JP2946471B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic printer such as a laser printer, an electrophotographic copying machine, and a transfer electrostatic recording printer.

[Prior Art] In a conventional laser printer, a developing sleeve is generally provided at a developing position around a photosensitive drum 11 as shown in FIG.
A toner is adhered to the photosensitive drum 11 by the developing sleeve 12. A transfer charger 13 is provided at a transfer position around the photoconductor drum 11, and the toner attached to the photoconductor drum 11 is sent to the transfer position by the transfer charger 13. Photographed on recording paper.

A transport path 14 for guiding the recording sheet to the transfer position is formed between the developing position and the transfer position. The recording paper is fed from a paper feeding unit (not shown) onto the conveyance path 14 via the registration roller 15, travels along the conveyance path 14 toward the photosensitive drum 11, and the recording paper leading end guide plate 16 and the pre-transfer roller
It is guided on the outer peripheral surface of the photosensitive drum 11 by 17 and is sent to the transfer position.

The guide plate 16 for adjusting the leading end of the recording paper is made of a polyester film, and is disposed at a position from the photosensitive drum 11 on the transport path 14. The transfer deviation caused by the jumping of the trailing edge of the recording paper that occurs when the trailing edge of the recording paper passes through 17 is prevented.

[Problems to be Solved by the Invention] In the above-described conventional laser printer, a part of the toner attached to the photosensitive drum 11 at the developing position falls on the guide plate 16 for adjusting the leading edge of the recording paper, and the guide for regulating the leading edge of the recording paper. The plate 16 becomes soiled with toner. In addition, the charging of the transfer charger 13 positively charges the guide plate 16 for adjusting the leading end of the recording paper, and the negatively charged toner attached to the photosensitive drum 11 is attracted to the guide plate 16 for adjusting the leading end of the recording paper by electrostatic force. As a result, toner contamination occurs on the guide plate 16 for regulating the leading edge of the recording paper.

As described above, when toner stain occurs on the guide proposal 16 for adjusting the leading edge of the recording paper, when the recording paper is guided by the guide plate 16 for regulating the leading edge of the recording paper, the toner stain occurs on the recording paper, particularly, on the front end of the recording paper. Will happen.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of preventing toner contamination on a guide plate for regulating the leading edge of a recording sheet, and thereby preventing toner contamination on a recording sheet.

[Means for Solving the Problems] A first image forming apparatus according to the present invention is an apparatus for regulating the leading edge of a recording sheet so that the upper surface of the recording sheet comes into contact with an image carrier on a conveyance path for guiding the recording sheet to a transfer position. A guide plate is provided, and a toner stain prevention cover for covering the upper surface of the recording paper leading edge adjusting guide plate is provided above the recording paper leading edge adjusting guide plate at a distance from the recording paper leading edge adjusting guide plate. It is characterized by having.

The image carrier includes a photosensitive drum used in an electrophotographic printer and an electrophotographic copying machine, a photosensitive member such as a photosensitive belt, a dielectric drum used in a transfer type electrostatic recording printer, and the like. As the guide plate for regulating the leading edge of the recording paper, for example, a polyester film is used.

In a second image forming apparatus according to the present invention, a guide plate for regulating a leading edge of a recording paper is disposed near an image carrier on a conveyance path for guiding the recording paper to a transfer position so that the upper surface of the recording paper is in contact with the leading end. Above the setting guide plate, a toner stain prevention cover for covering the upper surface of the recording paper tip setting guide plate is arranged at a distance from the recording paper tip setting guide plate. The front end of the recording paper conveyance direction is located rearward of the front end of the toner contamination prevention cover in the recording paper conveyance direction. As the guide plate for regulating the leading edge of the recording paper, for example, a polyester film is used.

The distance in the front-rear direction between the front end of the recording paper leading end guide plate in the recording paper conveyance direction and the front end of the toner contamination prevention cover in the recording paper conveyance direction is determined by the distance that the recording paper guided by the recording paper leading end guide plate is applied to the toner contamination prevention cover. It is preferable that the value is set to a large value within a range where the contact does not occur.

In a third image forming apparatus according to the present invention, a guide plate for regulating a leading edge of a recording paper is disposed near an image carrier on a conveying path for guiding the recording paper to a transfer position so that the upper surface of the recording paper is in contact with the leading end. On the upper side of the setting guide plate, a toner stain prevention cover for covering the upper surface of the recording paper tip adjusting guide plate is arranged at a distance from the recording paper tip adjusting guide plate. It is made of a conductor and is grounded. As a guide plate for recording paper tip adjustment,
For example, a polyester film containing carbon is used.

