JP2006235395A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus provided with a transfer device which can be made small by a simple configuration. <P>SOLUTION: The image forming apparatus includes; an endless transfer belt 5 to which a toner image formed in an image carrier is transferred; a meandering preventing guide portion 8 provided to an edge part in a width direction of a rear face of the transfer belt 5; a belt stretching means comprising a plurality of rollers including driving rollers for stretching and driving the transfer belt 5 and a primary transfer roller 62 for applying a primary transfer bias to the transfer belt 5; and a secondary transfer roller to which a secondary transfer bias is applied. In the image forming apparatus, the guide portion 8 is made of a conductive material and applies the transfer biases to the primary transfer roller 62 and the secondary transfer roller so that the toner image can be transferred to the surface area G of the transfer belt 5, where the guide portion 8 is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine having a transfer device that develops an electrostatic latent image into a toner image and transfers the toner image onto a recording sheet.

  For example, in this type of image forming apparatus, there is a transfer apparatus that uses an endless transfer belt that is stretched by a belt stretching means to transfer a toner image carried on a photoreceptor onto a recording sheet. It is installed. An image forming apparatus equipped with this transfer device temporarily transfers a toner image developed on a photoconductor as an image carrier onto a transfer belt, and then secondary transfer the transferred toner image onto a recording sheet as a transfer material. Then, an image is formed. For this reason, it is effective in forming a color image in which a plurality of color information is sequentially laminated and transferred, and an image with little misalignment of color images can be obtained.

  However, when an endless transfer belt is used as the intermediate transfer member, it is difficult to keep the plurality of rollers of the belt stretching means for stretching the transfer belt parallel, and a shifting force is generated while the transfer belt is running. Color misregistration occurs when colors overlap.

Conventionally, as a countermeasure, a guide portion is formed at the edge in the width direction of the back surface of the transfer belt, and a meander-preventing pulley is provided at the end of the belt of the belt stretching means such as a drive roller and a tension roller. There is one in which a guide portion is inserted into the groove of the transfer belt and the transfer belt is run to regulate the deviation (see, for example, Patent Document 1).
Japanese Patent No. 3499423

  However, according to the configuration described in Patent Document 1, the surface area of the transfer belt on which the guide portion is formed becomes a non-image area, and the width of the transfer belt is at least “the width of the image forming area” and “the guide portion”. ”Width”. As a result, when this type of device is downsized, the width of the guide portion has become one of the obstacles to downsizing.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus including a transfer device that can be reduced in size with a simple configuration.

  In order to achieve the above object, in the present invention, an endless transfer belt to which a toner image formed on an image carrier is transferred, and a meander-prevention device provided at the edge in the width direction of the back surface of the transfer belt. Belt stretching means comprising a guide section, a driving roller for stretching the transfer belt, and a primary transfer roller for applying a primary transfer bias to the transfer belt, and a secondary transfer bias applied In the image forming apparatus provided with the transfer device having the secondary transfer roller, the guide portion is formed of a conductive material, and the toner image can be transferred to the surface area of the transfer belt provided with the guide portion. As described above, a transfer bias is applied to the primary transfer roller and the secondary transfer roller.

  According to the configuration of the present invention, the guide portion for preventing meandering provided at the edge in the width direction of the back surface of the transfer belt is formed of a conductive material, and also in the surface region of the transfer belt provided with the guide portion. The transfer bias is applied to the primary transfer roller and the secondary transfer roller so that the toner image can be transferred. Accordingly, the surface portion of the transfer belt provided with the guide portion also functions as an area where the toner image can be transferred, that is, an image forming area. Therefore, the width of the transfer belt can be reduced without reducing the image forming area. . As a result, this type of image forming apparatus can be miniaturized. In addition, the configuration is very simple because it is only necessary to change the material of the guide portion.

(Embodiment)
A specific embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a schematic configuration diagram showing a schematic configuration of a four-cycle full-color image forming apparatus using a transfer apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus includes an image forming unit 1 for forming an image, a fixing unit 2, a paper feeding unit 3 in which the recording paper P is stored, and the recording paper P as an image forming unit. 1 and a paper supply path 4 that conveys the paper to the paper discharge unit 41 via the fixing unit 2.

