Patent Publication Number: US-10315878-B2

Title: Sheet conveying device, sheet discharging device incorporating the sheet conveying device and image forming apparatus incorporating the sheet conveying device and the sheet discharging device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2016-256775, filed on Dec. 28, 2016, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     This disclosure relates to a sheet conveying device, a sheet discharging device, and an image forming apparatus incorporating the sheet conveying device and the sheet discharging device. 
     Related Art 
     Sheet discharging devices that discharge a sheet are known to employ a photointerrupter to detect that the height of stack of image printed sheets in a sheet ejection tray has reached a predetermined height or above, and a feeler that projects upward from the sheet ejection tray and swings in a vertical direction such that the photointerrupter detects the feeler when the amount of loaded sheets on the sheet ejection tray is equal to or above the predetermined amount. 
     In a known sheet discharging device, a part of a full detection feeler that functions as a feeler projecting upwardly from the sheet ejection tray to contact a sheet on the sheet ejection tray can retreat manually, in order to connect a post processing device immediately after the sheet discharging device. The full detection feeler vertically swings in a regular printing mode and is manually changed in a retreating direction that is perpendicular to the vertical direction when the feeler contacts the sheet discharging device. 
     However, the sheet discharging device has a problem that, when a sheet is picked up from the sheet ejection tray, the sheet to be picked up is caught by the full detection feeler, and therefore the operability is deteriorated and the full detection feeler is damaged or broken. 
     Further, in order to connect the post processing device immediately after the sheet discharging device, the full detection feeler is manually retreated to a position at which the full detection feeler does not contact the sheet to be picked up. However, when the sheet is picked up while the full detection feeler is retreated to the above-described position, there are many operation processes to take, which is troublesome. 
     Furthermore, when the machine is operated (when the printing operation is performed), the full detection feeler needs to be returned manually before the operation. Therefore, when the full detection feeler is not returned, the sheet full state is not detected. Accordingly, prevention of a sheet stacking failure and a paper jam is fairly costly. 
     SUMMARY 
     At least one aspect of this disclosure provides a sheet conveying device including a contact body, a shaft, a sheet detector and a rotary body support. The contact body is configured to rotate while contacting a sheet in conveyance. The shaft is configured to rotate together with the contact body in a range of rotation of the contact body. The sheet detector is configured to detect presence of the sheet through detection of rotation of the shaft rotating with the contact body in contact with the sheet. The rotary body support is configured to rotatably support the contact body to the shaft that rotates together with the contact body in contact with the sheet, extending the range of rotation, in a same direction as the direction of rotation of the shaft. 
     Further, at least one aspect of this disclosure provides a sheet discharging device including a sheet discharging body, a sheet stacker and the above-described sheet conveying device. The sheet discharging body is configured to discharge the sheet. The sheet stacker is a stacker on which the sheet is discharged by the sheet discharging body. The sheet detector is a stack height detector configured to detect that the height of the sheet stacked on the sheet stacker is equal to or higher than a predetermined height. 
     Further, at least one aspect of this disclosure provides an image forming apparatus including one of the above-described sheet conveying device and the above-described sheet discharging device. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       An exemplary embodiment of this disclosure will be described in detail based on the following figured, wherein: 
         FIGS. 1A and 1B  are perspective views illustrating an exterior of an image forming apparatus according to an embodiment of this disclosure; 
         FIG. 2  is a cross sectional view illustrating the entire configuration of the image forming apparatus of  FIG. 1 ; 
         FIG. 3A  is a diagram illustrating a full detection feeler provided to a sheet discharging device included in the image forming apparatus of  FIG. 2 , when no sheet is stacked on a sheet stacker; 
         FIG. 3B  is a diagram illustrating the full detection feeler provided to the sheet discharging device, when an amount of sheets discharged on the sheet stacker exceeds a predetermined sheet stacking amount; 
         FIG. 4A  is a perspective view illustrating the full detection feeler of the sheet discharging device of  FIGS. 3A and 3B ; 
         FIG. 4B  is an exploded perspective view illustrating the configuration of detection of a sheet full state of the printed sheets; 
         FIG. 4C  is a perspective view illustrating a relation of a change of swing angle of a blocking member at the standby position of the full detection feeler and a detection by a photointerrupter; 
         FIG. 4D  is a perspective view illustrating a relation of the change of swing angle of the blocking member when the full detection feeler is in the sheet full state and the detection by the photointerrupter; 
         FIG. 5A  is a cross sectional view illustrating the sheet stacker and the full detection feeler in an initial standby state during a print job; 
         FIG. 5B  is a cross sectional view illustrating movement of the full detection feeler during the print job of  FIG. 5A ; 
         FIG. 5C  is a cross sectional view illustrating the sheet stacker and the full detection feeler when the full detection feeler is in contact with the sheet during the print job; 
         FIG. 5D  is a cross sectional view illustrating movement of the full detection feeler when the full detection feeler is in contact with the sheet during the print job of  FIG. 5C ; 
         FIG. 6A  is a cross sectional view illustrating the sheet stacker and the full detection feeler when the full detection feeler is in contact with the sheet during the print job; 
         FIG. 6B  is a cross sectional view illustrating movement of the full detection feeler during the print job of  FIG. 6A ; 
         FIG. 6C  is a cross sectional view illustrating the sheet stacker and the full detection feeler when the sheet is stacked in the sheet stacker during the print job; 
         FIG. 6D  is a cross sectional view illustrating movement of the full detection feeler during the print job of  FIG. 6C ; 
         FIG. 7A  is a diagram illustrating the sheet stacker and the full detection feeler when multiple sheets are stacked in the sheet stacker during the print job; 
         FIG. 7B  is a cross sectional view illustrating movement of the full detection feeler during the print job of  FIG. 7A ; 
         FIG. 8A  is a cross sectional view illustrating inconvenience of the sheet stacker and the full detection feeler when the printed sheet P′ is removed from the sheet stacker; 
         FIG. 8B  is a perspective view illustrating the full detection feeler of  FIG. 8A ; 
         FIG. 8C  is an enlarged view illustrating the full detection feeler of  FIG. 8A ; 
         FIG. 9A  is a perspective view illustrating a full detection feeler provided to a sheet discharging device according to Embodiment 1 of this disclosure, when the full detection feeler is in an initial standby state; 
         FIG. 9B  is a perspective view illustrating an engaging state of the full detection feeler of  FIG. 9A  and the photointerrupter; 
         FIG. 10A  is a perspective view illustrating the full detection feeler of  FIGS. 9A and 9B , with the sheet contact member and the feeler body rotating together to the swing upper limit position; 
         FIG. 10B  is an enlarged cross sectional view illustrating the sheet contact member and the feeler body of  FIG. 10A , viewed along a plane B; 
         FIG. 10C  is a perspective view illustrating the full detection feeler of  FIGS. 9A and 9B , that the feeler body is stopped at the swing upper limit position and the sheet contact member rotates from the swing upper limit position to a retracted position; 
         FIG. 10D  is an enlarged cross sectional view illustrating the sheet contact member and the feeler body of  FIG. 10C , viewed along a plane B; 
         FIGS. 11A, 11B, 11C and 11D  are diagrams illustrating an area around the sheet contact portion and a rotation support of the full detection feeler of  FIGS. 9A and 9B ; 
         FIGS. 12A and 12B  are diagrams illustrating yet another area around the sheet contact portion and the rotation support of the full detection feeler of  FIGS. 9A and 9B ; 
         FIGS. 13A, 13B and 13C  are diagrams illustrating yet another area around the sheet contact portion of the rotation support and the full detection feeler of  FIGS. 9A and 9B ; 
         FIGS. 14A, 14B, 14C and 14D  are diagrams illustrating removal of stacked sheet with the full detection feeler according to Embodiment 1; 
         FIGS. 15A, 15B and 15C  are diagrams illustrating a configuration and operations of the full detection feeler according to Embodiment 1; 
         FIGS. 16A, 16B and 16C  are diagrams illustrating the configuration and further operations of the full detection feeler according to Embodiment 1; 
         FIGS. 17A, 17B and 17C  are diagrams illustrating the configuration and yet further operations of the full detection feeler according to Embodiment 1; 
         FIG. 18  is a diagram illustrating a configuration of the full detection feeler having a second pressing force, according to Variation of this disclosure; 
         FIGS. 19A and 19B  are diagrams diagram illustrating movement of the full detection feeler according to Variation of  FIG. 18 ; and 
         FIG. 20  is a diagram illustrating a main part of the sheet conveying device according to Embodiment 2 of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It will be understood that if an element or layer is referred to as being “on”, “against”, “connected to” or “coupled to” another element or layer, then it can be directly on, against, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, if an element is referred to as being “directly on”, “directly connected to” or “directly coupled to” another element or layer, then there are no intervening elements or layers present. Like numbers referred to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements describes as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, term such as “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors herein interpreted accordingly. 
     Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, it should be understood that these elements, components, regions, layer and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure. 
     The terminology used herein is for describing particular embodiments and examples and is not intended to be limiting of exemplary embodiments of this disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Descriptions are given, with reference to the accompanying drawings, of examples, exemplary embodiments, modification of exemplary embodiments, etc., of an image forming apparatus according to exemplary embodiments of this disclosure. Elements having the same functions and shapes are denoted by the same reference numerals throughout the specification and redundant descriptions are omitted. Elements that do not demand descriptions may be omitted from the drawings as a matter of convenience. Reference numerals of elements extracted from the patent publications are in parentheses so as to be distinguished from those of exemplary embodiments of this disclosure. 
