JPH11237788A - Image forming device - Google Patents

Abstract

(57) Abstract: A toner image is formed on a photoreceptor in an image forming apparatus that visualizes an electrostatic latent image formed on a photoreceptor surface as a toner image by a two-component developer of a developing device. When the carrier in the developer adheres to the surface of the photoreceptor, the carrier is efficiently removed from the surface of the photoreceptor. SOLUTION: A carrier holding member 21 faces a photoreceptor.
And a voltage having a polarity opposite to that of the carrier is applied to the carrier holding member 21, and a carrier collection magnet 22 is provided inside the carrier holding member 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image bearing member, a latent image forming means for forming an electrostatic latent image on the image bearing member, and a toner having a toner and a magnetic carrier. The present invention relates to an image forming apparatus including a developing device that visualizes an image and a transfer unit that transfers the toner image to a transfer material.

[0002]

2. Description of the Related Art An image forming apparatus of the above-mentioned type configured as an electronic copying machine, a printer, a facsimile or a multifunction machine having at least two functions thereof has been conventionally known. In this type of image forming apparatus, the toner and the magnetic carrier are frictionally charged to polarities opposite to each other, and the toner is electrostatically transferred to an electrostatic latent image formed on the image carrier to form a toner image. . The carrier should not adhere to the surface of the image carrier. However, the carrier in the developer may adhere to the surface of the image carrier for some reason. For example, when the carrier is deteriorated, the carrier may be charged to the same polarity as the toner, and the carrier having the reversed charging polarity is electrostatically attached to the surface of the image carrier.

When the carrier adheres to the surface of the image carrier as described above, the carrier is transferred to the transfer material when the toner image on the surface of the image carrier is transferred to the transfer material by the transfer means. Image quality may be degraded. Further, transfer residual toner adhering to the surface of the image carrier after transfer of the toner image is generally removed by a cleaning member of a cleaning device, and the surface of the image carrier is cleaned. If the carrier adheres, the carrier may damage the image carrier, accelerate the deterioration of the cleaning member, and shorten the life of the cleaning member.

Therefore, a carrier collecting magnet is provided downstream of the developing unit in which the electrostatic latent image is visualized in the image carrier surface moving direction, and the carrier collecting magnet adheres to the surface of the image carrier by the carrier collecting magnet. An image forming apparatus has been proposed in which a carrier is sucked to remove the carrier (see Japanese Patent Application Laid-Open No. 5-66678). However, according to this configuration, the carrier is attracted from the surface of the image carrier only by the action of the magnetic force, so that the carrier attached to the surface of the image carrier may not be efficiently removed. If the magnetic amount of the carrier collection magnet is increased so that the magnetic force acting on the carrier attached to the surface of the image carrier increases, it is possible to efficiently remove the carrier on the surface of the image carrier. Then, when a magnetic toner is used as the toner of the developer, even the toner constituting the toner image on the surface of the image carrier is attracted and collected by the carrier collection magnet, and the toner image may be disturbed. .
For this reason, the amount of magnetism of the carrier collection magnet cannot be increased so much that the carrier collection efficiency decreases.

[0005] A method of recovering the carrier adhered to the surface of the image carrier from the surface of the image carrier by electrostatic force is also conceivable. For example, a voltage having a polarity opposite to the original charge polarity of the carrier is applied to a conductive carrier collecting member provided opposite to the surface of the image carrier, and the attached carrier is electrostatically transferred to the carrier collecting member. . According to this configuration,
Regardless of whether the toner is magnetic or non-magnetic, a large electrostatic force is exerted on the carrier attached to the surface of the image carrier, and the carrier can be removed from the surface of the image carrier.

However, as described above, the charge polarity of the carrier is reversed, and the carrier charged to the opposite polarity to the original polarity may adhere to the surface of the image carrier. In this case, as described above, Even if a voltage of reverse spin effect with the original charge polarity of the carrier is applied to the carrier collection member, the carrier having the inverted charge polarity cannot be electrostatically collected.

[0007]

SUMMARY OF THE INVENTION The present invention has been made based on the above-described novel recognition, and an object of the present invention is to determine whether the toner of a developer is a magnetic toner or a non-magnetic toner. Regardless of whether the carrier adhered to the surface of the image carrier remains at the original charge polarity or is inverted, the carrier adhered to the surface of the image carrier can be efficiently removed. An object of the present invention is to provide an image forming apparatus of the type described at the beginning.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an image forming apparatus of the type described at the outset, in which the electrostatic latent image is visualized with respect to the moving direction of the surface of the image carrier. In a region downstream of the developing section where the toner image is transferred and upstream of the transfer section where the transfer of the toner image is performed, a carrier collecting means for removing the carrier adhered to the surface of the image carrier by magnetic force and electrostatic force is provided. An image forming apparatus characterized by the above is proposed (claim 1).

At this time, the carrier recovery means is disposed opposite the surface of the image carrier and to which a voltage having a polarity opposite to the original charge polarity of the carrier is applied, and is disposed inside the carrier support member. It is advantageous to have a carrier collecting magnet.

