JP2011186276A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce generation of image defects due to lack of lubricity of a cleaning member in a plurality of image forming parts. <P>SOLUTION: As for toner used in a plurality of image forming parts Py, Pm, Pc, and PBk, at least two different melt indexes are set according to the difference of lubricity imparted to cleaning members at a contact area Ar between the cleaning members 6a, 6b, 6c, and 6d and image carriers 1a, 1b, 1c, and 1d. In a second toner supply mode, toner having a low melt index is supplied from a predetermined image forming part using toner having a low melt index to another image forming part using toner having a high melt index. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic printer or an electrophotographic copying machine that forms a color image on a recording material.

  As an image forming apparatus such as a printer or a copying machine that forms a color image on a recording material using electrophotographic technology, an in-line image forming apparatus is known. This in-line type image forming apparatus has four image forming units for forming toner images of colors of yellow, magenta, cyan, and black. In these four image forming units, yellow, magenta, cyan, and black toner images are formed on the outer peripheral surface (front surface) of the rotating photosensitive drum. Then, after the toner image is transferred from the surface of the photosensitive drum to the recording material, the transfer residual toner remaining on the surface of the photosensitive drum is scraped off and collected by a cleaning blade in contact with the surface of the photosensitive drum.

  As the cleaning blade, a flexible one such as urethane rubber is generally used. Usually, it is necessary to optimize various conditions such as rubber hardness, thickness, elastic modulus, and the amount of protrusion on the surface of the photosensitive drum. Since the photosensitive drum is rotated during image formation, the frictional resistance between the photosensitive drum and the cleaning blade increases. For this reason, the following problems may occur when low-printing printing continues, when printing on small-size paper continues, or when printing at high temperature and high humidity continues. The cleaning blade is turned up, the edge of the cleaning blade is chipped, and the cleaning blade is chattered (stick-slip) against the photosensitive drum surface. When the cleaning blade is turned over, printing becomes impossible. When the edge of the cleaning blade is chipped or chattered, the toner passes through the cleaning blade and appears as a vertical stripe image on the recording material.

  With respect to such a phenomenon, Patent Document 1 discloses that a toner is supplied onto a photosensitive drum by a developing unit at the time of non-image formation and this toner is used as a lubricant, whereby the cleaning blade is turned over, the edge is chipped, and chattered. A configuration for preventing the above has been proposed. In Patent Document 2 and Patent Document 3, it is proposed to select an image forming unit that should supply toner and an image forming unit that should collect toner for the purpose of effective use of toner and prevention of fullness of the waste toner tank. ing.

Japanese Patent Laid-Open No. 10-161426 JP 2001-175047 A JP 2002-31670 A

  In the above image forming apparatus, it is desired to prevent the occurrence of image defects due to insufficient lubricity of the cleaning blade with respect to the photosensitive drum surface in a plurality of image forming units.

  An object of the present invention is to provide an image forming apparatus capable of reducing the occurrence of image defects due to insufficient lubricity of a cleaning member in a plurality of image forming units.

  In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus that forms a color image on a recording material, and is arranged along a plurality of image forming units and the plurality of image forming units. A plurality of image forming units, each of which forms a toner image using a rotatable image carrier and toner of a predetermined color on the image carrier during image formation. Developing means for transferring, a transfer member for transferring a toner image formed on the image carrier to a recording material conveyed by the conveyance member, and a cleaning member in contact with the image carrier, from the image carrier And a cleaning member that removes unnecessary toner carried on the image carrier after the toner image is transferred to the recording material. The image forming apparatus includes a control unit, and the control unit performs non-image formation. Sometimes a predetermined picture A first toner supply mode in which a supply toner image formed on the image carrier of the forming unit by the developing unit is supplied to the contact area between the image carrier and the cleaning member by the image carrier; Sometimes the supply toner image formed by the developing means on the image carrier of a predetermined image forming unit is transferred to the transport member by the transfer member, and the supply toner image is transferred by the transport member to other than the predetermined image forming unit The toner image is conveyed to another image forming unit, and the toner image for supply is transferred from the conveying member to the image carrier by the transfer member of the other image forming unit, and the image carrier and the cleaning are transferred by the image carrier. A second toner supply mode for supplying to a contact area with the member, and the cleaning member for toner used in the plurality of image forming units At least two different melt indexes are set in accordance with the difference in lubricity given to the cleaning member in the contact area with the image carrier, and in the second toner supply mode, toner having a low melt index is used. The low-melt-index toner is supplied from the predetermined image-forming unit to another image-forming unit that uses the high-melt-index toner.

  According to the present invention, it is possible to provide an image forming apparatus capable of reducing the occurrence of image defects due to insufficient lubricity of the cleaning member in a plurality of image forming units.

(A) is an explanatory view showing the toner supply operation of the image forming unit in the first toner supply mode, and (b) is an operation timing chart of the image forming unit shown in (a). FIG. 6A is a diagram illustrating a toner supply operation of a toner supply image forming unit and a toner recovery operation of a toner recovery image formation unit in a second toner supply mode. (B) is a toner supply operation timing chart of the toner supply image forming unit and a toner recovery operation timing chart of the toner recovery image forming unit shown in (a). FIG. 4A is a schematic configuration diagram of an example of an image forming apparatus according to the first exemplary embodiment, and FIG. 4B is a block diagram of a hardware configuration for explaining a toner supply mode. It is a figure showing the correlation with the lubricity of a cleaning blade, and MI value of a toner. 6 is a schematic configuration diagram of a cartridge of an image forming apparatus according to Embodiment 2. FIG. FIG. 6 is a schematic configuration diagram of an image forming apparatus according to a third embodiment.

[Example 1]
(1) Example of Image Forming Apparatus In FIG. 3, (a) is a schematic configuration diagram of an example of an image forming apparatus according to the first embodiment, and (b) is a block diagram of a hardware configuration for explaining a toner supply mode. . This image forming apparatus is an inline type image forming apparatus in which a plurality of image forming units for forming toner images of yellow, magenta, cyan, and black are arranged in a line.

  The image forming apparatus 100 according to the first exemplary embodiment includes a first image forming unit Py and a second image forming unit Pm inside an image forming apparatus main body (not shown) that constitutes a housing of the image forming apparatus 100. And a third image forming unit Pc and a fourth image forming unit PBk. The first image forming unit Py is an image forming unit using yellow (Y) toner. The second image forming unit Pm is an image forming unit using magenta (M) toner. The third image forming unit Pc is an image forming unit using cyan (C) toner. The fourth image forming unit PBk is an image forming unit using black (Bk) toner. Reference numeral 10 denotes a rotatable transfer belt 10 as a conveying member. The first to fourth image forming units Py to PBk are arranged in a line from the upstream side (right side) to the downstream side (left side) in the rotation direction (arrow direction) of the transfer belt 10. Then, four color full-color images are formed by sequentially transferring toner images of four different colors formed by the image forming units Py to PBk onto the recording material P conveyed by the transfer belt 10.

