art]
Hereinafter, the detection element will be described with reference to FIG. 10, 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 a substrate 103 provided with a heating part 102 on one side lower part, and the lead wires 105a and 105b for taking out outputs from the electrodes 104a and 104b and the heating part 102 It is fixed to the lower pedestal 108 via lead pins 107a, 107b, 107c, 107d connected to the extracted 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. A silica gel filter 111 is fixed between the upper and lower metal meshes as fixing means 112 inside the casing 109 as a removing means for removing the interfering gas in the measurement atmosphere.
[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]
And even if interference gas or water vapor that is a disturbing component in the atmosphere enters the housing 109 through the opening 110, it is adsorbed by the silica gel filter 111, reducing the reaction of the interference gas to the gas sensitive part 101, The malfunction was prevented.
[0006]
[Problems to be solved by the invention]
In such a conventional detection element, the removing means adsorbs interfering components such as water vapor and gas in the atmosphere, and when the state of the atmosphere changes, the adsorbing substance is absorbed and released from the removing means according to the change. There is a problem that the sensitive part malfunctions due to the substance absorbed and released from the removing means, and it is required to prevent this malfunction.
[0007]
The present invention solves such a conventional problem, and can reduce the influence on the sensitive part even when the state of the atmosphere changes and the adsorbed substance is absorbed and released from the removing means, Even when the removing means is mechanically damaged or contaminated from the outside, the clogging of the disturbing component inflow restricting means can be prevented, and the change of the removing means is protected from the change of the atmospheric condition and the adsorbed substance is absorbed. It is an object of the present invention to provide a sensing element that can suppress emission and prevent absorption and emission of interfering components by making the operation state of the removing means steady.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the sensing element of the present invention includes a sensitive part whose resistance value changes according to the concentration of the detection target gas, a heating part that heats the sensitive part to a measurement temperature, and the sensitive part. A sensing element having a casing having an opening and a removing unit that reversibly adsorbs and removes a disturbing component of a measurement atmosphere in a form covering a part or all of the opening or inside the casing. In this embodiment, an interference component inflow restricting means is provided between the removing means and the sensitive part.
[0009]
According to the present invention, it is possible to obtain a sensing element that can alleviate the influence of the absorption and release of the disturbing component from the removing means due to the change of the atmosphere on the sensitive part, and can prevent malfunction when the atmosphere state changes.
[0010]
The other means is a means for preventing clogging between the removing means and the disturbing component inflow restricting means.
[0011]
According to the present invention, it is possible to obtain a detecting element that can prevent clogging of the disturbing component inflow restricting means even when the removing means is mechanically damaged or when dirt is mixed from the outside.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The present invention includes a sensing portion whose resistance value depending on the concentration of the detection target gas changes, a heating unit for heating the sensitive part to measure temperature, and today the body with the sensitive part encloses an opening, said opening the shape covering a part or all of the parts, or, the today internalization, in the detection device and a removal means for removing adsorbed reversibly adsorb interfering component of the measured atmosphere before Symbol removing means and the sensing unit By providing an opening as an interfering component inflow restricting means , and actively absorbing and releasing the adsorbed material from the removing means due to the change in atmosphere to the sensitive part with the atmosphere outside the housing. It has the effect of mitigating the influence on the sensitive part inside the casing.
[0019]
Also, a clogging prevention means is provided between the removing means and the disturbing component inflow restricting means, and the disturbing component is provided even when the removing means is mechanically damaged or contaminated from the outside. Clogging of the inflow restricting means can be prevented.
[0023]
Embodiments of the present invention will be described below with reference to the drawings.
[0024]
【Example】
Example 1
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
[0025]
In addition, the same part as a prior art example attaches | subjects the same number, and abbreviate | omits description.
