JPS6218578A - Developing device - Google Patents

Abstract

PURPOSE:To compact a developing device free of carrier attachment by installing two magnetic poles such as a main one and another one at the downstream of the main magnetic pole and specifying a center angle including two magnetic poles. CONSTITUTION:A magnet roll 30 is fixed and is formed integrally with a main magnet N1 having an N pole at the outside of an aluminum roll 31 and a sub- magnet having magnetic poles S3, S2, N2 and S1 at outward the downstream. The main magnetic pole N1 faces a photosensitive body at a magnet angle of +5 deg. (at upstream), and is located at a position where theta(S3-N1), the theta(S2-S3) of a repulsion magnetic field part, theta(N2-S2), theta(S1-N2) and theta(N1-S1) are 70 deg., 80 deg., 60 deg., 70 deg. and 80 deg., respectively. Said angle position is optimum, compared with that in the case where a crest regulating member 40 is moved and installed. Even if a clearance Hcut between the crest regulating member 40 and a developing sleeve 20 is changed to 0.4-0.7mm, a developer can be conveyed at an excellent developer density.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to electrophotography, electrostatic recording, etc., in which an electrostatic latent image formed on an image forming body is visualized using a developer. This invention relates to improvements in developing devices.

[Conventional technology]

Conventionally, one-component developers containing magnetic materials1. Alternatively, as a developing device using a two-component developer that uses a mixture of toner and a magnetic carrier, for example, a magnetic brush developing device as shown in FIG. 7 is used. In the figure, 1 is an image forming body that rotates in the direction of the arrow, for example, ZnO1S.
2 is a developing sleeve made of a non-magnetic cylindrical body which rotates in the direction of the arrow to transfer the developer to the developing area E.
While being conveyed to the developing sleeve 2, it is adhered to the developing sleeve 2 and forms spikes. Reference numeral 4 denotes a spike regulating member provided on the upstream side of the development area E, which regulates the thickness of the developer layer so that the electrostatic latent image is developed under the best condition.

Reference numeral 5 denotes a bias power supply applied to the developing sleeve 2, such as a DC bias to prevent toner scattering, developing fog, etc.
6 is a protective resistance.

In this magnetic brush developing device, there are two types: one is to fix the magnet roll 3 and rotate the developing sleeve 2 to perform development, and the other is to rotate the magnet roll 3 as well to perform development. The magnetic flux density and magnetic field distribution of the magnetic pole required for developer conveyance and the magnetic flux density and magnetic field distribution of the magnetic pole required for good development in the development area are generally different, and the magnetic roll rotating type is different from the fixed type. Compared to this, there are disadvantages such as a complicated drive mechanism, etc. Therefore, from this point of view, a magnet roll fixing system in which magnets with different magnetic forces are arranged is advantageous.

Regarding the direction of rotation of the developing sleeve, there are two methods in which development is performed while the rotating image forming body surface and the rotating developing sleeve surface rotate in the same direction (forward direction) in the developing area, and one method in which development is performed while rotating in the opposite direction. There is a method. However, when developing by rotating in the opposite direction, the density tends to decrease at the leading edge of the image (especially the leading edge of the solid area), and it is difficult to transport the developer stably in the developing area (it tends to stagnate on the developing side). Development is often performed by forward rotation.

[Problem that the invention seeks to solve]

Generally, the developing sleeve 2 has an outer diameter of about 40 to 50 mm, and the magnet roll 3 has about 6 to 10 poles. However, in recent years, in the copying machine industry, there has been a desire for a more compact, low-cost, and easy-to-use popular machine. The present invention is an improved developing device that is incorporated into a copying machine, etc., and contributes to making the copying machine more compact and reducing costs.The developing sleeve has a small diameter and has excellent conveyance of developer to the developing area. It is an object of the present invention to provide a developing device in which good copy images can be formed by sufficiently replacing old and new developers.

[Means for solving problems]

The above object has a five-pole fixed magnet body including a main magnetic pole 3 facing a rotating photoconductor, and a small diameter developing sleeve that rotates the outer periphery of the magnet body in a forward direction relative to the surface of the photoconductor to form a developer flow. A developing device characterized in that two magnetic poles, a main magnetic pole and a different polarity, are provided on the downstream side of the main magnetic pole, and the central angle θ included in the two magnetic poles is in the range of d<θ<186'. This is achieved by

[Effect]

The present inventors conducted research on a developing device having a small-diameter developing sleeve with an outer diameter of 9 to 25 mff1. The small-diameter developing sleeve had the following problems.

(1) The developer conveyance length, that is, the outer circumferential length of the developing sleeve is short.

(2) The width of the main magnet facing the image forming body in the development area, that is, the width of the spiked portion cannot be made wide.

(3) In the developing area, the gap suddenly widens from the shortest gap position between the image forming member and the developing sleeve.

