JP2009258319A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing the occurrence of faulty transfer caused by waviness of a transfer belt without causing shortening of the life of the transfer belt. <P>SOLUTION: In the image forming apparatus, an endless intermediate transfer belt 7 constituted by attaching meandering preventing ribs 28 to both ends in a width direction of the inner peripheral surface is wound round at least two rollers, and the meandering preventing ribs 28 attached to the intermediate transfer belt 7 are fit in fitting grooves formed on the outer periphery at both ends in a shaft direction of the roller, so as to regulate meandering of the intermediate transfer belt 7. In the apparatus, at least one of the meandering preventing ribs 28 is attached to the inner peripheral surface of the intermediate transfer belt 7 while the intermediate transfer belt 7 is tensioned in the width direction, a pulley 33 is arranged just before a transfer part in a recording material conveying direction, and also the meandering preventing rib 28 is fit in the fitting groove 33a formed on the outer periphery of the pulley 33. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a transfer belt such as an intermediate transfer belt that receives primary transfer of a toner image formed on an image carrier.

  In color image forming apparatuses such as color copying machines and color printers that form color images on paper by electrophotography, each color of magenta, cyan, yellow, and black formed on a plurality of image carriers such as photosensitive drums A system is adopted in which a toner image is primary-transferred sequentially on an endless intermediate transfer belt and superimposed to form a full-color image, and this full-color image is collectively transferred onto a recording material. As another method, a method of forming a full color image on a recording material by sequentially transferring and superimposing a color toner image on each image carrier on a recording material conveyed on a transfer belt is known. . Hereinafter, the intermediate transfer belt will be described in particular.

  By the way, the endless intermediate transfer belt is stretched and rotated around at least two rollers. The intermediate transfer belt includes a full color image on an image carrier, a primary transfer roller disposed opposite to the image carrier, and a recording material. A secondary transfer roller or the like that collectively transfers is in contact with the front surface or the back surface. Therefore, the intermediate transfer belt that moves while being in contact with the image carrier and the primary and secondary transfer rollers is likely to cause a slight deviation in tension at each position in the width direction, and the entire intermediate transfer belt is positioned in the width direction. The so-called meandering phenomenon that changes is frequently caused.

  As a method for preventing the occurrence of the meandering phenomenon of the intermediate transfer belt, meandering prevention ribs that are belt-like protrusions are attached to the inner surfaces of both ends of the intermediate transfer belt in the width direction, and the meandering prevention ribs of the stretching roller are attached to the meandering prevention ribs. There is generally known a method in which a fitting groove is formed at a corresponding position, and the intermediate transfer belt is rotated while fitting a meandering prevention rib in the fitting groove.

  By the way, the intermediate transfer belt needs to be formed into an endless shape, and as a method thereof, the end portions in the longitudinal direction of the plate-like base material can be joined to form an endless shape. There is a possibility that uneven running may occur due to a step in the belt or different curvature when bent.

  Therefore, in recent years, an intermediate transfer belt is formed by an inflation molding method. In this inflation molding method, the molten resin is ejected into a cylindrical shape in the process of molding the molten resin, and the ejected molten resin is conveyed while being cooled by an air flow, and then the cylindrical resin film is flattened. A roll-up system is adopted.

  However, in the above-described inflation molding method, since the cylindrical resin film is flattened and wound into a roll, the resin film has a crease mark, and there is a problem in that residual distortion that causes undulation of the intermediate transfer belt occurs. is there. In addition, due to the influence of the gate for feeding the resin to the die, which is the molten resin jet port of the cylinder, a subtle unevenness in the film thickness occurs in the formed cylindrical resin film, which also causes the undulation of the intermediate transfer belt. Cause.

  In addition, rubber is laminated on the surface of the base material to give elasticity to the cylindrical base material, adjust the resistance value of the base material, improve the releasability of the base material surface, etc. There are methods to coat materials with low energy, but heat is applied in the bonding, vulcanization, drying, and firing processes in these methods, so the temperature of the intermediate transfer belt can be reduced due to temperature non-uniformity during the cooling process. Rippling may occur.

