JPH0798545A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent inconvenience from occurring because carrier is attached on an image carrier. CONSTITUTION:In an image forming device having a developing device provided with a developing roller and a carrier recovery roller, a toner image obtained by developing an electrostatic latent image is formed by rotating the developing roller a prescribed time (t2) (referring to a figure (B) after the electrostatic latent image is started to be formed on a photoreceptor drum by actuating an exposure device (referring to a figure (A)). Besides, it is judged based on the action timing of the exposure device whether the carrier recovery roller is made to correspond to an inter-image part on the photoreceptor drum where the toner image is not formed or not (referring to a figure (C)). When the carrier recovery roller is made to correspond to the inter-image part, it is rotated (referring to a figure (D)). Thus, the image is prevented from being disordered caused by the carrier attached on the photoreceptor drum and attracted by the carrier recovery roller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to forming an electrostatic latent image on an image carrier and developing the electrostatic latent image with a developer containing a toner and a carrier to form an image. The present invention relates to an image forming apparatus that forms a toner image on a carrier.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, the surface of an image carrier is charged,
After exposure to form an electrostatic latent image, the electrostatic latent image is developed by a developing device. In a developing device for developing using a two-component developer containing a toner and a magnetic carrier, a sleeve arranged such that an outer peripheral surface faces a surface of an image carrier at a predetermined distance, and an inner peripheral side of the sleeve. And a developing roller composed of a permanent magnet disposed in the developing device. The toner and the magnetic carrier are charged to different polarities by frictional charging inside the developing device. The carrier, which has attracted the toner on the surface by being charged, is attracted in a brush shape on the outer circumference of the sleeve by the permanent magnet, and is transported to the vicinity of the surface of the image carrier together with the toner by rotating the sleeve.

The toner conveyed to the vicinity of the surface of the image carrier is attracted to the electrostatic latent image on the image carrier by the potential difference between the developing bias voltage applied to the sleeve and the electrostatic latent image, and the electrostatic latent image is formed. It is developed to form a toner image. Further, the carrier is collected in the developing device while being attracted to the sleeve by the magnetic force of the permanent magnet. On the other hand, in the image forming apparatus, the transfer material is brought into contact with the image carrier on which the toner image is formed by the development by the developing device, and the toner image is transferred to the transfer material. Next, the transfer material is peeled off from the image carrier, and the transfer image is fixed by the fixing device to form an image on the transfer material.

By the way, especially the particle size of the carrier is small,
Alternatively, when the magnetism of the carrier is weakened due to deterioration or the like, the carrier may adhere to the surface of the image carrier during development. The carrier attached to the image bearing member reduces the adhesion of the transfer material to the image bearing member at the time of transfer, leading to deterioration of the quality of the transferred image such as so-called white spots. Therefore, the developing device is often provided with a carrier collecting roller downstream of the developing roller. As described in Japanese Patent Laid-Open No. 61-200561, the carrier collecting roller is simultaneously rotated by the same driving source when the sleeve of the developing roller is rotated, and adheres to the image carrier during development. The magnetic force attracts the carrier to the surface. The carrier sucked onto the roller surface is scraped off from the roller surface by a scraper or the like and collected in the developing device.

However, it is difficult to scrape off all the carriers sucked onto the surface of the carrier collecting roller from the surface of the roller, and a part of the toner adhering to the surface of the carrier is separated from the carrier and the carrier is collected. Although it adheres to the surface of the roller, it is more difficult to scrape off this toner. Therefore, the surface of the roller that has passed through the disposing portion of the scraper or the like may be covered with the toner, or some amount of carrier may remain on the roller surface. As described above, since the carrier collecting roller is rotated simultaneously with the sleeve of the developing roller, the carrier collecting roller does not move even when the portion of the image carrier on which the toner image is formed passes near the carrier collecting roller. There is a problem that the toner image may be disturbed or dirt may be attached by the carrier and toner that are rotating and remain on the surface of the carrier recovery roller.

Further, in an image forming apparatus having a plurality of developing devices of the same polarity, since the polarities of the carriers of the developers used in the developing devices are the same, if only the upstream developing device is operated, the upstream A very small amount of the carrier that could not be completely collected by the carrier collecting roller of the developing device on the side is attracted to the surfaces of the developing roller and the carrier collecting roller of the developing device on the downstream side. As a result, when the state in which only the upstream developing device is operated and the downstream developing device is stopped is continued, the carrier is accumulated on the surface of the developing roller and the collecting roller of the downstream developing device, There is a possibility that the developing device may malfunction, the toner image may be disturbed, or dirt may be attached as described above.

Further, the carrier accumulated on the developing roll of the downstream developing device may attract a part of the toner forming the toner image by electrostatic force. Generally, in an image forming apparatus having a plurality of developing devices, toners of different colors are loaded in the developing devices, so that the toner sucked by the carrier and the toner of the developer loaded in the downstream developing device. There is also a problem that the colors are different, and if the developing device on the downstream side is operated while the toners of different colors are sucked, color mixing occurs.

The present invention has been made in consideration of the above facts, and an object of the present invention is to obtain an image forming apparatus capable of preventing the occurrence of inconvenience due to the carrier adhering to the image carrier.

