JP2978367B2 - Transfer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer apparatus, and more particularly, to a surface of an electrostatic latent image carrier incorporated in an image forming apparatus such as an electronic copying machine, a printer, a facsimile or the like. The present invention relates to a transfer device for electrostatically transferring a toner image formed on a sheet material such as transfer paper by a transfer roller.

[0002]

2. Description of the Related Art A typical transfer device used in the above image forming apparatus is a non-contact type using a corona discharger as a charge supply means for supplying charges to the electrostatic latent image carrier. Examples include those using a corona transfer method and those using a contact-type bias roller transfer method using a conductive roller as the charge supply means.

A transfer device using the former corona transfer method is constituted by a corona discharger or the like. As schematically shown in FIG. 3, the corona discharger 22 is used in a state where the corona discharger 22 is disposed at a predetermined interval from the photosensitive drum 21 as an electrostatic latent image carrier. The corona discharger 22 charges the transfer paper P from the rear side of the transfer paper P transferred between the rotating photosensitive drum 21 and the corona discharger 22 by applying a corona charge having a polarity opposite to that of the toner. Let it. As a result, the transfer paper P is partially attracted to the surface of the photosensitive drum 21 and the charged toner on the surface of the photosensitive drum 21 is transferred to the transfer paper P by Coulomb force.

However, when the above-described corona transfer type transfer device is used, the photosensitive drum 21 is acted upon by the action of static electricity.
Since the transfer paper P adsorbed on the paper is hard to be naturally separated, it is necessary to provide a separate separating means. In addition, since a high voltage is applied to the corona discharger 22, there is a disadvantage that a considerable amount of discharge products such as ozone and nitrogen oxide (NOx) harmful to the human body are generated.

A transfer device using the latter bias roller transfer method is composed of a transfer roller or the like having conductivity by mixing carbon or an alkali metal into a urethane resin. FIG.
As schematically shown in FIG. 1, the transfer roller 23 is used in a state where it is disposed at a position where the transfer roller 23 comes into contact with the photosensitive drum 21.
The transfer roller 23 includes the photosensitive drum 21 and the transfer roller 23.
Transfer paper P that has entered between the peripheral surfaces of the photosensitive drum 2
The toner image on the photosensitive drum 21 is transferred to the transfer paper P by a transfer voltage (a voltage having a polarity opposite to that of the toner) applied to the axial center of the transfer roller 23 while being pressed against the toner adhered to the one surface. . Since the transfer device of this type uses a weak current, the generation of discharge products such as ozone and NOx is considerably smaller than that of the former type of corona transfer type (1/20 to 1 of the current corona transfer type). / 30), and there is an advantage that transfer paper separating means is unnecessary.

When the transfer device of the bias roller transfer system is used, the transfer paper P is pressed against the surface of the photosensitive drum 21 by the surface of the transfer roller 23 in order to bring the transfer paper P into close contact with the photosensitive drum 21. Has become. Therefore, the toner near the center of the photosensitive drum 21 is
The toner is scattered and adheres to the peripheral portion of the image transferred onto the transfer paper P,
There is a problem that a so-called image dust phenomenon easily occurs.

In order to improve such a problem of the bias roller transfer system, the present applicant has proposed that the transfer roller 23 be in a non-contact state with the photosensitive drum 21 and the transfer paper P as schematically shown in FIG. , The transfer roller 23 is spaced apart from the photosensitive drum 21 by a distance larger than the thickness of the transfer paper P.
Has been previously proposed (Japanese Patent Application No. 4-284120) in order to prevent the occurrence of a hollow phenomenon or an image dust phenomenon on an image transferred to the transfer paper P.

In FIG. 5, reference numeral 24 denotes a pair of registration rollers for transferring the transfer paper, 25a and 25b guide members for guiding the transfer paper P to the surface of the photosensitive drum 21, and 26 denotes fixing means for the transferred transfer paper P. (Not shown).

In this prior art, the registration roller 24 feeds the transfer paper P at a constant speed equal to the peripheral speed of the surface of the photosensitive drum 21 in accordance with the rotation of the photosensitive drum 21, so that the transfer paper P is guided by the guide member 25a. , 25b to the photosensitive drum 21 side. The leading edge of the transfer paper P protrudes from the end of the lower guide member 25b, and the photosensitive drum 21
Transfer paper P comes into contact with the surface of the photosensitive drum 21 and moves at the same speed as the peripheral speed of the surface of the photosensitive drum 21, during which the toner image on the surface of the photosensitive drum 21 is transferred. .

