JPH05127543A - Toner image transfer device - Google Patents

Abstract

PURPOSE:To prevent the deterioration, the contamination and the meandering of a paper feeding belt by simple constitution, to obtain the printed matter of good quality and to easily attach/detach the paper feeding belt without damaging it. CONSTITUTION:A driving roller 4 and driven rollers 5 and 6 are rotatably supported by a supporting base plate 2 and a moving base plate 3 which are linearly coupled so as to be able to elongate and contract, and the paper feeding belt 1 having three-layer structure is spanned around the rollers 4-6. The base plates 2 and 3 are set to a state where they re fixed by a set screw 8 which penetrates a oblong hole 3a top screw them and a state where they are loosened to be able to elongate and contract, so that the belt 1 is easily attached/detached and prevented from being damaged. Then, both ends of the roller 4 is formed in a crown shape to prevent the belt 1 from meandering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner image for carrying a paper such as a paper or an OHP sheet in an electrophotographic apparatus and transferring the toner image formed on the surface of a toner image carrier such as a photosensitive drum. The present invention relates to a transfer device.

[0002]

2. Description of the Related Art In a toner image transfer method for transferring a toner image formed on a surface of a photosensitive drum to a sheet in an electrophotographic apparatus, a corona transfer that gives corona ions to the back side of the sheet while the sheet is in contact with the surface of the photosensitive drum. Method, a roller transfer method of forming a transfer electric field by pressing a conductive roller to which a voltage is applied to the back side of the paper, and a belt transfer method of forming a transfer electric field by a dielectric belt that also serves to convey the paper.
In recent years, a toner image transfer device using an endless paper conveyance belt made of a dielectric has been proposed, particularly from the viewpoint of reducing paper jam.

For example, Japanese Laid-Open Patent Publication No. 56-154772 describes a toner image transfer device that rotates a paper transport belt stretched by rollers to transport a paper and transfer a toner image.

Further, in the toner image transfer device described in Japanese Patent Laid-Open No. 63-85668, in order to facilitate the attachment / detachment of the paper carrying belt, a roller for stretching the paper carrying belt is rotatably supported. The support substrate and the movable substrate are flexibly coupled, and the movable substrate is bent so that the tension state of the sheet conveying belt with respect to the roller is relaxed and the sheet conveying belt is easily attached and detached. ..

The paper carrying belt is constructed by laminating a first layer of semiconductor material and a second layer of polyethylene, polyamide or the like. In principle, the paper carrying belt does not come into contact with toner, but in reality it is soiled by the toner being transported, the toner falling from the photosensitive drum, and the like, and if this dirt on the paper transport belt is left, the back surface of the paper is uncleaned. The paper transport belt is cleaned because it may become dirty. The cleaning is generally performed by an elastic blade, similar to the cleaning of the photosensitive drum.

In Japanese Laid-Open Patent Publication No. 56-123578, a transfer bias having a predetermined polarity is applied from the back side of the sheet holding surface of the sheet conveying belt, and after the sheet is conveyed, the sheet holding surface of the sheet conveying belt is the same as the transfer bias. Described is an electrophotographic apparatus which performs cleaning by exposing the surface of a paper conveyance belt and toner adhered to the surface to the same polarity by being exposed to polar corona discharge, repulsing both charges to retransfer the toner to the surface of the photosensitive drum. Has been done. Further, the roller which stretches and rotates the paper transport belt is manufactured by cutting a metal rod, press-fitting the shaft into a hollow roller, or molding a rubber layer on the outer periphery of the metal shaft, Since the quality of the printed matter is remarkably deteriorated when the sheet conveyance belt meanders during sheet conveyance, a sheet conveyance belt meandering prevention measure is usually taken.

Further, in order to improve maintainability such as maintenance and inspection of the apparatus, the toner image transfer apparatus can be unitized and detached from the main body, and the sheet conveying belt is pressed against the photosensitive drum. Thus, the supporting means for supporting the unit is separately provided.

[0008]

However, the bending mechanism of the supporting substrate and the moving substrate, which rotatably supports the roller that stretches the paper conveying belt in the conventional toner image transfer device, makes both substrates rotatable. A special stepped screw to be joined and a set screw for fixing are required, which requires a large number of components and is complicated and expensive. Moreover, when the movable substrate is rotated when the paper transport belt is attached or detached, the roller attached to the movable substrate is naturally not in the position where the roller is inscribed in the paper transport belt to shape the paper transport belt. There has been a problem that the inside of the paper transport belt comes into contact with a supporting substrate, a moving substrate, or a metal member such as an auxiliary member thereof, and is damaged.

