JP7268331B2 - Image forming apparatus and program - Google Patents

Description

The present invention relates to an image forming apparatus and program.

2. Description of the Related Art An image forming apparatus having a developing device that develops an electrostatic latent image formed on a photosensitive drum using a two-component developer containing toner and magnetic carrier is widely used.
Specifically, the action of the electric field and the magnetic field causes the toner in the developing device to adhere to the carrier, transport it to the developing region between the photoreceptor drum, and electrostatically transfer to the surface of the photoreceptor drum. On the other hand, the carrier is recovered in the developing device and adheres to the toner again, but part of the carrier is transferred to the surface of the photosensitive drum. In particular, since the surface coating of the carrier wears out due to durability and the resistance value decreases, the carrier easily adheres to the photosensitive drum due to charge injection by the developing bias.

When the carrier adheres to the photoreceptor drum, leakage may occur due to the transfer voltage applied at the transfer portion between the photoreceptor drum and the intermediate transfer belt. Leakage at the transfer portion leaves traces of leakage on the surface of the photosensitive drum, resulting in image defects such as black dots. In addition, the carrier that has passed through the transfer section is caught between the cleaning blade that cleans the surface of the photoreceptor drum and damages the surface of the photoreceptor drum and the edge of the cleaning blade. Therefore, it is necessary to remove the carrier adhering to the photosensitive drum.
In order to address such a problem, Patent Document 1 discloses that a carrier collection roller having a magnet inside is brought into contact with the surface of the photosensitive drum, and the carrier adhering to the photosensitive drum is moved to the carrier collection roller by the action of an electric field and a magnetic field. An image forming apparatus that transfers and collects is disclosed.

JP-A-6-332319

By the way, the carrier collection roller described above also collects the weakly charged toner on the photosensitive drum and the so-called fog toner adhering to the background portion. When the toner accumulates on the surface of the carrier recovery roller and fills the gap between the photoreceptor drum and the carrier recovery roller, the toner re-adheres to the photoreceptor drum and causes image contamination. In Patent Document 1, a scraper is brought into contact with the surface of the carrier recovery roller to remove the carrier, and the toner can be scraped off at the same time as the carrier. However, the small particle size toner tends to pass through between the scraper and the carrier recovery roller, resulting in low recovery efficiency. Also, the scraper damages the surface of the carrier collection roller.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an image forming apparatus having a recovery section for recovering the carrier on the photoreceptor drum. An object of the present invention is to provide an image forming apparatus and a program capable of preventing image contamination caused by toner that has been applied.

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 onto a sheet , a developing section that develops the toner image on the image carrier with a two-component developer containing toner and carrier, and a toner image carried by the image carrier. Image forming comprising: a transfer section for transferring; and a recovery section arranged downstream of the developing section and upstream of the transfer section in a rotation direction of the image carrier and recovering the carrier on the surface of the image carrier. Department and
a control unit that controls the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
A development bias in which an AC voltage is superimposed on a DC voltage is applied to the developing unit,
When the amount of carrier on the surface of the non-magnetic rotary member falls below a predetermined amount, the control unit controls the carrier to move from the developing unit to the surface of the image carrier more easily than during image formation. and executing a carrier supply mode for driving the image carrier, the developing section, and the recovery section, and in the carrier supplying mode, controlling the frequency of the AC component of the developing bias to be lower than that during image formation. It is characterized by

The invention according to claim 2 is the image forming apparatus according to claim 1 ,
The control section is characterized by executing the carrier supply mode when the area of the non-printing area during image formation exceeds a predetermined value.

The invention according to claim 3 is the image forming apparatus according to claim 1 ,
The controller may execute the carrier supply mode when the amount of rotation of the non-magnetic rotating body exceeds a predetermined amount.

The invention according to claim 4 is the image forming apparatus according to claim 1 ,
A motor for rotating the non-magnetic rotating body,
The controller may execute the carrier supply mode when the drive current of the motor falls below a predetermined value.
The image forming apparatus according to claim 5 ,
An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. and,
a control unit that controls the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
When the area of the non-printing area during image formation exceeds a predetermined value, or when the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, A carrier supply mode is executed in which the image carrier, the developing section and the recovery section are driven under conditions in which the carrier easily moves from the developing section to the surface of the image carrier.
The image forming apparatus according to claim 6 ,
An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. and,
a control unit that controls the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
When the amount of rotation of the non-magnetic rotating body exceeds a predetermined amount, or when the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, the control unit controls the amount of rotation of the non-magnetic rotating body to be lower than that during image formation. A carrier supply mode is executed in which the image carrier, the developing section, and the recovery section are driven under conditions in which the carrier easily moves from the developing section to the surface of the image carrier.
The image forming apparatus according to claim 7 ,
An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. and,
a control unit that controls the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
A motor for rotating the non-magnetic rotating body,
When the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, which is when the driving current of the motor falls below a predetermined value, the control unit controls the developing unit to operate more rapidly than during image formation. and carrying out a carrier supply mode in which the image carrier, the developing section, and the recovery section are driven under conditions in which the carrier easily moves from the surface of the image carrier to the surface of the image carrier.
The invention according to claim 8 is the image forming apparatus according to any one of claims 5 to 7 ,
A development bias in which an AC voltage is superimposed on a DC voltage is applied to the developing unit,
The controller is characterized in that, in the carrier supply mode, the potential difference between the surface potential of the image bearing member and the DC component of the developing bias is controlled to be greater than that during image formation.
The invention according to claim 9 is the image forming apparatus according to any one of claims 1 to 8 ,
The separation electrode has the same polarity as the recovery electrode,
The magnet has a demagnetizing region in a region on the downstream side of the separation pole and the upstream side of the recovery pole with respect to the separation pole in the rotation direction of the non-magnetic rotor.

