JPH0322941B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dryness detection device that detects changes in the moisture content of an atmosphere using a moisture-sensitive resistive element, and a dryness detection control device using the same.

Configurations of Conventional Examples and Problems There are conventional dryness detection methods that use, for example, an electrode type sensor or a relative humidity sensor as a sensor for humidity adjustment. Using these sensors,
At present, the dryness detection state differs depending on the temperature change inside the refrigerator or the high humidity of the outside air, making it difficult to perform the desired dryness detection.

Since the state of the drying atmosphere changes as described above, it has been impossible to accurately detect whether the object to be detected has dried. Therefore, for example, in a drying device controlled by a heater and humidity detection, insufficient drying or excessive drying occurs, and heating drying control etc. cannot be performed satisfactorily.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a dryness detection device and a dryness detection control device using the same, which solve the above-mentioned problems.

Structure of the Invention In order to achieve this object, the present invention provides a humidity sensing element that exhibits humidity sensitive resistance characteristics in response to changes in the amount of moisture in the atmosphere, a means for heating the humidity sensing element, and a means for heating the humidity sensing element that responds to changes in humidity. a resistance-signal conversion means for detecting an output signal of the signal conversion means, a maximum value point detection means for detecting a maximum value point of the output signal of the signal conversion means, and a timer that stops counting by the output signal from the maximum value point detection means. a first time counting means; a calculating means for calculating the first time counting output value;
a second time counting means that starts counting time based on the output signal of the maximum point detection means; and a comparison detection means that compares and detects the output value of the second time counting means and the output value obtained by the calculation means. The present invention provides a dryness detection device configured to include the following.

Further, there is provided a dryness detection control device which includes a heater provided in an air circulation system and includes a control means for controlling power to the heater based on a comparison detection signal of the detection device described above to perform dryness detection control. It is something to do.

Furthermore, the dryness detection device and the dryness detection control device are constructed using a ZrO ₂ —MgO-based metal oxide humidity-sensitive resistor element as the moisture-sensitive detection element.

Description of Examples Hereinafter, the present invention will be described in detail based on Examples.

FIGS. 1A and 1B show an embodiment of a humidity-sensitive sensing element constituting the apparatus of the present invention. In Figure 1, 1 is
This is a ZrO ₂ -MgO-based metal oxide humidity-sensitive resistor element (hereinafter simply referred to as a humidity-sensitive element). This moisture-sensitive element 1 is made by mixing raw materials in a ratio of (ZrO ₂ ) 0.7; (MgO) 0.3, wet-mixing them, drying them to form a powder raw material, molding the powder obtained above, and firing it (1200~
1300°C for 2 hours) and then fired as described above to obtain a ZrO ₂ -MgO-based element (1.5 x 1.5 x 0.2 mm plate shape).
RuO ₂ -based electrodes are baked on both sides of the electrode, and then a Pt--Ir based wire 2 is taken out from the electrodes. The Pt--Ir wire 2 is fixed to the lead wire fixing terminal 6a by welding. 3 is an element heater, such as a nichrome heater. 4 is a lead wire of the element heater 3;
It is fixed to the lead wire fixing terminal 6b by welding. 5 is an element fixed terminal board.

FIG. 2 is a characteristic diagram of absolute humidity versus electrical resistance value obtained by the humidity sensing element 1 of FIG. 1. In this figure 2, a current is passed through the heater 3 and the element 1 is heated to about 550 to 600.
Moisture sensitivity characteristics obtained by heating to about ℃ (element 1, 2)
(electrical resistance value between terminals).

FIG. 3 shows an embodiment of the dryness detection device according to the present invention. In FIG. 3, numeral 7 represents the entire humidity sensing structure including the humidity sensing element 1 shown in FIG. 8 is a power supply (2.8V) for heating the humidity sensing element 1 to about 550 to 600°C. Reference numeral 9 denotes a resistance-signal conversion means for converting a change in electrical resistance of the humidity sensing element 1 into an electrical signal. Reference numeral 10 denotes maximum value point detection means for detecting the maximum value point of the output signal of the resistance-signal conversion means 9.
Specifically, the maximum value point detecting means 10 detects whether the maximum value point is reached by slightly exceeding the maximum value point. Therefore, the maximum value point detecting means 10 detects the maximum value point and immediately outputs an output signal.

Reference numeral 11 denotes a first time counting means, which starts counting the time with the start signal B and sets the count value (zero) to the original initial value with the clear signal C.

14 is a second time counting means having exactly the same configuration as the first time counting means 11, but whose input section is negative logic.

