JPH05204263A - Image forming device having transfer material carrier - Google Patents

Abstract

PURPOSE:To maintain a contact pressure constant and to obtain an image which is free from a middle drop-out, image deviation, etc., by specifying the compression amt. and total pressure in the transfer position of the elastic layer of a transfer drum provided with a dielectric layer on the front surface and an elastic layer on the inner side thereof. CONSTITUTION:A transfer device 15 has a hollow drum 20 made of aluminum and flanges 21, 22 consisting of insulators and is constituted as the transfer drum provided with a transfer material carrying member on the outer peripheral surface of the hollow drum 20. This transfer material carrying member is formed by laminating a foamed elastic material layer 26, the conduction layer 27 and the dielectric layer 28 on the outer periphery of the hollow drum 20. More preferably the dielectric layer 28 is formed by polyvinylidine fluoride of sheet shape, etc.,, and the conductor layer 27 is formed by subjecting this dielectric sheet to vapor deposition of aluminum. The foamed elastic material layer 26 is more preferably constituted of a soft urethane foam and the thickness thereof is specified to 2 to 10mm. The total compression amt. of this elastic material layer 26 is 0 to 2mm in the transfer position and the total pressure in this range is confined to <=1kg/mm<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supports a transfer material carrier with a developed image (toner image) obtained by developing the image carrier with a developer by electrophotography or electrostatic recording. The present invention relates to an image forming apparatus for transferring an image onto a transfer material to obtain an image,
In particular, in a color copying machine or a color laser beam printer, which obtains a multicolor image by repeatedly transferring a developed image corresponding to the angular color component formed on the image carrier to the transfer material on the transfer material carrier multiple times. It can be suitably embodied.

2. Description of the Related Art Conventionally, as a transfer device used in, for example, a color electrophotographic copying machine, as shown in FIG. 7, parallel flanges 101, 102 and a connecting member for connecting both flanges 101, 102 are connected. And a transfer drum 105 having an opening 104 on the periphery is used. PVDF is provided in the opening 104 of the transfer drum 105.
A transfer material carrier 106, which is a dielectric layer such as (polyvinylidene fluoride), is wound. Further, a corona charger 107 is arranged inside the transfer drum 105, and the transfer process is performed by performing corona discharge from the back side of the transfer material carrier 106.

The transfer drum 105, as shown in FIG.
A gear 108 is formed on one of the flanges 102, and is meshed with a drum-shaped image carrier, that is, a gear (not shown) formed on one of the flanges of the photosensitive drum, and is rotationally driven.

Further, a convex hard rubber layer (not shown) is formed on the outer periphery of the flange, and the rubber layer comes into contact with the outer periphery of the photosensitive drum flange to thereby form the transfer drum and the image carrier. Is set to a predetermined position. At this time, the thickness of the rubber layer is selected so that a gap corresponding to the transfer material is formed between the transfer material carrier and the photosensitive drum.

Further, at the time of transfer, the transfer material and the photosensitive drum are pressed by a pressing member (not shown) from the back side of the transfer material carrier with a weak pressure so that the transfer material and the photosensitive drum come into contact with each other at a uniform pressure.

However, in the structure of such a conventional transfer drum, since there is almost no portion for holding the transfer material carrier on the peripheral surface of the transfer drum, there is a problem in its durability.

On the other hand, as a structure of a conventionally known transfer device, there is a so-called roller transfer device in which a transfer material carrier is composed of a transfer drum formed by stacking a dielectric layer on the outer periphery of a foam elastic layer. ..

Since this roller transfer device sets a proper contact pressure between the transfer material and the photosensitive drum by the deformation of the elastic foam layer of the transfer drum, the transfer drum having the elastic foam layer is applied to the photosensitive drum at a constant pressure. It is configured to be pressed with. In a transfer device including a transfer drum having such a foam elastic layer, since the dielectric layer is entirely held by the foam elastic layer from the back side, the durability of the dielectric layer is shown in FIG. It has the advantage that it is better than the transfer drum.

Further, since the roller transfer device does not require a corona charger, its merit has been attracting attention from the viewpoint that ozone is hardly generated.

[0010]

However, even such a roller transfer device has the following drawbacks.

