JPS5952424B2 - Toner charge amount measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring the amount of toner charge in a magnetic brush development method used in electrophotography, electrostatic recording, etc.
In particular, it relates to a simple and highly accurate measuring device that uses a magnet to hold developer.

In an electrophotographic or electrostatic recording process, there is a development step in which a developer is applied to the charge image formed on the medium in order to visualize the charge image.

This developing step is an extremely important process that determines image quality. In this developing process, the amount of toner charge in the developer is the most fundamental parameter and has a large effect on image quality. For this reason, it is required to accurately measure the amount of toner charge in the development, design, and maintenance of Ibaranao. To measure the amount of toner charge in a developer in a conventional magnetic brush development system, a blow-off method is generally used in which the toner and carrier constituting the developer are separated by blowing high-pressure air or gas.

As shown in FIG. 1, a predetermined amount of developer is poured into a metal mesh 2 fixed to a metal case 1, and high-pressure air 3 is blown in as shown by arrow A. By flying as shown by arrow B, measurement is performed using a capacitor C and an electrometer V connected in parallel to the metal case 1. FIG. 2 is a diagram illustrating the composition of the toner 5 and carrier as a developer.
Toner 5 is attracted onto carrier 4 by electrostatic charge.

Therefore, in the initial state, the sum of the charges on the carrier 4 and toner 5 is zero, but by blowing high-pressure air 3,
Since the toner 5 is separated from the carrier 4, assuming that the charge Q of the toner 5 disappears, "-Q" is created in the mesh 2.
electric charge is generated. This charge Q is determined by measuring the voltage V applied to the capacitor C. However, with this method, the measured values vary greatly depending on the material of the mesh 2, the fineness of the mesh, the pressure of the high-pressure air, the shape of the blowing nozzle, etc. This is mainly because when the toner 5 is blown into the mesh 2, it collides with the mesh 2 and is triboelectrically charged. Therefore, the present inventor has proposed a method shown in FIG. 3j that performs separation without using mesh 2.

This method involves depositing a predetermined amount of developer 7 on the surface of magnet 6,
Blow high pressure air 3 in the direction of arrow A. The carrier 4 is firmly attached to the magnet 6 by magnetic force, so it does not fly away, but the toner 5 is weakly attached to the carrier 4 by electrostatic force, so it can be easily blown away by the high-pressure air 3 as shown by arrow B. I can do it. Therefore, the amount of charge can be determined by the same method as explained in FIG.

In addition, the SW in the potential measurement circuit is set to 0N-0FF before measurement.
The capacitor C is provided to remove the electric charge stored in the capacitor C. In this method, when the pressure of the gas 3 to be blown increases, the brush-shaped developer (magnetic brush) 7 as shown in FIG. In extreme cases, the fourth
As shown in Figure C, it may fly off and attach to other poles. Also, since the developer is waving, high-pressure gas wind 3 reaches the inside of the magnetic brush 7.
Furthermore, since the developer adhered to the other electrode is not naturally blown by air, the carrier 4 and toner 5 are not separated, resulting in a decrease in measurement accuracy. SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus that solves the above-mentioned problems by forming a magnet in a shape that prevents developer from fluttering due to high-pressure gas wind.

A feature of the present invention is that a magnet is used as the developer holding means, and the central part of the magnet on the side that holds the developer is made higher than the peripheral part, thereby achieving the above object.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 5 shows one of the magnets of the toner charge amount measuring device according to the present invention.
A showing the embodiment is a plan view, and the mouth is a front view. In the figure, the magnet 8 that holds the developer has a two-stage shape with a high central portion, and the sample developer 9 is attached to the high inner magnet surface.

The magnetic lines of force of the flat magnet 6 as shown in Figure 6A form loops at the upper and lower magnetic pole faces, so the magnet line 10 bounces at the end of the magnet 6 (at the face), but at the center as shown at the opening in Figure 6. In the case of a magnet 8 with a raised part, the same magnetic poles are adjacent to each other, for example, N.
N, the lines of magnetic force 1' at the upper end repel each other and tend to stand vertically.

When high-pressure gas is blown onto the magnetic brush formed by attaching the sample developer to the magnets 6 and 8, the developer tends to stick along the lines of magnetic force at the flat end of the magnet 6 as shown in FIG. 6
At the upper end of the magnet 8, where the center of the drawing opening is one step higher, a force is applied to the developer to hold it perpendicularly along the direction of the magnetic lines of force, so the developer does not flutter and protrude beyond the magnet sample surface.
Furthermore, even if the developer were to scatter, it would adhere to the lower outer magnet surface and would not flow around to other poles, so it would not pose a problem during measurement. Furthermore, a specific example is shown in FIG. In the figure, the magnetic sample stage 8 has an outer diameter of Al7m.
m
It was made as a permanent magnet with a surface magnetic flux density of 1000 Gauss and a size of mm x height F5 mm, and a developer of 100 g was applied to the magnet surface N.
~200 mg was deposited, and measurements were taken by blowing a high-pressure gas (N2) wind of 1.5 kg/Cnl2 from a distance of 5 cm above the center of the magnet.

As a result of repeated measurements more than 10 times, the accuracy improved from about ±5% using the conventional flat magnet method to about ±3%.

Note that although the magnetic sample stage has been described in the above embodiments as having a cylindrical shape, it is not limited to a cylindrical shape, and the magnetic sample stage has a cylindrical shape.
．． S is also not specified. The present invention has been explained above with reference to the embodiments. According to the present invention, a simple method is employed in which a magnet is used as the developer holding means, and the central part of the magnet on the side that holds the developer is made higher than the peripheral part. Therefore, the effect of providing a highly accurate developer toner charge amount measuring device is significant.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining a conventional toner charge amount measuring device, FIG. 2 is a cross-sectional view for explaining the structure of a developer, and FIGS. 3 and 4 are another conventional toner charge amount measuring device. FIGS. 5 to 7 are cross-sectional views for explaining the toner charge amount measuring device according to the present invention. In the figures, 6 and 8 are magnets, and 9 is a developer.

Claims (1)

[Claims] 1 means for holding a developer containing toner and carrier; a means for blowing a high-pressure gas flow onto the developer from a direction other than perpendicular to the developer holding surface of the developer holding means; A toner charge amount measuring device equipped with a charge detection circuit for measuring the amount of toner, wherein a magnet is used as the holding means, and the center portion of the magnet on the developer holding side is made higher than the peripheral portion. Electric charge measuring device.