JPS58174860A - Charge level measuring apparatus - Google Patents

Abstract

PURPOSE:To determine charge level of a powdery material existing isolated directly in a simple and quick manner by measuring charge electrostatically introduced with a charge of the measuring powdery body and accumulated in a capacitor. CONSTITUTION:When a measuring powdery material 5 charged in positive polarity attaches (3-1) to the surface of a sample 6 to be measured, a negative charge is induced with a charge of the measuring powdery body 5 and flows in the direction of the arrow passing through a switch S and accumulated (3-2) in the sample 6 being measured to the level equal to the positive charge. Now when the switch S is opened and a suction nozzle 7 is operated to suck the measuring powdery body 5 of positive polarity peeled forcibly off the surface of the sample 6 being measured, charge of the negative polarity accumulated in the sample being measured is accumulated in one electrode of a capacitor 28 and the charge of the opposite polarity is accumulated in the other electrode thereof (3-3, 3-4). Therefore, when the capacity of the capacitor is represented by C and the voltage between both the electrodes V, the charge level of the measuring powdery body 5 can be determined by q=CXV.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a novel charge measuring device useful for measuring the charge amount of various powders.

[Technical background of the invention and its problems]

The charging characteristics of various powders, such as dry toner for electrophotographic equipment and coating powder for electrostatic coating equipment, are important, so a device that can accurately and easily measure the amount of charge of the powder is required. becomes.

Conventionally, devices applying the so-called blow-off method have been well known as devices for measuring the amount of charge of powder (see Electrophotography 16, (1977), 52i, Journal of the Japan Institute of Electrostatics 4, (1980), 134, etc.). . This device stores a mixture of powder and granules (powder and granules) in a cylindrical container called a blow-off cage, which has wire mesh with openings on both ends that allow only the powder to pass through but not the granules. Then, high-pressure air is blown from one end to release only the powder from the container through a wire mesh at the other end to separate the powder.

At this time, it is considered that the quantity of electricity possessed by the particles remaining in the container is equal in absolute value to the quantity of electricity carried away by the powder, and has opposite polarity.

Therefore, by measuring the amount of electricity in the remaining granules and the weight of the released powder, the amount of electricity per unit weight of the powder can be determined.

However, with this device, the amount of charge on the powder generally varies greatly depending on the pressure of the high-pressure gas, so the reproducibility of the measured value is poor. Moreover, not only that,
Since this device is originally intended for powder contained in a powder or granular material such as a two-component toner, it is not possible to directly measure the amount of charge of a powder that exists alone. Therefore, the scope of application of this device was extremely narrow.

As other devices, devices using a suction type 7 Alladay cage are known (S, Kitaoka #9, J
, Electrostatics, Dan (1979)
, 181). This device was proposed to measure the amount of charge on fine particles floating in air currents, for example, and collects charged powder by suctioning it into a conductive container called a Faraday cage. By measuring the amount of electricity and weight of the obtained powder, the amount of electricity per unit weight is determined.

In this device, when measuring the amount of charge on powder, it is necessary to separate the powder in the airflow from the airflow. For this purpose, filters are used.

Therefore, with this device, it is possible to measure the amount of charge of powder alone, but on the other hand, it is necessary to select and use a filter with an appropriate mesh size depending on the size of the powder to be measured. However, the operation becomes complicated. Furthermore, if the filter becomes clogged, measurement becomes impossible. Furthermore, since the suction operation is performed through a filter, the suction force is reduced and the ability to accumulate powder is small, and there is a drawback that the smaller the particle size of the powder, the greater the pressure loss.

[Object of the Invention] It is an object of the present invention to provide a device that eliminates all of the drawbacks of the conventional devices described above and easily measures the amount of charge of powder with high precision and good reproducibility.

