JP2004264840A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that can shorten the output time (first print-out time) of a 1st sheet and can be made small-sized. <P>SOLUTION: A sheet supply part is arranged at the lowermost part of a printer so as to be substantially horizontal. A main conveyance path for guiding a sheet from a transfer means to a fixing means is arranged in a substantially vertical direction so as to be along the back of the printer. The guide surface of a paper discharge guide constituting a conveyance path extending from the fixing means to a discharge means is plane. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and is particularly suitable for application to an image forming apparatus such as an electrophotographic copying machine, a printer, a word processor, and a facsimile apparatus for forming an image on a recording medium.

  FIGS. 4 and 5 show the configuration of a laser beam printer as an example of an image forming apparatus employing an electrophotographic method or another recording method according to the related art.

  That is, in the laser beam printer according to the prior art, the conveyance path of the recording material from the paper feeding unit to the fixing unit via the transfer unit is set to be substantially horizontal as shown in FIG. As shown in FIG.

  That is, first, in the laser beam printer shown in FIG. 4, on one end side of the apparatus, a paper feed cassette 101 for mounting a recording material and a paper feed roller 102 as paper feed means are provided.

  A transfer roller 103 as a transfer unit is provided at the center of the apparatus, and a fixing device 104 as a fixing unit is provided at the other end.

  A process cartridge 105 as an image forming unit, a laser scanner 106 as a light source, and the like are disposed above the conveying surface of the recording material P. The laser scanner 106 as the light source is configured to include a polygon mirror 106a and a return mirror 106b.

  Further, transport rollers 107a and 107b are disposed downstream of the paper feed roller 102, and are configured to be able to be sent to a nip portion between the transfer roller 103 and the photosensitive drum 108.

  Further, the recording material P that has passed through the nip between the transfer roller 103 and the photosensitive drum 108 is fixed on an image by the fixing device 104, and then is discharged onto the paper discharge tray 110 through the nip of the paper discharge roller pair 109. Is discharged.

  Then, the feeding of the recording material P, the transfer of the visible image (toner image) to the recording material P, and the heating and fixing of the visible image on the recording material P are sequentially performed by the process cartridge 105 and the laser scanner 106 described above. .

  When such a printer is miniaturized, the volume of the printer itself is reduced and the heat capacity is reduced. For this reason, the temperature inside the apparatus is significantly increased due to the heat of the fixing unit, which is a heating element.

  Therefore, some miniaturized printers adopt a configuration in which a fixing unit, which is a heat source, is arranged above the printer so as to increase the heat removal efficiency. Such a product is shown in FIG.

  That is, as shown in FIG. 5, in this image forming apparatus, a paper feed cassette 201 as a paper feed unit and a paper feed roller 202 as a paper feed unit are provided on the lower side, and a transfer unit as a transfer unit is provided in the center. Is provided, and a fixing device 204 as a fixing unit is provided on the upper side.

  Further, by providing a louver on the upper side or side surface of the exterior 205 covering the fixing device 204, the heat generated by the fixing device 204 can be efficiently discharged outside the apparatus.

  Then, the process cartridge 206 serving as an image forming unit and the laser scanner 207 having a polygon mirror 207a and a return mirror 207b serving as an optical unit are placed at substantially the same height as or lower than the fixing unit 204 serving as a fixing unit. The recording medium P is arranged, and the feeding of the recording material P, the transfer of the developed image to the recording material P, and the heating and fixing of the developed image on the recording material P are sequentially performed.

  After the image is fixed by the fixing device 204, the recording material P passes through a curved discharge guide to be in a posture in which the printing surface is turned down, and is discharged onto a discharge tray 209 by a pair of discharge rollers 208. Paper. In the image forming apparatus shown in FIG. 5, transport rollers 210a and 210b and a photosensitive drum 211 are provided downstream of the paper feed roller 202, and a motor 212 is further provided.

