JP2006031044A - Image forming apparatus - Google Patents

Abstract

A compact image forming apparatus is provided.
A transfer belt, a plurality of photosensitive drums arranged along the traveling side of the transfer belt, and a plurality of photosensitive drums. Each of which has a writing unit 8 for irradiating a laser beam, and the running side 21 of the transfer belt 20 on which the plurality of photosensitive drums 5M, 5C, 5Y, and 5Bk are arranged is inclined in the apparatus. It is inclined in the apparatus, and is arranged substantially parallel to the running side 21 of the transfer belt 20 on which the plurality of photosensitive drums 5M, 5C, 5Y, 5Bk are arranged.
[Selection] Figure 1

Description

  The present invention relates to a color image forming apparatus and a toner replenishing device used in the color image forming apparatus.

  Color image forming systems of color image forming apparatuses are roughly classified into four types: transfer drum system, intermediate transfer system, image on image system, and tandem system. In the “transfer drum system”, a transfer paper is wound around the surface of a transfer drum made of a dielectric film so as to face the photoreceptor, and each color of yellow (Y), magenta (M), cyan (C), and black (Bk) is obtained. On the other hand, a full color image is obtained by repeatedly superposing each color toner on a transfer paper by repeating an electrophotographic process of forming, developing and transferring an electrostatic latent image. The “intermediate transfer method” is a method of forming a full-color image by transferring each color toner image sequentially onto a drum or belt called an intermediate transfer member instead of the transfer paper used in the transfer drum method, and then transferring this onto the transfer paper at once. This is a method of retransferring to The “Image on Image method” is an electronic image formation, development, and transfer of electrostatic latent images for yellow (Y), magenta (M), cyan (C), and black (Bk) colors directly on a photoreceptor. This is a method of transferring onto a transfer paper by repeating the photographic process. The “tandem method” is a method for obtaining a full-color image on a transfer sheet by sequentially superimposing and transferring an image formed by an image forming unit onto a single transfer sheet conveyed to a transfer belt.

  The color image forming apparatus using each of these methods has advantages and disadvantages, but the tandem color image forming apparatus has many types of transfer paper that can be used, has high quality of full color images, and has high speed. It has an excellent characteristic that a full-color image can be obtained. In particular, the characteristic that a full color image can be obtained at a high speed is a characteristic that is not found in other color image forming apparatuses.

  In this tandem type image forming apparatus, four image forming units must be installed side by side on one running side of the transfer belt. Generally, in many cases, the upper running side of the transfer belt is arranged so as to extend in the horizontal direction, and four image forming units are arranged on the transfer belt. However, each image forming unit is provided with a photosensitive member provided with various means such as charging, developing, and cleaning around the image forming unit. When such image forming units are arranged in parallel on the transfer belt, image formation with a large lateral width is performed. It becomes a device and requires a large installation space.

Japanese Patent Laid-Open No. 10-239938

  Therefore, Patent Document 1 describes an image forming apparatus in which a transfer belt is set up vertically. With this configuration, the image forming units are arranged in the vertical direction along the transfer belt, so that the width of the image forming apparatus can be small, and an image forming apparatus with a small installation space can be provided.

  However, in the image forming apparatus in which the transfer belt is set up vertically, it is inevitable that the height of the housing becomes high. For this reason, in an image forming apparatus using the upper surface of a housing as a paper discharge tray as found in many printers in recent years, there is a problem that the position of the paper discharge tray becomes too high and workability is poor. there were.

  An object of the present invention is to provide a compact image forming apparatus in view of the above-described conventional problems.

  In order to achieve the above object, the present invention provides a transfer belt, a plurality of image carriers arranged along the running side of the transfer belt, and writing that irradiates laser light onto each of the plurality of image carriers. The transfer belt on which the plurality of image carriers are arranged is inclined in the apparatus, the writing unit is inclined in the apparatus, and the plurality of image carriers are arranged. The image forming apparatus is characterized in that the image forming apparatus is arranged substantially in parallel with the traveling side of the transfer belt.