  Thus, when undulation occurs in the intermediate transfer belt, the distance between the intermediate transfer belt and the image carrier and the distance between the recording material and the image carrier at the transfer portion vary, and as shown in FIG. A vertically long defective transfer portion corresponding to the wavy pattern of the intermediate transfer belt is generated in the image.

  In order to solve the above problem, Patent Document 1 proposes that the waviness of the intermediate transfer belt is stretched and eliminated by pushing the meandering prevention rib in the width direction of the intermediate transfer belt by the biasing force of the spring.

  In Patent Document 2, the shape of the primary transfer roller is a crown shape in which the diameter of the central portion is larger than the diameter of both end portions, so that the intermediate transfer belt in the transfer nip is moved from the central portion in the width direction to the end portions. A proposal has been made to eliminate the waviness of the intermediate transfer belt by stretching. In this case, the driving roller has an inverted crown shape and conveys the intermediate transfer belt while pulling both ends of the intermediate transfer belt in the width direction. Japanese Patent Application Laid-Open No. H11-228260 also discloses a method of increasing the friction coefficient at both ends of the drive roller as compared with the friction coefficient at the center as another method for increasing the conveying force at both ends of the drive roller.

  Patent Document 3 proposes to eliminate wrinkles and undulations of the intermediate transfer belt by pressing a rotating body or a plate-like member from the back side of the intermediate transfer belt immediately before the primary transfer portion. And this patent document 3 is also disclosing about the separation mechanism of a press member, and application of a bias.

  In Patent Document 4, the non-contact undulation amount detecting means such as a reflection sensor detects the undulation amount of the intermediate transfer belt, and an intermediate transfer is performed by moving a pressing member arranged immediately before the transfer portion according to the detection result. Proposals have been made to prevent the occurrence of transfer failure due to belt undulation and to extend the life of the intermediate transfer belt.

In Patent Document 5, the primary transfer roller is disposed so as to abut on the downstream side in the rotation direction of the image carrier with respect to the nip formed by the abutment of only the image carrier and the intermediate transfer belt, and until the transfer is completed. A configuration has been proposed in which the intermediate transfer belt is wound around the image carrier and the primary transfer roller, thereby preventing transfer failure due to wrinkles or undulations of the intermediate transfer belt on the downstream side of the primary transfer portion.
Japanese Patent Laid-Open No. 11-066532 JP 2003-122133 A JP-A-11-052759 Japanese Patent Laid-Open No. 11-258925 JP 2004-279638 A

  By the way, it is desirable that the intermediate transfer belt obtained by the inflation molding method eliminates the undulation in a state before the belt is stretched on the roller, but for this purpose, the inflation molded base material is stored and folded without being folded. If the substrate is transported or the base material is again put into the mold and the residual strain is removed over time, the cost will be significantly increased.

  The techniques proposed in Patent Documents 1 to 5 have the following problems.

  That is, in the configuration proposed in Patent Document 1, since the intermediate transfer belt is always pulled in the width direction, the life of the intermediate transfer belt is reduced. The meandering prevention ribs are required to have high adhesive strength, and the intermediate transfer belt is required to be strong enough not to bend at the base of the meandering prevention ribs. There are problems that the flexibility of the intermediate transfer belt is lowered and the cost is increased.

  In the configuration proposed in Patent Document 2, even if the intermediate transfer belt in the transfer nip is stretched from the center in the width direction to the end to eliminate the undulation of the intermediate transfer belt, it is not in time, just before the transfer nip. However, the undulation of the intermediate transfer belt is not eliminated, and there is a problem that a vertically long transfer defect occurs in the transferred image.

  The configuration proposed in Patent Document 3 has a problem that the life of the intermediate transfer belt is shortened because the pressing member is always in contact with the intermediate transfer belt while the intermediate transfer belt is being driven. In addition, since the intermediate transfer belt always receives a pressing force from the pressing member, the waviness of the intermediate transfer belt may be increased.

  In the configuration proposed in Patent Document 4, since it is necessary to arrange a large number of sensors on the intermediate transfer belt in accordance with the number of undulations generated in a plurality of locations in the width direction and the circumferential direction, this is not practical. In addition to requiring a large amount of cost, there is a problem that high detection accuracy cannot be obtained.

