JP3632245B2 - Color image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an electrophotographic color image forming apparatus used for printers, facsimiles, copiers, and the like, and more particularly to a color image forming apparatus having a plurality of developing devices on the outer periphery of a belt-like image carrier.
[0002]
[Prior art]
Conventional color image forming apparatuses are generally used in which a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit are arranged around a drum-shaped image carrier, and the color of the developing unit is switched. Therefore, there are known a rotary type in which a plurality of developing means are arranged and a linear type in which a plurality of developing means are slid. On the other hand, in the automatic multicolor copying machine disclosed in Japanese Utility Model Laid-Open No. 63-39239, a moving roller supported by an arm is provided inside the belt-shaped photosensitive member, and the moving roller is used to move the photosensitive member. A technique has been proposed in which the space occupied by a plurality of developing means is reduced by moving and moving the photosensitive member close to an arbitrary developing sleeve.
[0003]
[Problems to be solved by the invention]
However, in a color image forming apparatus in which color switching is performed by a moving developing unit that has been generally used in the past, the occurrence of vibration or impact is not avoided when the developing unit is moved, and toner leaks from the developing unit and the image leaks. There are problems such as splashing on top and contamination of the inside of the device with toner powder, and when a plurality of developing means are individually separated, a new open / close seal mechanism is added to make the device unnecessarily large. Rather, maintenance such as cleaning the device and replacing parts was required.
[0004]
On the other hand, in the color image forming apparatus disclosed in the above-mentioned publication using the belt-shaped image carrier that eliminates the movement of the developing means, the color image of each color is sequentially developed although the apparatus configuration is simplified. However, when performing color superposition for sequential transfer, the tension of the image carrier belt fluctuates due to the selected developing means, and the circumference from the exposure position to the transfer position changes, resulting in color misregistration during color superposition. .
[0005]
The present invention has been made in view of such conventional problems, and an object thereof is to provide a color image forming apparatus capable of preventing toner scattering due to separation / contact movement of the developing means. Another object of the present invention is to provide a color image forming apparatus excellent in color reproducibility by performing high-precision color superposition regardless of the tension fluctuation of the belt-shaped image carrier and preventing positional displacement between colors. It is to provide.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, a color image forming apparatus according to the present invention charges a belt-like image carrier stretched between a first support roller and a second support roller, and the image carrier. A charging unit; an exposure unit that forms an electrostatic latent image on the image carrier in accordance with image formation information; and a plurality of developing units that sequentially visualize the electrostatic latent image on the image carrier with a plurality of colors of toner. And a movable contact roller for urging the image carrier to the developing means, and a transfer means for transferring the developed toner image. And The contact roller is disposed in a region from the first support roller to the second support roller with respect to the moving direction of the image carrier, and the exposure unit places the image carrier on the first support roller. The transfer unit is arranged to be exposed at the wound part, and the transfer means is arranged to face the part where the image carrier is wound around the second support roller. In the color image forming apparatus, a contact width between the contact roller and the image carrier is larger than an effective development width of the developing unit and smaller than a contact width of the developing unit. It is characterized by that.
[0007]
In the color image forming apparatus of the present invention, the contact roller is formed of an elastic roller including an elastic body.
[0008]
Further, the color image forming apparatus according to the present invention is characterized in that a plurality of contact rollers are arranged facing the developing means.
[0009]
Further, in the color image forming apparatus of the present invention, the contact roller is composed of a first contact roller and a second contact roller, and an image carrier is provided in a region from the first contact roller to the second contact roller. Is brought into contact with at least a part of the developing means.
[0010]
Furthermore, the color image forming apparatus of the present invention is characterized in that the contact roller can be moved in the moving direction of the image carrier and that the image carrier is separated from and contacting the developing means in a non-image area of the image carrier. And
[0011]
Further, the color image forming apparatus of the present invention is provided with tension applying means for applying tension to the image carrier in a region from the first support roller to the second support roller in the moving direction of the image carrier. It is characterized by.
[0012]
Further, the color image forming apparatus of the present invention is characterized in that the charging means is disposed to face a portion where the image carrier is wound around the first support roller.
[0013]
Further, the color image forming apparatus of the present invention is characterized in that the exposure means is disposed so as to expose the image carrier around the first support roller and further downstream from the center.
[0014]
Furthermore, the color image forming apparatus of the present invention is characterized in that the first support roller transmits a driving force to the image carrier.
[0015]
Further, the color image forming apparatus of the present invention is characterized in that the developing means is disposed at a position fixed to the first support roller and the second support roller.
[0016]
Further, the color image forming apparatus of the present invention is characterized in that a cleaning unit that contacts the image carrier is disposed in a region from the second support roller to the first support roller in the moving direction of the image carrier. To do.
[0017]
Furthermore, the color image forming apparatus of the present invention is characterized in that a third support roller for supporting the image carrier is disposed in a region where the cleaning unit contacts the image carrier.
[0018]
Further, in the color image forming apparatus of the present invention, the first support roller, the second support roller, and the contact roller have the same outer diameter, and the rotation center of the first support roller and the rotation center of the second support roller are It is possible to position the rotation center of the contact roller on an elliptic arc curve having a focal point of.
[0021]
Further, the color image forming apparatus of the present invention is characterized in that at least two of the first support roller, the second support roller, and the contact roller are in contact with the image carrier over the entire width of the image carrier.
[0022]
Furthermore, the color image forming apparatus of the present invention is characterized in that the contact width between the cleaning means and the image carrier is smaller than the contact width between the image carrier and the third support roller.
