JPH0895388A - Carrier recovering device - Google Patents

Abstract

PURPOSE: To surely recover carrier from an image carrier by a recovery magnet even though the carrier stuck on the image carrier has small particle diameter and weak magnetic force. CONSTITUTION: When the carrier 2a stuck on the image carrier 1 is recovered by the recovery magnet 11 at a position on a downstream side in the moving direction of the image carrier from a developing area where developing is performed by supplying developer 2 from a developing device 20 to the image carrier 1, the recovery magnet 11 is provided to be in the proximity of the image carrier and to be capable of separating, and when the carrier stuck on the image carrier is attracted and recovered by the recovery magnet 11 at the position in the proximity of the image carrier, the directions of magnetic poles S and N at the recovery magnet 11 are arranged to be nearly the same as the moving direction of the image carrier 1, and when the recovery magnet 11 is separated from the image carrier, a guide member 12 guiding the carrier attracted by the recovery magnet 11 to the inside of the developing device is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier recovery device for recovering a carrier adhering to an image carrier when a developer is supplied from the developing device to the image carrier to develop the image carrier. A carrier configured to supply a developer from the device to the image carrier to perform development at a position downstream of the developing area in the moving direction of the image carrier and to collect the carrier attached to the image carrier by a collecting magnet. The present invention relates to a recovery device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, when a developing device supplies a developer to an image carrier to perform development, the carrier in the developer forms an image together with the toner. It was sometimes supplied to the carrier and adhered to the surface of the image carrier.

When the carrier adheres to the surface of the image carrier in this manner, the carrier damages the surface of the image carrier and causes a noise in an image formed.

Further, in recent years, in order to form an image with high accuracy, a carrier having a small particle size is used to improve the contact efficiency between the toner and the carrier to accelerate the start-up of charging of the toner, It has become possible to obtain a highly delicate image with a fine texture even in halftone and the like by reducing the variation in the amount of charge in (1) and forming an extremely flexible and delicate magnetic brush.

However, when a carrier having such a small particle size is used, the magnetic force in the carrier is weak,
Furthermore, the carrier easily adheres to the surface of the image carrier,
Further, when the developing bias voltage is increased in order to improve the reproducibility of the line image, there is a problem that more carriers adhere to the surface of the image carrier due to this.

Therefore, conventionally, various means have been developed in order to collect the carrier attached to the surface of the image carrier as described above.

A typical means for recovering the carrier attached to the surface of the image bearing member is to use a recovering magnet, and such a device is actually developed. As disclosed in Japanese Patent Laid-Open No. 120458, one of the magnetic poles of a collecting magnet is used to carry an image on one side of a magnetic pole at a position downstream of a developing area in which a developer is supplied from a developing device to the image carrier to perform development. Place it so that it faces the body,
The recovery magnet is rotated to move the recovery magnet closer to the image carrier or away from the image carrier, and the carrier attached to the image carrier is recovered for proximity to the image carrier. The magnetic force of the magnet attracts and collects it, and then the collecting magnet is rotated in the direction away from the image carrier, and the carrier collected from the image carrier as described above is guided along the guide member into the developing device. It was developed to be put back.

However, even when the carrier attached to the image carrier is collected by the collecting magnet as described above, it is difficult to reliably collect the carrier attached to the image carrier. , When a carrier having a small particle size and a weak magnetic force is used as described above, the carrier cannot be sufficiently recovered by this recovery magnet, and the image carrier is still scratched by the adhered carrier to form. There is a problem that noise is generated in the displayed image.

[0009]

SUMMARY OF THE INVENTION According to the present invention, the toner is attached to the image carrier at a position downstream of the developing area in which the developer is supplied from the developing device to the image carrier to perform development. It is an object of the present invention to solve the above-mentioned problems in the case where a carrier is attracted by a collecting magnet to collect the carrier.

That is, according to the present invention, when the carrier attached to the image carrier is attracted and collected by the collecting magnet as described above, the carrier attached to the image carrier has a small particle size and a weak magnetic force. Even if there is such a carrier, such a carrier can be reliably recovered from the image carrier by the recovery magnet and returned to the developing device, and the image carrier does not get scratched by the carrier to which a good image is formed. It is an object of the present invention to provide a carrier recovery device that can stably obtain the above.

[0011]

According to the present invention, in order to solve the above problems, a developing device supplies a developer to an image carrier and develops it downstream from a developing region in which the image carrier moves. At a position on the side, in the carrier recovery device that collects the carrier attached to the image carrier by the recovery magnet, the recovery magnet described above is provided so as to be close to and away from the image carrier and close to the image carrier. When the carrier attached to the image bearing member is attracted and collected by the collecting magnet at this position, the magnetic poles of the collecting magnet are arranged so as to be substantially in the same direction as the moving direction of the image bearing member. A guide member for guiding the carrier attracted to the collecting magnet into the developing device when the collecting magnet is separated from the image carrier is provided.