The image forming apparatus according to claim 2, wherein the developing device comprises: a developing case containing the developer; a developer agitating means for agitating the developer contained in the developing case; A developer carrying member opposed to the image carrier; and a developer carrying magnet disposed inside the developer carrying member, wherein at least one of the developer carrying member and the developer carrying magnet is rotationally driven. By doing
The developer supplied to the developer carrying member is transported to the developing section between the developer carrying member and the image carrier while being carried on the developer carrying member, and the transported developer causes the electrostatic latent image to be transferred. And a carrier collected from the surface of the image carrier to the carrier carrying member is separated from the carrier carrying member, and the separated carrier is directly used as the developer carrying member. It is advantageous to provide a carrier guiding means for guiding the carrier so that the carrier moves to a region in the developing case provided with the agent stirring means without being carried by the developing unit and transported to the developing unit. 3).

Further, in the image forming apparatus according to the third aspect of the present invention, the driving means for rotating and driving at least one of the carrier holding member and the carrier collection magnet to convey the carrier collected by the carrier holding member is provided. In addition to the above, it is advantageous that the carrier guiding means includes a scraping member for scraping and removing the carrier carried by the carrier carrying member from the carrier carrying member (claim 4).

Further, in the image forming apparatus according to the third aspect, the carrier collecting member is fixedly fixed, and the carrier holding member is rotationally driven so as to transport the collected carrier to the carrier holding member. And a driving means for rotating the developer carrying member so that the developer carrying magnet is immovably fixed and the developer carried by the developer carrying member is transported to the developing section. The carrier carried by the carrier carrying member is transferred to the developer carrying member after passing through the developing unit, and the carrier is moved before the developer carrying member reaches the developing unit again. The carrier collection magnet and the agent carrying magnet so that the carrier thus separated is separated from the developer carrying member and returns to a region in the developing case provided with the agent stirring means. With placing each pole of Tsu bets, by setting the rotational direction of the carrier carrying member and the developer carrying member, it is advantageous to configure the carrier guide means (claim 5).

Further, in the image forming apparatus according to the third aspect, the carrier collecting member is fixedly fixed, and the carrier holding member is rotationally driven so as to transport the collected carrier to the carrier holding member. And a driving means for rotating the developer carrying member so that the developer carrying magnet is immovably fixed and the developer carried by the developer carrying member is transported to the developing section. The carrier carried by the carrier carrying member and conveyed is separated from the carrier carrying member, and the separated carrier is provided with the agent stirring means without transferring to the developer carrying member. To return to the area inside the developing case, the carrier collecting magnet and the respective magnetic poles of the agent carrying magnet are arranged,
It is advantageous to configure the carrier guiding means by setting the rotation direction of the carrier carrying member and the developer carrying member (claim 6).

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic partial sectional view showing an example of an image forming apparatus configured as an electronic copying machine, a printer, a facsimile, or a multifunction peripheral thereof. The image forming apparatus shown here has a drum-shaped photoconductor 1 as an example of an image carrier.
The photosensitive member 1 is rotatably supported by a frame of an image forming apparatus main body (not shown).
Is rotated clockwise (in the direction of arrow A). At this time, the charging roller 2 as an example of the charging device is
It rotates while abutting the surface of. A voltage having a predetermined polarity is applied to the charging roller, whereby the surface of the photoconductor 1 is uniformly charged to a predetermined polarity, in this example, negative.

Next, the charged surface is irradiated with a light-modulated laser beam L emitted from an exposure apparatus (not shown), in this example, a laser optical unit, and thereby the surface of the photoreceptor is statically responsive to an image signal. An electrostatic latent image is formed. At this time, the absolute value of the surface potential of the photoconductor 1 irradiated with the laser light L decreases, and this constitutes an image portion, that is, an electrostatic latent image. The surface potential of the photoconductor 1 to which the laser beam L has not been applied does not substantially change, and this is a non-image portion, that is, a background portion. As shown in FIG. 2, a non-image portion (background portion)
The surface potential V ₁ of the can, for example -900 V, the surface potential V ₂ of the image portion (electrostatic latent image) is, for example, -200 V.

The above-described charging roller 2 and laser optical unit constitute an example of a latent image forming means for forming an electrostatic latent image on an image carrier composed of the photoreceptor 1. Instead of the charging roller 2,
An exposing device that uses a charging device such as a charging blade and a corona discharger disposed apart from the photoreceptor 1, or an image forming optical system that forms and projects an original image on the photoreceptor surface instead of the laser optical unit; Etc. can also be used. As described above, the image forming apparatus of the present example has the latent image forming unit that forms the electrostatic latent image on the image carrier.

The electrostatic latent image formed as described above is visualized as a toner image by the developing device 3, and the surface of a transfer material P made of, for example, transfer paper is transferred by a transfer roller 4 constituting an example of a transfer unit. Is transferred to The toner forming the toner image is charged to a predetermined polarity as described later, and a voltage having a polarity opposite to the charging polarity is applied to the transfer roller 4. The transfer roller 4 is driven to rotate in the direction of arrow B while abutting on the photoconductor 1 via the transfer material P. At this time, the toner on the photoconductor 1 is transferred at a transfer section 5 between the photoconductor 1 and the transfer roller 4. The image is electrostatically transferred onto the transfer material P. The transfer material P is transported in the direction of arrow C, passes through the transfer unit 5, passes through a fixing device (not shown), and the toner image transferred at this time is transferred onto the transfer material. Transfer roller 4
Instead, a transfer means such as a transfer blade, a transfer brush, or a corona discharger disposed apart from the photoreceptor 1 can be used. Further, the toner image formed on the photoreceptor may be primarily transferred to an intermediate transfer member, and then the toner image may be secondarily transferred to a final transfer sheet.
In this case, the intermediate transfer member constitutes a transfer material on which a toner image is transferred from the image carrier including the photosensitive member 1.