According to a fourth image forming apparatus of the present invention, a guide plate for regulating the leading edge of a recording paper is disposed near an image carrier on a conveyance path for guiding the recording paper to a transfer position so that the upper surface of the recording paper is in contact with the leading end. Above the setting guide plate, a toner stain prevention cover for covering the upper surface of the recording paper tip setting guide plate is arranged at a distance from the recording paper tip setting guide plate. The front end of the recording paper transport direction is located rearward in the recording paper transport direction from the front end of the toner contamination prevention cover in the recording paper transport direction, and the guide plate for regulating the leading edge of the recording paper is made of a conductive material and is grounded. And As the guide plate for regulating the leading edge of the recording paper, for example, a polyester film containing carbon is used.

The distance in the front-rear direction between the front end of the recording paper leading end guide plate in the recording paper conveyance direction and the front end of the toner contamination prevention cover in the recording paper conveyance direction is determined by the distance that the recording paper guided by the recording paper leading end guide plate is applied to the toner contamination prevention cover. It is preferable that the value is set to a large value within a range where the contact does not occur.

[Operation of the Invention] In the first image forming apparatus according to the present invention, the toner dropped from the image bearing member falls on the toner stain prevention cover,
It does not fall on the guide plate for regulating the leading edge of the recording paper. For this reason, even if the toner adhering to the image carrier drops, toner smear does not occur on the guide plate for regulating the leading end of the recording paper.

In the second image forming apparatus according to the present invention, the front end of the guide plate for regulating the leading edge of the recording paper in the recording paper transport direction is located at the rear end of the toner contamination prevention cover in the recording paper transport direction with respect to the recording paper transport direction. It is possible to effectively prevent toner falling from the carrier from adhering to the guide plate for regulating the leading edge of the recording paper.

Since the distance between the image carrier and the guide plate for regulating the leading edge of the recording paper can be increased, the guide plate for regulating the leading edge of the recording paper is charged to the opposite polarity to the charging polarity of the toner by charging the transfer charger. In this case, the attraction force of the toner due to the electrostatic force is reduced, and the amount of toner adhered to the guide plate for regulating the leading edge of the recording paper based on the electrostatic force is also reduced.

In the third image forming apparatus according to the present invention, the toner dropped from the image carrier falls on the toner contamination prevention cover,
It does not fall on the guide plate for regulating the leading edge of the recording paper. Further, since the guide plate for regulating the leading edge of the recording paper is made of a conductive material and is grounded, it is possible to prevent the guide plate for regulating the leading edge of the recording paper from being charged by charging the transfer charger, and the recording based on the electrostatic force is performed. It is possible to effectively prevent toner from adhering to the guide plate for regulating the leading edge of the paper.

In the fourth image forming apparatus according to the present invention, the front end in the recording paper conveyance direction of the recording paper leading end regulating guide plate is located rearward from the front end of the toner stain prevention cover, so that the toner falling from the image carrier is not moved to the recording paper front end. It can be effectively prevented from adhering to the regulating guide plate.

Further, since the guide plate for regulating the leading edge of the recording paper is made of a conductive material and is grounded, it is possible to prevent the guide plate for regulating the leading edge of the recording paper from being charged by charging the transfer charger, and the recording based on the electrostatic force is performed. It is possible to effectively prevent toner from adhering to the guide plate for regulating the leading edge of the paper.

Embodiment An embodiment in which the present invention is applied to a laser printer will be described below with reference to FIGS. 1 to 5. In the following description, the front is the left side of FIG.
The right side of the figure will be referred to respectively.

1 and 2 show a first embodiment of the present invention. A developing sleeve 2 is provided at a developing position around the photosensitive drum 1, and toner is attached to the photosensitive drum by the developing sleeve 2. A transfer charger 3 is disposed at a transfer position around the photosensitive drum 1, and the toner attached to the photosensitive drum 1 is sent to the transfer position by the transfer charger 3. Photographed on paper. The photosensitive drum 1 rotates at a constant speed in the direction of arrow A in FIG.

