JP2006064748A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus which prevents the occurrence of electrification due to slide friction between a recording medium and a guide member while restraining a minute gap from occurring between a recording medium and a toner image holder right in front of a transfer position. <P>SOLUTION: On an upstream side of a secondary transfer position N between an intermediate transfer belt 64 and a secondary transfer roll 80, a paper guide member 100 presses paper P against the intermediate transfer belt 64. In this case, the paper guide member 100 can be adjusted so as to move in the direction where the member 100 comes into contact with the back of the paper P to be conveyed or separates from the back of it. Accordingly, while a minute gap is restrained from occurring between a recording medium and the toner image holder, electrification due to slide friction between the recording medium and the guide member can be prevented. Even in the case that the part (flexible member 102) in the paper guide member 100 with which paper P comes into contact wears, pressing force exerted on the paper P can be adjusted. This prevents occurrence of electrification due to slide friction between the recording medium and the guide member while restringing a minute gap from occurring between the paper P and the intermediate transfer belt 64 and right in front of the secondary transfer position N. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus in which a toner image on a toner image holding member is transferred to a recording medium.

  For example, in an image forming apparatus in which a toner image on an intermediate transfer belt is transferred to a recording sheet, a guide member may be disposed to guide the recording sheet to a transfer position (for example, Patent Document 1, 2). Immediately before the transfer position, if a small gap occurs between the recording paper and the intermediate transfer belt, white spots may occur due to discharge, which may affect image quality. This is particularly noticeable. In order to prevent such a minute gap from occurring, a configuration is adopted in which the guide member is fixedly disposed immediately before the transfer position. As a material for such a guide member, a resin material is often used because high-precision processing is easy and a certain degree of elasticity is required. In addition, a paper having high resistance such as a dry paper or a coated paper is partially charged due to sliding friction with the guide member, and an image quality abnormality such as a toner dust or a stripe may occur at the time of transfer.

Furthermore, the resin guide member is easily worn by friction with the recording paper, and when used for a long period of time, the guide member is less restricted by the wear of the guide member, and the recording paper and the intermediate transfer belt A small gap is likely to occur between the two.
JP-A-9-204107 JP 2000-172083 A

  In consideration of the above facts, the present invention is capable of forming an image without causing toner dust due to sliding friction between a sheet and a guide member while suppressing a minute gap between the recording medium and the toner image holding member immediately before the transfer position. It is an object to provide an apparatus.

  The image forming apparatus according to the first aspect of the present invention includes a toner image holding member that conveys a toner image while holding the toner image, a transfer unit that transfers the toner image on the toner image holding member to a recording medium, and the transfer A guide member provided on the upstream side of the position, capable of adjusting movement toward and away from the back side of the recording medium to be conveyed, and guiding the recording medium in a direction in which the recording medium is pressed against the toner image holder; It is characterized by having.

  Here, the transfer means refers to means for transferring the toner image on the toner image holding member to a recording medium, and includes, for example, a transfer roll, a transfer discharger, a transfer belt, and the like.

  According to the image forming apparatus of the present invention described in claim 1, a toner image holding member (for example, a photosensitive member or an intermediate transfer member) conveys the toner image while holding it, and the transfer unit holds the toner image at the transfer position. The toner image on the body is transferred to a recording medium. On the upstream side of the transfer position, the guide member presses the recording medium toward the toner image holding member. Here, since the guide member can be moved and adjusted in a direction in which the guide member is in contact with or separated from the back side of the recording medium to be conveyed, even if the portion of the guide member that contacts the recording medium is worn, The pressure can be adjusted. As a result, it is possible to prevent sliding friction between the recording medium and the guide member due to excessive pressing force while suppressing the occurrence of a minute gap between the recording medium and the toner image holding body immediately before the transfer position. As a result, it is possible to obtain a high-quality image while suppressing the influence on the image quality due to the discharge of the minute gap portion (white void etc.) and the influence on the image quality due to the frictional charging (toner dust, streaks etc.).

  According to a second aspect of the present invention, in the configuration of the first aspect, the guide member is swingably supported and biased toward the toner image holding body, and the guide member The portion in contact with the recording medium is a thin-walled flexible member.

