JP4498395B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to a charge removal mechanism for a transfer material.

  The configuration of a conventional image forming apparatus is shown in FIG.

  A conventional image forming apparatus includes a photosensitive drum 101 as an image carrier. The photosensitive drum 101 is formed in a cylindrical shape and is supported by an apparatus main body (not shown) so as to be rotatable in the direction of the arrow R1. Around the photosensitive drum 101, a charging device 102 that uniformly charges the photosensitive drum 101 in order along its rotation direction, emits a laser beam corresponding to the original image, exposes the photosensitive drum 101, and forms an electrostatic latent image. An exposure device 103 for forming, a developing device 105 for forming a toner image by attaching toner to the electrostatic latent image, a transfer roller 106 as a transfer means for transferring the toner image on the photosensitive drum 101 to the paper P, and a photosensitive material after transfer. A cleaner 107 for removing residual toner on the drum 1 is disposed.

  On the other hand, on the upstream side of the photosensitive drum 101 in the transport direction (the right side in FIG. 7), a paper feed cassette 109 for loading and storing paper P to be image formed is mounted. A paper feed roller 110 is disposed above the front side of the paper feed cassette 109, and a transfer material conveyance path 111 is provided on the downstream side (left side in the figure). In the transfer material conveyance path 111, two pairs of conveyance rollers 112 as conveyance means for nipping and conveying the paper P from the front and back, a registration sensor 113 for detecting the leading edge of the paper P, and the charge of the paper P in contact with the paper. A neutralizing brush 115 is disposed as a neutralizing means to be removed, and a pre-transfer guide 116 that forms a part of the transfer material conveyance path 111 and guides the paper P to the transfer region is provided. A fixing device (not shown) for fixing the toner image transferred to the paper P is disposed on the downstream side of the photosensitive drum 101.

  When a print signal is input to the image forming apparatus from a host computer (not shown), the photosensitive drum 101 starts to rotate in the direction of the arrow R1 in the figure, and the charging device 102 uniformly charges the surface. At this time, the paper feed roller 110 rotates and the paper P is fed from the paper feed cassette 109. The fed paper P is nipped and conveyed by the conveying roller 112, and is sent to a position where the registration sensor 113 is tilted to stop. On the other hand, the charged surface on the surface of the photosensitive drum 101 is irradiated with laser light modulated by an image signal, and an electrostatic latent image is formed. Next, toner is attached to the electrostatic latent image by the developing roller 105a of the developing device 105 to form a toner image. The conveyance roller 112 is driven so as to synchronize with the toner image, and the paper P is brought into contact with the static elimination brush 115 and the back side thereof is neutralized by the static elimination brush 115, and transferred via the pre-transfer guide 116. The toner image on the photosensitive drum 1 is transferred by a fixing roller (fixing device) that enters the area and is applied with a transfer bias by a high voltage power supply (not shown). Thereafter, the toner image is fixed to the paper P by a fixing device (not shown), and is discharged to the outside of the apparatus main body. On the other hand, the photosensitive drum 101 in which the toner image disappears due to the transfer is prepared for the next image forming process in which the residual toner is removed by the cleaner 107 and the charging of the charging device 102 starts.

As described above, there is an image forming apparatus described in Patent Document 1 as an image forming apparatus that performs static elimination using a static elimination brush in front of a transfer unit.
Japanese Patent Application Laid-Open No. 06-51647

  However, in the above background art, a case where the leading edge of the paper P is caught on the static elimination brush 115 and the paper is clogged is assumed. When the paper P is thin and comes into contact with the static elimination brush 115, the tip of the paper P may be broken, leading to paper clogging.

The neutralizing brush 115 as the neutralizing means in FIG. 7 is arranged so that the neutralizing brush 115 blocks the trajectory through which the paper passes in order to enhance the neutralizing effect of the paper P. Then, so as to block the path of the paper, placing a charge eliminating unit, a paper tip, if you scratched the charge removing means is generated, if a paper jam there as a starting point occurs is because envisioned.

In order to achieve the above object, the image forming apparatus of the present invention comprises an image carrier that carries a toner image, a transfer nip formed with the image carrier, and the toner image on the image carrier as a transfer material. A transfer means for transferring, a charge removing means for discharging the transfer material facing the transfer material upstream of the transfer nip in the transfer material transport direction, and a transfer for transporting the transfer material upstream of the transfer nip in the transfer material transport direction A charge transporting means, wherein the charge eliminating means is arranged such that a leading edge of the transfer material transported by the transfer material transporting means in an image forming apparatus facing the transfer material between the transfer nip and the transfer material transporting means. wherein said transfer material conveying means so as not to contact the charge removing means is arranged, by the conveying speed of the transfer material conveying means transfer material to form a loop by faster than the conveying speed of the transfer means In which the transfer material is equal to or approaching the charge removing means.

