Resistive humidity sensor and method for manufacturing a resistive humidity sensor

Abstract

The present application provides a resistive humidity sensor that does not require external components for characteristic adjustment and a manufacturing method for the resistive humidity sensor. The resistive humidity sensor has a cylindrical insulating substrate (3), a pair of cap-shaped terminals (7, 7) fitted and fixed to both ends of the cylindrical insulating substrate (3), a resistive film (5) formed on the surface of the cylindrical insulating substrate (3) and electrically connected to the pair of cap-shaped terminals (7, 7), a slit (11) formed in the resistive film (5) in order to divide the resistive film (5) into two, and a humidity-sensing film (13) arranged to block the slit (11) and have a resistance value that changes according to changes in humidity.

Description

TECHNICAL FIELD

[0001] The present application relates to a resistance type humidity sensor and a manufacturing method of a resistance type humidity sensor. BACKGROUND

[0002] In FIG. 2 of Japanese Patent Application Publication No. S54-70096 (Patent Literature 1), a resistance type humidity sensor is disclosed in which a humidity sensing film 3 is overlaid on two electrodes 2 provided on both ends of a gap between the two electrodes 2 on the surface of a hollow cylindrical substrate 1 in a manner of covering the gap from above, and the resistance value of the humidity sensing film 3 between the two electrodes is measured by two electrode lead wires 4.

[0003] In addition, in Japanese Patent Application Publication No. H4-364456 (Patent Literature 2), Figure 2 a humidity sensor is disclosed which includes a humidity sensing element 1 formed in a substantially cylindrical shape or a substantially cylindrical shape, two conductor layers 2 provided on the surface of the humidity sensing element 1 with a gap 3 therebetween, and lead wires 4 provided on the two conductor layers 2. The humidity sensing element 1 is formed by impregnating a porous ceramic element with a humidity sensing polymer electrolyte.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. S54-70096, FIG. 2

[0007] Patent Literature 2: Japanese Patent Application Publication No. H4-364456 Figure 2

[0008] In a case where a user of the resistance type humidity sensor uses it without being aware of the rated current, a current exceeding the rated current flows, resulting in a problem that the resistance type humidity sensor cannot be used within a correct operation range. In addition, there is a case where the user erroneously causes an overcurrent exceeding the allowable current to flow in the resistance type humidity sensor, resulting in a problem that the resistance type humidity sensor is burned out.

[0009] In addition, in a case where an external resistance for characteristic adjustment is required, an external resistor needs to be additionally provided in the driving circuit. SUMMARY

[0010] An object of the present application is to provide a resistance type humidity sensor capable of preventing a current exceeding a required value from flowing as much as possible.

[0011] Another object of the present application is to provide a resistance type humidity sensor which does not require an external component for characteristic adjustment.

[0012] Another object of the present application is to provide a manufacturing method of a resistance type humidity sensor which does not require an external component for characteristic adjustment.

[0013] Technical solution for solving the problem

[0014] The resistance humidity sensor of the present application comprises: a cylindrical insulating base; a pair of cap-shaped terminals fitted and fixed to both ends of the cylindrical insulating base; a resistance film for characteristic adjustment formed on the surface of the cylindrical insulating base and electrically connected to the pair of cap-shaped terminals; a slit formed in the resistance film for dividing the resistance film into two; and a humidity sensing film arranged to block the slit, and the resistance value changes according to the change of humidity. According to the present application, a resistance humidity sensor capable of preventing the flow of current above a required level can be provided. In addition, by properly setting the resistance value of the resistance film, the necessity of externally connecting a resistance body as another component for characteristic adjustment can be eliminated. It should be noted that in the present application, "dividing into two" means dividing the resistance film into two parts, and is not limited to dividing the resistance film into 1 / 2.

[0015] The humidity sensing film can be theoretically arranged to block the slit. However, in the present application, it can also be arranged to entirely cover the resistance film and the slit between the pair of cap-shaped terminals.