[0024]
[Action]
According to the above configuration of the present invention, the contact roller is disposed in a region from the first support roller to the second support roller with respect to the moving direction of the image carrier, and the exposure unit places the image carrier on the first support roller. The transfer unit is arranged to be exposed to the part wound around the support roller, and the transfer unit is arranged opposite to the part around which the image carrier is wound around the second support roller. Therefore, it is not necessary to move the developing unit apart, and vibration and impact applied to the developing unit can be minimized.
[0025]
In addition, by forming the contact roller with an elastic roller including an elastic body, generation of vibration and impact due to movement of the contact roller is reduced, and a sufficiently large development nip between the image carrier and the developing means is secured. Can do.
[0026]
Furthermore, by providing a plurality of contact rollers facing the developing unit, the contact roller can be selected according to the type of toner or the outer diameter of the developing unit.
[0027]
Further, the contact roller is composed of a first contact roller and a second contact roller, and the image carrier is brought into contact with at least a part of the developing means in a region from the first contact roller to the second contact roller. As a result, the developing nip can be formed at the slack portion of the image carrier belt, so that the image carrier can be urged with a low pressure against the developing means and the development nip can be sufficiently large. Can do.
[0028]
Further, the contact roller can be moved in the moving direction of the image carrier, and the image carrier is separated from and brought into contact with the developing means in the non-image area of the image carrier, so that the toner adheres to the image area due to the separation and contact. Do not wake up.
[0029]
Further, by providing a tension applying means for applying a tension to the image carrier in a region from the first support roller to the second support roller with respect to the moving direction of the image carrier, the belt due to the positional deviation of the developing means. Thus, the length of the image carrier belt from the exposure position to the transfer position can be made constant by absorbing the fluctuation of the slack length by the tension applying means.
[0030]
Further, the charging means is disposed opposite to the portion where the image carrier is wound around the first support roller, so that even if the belt tension of the image carrier fluctuates, stable and uniform charging can be performed. it can.
[0031]
Further, since the exposure means is arranged to expose the image carrier around the first support roller and further downstream from the center, it is stable even if the belt tension of the image carrier fluctuates. Thus, exposure can be performed at a certain position.
[0032]
Furthermore, the first support roller transmits the driving force to the image carrier, so that the developing means can be disposed on the slack side of the image carrier belt, and fluctuations in development pressure due to fluctuations in the tension of the image carrier are reduced. can do.
[0033]
Further, since the developing unit is disposed at a position fixed to the first support roller and the second support roller, the developing unit can be used while being fixed to the color image forming apparatus main body. In addition, it is not necessary to move the developing unit apart, the toner can be easily replenished, and the developing unit can be easily attached and detached.
[0034]
Further, a cleaning unit that contacts the image carrier is disposed in a region from the second support roller to the first support roller with respect to the moving direction of the image carrier, so that the image carrier belt cleaning unit can be The region reaching the support roller can be the tension side of the belt.
[0035]
Further, by arranging a third support roller for supporting the image carrier in a region where the cleaning unit contacts the image carrier, the vibration of the image carrier belt by the cleaning unit can be prevented.
[0036]
In addition, the first support roller, the second support roller, and the contact roller have the same outer diameter, and the first support roller, the second support roller, and the contact roller have an elliptical arc curve that focuses on the rotation center of the first support roller and the rotation center of the second support roller. By making the contact roller rotation center positionable, the belt length of the image carrier from the first support roller to the second support roller can be kept constant regardless of the position of the contact roller.
[0037]
Further, by making the contact width between the contact roller and the image carrier larger than the effective development width of the developing unit, the contact state or proximity state between the image carrier and the developing unit in the effective development region can be kept constant. Can do.
[0038]
Further, by making the contact width between the contact roller and the image carrier larger than the effective developing width of the developing means and smaller than the contact width of the developing means, the end corners of the developing means are strongly attached to the image carrier. There is no contact.
[0039]
Further, at least two of the first support roller, the second support roller, and the contact roller are in contact with the image carrier over the entire width of the image carrier, thereby stably stretching the image carrier belt. , Can run stably.
[0040]
Further, by making the contact width between the cleaning means and the image carrier smaller than the contact width between the image carrier and the third support roller, the end corner of the third support roller is strongly brought into contact with the image carrier. There is no.
[0042]
【Example】
Hereinafter, the present invention will be described in detail with reference to the drawings.
[0043]
FIG. 1 is a cross-sectional view of an essential part showing an embodiment of a color image forming apparatus of the present invention.
[0044]
In the figure, reference numeral 10 denotes an image carrier formed in a belt shape, and this image carrier 10 is a flexible organic photoreceptor in which a charge generation layer and a charge transport layer are formed in this order on a nickel electroformed tube. It is. The image carrier 10 is stretched between a first support roller 11 that drives the image carrier 10 and rotates in the direction of arrow B, and a second support roller 12 that rotates following the movement of the image carrier 10. The Further, in the inside of the image carrier 10, a contact roller 13 that is driven to rotate with the movement of the image carrier 10 and urges the image carrier 10 toward the selected developing means, and is similarly driven and rotated by an arrow D. A tension roller 14 serving as a tension applying unit that moves in the direction and applies tension to the image carrier 10 and a third support roller 15 that supports the image carrier 10 from the rear surface of the cleaning unit are similarly rotated. . In particular, the contact roller 13 moves in the direction of arrow C in the non-image portion of the image carrier 10 according to the toner color to be developed, and urges the image carrier 10 toward a predetermined developing means. Is. However, an arc indicated by a two-dot chain line in the drawing indicates a position where the contact roller 13 is positioned corresponding to the developing means. A toner image of each color is sequentially formed on the image carrier 10 that is stretched and moved in this manner by an electrophotographic process such as charging, exposure, development, and transfer.