Regarding (1), it was concluded that the magnet roll does not necessarily need a large number of magnetic poles, such as 6 to 8 poles, and that a 3 to 5 pole magnet roll is appropriate.

(a) FIG. 3 is a graph showing the relationship between the developing sleeve diameter and developability. The magnet roll was set to 5 poles, and the developing sleeve diameter was set to 9, 15, 20, 25, and 30 m under the same conditions.
A comparative test was conducted on five types of m. As a result, when compared under the same rotational speed conditions, it was found that with 30 Dragon Φ, the developer transportability was lowered and the copy density was also lowered. That is, when reducing the diameter of the developing sleeve, it is possible to reduce the number of poles of the magnet roll;
As a pole, the outer diameter of the developing sleeve is 2511111 or less,
Preferably, by setting the length to 20 mm, sufficient developer transportability can be obtained.

(2) and (3) both require severe development conditions, so for development using a small diameter development sleeve,
Conducted many experiments. (For all data below, the outer diameter of the developing sleeve is 20 mm, and the magnetic roll has 5 poles.) (b) Figure 4 shows the relationship between the magnetic flux density of the main magnetic pole (■) facing the image forming body in the developing area and developability. The number of carriers attached to the image forming body during development was used as an index of developability. Even when the developing bias was changed, no significant difference was observed at 700 Gauss or higher. Although a significant difference was observed at 600 Gauss and S, it was within tolerance. 140 in the experiment
Tests have been conducted up to 0 Gauss, but there is no significant difference, and using a magnetic force higher than necessary will unnecessarily increase costs. The magnetic force measurement in the test of the present invention was carried out using a Gaussmeter (Gaussmeter 3251) manufactured by Yokogawa Hokushin Electric.
, Probe 3252-01), a probe having a Hall element as a sensor was provided at a position 2 mm apart from the surface of the developing sleeve, and the magnetic flux density was measured.

(C) Figure 5 shows the speed ratio (Vr/Vp) between the linear velocity (Vr) of the developing sleeve and the linear velocity (Vp) of the image forming body and the state of toner adhesion on the image forming body. , ■r/■p
〉3, it is in a saturated state. In this experiment, the image forming body and the developing sleeve were rotated in the same direction. The plurality of curves are 11 comparisons using different gears in the developing area and the ear cutting regulating plate portion.

In order to maintain the linear velocity of the outer circumference of the developing sleeve above a certain level with a small-diameter developing sleeve, it is necessary to increase the number of rotations of the developing sleeve. Providing a scraper (7 in FIG. 7 indicates a scraper) that comes into sliding contact with a small-diameter developing sleeve results in a large frictional resistance.

The present inventors developed a developing device as shown in Fig. 1, and without using a scraper to remove the developer from the developing area, provided magnetic poles of the same polarity adjacent to each other at the lower position, and repelled the developer between them. About peeling off the developer particles that have adhered to the periphery of the developing sleeve by a magnetic field and attaching new developer.
Several types of magnetic rolls were prototyped and examined. Figure 6 shows the magnet roll.The main magnetic pole N1 has a magnetic force of 750 gauss on the sleeve surface, and the auxiliary magnetic pole for conveyance has a magnetic force of 600 to 600 gauss.
It was set to 50 Gauss. In addition, the main magnetic pole N, and the downstream sub magnetic pole S
The included angle θ(S, -N+) with 3 is 70°, and the included angle θ(S, -N+) with 82 is 70°.
2-S3) was made as a prototype every 18 degrees over a range of 40° to 180°, and the prototype magnetic sleeve was replaced with the developing device shown in FIG. 1, and the installation was tested.

In the experiment, the exchange rate of the developer in the stirring tank with respect to the developer directly attached to the sleeve was measured for various magnetic sleeves, that is, the exchange rate of the developer. At the same time, we prepared a solid black original by binding the copy original, and conducted a test by making a copy of this original. If the replacement of old and new developer is insufficient, it is observed that the toner image on the transfer paper becomes whitish toward the rear edge.

The following table shows the included angle θ (s2-8.) of the repulsion magnetic field portion, the developer exchange rate at that time, and the results of the estimation of image density unevenness.

From the density unevenness in the above table, θ (S2 33) was required to be greater than the mark. However, the test was conducted with attention paid to the degree of developer filling in each case, and the test was conducted with the sub magnetic pole S2 buried in the developer in the stirring tank. Therefore θ(S
2-8. ) is 180 or more, the position of the sub-magnetic pole S2 will be located above the developing sleeve, which is not preferable in terms of the relationship with the spike-stand regulating member and the like. The included angle θ (S2 Ss) of the repulsive magnetic field part must be 600 or more and 180° or less, and the preferable condition is 700 to qO°.
Experiments have revealed that there is (F,, -8,).