[0016] The resistance film preferably does not contain a metal component that causes migration. This is because when migration extends between the slits, the characteristics of the humidity sensor change due to the occurrence of short circuit of the divided resistance film.

[0017] In addition, it is preferable to further have a protective film having moisture permeability that covers at least the humidity sensing film to protect the humidity sensing film. The protective film can also entirely cover the resistance film and the humidity sensing film between the pair of cap-shaped terminals. If such a protective film is formed, it is possible to prevent dirt from adhering to the humidity sensing film, and it is possible to prevent damage to the humidity sensing film and the resistance film before mounting on the circuit substrate.

[0018] In addition, a pair of lead wires can be connected to the pair of cap-shaped terminals, and one of the pair of lead wires is bent in a state of following the cylindrical insulating base and being parallel to the other lead wire, and is accommodated in a housing having a plurality of air holes. In this case, the pair of lead wires protrude from the housing. The humidity sensor of the present application can directly use the pair of lead wires as a fixing mechanism of the housing, and thus the number of components can be reduced.

[0019] Further, it is preferable that a part of the pair of cap-shaped terminals and a part of the pair of lead wires continuous to the pair of cap-shaped terminals are covered with a resin coating layer having insulating properties. Further, at least a part of the cap-shaped terminal of one of the pair of cap-shaped terminals and a part of the lead wire continuous to the cap-shaped terminal of one of the pair of cap-shaped terminals can be continuously covered with a resin coating layer having insulating properties. In this way, by making it possible to generate an attached hygroscopic film in the manufacturing process, it is possible to prevent corrosion of the pair of cap-shaped terminals and a part of the lead wire. Further, it is also possible to prevent generation of unnecessary short circuits.

[0020] The present application is directed to a manufacturing method of a resistance type humidity sensor, the resistance type humidity sensor including: a cylindrical insulating base; a pair of cap-shaped terminals fitted and fixed to both ends of the cylindrical insulating base; a resistance film for characteristic adjustment electrically connected to the pair of cap-shaped terminals; a slit formed in the resistance film in order to divide the resistance film into two; and a hygroscopic film provided so as to block the slit, a resistance value of which changes according to a change in humidity. In the present application, lead wires are connected to the pair of cap-shaped terminals, respectively, and the hygroscopic film is formed after the lead wires are connected to the pair of cap-shaped terminals. In this way, in a state in which the pair of lead wires are attached to a guide tape, respectively, subsequent processing can be continuously performed, and thus manufacturing efficiency can be improved. Further, when the hygroscopic film is formed before the lead wires are connected to the pair of cap-shaped terminals, connection of the lead wires is performed in a state in which the slit is covered with the hygroscopic film, and thus it is possible to prevent conductive substances contained in smoke generated at the time of connection of the lead wires from entering the slit and becoming a cause of a change in characteristics.

[0021] Further, if the formation of the resistance film, the formation of the slit, the formation of the hygroscopic film, the installation of the cap-shaped terminals, and the connection of the lead wires are all performed by an automated production line, manufacturing costs can be greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0022] FIG. 1 (A) is a diagram in which the cap-shaped terminals are made transparent in a state halfway through the manufacturing process of the resistance type humidity sensor of the present embodiment, (B) is a diagram after lead wires are welded to both sides of the cap-shaped terminals and a hygroscopic film and a protective film and a resin coating layer are applied, and (C) is a schematic cross-sectional view showing the configuration of a hygroscopic film formation portion of the resistance type humidity sensor of the present embodiment.

[0023] Figure 2 FIG. 2 is a graph showing characteristics of the above-described sample of the resistance type humidity sensor of the present embodiment.

[0024] Figure 3 (A) to (J) are diagrams showing the processes of an example of a method in the case of manufacturing a resistance type humidity sensor.

[0025] Figure 4 (A) and (B) are diagrams showing examples of a shipping form of the resistance type humidity sensor of the present embodiment.

[0026] Figure 5 (A) is a schematic sectional view showing different configurations of a moisture-sensing film forming portion of the resistance humidity sensor, (B) and (C) are diagrams showing other examples of the resin coating layer, and (D) is a diagram showing different examples of the case.

