JPH056862B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for measuring the moisture content of a sheet in a dryer part that can obtain accurate results even in a high temperature and humidity atmosphere in a paper making process, and a method for implementing this method. It relates to a device for.

[Prior art and its problems]

To put it simply, the papermaking process is a process in which most of the water is removed from a suspension in which raw materials are dispersed at a thin concentration (0.5 to 1.5%), and the wire part has a water content of 80 to 85%. Moisture content in press part approx.
It is removed to just under 60%, and then dried in the dryer section to the desired moisture content (varies depending on the type of paper, but in most cases 5-10%), but moisture management in this dryer section depends on the quality and drying of the product. This is extremely important as it has a significant impact on costs.

An infrared moisture meter is used to measure the moisture content of sheets in the dryer section. In principle, this infrared moisture meter uses the infrared absorption spectrum of the material to be measured that contains moisture, and uses measurement wavelength light (light with a wavelength that is absorbed by water) and reference wavelength light (light with a wavelength that is not absorbed by water). Information regarding water content is obtained by projecting light of different wavelengths onto the material to be measured and calculating the ratio of each amount of reflected light or each amount of transmitted light.

By the way, the configuration of conventionally used infrared moisture meters generally consists of the following: 1. A light source (incandescent bulb or tungsten halogen lamp); 2. A mirror and lens (which focuses the light from the light source and transmits it through an optical channel. 3. Filter wheel (Two types of infrared filters are attached to a rotating wheel, which alternately crosses the light beam to separate measurement wavelength light and reference wavelength light.) It consists of a synchronous motor and a drive/control circuit (rotating and controlling the filter wheel), and the light receiving section mainly consists of: 1 a dome mirror or condensing lens (focusing infrared rays from the material to be measured); 2 Consists of a detector and an amplifier (the detector performs photoelectric conversion and amplifies it to a predetermined voltage level).

When using such a conventional infrared moisture meter, the measurement wavelength and reference wavelength of the infrared ray used for moisture measurement are different when the moisture content of the material to be measured is in the range of 0 to 30% and when it is higher than that. (Normally, in low moisture regions, 1.9 μm is used as the measurement wavelength and 1.6 μm or 1.8 μm is used as the reference wavelength, but the amount of transmitted light or reflected light at the wavelength of 1.9 μm is not equal to the amount of absorbed light.) the signal emitted by the detector is a measurement of the amount of transmission or reflection, which decreases rapidly with increasing water content and is no longer able to respond linearly to changes in water content);
For this reason, it was necessary to replace the filter wheel, and there was a problem in that the measurement had to be interrupted each time.

Furthermore, there was a very serious problem: In actual measurement, when the measurement method is a reflection method, the above-mentioned light emitting part and light receiving part are integrated and housed in a case called a detection head, and the upper part of the measuring head is 100 to 300 mm above the material to be measured. When the measurement method is a transmission method, the case with the light projecting unit integrated is placed at a position of about 30 to 150 mm above the material to be measured, that is, the sheet (hereinafter referred to as the material to be measured). The case that integrates the light receiving part is installed at a position approximately 30 to 150 mm below the material to be measured, aligning the optical axis with the light emitting part (limitations on the installation distance are as follows:
It is not directly related to the area of the beam spot projected onto the material to be measured or the absorption of infrared rays, but it is necessary to prevent specularly reflected and specularly transmitted light from entering the detector, which is a noise component for moisture information, (This is determined by geometric conditions that take into account light intensity attenuation, etc., and it is extremely difficult with current technology to separate them any further.)

On the other hand, there are limits to the heat resistance and water resistance (humidity resistance) of the detection head or the components of the light emitting and receiving parts.
Normally, the temperature is below 50℃ and the humidity is below 80%.

On the other hand, the temperature near the drum surface of the dryer part is considerably higher than 50℃.
In addition, water vapor generated from the sheet is filled and forms a mist, creating an extremely hot and humid atmosphere, making it impossible for conventional infrared moisture meters to measure in close proximity to the material to be measured. Due to unfavorable conditions, it is not possible to reduce the noise components of reflected light and transmitted light, and a large amount of water vapor exists over a long distance between the material being measured and the light emitting and receiving ends, making it difficult to achieve the desired light intensity. This hinders accurate light emission and accurate reception of reflected and transmitted light, which not only results in low accuracy of measured values, but also poses problems in the durability of the measuring instrument due to high temperature and humidity. Therefore, there has been a need for a method and apparatus that can accurately measure the moisture content of a material to be measured over a long period of time in such a high temperature and humidity atmosphere.

[Means for solving problems]

The present invention solves the above-mentioned problems of the prior art, and eliminates the need to replace the interference filter even if the moisture content of the material to be measured changes significantly in a high-temperature, high-humidity atmosphere such as in a dryer part of the papermaking process. As a result of intensive research with the aim of providing a method and device that can be used to measure accurately over a long period of time, we have developed a method and device that can improve measurement accuracy by using an infrared-transmissive optical fiber in the optical path. It can withstand high temperature and humidity even if the beam projection position is moved close to the material to be measured, and the other measuring instruments are moved to a remote location with a good environment to improve durability, and the device is constructed using optical fibers. This product was developed after discovering that it has the advantage of being equipped with all the types of interference filters necessary to measure moisture content over a wide range and being able to measure any moisture content instantly. be.

