JP2014191071A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of efficiently preventing the damage of a cleaning blade caused by an excessive frictional force.SOLUTION: The image forming apparatus comprises: an image carrier; an image forming part forming a toner image on the image carrier; a transfer part transferring the toner image to a paper from the image carrier; a cleaning blade coming into contact with the image carrier, to remove transfer residual toner remaining on the image carrier after transfer; a toner storage part temporarily storing the toner removed by the cleaning blade and supplying it to a contact part between the cleaning blade and the image carrier; and a control part allowing the image forming part to form a toner image for toner supply determined according to a toner storage amount for each main scan position in the toner storage part and allowing this toner image to reach the cleaning blade in such a state that this toner image is un-transferred, to supply the toner to the toner storage part.

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus including a belt cleaning unit that cleans an intermediate transfer belt.

  In general, in an image forming apparatus (printer, copying machine, facsimile, etc.) using an electrophotographic process technology, a charged photosensitive drum is irradiated (exposed) with a laser beam based on image data. An electrostatic latent image is formed on the surface. Then, toner is supplied from the developing device to the photosensitive drum on which the electrostatic latent image is formed, so that the electrostatic latent image is visualized and a toner image is formed. The toner image is transferred directly or indirectly to the sheet via an intermediate transfer belt, and then heated and pressed by a fixing unit, whereby an image is formed on the sheet.

  In such an image forming apparatus, the toner remaining on the intermediate transfer belt after the toner image is transferred onto the sheet (hereinafter referred to as “transfer residual toner”) is removed by the belt cleaning unit. As a belt cleaning unit, one having a cleaning blade that scrapes off transfer residual toner by sliding on an intermediate transfer belt is known (for example, Patent Documents 1 and 2). This blade-type belt cleaning unit has a great effect of removing toner, can be mechanically compact, and is suitable for downsizing the apparatus.

  FIG. 1 is a diagram illustrating an example of a blade-type belt cleaning unit. As shown in FIG. 1, in the belt cleaning unit 80, the edge of the cleaning blade 81 is pressed against the intermediate transfer belt 421 with a predetermined force in order to reliably scrape off the transfer residual toner on the intermediate transfer belt 421. Therefore, a large frictional force is generated between the intermediate transfer belt 421 and the cleaning blade 81 at the press contact portion P1. This frictional force can cause the cleaning blade 81 to sag, damage the edge, or cause toner filming.

  On the other hand, toner is known to function as a lubricant that reduces friction. In the conventional belt cleaning unit 80, the toner removed from the intermediate transfer belt 421 is temporarily stored in the toner storage unit 86 formed by, for example, the storage roller 82, the intermediate transfer belt 421, and the damming member 83. The portion P1 is positively supplied. Thereby, since the frictional force generated in the press contact part P1 is reduced, it is possible to prevent the above-described problems from occurring.

An example of the toner storage state in the toner storage unit 86 is shown in FIG. FIG. 2A is a view of the toner reservoir 86 as seen from the front side of the image forming apparatus. FIG. 2B is a view of the toner storage unit 86 as viewed from the direction of the arrow X in FIG. 2A, that is, a diagram showing the distribution of the toner storage amount in the main scanning direction.
If an appropriate amount of untransferred toner is generated on the intermediate transfer belt 421 during image formation and the printing rate at the main scanning position (position in the width direction of the paper) is uniform, as shown in FIG. In addition, a substantially uniform amount of toner is stored along the main scanning direction. Accordingly, the toner is supplied uniformly over the main scanning direction, that is, over the entire width of the pressure contact portion P1.

  Here, the “printing rate at the main scanning position” means the ratio of the printing length at a specific main scanning position to the sheet length. For a line drawing formed over the entire length of the sheet, the printing rate at the main scanning position where the line drawing is formed is 100%. In addition, when “printing rate” is simply described, it means the ratio of the printing area to the sheet area.

As described above, since a predetermined amount of toner is stored in the toner storage unit 86, normally, even if the printing rate increases or decreases for each sheet, an appropriate amount of toner can be supplied to the press contact portion P1.
However, when images with a low printing rate are continuously printed, the amount of toner stored in the toner storage unit 86 decreases. When an appropriate amount of toner is not supplied to the press contact part P1, the frictional force increases, and the above-described problems such as damage to the cleaning blade 81 occur.
In the conventional image forming apparatus, when images with a low printing rate are continuously printed, a predetermined toner image (for example, a solid image) is formed on the intermediate transfer belt 421, and the toner image is not transferred and the cleaning blade A predetermined amount of toner is held in the toner reservoir 86 by reaching 81 and removing.

