Patent Publication Number: US-2023142336-A1

Title: Sheet conveyance apparatus, sheet processing apparatus, and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet conveyance apparatus for conveying sheets, a sheet processing apparatus for processing the sheets, and an image forming apparatus for forming images on sheets. 
     Description of the Related Art 
     Image forming apparatuses such as printers, copying machines and multifunction devices, and attachments thereof are equipped with a sheet conveyance apparatus for conveying sheets. The sheet conveyance apparatus is equipped with an actuator such as a motor or a sensor such as a sheet detection sensor, a control board for controlling the same or a power supply board terminal for supplying power thereto, and an electric cable connecting these components electrically. One example of a wiring method of such electric cables is a method in which guide members formed of resin that are molded into shapes along the wiring path are attached to a casing, and electric cables are supported by hooks provided on the guide members. Further, Japanese Patent Application Laid-Open Publication No. 2009-116114 discloses a cable wiring configuration for transmitting information from a scanner to a printer, wherein the cables are wired by having the cables nipped between projection pairs provided on a rear cover of the printer, or wired by having the cables hooked on L-shaped projections. 
     However, when guide members formed of resin is used, both the size of the guide members themselves and the space around the guide members are required to be large enough to ensure strength of the guide members and the workability for wiring the cables along the guide members, which leads to increase in size of the apparatus. Meanwhile, the wiring configuration according to the above-mentioned document has drawbacks in that the nipping and hooking of electric cables on each of the number of projections provided on the casing was troublesome, and there were demands to improve the workability of the wiring operation. 
     SUMMARY OF THE INVENTION 
     The present invention provides a sheet conveyance apparatus in which workability of a wiring operation can be improved while reducing a space required for wiring. 
     According to one aspect of the invention, a sheet conveyance apparatus includes a casing, an electric cable including a conductor and an insulator configured to cover the conductor, and a guide member attached to the casing and configured to guide the electric cable, wherein the guide member includes a wire-forming member formed of a metal wire, and wherein the electric cable is wired along the guide member with at least one of the electric cable and the guide member twisted around the other of the electric cable and the guide member. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view of an image forming apparatus according to a first embodiment. 
         FIG.  2    is a cross-sectional view of a lower sheet discharge unit according to the first embodiment. 
         FIG.  3    is a perspective view of a support wall according to the first embodiment. 
         FIG.  4    is a perspective view illustrating a wiring configuration according to the first embodiment. 
         FIG.  5    is a perspective view illustrating a guide member according to the first embodiment. 
         FIG.  6    is a perspective view illustrating a guide member according to a second embodiment. 
         FIG.  7    is a perspective view illustrating a part of a wiring configuration of the second embodiment. 
         FIGS.  8 A and  8 B  are each an explanatory view illustrating retention of a cable harness by the guide member according to the second embodiment. 
         FIGS.  9 A and  9 B  are each an explanatory view illustrating retention of the cable harness by the guide member according to the second embodiment. 
         FIG.  10    is an explanatory view illustrating retention of the bundle wire by the guide member according to the second embodiment. 
         FIG.  11    is a perspective view illustrating a guide member according to a third embodiment. 
         FIG.  12    is a perspective view illustrating a part of a wiring configuration according to the third embodiment. 
         FIG.  13    is a perspective view illustrating a part of a wiring configuration according to a fourth embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments according to the present disclosure will be described with reference to the drawings. 
     First Embodiment 
     At first, an outline of an image forming system, or apparatus, according to a first embodiment will be described.  FIG.  1    is a schematic view of an image forming system  1  according to the present embodiment. The image forming system  1  is composed of an image forming apparatus body  100 , an image forming apparatus  2 , a document feeder  3 , and a postprocessing apparatus  200 . The image forming system  1  forms an image on a sheet serving as a recording material, and if necessary, subjects the sheet to processing in the postprocessing apparatus  200  before outputting the sheet. Operations of respective apparatuses are described briefly, and thereafter, the postprocessing apparatus  200  will be described in detail. 
     The document feeder  3  conveys the document placed on a document tray  18  to image reading units  16  and  19 . The image reading units  16  and  19  are each an image sensor that reads image information from document surfaces, and images are read from both sides of a document in a single document conveyance. The document having the image information read therefrom is discharged onto a document discharge unit. Further, the image forming apparatus  2  reads the image information from a static document, including a document such as a booklet document which cannot be conveyed through the document feeder  3 , set on a platen glass by moving an image reading unit  16  in reciprocating movement by a driving device  17 . 
     The image forming apparatus body  100  is an electrophotographic device equipped with a direct-transfer-type image forming unit 1B. The image forming unit 1B includes a cartridge  20  equipped with a photosensitive drum  21 , and a laser scanner unit  40  arranged above the cartridge  20 . When performing an image forming operation, a surface of the photosensitive drum  21  being rotated is charged, and by exposing the surface of the photosensitive drum  21  by the laser scanner unit  40  based on image information, an electrostatic latent image is formed on the drum surface. The electrostatic latent image borne on the photosensitive drum  21  is developed into a toner image by charged toner, i.e., developer, and the toner image is conveyed to a transfer portion where the photosensitive drum  21  and a transfer roller  22  oppose one another. A controller of the image forming apparatus body  100  executes an image forming operation by the image forming unit 1B based on image information read by the image reading units  16  and  19  or image information received from an external computer via a network. 
     The image forming apparatus body  100  includes a storage  10  for storing sheets serving as recording material, and a sheet feeding apparatus  11  for feeding sheets one at a time from the storage  10 . The sheet fed from the sheet feeding apparatus  11  is subjected to skew correction at a registration roller, conveyed to a transfer portion, and at the transfer portion, has the toner image borne on the photosensitive drum  21  transferred thereto. A fixing unit  30  is arranged downstream of the transfer portion in a sheet conveyance direction. The fixing unit  30  includes a rotary member pair that nips and conveys the sheet and a heating element such as a halogen lamp for heating the toner image, and performs an image fixing process by heating and pressing the toner image on the sheet. 
     The sheet having passed through the fixing unit  30  is conveyed to the postprocessing apparatus  200 . In the case of a sheet to which image formation on a first side has been completed in duplex printing, the sheet having passed through the fixing unit  30  is reversed in the image forming apparatus body  100  and reconveyed to a registration roller  7 . Then, the sheet is passed through the transfer portion and the fixing unit  30  again to have an image formed on a second side thereof before being conveyed to the postprocessing apparatus  200 . 
     The image forming unit 1B described above is merely an example of an image forming unit for forming images on sheets, and it is also possible to use an intermediate transfer-type electrophotographic unit for transferring the toner image formed on a photosensitive member via an intermediate transfer body to the sheet. Furthermore, an inkjet-type or offset printing-type printing unit can also be used as the image forming unit. 
     Postprocessing Apparatus 
     The postprocessing apparatus  200  is a sheet processing apparatus for processing a sheet on which an image has been formed by the image forming apparatus body  100 . The postprocessing apparatus  200  is an example of a sheet conveyance apparatus in which sheets are conveyed. The postprocessing apparatus  200  according to the present embodiment includes a binding unit  220  serving as a processing unit for binding sheets, wherein the sheets received from the image forming apparatus body  100  are subj ected to a binding process before being discharged as a sheet bundle. Further, the postprocessing apparatus  200  can simply discharge the sheets received from the image forming apparatus body  100  without performing a binding process thereto. 
     The postprocessing apparatus  200  includes a sheet conveyance path  210 , a plurality of conveyance roller pairs arranged along the sheet conveyance path  210  and serving as conveyance members for conveying sheets, a sensor for detecting sheets passing through the sheet conveyance path  210 , an upper sheet discharge tray  301 , and a lower sheet discharge tray  401 . The sheet conveyance path  210  is branched inside a casing  201  of the postprocessing apparatus  200 , and includes a sheet discharge path leading to the upper sheet discharge tray  301  and a sheet discharge path leading to the lower sheet discharge tray  401 . The plurality of conveyance roller pairs includes an upper sheet discharge roller  229  for discharging sheets to the upper sheet discharge tray  301  and a lower sheet discharge roller  230  for discharging sheets to the lower sheet discharge tray  401 . 
     The binding unit  220  is provided on a conveyance path leading to the lower sheet discharge tray  401 . In the present embodiment, the sheet heading toward the lower sheet discharge tray  401  is reversed and conveyed by the upper sheet discharge roller  229  toward the binding unit  220 , passed through the binding unit  220 , and discharged onto the lower sheet discharge tray  401 . 
     The binding unit  220  includes an intermediate stacking portion  221  on which a plurality of sheets received from the image forming apparatus body  100  are stacked, and a stapler  222  for stapling the sheets stacked and aligned on the intermediate stacking portion  221 . A sheet bundle bound by the stapler  222  is pushed out from the intermediate stacking portion  221  by a push-out guide  224  driven by a guide driving unit  223  and transferred to the lower sheet discharge roller  230 . In a case where the sheet is discharged onto the lower sheet discharge tray  401  without performing a binding process, the sheet discharged onto the intermediate stacking portion  221  is transferred as it is by the push-out guide  224  to the lower sheet discharge roller  230 . 
     The postprocessing apparatus  200  includes a plurality of motors M for driving the plurality of conveyance roller pairs and the lifting and lowering of the upper sheet discharge tray  301  and the lower sheet discharge tray  401 , at least one sheet sensor  209  arranged along the sheet conveyance path  210 , and a sheet presence sensor  442  and a sheet leaning sensor  450  described later. A photoelectric sensor, such as a photo-interrupter or a photo-reflector, can be used as the sheet sensor  209  for generating detection signals corresponding to a presence or absence of a sheet detected using light. 
     These actuators and sensors operate based on command signals from a control unit  250  installed in the postprocessing apparatus  200 , or enter detection signals to the control unit  250 . Therefore, the postprocessing apparatus  200  is equipped with electric cables for electrically connecting the control unit  250  and the actuators or sensors, including a cable harness W described later. The postprocessing apparatus  200  is also equipped with electric cables for connecting a power supply board for supplying power to the actuators and sensors with the actuators or the sensors, and electric cables for connecting the control unit  250  of the postprocessing apparatus  200  with the control unit of the image forming apparatus body  100  in a communicable manner. 
