JP6531482B2 - Image forming apparatus, image forming system, and lubricant supplying method - Google Patents

Description

  The present invention relates to an image forming apparatus, an image forming system, and a lubricant replenishment method.

  In an electrophotographic image forming apparatus, as a means for removing residual toner such as untransferred toner and transfer residual toner on an image carrier (for example, a photosensitive member), for example, cleaning of a flat plate made of an elastic body There is known a cleaning device of a blade cleaning system in which a blade is brought into contact with the surface of an image carrier to remove residual toner on the image carrier.

  In recent years, there has been a demand for reducing the particle size of toner particles from the viewpoint of achieving high image quality, and as a method for obtaining such toner particles, for example, polymerization methods such as emulsion polymerization and suspension polymerization are used. However, since the adhesion between the toner particles and the image carrier increases as the toner particles become smaller, it becomes difficult to remove the residual toner on the image carrier. In particular, in the case of using a so-called polymerized toner produced by a polymerization method, the toner particles are close to spherical in shape, so that the cleaning failure occurs in which the toner particles pass through the rolling cleaning blade on the image carrier. There is a problem that it becomes easy and it becomes more difficult to remove the residual toner on the image carrier.

  In addition, when toner that slips off the cleaning blade is generated, toner aggregates are formed on the image carrier with the toner as a nucleus, and granular white spots (hereinafter referred to as "raindrops") occur in the beta image printed portion. . In order to cope with such quality problems such as "raindrops", a lubricant is currently supplied on the image carrier, and a film of the lubricant is formed to reduce the adhesion between the toner particles and the image carrier. I am cleaning. As a method of supplying a lubricant on the image carrier, a lubricant application method in which a brush is brought into contact with a rod-like lubricant, the lubricant is scraped off by the brush, and supplied to the surface of the image carrier, and a lubricant external additive (lubricant) There is an external toner addition system in which a toner image is formed by the toner contained to supply a lubricant.

  The toner external addition method is advantageous in terms of installation space and cost, since an application device such as a lubricant rod or a brush is not required as compared with the lubricant application method. However, in the toner external addition method, the amount of lubricant in the developing device fluctuates depending on the amount of consumption of toner, and as a result, the amount of lubricant coated on the image carrier fluctuates. Specifically, when printing an image with a low printing rate, only the lubricant released from the toner is preferentially consumed in the background portion, and new toner (lubricant) is not supplied to the developing device. Therefore, eventually, the supply and discharge balance and stabilize in a state where the amount of lubricant in the developing device is reduced. The lubricant on the image carrier can also be kept at a constant level initially, since only lubricant is supplied. However, when the amount of lubricant in the developing device decreases, the amount of lubricant supplied to the surface of the image carrier and hence the coverage decrease, making it impossible to reduce the amount of adhesion between the toner particles and the image carrier and causing raindrops. Lead to

  At present, after printing an image having a low printing rate, a toner patch image is formed on the image carrier outside the image forming area in order to maintain the amount of lubricant in the developing device. When the toner patch image is formed, the toner in the developing device is consumed and new toner is supplied to the developing device. When the toner is replenished, the lubricant is also replenished with the toner, so that the decrease in the amount of lubricant in the developing device can be suppressed. As a result, reduction in the amount of lubricant on the image carrier can be suppressed.

  Patent Document 1 discloses a contact transfer type image forming apparatus in which the amount of lubricant on the surface of the photosensitive member is maintained to improve the cleaning performance without the need to improve the cleaning performance of the transfer portion (transfer belt). It is disclosed. In the technology described in Patent Document 1, a toner image based on a patch for forcibly discharging a toner is formed on a non-image area of a photosensitive member using a toner added with a lubricant that makes the surface of the photosensitive member slippery. When the non-image area abuts on the transfer belt, the transfer belt is switched to the same polarity as the toner to prevent the transfer of the toner image onto the transfer belt.

JP 2011-7831 A

  However, even if the lubricant is supplied onto the photoreceptor by forming a toner patch image, the lubricant is scraped off by the cleaning blade in contact with the photoreceptor. Although the amount of lubricant scraped off by the cleaning blade can be reduced by reducing the charge amount of the toner patch image, the fact that the lubricant is scraped off by the cleaning blade does not change the fact that the toner patch image passes through the cleaning blade As a result, the amount of lubricant on the photoreceptor is reduced. Therefore, in order to stabilize the amount of lubricant on the photosensitive member at a certain level, there is a problem that the amount of toner patch image formed, that is, the amount of consumed toner for replenishing the lubricant to the photosensitive member is increased.

  An object of the present invention is to provide an image forming apparatus, an image forming system, and a lubricant replenishing method capable of suppressing a toner consumption amount for replenishing a lubricant to an image bearing member.

The image forming apparatus according to the present invention is
A rotatable first image carrier,
A toner image is formed on the first image carrier using a toner to which a lubricant is added, and the toner image is applied to the second image carrier by applying a transfer bias when the toner image passes through the transfer nip. An image forming unit to be transferred;
A toner patch image forming unit for forming a toner patch image on the first image carrier using the toner to which the lubricant is added according to the image formation history by the image forming unit;
A cleaning member that abuts on the first image carrier and removes toner remaining on the first image carrier without being transferred to the second image carrier;
An abutment / separating portion that abuts or separates the cleaning member from the first image carrier;
A control unit configured to control the contact / separation portion to separate the cleaning member from the first image carrier before the toner patch image formed on the first image carrier reaches the cleaning member; ,
Equipped with

An image forming system according to the present invention is
An image forming system comprising a plurality of units including an image forming apparatus, comprising:
A rotatable first image carrier,
A toner image is formed on the first image carrier using a toner to which a lubricant is added, and the toner image is applied to the second image carrier by applying a transfer bias when the toner image passes through the transfer nip. An image forming unit to be transferred;
A toner patch image forming unit for forming a toner patch image on the first image carrier using the toner to which the lubricant is added according to the image formation history by the image forming unit;
A cleaning member that abuts on the first image carrier and removes toner remaining on the first image carrier without being transferred to the second image carrier;
An abutment / separating portion that abuts or separates the cleaning member from the first image carrier;
A control unit configured to control the contact / separation portion to separate the cleaning member from the first image carrier before the toner patch image formed on the first image carrier reaches the cleaning member; ,
Equipped with

The lubricant replenishing method according to the present invention is
A rotatable first image carrier,
A toner image is formed on the first image carrier using a toner to which a lubricant is added, and the toner image is applied to the second image carrier by applying a transfer bias when the toner image passes through the transfer nip. An image forming unit to be transferred;
A toner patch image forming unit for forming a toner patch image on the first image carrier using the toner to which the lubricant is added according to the image formation history by the image forming unit;
A cleaning member that abuts on the first image carrier and removes toner remaining on the first image carrier without being transferred to the second image carrier;
An abutment / separating portion that abuts or separates the cleaning member from the first image carrier;
A lubricant supplying method in an image forming apparatus having the
Before the toner patch image formed on the first image carrier reaches the cleaning member, the contact and separation portion is controlled to separate the cleaning member from the first image carrier.