JP 2005-249915 A JP 2012-133267 A

However, when images with the printing ratios at the main scanning positions shifted are continuously printed, the amount of toner stored in the toner storage unit 86 is also biased in the main scanning direction, as shown in FIG.
In this case, for example, if the average printing rate when a predetermined number of images are formed is equal to or greater than a predetermined value, the toner is not supplied to the toner reservoir 86. Therefore, the toner storage amount is insufficient depending on the main scanning position. Then, partial wear of the cleaning blade 81 is promoted, and damage such as curling occurs.
On the other hand, if the average printing rate when a predetermined number of images are formed is less than a predetermined value, the toner is supplied to the toner reservoir 86. However, the toner is also supplied to the main scanning position where the toner is sufficiently stored. As a result, the amount of toner that is discarded increases, and the running cost increases.

  An object of the present invention is to provide an image forming apparatus capable of efficiently preventing damage to a cleaning blade due to excessive frictional force.

An image forming apparatus according to the present invention includes an image carrier,
An image forming unit for forming a toner image on the image carrier;
A transfer unit for transferring a toner image from the image carrier to a sheet;
A cleaning blade that contacts the image carrier and removes transfer residual toner remaining on the image carrier after transfer;
A toner reservoir that temporarily stores toner removed by the cleaning blade and supplies the toner to a contact portion between the cleaning blade and the image carrier;
A toner image for toner supply determined according to a toner storage amount at each main scanning position in the toner storage unit is formed on the image carrier by the image forming unit, and the toner image is not transferred and is cleaned. And a control unit that supplies the toner to the toner storage unit by reaching the blade.

  According to the image forming apparatus of the present invention, since the toner can be supplied to the pressure contact portion between the cleaning blade and the image carrier without excess or deficiency, it is possible to suppress an increase in frictional force and to discard the waste toner. Can be reduced. Therefore, it is possible to efficiently prevent the cleaning blade from being damaged by an excessive frictional force.

It is a figure which shows an example of a blade-type belt cleaning part. FIG. 6 is a diagram illustrating an example of a toner storage state in a toner storage unit. FIG. 6 is a diagram illustrating another example of a toner storage state in a toner storage unit. 1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment. FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus according to the embodiment. 6 is a flowchart illustrating an example of toner supply processing. FIG. 6 is a diagram illustrating a transition of a toner storage amount in a toner storage unit. It is a figure which shows another example of a blade-type belt cleaning part.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 4 is a diagram showing an overall configuration of the image forming apparatus 1 according to the embodiment of the present invention. FIG. 5 is a diagram illustrating a main part of a control system of the image forming apparatus 1 according to the embodiment.
The image forming apparatus 1 shown in FIGS. 4 and 5 is an intermediate transfer type color image forming apparatus using electrophotographic process technology. In the image forming apparatus 1, photosensitive drums 413 corresponding to four colors of CMYK are arranged in series in the running direction (vertical direction) of the intermediate transfer belt 421, and each color toner image is sequentially transferred to the intermediate transfer belt 421 in one procedure. The vertical tandem system is adopted.
That is, the image forming apparatus 1 transfers Y (yellow), M (magenta), C (cyan), and K (black) toner images formed on the photosensitive drum 413 to the intermediate transfer belt 421 (primary transfer). Then, after superimposing the four color toner images on the intermediate transfer belt 421, the toner images are transferred to the paper S (secondary transfer) to form an image.

  As illustrated in FIGS. 4 and 5, 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 paper transport unit 50, a fixing unit 60, and a control unit 100. .

  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 a program corresponding to the processing content from the ROM 102 and develops it in the RAM 103, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the developed program. At this time, various data stored in the storage unit 72 is referred to. The storage unit 72 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

  The control unit 100 also exchanges various data with an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. Send and receive. For example, the control unit 100 receives image data transmitted from an external device, and forms an image on the paper S based on the image data (input image data). The communication unit 71 is composed of a communication control card such as a LAN card, for example.