[0027] Explanation of reference numerals

[0028] 1: resistance humidity sensor; 3: cylindrical insulating base; 5: resistance film; 7: cap-shaped terminal; 9: lead wire; 11: slit; 13: moisture-sensing film; 15: protective film; 19: resin coating layer; 21: case. DETAILED DESCRIPTION

[0029] Hereinafter, an embodiment of the present application will be described in detail with reference to the drawings. FIG. 1(A) is a diagram in which the cap-shaped terminals 7, 7 are made transparent in a state halfway through the manufacturing process of the resistance humidity sensor 1 of the present embodiment, and FIG. 1(B) is a diagram after the lead wires 9, 9 are soldered to both sides of the cap-shaped terminals 7, 7 and the moisture-sensing film 13 and the protective film 15 and the resin coating layer 19 are implemented. FIG. 1(C) is a schematic diagram showing the configuration of the moisture-sensing film forming portion of the resistance humidity sensor 1 of the present embodiment. The resistance humidity sensor 1 in the halfway state shown in FIG. 1(A) is provided with a cylindrical insulating base 3 composed of a ceramic material and a resistance film 5 for adjusting characteristics formed on a large part of the surface of the outer peripheral surface of the cylindrical insulating base 3. The resistance film 5 is formed of a resistance material such as ruthenium oxide that does not generate migration. On both ends of the cylindrical insulating base 3, a pair of cap-shaped terminals 7, 7 made of metal are fitted in contact with the resistance film 5. The pair of cap-shaped terminals 7, 7 are respectively provided with plating of Cu and Sn on the surface of the cap-shaped body made of iron. The cap-shaped terminal 7 is provided with: an opening portion 7A that fits the cylindrical insulating base 3; a ring-shaped end surface portion 7B; a cylindrical portion 7C that is continuous with the ring-shaped end surface portion 7B and faces the outer peripheral surface of the end portion of the cylindrical insulating base 3; and a curved portion 7D that faces the end surface 3A of the end portion of the cylindrical insulating base 3. In addition, a ring-shaped slit 11 that extends around the entire circumference is formed in the resistance film 5 in order to divide the resistance film 5 into two. In addition, the shape of the cap-shaped terminals 7, 7 is not limited to the shape provided with the curved portion 7D as in the present embodiment, and the cap-shaped terminals 7, 7 can have an outer shape along the end surface of the cylindrical insulating base 3 without the curved portion 7D.

[0030] In the example shown in FIGS. 1 (B) and (C), the humidity sensing film 13 composed of an ionic humidity sensing polymer whose electric resistance value changes according to humidity change is formed so as to block the slit 11. The humidity sensing film 13 is formed by applying a mixture of a humidity sensing polymer and an additive polymer such as polyvinyl alcohol that increases the adhesion of the humidity sensing polymer to the cylindrical insulating substrate 3 and the water resistance of the humidity sensing polymer, and drying and curing the applied mixture, in a manner that fills the slit 11 and overlaps the electric resistance film 5. In this example, a protective film 15 is also formed that covers a portion of the electric resistance film 5 and the humidity sensing film 13 between the pair of cap-shaped terminals 7, 7. In this embodiment, the same polymer material as the basic polymer material used in forming the humidity sensing film 13 is used as the protective film 15. The protective film 15 has moisture permeability so that moisture, dust, and the like do not directly adhere to the humidity sensing film 13.

[0031] The humidity sensing film 13 is theoretically set so as to block the slit 11, and the protective film 15 is set so as to cover the humidity sensing film 13. However, the humidity sensing film 13 can of course be set so as to entirely cover the electric resistance film 5 and the slit 11 between the pair of cap-shaped terminals 7, 7. Note that in the case where the electric resistance film 5 is covered by the humidity sensing film 13, it is preferable that the humidity sensing film 13 not be in contact with the pair of cap-shaped terminals 7, 7. In this case, the smaller the size, the lower the adhesion of the humidity sensing film 13 to the electric resistance film 5, and thus the adhesion area of the humidity sensing film 13 can be effectively prevented from increasing and the humidity sensing film 13 from peeling. Also, in the case where the protective film 15 is formed on the humidity sensing film 13, it is preferable that the protective film 15 be formed so as not to be in contact with the pair of cap-shaped terminals 7, 7.

