JPH0311425B2 - - Google Patents

Description

[Detailed description of the invention]

This invention detects the three states of dryness, dew condensation, and frost as changes in impedance.
This invention relates to a frost identification sensor. Since humidity control is an important issue in various electrical devices, there is a demand for the development of excellent humidity sensors. Further, in certain devices, in addition to deterioration of characteristics due to dew condensation, deterioration of characteristics due to frost formation becomes a problem. For example, in the case of refrigerators, frost formation reduces efficiency, so it is necessary to remove the frost. Therefore, it is desired to develop a sensor that can detect frost formation. Conventionally, various types of dew condensation sensors have been developed, such as sensors that utilize changes in resistance due to dew condensation. On the other hand, frost sensors have been developed that utilize the fact that the resonant frequency of a resonator changes due to the adhesion of frost.
However, there has not yet been a single element capable of detecting both dew condensation and frost formation, that is, the three states of dryness, dew condensation, and frost formation. Therefore, the device
In order to detect which of the three states of dryness, dew condensation, and frost formation, at least two independent detection elements are required, which complicates the apparatus. Therefore, the main purpose of this invention is to
It is an object of the present invention to provide a sensor for identifying dryness, dew condensation, and frost formation that can accurately detect which of the three states of dew condensation and frost formation it is in. In summary, the present invention includes a sensor unit in which an electrode is formed on one side of a sensing element made of a ceramic plate, a plurality of sensing elements are separated by a predetermined interval by an insulating spacer, and each of the sensing elements is separated by a predetermined interval. By arranging the surfaces on which electrodes are formed to face each other on the inside, a space is formed between the sensor units to form a sensor body, and the space is free from drying, dew condensation, etc.
This is a dry/condensation/frost discrimination sensor that detects changes in impedance between opposing electrodes in the frost state and distinguishes between dry, dew condensation, and frost. Other objects and features of the present invention will become more apparent from the following detailed description with reference to the drawings. FIG. 1 is a perspective view for explaining an example of the dryness/condensation/frosting identification sensor of the present invention. First, ceramic plates 1 and 2 as sensing bodies are prepared. Ladder-shaped electrodes 3 and 4 (electrodes 3 are not shown in FIG. 1 because they are formed on the lower surface of the sensing element body 1) are formed on one side of each ceramic plate 1 and 2. Lead wires 5 and 6 are connected to a portion of each electrode 3 and 4. In this way, 2
Sensor units 7 and 8 are prepared. Next, the sensor units 7 and 8 are arranged facing each other at a predetermined interval so that the surfaces on which the electrodes 3 and 4 are formed face each other. Obtain a concrete example. As is clear from FIG. 2, the distance between each sensor unit 7, 8 is
It is kept constant by using insulating spacers 9a and 9b. Electrodes 3, 4 of sensor units 7, 8
Since the surfaces on which the electrodes are formed are arranged to face each other, dryness, dew condensation, and frost formation can be identified by adjusting the electrode spacing, regardless of the material of the ceramics composing the sensing elements 1 and 2. It is possible to adjust the spacing between air spaces, making it easy to adjust the values of each impedance for drying, dew condensation, and frost formation. Note that the electrodes 3 and 4 may be formed in the shape of a lattice or a porous plate, as shown in perspective views in FIGS. 3 and 4. By forming the electrodes in the shapes shown in FIGS. 1, 3, and 4, it is possible to increase the exposed area of the sensing element on the surface on which the electrodes are formed. The reason why the exposed area of the sensing elements 1 and 2 on the side where the electrodes are formed is increased will be explained later. The drying process of this invention shown in FIGS. 1 and 2
The dew condensation/frost formation identification sensor detects the three states of dryness, dew condensation, and frost formation by passing a current between the lead wires 5 and 6 between the electrodes 3 and 4 of each sensor unit 1 and 2.