     The control unit  250  includes at least one processor, and a storage device for storing control programs. The processor reads and executes a control program from the storage device to control the postprocessing apparatus  200 . The control unit  250  according to the present embodiment is connected to the control unit of the image forming apparatus body  100  in a manner capable of communicating mutually therewith, and controls the operation of the actuators based on the information notified from the control unit of the image forming apparatus body  100  and detection signals from sensors. 
     The postprocessing apparatus  200  includes an upper sheet discharge unit  300  and a lower sheet discharge unit  400  as sheet discharge destinations. The upper sheet discharge unit  300  is equipped with the upper sheet discharge tray  301  and the lower sheet discharge unit  400  is equipped with the lower sheet discharge tray  401 . The upper sheet discharge tray  301  and the lower sheet discharge tray  401  are both capable of moving up and down, that is, being lifted and lowered, with respect to the casing  201  of the postprocessing apparatus  200 . 
     The control unit  250  is equipped with sheet surface detection sensors for detecting upper surface positions of the sheets, that is, stacking height of the sheets, on the upper sheet discharge tray  301  and the sheets on the lower sheet discharge tray  401 , and if one of the sensors detects sheets, the corresponding tray is lowered in the direction of A2 or B2. Further, if removal of sheets on the upper sheet discharge tray  301  or the lower sheet discharge tray  401  is detected by the sheet surface detection sensor, the corresponding tray is lifted in the direction of A1 or B1. Thus, the upper sheet discharge tray  301  and the lower sheet discharge tray  401  are controlled to be lifted and lowered according to the stacked amount of the sheets such that the upper surface of the stacked sheets is maintained at a constant height. According to the present embodiment, the upper sheet discharge tray  301  serving as a first stacking portion and the lower sheet discharge tray  401  serving as a second stacking portion are respectively controlled to be lifted and lowered by a motor, but it is also possible to adopt a configuration where they are lifted and lowered by urging members such as springs. 
     In the following description and drawings, a Z axis direction refers to a vertical direction, or the gravity direction, in a state where the postprocessing apparatus  200  is installed on a horizontal plane. An X axis direction refers to a direction orthogonal to the Z axis direction and which is a direction along a side face of the postprocessing apparatus  200  on which the upper sheet discharge tray  301  and the lower sheet discharge tray  401  are provided. AY axis direction refers to a direction orthogonal to both the Z axis direction and the X axis direction. The X axis direction can be described as a sheet width direction of the sheet discharged onto the upper sheet discharge tray  301  or the lower sheet discharge tray  401 . Further, shapes and positional relationships of members that are detachably attached to the casing  201  with respect to the postprocessing apparatus  200  is described based on the state in which they are attached to the casing  201 . 
     Lower Sheet Discharge Unit 
     The upper sheet discharge unit  300  and the lower sheet discharge unit  400  adopt an approximately equivalent configuration. Only the lower sheet discharge unit  400  will be described below, but the upper sheet discharge unit  300  has a similar configuration. 
       FIG.  2    is a cross-sectional view of the postprocessing apparatus  200  illustrating the lower sheet discharge unit  400 , showing a state in which the postprocessing apparatus  200  is cut at a plane perpendicular to the X axis direction.  FIG.  3    is a perspective view illustrating a side face of the postprocessing apparatus  200  with the lower sheet discharge tray  401  removed.  FIG.  4    is a perspective view illustrating a side face of the postprocessing apparatus  200  shown in  FIG.  3    from an inner side of the casing  201 . 
     As illustrated in  FIG.  2   , the lower sheet discharge unit  400  includes the lower sheet discharge roller  230 , a support wall  430 , the lower sheet discharge tray  401 , a sheet presence lever  440 , a sheet presence flag  441 , the sheet presence sensor  442 , and a sheet leaning sensor  450 . 
     The lower sheet discharge roller  230  conveys sheets, or sheet bundles, conveyed within the postprocessing apparatus  200  to a sheet discharge direction Ds that is inclined upward toward the Y axis direction and discharges the sheets to the exterior of the casing  201  of the postprocessing apparatus  200 . The lower sheet discharge roller  230  is a pair of rollers, each roller rotating about a roller shaft that extends in the X axis direction. Further, the lower sheet discharge roller  230  is designed such that an upper side roller is moved toward and away from a lower side roller in the drawing to open and close the nip portion, thereby enabling a sheet bundle having been subjected to a binding process in the binding unit  220  to be discharged. 
     The lower sheet discharge tray  401  is protruded from the casing  201  of the postprocessing apparatus  200  in the Y axis direction. The lower sheet discharge tray  401  is a stacking portion on which sheets discharged from the inside of the casing  201  to the exterior are stacked. The lower sheet discharge tray  401  includes a stacking surface  401   a  serving as a sheet support surface on which sheets, or sheet bundles, discharged from the lower sheet discharge roller  230  are stacked. The stacking surface  401   a  is inclined upward toward a direction separating from the casing  201  in the Y axis direction. 
     The lower sheet discharge tray  401  is configured to be lifted and lowered with respect to the casing  201  by the driving force of the motor arranged in the casing  201 . As an actual configuration example, a belt stretched in the up-down direction in the casing  201 , wherein a frame supporting the lower sheet discharge tray  401  is connected to the belt and a belt pulley is driven by the driving force of the motor. 
     The support wall  430  is a wall member constituting at least a part of a side face, i.e., wall surface, of the casing  201  in the Y axis direction, which is extended in the Y axis direction and the Z axis direction. The casing  201  is an approximately rectangular parallelepiped structure, i.e., casing or apparatus body, including a frame body and an exterior member of the postprocessing apparatus  200 . 
     As illustrated in  FIG.  3   , the support wall  430  is disposed between a front frame  201 F and a rear frame  201 R constituting a frame body of the casing  201 . The front frame  201 F and the rear frame  201 R are positioned at the corner portion of the casing  201  when viewed from above, and they are both a pillar member extending in the Z axis direction. The front frame  201 F is positioned at the front side of the image forming system  1  in the X axis direction, and the rear frame  201 R is positioned at the rear side of the image forming system  1  in the X axis direction. 
     As illustrated in  FIG.  3   , sliding walls  432  serving as sliding members that can be lifted and lowered together with the lower sheet discharge tray  401  are provided on the support wall  430 . The sliding walls  432  have an abutting surface against which trailing edges, i.e., upstream edges in the sheet discharge direction Ds, of sheets stacked on the lower sheet discharge tray  401  are abutted. By having the sliding walls  432  against which the trailing edges of sheets are abutted move up and down with the lower sheet discharge tray  401 , the possibility of trailing edges of sheets being rubbed against the support wall  430  and damaged during lifting and lowering of the lower sheet discharge tray  401  can be reduced. 
     As illustrated in  FIGS.  3  and  4   , the sliding walls  432  are attached slidably approximately in the Z axis direction with respect to the support wall  430 , and each sliding wall  432  is urged upward by a tension spring  433 . The tension springs  433  are each a coil spring that has its axial direction arranged along the up-down direction, i.e., Z axis direction. When the lower sheet discharge tray  401  is lowered, the sliding walls  432  are moved downward following the lowering of the lower sheet discharge tray  401  by having tray abutment portions  432   a  pressed by the lower sheet discharge tray  401 . When the lower sheet discharge tray  401  is lifted, the sliding walls  432  are moved upward following the lifting of the lower sheet discharge tray  401  by urging force of the tension springs  433 . 
     Heights of the tray abutment portions  432   a  define a position at which the sliding walls  432  start to move following the movement of the lower sheet discharge tray  401 . In the present embodiment, among the four sliding walls  432 , one set of sliding walls arranged on the inner side in the X axis direction, i.e., sheet width direction, has a height of the tray abutment portions  432   a  that differs from the height of the tray abutment portions  432   a  of one set of sliding walls arranged on the outer side thereof. Therefore, in a state where the lower sheet discharge tray  401  is lowered for a predetermined distance from an initial position, one pair of sliding walls  432  arranged on the inner side start to move following the movement of the lower sheet discharge tray  401 . Thereafter, if the lower sheet discharge tray  401  is lowered further, the pair of sliding walls  432  arranged on the outer side also start to move following the movement of the lower sheet discharge tray  401 . According to such configuration, even if a large number of sheets is stacked, the possibility of trailing edges of sheets being rubbed against the support wall  430  and damaged during lifting and lowering of the lower sheet discharge tray  401  can be reduced. 
     The sheet presence lever  440 , the sheet presence flag  441 , the sheet presence sensor  442 , and the sheet leaning sensor  450  are provided to detect the state of sheets in the lower sheet discharge unit  400 . The sheet presence sensor  442  is a first sensor according to the present embodiment, and the sheet leaning sensor  450  is a second sensor according to the present embodiment. 
     Sheet Presence Detection 
     At first, the sheet presence lever  440 , the sheet presence flag  441 , and the sheet presence sensor  442  that serve as a detection mechanism for detecting presence and absence of sheets on the lower sheet discharge tray  401  are described. 
     As illustrated in  FIGS.  2  and  4   , the sheet presence lever  440  includes a sheet abutment portion  440   a , a flag abutment portion  440   b , and a swing shaft  440   c . The sheet presence lever  440  is supported via the swing shaft  440   c  on the lower sheet discharge tray  401 , and is capable of swinging about the swing shaft  440   c . The sheet presence lever  440  is a moving member, i.e., swinging member or first moving member, arranged on the lower sheet discharge tray  401  and moved when pressed by sheets on the lower sheet discharge tray  401 . 
     The sheet abutment portion  440   a  is movable by swinging of the sheet presence lever  440  between a protruding position, i.e., upper position, protruding upward of the stacking surface  401   a  of the lower sheet discharge tray  401  and a retracting position, i.e., lower position, where it is retrieved to a same height as the stacking surface  401   a . The flag abutment portion  440   b  pushes the sheet presence flag  441  when the sheet abutment portion  440   a  moves from the protruding position to the retracting position. 
     As illustrated in  FIGS.  2  and  4   , the sheet presence flag  441  includes a lever abutment portion  441   a , a sensor shielding portion  441   b , and a swing shaft  441   c . The sheet presence flag  441  is supported via the swing shaft  441   c  on the support wall  430 , and is capable of swinging about the swing shaft  441   c . The sheet presence flag  441  is a second moving member provided on the casing  201  and moved in linkage with the sheet presence lever  440 , i.e., first moving member. The sheet presence flag  441  is an example of a movable member that moves by being in contact with an object on an outside of the casing  201 , which, in this case, is the sheet presence lever  440 . The target object can also be an object other than sheets. 
