JP7389951B2 - Conveyance device and image forming device - Google Patents

Description

The present invention relates to a conveyance device that conveys sheets such as paper, and an image forming apparatus including a copying machine, a printer, a facsimile machine, or a multifunctional device thereof.

Conventionally, in image forming apparatuses such as copying machines and printers, in order to convey sheets sent out from a transfer belt such as a secondary transfer belt toward a fixing device, a conveyor belt is installed on the conveyance path from the transfer belt to the fixing device. There is a known device in which a device is installed (for example, see Patent Document 1).
The sheet onto which the image has been transferred at the transfer nip, where the transfer belt contacts an image carrier such as an intermediate transfer belt or a photoreceptor drum, is transported by the transfer belt, separated from the transfer belt, and then fixed by the transport belt. The image is transported toward the fixing nip of the device.

On the other hand, Patent Document 2 discloses a technique of installing a static eliminating member between a transfer roller and a conveyor belt. Immediately after passing through the transfer nip, the sheet having the image transferred thereto at the transfer nip where the transfer roller and the photoreceptor drum come into contact is neutralized by the static eliminating member, and then conveyed toward the fixing device by the conveyor belt.

In the technique of Patent Document 1 mentioned above, the conveyance belt is installed on the conveyance path from the transfer belt to the fixing device, so even if the conveyance path is long, the sheet cannot be reliably conveyed by the conveyance belt. can. However, because the sheet sent out from the transfer belt is conveyed by the conveyor belt in a charged state, the sheet is lifted by electrostatic force on the entrance side of the fixing device, and the sheet is not properly fed into the fixing nip. In some cases, problems such as the sheet folding at the edges may occur.
To deal with this, it is possible to apply the technique of Patent Document 2 and install a static eliminating member between the transfer belt and the conveyance belt to neutralize the static electricity from the sheet. However, if the static eliminating member is installed close to the sheet being transferred from the transfer belt to the conveyor belt in order to increase the static eliminating effect on the sheet, there is a possibility that the static eliminating member will impair the conveyance of the sheet. be.

The present invention was made in order to solve the above-mentioned problems, and provides a conveyance device and an image transfer device in which a sheet is smoothly conveyed without lifting due to electrostatic force in a conveyance path from a transfer belt to a fixing device. An object of the present invention is to provide a forming device.

The conveyance device according to the present invention includes a conveyance member that conveys the sheet on a conveyance path from the transfer belt to the fixing device, and a static eliminator that is installed in the middle of the conveyance path and eliminates static electricity from the sheet being conveyed by the conveyance member. , a moving mechanism that moves the static eliminating member in the width direction, and the conveying member is configured to move the static eliminator within a range in the width direction of the sheet conveyed on the conveyance path and within a range smaller than the range. the static eliminating member is formed so as to be close to the sheet conveyed on the conveyance path in a widthwise range different from a widthwise range in which the conveyance member contacts the sheet ;
According to the widthwise size of the sheet conveyed on the conveyance path, the moving mechanism moves the sheet close to the widthwise end of the sheet.

According to the present invention, it is possible to provide a conveyance device and an image forming apparatus in which a sheet is conveyed well without lifting due to electrostatic force on the conveyance path from the transfer belt to the fixing device.

1 is an overall configuration diagram showing an image forming apparatus in an embodiment of the present invention. FIG. 3 is an enlarged configuration diagram showing a part of the image forming section. FIG. 2 is a schematic diagram showing a secondary transfer belt device, a conveyance device, a fixing device, and the vicinity thereof. FIG. 3 is a top view showing a secondary transfer belt device, a conveyance device, and a fixing device. 1 is a diagram showing main parts of a conventional image forming apparatus. FIG. 7 is a top view showing a conveying device and its vicinity as Modification 1. FIG. FIG. 7 is a top view showing a transport device and its vicinity as Modification 2. FIG. FIG. 7 is a top view showing a conveyance device and its vicinity as a third modification. FIG. 7 is a schematic diagram showing a conveyance device and its vicinity as a fourth modification. 10 is a top view showing the conveyance device of FIG. 9 and its vicinity. FIG. It is a graph showing the relationship between the potential difference of the sheet before and after static elimination and the rank of dust/discharge marks. 7 is a graph showing the relationship between the position of a sheet in the transport direction during transport and the electric potential of the sheet.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and repeated explanations thereof will be simplified or omitted as appropriate.

First, the overall configuration and operation of the image forming apparatus 100 will be described with reference to FIGS. 1 and 2.
FIG. 1 is a block diagram showing a printer as an image forming apparatus, and FIG. 2 is an enlarged view showing a part of its image forming section.
As shown in FIG. 1, an intermediate transfer belt 8 (intermediate transfer belt device) is installed at the center of the image forming apparatus main body 100. Further, image forming units 6Y, 6M, 6C, and 6K corresponding to each color (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 8. Further, below the intermediate transfer belt 8, a secondary transfer belt device 69, a conveyance device 60, and a fixing device 50 are installed. Furthermore, a paper feeder 26 is installed below it.

Referring to FIG. 2, the image forming section 6Y corresponding to yellow includes a photoconductor drum 1Y, a charging section 4Y disposed around the photoconductor drum 1Y (photoconductor), a developing section 5Y, a cleaning section 2Y, It is composed of a lubricant supply device 3, a static eliminator, and the like. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process, static elimination process) is performed on the photoconductor drum 1Y, and a yellow image is formed on the photoconductor drum 1Y. Become.

The other three image forming sections 6M, 6C, and 6K have almost the same configuration as the image forming section 6Y corresponding to yellow, except that the toner colors used are different. A corresponding image is formed. Hereinafter, description of the other three image forming sections 6M, 6C, and 6K will be omitted as appropriate, and only the image forming section 6Y corresponding to yellow will be explained.

Referring to FIG. 2, photoreceptor drum 1Y is rotationally driven in a counterclockwise direction by a main motor. Then, the surface of the photoreceptor drum 1Y is uniformly charged at the position of the charging section 4Y (this is a charging process).
After that, the surface of the photoreceptor drum 1Y reaches the irradiation position of the laser beam L emitted from the exposure section 7, and the surface of the photoreceptor drum 1Y reaches the irradiation position of the laser beam L emitted from the exposure section 7, and the surface of the photoreceptor drum 1Y reaches the irradiation position in the width direction (direction perpendicular to the paper plane of FIGS. 1 and 2, and in the main scanning direction) at this position. An electrostatic latent image corresponding to yellow is formed by exposure scanning (this is an exposure process).

