JP2020101596A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that comprises a recovery mechanism for recovering a carrier on a photoreceptor drum, the image forming apparatus capable of certainly removing a toner attached to the recovery mechanism to prevent in advance dirt on an image caused by the toner.SOLUTION: An image forming apparatus has a recovery mechanism 416 that is arranged on the downstream side of a developing device 412 and on the upstream side of a primary transfer roller 422 in the direction of rotation of a photoreceptor drum 413, and recovers a carrier on a surface of the photoreceptor drum. The recovery mechanism includes a recovery sleeve 110A, and a recovery magnet roll 110B that has a recovery pole N1 and a peeling pole S2. The recovery sleeve has a plurality of inclined grooves 111 formed along a circumferential direction of the recovery sleeve. Each of the plurality of inclined grooves is provided to extend in an axial direction of the recovery sleeve, and the center in the axial direction of the recovery sleeve is formed inclined with respect to both ends in the axial direction of the recovery sleeve so that the center is located on the downstream side in the direction of rotation of a surface of the recovery sleeve.SELECTED DRAWING: Figure 5

Description

The present invention relates to an image forming apparatus.

An image forming apparatus having a developing device for developing an electrostatic latent image formed on a photosensitive drum using a two-component developer containing toner and a carrier having magnetism is widely used.
At the time of development by the developing device, the carrier is collected in the developing device and adheres to the toner again, but a part of the carrier is transferred to the surface of the photosensitive drum. When the carrier adheres to the photosensitive drum, leakage may occur due to the transfer voltage applied at the transfer portion between the photosensitive drum and the intermediate transfer belt. Further, the carrier that has passed through the transfer portion is sandwiched between the carrier and the cleaning blade that cleans the surface of the photosensitive drum, and damages the surface of the photosensitive drum and the edge of the cleaning blade.
In order to solve such a problem, in Patent Document 1, a collection roller having a magnet inside is brought into contact with the surface of the photoconductor drum, and the carrier attached to the photoconductor drum is transferred to the collection roller by the action of an electric field and a magnetic field. An image forming apparatus that collects and collects is disclosed.

Here, the collecting roller collects the weakly charged toner on the photosensitive drum and so-called fog toner attached to the background portion. If toner accumulates on the surface of the collection roller and the gap between the photoconductor drum and the collection roller is filled, the toner will reattach to the photoconductor drum and stain the image. Need to be removed.
In Patent Document 1, a scraper is brought into contact with the surface of the collecting roller to remove the carrier, and the toner can be scraped off at the same time as the carrier. However, the toner having a small particle diameter easily slips between the scraper and the collecting roller, and there is a problem that the collecting efficiency is low. Further, the scraper damages the surface of the collecting roller.

Therefore, conventionally, the recovery mechanism 416 shown in FIG. 11 has been used. The recovery mechanism 416 has a carrier recovery chamber 120 and a discharge screw 130 in addition to the recovery roller 110, and conveys the carrier recovered from the photosensitive drum 413 on the surface of the recovery sleeve 110A as the recovery sleeve 110A rotates. The carrier is retained at the peeling electrode S2. The carrier staying at the peeling pole S2 is taken in while rubbing the toner on the collecting roller 110, peeled together with the toner, and collected by the carrier collecting chamber 120 and the discharging screw 130. With this structure, the above problem can be avoided.

JP-A-6-332319

In the collecting mechanism 416 shown in FIG. 11, even if there is a small amount of carrier that cannot be separated from the collecting roller 110, the image quality is basically hardly affected. However, when a low coverage image that does not consume toner is continuously printed, image contamination due to the toner on the collection roller 110 gradually starts to occur. Since the carrier is a magnetic substance, it can be peeled off from the recovery roller 110 by a magnetic field action. However, the toner is a non-magnetic substance and is not subjected to a magnetic field action, and the toner adhesion amount is gradually increased. It is conceivable that the toner conveyed to the re-adhesion to the photosensitive drum 413.

The present invention has been made in view of the above problems, and in an image forming apparatus provided with a recovery mechanism for recovering a carrier on a photosensitive drum, the toner adhered to the recovery mechanism is reliably removed, An object of the present invention is to provide an image forming apparatus capable of preventing image stains caused by the above.

In order to solve the above problems, the image forming apparatus according to claim 1,
An image carrier that carries a toner image to be transferred to a sheet, a developing unit that develops the toner image on the image carrier with a two-component developer containing toner and carrier, and a toner image that the image carrier carries. And a recovery mechanism that is disposed downstream of the developing unit and upstream of the transfer unit in the rotation direction of the image carrier and that recovers the carrier on the surface of the image carrier. In an image forming apparatus having a section,
The recovery mechanism is a non-magnetic rotating body that faces the image carrier and is rotatable about an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body, and is arranged in the circumferential direction. A magnet having a plurality of magnetic poles along the line,
The magnet is arranged at least at a position close to the image carrier, and a recovery electrode for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and the recovery electrode. A peeling pole for peeling the carrier from the surface of the non-magnetic rotating body,
The non-magnetic rotating body has a plurality of groove portions formed along the circumferential direction of the non-magnetic rotating body,
Each of the plurality of grooves extends in the axial direction of the non-magnetic rotating body, and the center of the non-magnetic rotating body in the axial direction is the non-magnetic member with respect to both axial ends of the non-magnetic rotating body. It is characterized in that it is formed so as to be inclined so as to be located on the downstream side in the rotation direction of the surface of the rotating body.

The invention according to claim 2 is the image forming apparatus according to claim 1,
In each of the plurality of groove portions, in a cross section perpendicular to the axial direction of the non-magnetic rotor, the length of an arc passing through two points located on the outer circumference of the non-magnetic rotor is 1 to 2 of the carrier particle size. It is characterized by being twice as long.

According to a third aspect of the invention, in the image forming apparatus according to the first or second aspect,
Each of the plurality of groove portions is formed so that a cross-sectional shape perpendicular to the axial direction of the non-magnetic rotating body is U-shaped.

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects,
The cumulative groove portion length obtained by summing the lengths of arcs passing through two points located on the outer circumference of the non-magnetic rotating body in a cross section perpendicular to the axial direction of the non-magnetic rotating body of each of the plurality of groove portions is It is substantially the same as the value obtained by subtracting the cumulative groove length from the outer circumference in a cross section perpendicular to the axial direction of the non-magnetic rotating body.

According to a fifth aspect of the invention, in the image forming apparatus according to any one of the first to fourth aspects,
The non-magnetic rotating body has a retaining means for retaining the developer collected on the surface of the non-magnetic rotating body on a part of the surface of the non-magnetic rotating body.

According to a sixth aspect of the invention, in the image forming apparatus according to the fifth aspect,
The staying means is a magnetizing pattern of a plurality of magnetic poles arranged on the magnet, and one of the magnetic poles generates a magnetic attraction force acting in a direction in which the carrier is prevented from being conveyed due to the rotation of the non-magnetic rotating body. It is characterized by a magnetizing pattern.

The invention described in claim 7 is the image forming apparatus according to claim 5,
The staying means is a magnetic member that is arranged in close proximity to the surface of the non-magnetic rotating body and at a position where it abuts on any one of a plurality of magnetic poles arranged on the magnet. Characterize.

The invention described in claim 8 is the image forming apparatus according to claim 7,
The magnetic member is a thin metal plate made of a metal of a magnetic material that is disposed in close proximity to a position where the tip of the magnetic member comes into contact with any one of a plurality of magnetic poles arranged in the magnet. And

According to a ninth aspect of the invention, in the image forming apparatus according to the seventh aspect,
The staying means is a magnet member that is arranged in close proximity to the surface of the non-magnetic rotating body and abuts on any one of the plurality of magnetic poles arranged on the magnet. Characterize.

