JP2009020450A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for forming an image on a recording sheet while conveying it by means of a belt, the apparatus being designed so that even if the recording sheet is thin and contains moisture, the recording sheet is placed so as to be evenly extended on the conveying face of the belt. <P>SOLUTION: Paper 51 conveyed by resist rollers 57 comes into contact with a guide section 300. The guide section 300 is configured such that a flexible auxiliary guide member 302 is fixed at the center in the width direction of an inclining face 301 so as to project toward the belt 7. When the paper 51 comes into contact with the auxiliary guide member 302 as shown in (A) and bends as shown in (B), the part (the area of the contact with the auxiliary guide member 302) at the center in the width direction of the paper 51 is subject to: a force pressing the part down toward the surface of the belt 7; force pushing the part back toward this side against the conveying force exerted by the resist rollers 57; and frictional resistance exerted by the auxiliary guide member 302. Force indicated by arrow F is also exerted to the paper 51 in its width direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on a recording sheet such as paper or an OHP sheet, and more particularly to an image forming apparatus that forms an image on a recording sheet while the recording sheet is conveyed by a belt.

  2. Description of the Related Art Conventionally, there has been proposed an image forming apparatus that forms an image on a recording sheet via an image forming member such as a process unit disposed opposite to the belt while conveying the recording sheet by a belt. In this type of image forming apparatus, if the recording sheet is not uniformly stretched and placed on the conveying surface of the belt, wrinkles may occur on the recording sheet and a part of the image may be lost. Therefore, a projection (pressing plate 45) is provided on the guide member (upper chute 42) for guiding the recording sheet obliquely from the upper side toward the belt conveyance surface. (See, for example, paragraphs 0035 and 0036 of Patent Document 1).

When such a protrusion is provided, the recording sheet is pressed at the center in the width direction to the belt side below the protrusion, and gradually contacts the belt conveyance surface from the center toward both ends in the width direction. When the recording sheet gradually comes into contact with the belt conveyance surface from the center in the width direction in this way, air does not enter between the recording sheet and the belt, and the recording sheet is uniformly stretched and placed on the belt conveyance surface. be able to.
JP-A-9-175585

  However, the inventor of the present application has found that the image quality deteriorates when a recording sheet that has been left for a long time in a high humidity environment is used in the above-described conventional apparatus.

  That is, a recording sheet that has been left for a long time in a highly humid environment with a number of sheets stacked for a long time will be in a state where the center of the recording sheet is dry and only the end of the recording sheet is wet. The recording sheet having moisture only at the end portion has different rigidity between the center portion and the end portion.

  When the recording sheet having different rigidity at the center and the end is conveyed by a roller or the like as described above, the recording sheet has both the center in the width direction and both ends in the width direction (to the belt side). In the state where it hung down, it may be conveyed toward a guide member.

As described above, when the recording sheet is conveyed toward the guide member of the conventional apparatus, the central portion in the width direction of the recording sheet is pressed by the protrusion, and further protrudes and hangs down to the belt side. When the recording sheet is guided to the belt in this way, the recording sheet is placed on the belt in an M-shape, and is interposed between the belt width direction center, the belt width end, and the belt conveyance surface. There is a possibility that a gap is formed, and air cannot be sufficiently removed from the gap, resulting in a reduction in image quality. (See Figure 9)
Therefore, the present invention improves the image quality by uniformly extending the recording sheet on the conveying surface of the belt in an image forming apparatus that forms an image on the recording sheet while conveying the recording sheet by the belt. It was made for the purpose of doing.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a belt having a conveying surface on which a recording sheet is placed and conveyed, and an opposite image to the conveying surface of the belt, and an image is recorded on the recording sheet conveyed by the belt. The image forming member to be formed is disposed opposite to the conveying surface of the belt, and the contact surface to the recording sheet is formed so as to be closer to the conveying surface toward the downstream side in the recording sheet conveying direction and conveyed. A guide member that guides the recording sheet toward the conveyance surface of the belt, a conveyance member that conveys the recording sheet toward the guide member, and a downstream end of the guide member in the recording sheet conveyance direction attached to the guide member And a flexible auxiliary guide member projecting from the portion toward the conveying surface of the belt.