[Summary of the invention]

The apparatus of the present invention includes a sample system consisting of a sample stage that is insulated and supported and movable in the front-rear, left-right, and up-down directions, and a measurement sample placed on the sample stage and having measurement powder adhered to the surface; A measurement powder suction system comprising a suction nozzle supported in an insulating manner and disposed close to the measurement sample to separate the measurement powder from the dead measurement sample and sucking it together with air; , a conductive envelope, a conductive measurement powder collection container detachably attached to the inner wall of the envelope, and connected to the suction system on the upper side of the envelope. - An introduction pipe through which the powder to be measured and the air transferred from the suction system flow into the envelope in a tangential direction; and an exhaust pipe located below the pipe installation position, and further electrically connected to the suction system to separate the measured powder from the air and collect the measured powder. A measurement powder collection system that is;
An exhaust control system consisting of an exhaust means connected to the exhaust pipe via an insulating connecting pipe and using a timer-operated solenoid valve as an opening/closing means; one electrode is connected to the envelope and the other electrode is at a constant potential. A first charge measurement system consists of a capacitor (■) held in the capacitor (2), an electrostatic electrometer that measures the potential difference between the electrodes of the capacitor (2), and a recorder that records the potential difference, one electrode of which is connected to the sample stage. A second charge amount measurement consisting of a capacitor (1) connected to the capacitor (H) whose other electrode is held at a constant potential, an electrostatic electrometer that measures the potential difference between the electrodes of the capacitor (H), and a recorder that records the potential difference. The structure is characterized by comprising: a charge amount measuring system for at least one of the systems;

Below, the device of the present invention will be explained in more detail based on illustrated examples. FIG. 1 is a schematic diagram illustrating the mutual relationship of each element of the device of the present invention. In the figure, reference numeral 1 denotes a sample stage made of a suitable conductive material such as aluminum, brass, stainless steel, or copper. It is supported via a plate 2 by a table 3 that is movable in the front and back, left and right, and up and down directions. A measurement sample 6 having measurement powder 5 adhered to its surface is placed on the sample stage 1 via a conductive fitting 4 such as a screw fitting, and the sample system as a whole is constituted. .

Reference numeral 7 denotes a suction nozzle for forcibly separating the measurement powder 5 adhering to the surface of the measurement sample 6 from the surface and suctioning the measurement powder 5, which is connected to the measurement powder collection system described later through the path P. Introductory tube 1
Connect to 7. Route P.

For example, it is preferable to have a split structure with removable connectors 8° and 8' having a screw-fitting structure.

Further, the suction nozzle is supported by a fixed shaft 1 ( ) via an insulating plate 9 . In this case, inlet pipe 1 of path PI
If the connection strength with 7 is sufficiently large, the above-mentioned insulating support structure is not necessarily required.

A vacuum gauge 11 and an intake control valve 12 are attached to the path P1. Thus, the measuring powder suction system is constructed as a whole. Here, a schematic diagram of a suction nozzle according to the present invention K is shown as FIG. 2. In the figure, 201 is a nozzle body, 202
203 is an opening, and 203 is a threaded portion constituting one side of the connector 8 in FIG. 1, and its cross-sectional area 204 is equal to or slightly smaller than the cross-sectional area of an introduction pipe 17, which will be described later. The measured powder 5 sucked together with air through the opening 202 flows through the inside of the suction nozzle and reaches the collection system K. In this suction nozzle, the cross-sectional area of the opening 202 is such that the powder to be measured is smoothly sucked into the path P, and the powder to be measured is Cross-section 2
It is preferable that the area is smaller than the area of 04. In addition, the shape of the opening 202 is not particularly limited, but the reason is that the suction pressure can be made uniform throughout the opening, that it is easy to calculate the peeling area of the measurement powder in the measurement sample, etc. Preferably, the shape is rectangular.

13 Hafcinnium. A cyclone cage envelope made of a suitable electrically conductive material such as brass, stainless steel, copper, etc., and supported by a fixed shaft 15 via an insulating plate 14 made of a suitable electrically insulating material. .

The envelope 13 is generally cylindrical and has a tapered lower portion, indicated by X and Y in the figure.

It is preferable to have a split structure that can be disassembled at two positions.

An electrically conductive collection container 1 is attached to the inner wall of the envelope 13 in a detachable manner.
6 is installed. It is important that the collection container 16 is installed so that there is almost no gap between it and the inner wall of the envelope 13. If a gap is created between the two, some of the powder that has been sucked in will enter the gap. This not only causes an error in the measurement of the powder weight, but also causes an error in the measurement of the amount of charge since the capacitor (2), which will be described later, is in a charged state before the measurement in subsequent measurements of the amount of charge. The collection container 16 is made of a material that is highly conductive and lightweight, and is preferably an extremely thin aluminum plate with a gold-plated surface. In addition, in order to precisely measure the weight of the measurement powder collected in the collection container 16, assuming the use of a chemical balance that can measure up to 109 orders of magnitude, the weight of the collection container 16 is 2009 or less. It is preferable that it be limited to.

