JP2000352882A - Image forming device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To simplify the configuration of an image forming apparatus. SOLUTION: A base of an intermediate transfer drum 5 is formed of a rigid iron cylindrical member. The substrate is induction-heated by the excitation coil 11 to transfer and fix the toner image onto the transfer material P at the same time. Since the transfer and the fixing can be performed simultaneously, the configuration of the image forming apparatus can be simplified. In addition, since the required portion can be locally heated by the exciting coil 11 instead of heating the entire intermediate transfer drum 5 at the time of simultaneous transfer fixing, the thermal efficiency can be improved. Further, since the intermediate transfer drum 5 has rigidity, a sufficiently large pressure load can be generated by bringing the pressure roller 8 into contact with the intermediate transfer drum 5, so that the fixing performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine and a laser printer.

[0002]

2. Description of the Related Art An electrophotographic full-color image forming apparatus using an intermediate transfer member is known.

In this image forming apparatus, the process of primary transfer of a toner image formed on a photosensitive drum by primary charging, exposure and development onto an intermediate transfer member is repeated for four color toner images, and the process is repeated on the intermediate transfer member. The four color toner images are sequentially superimposed. Subsequently, these toner images are conveyed to the secondary transfer section by rotation of the intermediate transfer member. The secondary transfer unit is configured such that the intermediate transfer member is sandwiched between the secondary transfer roller and the secondary transfer opposing roller disposed on the front and back of the intermediate transfer member. The four-color toner images conveyed to the secondary transfer unit are pressed and secondarily transferred from the intermediate transfer body to the transfer material. The secondary-transferred toner images are conveyed by a fixing nip between a fixing roller and a pressure roller, which rotate while being pressed against each other, and are heated and pressed to be melted and fixed on the transfer material and fixed. You. Thus, the image formation ends.

In order to simplify the image forming process and the structure of the image forming apparatus, a belt-shaped intermediate transfer member (intermediate transfer belt) or an intermediate transfer member (intermediate transfer drum) made of a rigid material is used. There has also been proposed an image forming apparatus that performs so-called simultaneous transfer fixing by performing the above-described secondary transfer and fixing simultaneously.

[0005]

However, in the image forming apparatus which performs the above-described simultaneous transfer fixing, heat applied to the transfer material during the simultaneous transfer fixing is accumulated in the intermediate transfer member. The heat accumulated in the intermediate transfer member is gradually transmitted to the photosensitive drum arranged in contact with the intermediate transfer member, and causes the temperature of the photosensitive drum to rise. Then, when the temperature of the photosensitive drum rises, there is a problem that the charging characteristic of the photosensitive drum changes and image quality is deteriorated.

Further, when a belt-shaped intermediate transfer belt is used as the intermediate transfer member, the pressure load cannot be increased at the time of simultaneous fixing of the transfer, so that there is a problem that the fixing performance tends to decrease. On the other hand, when an intermediate transfer drum made of a rigid material is used as the intermediate transfer body, a halogen lamp may be used as a heat source for applying heat for fusing and fixing the toner to the transfer material during simultaneous transfer fixing. There was a problem that the whole was heated and efficiency was poor.

The present invention has been made in view of the above circumstances, and has as its object to provide an image forming apparatus which prevents deterioration of an image due to a change in charging characteristics of an image carrier. .

It is another object of the present invention to increase the pressure load during simultaneous transfer fixing to prevent a decrease in fixing performance, and to improve the thermal efficiency during simultaneous transfer fixing.

[0009]

According to a first aspect of the present invention, there is provided a first image bearing member rotatable, and a primary transfer member abutting on the first image bearing member. A second rotatable image carrier that forms a unit, and a pressure member that abuts on the second image carrier to form a transfer fixing unit;
After the toner image formed on the first image carrier is transferred to the second image carrier in the primary transfer section, the second image carrier is transferred to the second image carrier.
In the image forming apparatus for simultaneously transferring and fixing the toner image on the image carrier to the transfer material in the transfer and fixing section, the second image carrier is provided with a resin layer on the surface of an endless base made of magnetic metal. And an excitation coil is disposed in the vicinity of the transfer fixing unit and in close proximity to the inner surface of the base, and the excitation coil generates an induced current in the base to generate heat. .