  In the configuration proposed in Patent Document 5, there is a problem in that it is impossible to prevent a transfer failure that occurs due to toner scattering that occurs upstream of the transfer nip portion or a sudden change in the toner charge amount due to discharge.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of transfer failure due to undulation of the transfer belt without causing a decrease in the life of the transfer belt. It is to provide.

  In order to achieve the above object, according to the first aspect of the present invention, an endless transfer belt formed by attaching meandering prevention ribs to both ends in the width direction of the inner peripheral surface is wound around at least two rollers, and the transfer belt is wound around the transfer belt. In the image forming apparatus in which the meandering prevention rib attached is fitted into fitting grooves formed on the outer periphery of both end portions in the axial direction of the roller to restrict meandering of the transfer belt, at least one of the meandering prevention ribs Is attached to the inner peripheral surface of the transfer belt in a state where a tension in the width direction is applied to the transfer belt, and a pulley is arranged immediately before the recording material conveyance direction of the transfer portion, and a fitting groove formed on the outer periphery of the pulley And the meander-preventing rib is fitted.

  According to a second aspect of the present invention, in the first aspect of the present invention, the base material of the transfer belt is obtained by an inflation molding method.

  According to the present invention, at least one of the meandering prevention ribs is attached to the inner peripheral surface of the transfer belt in a state in which a tension in the width direction is applied to the transfer belt. The width of the wavy part of the transfer belt is narrower than the width of the non-wavy part, but the meandering prevention rib is fitted in the pulley fitting groove just before the transfer part, and the narrow wavy part of the transfer belt is Because it is forcibly pulled outward, the undulations that occurred on the transfer belt are eliminated immediately before the transfer part, and transfer defects due to the undulation of the transfer belt are prevented, and a good image can be obtained stably. It is done. Further, since the transfer belt is only partially pulled immediately before the transfer portion, the durability of the transfer belt is not lowered and the life is not shortened.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a color laser printer as an embodiment of an image forming apparatus according to the present invention. The illustrated color laser printer is a tandem type, and a magenta image forming unit is provided at the center of the main body 100. 1M, a cyan image forming unit 1C, a yellow image forming unit 1Y, and a black image forming unit 1K are arranged in tandem at regular intervals.

  Each of the image forming units 1M, 1C, 1Y, and 1K is provided with photosensitive drums 2a, 2b, 2c, and 2d, and charging rollers 3a, 3b, 3c, and 3d are disposed around the photosensitive drums 2a to 2d. 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d and drum cleaning devices 6a, 6b, 6c, 6d are arranged, respectively.

  Here, the photosensitive drums 2a to 2d are drum-shaped photosensitive members, and are rotationally driven at a predetermined process speed in the direction of the arrow (clockwise) by a motor (not shown). The charging rollers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined potential by a charging bias applied from a charging bias power source (not shown).

  Further, the developing devices 4a to 4d contain magenta (M) toner, cyan (C) toner, yellow (Y) toner, and black (K) toner, respectively, and are formed on the photosensitive drums 2a to 2d. In addition, the toner of each color is attached to each electrostatic latent image to visualize each electrostatic latent image as a toner image of each color.

  The transfer rollers 5a to 5d are arranged so as to be able to contact the photosensitive drums 2a to 2d via the intermediate transfer belt 7 in the respective primary transfer portions. Here, the intermediate transfer belt 7 is stretched between the secondary transfer counter roller 8 and the tension roller 9 and is disposed on the upper surface side of each of the photosensitive drums 2a to 2d. The roller 8 is disposed so as to be in contact with the secondary transfer roller 10 via the intermediate transfer belt 7 in the secondary transfer portion. A belt cleaning device 11 is provided in the vicinity of the tension roller 9.

  Incidentally, toner containers 12a, 12b, 12c, and 12d for supplying toner to the developing devices 4a to 4d are arranged in a line above the image forming units 1M, 1C, 1Y, and 1K in the apparatus main body 100. It is installed.

  In addition, a laser scanner unit (LSU) 13 is disposed below the image forming units 1M, 1C, 1Y, and 1K in the apparatus main body 100, and a paper feed cassette 14 is detachably attached to the bottom of the main body 100 below the image forming units. is set up. A plurality of sheets (not shown) are stacked and accommodated in the paper feed cassette 14, and a pickup roller 15 for taking out the paper one by one from the paper feed cassette 14 is taken out in the vicinity of the paper feed cassette 14. A feed roller 16 and a retard roller 17 are provided for feeding the fed paper to the transport path L.

