JPH09329583A - Measuring apparatus for friction charge amount of powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring apparatus by which the friction charge amount of a powder as a sample is measured with good accuracy and quickly by providing a gas supply means by which a vortex-flow gas is generated in the horizontal direction along a wire net face which the powder is blown off through its appertures. SOLUTION: A container is formed primarily of a wire net 3 and of a Faraday cage body 1, a powder 5 as a sample and a powder 6 as a contact partner are housed and arranged on the face of the wire net 3, and a compressed gas from a compressed gas nozzle 2 is blown. Meshes in the wire net 3 separate the powder 5 as the sample from the powder 6 as the contact partner when the gas is blown, and only the powder 5 is blown through the meshes in the wire net 3 so as to be selected. A gas inflow nozzle 7 is composed of a plurality of nozzles by which the compressed gas is blown into in parallel, and in a target direction, with reference to the end edge face of the body 1 including the wire net 3. When the compressed gas is blown from the compressed gas nozzle 2, the powder 5 which is blown off to the outside of the body 1 through the appertures in the wire net 3 is carried immediately to the outside of the body 1 due to the blowing, the vortex flow and the acceleration of the gas which is in parallel and in the tangent-line direction with reference to a direction in which the powder is blown off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charge amount measuring device capable of accurately, quickly, and easily measuring the amount of triboelectric charge between a sample powder and a contact partner powder.

[0002]

2. Description of the Related Art Generally, a means for measuring triboelectric charging characteristics of a sample powder is to mix a powder with a contact partner powder that imparts an electric charge to the sample powder, and to measure wind force, centrifugal force, mechanical force, impact force, electrostatic force, The frictionally charged particles are separated by applying vibration or the like, and the amount of electric charge remaining (remaining) on one powder is measured. That is, when there is a difference in particle size between the sample powder and the contacting partner powder, for example, if they are separated using a wire net, only the small particle size powder can be selectively removed through the openings of the wire net, so that they remain or remain. The amount of charge remaining on the powder having a relatively large particle size can be measured. Further, when either one of the sample powder and the contact partner powder is a ferromagnetic material,
The electrification amount of the ferromagnetic powder can be easily measured by selectively fixing only the ferromagnetic powder by using a magnet to separate the two. The method of using wind force to separate triboelectrically charged sample powder and contact partner powder and collecting large particle size powder with a wire net to measure the charge amount is called blow-off method and is the most common method. Is being used for. In this blow-off method, a mixture of sample powder and contact partner powder that have been premixed and have sufficient triboelectrification is contained in a metal cylinder (hereinafter referred to as the Faraday cage body) having a wire mesh stretched at least at one end. The main point is to blow compressed air from one end toward the wire mesh surface at the other end to separate the two.

That is, one of the sample powder and the contact partner powder has a particle size larger than the mesh opening of the wire mesh,
On the other hand, the grain size is smaller than that of the mesh. As a result, one of the separated powders is blown out of the Faraday cage body through the openings of the wire mesh. On the surface of the large particle size powder remaining inside the Faraday cage main body, the same amount as that of the small particle size powder blown out of the Faraday cage main body is removed, and the opposite electric charge remains. By measuring the amount, the triboelectric charge amount of both can be known. In addition, instead of blowing compressed air,
Even if a method of sucking gas through the Faraday cage main body and through the wire mesh surface is adopted, the triboelectric charge amount of both can be similarly measured.

[0004]

The above blow-off means has a simple structure and operation, and can quickly and accurately know the triboelectric charging characteristics of the sample powder and the contact partner powder. It is widely used as a method. However, the conventional blow-off charge amount measurement has the following problems, and its solution and elimination are desired.

(1) The sample powder separated in the Faraday cage body and the contact partner powder tend to electrostatically attract each other and coalesce again, and contact and separation tend to be repeated. In other words, the Faraday cage body acts as one kind of frictional charger, and it takes time to stabilize the charge measurement value, and it is difficult to measure the charge amount quickly.

(2) The blow-off operation causes frictional electrification between the sample powder and the inner wall surface of the Faraday cage body, and frictional electrification between the sample powder and the wire net, which makes it difficult to measure the amount of charge with high accuracy. (3) Since the separated powder easily adheres to the inner wall surface of the Faraday cage body or a part of the wire net, an error is likely to occur in the measured charge amount.

