JP3644357B2 - Capacitive moisture sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is a capacitance type moisture content sensor that detects the amount of moisture and the presence or absence of moisture.ToIt is related.
[0002]
[Prior art]
Conventionally, methods for measuring the amount of water are generally classified into an infrared absorption type, a microwave type, an electric resistance type, a capacitance type, and a weight type.
[0003]
However, in a moisture sensor that uses transmitted infrared light in the above infrared absorption type, the detection target must be made of a material that transmits infrared light. In this case, it is suitable for a thin paper or the like up to about several mm, but is not suitable for a material that does not transmit infrared light. Furthermore, in the moisture amount sensor using reflected infrared light, the reflection condition is greatly influenced by the uneven state and color of the surface of the detection target. That is, there is a problem in that it is not possible to determine whether the amount of light reduction with respect to the amount of irradiation light is due to moisture absorption or reflection conditions, and it is not possible to accurately detect the amount of moisture.
[0004]
In addition, the microwave method measures the amount of propagation energy loss caused by the complex dielectric constant, which causes a problem that the apparatus becomes complicated and the manufacturing cost is high.
[0005]
In addition, the electrical resistance formula is a method of measuring resistance components using the electrical conductivity of water, but in reality impurities such as salt (NaCl) contained in moisture were formed by electrolysis. The ionic conductivity is orders of magnitude greater, so the value that can be measured by resistance is actually the concentration of impurities dissolved in moisture.
[0006]
Furthermore, the gravimetric method is not suitable for online measurement because of its measurement principle.
[0007]
On the other hand, the capacitance type causes an error if a dielectric constant equivalent to that of water is present, but the above-mentioned application (fermentation process / cereal grains such as rice, etc.) that does not contain an organic solvent substance having a relative dielectric constant of 20 to 50・ When detecting the amount of water contained in each substance on-line or off-line with tea leaves, tobacco leaves, garbage, wood, soil, concrete fine aggregate, etc. while each is stationary or moving In addition, since there is no substance with a relative dielectric constant equivalent to that of water among substances present in rain detection, water level monitoring during bath hot water detection, human body seating detection, etc., it is possible to detect the amount of moisture with little error. There is a feature that the amount of water in the detection target can be detected by contacting the target.
[0008]
The principle of the capacitance type is based on the property that water is a substance (dielectric) that polarizes, and the capacitance value between a pair of electrodes 100a and 100b is measured as shown in FIG. This is a method of detecting the moisture content from the capacitance value. Here, the amount of water is expressed by the amount of water = water volume / (S × d), S is the area of the electrodes 100a and 100b, d is the distance between the electrodes, and S × d is the volume of the detection area.
And the water content and capacitance Cx are
Cx = [ε ′ (water) × water content + ε ′ (other) × (1−water content)] × ε0 × S / d
It becomes. Here, the relative dielectric constant ε ′ (water) of water is 80, the relative dielectric constant ε ′ (others) is 2 for wood, and 1 for air, and the capacitance depends on the amount of moisture in the detection region. Cx is determined. Although the value of the capacitance Cx depends on the size of the electrodes 100a and 100b, it shows several pF in a dry state and several tens pF in a state with a lot of moisture. (See, for example, Industrial Measurement Technology System Editorial Committee: Humidity and Moisture Measurement published by Nikkan Kogyo Shimbun 1965)
FIG. 38 shows the relationship between the moisture content and the capacitance Cx.
[0009]
[Problems to be solved by the invention]
Even in the capacitance type that can detect the amount of water in the detection object by contacting the detection object as described above, there are the following problems.
[0010]
That is, as shown in FIGS. 39A and 39B, the insulating structure 102 is disposed in the opening 101 on the inner wall of the container 105 as a structure, and the electrode surfaces face each other on the surface of the insulating structure 102. In the electrodes 100a and 100b arranged in parallel with each other, the detection object is buried between the electrodes 100a and 100b and remains as a deposit, and as a result, the capacitance detection circuit 103 measures the moisture content of the deposit between the electrodes 100a and 100b. As a result, there is a problem that the moisture content of the detection object is not reflected. For this purpose, a cleaning structure is required so as not to remain deposited. However, in order to provide the cleaning structure, there has been a problem that the manufacturing cost is increased. The output unit 104 that inputs the detection output of the capacitance detection circuit 103 outputs a voltage signal having an electric amount corresponding to the amount of moisture, for example, a voltage value, from the capacitance value detected by the capacitance detection circuit 103.
[0011]
In addition, the electrodes 100a and 100b protrude into the container 105, so that the movement of the detection target in the container 105 is hindered, a load is applied to the electrodes 100a and 100b, and deposits remain in other parts. There was a problem that. Therefore, it is necessary to give the structure of the electrodes 100a and 100b strong enough to withstand the load. As a result, there are problems that the electrode structure becomes large and the manufacturing cost increases.
[0012]
In FIG. 39 (b), Cx represents the capacitance due to the detection target.
[0013]
  The present invention has been made in view of the above-described problems. The object of the present invention is to determine the amount of moisture contained in the detection region when the detection region is an electric field region formed by a pair of electrodes. Measures in real time without error when the object to be detected is stationary or movingIn addition, the effects of stray capacitance between the center electrode and the insulator can be eliminated.It is an object to provide a capacitive moisture sensor. ,
[0015]
[Means for Solving the Problems]
  According to the first aspect of the present invention, in the invention of claim 1, an electric field region formed by a pair of electrodes is used as a detection region, and at least one electrode of the pair of electrodes is in contact with a detection object via an insulator. Is equivalent to the amount of moisture from the electrode part having a detection sensitivity surface, a capacitance detection circuit for detecting a capacitance value determined by the amount of moisture present in the detection region, and the capacitance value detected by the capacitance detection circuit And a moisture sensor circuit unit comprising at least an output circuit that outputs an electrical signal having a quantity of electricity to be generated.The pair of electrodes includes a first electrode and an annular second electrode formed so as to surround the first electrode, and an inner edge of the second electrode and an outer edge of the first electrode Is substantially the same over the entire circumference, and each electrode is positioned at the bottom of the recess formed in the insulator, and the height indicated on the height of the rib forming the recess or the inner wall surface of the recess An insulating material that covers the exposed surface of each electrode is filled in the recess with the position mark as a reference.It is characterized by that.