The program according to claim 10 ,
An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. a computer of an image forming apparatus comprising
Functioning as a control unit for controlling the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
A development bias in which an AC voltage is superimposed on a DC voltage is applied to the developing unit,
When the amount of carrier on the surface of the non-magnetic rotary member falls below a predetermined amount, the control unit controls the carrier to move from the developing unit to the surface of the image carrier more easily than during image formation. and executing a carrier supply mode for driving the image carrier, the developing section, and the recovery section, and in the carrier supplying mode, controlling the frequency of the AC component of the developing bias to be lower than that during image formation. It is characterized by
The program according to claim 11 ,
An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. a computer of an image forming apparatus comprising
Functioning as a control unit for controlling the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
When the area of the non-printing area during image formation exceeds a predetermined value, or when the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, A carrier supply mode is executed in which the image carrier, the developing section and the recovery section are driven under conditions in which the carrier easily moves from the developing section to the surface of the image carrier.
The program according to claim 12 ,
An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. a computer of an image forming apparatus comprising
Functioning as a control unit for controlling the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
When the amount of rotation of the non-magnetic rotating body exceeds a predetermined amount, or when the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, the control unit controls the amount of rotation of the non-magnetic rotating body to be lower than that during image formation. A carrier supply mode is executed in which the image carrier, the developing section, and the recovery section are driven under conditions in which the carrier easily moves from the developing section to the surface of the image carrier.
The program according to claim 13 ,
An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. a computer of an image forming apparatus comprising
Functioning as a control unit for controlling the amount of carrier carried by the recovery unit,
The recovery unit includes a non-magnetic rotator that faces the image carrier, supports a carrier, and rotates about an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotator. a magnet, and
The magnet is disposed at least at a position substantially facing the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a magnet for the recovery pole. a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
The image forming apparatus includes a motor for rotating the non-magnetic rotating body,
When the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, which is when the driving current of the motor falls below a predetermined value, the control unit controls the developing unit to operate more rapidly than during image formation. and carrying out a carrier supply mode in which the image carrier, the developing section, and the recovery section are driven under conditions in which the carrier easily moves from the surface of the image carrier to the surface of the image carrier.

According to the present invention, in an image forming apparatus provided with a collecting section for collecting carrier on a photoreceptor drum, toner on the collecting section is removed, and image contamination caused by toner adhering to the collecting section is removed. It is possible to provide an image forming apparatus and a program that can prevent the

1 is a diagram showing a schematic configuration of an image forming apparatus according to the present invention; FIG. 2 is a block diagram showing the functional configuration of the image forming apparatus; FIG. FIG. 4 is a diagram showing a schematic configuration of a carrier recovery mechanism; 4 is a flow chart showing the operation of the image forming apparatus; FIG. 5 is a diagram showing the relationship between the amount of carrier and the occurrence of toner contamination; 4 is a flow chart showing the operation of the image forming apparatus in carrier supply mode; FIG. 3 is a diagram showing the relationship between the amount of carrier on the surface of a photoreceptor drum and the potential difference between the surface potential of the photoreceptor drum and the developing bias; It is a figure which shows the effect of the Example which concerns on this invention.

Hereinafter, this embodiment will be described in detail based on the drawings. However, the scope of the invention is not limited to the illustrated examples.

FIG. 1 is a diagram schematically showing the overall configuration of an image forming apparatus 1 according to an embodiment of the invention. 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 electrophotographic process technology. That is, the image forming apparatus 1 transfers each color toner image of Y (yellow), M (magenta), C (cyan), and K (black) formed on the photosensitive drum 413 onto the intermediate transfer belt 421 (primary transfer). ), superimposing the four-color toner images on the intermediate transfer belt 421, and then transferring (secondary transfer) to the paper S to form an image.

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

As shown in FIG. 2, the image forming apparatus 1 includes an image reading section 10, an operation display section 20, an image processing section 30, an image forming section 40, a sheet conveying section 50, a fixing section 60, a storage section 70, a communication section 80 and A control unit 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, develops 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 developed program. For example, when the amount of carrier on carrier collection roller 140 decreases, control unit 100 executes a carrier supply mode, which will be described later.

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 transports the document D placed on the document tray by the transport mechanism and sends it to the document image scanning device 12 . The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents D placed on the document tray at once.

The document image scanning device 12 optically scans the document conveyed onto the contact glass from the automatic document feeder 11 or the document placed on the contact glass, and converts the light reflected from the document into a CCD (Charge Coupled Device). ) An image is formed on the light-receiving surface of the sensor 12a, and the document image is read. The image reading section 10 generates input image data based on the result of reading by the document image scanning device 12 . Predetermined image processing is performed on the input image data in the image processing section 30 .

The operation display unit 20 is composed of, for example, a liquid crystal display (LCD) 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 status display, operation status of each function, etc. according to a display control signal 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 or the like that performs digital image processing on image data of an input job (input image data) in accordance with initial settings or user settings. For example, the image processing unit 30 performs gradation correction based on gradation correction data (gradation correction table) under the control of the control unit 100 . The image processing unit 30 also performs various types of correction processing such as color correction and shading correction, compression processing, etc., on the input image data, in addition to tone correction. The image forming section 40 is controlled based on the image data subjected to these processes.

The image forming section 40 includes image forming units 41Y, 41M, 41C, 41K, 41Y, 41M, 41C, 41K, 41Y, 41M, 41K, 41K, 41Y, 41M, 41K, 41K, 41Y, 41M, 41M, 41K, 41K, 41M, 41M, 41K, 41K, 41K, and 41K, based on image-processed input image data. An intermediate transfer unit 42 and the like are provided.