That is, one aspect of the present invention is that when measuring the moisture content of a sheet using infrared rays as it passes through a wire part and a press part and then passes through a dryer part in a high temperature and humid atmosphere, light from a light source is transmitted through an interference filter. Obtain two measurement wavelength lights and two reference wavelength lights in the infrared region based on the infrared absorption spectrum of the material to be measured, and project each wavelength light onto the material to be measured on the one hand and receive the reflected light or transmitted light. On the other hand, the light source is guided directly to the photoelectric converter for correction of light intensity fluctuations, and an infrared transmitting optical fiber is used in the optical path to direct the light emitting and receiving light close to the material to be measured. At this position, water vapor is removed near the light emitting end of the optical fiber and the material to be measured by supplying dry gas.
This invention relates to a method for measuring the moisture content of a sheet in a dryer part, characterized in that the moisture content is determined by obtaining the light intensity ratio between the measurement wavelength light obtained in this way and the reference wavelength light, which is corrected for variations in the light source light intensity, using a photoelectric conversion value (hereinafter referred to as (sometimes referred to as the method of the present invention).

The other two aspects of the present invention are moisture measuring devices suitable for carrying out the method of the present invention, one of which is a dryer characterized by mainly comprising the following configurations (a) to (h). Part-time sheet moisture measuring device: (a) The light emitted from the light source is divided into four optical paths using four or four-branched infrared-transmissive optical fiber bundles, and four types of light are provided at the terminals of each optical path. (b) means for obtaining two measurement wavelength lights and two reference wavelength lights in the infrared region based on the infrared absorption spectrum of the material to be measured through an interference filter; Two beams, each with an optical shutter, are used to guide one beam to a light emitting end located close to the material to be measured and direct it to the material to be measured, and guide the other beam to a photoelectric converter. means for obtaining a total of 8 beams with 4 wavelengths by having a straight or bifurcated infrared transmission type optical fiber bundle downstream from each interference filter; (c) reflected light or transmitted light from the material to be measured; means consisting of an infrared-transmissive optical fiber bundle for receiving the light at a light-receiving end located close to the material to be measured and guiding it to a photoelectric converter; (d) a dehumidifier that substantially surrounds the light-emitting end to the vicinity of the material to be measured; means for supplying dry gas to the inside of a dehumidifying chamber that substantially surrounds the chamber and the light-receiving end close to the material to be measured to eliminate water vapor near the light-emitting end, the light-receiving end, and the material to be measured; (e) the optical shutter; sequentially selectively open and close the
means for sequentially and selectively guiding a predetermined beam to a photoelectric converter to photoelectrically convert a serial optical signal and then amplifying it with a DC amplifier and converting it into a serial analog voltage; (f) opening of the optical shutter that opens and closes first; means for generating a synchronizing pulse in synchronization with the opening of all optical shutters, and generating a sampling pulse in synchronization with each opening of all optical shutters; means for detecting the maximum peak of the analog voltage signal and converting it into a serial digital voltage signal; (h) a predetermined signal necessary for calculating the moisture content of the material to be measured by combining the synchronized pulse and the serial digital voltage signal; This invention relates to means for selectively identifying water content and calculating and displaying water content (hereinafter sometimes referred to as the first device of the present invention).

Furthermore, another type of moisture measuring device is the following (i) to (p).
A sheet moisture measuring device in a dryer part, characterized in that it mainly consists of: (i) four types of interference filters arranged on the same circumference at predetermined intervals on a rotating disk concentric with the circumference; A bundle of two or bifurcated infrared-transmissive optical fibers for dividing and guiding the light emitted from the light source into two beams at two predetermined positions close to the circumference and emitting the light toward the plate surface. from the light source to the rotating disk, and four types of interference filters pass through each beam while the rotating disk rotates, allowing two measurement wavelength lights and two reference lights based on the infrared absorption spectrum of the material to be measured to be generated. 2 beams for each wavelength of light, totaling 4 wavelengths 8
(j) a means for obtaining a beam; (j) said 2 provided from the light source to the rotating disk;
It consists of two infrared-transmissive optical fiber bundles with the optical axes of the tips aligned with the rear end of each of the book or bifurcated optical fiber bundles with a rotating disk in between, and the four types of interference filters are For each wavelength of light obtained by passing through, one of the two beams is guided to a light projection end located close to the material to be measured, and the other beam is guided to a photoelectric converter. means, (k) means consisting of an infrared-transmissive optical fiber bundle for receiving reflected light or transmitted light from the material to be measured at a light receiving end located close to the material to be measured and guiding it to a photoelectric converter; l) Dry gas is supplied to the inside of a dehumidifying chamber that almost surrounds the light emitting end close to the material to be measured, and a dehumidifying chamber that almost surrounds the light receiving end close to the material to be measured. means for eliminating water vapor near the material; (m) generating a synchronizing pulse every rotation in synchronization with the rotation of the rotating disk, and determining the timing at which each of the four types of interference filters crosses the two beams; (n) means for photoelectrically converting a serial optical signal entering the photoelectric converter and then amplifying it with a DC amplifier to convert it into a serial analog voltage signal; (o) means for converting the serial optical signal into a serial analog voltage signal; means for introducing the analog voltage signal and the sampling pulse into a sample-and-hold circuit, detecting the maximum peak of each analog voltage and converting it into a serial digital voltage signal; (p) means for introducing the synchronizing pulse and the serial digital voltage signal; (hereinafter sometimes referred to as the second device of the present invention). .

[Explanation of composition and action]

Hereinafter, the structure and operation of the first and second devices of the present invention will be explained with reference to the drawings, and the method of the present invention will also be explained.