[0018]
  Claim2In the invention of claim1'sThe invention is characterized in that the first electrode and the second electrode have substantially the same width.
[0020]
  Claim3In the invention of claim 1,Or 2In any one of the inventions described above, a shield box that covers the moisture sensor circuit unit is used as a heat sink for circuit components.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0036]
(Embodiment 1)
FIG. 1 is a perspective view of the entire capacitive moisture sensor 30 of the present embodiment. The outer shape of the bottom surface is substantially square and the electrode portion is arranged in the circular recess 10 at the center of the inner bottom portion. A moisture sensor housing 1 made of a synthetic resin insulator, a circuit board 2 made of a printed circuit board disposed in the moisture sensor housing 1, and a circuit component mounting portion of the circuit board 2 are covered. The shield box 3 arranged on the circuit board 1 and the lid 29 made of a conductor such as a metal plate attached to the opening of the moisture sensor housing 1 via the packing 4. .
[0037]
The moisture amount sensor housing 1 is formed of a molding material such as polycarbonate, polypropylene, polyphenylene sulfide, etc., and the thickness of the bottom portion of the concave portion 10 in which the electrode portion is disposed is formed to be about 5 mm to 0.1 mm. The recess 10 is formed by expanding the bottom wall outward as shown in FIGS. 2A to 2C, and is arranged concentrically so as to surround the circular electrode 5a at the center and the electrode 5a. The electrode portion is constituted by these electrodes 5a and 5b, and the outer surface of the bulging portion 22 of the moisture amount sensor housing 1 corresponding to the recess 10 is in contact with the detection object. A detection sensitivity surface 23 is formed.
[0038]
The electrodes 5a and 5b are filled with an insulating sealing material such as silicon rubber or epoxy resin by bonding and fixing a metal conductive plate (for example, copper, plated with copper, etc.) punched into an electrode shape at a predetermined position of the recess 10. The object 11 is filled in the recess 10 to cover the electrodes 5a and 5b. The filler 11 is preferably made of a material having a low dielectric constant. For example, silicon rubber has a relative dielectric constant of about 2 to 5. This filling 11 is intended to prevent a short circuit between the electrodes 5a and 5b due to condensed water when condensation occurs in the moisture sensor housing 1.
[0039]
As shown in FIG. 3, the circuit board 2 is placed on the columnar body 12 that is erected in the vicinity of the four corners on the bottom surface of the moisture amount sensor housing 1 around the recess 10, as shown in FIG. 3. It is fixed by screwing and fastening the fixing screw 13 to the upper surface side of the board. On the circuit board 2, as shown in FIG. 3, an electronic component constituting the moisture sensor circuit block 9 which is a moisture sensor circuit unit is mounted, and further, a metal plate formed by sheet metal processing so as to cover the electronic component. The shield box 3 is placed and fixed. The circuit on the circuit board 2 and the electrodes 5a and 5b are connected via a lead wire 40. The lid 29 and the operation reference point α of the circuit board 2 are connected by a lead wire 40 ′.
[0040]
As shown in FIG. 4, the moisture amount sensor circuit block 9 includes a capacitance detection circuit 6 that detects a capacitance value Cx of a detection region configured by an electric field region between a pair of electrodes 5 a and 5 b that configure the electrode unit, An output circuit 7 that outputs an electrical quantity corresponding to the capacitance value detected by the capacitance detection circuit 6, for example, a voltage signal, a power supply circuit 8 that supplies operating power to the capacitance detection circuit 6 and the output circuit 7, and these circuits Capacitor C for determining the impedance between the operation reference point α of the capacitance detection circuit 6 and the ground β by being connected between the grounds 6 to 8, that is, the operation reference point α of the capacitance detection circuit 6 and the ground β._EAnd is shielded by a shield box 3 deposited on the circuit board 1, and the operation reference point α is connected to the shield box 3.
[0041]
As a specific circuit of the capacitance detection circuit 6, a circuit using a PLL circuit shown in FIG. 5 is used. The circuit of FIG. 5 uses an oscillation circuit 15 in which an oscillation frequency is determined by a capacitance Cx depending on the amount of moisture of an object to be detected existing between electrodes 5a and 5b. It is detected by a PLL circuit 19 comprising a filter 17 and a VCO 18 to obtain a voltage according to the detected frequency, adjust this voltage to a desired characteristic of the output circuit 7, and output a signal having a voltage according to the amount of moisture. It has become. In other words, when the amount of moisture contained in the detection object existing between the electrodes 5a and 5b increases, the oscillation frequency of the oscillation circuit 15 decreases, and conversely, when the amount of moisture decreases, the oscillation frequency of the oscillation circuit 15 increases and the PLL is increased. In the circuit 19, the frequency of the VCO 18 is controlled in accordance with the oscillation frequency, and the voltage output from the low-pass filter 17 is changed in accordance with the amount of moisture. The output circuit 7 performs characteristic adjustment to increase / decrease the output voltage at a constant ratio in accordance with the increase / decrease of the amount of moisture detected by receiving this output.
[0042]
The power supply circuit 8 is configured by, for example, a three-terminal regulator IC.
[0043]
The power supply circuit 8 and the output circuit 7 have one end connected to the circuit board 1 side circuit and the other end provided at the end of the cable 20 led out through the shield box 3 and the lid 29 as shown in FIG. The power supply circuit 8 is supplied from the operation panel 14 via the cable 20 and the output signal of the output circuit 7 is output from the operation panel 14. Is sent to.
[0044]
The shield box 3 shown in FIG. 3 electromagnetically shields the moisture sensor circuit block 9.
[0045]
Thus, when the moisture amount sensor 30 of the present embodiment configured as described above is attached to the wall surface of the container 31 containing the detection object X, a window hole opened in the wall surface of the container 31 as shown in FIG. A bulging portion 22 corresponding to the concave portion 10 of the moisture amount sensor housing 1 is fitted to 32 from the outside of the container 31. Here, the amount of protrusion of the bulging portion 22 and the thickness of the wall of the container 31 are set to be substantially the same. Positioning is performed by directly contacting the outer bottom surface of the quantity sensor housing 1 and the outer wall surface of the container 31, and the outer surface of the bulging portion 22 facing the container 31, that is, the detection sensitivity surface 23 is the same surface as the inner wall surface of the container 31 ( To be flush with each other. Then, the moisture sensor 30 is fixed to the container 31 by mounting bolts (not shown) through which holes 28a, 28b, and 28c provided at the four corners of the lid 29, packing 4, and moisture sensor housing 1 are inserted.