  In the image forming apparatus 100 according to the first exemplary embodiment, the control unit 200 executes a predetermined image formation control sequence in accordance with a print command output from an external device (not shown) such as a host computer, and the image formation control sequence is performed. A predetermined image forming operation is performed. The control unit 200 includes a CPU and a memory such as a ROM and a RAM. The memory stores an image formation control sequence, a toner supply control sequence, various programs necessary for image formation, and the like. Each of the image forming units Py to PBk includes drum-type electrophotographic photosensitive members (hereinafter referred to as photosensitive drums) 1a, 1b, 1c, and 1d that are image carriers. In the first embodiment, as the photosensitive drums 1a to 1d, OPC (organic photo semiconductor) photosensitive drums having a negative charging characteristic with a diameter of 24 mm are used. Each of the photosensitive drums 1a to 1d is rotated at a peripheral speed (process speed) of 240 mm / sec in the arrow direction during image formation. Around each of the photosensitive drums 1a to 1d, charging rollers 2a, 2b, 2c, and 2d as charging members and exposure devices 3a, 3b, 3c, and 3d as exposure means are arranged along the rotation direction of the photosensitive drums 1a to 1d. And developing devices 4a, 4b, 4c, and 4d as developing means. Further, transfer rollers 8a, 8b, 8c, and 8d as transfer members and cleaning blades 6a, 6b, 6c, and 6d as cleaning members are disposed around the photosensitive drums 1a to 1d. The transfer belt 10 wound around the driving roller 7 and the driven roller 9 so as to straddle the photosensitive drums 1a to 1d of the image forming units Py to PBk is rotated in the direction indicated by the arrow by the rotation of the driving roller 7. It is rotated at a peripheral speed corresponding to the rotational peripheral speed. Transfer rollers 8a to 8d arranged to face the photosensitive drums 1a to 1d with the transfer belt 10 sandwiched on the inner peripheral surface (inner surface) side of the transfer belt 10 are in contact with the inner surface of the transfer belt 10. Then, the outer peripheral surface (surface) of the transfer belt 10 and the surfaces of the photosensitive drums 1a to 1d are opposed to each other with a predetermined gap therebetween, whereby the transfer nip portions Na and Nb are provided between the surface of the transfer belt 10 and the surfaces of the photosensitive drums 1a to 1d. , Nc, and Nd. Each of the image forming units Py to PBk has an image forming driving unit (hereinafter referred to as a driving unit) PyD, PmD, PcD, and PBkD as an image forming driving unit. Each of the driving units PyD to PBkD includes a charging bias power source (not shown), a laser diode (not shown), a polygon scanner motor (not shown), a driving motor (not shown), a developing bias power source (not shown), A transfer bias power source (not shown) is included. The charging bias power source is for applying a predetermined charging bias to the charging rollers 2a to 2d. The laser diode and the polygon scanner motor are for driving the exposure devices 3a to 3d. The drive motor is for rotating a developing sleeve 41 (to be described later) of the photosensitive drums 1a to 1d and the developing devices 4a to 4d. The developing bias power source is for applying a predetermined developing bias to the developing sleeve 41 of the developing devices 4a to 4d. The transfer bias power source is for applying a predetermined transfer bias to the transfer rollers 8a to 8d. In FIG. 3B, reference numeral 10D denotes a transfer belt drive unit as transfer member drive means. The transfer belt drive unit 10D has an adsorption bias power source (not shown), a belt drive motor (not shown), and the like. The suction bias power source is for applying a predetermined suction bias to the suction roller 11 described later. The belt drive motor is for rotating the drive roller 7.

An image forming operation of the image forming apparatus 100 according to the first exemplary embodiment will be described. The photosensitive drums 1a to 1d rotated by the driving motors of the driving units PyD to PBkD are arranged so that the outer peripheral surfaces (surfaces) of the photosensitive drums 1a to 1d have a predetermined polarity and are controlled by the charging rollers 2a to 2d during the rotation of the photosensitive drums 1a to 1d. It is charged uniformly to the potential. Each of the charging rollers 2a to 2d is an elastic roller having an actual resistance of 1 × 10 ⁵ Ω to which a DC voltage of −1.0 kV is applied from a charging bias power source. Then, the photosensitive drums 1a to 1d are brought into contact with the surface with a total pressure of 9.8 N and rotated following the rotation of the photosensitive drums 1a to 1d. The surfaces of the photosensitive drums 1 a to 1 d are charged to −400 V by the charging rollers 2 a to 2 d. Next, electrostatic latent images corresponding to the color component images (yellow, magenta, cyan, and black color component images) of the target color image are obtained on the surfaces of the photosensitive drums 1a to 1d by image exposure by the exposure devices 3a to 3d, respectively. An image (electrostatic image) is formed. Each of the exposure devices 3a to 3d forms an image on the surface of the photosensitive drums 1a to 1d via a polygon scanner (not shown) with a laser beam modulated by a laser diode in accordance with image information output from an external device. The polygon scanner is rotated at a predetermined speed by a polygon scanner motor, and scans and exposes a laser beam in the main scanning direction on the surface of the photosensitive drums 1a to 1d (a direction perpendicular to the recording material conveyance direction on the surface of the photosensitive drum). Thereby, electrostatic latent images are formed on the surfaces of the photosensitive drums 1a to 1d. At this time, the bright portion potential of the exposed portion on the surface of the photosensitive drums 1a to 1d by the laser beam becomes −200V. Writing of laser exposure by each of the exposure devices 3a to 3d is performed with a predetermined time delay from the position signal (BD signal) in the polygon scanner for each scanning line in the main scanning direction of the surface of the photosensitive drums 1a to 1d. In the sub-scanning direction of the surface of the photosensitive drums 1a to 1d (a direction parallel to the recording material conveyance direction on the surface of the photosensitive drums 1a to 1d), a recording material sensor 48 provided in the recording material conveyance path (FIG. 3B). The recording material detection signal (TOP signal) is delayed by a predetermined time. As a result, in each of the image forming portions Py to PBk, the laser exposure can always be performed at the same position on the surface of the photosensitive drums 1a to 1d.

  The electrostatic latent images on the photosensitive drums 1a to 1d are developed as toner images by the developing devices 4a to 4d. Each of the developing devices 4a to 4d has a developing container 43 that stores the toner t. In the developing container 43, a developing sleeve 41 as a developer carrying member is rotatably supported by the developing container 43 at an opening provided in the developing container 43 so as to face the surface of the photosensitive drums 1a to 1d. In the first embodiment, an elastic roller is used as the developing sleeve 41. In addition, a layer regulating blade 42 as a layer regulating member is supported on the developing container 43 in a state in contact with the outer peripheral surface (surface) of the developing sleeve 41 on the upstream side in the rotation direction of the developing sleeve 41. In each of the developing devices 4a to 4d, the developing sleeve 41 carries the toner t in the developing container 43 on the surface of the developing sleeve 41 while rotating. The toner t carried on the surface of the developing sleeve 41 is regulated to a toner layer having a constant thickness by the layer regulating blade 42. Then, the toner t of the toner layer is electrostatically discharged from the surface of the developing sleeve 41 onto the corresponding surface of the photosensitive drums 1a to 1d, and electrostatically attached to the electrostatic latent images on the surfaces of the photosensitive drums 1a to 1d. Is developed as a toner image. That is, the developing sleeve 41 is rotated at a peripheral speed of 120% in the forward direction with respect to the photosensitive drums 1a to 1d, and a predetermined developing bias (-350 V developing bias in the first embodiment) is supplied to the developing sleeve 41 from a developing bias power source. Is applied. As a result, the toner t in the toner layer on the surface of the developing sleeve 41 adheres to the electrostatic latent image, and the electrostatic latent image is developed as a toner image. The toner in the developing container 43 is a negatively charged nonmagnetic one-component toner. The development of the electrostatic latent image with toner is performed by a non-magnetic one-component contact development method.

  On the other hand, the recording material P is transported from the feeding cassette (not shown) to the outer peripheral surface (surface) of the transfer belt 10 from the most upstream side in the rotation direction of the transfer belt 10 by a predetermined recording material transport mechanism (not shown). An adsorption roller 11 as an adsorption member is provided at a position where the recording material P is conveyed on the surface of the transfer belt 10 so as to face the drive roller 9 with the transfer belt 10 interposed therebetween. A voltage of +1 kV is applied to the suction roller 11 as a suction bias from a suction bias power source. The recording material P transported to the surface of the transfer belt 10 is sandwiched between the outer peripheral surface (surface) of the suction roller 11 and the surface of the transfer belt 10 and transported to the state (nip transport). In this conveyance process, the suction roller 11 applies a charge to the recording material P, so that the recording material P is electrostatically attracted to the surface of the transfer belt 10. The recording material P adsorbed on the surface of the transfer belt 10 is conveyed to the transfer nip Na of the image forming unit Py as the transfer belt 10 rotates. A predetermined transfer bias (DC bias of +2 kV in this embodiment) is applied to the transfer roller 8a from a transfer bias power source, whereby the yellow toner image on the surface of the photosensitive drum 1a is transferred to the recording material P. Similarly, the recording material P is conveyed to the transfer nips Nb, Nc, and Nd of the image forming units Pm to PBk in the order of the image forming unit Pm, the image forming unit Pc, and the image forming unit PBk by the rotation of the transfer belt 10. Then, the magenta toner image on the surface of the photosensitive drum 1b is transferred onto the yellow toner image of the recording material P at the transfer nip portion Nb of the image forming portion Pm. Further, the cyan toner image on the surface of the photosensitive drum 1b is transferred to the transfer nip portion Nc of the image forming portion Pc so as to overlap the yellow toner image and the magenta toner image of the recording material P. Further, the black toner image is transferred to the transfer nip portion Nd of the image forming unit PBk so as to overlap the yellow toner image, the magenta toner image, and the cyan toner image of the recording material P. As a result, the recording material P carries four full-color unfixed toner images on the surface of the recording material P.

