JP2019200285A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that is able to prevent recording material conveyance failure caused by a guide part, while enabling reduction of force with which a recording material is pressed against an image carrier located upstream of a transfer unit.SOLUTION: In an image forming apparatus, a recording material conveyance speed of a pair of conveyance rollers 3 is higher than the conveyance speed of a surface of an image carrier 1. A first guide member 5 has a rotary member 7 rotatable around an axis X-Y parallel to a width direction orthogonal to the recording material conveyance direction. If a straight line orthogonal to a straight line passing through a conveyance nip N3 and connecting the rotation center of a first conveyance roller 3a and the rotation center of a second conveyance roller 3b is a conveyance nip line La, the position of the upstream end 7B1 of the rotary member is located on the same side as the first conveyance roller 3a with respect to the conveyance nip line La when the rotary member 7 is located at a first rotating position, and the position of the upstream end 7B1 of the rotary member 7 is located opposite the first conveyance roller 3a with respect to the conveyance nip line La when the rotary member 7 is located at a second rotating position.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system or an electrostatic recording system.

  2. Description of the Related Art Conventionally, for example, as an electrophotographic image forming apparatus, there is an intermediate transfer type image forming apparatus having an intermediate transfer belt which is an intermediate transfer body constituted by an endless belt as an image carrier. The intermediate transfer belt is stretched by a plurality of stretching rollers, and a secondary transfer roller disposed opposite to the secondary transfer inner roller that is one of the plurality of stretching rollers via the intermediate transfer belt. The outer transfer roller is brought into contact with the intermediate transfer belt to form a secondary transfer portion. The toner image carried on the intermediate transfer belt is conveyed by being sandwiched between the intermediate transfer belt and the secondary transfer outer roller at the secondary transfer portion by applying a secondary transfer bias to the secondary transfer outer roller, for example. Secondary transfer is performed on the recording material. The recording material is conveyed to the secondary transfer unit in synchronization with the toner image on the intermediate transfer belt by a pair of registration rollers as conveying members. A guide unit for guiding the recording material to the secondary transfer unit is provided downstream of the registration roller pair and upstream of the secondary transfer unit in the recording material conveyance direction.

  The guide portion includes a first guide member that restricts movement of the recording material in a direction approaching the intermediate transfer belt, and a second guide member that restricts movement of the recording material in a direction away from the intermediate transfer belt. Are often configured. The first guide member and the second guide member are arranged to face each other, and the recording material passes between the first guide member and the second guide member. As the first guide member, a member having a relatively high rigidity, such as a SUS plate, or a member formed by providing an elastic body at the tip of the secondary transfer portion in the conveyance direction of the SUS plate is known. (Patent Document 1).

  When the recording material is conveyed by the registration roller pair toward the secondary transfer portion, the following configuration is adopted to prevent the recording material from being pulled between the secondary transfer portion and the registration roller pair. Sometimes. That is, the recording material conveyance speed (hereinafter also referred to as “feeding speed”) by the pair of registration rollers may be faster than the recording material conveyance speed in the secondary transfer unit. Particularly in such a configuration, the recording material is pressed against the intermediate transfer belt on the upstream side of the secondary transfer portion after passing through the first guide member.

JP 2009-198562 A

  FIG. 10A is a schematic cross-sectional view (a cross section substantially perpendicular to the rotational axis direction of the secondary transfer inner roller 21) showing the configuration in the vicinity of the conventional secondary transfer portion N2. FIGS. 10B and 10C are enlarged schematic cross-sectional views in the vicinity of the guide portion 4 for explaining the conveyance state of the recording material P in the configuration of FIG.

  As shown in FIG. 10A, the guide portion 4 includes a first guide member 5 and a second guide member 6. The recording material P that has passed through the guide portion 4 is sandwiched between the intermediate transfer belt 1 and the secondary transfer outer roller 2 at the secondary transfer portion N2. As shown in FIG. 10B, the recording material P that has passed through the first guide member 5 and is sandwiched between the secondary transfer portions N2 contacts the intermediate transfer belt 1 on the upstream side of the secondary transfer portion N2. In other words, the posture is curved so as to protrude upward in the drawing, and is pressed against the intermediate transfer belt 1. This is because when the hardness of the secondary transfer outer roller 2 is lower than that of the secondary transfer inner roller 21 or when the width of the contact area between the secondary transfer outer roller 2 and the intermediate transfer belt 1 is the secondary transfer inner roller 21. This is particularly noticeable when the width of the contact area between the intermediate transfer belt 1 and the intermediate transfer belt 1 is widened upstream.

  In addition, the recording material P is pushed into the secondary transfer portion N2 by the registration roller pair 3 at a feeding speed faster than the conveyance speed in the secondary transfer portion N2. The registration roller pair 3 is controlled so as to have a constant rotational speed, but due to variations in the outer diameter of each roller of the registration roller pair 3, the feeding speed of the recording material P by the registration roller pair 3 varies. Sometimes.

  If the feeding speed of the recording material P by the registration roller pair 3 varies, the force with which the recording material P is pressed against the intermediate transfer belt 1 on the upstream side of the secondary transfer portion N2 varies. As a result, as shown in FIGS. 10B and 10C, the postures of the intermediate transfer belt 1 and the recording material P on the upstream side of the secondary transfer portion N2 vary. When such fluctuations occur, the speed difference between the moving speed of the surface of the intermediate transfer belt 1 carrying the toner image and the moving speed of the surface of the recording material P also increases, and the toner on the intermediate transfer belt 1 is increased. The image is disturbed in the transport direction. The toner image is transferred to the recording material P in the disordered state. FIG. 11A is a schematic diagram showing an undisturbed toner image on the recording material P, and FIG. 11B is a schematic diagram showing an irregular toner image on the recording material P. On the recording material P, when the toner image is disturbed as described above, the amount of toner covering the surface of the recording material P is increased as compared with the case where the toner image is not disturbed. In particular, when the speed difference between the conveyance speed of the recording material P at the secondary transfer portion N2 and the feeding speed of the recording material P by the registration roller pair 3 is large, the feeding speed of the recording material P by the registration roller pair 3 varies. Also grows. That is, the change in the posture of the intermediate transfer belt 1 and the recording material P on the upstream side of the secondary transfer portion N2 as shown in FIGS. 10B and 10C is promoted. As a result, the speed difference between the moving speed of the surface of the intermediate transfer belt 1 and the moving speed of the surface of the recording material P also increases, and density unevenness due to the disturbance of the toner image is promoted.

  Therefore, as shown in FIG. 10D, it is conceivable to use a guide portion 4 for forcibly bending the recording material P into an S shape. In this case, when the feeding speed of the recording material P by the registration roller pair 3 is fast, the recording material is relieved so as to relieve the force that the recording material P is strongly pressed against the intermediate transfer belt 1 as shown in FIG. P behaves like a broken line. That is, the recording material P has a curved posture so as to protrude in the direction toward the second guide member 6, that is, downward in the drawing, at the S-shaped bent portion of the guide portion 4. As a result, the difference in strength of the pressing force of the recording material P against the intermediate transfer belt 1 on the upstream side of the secondary transfer portion N2 due to the difference in the feeding speed of the recording material P by the registration roller pair 3 is alleviated. Density unevenness due to the disturbance of the toner image is suppressed. However, in the case of the configuration as shown in FIG. 10D, when the recording material P is sent from the registration roller pair 3 to the secondary transfer portion N2, the leading end of the recording material P in the transport direction is directed to the second guide member 6. There is a possibility that the recording material P may be poorly conveyed.

  Accordingly, an object of the present invention is to provide an image forming apparatus capable of reducing the force with which the recording material is pressed against the image carrier on the upstream side of the transfer portion, and suppressing the conveyance failure of the recording material by the guide portion. Is to provide.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention relates to an image carrier that carries and conveys a toner image, and a transfer that contacts the surface of the image carrier and forms a transfer portion that transfers the toner image from the image carrier to a recording material. A first conveying roller for conveying the recording material, and a second surface opposite to the first surface of the recording material, provided at a position in contact with the first surface to which the toner image of the recording material is transferred; A pair of conveying rollers, which are provided at contact positions, form a conveying nip in contact with the first conveying roller, and convey a recording material, and convey the recording material to the transfer unit; A guide portion provided downstream of the transport nip and upstream of the transfer portion in the recording material transport direction, for guiding the recording material toward the transfer portion, and the first surface of the recording material; A first guide member that guides the recording material oppositely, and the first guide portion Forming a conveyance path for conveying the recording material between the first guide member and the second guide member for guiding the recording material so as to face the second surface of the recording material. The conveying speed of the recording material by the pair of conveying rollers is faster than the moving speed of the surface of the image carrier, and the first guide member has a width direction substantially orthogonal to the conveying direction of the recording material. The rotating member has a rotating member capable of rotating between a first rotating position and a second rotating position with a substantially parallel axis as a rotation center, and the rotating member has a recording material at a leading end in a conveyance direction. Before reaching the upstream end of the rotating member in the conveyance direction of the material, the first rotating position is located at the first rotating position, and the recording material comes into contact with the recording material while passing through the transfer portion. In a cross-section substantially perpendicular to the axis. When the straight line perpendicular to the straight line passing through the conveyance nip and connecting between the rotation center of the first conveyance roller and the rotation center of the second conveyance roller is a conveyance nip line La, the rotating member is When positioned at the first rotation position, the position of the upstream end of the rotation member is positioned on the same side as the first conveyance roller with respect to the conveyance nip line La, and the rotation member is the second rotation. When positioned at the position, the upstream end of the rotating member is positioned on the opposite side of the transport nip line La from the first transport roller.