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the developing section 5Y, and the electrostatic latent image is developed at this position, forming a yellow toner image (this is a developing process).
Thereafter, the surface of the photoreceptor drum 1Y reaches a position facing the intermediate transfer belt 8 and the primary transfer roller 9Y, and at this position the toner image formed on the surface of the photoreceptor drum 1 is transferred to the surface of the intermediate transfer belt 8. (this is the primary transfer step). At this time, a small amount of untransferred toner remains on the photoreceptor drum 1Y.

Thereafter, the surface of the photoreceptor drum 1Y reaches a position facing the cleaning section 2Y, and at this position, the untransferred toner remaining on the photoreceptor drum 1Y is collected into the cleaning section 2Y by the cleaning blade 2a (cleaning ).
Here, inside the cleaning section 2Y, a lubricant supply device 3 (photoreceptor lubricant supply device) consisting of a lubricant supply roller 3a, a solid lubricant 3b, a compression spring 3c, etc. is provided. Then, the lubricant is scraped little by little from the solid lubricant 3b by the lubricant supply roller 3a rotating clockwise in FIG. 2, and the lubricant is supplied to the surface of the photoreceptor drum 1Y by the lubricant supply roller 3a. It turns out.
Finally, the surface of the photoreceptor drum 1Y reaches a position facing the static eliminating section, and the residual potential on the photoreceptor drum 1 is removed at this position.
In this way, a series of image forming processes performed on the photosensitive drum 1Y are completed.

Note that the above-described image forming process is performed in the other image forming sections 6M, 6C, and 6K in the same manner as in the yellow image forming section 6Y. That is, from the exposure section 7 disposed above the image forming section, laser light L based on image information is irradiated onto the photoreceptor drums 1M, 1C, and 1K of the respective image forming sections 6M, 6C, and 6K. be done.
Thereafter, the toner images of the respective colors formed on the respective photoreceptor drums 1M, 1C, and 1K through a developing process by the respective developing units 5M, 5C, and 5K are primary-transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

Here, the intermediate transfer belt 8 is stretched and supported by a plurality of roller members 16 to 22, and 40, and is rotated in the direction of the arrow in FIG. 3 by rotation of one roller member (drive roller 16) by a drive motor. Moved endlessly.
The four primary transfer rollers 9Y, 9M, 9C, and 9K each sandwich the intermediate transfer belt 8 with the photosensitive drums 1Y, 1M, 1C, and 1K to form a primary transfer nip. Then, a transfer voltage (primary transfer bias) having a polarity opposite to that of the toner is applied to the primary transfer rollers 9Y, 9M, 9C, and 9K.
The intermediate transfer belt 8 then travels in the direction of the arrow and sequentially passes through the primary transfer nip of the primary transfer rollers 9Y, 9M, 9C, and 9K. In this way, the toner images of each color on the photoreceptor drums 1Y, 1M, 1C, and 1K are primarily transferred onto the surface of the intermediate transfer belt 8 in an overlapping manner (this is a primary transfer process).

Thereafter, the intermediate transfer belt 8, on which the toner images of each color have been primarily transferred in a superimposed manner, reaches a position facing the secondary transfer belt 72 as a transfer belt. At this position, the secondary transfer opposing roller 40 and the secondary transfer roller 70 sandwich the intermediate transfer belt 8 and the secondary transfer belt 72 to form a secondary transfer nip (transfer nip). Then, the four-color toner images formed on the intermediate transfer belt 8 are secondarily transferred onto a sheet P such as paper that is conveyed to the position of this secondary transfer nip (this is a secondary transfer process). . At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 8.

After that, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning section 10. At this position, deposits such as untransferred toner attached to the surface of the intermediate transfer belt 8 are removed.
Further, the intermediate transfer belt 8 reaches the position of the intermediate transfer lubricant supply device 30 . At this position, lubricant is supplied to the surface of the intermediate transfer belt 8.
In this way, a series of transfer processes performed on the intermediate transfer belt 8 are completed.

Here, referring to FIG. 1, the sheet P conveyed to the position of the secondary transfer nip is transferred from a sheet feeding device 26 disposed below the apparatus main body 100 to a sheet feeding roller 27, a pair of registration rollers 28, etc. It is transported via.
Specifically, the paper feeding device 26 stores a plurality of sheets P, such as paper, stacked one on top of the other. Then, when the paper feed roller 27 is rotationally driven in the counterclockwise direction in FIG. 1, the uppermost sheet P is fed toward the registration roller pair 28 via the conveyance path.

The sheet P conveyed to the registration roller pair 28 (timing roller pair) temporarily stops at the roller nip position of the registration roller pair 28 whose rotational drive has been stopped. Then, in synchronization with the color image on the intermediate transfer belt 8, the registration roller pair 28 is rotationally driven, and the sheet P is conveyed toward the secondary transfer nip while being guided by the guide plate. In this way, a desired color image is transferred onto the sheet P.

After that, the sheet P to which the color image has been transferred at the position of the secondary transfer nip is conveyed by the secondary transfer belt 72, and after being separated from the secondary transfer belt 72, the sheet P is transferred to the position of the fixing device 50 by the conveying device 60. transported. Then, at this position, the color image transferred to the surface is fixed onto the sheet P by heat and pressure from the fixing roller 51 and the pressure roller 52 (this is a fixing step).
Thereafter, the sheet P is discharged from the apparatus by a pair of paper discharge rollers via a conveyance path. The sheets P discharged from the apparatus by the pair of paper discharge rollers are sequentially stacked on the stack section as an output image.
In this way, a series of image forming operations (printing operations) in the image forming apparatus are completed.

Next, referring to FIG. 2, the configuration and operation of the developing section 5Y (developing device) in the image forming section will be described in more detail.
The developing section 5Y includes a developing roller 51Y facing the photoreceptor drum 1Y, a doctor blade 52Y facing the developing roller 51Y, two conveyance screws 55Y arranged in a developer storage section, and a toner concentration in the developer. It is composed of a concentration detection sensor 56Y that detects . The developing roller 51Y is composed of a magnet fixed inside, a sleeve rotating around the magnet, and the like. A two-component developer G consisting of carrier and toner is accommodated in the developer accommodating portion.