     The lever abutment portion  441   a  is a portion that abuts against the flag abutment portion  440   b  of the sheet presence lever  440 . The lever abutment portion  441   a  is movable between a standby position that is protruded outside the casing  201  in the Y axis direction through a slit  430   a  ( FIG.  3   ) by the swinging of the sheet presence flag  441  and an operation position having moved toward an inner side of the casing  201  from the standby position. The slit  430   a  is an opening portion provided on the support wall  430 .  FIG.  2    illustrates a state in which the sheet presence flag  441  is at the standby position. The sensor shielding portion  441   b  is a member being detected by the sheet presence sensor  442  serving as a detecting portion. 
     The sheet presence sensor  442  is a sensor that is attached to the support wall  430  for detecting the swinging of the sheet presence flag  441 . The sheet presence sensor  442  is configured to output a detection signal according to the presence or absence of sheets on the lower sheet discharge tray  401 . 
     In the present embodiment, a photo-interrupter, i.e., transmissive photosensor, is used as the sheet presence sensor  442 , which is shielded of light by the sensor shielding portion  441   b  of the sheet presence flag  441 . Specifically, the sheet presence sensor  442  includes a light emitting portion, i.e., light emitting element such as an LED, and a light receiving portion, i.e., light receiving element such as a photodiode, that oppose one another. The signal, i.e., voltage value, generated by the light receiving portion varies according to the amount of light received by the light receiving portion. 
     When the lever abutment portion  441   a  is not pressed by the sheet presence lever  440 , the sheet presence flag  441  is arranged such that the sensor shielding portion  441   b  blocks an optical path from the light emitting portion to the light receiving portion. Further, when the lever abutment portion  441   a  is pressed by the sheet presence lever  440 , the sheet presence flag  441  is arranged such that the sensor shielding portion  441   b  is retrieved from the optical path from the light emitting portion to the light receiving portion. Further, when the lower sheet discharge tray  401  is positioned at an initial position, or home position, illustrated in  FIG.  2   , the flag abutment portion  440   b  of the sheet presence lever  440  is opposed to the lever abutment portion  441   a  of the sheet presence flag  441 . 
     According to such configuration, with the lower sheet discharge tray  401  positioned at the initial position as illustrated in  FIG.  2   , the sheet presence sensor  442  outputs a signal corresponding to the presence or absence of sheets on the lower sheet discharge tray  401 . That is, if no sheet is stacked on the lower sheet discharge tray  401 , the sheet abutment portion  440   a  of the sheet presence lever  440  is positioned at the protruding position and the sensor shielding portion  441   b  of the sheet presence flag  441  shields the sheet presence sensor  442 . In this case, the light receiving portion of the sheet presence sensor  442  outputs a signal corresponding to the shielded state. Meanwhile, if a sheet is stacked on the lower sheet discharge tray  401 , the sheet abutment portion  440   a  of the sheet presence lever  440  is pressed by the sheet and moves to the retracting position, and the sensor shielding portion  441   b  of the sheet presence flag  441  moves to a position so as not to shield the sheet presence sensor  442 . In this case, the light receiving portion of the sheet presence sensor  442  outputs a signal corresponding to the transmitted state. The control unit  250  ( FIG.  1   ) of the postprocessing apparatus  200  can determine the presence or absence of sheets stacked on the lower sheet discharge tray  401  based on the detection signal of the sheet presence sensor  442 . 
     Sheet Leaning Detection 
     Next, the sheet leaning sensor  450  serving as a detection mechanism for detecting that leaning of sheets has occurred in the lower sheet discharge unit  400  will be described. 
     As illustrated in  FIGS.  2  and  4   , the sheet leaning sensor  450  is attached to the support wall  430 . The sheet leaning sensor  450  is configured to output a detection signal corresponding to whether a trailing edge potion of the sheet discharged onto the lower sheet discharge tray  401  is leaning against the support wall  430 . 
     In the present embodiment, a photo reflector, i.e., reflective photosensor, that includes a light emitting portion, i.e., light emitting element such as an LED, that emits light to the outer side of the support wall  430  and a light receiving portion or detecting portion, i.e., light receiving element such as a photodiode, that detects reflected light from the sheet is used as the sheet leaning sensor  450 . The support wall  430  is provided with a window portion  430   b , i.e., opening portion, that transmits light from the light emitting portion of the sheet leaning sensor  450  and reflected light from the sheet. The signal, i.e., voltage value, generated by the light receiving portion varies according to the amount of light received by the light receiving portion. The sheet leaning sensor  450  is an example of a sensor including a light emitting portion that emits light to the exterior of the casing  201  through the opening portion and a light receiving portion that outputs a signal corresponding to the light reflected on a target object at the exterior of the casing  201  and entered through the opening portion. The target object can also be an object other than sheets. 
     The sheet leaning sensor  450  is arranged lower than a track through which the sheet having passed through the nip portion of the lower sheet discharge roller  230  is discharged. Further, the sheet leaning sensor  450  is arranged to detect sheets at a position above the stacking surface  401   a  of the lower sheet discharge tray  401  positioned at the initial position. In the present embodiment, the sheet leaning sensor  450  is arranged in a vicinity of the lower end of the lower sheet discharge roller  230 . 
     In a state where there is a sheet, referred to as a leaning sheet, leaning on the support wall  430 , the light emitted by the light emitting portion of the sheet leaning sensor  450  is reflected by the sheet and enters the light receiving portion. Meanwhile, if there is no sheet leaning on the support wall  430 , no reflected light from the sheet will enter the sheet leaning sensor  450 , such that the amount of light received by the light receiving portion is reduced at least compared to the case where there is a leaning sheet. The light receiving portion is configured to output either an analog signal corresponding to the amount of received light or a binary signal corresponding to whether the amount of received light is greater than a predetermined threshold value. In any case, the control unit  250  ( FIG.  1   ) of the postprocessing apparatus  200  can determine whether there is a leaning sheet present on the lower sheet discharge tray  401  based on the detection signal from the sheet leaning sensor  450 . 
     The sheet leaning sensor  450  is configured to detect the presence or absence of a sheet at a predetermined height position, such that it can also serve as a sensor for outputting a detection signal corresponding to whether a trailing edge portion of the sheet has passed a predetermined height position. 
     Control Example 
     One example of a method for controlling the lower sheet discharge tray  401  using the sheet presence sensor  442  and the sheet leaning sensor  450  will be described. At a point of time when a series of actions, that is, image forming job, in which the image forming system  1  forms an image on a sheet and discharges the sheet to the lower sheet discharge tray  401  is started, the lower sheet discharge tray  401  is assumed to be positioned at the initial position. The control unit  250  can confirm that there is no sheet on the lower sheet discharge tray  401  based on the detection signal of the sheet presence sensor  442 . 
     In a state where an image forming job is started and a first sheet is discharged onto the lower sheet discharge tray  401 , the detection signal of the sheet presence sensor  442  is switched. Thereby, the control unit  250  detects that a sheet has been stacked on the lower sheet discharge tray  401 . Thereafter, the control unit  250  outputs a command to a lifting/lowering motor of the lower sheet discharge tray  401  to lower the lower sheet discharge tray  401  for a predetermined distance whenever a predetermined number of sheets have been accumulated on the sheets discharged to the lower sheet discharge tray  401 . Thereby, the upper surface height of sheets stacked on the lower sheet discharge tray  401  can be maintained to a roughly constant height. 
     Meanwhile, if a signal representing sheet detection is output by the sheet leaning sensor  450  during execution of the image forming job, the control unit  250  outputs a command to the lifting/lowering motor to lower the lower sheet discharge tray  401 . Thereafter, if the signal output by the sheet leaning sensor  450  is switched to a signal representing that no sheet is detected, the control unit  250  stops the lowering of the lower sheet discharge tray  401 . Thereby, it becomes possible to prevent the sheets being discharged from the lower sheet discharge roller  230  from colliding against the leaning sheet and falling from the lower sheet discharge tray  401  or causing misalignment of sheets on the lower sheet discharge tray  401 . 
     One example of a control performed by the control unit  250  has been escribed above, and the control unit  250  can perform control of the lower sheet discharge tray  401  by also referring to detection signals from sensors other than the sheet presence sensor  442  and the sheet leaning sensor  450 . 
     Other Sensors 
     The sheet presence sensor  442  described above is an example of a sensor that outputs a detection signal according to whether a sheet is present or absent on the lower sheet discharge tray  401 . The sensor is not limited to a photosensor having light shielded by the sheet presence flag  441 , and any sensor for detecting movement of the sheet presence flag, such as a mechanical switch or a capacitance-type proximity sensor, can be used as the sheet presence sensor  442 . 
     Further, a sensor that directly detects the movement of the sheet presence lever  440   can be used instead of the sensor for detecting movement of the sheet presence flag  441  that moves in linkage with the sheet presence lever  440 . For example, a photo-interrupter can be arranged at a position where light is shielded by the flag abutment portion  440   b  of the sheet presence lever  440  according to the present embodiment. 
     Further, a sheet presence sensor outputting a detection signal according to the presence or absence of a sheet on the lower sheet discharge tray  401  can be disposed on the lower sheet discharge tray  401 . Specifically, a photo-interrupter that is shielded by a part of the sheet presence lever  440 , or a photo reflector that emits light to an upper direction of the stacking surface  401   a  and detects reflected light from the sheet, can be arranged in the interior of the lower sheet discharge tray  401 . In that case, a length of a cable harness W that is connected to the sheet presence sensor  442  described below is given sufficient margin so as to tolerate the positional changes of the sheet presence sensor  442  accompanying the lifting and lowering of the lower sheet discharge tray  401 . 
     The sheet leaning sensor  450  described above is an example of a sensor that outputs detection signals according to the presence or absence of leaning of a sheet on the lower sheet discharge tray  401 . As another configuration, for example, a photosensor that detects the swinging of a flag projected from the support wall  430  or a distance measurement sensor disposed above the lower sheet discharge roller  230  for detecting the distance in the height direction to a trailing edge portion of the highest sheet can be adopted as the sheet leaning sensor. 
