JP2001281997A - Developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device and the like where the flocculated lump of toner on the upstream side of a regulating blade is eliminated and the uneven coating of developer caused by the lump of toner is prevented in the latter half of long-term use even in the case of using one of the repulsive magnetic poles of a magnetic field generating means in a developer carrier as a developer layer thickness regulating pole in order to prolong the life of the developer. SOLUTION: The shaft center of a stirring and carrying screw 24 on the developing sleeve 21 side of the developing device 1 is positioned on a lower side in a gravity direction with respect to the shaft center of the sleeve 21. An S3 pole being the repulsive pole of a magnet roller 23 in the sleeve 21 is set as the developer layer thickness regulating pole, and an S1 pole is used as a developer peeling pole. The peak position of magnetic field in a sleeve surface perpendicular direction of the S1 pole is positioned upper in the gravity direction than the peak position of the magnetic field in the sleeve surface perpendicular direction of the S3 pole. A non-magnetic member 30 is arranged to a position higher in a vertical direction than the rotation center shaft of the screw on the more upstream side in a sleeve rotating direction than a regulating blade 20 and more downstream side than the position of the screw 24 as seen from the center of the sleeve 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly to a developing apparatus for developing an electrostatic latent image formed on an image carrier in accordance with a recorded image.

[0002]

2. Description of the Related Art Conventionally, various developing apparatuses for electrophotographic apparatuses have been proposed and put into practical use. It can be roughly 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 is a one-component jumping developing method using a magnetic toner. This developing method can provide high-quality image with an easy configuration, but has a drawback that a color image cannot be obtained because the toner contains a magnetic substance.

On the other hand, a one-component developing method using a non-magnetic toner can obtain a color image, 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, the two-component developing method uses a two-component developer consisting of a toner and a magnetic carrier, and conveys the toner to a developing area via a magnetic carrier by a developing sleeve.
The development is performed, and usually, the developing step is performed by bringing the developer into contact with the photosensitive drum. FIG. 5 shows the developing process.
This will be described with reference to FIG.

[0005] As shown in FIG. 5, the developing device 1 is provided with a developing sleeve 21, a magnet roller 23, stirring and conveying screws 24 and 25, and a regulating blade 20 in a developing container 27. Is housed.

First, the developer is pumped onto the developing sleeve 21 by the magnetic pole N3 of the magnet roller 23, which is disposed in the developing sleeve 21 in a non-rotating manner. Magnetic pole N
In the process of being transported as 3 → S2 → N1, the regulating blade 20
The thickness of the developer is regulated by the regulating electrode S2 and the developer is formed on the developing sleeve 21 as a thin layer. When the developer formed in the thin layer is conveyed to the development main pole S1, it is raised by magnetic force and is formed on the magnetic brush.

The spike-shaped developer comes into contact with the surface of the photosensitive drum 3 to develop an electrostatic latent image on the photosensitive drum 3. 27, is separated from the developing sleeve 21 by the repulsive magnetic field of the magnetic poles N3 and N2, and is collected in the developing container 27.

In the two-component development, as described above, magnetic poles of the same polarity are arranged side by side on the magnet roller 23, and the developer after the development is once peeled off from the developing sleeve 21 so that the image history is not left on the developing sleeve. It is common to do.

During development, a DC bias and an AC bias are applied to the developing sleeve 21 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 method of forming a latent image, the photosensitive drum 3 is scanned and exposed by a laser 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 of modulating the width (that is, the duration) of the driving pulse current of the laser in accordance with the density of a recorded image can obtain a high recording density (that is, a high resolution). And high gradation can be obtained.

In recent years, development of a two-component developing apparatus for further extending the service life and miniaturizing the developing apparatus has been promoted. In order to achieve a long service 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 27 is a developer layer thickness regulating portion in the vicinity of the regulating blade 20 provided. In a usual configuration, the developer layer thickness regulating pole S2 is provided by the regulating blade 20. The developer attracted to the developer layer thickness regulating pole in the rotation direction upstream of the developing sleeve 21 in this region is compressed between the developing sleeve and the developing container.

In order to weaken the compression of the developer, the regulating pole S
2 attracts the developer to the developing sleeve 21 (F
r: magnetic attraction force acting in a direction perpendicular to the developing sleeve is effective. As a method for this, the magnetization of the magnetic carrier in the developer is reduced (in the direction in which the magnetization of the magnetic carrier is reduced, the force of rubbing the toner image developed on the photoreceptor in the developing unit becomes weaker). In this respect, the magnetic field lines from the regulating pole S2 are unlikely to wrap around the adjacent magnetic poles, and a magnetic pattern can be constructed so as to extend as vertically as possible from the developing sleeve.

As one of the latter methods, a developing method in which one of the repulsive magnetic poles of a magnet roller in a developing sleeve is used 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 each magnetic pole are 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.

On the other hand, although development for miniaturization of the image apparatus itself has been advanced, charging, exposure, development,
There has been a limit to the size of the parts for each of the processes such as transfer, fixing, and cleaning.

Then, the drum cleaner of the image forming apparatus is removed, the transfer residual toner on the photosensitive drum is collected by a contact type charger, the photosensitive drum is returned to a desired potential, and the collected toner is discharged onto the photosensitive drum. A cleaner-less device that performs cleaning simultaneously with development by a developing device has also appeared. Here, the simultaneous cleaning with development is a method in which a small amount of toner remaining on the photosensitive drum after transfer is collected by a contact charging member, discharged, and collected by a fogging potential (so-called Vback) during development to a developing device.

According to this method, the transfer residual toner is collected and reused at the time of development, so that waste toner can be eliminated. In addition, there is a great advantage in terms of space, and a significant reduction in size can be achieved.

[0018]

However, in the case where one of the repelling poles as described above is used as the developer layer thickness regulating pole, a phenomenon occurs in which the density is reduced in the latter half of long-term use. .