  According to the present invention, it is possible to reduce the force with which the recording material is pressed against the image carrier on the upstream side of the transfer portion, while suppressing the conveyance failure of the recording material by the guide portion.

1 is a schematic sectional view of an image forming apparatus. It is the top view and side view of a 1st guide member. It is a schematic sectional drawing of the vicinity of a secondary transfer part. It is a schematic sectional drawing of the vicinity of a secondary transfer part. It is a schematic sectional drawing of the 1st guide member of a comparative example and an Example. It is typical sectional drawing for demonstrating the setting of the position of the upstream end of a rotation member. It is a schematic block diagram which shows the example of the control aspect of an image forming apparatus. It is the top view and side view of other examples of the 1st guide member. It is a schematic diagram for demonstrating the timing which rotates a rotation member. It is a schematic sectional drawing of the vicinity of the secondary transfer part for demonstrating a subject. It is a schematic diagram for demonstrating a subject.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

1. Overall Configuration and Operation of Image Forming Apparatus FIG. 1 is a schematic sectional view of an image forming apparatus 100 of the present embodiment. The image forming apparatus 100 according to the present exemplary embodiment has a function of a tandem type multifunction peripheral (copier, printer, or facsimile machine) that employs an intermediate transfer method and can form a full-color image using an electrophotographic method. ).

  The image forming apparatus 100 includes first, second, third, and fourth images that form yellow (Y), magenta (M), cyan (C), and black (K) images as a plurality of image forming units, respectively. It has image forming units UY, UM, UC, UK. For elements having the same or corresponding functions or configurations in the respective image forming units UY, UM, UC, UK, Y, M, C, K at the end of the code indicating that they are elements for any color are omitted. And may be described in a comprehensive manner. The image forming unit U includes a photosensitive drum 101, a charging roller 102, an exposure device 103, a developing device 104, a primary transfer roller 105, a drum cleaning device 106, and the like which will be described later.

  The image forming unit U includes a photosensitive drum 101 that is a rotatable drum type (cylindrical) photosensitive member (electrophotographic photosensitive member) as a first image carrier. The photosensitive drum 101 is rotationally driven at a predetermined peripheral speed in the direction of arrow R1 (clockwise) in the drawing. The surface of the rotating photosensitive drum 101 is uniformly charged to a predetermined potential having a predetermined polarity (negative polarity in this embodiment) by a charging roller 102 which is a roller-type charging member as a charging unit. The surface of the charged photosensitive drum 101 is scanned and exposed by an exposure device (laser scanner) 103 as an exposure unit, and an electrostatic image (electrostatic latent image) is formed on the photosensitive drum 101. The electrostatic image formed on the photosensitive drum 101 is developed (visualized) by supplying toner as a developer by a developing device 104 as developing means, and a toner image (developer image) is formed on the photosensitive drum 101. Is done. In this embodiment, the exposed portion (image portion) on the photosensitive drum 101 whose absolute value has been lowered by being exposed after being uniformly charged is charged with the same polarity as the charging polarity of the photosensitive drum 101. Toner adheres.

  An intermediate transfer belt 1 as a second image carrier, which is a rotatable intermediate transfer member constituted by an endless belt, is disposed so as to face the four photosensitive drums 101. The intermediate transfer belt 1 is stretched around a secondary transfer inner roller 21, a driving roller 22, first and second idler rollers 23 and 24, a tension roller 25, and a pressure roller 26 as a plurality of stretching rollers. Has been. The secondary transfer inner roller 21 functions as a counter member (counter electrode) of the secondary transfer outer roller 2 described later. The driving roller 22 is driven by a motor (not shown) having excellent constant speed, and circulates (rotates) the intermediate transfer belt 1. The intermediate transfer belt 1 is rotated (circulated) at a predetermined peripheral speed (surface moving speed) in the direction of arrow R2 (counterclockwise) in the drawing when the driving force is transmitted by the driving roller 22. In this embodiment, the intermediate transfer belt 1 rotates at a peripheral speed of 115 to 470 mm / sec. The first and second idler rollers 23 and 24 support the intermediate transfer belt 1 extending along the arrangement direction of the photosensitive drums 101Y, 101M, 101C, and 101K. The tension roller 25 applies a constant tension to the intermediate transfer belt 1. The tension roller 25 is urged from the inner peripheral surface side to the outer peripheral surface side of the intermediate transfer belt 1 by springs (not shown) that are elastic members as urging means at both ends in the rotational axis direction. ing. The pressing roller 26 projects the intermediate transfer belt 1 in the vicinity of the upstream side of the secondary transfer portion N2 described later to the outside, thereby improving the adhesion between the secondary transfer outer roller 2 described later and the intermediate transfer belt 1.

  On the inner peripheral surface side of the intermediate transfer belt 1, a primary transfer roller 105, which is a roller-type primary transfer member serving as a primary transfer unit, is disposed corresponding to each photosensitive drum 101. The primary transfer roller 105 is urged toward the photosensitive drum 101 via the intermediate transfer belt 1 to form a primary transfer portion (primary transfer nip) N1 where the photosensitive drum 101 and the intermediate transfer belt 1 are in contact with each other. The toner image formed on the photosensitive drum 101 as described above is primarily transferred onto the rotating intermediate transfer belt 1 in the primary transfer portion N1. During the primary transfer process, the primary transfer roller 105 is fed with a primary transfer power supply (high voltage power supply circuit) (not shown) by a polarity opposite to the normal charge polarity of the toner (the charge polarity of the toner during development) (this embodiment). In this case, a primary transfer bias (primary transfer voltage), which is a DC voltage having a positive polarity, is applied. For example, when forming a full-color image, toner images of each color Y, M, C, and K formed on each photosensitive drum 101 are superimposed on the intermediate transfer belt 1 in each primary transfer portion N1. The primary transfer is performed sequentially.

  On the outer peripheral surface side of the intermediate transfer belt 1, a secondary transfer outer roller 2 that is a roller-type secondary transfer member as a secondary transfer unit is disposed at a position facing the secondary transfer inner roller 21. The secondary transfer outer roller 2 is urged toward the secondary transfer inner roller 21 via the intermediate transfer belt 1, and a secondary transfer portion (secondary transfer portion) where the intermediate transfer belt 1 and the secondary transfer outer roller 2 come into contact with each other. Transfer nip) N2 is formed. The toner image formed on the intermediate transfer belt 1 as described above is recorded on a recording material (recording material) such as paper that is nipped between the intermediate transfer belt 1 and the secondary transfer outer roller 2 and conveyed in the secondary transfer portion N2. Secondary transfer onto medium, sheet) P. In this embodiment, during the secondary transfer process, the secondary transfer outer roller 2 is supplied with a secondary transfer power supply (high voltage power supply circuit) E by a reverse polarity (positive polarity in this embodiment) to the normal charging polarity of the toner. A secondary transfer bias (secondary transfer voltage) is applied.

  The recording material P is sent out one by one from a recording material container (not shown) by a pickup roller (not shown) and is conveyed by a pair of conveying rollers (not shown). Thereafter, the recording material P is conveyed to the secondary transfer portion N2 by the registration roller pair 3 in timing with the toner image on the intermediate transfer belt 1. The registration roller pair 3 includes a pair of registration rollers (conveyance rollers) including a first registration roller (first conveyance roller) 3a and a second registration roller (second conveyance roller) 3b. The first registration roller 3a and the second registration roller 3b come into contact with each other to form a conveyance nip (conveyance portion) N3 that is a contact portion. The first registration roller 3a contacts the first surface of the recording material P (the surface onto which the toner image is transferred immediately after passing through the registration roller pair 3). The second registration roller 3b contacts the second surface (the surface opposite to the first surface) of the recording material P. In this embodiment, both the first and second registration rollers 3a and 3b are driven by a drive motor as a drive source. However, at least one of the first and second registration rollers 3a and 3b may be driven by a driving source.

  Further, in the conveyance direction of the recording material P, a guide portion 4 that guides the recording material P toward the secondary transfer portion N2 is provided downstream of the conveyance nip N3 and upstream of the secondary transfer portion N2. The guide portion 4 is opposed to the first surface of the recording material P, can contact the first surface of the recording material P, and has a first guide member (upper guide member) 5 that guides the recording material P. Further, the guide portion 4 has a second guide member (lower guide member) 6 that faces the second surface of the recording material P, can contact the second surface of the recording material P, and guides the recording material P. The second guide member 6 forms a conveyance path 4 a for conveying the recording material P between the second guide member 6 and the first guide member 5. In the present embodiment, the first guide member 5 is disposed above the second guide member 6 in the gravity direction, and the second guide member 6 is disposed below the first guide member 5 in the gravity direction. The first guide member 5 regulates the movement of the recording material P in the direction approaching the intermediate transfer belt 1 (upward). The second guide member 6 regulates the movement of the recording material P in the direction away from the intermediate transfer belt 1 (downward). The guide part 4 will be described in more detail later.