  According to the image forming apparatus of the present invention described in claim 2, since the guide member is supported so as to be swingable and is urged toward the toner image holding member, it is possible to ensure a pressing force to the recording medium and to guide the guide member. Since the portion in contact with the recording medium is a thin flexible member, it can be deformed and restored corresponding to the recording medium. Thus, sliding friction between the recording medium and the guide member due to excessive pressing force can be prevented while suppressing a minute gap between the recording medium and the toner image holding body immediately before the transfer position.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the guide member is swingably supported and biased toward the toner image holding body, and the guide member The portion in contact with the recording medium is a plurality of resin ribs extending in the conveyance direction of the recording medium.

  According to the image forming apparatus of the present invention described in claim 3, since the guide member is supported so as to be swingable and is urged toward the toner image holding body, it is possible to secure a pressing force to the recording medium and to guide the guide member. Since the portions in contact with the recording medium are a plurality of resin ribs extending in the recording medium conveyance direction, the conveyance direction of the recording medium can be regulated with a simple configuration. This suppresses the occurrence of a minute gap between the recording medium and the toner image holding member immediately before the transfer position.

  According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the portion of the guide member that comes into contact with the recording medium rotates in accordance with the recording medium being conveyed. It is a roller.

  According to the image forming apparatus of the present invention described in claim 4, since the portion of the guide member that contacts the recording medium is a small roller that rotates following the contact with the conveyed recording medium, the recording medium can be smoothed. The sliding friction between the recording medium and the guide member can be prevented.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect of the present invention, the guide member having the small roller is supported to be swingable and biased toward the toner image holding body. It is characterized by that.

  According to the image forming apparatus of the present invention described in claim 5, since the guide member provided with the small roller is swingably supported and is urged toward the toner image holding body, the pressing force to the recording medium is reduced. While ensuring, sliding friction between the recording medium and the guide member can be prevented.

  An image forming apparatus according to a sixth aspect of the present invention is the configuration according to any one of the first to fifth aspects, wherein the image forming apparatus is attached to the guide member and is in contact with the back side of the recording medium to be conveyed. A base member that can be adjusted to move in the direction of separation, and the force by which the guide member presses the recording medium toward the toner image holding member is adjusted to move the base member according to at least the type of the recording medium or environmental conditions It is characterized by being adjusted by doing.

  Here, “attached to the guide member” means that it is directly or indirectly attached to the guide member. In addition to the case where the base member is directly attached to the guide member, other members (for example, The case where it attaches indirectly via a pressing spring etc. is also included.

  According to the image forming apparatus of the present invention described in claim 6, the base member can be moved and adjusted in a direction in which the base member is in contact with or separated from the back side of the recording medium to be conveyed. The guide member also moves. The force with which the guide member presses the recording medium against the toner image holding member is adjusted by moving and adjusting the base member according to at least the type of the recording medium or environmental conditions. In this way, by changing the pressing force on the recording medium according to at least the type of the recording medium or the environmental conditions, it is ensured that a minute gap is generated between the recording medium and the toner image holding body immediately before the transfer position. While suppressing, sliding friction between the recording medium and the guide member due to excessive pressing force can be prevented, and unnecessary discharge and charging that adversely affect image quality can be prevented.

  According to a seventh aspect of the present invention, there is provided the image forming apparatus according to the sixth aspect, wherein the base member can be manually moved and adjusted.

  According to the image forming apparatus of the present invention described in claim 7, since the base member can be manually moved and adjusted, the pressing force of the guide member to the recording medium can be adjusted with a simple configuration.

  According to an eighth aspect of the present invention, there is provided the image forming apparatus according to the sixth aspect, further comprising: a pressing force adjusting unit that adjusts the pressing force of the guide member against the recording medium by moving and adjusting the base member. The pressing force adjusting means adjusts the pressing force by moving and adjusting the base member based on a preset value at least according to the type or environmental condition of the recording medium.

  According to the image forming apparatus of the present invention described in claim 8, the pressing force adjusting means moves and adjusts the base member based on a preset value at least according to the type of the recording medium or the environmental condition and guides it. Since the pressing force of the member against the recording medium is adjusted, the pressing force can be reliably adjusted.

  According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the guide member contains an antistatic agent.

  According to the image forming apparatus of the present invention described in claim 9, since the antistatic agent is contained in the guide member, charging of the recording medium due to friction between the guide member and the recording medium can be prevented, and the image quality is adversely affected. Can be suppressed.