  In the present invention, it is effective that the writing unit includes a polygon mirror and the reflected light from the polygon mirror is irradiated onto each of the plurality of image carriers.

Furthermore, the present invention is effective when the polygon mirror is a single polygon mirror.
Furthermore, the present invention is effective when the optical path length from the polygon mirror to the plurality of image carriers is constant.

  Furthermore, the present invention includes a paper feeding unit below the apparatus main body, and a paper discharge unit above the apparatus main body, and the running side of the transfer belt on which the plurality of image carriers are arranged includes the paper feeding unit It is effective that the sheet is disposed with the side facing down and the paper discharge section side facing up.

Furthermore, the present invention is effective when the image carrier is a photosensitive drum.
Furthermore, the present invention is effective when a developing unit is provided for each of the plurality of image carriers.

Furthermore, the present invention is effective when the plurality of developing units are developed using toner and a carrier.
Furthermore, the present invention is effective when a cleaning unit is provided for each of the plurality of image carriers.

  Furthermore, the present invention is effective when the plurality of image carriers are unitized together with corresponding developing means and cleaning means to form a plurality of image forming units.

  Furthermore, in the present invention, a cleaning unit included in at least one of the plurality of image forming units, and a developing unit of the image forming unit adjacent to the at least one image forming unit are arranged in a vertical direction. It is effective if they are arranged so as to overlap each other.

Furthermore, the present invention is effective when a transfer material is conveyed on the transfer belt, and images formed on the plurality of image carriers are superimposed and transferred on the transfer material.
Further, the present invention provides a plurality of toner storage containers provided corresponding to the developing means, each of which stores toner, and the toner stored in the plurality of toner storage containers, respectively, to the corresponding developing means. It is effective to have toner replenishing means.

  Furthermore, the present invention is effective when the toner replenishing means comprises a toner transport tube connecting the developing means and the toner container and a powder pump, and the toner is replenished by operating the powder pump. is there.

  According to the configuration of the present invention, since the running side of the transfer belt is inclined with respect to the main body, the image forming apparatus can be made compact and can be easily arranged.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic view showing a color laser printer which is an example of a color image forming apparatus according to the present invention. The color laser printer 1 has a configuration in which a paper feeding unit 2 is arranged at the lower part of the apparatus main body and an image forming unit 3 is arranged above the paper feeding unit 2. The image forming unit 3 is provided with a transfer belt device arranged so as to be inclined so that the paper feed side is on the bottom and the paper discharge side is on the top. The transfer belt device 20 has an endless transfer belt 20 wound around a plurality of belt wheels 22, in this example, four belt wheels 22, and magenta in order from the bottom to the upper running side 21 of the transfer belt 20. Four image forming units 4M, 4C, 4Y, and 4Bk for (M), cyan (C), yellow (Y), and black (Bk) are arranged in parallel.

  FIG. 2 is an enlarged explanatory view showing a portion of the image forming unit 4C. In FIG. 2, M, C, and Y are added in order to distinguish each device constituting each image forming unit for each unit. This is indicated by the reference numeral.

  1 and 2, each of the image forming units 4M, 4C, 4Y, and 4Bk is provided with a photosensitive drum 5 as an image carrier, and the photosensitive drum 5 is rotated clockwise by driving means (not shown). Driven. Around the photosensitive drum 5, a charging roll 6 as a charging unit, a light writing unit 7 in which writing by a laser beam is performed by a writing unit 8, a developing device 10 as a developing unit, and a cleaning device 9 as a cleaning unit are provided. Yes. The developing device 10 is a two-component developing device composed of toner and a carrier, and the toner is replenished by a toner replenishing device (to be described later) corresponding to the amount of consumed toner.

