JP2000352879A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify constitution of an image forming device. SOLUTION: Relating to this device, a toner image is simultaneously transferred and fixed to a transfer material P by carrying out induction heating of magnetic metal constituting a substrate of an intermediate transfer belt 5 with an exciting coil 11. Since transferring and fixing are carried out simultaneously the image forming process is simplified and the constitution of the image forming device can be simplified. Furthermore, temperature of the intermediate transfer belt 5c can be instantly risen to the temperature necessary for fixing since its heat capacity is small. Therefore, 'on demand' can be realized. Moreover, the rise in temperature of a photoreceptor 1 that is installed in contact with the intermediate transfer belt 5 can be kept down because the temperature of the intermediate transfer drum 5 whose temperature was risen once can be easily lowered due to its small heat capacity and therefore deterioration of image definition resulting from any change in electrified characteristic caused by the rise in temperature of the photoreceptor drum 1 can be prevented.

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.

Further, for the purpose of simplifying the image forming process and simplifying the configuration of the image forming apparatus, an image forming apparatus that performs so-called simultaneous transfer and fixing, in which the above-described secondary transfer and fixing are performed simultaneously, has also been proposed. I have.

[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.

SUMMARY OF THE INVENTION 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. .

[0007]

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 an endless belt made of nickel.

[0009] The present invention according to claim 3 is the invention according to claim 1 or 2.
And a transfer bias power supply for applying a transfer bias to the pressing member.

[0010] The present invention according to claim 4 is based on claims 1 and 2,
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.

[0012]

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

<First Embodiment> 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 belt (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 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 drive roller 14 and a tension roller 15 by an intermediate transfer belt (intermediate transfer member) 5 as a second image carrier, and a photosensitive drum. In the primary transfer portion 6 a formed between the photosensitive drum 1 and the photosensitive drum 1, the toner image is transferred onto the surface of the intermediate transfer belt 5. In the primary transfer section 6a, the intermediate transfer belt 5 is pressed against the photosensitive drum 1 with a predetermined load by the primary transfer roller 16 from the inside of the intermediate transfer belt 5 in order to contact the transfer belt 5 with the surface of the photosensitive drum 1. I have. The intermediate transfer belt 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 belt 5. The transfer bias power supply 9 can perform both constant current control and constant voltage control. In this embodiment, the transfer bias power supply 9 controls the intermediate transfer belt 5 to a predetermined 1 to 10 μA (preferably 3 μA). Apply a constant current controlled DC bias. 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 magenta, cyan, and black toners. The magenta, cyan, and black toner images are superimposed.

Thereafter, a 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 belt 5 with a predetermined pressure is applied to the surface of the intermediate transfer belt 5 with a predetermined pressure. And is driven to rotate (or drive to rotate). At the same time, the intermediate transfer belt 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 belt 5 is heated. At this time, the surface temperature of the intermediate transfer belt 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 belt 5 in the transfer fixing section 6b is 100 ° C.
The power is controlled so that And the intermediate transfer belt 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. It should be noted that a small amount of toner remaining on the surface of the intermediate transfer belt 5 after the completion of the secondary transfer is removed by the cleaning device 7b movable in the direction of arrow K7 contacting the surface of the intermediate transfer belt 5 at a predetermined timing.

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

The photosensitive drum 1 is constituted 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 belt 5 is an endless belt (substrate) 5 made of nickel (magnetic metal) having a thickness of 50 μm.
An elastic resistive layer (resin layer) 5b is provided on the outer peripheral surface (surface) of a, and the outer peripheral length is formed to be 320 mm. The elastic resistance layer 5b has a resistance value of 10 ⁵ to 10 by dispersing carbon as conductive particles in silicone rubber.
^It is adjusted to ¹⁰ Ω · cm, and the thickness is 200 μm.
The intermediate transfer belt 5 is pressed against the photosensitive drum 1 by the primary transfer roller 16 shown in FIG. 1 at a total pressure of 500 g, 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 belt 5 includes a high-frequency power source 12
As a result, the excitation coil 11 is energized to generate an induced current, thereby generating 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 photosensitive drum 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, hardness 45 ° (Asker C). Pressure roller 8
Is movably disposed in the direction of arrow K8 in FIG. 1, and is pressed against the surface of the intermediate transfer belt 5 with a total pressure of 15 kg by pressing means (not shown) at a predetermined timing. The driven rotation (or drive rotation) is performed at a peripheral speed substantially equal to the peripheral speed. Pressure roller 8
Even if is pressed against the intermediate transfer belt 5 with a total pressure of 15 kg, there is no problem because the exciting coil 11 receives the pressure. That is, the intermediate transfer belt 5 is pressed by the pressure roller 8 and is sandwiched between the pressure roller 8 and the exciting coil 11.

