JP4765856B2 - Humidity sensor - Google Patents

Description

  The present invention relates to a humidity sensor that detects the humidity of the atmosphere surrounding the humidity sensor.

  As this type of humidity sensor, for example, a technique described in Patent Document 1, for example, is known. Conventionally known techniques including this technique will be described.

In the first place, the humidity sensor detects the relative humidity of the atmosphere (air) surrounding the sensor. The wet film must be exposed to air. Therefore, in a conventionally known technique, the sensor element is accommodated in a case for protecting the sensor element, and a case opening for circulating air inside and outside the case is formed in the case. Yes. Furthermore, in order to prevent dust, dust, water droplets, etc. from entering the inside of the case in combination with such air, a porous body formed with a large number of holes that allows air to pass through but does not allow dust, water droplets, etc. to pass through. A quality filter is disposed in the case opening.
Japanese Patent Laid-Open No. 10-142181

  By the way, using such a humidity sensor, for example, when trying to detect the humidity of an atmosphere in which a lot of tiny molecules such as cigarette smoke float, the cigarette smoke (tobacco molecules) passes through the pores of the porous filter, It may adhere to the surface of the sensor element (moisture sensitive film).

  Specifically, as shown in FIGS. 10A and 10B, the moisture-sensitive film has a large number of pores that open on the surface of the moisture-sensitive film and reach the inside of the moisture-sensitive film. Usually, dust, dust, water droplets, or the like that try to enter the case together with the air are captured and removed by the porous filter, and only air and water molecules contained in the air enter the case. The water molecules having conductivity enter the inside through the pore openings of the moisture sensitive film and adhere to the inner surface of the pores, or adhere to the surface of the moisture sensitive film, so that the dielectric constant of the moisture sensitive film is increased. Will change. That is, the dielectric constant of the moisture sensitive film changes according to the relative humidity of the air (the number of water molecules contained in the air). In this way, a change in the relative humidity of air is detected based on a change in dielectric constant (capacitance).

  However, when detecting the humidity of the atmosphere in which the tobacco molecules are floating, the tobacco molecules are extremely small, so they are not trapped or excluded by the porous filter, and are combined with the water molecules contained in the air inside the case. enter in. Then, as shown in FIG. 10 (a), the tobacco molecules that have entered the inside of the case enter the pores of the moisture sensitive film before the water molecules, and further, open the pore openings of the moisture sensitive membrane. May be blocked. When the opening of the moisture sensitive film pores is blocked with tobacco molecules, water molecules cannot adhere to the inner surface of the moisture sensitive film pores, and the dielectric constant of the moisture sensitive film decreases. End up. And even if the air actually has the same humidity, the electric capacity may be small.

  Conversely, the tobacco molecules that have entered the case together with the water molecules contained in the air enter the pores of the moisture-sensitive film before the water molecules, as shown in FIG. In some cases, more water molecules are adsorbed and adhered to the inner surface of the pores of the moisture sensitive film. If more water molecules adhere to the inner surface of the pores of the moisture sensitive film in this way, the dielectric constant of the moisture sensitive film increases, and even if the air actually has the same relative humidity, Capacity may increase.

  Specifically, the relationship between the output of the humidity sensor and the relative humidity is shown in FIG. As shown in FIG. 11, when the number of tobacco molecules floating in the atmosphere is small, the humidity sensor has a relationship between the sensor output shown as a straight line A and the relative humidity, for example. On the other hand, when the number of tobacco molecules floating in the atmosphere is large and the adsorption of water molecules to the inner surface of the pores of the moisture-sensitive film is suppressed by the tobacco molecules, the humidity sensor is relative to the sensor output indicated as a straight line B, for example. Take a relationship with humidity. On the other hand, when the number of tobacco molecules floating in the atmosphere is large and the adsorption of water molecules to the inner surface of the pores of the moisture sensitive film is promoted by the tobacco molecules, the humidity sensor, for example, outputs the sensor output and the relative humidity shown as a straight line C Take a relationship with. Here, for example, if the sensor output of the humidity sensor is “Vh”, when the number of tobacco molecules floating in the atmosphere is small, the relative humidity is detected as “Rha” and the tobacco floating in the atmosphere is detected. When the number of molecules is large, the relative humidity is detected as “Rhb” or “Rhc”. As described above, there is a concern that the detection accuracy according to the relative humidity of the atmosphere is lowered.

  In order to block the opening of the pores of the moisture-sensitive membrane or to attach tobacco molecules to the inner surface of the pores, for example, capture the size of numerous pores formed in the porous filter. -It is possible to make it small enough to be removed. However, the diameter of the tobacco molecule is approximately “0.4 nm”, which is very small. When such a porous filter capable of capturing and removing extremely small tobacco molecules is used, there is a concern that air circulation inside and outside the humidity sensor may be delayed and the responsiveness of the sensor may be deteriorated. Furthermore, the porous filter is likely to be clogged.