Image forming units 41Y, 41M, 41C, and 41K for the Y, M, C, and K components have similar configurations. For convenience of illustration and description, common components are indicated by the same reference numerals, and Y, M, C, or K is added to the reference numerals to distinguish them. In FIG. 1, only the components of the image forming unit 41Y for the Y component are denoted by reference numerals, and the components of the other image forming units 41M, 41C, and 41K are omitted.

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

The photosensitive drum 413 is, for example, an aluminum conductive cylindrical body (aluminum tube) having a drum diameter of 80 [mm], and an undercoat layer (UCL) and a charge generation layer (CGL) on the peripheral surface of the drum. Generation Layer) and a charge transport layer (CTL: Charge Transport Layer) are sequentially laminated to form a negatively charged organic photoreceptor (OPC: Organic Photo-conductor). The charge-generating layer is made of an organic semiconductor in which a charge-generating material (eg, phthalocyanine pigment) is dispersed in a resin binder (eg, polycarbonate), and generates a pair of positive and negative charges when exposed by the exposure device 411 . The charge-transporting layer consists of a hole-transporting material (electron-donating nitrogen-containing compound) dispersed in a resin binder (e.g., polycarbonate resin), and transports positive charges generated in the charge-generating layer to the surface of the charge-transporting layer. do.

The control unit 100 rotates the photoreceptor drum 413 at a constant peripheral speed by controlling the drive current supplied to a drive motor (not shown) that rotates the photoreceptor drum 413 .

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

The developing device 412 is a two-component developing device that uses a developer containing toner and carrier. form an image.
Specifically, the developing device 412 includes a developing sleeve 412a arranged to face the photosensitive drum 413 across the developing region. To the developing sleeve 412a, for example, a developing bias in which an AC voltage is superimposed on a DC voltage having the same polarity as the charging polarity of the charging device 414, that is, a negative polarity, is applied. Attach electrostatically. A developing magnet roll having a magnetic pole is arranged inside the developing sleeve 412a, and a magnetic brush is generated on the outer peripheral surface of the developing sleeve 412a by the magnetic field generated by the developing magnet roll, and the layer of the developer is formed on the developing sleeve. It is formed on the outer peripheral surface of 412a. Then, the developing sleeve 412a rotates counterclockwise in the figure, thereby conveying 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 412a by the magnetic field. In the development area, the toner is electrostatically transferred from the development sleeve 412 a to the electrostatic latent image formed on the surface of the photosensitive drum 413 . Note that the toner is not particularly limited, and commonly used known toners can be used. For example, it is possible to use a binder resin containing a coloring agent and, if necessary, a charge control agent, a release agent, and the like, and treated with an external additive. 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 slides on the surface of the photoreceptor drum 413, and removes transfer residual toner remaining on the surface of the photoreceptor drum 413 after the primary transfer.

The carrier recovery mechanism 416 is arranged downstream of the developing device 412 and upstream of the primary transfer nip between the primary transfer roller 422 and the photoconductor drum 413 in the rotation direction of the photoconductor drum 413 . Before the carrier adhering to 413 reaches the primary transfer nip, the carrier is recovered.
Details of the configuration of the carrier recovery mechanism 416 will be described later.

The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422 (transfer section), 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 stretched around a plurality of support rollers 423 in a loop. At least one of the plurality of supporting rollers 423 is configured as a driving roller, and the others are configured as driven rollers. For example, it is preferable that the roller 423A arranged downstream in the belt running direction from the primary transfer roller 422 for the K component is a drive roller. This makes it easier to keep the running speed of the belt in the primary transfer portion constant. As the drive roller 423A rotates, the intermediate transfer belt 421 runs in the arrow A direction at a constant speed.

The primary transfer roller 422 is arranged on the inner circumferential surface side of the intermediate transfer belt 421 so as to face the photosensitive drum 413 of each color component. A primary transfer nip for transferring a toner image from the photosensitive drum 413 to the intermediate transfer belt 421 is formed by pressing the primary transfer roller 422 against the photosensitive drum 413 with the intermediate transfer belt 421 therebetween.

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 drive roller 423A in the belt running direction. A secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the sheet S is formed by pressing the secondary transfer roller 424 against the backup roller 423B with the intermediate transfer belt 421 therebetween.

When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photosensitive drum 413 are sequentially superposed on the intermediate transfer belt 421 and primarily transferred. 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 side of the intermediate transfer belt 421 (the side in contact with the primary transfer roller 422). It is electrostatically transferred to 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 onto the sheet S. Specifically, a toner image is formed by applying a secondary transfer bias to the secondary transfer roller 424 and applying an electric charge having a polarity opposite to that of the toner to the back side of the sheet S (the side in contact with the secondary transfer roller 424). is electrostatically transferred to the paper S. The sheet S onto which the toner image has been transferred is conveyed toward the fixing section 60 .

The belt cleaning device 426 has a belt cleaning blade or the like that slides on the surface of the intermediate transfer belt 421, and removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after secondary transfer. Instead of the secondary transfer roller 424, a configuration in which a secondary transfer belt is stretched in a loop shape around a plurality of support rollers including the secondary transfer roller (a so-called belt-type secondary transfer unit) is adopted. Also good.

The fixing unit 60 fixes the toner image to the paper S by heating and pressurizing the paper S conveyed after the toner image is secondarily transferred at the fixing nip.

