JP2013215938A - Method of measuring plastic flow rate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of measuring a plastic flow rate in which a plastic flow rate is calculated taking advantage of the fact that an amount of electromagnetic wave absorbed by moisture in a plastic has a correlation with a plastic amount.SOLUTION: A granular plastic, for example, is irradiated with a 60 GHz terahertz wave, for example, and a correlation between an amount of residual terahertz wave not absorbed by the plastic and a plastic amount is acquired preliminarily. Then, the same plastic is irradiated with the terahertz wave under a condition that gives a similar correlation, and a plastic flow rate is calculated on the basis of the correlation by measuring an amount of residual terahertz wave.

Description

  The present invention relates to a method for measuring the flow rate of plastic, which indirectly calculates the flow rate of plastic using the detection of moisture in the plastic using electromagnetic waves in a predetermined band.

For example, there is a molding machine that forms a predetermined molded article using a pellet-shaped thermoplastic material. An example of such a molding machine is given as Patent Document 1.
In a molded product using a plastic material as in Patent Document 1, various plastic materials are often mixed and used. Therefore, it is necessary to grasp the amount of plastic material used. As a means of grasping the amount of plastic material, for example, a capacity type mixer that discharges material at a constant speed and controls the amount of discharged material with time, or a mass type that measures the mass (weight) of discharged material with a load cell There is a blender.

JP 2000-94447 A

However, in the capacity type mixer, the average value is used for the discharge amount for time management, and the mixing ratio cannot be guaranteed. In addition, in the mass type, installing a load cell requires selecting an installation location such as avoiding a location where vibration is generated, and if vibration is unavoidable, a problem arises in accuracy. Therefore, there has been a demand for an accurate method for measuring the amount of plastic used without causing problems as in the prior art.
The present invention has been made in order to solve the above-mentioned problems, and its purpose is to indirectly utilize the fact that electromagnetic waves absorbed by moisture in the plastic have a correlation according to the amount of plastic. The object is to provide a method for measuring the flow rate of plastics for calculating the flow rate.

In order to achieve the above object, according to the first aspect of the present invention, the residual electromagnetic wave that is not absorbed by the plastic is obtained by irradiating a granular, powdery, or liquid plastic with an electromagnetic wave in a band of 50 GHz to 1000 GHz. Based on the correlation by obtaining the electromagnetic wave in advance in the correlation with the change in the plastic amount, irradiating the electromagnetic wave on the plastic under the condition that the same correlation can be obtained, and measuring the remaining electromagnetic wave The gist is that the flow rate of the plastic is calculated.
The gist of the invention described in claim 2 is that, in addition to the configuration of the invention described in claim 1, the plastic passes through a predetermined passage and measures the remaining electromagnetic wave at the passage position.
Further, in the invention described in claim 3, in addition to the configuration of the invention described in claim 2, a plastic processing apparatus for processing the plastic supplied from the passage is disposed downstream of the passage. This is the gist.

According to a fourth aspect of the invention, in addition to the configuration of the first aspect of the invention, the electromagnetic wave oscillated from an oscillation device is transmitted through the plastic and arranged behind the plastic. The gist of this is that the apparatus receives the signal and measures it.
Further, in the invention according to claim 5, in addition to the configuration of the invention according to claim 4, the passage has a square cross section, and the oscillation device is arranged so that the electromagnetic wave is orthogonal to one surface of the passage. The gist of the present invention is that the receiving device has a receiving surface disposed at a position facing the surface facing the certain surface.
According to a sixth aspect of the invention, in addition to the configuration of the fifth aspect of the invention, the diffusing electromagnetic wave oscillated from the oscillating device is corrected in a parallel emission direction between the passage and the oscillating device. The gist of this is that an optical system for this purpose is arranged.
Further, in the invention described in claim 7, in addition to the configuration of the invention described in claim 6, an optical system for refracting the parallel electromagnetic waves in the convergence direction is disposed between the passage and the receiving device. The gist of this is.
Further, in the invention according to claim 8, in addition to the configuration of the invention according to any one of claims 1 to 3, the pre-electromagnetic wave oscillated from the oscillation device is reflected in the plastic, and the reflected wave is transmitted to the reception device. The gist is that it is received and measured.
Further, in the invention according to claim 9, in addition to the configuration of the invention according to any one of claims 1 to 3, the electromagnetic wave oscillated from the oscillation device is scattered in the plastic, and the scattered wave is transmitted to the reception device. The gist is to receive and measure.

