Patent Publication Number: US-10788786-B2

Title: Image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an image forming apparatus, and more particularly, relates to an image forming apparatus including a sheet guide that guides a sheet to a transfer nip area, and also including a development unit and a transfer unit. 
     Description of the Background Art 
     Japanese Unexamined Patent Application Publication No. 2007-225829 discloses an example of an image forming apparatus in the background art. The image forming apparatus in the background art includes a pre-transfer guide that guides a sheet conveyed to the transfer position to a better transfer position, and the pre-transfer guide includes a front surface guide member that guides the front surface of the sheet, and a back surface guide member arranged to face the front surface guide member across a sheet conveyance path. The front surface guide member is made of a conductive material and is grounded through a conductive member. Further, the front surface guide member and the back surface guide member are configured to abut against each other at protrusions formed outside an area of the back surface guide member through which the sheet passes. 
     In recent years, with miniaturization of image forming apparatuses, a sheet conveyance path has become shorter, and this causes a problem that static electricity charged on a conveyed sheet fails to be sufficiently eliminated before the sheet reaches a transfer position, resulting in transfer defects. 
     Therefore, there is a type of image forming apparatus in which a conductive member for static elimination is provided in each of a development unit at a printing side and a transfer unit at a non-printing side to efficiently eliminate static electricity charged on a paper surface. In this case, it is desirable to electrically conduct the conductive member at a side of the development unit and the conductive member at a side of the transfer unit to stabilize the surface potential of the sheet. 
     However, since the development unit and the transfer unit are mounted in the image forming apparatus separately and also the direction in which the development unit and the transfer unit are attached to and detached from the image forming apparatus is different, there is a problem that a configuration for electrically conducting the conductive member at the side of the development unit and the conductive member at the side of the transfer unit is complicated. 
     Therefore, a main object of the present invention is to provide a novel image forming apparatus. 
     Another object of the present invention is to provide an image forming apparatus capable of providing reliable conduction between a conductive member at the side of the development unit and a conductive member at the side of the transfer unit to suppress or prevent transfer defects. 
     SUMMARY OF THE INVENTION 
     A first invention is an image forming apparatus including an apparatus main body, a development unit, a transfer unit, a first guide member, and a second guide member. The development unit includes an image carrier on which a toner image is formed, and is attached to and detached from the apparatus main body in a longitudinal direction of the image carrier. The transfer unit is placed to face the image carrier, includes a transfer roller that transfers the toner image onto a paper sheet, and is attached to and detached from the apparatus main body in a direction in which the image carrier and the transfer roller face each other. The first guide member is provided in the transfer unit, guides the paper sheet to a transfer nip area formed by the image carrier and the transfer roller, and has conductivity. The second guide member is provided in the development unit, is placed to face the first guide member, guides the paper sheet to the transfer nip area, and has conductivity. At least one of the first guide member and the second guide member is grounded. Further, the image forming apparatus includes an elastic member that is provided between the first guide member and the second guide member, is placed outside a sheet passing area through which the paper sheet passes, and electrically connects the first guide member and the second guide member. The elastic member is elastically deformable in an attaching and detaching direction of the development unit and in an attaching and detaching direction of the transfer unit. 
     A second invention is dependent on the first invention, wherein the elastic member is a plate spring. 
     A third invention is dependent on the first or second invention, wherein the elastic member is provided on the front side in the insertion direction of the development unit from the sheet passing area. 
     A fourth invention is dependent on any one of the first to third inventions, wherein the elastic member is provided integrally with the second guide member. 
     A fifth invention is dependent on the fourth invention, wherein the elastic member includes a first incline that inclines to approach the first guide member as the first incline moves toward a back side in the insertion direction of the development unit, and a second incline that is formed on the back side of the first incline in the insertion direction of the development unit and inclines to approach the second guide member as the second incline moves toward the back side in the insertion direction of the development unit, and a coupling portion between the first incline and the second incline of the elastic member abuts against the first guide member. 