  The recording material P onto which the toner image has been transferred is conveyed to a fixing device 109 as a fixing unit by a conveying belt 107, a pre-fixing guide member 108, and the like. The fixing device 109 fixes (melts and adheres) the toner image to the recording material P by heating and pressing the recording material P carrying an unfixed toner image. The recording material P on which the toner image is fixed is discharged (output) to the outside of the main body of the image forming apparatus 100 by a discharge roller pair (not shown) or the like.

  In addition, toner (primary transfer residual toner) that is not transferred onto the intermediate transfer belt 1 and remains on the photosensitive drum 101 during the primary transfer process is removed from the photosensitive drum 101 by a drum cleaning device 106 as a photosensitive member cleaning unit. Collected. A belt cleaning device 27 as an intermediate transfer member cleaning unit is disposed on the outer peripheral surface side of the intermediate transfer belt 1 at a position facing the driving roller 22. Toner (secondary transfer residual toner) and paper powder that are not transferred to the recording material P and remain on the intermediate transfer belt 1 during the secondary transfer process are removed from the intermediate transfer belt 1 by the belt cleaning device 27 and collected. The In this embodiment, the belt cleaning device 27 electrostatically collects the secondary transfer residual toner on the intermediate transfer belt 1.

In this embodiment, the intermediate transfer belt 1 includes a base layer (back layer), an elastic layer (intermediate layer), and a surface layer. The base layer is formed so as to have a thickness of 0.05 to 0.15 [mm] by using a material in which carbon black is contained as an antistatic agent in a resin such as polyimide and polycarbonate, or various rubbers. . The elastic layer is formed to have a thickness of 0.1 to 0.500 [mm] by using a material in which an appropriate amount of an ionic conductive agent is contained in various rubbers such as CR rubber, urethane rubber, and silicone rubber. Yes. The surface layer is formed of a resin such as a urethane resin or a fluorine resin so that the thickness is 0.0002 to 0.020 [mm]. In this embodiment, the volume resistivity of the intermediate transfer belt 1 is 5 × 10 ⁸ to 1 × 10 ¹⁴ [Ω · cm] (23 ° C., 50% RH). In this embodiment, the intermediate transfer belt 1 has an MD1 hardness of 60 to 85 ° (23 ° C., 50% RH). In this embodiment, the static friction coefficient of the intermediate transfer belt 1 is 0.15 to 0.6 (23 ° C., 50% RH, type 94i manufactured by HEIDON). However, the intermediate transfer belt 1 may not be composed of a plurality of layers. For example, a single layer formed with a material containing an appropriate amount of carbon black as an antistatic agent in resins such as polyimide and polycarbonate, or various rubbers, and having a thickness of 0.05 to 0.15 [mm] It may be.

In this embodiment, the secondary transfer outer roller 2 includes a cored bar (base) and an elastic layer formed of ion conductive foamed rubber on the outer periphery of the cored bar. In this embodiment, the outer diameter of the secondary transfer outer roller 2 is 20 to 25 mm (typically 23.5 to 24.5 mm), and the electrical resistance value of the secondary transfer outer roller 2 is N / N (23 ° C., When measured by applying 2 kV at 50% RH), it is 1 × 10 ⁵ to 1 × 10 ⁸ Ω. In this embodiment, the elastic layer of the secondary transfer outer roller 2 has a thickness of 5 to 7 mm and a hardness of 24 to 50 degrees in Asker C hardness. Then, for example, a secondary transfer transfer bias of +1 to +7 KV is applied to the secondary transfer outer roller 2, and a secondary transfer current of +40 to +120 μA flows. In this embodiment, the secondary transfer outer roller 2 is arranged to be shifted to the upstream side in the rotation direction of the intermediate transfer belt 1 with respect to the secondary transfer inner roller 21. In this embodiment, the width of the contact area (secondary transfer portion N2) between the secondary transfer outer roller 2 and the intermediate transfer belt 1 is equal to the width of the contact area between the secondary transfer inner roller 21 and the intermediate transfer belt 1. Rather than upstream.

In the present embodiment, the primary transfer roller 105 includes a cored bar (base) and an elastic layer formed of ion conductive foam rubber on the outer periphery of the cored bar. In this embodiment, the outer diameter of the primary transfer roller 105 is 15 to 20 mm, and the electrical resistance value of the primary transfer roller 105 is 1 × 10 ⁵ when measured by applying 2 kV at N / N (23 ° C., 50% RH). ˜1 × 10 ⁸ Ω.

In this embodiment, the secondary transfer inner roller 21 includes a cored bar (base body) and an elastic layer formed of an electronic conductive rubber on the outer periphery of the cored bar. In this embodiment, the outer diameter of the secondary transfer inner roller 21 is 19 to 22 mm (typically 20 to 21 mm), the electrical resistance value is N / N (23 ° C., 50% RH), and 50 V is applied. When measured, it is 1 × 10 ⁵ to 1 × 10 ⁸ Ω. In this embodiment, the elastic layer of the secondary transfer inner roller 21 has a thickness of 1.5 to 2.5 mm and a hardness of Asker C hardness of 60 to 80 °.

  In the present embodiment, the registration roller pair 3 has a recording material P conveyance speed of 0.1 to 0. 0 to a recording material P conveyance speed of the secondary transfer portion N2. The recording material P is fed toward the secondary transfer portion N2 at a feeding speed that is 3% faster. The recording material P sent out by the registration roller pair 3 is guided by a guide portion 4 including a first guide member 5 and a second guide member 6 and is introduced into the secondary transfer portion N2.

2. Guide part Next, the guide part 4 in a present Example is further demonstrated. FIG. 2A is a schematic plan view of the first guide member 5 of the guide portion 4 in this embodiment as viewed from above in FIG. 2B and 2C are schematic side views seen from the X side in the XY line direction of FIG. FIG.2 (d) is the schematic side view seen from the S side of the ST line direction of Fig.2 (a). Here, the front end and the rear end of the guide portion 4 and the recording material P are the “front end” and the upstream end (downstream end) in the transport direction of the recording material P unless otherwise specified. The end (upstream end) is referred to as the “rear end”.

  As shown in FIG. 2A, the first guide member 5 includes a rotating member 7, a supporting member 8, a rotating shaft 9, a fixing member 10 for fixing the rotating shaft 9 to the rotating member 7, and a support. It has a bearing 11 that is fixed to the member 8 and rotatably supports the rotation shaft 9.

  The rotating member 7 includes a longitudinal direction arranged along a direction substantially orthogonal to the conveying direction of the recording material P (a direction substantially parallel to the rotational axis direction of the inner roller 21), and a short side substantially orthogonal to the longitudinal direction. A plate-like member having a predetermined length in each direction and a predetermined thickness and having a substantially rectangular shape in plan view. In this embodiment, the rotating member 7 is made of a SUS (stainless steel) plate. In this embodiment, the length of the rotating member 7 in the longitudinal direction is longer than the maximum value L4 of the length of the recording material P used in the image forming apparatus 100 in the same direction. Nevertheless, it passes through the length range of the rotating member 7 in the same direction in the longitudinal direction.

  The support member 8 is a plate-like member. That is, the support member 8 has a predetermined length in each of a longitudinal direction arranged along a direction substantially orthogonal to the conveyance direction of the recording material P and a short direction substantially orthogonal to the longitudinal direction, It has a predetermined thickness. The support member 8 has projecting portions 8a projecting downstream in the conveyance direction of the recording material P at both ends in the longitudinal direction. In this embodiment, the support member 8 is made of a SUS (stainless steel) plate. The support member 8 is disposed at a fixed position. A recess 8b that is recessed toward the rear end is formed between the protrusions 8a at both ends of the support member 8 in the longitudinal direction. The rotating member 7 is arranged such that a part on the front end side is disposed on the front end side with respect to the protruding portion 8 a of the support member 8, and the remaining part on the rear end side has a gap with the support member 8. These are disposed so as to be fitted into the recesses 8b.

  On the surface (upper surface) 7b (see FIG. 2 (b)) opposite to the surface (lower surface) 7a (see FIG. 2 (b)) of the rotating member 7 that can contact the recording material P, the rotating shaft 9 is provided. It is fixed by a fixing member 10. In the present embodiment, the rotation shaft 9 is disposed substantially parallel to the longitudinal direction of the rotation member 7 at the approximate center in the short direction of the rotation member 7. In this embodiment, the rotating shaft 9 is a cylindrical member having an outer diameter of 2 to 3 mm. The fixing member 10 fixes the rotating shaft 9 to the rotating member 7 at both ends in the longitudinal direction of the rotating member 7. And the bearing 11 is provided in the front-end | tip part of the protrusion part 8a of the both ends of the longitudinal direction of the supporting member 8, respectively. The bearing 11 supports the rotating member 7 so as to be rotatable around the rotation center axis XY by supporting the rotating shaft 9 so as to be rotatable. The axis XY is substantially parallel to the width direction substantially orthogonal to the conveyance direction of the recording material P.

