JP3337294B2 - Electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus using a so-called Carlson process for copying an original image onto a transfer material such as plain paper.

[0002]

2. Description of the Related Art An electrophotographic apparatus of the type described above is known, and as a transfer system of this type of apparatus, a transfer charger for applying a charge having a polarity opposite to that of toner and transferring the toner to transfer paper, A method has been used in which a charge is neutralized to combine with a separation charger for separating transfer paper from a photoreceptor. However, in the above-mentioned conventional transfer method, under various environmental conditions, for example, the transfer paper is changed from thin paper to thick paper, soft paper to hard paper, and aging from the beginning of work, and changes in ambient temperature and humidity at that time. It has been difficult to satisfy both conditions of always separating the transfer paper stably and obtaining a good image. On the other hand, there has been proposed a transfer means of a transfer-conveying-belt type in which an electric charge is applied to a dielectric belt to perform transfer, and a transfer sheet is adsorbed and conveyed. Further, among electrophotographic apparatuses employing transfer means of a transfer / conveyance belt type, an apparatus employing a negative / positive developing method is also known.

In a conventional electrophotographic apparatus employing a transfer-conveying belt system, a negative-positive developing system, that is, for example, a system in which a photosensitive member is negatively charged, and after image exposure, is developed with a negatively charged toner, is used. As a means for applying a positive charge to the dielectric belt, a charger arranged opposite to the photoreceptor via a transfer belt is used.

[0004]

However, in a conventional negative-positive developing system, an electrophotographic apparatus of a transfer-conveying belt system can obtain very good transfer, but the separation performance is slightly lowered. For this reason, when various bad conditions overlap, there is a problem that the transfer material is not separated from the photoconductor.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to provide a negative-positive developing type electrophotographic apparatus having a high quality image and a stable separation performance by a transfer belt system.

[0006]

In order to achieve the above object, the present invention provides an electrostatic latent image carrier for holding a charged toner, and a charging device for applying a charge to the electrostatic latent image carrier. Means, an electrostatic latent image forming means for forming an electrostatic latent image corresponding to a document image on the charged electrostatic latent image carrier, and a toner charged on the electrostatic latent image carrier. Developing means for supplying; transferring means for transferring the toner image formed by the developing means to a transfer material; transfer material supplying means for supplying a transfer material to a transfer position of the transfer means; Cleaning means for cleaning remaining toner remaining on the electrostatic latent image carrier, wherein the transfer means includes a transfer conveyance belt, and a bias for applying to the transfer conveyance belt a charge having a polarity opposite to the charged polarity of the toner. Application member, the transfer conveyance belt And a belt cleaning unit for cleaning the toner on the transfer / transport belt. The bias applying member is moved from the nip portion between the electrostatic latent image carrier and the transfer / transport belt in the transfer material transport direction. In an electrophotographic apparatus using a negative-positive developing system provided on the downstream side and transferring a toner image to a transfer material by the transfer conveyance belt, the bias applying member is orthogonal to a traveling direction of the transfer conveyance belt. When the width in the direction is L2, the width of the transfer conveyance belt is L5, the effective exposure width of the electrostatic latent image carrier is L1, and the effective charging width of the electrostatic latent image carrier is L3, the length of each width is long. Let L1 <L2 <
It is characterized in that L3 <L5 is set.

Further, in order to achieve the above object, the present invention provides an electrostatic latent image carrier for holding a charged toner, a charging means for applying a charge to the electrostatic latent image carrier, An electrostatic latent image forming unit for forming an electrostatic latent image corresponding to a document image on the electrostatic latent image carrier provided with, and an electrostatic latent image forming unit for supplying charged toner to the electrostatic latent image carrier. Developing means; transfer means for transferring the toner image formed by the developing means to a transfer material; transfer material supply means for supplying a transfer material to a transfer position of the transfer means; Cleaning means for cleaning the toner remaining on the electrostatic latent image carrier, wherein the transfer means is a transfer conveyance belt, a bias applying member for applying a charge of the opposite polarity to the charge polarity of the toner to the transfer conveyance belt, Run the transfer conveyor belt Moving means, and a belt cleaning means for cleaning toner on the transfer conveyance belt, wherein the bias applying member is located downstream of a nip portion between the electrostatic latent image carrier and the transfer conveyance belt in a transfer material conveyance direction. And an electrophotographic apparatus using a negative-positive developing method in which a toner image is transferred to a transfer material by the transfer conveyance belt, wherein the belt cleaning width L6 of the belt cleaning means is Assuming that the cleaning width of the electrostatic latent image carrier is L7 and the width of the transfer / conveying belt is L5, the relationship between the widths is L.
7 <L6 <L5.

The present invention is effective when a charge removing member for removing charge from the transfer conveyance belt is provided.

