JPS6123497B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention irradiates a sheet of paper with near-infrared rays, detects the near-infrared rays that interact with the paper, and obtains a signal regarding the amount of water contained or adsorbed in the sheet of paper, and also obtains a signal regarding the amount of water contained in or adsorbed to the sheet of paper. The present invention relates to a device that obtains signals related to water content and measures moisture content, moisture content, etc. using these signals. Signal related to moisture content (hereinafter simply referred to as moisture content signal)
There are transmission methods and multiple scattering methods as means for obtaining this. The former has an irradiating part and a light receiving part which are arranged facing each other so that the optical axis of the irradiating optical system and the optical axis of the receiving optical system almost coincide, and a sheet of paper is passed between them. , infrared rays of approximately 1.95 μm (light in the wavelength region absorbed by moisture. Hereinafter, this wavelength light is referred to as measurement light) and infrared rays of approximately 1.80 μm (light in the wavelength region not absorbed by moisture. Hereinafter, this wavelength A signal corresponding to the measurement light (hereinafter referred to as the M signal) and a signal corresponding to the reference light (hereinafter referred to as the R signal) are detected by the light receiving section. However, the quotient of these M signal and R signal (hereinafter referred to as M/R signal) is configured to be a water amount signal. The latter differs from the former in the following points. The optical axis of the irradiation-side optical system and the optical axis of the light-receiving side optical system are configured so that they do not match, and the measurement light and reference light from the irradiation section interact with the paper multiple times (much more times than the former). It is designed so that the light reaches the light receiving section. By the way, since the moisture content signal is a function of basis weight, a moisture meter is often provided with a basis weight detection section. As the basis weight detection unit, radiation, for example,
Those using β-rays are in practical use. The measurement principle utilizes the fact that when beta rays pass through paper, the amount of attenuation is related to the basis weight of the paper. In the transmission method or multiple scattering method described above,
When the raw material composition of paper changes, or when the so-called optical conditions of paper such as whiteness, basis weight, press pressure, etc. change,
An influence appears on the M/R signal, that is, the water content signal. In order to reduce these effects, paper machine operators had to change the constants in the moisture calculation formula depending on the paper type (brand), but this operation was not only complicated, but also Even for paper brands, the optical conditions mentioned above may change (without the operator's knowledge), so with conventional methods, it is difficult to continuously and accurately measure paper moisture content, moisture percentage, etc. It was difficult. In order to solve these drawbacks, an apparatus having a structure as described below has been attempted, focusing on the following facts (see Japanese Patent Laid-Open No. 154439/1983). The creation of this device is based on the fact that the R and M signals in the transmission mode or multiple scattering mode are controlled by the variables that govern the optical properties of the paper: number of layers n, transmittance f, reflectance r.
This is a function of the water content MW and the water content MW, and was made by focusing on the fact that these variables exhibit sensitivities to each signal as shown in the table below. In the table,
Rt and Mt indicate the R signal and M signal in the transmission type moisture meter, and Rn and Mn indicate the R signal in the multiple scattering type moisture meter.
signal, M signal is shown.

[Table] The configuration of the above device uses Mn/Rn as the water content signal.
The configuration is such that a signal (a signal with high moisture content sensitivity) is used to automatically compensate for error factors contained in this signal using other signals. A specific example of this is a device for measuring moisture content, moisture content, etc. of newspaper. Newspaper is manufactured by incorporating waste paper into raw material pulp, but the transmittance f varies greatly depending on the content of waste paper, which is a cause of error. Therefore, the moisture content signal Mn/Rn signal is configured to be compensated for using the Rn/Rt signal (a signal with high transmittance sensitivity). In such a device,
The Mn/Rn signal and Rn/Rt signal must be stably obtained. However, in an actual measuring device, a detection head consisting of upper and lower heads arranged opposite each other detects a signal while traveling back and forth within a predetermined range in the width direction of the paper on an O-shaped frame. During this running, the upper and lower heads may shift, especially in the Rn/lower head.