Although the transfer roller 23 is located apart from the surface of the photosensitive drum 21, the photosensitive drum 21
It is considered that the reason why the toner image on the front surface is well transferred to the transfer paper P without excess or shortage is that a minute corona discharge is generated from the transfer roller 23 toward the back surface of the transfer paper P. Good test results have been obtained for the transfer performance of the toner image.

The transfer paper P separates from the surface of the photosensitive drum 21 and reaches the upper surface of the support table 26.
, And then transferred along the support 26 as the photosensitive drum 21 rotates. As described above, the transfer paper P is bent at the portion immediately before contacting the surface of the photosensitive drum 21 and at the start end of the transfer paper P adjacent to the support base 26, and the elasticity of the transfer paper P itself caused by these bending is reduced. Acts as a pressing force on a portion in contact with the surface of the photosensitive drum 21.

The transfer speed of the transfer paper P and the guide members 25a,
The angles and the like of the guide surfaces Sa and Sb of 25b are set so as to conform to the conditions for making the transfer paper P closely contact the surface of the photosensitive drum 21 at a constant speed. For example, the guide members 25 a and 25 b are arranged so as to be close to the photosensitive drum 21 in order to bring the transfer paper P into close contact with the photosensitive drum 21.

As for the angles of the guide surfaces Sa and Sb of the guide members 25a and 25b, the transfer with respect to a tangent plane (shown by a broken line in FIG. 5) at the position where the leading end of the transfer paper P abuts on the surface of the photosensitive drum 21. By adjusting the angle θ of the paper P to a large value, the transfer paper P is pressed against the surface of the photosensitive drum 21 by the elasticity of the transfer paper P itself, brought into close contact with the surface of the photosensitive drum 21, and adjusted so as to escape from the transfer roller 23.

[0014]

However, when the guide members 25a and 25b whose angles are adjusted as described above are provided,
Since the guide members 25a and 25b become resistant to the movement of the transfer paper P, the transfer paper P is separated from the registration roller 24 provided on the upstream side of the photosensitive drum 21 at a moment.
There is a problem that the transfer paper P is momentarily delayed by the moving speed of the photosensitive drum 21 and a transfer deviation occurs. Further, paper dust may be generated due to friction between the transfer paper P and the guide members 25a and 25b, and the paper dust may cause a failure of each part of the image forming apparatus or a transfer failure.

Further, as described above, since the transfer roller 23 is not in contact with the transfer sheet P, gravity acts on the transfer sheet so that the transfer sheet P separates from the photosensitive drum 21 by its own weight. There is a possibility that the adhesion between P and the photosensitive drum 21 may be deteriorated (that is, floating may occur). Further, depending on the quality and thickness of the transfer paper P, the adhesion between the transfer paper P and the photosensitive drum 21 may be deteriorated. If the adhesion between the transfer sheet P and the photosensitive drum 21 is poor, transfer failure occurs, or the transfer sheet P contacts the transfer roller 23 and the transfer roller 2
There is a problem of picking up 3 dirt.

The present invention solves the above-described problems. In a transfer apparatus in which a transfer roller is arranged at a distance from an electrostatic latent image carrier larger than the thickness of a transfer sheet,
It is an object of the present invention to provide a transfer device having good adhesion of a transfer sheet to an electrostatic latent image carrier without bending the transfer sheet by a guide member.

[0017]

According to the present invention, in order to achieve the above object, an electrostatic latent image carrier is disposed at a position facing a transfer portion with a gap larger than the thickness of the transfer paper. is the a transfer device having a transfer roller for transferring the conveyed transfer paper between the toner image formed on the surface of the electrostatic latent image bearing member and the electrostatic latent image bearing member, wherein A transfer roller is arranged above the electrostatic latent image carrier, and the transfer paper receives an image transfer above the electrostatic latent image carrier.

[0018]

According to the above construction, since the transfer roller is disposed above the electrostatic latent image carrier, the transfer paper conveyed between the transfer roller and the electrostatic latent image carrier is statically held by its own weight. It rests on the latent electrostatic image bearing member and comes into close contact with the surface thereof. Therefore, since it is not necessary to press the transfer sheet with the electrostatic latent image carrier by bending the transfer sheet with the guide member, the guide member does not become resistant to the movement of the transfer sheet, and for example, the electrostatic latent image carrier The movement of the transfer paper is not affected even if the transfer paper is separated from the registration roller provided on the upstream side of the transfer paper.

Further, since the transfer roller is arranged at a distance larger than the thickness of the transfer paper from the electrostatic latent image carrier, the transfer paper is placed on the electrostatic latent image carrier by its own weight as described above. If it comes into close contact with the surface, it does not come into contact with the surface of the electrostatic latent image carrier.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a state in which a transfer apparatus to which the present invention is applied is used in a digital electronic copying machine.

