JP2825256B2 - Image forming device - Google Patents

Description

Description: Object of the Invention (Industrial Application Field) The present invention relates to an image forming apparatus such as an electrophotographic laser printer and a copying machine, and more particularly, to a toner remaining on an image carrier after transfer. To improvement of a dispersing means for dispersing.

(Prior Art) An image forming apparatus such as an electrophotographic laser printer includes a developing device that supplies toner to an electrostatic latent image formed on a cylindrical photoreceptor serving as an image carrier and visualizes the electrostatic latent image. And a transfer device for transferring an image formed on the photosensitive member with toner onto paper. Most of the toner on the photoconductor is transferred onto the paper by this transfer device, but a part of the toner remains on the photoconductor.

As shown in FIG. 11, there are various remaining states of the toner on the photosensitive member after the transfer. In the figure, A shows a case where normal transfer was performed. B is close to normal transfer but slightly excessive transfer, and the toner is positively charged to the opposite polarity by the transfer charger. This is likely to occur when solid black or the like is transferred. C is a case where the sheet remains in a lump due to insufficient transfer, and is likely to occur when the sheet floats from the transfer body during transfer due to carrier adhesion or paper wrinkling.
Further, the transfer residual toner in the unexposed portion is the surface potential Vo of the photoconductor.
Is lower than the developing bias Vb applied to the developing device, and is electrostatically attracted to the developing device. On the other hand, since the surface potential of the photoreceptor of the transfer residual toner in the exposed portion is increased by the exposure, the negatively charged toner is returned to the developing device and remains on the photoreceptor.

Of the transfer residual toner remaining on the photoconductor as described above, when the toner is uniformly scattered on the photoconductor as in the case of A and B, the light amount of the laser in the exposure process is sufficiently large,
Since the exposure area is sufficiently large relative to the size of the toner, even if toner adheres to the photoreceptor, it does not become a shadow of exposure, and the negative potential on the surface of the photoreceptor is attenuated to form a latent image. You. In addition, since the unexposed portion is reliably cleaned by the developing device as described above, no problem occurs in forming a latent image. However, when the toner remains in a lump as in the case of C, it is difficult to completely clean the toner by the developing device, and a positive memory is formed on a white background. If this portion corresponds to the next exposed portion, the light does not pass because the toner layer is thick and the diameter of the mass is large, and a negative memory is generated on a black background.

In order to remove the transfer residual toner as described above, a cleaner is conventionally provided between the transfer device on the outer periphery of the photoconductor and the pre-exposure device. Conventionally, this cleaner includes a blade that abuts on the surface of the photoreceptor to scrape off toner, and a collection box that collects the scraped toner.

(Problems to be Solved by the Invention) However, the conventional cleaner as described above has a structure in which the toner remaining on the photoreceptor is scraped into a collection box by a blade.
When copying about 1 to 3,000 sheets, the toner in the collection box becomes full and becomes unusable. For this reason, a complicated collecting mechanism and a collecting box must be provided, and the collecting box must be replaced each time to collect the toner, so that the structure is complicated and the user's hands and clothes become dirty and workability deteriorates. There was a problem. Also, depending on the type of equipment, the cleaner has to be discarded each time. Further, since the toner on the photoconductor is scraped off by the blade, the surface of the photoconductor may be damaged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a simple structure that eliminates the influence of residual toner on a photoconductor at the time of exposure, stabilizes image quality, prolongs the life of a photoconductor, and It is an object of the present invention to provide an image forming apparatus capable of improving performance.