  In the image forming apparatus of the present invention configured as described above, when the conveyance member conveys the recording sheet toward the guide member, the guide member directs the recording sheet conveyed by the conveyance member toward the conveyance surface of the belt. invite. When the recording sheet is placed on the conveyance surface of the belt, the image forming member disposed opposite to the conveyance surface of the belt forms an image on the recording sheet conveyed by the belt.

The guide member is formed so that a contact surface with the recording sheet is closer to the transport surface as it goes downstream in the recording sheet transport direction, and further, the guide member has a recording sheet transport direction of the guide member. A flexible auxiliary guide member protruding from the downstream end portion toward the conveying surface of the belt is attached. Since this auxiliary guide member is flexible, when the recording sheet comes into contact with the auxiliary guide member, the protruding portion (free end) of the auxiliary guide member bends downstream in the conveying direction. In addition, since the auxiliary guide member is more easily bent at both ends in the recording sheet width direction than the central portion in the recording sheet width direction, when the recording sheet comes into contact with the auxiliary guide member, the auxiliary guide member has a belt in the central portion in the width direction. It deforms into a shape that protrudes to the side. (Refer to FIG. 7 (B))
When the auxiliary guide member is bent in this way, a force that presses against the surface of the belt and a force that resists the conveying force by the conveying member act on the central portion in the width direction of the recording sheet.

  As described above, when a force resisting the conveying force is applied to the central portion in the width direction of the recording sheet, the central portion in the width direction of the recording sheet is appropriately stretched toward both ends in the width direction while being squeezed by the auxiliary guide member. The curvature is corrected.

  In addition, since the auxiliary guide member is deformed into a shape in which the central portion in the width direction protrudes toward the belt side, the central portion in the width direction of the recording sheet is extended toward both ends in the width direction due to the restoring force from the deformation, and is curved. Is corrected.

  Further, in such a state that the central portion in the width direction of the recording sheet is stretched and the curvature in the entire width direction is corrected, a force pressing from the auxiliary guide member to the surface of the belt acts on the central portion in the width direction. The recording sheet has a shape in which only the central portion in the width direction gently protrudes toward the belt conveyance surface. In this way, the recording sheet gradually protrudes from the center in the width direction to both ends in the width direction when only the center in the width direction protrudes gently toward the belt transport surface. Abut. As a result, air does not enter between the recording sheet and the belt conveyance surface, and the recording sheet can be uniformly stretched and placed on the belt conveyance surface. As a result, the image quality can be improved even when the end of the recording sheet is damp.

  Although the present invention is not limited to the following configuration, the auxiliary guide member is at least at the position facing the central portion in the width direction of the recording sheet conveyed to the conveyance member. The belt may be configured to protrude toward the conveyance surface of the belt from the downstream end in the conveyance direction.

  In this case, the recording sheet can be more reliably performed from the center of the recording sheet in the width direction of the recording sheet, and air can be further suppressed from entering between the recording sheet and the belt.

  The auxiliary guide member is provided symmetrically with respect to the center in the width direction of the recording sheet conveyed to the conveying member in the width direction, and the width of the recording sheet conveyed to the conveying member. The plate-shaped member comprised so that it might become smaller may be sufficient.

  With such a configuration, when the recording sheet comes into contact with the auxiliary guide member, the auxiliary guide member is reliably deformed by the shape in which the central portion in the width direction protrudes toward the belt side. The central portion in the width direction of the recording sheet is extended toward both ends in the width direction, and the curvature is more reliably corrected.

  In this case, the contact surface of the auxiliary guide member with respect to the recording sheet may be raised toward the recording sheet conveyance path side with respect to the contact surface of the guide member with respect to the recording sheet. In this case, the central portion in the width direction of the recording sheet can be pressed in the direction of the belt conveying surface even by the swell of the auxiliary guide member, and the recording sheet can be more uniformly stretched and placed on the belt conveying surface. it can.

  Furthermore, in this case, the tip of the auxiliary guide member may have a dimension in the recording sheet width direction of 40 mm or more. As a result of the experiment, it was found that with the A4 thin paper, the central range of 40 mm is particularly easy to dent on the belt side. For this reason, if the width | variety of the front-end | tip of an auxiliary guide member shall be 40 mm or more as mentioned above, the unevenness | corrugation of a recording sheet can be corrected still more favorably.