[0046]
Thus, when the moisture sensor 30 of this embodiment is attached to the container 31 as described above, the electrodes 5a and 5b do not directly touch the detection target X, and the detection sensitivity surface 23 is in the container 31. It does not protrude. Therefore, the detection object X is not buried between the electrodes 5a and 5B and does not hinder the movement. For example, the detection object X is a fermented product, rice, cereal, tea leaf, tobacco leaf, garbage, wood in the fermentation process. -In both soil and concrete fine aggregates, when the electric field region constituted by the pair of electrodes 5a and 5b is set as the detection region, the amount of moisture contained in the detection region is stationary. Even in the movement such as stirring and transporting, it can be detected in real time without error.
[0047]
In the present embodiment, as shown in FIG. 6A, the center electrode 5a is surrounded by an annular electrode 5b, and the distance d2 between the two is the same over the entire circumference. The amount of leakage of electric lines of force to the outside of the stray capacitance generated from the electrode can be reduced, the influence of stray capacitance between the center electrode 5a and the container 31 can be reduced, and the width of the electrode 5a, that is, the diameter d0, Since the width d1 of 5b is the same, the density of the electric lines of force is the same in the electrodes 5a and 5b as shown in FIG. 6B, so that the stray capacitance is reduced, and fluctuations such as the potential of the ground β, The moisture amount sensor 8 with less malfunction is realized even with respect to potential fluctuation due to leakage current.
[0048]
As shown in FIG. 7A, the electrode 5a is square, the surrounding electrode 5b is formed in a four-frame shape, and the length d0 of one side of the electrode 5a and the width d1 of the electrode 5b are the same dimensions. The distance d2 between the parallel sides of the two may be the same dimension for all four rounds. Also in this case, the influence on the stray capacitance can be reduced.
[0049]
The shape of the central electrode 5a is not a square or a circle, but a rectangle as shown in FIG. 7B, an oval as shown in FIG. 7C, or an ellipse as shown in FIG. 7D. It is also possible to combine the annular electrodes 5b corresponding to the respective shapes. In each figure, d0 = d1, and the distance d2 between the electrodes 5a and 5b is the same distance over the entire circumference in each example.
[0050]
By the way, for the positioning of the detection sensitivity surface 23, the contact surface is configured by contacting the flat outer bottom surface of the moisture sensor housing 1 and the outer wall surface of the container 31, but as shown in FIG. Protrusions 24 are formed at the four corners of the outer bottom surface of the moisture sensor housing 1, and the contact surface for positioning the detection sensitivity surface 23 is configured such that the front end surface of the protrusion 24 abuts the outer wall surface of the container 31. You may do it.
[0051]
Alternatively, as shown in FIG. 9, protrusions 31 a are formed on the outer wall surface of the container 31 corresponding to the four corners of the outer bottom surface 22 of the moisture sensor housing 1, and the moisture sensor housing is formed on the tip surface of the protrusion 1 a. The contact surface for positioning the detection sensitivity surface 23 may be configured so as to abut against the outer bottom surface of 1.
(Embodiment 2)
In the first embodiment, the outer wall surface and the inner wall surface of the container 31 containing the detection target object X correspond to flat surfaces, but at least the inner wall surface is a curved surface. The detection sensitivity surface 23 cannot be flush with the inner wall surface of the container 31.
[0052]
Therefore, in this embodiment, as shown in FIG. 10, the outer surface of the bulging portion 22, that is, the detection sensitivity surface 23 is curved so as to be flush with the arcuate inner wall surface of the container 31. In this case, the wall of the bulging portion 22, that is, the bottom wall of the recess 10 is substantially equal in thickness, and the distance between the electrodes 5 a and 5 b disposed on the bottom of the recess 10 and the detection sensitivity surface 23 is made equal.
[0053]
Further, in the case of the cylindrical container 31 whose inner and outer wall surfaces are both curved surfaces, the outer surface of the moisture amount sensor housing 1 around the bulging portion 22 can be brought into contact with the outer wall surface of the container 31 if it is a flat surface. Can not. Therefore, as shown in FIG. 11, when the bulging portion 22 is fitted from the outside into the window hole 32 of the container 31, the outer surface of the bulging portion 22, that is, the detection sensitivity surface 22 is just flush with the inner wall surface of the container 31. A cylindrical boss 33 is provided as an abutting portion for positioning so as to be in contact with the front end surface on the outer bottom surface near the four corners of the moisture sensor housing 1. If the container 31 is made of metal, the boss 33 is fixed by welding. In FIG. 11, reference numeral 34 indicates the welding site.
[0054]
(Embodiment 3)
In the first and second embodiments, the electrodes 5a and 5b are disposed on the same bottom surface of the concave portion 10, and the detection sensitivity surface 23 on the outside of the bulging portion 22 from the electrodes 5a and 5b. However, it is not necessary to equalize the distance from the electrodes 5a, 5b to the detection sensitivity surface 23.
[0055]
Therefore, in the present embodiment, as shown in FIGS. 12A to 12C, a protruding base 25 is formed in which the central portion of the bottom surface of the concave portion 10 of the moisture amount sensor housing 1 is higher than the surroundings. The configuration in which the electrode 5a is disposed on the lower surface and the electrode 5b is disposed on the lower bottom surface is employed. In this case, the thickness of the insulator at the projecting base 25 where the electrode 5a is disposed is made uniform, and the thickness of the insulator at the bottom surface where the electrode 5b is disposed is also made uniform. The detection sensitivity surface 23 is the same surface.
[0056]
Since other configurations are the same as those of the first embodiment, illustration is omitted.
[0057]
Thus, in the present embodiment, the thickness of the insulators at the portions where the electrodes 5a and 5b are arranged is uniform in each case, so that there is no difference in sensitivity, and a pair of electrodes 5a, When the electric field region constituted by 5b is used as a detection region, the amount of water contained in the detection region is determined in real time even when the detection target X is stationary or during movement such as stirring and conveyance. It can be detected without error.
