JP3347940B2 - Powder triboelectric charge measuring device - Google Patents

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 measuring the triboelectric charge amount between a sample powder and a contact partner powder accurately, quickly and easily.

[0002]

2. Description of the Related Art In general, a means for measuring the triboelectric charging characteristics of a sample powder is prepared by mixing a powder with a contact partner powder which imparts a charge to the sample powder and applying a wind force, centrifugal force, mechanical force, impact force, electrostatic force, or the like. Vibration or the like is applied to separate the triboelectrically charged two, and the amount of charge remaining (remaining) on one of the powders is measured. That is, when there is a difference in the particle diameter between the sample powder and the contact partner powder, for example, when separated using a wire mesh, only the small particle size powder can be selectively removed through the openings of the wire mesh. The amount of charge remaining on the powder having a relatively large particle size can be measured. Further, when one of the sample powder and the contact partner powder is a ferromagnetic material,
By selectively fixing only the ferromagnetic powder using a magnet to separate them, the charge amount of the ferromagnetic powder can be easily measured. The method of using a wind force to separate the triboelectrically charged sample powder and the contact partner powder, collecting large-diameter powder using a wire mesh, and measuring the charge amount is called a blow-off method. Is used regularly. In this blow-off method, a mixture of a sample powder and a contact partner powder which have been mixed in advance and have a sufficient triboelectric charge are accommodated in a metal cylinder (hereinafter referred to as a Faraday cage body) having a wire mesh stretched at least at one end. The main point is that compressed air is blown from one end to the wire mesh surface at the other end to separate them.

That is, either the sample powder or the contact partner powder has a particle size larger than the mesh of the wire mesh,
The other has a particle size smaller than the mesh of the wire 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 in the Faraday cage body, an equal amount of the opposite charge remains when the small particle size powder blown out of the Faraday cage body is removed, and the opposite 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 inside of the Faraday cage main body and the wire mesh surface is used, the triboelectric charge amount of both can be measured similarly.

[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 it is desired to solve and eliminate them.

(1) The sample powder separated in the Faraday cage main body and the contact partner powder tend to be electrostatically attracted to unite again and repeat contact and separation. That is, the Faraday cage body acts as one kind of friction charger, and it takes time to stabilize the measured charge value, and it is difficult to quickly measure the charge amount.

(2) The blow-off operation also causes frictional charging between the sample powder and the inner wall surface of the Faraday cage body and frictional charging between the sample powder and the wire mesh, making it difficult to measure the charge amount with high accuracy.

(3) Since the separated powder easily adheres to the inner wall surface of the Faraday cage main body and a part of the wire net, an error easily occurs in the measured charge amount.

(4) The large-diameter powder or the wire mesh is worn on the wire mesh surface, and the wear is caused by the wear, 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 does the separation take time, but sometimes the separation cannot be performed. Difficult to measure.

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

[0011]

According to a first aspect of the present invention, there is provided a cylindrical Faraday cage body made of a conductive metal having a compressed gas blowing port at one end and having an inner diameter that increases from one end to the other end. If, taken to the other end of the Faraday cage body
Ri attached tool detachably be stretched, attached by a wire mesh passing a sample powder of the file <br/> Radekeji sample powder and the contact partner powder housed in the body by blowing the compressed gas , To the fixture via a spacer
A contact arranged-loaded suction unit, and a contact mating powder charge amount measuring means for remaining in the Faraday cage body, the spacer or the fitting or pre
An end surface of the suction portion that contacts the spacer is provided with the suction member.
A vortex is generated in the direction of the outer circumference of the sample powder suction path in the drawing section
This is a device for measuring the amount of triboelectric charge of powder having a gas inflow groove to be formed .

[0012]

[0013]

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

[0015] The present invention has been made based on the following findings. That is, the present inventors,
As a result of intensive research and examination in response to the resolution and resolution of the above problems, when the flow of gas including the inside and outside of the Faraday cage body was properly controlled, (a) sample powder and contact partner powder Improved body separation efficiency,
(b) It has been found that the separated sample powder is efficiently blown off and removed, and (c) it is possible to measure at a high level of accuracy that has not been seen conventionally with (a) and (b). Thus, the present invention provides a powder triboelectric charge measuring device according to the present invention.

In the present invention, the Faraday gauge body is generally a cylindrical body having a configuration in which the inside diameter is widened from one end provided with a compressed gas blowing port to the other end provided with a wire mesh. are doing. The tubular body may have a configuration in which, for example, a plurality of tubular body pieces divided in the axial direction are engaged and combined. The wire mesh may be mounted on the other end of the tubular body by attaching a fitting that can be engaged with the other end, or the other end of the tubular body. May have a reduced diameter, and may be configured to be removable on the inner surface thereof.