The developing section 5Y configured in this manner operates as follows.
The sleeve of the developing roller 51Y is rotating in the direction of the arrow in FIG. The developer G carried on the developing roller 51Y by the magnetic field formed by the magnet moves on the developing roller 51Y as the sleeve rotates. Here, the developer G in the developing section 5Y is adjusted so that the ratio of toner (toner concentration) in the developer G is within a predetermined range. Specifically, when a low toner concentration is detected by the toner concentration sensor installed in the developing section 5Y, new toner is supplied from the toner container 58 into the developing section 5Y so that the toner concentration is within a predetermined range. will be replenished.
Thereafter, the toner supplied from the toner container 58 into the developer storage section is mixed and stirred together with the developer G by the two conveyance screws 55Y, and circulates through the two isolated developer storage sections (see FIG. 2). (This is a movement perpendicular to the page.) The toner in the developer G is attracted to the carrier by frictional charging with the carrier, and is supported on the developing roller 51Y together with the carrier by the magnetic force formed on the developing roller 51Y.

The developer G supported on the developing roller 51Y is conveyed in the direction of the arrow in FIG. 2 and reaches the position of the doctor blade 52Y. After the developer G on the developing roller 51Y is adjusted to an appropriate amount at this position, it is conveyed to a position facing the photosensitive drum 1Y (which is a developing area). Then, the toner is attracted to the latent image formed on the photoreceptor drum 1Y by the electric field formed in the development area. Thereafter, as the sleeve rotates, the developer G remaining on the developing roller 51Y reaches above the developer accommodating portion, and is separated from the developing roller 51Y at this position.
Note that the toner container 58 is installed in a detachable (replaceable) manner with respect to the developing section 5Y (image forming apparatus 100). When the toner container 58 is emptied of the new toner contained therein, it is removed from the developing section 5Y (image forming apparatus 100) and replaced with a new one.

Next, the intermediate transfer belt device in this embodiment will be described in detail with reference to FIG. 3 and the like.
Referring to FIG. 3, the intermediate transfer belt device includes an intermediate transfer belt 8, four primary transfer rollers 9Y, 9M, 9C, 9K, a drive roller 16, a driven roller 17, a pre-transfer roller 18, a tension roller 19, and a cleaning roller. It is composed of an opposing roller 20, a lubricant opposing roller 21, a backup roller 22, an intermediate transfer cleaning section 10, an intermediate transfer lubricant supply device 30, a secondary transfer opposing roller 40, and the like.
The intermediate transfer belt 8 forms a primary transfer nip by contacting the four photoreceptor drums 1Y, 1M, 1C, and 1K, each carrying a toner image of each color. The intermediate transfer belt 8 mainly includes eight roller members (driving roller 16, driven roller 17, pre-transfer roller 18, tension roller 19, cleaning opposing roller 20, lubricant opposing roller 21, backup roller 22, secondary transfer opposing roller 40). ) is stretched and supported by.
In this embodiment, the intermediate transfer belt 8 is made of a single layer or multiple layers of PVDF (vinyldene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), etc. A conductive material such as carbon black is dispersed therein.

The primary transfer rollers 9Y, 9M, 9C, and 9K are in contact with the corresponding photosensitive drums 1Y, 1M, 1C, and 1K via the intermediate transfer belt 8, respectively. Specifically, the yellow transfer roller 9Y contacts the yellow photoreceptor drum 1Y via the intermediate transfer belt 8, and the magenta transfer roller 9M contacts the magenta photoreceptor drum 1M via the intermediate transfer belt 8. The cyan transfer roller 9C contacts the cyan photosensitive drum 1C via the intermediate transfer belt 8, and the black transfer roller 9K contacts the cyan photosensitive drum 1C via the intermediate transfer belt 8. (for black) is in contact with the photosensitive drum 1K.

The drive roller 16 is located downstream of the four photoconductor drums in the running direction of the intermediate transfer belt, and the drive roller 16 is mounted on the inner circumference of the intermediate transfer belt 8 in a state where the intermediate transfer belt 8 is wound at a winding angle of approximately 120 degrees. It is arranged so that it comes into contact with the surface. The drive roller 16 is rotated clockwise in FIG. 3 by a drive motor controlled by a control section. As a result, the intermediate transfer belt 8 runs in a predetermined running direction (clockwise in FIG. 3).

The driven roller 17 is located upstream of the four photoconductor drums in the running direction of the intermediate transfer belt 8, and is positioned inside the intermediate transfer belt 8 with the intermediate transfer belt 8 being wound at a winding angle of about 180 degrees. It is arranged so as to be in contact with the circumferential surface. In the intermediate transfer belt 8, a portion from the driven roller 17 to the drive roller 16 is set to be a substantially horizontal surface. The driven roller 17 rotates clockwise in FIG. 3 as the intermediate transfer belt 8 travels.

Tension roller 19 is in contact with the outer peripheral surface of intermediate transfer belt 8 . The pre-transfer roller 18 , the cleaning opposing roller 20 , the lubricant opposing roller 21 , the backup roller 22 , and the secondary transfer opposing roller 40 are in contact with the inner peripheral surface of the intermediate transfer belt 8 .
An intermediate transfer cleaning section 10 (cleaning blade) is installed between the secondary transfer opposing roller 40 and the lubricant opposing roller 21 so as to come into contact with the cleaning opposing roller 20 via the intermediate transfer belt 8 .
An intermediate transfer lubricant supply device 30 is installed between the cleaning opposing roller 20 and the tension roller 19 so as to come into contact with the lubricant opposing roller 21 via the intermediate transfer belt 8 . The intermediate transfer lubricant supply device 30 is composed of a lubricant supply roller, a solid lubricant, a compression spring, etc., like the photoreceptor drum lubricant supply device 3. Then, the lubricant is scraped little by little from the solid lubricant by the lubricant supply roller rotating counterclockwise in FIG. 3, and the lubricant is supplied to the surface of the intermediate transfer belt 8 by the lubricant supply roller. Become.
All of the roller members 17 to 22 and 40, except for the drive roller 16, are driven to rotate as the intermediate transfer belt 8 travels.