     Wiring Path of Sensors 
     A wiring path of the sheet presence sensor  442  and the sheet leaning sensor  450  mentioned above will be described. As illustrated in  FIG.  4   , the sheet presence sensor  442  and the sheet leaning sensor  450  are attached to a rear surface of the support wall  430 , that is, inner side surface of the casing  201 . The sheet presence sensor  442  and the sheet leaning sensor  450  are electrically connected with the control unit  250  of the postprocessing apparatus  200  via a cable harness W wired along the support wall  430 . 
     The cable harness W is an example of an electric cable or a bundle of cables including a conductor or conducting wire for transmitting signals or power and an insulator or insulation covering the conductor. The cable harness W according to the present embodiment includes a signal line for transmitting the signals output from the sheet presence sensor  442  and the sheet leaning sensor  450  to the control unit  250 , and a power line, i.e., power supply line, for supplying power to the sheet presence sensor  442  and the sheet leaning sensor  450 . 
     The cable harness W is a branched cable including a trunk line W 0 , and a first branch line W 1  and a second branch line W 2  being branched from the trunk line W 0  at a branch portion Wb. The first branch line W 1  is connected to the sheet presence sensor  442 , and the second branch line W 2  is connected to the sheet leaning sensor  450 . 
     In the present embodiment, the sheet presence sensor  442  and the sheet leaning sensor  450  are arranged one above the other at a center portion of the support wall  430  in the X axis direction. That is, an installation range of a sensor substrate of the sheet presence sensor  442  in the X axis direction and an installation range of a sensor substrate of the sheet leaning sensor  450  in the X axis direction are overlapped, and the sheet presence sensor  442  is positioned lower than the sheet leaning sensor  450 . When viewed in the Z axis direction, the sheet presence sensor  442  and the sheet leaning sensor  450  are at least partially overlapped. 
     The first branch line W 1  of the cable harness W is extended upward from a connector portion of the sheet presence sensor  442 , and the second branch line W 2  is extended downward from a connector portion of the sheet leaning sensor  450 . Then, the first branch line W 1  and the second branch line W 2  merge at the branch portion Wb and become the trunk line W 0 . The trunk line W 0  is extended in the X axis direction along the support wall  430  and is connected to the control unit  250  via a relay connector and the like. 
     The trunk line W 0  is laid from the end portion of the support wall  430  in the X axis direction along the rear frame  201 R in a curved manner. The rear frame  201 R according to the present embodiment has an L-shaped cross section in top view, and includes a first portion  201 R a  that extends in the Y axis direction approximately perpendicularly to the support wall  430 , and a second portion  201 R b  that extends in the X axis direction approximately perpendicularly to the first portion  201 R a . Accordingly, the trunk line W 0  is wired along a corner portion, i.e., external corner, between the support wall  430  and the first portion  201 R a  of the rear frame  201 R and a corner portion, i.e., internal corner, between the first portion  201 R a  and the second portion  201 R b  of the rear frame  201 R. 
     Cable Guide 
     A configuration for wiring the cable harness W along the wiring path described above will be described. In the present embodiment, the cable harness W is supported by a guide member formed of a curved metal wire, i.e., wire-forming, and the guide member is attached to the casing  201 , by which the cable harness W is wired. 
     In the present embodiment, a guide wire formed by processing a metal wire having a circular cross section with a wire diameter of 0.5 mm to 1.0 mm using a wire-forming machine, for example, is adopted as the guide member. The metal material constituting the guide wire is not specifically limited, but for example, an aluminum wire, an iron wire, a stainless-steel wire, or a copper alloy wire containing brass or phosphor bronze can be used. Further, a flexural rigidity of the guide wire should at least be higher than the flexural rigidity of the electric cable being guided thereby. 
     As illustrated in  FIG.  4   , according to the present embodiment, a first guide wire  460  that guides the first branch line W 1  of the cable harness W and a second guide wire  470  that guides the trunk line W 0  of the cable harness W are used. Each of the first guide wire  460  and the second guide wire  470  is a wire-forming member, i.e., wire forming, that is formed by subjecting one metal wire to plastic deformation. Wire forming includes right-angled bending, bending along a smooth curve, and helical bending or coiling. Processing other than bending, such as thread cutting, punching, and chamfering, can be performed to a part of the wire-forming member. The first guide wire  460  serves as a first guide member for guiding a part of the electric cable, and the second guide wire  470  functions as a second guide member for guiding a different part of the electric cable. 
     By using the guide member formed by wire-forming a metal wire and having at least one of the electric cable and the guide member twist around the other, the electric cable is retained by the guide member, and by attaching the guide member to the casing, the electric cable is wired. Thereby, as described in detail below, the workability of the wiring operation can be improved while reducing the space required for wiring. 
     Details of a guide wire according to the present embodiment will be described below. As illustrated in  FIG.  4   , the first guide wire  460  includes a vertical guide portion  464  extended in an approximately vertical direction, i.e., Z axis direction, which guides the first branch line W 1  of the cable harness W along a direction in which the vertical guide portion  464  extends. The second guide wire  470  includes a horizontal guide portion  473  that extends in an approximately horizontal direction, i.e., X axis direction, and guides the trunk line W 0  of the cable harness W along a direction in which the horizontal guide portion  473  extends. In other words, according to the present embodiment, a main wiring direction of the first branch line W 1  also referred to as a first direction is the up-down direction, i.e., Z axis direction, and a main wiring direction of the trunk line W 0  also referred to as a second direction is the horizontal direction, i.e., X axis direction. 
     Since the second branch line W 2  of the cable harness W is short, according to the present embodiment, there is no guide member provided to guide the second branch line W 2 . If the length of the second branch line W 2 , that is, the length along a center line of the second branch line W 2  from the branch portion Wb to the connector portion of the sheet leaning sensor  450 , is considerably long, it may be possible to additionally provide a guide wire for guiding the second branch line W 2 . 
     First Guide Wire  460   
       FIG.  5    illustrates a state in which the first guide wire  460  and the second guide wire  470  are attached to the support wall  430 , with the cable harness W, the sheet presence sensor  442 , and the sheet leaning sensor  450  not shown. 
     As illustrated in  FIG.  5   , the first guide wire  460  includes a frame contact portion  461 , a vertical portion  462 , a horizontal portion  463 , the vertical guide portion  464 , at least one helical portion  465 , and a pressure contact portion  466 . 
     The frame contact portion  461  of the first guide wire  460  is positioned below an attaching portion  431   a  of the support wall  430  on which the sheet presence sensor  442  is attached. The frame contact portion  461  is extended obliquely with respect to the support wall  430  from an end  460   a  of the metal wire toward the lower direction in a direction separating from the support wall  430 , that is, frontward direction in the drawing in the Y axis direction, then bent approximately perpendicularly at two areas and returning to support wall  430 , thereby forming an approximately U-shaped form. 
     In a state where the support wall  430  is assembled as a part of the casing  201 , the frame contact portion  461  is arranged to come into contact with a sheet metal frame  201 M (refer to  FIG.  2   ) that constitutes a frame body of the postprocessing apparatus  200 . The sheet metal frame  201 M is an example of a conductive member that is electrically grounded, wherein the conductive member ca be a resin member having metal plated thereon or a sheet or wire material made of metal that is attached to the frame body. 
     The sheet metal frame  201 M is arranged on an inner side of the casing  201  with respect to the support wall  430  at a position opposed to the support wall  430  in the Y axis direction. Further, the sheet metal frame  201 M is electrically grounded. Therefore, the frame contact portion  461  having elasticity in the Y axis direction ensures electrical conduction of the first guide wire  460  with the sheet metal frame  201 M opposed to the support wall  430  in the Y axis direction. Thereby, the first guide wire  460  is electrically grounded via the sheet metal frame  201 M. In other words, the approximately U-shaped form of the frame contact portion  461  is one example of an elastic shape which generates elastic force for causing the frame contact portion  461 , i.e., contact portion of the guide member, to be in pressure contact with the sheet metal frame  201 M, i.e., conductive member. 
     The elastic shape causing the contact portion of the guide member to be in pressure contact with the conductive member is not limited to this example, and for example, the end portion of the first guide wire  460  can be simply bent with respect to the vertical portion  462  away from the support wall  430  toward the lower direction from the vertical portion  462 . Further, the frame contact portion  461  can be formed as a coil spring capable of extending and contracting in the Y axis direction. 
     The vertical portion  462  extends upward in the approximately vertical direction from the frame contact portion  461  and passes through the space between the sheet presence sensor  442  and the slit  430   a  through which the sheet presence flag  441  passes. The horizontal portion  463  is extended approximately horizontally, in the X axis direction, along the attaching portion  431   a  on which the sheet presence sensor  442  is attached. 
     The vertical guide portion  464  extends upward in the approximately vertical direction from the horizontal portion  463 . Two helical portions  465  are arranged in the vertical guide portion  464 . Each helical portion  465  has a helical shape, that is, coiled portion, in which the metal wire serving as the material is wound helically for at least one turn or more, that is, 360° or more. The portions other than the helical portion  465  of the vertical guide portion  464  is an extended portion that extends in the vertical direction serving as a wiring direction of the first branch line W 1 . 
     The helical portion  465  is a part that retains the first branch line W 1  by having the first guide wire  460  twist around (i.e., turn around or roll around) the first branch line W 1  (refer to  FIG.  4   ). In the description, the term “twisted around” refers to a state in which two elongated members, or thin thread members, that extend approximately in the same direction are intertwined with each other such that they are not easily separated even if they are relatively moved in an arbitrary direction intersecting the extending direction. In other words, a state in which one, referred to as α, of two thread members α and β is twisted around the other, referred to as β, refers to a state in which there is at least one part where α and β intersect one another at the front side of β when viewed from any direction of 360° within a plane orthogonal to the extending direction of α and β. 
     By setting the number of turns of each of the helical portions  465  to one or more, a state in which the first branch line W 1  is retained by the first guide wire  460  with the helical portion  465  twisted around the first branch line W 1  can be realized. That is, with the helical portion  465  twisted around the first branch line W 1 , even if the first branch line W 1  attempts to move in a direction intersecting the extending direction, i.e., Z axis direction, of the vertical guide portion  464  of the first guide wire  460 , the separation of the first branch line W 1  can be prevented by the helical portion  465 . 