Rt signal may fluctuate. Due to this deviation
Fluctuations in the Rn/Rt signals have been a factor in deteriorating measurement accuracy. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a measuring device for measuring moisture content, moisture content, etc. of paper, which reduces fluctuations in the Rn/Rt signal due to misalignment between the upper and lower heads, and has high measurement accuracy. Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 is an explanatory diagram of the configuration of a detection head of a measuring device according to an embodiment of the present invention. In FIG. 1, an upper head 1 having irradiation windows 4 and 4' and a lower head 2 having an entrance window 5 are disposed facing each other with a sheet of paper 3 sandwiched therebetween. Opposite surfaces of the upper and lower heads 1 and 2 are provided with reflective coatings 16 and 17. Inside the upper head 1, a rotary wheel 8 is installed which has a disc-shaped plate and is equipped with an optical filter 9 for measuring light and an optical filter 10 for reference light, and is composed of a lamp 6, lenses 7, 7', and a reflecting mirror 19. The light from the two optical systems is made into intermittent light, and the irradiation window 4
The paper 3 is irradiated from 4' and 4'. On the other hand, inside the lower head 2, a detection system consisting of a lens 11 and a photosensitive element 12 is constructed, and an electric signal corresponding to the amount of light incident from the entrance window 5 is detected. The optical axis A' ₁ (same as the central axis of the irradiation window 4') includes the lamp 6, the reflector 19,
and lens 7', and is the axis of the optical system that creates light that passes through the irradiation window 4'. Also, optical axis A ₂
(which is the same as the central axis of the entrance window 5) is the entrance window 5
This is the axis of an optical system consisting of a lens 11 and a photosensitive element 12 that detects light transmitted through the lens. Above, top/
The opposing state of the lower heads 1 and 2 means that these optical axes A' ₁ and
A ₂ is shifted in the X direction by an experimentally determined value x ₀ . Next, the positional relationship between the irradiation windows 4, 4', the entrance window 5, and the rotating wheel 8 will be explained in more detail with reference to FIG. Figure 2 A, B and C are Y ₁ −Y ₁ in Figure 1,
FIG. 2 is an explanatory diagram of the configuration in Y ₂ -Y ² and Y ₃ -Y ₃ cross sections (dimensions do not necessarily match). The irradiation windows 4 and 4' of the upper head 1 are provided at a distance in the paper flow direction (the direction of the arrow in the figure B, which coincides with the X direction), and the entrance window 5 is provided on the opposite surface of the lower head 2.
is a position facing the irradiation window 4', and x ₀ = x ₂ − _{x 1}
(x ₁ ... distance between the center line l ₁ of head 1 and the center of window 4', x ₂ ... distance between the center line l ² of the head and the center of window 5, x ₂ > x ₁ ) (Figure C). In addition, a rotating wheel 8 provided on the upper head 1
The positional relationship between the through holes (in which the filters 9 and 10 are buried and supported) and the irradiation windows 4 and 4' is as follows:
When an optical filter 9 or 10 is provided on either one of the optical paths associated with the irradiation windows 4 and 4', the other optical path is blocked by the disk portion. That is, the structure is such that the paper 3 is not irradiated with light from the irradiation windows 4 and 4' at the same time. Therefore, if the rotary wheel 8 is now rotated in the direction of the arrow in Fig. 3A, each filter will sequentially pass through the optical path associated with each irradiation window, and the signal shown in Fig. 3A will be emitted from the irradiation window 4'. But also,
The signal shown in FIG. 3B is obtained from the irradiation window 4, and the signal shown in FIG. 3C is input to the entrance window 5. In FIG. 3, the vertical axis represents the amount of light and the horizontal axis represents time, waveform R represents the signal from optical filter 10, waveform M represents the signal from optical filter 9, waveforms Rt and Mt
represents a signal from the irradiation window 4' that enters the entrance window 5, and waveforms Rn and Mn represent signals from the irradiation window 4 that enter the entrance window. Therefore,
The signals detected by the photosensitive element 12 are the Rt signal, Mt signal, Rn signal, and Mn signal corresponding to the waveform shown in FIG.