Fig. 1 is a system configuration diagram of the essential parts of an embodiment of the first device of the present invention, Fig. 2 is a diagram of the main system configuration of an embodiment of the second device of the present invention, and Fig. 3 is an example of a dehumidification chamber. FIG. 4 is a perspective view showing another example of a dehumidifying chamber, and FIG. 5 is a diagram showing an example of a time series of voltage signals produced by the apparatus of the present invention.

(i) First, the first device of the present invention will be explained with reference to FIG.

Structure of (a): In the drawing, 1 is a light source, preferably one that emits only infrared rays, but usually a halogen tungsten lamp or an incandescent lamp is used. 2 is a lens for converging the light emitted from the light source 1. Reference numeral 3 denotes a bundle of four or four-branched infrared transmission type optical fibers, which serves as an optical path through which light from the light source 1 that is focused by the lens 2 enters and travels as four beams. An example of an infrared transmitting optical fiber used in the present invention is a diaguide.
ST normal grade (DAIAGUIDEST, product name,
(manufactured by Dainichi Nippon Electric Cable Co., Ltd.) is shown. Reference numeral 4 denotes interference filters of different types provided at the terminals of each optical fiber 3, which transmit the light that has passed through each optical fiber 3 and convert it into infrared rays of four predetermined wavelengths in the infrared region. These four predetermined wavelengths are two measurement wavelengths and two reference wavelengths used for moisture measurement based on the infrared absorption spectrum of the material to be measured, and the measurement wavelengths are 1.43μm (for high moisture) and 1.95μm. μm (for low moisture), and 1.24 μm (for high moisture) and 1.82 μm (for low moisture) as reference wavelengths, so each of the four types of interference filters transmits light from light source 1. The infrared light has the above-mentioned predetermined wavelength. In this way, the means (a) for obtaining four types of predetermined wavelength light in the infrared region using the optical fiber bundle 3 is constructed.

Structure of (b): Reference numeral 5 denotes an infrared transmission type optical fiber bundle for guiding infrared rays of a predetermined wavelength transmitted through each interference filter 4 to a predetermined location. This optical fiber bundle 5 is provided as two or two branched optical fiber bundles 5a and 5b on the downstream side of each interference filter 4, and divides the infrared rays of each of the four wavelengths into two beams for a total of 8 beams. Two beams are obtained. And 2
One of the optical fiber bundles 5a among the two optical fiber bundles 5 guides one beam to a position close to the material to be measured 11 and emits light from there, so that its terminal is located as a light projection end 5aa at a position close to the material to be measured 11. The other optical fiber bundle 5b is connected to a photoelectric converter 16 and directs the other beam thereto. Reference numeral 6 denotes an optical shutter, which is provided in both the optical fiber bundles 5a and 5b.By opening and closing the optical shutter 6, a beam flows or disappears in the optical fiber bundles 5a and 5b. In this way, a means (b) is constructed in which the optical fiber 5 is used downstream of each interference filter 4 to perform the respective functions.

Configuration of (c): 7 is an infrared transmission type for receiving reflected or transmitted infrared light (FIG. 1 shows the case of only reflected light) from the material to be measured 11 and guiding it to the photoelectric converter 16. The light-receiving end 7a of the optical fiber bundle is placed at a light-receiving position close to the material to be measured 11, thus forming the means (c).

Configuration of (d): 12 is a dehumidification chamber, which includes a light emitting end 5aa and a light receiving end 7.
a is almost surrounded to the vicinity of the material to be measured 11. The dehumidifying chamber 12 may be a complete chamber with no gaps other than between the dehumidifying chamber 12 and the material to be measured 11, and the supplied dry gas may remove water vapor near the light emitting end 5aa, the light receiving end 7a, and the material to be measured 11. There may be gaps above or on the sides as long as they are effective for eliminating them. In such a dehumidifying chamber 12, in the case of receiving reflected light as shown in FIG. However, in the case of receiving transmitted light, two dehumidifying chambers installed on both sides of the material to be measured 11 are required as illustrated later. The dehumidification chamber 12 has a light emitting end 5aa and a light receiving end 7.
It can have various functions such as a holder and an integrating sphere when receiving transmitted light. Reference numeral 13 denotes an air pipe, which supplies dry gas sent from a dry gas source 14 into the dehumidifying chamber 12, and connects the light emitting end 5aa and the light receiving end 7a.
and remove water vapor near the material 11 to be measured.
For example, dry air, dry nitrogen, etc. are used as the dry gas.

A specific example of the dehumidification chamber 12 will be explained with reference to the drawings. The dehumidifying chamber 12 shown in FIG. 3 is used for receiving reflected light. This dehumidification chamber 12 has a holding part 12a that holds the light emitting end 5aa and the light receiving end 7a in proper positions.
and a dry gas supply port 12 to which the air supply pipe 13 is connected.
and a dehumidifying section 12b having a dehumidifying section 12b. This dehumidification chamber 12 has a U-shaped slit 12d that passes through the top and bottom.
is formed, and one side serves as a wall to connect the supply port 1.
A holding part 12a is provided on the upper surface of the dehumidifying part original body, and the other end is opened to the side, and the light emitting end 5aa and the light receiving end 7a are inserted into the slit 12d as shown in FIG. (In order to avoid complication in the drawing, Fig. 3 shows them integrated from the beginning to avoid confusion in the drawing.) By holding the lower surface of the dehumidifying chamber 12 close to the material to be measured 11 and supplying dry gas from the supply port 12c, the dehumidifying chamber 12 functions as described above.

