JP2005215488A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of restraining the swelling or the like of a recording medium, in the process of transporting in each part, and to provide a process cartridge. <P>SOLUTION: A guide part 61 for guiding paper 3 to a space between a photoreceptor drum 21 and a transfer roller 26 is provided with a pair of guide rollers 60 and 60. The pair of guide rollers 60 and 60 are constituted of a plurality of unit rollers 62 arranged in a line in a width direction, and the plurality of unit rollers 62 are arranged over nearly the entire length of the transfer roller 26. Each unit roller 62 is paired with a unit roller 62, arranged at a position symmetric with respect to the central position X of the transport path of the paper 3, and the paired unit rollers 62 and 62 are arranged, in a state where their rotation shafts 63 are inclined symmetrically in the width direction so as to come close to each other as the rotation shafts approach the downstream side, from an upstream side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus and a process cartridge thereof.

For example, in Patent Document 1 below, in an image forming apparatus, a guide unit for guiding a sheet as a recording medium between a photosensitive drum and a transfer roller is rotated around a rotation axis orthogonal to the sheet conveyance direction. A technique in which a moving guide roller is provided is disclosed. According to this configuration, the sheet can be guided between the photosensitive drum and the transfer roller by being guided straight along the conveyance direction by the guide roller.
JP 2002-72711 A

  By the way, since the paper to be conveyed is given tension in the conveyance direction, waviness and wrinkles in the width direction may occur in the conveyance process. In the technique of the above-mentioned reference 1, the guide roller simply guides the paper straight in the direction along the transport direction, and therefore the paper is sent between the photosensitive drum and the transfer roller while the waviness in the width direction is generated. There was a problem of causing a defect (transfer residual ghost). Such swells occur in the same way, for example, in the conveyance process to the fixing device and in the process of placing the conveyance belt mechanism on the belt, which may affect the quality of image formation.

  The present invention has been completed based on the above-described circumstances, and an object thereof is to provide an image forming apparatus and a process cartridge capable of suppressing the undulation of a recording medium in the conveying process of each unit.

As means for achieving the above object, the invention of claim 1 is directed to an image carrier that carries a visible image formed by developing an electrostatic latent image with a developer, and the image carrier. A transfer roller for transferring a visible image, which is arranged oppositely and carried on the image carrier, to the recording medium, and guides the conveyed recording medium between the image carrier and the transfer roller. In the image forming apparatus including the guide unit for the above, a tension applying unit that applies tension to the recording unit from the center to both ends in the width direction perpendicular to the conveyance direction of the recording medium. It is provided.
The “image carrier” of the present invention includes not only a photosensitive drum but also an intermediate transfer member.

  According to a second aspect of the present invention, there is provided a heating roller for fixing, a pressing roller disposed opposite to the heating roller and pressed against the heating roller, and a recording medium conveyed in a state where a visible image is transferred. In the image forming apparatus including a guide portion for guiding between the heating roller and the pressure roller, the guide portion may be moved from the center in the width direction orthogonal to the recording medium conveyance direction with respect to the recording medium. Tension applying means for applying tension toward both ends is provided.

  According to a third aspect of the present invention, there is provided a conveying belt mechanism for conveying the placed recording medium to an image forming position for forming a visible image on the recording medium, and the recording medium on a belt of the conveying belt mechanism. In the image forming apparatus including the guide unit for guiding the tension to the guide unit, tension is applied to the guide unit from the center toward both ends in the width direction perpendicular to the recording medium conveyance direction. The provision means is provided.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the guide portion is provided only on one side of the recording medium, and the tension applying means is provided on the recording medium. It is the structure which contacts the said single side | surface.

  According to a fifth aspect of the present invention, in the first aspect, the guide portion is provided only on one side of the recording medium, and the tension applying unit is in contact with the one side of the recording medium. On the other hand, a pair of conveying rollers that convey the recording medium at a speed equal to or lower than the passing speed of the recording medium that passes between the image carrier and the transfer roller on the upstream side in the conveying direction with respect to the guide unit. It is provided.

  According to a sixth aspect of the present invention, in the second aspect, the guide portion is provided only on one side of the recording medium, and the tension applying unit is in contact with the one side of the recording medium. On the other hand, at a speed equal to or lower than the passing speed of the recording medium passing between the heating roller and the pressing roller with the recording medium sandwiched from both sides upstream of the guide portion in the transport direction. A conveyance roller pair for conveying the recording medium is provided.

  According to a seventh aspect of the present invention, in the first aspect, the guide portion is provided only on one side of the recording medium, and the tension applying unit is in contact with the one side of the recording medium. On the other hand, on the upstream side in the transport direction with respect to the guide portion, a pair of transport rollers for transporting the recording medium with the recording medium sandwiched from both sides is provided, and the tension applying means is in contact with the pair of transport rollers. It is arranged at a position protruding from the plane including the position and the contact position of the image carrier and the transfer roller in a direction opposite to the one surface.

  According to an eighth aspect of the present invention, in the second aspect, the guide portion is provided only on one side of the recording medium, and the tension applying unit is in contact with the one side of the recording medium. On the other hand, on the upstream side in the transport direction with respect to the guide portion, a pair of transport rollers for transporting the recording medium with the recording medium sandwiched from both sides is provided, and the tension applying means is in contact with the pair of transport rollers. It is arrange | positioned in the position which protruded in the opposing direction with the said single side | surface from the plane containing a position and the contact position of the said heating roller and the said press roller.

  The invention according to a ninth aspect is the invention according to any one of the first to eighth aspects, wherein the tension applying means are arranged symmetrically across the center in the width direction, and each outer peripheral surface is The guide roller pair is configured so as to be able to contact the recording medium, and the guide roller pair is configured so that the rotation shafts of the guide roller approach each other from the upstream side to the downstream side in the transport direction. It is arranged to be inclined with respect to the width direction.

  According to a tenth aspect of the present invention, in the ninth aspect, the guide roller pair includes a plurality of unit rollers that contact different locations in the width direction with respect to the recording medium. And

  According to an eleventh aspect of the present invention, in the method according to any one of the first to eighth aspects, the tension applying means is arranged symmetrically with respect to the center in the width direction and is parallel to the width direction. The worm roller pair is configured to have a worm roller pair that rotates about an axis and has a thread groove formed on an outer peripheral surface that contacts the recording medium. Inclined with respect to the transport direction so as to be separated from the upstream side toward the downstream side.

  According to a twelfth aspect of the present invention, there is provided an image forming apparatus including a transport path for transporting a recording medium and a transport mechanism for transporting the recording medium along the transport path. On the other hand, there is provided a tension applying means that contacts only from one side of the recording medium and applies a tension from the center to both ends in the width direction orthogonal to the conveyance direction of the recording medium, and the tension applying means has a center in the width direction. A plurality of unit rollers which are arranged symmetrically with respect to each other and whose outer peripheral surfaces are provided so as to be able to come into contact with each other at different positions in the width direction with respect to the recording medium. Is configured such that the rotation shafts of each other are inclined with respect to the width direction so as to approach from the upstream side to the downstream side in the transport direction. And wherein the door.

  According to a thirteenth aspect of the present invention, there is provided an image forming apparatus including a conveyance path for conveying a recording medium and a conveyance mechanism for conveying the recording medium along the conveyance path. On the other hand, there is provided tension applying means that contacts only from one side of the recording medium and applies tension from the center toward both ends in the width direction orthogonal to the conveyance direction of the recording medium. It is configured to include a pair of worm rollers that are arranged symmetrically with respect to each other, rotate around a rotation axis that is parallel to the width direction, and have a thread groove formed on an outer peripheral surface that contacts the recording medium, and The pair of worm rollers is inclined with respect to the transport direction so that the screw grooves are separated from the upstream side in the transport direction toward the downstream side.

  According to a fourteenth aspect of the present invention, in the twelfth or thirteenth aspect of the present invention, the transport path has a curved path with respect to the transport direction, and is provided on the inner peripheral side of the curved path. The guide portion is provided with the tension applying means.

