JPS60467A - Developing device - Google Patents

Abstract

PURPOSE:To detect exactly a toner density by providing an auxiliary magnetic pole of the opposite polarity between the same pole opposed parts, respectively, and placing a toner density detecting member in the vicinity of this auxiliary magnetic pole. CONSTITUTION:When a nonmagnetic sleeve 4 is rotated in the direction as indicated with an arrow X, a developer 2 adsorbed onto the sleeve is carried toward a developing gap D from a doctor gap (d). In the vicinity of the developing gap D, the surface of a photosensitive drum 1 is slid and rubbed by a magnetic brush formed by the developer 2, and an electrostatic latent image formed on the drum 1 is developed. When the developer 2 which has passed through the developing gap D reaches the same pole opposed part, it is scraped down from the nonmagnetic sleeve 4 and collected into a developer tank 3. The collected developer 3 is stirred and mixed by an impeller 9 together with a toner 2a discharged from a toner tank 10 by a rotation of a toner feed roll 13, and thereafter, attracted onto the nonmagnetic sleeve 4 again and used for a development.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a developing device that converts an electrostatic charge image formed on the surface of an image carrier into a head image using a magnetic brush method.

[Prior Art J In image forming devices such as electrophotographic devices and electrostatic recording devices, η
In this method, an electrostatic latent image is formed on the surface of an image carrier (selenium photoreceptor, zinc oxide photoreceptor, organic photoconductor, dielectric material, etc.), and the electrostatic latent image is developed using a magnetic developer using a magnetic brush method. Develop,
Then, the image is fixed, covered, or the developed image is transferred onto a transfer sheet such as plain paper and then fixed to obtain the final image.

As the magnetic developer used in the magnetic brush method, a two-component developer which is a mixture of a ferromagnetic developer and toner particles is often used. This magnetic carrier is made of iron powder, ferrite powder, nickel powder, etc., or their surfaces are coated with E11 polymer, and the toner particles are made of resin in which additives such as color pigments and dyes are dispersed. The monthly charge is selected so that the primary particles and the toner particles are triboelectrically charged to opposite polarities due to their mixing.

When the above-mentioned two-component developer is used to perform electrostatic latent development, toner particles are consumed during development, so as development is repeated, the degree of dovetailing in the developer decreases. toner 111
If development is performed while the degree of ink is lowered, the image density will be lowered.

Therefore, when using a two-component developer, in order to maintain the toner concentration in the developer at a predetermined level (approximately 3 to 10%), a means for detecting the toner concentration is installed, and a signal from the detection unit is installed. Generally, a developing device is configured to replenish toner according to the amount of toner. Toner concentration detection methods often utilize the fact that the toner concentration in the developer changes and the magnetic permeability of the developer changes. For example, a Hall element is installed in the magnetic field of a permanent magnet member (). It has also been proposed to use a detection layer to detect magnetic flux leaking from the developer (see Japanese Patent Laid-Open No. 117047/1983), but Hall elements have high detection accuracy but are susceptible to temperature changes and have reliability problems. be.

Therefore, normally the developer forms part of the magnetic circuit of the detection coil, and the change in inductance of the detection coil is 1
〜Na concentration is often detected. (For example, JP-A-53
(Refer to No. 49,137 and No. 54-159233) Furthermore, in a developing device using a two-component developer, it is necessary to replenish the developer after development and mix it with the LC toner. In order to scrape off the developer after development from the non-magnetic sleeve, a permanent magnet member inside the non-magnetic sleeve is often provided with like-polarity opposing parts.

(For example, Jikko 51-19884@, Jikko 53-35
(Refer to Japanese Patent Publication No. 479, Japanese Patent Publication No. 56-47552, etc.) In a developing device having a permanent magnet member provided with like-polarity opposing parts, it is necessary to prevent the toner concentration detection member from being affected by the magnetic flux generated from the permanent magnet member. In order to achieve this, the concentration detecting member is installed between the same-polarity opposing parts. (For example, JP-A-52-124339, JP-A-52-12724i
(Refer to Publications No. 53-126944 and No. 54-76165.) However, if the toner concentration detection member is provided at such a position, the developer scraped off from the non-magnetic sleeve will not reach the toner concentration detection member. There was a problem in that the particles remained between the magnetic sleeve and the non-magnetic sleeve, reducing detection accuracy.

[Objective] The object of the present invention is to solve the problems of the prior art described above,
It is an object of the present invention to provide a developing device that can accurately detect toner once.

[Summary] The developing device of the present invention includes a non-magnetic sleeve that holds a bamboo carrier and a developer containing toner particles in F4, and a pair of scales that are fixedly disposed inside the non-magnetic sleeve and form opposing parts. a permanent magnet member having a plurality of magnetic poles including a magnetic pole;
In the developing device equipped with a toner concentration detecting member for detecting the toner concentration of the developer that has been oxidized, an auxiliary magnetic pole of opposite polarity is provided between the same-polarity opposing portions, and the auxiliary magnetic pole is provided in the vicinity of the auxiliary magnetic pole. It is characterized by the arrangement of a toner m degree detection section.