As described above, the image forming apparatus of this embodiment has a transfer means for transferring the toner image formed on the surface of the image carrier to a transfer material.

After transfer of the toner image to the transfer material P, the transfer residual toner attached to the surface of the photoconductor is removed by the cleaning member 7 of the cleaning device 6, and the surface of the photoconductor is cleaned. In the illustrated example, a cleaning blade having a leading edge pressed against the surface of the photoconductor is used as the cleaning member 7, and the transfer residual toner removed from the surface of the photoconductor is cleaned by a toner conveying member 9 provided in a cleaning case 8. It is transported out of the case. The surface of the photoconductor cleaned by the cleaning device 6 is irradiated with light from the neutralization lamp 10 to initialize the surface potential.

The developing device 3 includes a developing case 11 containing a powdery two-component developer D having a toner and a magnetic carrier, which are frictionally charged to opposite polarities, and a developing case 1.
And a stirring means for stirring the developer D contained in the first and second stirring members 12 and 13 in the illustrated example.
Constitutes the agent stirring means. At least a part of each carrier particle constituting the developer is made of a magnetic material. For example, carrier particles obtained by coating a surface of a core material made of low-resistance ferrite with a high-resistance resin coating layer made of, for example, a silicone resin are used. The average particle size of the carrier particles is, for example, about 50 μm, and the volume resistivity thereof is, for example, 10 ^{6 to} 10 ¹⁰ Ωcm. The toner may be a magnetic toner or a non-magnetic toner, and the toner and the magnetic carrier are mixed at a predetermined ratio, and if necessary, an additive is externally added thereto to form a two-component developer D. Is configured. Each toner particle is colored, for example, black or chromatic.

A developing sleeve 14 which is an example of a developer carrying member is provided above the first and second stirring members 12 and 13.
The developing sleeve 14 and the first and second stirring members 12 and 13 extend in parallel with each other and in parallel with the photoreceptor 1, and are arranged on the front and rear side walls of the developing case 11, that is, on the paper surface of FIG. On the other hand, it is rotatably supported on each side wall on the near side and the back side. The developing sleeve 14 is formed in a hollow cylindrical shape made of a conductive non-magnetic material, for example, aluminum, and is opposed to the photoconductor 1 with a predetermined gap.

Inside the developing sleeve 14, an agent-carrying magnet 15 is fixedly arranged, and its S pole and N pole are arranged in the circumferential direction of the developing sleeve 14 as shown in FIG.
, N ₁ , N ₂ , S ₁ , S ₂ , and S ₃ are attached to each magnetic pole.

As described above, the developing device 3 of the present embodiment has the developer carrying member configured as the developing sleeve 14 opposed to the image carrier composed of the photoreceptor 1, and is disposed inside the developer carrying member. And a magnet 15 for carrying the agent. Instead of the developing sleeve 14, a developer carrying member such as an endless belt may be used, or an endless belt-shaped image carrier may be used.

A partition plate 16 is arranged between the first stirring member 12 and the second stirring member 13 so that the inside of the developing case 8 is
One of the developer chamber is divided into R _1, R _2, the partition plate 16 two developer chamber through the opening formed in the end portion of the front and rear side in FIG. 1 of R _1, R ₂ mutually Communicating. The first stirring member 12 and the second stirring member 13 are driven to rotate by driving means (not shown), respectively, and transport the developer D in each of the developer chambers R ₁ and R ₂ while mixing and stirring. The developer D conveyed in this way circulates through the developer chambers R ₁ and R ₂ through the openings formed in the partition plate 16. When the developer D is thus mixed and stirred, the toner and the carrier are frictionally charged to polarities opposite to each other. In this example, the toner is negatively charged and the carrier is positively charged.

On the other hand, in the developing device 3 of the present embodiment, the agent carrying magnet 15 is fixedly fixed to the developing case 11, and the developing sleeve 14 is provided with a driving means (not shown) provided on the main body of the image forming apparatus. As a result, it is driven to rotate in the counterclockwise direction (arrow E direction) in the figure. The developer D supplied to the peripheral surface of the developing sleeve 14
Is carried on the peripheral surface of the developing sleeve 14 by the action of the magnetic force of the agent-carrying magnet 15 inside, and rises like a brush. The developing sleeve 14 rotates in the direction of the arrow E and is conveyed in the rotational direction. . At this time, the developing sleeve 14
The amount of the developer to be conveyed is regulated by a developer regulating means constituted by a doctor 17 opposed to the developing unit, and a predetermined amount of the developer is developed between the developing sleeve 14 and the photosensitive member 1 (developing area). 18. The developer conveyed through the developing unit 18 comes into contact with or comes close to the surface of the photoconductor.