     This disclosure is applicable to any image forming apparatus, and is implemented in the most effective manner in an electrophotographic image forming apparatus. 
     In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this disclosure is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes any and all technical equivalents that have the same function, operate in a similar manner, and achieve a similar result. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, preferred embodiments of this disclosure are described. Elements (for example, mechanical parts and components) having the same functions and shapes are denoted by the same reference numerals throughout the specification and redundant descriptions are omitted. 
     Here, it is to be noted in the following embodiments and variations that the term “swing” indicates a swing motion and a rotation in a forward direction and a backward direction at an angle of 360 degrees or smaller. 
     Now, a description is given of an electrophotographic image forming apparatus  100  for forming images by electrophotography. 
     First, a description is given of an exterior of an image forming apparatus  100  according to an embodiment of this disclosure, with reference to  FIG. 1 . 
       FIGS. 1A and 1B  are perspective views illustrating the exterior of the image forming apparatus  100  according to an embodiment of this disclosure. 
     It is to be noted that identical parts are given identical reference numerals and redundant descriptions are summarized or omitted accordingly. 
     The image forming apparatus  100  may be a copier, a facsimile machine, a printer, a multifunction peripheral or a multifunction printer (MFP) having at least one of copying, printing, scanning, facsimile, and plotter functions, or the like. According to the present example, the image forming apparatus  100  is an electrophotographic printer that prints toner images on recording media by electrophotography. 
     It is to be noted in the following examples that: the term “image forming apparatus” indicates an apparatus in which an image is formed on a recording medium such as paper, OHP (overhead projector) transparencies, OHP film sheet, thread, fiber, fabric, leather, metal, plastic, glass, wood, and/or ceramic by attracting developer or ink thereto; the term “image formation” indicates an action for providing (i.e., printing) not only an image having meanings such as texts and figures on a recording medium but also an image having no meaning such as patterns on a recording medium; and the term “sheet” is not limited to indicate a paper material but also includes the above-described plastic material (e.g., a OHP sheet), a fabric sheet and so forth, and is used to which the developer or ink is attracted. In addition, the “sheet” is not limited to a flexible sheet but is applicable to a rigid plate-shaped sheet and a relatively thick sheet. 
     Further, size (dimension), material, shape, and relative positions used to describe each of the components and units are examples, and the scope of this disclosure is not limited thereto unless otherwise specified. 
     Further, it is to be noted in the following examples that: the term “sheet conveying direction” indicates a direction in which a recording medium travels from an upstream side of a sheet conveying path to a downstream side thereof; the term “width direction” indicates a direction basically perpendicular to the sheet conveying direction. 
     In  FIG. 1 , “X” indicates a width direction of the image forming apparatus  100 , “Y” indicates a front-and-back direction that is perpendicular to the width direction X of the image forming apparatus  100 , “Z” indicates a vertical direction that is perpendicular to the width direction X of the image forming apparatus  100  and also perpendicular to the front-and-back direction Y of the image forming apparatus  100 , “Ya” indicates a sheet discharging direction that corresponds to a direction R of the front-and-back direction Y of the image forming apparatus  100 . 
     The image forming apparatus  100  in  FIGS. 1A and 1B  is a multi-functional image forming apparatus that includes a color laser printer  200 , an image reading device  301  and an auto document feeder (ADF)  302 . The color laser printer  200  is an apparatus body of the image forming apparatus  100 . The image reading device  301  that functions as a reading portion is disposed above the color laser printer  200  and includes a scanner and an image reading unit. The ADF  302  is a document feeding device disposed above the image reading device  301 . 
     A sheet feed tray  11  is disposed at the lower part of the color laser printer  200 . The sheet feed tray  11  is detachably attachable to the color laser printer  200  of the image forming apparatus  100  in the front-and-back direction Y and contains a sheet P or sheets P as sheet-shaped conveyance target member(s). 
     A sheet stacker  15  is disposed at the lower part of the color laser printer  200 . The sheet stacker  15  stacks a printed sheet P′ to be discharged after image formation performed in the color laser printer  200 . The sheet stacker  15  receives the printed sheet P′ to stack or load the printed sheet P′ in a state in which the leading end of the printed sheet P′ is directed to a downstream side of the sheet discharging direction Ya. 
     Further, a control unit  800  is disposed at an upstream side of the sheet discharging direction Ya of the sheet stacker  15  disposed above the color laser printer  200 . The control unit  800  is an interface that is used when instructions for operation are sent to the image forming apparatus  100 . 
     The image forming apparatus  100  is designed for users to perform various operations from one side thereof. That is, a user can operate the sheet feed tray  11 , the sheet stacker  15  and the control unit  800  of the image forming apparatus  100  from a front side in the front-and-back direction Y of the image forming apparatus  100  (i.e., the left side of  FIGS. 1A and 1B ). 
     Due to the exterior configuration of the image forming apparatus  100  with the control unit  800  disposed on the front side, as illustrated in  FIG. 1B , the printed sheet P′ stacked on the sheet stacker  15  cannot be picked up horizontally or in a horizontal direction to a front side F of the front-and-back direction Y (i.e., to the upstream side of the sheet discharging direction Ya). That is, as indicated by arrow A in  FIG. 1B , the printed sheet P′ is firstly lifted upwardly in the vertical direction Z and then is pulled out to the front side F of the front-and-back direction Y. 
     Now, a description is given of the entire configuration and functions of the image forming apparatus  100  of  FIGS. 1A and 1B , with reference to  FIG. 2 . 
       FIG. 2  is a cross sectional view illustrating the entire configuration of the image forming apparatus  100  of  FIG. 1 . 
     The color laser printer  200  includes an image forming device  50 , a sheet feeding device  60 , a fixing device  8  and a sheet discharging device  9 . The image forming device  50  performs image formation by electrophotography. The sheet feeding device  60  feeds the sheet P from the sheet feed tray  11  to the image forming device  50 . The fixing device  8  fixes an unfixed color or monochrome image transferred onto the sheet P in the image forming device  50  to the sheet P. The sheet P having a fixed toner image corresponds to the printed sheet P′. The sheet discharging device  9  functions as a recording medium discharging device to discharge the printed sheet P′ to the sheet stacker  15  after printing (fusing). 
     The image forming device  50  has a tandem-type intermediate transfer system in which a full color toner image, a two-color toner image, a three-color toner image or a monochrome toner image is formed with four process cartridges  51 . The process cartridges  51  are aligned corresponding to respective colors of black toner image, yellow toner image, magenta toner image and cyan toner image. 
     The four process cartridges  51  basically have an identical configuration to each other, except that the colors of respective toners used to form a color toner image are different. Therefore, the following description is given with reference numeral “ 51 ” without any suffix, K, Y, M and C, but is applied to any one of the process cartridges  51 Y,  51 M,  51 C, and  51 K. In  FIG. 2 , the reference numerals related to the process cartridge  51  are provided to the process cartridge  51  disposed at the extremely left side in the image forming apparatus  100 . 
     The process cartridge  51  (i.e. the process cartridges  51 K,  51 Y,  51 M and  51 C) includes a photoconductor  1 , a charging device  2 , an exposure device  3 , a developing device  4  and a cleaning device  5 . The photoconductor  1  functions as a rotatable image bearer. The charging device  2  uniformly charges a surface of the photoconductor  1 . The developing device  4  includes a developer cartridge  5 A and supplies toner onto the electrostatic latent image formed on the surface of the photoconductor  1  so as to develop the electrostatic latent image into a visible toner image. The cleaning device  5  cleans the surface of the photoconductor  1  after the toner image is transferred onto an intermediate transfer belt  6 . Since the photoconductor  1 , the charging device  2 , the exposure device  3 , the developing device  4  and the cleaning device  5  are integrally assembled in the process cartridge  51  (i.e. the process cartridges  51 K,  51 Y,  51 M and  51 C), these image forming parts are detachably attached to the casing of the color laser printer  200 . 
     The exposure device  3  is disposed between the charging device  2  and the developing device  4  in the color laser printer  200  as an apparatus body, for the photoconductor  1  of each process cartridge  51 . The exposure device  3  includes an optical writing head. The optical writing head of the exposure device  3  includes a light emitting element that uses a light emitting diode (LED) array to emit a light beam onto the charged surface of the photoconductor  1  so as to form an electrostatic latent image on the photoconductor  1 . 
     Through the operation instructed via the control unit  800 , the instruction of a copying operation or a printing operation is sent to the image forming apparatus  100 , the image formation starts in the image forming device  50 . The instruction of a printing operation via the control unit  800  is sent when image data is stored in the image forming apparatus  100 . The instruction of the printing operation is issued normally from a personal computer different from the image forming apparatus  100 . 
     The copying operation is performed based on a result of reading by the image reading device  301 , of an image formed on an original document conveyed from the ADF  302  or a result of reading by the image reading device  301 , of an image formed on an original document placed on top of an exposure glass of the image reading device  301 . 
     In image formation, the charging device  2  uniformly charges the surface of the photoconductor  1 . Then, based on an image data signal after color separation, the exposure device  3  emits a laser light beam form the light emitting element of the optical writing head of the exposure device  3  to the surface of the photoconductor  1 . Consequently, an electrostatic latent image is formed on the photoconductor  1  that rotates in a clockwise direction as indicated by arrows in  FIG. 2 . 