[Example] The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a sectional view showing one embodiment of the developing device of the present invention, FIG. 2 is a view taken along the line A-A in FIG. FIG. 4 is a diagram showing the output waveform of the circuit of FIG. 3.

First, in Figure 1, the magnetic force l! A developer 2 consisting of toner and toner is stored in a developer tank 3, and inside the developer tank 3, a cylindrical non-magnetic sleeve 4 is disposed opposite the photosensitive drum 1 rotating in the direction of arrow Z in the figure. It is arranged so that it can rotate freely. There are a plurality of non-magnetic sleeves (4 in the figure) on the surface of the non-magnetic sleeve 4.
A permanent magnet member 7, which is formed by fixing a permanent magnet 5 having 100 magnetic poles to a shaft 6, is fixedly disposed. Among the magnetic poles, the N pole is a developing magnetic pole located at a position facing the developing gap D;
The Sl and S2 poles are scraped magnetic poles forming the same polar opposite parts, n
The poles each represent an auxiliary magnetic pole provided between S+ and -82. Concentration detection members 8 are installed near the auxiliary l&ff1n. An impeller 9 is rotatably installed on the side of the toner concentration detection member 8, and a toner tank 10 containing toner 2a is arranged above the developer tank 3. At the lower opening of the toner 4W10, there is a toner supply roll 13 formed by fixing a porous elastic layer 12 around a shaft 11.
is rotatable. Further, a doctor member 14 is installed in the developer tank 3 to regulate the thickness of the developer in the non-magnetic sleeve 4.

The operation of the above-mentioned developing device can be explained as follows.

First, when the non-magnetic sleeve 4 is rotated in the direction of the arrow Xlj shown in the figure, the developer 2 adsorbed onto the sleeve is conveyed from the doctor gap d toward the development gap D. Near the developing gear D, a magnetic brush formed by the developer 2 rubs the surface of the photosensitive drum 1 to develop an electrostatic latent image (not shown) formed on the drum. After passing through the development gap D, the developer 3 reaches the same-polarity facing portion, is scraped off from the non-magnetic sleeve 4 by the repulsive magnetic field, and is collected into the developer tank 3.

Next, the collected developer 3 is stirred and mixed by the impeller 9 with the 1 and 2a discharged from the tank 10 by the rotation of the toner replenishing roll 3, and then again into the non-magnetic sleeve. When the developer 2 is sucked onto the sleeve 4 for development and is scraped off from the non-magnetic sleeve 4, the toner concentration in the developer is detected by the toner -15 degree detection member 8, and the detected toner concentration is detected. Accordingly, an external signal is output, and the rotation of the toner supply roll 13 is controlled by a drive means (not shown).

In this case, the auxiliary magnetic pole n
, the toner is conveyed along the non-magnetic sleeve 4 to the detection section of the degree detection member 8 . Since the density of magnetic powder in the transported developer changes depending on the toner concentration, the toner concentration can be detected by the toner concentration detection member.

The auxiliary [n plays the role of stably transporting the developer to the detection unit. On the other hand, if there is no auxiliary magnetic pole n, the conveyance force acting on the developer between the same poles is very weak, making the flow of the developer unstable, making detection difficult due to the accuracy of toner concentration. .

In addition, even if the auxiliary magnetic pole is too strong, it will not be able to scrape off enough, and if it is too weak, it will not be effective. 11
A range of 5 to 2/3 is appropriate. Also, the auxiliary magnet 11i (1
1>, as shown in FIG. 2, if it is the same as the length Ω of the magnetic tri(S, S) forming the homopolar opposing portion, the scraping effect will be hindered, so the length of the toner concentration detection member 8 is It is necessary to have a length approximately equal to the length Ω1 of the detection portion 8a.

Next, although various structures are known for the toner concentration detection member 8 that utilizes changes in the inductance of a detection coil, the one shown in FIG. 2 is suitable.

In the figure, the iron-shaped magnetic core 15a has a primary coil Le.
Similarly, the primary coil L+b and the secondary coil L2b are wound around the magnetic core 15b, forming two transformers. The secondary coils Lea and L+b are connected to the output terminal (not shown) of the oscillator 16, and the secondary coils L2a and L2b are connected to the signal input terminal (not shown) of the phase comparator 17, and Comparison signal detection coils LR+ and LR2 are wound around the secondary side of each transformer, and these are connected to a comparison signal input terminal of the phase comparator 17.

The output terminal (not shown) of the phase comparator 17 is connected to the input terminal (not shown) of the potential comparator 18, where it is compared with a reference voltage corresponding to a predetermined toner concentration, and a signal corresponding to the potential difference is generated. Output. The potential comparator 18 is connected to a load (drive source such as a motor) 20 via a drive circuit 19.

