JP2018189873A - Image formation device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device and program that can surely remove foreign matters on a charging member with deterioration of the charging member suppressed.SOLUTION: An image formation device comprises: an image carrier; an image carrier cleaning part that removes foreign matters on the image carrier; a charging member that abuts with a surface of the image carrier to rotate, and charges the surface of the image carrier by a prescribed voltage being applied; a charging member cleaning part that removes foreign matters on the charging member; removal capability change means that changes a size of a foreign matter removal capability by the charging member; a lubricant agent supply part that supplies a lubricant agent to the surface of the image carrier; lubricant agent information acquisition means that acquires lubricant agent information pertaining to an amount of lubricant agent in the surface of the image carrier; and control means that controls an action of the removal capability change means so that a relationship of the size of the capability change means gradually increasing in accordance with reduction in the lubricant agent based on the lubricant agent information acquired by the lubricant agent information acquisition means is satisfied.SELECTED DRAWING: Figure 8

Description

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

  Conventionally, the surface of a charged image carrier is exposed to form an electrostatic latent image, and a toner image obtained by developing the electrostatic latent image is transferred to a transfer member such as paper to form an image. There is an image forming apparatus. As a method for charging the surface of an image carrier in an image forming apparatus, a contact charging method in which a voltage is applied to a charging roller (charging member) that rotates in contact with the image carrier is widely used.

  In such a contact charging method, after a toner image is transferred from the image carrier to the transfer member, if foreign matter such as an external additive of toner remains on the surface of the image carrier, the foreign matter adheres to the charging member. There is. In the area where the foreign matter is adhered to the charging member, the discharge with the image carrier is hindered by the foreign matter, resulting in a charging failure in which the charge amount on the image carrier is insufficient. Since a toner image having an appropriate density is not formed in an area where charging failure occurs in the image carrier, charging failure leads to image quality failure such as density unevenness in a recorded image.

  On the other hand, conventionally, there is a technique for suppressing the occurrence of charging failure by providing a charging member cleaning unit that contacts the surface of the charging member and removes foreign matter from the charging member. For example, Patent Document 1 discloses a technique for removing foreign matter attached to a charging member by rotating a brush roller as a charging member cleaning unit while abutting against the surface of the charging member. The ability to remove foreign matter by the charging member cleaning unit is increased by increasing the pressure with which the charging member cleaning unit is brought into contact with the charging member, or by increasing the relative movement speed between the charging member cleaning unit and the charging member. Can be made.

Japanese Patent Laid-Open No. 2006-157048

  However, if the ability to remove foreign matter by the charging member cleaning unit is increased, the surface of the charging member is rapidly worn by the friction between the charging member cleaning unit and the charging member, so that the charging member deteriorates early. On the other hand, if the foreign matter removal capability of the charging member cleaning unit is reduced in order to suppress deterioration, the foreign matter cannot be reliably removed. As described above, the conventional technique has a problem that it is not easy to reliably remove the foreign matter on the charging member while suppressing deterioration of the charging member.

  An object of the present invention is to provide an image forming apparatus and a program that can more reliably remove foreign matter on a charging member while suppressing deterioration of the charging member.

In order to achieve the above object, the invention of the image forming apparatus according to claim 1 comprises:
An image forming apparatus for transferring a toner image obtained by developing an electrostatic latent image on the surface of an image carrier to a member to be transferred and forming an image on the member to be transferred,
The image carrier rotating about a predetermined rotation axis;
An image carrier cleaning unit that contacts the surface of the image carrier and removes foreign matter on the image carrier;
A charging member that contacts the surface of the image carrier and rotates as the image carrier rotates, and charging the surface of the image carrier by applying a predetermined voltage;
A charging member cleaning unit that contacts the surface of the charging member to remove foreign matter on the charging member;
A removal capability changing means for changing the size of the foreign matter removal capability by the charging member cleaning section;
A lubricant supply unit for supplying a lubricant to the surface of the image carrier;
Lubricant information acquisition means for acquiring lubricant information related to the amount of lubricant on the surface of the image carrier;
The operation of the removal capacity changing unit is performed so that a relationship in which the magnitude of the removal capacity gradually increases according to a decrease in the amount of the lubricant based on the lubricant information acquired by the lubricant information acquisition unit is satisfied. Control means for controlling;
It is characterized by having.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
The lubricant supply unit performs a supply operation of scraping the lubricant from a solid lubricant and supplying it to the surface of the image carrier,
In the supply operation, the amount of the lubricant scraped from the solid lubricant per predetermined time decreases as the total time for which the lubricant is supplied using the solid lubricant increases. Supply lubricant,
The lubricant information is information relating to the length of the total time,
The control means determines that the amount of the lubricant is smaller as the total time based on the lubricant information is longer.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect,
The lubricant information is information relating to the number of times images are formed on the transfer member during a period in which the lubricant using the solid lubricant is supplied by the lubricant supply unit.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect,
The lubricant information is information relating to a torque for rotating the image carrier against a frictional force between the surface of the image carrier and the image carrier cleaning unit,
The control means determines that the smaller the torque based on the lubricant information is, the smaller the amount of the lubricant is.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect,
An exposure unit provided on the downstream side of the charging member with respect to the moving direction of the surface of the rotating image carrier, and exposing the charged surface of the image carrier to form an electrostatic latent image;
A developing unit that is provided on the downstream side of the exposure unit in the moving direction and that develops the electrostatic latent image by supplying toner to the surface of the image carrier to form a toner image on the surface of the image carrier. When,
A transfer unit provided on the downstream side of the developing unit with respect to the moving direction and transferring the toner image to a transfer member;
At least a part of the charging member, the lubricant supply unit, and the transfer unit is moved between a first position where the charging member, the lubricant supply unit, and the transfer unit are in contact with the surface of the image carrier and a second position separated from the surface of the image carrier. Moving means to cause
A torque measuring unit for measuring the torque;
With
The lubricant information acquisition unit acquires the lubricant information by measuring the torque by the torque measurement unit, and when the torque measurement unit measures the torque, the moving unit causes the charging member, The lubricant supply unit and the at least part of the transfer unit are moved to the second position.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect,
The moving means moves the transfer unit between the first position and the second position,
The lubricant information acquisition unit is characterized in that, when the torque is measured by the torque measurement unit, the transfer unit moves at least the transfer unit to the second position.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects,
An exposure unit provided on the downstream side of the charging member with respect to the moving direction of the surface of the rotating image carrier, and exposing the charged surface of the image carrier to form an electrostatic latent image;
A developing unit that is provided on the downstream side of the exposure unit in the moving direction and that develops the electrostatic latent image by supplying toner to the surface of the image carrier to form a toner image on the surface of the image carrier. When,
A transfer unit provided on the downstream side of the developing unit with respect to the moving direction and transferring the toner image to a transfer member;
With
The image carrier cleaning unit is provided between the transfer unit and the charging member in the moving direction,
The lubricant supply unit is provided between the transfer unit and the image carrier cleaning unit in the moving direction.

The invention according to claim 8 is the image forming apparatus according to claim 1,
An exposure unit provided on the downstream side of the charging member with respect to the moving direction of the surface of the rotating image carrier, and exposing the charged surface of the image carrier to form an electrostatic latent image;
A developing unit that is provided on the downstream side of the exposure unit in the moving direction and that develops the electrostatic latent image by supplying toner to the surface of the image carrier to form a toner image on the surface of the image carrier. When,
A transfer unit provided on the downstream side of the developing unit with respect to the moving direction and transferring the toner image to a transfer member;
With
The developing unit is the lubricant supply unit that supplies the lubricant stored in the developing unit to the surface of the image carrier,
The lubricant information is information relating to a storage amount of the lubricant in the developing unit,
The control means determines that the greater the amount of lubricant stored based on the lubricant information, the greater the amount of lubricant on the surface of the image carrier.

The invention according to claim 9 is the image forming apparatus according to claim 8,
In the developing unit, the smaller the printing rate related to the amount of toner supplied to the image carrier in the formation of one image, the larger the amount of lubricant supplied to the image carrier in the formation of the one image. Supplying the lubricant in the form of
The lubricant information acquisition unit acquires the lubricant information based on the printing rate in the most recent predetermined number of image formations.

According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects,
The removal capability changing means changes the removal by changing at least one of a relative moving speed between the surface of the charging member cleaning unit and the surface of the charging member and a pressure exerted on the charging member by the charging member cleaning unit. It is characterized by changing the size of the ability.

According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect,
The charging member cleaning unit rotates so that the surface of the charging member cleaning unit rubs the surface of the charging member,
The removal capability changing means is characterized in that the relative movement speed is changed by changing at least one of a rotation speed and a rotation direction of the charging member cleaning unit.