Next, an image forming operation for performing full color printing of the color printer shown in FIG. 1 will be described using the magenta image forming unit 4M.
The photosensitive drum 5M charged by the charging roll 6M is driven with an LD (laser diode) (not shown) to irradiate the polygon mirror 80 with laser light, and the reflected light is reflected through the cylinder lens or the like. Optical writing of an optical image to be developed with magenta toner is performed by the writing unit 8 guided upward. By this optical writing, an electrostatic latent image based on image data sent from a host machine such as a personal computer is formed on the photosensitive drum 5M, and the latent image becomes a visible image of magenta toner by the developing device 10. Note that the writing unit 8 is configured to write the reflected light of the single polygon mirror 80 to each photosensitive drum 5. In this case, the writing unit 8 is arranged obliquely substantially parallel to the transfer belt 20, so It is easy to make the optical path length to the body constant.

  On the other hand, a sheet designated as a transfer material is fed from the sheet feeding unit 2, and the fed sheet is once abutted against a registration roller 23 provided on the upstream side in the conveyance direction of the transfer belt 20. Then, the sheet is fed onto the transfer belt 20 in synchronism with the visible image, and reaches the transfer position facing the photosensitive drum 5M by running of the belt. At this transfer position, a visible image of magenta toner is transferred to the paper by the action of the transfer roll 24 disposed on the back side of the transfer belt 20.

  In the same manner as the above image forming operation, in the other image forming units 4C, 4Y, and 4Bk, visible images are formed by the respective toners on the surfaces of the respective photosensitive drums 5, and these visible images are conveyed by the transfer belt 21. Each time the sheet to be transferred arrives at each transfer position, the transfer is performed. Therefore, in this color printer, a full-color image is superimposed and transferred onto a sheet in a short time almost the same as that of monochrome.

  The transferred paper is separated from the transfer belt 20 and fixed by the fixing device 30. The fixing device of this example is a belt fixing system, and a relatively soft fixing roller 32 made of, for example, a sponge roller is pressed on a rigid pressure roller 31, and the fixing roller 32 and its upstream side in the paper conveyance direction A belt 34 is wound around a heating roller 33 disposed on the belt. This belt fixing method has advantages such as shorter warm-up time than roller fixing.

  The sheet that has been fixed is discharged out of the machine as it is, or the reversing unit 42 for duplex printing is selectively switched. When the discharge to the outside of the apparatus is selected, the sheet is turned upside down and discharged on the back side to a discharge tray 40 provided on the upper surface of the apparatus main body. Backside paper discharge is an almost indispensable condition for the printer to arrange prints in page order. If double-sided printing is selected, the paper is sent to the reversing unit 42, where the front and back are reversed and sent to the double-sided conveyance path 43. The double-sided conveyance path 43 is disposed obliquely below the transfer belt 20 and substantially parallel to the transfer belt 20. When the double-sided conveyance path 43 is arranged obliquely in this way, it can be pulled out together with the transfer belt when the conveyance distance is shortened or a jam occurs. Note that the transfer paper that has passed through the double-sided conveyance path is subjected to image formation on the back surface in the same manner as described above, and is then discharged onto the discharge tray 40.

  As described above, in this embodiment, the double-sided conveyance path 43 is disposed obliquely substantially parallel to the transfer belt 20 so that the transfer material after fixing can be reversed and returned to the registration roller 23 side in the shortest distance. For example, if the double-sided conveyance path 43 is provided horizontally, the path will pass near the upper surface of the upper cassette. In this case, the transfer material must be lowered to the height level, and the conveyance path becomes long. .

  The color printer configured as described above is provided with four image forming units 4M, 4C, 4Y, and 4Bk, and sequentially transfers the toner images of the respective colors while the paper is conveyed by the transfer belt device 20. The image forming time can be greatly shortened as compared with an intermediate transfer system in which a single image unit is used to superimpose and transfer a toner image onto an intermediate transfer member and then collectively transfer to a sheet. At this time, since the color printer uses the four image forming units 4M, 4C, 4Y, and 4Bk, the running side 21 on which the image forming unit of the transfer belt 20 is arranged is inclined as described above. 2, in the adjacent image forming units 4, the cleaning device 9 and the developing device 10 of the adjacent unit are arranged so as to overlap each other in the vertical direction. For example, in the adjacent image forming units 4M and 4C, the cleaning device 9M of the image forming unit 4M and the developing device 10C of the image forming unit 4C are arranged so as to overlap each other in the vertical direction. Therefore, the length in the left-right direction can be shortened as compared with the transfer belt arranged horizontally.