     A sixth invention is dependent on any one of the first to fifth inventions, wherein the image forming apparatus further includes an urging member that is provided in the transfer unit and that urges the second guide member in a direction toward the development unit. 
     According to the present invention, it is possible to provide reliable conduction between the conductive member at the side of the development unit and the conductive member at the side of the transfer unit to suppress or prevent transfer defects. 
     The above object, other objects, features, and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustrative view illustrating a simplified configuration of an image forming apparatus according to a first embodiment of the present invention, when viewed from the front; 
         FIG. 2  is an illustrative view illustrating attaching and detaching directions of a development unit and a transfer unit; 
         FIG. 3  is a perspective view illustrating a structure of the transfer unit; 
         FIG. 4  is a front view illustrating the structure of the transfer unit in  FIG. 3 ; 
         FIG. 5  is a perspective view illustrating a structure of the development unit; 
         FIG. 6  is a front view illustrating the structure of the development unit in  FIG. 5 ; 
         FIG. 7  is an illustrative view illustrating a configuration of a second guide member; 
         FIG. 8A  is a right side view illustrating a configuration of an elastic portion; 
         FIG. 8B  is a front view illustrating the configuration of the elastic portion; 
         FIG. 8C  is a bottom view illustrating the configuration of the elastic portion; 
         FIG. 9  is an illustrative view illustrating a relationship between a first guide member and the second guide member; and 
         FIG. 10  is an illustrative view illustrating a configuration of an elastic portion according to a second embodiment and a relationship between the first guide member and the second guide member. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       FIG. 1  is an illustrative view illustrating a simplified configuration of an image forming apparatus  10  according to a first embodiment of the present invention.  FIG. 2  is an illustrative view illustrating attaching and detaching directions of a development unit  64  and a transfer unit  42 . The image forming apparatus  10  illustrated in  FIG. 1  is a multifunctional apparatus having a copying function, a printer function, a scanner function, a facsimile function, and the like, and forms a monochrome image on a recording medium by an electrophotographic method. It is noted that, as a recording medium, a paper sheet, an overhead projector sheet, or the like can be used, but a case where a paper sheet is used will be described below. 
     In this specification, the left side is defined as the left direction, and the right side is defined as the right direction in the horizontal directions when the image forming apparatus  10  is viewed from the front. Further, the front side of the image forming apparatus  10  is defined as the head direction (front direction), and the back side of the image forming apparatus  10  is defined as the rear direction (back direction) in the depth directions when the image forming apparatus  10  is viewed from above (below). 
     First, a configuration of the image forming apparatus  10  will be schematically described. As illustrated in  FIG. 1 , the image forming apparatus  10  includes: an apparatus main body  12  including an image former  30 ; and an image reading device  14  placed above the apparatus main body  12 . 
     The image reading device  14  includes a document platen  16  formed of a transparent material. A document pressing cover  18  is attached above the document platen  16  through a hinge or the like to be freely opened and closed. A document feed tray  20  is provided on the upper surface of the document pressing cover  18 , and an automatic document feeder (ADF) is provided therein. The ADF automatically feeds documents placed on the document feed tray  20  one by one to an image reading position  22  and discharges them to a document discharge tray  24 . 
     Further, an image reader  26  built in the image reading device  14  includes a light source, a plurality of mirrors, an imaging lens, a line sensor, and the like. The image reader  26  exposes a document surface with a light source, and guides reflected light reflected from the document surface to the imaging lens by a plurality of mirrors. Then, the reflected light is imaged on a light receiving element of the line sensor by the imaging lens. The line sensor detects the luminance and chromaticity of the reflected light imaged on the light receiving element, and image data is generated based on the image on the document surface. As the line sensor, a charge coupled device (CCD), a contact image sensor (CIS), or the like is used. 
