JP2000250311A - Developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a uniform black solid image by eliminating screw pitch unevenness of the black solid part, being liable to occur when adopting one of repulsing poles as the developer layer thickness controlling pole, in order to prolong the developer service life. SOLUTION: In the developing device arranging a magnet roller 23 in a developing sleeve, for agitating/transporting the two component developer consisting of magnetic carriers and non-magnetic toner by agitating/transporting by means of transporting screws 24 and 25 in a helical shape, adopting one of adjacent magnetic poles in same polarity among magnets consisting the magnet roller 23 as the developer layer thickness controlling pole controlling the developer layer thickness, and transporting the said developer controlled in the desired layer thickness by rotation of the developing sleeve 21, and performing the magnetic brush development for the electrostatic latent image on the image carrier, when assuming the diameter of the developing sleeve as A (mm), and the outside diameter of the transporting screw 24 as B (mm), and moreover, the pitch of the wing on the transporting screw 24 as 1 (mm), condition of the next formula is satisfied, A/B>=1.1, and 1<A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic latent image formed on an image carrier corresponding to an image to be recorded with a developer, and an image forming apparatus for recording the developed image on paper or the like.

Conventionally, various apparatuses have been proposed and put into practical use as electrophotographic developing apparatuses. It can be broadly classified into a developing device using a one-component developing method and a developing device using a two-component developing method. The one-component developing method is mostly a non-contact method, but a typical developing method uses a magnetic toner. There is a one-component jumping development method.

This developing method can provide high-quality image with a simple structure, but has a drawback that a color image cannot be obtained because the toner contains a magnetic substance.

In the one-component developing method using a non-magnetic toner, a color image can be obtained, but it is difficult to apply the toner on a developing sleeve, and at present, coating is performed with an elastic blade. Yes, it lacks stability and durability.

On the other hand, in the two-component developing method, a toner is transported to a developing area by a magnetic carrier to perform development. Usually, a developing step is performed by bringing a developer into contact with a photosensitive drum. Here, the developing step will be described with reference to FIG.

In the drawing, 30 is a developing sleeve, 35 is a magnet roller as a magnetic field generating means fixedly arranged in the developing sleeve, 31 and 32 are agitating screws, and 33 is a developer for forming a thin layer of developer on the surface of the developing sleeve. A regulating blade 34 is disposed at the developing container. The agitating screws 31 and 32 transport the developer in opposite directions, and the developer is transported from one agitating screw to the other agitating screw at both ends so that the developer circulates in one direction as a whole. Is done.

Here, a developing step of visualizing the electrostatic latent image by a two-component magnetic brush method using the above-described developing device and a circulating system of the developer will be described below.

First, as the developing sleeve 30 rotates, N
The developer pumped up by the three poles is regulated by the regulating blade 33 in the process of being transported from the S2 pole to the N1 pole, and a thin layer is formed on the developing sleeve 30. Here, when the developer formed in a thin layer is conveyed to the S1 pole, which is the main development pole, ears are formed by magnetic force. The electrostatic latent image is developed by the developer formed in the spike shape, and then the developing sleeve 30 is developed by the repulsive magnetic fields of the N3 pole and the N2 pole.
The upper developer is returned into the developer container 34. In the two-component development, as described above, a configuration is generally used in which magnetic poles of the same polarity are arranged side by side, and the developer after development is once peeled off from the developing sleeve so as not to leave an image history.

A DC bias and an AC bias are applied to the developing sleeve from a power source (not shown). In general, in the two-component developing method, by applying an AC bias, the developing efficiency is increased, and the image becomes high quality.

As a latent image forming method, an electrophotographic photosensitive member is scanned and exposed by a laser beam modulated in accordance with an image signal to be recorded, and a dot distribution shape, that is, a dot-like latent image is distributed corresponding to the image. There is known a method for forming an electrostatic latent image. Among them, the so-called pulse width modulation (PWM) method, which modulates the width (that is, the duration) of the driving pulse current of the laser in accordance with the density of the recorded image, can obtain a high recording density (that is, high resolution). And high gradation can be obtained.

Incidentally, in recent years, a developing apparatus and an image forming apparatus using a two-component developing device have been further downsized and improved in image quality.
Development of longer life is underway.

