JP2008170491A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is capable of preventing the breakage, etc. of a toner replenishing path, even when toner clogging due to toner blocking occurs in the connecting portion of a toner replenishing port and a stirring portion, in a developing unit. <P>SOLUTION: The image forming apparatus is a device which includes a plurality of photoreceptors and a plurality of developing units 4a and 4b (4c and 4d) and superimposes and transfers toner images formed on the respective photoreceptors on an intermediate transfer belt and is configured in such a manner that a plurality of toner containers for replenishing toner to the developing units 4a and 4b (4c and 4d) through the toner replenishing path 25 is arranged above from the intermediate transfer belt and the respective developing units 4a and 4b (4c and 4d) are arranged below from the intermediate transfer belt. In the image forming apparatus, an excessive toner recovery path 26 is arranged along the toner replenishing path 25 in parallel and both are communicated with each other through an excessive toner discharge port 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a color copying machine or a color printer that employs a system in which toner images formed on a plurality of photosensitive members are transferred on an intermediate transfer belt.

  In full-color copiers and printers that employ an electrophotographic system, toner images formed on a plurality of photoconductors are transferred onto an intermediate transfer belt, and then the full-color image on the intermediate transfer belt is printed on paper or the like. A method of batch transfer onto a recording medium is employed.

  By the way, this type of color image forming apparatus is provided with four developing units each containing magenta, cyan, yellow and black toners and four toner containers for supplying each color toner to each developing unit. . In particular, in a color tandem machine, it is advantageous from the viewpoint of first copying when the image forming unit including the photosensitive member is laid out below the intermediate transfer belt. Arranged at the top.

  When the configuration as described above is adopted, an intermediate transfer belt is disposed between the toner container and the developing device, and a toner supply path is formed in the frame of the intermediate transfer belt, and each toner container passes through the toner supply path. Thus, each color toner is supplied to each developing device.

In Patent Document 1, when toner is replenished from a toner container to a developing device via a replenishment route, an increase in the load on the stirring member of the developing device due to excessive feeding of toner to the developing device is detected. A toner replenishing device has been proposed in which the conveying operation of the conveying member in the replenishing path is stopped. Patent Document 2 proposes a toner transport device that reduces the amount of toner remaining in the transport path by operating an air flow generating means such as an air pump for a predetermined time at the end of the toner transport operation.
JP-A-2-007077 JP 2004-347726 A

  By the way, normally, the toner has low fluidity under a high temperature and high humidity environment, and toner clogging is likely to occur at the connecting portion between the toner replenishing port and the stirring portion in the developing device. Once this toner clogging occurs, the toner is not replenished to the developing unit, and the remaining amount of toner in the developing unit is rapidly reduced.

  In addition, when the toner sensor provided in the developing device detects toner empty, the toner is further fed to the developing device, so that the toner is blocked in the toner replenishing path and the toner replenishing path is broken.

  The present invention has been made in view of the above problems, and the intended process is that even when toner clogging occurs due to toner blocking at the connecting portion between the toner replenishing port and the stirring unit in the developing device, An object of the present invention is to provide an image forming apparatus capable of preventing a toner replenishment path from being damaged.

  In order to achieve the above object, the invention described in claim 1 is an apparatus that includes a plurality of photoconductors and a plurality of developing devices, and transfers a toner image formed on each photoconductor in an overlapping manner on an intermediate transfer belt. An image formed by arranging a plurality of toner containers for supplying toner to the developing device via a toner supply path above the intermediate transfer belt, and disposing each developing device below the intermediate transfer belt. In the forming apparatus, an excess toner recovery path is provided in parallel along the toner supply path, and both are communicated with each other through an excess toner discharge port.

  According to a second aspect of the present invention, in the first aspect of the present invention, the toner replenishment path and the excessive toner recovery path are formed integrally with the frame of the intermediate transfer belt, and the excessive toner discharge port is formed in a partition wall separating the two. It is formed.

  According to the present invention, the toner fluidity is lowered under a high temperature / high humidity environment or the like, so that toner clogging occurs due to toner blocking at the connecting portion between the toner replenishing port and the stirring portion in the developing device. However, since excessive toner in the toner replenishment path is discharged from the excessive toner discharge port to the excessive toner collection path, breakage of the toner replenishment path is reliably prevented.

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

  FIG. 1 is a front sectional view of an image forming apparatus according to the present invention. The illustrated image forming apparatus is a tandem type color image forming apparatus, and a magenta image forming unit 1M, The cyan image forming unit 1C, the yellow image forming unit 1Y, and the black image forming unit 1BK are arranged in a line at regular intervals.

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

  Here, the photosensitive trams 2a to 2d are drum-shaped photosensitive members, and are driven to rotate at a predetermined process speed in a direction indicated by an arrow (clockwise) by a driving device (not shown). The primary chargers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined potential by a charging bias applied from a charging bias power source (not shown).