  FIG. 2B shows a state when the recording material P does not pass through the guide portion 4. The rotating member 7 moves counterclockwise in FIG. 2B, that is, the tip moves downward (in the direction away from the intermediate transfer belt 1) and the rear end moves upward (in the direction approaching the intermediate transfer belt 1). It is urged | biased by the urging | biasing force of about 50-200 gf in the direction to rotate. In the present embodiment, as shown in FIG. 2D, the urging force is applied by the urging mechanism 12 as the urging means. The urging mechanism 12 includes a first connecting member 12a provided on the rotating member 7, a second connecting member 12b provided on the support member 8, a support base 12c provided on the support member 8, And a spring (tensile spring) 12d which is an elastic member as an urging member. The first connecting portion 12a is located at the end in the longitudinal direction of the rotation member 7 on the rear end side (in the vicinity of the edge of the rear end in this embodiment) from the position where the rotation shaft 9 of the rotation member 7 is disposed. Provided in the department. The second connecting portion 12 b is provided at a position facing the first connecting portion 12 a in the short direction of the support member 8. One end of a spring 12d disposed on the support base 12c is connected to the first connecting portion 12a, and the other end is connected to the second connecting portion 12b. As a result, the spring 12d applies the urging force by pulling up the rear end of the rotating member 7 in the short direction about the rotation center axis XY. Further, as shown in FIG. 2A, the surface (upper surface) 8d opposite to the surface (lower surface) 8c (see FIG. 2B) that can contact the recording material P of the support member 8 (see FIG. In b), the first rotation restricting member 13 is provided so that a part thereof protrudes into the recess 8b. In the present embodiment, two first rotation restricting members 13 are provided in the longitudinal direction of the support member 8. The rotation member 7 abuts against the first rotation restriction member 13, thereby restricting the rotation in the counterclockwise direction in FIG.

  FIG. 2C shows a state when the recording material P passes through the guide portion 4. When the recording material P passes through the guide portion 4, the rotating member 7 moves in the clockwise direction in FIG. 2C, that is, the leading end moves upward (in the direction approaching the intermediate transfer belt 1), and the trailing end is It rotates so as to move downward (in a direction away from the intermediate transfer belt 1). The support member 8 is provided with a second rotation restricting member 14 that restricts the rotation of the rotating member 7 in the clockwise direction in FIG. In the present embodiment, the second rotation restricting members 14 are provided at both ends in the longitudinal direction of the support member 8, respectively, and can be engaged with the ends in the longitudinal direction of the rotating member 7. Accordingly, when the recording material P passes through the guide portion 4, the second rotation restricting member 14 engages with the rotating member 7, whereby the rotating member 7 rotates clockwise in FIG. The rotation of the direction is restricted so that it cannot be rotated any further.

  In this embodiment, the biasing means of the rotating member 7 uses a spring as an elastic member. However, the present invention is not limited to this. For example, the elastic member may be a rubber member or a flexible member. A sheet member or the like may be used. Moreover, the 1st, 2nd rotation control members 13 and 14 are not limited to the aspect of a present Example, respectively, What is necessary is just to be able to control rotation of the rotation member 7. FIG. For example, at least one of the first and second rotation regulating members 13 and 14 may not be provided on the support member 8 but may be provided at an arbitrary position such as the rotation member 7. When the 1st, 2nd rotation control members 13 and 14 are provided in the rotation member 7, they can be comprised so that these may contact | abut (engage) the support member 8, for example.

  FIG. 3 is a schematic cross-sectional view of the vicinity of the guide portion 4 in this embodiment (a cross-section substantially perpendicular to the rotation axis direction of the secondary transfer inner roller 21), and the recording material P does not pass through the guide portion 4. (A state in which the rotation member 7 is located at the first rotation position). At this time, the rotation member 7 abuts on the first rotation restriction member 13, and the rotation member 7 and the support member 8 are disposed on substantially the same plane. In this state, the distance L8 between the tip of the rotating member 7 and the rotation center of the secondary transfer inner roller 21 in the moving direction of the surface of the intermediate transfer belt 1 was set to 20 to 30 mm. In this state, the distance (shortest distance) L5 between the tip of the rotating member 7 and the intermediate transfer belt 1 was set to 4 to 5 mm. In this state, the distance (shortest distance) L7 between the tip of the rotating member 7 and the second guide member 6 is set to 2 to 3 mm. With such a setting, the recording material P can be introduced into the secondary transfer portion N2 without breaking the front end, and the front end of the curled recording material P transfers the toner image on the intermediate transfer belt 1 to the secondary transfer portion. Scraping upstream of N2 can be suppressed. That is, when the distance L8 is larger than the above setting or the distance L5 is smaller than the above setting, the toner image on the intermediate transfer belt 1 is transferred to the secondary transfer portion by the leading edge of the recording material P curled in the direction approaching the intermediate transfer belt 1. There is a possibility of scraping on the upstream side of N2. On the other hand, when the distance L5 is larger than the above setting, or when the distance L8 is smaller than the above setting, there is a possibility that the recording material P enters the secondary transfer portion N2 such that the leading end of the recording material P is bent. Even when the distance L7 is larger than the above setting, the recording material P may enter the secondary transfer portion N2 such that the leading end of the recording material P is bent as described above. On the other hand, when the distance L7 is smaller than the above setting, the rotating member 7 is used until the leading edge of the recording material P reaches the secondary transfer portion N2 when the thick paper as the recording material P passes through the guide portion 4. In addition, the sliding conveyance resistance between the second guide member 6 and the recording material P may become too high. Therefore, the timing at which the leading edge of the recording material P reaches the secondary transfer portion N2 becomes unstable, and there is a possibility that the toner image cannot be transferred to a stable position in the conveyance direction of the recording material P.

  Further, the distance L2 between the tip of the rotation member 7 and the rotation center of the rotation member 7 in the short direction of the rotation member 7 was set to 20 to 22 mm. The distance L3 between the rotation center of the rotation member 7 and the rear end of the rotation member 7 in the short direction of the rotation member 7 was set to 20 to 22 mm. Note that the region of the distance L2 of the rotating member 7 in the conveyance direction of the recording material P is also referred to as a first region 7A, and the region of the distance L3 is also referred to as a second region 7B.

  Here, in this embodiment, the feeding speed of the recording material P by the registration roller pair 3 is higher than the conveyance speed of the recording material P in the secondary transfer portion N2 (that is, the moving speed of the surface of the intermediate transfer belt 1). The speed was set to be 0.3% faster than the conveyance speed of the recording material P at the secondary transfer portion N2. That is, in this embodiment, the feeding speed of the recording material P by the registration roller pair 3 is 115.35 mm / sec when the moving speed of the surface of the intermediate transfer belt 1 is 115 mm / sec and 471. It was set to 41 mm / sec.

  FIG. 4 is a schematic cross-sectional view of the vicinity of the guide portion 4 in this embodiment (a cross-section substantially perpendicular to the rotation axis direction of the secondary transfer inner roller 21), and the recording material P passes through the guide portion 4. (A state in which the rotation member 7 is located at the second rotation position). At this time, the rotating member 7 moves in a direction approaching the intermediate transfer belt 1 (a direction away from the second guide member 6) against the urging force of the urging mechanism 12, and a rear end thereof is the intermediate transfer belt. It rotates to move in a direction away from 1 (a direction approaching the second guide member 6). That is, the rotating member 7 is pushed up by the recording material P so that the first area 7A approaches the intermediate transfer belt 1, and the second area 7B moves away from the intermediate transfer belt 1 (approaches the second guide member 6). The recording material P is pushed down. As a result, the recording material P is brought into an S-shaped posture by the rotating member 7. Typically, until the leading edge of the recording material P reaches the secondary transfer portion N2, the first guide member 5 is substantially maintained in the state shown in FIG. When the leading end of the recording material P reaches the secondary transfer portion N2, the recording material P on the upstream side of the secondary transfer portion N2 takes a curved posture so as to protrude in a direction in contact with the intermediate transfer belt 1. I will try. As a result, a force in a direction approaching the intermediate transfer belt 1 is applied to the tip of the rotating member 7 by the recording material P upstream of the secondary transfer portion N2, and the state shifts to the state shown in FIG.

  In this way, the rotation member 7 changes the posture of the recording material P on the upstream side of the secondary transfer portion N2 by rotating according to the force applied to the tip portion (the first region 7A may be sufficient). Thus, the pressing force of the recording material P against the intermediate transfer belt 1 upstream of the secondary transfer portion N2 can be reduced. Then, by reducing this pressing force, the disturbance of the toner image on the intermediate transfer belt 1 can be reduced. At this time, even if the leading end of the rotating member 7 is closest to the intermediate transfer belt 1 by the second rotation restricting member 14, the distance L5 between the leading end of the rotating member 7 and the intermediate transfer belt 1 is 1.5. It was set to be up to 2.5 mm. At this time, the distance (shortest distance) L6 between the rear end of the rotating member 7 and the support member 8 is 2.5 to 3.5 mm at the maximum, and the recording material P is pushed down.