There is also a configuration in which a recording material is discharged upward from a fixing device, guided by a curved discharge guide, and discharged from the apparatus main body (for example, see Patent Document 1).
JP 2001-337499 A

  In the printer as described above, it is always desired to increase the speed. In particular, in order to reduce the time required for outputting the first sheet (first printout time), it is effective to shorten the transport path from the feeding of the recording material to the discharge of the recording material.

  In the conventional image forming apparatus shown in FIGS. 4 and 5, the discharge tray is arranged at an acute angle with respect to the transport path. Therefore, the recording material P after passing through the fixing unit is discharged to the discharge tray with the print surface facing down along the curved discharge guide.

  Therefore, in order to shorten the paper ejection guide, the radius of curvature must be reduced. However, if the paper ejection guide is configured with a small radius of curvature, there are adverse effects such as an increase in sliding noise when the recording material passes therethrough, and a tendency that the recording material is easily caught by the paper ejection guide.

  For this reason, the paper ejection guide after being fixed by the fixing means must have a gentle radius, and it is difficult to shorten the conveyance path by shortening the paper ejection guide.

  Also, in the technology disclosed in Japanese Patent Application Laid-Open No. H11-157, the discharge guide downstream of the fixing device has a curved shape, so that a large radius of curvature is required to prevent the recording material from being caught by the discharge guide. Therefore, there is a problem that it takes a long time for the fixed recording material to enter the discharge roller pair, and the first printout time becomes long. In addition, as printers become smaller, the space between product components such as paper feeding means, fixing means, and process cartridges, and the minimum required space such as the recording material transport path and the attachment / detachment trajectory of the process cartridge, and the product exterior Need to be as short as possible.

  Accordingly, it is an object of the present invention to provide an image forming apparatus which can solve the above-described problem and can shorten the output time (first printout time) of the first sheet and can be downsized. is there.

  In order to achieve the above object, an image forming apparatus according to the present invention is provided such that a sheet mounting portion for mounting a sheet, which is disposed substantially horizontally at a lower portion of an apparatus main body, and is mounted on the sheet mounting portion. A sheet feeding unit for feeding a sheet, an image carrier for carrying an image, a transfer unit for transferring the image carried on the image carrier to a printing surface of a sheet, and an image transferred by the transfer unit. Fixing means for fixing the printed surface of the sheet, discharging means for discharging the sheet on which the image has been fixed by the fixing means, and a substantially vertical direction disposed on the back side of the apparatus body, wherein the fixing means is provided from the sheet conveying means. A main conveyance path for guiding the sheet to the means, and a paper discharge guide having a guide surface for guiding the sheet by contacting the sheet and constituting a conveyance path from the fixing means to the paper discharge means. , Of the discharge guide Ido surface is a plane.

  According to the present invention, it is possible to provide an image forming apparatus that can shorten the output time (first printout time) of the first sheet and can be downsized.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all the drawings of the following embodiment, the same or corresponding parts are denoted by the same reference numerals. FIG. 1 shows a laser beam printer as an example of the image forming apparatus according to the embodiment.

  In the laser beam printer according to this embodiment, an electrophotographic method is used in which a photosensitive member as an image carrier is irradiated with a laser beam, and the laser beam is scanned and recorded.

  That is, as shown in FIG. 1, in the laser beam printer according to this embodiment, a sheet feeding unit 1 as a sheet placing unit, a sheet feeding roller 2 as a sheet feeding unit, conveyance rollers 3a and 3b, a registration sensor 4, a laser scanner 5 as an optical unit and a process cartridge 6 as an image forming unit are provided.

  In the laser beam printer illustrated in FIG. 1, a plurality of recording materials P are stacked in a paper feeding unit 1. These recording materials P are separated and fed one by one by a sheet feeding roller 2 disposed on the back side (the left side in FIG. 1) of the sheet feeding unit 1, and are conveyed to a transfer unit by conveyance rollers 3a and 3b. Conveyed. Here, the direction in which the user faces when the user sets the recording material P in the sheet feeding unit 1 is referred to as the back side, and the side opposite to the back side and the front side. In the present embodiment, as will be described later, the left side of FIG. 1 is the back side and the right side is the front side for the user to set a sheet from the right side of FIG.