The invention described in claim 10 is the image forming apparatus according to claim 5,
The staying means is a brush-like member that rotates on contact with a position on the surface of the non-magnetic rotating body that comes into contact with any one of a plurality of magnetic poles arranged on the magnet. And

The invention according to claim 11 is the image forming apparatus according to claim 5,
The staying means is an elastic member that is in contact with a position on the surface of the non-magnetic rotating body that comes into contact with any one of a plurality of magnetic poles arranged on the magnet.

According to the present invention, in an image forming apparatus having a recovery mechanism for recovering the carrier on the photosensitive drum, the toner adhering to the recovery mechanism is surely removed, and the image stain caused by the toner is prevented in advance. It is possible to provide an image forming apparatus capable of performing the above.

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to the present invention. FIG. 3 is a block diagram showing a functional configuration of the image forming apparatus. FIG. 3 is a diagram showing a schematic configuration of a developing device. It is a figure showing the schematic structure of the recovery mechanism concerning the present invention. It is the figure which showed the structure of the inclined groove. It is a figure explaining the formation method of an inclined groove. It is a figure explaining the magnetization pattern of the collection magnet roll as a retention means. It is the figure which showed the example of the retention means. It is a figure explaining the structure of a collection roller. It is a figure which shows the effect of the Example of this invention. It is a figure showing the schematic structure of the conventional recovery mechanism.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated example.

[Configuration of image forming apparatus]
FIG. 1 is a diagram schematically showing the overall configuration of an image forming apparatus 1 according to this embodiment. FIG. 2 is a block diagram showing the main functional configuration of the image forming apparatus 1 according to this embodiment. The image forming apparatus 1 shown in FIGS. 1 and 2 is an intermediate transfer type color image forming apparatus using an electrophotographic process technique. That is, the image forming apparatus 1 transfers the toner images of Y (yellow), M (magenta), C (cyan), and K (black) formed on the photosensitive drum 413 to the intermediate transfer belt 421 (primary transfer). ), the four color toner images are superposed on the intermediate transfer belt 421, and then transferred (secondarily transferred) to the paper S to form an image.

The image forming apparatus 1 employs a tandem system in which photosensitive drums 413 corresponding to four colors of YMCK are arranged in series in the running direction of the intermediate transfer belt 421, and the toner images of respective colors are sequentially transferred to the intermediate transfer belt 421. ..

As shown in FIG. 2, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a sheet conveying unit 50, a fixing unit 60, a storage unit 70, a communication unit 80, and The controller 100 is provided.

The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and the like. The CPU 101 reads out a program corresponding to the processing content from the ROM 102, expands it in the RAM 103, and centrally controls the operation of each block of the image forming apparatus 1 shown in FIG. 2 in cooperation with the expanded program.

The image reading unit 10 includes an automatic document feeder 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.
The automatic document feeder 11 conveys the document D placed on the document tray by a conveyance mechanism and sends it to the document image scanning device 12. The automatic document feeder 11 can continuously read the images (including both sides) of a large number of documents D placed on the document tray all at once.

The document image scanning device 12 optically scans a document conveyed from the automatic document feeding device 11 onto the contact glass or a document placed on the contact glass, and reflects light from the document on a CCD (Charge Coupled Device). ) The original image is read by forming an image on the light receiving surface of the sensor 12a. The image reading unit 10 generates input image data based on the reading result of the original image scanning device 12. The input image data is subjected to predetermined image processing in the image processing unit 30.

The operation display unit 20 is composed of, for example, a liquid crystal display (LCD: Liquid Crystal Display) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, image state displays, operation states of each function, and the like according to display control signals input from the control unit 100. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs operation signals to the control unit 100.

The image processing unit 30 includes a circuit that performs digital image processing on image data of an input job (input image data) according to initial settings or user settings. For example, the image processing unit 30 performs the gradation correction based on the gradation correction data (gradation correction table) under the control of the control unit 100. Further, the image processing unit 30 performs various correction processing such as color correction and shading correction, compression processing, and the like on the input image data in addition to the gradation correction. The image forming unit 40 is controlled based on the image data that has been subjected to these processes.

The image forming unit 40 forms an image with each color toner of Y component, M component, C component, and K component based on the image-processed input image data, and image forming units 41Y, 41M, 41C, 41K, An intermediate transfer unit 42 and the like are provided.

The image forming units 41Y, 41M, 41C, and 41K for the Y component, the M component, the C component, and the K component have the same configuration. For convenience of illustration and description, common components are denoted by the same reference numerals, and when distinguishing each, Y, M, C, or K is attached to the reference numerals. In FIG. 1, reference numerals are given only to the components of the image forming unit 41Y for the Y component, and reference numerals are omitted to the other components of the image forming units 41M, 41C and 41K.

The image forming unit 41 includes an exposure device 411, a developing device 412 (developing section), a photoconductor drum 413 (image carrier), a charging device 414, a drum cleaning device 415, a recovery mechanism 416, and the like.

The photoconductor drum 413 includes, for example, an undercoat layer (UCL: Under Coat Layer), a charge generation layer (CGL: Charge Generation Layer), a charge transport layer (on a peripheral surface of a conductive cylinder (aluminum tube) made of aluminum. It is a negative charge type organic photoconductor (OPC) in which CTLs (Charge Transport Layers) are sequentially laminated. The charge generation layer is made of an organic semiconductor in which a charge generation material (for example, phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate), and a pair of positive charge and negative charge are generated by exposure by the exposure device 411. The charge transport layer consists of a material in which a hole transport material (electron donating nitrogen-containing compound) is dispersed in a resin binder (for example, polycarbonate resin), and transports the positive charges generated in the charge generation layer to the surface of the charge transport layer. To do.

The control unit 100 controls the drive current supplied to the drive motor (not shown) that rotates the photoconductor drum 413 to rotate the photoconductor drum 413 at a constant peripheral speed (for example, 665 mm/s).

The charging device 414 uniformly charges the surface of the photoconductor drum 413 having photoconductivity to a negative polarity. The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photoconductor drum 413 with laser light corresponding to an image of each color component. Positive charges are generated in the charge generation layer of the photoconductor drum 413 and are transported to the surface of the charge transport layer, whereby surface charges (negative charges) of the photoconductor drum 413 are neutralized. An electrostatic latent image of each color component is formed on the surface of the photoconductor drum 413 due to the potential difference with the surroundings.

The developing device 412 is a two-component developing type developing device that uses a developer containing toner and a carrier, and visualizes the electrostatic latent image by adhering the toner of each color component to the surface of the photoconductor drum 413 to make the toner visible. Form an image.

Hereinafter, the configuration of the developing device 412 will be described in detail with reference to FIG.
The developing device 412 is a device for forming a toner image by depositing toner of each color component on the surface of the photosensitive drum 413, and as shown in FIG. 3, the first developing roller 412a and the second developing roller 412b. A supply roller 412c, a regulating blade 412d, a stirring roller 412e, and a transport roller 412f.

Each of the first developing roller 412a and the second developing roller 412b includes a rotatable developing sleeve, and a developing magnet roll arranged inside the developing sleeve. The first developing roller 412a and the second developing roller 412b are arranged in proximity to the photoconductor drum 413, and convey the developer to a developing area proximate to the photoconductor drum 413. The developing sleeve rotates counterclockwise in the figure. A plurality of magnetic poles that generate a magnetic field are arranged in the developing magnet roll.

The stirring roller 412e and the transport roller 412f are spiral screw members. The stirring roller 412e is rotated to mix and stir the toner and the carrier to frictionally charge the carrier. The transport roller 150 is transported from the stirring roller 140 by being rotated, and transports the frictionally charged developer to the supply roller 412c.

The supply roller 412c includes a rotatable supply sleeve and a supply magnet roll arranged inside the supply sleeve, and is arranged to face the transport roller 412f. Due to the magnetic field generated by the supply magnet roll of the supply roller 412c, a magnetic brush of the carrier is generated on the outer peripheral surface of the supply sleeve, and the developer layer containing toner carried on the magnetic brush is formed on the outer peripheral surface of the supply sleeve. It is formed. The supply sleeve rotates counterclockwise in the figure to supply the developer to the first developing roller 412a while carrying the developer on the outer peripheral surface of the supply sleeve by the magnetic field.