     An operation panel (not illustrated) that receives an input operation such as a print instruction from a user is provided on the front side of the image reading device  14 . The operation panel has a display with a touch panel, a plurality of operation buttons, and the like. 
     Further, the apparatus main body  12  is provided with a controller (not illustrated) including a CPU, a memory, and the like. The controller transmits a control signal to each part of the image forming apparatus  10  based on an input operation to the operation panel, or the like, and causes the image forming apparatus  10  to execute various operations. 
     The image former  30  includes an exposure unit (light scanning unit)  32 , a developing device  34 , a photoreceptor drum  36 , a cleaner unit (cleaning unit)  38 , a charging unit  40 , the transfer unit  42 , a fixing unit  44 , a toner supply device  46 , and the like, forms an image on a paper sheet conveyed from a sheet feed tray  48  and the like, and discharges the paper sheet on which the image has been formed to a sheet discharge tray  50 . For image data for forming an image on a paper sheet, image data read by the image reader  26  or image data transmitted from an external computer is used. 
     The photoreceptor drum  36  is an image carrier in which a photosensitive layer is formed on the surface of a cylindrical base body having conductivity, and is configured to be rotated about its axis by a rotation drive source (not illustrated) such as a motor. The charging unit  40  charges the surface of the photoreceptor drum  36  to a predetermined potential. The exposure unit  32  is configured as a laser scanning unit (LSU) having a laser emitter, a reflection mirror, and the like, and exposes the charged surface of the photoreceptor drum  36  to form an electrostatic latent image corresponding to image data on the surface of the photoreceptor drum  36 . The developing device  34  includes a developing tank for containing toner, supplies the toner to the surface of the photoreceptor drum  36 , and visualizes the electrostatic latent image formed on the surface of the photoreceptor drum  36  with the toner (forms a toner image). It is noted that a toner concentration detection sensor for detecting a toner concentration is provided inside the developing tank. If the toner concentration detected by the toner concentration detection sensor becomes lower than a predetermined value, toner is supplied from the toner supply device  46  to the developing tank. The cleaner unit  38  includes a cleaning blade abutting against the surface of the photoreceptor drum  36  and removes toner remaining on the surface of the photoreceptor drum  36  after development and image transfer. 
     However, in the image forming apparatus  10  of the first embodiment, the developing device  34 , the photoreceptor drum  36 , the charging unit  40 , and the cleaner unit  38  are further unitized, and a development unit  64  including them is provided to be attachable to and detachable from the apparatus main body  12 . Further, as illustrated in  FIG. 2 , the development unit  64  can be attached to and detached from (inserted into and removed from) the apparatus main body  12  in the longitudinal direction (front-rear direction) of the photoreceptor drum  36  (development unit  64 ). 
     Returning to  FIG. 1 , the transfer unit  42  is a unit that is placed on the right side of the development unit  64  and transfers a toner image formed on the surface of the photoreceptor drum  36  onto a paper sheet. The transfer unit  42  includes a transfer roller  422 . The transfer roller  422  is placed to face the photoreceptor drum  36  and is provided to press the photoreceptor drum  36 . At the time of image formation, a predetermined voltage is applied to the transfer roller  422  to form a transfer electric field between the photoreceptor drum  36  and the transfer roller  422 . Then, the effect of the transfer electric field causes the toner image formed on the outer peripheral surface of the photoreceptor drum  36  to be transferred to a paper sheet while the paper sheet passes through a nip area (transfer nip portion) between the photoreceptor drum  36  and the transfer roller  422 . 
     The transfer unit  42  is fixed to a right cover (not illustrated) provided on the right side surface of the apparatus main body  12 . The right cover is provided to be pulled out to the right. That is, the right cover is provided to be openable and closable in the left-right direction with respect to the apparatus main body  12 , and the transfer unit  42  is attached to and detached from the apparatus main body  12  in accordance with the opening and closing operation of the right cover. Therefore, as illustrated in  FIG. 2 , the transfer unit  42  is attached and detached in the left-right direction (the direction in which the photoreceptor drum  36  and the transfer roller  422  face each other). 