[Configuration of the invention]

(Means for Solving the Problems) An image forming apparatus according to the present invention that achieves the above object includes a charging unit that charges a rotatable photoconductor to a specific polarity, and a light beam applied to the photoconductor charged by the charging unit. Exposure means for forming an electrostatic latent image by irradiating, while supplying and developing a developer charged to the same polarity as a specific polarity to the electrostatic latent image formed on the photoreceptor by this exposure means, to develop, Developing means for removing the undeveloped portion of the residual developer; transfer means for electrostatically transferring the developer image formed by the developing means from the photoreceptor to a transfer material; A first conductive contact member provided in contact with the photoconductor on the downstream side in the rotation direction, and a photoconductive member on the downstream side in the rotation direction of the photoconductor with respect to the first conductive contact member. A second conductive contact member provided in contact with the second conductive contact member; The first and second conductive contact members are characterized by having voltage applying means for applying bias voltages of opposite polarities to each other.

(Operation) According to the above-described means, the bulk toner remaining on the photoreceptor after transfer can be dispersed backward by a plurality of dispersing means, and among these dispersed toners, The toner is temporarily sucked by the dispersing means to which the negative charge is supplied, and the toner having the negative charge is temporarily sucked by the dispersing means to which the positive charge is supplied, and is pushed out of the dispersing means. Thereafter, the toner is dispersed and adhered on the photoreceptor again, and the occurrence of memory due to residual toner at the time of exposure can be prevented. Therefore, a toner collecting box is not required, and a small cartridge can be obtained by integrally attaching the dispersing means to the developing device. Moreover, by forming the dispersing means with a soft member, the life of the photosensitive member can be extended without damaging the surface of the photosensitive member.

Hereinafter, an embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings.

FIGS. 1 to 4 show an embodiment of the present invention. In FIGS. 1 and 2, one mag roller 131 and two stirring rollers 132a and 132b are provided in a casing 133 of the developing device 104. The shaft directions are provided in parallel, and are driven to rotate in the directions of arrows a, b, and c by a driving source (not shown). The casing 133 is filled with a toner 134 as a developing device. In this casing 133, the drum-shaped photoconductor 101 is provided.
Are provided in parallel with the rollers 131 and 132, and are driven to rotate in the direction of arrow R by a drive source (not shown). Further, a dispersing means 109 is provided on the casing 133 in parallel with the photoreceptor 101. The dispersing means 109 includes a soft member such as a conductive rayon having an electric resistance of 10 ⁵ Ω to 10 ⁶ Ω as shown in FIG. A pair of brushes 135a, 135b formed in the above are mounted in parallel on the upstream side and the downstream side, respectively. The lower ends of the brushes 135a and 135b are in contact with the outer periphery of the photoconductor 101 in the width direction along the generatrix direction, and the width is wider than the maximum paper width and the image area to be used. One of the brushes 135b is electrically connected to a grid case of the charger 102 to be described later to be supplied with a negative charge, and the other brush 135a is connected to a positive side of a power supply terminal of the apparatus main body and has a positive charge. Supplied. This connection may be reversed. An insulating material such as a mylar sheet (not shown) is provided between the brushes 135a and 135b, and is electrically insulated.

Reference numeral 141 shown in FIG.
Reference numeral 142 denotes an incident position of light incident on 101, and reference numeral 142 denotes an electrostatic latent image forming unit.
The incident position of the laser beam from 103 to the photoreceptor 101, and reference numeral 136 shown in FIG. 2 is a handle provided on the casing 133 of the developing device 104.

Next, a case where one embodiment of the present invention is applied to a laser printer will be described with reference to FIG.

FIG. 4 shows a schematic configuration of an electrophotographic monochromatic laser printer.

The laser printer is electrically connected to a computer or a host system (external device) such as a word processor via a transmission device (not shown).
By writing dot image data from an external device and modulating the laser beam light to write on the photosensitive member, the written dot image data is developed and transferred onto paper.

That is, 100 is an apparatus main body, and a drum-shaped photoconductor 101 is provided in the main body 100.
It is rotated in the direction of arrow R by a drive source (not shown).

Around the photoreceptor 101, a charging charger 102 of a charge control type, an electrostatic latent image forming unit 103, a developing unit 104 provided with the dispersing unit 109, a transfer charger 105,
A pre-exposure unit 112 is sequentially arranged, and the photoconductor 101 is a developing unit.
It is integrated with 104.