Among them, in order to achieve a longer life,
It is necessary to adopt a configuration in which the developer is not compressed and to prevent deterioration of the toner and the carrier. The place where the developer is compressed in the developing container is a developer layer thickness regulating portion. In a normal configuration, the developer layer thickness regulating pole is located on the upstream side in the rotation direction of the developing sleeve from the regulating blade. In the region, the developer attracted to the developer layer thickness regulating electrode is compressed between the sleeve and the container.

In order to weaken the compression of the developer, the force (Fr; magnetic attraction force acting in a direction perpendicular to the development sleeve) of the developer layer thickness regulating pole attracting the developer to the development sleeve must be reduced. Is valid.

A method for this purpose is to reduce the magnetization of the magnetic carrier in the developer [in the direction in which the magnetization of the carrier is reduced, the force for rubbing the toner image developed on the photoreceptor in the developing section is reduced. It is the direction of higher image quality in that it becomes weaker. And constructing a magnet pattern such that the lines of magnetic force from the developer layer thickness regulating pole are unlikely to wrap around adjacent magnetic poles and exit as vertically as possible from the developing sleeve.

As one of the latter methods, a developing method using one of the repulsive magnetic poles of the developing sleeve as a developer layer thickness regulating pole has been proposed. When magnetic poles of the same polarity are adjacent to each other to form a repulsive magnetic field, the lines of magnetic force of the magnetic poles are substantially perpendicular to the developing sleeve surface. In this case, the rate of change of the magnetic flux density in the direction perpendicular to the developing sleeve surface is small. As a result, the force for attracting the developer to the developing sleeve decreases, and the degree of compression of the developer decreases.

[0016]

However, when the above configuration, that is, a configuration in which one of the repulsion poles is used as the developer layer thickness regulation pole, is adopted, the screw pitch is formed almost from the front end of the solid black image. Density unevenness occurred.

This phenomenon is caused by the fact that when the agent is supplied to the developer layer thickness regulating magnetic pole by the rotation of the stirring screw near the developing sleeve, the agent is supplied in a state where there is unevenness in the compression of the agent, and the agent is supplied as it is to the developing section. Occurs as a result of being transported to

Such a phenomenon is particularly likely to occur in a configuration in which the degree of compression of the developer in the developer layer thickness regulating magnetic pole is reduced. Further, this phenomenon is more likely to occur when the value of the magnetization of the magnetic carrier is reduced in the configuration in which the degree of compression of the developer is weakened.

The reason is that when the magnetization of the carrier is small, the degree of compression of the developer at the developer layer thickness regulating pole is further reduced, so that the developing screw supplied to the developer layer thickness regulating pole by the rotation of the stirring screw near the developing sleeve. This is because the influence of the compression unevenness of the agent becomes large.

An object of the invention according to the present application is to increase the life of the developer by using one of the repulsive magnetic poles (of the developing sleeve) as a developer layer thickness regulating electrode, which is likely to occur when black is generated. It is an object of the present invention to provide a developing device that can eliminate a screw pitch unevenness in a solid portion and can obtain a uniform black solid image, using the above configuration, and further reducing the magnetization of a magnetic carrier for a longer life. Another object of the present invention is to provide an image forming apparatus capable of outputting a uniform image without screw pitch unevenness.

[0021]

SUMMARY OF THE INVENTION In order to achieve the object of the present invention, a developing device includes a rotatable non-magnetic cylinder and a magnet inside the non-magnetic cylinder for forming a plurality of magnetic poles. A magnetic field generating means unequally disposed, a developing container for containing a two-component developer composed of a magnetic carrier and a non-magnetic toner, and a stirring and conveying means for stirring and conveying the two-component developer in the developing container. The developer having a desired layer thickness regulated by using one of adjacent magnet poles of the same polarity among the magnets constituting the magnetic field generating means as a developer layer thickness regulation pole for regulating a development layer thickness. Is transported by rotation of a non-magnetic cylinder, and a developing device for developing the electrostatic latent image on the image carrier by a magnetic brush, wherein the stirring and transporting means near the non-magnetic cylinder has spiral blades, and the diameter of the non-magnetic cylinder is Is A (mm), and the outer diameter of the stirring and conveying means is (Mm), when the pitch of the helical blade of the stirring 拌搬 feed means set to l (mm), and is characterized in satisfying the relation of A / B ≧ 1.1 and l <A.