  The conveyance path L extending in the vertical direction on the side of the apparatus main body 100 includes a conveyance roller pair 18 that conveys the sheet, and the secondary transfer counter roller 8 and the second transfer opposing roller 8 at a predetermined timing after the sheet is temporarily held. A registration roller pair 19 is provided to be supplied to the secondary transfer portion which is a contact portion with the next transfer roller 10. Next to the conveyance path L, another conveyance path L ′ used for forming an image on both sides of the sheet is formed, and a plurality of conveyance roller pairs 20 are appropriate for this conveyance path L ′. Are provided at regular intervals.

  By the way, the conveyance path L arranged in the vertical direction on one side in the apparatus main body 100 extends to the paper discharge tray 21 provided on the upper surface of the apparatus main body 100, and the fixing device 22 and the discharge path are in the middle. A paper roller pair 23 is provided.

  Next, an image forming operation by the color laser printer having the above configuration will be described with reference to FIG.

  When an image formation start signal is issued, the photosensitive drums 2a to 2d are driven to rotate at a predetermined process speed in the direction of the arrow in FIG. 1 (clockwise) in each of the image forming units 1M, 1C, 1Y, and 1K. The drums 2a to 2d are uniformly charged by the charging rollers 3a to 3d. The laser scanner unit 13 emits a laser beam modulated by a color image signal for each color, irradiates the surface of each photosensitive drum 2a to 2d with the laser beam, and each color is applied to each photosensitive drum 2a to 2d. An electrostatic latent image corresponding to the color image signal is formed.

  First, magenta toner is attached to the electrostatic latent image formed on the photosensitive drum 2a of the magenta image forming unit 1M by the developing device 4a to which a developing bias having the same polarity as the charged polarity of the photosensitive drum 2a is applied. The electrostatic latent image is visualized as a magenta toner image. This magenta toner image is transferred to the arrow shown in FIG. 1 by the action of the transfer roller 5a to which a primary transfer bias having a polarity opposite to that of the toner is applied at the primary transfer portion (transfer nip portion) between the photosensitive drum 2a and the transfer roller 5a. Primary transfer is performed on the intermediate transfer belt 7 which is rotationally driven in the direction.

  The intermediate transfer belt 7 on which the magenta toner image has been primarily transferred as described above moves to the next cyan image forming unit 1C. In the cyan image forming unit 1C as well, the cyan toner image formed on the photosensitive drum 2b is transferred to the magenta toner image on the intermediate transfer belt 7 in the primary transfer portion in the same manner as described above.

  Similarly, yellow and black toners respectively formed on the photosensitive drums 2c and 2d of the yellow and black image forming units 1Y and 1K on the magenta and cyan toner images superimposed and transferred on the intermediate transfer belt 7, respectively. The images are sequentially superimposed at each primary transfer portion, and a full-color toner image is formed on the intermediate transfer belt 7. The transfer residual toner which is not transferred onto the intermediate transfer belt 7 and remains on the photosensitive drums 2a to 2d is removed by the drum cleaning devices 6a to 6d, and the photosensitive drums 2a to 2d are prepared for the next image formation. It is done.

  Then, the pickup from the paper feed cassette 14 is performed in accordance with the timing at which the front end of the full color toner image on the intermediate transfer belt 7 reaches the secondary transfer portion (transfer nip portion) between the secondary transfer counter roller 8 and the secondary transfer roller 10. The sheet fed to the conveyance path L by the roller 15, the feed roller 16 and the retard roller 17 is conveyed to the secondary transfer unit by the registration roller pair 19. Then, a full-color toner image is collectively transferred from the intermediate transfer belt 7 to the sheet conveyed to the secondary transfer unit by the secondary transfer roller 10 to which a secondary transfer bias having a polarity opposite to that of the toner is applied. .

