JPH11304863A - Measuring method and device for static field of powder and grain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly measure a static field formed by powder and grain at a side wall part at real time without disturbing an electric field in a container or pipings, or electrifying a detection electrode of a sensor, and moreover provides a highly accurate electric field measurement value. SOLUTION: A static field sensor A is faced with a detetion port C2' of a grounding metal flat plate C as a dummy wall of a container or pipings, a simulated electrified object C2, comprising a metal flat plate on which a DC high voltage is applied, is made to with the static field sensor A in parallel, an amplification rate of an amplifier 51 of an electric field measuring device B is adjusted in the condition, where an equal electric field is formed between the metal flat plates for calibration, and the static field sensor is faced with a detection port in a wall of the container, thereby the static field formed by powder and grain is actually measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring an electrostatic field formed by particles flowing or accumulating in a container or a pipe, and relates to various kinds of powder processing systems (drying, drying, etc.).
Granulation, sizing, kneading, pneumatic transportation, etc.).

[0002]

2. Description of the Related Art Japanese Patent Publication No. 7-1291 discloses a method for detecting the charged potential of a granular material flowing in a fluidized bed (in a container). According to this method, a potential sensor is attached to an outer surface of a container through which a powder or a granular material flows with a gas, and a detection unit of the potential sensor is opposed to a detection port (a window) provided in the container. Air is injected into the plate-shaped gap between the two to form a vertical air curtain, which measures the potential of the granular material while preventing the granular material from contacting the detection part of the potential sensor. It is.

Japanese Patent Application Laid-Open No. 5-126883 discloses a technique for correcting a measurement error of a measuring instrument when sampling a conductive powder such as a developer used in a copying machine or the like and measuring its charged charge. A calibration method is disclosed. In this method, a predetermined voltage is applied while the conductive powder is dropped from the funnel, the charge amount of the powder at that time is measured by a suction type Faraday gauge, and the measured value is compared with a reference Faraday gauge. Then, the error is calibrated in advance for each charge measuring device.

[0004]

The above-mentioned prior art is intended to measure the potential of a flowing charged particulate material (floating charged particulate cloud), but has the following problems. there were. Since the potential of the floating charged particle cloud floating in the container has a maximum value at the center of the container and is close to zero volts at the side wall, the method of measuring the potential by installing a potential sensor on the side wall portion is as follows. The intended potential measurement value cannot be obtained. Since the air curtain is a laminar flow of air flowing along the back surface of the detection port of the container, there is also a case where the particles are introduced from the container into the detection unit of the potential sensor in reverse, and the particles are generated in the potential sensor. There is a problem that it is impossible to guarantee the original detection accuracy of the sensor. In order to obtain the highest potential from the floating charged particle cloud, the potential sensor is disposed inside the container instead of outside the side wall of the container. The potential detection electrode itself is charged due to collision with the potential detection electrode and the potential detection electrode itself is charged, causing a measurement error, or an ignitable discharge may occur between the potential detection electrode and the floating charged particle cloud. There is.

In the latter conventional technique, the amount of electric charge is measured by sampling a conductive powder and placing it in a Faraday gauge, and it is not possible to measure the powder material currently flowing in a container in real time. Also, the calibration method is very troublesome because it is performed using the sampled conductive powder.

When measuring the static electricity of a floating charged particle cloud, it is desirable to measure the amount of charge (charge density) of the granular material. However, the charge density must be specified in the area or volume of the measurement range. Must. However, it is impossible to specify the area or volume of the measurement range for the powder particles that are actually flowing in the container or the pipe.

However, the electric charge density and the electric field are closely related to each other, and the electric field is generated by the electric charge. Therefore, even if the electric charge of the floating charged particle cloud is detected as the electric field, the electric charge density is not limited to the electric charge density itself. Will be obtained. Further, in the case of a powder flowing in a container or a pipe, the electric field is maximized at a side wall portion of the container or the pipe.

[0008] The present invention, from such a viewpoint, the electrostatic field formed by the powder or particles flowing or accumulating in the vessel or pipe,
The electrostatic field of the granular material can be accurately measured in real time on the side wall without disturbing the electric field in the container or piping or the detection electrode of the sensor is charged, and the highly accurate electric field measurement value is obtained. A measurement method and apparatus have been proposed.

[0009]

According to a first aspect of the present invention, there is provided a method for measuring an electrostatic field formed by a granular material by a static electric field sensor through a detection port provided in a wall of a container or the like. A static electric field sensor faces a detection port of a grounded metal plate simulated on a wall of a container or the like, and a simulated charged object in which a high DC voltage is applied to the metal plate is opposed to the electrostatic field sensor in parallel, After calibrating the detection value of the electrostatic field sensor in a state where an equal electric field is formed between these metal flat plates, the electrostatic field sensor is made to face the detection port of the wall of the container or the like, and the electrostatic field formed by the granular material is measured. . That is, after the electrostatic field sensor is calibrated in advance by simulated measurement, the electrostatic field sensor is actually installed on a wall of a container or the like to perform actual measurement.

The method according to the second aspect of the present invention enables calibration at any time even after the electrostatic field sensor is installed on the wall of a container or the like. The method comprises a DC high voltage generating circuit and a metal plate, Using a calibration checker that applies a DC high voltage to a metal plate by a high-voltage generating circuit to make a simulated charged object, the metal plate is opposed to the electrostatic field sensor, and the detection value of the electrostatic field sensor is calibrated. The electrostatic field formed by the granules is measured.