The invention according to claim 12 is the image forming apparatus according to any one of claims 1 to 11,
For each of a plurality of divided areas obtained by dividing the toner image forming area of the image carrier in the direction of the rotation axis, the printing rate related to the amount of toner supplied in the formation of one image is formed in the past predetermined number of times. An integrated print rate acquisition means for acquiring an integrated print rate based on at least one of a value integrated over a predetermined number of times of image formation and a value obtained by integrating the print rate over a predetermined number of times of image formation;
The control means removes the removal so that a relationship in which the magnitude of the removal capability of the charging member cleaning unit gradually increases in accordance with an increase in the maximum value of the plurality of integrated print rates corresponding to the plurality of divided regions is satisfied. It is characterized by controlling the operation of the ability change means.

According to a thirteenth aspect of the present invention, in the image forming apparatus according to any one of the first to eleventh aspects,
For each of a plurality of divided areas obtained by dividing the toner image forming area of the image carrier in the direction of the rotation axis, the printing rate related to the amount of toner supplied in the formation of one image is formed in the past predetermined number of times. An integrated print rate acquisition means for acquiring an integrated print rate based on at least one of a value integrated over a predetermined number of times of image formation and a value obtained by integrating the print rate over a predetermined number of times of image formation;
The control means has a relationship in which the magnitude of the removal capability of the charging member cleaning unit gradually increases in accordance with an increase in the difference between the maximum value and the minimum value in the plurality of integrated printing rates corresponding to the plurality of divided regions. The operation of the removal capability changing means is controlled so as to be satisfied.

According to a fourteenth aspect of the present invention, in the image forming apparatus according to any one of the first to eleventh aspects,
For each of a plurality of divided areas obtained by dividing the toner image forming area of the image carrier in the direction of the rotation axis, the printing rate related to the amount of toner supplied in the formation of one image is formed in the past predetermined number of times. An integrated print rate acquisition means for acquiring an integrated print rate based on at least one of a value integrated over a predetermined number of times of image formation and a value obtained by integrating the print rate over a predetermined number of times of image formation;
The control unit satisfies a relationship in which the magnitude of the removal capability of the charging member cleaning unit gradually increases in accordance with an increase in the maximum value of the difference in the integrated printing rate in the divided areas adjacent to each other in the direction of the rotation axis. As described above, the operation of the removal capability changing means is controlled.

In order to achieve the above object, the program invention according to claim 15 provides:
An image carrier that rotates about a predetermined rotation axis, an image carrier cleaning unit that abuts on the surface of the image carrier to remove foreign matter on the image carrier, and abuts on the surface of the image carrier A charging member that rotates with the rotation of the image carrier and applies a predetermined voltage to charge the surface of the image carrier, and contacts the surface of the charging member to remove foreign matter on the charging member. A charging member cleaning unit to be removed; a removal capability changing means for changing the magnitude of the foreign substance removal capability by the charging member cleaning unit; and a lubricant supply unit for supplying a lubricant to the surface of the image carrier. A computer provided in an image forming apparatus for transferring a toner image obtained by developing an electrostatic latent image on the surface of the image carrier to a member to be transferred to form an image on the member to be transferred;
Lubricant information acquisition means for acquiring lubricant information related to the amount of lubricant on the surface of the image carrier,
The operation of the removal capacity changing unit is performed so that a relationship in which the magnitude of the removal capacity gradually increases according to a decrease in the amount of the lubricant based on the lubricant information acquired by the lubricant information acquisition unit is satisfied. Control means for controlling,
It is characterized by making it function as.

  According to the present invention, there is an effect that foreign matters on the charging member can be more reliably removed while suppressing deterioration of the charging member.

1 is a schematic diagram illustrating a schematic configuration of an image forming apparatus. 2 is a block diagram illustrating a main functional configuration of the image forming apparatus. FIG. It is a schematic diagram which shows the structure of an image forming unit. It is a schematic diagram which shows the experimental apparatus used for the experiment which pinpoints the relationship between the quantity of lubricant, and the quantity of the foreign material which slips through a cleaning part. It is a figure which shows the measurement result of a friction coefficient. It is a figure which shows the relationship between a friction coefficient and a torque. It is a figure explaining the method to adjust removal capability with an eccentric cam. It is a flowchart which shows the control procedure of the cleaning operation adjustment process. FIG. 10 is a diagram for describing a printing rate calculation method according to Modification 1; FIG. 10 is a schematic diagram showing a configuration of an image forming unit in Modification 2.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of an image forming apparatus and a program according to the invention will be described with reference to the drawings.

<Configuration of image forming apparatus>
FIG. 1 is a schematic diagram showing a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a main functional configuration of the image forming apparatus 1.
The image forming apparatus 1 includes a paper supply unit 2, a paper discharge unit 3, a control unit 10 (lubricant information acquisition unit, control unit, integrated print rate acquisition unit, computer), an image formation unit 20, and a storage unit 30. An operation unit 40, a display unit 50, a scanner 60, a transport unit 70, a communication unit 80, a bus 90, and the like. These units are connected via a bus 90.
The image forming apparatus 1 transports a sheet (a member to be transferred) stored in the sheet supply unit 2 by a transport roller 71 of a transport unit 70, and an image is electrophotographic on the transported sheet by the image forming unit 20. Is formed and discharged to the paper discharge unit 3.

  The control unit 10 includes a CPU 11 (Central Processing Unit), a RAM 12 (Random Access Memory), and a ROM 13 (Read Only Memory).

  The CPU 11 reads and executes the control program 131 stored in the ROM 13 and performs various arithmetic processes.

  The RAM 12 provides a working memory space to the CPU 11 and stores temporary data.

  The ROM 13 stores various control programs 131 executed by the CPU 11, setting data, and the like. Instead of the ROM 13, a rewritable nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

  The control unit 10 including the CPU 11, the RAM 12, and the ROM 13 performs overall control of each unit of the image forming apparatus 1 in accordance with the control program 131. For example, the control unit 10 causes the conveyance unit 70 to convey the sheet, and causes the image forming unit 20 to form an image on the sheet based on the image data stored in the storage unit 30.

  The storage unit 30 is configured by a DRAM (Dynamic Random Access Memory) or the like, and stores image data acquired by the scanner 60, image data input from the outside via the communication unit 80, history information to be described later, and the like. . These data and information may be stored in the RAM 12.

  The image forming unit 20 forms an image on a sheet based on the image data stored in the storage unit 30. The image forming unit 20 includes an image carrier 21 that is a drum-shaped photoconductor that carries an electrostatic latent image on the surface, an image carrier drive unit 211 (FIG. 2) that rotates the image carrier 21, and an image carrier. A torque measurement unit 212 that measures torque on the rotation shaft of the body 21, a lubricant supply unit 22 that supplies a lubricant to the surface of the image carrier 21, and a cleaning unit 23 that removes residual toner on the surface of the image carrier 21. (Image carrier cleaning unit), eraser 24 for neutralizing the surface of the image carrier 21, charging roller 25 (charging member) for uniformly charging the surface of the image carrier 21, and applying a voltage to the charging roller 25 A power supply unit 251 (FIG. 2), an exposure unit 26 that exposes the surface of the charged image carrier 21 to form an electrostatic latent image, and develops the electrostatic latent image using a developer containing toner. A toner image is formed on the surface of the image carrier 21 A developing unit 27, a primary transfer of the formed toner image to the intermediate transfer belt 281 in the transfer area, and a secondary transfer from the intermediate transfer belt 281 to the paper, and a fixing for fixing the toner image on the paper. The unit 29 and the like are provided. The image forming unit 20 includes a charging roller cleaning unit 252 (FIG. 3) that includes a cleaning roller 252 a and a foreign matter removal roller 252 b, and a cleaning drive unit 2521 (removal capability changing unit) that drives each unit of the charging roller cleaning unit 252. , A moving unit that moves the lubricant supply unit 22, the charging roller 25, and the transfer unit 28 between a first position that contacts the surface of the image carrier 21 and a second position that is separated from the surface of the image carrier 21. 201 (moving means).

  Among the above, the image carrier 21, the lubricant supply unit 22, the cleaning unit 23, the eraser 24, the charging roller 25, the charging roller cleaning unit 252, the exposure unit 26, and the developing unit 27 constitute the image forming unit U (FIG. 3). Is done. Four image forming units U are provided corresponding to respective colors of Y (yellow), M (magenta), C (cyan), and K (black), and Y, M, and Y along the upper horizontal surface of the intermediate transfer belt 281 are provided. They are arranged in the order of C and K.

FIG. 3 is a schematic diagram showing the configuration of the image forming unit U.
In each image forming unit U, along the outer peripheral surface of the image carrier 21, a lubricant supply unit 22, a cleaning unit 23, an eraser 24, a charging roller 25 and a charging roller cleaning unit 252, an exposure unit 26, and a developing unit 27 are provided. They are arranged in order.

The image carrier 21 is driven by an image carrier drive unit 211 to rotate around a predetermined rotation axis. A photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of the image carrier 21. Examples of the resin constituting the photosensitive layer include polycarbonate resin, silicone resin, polystyrene resin, acrylic resin, methacrylic resin, epoxy resin, polyurethane resin, vinyl chloride resin, and melamine resin.
The image carrier driving unit 211 rotationally drives the image carrier 21 at a rotation speed specified by a control signal from the control unit 10.
The torque measurement unit 212 measures the torque on the rotation shaft of the image carrier 21 and outputs the result to the control unit 10.