Referring to FIG. 3, secondary transfer opposing roller 40 is in contact with secondary transfer roller 70 via intermediate transfer belt 8 and secondary transfer belt 72. Referring to FIG. The secondary transfer counter roller 40 has a cylindrical metal core made of stainless steel or the like, and on the outer circumferential surface thereof, NBR having a volume resistance of about 10 ⁷ to 10 ⁸ Ω and a hardness (JIS-A hardness) of about 48 to 58 degrees is used. An elastic layer 83 (layer thickness is about 5 mm) made of rubber is formed.

Further, in the present embodiment, the secondary transfer opposing roller 40 is electrically connected to a power supply section, and a secondary transfer bias having a high voltage of about -5 kV is applied from the power supply section. The secondary transfer bias applied to the secondary transfer opposing roller 40 is used to secondary transfer the toner image that has been primarily transferred onto the surface of the intermediate transfer belt 8 onto the sheet P that is conveyed to the secondary transfer nip. This is a secondary transfer bias (DC voltage) having the same polarity as the toner polarity (in this embodiment, negative polarity). As a result, the toner carried on the toner carrying surface (outer peripheral surface) of the intermediate transfer belt 8 is electrostatically moved from the side of the secondary transfer facing roller 40 toward the side of the secondary transfer device 69 by the secondary transfer electric field. Become.
Note that in this embodiment, a negative polarity secondary transfer bias is applied to the secondary transfer opposing roller 40, but a positive polarity secondary transfer bias is applied to the secondary transfer roller 70 (secondary transfer belt 72). Alternatively, a secondary transfer bias can be applied to both rollers 40 and 70.

Next, the secondary transfer device 69 will be described in detail using FIGS. 3, 4, etc.
3, 4, etc., the secondary transfer device 69 includes a secondary transfer belt 72 as a transfer belt, a secondary transfer roller 70, a separation roller 71, a secondary transfer blade 73 (cleaning blade), etc. configured. By providing the secondary transfer belt device 69, the sheet P sent out from the secondary transfer nip can be conveyed well, and the separation of the sheet P from the secondary transfer belt 72 can be further improved. Can be done.

The secondary transfer belt 72 (transfer belt) is an endless belt stretched and supported by a plurality of roller members (secondary transfer roller 70 and separation roller 71), and is almost the same as the intermediate transfer belt 8. made of material. The secondary transfer belt 72 contacts the intermediate transfer belt 8 as a contact member to form a secondary transfer nip, and also conveys the sheet P sent out from the secondary transfer nip.

The secondary transfer roller 70 and the secondary transfer opposing roller 40 sandwich the intermediate transfer belt 8 and the secondary transfer belt 72 to form a secondary transfer nip. The secondary transfer roller 70 has an elastic layer having a hardness (Asker C hardness) of about 40 to 50 degrees formed (covered) on a hollow core made of stainless steel, aluminum, or the like. The elastic layer of the secondary transfer roller 70 is made of a rubber material such as polyurethane, EPDM, or silicone in which a conductive filler such as carbon is dispersed or an ionic conductive material is contained. can be formed into Note that, with reference to FIG. 4, the secondary transfer belt 72 is configured such that its widthwise range includes the widthwise range of the maximum size sheet P that can be passed through.
Further, the secondary transfer roller 70 is rotationally driven in the counterclockwise direction in FIG. 3 by a motor controlled by the control unit, and rotates (travels) the secondary transfer belt 72 in the counterclockwise direction in FIG. The roller 71 is rotated counterclockwise in FIG.

The separation roller 71 is disposed at the most downstream side in the conveyance direction of the sheet P with respect to the secondary transfer nip. The sheet P sent out from the secondary transfer nip is conveyed along the secondary transfer belt 72 running counterclockwise in FIG. It is separated from the secondary transfer belt 72 (curvature separation) by the secondary transfer belt 72 having a curved surface formed thereon. In this manner, in the apparatus using the secondary transfer belt 72, since curvature separation can be performed at the position of the separation roller 71, no special bias is applied to separate the sheets P.
Note that in this embodiment, the secondary transfer belt 72 is stretched by two roller members, the secondary transfer roller 70 and the separation roller 71, but the secondary transfer belt 72 is stretched by three or more roller members. 72 can also be configured to be stretched and supported.

The secondary transfer blade 73 comes into contact with the surface of the secondary transfer belt 72 and removes foreign matter such as toner and paper dust attached to the surface of the secondary transfer belt 72. The secondary transfer blade 73 is in pressure contact with the secondary transfer roller 70 via the secondary transfer belt 72 so as to be in contact with the secondary transfer roller 70 in a counter direction with respect to the running direction of the secondary transfer belt 72. The secondary transfer blade 73 has a plate-shaped blade main body made of a rubber material such as urethane rubber and having a thickness of about 1 to 5 mm, which is held in a holder made of a sheet metal.

Next, the fixing device 50 will be described in detail using FIGS. 3, 4, and the like.
As shown in FIG. 3, the fixing device 50 includes a fixing roller 51 as a fixing rotating body, a heater 53 as a heating means, a pressure roller 52 as a pressing rotating body, a pre-fixing guide plate 80, and the like. There is.
Here, the fixing roller 51 is a roller member with a multilayer structure in which an elastic layer and a release layer are sequentially laminated on a hollow core metal made of a metal material such as stainless steel, and is pressed against the pressure roller 52. to form a nip portion (fixing nip). The fixing roller 51 is rotated clockwise in FIG. 3 by a drive motor.
A heater 53 (heat source) serving as heating means is fixedly installed inside the fixing roller 51 having a hollow structure. Power is supplied from the power source to the heater 53, the fixing roller 51 is heated by radiant heat from the heater 53, and heat is further applied to the toner image on the sheet P from the heated surface of the fixing roller 51.
The pressure roller 52 mainly includes a core metal and an elastic layer formed on the outer peripheral surface of the core metal via an adhesive layer. The pressure roller 52 rotates counterclockwise in FIG. 2 as the fixing roller 51 rotates.
Further, the pre-fixing guide plate 80 is a plate-like member made of a metal material such as a zinc-treated steel plate, a heat-resistant resin material, or the like. The pre-fixing guide plate 80 is installed between the conveying device 60 and the fixing device 50 so as to face the non-fixing surface (lower surface) of the sheet P. Then, the sheet P (the sheet carrying the unfixed image) sent out from the conveyance device 60 is conveyed toward the fixing nip while being guided by the pre-fixing guide plate 80. Note that it is preferable that the pre-fixing guide plate 80 be grounded so that electric charges are not accumulated.
Note that, with reference to FIG. 4, the widthwise range of the fixing roller 51, the pressure roller 52, and the pre-fixing guide plate 80 includes the widthwise range of the maximum size sheet P that can be passed through. It is configured as follows.