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

  The transfer rollers 5a to 5d as primary charging means are arranged so as to be in contact with the photosensitive drums 2a to 2d through intermediate transfer belts in the primary transfer portions. Here, the intermediate transfer belt 7 is stretched between the secondary transfer counter roller 8 and the tension roller 9 and is disposed on the upper surface side of each of the photosensitive drums 2a to 2d. The roller 8 is disposed so as to be in contact with the secondary transfer roller 10 via the intermediate transfer belt 7 in the secondary transfer portion. A belt cleaning device 11 is provided in the vicinity of the tension roller 9. As a material for the intermediate transfer belt 7, for example, a dielectric resin such as polycarbonate, polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), or the like is selected.

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

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

  The conveyance path L extending in the vertical direction on the side of the apparatus main body 100 includes a conveyance roller 18 for conveying the recording material, and the secondary transfer counter roller 8 at a predetermined timing after temporarily waiting the recording material. A registration roller 19 is provided that supplies a secondary transfer portion that is in contact with the secondary transfer roller 10. Next to the conveyance path L, another conveyance path L ′ used for forming an image on both sides of the recording material is formed, and a plurality of conveyance rollers 21 are appropriately provided in the conveyance path L ′. Are provided at regular intervals.

  By the way, the transport path L arranged in the vertical direction on one side of the apparatus main body 100 extends to the paper discharge tray 21 provided on the upper surface of the apparatus main body 100, and the fixing device 22 and a plurality of them are in the middle. The paper discharge rollers 23 and 24 are provided.

  Next, an image forming operation by the color image forming apparatus having the above configuration will be described.

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

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

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

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

The full color toner image on the intermediate transfer belt 7 is picked up from the paper feed cassette 14 in accordance with the timing at which the leading edge of the full color toner image reaches the secondary transfer portion (transfer nip portion) between the secondary transfer counter roller 8 and the secondary transfer roller 10. The recording material fed to the transport path L by the roller 15, the feed roller 16 and the retard roller 17 is transported to the secondary transfer portion by the registration roller 19. Then, a full-color toner image is collectively transferred from the intermediate transfer belt 7 to the recording material conveyed to the secondary transfer portion by the secondary transfer roller 10 to which a secondary transfer bias having a polarity opposite to that of the toner is applied. The

  Thus, the recording material onto which the full-color toner image has been transferred is conveyed to the fixing device 22 where the full-color toner image is heated and pressurized to be thermally fixed on the surface of the transfer material, and the toner image is fixed. The transfer material is discharged onto the discharge tray 21 by the discharge rollers 23 and 24, and a series of image forming operations is completed. The transfer residual toner that is not transferred onto the recording material and remains on the intermediate transfer belt 7 is removed by the belt cleaning device 11, and the intermediate transfer belt 7 is prepared for the next image formation.

  Next, the gist of the present invention will be described with reference to FIGS. FIG. 2 is an exploded perspective view showing the configuration of the toner supply system.

  Each of the developing devices 4a to 4d is provided with a toner sensor (not shown) for detecting the remaining amount of toner accommodated therein, and the toner is consumed by repeating the image forming operation. When the toner sensor detects that the remaining amount of toner in the developing units 4a to 4d is less than a certain value, the toner is replenished from the toner containers 12a to 12d to the developing units 4a to 4d, respectively.

  2 and 3, the toner containers 12a to 12d and the developing containers 4a to 4d are disposed between the toner containers 12a to 12d next to the intermediate transfer belt 7 (front side in FIG. 1) and the developing devices 4a to 4d. An elongated toner container-like toner supply path and an excess toner recovery path 26 that extend horizontally along the direction in which the developing devices 4a to 4d are juxtaposed are formed integrally with the frame of the intermediate transfer belt 7, and these toner supply paths 25 are formed. In the excessive toner collecting path 26, toner transport screws 27 and 28 for transporting the replenished toner and the excessive toner are rotatably accommodated. FIG. 2 shows the configuration of a magenta toner supply system, but the same applies to other cyan, yellow, and black toner supply systems.

  As shown in FIG. 3, in the toner supply path 25, a total of four toner supply spaces S1 to S4 (S4 not shown) are formed in the length direction for each of the developing devices 4a to 4d by the partition wall 25a. In addition, the partition wall 29 that separates the toner supply path 25 and the excess toner collection path 26 has a rectangular excess toner discharge port 30 that allows the toner supply spaces S1 to S4 in the toner supply path 25 and the excess toner collection path 26 to communicate with each other. Are formed respectively. FIG. 3 shows the configuration of the supply system of magenta toner and cyan toner, but the configuration of the supply system of yellow toner and black toner is the same.