At this time, a predetermined bias voltage is applied to the developing sleeve 14 by the power supply 19 connected to the developing sleeve 14. As this bias voltage,
For example, a DC voltage of about −600 V may be used, but in this example, a bias voltage generated by superimposing an AC voltage on the DC voltage is applied to the developing sleeve 14 as shown in FIG. First voltage portion indicated by V ₃ of the voltage waveform shown in FIG. 3, for example -1600 V, the second voltage section shown in V ₄ is, for example, + 400V, the voltage V ₀ which intermediate is a -600V .

As described above, the background portion of the photosensitive member 1 is -900.
V, the electrostatic latent image is -200 V, so when this electrostatic latent image reaches the developing unit 18 facing the developing sleeve 14, the electrostatic latent image is also negatively charged in the developer conveyed to the developing unit 18. The toner electrostatically transfers to the electrostatic latent image, and the electrostatic latent image is visualized as a toner image. While the first voltage portion V ₃ shown in FIG. 3 acts to transfer the toner in the developer to the electrostatic latent image, the second voltage portion V ₄ is used to transfer the toner from the electrostatic latent image to the developing sleeve 14. The electrostatic latent image acts to electrostatically transfer the toner to the side, and the entire operation visualizes the electrostatic latent image. As described above, the developing sleeve 14 is moved from the latent image carrier to the developing sleeve 14.
By giving the toner a function of returning the toner to the side, the developing ability can be improved and the uniformity of the developed dots can be improved. The carrier in the developer conveyed to the developing unit 18 is bound by the magnetic force of the developer carrying magnet 15 in the developing sleeve 14 and does not normally move to the surface of the photoconductor 1.

The developer that has passed through the developing section 18 is continuously carried on the developing sleeve 14 and transported. Developing unit 1
8 is a developer carrying magnet 1 downstream of the developer conveying direction 8.
As shown by S ₂ and S ₃ in FIG. 1, magnetic poles of the same polarity are located adjacent to each other in the portion 5, and the developer reaches the region between the magnetic poles S ₂ and S _3. Then, the developer separates from the developing sleeve 14 in this region, and falls into a region inside the developing case 11 provided with the first stirring member 12 below.
Here, the developer is supplied to the first and second stirring members 12 and 13.
Is stirred as described above.

As described above, the image forming apparatus of this embodiment has the developing device 3 for visualizing an electrostatic latent image as a toner image by the developer D having a toner and a magnetic carrier. In the example, the developer-carrying magnet 15 is immovably fixed, and the developer-carrying member is rotated by driving means so as to convey the developer carried on the developer-carrying member composed of the developing sleeve 14 to the developing section 18. . On the other hand, the developer carrying member is immovably fixed, and the developer carrying magnet 15 is rotationally driven, for example, clockwise in FIG.
Alternatively, the two-component developer D may be conveyed to the developing unit 18 by rotating the developer carrying member and the magnet 15 for carrying the developer together. In short, by rotating at least one of the developer carrying member and the magnet for carrying the developer, the developer supplied to the developer carrying member is carried by the developer carrying member, and the developer carrying member and The developing device is conveyed to a developing section between the image carrier and the developing device so that the electrostatic latent image is visualized by the conveyed developer.

In the example shown in FIG. 1, the photosensitive member is charged and a portion of the charged surface exposed to light is used as an electrostatic latent image, and the electrostatic latent image has the same polarity as the charged polarity of the photosensitive member. The toner is selectively applied to the surface of the charged photoreceptor, and the unexposed portion is used as an electrostatic latent image. A normal development method in which a toner charged to a polarity is attached to the electrostatic latent image may be employed.

By the way, as described above, when the latent image carrier is visualized in the developing unit 18, the carrier in the developer does not adhere to the surface of the photoreceptor but stays in the developer. . However, as described above, a small amount of carrier may adhere to the surface of the photoconductor 1 for some reason.

For example, when the developer carried on the developing sleeve 14 passes through the doctor 17, it receives stress,
The so-called carrier film shaving, in which the coat layer controlling the carrier resistance is shaved over time, or the so-called carrier film or wax contained in the toner adheres to the surface of the carrier particles under the influence of heat or the like. When the carrier is spent and the carrier deteriorates, the carrier may be charged to the same polarity as the toner, and the carrier may be electrostatically attached to the electrostatic latent image on the photoconductor.

Further with respect to the developing sleeve 14, when a bias voltage is applied as shown in FIG. 3, the charging potential of the photosensitive member surface varies, the potential difference between the background portion on the second voltage portion V ₄ photoconductor When the size of the carrier becomes large, an electrostatic force greater than the magnetic force that causes the agent carrying magnet 15 to bind the carrier acts on the carrier, whereby the carrier may adhere to the background portion on the photoconductor.

When the carrier adheres to the photoreceptor surface as described above, when the toner image on the photoreceptor surface is transferred to the transfer material P in the transfer unit 5, the carrier is transferred onto the transfer material P. As a result, the image quality of the image on the transfer material is degraded, or when the carrier adhered on the photosensitive member reaches the cleaning member 7, the carrier damages the surface of the photosensitive member or deteriorates the cleaning member 7. May be promoted.