  Thus, the sheet on which the full-color toner image has been transferred is conveyed to the fixing device 22, and the sheet on which the full-color toner image has been fixed by being heated and pressurized and thermally fixed on the surface of the sheet. Then, the paper is discharged onto the paper discharge tray 21 by the paper discharge roller pair 23 to complete a series of image forming operations. The transfer residual toner that is not transferred onto the sheet and remains on the intermediate transfer belt 7 is removed by the belt cleaning device 11, and the intermediate transfer belt 7 is prepared for the next image formation.

  Next, the gist of the present invention will be described.

  First, a method for manufacturing the intermediate transfer belt 7 by the inflation molding method will be described with reference to FIG.

  FIG. 2 is a schematic diagram of an inflation molding apparatus. When manufacturing the intermediate transfer belt 7, first, carbon black for resistance value adjustment and coloring is mixed and melted in a resin such as pelletized PVDF. Next, the molten resin is extruded from the die 24 while kneading, and at the same time, air is blown out from the air cylinder 25 to form a cylindrical resin film 7A as a base material. It leads to the reverse funnel-shaped guide plate 26.

  Thereafter, the resin film 7A is guided to the pair of pinch rollers 27 by the guide plate 26, and the resin film 7A is wound between the pinch rollers 27 while being flattened. After the wound resin film 7A is cut to an appropriate length, an air bag (not shown) is attached from the inside so that the outer periphery of the cut resin film 7B (see FIG. 5) is in close contact with a mold (not shown). The resin film 7B is heated to a temperature of 140 ° C. in a state where the resin film 7B is in close contact with the mold, and the fold of the resin film 7B is extended.

  Next, the resin film 7B with the fold line extended is suspended between biaxial rollers (not shown), an adhesive is applied to the surface, and then a rubber material is applied, and then the resin film 7B is applied to a mold. Vulcanize by reinserting and heating. Then, the vulcanized resin film 7B is once removed from the mold and spread between two biaxial rollers to apply PTFE, and then PTFE is fired in a state where the resin film 7B is suspended.

  Finally, the resin film 7B is fitted again into the mold in order to adjust the circumferential length, the resin film 7B is heated to a temperature of around 160 ° C., cooled, and both edges in the width direction of the resin film 7B are aligned to make the width uniform. To obtain a desired intermediate transfer belt 7. In the present embodiment, the outer peripheral length of the intermediate transfer belt 7 is 400 mm, the width is 350 mm, the base material thickness is 150 μm, the rubber thickness is 150 μm, and the PTFE thickness is 15 μm.

Incidentally, undulation as shown in FIG. 3 inevitably occurs in a part of the intermediate transfer belt 7 manufactured through the above steps. The axial length of the undulation portion of the intermediate transfer belt 7 is shown in FIG. If the length when the wavy portion is stretched in the axial direction is L1 as shown in FIG. 4A, and the length is L2 as shown in FIG.
ΔL = | L1-L2 |
It is represented by In this embodiment, the wavy amount ΔL of the intermediate transfer belt 7 is 17 μm to 120 μm with respect to the width dimension of 350 mm.

  Thus, the meandering prevention ribs 28 are attached to both ends of the inner surface of the intermediate transfer belt 7 in the width direction. The process of attaching one of the meandering prevention ribs 28 will be described below with reference to FIG.

  FIG. 5 is a perspective view of a jig for attaching the meandering prevention rib 28 to the intermediate transfer belt 7. As shown in the figure, two meniscus pillars 29 obtained by vertically dividing a cylinder at its center are shown. The intermediate transfer belt 7 is fitted on these half-moon columns 29 from above, and the intermediate transfer belt 7 is erected so that one end face in the width direction is in contact with the base plate 30. Then, the pair of meniscus pillars 29 are expanded and the intermediate transfer belt 7 is fixed so as to be stretched from the inside.

  Next, the meandering prevention rib 28 to which the adhesive is applied is pressed and attached to the inner peripheral surface at one end in the width direction of the intermediate transfer belt 7 so as to be along the upper surface of the meniscus column 29. Here, the height of the meniscus column 29 is set lower than the width of the intermediate transfer belt 7 by the width of the meandering prevention rib 28.