[0045]
In the figure, reference numeral 20 denotes a charging roller which is a charging means. The charging roller 20 is in contact with the image carrier 10 at a light pressure so as to face a portion where the image carrier 10 is wound around the first support roller 11. And rotated following the image carrier 10. By applying a bias of about DC (−) 1200V to the charging roller 20, the surface of the image carrier 10 can be uniformly charged to a charging potential of about (−) 650V sequentially.
[0046]
Next, the charged image carrier 10 is image-exposed by the exposure means 30 at a portion where the image carrier 10 is wound around the first support roller 11 and downstream of the center, and the potential of the image exposure unit is (−) 50V to (−) 150V. The exposure means 30 includes a semiconductor laser (not shown), a polygon mirror 31, an imaging lens 32, a mirror 33, and the like. A beam 34 emitted from the semiconductor laser is polarized and scanned by the polygon mirror 31 and corrected by the imaging lens 32. Then, the light is reflected by the mirror 33 and applied to the image carrier 10. In this way, an electrostatic latent image is formed on the image carrier 10.
[0047]
Subsequently, the image carrier 10 on which the electrostatic latent image is formed is imaged by the contact roller 13 in a region from the first support roller 11 to the second support roller 12 in the moving direction A of the image carrier 10. The carrier 10 is urged toward the selected developing means to develop toner on the image portion, and the electrostatic latent image is visualized. The developing means includes a yellow developing device 41 having a yellow developing roller 45 for developing yellow toner, a magenta developing device 42 having a magenta developing roller 46 for developing magenta toner, and a cyan developing roller 47 for developing cyan toner. A cyan developing device 43 and a black developing device 44 having a black developing roller 48 for developing black toner. The electrostatic latent image of the image carrier 10 is activated by operating each developing device according to image color data. Develop one by one. The developing devices 41 to 44 are detachably positioned and fixed to the housing 40, and the developing rollers 45 to 48 are arranged at any position in contact or non-contact with the image carrier 10 during development. Also good.
[0048]
Subsequently, a toner image formed of toner of a predetermined color is transferred from the image carrier 10 to the intermediate transfer medium 51 by a primary transfer roller 50 that is a transfer unit. The primary transfer roller 50 is disposed to face a portion where the image carrier 10 is wound around the second support roller 12 with the intermediate transfer medium 51 interposed therebetween. At the time of transfer, the residual charge on the image carrier 10 is removed by the charge eliminating lamp 60 to reduce the transfer residue at the image edge portion.
[0049]
The toner remaining after transfer on the image carrier 10 is then sent to the cleaning unit 70, scraped off by the cleaning blade 71, and discharged into the internal space of the cleaning unit 70. In a portion where the cleaning blade 71 contacts the image carrier 10, a third support roller 15 is disposed on the back surface of the image carrier 10 to keep the relative positional relationship between the cleaning blade 71 and the image carrier 10 constant. Yes.
[0050]
Thereafter, the toner image of the next color formed by charging, exposing and developing again is transferred from the image carrier 10 to the intermediate transfer medium 51 by the primary transfer roller 50, and is overlaid on the intermediate transfer medium 51. Is done. Here, the intermediate transfer medium 51 is stretched between the driving roller 52, the first driven roller 53, and the second driven roller 54, and has a primary transfer roller 50 therein, and rotates in the direction of arrow F. It is driven by the driving roller 52, is given tension by the first driven roller, and moves in the direction of arrow E. The peripheral length of the intermediate transfer member 51 is preferably an integral multiple of the peripheral length of the image carrier 10 or a fraction of an integer in order to improve the transfer position accuracy. Further, it is possible to form a color image by performing similar color superposition without using the intermediate transfer medium 51 and using a transfer drum holding a recording material or a paper conveying belt.
[0051]
The color toner image formed by repeating such an operation for a predetermined color is separated from the leading edge of the image by the secondary transfer roller 55 that is urged toward the second driven roller 54 by performing a separating operation in the direction of arrow G. Are simultaneously transferred to the recording material 80 conveyed in accordance with the above.
[0052]
On the other hand, the transfer residual toner remaining on the intermediate transfer medium 51 after the secondary transfer is transferred to the second cleaning unit 56, scraped off by the second cleaning blade 57, and discharged to the internal space of the second cleaning unit 56. The The second cleaning unit 56 performs cleaning by moving toward the intermediate transfer medium 51 in the direction of arrow H in response to the operation of transferring the toner image to the recording material 80. It is held at a position separated from the other.
[0053]
On the other hand, the recording material 80 is fed along the paper path 81 according to the secondary transfer of the color toner image. From the paper feed tray 82 that stores a large number of recording materials 80 such as paper, the recording material 80 is moved in the direction of arrow I. The sheet is taken out by a sheet feeding roller 83 that is rotated in the direction of 1 and fed to a pair of gate rollers 84 and 85. The recording material 80 whose leading ends are aligned by the pair of gate rollers 84 and 85 rotates the gate roller 84 in the direction of arrow J so as to collectively transfer the color toner images superimposed on each other to a predetermined position of the recording material 80. Thus, the toner is fed toward the secondary transfer roller 55, and the color toner images on the intermediate transfer medium 51 are secondarily transferred onto the recording material 80 in a lump. Further, the recording material 80 is conveyed to the fixing unit 90, and after the toner image is heated and fixed, it is discharged to a discharge tray (not shown). The fixing unit 90 includes a heating roller 91 and a pressure roller 92. The fixing unit 90 rotates the heating roller 91 in the direction of the arrow K, and uses a heater provided inside the heating roller 91 as a heat source. The color toner image is heat-fixed.