That is, when the contact pressure between the image bearing member such as the photosensitive drum and the transfer drum is increased, the inside of the toner image is not transferred, which is a so-called hollow portion.

Further, if the amount of compression of the transfer drum is too large, the actual transferred image may deviate from the position where the image should be transferred onto the transfer material. This causes a color shift in the color image forming apparatus.

(Object of the Invention) It is an object of the present invention to provide an image forming apparatus capable of excellent transfer without a blank area.

Another object of the present invention is to provide an image forming apparatus in which the contact pressure between the image carrier and the transfer material carrier is constant.

Another object of the present invention is to provide an image forming apparatus capable of obtaining a high quality image without image shift or color shift.

Further objects and features of the present invention will become more apparent by reading the following detailed description with reference to the accompanying drawings.

According to the present invention, in order to achieve the above object, an image carrier, image forming means for forming a toner image on the image carrier, and a transfer position of the toner image on the image carrier. In the image forming apparatus having a transfer material carrier that carries the transfer material at the transfer position for transferring to the transfer material, the transfer material carrier has a dielectric layer on its surface and an inner side of the dielectric layer. And an elastic layer provided on the elastic layer. The elastic layer has a compression amount of 0 to 2 mm at the transfer position and a total pressure of 1 kg / mm or less in this range.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. FIG. 2 shows an embodiment in which the image forming apparatus according to the present invention is embodied in a color image forming apparatus such as an electrophotographic color laser beam printer.

Referring to FIG. 2, in the present embodiment, the color laser beam printer is provided with a photosensitive drum 1 having a diameter of 60 mm which is an image bearing member rotating in the direction of the arrow, and the primary charging is performed around the photosensitive drum 1. An exposure unit including a container 4, a semiconductor laser 5, a scanner motor 6, a polygon mirror 7 rotated by the scanner motor 6, a lens 8 and a mirror 9 is arranged. The light L emitted from the semiconductor laser 5 to which the video signal of the controller is input by the exposure means is scanned by the polygon mirror 7, then guided through the lens 8 and the mirror 9 to the photosensitive drum 1, and is latently formed on the photosensitive drum. Form an image.

Around the photosensitive drum 1, a developing device for converting a latent image on the photosensitive drum into a toner image is further arranged.
That is, the toner of yellow Y is stored and the developing sleeve 11
The developing device 10Y having Y, the toner of magenta M, the developing device 10M having the developing sleeve 11M, the toner of cyan C, the developing device 10C having the developing sleeve 11C, and the toner of black Bk are stored. A developing device 10Bk that stores and has a developing sleeve 11Bk is provided.

The transfer material P, which is a normal transfer paper, is stored in the paper feed cassette 12, and is fed one by one to the transfer device 15 by the paper feed roller 13 in the direction of arrow A. Transfer device 15
The configuration will be described later in detail.

The transfer sheet P held by the transfer device 15 passes through a transfer position facing the photosensitive drum, whereby the toner image on the photosensitive drum is electrostatically transferred. When multiple images of multiple colors are transferred onto a transfer paper, a toner image is formed on the photosensitive drum for each color, and the toner images on the image carrier are transferred one by one onto the transfer paper held by the transfer device. This transfer operation is repeated a desired number of times.

The toner remaining on the photosensitive drum 1 transferred onto the transfer paper P conveyed by the transfer device 15 is cleaned by the cleaner 16.
On the other hand, the toner image on the transfer paper P separated from the transfer device 15 is mixed and fixed by the heat fixing device 17, and is discharged onto the paper discharge tray 18. In this embodiment, the photosensitive drum 1, the charging device 4, the developing devices 10Y to 10Bk, and the cleaner 16 can be attached to and detached from the apparatus as an integrated cartridge.

Next, the transfer device 15 will be described.
FIG. 1 shows an embodiment of a transfer device constructed according to the present invention. The transfer device 15 includes an aluminum hollow drum 20 and flanges 21 and 22 made of an insulating material and arranged at both ends of the hollow drum 20, and a transfer material carrier is provided on the outer peripheral surface of the hollow drum 20. 120mm diameter
It is used as a transfer drum. A fixed shaft 23 is disposed so as to penetrate through the center of the transfer drum, and the transfer drum is rotatably supported by the fixed shaft by bearings 24 arranged on both flanges. A gear 25 is formed on one of the flanges 21, and the gear 25 meshes with a flange gear (not shown) of the photosensitive drum 1 driven by a drive source, whereby the transfer drum is rotationally driven. The transfer drum may be provided with a gripper that holds the transfer paper.