[0009]

In order to achieve the above object, the invention according to claim 1 is a latent image forming means for forming an electrostatic latent image on an image carrier, and a latent image forming means formed on the image carrier. A developing unit for developing the electrostatic latent image with a developer containing toner and a magnetic carrier to form a toner image on the image carrier, and a carrier arranged at a predetermined distance from the image carrier on the downstream side of the developing unit. When the collecting roller and the developing unit are developing the electrostatic latent image, the carrier is collected only when the carrier collecting roller corresponds to the portion of the image carrier on which the toner image is not formed. And a driving unit that drives the carrier collecting roller so as to be collected.

According to a second aspect of the present invention, a latent image forming means for forming an electrostatic latent image on the image carrier, a first sleeve arranged at a predetermined distance from the image carrier, and the first sleeve. A first magnetic field generating portion disposed on the inner circumference of the sleeve for generating a magnetic field, and including an electrostatic latent image formed on the image carrier, the toner and the magnetic carrier adhered to the first sleeve. A first developing roller that develops with a first developer to form a toner image on the image carrier, and a second sleeve that is disposed downstream of the first developing roller and at a predetermined distance from the image carrier. And a second magnetic field generator disposed on the inner circumference of the second sleeve to generate a magnetic field, and the electrostatic latent image formed on the image carrier is attached to the toner on the second sleeve. And a magnetic carrier and having the same polarity as the first developer. When the second developing roller that develops with the second developer to form a toner image on the image carrier and the first developing roller are developing the electrostatic latent image, the toner image on the image carrier is And a drive unit that drives the second developing roller only when the second developing roller corresponds to the portion not formed.

According to the second aspect of the present invention, the driving means causes the toner attached to the second sleeve of the second developing roller to attach to the image carrier when the second developing roller is driven. It is preferable to apply a bias voltage to the second developing roller.

[0012]

According to the invention of claim 1, an electrostatic latent image formed on the image carrier is developed with a developer containing toner and a magnetic carrier to form a toner image on the downstream side of the developing unit. When the carrier collecting roller is arranged at a predetermined distance and the developing unit is developing the electrostatic latent image, the carrier collecting roller corresponds to the portion of the image carrier on which the toner image is not formed. The carrier collecting roller is driven so that the carrier is collected only when the carrier is collected. As described above, a small amount of carriers may adhere to the image carrier due to development in the developing unit, and the carrier on the image carrier adheres to the surface of the carrier recovery roller arranged on the downstream side of the developing unit. It

Here, if the carrier collecting roller is driven during development in the developing section as in the conventional case, the carrier collecting roller is attracted to the surface of the carrier collecting roller and then remains on the surface without being scraped off from the carrier collecting roller. The carrier and the accumulated residual toner are successively supplied to the portion facing the image carrier, and the toner image is disturbed and dirt is attached by the carrier and the toner. On the other hand, according to the first aspect of the present invention, when the carrier collecting roller corresponds to the portion of the image carrier on which the toner image is formed, the carrier collecting roller is not driven, so that the carrier collecting roller remains on the surface. The toner or toner does not disturb the toner image or attach dirt.

Further, if the state where the driving of the carrier collecting roller is stopped while the developing section is developing is continued, the carrier is accumulated on the portion of the carrier collecting roller facing the image carrier, The deposited carrier may disturb the toner image on the image carrier. On the other hand, according to the first aspect of the invention, the carrier collecting roller is driven when the portion of the image carrier on which the toner image is not formed corresponds to the carrier collecting roller. The carriers are collected in a state where the carriers are accumulated, and thus it is possible to prevent a large amount of carriers from being accumulated on a part of the carrier recovery roller and to prevent the toner image from being disturbed.

Further, a member such as a scraper for scraping off the carrier adhering to the surface of the carrier collecting roller is generally in contact with the outer periphery of the carrier collecting roller, but as described above, the toner image is formed. Since the carrier collecting roller is driven only when the part where the mark is not formed corresponds to the carrier collecting roller, abrasion of the surface of the carrier collecting roller due to the scraper or the like is also reduced.

As described above, according to the first aspect of the invention, the carrier adheres to the image bearing member by the development by the developing unit, and the carrier is further attracted to the collecting roller and remains or accumulates, so that the toner image is disturbed or soiled. It is possible to prevent inconveniences such as adhesion. The carrier recovery roller may be provided in the developing device having the developing unit, or may be provided in the developing device provided on the downstream side of the developing device having the developing unit.

According to the second aspect of the invention, the first developing roller and the second developing roller are provided. The first developing roller includes a first sleeve arranged at a predetermined distance from the image carrier, and a first magnetic field generating unit arranged on the inner circumference of the first sleeve to generate a magnetic field. The electrostatic latent image formed on the body is developed with a first developer containing toner and magnetic carrier attached to the first sleeve to form a toner image on the image carrier. The second developing roller is disposed on the downstream side of the first developing roller at a predetermined distance from the image carrier, and the second developing roller is disposed on the inner circumference of the second sleeve to generate a magnetic field. 2 magnetic field generator,
And an electrostatic latent image formed on the image carrier is developed with a second developer containing toner and a magnetic carrier attached to a second sleeve and having the same polarity as the first developer. A toner image is formed on the carrier.