The two dehumidifying chambers 12 shown in FIG. 4 are used in pairs to receive transmitted light. The dehumidifying chamber 12 for light projection (the one used on the upper side in FIG. 4) and the dehumidifying chamber 12 for transmitted light reception (the one used on the lower side in FIG. 4) have a light emitting end 5aa and a light receiving end 7a, respectively.
It is also configured as a holder to satisfy the geometric conditions of 0° incidence with respect to the material 11 to be measured and diffuse transmitted light reception. That is, the dehumidifying chamber 12 for light emission holds the light emission end 5aa of the optical fiber bundle 5a perpendicular to the material to be measured 11, and completely surrounds the light emission end 5aa except for the side of the material to be measured 11. Inside, a conical nozzle 12e is provided surrounding the light emitting end 5aa, and is in communication with a dry gas supply port 12c. In addition, the dehumidification chamber 12 for receiving transmitted light includes the material 1 to be measured.
The interior of the chamber has a spherical shape and is completely closed except for the side of the material to be measured 11, so that it acts as an integrating sphere to receive the transmitted light that passes through the material 11 and is diffused. An end 7a is installed, and a bowl-shaped nozzle 12f and a cylindrical nozzle 12g are connected to the supply port 1 on the side facing the end 7a and the side facing the material to be measured 11.
It is provided together with 2c. An air supply pipe 13 is connected to these dry gas supply ports 12c.

Configuration (e): 16 is a photoelectric converter in which the temperature of the light receiving element PbS is kept constant by an electronic controller;
Thermal stability is ensured. Two beams for each predetermined wavelength obtained by the interference filter 4 are input to the photoelectric converter 16 through the following paths. That is, one beam passes through the optical fiber bundle 5a and is projected onto the material to be measured 11, and then the reflected light or transmitted light is input via the optical fiber bundle 7, and the other beam passes through the optical fiber bundle 5b. It is now entered as is. 17 is a DC amplifier that receives a voltage signal from the photoelectric converter 16 and amplifies it. An optical shutter 6 is provided in each of the optical fiber bundles 5a and 5b, and by sequentially selectively opening and closing the optical shutter 6, an input serial optical signal is photoelectrically converted, and then DC amplified and converted into a serial signal. Can be converted to analog voltage. The means (e) is configured in this way.

Structure of (f): 8 and 9 are photo sensors, which may be either reflective type or transmissive type. There is only one photosensor 8 to generate a synchronizing pulse in synchronization with the opening of the optical shutter 6 that opens and closes first, and the photosensor 9 generates a sampling pulse in synchronization with the opening of all the optical shutters 6. Each optical shutter 6 is installed in order to generate the image. The means (f) is configured in this way.

Configuration (g): 15 is an OR circuit which outputs a pulse every time a pulse is generated in any of the photosensors 9. 18 is a sample and hold circuit;
By inputting the output of the OR circuit 15 and the output of the DC amplifier 17 to the input stage, the DC amplifier 17 is synchronized with the sampling pulse from the OR circuit 15.
The individual maximum values of the serial analog voltages from are detected and output. Reference numeral 19 denotes an analog-to-digital conversion interface, which converts the serial analog maximum voltage inputted from the sample-and-hold circuit 18 into a serial digital voltage and outputs it. The means (g) is configured in this way.

(h) Configuration: 20 is an input/output interface that takes in synchronization pulses from the photosensor 8. Reference numeral 21 denotes a calculation/display unit, which receives the synchronizing pulse from the input/output interface 20, and immediately thereafter receives a data string consisting of 8 serial digital signals as one block, which is then combined and processed as described below. As illustrated, a predetermined signal necessary for calculating the moisture content of the material to be measured is selectively identified, and the moisture content is calculated and displayed. Means (h) is thus constructed.

The above-mentioned means (a) to (h) are the main components of the first device of the present invention.

The operation of the first device of the present invention is as follows. When each device is put into operation and the optical shutter 6 is opened for the first time, a synchronization pulse and a sampling pulse are generated by the photosensors 8 and 9, respectively, and are sent to the input/output interface 20 and the sample-and-hold circuit 18, respectively. input as well as a predetermined wavelength (e.g. 1.24μm)
The light passes through the optical fiber bundle 5a and is projected onto the material to be measured 11 from the light projecting end 5aa of the terminal, and the reflected light or transmitted light is received by the light receiving end 7a of the optical fiber bundle 7. At this time, a dehumidifying chamber 12 as shown in FIG. 3 or 4 is used for the light emitting end 5aa and the light receiving end 7a depending on whether reflected light or transmitted light is being received, and the light emitting end 5aa and the light receiving end 7a are covered. The light emitting end 5aa
Water vapor near the light receiving end 7a and the material to be measured 11 is removed and new water vapor is prevented from entering. Therefore, light is emitted and received at a position close to the material to be measured 11 and where most of the water vapor is present. It will be held in a hostile atmosphere.

The reflected or transmitted light from the material to be measured 11 received in this way passes through the optical fiber bundle 7 and is guided to the photoelectric converter 16, and then to the DC amplifier 17.
An analog voltage corresponding to the amount of reflected light that is precisely related to the moisture content of the material 11 to be measured is generated. This analog voltage is input to the sample-and-hold circuit 18 together with the sampling pulse generated by the photosensor 9, and the maximum value of the voltage is converted into digital data by the analog-to-digital conversion interface 19, which is then sent to the input/output interface 20. The synchronizing pulse from the photosensor 8 is taken into the arithmetic/display section 21 and becomes data _D1 based on reflected light or transmitted light.