  The present invention has been made in view of the above-described problems. That is, an object of the present invention is to exhibit an efficient charge removal of a transfer material while suppressing the occurrence of a jam.

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

(First embodiment)
FIG. 1 shows a first embodiment of the present invention. In the figure, 1 is a photosensitive drum as an image carrier, 9 is a transfer roller as transfer means, 12 is a resist upper roller, 13 is a resist lower roller, and 32 is a transfer material regulation in front of the transfer area. The upper guide 33 is a lower guide that regulates the conveyance direction of the transfer material in front of the transfer region. By forming a nip (transfer material transport portion) with the resist upper roller 12 and the resist lower roller 13, it functions as a transfer material transport means. Further, G in the figure is a perpendicular line passing through the center of the photosensitive drum 1 and the transfer roller 9 in contact with the outer peripheral surface of the photosensitive drum 1. H is a line in contact with the outer periphery of the registration roller 12 at a vertical line at the center of the registration roller pair of the registration upper roller 12 and registration lower roller 13.

J is a paper transport path after the front end of the paper bites into the transfer nip N in the transfer area. V 2 represents the outer peripheral speed of the photosensitive drum 1, and V 1 represents the outer peripheral speed of the registration roller pair 12 and 13. Reference numeral 31 in FIG. 1 is a non-woven cloth of polyethylene terephthalate fiber coated with a conductive paint in which carbon is dispersed in an acrylic resin binder, and is molded with a conductive double-sided adhesive tape on the upper guide 12. It is pasted. The surface resistance of the neutralizing cloth is 10 ⁴ to 10 ⁶ Ω.

  The photosensitive drum 1 is capable of printing on paper having an outer diameter of 30 mm, a length of 280 mm, and an LTR size width of 216 mm. An organophotoreceptor based on polycarbonate is applied to a 1 mm thick aluminum tube.

  The surface of the photoreceptor 1 is charged and exposed by the charging unit 2 and the exposure unit 3 to form a dark portion of −700V and a bright portion of −150V. The electrostatic latent image is developed with a toner image by the developing means 5. A toner (developer) having a particle size of 7 μm on average and manufactured by pulverization is used. The toner is negatively charged. The amount of charge is about 7 μC per gram.

The amount of toner on the photosensitive drum when solid printing is performed is about 1.0 to 1.5 mg / cm ² . The rotational peripheral speed V2 on the outer peripheral surface of the photosensitive drum is 200 mm / second. At the time of image formation, the drive motor 53 is controlled to rotate by the control device 51, the peripheral speed of the photosensitive drum is rotated by V2, and the paper sandwiched between the transfer roller 9 and the nip formed is also conveyed by V2. This peripheral speed is realized by rotating a photosensitive drum having an outer diameter of 30 mm at a rotational speed of 127.32 rpm.

The transfer roller 9 has an outer diameter of 17 mm and a core metal diameter of 8 mm. The elastic layer is a mixture of NBR and epichlorohydrin rubber and is foam-molded. The electric resistance of the elastic layer is about 10 ⁶ to 10 ⁹ Ωcm. The hardness when the Asker C hardness meter is brought into contact with the transfer roller surface with a pressing pressure of 500 gf is 28 °.

  The transfer of the toner image carried on the photosensitive drum 1 onto the paper serving as a transfer material is performed by applying a bias to the transfer roller core metal. The applied voltage is +1 kV to +6 kV.

  The resist upper roller 12 is made of nickel-plated iron and has an outer diameter of 14 mm, and the resist lower roller 13 is a steel core having an outer diameter of 10 mm wound with chloroprene rubber having a thickness of 2 mm, and the outer diameter is 14 mm. The cores of the upper resist roller 12 and the lower resist roller 13 are electrically grounded. The chloroprene rubber of the lower resist roller is electrically insulating. The residual toner after the transfer is collected by the cleaning device 7.

  The distance between the transfer nip N and the nip R between the registration roller pair is 45 mm.

  The upper guide 32 and the lower guide 33 are gin-coated steel plates obtained by galvanizing and chromating a steel sheet metal. Both the upper guide 32 and the lower guide 33 are electrically grounded. As the neutralization cloth 31, a neutralization tape model number 7784 manufactured by Okamoto Co., Ltd. was used. The resistance value on the gin-coated steel sheet is 0.46 MΩ when measured by contacting the probe at a distance of 10 mm with a multimeter 89IV manufactured by Fluke.

  The neutralizing cloth 31 is affixed to the upper guide 32 and is arranged so that the transfer material can be neutralized from the surface on the transfer area where the toner is transferred. This is because, depending on the resistance value of the transfer material, its thickness, etc., it is more effective to preferentially remove the toner on the side of the transfer material due to toner scattering. Further, the reason why the neutralizing cloth, which is a sheet-shaped neutralizing means, is adopted as the neutralizing means is that the possibility of being caught even when the transfer material comes into contact with the neutralizing needle or the neutralizing brush is low. In addition, the neutralization cloth has more discharges at the starting point than the neutralization needle, and even if there is some deterioration of the neutralization means, its neutralization performance is not easily impaired.