As described above, since the second developer has the same polarity as the first developer, the carrier adhered on the image carrier by the development by the first developing roller is the second developing roller. The magnetic field generated by the second magnetic field generator is attracted to the surface of the second sleeve. On the other hand, when the first developing roller is developing the electrostatic latent image, the drive means
The second developing roller is driven only when the second developing roller corresponds to the portion of the image carrier on which the toner image is not formed. Therefore, as in the case of the first aspect of the invention, the carrier adheres to the image carrier by the development by the first developing roller, and the carrier is further attracted to the second developing roller to remain or accumulate, thereby disturbing the toner image. It is possible to prevent the occurrence of inconveniences such as dusting and adhesion of dirt.

According to the second aspect of the invention, the driving means drives the second developing roller so that the toner attached to the second sleeve of the second developing roller adheres to the image carrier. It is preferable to apply a bias voltage to the developing roller. As a result, the toner attracted to the second sleeve and attached to the surface of the carrier or the like is attached again to the image carrier. Bias voltage is second
When the developing roller is driven, that is, when the second developing roller corresponds to the portion of the image carrier on which the toner image is not formed, the toner is the toner image on the image carrier. The toner adheres to a portion not formed and does not adversely affect the toner image formed on the image carrier, and the toner is prevented from being mixed with the toner of the second developer.

[0020]

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

[First Embodiment] FIG. 1 shows a schematic configuration diagram of an image forming apparatus 10 according to the first embodiment. The image forming apparatus 10 includes a photosensitive drum 12 as an image carrier. The photosensitive drum 12 has an insulating photoconductive layer formed on the surface thereof, and is rotated in the direction of arrow A in FIG. A charging corotron 14 is arranged at a predetermined portion on the outer circumference of the photosensitive drum 12. An exposure unit 16 is formed on the downstream side of the charging corotron 14 along the rotation direction of the photosensitive drum 12, and an exposure device 18 is provided corresponding to the exposure unit 16.

A developing device 20 is provided downstream of the exposure section 16.
Is provided. The configuration of the developing device 20 will be described later. The photoconductor drum 12 is provided downstream of the developing device 20.
A pre-transfer corotron 22, a transfer corotron 24, and a peeling corotron 26 are sequentially arranged at predetermined intervals from the surface of the above. The image receiving material P is fed by a conveying means (not shown) to
Is inserted between the transfer corotron 24 and the photosensitive drum 12 as indicated by a two-dot chain line. A peeling claw 28 is arranged on the downstream side of the peeling corotron 26 so that its tip comes into contact with the surface of the photoconductor drum 12, and a cleaning device 30 and a charge eliminating corotron 32 are arranged further downstream.

As shown in FIG. 2, the developing device 20 is disposed opposite to the casing 40 that stores the developer D, and the photosensitive drum 12 at the end of the casing 40 on the photosensitive drum 12 side at a predetermined distance. Developing roller 42 and developing roller 42
Carrier collecting roller 48, which is disposed below the photoconductor drum 12 at a predetermined distance from the photoconductor drum 12, and below the photoconductor drum 12 with the developing roller 42 in between (the diagonally lower right in FIG. 2).
The cylindrical paddle 5 arranged in parallel with the developing roller 42
4, a blender 56 arranged in parallel with the paddle 54 on the opposite side of the developing roller 42 with the paddle 54 interposed therebetween, and a wobble 58 arranged in parallel with the blender 56 on the opposite side of the paddle 54 across the blender 56. , Are provided.

The developing roller 42 is composed of a sleeve 44 made of a non-magnetic material and having a bottomed cylindrical shape and rotatable, and a permanent magnet 46 fixedly arranged on the inner peripheral side of the sleeve 44 as a magnetic field generating portion. Has been done. The permanent magnet 46 has an S ₁ magnetic pole formed in a portion facing the photosensitive drum 12,
Adjacent to this S ₁ magnetic pole, an N ₁ magnetic pole is formed on the counterclockwise side in FIG. 2, and an N ₂ magnetic pole is formed on the clockwise side in FIG.
_An S ₂ magnetic pole and an N ₃ magnetic pole are sequentially formed on the clockwise side of the ₂ magnetic poles. That is, except for the relationship between the N ₁ magnetic poles and the N ₃ magnetic poles, the S magnetic poles and the N magnetic poles are alternately formed, and N
The distance between the ₁ magnetic pole and the N ₃ magnetic pole is maximized.

A blade 60 is provided in parallel with the developing roller 42 and at a constant distance from the sleeve 44 in the vicinity of the portion where the S ₂ magnetic pole is formed on the outer peripheral side of the developing roller 42. Further, the sleeve 44 is connected to the high voltage power source 34, and a developing bias voltage is applied at the time of developing as described later.