Further, in the electrostatic field measuring apparatus according to the present invention, an electrostatic field sensor is installed at a detection port provided on a wall of a container or the like,
A static electric field sensor detects an electrostatic field formed by a granular material inside a container or the like and measures its value.It incorporates a DC high-voltage generation circuit and a metal plate, and uses a DC high-voltage generation circuit. A calibration checker is provided which applies a high DC voltage to the metal plate and uses the metal plate as a simulated charged object for the electrostatic field sensor.

In order to air-purge the electrostatic field sensor and prevent the particles from entering the inside, a sensor case having a built-in detection electrode and an electric field detection circuit was housed in the air-purge case as the electrostatic field sensor. Using a sensor, by supplying gas such as air into the air purge case, and ejecting the gas from the air purge hole at the tip of the air purge case, the static electric field formed by the granular material,
The measurement is preferably performed through the air purge hole and the detection hole of the sensor case.

The structure of the electrostatic field sensor is such that a sensor case is housed in a sensor housing tube, and is housed together with the sensor housing tube in an air purge case. It is preferable that an air passage for guiding gas to the air purge hole is formed between the sensor case and the sensor housing pipe.

[0014]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

First, an example of an electrostatic field sensor used in the present invention will be described. The electrostatic field sensor A shown in FIG. 1 has a cylindrical air purge case 1 connected to and held at the tip of a flex pipe 2 by a connection nut 3 and bends the flex pipe 2 so that the air purge case 1 can be arbitrarily formed. It can be directed in any direction.

As shown in FIG. 2, the air purge case 1 has a rear cylinder 4, a front cylinder 5 having a smaller diameter and fitted and fixed in the distal end thereof, and fitted and fixed in the distal end of the front cylinder 5. The air purge case main body 7 is formed by a front end cap 6 having a front end opening closed and a sensor 8 housed and held in the air purge case main body 7. The rear cylinder 4, the front cylinder 5, and the tip cap 6 are all made of metal. The tip cap 6 is provided with a circular recess 9 on the inner surface thereof, and a circular air purge hole 10 opening from the center of the recess 9 to the outer surface. Front cylinder 5 has middle cylinder 11
Is provided. The middle cylinder 11 is integrated with the front cylinder 5 by a flange 12. A gap 13 is formed between the front surface of the flange 12 and the inner surface of the tip cap 6.

The sensor 8 is a vibrating capacitance type or a chopper type in which a detection electrode and an electric field detection circuit are built in a square cylindrical (or cylindrical) metal sensor case 14. The capacitance between the electrodes is periodically changed by a mechanical means such as a piezoelectric tuning fork or the like to induce periodically changing charges on the detection electrodes. And outputs the signal.

The sensor case 14 penetrates through the middle cylinder 11 and is fixed to the middle cylinder 11 by a stopper 15. Packings 16 are provided at the front and rear ends of the middle cylinder 11 to close the gap with the sensor case 14 in front and rear. The distal end of the sensor case 14 protrudes into the concave portion 9 of the distal end cap 6 to form a gap 17 with the inner surface of the concave portion 9. The gap 17 has a rear end connected to the gap 13, and is opened outside the tip cap 6 by the air purge hole 10. At the tip of the sensor case 14, a tip cap 6
Detection hole 18 smaller than the air purge hole 10 (FIG. 3)
Is provided. This detection hole 18 is the air purge hole 1
The electric field is detected by the sensor 8 through the detection hole 18 and the air purge hole 10.

A common hose 1 is provided at the rear end of the sensor case 14.
9 is connected. This common hose 19 is connected to a cable 21 and an air hose 22 by a branch joint 20 outside the flex pipe 2 as shown in FIG. 1, and is used to connect a detection circuit in the sensor case 14 to an external electric device. The wiring also serves as a pipe for supplying air into the sensor case 14.

As shown in FIG. 2, a through-hole 23 is provided in the flange 12 of the middle cylinder 11, and an air supply pipe 24 is connected to the through-hole 23 by screwing the distal end thereof. An air hose 28 is connected to the air supply pipe 24 via a socket 25, a joint 26, a flexible tube 27, and the like in the flex pipe 2.
As shown in FIG. 1, the air hose 28 is connected to the common air hose 30 together with the air hose 22 by a branch joint 29 outside the flex pipe 2, and the sensor case 14 is connected through the air hose 22.
At the same time, air is supplied to the air hose 28 and the gaps 13 and 17. Note that FIG.
In the example, only one air supply pipe 24 is shown, but the number may be one or more.

Therefore, air is ejected from the air purge hole 10 through the gaps 13 and 17 around the tip of the sensor case 14, and at the same time, air supplied into the sensor case 14 is ejected from the detection hole 18. You. In this case, since the ejection pressure from the detection hole 18 is higher than the ejection pressure from the air purge hole 10, the air entering the gap 17 does not flow back to the detection hole 18. Since air is blown out from the air purge hole 10 at the tip of the air purge case main body 7, it is possible to prevent powders and dust from flowing into the air purge case main body 7 (air purging).
At the same time, air is also blown out from the detection hole 18 at the tip of the sensor case 14, so that the inflow of powders and dust into the detection hole 18 can be prevented twice (double air purge). The air that has entered the gap 13 from the air supply pipe 24 is removed from the gap 1 around the tip of the sensor case 14.
Since the gas is ejected from the air purge hole 10 after passing through the sensor 7, it is possible to prevent the powder or the like from adhering to the outer surface of the tip of the sensor case 14.