  The paper feed means 3 includes a paper feed cassette 31 in which the paper to be recorded P is accommodated, and the paper to be recorded P is fed from the paper feed cassette 31 by the rotation operation of the paper feed roller 32 provided in the paper feed means 3. It is configured to be sent out to the paper supply path 4 side. With this configuration, the recording paper P is reliably fed to the paper supply path 4 one by one. These paper feed cassettes 31 are configured to be detachable from the main body of the image forming apparatus.

  The recording paper P fed to the paper supply path 4 is conveyed toward the image forming unit 1 via the paper supply path 4. The image forming unit 1 forms a predetermined toner image on the recording paper P by an electrophotographic process, and is an image carrier that is rotatably supported in a predetermined direction (arrow direction in the figure). For example, a drum-shaped photoreceptor 11, and a charging roller 12, an exposure device 13, a developing rotary 14, a transfer device 15, a cleaning device 16, and a charge removal device (not shown) are provided along the periphery of the photoreceptor 11. I have.

  A high voltage is applied to the charging roller 12 from a high voltage power source (not shown), and the charging roller 12 applies a predetermined potential to the surface of the photoconductor 11 so that the surface of the photoconductor 11 is uniformly charged.

  The developing rotary 14 includes developing units 14C, 14M, 14Y, and 14K that store toners of cyan, magenta, yellow, and black, respectively. The developing units 14C, 14M, 14Y, and 14K are provided for the photosensitive member 11. It is rotatably held so as to be selectively opposed.

  The transfer device 15 is disposed so as to be in pressure contact with the photosensitive member 11 and has a transfer belt 5 (described later) that carries a toner image on the surface thereof, belt stretching means 6 that stretches and drives the transfer belt 5, and secondary transfer. A secondary transfer roller 7 to which a bias is applied and a cleaning brush roller 151 are provided.

  The belt stretching means 6 includes a driving roller 61 for stretching the transfer belt 5, a primary transfer roller 62 that applies a primary transfer bias to the transfer belt 5 that is a driven roller, a guide roller 63, and a transfer belt. 5 is provided with a tension roller 64 which is tensioned by a spring load so as to be movable in a direction crossing 5.

  The basic operation state of the image forming apparatus will be briefly described by taking the case of developing yellow as an example, but the same applies to the development of other colors. When performing image formation, the surface of the photoconductor 11 is uniformly charged by the charging roller 12, and then the photoconductor 11 is first converted into image data of a document subjected to image processing by the exposure device 13, for example. Based on the exposure. As a result, the surface potential of the photoconductor 11 is selectively attenuated, and an electrostatic latent image corresponding to yellow is formed on the surface of the photoconductor 11.

  On the other hand, the yellow developing device 14Y is rotated and held so as to be selectively opposed to the photoconductor 11. The yellow toner in the yellow developing device 14Y is fed into the supply roller by, for example, rotation of the stirring blade in the developing device 14Y, and at the same time a yellow toner thin layer is formed by the supply roller and the regulating blade. It is charged to positive polarity by friction between the blade and the developing roller. In this way, the uniformly formed yellow toner layer is conveyed to the opposite portion between the photoconductor 11 and the developing roller, and the yellow component toner is added to the electrostatic latent image formed on the surface of the photoconductor 11. By attaching (developing), a toner image having a color component corresponding to yellow is formed on the surface of the photoreceptor 11.

  A toner image having a color component corresponding to positive yellow formed on the surface of the photoconductor 11 was applied to the primary transfer roller 62 at the primary transfer nip where the photoconductor 11 and the transfer belt 5 abut. It is attracted to the transfer belt 5 by a negative transfer bias. As a result, the toner image visualized by the yellow developing device 14Y is transferred to the surface of the transfer belt 5 (primary transfer). After the transfer, the developing bias applied to the yellow developing device 14Y is stopped, and the developing bias is applied to the magenta developing device 14M that forms the next image.

  The toner remaining on the surface of the photoconductor 11 is removed by the cleaning device 16, and the residual charge on the surface of the photoconductor 11 is removed by the static eliminator. Then, the photoconductor 11 is charged again by the charging roller 12.