     Then, the developing device  4  includes the developer cartridge  5 A that contains one-component developer (i.e., toner). As the developer cartridge  5 A supplies toner, the developing device  4  develops the electrostatic latent image formed on the surface of the photoconductor  1  into a visible toner image with toner electrostatically attached thereto. It is to be noted that, when the developing device  4  uses two-component developer that includes toner and carrier, toner of the two-component developer is electrostatically attached to the electrostatic latent image on the photoconductor  1  to be developed into a visible toner image. 
     The above-described operations are performed in the four process cartridges  51  in parallel. The color laser printer  200  further includes primary transfer rollers  603  disposed opposing the respective photoconductors  1  with the intermediate transfer belt  6  therebetween. A primary transfer bias is applied to the intermediate transfer belt  6  and each primary transfer roller  603 . The intermediate transfer belt  6  is in contact with the photoconductors  1 . The respective toner images formed on the respective surfaces of the photoconductors  1  are sequentially transferred onto a surface of the intermediate transfer belt  6 . It is to be noted that the intermediate transfer belt  6  functions as an intermediate transfer body and is wound around a drive roller  601  and a driven roller  602 . 
     The transfer of the toner images from the photoconductors  1  onto the intermediate transfer belt  6  is performed at respect opposing positions of the photoconductors  1  facing the intermediate transfer belt  6 . After the photoconductor  1  passes the opposing position to the intermediate transfer belt  6 , residual toner remaining on the surface of the photoconductor  1  is removed by the cleaning device  5 , so that the photoconductor  1  is cleaned. 
     Along with the above-described operations, a sheet feeding operation starts to feed the sheet P to the image forming device  50 . The sheet P loaded in the sheet feed tray  11  is fed by rotation of a sheet feed roller  111 . The sheet P is then passes a relay roller  112  disposed in a single-side conveyance passage  12 , and brought to contact a nip region formed by a pair of registration rollers  14  that is temporarily stopped. Due to the contact of the sheet P to the nip region of the pair of registration rollers  14 , the sheet is curved. Accordingly, after the sheet P is corrected on an angular displacement that is a displacement to an axial direction of the pair of registration rollers  14 , the pair of registration rollers  14  starts the rotation thereof in synchronization with movement of the full-color toner image transferred onto the intermediate transfer belt  6 . Then, the sheet P is conveyed to a secondary transfer nip region formed between the intermediate transfer belt  6  and a secondary transfer roller  7  via the driven roller  602 . Then, the full-color toner image formed on the surface of the intermediate transfer belt  6  is applied with a secondary transfer bias having high electric potential by the secondary transfer roller  7 . Due to generation of a potential difference between the intermediate transfer belt  6  and the secondary transfer roller  7 , the full-color toner images formed on the intermediate transfer belt  6  is transferred onto the sheet P collectively. 
     The sheet P having the full-color toner image transferred thereon is fixed to the sheet P in the fixing device  8 , by application of heat and pressure. Further, the printed sheet V to which the color toner image is fixed is conveyed by a sheet discharging roller  95  and a sheet discharging driven roller  96  of the sheet discharging device  9  and is then discharged form an outlet port  90  of the sheet discharging device  9  before being stacked sequentially in the sheet stacker  15 . Accordingly, the printing operation is completed. The sheet discharging roller  95  and the sheet discharging driven roller  96  function as sheet discharging bodies by which the sheet P is discharged as the printed sheet P′. 
     By contrast, residual toner remaining on the surface of the intermediate transfer belt  6  without being transferred onto the sheet P at the secondary transfer nip region is removed by a belt cleaning device  604 , so that the intermediate transfer belt  6  is cleaned. 
     The sheet stacker  15  is formed on top of the color laser printer  200 , from the downstream side to the upstream side of the sheet discharging direction Ya (i.e., from the back side to the front side of the front-and-back direction Y) and being sloped toward the downward side in the vertical direction Z. The sheet stacker  15  has a sheet discharging rear end guide plate  93  that functions as a sheet discharging guide. The sheet discharging rear end guide plate  93  stands from the lowermost part of the sheet stacker  15 , upwardly toward an outlet port  90 . The sheet discharging guide is a member to regulate the position of the trailing end of the printed sheet P′ stacked in the sheet stacker  15  (i.e., the sheet discharging rear end guide plate  93 ) and to separate from the fixing device  8  provided to the color laser printer  200 . 
     The image forming apparatus  100  further includes a sheet reversing device  10 . The sheet reversing device  10  reverses the sheet P having a toner image on a first face thereof and guide the reversed sheet P to a duplex sheet conveyance passage  13  for duplex printing. The sheet reversing device  10  includes the sheet discharging roller  95 , a sheet reversing roller  97  and a passage switching member  98 . The sheet discharging roller  95  and the sheet reversing roller  97  change and reverse the sheet conveying direction of the leading end and the trailing end of the sheet P. The passage switching member  98  switches the direction of the sheet P from the single-side conveyance passage  12  to the duplex sheet conveyance passage  13 . 
     In addition, the image forming apparatus  100  further includes a bypass sheet tray  16  and a bypass sheet feed roller  161 , both are used when the sheet P is inserted from the bypass sheet tray  16 . 
     Further, the image forming apparatus  100  further includes a front cover  20  that opens and closed relative to the image forming apparatus  100 . The front cover  20  opens to release and expose the locations of the pair of registration rollers  14  and the secondary transfer roller  7 , disposed above the single-side conveyance passage  12 . When the front cover  20  is open toward the front side in the front-and-back direction Y of the image forming apparatus  100  (i.e., on the right side of  FIG. 2 ), the pair of registration rollers  14  and the secondary transfer roller  7  are exposed. Accordingly, a paper jam operation, maintenance check, and cleaning can be performed. The front cover  20  is also open to expose the duplex sheet conveyance passage  13 . As illustrated in  FIG. 2 , the image forming apparatus  100  further includes a sheet conveying unit  70 . 
     Now, a description is given of a full detection feeler  91  provided to the sheet discharging device  9 . 
       FIG. 3A  is a diagram illustrating the full detection feeler  91  provided to the sheet discharging device  9 , when no sheet is stacked on the sheet stacker  15 . Specifically, the amount of printed sheets P′ on the sheet stacker  15  is smaller than and equal to a predetermined sheet stacking amount and the full detection feeler  91  stands by at a (home) position.  FIG. 3B  is a diagram illustrating the full detection feeler  91  provided to the sheet discharging device  9 , when the amount of printed sheets P′ discharged on the sheet stacker  15  exceeds the predetermined sheet stacking amount and the full detection feeler  91  is located at a detection position. 
     As illustrated in  FIGS. 3A and 3B , the full detection feeler  91  is swingably disposed in the vicinity of the outlet port  90  through which the printed sheet P′ is discharged toward the sheet stacker  15 . The full detection feeler  91  includes a contact feeler portion  91   d  to contact the printed sheet P′ being discharged. The contact feeler portion  91   d  is fixed to the full detection feeler  91  and integrally rotates and swings together with the full detection feeler  91  as a single unit. The full detection feeler  91  is swingably supported to swing within a predetermined swinging range as a predetermined rotating range, which is described below. 
     When the stacking amount of the printed sheets P′ on the sheet stacker  15  is in an initial stacking state where the stacking amount is smaller than and equal to the predetermined stacking amount ( FIG. 3A  illustrates a state in which no printed sheet V is discharged on the sheet stacker  15 ), the full detection feeler  91  stands by a standby position as illustrated in  FIG. 3A . It is to be noted that the term “standby position” is explained below. 
     As illustrated in  FIG. 3B , when the stacking amount of the printed sheets P′ on the sheet stacker  15  exceeds the predetermined stacking amount, the full detection feeler  91  contacts an uppermost printed sheet P′ placed on top of a stack of the printed sheets P′ on the sheet stacker  15 . Based on the amount of swing of the full detection feeler  91  starting from the initial stacking state of the printed sheet P′ on the sheet stacker  15 , a full state of the printed sheets P′ on the sheet stacker  15  is determined. The detailed description of this operation is described below. 
     Now, a description is given of a configuration of detection of a sheet full state of the printed sheets P′ on the sheet stacker  15 , with reference to  FIGS. 4A through 4D . 
       FIG. 4A  is a perspective view illustrating the full detection feeler  91  of the sheet discharging device  9 .  FIG. 4B  is an exploded perspective view illustrating the configuration of detection of the sheet full state of the printed sheets P′.  FIG. 4C  is a perspective view illustrating a relation of a change of swing angle of a blocking member  91   c  at the standby position of the full detection feeler  91  and a detection by a photointerrupter  92 .  FIG. 4D  is a perspective view illustrating a relation of the change of swing angle of the blocking member  91   c  when the full detection feeler  91  is in the sheet full state and the detection by the photointerrupter  92 . 
     As illustrated in  FIG. 4A , the sheet discharging device  9  includes the sheet discharging rear end guide plate  93  and sheet discharging side guide plates  93   d  and  93   e . The sheet discharging rear end guide plate  93  extends in the width direction X and the vertical direction Z. The sheet discharging side guide plates  93   d  and  93   e  are both left and right sides of the sheet discharging rear end guide plate  93  and extend in the front-and-back direction Y and the vertical direction Z. The sheet discharging rear end guide plate  93  has a surface to guide the trailing end of the printed sheet P′. The sheet discharging side guide plates  93   d  and  93   e  have respective surfaces to guide both ends of the printed sheet P′. 
     Further, the sheet discharging device  9  includes the full detection feeler  91  having the contact feeler portion  91   d . Both left and right end portions of the full detection feeler  91  extend in the width direction X and are attached to and supported by the sheet discharging side guide plates  93   d  and  93   e.    