In particular, in the example shown in the figure, the metal tip cap 6 is provided with a recess 9 and the tip of the sensor case 14 is inserted into the recess 9 to form a gap 17, so that the sensor 8 is protected. Therefore, even if the detection hole 18 is housed in the air purge case main body 7, the detection performance of the sensor 8 can be ensured by bringing the detection hole 18 as close to the air purge hole 10 as possible.

When the electrostatic field sensor A as described above is actually used, as shown in FIG. 4, for example, a detection port provided on a side wall C1 of a fluid dryer C for drying while fluidizing a granular material. And a fluid dryer C
The electric field measuring device B is connected to the electrostatic field sensor A outside the device, and the static electric field of the side wall portion in the fluidized-bed dryer C is measured. Pre-calibrate the measurements as follows:

As shown in FIG. 5, the side wall C of the fluidized dryer C
1. A ground metal flat plate C1 'simulating 1 is prepared, the air purge case 1 of the electrostatic field sensor A is detachably attached to the detection port C2', and the metal flat plate C2 is opposed to the ground metal flat plate C1 'in parallel. A high DC voltage is applied to the metal flat plate C2 to form a simulated charged object, and an equal electric field is formed between the ground metal flat plate C1 ′ and the metal flat plate C2. The ground metal plate C1 'is electrically grounded.

Then, in the electric field measuring apparatus B, the gain of the amplifier 51 is adjusted by turning the sensitivity adjustment knob 50 of the electric field display section 49. This amplifier 51 includes an electrostatic field sensor A
Is amplified and displayed on the display unit 52, so that the value displayed on the display unit 52 is adjusted so as to correspond to the value of the electric field by the metal flat plate C2, which is the simulated charged object. B can be calibrated.

After calibration in this manner, the electrostatic field sensor A
Is attached to a detection port provided on the side wall C1 of the fluidized dryer C and measured. In this case, if the air purge hole 10 is directed toward the inside of the fluidized-bed dryer C and actual measurement is performed while air purging is performed as described above, the electric field generated by the granular material in the fluidized-bed dryer C, particularly the side wall, The electric field at the site can be accurately measured in real time. The external output terminal 5 is used to process the measured data with a personal computer or the like.
3 can be externally output.

The electric field measuring device B has a common air hose 3
A control mechanism of an air supply system for supplying air through the above-described manner is also provided.

Further, if the portable calibration checker D shown in FIGS. 6, 7 and 8 is used, the electric field measuring apparatus B can be calibrated at any time. Next, the structure of the calibration checker D will be described. I do.

The calibration checker D comprises a circuit board 32, a printed board 33, and a DC high voltage generating circuit E as shown in FIG. 8 mounted in a cylindrical main body case 31 as shown in FIGS. A power supply battery 34 is built in and the main body case 31
A power switch 36 and a battery cover 37 are provided on a rear cover 35 that closes the rear end of the battery. The printed board 33 is fixed to the front end of the circuit board 32 so as to be perpendicular to the axis of the main body case 31. A copper foil 38, which is a metal flat plate, is attached to the front surface of the printed circuit board 33, and a stopper 39 is fixed slightly inside the front end opening of the main body case 31 in parallel with the printed circuit board 33.

The DC high voltage generating circuit E shown in FIG. 8 boosts the DC voltage of the power supply battery 34 (for example, 1.5 V is applied to +
5V) booster circuit (DC / DC converter) 40
A constant voltage circuit 42 for setting the boosted voltage to a constant voltage within a predetermined range (for example, 1.5 V to 4 V) by a variable resistor 41; an oscillation driving circuit 43 oscillating by the constant voltage; A high frequency transformer 44 for boosting the high frequency voltage of the drive circuit 43; and a voltage doubler rectifier circuit 45 for rectifying and amplifying the secondary voltage of the high frequency transformer 44 to DC.
And a polarity changeover switch 47 for switching between the positive and negative polarities of the DC high voltage applied to the copper foil 38 from the voltage doubler rectifier circuit 45 via the resistor 46, and an operation confirmation lamp 48.

When calibration is performed using such a calibration checker D, the main body case 31 of the calibration checker D is mounted on the outer periphery of the tip of the air purge case 1 of the electrostatic field sensor A, as shown by a chain line in FIG. Are detachably fitted. At this time, when the distal end surface of the air purge case 1 is fitted to a position where it comes into contact with the stopper 39 in the main body case 31, the sensor 8 faces the copper foil 38 while maintaining a constant interval.

When the power switch 36 of the calibration checker D is turned on in this state, a constant DC high voltage having the polarity set by the polarity changeover switch 47 is applied to the copper foil 38. Is a simulated charged object charged to a constant high voltage. Therefore, the electric field measuring device B shown in FIG.
Then, the sensitivity adjustment knob 50 of the electric field display unit 49 is turned to adjust the amplification factor of the amplifier 51. This amplifier 51
Amplifies the output from the electrostatic field sensor A and displays it on the display unit 52, so that the value displayed on the display unit 52 is
The electric field measurement device B can be calibrated by adjusting the electric field measurement device B so as to correspond to the electric field value according to FIG.

After the calibration as described above, the calibration checker D
Is removed from the electrostatic field sensor A, the electrostatic field sensor A is attached to the detection port of the side wall C1 of the fluidized-bed dryer C, and the measurement is performed in the same manner as described above.