This phenomenon is caused by a long-term use, where a toner agglomerate (strictly speaking, a carrier is mixed in the agglomerate) occurs on the upstream side in the rotation direction of the developing sleeve of the regulating blade,
This is because the coating of the developer on the developing sleeve is hindered.

The agglomerated mass contains floating toner not stirred by the stirring / conveying screw and toner (and developer having a very high toner concentration) existing in the dead space in the gap between the stirring / conveying screw and the bottom surface of the developing container. And accumulates in the space on the upstream side of the regulating blade 20, starts to accumulate from below in the vertical direction of the space, gradually grows and grows, and hinders the developer coating on the developing sleeve.

If such a toner agglomerate is mixed with a developer circulating in the developing container and having a proper toner concentration, the above problem does not occur. In the configuration in which the two poles are the developer layer thickness regulating poles, the pressure on the developer upstream of the regulating blade is weak, so that the toner aggregate and the developer are not easily mixed.

The above situation is particularly likely to occur when performing simultaneous cleaning with development. that is,
Toner collected in the developing section (transfer residual toner once collected by the contact charger and discharged onto the photosensitive drum) is transferred by an external additive coated on the toner surface in order to improve fluidity. In many cases, the toner is removed by receiving a shear (shearing force) between the toner and the charging unit, and the toner is agglomerated due to the shear.
This is because it is difficult to mix with the developer in the developing container.

An object of the present invention is to use one of the repulsion magnetic poles of the magnetic field generating means in the developer carrying member as a developer layer thickness regulating pole in order to prolong the life of the developer. An object of the present invention is to provide a developing device that prevents developer coating unevenness caused by a toner agglomerate formed on the upstream side of a regulating blade, and an image forming apparatus including the developing device.

[0024]

The above object is achieved by a developing device and an image forming apparatus according to the present invention. In summary, the present invention provides a developing container containing a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed, a non-magnetic rotating developer carrier having a built-in magnetic field generating means, and a rotating stirring and conveying device. And a magnetic developer layer thickness regulating member, wherein one of two adjacent magnetic poles of the plurality of magnetic poles of the magnetic field generating means is a developer layer thickness regulating pole, and The body carries the developer supplied by the rotation of the stirring and conveying means, and the regulating member and the regulating pole cooperate to regulate the layer thickness of the developer carried on the developer carrying body,
Then, the developer carrier rotates in a direction to move in the opposite direction at the developing section facing the rotating image carrier, and conveys the regulated developer to the developing section, and In a developing device for performing a magnetic brush development of an electrostatic latent image with the conveyed developer, the developer carrier is regulated with respect to a rotation direction of the developer carrier as viewed from a center of the developer carrier. A non-magnetic member, which is higher in the vertical direction than the rotation center of the stirring and conveying means, is disposed in a portion upstream of the member and downstream of the stirring and conveying means.

According to the present invention, the developing device collects the toner remaining after the transfer of the toner image obtained by developing the electrostatic latent image on the image carrier to the transfer material by the developing unit. The cleaning device also serves as a cleaning unit for the image carrier. The closest portion between the regulating member and the developer carrier is located vertically below the position of the rotation center of the developer carrier.
The stirring and conveying means is provided with spiral blades coaxially around a rotation axis, and rotates the developer in the developing container in the longitudinal direction of the rotation axis by rotation of the stirring and conveying means. While transporting, the developer is supplied to the developer carrier. The magnetic carrier, in 1000 Gauss magnetic field, 30 emu / cm ³ or more, having 200 emu / cm ³ or less of the magnetization. The non-magnetic toner is generated by a polymerization method.

According to the present invention, there is provided an image forming apparatus for developing an electrostatic latent image formed on an image carrier using a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed by a developing device. An image forming apparatus including the apparatus.

[0027]

Embodiments of the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic sectional view showing an embodiment of the image forming apparatus of the present invention, and FIG. 2 is a sectional view showing a developing device installed in the image forming apparatus of FIG.

First, the image forming apparatus will be described with reference to FIG. The image forming apparatus in FIG. 1 is configured as an electrophotographic color printer.

As shown in FIG. 1, the printer includes a drum type electrophotographic photosensitive member, that is, an electrophotographic photosensitive drum 3 as an image carrier, and the photosensitive drum 3 rotates in the direction of an arrow. Around the photosensitive drum 3, a rotary developing device 1 including a charger 4 and developing devices 1C, 1M, 1Y, and 1K
A, an image forming unit including a static eliminator 11, a cleaning unit 12, and a laser beam scanner LS above the photosensitive drum 3 are arranged. A transfer drum 9 is provided below the photosensitive drum 3 and between the charge removing charger 11 and the developing device 1A, and a transfer charger 10 and the like are provided in the transfer drum 8.

Each of the developing devices 1C to 1K of the rotary developing device 1A
Contains a two-component developer containing a toner and a magnetic carrier, the developer of the developing device 1M contains a magenta toner,
The developer of the developing device 1C uses cyan toner, and the developing device 1Y
Contains yellow toner, and the developer of the developing device 1K contains black toner.

A copy original as an image to be recorded is read by an original reading device (not shown). This reader is
It has a photoelectric conversion element such as a CCD for electrically converting a developed image, and outputs image signals respectively corresponding to magenta image information, cyan image information, yellow image information, and black-and-white image information of a document. The scanner LS incorporates a semiconductor laser, and the semiconductor laser is controlled according to these image signals and emits a laser beam L. The output signal from the 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, scanning exposure is performed by the laser beam L modulated by the magenta image signal, and the photosensitive drum 3
A dot distribution latent image is formed thereon, and this latent image is reversely developed by a magenta developing device 1M fixed at a developing position in advance, and is visualized as a magenta toner image.