  FIG. 5A is a schematic cross-sectional view of the first guide member 5 of the comparative example (a cross section substantially orthogonal to the rotation axis of the secondary transfer inner roller 21). FIG. 5B is a schematic cross-sectional view of the first guide member 5 in this embodiment (a cross-section substantially orthogonal to the rotation axis of the secondary transfer inner roller 21). 5A and 5B show the state when the recording material P passes through the guide portion 4. FIG. The comparative example shown in FIG. 5A has a base 31 having the same configuration as that of the support member 8 in the present embodiment (however, the recess 8b is not provided), and a flexibility attached to the tip of the base 31. And a resin sheet 32 having. As the resin sheet 32, a resin sheet (trade name “Diaramy”) manufactured by Mitsubishi Plastics, Inc. was used. The thickness of the resin sheet 32 is 200 μm, and the free length in the conveying direction of the recording material P (corresponding to the distance L2 in this embodiment) is 20 to 22 mm.

  As shown in FIG. 5A, in the comparative example, the resin sheet 32 provided on the first guide member 5 is applied to the intermediate transfer belt 1 when a force in a direction approaching the intermediate transfer belt 1 is applied by the recording material P. Although it bends in the approaching direction, it does not push down the recording material P. On the other hand, as shown in FIG. 5B, in this embodiment, the rotating member 7 rotates as described above when a force in a direction approaching the intermediate transfer belt 1 is applied by the recording material P. The recording material P is pushed down. Here, the direction of the force by which the registration roller pair 3 pushes the recording material P is the P1 direction, and the conveyance direction of the recording material P guided by the first guide member 5 (the surface direction of the resin sheet 32 and the rotating member 7 is substantially parallel to the direction. Is the P2 direction. The angle formed between the P1 direction and the P2 direction is θ1 in the comparative example and θ2 in the present embodiment. At this time, the angle θ2 in the present embodiment is larger than the angle θ1 in the comparative example.

For example, when the recording material P is GF-C081 (manufactured by Oji Paper Co., Ltd.) (basis weight 81 g / m ² ) and Gurley stiffness (MD) 2.0 to 2.3 mN, θ1 is approximately 6 to 7 ° (comparison). Example) and θ2 were approximately 13 to 14 ° (in this example). That is, the force in the P1 direction in which the registration roller pair 3 pushes the recording material P is the same in the comparative example and the present embodiment. However, in this embodiment, the recording material P is bent in the P2 direction, so that the force in the P2 direction in which the recording material P is conveyed is reduced (relaxed). The greater the angle between the P1 direction and the P2 direction, the smaller the force in the P2 direction. As described above, when θ1 = 6 to 7 ° (comparative example) and θ2 = 13 to 14 ° (example), the force in the P2 direction in this example is (cos θ1−cos θ2) / It is reduced by cos θ1, that is, approximately 2%. When the recording material P is a paper of ColorCopy (manufactured by Mondi) having a basis weight of 400 g / m ² and a Gurley stiffness (MD) of 68 to 79 mN, θ1 is approximately 5 to 6 ° (comparative example), and θ2 is approximately 10 to 10. The force in the P2 direction to be reduced was 11% (this example), and was approximately 1%.

Table 1 shows the recording material P on the recording material P corresponding to the portion where the toner image is disturbed on the intermediate transfer belt 1 upstream of the secondary transfer portion N2 and the portion where the toner image is not disturbed. The result of having investigated the density nonuniformity (density difference) in is shown. As the recording material P, the above-described GF-C081 (plain paper) and a ColorCopy basis weight of 400 g / m ² (thick paper) were used.

  In the comparative example, the in-plane density unevenness (density difference) of the recording material P was 0.092 to 0.096 (concentration meter manufactured by X-Rite, the same applies hereinafter). In contrast, in this example, the in-plane density unevenness of the recording material P was reduced to 0.032 to 0.062, and a visually good image could be obtained.

  FIG. 6 is a schematic cross-sectional view (axis line) showing the conveyance path of the recording material P from the conveyance nip N3 to the secondary transfer portion N2 for explaining the setting of the position of the rear end (upstream end) of the rotating member 7. X-Y cross section). FIG. 6A shows a state when the recording material P does not pass through the guide portion 4 (a state in which the rotation member 7 is located at the first rotation position), and FIG. A state when the recording material P passes through the guide portion 4 (a state in which the rotation member 7 is located at the second rotation position) is shown. In the cross section shown in FIG. 6, a straight line that passes through the conveyance nip N3 and is substantially orthogonal to the straight line Lb that connects the rotation center of the first registration roller 3a and the rotation center of the second registration roller 3b is defined as a conveyance nip line La. As shown in FIG. 6A, when the rotation member 7 is located at the first rotation position, the position of the rear end (upstream end) 7B1 of the rotation member 7 is the first resist with respect to the conveyance nip line La. Located on the same side as the roller 3a. As a result, the rear end 7B1 of the rotation member 7 at the first rotation position is disposed at a position that does not interfere with the trajectory of the recording material P conveyed by the registration roller pair 3, and therefore the rear end 7B1 of the rotation member 7 It is possible to suppress the conveyance failure of the recording material P due to being caught on the recording medium. As shown in FIG. 6B, when the rotating member 7 is located at the second rotating position, the rear end (upstream end) 7B1 of the rotating member 7 is first with respect to the transport nip line La. It is located on the opposite side to the registration roller 3a (the same side as the second registration roller 3b). Thereby, the effect of reducing the force in the P2 direction as described above can be obtained.

  Here, as shown in FIG. 4, the secondary transfer portion N2 (more specifically, the upstream end portion of the surface of the intermediate transfer belt 1 of the secondary transfer portion N2 in the moving direction) and the rotating member 7 A straight line connecting the rotation center is defined as a transfer nip line L1. At this time, after the leading end of the recording material P reaches the rear end of the rotating member 7, the rotating member 7 rotates so that the rear end of the rotating member 7 is below (intermediate) the transfer nip line L1. It is preferable to enter the side opposite to the transfer belt 1 side. Thereby, the force with which the recording material P presses the intermediate transfer belt 1 on the upstream side of the secondary transfer portion N2 can be stably reduced.

  As described above, in this embodiment, the image forming apparatus 100 includes the pair of transport rollers 3 including the first transport roller 3a and the second transport roller 3b, the first guide member 5, and the second guide member 6. And a guide part 4 provided. In this embodiment, the image forming apparatus 100 is configured such that the conveyance speed of the recording material P by the pair of conveyance rollers 3 is faster than the moving speed of the surface of the image carrier (intermediate transfer belt) 1. In the present embodiment, the first guide member 5 has a first rotation position and a second rotation position about an axis XY that is substantially parallel to the width direction substantially orthogonal to the conveyance direction of the recording material P. And a rotating member 7 that can rotate between the two. The rotating member 7 is positioned at the first rotating position before the leading end in the conveying direction of the recording material P reaches the upstream end 7B1 of the rotating member 7 in the conveying direction of the recording material P. The rotating member 7 is configured to be rotatable from the first rotation position to the second rotation position by contacting the recording material P while the recording material P passes through the transfer portion N2. Here, in a cross section substantially perpendicular to the axis XY, a straight line that is substantially orthogonal to the straight line Lb that passes through the conveyance nip N3 and connects between the rotation center of the first conveyance roller 3a and the rotation center of the second conveyance roller 3b. Let it be a conveyance nip line La. At this time, when the rotation member 7 is located at the first rotation position, the position of the upstream end 7B1 of the rotation member 7 is located on the same side as the first conveyance roller 3a with respect to the conveyance nip line La. On the other hand, when the rotation member 7 is positioned at the second rotation position, the upstream end 7B1 of the rotation member 7 is positioned on the side opposite to the first conveyance roller 3a with respect to the conveyance nip line La. In this embodiment, a straight line connecting the transfer portion N2 and the rotation center of the rotation member 7 in a cross section substantially orthogonal to the axis XY is a straight line L1. At this time, when the rotation member 7 is located at the second rotation position, the upstream end 7B1 of the rotation member 7 is on the opposite side of the image carrier 1 with respect to the straight line L1.

  In this embodiment, the rotating member 7 includes a first region 7A downstream of the rotation center in the conveyance direction of the recording material P and a first area 7A upstream of the rotation center in the conveyance direction of the recording material P. 2 regions 7B. In this embodiment, the image forming apparatus 100 includes the urging unit 12 that urges the rotation member 7 to rotate in the direction from the second rotation position toward the first rotation position. The rotating member 7 is moved from the first rotating position to the second position against the urging force of the urging means 12 by the recording material P coming into contact with the first region 7A (typically, the downstream end 7A1). It rotates in the direction toward the rotation position. At the same time, the second area 7 </ b> B (typically, the upstream end 7 </ b> B <b> 1) presses the recording material 7 </ b> B away from the image carrier 1. Further, in this embodiment, the image forming apparatus 100 is configured to restrict the rotation of the rotation member 7 from the second rotation position to the first rotation position (first rotation restriction member). ) 13. Further, in this embodiment, the image forming apparatus 100 is provided with another rotation restricting member (second rotation member) that restricts the rotation of the rotation member 7 from the first rotation position toward the second rotation position. (Regulating member) 14. In this embodiment, the image forming apparatus 100 includes a support member 8 that supports the rotation member 7 so as to be rotatable. In this embodiment, the rotation member 7 and the support member 8 are plate-like members. In this embodiment, the rotating member 7 has the downstream end 7A1 of the rotating member 7 in the conveying direction of the recording material P positioned on the downstream side of the downstream end 8e of the supporting member 8 in the conveying direction of the recording material P. Are arranged as follows. In the present embodiment, the rotating member 7 is disposed on substantially the same plane as the support member 8 when positioned at the first rotating position.