  Although a so-called capacitive humidity sensor that detects changes in the relative humidity of the atmosphere based on changes in the dielectric constant (capacitance) of the moisture sensitive film has been described, the relative humidity of the atmosphere is determined based on changes in the impedance of the moisture sensitive film. The situation described above can also occur in a so-called resistance humidity sensor that detects a change.

  The present invention has been made in view of the above circumstances, and its purpose is to detect the relative humidity with high reliability even in an atmosphere in which a large number of extremely small molecules such as tobacco molecules are floating. It is to provide a humidity sensor that can be used.

  In order to achieve such an object, in the invention described in claim 1, a moisture-sensitive film in which a plurality of pores reaching the inside while opening on the surface is formed, and a surface including the inner surface of the pores of the moisture-sensitive film is provided. A humidity detecting element having a pair of electrodes for detecting a physical quantity of the moisture sensitive film that changes due to moisture adsorption, and an opening for accommodating the humidity detecting element inside and for circulating air inside and outside A photocatalytic filter, which is a porous filter coated with a photocatalyst, as a humidity sensor including a case in which a first case opening that is a portion is formed. It was decided to prepare for the case opening.

  First, the photocatalyst will be described. When light (especially ultraviolet light) is irradiated onto the photocatalyst, electrons are ejected from the surface of the photocatalyst, and the holes of the photocatalyst formed by the ejection of the electrons become positively charged holes. These holes have a strong oxidizing power and take electrons from nearby organic substances. By depriving the electrons in this way, the organic substance is known to break the bonds between the molecules forming the organic substance, eventually becoming carbon dioxide and water, and diverge into the atmosphere. It has been. Tobacco molecules (such as nicotine) are also organic substances.

  In the above-described configuration as the humidity sensor, the tobacco molecules are attracted to the photocatalyst having a positive charge and decomposed when passing through the photocatalytic filter together with air. That is, no matter how small the tobacco molecules are, the tobacco molecules are captured and eliminated by the photocatalytic filter, and are prevented from entering into the case together with the water molecules contained in the air. Therefore, even if the humidity sensor is in an atmosphere in which a large number of tobacco molecules are floating, the change in the characteristics of the moisture sensitive film as described in the column of problems can be reduced. As a result, even in an atmosphere where a lot of extremely small molecules such as tobacco molecules are floating, the relative humidity can be detected with high reliability.

  In such a configuration, the photocatalytic filter can be configured by spraying and coating the photocatalyst on the porous filter, for example, as in the invention described in claim 2. In addition, as such a photocatalyst, for example, titanium oxide (TiO 2) can be employed as in the invention described in claim 3.

  Moreover, in the structure in any one of Claims 1-3, in invention of Claim 4, for example, a recessed part is formed in the periphery of the said 1st case opening part of the said case, and it respond | corresponds to the said recessed part of the said case The photocatalytic filter is configured to have a frame member having a convex portion, and the photocatalytic filter is fixed to the case by press-fitting the convex portion of the frame member into the concave portion of the case. It was. Thereby, the humidity sensor can be realized with a simple configuration.

  In the configuration according to claim 4, for example, as in the invention according to claim 5, an adhesive is applied to the concave portion of the case, and the convex portion of the frame member and the concave portion of the case are The adhesive may be used for adhesion. Thereby, since the coupling | bonding of the said frame member and the said case is strengthened, it becomes difficult to form a clearance gap between these. As a result, the entry of tobacco molecules into the case through the gap between them is reduced, and the relative humidity of the atmosphere can be detected with higher reliability.

  On the other hand, in the configuration according to any one of claims 1 to 3, for example, in the invention according to claim 6, a protrusion is formed on a peripheral edge of the first case opening of the case, and is shorter than the length of the protrusion. The photocatalytic filter is configured by having a frame member in which a through hole is formed corresponding to the protrusion, and the photocatalytic filter is formed by caulking the protrusion of the case through the through hole of the frame member. The case was fixed. This also makes it possible to strengthen the coupling between the photocatalytic filter and the case.

  In the configuration according to any one of claims 4 to 6, for example, in the invention according to claim 7, a second case opening that is an opening for circulating air inside and outside is formed in the case, The photocatalytic filter is also provided in the second case opening. Thereby, since the opening area for circulating air increases, it becomes possible to detect the relative humidity of the atmosphere with higher reliability and higher responsiveness.