Further, the gas supply means for generating swirling gas in the horizontal direction along the surface of the wire mesh includes, for example, a hole, a hole or a hole in the end face of the fitting, the reduced diameter portion of the cylindrical body, the dedicated spacer or the gas suction cylinder. The grooves or steps can be easily provided by tangentially installing them . Their to, gas supply means for generating the vortex gas, etc. but blow flow amount from the Faraday cage body, the diameter of the blow flow when about 20 to 60 mm, for example fitting surface, of the cylindrical body Steps may be set at substantially equal intervals so that a gap of about 0.3 to 2.0 mm is formed on the end face of the reduced diameter portion, the dedicated spacer face, or the end face of the gas suction cylinder.

[0018]

The reference to examples below FIGS PREFERRED EMBODIMENTS be described.

FIG. 1 is a cross-sectional view showing the configuration of a main part of a device for measuring the triboelectric charge amount of a powder according to one embodiment of the present invention. In this embodiment, a configuration is adopted in which 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 smaller inner diameter side) of a cylindrical Faraday cage body 1 made of a conductive material and having an inner diameter that increases from one end to the other end side. ,
The other end of the Faraday cage body 1 (the side with the larger inner diameter)
A configuration is adopted in which it is stretched and attached detachably by the attachment 4. And, for the mounting fixture 4,
One end of the suction unit 10 is closely arranged and mounted via a spacer 11 having a gas blowing groove (gap) 7. Here, the gas blowing groove (gap) 7 of the spacer 11 is between 0.2 mm and 2.0 mm
It is provided in such a manner that tangential gaps are formed at substantially equal intervals with a level difference.

That is, as shown in plan view in FIG. 2, the dedicated spacer 11 has a depth of 0.2 so as to generate a vortex 13 of a suction / blow-off flow in the outer peripheral direction of the suction path 12 for the sample powder 5.
Gas flow of about ~ 2.0 mm (suction gas form) groove 7 is Katachi設. At the time of measuring the triboelectric charge amount of the sample powder 5, the fitting 4 attached to 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 blow and suction of the compressed gas are performed. Is performed simultaneously, the sample powder (for example, toner particles) 5 blown off through the openings of the wire netting 3 is immediately removed by the vortex 13 generated by the air flow sucked (blown) from the spacer 11.

Further, 8 is a capacitor (capacity C), 9
Is an electrometer for measuring the charge amount of the sample powder 5 from the charge voltage due to the charge remaining on the Faraday cage body 1 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 of an opposite charge remains on 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 |
Q | is obtained as | Q | = CV.

In this embodiment, the structure in which the gas suction groove 7 is formed in the spacer 11 is shown. However, a step is provided at substantially equal intervals and tangentially on one end surface of the attachment 4 or the suction portion 10. The gas suction groove 7 may be formed by providing a gap between the spacer 11 and the surface of the spacer 11. Alternatively, a fine hole may be provided instead of the gas suction groove 7, and the suction gas may be sucked from the fine hole. Do). In any case, it was confirmed that the sample powder 5 was most efficiently removed when it was installed in the outer circumferential direction of the suction gas blowing path 12 so as to generate the vortex 13 due to the suction gas. Further, in the case of this embodiment, the pressure of the gas sucked (inflow) from the gas suction groove 7 is a point, and in order to remove the sample powder 5 more efficiently, 300 to 3000 mmAq
A range of degrees is desirable.

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

In the configuration of the apparatus for measuring the amount of triboelectric charge shown in FIG . 1 , a toner-carrier mixture for electrophotography is placed in a Faraday cage body 1 in which a stainless steel wire mesh having an aperture of 40 μm is stretched as a wire mesh 3. Housed. Then, at the same time as blowing compressed air of 0.4 kg / cm2 from the compressed gas blowing port 2 having a diameter of 3 mm, the suction part 11 is sucked at a pressure of 2000 mmAq, and the toner powder (toner particles) is sucked through the opening of the wire mesh 3. Blow flow to 10 side.