[0032] Also, in this embodiment, the pair of cap-shaped terminals 7, 7 are soldered to the pair of lead wires 9, 9. Also, a portion of the pair of cap-shaped terminals 7, 7 and the pair of lead wires 9, 9 is covered by a resin coating layer 19, 19 formed by applying an insulating resin paint composed of an epoxy resin. The resin coating layer 19, 19 prevents corrosion of the cap-shaped terminals 7, 7 and the lead wires 9, 9 in the case where the humidity sensing film 13 and the protective film 15 come into contact with the cap-shaped terminals 7, 7 and the lead wires 9, 9 during the application process of the humidity sensing film 13 and the protective film 15. Also, the occurrence of reactions and precipitation of ions in the humidity sensing film can be suppressed, and the occurrence of abnormal characteristics can be suppressed.

[0033] In addition, if the dimensions of the test sample of the above embodiment are represented, the length LI between the ends of the pair of cap-shaped terminals 7, 7 is about 5.8 mm, the length between the opening portions 7A, 7A of the pair of cap-shaped terminals 7, 7 is about 2.8 mm, the length L2 of the cylindrical insulating base 3 is about 5.5 mm, the diameter D is about 1.5 mm, and the width of the slit is 0.13 ± 0.1 mm. In addition, the resistance value of the resistance-type humidity sensor 1 is preferably about 1 kΩ to 1000 kΩ depending on the balance with the surrounding circuit.

[0034] Figure 2 is a graph showing the characteristics of the above sample of the resistance-type humidity sensor of the present embodiment. As is clear from Figure 2 , the resistance value decreases in a substantially straight line on a logarithmic graph as the humidity increases. In addition, the entire characteristics can be shifted by changing the resistance value of the resistance film 5. Incidentally, if the resistance value of the resistance film 5 is lowered, the entire characteristics decrease, and if the resistance value of the resistance film 5 is increased, the entire characteristics increase.

[0035] [Manufacturing Method]

[0036] Hereinafter, one example of a method in the case of manufacturing the resistance-type humidity sensor of the configuration shown in Figs. 1 (A) to (C) will be described with reference to the drawings. Figure 3 First, the cylindrical insulating base 3[ Figure 3 (A)] is prepared. Next, after the resistance paste is applied to the cylindrical insulating base 3, firing is performed to form the resistance film 5[ Figure 3 (B)] for characteristics adjustment. In addition, the resistance film 5 can be formed in the necessary range. Then, a pair of cap-shaped terminals 7, 7[ Figure 3 (C)] are fitted to both ends of the cylindrical insulating base 3 in contact with the resistance film 5. In addition, in Figure 3 (C), the cap-shaped terminals 7, 7 are depicted as transparent.

[0037] Next, the slit 11[ Figure 3 (D)] is formed by laser cutting. In the laser cutting, the laser is fixed, and the cylindrical insulating base 3 is rotated to perform the cutting. Next, the lead wires 9, 9[ Figure 3 (E)] are soldered to the pair of cap-shaped terminals 7, 7. Then, the pair of cap-shaped terminals 7, 7 are coated with epoxy resin and dried[ Figure 3 (F)], and then the base portions of the lead wires 9, 9 are coated with epoxy resin and dried to form a resin coating layer 19[ Figure 3 (G)]. The resin coating layer 19 is formed for the purposes of protection and insulation.