  The direction of the transfer nip N and the nip R, that is, the direction in which the paper is conveyed by the nip, is a line connecting the transfer nip N and the nip R (a line connecting the center points of the nips) as a reference line X. It is as follows. The center of the transfer roller 9 is shifted from the center of the photosensitive drum 1 with respect to the vertical line, and the angle formed between the line G corresponding to the nip line of the transfer nip N and the reference line X is 20 °. Between the transfer nip N and the nip R, the line G is set to be on the upper side. On the other hand, in the registration roller pair, an angle formed by the line H corresponding to the nip line of the nip R and the reference line X is 15 °, and between the transfer nip N and the nip R, the line H is on the upper side, that is, the neutralizing cloth 31 is disposed. Is set to be on the side.

  The lower guide 33 is provided above the line (reference line X) connecting the transfer nip N and the nip R of the registration roller pair. A neutralizing cloth 31 is attached to the surface of the upper guide 32 on the paper passing side. The paper that exits the pair of registration rollers is conveyed along the line H, but the shape of the transfer guide is configured so that the line H does not cover the region where the neutralizing cloth 31 is pasted. The distance between the neutralizing cloth 31 and the line H is set to 0.5 mm or more. When passing curled paper as in a device that performs double-sided printing, the distance is 1.5 mm or more.

  In this embodiment, the end of the neutralizing cloth near the photosensitive drum is closest to the line H, but the distance between the ends is 1.0 mm. By providing the above-mentioned distance between the neutralizing cloth 31 and the line H, it is possible to suppress a paper jam caused by the leading edge of the paper being caught by the neutralizing cloth.

  Next, the paper conveying operation of this embodiment will be described. When image formation is started on the photosensitive drum 1 by image forming means (not shown), the paper 16 is conveyed in the direction of the photosensitive drum 1 in time with the toner image on the photosensitive drum 1. Then, under the control of the control device 51 as control means, the drive motor 52 rotates, the registration roller pair rotates at the peripheral speed V1, and the rotational peripheral speed is 204 mm / second faster than the peripheral speed of the photosensitive drum 1. Second, the paper sandwiched between the pair of registration rollers is also conveyed at 204 mm / second. The paper 16 is conveyed along a locus with the line H as a tangent. Then, the paper 16 faces the neutralizing cloth 31. When the leading edge of the paper 16 enters the transfer nip N, the paper 16 is transported by both the transfer nip N and the resist nip R. However, since there is a difference in transport speed of 2% between them, the paper loop is the same as that of the paper. It grows in the transportation process. At the moment when the leading end of the paper bites into the transfer nip N, that is, at the moment of contact, the paper feeding direction at the nip R is above the reference line X. Can do. Further, since the lower guide 33 is above the transfer nip N, a convex loop is secured on the upper side. In this embodiment, the edge height of the upper guide 32 from the photosensitive drum 1 is set so that the loop amount (loop height) from the lower guide 33 at this time becomes 2.0 mm. Furthermore, the amount of loop increases due to the conveyance of paper. The loop amount becomes higher by about 0.5 mm when the paper is transported by about 10 mm at the transfer nip N, and the distance between the neutralizing cloth 31 and the paper approaches 1.5 mm, and the neutralizing effect by the neutralizing cloth 31 is increased. Thereafter, the loop gradually becomes larger, and the paper 16 is conveyed while being in contact with the charge removal cloth 31. The paper is more stably discharged by contacting the discharging cloth.

When an image is formed using paper left in an environment with an air temperature of 15 ° C. and a humidity of about 10%, the paper is positively charged by contact with a resin component such as a paper feed roller. The amount of charge varies depending on the frictional conditions with the resin parts, the environment, and the paper, but it cannot be generally stated. However, in the case of paper having a basis weight of 64 g / m ² , the surface pressure is about 1 kgf / cm ² with chloroprene rubber. When transported in contact with pressure, it is charged to about +5 kV. (Measurement condition: When measured with a Trek electrometer MODEL341, suspended in the air without an electrode on the back) When the paper is charged, the toner image on the photosensitive drum is transferred to the paper before the transfer nip N However, at this time, since the paper and the photosensitive drum are transferred without being in close contact with each other, a blurred image is formed. This is called splattering. In order to prevent this scattering to some extent, the paper potential should be +1.5 kV. Further, in order to make the influence of the charging of the paper almost inconspicuous on the image, it is desirable to set the paper potential to +1 kV or less.