Further, according to the present invention, the width of the neutralizing member in a direction perpendicular to the traveling direction of the transfer / transport belt is L4, and the width of the bias applying member in a direction perpendicular to the traveling direction of the transfer / transport belt is L2. The width of the transfer conveyance belt is L
When it is set to 5, it is effective to set the length relationship of each width as L2 <L4 <L5.

Still further, according to the present invention, the charge removing member and the bias applying member are rollers rotatable around an axis substantially perpendicular to a traveling direction of the transfer / conveying belt.
It is effective.

[0011]

[0012]

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing the entire image forming system of the electrophotographic apparatus according to the present invention. In FIG. 1, when image formation is started, light is radiated to a photosensitive member 1 serving as an electrostatic latent image carrier by a static elimination lamp 2, and the surface potential of the photosensitive member 1 is reduced to 0 to −100.
V is set to the reference potential. Next, the photoconductor 1 is charged by the charging charger 3 as a charging unit, and the photoconductor potential is set to about -850V. The charged surface of the photoconductor 1 is exposed to an image by an electrostatic latent image forming unit. In this case, digital recording image information sent from a device not shown is received by a line driver circuit, and is amplified by a laser driver circuit. The digitally recorded image information is 1
This is an 8-bit multilevel signal per pixel, and the laser driver circuit activates the laser diode in response to the multilevel signal. The laser light emitted from the laser diode is reflected by the rotating polygon mirror 4, passes through the f-θ lens 5, and
The light is reflected by the mirror 6, the second mirror 7, and the third mirror 8, and the image is irradiated on the photoconductor 1. Here, the photosensitive member surface potential of the portion (image portion) irradiated with light is 0 to -100 V,
Since a bias of about −600 V is applied to the developing sleeve 10 in the developing unit 9 as the next developing unit on the image portion, the negatively charged toner in the developing unit 9 adheres. Since the non-image portion remains around -850 V, the toner does not adhere. Photoreceptor 1 with toner image
The front surface rotates, and a sheet of transfer material is sent from a sheet feeding unit (not shown) as a transfer material supply unit at a timing such that the leading end of the sheet and the leading end of the image coincide at the transfer position. The toner image on the surface of the photoconductor 1 is transferred to a sheet at a portion where the belt 20 and the photoconductor 1 are in contact with each other.

The sheet after the transfer is sent to the left in the drawing while being electrically attracted to the transfer / conveying belt 20, is separated by a curvature at the left end of the transfer / conveying belt 20, and is sent to a fixing unit (not shown). . In the fixing unit, the toner is fused to the paper by heat and pressure, and is discharged as a copy. On the other hand, the residual toner remaining on the photoreceptor 1 is scraped off by the cleaning brush 12 and the cleaning blade 13 in the cleaning unit 11, and the surface of the photoreceptor 1 becomes a state without toner, and the process proceeds to the next image forming step again.

As described above, the electrophotographic apparatus uses the negative-positive developing system in which the charging and the toner polarity are the same.

Next, a transfer / transport belt unit as a transfer unit will be described with reference to FIG. First, the transfer conveyance belt 20 is a medium resistance belt having a surface resistance of about 10 ⁶ to 10 ¹² Ω. The transfer conveyance belt 20 is wound around a driving roller 21 provided on the exit side of the transfer conveyance belt unit and a driven roller 22 provided on the entrance side, and is driven counterclockwise by the driving of the driving roller 21. The drive roller 21 has a core portion formed of a metal roller, and has a configuration in which a conductive rubber material is wound around the outer periphery of the metal roller. Inside the upper running side of the transfer conveyance belt 20, a bias applying roller 23 is provided on the driven roller 22 side.
However, the discharging roller 24 is arranged on the driving roller 21 side. The bias applying roller 23 is connected to a power supply (not shown) to apply a current to the transfer / transport belt 20, and the charge removing roller 24 is grounded. The bias applying roller 23 and the charge eliminating roller 24
It also serves as a backup roller for 0. In addition, the provision of the charge removing roller 24 prevents transfer failure due to accumulation of charges on the transfer conveyance belt 20.

A belt cleaning blade 25 for scraping off toner remaining on the belt is provided below the drive roller 21 of the transfer / conveyance belt 20, that is, after the paper is separated from the belt.

In the transfer / transport belt unit having such a configuration, the transfer / transport belt 20 is pressed against the photosensitive member 1 during image formation, and the distance between the driven roller 22 and the application roller 23 is appropriately set between the photosensitive member 1 and the transfer / transport belt 20. Transfer nip portion 26 that slides in width
Is formed. Then, the sheet on which the toner image has been transferred at the transfer nip portion 26 is pressed against the photosensitive member 1, and when it comes out of the transfer nip portion 26, it is electrically attracted to the transfer conveyance belt 20 and separated from the photosensitive member 1. You. At this time, since the application roller 23 is provided at a position where the sheet on the downstream side in the sheet conveyance direction is separated, the attraction force between the sheet and the transfer conveyance belt 20 increases in a region where the sheet is separated from the photoconductor 1. Further, the separability can be improved without impairing the transferability.