[0012]

In the carrier recovery device according to the present invention, at the position on the downstream side in the moving direction of the image carrier from the developing area,
When the carrier attached to the image bearing member is attracted and collected by the collecting magnet, the collecting magnet is provided close to and away from the image bearing member as described above, and as shown in FIG. At the position where the magnet 11 is brought close to the image carrier 1, the directions of the magnetic poles S and N in the recovery magnet 11 are
That is, the arrangement direction of the magnetic poles S and N is set to be substantially the same as the moving direction of the image carrier 1.
The lines of magnetic force from the magnetic poles S and N are increased, and the portion having a strong magnetic attraction force shown by the broken line acts on the image carrier 1.

Therefore, the carrier attached to the image bearing member is strongly attracted to the collecting magnet and collected, and even when a carrier having a small particle size and a weak magnetic force is used, The carrier attached to the image bearing member can be sufficiently collected by the collecting magnet.

Then, when the recovery magnet that has attracted and collected the carrier attached to the image carrier in this way is moved in a direction away from the image carrier, the carrier attracted to the recovery magnet moves along the guide member. It comes back into the developing device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

In the carrier recovery device of this embodiment, as shown in FIG. 2, a developing sleeve 21 provided with a magnet member 21a having a plurality of magnetic poles on the inner peripheral side of the developing device 20 is used as an image carrier in the developing area. 1 and the developing sleeve 2 so as to face each other at a required interval.
1 and the image carrier 1 are rotated in opposite directions to move the image carrier 1 and the developing sleeve 21 in the same direction in the developing area, and in the developing area, the toner 2a in the developer 2 from the developing sleeve 21. Is supplied to the image carrier 1 to form a toner image on the image carrier 1, and the carrier 2b supplied to the image carrier 1 together with the toner 2a and attached to the surface of the image carrier 1 is recovered, Carrier 2b recovered in this way
Is returned to the developing device 20.

Here, in the carrier recovery device of this embodiment, the recovery magnet 11 is attached to the rotary arm 13 at a position downstream of the developing area in the moving direction of the image carrier 1, and the rotary arm 13 is mounted. The collecting magnet 11 is rotated via 13 so that the collecting magnet 11 is moved toward and away from the image carrier 1 by this rotation.

Then, at the position where the recovery magnet 11 is rotated and brought close to the image carrier 1, the recovery magnet 11 is moved.
Of the magnetic poles S and N in the direction of movement of the image carrier 1 and the recovery magnet 11
, The magnetic pole located on the upstream side in the moving direction of the image carrier 1 is the S pole, and the magnet member 21 in the developing area is
The polarity was opposite to that of the N magnetic pole, which is the developing magnetic pole of a.

Further, in the carrier recovery apparatus in this embodiment, when the recovery magnet 11 is rotated as described above, the transfer paper (not shown) is adjusted to the timing of the registration roller 3 which sends the transfer paper to the image carrier 1. In the state where the lever 2 is rotated and the toner 2a in the developer 2 is supplied from the developing sleeve 21 to the image carrier 1, the recovery magnet 11 is moved to the image carrier 1. Between the images which do not supply the toner 2a to the image carrier 1 from the developing sleeve 21 while the carrier 2b attached to the surface of the image carrier 1 is collected by the collecting magnet 11. In this part, the collecting magnet 11 is rotated so as to be separated from the image carrier 1, and the carrier 2b collected by the collecting magnet 11 is returned into the developing device 20. Was Unishi.

When the carrier 2b thus collected by the collecting magnet 11 is returned into the developing device 20,
The collecting magnet 11 and the developing sleeve 2 which rotate as described above.
1, the guide member 12 is attached to the bottom of the developing device 20, and the carrier 2a collected from the image carrier 1 by the collecting magnet 11 is guided into the developing device 20 along the guide member 12. I chose

Here, in the carrier recovery device in this embodiment, the guide member 12 is formed of a conductive material, and the guide bias power source 14 has a polarity opposite to that of the carrier 2a. A recovery bias voltage was applied.

In the carrier recovery device of this embodiment, the toner 2a in the developer 2 is supplied from the developing sleeve 21 to the image carrier 1 as described above to recover the toner. The magnet 11 was brought close to the image carrier 1 so that the magnetic poles S and N in the recovery magnet 11 were oriented in substantially the same direction as the moving direction of the image carrier 1.