When the developer is guided to the first developing roller 412a, a magnetic brush is generated on the outer peripheral surface of the developing sleeve due to the magnetic field generated by the developing magnet roll of the first developing roller 412a, so that the layer of the developer moves to the developing sleeve. It is formed on the outer peripheral surface. Then, the developing sleeve is rotated counterclockwise in the drawing to carry the developer to the developing area closest to the photosensitive drum 413 while carrying the developer on the outer peripheral surface of the developing sleeve by the magnetic field. At this time, the regulating blade 412d regulates the thickness of the layer of the developer, so that a certain amount of the developer is conveyed to the developing area. In the developing area, the toner is electrostatically transferred from the developing sleeve of the first developing roller 412a to the electrostatic latent image formed on the surface of the photosensitive drum 413. On the other hand, a part of the developer on the developing sleeve of the first developing roller 412a is transferred to the second developing roller 412b by the action of the magnetic field. In the second developing roller 412b, a layer of the developer is formed on the developing sleeve similarly to the first developing roller 412a, and the developer is transferred to the photosensitive drum 413 in the developing area.
In this way, the developing device 412 supplies toner to the photoconductor drum 413 to visualize the electrostatic latent image with the toner.

The carrier is not particularly limited, and a commonly used known carrier can be used, and a binder type carrier or a coat type carrier can be used. The carrier particle size is not limited to this, but is preferably 15 to 100 μm. The toner is not particularly limited, and a commonly used known toner can be used. For example, a binder resin containing a colorant and, if necessary, a charge control agent, a release agent, etc., and treated with an external additive can be used. The toner particle size is not particularly limited, but is preferably about 3 to 15 μm.

The drum cleaning device 415 has a drum cleaning blade or the like that is in sliding contact with the surface of the photoconductor drum 413, and removes transfer residual toner remaining on the surface of the photoconductor drum 413 after the primary transfer.

The collecting mechanism 416 is arranged on the downstream side of the developing device 412 and on the upstream side of the primary transfer nip between the primary transfer roller 422 and the photosensitive drum 413 in the rotation direction of the photosensitive drum 413, and is arranged from the developing device 412 to the photosensitive drum 413. Before the carrier attached to the carrier reaches the primary transfer nip, the carrier is collected.
A detailed description of the configuration of the recovery mechanism 416 will be described later.

The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422 (transfer unit), a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, and the like.

The intermediate transfer belt 421 is an endless belt, and is stretched around a plurality of support rollers 423 in a loop shape. At least one of the plurality of support rollers 423 is a driving roller, and the others are driven rollers. For example, it is preferable that the roller 423A arranged downstream of the primary transfer roller 422 for the K component in the belt traveling direction is a drive roller. This makes it easy to keep the traveling speed of the belt at the primary transfer portion constant. The rotation of the drive roller 423A causes the intermediate transfer belt 421 to travel in the direction of arrow A at a constant speed.

The primary transfer roller 422 is arranged on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photoconductor drums 413 of the respective color components. The primary transfer roller 422 is pressed against the photoconductor drum 413 with the intermediate transfer belt 421 interposed therebetween, whereby a primary transfer nip for transferring a toner image from the photoconductor drum 413 to the intermediate transfer belt 421 is formed.

The secondary transfer roller 424 is arranged on the outer peripheral surface side of the intermediate transfer belt 421 so as to face the roller 423B (hereinafter referred to as “backup roller 423B”) arranged on the downstream side of the driving roller 423A in the belt traveling direction. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 interposed therebetween, thereby forming a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the sheet S.

When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photoconductor drum 413 are sequentially primary-transferred on the intermediate transfer belt 421 in an overlapping manner. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and a charge having a polarity opposite to that of the toner is applied to the back surface side of the intermediate transfer belt 421 (the side in contact with the primary transfer roller 422) to form a toner image. It is electrostatically transferred onto the intermediate transfer belt 421.

After that, when the sheet S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the sheet S. Specifically, a secondary transfer bias is applied to the secondary transfer roller 424, and a charge having a polarity opposite to that of the toner is applied to the back surface side of the sheet S (the side in contact with the secondary transfer roller 424), so that a toner image is obtained. Are electrostatically transferred to the paper S. The sheet S on which the toner image is transferred is conveyed toward the fixing unit 60.

The belt cleaning device 426 includes a belt cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 421, and removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer. Instead of the secondary transfer roller 424, a configuration in which the secondary transfer belt is stretched in a loop shape on a plurality of support rollers including the secondary transfer roller (so-called belt type secondary transfer unit) is adopted. Is also good.

The fixing unit 60 fixes the toner image on the sheet S by heating and pressing the sheet S that has been secondarily transferred with the toner image and is conveyed, at the fixing nip.

The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a transport path unit 53, and the like. The paper S (standard paper, special paper) identified on the basis of the basis weight, size, etc. is accommodated in each of preset types in the three paper feed tray units 51a to 51c constituting the paper feed unit 51. .. The transport path portion 53 has a plurality of transport roller pairs such as a registration roller pair 53a.

The sheets S stored in the sheet feeding tray units 51a to 51c are sent out one by one from the uppermost portion, and are conveyed to the image forming section 40 by the conveyance path section 53. At this time, the registration roller unit provided with the registration roller pair 53a corrects the inclination of the fed paper S and adjusts the conveyance timing. Then, in the image forming section 40, the toner images on the intermediate transfer belt 421 are secondarily transferred to one surface of the sheet S collectively, and the fixing section 60 performs a fixing step. The sheet S on which the image is formed is ejected to the outside of the machine by the sheet ejection unit 52 including the sheet ejection roller 52a.

The paper S may be long paper or roll paper. In this case, the paper S is accommodated in a paper feeding device (not shown) connected to the image forming apparatus 1, and the paper S held by the paper feeding device passes through the paper feeding port 54 from the paper feeding device. The sheet is supplied to the image forming apparatus 1 via the sheet, and is sent out to the conveyance path portion 53.

The storage unit 70 is composed of, for example, a nonvolatile semiconductor memory (so-called flash memory), a hard disk drive, or the like. The storage unit 70 stores various data including various setting information related to the image forming apparatus 1.

The communication unit 80 is composed of a communication control card such as a LAN (Local Area Network) card, and is connected to an external device (for example, a personal computer) connected to a communication network such as a LAN or a WAN (Wide Area Network). Sends and receives various data.

[Structure of collection mechanism]
Next, the configuration of the recovery mechanism 416 will be described in detail with reference to FIG.
The recovery mechanism 416 is a mechanism for recovering the carrier existing on the surface of the photosensitive drum 413, and includes a recovery roller 110, a carrier recovery chamber 120, a discharge screw 130, and the like, as shown in FIG. ..

The collection roller 110 has an axis parallel to the axis of the photoconductor drum 413 and is arranged so as to be close to the photoconductor drum 413. The collecting roller 110 is made of a non-magnetic member, and includes a collecting sleeve 110A rotatable about the axis of the collecting roller 110, and a collecting magnet roll 110B fixedly arranged inside the collecting sleeve 110A.
The recovery sleeve 110A functions as the non-magnetic rotating body of the present invention, and the recovery magnet roll 110B functions as the magnet of the present invention.

The collecting sleeve 110A is rotationally driven in the direction B in the drawing by a drive motor (not shown), and the traveling direction of the surface thereof is opposite at the position facing the photosensitive drum 413 rotating in the direction C in the drawing. Counter rotation. Further, a space is provided between the recovery sleeve 110A and the surface of the photosensitive drum 413.