When the first opened engineering shutter 6 is closed and then the second optical shutter 6 installed on another optical fiber bundle 5b that passes the same wavelength light as above is opened, the wavelength light passes through the optical fiber bundle 5b. , a photoelectric converter 16, and a DC amplifier 17, an analog voltage corresponding to the light intensity of the light source 1 is inputted to a sample-and-hold circuit 18 together with a sampling pulse generated by the photosensor 9 in the same manner as above, and an analog-to-digital conversion interface is input. 19, the maximum value of the voltage is converted into digital data and taken into the calculation/display unit 21, and becomes data _D2 for correcting the light amount of the light source 1. Calculation/display section 21 until the first optical shutter 6 opens
(no synchronization pulse is detected).

Similarly, other wavelengths (e.g. 1.43 μm,
The two optical shutters 6 are sequentially opened and closed for each of the light beams (1.82 μm and 1.92 μm), and the digital data D ₃ to D ₈ are input into the calculation/display section 21 .

An example of the time-series relationship among the synchronizing pulse, sampling pulse, and analog voltage generated by sequentially opening and closing the first to eighth optical shutters 6 is shown in FIG. In FIG. 5, A indicates a synchronizing pulse, B indicates a sampling pulse, and C indicates an analog voltage. Serial analog voltages having such a relationship are input to the sample-and-hold circuit 18 together with sampling pulses, and the individual maximum values of the voltages are converted into digital data by the analog-to-digital conversion interface 19, and each of the voltages shown below is converted into digital data. Data D ₁ to D ₈ are taken into the calculation/display section 21 as one block of data string for each synchronization pulse from the photosensor 8 via the input/output interface 20.

The order in which the optical shutters 6 are opened and closed does not necessarily need to be performed for each wavelength of light as described above, and the data obtained by opening and closing the eight optical shutters 6
As long as D ₁ to _{D 8} correspond to D ₁ to _{D 8} in the formula for calculating moisture content, the order of opening and closing may be arbitrary.

These data D ₁ to _{D 8} are selectively identified in the calculation/display unit 21, and for example, as explained below, equations (1) to (3) are selected in a predetermined order, and the moisture content is calculated. It will be displayed.

D ₁ : Data based on reflected light or transmitted light from the material to be measured with a wavelength of 1.24 μm D ₂ : Data based on light for correcting light intensity fluctuations with a wavelength of 1.24 μm D ₃ : Reflected light from the material to be measured with a wavelength of 1.43 μm Or data based on transmitted light D ₄ : Data based on light for correcting light intensity fluctuations with a wavelength of 1.43 μm D ₅ : Data based on reflected light or transmitted light from the material to be measured with a wavelength of 1.82 μm D ₆ : Light amount with a wavelength of 1.82 μm Data based on light for fluctuation correction D ₇ : Data based on reflected light or transmitted light from the material to be measured with a wavelength of 1.95 μm D ₈ : Data based on light for light intensity fluctuation correction with a wavelength of 1.95 μm D ₃ /D ₇ × D ₈ /D ₄ (1) D ₅ /D ₇ ×D ₈ /D ₆ (2) D ₁ /D ₃ ×D ₄ /D ₂ (3) The second term in each equation is a correction term for changes in light amount. This method takes advantage of the fact that the light projected onto the material to be measured and the light for correcting light intensity fluctuations are proportionally affected.

Determine the approximate moisture content of the material to be measured according to the value of formula (1), and if this value is greater than a certain value, it is considered to be low moisture, and the moisture content is calculated using formula (2). If it is small, it is assumed that the moisture content is high and the moisture content is calculated using equation (3), and if it is close to a constant value, the moisture content is calculated from both equations (2) and (3).

This constant value can be determined as appropriate based on technical experience, but
For example, values determined by the transmittance of individual interference filters with dominant wavelengths of 1.43 μm and 1.95 μm and the infrared absorption spectrum of the material to be measured can be adopted.

(ii) Next, a second apparatus of the present invention will be explained with reference to FIG.

Configuration (i): In the drawing, 1 is a light source, 2 is a lens, and these are the same as the first device of the present invention. 3' is a bundle of two or two branched infrared-transmissive optical fibers, and the light from the light source 1, which is focused by the lens 2, enters and becomes two beams, forming an optical path that travels from the light source 1 to the next one. It even has a rotating disk to explain. Reference numeral 10 denotes a rotating disk, and four types of interference filters 4 are arranged at predetermined intervals on the same circumference concentrically with the rotating disk.
This is the same as that described in connection with the apparatus of the present invention. The terminals of the optical fiber bundle 3' are arranged at two predetermined positions toward the plate surface close to the circumference where the interference filter 4 is arranged (hereinafter, these positions are referred to as the optical fiber bundle 3'). ), each interference filter 4 traverses the two beams emitted from these two optical fiber bundles 3', so that the In total, eight beams with four wavelengths are obtained, two beams for each of four wavelengths in total, including one measurement wavelength light and two reference wavelength lights. Since these eight beams must be obtained at different times because the data for each beam must be obtained separately, the terminal position of the optical fiber bundle 3' is such that an interference filter 4 is placed in the optical path of the two beams exiting therefrom at the same time. These two locations do not exist, and can be determined in various ways based on the arrangement of the interference filter 4 on the rotating disk 10. Generally, four interference filters are α゜, β゜,
When the optical fiber bundles 3' are arranged at intervals of γ゜ and δ゜, the optical fiber bundle 3'
Terminals should be installed. Standardly, four interference filters 4 are arranged at equal intervals of 90 degrees, and the terminal positions of the optical fiber bundles 3' at two locations are
For example, when the terminal position interval is 45 degrees, two beams of light of a predetermined wavelength can be obtained successively for the same interference filter 4, and the same can be done for other interference filters 4 in turn. During one rotation of the rotating disk 10, a total of 8 beams with 4 wavelengths, 2 beams for each of the 4 types of interference filters 4, are obtained at equal time intervals by the constant rotation of the rotating disk 10. In this way, the means (i) is configured.