  In the present embodiment, the main body of the meandering prevention rib 28 is made of a polyurethane material coated with a polyester film material that has poor stretchability and is easily adapted to an adhesive. In this case, a surface tape having an adhesive layer is attached to the outer surface of the polyester film material, and the surface tape is applied to the inner peripheral surface of the intermediate transfer belt 7 while peeling the release paper adhered to the surface tape. By pressing, the meandering prevention rib 28 can be stuck and fixed.

  Next, the process of attaching the other meandering prevention rib 28 will be described with reference to FIGS. 6 is a partial plan view showing the other step of attaching the meandering prevention rib, and FIG. 7 is a view in the direction of arrow A in FIG.

  When the other meandering prevention rib 28 is attached, the intermediate transfer belt 7 is suspended by at least two rollers (not shown), and one of the meanders already attached to the inner periphery of one end in the width direction of the intermediate transfer belt 7. The prevention rib 28 is fitted in a fitting groove formed at one end in the axial direction of the roller. As a result, one end of the intermediate transfer belt 7 in the width direction is positioned and movement of the intermediate transfer belt 7 in the width direction is restricted.

  In the above state, another roller is disposed inside the intermediate transfer belt 7, and the roller 31 is stretched with respect to the direction perpendicular to the axis of the roller 31 with the intermediate transfer belt 7 sandwiched between the rollers 31. Are arranged in an inclined state by an angle θ shown in FIG. Here, as shown in FIG. 6, fitting grooves 31 a and 13 b are respectively formed on the outer periphery of both ends in the axial direction of the roller 31, and one of the fitting grooves 31 a has already been formed on the inner peripheral surface of the intermediate transfer belt 7. One of the pasted meandering prevention ribs 28 is fitted.

  Thus, if the stretching roller 32 is rotationally driven in the direction of the arrow in FIG. 7 while the intermediate transfer belt 7 is traveling in the direction of the arrow in FIG. 6, the stretching roller 32 is in the direction perpendicular to the axis of the roller 31 as described above. Since it is inclined by a predetermined angle θ, the intermediate transfer belt 7 is pulled outward in the width direction by a component force F (see FIG. 6) of the driving force, and a predetermined tension is applied thereto. Then, with the intermediate transfer belt 7 pulled at a constant tension in this way, the other meandering prevention rib 28 is formed along the fitting groove 31b formed at the other axial end of the roller 31, as shown in FIG. Then, the meandering prevention rib 28 is affixed to the other end in the width direction of the intermediate transfer belt 7 and fixed. In the present embodiment, the cross-sectional shape of the meandering prevention rib 28 is a quadrangular shape having a bottom side of 5 mm, an upper side of 5 mm, and a height of 3 mm.

  As a result, the wobbling portion of the intermediate transfer belt 7 is stretched in the width direction, and the meandering prevention rib 28 is linearly attached as shown by a broken line in FIG. Therefore, when the tension applied to the intermediate transfer belt 7 at the time of attaching the meandering prevention rib 28 is removed, the meandering prevention rib 28 is formed at the wavy portion of the intermediate transfer belt 7 as shown by a solid line in FIG. The shape curved inward will be shown.

  Thus, in this embodiment, the intermediate transfer belt 7 having the meandering prevention ribs 28 attached to the inner peripheral surfaces at both ends in the width direction as described above is used. For example, the magenta image forming unit shown in FIG. In the 1M primary transfer portion, a pulley 33 is disposed immediately before the primary transfer portion (immediately before the transfer direction of the transfer belt 7), and is attached to the intermediate transfer belt 7 in a fitting groove 33a formed on the outer periphery of the pulley 33. The meandering prevention rib 28 is fitted. Although only the magenta image forming unit 1M is illustrated in FIG. 9, the other cyan image forming unit 1C, yellow image forming unit 1Y, and black image forming unit 1K also have a pair of pulleys 34, immediately before each primary transfer portion. 35 are arranged respectively.