A transport path 4 for transporting recording paper from a paper feed unit (not shown) to the transfer position is formed between the developing position and the transfer position. At the position from the photosensitive drum 1 on the transport path 4, a guide plate 5 for regulating the leading end of the recording paper is arranged substantially horizontally so that the upper surface of the recording paper comes into contact with the photosensitive drum. The guide sheet 5 for regulating the leading edge of the recording paper is for regulating the leading edge of the recording paper and feeding the recording paper to the transfer position. The lateral width of the guide sheet 5 for regulating the leading edge of the recording paper is formed to be larger than the width of the recording paper fed to the transport path 4.

A toner stain prevention cover 6 that covers the upper surface of the recording paper leading edge guide plate 5 is located above the recording paper leading edge guide plate 5.
Are arranged at an interval d with respect to the guide plate 5 for regulating the leading end of the recording paper. The interval d is set, for example, to 0.5 to 1.5 mm.

The recording paper leading end guide plate 5 and the toner stain prevention cover 6 are attached to an attachment member 7 supported by a printer frame (not shown). The guide plate 5 for regulating the leading edge of the recording paper and the toner stain prevention cover 6 are made of, for example, a polyester film.

In this embodiment, the front end of the recording paper leading end guide plate 5 and the front end of the toner stain prevention cover 6 are flush with each other.

In the above configuration, the recording paper (second
When the recording paper 8 travels along the transport path 4 toward the photosensitive drum 1 (indicated by an arrow B in FIG. 2), the recording paper 8 travels along the transport path 4. It enters between the conveyance path 4 and the guide plate 5 for regulating the leading edge of the recording paper. Then, the upper surface of the recording paper 8 is guided by the lower surface of the front end portion of the guide plate 5 for regulating the leading edge of the recording paper, and travels along the outer peripheral surface of the photosensitive drum 1 to the transfer position. Therefore, the recording paper 8 is fed onto the surface of the photosensitive drum 1 with its front end regulated. When the recording paper 8 is sent to the transfer position, the toner attached to the photosensitive drum 1 at the developing position is transferred onto the recording paper 8 by the transfer charger 3.

In this embodiment, since the toner stain preventing cover 6 is disposed at an upper position of the recording paper leading edge adjusting guide plate 5 with a space therebetween, the toner dropped from the photosensitive drum 1 is removed from the toner stain preventing cover 6. And does not fall on the guide plate 6 for regulating the leading edge of the recording paper.

For this reason, even if the toner attached to the photosensitive drum 1 drops, it is possible to prevent the toner from being stained on the guide plate 5 for regulating the leading end of the recording paper. Therefore, it is possible to prevent the toner from being stained on the recording paper again when the recording paper is guided by the recording paper leading end guide plate 5.

FIG. 3 shows a second embodiment of the present invention. Third
In the figure, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

This embodiment is different from the first embodiment in that the front end of the guide plate 5 for regulating the leading end of the recording paper is located behind the front end of the toner contamination preventing cover 6 by a distance l.

The distance l is set within a range in which the recording paper guided by the recording paper leading end guide plate 5 does not contact the toner stain prevention cover 6. Preferably, the trailing edge of the recording sheet is generated when the trailing edge of the recording sheet passes through the front end of the guide sheet 5 for regulating the leading edge of the recording sheet, so that the trailing edge of the recording sheet is covered with the toner stain preventing cover 6.
Is set within the range that does not touch, for example, 0.5 to 2.0 mm
Is set to More preferably, the distance 1 is such that the trailing edge of the recording sheet does not contact the toner stain prevention cover 6 due to the jump of the trailing edge of the recording sheet when the trailing edge of the recording sheet passes through the front end of the guide plate 5 for regulating the leading edge of the recording sheet. The value is set as large as possible within the range.

In this embodiment, since the front end of the recording paper tip adjusting guide plate 5 is located rearward from the front end of the toner contamination prevention cover 6, the toner falling from the photosensitive drum 1 is not guided by the recording paper tip adjusting guide plate 5. Can be prevented more effectively.

Further, since the distance between the photosensitive drum 1 and the guide plate 5 for regulating the leading edge of the recording paper can be increased, the guide plate 5 for regulating the leading end of the recording paper is set to the polarity opposite to the polarity of the charged toner by charging the transfer charger. Even if it is charged, the attraction force of the toner due to the charging is reduced, and the amount of toner adhering to the guide plate 5 for regulating the leading end of the recording paper based on the electrostatic force is also reduced.

Therefore, when the recording paper is guided by the recording paper leading end guide plate 5, toner contamination on the recording paper can be effectively prevented.