As shown in FIG. 1, an inflow restricting plate 1 provided with a pinhole 2 as a disturbing component inflow restricting means is fixed by a fixing means 3 between a silica gel filter 111 and a sensitive part 101. With the above configuration, the silica gel filter 111 absorbs and releases moisture adsorbed due to a change in ambient temperature. Moisture is absorbed and released from the atmosphere through the opening 110 or from the inside of the casing 109 through the pinhole 2 of the inflow restricting plate 1. However, since the absorption and release of moisture into the casing 109 is limited by the inflow restricting plate 1, the silica gel filter 111 performs most of the absorption and release with the atmosphere. Therefore, the inside of the humidity change today body 109 is minimized, it is possible to suppress a malfunction due moisture absorption released from silica gel filter 111 in the gas sensing portion 101 as shown in FIG.
[0026]
In addition, since the gas flow into the housing 109 is restricted by the pinhole 2, the short-term malfunction of the gas sensitive part 101 due to abrupt generation of the disturbing gas component that cannot be removed by the silica gel filter 111 is suppressed. be able to.
[0027]
In this embodiment, the dimensions of the inflow restricting plate 1 and the pinhole 2 are not particularly limited. However, the pinhole 2 of the inflow restricting plate 1 has an amount of silica gel filter 111, a volume inside the casing 109, and a gas sensitivity. It is determined by the sensitivity of the unit 101 to water vapor, the sensitivity to the detection gas, or the responsiveness. For example, if the gas sensor used in this embodiment, indicates the amount of related malfunctions for the pin hole diameter in FIG. When the silica gel filter 111 is about 1 g and the volume of the casing 109 is about 1000 mm ³ , the effect is hardly obtained when the hole diameter of the pinhole 2 is 3 mm or more. In addition, the error amount becomes half or less at 2 mm or less. Furthermore, if it is 0.1 mm or less, the sensitivity and response of the detection gas are lowered, so a range of 1 mm or less and 0.3 mm or more is desirable.
[0028]
Further, the inflow restricting plate 1 may have a plurality of pinholes 2 and need not be circular in shape, so that there is no difference in the function and effect.
[0029]
Further, as the disturbing component inflow restricting means, the pinhole 2 and the inflow restricting plate 1 are used in this embodiment. However, the disturbing component inflow restricting means is present between the removing means and the sensitive part and has an opening corresponding to the pinhole 2 in the present embodiment. as shown in FIG. 4 as long as the configuration using the gap between today body 109 and the inlet restrictor plate 1 constitutes an inflow restriction plate 1 two by a plate in the gap, such as any such one utilizing the configuration Similar effects can be obtained.
[0030]
Furthermore, in this example, moisture was absorbed and released due to changes in the temperature of the atmosphere, but there were gas components such as aldehydes, alcohols, hydrocarbons, nitrogen oxides, sulfides, and volatile organic compounds as disturbing components. The same effect can be obtained as long as it is a component that can be reversibly absorbed and released by a typical adsorption.
[0031]
Furthermore, the same action and effect as moisture can be obtained in the release from dirt such as oil and tobacco dust adhering to the removing means.
[0032]
Further, although the change in the atmosphere is the temperature, the same effect can be obtained for the absorption and release of the disturbing component due to the change in the wind speed, the pressure and the gas concentration.
[0033]
Further, although the silica gel filter is used as the removing means, the same effects can be obtained if a material that reversibly absorbs and desorbs the disturbing component is used . For example, when the removal means of activated carbon, as an interference component to be adsorbed, alcohol, volatile organic compounds, nitrogen oxides, hydrocarbons, water, dirt Jani such other oils and tobacco are considered, the absorption and release Temperature and wind speed can be considered as changes in the atmosphere.
[0034]
The same applies to the removal means based on zeolite.
In addition, there is no problem with the disturbing component and the removal means that are caused by irreversible adsorption because there is almost no absorption / release amount due to the change in atmosphere, and there is no malfunction due to the disturbing component.
[0035]
However, even in the case of chemical adsorption, the same effects as in the present embodiment can be obtained if the temperature of the atmosphere changes to the conditions under which the adsorbed material is desorbed.