Impedance changes between the two can be detected. First, in a dry state, the sensor unit 1,
The impedance between the two electrodes 3 and 4 is determined by the inductivity of the air layer existing in the air A (see FIG. 2) between the sensing elements 1 and 2. Next, in the dew condensation state, water droplets adhere between the sensing element bodies 1 and 2, so that the impedance between the electrodes 3 and 4 becomes extremely small due to electrical conduction of water. Furthermore, in a frosted state, water droplets adhering to the air space A between the sensing element 1 and the sensing element 2 turn into ice crystals, so the impedance between the electrodes 3 and 4 is reduced by the adhering ice. Determined by dielectric constant. In this way, the impedance between the electrodes 3 and 4 changes greatly depending on the atmosphere in the space A between the sensor units 7 and 8. Based on this change, three states of dryness, dew condensation, and frost formation can be detected. Next, the sensing element used in the present invention will be explained. Various ceramics can be used as the sensing element used in this invention, but
The ceramic may be either one that can extract ions in a dew-condensed state or one that does not. Even if ceramics that do not derive ions are used, the configuration of this sensor shows that in a dry state, the impedance is determined by the dielectric constant of the air in the space between the facing inner surfaces of the ceramic plate, and this value is determined by the dielectric constant of the air in the space between the opposing inner surfaces of the ceramic plate, and this value is determined by the condensation state. The impedance is larger than that in the dry state and the frosted state, and it is possible to distinguish between the dry state and the dew or frosted state. Furthermore, since dew condensation and frost formation have different impedances based on the difference in dielectric constant between water and ice, it is possible to distinguish between these conditions, and as a result, dryness and frost formation , it is possible to detect each state of frost formation. On the other hand, if ceramics are used that can extract ions into the adhering water under dew condensation, ions will be ejected into the dew condensation or water adhering between the sensing elements arranged opposite each other. As a result, the resistance value between each sensing element becomes extremely small compared to the other two states, especially when frost is formed, due to the electrical conduction of water based on these ions, and the difference in impedance becomes large. That is, as mentioned above, the impedance between the electrodes in a condensed state is determined by the electrical conduction of the water adhering to the space between each sensor unit. By configuring the sensing element, the interelectrode impedance value can be made smaller, and therefore the dew condensation state and the other two states can be more clearly distinguished. Examples of materials that can lead ions into attached water droplets include MgTiO ₃ ,
Titanium composite oxide ceramics consisting of ilmenite crystal structure such as ZnTiO ₃ and FeTiO ₃ , BaO−
TiO ₂ −NdO _3/2 ceramics, sulfate and phosphate ceramics, ceramics containing mainly MgO/SiO ₂ such as steatite and forsterite, spinel type, pyrochlore type, tungsten bronze type, rutile type Many ceramics can be used, such as , fluorescent type, etc. In the case of ceramics mainly composed of titanium composite oxide with an ilmenite crystal structure, other crystal structures such as perovskite, spinel, pyrochlore, tungstate bronze, etc. may be used as long as the properties are not affected. You may mix 1 type or multiple types. In addition, for example clay, rare earth,
_TiO2 , _SiO2 , _{Bi2O3 ,} ZnO, _{Fe2O3 , Sb2O3 ,}
Additives consisting of inorganic compounds such as MnCO ₃ , WO ₃ etc. may also be added. Also, for other crystalline ceramics, the coexistence of various additives for ceramic formation is permitted in the same manner as described for the titanium composite oxide having an ilmenite crystal structure.
Due to the elution of a small amount of ions from the ceramics during dew condensation, the interelectrode impedance decreases significantly during dew condensation. For this purpose, ceramics containing cations such as alkali metal ions and alkaline earth metal ions, and anions such as phosphate ions and sulfate ions are effective. As described above, according to the present invention, the sensor unit is provided with a sensor unit in which an electrode is formed on one side of a sensing element made of a ceramic plate, and a plurality of sensing elements are arranged.