A transfer material such as paper is taken out of the paper cassette C. The transfer material is conveyed to the transfer drum 9 via the paper guide 5a, the paper roller 6, and the paper guide 5b. It is held by the gripper 7 and is electrostatically wound around the transfer drum 9 by the contact roller 8 and its opposite pole. The transfer drum 9 rotates in the direction of the arrow in synchronization with the photosensitive drum 3, and the magenta image developed by the magenta developing device 1M is transferred to the transfer charger 10 by the transfer unit.
Is transferred to a transfer material. The transfer drum 9 continues rotating as it is to prepare for transfer of an image of the next color (cyan in the figure).

On the other hand, the photosensitive drum 3 is provided with a charge removing charger 11.
After being removed by the cleaning means 12 and being cleaned by the cleaning means 12, it is charged again by the charger 4 and receives the above-mentioned exposure by the laser beam L modulated by the next cyan image signal to form an electrostatic latent image. . During this time, the rotary developing device 1A rotates and the cyan developing device 1A is rotated.
C is set at a predetermined developing position, and the reversal development of the dot distribution electrostatic latent image corresponding to cyan is performed to form a cyan toner image.

The above-described steps are performed for yellow and black. When the transfer of the visible images (toner images) for four colors to the transfer material is completed, the transfer material is charged to the chargers 13 inside and outside the transfer drum 8. The electricity is removed by 14, the gripper 7 is released, and the toner is separated from the transfer drum 9 by the separation claw 15, and sent to the hot-press roller fixing device 17 by the transport belt 16. The fixing device 17 fixes the four color toner images overlapping on the transfer material.

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

The configuration of the image forming apparatus described above is an example. For example, the charger 4 is not a corona charger but a charging roller, and the transfer charger 7 is also a transfer roller. However, basically, an image is formed through the steps of charging, exposure, development, transfer, and fixing as described above.

Next, the developing device 1 (1M to 1K) installed in the image forming apparatus of FIG. 1 will be described with reference to FIG.

As shown in FIG. 2, the developing device 1 includes a developing container 27. The inside of the developing container 27 is divided into a developing chamber (first chamber) R1 and a stirring chamber (second chamber) R2 by a partition wall 29. A toner storage chamber R3 is formed above the stirring chamber R2 with a partition wall 29 interposed therebetween, and a replenishment toner (non-magnetic toner) 28 is stored in the toner storage chamber R3. A supply port 26 is provided in a portion of the partition wall 29 below the toner storage chamber R3, and an amount of supply toner 28 corresponding to the consumed toner is dropped and supplied into the stirring chamber R2 via the supply port 26.

A two-component developer 19 is contained in the developing chamber R1 and the stirring chamber R2. The developer 19 is obtained by externally adding 1% by weight of titanium oxide having an average particle diameter of 20 nm to a non-magnetic toner having an average particle diameter of 7.2 μm manufactured by a pulverization method, and has a magnetization value at 1000 Gauss. 20
It is mixed with a magnetic carrier having an average particle diameter of 5 μm / cm ³ and 35 μm. The mixing ratio of the developer 19 was such that the weight ratio of the non-magnetic toner was about 7%.

An opening is provided in a portion of the developing container 27 close to the photosensitive drum 3, and a developing sleeve 21 as a developer carrying member is installed so as to protrude outside from the opening. The developing sleeve 21 is rotatably incorporated in the developing container 27. In this embodiment,
The developing sleeve 21 is formed of a non-magnetic material cylinder such as SUS305AC, for example, and a magnet roller 23 as a magnetic field generating means is fixedly disposed inside the developing sleeve 21.

The magnet roller 23 includes a developing magnetic pole N1 and a developer layer thickness regulating pole S3 located upstream of the developing magnetic pole N1.
9 for transporting N.9.
The magnet roller 23 is such that the developing magnetic pole N1 is the photosensitive drum 3
Are disposed in the developing sleeve 21 so as to face the developing sleeve 21. The developing magnetic pole N1 is formed by the developing sleeve 21 and the photosensitive drum 3
A magnetic field is formed in the vicinity of the developing section between the developer and the developer transported in the direction of the arrow with the rotation of the developing sleeve 21 at this position. The developer forms a magnetic brush by the magnetic field and contacts the surface of the photosensitive drum 3. Then, the electrostatic latent image on the photosensitive drum 3 is developed. At this time, the developing sleeve 21 and the photosensitive drum 3 are located at a position close to the developing sleeve and the photosensitive drum (developing unit).
Move in opposite directions (counter direction).

During development, a power source 22 is connected to the developing sleeve 21.
As a result, an oscillation bias voltage obtained by superimposing a DC voltage on an AC voltage is applied. The dark part potential (non-exposed part potential) and the light part potential (exposed part potential) of the latent image are located between the maximum value and the minimum value of the above-mentioned vibration bias potential. , An alternating electric field is formed. In this alternating electric field, the toner and the carrier vibrate violently, and the toner shakes off the electrostatic restraining force on the developing sleeve and the carrier, and adheres to the photosensitive drum in an amount corresponding to the latent image potential.

In this embodiment, the dark portion potential of the photosensitive drum is
550 V, the light portion potential was -100 V, and a DC bias of -300 V and an AC bias of Vpp of 2.0 kV and a frequency of 6 kHz were applied to the developing sleeve. Also, the gap (S-D) at the closest part between the developing sleeve and the photosensitive drum
Gap) was set to 450 μm.

The developer that has been developed in the developing section is returned into the developing container 27 with the rotation of the developing sleeve 21,
It is peeled off from the developing sleeve 21 by the repulsive magnetic field formed by the magnetic poles S1 and S3, and falls into the developing chamber R1.
Collected.

A regulating blade 20 is provided below the developing sleeve 21. The regulating blade 20 is fixed to the developing container 27 and arranged at a predetermined distance from the developing sleeve 21, in this example, at 400 μm. The regulating blade 20 is made of a magnetic material such as iron, and magnetically regulates the layer thickness of the developer 19 on the developing sleeve 21.