  The registration sensor 4 is a sensor for synchronizing the position of the leading end of the recording material P with the light emission timing of the laser scanner 5 as an exposure light source and drawing an image from a predetermined position on the recording material P.

  Further, the process cartridge 6 is configured integrally with process means such as a photoreceptor 7 as an image carrier, a developing device 8 including a development carrier, a charging roller 9 and a cleaner 10, and is detachably attached to a printer. ing.

  The transfer roller 11 as a transfer unit is a roller for transferring a visible image on the photoconductor 7 onto the recording material P.

  Further, the fixing device 12 as a fixing unit is for heating and fixing a visible image on the recording material P. The fixing device 12 includes a pressure roller 12a rotatably supported and a heater unit 12b including a heating element. The pressure roller 12a and the heater unit 12b are provided so that the nip line F of the fixing device 12 is inclined to the front side. In the present invention, the fixing nip line F of the fixing device 12 is a tangent line of the pressure roller 12a at a contact point between the pressure roller 12a and the heater unit 12b.

  A discharge guide 13 is provided downstream of the fixing device 12 in the recording material conveyance direction. The discharge guide 13 has a plurality of discharge ribs 13b in the depth direction of the drawing. The discharge rib 13b has a discharge guide surface 13a formed flat. A discharge roller pair 14 is provided immediately downstream of the transport guide 13.

  The nip of the discharge roller pair 13 is located on a substantially extended surface of the discharge guide surface 13 a of the discharge guide 13.

  On the upper surface of the apparatus main body, a paper discharge tray 16 for receiving the recording material discharged by the discharge roller pair is provided. The paper discharge tray 16 also serves as an exterior of the apparatus main body.

  The recording material P placed on the paper feed unit 1 is fed by the paper feed roller 2 and is transported upward by the transport rollers 3a and 3b. The transfer roller 11 transfers the visible image on the photoconductor 7 to the sheet conveyed by the conveying rollers 3a and 3b. The recording material P on which the developed image has been transferred is conveyed while being sandwiched between the pressure roller 12a and the heater unit 12b. At that time, the visible image is fixed on the recording material P.

  The recording material P on which the developed image is fixed is guided by a discharge guide surface 13a of a discharge guide 13 provided from the fixing device 12 to the discharge roller pair 14. That is, the recording material P discharged from the fixing device 12 is bent toward the printing surface side by contacting the flat paper discharge guide surface 13a. Thereafter, the sheet is discharged onto a discharge tray 16 formed integrally with the outer cover 15 with the print surface facing down by a discharge roller pair 14 as discharge means including only a pair of discharge rollers. After the recording material P is discharged from the fixing device 12, the recording material P contacts only the paper discharge guide surface 13a before reaching the discharge roller pair 14. Here, the printing surface of the recording material P is a surface in contact with the photoconductor 7. That is, the printing surface of the recording material P is the right surface of the recording material being conveyed along the main conveyance path M in FIG.

  When the nip of the discharge roller pair 14 is located on an extended surface of the discharge guide surface 13a which is a flat surface as in the present embodiment, the fixing device 12 is compared with a case where the nip is guided by a curved guide. The first copy time can be shortened in order to shorten the transport distance until the recording material P discharged from the printer reaches the nip of the discharge roller pair 14. Further, since the recording material P is directly guided to the nip of the discharge roller pair by the discharge guide 13, the occurrence of a jam or the like can be prevented.

  In this embodiment, as shown in FIG. 1, the main conveyance path M that guides the recording material from the paper feed roller 2 to the transfer roller 11 and the fixing device 12 is substantially vertical with the fixing device 12 at the top. Are arranged in a straight line.