A plurality of magnetic poles (N1, N2, S1, S2, S3) that generate a magnetic field are arranged on the recovery magnet roll 110B. In addition, M in the figure indicates the magnetic flux distribution in the vicinity of the recovery roller 110 generated by these magnetic poles.
Further, the recovery roller 110 is connected to a power source (not shown), and a voltage in which an AC voltage is superimposed on a DC voltage is applied.
That is, the carrier c recovered on the surface of the recovery roller 110 by the magnetic force generated by the magnetic poles arranged in the recovery magnet roll 110B and the electrostatic force generated in the electric field is carried on the outer peripheral surface of the recovery sleeve 110A, and the recovery sleeve 110A. The sheet is conveyed on the surface of the collection roller 110 with the rotation in the direction indicated by B in FIG.

The carrier transport operation in the collecting roller 110 will be described in detail.
The recovery magnet roll 110B has a magnetic pole N1 at a position close to the photoconductor drum 413. The magnetic pole N1 is the strongest magnetic pole among the magnetic poles arranged on the recovery magnet roll 110B and functions as a recovery pole. Due to the magnetic force generated by the magnetic pole N1, the carrier c on the surface of the photosensitive drum 413 is attracted to the surface of the recovery sleeve 110A and recovered.
Further, as shown in FIG. 4, when the position of the recovery pole N1 is represented by an angle in the counterclockwise direction with respect to the center line D connecting the center of the recovery roller 110 and the photoconductor drum 413, the peak position thereof is obtained. For example, it is arranged at a position where θ1=5°, that is, a position slightly displaced downstream from the closest position P1 between the photosensitive drum 413 and the collection roller 110 in the rotational direction. As a result, the carrier easily attaches to the recovery sleeve 110A that counter-rotates with respect to the photosensitive drum 413.

Further, in the recovery magnet roll 110B, the magnetic poles S1 and N2 are arranged in this order so that the N poles and the S poles alternate from the magnetic pole N1 toward the downstream side in the rotation direction of the recovery sleeve 110A. These magnetic poles function as carrier poles, and the carrier c receives the magnetic force generated by these magnetic poles and moves while rolling on the surface of the recovery sleeve 110A.
As shown in FIG. 4, when the positions of the transport poles S1 and N2 are represented by counterclockwise angles based on a straight line connecting the center of the collection roller 110 and the collection pole N1, the respective peak positions are, for example, It is arranged at a position where θ2=80° and θ3=160°.

Further, the magnetic pole S2 is arranged downstream of the magnetic pole N2 in the rotation direction of the recovery sleeve 110A, and the magnetic pole S2 functions as a separation pole. That is, when the carrier c reaches the region (peeling pole portion P2) on the recovery sleeve 110A that abuts the magnetic pole S2, which is indicated by P2 in the figure, the carrier c cannot move to the downstream side, and therefore the peeling pole S2. When the carrier c that has reached the peeling pole portion P2 newly by the rotation of the collecting sleeve 110A is rolled while receiving the magnetic attraction force of the collecting sleeve 110A, the surface of the collecting sleeve 110A is rubbed.

If the position of the peeling pole S2 is represented by an angle in the counterclockwise direction with respect to the straight line connecting the center of the collecting roller 110 and the collecting pole N1, the peak position is arranged to be, for example, θ4=200°. It When the collecting roller 110 is arranged on the upstream side in the rotation direction of the collecting sleeve 110A with respect to the position P3 which is the highest in the vertical direction, the carrier peeled by the carrier collecting chamber 120 and the discharging screw 130 from the peeling pole S2. Recovery efficiency is reduced. On the other hand, when the recovery roller 110 is arranged on the downstream side in the rotation direction of the recovery sleeve 110A with respect to the position P4 where the recovery roller 110 projects most in the horizontal direction, the carrier is less likely to be separated from the separation pole S2, and the recovery roller 110 is rotated. There is a possibility that the toner may be transported to the closest position P1 to the photoconductor drum 413 and reattach to the photoconductor drum 413. Therefore, it is preferable that the separation pole S2 is arranged in the range of the downstream side of P3 and the upstream side of P4 in the rotation direction of the recovery sleeve 110A.
The magnetic force of the peeling pole S2 is set to be weaker than the magnetic force of the recovery pole N1. This facilitates peeling when the carrier retained in the peeling pole portion P2 exceeds a predetermined amount.

A magnetic pole S3 is arranged downstream of the magnetic pole S2 in the rotation direction of the recovery sleeve 110A. The magnetic pole S3 functions as a sealing pole. When the position of the sealing pole S3 is represented by a counterclockwise angle based on a straight line connecting the center of the collection roller 110 and the collection pole N1, the peak position is arranged to be, for example, θ5=320°. ..
A demagnetization region R is formed on the downstream side of the separation pole S2 and the upstream side of the sealing pole S3 in the rotation direction of the recovery sleeve 110A. Since the peeling pole S2 and the sealing pole S3 have the same polarity, they form a repulsive magnetic field, but the demagnetizing region R1 is arranged between them, so that the peeling pole S2 is downstream and sealed in the rotation direction of the recovery sleeve 110A. No magnetic field is formed in the region on the upstream side of the pole S3, and the magnetic force does not work.

The carrier recovery chamber 120 is disposed in the vicinity of the recovery roller 110, downstream of the peeling electrode S2 and upstream of the sealing electrode S3 in the rotation direction of the recovery sleeve 110A, and removes the carrier that has peeled off from the peeling electrode portion P2 and dropped. to recover.
A discharge screw 130, which is a spiral screw member, is disposed inside the carrier recovery chamber 120, and the carrier c recovered in the carrier recovery chamber 120 is discharged into a carrier recovery box (not shown) by the discharge screw 130 and discarded. To be done.

The operation of collecting the carrier by the collecting mechanism 416 has been described above. At this time, the collecting mechanism 416 also collects the weakly charged toner and the fog toner on the surface of the photosensitive drum 413.
The toner adheres to the photoconductor drum 413 due to electrostatic force, but weakly charged toner or fog toner has a weak adhesion force to the photoconductor drum 413 due to electrostatic force. At the position P1 closest to the photosensitive drum 413, the transfer roller 110 transfers to the recovery roller 110. Since the recovered toner t is a non-magnetic substance, it is not affected by the magnetic force generated by the magnetic poles of the recovery magnet roll 110B and moves while being fixed to the surface of the recovery sleeve 110A, but reaches the peeling pole portion P2. At this time, it is rubbed by the carrier c staying in the peeling pole portion P2, accumulated with the carrier c, peeled off from the peeling pole portion P2, and finally collected in the carrier collecting chamber 120.

The number of magnetic poles arranged on the recovery magnet roll 110B in the present embodiment is an example, and the carrier pole is not limited to the above number as long as the N pole and the S pole are alternately arranged.

[Method of collecting carrier and toner using inclined groove]
Next, with reference to FIG. 5, a method of recovering the carrier and the toner using the inclined groove formed on the surface of the recovery sleeve 110A will be described.

First, the structure of the inclined groove 111 will be described. The inclined groove 111 functions as a groove portion in the present invention.
5A is a perspective view of the recovery mechanism 416, and FIG. 5B is a side view of the recovery roller 110 seen from a direction orthogonal to the axial direction of the recovery roller 110. In FIG. 5A, the positions corresponding to the transport pole N2 and the peeling pole S2 on the surface of the recovery sleeve 110A are indicated by broken lines. The magnetic poles N1, S2 and S3 are omitted.
As shown in FIGS. 5A and 5B, a plurality of parallel inclined grooves 111 extending along the axial direction of the recovery roller 110 are formed on the surface of the recovery sleeve 110A. The inclined groove 111 is formed so as to be inclined from the axial center toward both ends so that the axial center of the collecting roller 110 is located downstream of the axial ends of the collecting roller 110 in the rotation direction B of the collecting sleeve 110A. ing.