Insulating spacers provide a predetermined distance, and
By arranging the surfaces on which the electrodes of the sensing element are formed to face each other on the inside, a space is formed between the sensor units to form the sensor body, making it possible to prevent dry, dew, and frost conditions. The atmosphere between each sensor unit can be detected as a change in the impedance value between each electrode. Furthermore, since the sensor has a relatively simple structure, it can provide excellent reliability and stable operation. Furthermore, since the material constituting the sensing element is not particularly limited, each state can be detected more accurately by using a temperature-compensated dielectric material. Example 1 Grid-shaped gold electrodes were formed at an interval of 1 mm on one side of two square plates made of MgTiO ₃ --CaTiO ₃ ceramics each having a length of 30 mm, a width of 6 mm, and a thickness of 0.8 mm. Next, the ceramic plates were placed facing each other with an interval of 0.3 mm so that the surfaces on which the electrodes were formed faced each other on the inside. The impedance between the electrodes of the dryness/condensation/frosting identification sensor constructed in this way was measured in three states: dry state, dew condensation state, and frosty state by applying an AC voltage of 1 V (50 Hz). The results showed an impedance value of 400MΩ in a dry state, 40KΩ in a dew state, and 20MΩ in a frosted state. As is clear from these three types of values, it is understood that the dryness, dew condensation, and frost formation discrimination sensor of Example 1 can clearly identify each state. Next, a description will be given of a dew condensation/frost formation detection device using the dryness/dew condensation/frost formation identification sensor of the present invention. FIG. 5 is a diagram showing an example of an impedance change in a dry state, a dew condensation state, and a frost state of the dryness/condensation/frosting identification sensor of the present invention. A dew condensation/frost detection device described below is configured using a dry/condensation/frost discrimination sensor having such characteristics. FIG. 6 is a block diagram for explaining an example of a dew condensation/frost formation detection device using the dryness/dew condensation/frost formation discrimination sensor of the present invention. Referring to Figure 6,
This device includes a detection section 10 including a dryness/condensation/frosting identification sensor of the present invention, two comparison circuits 11 and 12 to which the output of the detection section 10 is given, and a comparison circuit 11.
a first reference level setting means 13 that inputs a first reference level signal as a comparison signal to the comparison circuit 12, a second reference level setting means 14 that inputs a second reference level signal as a comparison signal of the comparison circuit 12, and a comparison circuit 1.
It is comprised of a discrimination circuit 15 (the part surrounded by the dot-dash dots in FIG. 6) which discriminates between the three states of dryness, dew condensation, and frost formation based on the outputs of signals 1 and 12. The detection unit 10 includes the dryness, dew condensation, and frost formation discrimination sensor of the present invention, and outputs a signal corresponding to the impedance that changes as shown in FIG. 1 in the three states of dryness, dew condensation, and frost formation. The output of the detection section 10 is given to a comparison circuit 11 as a first comparison means and a second comparison circuit 12 as a second comparison means. A first reference level signal is input to the first comparison circuit 11 by the first reference level setting means. As is clear from FIG. 5, the first reference level of this signal is set between the impedance of the detection unit 10 in the dew condensation state and the impedance of the detection unit 10 in the frost formation state. First comparison circuit 11
compares the impedance of the detection unit 10 and the first reference level, and outputs a high level signal when the impedance of the detection unit 10 is larger, and outputs a low level signal when the impedance of the detection unit 10 is smaller. Outputs the output signal. On the other hand, the second comparison circuit 12 receives a second reference level signal from the second reference level setting means. As is clear from Fig. 5, the second reference level of this signal is
It is set to a value between the impedance of the detection unit 10 in a dry state and the impedance of the detection unit 10 in a frosted state. Therefore, the second comparison circuit 12 compares the impedance of the detection section 10 with the second comparison circuit 12.
When the impedance of the detection unit 10 is larger than the reference level, a high level signal is output, and in the opposite case, a low level signal is output. In this way, the first and second comparison circuits 11,
12 outputs a high-level or low-level signal according to a change in the impedance of the detection unit 10. The output of each of these comparison circuits 11 and 12 is
As is clear from the relationships shown in the figure, they are shown in Table 1 below. In Table 1, H indicates a high level signal, and L indicates a low level signal.