[0058]
(Embodiment 4)
In any of the first to third embodiments, the electrodes 5a and 5b have a configuration in which a conductive metal plate punched into an electrode shape is bonded to the bottom surface of the recess 10, but in this embodiment, the electrode arrangement position is provided. As shown in FIGS. 13 to 15, the recesses A and B, which are recess marks corresponding to the electrode shape, are surrounded by ribs 26 formed integrally in the recess 10 of the moisture amount sensor housing 1. The central recess A is used as an arrangement site for the electrode 5a, and the outer annular recess B is used as an installation site for the electrode 5b.
[0059]
The material for forming the electrodes 5a and 5b disposed here may be a conductive metal plate punched into an electrode shape, a metal tape, or a metal powder. A metal tape or metal powder can be used for the electrodes 5a and 5b of the first to third embodiments.
[0060]
Since any of Embodiments 1 to 3 can be applied to other configurations, illustration and description thereof are omitted here.
[0061]
As described above, in this embodiment, since the positioning of the electrode placement position can be reliably set by the recessed portions A and B, variations in the positions of the electrodes 5a and 5b are eliminated, and the characteristics are stabilized.
[0062]
(Embodiment 5)
In the first to fourth embodiments, an electrode material such as a conductive metal plate punched into an electrode shape as the electrodes 5a and 5b is bonded and fixed to a predetermined position of the concave portion 10 of the moisture sensor housing 1. In the embodiment, as shown in FIG. 16, when the moisture sensor housing 1 is formed, a conductive metal plate forming the electrodes 5a and 5b is inserted and embedded in a portion corresponding to the bottom wall of the recess 10. It is.
[0063]
In the present embodiment configured as described above, the electrodes 5a and 5b can be disposed simultaneously with the manufacture of the moisture sensor housing 1 by insert molding, and the conductive metal plate constituting the electrodes 5a and 5b has an appropriate thickness. By using a thing, the intensity | strength of the bottom wall of the recessed part 10 can be strengthened.
[0064]
Further, a part of the electrodes 5a and 5b protrudes upward from the recess 10 to form connection terminals 41a and 41b which are directly soldered to the circuit board 2 as shown in FIG. 2 is not required.
[0065]
Since any of Embodiments 1 to 3 can be applied to other configurations, illustration and description thereof are omitted here.
[0066]
(Embodiment 6)
By the way, when the inner wall surface of the container 31 to which the moisture amount sensor 30 is attached is a curved surface, the detection sensitivity surface 23 needs to be a curved surface as described above. On the other hand, since the distance between the detection sensitivity surface 23 and each electrode 5a, 5b, that is, the thickness of the insulator interposed between them must be substantially uniform, the arrangement surface is also formed in a curved surface.
[0067]
On the other hand, the surfaces of the electrodes 5a and 5b must be finished so as to coincide with the arrangement surface, and when the electrodes are formed with a conductive metal plate, it is necessary to rely on a mold, resulting in an increase in cost. There is a problem of becoming. In addition, there is a problem that peeling is likely to occur in the case of adhesion fixation.
[0068]
On the other hand, when the electrodes 5a and 5b are embedded in the bottom wall of the recess 10 of the moisture amount sensor housing 1 by insert molding as in the fourth embodiment, the distance between the electrodes 5a and 5b and the detection sensitivity surface 23, that is, between them In order to control the thickness of the insulator, the mold needs a holding structure that holds the position of the conductive metal plate to be inserted in a predetermined position withstanding the pressure of pouring the synthetic resin into the mold. There is a problem that the structure is complicated and results in increased costs.
[0069]
In addition, since the elastic coefficient of the resin material forming the moisture sensor housing 1 is different from that of the metal conductive plate, the detection sensitivity surface 23 facing the inside of the container 31 is subjected to a load from the detection target X under use. There is a possibility that the resin molding site forming the sensitivity surface 23 bends and a crack occurs in the resin molding site at the boundary between the inserted metal conductive plate and the molding resin.
[0070]
Therefore, in the present embodiment, a metal vapor deposition film such as copper or aluminum is formed at a predetermined position of the concave portion 10 of the moisture sensor housing 1, and the electrodes 5a and 5b are configured by the metal vapor deposition film.
[0071]
That is, as shown in FIG. 18 or FIG. 19, as in the fourth embodiment, a metal vapor deposition film is deposited on the recesses A and B formed on the bottom surface of the recess 10 surrounded by the ribs 26. Let the metal vapor deposition films vapor-deposited on B be electrodes 5a and 5b. The surfaces of the electrodes 5a and 5b are subjected to solder plating or gold plating to prevent corrosion to form a protective film.
[0072]
Here, as an electrode forming method, the deposition is controlled so as to form a metal vapor deposition film in the recesses A and B, or a metal vapor deposition film including the periphery is formed, and the electrodes 5a and 5b are formed after this formation. Although there is any method of selectively peeling and forming so as to remove the part, any method may be adopted as appropriate.
[0073]
As described above, in this embodiment, since the electrodes 5a and 5b are formed of a metal vapor deposition film, cracking of the resin molding site and peeling of the electrodes 5a and 5b are unlikely to occur, and the electrodes 5a and 5b and the detection sensitivity surface 23 are not easily generated. It becomes easy to manage the distance, that is, the thickness of the resin molding portion interposed therebetween.
[0074]
Moreover, the intensity | strength of the moisture content sensor housing | casing 1 can be raised by forming a rib radially from a center part.
[0075]
In addition, since the structure of Embodiment 1 thru | or 4 should just be employ | adopted for another structure, illustration and description are abbreviate | omitted.
[0076]
(Embodiment 7)
In any of the first to sixth embodiments described above, in order to prevent the electrodes 5a and 5b from being short-circuited by dew condensation water generated inside the moisture sensor housing 1, for example, as shown in FIG. In this way, the concave portion 10 is filled with the filler 11 so as to cover the electrodes 5a and 5b, but the amount of the filler 11 can be substantially controlled by the weight and volume capacity. Since the electrostatic capacity value inside the moisture amount sensor housing 1 is different if the height is different, it is necessary to manage the amount of the filler 11, particularly the height. Therefore, as shown in FIG. 20, when the height H from the bottom of the recess 10 where the electrodes 5a and 5b are disposed to the opening is filled with the filling 11 to the height H, In this embodiment, the capacitance value is set to be a predetermined value.
