JP3229232B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in a color image forming apparatus using an electrophotographic system or an electrostatic recording system, such as a color copying machine and a color laser beam printer.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional electrophotographic color image forming apparatus. In FIG. 1, the color image forming apparatus includes a photosensitive drum 1 as an image carrier rotatably supported in the direction of an arrow, and the surface of the photosensitive drum 1 is uniformly charged around the photosensitive drum 1. Corona charger 2, image exposure means 3 for forming an electrostatic latent image on photosensitive drum 1 according to image information, developing device for developing the electrostatic latent image formed on photosensitive drum 1 into a visible image 4, a transfer device 5 including a transfer drum 5a as a recording material carrier, a cleaner 6 for removing the developer remaining on the photosensitive drum 1, and the like are provided.

In this embodiment, the image exposure means 3 comprises a polygon mirror, a lens system, etc., and uses a color image signal for each color obtained by color-separating a reflected light image obtained from a document scanning unit (not shown) by, for example, a color separation filter. A laser beam exposure for irradiating the modulated light image from the laser output portion or a light image E corresponding thereto onto the photosensitive drum 1 having a diameter of, for example, 62 mm to form an electrostatic latent image corresponding to a color image signal of each color. Device.

In this embodiment, a developing device 4 includes four developing devices such as a black developing device 4K, a cyan developing device 4C, a magenta developing device 4M, a yellow developing device, and a rotating body 4a rotating around a central axis 4b. Each of the developing units 4Y is mounted, and a rotary developing device that develops a latent image on the photosensitive drum 1 by rotating a required developing unit to a developing position facing the photosensitive drum 1 is used.

The operation sequence of the entire color image forming apparatus will be briefly described by taking a full color mode as an example. First, the photosensitive drum 1 is uniformly charged by the corona charger 2. Next, image exposure is performed on the original by a laser beam modulated by, for example, a cyan image signal, and an electrostatic latent image is formed on the photosensitive drum 1.
This latent image is stored in a cyan developing unit 4C which is previously set at a developing position.
Is developed, and a cyan visible image (toner image) is formed on the photosensitive drum 1 by a toner based on a resin.

On the other hand, transfer paper fed from a recording material cassette 7a (or 7b or 7c) by a transport system including a pickup roller, a paper feed guide, a paper feed roller and the like according to a paper path indicated by a dotted line in the drawing. Such a recording material P or the recording material P fed from the manual paper feed unit 40 is wound around the transfer drum 5a of the transfer device 5 in synchronization with a predetermined timing.

In this embodiment, the transfer device 5 includes a transfer drum 5a having a diameter of, for example, 164 mm, which is a recording material carrier, a transfer corona charger 5b for transferring a toner image on the photosensitive drum 1 to a recording material, Adsorbing corona charger 5 serving as an adsorbing and charging means for adsorbing a recording material onto transfer drum 5a
c, a suction (contact) roller 5g as its opposite pole,
A transfer drum 5a having an inner corona charger 5d and an outer corona charger 5e and rotatably supported
A recording material carrying sheet 5f made of a film-shaped dielectric material serving as a recording material carrying means is integrally stretched in a cylindrical shape in the peripheral opening area of the recording medium.

The transfer drum 5a is rotated in the direction shown by the arrow in synchronization with the photosensitive drum 1, and a cyan toner image developed by a cyan developing device 4C is transferred to a transfer charger 5b at a transfer portion.
Recording material P carried on recording material carrying sheet 5f by
Is transferred to

The transfer drum 5b continues to rotate as it is,
Prepare for the transfer of an image of the next color (for example, magenta).

The photosensitive drum 1 to which the toner image has been transferred is cleaned of residual matters such as residual toner by a cleaner 6, is uniformly charged again by a corona charger 2, and is modulated by the next magenta image signal. The light undergoes image exposure as described above. During this time, the developing device 4 rotates, and the magenta developing device 4M is fixed at a predetermined developing position and performs a predetermined magenta development.

The magenta toner image is also transferred to the recording material carried on the recording material carrying sheet 5f by the transfer charger 5b in the transfer section, and the magenta toner image is overlaid on the cyan toner image. The transfer drum 5a continues to rotate as it is to prepare for transfer of the next color (for example, yellow) image.