  As described above, according to this embodiment, it is possible to reduce the force with which the recording material P presses the intermediate transfer belt 1 on the upstream side of the secondary transfer portion N2. Thereby, the disturbance of the toner image on the intermediate transfer belt 1 can be reduced. More specifically, even when there is variation in the feeding speed of the recording material P by the registration roller pair 3, the difference in strength of the force with which the recording material P presses the intermediate transfer belt 1 on the upstream side of the secondary transfer portion N2 is reduced. Density unevenness due to the disturbance of the toner image on the intermediate transfer belt 1 is suppressed. That is, according to the present embodiment, the force of pressing the intermediate transfer belt 1 strongly by the recording material P on the upstream side of the secondary transfer portion N2 is reduced while suppressing the leading end of the recording material P from hitting the guide portion 4. be able to. According to this embodiment, it is possible to form a good image in which density unevenness is suppressed on the recording material P having a wide range of rigidity from thin paper to thick paper.

[Example 2]
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are the same as those of the image forming apparatus according to the first exemplary embodiment. Accordingly, in the image forming apparatus according to the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted. To do.

  In this embodiment, as shown in Table 2, according to the type of the recording material P, the conveyance speed of the recording material P in the secondary transfer portion N2 (that is, the moving speed of the surface of the intermediate transfer belt 1) and the registration roller The speed difference between the feed speed of the recording material P by the pair 3 is made variable. In this embodiment, the feeding speed of the recording material P by the registration roller pair 3 is made variable, and the speed difference is made variable. In this embodiment, as in the first embodiment, the feeding speed of the recording material P by the registration roller pair 3 is the conveyance speed of the recording material P in the secondary transfer portion N2 (that is, the moving speed of the surface of the intermediate transfer belt 1). ) Faster. However, in this embodiment, in the case of a recording material P of relatively high rigidity such as thick paper or synthetic paper formed of resin such as water-resistant paper, the feeding speed of the recording material P by the resist roller pair 3 is used. To reduce the speed difference.

  That is, since the thick paper having a large basis weight has a relatively high rigidity, even when the feeding speed of the registration roller pair 3 is the same, when the leading edge of the recording material P reaches the secondary transfer portion N2 and enters the state of FIG. The force with which the recording material P presses the intermediate transfer belt 1 upstream of the secondary transfer portion N2 is increased. Therefore, in this embodiment, in the case of a recording material P (thick paper, synthetic paper, etc.) having a Gurley stiffness of 18 mN or more, the moving speed of the surface of the intermediate transfer belt 1 and the feeding speed of the recording material P by the registration roller pair 3 The speed difference is reduced as shown in Table 2. Here, the speed difference is displayed as a percentage of the difference with respect to the moving speed of the surface of the intermediate transfer belt 1. As a result, even when the recording material P having relatively high rigidity is used, the recording material P moves the intermediate transfer belt 1 on the upstream side of the secondary transfer portion N2 by the first guide member 7 similar to the first embodiment. The pressing force can be reduced more stably.

  FIG. 7A is a schematic block diagram illustrating a control mode of a main part of the image forming apparatus 100 in the present embodiment. The operation of each unit of the image forming apparatus 100 is comprehensively controlled by the control unit 110 provided in the image forming apparatus 100. The control unit 110 is connected to a storage unit 111 configured with an electronic memory or the like. The storage unit 111 stores programs and setting information necessary for the operation of the image forming apparatus 100. In this embodiment, the storage unit 111 stores information indicating the relationship between the type of the recording material P as shown in Table 2 and the feeding speed of the recording material P by the registration roller pair 3 as table data or the like. An operation unit 112 provided in the image forming apparatus 100 is connected to the control unit 110. The operation unit 112 includes a display unit that displays information under the control of the control unit 110 and an input unit that inputs information such as various settings to the control unit 110. In addition, information can be input to the control unit 110 from an external device 200 such as a personal computer that is communicably connected to the image forming apparatus 100. In this embodiment, instruction information relating to image formation including information specifying the recording material P used for image formation is input to the control unit 110 from the operation unit 112 or the external device 200. When executing the image formation, the control unit 110 uses the information as shown in Table 2 stored in the storage unit 111 based on the information specifying the type of the recording material P included in the instruction information. The feeding speed of the recording material P by the registration roller pair 3 at the time of formation is determined. Then, the control unit 110 controls the drive motor 112 so as to achieve the determined feed speed, and drives the registration roller pair 3 to execute image formation.

  In this embodiment, the control unit 110 acquires information on the type of the recording material P based on instructions from an operator such as a user or a service person from the operation unit 112 or the external device 200. However, the present invention is not limited to this, and as the recording material type detection means, for example, the control unit 110 detects the recording material P based on the detection result of a media sensor that detects the basis weight or surface property of the recording material P. You may make it acquire the information regarding the kind of. Here, the type of recording material P can be distinguished from the recording material P such as attributes, manufacturer, brand, product number, basis weight, thickness, size, etc. based on general characteristics such as plain paper, thick paper, thin paper, and synthetic paper. Any arbitrary information is included. In this embodiment, as the types of recording material P that can be set, at least plain paper and cardboard can be selected according to the basis weight correlated with the stiffness, and a synthetic paper having a relatively high stiffness can be selected.

Table 3 shows the results of examining density unevenness (density difference) for Example 1 and this example in the same manner as described above for Example 1. As the recording material P, the aforementioned GF-C081 (plain paper), the aforementioned ColorCopy basis weight of 400 g / m ² (thick paper), the ColorCopy (made by Mondi) basis weight of 220 g / m ² , Gurley stiffness (MD) ) 18-20 mN (cardboard).

  In this embodiment, the feeding speed of the recording material P by the registration roller pair 3 is changed according to the basis weight having a correlation with the stiffness. Specifically, the feeding speed of the recording material P by the registration roller pair 3 is 0.3, which is the moving speed of the surface of the intermediate transfer belt 1 rather than the moving speed of the surface of the intermediate transfer belt 1 in the case of plain paper. %, And in the case of cardboard and synthetic paper, it was accelerated by 0.1%. As a result, in this embodiment, the density difference (density unevenness) is higher than that in the first embodiment (the feeding speed by the registration roller pair 3 is constant at a speed that is 0.3% faster than the moving speed of the surface of the intermediate transfer belt 1). Was able to be reduced.

  As described above, in this embodiment, the changing unit that changes the speed difference between the moving speed of the surface of the image carrier 1 and the conveying speed of the recording material P by the conveying member 3 according to the type of the recording material P is provided. Have. In the present embodiment, the control unit 110 has a function of a changing unit. Then, the changing unit 110 determines the speed difference when the recording material P is the second recording material having a larger basis weight than the first recording material than the speed difference when the recording material P is the first recording material. Make it smaller.

  As described above, according to the present embodiment, the feeding speed of the recording material P by the registration roller pair 3 is made variable according to the type (stiffness) of the recording material, so that the intermediate transfer belt 1 can be moved regardless of the type of the recording material P. The toner image disturbance can be reduced more stably.

[Example 3]
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are the same as those of the image forming apparatus according to the first exemplary embodiment. Accordingly, in the image forming apparatus according to the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted. To do.

  FIG. 8A is a schematic plan view of the first guide member 5 of the guide portion 4 in this embodiment as viewed from above in FIG. 8B and 8C are schematic side views seen from the X side in the XY line direction of FIG. 8A. FIG. 8B shows a state when the recording material P does not pass through the guide portion 4, and FIG. 8C shows a state when the recording material P passes through the guide portion 4. Yes.

  As illustrated in FIG. 8A, the first guide member 5 includes a rotation member 7, a support member 8, a rotation shaft 9, a fixing member 10, and a bearing 11, as in the first embodiment.

  In this embodiment, at least a part of the rotating member 7 is composed of the magnetic member 7. In particular, in this embodiment, the rotating member 7 is configured by attaching a magnetic member 7b to a main body 7c formed of a SUS plate similar to that of the first embodiment. In this embodiment, the support member 8 is attached with an excitation member 15 having a dielectric coil or the like. In the present embodiment, the magnetic member 7d provided on the rotating member 7 and the exciting member 15 provided on the supporting member 8 serve as holding means for holding the rotating member 7 in the state shown in FIG. 8B. The holding mechanism 16 is configured. 7 d of magnetic members are provided in the edge part of the longitudinal direction of the rotation member 7 in the rear end side rather than the position where the rotating shaft 9 of the rotation member 7 is arrange | positioned. The excitation member 15 is provided at a position facing the magnetic member 7 d in the short direction of the support member 8. The excitation member 15 is not limited to being attached to the support member 8, and can be placed at any place where the holding / releasing of the rotating member 7 can be controlled by acting on the magnetic member 7 d of the rotating member 7. Can be provided.

