JPH0736291A - Color image forming device - Google Patents

Abstract

PURPOSE:To provide a color image forming device preventing leakage, even through high voltage bias is applied to an attracting roller and a destaticizing roller of a transferring device, and preventing the damage and firing of the transferring device component member, etc. CONSTITUTION:In the color image forming device, assuming that the width in a longitudinal direction of the dielectric layer 30c is W1, the width in the longitudinal direction of the elastic layer 30b is W2, the width in the longitudinal direction of the attracting roller 48 is W3, the width in the longitudinal direction of the destatisizing roller 43 is W4 and the length of the side of the transferring material P in parallel with the longitudinal direction of the transferring drum 30A is W5, they are set so as to satisfies the following relation, W1>W2>=(W3 or W4)>=W5. Thus, the leaking to the elastic layer 30b and the aluminum cylinder 30a having the low resistance value is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus for transferring a toner image of each color formed on an image bearing member onto a transfer material by a transfer device to obtain a color image, and particularly to the transfer device. Have.

[0002]

2. Description of the Related Art In a color image forming apparatus, a process of forming a toner image on an image carrier by charging, exposing, and developing, and transferring the toner image on a transfer material each time the toner image is formed is repeated for each color. There is a color image forming apparatus that obtains a color image by superposing toner images of a plurality of colors on a transfer material. A color image forming apparatus of this type is disclosed in, for example, Japanese Patent No. 2607727 and Japanese Patent Laid-Open No. 50-5093.
It is put into practical use by the configuration described in Japanese Patent Publication No. 5 or the like.

FIG. 7 is an overall configuration diagram showing an example of such a color image forming apparatus. In the figure, a photosensitive drum 1 as an image bearing member is arranged substantially in the center of the apparatus main body,
A primary charger 3, which is a roller charger, a rotary developing device 4 having a plurality of developing devices 4a, 4b, 4c, and 4d, a transfer device 10, and a cleaner 26 are arranged around the photosensitive drum 1. A laser diode 11, which constitutes an exposure device, a polygon mirror 13 rotated by a high-speed motor 12, a lens 14, and a folding mirror 15 are arranged above the photosensitive drum 1.

The photosensitive drum 1 is constructed by applying a photoconductor made of an organic photoconductor (OPC) to the outer peripheral surface of an aluminum cylinder having a diameter of 40 mm. The photoconductor may be amorphous Si, CdS, Se or the like. or,
The photosensitive drum 1 is 100 m by a driving means (not shown).
It is rotated in the direction of the arrow at a peripheral speed of m / s.

The rotary developing device 4 is provided with a developing device support 9 which rotates about a rotation center axis 9a, and the developing device support 9 allows the yellow developing device 4a, the magenta developing device 4b, the cyan developing device 4c and the black developing device 4 to be developed. The container 4d is supported. Further, the developing devices 4a, 4b, 4c, and 4d include yellow toner, magenta toner, and cyan toner, which are one-component developers,
Each contains black toner.

In each of the developing devices 4a, 4b, 4c and 4d,
As shown in FIG. 8, the opening surfaces 5a, 5b, 5c, 5d
Developing sleeve 8 as a developer carrying member
a, 8b, 8c and 8d are provided. Further, in the developing devices 4a, 4b, 4c and 4d, coating rollers 6a and 6a are provided.
b, 6c, 6d, and toner regulating members 7a, 7b, 7
c and 7d are provided. And the developing sleeve 8
With the rotation of a, 8b, 8c, and 8d, the coating roller 6a,
Toner is applied onto 6b, 6c and 6d, and the toner layer thickness is regulated by the toner regulating members 7a, 7b, 7c and 7d to impart triboelectric charge to the toner, and at the same time, the developing sleeves 8a, 8b and 8c, A thin toner layer is formed on 8d. The toner regulating members 7a, 7b, 7c, 7d
Is preferably a material that is charged opposite to the charging polarity of the toner,
Nylon or the like is preferable when the toner is negatively charged, and silicone rubber or the like is preferable when the toner is positively charged.

The developing sleeves 8a to 8d of the developing devices 4a to 4d, respectively.
The peripheral speed of 8d is 1.0 to the peripheral speed ratio with respect to the photosensitive drum 1.
It is preferable to select it so that the range is 2.0 times.
When the developing devices 4a to 4d face the photosensitive drum 1, the developing devices 4a to 4d are driven so that their opening surfaces 5a to 5d always face the photosensitive drum 1. The driving method of these developing devices 4a to 4d is as described in detail in JP-A-50-93437.