Therefore, in the image forming apparatus of this embodiment,
As shown in FIG. 4, a carrier recovery means 20 is provided for removing the carrier adhered to the surface of the image carrier made of the photoconductor 1 by magnetic force and electrostatic force. 1 and 2
The carrier recovery means 20 shown in FIG. 1 is opposed to the surface of the image carrier made of the photoreceptor 1, and extends substantially parallel to the photoreceptor 1 over substantially the entire length of the photoreceptor 1 in the axial direction. Carrier member 21 and carrier carrier member 21
And a carrier collecting magnet 22 extending over substantially the entire length of the support member 21 in the axial direction. The carrier holding member 21 is made of a conductive non-magnetic material, for example, aluminum, and a power source 23 is connected to the carrier holding member 21. The power source 23 causes the carrier holding member 21 to have a polarity opposite to the original charge polarity of the carrier. A polarity, in this example, a negative voltage is applied. Carrier recovery magnet 22, N ₃ in FIG. 4,
As shown by N ₄ and S _4, it has magnetic poles of a predetermined polarity arranged along the circumferential direction of the carrier carrying member 21.

The symbol T in FIG. 4, the toner of the toner image formed on the photosensitive member surface schematically shown, in the code C ₁ is developing unit 18 (FIG. 1), schematically a carrier attached to the photosensitive member surface Is shown in “+” And “−” given to each of the toner T and the carrier indicate the charging polarity. When the carrier C ₁ reaches a position facing the carrier holding member 21 with the rotation of the photoconductor 1, the carrier C ₁ is a magnetic carrier at least a part of which is made of a magnetic material. 22
Is transferred from the photoreceptor surface to the surface of the carrier holding member 21 by the action of the magnetic force of Carrier carrying member 21 forms a use as a carrier recovery member for recovering the carrier C _1.

As described above, the carrier holding member 21
The carrier recovered in the are denoted by the reference numeral C ₂ in FIG. At that time, increasing the magnetic volume of the carrier recovery magnet 22, increasing the magnetic force acting on the carrier C _1, the recovery efficiency of the carrier C ₁ is increased. However, in this case, when the toner T adhered to the photoreceptor surface is a magnetic toner, the toner T is also collected by the carrier holding member 21 by the action of the magnetic force, and the toner image is disturbed. You. Therefore, when a magnetic toner at least partially composed of a magnetic material is used, the magnetic amount of the carrier collection magnet 22 cannot be made too large.
However, in this way the amount of magnetic small, when an attempt is recovered carrier C ₁ only by magnetic force, the recovery efficiency is reduced.

On the other hand, the carrier collecting means 20 of this embodiment
Has on its carrier bearing member 21 is applied the original charge polarity opposite polarity voltage of the carrier C ₁ is, since the carrier C ₁ deposited on the photosensitive member is recovered electrostatically carrier bearing member 21, the The problem that the collection efficiency is reduced can be prevented. Also, if the recovered adhesion carrier C ₁ only the electrostatic force, the charging polarity inversion carrier, be sucked electrostatically to the carrier carrying member 21 the carrier C ₁ and which has been negatively charged in the example of FIG. Although it is not possible, in the configuration of this example, the attached carrier is recovered even by the magnetic force,
Carriers whose charging polarity has been inverted can also be efficiently collected on the carrier holding member 21.

As described above, the carrier recovery means 20 of this embodiment
According to the method, the carrier C ₁ adhered to the photoreceptor is recovered by magnetic force and electrostatic force, so that the carrier T ₁ adheres to the surface of the photoreceptor regardless of whether the toner T is a magnetic toner or a non-magnetic toner. or carrier C ₁ that is still charged to the original charge polarity, or regardless of whether the polarity is reversed, it is possible to recover the adhesion carrier C ₁ efficiently carrier carrying member 21.

The carrier collecting means 20 can collect the carrier on the photoreceptor even if it is arranged at an appropriate position in the circumferential direction of the photoreceptor. The direction of movement of the surface of the image carrier comprising the body 1;
That is, in the direction of arrow A, the carrier collection means 20 is located in a region downstream of the developing unit 18 where the electrostatic latent image is visualized and upstream of the transfer unit 5 where the toner image is transferred. the provision of the attachment carrier C ₁ can be prevented from being sent to the site of the transfer section 5 and the cleaning member 7, deteriorated image quality of the transfer image carrier adheres onto the transfer material P, the cleaning member 7 It is possible to accelerate the deterioration or to prevent a problem that the surface of the photosensitive member is damaged.

Further, the carrier carrying member 21 to which a voltage having a polarity opposite to the original charge polarity of the carrier is applied and the carrier collecting magnet 22 are separated, and these are arranged along the moving direction of the surface of the photosensitive member 1. Figure 1
As shown in FIG. 2, by forming the carrier carrying member 21 in a cylindrical shape and disposing the carrier collecting magnet 22 inside the carrier carrying member 21, these can be made compact and the problem that the image forming apparatus becomes large in size is prevented. it can.

Further, when the carrier C ₂ adhered to the carrier carrying member 21 is transported by the carrying member 21 and separated from the carrier carrying member 21, there is a problem that a large amount of the carrier C ₂ remains on the carrier carrying member 21. Can be blocked. At this time, since the charge amount of the carrier separated from the carrier carrying member 21 is generally reduced, the carrier separated from the carrier carrying member 21 is transferred to the developing sleeve 14 as it is, and this is directly transferred to the developing unit 18. , The density of the toner image formed by the developer containing the carrier may locally decrease, and the image quality may be degraded.