A stirring and conveying screw 24 is provided in the developing chamber R1.
The screw 24 has a spiral blade wound around a screw shaft, the shaft is made of a magnetic material such as iron, and the blade is made of a molded member such as ABS. The screw 24 used had a diameter of 14 mm. By rotating the stirring and conveying screw 24 in the direction of the arrow in the figure, the developer 19 in the developing chamber R1 is conveyed in the longitudinal direction of the developing sleeve 21, and a part of the developer 19 is disposed at both ends in the longitudinal direction of the partition wall 29. It is delivered to the stirring chamber R2 through one opening (not shown).

A similar stirring / conveying screw 25 is provided in the stirring chamber R2.
The developer 19 in the stirring chamber R2 is transported along the longitudinal direction of the developing sleeve 21 in a direction opposite to the above. In this transporting process, the toner 28 supplied from the toner storage chamber R3 is mixed, so that the concentration of the developer 19 is restored. The developer whose concentration has been restored passes through the other opening (not shown) of the partition wall 29 in the longitudinal direction. Then, it is returned into the developing chamber R1.

According to the present invention, the center of the axis of the stirring and conveying screw 24 on the side close to the developing sleeve 21 is positioned below the axis of the developing sleeve in the direction of gravity.
Further, a magnetic pole S which forms a repulsive magnetic field of the magnet roller 23
Of the three poles and the S1 pole, the S3 pole is used as a developer layer thickness regulating pole, and the S1 pole is used as a developer stripping pole. The positional relationship between the magnetic poles S3 and S1 and the screw 24 will be described in detail.

The peak value of the magnetic field strength in the direction perpendicular to the surface of the S3 pole developing sleeve 21 is preferably 400 gauss or more and 1000 gauss or less. The peak value of the magnetic field strength is
400 gauss or more and 800 gauss or less are preferable. In this embodiment, the peak value of the magnetic field strength of the S3 pole was set to 600 gauss, and the peak value of the magnetic field strength of the S1 pole was set to 500 gauss.

The positional relationship between the S3 pole and the S1 pole is such that the peak position of the magnetic field in the direction perpendicular to the surface of the developing sleeve of the stripping pole S1 corresponds to the surface of the developing sleeve of the developing layer thickness regulating pole S3. Are positioned above the peak position of the strength of the magnetic field in the direction perpendicular to the direction of gravity. With such a positional relationship, the developer after the development is
From the developer (thus, no special stripping means is required), the developer is attracted by the magnetic attraction force of the regulating pole S3, and the developer is easily transported to the developing section. That is, it is easy to adopt a simple configuration for stripping the developer from the developing sleeve and supplying the developer to the developing sleeve.

In the present embodiment, the peak position of the magnetic field strength in the direction perpendicular to the surface of the developing sleeve 21 of the S3 pole and the tip (developing sleeve side) of the regulating blade 20 are located at the center position of the developing sleeve. The opening is 5 ° as a reference, that is, from the center 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 21. As a result, the rate of change of the magnetic field (magnetic field line density) in the direction perpendicular to the developing sleeve decreases. This corresponds to a reduction in the force for attracting the developer to the developing sleeve. Therefore, the force with which the developer is compressed at the developer layer thickness regulation pole S3 is weakened,
Deterioration of the developer such as toner deterioration and carrier spent is suppressed, and the life of the developer is extended.

However, the arrangement of the magnetic poles S3 and S1 and the stirring and conveying screw 24 is set to 30 ° C./8
When an endurance test for forming an image with an image ratio of 10% was performed in an environment showing a temperature and humidity of 0%, the image density corresponding to the vicinity of the central portion in the longitudinal direction of the developing sleeve 21 gradually decreased from about 10,000 sheets. I've been. When the number of sheets is 15,000, the image density at both ends in the longitudinal direction of the solid black portion is 1.14.
(X-write), the density at the center in the longitudinal direction was 1.32 (the image density of the initial black solid portion was 1.40).

At this time, when the amount of the developer coated on the developing sleeve 21 (the amount of the developer per unit area, mg / cm ² ) was actually measured, it was found that 25 mg was uniform in the longitudinal direction at the start of the test.
/ Cm ² , which was not changed at both ends at 25 mg / cm ² , but decreased to 18 mg / cm ² at the center where the solid concentration was reduced.

Further, the regulating blade 20 is removed, and a carrier return portion (a space on the upstream side in the rotation direction of the developing sleeve 21 of the regulating blade 20. The developer accumulates in this space, is compressed, and the charged charge is applied to the toner. Observation of (1) shows that in the region where the amount of coating in the central portion is low, agglomerates of toner are formed, which hinders the coating on the developing sleeve. On the other hand, at both ends, small toner aggregates have begun to be formed below the space of the carrier return portion in the direction of gravity.

Thereafter, when a part of the toner aggregate formed in the center portion is removed, and the regulating blade 20 is reattached to resume the image formation, the image density of the area where the aggregate is removed is around 1.40 at the initial stage. And the concentration was almost the same at both ends, but the area where the aggregates were not removed remained 1.32.

From this result, the decrease in the density in the central portion in the longitudinal direction is caused by the formation of a large toner agglomerate, which hinders the coating of the developer on the developing sleeve 21, and the developer does not come into contact with the photosensitive drum 3 in the developing section. It is considered that this occurred due to a state close to contact and a decrease in development efficiency.

As described above in the description of the conventional example, the toner aggregates are formed by floating toner that is not agitated by the agitating / conveying unit or toner existing in the dead space in the gap between the agitating / conveying screw and the bottom surface of the developing container. The developer (and the developer having a very high toner concentration) is stored in the space on the upstream side of the regulating blade by the stirring and conveying of the developer by the stirring and conveying screw near the developing sleeve.