FIG. 9 shows another specific example of the electrostatic field sensor.
In the air purge case 1 of the electrostatic field sensor A ′, the tip cap 6, the inner cylinder 70 and the outer cylinder 71 constitute an air purge case main body 7. Further, the sensor case 14 is
The sensor housing tube 7 is housed in the sensor housing tube 72 with the front end 72a closed via the front and rear sensor holding tubes 73 and 74.
2 are housed in the air purge case 1, and a gap 17 is formed between the sensor housing pipe 72 and the concave portion 9 of the tip cap 6. A plurality of air passages (lateral holes) 75 communicating with the gaps 17 are provided in the inner cylinder 70, and the air supply pipe 24 is connected to the rear end of each air passage 75.

The front and rear sensor holding cylinders 7 are provided between the outer peripheral surface of the sensor case 14 and the inner peripheral surface of the sensor housing tube 72.
A gap 76 is formed between 3 and 74. The air gap 76 communicates with an air passage 76 formed between the sensor case 14 and the front sensor holding cylinder 73, and the air passage 76 is formed between the outer surface of the distal end of the sensor case 14 and the distal end of the sensor storage tube 72. It communicates with a slight gap between the inner surface of 72a. Air is supplied to the gap 76 from another air supply pipe (not shown) provided on the outer periphery of the sensor storage pipe 72 through a hole 77 provided in the sensor storage pipe 72. In addition, a communication hole 72b that matches the detection hole 18 (FIG. 3) of the sensor case 14 is provided in the distal end portion 72a of the sensor storage tube 72.

Accordingly, in the air purge case 1, air is ejected from the air purge hole 10 through the space 17 around the distal end of the sensor storage tube 72,
Even within the sensor housing tube 72, the tip 7 of the sensor case 14
Since air is blown out from the communication hole 72b and the air purge hole 10 passing around the periphery of 2a, double air purging can be performed.

[0037]

As described above, the present invention forms a uniform electric field using a simulated charged object to which a high DC voltage is applied,
After calibrating the detection value of the electrostatic field sensor, the electrostatic field sensor is made to face the detection port of the wall of the container or the like, and the electrostatic field formed by the powder is measured. In addition, the electric field in the container or the pipe can be measured without being disturbed or the detection electrode of the sensor being charged.

According to the second and fifth aspects of the present invention, calibration can be easily performed using a dedicated calibration checker.

According to the third, fourth, sixth, and seventh aspects of the present invention, it is possible to accurately prevent powders and the like from flowing into the sensor case from the detection holes of the electrostatic field sensor, thereby enabling accurate detection. In addition, it is possible to prevent powder and particulate matter and dust from adhering to the outer surface of the distal end of the sensor case. In particular, according to the fourth and seventh aspects of the present invention, double air purging can be performed, so that the adhesion of powders and dust can be more reliably prevented, and the detection accuracy can be further improved.

[Brief description of the drawings]

FIG. 1 is an external side view of an example of an electrostatic field sensor used in the method of the present invention.

FIG. 2 is a sectional view of the electrostatic field sensor.

FIG. 3 is a front view of an air purge case of the electrostatic field sensor.

FIG. 4 is a schematic diagram of one embodiment of the method of the present invention.

FIG. 5 is a diagram showing a state in which an electric field measuring device is connected to an electrostatic field sensor and the electric field measuring device is calibrated using a metal flat plate as a simulated charged object.

FIG. 6 is a sectional view of an example of a calibration checker used in the method of the present invention.

FIG. 7 is a rear view of the above.

FIG. 8 is an electric circuit diagram of a DC high-voltage generating circuit incorporated in the calibration checker.

FIG. 9 is a cross-sectional view of another specific example of the electrostatic field sensor.

[Explanation of symbols]

 A ・ A ′ Electrostatic field sensor B Electric field measurement device 1 Air purge case 8 Sensor 10 Air purge hole 14 Sensor case 18 Detection hole B Electric field measurement device C Fluid dryer C1 Side wall C1 ′ Ground metal plate C2 ′ Detection port C2 Metal plate ( (Simulated charged object) D Calibration checker E DC high voltage generation circuit 38 Copper foil (simulated charged object) 72 Sensor storage tube 72b Communication hole 75/76 Air passage

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[Procedure amendment]

[Submission date] March 24, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Patent application title: Method and apparatus for measuring electrostatic field of granular material

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring an electrostatic field formed by particles flowing or accumulating in a container or a pipe, and relates to various kinds of powder processing systems (drying, drying, etc.).
Granulation, sizing, kneading, pneumatic transportation, etc.).

[0002]

2. Description of the Related Art Japanese Patent Publication No. 7-1291 discloses a method for detecting the charged potential of a granular material flowing in a fluidized bed (in a container). According to this method, a potential sensor is attached to an outer surface of a container through which a powder or a granular material flows with a gas, and a detection unit of the potential sensor is opposed to a detection port (a window) provided in the container. Air is injected into the plate-shaped gap between the two to form a vertical air curtain, which measures the potential of the granular material while preventing the granular material from contacting the detection part of the potential sensor. It is.

Further, Japanese Patent Application Laid-Open No. 5-126883 discloses a technique for correcting a measurement error of a measuring instrument when sampling a conductive powder such as a developer used in a copying machine and measuring the charged charge. A calibration method is disclosed. In this method, a predetermined voltage is applied while the conductive powder is dropped from the funnel, the amount of charge of the granular material at that time is measured with a suction type Faraday gauge, and the measured value is compared with a reference Faraday gauge. Then, the error is calibrated in advance for each charge measuring device.