In the configuration as described above, first, an electromagnetic wave in a frequency band of 50 GHz to 1000 GHz is irradiated from a oscillating device to granular, powdery or liquid plastic, and the residual electromagnetic wave not absorbed by the plastic is measured. By acquiring in advance in the correlation with the change, the measurement value corresponding to the water content state can be acquired. The range of 50 GHz to 1000 GHz is a wavelength band to which terahertz waves and millimeter waves belong.
In this way, the remaining electromagnetic wave applied to the plastic with an electromagnetic wave in the 50 GHz to 1000 GHz band is used as a water-containing parameter because the electromagnetic wave in the 50 GHz to 1000 GHz band (that is, terahertz wave and millimeter wave) is absorbed by moisture This is because the moisture does not boil and irradiation of the plastic does not affect the physical properties of the plastic. The amount of absorption is based on the positive correlation with the moisture content in the plastic, that is, the property that the amount of radio waves is absorbed as much as the moisture in the plastic increases. If the measurement conditions are the same for a plastic with a certain water content, the remaining electromagnetic wave that was not absorbed by the plastic when irradiated with electromagnetic waves in the band of 50 GHz to 1000 GHz (that is, the electromagnetic wave that was transmitted without being absorbed by the plastic) was theoretical. Indicates the same value.
Further, the measured value of the remaining electromagnetic wave varies depending on the amount of plastic to be measured even if the plastic has the same water content. In other words, when obtaining the characteristics of the residual electromagnetic wave with the quantity as a parameter for a plastic with a certain water content, a negative correlation is obtained in relation to the quantity of plastic because the residual electromagnetic wave decreases as the quantity of plastic increases. It will be.
Therefore, it is possible to calculate the amount of plastic by measuring the residual electromagnetic wave at the measurement position by obtaining in advance the correlation between the residual electromagnetic wave that has not been absorbed by the plastic and the change in the amount of plastic for a certain water-containing plastic. It becomes possible. By utilizing this action, it becomes possible to calculate the flow rate of the plastic at the measurement position. The flow rate of the plastic can be acquired as the amount of plastic at the measurement position at a certain moment, or can be acquired as the cumulative amount of the plastic that has passed through the measurement position from a certain point in time.

Based on the above theory, the actual correlation is such that the electromagnetic wave in the band of 50 GHz to 1000 GHz is absorbed by the plastic to obtain the characteristics of the amount of the plastic and the residual electromagnetic wave, and this is used as an index for the remaining residual actually obtained. The flow rate is calculated from the electromagnetic wave. In addition, in order to measure and calculate with the highest accuracy as the “conditions for obtaining the same correlation,” the correlation between the plastic actually used in the actual device and the measuring device (oscillator or receiver) is used in advance. However, it is not necessary to actually measure if a correlation can be obtained under the same conditions as the actual usage environment without taking such a method.
Table 1 shows that the wavelength used for electromagnetic waves is 60 GHz, the distance from the antenna of the oscillator to the front of the plastic material is 123 mm, the distance from the back of the plastic material to the antenna of the receiver is 123 mm, the transmitted electromagnetic wave intensity is 1131 mV with no material passing, and moisture It is an example of the characteristic figure which shows the correlation of the transmitted electromagnetic wave (residual electromagnetic wave) acquired about the plastic whose content is 0.1%, and the amount of flow-downs (amount of plastic). Theoretically, the correlation is as follows: Y: transmitted electromagnetic wave intensity, A: transmitted electromagnetic wave intensity without material passage, B: specific coefficient for each plastic, X: plastic passage amount,
Y = A-BX
However, when data is actually sampled, an error occurs as shown in Table 1. Therefore, there is no need to normalize the linear function based on the actual measurement value or to perform normalization. A linear function can be determined by taking an average value.