As shown in FIG. 7, the transfer device 10 includes a transfer drum 10A as a transfer material carrier, and the transfer drum 1
Around the 0, the static elimination charger 2, the suction roller 23, the static elimination roller 28, the separation claw 24, and the cleaner 27 are arranged. The transfer drum 10A has a gripper 22, which is a transfer material gripping member, at a proper position on the outer peripheral surface thereof. The transfer drum 10A is rotated in the arrow direction at substantially the same speed as the photosensitive drum 1 by a driving unit (not shown).

In the image forming apparatus having the above structure, first, the charger 3 is applied with a DC voltage of -700V and a frequency of 700H.
z, by applying a voltage obtained by superimposing an AC voltage of V _PP (peak-to-peak voltage) -1500 V, the charger 3 by which primary charging to about -700V surface of the photosensitive drum 1. Then
A signal in accordance with, for example, a yellow image pattern of the first color is input to the laser diode 11 to generate light of a yellow image pattern, and the photosensitive drum 1 is irradiated with the light through the optical path 16 to expose the photosensitive drum 1. An electrostatic latent image having a yellow image pattern with a light irradiation portion of about −100 V is formed on the surface. The electrostatic latent image of the yellow image pattern formed on the photosensitive drum 1 is developed by the yellow developing device 4a located in the developing unit facing the developing device 4 as the photosensitive drum 1 rotates, A first color yellow toner image is formed on the drum 1.

On the other hand, the transfer material in the transfer material cassette 17 is
The pickup roller 18 supplies the image to the transfer drum 10A of the transfer device 10 in synchronization with the image on the photosensitive drum 1. The transfer material supplied to the transfer drum 10A is gripped by the gripper 22 and is conveyed to the image transfer portion facing the photosensitive drum 1 by the rotation of the transfer drum 10A in the arrow direction. The yellow toner image on the photosensitive drum 1 is transferred to the transfer material conveyed to the image transfer portion by a transfer voltage applied between the transfer drum 10A and the photosensitive drum 1 from a power source (not shown).

At the same time as this transfer, charges are injected into the transfer material by the transfer voltage, and the transfer material is electrostatically adsorbed and held on the surface of the transfer drum 10A. Further, in general, in order to enhance the electrostatic attraction of the transfer material to the transfer drum 10a, the attraction roller 23 is provided near the transfer material feeding portion of the transfer drum 10A, and an attraction voltage is applied to the transfer roller. Gripper 22
After the gripping, the transfer material is configured to be electrostatically attracted to the transfer drum 10A.

After the transfer of the yellow toner image is completed, the photosensitive drum 1 is cleaned by a cleaner 26 having a cleaning member such as a fur brush or a blade to remove the residual toner on the surface, and then the primary charger 3 is used. An image forming process below the primary charging is performed.

Primary charging of the photosensitive drum 1 as described above, formation of an electrostatic latent image by exposure, formation of a toner image by development of the electrostatic latent image, superposition transfer of the obtained toner image onto a transfer material. Is also performed for magenta, cyan, and black for the second and subsequent colors, a color image obtained by superimposing and transferring toner images of four colors of yellow, magenta, cyan, and black on the transfer material can be obtained.

The transfer material on which the four color toner images have been transferred is then discharged by the discharging charger 2 arranged around the transfer drum 10A, and then the separation claw 24 on the downstream side thereof.
Thus, it is separated from the transfer drum 10A and sent to the fixing device 25. Then, the toner images of four colors are fixed by heating and pressurizing, the toner images are mixed and fixed to the transfer material, and a full-color permanent image is formed. Then, the toner images are discharged outside the image forming apparatus. Preferably, the residual toner on the surface of the transfer drum 10A from which the transfer material has been peeled off is cleaned by a cleaner 27 including a cleaning member such as a fur brush or a blade.

[0015]

Further, at the same time when the transfer material is separated from the transfer drum 10A by the separation claw 24, the charge eliminating roller 28 is brought into contact with the transfer drum 10A. As a result, the transfer drum 10A applies the AC bias 300 to the DC bias 0 ± 200 V applied to the charge eliminating roller 28.
The 0 V _PP frequency of 500 Hz is applied to remove the static electricity by the superimposed bias.

On the other hand, in preparation for the next image formation, when the transfer material starts to be conveyed from the transfer material cassette 17 by the pickup roller 18, the suction roller 23 is brought into contact with the transfer drum 10A almost at the same time and is applied to the suction roller 23. The transfer material is electrostatically adsorbed on and supported by the transfer drum 10A by the applied DC bias of -700 to -1000V.

The bias value used in the transfer device of the image forming apparatus according to this structure is as follows: transfer bias: 500V to 7KV (direct current) adsorption bias: -500V to 1.5KV (direct current) static elimination bias: AC2KV _{pp to} 5KV _PP , Frequency 5
00 Hz to 1 KHz (alternating current).

