JP3472399B2 - Color image forming equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly to a color image forming apparatus capable of forming a full-color image and a monochrome monochrome image such as a character image. About. [0002] With the spread of electronic devices, so-called laser printers using an electrophotographic process and laser technology have been widely used as output devices of computers. The laser printer reads image information of a document using an optical writing unit, forms an electrostatic latent image on a photoconductor drum based on the read image information, and uses a toner supplied from a developing device to form a static image on the photoconductor. The latent image is visualized, the toner image is transferred to a transfer sheet via an intermediate transfer member constituted by a belt or the like, and is fused and fixed by a fixing device or the like.
In recent years, color laser printers have been widely used in order to respond to the demand for full-color output. The color laser printer uses three colors of cyan, magenta and yellow or four colors of cyan, magenta, yellow and black. Overlay to form a full color image. FIG. 4 is a diagram showing a schematic configuration of a color image forming apparatus disclosed in JP-A-6-250474, wherein 1Y is a yellow image forming section, 1M is a magenta image forming section, 1C is a cyan image forming section, and 1K is Each of the image forming units is a photosensitive drum 2 (Y, M, C, K), a charging device 3 (Y, M, C, K), and an exposing device 4 (Y, M, C,
K), developing device 5 (Y, M, C, K), cleaning device 6 (Y, M, C, K), transfer device 13 (Y, M, C,
K). Further, 8 is a conveyor belt, 9 is a conveyor belt driving roller, 10 is a conveyor belt driven roller,
Reference numeral 11 denotes a recording paper (recording paper), 12 denotes a paper feed tray, 14 denotes a fixing device, and 15 denotes a paper discharge tray. The above image forming units 1Y, 1M, 1C, 1K
Are linearly arranged along the conveyance belt 8, and the conveyance belt 8 is driven to rotate in the direction of arrow 10 by the rotation of the driving roller 9, whereby the recording paper 11 is sequentially conveyed along the four image forming portions. . A paper feed tray 12 is provided below the transport belt 8, and the recording paper 11 sent from the paper feed tray 12 is attracted to the transport belt 8 and sequentially passes through each image forming unit. At this time, the toner image formed on the photoreceptor drum 2Y of the yellow image forming unit 1Y is transferred onto the recording paper 11 by the transfer device 13Y at the transfer position 7Y, and is subsequently transferred to the image forming units 1M, 1C, and 1K. Similarly, magenta, cyan, and black toner images are recorded and transferred to the same position on the image 11 to form toner images of four colors. Is discharged. The toner remaining on the surface of each photoconductor drum is removed by a cleaning device 6 provided in each image forming unit, and prepares for the next image forming cycle. As shown in FIG. 5, as the exposure device 4, a modulation signal obtained by subjecting an image signal corresponding to a document image to predetermined image processing is transmitted from the image forming processing unit 24 (see FIG. 4) in synchronization with the image forming timing. A so-called laser scanner, which is sequentially sent out, reflects a laser beam 17 from a laser light source 16 with a polygon scanner 18, further refracts an optical path with a mirror 19, and exposes the surface of the photosensitive drum 2, is used. ing. In this laser scanner, the main scanning is performed in the axial direction 21 of the photosensitive drum 2 by rotating the polygon scanner 18 in the direction of arrow 20, and the photosensitive drum 2 is rotated in the direction of arrow 22 by rotating the photosensitive drum 2. The sub-scan is performed in a direction 23 orthogonal to the axial direction 21 of FIG. [0004] However, since a glossy color image generally looks more beautiful, a glossy toner is used. As described above, the color image is formed of four color image forming sections. For example, when a character image is formed using a black toner of a color image forming apparatus, the character image becomes glaring and glossy and is difficult to see, and the image quality is significantly deteriorated as compared with a conventional black and white image forming apparatus. there were. Another color image forming apparatus is disclosed in Japanese Patent Application Laid-Open No. 4-284468. FIG. 6 shows a schematic configuration thereof, and portions having the same functions as those in FIG. 4 are denoted by the same reference numerals. In this color image forming apparatus, two photosensitive drums 2KBk and 2YMC are arranged along a conveyor belt 8, and one photosensitive drum 2
A high-gloss black toner developing unit 5K for color images and a low-gloss black toner developing unit 5Bk for character images are provided around KBk, and the other photoreceptor and the ram 2YMC around the ram 2YMC. By providing the developing units 5Y, 5M, and 5C for the high gloss yellow, magenta, and cyan colors, the image quality of the color image and the character image can be compatible. [0005] Also, two sets of image forming units 1YMC and 1KBk are arranged along the conveying belt 8, and the image forming units 1YM
Around the photosensitive drum 2YMC on the C side, yellow, magenta, and cyan toner developing units 5Y, 5Y for color images are provided.