  As described above, according to the image forming apparatus of the present invention, the recording medium and the guide member due to excessive pressing force can be suppressed while suppressing a minute gap between the recording medium and the toner image holding body immediately before the transfer position. It has an excellent effect of preventing sliding friction.

A first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.
(Outline configuration of image forming apparatus)
FIG. 1 shows a schematic configuration of the image forming apparatus 10. The image forming apparatus 10 includes an image forming apparatus main body 12, and an open / close cover 16 is provided on the upper portion of the image forming apparatus main body 12. The opening / closing cover 16 is rotatable about a rotation fulcrum 14. A paper feeding unit 18 is disposed below the image forming apparatus main body 12.

  The paper feed unit 18 includes a paper feed cassette 22 in which the paper P is stored. A feed roll 24 and a retard roll 26 are arranged opposite to each other in the vicinity of the back end of the paper feed cassette 22. The feed roll 24 supplies the paper P from the paper feed cassette 22, and the retard roll 26 passes the supplied paper P one by one.

  A conveyance path 28 is formed on the paper discharge side of the feed roll 24 and the retard roll 26 and serves as a paper path to the discharge port 30. The conveyance path 28 is formed on the back side (right side in FIG. 1) of the image forming apparatus main body 12 and is formed substantially vertically from the paper feeding unit 18 to the fixing device 90. A pair of resist rolls 32 is arranged on the conveyance path 28, and a secondary transfer roll 80 and a secondary transfer backup roll 72 are arranged opposite to each other on the downstream side of the resist roll 32.

  A pair of discharge rolls 34 is disposed near the discharge port 30 of the conveyance path 28. A discharge portion 36 is provided above the opening / closing cover 16 from the discharge port 30. The discharge portion 36 is low on the discharge port 30 side, and is inclined so as to gradually increase toward the front direction (left direction in FIG. 1).

  A rotary developing device 38 is disposed substantially at the center of the image forming apparatus main body 12. The rotary developing device 38 includes developing units 42a to 42d that form toner images of four colors of yellow, yellow, magenta, cyan, and black in the developing unit main body 40, respectively. The rotary developing device center 44 rotates counterclockwise in FIG. Each of the developing units 42a to 42d includes developing rolls 46a to 46d, and is pressed in the radial direction of the developing unit main body 40 by elastic bodies 48a to 48d such as coil springs. The developing rolls 46 a to 46 d are arranged on the outer periphery of the developing device main body 40 at 90 ° intervals with the rotary developing device center 44 as the center.

  The rotary developing device 38 is arranged so that the photosensitive member 50 is in contact therewith, and the latent image on the photosensitive member 50 is caused by the developing rolls 46a to 46d sequentially facing the photosensitive member 50 by the rotation of the developing device main body 40. The toner is developed with each color toner. The photoconductor 50 is rotatable about a rotation support shaft 49, and is rotated in the clockwise direction (arrow C direction) in FIG. 1 by a drive motor (not shown). When the developing rolls 46 a to 46 d are not in contact with the photoreceptor 50, a part of the outer periphery of each of the developing rolls 46 a to 46 d protrudes 2 mm from the outer periphery of the developing device main body 40 in the radial direction. In addition, tracking rolls (not shown) are provided coaxially at both ends of each of the developing rolls 46a to 46d so as to be rotatable. The tracking roll (not shown) has a diameter slightly larger than the diameter of the developing rolls 46 a to 46 d and comes into contact with flanges (not shown) provided at both ends of the photoreceptor 50. As a result, a predetermined gap is formed between the developing rolls 46 a to 46 d and the photoreceptor 50.

  Below the photoconductor 50, a charging roll 52 as a charging device for uniformly charging the photoconductor 50 is provided. In addition, a photoreceptor cleaner 54 is held on the photoreceptor 50 so as to hang from the rotation support shaft 49, and the photoreceptor 50 and the photoreceptor cleaner 54 are integrated. The photoreceptor cleaner 54 includes a cleaning blade 56 that scrapes waste toner remaining on the photoreceptor 50 after the primary transfer, and a toner collection bottle 58 that collects waste toner scraped by the cleaning blade 56.

  The back side (the right side in FIG. 1) of the toner collection bottle 58 forms a part of the conveyance path 28, and ribs (not shown) and the like are formed, and the paper P is smoothly conveyed. It is a curved surface.