FIG. 5C is a cross-sectional view and a side view of the end portion of the collection roller 110 as seen from a direction orthogonal to the axial direction of the collection roller 110. In addition, in FIG. 5C, the position corresponding to the peeling pole S2 on the surface of the recovery sleeve 110A is indicated by a broken line.
Further, the total length in the axial direction of the collection roller 110 is L1 (for example, L1=349 [mm]), the total length in the axial direction of the collection magnet roll 110B is L2 (for example, L2=335 [mm]), and the maximum length in the width direction of the sheet. (Image forming area) is represented by L3 (for example, L3=330 [mm]). That is, the recovery magnet roll 110B is formed such that the overall length L2 in the axial direction is shorter than the overall length L1 in the axial direction of the recovery roller 110 and longer than the maximum length in the width direction of the paper (image forming area) L3. Is formed.
As shown in FIG. 5C, the inclined groove 111 is formed on the surface of the recovery sleeve 110A over the entire length of the recovery magnet roll 110B. That is, the inclined groove 111 is formed outside the image forming area. Further, an end region 112 where the inclined groove 111 is not provided is formed in a region on the surface of the collection sleeve 110A where the collection magnet roll 110B is not arranged inside.

Next, a method of transporting the carrier and the toner by the inclined groove 111 will be described.
As described above, the carrier collected on the surface of the collecting roller 110 is conveyed to the peeling pole portion P2 as the collecting sleeve 110A rotates, and is peeled from the surface of the collecting sleeve 110A together with the toner.
On the other hand, some carriers drop into the inclined groove 111. Due to the above-described inclined structure, the inclined groove 111 comes into contact with the separation pole S2 sequentially from the center in the axial direction toward both ends as the recovery sleeve 110A rotates. Therefore, the carrier dropped in the inclined groove 111 receives the magnetic attraction force of the separation pole S2 and moves along the inclined groove 111 from the axial center of the recovery roller 110 toward both ends.

Here, as shown in FIG. 5C, the carrier conveyed along the inclined groove 111 to both ends of the collecting roller 110 in the axial direction falls in the end region 112 in the direction indicated by E in the figure. As described above, since the inclined groove 111 is not formed in the end region 112 and the recovery magnet roll 110B is not arranged inside, the magnetic field does not act, so that the carrier exiting the inclined groove 111 is It falls according to gravity and is recovered by the carrier recovery chamber 120 and the discharge screw 130.

Further, when the carrier is transported along the inclined groove 111, the toner is also transported at the same time.
That is, a part of the toner drops into the inclined groove 111 like the carrier. Since the toner is a non-magnetic material, it is not affected by the magnetic force generated by the magnetic poles of the collecting magnet roll 110B, but when the carrier moves along the inclined groove 111, the toner in the inclined groove 111 slides by the moving carrier. Then, it is conveyed to both ends of the inclined groove 111 together with the carrier, and is discarded together with the carrier.

[Cross-section structure of inclined groove]
Next, the cross-sectional structure of the inclined groove 111 will be described with reference to FIG.

FIG. 6A is a diagram showing the shape of the cross section of the collection sleeve 110A in a plane perpendicular to the axial direction of the collection roller 110.
As shown in FIG. 6A, the inclined groove 111 is formed so that its cross section has a U shape. The U-shape makes the carrier less likely to be clogged than the V-shaped groove having a sharp bottom. In the cross section, it is desirable that the length (c ₂ ) of the arc passing through the uppermost two points of the inclined groove 111 (two points located on the outer circumference of the recovery sleeve 110A) and the width of the bottom surface be substantially the same.

The length (c ₂ ) of the arc passing through the uppermost two points of the inclined groove 111 (two points located on the outer circumference of the recovery sleeve 110A) is the particle size of the carrier (for example, 33±5 [μm]). Greater than. If the width of the inclined groove 111 is smaller than the particle size of the carrier, it becomes difficult for the carrier to move along the inclined groove 111, but if it is too wide, smooth movement is hindered. Therefore, it is desirable that the length (c ₂ ) of the arc is 1 to 2 times the particle size of the carrier.

Further, the depth (b) of the inclined groove 111 is preferably 1 to 2 times the particle diameter of the carrier, but in the height direction of the inclined groove 111, if one carrier enters, the toner is sufficiently rubbed. Therefore, the depth may be half the carrier particle size. By making the inclined groove 111 shallow, for example, even when the amount of carrier on the surface of the recovery roller 110 is very small, the amount of carrier that enters the inclined groove 111 can be minimized. It is possible to sufficiently rub the area on the surface of which the inclined groove 111 is not formed.

Moreover, although the plurality of inclined grooves 111 are formed along the circumferential direction of the recovery sleeve 110A, there is an appropriate value for the interval between the adjacent inclined grooves 111.
In FIG. 6A, a ₁ and a ₂ represent the distance between the groove center 111a of one inclined groove 111 and the groove center 111a of the adjacent inclined groove 111. Specifically, a ₁ is the groove center of two adjacent inclined grooves 111 when the groove center 111a of the inclined groove 111 is a point on the circumference of a circle whose center is the center of the axis of the collection roller. It represents the central angle between 111a. a ₂ represents the length of an arc passing through the groove centers 111 a of two adjacent inclined grooves 111.
b represents the depth of the inclined groove 111, and specifically, represents the distance from the groove center 111a of the inclined groove 111 to the uppermost portion of the inclined groove 111.
c ₁ and c ₂ represent the width of the uppermost portion in the cross section of the inclined groove 111. Specifically, when the cross section of the inclined groove 111 is approximated to a V shape having the groove center 111a as the bottom, c ₁ represents the angle at the groove center 111a. c ₂ represents the length of the arc passing through the two uppermost points (two points located on the outer circumference of the recovery sleeve 110A) of the inclined groove 111. In the following description, the angle represented by c ₁ may be referred to as the groove portion angle, and the length represented by c ₂ may be referred to as the groove portion length.
d represents the length of a region between two adjacent inclined grooves 111 on the surface of the recovery sleeve 110A. In the following description, a region of the surface of the recovery sleeve 110A excluding the groove may be referred to as a surface portion, and a length represented by d may be referred to as a surface portion length.

The relationship between the above a _{1 to} d and the number of the inclined grooves 111 formed in the recovery sleeve 110A will be described using a specific example shown in FIG. 6B.
The values of a _{1 to} d in Reference Example 1 and Reference Example 2 shown in FIG. 6B are set as follows. That is, when the outer diameter of the recovery sleeve 110A and the number of the inclined grooves 111 are set to the values shown in FIG. 6B, a ₁ and a ₂ are calculated by the following equations (1) and (2), respectively. It
a ₁ =360/number of inclined grooves... (1)
a ₂ =circumferential length of collection sleeve/number of inclined grooves (2)
Further, when b and c1 are set to the values shown in FIG. 6B, the following expression (3) is established.
tan(c ₁ /2)≈(c ₂ /2)*b...(3)
That is, c ₂ is calculated by the following equation (4).
c ₂ ≈tan(c ₁ /2)*2*b (4)
Further, d is calculated by the following equation (5).
_{d = a 2 -c 2 ··· (} 5)

The cumulative groove length c _{all obtained} by accumulating the groove length c ₂ over the entire circumference of the recovery sleeve 110A and the cumulative surface length d _all accumulated by accumulating the surface length d over the entire circumference of the recovery sleeve 110A are as follows. It is calculated by equations (6) and (7).
c _all =c ₂ *Number of inclined grooves (6)
d _all =d*number of surface portions (7)
In the formula (7), the number of surface portions is the same as the number of inclined grooves.

That is, in Reference Example 1, c _all =0.178*40=7.150 [mm] and d _all =1.08*40=43.115 [mm], and the ratio is c _all :d _all ≈. It is calculated as 1:6.
Further, in Reference Example 2, c _all =0.178*100=17.87 [mm], d _all =0.066*100=60.66 [mm], and the ratio is c _all :d _all ≈. It is calculated as 1:3.39.