The configuration and operation of the transport device 60, which is characteristic of the image forming apparatus 100 according to the present embodiment, will be described in detail below.
As shown in FIGS. 3 and 4, the conveyance device 60 is a device for conveying the sheet P sent out from the secondary transfer belt device 69 toward the fixing device 50. By installing the conveyance belt 61 (conveyance device 60) on the conveyance path from the secondary transfer belt 72 to the fixing device 50 in this way, the sheet P can be reliably transported by the conveyance belt 61 even if the conveyance path is long. can be transported to
The conveying device 60 in this embodiment includes a conveying belt 61 as a conveying member, a driving roller 62, a driven roller 63, a static eliminating needle 64 as a static eliminating member, a frame 65, and the like.

The conveyance belt 61 functions as a conveyance member that conveys the sheet P on the conveyance path from the secondary transfer belt 72 (transfer belt) to the fixing device 50. The conveyor belt 61 is stretched and supported by a plurality of roller members (a drive roller 62 and a driven roller 63), and is driven counterclockwise in FIG. 3 by rotation of the drive roller 62 by a drive motor ( (endless movement). The conveyor belt 61 can be formed of EPDM (ethylene propylene diene rubber), PVDF (vinyldene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), etc. . The driving roller 62 and the driven roller 63 are two roller parts arranged side by side on a shaft part with a gap, and are rotatably held in the frame 65 (casing) of the device 60 via bearings. has been done.

Here, with reference to FIG. 4, the conveyance belt 61 (conveyance member) in this embodiment is within the range M in the width direction of the sheet P conveyed on the conveyance path in the conveyance device 60, and within the range M It is formed so as to be in contact with the sheet P within a smaller range. In other words, the belt width (the length in the width direction perpendicular to the conveyance direction, which is the length in the vertical direction in FIG. 4) of the conveyor belt 61 is the width direction of the sheet P conveyed on the conveyance path. It is formed to be within a range M and smaller than the range M.
In particular, in this embodiment, two conveyor belts 61 are arranged side by side with gaps at equal intervals in the width direction centering on a central reference indicated by a dashed-dotted line. It is arranged so that it falls within the range M. Further, the conveyance surfaces of these two conveyance belts 61 are configured to be exposed through an opening formed in a frame 65 (casing) of the conveyance device 60.
Note that the two conveyor belts 61 are configured to be able to convey a sheet P of the minimum size that can be passed through the image forming apparatus 100. Specifically, the two conveyor belts 61 are arranged so as to fall within a range M' in the width direction of the sheet P of the smallest size.

Referring to FIGS. 3 and 4, the static eliminating needle 64 is installed in the middle of the conveying path in the conveying device 60, and functions as a static eliminating member that eliminates static from the sheet P being conveyed by the conveying belt 61 (conveying member). . The static eliminating needle 64 (static eliminating member) is a thin metal plate with a plurality of needle-like members arranged on the tip side (upper side in FIG. 3), and is grounded.
In the present embodiment, the static eliminator 64 (static eliminator) is applied to the sheet P transported on the transport path in the transport device 60 in a range in the width direction that is different from the range in the width direction where the transport belt 61 contacts the sheet P. It is formed so as to be close to P. That is, the static eliminating needle 64 is formed so as to be close to the sheet P conveyed on the conveyance path in a range in the width direction where the conveyance belt 61 is not installed (outside the belt width range of the conveyance belt 61). ing. Such a range in the width direction of the static elimination needle 64 is a range that does not hinder the conveyance of the sheet P by the conveyance belt 61.
In particular, in this embodiment, two static eliminating needles 64 (static eliminating members) are arranged side by side at equal intervals in the width direction centering on a central reference indicated by a dashed line. The needles 64 are arranged at both ends in the width direction outside the range of the conveyor belt 61. Further, the tips of these two static elimination needles 64 are exposed from an opening formed in the frame 65 (housing) of the conveyance device 60 and are opposed to (or (light contact). Specifically, the static eliminating needle 64 is arranged so that the position of its tip in the height direction is equal to or slightly protrudes above the conveying surface of the conveying belt 61.
Further, the static eliminating needle 64 (static eliminating member) is located at a position sufficiently away from the most downstream part of the secondary transfer belt 72 (the position of the separation roller 71), and approximately at the center of the conveying belt 61 in the conveying direction. is placed in a position corresponding to

As described above, in the present embodiment, the static eliminating needle 64 is installed in the middle of the conveyance path by the conveyor belt 61 and outside the range in the width direction of the conveyor belt 61 so as to be able to approach the sheet P being conveyed. Therefore, in the conveyance path from the secondary transfer belt 72 to the fixing device 50, the sheet P is conveyed well without lifting due to electrostatic force.

Specifically, when a static eliminating member is not provided in the conveying path from the secondary transfer belt 72 to the fixing device 50, as in the conventional conveying device 160 shown in FIG. The sheet P charged by applying a bias (in this embodiment, the sheet is charged with negative polarity) is separated from the secondary transfer belt 72 and carried on the conveyor belt 61 without applying a separation bias. Therefore, the sheet P is conveyed toward the fixing device 50 by the conveyor belt 61 in a charged state. Therefore, referring to the part surrounded by the broken line in FIG. 5(A), the sheet P is lifted by electrostatic force on the entrance side of the fixing device 50, and the sheet P is not properly fed into the fixing nip. Problems such as the sheet P folding at the edges are likely to occur.
On the other hand, in the present embodiment, the static eliminating needle 64 is brought close to the sheet P that is conveyed in almost intimate contact with the conveyor belt 61 due to the gravity of the sheet P and the conveyance force of the conveyor belt 61. Since the static electricity is removed, the phenomenon in which the sheet P is lifted up by electrostatic force on the conveyance path leading to the fixing nip is reduced. Therefore, the sheet P is fed into the fixing nip well, and problems such as folding of the edges of the sheet P are less likely to occur.