     By increasing the number of turns of the helical portion  465 , it becomes possible to limit the inclination of the first branch line W 1  at the helical portion  465  and to further reduce the risk of the first branch line W 1  falling from the first guide wire  460 . Meanwhile, if the number of turns for each of the helical portions  465  or the number of helical portions  465  being provided is increased excessively, the work related to twisting the helical portion  465  around the first branch line W 1  becomes too troublesome. 
     According to the present embodiment, by arranging helical portions  465  having approximately two turns at two areas distant from one another, the helical portions  465  can firmly retain the first branch line W 1  and prevent falling of the first branch line W 1  while suppressing the number of turns and number of areas of the helical portions  465 . The number of turns of the helical portion  465  provided at one area is preferably 1 turn or greater and 5 turns or smaller, and even more, it is preferably 1.5 turns or greater and 3 turns or smaller. It is also possible to have three or more helical portions  465  provided on the vertical guide portion  464 , and even further, the entire vertical guide portion  464  can be formed as one continuous helical shape. 
     The pressure contact portion  466  is provided at a portion extending from the upper end of the vertical guide portion  464  in a bent manner in the X axis direction. The pressure contact portion  466  is a portion that utilizes the elasticity of the metal wire constituting the first guide wire  460  to abut against the second guide wire  470  and ensure electrical conduction. The pressure contact portion  466  according to the present embodiment has a shape of a torsion coil spring and adopts a configuration to acquire reaction force from the support wall  430  by hanging an end  460   b  of the first guide wire  460  to a spring hook portion  430   c  of the support wall  430 . That is, the torsion coil spring-shape of the pressure contact portion  466  is an example of an elastic shape that generates elastic force for enabling pressure contact between a first guide wire, i.e., first guide member, and an abutment portion  472 , i.e., contact portion. 
     The elastic shape for realizing the pressure contact between the first guide member and the contact portion of a second guide member is not limited to the torsion coil spring. For example, it is possible to adopt a wire clip shape, such as a paper clip formed of a looped wire, as the pressure contact portion  466  and to nip the abutment portion  472  of the second guide wire  470  by the clip. Further, it is also possible to adopt a bent shape such as the frame contact portion  461  as the pressure contact portion  466  and hang the tip portion of the bent shape to a rib provided on the support wall  430  to thereby generate contact pressure against the abutment portion  472 . It is also possible to have the second guide wire  470  adopt the elastic shape for causing the abutment portion  472  to be in pressure contact with the first guide wire  460 . 
     Second Guide Wire  470   
     As illustrated in  FIG.  5   , the second guide wire  470  includes a horizontal portion  471 , the abutment portion  472 , the horizontal guide portion  473 , at least one helical portion  475 , and a hook portion  474  ( FIG.  4   ). 
     The horizontal portion  471  is a portion that extends from an end portion of the second guide wire  470  hooked to the hole on the support wall  430  through a space formed between the support wall  430  and the sheet leaning sensor  450  attached to an attachment portion  431   b  toward an approximately horizontal direction, i.e., X axis direction. The abutment portion  472  is a portion that bends downward in a clank shape from the horizontal portion  471  and extending again in the approximately horizontal direction. The abutment portion  472  is a portion that abuts against the pressure contact portion  466  of the first guide wire  460 . By the abutment portion  472  being abutted against the pressure contact portion  466 , the electrical conduction between the second guide wire  470  and the first guide wire  460  is ensured, and the second guide wire  470  is electrically grounded via the first guide wire  460 . 
     The horizontal guide portion  473  is a portion that extends in an approximately horizontal direction, i.e., X axis direction, from the abutment portion  472 . Three helical portion  475  are arranged on the horizontal guide portion  473  in a manner spaced apart from one another. Each of the helical portions  475  is coil shaped, i.e., coiled portion, that is formed by winding a metal wire serving as the material for at least one turn, i.e., 360°, or more in a helical shape. The portions of the horizontal guide portion  473  other than the helical portions  475  are extended linearly in an approximately horizontal direction. 
     The helical portion  475  is a portion that retains the first branch line W 1  by the second guide wire  470  twisting around the trunk line W 0  (refer to  FIG.  4   ). In the present embodiment, the helical portion  475  turned for approximately two turns, that is, 1 turn or more and 3 turns or less, is arranged at three areas spaced apart from one another, such that the helical portion  475  is downsized as much as possible while retaining the trunk line W 0  by the helical portion  475  steadily and preventing the trunk line W 0  from falling. It is also possible to arrange 4 or more, or 2 or less, helical portions  475  in the horizontal guide portion  473 , or to form the entire horizontal guide portion  473  as one continuous helical portion  475 . 
     The hook portion  474  is arranged at the tip of the horizontal guide portion  473  ( FIG.  4   ). The hook portion  474  is hook-shaped such that the end portion of the second guide wire  470  can be hooked on and fixed to a part of the casing  201 . (3) Rib for attaching Guide Wire 
     A plurality of ribs  435   a  to  435   k  are provided on the support wall  430  as projections for attaching the first guide wire  460  and the second guide wire  470  to the casing  201  ( FIGS.  4  and  5   ). The ribs  435   a  to  435   k  can be formed integrally with the support wall  430  by using a common resin material as the support wall  430 . 
     As illustrated in  FIG.  5   , the rib  435   a  is provided between the attaching portion  431   a  of the sheet presence sensor  442  and the slit  430   a  for the sheet presence flag  441 , and sets a position of the vertical portion  462  in the X axis direction of the first guide wire  460 . The rib  435   b  sets a position of the bent portion of the first guide wire  460  between the horizontal portion  463  and the vertical guide portion  464 . The rib  435   c  is provided between the two helical portions  465  of the first guide wire  460  and between the vertical guide portion  464  and one of the tension springs  433  for the sliding walls, and sets a position of the vertical guide portion  464  in the X axis direction. The ribs  435   d  and  435   e  set the position of the bent portion of the first guide wire  460  between the vertical guide portion  464  and the pressure contact portion  466 . The rib  435   f  sets a position in the X axis direction of the pressure contact portion  466  of the first guide wire  460  together with the spring hook portion  430   c . The ribs  435   a  to  435   f  and the spring hook portion  430   c  enable the first guide wire  460  to be retained without falling from the support wall  430 . 
     The vertical guide portion  464  of the first guide wire  460  is positioned in the X axis direction by being sandwiched from both sides in the X axis direction by the ribs  435   b ,  435   c , and  435   d . Further, the vertical guide portion  464  is positioned in the Z axis direction by having its bent portion retained by the ribs  435   b  and  435   d . Further, the vertical guide portion  464  is positioned at a position in contact with or adjacent to the support wall  430  with respect to the Y axis direction by having both end portions of the first guide wire  460  fixed to the support wall  430  as described later. 
     As described, by having the vertical guide portion  464  positioned with respect to the support wall  430 , the wiring path of the cable harness W guided by the vertical guide portion  464  is determined. The configuration is not limited to the example where the vertical guide portion  464  is directly in contact with and positioned by the ribs  435   b  to  435   d , and the vertical guide portion  464  and the cable harness W can be positioned by having the cable harness W retained by the vertical guide portion  464  contact the ribs  435   b  to  435   d . 
     The heights of the ribs  435   b  to  435   d , that is, height in which the ribs are protruded in the Y axis direction from the support wall  430 , arranged along the vertical guide portion  464  should preferably be as low as possible within the range capable of retaining the vertical guide portion  464  stably. For example, the heights of the ribs  435   b  to  435   d  can be set to approximately the same as or shorter than an outer diameter of the helical portion  465 . Thereby, it becomes possible to suppress the space required for wiring the cable harness W from being substantially increased by the presence of the ribs  435   b  to  435   d . 
     Further, as illustrated in  FIG.  5   , the ribs  435   e  and  435   f  set the position of the abutment portion  472  of the second guide wire  470  in the Z axis direction. The ribs  435   g  and  435   h  support the horizontal guide portion  473  of the second guide wire  470  from below and set the position thereof in the Z axis direction. As illustrated in  FIG.  4   , the rib  435   i  has a surface that presses the horizontal guide portion  473  of the second guide wire  470  from above and a surface opposed to the support wall  430  in the Y axis direction, setting the positions of the horizontal guide portion  473  in the Z axis direction and the Y axis direction. The rib  435   j  presses the horizontal guide portion  473  of the second guide wire  470  from above and sets the position of the horizontal guide portion  473  in the Z axis direction. The rib  435   k  is a part on which the hook portion  474  of the second guide wire  470  is hung. These ribs  435   e  to  435   k  enable the second guide wire  470  to be retained without falling from the support wall  430 . 
     The horizontal guide portion  473  of the second guide wire  470  is positioned in the Z axis direction by having the lower surface thereof supported by the ribs  435   g  and  435   h  and pressed from above by the ribs  435   i  and  435   j . Further, the horizontal guide portion  473  is positioned at a position abutted against or adjacent to the support wall  430  in the Y axis direction by the hook-shaped rib  435   i . Further, the horizontal guide portion  473  is positioned in the X axis direction by having both end portions of the second guide wire  470  fixed to the support wall  430  as described below. As described, by having the horizontal guide portion  473  positioned with respect to the support wall  430 , the wiring path of the cable harness W guided by the horizontal guide portion  473  is determined. The configuration is not limited to the example in which the horizontal guide portion  473  is positioned by being directly abutted against the ribs  435   g  to  435   j , and the horizontal guide portion  473  and the cable harness W can be positioned by having the cable harness W retained by the horizontal guide portion  473  abut against the ribs  435   g  to  435   j . 
     The heights of the ribs  435   g  to  435   j , that is, protruding height in the Y axis direction from the support wall  430 , arranged along the horizontal guide portion  473  should also preferably be as low as possible within the range capable of retaining the horizontal guide portion  473  stably. For example, the heights of the ribs  435   g ,  435   h , and  435   j  can be set to approximately the same as or smaller than the outer diameter of the helical portion  475 . Thereby, the space required for wiring the cable harness W can be suppressed from being substantially increased by the presence of the ribs  435   g ,  435   h , and  435   j . 