When a so-called screw 24 having a spiral blade around the shaft is used as the developer stirring and conveying means,
As shown in FIG. 2, the developer advances in the longitudinal direction of the screw 24 while rotating clockwise with respect to the axis of the screw 24. By the rotation of the developer about this axis, the separated toner is gradually carried to the regulating blade 20 side, starts to accumulate from below in the vertical direction of the space of the carrier return portion, gradually grows and grows, and Inhibits the coat on the sleeve.

If such toner agglomerates are mixed with a developer in which the toner circulating in the developing container is properly maintained, the above-mentioned problem does not occur, but the repulsion as in the present invention. In a configuration in which one of the poles is used as the developer layer thickness regulating pole, the pressure on the developer upstream of the regulating blade is weak, and it is difficult to mix the toner aggregate and the developer.

Therefore, as a result of some investigations, in the present invention, the regulating blade 2 is viewed from the center of the developing sleeve 21.
As shown in FIG. 2, the upstream side of the developing sleeve in the rotation direction of the developing sleeve and the downstream side in the rotation direction of the developing sleeve from the position of the stirring and conveying screw 24 to a position vertically higher than the rotation center axis of the screw 24. The magnetic member 30 was arranged. As a result, in the second half of the endurance test, the toner layer thickness regulating portion does not generate toner agglomerates on the upstream side of the regulating blade 20 in the rotation direction of the developing sleeve, and inhibits the developer coating on the developing sleeve 21. Such problems did not occur.

This is considered to be due to the following two reasons. One is that the non-magnetic member 30 is located at a position higher than the rotation center of the stirring / conveying screw 24, so that the floating toner not stirred by the stirring / conveying section or the dead toner in the gap between the screw 24 and the bottom surface of the developing container 27. This is because the toner (and the developer having a very high toner concentration) existing in the space becomes difficult to be supplied to the regulating blade 20 portion. The second reason is that, even if supplied, the non-magnetic member 30 crushes the space for the developer and the toner aggregates, and a moderate share is applied to this portion, so that the developer and the toner aggregates are easily mixed. Because it becomes.

In the present embodiment, a position for regulating the thickness of the developer layer is located on the upstream side in the rotation direction of the developing sleeve from the regulating blade 20 and on the downstream side in the rotation direction of the developing sleeve from the stirring and conveying screw 24 near the developing sleeve 21. Although the non-magnetic member 30 is arranged at a position vertically higher than the center of the rotation axis of the screw 24, the non-magnetic member 30 may be formed by partially deforming the developing container 27.

In the present embodiment, the photosensitive drum 3 and the developing sleeve 21 are rotated in the counter direction in the developing section. However, 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, it is easier to configure the developer compression degree of the present embodiment to be smaller. This is because the developer not adsorbed to the developing sleeve 21 exists in the lower part in the direction of gravity in the developing container 27. When the transfer unit is located below the photosensitive drum 3, the configuration of the developing device is simplified by rotating the developing sleeve and the photosensitive drum in the counter direction.

As described above, in the present embodiment, the developer carrying member is rotated in the direction in which it is moved in the opposite direction in the developing section facing the image carrying member, and the repelling magnetic pole of the magnetic field generating means in the developer carrying body is rotated. One magnetic pole is a developer layer thickness regulating pole, and the developer agitating / conveying means is located upstream of the regulating member with respect to the developer carrier with respect to the rotation direction of the developer carrier when viewed from the center of the developer carrier. A non-magnetic member vertically higher than the rotation center of the agitating / conveying means is arranged on the downstream side, so that the floating toner which is not agitated by the agitating / conveying means or a dead space in the gap between the screw and the bottom surface of the developing container. It is possible to make it difficult for the toner present in the toner to be supplied to the portion of the regulating member, and even if the toner is supplied, the space for the developer and the toner agglomerate is crushed by the non-magnetic member, and an appropriate share is applied to this portion to remove the toner. The toner and the toner agglomerate can be easily mixed, and as a result, the developer life can be prolonged, and also, in the latter half of long-term use, the unevenness of the developer due to the toner agglomerate can be prevented from occurring. Thus, an image without a decrease in density can be stably obtained over a long period of time.

Embodiment 2 FIG. 3 is a schematic sectional view showing another embodiment of the image forming apparatus of the present invention.

The image forming apparatus of the present embodiment employs a simultaneous development and cleaning system, in which the developing device used in the first embodiment is used.

The toner aggregate as described in the first embodiment is
This is particularly likely to occur when cleaning is performed simultaneously with development. That is, after the toner collected in the developing unit, that is, the transfer residual toner, is once collected in the contact charger, the toner discharged on the photosensitive drum is uniformly coated on the toner surface in order to improve fluidity. When the external additive receives a share in the transfer section and particularly in the charging section, the external additive is often removed, or the toner is often aggregated due to the share, and is mixed with the developer in the developing container. Because it is difficult. Such collected toner is likely to aggregate with each other even when collected in the developing container.

Hereinafter, an image forming operation of the image forming apparatus according to the present embodiment will be described.

In FIG. 3, first, the original G is set on the original table 40 with the surface to be copied facing downward. Next, copying is started by pressing the copy button. The original irradiating lamp, short focus lens array, and CCD sensor form an integrated unit 39 to scan while irradiating, and the reflected light of the illumination scan light on the original surface is imaged by the short focus lens array to form a CCD sensor. Is incident on.

The CCD sensor includes a light receiving section, a transfer section, and an output section. In the CCD light receiving unit, the optical signal is converted into a charge signal, and the transfer unit sequentially transfers the light signal to the output unit in synchronization with a clock pulse. At the output unit, the charge signal is converted into a voltage signal, amplified, and reduced in impedance. Output. The analog signal obtained in this way is subjected to well-known image processing, converted into a digital signal, and sent to a printer unit.

The printer section receives the image signal and forms an electrostatic latent image on the surface of the photosensitive drum 3.