〔Example〕

FIG. 1 is a sectional view of essential parts of a developing device showing an embodiment of the present invention, and FIG. 2 shows a copying machine to which the developing device of FIG. 1 is installed.

Reference numeral 10 denotes an image forming body, which is an organic photoreceptor having the following configuration and having a diameter of 50 mm and rotates at 200 rpm in the direction of the arrow.

(Structure of organic photoreceptor) Support body: Made of aluminum 50xtxΦ
Drum intermediate layer: Vinyl chloride-vinyl acetate copolymer (0.1 μm thick) Charge transport layer: Triphenylaminostyryl dispersed in polycarbonate (20 μm thick) Charge generation Layer: A layer in which a bisazo pigment is dispersed in polycarbonate (1 μm thick) The positively charging photoreceptor formed by sequentially laminating the above layers is a two-component developer and has the following structure.

(Developer composition) Toner: Negative powder with an average particle size of 12 μm, containing 7% by weight of carbon black dispersed in styrene acrylic resin and externally adding 0.4% by weight of hydrophobic silica. Chargeable.

Carrier: A carrier with an average particle size of 70 μm, which is made by coating ferrite particles with a diameter of 70 μm with styrene acrylic resin. .

Developer: A mixture of 95% by weight of the carrier and 5% by weight of the toner.

The developing sleeve was made of aluminum and was a thin cylinder with a wall thickness of 1 mm, and the outer surface was roughened by sandblasting (#30). It rotates in the direction of the arrow at a circumferential velocity of about 3.3 Vp, based on the data shown in FIG. 5, relative to the linear velocity Vp of the image forming body 10.

The gloss is fixed with a magnet roll, and the main magnet N1 with the N pole facing outward on the aluminum roll 31, and N3 and N facing outward in the downstream direction.
2, N2, and Sl magnetic poles are integrally molded. The magnetic force of each magnetic pole on the developing sleeve surface is 750 Gauss for the main magnetic pole N1, 450 Gauss for the sub magnetic pole, 650 Gauss for S, 600 Gauss for N2, and 450 Gauss for Sl.

The main magnetic pole N faces the photoreceptor at a magnet angle of 10"5° (upstream side), θ(ss - Nl) is 70°, θ(N2-N3) of the repulsive magnetic field is 80°, θ(N2 82 )
is i, θ(St −N2 ) is 70, θ(Nt −8t
) is the distribution position of Pi. (See Figure 6) Here, the main magnetic pole N has a cross-sectional shape with a width of 8 mttt and a thickness of 6 mm, and the sub magnetic poles S1, N2, N8, and N2 have a cross-sectional shape of 5 mm width and 4 mm thickness. be.

40 is a spike regulating member, which has a diameter of 0.51 with the circumferential surface of the developing sleeve.
It is set with a gap 3 of +u. On the other hand, the image forming body 10
The gap between the developing sleeve and the developing area E- is 0.
It is 51mm. The spike control member 40 is a sub magnet N2.
, Sl, and radially disposed at about 70'' with respect to the horizontal axis.

Note that the above angular position is the best angular position in comparison with the case where the bristling regulating member 40 is moved back and forth, and is the best angular position (the gap between the buffing regulating member 40 and the developing sleeve distribution).
(Even if cut is varied (0.4 to 0.7), the developer is transported with good developer density.

The developer adhering to the circumferential surface of the developing sleeve is regulated by the bristling regulating member 40, becomes a constant thickness, adheres to the developing sleeve, and is conveyed to the developing area E. On the other hand, the surplus developer whose conveyance is prevented by the spike control member 40 moves on a guide plate 41 having a gentle slope of about ICP with respect to the horizontal direction, and moves to the inlet of the toner replenishing screw 42. 42
The toner supply screen 142 is entered from a.

An amount corresponding to the toner consumed by development is replenished from the toner supply screw 42, so that the toner concentration is kept constant. The new toner conveyed on the screw mixes with the developer that has flowed in from the inflow port 42a, and falls into the stirring tank 52 from the drop port 42b.

Inside the casing 51, there is a stirring means 53 spaced apart from the outer wall by several millimeters. The stirring means 53 is an elliptical blade with a diameter of 32 mm, which rotates at 200 pm in the same direction as the developing sleeve, and collects the old developer removed from the developing sleeve between the magnetic poles Ss and 82 and the drop port 42b. The replenishment toner that has fallen further and the developer in the stirring tank 52 are stirred and mixed. The agitated and mixed developer is newly attracted by the sub magnetic poles S2 and N2, and instead of the old developer that was peeled off between the magnetic poles S3 and 82, it adheres to the circumferential surface of the developing sleeve and flows toward the developing area E. The image is transported and developed in the development area E.