  Further, when the auxiliary guide member is constituted by the plate-like member described above, a pressing member that presses the guide sheet and the recording sheet guided by the auxiliary guide member toward the belt over the entire recording sheet width direction. And an auxiliary pressing member that is attached to the pressing member and presses the recording sheet toward the belt through a gap between the auxiliary guide member and the pressing member. In this case, the recording sheet guided to the conveying surface of the belt by the guide member and the auxiliary guide member is pressed toward the belt over the entire recording sheet width direction by the pressing member, and the recording sheet is made even better. It can be stretched and placed on the conveyor surface of the belt. Further, in this case, the central portion in the width direction of the recording sheet continues to receive the auxiliary guide member, the auxiliary pressing member, and the pressing force from the pressing member in the belt direction without interruption. For this reason, the recording sheet can be brought into contact with the conveyance surface of the belt from the central portion of the recording sheet width, and the recording sheet can be evenly stretched and placed on the conveyance surface of the belt.

  Further, as described above, in the case where the auxiliary guide member protrudes toward the conveyance surface of the belt at least at the center portion in the recording sheet width direction of the guide member as compared to both ends of the guide member in the recording sheet width direction. The amount of protrusion of the auxiliary guide member toward the belt side may gradually decrease from the central portion of the recording sheet in the width direction toward both ends. Also in this case, as described above, the recording sheet can be more reliably executed from the center of the recording sheet width direction to the belt conveyance surface, and the recording sheet can be uniformly stretched on the belt conveyance surface. The effect that it can perform more reliably arises.

  In each of the image forming apparatuses, the contact surface of the guide member to the recording sheet may be configured to intersect at an angle of 45 ° to 90 ° with respect to the conveyance surface of the belt. Such a configuration also facilitates downsizing of the image forming apparatus.

  In each of the image forming apparatuses, the contact surface of the guide member with respect to the recording sheet may have a central portion in the recording sheet width direction that swells toward the recording sheet conveyance path compared to both ends in the recording sheet width direction. Good. In this case, the central portion in the width direction of the recording sheet is pressed toward the conveying surface of the belt by the bulge also by contacting the guide member. Therefore, in this case, the central portion in the width direction of the recording sheet can be pressed in two steps in the belt direction, and the recording sheet can be more uniformly stretched and placed on the conveying surface of the belt.

  In each of the image forming apparatuses, the image forming member supports a plurality of photosensitive drums on which an electrostatic latent image is formed and the plurality of photosensitive drums, and is detachable from the image forming apparatus main body. A drum frame, and the guide member may be provided integrally with the drum frame. In this case, since the guide member is provided integrally with the drum frame, the entire image forming apparatus can be further reduced in size.

[Overall Configuration of Color Laser Printer 1]
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a configuration of a color laser printer (hereinafter simply referred to as a printer) 1 as an image forming apparatus to which the invention is applied. As shown in FIG. 1, the printer 1 includes a main body 2 in which a paper feeding unit 5 that supplies paper 51 as an example of a recording sheet, and an image forming member that forms an image on the paper 51 supplied from the paper feeding unit 5. As an example, the image forming unit 6 and a belt 7 that conveys the paper 51 through a portion facing the image forming unit 6 are provided.

  In the following description, unless otherwise specified, each direction is shown with the vertical direction shown in FIG. 1 as the top and bottom, the left side in FIG. 1 as the front, the right side as the back, and the front side of the paper of FIG. Here, the left and right are defined based on the direction viewed from the person standing on the front side of the printer 1. Further, a direction perpendicular to the conveyance direction of the paper 51 and extending to the right side and the left side is a width direction as an example of the recording sheet width direction.

  The paper feed unit 5 includes a paper feed tray 50 that is detachably attached to the main body 2 below the main body 2 and a paper supply mechanism 58 that supplies the paper 51 from the paper feed tray 50 to the belt 7. . The paper supply mechanism 58 includes a paper feed roller 52, a separation roller 53, a separation pad 54, and the like provided at the front end of the paper feed tray 50, and the paper 51 is separated one by one by this and sent upward. It is done. The paper 51 transported upward is passed between the paper dust removing roller 55 and the pinch roller 56, and then the paper powder is removed. Then, the paper 51 is temporarily locked by a registration roller 57 as an example of a transport member. When the registration roller 57 rotates at an appropriate timing, the paper 51 locked to the registration roller 57 is guided to a guide 59 and a guide unit 300 described later and placed on the surface (conveying surface) of the belt 7.