  A fifteenth aspect of the present invention is the recording medium according to any one of the twelfth to fourteenth aspects, wherein the conveyance mechanism is disposed on the upstream side and the downstream side in the conveyance direction with respect to the tension applying unit, respectively. A conveyance roller pair that conveys the medium sandwiched from both sides is provided, and the upstream conveyance roller conveys the recording medium at a speed equal to or higher than the conveyance speed of the downstream conveyance roller pair. .

  According to a sixteenth aspect of the present invention, in the recording medium according to any one of the twelfth to fourteenth aspects, the transport mechanism is disposed upstream and downstream in the transport direction with respect to the tension applying unit, and the recording is performed. A pair of conveying roller pairs that convey the medium from both sides, and the tension applying unit includes a contact position of the upstream conveying roller pair and a contact position of the downstream conveying roller pair. From the above, it is arranged at a position protruding in the direction opposite to the one side.

  According to a seventeenth aspect of the present invention, in the apparatus according to the tenth or twelfth aspect, the plurality of unit rollers are linearly arranged along the width direction.

  According to an eighteenth aspect of the present invention, an image carrier that is detachably attached to the image forming apparatus main body and carries a visible image formed by developing an electrostatic latent image with a developer, and the image carrier. A transfer roller for transferring a visible image, which is arranged oppositely and carried on the image carrier, to the recording medium, and guides the conveyed recording medium between the image carrier and the transfer roller. In the process cartridge having a guide portion for providing a tension to the guide portion, tension is applied to the guide portion to apply tension to the recording medium from the center toward both ends in the width direction perpendicular to the recording medium conveyance direction. It is characterized by that.

  According to a nineteenth aspect of the present invention, in the configuration according to the eighteenth aspect, the guide portion is provided only on one side with respect to the recording medium, and the tension applying means is in contact with the one side of the recording medium. It is characterized by becoming.

  According to a twentieth aspect of the invention, in the invention according to the eighteenth aspect, the guide portion is provided only on one side with respect to the recording medium, and the tension applying unit is in contact with the one side of the recording medium. On the other hand, the image carrier and the transfer roller are provided on the upstream side of the guide portion of the image forming apparatus main body in the transport direction and at a speed equal to or higher than the transport speed of a pair of transport rollers that transport the recording medium. The recording medium is allowed to pass through.

  According to a twenty-first aspect of the invention, in the eighteenth aspect, the guide portion is provided only on one side with respect to the recording medium, and the tension applying means is in contact with the one side of the recording medium. On the other hand, the tension applying means is provided on the upstream side in the transport direction with respect to the guide portion of the image forming apparatus main body, and a contact position of a transport roller pair that transports the recording medium from both sides, and the image. It is characterized by being arranged at a position protruding in a direction opposite to the one surface from a plane including the contact position of the carrier and the transfer roller.

  According to a twenty-second aspect of the present invention, in the method according to any one of the eighteenth to twenty-first aspects, the tension applying means is disposed symmetrically across the center in the width direction, and each outer peripheral surface is The guide roller pair is configured so as to be able to contact the recording medium, and the guide roller pair is configured so that the rotation shafts of the guide roller approach each other from the upstream side to the downstream side in the transport direction. It is arranged to be inclined with respect to the width direction.

  According to a twenty-third aspect of the present invention, in the twenty-second aspect, each of the pair of guide rollers includes a plurality of pairs of unit rollers that contact different locations in the width direction with respect to the recording medium. It is characterized by that.

  According to a twenty-fourth aspect of the invention, there is provided the rotating mechanism according to any one of the eighteenth to twenty-first aspects, wherein the tension applying means is arranged symmetrically with respect to the center of the width direction and is parallel to the width direction. The worm roller pair is configured to have a worm roller pair that rotates about an axis and has a thread groove formed on an outer peripheral surface that contacts the recording medium. Inclined with respect to the transport direction so as to be separated from the upstream side toward the downstream side.

<Invention of Claims 1 and 18>
According to this configuration, the recording medium is guided between the image carrier and the transfer roller while being pulled from the center in the width direction to both ends by the tension applying unit. Therefore, the transfer process can be performed on the recording medium in a state in which the waviness and wrinkles in the width direction are suppressed, thereby improving the quality of image formation.

<Invention of Claim 2>
According to this configuration, the recording medium is guided between the heating roller and the pressing roller for fixing in a state where the recording medium is pulled from the center in the width direction to both ends by the tension applying unit. Accordingly, the fixing process can be performed on the recording medium in a state in which the waviness and wrinkles in the width direction are suppressed, thereby improving the quality of image formation.

<Invention of Claim 3>
According to this configuration, the recording medium is placed on the belt (for example, the tandem belt of the tandem image forming apparatus) of the conveyance belt mechanism in a state where the recording medium is pulled from the center in the width direction to both ends by the tension applying unit. . Accordingly, it is possible to transport the recording medium to the image forming position while suppressing the waviness and wrinkles in the width direction, thereby improving the quality of image formation.

<Invention of Claims 4 and 19>
According to this configuration, the tension applying unit is configured to apply tension by contacting only one side of the recording medium, and the apparatus can be reduced in size as compared with a configuration contacting from both sides of the recording medium.

<Invention of Claims 5 and 20>
According to this configuration, the tension applying unit is configured to apply the tension by contacting only one surface of the recording medium, and the image bearing member and the tension are provided by the transport roller provided on the upstream side of the guide unit in the transport direction. The recording medium is conveyed at a speed equal to or lower than the recording medium passing speed by the transfer roller. Thereby, the recording medium nipped by the image carrier, the transfer roller, and the conveying roller pair is pulled along the conveying direction, and the contact pressure between one side of the recording medium and the tension applying unit can be increased to some extent. The tension in the width direction by the tension applying means can be increased.

<Invention of Claim 6>
According to this configuration, the tension applying unit is configured to apply tension by contacting only one surface of the recording medium, and the heating roller and the pressing force are provided by the transport roller provided on the upstream side in the transport direction with respect to the guide unit. The recording medium is conveyed at a speed equal to or lower than the recording medium passing speed by the roller.
Accordingly, the recording medium nipped by the heating roller, the pressing roller, and the conveying roller pair is pulled along the conveying direction, and the contact pressure between one surface of the recording medium and the tension applying unit can be increased to some extent. Accordingly, the tension in the width direction by the tension applying means is increased, and the waviness in the width direction of the recording medium can be more reliably suppressed.

<Invention of Claims 7 and 21>
According to this configuration, the tension applying unit applies the tension by contacting only one side of the recording medium, and sandwiches the recording medium from both sides upstream of the guide unit in the transport direction. A pair of conveyance rollers for conveying the recording medium is provided, and the tension applying unit determines a contact position of the conveyance roller pair provided on the upstream side in the conveyance direction with respect to the guide portion and a contact position of the image carrier and the transfer roller. It arrange | positions in the position which protruded in the opposing direction with one side from the plane to include.
As a result, the recording medium nipped by the image carrier, the transfer roller, and the conveying roller pair is conveyed in a bent state via the tension applying unit, and the contact pressure between one side of the recording medium and the tension applying unit is reduced. It can be raised to some extent. Therefore, the tension in the width direction by the tension applying means can be increased, and the waviness in the width direction of the recording medium can be more reliably suppressed.

<Invention of Claim 8>
According to this configuration, the tension applying unit applies the tension by contacting only one side of the recording medium, and sandwiches the recording medium from both sides upstream of the guide unit in the transport direction. A pair of conveyance rollers for conveying the recording medium is provided, and the tension applying unit includes a contact position of the conveyance roller pair provided on the upstream side in the conveyance direction with respect to the guide portion, and a contact position of the heating roller and the pressing roller. It arrange | positions in the position which protruded from the plane in the opposing direction with one side.
Thus, the recording medium nipped by the heating roller, the pressing roller, and the conveying roller pair is conveyed in a bent state via the tension applying unit, and the contact pressure between one side of the recording medium and the tension applying unit is increased to some extent. Can be high. Therefore, the tension in the width direction by the tension applying means can be increased, and the waviness in the width direction of the recording medium can be more reliably suppressed.