In this way, as shown in FIG. 1, the portion of the recovery magnet 11 having a strong magnetic attraction acts on the image carrier 1 and the carrier 2a attached to the image carrier 1 is recovered. It is strongly attracted by the magnetic attraction force of the use magnet 11, and is electrically attracted to the guide member 12 to which the recovery bias voltage having the opposite polarity to the carrier 2a is applied from the recovery bias power source 14 to the image carrier 1. The adhered carrier 2a can be reliably recovered by the recovery magnet 11, and the carrier 2a having a small particle size and a weak magnetic force.
Even when the above is used, the carrier 2a can be reliably recovered by the recovery magnet 11.

When the recovery magnet 11 is brought close to the image carrier 1 as described above, the S pole located upstream of the recovery magnet 11 in the moving direction of the image carrier 1 is a magnet in the developing area. Since it approaches the N pole, which is the developing magnetic pole of the member 21a, a part of the magnetic force lines from the N magnetic pole of the developing magnetic pole goes toward the magnetic pole S of the recovery magnet 11, and the action of the magnetic force lines causes the developing sleeve 21 to move away from the developing sleeve 21. The developing area in which the toner 2a in the developer 2 is supplied to the image carrier 1 to develop the image carrier 1 is expanded, and more efficient development can be performed.

After the carrier 2a attached to the image carrier 1 is collected by the collecting magnet 11 as described above,
When the inter-image portion where the toner 2a was not supplied to the image carrier 1 was guided from the developing sleeve 21, the collecting magnet 11 was rotated by the rotating arm 13 in the direction of separating it from the image carrier 1.

Here, when the recovery magnet 11 is rotated so as to be separated from the image carrier 1, the recovery magnet 11 is attracted to the recovery magnet 11 as the recovery magnet 11 rotates, and the recovery magnet 11 is recovered. The carrier 2b thus formed is the guide member 1 described above.
As the collecting magnet 11 gradually moves away from the guide member 12 as the collecting magnet 11 moves toward the developing device 20 side, the attracting force of the carrier 2a by the collecting magnet 11 decreases, and the collected carrier 2a becomes the developing sleeve 21. The magnetic attraction force of the magnet member 21a provided on the inner peripheral side of the developing roller 21 attracts the developing sleeve 21 and returns the developer 2 on the developing sleeve 21 into the developing device 20.

Further, as described above, when the recovery magnet 11 is rotated to separate from the image carrier 1 in the inter-image portion where the toner 2a is not supplied from the developing sleeve 21 to the image carrier 1, the image carrier is carried. The toner image formed on the body 1 was not disturbed by the movement of the carrier 2a.

After returning the carrier 2b collected by the collecting magnet 11 to the inside of the developing device 20 along the guide member 12 as described above, the toner 2a is supplied from the developing sleeve 21 to the image carrier 1. Before the portion on which the toner image is formed is guided by the rotating arm 13, the collecting magnet 11 located at a position separated from the image carrier 1 is rotated, and the collecting magnet 11 is imaged as described above. The carrier 2b attached to the image carrier 1 is returned to a position close to the carrier 1, and the carrier 2b attached to the image carrier 1 is collected by the collecting magnet 11 as described above, and such an operation is repeated.
In this way, the carrier 2a attached to the image carrier 1
Therefore, continuous development can be suitably performed while collecting the above.

Further, as described above, the recovery magnet 11 located at a position separated from the image carrier 1 is rotated to rotate the image carrier 1
In the case of returning to a position close to, the magnetic pole near the developing sleeve 21 in the collecting magnet 11 is set to the S pole as described above, and the polarity is opposite to the N pole which is the developing magnetic pole of the magnet member 21a. The south pole of the working magnet 11 is attracted to the north pole of the magnet member 21a,
The recovery magnet 11 can be returned smoothly.

In the carrier recovery device of this embodiment, when the recovery magnet 11 is moved toward and away from the image carrier 1, the recovery magnet 11 is attached to the rotating arm 13 and rotated. However, the method of bringing the recovery magnet 11 close to and away from the image carrier 1 is not particularly limited to such a method.

For example, as shown in FIGS. 3A and 3B and FIGS. 4A and 4B, at the position where the recovery magnet 11 is brought close to the image carrier 1, the recovery magnet 11 is The directions of the magnetic poles S and N of the magnet 11 are set to be substantially the same as the moving direction of the image carrier 1, and from this state, the recovery magnet 11 is slid in the direction away from the image carrier 1 and separated. It is also possible to slide the recovery magnet 11 so as to be close to or away from the image carrier 1.