In this process, the charge amount measured by the electrometer 9 connected to the Faraday cage body 1 increases with the blowing of the compressed gas from the compressed gas blowing port 2, and after 3 seconds, the charge inside the Faraday cage body 1 is increased. All of the toner powder 5 was blown off and the measured charge amount was saturated. When the weight of the Faraday cage with the sample (toner / carrier mixture) filled was measured before and after the measurement of the triboelectric charge, the difference in weight 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, no toner adhered to the lower end of the Faraday cage main body 1 and the lower surface of the wire mesh 3 after the measurement of the triboelectric charge amount, and it was found that the effect of removing the sample powder 5 was 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 (not provided with a mechanism for generating a vortex flow along the lower surface of the wire mesh). In this case, it took not less than 20 seconds for the charge amount to reach saturation, and the saturation charge amount was also about 1.5 times the value in the example. This difference in the amount of charge is due to the frictional charge due to the repeated contact and separation with the carrier several times before all the toner in the Faraday cage body is blown out of the Faraday cage body through the mesh of the wire mesh. You can say that.

FIGS. 3 and 4 show a comparison between measurement examples using the frictional charge measuring device shown in FIG. 1 and a conventional frictional charge measuring device. FIG. 3 shows the relationship between the measurement time and the measured value when the triboelectric charge amount was measured using a positively charged toner (styrene-acrylic high-hardness toner) as a sample powder. a shows the case of the conventional measuring device. FIG. 4 shows the relationship between the measurement time and the measured value when the triboelectric charge amount was measured using a negatively charged toner (a polyester-based toner containing a silica-based external additive) as a sample powder. And the curve b shows the case of the conventional measuring device.

As can be seen from the comparison of the characteristics shown in FIGS. 3 and 4 , in the case of the triboelectric charge measuring device of the present invention,
In addition, the amount of triboelectric charge can be accurately measured.

Further, in the measurement of the amount of triboelectric charging, the weight loss of the sample before and after the measurement is larger than the amount of the sample powder, which indicates that the carrier surface is worn on the wire mesh surface by the blowing operation. Furthermore, after the measurement, a small amount of toner was reattached to the lower end of the Faraday cage body, and it was confirmed that it was difficult to completely remove the sample powder. It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. For example, the gas inflow path for inflow or supply to generate a vortex along the surface of the wire mesh may be a hole type or a nozzle type in addition to a groove type (gap).

[0030]

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) The sample powder separated in the Faraday cage body and the contact partner powder electrostatically attract each other and unite again to repeat contact and separation. A so-called Faraday cage body is a kind of friction charger. The triboelectric charge can be measured quickly and accurately.

(2) Selective removal efficiency of sample powder is high,
Further, even in the blow-off operation, the frictional charge between the sample powder and the inner wall of the Faraday cage body and the frictional charge between the sample powder and the wire mesh can be suppressed to a very small amount, so that an accurate amount of frictional charge can be measured.

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

(4) There is no error in the measured charge amount due to the occurrence of abrasion of the contact partner powder or the wire mesh on the wire mesh surface or the generation of the charge amount due to the abrasion. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a main part 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 frictional charge amount measuring device of FIG. 1;

FIG. 3 is a characteristic diagram showing a measurement characteristic of a triboelectric charge amount of a positively charged toner by the triboelectric charge amount measuring device of the embodiment in comparison with a case of using a conventional triboelectric charge amount measuring device.

FIG. 4 is a characteristic diagram showing measurement characteristics of a triboelectric charge amount of a negatively charged toner by the triboelectric charge amount measurement device of the embodiment, in comparison with a case of using a conventional triboelectric charge amount measurement device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Faraday cage main body 2 ... Compressed gas blowing port (nozzle) 3 ... Wire mesh 4 ... Attachment 5 ... Sample powder (small particle size) 6 ... Contact partner powder (large particle size) 7 ... ... Gas inflow means 8 ... Condenser 9 ... Electometer 10 ... Suction unit 11 ... Spacer 12 ... Suction path 13 ... Swirl

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-214454 (JP, A) JP-A-3-105265 (JP, A) JP-A-52-84779 (JP, A) 68048 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 27/60 G01R 29/24

Claims (1)

(57) [Claims] 1. A cylindrical Faraday cage body made of a conductive metal, having a compressed gas blowing port at one end, and having an inner diameter increasing from the one end to the other end side, and attached to the other end of the Faraday cage body. Depending on the tool
Removably be stretched-mounted, and a wire mesh passing the sample powder in blowing the compressed gas out of the Faraday cage sample powder and the contact partner powder housed in the body, the fixture, the spacer Through close contact
A suction unit mounted thereon ; and a charge amount measuring unit for a contact partner powder remaining in the Faraday cage body , wherein the spacer or the attachment or the suction unit is provided.
The end face that comes into contact with the spacer of
To create a vortex in the outer circumferential direction of the suction path of the sample powder
An apparatus for measuring a triboelectric charge amount of a powder, wherein a body inflow groove is formed .