Therefore, in the image forming apparatus of this embodiment,
The carrier collected by the carrier carrying member 21 from the surface of the image carrier composed of the photoreceptor 1 is separated from the carrier carrying member 21, and the separated carrier is directly carried on the developer carrying member composed of the developing sleeve 14. Carrier guiding means for guiding the carrier is provided so that the carrier is moved to a region in the developing case 11 provided with the agent stirring means without being transported to the developing unit 18. Hereinafter, specific examples thereof will be clarified.

In the example shown in FIGS. 1 and 4, the carrier collecting magnet 22 is fixedly mounted on the developing case 11, and the carrier holding member 21 is provided with a driving means (not shown) provided on the main body of the image forming apparatus. Accordingly, the carrier C ₂ , which is rotated in the counterclockwise direction (the direction of arrow F) in FIGS. 1 and 4, for example, and collected on the surface of the carrier holding member 21, is conveyed in the rotation direction of the holding member 21. . The carrier holding member 21 is fixed immovably,
The carrier recovery magnet 22 is rotated instead, or carrier carrying member 21 and the carrier C ₂ on the carrier carrying member 21 the carrier recovery magnet 22 both driven to rotate may carry. In short, in order to transport the carrier C ₂ collected in the carrier carrying member 21, it may be provided drive means for rotating at least one of said carrier carrying member 21 and the carrier recovery magnet 22.

As shown in FIGS. 1 and 4, a portion of the carrier holding member 21 on the downstream side in the rotation direction of the carrier holding member 21 with respect to the region where the carrier holding member 21 and the photosensitive member 1 face each other. the tip of the scraping member 24 for removing scraping carrier C ₂ being conveyed is from the carrier bearing member 21 is pressed against. Further, an end portion 11 </ b> A of the developing case 11 is provided below the carrier holding member 21.
And a guide member 25 fixed to the developing case 11 is disposed between the carrier carrying member 21 and the developing sleeve 14.

From the surface of the photoreceptor 1, the carrier holding member 21
The carrier C ₂ collected by the carrier C is conveyed while being carried by the carrier member 21, and is separated from the carrier carrier member 21 by the scraping member 24. At this time, in the illustrated example, the carrier collection magnet 22 on the upstream side of the scraping member 24 with respect to the rotation direction of the carrier holding member 21.
The magnetic poles of the same polarity are positioned adjacent to each other in the circumferential direction of the carrier holding member 21 as indicated by N ₃ and N ₄ in FIG. As a result, the carrier C ₂ is very easily separated from the carrier holding member 21, and the carrier C ₂ is easily separated by the action of the scraping member 24.
Separated from Since the carrier recovery means 20 of the carrier bearing member 21 and the carrier recovery magnet 22 is provided on the lower region of the photosensitive member 1, the carrier C ₂ on the carrier carrying member, by utilizing its own weight It can be efficiently separated from the carrier carrying member 21.

The carrier separated from the carrier carrying member and falling downward is indicated by reference numeral C _{3 in} FIG. 4, and the carrier C ₃ is provided with the end 11 A of the developing case 11 and the guide member 25. While being guided by the developer, it is dropped into a region in the developing case provided with the agent stirring means including the first and second stirring members 12 and 13. The carrier C ₃ separated from the carrier carrying member 21 moves to the side of the developing sleeve 14, and is not carried by the sleeve 14 to the developing unit 18 as it is. Guide member 2
5, the effect can be further enhanced. However, depending on the arrangement state of the developer carrying member and the developing sleeve 14, even if the guide member 25 is omitted, the carrier C ₃ separated from the carrier carrying member 21 can be removed. It can be immediately dropped on the first stirring member 12. As described above, in this example, the above-described carrier guiding means includes the scraping member 24,
Although it has the magnetic poles N ₃ and N ₄ of the same polarity of the carrier collecting magnet 22 in the vicinity thereof and the guide member 25, the carrier guide means may be constituted by the scraping member 24 alone.

The carrier guided to the bottom of the developing case by the carrier guiding means is sufficiently mixed and stirred with the developer D present by the rotating first and second stirring members 12 and 13, and the charge amount thereof is increased. And a large amount of toner adheres to the carrier. Since the developer is carried on the developing sleeve 14 and transported to the developing unit 18 as described above, it is possible to prevent a problem that the density of the developed toner image locally decreases.

In the above-described example, the carrier C ₂ on the carrier holding member 21 is scraped off by the scraping member 24. However, according to this configuration, a large stress is applied to the carrier and the life thereof may be shortened. is there. Therefore, in the example shown in FIG. 5, the scraping member 24 and the guide member 25 shown in FIGS. 1 and 4 are not provided. Instead, the carrier carrying member 21 is arranged close to the developing sleeve 14 and the carrier carrying member 21
Is rotated clockwise (in the direction of arrow G), and among the magnetic poles S ₂ , S ₃ of the same polarity of the agent carrying magnet 15, the magnetic pole S ₂ on the upstream side in the developing sleeve rotation direction and the carrier recovery opposing the magnetic pole S _2. pole N ₄ of use magnet 22 is in the opposite polarity. Other configurations are not substantially different from those shown in FIGS.

