JP2005266225A - Transfer material transport guide mechanism for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer material transport guide mechanism, in which a satisfactory transfer image can be obtained by hindering image blurs, image shrinkage, etc., using a simple structure, when a transfer material fed upwardly from a pair of registration rollers is guided to a transfer nip. <P>SOLUTION: When a transfer material is conveyed upward by the pair of registration rollers 12, the direction in which the transfer material is conveyed is smoothly altered in the direction of a transfer nip 16 by the elasticity of an elastic sheet 15, which is located on the photoreceptor drum side of a pair of guide plates 14a and 14b, without causing the transfer material to collide with a photoreceptor drum 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a transfer material conveyance guide mechanism of an image forming apparatus, and more particularly to a transfer material conveyance guide mechanism that guides a transfer material fed upward from a pair of registration rollers to a transfer nip portion between a photosensitive drum and a transfer roller.

  In an electrophotographic image forming apparatus, a charging unit, an exposing unit, a developing unit, and the like are provided around the photosensitive drum. Then, after the photosensitive drum is charged by the charging unit, exposure is performed by the exposure unit, an electrostatic latent image is formed on the surface of the photosensitive drum, and developed by the developing unit. Thereafter, the developed toner image is transferred onto the transfer material by the transfer means, and further fixed by the fixing means, and the image-formed transfer material is discharged to the discharge portion.

  As a transfer unit of such an image forming apparatus, a transfer roller that contacts the photosensitive drum and forms a transfer nip portion is disposed. Then, the transfer material is conveyed from the paper supply unit to the transfer nip portion via the registration roller pair. In the transfer nip portion, a toner image on the photosensitive drum is transferred to a transfer material by applying a transfer bias voltage to the transfer roller. At this time, in order to accurately transfer the toner image on the surface of the photosensitive drum onto the transfer material and obtain a good image, the transfer material conveyed from the pair of registration rollers is guided to a good position in the transfer nip portion. There is a need. For this purpose, a pair of guide plates are provided on the upstream side of the transfer nip portion in the transfer material conveyance direction to guide the transfer material conveyed from the registration roller pair to a good position in the transfer nip portion.

  In recent years, with the increase in the number of multifunction peripherals equipped with a copying function and a printer function, in order to reduce the size of the apparatus and increase the speed of image formation, the image forming means, the fixing means, etc. are arranged in the vertical direction to transfer the transfer material. An increasing number of apparatuses are equipped with a vertical transport path for transporting upward. In the image forming apparatus having such a vertical conveyance path, the conveyance direction of the transfer material between the registration roller pair and the transfer nip portion does not become a straight line in order to shorten the conveyance path.

  Therefore, guide plates 24a and 24b as shown in FIG. 5 are provided on the upstream side of the transfer nip portion in the transfer material conveyance direction, and the transfer nip portion is conveyed along the guide plate in the transfer nip portion in the transfer material conveyance direction. A method of guiding to a proper position can be considered. Since a bias voltage is applied to the transfer roller 29, if the position of the guide plate 24a on the transfer roller 29 side is too close to the transfer roller 29 side, the transfer material is affected by the bias voltage, causing transfer defects and transfer baldness. May occur. Therefore, in order to ensure good transferability, the guide plate 24a on the transfer roller 29 side cannot be brought close to the transfer roller 29. With such a structure, as shown in FIG. 5, both guide plates 24a, 24b The gap at the exit of the door must be narrow. Then, the transferred transfer material receives the resistance of the two guide plates 24a and 24b, and image shrinkage tends to occur in an image formed on the transfer material.

  Therefore, as shown in FIG. 6, if the direction of the guide plate 34b on the photosensitive drum side is directed to the photosensitive drum side, the gap between the outlets of both guide plates 34a and 34b becomes wide, and the image shrinkage problem can be solved. However, the transfer direction of the transfer material guided by the guide plates 34a and 34b is directed not to the transfer nip portion but to the photosensitive drum side. Therefore, the tip of the transfer material that is separated from the guide plates 34a and 34b once collides with the photosensitive drum 35 and then changes its direction to the transfer nip portion 36, and the image formed on the transfer material due to the jump of the transfer material is displayed on the image. Blur is likely to occur.