<Invention of Claim 9 and Claim 22>
According to this configuration, the guide roller pair is provided that is arranged symmetrically with respect to the center in the width direction and whose outer peripheral surfaces are provided so as to be able to contact the recording medium. The pair of guide rollers is arranged so as to be inclined with respect to the width direction so that the rotation shafts of the guide roller pair approach each other from the upstream side to the downstream side in the transport direction. That is, the conveyed recording medium receives a tension from the center toward both ends at the contact position with the rotating guide roller pair, thereby suppressing the waviness in the width direction. In addition, since the recording medium can be stably moved straight along the conveyance direction by the rotation of the guide roller pair, more stable conveyance can be performed.

<Invention of Claims 10 and 23>
For example, when a pair of guide rollers having a certain width is used, the contact state between the outer peripheral surface of each guide roller and the recording medium may be uneven. In addition, since the contact positions of the both ends of the guide rollers and the recording medium are greatly shifted in the conveying direction, the recording medium may not be conveyed in a balanced manner.
Therefore, in this configuration, each of the guide roller pairs is a plurality of unit rollers that are in contact with different positions in the width direction with respect to the recording medium, so that more stable conveyance can be performed.

<Invention of Claims 11 and 24>
According to this configuration, the tension applying unit rotates about the rotation axis that is symmetrically disposed across the center in the width direction and is parallel to the width direction, and the thread groove is formed on the outer peripheral surface that contacts the recording medium. This is realized by a pair of worm rollers formed. The pair of worm rollers is inclined with respect to the transport direction so that the screw grooves are separated from the upstream side in the transport direction toward the downstream side. Therefore, the recording medium is guided by receiving a tension from the center toward both ends by the pair of worm rollers.
With such a configuration, it is possible to obtain the same effect as the configuration of the above-described claim 10 and reduce the number of parts with only one pair of worm rollers without providing a plurality of unit rollers.
It was.

<Invention of Claim 12>
According to this configuration, the tension applying unit is configured to apply tension by contacting only one side of the recording medium, and the apparatus can be reduced in size as compared with a configuration contacting from both sides of the recording medium.
The tension applying means is a plurality of unit rollers which are arranged symmetrically with respect to the center in the width direction, and each outer peripheral surface is provided so as to be able to contact different positions in the width direction with respect to the recording medium. It is configured. The paired unit rollers are arranged so as to be inclined with respect to the width direction so that their rotation axes approach each other from the upstream side to the downstream side in the transport direction. As a result, the conveyed recording medium receives a tension from the center toward both ends at the contact position with the plurality of rotating unit rollers, thereby suppressing waviness in the width direction and the like. Moreover, since the recording medium can be stably moved straight along the transport direction by the rotation of the paired unit rollers, more stable transport can be performed.

<Invention of Claim 13>
According to this configuration, the tension applying unit is configured to apply tension by contacting only one side of the recording medium, and the apparatus can be reduced in size as compared with a configuration contacting from both sides of the recording medium.
Further, the tension applying means is a worm that is symmetrically arranged with respect to the center in the width direction and rotates around a rotation axis that is parallel to the width direction and in which a thread groove is formed on the outer peripheral surface in contact with the recording medium. Realized by a pair of rollers. The pair of worm rollers is inclined with respect to the transport direction so that the screw grooves are separated from the upstream side in the transport direction toward the downstream side. Therefore, the recording medium is guided by receiving a tension from the center toward both ends by the pair of worm rollers.
With such a configuration, it is possible to obtain the same effect as the configuration of the above-described claim 12 with only one pair of worm rollers without providing a plurality of unit rollers, and it is possible to reduce the number of parts.

<Invention of Claim 14>
When there is a configuration in which the recording medium passes through the curved conveyance path, the frictional resistance between the inner peripheral surface of the curved path and the recording medium is larger than the flat path, and a stronger force is resisted against this. Thus, the recording medium is pulled and conveyed. In other words, it is considered that the curved path is more likely to swell in the width direction of the recording medium than the flat path.
Therefore, according to the present configuration, the tension applying means is provided on the inner peripheral side of the curved transport path so as to transport the recording medium while suppressing waviness in the width direction of the recording medium.

<Invention of Claim 15>
According to this configuration, the tension applying unit is disposed on the upstream side and the downstream side in the transport direction with respect to the tension applying unit, has the transport roller pair that transports the recording medium from both sides, and has the downstream side. The conveyance roller pair upstream of the conveyance roller pair conveys the recording medium at a higher speed. As a result, the recording medium nipped by both the upstream and downstream conveying roller pairs is pulled along the conveying direction, and the contact pressure between one side of the recording medium and the tension applying means can be increased to some extent, and tension is applied. The tension in the width direction by the means can be increased.

<Invention of Claim 16>
According to this configuration, the tension applying unit is arranged at a position protruding in a direction facing the one surface from a plane including the contact position of the upstream conveyance roller pair and the contact position of the downstream conveyance roller pair. Yes.
Thereby, the recording medium nipped by both the upstream and downstream conveying roller pairs is conveyed in a bent state via the tension applying means, and the contact pressure between one side of the recording medium and the tension applying means is increased to some extent. can do. Therefore, the tension in the width direction by the tension applying means can be increased, and the waviness in the width direction of the recording medium can be more reliably suppressed.

<Invention of Claim 17>
According to this configuration, the plurality of unit rollers are arranged linearly along the width direction. Therefore, the recording medium receives tension from each unit roller at the same position in the transport direction, and can perform more stable transport.

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS.
1. Configuration of the Present Embodiment FIG. 1 is a side sectional view of an essential part showing an embodiment of a laser printer as an image forming apparatus of the present invention. In FIG. 1, a laser printer 1 includes a feeder unit 4 for feeding a sheet 3 as a recording medium in a main body casing 2 and an image forming unit for forming a predetermined image on the fed sheet 3. 5 etc.

(1) Configuration of Feeder Unit The feeder unit 4 includes a paper feed tray 43 that is detachably attached to the bottom of the main body casing 2, a paper pressing plate 6 provided in the paper feed tray 43, and a paper feed tray. 43, a sheet feeding roller 7 and a sheet feeding pad 8 provided above one end of the sheet 43, a sheet conveying roller 59 provided downstream of the sheet feeding roller 7 in the sheet conveying direction, and the sheet conveying roller 59 And a registration roller 9 as a pair of conveyance rollers according to the present invention provided on the downstream side in the conveyance direction of the sheet 3.

  The sheet pressing plate 6 can stack the sheets 3 in a stacked manner, and is supported so that the end far from the sheet feeding roller 7 can swing, and the near end rotates in the vertical direction. It is made possible and is urged upward by a spring (not shown) from the back side. Therefore, the sheet pressing plate 6 is rotated downward against the urging force of the spring with the end portion far from the sheet feeding roller 7 as a fulcrum as the amount of stacked sheets 3 increases. The paper feed roller 7 and the paper feed pad 8 are disposed to face each other, and the paper feed pad 8 is pressed toward the paper feed roller 7 by a spring 10 disposed on the back side of the paper feed pad 8. .

  The uppermost sheet 3 on the sheet pressing plate 6 is pressed toward the sheet feeding roller 7 by a spring (not shown) from the back side of the sheet pressing plate 6, and the sheet feeding roller 7 and the sheet feeding are rotated by the rotation of the sheet feeding roller 7. After being sandwiched between the pads 8, the sheets are fed one by one. The fed paper 3 is sent to the registration roller 9 by the transport roller 59. The registration roller 9 is composed of two rollers, a driving roller 44 provided on the main body casing 2 side and a driven roller 45 provided on the process unit 12 side, which will be described later, and the sheet 3 sent from the conveying roller 59. Between the driving roller 44 and the driven roller 45, and sent to the image forming unit 5 after a predetermined registration.