     Returning to  FIG. 1 , the fixing unit  44  includes a heat roller  440  and a pressure roller  442 , and is placed above the transfer unit  42 . The heat roller  440  is set to have a predetermined fixing temperature, and the toner image transferred onto the paper sheet is melted, mixed, and pressed when the paper sheet passes through a nip area (fixing nip portion) between the heat roller  440  and the pressure roller  442 , so that the toner image is thermally fixed to the paper sheet. 
     Further, in such an apparatus main body  12 , a first sheet conveyance path L 1  is formed for sending the paper sheet placed on the sheet feed tray  48  to the sheet discharge tray  50  via the transfer nip portion and the fixing nip portion. Further, in the apparatus main body  12 , when duplex printing is performed on a paper sheet, a second sheet conveyance path L 2  is formed for returning the paper sheet that has been subjected to single-sided printing and then passed through the fixing nip portion to the first sheet conveyance path L 1  on the upstream side of the transfer nip portion in the sheet conveyance direction. In the first sheet conveyance path L 1 , a registration roller  56  is provided, and also in the first sheet conveyance path L 1  and the second sheet conveyance path L 2 , a plurality of conveyance rollers  58  and  62  are provided, as appropriate, for giving a driving force to the paper sheet in an auxiliary manner. 
     When single-sided printing is performed in the apparatus main body  12 , a paper sheet placed on the sheet feed tray  48  is guided to the first sheet conveyance path L 1  one by one by a pickup roller  52  and a separation roller  54 , and conveyed to the registration roller  56 . Then, the registration roller  56  conveys the paper sheet to the transfer nip portion at a timing when the leading end of the paper sheet and the leading end of the image information (toner image) on the photoreceptor drum  36  are aligned, and the toner image is transferred onto the paper sheet. Thereafter, the paper sheet passes through the fixing nip portion, so that unfixed toner on the paper sheet is thermally fixed. The paper sheet that has been thermally fixed is conveyed through the first sheet conveyance path L 1  by the conveyance roller  58  and a discharge roller  60 , and is discharged to the sheet discharge tray  50 . 
     On the other hand, when duplex printing is performed, the discharge roller  60  is rotated in reverse when the trailing end of the paper sheet that has been subjected to the single-sided printing and then passed through the fixing nip portion reaches the discharge roller  60 , so that the paper sheet is conveyed in the opposite direction to be guided to the second sheet conveyance path L 2 . The paper sheet, when arriving at the second sheet conveyance path L 2 , is conveyed through the second sheet conveyance path L 2  by the conveyance roller  62 , and is guided to the first sheet conveyance path L 1  on the upstream side of the registration roller  56  in the sheet conveyance direction. At this time, the front and back sides of the paper sheet are reversed, and thereafter, the paper sheet passes through the transfer nip portion and the fixing nip portion, whereby printing is performed on the back surface of the paper sheet. 
     It is noted that, to the image forming apparatus  10  as described above, a manual sheet feed tray or an external sheet feed unit may be attached. In such a case, in place of the sheet feed tray  48 , paper sheets may be fed from the manual sheet feed tray or the external sheet feed unit to the first sheet conveyance path L 1 . 
     In the conventional image forming apparatus configured as described above, the sheet conveyance path tends to be shortened in recent years as the image forming apparatus is downsized. If the sheet conveyance path is short, the static electricity charged on a paper sheet may not be sufficiently eliminated before the paper sheet reaches the transfer position. As described above, the effect of the transfer electric field causes a toner image formed on the outer peripheral surface of the photoreceptor drum  36  to be transferred to a paper sheet while the paper sheet passes through the transfer nip portion. Here, if the paper sheet passes through the transfer nip portion while the paper sheet is charged with static electricity, there are problems that it is difficult to transfer the toner image onto the charged portion of the paper sheet and also transfer defects occur such as jitter (a horizontal black band) formed at the trailing end of the paper sheet. 