  FIG. 2 shows the potential after passing the paper charged to the potential +5 kV and the vicinity of the neutralizing cloth 31. The horizontal axis is the distance between the static elimination cloth 31 and the paper 16. The vertical axis represents the potential of the paper 16 after passing through the vicinity of the neutralizing cloth. When the distance between the paper and the neutralizing cloth is 4 mm or more, the neutralizing effect is small. However, if the distance between the paper and the neutralizing cloth is closer than that, the amount of charge removed from the paper by the neutralizing cloth increases. That is, the charge eliminating effect is increased. When the distance between the paper and the neutralizing cloth is 1.5 mm, the potential of the paper can be +1.5 kV, the potential can be +1 kV when the distance is 1.0 mm, and +500 V or less when the distance is 0.7 mm. In the present embodiment, the effect of removing electricity by the electricity removing cloth starts to appear on the image more than 10 mm after the leading edge of the paper bites into the transfer nip N. This is because a paper loop is formed and the distance from the neutralizing cloth is reduced. However, it is not the case that the neutralization effect is not exhibited at all in the range corresponding to the front end portion of the paper. As described above, the paper is transported in the direction of the tangent H from the nip R, and therefore, the range corresponding to the leading end portion of the paper once approaches the static eliminating cloth 31 in the transport process. If the position where the neutralizing cloth 31 is affixed is a position 15 mm from the transfer nip, the neutralization effect begins to occur more greatly from a position 25 mm from the front end of the paper. Then, after 25 mm, the paper is transported in proximity to or in contact with the neutralizing cloth, so that it is transported while being more reliably neutralized. What range of the paper the static elimination effect of the paper loop is exerted on may be set in accordance with the guide shape and the location of the static elimination cloth. In this embodiment, the transfer roller and the registration roller pair are arranged so that a convex loop is formed toward the transfer guide side to which the neutralizing cloth is attached, and the lower guide is the transfer nip N and the nip of the registration roller pair. The position was set higher than the line connecting R. Furthermore, the peripheral speed of the registration roller was made larger than the peripheral speed of the photosensitive drum so that the paper loop gradually increased during paper conveyance.

  With the configuration as described above, it is possible to surely remove the charge of the paper and prevent the image from being scattered while preventing the paper jam due to the paper leading edge portion being caught on the charge removal cloth.

(Second Embodiment)
FIG. 3 shows a second embodiment of the present invention. Since the approximate configuration is the same as that of the first embodiment, different components will be mainly described. In addition, since what has the same number as the component demonstrated in 1st Embodiment has the same function, description is omitted.

  The upper guide 67 of the present embodiment has a concave portion, and a static elimination needle 65 as a static elimination means is disposed in the concave portion. Since the registration roller pair and the transfer roller 9 operate in the same manner as in the first embodiment, the behavior of the paper has a paper transport path such as J as in the first embodiment.

  Both the upper guide 67 and the lower guide 66 are electrically grounded. As the static elimination needle 65 as the static elimination means, a static elimination needle having needle tips aligned at a pitch of 2 mm was used. The static elimination needle 65 is ensured to be electrically conductive with the upper guide 67.

  In the direction of the transfer nip N and the nip R, that is, the direction in which the paper is conveyed by the nip, the transfer nip N, the nip R, and the reference line X have the same relationship as in the first embodiment.

  The lower guide 66 is provided above the line connecting the transfer nip N and the nip R of the registration roller pair. Further, a static elimination needle 65 is disposed in the upper guide 67 in the vicinity of the sheet passing surface. The conveyance of the paper exiting the registration roller pair follows the line H, but the shape of the transfer guide is configured so that the line H does not cover the area where the static elimination needle 65 is disposed. The distance between the tip of the static elimination needle 65 and the line H is 0.5 mm or more. When passing curled paper as in a device that performs double-sided printing, the distance is 1.5 mm or more.

  By providing the above-mentioned distance between the static elimination needle 65 and the line H, it is possible to suppress a paper jam due to the leading edge of the paper being caught by the static elimination cloth. The distance between the portion other than the concave portion of the upper guide 67 and the tip of the static elimination needle 65 is 2.0 mm. In addition, a recess is provided in the upper guide 67 where the static elimination needle 65 is disposed, but the space between the line H and the recess is sufficiently secured so that the leading end of the paper is not caught in the recess. As a result, the leading edge of the paper is not caught in the recess.

  The paper conveying operation of the present embodiment is the same as that of the first embodiment except for the following.

  The paper 16 is conveyed along the locus of the line H. Then, the paper 16 faces the static elimination needle 65. As described in the first embodiment, when the leading edge of the paper 16 enters the transfer nip N, a convex loop is formed on the static elimination needle 65 side. Furthermore, the amount of loop increases due to the conveyance of the paper. The loop amount increases by about 0.5 mm when the paper is conveyed by about 10 mm at the transfer nip N, the distance between the tip of the static elimination needle 65 and the paper approaches 2.5 mm, and the static elimination effect by the static elimination needle 65 increases.