  The feeder unit 4 further includes a manual feed tray 57 and a paper feed roller 58 for feeding the paper 3 stacked on the manual feed tray 57, and is stacked on the manual feed tray 57. The paper 3 to be fed can be sent to the transport roller 59 by the paper feed roller 58.

(2) Configuration of Image Forming Unit The image forming unit 5 includes a scanner unit 11, a process unit 12 as a process cartridge as defined in claim 18, a fixing unit 13, and the like.

(A) Configuration of Scanner Unit The scanner unit 11 is provided in the upper part in the main body casing 2, and includes a laser light emitting unit (not shown), a polygon mirror 14 that is driven to rotate, lenses 15 and 16, and reflecting mirrors 17 and 18. , 19, and the like, and a polygon beam 14, a lens 15, reflecting mirrors 17 and 18, a lens 16, and a reflecting mirror 19, as indicated by a chain line, a laser beam based on predetermined image data emitted from the laser emitting section. Are passed or reflected in this order to irradiate the surface of the photosensitive drum 21 of the process unit 12 described later by high-speed scanning.

(B) Configuration of Process Unit Next, the process unit 12 will be described with reference to FIG.
FIG. 2 is an enlarged side sectional view showing the process unit 12. In the figure, a process unit 12 is disposed below the scanner unit 11 and is detachably mounted on the main body casing 2, and a photosensitive drum 21, a developing cartridge 36, and a scorotron charger 25. , A transfer roller 26, a pair of guide rollers 60, 60, and the like. The developing cartridge 36 is detachably attached to the drum cartridge 20 and includes a developing roller 22, a layer thickness regulating blade 23, a supply roller 24, a toner box 27, and the like.

  The toner box 27 is filled with a positively charged non-magnetic one-component toner as a developer. Examples of the toner include polymerizable monomers such as styrene monomers such as styrene, and acrylic monomers such as acrylic acid, alkyl (C1 to C4) acrylate, and alkyl (C1 to C4) methacrylate. Polymerized toners obtained by copolymerization by a known polymerization method such as suspension polymerization are used. Such a polymerized toner is spherical and has very good fluidity. Such a toner is blended with a colorant such as carbon black, wax, and the like, and an additive such as silica is added to improve fluidity. The particle diameter is about 6 to 10 μm.

  The toner in the toner box 27 is agitated by an agitator 29 supported by a rotating shaft 28 provided at the center of the toner box 27 and discharged from a toner supply port 30 opened at a side portion of the toner box 27. . Note that a toner remaining amount detection window 40 is provided on the side wall of the toner box 27 and is cleaned by a cleaner 39 supported by the rotary shaft 28.

  A supply roller 24 is disposed at a side position of the toner supply port 30 so as to be rotatable in the direction of the arrow (counterclockwise), and the developing roller 22 faces the supply roller 24 in the direction of the arrow ( It is arranged to be rotatable counterclockwise. The supply roller 24 and the developing roller 22 are in contact with each other in a state where each of them is compressed to some extent.

  The supply roller 24 has a metal roller shaft covered with a roller made of a conductive foam material. The developing roller 22 has a metal roller shaft covered with a roller made of a conductive rubber material. More specifically, the roller portion of the developing roller 22 has a urethane rubber or silicone rubber coating layer containing fluorine on the surface of a roller body made of conductive urethane rubber or silicone rubber containing carbon fine particles. It is covered. A predetermined developing bias is applied to the developing roller 22 with respect to the photosensitive drum 21.

  In addition, a layer thickness regulating blade 23 is disposed in the vicinity of the developing roller 22. This layer thickness regulating blade 23 includes a blade main body 37 made of a metal leaf spring material, and a pressing portion 38 having a semicircular cross section made of insulating silicone rubber provided at the tip of the blade main body 37. The end of the blade body 37 opposite to the pressing portion 38 is supported by the developing cartridge 36 near the developing roller 22, and the pressing portion 38 is pressed against the developing roller 22 by the elastic force of the blade body 37. It is configured as follows.

  The toner discharged from the toner supply port 30 is supplied to the developing roller 22 by the rotation of the supplying roller 24. At this time, the toner is positively frictionally charged between the supplying roller 24 and the developing roller 22, and further developed. As the developing roller 22 rotates, the toner supplied onto the roller 22 enters between the pressing portion 38 of the layer thickness regulating blade 23 and the developing roller 22, where the toner is more sufficiently frictionally charged and constant. It is carried on the developing roller 22 as a thin layer.

  The photosensitive drum 21 is disposed at a side position of the developing roller 22 so as to be rotatable in the arrow direction (clockwise) in a state of facing the developing roller 22 with a predetermined interval. The photosensitive drum 21 is formed of a positively chargeable photosensitive layer having a drum body grounded and a surface portion made of polycarbonate or the like.

  The scorotron charger 25 is disposed above the photosensitive drum 21 at a predetermined interval so as not to contact the photosensitive drum 21. The scorotron charger 25 is a positively charged scorotron charger that generates corona discharge from a charging wire such as tungsten, and is configured to uniformly charge the surface of the photosensitive drum 21 to a positive polarity. ing.

  The surface of the photosensitive drum 21 is uniformly positively charged by the scorotron charger 25 and then exposed by high-speed scanning of the laser beam from the scanner unit 11 to form an electrostatic latent image based on predetermined image data. Is done. Next, the electrostatic latent image formed on the surface of the photosensitive drum 21 when the positively charged toner carried on the developing roller 22 comes into contact with the photosensitive drum 21 by the rotation of the developing roller 22. That is, the surface of the photosensitive drum 21 that is uniformly positively charged is supplied to a portion of the photosensitive drum 21 that is exposed to a laser beam and the potential of which is lowered, and is selectively carried to be visualized. Development is achieved.

  The transfer roller 26 is disposed below the photosensitive drum 21 so as to face the photosensitive drum 21, and is supported by the drum cartridge 20 so as to be rotatable in the arrow direction (counterclockwise direction). In the transfer roller 26, a metal roller shaft is covered with a roller made of a conductive rubber material, and a predetermined transfer bias is applied to the photosensitive drum 21. Therefore, the visible image carried on the photosensitive drum 21 is transferred to the sheet 3 while the sheet 3 passes between the photosensitive drum 21 and the transfer roller 26.

(C) Configuration of Fixing Unit As shown in FIG. 1, the fixing unit 13 is disposed on the downstream side of the process unit 12, and includes a heating roller 32, a pressing roller 31 pressed against the heating roller 32, and these heating units. A pair of conveying rollers 33 and guide roller pairs 70 and 70 provided on the downstream side of the roller 32 and the pressing roller 31 are provided. The heating roller 32 is made of a metal and has a halogen lamp for heating, and the toner transferred onto the paper 3 in the process unit 12 is passed while the paper 3 passes between the heating roller 32 and the pressing roller 31. Then, the sheet 3 is transported to the paper discharge path 56 by the transport roller 33. The paper 3 sent to the paper discharge path 56 is sent to a paper discharge roller 34 described later, and is discharged onto the paper discharge tray 35 by the paper discharge roller 34.

  In the laser printer 1, the toner remaining on the photosensitive drum 21 after being transferred onto the sheet 3 by the transfer roller 26 is recovered by the developing roller 22, and the residual toner is recovered by a so-called cleanerless system. . If the toner remaining on the photosensitive drum 21 is collected by such a cleaner-less method, there is no need to provide a cleaning device such as a blade or a waste toner storage unit, so that the configuration of the device is simplified, the size is reduced, and the cost is reduced. Can be achieved.

(3) Configuration of Double-Sided Image Forming Unit The laser printer 1 is provided with a reverse conveying unit 52 as a double-sided image forming unit in order to form images on both sides of the paper 3. The reverse conveyance unit 52 includes a paper discharge roller 34, a reverse conveyance path 53, a flapper 54, and a belt conveyor 55.