  An exposure device 60 is disposed on the lower back side of the rotary developing device 38, and the exposure device 60 writes a latent image on the photosensitive member 50 charged by the charging roll 52 with a light beam such as a laser beam. Further, an intermediate transfer device 62 is provided above the rotary developing device 38. The intermediate transfer device 62 primarily transfers a toner image visualized by the rotary developing device 38, and a secondary transfer position N described later. It is supposed to be transported up to.

  The intermediate transfer device 62 includes an intermediate transfer belt 64 as an intermediate transfer member, a primary transfer roll 66, a wrap-in roll 68, a wrap-out roll 70, a secondary transfer backup roll 72, a scraper backup roll 74, and a brush backup roll 76.

  The intermediate transfer belt 64 is an endless belt having elasticity, and is stretched in a substantially flat rectangular shape so as to have a long side and a short side above the rotary developing device 38. The long side on the upper surface side of the intermediate transfer belt 64 is stretched so as to be substantially parallel to the discharge portion 36 provided on the upper portion of the image forming apparatus main body 12.

  The intermediate transfer belt 64 includes a wrap-in roll 68 disposed on the upstream side of the primary transfer roll 66 below the long side of the intermediate transfer belt 64, and a wrap-out roll 70 disposed on the downstream side of the primary transfer roll 66. 1 is provided with a primary transfer portion (image carrier wrap region) that comes into contact with the photosensitive member 50 in a wrap-like manner, and is wound around the photosensitive member 50 by a predetermined range and is driven by the rotation of the photosensitive member 50 to counterclockwise in FIG. It rotates in the direction of arrow K.

  The intermediate transfer belt 64 is supported from the inner peripheral side by five rolls of a wrap-in roll 68, a wrap-out roll 70, a secondary transfer backup roll 72, a scraper backup roll 74, and a brush backup roll 76. The toner image on the photoconductor 50 is primary-transferred by the primary transfer roll 66 in the order of yellow, magenta, cyan, and black, and the secondary transfer is performed while holding the primary-transferred toner image. It is conveyed toward the roll 80. Note that the wrap-in roll 68 and the wrap-out roll 70 are separated from the photoconductor 50.

  On the back side (right side in FIG. 1) of the intermediate transfer belt 64, a flat portion (short side) is formed by the wrap-out roll 70 and the secondary transfer backup roll 72, and this flat portion becomes the secondary transfer portion. Then, it faces the conveyance path 28.

  Note that, in the secondary transfer portion, the wrap-out roll 70 is arranged so that the intermediate transfer belt 64 and the conveyance path 28 form an acute angle (an angle of 12 ° in the present embodiment).

  A secondary transfer roll 80 is opposed to the secondary transfer backup roll 72 of the intermediate transfer device 62 with the conveyance path 28 interposed therebetween. That is, the secondary transfer position N in the secondary transfer portion is between the secondary transfer roll 80 and the secondary transfer backup roll 72. The secondary transfer roll 80 is rotated to convey the paper P between the intermediate transfer belt 64 and the intermediate transfer belt 64 and the paper P at the same time as the secondary transfer roll 80. It is sandwiched between the secondary transfer backup roll 72. As a result, the toner image primarily transferred to the intermediate transfer belt 64 is secondarily transferred to the paper P at the secondary transfer position N.

  Here, the secondary transfer roll 80 is separated from the intermediate transfer belt 64 while the intermediate transfer belt 64 rotates three times, that is, while the toner images of three colors of yellow, magenta, and cyan are conveyed. When the image is transferred, it comes into contact with the intermediate transfer belt 64.

  Note that a predetermined potential difference is generated between the secondary transfer roll 80 and the secondary transfer backup roll 72. For example, when the secondary transfer roll 80 is set to a high voltage, the secondary transfer roll 80 The backup roll 72 is connected to the ground (GND).

  A reflective photosensor 78 is fixed to the back surface (inside) of the open / close cover 16 above the long side of the intermediate transfer belt 64. The reflective photosensor 78 reads a toner patch formed on the intermediate transfer belt 64, detects the position of the intermediate transfer belt 64 in the rotational direction, and detects the density of the toner image.

  An intermediate transfer belt cleaner 82 is disposed on the front side of the intermediate transfer belt 64 (left side in FIG. 1). The intermediate transfer belt cleaner 82 includes a scraper 84, a brush roll 86, a toner collection box 88, and a swing support shaft 89, and swings about the swing support shaft 89.