  Thereafter, similarly, the toner images of the respective colors are superimposed on the surface of the transfer belt 5 in the order of charging, exposure, development, and transfer for each color, and after the color toner image is formed on the transfer belt 5, 2 The next transfer roller 7 is pressed against the transfer belt 5. In synchronization with these operations, the recording paper P provided in the paper feed cassette 31 is conveyed to the paper supply path 4 by the paper feed roller 32. The recording paper P conveyed to the paper supply path 4 is synchronized with the color toner image formed on the transfer belt 5 by a pair of registration rollers 42 while being transferred between the transfer belt 5 and the secondary transfer roller 7. It is fed into the nip part. A negative transfer bias opposite to the toner polarity is applied to the secondary transfer roller 7. As a result, the color toner image formed in a laminated state on the surface of the transfer belt 5 is transferred onto the recording paper P by the secondary transfer roller 7.

  The recording paper P to which the color toner image is transferred is conveyed from the image forming unit 1 toward the fixing unit 2. The fixing unit 2 is disposed on the downstream side of the image forming unit 1 in the sheet conveyance direction. The recording sheet P on which the color toner image is transferred in the image forming unit 1 is heated by the fixing unit 2. The color toner image is fixed on the recording paper P by being sandwiched and heated by the roller 21 and the pressure roller 22 pressed against the heating roller 21. Next, the recording paper P on which the image is formed in the fixing unit 2 from the image forming unit 1 is discharged onto the paper discharge unit 41. Thereafter, image formation is performed in the same manner.

  Next, a specific configuration of the transfer device according to the characterizing portion of the present invention will be described with reference to FIGS. 2 is a block diagram showing a schematic configuration in the longitudinal direction of the primary transfer portion of the transfer device, FIG. 3 is a block diagram showing a schematic configuration in the longitudinal direction of the tension roller portion of the transfer device, and FIG. FIG. 5 is a block diagram showing a schematic configuration in the longitudinal direction of the guide roller portion of the transfer device. FIG. 6 is a schematic cross-sectional view of a primary transfer portion of the transfer device.

  As shown in FIG. 2, in the primary transfer portion, the transfer belt 5 is disposed so that the front surface faces the photoreceptor 11 and the back surface contacts the primary transfer roller 62. This transfer belt 5 is provided with conductivity by using a conductive material such as carbon to a resin such as polyimide having a circumferential length of about 377 mm and a thickness of 100 μm, and the surface resistance (ρSb) is 1E + 10 (Ω / □) and volume resistance (ρVb) are adjusted to a range of 1E + 8 (Ω · cm). For measurement of surface resistance and volume resistance, “HIRESTA” and “HRS probe” manufactured by Dia Instruments Co., Ltd. were used. Further, the width H of the transfer belt 5 is formed to be substantially the same as the width h0 (image forming area in the width direction) of the photoconductor 11.

  As the transfer belt 5, either a single-layer belt or a laminated belt whose conductivity is controlled as described above can be used. Examples of the material of the transfer belt 5 include polyimide (PI), polyetheretherketone (PEEK), polyarylene sulfide (PAS), polyamideimide (PAI), polyethersulfone (PES), and polyethernitrile (PEN). ), Polyphenylene sulfide (PPS), thermoplastic polyimide (TPI), or the like can be used. Among these, it is particularly preferable to use polyimide in view of requirements such as heat resistance and mechanical strength. Other than this, a fluorine-based belt (ETEF), a polyvinylidene fluoride (PVDF) single-layer belt, a laminated belt, or a single-layer belt using various elastomers. Or a laminated belt can be used.

  In order to prevent the transfer belt 5 from meandering at the edge in the width direction of the surface (back surface) opposite to the surface (toner carrying surface) of the transfer belt 5, the meandering prevention formed of a conductive material is used. The guide portion 8 is attached with, for example, a conductive adhesive. The guide part 8 is made of, for example, low hardness conductive urethane having a thickness of 0.5 mm and a width of 4 mm. This guide portion 8 can impart conductivity by mixing a conductive material such as carbon into a resin such as urethane, and the same as the transfer belt 5 described above by appropriately adjusting the mixing amount of the conductive material. , Surface resistance (ρSg), and volume resistance (ρVg) are preferably adjusted.