Based on the above, _call : d _all was calculated for the recovery sleeve 110A (recovery sleeves 1 to 7) in which various inclined grooves 111 shown in FIG. 6C were formed. The particle size of the carrier is set to 35±5 [μm], c ₂ =40 [μm] is assumed to be one carrier, and c ₂ =80 [μm] is assumed to be a groove length capable of accommodating two carriers. ..

Here, as the number of the inclined grooves 111 on the collecting sleeve 110A is increased, the area of the surface portion is reduced, so that the amount of adhered toner on the surface portion is reduced and the toner stain on the collecting roller 110 is reduced. On the other hand, when the tilted groove 111 is increased to the maximum, most of the carriers are present in the tilted groove 111, so that the carrier is conveyed in the circumferential direction of the recovery sleeve 110A and retained in the peeling pole portion P2. The function is lowered, and only the function of transporting the carrier along the inclined groove 111 is improved.
Therefore, in order to sufficiently exert all of the function of conveying the carrier in the circumferential direction of the recovery sleeve 110A, the function of rubbing the toner in the separation pole portion P2, and the function of conveying the carrier and the toner along the inclined groove 111, the cumulative groove is required. It is desirable that the ratio of the section length to the cumulative surface section length is c _all :d _all =1:1. Further, it is more desirable to design the angle a ₁ between the groove centers 111a such that c ₂ is 80 [μm] that can accommodate two carriers.

As shown in FIG. 6C, in the collection sleeve 6 and the collection sleeve 7, c _all :d _all =1:1 was established. Further, in the recovery sleeve 6, the groove length c ₂ is 80 [μm] which can accommodate two carriers. Therefore, of the recovery sleeves 1 to 7 shown in FIG. 6C, the recovery sleeve 6 is the optimum condition for exhibiting all the above-mentioned functions of the recovery roller 110.

[Staying means]
Hereinafter, the retention means for the recovery sleeve 110A will be described.
In order to move the carriers along the inclined grooves 111, it is necessary that a sufficient amount of carriers are retained in the inclined grooves 111. Therefore, the staying means described below reduces the conveying force of the developer supplied from the developing device 412 along the circumferential direction of the recovery sleeve 110A on a part of the surface of the recovery sleeve 110A, and the surface of the recovery sleeve 110A. Stay in. As a result, the amount of carrier that drops and stays in the inclined groove 111 can be increased.

As the staying means, a magnetizing pattern of the collecting magnet roll 110B can be mentioned.
FIG. 7 is a diagram illustrating a carrier retention assisting method based on the magnetizing pattern of the collecting magnet roll 110B. The broken line in FIG. 7 represents the collecting roller 110 not provided with the collecting means (hereinafter referred to as the normal collecting roller 110), and the solid line represents the collecting roller 110 having a magnetized pattern as the collecting means.
In the normal recovery roller 110, as shown in FIG. 4, the recovery pole N1 is θ1=5[°] based on the center line D, the transport pole S1, the transport pole N2, the peeling pole S2, and the sealing pole S3. Is a position represented by θ2=80[°], θ3=160[°], θ4=200[°], θ5=320[°] with reference to the straight line connecting the center of the recovery roller 110 and the recovery pole N1. 7, the counterclockwise angle with respect to the center line D is shown as a positive value and the clockwise angle is shown as a negative value.

FIG. 7A is a graph showing the magnetic flux density of the magnetic field generated by each magnetic pole of the recovery magnet roll 110B, and the vertical axis shows the magnetic flux density. The magnetic flux density of the magnetic field generated in the S pole is shown as a negative value.
As shown in FIG. 7(A), in the collecting roller 110 provided with the staying means, an inflection point of the magnetic flux density indicated by X in the drawing is provided, and the position of the transport pole S1 is rotated counterclockwise from the normal collecting roller 110. It was placed at a position deviated from. As a result, the pole width of the recovery pole N1 (the area in which the magnetic field is generated in the circumferential direction of the recovery magnet roll 110B) is made wider than that of a normal recovery roller.

FIG. 7B is a graph showing the magnetic attraction force fθ acting in the tangential direction of the collection sleeve 110A, that is, the carrier transport direction or the opposite direction, of the magnetic attraction force generated by each magnetic pole of the collection magnet roll 110B. , The vertical axis represents the magnetic attraction force fθ. The magnetic attraction force fθ is a value calculated based on the magnetic flux density shown in FIG. Note that the magnetic attraction force fθ acting in the same direction as the carrier transport direction, that is, the same as the rotation direction B of the recovery sleeve 110A, is a negative value, in the direction that obstructs carrier transport, that is, in the direction opposite to the rotation direction B of the recovery sleeve 110A. The magnetic attraction force fθ that works is shown as a positive value.
As shown in FIG. 7B, by providing the inflection point X, it is possible to increase the value of the magnetic attraction force fθ that acts in the direction in which the conveyance of the carrier is obstructed at the position where the inflection point X is provided. it can. That is, at the position where the inflection point X is provided, the retention amount of the carrier can be increased as compared with the normal recovery roller 110.

FIG. 7C is a graph showing the magnetic attraction force fr acting in the normal direction of the collection sleeve 110A, that is, the central direction of the collection roller 110, of the magnetic attraction force generated by each magnetic pole of the collection magnet roll 110B. The magnetic attraction force fr is a value calculated based on the magnetic flux density shown in FIG.
As shown in FIG. 7C, since the magnetic attraction force fθ acting in the carrier transport direction is increased by providing the inflection point X, the magnetic attraction force fr acting in the center direction of the collection roller 110 at the collection pole N1 becomes large. Get smaller.

That is, the carrier can be retained on the recovery sleeve 110A by setting a magnetization pattern capable of retaining the carrier as shown in FIG. As a result, the carrier retention amount in the inclined groove 111 can be increased and the efficiency of carrier removal using the inclined groove 111 can be improved.
The position at which the inflection point X is provided is not limited to the recovery pole N1 and may be provided at another magnetic pole. However, if the inflection point X is provided on the peeling pole S2, it becomes difficult for the deposited carrier to peel off from the peeling pole S2, so it is not preferable to provide the inflection point on the peeling pole S2.

A magnetic member can be used as the carrier retention means. The magnetic member 140A here refers to a member made of a ferromagnetic material.
FIG. 8A shows an example of the magnetic member. As an example of the magnetic member 140A, a flat metal thin plate made of a ferromagnetic metal can be used. By disposing the magnetic member 140A at the position of the transport pole S1 with a gap from the surface of the collection roller 110, the carrier can be retained at a position close to the magnetic member 140A on the collection sleeve 110A by the magnetic field action. The size of the magnetic member 140A and the size of the gap with the recovery roller 110 are not limited. Further, as the magnetic member 140A, a thin metal plate on a flat plate, a spike cutting restriction plate made of a ferromagnetic metal, a metal roller, or the like can be used. Since the member made of a non-magnetic material is not affected by the magnetic field, the position where the magnetic member 140A, which is not suitable as the staying means, is brought close to is not limited to the carrier pole S1 and may be brought close to another magnetic pole. However, when the magnetic member 140A is brought close to the peeling pole S2, the deposited carrier becomes difficult to peel from the peeling pole S2, which is not preferable.

Further, as the magnetic member 140A, a magnet member may be placed close to the magnetic member 140A instead of the thin metal plate. Similarly, the carrier can be retained by the action of a magnetic field.
As in the case of the thin metal plate, the magnet member is not particularly limited in configuration including dimensions, as long as it is provided with a gap and is brought close to the recovery roller 110, and can be brought close to any magnetic pole other than the peeling pole S2. Good.

A brush-like member may be used as the retention means.
FIG. 8B shows an example of the brush-shaped member. As the brush-like member 140B, a brush that comes into contact with the recovery roller 110 and can be driven and rotated can be used. The configuration of the brush-shaped member 140B is not particularly limited, including the dimensions, as long as the bristles can be brought into contact with the surface of the collection roller 110 so as to bite into it. Since the carrier is pressed against the surface of the collection sleeve 110A by the tip of the brush bristles, the carrier can be retained at the contact position of the bristles.
Note that, in FIG. 8B, the brush-like member 140B is brought into contact with the position of the transport pole S1, but for the same reason as above, except for the peeling pole S2, it is brought into contact with the position of another magnetic pole. You may let me.