  The paper discharge roller 34 includes a pair of rollers and is configured to be able to switch between forward rotation and reverse rotation. As described above, the paper discharge roller 34 rotates in the forward direction when the paper 3 is discharged onto the paper discharge tray 35, but rotates in the reverse direction when the paper 3 is reversed. The reverse conveyance path 53 is provided along the vertical direction so that the paper 3 can be conveyed from the paper discharge roller 34 to the belt conveyor 55 disposed below the image forming unit 5. The end portion is disposed near the paper discharge roller 34, and the downstream end portion thereof is disposed near the belt conveyor 55.

  The flapper 54 is swingably provided so as to face a branch portion between the paper discharge path 56 and the reverse conveyance path 53, and the paper is reversed by the paper discharge roller 34 by excitation or non-excitation of a solenoid (not shown). 3 is configured to be able to be switched from the direction toward the paper discharge path 56 to the direction toward the reverse conveyance path 53. The belt conveyor 55 is located above the paper feed tray 43, and its upstream end is disposed near the rear end of the reverse conveyance path 53, and its downstream end is below the registration roller 9. It is provided in the substantially horizontal direction so that it may be arrange | positioned.

  When images are formed on both sides of the paper 3, the reverse conveyance unit 52 is operated as follows. That is, when the sheet 3 having an image formed on one side is sent from the sheet discharge path 56 to the sheet discharge roller 34 by the transport roller 33, the sheet discharge roller 34 rotates forward with the sheet 3 interposed therebetween. Then, the paper 3 is once transported toward the outside (the discharge tray 35 side), and when the majority of the paper 3 is sent to the outside and the rear end of the paper 3 is sandwiched between the paper discharge rollers 34, the paper 3 rotates forward. To stop. Next, the paper discharge roller 34 rotates in the reverse direction, and the flapper 54 switches the transport direction so that the paper 3 is transported to the reverse transport path 53, and the reverse transport path 53 in the reverse direction of the paper 3. To be transported. When the conveyance of the paper 3 is completed, the flapper 54 is switched to the original state, that is, the state in which the paper 3 sent from the conveyance roller 33 is sent to the paper discharge roller 34. Next, the sheet 3 conveyed in the reverse direction to the reversal conveyance path 53 is conveyed to the belt conveyor 55, reversed from the belt conveyor 55 in the upward direction, and sent to the registration rollers 9. The paper 3 conveyed to the registration roller 9 is turned over and sent again to the image forming unit 5 after a predetermined registration, whereby a predetermined image is formed on both sides of the paper 3.

(4) Configuration of Guide Roller Pair in Process Unit In this laser printer 1, in the process unit 12, the sheet 3 is placed between the photosensitive drum 21 and the transfer roller 26 on the upstream side in the conveyance direction of the sheet 3 with respect to the transfer roller 26. A guide portion 61 is provided for guiding the vehicle. The guide portion 61 has a guide surface 61a that is inclined so that its upper surface approaches the photosensitive drum 21 side from the upstream side toward the downstream side, and the uppermost end (most photosensitive drum) of the guide surface 61a. 21 is provided with guide roller pairs 60, 60 (these guide roller pairs 60, 60 are non-driven rollers that are not driven by a motor or the like).

Next, a specific configuration of the guide roller pair 60, 60 will be described with reference to FIG. In FIG. 3, the upper side of the drawing is the downstream side in the conveyance direction of the paper 3, and the lower side of the drawing is the upstream side.
The guide roller pair 60, 60 is composed of a plurality of unit rollers 62 arranged in a line in a direction orthogonal to the conveyance direction of the sheet 3 (hereinafter referred to as “width direction”). The plurality of unit rollers 62 are arranged over almost the entire length of the transfer roller 26. Each unit roller 62 has a rotating shaft 63 and a disk member 64 formed by integral molding of resin. Each unit roller 62 is paired with a unit roller 62 disposed at a symmetrical position with respect to the center position X of the conveyance path of the sheet 3 (that is, the center position in the width direction of the photosensitive drum 21).

The paired unit rollers 62, 62 are arranged in a state of being symmetrically inclined with respect to the width direction so that the rotation shafts 63 approach each other from the upstream side toward the downstream side. . In other words, each unit roller 62 disposed on one end side in the width direction from the center position X (the right side in FIG. 3) has the rotation shaft 63 on the center position X side from the end portion on the one end side. Are arranged so as to be inclined so that their end portions are located on the downstream side in the transport direction. On the other hand, each unit roller 62 arranged on the other end side in the width direction from the center position X (the left side in FIG. 3) has the rotation shaft 63 on the center position X side from the end on the other end side. Are arranged so as to be inclined so that their end portions are located on the downstream side in the transport direction.
In this embodiment, a central unit roller 65 in which the rotation shaft 63 is arranged in parallel to the width direction is provided at the central position X.

In the present embodiment, as shown in FIG. 4, the guide roller pair 60, 60 has a line segment L at which the contact position 47 in contact with the sheet 3 connects the center of the photosensitive drum 21 and the center of the transfer roller 26. And the circumference of the photosensitive drum 21 and the tangent line T of the photosensitive drum 21 drawn from the intersection P (the tangent line at the nip portion between the photosensitive drum 21 and the transfer roller 26). Has been placed. Further, the contact position 47 is in relation to the contact position 50 sandwiching the sheet 3 between the driving roller 44 of the registration roller 9 and the driven roller 45 disposed on the upstream side in the conveyance direction of the sheet 3 with respect to the guide roller pair 60, 60. Arranged more on the photosensitive drum 21 side in the direction in which the line segment L extends (that is, the contact position 50 of the registration roller 9 is more transferred in the direction in which the line segment L extends than the contact position 47 of the guide roller pair 60, 60). Arranged on the roller 26 side).
With such a configuration, the “tension applying means protrudes in a direction opposite to the one surface from the plane including the contact position of the conveying roller pair and the contact position of the image carrier and the transfer roller” according to claim 7 of the present invention. The “arranged” position is realized.

(5) Configuration of Guide Roller Pair in Fixing Unit As specifically shown in FIG. 6, in the fixing unit 13, the sheet 3 is placed on the upstream side in the conveyance direction of the sheet 3 with respect to the heating roller 32. A guide portion 71 is provided for guiding between the two. The guide portion 71 has a guide surface 71a inclined such that the upper surface thereof approaches the heating roller 32 side from the upstream side toward the downstream side, and the uppermost end (most heating roller) of the guide surface 71a. Guide roller pairs 70 and 70 (the guide roller pairs 70 and 70 are non-driven rollers that are not driven by a motor or the like) are provided in a portion close to 32.

  The guide roller pair 70, 70 in the fixing unit has the same configuration as the guide roller pair 60, 60 in the process unit 12, and a detailed description thereof is omitted. Briefly, the guide roller pair 70, 70 is composed of a plurality of unit rollers arranged in a line in the width direction. Each unit roller also forms a pair with a unit roller arranged at a symmetrical position with respect to the center position X of the conveyance path of the sheet 3 (that is, the center position in the width direction of the heating roller 32 and the pressing roller 31). The paired unit rollers are arranged in a state of being symmetrically inclined with respect to the width direction so that the rotation axes of the unit rollers approach each other from the upstream side toward the downstream side.

2. Advantages of the present embodiment (1) According to the present embodiment, as shown in FIG. 5 (the dotted arrow on the paper is the transport direction of the paper 3), the paper 3 contacts the guide roller pair 60, 70. While being conveyed, a tension (arrow in the same figure) from the central position X toward the one end side in the downstream direction by each unit roller 62 arranged on one end side in the width direction (right side in FIG. 5). Y1) is given. On the other hand, the tension from the central position X toward the other end side in the downstream direction by the unit rollers 62 arranged on the other end side in the width direction (left side in FIG. 5) (arrow Y2 in the figure). Is granted. In other words, the sheet 3 is guided by the guide roller pairs 60 and 70 in the conveying direction, and is given a pulling force to both ends in the width direction (left and right direction in FIG. 5).
In addition, since the unit rollers 62 of the guide roller pair 60 and 70 are arranged at symmetrical positions with respect to the central position X, the sheet 3 is given equal tension to the left and right with respect to the central position X. Thus, the sheet 3 is conveyed straight along the conveyance direction.
As a result, the process unit 12 can perform transfer processing by guiding the sheet 3 between the photosensitive drum 21 and the transfer roller 26 in a state in which waviness and wrinkles in the width direction are suppressed. Similarly, the fixing unit 13 can perform the fixing process by guiding the sheet 3 between the heating roller 32 and the pressing roller 31 in a state in which waviness and wrinkles in the width direction are suppressed. Therefore, it is possible to improve the quality of image formation.