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 a transport mechanism and sends it out 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 a document tray all at once.
The document image scanning device 12 optically scans a document conveyed on the contact glass from the automatic document feeder 11 or a document placed on the contact glass, and reflects light from the document to a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and an original image is read. The image reading unit 10 generates input image data based on the reading result by the document 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 configured by, 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, an image status display, an operation status of each function, and the like in accordance with 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 an operation signal to the control unit 100.

  The image processing unit 30 includes a circuit that performs digital image processing on input image data according to initial settings or user settings. For example, the image processing unit 30 performs tone correction based on tone correction data (tone correction table) under the control of the control unit 100 (image density control). Further, the image processing unit 30 performs various correction processes such as color correction and shading correction, a compression process, 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 subjected to these processes.

  The image forming unit 40 includes an image forming unit 41 and an intermediate transfer unit 42 for forming an image using colored toners of Y component, M component, C component, and K component based on input image data. The writing range of the image formed by the image forming unit 40 is set in advance.

  The image forming unit 41 includes four image forming units 41Y, 41M, 41C, and 41K for Y component, M component, C component, and K component. Since the image forming units 41Y, 41M, 41C, and 41K have the same configuration, for convenience of illustration and description, common constituent elements are denoted by the same reference numerals, and when distinguished from each other, the reference numerals Y, M, and C are used. Or K. In FIG. 4, reference numerals are given only to the components of the image forming unit 41Y for the Y component, and reference numerals of the constituent elements 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, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, and the like.

The photosensitive drum 413 includes, for example, an undercoat layer (UCL), a charge generation layer (CGL), and a charge transport layer (CTL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube). : A negatively charged organic photoconductor (OPC) in which Charge Transport Layers are sequentially stacked.
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 generates a pair of positive charges and negative charges upon exposure by the exposure device 411. The charge transport layer consists of a hole transport material (electron donating nitrogen-containing compound) dispersed in a resin binder (for example, polycarbonate resin), and transports positive charges generated in the charge generation layer to the surface of the charge transport layer. To do.

The charging device 414 uniformly charges the surface of the photoconductive drum 413 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 the image of each color component. The positive charge generated in the charge generation layer of the photosensitive drum 413 is transported to the surface of the charge transport layer, so that the surface charge (negative charge) of the photosensitive drum 413 is neutralized. An electrostatic latent image of each color component is formed on the surface of the photosensitive drum 413 due to a potential difference from the surroundings.

The developing device 412 contains a developer of each color component (for example, a two-component developer composed of a toner having a small particle diameter and a magnetic material), and the toner of each color component is attached to the surface of the photosensitive drum 413. The electrostatic latent image is visualized to form a toner image.
The drum cleaning device 415 includes a drum cleaning blade that is in sliding contact with the surface of the photosensitive drum 413, and removes transfer residual toner remaining on the surface of the photosensitive drum 413 after primary transfer.

  The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning unit 80, 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 configured by a driving roller, and the other is configured by a driven roller. For example, it is preferable that the roller 423A disposed downstream of the K component primary transfer roller 422 in the belt traveling direction is a drive roller. This makes it easy to keep the belt running speed constant in the primary transfer portion. As the driving roller 423A rotates, the intermediate transfer belt 421 travels in the direction of arrow A at a constant speed.

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

  The secondary transfer roller 424 is disposed on the outer peripheral surface side of the intermediate transfer belt 421 so as to face a roller 423B (hereinafter referred to as “backup roller 423B”) disposed 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 paper S.

When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photosensitive drum 413 are primarily transferred to the intermediate transfer belt 421 in order. Specifically, the toner image is electrostatically transferred to the intermediate transfer belt 421 by applying a voltage (transfer bias) having a polarity opposite to that of the toner to the primary transfer roller 422.
Thereafter, 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, the toner image is electrostatically transferred onto the paper S by applying a voltage (transfer bias) having a polarity opposite to that of the toner to the secondary transfer roller 424. The sheet S to which the toner image is transferred is conveyed toward the fixing unit 60.

  Instead of the secondary transfer roller 424, a configuration (so-called belt-type secondary transfer unit) in which a secondary transfer belt is looped around a plurality of support rollers including the secondary transfer roller is adopted. Also good.

  The belt cleaning unit 80 includes a cleaning blade 81 (see FIG. 5) 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 secondary transfer. Details of the belt cleaning unit 80 will be described later.