Further, the image carrier and the non-magnetic cylinder move in opposite directions to each other at a portion where the image carrier and the non-magnetic cylinder face each other.

Furthermore, the magnetic carrier in the two-component developer has a magnetic field of 1000 [Gauss] and has a magnetic carrier of 30 emu /
It has a magnetization of not less than cm ^{3 and not} more than 200 emu / cm ³ .

An image forming apparatus for realizing the object of the invention according to the present application has a developing device having the above-described configuration, and develops an electrostatic latent image on an image carrier by the developing phase. Things.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an electrophotographic color printer to which the present invention can be applied. This printer includes an electrophotographic photosensitive drum 3 which rotates in the direction of an arrow. Around the photosensitive drum 3, a charger 4 and developing units 1M, 1C, 1Y, 1
An image forming means including a rotary developing device 1 provided with Bk, a transfer discharger 10, a cleaning means 12, and an LED exposing means LE disposed above the photosensitive drum 3 in the drawing is arranged.

Each developing device contains a two-component developer containing toner particles and carrier particles. The developer of the developing device 1M contains magenta toner, the developer of the developing device 1C contains cyan toner, the developer of the developing device 1Y contains yellow toner, and the developer of the developing device 1Bk contains black toner.

The document to be copied is read by a document reading device (not shown). This reading device has a photoelectric conversion element for converting a document image such as a CCD into an electric signal, and outputs image signals corresponding to magenta image information, cyan image information, yellow image information, and monochrome image information of the document, respectively. I do. The LED exposing means performs exposure by controlling on-off of light emission in accordance with these image signals. Note that an output signal from a device such as a computer can be printed out.

The sequence of the entire color printer will be briefly described by taking a full color mode as an example. First, the photosensitive drum 3 is uniformly charged by the charger 4. Next, L controlled by the magenta image signal
Exposure is performed by the ED array L, and a dot distribution latent image is formed on the photosensitive drum 3, and this latent image is reversely developed by a magenta developing unit 1M previously set at a development position.

After being taken out of the cassette C, the paper feed guide 5
a, the transfer material such as paper which has advanced through the paper feed roller 6 and the paper feed guide 5b is held by the gripper 7 of the transfer drum 9, and is electrostatically transferred by the contact roller 8 and its opposite pole. 9 wrapped around. The transfer drum 9 rotates in the direction of the arrow in synchronization with the photosensitive drum 3, and the magenta visual image developed by the magenta developing device 1M is transferred to a transfer material by a transfer charger 10 in a transfer section. The transfer drum 9 continues to rotate as it is to prepare for transfer of an image of the next color (cyan in FIG. 1).

On the other hand, the photosensitive drum 3 is neutralized by the charger 11, cleaned by the cleaning means 12, charged again by the charger 4, and exposed as described above by the LED array L controlled by the next cyan image signal. As a result, an electrostatic latent image is formed. During this time, the developing device 1 rotates, and the cyan developing device 1C is fixed at a predetermined developing position, performs reversal development of the electrostatic latent image corresponding to cyan, and forms a cyan visible image.

Subsequently, the following steps are performed on the yellow image signal and the black image signal, respectively.
When the transfer of the four-color image (toner image) is completed, the transfer material is neutralized by the chargers 13 and 14 to release the gripper 7, and is separated by the transfer drum 9 by the separation claw 15 to be separated by the transfer belt. At 16, it is sent to a fixing device (a hot-press roller fixing device) 17. The fixing device 17 fixes the visible images of four colors overlapping on the transfer material.

Thus, a series of full-color print sequences is completed, and a desired full-color print image is formed.

This configuration is merely an example.
Is not a corona charger, but a charging roller, an exposure unit is a semiconductor laser, and the transfer charger 7 is also a transfer roller. There are various methods, but basically, as described above, charging, An image is formed through the steps of exposure, development, transfer, and fixing.

Next, a magenta developing device 1M, which is one of the developing devices of the present embodiment, will be described with reference to the drawings.