(4) The large particle size powder or the wire mesh is worn on the surface of the wire mesh, and this wear causes charging, which may cause an error in the measured charge amount.

(5) As the amount of triboelectric charge between the sample powder and the contact partner powder increases, not only separation takes time, but sometimes separation may not be possible. It is difficult to measure.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a powder triboelectric charge amount measuring device capable of accurately and quickly measuring the triboelectric charge amount of a sample powder.

[0010]

According to a first aspect of the present invention, there is provided a Faraday gauge main body made of a conductive metal having a compressed gas blowing port at one end, and the other end of the Faraday gauge main body. A wire net for selectively passing the sample powder out of the sample powder and the contact partner powder contained in the gauge body by blowing the compressed gas; and a gas flowing in a horizontal direction along the outer surface of the wire net, and A powder supply means for generating a vortex flow along the wire mesh surface; and a charge amount measuring means for measuring the charge amount of the contact partner powder remaining in the Faraday gauge body. This is a triboelectric charge amount measuring device. The invention of claim 2 is
The powder triboelectric charge amount measuring device according to claim 1, wherein the gas supply means for generating a vortex flow along the outer peripheral edge of the wire mesh comprises:
It is characterized by a plurality of nozzles set at substantially constant intervals and directions.

According to a third aspect of the present invention, in the powder triboelectric charge amount measuring device according to the first or second aspect, the gas supply means for generating a vortex flow along the outer peripheral edge of the wire mesh is attached to the outer periphery of the wire mesh. It is characterized in that a plurality of tangential directions are set.

According to a fourth aspect of the present invention, in the powder contact electrification amount measuring apparatus according to any one of the first to third aspects, a gas containing sample powder is provided on the installation surface of the gas supply means for introducing the gas. It is characterized in that a gas suction mechanism for sucking in is connected in series.

According to the present invention, a Faraday gauge main body having a wire mesh at least at one end is installed, and the frictionally charged sample powder and contact partner powder are accommodated therein, and compressed gas is blown into the Faraday gauge main body to pass through the wire mesh. This is an improvement of the device that selectively blows off one of the powders and measures the charge amount of the powder remaining in the Faraday gauge body. That is, it is characterized in that the blow flow type triboelectric charge measuring device is additionally provided with a gas supply means for generating a vortex gas in a horizontal direction along a wire mesh surface for blowing the powder through the openings.

The present invention was made based on the following knowledge. That is, the present inventors,
As a result of repeated studies and studies to solve and solve the above problems, when the gas flow inside and outside the Faraday cage body is properly controlled, (a) sample powder and contact partner powder To improve the efficiency of body separation,
It was found that (b) the separated sample powder can be efficiently blown off and removed, and (c) it becomes possible to measure with a high level of accuracy that was not seen in the past with (a) and (b) above. As a result, a powder triboelectric charge amount measuring device according to the present invention has been provided.

In the present invention, the Faraday gauge body is generally formed as a cylindrical body having a structure in which the inner diameter is enlarged from one end side having a compressed gas blowing port to the other end side to which a wire net is attached. are doing. The tubular body may have a configuration in which a plurality of axially divided tubular pieces are engaged and combined with each other. Further, the wire mesh may be mounted by arranging the wire mesh on the other end side of the tubular body and mounting a fitting tool engageable with the other end side, or alternatively, the other end side of the tubular body. The diameter may be reduced, and it may be detachably arranged on the inner side surface.

Further, the gas supply means for generating the vortex gas in the horizontal direction along the wire mesh surface is, for example, a fixture, a reduced diameter portion of a cylindrical body, a dedicated spacer or an end surface portion of a gas suction cylinder, and has a hole or a hole. It can be easily attached by installing the groove or step in the tangential direction. Of course, it does not matter even if the nozzle for gas supply is installed independently. The gas supply means for generating the vortex gas varies depending on the amount of blow flow from the Faraday gauge main body, but when the diameter of the blow flow is about 20 to 60 mm, for example, the diameter of the mounting surface or the cylindrical body is reduced. The steps may be set at approximately equal intervals so that a gap of about 0.3 to 2.0 mm is formed on the end surface of the part, the dedicated spacer surface, or the end surface of the gas suction cylinder.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments will be described below with reference to FIGS.