  The fixing unit 60 includes a fixing surface side member 61 disposed on the fixing surface (surface on which the toner image is formed) side of the paper, and a back surface side supporting member disposed on the back surface (surface opposite to the fixing surface) side of the paper. 62, a heating source 63, and the like. In the case of roller type fixing, the fixing roller is the fixing surface side member 61 (see FIG. 4), and in the case of belt type fixing, the fixing belt is the fixing surface side member 61. Further, in the case of belt type pressurization, the pressure belt becomes the back side support member 62 (see FIG. 4), and in the case of roller type pressurization, the pressure roller becomes the back side support member 62. When the back surface side support member 62 is pressed against the fixing surface side member 61, a fixing nip for nipping and transporting the paper S is formed.

  The fixing unit 60 fixes the toner image on the paper S by heating and pressurizing the paper S on which the toner image is secondarily transferred and conveyed at the fixing nip. The fixing unit 60 is disposed in the fixing device F as a unit. An air separation unit that separates the sheet S from the fixing surface side member 61 or the back surface side support member 62 by blowing air may be arranged in the fixing device F.

The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a first transport unit 53, a second transport unit 54, and the like.
In the three paper feed tray units 511 to 513 constituting the paper feed unit 51, paper S (standard paper, special paper) identified based on basis weight, size, or the like is stored for each preset type. .

  The first transport unit 53 includes a plurality of transport roller units including an intermediate transport roller unit 531, a loop roller unit 532, and a registration roller unit 533. The first transport unit 53 transports the paper S fed from the paper feed unit 51 or an external paper feed device (not shown) to the image forming unit 40 (secondary transfer unit).

  The 2nd conveyance part 54 is provided with the switchback path | route 541 and the conveyance path 542 for back surfaces by which the some conveyance roller part is arrange | positioned. The second transport unit 54 once transports the paper S to the switchback path 541, then switches back and transports the paper S to the back surface transport path 542, thereby reversing the paper S, and the first transport unit 53 (loop roller) To the upstream of the section 532.

  The paper S fed from the paper feeding unit 51 or an external paper feeding device (not shown) is conveyed to the image forming unit 40 by the first conveying unit 53. Then, when the sheet S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to one surface (front surface) of the sheet S at a time, and a fixing process is performed in the fixing unit 60. The The paper S on which the image is formed is discharged out of the apparatus by a paper discharge unit 52 having a paper discharge roller 52a.

  The configuration of the belt cleaning unit 80 according to the embodiment is the same as the conventional one. That is, as shown in FIG. 1, the belt cleaning unit 80 includes a cleaning blade 81, a storage roller 82, a damming member 83, a recovery screw 84, a casing 85, and the like.

  Each member constituting the belt cleaning unit 80 is attached to the casing 85. A bottom portion of the casing 85 serves as a waste toner storage portion 89 that stores and discards the toner removed from the intermediate transfer belt 421. A recovery screw 84 is disposed in the waste toner storage unit 89. The collection screw 84 conveys the toner stored in the waste toner storage unit 89 to the back side, for example, with respect to the paper surface, and discharges the toner outside the casing 85.

  The cleaning blade 81 is made of an elastic body such as urethane rubber. The cleaning blade 81 is disposed in a state where the edge on one end side is in pressure contact with the intermediate transfer belt 421 with a predetermined force. The other end side of the cleaning blade 81 is fixed to a blade support member 87 attached to the casing 85 with an adhesive or the like. When the cleaning blade 81 is in sliding contact with the intermediate transfer belt 421, the transfer residual toner remaining on the intermediate transfer belt 421 is scraped off.

The storage roller 82 is disposed rotatably with respect to the belt traveling direction A in a state where it is in pressure contact with the intermediate transfer belt 421 on the upstream side of the pressure contact portion P1 between the cleaning blade 81 and the intermediate transfer belt 421. For the storage roller 82, for example, a sponge roller, a rubber roller, or a resin roller can be applied.
The storage roller 82 may be configured to be connected to a drive motor so as to be able to rotate independently of the intermediate transfer belt 421, or to be rotated along with the travel of the intermediate transfer belt 421. .

  The dam member 83 is a sheet-like member made of, for example, polyethylene terephthalate (PET). One end side of the damming member 83 hangs down and contacts the surface of the storage roller 82. The storage roller 82 is pinched by the intermediate transfer belt 421 and the blocking member 83. The other end side of the damming member 83 is fixed to a sheet holding member 88 attached to the casing by a double-sided tape or the like.