  Moreover, in the structure in any one of Claims 1-7, if a photocatalyst is coated on the whole case surface, for example according to the invention described in Claim 8, more tobacco molecules floating in the atmosphere are decomposed. Therefore, the reliability in detecting the relative humidity of an atmosphere in which a large number of extremely small molecules such as tobacco molecules are floating can be further improved.

  For example, as in the invention described in claim 9, the dielectric constant of the moisture-sensitive film changes according to humidity, and the humidity sensor is based on a change in dielectric constant of the moisture-sensitive film. It can be configured as a capacitive humidity sensor that detects humidity.

(First embodiment)
A humidity sensor according to a first embodiment of the present invention will be described below with reference to FIG. The humidity sensor according to the present embodiment covers the case opening with a photocatalyst filter coated with a photocatalyst made of, for example, titanium oxide (TiO2) sprayed onto the porous filter, as will be described in detail below. And provided in the case opening. This makes it possible to detect the relative humidity with high reliability even in an atmosphere in which many small molecules such as tobacco molecules are floating.

  FIG. 1A is a plan view showing a planar structure of the present embodiment. Moreover, FIG.1 (b) is a partial side sectional view which shows the side structure of the embodiment, and FIG.1 (c) is an exploded view of FIG.1 (b). As shown in FIGS. 1 (a) to 1 (c), the humidity sensor 10 of the present embodiment basically has the humidity detecting element 20 and the lead terminal 30 formed in, for example, a bottomed rectangular tube shape. The case 11 is provided on the inner bottom surface.

  Among these, as shown in FIGS. 1A to 1C, the humidity detecting element 20 is placed on the inner bottom surface of the case 11 and is separated on the same plane on the substrate 21 made of, for example, silicon. A pair of electrodes 22a and 22b arranged opposite to each other, a dielectric constant (physical quantity) changes according to a change in humidity of an atmosphere surrounding the humidity sensor 10, and a pair of electrodes 22a and 22b and a moisture sensitive film 23 covering the electrodes. And a humidity detector 24 having the following. The humidity sensor 10 also includes a circuit unit 25 on the substrate 21 that detects the relative humidity of the atmosphere based on a change in capacitance between the electrodes 22 a and 22 b in the humidity detection element 20.

  In addition, although the shape of a pair of electrode 22a and 22b is not specifically limited, In this Embodiment, as shown to Fig.1 (a), the comb-tooth shape is employ | adopted. As a result, the arrangement area of the humidity detector 24 can be reduced, and the area where the pair of electrodes 22a and 22b face each other can be increased, and the capacitance between these electrodes that changes as the humidity of the atmosphere changes. The amount of change increases. As a result, the sensitivity concerning the humidity detection of the humidity sensor 10 is improved. Further, since the detection principle of such a capacitive humidity sensor is generally known, a detailed description thereof is omitted here.

  On the other hand, as shown in FIGS. 1A to 1C, the lead terminal 30 is formed in, for example, a substantially rectangular shape, and a plurality of (two in this embodiment) are provided at one end of the case 11 with a predetermined number. The case 11 is arranged at intervals and is provided in the case 11 so as to penetrate the side wall of the case 11. The plurality of lead terminals 30 are electrically connected to a pad portion (not shown) made of aluminum, for example, of the circuit portion 25 via bonding wires 31. Then, information on the relative humidity of the atmosphere obtained through the circuit unit 25 is sequentially transmitted as “circuit unit 25 (precisely pad portion) → bonding wire 31 → lead terminal 30”, and is output to the outside of the humidity sensor 10. .

  Here, as shown in FIGS. 1B and 1C, the case 11 is formed, for example, in the shape of a bottomed rectangular tube having a case opening 11a opened upward. In the first place, the humidity sensor 10 detects the relative humidity of the atmosphere (air) surrounding the humidity sensor 10. Therefore, the humidity detection element 20 that is the detection unit of the humidity sensor 10, more precisely, the moisture sensitive film 23 must be exposed to the atmosphere. In addition, such an atmosphere must be exchanged suitably inside and outside the case 11. Therefore, a case opening 11 a for circulating air inside and outside the case 11 is formed on the upper surface of the case 11.

  However, the case opening 11 a becomes a factor that dust, dust, water droplets, or the like enter the case 11 together with the air. Therefore, as shown in FIG. 1, the photocatalytic filter 40 in which a large number of holes of such a size as to allow air to pass therethrough but not allow dust or water droplets to pass through is covered with the case opening 11a. It is provided in the part 11a.