The paper conveying unit 50 includes a paper feeding unit 51, a paper discharging unit 52, a conveying path unit 53, and the like. The three paper feed tray units 51a to 51c constituting the paper feed unit 51 store paper S (standard paper, special paper) identified based on basis weight, size, etc. for each preset type. . The transport path portion 53 has a plurality of transport roller pairs such as a registration roller pair 53a.

The paper sheets S accommodated in the paper feed tray units 51 a to 51 c are sent out one by one from the top and conveyed to the image forming section 40 by the conveying path section 53 . At this time, the skew of the fed sheet S is corrected and the transport timing is adjusted by the registration roller section in which the registration roller pair 53a is arranged. Then, in the image forming section 40 , the toner images on the intermediate transfer belt 421 are collectively secondary-transferred onto one side of the sheet S, and the fixing section 60 performs a fixing process. The sheet S on which the image has been formed is discharged to the outside of the apparatus by a discharge section 52 having a discharge roller 52a.

Note that the paper S may be long paper or roll paper. In this case, the paper S is accommodated in a paper feeder (not shown) connected to the image forming apparatus 1, and the paper S held by the paper feeder passes through the paper feed port 54 from the paper feeder. The paper is supplied to the image forming apparatus 1 via the transport path portion 53 .

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

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

Next, with reference to FIG. 3, the configuration of carrier recovery mechanism 416 will be described in detail.
The carrier recovery mechanism 416 is a mechanism for recovering the carrier present on the surface of the photoreceptor drum 413, and as shown in FIG. Prepare.

The carrier recovery roller 110 includes a rotatable non-magnetic recovery sleeve 110A and a recovery magnet roll 110B fixedly arranged inside the recovery sleeve 110A, and is arranged to face the photosensitive drum 413. Note that the carrier collection roller 110 functions as a collection section in the present invention, the collection sleeve 110A functions as a non-magnetic rotating body in the present invention, and the collection magnet roll 110B functions as a magnet in the present invention.

The collecting sleeve 110A is rotationally driven in the direction of B in the drawing, and at a position facing the photosensitive drum 413 rotating in the direction of C in the drawing, counter-rotates so that the advancing direction of its surface is opposite. A gap is provided between the recovery sleeve 110A and the surface of the photosensitive drum 413. As shown in FIG.

A plurality of magnetic poles (N1, N2, N3, S1, S2) that generate a magnetic field are arranged on the collection magnet roll 110B. As shown in FIG. 3, the plurality of magnetic poles (N1, N2, N3, S1, S2) are arranged so that N poles and S poles alternate. Note that M in the drawing indicates the magnetic flux distribution in the vicinity of the carrier recovery roller 110 generated by these magnetic poles.
Further, the carrier collection roller 110 is connected to a power source (not shown), and is applied with a voltage in which an AC voltage is superimposed on a DC voltage.
That is, the carrier c collected on the surface of the carrier collection roller 110 is attracted to the outer peripheral surface of the collection sleeve 110A by the magnetic force generated by the magnetic poles arranged on the collection magnet roll 110B and the electrostatic force generated in the electric field. When carried on the surface of 110A, it is conveyed on the surface of carrier recovery roller 110 as it rotates in the direction indicated by B in the figure.

A carrier conveying operation of the carrier collecting roller 110 will be described in detail.
The collection magnet roll 110B has a magnetic pole N1 so as to substantially face the photosensitive drum 413. As shown in FIG. The magnetic pole N1 functions as a recovery pole. That is, the magnetic force generated by the magnetic pole N1 draws the carrier c on the surface of the photosensitive drum 413 to the surface of the collection sleeve 110A and collects it.
As shown in FIG. 3, if the center line connecting the center of the carrier recovery roller 110 and the photosensitive drum 413 is L1, and the counterclockwise angle with respect to the center line L1 is represented by θ, the recovery pole is N1 is arranged so that its peak position is θ=0 to 10°. That is, by arranging the recovery pole N1 at a position slightly shifted from the position where the photoreceptor drum 413 and the carrier recovery roller 110 are closest to each other, the carrier adheres to the recovery sleeve 110A counter-rotating with respect to the photoreceptor drum 413. easier.

Further, on the collection magnet roll 110B, magnetic poles S1, N2, and S2 are arranged in this order from the magnetic pole N1 toward the downstream side in the rotation direction of the collection sleeve 110A so that the N pole and the S pole alternate. . These magnetic poles function as transport poles, and the carrier c receives the magnetic force generated by these magnetic poles and moves while rolling on the surface of the collection sleeve 110A.

A magnetic pole N3 is arranged at the most downstream position in the rotational direction of the collection sleeve 110A. Magnetic pole N3 functions as a separation pole. That is, when the carrier c reaches the area (separation pole portion P) on the collection sleeve 110A that abuts against the magnetic pole N3, indicated by P in the drawing, the carrier c cannot move further downstream, so that the separation pole N3 The carrier c stays at the separation pole P while rolling under the magnetic attraction force of , and rubs the surface of the collection sleeve 110A while involving the carrier c newly reaching the separation pole P due to the rotation of the collection sleeve 110A.

A demagnetization region R is formed downstream of the separation pole N3 and upstream of the recovery pole N1 in the rotational direction of the recovery sleeve 110A. Since the recovery pole N1 and the separation pole N3 have the same polarity, they form a repelling magnetic field. No magnetic field is formed in the region upstream of the , and the magnetic force does not act. As a result, the carrier c staying in the stripping pole N3 drops by its own weight and is recovered in the carrier recovery chamber 120 when it exceeds a certain amount.

