JP2941358B2 - 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 sent from a paper feed unit (not shown) onto the transport path 14 via the registration roller 5, travels toward the photosensitive drum 11 through the transport path 14, and the recording paper leading end guide plate 16 and the transfer It is guided by the front roller 17 on the outer peripheral surface of the photosensitive drum 11 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 on the transport path 14 from the photosensitive drum 11. This prevents transfer deviation due to jumping of the trailing edge of the recording paper that occurs when the trailing edge of the recording paper passes through the roller 17.

[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. Toner contamination occurs on the tip regulating guide plate 16.

As described above, when the recording paper leading edge adjusting guide plate 16 is stained with toner, when the recording paper is guided by the recording paper leading edge adjusting guide plate 16, the toner stain on the recording paper, particularly, the front end portion 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. The guide plate for regulating the leading edge of the recording paper is made of a conductive material, and a bias voltage having the same polarity as the charge polarity of the toner is applied to the guiding plate for regulating the leading end of the recording paper.

The image carrier includes a photosensitive drum, a photosensitive belt used in an electrophotographic printer and an electrophotographic copying machine, a dielectric drum used in a transfer type electrostatic recording printer, and the like. As the guide plate for regulating the leading end of the recording paper, for example, a polyester film containing carbon 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 in the recording paper conveyance direction is located rearward in the recording paper conveyance direction from the front end in the recording paper conveyance direction of the toner contamination prevention cover, and the guide plate for adjusting the recording paper leading end is made of a conductor and the guiding plate for adjusting the recording paper leading end. , A bias voltage having the same polarity as the charging polarity of the toner is applied. 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.

Further, since the guide plate for regulating the leading edge of the recording paper is made of a conductive material and a voltage having the same polarity as the charging polarity of the toner is applied to the guide plate for regulating the leading edge of the recording paper, the guide plate for regulating the leading edge of the recording paper and the toner A repulsive force acts between them to prevent the toner from adhering to the guide plate for regulating the leading edge of the recording paper due to electrostatic force.

In the second image forming apparatus according to the present invention, since the front end of the guide plate for regulating the leading end of the recording paper in the recording paper transport direction is located rearward from the front end of the toner stain prevention cover, the toner falling from the image carrier is prevented from falling by the leading end of the recording paper. 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 a voltage having the same polarity as the charging polarity of the toner is applied to the guide plate for regulating the leading edge of the recording paper, the guide plate for regulating the leading edge of the recording paper and the toner A repulsive force acts between them to prevent the toner from adhering to the recording paper leading end guide plate due to electrostatic force.

Embodiment An embodiment in which the present invention is applied to a laser printer will be described below with reference to FIGS. 1 to 3. 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 disposed at a developing position around the photosensitive drum 1, and toner is attached to the photosensitive drum 1 by the developing sleeve 2. Also, the photosensitive drum 1
A transfer charger 3 is disposed at a transfer position around the
The toner adhering to the photosensitive drum 1 is transferred to the recording paper sent to the transfer position by the transfer charger 3. 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.

The guide plate 5 for regulating the leading end of the recording paper is made of a conductor such as a polyester film containing carbon. A voltage having the same polarity as the charging polarity of the toner is applied to the recording paper leading end guide plate 5 by a DC power supply 8. In this example, since the charge polarity of the toner is negative, a negative voltage is applied to the guide plate 5 for regulating the leading end of the recording paper.

The voltage applied to the guide plate 5 for regulating the leading edge of the recording paper may be, for example, a pulsating voltage obtained by level-shifting an AC voltage as long as the polarity is the same as the charging polarity of the toner.

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. As the toner stain prevention cover 6, for example, a polyester film is used. 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).

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 9 is fed onto the conveyance path 4 (indicated by a dashed line 9 in the figure), the recording paper 9 advances in a direction toward the photosensitive drum 1 along the conveyance path 4 (a direction indicated by an arrow B in FIG. 2). 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 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 is moved along the outer peripheral surface of the photosensitive drum 1 to the transfer position. Therefore, the recording paper 9 is fed onto the surface of the photosensitive drum 1 with its front end regulated. When the recording paper 9 is sent to the transfer position, the toner attached to the photosensitive drum 1 at the developing position is transferred onto the recording paper 9 by the transfer charger 3.