M, 5C, a charging device 3, an exposure device 4, and a cleaning device 6 are provided. Around the photosensitive drum 2KBk on the other image forming unit 1KBk side, a high gloss black toner developing unit 5K for color image, a low gloss black toner developing unit 5Bk for character image forming, a charging device 3, An exposure device 4 and a cleaning device 6 are provided. Further, the recording paper 11 has two sets of image forming units 1KBk, 1YMC
Are conveyed sequentially, and the conveying belt 8 is driven to rotate in the direction of arrow 10 by a roller 9, one of which is a driving roller. The paper feed tray 12 is provided below the conveyor belt. The recording paper sent out from the paper feed tray 12 is attracted to the conveyance belt 8 and the two sets of image forming units 1KBk, 1YMC
Sequentially pass along. Next, a case where a color image is formed by this apparatus will be described. First, at the time of color image formation, in the upstream image forming section 1YMC, the laser beam 17Y corresponding to each color of yellow, magenta, and cyan is provided.
Each of the developing devices 5Y, 5M, and 5C is synchronized with the exposure by the MC by a photosensitive mechanism (not shown) or the like.
The developer is brought into contact with and separated from the surface of the MC, and only the developing device corresponding to the laser writing color operates to perform development. That is, the photosensitive drum 2Y
In the first rotation of the MC, only the developing device 5Y corresponding to yellow is operable, and the other developing devices 5M and 5C are inoperable. Similarly, only the developing device 5M corresponding to magenta can operate in the second rotation, and only the developing device 5C for cyan can operate in the third rotation. The photosensitive drum 2YMC, which is driven to rotate in the direction of the arrow 24, is first uniformly charged by a charging device 3YMC, and then, in an exposure device 4YMC, a laser beam modulated by a signal corresponding to yellow of an image. Exposes the surface of the photoreceptor drum 2YMC to form an electrostatic latent image. Next, the electrostatic latent image advances to the yellow developing device 5Y and is developed with yellow toner. This yellow toner image reaches a transfer position 7YMC as the photosensitive drum 2YMC rotates. On the other hand, the recording paper 11 is transported from the paper feed tray 12 to the transfer position 7YMC in synchronization with the rotation of the photosensitive drum 2YMC, and the yellow toner image is recorded on the transport belt 8 from the surface of the photosensitive drum 2YMC by the transfer device 3YMC. The image is transferred to the surface of the paper 11. The recording paper 11 after the transfer continues to rotate while being electrostatically or mechanically wound on the transport belt 8. Further, the yellow toner remaining on the surface of the photoconductor drum 2YMC after the transfer is removed by the cleaning device 6YMC and is prepared for the next image forming cycle. A similar operation is performed on the photosensitive drum 2YMC.
Each rotation is repeated for magenta and cyan, and the conveyance belt 8 makes three rotations, so that the yellow, magenta, and cyan toner images are transferred onto the surface of the recording paper in an aligned manner. However, at the third rotation of the conveyor belt 8, the downstream image forming unit 1KBk is also in the operating state, and the photosensitive drum 2 that is rotationally driven in the direction of arrow 25.
The KBk is first uniformly charged by the charging device 3KBk, and then the surface of the photosensitive drum 2KBk is exposed by a laser beam modulated by a signal corresponding to black of a color image in the exposing device 4KBk to thereby form an electrostatic latent image. Is formed.