  As described above, in the present embodiment, one of the meandering prevention ribs 28 is attached to the inner peripheral surface of the intermediate transfer belt 7 with the tension in the width direction applied to the intermediate transfer belt 7, so that the transfer with the pulley 33 disposed thereon is performed. The width of the wavy portion of the intermediate transfer belt 7 is narrower than the width of the portion where there is no wavy as shown by the solid line in FIG. 8 except immediately before the transfer portion, but the fitting groove 33a of the pulley 33 immediately before the transfer portion. The meandering prevention rib 28 is fitted to the intermediate transfer belt 7 and the narrow wavy portion of the intermediate transfer belt 7 is forcibly pulled outward in the width direction as indicated by a broken line in FIG. The undulation is eliminated immediately before the transfer portion, and transfer failure due to the undulation of the intermediate transfer belt 7 is prevented, and a good image can be stably obtained. In addition, when a transfer failure situation was confirmed by forming a half-density image in an actual machine, it was confirmed that a transfer failure as shown in FIG. 10 did not occur.

  Since the intermediate transfer belt 7 is only partially pulled immediately before the transfer portion, its durability is not lowered and the life is not shortened.

  Although the present invention has been described with respect to an embodiment in which the present invention is applied to a color laser printer, the present invention is naturally applicable to other arbitrary image forming apparatuses as well. Although the present invention has been described with respect to an embodiment in which the present invention is applied to an image forming apparatus employing an intermediate transfer system, the present invention sequentially transfers toner images onto a recording material while the recording material is conveyed by a transfer belt. Of course, the present invention can be similarly applied to an image forming apparatus that employs the method.

1 is a cross-sectional view of an image forming apparatus (color laser printer) according to the present invention. It is a block diagram of an inflation shaping | molding apparatus. FIG. 6 is a partial perspective view showing undulation of an intermediate transfer belt. (A) is a diagram showing the axial length of the wavy portion of the intermediate transfer belt, (b) is a diagram showing the axial length of the portion of the intermediate transfer belt where there is a wave. FIG. 6 is a perspective view of a jig for attaching one meandering prevention rib to the intermediate transfer belt. FIG. 6 is a partial plan view showing a process of attaching the other meandering prevention rib to the intermediate transfer belt. It is a figure of the arrow A direction of FIG. FIG. 4 is a partial plan view of one end in the width direction of the intermediate transfer belt. FIG. 3 is a partial side view illustrating a configuration of a primary transfer unit in a magenta image forming unit of the image forming apparatus according to the present invention. It is a figure which shows the example of the transfer defect image by a wave.

Explanation of symbols

1M Magenta image forming unit 1C Cyan image forming unit 1Y Yellow image forming unit 1K Black image forming unit 2a to 2d Photosensitive drum 3a to 3d Charging roller 4a to 4d Developing device 5a to 5d Transfer roller 6a to 6d Drum cleaning device 7 Intermediate transfer belt 7A, 7B Resin film 8 Secondary transfer counter roller 9 Tension roller 10 Secondary transfer roller 11 Belt cleaning device 12a-12d Toner container 13 Laser scanner unit (LSU)
DESCRIPTION OF SYMBOLS 14 Paper feed cassette 15 Pickup roller 16 Feed roller 17 Retard roller 18 Conveyance roller pair 19 Registration roller pair 20 Conveyance roller pair 21 Paper discharge tray 22 Fixing device 23 Paper discharge roller pair 24 Dies 25 Air cylinder 26 Guide plate 27 Pinch roller 28 Meander Prevention rib 29 Half-moon pillar 30 Base plate 31 Roller 31a, 31b Roller fitting groove 32 Stretching roller 33 Pulley 33a Pulley fitting groove 100 Image forming apparatus main body L, L ′ Conveyance path

Claims (2)

An endless transfer belt formed by attaching meandering prevention ribs to both ends in the width direction of the inner peripheral surface is wound around at least two rollers, and the meandering prevention ribs attached to the transfer belt are attached to both ends in the axial direction of the rollers. In the image forming apparatus in which the meandering of the transfer belt is regulated by fitting into a fitting groove formed on the outer periphery,
At least one of the meandering prevention ribs is attached to the inner peripheral surface of the transfer belt with a tension in the width direction applied to the transfer belt, and a pulley is disposed immediately before the recording material conveyance direction of the transfer portion, and the outer periphery of the pulley An image forming apparatus, wherein the meandering prevention rib is fitted into a fitting groove formed in the above.   The image forming apparatus according to claim 1, wherein a base material of the transfer belt is obtained by an inflation molding method.

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