  The scraper 84 is made of a thin plate such as stainless steel, and scrapes and cleans waste toner (adhered matter) remaining on the intermediate transfer belt 64 after the secondary transfer. A voltage having a polarity opposite to that of the toner is applied to the scraper 84. The scraper backup roll 74 disposed to face the scraper 84 rotates with the intermediate transfer belt 64 interposed between the scraper 84 and the scraper 84 when the scraper 84 scrapes off the waste toner. The brush roll 86 is made of a brush made of acrylic or the like that has been subjected to conductive treatment, and further scrapes off waste toner (adhered matter) remaining after cleaning by the scraper 84. The brush backup roll 76 disposed opposite to the brush roll 86 rotates with the intermediate transfer belt 64 interposed between the brush roll 86 and the brush roll 86 when scraping off the waste toner. The scraper 84 and the brush roll 86 are separated from the intermediate transfer belt 64 while the intermediate transfer belt 64 conveys the toner image, so that they come into contact with the intermediate transfer belt 64 at a predetermined timing. It has become. The toner collection box 88 collects the toner scraped by the scraper 84 and the brush roll 86.

  The intermediate transfer device 62, the photosensitive member 50, the charging roll 52, the photosensitive member cleaner 54, and the intermediate transfer belt cleaner 82 are integrated to form a part of the image forming unit 96.

A fixing device 90 is disposed above the secondary transfer position N. The fixing device 90 includes a heating roll 92 and a pressure roll 94. The toner image secondarily transferred onto the paper P by the secondary transfer roll 80 and the secondary transfer backup roll 72 is heat-fixed on the paper P, and the discharge roll. Transport toward 34.
(Paper pressing mechanism to the intermediate transfer belt)
FIG. 2 shows a schematic configuration of a paper pressing mechanism that presses the paper P toward the intermediate transfer belt 64 on the upstream side of the secondary transfer position N between the intermediate transfer belt 64 and the secondary transfer roll 80. . As shown in FIG. 2, a paper guide member 100 is provided on the upstream side of the secondary transfer position N (near the portion where the paper P enters the secondary transfer position N).

  The paper guide member 100 presses the paper P toward the intermediate transfer belt 64, and a thin-walled (film-like) flexible member 102 is provided at a portion where the paper guide member 100 contacts the paper P. Yes. As shown in FIG. 3, the flexible member 102 has a rectangular shape in which the conveyance direction D of the sheet P is a short side and the direction perpendicular to the conveyance direction D of the sheet P is a long side. The flexible member 102 is preferably made of a material that can be processed with high accuracy and can be elastically deformed and elastically restored in accordance with the quality of the paper P. For example, a polyethylene terephthalate (PET) film ( As an example, “Mylar” (trade name of DuPont) or a polypropylene (PP) film can be used. The polyethylene terephthalate film is a thermoplastic resin obtained by an esterification reaction between dimethyl terephthalate and ethylene glycol. Here, the flexible member 102 preferably contains an antistatic agent. The antistatic agent may be kneaded in advance in the material of the flexible member 102 or may be applied to the surface of the flexible member 102. Examples of the antistatic agent include semiconductive metal oxide and carbon black.

  As shown in FIG. 2, the base side (the lower side in FIG. 2) of the flexible member 102 is fixed to the plate-like support member 104 with an adhesive. A rotation shaft 106 supported by the image forming apparatus main body 12 (see FIG. 1) is provided on one end side of the support member 104 (opposite side of the attachment end portion of the flexible member 102). The shaft 106 is supported so as to be swingable. One end of a pressing spring 108 as an urging means is attached to one side of the support member 104 (the side opposite to the side where the paper P is transported as viewed from the support member 104 (the right side in FIG. 2)). In this embodiment, the pressing spring 108 is a coil spring. The other end of the pressing spring 108 is attached to the base member 110.

  The base member 110 can be moved and adjusted in a direction (in the direction of arrow E in FIG. 2) that is in contact with and away from the back side (the right side in FIG. 2) of the conveyed paper P. In accordance with this, the paper guide is adjusted. The member 100 can be moved and adjusted in a direction (in the direction of arrow E in FIG. 2) in which the member 100 is swung together with the rotating shaft 106 and is in contact with or separated from the back side of the paper P (right side in FIG. That is, the paper guide member 100 is urged toward the intermediate transfer belt 64 by moving the base member 110 in a direction in contact with the back side of the paper P. Thus, the force with which the paper guide member 100 presses the paper P against the intermediate transfer belt 64 is adjusted by moving and adjusting the base member 110.