  Specifically, as shown in FIG. 1, a plurality (four in this embodiment) of circular recesses 12 are appropriately disposed on the periphery of the case opening 11a (more precisely, each corner of the case 11). And a suitable diameter. On the other hand, the photocatalytic filter 40 includes an annular frame member 41 having a plurality of (four in the present embodiment) convex portions 42 formed with a height and a diameter corresponding to the concave portion 12 of the case 11 formed in this way. It is configured. The photocatalytic filter 40 is fixed to the upper surface of the case 11 by press-fitting the convex portions 42 of the frame member 41 into the concave portions 12 of the case 11. In this manner, the photocatalytic filter 40 circulates air inside and outside the case 11 and suppresses entry of dust, dirt, water droplets, or the like into the case 11.

  By the way, as described in the problem column, for example, when detecting humidity in an atmosphere in which a lot of tiny molecules such as cigarette smoke float, the photocatalyst is not coated on the porous filter covering the case opening 11a. The following problems may occur.

  That is, the tobacco molecule has a diameter of about “0.4 nm” and is extremely small compared to dust, dust, or water droplets. For this reason, a hole of a size formed for the purpose of capturing / excluding dust, dust or water droplets cannot capture tobacco molecules, and the tobacco molecules enter the case 11 together with water molecules contained in the air. Resulting in.

  Thus, the tobacco molecules that have entered the inside of the case 11 open on the surface of the moisture sensitive film 23 and enter the pores reaching the inside of the moisture sensitive film 23 before entering the water molecules. Furthermore, the pore opening of the moisture sensitive film 23 may be blocked. Thus, if the opening of the pores of the moisture sensitive film 23 is blocked by tobacco molecules, the water molecules cannot adhere to the inner surfaces of the pores of the moisture sensitive film 23, and the moisture sensitive film 23. The dielectric constant is reduced. And even if air actually has the same relative humidity, the electric capacity may become small. Conversely, the tobacco molecules that have entered the case 11 together with the water molecules contained in the air enter the pores of the moisture-sensitive film 23 before the water molecules, and further adsorb more water molecules. In some cases, the moisture sensitive film 23 may adhere to the pore content surface. If more water molecules adhere to the inner surface of the pores of the moisture sensitive film 23 in this way, the dielectric constant of the moisture sensitive film 23 increases, and even if the air actually has the same relative humidity, Capacity may increase. As described above, there is a concern that the detection accuracy according to the relative humidity of the atmosphere is lowered.

  Therefore, the photocatalytic filter 40 of the present embodiment is configured by spraying and coating a porous catalyst with a photocatalyst made of, for example, titanium oxide (TiO 2).

  When the photocatalyst is irradiated with light, particularly ultraviolet light, electrons are ejected from the surface of the photocatalyst. The hole of the photocatalyst formed by the electron jumping out becomes a positively charged hole (hole), has a strong oxidizing power, and deprives the electron from nearby organic matter. By depriving the electrons in this way, the organic substance is disconnected from the bonds between the molecules forming the organic substance, and eventually becomes carbon dioxide and water, and is emitted into the atmosphere. Tobacco molecules (such as nicotine) are also organic substances.

  When the photocatalyst having such a function is coated on the porous filter, when the tobacco molecule tries to pass through the photocatalytic filter 40, the tobacco molecule is attracted to the photocatalyst having a positive charge and decomposed. It will be. That is, even if the humidity sensor is placed in an atmosphere where a large number of tobacco molecules are floating, the tobacco molecules are captured and eliminated by the photocatalytic filter 40 and enter the inside of the case 11 together with the water molecules contained in the air. Is suppressed. As a result, even in an atmosphere where a lot of extremely small molecules such as tobacco molecules are floating, the relative humidity can be detected with high reliability.

  The first embodiment can also be implemented as the following form, for example.

  In the first embodiment, the photocatalytic filter 40 is fixed to the case 11 by press-fitting the convex portions 42 of the frame member 41 into the concave portions 12 of the case 11. The fixing mode is not limited to this. In addition, for example, as shown in FIG. 2 as a view corresponding to FIG. 1C, the adhesive 13 is applied to each concave portion 12 of the case 11, and the convex portion 42 of the frame member 41 and each of the case 11 are applied. The humidity sensor 10a may be configured by fixing the recesses 12 by bonding them with the adhesive 13.

  In the first embodiment, as shown in FIG. 1, a plurality of circular recesses 12 are formed at an appropriate depth and an appropriate diameter on the periphery of the case opening 11 a, and the frame member 41. In addition, the convex portions 42 are formed with a height and a diameter corresponding to each concave portion 12. On the contrary, a plurality of convex portions are formed on the periphery of the case opening with an appropriate depth and an appropriate diameter, and the frame member constituting the photocatalytic filter is recessed with a height and a diameter corresponding to each convex portion. It is good also as forming. Moreover, the shape of such a recessed part and a convex part is not restricted circularly, and is arbitrary.