As shown in FIG. 9, a transfer drum 10A in the transfer device of the present color image forming apparatus has a 5 mm thick foamed elastic layer 10b mounted on a 5 mm thick aluminum cylinder 10a, and further, the A dielectric layer 10c made of a polyvinylidene fluoride (PVdF) film having a thickness of 75 μm is coated on the top.

By the way, as shown in FIG. 10, the longitudinal width W1 of the dielectric layer 10c is the longitudinal width W2 of the elastic foam layer 10b, and the longitudinal width W4 of the charge eliminating roller 28 is
When the width W3 of the suction roller 23 in the longitudinal direction is equal to or smaller than the width W3, that is, when W1 ≦ W2, W3, and W4, when a high-voltage bias is applied to the suction roller 23 and the static elimination roller 28, the elastic foam layer 10b. The electrical resistance value of 1 is as low as a volume resistance value of 1 × 10 ⁶ Ω · cm or less, and in particular, a leak may occur at the end of the aluminum cylinder 10a.

In order to prevent such a leak,
As shown in FIG. 11, even if the flange portions 10d formed at both ends of the aluminum cylinder 10a are made of a high resistance material such as a plastic resin, the width W1 of the dielectric layer 10c is different from that of the other case, as described above. If it is equal to or less than that of the member, the electrical resistance value of the elastic foam layer 10b is not high (especially, the resistance value is low under high humidity), and similarly, leakage may occur. When a leak occurs, a large current locally flows, which causes problems such as damage to the transfer device constituent members or ignition.

Therefore, an object of the present invention is to provide a color image forming apparatus in which leakage is prevented and damages to the transfer device constituent members and the like are prevented, even if a high voltage bias is applied to the attraction roller and the static elimination roller. Is.

[0022]

The above object can be achieved by a color image forming apparatus according to the present invention. In summary, the present invention comprises a transfer device for sequentially superposing and transferring the toner images of the respective colors sequentially formed on the image carrier onto the transfer material carried on the transfer material carrier. Has a conductive cylindrical member, an elastic layer provided on the cylindrical member, and a dielectric layer provided on the elastic layer, and further electrostatically attracts a transfer material onto the transfer material carrier. In a longitudinal direction of the dielectric layer, in a color image forming apparatus having a suction roller for discharging and a discharging roller for discharging the transfer material carrier after the transfer material is separated from the transfer material carrier. A width W1, a longitudinal width W2 of the elastic layer, a longitudinal width W3 of the suction roller, a static elimination roller longitudinal width W4, and a transfer material in the longitudinal direction of the transfer material carrier. Between parallel side sizes W5 W1> W2 ≧ (W3 or W4) The color image forming apparatus has a relationship of ≧ W5.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. In the embodiment described below, the color image forming apparatus of the present invention is embodied in the color image forming apparatus shown in FIG. Therefore, detailed description of the overall configuration and functions of the color image forming apparatus will be omitted.

Embodiment 1 A first embodiment of a color image forming apparatus according to the present invention will be described with reference to FIGS. As shown schematically in FIG. 2, the transfer device of the present color image forming apparatus includes a transfer material around a transfer drum 30A, which is a transfer material supporting means, which is arranged so as to face the photosensitive drum 1 which is an image carrier. A static elimination roller 43 that neutralizes and electrically initializes the transfer drum 30A after P separation, a suction roller 48 that applies an initial suction force to the transfer drum 30A, and a transfer material P after transfer is separated from the transfer drum 30A. A separating device 44 is provided.

In the transfer drum 30A, an elastic layer 30b made of foamed rubber is fitted on an aluminum cylinder 30a, and further, a polyvinylidene fluoride (PVd) having a thickness of 75 μm is formed thereon.
F) It is configured to cover the dielectric layer 30c of the film.

In this embodiment, as schematically shown in FIG. 1, the transfer device constituting member is composed of a dielectric layer 30c having a longitudinal width W1 = 232 mm and an elastic layer 30b having a longitudinal width W.
2 = 228 mm, the longitudinal width W3 of the suction roller 48 =
224 mm, the width W4 in the longitudinal direction of the static elimination roller 43 = 22
The size of the side of the transfer material P parallel to the longitudinal direction of the transfer drum 30A was W5 = 210 mm.

That is, the size W5 of the side of the transfer material P and the widths W1, W2, W3 and W4 of the above-mentioned constituent members of the transfer device.
The relationship between them is W1>W2> (W3 or W4)> W5 ....