[Table] The outputs of the comparison circuits 11 and 12 are given to the discrimination circuit 15. The discrimination circuit 15 includes two inverters.
It is composed of I ₁ , I ₂ and three Noah gates G ₁ , G ₂ , and G ₃ . The output of the first comparator circuit 11 is applied to an input terminal of an inverter _I1 and one input terminal of a NOR gate _G3 . The output of the inverter _I1 is given to one input terminal of each of the NOR gates _G1 and _G2 .
On the other hand, the output of the second comparison circuit 12 is
It is applied to the input terminal of _I2 , the other terminal of NOR gate _G2 , and the other input terminal of NOR gate _G3 . The output of inverter _I2 is given to the other input terminal of NOR gate _G1 . Note that this discrimination circuit 15 employs positive logic. The determination circuit 15 configured as described above determines the three states of dryness, dew condensation, and frost formation as follows. Now, in a dry state, as is clear from Table 1, both comparison circuits 11 and 12 output high level signals. The high level signal from the first comparator circuit 11 is connected to the inverter _I1 and the NOR gate _G3.
given to. The high level signal input to inverter _I1 is inverted to a low level signal,
Given to Noah Gate G ₁ and G ₂ . On the other hand, the high level signal from the second comparison circuit 12 is applied to the inverter I ₂ , the NOR gate G ₂ and the NOR gate G ₃
given to. The high level signal input to the inverter _I2 is inverted to a low level signal and is applied to the NOR gate _G1 . As described above, in a dry state, only the NOR gate _G1 receives a low level signal to both of its input terminals. Therefore, only NOR gate _G1 outputs a high level signal. Similarly, when the detection unit 10 is in a frosted state, as is clear from Table 1, the first comparison circuit 11 outputs a high level signal, and the second comparison circuit 12 outputs a low level signal. In order to output
_Only NOR gate G2 receives a low level signal at both of its input terminals. Therefore, only NOR gate _G2 outputs a high level signal.
Further, when the detection unit 10 is in a dew condensation state, the first
Since the second comparator circuits 11 and 12 both output low level signals, only the NOR gate G ₃ receives a low level signal to both input terminals, so only the NOR gate G ₃ outputs a high level signal. Outputs the signal. As is clear from the above description, the NOR gate G ₁ outputs a signal in a dry state, the NOR gate G ₂ outputs a signal in a frosted state, and the NOR gate G ₃ outputs a signal in a dewy state. Therefore, drying
It becomes possible to distinguish between three states: dew condensation and frost formation. FIG. 7 is a circuit diagram for more specifically explaining the dew condensation and frost formation detection device shown in FIG.
FIGS. 8 and 9 are diagrams for explaining the operation of the circuit shown in FIG. 7. The circuit shown in FIG. 7 includes a dryness/condensation/frosting identification sensor 20 of the present invention, a MOS-FET 26, comparators 21, 22, and a discrimination circuit 25 similar to that shown in FIG. The part indicated by the dashed line) is the basic component. As shown in FIG. 5, the impedance of the dryness, dew condensation, and frost formation identification sensor 20 changes in three states: dryness, dew condensation, and frost formation. Dry/condensation/frosting identification sensor 20
The change in impedance of is expressed as the change in voltage,
It is input to the gate terminal of MOS-FET26. This input is amplified and inverted by the MOS-FET 26 and input to the operational amplifiers 21 and 22 as comparators. Each operation amplifier 21, 22 has a first
and a second reference level voltage are respectively input. The outputs of the operational amplifiers 21 and 22 are
The signal is applied to the discrimination circuit 25. The configuration of the discrimination circuit 25 is the same as that of the discrimination circuit 15 shown in FIG. 6, so the explanation thereof will be omitted by assigning corresponding reference numbers. In the circuit shown in FIG. 7 configured in this way, the impedance of the dryness/condensation/frost discrimination sensor 20 changes in the three states of dryness, dew condensation, and frost formation, so the dryness/condensation/frost discrimination sensor 20 changes. Outputs voltage changes corresponding to changes in impedance. The change in voltage at node X of the circuit of FIG. 7 is shown in FIG. Dry/condensation/frost identification sensor 2
The output voltage from 0 is amplified by MOS-FET26.