  Here, the paper 51 placed on the conveyance surface of the belt 7 is conveyed from the near side to the back side, and the direction in which the paper 51 is conveyed by the conveyance surface of the belt 7 is thus conveyed in the belt. The direction is DT (see FIG. 1).

  The image forming unit 6 includes a scanner unit 61, a process unit 62, and a fixing unit 64 configured as follows. The scanner unit 61 is provided on the upper portion of the main body 2 and includes a laser light emitting unit, a polygon mirror, a plurality of lenses and a reflecting mirror (not shown). In the scanner unit 61, the laser beam emitted from the laser emission unit corresponding to each color of cyan, magenta, yellow, and black is scanned at high speed in the left-right direction by the polygon mirror, and passed or reflected by a plurality of lenses and reflecting mirrors. Thereafter, the photosensitive drum 31 corresponding to each color is irradiated.

  The process unit 62 is disposed between the scanner unit 61 and the belt 7, and includes a photosensitive unit 3 and a developing cartridge 40 that is provided for each color and can be individually attached to and detached from the photosensitive unit 3. . The photosensitive unit 3 is detachably attached to the main body 2, and four drum subunits 30 are arranged in the horizontal direction below the photosensitive unit 3. Each drum subunit 30 is provided with a developing cartridge 40 containing cyan, magenta, yellow, or black toner at a predetermined position. Each drum subunit 30 includes a photosensitive drum 31 and a scorotron charger 32, and the developing cartridge 40 includes a developing roller 41 that supplies toner stored therein to the photosensitive drum 31.

  Therefore, the photosensitive drum 31 is uniformly charged by the scorotron charger 32, and then an electrostatic latent image based on the image data is formed by the laser light emitted from the scanner unit 61. Then, the toner is supplied to the surface via the developing roller 41 so that the toner image is carried on the surface.

  A transfer roller 74 is disposed on each photosensitive drum 31 with the belt 7 interposed therebetween. Further, the endless belt 7 is stretched between the driving roller 71 and the driven roller 72, and the paper 51 placed on the belt 7 between the photosensitive drum 31 and the transfer roller 74 as described above. While being conveyed, the toner images of the respective colors are transferred to the paper 51. That is, a transfer bias is applied to each transfer roller 74 from a high voltage substrate (not shown), and the toners of the respective colors carried on the respective photosensitive drums 31 are sequentially transferred onto the paper 51 by the transfer bias.

  The fixing unit 64 is supplied with the paper 51 conveyed by the belt 7 through the part facing the four photosensitive drums 31, and the fixing unit 64 includes a heating roller 81 and a pressure roller 82. A halogen lamp is provided in the heating roller 81, and the halogen lamp heats the surface of the heating roller 81 to a fixing temperature. The pressure roller 82 is disposed so as to be in pressure contact with the heating roller 81, and the toner image on the sheet 51 is thermally fixed by conveying the sheet 51 while sandwiching the sheet 51 with the heating roller 81.

  The sheet 51 on which the toner image is thermally fixed by the fixing unit 64 is conveyed by a plurality of conveyance rollers 92 along a sheet discharge-side conveyance path 91 extending upward from the exit of the fixing unit 64 and is discharged to a sheet discharge tray 93. . The paper discharge tray 93 is formed as an appropriate depression on the upper surface of the main body 2, and the sheets discharged from the paper discharge side conveyance path 91 are accumulated.

[Configuration of Photosensitive Unit 3]
FIG. 2 is a perspective view illustrating the configuration of the photoreceptor unit 3 from the lower surface side. As shown in FIG. 2, the photosensitive unit 3 as an example of a drum frame includes the above-described four drum subunits 30, a front beam 36, a rear beam 37, and a pair of side plates 38. . Further, the side plate 38 is provided with a pressing member 100 described below in a swingable manner, and the rear beam 37 is provided with a guide portion 300. 1 and 2, the configuration of the pressing member 100 and the guide unit 300 is schematically shown, and the detailed portions are partially omitted.

[Configuration of Pressing Member 100]
As shown in FIG. 3, the pressing member 100 is integrated with a long base portion 101 spanning in the width direction, arm portions 102 integrally formed at both ends of the base portion 101, and a central lower surface of the base portion 101. A molded pressing portion 103 and a protruding member 104 as an example of an auxiliary pressing member protruding from the front end surface of the pressing portion 103 are provided.