  In addition, rectangular toner outlets 31 are formed at the bottoms of the toner supply spaces S1 to S4 of the toner supply path 25. These toner outlets 31 are rectangular openings opened on the upper surfaces of the developing devices 4a to 4d. Connected to the toner inlet 32. The cover 33 that covers the upper surfaces of the toner supply path 25 and the excess toner collection path 26 is formed with rectangular toner inlets 34 that open to the toner supply spaces S1 to S4 in the toner supply path 25, respectively. As shown in FIG. 2, a rectangular toner outlet 35 that opens to the bottom of one end of each of the toner containers 12 a to 12 d is connected to the toner inlet 34.

  Thus, when a toner sensor (not shown) detects that the remaining amount of toner in each of the developing devices 4a to 4d is less than a certain value, the corresponding toner in the toner supply path 25 from each toner container 12a to 12d. The toner is supplied to the replenishment spaces S1 to S4, and the toner is transported in the toner replenishment spaces S1 to S4 by the toner transport screw 27 in the direction of the arrow in FIG. Is done. In this case, the fluidity of the toner is lowered, for example, under a high temperature / high humidity environment, and toner blocking is likely to occur at the connection portion between the toner replenishing port and the stirring portion in the toner clogging developers 4a to 4d. Once this toner clogging occurs, toner supply to the developing devices 4a to 4d is not performed, and the remaining amount of toner in the developing devices 4a to 4d is rapidly reduced.

  When the toner empty is detected by the toner sensor in the developing devices 4a to 4d that are no longer replenished with toner as described above, the toner is further fed to the developing devices 4a to 4d, so there is no discharge path for excess toner. Therefore, the toner replenishment spaces S1 to S4 of the toner replenishment path 25 are pressed and solidified with toner, and eventually the conveying screw 27 is damaged.

  However, in the present embodiment, the excessive toner recovery path 26 is provided in parallel with the toner supply path 25, and the toner supply spaces S1 to S4 of the toner supply path 25 and the excessive toner recovery path 26 are provided in the partition wall 29 that separates the two. The toner replenishment path is formed even if toner clogging occurs due to toner blocking at the connecting portion between the toner replenishment port and the agitation unit in the developing devices 4a to 4d. 25 excess toner is discharged from the excess toner discharge port 30 to the excess toner recovery path 26, so that damage to the toner replenishment path 25 is reliably prevented. Excess toner discharged from the toner replenishment path 25 to the excessive toner recovery path 26 is transported through the excessive toner recovery path 26 in the direction of the arrow by the toner transport screw 28 rotating in the direction of the arrow in FIG. .

1 is a front sectional view of an image forming apparatus (color image forming apparatus) according to the present invention. FIG. 3 is an exploded perspective view illustrating a configuration of a toner supply system of the image forming apparatus according to the present invention. FIG. 3 is an exploded perspective view illustrating a configuration of a toner supply system of the image forming apparatus according to the present invention.

Explanation of symbols

1M Magenta image forming unit 1C Cyan image forming unit 1Y Yellow image forming unit 1BK Black image forming unit 2a to 2d Photosensitive drum (photoconductor)
3a to 3d Primary charger 4a to 4d Developer 5a to 5d Transfer roller 6a to 6d Cleaning device 7 Intermediate transfer belt 8 Secondary transfer counter roller 9 Tension roller 10 Secondary transfer roller 11 Belt cleaning device 12a to 12d Toner container 13 Laser Scanner unit (LSU)
DESCRIPTION OF SYMBOLS 14 Paper feed cassette 15 Pickup roller 16 Feed roller 17 Retard roller 18 Conveyance roller 19 Registration roller 20 Conveyance roller 21 Discharge tray 22 Fixing device 23, 24 Discharge roller 25 Toner replenishment path 25a Bulkhead 26 Excess toner collection path 27, 28 Toner Conveying screw 29 Partition 30 Excess toner outlet 31 Toner outlet 32 Toner inlet 33 Cover 34 Toner inlet 35 Toner outlet L, L ′ Conveying path S1 to S4 Toner replenishing space

Claims (2)

A device that includes a plurality of photosensitive members and a plurality of developing devices, and transfers toner images formed on the respective photosensitive members while being superimposed on an intermediate transfer belt, and supplies toner to the developing devices via a toner replenishing path. In the image forming apparatus in which a plurality of toner containers are disposed above the intermediate transfer belt and the developing devices are disposed below the intermediate transfer belt.
An image forming apparatus comprising: an excess toner collecting path arranged in parallel along the toner replenishing path, and both communicating with each other via an excess toner discharge port. 2. The image forming apparatus according to claim 1, wherein the toner replenishing path and the excessive toner collecting path are formed integrally with a frame of the intermediate transfer belt, and the excessive toner discharge port is formed in a partition wall separating the two.

Images