FIG. 1 is a sectional view showing a structural example of a powder triboelectric charge amount measuring device according to the present invention. In FIG. 1, reference numeral 1 denotes a tubular Faraday cage body having an enlarged inner diameter from one end to the other end made of a conductive material, and 2 denotes one end (smaller inner diameter side) of the Faraday cage body 1. The compressed gas nozzle 3 for blowing the compressed gas is a wire mesh detachably stretched and attached to the other end (the side having a large inner diameter) of the Faraday cage body 1 by a mounting tool 4. Here, the wire net 3 primarily forms a container with the Faraday cage main body 1, and the sample powder 5 and the contact partner powder 6 are housed and arranged on the surface of the wire net 3 and the powder from the compressed gas nozzle 2 is discharged. A compressed gas (for example, air) is blown. The mesh of the wire mesh 3 is separated by spraying the compressed gas into the sample powder 5 and the contact partner powder 6, and only the sample powder 5 is (selectively) blown through the mesh of the wire mesh 3. It is selected.

Further, 7 is arranged in the vicinity of a fixture 4 for detachably stretching and mounting the wire netting 3, and is parallel (horizontal direction) to the end face of the Faraday cage main body 1 including the wire netting 3 and tangential line. A plurality of nozzles that blow compressed gas (for example, air) in one direction. That is, the sample powder 5 blown out of the Faraday cage main body 1 through the openings of the wire net 3 by blowing the compressed gas from the compressed gas nozzle 2 is substantially horizontal to the blowing direction and is tangential to the direction. The compressed gas is blown, swirled, and accelerated so that it can be immediately transported to the outside of the Faraday cage body 1.

FIG. 2 is a plan view showing an example of the arrangement of a plurality of nozzles 7 for injecting compressed gas. In this case, the gas blown in from a substantially horizontal direction flows through the mesh of the wire mesh 3 into the Faraday. The sample powder 5 blown out of the cage body 1 is immediately eliminated as a spiral flow.
That is, in the case of this embodiment, the gas flow introduced in the horizontal direction generates a vortex flow along the peripheral edge of the wire net 3 and
Thus, the sample powder 5 blown off through the openings will be quickly and efficiently blown off.

Further, 8 is a condenser (capacity C), 9
Is an electrometer for measuring the charge amount of the sample powder 5 from the charging voltage due to the charges remaining on the Faraday cage body 1 side after being blown out of the Faraday cage body 1. That is, when the sample powder 5 is taken out of the Faraday cage main body 1, an equivalent amount and the opposite electric charge remain in the contact partner powder 6. Therefore, since this charge charges the capacitor 8 connected to the Faraday cage body 1, the voltage (V) across the capacitor 8 is measured by the electrometer 9, and the charge amount of the sample powder 5 |
The configuration is such that Q | is obtained as | Q | = CV.

In this configuration example, if a cylindrical shield is arranged on the blow flow side to converge the blow flow flow, it is possible to reliably avoid the blow flow powder from scattering. You can also

FIG. 3 is a cross-sectional view showing the essential structure of a powder frictional charge amount measuring device according to another embodiment. In this embodiment, the suction unit 10 is closely attached to the blow-off side of the sample powder 5. That is, the compressed gas nozzle 2 is attached to one end (the side having a small inner diameter) of the tubular Faraday cage body 1 made of a conductive material, the inner diameter of which is increased from one end to the other end, and the wire mesh 3 is attached. The Faraday cage body 1 is detachably stretched and attached to the other end (the side having a large inner diameter) by a mounting tool 4. Then, one end of the suction part 10 is closely arranged and attached to the fitting 4 through a spacer 11 having a gas blowing groove (gap) 7 '.
Here, the gas blowing groove (gap) of the spacer 11
7'is provided in such a manner that a tangential gap is formed between the lower end surface of the fixture 4 and the lower surface of the fixture 4 at steps of about 0.2 to 2.0 mm at substantially equal intervals.