  The arm portion 102 is formed so as to extend from both ends of the base portion 101 to the front side, and a pin 102A that is swingably supported by the side plate 38 of the photosensitive unit 3 is formed at the tip thereof. In addition, a coil-shaped portion that is a central portion of the torsion spring 110 is attached to the pin 102A. One end of the torsion spring 110 is supported at an appropriate position of the arm unit 102 and the other end is supported at an appropriate position of the photoconductor unit 3, so that the base unit 101 is attached to the belt when the photoconductor unit 3 is mounted at a proper position. Energize in 7 directions. As a result, the paper 51 can be pressed against the surface of the belt 7 via the pressing surface 103 </ b> A formed flat on the lower surface of the pressing portion 103.

  In addition, the pressing surface 103A can be brought close to the surface of the belt 7 in parallel when the photosensitive unit 3 is mounted at a regular position, and the base portion 101 becomes closer to the downstream side in the conveyance direction of the paper 51. It is formed so that the width gradually increases from the central part to both end directions. For this reason, the pressing member 100 can press the belt 51 over the entire width direction of the paper 51 while extending the paper 51 from the central portion in the width direction toward both ends in the width direction. Further, the projecting member 104 is formed integrally with the pressing member 110 and is formed so as to protrude from the front end surface of the pressing portion 103 to directly below the front end edge of the base portion 101. (See FIG. 5A).

[Configuration and operation of guide unit 300]
As shown in FIG. 2 and FIG. 4 as a partially enlarged view thereof, a guide portion 300 is provided on the front side of the pressing member 100. The guide unit 300 includes an inclined surface 301 as an example of a guide member formed integrally with the front beam 36, and an auxiliary guide made of a rectangular PET film having a thickness of 350 μm at the center of the inclined surface 301 in the width direction. The member 302 is fixed.
The inclined surface 301 is inclined by 45 ° with respect to the belt conveyance direction DT (belt conveyance surface 7A) of the paper 51.

  Further, a PET film 303 having a thickness of 38 μm is stuck to the auxiliary guide member 302 with a slight gap on the inclined surfaces 301 on both the left and right sides of the auxiliary guide member 302. More specifically, the auxiliary guide member 302 is formed to protrude from the lower end of the inclined surface 301 at a position facing the center in the width direction of the paper 51 conveyed by the registration roller 57. Further, the auxiliary guide member 302 is provided symmetrically with respect to the center in the width direction of the paper 51 conveyed by the registration rollers 57 in the width direction, and the width is smaller than the width of the paper 51. ing.

  FIG. 5A is an enlarged cross-sectional view illustrating an enlarged configuration in the vicinity of the guide unit 300 in FIG. As shown in FIG. 5A, the auxiliary guide member 302 is configured to protrude downward (belt side) from the lower end of the guide member 300. More specifically, the portion of the auxiliary guide member 302 that protrudes downward from the lower end of the inclined surface 301 is configured to overlap the protruding member 104 of the pressing member 100 in the belt conveyance direction DT. In this embodiment, the protrusion amount from the lower end of the inclined surface 301 of the auxiliary guide member 302 is 1.5 mm as shown in FIG.

  Further, as shown by a broken line in FIG. 5A, the leading edge of the paper 51 conveyed to the registration roller 57 contacts the auxiliary guide member 302 and the PET film 303 on the inclined surface 301 at an angle of about 45 °. .

  Here, as shown in FIG. 6 as an end view taken along the line AA in FIG. 5A, the contact surface of the inclined surface 301 with the paper 51 is at the center in the width direction on the conveyance path side of the paper 51 (belt). The contact surface of the auxiliary guide member 302 with respect to the paper 51 is raised more than the inclined surface 301 and the PET film 303 by the thickness of the PET film 303. The width W of the auxiliary guide member 302 is 40 mm. This width is smaller than the entire width of the sheet 51 to be conveyed. Therefore, the unevenness of the sheet 51 is corrected to some extent by the leading end abutting on the auxiliary guide member 302 and the PET film 303 and the conveyance direction being changed, and the sheet 51 is further increased by the above-described rise of the inclined surface 301 and the auxiliary guide member 302. The center part in the width direction of 51 is pressed downward. FIG. 6 is drawn slightly exaggerated.