FIG. 2 is a configuration diagram showing a magenta developing device 1M according to the embodiment of the present invention. The present developing device includes a developing container 27 as shown in FIG. The inside of the developing container 27 is partitioned into a developing chamber (first chamber) R1 and a stirring chamber (second chamber) R2 by a partition wall 29, and a toner storage chamber R3 is provided above the stirring chamber R2 with a partition wall 26 therebetween. A replenishment toner (non-magnetic toner) 28 is formed in the toner storage chamber R3. In addition, a supply port 26a is provided in the partition wall 26, and an amount of supply toner 28 corresponding to the toner consumed through the supply port 26a is dropped and supplied into the stirring chamber R2.

On the other hand, the developer 19 is accommodated in the developing chamber R1 and the stirring chamber R2. The developer 19 is obtained by adding 1% by weight of titanium oxide having an average particle size of 20 nm to a toner having an average particle size of 8 μm manufactured by a pulverization method, and has a magnetization value of 270 em at 1000 Gauss.
a two-component developer comprising u / cm ³ and a magnetic carrier having an average particle size of 35 μm. The mixing ratio was such that non-magnetic toner was about 7% by weight.

An opening is provided in a portion of the developing container 27 which is close to the photosensitive drum 3, and the opening is formed through the opening.
1 protrudes outside. The developing sleeve 21 is rotatably incorporated in the developing container 27. In the present embodiment, the developing sleeve 21 is, for example, SUS3.
A rotor magnet 23 as a magnetic field generating means composed of a plurality of magnets is fixed inside of a non-magnetic material such as 05 AC.

The rotor magnet 23 includes a developing magnetic pole N1 and a developer layer thickness regulating pole S3 located downstream of the developing magnetic pole N1.
9 for transporting N.9.
The developing magnet N1 of the rotor magnet 23 is
Are disposed in the developing sleeve 21 so as to face the developing sleeve 21.

The developing magnetic pole N1 forms a magnetic field near the developing section between the developing sleeve 21 and the photosensitive drum 3, and the magnetic field forms a magnetic brush. In this position,
As the developing sleeve rotates, the developer carried in the direction of the arrow contacts the photosensitive drum and develops the electrostatic latent image on the photosensitive drum.

At this time, at a position (developing portion) near the developing sleeve and the photosensitive drum, the developing sleeve and the photosensitive drum move in opposite directions (counter direction). The developer that has been developed at the N1 pole is peeled off from the developing sleeve 21 by the repulsive magnetic field formed by the S1 and S3 poles, and falls into the developing chamber R1.

In this embodiment, a developing sleeve having a diameter of 16 mm was used.

A power supply 21 applies an oscillating bias voltage obtained by superimposing a DC voltage on an AC voltage to the developing sleeve. The dark portion potential (non-exposed portion potential) and the light portion potential (exposed portion potential) of the latent image are located between the maximum value and the minimum value of the vibration bias potential.

Thus, an alternating electric field whose direction changes alternately is formed in the developing section. In this alternating electric field, the toner and the carrier vibrate violently, and the toner shakes off the electrostatic restraint on the sleeve and the carrier, and the amount of the toner corresponding to the latent image potential adheres to the photosensitive drum.

In this embodiment, the dark potential of the photosensitive drum is -550 V, the light potential is -100 V, and the developing sleeve has a DC bias of -300 V and an AC bias of Vpp 2.0 kV, Frq. 6 kHz is applied.

The blade 18 is arranged below the developing sleeve 21 at a predetermined distance from the developing sleeve 21. The distance between the developing sleeve 21 and the blade 18 is 400 μm. The blade 18 is fixed to the developing container 27. The blade 18 is made of a magnetic material such as iron, and magnetically regulates the thickness of the developer 19 on the developing sleeve 21.

A transport screw 24 having spiral blades shown in FIG. 4 is accommodated in the developing chamber R1. The transport screw 24 has a diameter of 14 mm and a pitch of 1
The thing of 5 mm was used.