When the counterclockwise angle with respect to the center line L1 is represented by θ1, the separation pole N3 has a peak position of θ1=160 to 220°. However, considering the recovery efficiency of the carrier recovery chamber 120, it is desirable that the separation pole N3 be arranged downstream in the rotation direction of the recovery sleeve 110A from the position where the carrier recovery roller 110 is highest in the vertical direction. On the other hand, when the distance between the separation pole N3 and the recovery pole N1 is short, the carrier c separated from the separation pole N3 rides on the magnetic field of the recovery pole N1, is attracted to the recovery pole N1, and adheres to the recovery sleeve 110A again. put away. Therefore, when the counterclockwise angle with respect to the vertical direction indicated by L2 in the figure is represented by θ2, the separation pole N3 is more preferably within the range of the value of θ1 described above and θ2=0 to 30. It is desirable to be placed in the range of °.

A discharge screw 130, which is a helical screw member, is arranged inside the carrier recovery chamber 120, and the carrier c collected in the carrier recovery chamber 120 is discharged by the discharge screw 130 into a carrier recovery box (not shown) for disposal. be done.

Note that the number of magnetic poles arranged on the collection magnet roll 110B in this embodiment is an example, and is not limited to the number described above.

[Carrier supply mode]
Next, the carrier supply mode executed by the image forming apparatus 1 according to this embodiment will be described with reference to the drawings.

The carrier collection roller 110 has the function of collecting the carrier on the surface of the photosensitive drum 413 as described above.
At this time, weakly charged toner and fog toner on the surface of the photosensitive drum 413 are also collected by the carrier collection roller 110 . Toner adheres to the photosensitive drum 413 due to electrostatic force, but weakly charged toner, fogging toner, etc., have weak adhesion to the photosensitive drum 413 due to electrostatic force. and the photoreceptor drum 413 are transferred to the carrier collection roller 110 . Since the collected toner t is nonmagnetic, it is not affected by the magnetic force generated by the magnetic poles of the collection magnet roll 110B, and moves while being fixed on the surface of the collection sleeve 110A, but reaches the separation pole portion P. At this time, the particles are rubbed by the carrier c staying at the separation pole P, deposited together with the carrier c, and finally recovered in the carrier recovery chamber 120 .

However, if the amount of carrier on the collection sleeve 110A is small, the amount of carrier deposited on the separation pole P decreases, and the toner cannot be sufficiently collected at the separation pole P, so toner accumulates on the collection sleeve 110A. It will be done. When the toner on collection sleeve 110A fills the gap between photoreceptor drum 413 and carrier collection roller 110, the toner on carrier collection roller 110 adheres to photoreceptor drum 413 again, causing toner stains on the paper. do.
Therefore, since an appropriate amount of carrier is required on the surface of recovery sleeve 110A, in the present embodiment, the amount of carrier on the surface of carrier recovery roller 110 is less than the amount required to recover the toner on the surface of carrier recovery roller 110. If so, a carrier supply mode is executed to supply the carrier.

In the carrier supply mode, conditions are set so that the carrier easily moves from the developing device 412 to the photosensitive drum 413, and then the developing sleeve 412a of the developing device 412, the photosensitive drum 413, and the carrier recovery roller 110 are driven. As a result, the carrier moved from the developing device 412 to the photosensitive drum 413 is recovered by the carrier recovery roller 110, and the amount of carrier on the surface of the carrier recovery roller 110 can be increased.

Next, the operation of the image forming apparatus 1 according to this embodiment will be described with reference to FIG. Note that the processing in FIG. 4 is realized by cooperation between the control unit 100 and the programs stored in the storage unit 70. FIG.

First, the controller 100 determines whether or not the amount of carrier on the surface of the carrier collection roller 110 is below the minimum required amount (step S1).
Here, the minimum necessary amount of carrier on the surface of carrier recovery roller 110 will be described. The minimum required amount of carrier depends on the magnetic force of the separation pole N3. FIG. 5 shows the relationship between the toner contamination and the amount of carrier on the carrier collection roller 110. As shown in FIG. In FIG. 5, "magnetic force" indicates the magnetic force of the separation pole N3, and "longitudinal direction" indicates the axial length of the carrier recovery roller 110. The x indicates that toner stains did not occur on the body drum 413, and that they occurred. When the length of the carrier collection roller 110 in the longitudinal direction is 330 mm and the magnetic force of the separation pole N3 is 45 [mT], toner stains occur when the carrier amount is less than 3.0 [g]. The minimum required amount of carrier to prevent contamination is {3 [g]/330 [mm]}*1000=9.090909 [g/m]. Therefore, there is a need to maintain a greater amount of carrier on carrier collection roller 110 .
A predetermined amount of carrier is supplied to the carrier recovery roller 110 in the initial state, but when the carrier on the surface of the carrier recovery roller 110 is gradually removed and reaches the minimum required amount, the carrier is supplied. .

It should be noted that it may be determined whether or not the amount of carrier on the surface of carrier collection roller 110 is less than the minimum required amount based on the amount of rotation of collection sleeve 110A. That is, since the carrier is slid on the peeling pole P by rotating the collection sleeve 110A, the carrier on the carrier collection roller 110 is removed as the amount of rotation increases. Therefore, the amount of rotation of the collection sleeve 110A from the reference time to the occurrence of toner contamination is measured in advance, and when the amount of rotation is reached during image formation, it is determined that the minimum required amount of carrier has been reached. , it is possible to implement a carrier supply mode.

Alternatively, the driving current for rotating the collection sleeve 110A may be monitored, and when the driving current is less than a predetermined value, it may be determined that the carrier has fallen below the minimum required amount. Carriers staying at the separation pole P act as a load on the rotational torque of the recovery sleeve 110A, but when the staying carriers at the separation pole P decrease, the driving torque decreases and the driving current decreases. Therefore, it is possible to measure the drive current in advance at the time when the toner smear occurs, and when the current value is reached, it is determined that the carrier has reached the minimum required amount, and the carrier supply mode can be executed. be.