Therefore, one of the problems to be solved by the present invention is that when the paper carrying belt is attached or detached, the paper carrying belt comes into contact with a metal member such as a supporting substrate, a moving substrate or an auxiliary member thereof, and is damaged. It is to be able to prevent sticking.

Further, since the back surface of the paper holding surface of the paper conveyance belt is always exposed to the transfer corona discharge, it is also exposed to ozone generated by the transfer corona discharge. Further, since the roller is stretched between the rollers and the turning force is given by the rollers, the rollers always rub against the rollers. Therefore, the paper conveying belt is mechanically and electrically fatigued and has a short life.

Therefore, another problem to be solved by the present invention is to prolong the service life of the sheet conveying belt used in such a state.

Further, a transfer bias having a predetermined polarity is applied to the paper carrying belt from the back side of the paper holding surface for transferring the toner image, and after carrying the paper, the paper carrying surface of the paper carrying belt has the same polarity as the transfer bias. The transfer bias is applied in order to charge the surface of the paper conveyance belt and the toner attached to the surface to the same polarity by being exposed to the corona discharge, and repel the charges of both to retransfer the toner to the surface of the photosensitive drum for cleaning. Means, corona discharge means, and control circuit are required, which is complicated and expensive. Therefore,
Another problem to be solved by the present invention is to make it possible to simplify the cleaning means.

Furthermore, the roller for tensioning the paper transport belt is expensive because it is manufactured by cutting a metal rod, press-fitting the shaft into a hollow roller, or molding a rubber layer on the metal shaft. There is a problem in that the accuracy is reduced when it is composed of a plurality of parts.

Therefore, another problem to be solved by the present invention is to reduce the cost and improve the accuracy of the roller that stretches the paper conveying belt.

Further, the means for preventing the meandering of the sheet conveying belt increases the number of constituent parts of the toner image transfer device and complicates the structure.

Therefore, another problem to be solved by the present invention is to simplify the structure of the sheet conveying belt meandering preventing means.

Further, the supporting means for supporting the paper carrying belt in pressure contact with the photosensitive drum is complicated and expensive.

Therefore, another problem to be solved by the present invention is to simplify the structure of the means for supporting the sheet conveying belt in pressure contact with the photosensitive drum.

[0019]

According to the present invention, there is provided a support substrate, a movable substrate coupled to the support substrate, coupling means for coupling the support substrate and the movable substrate, and a rotatably supported support substrate. One roller, a second roller rotatably supported on the movable substrate, and a paper transport belt that is stretched around the two rollers and transports the paper so as to contact the surface of the toner image carrier. In the equipped toner image transfer device,
The coupling means may change the coupling of the movable substrate to the support substrate to a fixed state and a semi-fixed state in which linear relative movement is possible.

The sheet conveying belt has a laminated structure in which layers made of a high resistance material are formed on both sides of a support layer made of an elastic material, and the toner image on the surface of the toner image carrier is electrostatically transferred onto the sheet. The transfer electric field having a predetermined polarity is applied from the side opposite to the paper holding surface of the paper conveyance belt to transfer the toner image from the toner image carrier surface to the paper, and then the transfer electric field is applied. Is applied, and the cleaning means is configured to retransfer the toner attached to the paper transport belt to the toner image carrier by charging the paper transport belt to the same polarity as the toner by frictional charging. The at least two rollers that stretch the paper transport belt are hollow rollers obtained by integrally compressing both ends of a metal seamless tube by pressure and then cutting the support shaft portion. At least one of the rollers has a crown shape, and the support mechanism that supports the both substrates so that the paper transport belt contacts the toner image carrier is A guide member for guiding both substrates so as to be movable substantially parallel to the toner image carrier, and an elevating mechanism for pivotally supporting the guide members so as to be vertically movable,
An elastic force imparting member for pressing the sheet conveying belt against the toner image carrier is provided.

[0021]

Since the coupling relationship between the supporting substrate that rotatably supports the roller that stretches the sheet conveying belt and the moving substrate is linearly expanded and contracted to stretch or loosen the sheet conveying belt, the sheet conveying belt is stretched. It is possible to prevent the paper transport belt from being damaged by contact with a metal member such as a support substrate, a moving substrate, or an auxiliary member thereof when the paper is attached or detached.

Further, the paper conveying belt having a three-layer laminated structure of the support layer and the high resistance layers formed on both surfaces thereof can withstand corona ions, ozone and mechanical friction, and thus the paper conveying belt has a long life. At the same time, the charge for transferring the toner image is held.