(Second Embodiment)
Next, a second embodiment of the humidity sensor according to the present invention will be described with reference to FIGS. 3 (a) and 3 (b). In FIG. 3, the same elements as those shown in FIGS. 1 and 2 are denoted by the same reference numerals, and overlapping descriptions of these elements are omitted.

  FIG. 3A is a partial side sectional view showing a side structure of the present embodiment, and FIG. 3B is an exploded view of FIG. As shown in FIGS. 3A and 3B, the present embodiment also has a structure according to the first embodiment. However, in the humidity sensor 10b of the present embodiment, the projection 14 is formed on the periphery of the case opening 11a, and the frame member 41a in which the through hole 43 shorter than the length of the projection 14 is formed corresponding to the projection 14 is provided. And constitute the photocatalytic filter 40a. Then, the photocatalytic filter 40a is fixed to the case 11 by caulking the protrusions 14 of the case 11 through the through holes 43 of the frame member 41a.

  Specifically, as shown in FIG. 3B, a plurality (four in the present embodiment) of circular protrusions 14 are provided on the periphery of the case opening 11a (more precisely, each corner of the case 11). Is formed with a length “L1” and an appropriate diameter, for example. On the other hand, the photocatalytic filter 40a has, for example, a frame member formed with a plurality of through holes 43 having a length “L2” and an appropriate inner diameter (four in the present embodiment) corresponding to the positions where the projections 14 are formed. 41a. Here, the length “L1” of the protrusion 14 is formed longer than the length “L2” of the through hole 43. Therefore, when the protrusion 14 of the case 11 is fitted into the through hole 43 of the frame member 41 a, the tip end portion of the protrusion 14 protrudes from the through hole 43. When only the portion protruding from the through hole 43 of the protrusion 14 is heated, the portion protruding from the through hole 43 of the protrusion 14 is melted and becomes larger than the diameter of the through hole 43 as shown in FIG. Thereby, the part which protruded from the through-hole 43 of the processus | protrusion 14 played the role of the hook, and the processus | protrusion 14 of the case 11 does not escape from the through-hole 43 of the frame member 41a. As a result, the coupling force between the photocatalytic filter 40a and the case 11 can be increased.

(Third embodiment)
Next, a third embodiment of the humidity sensor according to the present invention will be described with reference to FIG. In FIG. 4, the same elements as those shown in FIGS. 1 to 3 are denoted by the same reference numerals, and redundant descriptions of these elements are omitted.

  FIG. 4 is a diagram corresponding to FIG. 1B and is a partial side sectional view showing a side structure of the present embodiment. As shown in FIG. 4, this embodiment also has a structure according to the first embodiment. However, in the humidity sensor 10c of the present embodiment, the photocatalyst is sprayed on the entire surface of the case 11, that is, all components except the humidity detection element 20 and the lead terminal 30, and the coating 50 is formed. Thereby, in addition to the effect of the first embodiment, the following effect can be newly obtained. That is, according to the humidity sensor 10c of the present embodiment, more tobacco molecules floating in the atmosphere surrounding the humidity sensor 10c can be decomposed, so that there are many extremely small molecules such as tobacco molecules. The reliability in detecting the relative humidity of the floating atmosphere can be further enhanced.

  In addition, the said 3rd Embodiment can also be implemented as the following forms, for example according to the previous 1st Embodiment.

  In the third embodiment, the photocatalytic filter 40 is fixed to the case 11 by press-fitting the convex portions 42 of the frame member 41 into the concave portions 12 of the case 11. The fixing mode is not limited to this. In addition, for example, as shown in FIG. 5 as a diagram corresponding to FIG. 4, the adhesive 13 is applied to each concave portion 12 of the case 11, and the convex portion 42 of the frame member 41 and each concave portion 12 of the case 11 are The humidity sensor 10d may be configured by fixing them with the adhesive 13.

  In the third embodiment, as shown in FIG. 4, a plurality of circular recesses 12 are formed at an appropriate depth and an appropriate diameter on the periphery of the case opening 11 a, and the frame member 41. In addition, the convex portions 42 are formed with a height and a diameter corresponding to each concave portion 12. Conversely, a plurality of circular convex portions are formed with appropriate depth and appropriate diameter on the periphery of the case opening, and the height and diameter corresponding to each convex portion are formed on the frame member constituting the photocatalytic filter. It is good also as forming a recessed part in. Moreover, the shape of such a recessed part and a convex part is not restricted circularly, and is arbitrary.