The lubricant supply unit 22 includes a solid lubricant 221, a lubricant application member 222, and an application member cleaning roller 223.
The solid lubricant 221 is pressed against the lubricant application member 222 by an elastic member (not shown).
As the lubricant application member 222, one having a form such as a brush or a sponge can be used. Of these, brushes are suitable for practical use. The lubricant application member 222 is installed so as to contact both the solid lubricant 221 and the image carrier 21 and is rotationally driven by a motor (not shown). The lubricant application member 222 performs a supply operation of scraping off lubricant particles (lubricant) from the solid lubricant 221 by the rotation and supplying it to the surface of the image carrier 21. The rotational speed of the lubricant application member 222 may be appropriately changed according to changes in external environmental factors.
The lubricant application member 222 also has a function of collecting a part of the toner remaining on the surface of the image carrier 21 without being transferred to the paper. In order to enhance the toner recovery function, a predetermined bias voltage may be applied to the lubricant application member 222.
The application member cleaning roller 223 removes residual toner adhering to the lubricant application member 222 and cleans the application member cleaning roller 223. Instead of the application member cleaning roller 223, a blade for removing residual toner attached to the lubricant application member 222 may be provided. The blade in this case may be constituted by a part of the housing of the image forming unit U.

  Although it does not restrict | limit especially as a lubricant, A fatty acid metal salt, silicone oil, a fluorine resin etc. can be used individually or in mixture of 2 or more types. Of these, fatty acid metal salts are particularly preferred. As the fatty acid, a linear hydrocarbon is preferable. For example, myristic acid, palmitic acid, stearic acid, oleic acid and the like can be used, and stearic acid is more preferable. Examples of the metal include lithium, magnesium, calcium, strontium, zinc, cadmium, aluminum, cerium, titanium, and iron. Among these, zinc stearate, magnesium stearate, aluminum stearate, iron stearate and the like are preferable, and zinc stearate is particularly preferable.

The cleaning unit 23 has a flat plate-shaped cleaning blade made of an elastic body, and is brought into contact with the surface of the image carrier 21 so that the cleaning blade adheres to the surface of the image carrier 21 and is transferred to the intermediate transfer belt 281. Foreign matter such as toner remaining without being removed is removed.
As physical properties of the cleaning blade, rebound resilience and hardness are important. The rebound resilience is preferably 10 to 80% at 25 ° C., more preferably 30 to 70%. Further, the hardness (here, JIS A hardness) is preferably 20 ° to 90 °, and particularly preferably 60 ° to 80 °. If the hardness is less than 20 °, the cleaning blade is too soft and the blade is likely to turn up. On the other hand, when the hardness is greater than 90 °, it becomes difficult to follow the slight irregularities or foreign matter of the image carrier 21, and toner particles and toner external additives are likely to slip through.

  The eraser 24 has a light source device such as a tungsten lamp or an LED (Light Emitting Diode) array, and discharges the surface of the image carrier 21 by irradiating the surface of the image carrier 21 with light from the light source device.

  The charging roller 25 is a cylindrical member that abuts on the surface of the image carrier 21 and rotates following a predetermined rotation axis as the image carrier 21 rotates. The charging roller 25 has a configuration in which a conductive rubber elastic layer is provided around a cylindrical metal shaft. The conductive rubber elastic layer is made of an elastic material such as epichlorohydrin rubber, nitrile rubber, ethylene-propylene-diene rubber, silicone rubber, urethane rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber, natural rubber, ketjen black, In order to impart a predetermined surface roughness to the surface of the elastic layer composed of carbon black such as acetylene black, graphite, metal powder, conductive metal oxide, and a conductive agent such as an ionic conductive agent mixed therein, A surface layer made of a resin containing organic fine particles or inorganic fine particles having an average particle diameter of several μm to several tens of μm is provided.

In the vicinity of the charging roller 25, a charging roller cleaning unit 252 (charging member cleaning unit) that contacts the surface of the charging roller 25 and removes foreign matter on the charging roller 25 is provided. The foreign matter on the charging roller 25 is, for example, a toner or an external additive transferred to the image carrier 21 or the like.
The charging roller cleaning unit 252 is in contact with the charging roller 25 and rotates to rotate. A foreign matter removing roller 252b to be removed from the cleaning roller 252a.

The cleaning roller 252a is provided such that an inter-axis distance with respect to the charging roller 25 is adjustable, and rotates in a state where a predetermined pressure is applied to the charging roller 25. The cleaning roller 252a rotates in such a state to rub the surface of the charging roller 25, thereby removing foreign matter on the charging roller 25.
As the cleaning roller 252a, one having a form such as a brush or a sponge can be used. Of these, brushes are suitable for practical use. As a material of the cleaning roller 252a, any material capable of removing or collecting foreign matters can be selected, and for example, a cloth or a resin can be used.
The cleaning drive unit 2521 rotates the cleaning roller 252a at a predetermined rotation direction and rotation speed under the control of the control unit 10.

The foreign matter removing roller 252b rotates while being pressed against the cleaning roller 252a. Further, the foreign matter removing roller 252b may be further configured to be able to remove foreign matter on the foreign matter removing roller by bringing a blade (not shown) into pressure contact therewith. Note that the foreign matter on the cleaning roller 252a may be removed by a blade instead of the foreign matter removing roller 252b. The blade in this case may be constituted by a part of the housing of the image forming unit U.
The cleaning drive unit 2521 rotates the foreign matter removal roller 252b at a predetermined rotation direction and rotation speed under the control of the control unit 10.

  The power supply unit 251 uniformly charges the surface of the image carrier 21 by applying an AC bias voltage, in which an AC voltage is superimposed on a DC voltage, as the charging driving voltage to the driven rotating charging roller 25. Let

  The exposure unit 26 includes an LD (Laser Diode) as a light emitting element, and exposes the surface of the image carrier 21 charged by the charging roller 25 by irradiating a laser beam so that the electrostatic latent image is formed on the image carrier 21. Form an image. In FIG. 1, four exposure units 26 corresponding to the four image forming units are provided. Instead, the laser light from the single exposure unit 26 is separated by an anti-transmission mirror or the like. In other words, it may be configured to be guided to the image carrier 21 of each imaging unit.

  The developing unit 27 includes a developing sleeve 271 (developing roller) disposed so as to face the surface of the image carrier 21. For example, a DC development bias voltage having the same polarity as the charging polarity of the charging roller 25 or a developing bias voltage in which a DC voltage having the same polarity as the charging polarity of the charging roller 25 is superimposed on an AC voltage is applied to the developing sleeve 271. The The developing unit 27 supplies a developer containing toner supplied from a toner bottle (not shown) to the surface of the developing sleeve 271 having a predetermined developing bias potential, so that the toner in the developer is on the surface of the developing sleeve 271. The toner image is formed on the surface of the image carrier 21 by being attached to the electrostatic latent image on the surface of the image carrier 21.

  The developer used in the developing unit 27 includes toner and a carrier for charging the toner. As the toner, various known toners can be used. In order to adjust the chargeability and fluidity of the toner by including a colorant in the binder resin, and if necessary, a charge control agent and a release agent. What processed the external additive of this can be used. As the external additive, for example, a fine metal oxide such as silica or titania is used. The particle size of the external additive is not particularly limited, but can be, for example, about 30 [nm] to 100 [nm]. Further, the particle size of the toner is not particularly limited, but may be, for example, about 3 [μm] to 15 [μm]. Various known carriers can be used as the carrier, and a binder type carrier, a coat type carrier, and the like can be used. The particle size of the carrier is not particularly limited, but can be about 15 [μm] to 100 [μm].

The transfer unit 28 includes two belt conveyance rollers 282, four primary transfer rollers 283 arranged to face each image carrier 21, a pair of secondary transfer rollers 285, the belt conveyance rollers 282, and the primary. An intermediate transfer belt 281 that spans around the transfer roller 283 and passes between the pair of secondary transfer rollers 285, and a belt cleaning unit 284 that removes toner remaining on the intermediate transfer belt 281 are provided.
In the transfer unit 28, toner moves from the surface of the rotating image carrier 21 to the intermediate transfer belt 281 by rotating the intermediate transfer belt 281 while applying a bias voltage having a reverse polarity to the toner to the primary transfer roller 283. Transcribed. Further, after the toner of each color of Y, M, C, and K is superimposed and transferred, the sheet passes between the secondary transfer roller to which a predetermined bias voltage is applied and the intermediate transfer belt 281, so that the intermediate transfer is performed. A color toner image is transferred from the belt 281 to the paper. The toner remaining on the intermediate transfer belt 281 without being transferred to the paper is removed by the cleaning blade of the belt cleaning unit 284.