[0077]
Therefore, by filling the filler 11 up to the depth H of the concave portion 10, the capacitance value inside the moisture sensor housing 1 can be stabilized to a predetermined value.
[0078]
Further, in the case where the recesses A and B, which are the arrangement portions of the electrodes 5a and 5b, are formed by the rib 26 as in the fourth to sixth embodiments, the height H ′ of the rib 26 is set to a predetermined value as shown in FIG. By setting the height to the height H ′, the filling 11 is filled in the recesses A and B to stabilize the capacitance value inside the moisture amount sensor housing 1 at a predetermined value. It can be made.
[0079]
The capacitance value due to the filler 11 is as follows.
[0080]
That is, as shown in FIG. 22, the height of the filling 11 filling the recess 11 in which the electrodes 5a and 5b are disposed is H, and is interposed between the electrodes 5a and 5b and the detection sensitivity surface 23. Assuming that the thickness of the synthetic resin molding part is h, the equivalent circuit on the detection object side (Cx) is the capacitance value Ca of the synthetic resin molding part and the moisture content of the detection object as shown in FIG. The capacitance value Cb can be represented by a series circuit of the capacitance value Ca ′ of the synthetic resin molding site. Here, the capacitance value of the synthetic resin molding part can be expressed by Ca (and Ca ′) or Cx = K / H ′. K is a constant determined by the dielectric constant of the synthetic resin molding site and the area of the electrode 5a or 5b.
[0081]
On the other hand, as shown in FIG. 23B, the equivalent circuit on the filler side (Cx ′) is the capacitance value Cc of the filler 11, the capacitance value Cd of air, and the capacitance value Cc of the charging agent 11. It can be shown by a series circuit of '. Here, the capacitance value of the synthetic resin molding part can be expressed by Cc (and Cc) or Cx ′ = K / H. K is a constant determined by the dielectric constant of the filler 11 and the area of the electrode 5a or 5b.
[0082]
Accordingly, the capacitance value Cx ′ on the side of the filling 11 changes depending on the thickness (height) H, and management of the thickness (height) H is necessary.
[0083]
(Embodiment 8)
In the first to seventh embodiments, the shield box 3 is disposed on the circuit board 2 so as to cover the moisture sensor circuit block 9 mounted on the circuit board 2, and electromagnetic shielding is performed. In order to achieve electromagnetic shielding, in this embodiment, in addition to the shield box 3, sheet metal processing is performed along the inner wall surface of the moisture sensor housing 1 and the bottom surface around the recess 10 as shown in FIGS. 24 and 25. A metal shield frame 27 made of copper is disposed, and in the circuit shown in FIG. 4, it is connected together with the shield box 3 to a ground (0 V) line which is the operation reference point α of the circuit of the moisture amount sensor circuit block 9.
[0084]
Thus, in the present embodiment, the FM broadcast or amateur radio frequency electric OR that matches the frequency band (several tens of MHz to several hundreds of MHz) used in the moisture amount sensor circuit block 9 by the action of the shield box 3 and the metal shield frame 27. Can be shielded even if the error occurs, and the cause of malfunction can be eliminated. On the contrary, it is possible to prevent radiation waves from being radiated from the inside to the outside, and it is possible to eliminate the possibility of inducing a malfunction of the external device.
[0085]
Since the other configuration of the present embodiment shown in the figure is the same as that of the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted. Needless to say, the configuration using the metal shield frame 27 can be applied to the second to seventh embodiments other than the first embodiment or the embodiments described later.
[0086]
(Embodiment 9)
In any of the above embodiments, the shield box 3 is disposed on the circuit board 2 so as to cover the moisture sensor circuit block 9. In this embodiment, the shield box 3 is disposed on the moisture sensor circuit block 9. This is also used as a heat radiating plate of the three-terminal regulator 80 constituting the power supply circuit 8.
[0087]
That is, as shown in FIGS. 26 (a) to 26 (c), the package surface of the three-terminal regulator 80 and the heat radiating metal plate portion are brought into contact with the mounting piece 3a integrally formed on the outside of the box from the side end portion of the shield box 3. It is fixed by screws 81 and nuts 82.
[0088]
Here, the three-terminal regulator 30 uses a high frequency frequency range of several tens of MHz to several hundreds of MHz, and an impedance such as a capacitance value of about several pF is as small as several hundred Ω, so that a current of several hundred mA is high speed. It tends to flow and generate heat.
[0089]
On the other hand, the moisture sensor housing 1 is required to be miniaturized, and if a single heat sink is used exclusively, it is necessary to avoid the use of a heat sink because it increases size, increases costs, and increases the number of parts.
[0090]
From these points, by using the shield box 3 also as the heat radiating plate of the three-terminal regulator 80 as in the present embodiment, heat can be radiated from the three-terminal regulator 80 without separately providing a heat radiating plate.
[0091]
(Embodiment 10)
As described above, the moisture sensor 30 of each embodiment has an electric amount corresponding to the moisture amount by detecting the capacitance value of the detection region constituted by the pair of electrodes 5a and 5b by the capacitance detection circuit 6. Although an electric signal is output from the output circuit 7, the actual operation of the capacitance detection circuit 6 does not operate only with the capacitance value Cx formed by the pair of electrodes 5a and 5b. ), A stray capacitance C1 exists between the wall surface of the container 31 and the outer electrode 5b, and this stray capacitance C1 is a factor that makes circuit operation unstable.
[0092]
The operation reference point α of the moisture sensor circuit block 9 is electrically floating from the ground, but when the container 31 into which the detection target X is placed is a conductor, the container 31 itself is connected (grounded) to the ground β. Is in a state. Accordingly, some impedance exists between the potential of the operation reference point α and the ground β. This impedance characteristic cannot be defined because it depends on the outside of the moisture sensor 30.
[0093]
Therefore, in this embodiment, an electronic component having an impedance that is clearly smaller than this impedance is inserted, and the circuit configuration is such that the impedance between the operation reference point α and the ground β is determined.
[0094]
Here, in any of the water content sensors 30 of the above-described embodiments, the container 31 that is a conductor is fixed by a mounting bolt that is a conductor, while the lid 29 of the water content sensor housing 1 of the water content sensor 30. Is made of a conductive material, so that the lid 29 is electrically connected to the ground β via a mounting bolt and a container 31.