     Therefore, there is a type of image forming apparatus in which a conductive member for static elimination is provided in each of the development unit on the printing side and the transfer unit on the non-printing side. In this case, to stabilize the surface potential of the paper sheet, it is desirable to electrically conduct the conductive member at the side of the development unit and the conductive member at the side of the transfer unit. 
     However, since the development unit and the transfer unit are attached to the image forming apparatus separately and also the direction in which the development unit and the transfer unit are attached to and detached from the apparatus main body of the image forming apparatus is different, there is a problem that the configuration for electrically conducting the conductive member at the side of the development unit and the conductive member at the side of the transfer unit is complicated. Therefore, in the first embodiment, the development unit  64  and the transfer unit  42  have the following configurations. 
       FIG. 3  is a perspective view illustrating a structure of the transfer unit  42 .  FIG. 4  is a front view illustrating the structure of the transfer unit  42  in  FIG. 3 .  FIG. 5  is a perspective view illustrating a structure of the development unit  64 .  FIG. 6  is a front view illustrating the structure of the development unit  64  in  FIG. 5 .  FIG. 7  is an illustrative view illustrating a configuration of a second guide member  70 .  FIG. 8A  is a right side view illustrating a configuration of an elastic portion  702 .  FIG. 8B  is a front view illustrating the configuration of the elastic portion  702 .  FIG. 8C  is a bottom view illustrating the configuration of the elastic portion  702 . 
     As illustrated in  FIGS. 3 and 4 , the transfer unit  42  includes a transfer housing  420 , a first guide member  424 , and an urging member  426  in addition to the transfer roller  422  described above. The transfer roller  422 , the first guide member  424 , the urging member  426 , and the like are integrally held by the transfer housing  420  in a predetermined arrangement fashion. Further, the transfer housing  420  is held by a right cover provided on the right side surface of the apparatus main body  12 . 
     The first guide member  424  is a conveyance guide that is provided to face the first sheet conveyance path L 1  and guides a paper sheet conveyed by the registration roller  56  to the transfer nip portion, and is formed of a conductive metal or the like in a long plate shape. The first guide member  424  is also formed in a flat plate shape that is substantially parallel to the rotation axis of the transfer roller  422 . Both ends of the first guide member  424  in the longitudinal direction are held to be attachable to and detachable from the transfer housing  420  by engagement or the like. Further, the first guide member  424  is provided in a region corresponding to at least the transfer roller  422  in the longitudinal direction (front-rear direction) of the transfer roller  422  (transfer unit  42 ). In other words, the first guide member  424  is provided in a region corresponding to at least a sheet passing area that contacts the paper sheet. However, the first guide member  424  extends to the outside of the sheet passing area, that is, regions corresponding to non-sheet passing areas around the sheet passing area. 
     The urging member  426  abuts against the right side surface of the first guide member  424 , and urges the first guide member  424  in a direction toward the development unit  64  (first sheet conveyance path L 1 ) with a predetermined pressure. For example, the urging member  426  is a compression coil spring, and has a cylindrical shape in which a wire material made of a conductive metal or the like is spirally wound. The urging member  426  is also electrically connected to a grounding current path. Although not illustrated, the grounding current path includes a resistor and the like, and is grounded via a metal frame of the apparatus main body  12  and the like. Further, as described above, since the urging member  426  and the first guide member  424  abut against each other, the first guide member  424  is electrically connected to the grounding current path via the urging member  426 . That is, the first guide member  424  is grounded. Therefore, the first guide member  424  also functions as a static elimination member that eliminates the static electricity charged in a paper sheet when the paper sheet conveyed through the first sheet conveyance path L 1  is guided. 