  The fixing unit 29 heats and pressurizes the paper on which the toner image is transferred to fix the toner image on the paper. The fixing unit 29 includes a pair of rollers including a heating roller and a pressure roller that sandwich the paper. The heating roller is heated to a predetermined target temperature (for example, a temperature within a range of 180 ° C. or higher and 200 ° C. or lower) by a heater as a heating source. The pressure roller is urged toward the heating roller by an elastic member (not shown). The sheet on which the toner image has been transferred passes through the nip portion between the heating roller and the pressure roller, whereby the toner image is fixed on the sheet. The sheet on which the toner image is fixed is transported by the transport roller 71 of the transport unit 70 and sent to the paper discharge unit 3.

  The moving unit 201 includes a lubricant supply unit 22, a charging roller 25, and a transfer unit 28 between a first position where the lubricant supply unit 22, the charging roller 25, and the transfer unit 28 are in contact with the surface of the image carrier 21 and a second position separated from the surface of the image carrier 21. Move. The configuration of the moving unit 201 is not particularly limited. In the present embodiment, the moving unit 201 is moved up and down according to the operation of a lifting motor such as a stepping motor or a servo motor along a support column extending in the radial direction of the image carrier 21. The lubricant supply unit 22, the charging roller 25, and the transfer unit 28 may be fixed to the member.

  In the image forming unit U of the present embodiment, the lubricant supply unit 22 is provided between the toner image transfer position to the transfer unit 28 and the cleaning unit 23 in the moving direction of the surface of the rotating image carrier 21. Although provided, the lubricant supply unit 22 may be provided on the downstream side of the cleaning unit 23 in the moving direction. In this case, it is preferable to provide a leveling member for extending the lubricant particles supplied to the surface of the image carrier 21 further downstream of the lubricant supply unit 22. However, compared with such a configuration, the configuration of the present embodiment shown in FIG. 3 is more preferable. This is because if the lubricant supply unit 22 is provided on the downstream side of the cleaning unit 23, the charging roller 25 is significantly contaminated by the supplied lubricant.

  The operation unit 40 includes input devices such as operation keys and a touch panel arranged on the screen of the display unit 50, converts an input operation on these input devices into an operation signal, and outputs the operation signal to the control unit 10.

  The display unit 50 includes a display device such as an LCD (Liquid crystal display). Under the control of the control unit 10, the state of the image forming apparatus 1, an operation screen including operation buttons to be input to the touch panel, and the like Is displayed.

  The scanner 60 reads an image formed on a sheet under the control of the control unit 10 to generate image data, and causes the storage unit 30 to store the generated image data.

  The transport unit 70 includes a plurality of transport rollers 71 that move the paper by rotating in a state where the paper is sandwiched, and the transport roller 71 is rotationally driven under the control of the control unit 10 so that the paper is moved along a predetermined transport path. Transport. The conveyance unit 70 may include a reversing mechanism (not shown) that reverses the front and back of the sheet on which the fixing process has been performed by the fixing unit 29 and conveys the sheet to the secondary transfer roller 285.

  Under the control of the control unit 10, the communication unit 80 communicates with a computer or other image forming apparatus on the network to transmit / receive image data, print job data, and the like.

<Overview of charging roller cleaning method>
Next, a method for cleaning the charging roller 25 will be described.
In the image forming apparatus 1 of the present embodiment, the image carrier 21 and the charging roller 25 are in contact with each other, so that foreign matter on the image carrier 21 that cannot be completely removed by the cleaning unit 23 adheres to the surface of the charging roller 25. To do. Here, the foreign matter that passes through the cleaning blade of the cleaning unit 23 and adheres to the charging roller 25 is mainly an external additive of the toner. In some cases, the toner itself or other foreign matters may remain and adhere to the charging roller 25. Since all foreign matters that have passed through the cleaning unit 23 normally come into contact with the charging roller 25, the more foreign matter that passes through the cleaning unit 23, the greater the amount of foreign matter that adheres to the charging roller 25.

  The foreign matter adhering to the charging roller 25 is removed by the charging roller cleaning unit 252 as described above. However, in order to reliably remove foreign matter from the surface of the charging roller 25, the pressure at which the charging roller cleaning unit 252 is brought into contact with the charging roller 25 is increased, or the charging roller cleaning unit 252 and the charging roller 25 are When the removal speed (cleaning ability) of the foreign matter is increased by increasing the moving speed, the surface of the charging roller 25 is rapidly worn by the friction between the charging roller cleaning unit 252 and the charging roller 25, and the charging roller. 25 will deteriorate early. On the other hand, if the charge roller cleaning unit 252 has a small foreign matter removal capability, the foreign matter cannot be reliably removed.

  Therefore, in the cleaning method of the charging roller 25 of the present embodiment, based on factors that affect the number of foreign matters that pass through the cleaning unit 23, the foreign matter removal capability of the charging roller cleaning unit 252 is increased when the number of foreign matters increases. When the amount of foreign matter decreases, control is performed to reduce the foreign matter removal capability of the charging roller cleaning unit 252. The above factor is specifically the amount of lubricant on the surface of the image carrier 21.

<Relationship between amount of lubricant and amount of foreign matter adhering to charging roller>
Hereinafter, the relationship between the amount of lubricant on the surface of the image carrier 21 and the amount of foreign matter that passes through the cleaning unit 23 (that is, the amount of foreign matter attached to the charging roller 25) will be described.

FIG. 4 is a schematic diagram showing an experimental apparatus used in an experiment for specifying the relationship between the amount of lubricant and the amount of foreign matter that passes through the cleaning unit 23.
In this experiment, first, as shown in FIG. 4A, the image carrier 21 is installed in a lubricant application mechanism including a lubricant supply unit 22 and a leveling member 224 for leveling the lubricant. . Then, by this lubricant application mechanism, the lubricant was uniformly supplied to the surface of the image carrier 21 while rotating the image carrier 21.
Next, as shown in FIG. 4B, the image carrier 21 was installed in the toner application mechanism including the cleaning unit 23 and the developing unit 27. With the toner application mechanism, a small amount of toner corresponding to the residual toner after transfer was supplied to the image carrier 21 while rotating the image carrier 21 and passed through the cleaning unit 23. Here, the toner used is one in which the external additive contains Si atoms.
Further, the amount of Si atoms on the image carrier 21 immediately after passing through the cleaning unit 23 was measured by an X-ray photoelectron spectrometer.
In addition, the friction coefficient was measured at the site where the measurement of the Si amount was completed. Here, the dynamic friction coefficient (nel friction coefficient) when a predetermined fabric (flannel) was brought into contact with a specific position of the rotating image carrier 21 was measured.
The above experiment was repeatedly performed by changing the supply amount of the lubricant.

FIG. 5 is a diagram showing the measurement results of the friction coefficient. The graph of FIG. 5 plots the measured Si amount (the amount of slipping of the external additive) against the measurement result of the friction coefficient in the above experiment. As shown in FIG. 5, the friction coefficient and the slipping amount of the external additive have a positive correlation. The friction coefficient increases as the amount of lubricant on the surface of the image carrier 21 decreases. In other words, the result of FIG. 5 indicates that the amount of slipping of the external additive increases as the lubricant decreases.
Therefore, it is confirmed that the amount of lubricant on the surface of the image carrier 21 and the amount of foreign matter that passes through the cleaning unit 23, that is, the amount of foreign matter attached to the charging roller 25 have a negative correlation. It was.

  Based on the above experimental results, in the present embodiment, the lubricant information related to the amount of lubricant on the image carrier 21 is acquired, and the cleaning ability by the charging roller cleaning unit 252 is determined according to the amount of lubricant based on the lubricant information. To control. Specifically, the lubricant based on the lubricant information is satisfied so that the relationship of gradually increasing the foreign matter removal capability of the charging roller cleaning unit 252 as the amount of lubricant on the image carrier 21 decreases. The removal ability is controlled in accordance with the amount of. The gradual increase of the removal capability in the above means that the removal capability increases in a manner in which the removal capability does not decrease according to the decrease in the lubricant, that is, monotonous non-decrease (monotonic increase in a broad sense).

<Method for estimating the amount of lubricant>
The amount of lubricant on the surface of the image carrier 21 is difficult to directly measure, but can be estimated by the following method, for example.
As a first method, it can be estimated based on the total time that the lubricant is supplied using the same solid lubricant 221.
The lubricant supply unit 22 in the image forming apparatus 1 of the present embodiment rotates from the solid lubricant 221 by rotating the lubricant application member 222 while pressing the solid lubricant 221 against the lubricant application member 222 by an elastic member. The lubricant particles are scraped off and supplied to the image carrier 21. In such a configuration, as the lubricant is scraped off from the solid lubricant 221, the pressing force by the elastic member is weakened and the amount of lubricant scraped off per unit time is reduced. Further, due to the shape of the portion of the solid lubricant 221 that contacts the lubricant application member 222 being deformed into a shape along the surface of the lubricant application member 222, the lubricant application member 222 is changed over time. The cutting efficiency is reduced, and the amount of lubricant that is scraped per unit time is reduced. Also, the amount of lubricant scraped off per unit time is reduced by the surface of the solid lubricant 221 being contaminated with toner.
Therefore, in this embodiment, the amount of the lubricant supplied from the lubricant supply unit 22 per unit time decreases as the total time of supplying the lubricant using the same solid lubricant 221 increases. To do. Therefore, the current lubricant supply amount is obtained by acquiring the relationship between the total time and the lubricant supply amount per unit time in advance and storing it in the storage unit 30 as table data and referring to the table data according to the total time. That is, the amount of lubricant on the image carrier 21 can be estimated. In this case, the total time corresponds to the lubricant information.