  Thereafter, the loop gradually becomes larger, and the paper 16 extends along other than the concave portion of the upper guide 67. Then, the distance between the paper 16 and the static elimination needle 65 is substantially fixed to 2.0 mm, which is the distance between the portion other than the concave portion of the upper guide 67 and the tip of the static elimination needle 65, and the distance between the static elimination needle 65 and the paper 16. As a result, a stable static elimination effect is exhibited.

  In addition, since the electrical conductivity between the upper guide 67 and the static elimination needle 65 is ensured, both are converged to the ground potential. For this reason, the upper guide 67 also exhibits a certain degree of static elimination effect. However, since the upper guide 67 faces the paper 16 on the surface, electric field concentration is unlikely to occur. On the other hand, in a region where static elimination is performed by the static elimination needle 65, an effective static elimination effect due to concentration of the electric field is exhibited. Therefore, as in the present embodiment, by using a static elimination needle as a static elimination means for static elimination before transfer, and stabilizing the distance from the static elimination needle, a stable static elimination effect that cannot be obtained only by the transfer guide is obtained. It is demonstrated.

( First reference example )
FIG. 4 shows a first reference example of the present invention.

This reference example shows an example in which the present invention is implemented in an apparatus in which a registration roller pair is close to a photosensitive drum.

  When the pair of registration rollers is close to the photosensitive drum, the paper before transfer can be kept waiting in the vicinity of the photosensitive drum, so that the paper conveyance path can be shortened and the apparatus can be miniaturized. In FIG. 4, reference numeral 1 denotes a photosensitive drum as an image carrier, and 9 denotes a transfer roller as a transfer unit, which forms a transfer nip with the photosensitive drum 1 and transfers the toner on the photosensitive drum 1 to paper. 16 is paper, 31 is a neutralizing cloth as a static eliminating means, 34 is a resist upper roller, and 35 is a resist lower roller. The registration upper roller 35 is a conveying unit that conveys paper in pairs with the registration lower roller. Reference numerals 36 and 37 denote conveyance rollers, which are conveyance means for conveying the paper in pairs with the conveyance rollers 36 and 37. Reference numeral 38 denotes an upper guide, 39 denotes a lower guide, and 40 and 41 denote conveyance guides. In the drawing, T is a nip of a pair of registration rollers, and S is a nip of a pair of conveying rollers. V3 indicates the peripheral speed of the conveying roller, and V4 indicates the peripheral speed of the registration roller. Line E is a perpendicular line of the line passing through the centers of the transport rollers 36 and 37 and is in contact with the outer periphery of the transport roller. Line F is a perpendicular line of the line passing through the centers of the registration roller rollers 34 and 35 and is in contact with the outer periphery of the registration roller. The same reference numerals as those in the first embodiment denote the same members. The peripheral speed of the photosensitive drum 1 is 100 mm / second. The resist upper roller 34 is made of iron with nickel plating on the surface and has an outer diameter of 14 mm. The upper resist roller 34 is electrically grounded. The lower roller of the resist is formed by winding chloroprene rubber having a conductive property by dispersing carbon on an iron core bar having an outer diameter of 10 mm, and having an outer diameter of 14 mm. The mandrel is electrically grounded.

  Assuming that the line connecting the registration nip T and the conveyance roller nip S is a reference line Y, the following is obtained. The angle formed by the line F corresponding to the nip line of the registration nip T and the reference line X is 10 °, and the line F is located above the reference line Y, that is, on the neutralization cloth 31 side, between the registration nip T and the conveyance roller nip S. It is set. On the other hand, in the conveyance rollers 36 and 37, the angle formed by the line E corresponding to the nip line of the nip S and the reference line Y is 15 °, and between the registration nip T and the conveyance roller nip S, the line E is above the reference line Y. The neutralization cloth 31 is set on the side where it is disposed.

The upper registration roller 34 and the lower registration roller 35 are rotated by the rotational drive of the motor 54 controlled by the control device 56. The rotational peripheral speed V4 is controlled to 100 mm / second. The paper in the nip is conveyed at V4. The conveyance guide sheet metal 40 is a zinc-plated iron sheet metal, and is provided above the registration nip T and the conveyance roller nip S. A neutralizing cloth 31 is attached to the conveyance surface. The conveyance guide 41 is a galvanized iron sheet metal having a mountain shape. The conveyance roller 36 is made of polyacetal and has an outer diameter of 14 mm. The conveying roller 37 is formed by winding an insulating chloroprene rubber with a thickness of 2 mm on an iron core having an outer diameter of 10 mm, and the outer diameter is 14 mm. The transport rollers 36 and 37 are rotated by receiving the rotational drive of the motor 55 controlled by the control of the control device 56. The conveying roller 36 rotates at a rotational peripheral speed of 104 mm / second (V3), and the paper is also conveyed by the conveying rollers 36 and 37 at 104 mm / second.