Next, a state where the paper 51 is guided by the inclined surface 301 and the auxiliary guide member 302 will be described.
When the sheet 51 is left for a long time in a high humidity environment in a state where a plurality of sheets are stacked, the center part is in a dry state and the end part is in a humid state. When the paper 51 is conveyed by the registration rollers 57 in such a state, the paper 51 is in a state where both the central portion in the width direction of the recording sheet and both end portions in the width direction hang down (to the belt side) (M-shaped). In the curved state) toward the inclined surface 301 and the auxiliary guide member 302. (See FIG. 7B).

  When the paper 51 is further conveyed, as shown in FIG. 7A, the leading end of the paper 51 comes into contact with the free end of the flexible auxiliary guiding member 302, and the leading end of the auxiliary guiding member 302 is moved. The paper 51 is conveyed while being bent to the back side. Then, due to the restoring force of the auxiliary guide member 302, the sheet 51 is pressed down toward the center of the width direction (contact portion with the auxiliary guide member 302) toward the surface of the belt 7 and the conveying force by the registration rollers 57. The force that pushes back and pushes it toward you works.

  In this way, a force that pushes back toward the near side acts against the conveying force by the registration rollers 57, so that the central portion in the width direction of the paper 51 is appropriately stretched toward both ends while being rubbed by the auxiliary guide member 302, and is curved. Is corrected.

  Furthermore, since the free end of the auxiliary guide member 302 bends to the back side, the contact area between the paper 51 and the vicinity of the free end of the auxiliary guide member 302 increases, so the width direction center portion of the paper 51 (auxiliary guide member 302). The frictional resistance with the vicinity of the free end of the auxiliary guide member 302 acts reliably on the contact portion).

As the frictional resistance acts in this manner, the central portion in the width direction of the paper 51 is appropriately stretched toward both ends while being squeezed by the auxiliary guide member 302, and the curvature is corrected.
Further, the auxiliary guide member 302 is more easily bent at both ends in the width direction than at the center portion in the width direction. For this reason, as illustrated in FIG. 7B as a B view of FIG. 7A, the auxiliary guide member 302 is deformed into a bowl shape whose central portion protrudes downwardly. Then, a force that spreads the paper 51 from the central portion in the width direction toward both ends in the width direction as indicated by an arrow F is applied to the portion of the paper 51 that is curved toward the auxiliary guide member 302 side by the restoring force of the auxiliary guide member 302. Works. As a result, the central portion in the width direction of the paper 51 is stretched and the curvature is corrected.

  Further, in such a state that the central portion in the width direction of the paper 51 is stretched and the curvature is corrected, a force to push down from the auxiliary guide member 302 to the surface of the belt 7 acts on the central portion in the width direction. Only the central part in the width direction has a shape that gently protrudes toward the conveying surface of the belt.

  As described above, the sheet 51 has a shape in which only the central portion in the width direction protrudes gently on the belt conveyance surface, and gradually moves from the central portion in the width direction toward both end portions in the width direction toward the belt conveyance surface. Abutting against the transfer surface. As a result, air does not enter between the recording sheet and the belt, and the recording sheet can be uniformly stretched on the conveying surface of the belt. As a result, the image quality can be improved.

  In particular, in an experiment using A4 plain paper of 64 g / m 2, it was confirmed that a portion up to 40 mm in the center in the width direction corresponds to a region recessed downward as illustrated in FIG. 7B. The experiment will be described in detail. First, toner uniformly adheres across the width direction on the inclined surface 301 with the auxiliary guide member 302 removed. Thereafter, a plurality of sheets 51 are continuously conveyed by the registration rollers, and the sheet 51 and the auxiliary guide member 302 are brought into sliding contact with each other. Then, an area of the auxiliary guide member 302 in which the toner is peeled off in sliding contact with the paper 51 is confirmed. The area where the toner is peeled is an area where the toner 51 is slidably contacted, and the area where the toner remains is an area where the toner 51 is not slidably contacted. Since the paper 51 and the auxiliary guide member 302 are not slidably contacted when the paper 51 is recessed downward, the area where the toner remains is confirmed as an area corresponding to the area where the paper 51 is recessed downward in the width direction. Is done.