The transport screw 24 is rotated in the direction indicated by the arrow in the figure, and the developer 19 in the developing chamber R 1 is transported in the longitudinal direction of the developing sleeve 21 by the rotation of the transport screw 24. In the present embodiment, the transport screw 24 is disposed below the developing sleeve 21 in the direction of gravity. The reason for this is that, as will be described later, the uppermost surface of the developer accommodated in the transport screw 24 is set between the developer layer thickness regulating electrode and the stripping electrode.

On the other hand, the transport screw 2
Conveying screw 2 having a spiral blade having the same structure as that of the conveying screw 2
5 are accommodated. The transport screw 25 has a diameter of 14 mm, similar to the transport screw 24.
The rotation of the transport screw 25 causes the toner to be transported along the longitudinal direction of the developing sleeve 21 in a direction opposite to the transport direction of the toner by the transport screw 24 in the developing chamber R1. It falls naturally into R2. The developing chamber R1 and the storage chamber R2 communicate with each other at both ends in the longitudinal direction of the two screws, and the toner sent in one direction by the conveying screw 25 is transferred in one direction together with the magnetic carrier by the conveying screw 24 of the developing chamber R1. And the developer is circulated as a whole.

Here, the toner used in the present embodiment will be described. In the present embodiment, one having a triboelectric charge of about 2.0 × 10 ⁻² C / kg was used.

The toner having a volume average particle diameter of 4 to 15 μm can be suitably used. Here, as the volume average particle diameter of the toner, for example, the one measured by the following measurement method is used.

As a measuring device, Coulter Counter T
Using an A-II type (manufactured by Coulter), an interface (manufactured by Nikkaki) for outputting a number average distribution and a volume average distribution and a CX-i personal computer (manufactured by Canon) are connected, and primary electrolyte is sodium chloride. 1% NaC
Adjust the aqueous solution.

The measuring method is as follows.
In 150 ml, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant, and 0.5 to 50 mg of a measurement sample is further added.

The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the particle size distribution of particles of 2 to 40 μm was measured using the Coulter Counter TA-II with an aperture of 100 μm. Is measured to determine the volume distribution. From these determined volume distributions, the volume average particle size of the sample is obtained.

In addition to the toner described above,
By coating the (toner) surface with an external additive, there are two effects in terms of hardware. One is that the fluidity is improved, and the replenishment toner is easily mixed and stirred with the two-component developer in the developing container. That is, the releasability of the toner (developed on the drum) from the photosensitive drum is increased, and transfer efficiency is improved.

The external additive used in the present invention preferably has a particle size of 1/10 or less of the weight average particle size of the toner particles from the viewpoint of durability when added to the toner. The particle size of the additive means an average particle size obtained by observing the surface of the toner particles with an electron microscope. As the external additive, for example, the following are used.

Metal oxides (aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide, etc.), nitrides (silicon nitride, etc.), carbides (silicon carbide, etc.) Salts (calcium sulfate, barium sulfate, calcium carbonate, etc.), fatty acid metal salts (zinc stearate, calcium stearate, etc.), carbon black, silica, etc.

The external additive is used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the toner particles.
0.05 to 5 parts by weight are used. These external additives may be used alone or in combination. Those subjected to a hydrophobic treatment are more preferable.

In this embodiment, the average particle size is 20 m
m of titanium oxide externally added by 1% by weight.

Next, as the carrier constituting the developer used in the present invention together with the above-mentioned toner, conventionally known carriers can be used. For example, magnetite as a magnetic material is dispersed in a resin. A resin carrier formed by dispersing carbon black for conductivity and resistance adjustment, or a resin carrier coated with a magnetite simple substance resin such as ferrite and resistance adjustment may be used. The method for producing these magnetic carriers is not particularly limited.

In the present embodiment, the magnetic carrier has a weight average particle diameter of 20 to 100 μm, preferably
Those having a thickness of 20 to 70 μm were used.

Next, the positional relationship between the developer layer thickness regulating electrode of the developing device used in the present embodiment, the stripping electrode that forms a repulsive magnetic field together with the screw near the developing sleeve, including its operation, will be described. It will be described in detail.

In the present embodiment, of the S3 pole and the S1 pole that form a repulsive magnetic field, the S3 pole is used as a developer layer thickness regulating pole, and the S1 pole is used as a developer stripping pole.
The peak value of the magnetic field strength in the direction perpendicular to the developing sleeve surface of the S3 pole is 400 to 1000 gauss, and the peak value of the magnetic field strength in the direction perpendicular to the sleeve surface of the S1 pole is 4
It is preferably from 00 Gauss to 800 Gauss.