  Next, the operation will be described. The paper transported by the transport rollers 36 and 37 is transported along the broken line E. Thereafter, the resist nip T is reached after contacting the resist upper roller 34. The upper registration roller 34 and the lower registration roller 35 do not move immediately even when the leading edge of the paper 16 reaches the registration nip T. After reaching 10msec, it starts to rotate. Since the conveying rollers 36 and 37 continue to feed the paper while the registration roller pair is stopped, a loop is formed between the registration roller and the conveying roller. The direction in which the loop is formed is the upper side and the side close to the charge removal cloth 31. The nip line E of the transport rollers 36 and 37 is directed upward from the reference line Y between T and S, and the nip line F of the registration nip T is directed upward from the reference line Y between T and S. Because. In addition, the fact that a part of the conveyance guide 41 is higher than the nip S of the conveyance roller is one of the reasons that the loop can be easily formed on the upper side. The distance between the registration nip T and the conveyance roller nip S is 50 mm.

  By rotating the pair of registration rollers 10 msec after reaching the leading edge of the paper, a loop of about 4 mm is formed, and the paper is conveyed while being close to the static eliminating cloth 31. As a result, the paper is neutralized. Further, the loop amount increases thereafter, and the paper is more reliably brought into contact with the static eliminator, and the static electricity is eliminated while performing more stable static elimination. After neutralization, the paper passes through the registration roller pair, but the upper resist roller 34 is metal, and the surface layer of the lower resist roller 35 is conductive, and both rollers are electrically grounded. Not charged. Thereafter, the paper is guided by transfer guides 38 and 39 to be used for image transfer.

  In the present embodiment, the paper is neutralized before the registration roller, and the paper is not charged by the registration roller, so image defects (scattering) due to paper charging do not occur. Further, since the leading edge of the paper 16 does not touch the static eliminating cloth 31 during the conveyance, no paper jam occurs. With the configuration described above, paper jams can be prevented while preventing scattering due to charging of paper even when the registration rollers are provided close to the photosensitive drum.

( Second reference example )
FIG. 5 shows a second reference example of the present invention.

This reference example describes the case of an apparatus that performs printing on an insulating film such as an OHP sheet that is a transfer material. When printing on paper, neutralization is sufficiently effective on one side. The reason is that the paper has fine holes, and neutralization can be performed on both sides by bringing the neutralization member close to one side. On the other hand, in the case of an insulating sheet, since the through-hole is not open like paper, it is necessary to carry out static elimination on both sides. 5, 1 is a photosensitive drum, 9 is a transfer roller, 31 is a static eliminating cloth, 42 is a resist upper roller, 43 is a resist lower roller, 44 and 45 are transport rollers, 46 is an upper guide, 47 is a lower guide, 48 and 49 are conveyance guides, and 50 is a sheet for OHP. In the figure, L is the nip of the registration roller pair, and K is the nip of the conveyance roller pair. V5 indicates the peripheral speed of the conveying roller, and V6 indicates the peripheral speed of the registration roller. A line C is a perpendicular line of the line passing through the centers of the transport rollers 44 and 45 and is in contact with the outer periphery of the transport roller. A line D is a perpendicular line of a line passing through the centers of the upper and lower rollers 42 and 43 and is in contact with the outer periphery of the registration roller. Note that the same reference numerals as those described above denote the same members unless otherwise specified.

  The peripheral speed of the photosensitive drum 1 is 100 mm / second. The resist upper roller 42 is made of iron with nickel plating on the surface and has an outer diameter of 14 mm. The upper resist roller 42 is electrically grounded. The lower resist roller 43 is formed by winding a conductive chloroprene rubber having a thickness of 2 mm on an iron core bar having an outer diameter of 10 mm, and having an outer diameter of 14 mm. The mandrel is electrically grounded.

  The registration roller controls rotation stop by a clutch (not shown). The rotational peripheral speed V6 of the resist upper roller 42 and the resist lower roller 43 is 100 mm / second.

  The conveyance guide sheet metals 48 and 49 are galvanized iron sheet metals, which form an S-shaped conveyance path, and a static elimination cloth 31 is pasted on the side far from the line C at a high portion of the conveyance guide 48. In addition, the neutralizing cloth 31 is pasted on a portion of the lower part of the transport guide 49 that is far from the line D. The conveyance roller 44 is made of polyacetal and has an outer diameter of 14 mm. The conveying roller 45 is formed by winding an insulating chloroprene rubber with a thickness of 2 mm on an iron core bar having an outer diameter of 10 mm and an outer diameter of 14 mm. The rotational peripheral speed V5 of the transport rollers 44 and 45 is 104 mm / second.

  Next, the operation will be described.