Structure (j): 5' is an infrared-transmissive optical fiber bundle for guiding light of a predetermined wavelength transmitted through the interference filter 4 to a predetermined location. This optical fiber bundle 5' is a two or bifurcated optical fiber bundle 5a whose tips are coaxially sandwiched between the terminals of the two optical fiber bundles 3' which are the optical path of the light source light and the rotating disk 10. ',5
b', and the terminal of one optical fiber bundle 5a' serves as a light emitting end 5aa' for the material to be measured 11.
One of the two beams is projected onto the material to be measured 11, and the other optical fiber bundle 5b' is installed at a position close to the photoelectric converter 16.
is connected to the other beam and directs the other beam to it. Therefore, as the rotating disk 10 rotates, each wavelength light that has passed through the four types of interference filters 4 is guided to the above-mentioned predetermined location. In this way, the means (j) is constructed.

Configuration (k): Similar to the means (c) of the first device of the present invention, the optical fiber bundle 7 receives reflected light or transmitted light from the material to be measured 11 at a position close to the material to be measured 11. A means (k) for guiding the light to the photoelectric converter 16 is constructed.

Configuration of (l): The same means (l) as the means (d) described in the first device of the present invention is configured.

Configuration (m): Photosensors 8 and 9 similar to those explained in the means (f) of the first device of the present invention are used, and the rotating disk 1
One photosensor 8 generates a synchronous pulse every rotation in synchronization with the rotation of the light source 1, and each of the four interference filters 4 generates a sampling pulse in synchronization with the timing at which the two beams from the light source 1 cross. Two photosensors 9 for generating the light are installed to constitute the means (m).

(n): Configuration A photoelectric converter 16 and a DC amplifier 17 are installed in the same way as explained in the means (e) of the first device of the present invention, and the material to be measured 11 is input to the photoelectric converter 16. A means (n) for converting a serial optical signal from a serial optical signal into a serial analog voltage signal is configured.

Configuration of (o): OR circuit 1 similar to means (g) of the first device of the present invention
5. Means (o) for detecting the maximum peak of the serial analog voltage converted and amplified by the means (n) and converting it into a serial digital voltage signal using the sample-and-hold circuit 18 and the analog-to-digital conversion interface 19; is configured.

Configuration (p): Similar to the means (h) of the first device of the present invention, means for calculating and displaying the moisture content of the material 11 to be measured ( p) is configured.

The above-mentioned means (i) to (p) are the main components of the second device of the present invention.

The operation of the second invention device described above is as follows.

An example will be explained in which four interference filters 4 are arranged at equal intervals of 90 degrees on a rotating disk and the end intervals of the optical fiber bundles 3' are 45 degrees. When the rotating disk 10 is rotated with each device in operation, when the first interference filter 4 first crosses the first of the two beams coming from the two terminals of the optical fiber bundle 3', the photosensor Synchronization pulses and sampling pulses are generated by 8 and 9, respectively, and are input to the input/output interface 20 and the sample-and-hold circuit 18, respectively. .mu.m) passes through the optical fiber bundle 5a'.

Thereafter, the process is exactly the same as the operation when the optical shutter 6 is first opened and closed in the above description of the operation of the first device of the present invention. That is, the light that has passed through the optical fiber bundle 5a' is projected onto the material to be measured 11 from the light emitting end 5aa', and its reflected light or transmitted light is received at the light receiving end 7a. 12, the above-mentioned light emission and light reception are carried out at a position close to the material to be measured 11 while excluding moisture in the vicinity, and the light thus received is photoelectrically converted, and the detected maximum The value is converted into digital data and taken into the arithmetic/display section 21 along with the synchronization pulse, and becomes data D1 based on reflected light or transmitted light.

Next, when the same interference filter 4 crosses the second beam, the same wavelength light as above passes through the optical fiber bundle 5b' and is directly input to the photoelectric converter 16, and a sampling pulse is generated at the photosensor 9. Hereinafter, in exactly the same manner as in the case of opening and closing the second optical shutter 6 in the above description of the operation of the first device of the present invention, light of a predetermined wavelength passes through the optical fiber bundle 5b' and is photoelectrically converted, and the light source 1
The maximum value of the analog voltage corresponding to the amount of light is converted into digital data and taken into the calculation/display unit 21,
This becomes data D2 for light amount correction.

Thereafter, the other interference filters 4 sequentially cross the two beams in the same way, and each data D1 to D8 is transmitted in the same way as in the case of the first inventive device using a synchronizing pulse inputted every rotation of the rotating disk 10. is taken into the calculation/display unit 21 as an example of one block of data. Four interference filters 4 on rotating disk 10
Due to the relationship between the arrangement of There is no problem as long as the The moisture content of these data D1 to D8 is calculated and displayed in exactly the same manner as described above regarding the operation of the first apparatus of the present invention.