As shown in FIG. 3, a sprocket 62 is arranged outside the casing 40, and the sprocket 62 is coaxially connected to the sleeve 44 at the bottom of the sleeve 44 of the developing roller 42. The sprocket 62 meshes with a sprocket 64 pivotally supported by the casing 40, and the sprocket 64 meshes with a sprocket 66 attached to a drive shaft of a motor 68 arranged outside the casing 40. Therefore, the developing roller 42
The sleeve 44 is rotated counterclockwise in FIG. 2 by transmitting the driving force of the motor 68 via the sprockets 62, 64 and 66.

On the other hand, the carrier collecting roller 48 is made of a non-magnetic material and has a cylindrical shape with a bottom and is rotatable.
0, and a permanent magnet 52 as a magnetic field generating unit fixedly arranged on the inner peripheral side of the sleeve 50. The permanent magnet 52 has an S magnetic pole formed in a portion facing the photosensitive drum 12, and an N magnetic pole is formed adjacent to the S magnetic pole on the counterclockwise side and the clockwise side in FIG. Further, the casing 40 is provided on the outer peripheral side of the carrier collecting roller 48.
A scraper 70 is provided between the S magnetic pole and the N magnetic pole located on the inner side, in parallel with the carrier collecting roller 48 and with its tip end in contact with the carrier collecting roller 48.

As shown in FIG. 3, a sprocket 72 is arranged outside the casing 40. The sprocket 72 is coaxially connected to the sleeve 50 at the bottom of the sleeve 50 of the carrier collecting roller 48. The sprocket 72 meshes with a sprocket 74 pivotally supported by the casing 40, and the sprocket 74 is attached to the casing 4
It meshes with a sprocket 76 attached to the drive shaft of a motor 78 arranged outside the zero position. Therefore, the sleeve 50 of the carrier collecting roller 48 is formed by the sprockets 72, 7
The driving force of the motor 78 is transmitted via the motors 4 and 76, whereby the motor 78 is rotated clockwise in FIG.

As shown in FIG. 1, the motors 68, 78 are connected to the controller 36 via drivers 80, 82. The control device 36, the driver 82, the motor 78,
The sprockets 72, 74, 76 constitute the driving means of the invention of claim 1. The control device 36 includes an exposure device 18,
The high voltage power source 34 and the like are also connected. The control device 36 includes a microcomputer and the like, and controls the operation of each part of the image forming apparatus 10.

Next, as an operation of the first embodiment, an image recording operation on the image receiving material P by the image forming apparatus 10 will be described first. In the developing device 20 of the image forming apparatus 10, the paddle 54 is rotated counterclockwise in FIG. 2 by the driving force of a motor (not shown), so that the developer D accumulated in the lower portion of the casing 40 is transferred to the developing roller 42. The developer D, which has been conveyed toward the developing roller 42 and is located on the carrier collecting roller 48 side in the casing 40, is conveyed to the blender 56 side. Blender 56
2 is rotated in the clockwise direction in FIG. 2 by the driving force of a motor (not shown), whereby the developer D conveyed by the paddle 54, the developer D accumulated in the lower portion of the casing 40, and the toner supply device (not shown) develop. Bowl 20
The toner supplied into the casing 40 is mixed and stirred.

The wobble 58 is rotated counterclockwise in FIG. 2 by the driving force of a motor (not shown), and the developer D carried by the rotation of the blender 56 and the wobble 58 are accumulated below the casing 40. The developer D is mixed and stirred. By the mixing and stirring by the blender 56 and the wobble 58, the carrier and the toner included in the developer D are charged negative and positive, respectively. On the other hand, the developer D supplied to the developing roller 42 is attracted to the sleeve 44 in a magnetic brush state along the magnetic lines of force generated by the carrier from the permanent magnet 46. The toner adheres to the surface of the carrier by electrostatic force.

The developer D attracted to the sleeve 44 in the form of a magnetic brush is conveyed along with the rotation of the sleeve 44 when the motor 68 is driven, and the developer D is absorbed by the blade 60 when passing through the blade 60 installation site. After a portion of the passage is blocked to make the height constant, the portion reaches the portion facing the photoconductor drum 12.

On the other hand, the charging corotron 14 of the image forming apparatus 10 charges the surface of the photoconductor drum 12 by attaching ions generated by corona discharge to the surface of the photoconductive layer of the photoconductor drum 12. In the exposure device 18, image data obtained by reading an image of an original by a reading device (not shown) is input from the control device 36. The exposure device 18 emits a laser beam modulated according to the image data from a laser diode, scans the laser beam with a scanning means such as a polygon mirror, and causes the surface of the photoconductor drum 12 located in the exposure section 16 to scan. Irradiate.

As a result, the portion of the surface of the photosensitive drum 12 irradiated with the laser beam is discharged according to the amount of the laser beam, and an electrostatic latent image corresponding to the image of the original is formed on the surface of the photosensitive drum 12. It As shown in FIG. 4 (A), the exposure device 18 is operated such that a plurality of images are continuously exposed with a constant pause time t ₁ for each exposure of one image.