In the present embodiment, the peak value of the magnetic field strength of the S3 pole is set to 600 gauss, and the peak value of the magnetic field strength of the S1 pole is set to 500 gauss. Further, on the developing sleeve, the positional relationship between the S3 pole and the S1 pole is as follows:
The peak position of the magnetic field in the direction perpendicular to the developing sleeve surface of the first developing sleeve surface is positioned higher in the direction of gravity than the peak position of the magnetic field intensity of the developer layer thickness regulating magnetic pole S3 perpendicular to the developing sleeve surface. It adopts a simple configuration.

With such a configuration, the developer after development is easy to fall (no special stripping means is required), and the developer is attracted by magnetic attraction by the developer layer thickness regulation pole, and the developer is developed. Easy to transport to parts. In other words, it is easy to adopt a simple configuration for peeling off the agent from the developing sleeve and supplying the agent to the developing sleeve.

In the present embodiment, the peak position of the magnetic field intensity in the direction perpendicular to the developing sleeve surface of the S3 pole and the tip of the regulating blade (developing sleeve side) are 5 ° in this embodiment.
(Based on the center position of the developing sleeve).

Since the S3 pole forms a repulsive magnetic field with the S1 pole, the magnetic field lines of the S3 pole tend to diverge perpendicularly to the developing sleeve. As a result, the change in the magnetic field (magnetic field line density) in the direction perpendicular to the developing sleeve is reduced. This means that the force for attracting the developer to the developing sleeve is reduced. With such a configuration, the force with which the developer is compressed at the developer layer thickness regulation electrode is reduced, so that deterioration of the developer such as toner deterioration and spent carrier is suppressed, and the life of the developer is extended. .

However, as in the present embodiment, a configuration is adopted in which one magnetic pole of the repulsive magnetic poles is used as the developer layer thickness regulating pole, and the stirring and conveying screw is arranged near the developer layer thickness regulating pole. In this case, screw pitch-like density unevenness occurred at the tip of the solid black image.

This phenomenon is caused by the fact that when the agent is supplied to the developer layer thickness regulating magnetic pole by the rotation of the stirring screw near the developing sleeve, the agent is supplied in a state where there is uneven compression of the agent, and the agent is developed as it is. This occurs as a result of being transported to the department.
Such a phenomenon is particularly likely to occur in the configuration of the present invention in which the degree of compression of the developer at the developer layer thickness regulation electrode is weak.

As a result of some investigations, when one of adjacent magnetic poles having the same polarity forming a repulsive magnetic field is used as a developer layer thickness regulating pole for regulating the developing layer thickness, the diameter of the developing sleeve is set to A (mm). ), When the outer diameter of the stirring screw is B (mm) and the pitch of the screw is 1 (mm), a screw pitch is obtained by taking a configuration satisfying the relationship of A / B ≧ 1.1 and 1 <A. It was found that non-uniform density did not occur.

As described above, in the configuration of this embodiment, A is 16 (mm), B is 14 (mm), and 1 is 15 (mm).
(Mm).

Therefore, A / B [= 1.14] ≧ 1.1 and l [= 15] <A [= 16], which satisfies the above equation.

The smaller the pitch of the stirring and conveying screw and the smaller the screw diameter, the smaller the force acting in the direction diverging around the screw shaft when the screw rotates and the agent is stirred and conveyed. As a result, the compression unevenness of the agent supplied to the developer layer thickness regulation electrode is reduced.

If the diameter of the developing sleeve is small, the diameter of the screw becomes small, and the developing sleeve and the screw come closer to each other, so that the developer is easily affected by the compression of the agent due to the rotation of the screw.

This configuration is particularly necessary when the diameter of the developing sleeve is 25 mm or less.

In the present embodiment, by adopting the above structure, screw pitch-like density unevenness did not occur.

In the present embodiment, as shown in FIG. 2, the photosensitive drum 3 and the developing sleeve 21 are configured to rotate in the counter direction in the developing section, but the present invention is not limited to this.