  According to the present invention, since the cleaning member is separated from the first image carrier before the toner patch image formed on the first image carrier reaches the cleaning member, the lubricant in the toner patch image is separated by the cleaning member. Can be prevented from being scraped off. Therefore, the amount of toner patch image formation necessary to stabilize the amount of lubricant on the first image carrier at a certain level, that is, the amount of toner consumed for replenishing the lubricant to the first image carrier is suppressed. Can.

FIG. 1 schematically shows an entire configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing a main part of a control system of the image forming apparatus in the present embodiment. 3A and 3B schematically show a partial configuration of the image forming apparatus in the present embodiment. It is a flowchart which shows lubricant supply operation | movement of the image forming apparatus in this Embodiment. FIG. 6 is a view showing the amount of lubricant when the drum cleaning blade is in contact with and separated from the photosensitive drum. It is explanatory drawing explaining the behavior of the lubricating agent supplied to a drum cleaning blade. FIG. 7A is a view showing the operation of the photosensitive member and the developing roller during development, and FIG. 7B is a view showing the operation of the photosensitive member and the rubber roller during transfer. It is a figure which shows the amount of lubricants and the transfer efficiency on the photoreceptor according to the transfer voltage.

  Hereinafter, the present embodiment will be described in detail based on the drawings. FIG. 1 is a view schematically showing an entire configuration of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 2 shows the main part of the control system of the image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 shown in FIGS. 1 and 2 is an intermediate transfer type color image forming apparatus using an electrophotographic process technology. That is, the image forming apparatus 1 includes Y (yellow), M (magenta), C (cyan), and K (black) formed on the photosensitive drum 413 (corresponding to the “first image carrier” of the present invention). The toner images of each color are transferred (primary transfer) onto the intermediate transfer belt 421 (corresponding to the “second image carrier” of the present invention), and the four color toner images are superimposed on the intermediate transfer belt 421. (Secondary transfer) to form an image.

  Further, in the image forming apparatus 1, photosensitive drums 413 corresponding to four colors of Y, M, C, and K are arranged in series in the traveling direction of the intermediate transfer belt 421, and each color toner image is sequentially transferred onto the intermediate transfer belt 421 in one procedure. A tandem system is adopted.

  As shown in FIG. 2, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a sheet conveyance unit 50, a fixing unit 60, and a control unit 100.

  The control unit 100 includes a central processing unit (CPU) 101, a read only memory (ROM) 102, a random access memory (RAM) 103, and the like. The CPU 101 reads out a program corresponding to the processing content from the ROM 102, develops it in the RAM 103, and cooperates with the developed program to centrally control the operation of each block of the image forming apparatus 1. At this time, various data stored in the storage unit 72 are referred to. The storage unit 72 includes, for example, a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive. In the present embodiment, the storage unit 72 stores history information indicating the toner image formation history (corresponding to “image formation history” of the present invention) by the image forming unit 40. The history information includes information such as the number of printed sheets and the printing rate.

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

  The image reading unit 10 includes an automatic document feeder 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.

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

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

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

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

  The image forming unit 40 forms an image forming unit 41 Y, 41 M, 41 C, 41 K, and an intermediate transfer unit 42 for forming an image with each color toner of Y component, M component, C component and K component based on input image data. Etc. The image forming unit 40 corresponds to the “image forming unit” and the “toner patch image forming unit” in the present invention.

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

  The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, a charge amount adjustment unit 416, and the like.

  The photosensitive drum 413 is made of, for example, an organic photosensitive member in which a photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of a drum-like metal base. 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, melamine resin and the like.

  The control unit 100 controls a drive current supplied to a drive motor (not shown) for rotating the photosensitive drum 413, whereby the photosensitive drum 413 rotates at a constant circumferential speed.

  The charging device 414 is, for example, a charger and generates corona discharge to uniformly charge the surface of the photoconductive photosensitive drum 413 to a negative polarity (for example, -500 [V]: background portion). Let

  The exposure device 411 is formed of, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with a laser beam corresponding to the image of each color component. As a result, an electrostatic latent image of each color component is formed on the image portion of the surface of the photosensitive drum 413 irradiated with the laser light due to the potential difference (for example, -450 [V]) with the background portion.

  The developing device 412 is a developing device of a two-component reverse type, and makes the toner of each color component adhere to the surface of the photosensitive drum 413 to visualize the electrostatic latent image to form a toner image. In the present embodiment, a lubricant having lubricity is added to the toner. Examples of the lubricant include fatty acid metal salts, silicone oils, fluorine resins and the like, and these can be used singly or in combination of two or more. In particular, fatty acid metal salts are preferred. As the fatty acid, linear hydrocarbons are preferable, and for example, myristic acid, palmitic acid, stearic acid, oleic acid and the like are preferable, and stearic acid is more preferable. Examples of the metal include lithium, magnesium, calcium, strontium, zinc, cadmium, aluminum, cerium, titanium, iron and the like. Among these, zinc stearate, magnesium stearate, aluminum stearate, iron stearate and the like are preferable, and in particular, zinc stearate is most preferable. In the present embodiment, 0.2 parts by weight of zinc stearate is added to the weight of the toner.

  The developing device 412 includes a developing sleeve 412A disposed to face the photosensitive drum 413 via the developing region. For example, a DC developing bias (for example, -400 [V]) having the same polarity as the charging polarity of the charging device 414 or a DC voltage having the same polarity as the charging polarity of the charging device 414 is superimposed on the developing sleeve 412A. A development bias is applied. As a result, reverse development is performed in which toner is attached to the electrostatic latent image formed by the exposure device 411.

  The drum cleaning device 415 includes a flat drum cleaning blade 415A (corresponding to the “cleaning member” of the present invention) made of an elastic material, which is in contact with the surface of the photosensitive drum 413, and is transferred to the intermediate transfer belt 421. Toner remaining on the surface of the photosensitive drum 413 without being removed.

  Examples of physical properties of the drum cleaning blade 415A include impact resilience and hardness. The rebound resilience is preferably 10 to 80 [%] at a temperature of 25 [[deg.] C.], and more preferably 30 to 70 [%]. Further, JISA hardness is preferably 20 to 90 [°], and particularly preferably 60 to 80 [°]. If the JISA hardness is less than 20 [.degree.], The drum cleaning blade 415A is too soft and it is easy for the blade to come off. On the other hand, when the JISA hardness is greater than 90 [.degree.], It becomes difficult to follow slight irregularities or foreign matter on the photosensitive drum 413, and toner particles easily slip through. The contact load of the drum cleaning blade 415A with respect to the photosensitive drum 413 is preferably 0.1 to 40 [N / m], and more preferably 1 to 25 [N / m]. If the contact load is less than 0.1 [N / m], the cleaning power is insufficient and the image is likely to be stained. On the other hand, when the contact load is larger than 40 [N / m], the frictional force between the drum cleaning blade 415A and the photosensitive drum 413 becomes large, and image blurring or the like is easily generated. The contact load can be measured by pressing the tip edge of the drum cleaning blade 415A against the balance and placing a sensor such as a load cell at the contact position of the tip edge of the drum cleaning blade 415A against the photosensitive drum 413. The method of measuring electrically etc. is used.