  Since the fixing device 12 is disposed at the uppermost portion of the main transport path M, heat generated from the fixing device 12 is transmitted from a louver portion (not shown) formed on the outer cover 15 to the outside of the apparatus. Is discharged.

  The heat generated from the heat source goes upward. Therefore, the heat generated from the fixing device 12 hardly affects the process cartridge 6 and the laser scanner 5 arranged below or horizontally with respect to the fixing device 12. Therefore, a good output image can always be obtained.

  In the image forming apparatus according to the embodiment, the main transport path M is provided substantially in parallel with the rear surface (rear surface) of the apparatus main body and substantially vertically close to the rear surface of the printer. With this configuration, the sheet feeding unit 1 provided on the bottom surface side of the apparatus main body and the paper discharge tray 16 provided on the upper surface side of the apparatus main body and forming the exterior can be located further inside the apparatus main body. It becomes. As a result, the amount of protrusion of the paper feeding unit 1 and the discharge tray 16 toward the front side is reduced, and the installation area of the apparatus main body can be reduced.

  In this embodiment, a paper feed cover 17 that can be opened and closed is provided on the front side of the paper feed unit 1. When the paper supply cover 17 is opened to the front side, the recording material P can be placed on the paper supply cover 17 and can be closed when not in use.

  Then, the main transport path M is moved toward the back side of the apparatus main body, and the amount of protrusion from the front of the paper feeding unit 1 is reduced, so that the paper feeding cover 17 can be made smaller. The size can be reduced.

  The image forming apparatus according to the embodiment further includes a motor 18 and an optical stay 19.

  In the image forming apparatus according to the embodiment configured as described above, the sheet feeding unit 1 is configured to be substantially horizontal, and the recording material P separated from the sheet feeding unit 1 by the sheet feeding roller 2 is After being bent in a direction of about 90 °, the sheet is conveyed substantially vertically upward along the main conveyance path M.

Then, by increasing the angle theta ₁ of the conveying path this direction from the sheet feeding unit 1 and the sheet feeding roller 2 to the transfer roller 11, it is possible to reduce the force to bend the recording material. This makes it possible to convey a thicker and thicker recording material, and to reduce the sliding noise of the recording material P during conveyance.

However, if the angle θ ₁ is increased to an obtuse angle, the front side (the right side in FIG. 1) of the paper supply unit 1 will be lowered, or the conveyance path from the paper supply roller 2 to the transfer roller 11 will be the back side (in FIG. 1). (Left side). Therefore, the size of the printer in the vertical direction or the depth direction becomes large.

  Therefore, in this embodiment, the paper feed unit 1 is disposed substantially horizontally, and the angle formed by the paper feed unit 1 and the main transport path M from the paper feed roller 2 to the transfer roller 11 is set to about 90 °. The paper unit 1 and the main transport path M are arranged close to the bottom and back of the image forming apparatus, respectively. As a result, it is possible to achieve a balance between securing the sheet feeding performance and reducing the size of the printer.

  Further, the recording material P after passing through the transfer roller 11 is conveyed in a substantially vertical direction as described above, and enters the fixing device 12. Here, in the fixing device 12, the heater unit 12b is brought into contact with the pressure roller 12b with a predetermined pressure, and when the recording material P passes between the pressure roller 12a and the heater unit 12b, heat and pressure are applied. The image on the surface is fixed.

  In this embodiment, the nip of the fixing device 12 is arranged so as to be inclined such that the heater unit 12b side is below the pressure roller 12a. When the recording material P passes through the fixing device 12, the recording material P is bent toward the printing surface with respect to the main transport path M. Therefore, the inclination of the paper discharge guide 13 with respect to the main transport path can be increased, and the height from the fixing device 12 to the discharge roller pair 14 can be reduced.