Subsequently, the above-described process is performed on the image formation and transfer of yellow and black, and when the superimposition transfer of the toner images of four colors is completed, the recording material is neutralized by the separation charger 5h and separated. The transfer roller 5a is separated from the transfer drum 5a by a separation means 8 such as a nail, and is fixed by a heat roller fixing device 9 by a suitable conveyance means according to a paper path indicated by a dotted line in the figure.
, And are fixed collectively, and are discharged onto an external tray 10.

[0013] Thus, a series of full-color print sequences is completed, and a required full-color print image is formed.

However, the above-described image forming apparatus has the following disadvantages.

A) Since the developing device is a rotary developing device, it takes a long time to rotate the developing device and move a required developing device to a developing position, and it takes a considerable time to complete image formation. Would.

For example, when one sheet of A3 size, which is a standard recording material, or two sheets of A4 size or letter size are adsorbed on the recording material carrying sheet 5f of the transfer drum 5a as conventionally known, Since the distance between the sheets is reduced, the latent image to be developed on the photosensitive drum is often passed, especially when the required developing device of the developing device is moved to the developing position, so that it is often too late to develop. Development cannot be performed until the transfer drum has been rotated once, so that the photosensitive drum must also perform extra rotation, and the time from the start to the completion of the image forming operation becomes longer.

B) Further, when the developing device uses a developing device using a two-component developer described later, carrier and toner are liable to be scattered. At this time, in the rotary developing device, the toner scatters from the developing device moved to a lower position in the direction of gravity, thereby contaminating the inside of the image forming apparatus.

C) Further, since the diameter of the photosensitive drum is small, the photosensitive drum is easily damaged many times by transfer charging. That is, a drum using an organic photoconductor (OPC) as a photoconductor (hereinafter, abbreviated as an OPC drum) is generally used as the photoconductor drum for low cost and harmless industrial reasons. At this time, the photosensitive member is negatively charged, and is positively charged during transfer. Here, if positive transfer charging is performed without using a recording material, the photoconductor receives positive charging, and the photoconductor changes to the positive potential side.

Generally, when OPC is used on the negative charging side,
Receiving a positive charge makes it difficult to return to the negative potential side, and thereafter has the disadvantage that the charge is not stabilized and the image becomes unstable.

In order to solve the above-mentioned drawbacks, there has been proposed an image forming apparatus using a photosensitive drum having a large diameter and a developing device fixedly arranged.

An example of a conventional electrophotographic color image forming apparatus having such a configuration will be described with reference to FIG.
Note that members corresponding to the color image forming apparatus in FIG.
Components and elements will be described with the same reference numerals. FIG.
Here, the photosensitive drum 1, the transfer drum 5a, and the four fixedly arranged developing devices, that is, the developing devices 4Y, 4C, 4M,
Although not shown except for 4K, the configuration is the same as that of FIG.

In this embodiment, the photosensitive drum 1 as an image carrier
Denotes a large-diameter photosensitive drum having a diameter of 180 mm, which is rotatably supported in the direction of the arrow shown in the figure. Four developing devices 4Y and 4 containing developers (toners) of different colors for developing the electrostatic latent image formed on the photosensitive drum 1 into a visible image.
A developing device having a fixed arrangement of 4C, 4M, and 4K, a transfer device including a transfer drum 5a as a recording material carrier, and the like are provided.

Developing devices 4Y, 4C, 4M, 4K in this configuration
The operation at the time of development will be described in detail. In this configuration,
A plurality of developing devices 4 </ b> Y and 4 </ b> C around the photosensitive drum 1 from the upstream side to the downstream side in the moving direction (rotation direction) of the photosensitive drum 1.
4M and 4K are arranged in a predetermined order, and when the developing devices are sequentially operated to develop a latent image sequentially formed on the photosensitive drum, the developing operation of the developing device This is repeated toward the upstream side from the moving direction.

That is, the operation of each color developing device was different from the arrangement order, and was performed in the order of magenta, cyan, yellow, and black. That is, the developing operation is started from the magenta developing device 4M, and is performed in order from the downstream in the rotation direction of the photosensitive drum 1 to the upstream. However, since the flow from the yellow developing device 4Y to the black developing device 4K shifts from the most upstream to the most downstream, the order may not be strictly from upstream to downstream, but this is only at the switching point of the developing device. Therefore, it can be said that the order is substantially from downstream to upstream.

Further, during the continuous image formation, the operation order of the developing device is repeated so that the order of use of the developing device is always upstream from the downstream in the rotation direction of the photosensitive drum.