As a second method, the amount of lubricant is estimated on the basis of torque for rotating the image carrier 21 against the frictional force between the surface of the image carrier 21 and the cleaning unit 23. Can do.
There is a correlation between the amount of lubricant on the image carrier 21 and the above torque. In order to confirm this, the following experiment was conducted. That is, a torque measurement unit for measuring torque on the rotation shaft of the image carrier 21 was attached to the toner supply mechanism shown in FIG. 4B, and the friction coefficient and torque when the supply amount of the lubricant was changed were measured.

  FIG. 6 is a diagram illustrating the relationship between the friction coefficient and the torque. As shown in FIG. 6, it can be seen that the torque decreases as the friction coefficient increases (that is, the amount of lubricant on the image carrier 21 decreases and the amount of external additive slipping through increases). This is because when the amount of lubricant decreases and the amount of external additive passing between the cleaning blade and the image carrier 21 increases, a large number of external additives are interposed between the cleaning blade and the image carrier 21. It is considered that this is because the cleaning blade and the image carrier 21 are easily moved relative to each other due to the rolling effect of the external additive. In other words, when the amount of the lubricant increases and the external additive passing between the cleaning blade and the image carrier 21 decreases, the contact area between the cleaning blade and the image carrier 21 increases and the relative movement occurs. As a result, the torque is considered to increase.

From the above results, in the image forming apparatus 1 of the present embodiment, the larger the measured torque value by the torque measuring unit 212 (FIG. 2), the greater the amount of lubricant, and the smaller the measured torque value, the greater the amount of lubricant. It can be determined that there are few. The torque may be a substitute characteristic by measuring the driving current of the driving motor of the image carrier driving unit 211.
Therefore, the relationship between the torque and the lubricant supply amount per unit time is acquired in advance and stored in the storage unit 30 as table data, and the table data is referred to by the torque measurement value by the torque measurement unit 212 (FIG. 2). Thus, the current amount of lubricant supplied, that is, the amount of lubricant on the image carrier 21 can be estimated. In this case, the measured torque value corresponds to the lubricant information.

  Further, when measuring the torque, it is desirable to separate each member other than the cleaning blade of the cleaning unit 23 from the image carrier 21. In the present embodiment, the lubricant supply unit 22, the charging roller 25, and the transfer unit 28 that are in contact with the image carrier 21 are moved to a second position separated from the image carrier 21 by the moving unit 201. Measurement by the torque measuring unit 212 is performed. Of the lubricant supply unit 22, the charging roller 25, and the transfer unit 28, the transfer unit 28 has the greatest drag on the image carrier 21, so at least the transfer unit 28 is moved to the second position. The torque may be measured in a state where

<Adjustment method of foreign matter removal ability by cleaning roller>
Next, a method for adjusting the removal capability of the foreign matter on the charging roller 25 by the cleaning roller 252a will be described.
First, the foreign matter removal capability can be increased by increasing the relative movement speed between the surface of the cleaning roller 252a and the surface of the charging roller 25. Specifically, the rotation direction of the cleaning roller 252a by the cleaning drive unit 2521 is controlled so that the moving direction of each contact position between the cleaning roller 252a and the surface of the charging roller 25 is opposite, or at the contact position described above. By controlling the rotational speed of the cleaning roller 252a so that the speed difference between the surface of the cleaning roller 252a and the surface of the charging roller 25 is increased, the ability to remove foreign matter can be increased. In order to reduce the foreign matter removal capability, the control opposite to the above may be performed.
In this case, in the storage unit 30, settings relating to the rotation direction and rotation speed of the cleaning roller 252a appropriate to the amount of lubricant on the image carrier 21 (hereinafter referred to as setting of cleaning conditions). By storing the data as table data, it is possible to appropriately adjust the removal capability according to the amount of the lubricant.

Secondly, the foreign substance removal capability can be increased by increasing the pressure exerted on the charging roller 25 by the cleaning roller 252a. Specifically, the pressure can be changed by changing the interaxial distance between the charging roller 25 and the cleaning roller 252a. For example, as shown in FIG. 7, by providing an eccentric cam 252c in the vicinity of the cleaning roller 252a and changing the angle of the eccentric cam 252c by driving operation of the cleaning drive unit 2521, the position of the cleaning roller 252a is moved up and down. The distance between the axes can be changed.
In this case, the storage unit 30 stores, as table data, settings (setting of cleaning conditions) relating to an appropriate interaxial distance (or eccentric cam angle) with respect to the amount of lubricant on the image carrier 21. Therefore, the removal capability can be adjusted appropriately according to the amount of the lubricant.

<Method for controlling operation of charging roller cleaning unit>
Next, a control method by the control unit 10 when adjusting the operation of the charging roller cleaning unit 252 will be described.
FIG. 8 is a flowchart illustrating a control procedure of the cleaning operation adjustment process of the charging roller cleaning unit 252.
The cleaning operation adjustment process is started when a predetermined condition is satisfied or according to an instruction based on an input operation to the operation unit 40 by the user. The predetermined condition is not particularly limited. For example, the image forming apparatus 1 has been operated for a predetermined time after the end of the most recent cleaning operation adjustment process, and a predetermined number of image formations have been performed after the end of the most recent cleaning operation adjustment process. The environmental conditions (temperature, humidity, etc.) of the image forming apparatus 1 fluctuate by a predetermined value or more.

  When the cleaning operation adjustment process is started, the control unit 10 acquires lubricant information related to the amount of lubricant on the image carrier 21 (step S101). For example, the control unit 10 acquires, as the lubricant information, the total time that the lubricant is supplied using the same solid lubricant 221. Alternatively, the control unit 10 causes the torque measurement unit 212 to measure the torque of the rotation shaft of the image carrier 21 and acquires the measurement result as lubricant information. What information is acquired as the lubricant information is determined according to the operation setting of the image forming apparatus 1 stored in the storage unit 30 in advance.

  The control unit 10 acquires a cleaning condition setting corresponding to the acquired lubricant information (step S102). For example, when the control unit 10 acquires the above total time as the lubricant information, the controller 10 refers to the table data stored in the storage unit 30 and the amount of lubricant corresponding to the acquired total time. And by referring to another table data, the setting of the cleaning condition corresponding to the amount of the lubricant is obtained. In addition, when the control unit 10 acquires the measurement result of the torque as the lubricant information, the control unit 10 refers to the table data stored in the storage unit 30 and determines the lubricant corresponding to the acquired torque. The amount is acquired, and the setting of the cleaning condition corresponding to the amount of the lubricant is acquired with reference to another table data. In addition, you may acquire the setting of cleaning conditions directly from said total time or the measured value of torque, without acquiring the quantity of a lubricant. In this case, table data indicating the relationship between the total time and the setting of the cleaning condition and table data indicating the relationship between the torque and the setting of the cleaning condition may be stored in the storage unit 30.

The control unit 10 adjusts the operation of the charging roller cleaning unit 252 based on the acquired cleaning condition setting (step S103). Specifically, the control unit 10 outputs a control signal to the cleaning drive unit 2521 based on the acquired setting of the cleaning condition, and changes the rotation direction and rotation speed of the cleaning roller 252a and the angle of the eccentric cam 252c. Let
When the process of step S103 ends, the control unit 10 ends the cleaning operation adjustment process.

(Modification 1)
Subsequently, Modification 1 of the above embodiment will be described. In this modification, the cleaning operation by the charging roller cleaning unit 252 is adjusted based on the distribution of the cumulative printing rate in the main scanning direction (the rotation axis direction of the image carrier 21 and the charging roller 25) in image formation on the paper. This is different from the above embodiment. Hereinafter, differences from the above embodiment will be described.

  As described above, the amount of the external additive that passes through the cleaning blade of the cleaning unit 23 is affected by the amount of the lubricant, but it is also affected by the image pattern of the image to be formed. Most of the external additive that slips through the cleaning blade comes from residual toner. Therefore, in the portion where the printing ratio (print coverage) in the image is large, the residual toner also increases, and as a result, the amount of the external additive that passes through the cleaning blade also increases. Here, the printing rate is a value corresponding to the amount of toner supplied in a specific area in the image (or the surface of the corresponding image carrier 21), and is highest in the solid image formation area.