A drum-shaped electrophotographic photosensitive member as an image carrier, that is, a photosensitive drum 3, is driven to rotate at a predetermined peripheral speed around a central support shaft, and is driven to rotate in the direction of arrow B during the rotation process. The charger 31 receives a uniform charging process of negative polarity.

In the present invention, a commonly used organic photoreceptor or the like can be used for the photosensitive drum 3, but the organic photoreceptor has a surface layer made of a material having a resistance of 10 ⁹ to 10 ¹⁴ Ωcm. It is preferable to use a photoreceptor or an amorphous silicon photoreceptor, and when these are used, charge injection charging can be realized, which is effective in preventing ozone generation and reducing power consumption. In addition, the chargeability can be improved.

In this embodiment, a negatively chargeable organic photoreceptor is used.
A photosensitive drum was used in which the following first to fifth layers were provided in order from the bottom on an aluminum drum base having a diameter of 30 mm.

The first layer is an undercoat layer, which is made of aluminum.
Provided to smooth out defects in the body, etc.
Electric layer. The second layer is a positive charge injection preventing layer,
Positive charge injected from the minium substrate charges the photoconductor surface
Plays a role in preventing the cancellation of the negative charge
10 with Milan resin and methoxymethylated nylon ⁶
1μm thick intermediate layer with resistance adjusted to about Ωcm
You.

The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates positive and negative charge pairs upon exposure. 4th
The layer is a charge transport layer, and is made of a P-type semiconductor in which hydrazone is dispersed in a polycarbonate resin. Therefore, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor.

The fifth layer is a charge injection layer, which is a coating layer of a material in which ultrafine SnO ₂ particles are dispersed as conductive fine particles in a binder of an insulating resin. Specifically, a coating liquid in which 70% by weight of ultra-fine SnO ₂ fine particles having a particle size of 0.03 μm, which has been reduced in resistance (conducted) by doping antimony which is a light-transmitting conductive filler, is dispersed in an insulating resin is used. It was prepared and applied to a thickness of 3 μm by a suitable coating method such as dipping coating method, spray coating method, roll coating method, and beam coating method to form a charge injection layer.

In this embodiment, a magnetic brush charging system is used as the charger 31. This magnetic brush charger 31
It has a support sleeve made of a rotatable non-magnetic member with an outer diameter of 16 mm, a fixed magnet is provided inside the support sleeve, and the magnetic field as a contact charging member supports the magnetic particles as a brush on the surface of the sleeve, The magnetic particles are transported with the rotation of the sleeve.

The rotation of the support sleeve is in the direction of arrow B with respect to the rotation direction A of the photosensitive drum 3, that is, the counter direction in which the opposing portion moves in the opposite direction. In this embodiment, the rotation speed of the photosensitive drum is 100 mm /. The support sleeve was rotated at 150 mm / sec for seconds. By applying a charging voltage to the sleeve, electric charges are given from the magnetic particles to the surface of the photosensitive drum 3, and the photosensitive drum 3 is charged to a potential corresponding to the charging voltage. The higher the rotation speed, the better the uniformity of charging tends to be.

The magnetic particles used as the contact charging member of the charger 31 have an average particle diameter of 10 to 100 μm, a saturation magnetization of 20 to 250 emu / cm ³ , and a resistance of 10 ² to 10 ¹⁰ Ω.
cm is preferable, and considering that there is an insulation defect such as a pinhole in the photosensitive drum 3, it is 10 ⁶ Ωc
m or more are preferable. In order to improve the charging performance, it is better to use one having as small a resistance as possible. In this embodiment, the average particle diameter is 25 μm and the saturation magnetization is 200 emu / c.
Magnetic particles having m ³ and a resistance of 5 × 10 ⁶ Ωcm were used.

The resistance value of the magnetic particles is such that the bottom area is 228 mm.
After placing 2g of the magnetic particles in the ^second metal cell, 6.6kg /
The weight was measured in mm ² and a voltage of 100 V was applied to measure.

As the magnetic particles, a resin carrier formed by dispersing magnetite as a magnetic material in a resin and dispersing carbon black for conductivity and resistance adjustment;
Alternatively, oxidize the surface of magnetite alone such as ferrite.
A magnet whose resistance has been adjusted by reduction or a magnet whose surface is coated with a resin such as ferrite and whose resistance has been adjusted can be used.

In this embodiment, the nip width formed between the magnetic brush made of magnetic particles and the surface of the photosensitive drum 3 is adjusted to be approximately 6 mm.
In this state, by applying an alternating voltage of a rectangular wave having an amplitude of 700 V and a frequency of 1000 Hz to the support sleeve with respect to a DC voltage of -600 V, good charging properties could be obtained.

When the surface of the photosensitive drum 3 is uniformly charged as described above, the solid-state laser element 102 is turned on and off in response to the image signal by the light emission signal generator 101 in the laser scanning section 100 shown in FIG. Then, the laser light emitted from the laser element 102 is converted into a substantially parallel light beam by the collimator lens system 103, and further scanned in the direction of the arrow c by the rotating polygon mirror 104 rotating in the direction of the arrow b, and the fθ lens groups 105a and 105b , 105c, and irradiates the photosensitive drum 3 to the scanned surface 1 of the photosensitive drum.
An exposure distribution for one scan of an image is formed on the scanning surface 06, and the scanning surface 106 is scrolled by a predetermined amount perpendicular to the above-mentioned scanning direction for each scanning, so that the scanning surface 106 corresponds to an image signal on the scanning surface 106. An exposure distribution, that is, an electrostatic latent image is obtained.

This latent image is developed by the developing device 1, and the obtained toner image is electrostatically transferred onto a transfer material by a transfer charger 27. Thereafter, the transfer material is separated from the photosensitive drum 3 by a separation charger 28. Then, it is sent to the fixing device 17 where it is thermally fixed and an image is output.

In this embodiment, the developing device 1 has the same configuration as the developing device 1 used in the first embodiment and shown in FIG. Hereinafter, FIG. 2 will be referred to as needed.