As can be seen from the above description, the relationship between the first and second devices of the present invention and the method of the present invention is as follows. That is, means (a) and means (i) are devices for transmitting the light from the light source 1 through the interference filter 4 to obtain measurement wavelength light and reference wavelength light based on the infrared absorption spectrum of the material to be measured 11, Means (b) and
(c) and means (j) and (k) are: on the one hand, light of each wavelength is emitted from a position close to the material to be measured 11, and the reflected light or transmitted light is received at a position close to the material to be measured 11; This is a device for guiding the optical fiber bundles 3, 5, and 7 to the photoelectric converter 16, and directly guiding the optical fiber bundles 3, 5, and 7 to the photoelectric converter 16 for correction of light intensity fluctuations of the light source.
The optical fiber bundles 3', 5', and 7 are those in which an infrared-transmissive optical fiber is used in the above-mentioned optical path to enable light projection and reception close to the material to be measured 11, and means ( d) and means (l) are devices for emitting and receiving light while removing moisture near the light emitting end 5aa or 5aa', the light receiving end 7a, and the material to be measured 11 by supplying dry gas; At the same time, the light emitting end 5aa or 5aa' and the light receiving end 7a are connected to the material to be measured 1.
Means (e), (f), (g) and (h) and means (m), (n), (o) and
(p) is a device for determining the moisture content by obtaining the light intensity ratio between the obtained measurement wavelength light and the reference wavelength light, which is corrected for fluctuations in the light source light intensity, from the photoelectric conversion value. Therefore, it can be seen that the first and second apparatuses of the present invention are suitable apparatuses for carrying out the method of the present invention.

〔effect〕

The present invention uses an optical fiber that efficiently transmits infrared rays in the optical path of the infrared rays when measuring the moisture content of a sheet in the dryer part of the papermaking process in a high temperature and humid atmosphere using an infrared moisture meter, and also transmits and receives light. By performing the measurement at a position close to the material to be measured while removing nearby moisture, the following effects can be obtained.

(b) Since the optical fiber is heat resistant, there is no problem in installing the optical fiber end close to the high temperature drying drum, and therefore the light emitting end and light receiving end were installed close to the material to be measured. This significantly improves the geometric conditions that cause light intensity attenuation between the material to be measured and the light emitting and receiving ends compared to conventional infrared moisture meters, further improving measurement accuracy. I can do it.

(b) In this dryer part, which is particularly humid, the moisture is in the form of a mist near the surface of the material to be measured, and conventional infrared moisture meters can emit a predetermined amount of light and accurately receive reflected or transmitted light. However, in the present invention, by bringing the light emitting end and the light receiving end close to the material to be measured and supplying dry gas in the vicinity, this mist-like moisture can be removed from the light emitting and receiving ends. By completely excluding it from the light receiving optical path, measurement accuracy can be further improved.

(c) Optical fibers are used in the optical path to transmit the light from the light source through an interference filter to obtain infrared rays, and the optical path is configured in various ways to accommodate any situation with a wide range of moisture content. Various types of interference filters can be arranged in advance, thereby eliminating the need to replace interference filters depending on the moisture content.

(d) By using an optical fiber along the entire optical path from the light source to the photoelectric converter, the necessary length of light including the transmitting end and the receiving end that emits and receives infrared rays to the material being measured. Only the fiber and the dehumidifying chamber are placed in the dryer part area under a high temperature and humid atmosphere, and other light sources, interference filters,
All of the equipment below the photoelectric converter can be placed outside the dryer part, and as a result, the infrared moisture meter can be used without being affected by high temperature and humidity, reducing breakdowns and greatly improving durability. Therefore, moisture can be measured over a long period of time without decreasing measurement accuracy.

(E) According to the present invention, it has become possible to continuously measure the moisture content of sheets with high precision in the papermaking process, such as inside a hot and humid dryer part, which was previously impossible. , for example, JP-A-60-62778 and JP-A-61-
It is possible to construct an automatic control system using a known drying drum as an operation unit, such as that disclosed in Public Law No. 75898, to manage sheet moisture in the papermaking process with good responsiveness and controllability.
High-quality sheet products with even moisture content can now be manufactured at low cost.

[Brief explanation of drawings]

Fig. 1 is a system configuration diagram of the essential parts of an embodiment of the first device of the present invention, Fig. 2 is a diagram of the main system configuration of an embodiment of the second device of the present invention, and Fig. 3 is a diagram of the main part system configuration of an embodiment of the device of the present invention.
FIG. 4 is a perspective view showing another example of the dehumidification chamber, FIG. 5 is a diagram showing an example of a time series of voltage signals in the device of the present invention. In the drawings, 1... light source, 2... lens, 3, 3'... optical fiber bundle, 4... interference filter, 5, 5'...
Optical fiber bundle, 5a, 5a'... Two optical fiber bundles or one of two branched optical fiber bundles, 5aa, 5aa'...
Light emitting end, 5b, 5b'...the other bundle of two or two branched optical fibers, 6...optical shutter, 7
... Optical fiber bundle, 7a... Light receiving end, 8... Photo sensor, 9... Photo sensor, 10... Rotating disk, 11
... Material to be measured, 12... Dehumidification chamber, 12a... Hold section, 12b... Dehumidification section, 12c... Supply port, 12d...
Slit, 12e... Conical nozzle, 12f... Bowl-shaped nozzle, 12g... Cylindrical nozzle, 13... Air supply pipe,
14... Dry gas source, 15... OR circuit, 16... Photoelectric converter, 17... DC amplifier, 18... Sample and hold circuit, 19... Analog-to-digital conversion interface, 20... Input/output interface, 21... Operation Display section, A...Synchronization pulse, B
...Sampling pulse, C...Analog voltage.