  In addition, by making the main transport path M from the paper feeding means to the fixing means substantially vertical, not only the angle formed by the main transport path M and the paper discharge tray 16 is reduced, but also the nip of the fixing device 12 is reduced. Since the line F is inclined, the angle at which the recording material P is bent by the paper ejection guide 13 can be reduced.

  Therefore, the paper ejection guide 13 can be constituted by a plurality of ribs along the conveyance direction on a plane that is short and does not have a curved portion, so that it is possible to reduce the size and the shape of the component and reduce the cost of the component. Thus, the generation of the rubbing noise with the recording material can be reduced.

  When the discharge guide 13 is shortened, the recording material can be discharged onto the discharge tray 16 by using only one of the plurality of discharge roller pairs, so that the roller pair, the bearing, and the roller are driven. And a plurality of components such as a spring for biasing the pair of gears and rollers can be reduced, and the cost can be significantly reduced.

  Also, by shortening the transport path, the time required from paper feeding to paper discharging can be shortened even at the same printing speed. In this embodiment, the transport distance from the nip center of the fixing device 12 to the nip of the discharge roller pair 14 can be reduced to 50 mm or less.

  When the recording material P passes through the fixing nip, the moisture on the printing surface heated by the heater unit 12b instantaneously dries, and the opposite surface dries slowly. Curling (vertical curling) as an axis is likely to occur. In order to prevent this, in the present embodiment, the paper ejection guide 13 with which the recording material P comes into contact immediately after passing through the fixing device is inclined with respect to the nip of the fixing device 11, and the direction perpendicular to the conveyance direction of the recording material P is set as the axis. By giving a curl (lateral curl), the curl of the recording material after the sheet is discharged is removed.

Table 1 includes a angle theta ₄ between the nip line and the sheet discharge guide guide surface of the fuser, it illustrates the relationship between the curl direction and the curl amount of recording material after the sheet discharge. In the item of the curl amount in Table 1, ○ indicates that the curl amount is small, Δ indicates that the curl amount is medium, and x indicates that the curl amount is large.

  As shown in Table 1, when the angle of the guide surface 13a of the discharge guide with respect to the fixing nip line F of the fixing device 12 is small, the recording material P after the discharge has a curl in the vertical direction, and the discharge guide is inclined. Later, a horizontal curl occurs gradually. Further, when the recording material is thick and has high rigidity, horizontal curl due to bending of the paper ejection guide is likely to occur. As shown in Table 1 showing the experimental results, if the angle of the discharge guide surface 13a of the discharge guide 13 with respect to the nip line F of the fixing device 12 is in the range of 15 ° to 30 °, the curl correction is performed between the thick paper and the plain paper. It can be seen that is possible. In the present embodiment, the curl correction of the recording material after the discharge and the reduction in the height of the main body are both achieved by inclining the discharge guide angle by about 25 ° with respect to the fixing nip.

Also, if too large an angle theta ₃ between the nip line F and the main transport M of the fixing device 12, the behavior of the recording material before entering the fixing nip becomes violent, it is possible that the unfixed image is disturbed . On the other hand, when the fixing device 12 nip line F and the main conveying path M and the angle theta ₃ is small, the bending amount because itself is reduced, the angle theta ₂ is small becomes apparatus of the sheet discharge guide 13 with respect to the main conveying path M The height of the body increases. Considering the size of the image and the apparatus main body, the angle theta ₃ between the nip line F and the main conveying surface M of the fixing device 12 is preferably in the range of angles of 10 ° or more than 35 °. Therefore, in this embodiment, the angle theta ₃ between the fixing nip and the main conveying path M is, for example, 25 °.

