JP4202771B2 - Airtight structure of circuit board with sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an airtight structure of a circuit board housed together with a sensor in a protective tube, and particularly suitable for use in a temperature sensor, a humidity sensor, or the like that measures a physical quantity (for example, temperature, humidity, etc.) of an atmosphere to be measured. The circuit board has an airtight structure.
[0002]
[Prior art]
Conventionally, in a semiconductor manufacturing apparatus or the like, it is necessary to keep the internal environment constant, so that a small sensor and its circuit board are housed in a protective tube, and the physical quantity (for example, temperature) of the atmosphere to be measured , Humidity, etc.) are constantly measured by sensors. In such a sensor, an electronic circuit for outputting a detection signal from the detection element to the outside is mounted on the circuit board. When the circuit board is exposed to the atmosphere outside the protective tube, moisture in the atmosphere ( The electrical characteristics of electronic components such as ICs mounted on the circuit board change due to the influence of humidity), the resistance value of the wiring on the circuit board changes, or rusting causes disconnection. In order to reduce the measurement accuracy, reliability, durability, etc. of the sensor, it is required to perform waterproof / moisture-proofing on the circuit board, or to completely block the circuit board from the outside air as an airtight structure.
[0003]
As a method of applying a waterproof and moisture-proof treatment to the circuit board, for example, a method of sealing the circuit board using a heat shrinkable insulator is conceivable.
[0004]
As the hermetic structure of the circuit board, for example, an O-ring is used for sealing, or the hermetic structure shown in FIG.
The circuit board airtight structure shown in FIG. 7 is such that the circuit board 2 is housed in the protective tube 1 and hermetically sealed with a potting material (thermosetting resin or the like) 3. 4 is a temperature sensor, 5 is a humidity sensor, 6 is a cable connected to the circuit board 2, 7 is a vent hole formed in the front end of the protective tube 1, and 8 is a cable lead formed on the rear end surface of the protective tube 1. An outlet 9 is a lead wire for connecting the circuit board 2 to the temperature sensor 4 and the humidity sensor 5. The circuit board 2 is mounted with wiring patterns and electronic circuits for outputting detection signals from the temperature sensor 4 and the humidity sensor 5 to the outside, and most of them are covered with the potting material 3. The temperature sensor 4 and the humidity sensor 5 are located in front of the circuit board 2 and housed in the protective tube 1, and are exposed to the outside air flowing in from the vent hole 7.
[0005]
Further, as another airtight structure, there is also known a structure in which a sensor connection portion is made airtight using a cone and a cap (see, for example, Patent Document 1). It should be noted that the applicant has not found any prior art documents closely related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in the present specification.
[0006]
[Patent Document 1]
JP 2001-275245 A (page 3, paragraphs “0016” to “0021”, FIG. 1)
[0007]
The sensor connection part structure described in Japanese Patent Application Laid-Open No. 2001-275245 has a sealing effect on the taper hole of the cap and an effect of preventing the cable from coming off by pressing the cable outer cover on the tapered inner surface of the cap. The cable core wire protection effect is achieved at the same time.
[0008]
[Problems to be solved by the invention]
However, the waterproof / moisture-proof treatment of the circuit board using the heat-shrinkable insulator described above requires that the heat-shrinkable insulator be heated and softened by heating means after the circuit board is stored in the heat-shrinkable insulator. Is accompanied by annoyance.
[0009]
Since the airtight structure by the O-ring requires means or members for fastening the object, the number of parts increases. Moreover, since the contact area of the press contact portion is small, the reliability of the seal is low.
[0010]
The airtight structure of the circuit board shown in FIG. 7 requires that the potting material 3 heated and melted is injected into the protective tube 1 to be solidified, so that care must be taken not to mix air during the injection. When the protective tube 1 is long, the air escape is worsened, so careful attention must be paid and workability is inferior. Moreover, since it takes time until the potting material 3 is solidified, the assembling work time becomes long and the productivity is lowered. Further, when the circuit board 2 or the sensors 4 and 5 need to be replaced, the potting material 3 must be melted or softened by heating and extracted from the protective tube 1, so that the replacement work is troublesome and practically reused. Can not do it.