A paper cassette 106 is provided in the main body 100, and paper as a recording medium taken out of the paper cassette 106 by a paper feed roller 107 is fed between the photoconductor 101 and the transfer charger 105. Image transfer unit 108 and fixing unit 118
After that, the paper is guided to the paper discharge roller 113 and discharged to the paper discharge unit 114.

The electrostatic latent image forming unit 103 includes a semiconductor laser oscillator (not shown) that generates a laser beam light modulated in accordance with dot image data from an external device (not shown), and a laser output from the laser oscillator. A lens system (not shown) such as a collimator lens for condensing the light beam, a four-sided rotating mirror (polygon mirror) 116 for scanning the laser beam light condensed by this lens system, and a high-speed rotating mirror 116 A mirror motor 117 for rotating, a lens 121 for correctly guiding the laser beam light scanned by the rotating mirror to the photoconductor, and a laser beam
Reflecting mirrors 119 and 120 for reflecting in the direction of 01, rotating mirror 1
It comprises a light beam detector (not shown) for detecting the laser beam light scanned at 16.

In such a configuration, when a print start signal is received from an external device, the photoconductor 101 rotates, and the photoconductor 101 is uniformly charged by the charging charger 102 so as to have a surface potential of, for example, about 600 V.

Next, when receiving the dot image data from the external device, the charged latent image forming unit 103 outputs a laser beam light modulated in accordance with the dot image data, and the charged photoconductor 101 is charged by the laser beam light. By scanning and exposing the surface, an electrostatic latent image is formed on the surface of the photoconductor 101. The electrostatic latent image formed on the photoreceptor 101 is developed by a reversal development by a developing device 104 having a mag roller 131 and stirring rollers 132a and 132b to be visualized to become a toner image. Then, the toner image on the photoreceptor 101 is transferred to the sheet conveyed from the sheet feeding cassette 106 in the image transfer unit 108.

The sheet on which the toner image has been transferred is conveyed to a fixing device 118, where the toner image is fixed, and then discharged to a discharge section 114 by a discharge roller 113, and not shown from the photoreceptor 101 by a transfer charger 105. After the toner image is transferred onto the paper, the toner remaining on the photoconductor 101 is dispersed by the dispersing means 109 by an operation described later, and then the pre-exposure device 112 such as a red LED is used.
The surface of the photoconductor 101 is uniformly discharged by the light emitted from the light source.

Next, the operation of the dispersing means 109 will be described with reference to FIGS.

5 to 7 show the case of insufficient transfer toner, and FIGS. 8 to 10 show the case of excess transfer toner. A positive voltage is applied to the brush 135a and a negative voltage is applied to the brush 135b. Photoconductor that moves in the arrow X direction
When there is a toner mass 150 on the surface of 101 as shown in FIG. 5, when the toner mass 150 passes under the brush 135a, the toner mass 150 having a transfer-deficient negative charge becomes
The brush 135a to which the plus voltage is applied is sucked.
When the photoconductor 101 further moves in the direction of arrow X, the brush 135 is
Since the brush 135a has no toner holding ability, the toner mass 150 sucked by the
Come out behind. That is, the brush 135a sucks the insufficient transfer toner mass 150 by electrostatic force, but since the amount of toner that can adhere to the brush 135a is small, the brush 135a
Since the toner 150 is in contact with the width direction of the photoconductor 101, the toner 150 once suctioned gradually adheres to another portion of the surface of the photoconductor 101. At this time, since a negative voltage is applied to the other brush 135b, the toner mass 15 having a negative charge is
0 is not sucked by the brush 135b, but is disturbed by the brush 135b and dispersed on the surface of the photoreceptor 101 as shown in FIG.