     As illustrated in  FIGS. 5 and 6 , the development unit  64  includes a development housing  640  and the second guide member  70  in addition to the components described above. In  FIGS. 5 and 6 , for the sake of simplicity, the photoreceptor drum  36 , the charging unit  40 , and the cleaner unit  38  are omitted. The development housing  640  integrally holds the components of the development unit  64  such as the second guide member  70  in a predetermined arrangement fashion. Further, a developing tank for containing toner is formed inside the development housing  640 . 
     The second guide member  70  is a conveyance guide that is provided to face the first sheet conveyance path L 1  and guides a paper sheet conveyed by the registration roller  56  to the transfer nip portion, and is formed of a conductive metal or the like in a long plate shape. The second guide member  70  is also formed in a flat plate shape substantially parallel to the rotation axis of the photoreceptor drum  36 , and is placed at a position facing the first guide member  424 . In other words, the first guide member  424  and the second guide member  70  are placed to face each other across the first sheet conveyance path L 1 , the first guide member  424  guides a non-printing surface of a paper sheet (a surface not in contact with the photoreceptor drum  36 ), and the second guide member  70  guides a printing surface of the paper sheet (a surface in contact with the photoreceptor drum  36 ). 
     Further, both ends of the second guide member  70  in the longitudinal direction are held to be attachable to and detachable from the development housing  640  by fastening or engagement. The second guide member  70  is also provided at least in a region corresponding to the sheet passing area in the longitudinal direction (front-rear direction) of the photoreceptor drum  36  (development unit  64 ). However, the second guide member  70  extends to the outside of the sheet passing area, that is, regions corresponding to non-sheet passing areas around the sheet passing area (see  FIG. 7 ). 
     As illustrated in  FIGS. 5 to 7 , the second guide member  70  also has the elastic portion  702 . In this embodiment, the elastic portion  702  is provided integrally with the second guide member  70 . The elastic portion  702  is a plate spring, and is provided outside the sheet passing area (in the non-sheet passing area). Specifically, the elastic portion  702  is provided on the front side of the sheet passing area, that is, on the front side in the insertion direction of the development unit  64 . The elastic portion  702  is provided at the lower end portion of the second guide member  70  in the vertical direction. In other words, the elastic portion  702  is provided on the opposite side of the photoreceptor drum  36  in the vertical direction. 
     Further, as illustrated in  FIGS. 8A to 8C , the elastic portion  702  is formed in a substantially long plate shape extending in the longitudinal direction (front-rear direction) of the development unit  64 , and includes a first incline  702   a , a second incline  702   b , and a long hole  702   c . The first incline  702   a  is formed in a flat plate shape, and inclines to approach the right side, that is, the transfer unit  42  (first guide member  424 ) toward the back side in the insertion direction of the development unit  64  (from the front side toward the back side). The second incline  702   b  is formed in a flat plate shape, is formed on the back side of the first incline  702   a  (the back side in the insertion direction of the development unit  64 ), and inclines to approach the left side, that is, the development unit  64  (a main body of the second guide member  70 ) toward the back side in the insertion direction of the development unit  64 . The first incline  702   a  and the second incline  702   b  constitute the main body of the elastic portion  702 . Accordingly, the elastic portion  702  is formed in a substantially U shape (V shape) that opens toward the development unit  64  (left side) when viewed from above (below). That is, the elastic portion  702  is formed to open toward the second guide member  70  where the elastic portion  702  is provided and to protrude toward the first guide member  424  where the elastic portion  702  is not provided. 
     Further, an end of the second incline  702   b  on the back side (the back side in the insertion direction of the development unit  64 ) is coupled to the main body of the second guide member  70  via a coupling portion (bending portion)  702   d . However, the second incline  702   b  is provided to be inclined at a predetermined angle θ (for example, 30°) with respect to the main body of the second guide member  70 . 