Although not solving the above technical problems, there is an invention described in Japanese Patent Application Laid-Open No. 2002-139930 as a prior art. Here, in addition to the rigid guide plate, an elastic member is provided to improve the transfer performance of the transfer material.
JP 2002-139930 A

  In the invention described in Japanese Patent Application Laid-Open No. 2002-139930, the transfer material conveyance direction is regulated by the rigid guide plate below the registration roller pair in the transfer material conveyance direction, so that the transfer material is guided downstream in the transfer material conveyance direction. When moving away from the plate, it is not possible to solve the occurrence of image misalignment or image blur due to the jump of the transfer material at the exit of the guide plate, the return of bending of the transfer material, or the like. In particular, when the transfer material conveyance speed at the transfer nip portion is larger than the transfer material conveyance speed at the registration roller pair, the transfer material positioned between the registration roller pair and the transfer nip portion does not sag, and the transfer material conveyance is performed. It is difficult to solve the image blur or the like by the elastic member provided on the upstream side in the direction.

  An object of the present invention is to have a simple structure and to suppress image blurring and image shrinkage when a transfer material fed upward from a pair of registration rollers is guided to a transfer nip portion, so that a good transfer image can be obtained. It is to provide a transfer material conveyance guide mechanism.

  A transfer material conveyance guide mechanism according to claim 1 guides a transfer material fed upward from a pair of registration rollers to a transfer nip portion between a photosensitive drum and a transfer roller, and transfers the transfer material to the photosensitive member. A pair of guide plates for guiding toward the drum, and an elastic sheet provided on a guide plate on the photosensitive drum side of the pair of guide plates and having a free end on the downstream side in the transfer material conveyance direction. Yes.

  The transfer material conveyance guide mechanism is provided between the registration roller pair and the transfer nip portion, and guides the transfer material toward the photosensitive drum. Here, in an image forming apparatus having a vertical conveyance path for conveying a transfer material upward, the conveyance path is shortened, and the conveyance path between the registration roller pair and the transfer nip portion is often not in a straight line. In such a case, when the transfer material is guided using the transfer material conveyance guide mechanism of the present invention, the transfer material can be smoothly transferred to the photosensitive drum without causing the transfer material to collide with the photosensitive drum by the elastic sheet provided on the guide plate. Can be guided to. For this reason, generation | occurrence | production of an image blur etc. can be suppressed. In addition, since the transfer material is guided by the elastic sheet, the conveyance resistance is smaller than when the transfer material is guided by a highly rigid guide plate as in the prior art, and image shrinkage occurs in the image formed on the transfer material. Can be suppressed.

  A transfer material conveyance guide mechanism according to a second aspect is the mechanism according to the first aspect, wherein the elastic sheet is provided such that the conveyance direction of the transfer material guided by the elastic sheet faces the transfer nip portion.

  In this mechanism, the transfer material is guided to the transfer nip portion by the elastic sheet. Accordingly, the transfer material mainly comes into sliding contact with the elastic sheet, and the transfer resistance of the transfer material can be suppressed as compared with the case where the transfer material is guided by a highly rigid guide plate as in the prior art.

  The transfer material conveyance guide mechanism according to claim 3 is the mechanism according to claim 1 or 2, wherein the elastic sheet is provided on the base layer and the surface of the base layer on the side through which the transfer material passes. And a plurality of contact layers formed intermittently in a direction orthogonal to the transfer material transport direction and continuous in the transfer material transport direction.

  In this mechanism, the surface of the elastic sheet that contacts the transfer material is formed continuously in the transfer material transport direction and intermittently in a direction perpendicular to the transfer material transport direction. With such a structure, the elastic sheet base layer can ensure the elasticity of the elastic sheet, reduce the contact area between the elastic sheet and the transfer material, and extend the life of the elastic sheet.

  According to the transfer material conveyance guide mechanism of the present invention, in an image forming apparatus provided with a vertical conveyance path, it is possible to improve the conveyance performance between the registration roller pair and the transfer nip portion, and to suppress the deterioration of the formed image quality.

  FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 1 in which an embodiment of the present invention is adopted. The image forming apparatus 1 mainly includes a document reading unit 2, an image forming unit 3, and a paper feed cassette 4. The image forming unit 3 includes a photosensitive drum 5 and an exposure device 7, and further includes a charging device 6, a developing device 8, a transfer roller 9, and a cleaning device 10 disposed around the photosensitive drum 5. Further, the image forming apparatus 1 has a vertical conveyance path for conveying the transfer material upward. A registration roller pair 12 is disposed upstream of the photosensitive drum 5 in the transfer material conveyance direction, and a transfer material conveyance mechanism 50 (shown in FIG. 2) is provided above the registration roller pair 12. Further, a fixing device 11 is disposed on the downstream side of the photosensitive drum 5 in the transfer material conveyance direction, and an in-body sheet discharge unit 13 is provided at substantially the center of the image forming unit 3.

  Next, the transfer material conveyance guide mechanism 50 will be described. As shown in FIG. 2, the registration roller pair 12 is disposed at the lower left portion of the transfer nip portion 16, and the transfer material conveyance guide mechanism 50 is disposed between the registration roller pair 12 and the transfer nip portion 16. . The transfer material conveyance guide mechanism 50 includes a first and second guide plates 14a and 14b and an elastic sheet 15 provided between the two guide plates 14a and 14b. The guide plates 14a and 14b and the elastic sheet 15 extend long in the direction orthogonal to the transfer material conveyance direction (that is, the axial direction of the photosensitive drum), and have a short width (length) in the transfer material conveyance direction. It is formed in a shape. The first guide plate 14a on the transfer roller 9 side is divided into an upstream portion and a downstream portion in the transfer material conveyance direction, and the upstream portion is formed along the transfer material conveyance direction from the registration roller pair 12, The downstream portion is formed to be bent slightly from the upstream portion toward the transfer nip portion 16 with a predetermined distance from the transfer roller 9. Similar to the first guide plate 14a, the second guide plate 14b on the photosensitive drum 5 side is divided into an upstream portion and a downstream portion in the transfer material conveyance direction, and the upstream portion is directed toward the transfer nip portion 16. The downstream portion is formed to bend from the upstream portion to the photosensitive drum 5 side. Here, if an elastic sheet 15 to be described later is bonded to the upstream portion, it is considered that the downstream portion may be deleted. However, a strong transfer material such as an OHP sheet or cardboard is in contact with the elastic sheet 15. The elastic sheet 15 may be greatly bent, and the transfer material may be vibrated due to the large bending of the elastic sheet 15. At this time, the downstream portion of the second guide plate 14b regulates the bending of the elastic sheet, so that it is possible to prevent the transfer material from greatly deviating from the conveyance path and to generate a jam, thereby suppressing the vibration of the transfer material. Therefore, it is possible to prevent the transfer image from being disturbed.

  The elastic sheet 15 is divided into an adhesive part and a non-adhesive part. The adhesive portion is bonded to the upstream side of the transfer material transport direction of the second guide plate 14b by the adhesive layer 15d (see FIG. 3), and the non-adhesion portion downstream of the transfer material transport direction is a free end, and the free end The portion faces the transfer nip portion 16.

  The structure of the elastic sheet 15 will be described in detail. As shown in FIG. 3B, the elastic sheet 15 is composed of a plurality of layers, and the surface layer 15a, which is a contact surface with the transfer material, has a conductive superpolymer PE film having low friction and wear resistance. A material is used, and the base material layer 15b is a PET film material. These layers 15a and 15b are pasted by the adhesive layer 15c. Moreover, the base material layer 15b is affixed on the 2nd guide plate 14b by the contact bonding layer 15d. By using a PET film as the base material layer 15b, the elastic sheet 15 can ensure the necessary elasticity for changing the transfer material transport direction. Further, by using a conductive ultra-polymer PE film material having low friction and wear resistance for the surface layer 15a in contact with the transfer material, image scattering due to frictional charging between the transfer material and the elastic sheet can be prevented. At the same time, the life of the elastic sheet 15 can be ensured. It should be noted that the end portion of the adhesion portion of the surface layer 15a is in contact with the second guide plate (made of metal) 14b in order to release the charge generated in the surface layer 15a due to the friction between the surface layer 15a and the transfer material ( Not shown). Moreover, in order to suppress image scattering, the first guide plate 14a uses a conductive resin material.