[0011]
The connection structure of the sensor described in Japanese Patent Application Laid-Open No. 2001-275245 has a problem that the assembly work is troublesome because it is necessary to spread the cable jacket and cover the cone.
[0012]
The present invention has been made to solve the above-described conventional problems, and the object of the present invention is to have a simple structure, a small number of parts, excellent workability in assembling, and reliable sealing. Another object of the present invention is to provide an airtight structure of a circuit board having a sensor.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the first invention provides an airtight structure of a circuit board having a sensor for hermetically sealing a circuit board electrically connected to a sensor for measuring a physical quantity of an atmosphere to be measured in a protective tube. A first storage chamber having a vent hole communicating with the outside in the protective tube and storing the sensor; a second storage chamber having a cable outlet and storing the circuit board; The first and second storage chambers are hermetically partitioned by a first seal member, and the cable outlet is hermetically sealed by a second seal member and an end cap. The sealing member is formed of an elastic material, and a cylindrical portion that fits into the cable outlet of the protective tube, a conical portion that is integrally extended to the rear end side of the cylindrical portion, and an outer periphery of the cylindrical portion The protective pipe cable A flange that is in close contact with a side opening end surface; and a cable hole through which the cable passes. The end cap has a tapered hole into which a conical portion of the second seal member is fitted. By fixing to the side opening end, the conical part of the second seal member is pressed against the cable at the inner surface of the tapered hole, the flange is pressed against the cable outlet side opening end surface of the protective tube , The cable hole of the second seal member is formed such that the hole diameter on the conical portion side is slightly larger than the outer diameter of the cable, and the hole diameter on the cylindrical portion side is larger than the hole diameter on the conical portion side. It is.
[0017]
In the second invention, the cable is inserted into the hole of the second seal member and the end cap, the second seal member is fitted to the cable outlet of the protective tube, and the end cap has the cone of the second seal member. When the flange and the flange are pressed, the conical portion is pressed against the outer periphery of the cable to seal the gap between the cable and the cable hole of the second seal member, and the flange is pressed against the cable outlet opening side end surface of the protective tube. Seal the cable outlet. Further, the conical portion and the taper hole are in close contact with each other so that the gap between the second seal member and the end cap is hermetically sealed.
[0018]
In a second aspect based on the first aspect , the end cap is fixed to the protective tube by press-fitting or screwing.
[0019]
In the second aspect of the present invention, the end cap can be easily attached and detached for both press fitting and screwing, and the circuit board can be taken out.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
1 is a cross-sectional view showing an embodiment of an airtight structure of a circuit board having a sensor according to the present invention, FIG. 2 is a cross-sectional view showing a state in which the circuit board is sealed by a first sealing member, and FIG. 3 is a circuit board. 4A, 4B, and 4C are a front view, a side view, and a cross-sectional view taken along line AA of the first seal member, and FIGS. 5A, 5B, and 5C. These are the front view, side view, and BB line sectional view of a 2nd seal member. The present embodiment shows an example applied to a circuit board having a temperature / humidity sensor.
[0021]
In these drawings, a temperature / humidity sensor generally indicated by reference numeral 10 is connected to a protective tube 1, a circuit board 2 housed in the protective tube 1, and a lead wire 9 connected to the front end side of the circuit board 2. The first and second air-tight structures of the circuit board 2 together with the conventionally known temperature sensor 4 and humidity sensor 5, the cable 6 connected to the rear end side of the circuit board 2, and the protective tube 1. The sealing members 11 and 12 and the end cap 13 are included.