(Fourth embodiment)
Next, a fourth embodiment of the humidity sensor according to the present invention will be described with reference to FIG. In FIG. 6, the same elements as those shown in FIGS. 1 to 5 are denoted by the same reference numerals, and overlapping descriptions of these elements are omitted.

  FIG. 6 is a partial side cross-sectional view corresponding to FIG. 3A and showing the side cross-sectional structure of the present embodiment. As shown in FIG. 6, this embodiment also has a structure according to the second and third embodiments. That is, as shown in FIG. 6, in the humidity sensor 10 e of the present embodiment, the protrusion 14 is formed on the periphery of the case opening 11 a, and the through hole 43 shorter than the length of the protrusion 14 corresponds to the protrusion 14. The photocatalytic filter 40a is configured by having the frame member 41a formed in this manner. Then, the photocatalytic filter 40a is fixed to the case 11 by caulking the protrusions 14 of the case 11 through the through holes 43 of the frame member 41a. Further, the photocatalyst is sprayed on the entire surface of the case 11, that is, all the components except the humidity detecting element 20 and the lead terminal 30, and the coating 50 is made. Thereby, the effect according to the effect of previous 2nd and 3rd embodiment comes to be acquired.

(Fifth embodiment)
Next, a fifth embodiment of the humidity sensor according to the present invention will be described with reference to FIGS. In FIG. 7, the same elements as those shown in FIGS. 1 to 6 are denoted by the same reference numerals, and redundant descriptions of these elements are omitted.

  FIG. 7A is a plan view showing a planar structure of the present embodiment. Moreover, FIG.7 (b) is a partial side sectional view which shows the side structure of the embodiment, and FIG.7 (c) is a figure which shows the planar structure of the embodiment from the back side. As shown in FIGS. 7A to 7C, this embodiment also has a structure according to the first embodiment. However, in the humidity sensor 10f of the present embodiment, not only the (first) case opening 16a for circulating air inside and outside is formed on the front side of the case 16, but also on the back side of the case 16. Also, a (second) case opening 16b for allowing air to flow inside and outside is formed. The photocatalytic filters 40 and 45 are provided in the two case openings 16a and 16b, respectively, so as to cover the two case openings 16a and 16b, respectively.

  Specifically, as shown in FIGS. 7A and 7B, the case 16 is formed, for example, in a bottomed rectangular tube shape having a case opening 16a that is open upward. Further, as shown in FIG. 7C, the case 16 has a case opening 16b formed of a plurality of (for example, four in the present embodiment) openings having a rectangular shape on the inner bottom surface. By forming the case opening 16b in such a shape, air can be further circulated in and out of the case 16, and the humidity detecting element 20 can be stably supported in the case 16.

  By the way, such a case opening 16b becomes a factor that dust, dust, water droplets or the like enter the case 16 together with air. Therefore, as shown in FIG. 7 (c), the photocatalytic filter 45 in which a large number of holes of a size that does not allow passage of air and dust, water droplets, etc. is formed covers the case opening 16b. And provided in the case opening 16b.

  However, as described in the description of the first embodiment and as described in the section of the problem, if the photocatalyst is not coated on the porous filter covering the case opening 16b, for example, tobacco smoke If an attempt is made to detect the humidity of an atmosphere in which a number of extremely small molecules float, there is a concern that the detection accuracy relating to the relative humidity of the atmosphere may be reduced. Therefore, in the humidity sensor 10f according to the present embodiment, the photocatalyst filter 45 in which a photocatalyst made of, for example, titanium oxide (TiO2) is sprayed onto the porous filter and coated is covered with the case opening 16b. 16b. Thereby, while the effect according to the effect of 1st Embodiment is acquired, since the opening area for distribute | circulating air increases, the relative humidity of atmosphere is detected with higher reliability and high responsiveness. Will be able to.

  Note that the fifth embodiment can also be implemented as, for example, the following forms.

  In the fifth embodiment, the photocatalytic filter 40 is fixed to the case 16 by press-fitting the convex portions 42 of the frame member 41 into the concave portions 17 of the case 16. The fixing mode is not limited to this. In addition, for example, as shown in FIG. 8 as a diagram corresponding to FIG. 7B, the adhesive 18 is applied to each concave portion 12 of the case 16, and the convex portion 42 of the frame member 41 and each of the case 16 are applied. The humidity sensor 10g may be configured by fixing the concave portion 17 with the adhesive 18 to fix them.

(Sixth embodiment)
Next, a sixth embodiment of the humidity sensor according to the present invention will be described with reference to FIG. In FIG. 9, the same elements as those shown in FIGS. 1 to 8 are denoted by the same reference numerals, and redundant descriptions of these elements are omitted.