In step S1, if the controller 100 determines that the amount of carrier is not less than the minimum required amount (step S1: NO), it repeats the process of step S1. is suspended (step S2).

Subsequently, the control section 100 executes the carrier supply mode (step S3).
The operation of the image forming apparatus 1 in the carrier supply mode will be described with reference to FIG. Note that the processing in FIG. 6 is realized by cooperation between the control unit 100 and the programs stored in the storage unit 70. FIG.

In the carrier supply mode, the controller 100 first increases the surface potential of the photosensitive drum 413 by a predetermined amount (step S31).
As the potential difference ΔV between the surface potential V0 of the photoreceptor drum 413 and the developing bias Vdc increases, the carrier is more likely to be supplied to the photoreceptor drum 413 . Specifically, as described above, a developing bias in which an AC voltage is superimposed on a DC voltage of negative polarity is applied to the developing sleeve 412a, and the surface of the photosensitive drum 413 is negatively charged by the charging device 414. there is For example, if the developing bias Vdc is −580 V and the surface potential V0 of the photosensitive drum 413 is −700 V, the positively charged carrier is attracted from the developing sleeve 412a to the photosensitive drum 413 by the electrostatic force acting on the electric field. . However, it stays on the developing sleeve 412a due to the magnetic force generated in the developing sleeve 412a. At this time, if the surface potential V0 of the photosensitive drum 413 is raised to −900 V, the electrostatic force acting on the electric field increases, and the carrier moves from the developing sleeve 412a to the photosensitive drum 413. FIG.

FIG. 7 is a diagram showing the relationship between the carrier amount on the surface of the photosensitive drum 413 and the potential difference ΔV=|Vdc−V0|. The vertical axis indicates the number of carriers measured per unit area of the surface of the photosensitive drum 413, and the horizontal axis indicates ΔV. During image formation, the potential difference ΔV is set within the range indicated by D in the figure. can be increased.
Therefore, in step S31, the charging device 414 is controlled to raise the surface potential V0 of the photosensitive drum 413 in order to increase the potential difference ΔV. The same effect can be obtained even if the developing bias Vdc is decreased by the same value.

Subsequently, the controller 100 rotates the developing sleeve 412a, the photosensitive drum 413, and the carrier recovery roller 110 (step S32).
Next, the controller 100 applies a developing bias to the developing device 412 (step S33).

Next, the control unit 100 starts counting time (step S34).
The carrier supply mode is executed only for a predetermined time that is considered necessary for supplying the carrier.
The control unit 100 determines whether or not a predetermined time has passed (step S35), and if it determines that it has not passed (step S35: NO), it repeats the process of step S35. S35: YES), the process proceeds to step S36.

In step S36, the control unit 100 restores the surface potential of the photosensitive drum 413 to the surface potential at the time of image formation.
The above processing completes the carrier supply mode.

When the carrier supply mode is completed, returning to FIG. 4, the image forming operation is restarted (step S4).
Thus, the control in FIG. 4 is completed.

As described above, the image forming apparatus 1 according to this embodiment has the carrier recovery mechanism 416 downstream of the developing device 412 and upstream of the primary transfer nip portion in the rotation direction of the photosensitive drum 413 . The carrier collection roller 110 includes a collection sleeve 110A and a collection magnet roll 110B. The collection pole of the collection magnet roll 110B collects the carrier and toner on the surface of the photosensitive drum 413, and the separation pole collects the carrier together with the toner. Release from roller 110 . Further, when the amount of carrier on the carrier recovery roller 110 falls below the minimum required amount, the carrier supply mode is executed to supply the carrier.
Therefore, according to the image forming apparatus 1 according to the present embodiment, the carrier on the photosensitive drum 413 is efficiently collected, the toner on the carrier collection roller 110 is removed, and image contamination caused by the toner is prevented. be able to.

In the above embodiment, the potential difference between the surface potential of the photosensitive drum 413 and the developing bias is increased in the carrier supply mode. You get the effect.
As described above, a developing bias obtained by superimposing an AC voltage on a DC voltage is applied to the developing sleeve 412a. making it easier. The carrier has a large particle diameter and is less likely to vibrate than the toner. However, if the frequency component is lowered to slow down the vibration speed, the carrier will also be easily separated from the developing sleeve 412a by vibration. When the developing sleeve 412a is separated from the developing sleeve 412a, the influence of the magnetic field generated in the developing sleeve 412a is weakened, so that the electrostatic force acting on the electric field between the developing sleeve 412a and the photosensitive drum 413 attracts the toner to the photosensitive drum 413. FIG. Therefore, for example, if the frequency component of the AC voltage during image formation is 10 kHz, it is effective to reduce it to 3000 Hz in the carrier supply mode.

Further, in the above embodiment, the carrier supply mode is executed when the amount of carrier on the surface of the carrier collection roller 110 falls below the minimum required amount, but the present invention is not limited to this. For example, the relative amount of carrier to toner on carrier collection roller 110 may be used to determine whether to carry out the carrier supply mode.
Specifically, there is a method of determining based on the area of the non-printing area formed on the photosensitive drum 413 from a predetermined reference time such as after the previous carrier supply operation or the initial state of the carrier collection roller 110 . . That is, since fogging toner and weakly charged toner tend to adhere to the non-printing area on the surface of the photosensitive drum 413, the amount of toner collected by the carrier collecting roller 110 increases when the low coverage image continues to be printed. Increases the amount of carrier required for recovery. Therefore, the area of the non-printing area formed from the reference time to the occurrence of toner contamination is measured in advance, and it is determined that it is necessary to supply the carrier when the area is reached during image formation. Execute carrier supply mode.