However, as shown in FIG. 2, when the thickness of the developer layer is regulated at the lower portion in the direction of gravity of the developing device, a configuration having a small developer compression degree as in the present configuration is easier to produce. That is, the developer not adsorbed on the developing sleeve exists in the lower part in the direction of gravity in the container, and when the transfer unit is located below the photosensitive drum, the developing sleeve and the photosensitive drum rotate in the counter direction. Such a configuration simplifies the configuration of the developing device.

As described above, the rotatable non-magnetic cylinder,
A magnetic field generating means inside the non-magnetic cylinder in which magnets for forming a plurality of magnetic poles are unequally arranged; a developing container for containing a two-component developer composed of a magnetic carrier and a non-magnetic toner; And a stirring and conveying means for stirring and conveying the two-component developer, wherein one of adjacent magnet poles of the same polarity among the magnets constituting the magnetic field generating means is used to regulate a developing layer thickness. In a developing device which is used as a regulating pole and conveys the developer regulated to a desired layer thickness by rotation of a non-magnetic cylinder, and develops an electrostatic latent image on the image carrier with a magnetic brush, stirring in the vicinity of the non-magnetic cylinder The conveying means has a spiral blade, the diameter of the non-magnetic cylinder is A (mm), the outer diameter of the stirring and conveying means is B (mm), and the pitch of the spiral blade of the stirring and conveying means is l (mm). ), A / B ≧ 1.1 and l <A By adopting a satisfying configuration, it is possible to form a uniform black solid image without a screw pitch-like density unevenness and with a long service life.

[Comparative Example 1] In this comparative example, the developing sleeve diameter [A] is 24 m compared to the configuration of the first embodiment.
m, a screw having an outer diameter [B] of 20 mm and a screw pitch [l] of 20 mm was used. All other configurations are the same as in the first embodiment.

In this configuration, the relationship of A / B ≧ 1.1 and 1 <A is satisfied, and as a result of outputting an A4 size black solid image, a uniform black solid image without screw pitch-like density unevenness is obtained. An image could be formed.

[Comparative Example 2] In this comparative example, the developing sleeve diameter [A] is 24 m compared to the configuration of the first embodiment.
m, a screw having an outer diameter [B] of 20 mm and a screw pitch [l] of 25 mm was used. All other configurations are the same as in the first embodiment.

In this configuration, the relationship of A / B ≧ 1.1 and 1 <A is not satisfied, and as a result of outputting a solid black image of A4 size, density unevenness in the form of a screw pitch is observed from the leading end of the image. Occurred.

[Comparative Example 3] In this comparative example, the developing sleeve diameter [A] is 16 m compared to the configuration of the first embodiment.
m, a screw having an outer diameter [B] of 14 mm and a screw pitch [l] of 20 mm was used. All other configurations are the same as in the first embodiment.

In this configuration, the relationship of A / B ≧ 1.1 and 1 <A is not satisfied, and as a result of outputting a solid black image of A4 size, a screw pitch-like density unevenness is generated from the leading end of the image. Occurred.

[Second Embodiment] In the present embodiment, 1000 magnetic carriers are used in a two-component developer.
A magnetic field having a magnetization of 150 emu / cm ³ in a Gaussian magnetic field was used. All other conditions were the same as in the first embodiment.

In the structure similar to that of the first embodiment, one of the repulsion magnetic poles is used as a magnetic pole for regulating the thickness of the developer layer, and the intensity of the magnetization of the carrier is further reduced. At the thickness regulating electrode, the compressive force of the developer is weakened, and the life of the developer is further extended.

However, with such a configuration,
As compared with the first embodiment, screw pitch-like density unevenness is more likely to occur.

When the magnetization of the carrier is small, the degree of compression of the agent at the developer layer thickness regulating electrode is further reduced.
The toner is supplied to the developer layer thickness regulating magnetic pole by the rotation of the stirring screw near the developing sleeve. This is because the influence of the compression unevenness of the agent becomes large.