  The charge amount adjustment unit 416 is provided on the upstream side of the drum cleaning blade 415 A in the rotational direction of the photosensitive drum 413 and on the downstream side of the primary transfer nip, and is not transferred to the intermediate transfer belt 421. Adjust the amount of charge on the toner remaining on the The charge amount adjustment unit 416 is a corotron charger using corona discharge, a scorotron charger, a discharging needle using a discharging needle, a non-woven fabric or the like, or an electrode or roller facing a photosensitive drum 413 with a minute gap. Alternatively, any roller such as a contact roller may be used as long as it can adjust the charge amount of the toner. The voltage applied when adjusting the charge amount may be any one of a DC voltage, an AC voltage, and a DC voltage on which an AC voltage is superimposed. Further, since the charge amount adjustment unit 416 is a means for adjusting the charge amount of toner reaching the drum cleaning blade 415A, the downstream side of the developing device 412 and the upstream side of the drum cleaning blade 415A in the rotational direction of the photosensitive drum 413 If it is, it may be arranged at any position.

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

  The intermediate transfer unit 42 is configured by an endless belt, and is stretched around a plurality of support rollers 423 in a loop. At least one of the plurality of support rollers 423 is configured by a drive roller, and the other is configured by a driven roller. For example, it is preferable that the roller 423A disposed downstream of the primary transfer roller 422 for the component K in the belt traveling direction is a driving roller. This makes it easy to keep the running speed of the belt in the primary transfer nip constant. As the drive roller 423A rotates, the intermediate transfer belt 421 travels at a constant speed in the arrow A direction.

  The intermediate transfer belt 421 is a belt having conductivity and elasticity, and has on its surface a high resistance layer having a volume resistivity of 8 to 11 [log Ω · cm]. The intermediate transfer belt 421 is rotationally driven by a control signal from the control unit 100. The material, thickness and hardness of the intermediate transfer belt 421 are not limited as long as they have conductivity and elasticity.

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

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

  When the intermediate transfer belt 421 passes through the primary transfer nip, the toner image on the photosensitive drum 413 is sequentially superimposed on the intermediate transfer belt 421 and primarily transferred. Specifically, the toner image is formed by applying a primary transfer bias to the primary transfer roller 422 and applying charges of the reverse polarity to the toner on the back side of the intermediate transfer belt 421 (the side that contacts the primary transfer roller 422). The toner image is electrostatically transferred to the intermediate transfer belt 421.

  Thereafter, when the sheet S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the sheet S. Specifically, a secondary transfer bias is applied to the secondary transfer roller 424, and a charge having a polarity opposite to that of the toner is applied to the back side of the sheet S (the side that contacts the secondary transfer roller 424). Is electrostatically transferred to the sheet S. The sheet S on which the toner image has been transferred is conveyed toward the fixing unit 60.

  The belt cleaning device 426 removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer. Here, instead of the secondary transfer roller 424, a configuration in which the secondary transfer belt is stretched in a loop shape (a so-called secondary transfer unit of a belt type) is adopted to a plurality of support rollers including the secondary transfer roller. Also good.

  The fixing unit 60 includes an upper fixing unit 60A having a fixing surface side member disposed on the fixing surface (surface on which a toner image is formed) side of the sheet S, and a back surface of the sheet S (surface opposite to the fixing surface) side. A lower fixing unit 60B having a back side support member to be disposed, a heating source 60C, and the like are provided. By pressing the back surface side supporting member against the fixing surface side member, a fixing nip for holding and conveying the sheet S is formed.

  The fixing unit 60 fixes the toner image on the sheet S by heating and pressurizing the sheet S on which the toner image has been secondarily transferred and conveyed at the fixing nip. The fixing unit 60 is disposed as a unit in the fixing device F. In the fixing unit F, an air separation unit may be disposed to separate the sheet S from the fixing surface side member or the back surface side supporting member by blowing air.

  The sheet conveyance unit 50 includes a sheet feeding unit 51, a sheet discharge unit 52, a conveyance path unit 53, and the like. In the three sheet feeding tray units 51a to 51c constituting the sheet feeding unit 51, sheets S (standard sheets and special sheets) identified based on basis weight, size and the like are stored for each preset type. . The transport path portion 53 has a plurality of transport rollers such as the registration roller body 53a.

  The sheets S accommodated in the sheet feeding tray units 51 a to 51 c are fed one by one from the top and conveyed by the conveyance path unit 53 to the image forming unit 40. At this time, the inclination of the fed sheet S is corrected and the transport timing is adjusted by the registration roller unit in which the registration roller pair 53a is disposed. Then, the toner image of the intermediate transfer belt 421 is secondarily transferred collectively on one side of the sheet S in the image forming unit 40, and the fixing process is performed in the fixing unit 60. The sheet S on which an image has been formed is discharged outside the apparatus by the discharge unit 52 provided with a discharge roller 52a.

  By the way, in recent years, there is a demand for reducing the particle diameter of toner particles from the viewpoint of image quality improvement. However, since the adhesion between the toner particles and the photosensitive drum 413 increases with the reduction of the toner particle size, removal of the residual toner on the photosensitive drum 413 becomes difficult. In particular, when a polymerized toner is used, since the shape of the toner particles is close to a spherical shape, cleaning defects in which the toner particles pass through the rolling drum cleaning blade 415A on the photosensitive drum 413 are more likely to occur. There is a problem that the removal of the residual toner on the photosensitive drum 413 becomes difficult.

  In addition, when toner that slips off the drum cleaning blade 415A is generated, toner aggregates are formed on the photosensitive drum 413 with the toner as a nucleus, and white spots on the granular image printing portion (hereinafter referred to as "raindrops") Occurs. In the present embodiment, in order to cope with such quality problems such as "raindrops", a lubricant is supplied on the photosensitive drum 413, and a coating of the lubricant is formed to form an adhesive force between the toner particles and the photosensitive drum 413. Cleaning is done in a state where the In the present embodiment, as a method of supplying a lubricant onto the photosensitive drum 413, a toner external addition system is adopted in which a toner image is formed by toner containing a lubricating external additive (lubricant) and the lubricant is supplied. .

  However, in the toner external addition method, the amount of lubricant in the developing device 412 fluctuates depending on the amount of toner consumption, and as a result, the amount of lubricant coated on the photosensitive drum 413 fluctuates. Specifically, when an image with a low printing rate is printed, only the lubricant released from the toner is preferentially consumed in the background portion, and new toner (lubricant) is not supplied to the developing device 412. Therefore, eventually, the supply and discharge balance and stabilize in a state where the amount of lubricant in the developing device 412 is reduced. The lubricant on the photosensitive drum 413 can also be maintained at a constant level because only the lubricant is initially supplied. However, when the amount of lubricant in the developing device 412 decreases, the amount of lubricant supplied to the surface of the photosensitive drum 413 and hence the coverage decrease, and it becomes impossible to reduce the amount of adhesion between toner particles and the photosensitive drum 413, It leads to the occurrence of raindrops.