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the base of the second image bearing member is a rigid iron cylindrical member. .

According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, a transfer bias power supply for applying a transfer bias to the pressing member is provided.

According to a fourth aspect of the present invention, there is provided the first and second aspects.
In the image forming apparatus of (3), cooling for cooling the surface of the second image carrier on the downstream side of the transfer fixing unit in the rotation direction of the second image carrier and on the upstream side of the primary transfer unit. Having a device.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the cooling device is a cooling fan that blows air onto the surface of the second image carrier.

According to a sixth aspect of the present invention, there is provided the first and second aspects.
3. The image forming apparatus according to 3, 4, or 5, wherein the first image carrier is an amorphous silicon photoconductor.

[0015]

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

Embodiment 1 FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG.
This is a four-color full-color electrophotographic image forming apparatus using an intermediate transfer drum (intermediate transfer member) as a second image carrier. Further, the image forming apparatus is an image forming apparatus that performs so-called simultaneous transfer and fixing, in which secondary transfer and fixing of a toner image are performed simultaneously. FIG. 1 is a diagram schematically illustrating a longitudinal section of the image forming apparatus.

First, an outline of the configuration and operation of the entire image forming apparatus will be described.

The image forming apparatus shown in FIG. 1 includes a drum type electrophotographic photosensitive member (hereinafter, referred to as "photosensitive drum") 1 as a first image carrier. The photosensitive drum 1 is driven to rotate at a predetermined peripheral speed (process speed) in the direction of arrow R1 by a driving unit (not shown). The photosensitive drum 1 will be described later in detail.

The surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential by a charging roller 2 as a charging device.

The surface of the charged photosensitive drum 1 is subjected to a scanning exposure (image exposure) by a laser beam 3 from an exposure device whose ON / OFF is controlled in accordance with the first image information, thereby obtaining a first electrostatic image. A latent image is formed.

The electrostatic latent image thus formed is developed with a toner by a developing device 4 as a toner image. The developing device 4 includes a first developing device 4a containing yellow toner as the first color toner, a second developing device 4b containing magenta toner as the second color toner, and cyan as the third color toner. The third developing device 4c containing the toner and the fourth developing device 4d containing the black toner as the fourth color toner are integrated. First, the first electrostatic latent image is developed as a yellow toner image by attaching the yellow toner by the first developing device 4a. As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used, and a combination of image exposure and reversal developing is often used.

The developed first (yellow) toner image is transferred to a primary transfer section 6a formed between an intermediate transfer drum (intermediate transfer member) 5 as a second image carrier and the photosensitive drum 1. Is transferred from the photosensitive drum 1 to the surface of the intermediate transfer drum 5. In the primary transfer section 6a, the intermediate transfer drum 5
The intermediate transfer drum 5 is pressed against the photosensitive drum 1 with a predetermined load by a pressurizing unit (not shown) in order to contact the photosensitive drum 1 with the surface of the photosensitive drum 1. The intermediate transfer drum 5 has a circumference slightly longer than a transfer material such as paper on which a color image is finally formed, and the toner image formed on the photosensitive drum 1 When a voltage having a polarity opposite to the charging polarity of the toner is applied by a transfer bias power supply (high-voltage power supply) 9, primary transfer is electrostatically performed on the surface of the intermediate transfer drum 5. The above-described transfer bias power supply 9 can perform both constant current control and constant voltage control. In this embodiment, the transfer bias power supply 9
To apply a constant current controlled DC bias to a predetermined 1 to 10 μA (preferably 3 μA). Then, a small amount of toner remaining on the surface of the photosensitive drum 1 after the completion of the primary transfer is removed by the cleaning device 7a.