FIG. 2 shows a sectional view of the copying machine with the above-described developing device installed, and 61 in the figure shows the band i! 62 is a document table glass, 63 is a focusing light transmitter, 64 is a light source, 65 is a transfer foreshock "light source, 66 is a transfer device, 67 is a separation static eliminator, 6
8 is a heat roller fixing device, 69 is a pre-cleaning static eliminator,
70 is a cleaning device, and 71 is a cleaning blade within the device.

The image forming body 10 rotating in the direction of the arrow is first uniformly charged at +600V by the charger 61. Next, a document on the document platen glass 62 is placed on the charging surface.

The reflected light scanned by the light source 64 is focused by the light transmission body 63, and image exposure is performed to form an electrostatic image.

This electrostatic image is developed into a toner image by the developing device.

The toner image formed on the image forming body 10 is transferred onto a transfer paper P by a transfer device 66, and the transfer paper P is separated from the image forming body 10 by a separation static eliminator 67 and fixed by a heat roller fixing device. It is then ejected from the aircraft.

Even when continuous copying of a solid black manuscript is performed using a copying machine equipped with the developing device according to the present invention as described above, there is no density unevenness in both the longitudinal direction and the transfer paper traveling direction, and the blackness is maintained at a sufficiently high level. The density was developed. Of course, good development results were also obtained for copies of fine print originals.

However, in order to perform continuous copying of the above-mentioned solid black original and maintain good development, the necessary and sufficient developer must be present in the casing 51, so that the stirring means can be used in the developing device shown in FIG. Regarding the diameter in the depth direction of 53, the lower end position 53 a is 0%, the upper end position 53 b is 100%,
If we call this the developer filling rate, then the developer filling rate η
It was concluded that it is necessary for the ratio to be between 70% and 100%.

The developing device according to the present invention has been described above, but the image forming body used in the present invention includes an intermediate layer provided on a base such as metal or conductive plastic, if necessary.
On top of this, Zn, AA! , Sb, Cd.

A photosensitive layer in which a photoconductive substance such as an oxide, iodide, sulfide, or selenide of Mo or Hg is dispersed in a binder resin;
Some are provided with a photosensitive layer or an organic photosensitive layer made of vapor-deposited Se, Si, or an alloy of Se and Te, Sb, Bi, or the like.

Further, as the organic photoreceptor, perylene derivatives, chlordian blue, methylscalyllium, bisazo pigments,
A charge generation layer in which an organic photoconductive substance such as a polycyclic pigment is dispersed in a resin as necessary, and an oxadiazole derivative, a pyrazoline derivative, a polyarylalkane aromatic amino compound, polyvinyl carbazole, etc. are dissolved in a resin as necessary. Alternatively, there is a positively chargeable or negatively chargeable composite photoreceptor comprising a dispersed charge transport layer. The present invention is applicable to any of these photoreceptors.

Further, the developer is not limited to the above-mentioned ones, and the present invention is also applicable to one-component developers.

Furthermore, the gap between the spike control member and the developing sleeve and the gap between the developing sleeve and the image forming body are not limited to those in this embodiment. For these as well, the optimum gap value is 0.
It is preferably in the range of 1-1.2 mm and 0.3-'2.0 mm.

〔Effect of the invention〕

As explained above, according to the developing device of the present invention, the device is more compact and lower cost than ever before, almost no carrier adhesion is observed, and high-quality copied images continue to be produced even when continuous copying is performed at high density. This resulted in the following effects being obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a developing device showing an embodiment of the present invention. FIG. 2 is a sectional view of a copying machine equipped with the developing device shown in FIG. 1. FIG. 3 is a graph showing the relationship between sleeve diameter and copy density. FIG. 4 is a graph showing the relationship between magnetic flux density and attached carriers. FIG. 5 is a graph showing the relationship between V r / V p and toner adhesion amount. FIG. 6 is a cross-sectional layout diagram of the magnet roll. FIG. 7 is a sectional view of a conventional developing device. 10... Image forming body Red... Developing sleeve 30... Magnet roll 31...
...Main magnet 32.33...Sub magnet 40.
..... Ear standing regulation member 51 ..... casing
53...Stirring means 1)e...Developer E...Development area Applicant: Roku Konishi Photo Industry Co., Ltd. Figure 1 J Figure 3 Sleeve size Figure 4 rv/Q Figure 6 Figure 7

Claims (2)

[Claims] (1) It has a 5-pole fixed magnet body including a main pole facing the rotating photoconductor, and a small-diameter developing sleeve that rotates the outer periphery of the magnet body in the forward direction relative to the photoconductor surface to form a developer flow. In the developing device, two magnetic poles, a main magnetic pole and a different pole, are provided on the downstream side of the main magnetic pole, and the central angle θ included in the two magnetic poles is 60°.
A developing device characterized by having a range of °<θ<180°. (2) The small diameter developing sleeve is 9 mm to 25 mm.
The developing device according to claim 1, having an outer diameter of .