As a result of this construction, the yellow toner of the two-component developer in the most upstream yellow developing device 4Y scatters, and the cyan, magenta and black developing devices 4Y on the downstream side are scattered.
C, 4M, and 4K were mixed, but because of low visibility,
No problems due to color mixing occurred on the formed image.

Also, the color mixture due to the scattering of magenta toner and the color mixture due to the scattering of cyan toner in the magenta developing unit 4M are similarly weak in luminosity, so that there was no problem on the formed image.

Thus, according to such a configuration, it is possible to form a good image without problems such as color mixing in image formation.

Further, as a result of the developing order of the developing unit being periodically performed from the downstream to the upstream during the continuous image formation, continuous copying is performed when A3 size recording material or two A4 size recording materials are sucked. This eliminates the need for idle rotation of the transfer drum, which is a disadvantage of the conventional image forming apparatus shown in FIG.

This point will be further described with reference to FIG. 5 using the A3 size as an example. As described above, the transfer drum 5
When the recording material P of A3 size is fed to a, there is a portion amm where the recording material P is not present on the transfer drum 5a. The distance a is the distance b1 mm between the adjacent developing units (the distance between the black developing unit 4K and the magenta developing unit 4M), b2 mm (the distance between the magenta developing unit 4M and the cyan developing unit 4C), b3
mm (the distance between the cyan developing unit 4C and the yellow developing unit 4Y).

First, when a toner image of each color is transferred to one A3 size recording material, the developing operation is performed in the order of the cyan developing device 4C and the yellow developing device 4Y starting from the magenta developing device 4M and moving upstream. The developing operation is shifted from the upstream yellow developing unit 4Y to the most downstream black developing unit 4K, and is ended. Thus, the formation of these toner images is
The transfer drum 5a is (ab2) mm, (ab3) m
Since the switching of the developing units may be performed while the rotation is performed by m and (a + b1 + b2 + b3) mm, no problem occurs.

Next, when the second sheet of recording paper is fed continuously during continuous copying, the distance from the trailing edge of the first sheet to the leading edge of the second sheet is only amm as described above. .
However, in this example, the downstream magenta developing device 4M
From the cyan developing unit 4C to the yellow developing unit 4Y, and finally, the developing operation is shifted from the most upstream yellow developing unit 4Y to the most downstream black developing unit 4K. Because it will be repeated
When the developing operation is switched from the black developing device 4K to the magenta developing device 4M, the rear end of the black latent image on the photosensitive drum 1, that is, the rear end of the last latent image of the first sheet has passed through the black developing device 4K. At this time, the tip of the first magenta latent image of the second sheet is (a-b1) mm upstream from the magenta developing device 4M.
At a distance of For this reason, since the developing device can be switched during this period, it is not necessary to rotate the transfer drum 5a one more turn.

Therefore, it is not necessary to waste time, as in the above-described rotary developing system shown in FIG. 4, in which the transfer drum 5a is idlely rotated for each color before the next development is started. Thus, the copying speed was reduced and the machine performance was not deteriorated.

Since two or more developing units do not perform the developing operation at the same time, as shown in FIG. 5, only one developing unit is driven by one motor M through each color clutch CY, CC, CM, CM. The development operation can be executed by driving
Accordingly, the other developing device is not driven during the development of one latent image, so that the torque does not fluctuate, so that good development can be performed.

[0035]

However, in the above-mentioned prior art, the switching of the developing device is performed by the operation of moving the developing device toward and away from the photosensitive drum. Therefore, when an image is output at a high speed, the developing device is switched for one second. In the following, it is necessary to make contact and disengagement in a few milliseconds, and as a result, the device becomes large-scale or the speed of disengagement increases,
In particular, a stable image can be obtained over a long period of time due to pitch unevenness caused by a shock when the developing unit comes into contact with the photoconductor drum, or scratches or deposits of developer on the photoconductor drum. Was difficult.

There is also a method in which the switching of the developing device is performed not by the detachment operation but by a so-called cut-off operation. It took too long to completely remove the developer on the developing sleeve, and it was difficult to use it in a high-speed full-color copying machine.

As described above, it has been extremely difficult to stably output high-speed full-color image formation over a long period of time using the conventional technology.

Therefore, a main object of the present invention is to stably obtain a high-quality image even at a high speed, and to cut off the ears on the developer carrying member in an extremely short time after the completion of the developing operation. It is to provide a developing device.