[0004]

The above-mentioned prior art is intended to measure the potential of a flowing charged particulate material (floating charged particulate cloud), but has the following problems. there were. Since the potential of the floating charged particle cloud floating in the container has a maximum value at the center of the container and is close to zero volts at the side wall, the method of measuring the potential by installing a potential sensor on the side wall portion is as follows. The intended potential measurement value cannot be obtained. Since the air curtain is a laminar flow of air flowing along the back surface of the detection port of the container, there is also a case where the particles are introduced from the container into the detection unit of the potential sensor in reverse, and the particles are generated in the potential sensor. There is a problem that it is impossible to guarantee the original detection accuracy of the sensor. In order to obtain the highest potential from the floating charged particle cloud, the potential sensor is disposed inside the container instead of outside the side wall of the container. The potential detection electrode itself is charged due to collision with the potential detection electrode and the potential detection electrode itself is charged, causing a measurement error, or an ignitable discharge may occur between the potential detection electrode and the floating charged particle cloud. There is.

In the latter conventional technique, the amount of electric charge is measured by sampling a conductive powder and placing it in a Faraday gauge, and it is not possible to measure the powder material currently flowing in a container in real time. Also, the calibration method is very troublesome because it is performed using the sampled conductive powder.

When measuring the static electricity of a floating charged particle cloud, it is desirable to measure the amount of charge (charge density) of the granular material. However, the charge density must be specified in the area or volume of the measurement range. Must. However, it is impossible to specify the area or volume of the measurement range for the powder particles that are actually flowing in the container or the pipe.

However, the electric charge density and the electric field are closely related to each other, and the electric field is generated by the electric charge. Therefore, even if the electric charge of the floating charged particle cloud is detected as the electric field, the electric charge density is not limited to the electric charge density itself. Will be obtained. Further, in the case of a powder flowing in a container or a pipe, the electric field is maximized at a side wall portion of the container or the pipe.

[0008] The present invention, from such a viewpoint, the electrostatic field formed by the powder or particles flowing or accumulating in the vessel or pipe,
The electrostatic field of the granular material can be accurately measured in real time on the side wall without disturbing the electric field in the container or piping or the detection electrode of the sensor is charged, and the highly accurate electric field measurement value is obtained. A measurement method and apparatus have been proposed.

[0009]

According to a first aspect of the present invention, there is provided a method for measuring an electrostatic field formed by a granular material by an electrostatic field sensor through a detection port provided in a wall of a container. With the electrostatic field sensor facing the detection port of the grounded metal plate simulating the wall of the container,
A simulated charged object with a high DC voltage applied to a metal plate is opposed in parallel, and after the detection value of the electrostatic field sensor is calibrated with an equal electric field formed between these metal plates, the electrostatic field sensor is used to detect the wall of the container. Measure the static electric field formed by the granules while facing the mouth. That is, after the calibration of the electrostatic field sensor is performed in advance by the simulated measurement, the electrostatic field sensor is actually installed on the wall of the container and the actual measurement is performed.

The method according to the second aspect of the present invention enables calibration at any time even after the electrostatic field sensor is installed on the wall of the container. The method incorporates a detection electrode and an electric field detection circuit as the electrostatic field sensor. A sensor in which a sensor case is housed in an air purge case is used, and a checker having a DC high voltage generation circuit and a metal plate built in a main body case is used as a calibration checker for the electrostatic field sensor. Then, the main body case of the calibration checker is detachably attached to the tip of the air purge case of the electrostatic field sensor, and a DC high voltage is applied to a metal plate by a DC high voltage generation circuit, and the metal plate is used as a simulated charged object. After calibrating the detection value of the electrostatic field sensor, the calibration checker is removed from the electrostatic field sensor, gas is supplied into the air purge case of the electrostatic field sensor, and gas is ejected from the air purge hole at the tip of the air purge case. While doing so, the electrostatic field formed by the granular material is measured through the air purge hole and the detection hole of the sensor case.

Further, in the electrostatic field measuring apparatus according to the present invention, an electrostatic field sensor is installed at a detection port provided in a wall of the container, and an electrostatic field formed by the powder and granules inside the container is detected by the electrostatic field sensor. A DC high voltage generating circuit and a metal plate are built in a main body case, and this main body case is detachably attached to the tip of an air purge case of the electrostatic field sensor, and a DC high voltage A calibration checker is provided which can apply a DC high voltage to the metal plate by a voltage generating circuit to make the metal plate a simulated charged object.

In order to air-purge the electrostatic field sensor and prevent the particles from entering the inside, a sensor case having a built-in detection electrode and an electric field detection circuit was housed in the air-purge case as the electrostatic field sensor. Using a sensor, a gas is supplied into the air purge case, and the gas is ejected from the air purge hole at the tip of the air purge case. Measure through the detection hole.

The structure of the electrostatic field sensor is such that a sensor case is housed in a sensor housing tube, and is housed together with the sensor housing tube in an air purge case. It is preferable that an air passage for guiding gas to the air purge hole is formed between the sensor case and the sensor housing pipe.

[0014]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

First, an example of an electrostatic field sensor used in the present invention will be described. The electrostatic field sensor A shown in FIG. 1 has a cylindrical air purge case 1 connected to and held at the tip of a flex pipe 2 by a connection nut 3 and bends the flex pipe 2 so that the air purge case 1 can be arbitrarily formed. It can be directed in any direction.

As shown in FIG. 2, the air purge case 1 has a rear cylinder 4, a front cylinder 5 having a smaller diameter and fitted and fixed in the distal end thereof, and fitted and fixed in the distal end of the front cylinder 5. The air purge case main body 7 is formed by a front end cap 6 having a front end opening closed and a sensor 8 housed and held in the air purge case main body 7. The rear cylinder 4, the front cylinder 5, and the tip cap 6 are all made of metal. The tip cap 6 is provided with a circular recess 9 on the inner surface thereof, and a circular air purge hole 10 opening from the center of the recess 9 to the outer surface. Front cylinder 5 has middle cylinder 11
Is provided. The middle cylinder 11 is integrated with the front cylinder 5 by a flange 12. A gap 13 is formed between the front surface of the flange 12 and the inner surface of the tip cap 6.