As described above, in the present embodiment, the nickel layer on the inner surface of the intermediate transfer belt is induction-heated to transfer and fix the toner image onto the transfer material P at the same time, thereby achieving a simple image forming process and a simple structure. The final image can be obtained by the image forming apparatus described above. That is, an inexpensive image forming apparatus can be provided. Further, since the heat capacity of the intermediate transfer belt 5 itself is much smaller than that of an intermediate transfer drum or the like, which is a drum-shaped intermediate transfer member, the temperature can be instantaneously increased to a temperature required for fixing. Therefore, an on-demand image forming apparatus can be provided. Further, the temperature of the intermediate transfer belt 5 once heated is small because the heat capacity is small, so that the temperature tends to decrease, and the temperature of the photosensitive drum 1 arranged in contact with the intermediate transfer belt 5 can be suppressed from rising. It is also possible to effectively prevent the image quality from deteriorating due to a change in charging characteristics due to temperature.

<Second Embodiment> FIG. 3 shows a second embodiment. In the present embodiment, in addition to the configuration of the first embodiment, a transfer bias power supply 9 is further connected to the pressing roller 18 so that a secondary transfer bias is applied to the pressing roller 18 at the time of simultaneous transfer fixing. I have to. 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 belt 5, and the pressure roller 18. However, the photosensitive drum 1 and the intermediate transfer belt 5 show a part thereof.

As shown in FIG. 4, the pressure roller 18 is constituted by providing a conductive elastic layer 18b on a core metal 18a made of iron having an outer diameter of 15 mm. Conductive elastic layer 18b
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 18 has an outer diameter of 25 mm and a hardness of 45 ° (Asker C) as a whole, and is arranged movably in the direction of arrow K18. The pressure roller 18 is pressed against the surface of the intermediate transfer belt 5 with a total pressure of 15 kg by a pressure unit (not shown) at a predetermined timing, and is driven (or driven) by a peripheral speed substantially equal to the peripheral speed of the intermediate transfer belt 5 (or Drive rotation).

When the transfer material P is conveyed to the transfer fixing section 6b at a predetermined timing, the core metal 18a of the pressure roller 18
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 belt 5 are secondarily transferred collectively 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 belt 5 is transferred onto the transfer material P with high transfer efficiency by applying the secondary transfer bias during the simultaneous transfer and fixing to the pressing roller 18. The transfer can be fixed simultaneously.

<Third Embodiment> FIG. 5 shows a third embodiment. In the present embodiment, in addition to the configuration of the above-described second embodiment, the rotation direction of the intermediate transfer belt 5 (arrow R5) is further added.
The cooling device 19 is disposed on the downstream side of the transfer fixing unit 6b (in the direction) and on the upstream side of the cleaning device 7b. Note that the steps up to the simultaneous transfer fixing are the same as those in the above-described second embodiment, and thus the description thereof is omitted.

As described above, the temperature of the heated portion of the surface of the intermediate transfer belt 5 at the time of simultaneous transfer fixing is controlled to 100 ° C. However, even after the simultaneous transfer fixing, the intermediate transfer belt 5 is heated. Surface temperature does not drop easily. In this state, when the heated portion of the intermediate transfer belt 5 reaches the photosensitive drum 1, the photosensitive drum 1 is in contact with the intermediate transfer belt 5, so that the temperature of the photosensitive drum 1 is increased by the heated portion of the intermediate transfer belt 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 belt 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 belt 5 is cooled by the cooling device 19. As the cooling device 19, 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 belt 5.

As described above, in the present embodiment, the surface of the intermediate transfer belt 5 is cooled after the simultaneous transfer and fixing, thereby preventing the temperature of the photosensitive drum 1 in contact with the intermediate transfer belt 5 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.

[0036]

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. Also, the second image carrier itself has a small heat capacity,
The temperature can be raised instantaneously to the temperature required for fixing. Therefore, an on-demand image forming apparatus can be provided. Further, since the heat capacity of the second image carrier once heated is small, the temperature is easily lowered, and the temperature rise of the first image carrier which is arranged in contact with the second image carrier can be suppressed. Therefore, it is possible to effectively prevent a change in charging characteristics due to a rise in the temperature of the first image carrier and a reduction in image quality.

[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 belt, 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 belt, 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 belt) 5a Substrate (endless belt) 5b Resin layer (elastic resistance layer) 6a Primary transfer part 6b Transfer fixing part 8, 18 Addition Pressure member (pressure roller) 9 Transfer bias power supply 11 Excitation coil 19 Cooling device (cooling fan) P Transfer material

Claims (5)

[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 an endless belt made of nickel. 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.