Further, when the paper transport belt is driven by rollers to rotate, the toner adhered to the paper transport belt by frictionally charging the paper transport belt to the same polarity as the toner attached to the paper transport belt. Can be retransferred to the toner image carrier by repulsive force to remove the toner, and the cleaning means can be simplified.

Further, the integral compression molding and cutting of both ends of the metal seamless pipe for forming the supporting shaft portion of the roller for stretching the paper transport belt reduce the cost and improve the accuracy.

Further, since the crown-shaped roller prevents the stretched sheet conveying belt from meandering, the meandering preventing mechanism has a simple structure.

The support mechanism facilitates the operation of pressing and separating the paper carrying belt from the toner carrying member, so that the work of replacing the paper carrying belt is facilitated.

[0027]

Embodiments of the present invention will be described below with reference to the embodiments.

FIG. 2 is a vertical sectional side view of a laser printer which is an electrophotographic apparatus using the toner image transfer apparatus according to the present invention. The photosensitive drum 50 is a cylindrical aluminum tube on which a photoconductive substance such as an organic photosensitive material is vapor-deposited or applied in a thin film form, and a supporting shaft is added. The charger 51 is applied with a high voltage to generate corona ions, and uniformly charges the outer peripheral surface of the photosensitive drum 50. The optical unit 52 generates intermittent laser light in accordance with an image signal given by a control means (not shown), and the photosensitive drum 5 is uniformly charged.
The surface of 0 is exposed to form an electrostatic latent image. The developing device 53 causes a developer to act on the surface of the photosensitive drum 50 to develop the electrostatic latent image and form a toner image on the surface of the photosensitive drum.
The paper feed rollers 54 and 55 are provided opposite to the paper feed cassettes 56 and 57, and the papers set in the paper feed cassettes 56 and 57 are extracted and supplied to the toner image transfer device 58. The toner image transfer device 58 places and conveys a sheet on a sheet conveying belt which is stretched and rotated, and brings the sheet into contact with the surface of the photosensitive drum 50 to form a toner image on the surface. Is electrostatically transferred to the paper. The fixing device 59 fixes the toner image transferred onto the sheet onto the sheet by heat and pressure. The paper discharge device 60 discharges the paper on which the toner image is fixed onto a top paper discharge tray 62 formed on the top surface of the laser printer body 61 or a side paper discharge tray 63 formed on the side surface.

FIG. 1 is a perspective view showing a state in which the paper transport belt is stretched around the paper transport belt tensioning mechanism in the toner image transfer device 58. 1 is a paper transport belt, 2 is a support substrate, and 3 is a support. A movable substrate 4 linearly extensible and contractable with respect to the substrate 2 is a driving roller which also serves as a driving means for stretching and rotating the paper transport belt 1, and 5, 6
Is a driven roller that stretches the paper transport belt 1 to guide the rotation of the paper transport belt 1, and 7 is a pressing roller. The driving roller 4 and the pressing roller 7 are rotatably supported by the supporting substrate 2, and the driven rollers 5 and 6 are rotatably supported by the moving substrate 3.

The movable substrate 3 is connected to the support substrate 2 so that the movable substrate 3 can expand and contract.
A set screw 8 penetrating a is screwed into the supporting substrate 2 to fix or loosen the moving substrate 3 to the supporting substrate 2. The positioning when the movable substrate 3 is fixed in the stretched state in order to give a proper tension to the stretched sheet conveying belt 1 is performed by fitting the positioning holes 2a formed in the support substrate 2 and the positioning protrusions 3b formed in the movable substrate 3. In order to prevent the rotation when it is loosened so that it can expand and contract, the claw 3c formed on the moving substrate 3 is brought into contact with the edge of the supporting substrate 2.

In FIG. 1, the sheet carrying belt 1 is stretched around the rollers 4, 5, 6, 7 and then the movable substrate 3 is extended to fit the positioning protrusions 3b into the positioning holes 2a. It shows a state in which the belt 1 is tensioned and fixed with a set screw 8. When the paper transport belt 1 is attached to or detached from the rollers 4 to 7, the set screw 8 is loosened to linearly retract the moving substrate 3. Perform in a contracted state.

Such a structure has an advantage that the paper carrying belt 1 can be easily attached and detached with high accuracy, and the paper carrying belt 1 is hardly damaged.

FIG. 3 is a vertical cross-sectional side view showing a state in which a charging device and a cleaner are added to the paper transport belt tensioning mechanism of the toner image transfer device 58 to charge and clean the paper transport belt 1. .. Reference numeral 11 denotes a charger that applies a transfer electric field from the back of the paper holding surface of the paper transport belt 1 by corona discharge, and is detachably installed on the support substrate 2. Reference numeral 12 is a cleaner for removing toner adhering to the surface of the sheet conveying belt 1, which is scraped off from the sheet conveying belt 1 by an elastic cleaning blade 13 that rubs the surface of the sheet conveying belt 1 and the cleaning blade 13. A waste toner storage box 14 for storing toner is provided.