[0038] Next, the hygroscopic liquid is applied so as to cover the slit 11 and dried, whereby the hygroscopic film 13[ Figure 3(H)]. Next, a protective liquid is applied to the moisture-sensitive membrane 13 and the resistive membrane 5 in a manner that covers the moisture-sensitive membrane 13, forming a protective film 15. Figure 3 (I)]. In this state, the pair of leads 9 can also be clamped together, but it can also be done as follows: Figure 3 As shown in (J), the shape is made such that one of the pair of leads 9 is bent and extends parallel to the other lead 9.

[0039] In such Figure 3 (J) In the case of forming as described above, it is also possible to... Figure 4 It is housed in the casing 21 as shown in (A). It should be noted that... Figure 4 In (A), to allow visibility of the interior of the housing 21, the front door 21A of the housing 21 is removed. That is, one of the leads 9 is bent along the cylindrical insulating substrate 3 and parallel to the other lead 9, and then housed within the housing 21, which has multiple vent holes 21B in the front door 21A. In this way, if the pair of leads 9 protrudes from the housing 21, they can be directly used as a fixing mechanism for the housing 21, thus reducing the number of components. Furthermore, in the humidity sensor of this embodiment, the size of the housing 21 can be significantly reduced when the resistance value of the resistive film 5 is not set to an appropriate value and the characteristic adjustment resistor is replaced with another component.

[0040] In addition, such as Figure 4 As shown in (B), two leads 9, 9 can be sandwiched between a pair of tapes 22 to form a roll, thus forming a shipping package.

[0041] It should be noted that, in Figure 3 After step (D), when the moisture-sensitive film 13 has been formed, the slit 11 and the resistive film 5 can be covered with a moisture-sensitive liquid, and then the lead 9 can be soldered to the cap-shaped terminal 7. When the moisture-sensitive film 13 is formed before connecting the leads 9, 9 to the pair of cap-shaped terminals 7, 7, the connection of the leads 9 is performed while the slit 11 is covered by the moisture-sensitive film 13. Therefore, it is possible to prevent conductive substances contained in the soot generated during lead connection from entering the slit and causing deviations in characteristics. Furthermore, the formation of the protective film 15 can be performed after the formation of the moisture-sensitive film 13, or it can be combined with... Figure 3 The manufacturing process is also carried out after connecting lead 9.

[0042] [other]

[0043] In the above embodiment, a protective film 15 is used to cover the top of the moisture-sensitive film 13, but as... Figure 5 As shown in (A), the resistive film 5 located between a pair of cap-shaped terminals 7, 7 can also be covered with a protective film 15. Additionally, as...Figure 5 As shown in (B) and (C), at least a part of the cap-shaped terminal 7 on one side of the pair of cap-shaped terminals 7 and a part of the lead 9 continuous to the cap-shaped terminal on the one side can also be continuously covered with the resin coating layer 19 having insulating properties. Further, if the protrusion 10 formed by bending the lead 9 in such a manner that one side of the lead is away from the other side of the lead is provided to the lead on one side, the protrusion 10 can be used as a positioning mechanism at the time of mounting to the circuit board. Also, as shown in (D), the housing 21 can also be provided as a cylindrical structure having air permeability. In addition, the housing 21 of the cylindrical structure having air permeability can also be formed using a heat shrink tube. If the heat shrink tube is used, the housing 21 can be manufactured inexpensively, and the housing 21 can be fixed simply, and the movement of the housing 21 can be prevented simply. Figure 5 (D), the housing 21 can also be provided as a cylindrical structure having air permeability. In addition, the housing 21 of the cylindrical structure having air permeability can also be formed using a heat shrink tube. If the heat shrink tube is used, the housing 21 can be manufactured inexpensively, and the housing 21 can be fixed simply, and the movement of the housing 21 can be prevented simply.

[0044] In addition, the formation of the resistance film 5, the formation of the slit 11, the formation of the moisture sensing film 13, the mounting of the cap-shaped terminal 7, and the connection of the lead 9 can also be all performed by an automated production line. In this way, the manufacturing cost can be reduced greatly.