     As described, since at least a part, or even all, of the projections for fixing the guide member, which are the ribs  435   a  to  435   k , are molded integrally with the support wall  430 , manufacturing costs and number of steps can be cut down compared to the case where members for fixing the guide members are provided individually from the support wall  430 . Furter, since the space occupied by the projections, which are the ribs  435   a  to  435   k , is extremely small, the space required to wire the cable harness W can be cut down even further compared to a case where members for fixing the guide members are provided individually from the support wall  430 . 
     The first guide wire  460  and the second guide wire  470  are members that are formed by bending a wire in advance according to the shape to be assembled defined by the ribs  435   a  to  435   k . For example, the first guide wire  460  has bent portions that have been bent approximately perpendicularly at positions corresponding to corner portions of the ribs  435   b ,  435   d , and  435   e  in a state after being attached to the support wall  430 . The helical portions  465  and  475  mentioned above also have a coiled shape that has been formed when creating the first guide wire  460  and the second guide wire  470 . 
     Method for Attaching Cable Harness and Guide Wire 
     A method for attaching the sheet leaning sensor  450 , the sheet presence sensor  442 , the first guide wire  460 , the second guide wire  470 , and the cable harness W to the support wall  430  will be described with reference to  FIGS.  4  and  5   . 
     (1) At first, one of two end portions of the second guide wire  470  is attached to the support wall  430  as temporary fixing of the second guide wire  470 . That is, one of the end portions of the second guide wire  470  is fixed to the support wall  430  by passing the horizontal portion  471  of the second guide wire  470  from a rear surface side of the support wall  430  through a hole  430   d  on the support wall  430 . Thereby, one of the end portions of the second guide wire  470  is retained by the hole  430   d  serving as a first retaining portion. Further, the abutment portion  472  of the second guide wire  470  is abutted against the rear surface of the support wall  430  and the horizontal guide portion  473  is extended approximately in the X axis direction along the rear surface of the support wall  430 . In this state, the hook portion  474  positioned at the other end portion of the second guide wire  470  is kept free without being fixed to the support wall  430 . 
     (2) The first branch line W 1  is attached to the first guide wire  460 , that is, the first branch line W 1  and the first guide wire  460  are integrated. In other words, the cable harness W having the first branch line W 1  connected to the connector portion of the sheet presence sensor  442  is held by hand, and the helical portion  465  on the upper side of the first guide wire  460  is wound around the area close to the branch portion Wb of the first branch line W 1 . Specifically, the first branch line W 1  is fit to an opened part of the helical portion  465 , and thereafter, the first branch line W 1  is pushed into the inner side of the helical portion  465  while winding the first branch line W 1  and the sheet presence sensor  442  in the helix direction of the helical portion  465 . Thereby, the helical portion  465  is twisted around the first branch line W 1 . A similar operation is performed for the other helical portion  465 . Thereby, the first branch line W 1  is retained by the first guide wire  460  with each of the helical portions  465  twisted around the first branch line W 1 . 
     (3) One of the end portions of the first guide wire  460  is attached to the support wall  430  as temporary fixing of the first guide wire  460 . That is, the frame contact portion  461  of the first guide wire  460  is positioned below the attaching portion  431   a  of the sheet presence sensor  442 , the vertical portion  462  is positioned on the side of the attaching portion  431   a , and the horizontal portion  463  is positioned above the attaching portion  431   a . 
     (4) The sheet presence sensor  442  is attached to the support wall  430 . That is, with the frame contact portion  461  of the first guide wire  460  positioned as described in (3), the sheet presence sensor  442  is fixed to the attaching portion  431   a  by screwing or snap-fitting. Thereby, one of the end portions of the first guide wire  460  is retained in the space between the wall surface of the support wall  430 , the attaching portion  431   a , and the sheet presence sensor  442 , i.e., the first retaining portion. 
     (5) The remaining part of the first guide wire  460  is attached to the support wall  430  as proper fixing of the first guide wire  460 . That is, the vertical guide portion  464  of the first guide wire  460  retaining the first branch line W 1  is laid along the ribs  435   b  to  435   d . Then, with the pressure contact portion  466  of the first guide wire  460  overlapped with the abutment portion  472  of the second guide wire  470 , the end portion of the first guide wire  460  is hung on the spring hook portion  430   c  of the support wall  430  and fixed thereto. Thereby, the other end portion of the first guide wire  460  will be retained by the spring hook portion  430   c  serving as a second retaining portion. Further, an arm portion opposite to the spring hook portion  430   c  of the pressure contact portion  466  which is a torsion coil spring comes to be in pressure contact with the abutment portion  472 , such that conduction of the first guide wire  460  and the second guide wire  470  is ensured. Further, by having both end portions of the first guide wire  460  fixed, the first branch line W 1  will be in a state guided by the vertical guide portion  464  and wired along the support wall  430 . 
     (6) The sheet leaning sensor  450  is attached to the support wall  430 . That is, the sheet leaning sensor  450  is fixed to the attachment portion  431   b  of the support wall  430  by screwing or snap-fitting. 
     (7) The trunk line W 0  is attached to the second guide wire  470 , that is, the trunk line W 0  and the second guide wire  470  are integrated. In other words, each of the helical portions  475  provided on the horizontal guide portion  473  of the second guide wire  470  are wound around the trunk line W 0  of the cable harness W. In this state, since the other end portion of the second guide wire  470 , that is, the hook portion  474 , is not fixed to the support wall  430 , such that the helical portion  475  can be easily wound around the trunk line W 0  in a similar method as that described in (2). Thereby, the trunk line W 0  is retained by the second guide wire  470  with each of the helical portions  475  twisted around the trunk line W 0 . 
     (8) The remaining part of the second guide wire  470  is attached to the support wall  430  as proper fixing of the second guide wire  470 . That is, the horizontal guide portion  473  of the second guide wire  470  retaining the trunk line W 0  is laid along the ribs  435   g  to  435   j . Then, the hook portion  474  of the second guide wire  470  is hooked to the rib  435   k  serving as the second retaining portion and fixed thereto. By having both end portions of the second guide wire  470  fixed, the trunk line W 0  will be in a state guided by the horizontal guide portion  473  and wired along the support wall  430 . 
     Advantages of Present Embodiment 
     As described above, according to the present embodiment, the electric cable, i.e., the cable harness W, is retained by guide members, i.e., the first guide wire  460  and the second guide wire  470 , which are wire-forming members formed of a wire material made of metal, and the guide members are attached to the casing  201  to thereby allow the electric cable to be wired. In the attached state, the first guide wire  460  and the second guide wire  470  retain the cable harness W by being twisted around the cable harness W. Therefore, the space required to arrange the cable harness W can be reduced compared to a case where resin guides having U-shaped cross-sections are continuously arranged along the wiring path of the cable harness W. 
     Further, by twisting the helical portions  465  and  475  of the first guide wire  460  and the second guide wire  470  around the cable harness W and attaching the first guide wire  460  and the second guide wire  470  to the casing  201 , the cable harness W can be wired on the casing  201 . Therefore, the workability of wiring the cable harness W can be improved compared to a configuration where the cable harness W must be nipped by or hooked on a large number of projections formed on the casing  201 . 
     Especially according to the present embodiment, an occupation volume in which the cable harness W is retained by the first guide wire  460  and the second guide wire  470 , which are the vertical guide portion  464  and the horizontal guide portion  473 , is approximately equivalent to a volume of a cylinder having the same outer diameter as the helical portions  465  and  475 . Therefore, the space required for wiring the cable harness W can be further reduced. 
     Further, the first guide wire  460  and the second guide wire  470  are each formed in a shape capable of having the helical portions  465  and  475  twisted around the cable harness W in a state where one end portion of the guide wire is retained by the support wall  430  and the other end portion of the guide wire is not retained by the support wall  430 . That is, the shape, i.e., pitches and number of turns, of the helical portion  465  is determined such that the helical portion  465  can be easily twisted around the first branch line W 1  by turning the other end portion of the first guide wire  460  around the first branch line W 1 . Similarly, the shapes, i.e., pitches and number of turns, of the helical portion  475  is determined such that the helical portion  475  can be easily twisted around the trunk line W 0  by turning the other end portion of the second guide wire  470  around the trunk line W 0 . According to such configuration, the operation for having the cable harness W retained by the first guide wire  460  and the second guide wire  470  can be performed at positions distant from the support wall  430 , such that the operation space is easily ensured and the workability is enhanced. 
     Further according to the present embodiment, as illustrated in  FIG.  5   , the first branch line W 1  and one of the tension springs  433  for the sliding walls  432  are arranged adjacently. The sliding walls  432  and the sheet presence sensor  442  at the connection destination of the first branch line W 1  correspond to various sizes of sheets, such that they are preferably arranged near the center of the support wall  430  in the X axis direction. According to this arrangement, the space required for the wiring of the first branch line W 1  is small, such that the first branch line W 1  can be wired through the space formed between the sheet presence sensor  442  and the tension spring  433  in the X axis direction. 
     In the arrangement where the sliding walls  432  are arranged close to the first branch line W 1 , if the first branch line W 1  comes into contact with the sliding walls  432  during movement of the sliding walls  432 , for example, the insulator of the first branch line W 1  may be worn, and the conductor arranged therein may be exposed, causing short circuit. Regarding this drawback, according to the present embodiment, the first branch line W 1  is wired through the inner side of two helical portions  465 , such that the first branch line W 1  is retained approximately in parallel with the tension spring  433 . Thereby, the first branch line W 1  and the sliding walls  432  are prevented from being in contact with each other, and the first branch line W 1  can be protected from the tension spring  433  serving as the movable part. 
     Further, a sheet metal frame not shown of the sheet processing apparatus is adjacently arranged on the rear side of the horizontal guide portion  473  of the second guide wire  470 . In order to protect the cable harness W from the edge of the sheet metal frame, helical portions  475  can be arranged at three areas in midway of the horizontal guide portion  473 . Since the horizontal guide portion  473  is longer than the vertical guide portion  464  of the first guide wire  460 , the number of helical portions  475  are increased to three so as to prevent sagging of the cable harness W between the helical portions. According to this configuration, even if the edge of the sheet metal frame comes into contact with the surface of the helical portion  475 , the trunk line W 0  passing through the inner side of the helical portion  475  can be prevented from being in contact with the edge of the sheet metal frame and damaged thereby. 