The sensor 8 is a vibrating capacitance type or a chopper type in which a detection electrode and an electric field detection circuit are built in a square cylindrical (or cylindrical) metal sensor case 14. The capacitance between the electrodes is periodically changed by a mechanical means such as a piezoelectric tuning fork or the like to induce periodically changing charges on the detection electrodes. And outputs the signal.

The sensor case 14 penetrates through the middle cylinder 11 and is fixed to the middle cylinder 11 by a stopper 15. Packings 16 are provided at the front and rear ends of the middle cylinder 11 to close the gap with the sensor case 14 in front and rear. The distal end of the sensor case 14 protrudes into the concave portion 9 of the distal end cap 6 to form a gap 17 with the inner surface of the concave portion 9. The gap 17 has a rear end connected to the gap 13, and is opened outside the tip cap 6 by the air purge hole 10. At the tip of the sensor case 14, a tip cap 6
Detection hole 18 smaller than the air purge hole 10 (FIG. 3)
Is provided. This detection hole 18 is the air purge hole 1
The electric field is detected by the sensor 8 through the detection hole 18 and the air purge hole 10.

A common hose 1 is provided at the rear end of the sensor case 14.
9 is connected. This common hose 19 is connected to a cable 21 and an air hose 22 by a branch joint 20 outside the flex pipe 2 as shown in FIG. 1, and is used to connect a detection circuit in the sensor case 14 to an external electric device. The wiring also serves as a pipe for supplying air into the sensor case 14.

As shown in FIG. 2, a through-hole 23 is provided in the flange 12 of the middle cylinder 11, and an air supply pipe 24 is connected to the through-hole 23 by screwing the distal end thereof. An air hose 28 is connected to the air supply pipe 24 via a socket 25, a joint 26, a flexible tube 27, and the like in the flex pipe 2.
As shown in FIG. 1, the air hose 28 is connected to the common air hose 30 together with the air hose 22 by a branch joint 29 outside the flex pipe 2, and the sensor case 14 is connected through the air hose 22.
At the same time, air is supplied to the air hose 28 and the gaps 13 and 17. Note that FIG.
In the example, only one air supply pipe 24 is shown, but the number may be one or more.

Therefore, air is ejected from the air purge hole 10 through the gaps 13 and 17 around the tip of the sensor case 14, and at the same time, air supplied into the sensor case 14 is ejected from the detection hole 18. You. In this case, since the ejection pressure from the detection hole 18 is higher than the ejection pressure from the air purge hole 10, the air entering the gap 17 does not flow back to the detection hole 18. Since air is blown out from the air purge hole 10 at the tip of the air purge case main body 7, it is possible to prevent powders and dust from flowing into the air purge case main body 7 (air purging).
At the same time, air is also blown out from the detection hole 18 at the tip of the sensor case 14, so that the inflow of powders and dust into the detection hole 18 can be prevented twice (double air purge). The air that has entered the gap 13 from the air supply pipe 24 is removed from the gap 1 around the tip of the sensor case 14.
Since the gas is ejected from the air purge hole 10 after passing through the sensor 7, it is possible to prevent the powder or the like from adhering to the outer surface of the tip of the sensor case 14.

In particular, in the example shown in the figure, the metal tip cap 6 is provided with a recess 9 and the tip of the sensor case 14 is inserted into the recess 9 to form a gap 17, so that the sensor 8 is protected. Therefore, even if the detection hole 18 is housed in the air purge case main body 7, the detection performance of the sensor 8 can be ensured by bringing the detection hole 18 as close to the air purge hole 10 as possible.

When the electrostatic field sensor A as described above is actually used, as shown in FIG. 4, for example, a detection port provided on a side wall C1 of a fluid dryer C for drying while fluidizing a granular material. And a fluid dryer C
The electric field measuring device B is connected to the electrostatic field sensor A outside the device, and the static electric field of the side wall portion in the fluidized-bed dryer C is measured. Pre-calibrate the measurements as follows:

As shown in FIG. 5, the side wall C of the fluidized dryer C
1. A ground metal flat plate C1 'simulating 1 is prepared, the air purge case 1 of the electrostatic field sensor A is detachably attached to the detection port C2', and the metal flat plate C2 is opposed to the ground metal flat plate C1 'in parallel. A high DC voltage is applied to the metal flat plate C2 to form a simulated charged object, and an equal electric field is formed between the ground metal flat plate C1 ′ and the metal flat plate C2. The ground metal plate C1 'is electrically grounded.

Then, in the electric field measuring apparatus B, the gain of the amplifier 51 is adjusted by turning the sensitivity adjustment knob 50 of the electric field display section 49. This amplifier 51 includes an electrostatic field sensor A
Is amplified and displayed on the display unit 52, so that the value displayed on the display unit 52 is adjusted so as to correspond to the value of the electric field by the metal flat plate C2, which is the simulated charged object. B can be calibrated.

After calibration in this manner, the electrostatic field sensor A
Is attached to a detection port provided on the side wall C1 of the fluidized dryer C and measured. In this case, if the air purge hole 10 is directed toward the inside of the fluidized-bed dryer C and actual measurement is performed while air purging is performed as described above, the electric field generated by the granular material in the fluidized-bed dryer C, particularly the side wall, The electric field at the site can be accurately measured in real time. The external output terminal 5 is used to process the measured data with a personal computer or the like.
3 can be externally output.