[0045] Further, the position of the slit 11 is not limited to the central position of the resistance film 5. Also, the slit 11 is not limited to the case where it is formed orthogonal to the central axis of the cylindrical insulating base 3, and can of course be formed in a manner that is not orthogonal to the central axis.

[0046] Industrial applicability

[0047] According to the present application, a resistance type humidity sensor that can prevent a current of a required value or more from flowing can be provided. In addition, by appropriately setting the resistance value of the resistance film for characteristic adjustment, the necessity of externally connecting a resistance body as another component for characteristic adjustment can be eliminated, and a humidity sensor device can be constructed inexpensively and in a small size.

Claims

1. A resistive humidity sensor, characterized in that, This resistive humidity sensor features: Cylindrical insulating substrate; A pair of cap-shaped terminals are fitted and fixed to both ends of the cylindrical insulating substrate; A resistive film for characteristic adjustment is formed on the surface of the cylindrical insulating substrate and electrically connected to the pair of cap-shaped terminals; A slit is formed in the resistive film to divide it into two parts; as well as A moisture-sensitive membrane is configured to block the slit, and its resistance value changes according to the humidity.

2. The resistive humidity sensor according to claim 1, characterized in that, The moisture-sensitive membrane is configured to integrally cover the resistive membrane and the slit located between the pair of cap-shaped terminals.

3. The resistive humidity sensor according to claim 1 or 2, characterized in that, The resistive film does not contain any metallic components that would cause migration.

4. The resistive humidity sensor according to claim 1 or 2, characterized in that, The resistive humidity sensor also includes a moisture-permeable protective film that covers and protects the moisture-sensing film.

5. The resistive humidity sensor according to claim 4, characterized in that, The protective film completely covers the resistive film and the moisture-sensitive film between a pair of cap-shaped terminals.

6. The resistive humidity sensor according to claim 1 or 2, characterized in that, A pair of leads are connected to the pair of cap-shaped terminals. The resistive humidity sensor is housed within a housing with multiple vent holes, with one of the leads of the pair of leads bent along the cylindrical insulating substrate and parallel to the other lead. The pair of leads protrude from the housing.

7. The resistive humidity sensor according to claim 6, characterized in that, The pair of cap-shaped terminals and a portion of the pair of leads continuous with the pair of cap-shaped terminals are covered with an insulating resin coating.

8. The resistive humidity sensor according to claim 6, characterized in that, At least a portion of one of the cap-shaped terminals of the pair of cap-shaped terminals and a portion of the lead wire continuous with the cap-shaped terminal of that pair are continuously covered by an insulating resin coating.

9. A method for manufacturing a resistive humidity sensor, This resistive humidity sensor features: Cylindrical insulating substrate; A pair of cap-shaped terminals are fitted and fixed to both ends of the cylindrical insulating substrate; A resistive film for characteristic adjustment is electrically connected to the pair of cap-shaped terminals; A slit is formed in the resistive film to divide it into two parts; as well as A moisture-sensitive membrane is configured to block the slit, and its resistance changes according to variations in humidity. Its features are, Leads are connected to each of the pair of cap-shaped terminals. The moisture-sensitive film is formed after the lead wire is connected to the pair of cap-shaped terminals.

10. A method for manufacturing a resistive humidity sensor, This resistive humidity sensor features: Cylindrical insulating substrate; A pair of cap-shaped terminals are fitted and fixed to both ends of the cylindrical insulating substrate; A resistive film for characteristic adjustment is electrically connected to the pair of cap-shaped terminals; A slit is formed in the resistive film to divide it into two parts; as well as A moisture-sensitive membrane is configured to block the slit, and its resistance changes according to variations in humidity. Its features are, Leads are connected to each of the pair of cap-shaped terminals. The moisture-sensitive film is formed before the lead is connected to the pair of cap-shaped terminals.

11. The method for manufacturing a resistive humidity sensor according to claim 9 or 10, characterized in that, The formation of the resistive film, the formation of the slit, the formation of the moisture-sensitive film, the installation of the cap-shaped terminal, and the connection of the lead wire are all performed through an automated production line.

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