  Residual toner and other residues remaining on the surfaces of the photosensitive drums 1a to 1d without being transferred to the recording material P after the toner image is transferred are scraped off by the cleaning blades 6a to 6d in contact with the surfaces of the photosensitive drums 1a to 1d. Removed. The cleaning blade also removes the retransfer toner that was once transferred to the recording material P in the image forming section upstream in the recording material conveyance direction but reversely transferred to the photosensitive drum surface in the image forming section downstream in the recording material conveyance direction. The That is, the retransfer toner that has been once transferred to the recording material P by the image forming unit Py on the upstream side in the recording material conveyance direction but is reversely transferred to the surface of the photosensitive drum 1b of the image forming unit Pm on the downstream side in the recording material conveyance direction is cleaned. It is removed by the blade 6b. The retransfer toner that has been once transferred to the recording material P by the image forming portion Pm upstream in the recording material conveyance direction but is reversely transferred to the surface of the photosensitive drum 1c of the image forming portion Pc downstream in the recording material conveyance direction is the cleaning blade 6c. Removed by. The retransfer toner that has been once transferred to the recording material P by the image forming portion Pc on the upstream side in the recording material conveyance direction but is reversely transferred to the surface of the photosensitive drum 1d of the image forming portion PBk on the downstream side in the recording material conveyance direction is the cleaning blade 6d. Removed by. The residual toner and the retransfer toner are referred to as “unnecessary toner”.

  The recording material P carrying the unfixed full-color toner image transferred as described above is separated from the surface of the transfer belt 10 by the curvature of the surface of the transfer belt 10 on the most downstream side in the rotation direction of the transfer belt 10. The recording material P separated from the surface of the transfer belt 10 is introduced into a fixing nip portion between a heat fixing member and a pressure member of a fixing device (not shown). The recording material P is heated and fixed on the recording material P by receiving heat and pressure while being nipped and conveyed by the heat fixing member and the pressure member at the fixing nip portion. The recording material P exiting the fixing nip portion of the fixing device is discharged onto a discharge tray (not shown) provided outside the image forming apparatus main body by a predetermined recording material discharge mechanism (not shown).

  If toner remains on the surface of the transfer belt 10 and adheres to it, it may cause the backside of the recording material P or image stains. Residual toner remaining on the surface of the transfer belt 10 may be jammed or fog toner adhering to a non-image area, or color deviation detection for color deviation control or toner image density control. Color misregistration detection toner image transferred from .about.1d. The toner that remains on and adheres to the surface of the transfer belt 10 is removed by a transfer belt cleaning blade 12 as a conveying member cleaning member.

(2) Toner Manufacturing Method A toner manufacturing method used in the image forming apparatus according to the first exemplary embodiment will be described. First, an example of manufacturing toner particles will be described. In a four-necked vessel, 720 parts of ion-exchanged water, 940 parts of a 0.1 mol / liter Na ₃ PO ₄ aqueous solution and 15.0 parts of a 1.0 mol aqueous HCl solution are added, and a high-speed stirring device TK-homomixer is added. The temperature was maintained at 60 ° C. while stirring at 12,000 rpm. To this, 80 parts of a 1.0 mol / liter-CaCl ₂ aqueous solution was gradually added to prepare an aqueous dispersion medium containing a fine hardly water-soluble dispersion stabilizer Ca ₃ (PO ₄ ) ₂ .
Styrene monomer 64.0 parts by mass n-butyl acrylate 16.0 parts by mass Copper phthalocyanine pigment (Pigment Blue 15: 3) 6.50 parts by mass Styrenic resin (Mw = 2520, Mw / Mn = 1.58) 20 parts by mass Polyester resin 5.0 parts by weight Negative charge control agent (aluminum compound of 3,5-di-tert-butylsalicylic acid)
0.5 parts by weight negative charge control resin 0.5 parts by weight wax [Fischer-Tropsch wax, endothermic main peak temperature 78.2 ° C.]
10 parts The monomer mixture obtained by mixing the monomers from the above styrene monomer to wax was dispersed with an attritor for 3 hours. A monomer composition obtained by adding 7.2 parts by mass of 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, which is a polymerization initiator, to the monomer mixture is added to an aqueous dispersion medium. The mixture was granulated for 5 minutes while maintaining the rotational speed of the high-speed stirrer at 12,000 rpm. Thereafter, the high-speed stirrer was changed to a propeller stirrer, the internal temperature was raised to 70 ° C., and the reaction was allowed to proceed for 5 hours with slow stirring.

  Next, the temperature inside the container was raised to 80 ° C. and maintained for 3 hours, and then gradually cooled to a temperature of 30 ° C. at a cooling rate of 1 ° C. per minute, whereby slurry 1 was obtained. Dilute hydrochloric acid was added to the container containing the slurry 1 to remove the dispersion stabilizer. Further, filtration, washing, and drying were performed to obtain polymer particles (toner particles) having a weight average particle size of 5.6 μm, a weight average molecular weight of 42,000, and a number average molecular weight of 7,300. The toner particles are a raw material for cyan toner. In order to produce toner particles of toners of other colors such as magenta, yellow, and black, the pigment copper phthalocyanine pigment (Pigment Blue 15: 3) may be replaced with another pigment or carbon black. In order to change the melt index (MI value) of a toner of a certain color, the number of parts by mass of 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, which is a polymerization initiator, may be increased or decreased. . The melt index will be described later.

Next, an example of toner production will be described. Using a Henschel mixer, 100 parts of toner particles are mixed with 1.4 parts of hydrophobic silica having a specific surface area of 200 m ² / g by BET method and 0.1 part of titanium oxide having a specific surface area of 100 m ² / g by BET method. The mixing step is performed at 4000 rpm for 120 seconds (mixing step 1). The hydrophobicity of 1.4 parts of hydrophobic silica is 81. The hydrophobicity of 0.1 part of titanium oxide is 60. Henschel mixer is manufactured by Mitsui Mining. Thereafter, a pause process for 120 seconds is taken (pause process 1). Immediately after the pause process for 120 seconds, the mixing process is resumed, and a mixing process for 140 seconds is performed (mixing process 2). Thereafter, a pause process of 120 seconds is taken (pause process 2). After 120 seconds, mixing was resumed immediately and mixing was continued for 160 seconds (mixing step 3). Thereafter, a pause process of 120 seconds is taken (pause process 3). Immediately after 120 seconds, mixing was resumed and mixing was continued for 160 seconds (mixing step 4). By repeating the mixing step and the pause step, the maximum temperature reached in the tank was about 30 ° C. A toner was obtained as described above.

<Explanation of melt index>
It was found that the level of occurrence of image defects (hereinafter referred to as image defects due to insufficient lubricity) caused by turning of the cleaning blade, chipping of the edge portion, chattering, and the like varies depending on the color of the toner. This is considered to be because the lubricity given to the cleaning blade differs depending on the color of the toner. Therefore, in an image forming unit in which a large amount of toner that is likely to cause turning, chipping at the edge, or chatter is collected on the cleaning blade, it is necessary to take measures according to the lubricity that the toner imparts to the cleaning blade. Accordingly, the inventors of the present patent application have found a melt index (hereinafter referred to as MI value) as a parameter that serves as a guideline for toner lubricity. The smaller the MI value, the lower the viscosity of the toner and the higher the lubricating effect of the cleaning blade.

  A method for measuring the MI value, which is a toner parameter that affects the lubricity of the cleaning blades 6a to 6d, will be described. The MI value is a measured value of the toner discharge amount in 10 minutes at a predetermined temperature and load. In the present Example 1, it is set as the value measured on condition of the following. This measurement basically conforms to <JIS standard K-7210>. Semi-automatic 2-A Melt Index (Toyo Seiki Co. Ltd) is used as a measuring device. An orifice having a hollow inner diameter of 2.095 mm is put, and the temperature is adjusted to 110 ° C. in advance, and 3 to 8 g of a toner sample is weighed and put therein. At this time, the metal piston is set while being careful not to enter air bubbles, and the temperature is maintained at 110 ° C. for 5 minutes or more. Thereafter, the measurement is performed while applying a constant load such that the sum of the piston and the weight becomes 98 N (10.0 kgf). The measurement may be performed at an arbitrary time and converted to a toner discharge amount of 10 minutes.