[0022]
The protective tube 1 is a pipe whose front end side is closed and whose rear end side is open, a plurality of vent holes 7 are formed on the peripheral surface of the front end portion, and the rear end side opening portion is a cable for guiding the cable 6 to the outside A lead-out port 8 is formed. The inside of the protective tube 1 is housed in two front and rear storage chambers, that is, the temperature sensor 4 and the humidity sensor 5 by the first seal member 11 and communicates with the outside through the vent hole 7. And the cable outlet 8 is hermetically partitioned into a second storage chamber 16 for storing the circuit board 2, and the cable outlet 8 is defined by the second seal member 12 and the end cap 13. It is airtightly sealed.
[0023]
Here, in the present embodiment, the protective tube 1 is constituted by the first and second metal pipes 1A and 1B formed of stainless steel or the like, and the vent hole 7 is provided in the first metal pipe 1A. Although the example in which the temperature sensor 4 and the humidity sensor 5 are housed inside and the circuit board 2 is housed in the second metal pipe 1B is shown, the protective tube 1 is formed by one metal pipe, without being limited thereto. Of course, it may be.
[0024]
The circuit board 2 is rectangular and has a length and width that can be accommodated in the protective tube 1, and outputs detection signals from the temperature sensor 4 and the humidity sensor 5 to the outside on the front and back surfaces of the circuit board 2 via a cable 6. An electronic circuit (not shown) is formed, and rectangular recesses 17 (FIG. 3) for positioning the first seal member 11 to prevent positional displacement in the front-rear direction are formed on both side surfaces near the front end. . The length of the recess 17 is slightly larger than the length of the first seal member 11 in the axial direction.
[0025]
As the temperature sensor 4, for example, a metal thin film resistor such as platinum formed on an insulating substrate such as ceramic is used. Similarly, as the humidity sensor, for example, a pair of comb-shaped counter electrodes made of platinum or the like opposed to each other on an insulating substrate is formed, and these comb-shaped electrodes are covered with a moisture-sensitive resistor and made conductive.
[0026]
In FIG. 4, the first seal member 11 for hermetically partitioning the first storage chamber 15 and the second storage chamber 16 of the protection tube 1 is made of the protection tube 1 by an elastic material such as fluorine rubber or neoprene rubber. Is formed in a cylindrical body having an outer diameter smaller than the inner diameter, and a substrate holding hole 20 is formed in the front and rear surfaces of the circuit board 2 so as to hold the front end portion of the circuit board 2. First and second seal projections 21 and 22 made of a continuous annular body are integrally projected on the inner peripheral surface and the outer peripheral surface of the seal member 11. In addition, since it will be slippery if the 1st sealing member 11 is manufactured with a fluororubber, the press injection to the protective tube 1 can be performed easily.
[0027]
The substrate holding hole 20 is a rectangular through-hole having substantially the same size as the cross-sectional shape of the circuit board 2 where the concave portion 17 is formed, and the first seal protrusion 21 projects integrally at the center of the inside. Has been. The first seal projection 21 is formed of a triangular protrusion having a cross-sectional shape, and is formed so that the space surrounded by the top portion thereof is slightly smaller than the cross-sectional shape of the concave portion 17 of the circuit board 2. For this reason, when the first seal member 11 is fitted into the concave portion 17 of the circuit board 2, the first seal protrusion 21 is pressed against the circuit board 2, and the gap between the circuit board 2 and the board holding hole 20 is hermetically sealed. Seal.
[0028]
Similarly, the second seal projection 22 is formed of a protrusion having a triangular cross-sectional shape, and has an outer diameter (top diameter) slightly larger than the inner diameter of the protective tube 1. Accordingly, when the first seal member 11 is press-fitted into the protective tube 1 together with the circuit board 22, the second seal protrusion 22 is pressed against the inner peripheral surface of the protective tube 1, and the protective tube 1 and the first seal member 11 are pressed. Airtightly seal the gap.
