JPH02147963A - Method for measuring electric field intensity distribution of development area in magnetic brush developing method - Google Patents

Abstract

PURPOSE:To obtain good images by a method wherein capacitance of each measurement electrode is calculated from respective waveforms of applied voltage from ac power source and current flowing to electrode to be measured, and electric field intensity in development width is obtained from this capacitance distribution. CONSTITUTION:AC voltage is applied between an electrode 3 to be measured and a sleeve 1, and while developer is carried with the sleeve 1 rotated, a waveform of applied voltage from ac power source and a waveform of current flowing into the electrode 3 to be measured are obtained for each position of the electrode 3 to be measured by an oscilloscope 5. Then, capacitance C of the developer is calculated by equation I. Dielectric constant epsilons is calculated from this capacitance C with an equation II, and electric field intensity E is further calculated with an equation III. This enables measurement of electric field intensity distribution in a developing area and good images to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for measuring electric field intensity distribution in a developing area in a magnetic brush developing method employed in electrophotography.

(Prior Art) In electrostatic photographic devices such as copiers, a magnetic brush development method is generally employed as a means for developing an electrostatic latent image of an original image formed on a photoreceptor drum. .

This magnetic brush development method uses a one-component or two-component magnetic developer to form a developer magnetic brush on a developer conveying sleeve, and causes this magnetic brush to rub against a photoreceptor drum. This is done by attaching toner to the electrostatic latent image using electrostatic attraction.

Therefore, measuring the electric field strength distribution in the area where the magnetic brush contacts the photoreceptor drum, that is, the developing area, has extremely important significance in analyzing the obtained image. The law is still unknown.

It is therefore an object of the present invention to provide a method for measuring the electric field strength distribution in the development zone.

(Means for Solving the Problems) According to the present invention, a rotatable drum having a linear measuring electrode surrounded by a wide ground electrode on its circumferential surface is disposed near the developer conveying sleeve. , applying an alternating current voltage between the sleeve and the measurement electrode, supplying developer onto the sleeve to form a magnetic brush, and transporting the developer so that the magnetic brush rubs against the drum surface. At the same time, the capacitance at each position of the measurement electrode is calculated from the applied voltage from the AC power supply and the waveform of the current flowing through the measurement electrode, and the electrolytic strength within the development width is determined from the distribution of this capacitance. A method of characterizing is provided.

(Function) As is clear from FIG. 1 showing the electric circuit diagram of the measuring device used to suitably carry out the measuring method of the present invention,
The present invention recognizes that the developer Fl (magnetic brush layer) interposed between the photoreceptor drum surface and the developer conveying sleeve during development is electrically equivalent to a parallel circuit of a resistor R and a capacitor C. As a precondition, the electric field strength distribution is calculated from the change in capacitance.

This change in the electrostatic organ quantity is calculated from each waveform of the applied voltage from the AC power source and the current flowing through the measurement electrode.

(Preferred Embodiment of the Invention) In FIG. 2, which briefly shows the overall structure of an apparatus for suitably carrying out the measuring method of the present invention, this apparatus generally consists of a developer withdrawal sleeve 1. It consists of an insulating cylindrical body 2 placed near the.

The insulating cylindrical body 2 corresponds to the photosensitive drum,
It is provided with a measuring electrode 3 extending in the axial direction of its circumferential surface.

Further, as is clear from FIG. 3, which is a perspective view of this cylinder 2, the measuring electrode 8i3 is provided so as to be sandwiched between the wide ground electrodes 4.4.

That is, current flows into the measurement electrode 3 only from the surface of the sleeve 1 that is closest to the electrode 3, and all current from the surrounding area flows into the ground electrode 4.4. This makes it possible to accurately measure the distribution of electric field strength.

The distance between the measurement electrode 3 and the earth electrode 4 is 0.1 to 1
It is set in the range of ma+.

The width d of the measuring electrode 3 is preferably in the range of 1.1 to 0.5 tmm, and the width of the ground electrode 4 is 5 tmm.
It is preferable that the thickness is not less than mm.

The distance 1sI between the insulating cylindrical body 2 and the sleeve 1 is set to about 1 to 2 mm, as in a normal copying machine.

In the present invention, the measuring electrode 3 is fixed in position near the sleeve 1 (development area), and is connected to an AC power source 7 via an oscilloscope 5, so that an AC power source 7 is connected between the electrode 3 and the sleeve 1. Voltage can be applied.