FIG. 3 is an explanatory view showing another embodiment of the present invention. The effective exposure width of the laser beam imaged on the photosensitive member 1, the width of the bias applying roller 23, and the charging of the photosensitive member 1 by the charger 3
, The width of the transfer roller 20, the width of the belt cleaning blade 25 for cleaning the transfer conveyor belt 20, and the photosensitive member 1.
Are shown between the cleaning widths.

First, according to the present invention, when the width of the transfer / conveying belt 20 is L5, the effective charging width is L1, the width of the bias applying roller 23 is L2, and the effective charging width is L3, the length between the respective widths is defined. As is clear from FIG. 3, the relationship is L1 <L
2 <L3 <L5.

With this setting, the bias applying roller 23
Is smaller than the width L5 of the transfer / conveyance belt 20,
As shown in FIG. 4, both ends 20 a of the transfer / conveyance belt 20 are bent downward, so that the transfer / conveyance belt 20 can be prevented from shifting. Further, by setting the width L2 of the bias applying roller 23 to be longer than the effective exposure width L1 and shorter than the effective charging width L3, proper transfer is performed and electric charges of the opposite polarity to the toner are not accumulated on the photosensitive member 1. Image formation.

Further, in the present invention, the transfer conveying belt 20 is used.
Is the width of L5, and the width L6 of the belt cleaning blade 25 is
When the cleaning width L7 of the photoconductor 1 is set, the length relationship between the widths is set as L7 <L6 <L5.

With this setting, the width L6 of the belt cleaning blade 25 is longer than the cleaning width L7 of the photoconductor 1, so that there are residual toner on the photoconductor 1 that cannot be removed by cleaning or toner accumulated on the side. Can be removed by the belt cleaning blade 25 even if the transfer to the transfer / conveying belt 20. Further, since the width L6 of the belt cleaning blade 25 is shorter than the width L5 of the transfer conveyance belt 20, the transfer conveyance belt 20 can be prevented from shifting.

Further, in the present invention, when the width of the bias applying roller 23 is L2, the width of the discharging roller 24 is L4, and the width of the transfer / conveying belt 20 is L5, the relationship between the widths is represented by L2. <L4 <L5.

With this setting, the bias applying roller 23
The width L4 of the charge removing roller 24 is longer than the width L2 of the charge removing roller 24, so that the function of the charge removing roller 24 for preventing transfer failure due to accumulation of charges on the transfer conveyance belt 20 can be stably performed. Further, since the width L4 of the charge removing roller 24 is shorter than the width L5 of the transfer conveyance belt 20, the bias applying roller 23
In the same manner as described above, the deviation of the transfer conveyance belt 20 can be prevented.

Incidentally, the bias applying member and the charge removing member provided on the transfer / conveying belt 20 may be constituted by fixed members. However, in this case, if vibration occurs at the time of applying a bias, image quality is adversely affected. Therefore, the bias applying member and the static elimination member are changed as in the above-described embodiment.
By configuring the bias applying roller 23 and the charge eliminating roller 24 that rotate in contact with the transfer conveyance belt 20 while the belt is running, vibration during bias application can be suppressed.
High quality images can be provided.

[0027]

According to the first aspect of the present invention, the biasing member of the transfer / transport belt is shorter than the transfer / transport belt, so that the transfer / transport belt can be prevented from shifting. When the width of the member is longer than the effective exposure width and shorter than the effective charging width, proper transfer is performed and image formation is performed without accumulating charges of opposite polarity to toner on the electrostatic latent image carrier. Can be.

According to the second aspect of the present invention, it is possible to remove, by the cleaning on the transfer / conveying belt, the toner which has not been completely removed by the cleaning on the electrostatic latent image carrier of the transfer / conveying belt or the toner accumulated on the side. In addition, since the width of cleaning of the transfer conveyance belt is shorter than that of the transfer conveyance belt, it is possible to prevent the transfer conveyance belt from shifting.

According to the third aspect of the present invention, since the charge removing member for removing the charge from the transfer conveyance belt is provided, it is possible to prevent a transfer failure due to accumulation of electric charges on the transfer conveyance belt.

According to the fourth aspect of the invention, the width of the charge removing member is made longer than the width of the bias applying member of the transfer carrying belt, so that the charge removing of the transfer carrying belt can be stably performed.