  In the present embodiment, since the width W of the auxiliary guide member 302 is 40 mm, the curvature of the region of the area recessed below the center of the sheet 51 is mainly corrected, and as a result, the entire curve of the sheet 51 is corrected. Is corrected more effectively.

In particular, the frictional resistance from the auxiliary guide member 302 acts particularly strongly on the portion of the paper 51 that is curved toward the auxiliary guide member 302, so that the unevenness of the paper 51 can be corrected more satisfactorily.
As described above, the width W of the auxiliary guide member 302 is particularly preferably 40 mm, but the width W may be 40 mm or more. In other words, it is desirable that the width W is 40 mm or more, because the auxiliary guide member 302 can effectively apply a correcting force to a portion of the paper 51 that is recessed below the center in the width direction.

  Further, as shown in FIG. 7A, since the auxiliary guide member 302 and the protruding member 104 overlap in the belt conveyance direction DT, the sheet 51 has a central portion in the width direction toward the surface of the belt 7. Can continue to be applied without interruption until reaching the pressing surface 103A. For this reason, the paper 51 can be brought into contact with the surface of the belt 7 from the center in the width direction, and the paper 51 can be pressed while being extended by the pressing surface 103A of the pressing member 100 as described above.

[Effects and modifications of this embodiment]
As described above, in the present embodiment, when the leading edge of the paper 51 comes into contact with the auxiliary guide member 302, when the paper 51 is further conveyed and the auxiliary guide member 302 is bent, and further, the paper 51 In three stages at the time when the pressing member 100 is pressed against the surface of the belt 7, the unevenness of the paper 51 can be corrected and extended in the width direction as described above. Accordingly, even when the paper 51 is thin and damp, the paper 51 can be uniformly stretched on the surface of the belt 7 and an accurate image can be formed on the paper 51.

  In the above embodiment, the inclined surface 301 is provided integrally with the photosensitive unit 3, and the inclined surface 301 is inclined by 45 ° with respect to the belt conveyance direction DT (belt conveyance surface) of the paper 51. Since the path is shortened, the entire printer 1 can be favorably downsized. Furthermore, since the auxiliary guide member 302 is also a simple configuration in which a rectangular PET film is simply fixed to the inclined surface 301, the manufacturing cost can be reduced well. Furthermore, since the auxiliary guide member 302 is flexible, when a thick thick paper is used as the paper 51, the auxiliary guide member 302 is pushed by the paper 51 and greatly deformed. For this reason, even when the auxiliary guide member 302 is greatly protruded in the conveyance path of the paper 51 in order to extend the thin paper 51 more uniformly and uniformly, it is possible to convey the thick thick paper well without clogging. .

  In addition, at least at a position facing the central portion in the width direction of the paper 51 conveyed to the registration roller 57, it protrudes from the lower end of the inclined surface 301 toward the conveyance surface of the belt. With such a configuration, when the paper 51 comes into contact with the auxiliary guide member 302, the auxiliary guide member 302 is reliably deformed by the shape in which the central portion in the width direction protrudes toward the belt side. By the force, the central portion in the width direction of the paper 51 is extended toward both ends in the width direction, and the curvature is more reliably corrected.

  Although not shown, there is a registration detection sensor for detecting the paper 51 at the center in the width direction of the guide 59. The registration sensor abuts on the paper 51 from above so that the paper 51 is shown in FIG. It can be considered that it is easy to bend in an M shape as illustrated in FIG. On the other hand, in the present embodiment, even when the paper 51 is bent in an M shape as described above, the paper 51 can be uniformly extended on the surface of the belt 7.

  The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist of the present invention. For example, as shown in FIG. 8A, the auxiliary guide member 302 is provided over the entire width direction of the inclined surface 301, and protrudes toward the belt 7 from the center in the width direction toward both ends in the width direction. It may be provided in a saddle shape so that the current gradually decreases. In this case, the same effect as in the above embodiment is produced.

  Further, as shown in FIG. 8B, the auxiliary guide member 302 may be provided in a rectangular shape across the entire width direction of the inclined surface 301. In this case, the effect of bringing the paper 51 into contact with the belt 7 from the central portion in the width direction is slightly reduced, but by deforming as shown in FIG.