According to the present invention, the transfer material carrier is formed by laminating the foamed elastic body layer 26, the conductor layer 27 and the dielectric layer 28 on the outer periphery of the hollow drum 20 with an adhesive or the like. To be done. In addition, the hollow drum 20 and the conductor layer 27
And are electrically connected to. Preferably, the dielectric layer 2
8 is made of sheet-like polyvinylidene fluoride, polyethylene terephthalate or fluorinated ethylene propylene copolymer, and the conductor layer 27 is formed by subjecting this dielectric sheet to aluminum vapor deposition. The dielectric layer is used for good electrostatic adsorption of the transfer paper on the transfer drum.
^It is preferably ¹² Ωcm or more. The conductor layer is an electrode that applies a transfer voltage, and is preferably 10 ⁵ Ωcm or less.

Preferably, the elastic foam layer 26 is made of soft urethane foam and has a thickness of 2 to 10.
mm is appropriate, preferably 3-5 mm. The reason for this is that in order to secure the elasticity of the flexible urethane foam, a thickness of at least about 3 mm is preferable, and in order to form the elastic foam layer 26 by winding and adhering this urethane foam around the transfer drum, This is because if the foam is thicker than 5 mm, the distortion when wound around the transfer drum becomes large, wrinkles and the like are likely to occur at the time of bonding, and workability also deteriorates. The density of this flexible urethane foam is preferably 20 to 150 kg / m ³ .

In general, as shown in FIG. 3, the flexible urethane foam exhibits a characteristic that the load rises to some extent in the initial deformation region, the load changes gradually from a certain point, and finally the load increases again. .. In the present invention, by utilizing the portion where the change of the load is gentle, that is, the portion where the load characteristic with respect to the compression is substantially flat, the deformation amount of the transfer material carrier, that is, the foam elastic layer 26 is wide. Within the range, it is possible to realize a good transfer in which the toner image is not missing in a wide range of deformation of the elastic foam layer 26.

In FIG. 4, the load characteristics of the soft urethane foam used as the foamed elastic layer 26 in this embodiment are shown by a solid line. Specifically, when the layer load is 300 g to 800 g, there is no color misregistration transfer. Therefore, a wide range of 0 mm to 2.0 mm is obtained as the allowable range of the radial deformation amount due to the contact between the transfer drum 15 and the photosensitive drum 1. Was given. Further, as a result of the experiment, the deformation amount is within 0 to 2.0 mm and the load is 1 k.
It was found that the hollowing-out can be prevented if it is less than g / mm (dotted line in FIG. 4). Here, the amount of deformation of the elastic layer is the amount when the transfer paper does not exist at the transfer position. If the amount of deformation is larger than 2.0 mm, the actual transfer image is transferred from the regular position where the image should be transferred onto the transfer paper. The shift caused color shift. This color misregistration occurred in a direction substantially orthogonal to the rotation direction of the transfer drum. The thickness of the transfer paper usable in this apparatus is about 0.1 mm to 0.15 mm. As the elastic layer of this embodiment, silicon sponge can be used because it has the same load characteristics as the soft urethane foam.

However, a rigid urethane foam (having a density greater than 150 kg / m ³ ) as the elastic layer
As shown in FIG. 4, in other foams such as the above, the rate of increase in load with respect to the amount of deformation is large, and the amount of deformation is very small with respect to the load range of 1 kg / mm or less, which easily causes hollowing.

As a result, even if the axial distance between the transfer drum 15 and the photosensitive drum 1 is made constant by using the foamed elastic layer 26 such as soft urethane foam, the transfer drum outer diameter accuracy and the eccentricity are increased. Even if the accuracy is roughened to some extent, it is possible to obtain a high-quality image in which a hollow image does not occur within the large allowable range described above.

5 and 6 show another embodiment of the present invention.