[0039]

[0040]

The above object is achieved by a developing apparatus according to the present invention. In summary, the present invention provides a developer container containing a developer including a toner and a carrier,
A first developer carrier and a second developer carrier for carrying and transporting the developer in the developer container to develop the electrostatic latent image on the image carrier; In the developing device for transferring the developer from the first developer carrier to the second developer carrier by rotating the first developer carrier and the second developer carrier in the same direction, after the developing operation is completed. The developing device is characterized in that the first developer carrier is rotated in a direction opposite to that during the developing operation, and the second developer carrier is rotated in the same direction as during the developing operation.

According to one embodiment of the present invention, there is provided first magnetic field generating means fixedly disposed inside the first developer carrier, wherein the first developer carrier pumps the developer, A first magnetic field generating means for generating a magnetic field so as to be transferred to the second developer carrier, and a second magnetic field generating means fixedly disposed inside the second developer carrier,
And a second magnetic field generating means for generating a magnetic field so as to convey the developer delivered from the developer carrier and remove the developer having passed through the developing unit from the second developer carrier.

According to another embodiment of the present invention, the first
All the developer on the developer carrier is delivered to the second developer carrier. According to another embodiment of the present invention, the apparatus further includes a supply unit that supplies a developer to the first developer carrier, and the supply unit supplies the first developer carrier during a developing operation and after the developing operation is completed. And rotate in the same direction. According to still another embodiment of the present invention, the positions of the first developer carrier and the second developer carrier with respect to the image carrier during the developing operation and after the end of the developing operation are unchanged.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color image forming apparatus provided with a developing device according to the present invention will be described in more detail with reference to the drawings. Note that members having the same functions as the members described above are denoted by the same reference numerals.

Embodiment 1 As shown in FIG. 1, the color image forming apparatus of Embodiment 1
It has a digital color image reader at the top and a printer at the bottom.

In the reader section, the original 30 is placed on the original platen 3
1, and the reflected light image from the original 30 obtained by exposure and scanning by the exposure lamp 32 is
To collect the color-separated image signal.

The color separation image signal is amplified by an amplifier circuit (not shown), processed by a video processing unit (not shown), and sent to a printer unit.

In the printer section, the photosensitive drum 1 serving as an image carrier has a large diameter of 180 mm and is rotatably carried in the direction of the arrow shown in the figure.

Around the photosensitive drum 1, a pre-exposure lamp 11 for initializing the surface of the photosensitive drum 1, a corona charger 2 for uniformly charging the surface of the photosensitive drum 1, and on the photosensitive drum 1 Image exposure means 3 for forming an electrostatic latent image corresponding to image information, a potential sensor 12 for detecting the potential of the surface of the photosensitive drum 1, and developing the electrostatic latent image formed on the photosensitive drum 1 into a visible image Four fixedly arranged developing devices for storing developers (toners) of different colors, that is, a developing device 4Y
4C, 4M, 4K, light detecting means 13 for detecting the amount of toner on the photosensitive drum 1, a transfer device 5 including a transfer drum 5a as a recording material carrier, and removing the developer remaining on the photosensitive drum 1 Cleaners 6 and the like are provided.

The image exposure means 3 comprises a polygon mirror 3a, a lens 3b, a mirror 3c, and the like, and receives a laser beam E from a laser output unit modulated by a color image signal of each color separated from the reader unit. Polygon mirror 3
The light is reflected by a, and is projected on the surface of the photosensitive drum 1 through the lens 3b and the mirror 3c to form an electrostatic latent image corresponding to a color image signal of each color.

When an image is formed by the printer unit, the photosensitive drum 1 is rotated in the direction of the arrow shown in the figure, first, the surface of the photosensitive drum 1 is neutralized by the pre-exposure lamp 11 and initialized, and then the photosensitive drum 1 is rotated by the corona charger 2. The surface of the drum 1 is uniformly charged, and the surface of the photoreceptor drum 1 is sequentially irradiated with a light image E corresponding to an image signal of each color separated by the image exposing means 3 to sequentially form an electrostatic latent image in a predetermined color order. To form

Next, a predetermined developing device is operated in the order of magenta (M), cyan (C), yellow (Y), and black (K) in a predetermined developing order, so that the latent image on the photosensitive drum 1 is changed. Is developed, and a toner image based on resin is formed on the photosensitive drum 1 sequentially. Each of the developing devices 4M, 4C, 4Y, and 4K, which are fixedly disposed developing devices, is configured such that a required developing device is selectively used in accordance with the color of a latent image formed by the cutting operation described later in detail. The developing operation is performed on the drum 1.