     The long hole  702   c  is a long hole (slot hole) formed over the first incline  702   a  and the second incline  702   b  and extending in the front-rear direction. The long hole  702   c  is also formed at a substantially center in the width direction (vertical direction) of the elastic portion  702 . 
     As illustrated in  FIG. 9 , the elastic portion  702  is placed at a position facing the first guide member  424 , and abuts against the first guide member  424  in a state where the development unit  64  and the transfer unit  42  are attached to the apparatus main body  12 . Specifically, a coupling portion (bending portion)  702   e  that couples the first incline  702   a  and the second incline  702   b  abuts (presses) against the first guide member  424 . 
     Further, the elastic portion  702  is elastically deformable around the bending portion  702   d  that couples the first incline  702   a  and the main body of the second guide member  70 , and also elastically deformable around the coupling portion  702   e  that couples the first incline  702   a  and the second incline  702   b . That is, the elastic portion  702  is elastically deformable in the front-rear direction and in the left-right direction (the attaching and detaching direction of the development unit  64  and the attaching and detaching direction of the transfer unit  42 ). 
     Accordingly, either in a case where the transfer unit  42  is attached to and detached from the apparatus main body  12  with the development unit  64  attached to the apparatus main body  12  or in a case where when the development unit  64  is attached to and detached from the apparatus main body  12  with the transfer unit  42  attached to the apparatus main body  12 , the elastic portion  702  (second guide member  70 ) and the first guide member  424  can reliably abuts against each other. That is, it is possible to provide conduction (electric connection) between the second guide member  70  and the first guide member  424 . Accordingly, this makes it possible to ground the second guide member  70  and the first guide member  424  and bring the second guide member  70  and the first guide member  424  into the same potential, so that the surface potential of the paper sheet can be stabilized and transfer defects can be suppressed or prevented. 
     Further, in the first embodiment, since the elastic portion  702  is a plate spring, the second guide member  70  and the first guide member  424  can reliably abut against each other with a simple configuration. 
     Moreover, in the first embodiment, the elastic portion  702  is provided on the front side of the sheet passing area, that is, on the front side in the insertion direction of the development unit  64 . Generally, a high-voltage board is placed on the back side of the apparatus main body  12 . The elastic portion  702  provided on the front side of the sheet passing area can prevent the static elimination performance from being reduced due to the influence of such a high-voltage board. 
     Furthermore, in the first embodiment, the elastic portion  702  is provided integrally with the second guide member  70 . Therefore, as compared with a case where the elastic portion  702  is provided as a separate member, it is possible to provide a simplified structure and also reduce a number of parts. 
     Further, in the first embodiment, the elastic portion  702  includes a first incline  702   a  that inclines to approach the transfer unit  42  (first guide member  424 ) toward the back side in the insertion direction of the development unit  64 , and a second incline  702   b  that is continuously formed on the back side of the first incline  702   a  and inclines to approach the development unit  64  (the main body of the second guide member  70 ) toward the back side in the insertion direction of the development unit  64 . Accordingly, the elastic portion  702  can be prevented from being caught by components around the elastic portion  702  either in the case where the transfer unit  42  is attached to and detached from the apparatus main body  12  or in the case where the development unit  64  is attached to and detached from the apparatus main body  12 . This can prevent the component parts from being damaged (scratched), so that the development unit  64  and the transfer unit  42  can be attached to and detached from the apparatus main body  12  smoothly. 
     Further, in the first embodiment, the elastic portion  702  is provided on the opposite side of the photoreceptor drum  36  in the vertical direction. Accordingly, the elastic portion  702  or the photoreceptor drum  36  can be prevented from being damaged due to the elastic portion  702  and the photoreceptor drum  36  coming into contact with each other. 