  The storage roller 82 is pinched by the intermediate transfer belt 421 and the blocking member 83. That is, the intermediate transfer belt 421, the storage roller 82, and the damming member 83 form a toner storage portion 86 that stores the toner scraped off by the cleaning blade 81.

  Immediately after shipment from the factory or after the cleaning unit 80 is replaced by a maintenance operation, a solid image having a predetermined length with a maximum printing width is formed on the intermediate transfer belt 421, and reaches the cleaning blade 81 without being transferred, and is removed. As a result, an appropriate amount of toner is stored in the toner storage unit 86.

  The transfer residual toner remaining on the intermediate transfer belt 421 after the secondary transfer is scraped off by the cleaning blade 81, falls as it is, and is stored in the toner storage unit 86. The toner stored in the toner storage unit 86 is supplied to the press contact portion P1 as the intermediate transfer belt 421 travels. Further, the toner stored in the toner storage unit 86 passes through the gap with the weir member 83 little by little as the storage roller 82 rotates, and falls into the waste toner storage unit 89.

  In addition, the toner storage unit 86 is configured to forcibly discharge when the amount of stored toner increases. For example, a configuration in which toner leaks from an opening (not shown) formed in the vicinity of the other end side (sheet holding member 88 side) of the damming member 83 when the toner volume increases can be applied to the toner storage portion 86. . Further, for example, in the toner storage unit 86, when the stored toner exceeds a certain amount, the contact state between the weir member 83 and the storage roller 82 is released by the pressure, and a pressure adjusting valve such that the toner falls. Configuration can be applied.

  In the belt cleaning unit 80, the toner stored in the toner storage unit 86 is supplied to the press contact portion P1 between the cleaning blade 81 and the intermediate transfer belt 421, so that an excessive frictional force is not generated in the press contact portion P1. Therefore, it is possible to prevent the cleaning blade 81 from being damaged by an excessive frictional force.

  Here, if an appropriate amount of untransferred toner is generated in image formation and a constant amount of toner is always stored in the toner storage portion 86, an appropriate amount of toner is supplied to the press contact portion P1 without any problem. However, if image formation with a low printing rate is continuously performed, the amount of toner remaining after transfer decreases, and the amount of toner stored in the toner storage section 86 decreases. Therefore, in the present embodiment, the control unit 100 monitors the toner storage amount of the toner storage unit 86 and supplies the toner without excess or deficiency as necessary.

  As described above, the image forming apparatus 1 transfers the toner image from the intermediate transfer belt 421 (image carrier), the image forming unit 40 that forms a toner image on the intermediate transfer belt 421, and the sheet S from the intermediate transfer belt 421. A cleaning blade 81 that contacts the secondary transfer portion (transfer portion) and the intermediate transfer belt 421 and removes transfer residual toner remaining on the intermediate transfer belt 421 after the transfer, and the toner removed by the cleaning blade 81 temporarily The toner storage unit 86 stores and supplies the pressure contact portion P1 between the cleaning blade 81 and the intermediate transfer belt 421, and the control unit 100 that adjusts the toner storage amount in the toner storage unit 86.

  FIG. 6 is a flowchart illustrating an example of the toner supply process according to the embodiment. The toner supply process illustrated in FIG. 6 is realized by, for example, the CPU 101 executing a predetermined program stored in the ROM 102 when image formation is started.

  In step S101, the control unit 100 determines whether or not a predetermined number (for example, every 1000 sheets) of image forming processing has been performed. If the control unit 100 determines that the predetermined number of image forming processes have been performed, the control unit 100 proceeds to step S102. If the control unit 100 determines that the predetermined number of image forming processes have not been performed, the control unit 100 proceeds to step S101.

In step S102, the control unit 100 acquires the current toner storage amount for each main scanning position. The toner storage amount at each main scanning position is a toner storage amount in each region obtained by dividing the main scanning direction into a predetermined number (for example, 30 equal parts) (see FIG. 7).
For example, the difference between the residual toner amount (integrated value) at each main scanning position and the discharged toner amount (integrated value) discharged from the toner storage unit 86 is set as the current toner storage amount for each main scanning position. be able to. The transfer residual toner amount can be obtained from the printing rate and the printing length at the main scanning position.