An elastic member may be used as the retention means.
FIG. 8A shows an example of the sheet member. As the sheet member 140C, a plate-shaped member in which an elastic member 142 such as a urethane sheet is arranged on a base material 141 such as PET can be used.
When the sheet member 140C is arranged such that the tip of the elastic member 142 contacts the collection roller 110, the tip of the elastic member 142 bends and the tip of the elastic member 142 presses the carrier against the surface of the collection sleeve 110A. The carrier can be retained at the contact position of the tip of the member 142. The sheet member 140C is not particularly limited in its configuration including dimensions as long as it can be arranged so that the tip of the elastic member 142 bites into the surface of the collection roller 110.
Although the sheet member 140C is brought into contact with the position of the transport pole S1 in FIG. 8C, it is brought into contact with the position of another magnetic pole except the peeling pole S2 for the same reason as above. May be.

That is, the carrier can be retained on the recovery sleeve 110A by using a member capable of retaining the carrier as shown in FIG. As a result, the carrier retention amount in the inclined groove 111 can be increased and the efficiency of carrier removal using the inclined groove 111 can be improved.

[effect]
As described above, the image forming apparatus 1 according to the present embodiment includes the collecting mechanism 416, and the plurality of inclined grooves 111 are formed in the circumferential direction on the surface of the collecting sleeve 110A of the collecting roller 110. Each of the inclined grooves 111 extends in the axial direction of the collecting roller, and is formed so as to be inclined so that the center in the axial direction is located on the downstream side in the rotational direction of the collecting sleeve 110A with respect to both ends in the axial direction. There is. Therefore, the toner that cannot be completely collected in the peeling pole portion P2 can be collected by rubbing the inclined groove 111 with the carrier. In addition, the above-described inclined shape allows the sheet to be reliably transported to the outside of the image forming area. As a result, it is possible to prevent image stains due to the toner attached to the collecting roller 110.

Further, the inclined groove 111 is formed to have a U-shape in cross section, and the length connecting the two uppermost points is formed to be 1 to 2 times the carrier particle diameter. Therefore, the carrier can be smoothly conveyed toward the end without being clogged in the inclined groove 111. It should be noted that the carrier can be smoothly transported by any one of the above configurations.

Further, the inclined groove 111 is formed such that the cumulative groove length is substantially the same as the cumulative surface length. Therefore, it is possible to carry out the carrier transportation in the peeling pole portion P2 and the carrier transportation by the inclined groove 111 in a suitable balance.

Further, by providing the retention means, the developer can be retained on the surface of the recovery sleeve 110A. Thereby, the carrier can be sufficiently retained in the inclined groove 111, and the carrier transfer efficiency by the inclined groove 111 can be improved.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

According to the method described below, the carrier removing effect by the collecting roller provided with the inclined groove 111 according to the present invention was verified.

(Comparative Example 1)
The groove structure is not formed on the surface of the recovery sleeve 110A.
(Comparative example 2)
A groove structure (straight groove) that is not inclined in the axial direction of the collection roller 110 is provided on the surface of the collection sleeve 110A. The number of straight grooves is 40, the distance between adjacent straight grooves is a ₁ =9[°], groove depth b=75±25 [μm], groove angle c ₂ =100[°], cross section U shape did.

(Example 1)
On the surface of the collection sleeve 110A, an inclined groove 111 inclined by 11[°] with respect to the axial direction of the collection roller 110 was provided, with the axial center of the collection roller 110 being the downstream side and both ends being the upstream side. The number of the inclined grooves 111 is 40, the distance a ₁ between adjacent straight grooves is 9°, the groove depth b is 75±25 μm, the groove angle c _{2 is} 100°, and the cross-section is U-shaped. And

(Example 2)
The inclined groove 111 similar to that in Example 1 was formed on the surface of the recovery sleeve 110A.
Further, as the staying means, the magnetizing pattern of the collecting magnet roll 110B was set to the condition shown in FIG.
The collection roller 110 has the specifications shown in FIG. 9 and has the magnetization pattern shown by the solid line in FIG. Further, as in FIG. 7, in FIGS. 9C and 9D, the counterclockwise angle with respect to the center line D is shown as a positive value, and the clockwise angle is shown as a negative value. ..
The "sleeve length" shown in FIG. 9(A) is the axial length of the recovery sleeve 110A, which is L1 in FIG. 5(C), and the "magnetization width" is the recovery magnet roll 110B. The length in the axial direction, which is L2 in FIG. 5(C), represents the fluctuation amount of the outer diameter due to the rotation of the collection roller 110, and the “runout” represents the fluctuation amount.
The “angle” shown in FIG. 9B is an anticlockwise clock with an arbitrary point on the outer circumference of the recovery magnet roll 110B as a reference line that connects the center of the recovery roller 110 and the recovery pole N1 as shown in FIG. It is a value expressed by the angle of rotation, and the peak position of each magnetic pole is shown in FIG. 9(B). “Br” represents the magnetic flux density, and in FIG. 9B, the magnetic flux density at the peak position of each magnetic pole is shown.
Further, the “pole width” indicates the value of the central angle with respect to the arc connecting two points on the circumference of the recovery magnet roll 110B in FIG. Regarding the pole width of the recovery pole N1, “80% value=31±1[°]” means that the magnetic flux density (177.6 [mT] at the peak position of the recovery pole N1 is as shown in FIG. 9C. ]) 80% value (142.08 [mT]) or more of the area having a magnetic flux density is an area having an angle of approximately −10 [°] to 21 [°], and a pole width between them is approximately 31 [°]. ] Is shown. In addition, as for the separation electrodes S2 to S3, "3 to -10 [mT]: 55[°] or more" is defined as the separation electrode S2 and the sealing electrode S3 as shown in FIG. 9D. In the region between, it is shown that the pole width at which the magnetic flux density is 3 to −10 [mT] is 55 [°] or more.

(Example 3)
The inclined groove 111 similar to that in Example 1 was formed on the surface of the recovery sleeve 110A.
Further, as a retention means, a magnetic member 140A made of a ferromagnetic metal thin plate was brought into contact. The magnetic member 140A has a thickness of 1.0 [mm], and has a gap of 0.3 [mm] from the recovery sleeve 110A and is arranged so as to be close to the transport pole S1.

(Example 4)
The inclined groove 111 similar to that in Example 1 was formed on the surface of the recovery sleeve 110A.
Further, a brush-like member 140B was brought into contact as a retaining means. The brush-like member 140B has a shaft φ6 [mm], the amount of bite into the collecting roller 110 is 0.5 [mm], and the brush-like member 140B is arranged so as to be driven and rotated by the collecting sleeve 110A.

(Example 5)
The inclined groove 111 similar to that in Example 1 was formed on the surface of the recovery sleeve 110A.
Further, the sheet member 140C was brought into contact as a retaining means. In the sheet member 140C, an elastic member 142 made of a urethane sheet having a thickness of 0.1 [mm] and a free length of 5 [mm] is arranged on a base material 141 made of PET, and the elastic member 142 with respect to the recovery sleeve 110A is provided. The tip was set so that the bite amount was 2 [mm].

<Common conditions>
The photosensitive drum 413 was rotated so that the linear velocity on the surface of the photosensitive drum 413 was 650 [mm/sec].

In the developing device 412, a two-component developer (toner particle diameter: 6.5 [μm], carrier particle diameter: 33 [μm]) is used, and the outer diameters of the first developing roller 412a and the second developing roller 412b are A developing magnet roll is arranged inside a 25 [mm] developing sleeve, the first developing roller 412a has a linear velocity ratio of 1.0 with respect to the photoconductor, and the second developing roller 412b has the linear velocity ratio with respect to the photoconductor. It was rotated in the width direction so that the linear velocity ratio was 1.2. Further, the thickness of the regulating blade 412d is set to 1.0 [mm], and the regulating blade 412d is arranged so that the gap between the regulating blade 412d and the first developing roller 412a is 0.66±0.03 [mm]. The carry amount of the carrier was set to 220 [g/m ² ]. Further, the developing bias applied to the developing sleeve a is a bias in which an AC voltage is superimposed on a DC voltage.