Reference numeral 12 denotes a calculation means for calculating the signal obtained by the first time counting means 11 using a predetermined calculation function to obtain an output signal.

Reference numeral 13 denotes signal comparison and detection means, which compares and detects the respective output signals obtained by the second time counting means 14 and the calculation means 12. Further, signal A is an output signal obtained by comparison detection means 13.

FIG. 4 shows an example of the resistance-signal conversion means 9, in which the resistance change of the humidity sensing element 1 is transferred to the resistors R ₁ , R ₂ ,
R ₃ , R ₄ , rectifier D ₁ , D ₂ , capacitor C ₁ , amplifier
DC voltage signal conversion is obtained by OP ₁ .

FIG. 5 shows an example of the maximum point detection means 10 of the output signal of the resistance-signal conversion means 9. Immediately after the resistance-signal conversion means 9 exceeds the maximum value point of the input signal, the output signal changes from "low" to "high".
Its composition is rectifier D ₃ , D ₄ , capacitor C ₂ , resistor R ₅ , R ₆ , field effect transistor FET ₁ ,
Consists of FET ₂ and voltage comparator COP ₁ . Its operation is to discharge the charge charged in the capacitor _C2 by the reset signal, then charge the input signal to the capacitor _C2 , and then output the voltage to the voltage comparator.
A portion of the voltage charged to capacitor _C2 at COP ₁ is compared with the input signal. As a result, the output signal is obtained immediately after the input signal passes the maximum value point.

FIG. 6 shows an example of the first time counting means 11. Its configuration is AND circuit, counter, D/A
Consists of a converter. Further, when the counter is operated, the clear signal C returns the counter to its initial state. Next, a start signal B is applied, and by applying an input signal, time measurement is started at the time pitch of the clock signal. Then, the signal obtained by the counter is D/A (digital-to-analog) converted,
The output is obtained as an output signal corresponding to time.

FIG. 7 shows an example of the calculation means 12. This calculation means includes an amplifier OP ₂ , a resistor R ₇ , and a variable resistor.
It consists of R ₃ composition. As for its operation, a signal obtained by calculating the input signal is obtained by setting the variable resistor _R8 . For example, when R ₇ =R ₈ and R ₈ are at positions where the output is divided into two, the input signal is 1 and the output signal is 2.

In this case, the calculation (integration) count is 2.

FIG. 8 shows an example of the comparison detection means 13.
This comparison detection means 13 uses a voltage comparator, and an output signal is obtained by comparing input signals.

FIG. 9 shows an example of the second time counting means 14. This second time counting means 14 is basically the same as the configuration example of the first time counting means 11 shown in FIG. 6, but an inverter IN is provided at the input section.
The difference is that the input logic is negative logic. Therefore, time measurement is started when the input signal is reversed from "high" to "low".

FIG. 10 is a graph showing the humidity detection state of the dryness detection device constructed according to the present invention. This 10th
The figure shows the detected state of the absolute humidity inside the drying chamber obtained when a heater is installed in the drying chamber, the material to be dried is inserted into the drying chamber, and the article is heated and dried. The horizontal axis represents time, and the vertical axis represents the amount of moisture in the atmosphere inside the refrigerator.

Note that FIG. 10 shows the case where the amount of heat generated by the heater is constant per hour.

FIG. 11 shows an embodiment of a dryness detection control device using the dryness detection device of the present invention. The drying device 15 of this drying detection control device is composed of a series of air circulation structures including, for example, a heater 16, an insertion chamber 18 for the object to be dried 17, a cooling fin 19, and a ventilation duct 20. A drain port 22 is provided to take out the drain port 21. A humidity sensing structure 7 is provided in a part of this air circulation system to detect the humidity inside the refrigerator.

As for the overall system configuration of the dryness detection control device, the humidity detection signal from the humidity sensing structure 7 provided in the refrigerator is sent to the detection section 23 which together with the humidity sensing structure 7 constitutes the dryness detection device shown in FIG. The power of the heater 16 in the drying device 15 is controlled by the heating control means 24 based on the input and obtained dryness detection signal.

Next, the operation of the dryness detection and control device of the present invention will be explained.