  Since the printing rate is usually not constant in the main scanning direction, the amount of slippage of the external additive increases as the printing rate increases in the main scanning direction, and the amount of slipping out of the external additive decreases as the printing rate decreases. Become. In this way, when images are continuously formed in a pattern having unevenness in the amount of the external additive, a large amount of external additive adheres to the charging roller 25 in a region where the printing rate is large, while a region where the printing rate is small. Then, the adhesion amount of the external additive is reduced, and the adhesion amount of the external additive is biased on the charging roller 25. When a deviation in the amount of the external additive is generated, the charged potential varies according to the amount of the external additive, which leads to poor image quality such as uneven density in the recorded image.

  Therefore, in the present modification, as shown in FIG. 9, the toner image forming region R in the image carrier 21 is divided into n regions c1 to cn (segmented regions) in the rotation axis direction, and each region c is divided. The printing rate in forming one image is calculated. For example, in the case of an image as shown in FIG. 9, the printing rate is 100% in each of the areas ci to cj, and the printing rate is 50% in the other areas c. Further, for each region c, an integrated printing rate over a plurality of times of image formation is calculated. Here, the integrated print rate is a value obtained by integrating the print rate in the formation of one image over the past predetermined number of image formations, and the print rate over the most recent predetermined number of image formations. It is calculated based on at least one of the values obtained by integrating. This integrated printing rate is a value having a correlation with the adhesion amount of the external additive resulting from image formation in a desired period in the past and the future. Therefore, by adjusting the foreign matter removal capability of the cleaning roller 252a based on the integrated printing rate of each region c, foreign matters such as external additives can be more reliably removed while suppressing deterioration of the charging roller 25. it can.

  Below, the specific adjustment method of the removal capability based on the integrated printing rate of each area | region c is demonstrated.

  The first method is a control method based on the maximum value of the integrated print rate in the areas c1 to cn. That is, when the maximum value is equal to or greater than a predetermined reference value (or when predicted to be equal to or greater than the reference value), the foreign matter removal capability by the cleaning roller 252a is increased. In the region c where the integrated printing rate is large, the amount of external additive attached increases in accordance with the integrated printing rate. Therefore, by increasing the foreign matter removal capability in accordance with the maximum value of the integrated printing rate, the contamination amount of the charging roller 25 can be set to a desired amount even when the foreign matter adheres to a part of the rotation axis direction of the charging roller 25. The following can be suppressed.

  The second method is a control method based on the difference between the maximum value and the minimum value of the integrated printing rate in the areas c1 to cn. That is, when the difference between the maximum value and the minimum value is equal to or greater than a predetermined reference value (or when it is predicted that the difference is equal to or greater than the reference value), the foreign matter removal capability by the cleaning roller 252a is increased. Thereby, the dispersion | variation in the adhesion amount of the foreign material on the charging roller 25 can be suppressed in a predetermined range about the rotation axis direction. If there is a variation in the amount of adhered foreign matter, the variation leads to uneven density in the formed image. Therefore, the occurrence of uneven density can be suppressed by increasing the foreign substance removal capability by the above control.

  The third method is a method of controlling based on the maximum value of the difference in the integrated printing rate between adjacent areas c. That is, when the maximum value of the difference is equal to or greater than a predetermined reference value (or when it is predicted that the difference is equal to or greater than the reference value), the foreign matter removing ability by the cleaning roller 252a is increased. When the adhering amount of the external additive is different between the adjacent regions c, and the charging potential is thereby different, the density difference in the formed image is noticeable due to the edge effect. Therefore, by increasing the foreign substance removal capability by the above-described control, it is possible to suppress the occurrence of image quality defects due to such density differences.

  The above three controls may be used in combination. The above three controls may be combined with the control according to the amount of lubricant described in the above embodiment.

(Modification 2)
Next, Modification 2 of the above embodiment will be described. This modification differs from the above embodiment in the method of supplying the lubricant to the image carrier 21. Hereinafter, differences from the above embodiment will be described.

FIG. 10 is a schematic diagram showing a configuration of the image forming unit U in the present modification.
The image forming unit U of this modification is not provided with the lubricant supply unit 22, and the lubricant is supplied onto the image carrier 21 by the developing unit 27. That is, a developer containing toner and lubricant particles is supplied to the developing unit 27, and the developing unit 27 supplies the lubricant onto the image carrier 21 in the same manner as the toner supply. The developing unit 27 supplies more lubricant per unit time to the image carrier 21 as the lubricant storage amount in the developing unit 27 increases. Therefore, in this modification, the amount of lubricant on the image carrier 21 can be estimated based on the amount of lubricant stored in the developing unit 27, and the lubricant information in this modification is stored in the developing unit 27. This is information relating to the amount of lubricant stored.

  Lubricant particles supplied to the developing unit 27 are normally charged with a polarity opposite to that of the toner, and are supplied in a large amount to a white part (an area other than the electrostatic latent image area to which the toner adheres) in the formed image. For this reason, the larger the proportion of the white portion in the formed image, that is, the smaller the printing rate, the greater the amount of lubricant supplied. Therefore, the current amount of lubricant stored in the developing unit 27 (that is, the amount of lubricant on the image carrier 21) can be estimated based on the printing rate in the most recent predetermined number of image formations. For this reason, in this modification, the printing rate in the most recent predetermined number of image formations is used as the lubricant information.

Instead of the above, the amount of lubricant may be estimated based on the torque on the rotation shaft of the image carrier 21.
Although not shown in FIG. 10, a toner recovery member may be disposed upstream of the cleaning unit 23. The toner recovery member presses the cleaning member against the image carrier 21 and rotates to assistly remove the toner in front of the cleaning unit 23. A brush is suitable as the cleaning member, but a sponge may be used.

As described above, the image forming apparatus 1 according to the present embodiment transfers the toner image obtained by developing the electrostatic latent image on the surface of the image carrier 21 to the transfer member and places the toner image on the transfer member. In the image forming apparatus 1 for forming an image, an image carrier 21 that rotates about a predetermined rotation axis, and a cleaning unit that contacts the surface of the image carrier 21 and removes foreign matter on the image carrier 21 23, a charging roller 25 that contacts the surface of the image carrier 21 and rotates as the image carrier 21 rotates, and charges the surface of the image carrier 21 when a predetermined voltage is applied. A charging roller cleaning unit 252 that contacts the surface of the charging roller 25 to remove foreign matter on the charging roller 25, a cleaning drive unit 2521 that changes the size of the foreign matter removal capability of the charging roller cleaning unit 252, and the image carrier 21. Supply lubricant to the surface The lubricant supply unit 22 and the control unit 10 acquire the lubricant information relating to the amount of lubricant on the surface of the image carrier 21 (lubricant information acquisition means), and are acquired. The operation of the cleaning drive unit 2521 is controlled so as to satisfy the relationship in which the magnitude of the removal capability gradually increases according to the decrease in the amount of lubricant based on the lubricant information (control means).
In such a configuration, the amount of foreign matter adhering to the charging roller 25 has a negative correlation with the amount of lubricant on the surface of the image carrier 21. Therefore, by controlling the magnitude of the removal capability as described above, the removal capability of the foreign matter is reduced when the amount of foreign matter adhering to the charging roller 25 is small, and the charging roller cleaning unit 252 and the charging roller 25 It is possible to prevent the surface of the charging roller 25 from being worn by rubbing and to prevent the deterioration of the charging roller 25 at an early stage, thereby extending the life. Further, when the amount of foreign matter adhering to the charging roller 25 is small, the foreign matter removal capability can be increased, and the foreign matter on the charging roller 25 can be more reliably removed. As a result, it is possible to achieve both suppression of image quality defects in the recorded image and high durability of the charging roller 25.

  The lubricant supply unit 22 performs a supply operation of scraping the lubricant from the solid lubricant 221 and supplying the lubricant to the surface of the image carrier 21. In the supply operation, the supply of the lubricant using the solid lubricant 221 is performed. Lubricant is supplied in such a manner that the amount of lubricant scraped from the solid lubricant 221 per predetermined time decreases as the total time performed increases, and the lubricant information is information related to the length of the total time. Therefore, the control unit 10 determines that the amount of lubricant is smaller as the total time based on the lubricant information is longer (control means). According to this, the amount of the lubricant can be estimated by an easy process of obtaining the total time, and the foreign matter removing ability by the charging roller cleaning unit 252 can be appropriately adjusted.

  The lubricant information is information relating to the number of times images are formed on the transfer member during the period in which the lubricant supply unit 22 supplies the lubricant using the solid lubricant 221. According to this, the amount of the lubricant can be estimated by an easy process of acquiring the number of image formations, and the foreign matter removal capability of the charging roller cleaning unit 252 can be appropriately adjusted.

  The lubricant information is information relating to torque for rotating the image carrier 21 against the frictional force between the surface of the image carrier 21 and the cleaning unit 23, and the control unit 10 It is determined that the smaller the torque based on the information, the smaller the amount of lubricant (control means). According to this, the amount of lubricant can be estimated by an easy process of acquiring torque, and the foreign matter removal ability of the charging roller cleaning unit 252 can be adjusted appropriately.