As shown in FIG. 4B, the control device 36 causes the developing device 20 to perform development at a timing delayed by a predetermined time t ₂ from the operation timing of the exposure device 18 in synchronization with the operation of the exposure device 18. . That is, the high voltage power supply 34 is turned on to apply the developing bias voltage to the sleeve 44 of the developing roller 42, and the motor 68 is driven to rotate the sleeve 44. The predetermined time t ₂ is the exposure unit 1
6 is the time required for the portion on which the electrostatic latent image is formed to reach the site where the developing unit 20 is provided by the rotation of the photosensitive drum 12, and the portion on the photosensitive drum 12 on which the electrostatic latent image is formed. When the head of the developing device reaches the developing device 20, the developing device 20 starts the development.

As a result, of the developer D attracted to the sleeve 44 and reaching the portion facing the photoconductor drum 12, only the positively charged toner is charged with the developing bias voltage applied to the sleeve 44 and the photoconductor. Due to the potential difference from the electrostatic latent image portion formed on the drum 12, the photosensitive drum 1
2 It is adsorbed to the electrostatic latent image portion on the surface. As a result, the electrostatic latent image is developed and a toner image is formed on the surface of the photosensitive drum 12. On the other hand, during the development, most of the negatively charged carriers are still attracted to the sleeve 44 due to the developing bias voltage and the magnetic force of the S ₁ magnetic pole, and the development is performed as the sleeve 44 rotates. It is conveyed inside the container 20 and is separated from the sleeve 44 between the N ₁ magnetic pole and the N ₃ magnetic pole having almost no magnetic force.

However, the magnetic force of the S ₁ magnetic pole does not sufficiently act on a small portion of the carrier whose magnetic performance is deteriorated due to the deterioration, and is attached to the surface of the photosensitive drum 12 away from the sleeve 44. The carrier attached to the surface of the photoconductor drum 12 is attracted to the sleeve 50 of the carrier collection roller 48 by the magnetic force of the S magnetic pole of the permanent magnet 52 when the photoconductor drum 12 slightly rotates and corresponds to the carrier collection roller 48. It The carrier adsorbed on the sleeve 50 is carried into the developing device 20 when the sleeve 50 is rotated, and is carried to the scraper 7.
Most of it is scraped off from the surface of the sleeve 50 by 0, but a part remains on the surface of the sleeve 50 and is conveyed to a portion facing the photoconductor drum 12 by further rotation of the sleeve 50.

On the other hand, the controller 36 controls the developing roller 4
In consideration of the time t ₃ required for the toner image formed in the two disposition parts to reach the disposition part of the carrier recovery roller 48, the carrier recovery roller 48 is placed on the part of the photosensitive drum 12 where the toner image is formed. It is determined whether or not they correspond (see FIG. 4C). When the carrier recovery roller 48 corresponds to the portion on the photosensitive drum 12 where the toner image is formed, the motor 78 is not driven. Sleeve 5
0 is stopped, and the motor 78 is driven for a predetermined time each time when the carrier collecting roller 48 corresponds to the inter-image portion where the toner image is not formed (the portion B shown in FIG. 5) as shown in FIG. Then, the sleeve 50 is rotated (see FIG. 4D).

Therefore, the rotation of the sleeve 50 is stopped and remains on the surface of the sleeve 50 when the portion of the photosensitive drum 12 on which the toner image is formed passes through the portion where the carrier collecting roller 48 is disposed. The toner image is prevented from being disturbed by the existing carrier, and the toner adhered to the surface of the remaining carrier or the surface of the sleeve 50 does not adhere to the toner image as dirt. Further, while the rotation of the sleeve 50 is stopped, the carrier is gradually deposited on the portion of the sleeve 50 facing the photoconductor drum 12, but the carrier collecting roller 48 is placed on the portion where the toner image is not formed. Since the sleeve 50 is rotated when corresponding, the carrier is collected with a slight amount of the carrier accumulated on the surface of the sleeve 50, and a large amount of the carrier is accumulated on a part of the carrier recovery roller. And the toner image is prevented from being disturbed.

On the other hand, the portion of the photoconductor drum 12 on which the toner image is formed is transferred to the transfer corotron 22 after the electric potential is changed at the site where the pretransfer corotron 22 is disposed in order to facilitate transfer by discharge of the pretransfer corotron 22. 24 Move to the installation site. Further, the image receiving material P is conveyed between the photoconductor drum 12 and the transfer corotron 24 by a conveying unit (not shown), comes into contact with the surface of the photoconductor drum 12, and is negatively charged by the transfer corotron 24. As a result, each toner forming the toner image formed on the photosensitive drum 12 is adsorbed to the image receiving material P, and the toner image is transferred to the image receiving material P.

The image-receiving material P to which the toner image has been transferred is charged again by the peeling corotron 26 and is then charged on the photosensitive drum 12.
1 is conveyed from a path indicated by a chain double-dashed line in FIG. 1 by a conveying unit (not shown) and is heated by a fixing device (not shown), and the transferred toner image is fixed and then discharged to the outside of the image forming apparatus 10. To be done. When the peeling of the image receiving material P by the peeling corotron 26 fails, the image receiving material P together with the photosensitive drum 12 is peeled off.
After being conveyed to the eight disposition sites, the peeling claws 28 physically peel the strips. The surface of the portion of the photoconductor drum 12 that has passed the portion where the peeling claw 28 is disposed is cleaned by the cleaning device 30 to remove the toner and the like remaining on the surface, and then the charge removal corotron 32 remains on the photoconductor drum 12. The charge that is being stored is neutralized.