  Incidentally, as shown in FIG. 3, if the inclination angle of the transfer belt 20 is θ, if the angle θ is small, the adjacent developing device 10 and the cleaning device 9 cannot be disposed so as to overlap each other as described above. If the angle θ is close to 90 degrees, the length in the left-right direction can be greatly shortened, but a certain height is required in the vertical direction, and the position of the paper discharge tray becomes too high. Therefore, it is preferable to set the inclination angle θ of the transfer belt 20 to 35 degrees to 55 degrees. When the inclination angle θ is set between 35 degrees and 55 degrees, as shown in FIG. 3, when the transfer belt 20 is in contact in the third quadrant with the rotation center O of the photosensitive drum 5 as the origin, The development position, that is, the position where the magnetic brush formed on the development roller 11 contacts can be in the fourth quadrant of the photosensitive drum 5.

  In this way, the developing device 10 arranged to develop in the fourth quadrant of the photosensitive drum 5 is, for example, compared with a developing device installed at the same level as the rotational center of the photosensitive drum 5 or above it. There is an advantage that toner drop is reduced. Further, when the inclination angle θ of the transfer belt 20 is set to 35 to 55 degrees, and the transfer belt 20 is in contact with the third quadrant with the rotation center O of the photosensitive drum 5 as the origin, the cleaning blade 90 and the fur of the cleaning device 9 are in contact. The brush 91 can be in contact with the second quadrant of the photosensitive drum 5.

  The cleaning device 9 arranged in this way has better cleaning properties than a cleaning device 9 that is in contact with a cleaning member such as a cleaning blade almost directly above the photosensitive drum 5.

  Now, in the color printer in which the transfer belt 20 is inclined and the image forming units 4M, 4C, 4Y, and 4Bk are arranged along the inclination, the transfer belt 20 is arranged almost diagonally as shown in FIG. ing. In such a layout, when the running side 21 of the transfer belt 20 is driven so as to move from below to above, and the lower end side of the main body is provided with a paper feed unit and the paper discharge unit is provided on the upper end side, from the paper feed unit to the transfer belt 20. The conveyance path from the transfer belt 20 to the paper discharge unit can be shortened, which is extremely advantageous.

  Further, an image forming apparatus such as a printer has a substantially rectangular parallelepiped housing. When the inclined transfer belt 20 is provided in this type of printer, a space having a substantially triangular cross section is formed above and below the transfer belt 20. . In this embodiment, a toner container 100 is installed in the upper space, and a waste toner tank 93 is installed in the lower space. In this case, since the toner container 100 and the waste toner tank 93 have a very high degree of freedom in shape, the toner storage container 100 and the waste toner tank 93 are provided with a shape corresponding to the formed triangular space and an inclined surface in the same direction as the inclination of the transfer belt 20. Can be opposed. Therefore, it is possible to reliably prevent the space having a triangular cross section from becoming a large dead space.

Next, the toner image forming units 4M, 4C. 4Y. A toner replenishing device that replenishes 4 Bk will be described.
A uniaxial eccentric screw pump which is a suction type powder pump 110 is provided in the vicinity of or integrally with the developing device 10. As shown in FIG. 4, the powder pump 110 is composed of a rotor 142 made of a screw having an eccentric shape made of a rigid material such as metal, and an elastic body such as rubber, and a double screw shape. And a holder 144 made of a resin material that encloses these and forms a powder conveyance path. The rotor 142 is rotationally driven through a gear 46 integrally connected to a drive shaft 145 connected by a pin joint. Reference numeral 147 denotes an electromagnetic clutch, and the operation of the powder pump 110 is controlled by the clutch.