[0029]
The first seal member 11 includes a vertical cut 24 that opens the substrate holding hole 20 to the outer periphery (side) of the first seal member 11, and the protective tube 1 when mounted on the circuit board 2. A meat stealing portion 25 that facilitates elastic deformation during press-fitting into the inside is formed. As shown in FIG. 4A, the notch 24 is formed so as to reach the lower surface of the first seal member 11 from the center in the width direction of the bottom surface of the substrate holding hole 20. However, the present invention is not limited to this, and as shown by a two-dot chain line, it may be a notch 24 ′ formed horizontally so as to reach from one side surface of the substrate holding hole 20 to one side surface of the first seal member 11. If such a cut 24 or 24 ′ is formed, the substrate holding hole 20 can be opened to the side of the first seal member 1 by elastic deformation of the first seal member 11. Even after the sensors 4 and 5 and various electronic components are mounted, the first seal member 11 can be easily mounted on the concave portion 17 from the side of the circuit board 2.
[0030]
The meat stealing portion 25 is formed in an arc shape on the front and rear surfaces of the first seal member 11 and above and below the substrate holding hole 20.
[0031]
In FIG. 5, the second sealing member 12 is formed of an elastic material such as fluorine rubber or neoprene rubber, and is the rear opening end of the protective tube 1, similar to the first sealing member 11. A cylindrical portion 12A that is fitted or press-fitted into the outlet port 8, a conical portion 12B that extends integrally on the rear end side of the cylindrical portion 12A, and a protective tube that is integrally projected from the outer periphery of the cylindrical portion 12A. A cable hole 30 through which the cable 6 passes is formed at the center. The cable hole 30 is formed in a different diameter hole in which the hole diameter on the cylindrical part 12A side is larger than the hole diameter on the conical part 12B side. This is because when the end of the cable 6 on the side of the circuit board 2 is pulled out to the front of the second seal member 12, it is bent radially outward so as to overlap the rear end of the circuit board 2 as shown in FIG. Because.
[0032]
In FIG. 1, the end cap 13 has a tapered hole 31 into which the conical portion 12 </ b> B of the second seal member 12 is fitted, and a pressing surface 32 that presses the flange 12 </ b> C of the second seal member 12. Yes. The tapered hole 31 has an inner surface inclined angle substantially equal to the inclined angle of the conical portion 12B, a maximum hole diameter substantially equal to the maximum outer diameter of the conical portion 12B, and a minimum hole diameter slightly larger than the outer diameter of the cable 6. Yes. The pressing surface 32 is an annular surface surrounding the maximum hole diameter side opening of the tapered hole 31 and presses the rear surface of the flange 12C.
[0033]
When the circuit board 2 is assembled into the protective tube 1, the first seal member 11 is previously attached to the concave portion 17 of the circuit board 2, and the second seal member 12 and the end cap 13 are fitted to the cable 6. deep. When the first seal member 11 is attached to the concave portion 17 of the circuit board 2, as described above, the notch 24 of the first seal member 11 is opened to the left and right so that the board holding hole 20 is below the first seal member 11. To open. Then, when the concave portion 17 of the circuit board 2 is inserted into the board holding hole 20 from this open part, the first seal member 11 is attached to the circuit board 2 without inserting the sensors 4 and 5 into the board holding hole 20. Can do.
[0034]
Next, the circuit board 2 is inserted into the protective tube 1 together with the first seal member 11. At this time, the first seal member 11 is press-fitted because the outer diameter of the second seal protrusion 22 is larger than the inner diameter of the protective tube 1, and the second seal protrusion 22 is pressed against the inner peripheral surface of the protective tube 1. In addition, since the first seal member 11 is elastically deformed in the direction of reducing the diameter by this press-fitting, the first seal projection 21 is strongly pressed against the circuit board 2 and the two surfaces facing each other with the notch 24 interposed therebetween are strongly pressed. Adhere closely. As a result, a gap between the circuit board 2 and the board holding hole 20 of the first seal member 11, a gap between the protective tube 1 and the first seal member 11, and a notch 24 in the first seal member 11 are formed. The portion is hermetically sealed, and the first and second storage chambers 15 and 16 are partitioned so as to maintain an airtight state.