  FIG. 4 shows the correlation between the lubricity received by the cleaning blades 6a to 6d used in the first embodiment and the MI value of the toner. The lubricity received by the cleaning blades 6a to 6d is considered as a parameter corresponding to the chatter phenomenon of the cleaning blades 6a to 6d. When the cleaning blades 6a to 6d are swayed (stick slip) with respect to the surfaces of the photosensitive drums 1a to 1d, toner passes through the cleaning blades 6a to 6d and contaminates the surfaces of the charging rollers 2a to 2d to cause image defects. Therefore, as an index of lubricity, the vertical axis of FIG. 4 shows the image defect rank of the surface contamination of the charging rollers 2a to 2d. The temperature inside the image forming apparatus main body is 30 ° C. The image defect rank is an image defect rank when the printing operation is performed until the end of the durable life of the cleaning blades 6a to 6d under the condition of low printing (about 1%). As the image defect rank, ◯: no image defect occurred, Δ: slight occurrence, x: occurrence. The Δ level is an image allowable level, but aims at an image allowable limit level exceeding the Δ level. Actually, black toners having three levels of MI values of ○, Δ, and × of image defect ranks were prepared and examined. The MI value shown on the horizontal axis in FIG. 4 is a relative value with respect to ◯, Δ, and x of the image defect rank. As a result, there was a correspondence between the MI value ratio and the image defect rank. As can be seen from FIG. 4, it was proved that the toner having a lower MI value gives higher lubricity to the cleaning blades 6a to 6d. In the first embodiment, the relative value of the MI value is 1.08, and the image allowable limit level can be achieved. However, this threshold value is not unambiguous because it fluctuates by changing the conditions of the image forming process (charging, exposure, development, and transfer processes).

  Next, a toner supply mode for supplying toner to the cleaning blades 6a to 6d in order to reduce the occurrence of image defects due to insufficient lubricity of the cleaning blades 6a to 6d of the image forming units Py to PBk will be described. Two types of toner supply modes are stored in the memory of the control unit 200. One is a toner supply mode (hereinafter referred to as a first toner supply mode) for supplying toner from a predetermined image forming unit to the same predetermined image forming unit. The first toner supply mode is stored for each of the image forming units Py to PBk. The other is a toner supply mode (hereinafter referred to as a second toner supply mode) for supplying toner from a predetermined image forming unit using a toner having a low MI value to another image forming unit using a toner having a high MI value. ). In the second toner supply mode, a toner having a low MI value refers to a toner that imparts high lubricity to the cleaning blade, and a toner having a high MI value refers to a toner that imparts low lubricity to the cleaning blade. Specific numerical values of the MI values of the toners used in the image forming units Py to PBk will be described later. This second toner supply mode is a combination of an image forming unit using a toner with a low MI value and an image forming unit using a toner with a high MI value among the four image forming units Py to PBk. It is stored for each forming unit.

  A toner supply control sequence according to the first toner supply mode will be described with reference to FIGS. FIG. 1 shows a toner supply control sequence related to the image forming unit Py. FIG. 1A is an explanatory diagram showing the toner supply operation of the image forming unit Py, and FIG. 1B is an operation timing chart of the image forming unit Py shown in FIG. In FIG. 1B, the horizontal axis represents time, and the vertical axis represents ON / OFF of the charging bias power source, the exposure apparatus, and the developing bias, and the transfer bias potential. The first toner supply mode is performed in the post-rotation process (during non-image formation) after the image forming operation by the image forming control sequence is completed. For the convenience of describing the first toner supply mode, the pre-rotation process and the image forming process of the image forming operation by the image forming control sequence of the image forming unit Py will be described. The pre-rotation process is a period in which the photosensitive drum 1a is rotated in accordance with a print command and the charging roller 2a, the developing roller 41, and the transfer roller 8a are subjected to a predetermined pre-image formation operation. In the image forming process, after the pre-rotation process is completed, an image forming process is performed on the photosensitive drum 1a that continues to rotate, and a recording material carrying a toner image is conveyed to the fixing device, and the first image is formed. Is the period during which When image formation is continuously performed, the image formation process is repeated, and the image formation process is repeated for a predetermined number of prints. The post-rotation stroke refers to the charging roller 2a, the exposure device 3a, the developing roller 41, and the transfer roller by rotating the photosensitive drum 1a even after the image forming step of the last print command is completed in order to switch to the first toner supply mode. This is a period during which 8a performs a predetermined post-image operation.

  In the pre-rotation process, first, the charging bias power source is turned on and a charging bias is applied to the primary charging roller 2a to charge the surface of the photosensitive drum 1a. Next, after applying a positive (+) transfer bias from the transfer bias power source to the transfer roller 8 a, the developing bias power source is turned on and a developing bias (DC voltage) is applied to the developing roller 41.

  In the image forming process, the exposure device 3a is turned on, an electrostatic latent image is formed on the surface of the photosensitive drum 1a by the exposure device 3a, and the exposure device 3a is turned off. In parallel with the formation of the electrostatic latent image on the surface of the photosensitive drum 1a by the exposure device 3a, the electrostatic latent image is developed as a toner image by using the developing roller 41 with toner. The toner image on the surface of the photosensitive drum 1a is transferred onto the recording material P held on the surface of the transfer belt 10 by the transfer bias applied to the transfer roller 8a. As a result, an unfixed toner image is formed on the recording material P.

  In the post-rotation stroke, the charging bias is continuously applied to the charging roller 2a from the previous rotation stroke, and the developing bias is applied to the developing roller 41. The surface of the photosensitive drum 1a is charged to −400 V by a charging roller 2a to which a charging bias is applied. In this state, a transfer bias having a polarity of 0 (zero) or negative (-) different from the polarity of the transfer bias applied in the image forming process is applied from the transfer bias power source to the transfer roller 8a. Next, the exposure device 3a is turned on, and after the toner supply electrostatic latent image (toner supply electrostatic image) is formed in a predetermined region on the surface of the photosensitive drum 1a by the exposure device 3a, the exposure device 3a is turned off. The toner supplying electrostatic latent image on the surface of the photosensitive drum 1a is developed as a toner supplying toner image (supplying toner image) T by using the toner t by the developing roller 41 to which a developing bias is applied ((toner image of FIG. 1). b)). Next, the charging bias power supply is turned off and the developing bias power supply is turned off. The toner image T on the surface of the photosensitive drum 1a is conveyed toward the cleaning blade 6a through the transfer nip portion Na as the photosensitive drum 1a rotates. The toner image T on the surface of the photosensitive drum 1a adheres to the surface of the photosensitive drum 1a by the transfer bias of 0 (zero) or negative (-) polarity applied to the transfer roller 8a when passing through the transfer nip portion Na. Maintained. The toner image T on the surface of the photosensitive drum 1a is supplied to a contact area (drum cleaning nip area) Ar between the surface of the photosensitive drum 1a and the cleaning blade 6a as the photosensitive drum 1a rotates.

  Next, a toner supply control sequence according to the second toner supply mode will be described with reference to FIGS. 2A and 2B, the toner supply control sequence for the image forming unit Pm using toner that imparts high lubricity to the cleaning blade and the image forming unit PBk that uses toner that imparts low lubricity to the cleaning blade is illustrated. Show. For convenience of explanation, an image forming unit using toner that imparts high lubricity to the cleaning blade is referred to as a toner supply image forming unit (predetermined image forming unit). An image forming unit that uses toner that imparts low lubricity to the cleaning blade is referred to as a toner collection image forming unit (an image forming unit other than a predetermined image forming unit). FIG. 2A is a diagram illustrating a toner supply operation of the toner supply image forming unit Pm and a toner recovery operation of the toner recovery image forming unit PBk. FIG. 7B is a toner supply operation timing chart of the toner supply image forming unit Pm and a toner recovery operation timing chart of the toner recovery image forming unit PBk shown in FIG. In FIG. 2A, the horizontal axis represents time, and the vertical axis represents ON / OFF of the charging bias power source, the exposure apparatus, and the developing bias, and the transfer bias potential.

  The second toner supply mode is performed in a post-rotation stroke (during non-image formation) after the image formation process by the image formation control sequence is completed. In the toner supply image forming unit Pm, the pre-rotation process and the image formation process of the image forming process according to the image formation control sequence are the same as those in the first toner supply mode. Is omitted.