In FIG. 1, reference numeral 10 denotes a photosensitive drum as an electrostatic latent image carrier, which is made of an amorphous silicon (a-Si) or other photosensitive material on the surface of a metal tube made of aluminum or the like. A photosensitive layer is formed. The photoconductor drum 10 is disposed substantially horizontally within the main body 11 of the copying machine, and is rotationally driven in a counterclockwise direction indicated by an arrow A by a driving system (not shown) provided in the main body 11. This rotation direction is set to be in the forward direction with respect to the transfer direction of the transfer paper P, similarly to the rotation drive of the transfer roller 1 in the clockwise direction (direction of arrow B) described later.

Around the photosensitive drum 10, a charging means 6, a developing means 4, a non-contact type transfer roller 1 and a charge removing / cleaning means 7 are arranged along the rotation direction of the photosensitive drum 10 in that order. Have been. An exposing unit 5 is provided below the charging unit 6. Between the charging unit 6 and the developing unit 4, the photosensitive drum 10 is connected to the exposing unit 5.
The exposure is performed by the laser light L from the camera.

In the electronic copying machine having the above-described configuration, first, a corona discharge or the like is performed by the charging means 6 to charge the surface photosensitive layer of the photosensitive drum 10. An original (not shown) is placed on the surface of the charged photosensitive drum 10.
The exposure unit 5 irradiates the laser beam L based on the image read from the device, thereby forming an electrostatic latent image.
This electrostatic latent image is developed with toner by the developing means 4 to become a toner image.

On the other hand, the transfer paper P is taken out from the paper supply cassette 9 by the paper supply roller 3 and is opposed to the upper guide member 15.
a and a peripheral speed of the surface of the photoconductive drum 10 corresponding to the rotation (arrow A) of the photoconductive drum 10 by a pair of registration rollers 2 along a transfer paper transporting path constituted by the lower guide member 15a and the lower guide member 15b. It is conveyed between the photosensitive drum 10 and the transfer roller 1 at a peripheral speed.

The transferred paper P is transferred to the photosensitive drum 1
During the contact with the surface of the photosensitive drum 10, a voltage having a polarity opposite to that of the toner image on the surface of the photosensitive drum 10 is applied to the transfer roller 1. The charged toner is transferred to the surface of the transfer paper P. Since the transfer paper P is in close contact with the photosensitive drum 10 by its own weight with a stable contact force, the occurrence of image unevenness in the transferred image on the transfer paper P is prevented.

The transfer paper P on which the toner image has been transferred is separated from the surface of the photosensitive drum 10 and is heated and pressed while passing between the pair of rollers by the fixing means 8, so that the toner image is transferred onto the transfer paper P. Is established. When the leading end of the transfer sheet P reaches the fixing unit 8, the transfer sheet P is transported by both the fixing unit 8 and the registration roller 2. Thereafter, the rear end portion is separated from the registration roller 9, and the transfer paper P is discharged onto the discharge tray 13 according to the rotation of the photosensitive drum 10 and the roller constituting the fixing unit 8. Although the toner image is transferred to the lower surface of the transfer paper P which is separated from the photosensitive drum 10 and advances to the fixing means 8, the distance between the transfer roller 1 and the fixing means 8 is short. Does not come into contact with the guide member 16. Therefore, the toner image before fixing is not damaged.

On the other hand, after the transfer, the charge removing / cleaning means 7
Thus, the remaining toner on the surface of the photosensitive drum 10 is removed and the charge is removed.
When rotated, it is ready for the next charging.

[0028] In an electronic copying machine having such a configuration, the transfer apparatus of this embodiment, the transfer portion of the photosensitive drum 10
Are arranged at a position facing each other with a gap larger than the thickness of the transfer paper P, and the toner image formed on the surface of the photosensitive drum 10 is transferred to the transfer paper P conveyed between the photosensitive drum 10. The transfer roller 1 is provided above the photosensitive drum 10.

FIG. 2 shows the transfer roller 1 and the photosensitive drum 10
It is a principal part side view which shows arrangement | positioning relationship. As shown in FIG. 1, the transfer roller 1 is located at a position opposing and close to the surface of the photosensitive drum 10 with an interval d larger than the thickness of the transfer paper P (FIG. 1). (Not shown).