The collecting roller 110 is configured such that the collecting magnet roll 110B is arranged inside the collecting sleeve 110A having an outer diameter of 25 [mm]. The clearance between the photosensitive drum 413 and the photosensitive drum 413 at the closest position P1 to the photosensitive drum 413 is 0.30±0.05 [mm], and the linear velocity on the surface of the recovery sleeve 110A is 150 [mm]. /Sec] and counter-rotated with respect to the photoconductor drum 413. Further, the voltage applied to the collecting roller 110 is −400 [V] with respect to the surface potential of the photosensitive drum 413, Vpp of the AC voltage is 1.0 [kV], the duty ratio is 50 [%], and the frequency is It was set to be 2.5 [kHz].

Under the above-mentioned conditions, a horizontal band chart with a printing rate of 5% was continuously printed on 100,000 sheets, and the toner adhesion amount on the collecting sleeve 110A was detected every 20,000 sheets. To detect the toner adhesion amount, the toner was peeled off with a transparent adhesive tape, and the dirt of the collection roller 110 was evaluated by judging the density of the toner with a densitometer. Image noise was visually confirmed every 20,000 sheets.
FIG. 10 shows the evaluation results of dirt and image noise of the collection roller 110. The dirt evaluation of the collecting roller 110 was x (0.6≦x), Δ (0.3≦x<0.6), and ◯ (0≦x<0.3) based on the reflection density x. .. In addition, in the evaluation of image noise stains, x was generated and ◯ was not generated.

As shown in FIG. 10, in Comparative Example 1, at the time of 20 kp printing, the collection roller 110 became more dirty and image noise was generated. Further, as the continuous printing was performed, the stain and the image noise became worse.
In Comparative Example 2 as well, as in Comparative Example 1, the collection roller 110 was stained and image noise was generated.
In Example 1, the collecting roller 110 was soiled at the time of 20 kp printing, but it was suppressed to the extent that image noise was not generated.
In Example 2, at the time of 100 kp printing, the collecting roller 110 did not become dirty and image noise did not occur.

As described above, in each of the examples, it was shown that the collecting roller 110 can be prevented from being contaminated and image noise, and that the retention means can improve the carrier removal efficiency.

[Other Embodiments]
The specific description has been given above based on the embodiment according to the present invention, but the above embodiment is a preferred example of the present invention and is not limited to this.

In the above-described embodiment, the carrier rubbed by the peeling pole portion P2 is assumed to fall by its own weight and be collected, but the present invention is not limited to this. For example, a separate magnet may be provided in the vicinity of the peeling pole portion P2 to recover by magnetic force, or a fan may be provided in the vicinity of the collecting roller 110 to blow air to blow the carrier away from the peeling pole portion P2. May be

Further, in the above description, an example in which a non-volatile memory, a hard disk or the like is used as a computer-readable medium of the program according to the present invention is disclosed, but the invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. Further, a carrier wave is also applied as a medium for providing the data of the program according to the present invention via a communication line.

In addition, the detailed configuration of each device forming the image forming apparatus and the detailed operation of each device can be appropriately changed without departing from the scope of the present invention.

1 image forming apparatus 100 control unit 40 image forming unit 412 developing device (developing unit)
413 Photoreceptor drum (image bearing member)
416 Collection Mechanism 110 Collection Roller 110A Collection Sleeve (Non-Magnetic Rotating Body)
110B Recovery magnet roll (magnet)
111 inclined groove (groove part)
120 Carrier recovery chamber 130 Discharge screw 140A Magnetic member (metal thin plate, magnet member; retention means)
140B Brush-like member (retention means)
140C sheet member (retention means)
141 Base material 142 Elastic member 422 Primary transfer roller (transfer part)
70 storage unit N1 recovery electrode S2 peeling electrode P2 peeling electrode unit

Claims (11)

An image carrier that carries a toner image to be transferred to a sheet, a developing unit that develops the toner image on the image carrier with a two-component developer containing toner and carrier, and a toner image that the image carrier carries. And a recovery mechanism that is disposed downstream of the developing unit and upstream of the transfer unit in the rotation direction of the image carrier and that recovers the carrier on the surface of the image carrier. In an image forming apparatus having a section,
The recovery mechanism is a non-magnetic rotating body that faces the image carrier and is rotatable about an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body, and is arranged in the circumferential direction. A magnet having a plurality of magnetic poles along the line,
The magnet is arranged at least at a position close to the image carrier, and a recovery electrode for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and the recovery electrode. A peeling pole for peeling the carrier from the surface of the non-magnetic rotating body,
The non-magnetic rotating body has a plurality of groove portions formed along the circumferential direction of the non-magnetic rotating body,
Each of the plurality of grooves extends in the axial direction of the non-magnetic rotating body, and the center of the non-magnetic rotating body in the axial direction is the non-magnetic member with respect to both axial ends of the non-magnetic rotating body. An image forming apparatus, which is formed so as to be inclined so as to be positioned on a downstream side of a surface of a rotating body in a rotation direction. In each of the plurality of groove portions, in a cross section perpendicular to the axial direction of the non-magnetic rotor, the length of an arc passing through two points located on the outer circumference of the non-magnetic rotor is 1 to 2 of the carrier particle size. The image forming apparatus according to claim 1, wherein the image forming apparatus is twice as long. The image forming apparatus according to claim 1, wherein each of the plurality of groove portions is formed such that a cross-section of the non-magnetic rotating body perpendicular to the axial direction has a U shape. .. The cumulative groove portion length obtained by summing the lengths of arcs passing through two points located on the outer circumference of the non-magnetic rotating body in a cross section perpendicular to the axial direction of the non-magnetic rotating body of each of the plurality of groove portions is The image forming apparatus according to any one of claims 1 to 3, wherein the value is substantially the same as the value obtained by subtracting the cumulative groove portion length from the outer circumference in a cross section perpendicular to the axial direction of the non-magnetic rotating body. 5. A retaining means for retaining the developer collected on the surface of the non-magnetic rotating body on a part of the surface of the non-magnetic rotating body is included. The image forming apparatus described. The staying means is a magnetizing pattern of a plurality of magnetic poles arranged on the magnet, and one of the magnetic poles generates a magnetic attraction force acting in a direction in which the carrier is prevented from being conveyed due to the rotation of the non-magnetic rotating body. The image forming apparatus according to claim 5, wherein the image forming apparatus is a magnetized pattern. The staying means is a magnetic member that is arranged in close proximity to the surface of the non-magnetic rotating body and at a position where it abuts on any one of a plurality of magnetic poles arranged on the magnet. The image forming apparatus according to claim 5, wherein the image forming apparatus is an image forming apparatus. The magnetic member is a thin metal plate made of a metal of a magnetic material that is disposed in close proximity to a position where the tip of the magnetic member comes into contact with any one of a plurality of magnetic poles arranged in the magnet. The image forming apparatus according to claim 7. The staying means is a magnet member that is arranged in close proximity to the surface of the non-magnetic rotating body and abuts on any one of the plurality of magnetic poles arranged on the magnet. The image forming apparatus according to claim 7, which is characterized in that. The staying means is a brush-like member that rotates on contact with a position on the surface of the non-magnetic rotating body that comes into contact with any one of a plurality of magnetic poles arranged on the magnet. The image forming apparatus according to claim 5. The retaining means is an elastic member that is in contact with a position on the surface of the non-magnetic rotating body that abuts on any one of a plurality of magnetic poles arranged on the magnet. 5. The image forming apparatus according to item 5.

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