(2) Also, if each guide roller pair 60, 70 is wider than the unit roller 62, the outer peripheral surface of the disk member 64 is wider than the outer peripheral surface of each guide roller pair 60, 70 and the sheet 3. There is a risk of non-uniform contact. Further, the contact position between the both ends of the disk member and the paper 3 is greatly shifted in the transport direction, and there is a possibility that the paper 3 cannot be transported in a balanced manner.
Therefore, in the present embodiment, each of the guide roller pairs 60 and 70 is configured by a plurality of unit rollers 62 that are in contact with different positions in the width direction with respect to the sheet 3, and more stable conveyance can be performed.
Moreover, the unit rollers 62 are arranged linearly along the width direction. Accordingly, the sheet 3 receives tension from each unit roller 62 at the same position in the transport direction, and can be transported more stably.

  (3) In this embodiment, the pair of guide rollers 60 and 70 as tension applying means is configured to apply tension by contacting only one side (the lower surface in FIG. 1 and the like) of the sheet 3. As another configuration, for example, a configuration in which a pair of guide rollers 60 and 70 are sandwiched from both sides (upper and lower surfaces) of the paper is conceivable, but this embodiment can reduce the size of the apparatus compared to this configuration. Can be planned.

(4) Further, as shown in FIG. 4, the guide roller pair 60 is moved from the plane including the contact position 50 of the registration roller 9 and the contact position P of the photosensitive drum 21 and the transfer roller 26 to the opposite direction to one side ( In the same figure, it was set as the structure arrange | positioned in the position which protruded on the paper surface direction. As a result, when the sheet 3 is transferred between the photosensitive drum 21 and the transfer roller 26, the sheet 3 is conveyed in a bent state via the guide roller pair 60, 60 by the conveying force of the nip portion. The sliding contact is made in a state of being pressed against the contact position 47. Therefore, it is possible to reliably suppress wrinkles and the like by increasing the tension in the width direction by the guide roller pair 60 to a greater force.
The unit rollers 62 of the guide roller pair 60 are easily worn by the sliding contact, but the friction generated between the guide roller pair 60 and 60 and the sheet 3 is reduced by the rotation of the guide roller pair 60 and 60. can do. Therefore, even when such a laser printer 1 is used over a long period of time, the wear of the guide roller pair 60, 60 due to the sliding contact of the paper 3 is reduced, and the discharge during transfer is less likely to occur. Quality images can be formed over a long period of time. The same effect can be obtained by the pair of guide rollers 70 and 70 of the fixing unit 13.

  (5) When the guide roller pair 60, 60 is provided as shown in FIG. 4, the sheet 3 conveyed from the registration roller 9 is contacted with the contact position 47 of the guide roller pair 60, 60 before being transferred. Since the contact is made on the photosensitive drum 21 side with respect to the tangent T, the guide roller pair 60, 60 is first fed so as to come into contact with the surface of the photosensitive drum 21. The sheet 3 that has come into contact with the photosensitive drum 21 is then sent between the photosensitive drum 21 and the transfer roller 26 in a state in which the sheet 3 is tightly wound around the surface of the photosensitive drum 21 and transferred at the nip portion. It is conveyed while. Therefore, for example, when such a pair of guide rollers 60, 60 is not provided, immediately before the sheet 3 conveyed from the registration roller 9 is sent between the photosensitive drum 21 and the transfer roller 26, In order to form a gap with the photosensitive drum 21, the transfer bias applied from the transfer roller 26 may cause a discharge in the gap and cause a transfer failure. Since the sheet 3 before transfer can be wound tightly around the surface of the photosensitive drum 21, a discharge is applied between the sheet 3 and the photosensitive drum 21 by a transfer bias applied from the transfer roller 26. It is possible to effectively prevent the formation of a gap that causes a transfer failure and to reduce transfer defects. The same effect can be obtained by the pair of guide rollers 70 and 70 of the fixing unit 13.

<Embodiment 2>
FIG. 7 shows a second embodiment (corresponding to the inventions of claims 12, 14 and 16).
In the present embodiment, the guide roller is provided in a curved path portion of the conveyance path of the paper 3. In addition, the same code | symbol as Embodiment 1 is attached | subjected and the overlapping description is abbreviate | omitted, and only a different part is demonstrated below.
Specifically, as shown in FIG. 7, for example, the inside of the curved path portion 82 between the paper feed roller 7 and the transport roller 59 and the curved path portion 83 between the transport roller 59 and the registration roller 9. Are provided with guide roller pairs 80 and 81, respectively. The pair of guide rollers 80 and 81 is composed of a plurality of unit rollers arranged in a line in the width direction as in the first embodiment. Each unit roller also forms a pair with a unit roller arranged at a symmetrical position with respect to the center position of the transport path of the sheet 3 (that is, the center position X in the width direction of the transport roller 59 and the registration roller 9). The paired unit rollers are arranged in a state of being symmetrically inclined with respect to the width direction so that the rotation axes of the unit rollers approach each other from the upstream side toward the downstream side.

Further, in the present embodiment, for each of the guide roller pairs 80 and 81, “the tension applying means includes the contact position of the upstream transport roller pair and the contact position of the downstream transport roller pair”. The arrangement | positioning in the position which protruded from the plane in the opposing direction with respect to the single side | surface is implement | achieved.
Even with such a configuration, the sheet 3 can be transported in a state where waviness and wrinkles in the width direction are suppressed, and the same effects as the effects (2) to (4) of the first embodiment can be obtained. Can do.

<Embodiment 3>
8 and 9 show a second embodiment (corresponding to the invention of claim 3).
The present embodiment is an example in which the present invention is applied to a so-called tandem type laser printer including a plurality of image forming units corresponding to a plurality of colors.
Specifically, as shown in FIG. 8, in the laser printer 90, for example, image forming units 91 corresponding to four colors of yellow, magenta, cyan, and black are arranged in a line, and a tandem belt mechanism is provided below the image forming units 91. 92 is arranged. A sheet 96 conveyed by a sheet feeding roller 94 and a conveying roller 95 from a sheet tray 93 provided on the lower side of the tandem belt mechanism 92 is provided in a conveying path between the conveying roller 95 and the tandem belt mechanism 92. It is placed on the conveyance belt 92 a of the tandem belt mechanism 92 through the guide portion 97. The paper 96 placed on the transport belt 92a is sequentially transported to the image forming position of each image forming unit 91 by the tandem belt mechanism 92.

Each image forming unit 91 has the same configuration except for the color of the toner accommodated therein. Each image forming unit 91 includes a process unit 98 and a scanner unit 99. Among these, the process unit 98 includes a photosensitive drum 100, a cleaner (not shown) arranged so as to surround the peripheral surface of the photosensitive drum 100, a charger 101, and a developing device 102.
The developing device 102 also serves as the toner container 103 and forms a housing on the front end side of the process unit 98. The photosensitive drum 100, the cleaner, and the charger 101 are held by a frame of the casing on the rear end side of the process unit 98.
The developing device 102 contains toner of each color inside, and a developing roller 104 is rotatably held in a lower opening. A supply roller 105 is pressed against the developing roller 104, and the toner is supplied to the peripheral surface of the developing roller 104 so that the toner is rubbed by the supply roller 105.

