JP2791405B2 - Image forming device - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus such as a laser printer or a copying machine, and more particularly to a method for removing toner remaining on an image carrier after transfer. The present invention relates to improvement of dispersion means for dispersion.

(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.

The remaining state of the toner on the photoreceptor after the transfer is the eleventh state.
There are various ways as shown in the figure. 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 electrostatically attracted to the developing device because the surface potential Vo of the photoconductor is lower than the developing bias Vb applied 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 does not return to the developing device but 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. Further, when this portion corresponds to the next exposed portion, since the toner layer is thick and the diameter of the lump is large, light does not pass therethrough, and a black negative memory is generated.

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 photoreceptor is scraped off by the blade, the surface of the photoreceptor may be damaged, and the toner may be scattered around to cause contamination.

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

[Configuration of the invention]

(Means for Solving the Problems) According to an image forming apparatus of the present invention that achieves the above object, a charging unit that charges a rotatable photoconductor to a specific polarity, and a light is applied to the photoconductor charged by the charging unit. Exposure means for forming an electrostatic latent image by irradiating the developer, and a developer charged to the same polarity as a specific polarity is supplied to the electrostatic latent image formed on the photoreceptor by the exposure means for development. Developing means for removing a residual developer in an unexposed portion; transfer means for electrostatically transferring a developer image formed by the developing means from a photosensitive member to a transfer material; A first dispersing means provided in contact with the photoreceptor on the downstream side in the rotation direction of the photoreceptor, for smoothing residual developer remaining on the photoreceptor transferred by the transfer means;
On the downstream side in the rotation direction of the photoconductor with respect to the dispersing means,
A contact member provided in contact with the photoreceptor; and a voltage applying unit for applying a voltage having a polarity opposite to a specific polarity to the contact member. The contact unit absorbs the residual developer smoothed by the first dispersion unit. A second dispersing means for dispersing the residual developer on the photoreceptor by releasing the adsorbed residual development on the photoreceptor again; and The image forming apparatus further includes a scattering prevention member disposed to prevent the developer dispersed by the first dispersion unit from scattering.

(Operation) According to the above-mentioned means, a lump of toner remaining on the photoreceptor after transfer can be dispersed backward by a plurality of dispersing means, thereby preventing the occurrence of memory due to the residual toner during exposure. Can be. 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 cleaning means with a soft member, the life of the photosensitive member can be extended without damaging the surface of the photoreceptor. Further, by providing the toner scattering prevention means upstream of the dispersing means in the rotation direction of the photoreceptor, toner scattering can be prevented, damage to the apparatus can be prevented, and the life can be further extended.

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, a casing 133 of a developing device 104 includes one mag roller 131 and two stirring rollers 132a and 132b. 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 developer. 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 has a pair of brushes 135a, a soft member such as conductive rayon as shown in FIG. 135b are mounted in parallel on the upstream side and the downstream side, respectively. The lower ends of these 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. Further, a toner scattering prevention sheet 137 formed of a urethane sheet having a thickness of 0.1 mm to 0.2 mm is provided on the upper surface of the brush 135a so that the tip thereof contacts the photoconductor 101 at a plurality of locations in the width direction (width direction). Installed. A positive voltage is applied to the brush 135b on the further downstream side.

Reference numeral 141 shown in FIG.
Reference numeral 142 denotes the incidence of light incident on 101, and reference numeral 142 denotes the electrostatic line image forming unit 10.
The incident position of the laser beam incident on the photoconductor 101 from the third position, the second position
Reference numeral 136 shown in the figure 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 ray 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 101, reflection mirrors 119 and 120 for reflecting the laser beam light in the direction of the photoconductor 101, and a laser beam scanned by the rotating mirror 116 It comprises a light beam detector (not shown) for detecting light.