[0095]
Accordingly, an electronic component that determines the impedance between the lid 29 and the movement reference point α and between the movement reference point α and the ground β, for example, the capacitor C_EIs inserted as shown in FIG.
[0096]
The stray capacitance C1 generated between the wall surface of the container 31 and the outer electrode 5b is the capacitor C_ETogether with the capacitance detection circuit 6, as shown in FIG._EAnd the combined capacitance value C of the stray capacitance C1 is C = (C1 × C_E) / (C1 + C_EThe combined capacitance value C becomes a cause of malfunction of the capacitance detection circuit 6.
[0097]
The stray capacitance C1 is a value that varies depending on the moisture content of the detection target X. This is because it varies depending on the moisture content of the detection object X between the electrode 5b and the container 31 in the same manner as the electrostatic capacitance value Cx that is originally desired to be detected.
[0098]
Here, in order to make the composite capacitance value C as constant as possible, the stray capacitance C1 >> C_EThen C = C_EThus, the operation of the capacitance detection circuit 6 is operated only by Cx. Therefore, in order to increase the stray capacitance C1, the distance between the external electrode 5b and the wall surface of the container 31 should be as close as possible structurally.
[0099]
For example, in the structure equivalent to the structure of the first embodiment as shown in FIG. 28, when the outer diameter of the outer electrode 5b is φ90 mm, the outer diameter of the bulging portion 22 concentric with the electrode 5b is φ110 mm. The distance between the inner surface of the window hole 32 of the 31 and the electrode 5b is narrowed to about 10 mm so that the stray capacitance C1 is increased.
[0100]
In FIG. 27, Z1 and Z2 are impedance elements in the capacitance detection circuit 6, and AP is an operational amplifier.
[0101]
The configuration of this embodiment can be adopted in any of the above-described embodiments. Therefore, other configurations are not shown here, and descriptions thereof are omitted.
(Embodiment 11)
In each of the above embodiments, the moisture sensor housing 1 of the moisture sensor 30 is provided with a pair of electrodes 5a and 5b. However, when the container 31 containing the detection target X is a metal container, The container 31 can be used as one of a pair of electrodes constituting the detection region. In this embodiment, the container 31 is used as an electrode. That is, as shown in FIG. 29, an electrode 5a similar to that of the first embodiment is disposed at the center of the bottom surface of the recess 10 of the moisture sensor housing 1, and the electrode constituting the detection region with this electrode 5a is used as the moisture sensor housing. The body 31 is constituted by a metal container 31 to which the body 1 is attached. The container 31 is connected to the ground β as shown in FIG. 30 and is also connected to the operation reference point α of the circuit of the moisture amount sensor block 8.
[0102]
Thus, in the moisture amount sensor block 8 of the present embodiment, an electric field region constituted by the electrode constituted by the container 31 and the electrode 5a disposed in the recess 10 of the moisture amount sensor housing 1 is used as a detection region. The moisture content of the detection object X in the container 31 is detected using the outer surface of the bulging portion 22 forming the recess 10 in which the electrode 5a is disposed as the detection sensitivity surface 23 as in the above embodiments.
[0103]
The circuit configuration of the moisture sensor block 8 is the same as that of the first embodiment.
[0104]
The structure of the moisture sensor housing 1 and the structure of the electrode 5a are the same as those of the first embodiment. Therefore, the same components are denoted by the same reference numerals and the description thereof is omitted, but the structures of the other embodiments described above. Of course, it may be adopted.
Embodiment 12
By the way, when the present invention uses a capacitance type moisture sensor, for example, as a moisture sensor for measuring the moisture content of a garbage treatment agent infested with microorganisms, the garbage treatment tank actually has a garbage treatment inside. Along with the agent, there is also garbage itself. And when the component which comprises a garbage was measured, there was much moisture.
[0105]
The moisture content of the garbage treatment agent that is the detection target X is about 60% at the maximum by weight%, and is generally on the dry side. Even if the detection target X has such a moisture content, if the garbage itself occupies a detection region formed between the electrodes 5a and 5b, the moisture sensor outputs a detection output corresponding to the moisture content of the garbage. It will be output, and it will not be possible to measure the moisture content of the garbage treatment agent that is originally required.
[0106]
By the way, the general size of garbage is crushed immediately after being put into the garbage processing machine, and the crushed garbage is actually passed through various sieve sizes to obtain the ratio of the remaining garbage. As a result, it was found that the garbage was crushed to a size of about 15 mm. Therefore, it was found that if the detection area has a margin and is about 20 mm or more, the detection area is not filled with garbage.
[0107]
Therefore, the present inventors obtained the relationship between the size and distance of the pair of electrodes 5a and 5b that determine the detection area and the detection area using the experimental electrode unit shown in FIG.
[0108]
In this experiment, an electrode width W of a pair of strip-shaped electrodes 5a and 5b made of a copper foil tape having a thickness of 0.1 mm and a length of 115 mm is 24 mm, and the distance P between the electrodes 5a and 5b is 2 mm. An electrode having a configuration, an electrode width W of a pair of strip-shaped electrodes 5a, 5b made of a copper foil tape having the same thickness and length as described above is 10 mm, and an electrode having a distance P of 30 mm between both electrodes 5a, 5b Of the pair of strip electrodes 5a and 5b made of a copper foil tape having the same thickness and length as described above, one electrode width W is 5 mm, the other electrode width W is 25 mm, and both electrodes 5a , 5b, and an electrode portion having an electrode configuration with a distance P of 20 mm, a box-shaped non-conductive having a square bottom surface with a thickness of 1 mm and a side length of 115 mm, and a height of 40 mm The electrodes 5a and 5b are attached to the outer bottom surface of the conductive resin case PC, and the resin When water was put inside the case PC and the water level at this time was increased to 5 mm, 10 mm, 25 mm,..., The interelectrode capacitance was measured, and the interelectrode capacitance of each electrode portion is shown in FIG. It became a value like this. 32a, the electrode width of the electrodes 5a and 5b is 24 mm, and the distance between the electrodes 5a and 5b is 2 mm. As a result of measuring the interelectrode capacitance of the electrode portion having the electrode configuration of 10 mm and the distance between the electrodes 5a and 5b being 30 mm, the electrode width of one of the electrodes 5a and 5b is 5 mm and the width of the other electrode is 25 mm. The measurement result of the capacity | capacitance between electrodes of the electrode part of the electrode structure whose distance between electrodes 5a and 5b is 20 mm is shown.