Next, this electrostatic latent image is used as a black toner developer for color 5K.
And the image is developed with the black toner for color.
The black toner image for color is formed on the recording paper 11 that is wound around the conveyance belt 8 and conveyed.
In the state where it is aligned with magenta and cyan multiple transfer,
Furthermore, multiple transcription is performed. That is, in the third rotation of the transport belt, the transfer of cyan and color black toner images is performed sequentially. The recording paper on which the color images are formed by multi-transfer of the four color toner images in this manner is peeled off the transport belt by a peeling means (not shown), sent to the fixing device 14 by the transport belt 8, and the toner image is printed on the recording paper. Establish. After undergoing the fixing process by the fixing device 14, the sheet is discharged to a sheet discharge tray 15. However, in the conventional color image forming apparatus as described above, when a color image and a character image are mixed, the transfer belt 8 is developed and transferred to the magenta toner image and the low-gloss black The development and transfer of the toner image may be performed, but even in this case, the transport belt 8 must rotate three times. That is,
When outputting a color image or an image in which both a color image and a character image are present, the transport belt needs to rotate three times, which takes a long time to transport, and takes a long time to output. Was. In addition, since the recording paper is wound around the transport belt and transported in rotation, it is necessary to prevent the recording paper from separating from the transport belt even at the curvature portion, and the type of paper is limited. Further, when a means for reciprocating the recording paper in a linear path without rotating the paper is used, the mechanism and control become complicated, and the transportation path of the recording paper becomes longer with any of the means, so that the medium during the conveyance is not used. There is a problem in that it is easily affected by Iran, and the possibility of color shift and position shift increases. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problems, and has as its object to provide a color image forming apparatus which can achieve both high-quality output of a color image and a character image and which can output at high speed. I have. According to the present invention, there is provided, in accordance with the present invention, four image forming sections having glossy yellow, magenta, cyan, and black developers for a color image; In a color image forming apparatus in which a plurality of image forming units including one image forming unit having a non-glossy black developer for an image are arranged in a straight line along a recording paper conveyance path, A recording paper transporting path for transporting recording paper from a paper feed tray to the color image forming section, while disposing the image forming section downstream of the recording paper transporting path of the color image forming section; A recording paper transport path for transporting the recording paper from a paper feed tray to the image forming section for the character image; a recording paper transport path for transporting the recording paper to the image forming section for the color image; and an image for the character image Recording paper to forming unit The problem is solved by providing the recording paper transport path for transporting the paper feed tray on both sides of the paper feed tray. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of a color image forming apparatus according to a reference example. Reference numeral 31 denotes a yellow image forming unit, 32 denotes a magenta image forming unit, 33 denotes a cyan image forming unit, 34 denotes a high gloss black image forming unit, 35