On the other hand, in the case of excessive transfer toner, the polarity of the toner 151 is inverted as shown in FIG. Accordingly, even if the photoconductor 101 advances in the direction of arrow X and passes under the brush 135a as shown in FIG. When the brush 135b reaches below the other brush 135b, a negative voltage is applied to the brush 135b.
The toner 151 having a positive charge is temporarily sucked by the brush 135b and dispersed and adheres to the photoconductor 101 as shown in FIG. Therefore, there is no problem even if the toner 151 is in a lump. At this time, since the brushes 135a and 135b are formed of a soft member and are in contact with the photoreceptor 101 in the width direction, that is, in the state of abdomen, and the contact pressure is extremely weak, the toner 151 does not move.

According to the present embodiment, the transfer residual toner 15 on the photoconductor 101
0, 151 are uniformly dispersed after passing under the brush 135b, so that the occurrence of memory due to residual toner at the time of exposure can be prevented. Therefore, the conventional toner collection box is not required, and the transfer member 101 and the developing device 104
In addition, the dispersing means 109 for removing the memory can be integrated into a cartridge, and the apparatus can be reduced in size and weight. Further, since the brush 135 is formed of a soft member and is in contact with the photoconductor 101 in the width direction, the life of the photoconductor 101 can be prolonged, and the image quality can be improved.

In the above embodiment, the case where the number of the brushes 135 provided in the dispersing means 109 is two has been described, but the number of the brushes 135 may be three or more. The member attached to the dispersion means 109 is not limited to the brush 135, but may be a blade, a sponge-like member, or the like.

〔The invention's effect〕

As described above, according to the present invention, a toner having a positive or negative charge remaining on a photoreceptor, which is a post-transfer image carrier, is transferred to a plurality of stages to which a negative or positive charge is supplied, respectively. Since the toner is temporarily electrostatically sucked by the dispersing means and dispersed and adhered on the photoreceptor, it is possible to prevent the occurrence of memory due to massive residual toner remaining on the photoreceptor, and a toner collection box. This makes it possible to reduce the size and weight of the apparatus by making it a cartridge, and to prolong the life of the photoreceptor and improve the image quality.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a main part of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a perspective view of FIG. 1, FIG. 3 is an exploded perspective view showing dispersing means of FIG. FIG. 4 is a longitudinal sectional view showing a laser printer to which the dispersion apparatus according to the present embodiment is applied, FIGS. 5 to 10 are explanatory views showing the operation of the present embodiment, and FIG. 11 remains on the photoreceptor. FIG. 3 is an explanatory diagram illustrating a toner. 101 photoreceptor (image carrier), 104 developing device, 109 dispersing means, 150, 151 toner.

Continuing from the front page (72) Inventor Seiichiro Fushimi 70 Yanagimachi, Yuki-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Yanagicho Plant (72) Inventor Yoshihiko Sugiyama 70-Yanagicho, Yuki-ku, Kawasaki-shi, Kanagawa (56) References JP-A-58-142366 (JP, A) JP-A-59-123872 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 21/10-21 / 12 G03G 15/08 507 G03G 15/24

Claims (1)

(57) [Claims] A charging means for charging the rotatable photosensitive member to a specific polarity; an exposure means for forming an electrostatic latent image by irradiating light to the photosensitive member charged by the charging means; Developing means for supplying and developing a developer charged to the same polarity as the specific polarity to the electrostatic latent image formed on the photoreceptor by exposure means, and removing residual developer in unexposed portions, Transfer means for electrostatically transferring the developer image formed by the developing means from the photoconductor to a transfer material; and abutting on the photoconductor on the downstream side in the rotation direction of the photoconductor with respect to the transfer means. A first conductive abutting member provided on the photosensitive member, and a second conductive member provided in contact with the photosensitive member on the downstream side in the rotation direction of the photosensitive member with respect to the first conductive abutting member. A contact member, and the first and second conductive contacts An image forming apparatus; and a voltage applying means for applying a reverse polarity of the bias voltage each other member.