  As shown in FIG. 3, the guide portion 8 is configured to enter a groove of a meander-preventing pulley 641 attached to the end portion of the tension roller 64. A load of one end 2 kgf is applied to the bearing portion of the tension roller 64 by a spring (not shown) to form a tension for stretching the transfer belt 5.

  The primary transfer roller 62 and the secondary transfer roller 7 can apply a transfer bias so that the toner image can be transferred also on the surface region G of the transfer belt 5 provided with the guide portion 8. It is configured.

  As shown in FIG. 2, the primary transfer roller 62 to which the primary transfer bias is applied includes, for example, a central portion 621 that contacts the back surface of the transfer belt 5 having an outer diameter of φ12 mm, and a guide portion 8 having an outer diameter of φ11 mm. It is comprised with the edge part 622 which touches. The width h1 of the primary transfer roller 62 (the width of the central portion 621 + the width of the end portion 622) is formed substantially the same as the width H of the transfer belt 5, and the primary transfer roller 62 has its width h1. A transfer bias application region is formed over the entire direction. The primary transfer roller 62 is formed of, for example, a conductive metal roller such as stainless steel or aluminum. As shown in FIG. 6, the primary transfer roller 62 is disposed so as to form a gap of about 0.3 mm with respect to the photoconductor 11, so that the nip position A between the photoconductor 11 and the transfer belt 5, The distance AB between the primary transfer roller 62 and the nip position B of the transfer belt 5 is separated by 3 mm.

  With this configuration, when a primary transfer bias is applied to the end portion of the core metal 623 of the primary transfer roller 62 from a power source (not shown), transfer is performed over the entire width h1 direction of the primary transfer roller 62 including the end portion 622. A bias is applied. As a result, the primary transfer bias is also applied to the surface region G of the transfer belt 5 provided with the guide portion 8, and the toner image carried on the photoconductor 11 covers the entire width H direction of the transfer belt 5. Thus, transfer to the transfer belt 5 side becomes possible.

  As shown in FIG. 4, the secondary transfer roller 7 to which the secondary transfer bias is applied has a conductive urethane foam material having an outer diameter of φ16 mm and a total resistance of 1E + 9 (Ω) as a conductive metal core. A conductive sponge layer is formed by bonding with an adhesive. The width h2 of the secondary transfer roller 7 is formed substantially the same as the width H of the transfer belt 5, and the secondary transfer roller 7 serves as a transfer bias application region over the entire area in the width h2 direction. The holding portion of the secondary transfer roller 7 is provided with a spring member (not shown) so as to be pressed against the driving roller 61 with a load of 1 kgf at one end, and a conductive sponge layer is formed by the pressing force of the spring member. The central portion of the secondary transfer roller 7 provided with nips about 0.2 mm to form a nip.

  The driving roller 61 that also serves as the secondary transfer counter roller has a central portion 611 facing the central portion of the transfer belt 5 with an outer diameter of φ20 mm, and the base layer is assembled to a metal core 613. It is a conductive metal roller such as aluminum having a diameter of 18 mm. A solid rubber material such as a terpolymer (EPDM) of ethylene propylene diene having a volume resistance of 1E + 6 (Ω · cm) is wound around the metal roller as a surface layer with a thickness of 1 mm. The same solid rubber material is wound around the end 612 with a thickness of 0.5 mm. The end portion 612 of the driving roller 61 is configured to be freely rotatable with respect to the core metal 613 of the driving roller 61 and is driven by the guide portion 8, so that the central portion 611 and the end portion 612 of the driving roller 61 Thus, there is no difference in the transportability of the transfer belt 5. Although not shown, the metal core 613 is connected to the ground.

  The secondary transfer roller 7 is configured to be detachable from the transfer belt 5 by a detachment mechanism (not shown), and is separated from the transfer belt when a multicolor toner image is formed on the transfer belt 5. Is done. Further, after the color toner image is formed on the transfer belt 5 in a laminated state, it is controlled so as to come into contact therewith.

  With this configuration, when a secondary transfer bias is applied to the end of the core 71 of the secondary transfer roller 7 from a power source (not shown), the width h2 of the secondary transfer roller 7 is passed through the conductive sponge layer of the secondary transfer roller 7. A transfer bias is applied over the entire direction. As a result, the toner image carried over the entire width H direction on the transfer belt 5 including the surface area G of the transfer belt 5 provided with the guide portion 8 is transferred to the recording paper P side as a transfer material. .