The carrier C ₂ is transferred from the photosensitive member 1 to the carrier carrying member 21, and the carrier C ₂ carried by the carrying member 21 and conveyed in the rotation direction reaches a region between the magnetic poles N ₄ and S ₂ facing each other. The carrier C ₂ is transferred to the surface of the developing sleeve 14 by the action of the magnetic field formed by these and the rotation of the carrier carrying member 21 and the developing sleeve 14. The carriers transferred in this way are the magnetic poles S ₂ , S ₃ adjacent to each other of the agent carrying magnet 15 and having the same polarity.
It will be located between. Therefore, this carrier C
₃ is the first and second stirring members 12 and 13 together with another developer.
Drop to the bottom of the developing case provided with. In this case, the carrier collected by the carrier carrying member 21 is not carried on the developing sleeve 14 as it is and is not transported to the developing unit 18.

As described above, in the image forming apparatus shown in FIG. 5, the carrier recovering magnet 22 is fixed and the carrier supporting member 21 is transported to the carrier supporting member 21 so as to transport the carrier C _2. A driving unit for rotating the member 21 is provided, and the developer carrying magnet 15 is immovably fixed, and the developer carrying member D is transported to the developing section 18 by the developer carrying member. A driving unit for rotating the member is provided, and the carrier C ₂ carried and carried by the carrier carrying member 21 is transferred to the developer carrying member after passing through the developing unit 18, and the developer carrying member Before returning to the developing section 18, the carrier recovery magnet is moved so that the transferred carrier is separated from the developer carrying member and returns to the area in the developing case provided with the developer stirring means. 22 and the magnet 15 for carrying the agent
The above-described carrier guiding means is configured by arranging the magnetic poles of the above and setting the rotation directions of the carrier carrying member 21 and the developer carrying member.

As shown in FIG. 5, the carrier holding member 21
If the magnetic pole N ₃ having the same polarity as the magnetic pole N ₄ is provided in the portion of the carrier collecting magnet 22 downstream of the magnetic pole N _{4 with} respect to the rotation direction of Even when the carrier does not move, the carrier can be dropped downward in the region between the magnetic poles N ₄ and N ₃ .

In the example shown in FIG. 6, the magnetic poles of the carrier collecting magnet 22 are arranged as shown, and the developing sleeve rotation of the magnetic poles S ₂ and S ₃ of the same polarity of the agent supporting magnet 15 is rotated. and magnetic pole S ₂ of the upstream side, the magnetic pole S ₅ of opposed carrier recovery magnet 22 is in the same polarity thereto. The magnetic pole S ₆ located on the downstream side of the magnetic pole S _{5 in} the rotation direction of the carrier holding member 21 has the same polarity as the magnetic pole S ₅ . The magnetic pole N ₅ facing the photoreceptor 1 has a polarity opposite to that of the magnetic pole S ₅ . The other configuration of the image forming apparatus illustrated in FIG. 6 is not different from the configuration illustrated in FIG.

When the carrier C ₂ collected from the photoreceptor 1 and carried by the carrier carrying member 21 and transported in the rotation direction G reaches the region between the magnetic poles S ₅ and S ₂ facing each other, these magnetic poles are used. Since the polarities of S ₅ and S ₂ are the same,
The carrier does not move to the side of the developing sleeve 14. When the carrier reaches a region between the magnetic pole S ₅ and the adjacent magnetic pole S ₆ , the magnetic poles S ₅ and S ₆ have the same polarity. Fall down. At this time, the carrier passes through the region between the magnetic poles S ₂ and S ₃ of the same polarity of the agent-carrying magnet 15, but at this time, the carrier falls downward without being attracted to the developing sleeve. Thus, also in this example, the carrier C ₃ separated from the carrier carrying member 21 is not carried on the developing sleeve 14 as it is and is not conveyed to the developing unit 18.

As described above, in the image forming apparatus shown in FIG. 6, in order to fix the carrier collecting magnet 22 immovably and to convey the carrier C ₂ collected by the carrier holding member 21, A driving means for rotating the member 21 is provided, and the developer carrying magnet 15 is immovably fixed, and the developer carrying member is transported to the developing section 18 by the developer carrying member. provided a driving means for rotating the member, the carrier C ₂ is conveyed while being carried on the carrier carrying member 21 is separated from the carrier bearing member 21, and the carrier C ₃ that the separation, migration to the developer carrying member The carrier collecting magnet 22 and the agent carrying magnet 15 are returned to the region inside the developing case provided with the agent stirring means without performing the operation.
The above-described carrier guiding means is configured by arranging the magnetic poles of the above and setting the rotation directions of the carrier carrying member 21 and the developer carrying member.

In the example shown in FIGS. 5 and 6, when the carrier is separated from the carrier holding member 21, no large stress is applied to the carrier, and the life of the carrier can be prevented from being shortened.

[0058]

According to the image forming apparatus of the first aspect, regardless of whether the toner in the developer is a magnetic toner or a non-magnetic toner, the carrier adhered to the surface of the image bearing member is removed. Regardless of whether the original charging polarity remains or the charging polarity is reversed, the carrier attached to the surface of the image carrier can be efficiently collected.