On the other hand, a recording material P such as a transfer sheet fed from a recording material cassette 7a (or 7b or 7c) by a transport system including a pickup roller, a paper feed guide, a paper feed roller, etc., at a predetermined timing. Synchronously, the transfer device 5
Is wound around the transfer drum 5a.

In this embodiment, the transfer device 5 includes a transfer drum 5a having a diameter of 180 mm as a recording medium carrier, a transfer corona charger 5b for transferring a toner image on the photosensitive drum 1 to a recording material, An adsorption corona charger 5c, which is an adsorption charger for adsorbing the recording material onto the transfer drum 5a;
The transfer drum 5a has a suction (contact) roller 5g as an opposite pole, an inner charger 5d, and an outer corona charger 5e. A recording material carrying sheet 5f made of a dielectric material serving as a recording material carrying means is integrally stretched in a cylindrical shape. As the recording material supporting sheet 5f, a dielectric sheet such as a polycarbonate film is used.

The transfer drum 5a is rotated in the direction shown by the arrow in synchronization with the photosensitive drum 1, and the toner image developed by the magenta developing device 4M is carried on a recording material carrying sheet 5f by a transfer charger 5b in a transfer section. It is transferred to the recorded recording material. The transfer drum 5b continues to rotate as it is to prepare for the transfer of the next color (for example, cyan) image.

The photosensitive drum 1 on which the toner image has been transferred is cleaned by a cleaner 6 to remove extraneous matter such as residual toner, is uniformly charged again by the corona charger 2, and is modulated by the next cyan image signal. The light undergoes image exposure as described above.

The cyan latent image is developed by a cyan developing device 4C to form a cyan toner image. The cyan toner image is transferred to a recording material carried on a recording material carrying sheet 5f by a transfer charger 5b at a transfer portion. Transferred to
The cyan toner image is transferred onto the magenta toner image.
The transfer drum 5b continues to rotate as it is, and prepares for transfer of an image of the next color (for example, yellow).

Subsequently, the above-described process is performed for image formation and transfer of yellow and black, and when the overlapping transfer of the toner images of four colors is completed, the recording material is discharged by the separating charger 5h. Next, the separation push-up roller 8
b, and is separated from the transfer drum 5a by the action of the separation claw 8a, sent to the heat roller fixing device 9 by the transporting means, fixed collectively, and discharged onto the external tray 10.

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

Next, when an image is formed on both sides of the recording material, the recording material is discharged from the heat roller fixing device 9 and immediately after that, the conveyance path switching guide 19 is driven so that the recording material is conveyed vertically. Through the path 20, the light is once led to the inversion path 21a. Thereafter, the recording material is retracted in a direction opposite to the direction in which the recording material is fed, with the rear end of the fed recording material being the leading end, and stored in the intermediate tray 22 by the reverse rotation of the reversing roller 21 b. Thereafter, the recording material is again conveyed from the intermediate tray 22 to the transfer device 5, and an image is formed on the other surface by the image forming process described above.

Further, in order to prevent scattering of powder on the recording material carrying sheet 5f of the transfer drum 5a and adhesion of oil on the recording material, etc., the fur brush 14 and the fur brush via the recording material carrying sheet 5f are used. The cleaning is performed by a backup brush 15 facing the oil removal roller 16 and a backup brush 17 facing the oil removal roller 16 via the oil removal roller 16 and the recording material carrying sheet 5f. Such cleaning is performed before or after image formation, and is performed at any time when a jam (paper jam) occurs. Further, in the present embodiment, the eccentric cam 25 is operated at a desired timing, and the cam follower 5i integrated with the transfer drum 5a.
, The gap between the recording material carrying sheet 5f and the photosensitive drum 1 can be set arbitrarily. For example, during standby (standby) or when the power is off, the interval between the transfer drum 5a and the photosensitive drum 1 is increased.

Further, the recording material on which the one-side (first surface) image has been formed and fixed is once discharged to the paper discharge tray 10, and the recording material is directed upward from the second surface to the manual paper supply roller 41 from the manual paper supply unit 40. To perform image formation on the second surface. In the case of monochrome image copying, only the black developing device 4Bk operates.

Further, a double-sided copy mode for copying a black-and-white image and an image forming mode in which one color image of a recording material is used and the other surface is a black-and-white image can be selectively executed.

Next, the developing device and the developer used in each developing device will be further described.