In the above, as a specific aspect, a method of measuring the remaining electromagnetic wave by causing the receiving device disposed behind the plastic to receive the electromagnetic wave in the band of 50 GHz to 1000 GHz oscillated from the oscillation device. Can be considered. This allows the oscillation device and the reception device to be arranged when there is a space in front and rear, and contributes to accurate measurement. This configuration can be shown by a schematic diagram as shown in FIG. In this case, the oscillator 110 and the receiver 111 are arranged with a passage 112 through which granular, powdery, or liquid plastic flows down. Although it is possible to measure the plastic without necessarily passing through the passage 112, it is actually preferable to pass through the passage 112 in terms of accurate measurement.
In this case, the passage 112 has a square cross section, the oscillation device 110 oscillates so that the electromagnetic wave is orthogonal to one surface with the passage, and the reception device 111 is in a position facing the surface opposite to the one surface. It is more preferable in terms of accurate measurement to arrange the receiving surface. Therefore, the oscillation device 110 is preferably oscillated from a directional antenna.

Further, it is conceivable to measure the remaining electromagnetic wave by reflecting the electromagnetic wave in the band of 50 GHz to 1000 GHz oscillated from the oscillation device within the plastic and receiving the reflected wave by the receiving device. This configuration can be shown by a schematic diagram as shown in FIG.
Further, a method of measuring the remaining electromagnetic wave by scattering the electromagnetic wave in the plastic and causing the receiving device to receive the scattered wave is conceivable. This configuration can be shown by a schematic diagram as shown in FIG. Here, the scattered wave is reflected by the scattering plate 113.
In addition, it is also possible to dispose a lens on the path in order to appropriately collect electromagnetic waves, or to dispose a reflecting mirror in order to change the path.
Moreover, the powdery or liquid plastic used in the present invention is a concept including both thermoplasticity and thermosetting, and further includes an elastomer.

  According to the invention described in each of the above claims, the correlation between the residual electromagnetic wave that was not absorbed by the plastic and the flow rate of the plastic by using the electromagnetic wave in the band of 50 GHz to 1000 GHz was obtained in advance, Since the electromagnetic wave is detected and the flow rate of the plastic can be calculated based on the correlation, it is possible to know how much the plastic has flowed without actually measuring the weight of the plastic.

The front schematic diagram of embodiment of this invention. The partial cross section front schematic diagram which expanded the principal part of the same embodiment. The plane cross-sectional schematic diagram which expanded the principal part of the same embodiment. The block diagram explaining the electric constitution of the control system of the same embodiment. Explanatory drawing explaining an example of the numerical icon displayed on a monitor. The schematic diagram explaining the arrangement | positioning state of an oscillation apparatus and a receiver. The schematic diagram explaining the arrangement | positioning state of an oscillation apparatus and a receiver. The schematic diagram explaining the arrangement | positioning state of an oscillation apparatus and a receiver.

Hereinafter, specific embodiments in which the present invention is applied to a plastic material supply system (hereinafter referred to as a supply system) will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a simplified supply system. The supply system is connected to the hopper 11 that accommodates the pellet-shaped plastic material, the cylinder device 12 that pushes the plastic material in the hopper 11 forward, the passage 13 of the plastic material supplied from the cylinder device 12, and the passage 13. The molding machine 14 is configured to receive a plastic material and mold a molded product.
A flexible hose is connected to the hopper 11 from a tank device (not shown) so that a plastic material is supplied. When the plastic material of the hopper 11 decreases, new plastic material is sequentially supplied from the tank device to the hopper 11 based on detection of a sensor (not shown) in the hopper 11. The cylinder device 12 is configured such that an internal screw 16 is rotated by driving an attached motor 15 to push the plastic material in the hopper 11 forward and drop it into the passage 13.