[0036]
In addition, although a heating drive type gas sensor is used as the detection element, a polymer type or a heating drive type humidity sensor, a solid electrolyte type gas sensor, a biosensor, etc., as long as the detection element can cause a malfunction due to the above-described interference component. There is no difference in the function and effect of any method and detection element to be detected.
[0037]
(Example 2)
FIG. 5 shows the configuration of the second embodiment of the present invention. The same parts as those in the conventional example and the first embodiment of the present invention are designated by the same reference numerals and the description thereof is omitted.
[0038]
In FIG. 5, a metal mesh plate 4 is fixed by a fixing means 112 between the silica gel filter 111 and the inflow restricting plate 1 as a clogging preventing means.
[0039]
With the above configuration, even when the silica gel filter 111 is damaged by vibration or impact, the broken pieces and broken powder are prevented from dropping onto the inflow restricting plate 1 and also due to dirt, oil, dust, etc. from the atmosphere. Clogging of the pinhole 2 can be prevented.
[0040]
In the present embodiment, the metal mesh plate 4 is used as the clogging preventing means. However, if the silica gel filter is broken or the gas passes through without passing through the powder, the filter material for dust prevention such as resin or fiber is used. , No difference in its effects.
[0041]
( Reference Example 1 )
FIG. 6 shows the configuration of the first reference example. The same parts as those of the conventional example and the first and second embodiments of the present invention are designated by the same reference numerals, and the description thereof is omitted.
[0042]
In FIG. 6, the activated carbon sheet 5 is fixed to the lower part of the inflow restricting plate 1 by the fixing means 6 as the disturbing component adsorbing means.
[0043]
With the above configuration, the interference component that has passed through the inflow restricting plate 1 is adsorbed and removed by the activated carbon sheet 5, so that the interference component can be prevented from entering the housing 109. Can be prevented. Further, this effect can be obtained not only for the disturbing components such as gas and moisture emitted from the silica gel filter 111 but also for the disturbing components that have passed without being removed by the silica gel filter 111. FIG. 7 shows the sensitivity to CO ₂ and ethanol with and without the activated carbon sheet 5. As shown in the figure, the sensitivity to alcohol is greatly improved. Moreover, since the trace amount interference component after passing through the silica gel filter 111 and the inflow restricting plate 1 is adsorbed by the activated carbon sheet 5, there is an effect that the adsorption performance of the activated carbon sheet 5 can be maintained over a long period of time.
[0044]
In this reference example, the activated carbon sheet 5 is used as the disturbing component adsorbing means, but the same effect can be obtained as long as the material adsorbs the disturbing component such as silica gel and zeolite.
[0045]
( Reference Example 2 )
FIG. 8 shows the configuration of the second reference example. The same parts as those of the conventional example, the first and second embodiments of the present invention , and the first reference example are denoted by the same reference numerals, and description thereof is omitted.
[0046]
A thermal insulation cap 7 made of styrene foam is installed so as to cover the casing 109 as a relaxation means for relaxing the temperature change of the silica gel filter 111 due to a change in ambient temperature.
[0047]
With the above configuration, even when the temperature of the atmosphere changes, the temperature change of the silica gel filter 111 is reduced, and moisture absorption / release from the silica gel filter 111 due to the temperature change is suppressed. As a result, the humidity change inside the casing 109 is reduced, and the malfunction of the gas sensitive part is reduced. In addition, since the influence of the wind speed of the atmosphere can be mitigated at the same time by the heat insulating cap 7, it is possible to prevent moisture from being absorbed and released from the silica gel filter 111 by the wind.
[0048]
In this reference example, the heat insulating cap 7 is made of styrene foam as a relaxation means. However, any material and configuration having a heat insulating effect may be used, and there is no difference in the function and effect.
[0049]
In this reference example, the change in atmosphere is assumed to be a change in temperature, but the change in atmosphere to be mitigated varies depending on the material of the removal means and the type of interfering component, but the effect varies depending on the temperature, humidity, wind speed, gas concentration, etc. There is no difference.