  In the post-rotation stroke of the toner supply image forming portion Pm, the charging bias is continuously applied to the charging roller 2b and the developing bias (DC voltage) is applied to the developing roller 41 from the pre-rotation stroke of the toner supply image forming portion Pm. Yes. Further, a transfer bias having a positive (+) polarity is applied from the transfer bias power source to the transfer roller 8b from the previous rotation stroke of the toner supply image forming unit Pm. First, the exposure device 3b of the toner supply image forming unit Pm is turned on, and a toner supply electrostatic latent image (toner supply electrostatic image) is formed in a predetermined area on the surface of the photosensitive drum 1b by the exposure device 3b. Turn off. The toner supplying electrostatic latent image on the surface of the photosensitive drum 1b is developed as a toner supplying toner image (supplying toner image) T by using the toner t by the developing roller 41 to which a developing bias is applied ((toner image of FIG. 2). b)). Next, the charging bias power supply is turned off and the developing bias power supply is turned off. The toner image T on the surface of the photosensitive drum 1b is conveyed toward the transfer nip portion Nb as the photosensitive drum 1b rotates. The toner image T on the surface of the photosensitive drum 1b is transferred and transferred from the surface of the photosensitive drum 1b to the surface of the transfer belt 10 by the transfer bias having a positive (+) polarity applied to the transfer roller 8b in the transfer nip portion Nb. . Next, a transfer bias of 0 (zero) or negative (-) polarity is applied from the transfer bias power source to the transfer roller 8b, and the transfer of the toner image T from the surface of the photosensitive drum 1b to the surface of the transfer belt 10 is stopped. The toner image T on the surface of the transfer belt 10 is conveyed from the transfer nip portion Nb of the toner supply image forming portion Pm to the transfer nip portion Nc of the toner recovery image forming portion Pc as the transfer belt 10 rotates.

  In the image forming process of the toner recovery image forming unit PBk, the charging bias power source of the toner recovery image forming unit PBk is turned off before the charging bias power source is turned off in the image forming process of the toner supply image forming unit Pm. In the image forming process, the exposure device 3b of the toner supply image forming unit Pm is turned off, and at the same time, the exposure device 3d of the toner recovery image forming unit PBk is turned off. In the post-rotation stroke, the developing bias power source of the toner recovery image forming unit PBk is turned off before the developing bias power source is turned off in the post-rotation stroke of the toner supply image forming unit Pm. Further, in the post-rotation stroke, the toner recovery image forming unit is configured to apply the transfer bias of 0 (zero) or negative (-) polarity from the transfer bias power source to the transfer roller 8b in the post-rotation stroke of the toner supply image forming unit Pm. Turn off the development bias power supply of PBk. At the same time as the developing bias power source of the toner recovery image forming portion PBk is turned off, a transfer bias having a negative (−) polarity with respect to the surface potential of the photosensitive drum 1d is applied from the transfer bias power source to the transfer roller 8d. As a result, the toner image T on the surface of the transfer belt 10 flies from the surface of the transfer belt 10 to the surface of the photosensitive drum 1d at the transfer nip portion Nd, and is transferred and collected. Even if the transfer bias applied to the transfer roller 8d is the same as the surface potential of the photosensitive drum 1d, a certain amount of toner can be collected. In order to collect a larger amount of toner, it is preferable to apply a transfer bias having a negative (-) polarity with respect to the surface potential of the photosensitive drum 1d. The toner image T transferred to the surface of the photosensitive drum 1d is supplied to a contact area (drum cleaning nip area) Ar between the surface of the photosensitive drum 1d and the cleaning blade 6d as the photosensitive drum 1d rotates. As described above, the switching timing of the charging bias, developing bias, transfer bias power supply and exposure apparatus in the second toner supply mode is shown. However, the present technology can be realized at other timings. That is, another timing may be used as long as the toner supplied from the toner supply image forming unit Pm can be recovered by the toner recovery image forming unit PBk during the post-rotation.

  When the toner image for toner supply is formed on the surface of the photosensitive drum, it is preferable to set the developing bias so that the development contrast between the light portion potential of the exposed portion on the surface of the photosensitive drum and the developing bias is maximized. At this time, the toner supply toner image formed on the surface of the photosensitive drum is a solid image (a toner image having a maximum image density). In the first exemplary embodiment, as the toner image for toner supply, a solid image having a short horizontal band in the sub-scanning direction on the surface of the photosensitive drum is formed over the entire image forming area in the main scanning direction on the surface of the photosensitive drum. The dimension of the solid image on the surface of the photosensitive drum in the sub-scanning direction is 63 mm.

  The image forming apparatus according to the first exemplary embodiment is configured such that the control unit 200 appropriately selects and switches between two types of toner supply modes, a first toner supply mode and a second toner supply mode. The first toner supply mode is selected when image defects due to insufficient lubrication of the cleaning blades 6a to 6d are likely to occur in the image forming units Py to PBk. When the first toner supply mode is selected, the toner of the developing devices 4a to 4d can be supplied to the contact area Ar between the photosensitive drums 1a to 1d and the cleaning blades 6a to 6d in each of the image forming units Py to PBk. As a result, it is possible to prevent image defects from occurring due to insufficient lubricity of the cleaning blades 6a to 6d. The second toner supply mode is selected when an image defect is likely to occur due to insufficient lubricity of the cleaning blade 6d of the image forming unit PBk using black toner. When the second toner supply mode is selected, the toner of the image forming units Py, Pm, and Pc using toner that imparts high lubricity to the cleaning blade 6d of the image forming unit PBk is used as the photosensitive drum and the cleaning blade of the image forming unit PBk. Can be supplied to the contact area Ar. As a result, it is possible to prevent the occurrence of image defects due to insufficient lubricity of the cleaning blade 6d of the image forming unit PBk.

  Image defects caused by insufficient lubrication of the cleaning blade, especially chattering on the surface of the photosensitive drum, can occur when low-printing (printing rate of less than 3% per recording material) continues or in high-temperature and high-humidity environments. It tends to occur below. Therefore, the image forming apparatus according to the first exemplary embodiment uses the first toner supply mode based on the average print rate during image formation of each of the image forming units Py to PBk and the temperature inside or outside the image forming apparatus main body. Alternatively, the configuration is such that the mode is automatically switched to the second toner supply mode. In FIG. 3B, reference numeral 45 denotes a temperature sensor as a temperature detection member. The temperature sensor 45 detects the temperature inside the image forming apparatus main body. Reference numerals 47a, 47b, 47c, and 47d denote pixel count units provided corresponding to the image forming units Py, Pm, Pc, and PBk. Each of the pixel counting units 47a to 47d counts the number of pixels of the print image based on the corresponding image information every time the image forming units Py to PBk receiving the print command print one sheet. The control unit 200 takes in the count value of the number of pixels from each of the pixel count units 47a to 47d and stores it as a printing rate per page (= pixel count number / number of sheets). The count value of the number of pixels is taken in units of a printing rate of 0.1% per sheet, and the second decimal place is rounded off for each sheet. Then, based on the printing rate per sheet, the average printing rate during a predetermined period at the time of image formation, that is, the first toner supply mode and the second toner supply mode, from the previous toner supply mode to the next toner supply mode. The average printing rate during image formation is determined. That is, the value obtained by integrating the printing rate per sheet from the time of toner discharge in the toner supply mode performed last time / the number of prints accumulated from the time of toner discharge in the toner supply mode performed last time is obtained as the average printing rate. Storage media 46a, 46b, 46c, and 46d (FIG. 3A) are provided in the developing containers 43 of the developing devices 4a to 4d of the image forming units Py to PBk. As the storage media 46a to 46d, NV-RAM (Non Volatile-RAM) having a storage capacity of 2 kbytes is used, but the storage media 46a to 46d are not limited to this, and are storage media such as magnetic storage media and optical storage media. There may be. The recording medium 46a stores the threshold body temperature and the threshold average printing rate of the image forming unit Py. The storage medium 46b stores the threshold body temperature and the threshold average printing rate of the image forming unit Pm. The storage medium 46c stores a threshold temperature and a threshold average printing rate of the image forming unit Pc. The storage medium 46d stores the threshold main body temperature and the threshold average printing rate of the image forming unit PBk. The threshold body temperature stored in each of the recording media 46a to 46d is 19 ° C., and the threshold average printing rate is 3%. The control unit 200 fetches a detected temperature inside the image forming apparatus main body (hereinafter referred to as a main body temperature) from the temperature sensor 45 every time the image forming operation according to the print command is completed in each of the image forming units Py to PBk. The body temperature and the threshold body temperature are compared. Each time the image forming operation according to the print command is completed in each of the image forming units Py to PBk, the above average printing rate is obtained for each of the image forming units Py to PBk, and this average printing rate corresponds to this average printing rate. The threshold average printing rates of the image forming units Py to PBk are compared. When the internal temperature is lower than the threshold internal temperature or the average printing rate is equal to or higher than the threshold average printing rate, the mode is switched to the first toner supply mode. When the internal body temperature is equal to or higher than the threshold internal temperature, and the average print rate of the image forming unit PBk using the black toner is less than the threshold average print rate among the average print rates at the time of image formation of the image forming units Py to PBk To the second toner supply mode. When the internal temperature is equal to or higher than the threshold internal temperature and the average printing rate of the image forming unit PBk is equal to or higher than the threshold average printing rate, the first toner supply mode is selected.