     Incidentally, the inner diameter of the helical portion  465  is set with some margin from the diameter of the first branch line W 1 . The outer diameter of the helical portion  465  is a value having added twice the wire diameter of the wire material used as the material of the first guide wire  460  to the inner diameter. 
     In the case of a guide made of resin, a total amount of a thickness of a base portion of the guide attached to the support wall  430 , a thickness of the hook shape protruded from the base portion, and a space between the base portion and the hook shape through which the cable harness is passed, is the thickness required for wiring. The thicknesses of the base portion and the hook shape are varied according to the required strength or fire-resistance, and for example, it is approximately between 1.0 mm and 1.6 mm. Therefore, when a cable harness having a diameter of 3 mm is used, a thickness of 7.2 mm was required for wiring the cable harness, assuming that the width of the space through which the cable harness is passed is 4 mm and the thickness of the base portion and hook shape is 1.6 mm. The thickness is increased further if reinforcement ribs are formed to ensure the strength of the hook portions. 
     Meanwhile, according to the present embodiment, the first guide wire  460  is formed by a wire having a wire diameter of 0.5 mm, for example, and the first branch line W 1  is retained by the helical portions  465 . In this case, even if the inner diameter of the helical portion  465  is set to 4 mm, which is the same width as the space between the base portion and hook shape described earlier, the thickness of the helical portion  465  can be as small as 5.0 mm, such that a reduction of thickness of 2.2 mm is enabled. The sheet metal frame of the postprocessing apparatus  200  and the mechanism within the apparatus are arranged on the rear surface of the support wall  430 , such that by reducing the necessary thickness for wiring the cable harness W, that is, the width occupied in the Y axis direction, the space within the casing  201  can be utilized efficiently while protecting the cable harness W. 
     Further according to the present embodiment, the first guide wire  460  is made to come into contact with a sheet metal frame  201 M of the casing  201  and grounded. Since the first guide wire  460  made of the metal wire is grounded, the first guide wire  460  can be provided with a function to cope with electrostatic discharge (ESD). Further, since the second guide wire  470  is grounded via the first guide wire  460 , the second guide wire  470  can also be provided with a function to cope with ESD. 
     Specifically, according to the present embodiment, sensors, which are the sheet presence sensor  442  and the sheet leaning sensor  450 , formed to detect the sheet on the outer side of the support wall  430  through the opening portions, which are the slit  430   a  and the window portion  430   b , formed on the support wall  430  are used. According to this configuration, a portion, that is, the vertical portion  462 , that passes the circumference of the opening portion, i.e., the slit  430   a , along the support wall  430  is provided on the first guide wire  460 , independently from the portion, i.e., the vertical guide portion  464 , for guiding the cable harness W. Further, the second guide wire  470  also has a portion, i.e., the horizontal portion  471 , that passes the circumference of the opening portion, i.e., the window portion  430   b , along the support wall  430  independently from the portion, i.e., the horizontal guide portion  473 , for guiding the cable harness W. 
     According to this configuration, even if a part of the user body in a charged state comes close to the opening portion of the support wall  430  and electrostatic discharge enters the casing  201 , for example, the current can be released to ground potential by the first guide wire  460  and the second guide wire  470 . Therefore, the sheet presence sensor  442 , the sheet leaning sensor  450 , the control unit  250 , and other electronic components can be protected from electrostatic discharge. Further, by adopting an elastic shape as the first guide wire  460  and the second guide wire  470 , a conduction path to the ground potential can be ensured more reliably. 
     Furthermore, the first guide wire  460  and the second guide wire  470  serving as guide members according to the present embodiment are wire-forming members that are manufactured by bending metal wires from various directions by a wire-forming machine and the like, such that there is no need for a resin mold. Therefore, initial costs can be suppressed compared to a case where resin guide members are used. 
     Further, if fine-tuning of the wire length of the cable harness W or the wiring path is necessary, in a case where resin guide members are used, the molds must be cut or welded to realize adjustment, such that the costs for modification tends to be increased. In comparison, the guide member according to the present embodiment which is a wire-forming member formed of metal wire can cope with such fine-tuning with a relatively low cost by changing and adjusting programs of the wire forming machine. 
     According further to the guide members formed of resin, flashes and steps that may be generated at cavities and cores of a mold must be managed strictly to fall within a predetermined reference, such as 0.1 mm or less, so as not to damage the insulator of the cable harness by the guide member, and a periodical mold maintenance is required. Further, according to guide members formed of resin, the mold must be rounded to eliminate edges therefrom, but there are areas such as the joint between slides where rounding cannot be performed. There are limitations related to manufacture and design since it is necessary to consider a design in which such areas are not positioned along the wiring path of the cable harness. 
     In contrast, the guide member according to the present embodiment which is a wire-forming member formed of a metal wire does not require any management and maintenance of joints as in the case of molds, and edges are normally not generated during manufacture other than the cut surfaces at both ends of the metal wire. Therefore, the risk of damaging the cable harness can be suppressed. Specifically, the risk of damaging the cable harness can be suppressed even further by using a wire material having a round cross-sectional shape. Modified Example 
     The helical portions  465  and  475  described above have cylindrical shapes, but the helical shapes thereof can also be formed by repeatedly bending the wire material to form a polygonal shape when viewed in the axial direction. For example, the helical portions  465  and  475  can be formed in a square column shape in which the wire material is bent to form a square shape when viewed in the axial direction, that is, the direction in which the cable harness W is wired. 
     Further according to the present embodiment, the first branch line W 1  guided by the first guide wire  460  is extended approximately linearly in the Z axis direction, and the trunk line W 0  guided by the second guide wire  470  is extended approximately linearly in the X axis direction. The present technique is not limited to this example, and the guide member can guide the electric cable along a bent or curved wiring path. In that case, the helical portions  465  and  475  are arbitrarily arranged at and oriented along the wiring path. 
     Second Embodiment 
     A guide member according to a second embodiment will be described. The guide member according to the present embodiment has a shape that differs from the guide member according to the first embodiment. In the following description, the elements denoted with the same reference numbers as the first embodiment are assumed as having an equivalent configuration and effect as those described in the first embodiment, and only the parts that differ from the first embodiment will mainly be described. 
       FIG.  6    is a perspective view illustrating a wiring configuration of the postprocessing apparatus  200  equipped with a second guide wire  480  according to the present embodiment viewed from a rear side of the support wall  430 , with the cable harness W not attached.  FIG.  7    is a perspective view illustrating a state in which the second guide wire  480  with the cable harness W attached thereto is mounted on the support wall  430 . 
     As illustrated in  FIG.  6   , the second guide wire  480  according to the present embodiment has a wave shape in which projections and recesses (or ridges and valleys) are repeatedly formed in a predetermined direction intersecting with the direction, i.e., intersecting direction, especially the Z direction, along the main wiring direction, i.e., X axis direction, of the cable harness W, i.e., trunk line W 0 . More specifically, the second guide wire  480  according to the present embodiment includes connecting portions  486  composed of crank shapes, i.e., rectangular waves, formed by right-angled bends. 
     Each connecting portion  486  includes at least two cranked portions  485  that are arranged continuously in the wiring direction. Each cranked portion  485  that corresponds to one rectangular wave includes a rising portion  485   a  that rises upward in a right-angled bend from an extended portion that extends in an extending direction, i.e., X axis direction, of a horizontal guide portion  483 , and a parallel portion  485   b  that extends in parallel with the extending direction from the second right-angled bend. Further, each cranked portion  485  includes a falling portion  485   c  that returns downward at a third right-angled bend, and returns to the extended portion of the horizontal guide portion  483  at the fourth right-angled bend. Such cranked portion  485  is provided at least at two areas in the horizontal guide portion  483 . 
     Then, as illustrated in  FIG.  7   , the cable harness W and the cranked portions  485  are intertwined such that the cable harness W, i.e., trunk line repeatedly passes a front side of the rising portion  485   a  from one side toward the other side in the wiring direction, i.e., X axis direction, then returns by passing the rear side of the falling portion  485   c . That is, when viewed in the direction, i.e., Y axis direction, intersecting both the wiring direction of the cable harness W, i.e., X axis direction, and the predetermined direction, i.e., Z axis direction, the cable harness W is in a state alternately passing the front side and the depth side of the second guide wire  480  along the wiring direction. 
     If the cable harness W is considered as the subject, the connecting portions  486  of the second guide wire  470  are wound around the cable harness W along the wiring direction. When viewed from any direction of 360° within a plane orthogonal to the wiring direction, i.e., X axis direction, there is at least one area where the second guide wire  470  intersects the cable harness W on the front side of the cable harness W. The relationship between the second guide wire  480  and the cable harness W according to the present embodiment can be described as one aspect in which one of the two thread members is twisted around (i.e., turned around or rolled around) the other. If the second guide wire  470  is considered as the subject, the cable harness W is wound around the second guide wire  470  along the wiring direction, such that in the present embodiment, the cable harness W and the second guide wire  470  can also be described as being twisted around each other. 
     We will now describe the necessary number of contact areas, i.e., intersecting points, between the guide member retaining the cable harness and the cable harness. As illustrated in  FIG.  8 A , if there is only one contact, or intersection, the cable harness will easily separate from the guide member ( FIG.  8 B ). If there are two contacts, i.e., intersections, as illustrated in  FIG.  9 A , the turning of the cable harness in a direction in which the right end thereof in the drawing heads toward the depth direction and the left end thereof heads toward the front direction is not restricted, such that the cable harness will separate relatively easily ( FIG.  9 B ). If there are three contacts, or intersections, as illustrated in  FIG.  10   , the turning in both directions is restricted by the contact area positioned at the center, such that the cable harness will not easily separate from the guide member. 
     In the present embodiment, as illustrated in  FIGS.  6  and  7   , the connecting portions  486  are provided, each connecting portion  486  having at least two cranked portions  485  arranged continuously. In the illustrated example, there are three connecting portions  486  each composed of two cranked portions  485  provided on the horizontal guide portion  483 . In the area between the connecting portions  486 , the horizontal guide portion  483  serves as an extended portion that extends linearly and approximately in parallel with the wiring direction of the cable harness W, i.e., X axis direction. The number in which one connecting portion  486  intersects with the cable harness W in the Y axis direction is set to three or more, the number being the total number of the rising portions  485   a  and falling portions  485   c . Meanwhile, the number in which one connecting portion  486  intersects with the cable harness W is set to  10  or less, preferably six or less, such that the operation of intertwining the cable harness W with the connecting portions  486  is not too complex. However, the entire horizontal guide portion  483  can be formed to have one continuous wave shape in which the cranked portions  485  are formed continuously. 