  Therefore, in the present embodiment, after printing an image with a low printing rate, a toner patch image is formed in a patch image forming area outside the image forming area in order to maintain the amount of lubricant in the developing device 412. Specifically, light is selectively irradiated by the exposure device 411 onto a patch image forming area on the surface of the photosensitive drum 413 uniformly charged by the charging device 414, and toner is applied to the exposure area irradiated with the light. To form a toner patch image (solid image). The patch image forming area is between the toner image forming area where the toner image corresponding to the input image data is formed in the rotation direction of the photosensitive drum 413 on the surface of the photosensitive drum 413, that is, the toner image forming area It is located between the toner image forming area (between images). The patch image forming area is preferably equal to or wider than the toner image forming area in the axial direction of the photosensitive drum 413. When the toner patch image is formed, the toner in the developing device 412 is consumed, and new toner is supplied to the developing device 412. When the toner is replenished, the lubricant is also replenished with the toner, so that the decrease in the amount of lubricant in the developing device 412 can be suppressed. As a result, reduction in the amount of lubricant on the photosensitive drum 413 can be suppressed.

  Next, the behavior of the lubricant when forming a toner image on the photosensitive drum 413 using the toner to which the lubricant is added will be described with reference to FIG. 3A. FIG. 3A is a view schematically showing a partial configuration of the image forming apparatus 1. In FIG. 3A, the supply direction DR1 in which the toner to which the lubricant is added is supplied to the photosensitive drum 413, the transfer direction DR2 in which the toner image is transferred from the photosensitive drum 413 to the intermediate transfer belt 421, the contact direction on the surface of the photosensitive drum 413. A scraping direction DR3 in which the drum cleaning blade 415A in contact with the surface scrapes and removes the toner remaining on the surface of the photosensitive drum 413 is shown.

  By applying a developing bias to the developing sleeve 412A included in the developing device 412, a lubricant is supplied onto the photosensitive drum 413 together with the toner, and thereafter, the photosensitive drum 413 and the primary transfer roller 422 are interposed via the intermediate transfer belt 421. Reaches the primary transfer nip formed between In the primary transfer nip, a part of the lubricant supplied onto the photosensitive drum 413 is transferred to the intermediate transfer belt 421 together with the toner, and the other lubricants together with the transfer residual toner, or as a lubricant alone, on the photosensitive drum 413 It remains. Thereafter, the lubricant remaining on the photosensitive drum 413 reaches the position of the drum cleaning blade 415A. A part of the lubricant adhering to the toner is scraped together with the toner by the drum cleaning blade 415A in contact with the photosensitive drum 413, and a part of the lubricant is separated from the toner and the drum together with the lubricant originally present alone While staying on the edge of the cleaning blade, it passes through the drum cleaning blade 415A and is fixed on the photosensitive drum 413. The lubricant adhering to the toner staying at the edge of the drum cleaning blade 415A continues to be released one by one. The lubricant originally fixed on the photosensitive drum 413 is scraped off by the toner staying on the drum cleaning blade 415A and the toner rushing on the drum cleaning blade 415A acting as an abrasive. .

  As described with reference to FIG. 3A, even if the lubricant is supplied onto the photosensitive drum 413 by forming a toner patch image, the lubricant is scraped by the drum cleaning blade 415A in contact with the photosensitive drum 413. To be taken. Although the amount of lubricant scraped off by the drum cleaning blade 415A can be reduced by reducing the charge amount of the toner patch image, there is no change in the fact that the lubricant is scraped off by the drum cleaning blade 415A. By passing the toner patch image, the amount of lubricant on the photosensitive drum 413 is reduced. Therefore, in order to stabilize the lubricant amount on the photosensitive drum 413 at a certain level, there is a problem that the formation amount of the toner patch image, that is, the toner consumption amount for replenishing the lubricant to the photosensitive drum 413 increases. is there.

  Therefore, in the present embodiment, the drum cleaning blade 415A is configured to be in contact with or separated from the photosensitive drum 413 by the contact separation portion 80 (see FIG. 2) having a known configuration. Ru. The contact / separation part 80 receives a control signal from the control unit 100 to contact the photosensitive drum 413 with a position (see FIG. 3A) and a position away from the photosensitive drum 413 (see FIG. 3B). Move between FIG. 3B shows the drum cleaning blade 415A separated from the photosensitive drum 413.

The control unit 100 determines, for example, whether or not any of the following (a) and (b) is satisfied, and when it is determined that the following is satisfied, a printing operation mode for forming a toner image on the photosensitive drum 413 It is controlled to execute a lubricant replenishment mode in which lubricant is supplied onto the photosensitive drum 413 by temporarily interrupting normal image formation and forming a toner patch image.
(A) The printing rate in the print job falls below a predetermined value.
(B) The cumulative average printing rate falls below a predetermined value.
The accumulated average printing rate is a value obtained by dividing the accumulated printing rate by the accumulated printing number, and is calculated by the control unit 100. The cumulative printing rate is the printing rate integrated until each printing. The cumulative print count is the count obtained by counting the print count of each print. Control unit 100 refers to the history information stored in storage unit 72 to calculate the cumulative printing rate and the cumulative number of printed sheets.

  Specifically, the control unit 100 moves the drum cleaning blade 415A to a position separated from the photosensitive drum 413 in the lubricant replenishment mode. This can prevent the lubricant in the toner patch image from being scraped off by the drum cleaning blade 415A. Therefore, it is possible to suppress the formation amount of the toner patch image necessary to stabilize the lubricant amount on the photosensitive drum 413 at a certain level, that is, the toner consumption amount for replenishing the lubricant to the photosensitive drum 413 .

  The control unit 100 temporarily interrupts the charging operation of the photosensitive drum 413 by the charging device 414, and applies a developing bias to the developing sleeve 412A, whereby a lubricant is formed on the patch image forming area on the surface of the photosensitive drum 413. May be attached to form a toner patch image (bias development).

  By stopping the charging by the charging device 414 and performing bias development, the lubricant attached to the photosensitive drum 413 can be charged to the positive side. Since the primary transfer voltage is positive polarity (for example, +500 [V]), the transfer of the lubricant to the intermediate transfer belt 421 in the primary transfer can be suppressed, and thus, the toner for supplying the lubricant to the photosensitive drum 413 Consumption can be reduced.

  FIG. 4 is a flowchart showing an operation example of lubricant supply of the image forming apparatus 1 in the present embodiment. Step S101 in FIG. 4 is started by starting the execution of the print job.

  First, the control unit 100 refers to the history information stored in the storage unit 72, and calculates the cumulative number of printed sheets during the execution of the print job (step S101). Next, the control unit 100 reads the print rate of the print job up to the previous time stored in the storage unit 72 as history information, and adds the print rate of the current print job to the read print rate to perform cumulative printing. The rate is calculated (step S102). Next, the control unit 100 calculates an accumulated average printing rate by dividing the accumulated printing rate calculated in step S102 by the accumulated printing number calculated in step S101 (step S103).

  Next, the control unit 100 determines whether the cumulative number of printed sheets is a predetermined number (step S104). As a result of the determination, if the cumulative number of printed sheets is the predetermined number (Yes at step S104), the control unit 100 determines whether the cumulative average printing rate is less than the predetermined printing rate (step S105).

  As a result of the determination, if the accumulated average printing rate is not less than the predetermined printing rate (No at Step S105), the process proceeds to Step S107. On the other hand, when the accumulated average printing rate is less than the predetermined printing rate (step S105, Yes), the control unit 100 performs control so as to execute the lubricant replenishment mode (step S106).