  Furthermore, although the material which comprises the auxiliary guide member 302 is a PET film comparatively preferable, not only a PET film but a various material can be used if it is a flexible material. Furthermore, the image forming member in the present invention is not limited to the member that forms an image by the electrophotographic method as in the above-described embodiment, and a member that forms an image by various methods such as ink ejection is applied. Can do.

  Further, the auxiliary guide member 302 may be configured such that the amount of protrusion from the lower end of the inclined surface 301 of the auxiliary guide member 302 is greater than 1.5 mm. Further, the inclined surface 301 may be close to a flat surface, or at least such that the central portion in the width direction is not recessed.

1 is a longitudinal sectional view illustrating a configuration of a color laser printer to which the present invention is applied. It is a perspective view showing the structure of the photoconductor unit of the color laser printer. It is a perspective view showing the structure of the pressing member of the color laser printer. It is the elements on larger scale showing the structure of the press member and guide part of the color laser printer. It is an expanded sectional view showing the composition near the above-mentioned guide part. It is a cut end view showing the composition of the guide part in detail. It is explanatory drawing which illustrates operation | movement of the guide part. It is a schematic diagram showing the structure of the modification of the said guide part. It is explanatory drawing explaining the problem of a conventional apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Color laser printer 3 ... Photosensitive unit 6 ... Image forming part 7 ... Belt 30 ... Drum subunit 31 ... Photosensitive drum 40 ... Developing cartridge 51 ... Paper 57 ... Registration roller 59 ... Guide 61 ... Scanner part 62 ... Process part 74 ... Transfer roller 100 ... Pressing member 104 ... Projecting member 300 ... Guide part 301 ... Inclined surface 302 ... Auxiliary guide member

Claims (10)

A belt having a conveying surface for loading and conveying a recording sheet;
An image forming member disposed opposite to the conveying surface of the belt and forming an image on a recording sheet conveyed by the belt;
The belt is opposed to the conveyance surface of the belt, and a contact surface to the recording sheet is formed so as to be closer to the conveyance surface toward the downstream side in the recording sheet conveyance direction. A guide member for guiding toward the surface;
A conveying member that conveys the recording sheet toward the guide member;
A flexible auxiliary guide member attached to the guide member and projecting from the downstream end of the guide member in the recording sheet conveyance direction toward the conveyance surface of the belt;
An image forming apparatus comprising:   The auxiliary guide member protrudes toward the conveyance surface of the belt from the downstream end in the conveyance direction of the guide member at least at a position facing the central portion in the width direction of the recording sheet conveyed to the conveyance member. The image forming apparatus according to claim 1, wherein:   The auxiliary guide member is provided symmetrically with respect to the center in the width direction of the recording sheet conveyed to the conveying member in the width direction, and the width is larger than the width of the recording sheet conveyed to the conveying member. The image forming apparatus according to claim 2, wherein the image forming apparatus is a plate-shaped member configured to be small.   4. The image forming apparatus according to claim 3, wherein the contact surface of the auxiliary guide member with respect to the recording sheet is raised to the recording sheet conveyance path side than the contact surface of the guide member with respect to the recording sheet.   5. The image forming apparatus according to claim 3, wherein the tip of the auxiliary guide member has a dimension in the recording sheet width direction of 40 mm or more. A pressing member that presses the recording sheet guided by the guide member and the auxiliary guide member toward the belt over the entire recording sheet width direction; and
An auxiliary pressing member attached to the pressing member and pressing the recording sheet toward the belt from a gap between the auxiliary guide member and the pressing member;
The image forming apparatus according to claim 3, further comprising:   3. The image forming apparatus according to claim 2, wherein the amount of protrusion of the auxiliary guide member toward the belt side gradually decreases from the center of the recording sheet in the width direction toward both ends.   The image forming apparatus according to claim 1, wherein a contact surface of the guide member with respect to the recording sheet intersects with a conveyance surface of the belt at an angle of 45 ° or more and less than 90 °. .   In the contact surface of the guide member to the recording sheet, the portion facing the central portion in the width direction of the recording sheet is raised toward the recording sheet conveyance path side compared to the portion facing the both ends in the width direction of the recording sheet. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The image forming member is:
A plurality of photosensitive drums on which electrostatic latent images are formed;
A drum frame that supports the plurality of photosensitive drums and is detachable from the image forming apparatus body;
With
The image forming apparatus according to claim 1, wherein the guide member is provided integrally with the drum frame.

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