Denotes a low-gloss black image forming unit, and each image forming unit is linearly arranged along the recording paper transport path. In each image forming unit, a is a photosensitive drum, b is a charging device, c is an exposing device, d is a developing device, e is a cleaning device, and f is a transfer device. Is attached. Therefore, for example, the photosensitive drum of the yellow image forming unit 31 is denoted by 31a, and the transfer device of the low gloss black image forming unit 35 is denoted by 35f. The recording paper 36 is stored in a paper feed tray 37 and sent out one by one to a recording paper transport path including a transport belt 39, a driving roller 40, and a driven roller 41 via a part 38 of the recording paper transport path. The driving roller 40 and the driven roller 41 rotate in the directions indicated by arrows, and as a result, the recording paper moves on the conveyor belt 39 in the direction indicated by the arrow 42. Reference numeral 43 denotes a fixing device, and reference numeral 44 denotes an image processing unit that controls the exposure devices 31c, 32c, 33c, 34c, and 35c of each image forming unit. In the color image forming apparatus constructed as described above, the surface of the photosensitive drum 31a is uniformly charged by the charging device 31b, and is then exposed by the exposure device 31c in a pattern corresponding to the image to be output. An electrostatic latent image is formed on the surface of the drum 31a. Next, the electrostatic latent image is developed
The toner image is formed by developing at d, and when the recording paper is transported to the transfer position 31g by the transport belt 39, the toner image is transferred onto the recording paper. The charging process, the exposure process, the toner image developing process, the transfer process, and the like described above are sequentially performed in the image forming units of the respective colors. When the recording paper reaches the transfer positions 32 g to 35 g of the image forming units of the respective colors, the toner A color image in which the images are sequentially superimposed on the recording paper 36 is obtained, and thereafter, the toner remaining on each photosensitive drum is removed by the cleaning devices 31e to 35e. Therefore, an image in which a toner image of all colors and a low-gloss black toner image are superimposed on the recording paper 36 by one pass of the recording paper 36 can be obtained. That is, in the case of a document containing only a color image, a glossy high-quality color image can be formed using the four colors of yellow, magenta, cyan, and black with high gloss. A glossy black toner is used, and a low-gloss black image forming section 35 is used to obtain a low-gloss, easy-to-read character image. In the case of a document in which a color image and a character image are mixed, a high-gloss four-color image is used. By using the low-gloss black toner, it is possible to obtain a desired high-quality image only by conveying the recording paper 36 once. In the above-described reference example, even in the case of a document having only a character image, the recording paper 36 passes through the image forming sections 31 to 34 of high gloss toner, and the recording paper 36 and the photosensitive drums 31a to 34a are separated. When the contact occurs, the respective photoconductor drums tend to be worn and the life of the photoconductor drums tends to be shortened. Further, if the toner image transfer from each photoconductor drum to the recording paper is performed in a non-contact corona transfer in order to keep the photoconductor drum and the recording paper out of contact, ozone is generated, which is not desirable in terms of environmental conservation. In order to further prevent wear of the photosensitive drum,
Providing a contact / separation mechanism in the image forming units 31 to 34 so that the image forming unit performs the contact / separation operation with respect to the conveyor belt 39 when forming only a character image, not only complicates the structure and control, but also In addition, the positional relationship between the photosensitive drums of each color is slightly shifted due to the contact / separation operation, and a shift between colors (color shift) occurs when colors are superimposed. Conversely, it is conceivable to provide a contact / separation mechanism on the transport belt, but it is necessary to move the members in contact with the transport belt, for example, a driving roller, a driven roller, a transfer roller, and the like together. Becomes complicated. Therefore, by configuring as in the second reference example described below, the recording sheet is not passed through an image forming unit that is unnecessary for image formation, despite the mechanism that does not generate ozone and the like and the mechanism is simple. Wear can be reduced. FIG. 2 is a view showing a second reference example. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The difference between the reference example shown in FIG. 2 and the reference example shown in FIG. 1 is that the image forming units 31 to 34 which form a high gloss toner image as a recording paper conveyance path from the paper supply tray 37 are used.