As shown in FIG. 2, the transfer roller 1 has a roller body (volume electrical resistivity: ρv = 10) made of conductive rubber.
^{6 ~10 7 Ω · cm) 1a} , consists of a metallic rotating shaft 1b and insulating roller 1c. The roller body 1a has at least a length in the axial direction of the toner image forming area 10A on the surface of the photosensitive drum 10, and is fixed in the form of a long axis roller around the rotation axis 1b. Further, as the roller body 1a, a roller body made of a conductive resin material such as a polystyrene resin or a urethane resin mixed with carbon or an alkali metal, a conductive rubber material, or the like can be used.
The roller body 1a and the rotating shaft 1b are electrically connected.

A voltage having a polarity opposite to that of the charged toner adhered to the surface of the photosensitive drum 10 is applied to the rotating shaft 1b from the power supply 12 to the rotating shaft 1b via a contact terminal (not shown) at the time of transfer. When a voltage is applied to discharge electricity toward the photoconductor drum 10, the transfer paper P is charged as described above, and the charged toner attached to the surface of the photoconductor drum 10 separates from the surface of the photoconductor drum 10 and moves away from the transfer paper P. Transfer to the top.

In order to regulate the distance d (= 0.5 mm) between the surface of the photosensitive drum 10 and the surface of the transfer roller 1, both ends of the roller body 1a are provided with rollers 1 made of insulating resin.
c is provided. Since the interval d is maintained by the contact of the roller 1c with the surface of the photoreceptor drum 10, it can be appropriately adjusted by replacing the roller 1c with a roller 1c having a different diameter.

The distance d may be larger than the thickness of the transfer paper P, and may be the same as the case where the transfer roller 1 is arranged below the photosensitive drum 10 as shown in FIG.
When the transfer roller 1 is positioned above the photosensitive drum 10 as shown in FIGS. 1 and 2, the transfer paper P adheres to the photosensitive drum 10 by its own weight, so that the distance d is smaller than that in FIG. It is possible to

This is for the following reason. As described above with reference to FIG. 5, when the transfer roller 23 is positioned below the photosensitive drum 21, gravity occurs on the transfer paper P in a direction away from the photosensitive drum 21 by its own weight. It comes closer to the transfer roller 23. Transfer paper P
When the transfer roller 23 comes into contact with the transfer roller 23, the transfer roller 23 is contaminated. Therefore, in practice, the distance between the transfer roller 23 and the photosensitive drum 21 must be relatively large. On the other hand, in this embodiment, the transfer paper P is separated from the transfer roller 1 by its own weight, so that the distance d between the photosensitive drum 10 and the transfer roller 1 can be made as small as possible.

If the distance d can be reduced,
Since the transfer efficiency is improved, the current required for the transfer can be further reduced. The smaller the current, the more harmful ozone to the human body and NOx which adversely affects the photoreceptor
This has the effect of reducing the generation of discharge products such as. Further, since the transfer roller 1 is arranged at a distance d larger than the thickness of the transfer paper P from the photoconductor drum 10, the transfer paper P is placed on the photoconductor drum 10 by its own weight as described above and If it comes into close contact with the transfer roller 1, it does not come into contact with the surface of the transfer roller 1. Therefore, it is possible to prevent the transfer paper P from picking up dirt on the transfer roller 1.

In the conventional example shown in FIG.
The adhesion of the transfer paper P to the transfer paper P deteriorates. Then, the adhesiveness of the transfer paper P to the photosensitive drum 10 is also deteriorated depending on the quality and thickness of the transfer paper P. Such poor adhesion results in poor transfer.

On the other hand, if the transfer roller 1 is positioned above the photosensitive drum 10 as described above, gravity occurs on the transfer paper P in the direction in which the transfer paper P comes into contact with the photosensitive drum 21 by its own weight. The adhesion of the transfer paper P to the photosensitive drum 10 is improved. If the adhesion is improved, the occurrence of transfer failure can be prevented.

When the transfer roller 1 is disposed below the photosensitive drum 10 as shown in FIG. 5, the guide members 25a and 25b whose angles have been adjusted to bend the transfer paper P.
However, according to the configuration of the present embodiment, a guide member for bending the transfer paper P is unnecessary. That is, when the transfer roller 1 is positioned above the photosensitive drum 10 as described above, gravity acts on the transfer paper P so that the transfer paper P comes into close contact with the photosensitive drum 10 by its own weight. The transfer paper P can be brought into close contact with the photosensitive drum 10 without using a guide member whose angle has been adjusted.

The guide members 15a, 15b shown in FIG.
No angle adjustment for bringing the transfer paper P into close contact with the guide members 25a and 25b shown in FIG.
In other words, the guide members 25a and 25b shown in FIG. 5 not only constitute the transfer path of the transfer paper P but also make the transfer paper P approach the photosensitive drum 21 and have an angle so as to be upright. The transfer paper P is not brought into contact with the transfer roller 23, and the leading end of the transfer paper P is guided to a predetermined position so as to be brought into close contact with the surface of the photosensitive drum 21. In contrast, the guide member 15 shown in FIG.
Reference numerals a and 15b are merely for configuring the transfer path of the transfer paper P.