[0035]
Next, the cylindrical portion 12 </ b> A of the second seal member 12 is fitted to the cable outlet 8 of the protective tube 1, and the flange 12 </ b> C is brought into close contact with the cable outlet opening side opening end surface of the protective tube 1. Further, the end cap 13 is moved forward along the cable 6 to cover the second seal member 12 and fixed to the protective tube 1 by press fitting. Then, the pressing surface 32 of the end cap 13 presses the flange 12 </ b> C of the second seal member 12 from the rear to press-contact the cable outlet opening side end surface of the protective tube 1, and the inner surface of the tapered hole 31 is the second sealing member. The 12 conical portions 12B are pressed so that the inner peripheral surface of the small-diameter portion of the cable hole 30 is pressed against the jacket of the cable 6. Therefore, the cable outlet 8 is hermetically sealed, and the gap between the cable 6 and the second seal member 12 and the end cap 13 is hermetically sealed, thereby completing the sealing structure of the circuit board 2.
[0036]
The attachment structure of the end cap 13 to the protective tube 1 is not limited to press-fitting and may be fixed by screwing a male screw 34 and a female screw 35 as shown in FIG.
[0037]
According to the airtight structure of the circuit board 1 having such a temperature / humidity sensor 10, the first sealing member 11 having the board holding hole 20 is formed of an elastic material, and the inner peripheral surface of the board holding hole 20 and the first sealing member 11 are formed. Since the first and second seal protrusions 21 and 22 are integrally projected on the outer peripheral surface of the seal member 11 and the substrate holding hole 20 can be opened by the notch 24, the first seal member 11 Can be easily mounted from the side of the circuit board 2. Further, when the first seal member 11 is press-fitted into the protective tube 1, the first and second seal protrusions 21 and 22 can be pressed against the circuit board 2 and the protective tube 1, respectively, and at the same time, the notch 24 part is also in close contact. Therefore, the first storage chamber 15 and the second storage chamber 16 in the protective tube 1 can be well partitioned while maintaining an airtight state. Therefore, it is not necessary to use a potting material or an O-ring, and it is possible to provide an airtight structure having a simple structure, a small number of parts, and excellent sealing performance.
Further, since the first seal member 11 only needs to be press-fitted together with the circuit board 2 into the protective tube 1, the circuit board 2 can be assembled easily and in a short time.
[0038]
In order to keep the cable outlet 8 of the protective tube 1 airtight, the second seal member 12 and the end cap 13 are attached to the cable 6, and the cylindrical portion 12 A of the second seal member 12 is connected to the cable guide of the protective tube 1. The flange 12C is fitted to the outlet 8 so as to be in close contact with the opening end face of the protective tube 1 on the cable outlet side, and the tapered hole 31 of the end cap 13 is pressed against the conical portion 12B of the second seal member 12 so that the flange 12C is protected. Since it is only necessary to press against the opening end face of one cable outlet side, the assembly work of the second seal member 12 and the end cap 13 is easy and can be assembled in a short time. Further, there is no need to use a potting material or an O-ring, and the cable outlet 8 can be reliably sealed. Further, since the second seal member 12 and the end cap 13 can increase the contact area of the pressure contact portion by the pressure contact between the conical portion 12B and the tapered hole 31, the cable 6, the second seal member 12, and the end cap 13 can be increased. The gap with the cap 13 can also be reliably sealed. Therefore, it is possible to provide an airtight structure with excellent waterproof and moisture resistance.
[0039]
In the above-described embodiment, the substrate holding hole 20 of the first seal member 11 is configured to be openable by the notch 24. However, the structure in which the substrate holding hole 20 in the present invention can be opened is not limited to this. The first seal member 11 is composed of two divided pieces each having a half structure formed by dividing the first seal member 11 by a plane passing through the axis or a plane passing through the substrate holding hole 20 in parallel with the first seal member 11. A concave portion that serves as a substrate holding hole may be formed between the closely joined surfaces. In this case, it is desirable to form an engaging portion for positioning on the joint surface.
[0040]
Moreover, although the above-mentioned embodiment showed the example applied to the circuit board 2 used for the temperature / humidity sensor 10, it is applicable also to the circuit board which has sensors, such as a pressure sensor.