The above-described series of image forming processes, that is, each of the image forming processes of charging, exposure, development, primary transfer, and cleaning is repeated for the remaining three colors, that is, magenta, cyan, and black toners. Above, the four color toner images of yellow, magenta, cyan, and black are superimposed.

Thereafter, the pressing roller 8 (pressing member) as a simultaneous transfer fixing means which is movable in the direction of arrow K8 and is separated from the surface of the intermediate transfer drum 5 with a predetermined pressure is applied to the surface of the intermediate transfer drum 5 with a predetermined pressure. And is driven to rotate (or drive to rotate). At the same time, the intermediate transfer drum 5
A current is supplied from a high-frequency power supply 12 to an exciting coil 11 disposed close to and along the inner surface of the base 5a (see FIG. 2), whereby the intermediate transfer drum 5 is heated. At this time, the surface temperature of the intermediate transfer drum 5 is
And a high-frequency power supply 1 according to the detection signal.
A current of 2 to 300 to 1000 W is supplied, and the surface temperature of the intermediate transfer drum 5 in the transfer fixing section 6b is 100 ° C.
The power is controlled so that And the intermediate transfer drum 5
The upper four color toner images are transferred and fixed in the transfer fixing section 6 in the direction of arrow Kp.
b, the toner image is secondarily transferred collectively to the surface of the transfer material P conveyed at a predetermined timing. As a result, a full-color permanent image of four colors is formed and discharged to the outside of the image forming apparatus main body. Note that a small amount of toner remaining on the surface of the intermediate transfer drum 5 after the completion of the secondary transfer is removed by the cleaning device 7b movable in the direction of arrow K7 coming into contact with the surface of the intermediate transfer drum 5 at a predetermined timing.

FIG. 2 is an enlarged vertical sectional view of the photosensitive drum 1, the intermediate transfer drum 5, and the pressure roller 8. However, the photosensitive drum 1 and the intermediate transfer drum 5 show a part thereof.

The photosensitive drum 1 is configured by providing a photoconductive layer 1b made of amorphous silicon on the outer peripheral surface of a cylindrical aluminum base 1a. The entire photosensitive drum 1 has an outer diameter of 30 mm and is driven to rotate at a peripheral speed of 90 mm / sec in the direction of arrow R1 by driving means (not shown).

The intermediate transfer drum 5 is formed by providing an elastic resistance layer (resin layer) 5b on the outer peripheral surface (surface) of a cylindrical iron (magnetic metal) base 5a having a thickness of 1 mm. The elastic resistance layer 5b has a resistance value of 10 ⁵ to 1 by dispersing carbon as conductive particles in silicone rubber.
It is adjusted to 0 ¹⁰ Ω · cm and the thickness is 1 mm. The entire intermediate transfer drum 5 has an outer diameter of 100 mm and a hardness of 4
5 ° (JIS A). Intermediate transfer drum 5
Is pressed against the photosensitive drum 1 at a total pressure of 500 g by a pressing means (not shown), and is driven to rotate in the direction of arrow R5 at substantially the same peripheral speed as the photosensitive drum 1. The intermediate transfer drum 5 generates an induced current when the excitation coil 11 is energized by the high frequency power supply 12 and generates heat.

The pressure roller 8 has a 5 mm-thick silicone rubber elastic layer 8 on an iron core 8 a having an outer diameter of 15 mm.
b. The surface of the pressure roller 8 is covered with a 50 μm-thick PFA tube in order to enhance the releasability. The pressure roller 8 as a whole has an outer diameter of 25 mm and a hardness of 45 ° (Asker C). The pressure roller 8 is disposed so as to be movable in the direction of arrow K8 in FIG.
As a result, the toner is pressed against the surface of the intermediate transfer drum 5 with a total pressure of 15 kg, and is driven (rotated) at a peripheral speed substantially equal to the peripheral speed of the intermediate transfer drum 5. When the pressure roller 8 comes into contact with the intermediate transfer drum 5, a transfer fixing section 6b is formed between them.