17 is an introduction pipe arranged on the upper side of the envelope 13;
The mixed air flow of the measurement powder and air sucked through the path P1 is caused to flow in the tangential direction of the envelope 13. Reference numeral 18 denotes an exhaust pipe attached vertically to the top of the envelope 13, and its cross-sectional area is larger than the cross-sectional area of the introduction pipe 17, and its lower end opening is connected to the introduction pipe 17 as shown in the figure. placed below the position. The exhaust pipe 18 is connected to an exhaust/control system via an insulated connection pipe 19. The mixed airflow of the powder to be measured and air transferred from the suction system is passed from the introduction pipe 17 to the envelope 1.
It is introduced tangentially above 3. Due to the difference in specific gravity between the measured powder and air, the difference in centrifugal force that acts on the measured powder, and the like, the measured powder and air are separated and the measured powder is deposited at the bottom of the collection container 16, while the air is deposited at the bottom of the exhaust pipe 18. It is sucked into the exhaust/control system, which will be described later, through the opening at the bottom. The reason why the lower end opening of the exhaust pipe 18 is located lower than the position of the introduction pipe 17 is that when the measured powder is separated from the air as described above, a part of the measured powder is evacuated and controlled together with the air. This is to prevent it from being sucked into the system.

The measurement powder collection system configured as described above is connected to the exhaust/control system via the insulated connection pipe 19. 20
is a solenoid valve that is interposed in the path P, and together with an exhaust means such as the vacuum exhaust fan 21, serves as a means for opening and closing the path P. The solenoid valve silver is electrically connected to a timer n and a timer switch. Further, a vacuum gauge U and a leak pulp δ are arranged in the path P2, thereby configuring the entire exhaust/control system.

The capacitor is a capacitor that stores the amount of charge of the collected powder to be measured, and one electrode is electrically connected to the envelope 13.
The other electrode is, for example, grounded and held at a constant potential.

Between both electrodes is an electrostatic electrometer to measure the generated potential.
is connected, and its potential is recorded by a recorder 30K, thereby forming a first charge amount measurement system. In addition, the capacitor 1 is a capacitor that accumulates the amount of charge of the opposite polarity of the sucked measurement powder of the measurement sample, and one electrode is electrically connected to the sample stage 1, and the other electrode is connected to the ground, for example. is held at a constant potential. An electrostatic potential meter for measuring the generated potential is connected between both electrodes, and the potential is recorded between the recorders and recorded as a second
A charge amount measurement system is constructed. Although FIG. 1 shows an apparatus that is equipped with the first and second charge amount measurement systems at the same time, the apparatus of the present invention can be equipped with either one of these measurement systems based on the measurement principle described later. Even if it is, inconveniences can occur.

First, the measurement principle of the apparatus of the present invention will be explained with reference to a schematic diagram of the second charge amount measurement system shown in FIG. The diagram a-(t) shows a state in which the positively charged measurement powder 5 is adhered to the surface of the measurement sample 6. Figure 3-121 shows a state in which a negative charge is induced by the charge on the measurement powder 5, flows through the switch S in the direction of the arrow, and is accumulated in the measurement sample 6 in an amount equal to the amount of positive charge (opposite polarity). . When the switch S is opened and the suction nozzle 7 is activated to forcibly separate the positive polarity measurement powder 5 from the surface of the measurement sample 60 and suck it, the negative polarity accumulated in the measurement sample is removed from the capacitor. accumulated on the electrodes of
Charges of opposite polarity are accumulated on the other electrode, and 3-(3)
, 3-f4). 3-(3
) shows a state in which charges are partially accumulated, and FIG. 3-(4) shows a state in which all charges are accumulated. Therefore, if the capacitance of the capacitor is C, and the potential between the electrodes of the capacitor in the state shown in Figure 3-(4) is The charge amount of 5 can be determined as q=CxV. Furthermore, since the weight (M) of the measured powder 5 peeled off and sucked by the suction nozzle 7 can be determined by weighing the collection container 16, the amount of charge per unit weight of the measured powder 5 can be determined by the amount of charge per unit weight of the measured powder 5. It can be calculated as

The principle is the same for the first charge amount measurement system.