  Next, the control unit 100 resets the value of the cumulative number of printed sheets, that is, sets the value to 0 (step S107).

  Next, the control unit 100 resets the value of the accumulated printing rate, that is, sets the value to 0 (step S108). Thereafter, the process returns to the front of step S101.

  Returning to the determination in step S104, if the accumulated number of printed sheets is not the predetermined number (No in step S104), the control unit 100 performs control to execute the printing operation mode (step S109). Finally, the control unit 100 determines whether the print job being executed has ended (step S110). As a result of the determination, when the print job being executed is ended (Yes in step S110), the image forming apparatus 1 ends the process in FIG. On the other hand, when the print job being executed has not ended (step S110, No), the process returns to the front of step S101.

  As described above in detail, the image forming apparatus 1 according to the present embodiment forms a toner image on the photosensitive drum 413 using the rotatable photosensitive drum 413 and the toner to which the lubricant is added, and the toner image is formed. When passing through the primary transfer nip, the image forming unit 40 transfers the toner image to the intermediate transfer belt 421 by applying a primary transfer bias, and the toner to which a lubricant is added according to the image formation history by the image forming unit 40 And a toner patch image forming portion (image forming portion 40) that forms a toner patch image on the photosensitive drum 413 using the above, and the photosensitive drum 413 without contact with the intermediate transfer belt 421 and remaining on the photosensitive drum 413 A drum cleaning blade 415A for removing toner, and the drum cleaning blade 415A against the photosensitive drum 413, and To separate the drum cleaning blade 415A from the photosensitive drum 413 before the toner separation image formed on the photosensitive drum 413 reaches the drum cleaning blade 415A. Control unit 100 that controls the contact / separation unit 80

  According to this embodiment configured as described above, since the lubricant in the toner patch image can be prevented from being scraped off by the drum cleaning blade 415A, the amount of lubricant on the photosensitive drum 413 can be maintained at a certain level. It is possible to suppress the formation amount of the toner patch image necessary for stabilization, that is, the toner consumption amount for supplying the lubricant to the photosensitive drum 413.

  Although the above (a) and (b) were mentioned as conditions which perform lubricant supply mode in the above-mentioned embodiment, it does not restrict to this. For example, the amount of lubricant on the photosensitive drum 413 may be measured, and the control unit 100 may be controlled to execute the lubricant replenishment mode based on the measurement result.

  In the above embodiment, the intermediate transfer belt 421 corresponds to the “second image carrier” of the present invention. However, even if the sheet S corresponds to the “second image carrier” of the present invention. good.

  In addition, any of the above-described embodiments is merely an example of implementation for carrying out the present invention, and the technical scope of the present invention should not be interpreted in a limited manner by these. That is, the present invention can be implemented in various forms without departing from the scope or main features of the present invention.

  The present invention can be applied to an image forming system configured of a plurality of units including an image forming apparatus. The plurality of units include, for example, an external device such as a post-processing device and a network-connected control device.

  Finally, the results of evaluation experiments (Examples 1 to 4 and Comparative Examples 1 and 2) performed by the present inventors for confirming the effectiveness in the above embodiment will be described.

  Before conducting the evaluation experiment, the influence of the drum cleaning blade on the amount of lubricant on the photosensitive drum was examined using the above-mentioned image forming apparatus. The configuration is such that the drum cleaning blade can be in contact with or separated from the photosensitive drum, and in each of the contact state and the separation state, the vertical band pattern (image) of printing ratio 20 [%] is 1000 sheets of A4 It was formed on paper.

  Regarding the amount of lubricant, after image formation on 1000 A4 sheets, when the drum cleaning blade is in contact, the portion of the surface layer of the photosensitive drum that has passed through the drum cleaning blade is cut out, while the drum cleaning blade is separated In the surface layer of the photosensitive drum, an image portion passing through the drum cleaning blade was cut out and substituted by the ratio of zinc in zinc stearate determined by the X-ray photoelectron photometric analyzer. Incidentally, in consideration of the fluctuation of the lubricant amount in the developing device due to durability (processing of forming an image on 1000 sheets of A4 size), evaluation was performed using a new developing device in which toner is new.

  FIG. 5 is a diagram showing the amount of lubricant on the photosensitive drum when the drum cleaning blade is in contact and separation. As shown in FIG. 5, when the drum cleaning blade is in contact with the photosensitive drum, the lubricant supplied to the photosensitive drum and the lubricant immobilized on the photosensitive drum are scraped off by the drum cleaning blade. As a result, the amount of lubricant on the photosensitive drum is reduced.

Configuration of Image Forming Apparatus According to Embodiments 1 to 6 and Comparative Examples 1 and 2
Hereinafter, the results of the evaluation experiment will be described. As the image forming apparatus according to Examples 1 to 6 and Comparative Examples 1 and 2, the image forming apparatus 1 having the configuration of FIGS. 1 and 2 was used. Then, the photosensitive drum, the developing device, the intermediate transfer unit (transfer device), the toner, the drum cleaning blade and the like were set as follows.
(1) Photosensitive drum As the photosensitive drum, a drum-shaped organic photosensitive member in which a photosensitive layer of 25 [μm] thickness made of polycarbonate resin is formed on the outer peripheral surface of a drum-shaped metal base made of aluminum is used. . The photosensitive drum rotates at 400 mm / sec.
(2) Developing Device The developing device includes a developing sleeve that is rotationally driven at a rotational speed of 600 [mm / min], to which a developing bias having the same polarity as the surface potential of the photosensitive drum is applied. A developer in which reversal development was performed was used.
(3) Intermediate Transfer Unit As an intermediate transfer belt, an endless belt made of a polyimide resin to which conductivity was imparted was used. In addition, one transfer roller is provided, which is in pressure contact with the photosensitive drum via the belt and to which a primary transfer bias having a reverse polarity to the toner charging polarity is applied.
(4) Drum cleaning blade As a drum cleaning blade, the impact resilience modulus of urethane rubber is 50 [%] (25 [° C]), JISA hardness is 70 [°], thickness is 2.00 [mm], free One having a length of 10 mm and a width of 324 mm was used. The drum cleaning blade can be in contact with or separated from the photosensitive drum. The contact load on the photosensitive drum at the time of contact was set to 20 [N / m], and the contact angle was set to 15 [°].
(5) Toner The toner constituting the two-component developer is made of toner particles having a volume average particle diameter of 6.5 μm manufactured by the emulsion polymerization method, and has negative chargeability. The toner particles to which 0.2 parts by weight of zinc stearate as a lubricant was added were used as toner.

  In the above image forming apparatus, the surface potential of the photosensitive drum in the non-exposed area is -750 [V], the surface potential of the photosensitive drum in the exposed area is -100 [V], and the developing sleeve has a frequency of 6000 Hz. , An amplitude of 800 [V] and a direct current component of -550 [V] were applied.

  Using the above-described image forming apparatus, the toner in the developing device is refilled in advance for each durability, and the amount of lubricant is equalized. Carried out.

Comparative Example 1
In Comparative Example 1, the primary transfer voltage was +500 [V], and the transfer efficiency was 95 [%] or more. In this case, the amount of adhered toner after transfer is 0.5 [g / m ² ].
Between the printing rate of 15% to 30%, no raindrops occurred, but in the area of the low printing rate of 12% or less, the raindrops due to the lubricant shortage occurred.