     As illustrated in  FIG. 4B , a first swing support  93   a  that functions as a first rotation support is disposed on the sheet discharging side guide plate  93   d  and a first swing support  93   b  that functions as a first rotation support is disposed on the sheet discharging side guide plate  93   e . The first swing supports  93   a  and  93   b  are bearings. 
     On both ends in the width direction X of the full detection feeler  91 , first swing target supports  91   a  and  91   b  that function as first rotation target supports are mounted integrally. The first swing target supports  91   a  and  91   b  are swing fulcrums as coaxial rotation fulcrums. The first swing target support  91   a  of the full detection feeler  91  is attached to and supported by the first swing support  93   a  of the sheet discharging side guide plate  93   d . The first swing target support  91   b  of the full detection feeler  91  is attached to and supported by the first swing support  93   b  of the sheet discharging side guide plate  93   e.    
     Further, a photointerrupter  92  is provided in the vicinity of the first swing support  93   b  of the sheet discharging side guide plate  93   e.    
     As illustrated in  FIG. 4C , the photointerrupter  92  is an optical transmissive photosensor having a light emitting part  92   a  and a light receiving part  92   b . The photointerrupter  92  detects swing of the blocking member  91   c  attached to the end of the full detection feeler  91  that integrally swings together with the contact feeler portion  91   d  in contact with the printed sheet P′. By so doing, the photointerrupter  92  functions as a height detector to detect that the stacking amount of the printed sheets P′ stacked in the sheet stacker  15  is equal to or greater than the predetermined height. 
     The blocking member  91   c  that functions as a light blocking portion mounted on the end portion of the full detection feeler  91  performs transmission and blockage of an optical path of the laser light beam emitted from the light emitting part  92   a . By so doing, the light receiving part  92   b  generates a signal related to whether the sheet full state is detected or not. 
     Based on the signal related to whether the sheet full state is detected or not, sent from the light receiving part  92   b  of the photointerrupter  92 , a controller included in the image forming apparatus  100  determines whether the sheet stacker  15  is full with the printed sheets P′ or not, and finally determines whether the print job is interrupted or continued. The controller then sends an instruction signal to devices and mechanisms related to the print job to control the devices and the mechanisms. 
     As illustrated in  FIG. 4C , when the full detection feeler  91  is in the standby state in which the stack amount of the printed sheets P′ on the sheet stacker  15  is in the initial stacking state in which the stack amount of the printed sheets P′ is equal to or smaller than a regular amount, light emitted from the light emitting part  92   a  of the photointerrupter  92  is blocked by the blocking member  91   c  of the full detection feeler  91 . 
     As illustrated in  FIG. 4D , when the full detection feeler  91  is in the sheet full stacking state, light emitted from the light emitting part  92   a  of the photointerrupter  92  is not blocked by the blocking member  91   c  of the full detection feeler  91  (in a light transmission state). 
     Now, a description is given of movement of the full detection feeler  91  during the print job, with reference to  FIGS. 5A, 5B, 5C, 5D, 6A, 6B, 6C, 6D, 7A and 7B . 
     Specifically,  FIGS. 5A, 6A and 7A  are cross sectional views illustrating the sheet stacker  15  and the full detection feeler  91 .  FIGS. 5B, 6B and 7B  are enlarged views illustrating the full detection feeler  91  in the state illustrated in  FIGS. 5A, 6A and 7A , respectively. 
     As illustrated in  FIGS. 5A and 5B , the blocking member  91   c  of the full detection feeler  91  in the in the initial standby state blocks light (light path) from the light emitting part  92   a  of the photointerrupter  92 . 
     At this time, the full detection feeler  91  is at a location occupying an equilibrium position (hereinafter, referred to as a “standby position”) in the predetermined swinging range of the full detection feeler  91  by the own weight of the full detection feeler  91  including the contact feeler portion  91   d  (about the first swing target support  91   a ). 
     As the print job starts, the printed sheet P′ conveyed from the fixing device  8  is guided by the sheet discharging roller  95  and the sheet discharging driven roller  96  toward the sheet discharging device  9 . Then, as illustrated in  FIGS. 5C and 5D , the printed sheet P′ contacts the contact feeler portion  91   d  of the full detection feeler  91  to be conveyed by pushing and rotating the contact feeler portion  91   d . At this time, the blocking member  91   c  rotates from a position at which light (or a light path) is blocked to a position at which the light (or the light path) is not blocked (i.e., the transmission state). 
     Further, as the printed sheet P′ is conveyed, the printed sheet P′ is further conveyed to the sheet stacker  15  by further pushing and rotating the contact feeler portion  91   d  of the full detection feeler  91 , as illustrated in  FIGS. 6A and 6B . 
     When the printed sheet P′ is completely discharged to the sheet stacker  15 , as illustrated in  FIGS. 6C and 6D , the printed sheet P′ is stacked on the sheet stacker  15  located below or at a lower position relative to the contact feeler portion  91   d.    
     When the contact feeler portion  91   d  of the full detection feeler  91  is separated from the printed sheet P′ and the full detection feeler  91  returns to the initial standby state due to the weight of the contact feeler portion  91   d  (the state illustrated in  FIGS. 5A and 5B ), the blocking member  91   c  of the full detection feeler  91  returns to the state in which the light emitting part  92   a  of the photointerrupter  92  blocks the light (or the light path). 
     A duration of contact of the printed sheet P′ (A4 size, portrait orientation) and the contact feeler portion  91   d  is approximately 2 seconds and a duration of a transmission state of the photointerrupter  92  is a constant duration (approximately 2 seconds). 
     According to these conditions, in a case in which the transmission state of the photointerrupter  92  is less than a predetermined duration (approximately 3 seconds) longer that the constant duration (approximately 2 seconds), even when the transmission state of the photointerrupter  92  is detected, the controller does not determine that the sheet stacker  15  is full with the printed sheets P′ (sheet full) but determines that the sheet stacker  15  is not full (sheet not full). In a case in which the transmission state reaches and continues over the predetermined duration (approximately 3 seconds), the controller determines that the sheet stacker  15  is full with the printed sheets P′ and determines to interrupt the print job. Then, the controller sends an instruction signal of determinations to the devices and mechanisms related to the print job to control the devices and mechanisms. 
     When multiple sheets P are printed, the printed sheets P′ are sequentially stacked onto the sheet stacker  15 . As described above, due to swing of the full detection feeler  91  in response to the sheet discharging operation of the multiple printed sheets P′ to the sheet stacker  15 , the blocking member  91   c  of the full detection feeler  91  repeatedly performs blockage and transmission of light of the photointerrupter  92 . 
     As illustrated in  FIGS. 7A and 7B , in a case in which the multiple printed sheets P′ are stacked on the sheet stacker  15 , even after the sheet discharging operation is completed, the blocking member  91   c  of the full detection feeler  91  does not block the light (or the light path) of the photointerrupter  92  (the transmission state). Since the transmission state lasts longer than the predetermined duration (approximately 3 seconds), the controller determines that the sheet stacker  15  is full with the printed sheets P′. Therefore, the controller determines to interrupt or stop the print job and sends the instruction signals to the devices and mechanisms related to the print job to stop the print job. As described above, the controller determines whether the sheet stacker  15  is full of the printed sheets P′ using a sheet detector of the full detection feeler  91  and the photointerrupter  92 , so as to interrupt or stop the print job. 
     It is to be noted that, in  FIG. 7A , the printed sheets P′ stacked in the sheet stacker  15  is schematically illustrated. However, the trailing end in the sheet conveying direction of each of the printed sheets P′ stacked on the slope of the sheet stacker  15  contacts the sheet discharging rear end guide plate  93  disposed along the width direction to be loaded on the sheet stacker  15 . 
     A description is given of how to remove the printed sheet P′, with reference to  FIGS. 8A, 8B and 8C . 
       FIG. 8A  is a cross sectional view illustrating the sheet stacker  15  and the full detection feeler  91  when the printed sheet P′ is removed from the sheet stacker  15 .  FIG. 8B  is a perspective view illustrating the full detection feeler  91  of  FIG. 8A .  FIG. 8C  is an enlarged view illustrating the full detection feeler  91  of  FIG. 8A . 
     As illustrated in  FIGS. 8A through 8C , when the printed sheet P′ is removed from the sheet stacker  15 , the leading end of the contact feeler portion  91   d  of the full detection feeler  91  rotates upwardly. This rotation of the full detection feeler  91  causes a base of the full detection feeler  91  contacts a regulator  93   c  attached to the sheet discharging side guide plate  93   e  to be engaged with the regulator  93   c . Therefore, the rotation of the full detection feeler  91  is limited, that is, the full detection feeler  91  cannot rotate further upwardly. The regulator  93   c  is a stopper of the full detection feeler  91 . The regulator  93   c  is fixedly attached to a portion of the sheet discharging side guide plate  93   e , outside from a guide surface of the sheet discharging side guide plate  93   e  in the width direction X. 
     As illustrated in  FIG. 8C , the full detection feeler  91  is swingably disposed within a predetermined swinging range θ 2  between a standby position Sa (see  FIGS. 5A and 5B ) at which the full detection feeler  91  is located in the standby state and a swing upper limit position Sb at which the regulator  93   c  regulates the rotation of the full detection feeler  91 . Further, the full detection feeler  91  detects the height of the printed sheets P′ stacked in the sheet stacker  15  within a swinging range θ 1  between the standby position Sa and a full state detection position Sc (see  FIGS. 7A and 7B ). The standby position Sa, the swing upper limit position Sb and the full state detection position Sc illustrated in  FIG. 8C  are respective positions of the leading end of the contact feeler portion  91   d  of the full detection feeler  91 . 