FIG. 4 shows a third embodiment of the present invention. 4th
In the figure, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

This embodiment is different from the first embodiment in that the guide plate 51 for regulating the leading end of the recording paper line is made of a conductor such as polyester containing carbon and is grounded.

In this embodiment, since the toner stain prevention cover 6 is arranged at an interval above the recording paper leading edge guide plate 51, the toner falling from the photosensitive drum 1 is not guided by the recording paper leading edge guiding guide. It can be prevented from adhering to the plate 51.

Further, since the recording paper leading end guide plate 51 is made of a conductive material and is grounded, it is possible to prevent the recording paper leading end guide plate 51 from being charged by charging the transfer charger, and to reduce the power to a positive power. It is possible to effectively prevent toner from adhering to the recording paper leading end guide plate 51 based on the above.

Therefore, when the recording paper is guided by the pre-transfer recording paper guide plate 51, the generation of toner stain on the recording paper can be more effectively prevented.

FIG. 5 shows a fourth embodiment of the present invention. Fifth
In the figure, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the point that the front end of the recording paper leading edge adjusting guide plate 51 is located behind the front end of the toner stain prevention cover 6 and that the recording paper leading edge adjusting guide plate 51 is made of a conductive material such as polyester containing carbon. The second embodiment is different from the first embodiment in that the first embodiment is formed with a ground.

In this embodiment, since the front end of the recording paper leading edge adjusting guide plate 51 is located behind the front end of the toner stain prevention cover 6, the toner falling from the photosensitive drum 1 is not guided by the recording paper leading edge guiding guide plate 51. Can be effectively prevented from adhering to the surface.

Further, since the recording paper leading end guide plate 51 is made of a conductive material and grounded, it is possible to prevent the recording paper leading end guiding plate 51 from being charged by charging of the transfer charger, thereby reducing electrostatic force. The toner can be prevented from adhering to the guide plate 51 for regulating the leading edge of the recording paper.

Therefore, when the recording paper is guided by the recording paper leading end guide plate 51, it is possible to very effectively prevent the recording paper from being stained with toner.

In each of the above embodiments, the guide plate 5 for regulating the leading edge of the recording paper,
Between the transfer position 51 and the transfer position, a pre-transfer roller is provided in close proximity to the photosensitive drum 1, and the recording paper guided by the recording paper leading end guide plates 5, 51 is moved between the photosensitive drum 1 and the pre-transfer roller. It may be sent in between.

In each of the above embodiments, aluminum may be vapor-deposited on the upper surface of the toner stain prevention cover 6 and the aluminum-deposited surface may be grounded. This makes it difficult for the toner stain prevention cover 6 to be charged, and prevents toner from being sucked from the surface of the photosensitive drum 1 to the toner stain prevention cover 6 by electrostatic force. , 5 and 51 can be prevented more effectively.

Further, the present invention can be applied to a laser printer using a photosensitive belt instead of the photosensitive drum 1.

Further, the present invention can be applied to an image forming apparatus other than a laser printer, such as an electrophotographic printer, an electrophotographic copying machine, and a transfer electrostatic recording printer.

[Effect of the Invention] In the first image forming apparatus according to the present invention, even if the toner attached to the image carrier drops, it is possible to prevent the toner contamination on the guide plate for regulating the leading edge of the recording paper. Therefore, it is possible to prevent the recording paper from being stained with toner when the recording paper is guided by the recording paper leading end guide plate.

In the second image forming apparatus according to the present invention, it is possible to more effectively prevent toner falling from the image carrier from adhering to the guide plate for regulating the leading edge of the recording paper. Even if the guide plate for regulating the leading edge of the recording paper is charged to the polarity opposite to the polarity of the toner and the charge by charging the transfer charger, the toner suction force due to the electrostatic force is reduced, and the leading edge of the recording paper is regulated based on the electrostatic force. The amount of toner adhering to the guide plate is also reduced. Therefore, when the recording paper is guided by the recording paper leading end regulating guide plate, it is possible to effectively prevent the recording paper from being stained with toner.

According to the third image forming apparatus of the present invention, it is possible to prevent the toner falling from the image carrier from adhering to the guide plate for regulating the leading edge of the recording paper. Also, it is possible to prevent the guide plate for regulating the leading edge of the recording paper from being charged by charging the transfer charger,
Adhesion of toner to the guide plate for regulating the leading edge of the recording paper based on electrostatic force can be effectively prevented. Therefore, when the recording paper is guided by the pre-transfer recording paper guide plate, it is possible to more effectively prevent the recording paper from being stained with toner.