  Table 1 shows the degree of occurrence of toner slippage due to the chatter of the cleaning blades 6a to 6d when the image forming units Py to PBk are switched to the first toner supply mode, with ranks of ◯, Δ, and X. ○ does not occur, Δ indicates slight occurrence (image limit level), and x indicates occurrence. As can be seen from Table 1, the toner slipping phenomenon tends to deteriorate under black (Bk) toner, low printing (average printing rate of less than 3%), and high temperature (internal temperature of 23 ° C. or more). The rank was determined based on the same criteria as in FIG. The high printing in the average printing rate column has a printing rate of 3% or more per recording material.

  Here, the inventor of the present application transfers the fourth image forming unit PBk using black (Bk) toner to the fourth image forming unit Py, Pm, Pc in the second toner supply mode. A study was conducted to supply toner from a predetermined image forming unit. The results are shown in Table 2. As shown in Table 2, the MI value of yellow toner is 1.00. The MI value of magenta toner is 0.86. The MI value of cyan toner is 0.93. The MI value of black toner is 1.29. That is, yellow, magenta, cyan, and black toners have different levels of lubricity given to the cleaning blades 6a, 6b, 6c, and 6d of the corresponding image forming portions Py, Pm, Pc, and PBk. In Table 2, A in the mode column is the first toner supply mode, and B is the second toner supply mode. As shown in Table 2, the black toner has a higher MI value than the yellow, magenta, and cyan toners. If the MI value of the black toner is set to the same level as the MI values of the yellow, magenta, and cyan toners, the fixing property of the black toner is lowered and image defects occur. Therefore, although it is difficult to improve the black toner, the lack of lubricity of the cleaning member in PBk can be compensated by using a toner having a high MI value such as yellow, magenta, and cyan. Therefore, the current MI value of the black toner shown in Table 2 is the minimum value at which the second toner supply mode (Mode B in Table 2) can be implemented. The MI values of yellow, magenta, and cyan toners are all 1.0 or less. The MI values of the yellow, magenta, and cyan toners are below the MI value threshold value of 1.08 obtained in FIG. For this reason, in the image forming unit Py using yellow toner, the image forming unit Pm using magenta toner, and the image forming unit Pc using cyan toner, sufficient lubricity is given to the cleaning blades 6a, 6b, and 6c. be able to. As a result of the examination, the image forming unit PBk using a black toner having a low cleaning blade lubricity (high MI value) and another color toner having a high cleaning blade lubricity (low MI value). Py, Pm, and Pc toners were supplied. Then, in the image forming portion PBk using black toner, the lubricity of the cleaning blade 6d was improved and the toner slipping phenomenon was improved. Thus, it has been proved that it is effective to supply the toner of the image forming units Py, Pm, and Pc using the toner having the low MI value to the image forming unit PBk using the toner having the high MI value. It has also been confirmed that the same effect can be obtained with any toner in the image forming portions Py, Pm, and Pc supplied to the image forming portion PBk using toner having a high MI value.

  From the above results, in the image forming apparatus of the first embodiment, as shown in Table 3, the threshold internal temperature of each storage medium 46a to 46d is set to 19 ° C., and the threshold average printing rate is set to 3%. Yes. The control unit 200 compares the internal temperature of the main body captured from the temperature sensor 45 with the threshold internal temperature of the storage media 46a to 46d every time the image forming operation according to the print command is completed in each of the image forming units Py to PBk. When the internal temperature is lower than the threshold internal temperature, the first print rate is the first regardless of the comparison result between the average print rate at the time of image formation of the image forming units Py to PBk and the threshold average print rate of the storage media 46a to 46d. Toner supply mode is selected. Then, the charging bias power source, laser diode and polygon scanner motor, driving motor, developing bias power source, transfer bias power source and the like of the driving units PyD to PBkD are controlled so that the image forming units Py to PBk are switched to the first toner supply mode. To do. The average printing rate of the image forming unit PBk using the black toner among the average printing rates at the time of image formation of each of the image forming units Py to PBk is equal to or higher than the threshold main body temperature of the storage media 46a to 46d. If it is less than the average printing rate, the second toner supply mode is selected. The driving unit PmD is configured to switch the image forming unit Pm using magenta toner having the lowest MI value and the image forming unit PBk using black toner among the image forming units Py, Pm, and Pc to the second toner supply mode. , PBkD are controlled. That is, the charging bias power source, laser diode and polygon scanner motor, driving motor, developing bias power source, transfer bias power source, and the like of the driving units PmD and PBkD are controlled. In the second toner supply mode, the supply of toner to the image forming unit PBk is not limited to the image forming unit Pm. In consideration of the toner consumption of the image forming unit Pm, the image forming unit starts from one or two of the other two image forming units Py and Pc other than the image forming unit Pm and has sufficient remaining toner. You may make it supply a toner to PBk. Further, a fixed amount of toner may be supplied from each of the three image forming units Py, Pm, and Pc to the image forming unit PBk. The first toner supply mode is selected when the internal temperature is equal to or higher than the threshold internal temperature and the average printing rate of the image forming unit PBk is equal to or higher than the threshold average printing rate. In this embodiment, since the black toner has low lubricity, the average print rate of the image forming unit PBk is referred to. However, not only the image forming unit PBk but also the average print rate of the image forming unit having insufficient toner lubricity is referred to. can do.

  The image forming apparatus according to the first exemplary embodiment can supply toner to the contact area between the surface of the photosensitive drum and the cleaning blade in each image forming unit by switching to the first toner supply mode. This can reduce the occurrence of image defects due to insufficient lubrication of the cleaning member in each image forming unit. Also, by switching to the second toner supply mode, the surface of the photosensitive drum of the image forming unit that uses toner with low lubricity (toner with high MI value) from the image forming unit that uses toner with high lubricity (toner with low MI value) The toner can be supplied to the contact area between the cleaning blade and the cleaning blade. Accordingly, it is possible to reduce the occurrence of image defects due to insufficient lubrication of the cleaning member in the image forming unit using toner having low lubricity.

[Example 2]
Another example of the image forming apparatus will be described. In the image forming apparatus according to the second embodiment, the same members / portions as those in the image forming apparatus according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. FIG. 5 is a schematic configuration diagram of a cartridge of the image forming apparatus according to the second embodiment. The image forming apparatus according to the second embodiment has the same configuration as the image forming apparatus according to the first embodiment except for the following configuration.
In each of the image forming units Py to PBk, the photosensitive drums 1a to 1d, the charging rollers 2a to 2d, the developing devices 4a to 4d, and the cleaning blades 6a to 6d are integrated as process cartridges 51a, 51b, 51c, and 51d via a frame member 50. It has become. That is, the photosensitive drums 1a to 1d, the charging rollers 2a to 2d, the developing devices 4a to 4d, and the cleaning blades 6a to 6d are accommodated and integrated at predetermined positions inside the frame member 50 to form process cartridges 51a to 51d. Yes. Hereinafter, the process cartridge is referred to as a cartridge. Storage media 46 a to 46 d are provided at predetermined positions on the outer peripheral surface of the frame member 50. The cartridges 51a to 51d are detachably mounted on the image forming apparatus main body. In the second embodiment, a protrusion (not shown) is provided on the outer surface of the frame member 50 of the cartridges 51a to 51d, and a recess (not shown) for holding the protrusion is provided in the image forming apparatus main body. When the cartridges 51a to 51d are mounted on the image forming apparatus main body, the cartridges are pushed into the image forming apparatus main body while the protrusions of the cartridges 51a to 51d are held in the concave portions of the image forming apparatus main body. Thus, the cartridges 51a to 51d are mounted at predetermined printing operation positions of the image forming apparatus main body. When removing the cartridges 51a to 51d from the main body of the image forming apparatus, the cartridges 51a to 51d are pulled out from the printing operation position to the outside of the main body of the image forming apparatus while the protrusions of the cartridges 51a to 51d are held in the recesses of the main body of the image forming apparatus. .