The scanner unit 99 includes a laser light emitting unit (not shown), a polygon mirror 106 that is rotationally driven, lenses 107 and 108, reflecting mirrors 109, 110, and 111, and the like, and each color image emitted from the laser light emitting unit. The laser beam based on the data is passed or reflected in the order of the polygon mirror 106, the lens 107, the reflecting mirrors 109 and 110, the lens 108, and the reflecting mirror 111 as shown by the chain line in FIG. An electrostatic latent image is formed on the surface of the drum 100 by high-speed scanning.
The electrostatic latent image formed on the surface of the photosensitive drum 100 of each process unit 98 is developed with toner of each color by the developing device 102 and transferred onto the paper 96 by the transfer roller 112. As a result, on the paper 96 conveyed on the conveyance belt 92 a of the tandem belt mechanism 92, the respective color images are sequentially transferred by the image forming units 91 to form a color image. In FIG. 8, reference numeral 114 denotes a fixing device including a heating roller and a pressing roller, and reference numeral 115 denotes a paper discharge roller corresponding to the paper discharge roller 34 of the first embodiment.

In the present embodiment, as shown in an enlarged view in FIG. 9, the same configuration as the guide roller pairs 60 and 70 in the first embodiment is provided in the guide portion 97 for guiding the paper 3 onto the conveyance belt 92 a of the tandem belt mechanism 92. The guide roller pair 113 is provided.
With such a configuration, the sheet 96 is placed on the conveyance belt 92 a of the tandem belt mechanism 92 while being pulled from the center in the width direction to both ends by the guide roller pair 113. Accordingly, the sheet 96 can be conveyed to the image forming position of each image forming unit 91 in a state where waviness and wrinkles in the width direction are suppressed, thereby improving the image forming quality.

<Embodiment 4>
FIG. 10 shows a fourth embodiment (corresponding to the inventions of claims 11 and 24). The difference from the first embodiment is that a worm roller pair 120 is provided instead of the guide roller pair 60, and the other points are the same as in the first embodiment. Therefore, the same reference numerals as those in the first embodiment are given and the redundant description is omitted, and only different points will be described next. In FIG. 10, the upper side of the paper is the downstream side in the transport direction of the paper 3, and the lower side of the paper is the upstream side.
As shown in FIG. 10, each worm roller 120 has a spiral thread groove 122 cut on the outer peripheral surface of the rotating shaft body 121, and each of the worm rollers 120 has the rotating shaft body 121 in the width direction. They are arranged in parallel. Further, the worm rollers 120 arranged symmetrically with respect to the center position X are symmetrical with respect to the transport direction so that the screw grooves are separated from the upstream side in the transport direction toward the downstream side. It is arranged to incline.
With such a configuration, the same effects as those of the first embodiment can be obtained, and the number of parts can be reduced.

<Embodiment 5>
11 and 12 show a fifth embodiment (configuration included in the inventions of claims 1 and 18). The difference from the first embodiment is that a rib pair 130 formed so as to rise from the guide surface 61a is provided instead of the guide roller pair 60, and the other points are the same as in the first embodiment. Therefore, the same reference numerals as those in the first embodiment are given and the redundant description is omitted, and only different points will be described next. In FIG. 11, the upper side of the paper surface is the downstream side in the conveyance direction of the paper 3, and the lower side of the paper surface is the upstream side.
In the present embodiment, as shown in FIG. 11, a plurality of ribs 130 are arranged in parallel along the width direction on the guide surface 61 a of the guide portion 61. The ribs 130 disposed symmetrically with respect to the center position X are configured to be symmetrically inclined with respect to the transport direction so as to be separated from each other from the upstream side toward the downstream side. Further, as shown in FIG. 12, each rib 130 is configured to be inclined so that the downstream extension line of the upper surface 130 a faces the photosensitive drum 21 side.
With such a configuration, although the problem of wear due to sliding contact with the paper 3 occurs, other effects can be obtained as in the first embodiment.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention, and further, within the scope not departing from the gist of the invention other than the following. Various modifications can be made.
(1) In the first and second embodiments, each unit roller 62 is individually provided on the guide unit 61 of the process unit 12, but the unit rollers 62 are unitized into a plurality of units. The configuration may be such that a plurality of unit rollers 62 can be attached to the guide portion 61 in a lump.

  (2) The present invention can be applied not only to the above-described printer (laser printer) but also to a facsimile machine or a multifunction machine having a printer function and a scanner function.

  (3) Of course, the configuration may be such that the worm roller pair of the fourth embodiment or the rib pair of the fifth embodiment is applied to the fixing unit 13, the second embodiment, and the third embodiment of the first embodiment.

  (4) The guide roller pair 60, 70, 80, 81, 113 may be driven by a motor or the like. Moreover, you may provide the press roller pressed so that the guide roller pair 60,70,80,81,113 pair may be opposed. In this case, at least one of the guide roller pair 60, 70, 80, 81, 113 and the pressing roller may be driven by a motor or the like.

  (5) In the first embodiment, the guide roller 60 of the process unit 12 is moved from the plane including the contact position P of the photosensitive drum 21 and the transfer roller 26 and the contact position 50 of the registration roller 9 to the photosensitive drum 21 side (paper However, the configuration is not limited to this, and the following configuration may be used. That is, the conveyance speed of the registration roller 9 is set to be equal to or less than the conveyance speed of the sheet 3 passing between the photosensitive drum 21 and the transfer roller 26 and is pulled in the conveyance direction by the nip between the registration roller 9 and the photosensitive drum 21 and the transfer roller 26. It may be configured such that the guide roller 60 is in contact with the sheet 3 in a state in which the sheet 3 is in contact (corresponding to the configuration of claim 6).

1 is a side sectional view of a main part of a laser printer according to Embodiment 1 of the present invention. Side sectional view showing the process unit on an enlarged scale An enlarged plan view of the process unit Cross-sectional side view of the main part showing an enlarged part of the drum cartridge of the process unit Schematic showing the tension applied to the paper by a pair of guide rollers An enlarged side sectional view of the fixing unit Sectional side view which expands and shows the curved path | route part of Embodiment 2. Schematic diagram of laser printer of embodiment 3 Schematic diagram showing enlarged tandem belt mechanism Plan sectional drawing which expands and shows the process unit of Embodiment 4. FIG. 9 is an enlarged plan view showing the process unit of the fifth embodiment. Cross-sectional side view of the main part showing an enlarged part of the drum cartridge of the process unit

Explanation of symbols

1,90 ... Laser printer (image forming apparatus)
3,96 ... paper (recording medium)
9 ... Registration roller (conveyance roller)
12 ... Process unit (process cartridge)
21 ... Photosensitive drum (image carrier)
26 ... Transfer roller 31 ... Pressing roller 32 ... Heating roller 44 ... Drive roller (conveyance roller)
45 ... driven roller (conveyance roller)
50 ... contact position 59 ... conveying roller (conveying roller)
60, 70, 80, 81, 113 ... Guide roller pair 61, 71, 97 ... Guide portion 62 ... Unit roller 63 ... Rotating shaft 82, 83 ... Curve path portion 92 ... Tandem belt mechanism (conveying belt mechanism)
92a ... Conveying belt 120 ... Worm roller pair 122 ... Screw groove 130 ... Rib pair P ... Contact position X ... Center position

Claims (24)