     When the sheet stacker  15  is full with the printed sheets P′ and the controller stops the print job, the printed sheets P′ stacked in the sheet stacker  15  cannot be removed from the sheet stacker  15  horizontally or in the horizontal direction to the upstream side of the sheet discharging direction Ya (i.e., to the front side F of the front-and-back direction Y), because the control unit  800  is disposed above the sheet discharging rear end guide plate  93  that rises from the bottom of the sheet stacker  15 . Therefore, the printed sheet P′ is firstly lifted upwardly in the vertical direction Z and then is pulled out to the front side F of the front-and-back direction Y. Specifically, the printed sheet P′ is removed from the sheet stacker  15  in a movement path indicated by arrow A in  FIG. 8A . 
     Further, a user or an operator normally uses the image forming apparatus  100  when standing at the front side of the image forming apparatus  100  as illustrated in  FIG. 1B  and  FIG. 2  (i.e., the front side F of the front-and-back direction Y). However, the image reading device  301  is disposed at the rear side in the horizontal direction of the image forming apparatus  100  (i.e., the rear side R of the front-and-back direction Y). The image reading device  301  also functions as a ceiling of the image forming apparatus  100 . In addition, the control unit  800  is disposed at the front side F of the image forming apparatus  100 . Therefore, a direction to remove the printed sheet P′ is limited and a space for removal of the printed sheet P′ is relatively narrow. Accordingly, it is not easy to remove the printed sheet P′ from the image forming apparatus  100 . Further, when the printed sheet P′ is removed from the sheet stacker  15 , in order to reduce a distance of movement of the printed sheet P′, that is, the movement path indicated by arrow A in  FIG. 8A , the printed sheet P′ is occasionally removed toward the front side of the image forming apparatus  100  (i.e., the front side F of the front-and-back direction Y) quickly. 
     At this time, since the full detection feeler  91  is disposed above the movement path A of the printed sheet P′ to be removed from the sheet stacker  15 , the full detection feeler  91  rotates to the state illustrated in  FIG. 8A  when the printed sheet P′ is removed. However, since the upper limit of rotation of the full detection feeler  91  is regulated by the regulator  93   c , when the full detection feeler  91  is rotated beyond the swing upper limit position Sb, the trailing end of the printed sheet P′ is likely to be caught by the contact feeler portion  91   d  of the full detection feeler  91 , and therefore the operability of removing the printed sheet V is degraded. In addition, the full detection feeler  91  can be damaged or broken and the printed sheet P′ can be damaged. 
     Generally, in the image forming apparatus  100  illustrated in  FIG. 2 , in a case in which the scanner is disposed above the sheet stacker  15  of the sheet discharging device  9 , the scanner acts as the ceiling of the sheet stacker  15  of the sheet discharging device  9 . Since the printed sheets P′ to be stacked in the sheet stacker  15  are likely to contact the scanner and easily become displaced or untidy, a full state detecting mechanism is provided to the image forming apparatus  100 . 
     Further, when performing a full front operation, in which a jammed sheet is removed from the color laser printer  200  by opening the front cover  20  on the side on which the control unit  800  is disposed, the following inconvenience is likely to occur. In the full front operation, the trailing end of the sheet P after image formation is discharged in the sheet stacker  15  on a side close to the control unit  800 . In this case, since the sheet discharging device  9  and the control unit  800  are disposed on the front side of the sheet stacker  15  (on the side of the control unit  800 ), it is difficult to visually recognize removal of the printed sheet P′ from the sheet stacker  15 , resulting in the above-described inconvenience. 
     In order to eliminate the above-described inconvenience, the upper limit of swing (rotation) of the full detection feeler  91  is set to a higher level, the full detection feeler  91  is likely to stay at the higher upper limit position. Therefore, the return of the full detection feeler  91  to the standby position Sa becomes unstable or the return operation of the full detection feeler  91  takes long, and therefore it is likely that an incorrect detection of the sheet full state is performed. In order to address this inconvenience, the full detection feeler  91  is set to a position at which the full detection feeler  91  stably returns to the standby position in the initial standby state and the control operation is reliably performed. 
     Here, a description is given of the position of the full detection feeler  91  of the sheet discharging device  9  in  FIGS. 8A through 8C . In the above-described full detection feeler  91 , the first swing target supports  91   a  and  91   b , the blocking member  91   c  and the contact feeler portion  91   d  are integrally formed by resin as a single unit. The full detection feeler  91  is formed extending in the width direction X, longer than the width of the maximum sheet size usable for at least printing. The contact feeler portion  91   d  is integrally formed at a substantially center of the full detection feeler  91  that is opposed to the sheet P. The contact feeler portion  91   d  of the full detection feeler  91  swings together with the full detection feeler  91  as a single unit, in the predetermined swinging range. 
     In the above-described examples, after the printed sheet P′ is removed, the full detection feeler  91  returns from the swing upper limit position Sb to the initial standby state, that is, the standby position Sa illustrated in  FIG. 8B  due to the weight thereof. However, the movement of the full detection feeler  91  is not limited thereto. For example, the full detection feeler  91  may return to the initial standby state due to a biasing force applied by a weight or a spring. 
     In the above description, an A4 size (portrait orientation) is used as an of a sheet size used for printing but any sheet size can be applied to this disclosure as long as the sheet is a cut sheet. 
     Further, the regulator  93   c  is disposed at one position illustrated in  FIG. 8B  in the above description but the number and position of the regulator  93   c  is not limited thereto. For example, multiple regulators  93   c  may be disposed on the sheet discharging side guide plate  93   d  in the width direction X. 
     As described above, the swing upper limit position Sb is set for the full detection feeler  91  in order to remove the printed sheet P′ smoothly. However, when the full detection feeler  91  is rotated beyond the swing upper limit position Sb, the trailing end of the printed sheet P′ is likely to be caught by the contact feeler portion  91   d  of the full detection feeler  91 , and therefore the operability of removing the printed sheet P′ is degraded. In addition, the full detection feeler  91  can be damaged or broken and the printed sheet P′ can be damaged. 
     Embodiment 1 
     A description is given of a sheet discharging device according to Embodiment 1 of this disclosure, with reference to  FIGS. 9A and 9B . 
     Specifically,  FIG. 9A  is a perspective view illustrating a full detection feeler  901  provided to a sheet discharging device  9 A according to Embodiment 1 of this disclosure, when the full detection feeler  901  is in an initial standby state.  FIG. 9B  is a perspective view illustrating an engaging state of the full detection feeler  901  of  FIG. 9A  and the photointerrupter  92 . 
     The sheet discharging device  9 A according to Embodiment 1 illustrated in  FIGS. 9A and 9B  functions as a recording medium discharging device. While the sheet discharging device  9  illustrated in  FIGS. 2 through 8C  includes the full detection feeler  91 , the sheet discharging device  9 A according to Embodiment 1 includes the full detection feeler  901 . The configuration and operations of the full detection feeler  901  according to Embodiment 1 are described, focusing on features different from the full detection feeler  91  illustrated in  FIGS. 2 through 8C . 
     The full detection feeler  901  includes a sheet contact member  903  and a feeler body  902 . The sheet contact member  903  functions as a contact member that is rotated or swung by contact with a sheet. The feeler body  902  is a shaft that is rotated or swung together with the sheet contact member  903  within a predetermined swinging range that is a predetermined rotating range of the sheet contact member  903 . The sheet contact member  903  is attached to a substantially center in the width direction X of the feeler body  902  that is a separated part different from the sheet contact member  903 . 
     On both left and right ends in the width direction X of the feeler body  902 , first swing target supports  901   a  and  901   b  that function as first rotation target supports are mounted integrally. The first swing target supports  901   a  and  901   b  are swing fulcrums as coaxial rotation fulcrums. The first swing target support  901   a  of the full detection feeler  901  is attached and supported to the first swing support  93   a  of the sheet discharging side guide plate  93   d . The first swing target support  901   b  of the full detection feeler  901  is attached and supported to the first swing support  93   b  of the sheet discharging side guide plate  93   e.    
     Further, the photointerrupter  92  is provided in the vicinity of the first swing support  93   b  of the sheet discharging side guide plate  93   e.    
     Further, a blocking member  91   c  is integrally provided at an end of the first swing target support  901   b  of the feeler body  902 . The blocking member  91   c  blocks and transmits light along the light path between the light emitting part  92   a  and the light receiving part  92   b  of the photointerrupter  92  that is attached to the sheet discharging side guide plate  93   e.    
     It is to be noted that movement of swing of the blocking member  91   c  that is integrally formed on the feeler body  902  of the full detection feeler  901  and the configuration and operations of sheet full detection based on blocking of light of the photointerrupter  92  are identical to the above-described configuration and operations. In addition, after the printed sheet P′ is removed, the full detection feeler  901  returns from the swing upper limit position Sb to the initial standby state, that is, the standby position Sa due to the weight thereof. However, the movement of the full detection feeler  901  is not limited thereto. For example, the full detection feeler  901  may return to the initial standby state due to a biasing force applied by a weight or a spring, which is also same as the above-described configuration and operations. 
     Now, a description is given of a swing range of the sheet contact member  903  and the feeler body  902  of the full detection feeler  901 , with reference to  FIGS. 10A, 10B, 10C and 10D . 