It is inverted and output. This output voltage, ie, the voltage at node Y in FIG. 7, is shown in FIG. As is clear from FIG. 9, the output voltage at the connection point Y has a maximum value in a dry state, a minimum value in a dew condensation state, and an intermediate value in a frosted state.
The output voltage of the MOS-FET 26 is input to the operational amplifiers 21 and 22. On the other hand, each operational amplifier 21, 22 has variable resistors 23, 2.
The first and second reference level voltages whose levels are set by 4 are input. The first and second reference level voltages are chosen to have values as shown in FIG. That is, the first reference level voltage is selected to be a value between the output voltage in the frosted state and the output voltage in the condensed state, and the second reference level voltage is selected to be between the output voltage in the dry state and the output voltage in the frosted state. A value between . Each of the operational amplifiers 21 and 22 compares the output voltage of the MOS-FET 26 with a first reference level voltage or a second reference level voltage. Therefore, the change in impedance of the dryness/condensation/frost identification sensor 20 is compared as a change in voltage. Each of the operational amplifiers 21 and 22 outputs a high level signal when the output voltage of the MOS-FET 26 is higher, and outputs a low level signal in the opposite case. The output signals of the operational amplifiers 21 and 22 are similar to the output truth values shown in Table 1 for the comparison circuits 11 and 12 of FIG. The output signals from each of the operational amplifiers 21 and 22 are input to the discrimination circuit 25, but the operation of the discrimination circuit 25 is the same as that of the discrimination circuit 15 in FIG. 6, so a description thereof will be omitted. The circuits shown in FIGS. 6 and 7 are merely examples of a dew condensation/frost detection device using the dryness/condensation/frost detection sensor of the present invention.
Therefore, it should be pointed out that the first and second comparison circuits and discrimination circuit can be modified in various ways within the range that can be easily conceived by those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a perspective view for explaining a specific example of the dryness, dew condensation, and frost formation identification sensor of the present invention.
FIG. 2 is a longitudinal cross-sectional view of a specific example of the dryness/condensation/frost identification sensor of the present invention. FIGS. 3 and 4 are perspective views showing other examples of electrode shapes used in the dryness/condensation/frosting identification sensor of the present invention. FIG. 5 is a diagram showing an example of the impedance characteristics of the dryness/condensation/frosting identification sensor of the present invention. FIG. 6 is a block diagram of an example of a dew/frost detection device using the dryness/condensation/frost identification sensor of the present invention, and FIG. 7 is a block diagram of the dew/frost detection device shown in the block diagram in FIG. It is a specific circuit diagram of a frost detection device. FIG. 8 is a diagram showing the output voltage at the connection point X of the circuit of FIG. FIG. 9 is a diagram showing the output voltage at connection point Y of the circuit of FIG. 7. In the figure, 1 and 2 are ceramic plates as sensing elements, 3 and 4 are electrodes, and 7 and 8 are sensor units.

Claims (1)

[Scope of Claims] 1. A sensor unit comprising a sensing element made of a ceramic plate and an electrode formed on one side, a plurality of sensing elements separated by a predetermined interval by an insulating spacer, and an electrode of the sensing element. By facing each other on the inside,
The sensor body is constructed by forming an air space between the sensor units, and changes in impedance during drying, dew condensation, and frost formation in the air space are detected between opposing electrodes. Dryness, dew condensation, and frost detection sensor that identifies three conditions of frost. 2. The drying/condensation/frosting identification sensor according to claim 1, wherein the area of the electrode is smaller than the exposed area of the sensing element on the surface on which the electrode is formed. 3. The drying/condensation/frosting discrimination sensor according to claim 1 or 2, wherein the sensing element is made of ceramics capable of deriving ions in a dew-condensed state.