According to the image forming apparatus of the second aspect,
The carrier collecting means can be downsized.

According to the image forming apparatus of the third aspect,
The problem that the carrier collected by the carrier carrying member is transported to the developing section as it is can be prevented.

According to the image forming apparatus of the fourth aspect,
With the simple configuration, it is possible to prevent a problem that the carrier collected by the carrier carrying member is directly transported to the developing unit.

According to the image forming apparatus of the fifth and sixth aspects, it is possible to prevent the carrier collected on the carrier carrying member from being transported to the developing section without applying excessive stress to the carrier.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view illustrating an example of an image forming apparatus.

FIG. 2 is a diagram illustrating an electrostatic latent image of a photoconductor and a surface potential of a background portion.

FIG. 3 is a diagram illustrating a waveform of a bias voltage applied to a developing sleeve.

FIG. 4 is an enlarged cross-sectional view schematically showing a part of FIG. 1 and carrier and toner particles.

FIG. 5 is a sectional view similar to FIG. 4, showing another example.

FIG. 6 is a sectional view similar to FIG. 4, but showing still another example.

[Explanation of symbols]

Reference Signs List 3 developing device 5 transfer unit 11 developing case 15 agent holding magnet 18 developing unit 20 carrier collecting means 21 carrier holding member 22 carrier collecting magnet C ₁ carrier C ₂ carrier C ₃ carrier D developer N ₁ magnetic pole N ₂ magnetic pole N ₃ pole N ₄ pole N ₅ pole S ₁ pole S ₂ pole S ₃ pole S ₄ pole S ₅ pole S ₆ pole T toner

Claims (6)

[Claims] An image bearing member, a latent image forming means for forming an electrostatic latent image on the image bearing member, and a developer having a toner and a magnetic carrier, the electrostatic latent image is visualized as a toner image. Forming apparatus, and a transfer unit for transferring the toner image to a transfer material, the developing unit, in which the electrostatic latent image is visualized with respect to the moving direction of the surface of the image carrier, is performed. A carrier collecting means for removing a carrier attached to the surface of the image carrier by a magnetic force and an electrostatic force is provided in a region on the downstream side and upstream of a transfer portion where a toner image is transferred. Image forming device. 2. The carrier recovery member according to claim 1, wherein said carrier recovery means is opposed to a surface of said image bearing member, and is applied with a voltage having a polarity opposite to the original charge polarity of said carrier. The image forming apparatus according to claim 1, further comprising a carrier collection magnet. 3. The image forming apparatus according to claim 2, wherein the developing device includes: a developing case containing the developer; a developer agitating unit for agitating the developer contained in the developing case; and a developer carrying member opposed to the image carrier. And a developer-carrying magnet disposed inside the developer-carrying member. The developer supplied to the developer-carrying member by rotating at least one of the developer-carrying member and the magnet for carrying a developer. While carrying the developer on the developer carrying member, the developer is transported to a developing section between the developer carrying member and the image carrier, and the electrostatic latent image is visualized by the transported developer. The carrier collected from the surface of the image carrier by the carrier carrier is separated from the carrier carrier, and the separated carrier is carried by the developer carrier as it is and transported to the developing unit. Is The image forming apparatus according to claim 2, further comprising a carrier guiding unit that guides the carrier so that the carrier moves to an area in the developing case provided with the agent stirring unit. 4. A driving means for rotating at least one of the carrier holding member and a carrier collection magnet for transferring the carrier collected by the carrier holding member, and the carrier guiding means includes a carrier holding member. 4. The image forming apparatus according to claim 3, further comprising: a scraping member configured to scrape and remove the carrier carried and carried by the carrier from the carrier carrying member. 5. A device for fixing the carrier collection magnet immovably, and a driving unit for rotating and driving the carrier holding member so as to transport the collected carrier to the carrier holding member, and the agent holding magnet. And a driving unit for rotating the developer carrying member so that the developer carried by the developer carrying member is conveyed to the developing section, and the carrier carried by the carrier carrying member is provided. The transferred carrier moves to the developer carrying member portion after passing through the developing section, and before the developer carrying member section reaches the developing section again, the transferred carrier is separated from the developer carrying member and The carrier recovery magnet and the respective magnetic poles of the agent carrying magnet are arranged so as to return to the region in the developing case provided with the agent stirring means, and the carrier holding member is provided. The image forming apparatus according to claim 3, wherein the carrier guide unit is configured by setting a rotation direction of the developer carrying member. 6. A driving means for rotating the carrier holding member so as to fix the carrier collection magnet immovably, and to convey the collected carrier to the carrier holding member, and the agent holding magnet. And a driving unit for rotating the developer carrying member so that the developer carried by the developer carrying member is conveyed to the developing section, and the carrier carried by the carrier carrying member is provided. The carrier is separated from the carrier supporting member, and the separated carrier is returned to an area in the developing case provided with the agent stirring means without moving to the developer supporting member. By arranging the magnetic poles of the collection magnet and the agent-carrying magnet, and by setting the rotation direction of the carrier-carrying member and the developer-carrying member, The image forming apparatus according to claim 3, wherein the carrier guiding unit is configured.