An image carrier that carries a visible image formed by developing the electrostatic latent image with a developer, and a visible image carried on the image carrier that is disposed opposite to the image carrier. In an image forming apparatus comprising: a transfer roller for transferring to a recording medium; and a guide portion for guiding the recording medium being conveyed between the image carrier and the transfer roller.
An image forming apparatus, comprising: a tension applying unit that applies tension to the recording medium from the center toward both ends in the width direction perpendicular to the conveyance direction of the recording medium. A fixing heating roller, a pressing roller disposed opposite to the heating roller and pressed against the heating roller, and a recording medium conveyed with a visible image transferred thereon, the heating roller and the pressing roller In an image forming apparatus provided with a guide portion for guiding between,
An image forming apparatus, wherein the guide portion is provided with a tension applying unit that applies tension to the recording medium from the center toward both ends in the width direction perpendicular to the conveyance direction of the recording medium. A conveying belt mechanism for conveying the mounted recording medium to an image forming position for forming a visible image on the recording medium, and a guide unit for guiding the recording medium onto the belt of the conveying belt mechanism In an image forming apparatus comprising:
An image forming apparatus, comprising: a tension applying unit that applies tension to the recording medium from the center toward both ends in the width direction perpendicular to the conveyance direction of the recording medium. 4. The guide according to claim 1, wherein the guide portion is provided only on one side of the recording medium, and the tension applying means is configured to contact the one side of the recording medium. The image forming apparatus according to any one of the above. The guide portion is provided only on one side of the recording medium, and the tension applying unit is configured to contact the one side of the recording medium,
A pair of transport rollers for transporting the recording medium at a speed equal to or lower than the passing speed of the recording medium passing between the image carrier and the transfer roller is provided upstream of the guide portion in the transport direction. The image forming apparatus according to claim 1. The guide portion is provided only on one side of the recording medium, and the tension applying unit is configured to contact the one side of the recording medium,
A pair of conveyance rollers for conveying the recording medium at a speed equal to or lower than the passage speed of the recording medium passing between the heating roller and the pressing roller is provided on the upstream side in the conveyance direction with respect to the guide portion. The image forming apparatus according to claim 2. The guide portion is provided only on one side of the recording medium, and the tension applying unit is configured to contact the one side of the recording medium,
A pair of conveyance rollers for conveying the recording medium with the recording medium sandwiched from both sides is provided on the upstream side in the conveyance direction with respect to the guide portion,
The tension applying means is disposed at a position protruding in a direction facing the one surface from a plane including a contact position of the pair of conveying rollers and a contact position of the image carrier and the transfer roller. The image forming apparatus according to claim 1. The guide portion is provided only on one side of the recording medium, and the tension applying unit is configured to contact the one side of the recording medium,
A pair of conveyance rollers for conveying the recording medium with the recording medium sandwiched from both sides is provided on the upstream side in the conveyance direction with respect to the guide portion,
The tension applying means is arranged at a position protruding in a direction facing the one surface from a plane including a contact position of the conveying roller pair and a contact position of the heating roller and the pressing roller. The image forming apparatus according to claim 2. The tension applying means includes a pair of guide rollers that are arranged symmetrically with respect to the center in the width direction, and each outer peripheral surface is provided so as to be in contact with the recording medium. The rotary shafts of each other are arranged to be inclined with respect to the width direction so as to approach each other from the upstream side toward the downstream side in the transport direction. The image forming apparatus according to claim 8. The image forming apparatus according to claim 9, wherein the pair of guide rollers includes a plurality of unit rollers that are in contact with different portions of the recording medium in the width direction. The tension applying means is arranged symmetrically with respect to the center in the width direction and rotates around a rotation axis that is parallel to the width direction, and a thread groove is formed on the outer peripheral surface that contacts the recording medium. With a pair of warm rollers,
The worm roller pair is inclined with respect to the transport direction so that the screw grooves are separated from the upstream side in the transport direction toward the downstream side. The image forming apparatus according to claim 8. In an image forming apparatus comprising a transport path for transporting a recording medium, and a transport mechanism for transporting the recording medium along the transport path,
In the middle of the transport path, there is provided tension applying means that contacts the recording medium from only one side thereof and applies tension toward the both ends from the center in the width direction perpendicular to the transport direction of the recording medium,
The tension applying means is a plurality of units which are arranged symmetrically with respect to the center in the width direction, and each outer peripheral surface is provided so as to be able to come into contact with a different location in the width direction with respect to the recording medium. The unit rollers that are paired with each other are arranged to be inclined with respect to the width direction so that their rotation axes approach each other from the upstream side to the downstream side in the transport direction. An image forming apparatus having the structure. In an image forming apparatus comprising a transport path for transporting a recording medium, and a transport mechanism for transporting the recording medium along the transport path,
In the middle of the transport path, there is provided tension applying means that contacts the recording medium from only one side thereof and applies tension toward the both ends from the center in the width direction perpendicular to the transport direction of the recording medium,
The tension applying means is arranged symmetrically with respect to the center in the width direction and rotates around a rotation axis that is parallel to the width direction, and a thread groove is formed on the outer peripheral surface that contacts the recording medium. With a pair of warm rollers,
The pair of worm rollers is inclined with respect to the transport direction so that the screw grooves are separated from the upstream side in the transport direction toward the downstream side. . The transport path has a curved path with respect to the transport direction;
The image forming apparatus according to claim 12, wherein the tension applying unit is provided in a guide portion provided on an inner peripheral side of the curved path. The transport mechanism is disposed on the upstream side and the downstream side in the transport direction with respect to the tension applying unit, has a transport roller pair for transporting the recording medium from both sides, and the upstream transport roller The image forming apparatus according to claim 12, wherein the recording medium is conveyed at a speed equal to or higher than a conveyance speed of the conveyance roller pair on the downstream side. The transport mechanism is disposed on the upstream side and the downstream side in the transport direction with respect to the tension applying unit, and has a pair of transport roller pairs that transport the recording medium from both sides,
The tension applying means is arranged at a position protruding in a direction facing the one surface from a plane including a contact position of the upstream conveying roller pair and a contact position of the downstream conveying roller pair. The image forming apparatus according to claim 12, wherein the image forming apparatus is an image forming apparatus. The image forming apparatus according to claim 10, wherein the plurality of unit rollers are linearly arranged along the width direction. An image carrier that is detachably attached to the main body of the image forming apparatus and carries a visible image formed by developing an electrostatic latent image with a developer, and the image carrier disposed opposite to the image carrier. A transfer roller for transferring a visible image carried on the carrier to a recording medium; and a guide unit for guiding the conveyed recording medium between the image carrier and the transfer roller. In the process cartridge
A process cartridge, wherein the guide portion is provided with a tension applying unit that applies tension to the recording medium from the center toward both ends in the width direction orthogonal to the conveyance direction of the recording medium. 19. The process cartridge according to claim 18, wherein the guide portion is provided only on one side with respect to the recording medium, and the tension applying unit is configured to contact the one side of the recording medium. . The guide portion is provided only on one side of the recording medium, and the tension applying unit is configured to contact the one side of the recording medium,
The image carrier and the transfer roller are provided on the upstream side in the transport direction with respect to the guide portion of the image forming apparatus main body, and the recording medium is transported at a speed equal to or higher than the transport speed of a pair of transport rollers that transport the recording medium. The process cartridge according to claim 18, wherein the process cartridge is passed. The guide portion is provided only on one side of the recording medium, and the tension applying unit is configured to contact the one side of the recording medium,
The tension applying unit is provided on the upstream side of the guide direction in the image forming apparatus main body with respect to the conveyance direction, and a contact position of a conveyance roller pair that conveys the recording medium from both sides, the image carrier, and the image carrier 19. The process cartridge according to claim 18, wherein the process cartridge is disposed at a position protruding from a plane including a contact position of the transfer roller in a direction opposite to the one surface. The tension applying means includes a pair of guide rollers that are arranged symmetrically with respect to the center in the width direction, and each outer peripheral surface is provided so as to be in contact with the recording medium. The rotary shafts of each other are arranged to be inclined with respect to the width direction so as to approach each other from the upstream side to the downstream side in the transport direction. 21. The process cartridge according to any one of 21. 23. The process cartridge according to claim 22, wherein each of the pair of guide rollers includes a plurality of unit rollers that are in contact with different portions of the recording medium in the width direction. The tension applying means is arranged symmetrically with respect to the center in the width direction and rotates around a rotation axis that is parallel to the width direction, and a thread groove is formed on the outer peripheral surface that contacts the recording medium. With a pair of warm rollers,
The worm roller pair is inclined with respect to the transport direction so that the screw grooves are separated from the upstream side in the transport direction toward the downstream side. The process cartridge according to claim 21.

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