In the previous embodiment, the axial distance between the transfer drum 15 and the photosensitive drum 1 is constant, and the contact deformation amount of the transfer material carrier on the transfer drum 15 is 0.1 mm or more. According to the present embodiment, since the permissible deformation amount of the transfer material carrier is large, the transfer drum 15 can be brought into contact with and separated from the photosensitive drum 1 so that the jam processing can be easily performed. Is.

The embodiment shown in FIG. 5 shows an embodiment in which the transfer drum 15 can be brought into contact with and separated from the photosensitive drum 1. That is, the transfer drum 15 is held by the arm 31 that swings around the shaft 31, and the transfer drum 15 moves toward and away from the photosensitive drum 1 by the rotation of the scanning lever 32 that interlocks with the swing arm 31. Composed.

In the embodiment shown in FIG. 6, on the flanges 21 and 22 of the transfer drum, a hard rubber layer abutting portion 33 as in the conventional transfer drum described with reference to FIG. 7 is used.
Is attached to the surface of the transfer drum so as to be minus. In the present embodiment, the transfer drum 15 is pressed toward the photosensitive drum 1 by a spring 34 or the like that is strong enough so that the rubber layer abutting portion 33 contacts the flange of the photosensitive drum 1.

As described above, even when the support shaft of the transfer device is pressed by the spring in order to keep the contact pressure constant, by providing the abutting portion 33 on the transfer drum, the transfer side and the non-drive side of the transfer device are provided. It is possible to prevent a difference in contact pressure from occurring.

Although not shown in FIG. 2, a separation static eliminator for separating the transfer paper on which the toner image has been transferred from the transfer drum around the transfer drum; Separation claws for guiding the transfer paper to the transfer material conveying path for conveying the transfer paper to the fixing device 17, a transfer drum cleaner for removing toner adhering to the surface of the transfer drum after the transfer material is separated, and a transfer voltage applied to the transfer drum. A static eliminator or the like for removing and initializing the above is provided, and a power supply for supplying a predetermined transfer voltage to the transfer drum is provided.

Next, the contact for applying the transfer voltage from the power source to the transfer drum will be described. When a transfer voltage is applied by bringing the contact connected to the power supply into contact with the shaft end of the rotating shaft of the transfer drum, the side surface of the drum housing, or the surface of the drum housing, the contact is outside the transfer drum. Toner scattered due to jam or the like adheres to the contact point to cause contact failure, or sparks due to high voltage are likely to occur, so noise is likely to occur and this noise adversely affects electrical components. There were drawbacks such as.

Therefore, according to this embodiment, the contact portion for supplying the transfer voltage (current) to the transfer drum is provided inside the transfer drum to improve the durability and reliability of the contact portion.

FIG. 8 shows an embodiment of a transfer drum having a contact portion inside. The inner surface of the dielectric layer 28 on which aluminum is vapor-deposited is electrically connected to the aluminum drum 20 by a conductor 29.

When the transfer drum 15 rotates about the fixed shaft 23 as described above, the contact 35 for applying a high voltage for transfer to the transfer drum 15 in the transfer step naturally becomes a sliding contact. In this embodiment, since the contact 35 is arranged inside the hollow aluminum drum 20 and the fixed shaft 23 is formed as a hollow pipe, the high voltage lead wire 34 from the power source 38 for transfer is fixed to the fixed shaft 23. Through the hole formed in the fixed shaft 23 and connected to the contact 35. The contact 35 is fixed to a contact fixing member 37 attached to the fixed shaft 23 in the drum 20, and is elastically pressed with a ring-shaped metal plate 36 serving as a counter contact fixed to the inner surface of the first flange 22. It is in electrical contact. Figure 9
The enlarged structure of this contact is shown in FIG. A part of the ring-shaped metal plate 36 serving as the opposite contact 36a extends to the inner surface of the aluminum drum 20 and is joined to the drum 20. Therefore, the ring-shaped metal plate 36 is also electrically connected to the aluminum deposition surface on the inner surface of the dielectric layer 28 via the aluminum drum 20 and the conductor 29, and the high voltage from the power source 38 for transfer causes the contact 35 to pass. It will be applied to the aluminum drum 20 and the aluminum vapor deposition surface via the.