  As shown in FIG. 2, the image forming apparatus 10 (see FIG. 1) is provided with a control unit 111. The control unit 111 includes a pressing force adjusting unit 112, and the pressing force adjusting unit 112 is connected to the base member 110. The pressing force adjusting unit 112 moves and adjusts the base member 110 based on the setting value of the pressing force set in advance in the look-up table according to the type of the paper P and the temperature and humidity (environmental conditions), thereby adjusting the sheet guide member 100. The pressing force on the paper P is adjusted.

  An output end of the temperature / humidity sensor 114 is connected to the pressing force adjusting unit 112. The temperature / humidity sensor 114 is arranged on the upstream side (lower side in FIG. 2) in the paper transport direction from the position where the flexible member 102 and the paper P are in contact with each other, and detects the temperature and humidity at this arrangement position. Thus, temperature and humidity data are output to the pressing force adjustment unit 112. Note that the temperature / humidity sensor 114 does not have to be located in the present embodiment as long as the temperature / humidity sensor 114 is arranged near the position where the flexible member 102 and the paper P contact each other.

In addition, the output end of the paper type setting unit 116 is connected to the pressing force adjustment unit 112. The paper type setting unit 116 stores data related to the paper type selected by the user in the paper selection mode of the control panel (not shown), and outputs the data related to the paper type to the pressing force adjustment unit 112. In the paper selection mode of the present embodiment, the paper P on which an image is formed by the image forming apparatus 10 (see FIG. 1) is plain paper, recycled paper, high-quality paper, cardboard, which has different thickness and strength against bending. , OHP, envelope, or postcard can be selected.
(Operation and action of image forming apparatus)
Next, the operation and action of the image forming apparatus 10 according to the embodiment will be described.

  The photoconductor 50 shown in FIG. 1 is uniformly negatively charged by the charging roll 52, and the charged photoconductor 50 is exposed to light from the exposure device 60 to form a latent image. The latent image on the photoreceptor 50 formed by the exposure device 60 is developed sequentially with yellow, magenta, cyan, and black toner images by the rotary developing device 38, and the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 64 in sequence. Are superimposed. The intermediate transfer belt 64 conveys the toner image while holding it, and the secondary transfer roll 80 transfers the toner image on the intermediate transfer belt 64 onto the paper P.

  As shown in FIG. 2, on the upstream side of the secondary transfer position N between the intermediate transfer belt 64 and the secondary transfer roll 80, the paper guide member 100 presses the paper P against the intermediate transfer belt 64. The base member 110 shown in FIG. 2 can be moved and adjusted in a direction (in the direction of arrow E in FIG. 2) that is in contact with and away from the back side of the paper P to be transported. The guide member 100 swings. The paper guide member 100 can be moved and adjusted in a direction of moving toward and away from the back side (the right side in FIG. 2) of the conveyed paper P by swinging, so that the paper guide member 100 contacts the paper P on the paper guide member 100. Even if the portion to be worn (flexible member 102) is worn, the pressing force on the paper P can be adjusted.

  Here, the force with which the sheet guide member 100 presses the sheet P against the intermediate transfer belt 64 is determined by the pressing force adjustment unit 112 that adjusts the pressing force of the sheet guide member 100 against the sheet P at least the type or temperature / humidity (environment of the sheet P). It is adjusted by adjusting the movement of the base member 110 based on the set value of the pressing force set in advance according to the conditions. That is, the temperature / humidity data measured by the temperature / humidity sensor 114 and the data regarding the paper type in the paper type setting unit 116 are output to the pressing force adjustment unit 112, and the pressing force adjustment unit 112 receives the temperature / humidity data. Based on the paper type data, the base member 110 is moved and adjusted so that the set value of the pressing force (corresponding to the temperature and humidity and the paper type) set in advance on the lookup table is obtained.

  Specifically, for example, in the case of thick paper having a temperature of 10 ° C. or less, a relative humidity of 15% or less, and a paper type having a basis weight of 150 gsm or more, the pressing force of the paper guide member 100 on the paper P is increased. As a result, the contact distance between the sheet P and the intermediate transfer belt 64 from the portion where the sheet P is pressed against the intermediate transfer belt 64 to the secondary transfer position N can be secured above a certain level. In the case where the pressing force to the paper P by the paper guide member 100 is larger than the state shown in FIG. 2, the base member 110 is in contact with the back side of the paper P (the right side in FIG. 2). Is moved to the state shown in FIG.