First, the developer will be described. Each developer is a two-component developer composed of a magnetic carrier and magenta, yellow, cyan, and black toners corresponding to each developing device.

Each color developer is composed of toner T (g) and carrier C
The ratio of (g) is, for example, {T / (T + C)} × 100 = 4.5 (%) for yellow, and 6 (%) for magenta, cyan, and black.

As the carrier, a carrier in which Cu—Zn—Fe ferrite particles are surface-coated with a silicone resin is used.

The toner composition includes: a polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts chromium complex of di-tert-butylsalicylic acid 2 parts each color Pigment (as described below) ... 4 parts.

The above compound is sufficiently premixed by a Henschel mixer, melt-kneaded by a twin-screw extruder, cooled, coarsely pulverized to about 1 to 2 mm using a hammer mill, and then finely pulverized by an air jet method. Finely ground.
Further, the obtained finely pulverized product was classified and selected from 2 to 10 μm to obtain colorant-containing resin particles.

Further, as an external additive, titanium oxide having a particle size of 0.05 μm was added to 100 parts of the above-mentioned colorant-containing resin particles in an amount of 1.0%.
Parts of strontium titanate was added to obtain a toner. In addition, as each color pigment, yellow; azo pigment magenta; quinacridone pigment cyan; phthalone anine pigment black; and carbon black were used.

Next, FIGS. 2 and 3 show the developing units for each color.
This will be described with reference to FIG. FIG. 2 shows a black developing device 4K, and FIG. 3 shows a yellow developing device 4Y. The magenta developing device 4M has the same configuration as the black developing device 4K, and the cyan developing device 4C has the same configuration as the yellow developing device.

[0071] black developer 4K shown in FIG. 2, includes a developer container 116, the inside of the developer container 116 is partitioned into a developing chamber R ₁ and the stirring chamber R ₂ by a partition wall 117. The developing chamber R ₁ and the stirring chamber R ₂ each conveying screws 113 and 114 are arranged so as to rotate in the direction of the arrow.

The developer in the developing chamber R ₁ and the stirring chamber R ₂ are constantly stirred by the conveying screws 113 and 114, and the toner concentration is measured by a developer concentration measuring device (not shown).
When necessary, a required amount of toner is supplied from a toner supply device (not shown), and a constant concentration of the developer is always supplied to the first and second developing sleeves 111 and 111 'arranged as follows.

An opening is provided in a portion of the developer container 116 close to the photosensitive drum 1, and first and second developing sleeves 111 as a developer carrying member are provided through the opening.
111 ′ is disposed so as to protrude halfway to the outside, and is incorporated in the developer container 116 so as to rotate in the m and n directions, respectively. The first developing sleeve 111 is provided on the upstream side of the photosensitive drum 1 in the rotation direction.
11 'are arranged on the downstream side, respectively.

In this embodiment, both developing sleeves 111 and 11 are used.
The outer diameter of 1 ′ was 16 mm, and its peripheral speed was 280 mm / sec. Also, both developing sleeves 11
1, 111 ′ are 60 mm apart from the photosensitive drum 1, respectively.
It is arranged to be 0 μm.

The developing sleeves 111 and 111 'are made of a non-magnetic material, and have a magnet 11 serving as a magnetic field generating means therein.
2, 112 'are respectively fixed.

The magnet 112 of the first developing sleeve 111 is
Developing magnetic pole N2 and pumping pole S for pumping up the developer
1. Magnetic poles N ₁ , S for regulating and transporting the amount of developer
_2, the magnetic pole S ₃ for passing the developer to the second developing sleeve 111 'is disposed.

The magnet 11 of the second developing sleeve 111 ′
2 ′ is a magnetic pole N ₃ for receiving the developer from the developing magnetic pole S ₄ and the first developing sleeve 111 and transporting the developer to the developing magnetic pole S _4, and transporting the developer after development.
The magnetic poles N ₄ , S ₅ , and N ₅ to be collected at 3 are arranged.

Magnetic pole S in first developing sleeve 111
₁ , S ₃ , the magnetic pole N in the second developing sleeve 111 ′
₃ and N ₅ are in a repulsive pole relationship. As a result, there is almost no developer between the first and second developing sleeves 111 and 111 ′ and the conveying screw 113,
From the magnetic pole N5 of the developing sleeve 111 ', the conveying screw 1
The developer collected in 13 is circulated such that it is pumped up by the pumping pole S1 of the first developing sleeve 111 and is conveyed to the developing section.