Therefore, in the apparatus of the present invention, it is sufficient that the charge amount measuring system is disposed in at least one of the sample system and the collection system.

However, if the specific gravity of the measured powder is small and fine and it is difficult to collect it with the above-mentioned collection system (difficult to measure its weight), the difference in weight between before and after measurement of the measured sample By finding M from the equation and finding q from the first charge amount measurement system, (1/M can be calculated.

The device of the present invention operates under pressure as follows.

First, switch B is turned on to open the solenoid valve, and the vacuum exhaust fan 21 is operated to suck air from the intake G1 nozzle 7. At this time, the distance between the measurement sample 6 and the opening of the suction nozzle 7 is adjusted by appropriately moving the table 3, and the suction control valve 12 and the leak pulp 5 are adjusted to create a vacuum at the opening of the suction nozzle 7. The temperature is adjusted to such an extent that the measurement powder 5 can be forcibly peeled off from the surface of the measurement sample 60. For example, when the amount of charge of the powder 5 to be measured is large or the particle size is small, the distance between the suction nozzle 7 and the measurement sample 6 is shortened and the degree of vacuum is increased. At this time, Sada.

Moderate is regulated by the amount of air discharged by the vacuum exhaust fan 21,
If the exhaust air volume is increased to increase the degree of vacuum, care should be taken as this may cause measurement powder to leak from the collection system. Normally, the degree of vacuum is 100 to 5000111
11A (1) The amount of exhaust air, that is, the amount of inflow into the cyclone cage is preferably about 0.2 to 5 m3/mjR.

During the above preparatory process, the capacitor station 28 is short-circuited. Once the operating conditions are determined, timer 4 is set for a sufficiently long time, measurement sample 6 is mounted and fixed via metal fitting 4, the solenoid valve is opened by timer n, and vacuum exhaust fan 21 is activated. Then, the powder to be measured 5 is sucked.

Normally, the table 3 is moved at a constant speed of, for example, 10 cm/cm. The suction nozzle 6 fixed at a predetermined position continues to suction the measured powder 5. The measured powder flows into the cyclone cage from the introduction pipe 17 through the path P1, is separated from the air, and is deposited at the bottom of the collection container 16. The separated air is discharged out of the system through path P.

The amount of charge of the measured powder deposited at the bottom of the collection container 16 is the first
It is measured by the charge amount measurement system and recorded on the recorder 30. The weight of the powder to be measured is determined by disassembling the envelope 13 and measuring the weight of the collection container 160 taken out. In this way, the amount of charge per unit weight of the measured powder can be calculated and determined.

By using the device of the present invention, it is also possible to measure the charge distribution of the measurement powder on the surface of the measurement sample. For example, vertical 30
An applied voltage of 50 KV and an air pressure of 1 kl/cm2. The measurement sample was a 109 electrostatically coated paint (approximately 50 μ steel powder with white pigment dispersed in acrylic resin) at a distance of 50 crrL from the nozzle, and the sample was divided into 6 parts. The amount of charge was measured. The result is the fourth
Shown in the figure. The unit of numerical value in each division is μC/9.

Furthermore, the apparatus of the present invention can also determine the amount of charge during development of a one-component toner in an electrophotographic apparatus. For example, a description will be given of a touchdown developing type developer in which one-component toner 502 is charged and developed using a charge injection electrode 501 shown in FIG. First, hopper 503
The one-component toner 502 filled with K moves while adhering to the rotating surface of the grounded developing roll 5040, contacts the charge injection electrode 501, and a high voltage 505 is applied thereto. As a result, a charged one-component toner 502' is obtained.

Here, the suction nozzle 7 according to the present invention was arranged at a position in contact with the photoreceptor, and the amount of charge of the one-component toner 502' was measured. The measurement conditions at this time were: a distance of 5 days between the suction nozzle opening and the rotating surface of the developing roll, a cross-sectional width of the suction nozzle opening of 2 mm, a rectangle with a length of 260 m, and a vacuum level of 3000 Aq.
.

The exhaust air volume was 2 m3/miR. As a result, the applied voltage (5
05 voltage) When the voltage is 100OV, the toner is 13μC/G
It was found that it is charged with l.