In the above description, the motor 78 is driven for a predetermined time to rotate the sleeve 50 every time when the carrier collecting roller 48 corresponds to the inter-image portion where the toner image is not formed. It is not limited to this. As an example, as shown in FIG. 6, the time interval for rotating the carrier recovery roller may be changed according to the image amount of the toner image (toner amount, that is, the density of the toner image).

FIG. 6A shows the case where the image amount is large, that is, the density of the toner image is high. In such a case, the amount of carrier attached to the surface of the photoconductor drum 12 becomes relatively large, so that the sleeve 50 is rotated every time the carrier recovery roller 48 corresponds to the inter-image portion. On the other hand, FIG. 6B shows a case where the image amount is small, that is, the density of the toner image is low. In such a case, the amount of the carrier adhered to the surface of the photoconductor drum 12 is relatively small. Therefore, when the carrier recovery roller 48 corresponds to the inter-image part, the ratio of once every plural times (in the figure, once every two times). The sleeve 50 is rotated at a rotation rate. Accordingly, the rotation amount of the sleeve 50 can be suppressed to a necessary minimum, and deterioration of the scraper 70 in contact with the sleeve 50 can be suppressed. The size of the image amount (toner image density) can be determined by referring to the exposure data or the like output to the exposure device 18 in the control device 36.

Further, the rotation of the sleeve 50 of the carrier collecting roller 48 is not limited to the rotation when the inter-image portion corresponds to the carrier collecting roller 48 as described above, but as shown in FIG. Corresponding to the plurality of images, the sleeve 50 is rotated for a predetermined period of time between the instruction to record the plurality of images on P and the arrival of the portion where the toner image is formed on the portion where the carrier recovery roller 48 is provided The rotation of the sleeve 50 is stopped until the plurality of toner images pass through the portion where the carrier collecting roller 48 is disposed.
The sleeve 50 may be rotated again for a predetermined time after all of the plurality of toner images have passed through the portion where the carrier collecting roller 48 is disposed.

Further, the rotation of the sleeve of the carrier collecting roller 48 is not limited to the one in which the driving force of the motor 78 is transmitted via a sprocket or the like as shown in FIG. For example, it is also possible to drive by the mechanism shown in FIG. In FIG. 8, the casing 4 is attached to the bottom of the sleeve 50 of the carrier collecting roller 48.
One end of a one-way clutch 86 arranged outside 0 is coaxially connected to the sleeve 50. The one-way clutch 86 transmits the rotational force in the clockwise direction of FIG. 8 applied to the cam 88 on the other end side to the sleeve 50 on the one end side, and the rotational force in the counterclockwise direction of FIG. 8 is applied to the cam 88. In this case, this rotational force is not transmitted.

An elliptical cam 88 is attached to the other end of the one-way clutch 86. The cam 88 is attached so that the end portion in the elliptical shape in the longitudinal direction projects to the outer peripheral side of the sleeve 50, and a hole is formed in the tip portion of the protruding portion, and one end of the tension coil spring 90 is formed in this hole. It is hooked and one end of the wire 92 is locked. The other end of the tension coil spring 90 is locked to a bracket formed outside the casing 40. The wire 92 has an intermediate portion wound around a pulley 94 pivotally supported by the casing 40, and the other end of the wire 92 is attached to a movable shaft 96A of a solenoid 96 fixed to the casing 40 by a bracket (not shown). There is.

The operation of this mechanism will be described. Solenoid 9
When the exciting coil is energized, 6 attracts the movable shaft 96A and moves it in the direction of arrow C in FIG. As a result, the wire 92 is also pulled in the direction of arrow C, and the cam 88 moves the tension coil spring 90.
Against the biasing force generated by the pulling of the sleeve 50, the sleeve 50 is rotated clockwise about the axis of the sleeve 50 to a position D shown by an imaginary line in FIG. Cam 88 at this time
Rotation of the sleeve 50 via the one-way clutch 86.
And the sleeve 50 is also rotated clockwise in FIG.

When the energization of the exciting coil of the solenoid 96 is stopped, the movable shaft 96A is returned to the position shown in FIG. 8 by the urging force of a compression coil spring (not shown) housed in the solenoid 96, and the cam 88 moves. Tension coil spring 90
It is rotated to the position shown by the solid line in FIG.
At this time, the rotational force is not transmitted to the sleeve 50 by the one-way clutch 86. Therefore, by repeatedly energizing the energizing coil of the solenoid 96 and stopping energizing, the sleeve 50 can be rotated stepwise by a predetermined rotation angle.

[Second Embodiment] Next, a second embodiment of the present invention will be described. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG.
The image forming apparatus 100 according to the second embodiment includes a first developing device 20A and a second developing device 20B on the downstream side of the first developing device 20A. Each of the first developing device 20A and the second developing device 20B has substantially the same configuration as the developing device 20 described in the first embodiment, but the carrier collecting roller 48 is provided only in the second developing device 20B. Has been. In addition, a first developer used in the first developing device 20A,
The second developer used in the second developing device 20 has a different toner color but is charged to the same polarity.