The electric field measuring device B has a common air hose 3
A control mechanism of an air supply system for supplying air through the above-described manner is also provided.

Further, if the portable calibration checker D shown in FIGS. 6, 7 and 8 is used, the electric field measuring apparatus B can be calibrated at any time. Next, the structure of the calibration checker D will be described. I do.

The calibration checker D comprises a circuit board 32, a printed board 33, and a DC high voltage generating circuit E as shown in FIG. 8 mounted in a cylindrical main body case 31 as shown in FIGS. A power supply battery 34 is built in and the main body case 31
A power switch 36 and a battery cover 37 are provided on a rear cover 35 that closes the rear end of the battery. The printed board 33 is fixed to the front end of the circuit board 32 so as to be perpendicular to the axis of the main body case 31. A copper foil 38, which is a metal flat plate, is attached to the front surface of the printed circuit board 33, and a stopper 39 is fixed slightly inside the front end opening of the main body case 31 in parallel with the printed circuit board 33.

The DC high voltage generating circuit E shown in FIG. 8 boosts the DC voltage of the power supply battery 34 (for example, 1.5 V is applied to +
5V) booster circuit (DC / DC converter) 40
A constant voltage circuit 42 for setting the boosted voltage to a constant voltage within a predetermined range (for example, 1.5 V to 4 V) by a variable resistor 41; an oscillation driving circuit 43 oscillating by the constant voltage; A high frequency transformer 44 for boosting the high frequency voltage of the drive circuit 43; and a voltage doubler rectifier circuit 45 for rectifying and amplifying the secondary voltage of the high frequency transformer 44 to DC.
And a polarity changeover switch 47 for switching between the positive and negative polarities of the DC high voltage applied to the copper foil 38 from the voltage doubler rectifier circuit 45 via the resistor 46, and an operation confirmation lamp 48.

When calibration is performed using such a calibration checker D, the main body case 31 of the calibration checker D is mounted on the outer periphery of the tip of the air purge case 1 of the electrostatic field sensor A, as shown by a chain line in FIG. Are detachably fitted. At this time, when the distal end surface of the air purge case 1 is fitted to a position where it comes into contact with the stopper 39 in the main body case 31, the sensor 8 faces the copper foil 38 while maintaining a constant interval.

When the power switch 36 of the calibration checker D is turned on in this state, a constant DC high voltage having the polarity set by the polarity changeover switch 47 is applied to the copper foil 38. Is a simulated charged object charged to a constant high voltage. Therefore, the electric field measuring device B shown in FIG.
Then, the sensitivity adjustment knob 50 of the electric field display unit 49 is turned to adjust the amplification factor of the amplifier 51. This amplifier 51
Amplifies the output from the electrostatic field sensor A and displays it on the display unit 52, so that the value displayed on the display unit 52 is
The electric field measurement device B can be calibrated by adjusting the electric field measurement device B so as to correspond to the electric field value according to FIG.

After the calibration as described above, the calibration checker D
Is removed from the electrostatic field sensor A, the electrostatic field sensor A is attached to the detection port of the side wall C1 of the fluidized-bed dryer C, and the measurement is performed in the same manner as described above.

FIG. 9 shows another specific example of the electrostatic field sensor.
In the air purge case 1 of the electrostatic field sensor A ′, the tip cap 6, the inner cylinder 70 and the outer cylinder 71 constitute an air purge case main body 7. Further, the sensor case 14 is
The sensor housing tube 7 is housed in the sensor housing tube 72 with the front end 72a closed via the front and rear sensor holding tubes 73 and 74.
2 are housed in the air purge case 1, and a gap 17 is formed between the sensor housing pipe 72 and the concave portion 9 of the tip cap 6. A plurality of air passages (lateral holes) 75 communicating with the gaps 17 are provided in the inner cylinder 70, and the air supply pipe 24 is connected to the rear end of each air passage 75.

The front and rear sensor holding cylinders 7 are provided between the outer peripheral surface of the sensor case 14 and the inner peripheral surface of the sensor housing tube 72.
A gap 76 is formed between 3 and 74. The air gap 76 communicates with an air passage 76 formed between the sensor case 14 and the front sensor holding cylinder 73, and the air passage 76 is formed between the outer surface of the distal end of the sensor case 14 and the distal end of the sensor storage tube 72. It communicates with a slight gap between the inner surface of 72a. Air is supplied to the gap 76 from another air supply pipe (not shown) provided on the outer periphery of the sensor storage pipe 72 through a hole 77 provided in the sensor storage pipe 72. In addition, a communication hole 72b that matches the detection hole 18 (FIG. 3) of the sensor case 14 is provided in the distal end portion 72a of the sensor storage tube 72.

Accordingly, in the air purge case 1, air is ejected from the air purge hole 10 through the space 17 around the distal end of the sensor storage tube 72,
Even within the sensor housing tube 72, the tip 7 of the sensor case 14
Since air is blown out from the communication hole 72b and the air purge hole 10 passing around the periphery of 2a, double air purging can be performed.

[0037]

As described above, the present invention forms a uniform electric field using a simulated charged object to which a high DC voltage is applied,
After calibrating the detection value of the electrostatic field sensor, the electrostatic field sensor is made to face the detection port of the wall of the container, and the actual measurement of the electrostatic field formed by the granular material is performed. Without having to disturb the electric field in the container or the pipe or charging the detection electrode of the sensor, it is possible to accurately measure in real time at the side wall portion and obtain a highly accurate electric field measurement value.