The developer conveying sleeve 1 has a structure 9 that is exactly the same as that used in ordinary electrophotographic devices, for example,
A magnet (not shown) is built inside, and as the sleeve rotates, the developer supplied onto the sleeve 1 is conveyed to the gap 10 between the sleeve 2 and the cylindrical body 2 (ie, the developing area).

Calculation of capacitance distribution According to the present invention, the above measurement device is used, and the measurement electrode 3 is
While rotating the sleeve 1 and transporting the developer, the oscilloscope 5 measures the waveform of the voltage applied from the AC power supply and the measurement at each position of the measurement electrode 3. The waveform of the current flowing into the electrode 3 is obtained.

An example of this waveform is shown in FIG.

As is clear from FIG. 4, when the applied voltage is X and the measured current is y, the following equation is given.

X x V QCosωt ■1+1+e1++18
■y=I6cos(ct+t+ψ) + E/R---
----■ In the formula, E is a DC electromotive force that is thought to be generated due to friction of the developer, ω is the angular frequency, and R is the resistance value of the developer.

Here, the electrostatic capacitance C of the developer (corresponding to the capacitor in FIG. 1) is expressed by the following equation.

In the formula, V is the applied voltage, ω is the angular frequency, 11 is the current value (direct) when voltage V=O (excluding flow), See Figure 5, which shows a partially enlarged view of Figure 4. Light.

That is, from the waveform shown in FIG. 4, the capacitance C is calculated using equation 0.

In the present invention, the specific electrostatic rate ε3 is determined from the capacitance C calculated as described above, and the electric field strength E is calculated from this.

That is, C;ε. ε3− ・・・・・・・・・・・・・・・
■In the formula, ε0 is the vacuum permittivity (8,85x 10-”F/
m), S is the area of the measuring electrode (@2), and d is the effective distance between the measuring electrode and the sleeve (see Figure 2). From this, 65 is calculated, and further, from the following formula, the electric field is The intensity is calculated.

As is clear from Fig. 2, the effective distance lid is calculated by the following formula, (R+D+r-Rcosθ)2" (R51nθ)2=
(d+r)” .....■ holds true, so the effective distance d can be found from the formula 0.

Thus, according to the present invention, the electric field intensity distribution can be obtained by measuring the oscilloscope waveform at each measurement electrode position (represented by θ in FIG. 2) and determining the electric field intensity from each of the above equations.

(Effects of the Invention) According to the present invention, it is possible to measure the electric field strength distribution in the development area, which has extremely important significance in setting development conditions for obtaining a good image.

(Example) Using a Sanda Kogyo copying machine (DC-112C), the capacitance distribution within the development width (-10'≦θ≦+10'') was measured.

Dumped blood Ezu beans cut: 1. Omm Drum-sleeve pressure 1!1: 1.1mo+sleeve: Main pole position +3.5゛Main pole 800 Gauss φ 38++ui Sleeve peripheral speed 400mm/sec Developer: Two-component developer ferrite carrier, center particle diameter 80μm resistance 10'Ω
cm Toner, negatively charged toner with an average particle diameter of 11 μm The toner concentration is such that the specific surface area ratio of carrier and toner is 1=1
It was set so that

Measuring electrode, length 28 mm Width 0.5 m + n Earth electrode, length 28 ma + width 10 mm Distance between earth electrode and measuring electrode 0.5 ff 1 m From this capacitance distribution, the specific electric rate (ε8) and the electric field are calculated from the above formulas. The distribution of intensity (E) was calculated.

The results are shown in Table 1.

Table 1

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram of a measuring device used to suitably implement the measuring method of the present invention, FIG. 2 is a diagram briefly showing the overall structure of the measuring device used in the present invention, and FIG. , FIG. 4 is a diagram showing an oscilloscope waveform, and FIG. 5 is a partially enlarged view of the oscilloscope waveform in FIG. 4.

Claims (1)

[Claims] (1) A rotatable drum equipped with a linear measuring electrode surrounded by a wide ground electrode on its circumferential surface is placed near the developer conveying sleeve, and an AC voltage is applied between the sleeve and the measuring electrode. The developer is supplied onto the sleeve to form a magnetic brush, and the developer is transported so that the magnetic brush rubs against the drum surface. A method characterized by calculating the capacitance for each position of the measuring electrode from each waveform of the flowing current, and determining the electrolytic strength within the development width from the distribution of this capacitance.