In addition, when discharging needles 164 (static eliminating member) are provided between the secondary transfer belt device 69 and the conveying device 160 as in the conveying device 160 shown in FIG. 5(B), the static eliminating effect on the sheet P is enhanced. Therefore, the static elimination needle 164 must be installed close to the sheet P transferred from the secondary transfer belt 72 to the transport belt 61, and there is a possibility that the static elimination needle 164 may impair the conveyance of the sheet P. There is. That is, referring to the part surrounded by the broken line in FIG. 5(B), when the sheet P is transferred from the secondary transfer belt 72 to the conveyor belt 61, it tends to interfere with the static elimination needle 164.
On the other hand, in the present embodiment, the sheet P is transported in a state that is in close contact with the transport belt 61 due to the gravity of the sheet P and the transport force of the transport belt 61, and the sheet P is placed in a position that does not interfere with the transport. Since the static elimination needle 64 is brought close to eliminate static electricity from the sheet P, the sheet P is transported smoothly on the transport path from the secondary transfer belt 72 to the fixing device 50.
In particular, since the static eliminating needle 64 is installed at a position sufficiently away from the secondary transfer belt device 69, the electric charge applied to the sheet P at the position of the secondary transfer belt device 69 is naturally discharged into the air. In a state where the potential of the sheet P has decreased to a certain extent, the static electricity on the sheet P is eliminated by the static elimination needle 64. Therefore, the change in the potential of the sheet P due to static elimination becomes small, and the toner on the sheet P becomes difficult to scatter. That is, it is possible to prevent image quality from deteriorating due to image dust.

Further, in this embodiment, since the static eliminating needle 64 having a pointed tip is used as the static eliminating member, the electric charge stored in the sheet P sent from the secondary transfer belt 72 is concentrated and discharged to the needle part. Therefore, it is possible to efficiently eliminate static electricity from the sheet P with a simple configuration.
In this embodiment, the static eliminating needle 64 (static eliminating member) is grounded, but a predetermined DC voltage (or AC voltage) may be applied to the static eliminating needle 64 (static eliminating member) from a power source.

Here, in this embodiment, as shown in FIG. 4, the static eliminating needle 64 (static eliminating member) is formed so as to be close to at least the widthwise end of the sheet P conveyed on the conveying path in the conveying device 60. has been done.
Specifically, one of the two static elimination needles 64 (the upper static elimination needle in FIG. 4) is arranged close to one end of the sheet P in the width direction; The static elimination needle 64 (the lower static elimination needle in FIG. 4) is arranged close to the other end of the sheet P in the width direction. That is, the sheet P conveyed by the conveyor belt 61 comes into contact with the conveyor belt 61 at its center in the width direction, and faces (or comes into sliding contact with) the static elimination needles 64 at both ends in the width direction.
Since the above-described lifting of the sheet P due to electrostatic force on the inlet side of the fixing device 50 is likely to occur at both ends of the sheet P in the width direction, as in this embodiment, static electricity is removed from both ends of the sheet P in the width direction. By actively bringing the needle 64 close to the needle 64, it is possible to reduce such lifting of the sheet P and to prevent the occurrence of edge folding.

<Modification 1>
FIG. 6 is a top view showing a transport device 60 and its vicinity as Modification 1, and corresponds to FIG. 4 in this embodiment.
As shown in FIG. 6, unlike the present embodiment, the conveying device 60 in Modification 1 has static eliminating needles 64 installed at both ends in the width direction, as well as static eliminating needles 64 installed at the center in the width direction. A needle 64 is installed. These three static eliminating needles 64 are all located at the center of the conveyor belt 61 in the conveyor direction, and are installed outside the range of the conveyor belt 61 in the width direction.
The conveyance device 60 in Modification 1 configured as described above also allows the sheet P to be transported smoothly without being lifted up due to electrostatic force in the conveyance path from the secondary transfer belt 72 to the fixing device 50, as in the present embodiment. can be transported to
In particular, in Modification 1, since the neutralization needle 64 actively eliminates static electricity from the widthwise central portion of the sheet P in addition to the widthwise both ends thereof, it is possible to further reduce image quality deterioration due to image dust.

<Modification 2>
FIG. 7 is a top view showing a transport device 60 and its vicinity as a second modification, and corresponds to FIG. 4 in this embodiment.
As shown in FIG. 7, the transport device 60 in Modification 2 is provided with a moving mechanism 91 that moves the static eliminating needle 64 (static eliminating member) in the width direction (vertical direction in FIG. 7).
Then, the static eliminating needle 64 (static eliminating member) is moved by the moving mechanism 91 so as to be close to the widthwise end of the sheet P according to the widthwise size of the sheet P conveyed on the conveyance path in the conveyance device 60. Ru. Specifically, as shown in FIG. 7A, when a sheet P having a width direction length of M1 (for example, an A4 lengthwise size sheet P) is conveyed, the movement is controlled by the control unit 90. The mechanism 91 moves the static eliminating needle 64 in the direction of the black arrow (towards the center in the width direction) in accordance with the width direction size M1. On the other hand, as shown in FIG. 7B, when a sheet P having a length in the width direction of M2 (>M1) (for example, an A3 vertical size sheet P) is conveyed, the control unit 90 The static eliminating needle 64 is moved in the direction of the black arrow (towards the end in the width direction) in accordance with the width direction size M2 by the moving mechanism 91 controlled by the moving mechanism 91 .
In the conveying device 60 in the second modified example configured in this manner, the sheet P can be favorably conveyed without lifting due to electrostatic force, regardless of the widthwise size of the sheet P being conveyed.
Note that as the moving mechanism 91 for moving the static eliminating needle 64, for example, a rack and pinion mechanism, a cam mechanism, or the like can be used. Further, the widthwise size of the sheet P may be detected directly by a size detection sensor 93 installed in the paper feeder 26 or the like, or by a user on the operation panel 92 installed on the exterior of the apparatus main body 100. It may be detected indirectly based on the input information regarding the sheet P. The moving mechanism 91 is then controlled by the control unit 90 based on such detection results.
In addition, when the static elimination needle 64 is configured to be moved manually, it is linked to the manual movement of the side fence (a member that determines the position of the sheet P in the width direction) of the paper feeder 26 in the width direction. Thus, the static eliminating needle 64 can be moved in the width direction.