  A toner suction portion 148 is provided at the tip of the holder 144, that is, the right end in FIG. 4, and is connected to the toner suction portion 148 and a toner connection port 165 provided in a nozzle 160 described later by a toner transfer tube 149. ing. As the toner transfer tube 49, for example, a flexible tube having a diameter of 4 to 10 mm and made of a rubber material having excellent toner resistance (for example, polyurethane, nitrile, EPDM, silicon, etc.) is extremely used. It is effective and the flexible tube can be easily piped in any direction, up, down, left and right. In the toner replenishing device configured as described above, the single-shaft eccentric screw pump, which is the powder pump 110, is capable of continuous quantitative transfer at a high solid-gas ratio, and is an accurate toner proportional to the rotational speed of the rotor 142. It is known that the transfer amount can be obtained. Therefore, when a toner replenishment command is issued by image density detection or the like, the powder pump 110 is operated, and the requested amount of toner is replenished to the developing device 40.

  On the other hand, the set unit provided in the main body of the image forming apparatus in which the toner container 1 is set is configured as a separate unit from the developing device 10. In this set portion, a nozzle 160 having a circular cross section inserted into the toner bag 102 is erected, and the toner storage container 100 is set from above to the set portion of the image forming apparatus main body. The nozzle 160 provided in the set portion is provided with a tip member 161 formed in a conical shape in the upper part by integral molding or fixing, and an air supply path 162 and a toner supply path 163 are provided following the tip member 161. Is provided. The inside of the nozzle 160 has a double tube structure, and the toner supply path 163 is bent at the lower end of the nozzle 160 to the left in the figure, and a toner connection port 65 to which the toner transfer tube 149 is connected at the tip thereof. Is provided. The air supply path 162 is bent to the right in the figure above the toner supply path 163 and reaches the air connection port 164.

  In the present embodiment, the air connection port 164 is connected to an air pump 151 serving as an air supply unit via an air transfer pipe 152. When the air pump 151 is activated, air is ejected from the pump into the toner storage container 100 through the air transfer pipe 152 and the air supply path 162. Then, the air blown into the toner storage container 100 flows through the toner layer while diffusing the toner.

  The toner replenishing device configured as described above includes image forming units 4M, 4C,. 4Y. 4Bk and the toner storage container 100 can be reliably replenished even if they are separated from each other. 4Y. It can be installed at any location without being restricted by 4Bk. Therefore, in the color printer in which the transfer belt 20 is inclined and the image forming units 4M, 4C, 4Y, 4Bk are arranged along the inclination, the image forming units 4M, 4C,. 4Y. It is not necessary to make a space for the toner storage portion between 4Bk, and the image forming units 4M, 4C. 4Y. 4Bk can be arranged closer to each other.

  Further, although the belt fixing device 30 is used in the embodiment shown in FIG. 1, even the belt fixing device 30 is sent to the fixing device obliquely from below along the transfer belt 20 inclined to the sheet. Can be arranged below the fixing roller 32 at a height level. Accordingly, even if a sufficient nip width between the fixing roller 32 and the pressure roller 31 is ensured, the sheet that has passed through the nip is conveyed in a substantially horizontal direction, and can be smoothly conveyed to the discharge tray 40 at the top of the main body. it can. By the way, when the paper is fed from the horizontal direction to the nip between the fixing roller 32 and the pressure roller 31, when the paper is passed, it is sent obliquely downward, and a large angle is reversed for transporting the paper to the discharge tray 40 at the top of the main body. Need a mechanism to make.

  In the embodiment shown in FIG. 1, the fixing device 30 is disposed above the inclined transfer belt 20 and further above the writing unit 8 at a height level. Therefore, it is difficult for the writing unit 8 to receive the heat of the fixing device 30 directly. In addition, a recess 41 is formed between the fixing device 30 and the writing unit 8 so as to have a substantially V-shape for securing the number of sheets of the paper discharge tray 40. The recess 41 forms the fixing device 30 and the writing unit. There is a space outside the plane between the eight. With this configuration, the writing unit 8 is less likely to receive the heat of the fixing device 30 directly, and the writing unit 8 can greatly reduce fluctuations in the characteristics of the optical system due to the heat of the fixing device 30.