〔Effect of the invention〕

As is clear from the above explanation, according to the device of the present invention,
It is possible to directly determine the amount of charge of powder that exists alone, such as one-component toner for electrophotographic equipment or coating powder in electrostatic coating.■It is possible to determine the amount of charge simply and quickly.■Measurement sample The amount of charge on a portion of the sample can be determined. ■ The distribution of the amount of charge on the measurement sample can be determined.
■The amount of charge can be determined regardless of the particle size and specific gravity of the powder to be measured.■Measurement costs are reduced because no consumables such as filters are used.Their industrial value is extremely high. It's large.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an example showing the mutual relationship of each element of the device of the present invention, Fig. 2 is a view from left F showing an example of a suction nozzle according to the device of the present invention, and Fig. 3 is a diagram of the device of the present invention. A schematic diagram for explaining the measurement principle; FIG. 4 is a diagram showing the charge distribution on the surface of a measurement sample using the device of the present invention; FIG. It is a state diagram applied to quantity measurement. 1... Sample stand 2, 9, 14... Insulating plate 3... Table 4... Mounting bracket 5...
・Measurement powder 6...Measurement sample 7...Suction nozzle 8, 8'...Connector 10, 15...Fixed shaft 11.24...Vacuum needle 12...Intake control valve 13. ... Envelope 16 ... Collection container 1
7...Introduction pipe 18...Exhaust pipe 19...
Insulated connection pipe side...Solenoid valve 21...Vacuum exhaust equipment...Timer 3...Switch 5...
・Leak Valve...Capacitor In, 29...
Electrostatic potential difference measurement... Capacitor ■ Addition... Recorder Ps, Pt... Path 201... Nozzle body 202... Opening 203... Threaded part
204...Cross section 501...Charge injection electrode 502
, 502'...One-component toner 503...Hopper 504...Developing roll 505--High voltage Fig. 3 Fig. 4 Fig. 5

Claims (1)

[Claims] 1. Consists of a sample stand supported insulatingly and movable in the front-rear, left-right, and up-down directions, and a measurement sample placed on the sample stand trap and having measurement powder adhered to the surface. Sample system; Measurement powder suction system consisting of a suction nozzle that is insulated supported and placed close to the measurement sample to separate the measurement powder from the measurement sample and suck it together with air; Insulation support and a conductive envelope, a conductive measurement powder collection container detachably attached to the inner wall of the envelope, and connected to the suction system at the upper side of the envelope. an inlet pipe which is arranged at It consists of an exhaust pipe located below the installation position of the introduction pipe, and is electrically connected to the suction system to separate the measured powder from the air and collect the measured powder. a measurement powder collection system which is a cyclone type cage; an exhaust control system 1 which is connected to the exhaust pipe via an insulating connecting pipe and is composed of a timer-operated solenoid valve and an exhaust means which uses the solenoid valve as an opening/closing means; a capacitor I having one electrode connected to the envelope and the other electrode being held at a constant potential;
A first charge measurement system consisting of an electrostatic electrometer that measures the potential difference between the electrodes of the capacitor (1) and a recorder that records the potential difference, one electrode being connected to the sample stage and the other electrode being kept at a constant potential. At least one of the second charge amount measuring system consisting of a capacitor (■) held in the capacitor (2), an electrostatic electrometer that measures the potential difference between the electrodes of the capacitor (2), and a recorder that records the potential difference. A charge amount measuring device comprising: a charge amount measuring system; 2. A charge amount measuring device according to claim 1, which simultaneously includes a first charge amount measuring system and a second charge amount measuring system. 3. The charge amount measuring device according to claim 1, wherein the suction system and the collection system are detachable. 4. The charge amount measuring device according to claim 1, wherein the cross-sectional shape of the suction opening of the suction nozzle is rectangular, and the cross-sectional area of the opening is smaller than the cross-sectional area of the introduction tube. 5. The charge amount measuring device according to claim 1, wherein the cyclone cage has a divided structure including the top of the envelope, the envelope, and the collection container. 6. The charge amount measuring device according to claim 1, wherein the collection container has a weight of 2,002 kg or less. l The degree of vacuum during operation of the suction nozzle is 100 to 5000
The charge amount measuring device according to claim 1, which is mAq. 8. The charge amount measuring device according to claim 1, wherein the amount of the measured powder and the air flowing into the cyclone cage is 0.2 to 5 Li.