From the relationship between the tilt and the sheet discharge guide slope of the nip line F of the fixing device 12, the angle theta ₂ between the main conveying path M of the sheet discharge guide surface 13a and the main conveying path M of the sheet discharge guide 13 25 ° or more What is necessary is just to set to 65 degrees. However, reducing the angle theta ₂ of the guide surface 13a of the sheet discharge guide 13 and the main conveying path M, the height direction becomes large apparatus. Given the height of the apparatus main body, it is preferable that the angle theta ₂ of the discharge guide surface 13a and the main conveying path M of the sheet discharge guide 13 to 40 ° or more. That is, the angle theta ₂ of the discharge guide surface 13a and the main conveying path M of the paper guide 13 is desirably 40 ° or more 65 ° or less, in this one embodiment, be about 50 °.

  Next, a case of the laser beam printer according to the embodiment will be described. 2 and 3 show a housing of the laser beam printer.

  As shown in FIGS. 2 and 3, the housing of the laser beam printer according to this embodiment includes an optical stay 19 made of sheet metal for holding the laser scanner 5, side plates 20 and 21 made of sheet metal, and transport rollers 3a and 3b. And a transfer plate 22 made of resin for holding transfer means such as the transfer roller 11 and a bottom plate 23 below the sheet feed means.

  The optical stay 19, the transport plate 22, and the bottom plate 23 are fixed between the left and right side plates 20, 21 with screws. Further, a drive cover 24 is attached to an outer surface of the side plate 20 with a screw at an attachment portion 24a.

  Further, as shown in FIG. 2, the laser scanner 5 according to the embodiment is configured to transfer a transfer unit such as a transfer roller 11 from a paper feed unit such as a paper feed unit 1 and a paper feed roller 2 by conveying rollers 3a and 3b. It is disposed at a position facing a so-called main transport path M (sheet feeding unit to transfer unit to fixing unit), which passes through to a fixing unit 12 as a fixing unit, and above the sheet feeding unit 1.

  By arranging the laser scanner 5 in this manner, it is possible to irradiate the photosensitive member 7 with laser light in a direction substantially perpendicular to the main transport path M.

  Further, since the laser scanner 5 can be kept away from the fixing device 12 which is a heat source, there is an advantage that the laser scanner 5 is hardly affected by the heat from the fixing device 12.

  In the image forming apparatus according to this embodiment, the laser scanner 5 is not provided with a folding mirror as in the related art. The laser scanner 5 is arranged substantially horizontally on the front side of the apparatus. Thereby, the scanner motor 5b for rotating the polygon mirror 5a can be set in a horizontal state.

  Therefore, it is possible to prevent a load from acting on the bearing of the scanner motor 5b. Therefore, it is possible to suppress the occurrence of problems such as shortening of the life of the scanner motor 5b due to scraping of the bearing, and it is possible to use the scanner motor 5b for a long time.

  Here, the laser light scanned by the polygon mirror 5a is adjusted to a predetermined spot diameter by a lens (not shown), and then reaches the surface of the photoconductor 7. In addition, since the polygon mirror 5a and the photoconductor 7 can be aligned straight without providing a folding mirror, the laser light path length Lr is dominant in the depth of the printer (in the horizontal direction in FIG. 1).

  In this embodiment, the diameter of the photoconductor 7, the horizontal size of the transfer roller 11 and the like, and the distance from the center of the polygon mirror 5a to the front of the image forming apparatus are reduced. Therefore, the depth dimension D of the printer is set to 1.5 times or more and 2 times or less of the laser light path length Lr. The rear end side of the recording material P placed in the paper feeding unit 1 in the feeding direction is supported by an openable and closable paper feed cover 17 so as to be dimensioned in the horizontal direction (front-rear direction) of the apparatus main body. Can be shortened.

  As shown in FIGS. 2 and 3, the laser scanner 5 is fixed substantially at the center of the optical stay 19 supported by the right side plate 20 and the left side plate 21. There is space between them. Therefore, the motor 18 as a drive source is disposed inside the right side plate 20, and a pinion gear (not shown) is fixed to the outside of the right side plate 20 by a screw so as to protrude.