First developing device 2 as first developing roller
The developing roller 42A of 0A includes a sleeve 44A as a first sleeve and a permanent magnet 4 as a first magnetic field generator.
6A, and the sleeve 44A is connected to the motor 68A via a driving force transmission mechanism composed of a plurality of sprockets as in the first embodiment. The motor 68A is connected to the control device 36 via a driver 80A. Further, the developing roller 42B of the second developing device 20B as the second developing roller is the sleeve 44 as the second sleeve.
B and a permanent magnet 46B as a second magnetic field generating unit, and the motor 6 via the same driving force transmission mechanism as described above.
8B, the motor 68B is a driver 80B
Is connected to the control device 36 via. The control device 36, the driver 80B, the motor 68B and the like constitute the driving means of the invention of claim 2.

Next, the operation of the second embodiment will be described. The control device 36 designates the color of the image to be recorded on the transfer material P from the outside, and causes one of the first developing device 20A and the second developing device 20B to perform development in accordance with the designated color. Regarding the carrier collecting roller 48, the carrier collecting roller 48 is the photosensitive member in both cases where the first developing device 20A is developing and the second developing device 20B is developing. When the drum 12 does not correspond to the portion where the toner image is formed, the motor 7
8 is driven to rotate the sleeve 50. This allows
As in the first embodiment, the carrier or toner once adsorbed by the sleeve 50 of the carrier collecting roller 48 is prevented from disturbing the toner image on the photoconductor drum 12 or attaching dirt.

Next, the operation when the first developing device 20A is developing will be described. Since the developer D has the same polarity in the first developing device 20A and the second developing device 20B, the polarity of the magnetic pole formed in the portion of the permanent magnet of the developing roller 42A facing the photosensitive drum 12 is the same as that of the magnetic pole. The polarity of the magnetic pole formed in the portion of the developing roller 42B that faces the photosensitive drum 12 of the permanent magnet is the same. Therefore, the carrier of the first developer adhering to the surface of the photosensitive drum 12 while the first developing device 20A is developing is adsorbed to the outer periphery of the sleeve 44B of the second developing roller 42B. become. Further, the toner of the first developer is slightly attached to the surface of the carrier adsorbed by the sleeve 44B.

Therefore, the control device 36 controls the first developing device 2
Based on the timing when the sleeve 44A of the developing roller 42A of 0A starts rotating (see FIG. 10A), the toner image formed at the disposing portion of the developing roller 42A is disposed on the developing roller 42B of the second developing device 20B. Considering the time t ₄ required to reach the portion, the developing roller 42B and the photosensitive drum 1
It is determined whether or not the second toner image corresponds to the portion where the toner image is formed (see FIG. 10B), and the second developing roller 42B
, When the toner image on the photosensitive drum 12 corresponds to the inter-image portion where the toner image is not formed,
B is driven for a predetermined time to rotate the sleeve 44B (see FIG. 1).
0 (C)), the high voltage power supply 34 is controlled to apply a developing bias voltage to the sleeve 44B in synchronization with the rotation of the sleeve 44B (see FIG. 10D).

As a result, the toner adhering to the carrier attracted to the sleeve 44B of the developing roller 42B is
When the developing bias voltage is applied to the sleeve 44B, the developing bias voltage is attracted to the inter-image portion on the surface of the photosensitive drum 12. Therefore, when the second developing device 20B is actuated, the toner of the first developer having a color different from that of the toner of the second developer remains on the surface of the sleeve 44B of the developing roller 42B, so that the color mixture occurs. Occurrence or development device 2
It is possible to prevent the toner of the first developer from mixing into the inside of 0B. The toner attached to the interimage portion on the surface of the photosensitive drum 12 is removed by the cleaning device 30 without being transferred to the transfer material P.

The carrier attracted to the sleeve 44B is rotated by the sleeve 44B when the second developing roller 42B corresponds to the inter-image portion on the photosensitive drum 12, as described above. Developer 2
Since the toner image is collected inside 0B, it is also possible to prevent the toner image from being disturbed.

The timing of the rotation of the sleeve 44B of the developing roller 42B of the second developing device 20B and the application of the developing bias voltage when the first developing device 20A is developing are as shown in FIG. Not limited to
As described in the first embodiment, the time interval for rotating the sleeve 44B and applying the developing bias voltage may be changed according to the image amount of the toner image (toner amount, that is, the density of the toner image). (See Figure 6). Also,
As shown in FIG. 7, after the recording of a plurality of images on the transfer material P is instructed until the toner image portion reaches the developing roller 42B installation site, and the plurality of toner images are all located at the developing roller 42B installation site. After passing through, the sleeve 44B may be rotated and the developing bias voltage may be applied.