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 electrostatic latent image forming unit 103 outputs a laser beam light modulated according to the dot image data, and the photoconductor 101 charged by the laser beam light is charged. By performing scanning exposure on the surface of the photoconductor 101, an electrostatic latent image is formed on the surface of the photoconductor 101. The electrostatic latent image formed on the photoreceptor 101 is visualized by reversal development by the latent image device 104 having the mag roller 131 and the stirring rollers 132a and 132b to become a toner image. Then, the toner image on the photoconductor 101 is transferred by the transfer charger 105 on the sheet conveyed from the sheet 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 paper discharge unit 114 by a paper discharge roller 113. After the toner image is transferred from the photoconductor 101 to the paper (not shown) by the transfer charger 105, the toner remaining on the photoconductor 101 is dispersed by a dispersing unit 109 by an operation described later, and then the pre-exposure of a red LED or the like is performed. Container 112
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. If there is a toner mass 150 on the surface of the photoconductor 101 moving in the direction of arrow X as shown in FIG.
When passing under the brush 135b on the downstream side, which is smoothed at 135a, the toner mass 150 having a transfer-deficient negative charge is
Brush to which a positive voltage is applied as shown in FIG.
Suctioned to 135b. When the photosensitive member 101 further moves in the direction of arrow X, the toner mass 150 once sucked by the brush 135b naturally exits behind the brush 135b as shown in FIG. come. In other words, the brush 135b sucks the transfer-deficient toner mass 150 by electrostatic force.However, the brush 135b is once sucked because the amount of toner that can adhere to the brush 135b is small, and because the brush 135b is in contact with the photoconductor 101 in the width direction. The toner 150 gradually adheres to other portions of the surface of the photoconductor 101.

On the other hand, in the case of excessively transferred toner, as shown in FIG. 8, the toner 151 is uniformly dispersed on the transfer body 101, the polarity is inverted, and the toner 151 has the same polarity as the brush 135b. Therefore, even if the photoconductor 101 moves in the direction of the arrow X and passes under the brush 135b as shown in FIG. 9, the photoconductor 101 is adsorbed on the photoconductor 101 without being sucked. That is, as shown in FIG. 10, the toner 151 passes under the brush 135b,
It is located on the transfer material 101 at the same position as before the passage. At this time, the brush 135b is formed of a soft member and the photosensitive member 101
And the contact pressure is extremely weak, so that the toner 151 is not moved. Therefore, the toner 151 is uniformly dispersed.

According to the present embodiment, the transfer residual toner 15 on the photoconductor 101
0, 151 are uniformly dispersed after passing under the brushes 135a, 135b, so that it is possible to prevent the occurrence of memory due to residual toner during exposure. Therefore, unlike the conventional case, a toner collection box is not required, and the transfer body 101, the developing device 104, and 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 brushes 135a and 135b are formed of a soft member and are in contact with the photoconductor 101 in the width direction, the life of the photoconductor 101 can be extended without damaging the photoconductor 101, and the image quality can be improved. Also, a sheet for preventing toner scattering
137 can prevent toner 150, 151 from scattering,
The device including the photoconductor 101 can be prevented from being damaged.

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 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, the massive toner remaining on the photoreceptor, which is the image carrier after transfer, is dispersed by the dispersing means formed in a plurality of stages, and the sheet is further dispersed in the dispersing means. Is attached to prevent the toner from scattering, so it is possible to prevent the occurrence of memory due to massive residual toner remaining on the photoreceptor, eliminating the need for a toner collection box, and making the cartridge compact and lightweight. And the life of the device including the photoreceptor can be prolonged, and the image quality can be improved.

[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, and FIG.
FIG. 4 is a perspective view showing the dispersing means, FIG. 4 is a longitudinal sectional view showing a laser printer to which the dispersing means according to the present embodiment is applied, and FIGS. 5 to 10 are cross-sectional views for explaining the operation of the present embodiment. ,
FIG. 11 is an explanatory diagram showing the toner remaining on the photoconductor. 101 photoreceptor (image carrier), 104 developing device, 109 dispersing means, 137 toner scattering prevention sheet, 150, 151 toner.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-188684 (JP, A) JP-A-58-142366 (JP, A) JP-A-60-168184 (JP, A) JP-A-63-1988 241587 (JP, A) JP-A-62-203182 (JP, A) JP-A-62-89673 (JP, U) JP-A-62-170967 (JP, U) (58) Fields investigated (Int. ^6, DB name) G03G 21/00 310 - 334 G03G 15/08 507 B G03G 13/22 - 13/24

Claims (1)

(57) [Claims] A charging means for charging a rotatable photosensitive member to a specific polarity; an exposure means for forming an electrostatic latent image by irradiating the photosensitive member charged by the charging means with light; 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 dispersing means for smoothing residual developer remaining on the photoreceptor to which the transfer has been performed by the transfer means; and a downstream side in the rotation direction of the photoreceptor with respect to the first dispersing means. In contact with the photoconductor And a voltage applying means for applying a voltage having a polarity opposite to the specific polarity to the contact member, and adsorbs the residual developer smoothed by the first dispersing means. Second dispersing means for dispersing the residual developer on the photoreceptor by releasing the residual developer onto the photoreceptor again; and a rotating direction of the photoreceptor with respect to the first dispersing means. An image forming apparatus, comprising: a scattering prevention member disposed upstream and configured to prevent scattering of the developer dispersed by the first dispersion unit.