  When energization to the dielectric coil of the exciting member 15 is turned on and excitation is turned on, the exciting member 15 and the magnetic member 7d are magnetically fixed, and the rotating member 7 is held in the state of FIG. 8B. Is done. When the energization to the dielectric coil of the exciting member 15 is turned off and the excitation is turned off, the holding of the rotating member 7 is released. Accordingly, the rotating member 7 moves in the clockwise direction in FIG. 8B, that is, the tip moves upward (direction approaching the intermediate transfer belt 1), and the rear end moves downward (direction away from the intermediate transfer belt 1). It is possible to rotate to move. That is, the first guide member 5 can be changed from the state shown in FIG. 8B to the state shown in FIG. In this embodiment, the rotating member 7 can be rotated in the clockwise direction in FIGS. 8B and 8C by its own weight when the exciting member 15 is turned off. Further, the support member 8 is provided with a rotation restriction member 14 similar to the second rotation restriction member 14 in the first embodiment. Thereby, when the rotation member 7 rotates as described above, the rotation restriction member 14 engages with the rotation member 7, whereby the rotation of the rotation member 7 is restricted, and the rotation is further performed. I can't do it.

  The holding means for holding the rotating member 7 so as not to rotate is not limited to the aspect of the present embodiment, and the rotating member 7 is held so as not to rotate, and can be rotated. It can be set as the arbitrary aspects which can be switched to the state to perform. For example, the holding principle of the holding means is not limited to that based on magnetic force, and may be based on physical engagement or the like.

  The distances L2, L3, L4, and L5 (when the recording material P passes and when it does not pass), L6, L7, and L8 in this embodiment, and the reason thereof are described in the embodiment described with reference to FIGS. This is the same as the setting in 1 and the reason. Further, the setting of the feeding speed of the recording material P by the registration roller pair 3 in this embodiment is the same as that in the first embodiment. Although not limited to this, by making the distance L3 (second region) longer than the distance L2 (first region), the rotating member 3 can be easily rotated by its own weight.

  In this embodiment, when the recording material P does not pass through the guide portion 4, the first guide member 7 is in the state shown in FIG. On the other hand, when the recording material P passes through the guide portion 4, the first guide member 7 can be rotated at a predetermined timing to be in the state shown in FIG. As a result, the rear end of the rotating member 7 can push down the recording material P. Also in the present embodiment, the rotating member 7 rotates according to the force applied to the tip end portion (the first region 7A only), so that the posture of the recording material P on the upstream side of the secondary transfer portion N2 is changed. In other words, the pressing force of the recording material P against the intermediate transfer belt 1 upstream of the secondary transfer portion N2 can be reduced. Then, by reducing this pressing force, the disturbance of the toner image on the intermediate transfer belt 1 can be reduced.

  FIG. 9 is an explanatory diagram showing ON / OFF timing of the excitation member 15. The horizontal axis in FIG. 9 indicates time, and the vertical axis indicates the ON / OFF state of the excitation member 15. After the time when the leading end of the recording material P reaches the rear end (upstream end) of the rotating member 7 in the conveyance direction of the recording material P, when the recording material P passes through the guide portion 4, the excitation member 15. Is turned off. In particular, in this embodiment, in the conveyance direction of the recording material P, after the time when the leading end of the recording material P reaches the rear end of the rotating member 7 and before the time when the rotating member 7 reaches the rotation center. At the timing (timing T1 to T2 in FIG. 9), the exciting member 15 is turned off. In this embodiment, the distance L3 (see FIG. 3) is set to 20 to 22 mm. Therefore, when the feeding speed of the recording material P by the registration roller pair 3 is 115.35 mm / sec, the excitation member 15 is between 174 and 190 msec after the leading end of the recording material P passes the rear end of the rotating member 7. Is turned off. When the feeding speed of the recording material P by the registration roller pair 3 is 471.41 mm / sec, the excitation member 15 is moved 43 to 47 msec after the front end of the recording material P passes the rear end of the rotating member 7. It is turned off. As a result, the support member 8 is magnetically applied to the region (first region) 7A downstream from the rotation center of the rotation member 7 at the timing at which the front end of the recording material P and the portion on the rear end side from the front end can contact. The fixed rotation member 7 can be rotated. By doing in this way, it can suppress that the front-end | tip of the recording material P gets caught in the rotation member 7, and can convey the recording material P stably.

  In the present embodiment, the excitation member 15 is moved after the rear end of the recording material P reaches the front end of the rotating member 7 in the conveyance direction of the recording material P and the front end of the next recording material P rotates. The excitation member 15 is turned on at a timing (not shown) before reaching the rear end of the moving member 7.

  FIG. 7B is a schematic block diagram illustrating a control mode of a main part of the image forming apparatus 100 in the present embodiment. In the present embodiment, the excitation member 15 is connected to the control unit 110. The control unit 110 turns on / off the excitation member 15 at the above-described timing according to the program stored in the storage unit 111. The timing at which the leading edge and the trailing edge of the recording material P reach a predetermined position depends on the conveyance timing of the recording material P by the registration roller pair 3 or the like, the conveyance speed or feeding speed of the recording material P, the conveyance path length of the recording material P, etc. Based on this, the control unit 110 can make a determination. Alternatively, an optical sensor or the like as a recording material detection unit that detects the leading edge or the trailing edge of the recording material P is provided on the conveyance path of the recording material P, and the control unit 110 controls the leading edge of the recording material P or the like based on the detection result. The timing at which the rear end reaches a predetermined position may be determined.

In this embodiment, the angle θ2 when the recording material P is GF-C081 (manufactured by Oji Paper Co., Ltd.) (basis weight 81 g / m ² ) and Gurley stiffness (MD) 2.0 to 2.3 mN (plain paper). (See FIG. 5B) was approximately 13 to 14 °. In this example, when the recording material P is a paper (cardboard) having a basis weight of 400 g / m ² and a stiffness of 68 to 79 mN of ColorCopy (manufactured by Mondi), the angle θ2 is about 10 to 11 °. Also in this example, when the density unevenness (density difference) was examined in the same manner as described in Example 1, the same result as in Example 1 was obtained.

  Here, also in this embodiment, after the leading end of the recording material P passes through the rear end of the rotation member 7, the rotation member 7 rotates and the rear end of the rotation member 7 is in relation to the transfer nip line L1. It is preferable to enter the lower side (the side opposite to the intermediate transfer belt 1 side) (see FIG. 4). Thereby, the force with which the recording material P presses the intermediate transfer belt 1 on the upstream side of the secondary transfer portion N2 can be stably reduced.

  As described above, in this embodiment, the rotating member 7 is held at the first rotating position, and the holding means 15 capable of releasing the holding and allowing the rotating member 7 to rotate is provided. . The rotating member 7 includes a first area 7A downstream of the rotation center in the conveyance direction of the recording material P, and a second area 7B upstream of the rotation center in the conveyance direction of the recording material P. It has. Then, when the recording material P comes into contact with the first region 7A (typically the downstream end 7A1) in a state where the holding by the holding unit 15 is released, the rotating member 7 is moved to the second region 7B (typically The upstream end 7B1) presses the recording material P in a direction away from the image carrier 1. In particular, in the present embodiment, the holding means 15 is an exciting member that can hold the rotating member 7 by a magnetic force and release the holding by the magnetic force so that the rotating member 7 can be rotated. . In the present exemplary embodiment, the image forming apparatus 100 includes the rotation restriction member 14 that restricts the rotation of the rotation member 7 from the first rotation position toward the second rotation position. In the present embodiment, the holding means 15 rotates when the recording material P passes through the guide portion 4 after the leading end of the recording material P in the conveying direction reaches the upstream end 7B1 of the rotating member 7. The holding of the member 7 is released. In this embodiment, the holding unit 15 holds the rotating member 7 before the next recording material P is conveyed in the conveying direction before the leading end reaches the upstream end 7B1 of the rotating member 7.

  As described above, according to the present embodiment, the same effects as in the first embodiment can be obtained, and the conveyance timing of the recording material P can be improved by controlling the timing at which the rotation member 7 rotates.

[Example 4]
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are the same as those of the image forming apparatus according to the first exemplary embodiment. Accordingly, in the image forming apparatus according to the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted. To do.

  In this embodiment, as shown in Table 4, depending on the type of the recording material P, the excitation member 15 is always turned on at the time of image formation, or the excitation member 15 is turned on / off similarly to the embodiment 3 at the time of image formation. Select whether to perform control. As shown in Table 4, the recording material P (thin paper or the like) having a Gurley stiffness of 0.31 mN or less has a stiffness that is about an order of magnitude lower than that of plain paper having a Gurley stiffness of 2 to 15 mN. For this reason, the force with which the recording material P presses the intermediate transfer belt 1 is also reduced by an order of magnitude. In this case, the postures of the intermediate transfer belt 1 and the recording material P on the upstream side of the secondary transfer portion N2 as described above with reference to FIGS. Therefore, the density unevenness (density difference) examined in the same manner as described in the first embodiment is 0.032 or less, and the density unevenness (density) even when the recording material P is placed in the S-shape by the rotating member 7. Difference) was never smaller than 0.032. Therefore, in this embodiment, in the case of the recording material P having relatively low rigidity such as thin paper, it is important to lower the conveyance resistance as much as possible to increase the conveyance stability, and the recording material P is not pushed down by the rotating member 7. Not performed.

  On the other hand, as shown in Table 4, in the case of the recording material P having relatively high rigidity such as plain paper, thick paper, synthetic paper, etc., the excitation member 15 is turned on / off in the same manner as in the third embodiment, so that the rotating member 7, the recording material P is pushed down. Thus, in the case of a recording material P of a relatively high rigidity type such as plain paper, cardboard, or synthetic paper made of resin such as water-resistant paper, two recording materials P are used in the same manner as in the third embodiment. The force for pressing the intermediate transfer belt 1 upstream of the next transfer portion N2 can be reduced.