     As described, if the cable harness W is intertwined to the connecting portions  486  including at least two cranked portions  485 , as illustrated in  FIG.  7   , the cable harness W intersects at three or more areas with the second guide wire  480  in one connecting portion  486 . Thereby, the cable harness W will not be turned with respect to the second guide wire  480  when viewed in the Z axis direction. Further, even if the cable harness W attempts to move in an arbitrary direction intersecting with the extending direction of the cable harness W, i.e., X axis direction, the cable harness W will interfere with a part of the cranked portions  485 . Therefore, the cable harness W will be retained without falling from the second guide wire  480 . 
     Even according to the present embodiment, the cable harness W can be intertwined with the connecting portions  486  while having one of the end portions of the second guide wire  480  retained on the support wall  430  and winding the other end portion of the second guide wire  480  around the cable harness W. In other words, the widths and heights of the cranked portions  485  are set such that the cable harness W can be easily intertwined with the cranked portions  485  by winding the second guide wire  480  around the cable harness W. 
     The method for attaching the second guide wire  480  to the support wall  430  is basically the same as the first embodiment. The first guide wire  460  similar to that of the first embodiment can be used, or the first guide wire  460  having cranked shapes can be used instead of the helical portions  465 . 
     As described, also according to the present embodiment, by having the electric cable retained by the guide member formed of a metal wire material and attaching the guide member to the casing, the space required for wiring the electric cable can be reduced while improving the workability of the wiring operation. 
     One of the advantages of the present embodiment is that the second guide wire  480  can be formed more easily. That is, the guide member according to the first embodiment has helical portions  465  and  475  having helical shapes formed continuously with the linear portion, such that there is a need to cautiously set the processing conditions of the wire-forming process. In contrast, the second guide wire  480  according to the present embodiment includes the cranked portions  485  composed of right-angle bends as the shapes for retaining the cable harness W, such that the bending process can be performed more easily. 
     According further to the present embodiment, the cable harness W is wired in a manner stitched between the cranked portions  485  of the second guide wire  480 , such that when the cable harness W is pulled in the wiring direction, the frictional force received from the cranked portions  485  restricts the movement of the cable harness W. Therefore, even if external force is applied in the direction pulling the cable harness W after having the cable harness W retained in the second guide wire  480 , the cable harness W will not be easily displaced with respect to the second guide wire  480 . 
     Third Embodiment 
     A guide member according to a third embodiment will be described. The guide member according to the present embodiment is a modified example of the guide member according to the second embodiment. In the following description, the elements denoted with the same reference numbers as the first embodiment are assumed as having an equivalent configuration and effect as those described in the first embodiment, and only the parts that differ from the first embodiment will mainly be described. 
       FIG.  11    is a perspective view illustrating a wiring configuration of the postprocessing apparatus  200  equipped with a second guide wire  490  according to the present embodiment viewed from a rear side of the support wall  430 , with the cable harness W not attached.  FIG.  12    is a perspective view illustrating a state in which the second guide wire  490  with the cable harness W attached thereto is mounted on the support wall  430 . 
     According to the second embodiment, the cable harness W is intertwined with the connecting portions  486  having a perpendicularly cranked shape, i.e., rectangular waves, of the second guide wire  480 , whereas in the present embodiment, a second guide wire  490  having connecting portions  496  of triangular cranked shapes, i.e., triangular waves, is used. As illustrated in  FIG.  11   , the connecting portions  496  include at least two triangular cranked portions  495  that are formed continuously in the wiring direction of the cable harness W, i.e., the X axis direction. 
     Each triangular cranked portion  495  includes a rising portion  495   a  that rises upward by being bent in an obtuse angle from the extended portion that extends in the extending direction, i.e., X axis direction, of a horizontal guide portion  493 , and a falling portion  495   b  that extends downward by being bent in an acute angle from the rising portion. The triangular cranked portion  495  returns to the extended portion at the second bent portion bent in the obtuse angle from the falling portion  495   b . The angles of the obtuse angle and the acute angle are, for example, 120° and 60° in the inner side angles of the bent portion. 
     That is, the connecting portions  496  according to the present embodiment are formed in the shapes of triangular waves as another example of the wave shapes that are formed in the shapes of repeated projections and recesses in the predetermined direction, i.e., intersecting direction, especially the Z axis direction, intersecting with the wiring direction of the main wiring direction, i.e., X axis direction, of the cable harness W, i.e., the trunk line W 0 . 
     Then, as illustrated in  FIG.  12   , the cable harness W and the triangular cranked portions  495  are intertwined such that the cable harness W, i.e., the trunk line repeatedly passes a front side of the rising portion  495   a  from one side toward the other side in the wiring direction, i.e., X axis direction, then returns by passing a rear side of the falling portion  495   b . In other words, when viewed in the direction, i.e., Y axis direction, intersecting both the wiring direction of the cable harness W, i.e., X axis direction, and the predetermined direction, i.e., Z axis direction, the cable harness W is passed alternately through the front side and the depth side of the second guide wire  490  along the wiring direction. The relationship between the second guide wire  490  and the cable harness W according to the present embodiment can also be referred to as one aspect in which one of the two thread members is twisted around the other. 
     As described, if the cable harness W is intertwined with the connecting portions  496  including at least two triangular cranked portions  495 , as illustrated in  FIG.  12   , the cable harness W is intersected at least at three areas of the second guide wire  490  in one connecting portion  496 . According to this configuration, the cable harness W will not be turned with respect to the second guide wire  490  when viewed in the Z axis direction. Further, even if the cable harness W attempts to move in an arbitrary direction intersecting the extending direction of the cable harness W, i.e., X axis direction, the cable harness W will interfere with a part of the triangular cranked portions  495 . Therefore, the cable harness W will be retained without falling from the second guide wire  490 . 
     Also according to the present embodiment, the cable harness W can be intertwined with the connecting portions  496  while having one of the end portions of the second guide wire  490  retained on the support wall  430  and the other end portion of the second guide wire  490  wound around the cable harness W. In other words, the widths and heights of the triangular cranked portions  495  are set such that the cable harness W can be easily intertwined with the triangular cranked portions  495  by winding the second guide wire  490  around the cable harness W. 
     The method for attaching the second guide wire  490  to the support wall  430  is basically the same as the first embodiment. The first guide wire  460  similar to that of the first embodiment can be used, or the first guide wire  460  having triangular cranked shapes can be used instead of the helical portions  465 . 
     As described, also according to the present embodiment, by having the electric cable retained by the guide member formed of a metal wire material and attaching the guide member to the casing, the space required for wiring the electric cable can be reduced while improving the workability of the wiring operation. 
     Modified Example 
     The connecting portions  486  and  496  of the second guide wire  490  according to the second and third embodiments are merely examples of the wave shapes in which projections and recesses in the predetermined direction are continuously repeated along the wiring direction, and for example, wave-shaped connecting portions in which semicircles facing up and semicircles facing down are continuously formed can be used. 
     Fourth Embodiment 
     A guide member according to a fourth embodiment will be described. In the following description, the elements denoted with the same reference numbers as the first embodiment are assumed as having an equivalent configuration and effect as those described in the first embodiment, and only the parts that differ from the first embodiment will mainly be described. 
       FIG.  13    is a perspective view illustrating a state in which a second guide wire  500  according to the present embodiment with the cable harness W attached thereto is mounted on the support wall  430 . A horizontal guide portion  503  of the second guide wire  500  according to the present embodiment is formed linearly in a manner approximately horizontally with the X axis direction which is the main wiring direction of the cable harness W, i.e., the trunk line W 0 . 
     The cable harness W is twisted helically around the horizontal guide portion  503 . Therefore, when viewed from any direction of 360° within a plane orthogonal to the wiring direction, i.e., X axis direction, there is at least one area where the second guide wire  500  intersects with the cable harness W on the front side of the cable harness W. In other words, the relationship between the second guide wire  500  and the cable harness W according to the present embodiment can be described as one example of an aspect in which one of the two thread members is twisted around the other. 
     The number and intervals of the twisting of the cable harness W around the horizontal guide portion  503  is determined by taking into consideration the number of cables in the cable harness W and the length of the horizontal guide portion  503 , for example. If the cable harness W is loosened or separated, it is desirable to twist the cables of the cable harness W in advance. Other Examples 
     The above embodiments have illustrated a wiring configuration of the cable harness W connecting the control unit  250  to the sheet presence sensor  442  and the sheet leaning sensor  450  in the postprocessing apparatus  200 . The techniques described in the present disclosure is not limited to this example, and can be applied to wirings in general adopted in sheet conveyance apparatuses. The sheet conveyance apparatuses refer to apparatus for conveying sheet materials in general, and for example, they can be an image forming apparatus body for forming images on sheets while conveying sheets, or an image reading apparatus for reading image information while conveying sheets. 
     For example, various sensors are arranged in the sheet conveyance apparatus with the aim to control sheet conveyance, detect conveyance abnormalities, and detect stacked amount of sheets, for example. Examples include the sheet sensor  209  ( FIG.  1   ) for detecting sheets along the conveyance path of the postprocessing apparatus  200 , and a full-load detection sensor for detecting that the stacked amount of sheets on the sheet discharge tray has reached an upper limit. Further, various actuators are disposed in the sheet conveyance apparatus, such as a motor for driving conveyance members such as roller pairs and belts for conveying sheets, a motor for lifting and lowering stacking portions, and a solenoid for opening and closing a nip portion of the roller pair. The technique taught in the present disclosure is applicable to the wiring configuration of electric cables connecting such sensors or actuators with the control unit of the sheet conveyance apparatus. 
     The technique according to the present disclosure is applicable not only to electric cables connecting sensors or actuators with control units, but also to wiring configurations of electric cables connecting power supply boards with devices receiving power supply from the power supply boards or to electric cables connecting control units with relay boards. 
     Other Embodiments 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-183831, filed on Nov. 11, 2021, which is hereby incorporated by reference herein in its entirety.