[0054]
In this manner, a color toner image composed of a plurality of colors of toner is fixed on the recording material 80, and a series of color image forming operations is completed. Further, when forming color images continuously, the same image forming process is repeated, and when forming a monochromatic image, only the image forming process for one color is performed.
[0055]
As described above, the contact roller 13 is disposed in the region from the first support roller 11 to the second support roller 12 with respect to the moving direction A of the image carrier 10, and the exposure unit 30 holds the image carrier 10. A primary transfer roller 50 serving as a transfer unit is disposed so as to be exposed at a portion wound around the first support roller 11, and is disposed opposite to a portion where the image carrier 10 is wound around the second support roller 12. As a result, the developing means 41 to 44 are selected by the movement of the contact roller 13, so that it is not necessary to move the developing means apart, and vibration and impact applied to the developing means can be minimized, and the toner in the apparatus can be reduced. Contamination can be prevented and image deterioration due to scattered toner can be prevented. The first support roller 11, the second support roller 12, and the contact roller 13 are made by fitting a flange to a metal sleeve or the like, and the outer peripheral surface is roughened or the outer peripheral surface is covered with resin. Can be used. An exposure unit 30 is disposed to expose the image carrier 10 around the first support roller 11, and a primary transfer roller 50 serving as a transfer unit winds the image carrier 10 around the second support roller 12. By being arranged opposite the applied portion, it is possible to perform exposure at a position where the belt tension fluctuation of the image carrier is small. Even if the belt tension of the image carrier fluctuates, the development position and the transfer position Since exposure can be performed at a position where the belt tension is similar, and transfer can be stably performed at a constant position, the belt length of the image carrier 10 from the exposure position to the primary transfer position is constant. Therefore, it is possible to form a color image with no color misregistration and excellent color reproducibility. Further, if the exposure means 30 is arranged to expose the image carrier 10 around the first support roller 11 and downstream of the center, the image carrier at the exposure position, the development position and the transfer position. Since ten tension states can be obtained, color misregistration can be further reduced, which is desirable.
[0056]
In particular, when the contact roller 13 is moved in the direction of arrow C, the image carrier 10 is moved away from and in contact with the developing rollers 45 to 48 in the non-image region of the image carrier 10. Therefore, it is possible to form a color image with high color purity.
[0057]
Further, by providing tension applying means 14 for applying tension to the image carrier 10 in a region from the first support roller 11 to the second support roller 12 in the moving direction A of the image carrier 10, The tension applying means 14 absorbs the fluctuation of the slack length of the belt-shaped image carrier 10 due to the positional deviation of the developing rollers 45 to 48, and the length of the image carrier 10 from the exposure position to the transfer position is made constant. In addition, it is possible to provide a color image forming apparatus having a large development position margin and excellent color reproducibility. The tension applying means 14 is configured to urge a rotatable roller so as to be movable in the direction of arrow D by a spring or the like. However, the tension applying means 14 is arranged so as to reduce the winding angle of the belt. It is desirable to reduce the biasing force. On the other hand, the tension applying unit 14 may be configured not by a roller but by a spring that is in sliding contact with the belt, or may be configured to be movable integrally with the contact roller 13.
[0058]
Further, regarding the charging roller 20 as a charging means, by disposing the image carrier 10 so as to face the portion around the first support roller 11, even if the belt tension of the image carrier 10 fluctuates, Since the relative positional relationship between the image carrier 10 and the charging roller 20 can be kept constant, the image carrier 10 can be stably and uniformly charged, and a color image having excellent gradation can be formed. In particular, when contact charging is used, since the contact state can be made constant, uniform charging is possible without causing charge injection. If a corona charger using a scorotron is used as the charging means, non-contact charging is possible, but there is a problem that ozone is generated.
[0059]
Further, since the first support roller 11 transmits the driving force to the image carrier 10, the developing devices 41 to 44 can be disposed on the slack side of the belt-like image carrier 10. Color with excellent color reproducibility without color misregistration by reducing fluctuations in development pressure due to ten tension fluctuations, reducing fluctuations in image density, and making the length of the image carrier from the exposure position to the transfer position constant. An image can be formed. The end portion of the image carrier 10 is guided by the first support roller 11 to prevent meandering, and a high friction coefficient such as roughening is provided so that the image carrier 10 does not slip with respect to the first support roller 11. It is desirable to perform the conversion process.
[0060]
Furthermore, each developing device 41 to 44 is disposed at a position fixed to the first support roller 11 and the second support roller 12, so that each developing device 41 to 44 is a main body of the color image forming apparatus. Since it can be used with its position fixed, it is not necessary to move the developing devices 41 to 44 apart, the toner can be easily replenished, and the developing devices 41 to 44 can be easily attached and detached. Toner replenishment and replacement of the developing devices 41 to 44 can be made into user maintenance. Similarly, since there is no separation / contact movement of each of the developing devices 41 to 44, not only can the toner scattering due to the separation / contact movement be prevented, but also color switching is possible by the movement of the small and light contact roller 13, so that the color switching is performed. It can be performed at high speed and is useful for speeding up the color image forming apparatus.