In the fourth image forming apparatus according to the present invention, it is possible to effectively prevent the toner falling from the image carrier from adhering to the guide plate for regulating the leading edge of the recording paper. Further, the charging of the transfer charger can prevent the guide plate for regulating the leading edge of the recording paper, and the toner can be prevented from adhering to the guiding plate for regulating the leading edge of the recording paper based on electrostatic force. Therefore, when the recording paper is guided by the recording paper leading end guide plate, it is possible to very effectively prevent the recording paper from being stained with toner.

[Brief description of the drawings]

FIGS. 1 and 2 show a first embodiment of the present invention, and FIG. 1 is a schematic configuration diagram near a transfer position in a laser printer. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is a view corresponding to FIG. 2 showing a second embodiment of the present invention. FIG. 4 is a view corresponding to FIG. 2 showing a third embodiment of the present invention. FIG. 5 is a view corresponding to FIG. 2 showing a fourth embodiment of the present invention. FIG. 6 shows a conventional example, and is a schematic configuration diagram near a transfer position in a laser printer. 1 ... Photoreceptor drum, 4 ... Conveying path, 5, 51 ... Guide plate for regulating recording paper leading edge, 6 ... Toner stain prevention cover.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B65H 5/36 G03G 15/00

Claims (10)

(57) [Claims] A guide plate for adjusting a leading edge of a recording paper is disposed near an image carrier on a conveyance path for guiding the recording sheet to a transfer position so that an upper surface of the recording paper is in contact with the image bearing member. An image forming apparatus provided with an anti-toner cover which covers an upper surface of the recording paper leading end guide plate at a distance from the recording paper leading end guide plate. 2. The image forming apparatus according to claim 1, wherein the guide plate for regulating the leading end of the recording paper is made of a polyester film. 3. A guide plate for adjusting a leading edge of a recording paper is disposed near an image bearing member on a conveyance path for guiding the recording sheet to a transfer position so that an upper surface of the recording paper is in contact with the image bearing member. In addition, a toner stain prevention cover is provided at a distance from the recording paper leading edge adjusting guide plate and covers the upper surface of the recording paper leading edge adjusting guide plate. An image forming apparatus which is located on the rear side in the recording paper conveyance direction from the front end of the toner contamination prevention cover in the recording paper conveyance direction. 4. The image forming apparatus according to claim 3, wherein the guide plate for regulating the leading end of the recording paper is made of a polyester film. 5. The distance between the front end of the recording paper leading end guide plate in the recording paper transport direction and the front end of the toner stain prevention cover in the recording paper transport direction in the front-rear direction is determined by the length of the recording paper guided by the recording paper leading end guide plate. 4. The image forming apparatus according to claim 3, wherein the value is set to a large value within a range that does not make contact with the toner stain prevention cover. 6. A guide plate for adjusting the leading edge of a recording sheet is provided near the image bearing member on a conveyance path for guiding the recording sheet to a transfer position so that the upper surface of the recording sheet is in contact with the image bearing member. A toner dirt prevention cover that covers an upper surface of the recording paper tip adjusting guide plate at a distance from the recording paper tip adjusting guide plate, the recording paper tip adjusting guide plate is made of a conductor, and An image forming apparatus that is grounded. 7. The image forming apparatus according to claim 6, wherein the guide plate for regulating the leading end of the recording paper is made of a polyester film containing carbon. 8. A guide plate for adjusting the leading edge of a recording sheet is provided near the image bearing member on a transport path for guiding the recording sheet to a transfer position so that the upper surface of the recording sheet is in contact with the image bearing member. In addition, a toner stain prevention cover is provided at a distance from the recording paper leading edge adjusting guide plate and covers the upper surface of the recording paper leading edge adjusting guide plate. An image forming apparatus wherein the toner stain prevention cover is located on the rear side in the recording paper transport direction from the front end in the recording paper transport direction, and the guide plate for regulating the leading edge of the recording paper is made of a conductor and grounded. 9. The image forming apparatus according to claim 8, wherein the guide plate for regulating the leading end of the recording paper is made of a polyester film containing carbon. The distance between the front end of the recording paper leading end guide plate in the recording paper transport direction and the front end of the toner contamination prevention cover in the recording paper transport direction is determined by the distance between the recording paper guided by the recording paper leading end guide plate. 9. The image forming apparatus according to claim 8, wherein the value is set to a large value within a range that does not make contact with the toner stain prevention cover.