According to the above circuit configuration, when the oscillation output from the oscillator is applied to each of the secondary coils L+aa and 1-1b, an output signal corresponding to the degree of coupling of each magnetic circuit is transmitted to the secondary coils 1-2a and L2. b.

Here, when the degrees of coupling of both magnetic circuits are equal, the outputs of the secondary coils L2a and L2b are in opposite phases, so they cancel each other out, and the operating output thereof becomes zero. However, if the degrees of coupling between the two magnetic circuits are different, the output of one of the secondary coils L2b becomes larger and a differential output is generated according to the difference in the degrees of coupling, so the differential output The phase comparator 18
is compared with a reference value, and a phase detection output corresponding to the phase is output.

J, that is, when the tonneau temperature is equal to the set value, the phase detection output is 0 (see Figure 4 (a) > 4iQE
By adjusting the voltage 1F, when the donor concentration changes and the magnetic permeability of the developer changes, a phase detection output (see Figure 4 (b)) corresponding to the change in magnetic permeability is output.゛It's fine.

a3 In this 1 to 1 concentration detection section H, for example,
Using a screw core made of magnetic material such as soft ferrite,
If this is installed on the reference magnetic circuit side, sensitivity adjustment becomes possible.

As mentioned above, according to this 1-boo iF1 degree detection part shrine, the output signals of the two magnetic circuits are compared to detect the 11-na1 concentration, so it is not affected by changes in temperature and humidity 4T or any environmental conditions. Virtually unaffected and highly reliable detection of toner concentration is now possible.

Specific example] Fig. 1 - C1 photoreceptor drum 1 and Se drum (
A stainless steel cylinder with an outer diameter of 32 mm was used as the non-magnetic sleeve 4, and a [3a-ferrite magnet with an outer diameter of 29.3 mm] was used as the permanent magnet 5. In addition, in the permanent magnet 5, the magnetic flux density on the sleeve is set to 850Q for the N pole and 650G for the 3 poles.However, the length of the magnetic poles is 270n+m), and n tri is 200
G, the magnetic pole length is 40 mm, and the angle between 11 poles is 01-7
5°, e2 = 90', e3 = 60'. I
The l agent is an iron powder carrier with a particle size of 100 to 200 μm (Japan-Korea Ippon Iron Powder @ EF V 200/300) and a particle size of 5 to 200 μm.
2011m 1-ner particles were used.

Then, the developing gear V knob D and the doctor gear I7 knob d were set to 4.0 mm and 4.5 mm, respectively, and the non-moxibustion speed test was performed. As a result, the number of sheets from 711 and the density from 1 to Na1 (reading value of the detection member) was as shown by curve C1 in FIG. 5, and an extremely good result was obtained.

Further, when the n-pole was changed to 135G and 410G and the same experiment as above was carried out at a temperature of 135°C, the same results as above were obtained.

[Comparative Example] First, as a result of conducting an experiment on the same strip 1'1 as in the specific example except that the n-pole was not provided, the concentration of 1-ner was as shown in the curve 0 in FIG.
As shown at 2°C, the toner density decreased in proportion to the number of sheets.

Next, the specific example and FBI except that ntifi was set to 50Q
As a result of conducting an experiment with an N pole, the toner concentration showed the same tendency as described above, and no effect of the N pole was observed.

Further, in a specific example, when the length of the n-pole exceeds 15 On+m, the scraping effect at the same-pole opposing portion is weakened, and the developer accumulates at the same-pole opposing portion.

[Effect 1] As described above, according to the present invention, it is possible to accurately and stably detect the toner concentration in the developer.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment of the developing device of the present invention, FIG. This figure shows the output waveform of the circuit of FIG. 3, and FIG. 5 shows the relationship between 1 to 1'fA and the number of copies. 1: Photosensitive drum, 2: Developer, 4: Nonmagnetic sleeve,
7: Permanent magnet member, 8: Toner 111 degree detection member
Figure A Figure 2 Figure 3 Figure 4 Figure 5 Number of Copies Procedural Amendment Document Indication of Visit Incident 1982 Patent Application No. 109057 Title of the Invention
Date of the order to correct the developing device: September 27, 1982 (shipment date) Drawings subject to correction.

Claims (1)

[Claims] 1. A non-magnetic sleeve that holds and covers a developer containing magnetic carrier particles and 1-boo particles, and two same-polarity opposing portions fixed inside the non-magnetic sleeve and arranged in a C-position. In a developing device including a permanent magnet part having a plurality of magnetic poles including a magnetic pole, and a toner concentration detection member for detecting toner I'1 degree of the developer conveyed on the non-magnetic sleeve, An auxiliary magnetic pole of opposite polarity is provided between the opposing parts, and the dove-a degree detection part 4A is arranged close to the auxiliary magnetic pole.
2. The developing device according to claim 1, wherein the auxiliary magnetic pole has a length corresponding to the length of the detecting section of the toner concentration detecting member. , the developing device according to claim 1, wherein the strength of the auxiliary magnetic pole is 115 to 2/3 of the strength of the magnetic pole forming the same-polar facing portion.