Further, the structure of the carrier recovery roller 48 is not limited to that described above, and an electromagnet may be used instead of the permanent magnet, for example. Further, it is possible to use a general cylindrical roller instead of the sleeve, and dispose the electromagnet or the permanent magnet at a position where a magnetic field is generated at a portion where the roller and the photosensitive drum face each other. Further, the developing roller is not limited to the developing roller having a configuration in which the permanent magnet is fixedly arranged and the sleeve arranged on the outer periphery of the permanent magnet is rotated as described in the above-mentioned embodiment. A magnetic roller may be provided as a magnetic field generator on the peripheral side, and a developing roller configured to rotate the magnetic roller may be used. It is also possible to use a developing roller configured to rotate the sleeve and the magnetic field generator, respectively.

Furthermore, in the above description, a drum-shaped photosensitive member has been described as an example of the image bearing member, but a belt-shaped or film-shaped photosensitive member may be used. Further, although the present invention has been described above by taking the image forming apparatus 10 shown in FIG. 1 and the image forming apparatus 100 shown in FIG. 9 as examples, the image forming apparatus to which the present invention is applicable is not limited to the above. For example, as disclosed in Japanese Patent Laid-Open No. 3-209276, it has two exposing devices and three developing devices, a negative latent image is formed by the first exposing device, and reverse development is performed by the first developing device. The present invention is applied to an image forming apparatus or the like in which a positive latent image is formed by a second exposure device, and positive development is performed in a second developing device and a third developing device using toner of a color different from that of the first developing device. It goes without saying that it is possible to apply

[0059]

As described above, according to the first aspect of the invention, when the developing section is developing the electrostatic latent image, the carrier is collected on the portion of the image carrier on which the toner image is not formed. Since the carrier collecting roller is driven so that the carrier is collected only when the corresponding rollers are used, the carrier adheres to the image carrier by the developing section, and the carrier is further attracted to the collecting roller and remains or An excellent effect is obtained in that it is possible to prevent the occurrence of inconveniences such as the toner image being disturbed and the dirt attached due to the accumulation.

According to a second aspect of the present invention, when the first developing roller is developing the electrostatic latent image, the second developing roller is provided on the portion of the image carrier on which the toner image is not formed. Since the second developing roller is driven only when corresponding, the carrier adheres to the image carrier by the development by the first developing roller, and the carrier is further attracted to the second developing roller and remains or accumulates. As a result, it is possible to prevent the occurrence of inconveniences such as the disturbance of the toner image and the attachment of dirt.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is a schematic configuration diagram of a developing device.

FIG. 3 is a schematic view showing a driving mechanism of a developing roller and a carrier collecting roller of a developing device.

FIG. 4A to FIG. 4D are timing charts for explaining an example of the timing of rotating the carrier recovery roll.

FIG. 5 is a conceptual diagram showing a state in which an inter-image portion on a photosensitive drum corresponds to a carrier recovery roll.

6A and 6B are timing charts for explaining a case where the timing of rotating the carrier recovery roll is changed according to the toner image density.

FIG. 7 is a timing chart illustrating another example of the timing of rotating the carrier recovery roll.

FIG. 8 is a schematic view showing another example of the drive mechanism of the carrier recovery roller.

FIG. 9 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

10A to 10D are timings for explaining the timing of operating the downstream developing device while operating the upstream developing device, and the timing of applying a bias voltage to the downstream developing device. It is a chart.

[Explanation of symbols]

 Reference Signs List 10 image forming apparatus 12 photoconductor drum 20 developing device 42 developing roller 44 sleeve 46 permanent magnet 48 carrier collecting roller 50 sleeve 52 permanent magnet 100 image forming apparatus

Claims (3)

[Claims] 1. A latent image forming means for forming an electrostatic latent image on an image carrier, and an electrostatic latent image formed on the image carrier is developed with a developer containing toner and a magnetic carrier to carry the image. A developing unit for forming a toner image on the body, a carrier collecting roller arranged at a downstream side of the developing unit at a predetermined distance from the image carrier, and the developing unit developing the electrostatic latent image. In this case, drive means for driving the carrier collecting roller so that the carrier is collected only when the carrier collecting roller corresponds to a portion of the image carrier on which the toner image is not formed, Forming equipment. 2. A latent image forming means for forming an electrostatic latent image on an image carrier, a first sleeve disposed at a predetermined distance from the image carrier, and an inner circumference of the first sleeve. A first magnetic field generating section arranged to generate a magnetic field; and an electrostatic latent image formed on the image bearing member by a first developer containing toner and magnetic carrier attached to the first sleeve. A first developing roller that develops to form a toner image on the image carrier; a second sleeve that is disposed downstream of the first developing roller at a predetermined distance from the image carrier; and a second sleeve. A second magnetic field generator disposed on the inner circumference of the sleeve to generate a magnetic field; and an electrostatic latent image formed on the image carrier, including a toner and a magnetic carrier attached to the second sleeve, The second developer having the same polarity as the first developer is used. A portion where the toner image is not formed on the image carrier when the second developing roller that forms the toner image on the image carrier and the first developing roller are developing the electrostatic latent image. An image forming apparatus including: a driving unit that drives the second developing roller only when the second developing roller corresponds to. 3. The driving means, when driving the second developing roller, causes the second developing roller to adhere toner attached to the second sleeve of the second developing roller to the image carrier. The image forming apparatus according to claim 2, wherein a bias voltage is applied.