[0109]
From this result, if the water level at which the interelectrode capacitance does not change even if the water level is increased is defined as the detection region D in the depth direction from the electrode surface, the depth dimension of the detection region D is parallel to and far from the electrodes 5a and 5b. It was found to be about half of the distance between the edges, ie the total width (50 mm).
[0110]
Thus, by configuring a moisture sensor that detects the moisture content of the garbage disposal agent that is the detection target X of the moisture content of the garbage disposal machine that satisfies the above-described conditions, the garbage disposal agent is accurately configured. It became possible to detect the amount of water.
[0111]
Therefore, the relationship between the circular electrode 5a and the annular electrode 5b in the configuration of the first embodiment is dealt with by the mixture mixed with the detection target object X based on the above conditions, for example, as shown in FIG. As shown in (b), if the electrode portion is composed of a circular electrode 5a having a diameter of d0 and an annular electrode 5b having an inner diameter of (d2 × 2) + d0 and a width of d1, both electrodes 5a, Electrode 5a so that the distance (d1 + d2 + d0) between the distant ends of the parallel edges of 5b is at least twice (L) of the depth dimension (L / 2) of the detection region D <20 mm for garbage disposal agent>. By setting the width dimension and the interval of 5b, it was possible to realize an electrode part in which garbage other than the detection object X corresponding to the detection region D does not fill the detection region.
[0112]
That is, by making the distance between the far edges of the parallel edges of the electrodes 5a and 5b more than twice the size of the mixture other than the detection object X, the mixture does not fill up the detection region, and the detection object It is possible to reliably detect the moisture content of the object X.
[0113]
FIG. 34 (a) shows a case corresponding to the electrodes 5a and 5b having the shape shown in FIG. 7 (a). In this case, the dimension of one side of the central electrode 5a is d0, and the width dimension of the surrounding electrode 5b. Is the depth dimension of the detection region D determined by the size of the pair of electrodes 5a and 5b, where d1 is the dimension between the side of the electrode 5a and the inner side of the electrode 5b facing the electrode 5b. In order to satisfy the above condition of 20 mm or more, based on the results of the experiment, the distance (= d1 + d2 + d0) between the edges that are far from each other among the parallel edges of the electrodes 5a and 5b is shown in FIG. As shown in FIG. 34 (b), the width dimensions and intervals of the electrodes 5a and 5b may be set so as to be at least twice (L) of the depth dimension 20 mm (L / 2) of the detection region D.
(Embodiment 13)
In the twelfth embodiment, the distance between the electrodes 5a and 5b is increased in order to eliminate the influence of the mixture other than the detection target X, but the output value of the output circuit 7 of the moisture amount sensor circuit block 9 is monitored. If it is, it can be determined that a water content that is clearly larger than expected or a material having a smaller water content has moved to the detection region.
[0114]
Therefore, in the present embodiment, it is determined that, for example, a voltage signal output from the output circuit 7 and a preset amount of water as shown in FIG. The reference value VH that can be determined is compared with the reference value VL that can be determined that the amount of moisture is small. As shown, by providing a determination circuit 7a that outputs a signal indicating the presence or absence of contaminants to the operation panel 14, the distance between the electrodes 5a and 5b can be dealt with even less than twice the distance of the mixture.
[0115]
That is, in this embodiment, it is not necessary to configure the electrode part considering the mixture, and the electrode part can be made small.
[0116]
【The invention's effect】
  The invention according to claim 1 is an electrode in which an electric field region constituted by a pair of electrodes is a detection region, and a surface in which at least one of the pair of electrodes is in contact with a detection target via an insulator is a detection sensitivity surface. And a capacitance detection circuit for detecting a capacitance value determined by the amount of moisture present in the detection region, and an electric signal having an amount of electricity corresponding to the amount of moisture from the capacitance value detected by the capacitance detection circuit A water content sensor circuit unit comprising at least an output circuit that outputs the amount of water contained in the detection target in real time even when the detection target is moving as well as stationary. Since at least one of the pair of electrodes constituting the electrode portion does not directly touch the object to be detected, the electrode can be easily cleaned, and the electrode can be dissolved by metal ions in moisture. Furthermore, since it is protected by an insulator, the wear of the detection sensitivity surface becomes uniform, and it becomes difficult to make unevenness on the sensitivity detection surface to obstruct the flow of the detection object. There is an effect that there is no possibility of causing accumulation of the liquid and obstruction of the flow, and there is little possibility that the detection object is buried between the other electrode.
In addition, the pair of electrodes includes a first electrode and an annular second electrode formed so as to surround the first electrode, and the inner edge of the second electrode and the outer edge of the first electrode. Therefore, the effect of stray capacitance generated between the center electrode and the insulator can be eliminated.
  Further, each electrode is positioned at the bottom of the recess formed in the insulator, and the exposed surface of each electrode is defined based on the height position of the rib forming the recess or the height position marked on the inner wall surface of the recess. Since the insulating material to be covered is buried in the recess, it is possible to prevent the short circuit between the electrodes due to water due to dew condensation, etc., and to manage the height position of the insulating material, that is, the amount of the insulating material, As a result, there is an effect that the detection characteristic can be stabilized by eliminating the variation in the capacitance value due to the insulator.
[0131]
  Claim2The invention of claim1'sIn the present invention, since the width of the first electrode and the width of the second electrode are substantially the same, the lines of electric force from both electrodes can be made equal, and as a result, the influence of stray capacitance can be reduced.
[0133]
  Claim3The invention of claim 1Or 2In the present invention, since the shield box that covers the moisture sensor circuit portion is used as a heat sink for circuit components, there is no need to separately provide a heat sink for the circuit components. Therefore, the moisture sensor housing can be reduced in size and cost. Can be achieved.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a first embodiment.
FIG. 2 (a) is a plan view of the moisture sensor housing of the above.
(B) is a sectional side view of the moisture sensor housing of the above.
(C) is a sectional side view showing a state in which the concave portion of the moisture content sensor casing is filled with a filler.