     Specifically,  FIG. 10A  is a perspective view illustrating the sheet contact member  903  and the feeler body  902  rotating together to the swing upper limit position Sb.  FIG. 10B  is an enlarged cross sectional view illustrating the sheet contact member  903  and the feeler body  902  of  FIG. 10A , viewed along a plane B.  FIG. 10C  is a perspective view illustrating that the feeler body  902  is stopped at the swing upper limit position Sb and the sheet contact member  903  rotates from the swing upper limit position Sb to a retracted position Sd.  FIG. 10D  is an enlarged cross sectional view illustrating the sheet contact member  903  and the feeler body  902  of  FIG. 10C , viewed along a plane B. 
     The sheet contact member  903  and the feeler body  902  are separate parts and are mounted on the full detection feeler  901 . The sheet contact member  903  and the feeler body  902  are integrally formed by resin. 
     As illustrated in  FIGS. 10A and 10B , the full detection feeler  901  to which the sheet contact member  903  and the feeler body  902  are integrally attached rotates about the first swing target supports  901   a  and  901   b , to the swing upper limit position Sb that is the upper limit in the predetermined swinging range. When the full detection feeler  901  occupies the swing upper limit position Sb, the feeler body  902  contacts the regulator  93   c  of the sheet discharging side guide plate  93   e  to be engaged therewith, as illustrated in  FIGS. 8B and 8C . By so doing, the further rotation of the feeler body  902  is restricted (see  FIG. 14B ). 
     As illustrated in  FIGS. 10C and 10D , the sheet contact member  903  is disposed swingable to the feeler body  902  about a second swing support  904 , exceeding the predetermined swinging range in the same direction as the swing direction of the feeler body  902 . The second swing support  904  that functions as a rotation support is attached to the feeler body  902 . The second swing support  904  supports the sheet contact member  903  to rotate to the feeler body  902 , exceeding the predetermined rotation range, in the same direction as the direction of rotation of the feeler body  902  that rotates together with the sheet contact member  903  in contact with the sheet P. The detailed configuration of the second swing support  904  is described below. 
     According to the above-described configuration, the sheet contact member  903  and the feeler body  902  swing together to the swing upper limit position Sb and the sheet contact member  903  further rotates about the second swing support  904 , exceeding the predetermined swinging range while the feeler body  902  is engaged at the swing upper limit position Sb. By so doing, the sheet contact member  903  retreats to the retracted position Sd. 
     The sheet contact member  903  is significantly different from the contact feeler portion  91   d  having a claw shape as illustrated in  FIGS. 3A through 8C  in the following features. Specifically, different from the contact feeler portion  91   d , the sheet contact member  903  has bearings  903   a  and  903   b , provided with a large area to contact the sheet P, and has a round chamfering portion to prevent damage to the end of the printed sheet P′ when the printed sheet P′ is removed from the sheet stacker  15 . 
     In addition, the sheet contact member  903  may have a resin portion to contact the end of the printed sheet P′ and have an appropriate surface treatment. 
     As described above, the full detection feeler  901  includes the sheet contact member  903  and the feeler body  902 . The feeler body  902  includes the first swing target support  901   a  that is swingably supported by the first swing supports  93   a , the first swing target support  901   b  that is swingably supported by the first swing support  93   b  (see  FIGS. 9A and 9B ), and the second swing support  904 . 
     A detailed description is given of the configuration of the sheet contact member  903  and the second swing support  904  of the full detection feeler  901 , with reference to  FIGS. 11A, 11B, 11C, 11D, 12A, 12B, 13A, 13B and 13C . 
       FIGS. 11A, 11B, 11C and 11D  are diagrams illustrating an area around the sheet contact portion and a rotation support of the full detection feeler of  FIGS. 9A and 9B .  FIGS. 12A and 12B  are diagrams illustrating yet another area around the sheet contact portion and the rotation support of the full detection feeler of  FIGS. 9A and 9B .  FIGS. 13A, 13B and 13C  are diagrams illustrating yet another area around the sheet contact portion of the rotation support and the full detection feeler of  FIGS. 9A and 9B . 
     As illustrated in  FIGS. 11A and 11B , the second swing support  904  is part of the feeler body  902  and includes bearings  902   a  and  902   b  and a shaft  905 . The bearings  902   a  and  902   b  are integrally formed in the feeler body  902 . The shaft  905  in inserted into the bearings  902   a  and  902   b . A spring receiver  902   c  is disposed in the vicinity of the second swing support  904  and is integrally formed in the feeler body  902 . The spring receiver  902   c  includes a torsion coil spring  906  attached thereto in an attachment state. 
     As illustrated in  FIGS. 11C and 11D , the torsion coil spring  906  that functions as a biasing force setting body is a pair member in which two coil portions are connected by a connecting member  906   c . The torsion coil spring  906  is attached to the feeler body  902  in a state in which the connecting member  906   c  is engaged to a recessed portion formed in the spring receiver  902   c  of the feeler body  902 . 
     Further, in a state in which the sheet contact member  903  is arranged as illustrated in  FIG. 12A , the shaft  905  is attached to pass through the bearings  902   a  and  902   b  of the feeler body  902 , the bearings  903   a  and  903   b  of the sheet contact member  903  and an inner circumference of the torsion coil spring  906  attached to the spring receiver  902   c , as illustrated in  FIG. 12B . 
     Then, a retaining ring  907  is attached to a groove  905   a  of the shaft  905  that is attached as described above. Accordingly, the shaft  905  is prevented from coming off in a thrust direction (i.e., an axial direction). As a result of this assembly, the sheet contact member  903  can swing to the feeler body  902  about the shaft  905  that functions as a fulcrum and is supported by the bearings  903   a  and  903   b.    
     As illustrated in  FIGS. 13A and 13B , the connecting member  906   c  of the torsion coil spring  906  is attached to the spring receiver  902   c  of the feeler body  902 . The torsion coil spring  906  has one end portion  906   a  and an opposed end portion  906   b , both of which are locked to the sheet contact member  903 . According to this configuration, as illustrated in  FIG. 13B , the biasing force applied by the torsion coil spring  906  acts in a direction to swing the sheet contact member  903  about the shaft  905 , to the feeler body  902  in the counterclockwise direction. Specifically, the torsion coil spring  906  functions as a biasing force setting body to set a biasing force in an opposite direction to the direction of rotation of the feeler body  902  so as to rotate the sheet contact member  903  at the second swing support  904 , in the direction of rotation of the feeler body  902 , to the feeler body  902 . 
     Accordingly, as illustrated in  FIG. 13C , when a pressing force FC is applied from outside against the biasing force applied by the torsion coil spring  906 , the sheet contact member  903  rotates about the shaft  905  in the clockwise direction. After the pressing force FC is released, the sheet contact member  903  returns to the state illustrated in  FIGS. 13A and 13B  by the biasing force applied by the torsion coil spring  906 . 
       FIGS. 14A, 14B, 14C and 14D  are diagrams illustrating removal of stacked printed sheet P′ with the full detection feeler  901  according to Embodiment 1. 
     As illustrated in  FIG. 14A , when the printed sheets P′ fully stacked in the sheet stacker  15  are removed in a direction indicated by arrow A, the sheet contact member  903  of the full detection feeler  901  is lifted by the trailing end of the stacked printed sheets P′. Therefore, the sheet contact member  903  in contact with the trailing end of the printed sheets P′ moves (rotates) together with the feeler body  902 , about the first swing target supports  901   a  and  902   b , to the swing upper limit position Sb as illustrated in  FIG. 14B . 
     Then, as illustrated in  FIG. 14C , when the printed sheets P′ are further removed from the sheet stacker  15 , the sheet contact member  903  alone moves (rotates) about the shaft  905  of the second swing support  904 , and swings to the retracted position Sd beyond the predetermined swinging range. The swinging direction of the sheet contact member  903  about the second swing support  904  is the same direction as the sheet removing direction of the printed sheets P′ stacked in the sheet stacker  15  (or the direction separating from the sheet stacker  15 ). 
     Now, a description is given of the configuration and operations including a pressing operations of the sheet contact member  903  of the full detection feeler  901 , with reference to  FIGS. 15A, 15B, 15C, 16A, 16B, 16C, 17A, 17B and 17C . 
     In a state illustrated in  FIG. 15A , the sheet contact member  903  at the standby position Sa is pressed in a direction indicated by arrow C, thereby moving (rotating) the sheet contact member  903  and the feeler body  902  (i.e., the full detection feeler  901 ) together about the first swing target supports  901   a  and  901   b . A force to be applied for the above-described operation is referred to as a “first pressing force.” That is, the first pressing force is a force to press the sheet contact member  903  by conveyance (discharge) of the printed sheets P′. In other words, the first pressing force is also a force to rotate the feeler body  902  together with the sheet contact member  903  in the direction of rotation of the feeler body  902  by pressing the sheet contact member  903  by the printed sheets P′ stacked in the sheet stacker  15 . 
     After detection of the sheet full state, the full detection feeler  901  moves to the swing upper limit position Sb illustrated in  FIG. 15B , along with removal of the printed sheets P′ from the sheet stacker  15 . 
     In a state illustrated in  FIG. 15B , the sheet contact member  903  is pressed further in a direction indicated by arrow C 2 , thereby moving (rotating) the sheet contact member  903  about the second swing support  904 , to the feeler body  902 . A force to be applied for the above-described operation is referred to as a “second pressing force.” That is, the second pressing force is a force to press the sheet contact member  903  by removal of the printed sheets P′. With the second pressing force, the sheet contact member  903  that has moved (rotated) about the second swing support  904  moves (rotates) to the retracted position Sd as illustrated in  FIG. 15C , which is similar to  FIG. 14D . 