First, as an example of the operation of the dryness detection device, for example, the drying device 15 shown in FIG.
This will be explained using an example. Drying equipment 1 in Figure 11
When the moisture-containing material 17 is heated and dried by the heater 16 installed in Figure 5 with a constant amount of heat per hour, the moisture content in the atmosphere inside the refrigerator will be equal to the moisture content shown in Figure 10 above. Obtained with time characteristics.
This temporal characteristic corresponds to the output signal obtained by the resistance-signal conversion means 9. According to Figure 10, the moisture content of the atmosphere increases with heating drying time.
The water content drops beyond the maximum water content point D, and F
When reaching the point, the signal obtained by the resistance-signal conversion means 9 of FIG. 3 (described below in FIG. F point) is detected, and its output signal is inverted from "low" to "high". Next, in response to the inverted signal, the second time counting means 14 (assumed to have been cleared to the initial value [zero] by the clear signal C) starts counting time. At this time, it is assumed that the start signal B has already been input at the start of heating drying, and time counting is started by the logical product of this B signal and the inverted signal obtained by the maximum value point detection means 10. Next, the first time counting means 11 (similar to the second time counting means 14, clear signal C)
It is assumed that the start signal B is cleared to the initial value [zero] and the start signal B has already been input at the start of heating drying. ), the time counting starts from the start of heating drying, and the time counting stops at the reversal signal obtained by the maximum point detection means 10, and the elapsed drying time
T ₁ is retained. By the way, the relationship between the elapsed drying times _T1 and _T2 at the drying point G shown in FIG. 10 has been clarified by the present invention.

The drying completion time T is T=T ₁ +T ₂ , and T ₂ =H·T ₁ (H=drying detection constant).

Therefore, the drying completion time T is T=T ₁ +H·T ₁ .

The above conditions are conditions for dryness detection obtained by the present invention. The present inventors have discovered that the dryness detection constant H does not vary depending on the amount of material to be dried. That is, the drying completion time T is determined by the heating elapsed time _T1 until the atmospheric moisture content in the drying object insertion storage 18 reaches the maximum value.

Then, we return to the explanation of the operation and continue the explanation.

The value of time counted by the first time counting means 11 is calculated by a function that is multiplied by, for example, H by the calculating means 12. The value of H is the material to be dried 17
It is determined by the material, but ranks 1 to 5 are appropriate.

That is, the output signal obtained by the calculation means 12 is multiplied by H. While drying with the heater 16, the calculation means 12 is measuring time and its output is increasing. Therefore, the comparison detection means 13 compares and determines the signal obtained by the second time counting means 14 and the output signal obtained by the calculation means 12, and determines whether the output signal of the calculation means 12 is better. At the point when the size increases, the output of the comparison detection means 13 is reversed (("high" → "low"), indicating that it is dry. Therefore, if the dry state at this time is explained in FIG. 10, it is point G. Also, point G corresponds to the above H
It can be varied by setting constants. That is, the desired degree of drying can be adjusted. In conjunction with the characteristic results shown in FIG. 10, it was confirmed by the present invention that this corresponds well to the moisture content of the material to be dried 17 and the moisture content of the surrounding atmosphere.

As a specific example, when the water content was 100 c.c. and the heating power was 1.2 KW, the time T ₁ to point F shown in FIG. 10 was about 180 seconds, or T ₂ was 810 seconds.

That is, the total heating time T is T=T ₁ +T ₂ =180+810=990 (seconds), and T ₂ is T ₂ =H·T ₁ =4.5×180=810 (seconds).

As described above, the dryness detection device of the present invention can detect the point of dryness. The drying time can be expressed as T ₁ +H·T ₁ .

Next, the operation of the dryness detection control device, which is the second invention, will be explained with reference to FIG. 11.

The detection signal obtained above is used to control the power applied to the heater 16 provided in the air circulation system by the heating control means 24, such as a relay circuit, to perform heating drying control. For example, an example of the heating control means 24 is shown in FIG. Its composition is transistors Tr ₁ , Tr ₂ , resistors R ₉ , R ₁₀ , relay
It consists of LY ₁ and switch SW ₁ . and,
At the start of heating drying, the switch SW ₁ is closed momentarily to activate the relay circuit and apply power to the heater 16. Next, in response to the drying end signal obtained from the drying detection device, the relay circuit shown in FIG. 12 constituting the heating control means 24 is turned OFF.
The power supply to the heater 16 is cut off, and the heating drying ends.

Next, the third feature of the present invention is that by particularly using a ZrO ₂ --MgO system as a moisture sensing element, the absolute amount of moisture in the atmosphere can be accurately detected. Conventionally, there are SnO ₂ -based moisture sensing elements. However, this method is sensitive to organic gas and moisture, and organic gas has a much higher detection sensitivity than humidity, making it unsuitable for heat drying and causing malfunctions.