That is, as shown in plan view in FIG. 4, the dedicated spacer 11 has a depth of 0.2 so as to generate a vortex 13 of suction / blow-off flow in the outer peripheral direction of the suction passage 12 for the sample powder 5.
A gas inflow (gas blowing or gas sucking) groove 7'of about 2.0 mm is formed. And the sample powder 5
At the time of measuring the triboelectric charge amount, the fitting 4 mounted on the Faraday cage body 1 and one end of the suction unit 10 are brought into close contact with each other via the spacer 11 and the compressed gas is blown and sucked at the same time. The sample powder (for example, toner particles) 5 blown off through the openings 3 is immediately removed by the vortex 13 generated by the air flow sucked (blown) from the spacer 11.

In this embodiment, the gas suction groove 7'is formed in the spacer 11; however, one end face of the attachment 4 or the suction portion 10 is provided with a step in the tangential direction at substantially equal intervals. It is also possible to adopt a structure in which a gap is provided between the spacer 11 surface and the gas suction groove 7 ',
Further, instead of the gas suction groove 7 ′, a fine hole may be provided so that the sucked gas is sucked (flows in) from this fine hole. In any case, it was confirmed that the removal efficiency of the sample powder 5 was highest when the suction gas was installed in the outer peripheral direction of the blowing path 12 so as to generate the vortex 13 by the suction gas. Further, in the case of this embodiment, the point is the pressure of the gas sucked (flowed) from the gas suction groove 7 ′, and in order to remove the sample powder 5 more efficiently, it is 300 to 3000 mm.
A range around Aq is desirable.

Next, an example of measuring the triboelectric charge amount of the electrophotographic toner by the triboelectric charge amount measuring apparatus according to this embodiment will be described.

In the structure of the triboelectrification amount measuring device shown in FIG. 3, a toner / carrier mixture for electrophotography is placed in a Faraday cage body 1 in which a wire net 3 made of stainless steel having an opening of 40 μm is stretched. Accommodated. Then, 0.4 kg / cm ² of compressed air is blown from the compressed gas blowing port 2 having a diameter of 3 mm, and at the same time, the suction portion 11 is sucked at a pressure of 2000 mmAq, and the toner powder (toner particles) is sucked through the openings of the wire mesh 3. Blow-flow was made to the part 10 side.

In this process, the amount of charge measured by the electrometer 9 connected to the Faraday cage main body 1 increases with the compressed gas blowing from the compressed gas blowing port 2, and after 3 seconds, the inside of the Faraday cage main body 1 is discharged. All of the toner powder 5 was blown off and the measured charge amount was saturated. The weight of the Faraday cage filled with the sample (toner / carrier mixture) was measured before and after the measurement of the triboelectric charge amount. The weight difference after 3 seconds of blowing time was equivalent to the weight of the sample powder 5. It was confirmed that the toner powder 5 in the sample was almost completely blown off. Further, it was found that no toner adhered to the lower end of the Faraday cage body 1 and the lower surface of the wire net 3 after the triboelectric charge measurement, and the effect of removing the sample powder 5 was very excellent.

On the other hand, for comparison, the triboelectric charge amount was measured under the same conditions as above using a conventional triboelectric charge amount measuring device (which does not have a mechanism for generating a vortex flow along the lower surface of the wire mesh). In this case, not only 20 seconds or more were required until the charge amount reached saturation, but the saturation charge amount was about 1.5 times the value of the embodiment. This difference in the amount of charge is due to the amount of frictional charge due to repeated separation and contact with the carrier multiple times before all the toner in the Faraday cage body was blown out of the Faraday cage body through the mesh openings. You can say that.

FIGS. 5 and 6 show comparative examples of measurement by the triboelectric charge amount measuring device shown in FIG. 3 and the conventional triboelectric charge amount measuring device. FIG. 5 shows the relationship between the measurement time and the measured value when the triboelectric charge amount was measured using positively charged toner (styrene acrylic high hardness toner) as the sample powder. Curve A is the curve obtained by the measuring device of the example. a shows the case of the conventional measuring device, respectively. Further, FIG. 6 shows the relationship between the measurement time and the measured value when the triboelectric charge amount was measured using a negatively charged toner (polyester toner containing a silica-based external additive) as a sample powder, and the curve B is the measuring device of the example. And the curve b shows the case by the conventional measuring device.

As can be seen from the characteristic comparison of FIG. 5 and FIG. 6, in the case of the triboelectric charge measuring device of the present invention, the
In addition, the triboelectric charge amount can be accurately measured.