As described above, in the present embodiment, the substrate 5a formed of a magnetic metal on the inner surface of the intermediate transfer drum 5 is induction-heated, and the toner image is transferred and fixed onto the transfer material P at the same time. The final image can be obtained by the image forming process and the image forming apparatus having a simple configuration. That is, an inexpensive image forming apparatus can be provided.

Further, since the intermediate transfer drum 5 having a rigid base 5a is used as the intermediate transfer member, the pressure roller 4 is brought into contact with the intermediate transfer drum 5 to generate a sufficiently large pressure load. Therefore, the fixing performance can be improved.

Further, since the required portion can be locally heated by the exciting coil 11 instead of heating the entire intermediate transfer drum 5 at the time of simultaneous transfer fixing, the thermal efficiency can be improved.

<Second Embodiment> FIG. 3 shows a second embodiment. In the present embodiment, in addition to the configuration of the first embodiment, the transfer bias power supply 9 is further connected to the pressing roller 14 as a pressing member, and the secondary transfer is performed on the pressing roller 14 at the time of simultaneous transfer fixing. A bias is applied.
Note that the process up to the primary transfer is the same as that of the first embodiment, and thus the description thereof is omitted.

FIG. 4 is an enlarged vertical sectional view of the photosensitive drum 1, the intermediate transfer drum 5, and the pressure roller 14. However, the photosensitive drum 1 and the intermediate transfer drum 5 show a part thereof.

As shown in FIG. 4, the pressure roller 14 is constituted by providing a conductive elastic layer 14b on a core metal 14a made of iron having an outer diameter of 15 mm. Conductive elastic layer 14b
Is formed by foaming EPDM in which carbon as conductive particles is dispersed and the resistance value is adjusted to 10 ⁷ to 10 ¹⁰ Ω · cm. The pressure roller 14 has an outer diameter of 25 mm and a hardness of 45 ° (Asker C) as a whole, and is arranged to be movable in the direction of arrow K14. The pressure roller 14 is pressed against the surface of the intermediate transfer drum 5 with a total pressure of 15 kg by a pressure means (not shown) at a predetermined timing, and is driven to rotate (or rotate) at a peripheral speed substantially equal to the peripheral speed of the intermediate transfer drum 5. Drive rotation).

When the transfer material P is conveyed to the transfer fixing section 6b at a predetermined timing, the core metal 14a of the pressure roller 14
A predetermined secondary transfer bias is applied by the transfer bias power supply 9. As a result, the four color toner images on the intermediate transfer drum 5 are collectively secondary-transferred onto the transfer material P, and are simultaneously heated and pressed to be fixed. The permanent image obtained by this fixing is discharged outside the image forming apparatus main body. The secondary transfer bias is controlled at a constant voltage.

As described above, in the present embodiment, the toner image on the intermediate transfer drum 5 is transferred with high transfer efficiency by applying the secondary transfer bias to the pressure roller 14 at the time of simultaneous transfer fixing. And can be fixed simultaneously.

Third Embodiment FIG. 5 shows a third embodiment. In the present embodiment, in addition to the configuration of the first embodiment, the rotation direction of the intermediate transfer drum 5 (arrow R5
The cooling device 15 is disposed downstream of the transfer fixing unit 6b (in the direction) and upstream of the cleaning device 7b. Note that the steps up to the simultaneous transfer fixing are the same as those in the first embodiment, and thus the description thereof is omitted.

As described above, the temperature of the heated portion on the surface of the intermediate transfer drum 5 is controlled to 100 ° C. during the simultaneous transfer fixing, but even after the simultaneous transfer fixing, the intermediate transfer drum 5 is heated. Surface temperature does not drop easily. In this state, when the heated portion of the intermediate transfer drum 5 reaches the photosensitive drum 1, the photosensitive drum 1 is in contact with the intermediate transfer drum 5, so that the heated temperature of the photosensitive drum 1 is increased by the heated portion of the intermediate transfer drum 5. . Since the charging characteristics of the photosensitive drum 1 change when the temperature is increased, the image quality may be reduced. Therefore, it is desirable that the surface of the intermediate transfer drum 5 after the transfer and fixing is not so hot.