[0061]
On the other hand, in this embodiment, the cleaning means 70 that contacts the image carrier 10 is arranged in the region from the second support roller 12 to the first support roller 11 in the moving direction A of the image carrier 10. However, with this configuration, the region from the contact position of the image carrier 10 to the cleaning blade 71 to the first support roller 11 can be the tension side of the belt. Therefore, it is possible to form a high-definition color image with little jitter.
[0062]
Further, by providing the third support roller 15 that supports the image carrier 10 in a region where the cleaning blade 71 contacts the image carrier 10, vibration of the image carrier 10 by the cleaning unit 70 can be prevented. Therefore, the length of the belt of the image carrier 10 from the second support roller 12 to the first support roller 11 can be made constant, and a color image excellent in color reproducibility without color misregistration can be formed. As the cleaning means, a roller or a brush can be used in addition to the blade.
[0063]
Next, the positional relationship between the contact roller 13 and the developing rollers 45 to 48 will be described with reference to FIGS.
[0064]
FIG. 2 is a cross-sectional view of the main part showing the operating state of the contact roller when non-contact development is performed. The belt-shaped image carrier 210 urges the contact roller 213 toward the development roller 240. Thus, the gap rollers 241 disposed at both ends of the developing roller 240 are brought into contact with each other, and the developing roller 240 is positioned with respect to the developing roller 240 via a gap determined by the outer diameter of the gap roller 241 and the outer diameter of the developing roller 240. . A toner layer having a thickness smaller than the gap is formed on the developing roller 240, and the toner is developed by flying with an electrostatic latent image and a developing bias voltage. In such non-contact development, the developing roller 240 is not rubbed against the image carrier 210 via the toner layer, so that the image carrier 210 is not worn and has excellent durability.
[0065]
FIG. 3 is a cross-sectional view of the main part showing the operating state of the contact roller when contact development is performed. The contact roller 313 includes an elastic roller in which an elastic layer 312 such as rubber is formed around a metal shaft 311. Thus, the belt-shaped image carrier 310 urges the contact roller 313 toward the developing roller 340, so that the contact roller 313 is deformed by the tension of the image carrier 310 and at the same time the developing roller 340. It undergoes deformation due to indirect contact with. Thus, a contact nip is formed between the image carrier 310 and the developing roller 340, and the toner on the developing roller 340 is developed by the electrostatic latent image and the developing bias voltage. In such contact development, since the image carrier 310 and the developing roller 340 are close to each other with a minute gap through the toner layer, the developing electrode effect by the developing roller 340 is remarkably obtained and a high-resolution image is formed. In addition, since the developing roller 340 is in contact with the entire width of the developing roller 340, the vibration of the image carrier 310 and the developing roller 340 can be absorbed to form a high-definition image with little jitter. The elastic layer 312 is preferably formed of a flexible elastic body having a rubber hardness (JIS A) of 60 degrees or less, such as a flexible foam material such as polyurethane foam, polystyrene foam, polyethylene foam, elastomer foam, rubber foam, , Rubber materials such as natural rubber, silicone rubber, urethane rubber, butadiene rubber, chloroprene rubber, neoprene rubber, NBR, and elastomer materials including styrene resin, vinyl chloride resin, polyurethane resin, polyethylene resin, methacrylic resin, etc. it can. However, for the foamed member, either single bubble or continuous bubble can be used, but if the winding angle of the image carrier 310 around the contact roller 313 is 50 degrees or less, a large contact width can be obtained with a small urging force. This is preferable because it can reduce the compression set of the foamed member.
[0066]
FIG. 4 is a cross-sectional view of an essential part showing another embodiment in which the same number of contact rollers as the developing means are provided in the color image forming apparatus of the present invention, and the belt-like image carrier 410 is connected to the developing roller 445 for each color. The abutting rollers 421 to 424 urging ˜448 are arranged in the same number as the number of developing rollers, and are rotatably supported by the support bases 425 to 428, respectively, and the slider 430 is selected on the slide base 429 to select a development color. Accordingly, the selected one of the contact rollers 421 to 424 is urged in the direction of arrows M1 to M4 by moving in the direction of arrow L accordingly. In this way, by providing a contact roller corresponding to the developing roller, the outer diameter or pressure of the contact roller according to the development parameters such as the particle size for each toner color of the developing means, the charge amount, or the outer diameter of the developing roller. By selecting the hardness, density fluctuation due to uneven development parameters can be prevented, and a color image with little image density fluctuation and excellent color reproducibility can be formed. Note that not only the contact roller but also a tension roller or the like can be provided on the slide table 429 to reduce the number of parts.
[0067]
FIG. 5 is a cross-sectional view of an essential part showing still another embodiment in which the contact roller is divided and provided in the color image forming apparatus of the present invention. The contact roller is a first contact roller 521 and a second contact roller. The image carrier 510 is urged toward the developing roller 540 by the first contact roller 521 and the second contact roller. The first abutting roller 521 and the second abutting roller 522 are respectively suspended from a first urging force applying means 523 and a second urging force applying means 524 configured by springs or the like, and the first urging force applying means 523 and the second urging force applying means 523. The second urging force applying means 524 is fixed to the slide base 525. Therefore, in the region from the first contact roller 521 to the second contact roller 522, the image carrier 510 can be brought into contact with at least a part of the developing roller 540, and the developing nip is formed at the slack portion of the image carrier 510. Therefore, the image carrier can be urged to the developing roller 540 with a low pressure, and a sufficiently large development nip can be secured, so that the gap between the image carrier 510 and the developing roller 540 can be secured. The color image forming apparatus which absorbs the vibration generated in the above and forms a high-resolution color image with little jitter, has little wear on the image carrier, and has excellent durability can be provided. When the peripheral speed of the developing roller 540 is higher than the peripheral speed of the image carrier 510, preferably 1 to 3 times the peripheral speed, an image with high density and less toner adhesion (fogging) to the non-image area is formed. However, since vibration is generated due to a difference in peripheral speed between the image carrier 510 and the developing roller 540, such a configuration is used in that the image carrier 510 is brought into contact with the developing roller 540 with as low pressure as possible. Is preferred.