  In this way, the paper guide member 100 is appropriately biased toward the intermediate transfer belt 64, so that a pressing force on the paper P can be secured. Further, since the portion of the paper guide member 100 that contacts the paper P is the thin flexible member 102, it can be deformed and restored corresponding to the paper P. Further, since the antistatic agent is contained in the flexible member 102 of the paper guide member 100, charging of the paper P due to friction between the flexible member 102 and the paper P can be prevented.

As described above, it is possible to suppress a minute gap between the sheet P and the intermediate transfer belt 64 immediately before the secondary transfer position N. As a result, it is possible to obtain a high-quality image by suppressing the influence on the image quality due to the discharge of the minute gap portion (white void etc.) and the influence on the image quality due to the sliding friction between the recording medium and the guide member (toner dust, streaks, etc.). . In particular, by changing the pressing force on the paper P according to the type and temperature / humidity (environmental conditions) of the paper P, the occurrence of charging of the recording medium due to the fine gap and sliding friction between the recording medium and the guide member can be reliably suppressed. Therefore, useless discharge and charging that adversely affect image quality can be reliably prevented.
(Second Embodiment)
Next, a second embodiment of the image forming apparatus will be described with reference to FIGS. In the first embodiment, as illustrated in FIGS. 2 to 4, the case where the thin flexible member 102 is provided in the portion of the paper guide member 100 that contacts the paper P has been described. In the second embodiment, as shown in FIGS. 5 and 6, a portion of the paper guide member 100 that contacts the paper P extends in the transport direction of the paper P (the direction of arrow D in FIG. 6). The other feature is that it is substantially the same as that of the first embodiment, and therefore, the same reference numerals are given and description thereof is omitted.

  As shown in FIGS. 5 and 6, resin ribs 118 are formed on the support member 104 on the surface facing the paper P conveyance path. As shown in FIG. 6, a plurality of ribs 118 are formed at predetermined intervals along the width direction of the support member 104 (direction perpendicular to the conveyance direction D of the paper P). The front end portion 118A of the rib 118 protrudes slightly from the front end side (the upper side in FIG. 6) of the support member 104.

As shown in FIG. 5, the paper guide member 100 is swingably supported and biased toward the intermediate transfer belt 64, so that a pressing force to the paper P can be secured and the paper P of the paper guide member 100 can be secured. Since the portions that come into contact with the plurality of resin ribs 118 extending in the conveyance direction D (see FIG. 6) of the paper P can be controlled, the conveyance direction of the paper P can be regulated with a simple configuration. As a result, the occurrence of a minute gap between the sheet P and the intermediate transfer belt 64 immediately before the secondary transfer position N is suppressed.
(Third embodiment)
Next, a third embodiment of the image forming apparatus will be described with reference to FIGS. In the third embodiment, the portion of the paper guide member 100 that contacts the paper P is a roller 120 as a small roller that rotates following the contact with the paper P being conveyed. Other configurations are substantially the same as those in the first embodiment, and thus the same reference numerals are given and description thereof is omitted.

  As shown in FIG. 8, arms 104 </ b> A and 104 </ b> A are formed on both sides of the support member 104 in the width direction (the direction perpendicular to the conveyance direction D of the paper P) and protrude toward the front end side (upper side in FIG. 8). ing. A shaft 122 is fixed to the arms 104A and 104A, and the shaft 122 has an axial direction orthogonal to the paper P transport direction (arrow D direction).

  A plurality of rollers 120 are arranged on the shaft 122 at predetermined intervals along the axial direction of the shaft 122. Each roller 120 has a substantially cylindrical shape in which a shaft hole (not shown) is formed in the shaft center portion. The inner diameter of the shaft hole of the roller 120 is slightly larger than the outer dimension of the shaft 122. Accordingly, when the shaft 122 is inserted into the shaft hole of the roller 120, the roller 120 is rotatable about the shaft 122. The roller 120 is a resin molded product in the present embodiment, but may be a metal molded product.