Further, in this triboelectric charge amount measurement, the weight loss of the sample before and after the measurement is larger than the amount of the sample powder, and it is shown that the carrier surface is abraded on the wire mesh surface by the blowing operation. Further, it was also confirmed that it was difficult to completely remove the sample powder, because a small amount of toner was reattached to the lower end of the Faraday cage body after the measurement. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. For example, the gas inflow path for inflowing or supplying in order to generate a vortex flow along the wire mesh surface may be a groove type (gap), a hole type or a nozzle type.

[0033]

According to the powder charge measuring device of the present invention,
The following functions and effects can be easily obtained. For example, quality control of toner for developing and forming a high-quality electrophotographic image with good reproducibility and evaluation of charging characteristics of various materials can be easily performed. .

(1) A friction charger of which the so-called Faraday cage body is a kind of friction charger, in which the sample powder separated in the Faraday cage body and the contact partner powder electrostatically attract and coalesce again to repeat contact and separation. Since it does not work, the amount of triboelectrification can be measured quickly and accurately.

(2) High efficiency of selective removal of sample powder,
In addition, since the triboelectric charging between the sample powder and the inner wall of the Faraday cage body and the triboelectric charging between the sample powder and the wire net can be suppressed to a very small amount even by the blow-off operation, the triboelectric charge amount can be accurately measured.

(3) Since the separated sample powder is prevented from adhering to the inner wall of the Faraday cage main body or a part of the wire mesh, there is no possibility of causing an error in the measured charge amount.

(4) Accurate measurement of the triboelectric charge amount, because there is no error in the measured charge amount due to wear of the contact partner powder or wire mesh on the wire mesh surface, and generation of charge amount due to wear. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part configuration of a triboelectric charge amount measuring device according to an embodiment.

FIG. 2 is a plan view showing an arrangement state of gas inflow means in the triboelectric charge amount measuring device of FIG.

FIG. 3 is a cross-sectional view showing a main part configuration of a triboelectric charge amount measuring device according to another embodiment.

FIG. 4 is a plan view showing a disposition state of gas inflow means in the triboelectric charge amount measuring device of FIG. 3;

FIG. 5 is a characteristic diagram showing the measurement characteristics of the triboelectric charge amount of positively charged toner by the triboelectric charge amount measuring apparatus of another embodiment in comparison with the case of a conventional triboelectric charge amount measuring apparatus.

FIG. 6 is a characteristic diagram showing the measurement characteristics of the triboelectric charge amount of the negatively charged toner by the triboelectric charge amount measuring apparatus of another embodiment in comparison with the case of the conventional triboelectric charge amount measuring apparatus.

[Explanation of symbols]

 1 …… Faraday cage body 2 …… Compressed gas injection port (nozzle) 3 …… Metal mesh 4 …… Mounting tool 5 …… Sample powder (small particle size) 6 …… Contact partner powder (large particle size) 7, 7 '... Gas inflow means 8 ... Condenser 9 ... Electrometer 10 ... Suction part 11 ... Spacer 12 ... Suction path 13 ... Eddy current

Claims (4)

[Claims] 1. A Faraday gauge main body made of a conductive metal having a compressed gas blowing port at one end, and a sample powder which is stretched over the other end of the Faraday gauge main body and accommodated in the Faraday gauge main body. Wire mesh for selectively passing the sample powder among the contact partner powder by blowing the compressed gas, and gas supply for injecting gas horizontally along the outer surface of the wire mesh and generating vortex along the wire mesh surface A frictional charge amount measuring device for powder, comprising: a means and a charge amount measuring means for measuring a charge amount of the contact partner powder remaining in the Faraday gauge body. 2. The friction of powder according to claim 1, wherein the gas supply means for generating a vortex flow along the outer peripheral edge of the wire mesh is a plurality of nozzles set at substantially constant intervals and directions. Charge amount measuring device. 3. A plurality of gas supply means for generating a vortex flow along the outer peripheral edge of the wire mesh are set in a tangential direction with respect to the outer circumference of the wire mesh. Powder triboelectric charge measuring device. 4. The gas suction mechanism for sucking the gas containing the sample powder is continuously provided on the installation surface of the gas supply means for inflowing the gas. Powder contact charge amount measuring device.