According to the second and fourth aspects of the invention, the electrostatic field sensor accommodates the sensor case in the air purge case and ejects gas from the air purge hole at the tip of the air purge case. Precisely prevent the flow into the sensor case through the detection hole of the electrostatic field sensor.
The detection can be performed with high accuracy, and the attachment of powder or particles to the outer surface of the tip of the sensor case can be prevented. Further, the calibration can be easily performed at any time by using a detachable dedicated calibration checker at the tip of the air purge case.

According to the third and fifth aspects of the present invention, since double air purging can be performed, the adhesion of powder or dust can be more reliably prevented, and the detection accuracy can be further improved.

[Brief description of the drawings]

FIG. 1 is an external side view of an example of an electrostatic field sensor used in the method of the present invention.

FIG. 2 is a sectional view of the electrostatic field sensor.

FIG. 3 is a front view of an air purge case of the electrostatic field sensor.

FIG. 4 is a schematic diagram of one embodiment of the method of the present invention.

FIG. 5 is a diagram showing a state in which an electric field measuring device is connected to an electrostatic field sensor and the electric field measuring device is calibrated using a metal flat plate as a simulated charged object.

FIG. 6 is a sectional view of an example of a calibration checker used in the method of the present invention.

FIG. 7 is a rear view of the above.

FIG. 8 is an electric circuit diagram of a DC high-voltage generating circuit incorporated in the calibration checker.

FIG. 9 is a cross-sectional view of another specific example of the electrostatic field sensor.

[Description of Signs] A · A ′ Static Electric Field Sensor B Electric Field Measuring Device 1 Air Purge Case 8 Sensor 10 Air Purge Hole 14 Sensor Case 18 Detection Hole B Electric Field Measuring Device C Fluid Dryer C1 Side Wall C1 ′ Ground Metal Plate C2 ′ Detection Port C2 Metal plate (simulated charged object) D Calibration checker E DC high voltage generating circuit 38 Copper foil (simulated charged object) 72 Sensor storage tube 72b Communication hole 75/76 Air passage

Continuing on the front page (72) Inventor Norifumi Suzuki 480-158 Nitonamachi, Chuo-ku, Chiba City, Chiba Prefecture (72) Inventor Yasuo Morikawa 5-25-17, Nobitome, Niiza City, Saitama Prefecture Higashi Nippori 2 39-10 401 (72) Inventor Yoshihiro Ito 3-10-18 Kitamachi, Nerima-ku, Tokyo Inside Fuji Powder Co., Ltd.

Claims (7)

[Claims] 1. A method for measuring an electrostatic field formed by a granular material by an electrostatic field sensor through a detection port provided in a wall of a container or the like, the method comprising: With the electrostatic field sensor facing the mouth, a simulated charged object having a high DC voltage applied to a metal plate is opposed to the electrostatic field sensor in parallel, and a static electric field is formed in a state where a uniform electric field is formed between the metal plates. After calibrating a detection value of the electric field sensor, the electrostatic field sensor is made to face a detection port of a wall of the container or the like, and an electrostatic field formed by the powder is measured. Measuring method. 2. A method for measuring an electrostatic field formed by a granular material by an electrostatic field sensor through a detection port provided in a wall of a container or the like, comprising: a DC high voltage generating circuit; Using a calibration checker that applies a DC high voltage to a metal plate by a high-voltage generating circuit to make a simulated charged object, the metal plate is opposed to the electrostatic field sensor, and the detection value of the electrostatic field sensor is calibrated. A method for measuring an electrostatic field of a granular material, comprising measuring an electrostatic field formed by the granular material. 3. A sensor in which a sensor case containing a detection electrode and an electric field detection circuit is housed in an air purge case as an electrostatic field sensor, and a gas such as air is supplied into the air purge case. 3. The method according to claim 1, wherein an electrostatic field formed by the granular material is measured through the air purge hole and a detection hole of the sensor case while ejecting gas from an air purge hole at a tip of the purge case. The method for measuring the electrostatic field of a granular material as described in the above. 4. A sensor case is housed in a sensor housing tube, and is housed together with the sensor housing tube in an air purge case, and an air passage formed between the sensor case and the sensor housing tube also receives air or the like. The method according to claim 3, wherein the gas is supplied and the gas is ejected from an air purge hole. 5. An electrostatic field sensor is installed at a detection port provided on a wall of a container or the like, and an electrostatic field formed by the granular material inside the container or the like is detected by the electrostatic field sensor and the value is measured. In the electric field measuring apparatus, a DC high voltage generating circuit and a metal plate are built in, and a DC high voltage is applied to the metal plate by the DC high voltage generating circuit, and the metal plate is used as a simulated charged object for the electrostatic field sensor. An electrostatic field measuring device for a granular material, comprising: a checker for a powder. 6. An electrostatic field sensor according to claim 1, wherein a sensor case including a detection electrode and an electric field detection circuit is housed in an air purge case, and a gas such as air is supplied into the air purge case. 6. The electrostatic field measuring apparatus for powdery and granular materials according to claim 5, wherein the apparatus has a structure in which a gas is ejected from an air purge hole at a tip end. 7. A sensor case is housed in a sensor housing tube, and is housed together with the sensor housing tube in an air purge case, between the sensor housing tube and the air purge case, and between the sensor case and the sensor housing tube. 7. An apparatus for measuring electrostatic field of a granular material according to claim 6, wherein an air passage for introducing gas to an air purge hole is formed between the air purge holes.