It becomes a time-series signal of signal, Rt signal,... Using these signals, the Mn/Rn signal and the Rn/Rt signal are created and subjected to arithmetic processing in the next stage arithmetic section. Next, the operation in the above configuration will be explained. FIG. 4 is a diagram showing the relationship between the rate of change y of the Rn signal or Rt signal and the amount of deviation x. The amount of deviation x is the optical axis
The distance between A′ ₁ and A ₂ is the direction in which the distance x′ ₀ (see Figure 1) between the optical axis A ₁ and the optical axis A ₂ of the optical system that creates the transmitted light of the irradiation window 4 is larger. positive, optical axes A′ ₁ and A ₂
The state in which the values match is defined as x=0. On the other hand, the rate of change y is determined based on the value of the Rn signal or Rt signal when the amount of deviation x=0. graph t
shows the characteristics of the Rt signal, and graph n shows the characteristics of the Rn signal. As is clear from Fig. 4, when the amount of deviation x is around ₀ ,
The rate of change y of the Rt signal and the Rn signal is approximately equal.
Therefore, by setting the deviation amount x ₀ in advance,
If the lower heads 1 and 2 are disposed opposite each other, the amount of change in the Rn/Rt signal will be small relative to the amount of deviation from the installed state. Figure 5 shows the amount of change y′ of the Rn/Rt signal and the amount of deviation x
This is the relationship. The amount of change y' is determined using the Rn/Rt signal when the amount of deviation x=0 as a reference value. Graph 1 is based on a measuring device according to the present invention, and graph 2 is based on a measuring device in which the upper and lower heads 1 and 2 are disposed facing each other with the amount of deviation x=0. As is clear from FIG. 5, the measuring device according to the present invention can obtain a stable Rn/Rt signal with respect to the amount of deviation. Therefore, the measuring device according to the present invention can accurately measure the moisture content, moisture content, etc. of paper, and has great effects in this field.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of a detection head of a measuring device according to an embodiment of the present invention, and FIG. 2 is a sectional view of FIG. ₁ , where A is Y ₁ - Y 1 and B is Y ₂ - ^{Y 2} , Ha is Y ₃ − _{Y 3}
, FIG. 3 is an explanatory diagram of the output signal in the device of FIG. 1, FIG. 4 is a diagram of the relationship between the rate of change y of the Rn signal or Rt signal and the amount of deviation x, and FIG.
FIG. 3 is a relationship diagram between the amount of change y' of the Rt signal and the amount of deviation x. 1... Upper head, 2... Lower head, 3... Sheet of paper, 4 and 4'... Irradiation window, 5... Entrance window, 6... Lamp, 7, 7' and 11... Lens, 8... Rotating wheel, 9 and 10... Optical filter, 12... Photosensitive element, 16 and 17
...Reflective coating, x ₀ ...Amount of deviation.

Claims (1)

[Scope of Claims] 1. A first head on either the upper head or the lower head.
and a second irradiation window is provided on the other side, and an entrance window is provided opposite to the second irradiation window, and a sheet of paper is poured into the gap formed by arranging the upper and lower heads to face each other. The first irradiation window and the entrance window constitute a multiple scattering type optical system in which the paper and the light are transmitted and scattered multiple times, and the second irradiation window and the entrance window constitute a transmission type optical system in which the light passes through the paper once. comprises an optical system, and irradiates the first and second rays with measurement light that is light in a wavelength range that is absorbed by moisture in the paper and reference light that is light in a wavelength range that is not absorbed by moisture in the paper. The measurement light and the reference light emitted from the window and interacting with the paper are guided to the photosensitive element through the incidence window and detected, and the measurement signal Mn and the reference light obtained by the multiple scattering type optical system are detected. By inputting the signal Rn and the reference signal Rt obtained by the transmission type optical system to create an Mn/Rn signal and an Rn/Rt signal, and compensating the Mn/Rn signal with the Rn/Rt signal, In the apparatus that performs calculation to compensate for the influence of transmittance fluctuation when light passes through paper, and measures the amount of water or moisture content contained in the paper from the Mn/Rn signal obtained by the calculation, An apparatus for measuring moisture content or moisture percentage of paper, characterized in that the central axis of the second irradiation window and the central axis of the incident window are separated by a predetermined distance.