  Furthermore, in the embodiment shown in FIG. 1, the transfer belt 20 is configured to be rotatable about at least one of the belt wheels 22 on the running side 21, and this configuration makes it easy even if a jam occurs on the transfer belt 20. Can be processed. Since the transfer belt 20 is a monochrome print, the belt wheel 22a is lowered to a position indicated by a chain line. The lowered transfer belt 20 abuts only on the black image forming unit 20Bk and is separated from the photosensitive drum 5 of the other image forming unit 4.

1 is a schematic diagram illustrating an overall configuration of a color image forming apparatus of the present invention. FIG. 2 is an explanatory view showing an enlarged image forming unit in the color image forming apparatus of FIG. 1. FIG. 2 is an explanatory diagram showing an arrangement relationship in the color image forming apparatus of FIG. 1. FIG. 3 is a cross-sectional explanatory view showing an embodiment of a toner supply device of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color printer 4M, 4C, 4Y, 4Bk Image forming unit 5M, 5C, 5Y, 5Bk Photosensitive drum 8 Writing unit 9 Cleaning device 10 Developing device 20 Transfer belt 21 Traveling side 22 Belt wheel 30 Fixing device 40 Paper discharge tray 100 Toner Storage container

Claims (14)

A transfer belt, and a plurality of image carriers disposed along the running side of the transfer belt;
A writing unit for irradiating each of the plurality of image carriers with laser light,
The transfer belt on which the plurality of image carriers are arranged is inclined in the apparatus, the writing unit is inclined in the apparatus, and the transfer belt on which the plurality of image carriers are arranged An image forming apparatus, wherein the image forming apparatus is disposed substantially parallel to a running side.   The image forming apparatus according to claim 1, wherein the writing unit includes a polygon mirror, and irradiates reflected light from the polygon mirror onto each of the plurality of image carriers.   The image forming apparatus according to claim 2, wherein the polygon mirror is a single polygon mirror.   The image forming apparatus according to claim 2, wherein an optical path length from the polygon mirror to the plurality of image carriers is constant. A paper feed unit is provided below the device main body, and a paper discharge unit is provided above the device main body.
2. The running side of the transfer belt on which the plurality of image carriers are arranged is arranged so as to be inclined so that the paper feed unit side is down and the paper discharge unit side is up. The image forming apparatus described in 1.   The image forming apparatus according to claim 1, wherein the image carrier is a photosensitive drum.   The image forming apparatus according to claim 1, further comprising a developing unit for each of the plurality of image carriers.   The image forming apparatus according to claim 7, wherein the plurality of developing units perform development using toner and a carrier.   The image forming apparatus according to claim 1, further comprising a cleaning unit for each of the plurality of image carriers.   The image forming apparatus according to claim 9, wherein the plurality of image carriers are unitized together with corresponding developing units and cleaning units to form a plurality of image forming units.   Among the plurality of image forming units, the cleaning unit included in at least one image forming unit and the developing unit of the image forming unit adjacent to the at least one image forming unit are arranged so as to overlap each other in the vertical direction. The image forming apparatus according to claim 10, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein a transfer material is conveyed on the transfer belt, and images formed on the plurality of image carriers are superimposed and transferred on the transfer material. A plurality of toner storage containers provided corresponding to the developing means, each storing toner;
The image forming apparatus according to claim 1, further comprising: a toner replenishing unit that conveys the toner stored in the plurality of toner storage containers to a corresponding developing unit.   14. The toner supply unit according to claim 13, wherein the toner supply unit includes a toner transport tube that connects the developing unit and the toner storage container, and a powder pump, and supplies the toner by operating the powder pump. Image forming apparatus.

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