  FIG. 9 is a partial side sectional view showing the side structure of the present embodiment. As shown in FIG. 9, this embodiment also conforms to the second embodiment shown in FIG. 3A and the fourth embodiment shown in FIG. It has a structure. That is, in the humidity sensor 10h of the present embodiment, the projection 19 is formed on the periphery of the case opening 16a, and the frame member 41a in which the through hole 43 shorter than the length of the projection 19 is formed corresponding to the projection 19 is provided. And constitute the photocatalytic filter 40a. Then, the photocatalytic filter 40a is fixed to the case 16 by caulking the protrusions 19 of the case 16 via the through holes 43 of the frame member 41a. A case opening 16b for allowing air to flow inside and outside is also formed on the back side of the case 16, and the photocatalytic filter 45 is provided in the case opening 16b so as to cover the case opening 16b. Thereby, the effect according to the second embodiment and the fourth embodiment is obtained.

(Seventh embodiment)
Next, a seventh embodiment of the humidity sensor according to the present invention will be described. This embodiment has a structure according to the third embodiment shown in FIG. 4 and the fifth embodiment shown in FIGS. 7A to 7C.

  That is, as shown in FIG. 7, in the humidity sensor 10 i of the present embodiment, a (first) case opening 16 a for allowing air to flow inside and outside is formed on the surface side of the case 16. In addition, a (second) case opening 16b for allowing air to flow inside and outside is also formed on the back side of the case 16. The photocatalytic filters 40 and 45 are provided in the two case openings 16a and 16b, respectively, so as to cover the two case openings 16a and 16b, respectively. In addition, the photocatalyst is sprayed on the entire surface of the case 16, that is, all components except the humidity detection element 20 and the lead terminal 30, so that the coating 50 is formed. As a result, the effects of the third and fifth embodiments can be obtained.

  Note that the seventh embodiment can also be implemented as, for example, the following forms.

  In the seventh embodiment, the photocatalytic filter 40 is fixed to the case 16 by press-fitting the convex portions 42 of the frame member 41 into the concave portions 17 of the case 16. The fixing mode is not limited to this. In addition, for example, as shown in FIG. 8, the adhesive 18 is applied to each concave portion 12 of the case 16, and the convex portion 42 of the frame member 41 and each concave portion 17 of the case 16 are bonded by this adhesive 18. Then, these may be fixed and the humidity sensor 10j may be configured.

(Eighth embodiment)
Next, an eighth embodiment of the humidity sensor according to the present invention will be described. This embodiment has a structure according to the fourth embodiment shown in FIG. 6 and the sixth embodiment shown in FIG.

  That is, as shown in FIG. 9, in the humidity sensor 10 k of the present embodiment, a (first) case opening 16 a for allowing air to flow inside and outside is formed on the surface side of the case 16. In addition, a (second) case opening 16b for allowing air to flow inside and outside is also formed on the back side of the case 16. The photocatalytic filters 40a and 45 are provided in the case openings 16a and 16b, respectively, in a state of covering the case openings 16a and 16b. Further, a protrusion 19 is formed on the periphery of the case opening 16a, and a photocatalytic filter 40a is configured by having a frame member 41a in which a through hole 43 shorter than the length of the protrusion 19 is formed corresponding to the protrusion 19. Then, the photocatalytic filter 40a is fixed to the case 16 by caulking the protrusions 19 of the case 16 via the through holes 43 of the frame member 41a. Further, the photocatalyst is sprayed on the entire surface of the case 16, that is, all components except the humidity detecting element 20 and the lead terminal 30, so that the coating 50 is made. Thereby, the effect according to the effect of previous 4th and 6th embodiment comes to be acquired.

(Other embodiments)
In each of the above-described embodiments (including modifications), the photocatalyst filters 40, 40a, and 45 are configured by spraying and coating a photocatalyst made of titanium oxide (TiO2) on the porous filter. It is not limited to titanium oxide. In short, it is possible to coat a porous filter, which has strong oxidizing power when irradiated with light, and captures and decomposes small organic substances such as tobacco molecules as they pass through the filter. If it can, the material is arbitrary. Further, the configuration method for configuring the photocatalytic filters 40, 40a, 45 using such a photocatalyst is not limited to spraying. In addition, the photocatalytic filter may be configured by impregnation, for example.

  In each of the above embodiments (including modifications), it has been realized as a capacitive humidity sensor that detects a change in the humidity of the atmosphere as a change in the capacitance between the comb-shaped electrodes 22a and 22b. It is not limited to this. Further, the detection principle is not limited to this. Alternatively, for example, a resistance humidity sensor that detects a change in humidity of the atmosphere as a change in impedance of the moisture-sensitive film 23 may be realized.