On the other hand, ZrO ₂ --MgO-based humidity sensing elements have low gas sensitivity to organic gases and high sensitivity to humidity.
Therefore, by using a ZrO ₂ --MgO system for the humidity sensing element, a dryness detection device and a dryness detection control device that are better and do not malfunction can be obtained.

In addition, the ZrO ₂ −MgO moisture sensing element
It is heated to about 500 to 600 degrees Celsius and uses changes in electrical conductivity due to chemical adsorption of water, so its major feature is that it can be used at drying atmosphere temperatures as high as 600 degrees Celsius. Of course, ZrO ₂ − can be used as a moisture-sensitive element.
Elements other than MgO-based elements that exhibit high sensitivity to humidity may also be used.

Effects of the Invention As described above, the present invention detects the amount of moisture generated when drying an object based on the humidity of the atmosphere, detects the maximum point, and calculates the time elapsed up to that point. The present invention makes it possible to detect the end time of dryness detection for the first time. This creates a very efficient dryness sensing and control system that will not over-dry or under-dry. Also,
At the end of drying, the dryness detection signal can be used to generate a warning sound using a buzzer or the like.

Furthermore, by varying the calculation coefficient H, it is possible to stop drying at a desired dry state. That is, the present invention has made it possible to control drying during drying, which was previously considered impossible. Note that the present invention can be used for high-temperature dry detection up to about 600°C.

As described above, the present invention is of great value both industrially and industrially. Note that the example described above is just one implementation, and it goes without saying that the invention is not limited to this.

[Brief explanation of the drawing]

FIGS. 1A and 1B are a top view and a configuration diagram as seen from the front showing an embodiment of a humidity sensing element constituting the device of the present invention, and FIG. 2 is a characteristic diagram showing an example of the moisture sensitivity characteristics of the humidity sensing element. FIG. 3 is a block diagram showing an embodiment of the dryness detection device according to the present invention, and FIG. 4 is a circuit diagram showing an embodiment of the resistance-signal conversion means constituting the device.
FIG. 5 is a circuit diagram showing an embodiment of the maximum point detection means, FIG. 6 is a circuit diagram showing an embodiment of the first time counting means, and FIG. 7 is an embodiment of the calculation means. FIG. 8 is a block diagram showing an embodiment of the comparison detection means, FIG. 9 is a block diagram showing an embodiment of the second time counting means, and FIG. 10 explains the present invention. FIG. 11 is a configuration diagram showing an embodiment of the dryness detection control device according to the present invention, and FIG. 12 is an embodiment of the heating control means constituting the device. FIG. 1... Humidity sensing element (ZrO ₂ -MgO metal oxide humidity sensitive resistor element), 3... Element heating means (element heating heater), 9... Resistance-signal conversion means, 10
...Maximum point detection means, 11...First time counting means, 12...Calculating means, 13...Comparison detection means, 14...Second time counting means, 16...Heating heater, 24... Heating control means.

Claims (1)

[Scope of Claims] 1. A humidity sensing element that exhibits humidity-sensitive resistance characteristics in response to changes in the amount of moisture in the atmosphere, means for heating this humidity sensing element, and a resistor that detects an output signal corresponding to changes in humidity of the humidity sensing element. - a signal converting means, a maximum point detecting means for detecting the maximum point of the output signal of the resistor-signal converting means, and a first time counter that stops counting time at the output signal of the maximum point detecting means. means, a calculation means for calculating the first time count output value, a second time counting means for starting time counting based on the output signal of the maximum point detection means, and an output of the second time counting means. A dryness detection device characterized by comprising: comparison detection means for comparing and detecting the value and the output value obtained by the calculation means. 2. The dryness detection device according to claim 1, wherein a ZrO ₂ -MgO metal oxide humidity sensitive resistor element is used as the humidity detection element. 3. a humidity sensing element that exhibits humidity-sensitive resistance characteristics in response to changes in the amount of moisture in the atmosphere, means for heating the humidity sensing element, and resistance-signal conversion means for detecting an output signal corresponding to changes in humidity of the humidity sensing element; maximum value point detection means for detecting the maximum value point of the output signal of the resistance-signal conversion means; first time counting means for stopping time counting at the output signal of the maximum value point detection means; a calculation means for calculating a time count output value; a second time counting means for starting time counting using the output signal of the maximum point detection means; Comparing and detecting means for comparing and detecting the obtained output value, a heater placed in an air circulation system, and a control means for controlling power to the heater based on a comparison detection signal from the comparing and detecting means. A dryness detection control device characterized by: 4. The dryness detection control device according to claim 3, wherein a ZrO ₂ -MgO metal oxide humidity sensitive resistor element is used as the humidity detection element.