<Modification 3>
FIG. 8 is a top view showing a transport device 60 and its vicinity as a third modification, and corresponds to FIG. 4 in this embodiment.
As shown in FIG. 8, the conveyance device 60 in Modification 3 uses a plurality of conveyance rollers instead of the conveyance belt 61 as a conveyance member that conveys the sheet P on the conveyance path from the secondary transfer belt 72 to the fixing device 50. 68 are provided.
Specifically, each of the three conveying rollers 68 has a plurality of roller parts formed on a shaft part with gaps in the width direction. The three conveyance rollers 68 are arranged in parallel at intervals in the conveyance direction, and each conveys the sheet P by rotating along the conveyance direction.
Also in Modified Example 3, the sheet P being conveyed is located on the conveyance path in the conveyance device 60 and outside the range in the width direction of the roller portion (outside the range of the roller width) of the roller portion functioning as a conveyance member in the conveyance roller 68. A static eliminating needle 64 is installed so that it can be approached.
The conveyance device 60 in Modification 3 configured in this manner also allows the sheet P to be transported smoothly without lifting due to electrostatic force in the conveyance path from the secondary transfer belt 72 to the fixing device 50, as in the present embodiment. can be transported to

<Modification 4>
FIG. 9 is a top view showing a transport device 60 and its vicinity as a fourth modification, and corresponds to FIG. 3 in this embodiment. FIG. 10 is a top view showing a transport device 60 and its vicinity as a fourth modification, and corresponds to FIG. 4 in this embodiment.
As shown in FIGS. 9 and 10, the conveying device 60 in Modification 4 also includes a conveying belt 61, a driving roller 62, a driven roller 63 as conveying members, and the same as in the present embodiment and Modifications 1 to 3. , a static eliminating needle 64 as a static eliminating member, a frame 65, and the like. Here, the conveyance device 60 in Modification 4 is further provided with a suction fan 66 as a contact assisting means. This suction fan 66 functions as an adhesion assisting means for bringing the sheet P conveyed along the conveyance path into close contact with the conveyance belt 61.
Specifically, the suction fan 66 is installed on the frame 65 so as to face the inner circumferential surface of the conveyor belt 61, and draws the sheet P (the sheet P conveyed by the conveyor belt 61) through the conveyor belt 61. is placed so as to face the Further, the conveyor belt 61 has a plurality of holes (through holes small enough not to hinder the conveyance of the sheet P) over the entire belt surface. Further, the suction fan 66 is controlled to be in the on state (suction state) at least when the sheet P is on the conveyor belt 61.
In this way, by installing the suction fan 66 (adhesion assisting means), the conveyor belt 61 can be kept in close contact with the conveyor belt 61 even when various disturbances occur, compared to a structure in which the sheet P is brought in close contact with the conveyor belt 61 only by gravity. On the other hand, the sheet P is stably and closely attached. Therefore, the distance between the sheet P being conveyed and the static eliminating needle 64 (static eliminating member) is stable without variation, and the function of the static eliminating needle 64 is efficiently exhibited, so that the sheet P is conveyed well without lifting due to electrostatic force. be done. In particular, in Modification 4, instead of using a means for bringing the conveyor belt 61 into close contact with the conveyor belt 61 by electrostatic force as the adhesion assisting means, a suction fan 66 that does not generate such an electrostatic force is used. It does not affect the static elimination efficiency of the static eliminating member).
In Modified Example 4, the static eliminating needle 64 (static eliminating member) is located at a position relative to the conveying direction (the conveying direction of the sheet P in the conveying path, which is the left-right direction in FIGS. 9 and 10). The position approximately coincides with the position in the transport direction. That is, the static elimination needle 64 and the suction fan 66 are arranged so that their positions in the left-right direction in FIGS. 9 and 10 substantially coincide with each other. This is because at a position close to the suction fan 66 in the transport direction, the suction force against the sheet P is stronger and the adhesiveness of the sheet P to the transport belt 61 is higher than at a position farther away. That is, by positioning the static eliminating needle 64 and the suction fan 66 close to each other in the transport direction, the static eliminating needle 64 can efficiently perform its function.

Further, in the fourth modification, the static eliminating needle 64 (static eliminating member) is arranged such that the position of the static eliminating needle 64 (static eliminating member) in the conveying direction of the sheet P on the conveying belt 61 is at the center or downstream of the center. That is, referring to FIG. 10, the static eliminating needles 64 are arranged so that the positional relationship in the conveying direction on the conveying belt 61 satisfies X1≧X2. Note that X1+X2 is the length of the conveying surface of the conveying belt 61 in the conveying direction.
As a result, the occurrence of abnormal images (dust/discharge traces) due to static elimination is reduced, and static electricity is efficiently removed from the sheet P by the static elimination needle 64 after the potential drops below a certain level due to natural discharge. .
Specifically, FIG. 11 is a graph showing the relationship between the potential difference (paper potential difference) of the sheet P before and after static electricity removal and the occurrence of abnormal images (dust/discharge traces). As shown in Figure 11, the abnormal image tends to worsen as the potential difference increases, and the range in which the image becomes acceptable (rank 4 or higher) is 1 kV or less when the environment in which the device is used is high temperature and high humidity. In addition, when the temperature is low and humidity is low, it is necessary to lower the voltage to 6 kV or less.
On the other hand, FIG. 12 is a graph showing the relationship between the position of the sheet P in the transport direction during transport and the potential of the sheet P (paper potential). As shown in FIG. 12, the sheet P gradually discharges during transportation, so the potential decreases compared to immediately after the secondary transfer process. ) will not reach completely 0V. On the other hand, since the potential of the sheet P becomes 0V after passing through the static elimination needle 64 (static elimination member), the potential difference between 0V and before passing becomes the potential difference before and after static elimination. In order to bring dust/discharge marks to an acceptable level, the potential difference (paper potential difference) before and after static elimination needs to be within the range explained in FIG. 11 (1 kV or less at high temperature and high humidity, and 6 kV or less at low temperature and low humidity). Therefore, by positioning the static eliminating needle 64 in the conveying direction at the center of the conveying belt 61 or downstream of the center, the static eliminating needle 64 can be efficiently used while reducing the occurrence of abnormal images (dust/discharge traces). It becomes possible to eliminate static electricity.