[0041]
【The invention's effect】
As described above, according to the airtight structure of the circuit board having the sensor according to the first invention, the assembly work of the first seal member to the circuit board is easy and can be assembled in a short time, and the protective tube Can be partitioned into a first storage chamber and a second storage chamber while maintaining an airtight state by the first seal member, and water, moisture, etc. pass through the first storage chamber to the second storage chamber. It is possible to surely prevent intrusion into the water. Further, it is not necessary to use a potting material or an O-ring, and an airtight structure having a high sealing performance can be provided with a minimum number of parts.
[0042]
According to the airtight structure of the circuit board having the sensor according to the second invention, the cable outlet can be hermetically sealed, there is no need to use a potting material or an O-ring, and the second seal member and the end cap Assembling work is easy and can be assembled in a short time. In addition, since the conical portion of the second seal member is pressed against the cable by the end cap, the contact area is large, and the gap between the cable, the second seal member, and the end cap can be satisfactorily sealed.
[0043]
According to the airtight structure of the circuit board having the sensor according to the third invention, the end cap can be attached and detached, and when the circuit board or the sensor needs to be replaced, it can be easily taken out from the protective tube. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of an airtight structure of a circuit board having a sensor according to the present invention.
FIG. 2 is a cross-sectional view showing a state where a circuit board is sealed by a first sealing member.
FIG. 3 is a plan view of a circuit board.
4A, 4B, and 4C are a front view, a side view, and a cross-sectional view taken along line AA of the first seal member, respectively.
FIGS. 5A, 5B, and 5C are a front view, a side view, and a cross-sectional view taken along line BB of the second seal member, respectively.
FIG. 6 is a cross-sectional view of a main part showing another embodiment of the present invention.
FIG. 7 is a cross-sectional view showing an airtight structure of a conventional circuit board.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Protective tube, 2 ... Circuit board, 4 ... Temperature sensor, 5 ... Humidity sensor, 6 ... Cable, 7 ... Air hole, 8 ... Cable outlet, 10 ... Temperature / humidity sensor, 11 ... 1st sealing member, 12 2nd seal member, 12A ... cylinder, 12B ... conical part, 12C ... flange, 13 ... end cap, 15 ... first storage chamber, 16 ... second storage chamber, 20 ... substrate holding hole, 21 ... 1st sealing protrusion, 22 ... 2nd sealing protrusion, 24 ... notch, 30 ... hole for cables, 31 ... taper hole.

Claims (2)

An airtight structure of a circuit board having a sensor that hermetically seals a circuit board electrically connected to a sensor that measures a physical quantity of an atmosphere to be measured in a protective tube,
Forming a first storage chamber having a vent hole communicating with the outside and storing the sensor inside the protective tube; and a second storage chamber having a cable outlet and storing the circuit board; The first and second storage chambers are hermetically partitioned by a first seal member, and the cable outlet is hermetically sealed by a second seal member and an end cap;
The second seal member is made of an elastic material and is fitted into the cable outlet port of the protective tube, a conical portion integrally extended to the rear end side of the tube portion, and the tube A flange projecting integrally on the outer periphery of the part and in close contact with the cable outlet opening end surface of the protective tube, and a cable hole through which the cable passes,
The end cap has a tapered hole into which the conical portion of the second seal member is fitted, and is fixed to the cable outlet opening side opening end portion of the protective tube, so that the second end is formed on the inner surface of the tapered hole. Pressing the conical portion of the sealing member against the cable, pressing the flange against the cable outlet opening end surface of the protective tube ,
The cable hole of the second seal member is formed such that the hole diameter on the conical portion side is slightly larger than the outer diameter of the cable, and the hole diameter on the cylindrical portion side is larger than the hole diameter on the conical portion side. An airtight structure of a circuit board having a sensor. In the airtight structure of the circuit board having the sensor according to claim 1,
An airtight structure of a circuit board having a sensor, wherein the end cap is fixed to a protective tube by press-fitting or screwing .

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