When the transfer roller 1 is disposed above the photosensitive drum 10 as described above, the transfer paper P conveyed between the transfer roller 1 and the photosensitive drum 10 is moved by its own weight. So that it sits on top and sticks to its surface,
It is not necessary to press the transfer paper P against the photosensitive drum 10 by bending the transfer paper P with the guide member. Therefore, there is no need to provide a guide member that resists the movement of the transfer paper,
For example, when the transfer sheet P separates from the registration roller 2 provided on the upstream side of the photosensitive drum 10, the movement of the transfer sheet P is not affected. In other words, there is no problem that the transfer deviation occurs due to the delay of the moving speed of the photosensitive drum 21 at the moment when the transfer paper P separates from the registration roller 2. Further, the transfer paper P and the guide members 15a,
Since no paper dust is generated by friction with 15b,
Neither the failure of each part of the image forming apparatus nor the occurrence of transfer failure due to paper dust does not occur.

FIG. 1 shows an apparatus using a rotating photoreceptor drum 10 as an electrostatic latent image carrier. However, the configuration of the present invention also corresponds to a method in which an endless belt-shaped photoreceptor is rotated in a cyclic manner. Can be done. The charge supply means is not a rotating roller body such as the transfer roller 1,
A photoconductor 10 fixed at a position facing the transfer portion of the photoconductor 10 can also be used.

When the transfer roller 1 is disposed above the photosensitive drum 10, the exposing means 5 serving as a light source is
Is difficult to dispose above the analog P, the analog P which reads the original image and exposes the photosensitive drum 10 with the same light is used.
It is not easy to adopt this transfer device in a PC (Plain Paper Copier). However, in the digital PPC as shown in FIG. 1, since the light for reading the document and the light for exposing are independent from each other, the degree of freedom of the exposure position is large, so that this embodiment can be easily applied. Therefore, the transfer apparatus of this embodiment is suitable for an apparatus using a laser optical system and an LED (light emitting diode) optical system as exposure means, such as a facsimile, a printer, and a digital PPC.

[0043]

As described above, in the transfer device of the present invention, the transfer roller is disposed above the electrostatic latent image carrier, and the transfer paper is subjected to image transfer above the electrostatic latent image carrier. Therefore, the transfer paper is placed on the electrostatic latent image carrier by its own weight and adheres to the surface thereof. Therefore, it is possible to realize a transfer device having good adhesion of the transfer sheet to the electrostatic latent image carrier without bending the transfer sheet by the guide member. Since the transfer paper has good adhesion to the electrostatic latent image carrier, occurrence of transfer failure is prevented, and the transfer roller is arranged at a distance larger than the thickness of the transfer paper from the electrostatic latent image carrier. Therefore, the transfer paper is reliably separated from the transfer roller, and the transfer paper is prevented from picking up dirt on the transfer roller. Also,
Since there is no need to use a guide member that bends the transfer paper, there is no resistance to the movement of the transfer paper, and the occurrence of transfer deviation due to this is prevented. At the same time, paper dust due to rubbing with the guide member is less likely to be generated, so that failure of each part of the image forming apparatus and occurrence of transfer failure are also prevented.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing an electronic copier including a transfer device according to an embodiment of the present invention.

FIG. 2 is a side view of a main part schematically showing a state in which the transfer device according to one embodiment of the present invention is disposed on a photosensitive drum.

FIG. 3 is a front view schematically showing a conventional example using a corona transfer method.

FIG. 4 is a front view schematically showing a conventional example using a bias roller transfer method.

FIG. 5 is a front view schematically showing a main part of a prior art provided with a non-contact type transfer roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transfer roller 1a ... Roller body 1b ... Rotating shaft 1c ... Roller 10 ... Photoconductor drum P ... Transfer paper

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/16

Claims (1)

(57) [Claims] 1. A are spaced larger gap than the thickness of the rolling <br/> transfer paper to the opposing position of the transfer portion of the electrostatic latent image bearing member, is formed on the surface of the latent electrostatic image bearing member a transfer apparatus having a transfer roller for transferring the conveyed transfer paper between the toner image and the latent electrostatic image bearing member have to place the transfer roller above said electrostatic latent image bearing member ,
A transfer device, wherein a transfer sheet receives an image transfer above the electrostatic latent image carrier.