  Further, since the laser scanner 5 and the motor 18 are arranged so as to overlap with each other in the direction of the rotation axis of the photoreceptor 7, it is not necessary to newly provide a motor installation place, and it is possible to reduce the size in the cross-sectional direction. it can.

  Further, since the motor 18 is disposed inside the right side plate 20, only the thickness of the gear train meshing with the pinion gear (not shown) is provided on the outside, so that the apparatus body can be downsized in the width direction. be able to.

  Further, by disposing the fixing device 12 and the motor 18 at the upper corner of the printer so as to disperse the heat source, it is possible to avoid a local temperature rise.

  In such a configuration, the attachment / detachment of the process cartridge 6 is performed by opening the discharge tray 16 and in an upper portion between the transport path and the laser scanner 5. As a result, the distance from the opening formed by opening the discharge tray 16 to the process cartridge can be shortened, so that the accessibility to the cartridge is improved, which is preferable in terms of usability.

  An optical cover is provided between the right side plate 20 and the left side plate 21 so as to cover the laser scanner 5 and the motor 18.

  As a result, since there is no convex portion due to the motor 18 in the attachment / detachment trajectory of the process cartridge, not only can the entire conveyance path be overlooked when the process cartridge is removed at the time of jam clearance, but also the recording that has caused a paper jam. When removing the material, since there is no convex portion with which the user's hand comes in contact, it is possible to improve the jam removability.

  As described above, one embodiment of the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.

  For example, the numerical values given in the above embodiment are merely examples, and different numerical values may be used as needed.

  The fixing device 12 includes a pressure roller 12a rotatably supported as a fixing unit and a heater unit 12b including a heating element. However, a heating roller having a heating element and a pressure roller pressed against the heating roller are used. A pair of rollers (a pair of rotating bodies) may be configured by the rollers, and the recording material may be nipped and conveyed by the pressing roller and the heat roller.

  In this embodiment, a laser printer is described as an example of the configuration of the image forming apparatus. However, the present invention is not necessarily limited to a laser printer, and can be applied to a copying machine, a facsimile, a monochrome copying machine, and the like. .

  As described above, the paper feeding unit is disposed substantially horizontally at the lower portion of the housing, and the main conveyance path including the paper feeding unit, the transfer unit, and the fixing unit is substantially vertically close to the rear side of the housing. The image forming apparatus is disposed above the fixing unit, and the discharge guide is formed on the printing surface side of the recording material on a printing surface side of the recording material, the flat surface being inclined at an angle range of 40 ° to 65 °. Therefore, the height of the image forming apparatus can be kept low, and a curved portion can not be provided in the paper ejection guide, so that the image forming apparatus can be made thinner and smaller.

  In addition, since the nip of the fixing unit is inclined at an angle of 10 ° or more and 30 ° or less with respect to the main transport path, it is possible to smoothly transfer the recording material from the main transport path to the discharge guide. Therefore, the sliding noise can be reduced.

  Further, by shortening the length of the paper ejection guide to 50 mm or less, the time for the recording material to pass through the paper ejection guide can be shortened, and the first printout time can be shortened.

  Further, since only one pair of discharge rollers is used, gears and bearings for driving the rollers are not required, thereby reducing the cost of the apparatus.

  In addition, since the optical unit is configured without the folding mirror, the optical unit with a reduced number of components can be horizontally disposed at a position distant from the fixing unit, so that the heat of the fixing unit can be reduced. In addition to being less affected, the wear resistance of the bearing of the scanner motor that rotates the polygon mirror can be improved.

  Further, the depth of the image forming apparatus is set to be 1.4 to 2 times the distance from the rotation center of the polygon mirror in the optical means to the surface of the photoreceptor, and the latter half of the sheet feeding unit outside this range can be opened and closed. With this configuration, the depth of the apparatus can be reduced by closing the cover when not in use.