  Next, an image forming operation will be briefly described. At the time of image formation, the photosensitive drum 5 is charged by the charging device 6 and exposed to light from the exposure device 7 to form an electrostatic latent image on the surface of the photosensitive drum 5. The electrostatic latent image is developed by the developing device 8. On the other hand, the transfer material conveyed from the paper feed cassette 4 is conveyed upward by the registration roller pair 12 and guided to the transfer position by the transfer material conveyance mechanism 50. Then, the toner image is transferred to the transfer material by the transfer roller 9, fixed by heating and pressing by the fixing device 11, and discharged to the in-body discharge unit 13. Residual toner remaining on the photosensitive drum 5 is cleaned by the cleaning device 10 and discarded in a waste toner container (not shown).

  Next, transfer of the transfer material will be described in detail. As shown in FIGS. 1 and 2, in this image forming apparatus, when an image is formed, the transfer material is fed from the sheet feeding unit 4 and conveyed upward by the registration roller pair 12. At this time, the upstream side portion of the pair of guide plates 14 a and 14 b is guided toward the photosensitive drum 5. However, since the elastic sheet 15 is provided toward the transfer nip portion 16, when the transfer material slides on the elastic sheet 15, the elasticity of the elastic sheet 15 prevents the transfer material from colliding with the photosensitive drum 5. The transport direction is smoothly changed in the direction of the transfer nip portion 16. Accordingly, it is possible to suppress the occurrence of image blur due to the transfer material splashing. Further, since the elastic sheet 15 has a smaller conveyance resistance with respect to the transfer material than that of the conventional guide plate, it is possible to suppress the occurrence of image shrinkage in the image formed on the transfer material.

[Other Embodiments]
As another embodiment, the structure of the elastic sheet can be as shown in FIG. This elastic sheet 15 ′ is composed of a base material layer 15b ′ and a surface layer 15a ′ in contact with the transfer material, and both layers 15a ′ and 15b ′ are attached by an adhesive layer 15c ′. The surface layer 15a ′ employs a conductive ultra-polymer PE film material having low friction and wear resistance, and the substrate layer 15b ′ employs a conductive PET film material. Here, the conductive polymer PE film layer of the surface layer 15a ′ that comes into contact with the transfer material is placed on the conductive PET film of the base material layer 15b ′ with a certain interval in the longitudinal direction (axial direction of the photosensitive drum). It is affixed intermittently. Specifically, it is continuous in the transfer material conveyance direction and intermittently formed in a direction perpendicular to the transfer material conveyance direction. By adopting such a configuration, the transfer material and the surface layer 15a ′ of the elastic sheet 15 ′ can be secured while ensuring appropriate elasticity of the elastic sheet 15 ′ by the base material layer 15b ′ formed of the PET film material. By reducing the contact area and reducing the conveyance resistance with respect to the transfer material, the occurrence of image shrinkage can be suppressed.

1 is a configuration diagram of an image forming apparatus. The conceptual diagram of a transfer material conveyance guide mechanism. The block diagram of an elastic sheet. Configuration diagram of other types of elastic sheets The conceptual diagram of the conventional transfer material conveyance guide mechanism 1. FIG. The conceptual diagram of the conventional transfer material conveyance guide mechanism 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 5 Photoconductor drum 9 Transfer roller 12 Registration roller pair 14a, 24a, 34a Transfer roller side guide plate 14b, 24b, 34b Photoconductor drum side guide plate 15 Elastic sheet 15a, 15a 'Contact surface 15b with a transfer material , 15b ′ Base material layer 15c Adhesive layer 16 Transfer nip 50 Transfer material conveyance guide mechanism

Claims (3)

A transfer material conveyance guide mechanism for guiding a transfer material fed upward from a pair of registration rollers to a transfer nip portion between the photosensitive drum and the transfer roller;
A pair of guide plates for guiding the transfer material toward the photosensitive drum;
An elastic sheet provided on the photosensitive drum side guide plate of the one guide plate and having a free end on the downstream side in the transfer material conveyance direction;
A transfer material conveyance guide mechanism.   The transfer material conveyance guide mechanism according to claim 1, wherein the elastic sheet is provided so that a conveyance direction of the transfer material guided by the elastic sheet faces a transfer nip portion.   The elastic sheet is provided on the surface of the base material layer and the surface of the base material layer through which the transfer material passes, and is continuous in the transfer material transport direction and intermittently in a direction orthogonal to the transfer material transport direction. The transfer material conveyance guide mechanism according to claim 1, further comprising a plurality of contact layers formed.

Images