  The OHP sheet transported by the transport rollers 44 and 45 is transported along the broken line C, transported along the transport guide 49, and then passes through the slope on the transfer roller side of the transport guide 49 to the registration nip L. To reach. Since the neutralizing cloth 31 does not have the neutralizing cloth in the region through which the leading end of the OHP sheet 50 passes, the OHP sheet 50 is not clogged by the hook of the leading end of the OHP sheet. The upper resist roller 42 and the lower resist roller 43 do not move immediately even when the leading end of the OHP sheet 50 reaches the resist nip L. After reaching, it starts to rotate after 20 msec. Since the transport rollers 44 and 45 continue to feed the OHP sheet while the registration roller pair is stopped, a loop is formed between the registration rollers and the transport roller. The reason why the loop is S-shaped is that the shape of the loop is regulated by the conveyance guide 48 and the conveyance guide 49. The portion where the S-shaped loop is convex is the portion where the neutralization cloth is pasted, and the OHP sheet 50 approaches the neutralization cloth. The gap between the conveyance guide 48 and the conveyance guide 49 is 4 mm. The distance between the registration nip L and the conveyance roller nip K is 70 mm. By rotating the registration roller pair 20 msec after reaching the leading edge of the OHP sheet, a loop of about 4 mm is formed, and the OHP sheet 50 is conveyed while being close to the static eliminating cloth 31. As a result, the OHP sheet 50 is neutralized.

  After neutralization, the resist roller passes through the pair of resist rollers, but the resist upper roller 42 is made of metal, and the surface layer of the resist lower roller 43 is conductive and both rollers are electrically grounded. The sheet 50 is not frictionally charged. Thereafter, the OHP sheet is guided by transfer guides 46 and 47 to be used for image transfer.

In this reference example , both sides of the OHP sheet 50 are neutralized in front of the registration roller, and the OHP sheet is not charged by the registration roller. Therefore, image defects (scattering) due to the charging of the OHP sheet. Does not occur. Further, since the leading end of the OHP sheet 50 does not touch the neutralizing cloth 31 during the conveyance, the OHP sheet is not clogged. With the configuration described above, even when an image is formed on an insulating sheet such as an OHP sheet, scattering due to charging can be prevented.

( Third reference example )
FIG. 6 shows a third reference example of the present invention.

In this reference example, a paper loop before transfer is formed by a so-called guide. Those having the same functions as described in the first reference example are intended to designated by the same numerals as described in the first reference example. 6, 1 is a photosensitive drum, 9 is a transfer roller, 31 is a static eliminating cloth, 59 is a resist upper roller, 60 is a resist lower roller, 61 and 62 are transport rollers, 46 is an upper guide, 47 is a lower guide, Reference numerals 57 and 58 denote conveyance guides which are paper conveyance regulating members, and reference numeral 16 denotes paper.

  In the figure, V7 indicates the peripheral speed of the conveying roller, and V8 indicates the peripheral speed of the registration roller. Line U is a perpendicular line of the line passing through the centers of the transport rollers 44 and 45 and is in contact with the outer periphery of the transport roller. A line W is a perpendicular line of the line passing through the centers of the registration roller rollers 42 and 43 and is in contact with the outer periphery of the registration roller. In addition, the same code | symbol as the above shows the same member.

  The peripheral speed of the photosensitive drum 1 is 100 mm / second. The resist upper roller 42 is made of iron with nickel plating on the surface and has an outer diameter of 14 mm. The upper resist roller 42 is electrically grounded. The lower resist roller 43 is formed by winding a conductive chloroprene rubber having a thickness of 2 mm on an iron core bar having an outer diameter of 10 mm, and having an outer diameter of 14 mm. The mandrel is electrically grounded.

  The registration roller controls rotation stop by a clutch (not shown). The rotational peripheral speed V8 of the resist upper roller 42 and the resist lower roller 43 is 100 mm / second.

  The conveyance guide metal plates 57 and 58 are galvanized iron metal plates, and form a conveyance path having a space in which the paper 16 can form a loop on the upper side. The conveyance roller 44 is made of polyacetal and has an outer diameter of 14 mm. The conveying roller 45 is formed by winding an insulating chloroprene rubber with a thickness of 2 mm on an iron core bar having an outer diameter of 10 mm and an outer diameter of 14 mm. The rotational peripheral speed V5 of the transport rollers 44 and 45 is 104 mm / second.