     It is noted that, in the first embodiment, the elastic portion  702  is provided integrally with the second guide member  70 , but it is not necessary to be limited to this. Although not illustrated, for example, the elastic portion  702  may be formed of a member separated from the second guide member  70 . In this case, the member (elastic member) constituting the elastic portion  702  has conductivity, and the elastic portion  702  is fixed to the second guide member  70  by being fastened, welded, bonded, or the like. 
     Second Embodiment 
     The image forming apparatus  10  according to a second embodiment is the same as the image forming apparatus  10  according to the first embodiment except that an elastic portion is provided at the side of the transfer unit  42 . Accordingly, different parts from the first embodiment will be described but the same explanation will be not repeated. 
       FIG. 10  is an illustrative view illustrating a configuration of an elastic portion  428  according to the second embodiment and a relationship between the first guide member  424  and the second guide member  70 . As illustrated in  FIG. 10 , in the second embodiment, the elastic portion  702  is eliminated, and the elastic portion  428  is provided in place of the elastic portion  702 . 
     The elastic portion  428  is formed of a member separated from the first guide member  424 , and the member (elastic member) constituting the elastic portion  428  has conductivity. The elastic portion  428  is fixed to the first guide member  424  by being fastened, welded, bonded, or the like. 
     It is noted that the elastic portion  428  has the same configuration as the elastic portion  702  of the first embodiment except that its left-right direction is different (opposite). In brief, the elastic portion  428  is provided on the front side of the sheet passing area, and is provided at the lower end portion of the first guide member  424 , which is difficult to be seen in  FIG. 10 . That is, the elastic portion  428  is provided on the opposite side of the transfer roller  422  in the vertical direction. 
     The elastic portion  428  also includes a first incline that inclines to approach the left side, that is, the development unit  64  (second guide member  70 ) toward the back side in the insertion direction of the development unit  64 , and a second incline that is continuously formed on the back side of the first incline and inclines to approach the right side, that is, the transfer unit  42  (first guide member  424 ) toward the back side in the insertion direction of the development unit  64 . Therefore, the elastic portion  428  is elastically deformable in the front-rear direction and in the left-right direction (the attaching and detaching direction of the development unit  64  and the attaching and detaching direction of the transfer unit  42 ). 
     According to the second embodiment, similarly to the first embodiment, it is possible to provide reliable conduction between the second guide member  70  and the first guide member  424 . 
     It is noted that, in each of the above-described embodiments, the image forming apparatus  10  is configured as a multifunction peripheral, but the image forming apparatus of the present invention may be configured as a printer, a copying machine, or a facsimile. 
     Further, the specific shape and so on described in the above-described embodiments are examples, and their variations are possible according to an actual product as appropriate. 
     Furthermore, in the above-described embodiments, the elastic portion  702  is provided outside the sheet passing area and on the front side of the sheet passing area, but it is not necessary to be limited to this. For example, the elastic portion  702  (the same applying to the elastic portion  428 ) may be provided outside the sheet passing area and on the back side of the sheet passing area. Even in this case, similarly to the above-described embodiments, it is possible to provide reliable conduction between the second guide member  70  and the first guide member  424 . 
     Furthermore, in the above-described embodiments, the elastic portion  702  is provided at the lower end portion of the second guide member  70  in the vertical direction, but it is not necessary to be limited to this. For example, the elastic portion  702  may be provided at the upper end portion or the center portion of the second guide member  70  in the vertical direction. Even in this case, similarly to the above-described embodiments, it is possible to provide reliable conduction between the second guide member  70  and the first guide member  424 . 
     Further, in the above-described embodiments, the first incline  702   a  and the second incline  702   b  included in the elastic portion  702  (the same applying to the elastic portion  428 ) are formed in a flat plate shape, but the first incline  702   a  and the second incline  702   b  may be curved. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           10  Image forming apparatus 
           12  Apparatus main body 
           36  Photoreceptor drum 
           42  Transfer unit 
           422  Transfer roller 
           424  First guide member 
           64  Development unit 
           70  Second guide member 
           702  Elastic portion