According to the fifth aspect, by using rollers as the charge removing member and the bias applying member, vibration at the time of applying a bias can be suppressed, and a high quality image can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an entire image forming system of an electrophotographic apparatus according to the present invention.

FIG. 2 is an enlarged explanatory view of the transfer and conveyance belt unit of FIG. 1;

FIG. 3 is an explanatory diagram showing a length relationship among an effective exposure width, a bias application roller width, an effective charging width, a charge removing roller width, a transfer conveyance belt width, a belt cleaning blade width, and a cleaning width. .

FIG. 4 is a cross-sectional view of a transfer conveyance belt at a bias application roller portion.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 charging charger 9 developing unit 11 cleaning unit 20 transfer / conveying belt 21 drive roller 22 driven roller 23 bias application roller 24 static elimination roller 25 belt cleaning blade 26 transfer nip L1 effective exposure width L2 bias application roller width L3 effective charging Width L4 Width of static elimination roller L5 Width of transfer conveyance belt L6 Width of belt cleaning blade, L7 Cleaning width

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-110586 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/00 518 G03G 21 /Ten

Claims (5)

(57) [Claims] 1. An electrostatic latent image carrier for holding a charged toner, a charging unit for applying an electric charge to the electrostatic latent image carrier, and the electrostatic latent image carrier provided with the electric charge An electrostatic latent image forming means for forming an electrostatic latent image corresponding to a document image, a developing means for supplying charged toner to the electrostatic latent image carrier, and a developing means formed by the developing means. Transfer means for transferring a toner image to a transfer material, transfer material supply means for supplying a transfer material to a transfer position of the transfer means,
A cleaning unit for cleaning the toner remaining on the electrostatic latent image carrier after the transfer, wherein the transfer unit applies a charge having a polarity opposite to the charged polarity of the toner to the transfer conveyance belt; A bias applying member, a driving unit that runs on the transfer / conveying belt, and a belt cleaning unit for cleaning toner on the transfer / conveying belt, wherein the bias applying member includes the electrostatic latent image carrier and the transfer / conveying belt. An electrophotographic apparatus using a negative-positive developing method provided on the downstream side of the nip portion in the transfer material transport direction from the nip portion to transfer the toner image to the transfer material by the transfer transport belt, wherein the bias applying member The width in the direction orthogonal to the traveling direction of the transfer / transport belt is L2, the width of the transfer / transport belt is L5, and the effective exposure of the electrostatic latent image carrier An electrophotographic apparatus, wherein a width relationship is set to L1, and an effective charging width of the electrostatic latent image carrier is set to L3, and a length relation of each width is set to L1 <L2 <L3 <L5. 2. An electrostatic latent image carrier for holding a charged toner, a charging unit for applying a charge to the electrostatic latent image carrier, and the electrostatic latent image carrier provided with the charge An electrostatic latent image forming means for forming an electrostatic latent image corresponding to a document image, a developing means for supplying charged toner to the electrostatic latent image carrier, and a developing means formed by the developing means. Transfer means for transferring a toner image to a transfer material, transfer material supply means for supplying a transfer material to a transfer position of the transfer means,
A cleaning unit for cleaning the toner remaining on the electrostatic latent image carrier after the transfer, wherein the transfer unit applies a charge having a polarity opposite to the charged polarity of the toner to the transfer conveyance belt; A bias applying member, a driving unit that runs on the transfer / conveying belt, and a belt cleaning unit for cleaning toner on the transfer / conveying belt, wherein the bias applying member includes the electrostatic latent image carrier and the transfer / conveying belt. An electrophotographic apparatus using a negative-positive developing method, which is provided on the downstream side in the transfer material transport direction from the nip portion and transfers the toner image to the transfer material with the transfer transport belt, wherein the belt of the belt cleaning means Cleaning width L
6 is characterized in that, when the cleaning width of the electrostatic latent image carrier of the cleaning means is L7 and the width of the transfer / transport belt is L5, the relationship of the widths is set to L7 <L6 <L5. Electrophotographic apparatus. 3. An electrophotographic apparatus according to claim 1, further comprising a charge removing member for removing charge from said transfer conveyance belt. 4. The electrophotographic apparatus according to claim 3, wherein a width of the charge removing member in a direction orthogonal to a traveling direction of the transfer transport belt is L4, and a width of the bias applying member is orthogonal to a travel direction of the transfer transport belt. An electrophotographic apparatus, wherein when the width in the direction of the transfer is L2 and the width of the transfer conveyance belt is L5, the length relationship between the widths is set as L2 <L4 <L5. 5. The electrophotographic apparatus according to claim 3, wherein the charge removing member and the bias applying member are rollers rotatable about an axis substantially orthogonal to a traveling direction of the transfer conveyance belt. Electrophotographic equipment.