According to the above construction, as the transfer drum 15 rotates, the contact 35 slides on the ring-shaped metal plate 36 in an electrically contacting state, and a transfer voltage is applied to the transfer drum 15 from the transfer power source 38. As well as being surely applied, the contact 35 and the ring-shaped metal plate 36 serving as a counter contact are arranged inside the hollow drum 20, so that even if toner or the like is scattered in the machine due to a jam or the like, the contact portion is not contacted. There is no adhesion, and therefore no contact failure or sparking due to high voltage is eliminated. Further, since the high voltage lead wire 34 from the transfer power source 38 to the contact 35 passes through the inside of the fixed shaft 23, there is an advantage that noise from the lead wire 34 can be prevented.

FIG. 10 is a schematic sectional view showing a second embodiment of a transfer drum having a contact portion inside. In this embodiment, the high voltage from the transfer power source 38 is applied to the hollow aluminum drum 20 through the slip ring 39. Since the slip ring 39 is mounted between the fixed shaft 23 and the aluminum drum 20, The end of 20 on the side of the first flange 22 is a closed side wall 20a that is not opened, and a circular opening is formed in the center of this side wall 20a, and a slip ring 39 is attached to this opening. .. The high voltage lead wire 34 from the transfer power source 38 passes through the inside of the fixed shaft 23 as in the first embodiment, and is further connected to the slip ring 39 through the hole formed in the fixed shaft 23. Also in this embodiment, although not shown, the aluminum drum 20 is electrically connected to the aluminum deposition surface on the inner surface of the dielectric layer (see FIG. 8) through a suitable conductor.

According to the above structure, since the slip ring 39 is electrically connected to the aluminum drum 20, the high voltage from the power source 38 for transfer is high voltage lead wire 34.
And, it is surely applied to the aluminum drum 20 and the aluminum vapor deposition surface of the inner surface of the dielectric film through the slip ring 39. Of course, since the slip ring 39 is arranged inside the hollow drum 20, it is possible to prevent jamming. Even if toner or the like scatters inside the machine, it does not adhere to the contact portion of the slip ring 39, and therefore no contact failure or sparking due to high voltage is eliminated. Further, since the high voltage lead wire 34 from the transfer power source 38 to the slip ring 39 passes through the inside of the fixed shaft 23,
There are advantages similar to those of the first embodiment, such as noise from the lead wire 34 can be prevented.

Although the transfer drum 15 is configured to rotate around the fixed shaft 23 in the first and second embodiments, a rotary shaft is attached to the transfer drum 15 and the transfer drum 15 is rotated by the rotation of this rotary shaft. The present invention can be applied to the case where the above configuration is adopted. FIG. 11 shows a third embodiment of a transfer drum having such a contact portion inside.

Also in this embodiment, the rotary shaft 40 attached to the transfer drum 15 is formed in a hollow pipe shape.
The rotating shaft 40 is rotatably supported by a bearing 41. Also, the aluminum hollow drum 42
(Not shown) is electrically connected to the aluminum vapor deposition surface on the inner surface of the dielectric layer (see FIG. 8) through a suitable conductor. On the other hand, a bearing 46 is attached to the inner surface of one opening end of the rotating shaft 40, a rod-shaped contact fixing member 45 is inserted into the bearing 46, and the rear end portion is fixed, so that the contact fixing member 45 is fixed to the rotating shaft 40. On the contrary, fix it coaxially. At the rear end of the contact fixing member 45, a terminal for connecting the high voltage lead wire 34 from the power source 38 for transfer is provided. Further, the contact point 44 is attached to the tip of the contact point fixing member 45, and the contact point 44 is elastically pressed to the conductor plate, which is the counter contact point member fixed in the rotating shaft 40, which is the metal plate 43 in this embodiment. Contact. This metal plate 4
A part 43 a of the metal 3 extends to the inner surface of the aluminum drum 42 and is joined to the drum 42. Therefore, the metal plate 43 is also electrically connected to the aluminum deposition surface on the inner surface of the dielectric layer through the aluminum drum 42 and a conductor (not shown), and the high voltage from the transfer power source 38 causes the contact point 44 and the metal plate 43. Is applied to the aluminum drum 42 and the aluminum vapor deposition surface on the inner surface of the dielectric layer via.