[0050]
( Reference Example 3 )
FIG. 9 shows the configuration of the third reference example. The same parts as those of the conventional example and the first and second embodiments, the first and second reference examples of the present invention are designated by the same reference numerals, and the description thereof is omitted.
[0051]
As an operation state stabilizing means, a heater 8 and a temperature measuring means 9 are installed inside the silica gel filter 111, and the heater 8 receives power supply from the control means 10 and heats the silica gel filter 111. The control means 10 receives the signal from the temperature measuring means 9 and adjusts the power supplied to the heater 8 so that the temperature of the silica gel filter 111 becomes constant.
[0052]
With the above configuration, since the temperature of the silica gel filter 111 is always kept constant regardless of the temperature of the atmosphere, moisture absorption / release due to temperature change can be prevented. As a result, the humidity change inside the casing 109 due to the temperature change can be prevented, and malfunction of the gas sensitive unit 101 can be prevented.
[0053]
【The invention's effect】
As described above, according to the present invention, a sensitive part whose resistance value changes according to the concentration of the gas to be detected, a heating part that heats the sensitive part to a measurement temperature, and an opening that includes the sensitive part. In the detection element having a housing and a removing unit that reversibly adsorbs and removes a disturbing component of the measurement atmosphere in a form that covers a part or all of the opening or inside the housing. by providing those having an opening as an interfering component flowing limiting means between means and said sensitive part, it can be prevented from malfunctioning due to absorption and desorption of interfering substances from the removal means when the atmosphere is changed further by removing means An advantageous effect is obtained in that the influence of the disturbing component that cannot be removed and the pollutant in the atmosphere on the sensitive part can be suppressed, and the malfunction can be reduced.
[0054]
In addition, by providing a clogging prevention means between the removing means and the disturbing component inflow restricting means, it is possible to prevent clogging of the disturbing component inflow restricting means due to mechanical damage of the removing means and external contamination, and reliable over a long period of time. The effect which can provide a highly sensitive sensing element is acquired.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a sensing element according to Example 1 of the present invention. FIG. 2 is a graph showing a relationship between a pinhole diameter and an error of the sensing element. utilizing the gap between today body in cross-section (inlet restriction plate one showing an example of a configuration of the interference gas inflow limiting means sensing device according to an embodiment 1 of the graph 4 (a) the present invention showing the ambient temperature characteristics if you did this)
(B) Sectional view showing an example of the configuration of the interference gas inflow restricting means of the sensing element according to Embodiment 1 of the present invention (in the case of two inflow restricting plates)
5 is a cross-sectional view showing the structure of a sensing element according to Example 2 of the present invention. FIG. 6 is a cross-sectional view showing the structure of the sensing element according to Reference Example 1. FIG. 8 is a cross-sectional view showing the structure of a sensing element according to Reference Example 2. FIG. 9 is a cross-sectional view showing the structure of a sensing element according to Reference Example 3. FIG. 10 is a cross-sectional view showing the structure of a conventional sensing element. ]
DESCRIPTION OF SYMBOLS 1 Inflow restriction board 2 Pinhole 4 Metal mesh board 5 Activated carbon sheet 7 Heat insulation cap 8 Heater 9 Temperature measuring means 10 Control means 101 Sensing part 109 Housing 110 Opening part 111 Silica gel filter

Claims (2)

A sensitive part of the resistance value depending on the concentration of the detection target gas changes, said sensitive part and a heating section for heating the measured temperature, and today the body having an opening and containing the sensitive part, a part of the opening or in the form of covering the whole, or the in today internalization, in the detection device and a removal means for removing adsorbed reversibly adsorb interfering component of the measured atmosphere between the front Symbol removing means and the sensing unit A sensing element provided with an opening as a disturbing component inflow restricting means.    The detecting element according to claim 1, wherein a clogging preventing means is provided between the removing means and the disturbing component inflow restricting means.

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