The pattern of the magnetic poles is adjusted so that the developer is transferred 100% from the S ₃ pole of the first developing sleeve 111 to the N ₃ pole of the second developing sleeve 111 ′. The developer does not completely exist between the repulsion poles S _{1 and} S _{3 and} between N _{3 and} N _{5 of the} developing sleeves 111 and 111 ′.

The magnetic poles N ₁ and S _{2 of} the first developing sleeve 111
A developing blade 131 is disposed facing the gap therebetween,
The distance from the sleeve is set to 800 μm.

The developing blade 131 is made of aluminum, SU
It is made of a non-magnetic material such as S316, and regulates the layer thickness of the developer on the first and second developing sleeves 111 and 111 '.

Next, the operation of the black developing device 4K will be described with reference to FIG.

First and second developing sleeves 111 and 11
A DC bias on which an AC bias (2 kHz, a rectangular wave of 2 kVpp) is superimposed is applied to 1 'by a bias applying unit (not shown). By rotating the first developing sleeve 111 in the direction of arrow m, a predetermined amount (about 45 mg / cm
² ) The developer is supplied to the developing pole N2, and the photosensitive drum 1
The image flies to the color separation latent image formed thereon, and the first development is performed.

After the development, the developer is transferred from the magnetic pole S ₃ of the first developing sleeve 111 to the second developing sleeve 11 as described above.
It is passed 100% to pole N ₃ 1 '.

[0085] The second development sleeve 111 'is rotated in the same manner n direction as the first development sleeve 111, the second developing sleeve 111' by a developing pole S ₄ of the second development is carried out.

By performing development twice for one latent image in this manner, there is no resulting image abnormality on the boundary line of the solid image, the halftone portion is uniform, and the solid portion of the high density portion is formed. A high quality image which was sufficiently projected was obtained.

After the development is completed, the developer is supplied to the second developing sleeve 1.
11 'is conveyed by the magnetic poles N _4, S _5, N _5, and as described above, the second developing sleeve 111 by the action of the repelling poles of N _5, N _3' falls from above, it is collected in the conveyor screw 113 .

Conventionally, the developing sleeve was separated from the photosensitive drum at the end of the development, but in the present embodiment, the second developing sleeve 111 'continues to rotate after the end of the development, and only the first developing sleeve 111 moves in the m' direction. By cutting at the same peripheral speed as during the development, the ears are cut off. The developer is transferred from the first developing sleeve 111 to the second developing sleeve 111 ′.
% Of the developing sleeves 111 and 11
The repulsion pole S ₃ -S is provided between 1 ′ and the conveying screw 113.
_1, since the developer by the action of N ₅ -N ₃ does not exist, no residence of the developer between both the developing sleeve 111, 111 '. Therefore, unlike the conventional ear cutting, the ear cutting can be performed in a very short time.

In this embodiment, the peripheral speed of the sleeve is 200 mm /
In the second case, a φ16 sleeve is used. If the rise time of the motor is ignored, the distance between the magnetic poles S _{3 and} N ₂ in the first developing sleeve 111 is almost 90 °. Can be finished. For this reason, it has become possible to stably switch the developing device at a high speed when using a large-sized drum, which was extremely difficult with the conventional full color.

Next, the yellow developing unit shown in FIG. 3 will be described. Members having the same functions as those of the components of the black developing device shown in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.

A major difference from the above-described black developing device of FIG. 2 is that a third developing sleeve 124 for pumping up the developer is disposed on the transport screw 113. This is because, due to the arrangement of the yellow developing device 4Y and the cyan developing device 4C with respect to the photosensitive drum 1, it is difficult to pump up the developer using only the first developing sleeve.

The magnet 125 is provided in the third developing sleeve 124.
Are fixedly arranged. The magnet 125 has magnetic poles N ₆ , S ₆ ,
Has N _7, the third developing sleeve by the action of the magnetic poles N ₆ 1
24 rotates in the C direction, so that the transport screw 1
The developer is pumped up from 13 and transported by the magnetic poles S ₆ and N ₇ to supply the developer to the first developing sleeve 111.

At the time of development, the third developing sleeve 1 described above is used.
The developer from 24 is supplied to the first developing sleeve 111. After the supply, the operation is the same as that of the black developing device shown in FIG. However, the development pole of the second developing sleeve 111 'becomes N _4.