In this embodiment, since the transfer drum 15 is rotated by the rotation of the rotary shaft 40, the first and second two flanges 47 and 48 made of an insulating material are attached to the openings at both ends of the aluminum drum 42. It is not necessary to integrally form a gear for driving on the outer peripheral surface of one side.

Also in this embodiment, since the contact point 44 and the metal plate 43 are arranged inside the rotary shaft 40, that is, inside the transfer drum 15, the same function and effect as those of the first and second embodiments are obtained. Is clearly obtained, and the description thereof is omitted. Further, in this embodiment, since the contact point 44 is located substantially at the center of the rotary shaft 40, there is an advantage that the durability of the sliding portion is further improved.

In the above embodiment, the case where the present invention is applied to the electrophotographic color laser beam printer has been described, but the present invention is applicable to other electrophotographic printers.
It is of course applicable to an image forming apparatus such as a copying machine, or an image forming apparatus such as a printer or a copying machine other than the electrophotographic system. Further, the configuration, shape, materials, etc. of the transfer drum and the contact portion can be variously modified and changed as required.

[0049]

As described above, according to the present invention, the elastic layer of the transfer material carrier has a compression amount of 0 to 2 mm at the transfer position and the total pressure in this range is 1 kg / mm or less. The contact pressure of the transfer material carrier can be kept constant, and the transfer can be performed without any void. In addition, it was possible to obtain a high-quality image with no image shift or color shift.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of one embodiment of a transfer device constructed in accordance with the present invention.

FIG. 2 is a sectional view of a color image forming apparatus which is an embodiment of the image forming apparatus according to the present invention.

FIG. 3 is a load characteristic diagram of a flexible urethane foam.

FIG. 4 is a load characteristic diagram of the elastic foam layer according to the present invention.

FIG. 5 is a sectional view of a color image forming apparatus that is another embodiment of the image forming apparatus according to the present invention.

FIG. 6 is a front view showing a relationship between a transfer drum and a photosensitive drum in still another embodiment of the image forming apparatus according to the present invention.

FIG. 7 is a perspective view of a conventional transfer drum.

FIG. 8 is a schematic cross-sectional view showing a first embodiment of a transfer drum having a contact portion inside.

9 is a schematic cross-sectional view showing an enlarged contact portion of the transfer drum of FIG.

FIG. 10 is a schematic cross-sectional view showing a main part of a transfer drum according to a second embodiment of the present invention.

FIG. 11 is a schematic sectional view showing a main part of a transfer drum according to a third embodiment of the present invention.

Claims (9)

[Claims] 1. An image carrier, an image forming means for forming a toner image on the image carrier, and a transfer material at the transfer position for transferring the toner image of the image carrier to the transfer material at the transfer position. In an image forming apparatus having a transfer material carrier to be carried, the transfer material carrier is provided with a dielectric layer on the surface thereof and an elastic layer provided inside the dielectric layer, and the elastic layer is An image forming apparatus characterized in that the compression amount at the transfer position is 0 to 2 mm and the total pressure is 1 kg / mm or less in this range. 2. The image forming apparatus according to claim 1, wherein the elastic layer is a foam. 3. The image forming apparatus according to claim 2, wherein the elastic layer is urethane foam. 4. The density of the elastic layer is 20 to 150 kg /
The image forming apparatus according to claim 1, wherein the image forming apparatus is m ³ . 5. The image forming apparatus according to claim 1, wherein the transfer material carrier has a conductive layer inside the dielectric layer, and power is supplied to the conductive layer. 6. The image forming apparatus according to claim 5, wherein the conductive layer is provided between the dielectric layer and the elastic layer. 7. The image forming apparatus according to claim 6, wherein the conductive layer is provided inside the elastic layer and supports the elastic layer. 8. The toner images of a plurality of colors can be formed on the carrier, and the plurality of toner images can be sequentially and multiple-transferred onto the transfer material carried on the transfer material carrier. Item 7. An image forming apparatus according to any one of items 1 to 7. 9. The image forming apparatus according to claim 8, wherein the apparatus is capable of forming a full-color image on a transfer material.