  Similar to the image forming apparatus of the first embodiment, the image forming apparatus according to the second embodiment stores and stores the internal temperature and temperature stored in the main body from the temperature sensor 45 every time the image forming operation according to the print command is completed in each of the image forming units Py to PBk. The threshold internal temperature of the media 46a to 46d is compared. The comparison between the main body temperature and the threshold main body temperature is not limited to this, and may be performed when the cartridges 51a to 51d are mounted on the main body of the image forming apparatus. Further, regarding the average printing rate, by providing the storage media 46a to 46d in the cartridge, the history of the average printing rate unique to the cartridge can be used even when the cartridge is detached, so that the toner supply mode can be selected with higher accuracy. Can do.

  Also in the image forming apparatus according to the first exemplary embodiment, by switching to the first toner supply mode, the toner image for supplying toner can be supplied to the contact area between the surface of the photosensitive drum and the cleaning blade in each image forming unit. Also, by switching to the second toner supply mode, the surface of the photosensitive drum of the image forming unit that uses toner with low lubricity (toner with high MI value) from the image forming unit that uses toner with high lubricity (toner with low MI value) The toner can be supplied to the contact area between the cleaning blade and the cleaning blade. Therefore, the same effect as the image forming apparatus of the first embodiment can be obtained.

[Example 3]
Another example of the image forming apparatus will be described. In the image forming apparatus according to the third embodiment, the same members and portions as those in the image forming apparatus according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. FIG. 6 is a schematic configuration diagram of the image forming apparatus according to the third embodiment. The image forming apparatus shown in the third embodiment uses an intermediate transfer belt 10A instead of the transfer belt 10 of the image forming apparatus of the first embodiment. The intermediate transfer belt 10A is arranged along the first to fourth image forming portions Py to PBk. The first to fourth image forming units Py to PBk are arranged in a line from the upstream side (right side) to the downstream side (left side) in the rotation direction (arrow direction) of the intermediate transfer belt 10A. Then, the toner images of four different colors formed by the image forming portions Py to PBk are sequentially transferred onto the outer peripheral surface (front surface) of the intermediate transfer belt 10A, whereby a four-color full color image is formed on the surface of the intermediate transfer belt 10A. To form. The intermediate transfer belt 10A is wound around the driving roller 7, the driven roller 9, and the secondary transfer counter roller 13 so as to straddle the photosensitive drums 1a to 1d of the image forming portions Py to PBk. The intermediate transfer belt 10A is rotated in the direction of the arrow by the rotation of the driving roller 7 at a peripheral speed corresponding to the rotational peripheral speed of the photosensitive drums 1a to 1d. Transfer rollers 8a to 8d as first transfer members disposed so as to face the photosensitive drums 1a to 1d with the intermediate transfer belt 10A sandwiched on the inner peripheral surface (inner surface) side of the intermediate transfer belt 10A are intermediate transfer belts. 10A is in contact with the inner surface. The first transfer is performed between the surface of the intermediate transfer belt 10A and the surfaces of the photosensitive drums 1a to 1d by causing the outer peripheral surface (surface) of the intermediate transfer belt 10A and the surfaces of the photosensitive drums 1a to 1d to face each other with a predetermined gap. Nip portions Na, Nb, Nc, and Nd are formed. In the image forming apparatus shown in the third embodiment, the secondary transfer roller 14 as the second transfer member is disposed so as to face the secondary transfer counter roller 13 with the intermediate transfer belt 10A interposed therebetween. A second transfer nip portion Nt is formed between the outer peripheral surface (front surface) of the secondary transfer roller 14 and the surface of the intermediate transfer belt 10A.

  An image forming operation of the image forming apparatus according to the third exemplary embodiment will be described. In the image forming apparatus according to the third exemplary embodiment, toner images are formed on the surfaces of the photosensitive drums 1a to 1d of the image forming units Py to PBk as in the image forming apparatus according to the first exemplary embodiment. The toner images formed on the surfaces of the photosensitive drums 1a to 1d of the image forming portions Py to PBk are outer peripheral surfaces (surfaces) of the intermediate transfer belt 10A rotated at a peripheral speed corresponding to the rotational peripheral speed of the photosensitive drums 1a to 1d. ). That is, in the transfer nip portion Na of the image forming portion Py, a predetermined transfer bias is applied to the transfer roller 8a from the transfer bias power source, whereby the yellow toner image on the surface of the photosensitive drum 1a is transferred to the surface of the intermediate transfer belt 10A. . Similarly, at the transfer nip portion Nb of the second image forming portion Pm, a predetermined transfer bias is applied from the transfer bias power source to the transfer roller 8b, whereby the magenta toner image on the surface of the photosensitive drum 1b becomes the surface of the intermediate transfer belt 10A. And transferred onto the yellow toner image. In the transfer nip portion Nc of the third image forming portion Pc, a predetermined transfer bias is applied to the transfer roller 8c from the transfer bias power source. As a result, the cyan toner image on the surface of the photosensitive drum 1c is transferred so as to overlap the yellow toner image and the magenta toner image on the surface of the intermediate transfer belt 10A. In the transfer nip Nd of the fourth image forming unit PBk, a predetermined transfer bias is applied to the transfer roller 8d from the transfer bias power source. As a result, the black toner image on the surface of the photosensitive drum 1c is transferred so as to overlap the yellow toner image, the magenta toner image, and the cyan toner image on the surface of the intermediate transfer belt 10A. As a result, four full-color unfixed toner images are carried on the surface of the intermediate transfer belt 10A. The toner image carried on the surface of the intermediate transfer belt 10A is conveyed to the transfer nip portion Nt as the intermediate transfer belt 10A rotates. The recording material P is transported to the transfer nip portion Nt by a predetermined recording material transport mechanism (not shown) from a feeding cassette (not shown). The recording material P is sandwiched between the surface of the intermediate transfer belt 10A and the outer peripheral surface (front surface) of the transfer roller 14 at the transfer nip portion Nt, and is transported to the state (nip transport). A toner image on the surface of the intermediate transfer belt 10A is transferred onto the recording material P by applying a predetermined transfer bias from a transfer bias power source (not shown) to the transfer roller 14 at the transfer nip Nt. The recording material P carrying the toner image is separated from the surface of the intermediate transfer belt 10A by the curvature of the surface of the intermediate transfer belt 10A. The recording material P separated from the surface of the intermediate transfer belt 10 is introduced into a fixing nip portion between a heat fixing member and a pressure member of a fixing device (not shown). The recording material P is heated and fixed on the recording material P by receiving heat and pressure while being nipped and conveyed at the fixing nip portion. Then, the recording material P is discharged onto a discharge tray (not shown) provided outside the image forming apparatus main body by a predetermined recording material discharge mechanism (not shown).

  The image forming apparatus according to the third embodiment, similar to the image forming apparatus according to the first embodiment, stores and stores the internal temperature captured from the temperature sensor 45 every time the image forming operation according to the print command is completed in each of the image forming units Py to PBk. The threshold values of the media 46a to 46d are compared with the temperature inside the main body. In each of the image forming units Py to PBk, the photosensitive drums 1a to 1d, the charging rollers 2a to 2d, the developing devices 4a to 4d, and the cleaning blades 6a to 6d are integrated as process cartridges 51a, 51b, 51c, and 51d through a frame member 50. It may be made.

  Also in the image forming apparatus according to the third exemplary embodiment, by selecting the first toner supply mode, toner can be supplied to the contact area between the surface of the photosensitive drum and the cleaning blade in each image forming unit. In addition, by selecting the second toner supply mode, the photosensitive drum of the image forming unit that uses toner with low lubricity (toner with high MI value) is changed from the image forming unit that uses toner with high lubricity (toner with low MI value). Toner can be supplied to the contact area between the surface and the cleaning blade. Therefore, the same effect as the image forming apparatus of the first embodiment can be obtained.