表１において、項目「滑剤補給モード」の「なし」は、滑剤補給モードがないことを示し、同項目の「あり」は、滑剤補給モードがあることを示す。また、項目「印字率」の「雨だれ」は、その印字率で雨だれが発生したことを示し、同項目の「○」は、その印字率で雨だれが発生しなかったことを示す。また、項目「Ａ４枚数換算」の例えば「３０」は、滑剤補給モードにおけるトナーパッチ像の形成量をＡ４サイズに振ったときの枚数を示す。 Table 1 shows the occurrence of raindrops for each of Examples 1 to 6 and Comparative Examples 1 and 2.

In Table 1, "none" of the item "lubricant replenishment mode" indicates that there is no lubricant replenishment mode, and "presence" of the same item indicates that there is a lubricant replenishment mode. Also, "raindrop" in the item "printing rate" indicates that raindrops have occurred at that printing rate, and "o" in the same item indicates that no raindrops have occurred at that printing rate. For example, "30" in the item "A4 sheet number conversion" indicates the number of sheets when the toner patch image formation amount in the lubricant replenishment mode is changed to A4 size.

Comparative Example 2
In Comparative Example 2, when the printing rate was less than 15%, normal image formation was temporarily interrupted every 10000 sheets of printing, and the lubricant replenishment mode was executed. The primary transfer voltage (+500 [V]) is equivalent to that of Comparative Example 1, and the primary transfer voltage in the lubricant replenishment mode is also equivalent to the primary transfer voltage in the normal image formation (printing operation mode). In the lubricant replenishment mode, a toner patch image is formed on the photosensitive drum through development and transfer. The toner patch image is an A4 size sheet with an image coverage of 100%, and the toner patch image formation method is the same as that for normal image formation (the above-described toner patch image formed by charging, exposing, developing is formed Adopted another method). The drum cleaning blade is in pressure contact with the photosensitive drum as in normal image formation. The image formation amount of the toner patch image in the lubricant supply mode was shaken by A4 number of sheets to confirm the occurrence of the raindrop. As a result, by setting the image formation amount of the toner patch image in the lubricant replenishment mode to 50 sheets of A4 size, improvement of the raindrop was observed at a printing rate of 12% as compared with Comparative Example 1.

[Experimental method and experimental result in Example 1]
In the first embodiment, when the printing rate is less than 15%, the normal image forming process is temporarily interrupted every 10000 sheets of printing, and the lubricant replenishment mode is executed. The primary transfer voltage (+500 [V]) is equivalent to Comparative Examples 1 and 2, and the primary transfer voltage in the lubricant replenishment mode is also equivalent to the primary transfer voltage in normal image formation. In the lubricant replenishment mode, the toner patch image is formed on the photosensitive drum through development and transfer, and the drum cleaning blade is separated from the photosensitive drum before the toner patch image reaches the drum cleaning blade. As described above, the drum cleaning blade scrapes off a part of the lubricant together with the transfer residual toner, and the lubricant originally present on the photosensitive drum is also scraped off by the drum cleaning blade. However, by forming the toner patch image while separating the drum cleaning from the photosensitive drum as in the first embodiment, the amount of lubricant scraped off by the drum cleaning blade can be made zero. The toner patch image was an image having a printing rate of 100% at A4, and the toner patch image was formed by the same method as the normal image formation. The image formation amount of the toner patch image in the lubricant supply mode was shaken by A4 number of sheets to confirm the occurrence of the raindrop. As a result, by setting the image formation amount of the toner patch image in the lubricant replenishment mode to 40 sheets of A4 size, improvement in raindrops was observed at a printing rate of 10% as compared with Comparative Example 2. As the toner consumption amount of the toner patch image in the lubricant supply mode, a reduction of 60% was realized in comparison with Comparative Example 2. In Comparative Example 2, since a raindrop occurred at a printing rate of 10% or less in 50 sheets of the lubricant replenishment mode A4 size, the reduction rate can be obtained from the following formula.
Reduction rate = (50 [sheets]-20 [sheets]) / 50 [sheets] x 100 = 60 [%]

[Experimental method and experimental result in Example 2]
In the second embodiment, the separation timing of the drum cleaning blade in the lubricant replenishment mode is different from that in the first embodiment, and the drum cleaning blade is separated from the photosensitive drum before the start of the development of the toner patch image and the transfer operation. In this way, it is possible to prevent the vibration of the photosensitive drum caused by the separating operation of the drum cleaning blade from adversely affecting development and transfer, and to form the toner patch image more stably. In addition, as shown in Table 1, the confirmation result of the generation | occurrence | production condition of a raindrop is equivalent to Example 1. FIG.

[Experimental method and experimental result in Example 3]
In the third embodiment, the separation timing of the drum cleaning blade in the lubricant replenishment mode is different from the first and second embodiments, and the drum cleaning blade is separated before the rotational driving of the photosensitive drum is started. By doing this, it is possible to prevent torque fluctuation of the photosensitive drum due to the separation operation of the drum cleaning blade, damage to the drum cleaning blade, and scattering of toner accumulated on the edge of the drum cleaning blade. In addition, as shown in Table 1, the confirmation result of the generation | occurrence | production condition of a raindrop is equivalent to Example 1. FIG.

[Experimental method and experimental result in Example 4]
Before describing the experimental method and the experimental results in Example 4, the behavior of lubricant supply at the drum cleaning blade will be described with reference to FIG. A part of the lubricant particles 112 is scraped off by the drum cleaning blade 415A together with the toner 110, and a part of the lubricant particles 112 is separated from the toner 110 and retained at the edge of the drum cleaning blade 415A, and a part thereof is the drum cleaning blade And fixed as a lubricant 120 on the photosensitive drum 413. In short, the lubricant remaining on the edge of the drum cleaning blade is gradually supplied onto the photosensitive drum. From these facts, it is possible to gradually supply and fix the lubricant on the photosensitive drum by supplying a certain amount of lubricant together with the toner to the edge of the drum cleaning blade. However, the toner that has been staying for a long time at the edge of the drum cleaning blade has a large effect as an abrasive because the lubricant is advancing, so it scrapes off the lubricant that has already been fixed on the photosensitive drum. The action is great. Also, if the printing rate for a predetermined number of printed sheets is less than the predetermined printing rate, that is, if the amount of lubricant on the photosensitive drum is insufficient, rain drops will occur when the drum cleaning blade is in contact with the photosensitive drum. May be the cause of

  Therefore, in the fourth embodiment, when the printing rate is less than 15%, the normal image forming process is temporarily interrupted every 10000 sheets of printing, and the lubricant replenishment mode described later is executed. The primary transfer voltage (+500 [V]) is equivalent to Comparative Examples 1 and 2, and the primary transfer voltage in the lubricant replenishment mode is also equivalent to the primary transfer voltage in normal image formation. In the lubricant supply mode, the toner patch image is formed on the photosensitive drum through the developing and transferring operations, and the drum cleaning blade is separated from the photosensitive drum before the toner patch image reaches the drum cleaning blade. Most of the toner accumulated at the edge of the drum cleaning blade is moved from the drum cleaning blade by falling due to its own weight when the drum cleaning blade is separated from the photosensitive drum and rotational driving of the photosensitive drum after separation. That is, the toner that has remained at the edge of the drum cleaning blade for a long time, more specifically, the toner whose lubricant has been released is removed.