  The image forming apparatus 1 is provided on the downstream side of the charging roller 25 in the moving direction of the surface of the rotating image carrier 21, and exposes the surface of the charged image carrier 21 to form an electrostatic latent image. The toner is supplied to the surface of the image carrier 21 and the electrostatic latent image is developed to form a toner image on the surface of the image carrier 21. At least a part of the developing unit 27, a transfer unit 28 that is provided on the downstream side of the developing unit 27 in the moving direction and transfers the toner image to the transfer target member, the charging roller 25, the lubricant supply unit 22, and the transfer unit 28. A moving unit 201 that moves between a first position that contacts the surface of the image carrier 21 and a second position that is separated from the surface of the image carrier 21, and a torque measuring unit 212 that measures torque. , The control unit 10 is torque When the torque is measured by the fixing unit 212 to acquire the lubricant information and the torque is measured by the torque measuring unit, at least a part of the charging roller 25, the lubricant supply unit 22, and the transfer unit 28 is moved by the moving unit 201. Move to the second position (lubricant information acquisition means). Thereby, since the number of members in contact with the image carrier 21 at the time of torque measurement can be reduced, the drag exerted on the image carrier 21 by the cleaning unit 23 can be more accurately reflected on the measured torque. Can do. Therefore, the amount of the lubricant on the image carrier 21 can be estimated more accurately based on the torque measurement result.

  The moving unit 201 moves the transfer unit 28 between the first position and the second position, and the control unit 10 moves at least the transfer unit 28 by the moving unit 201 when the torque is measured by the torque measuring unit. Move to the second position (lubricant information acquisition means). According to this, since it is possible to eliminate the influence of the transfer unit 28 having the greatest drag on the image carrier 21 except for the cleaning unit 23 on the measured torque value, the transfer unit 28 can be more accurately based on the torque measurement result. In addition, the amount of lubricant on the image carrier 21 can be estimated.

  The cleaning unit 23 is provided between the transfer unit 28 and the charging roller 25 in the moving direction, and the lubricant supply unit 22 is provided between the transfer unit 28 and the charging roller cleaning unit 252 in the moving direction. It has been. According to such a configuration, when the lubricant is excessively supplied by the lubricant supply unit 22, the lubricant can be collected by the cleaning unit 23 before the charging roller 25. Occurrence of defects that are contaminated by the lubricant can be suppressed.

  The developing unit 27 is a lubricant supply unit 22 that supplies the lubricant stored in the developing unit 27 to the surface of the image carrier 21. The lubricant information includes the amount of lubricant stored in the developing unit 27. The control unit 10 determines that the larger the amount of lubricant stored based on the lubricant information, the greater the amount of lubricant on the surface of the image carrier 21 (control means). According to this, the amount of lubricant can be estimated by an easy process of acquiring the amount of lubricant stored in the developing unit 27, and the foreign matter removal capability of the charging roller cleaning unit 252 can be adjusted appropriately.

  In addition, the developing unit 27 decreases the supply amount of the lubricant to the image carrier 21 in the formation of the one image as the printing rate related to the supply amount of the toner to the image carrier 21 in the formation of the one image is smaller. The lubricant is supplied in many modes, and the control unit 10 acquires the lubricant information based on the printing rate in the most recent predetermined number of image formations (lubricant information acquisition means). According to this, the amount of the lubricant can be estimated by an easy process of acquiring the printing rate, and the foreign matter removing ability by the charging roller cleaning unit 252 can be appropriately adjusted.

  The cleaning drive unit 2521 is removed by changing at least one of the relative movement speed between the surface of the charging roller cleaning unit 252 and the surface of the charging roller 25 and the pressure exerted on the charging roller 25 by the charging roller cleaning unit 252. Change the size of the ability. Thereby, the magnitude | size of removal capability can be changed easily and reliably by changing operation | movement of the charging roller cleaning part 252. FIG.

  Further, the charging roller cleaning unit 252 rotates so that the surface of the charging roller cleaning unit 252 rubs against the surface of the charging roller 25, and the cleaning driving unit 2521 has at least one of the rotation speed and the rotation direction of the cleaning roller 252a. The relative movement speed is changed by changing. Thereby, the magnitude | size of removal capability can be changed easily and reliably with the simple method of changing the rotational speed and rotation direction of the cleaning roller 252a.

  In addition, the control unit 10 sets a print rate related to the amount of toner supplied in the formation of one image for each of a plurality of divided regions obtained by dividing the toner image forming region in the image carrier 21 in the direction of the rotation axis. An integrated print rate is acquired based on at least one of a value integrated over the number of image formations and a value obtained by integrating the print rate over a predetermined number of image formations (integrated print rate acquisition means). The operation of the cleaning drive unit 2521 is controlled so that the relationship in which the magnitude of the removal capability of the charging roller cleaning unit 252 gradually increases as the maximum value of the plurality of integrated print ratios corresponding to the plurality of regions c increases is satisfied. (Control means). Thereby, even when a foreign substance adheres to a part of the rotation axis direction of the charging roller 25, the removal capability of the charging roller cleaning unit 252 is appropriately adjusted to keep the contamination amount of the charging roller 25 below a desired amount. be able to.

  In addition, the control unit 10 satisfies the relationship in which the magnitude of the removal capability of the charging roller cleaning unit 252 gradually increases in accordance with an increase in the difference between the maximum value and the minimum value in a plurality of integrated printing rates corresponding to a plurality of divided regions. Thus, the operation of the cleaning drive unit 2521 is controlled (control means). Thereby, the dispersion | variation in the adhesion amount of the foreign material on the charging roller 25 can be suppressed in a predetermined range about the rotation axis direction. As a result, the occurrence of density unevenness in the formed image can be suppressed.

  Further, the control unit 10 satisfies a relationship in which the magnitude of the removal capability of the charging roller cleaning unit 252 gradually increases in accordance with the increase in the maximum value of the difference between the integrated printing rates in the divided areas adjacent in the direction of the rotation axis. The operation of the cleaning drive unit 2521 is controlled (control means). When the adhering amount of the external additive is different between the adjacent regions c, and the charging potential is thereby different, the density difference in the formed image appears remarkably due to the edge effect. The occurrence of poor image quality due to such a density difference can be suppressed.

  The control program of the present embodiment is acquired by the lubricant information acquisition unit that acquires the lubricant information related to the amount of lubricant on the surface of the image carrier 21 by the control unit 10 provided in the image forming apparatus 1. The control unit controls the operation of the cleaning drive unit 2521 so that the relationship in which the magnitude of the removal capability gradually increases according to the decrease in the amount of lubricant based on the lubricant information is satisfied. Thereby, the foreign matter on the charging roller 25 can be more reliably removed while suppressing the deterioration of the charging roller 25. Therefore, it is possible to achieve both high durability of the charging roller 25 and suppression of image quality defects in the recorded image.

Note that the present invention is not limited to the above-described embodiments and modifications, and various modifications can be made.
For example, in the above-described embodiment and each modification, the total time of supplying the lubricant from the solid lubricant 221, the torque of the rotation shaft of the image carrier 21, or the amount of lubricant stored in the developing unit 27 in Modification 2 is used. Based on this, the amount of lubricant on the image carrier 21 is estimated to obtain the lubricant information. However, the method for estimating the amount of lubricant is not limited to this, and there is a correlation with the amount of lubricant. The amount of lubricant may be estimated using any factor. Alternatively, the amount of lubricant on the image carrier 21 may be directly measured, and the measurement result may be used as lubricant information.

  In the said embodiment and each modification, although demonstrated using the example which acquires cleaning conditions by referring table data using lubricant information, it is not restricted to this, For example, cleaning conditions every time based on lubricant information May be calculated.

  In the above embodiment and each modification, the removal capability is increased by changing at least one of the relative movement speed between the surface of the cleaning roller 252a and the surface of the charging roller 25 and the pressure exerted on the charging roller 25 by the cleaning roller 252a. However, the present invention is not limited to this, and the removal capability may be changed by another method.

  Although several embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, and includes the scope of the invention described in the claims and equivalents thereof. .