When the recovery magnet 11 is slid so as to be close to or away from the image carrier 1, when the recovery magnet 11 is separated from the position close to the image carrier 1. The carrier 2b collected by the collecting magnet 11 is returned to the inside of the developing device 20 as described above, and the collecting magnet 1 is separated from the image carrier 1.
When returning 1 to a position close to the image carrier 1, it is necessary to prevent the recovered carrier 2a from being guided to the image carrier 1 side again along with the recovery magnet 11.

Therefore, when the recovery magnet 11 is separated from the position close to the image carrier 1, (A) in FIG.
As shown in (B), the recovery magnet 11 is slid so as to be gradually separated from the guide member 12, and the carrier 2a by the recovery magnet 11 is moved in the same manner as in the above embodiment.
The attracting force of the carrier 2a is gradually reduced, and the recovered carrier 2a is attracted to the developing sleeve 21 by the magnet member 21a and returned to the developing device 20 together with the developer 2 on the developing sleeve 21. Alternatively, as shown in FIGS. 4A and 4B, the guide member 12 is provided with a restraining portion 12a that suppresses the carrier 2a from returning to the image carrier 1 side, and the recovery magnet 11 is attached to the image carrier. 1 when the carrier 2a is returned to the position close to
2a so as not to return to the image carrier 1 side, and the recovery magnet 11 is separated from the restraining part 12a to prevent the image carrier 1 from being returned.
When returning to a position close to, the magnetic attraction force from the recovery magnet 11 is weakened, and the carrier 2a held by the holding portion 12a can be returned to the developing device 20.

[0034]

As described above in detail, in the carrier collecting apparatus according to the present invention, the collecting magnet is brought close to the image carrier at a position downstream of the developing area in the moving direction of the image carrier. The carrier adhered to is collected, and when the carrier for collection is returned to the developing device along the guide member by separating the carrier for collection from the image carrier, at the position where the magnet for collection is brought close to the image carrier, Since the direction of the magnetic poles in the recovery magnet is set to be substantially the same as the moving direction of the image carrier, the magnetic attraction lines from the magnetic poles of the recovery magnet increase and the portion where the magnetic attraction force becomes stronger is the image carrier. When the carrier adhering to the image carrier is strongly attracted to the recovery magnet to be reliably recovered, it becomes particularly prominent when a carrier having a small particle size and a weak magnetic force is used. It also such carrier is adapted to be reliably recovered from the image carrier by the recovery magnet.

As a result, when the carrier recovery device according to the present invention is used, the carrier adhering to the surface of the image bearing member is not recovered but remains on the surface of the image bearing member as in the conventional case, and the carrier causes the surface of the image bearing member. No scratches and no noise is generated in the formed image, and good image formation can be stably performed over a long period of time.

[Brief description of drawings]

FIG. 1 shows a carrier recovery device according to the present invention,
When the collecting magnet is arranged such that the direction of the magnetic pole of the collecting magnet is almost the same as the moving direction of the collecting member at a position close to the image carrier, the magnetic force lines and the magnetic attraction of the collecting magnet are arranged. It is the schematic which showed the state of force.

FIG. 2 is a schematic explanatory view showing a state in which the carrier collecting device according to the embodiment of the present invention collects the carrier attached to the image carrier by the collecting magnet and returns the carrier into the developing device.

FIG. 3 is a schematic explanatory view showing a state in which a carrier collecting device according to another embodiment of the present invention collects carriers attached to an image carrier by a collecting magnet and returns the carriers into a developing device.

FIG. 4 is a schematic explanatory view showing a state in which a carrier collecting device according to still another embodiment of the present invention collects carriers attached to an image carrier by a collecting magnet and returns the carriers into a developing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Developer 2a Carrier 11 Recovery magnet 12 Guide member 13 Rotating arm 20 Developing device 21 Developing sleeve 21a Magnet member S, N Magnetic pole

Claims (1)

[Claims] 1. A carrier magnet attached to an image carrier is attracted by a collecting magnet at a position on the downstream side in the moving direction of the image carrier from a developing area where a developer is supplied from the developing device to the image carrier to perform development. In the carrier collecting device for collecting, the above-mentioned collecting magnet is provided so as to be close to and away from the image carrier, and the carrier attached to the image carrier is attracted and collected by the collecting magnet at a position close to the image carrier. In this case, the magnetic poles of the collecting magnet are arranged so as to be substantially in the same direction as the moving direction of the image carrier, and when the collecting magnet is separated from the image carrier, A carrier recovery device comprising a guide member for guiding the attracted carrier into the developing device.