When the toner adhering to the surface of the photosensitive drum 50 is negatively charged, the charger 11 gives positive ions having a polarity opposite to that of the toner to the back surface of the sheet holding surface of the sheet conveying belt 1 by the charger 11. The upper toner is attracted to the paper on the paper transport belt 1 by electrostatic force to realize the transfer of the toner image. The cleaning blade 13 is elastically pressed against the rotating sheet carrying belt 1 after finishing the sheet carrying and scrapes off the toner by the mechanical force, but in order to remove the fine particle toner which cannot be scraped off, the sheet carrying belt 1 is carried. The material is selected so that the frictional charging polarity with the driving roller 4 and the like when the belt 1 rotates becomes the same as the charging polarity of the toner, and the toner is retransferred to the photosensitive drum 50 by the repulsive force of both. In this way, the cleaning of the paper transport belt 1 is promoted. In order to enhance the toner retransfer function, the high voltage supply to the charger 11 is stopped before and after the sheet is conveyed so that the amount of accumulated charge due to frictional charging is increased.

FIG. 4 is a perspective view of the drive roller 4 which stretches and rotates the sheet conveying belt 1. The drive roller 4 is
A hollow metal seamless tube is compression-molded at both ends by pressure and then cut to form a support shaft portion, and both ends of the belt tension surface are crowned to prevent meandering of the sheet conveying belt 1. It has a shape.

FIG. 5 is a side view showing a state in which the paper transport belt tensioning mechanism, the charger and the cleaner are unitized. A unit base 15 screwed to the lower part of the conveyor belt stretching unit houses the toner storage box 14 therein,
The suspension blade 16 presses the cleaning blade 13 against the surface of the sheet conveying belt 1. A slide base 17 is attached to the lower surface of the unit base 15 for sliding the conveyor belt stretching unit on and off the supporting mechanism on the laser printer body 61 side.

FIGS. 6 and 7 show a state in which the conveyor belt stretching unit is attached to and detached from the laser printer main body 61. The support mechanism for supporting the conveyor belt stretching unit in the laser printer main body 61 includes the slide base 17
The inner end of the unit attachment / detachment guide 18 for inserting and removing is supported by the main body side plate 20 by the rotation link 19, and the push-up plate 21 provided at the outer end faces the push-up lever 23 installed on the main body bottom plate 22. .. The positioning pin 24 engages with the conveyor belt tensioning unit for positioning, and the driven gear 25 provided at the shaft end of the drive roller 4 meshes with the drive gear 26 to receive the rotational force of the paper conveyor belt.

When the push-up lever 23 is tilted and the unit attaching / detaching guide 18 is pulled down, the driven gear 25 is moved to the drive gear 26.
Away from the photosensitive drum 50 and the unit attachment / detachment guide 18 moves toward the front,
The slide base 1 for the unit attachment / detachment guide 18 without contacting the paper transport belt 1 with the photosensitive drum 50.
7 (Conveyor belt tension unit) can be freely inserted and removed. The attachment / detachment of the sheet conveying belt 1 to / from the detached conveying belt stretching unit is performed by expanding and contracting the moving substrate 3 with respect to the supporting substrate 2 as described above.

In order to mount the carrier belt tension unit on which the paper carrier belt 1 is stretched on the laser printer body 61, the slide base 17 is inserted into the unit mount guide 18 while the unit mount guide 18 is pulled down. , The push-up lever 23 is raised, and the unit attachment / detachment guide 18
By pushing the outer end of the unit while pushing it up, the rotation link 19 rotates, and the inner end of the unit attachment / detachment guide 18 also rises. As a result, the conveyor belt stretching unit is pushed up while being pushed into the laser printer main body 61 to press the paper conveyor belt 1 against the photosensitive drum 50 and engage the unit positioning pin 24, and further, the driven gear 25 drives the drive gear. Mesh with 26.

[0040]

As described above, according to the present invention, the coupling relationship between the support substrate and the moving substrate that rotatably supports the roller that stretches the paper transport belt is linearly expanded and contracted to the paper transport belt. Since the sheet feeding belt is given or loosened, it is possible to prevent the sheet feeding belt from being damaged by coming into contact with a metal member such as a supporting substrate, a moving substrate, or an auxiliary member thereof when the belt is attached or detached.