As described above, the conveyance device 60 in this embodiment includes a conveyance belt 61 (conveyance member) that conveys the sheet P on the conveyance path from the secondary transfer belt 72 (transfer belt) to the fixing device 50, and a conveyance path A static eliminating needle 64 (static eliminating member) is installed in the middle of the sheet P to eliminate static electricity from the sheet P being conveyed by the conveying belt 61. The conveyance belt 61 is formed so as to be in contact with the sheet P within a range M in the width direction of the sheet P conveyed on the conveyance path and within a range smaller than the range M. The static eliminating needle 64 is formed so as to be close to the sheet P in a range in the width direction that is different from the range M in the width direction where the transport belt 61 contacts the sheet P transported on the transport path.
As a result, the sheet P is smoothly transported on the transport path from the secondary transfer belt 72 to the fixing device 50 without being lifted up due to electrostatic force.

Note that in this embodiment, the present invention is applied to an image forming apparatus 100 that is provided with a secondary transfer belt device 69 that includes a secondary transfer belt 72 as a transfer belt. On the other hand, it does not include an intermediate transfer body such as an intermediate transfer belt or an intermediate transfer drum, but instead uses a photoconductor drum (photoconductor) on which a toner image developed by a developing section is formed, and the toner image is transferred by contacting the photoconductor drum. A transfer belt for forming a nip and transferring a toner image on a photoreceptor drum to a sheet conveyed to the transfer nip, a so-called direct transfer type image forming apparatus. The present invention can be applied.
Further, in this embodiment, the present invention is applied to an image forming apparatus 100 that forms a color image. On the other hand, the present invention can also be applied to an image forming apparatus that forms only monochrome images.
Further, in this embodiment, the needle-shaped static eliminating needle 64 is used as the static eliminating member installed in the transport device 60, but the static eliminating member is not limited to this, and for example, the static eliminating member may be a wire-shaped static eliminating wire or the like. , flocked static-eliminating hair, etc. can also be used.
Even in such cases, effects similar to those of this embodiment can be obtained.

Note that it is clear that the present invention is not limited to this embodiment, and that this embodiment can be modified as appropriate within the scope of the technical idea of the present invention in addition to what is suggested in this embodiment. be. Further, the number, position, shape, etc. of the constituent members are not limited to those in this embodiment, and can be set to a number, position, shape, etc. suitable for implementing the present invention.

Note that in this specification and the like, the term "sheet" is defined to include all sheet-like recording media such as coated paper, label paper, OHP sheet, metal sheet, etc. in addition to paper.
Furthermore, in the specification of this application, etc., the state in which the static eliminating member is close to the sheet includes a state in which the static eliminating member faces the sheet with a slight gap, as well as a state in which the static eliminating member is in contact with the sheet. It is defined as

50 fixing device,
60 conveyance device,
61 conveyor belt (conveyor member),
64 Static elimination needle (static elimination member),
66 Suction fan (adhesion assisting means),
68 conveyance roller (conveyance member),
69 Secondary transfer device,
72 Secondary transfer belt (transfer belt),
91 Moving mechanism,
100 Image forming device (image forming device main body),
P sheet.

Japanese Patent Application Publication No. 2018-72749 Japanese Patent Application Publication No. 2004-43070

Claims (8)

a conveyance member that conveys the sheet in a conveyance path from the transfer belt to the fixing device;
a static eliminating member that is installed in the middle of the conveying path and eliminates static electricity from the sheet being conveyed by the conveying member;
a moving mechanism that moves the static eliminating member in the width direction;
Equipped with
The conveyance member is formed so as to be in contact with the sheet within a range in the width direction of the sheet conveyed on the conveyance path and within a smaller range than the width direction of the sheet,
The static eliminating member is
formed so as to be close to the sheet conveyed on the conveyance path in a widthwise range different from a widthwise range in which the conveyance member contacts the sheet;
The conveying device is characterized in that the moving mechanism moves the sheet so as to be close to the widthwise end of the sheet according to the widthwise size of the sheet conveyed on the conveyance path. The conveyance member is a conveyance belt, and the belt width is within a range in the width direction of the sheet conveyed on the conveyance path and is smaller than the range;
2. The conveyance device according to claim 1, wherein the static eliminator is formed so as to be close to the sheet conveyed on the conveyance path in a widthwise range where the conveyance belt is not installed. 3. The conveyance apparatus according to claim 1, further comprising a contact assisting means for bringing the sheet conveyed along the conveyance path into close contact with the conveyance member. a conveyance member that conveys the sheet in a conveyance path from the transfer belt to the fixing device;
a static eliminating member that is installed in the middle of the conveying path and eliminates static electricity from the sheet being conveyed by the conveying member;
a suction fan for bringing the sheet conveyed along the conveyance path into close contact with the conveyance member;
Equipped with
The conveyance member is formed so as to be in contact with the sheet within a range in the width direction of the sheet conveyed on the conveyance path and within a smaller range than the width direction of the sheet,
The static eliminating member is
formed so as to be close to the sheet conveyed on the conveyance path in a widthwise range different from a widthwise range in which the conveyance member contacts the sheet;
A conveyance device characterized in that a position of the sheet in the conveyance path in the conveyance direction substantially coincides with a position of the suction fan in the conveyance direction. The conveying member is a conveying belt,
5. The conveying device according to claim 4 , wherein the static eliminator is positioned at the center of the conveyor belt in the sheet conveyance direction or downstream of the center. 6. The conveyance device according to claim 1, wherein the static eliminating member is formed so as to be close to at least a widthwise end of the sheet conveyed on the conveyance path. 7. The conveying device according to claim 1, wherein the static eliminating member is a static eliminating needle. An image forming apparatus comprising: the conveying device according to any one of claims 1 to 7, the transfer belt, and the fixing device.

Images