[0068]
FIG. 6 is a cross-sectional view of an essential part showing still another embodiment in which the developing means is arranged on a non-arc curve in the color image forming apparatus of the present invention, and the first support roller 611 and the second support roller 612 are in contact with each other. The contact roller 613 has the same outer diameter, and the rotation center of the contact roller 613 can be positioned on an elliptical arc curve 600 with the rotation center of the first support roller 611 and the rotation center of the second support roller 612 as the focal point. The image carrier 610 moving in the direction of the arrow P moves the contact roller 613 in the direction of the arrow Q, so that the developing rollers 645 to 645 of the developing means 641 to 644 similar to those shown in FIG. 648 is energized. With this configuration, the belt length of the image carrier 610 from the first support roller 611 to the second support roller 612 can be kept constant regardless of the position of the contact roller 613. The belt length of the image carrier 610 from the exposure position of the support roller 611 to the transfer position of the second support roller 612 can be kept constant to form a color image with excellent color reproducibility without color misalignment. A simple structure for supporting the image carrier in a fixed position without the need can be realized. In the case where the first support roller 611, the second support roller 612, and the contact roller 613 are not the same outer diameter, the first support roller 611, the second support roller 612, and the contact roller 613 have the same outer diameter ratio. The focal position on the second support roller 612 side is deviated according to the elliptic arc curve in which the focal position on the one support roller 611 side is deviated or the ratio of the outer diameters of the second support roller 612 and the contact roller 613. Although a slight error occurs by using the elliptical arc curve, the belt length of the image carrier 610 from the first support roller 611 to the second support roller 612 is kept constant regardless of the position of the contact roller 613. Can do.
[0069]
As described above, according to each of the above-described embodiments, a belt-like image carrier can be used to form a color image without color misregistration. It is desirable to reduce the number as much as possible. When such downsizing is promoted, it is necessary to pay attention to fatigue failure due to repeated bending of the image carrier. Therefore, it is desirable that the image carrier used in the present invention has a thickness that is two or more orders of magnitude smaller than the outer diameter of the roller having the smallest outer diameter among the first support roller, the second support roller, and the contact roller. By doing so, it is possible to prevent cracking and deformation of the image carrier due to repeated bending of about 100,000 to 1 million times, and to provide a color image forming apparatus with excellent durability and high reliability. it can.
[0070]
FIG. 7 is a view for explaining the width of each member used in the color image forming apparatus in the embodiment as shown in FIG. 1 of the present invention. The width of the photosensitive layer is less than this based on the width of the image carrier belt. The width of the first support roller, the width of the second support roller, and the width of the third support roller are configured to be larger than this. In addition, the width of the process related to image formation is desirably smaller than the width of the photosensitive layer described above. In order from the widest width, the cleaning width, the charging roller width, the developing roller width, the contact roller width, the primary transfer roller width, The effective development width and the effective exposure width are used.
[0071]
By adopting such a configuration, first, the width of the contact roller where the contact roller and the image carrier are in contact with each other is set to be larger than the effective development width for forming the toner layer on the developing roller. Since the contact state or proximity state between the image carrier and the developing means can be kept constant, fluctuations in development density can be prevented, and a color image having excellent gradation can be formed. Further, the width of the contact roller between the contact roller and the image carrier is larger than the effective development width for forming the toner layer on the development roller, and the width of the development roller where the development roller is in contact with the image carrier. By reducing the size, the end corner of the developing roller is not strongly brought into contact with the image carrier, so that the image carrier belt is not damaged and the durability and reliability of the color image forming apparatus are improved. be able to.
[0072]
Next, at least two of the first support roller, the second support roller, and the contact roller are in contact with the image carrier over the entire width of the image carrier, thereby stably stretching the image carrier belt. At the same time, since it can run stably, an excessive stress is not generated on the image carrier, and a color image forming apparatus having excellent durability and color reproducibility can be provided.
[0073]
Furthermore, by making the contact width between the cleaning means and the image carrier smaller than the contact width between the image carrier and the third support roller, the contact state between the cleaning means and the image carrier is not dependent on the position in the width direction. It is uniform to prevent poor cleaning, and the end corners of the third support roller do not come into strong contact with the image carrier. A high color image forming apparatus can be provided.
[0074]
Therefore, according to this embodiment, a belt-shaped image carrier can be stably run, and a small color image forming apparatus having excellent durability of the image carrier can form a color image with excellent color reproducibility. Can do.
[0075]
【The invention's effect】
As described above, according to the present invention, the contact roller is disposed in the region from the first support roller to the second support roller with respect to the moving direction of the image carrier, and the exposure means removes the image carrier from the first support roller. The transfer unit is arranged to be exposed to the part wound around the one support roller, and the transfer means is arranged opposite to the part around which the image carrier is wound around the second support roller. Since the selection of the means is not required, it is not necessary to move the developing means apart and vibration and impact applied to the developing means can be minimized, preventing toner contamination in the apparatus and preventing image deterioration due to scattered toner. be able to.