After the development is completed, the second developing sleeve 111 ′
Means that the first developing sleeve 111 and the third developing sleeve 124 rotate in the m ′ direction, the c ′ direction, and the direction opposite to the developing direction at the same speed as the developing speed, respectively. , The developer on the sleeve is immediately removed.

[0095] By adopting the above-described configuration in each developing unit, it is possible to output a high quality image at a high speed, and furthermore, it is possible to prevent the occurrence of pitch unevenness and deposits on the photosensitive drum due to switching of the developing unit. Thus, a stable image can be obtained over a long period of time.

Second Embodiment Next, a second embodiment of the present invention will be described again with reference to FIG. In the present embodiment, the operation at the time of development is the same as that of the first embodiment.
The developing sleeve 111 'rotates by a half rotation of the sleeve, and the third developing sleeve 124 stops immediately after the end. After the half rotation of the sleeve, the second developing sleeve 111 'continues to rotate as it is, and only the first developing sleeve 111 rotates at a double speed in the reverse direction by half a rotation and stops.

By performing the above operation, the stop time is slightly delayed. However, since the amount and state of the developer in the developer container inside the blade 131 can be made the same as in the development, the following operation can be performed. As the developing sleeve is rotated during image formation, a stable coating of the developer can be secured, so that the uniformity of the image at the leading end of the output image can be stably maintained even at high speed.

[0098]

As described above, according to the present invention,
Since the developing operation is performed by the first developer carrier and the second developer carrier, a high-quality image can be stably obtained even at a high speed. Is rotated in the opposite direction and the second developer carrier is rotated in the same direction as during the developing operation, so that the cutting of the ears on the first developer carrier and the second developer carrier can be performed in a very short time. .

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an electrophotographic color image forming apparatus to which the present invention is applied.

FIG. 2 is a sectional view showing the black or magenta developing device of FIG.

FIG. 3 is a sectional view showing a yellow or cyan developing device of FIG. 1;

FIG. 4 is an overall configuration diagram showing an example of a conventional electrophotographic color image forming apparatus.

FIG. 5 is an explanatory view of a sequence of developing devices, a developing operation, and a transfer operation in another conventional electrophotographic color image forming apparatus.

[Explanation of symbols]

Reference Signs List 1 photoconductor drum (image carrier) 4Y, 4M, 4C, 4K developing device (developing device) 111 first developing sleeve (first developer carrier) 111 'second developing sleeve (second developer carrier) 112 , 112 ′ magnet (magnetic field generating means) 116 developer container 124 third developing sleeve

──────────────────────────────────────────────────続 き Continuation of the front page (72) The inventor Takao Ogata 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-8-286503 (JP, A) JP-A Sho-59 -24866 (JP, A) Japanese Utility Model 2-119656 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 15 / 08-15/095

Claims (5)

(57) [Claims] 1. A developer container containing a developer containing a toner and a carrier, and a first developer carrying and transporting the developer in the developer container to develop an electrostatic latent image on an image carrier. A carrier and a second developer carrier, wherein during the developing operation, the first developer carrier and the second developer carrier are rotated in the same direction to move the first developer carrier from the first developer carrier. Second
In the developing device that transfers the developer to the developer carrying member, after the developing operation is completed, the first developer carrying member is rotated in a direction opposite to that in the developing operation, and the second developer carrying member is rotated in a direction opposite to the developing operation. A developing device characterized by rotating in the same direction. 2. A first magnetic field generating means fixedly disposed inside the first developer carrier, wherein a developer is pumped to the first developer carrier, and is pumped to the second developer carrier. First magnetic field generating means for generating a magnetic field so as to be transferred to the second developer carrier, and second magnetic field generating means fixedly disposed inside the second developer carrier, the second magnetic field generating means being delivered from the first developer carrier. And transports the developer that has passed through the developing section to the second
2. The developing device according to claim 1, further comprising second magnetic field generating means for generating a magnetic field so as to remove the magnetic field from the developer carrier. 3. The developing device according to claim 1, wherein all of the developer on the first developer carrier is delivered to the second developer carrier. 4. A supply device for supplying a developer to the first developer carrier, wherein the supply device rotates in the same direction as the first developer carrier during a developing operation and after the developing operation is completed. The developing device according to any one of claims 1 to 3, wherein: 5. The image forming apparatus according to claim 1, wherein the positions of the first developer carrier and the second developer carrier with respect to the image carrier during a developing operation and after the end of the developing operation are unchanged. Any of the developing devices.