  Next, the operation will be described. The paper 16 transported by the transport rollers 44 and 45 is transported along the broken line U. When the paper 16 enters between the transport guides 57 and 58, the traveling direction is regulated by the transport guides 57 and 58 and transported along the broken line P. Is done. Thereafter, the sheet reaches the nip between the upper registration roller 42 and the lower registration roller 43 through the slope of the conveyance guide 57 on the upper registration roller 42 side. Since the neutralizing cloth 31 does not exist in the region through which the front end of the paper 16 passes, clogging due to catching of the front end of the paper does not occur. The upper registration roller 42 and the lower registration roller 43 do not move immediately even when the leading edge of the paper 16 reaches the nip between the upper registration roller 42 and the lower registration roller 43. After reaching, it starts to rotate after 20 msec. Since the conveyance rollers 44 and 45 continue to feed the paper 16 while the registration roller pair is stopped, a paper loop is formed between the registration rollers 42 and 43 and the conveyance rollers 44 and 45. The loop is a space between the conveyance guides 48 and 49, and the upper side has a convex shape. That is, a loop is formed so as to be close to the static elimination cloth 31. This is because the broken line P and the broken line Q have the upper vector. The place where the loop becomes convex is the place where the neutralizing cloth is pasted, and the paper 16 approaches the neutralizing cloth. By rotating the registration roller pair 20 msec after the leading edge of the paper arrives, a loop of about 4 mm is formed, and the paper 16 is conveyed while being close to the static eliminating cloth 31. As a result, the paper 16 is stably discharged.

  The paper 16 passes through the pair of registration rollers after being neutralized by the neutralizing cloth, but the upper resist roller 42 is made of metal, and the surface layer of the lower resist roller 43 is conductive, and both the rollers are electrically grounded. Therefore, the paper 16 is not frictionally charged. Thereafter, the paper 16 is guided by transfer guides 46 and 47 to be used for image transfer.

  Then, since the transfer is performed on the paper that has been sufficiently neutralized by the neutralizing cloth 31, a beautiful image output in which no scattered image is generated can be obtained. Further, since the leading edge of the paper does not come into contact with the neutralizing cloth, a jam that occurs when the leading edge of the paper is caught by the static eliminating means does not occur.

In the above-described embodiments and reference examples , a printer is exemplified as an image forming apparatus. However, the present invention is not limited to this, and other image forming apparatuses such as a copying machine and a facsimile machine, or these The image forming apparatus may be another image forming apparatus having a combination of functions, and the same effect can be obtained by applying the present invention to the image forming apparatus.

  Moreover, while various embodiments of the invention have been shown and described, the spirit and scope of the invention are not limited to the specific descriptions and figures within the specification. For example, it is needless to say that the present invention can also be applied when transferring from an intermediate transfer member to paper or the like.

It is a figure explaining the structure of the transfer apparatus periphery which concerns on the 1st Embodiment of this invention. It is a figure explaining the experimental result of the structure concerning the 1st Embodiment of this invention. It is a figure explaining the structure around the transfer apparatus which concerns on the 2nd Embodiment of this invention. It is a figure explaining the structure of the transfer device periphery which concerns on the 1st reference example of this invention. Is a diagram illustrating a configuration around a transfer apparatus according to a second exemplary embodiment of the present invention. It is a diagram illustrating a third configuration of the peripheral transfer apparatus according to a reference example of the present invention. It is a figure which shows the conventional image forming apparatus.

1 Photosensitive drum (image carrier)
2 Charging means 3 Exposure means 5 Development means 7 Cleaning device 9 Transfer roller (transfer means)
12 registration upper roller 13 registration lower roller 31 (static elimination cloth) static elimination means 32, 67 upper guide 33, 66 lower guide 51, 56 control device (control means)
52, 53, 54, 55 Drive motor 65 Static elimination needle

Claims (4)

An image carrier that carries a toner image; a transfer unit that forms a transfer nip with the image carrier; and a transfer unit that transfers the toner image on the image carrier to a transfer material; and an upstream side of the transfer nip in the transfer material conveyance direction And a transfer material transporting means for transporting the transfer material upstream of the transfer nip in the transfer material transport direction. And an image forming apparatus facing the transfer material between the transfer material conveying means,
The transfer material conveying means is arranged so that the leading edge of the transfer material conveyed by the transfer material conveying means does not contact the charge eliminating means, and the conveying speed of the transfer material conveying means is higher than the conveying speed of the transfer means. An image forming apparatus, wherein the transfer material forms a loop by being fast, whereby the transfer material approaches the charge eliminating unit.   The image carrier is a rotatable photosensitive drum, and the transfer unit is a transfer roller that can rotate at the same speed as the photosensitive drum, and the transfer material conveying unit according to the rotational speed of the photosensitive drum. The image forming apparatus according to claim 1, further comprising a control unit that controls a conveyance speed of the image forming apparatus.   The image forming apparatus according to claim 1, wherein the neutralizing unit is a sheet-shaped neutralizing cloth. Claim direction for conveying the transfer material of the transfer material conveying means, said a transfer material transporting portion of the transfer material conveyance unit, the straight line which connects the transfer nip, wherein said a charge-eliminating unit side The image forming apparatus according to any one of claims 1 to 3.

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