Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2001-07-03
2004-06-29
Nghiem, Michael (Department: 2863)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C073S335040
Reexamination Certificate
active
06756793
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a capacitance type moisture sensor having the capability of accurately detecting amounts of water, and a method of producing the same sensor.
2. Disclosure of the Prior Art
Capacitance type moisture sensor is known as a kind of conventional moisture sensor, and detects amounts of water from a change of capacitance between a pair of electrodes in accordance with the nature that water is a polarization (dielectric) material.
For example, this type of moisture sensor is built in a garbage disposing apparatus, and used to detect amounts of water in the garbage. That is, as shown in
FIGS. 21A and 21B
, the moisture sensor comprises an electrically-insulating panel
2
P, which is attached to an opening formed in a garbage vessel
100
P of the garbage disposing apparatus, a pair of electrodes
30
P,
35
P arranged in parallel on the electrically-insulating panel, a capacitance detecting circuit
40
P for detecting a capacitance value (Cx) between the electrodes, and an output circuit
42
P for providing an electrical signal corresponding to the amounts of water according to outputs from the capacitance detecting circuit.
In this moisture sensor, the amounts of water (M) is represented by the equation (1):
M=V/
(
S*d
) (1)
wherein “V” is a volume of water, “S” is an area of the electrode, “d” is a distance between the electrodes. Therefore, “S*d” gives a volume of a moisture detection region. A relationship between the amounts of water (M) and the capacitance (Cx) is shown in FIG.
22
. This relationship is also expressed by the following equation (2):
Cx=[∈
1′(water)*
M+∈
2′(others)*(1−
M
)]×∈′0*
S/d
(2)
wherein (∈1′) is the dielectric constant of water (=80) and (∈2′) is a relative dielectric constant of a material other than water. For example, when the material other than water is woods, the relative dielectric constant (∈2′) is 2. When the material other than water is the air, the relative dielectric constant (∈2′) is 1. Thus, the capacitance (Cx) can be determined by the amounts of water in the detection region. In addition, the capacitance value (Cx) depends on the electrode size.
However, there is still plenty of room for improvement in the conventional moisture sensor from the following viewpoints. That is, since these electrodes project toward the interior of the garbage vessel, a space between the electrodes is easily filled with the garbage. In this case, the capacitance detecting circuit may detect only the amounts of water of the garbage caught between the electrodes. Therefore, to accurately detect a change of the amounts of water of the garbage in the garbage vessel, a cleaning mechanism for frequently removing the garbage caught between the electrodes is needed. This leads to an increase in production cost.
In addition, since the garbage is usually stirred in the garbage vessel to facilitate decomposition of the garbage, there is a problem that a breakage of the moisture sensor is accidentally caused by a collision of the garbage with the electrodes. Moreover, the electrically-insulating panel supporting the electrodes needs a mechanical strength sufficient for withstanding a load for stirring. This also leads to a further increase in production cost.
SUMMARY OF THE INVENTION
Therefore, a primary object of the present invention is to provide a capacitance type moisture sensor, which can accurately detect amounts of water of an object in a real-time manner without using the above-described cleaning mechanism for electrodes.
That is, this moisture sensor comprises a sensor housing having a electrically-insulating wall, a pair of electrodes disposed on the sensor housing, and a circuit unit. An outer surface of the electrically-insulating wall faces a space where amounts of water should be detected. On an inner surface of the electrically-insulating wall, at least one of the electrodes is formed. An electric field developed between the electrodes is defined as a moisture detecting region. The circuit unit includes a capacitance detecting circuit for detecting a capacitance value between the electrodes, which changes in response to the amounts of water in the moisture detecting region, and an output circuit for providing an electrical signal corresponding to the amounts of water according to the capacitance value detected by the capacitance detecting circuit.
With respect to the moisture sensor of the present invention, since the electric field developed between the electrodes provides the moisture detecting region outside the sensor housing through the electrically-insulating wall, it is not necessary to allow the electrodes to project toward the space where the amounts of water should be detected. In particular, when the moisture sensor is used in a garbage disposing apparatus, it is possible to eliminate the problem that the breakage of the moisture sensor is caused by the collision of the garbage with the electrodes, and accurately detect the amounts of water in the garbage in the real-time manner, while preventing the increase in production cost.
In the above moisture sensor, it is preferred that at least one of the electrodes is a metal film deposited on the inner surface of the electrically-insulating wall. In this case, even when the electrically-insulating wall has a curved surface, good adhesion strength between the electrode(s) and the electrically-insulating wall can be obtained. In addition, it is possible to easily form the electrodes on the sensor housing having a complex shape. Moreover, even when a plurality of ribs described later are formed on the inner surface of the electrically-insulating wall, it is possible to easily form a desired electrode pattern. Alternatively, the electrodes may be formed by means of an insert molding, or metal bonding.
With respect to the above moisture sensor, it is preferred that the sensor housing has a concave formed in an inner surface of a bottom wall thereof and a convex formed on an outer surface of the bottom wall at a position opposed to the concave, and a bottom surface of the concave is the inner surface of the insulating wall and a top surface of the convex is the outer surface of the insulating wall. In this case, for example, when the moisture sensor of the present invention is attached to a garbage vessel of the garbage disposing apparatus, only the top surface of the convex is exposed to the interior of the garbage vessel. Therefore, it is possible to minimize an area of the moisture sensor exposed to the garbage put in the garbage vessel. In addition, since the moisture sensor is attached to the garbage vessel such that the top surface of the convex is flush with the inner surface of the garbage vessel, it is possible to avoid a situation that a movement of the garbage in the garbage vessel by stirring is obstructed, or a situation that an excessive force is loaded to the moisture sensor by the stirring.
With respect to the above moisture sensor, it is preferred that the pair of electrodes are composed of a ring-shaped electrode having an open center and a central electrode, which is disposed in the open center of the ring-shaped electrode such that a circumference of the central electrode is spaced from an inner circumference of the ring-shaped electrode by a constant distance. In particular, it is preferred that the pair of electrodes are composed of a ring-shaped electrode having an annular open center and a central electrode having a circular shape, and the ring-shaped electrode is disposed in a concentric manner with respect to the central electrode such that an outer circumference of the central electrode is spaced from an inner circumference of the ring-shaped electrode by a constant distance. Alternatively, it is preferred that the pair of electrodes are composed of a ring-shaped electrode having a rectangular open center and a central electrode having a rectangular s
Hirono Atsuyuki
Mori Hideo
Takada Yuji
Yoshikawa Keisuke
Matsushita Electric & Works Ltd.
Nghiem Michael
Rader & Fishman & Grauer, PLLC
LandOfFree
Capacitance type moisture sensor and method of producing the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Capacitance type moisture sensor and method of producing the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Capacitance type moisture sensor and method of producing the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3295790