1 Image forming apparatus 10 Control unit (lubricant information acquisition means, control means, integrated printing rate acquisition means, computer)
DESCRIPTION OF SYMBOLS 20 Image formation part 21 Image carrier 211 Image carrier drive part 212 Torque measurement part 22 Lubricant supply part 221 Solid lubricant 222 Lubricant application member 223 Application member cleaning roller 23 Cleaning part (image carrier cleaning part)
24 Eraser 25 Charging roller (Charging member)
252 Charging roller cleaning unit (charging member cleaning unit)
252a Cleaning roller 252b Foreign matter removal roller 252c Eccentric cam 2521 Cleaning drive unit (removal capability changing means)
26 Exposure unit 27 Development unit 28 Transfer unit 29 Fixing unit 201 Moving unit (moving means)
c, c1 to cn region (partition region)
R toner image forming region U image forming unit

Claims (15)

An image forming apparatus for transferring a toner image obtained by developing an electrostatic latent image on the surface of an image carrier to a member to be transferred and forming an image on the member to be transferred,
The image carrier rotating about a predetermined rotation axis;
An image carrier cleaning unit that contacts the surface of the image carrier and removes foreign matter on the image carrier;
A charging member that contacts the surface of the image carrier and rotates as the image carrier rotates, and charging the surface of the image carrier by applying a predetermined voltage;
A charging member cleaning unit that contacts the surface of the charging member to remove foreign matter on the charging member;
A removal capability changing means for changing the size of the foreign matter removal capability by the charging member cleaning section;
A lubricant supply unit for supplying a lubricant to the surface of the image carrier;
Lubricant information acquisition means for acquiring lubricant information related to the amount of lubricant on the surface of the image carrier;
The operation of the removal capacity changing unit is performed so that a relationship in which the magnitude of the removal capacity gradually increases according to a decrease in the amount of the lubricant based on the lubricant information acquired by the lubricant information acquisition unit is satisfied. Control means for controlling;
An image forming apparatus comprising: The lubricant supply unit performs a supply operation of scraping the lubricant from a solid lubricant and supplying it to the surface of the image carrier,
In the supply operation, the amount of the lubricant scraped from the solid lubricant per predetermined time decreases as the total time for which the lubricant is supplied using the solid lubricant increases. Supply lubricant,
The lubricant information is information relating to the length of the total time,
The image forming apparatus according to claim 1, wherein the control unit determines that the amount of the lubricant is smaller as the total time based on the lubricant information is longer.   The lubricant information is information relating to the number of times images are formed on a transfer member during a period in which the lubricant supply unit using the solid lubricant is supplied by the lubricant supply unit. Item 3. The image forming apparatus according to Item 2. The lubricant information is information relating to a torque for rotating the image carrier against a frictional force between the surface of the image carrier and the image carrier cleaning unit,
The image forming apparatus according to claim 1, wherein the control unit determines that the amount of the lubricant is smaller as the torque based on the lubricant information is smaller. An exposure unit provided on the downstream side of the charging member with respect to the moving direction of the surface of the rotating image carrier, and exposing the charged surface of the image carrier to form an electrostatic latent image;
A developing unit that is provided on the downstream side of the exposure unit in the moving direction and that develops the electrostatic latent image by supplying toner to the surface of the image carrier to form a toner image on the surface of the image carrier. When,
A transfer unit provided on the downstream side of the developing unit with respect to the moving direction and transferring the toner image to a transfer member;
At least a part of the charging member, the lubricant supply unit, and the transfer unit is moved between a first position where the charging member, the lubricant supply unit, and the transfer unit are in contact with the surface of the image carrier and a second position separated from the surface of the image carrier. Moving means to cause
A torque measuring unit for measuring the torque;
With
The lubricant information acquisition unit acquires the lubricant information by measuring the torque by the torque measurement unit, and when the torque measurement unit measures the torque, the moving unit causes the charging member, The image forming apparatus according to claim 4, wherein the at least part of the lubricant supply unit and the transfer unit is moved to the second position. The moving means moves the transfer unit between the first position and the second position,
The image forming apparatus according to claim 5, wherein the lubricant information acquiring unit moves at least the transfer unit to the second position by the moving unit when the torque measuring unit measures the torque. apparatus. An exposure unit provided on the downstream side of the charging member with respect to the moving direction of the surface of the rotating image carrier, and exposing the charged surface of the image carrier to form an electrostatic latent image;
A developing unit that is provided on the downstream side of the exposure unit in the moving direction and that develops the electrostatic latent image by supplying toner to the surface of the image carrier to form a toner image on the surface of the image carrier. When,
A transfer unit provided on the downstream side of the developing unit with respect to the moving direction and transferring the toner image to a transfer member;
With
The image carrier cleaning unit is provided between the transfer unit and the charging member in the moving direction,
The image forming apparatus according to claim 1, wherein the lubricant supply unit is provided between the transfer unit and the image carrier cleaning unit in the moving direction. . An exposure unit provided on the downstream side of the charging member with respect to the moving direction of the surface of the rotating image carrier, and exposing the charged surface of the image carrier to form an electrostatic latent image;
A developing unit that is provided on the downstream side of the exposure unit in the moving direction and that develops the electrostatic latent image by supplying toner to the surface of the image carrier to form a toner image on the surface of the image carrier. When,
A transfer unit provided on the downstream side of the developing unit with respect to the moving direction and transferring the toner image to a transfer member;
With
The developing unit is the lubricant supply unit that supplies the lubricant stored in the developing unit to the surface of the image carrier,
The lubricant information is information relating to a storage amount of the lubricant in the developing unit,
2. The image formation according to claim 1, wherein the control unit determines that the amount of the lubricant on the surface of the image carrier increases as the amount of the lubricant stored based on the lubricant information increases. apparatus. In the developing unit, the smaller the printing rate related to the amount of toner supplied to the image carrier in the formation of one image, the larger the amount of lubricant supplied to the image carrier in the formation of the one image. Supplying the lubricant in the form of
The image forming apparatus according to claim 8, wherein the lubricant information acquiring unit acquires the lubricant information based on the printing rate in the most recent predetermined number of image formations.   The removal capability changing means changes the removal by changing at least one of a relative moving speed between the surface of the charging member cleaning unit and the surface of the charging member and a pressure exerted on the charging member by the charging member cleaning unit. The image forming apparatus according to claim 1, wherein the capacity is changed. The charging member cleaning unit rotates so that the surface of the charging member cleaning unit rubs the surface of the charging member,
The image forming apparatus according to claim 10, wherein the removal capability changing unit changes the relative movement speed by changing at least one of a rotation speed and a rotation direction of the charging member cleaning unit. For each of a plurality of divided areas obtained by dividing the toner image forming area of the image carrier in the direction of the rotation axis, the printing rate related to the amount of toner supplied in the formation of one image is formed in the past predetermined number of times. An integrated print rate acquisition means for acquiring an integrated print rate based on at least one of a value integrated over a predetermined number of times of image formation and a value obtained by integrating the print rate over a predetermined number of times of image formation;
The control means removes the removal so that a relationship in which the magnitude of the removal capability of the charging member cleaning unit gradually increases in accordance with an increase in the maximum value of the plurality of integrated print rates corresponding to the plurality of divided regions is satisfied. The image forming apparatus according to claim 1, wherein the operation of the capability changing unit is controlled. For each of a plurality of divided areas obtained by dividing the toner image forming area of the image carrier in the direction of the rotation axis, the printing rate related to the amount of toner supplied in the formation of one image is formed in the past predetermined number of times. An integrated print rate acquisition means for acquiring an integrated print rate based on at least one of a value integrated over a predetermined number of times of image formation and a value obtained by integrating the print rate over a predetermined number of times of image formation;
The control means has a relationship in which the magnitude of the removal capability of the charging member cleaning unit gradually increases in accordance with an increase in the difference between the maximum value and the minimum value in the plurality of integrated printing rates corresponding to the plurality of divided regions. The image forming apparatus according to claim 1, wherein the operation of the removal capability changing unit is controlled so as to be satisfied. For each of a plurality of divided areas obtained by dividing the toner image forming area of the image carrier in the direction of the rotation axis, the printing rate related to the amount of toner supplied in the formation of one image is formed in the past predetermined number of times. An integrated print rate acquisition means for acquiring an integrated print rate based on at least one of a value integrated over a predetermined number of times of image formation and a value obtained by integrating the print rate over a predetermined number of times of image formation;
The control unit satisfies a relationship in which the magnitude of the removal capability of the charging member cleaning unit gradually increases in accordance with an increase in the maximum value of the difference in the integrated printing rate in the divided areas adjacent to each other in the direction of the rotation axis. The image forming apparatus according to claim 1, wherein the operation of the removal capability changing unit is controlled as described above. An image carrier that rotates about a predetermined rotation axis, an image carrier cleaning unit that abuts on the surface of the image carrier to remove foreign matter on the image carrier, and abuts on the surface of the image carrier A charging member that rotates with the rotation of the image carrier and applies a predetermined voltage to charge the surface of the image carrier, and contacts the surface of the charging member to remove foreign matter on the charging member. A charging member cleaning unit to be removed; a removal capability changing means for changing the magnitude of the foreign substance removal capability by the charging member cleaning unit; and a lubricant supply unit for supplying a lubricant to the surface of the image carrier. A computer provided in an image forming apparatus for transferring a toner image obtained by developing an electrostatic latent image on the surface of the image carrier to a member to be transferred to form an image on the member to be transferred;
Lubricant information acquisition means for acquiring lubricant information related to the amount of lubricant on the surface of the image carrier,
The operation of the removal capacity changing unit is performed so that a relationship in which the magnitude of the removal capacity gradually increases according to a decrease in the amount of the lubricant based on the lubricant information acquired by the lubricant information acquisition unit is satisfied. Control means for controlling,
A program characterized by functioning as

Images