  The control mode of the main part of the image forming apparatus 100 in this embodiment is the same as that shown in FIG. In the present embodiment, the storage unit 111 stores information indicating the relationship between the type of the recording material P as shown in Table 4 and the necessity of ON / OFF control of the excitation member 15. When executing the image formation, the control unit 110 is based on information specifying the type of the recording material P included in the instruction information from the operation unit 112 or the external device 200, as shown in Table 4 in the storage unit 111. From the information, the necessity of ON / OFF control of the excitation member 15 at the time of image formation is determined. Then, the control unit 110 always turns on the excitation member 15 during image formation or performs ON / OFF control at a predetermined timing according to the determination result.

  As described above, the present embodiment includes a switching unit that selectively switches between the next first mode and the second mode. The first mode is a mode in which the rotation member 7 is maintained at the first rotation position when the recording material P passes through the guide portion 4. The second mode is a mode in which the rotating member 7 is allowed to rotate to the second rotation position when the recording material P passes through the guide portion 4. In the present embodiment, the control unit 110 has a function of a switching unit. In this embodiment, the switching unit 110 selectively switches between the first mode and the second mode according to the type of the recording material P. In particular, in this embodiment, the switching unit 110 sets the first mode when the recording material P is the first recording material, and the second mode when the recording material P is the second recording material having a larger basis weight than the first recording material. Mode.

  As described above, according to the present exemplary embodiment, the same effect as that of the third exemplary embodiment is obtained, and the recording material P on which the toner image on the intermediate transfer belt 1 is not disturbed by the recording material P pressing the intermediate transfer belt 1 does not matter. In this case, priority can be given to conveyance stability.

[Others]
As mentioned above, although this invention was demonstrated according to the specific Example, this invention is not limited to the above-mentioned Example.

  In the above-described embodiments, the case where the belt-shaped image carrier is an intermediate transfer belt has been described. However, the image carrier formed of an endless belt is not limited to the intermediate transfer belt. Examples of such a belt-shaped image carrier include a photosensitive belt and an electrostatic recording dielectric belt in addition to the intermediate transfer belt. Further, when the image carrier is an endless belt, the posture of the belt and the recording material on the upstream side of the transfer portion is relatively easily changed, so that the present invention is particularly effective. However, the image carrier is not limited to a belt-like one, and may be a drum-like one provided with a cylindrical base, or a drum-like one formed by stretching a sheet on a frame. .

  Further, the rotating member provided in the guide member is configured to be rotated by the force applied by the recording material or by its own weight, as in the above-described embodiment, from the viewpoint of simplification of the configuration, miniaturization, and the like. preferable. However, it is good also as a structure which rotates a rotation member with the drive device provided with the drive source if desired.

  The present invention can be implemented in another embodiment in which a part or all of the configuration of the above-described embodiment is replaced with the alternative configuration. Therefore, it can be carried out without distinction between a tandem type / 1 drum type, a charging method, an electrostatic image forming method, a developing method, a transfer method, and a fixing method. In the above-described embodiments, the main part related to the formation / transfer of the toner image has been mainly described. However, the present invention includes a printer, various printing machines, a copier, a FAX, in addition to necessary equipment, equipment, and a housing structure. It can be implemented in various applications such as a multifunction machine.

DESCRIPTION OF SYMBOLS 1 Intermediate transfer belt 2 Secondary transfer outer roller 3 Registration roller pair 4 Guide portion 5 First guide member 6 Second guide member 7 Rotating member 8 Support member

Claims (16)

An image carrier that carries and conveys a toner image;
A transfer member that contacts a surface of the image carrier and forms a transfer portion for transferring a toner image from the image carrier to a recording material;
A position provided at a position in contact with the first surface to which the toner image of the recording material is transferred, a position at which the first conveying roller for conveying the recording material, and a second surface on the opposite side of the recording material from the first surface. A pair of conveyance rollers that convey the recording material to the transfer unit, and a second conveyance roller that forms a conveyance nip in contact with the first conveyance roller and conveys the recording material,
A guide unit that is provided downstream of the transfer nip and upstream of the transfer unit in the conveyance direction of the recording material and guides the recording material toward the transfer unit, and is opposed to the first surface of the recording material. Forming a conveyance path for conveying the recording material between the first guide member for guiding the recording material and the first guide member, and guiding the recording material opposite to the second surface of the recording material. In an image forming apparatus having a guide portion including two guide members,
The conveyance speed of the recording material by the pair of conveyance rollers is faster than the movement speed of the surface of the image carrier,
The first guide member is a rotation member that can rotate between a first rotation position and a second rotation position about an axis substantially parallel to a width direction substantially orthogonal to the conveyance direction of the recording material. Have
The rotating member is positioned at the first rotating position before the leading end of the recording material in the conveying direction reaches the upstream end of the rotating member in the recording material conveying direction. It is configured to be able to rotate from the first rotation position to the second rotation position by contacting the recording material during passage,
In a cross section substantially perpendicular to the axis, a straight line that is substantially perpendicular to a straight line that passes through the conveyance nip and connects between the rotation center of the first conveyance roller and the rotation center of the second conveyance roller is defined as a conveyance nip line La. When the rotation member is located at the first rotation position, the position of the upstream end of the rotation member is located on the same side as the first conveyance roller with respect to the conveyance nip line La, and the rotation When the moving member is located at the second rotation position, the upstream end of the rotation member is located on the opposite side of the conveyance nip line La from the first conveyance roller. Image forming apparatus.   In a cross section substantially orthogonal to the axis, when a straight line connecting the transfer portion and the rotation center of the rotation member is a straight line L1, when the rotation member is located at the second rotation position, The image forming apparatus according to claim 1, wherein the upstream end of the rotating member is on the opposite side of the straight line L <b> 1 from the image carrier.   3. A changing unit that changes a speed difference between a moving speed of the surface of the image carrier and a conveying speed of the recording material by the conveying member according to a type of the recording material. The image forming apparatus described in 1.   The changing unit reduces the speed difference when the recording material is a second recording material having a basis weight larger than that of the first recording material than the speed difference when the recording material is the first recording material. The image forming apparatus according to claim 3. The rotating member includes a first area downstream of the rotation center in the recording material conveyance direction, and a second area upstream of the rotation center in the recording material conveyance direction, Biasing means for biasing the rotating member to rotate in a direction from the second rotation position toward the first rotation position;
The rotating member rotates in a direction from the first rotating position toward the second rotating position against the urging force of the urging means when the recording material abuts on the first region. The image forming apparatus according to claim 1, wherein the second region presses the recording material in a direction away from the image carrier.   The image forming apparatus according to claim 5, further comprising a rotation restricting member that restricts rotation of the rotating member from the second rotating position toward the first rotating position.   7. The image according to claim 5, further comprising another rotation restricting member that restricts rotation of the rotating member in a direction from the first rotating position toward the second rotating position. 8. Forming equipment. Holding means capable of holding the turning member at the first turning position and releasing the holding so that the turning member can turn;
The rotating member includes a first area downstream of the rotation center in the recording material conveyance direction, and a second area upstream of the rotation center in the recording material conveyance direction, The rotating member is configured to press the recording material in a direction away from the image carrier when the recording material comes into contact with the first region in a state where the holding by the holding unit is released. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The holding means is an exciting member capable of holding the rotating member by magnetic force and releasing the holding by the magnetic force so that the rotating member can rotate. The image forming apparatus according to 8.   10. The image forming apparatus according to claim 8, further comprising a rotation restricting member that restricts rotation of the rotating member in a direction from the first rotating position toward the second rotating position. 11. .   The holding means releases the holding of the rotating member when the recording material passes through the guide portion after the leading end of the recording material in the conveying direction reaches the upstream end of the rotating member. 11. The rotating member is held before the leading end of the next recording material in the conveying direction reaches the upstream end of the rotating member. The image forming apparatus described in 1.   A first mode in which the rotating member is maintained at the first rotating position when the recording material passes through the guide portion; and the rotating member of the rotating member when the recording material passes through the guide portion. 12. The image forming apparatus according to claim 8, further comprising: a switching unit that selectively switches between a second mode in which rotation to the second rotation position is allowed.   The image forming apparatus according to claim 12, wherein the switching unit selectively switches between the first mode and the second mode according to a type of recording material.   The switching unit sets the first mode when the recording material is the first recording material, and sets the second mode when the recording material is the second recording material having a basis weight larger than that of the first recording material. The image forming apparatus according to claim 13.   A support member that rotatably supports the rotation member, wherein the rotation member and the support member are plate-like members, and the rotation member is a downstream end of the rotation member in the conveyance direction of the recording material; Is disposed on the downstream side of the downstream end in the recording material conveyance direction of the support member, and the pivot member is substantially flush with the support member when the pivot member is located at the first pivot position. The image forming apparatus according to claim 1, wherein the image forming apparatus is disposed on the image forming apparatus.   The image forming apparatus according to claim 1, wherein the image carrier is an endless belt stretched around a plurality of stretch rollers.

Images