Further, the paper conveying belt having a three-layer structure of the support layer and the high resistance layers formed on both surfaces thereof can withstand corona ions, ozone and mechanical friction, and thus the life of the paper conveying belt is prolonged. At the same time, the charge for transferring the toner image can be effectively retained.

Further, when the sheet conveying belt is driven by a roller to rotate, the toner is attached to the sheet conveying belt by frictionally charging the sheet conveying belt to the same polarity as the toner attached to the sheet conveying belt. Can be retransferred to the toner image carrier by repulsive force to remove the toner, and the cleaning means can be simplified.

Further, the integral compression molding and cutting of both ends of the metal seamless pipe for forming the support shaft portion of the roller for stretching the paper transport belt can reduce the cost and improve the accuracy. it can.

Further, since the crown-shaped roller prevents the stretched sheet conveying belt from meandering, the meandering preventing mechanism can be made simple.

The support mechanism facilitates the operation of pressing and separating the paper carrying belt from the toner carrier so that the work of replacing the paper carrying belt is facilitated.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state in which a sheet conveying belt is stretched around a sheet conveying belt stretching mechanism in a toner transfer device according to the present invention.

FIG. 2 is a vertical sectional side view of a laser printer which is an electrophotographic apparatus using the toner image transfer apparatus according to the present invention.

FIG. 3 is a vertical cross-sectional side view showing a state in which a charging device and a cleaner are added to the paper transport belt tensioning mechanism of the toner image transfer device according to the present invention to charge and clean the paper transport belt.

FIG. 4 is a perspective view of a drive roller used in the toner image transfer device according to the present invention.

FIG. 5 is a side view showing a state in which a sheet conveying belt tensioning mechanism, a charger and a cleaner of the toner image transfer device according to the present invention are unitized.

FIG. 6 is a front view showing a state in which the conveyor belt stretching unit of the toner image transfer device according to the present invention is attached to and detached from the laser printer main body.

FIG. 7 is a front view showing a state in which the conveyor belt stretching unit of the toner image transfer device according to the present invention is attached to and detached from the laser printer main body.

[Explanation of symbols]

 1 Paper Conveyor Belt 2 Support Substrate 2a Positioning Hole 3 Moving Substrate 3a Oblong Hole 3b Positioning Protrusion 3c Claw 4 Drive Roller 5,6 Driven Roller 8 Set Screw 11 Transfer Charger 12 Cleaner 13 Cleaning Blade 15 Unit Base 16 Lifting Spring 17 Slide base 18 Unit attachment / detachment guide 19 Rotation link 23 Push-up lever 50 Photosensitive drum 51 Charger 52 Optical unit 53 Developer 58 Toner image transfer device 59 Fixing device 61 Laser printer body

Claims (6)

[Claims] 1. A support substrate, a movable substrate coupled to the support substrate, coupling means for coupling the support substrate and the movable substrate, and a first roller rotatably supported on the support substrate.
Toner image transfer provided with a second roller rotatably supported on the movable substrate, and a paper transport belt which is stretched around the two rollers and transports the paper so as to contact the surface of the toner image carrier. In the apparatus, the coupling means is capable of changing the coupling of the movable substrate to the support substrate into a fixed state and a semi-fixed state in which linear relative movement is possible, and a toner image transfer apparatus. 2. The sheet conveying belt according to claim 1,
It is a laminated structure in which layers made of a high resistance material are formed on both sides of a support layer made of an elastic material, and is characterized by holding an electric charge that generates an electric field for transferring the toner image on the surface of the toner image carrier to a sheet. Toner image transfer device. 3. The transfer electric field according to claim 1, wherein a transfer electric field having a predetermined polarity is applied from a side opposite to a paper holding surface of the paper conveying belt to transfer the toner image from the surface of the toner image carrier to the paper. Of the toner is transferred to the toner image carrier by recharging the paper conveying belt to the same polarity as the toner by frictional charging. 4. The hollow roller according to claim 1, wherein the at least two rollers around which the sheet conveying belt is stretched are formed by integrally compressing both ends of a metal seamless pipe by pressure and then cutting the supporting shaft portion. And a toner image transfer device. 5. The toner image transfer device according to claim 1, wherein at least one of the rollers has a crown shape. 6. The support mechanism according to claim 1, wherein the support mechanism that supports the two substrates so that the paper transport belt contacts the toner image carrier can move the both substrates substantially parallel to the toner image carrier. A guide member that guides the guide member, an elevating mechanism that vertically supports the guide member, and an elastic force applying member that presses the sheet conveying belt against the toner image carrier. Toner image transfer device.