  The toner patch image in Example 4 was a horizontal band pattern (image) with a printing rate of 20% on A4 size paper. The formation method of the toner patch image is the same as that of normal image formation. Further, the drum cleaning blade is brought into contact with the photosensitive drum at the timing when a part of the first toner patch image in the rotational direction of the photosensitive drum reaches the contact position of the drum cleaning blade against the photosensitive drum. After that, we decided to maintain the contact. As a result, after the toner whose lubricant has been released has been removed from the edge of the drum cleaning blade, the toner sufficiently adhered to the lubricant is supplied to the drum cleaning blade, whereby the lubricant cleaning action by the drum cleaning blade is reduced. The lubricant can be replenished to the photosensitive drum while making maximum use.

The image formation amount of the toner patch image in the lubricant supply mode was shaken by A4 number of sheets to confirm the occurrence of the raindrop. Compared to Example 1, although the time required for the lubricant replenishment mode required three times, the toner consumption amount could be reduced by 40%. In Example 1, since raindrops occurred in the lubricant replenishment mode A4 size 20 sheets (print rate 100%) and print rate 10% or less, the required time and reduction rate can be obtained from the following formula.
Required time = 60 [sheets] / 20 [sheets] = 3 times Reduction rate = (20 [sheets] x 100 [%]-60 [sheets] x 20 [%]) / (20 [sheets] x 100 [%] ) × 100 = 40 [%]
In Example 4, when it is difficult to contact the drum cleaning blade while rotating the photosensitive drum because the rotational speed of the photosensitive drum is high, the drum cleaning blade is temporarily stopped after the photosensitive drum is stopped. You may make it abut.

[Experimental method and experimental result in Example 5]
Before describing the experimental method and the experimental result in Example 5, the control result of the amount of lubricant in the primary transfer region performed using the evaluation device shown in FIGS. 7A and 7B will be described. In FIG. 7A, reference numeral 511 denotes a photosensitive member in which a photosensitive layer of 25 [μm] thickness made of polycarbonate resin is provided on the surface of an aluminum cylindrical member having a diameter of 100 [mm] and a length of 100 [mm]. It is connected. The reference numeral 513 denotes a developing roller of 30 mm in diameter, and 250 g / m ² of developer is held on the circumferential surface of an aluminum sleeve. The photosensitive member 511 and the developing roller 513 face each other at a distance of 250 μm. The developing roller 513 is applied with an alternating voltage having a frequency of 6000 Hz, an amplitude of 800 V, and an offset of −450 V. In this state, the developing roller 513 is rotated at 600 [mm / s] in the direction of arrow c, and then the photosensitive member 511 is rotated once at 400 [mm / s] in the direction of arrow b. As a result, the toner contained in the developer held on the circumferential surface of the developing roller 513 adheres onto the photosensitive member 511, and a toner layer of 5 [g / m ² ] is formed on the photosensitive member 511.

  Next, the developing roller 513 is separated from the photosensitive member 511, and the rubber roller 512 provided with a conductive rubber layer on the surface is brought into contact with the photosensitive member 511. In this state, an arbitrary voltage (transfer voltage) is applied to the core metal of the rubber roller 512, and the photosensitive member 511 is rotated once in the direction of the arrow b at 400 [mm / s]. Since the rubber roller 512 is in contact with the photosensitive member 511, the rubber roller 512 follows the photosensitive member 511 and rotates in the direction of arrow d. After one rotation of the photosensitive member 511, the toner image on the photosensitive member 511 is transferred onto the rubber roller 512.

The voltage applied to the rubber roller 512 was changed, and the weight of the toner remaining on the photosensitive member 511 at that time and the amount of lubricant were measured. The transfer efficiency was determined from the weight of the toner formed on the photosensitive member 511 and the amount of toner remaining on the photosensitive member 511 after transfer.
Specifically, the transfer efficiency was determined from the following equation (1).
Transfer efficiency [%] = (1−weight of transfer residual toner on photoreceptor 511 after transfer / weight of toner on photoreceptor 511 after development) × 100 [%]
The amount of lubricant was substituted by the ratio of zinc in zinc stearate determined by X-ray photoelectron spectroscopy.

FIG. 8 is a graph showing the amount of lubricant on the photosensitive member 511 and the transfer efficiency according to the transfer voltage. In FIG. 8, the solid line indicates the amount of lubricant on the photosensitive member, and the dotted line indicates the transfer efficiency. As apparent from FIG. 8, when the transfer voltage exceeds a certain value (about 700 [V] in FIG. 8), it can be seen that the amount of lubricant remaining on the photosensitive member 511 increases. On the other hand, it is also understood that when the transfer voltage is increased too much, the transfer efficiency decreases. The following can be said from this.
The amount of lubricant supplied onto the photosensitive member can be increased by increasing the transfer voltage.
• If the transfer voltage is increased too much, the transfer efficiency will decrease.
Since the reduction of the transfer efficiency adversely affects the finally formed image, there is an upper limit to the transfer voltage that can be set during image formation, and there is a limitation in increasing the lubricant supply amount to the photosensitive member 511. On the other hand, when forming a toner patch image to be formed outside the image forming area, there is no restriction on the image quality and transfer efficiency of the finally formed image, so the transfer voltage is further increased and the lubricant supply amount to the photosensitive member is increased. can do.

  Based on the results shown in FIG. 8, in Example 5, when the printing rate is less than 15%, the normal image forming process is temporarily interrupted every 10000 sheets of printing, and the lubricant replenishment mode described later is executed. In the lubricant replenishment mode, the toner patch image is formed on the photosensitive member through the developing and transferring operations, and the drum cleaning blade is separated from the photosensitive member before the toner patch image reaches the drum cleaning blade. As described above, a part of the lubricant is scraped off together with the transfer residual toner in the drum cleaning blade, and the lubricant originally present on the photosensitive member is also scraped off by the drum cleaning blade. By forming the toner patch image while separating the blade, the amount of lubricant scraped off by the drum cleaning blade can be reduced to zero.

  The toner patch image in Example 5 is a pattern (image) with a printing ratio of 100% on A4 size paper, and the toner patch image is formed in the same manner as in the normal image formation.

  In Example 5, the primary transfer voltage in the lubricant replenishment mode was set to 900 [V]. As described with reference to FIG. 8, when the primary transfer voltage is set to 900 [V], the amount of lubricant supplied to the photosensitive member by peeling from the toner in the transfer region increases. On the other hand, when the primary transfer voltage is set to 900 [V], the transfer efficiency decreases and the image quality also deteriorates. This deterioration in image quality can not be ignored during normal image formation, but such a decrease in transfer efficiency does not pose a problem in the formation of a toner patch image in the lubricant replenishment mode.