[0076]
In addition, by forming the contact roller with an elastic roller including an elastic body, generation of vibration and impact due to movement of the contact roller is reduced, and a sufficiently large development nip between the image carrier and the developing means is secured. In addition, a one-component non-magnetic toner can be pressed and developed to form a high-definition, high-resolution color image.
[0077]
Further, by arranging a plurality of contact rollers facing the developing means, the outer diameter of the contact roller or the diameter of the toner for each toner color of the developing means, the charge amount, or the development parameter such as the outer diameter of the developing roller can be reduced. By selecting the pressure or the hardness, it is possible to prevent density fluctuation due to uneven development parameters and to form a color image with little image density fluctuation and excellent color reproducibility.
[0078]
Further, the contact roller is composed of a first contact roller and a second contact roller, and the image carrier is brought into contact with at least a part of the developing means in a region from the first contact roller to the second contact roller. As a result, the developing nip can be formed at the slack portion of the image carrier belt, so that the image carrier can be urged with a low pressure against the developing means and the development nip can be sufficiently large. Therefore, it is possible to provide a color image forming apparatus that absorbs the vibration of the image carrier and forms a high-resolution color image with little jitter, and has low durability and excellent durability.
[0079]
Further, the contact roller can be moved in the moving direction of the image carrier, and the image carrier is separated from and brought into contact with the developing means in the non-image area of the image carrier, so that the toner adheres to the image area due to separation and contact. Since it does not occur, a color image with high color purity can be formed.
[0080]
Further, by providing a tension applying means for applying a tension to the image carrier in a region from the first support roller to the second support roller with respect to the moving direction of the image carrier, the belt due to the positional deviation of the developing means. The length of the image carrier belt from the exposure position to the transfer position can be made constant by absorbing the fluctuation of the slackness of the image by the tension application means, the development position margin is large, and the color reproducibility is excellent. A color image forming apparatus can be provided.
[0081]
Further, the charging means is disposed opposite to the portion where the image carrier is wound around the first support roller, so that even if the belt tension of the image carrier fluctuates, stable and uniform charging can be performed. And a color image having excellent gradation can be formed. In particular, when contact charging is used, since the contact state can be made constant, uniform charging is possible without causing charge injection.
[0082]
Further, since the exposure means is arranged to expose the image carrier around the first support roller and further downstream from the center, it is stable even if the belt tension of the image carrier fluctuates. Since exposure can be performed at a fixed position, exposure can be performed in the tension state of the image carrier similar to that of the developing unit, and a color image excellent in color reproducibility without color misregistration can be formed.
[0083]
Further, since the first support roller transmits the driving force to the image carrier, the developing means can be disposed on the slack side of the image carrier belt. Thus, the image density variation can be reduced, the length of the image carrier from the exposure position to the transfer position can be kept constant, and a color image excellent in color reproducibility without color misregistration can be formed.
[0084]
Further, since the developing unit is disposed at a position fixed to the first support roller and the second support roller, the developing unit can be used while being fixed to the color image forming apparatus main body. In addition, it is not necessary to move the developing unit apart, the toner can be easily replenished, the developing unit can be easily attached and detached, and the toner can be replenished and the developing unit can be replaced by user maintenance.
[0085]
Further, the transfer means is disposed opposite to the portion where the image carrier is wound around the second support roller, so that even if the tension of the image carrier fluctuates, the image is stably transferred at a fixed position. Therefore, a color image excellent in color reproducibility can be formed by preventing color misregistration in primary transfer color superposition.
[0086]
Further, a cleaning unit that contacts the image carrier is disposed in a region from the second support roller to the first support roller with respect to the moving direction of the image carrier, so that the image carrier belt cleaning unit can be Since the area extending to the support roller can be the tension side of the belt, the image carrier belt expansion and contraction due to the cleaning means is not given to the exposure section, development section, and transfer section, and high-definition color with little jitter An image can be formed.
[0087]
Further, since the third support roller for supporting the image carrier is disposed in the area where the cleaning unit contacts the image carrier, the vibration of the image carrier belt by the cleaning unit can be prevented. The length of the image carrier belt from the support roller to the first support roller is kept constant, and a color image excellent in color reproducibility without color misregistration can be formed.
[0088]
In addition, the first support roller, the second support roller, and the contact roller have the same outer diameter, and the first support roller, the second support roller, and the contact roller have an elliptical arc curve that focuses on the rotation center of the first support roller and the rotation center of the second support roller. By making the contact roller rotation center positionable, the belt length of the image carrier from the first support roller to the second support roller can be kept constant regardless of the position of the contact roller. In addition to forming a color image having excellent color reproducibility, a simple structure is possible in which the tension roller is omitted and the image carrier is supported at a fixed position.
[0089]
Further, by making the contact width between the contact roller and the image carrier larger than the effective development width of the developing unit, the contact state or proximity state between the image carrier and the developing unit in the effective development region can be kept constant. Therefore, variation in development density can be prevented, and a color image having excellent gradation can be formed.
[0090]
Further, by making the contact width between the contact roller and the image carrier larger than the effective development width of the developing means and smaller than the contact width of the developing means, the end corners of the developing means are strongly attached to the image carrier. Since the contact is not caused, the image carrier belt is not damaged and the reliability of the apparatus is not lowered.