In addition to a path 38 for sending the recording paper to a conveyance belt 39 for conveying the recording paper, a bypass conveyance path 45 for conveying the recording paper 36 directly from the paper feed tray 37 to an image forming unit 35 for forming a low-gloss black toner image is provided. It is a point that has. Thus, the image forming unit 35 of the low gloss black toner for the character image is arranged on the downstream side of the recording paper conveyance path 38, and a simple path switch (not shown) is provided. By providing a bypass transport path 45 having a simple structure for bypassing and transporting the recording paper 36 to the transfer position 35g of the unit 35, the recording paper is transported via the bypass transport path 45 at the time of forming a character image, thereby forming a color image. Part 3
Since the photosensitive drums 31a to 34g do not pass through the transfer positions 31g to 34g of the photosensitive drums 31a to
34a can be prevented from being worn. When a character image is further formed. By switching the recording paper transport mechanism and the drive mechanism of the image forming unit 35 for forming a character image to the high-speed mode, it is possible to increase the speed of forming a character image. Next, an embodiment of a color image forming apparatus according to the present invention will be described. FIG. 3 is a diagram showing an embodiment of the present invention. The difference from FIG. 2 is that paper can be fed from both sides of the paper feed tray 37 and a route to the color image forming units 31 to 34 is provided. The point is that a path to the image forming unit 35 for forming a character image is provided on the opposite side of the adjacent sheet feeding tray. That is, in the reference example shown in FIG. 2, a space is required to separately provide the transport path 45, and therefore, the apparatus may be increased in size. Therefore, as shown in FIG. 3, the paper feed tray is configured to be able to feed paper from both sides of the paper feed tray, and the path to the image forming section 35 for forming a character image is provided from the side opposite to the path to the color image forming section. This makes it possible to reduce the size of the apparatus, switch the transport path with a simple configuration, and perform character image formation (use of a low-gloss black toner) faster because the transport path is shorter. As described above, according to the color image forming apparatus of the present invention, the image forming section for the character image is arranged downstream of the recording paper transport path of the image forming section for the color image. A recording paper transport path for transporting recording paper from the paper feed tray to the color image forming section, and a recording paper transport path for transporting recording paper from the paper tray to the text image forming section. A recording paper transport path for transporting the recording paper to the image forming section for color images and a recording paper transport path for transporting the recording paper to the image forming section for character images face both sides of the paper feed tray. The recording paper can be conveyed to the character image forming unit without passing through the color image forming unit when forming the character image, so that the contact between the photosensitive drum and the recording paper can be achieved. Wear of the photoconductor drum can be prevented, It is effective in extending the life of the photosensitive drum. In addition, at the time of forming a character image, the operation can be controlled independently of the image forming section for forming a color image. Therefore, if the linear speed is increased, a character image with no gloss can be formed at a high speed. Further, since the transport path of the recording paper can be shortened, the apparatus can be reduced in size, and the shortened transport path is effective in forming a glossy character image at higher speed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a schematic configuration of a color image forming apparatus of a reference example. FIG. 2 is a diagram showing a second reference example. FIG. 3 is a diagram showing an embodiment of the present invention. FIG. 4 is a diagram showing a schematic configuration of a conventional color image forming apparatus. FIG. 5 is a diagram showing a configuration of an exposure apparatus. FIG. 6 is a diagram illustrating a schematic configuration of a conventional color image forming apparatus. [Description of Signs] 31: yellow image forming unit, 32: magenta image forming unit, 33: cyan image forming unit, 34: black image forming unit (high gloss) 35: black image Forming part (low gloss), 36 ...
Recording paper, 37: paper feed tray, 38: transport path,
39: conveyor belt, 40: drive belt, 41
.. A driven belt, 44... An image processing unit, 45.

Continuation of the front page (72) Inventor Tomonori Yabuta 10-3 Kitamura, Tottori City, Tottori Prefecture Inside Ricoh Microelectronics Co., Ltd. (56) References JP-A-4-107576 (JP, A) JP-A 8-95333 (JP) JP-A-3-28865 (JP, A) JP-A-62-212960 (JP, A) JP-A-5-341617 (JP, A) JP-A-6-211364 (JP, A) 63-212960 (JP, A) JP-A-6-83158 (JP, A) JP-B-62-30431 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/01 -15/01 117 G03G 15/00 510

Claims (1)

(57) [Claims 1] Glossy yellow for color images,
A plurality of image forming sections including four image forming sections having magenta, cyan, and black developers and one image forming section having a non-glossy black developer for a character image are transported through a recording paper transport path. In the color image forming apparatus arranged in a straight line along the line, the image forming section for the character image is arranged downstream of the recording paper conveyance path of the image forming section for the color image, and the color is formed from a paper feed tray. A recording paper transport path for transporting the recording paper to the image forming section for the image, and a recording paper transport path for transporting the recording paper from the paper feed tray to the image forming section for the character image; A recording paper transport path for transporting the recording paper to the image forming unit and a recording paper transport path for transporting the recording paper to the image forming unit for character images are provided opposite to both sides of the paper feed tray. Color image forming apparatus .