[Other examples]
In the image forming apparatus 100 according to the first to third embodiments, the toner used in the first to fourth image forming units is set to 4 according to the difference in lubricity given to the cleaning blade in the contact area between the photosensitive drum surface and the cleaning blade. Two MI values are set. The MI value is not limited to four, and the initial purpose can be achieved if at least two MI values are set. In the image forming apparatuses according to the first to third embodiments, the image forming unit PBk that uses toner having a high MI value is used in the recording material conveyance direction with respect to the image forming units Py, Pm, and Pc that use toner having a low MI value. It is arranged on the downstream side (downstream in the rotation direction of the transfer belt and the intermediate transfer belt). In this case, the transfer belt 10 and the intermediate transfer belt 10A are rotated in the same direction as the rotation direction of the transfer belt 10 and the intermediate transfer belt 10A during image formation. As a result, toner can be supplied from the image forming units Py, Pm, and Pc that use toner having a low MI value to the image forming unit PBk that uses toner having a high MI value. Here, the recording material conveyance direction refers to the rotation direction of the transfer belt 10 and the intermediate transfer belt 10A during image formation. Further, the downstream side in the recording material conveyance direction refers to the downstream side in the rotation direction of the transfer belt 10 and the intermediate transfer belt 10A. When the image forming unit PBk using the toner having a high MI value is disposed on the upstream side in the recording material conveyance direction with respect to the image forming units Py, Pm, and Pc using the toner having the low MI value, the transfer belt 10 is used. The intermediate transfer belt 10A is rotated in the direction opposite to the recording material conveyance direction. That is, the transfer belt 10 and the intermediate transfer belt 10A are rotated in a direction opposite to the rotation direction of the transfer belt 10 and the intermediate transfer belt 10A during image formation. Here, the upstream side in the recording material conveyance direction refers to the upstream side in the rotation direction of the transfer belt 10 and the intermediate transfer belt 10A. As a result, toner can be supplied from the image forming units Py, Pm, and Pc that use toner having a low MI value to the image forming unit PBk that uses toner having a high MI value. Accordingly, it is preferable that the image forming portions Py, Pm, and Pc that use toner with a low MI value are disposed upstream of the image forming portion PBk that uses toner with a high MI value in the recording material conveyance direction. In the image forming apparatus 100 according to the first to third exemplary embodiments, the image forming unit PBk that uses toner having a high MI value is the highest in the recording material conveyance direction with respect to the image forming units Py, Pm, and Pc that use toner having a low MI value. You may arrange | position in the upstream. In this case, the transfer belt cleaning 12 is separated from the transfer belt 10 surface so that the transfer belt cleaning surface 12 is not cleaned by the transfer belt cleaning 12, and the transfer belt 10 is rotated in the direction opposite to the recording material conveyance direction. What is necessary is just to comprise. As a result, toner can be supplied from the image forming units Py, Pm, and Pc that use toner with a low MI value to the image forming unit PBk that uses toner with a high MI value.

  The temperature sensor is not limited to the inside of the image forming apparatus body (inside the image forming apparatus), and may be provided around the image forming apparatus body (around the image forming apparatus). In this case, the main body ambient temperature detected by the temperature sensor may be compared with the threshold main body temperature, and the first toner supply mode or the second toner supply mode may be switched according to the result. A humidity sensor may be used instead of the temperature sensor. In this case, a predetermined threshold body humidity is stored in each of the storage media 46a to 46d instead of the threshold body temperature. Then, the internal humidity of the main body or the humidity around the main body detected by the humidity sensor and the threshold internal humidity may be compared, and the first toner supply mode or the second toner supply mode may be switched according to the result. . A temperature sensor and a humidity sensor may be used in combination. In this case, each of the storage media 46a to 46d stores a threshold body temperature and a predetermined threshold body humidity. The main body temperature or the main body ambient temperature detected by the temperature sensor is compared with the main body ambient temperature, and the main body humidity or the main body ambient humidity is compared with the threshold main body humidity. The mode may be switched to the second toner supply mode.

1a, 1b, 1c, 1d: photosensitive drum, 2a, 2b, 2c, 2d: charging roller, 3a, 3b, 3c, 3d: exposure device, 4a, 4b, 4c, 4d: developing device, 6a, 6b, 6c, 6d: cleaning blade, 8a, 8b, 8c, 8d: transfer roller, 10: transfer belt, 10A: intermediate transfer belt, 45: temperature sensor, 50: frame member, 51a, 51b, 51c, 51d: cartridge, 200: control , Ar: contact area between photosensitive drum and cleaning blade, P: recording material, T: toner image for toner supply, t: toner

Claims (7)

An image forming apparatus for forming a color image on a recording material, comprising: a plurality of image forming units; and a rotatable conveying member arranged along the plurality of image forming units, wherein the plurality of image forming units Each of the units includes a rotatable image carrier, a developing unit that forms a toner image using toner of a predetermined color on the image carrier during image formation, and the toner image formed on the image carrier. A transfer member for transferring to a recording material conveyed by the member, and a cleaning member in contact with the image carrier, wherein a toner image is transferred from the image carrier to the recording material and then carried on the image carrier. And an image forming apparatus having a cleaning member for removing unnecessary toner.
A control unit, wherein the control unit causes the image carrier and the cleaning member to supply a supply toner image formed by the developing unit on the image carrier of a predetermined image forming unit during non-image formation. A first toner supply mode to be supplied to a contact area with the toner, and a toner image for supply formed by the developing means on the image carrier of a predetermined image forming portion during non-image formation is transferred to the transport member by the transfer member Then, the supply toner image is conveyed to another image forming unit other than the predetermined image forming unit by the conveyance member, and the supply toner image is transferred from the conveyance member to the image by the transfer member of the other image forming unit. And a second toner supply mode for transferring to the contact area between the image carrier and the cleaning member by the image carrier and transferring the plurality of images to the carrier. At least two different melt indexes are set in accordance with the difference in lubricity given to the cleaning member in the contact area between the cleaning member and the image carrier for the toner used in the image forming section, and the second toner supply mode Then, the low-melt-index toner is supplied from the predetermined image-forming unit using the low-melt-index toner to another image-forming unit using the high-melt-index toner.   The image forming apparatus includes a detection member that detects a temperature and humidity inside or around the image forming apparatus, and the control unit detects the second temperature based on the temperature, humidity, or temperature and humidity detected by the detection member. The image forming apparatus according to claim 1, wherein the image forming apparatus is switched to a toner supply mode.   The image forming apparatus includes a detection member that detects a temperature and humidity inside or around the image forming apparatus, and the control unit detects the temperature, humidity, or temperature and humidity detected by the detection member, and at the time of image formation. 2. The image forming apparatus according to claim 1, wherein the second toner supply mode is switched based on an average printing rate obtained using a printing rate of a toner image on a recording material.   The rotation direction of the conveyance member during image formation by another image forming unit using the toner having the high melt index with respect to the predetermined image forming unit using the toner having the low melt index among the plurality of image forming units 2. The apparatus according to claim 1, wherein when arranged on the upstream side, in the second toner supply mode, the conveyance member is rotated in a direction opposite to a rotation direction of the conveyance member during image formation. Image forming apparatus.   The rotation direction of the conveyance member during image formation by another image forming unit using the toner having the high melt index with respect to the predetermined image forming unit using the toner having the low melt index among the plurality of image forming units 2. The image according to claim 1, wherein when disposed on the downstream side, in the second toner supply mode, the conveying member rotates in the same direction as the rotation direction of the conveying member during image formation. Forming equipment.   The transfer member transfers a toner image carried by the image carrier to a recording material conveyed by the conveyance member during image formation, and a transfer bias having a predetermined polarity between the recording material and the image carrier. When the toner image formed by the developing means on the image carrier in a predetermined image forming unit during non-image formation is transferred to the transport member by the transfer member, the transport member, the image carrier, The image forming apparatus according to claim 1, wherein a transfer bias having a predetermined polarity different from the polarity of the predetermined transfer bias is applied during the period.   In the plurality of image forming units, the image carrier, the developing unit, and the cleaning member are integrated as a process cartridge via a frame member, and the process cartridge is removable from the image forming apparatus main body of the image forming apparatus. The image forming apparatus according to claim 1, wherein the image forming apparatus is mounted.