FIG. 1 is a sectional view showing an image forming apparatus according to an embodiment of the present invention. FIG. 1 is a perspective view showing a main part of an image forming apparatus according to an embodiment of the present invention. FIG. 1 is a perspective view showing a main part of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating an image forming apparatus according to the related art. FIG. 3 is a cross-sectional view illustrating an image forming apparatus according to the related art.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Paper feed part 2 Paper feed roller 3a, 3b Transport roller 4 Registration sensor 5 Laser scanner 5b Scanner motor 5a Polygon mirror 6 Process cartridge 7 Photoconductor 8 Developing device 9 Charging roller 10 Cleaner 11 Transfer roller 12 Fixing device 12a Pressure roller 12b Heater unit 13 Discharge guide 13a Rib 14 Discharge roller pair 15 Exterior cover 16 Discharge tray 17 Cover 18 Motor 19 Optical stay 20, 21 Side plate 22 Transport plate 23 Bottom plate 24 Drive cover 24a Mounting portion

Claims (11)

For placing a sheet, a sheet placing portion arranged substantially horizontally at a lower portion of the apparatus main body,
Sheet feeding means for feeding a sheet placed on the sheet placing portion,
An image carrier for carrying an image,
Transfer means for transferring the image carried on the image carrier to the printing surface of the sheet,
Fixing means for fixing the image transferred by the transfer means to the printing surface of the sheet,
Discharging means for discharging the sheet on which the image is fixed by the fixing means,
A main conveyance path that is arranged in a substantially vertical direction on the back side of the apparatus main body and guides a sheet from the sheet feeding unit to the fixing unit;
A sheet guide that has a guide surface that guides the sheet by contacting the sheet, and that constitutes a conveyance path from the fixing unit to the discharge unit.
An image forming apparatus, wherein a guide surface of the discharge guide is flat.   The image forming apparatus according to claim 1, wherein a guide surface of the discharge guide is inclined at an angle of 40 ° or more and 65 ° or less with respect to a printing surface of the sheet with respect to the main transport path. .   The guide surface of the discharge guide is inclined at an angle of 15 ° or more and 30 ° or less with respect to the printing surface of a sheet with respect to a nip line of the fixing unit. Image forming device.   4. The fixing device according to claim 1, wherein a nip line of the fixing unit is inclined at an angle of 10 ° to 35 ° with respect to the printing surface of the sheet with respect to the main transport path. 2. The image forming apparatus according to claim 1. The discharge means has a pair of discharge rollers,
5. The image forming apparatus according to claim 1, wherein a conveyance distance from a nip of the fixing unit to a nip of the discharge roller pair is 50 mm or less. 6. The discharge means has a pair of discharge rollers,
5. The image forming apparatus according to claim 1, wherein a nip of the discharge roller pair is located on a substantially extended surface of a guide surface of the discharge guide. 6. Having optical means for irradiating the image carrier with light,
7. The apparatus according to claim 1, wherein the optical unit is arranged so as to irradiate the light at substantially a right angle to the main transport path above the sheet placement unit on the front side of the apparatus main body. The image forming apparatus according to claim 1. The optical means has a polygon mirror,
The image forming apparatus according to claim 7, wherein an optical path from the polygon mirror to the image carrier is in one plane. A housing that holds the transfer unit and the fixing unit,
9. The device according to claim 8, wherein a size of the housing along a depth direction is 1.4 times or more and 2 times or less of a distance from a rotation center of the polygon mirror to a surface of the image carrier. Image forming apparatus. The sheet placement unit has a paper feed cover that can be opened in the front direction of the apparatus body,
10. The sheet feeder according to claim 1, wherein a rear end side of a sheet placed on the sheet placing portion in a sheet feeding direction by the sheet feeding unit is supported by the sheet feeding cover. An image forming apparatus according to claim 1.   The image forming apparatus according to claim 10, wherein the size along the depth direction of the housing is a distance from a front surface to a rear surface of the housing when the sheet feeding cover is closed. .

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