Claims (1)

[Claims] 1. When measuring the moisture content of a sheet passing through a wire part and a press part and then proceeding through a dryer part in a hot and humid atmosphere using infrared rays,
transmitting the light from the light source through an interference filter to obtain two measurement wavelength lights and two reference wavelength lights in the infrared region based on the infrared absorption spectrum of the material to be measured;
On the one hand, the light of each wavelength is projected onto the material to be measured, and the reflected light or transmitted light is received and guided to a photoelectric converter, and on the other hand, the light is directly guided to the photoelectric converter for correction of fluctuations in light intensity of the light source. Using an infrared transmitting optical fiber in the optical path, the above light emission and light reception are performed at a position close to the material to be measured while supplying dry gas to eliminate water vapor near the light emitting end of the optical fiber and the material to be measured. A method for measuring the moisture content of a sheet in a dryer part, characterized in that the moisture content of a sheet in a dryer part is determined by obtaining a light intensity ratio between the measurement wavelength light obtained in this way and the reference wavelength light, which is corrected for fluctuations in the light source light intensity, using a photoelectric conversion value. 2. A sheet moisture measuring device in a dryer part, characterized by mainly consisting of the following configurations (a) to (h): (a) an infrared transmission type light beam emitted from a light source into four or four branches; The fiber bundle divides the light into four optical paths, and through four types of interference filters installed at the ends of each optical path, two measurement wavelength lights and two reference wavelength lights in the infrared region based on the infrared absorption spectrum of the material to be measured are transmitted. (b) dividing the infrared rays transmitted through the individual interference filters into two beams for each wavelength, and guiding one beam to a projection end located close to the material to be measured and projecting it onto the material to be measured; In order to guide the other beam to the photoelectric converter, two or two branched infrared transmitting optical fiber bundles each having an optical shutter are provided downstream from each interference filter, and in total there are four means for obtaining a beam of eight wavelengths; (c) an infrared transmitting optical fiber bundle for receiving reflected light or transmitted light from the material to be measured at a light receiving end located close to the material to be measured and guiding it to a photoelectric converter; (d) supplying dry gas to the inside of a dehumidifying chamber that substantially surrounds the light emitting end close to the material to be measured and a dehumidifying chamber that substantially surrounds the light receiving end close to the material to be measured; means for eliminating water vapor near the light receiving end and the material to be measured; (e) selectively opening and closing the optical shutter in sequence;
means for sequentially and selectively guiding a predetermined beam to a photoelectric converter to photoelectrically convert a serial optical signal and then amplifying it with a DC amplifier and converting it into a serial analog voltage; (f) opening of the optical shutter that opens and closes first; means for generating a synchronizing pulse in synchronization with the opening of all optical shutters, and generating a sampling pulse in synchronization with each opening of all optical shutters; (g) directing said serial analog voltage and sampling pulse to a sample and hold circuit to (h) means for detecting the maximum peak of the analog voltage signal and converting it into a serial digital voltage signal; (h) combining the synchronized pulse and the serial digital voltage signal to generate a predetermined signal necessary for calculating the moisture content of the material to be measured; A means of selectively identifying, calculating and displaying moisture content. 3. A sheet moisture measuring device for a dryer part, characterized in that it mainly consists of the following configurations (i) to (p): (i) four types of interference filters arranged at predetermined intervals on the same circumference; Two or It has a bifurcated infrared-transmitting optical fiber bundle from the light source to the rotating disk, and four types of interference filters pass through each beam while the rotating disk rotates, allowing the beam to be measured based on the infrared absorption spectrum of the material to be measured. 2 beams each for the two measurement wavelength lights and the two reference wavelength lights, for a total of 4 wavelengths 8
(j) means for obtaining the beam; (j) said 2 provided from the light source to the rotating disk;
It consists of two infrared-transmissive optical fiber bundles with the optical axes of the tips aligned with the rear end of each of the book or bifurcated optical fiber bundles with a rotating disk in between, and the four types of interference filters are For each wavelength of light obtained by passing through, one of the two beams is guided to a light projection end located close to the material to be measured, and the other beam is guided to a photoelectric converter. means, (k) means consisting of an infrared-transmissive optical fiber bundle for receiving reflected light or transmitted light from the material to be measured at a light receiving end located close to the material to be measured and guiding it to a photoelectric converter; l) Dry gas is supplied to the inside of a dehumidifying chamber that almost surrounds the light emitting end close to the material to be measured, and a dehumidifying chamber that almost surrounds the light receiving end close to the material to be measured. means for eliminating water vapor near the material; (m) generating a synchronizing pulse every rotation in synchronization with the rotation of the rotating disk, and adjusting the timing at which each of the four types of interference filters crosses the two beams; means for synchronously generating sampling pulses; (n) means for photoelectrically converting the serial optical signal input to the photoelectric converter and then amplifying it with a DC amplifier to convert it into a serial analog voltage signal; (o) means for converting the serial optical signal into a serial analog voltage signal; (p) means for directing the analog voltage signal and the sampling pulse to a sample-and-hold circuit to detect the maximum peak of each analog voltage and convert it into a serial digital voltage signal; Means for calculating and displaying the moisture content by selectively identifying predetermined signals necessary for calculating the moisture content of the material to be measured in combination.