The passage 13 is constituted by a cylindrical body having a rectangular cross section. As shown in FIGS. 2 and 3, the oscillator 18 and the receiver 19 are equidistant from the wall surfaces 13a and 13b at the front and rear positions facing the two parallel wall surfaces 13a and 13b of the passage 13, respectively. It is arranged. Between the oscillator 18 and the first wall surface 13a and between the second wall surface 13b and the receiver 19, first and second lenses 22 and 23 are arranged at equal distances from the respective wall surfaces 13a and 13b. Has been. With such a configuration, the terahertz wave oscillated from the oscillator 18 is irradiated onto the plastic in the passage 13 and absorbed by the plastic, and the remaining terahertz wave transmitted without being absorbed by the plastic is received by the receiver 19. Can be received and measured.
The oscillator 18 includes an oscillation circuit, an amplifier circuit, a control unit, and the like (not shown), and irradiates a terahertz wave having a predetermined frequency from the directional horn antenna 21 toward the passage 13. The first lens 22 corrects the terahertz wave radiated from the horn antenna 21 in a parallel emission direction. By correcting in the parallel injection direction, the arrival distance of the terahertz wave to the plastic material can be averaged, and a more accurate measurement value can be obtained. The terahertz wave that has passed through the first lens 22 is orthogonal to the wall surfaces 13 a and 13 b of the passage 13. The receiver 19 includes a receiver circuit, an amplifier circuit, a control unit, and the like (not shown), and receives radio waves from a directional horn antenna 24. The second lens 23 converges the remaining terahertz wave transmitted without being absorbed among the terahertz waves irradiated to the plastic in the passage 13 from the parallel emission direction toward the horn antenna 24 of the receiver 19. To refract.

Next, the electrical configuration of the control system having the oscillator 18 and the receiver 19 configured as described above as main components will be described with reference to FIG.
The control system includes a controller MC that is a control device. The controller MC includes a known central processing unit (CPU), a memory such as a ROM and a RAM, a timer, and the like. The controller MC is connected to the oscillator 18, the receiver 19, an input operation unit 30 and a monitor 31, each of which includes a keyboard and a mouse. The ROM stores a residual terahertz wave (a terahertz wave transmitted through plastic) based on a control program for controlling the oscillator 18 and the receiver 19 and a numerical value corresponding to the terahertz wave intensity obtained from the oscillator 18 and the receiver 19. ) And a calculation program for calculating the flow rate of the corresponding plastic, a display program for displaying the calculation result on the monitor 31, and various programs such as an OS (Operation System) are stored. The RAM stores correlation data between the remaining terahertz wave and the flow rate of the plastic to be applied to the calculation program.

  The controller MC inputs the correlation data, specifically, A in the linear expression of Y = A−BX (no material passing) in the coordinates where the Y-axis direction is the transmitted terahertz wave intensity and the X-axis direction is the plastic passage amount. The correlation is set based on the correlation data between the transmitted terahertz wave intensity of the state) and B (input of a specific coefficient for each plastic). This is obtained as a correlation as shown in Table 2, for example. Table 2 shows the amount of plastic actually flowing down the passage 13 based on the oscillator 18 and the receiver 19 set in the supply system and the remaining terahertz wave as sampling data. The value is calculated. That is, the correlation is obtained based on the data acquired for the actual machine. In Table 2, the wavelength used for the terahertz wave is 60 GHz, the distance from the horn antenna 21 of the oscillator 18 to the front surface of the plastic material is 123 mm, the distance from the back surface of the plastic material to the horn antenna 24 of the receiver 19 is 123 mm, and no material passes through. The transmitted terahertz wave intensity (that is, the value of A) in the state was 1131, and the specific coefficient (that is, the value of B) for each plastic was 7.7.