In this embodiment, the toner stain prevention cover 6 is arranged at an interval above the recording paper leading edge guide plate 5, so that the toner dropped from the photosensitive drum 1 can be And does not fall on the guide plate 5 for regulating the leading edge of the recording paper. For this reason, even if the toner adhering to the photosensitive drum 1 falls, the guide plate 5 for regulating the leading end of the recording paper.
Can be prevented from being stained with toner.

Further, the guide plate 5 for regulating the leading end of the recording paper is made of a conductor,
Since a voltage having the same polarity as the charged polarity of the toner is applied to the guide plate 5 for adjusting the leading edge of the recording paper, a repulsive force acts between the guide plate 5 for adjusting the leading edge of the recording paper and the toner. Adhesion of toner to the tip regulating guide plate 5 is prevented.

Therefore, when the recording paper is guided by the recording paper leading end guide plate 5, it is possible to prevent the recording paper from being stained with toner.

 FIG. 3 shows a second embodiment of the present invention.

3, the same components as those in FIG. 2 are denoted by the same reference numerals, and the 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 1 is set within a range in which the recording paper guided by the recording paper leading end guide plate 6 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, the guide plate 5 for regulating the leading end of the recording paper is made of a conductor,
Since a voltage having the same polarity as the charged polarity of the toner is applied to the guide plate 5 for adjusting the leading edge of the recording paper, a repulsive force acts between the guide plate 5 for adjusting the leading edge of the recording paper and the toner. Adhesion of toner to the tip regulating guide plate 5 is prevented.

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.

In each of the above embodiments, a pre-transfer roller is provided between the recording sheet leading end guide plate 5 and the transfer position in proximity to the photoconductor 1 so that the recording sheet guided by the recording sheet leading end guide plate 5 is moved. It may be sent between the photosensitive drum 1 and the pre-transfer roller.

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. Further, the present invention can be applied to a laser printer using a photoconductor bell instead of the photoconductor 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 from being stained 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 a voltage having the same polarity as the charging polarity of the toner is applied to the guide plate for regulating the leading edge of the recording paper, the guide plate for regulating the leading edge of the recording paper and the toner There is a repulsion between them. Therefore, it is possible to prevent toner from adhering to the guide plate for regulating the leading edge of the recording paper due to electrostatic force. 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. Further, since the guide plate for regulating the leading edge of the recording paper is made of a conductor, and a voltage having the same polarity as the charging polarity of the toner is applied to the guide plate for regulating the leading edge of the recording paper,
A repulsive force acts between the recording sheet leading end guide plate and the toner. Therefore, it is possible to prevent toner from adhering to the guide plate for regulating the leading edge of the recording paper due to electrostatic force. Therefore,
When the recording sheet is guided by the recording sheet leading end guide plate, it is possible to prevent the toner stain on the recording sheet.

[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 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 ... Guide plate for regulating the leading edge of recording paper, 6 ... Toner stain prevention cover.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B65H 5/36 G03G 15/00

Claims (5)

(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. A toner dirt prevention cover that covers the top surface of the recording paper tip adjusting guide plate at a distance from the recording paper tip adjusting guide plate, and the recording paper tip adjusting guide plate is made of a conductor; An image forming apparatus in which a voltage having the same polarity as the charged polarity of the toner is applied to the guide plate for regulating the leading edge of the recording paper. 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 containing carbon. 3. 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. The guide plate for regulating the leading edge of the recording paper is made of a conductor, and the guide plate for regulating the leading edge of the recording paper is located on the rear side in the recording paper transport direction from the front end of the toner stain prevention cover in the recording paper transport direction. An image forming apparatus to which voltages of the same polarity are applied. 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 containing carbon. 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.