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these.

According to the following method, the carrier supply mode according to the present invention and its comparative example were implemented, and the effect of suppressing toner contamination by the carrier supply mode was evaluated. Note that the relationship between the implementation time and the carrier supply amount in the carrier supply mode is that the supply amount is 0.2 [g] for an implementation time of 10 seconds, and the supply amount is 0.35 [g] for an implementation time of 20 seconds. is.

(Example 1)
In the initial state before image formation, 3 [g] of carrier was supplied to the peeling pole portion P of the carrier collection roller 110 .
The length in the paper transport direction of the non-printing area during image formation was integrated, and the carrier supply mode was performed for 10 seconds every time 3 [km] of printing was performed.
(Example 2)
In the initial state before image formation, 3 [g] of carrier was supplied to the peeling pole portion P of the carrier collection roller 110 .
The drive current measured in the initial state before image formation was stored in a memory, and the drive current of the motor for rotationally driving the carrier collection roller 110 during image formation was monitored. When the drive current fell below the initial value of 48 [mA], the carrier supply mode was performed for 10 seconds. The drive torque in the initial state was 42 [mNm], and the drive torque at the start of the carrier supply mode was 40 [mNm].
(Comparative example 1)
The configuration is such that the carrier supply mode is not implemented, and a scraper is brought into contact with the carrier recovery roller 110 to scrape the toner on the surface of the carrier recovery roller 110 with the scraper.
(Comparative example 2)
The configuration is such that the carrier supply mode is not implemented and the scraper is not brought into contact with the carrier recovery roller 110 .

<Common conditions>
The diameter of the photosensitive drum 413 is φ100, and the photosensitive drum 413 was rotated so that the surface linear velocity was 650 [mm/sec].
The collection sleeve 110A had a diameter of φ25, and was rotated so that the surface linear velocity was 150 [mm/sec].
Further, the magnetic force of the recovery pole N1 is set to 150 [mT], and the center line L1 connecting the center of the photoreceptor drum 413 and the center of the carrier recovery roller 110 is 5[°] downstream in the rotation direction of the photoreceptor drum 413. ] The recovery pole N1 was arranged so that the shifted position was the peak position.
The distance between the surfaces of the photoreceptor drum 413 and the carrier collection roller 110 at the position where they face each other is set to 0.3 [mm].
The developing bias applied to the developing sleeve 412a is such that the DC voltage is -400 [V] with respect to the surface potential of the photosensitive drum 413, the AC voltage Vpp is 1000 [V], the duty ratio is 50 [%], and the frequency is It was set to be 2.5 [kHz].

FIG. 8 shows the results of measuring the number of printed sheets until toner stains occur on the paper after continuous printing at a coverage rate of 10%. Note that "number of printed sheets" in FIG. 8 indicates the number of printed sheets before toner stains occur on the sheet. Further, in the embodiment, the carrier supply mode is executed at the timing described above during printing, and the cumulative number of printed sheets from the initial state is counted. In addition, regarding the effect of suppressing toner contamination, 〇 means that toner contamination does not occur even if a large amount of printing is performed, so the effect of suppressing toner contamination is high. Therefore, it is shown that the effect of suppressing toner contamination is low.

As shown in FIG. 8, in Examples 1 and 2, toner stains did not occur on the paper even after printing at 1000 [kp].
On the other hand, in Comparative Example 1, toner contamination occurred at the time of printing of 120 [kp]. In Comparative Example 1, while the carrier was scraped off by the scraper, the toner having a smaller particle size than the carrier slipped through the scraper and adhered to the surface of the carrier collection roller 110 . It is considered that the toner spreads on the surface of the carrier recovery roller, weakening the magnetic field of the recovery magnet roll 110B, and the recovery amount of the carrier and toner at the separation pole P using magnetic force becomes insufficient. Between the scraper and the carrier recovery roller 110, the carrier rubbed against the surface of the carrier recovery roller 110, causing scratches, and thus the carrier recovery roller 110 needed to be replaced.
In Comparative Example 2, the toner reattached from the carrier collection roller 110 to the photosensitive drum 413 at the time of printing of 98 [kp], and toner stains occurred on the paper.
As described above, in Examples 1 and 2, execution of the carrier supply mode was shown to be effective in collecting toner on the carrier collection roller 110 and preventing toner contamination.

[Other embodiments]
As mentioned above, although it explained concretely based on the embodiment concerning the present invention, the above-mentioned embodiment is a suitable example of the present invention, and is not limited to this.

In the above embodiment, the carrier rubbed by the peeling poles P is dropped by its own weight and collected, but the present invention is not limited to this. For example, a separate magnet may be provided in the vicinity of the separation pole P to recover the carrier by magnetic force, or a fan may be provided in the vicinity of the carrier recovery roller 110 to blow air to blow the carrier away from the separation pole P. may be configured.

Also, in the above description, an example using a non-volatile memory, a hard disk, etc. is disclosed as a computer-readable medium for the program according to the present invention, but the present invention is not limited to this example. As other computer-readable media, portable recording media such as CD-ROMs can be applied. A carrier wave is also applied as a medium for providing program data according to the present invention via a communication line.

In addition, the detailed configuration and detailed operation of each device that constitutes the image forming apparatus can be changed as appropriate without departing from the gist of the present invention.