In step S103, the control unit 100 determines whether toner supply is necessary based on the toner storage amount for each main scanning position acquired in step S102. The control unit 100 proceeds to step S104 when it is determined that toner supply is necessary, and proceeds to step S101 when it is determined that toner supply is unnecessary.
Regarding the necessity of toner supply, for example, whether or not the toner storage amount at at least one main scanning position is below a predetermined value, whether or not the toner storage amount at a predetermined ratio of the main scanning position is below a predetermined value, Alternatively, the determination is made based on whether or not the total toner storage amount is below a predetermined value. It should be noted that other determination criteria may be used to determine the necessity of toner supply.

  In step S104, the control unit 100 determines a toner supply amount for each main scanning position. Specifically, the difference between the target value at the main scanning position and the current toner storage amount is the toner supply amount for each main scanning position. The target value is an optimal amount of toner stored in the toner storage unit 86 that is not excessive or insufficient, and is a value set in advance for each main scanning position.

Here, the target value may be different for each main scanning position. Normally, both ends in the main scanning direction of the toner reservoir 86 are open, and the stored toner can fall. For this reason, even if toner is supplied to both ends in the main scanning direction so as to have a toner storage amount equivalent to that in the central portion, a part of the toner falls and is discarded as it is.
In view of this, it is preferable to set the target values at both ends in the main scanning direction to be smaller than the target values at the central portion in anticipation of toner falling from both ends in the main scanning direction. This can prevent wasteful consumption of toner.

  Furthermore, since the toner is granulated at a high temperature and its fluidity is lowered, the tendency of toner storage at both ends in the main scanning direction depends on the temperature. Therefore, the temperature of the toner storage unit 86 is detected by a temperature sensor arranged in the vicinity of the toner storage unit 86, and the expected amount of toner falling from both ends in the main scanning direction is changed according to the detection result to change the target value. Settings may be made. It should be noted that it is possible to set a target value suitable for each temperature environment by arranging temperature sensors in the vicinity of both ends of the main scanning direction.

  Further, for example, the target value may be set for each main scanning position in consideration of the toner storage tendency due to image formation after toner supply. The toner storage tendency can be grasped to some extent by predicting the amount of residual toner to be generated in the future based on, for example, image data on which image formation is performed (printing rate at the main scanning position). In this case, the target value is set to be lower for the main scanning position where the toner is easily stored, and the target value is set to be higher for the main scanning position where the toner is not easily stored.

  In step S105, the control unit 100 supplies the toner to the toner storage unit 86 by forming a toner image reflecting the determined toner supply amount on the intermediate transfer belt 421 and reaching the cleaning blade 81 without being transferred. Let At this time, the toner supply amount may be adjusted by the image density of the toner image, or may be adjusted by the print length of the toner image. The toner supply operation is performed between sheets on which normal image formation is not performed.

  In step S106, the control unit 100 determines whether a series of image forming processes has been completed. A series of image forming processes is a process of forming an image for the number of sheets set by a signal (for example, a print job) instructing image formation. Then, the control unit 100 ends the toner supply process when it is determined that a series of image forming processes has been completed, and performs the processing after step S101 when it is determined that the series of image forming processes has not been completed. repeat.

  In the flowchart shown in FIG. 6, it is determined whether or not toner supply is necessary every time a predetermined number of images are formed. However, the amount of toner stored in the toner storage unit 86 is constantly monitored, and the amount of toner stored for each main scanning position is determined. The toner may be supplied when the toner storage amount falls below a predetermined value.

In the following, a specific description will be given of a case where images having a low printing rate are continuously formed at the central portion in the main scanning direction (hereinafter “center portion”) and the right end portion in the main scanning direction (hereinafter “right end portion”).
As shown in FIG. 7A, when a predetermined number of images are formed, the amount of toner stored in the central portion and the right end portion decreases. In this case, as shown in FIG. 7B, a large toner supply amount is set for the central and right end main scanning positions, and a small toner supply amount is set for the other main scanning positions. . In FIG. 7, the target values at both ends in the main scanning direction are set lower than the target value at the center.

Then, a toner image reflecting the toner supply amount for each main scanning position is formed on the intermediate transfer belt 421. As a result, as shown in FIG. 7C, the toner storage amount in the toner storage unit 86 is in an optimal state that substantially matches the target value.
Since the toner is appropriately supplied to the main scanning position where the toner storage amount is small, it is possible to prevent the frictional force at the press contact portion P1 from being partially excessive due to the lack of toner. Further, since the toner is supplied to the main scanning position where the toner storage amount is large so that the toner is excessive and is not discarded, it is possible to prevent the toner from being wasted.