FIG. 3 is a cross-sectional view in which a part of the above is attached to a container and can be omitted.
FIG. 4 is a circuit configuration diagram of the above.
FIG. 5 is a specific configuration diagram of the moisture sensor circuit block of the above.
FIG. 6 is an explanatory diagram of the electrode part.
FIGS. 7A to 7D are configuration explanatory views of other examples of the electrode unit same as above. FIGS.
FIG. 8 is a cross-sectional view of another example of the positioning configuration of the detection sensitivity surface of the above.
FIG. 9 is a cross-sectional view of another example of the positioning configuration of the detection sensitivity surface of the above.
FIG. 10A is a plan view of a moisture sensor housing of the second embodiment.
(B) is a sectional side view of the moisture sensor housing of the above.
(C) is a side cross section which shows the state which filled the filling into the recessed part of the moisture content sensor housing | casing same as the above.
FIG. 11 is a cross-sectional view in which a part of the above is attached to a container and can be omitted.
FIG. 12A is a plan view of a moisture sensor housing of the third embodiment.
(B) is a sectional side view of the moisture sensor housing of the above.
(C) is a side cross section which shows the state which filled the filling into the recessed part of the moisture content sensor housing | casing same as the above.
FIG. 13A is a plan view of an example of a moisture sensor housing of the fourth embodiment.
(B) is a side view of an example of a moisture amount sensor housing | casing same as the above.
(C) is a front view of an example of a moisture amount sensor housing | casing same as the above.
FIG. 14A is a plan view of another example of the moisture amount sensor casing of the above.
(B) is a side view of another example of the moisture amount sensor casing of the above.
(C) is a sectional side view of another example of the moisture sensor housing of the above.
(D) is a II cross-sectional view of another example of the moisture amount sensor casing same as the above.
FIG. 15 (a) is a plan view of another example of the moisture sensor housing of the above.
(B) is a side view of another example of the moisture sensor housing of the above.
(C) is a sectional side view of another example of the moisture amount sensor housing of the above.
(D) is a II sectional view of another example of the moisture amount sensor casing same as the above.
FIG. 16A is a plan view of a moisture sensor housing of the fifth embodiment.
(B) is a sectional side view of the moisture sensor housing of the above.
(C) is an II cross-sectional view of the moisture sensor housing of the above.
(D) is a front view of the moisture content sensor housing | casing same as the above.
FIG. 17 is a cross-sectional view of the above.
FIG. 18A is a plan view of a moisture sensor housing of the sixth embodiment.
(B) is a side view of the moisture sensor housing of the above.
(C) is a sectional side view of the moisture sensor housing of the above.
(D) is a II cross-sectional view of the moisture sensor housing of the above.
FIG. 19 (a) is a plan view of another example of the moisture sensor housing of the above.
(B) is a side view of another example of the moisture sensor housing of the above.
(C) is a sectional side view of another example of the moisture amount sensor housing of the above.
(D) is a II sectional view of another example of the moisture amount sensor casing same as the above.
FIG. 20 is a cross-sectional view of a moisture sensor housing showing a state in which a filler according to a seventh embodiment is filled.
FIG. 21 is a cross-sectional view of a moisture sensor housing of another example showing a state where the same filling material is filled.
FIG. 22 is an explanatory diagram of a capacitance value when the above configuration is used.
FIG. 23A is an equivalent circuit of the capacitance value on the detection target side when the above configuration is used.
(B) is an equivalent circuit of the capacitance value on the packing side when the above-described configuration is used.
FIG. 24 is a cross-sectional view of an eighth embodiment.
FIG. 25 is a top view of the moisture sensor housing of the above.
FIG. 26A is a side view of the main part of the ninth embodiment.
(B) is a top view in which a part of the main part is omitted.
(C) is a side view in which a part of the above is omitted and broken.
FIG. 27A is a circuit diagram of a main part of the tenth embodiment.
(B) is the equivalent circuit schematic of the principal part same as the above.
FIG. 28 is an explanatory diagram of the above.
FIG. 29 is a cross-sectional view showing a state where the container is attached to the container according to the eleventh embodiment.
FIG. 30 is a circuit configuration diagram of the above.
31 is a perspective view of an electrode portion for explaining the principle of Embodiment 12. FIG.
FIG. 32 is a graph showing experimental data using electrode parts for explaining the principle of the above.
FIG. 33 is an explanatory diagram of an example of the electrode same as above.
FIG. 34 is an explanatory diagram of another example of the electrode of the above.
35 is a circuit configuration diagram of Embodiment 13. FIG.
FIG. 36 is a timing chart for the operation same as above.
FIG. 37 is a diagram illustrating the principle of a capacitive moisture amount detection sensor.
FIG. 38 is a diagram illustrating the relationship between the detected capacitance value and the amount of moisture.
FIG. 39 (a) is a plan view in which a part of a conventional electrode portion can be omitted.
(B) is a circuit connection diagram same as the above.
[Explanation of symbols]
1 Moisture sensor housing
2 Circuit board
3 Shield box
4 Packing
5a, 5b electrode
10 recess
29 lid

Claims (3)

An electric field region constituted by a pair of electrodes is used as a detection region, and an electrode portion in which at least one of the pair of electrodes is in contact with a detection target via an insulator has a detection sensitivity surface; and within the detection region At least from a capacitance detection circuit that detects a capacitance value determined by the amount of moisture present in the capacitor, and an output circuit that outputs an electrical signal having an amount of electricity corresponding to the moisture amount from the capacitance value detected by the capacitance detection circuit A moisture sensor circuit unit configured, wherein the pair of electrodes includes a first electrode and an annular second electrode formed so as to surround the first electrode; The distance between the inner edge of the electrode and the outer edge of the first electrode is substantially the same over the entire circumference, and each electrode is positioned at the bottom of the recess formed in the insulator, and the height of the rib forming the recess is increased. Height or height on the inner wall of the recess Capacitive moisture content sensor of the exposed surface of each electrode relative to the indicia buried insulator within the recess of the蔽 characterized formed Rukoto. 2. The capacitance type moisture sensor according to claim 1, wherein the first electrode and the second electrode have substantially the same width . 3. The capacitance type moisture sensor according to claim 1 , wherein a shield box that covers the moisture sensor circuit unit is used as a heat sink for circuit components .

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