1 image forming apparatus 100 control section 40 image forming section 412 developing device (developing section)
413 photoreceptor drum (image carrier)
416 carrier recovery mechanism 110 carrier recovery roller (recovery unit)
110A recovery sleeve (non-magnetic rotor)
110B recovery magnet roll (magnet)
120 carrier recovery chamber 130 discharge screw 421 intermediate transfer belt 422 primary transfer roller (transfer section)
70 storage part N1 recovery pole N3 separation pole P separation pole

Claims (13)

An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. and,
a control unit that controls the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
A development bias in which an AC voltage is superimposed on a DC voltage is applied to the developing unit,
When the amount of carrier on the surface of the non-magnetic rotary member falls below a predetermined amount, the control unit controls the carrier to move from the developing unit to the surface of the image carrier more easily than during image formation. and executing a carrier supply mode for driving the image carrier, the developing section, and the recovery section, and in the carrier supplying mode, controlling the frequency of the AC component of the developing bias to be lower than that during image formation. An image forming apparatus characterized by: 2. The image forming apparatus according to claim 1 , wherein the controller executes the carrier supply mode when an area of a non-printing area during image formation exceeds a predetermined value. 2. The image forming apparatus according to claim 1 , wherein the controller executes the carrier supply mode when the amount of rotation of the non-magnetic rotating body exceeds a predetermined amount. A motor for rotating the non-magnetic rotating body,
The image forming apparatus according to claim 1 , wherein the controller executes the carrier supply mode when the drive current of the motor falls below a predetermined value. An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. and,
a control unit that controls the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
When the area of the non-printing area during image formation exceeds a predetermined value, or when the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, an image forming apparatus characterized by executing a carrier supply mode in which the image carrier, the developing section, and the recovery section are driven under conditions in which the carrier easily moves from the developing section to the surface of the image carrier. . An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. and,
a control unit that controls the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
When the amount of rotation of the non-magnetic rotating body exceeds a predetermined amount, or when the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, the control unit controls the amount of rotation of the non-magnetic rotating body to be lower than that during image formation. An image forming apparatus characterized by executing a carrier supply mode in which the image carrier, the developing section, and the recovery section are driven under conditions in which the carrier easily moves from the developing section to the surface of the image carrier. An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. and,
a control unit that controls the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
A motor for rotating the non-magnetic rotating body,
When the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, which is when the driving current of the motor falls below a predetermined value, the control unit controls the developing unit to operate more rapidly than during image formation. and carrying out a carrier supply mode in which the image carrier, the developing section, and the recovery section are driven under conditions in which the carrier easily moves from the surface of the image carrier to the surface of the image carrier. A development bias in which an AC voltage is superimposed on a DC voltage is applied to the developing unit,
6. The controller controls the potential difference between the surface potential of the image bearing member and the DC component of the developing bias in the carrier supply mode to be greater than that during image formation. 8. The image forming apparatus according to any one of 7 . The separation electrode has the same polarity as the recovery electrode,
9. The magnet has a demagnetized region in a region on the downstream side of the separation pole and the upstream side of the recovery pole with respect to the separation pole in the direction of rotation of the non -magnetic rotor. The image forming apparatus according to any one of . An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. a computer of an image forming apparatus comprising
Functioning as a control unit for controlling the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
A development bias in which an AC voltage is superimposed on a DC voltage is applied to the developing unit,
When the amount of carrier on the surface of the non-magnetic rotary member falls below a predetermined amount, the control unit controls the carrier to move from the developing unit to the surface of the image carrier more easily than during image formation. and executing a carrier supply mode for driving the image carrier, the developing section, and the recovery section, and in the carrier supplying mode, controlling the frequency of the AC component of the developing bias to be lower than that during image formation. A program characterized by An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. a computer of an image forming apparatus comprising
Functioning as a control unit for controlling the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
When the area of the non-printing area during image formation exceeds a predetermined value, or when the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, A program characterized by executing a carrier supply mode for driving the image carrier, the developing section, and the collecting section under conditions in which the carrier easily moves from the developing section to the surface of the image carrier. An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. a computer of an image forming apparatus comprising
Functioning as a control unit for controlling the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
When the amount of rotation of the non-magnetic rotating body exceeds a predetermined amount, or when the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, the control unit controls the amount of rotation of the non-magnetic rotating body to be lower than that during image formation. A program for executing a carrier supply mode in which the image carrier, the developing section, and the recovery section are driven under conditions in which the carrier easily moves from the developing section to the surface of the image carrier. An image carrier that carries a toner image to be transferred onto a sheet of paper; 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 carried by the image carrier is transferred. and a collection unit arranged downstream of the developing unit and upstream of the transfer unit in the rotational direction of the image carrier for collecting the carrier on the surface of the image carrier. a computer of an image forming apparatus comprising
Functioning as a control unit for controlling the amount of carrier carried by the recovery unit,
The collection unit includes a non-magnetic rotating body that faces the image carrier, supports a carrier, and rotates around an axis parallel to the axis of the image carrier, and is fixedly arranged inside the non-magnetic rotating body. a magnet, and
The magnet is disposed at least at a position substantially opposed to the image carrier, and includes a recovery pole for recovering the carrier on the surface of the image carrier to the surface of the non-magnetic rotating body, and a separation pole disposed on the downstream side in the rotation direction of the non-magnetic rotor for separating the recovered carrier from the surface of the non-magnetic rotor;
The image forming apparatus includes a motor for rotating the non-magnetic rotating body,
When the amount of carrier on the surface of the non-magnetic rotating body falls below a predetermined amount, which is when the driving current of the motor falls below a predetermined value, the control unit controls the developing unit to operate more rapidly than during image formation. A program for executing a carrier supply mode for driving the image carrier, the developing section, and the recovery section under conditions in which the carrier easily moves from the surface of the image carrier to the surface of the image carrier.

Images