  According to the present embodiment having the above configuration, the guide portion 8 is formed of a conductive material, and the toner image can be transferred even on the surface region of the transfer belt 5 provided with the guide portion 8. A transfer bias is applied to the secondary transfer roller 62 and the secondary transfer roller 7. Accordingly, the surface portion of the transfer belt 5 provided with the guide portion 8 also functions as an area where the toner image can be transferred, that is, an image forming area. Therefore, the width of the transfer belt 5 is reduced without reducing the image forming area. be able to. As a result, this type of image forming apparatus can be miniaturized. Further, the configuration is very simple because it is only necessary to change the material of the guide portion 8.

  According to the experiment results of the present inventors, the surface resistance (ρSb) of the transfer belt 5 is preferably the above-mentioned value, but if it is 1E + 7 to 13 (Ω / □), it is in a voltage region used in a general-purpose high-voltage circuit. Can be transferred. Since the volume resistance (ρVb) varies depending on the thickness of the member, it can be expressed as a product of ρVb and the thickness tb (cm) (ρVb × tb) as long as it is 1E + 4 to 11 (Ω · cm). Can be transferred in the voltage range used in the above.

The above-described embodiment is a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.
For example, in the above-described embodiment, the copying machine has been described as an example. However, the present invention is not limited to, for example, a facsimile machine, a multifunction machine having various functions such as a copying function, a printer function, a scanner function, and a facsimile function. It is applicable to.

  In the above-described embodiment, the drum-shaped photoconductor 11 is used. However, the shape of the photoconductor 11 is not limited, and a known shape other than the above-described drum shape can be used. Examples of the shape include a sheet shape, a belt shape, and a web shape.

  In the above-described embodiment, the case where the present invention is applied to a four-cycle color image forming apparatus has been described in detail. However, for example, an image forming apparatus in which a guide portion is provided on the back surface of a tandem type transfer belt. Applicable.

  In the above-described embodiment, the meandering-preventing guide portions 8 are provided on both sides of the back surface of the transfer belt 5, but of course, any one of the back surfaces of the transfer belt 5 may be used.

  As an application example of the present invention, an image provided with a transfer device using an endless transfer belt stretched by a belt stretching means for transferring a toner image carried on a photosensitive member to a recording sheet. Examples include a forming apparatus.

1 is a schematic configuration diagram illustrating a schematic configuration of a four-cycle full-color image forming apparatus using a transfer device according to an embodiment of the present invention. FIG. 2 is a configuration diagram illustrating a schematic configuration in a longitudinal direction of a primary transfer portion of the transfer apparatus illustrated in FIG. 1. FIG. 2 is a configuration diagram illustrating a schematic configuration in a longitudinal direction of a tension roller portion of the transfer device illustrated in FIG. 1. FIG. 2 is a configuration diagram illustrating a schematic configuration in a longitudinal direction of a secondary transfer portion of the transfer apparatus illustrated in FIG. 1. It is a block diagram which shows schematic structure of the longitudinal direction of the guide roller part of the transfer apparatus shown in FIG. FIG. 2 is a cross-sectional view illustrating a schematic configuration of a primary transfer portion of the transfer apparatus illustrated in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 ... Transfer belt, 6 ... Belt stretching means, 7 ... Secondary transfer roller, 8 ... Guide part, 15 ... Transfer device, 61 ... Drive roller, 62 ... Primary transfer roller, 612, 622 ... End part, G ... Surface area

Claims (1)

An endless transfer belt to which a toner image formed on the image carrier is transferred, a meandering-preventing guide provided at the widthwise edge of the back surface of the transfer belt, and the transfer belt is stretched and driven And a belt stretching means comprising a plurality of rollers including a primary transfer roller for applying a primary transfer bias to the transfer belt, and a secondary transfer roller to which a secondary transfer bias is applied. In an image forming apparatus provided with a transfer device,
The guide portion is formed of a conductive material, and the primary transfer roller and the secondary transfer roller are configured such that the toner image can be transferred onto a surface area of a transfer belt provided with the guide portion. A transfer bias is applied to the image forming apparatus.

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