In the transfer device constructed as described above, as shown in FIG. 2, the transfer material P supplied from the transfer material cassette 50 to the transfer drum 30A is given an initial suction force by the suction roller 48, The transfer drum 30A is electrostatically adsorbed. At the time of this suction, the suction roller 4
The bias value applied to 8 is -700V.
As shown in FIG. 5, the electric field shielding effect of the dielectric layer 30c of the PVdF film and the above width relation cause the adsorption roller 48 to move to the conductive elastic layer 30b (volume resistance value 1 × 10 ^6).
Ω · cm or less) or leakage to the aluminum cylinder 30a can be prevented.

Further, after the toner image on the photosensitive drum 1 is transferred to the transfer material P, the transfer material P is separated from the transfer drum 30A by the separating device 44 and discharged. After that, the charge eliminating roller 43 is brought into contact with the dielectric layer 30c on the surface of the transfer drum 30A, and the charge of the dielectric layer 30c is eliminated. At this time, the bias value applied to the charge eliminating roller 43 has a frequency of 7
00 Hz, AC bias 3 KV _PP , but as shown in FIG. 4, the resistance value is low due to the electric field shielding effect by the dielectric layer 30c of the PVdF film and the above width relationship.
Conductive elastic layer 30b or aluminum cylinder 30
It is possible to prevent the leak to a.

By setting the width W1 of the dielectric layer 30c to be larger, the attraction roller 48 or the static elimination roller 4
3 can prevent a large current from leaking to the conductive elastic layer 30b or the aluminum cylinder 30a having a low resistance value, and in particular, can prevent a large current from leaking from the end faces of both rollers.

By configuring the transfer device as described above, the following effects can be obtained in addition to the prevention of leakage.

Since the width W3 of the suction roller 48 and the width W4 of the static elimination roller 43 are larger than the width W5 of the transfer material P, the transfer material P is attracted to the transfer drum 30A and transferred to the transfer drum 30.
The static elimination of A can be reliably performed. Thereby, a good image can be obtained.

Further, since the width W2 of the elastic layer 30b is larger than the width W3 of the suction roller 48 and the width W4 of the static elimination roller 43, the suction roller 48 and the static elimination roller 43 are surely attached to the transfer drum 30A in the longitudinal direction thereof. Can be contacted. Therefore, the suction of the suction roller 48 to the transfer drum 30A and the static elimination of the transfer drum 30A by the static elimination roller 43 can be performed uniformly, and a good image without image unevenness can be obtained.

Second Embodiment Next, a second embodiment of the color image forming apparatus according to the present invention will be described with reference to FIG. The description of the present embodiment will be made only for the transfer device which is a characteristic part of the present invention.

In this embodiment, as described with reference to FIG. 11, the transfer drum 30A is formed by fixing the flange portions 30d made of a high resistance material such as plastic resin to both ends of the aluminum cylinder 30a. Further, the longitudinal width W1 of the dielectric layer 30c, the longitudinal width W2 of the elastic layer 30b, the longitudinal width W3 of the suction roller 48,
Of the width W4 in the longitudinal direction of the charge eliminating roller 43 and the transfer material P,
The relationship between the sizes W1 of the sides parallel to the longitudinal direction of the transfer drum 30A is W1> W2 = W3 = W4 = W5 ... As schematically shown in FIG.

The specific dimensions of the dielectric layer 30c are W1 = 217 mm in the longitudinal direction, W2 = 210 to 212 mm in the longitudinal direction of the elastic layer 30b, and W3 = 210 in the longitudinal direction of the suction roller 48. ~ 212mm, static elimination roller 4
3, width W4 in the longitudinal direction = 210 to 212 mm, transfer material P
The width W5 was set to 210 mm.

As described above, the width W1 in the longitudinal direction of the dielectric layer 30c is set to the widths W2, W3 of the above-mentioned constituent members of the transfer device.
Since the width is larger than W4 and the width W5 of the transfer material, it is possible to prevent the leak from the attraction roller 48 or the static elimination roller 43 to the conductive elastic body layer 30b or the aluminum cylinder 30a having a low resistance value.

Further, the width W2 in the longitudinal direction of each of the conductive elastic layer 30b, the suction roller 48, and the static elimination roller 43,
By setting W3 and W4 to be substantially uniform in accordance with the width W5 of the transfer material P, it is possible to reduce the size of the apparatus main body in these width directions.

Third Embodiment Next, a third embodiment of the color image forming apparatus according to the present invention will be described with reference to FIG. The description of the present embodiment will be made only for the transfer device which is a characteristic part of the present invention.