Therefore, in the present embodiment, the transfer fixing unit 6
b, after the simultaneous transfer fixing is performed, the cleaning device 7b
Before the cleaning is performed, the intermediate transfer drum 5 is cooled by the cooling device 15. As the cooling device 15, for example, a cooling fan can be used. Air is blown onto the surface of the photosensitive drum 5 by a cooling fan, thereby cooling the surface of the intermediate transfer drum 5.

As described above, in the present embodiment, by cooling the surface of the intermediate transfer drum 5 after the simultaneous transfer and fixing, the temperature of the photosensitive drum 1 in contact with the intermediate transfer drum 5 is prevented from rising, and The image quality is prevented from deteriorating due to a change in charging characteristics caused by the temperature rise of the drum 1.

[0041]

As described above, according to the present invention,
An image forming apparatus having a simple image forming process and a simple structure by inductively heating a magnetic metal constituting a base of a second image carrier by an exciting coil and transferring and fixing a toner image on a transfer material at the same time. To obtain the final image. That is, an inexpensive image forming apparatus can be provided.

Further, since an iron member having a rigid body is used as the intermediate transfer member, a sufficiently large pressing load can be generated by bringing the pressing member into contact with the intermediate transfer member. Performance can be improved.

Further, since the required portion can be locally heated by the exciting coil instead of heating the entire intermediate transfer member at the time of simultaneous transfer fixing, the thermal efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is an enlarged longitudinal sectional view illustrating a schematic configuration of a photosensitive drum, an intermediate transfer drum, and a pressure roller according to the first embodiment.

FIG. 3 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a second embodiment.

FIG. 4 is an enlarged longitudinal sectional view illustrating a schematic configuration of a photosensitive drum, an intermediate transfer drum, and a pressure roller according to a second embodiment.

FIG. 5 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st image carrier (photosensitive drum) 5 2nd image carrier (intermediate transfer drum) 5a Substrate 5b Resin layer (elastic resistance layer) 6a Primary transfer part 6b Transfer fixing part 8,14 Pressure member (Pressure) Roller) 9 Transfer bias power supply 11 Excitation coil 15 Cooling device (Cooling fan) P Transfer material

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H032 AA05 AA14 BA05 BA08 BA16 BA19 BA21 BA23 BA30 2H033 AA02 BA08 BA10 BA25 BA26 BA29 BA30 BB02 BB13 BB14 BB19 BB21 BB22 BB34 BD01 BE06 BE09 2H078 AA11 CC06 DD53 DD29 DD29 DD29

Claims (6)

[Claims] A first rotatable image carrier; and a first rotatable image carrier.
A rotatable second image carrier abutting on the image carrier to form a primary transfer portion, and a pressure member abutting on the second image carrier to form a transfer fixing portion Transferring the toner image formed on the first image carrier to the second image carrier in the primary transfer unit, and then transferring the toner image on the second image carrier to the transfer fixing unit. In the image forming apparatus, the second image carrier is formed by providing a resin layer on a surface of an endless base made of a magnetic metal, and in the vicinity of the transfer fixing unit, An image forming apparatus, further comprising: an excitation coil disposed close to an inner surface of the base, wherein the excitation coil generates an induced current in the base to generate heat. 2. The image forming apparatus according to claim 1, wherein the base of the second image bearing member is a rigid iron-made cylindrical member. 3. The image forming apparatus according to claim 1, further comprising a transfer bias power supply for applying a transfer bias to the pressing member. 4. A cooling device for cooling the surface of the second image carrier at a position downstream of the transfer fixing unit with respect to a rotation direction of the second image carrier and upstream of the primary transfer unit. The image forming apparatus according to claim 1, 2 or 3, wherein: 5. The image forming apparatus according to claim 4, wherein the cooling device is a cooling fan that blows air onto the surface of the second image carrier. 6. The image forming apparatus according to claim 1, wherein the first image carrier is an amorphous silicon photoreceptor.