BRIEF DESCRIPTION OF THE DRAWINGS (a) is a top view which shows planar structure about 1st Embodiment of the humidity sensor concerning this invention. (B) is side surface sectional drawing which shows the side surface structure along the IB-IB line of (a). (C) is an exploded view of (b). The partial side sectional view which decomposes | disassembles and shows a side structure about the modification of the said 1st Embodiment. (A) is a partial side sectional view showing a side surface structure of a second embodiment of a humidity sensor according to the present invention. (B) is an exploded view of (a). (A) is a top view which shows planar structure about 3rd Embodiment of the humidity sensor concerning this invention. (B) is a partial side sectional view showing a side structure. The partial side sectional view which decomposes | disassembles and shows a side structure about the modification of the same 3rd Embodiment. The partial side sectional view which shows the side structure of 4th Embodiment of the humidity sensor concerning this invention. (A) is a top view which shows planar structure about 5th (and 7th) embodiment of the humidity sensor concerning this invention. (B) is side surface sectional drawing which shows the side surface structure along the IIB-IIB line | wire of (a). (C) is a figure which shows a back surface structure. The partial side sectional view which decomposes | disassembles and shows a side structure about the modification of the said 5th (and 7th) embodiment. The partial side sectional view showing the side structure of the 6th (and 8th) embodiment of the humidity sensor concerning the present invention. (A) is the schematic diagram which showed a mode that a tobacco molecule block | closes the pore opening part of a moisture-sensitive film, and a water molecule cannot adhere to the pore inner surface. (B) is the schematic diagram which showed a mode that the tobacco molecule adhering to the pore inner surface of a moisture-sensitive film further adsorbed a water molecule, and more water molecules adhered to the pore inner surface. A graph showing the relationship between the actual relative humidity of the atmosphere and the sensor output, in addition to the number of tobacco molecules floating in the atmosphere.

Explanation of symbols

10 to 10 k ... humidity sensor, 11, 16 ... case, 11a, 16a ... (first) case opening, 12, 17 ... recess, 13, 18 ... adhesive, 14, 19 ... projection, 16b ... (second) Case opening, 20 ... Humidity detection element, 21 ... Substrate, 22a, 22b ... Comb-shaped electrode (electrode for humidity detection), 23 ... Humidity sensitive film, 24 ... Humidity detection part, 25 ... Circuit part, 30 ... Lead Terminals 31 ... bonding wires 40, 40a, 45 ... photocatalytic filters, 41, 41a ... frame members, 42 ... convex parts, 43 ... through holes, 50 ... photocatalytic coating.

Claims (9)

Detects the physical quantity of a moisture-sensitive film that has a plurality of pores that open to the inside while opening at the surface, and the moisture-sensitive film that changes as a result of moisture adsorbing on the surface of the moisture-sensitive film, including the inner surface of the pores. A humidity detecting element having a pair of electrodes for
In a humidity sensor comprising a case in which the humidity detection element is housed inside and a first case opening that is an opening for circulating air inside and outside is formed,
A humidity sensor, wherein a photocatalytic filter, which is a porous filter coated with a photocatalyst, is provided in the first case opening so as to cover the first case opening.   The humidity sensor according to claim 1, wherein the photocatalyst filter is coated by spraying the photocatalyst on the porous filter.   The humidity sensor according to claim 1, wherein the photocatalyst is titanium oxide. The case has a recess formed in a peripheral edge of the first case opening, and the photocatalytic filter has a frame member having a protrusion corresponding to the recess of the case.
The humidity sensor according to claim 1, wherein the photocatalytic filter is fixed to the case by press-fitting the convex portion of the frame member into the concave portion of the case.   The humidity sensor according to claim 4, wherein an adhesive is applied to the concave portion of the case, and the convex portion of the frame member and the concave portion of the case are bonded together by the adhesive. The case has a protrusion formed on the periphery of the first case opening, and the photocatalytic filter has a frame member in which a through hole shorter than the length of the protrusion is formed corresponding to the protrusion. And
The humidity sensor according to claim 1, wherein the photocatalytic filter is fixed to the case by caulking the protrusion of the case via the through hole of the frame member.   7. The case according to claim 4, wherein the case is formed with a second case opening which is an opening for allowing air to flow inside and outside, and the photocatalytic filter is also provided in the second case opening. The humidity sensor according to any one of the above.   The humidity sensor according to any one of claims 1 to 7, wherein the entire surface of the case is coated with a photocatalyst.   The moisture-sensitive film has a dielectric constant that changes according to humidity, and the humidity sensor is a capacitive humidity sensor that detects humidity based on a change in dielectric constant of the moisture-sensitive film. The humidity sensor according to any one of 1 to 8.

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