In the present embodiment, the toner of the two-component developer 19 used in the developing device 1 may be a toner manufactured by a pulverizing method. For example, if a toner manufactured by a polymerization method is used, the toner of the present embodiment may be used. Such simultaneous cleaning with development is more preferable. This is because the polymerized toner has a shape close to a sphere and its surface is uniformly coated with an external additive, so that the releasability of the toner image from the photosensitive drum is extremely improved, and the transfer residual toner itself is reduced. Because.

When the transfer efficiency (toner amount per unit area transferred onto paper / toner amount per unit area on the photosensitive drum) of the pulverized toner and the polymerized toner was compared, the pulverized toner was 90%. On the other hand, when the polymerized toner was used, the ratio was as high as 97%.

When such a polymerized toner is used,
In addition to the very small amount of transfer residual toner and the high releasability, when performing simultaneous cleaning of contact charging / development, a decrease in charging ability is reduced, and the transfer residual toner on the photosensitive drum by the contact charging member is reduced. This facilitates the process of collecting and discharging the toner, improves the recovery of the transfer residual toner on the photosensitive drum by the developing device, and makes it difficult to generate a positive ghost or the like.

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, a Coulter counter TA-II (manufactured by Coulter) was used, and 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) were connected. The electrolyte is a 1-grade sodium chloride aqueous solution.
% NaCl was prepared.

A surfactant (preferably an alkyl benzene sulfonate) is added as a dispersant to 100 to 150 ml of the above electrolyte solution in an amount of 0.1 to 5 ml, and a toner of a measurement sample is added in an amount of 0.5 to 50 mg. Then, the electrolytic solution in which the sample is suspended is 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 is measured using a 100 μm aperture by a Coulter counter TA-II.
Find the volume distribution. From this volume distribution, the volume average particle size of the toner is obtained.

When the surface of the toner described above is coated with an external additive, two mechanical effects are exhibited. One is that the fluidity of the toner is improved, and the supplied toner 28 supplied from the toner storage chamber R3 in FIG.
Is easy to mix with the two-component developer 19 in the
The other is that the external additive intervenes on the toner surface,
That is, the releasability of the toner image from the photosensitive drum 3 is increased, and the transfer efficiency is improved.

The particle size of the external additive is 1/10 of the weight average particle size of the toner particles from the viewpoint of durability when added to the toner.
The following is preferred. The particle diameter of the external additive means an average particle diameter thereof 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.),
Metal salts (calcium sulfate, barium sulfate, calcium carbonate, etc.), aliphatic 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, preferably 0.05 to 100 parts by weight, based on 100 parts by weight of the toner particles.
~ 5 parts by weight are used. These external additives may be used alone or in combination of two or more. It is more preferable that the external additive has been subjected to a hydrophobic treatment.

In this example, the toner of the two-component developer 19 was externally added with 1% by weight of titanium oxide having an average particle diameter of 20 nm.

In the present invention, as the magnetic carrier of the two-component developer 19, conventionally known ones can be used. For example, magnetite is dispersed as a magnetic material in a resin, and carbon black is used for conductivity and resistance adjustment. Dispersed and formed, magnetite simple substance surface such as ferrite is subjected to oxidation and reduction treatment to adjust resistance, or magnet single substance such as ferrite is coated with resin and resistance adjusted. be able to. The method for producing these magnetic carriers is not particularly limited.

In this embodiment, the magnetic carrier has a weight average particle diameter of 20 to 100 μm, preferably 20 to 70 μm.
mm.

The transfer residual toner remains on the surface of the photosensitive drum 3 after the transfer of the toner image obtained by the development. In many cases, the charge polarity of the transfer residual toner is reversed due to peeling discharge or the like at the time of transfer, and it is difficult to collect the toner having the polarity reversed in the developing device 1 simultaneously with development. Therefore, the transfer residual toner that has reached the charging area with the rotation of the photosensitive drum 3 is taken into the magnetic brush charger 31, and the toner is charged normally by rubbing with the magnetic brush (in this example, negative charging).

At this time, if only a DC voltage is applied to the magnetic brush via the support sleeve, toner is not sufficiently taken into the magnetic brush, but if an alternating voltage is applied, the photosensitive drum 3 and the charger 31 The toner is easily taken into the magnetic brush by the vibration effect of the electric field during the period.

In the present embodiment, an image forming apparatus using the contact charging device 31 using such magnetic particles and using the simultaneous development and cleaning method in the developing device 1 is used. The developing sleeve 21 is rotated in a direction to move in the opposite direction at the developing section facing the photosensitive drum 3, and one of the repulsive magnetic poles S3 and S1 of the magnet roller 23 is used as a developer layer thickness regulating pole. On the other hand, with respect to the rotation direction of the developing sleeve as viewed from the center of the developing sleeve, a portion of the non-magnetic material which is higher in the vertical direction than the rotation center of the screw in a portion upstream of the regulating blade and downstream of the stirring and conveying screw 24 means. The member 30 was arranged.

As a result, when a durability test was performed to form an image having an image ratio of 10% under a temperature / humidity environment of 30 ° C./80%, the image density of the black solid portion was initially 1.40. Even at the time of 45,000 sheets, it was kept at 1.40.

As described above, according to this embodiment, even if the simultaneous development and cleaning method is performed by the developing device using the contact charger using magnetic particles, the life of the developer can be prolonged, and the toner aggregation in the latter half of long-term use can be achieved. It is possible to prevent the occurrence of uneven coating of the developer due to the clumps, and it is possible to stably obtain an image without a decrease in density over a long period of time.

Embodiment 3 This embodiment is different from Embodiment 1 in that the developing device 1 shown in FIG.
As the magnetic carrier of the component developer 19, 150 emu /
cm ³ was used. Other configurations of the present embodiment are the same as those of the first embodiment.