     Consequently, the biasing force applied against the second pressing force is set based on the biasing force applied by the biasing member of the torsion coil spring  906  (see  FIGS. 13A through 13C . However, the setting of the biasing force is not limited thereto and any other configuration can be applied to this disclosure. 
     The biasing force applied against the second pressing force is greater than the pressing force by which the printed sheet P′ is conveyed and the sheet contact member  903  is pressed and smaller than the pressing force by which the sheet contact member  903  is pressed along with removal of the printed sheet P′. That is, the biasing force of the torsion coil spring  906  is set to meet the relation of “the first pressing force&lt;the second pressing force” and the relation of “the biasing force&lt;the second pressing force.” 
     During the print job, the load to the full detection feeler corresponds to the contact force by the printed sheet P′ during conveyance for discharging, and therefore the full detection feeler swings within a range in which the full detection feeler moves by the first swing support. Therefore, the first pressing force does not exceed the biasing force of the torsion coil spring  906  in the above-described state. Consequently, the sheet contact member  903  does not move (rotate) about the second swing support  904  and the sheet contact member  903  has a constant relative position to the feeler body  902 . Accordingly, the full state detection can be performed by the photointerrupter  92 . 
     Further, the torsion coil spring  906  that is used to apply the biasing force against the second pressing force is attached to the shaft  905  of the second swing support  904  (through the inner circumference of the shaft  905 ), and therefore an effect of space saving can be achieved. 
     As described above, the biasing force against the second pressing force is greater than the first pressing force and smaller than the second pressing force. However, the maximum biasing force is set so as not to cause any damage to the sheet by the second pressing force (for example, the printed sheet P′ is scratched or torn) when the printed sheet P′ stacked in the sheet stacker  15  is removed. In this setting, the type of the sheet P′ to be removed (for example, a thin paper and a film sheet are damaged more easily than a regular sheet) is taken into consideration. However, instead of considering the type of the sheet P′, an adjusting mechanism by which the biasing force can be adjusted may be provided. 
     It is to be noted that the biasing force against the second pressing force is not limited to be applied by the biasing member including the torsion coil spring  906 . For example, a biasing force against the second pressing force may be applied according to a self-weight moment of the sheet contact member (a contact member) and the feeler body (a shaft) having the material, center of gravity, shape and so forth appropriately devised to generate the moment) or may be applied by a weight as a separate part attached to the sheet contact member (a contact member) and the feeler body (a shaft). However, the biasing force is set to cause the sheet contact member  903  to return to the standby position Sa. 
     As illustrated in  FIG. 16A , a pair of ribs  903   c  is provided on an opposite side of the sheet contact member  903 , on which the sheet contact member  903  and the printed sheet P′ contact with each other. The pair of ribs  903   c  functions as a protect portion to protect the one end portion  906   a  and the opposed end portion  906   b  of the torsion coil spring  906 . The pair of ribs  903   c  has a length greater than the core diameter of the torsion coil spring  906  and is disposed to enclose the one end portion  906   a  and the opposed end portion  906   b  of the torsion coil spring  906 . By so doing, the end portions of the torsion coil spring  906  are safe without being exposed or touched by mistake. Further, the pair of ribs  903   c  can prevent the torsion coil spring  906  from coming off. 
     As illustrated in  FIG. 16B , a recess  903   d  is formed in the sheet contact member  903  in order to provide a gap distance between the leading end of the one end portion  906   a  of the torsion coil spring  906  and the leading end of the opposed end portion  906   b  of the torsion coil spring  906  and the sheet contact member  903 . According to this configuration, when the sheet contact member  903  is swung or rotated about the shaft  905  of the second swing support  904 , the circumferential surface of the core at the end portions of the torsion coil spring  906  contact the sliding surface in the recess  903   d , which can prevent a burred portion formed at the leading end of the sheet contact member  903  from contacting the sliding surface in the recess  903   d . Accordingly, the sheet contact member  903  can return to the swing upper limit position and further to the standby state reliably, and therefore the sheet full state detection can be performed reliably. 
     It is to be noted that, since the leading end of the one end portion  906   a  of the torsion coil spring  906  and the leading end of the opposed end portion  906   b  of the torsion coil spring  906  are deformed (compress or extend) in the front-and-back direction Y along with swing of the sheet contact member  903 , the recess  903   d  is formed by taking the deformation of the torsion coil spring  906 . 
     Further, as illustrated in  FIG. 16B , when the sheet contact member  903  is swung or rotated about the shaft  905  of the second swing support  904 , a cut portion  902   d  that functions as a retracting portion to retract the sheet contact member  903  is formed in the feeler body  902 . According to this configuration, as illustrated in  FIG. 16C , the cut portion  902   d  can be used as a swinging range of the sheet contact member  903  to the retracted position Sd (see  FIGS. 14C, 14D and 15C ), and therefore a further space saving in the layout can be achieved. 
     As illustrated in  FIG. 16B , a first regulator  902   e  is provided to the feeler body  902  on the printed sheet removing side, as a plane in the width direction X. The first regulator  902   e  regulates the swinging range of the sheet contact member  903  when the sheet contact member  903  swings about the second swing support  904 , exceeding the predetermined swinging range. 
     By disposing the first regulator  902   e  in the vicinity of the feeler body  902 , the height of accumulation of the parts can be reduced, and therefore variation in the second pressing force can be reduced. Accordingly, the operability without variation can be achieved. 
     The feeler body  902  is elastically formed by resin and extends in the width direction X. Therefore, the material of the feeler body  902  is set to resin, even after the swing of the feeler body  902  is regulated by the first regulator  902   e , by using twist and bend of the feeler body  902  due to elasticity of resin material, the sheet contact member  903  can be swung to the position illustrated in  FIGS. 17A and 17B . That is, after the sheet contact member  903  alone reaches the retracted position Sd, the sheet contact member  903  swings from the retracted position Sd further to a flexibly retracted position Se due to elastic deformation of the feeler body  902 , as illustrated in  FIG. 17B . 
     When the feeler body  902  is elastically deformed to cause the sheet contact member  903  to swing to the flexibly retracted position Se as illustrated in  FIGS. 17A and 17B , a second regulator  810   a  that regulates the sheet contact member  903  is provided to a cover  810  that is disposed at the upper part of the sheet discharging device  9 A. The second regulator  810   a  is formed on a vertical plane along the vertical direction Z of the cover  810 . 
     As described above, by providing the second regulator  810   a  to the cover  810  at the upper part of the sheet discharging device  9 A when the feeler body  902  further moves due to elastic twist thereof, the further twist of the feeler body  902  can be prevented, and therefore breakage of the sheet contact member  903  can also be prevented. Accordingly, the operability of removal of the sheets stacked in the sheet stacker can be enhanced. 
     As described above, the sheet discharging device  9  according to Embodiment 1 of this disclosure includes a sheet discharging body such as the sheet discharging roller  95  and the sheet discharging driven roller  96 , a sheet stacker such as the sheet stacker  15 , a contact body such as the sheet contact member  903 , a shaft such as the feeler body  902 , and a stack height detector such as the full detection feeler  91  and the photointerrupter  92 . The sheet discharging body is configured to discharge the sheet such as the sheet P′. The sheet stacker is a stacker on which the sheet discharged by the sheet discharging body. The contact body is configured to rotate while contacting the sheet. The shaft is configured to rotate together with the contact body in a range of rotation of the contact body. The stack height detector is configured to detect that the height of the sheet stacked on the sheet stacker is equal to or higher than the predetermined height through detection of rotation of the shaft rotating with the contact body in contact with the sheet. The sheet discharging device according to Embodiment 1 of this disclosure further includes a rotary body support configured to rotatably support the contact body to the shaft that rotates together with the contact body in contact with the sheet, extending the range of rotation, in a same direction as the direction of rotation of the shaft. 
     According to Embodiment 1, when the printed sheet P′ is removed from the sheet stacker  15 , the printed sheet P′ and the sheet contact member  903  contact with each other, and the sheet contact member  903  swings and retracts in the substantially same direction as the sheet removing direction of the printed sheet P′ stacked on the sheet stacker  15 . Accordingly, the preferable performance of sheet removal of the sheet stacked on the sheet stacker  15  can be maintained without retracting and returning the sheet contact member  903 , and therefore the operability can be enhanced. 
     In addition, the full detection feeler  901  can be prevented from being damaged or broken and the printed sheet P′ can be prevented from being damaged. Further, the failure caused by forgetting of return of the sheet contact member  903  can be prevented before the occurrence. 
     Now, a description is given of the biasing force against the second pressing force, with reference to  FIGS. 18, 19A and 19B . 
       FIG. 18  is a diagram illustrating a configuration of the full detection feeler  901  having the second pressing force, according to Variation of this disclosure.  FIGS. 19A and 19B  are diagrams illustrating movement of the full detection feeler  901  according to Variation of  FIG. 18 , to explain the principle of generation of the biasing force against the second pressing force of this Variation. 
     The configuration of Variation illustrated in  FIG. 18  is different from the configuration of Embodiment 1 illustrated in  FIGS. 9A through 17C , in that a sheet contact member  913  is employed instead of the sheet contact member  903 , that a feeler body  912  is employed instead of the feeler body  902 , and that a compression coil spring  916  is employed instead of the torsion coil spring  906 . The feeler body  912  according to Variation is different from the feeler body  902  according to Embodiment 1, in that a taper  912   a , which functions as a second taper, can be engaged with the taper  913   a  of the sheet contact member  913  and is formed in part of the feeler body  912  in the width direction X and in that the taper  912   a  of the feeler body  912  is formed integrally with a shaft  912   b  that functions as a second swing support. 