  The controller MC acquires sampling data of transmitted electromagnetic wave intensity at a predetermined timing (every second in the present embodiment) over time based on the calculation program, and compares the correlation to calculate the corresponding plastic passage amount. At the same time, the amount of plastic passing from the reference time when measurement was started is integrated. Complementary calculation is performed between sampling data. Table 3 is a graph showing the characteristics of the transmitted electromagnetic wave intensity and the time obtained by acquiring the transmission electromagnetic wave intensity sampling data and performing the complementary calculation. Table 4 is a graph showing the characteristics of the plastic passage amount and time corresponding to Table 3. The controller MC displays Tables 3 and 4 on the monitor 31, and displays the integrated plastic passage amount from the reference time to the present time and the current plastic passage amount as numerical values, for example, as shown in FIG. Although Tables 3 and 4 currently display 30 seconds after the start, they are scrolled with time to always display a certain range (here, 30 seconds).

With the configuration described above, the following effects are achieved in the present embodiment.
(1) Since the accumulated plastic passage amount up to the present time displayed on the monitor 31 and the current plastic passage amount can be recognized as numerical values, the amount of plastic passing through can be understood based on the numerical values, so how much plastic is used (used) You can see in real time.
(2) Since Tables 3 and 4 are displayed, it is possible to know the history of plastic injection.
(3) Since the passage 13 is formed in a rectangular shape so as to irradiate the terahertz wave as uniformly as possible, and the terahertz wave is corrected in the parallel emission direction by the first lens 22, this is an indirect measurement. Nevertheless, it is possible to obtain an accurate value with high measurement value accuracy.

The present invention may be embodied as follows.
In the embodiment, the linear function is obtained by normalization based on the actually measured value. However, the linear function may be calculated by taking an average value unless normalization is executed.
The lenses 22 and 23 may be composed of a plurality of lens bodies.
In the embodiment, terahertz waves are used as electromagnetic waves for moisture measurement, but millimeter waves can also be used.
-The table | surface and numerical value displayed on the monitor 31 in embodiment may be made to display with another pattern. For example, it is possible to display the amount of plastic passing in a past time.
-Although this invention was applied to the supply system of a plastic material, it is also possible to apply to other systems.
In addition, the present invention may be implemented in a modified form without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 13 ... Passage | path, 18 ... Oscillator for irradiating electromagnetic waves, 19 ... Receiver, MC ... Controller.

Claims (9)

  A granular, powdery, or liquid plastic is irradiated with an electromagnetic wave in a band of 50 GHz to 1000 GHz, and the residual electromagnetic wave that is not absorbed by the plastic is obtained in advance in correlation with the change in the plastic amount. The plastic is characterized in that the flow rate of the plastic is calculated based on the correlation by irradiating the plastic with the electromagnetic wave under a condition for obtaining the correlation and measuring the remaining electromagnetic wave. Flow rate measurement method.   The method for measuring a flow rate of plastic according to claim 1, wherein the plastic passes through a predetermined passage and the remaining electromagnetic wave is measured at the passage position.   The plastic flow rate measuring method according to claim 2, wherein a plastic processing device for processing the plastic supplied from the passage is disposed downstream of the passage.   The plastic flow rate according to any one of claims 1 to 3, wherein the electromagnetic wave oscillated from an oscillating device is measured by being received by a receiving device disposed behind the plastic through the plastic. Measuring method.   The passage has a square cross section, the oscillating device oscillates so that the electromagnetic wave is orthogonal to a certain surface of the passage, and the receiving device is located at a position facing the surface facing the certain one surface. The method for measuring a plastic flow rate according to claim 4, wherein:   6. The plastic according to claim 5, wherein an optical system for correcting the diffusing electromagnetic waves oscillated from the oscillation device in a parallel emission direction is disposed between the passage and the oscillation device. Flow rate measurement method.   7. The plastic flow rate measuring method according to claim 6, wherein an optical system for refracting the parallel electromagnetic waves in a convergence direction is disposed between the passage and the receiving device.   The method for measuring the flow rate of plastic according to any one of claims 1 to 3, wherein a pre-electromagnetic wave oscillated from an oscillating device is reflected in the plastic and the reflected wave is received by a receiving device. .   The method for measuring a flow rate of plastic according to any one of claims 1 to 3, wherein the electromagnetic wave oscillated from an oscillation device is scattered in the plastic, and the scattered wave is received by a receiving device. .

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