As a result of some investigations, it was found that this embodiment
Thus, the rotatable non-magnetic cylinder and the inside of the non-magnetic cylinder
The magnets to form multiple magnetic poles
Magnetic field generating means and a magnetic carrier and a non-magnetic toner.
Developing container containing a two-component developer,
And a stirring and conveying means for stirring and conveying the two-component developer.
Adjacent magnets of the plurality of magnets of the magnetic field generating means
Layer thickness regulating electrode that regulates the thickness of the developing layer for one of the magnetic poles
As a non-magnetic material.
The electrostatic latent image on the image carrier is conveyed by rotating the conductive cylinder
In a developing device for brush development, the non-magnetic cylinder
The side stirring and conveying means has a spiral blade, and the non-magnetic cylinder
Is A (mm), and the outer diameter of the stirring and conveying means is B (m).
m), the pitch of the spiral blades of the stirring and conveying means is l (m
m), in addition to the structure that satisfies the relationship of A / B ≧ 1.1 and 1 <A,
The magnetization of the magnetic carrier in a magnetic field of 1000 Gauss
And 30 emu / cm^Three[30 emu / cm ^ThreeLess than
Can be coated on the developing sleeve.
30 emu / cm^ThreeIt was above. ], 2
00 emu / cm^ThreeFurther longevity by:
With screw life, there is no screw pitch-like density unevenness,
A single solid black image can be formed.

[0091]

As described above, according to the present invention, not only the life of the developer can be prolonged, but also a uniform black solid image free of screw pitch-like density unevenness can be obtained.

When the above configuration is employed and the magnetization of the magnetic carrier in the developer is further reduced, not only a uniform image can be obtained over the entire surface, but also a longer life can be achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a full-color image forming apparatus according to the present invention.

FIG. 2 is a sectional view of a developing device according to the embodiment of the present invention.

FIG. 3 is a schematic side view showing a known developing device used for explaining a conventional example.

FIG. 4 is a front view of the transport screw of FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 rotation developing device 1M, 1C, 1Y, 1Bk developing device 3 photosensitive drum 18 blade 19 developer 21 developing sleeve 23 rotor magnet 24, 25 transport screw 26 partition 26a supply port 27 developing container 28 supply toner R1 developing room R2 stirring room R3 Toner storage room

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiro Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Takao Ogata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon In-house F term (reference) 2H005 BA00 EA02 FA01 2H031 AA12 AB02 AC01 AC08 AC19 AC20 AC31 AC34 AD01 AD09 BA04 BB01 CA11 FA01 2H077 AB02 AB07 AB15 AC02 AD06 AD13 AD18 AD36 EA03 EA15 GA13 GA17

Claims (5)

[Claims] 1. A two-component nonmagnetic toner comprising: a rotatable non-magnetic cylinder; magnetic field generating means inside the non-magnetic cylinder, wherein magnets for forming a plurality of magnetic poles are unequally disposed; and a magnetic carrier and a non-magnetic toner. A magnetic container having a developer container for storing the developer, and stirring and conveying means in the developing container for stirring and conveying the two-component developer, wherein adjacent magnetic poles of magnets constituting the magnetic field generating means are adjacent to each other; Is used as a developer layer thickness regulating electrode for regulating the thickness of the developing layer, the developer regulated to a desired layer thickness is transported by rotation of a non-magnetic cylinder, and the electrostatic latent image on the image carrier is In a developing device for magnetic brush development, the stirring and conveying means near the non-magnetic cylinder has spiral blades, the diameter of the non-magnetic cylinder is A (mm), the outer diameter of the stirring and conveying means is B (mm), The pitch of the spiral blade of the stirring and conveying means was set to l (mm). A developing device, wherein A / B ≧ 1.1 and 1 <A. 2. The developing device according to claim 1, wherein the image carrier and the non-magnetic cylinder move in opposite directions at an opposing portion between the image carrier and the non-magnetic cylinder. 3. The magnetic carrier in the two-component developer,
30 emu / cm in a magnetic field of 1000 [Gauss]
³ above, the developing device according to claim 1 or 2, characterized in that it has the following magnetization 200 emu / cm ^3. 4. The rotatable non-magnetic cylinder has a diameter of 10
2 mm or more and 25 mm or less.
3. The developing device according to claim 1. 5. An image forming apparatus comprising the developing device according to claim 1, wherein the developing device develops an electrostatic latent image on an image carrier.