The image formation amount of the toner patch image in the lubricant supply mode was shaken by A4 number of sheets to confirm the occurrence of the raindrop. The toner consumption amount in the lubricant replenishment mode can be reduced by 25% as compared with Example 1. In Example 1, since raindrops occurred at 20 sheets of the lubricant replenishment mode A4 size and the printing rate is 10% or less, the reduction rate can be obtained from the following formula.
Reduction rate = (20 [sheets]-15 [sheets]) / 20 [sheets] x 100 = 25 [%]

[Experimental method and experimental result in Example 6]
In the sixth embodiment, when the printing rate is less than 15%, the normal image forming process is temporarily interrupted every 1000 sheets of printing, and the lubricant replenishment mode described later is executed. The primary transfer voltage (+500 V) is equivalent to Comparative Examples 1 and 2, and the primary transfer voltage in the lubricant replenishment mode is also equivalent to the primary transfer voltage in normal image formation. In the lubricant replenishment mode, the toner patch image is formed on the photosensitive member through the developing and transferring operations, and the drum cleaning blade is separated from the photosensitive member before the toner patch image reaches the drum cleaning blade. As described above, a part of the lubricant is scraped off together with the transfer residual toner in the drum cleaning blade, and the lubricant originally present on the photosensitive member is also scraped off by the drum cleaning blade. By forming the toner patch image while separating the blade, the amount of lubricant scraped off by the drum cleaning blade can be reduced to zero.

  The toner patch image in Example 6 is a pattern (image) of 100% printing rate on A4 size paper. In the toner patch image forming method, a lubricant is added to the patch image forming area on the surface of the photosensitive drum by temporarily interrupting the charging operation of the photosensitive drum by the charging device and applying a developing bias to the developing sleeve. Toner was attached to form a toner patch image (bias development). That is, although the charging polarity of the lubricant used in Example 6 is plus polarity, it is not charged to minus polarity by the charging device unlike in the normal image formation. Since the primary transfer voltage has a positive polarity (for example, +500 [V]) and is in a repulsion relationship with the charging polarity of the lubricant, electrostatic transfer of the lubricant to the intermediate transfer belt can be suppressed in the primary transfer. Therefore, bias development in which the charging device is stopped can suppress transfer of the lubricant to the intermediate transfer belt in primary transfer, as compared with normal image formation, and can increase the amount of lubricant remaining on the photosensitive member.

The image formation amount of the toner patch image in the lubricant supply mode was shaken by A4 number of sheets to confirm the occurrence of the raindrop. The toner consumption amount in the lubricant replenishment mode can be reduced by 15% as compared with Example 1. In Example 1, since raindrops occurred at 20 sheets of the lubricant replenishment mode A4 size and the printing rate is 10% or less, the reduction rate can be obtained from the following formula.
Reduction rate = (20 [sheets]-17 [sheets]) / 20 [sheets] x 100 = 15 [%]

Reference Signs List 1 image forming apparatus 10 image reading unit 20 operation display unit 21 display unit 22 operation unit 30 image processing unit 40 image forming unit 50 sheet conveyance unit 60 fixing unit 71 communication unit 72 storage unit 80 contact separation unit 100 control unit 101 CPU
102 ROM
103 RAM
110 toner 112 lubricant particle 120 lubricant 413 photosensitive drum 415A drum cleaning blade 421 intermediate transfer belt

Claims (9)

A rotatable first image carrier,
A toner image is formed on the first image carrier using a toner to which a lubricant is added, and the toner image is applied to the second image carrier by applying a transfer bias when the toner image passes through the transfer nip. An image forming unit to be transferred;
A toner patch image forming unit for forming a toner patch image on the first image carrier using the toner to which the lubricant is added according to the image formation history by the image forming unit;
A cleaning member that abuts on the first image carrier and removes toner remaining on the first image carrier without being transferred to the second image carrier;
An abutment / separating portion that abuts or separates the cleaning member from the first image carrier;
A control unit configured to control the contact / separation portion to separate the cleaning member from the first image carrier before the toner patch image formed on the first image carrier reaches the cleaning member; ,
Equipped with
The control unit is configured to compare, when the toner patch image formed by the toner patch image forming unit passes through the transfer nip, the toner image formed by the image forming unit through the transfer nip. , Control to increase the transfer bias,
Image forming apparatus. The image formation history is a printing rate of a toner image formed by the image forming unit.
An image forming apparatus according to claim 1. The control unit separates the cleaning member from the first image carrier before the toner patch image is formed by the toner patch image forming unit.
An image forming apparatus according to claim 1. The control unit separates the cleaning member from the first image carrier before the rotation of the first image carrier starts.
An image forming apparatus according to claim 3. The control unit separates the cleaning member from the first image carrier before the toner patch image formed by the toner patch image forming unit reaches the cleaning member, and then the toner patch image is released from the toner patch image. Bringing the cleaning member into contact with the first image carrier at a timing when the cleaning member is reached;
The image forming apparatus according to any one of claims 1 to 4. The toner patch image forming unit forms the toner patch image on the first image carrier by a bias developing method.
The image forming apparatus according to any one of claims 1 to 5 . When the image forming history satisfies a predetermined condition, the control unit interrupts the formation of the toner image by the image forming unit and starts the formation of the toner patch image by the toner patch image forming unit, and the toner After the formation of the patch image is completed, the value of the image forming history is reset to resume the formation of the toner image by the image forming unit.
The image forming apparatus according to any one of claims 1 to 6 . An image forming system comprising a plurality of units including an image forming apparatus, comprising:
A rotatable first image carrier,
A toner image is formed on the first image carrier using a toner to which a lubricant is added, and the toner image is applied to the second image carrier by applying a transfer bias when the toner image passes through the transfer nip. An image forming unit to be transferred;
A toner patch image forming unit for forming a toner patch image on the first image carrier using the toner to which the lubricant is added according to the image formation history by the image forming unit;
A cleaning member that abuts on the first image carrier and removes toner remaining on the first image carrier without being transferred to the second image carrier;
An abutment / separating portion that abuts or separates the cleaning member from the first image carrier;
A control unit configured to control the contact / separation portion to separate the cleaning member from the first image carrier before the toner patch image formed on the first image carrier reaches the cleaning member; ,
Equipped with
The control unit is configured to compare, when the toner patch image formed by the toner patch image forming unit passes through the transfer nip, the toner image formed by the image forming unit through the transfer nip. , Control to increase the transfer bias,
Imaging system. A rotatable first image carrier,
A toner image is formed on the first image carrier using a toner to which a lubricant is added, and the toner image is applied to the second image carrier by applying a transfer bias when the toner image passes through the transfer nip. An image forming unit to be transferred;
A toner patch image forming unit for forming a toner patch image on the first image carrier using the toner to which the lubricant is added according to the image formation history by the image forming unit;
A cleaning member that abuts on the first image carrier and removes toner remaining on the first image carrier without being transferred to the second image carrier;
An abutment / separating portion that abuts or separates the cleaning member from the first image carrier;
A lubricant supplying method in an image forming apparatus having the
Before the toner patch image formed on the first image carrier reaches the cleaning member, the contact and separation portion is controlled to separate the cleaning member from the first image carrier .
And, when the toner patch image formed by the toner patch image forming unit passes through the transfer nip, the transfer is performed compared to when the toner image formed by the image forming unit passes through the transfer nip. Lubrication method that controls to increase bias .

Images