  Since the roller 120 is configured to follow and rotate when coming into contact with the conveyed paper P, the paper P can be smoothly conveyed. Further, since the sheet guide member 100 including the rollers 120 is supported so as to be swingable and is urged toward the intermediate transfer belt 64, a pressing force to the sheet P can be secured. 9, the pressing force of the paper guide member 100 against the paper P by moving the base member 110 in a direction in contact with the back side of the paper P (the right side of FIG. 9) than in the state shown in FIG. 7. Is in a state of increasing.

  In the first to third embodiments, the pressing force adjusting unit 112 adjusts the pressing force on the paper P by moving and adjusting the base member 110. The member 110 may be configured to move and adjust.

  In the first to third embodiments, the case where the toner image holding member is the intermediate transfer belt 64 has been described. However, the toner image holding member is a photosensitive member, and the portion between the photosensitive member and the transfer unit is used. The present invention is also applicable when guiding a sheet (recording medium) to a transfer position.

  Further, in the first to third embodiments, the case where the secondary transfer roll 80 is used as the transfer unit has been described as an example, but the present invention can also be applied to the case where a transfer discharger, a transfer belt, or the like is used as the transfer unit. .

  Furthermore, in the first to third embodiments, the paper guide member 100 is moved and adjusted in the direction in which the paper guide member 100 is moved toward and away from the back side of the paper P to be transported. The sheet guide member 100 may be moved in parallel with the back surface side of the sheet P to be adjusted and adjusted in the direction of contact.

1 is a cross-sectional view schematically showing the inside of an image forming apparatus according to an embodiment of the present invention. It is a schematic block diagram of the paper pressing mechanism which concerns on 1st Embodiment. It is a front view which shows the paper guide member which concerns on 1st Embodiment. FIG. 3 is a state diagram of a sheet pressing mechanism showing a state in which a pressing force to a sheet by a sheet guide member is larger than the state illustrated in FIG. 2. It is a schematic block diagram of the paper pressing mechanism which concerns on 2nd Embodiment. It is a front view which shows the paper guide member which concerns on 2nd Embodiment. It is a schematic block diagram of the paper pressing mechanism which concerns on 3rd Embodiment. It is a front view which shows the paper guide member which concerns on 3rd Embodiment. FIG. 8 is a state diagram of the paper pressing mechanism showing a state in which the pressing force to the paper by the paper guide member is larger than the state shown in FIG. 7.

Explanation of symbols

10 Image forming apparatus 64 Intermediate transfer belt (toner image holding member)
80 Secondary transfer roll (transfer means)
100 Paper guide member (guide member)
102 flexible member 110 base member 112 pressing force adjusting unit (pressing force adjusting means)
118 Rib 120 Roller (small roller)
N Secondary transfer position (transfer position)
P paper (recording medium)

Claims (9)

A toner image carrier that conveys the toner image while holding the toner image;
Transfer means for transferring the toner image on the toner image holding member to a recording medium;
A guide that is provided upstream of the transfer position and can be adjusted to move toward and away from the back side of the conveyed recording medium, and guides the recording medium in a direction of pressing the toner image holding body. Members,
An image forming apparatus comprising:   The guide member is swingably supported and biased toward the toner image holding member, and a portion of the guide member that contacts the recording medium is a thin flexible member. The image forming apparatus according to claim 1.   The guide member is swingably supported and biased toward the toner image holding body, and a portion of the guide member that contacts the recording medium has a plurality of resin ribs extending in the recording medium conveyance direction. The image forming apparatus according to claim 1, wherein:   The image forming apparatus according to claim 1, wherein a portion of the guide member that contacts the recording medium is a small roller that rotates following the recording medium being conveyed.   The image forming apparatus according to claim 4, wherein the guide member including the small roller is swingably supported and is urged toward the toner image holding body. A base member that is attached to the guide member and has a base member that can be moved and adjusted in a direction of moving toward and away from the back side of the recording medium to be conveyed;
2. The force by which the guide member presses the recording medium toward the toner image holding member is adjusted by moving and adjusting the base member according to at least the type of the recording medium or environmental conditions. 6. The image forming apparatus according to any one of items 1 to 5.   The image forming apparatus according to claim 6, wherein the base member can be manually moved and adjusted. A pressing force adjusting means for adjusting the pressing force of the guide member against the recording medium by adjusting the movement of the base member;
7. The pressing force adjusting means adjusts the pressing force by moving and adjusting the base member based on a preset value at least according to the type or environmental condition of the recording medium. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the guide member contains an antistatic agent.

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