In Example 1, 100 magnetic carriers were used.
Although the one having a magnetization of 250 emu / cm ³ at 0 gauss is used, when a carrier having a small magnetization is used in the configuration of the first embodiment, the pressure of the developer at the developer layer thickness regulation pole S3 is further reduced. As a result, the life of the developer is prolonged, but on the other hand, agglomerates of the toner are likely to be generated.

As a result of some studies, as a magnetic carrier of a two-component developer, if the magnetization in a magnetic field of 1000 gauss is 30 emu / cm ³ or more and 200 emu / cm ³ or less, the generation of toner aggregates is suppressed. be able to.

Therefore, also in this embodiment, the developing sleeve 21 of the developing device 1 is rotated in the direction in which it is moved in the opposite direction in the developing section facing the photosensitive drum 3, and the magnetic repulsion poles S3 and S1 of the magnet roller 23 are rotated. One magnetic pole S3 is used as a developer layer thickness regulating pole, and the developing sleeve 21 is positioned upstream of the regulating blade and downstream of the stirring and conveying screw 24 with respect to the developing sleeve 21 with respect to the rotation direction of the developing sleeve when viewed from the center of the developing sleeve. By arranging the non-magnetic member 30 vertically higher than the rotation center of the screw in the portion, the life of the developer is extended, and uneven coating of the developer due to the toner aggregate in the latter half of long-term use is generated. Thus, an image can be stably obtained without a decrease in density over a long period of time.

[0112]

As described above, according to the present invention,
The developer carrier is rotated in the direction opposite to the direction of movement in the developing section facing the image carrier, and one of the repulsive magnetic poles of the magnetic field generating means in the developer carrier is used as a developer layer thickness regulating pole, and the developer is developed. With respect to the rotation direction of the developer carrier when viewed from the center of the developer carrier with respect to the developer carrier, the rotation center of the stirring / transporting means is provided at a portion upstream of the regulating member and downstream of the developer stirring / conveying device. The non-magnetic member that is higher than the non-magnetic member is arranged in the vertical direction, so that the occurrence of toner agglomerates on the upstream side of the developer regulating section can be suppressed, and the life of the developer can be prolonged. Thus, it is possible to prevent the occurrence of uneven coating of the developer caused by the above, and it is possible to stably obtain an image without a decrease in density over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of an image forming apparatus of the present invention.

FIG. 2 is a schematic sectional view illustrating a developing device installed in the image forming apparatus of FIG.

FIG. 3 is a schematic sectional view showing another embodiment of the image forming apparatus of the present invention.

FIG. 4 is a schematic diagram illustrating a laser scanning unit of the image forming apparatus of FIG. 3;

FIG. 5 is a schematic sectional view showing a conventional developing device.

[Explanation of symbols]

 1M to 1K Developing device 3 Photosensitive drum 19 Two-component developer 20 Regulator blade 21 Developing sleeve 23 Magnet roller 24 Stirring and conveying screw 30 Non-magnetic member S1 Repulsive magnetic pole S3 Restrictive pole (repulsive magnetic pole)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/08 507 G03G 15/08 507B 507E F term (Reference) 2H005 AB06 EA02 FA02 2H031 AB02 AC11 AC14 AC19 AC31 AC33 AC34 AD03 AD11 AD13 BA05 BA09 CA11 CA13 DA01 2H077 AA37 AB02 AB15 AC02 AC16 AD02 AD06 AD13 AD16 AD18 AD24 AD31 AD36 AE06 BA08 CA01 CA02 EA03 GA01

Claims (7)

[Claims] 1. A non-magnetic rotating developer carrier containing a magnetic field generating means, a rotating stirring and conveying means, and a developing container containing a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed. A magnetic developer layer thickness regulating member, wherein one of two adjacent magnetic poles of the same magnetic pole of the plurality of magnetic poles of the magnetic field generating means is a developer layer thickness regulating pole, and the developer carrier is Carrying the developer supplied by the rotation of the stirring and conveying means, the regulating member and the regulating pole cooperate to regulate the layer thickness of the developer carried on the developer carrying member,
Then, the developer carrier rotates in a direction to move in the opposite direction at the developing section facing the rotating image carrier, and conveys the regulated developer to the developing section, and In the developing device for performing a magnetic brush development of an electrostatic latent image with the transported developer, the developing device is configured such that, with respect to the developer carrier, the rotation direction of the developer carrier as viewed from the center of the developer carrier is regulated. A developing device, wherein a non-magnetic member that is higher in the vertical direction than the rotation center of the stirring and conveying means is arranged in a portion upstream of the member and downstream of the stirring and conveying means. 2. The image forming apparatus according to claim 1, wherein the developing device collects toner remaining after transfer of a toner image obtained by developing the electrostatic latent image on the image carrier to a transfer target material by the developing unit. 2. The developing device according to claim 1, wherein said developing device also serves as a cleaning means for said carrier. 3. The developing device according to claim 1, wherein a closest portion between the regulating member and the developer carrier is located vertically below a position of a rotation center of the developer carrier. 4. The stirring and conveying means has a spiral blade provided coaxially around a rotation axis, and the developer in the developing container is moved in the longitudinal direction of the rotation shaft by rotation of the stirring and conveying means. The developing device according to claim 1, wherein the developer is supplied to the developer carrying member while being transported while rotating in a direction. 5. The magnetic carrier according to claim 1, wherein the magnetic carrier is at least ³⁰ emu / cm ³ and 200 emu in a magnetic field of 1000 gauss.
The developing device according to claim 1, having a magnetization of not more than / cm ³ . 6. The developing device according to claim 1, wherein said non-magnetic toner is produced by a polymerization method. 7. An image forming apparatus for developing an electrostatic latent image formed on an image carrier using a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed by a developing device, wherein the developing device is used. An image forming apparatus comprising the developing device according to any one of Items 1 to 6.