[0091]
Further, at least two of the first support roller, the second support roller, and the contact roller are in contact with the image carrier over the entire width of the image carrier, thereby stably stretching the image carrier belt. Therefore, it is possible to provide a color image forming apparatus excellent in durability and color reproducibility without generating excessive stress on the image carrier because it can be stably driven.
[0092]
Further, by making the contact width between the cleaning means and the image carrier smaller than the contact width between the image carrier and the third support roller, the end corner of the third support roller is strongly brought into contact with the image carrier. Therefore, the image bearing belt is not damaged by the cleaning unit, and a highly reliable color image forming apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential part showing an embodiment of a color image forming apparatus of the present invention.
FIG. 2 is a cross-sectional view of an essential part showing an operating state of a contact roller when non-contact development is performed in the color image forming apparatus of the present invention.
FIG. 3 is a cross-sectional view of an essential part showing an operating state of a contact roller when contact development is performed in the color image forming apparatus of the present invention.
FIG. 4 is a cross-sectional view of an essential part showing another embodiment in which the same number of contact rollers as the developing means are provided in the color image forming apparatus of the present invention.
FIG. 5 is a cross-sectional view of an essential part showing still another embodiment in which the contact roller is divided and provided in the color image forming apparatus of the present invention.
FIG. 6 is a cross-sectional view of an essential part showing still another embodiment in which the developing means is arranged on a non-arc curve in the color image forming apparatus of the present invention.
FIG. 7 is a diagram illustrating the width of each member used in the color image forming apparatus according to an embodiment of the present invention.
[Explanation of symbols]
10, 210, 310, 410, 510, 610 Image carrier
11, 611 First support roller
12, 612 Second support roller
13, 213, 313, 421, 422, 423, 424 Contact roller
14 Tension roller
15 Third support roller
20 Charging roller
30 Exposure means
40 housing
41, 641 Yellow developer
42,642 Magenta developer
43, 643 Cyan developer
44, 644 Black developer
45,645 Yellow development roller
46,646 Magenta developing roller
47, 647 Cyan developing roller
48,648 Black development roller
50 Primary transfer roller
51 Intermediate transfer media
52 Driving roller
53 First driven roller
54 Second driven roller
55 Secondary transfer roller
56 Second cleaning means
57 Second cleaning blade
60 Static elimination lamp
70 Cleaning means
71 Cleaning blade
240, 340, 445, 446, 447, 448, 540 Developing roller
241 Gap roller
311 shaft
312 Elastic layer
521 First contact roller
522 Second contact roller
523 First biasing force applying means
524 Second biasing force applying means
525 slide base
600 Elliptic arc curve

Claims (15)

A belt-like image carrier stretched between the first support roller and the second support roller, a charging means for charging the image carrier, and an electrostatic latent image on the image carrier according to image formation information An exposure unit for forming the image, a plurality of developing units for sequentially developing the electrostatic latent image on the image carrier with a plurality of colors of toner, and a movable contact for biasing the image carrier to the developing unit. distribution and contact roller, the developed toner image have a transfer means for transferring, the contact roller in the region leading to the second support roller from the first support roller relative to the moving direction of said image bearing member And the exposure means is arranged to expose the image carrier around the first support roller, and the transfer means is a part around the image carrier around the second support roller. a color image forming apparatus which is arranged to face the front Greater than the effective developing width of the developing unit contact width between the contact roller and the image bearing member, and a color image forming apparatus characterized by smaller than the contact width of the developing unit. The color image forming apparatus according to claim 1, wherein the contact roller is formed of an elastic roller including an elastic body. The color image forming apparatus according to claim 1, wherein a plurality of the contact rollers are disposed to face the developing unit. The contact roller is composed of a first contact roller and a second contact roller, and the image carrier is at least one of the developing means in a region from the first contact roller to the second contact roller. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is in contact with a portion. 2. The contact roller according to claim 1, wherein the contact roller is movable in the moving direction of the image carrier and the image carrier is separated from and contacted with the developing means in a non-image area of the image carrier. The color image forming apparatus according to 2 or 4. 2. A tension applying means for applying a tension to the image carrier is disposed in a region from the first support roller to the second support roller with respect to the moving direction of the image carrier. The color image forming apparatus described. 2. The color image forming apparatus according to claim 1, wherein the charging unit is disposed to face a portion where the image carrier is wound around the first support roller. 2. A color image forming apparatus according to claim 1, wherein said exposure means is arranged so as to expose the image carrier at a portion around said first support roller and further downstream from the center. The color image forming apparatus according to claim 1, wherein the first support roller transmits a driving force to the image carrier. The color image forming apparatus according to claim 1, wherein the developing unit is disposed at a position fixed to the first support roller and the second support roller. 2. The color according to claim 1, wherein a cleaning unit that contacts the image carrier is disposed in a region from the second support roller to the first support roller with respect to a moving direction of the image carrier. Image forming apparatus. 12. The color image forming apparatus according to claim 11, wherein a third support roller for supporting the image carrier is disposed in a region where the cleaning unit contacts the image carrier. The first support roller, the second support roller, and the abutment roller have the same outer diameter, and an elliptical arc curve that focuses on the rotation center of the first support roller and the rotation center of the second support roller. 2. The color image forming apparatus according to claim 1, wherein the rotation center of the contact roller can be positioned. 2. The color image according to claim 1, wherein at least two of the first support roller, the second support roller, and the contact roller are in contact with the image carrier over the entire width of the image carrier. Forming equipment. 13. The color image forming apparatus according to claim 12, wherein a contact width between the cleaning unit and the image carrier is made smaller than a contact width between the image carrier and the third support roller.

Images