     It is to be noted that the first swing support according to Variation is identical to the first swing support illustrated in  FIGS. 9A through 10D . Since the first swing support is not directly related to the explanation of the principle of generation of the biasing force against the second pressing force of Variation, the description of the first swing support is omitted here. 
     As illustrated in  FIG. 18 , the sheet contact member  913  includes a spring receiver  913   c  in an inner circumference of a shaft through hole  913   b  formed at the right side end of the sheet contact member  913 . The left side end of the compression coil spring  916  is attached to and engaged with the spring receiver  913   c.    
     As illustrated in  FIG. 18 , the feeler body  912 , the sheet contact member  913  and the compression coil spring  916  are disposed in this order from the left. In assembly, the shaft  912   b  of the feeler body  912  is inserted into the shaft through hole  913   b  of the sheet contact member  913 , and then is inserted into the inner circumference of the compression coil spring  916 . The right end portion of the compression coil spring  916  is supported by a wall of the sheet discharging side guide plate  93   d . Consequently, the sheet contact member  913  is constantly biased by the biasing force of the compression coil spring  916  in the thrust direction of the feeler body  912 , and therefore the pressing force is generated. That is, the compression coil spring  916  functions as a biasing force setting member to set the biasing force in an opposite direction to the direction of rotation of the feeler body  912  so as to rotate the sheet contact member  913  at the shaft  912   b  that functions as a second swing support, in the direction of rotation of the feeler body  912 , to the feeler body  912 . 
     As illustrated in  FIG. 19A , while the taper  912   a  of the feeler body  912  and the taper  913   a  of the sheet contact member  913  are contacted and engaged with each other, the sheet contact member  913  is biased by the compression coil spring  916  in the thrust direction of the feeler body  912 . In the above-described state, the feeler body  912  contacts the regulator  93   c  to be locked by the regulator  93   c , that is, the feeler body  912  is in a locked state, which is the same as in  FIGS. 14A through 14D . The fixed position of the taper  913   a  of the sheet contact member  913  in this state is represented as “D”. From this fixed position D, the sheet contact member  913  is swung in a direction indicated by arrow in  FIG. 19A  against the biasing force of the compression coil spring  916  that biases the feeler body  912  that is in the locked state by the regulator  93   c , exceeding the predetermined swinging range. Consequently, the fixed position D of the fixed position of the taper  913   a  of the sheet contact member  913  moves to the position as illustrated in  FIG. 19B . As a result, the sheet contact member  913  causes the compression coil spring  916  to shrink by the amount of Ax. Since this amount acts as the pressing force to the sheet contact member  913 , the biasing force to be applied against the second pressing force can be set. 
     According to this configuration, the compression coil spring  916  that is used in the thrust direction can be directly attached to the shaft  912   b  of the feeler body  912  that functions as a second swing support. Therefore, the configuration according to Variation can achieve the same effect as the configuration according to Embodiment 1. 
     Embodiment 2 
     The configuration of Embodiment 1 and the configuration of Variation are applied to the sheet discharging device  9 A that is included in the image forming apparatus  100  and functions as a sheet discharging device that conveys a sheet-like transfer target medium such as a sheet to be discharged from the image forming apparatus  100 . These configurations can be applied to a sheet conveying device that feeds a sheet-like transfer target medium such as a sheet to be fed in the image forming apparatus  100 , as described in Embodiment 2. In this case, if a known technique is employed to a sheet conveying device that feeds a sheet-like transfer target medium such as a sheet to be fed in an image forming apparatus, when a jammed sheet is removed from the sheet conveying device that includes a sheet detection feeler to detect the sheet by swinging a contact member that contacts the fed sheet, the same inconvenience as the sheet detection feeler of the above-described sheet discharging device may occur. 
     Specifically, instead of the above-described inconvenience that occurs when the sheet is removed from the sheet discharging tray in the sheet discharging device that includes the full detection feeler, the same inconvenience is generated when a paper jam occurs in the vicinity of the sheet detection feeler in a sheet conveyance passage of the sheet conveying device. 
     When a jammed sheet is removed from a jammed sheet remaining position in the vicinity of the sheet detection feeler, the jammed sheet is caught by the sheet detection feeler, and therefore the operability of removal of the jammed sheet becomes worse and the sheet detection feeler is damaged or broken. Further, when the sheet detecting feeler is employed instead of the full detection feeler and a manual retraction of the sheet detecting feeler is performed to remove the jammed sheet after retracting the sheet detection feeler manually to a position at which the jammed sheet does not contact, there are many operation processes to take, which is troublesome. Furthermore, when the machine is operated (when the printing operation is performed), the sheet needs to be returned manually before the operation. Therefore, when the sheet detection feeler is not returned, the sheet full state is not detected. Accordingly, prevention of a sheet stacking failure and a paper jam is fairly costly. 
     Now, a description is given of a sheet conveying device  700  according to Embodiment 2 of this disclosure. 
       FIG. 20  is a diagram illustrating a main part of the sheet conveying device  700  according to Embodiment 2 of this disclosure. Specifically,  FIG. 20  illustrates the sheet conveying device  700  that exposes the main part with the front cover  20  of  FIG. 2  open. 
     The front cover  20  includes the sheet conveying unit  70  (see  FIG. 2 ) that supports the secondary transfer roller  7  and the right side roller of the pair of registration rollers  14  and opens and closes relative to the apparatus body of the color laser printer  200 , as illustrated in  FIG. 2 . 
     As illustrated in  FIG. 20 , the configuration according to Embodiment 2 is different from the configuration according to Embodiment 1, in that a sheet detection feeler  901 A is applied to the sheet conveying device  700 , instead of the full detection feeler  901  included in the sheet discharging device  9 A. 
     The sheet detection feeler  901 A is not used as a detector to detect the height of the sheets stacked in the sheet stacker  15 , together with the full detection feeler  901  and the photointerrupter  92 , but is used as a detector to detect passage of the sheet P one by one in the sheet conveying device  700 , together with the photointerrupter  92 . 
     Similar to the configuration according to Embodiment 1 described above, the sheet detection feeler  901 A includes the sheet contact member  903 , the feeler body  902  and the second swing support  904 . The sheet contact member  903  functions as a contact body that swings together with the sheet while contacting the sheet. The feeler body  902  that functions as a shaft that swings together with the sheet contact member  903  in the range of rotation of the sheet contact member  903 . The second swing support  904  is provided to the feeler body  902 . The configuration and functions of the sheet detection feeler  901 A are identical to the full detection feeler  901 , except that the above-described features. Accordingly, the presence or absence of the sheet P is determined with a sheet detecting member such as the sheet detection feeler  901 A and the photointerrupter  92  to interrupt or stop the print job. 
     As described above, the sheet conveying device such as the sheet conveying device  700  according to Embodiment 2 of this disclosure includes a contact body such as the sheet contact member  913 , a shaft such as the feeler body  912 , and a sheet detector such as the full detection feeler  91  and the photointerrupter  92 . The contact body is configured to rotate while contacting the sheet. The shaft is configured to rotate together with the contact body in a range of rotation of the contact body. The sheet detector is configured to detect presence of the sheet through detection of rotation of the shaft rotating with the contact body in contact with the sheet. The sheet conveying device according to Embodiment 2 of this disclosure further includes a rotary body support configured to rotatably support the contact body to the shaft that rotates together with the contact body in contact with the sheet, extending the range of rotation, in a same direction as the direction of rotation of the shaft. 
     According to Embodiment 2, the performance of sheet conveyance can be enhanced without retracting and returning the sheet contact member  903 , and therefore the sheet contact member  903  and the sheet can be prevented from being damaged or torn. Further, the failure caused by forgetting of return of the sheet contact member  903  can be prevented before the occurrence. 
     An image forming apparatus to which this disclosure is applied is explained with the image forming apparatus  100  that forms image by electrophotography. However, the configuration of an image forming apparatus to which this disclosure is applied is not limited to the image forming apparatus  100 . For example, any image forming apparatus can be applied as long as the image forming apparatus includes a sheet discharging device to discharge a recording medium. For example, this disclosure can be applied to an inkjet image forming apparatus that forms an image using at least one liquid inkjet print head, a printing apparatus such as a stencil printing machine, a post processing device or finisher including at least one function of a sorting function, a punching function and a binding function, or a multifunction machine having the above-described functions. 
     Further, the sheet conveying device is not limited to a sheet conveying device disposed in the sheet conveyance passage in the vicinity of the pair of registration rollers as described above. For example, the sheet conveying device may be disposed in a sheet conveyance passage in the vicinity of a multiple step sheet feeder and a bank type sheet feeder. 
     In the above-described embodiments, the sheet P is used as a sheet-like transfer target medium that is conveyed or on which an image is formed. However, the sheet P is not limited thereto but also includes thick paper, postcard, envelope, plain paper, thin paper, coated paper, art paper, tracing paper, and the like. Further, as a transfer target medium other than a paper material, the sheet P further includes a non-paper material such as OHP sheet, OHP film, resin film, and any other sheet-shaped material to be conveyed or on which an image can be formed. 
     The above-described embodiments are illustrative and do not limit this disclosure. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements at least one of features of different illustrative and exemplary embodiments herein may be combined with each other at least one of substituted for each other within the scope of this disclosure and appended claims. Further, features of components of the embodiments, such as the number, the position, and the shape are not limited the embodiments and thus may be preferably set. It is therefore to be understood that within the scope of the appended claims, the disclosure of this disclosure may be practiced otherwise than as specifically described herein.