As described above, the control unit 100 causes the image forming unit 40 to transfer the toner image for toner supply determined according to the toner storage amount (see FIG. 7A) for each main scanning position in the toner storage unit 86 to the intermediate transfer belt 421. The toner is supplied to the toner reservoir 86 by being formed on the (image carrier) and reaching the cleaning blade 81 without transferring this toner image.
“According to the toner storage amount” means that the larger the toner storage amount at the main scanning position, the smaller the toner supply amount, and the smaller the toner storage amount at the main scanning position, the larger the toner supply amount. .

  According to the image forming apparatus 1, since the toner is supplied to the pressure contact portion P1 between the cleaning blade 81 and the intermediate transfer belt 421 without excess or deficiency, it is possible to suppress an increase in frictional force and reduce waste toner. can do. Therefore, it is possible to efficiently prevent the cleaning blade 81 from being damaged by an excessive frictional force. Furthermore, a highly reliable image forming apparatus capable of maintaining stable image quality is provided.

[Modification]
FIG. 8 is a diagram illustrating another example of a blade-type belt cleaning unit. Constituent elements similar to those of the embodiment are denoted by the same reference numerals.
A belt cleaning unit 80A shown in FIG. 8 differs from the belt cleaning unit 80 shown in FIG. 1 in that the cleaning blade 81 is in contact with the intermediate transfer belt 421 from below. The toner scraped off by the cleaning blade 81 is deposited on the end of the cleaning blade 81 as it is, and is constantly supplied to the press contact part P1. That is, in the belt cleaning unit 80 </ b> A, the toner storage unit 86 that stores the toner removed by the cleaning blade 81 is defined by the intermediate transfer belt 421 and the cleaning blade 81.

  Also in the belt cleaning unit 80A having such a configuration, it is possible to efficiently prevent damage to the cleaning blade 81 due to excessive frictional force by supplying toner without excess or deficiency as in the embodiment.

As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and can be changed without departing from the gist thereof.
For example, the present invention can also be applied to a case where a cleaning unit of a photoconductor (photosensitive drum or photosensitive belt) as an image carrier has a toner storage unit.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image reading part 20 Operation display part 30 Image processing part 40 Image forming part 50 Paper conveyance part 60 Fixing part 80, 80A Belt cleaning part 81 Cleaning blade 82 Storage roller 83 Damping member 84 Recovery screw 85 Casing 86 Toner Storage unit 89 Waste toner storage unit 100 Control unit 421 Intermediate transfer belt (image carrier)

Claims (8)

An image carrier;
An image forming unit for forming a toner image on the image carrier;
A transfer unit for transferring a toner image from the image carrier to a sheet;
A cleaning blade that contacts the image carrier and removes transfer residual toner remaining on the image carrier after transfer;
A toner reservoir that temporarily stores toner removed by the cleaning blade and supplies the toner to a contact portion between the cleaning blade and the image carrier;
A toner image for toner supply determined according to a toner storage amount at each main scanning position in the toner storage unit is formed on the image carrier by the image forming unit, and the toner image is not transferred and is cleaned. An image forming apparatus comprising: a control unit that supplies toner to the toner storage unit by reaching the blade.   The control unit compares a current toner storage amount for each main scanning position with a preset target value, and determines the toner image for toner supply based on the difference. The image forming apparatus according to 1.   The image forming apparatus according to claim 2, wherein the target value is different for each main scanning position.   The image forming apparatus according to claim 3, wherein the target value at both ends in the main scanning direction is smaller than the target value at a central portion in the main scanning direction.   5. The image forming apparatus according to claim 2, wherein the control unit changes the target value in accordance with a temperature in the vicinity of the toner storage unit.   The image forming apparatus according to claim 1, wherein the control unit controls the amount of toner to be supplied based on a printing rate or a printing length of a toner image at a main scanning position. A storage roller in contact with the image carrier;
A weir member that abuts the storage roller and holds the storage roller together with the image carrier, and
The cleaning blade comes into contact with the image carrier from above, and the removed toner falls and is stored in the toner reservoir defined by the image carrier, the storage roller, and the weir member. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   2. The cleaning blade comes into contact with the image carrier from below, and the removed toner is stored in the toner storage portion defined by the image carrier and the cleaning blade. 7. The image forming apparatus according to any one of items 1 to 6.

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