In this embodiment, the transfer drum 30A
Is formed by fixing flange portions 30d made of a high resistance material such as a plastic resin to both ends of a metal cylinder 30a made of a metal pipe such as aluminum or stainless steel, and a circumferential end of the dielectric layer 30e in a radius direction. It was bent inward in the direction so as to cover the end portion in the longitudinal direction of the elastic layer 30b.

Further, the width W of the dielectric layer 30e in the longitudinal direction is
1, the longitudinal width W2 of the elastic layer 30b, the suction roller 4
The width W3 in the longitudinal direction of No. 8, the width W4 in the longitudinal direction of the charge eliminating roller 43, and the size W5 of the side of the transfer material P parallel to the longitudinal direction of the transfer drum 30A are W1>W2> ( W3 or W4)> W5 ...

Further, in this embodiment, the dielectric layer 30 is used.
e is formed of a PVdF sheet of 75 μm, and the metal cylinder 30a and the elastic layer 30b (volume resistance value 1 × 10 ⁶ Ω · c
m or less) is integrally combined.

As described above, by constructing the transfer device of this embodiment, the suction roller 48 has a range of -700V to -10V.
Applying a DC bias of 00V to the static elimination roller 43 for 3K
Even if an AC bias of V _{PP to 5} KV _PP is applied,
The dielectric layer 30e made of a high resistance PVdF sheet and the flange portion 30d made of a high resistance resin can prevent leakage to the elastic layer 30b which is a low resistance member and the metal cylinder 30a.

[0044]

As is apparent from the above description, in the color image forming apparatus according to the present invention, the transfer device includes the longitudinal width W1 of the dielectric layer, the longitudinal width W2 of the elastic layer, and the suction roller. Between the width W3 in the longitudinal direction, the width W4 in the longitudinal direction of the discharging roller, and the size W5 of the side of the transfer material parallel to the longitudinal direction of the transfer material carrier, W1> W2 ≧ (W3 or W4) ≧ With the configuration having the relationship of W5, even if a high-voltage bias is applied to the transfer material carrier from the attraction roller or the static eliminator roller, leakage is prevented, and the disadvantages such as damage to the transfer device constituent members, ignition, etc. Can be prevented.

Further, with the above structure, the transfer material can be surely adsorbed by the adsorbing roller, and the charge on the surface of the dielectric layer can be surely removed by the charge removing roller.

Further, since such adsorption and static elimination can be performed uniformly on the transfer material carrier, a clear image without unevenness in light and shade can be obtained.

Further, by setting the widths of the conductive elastic layer, the attraction roller, and the static elimination roller in the longitudinal direction to be substantially uniform according to the width of the transfer material, it is possible to reduce the size of the apparatus main body in these width directions. Can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a characteristic part of a first embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a schematic sectional view of the transfer device shown in FIG.

3 is an explanatory view of a main part including a suction roller of FIG.

FIG. 4 is an explanatory view of a main part including a charge eliminating roller of FIG.

FIG. 5 is a schematic sectional view of a transfer device according to a second embodiment.

FIG. 6 is a schematic sectional view of a transfer device according to a third embodiment.

FIG. 7 is an overall configuration diagram showing a conventional color image forming apparatus.

8 is a configuration diagram showing the developing device of FIG. 7. FIG.

9 is a cross-sectional view taken along line AA of FIG. 10 showing the transfer device of FIG.

10 is a longitudinal cross-sectional view of the transfer device of FIG.

FIG. 11 is a sectional view similar to FIG. 10, showing another conventional transfer device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 30A Transfer drum (transfer material carrier) 30a Aluminum cylinder (conductive cylindrical member) 30b Elastic layer 30c Dielectric layer 48 Adsorption roller 43 Static elimination roller P Transfer material

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Toshiaki Miyashiro 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takehiko Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (1)

[Claims] 1. A transfer device for sequentially superposing and transferring a toner image of each color formed on an image carrier onto a transfer material carried on a transfer material carrier, wherein the transfer material carrier is electrically conductive. A cylindrical member, and an elastic layer provided on the cylindrical member,
A suction roller for electrostatically adsorbing the transfer material onto the transfer material carrier, and a dielectric material layer provided on the elastic material layer, and after the transfer material is separated from the transfer material carrier. A static elimination roller for eliminating static electricity from the transfer material carrier, a longitudinal width W1 of the dielectric layer, a longitudinal width W2 of the elastic layer, and a longitudinal direction of the suction roller. Width W3, the width W4 in the longitudinal direction of the static elimination roller, and the size W5 of the side of the transfer material parallel to the longitudinal direction of the transfer material carrier.
A color image forming apparatus having a relationship of W1> W2 ≧ (W3 or W4) ≧ W5.