Patent Publication Number: US-9411306-B2

Title: Image forming apparatus and maintenance method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(a) from Korean Patent Application No. 10-2013-0127666 filed Oct. 25, 2013 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present general inventive concept relates to an image forming apparatus. More particularly, the present general inventive concept relates to an image forming apparatus including an image forming unit in which a developing member and an image carrier are selectively in contact with or spaced apart from each other and a maintenance method of the image forming apparatus. 
     2. Description of the Related Art 
     Generally, a photographing unit including an image carrier and a developing unit including a developing member that are used in an electro-photographic image forming apparatus are components having a certain lifetime so that they may need to be replaced with new units after a certain number of print media are printed. 
     For this, the photographing unit and the developing unit are detachably disposed in a main body frame of the image forming apparatus, and the photographing unit and the developing unit are hinge-connected to be rotated by a predetermined angle with respect to each other so that the image carrier of the photographing unit and the developing member of the developing unit may be selectively in contact with or spaced apart from each other. To rotate the developing unit a predetermined angle with respect to the photographing unit is performed by a contact-separating unit which is separately disposed. A lever member is disposed at one end of the contact-separating unit, and, if the user rotates the lever member, the developing unit is rotated by a predetermined angle with respect to the photographing unit so that the developing member is in contact with or spaced apart from the image carrier. 
     In a case of assembly of a conventional image forming apparatus, after a photographing unit  201  and a developing unit  203  are mounted, as illustrated in  FIG. 1 , if a lever member  210  is rotated upward (in a direction of an arrow AA illustrated in  FIG. 1 ), a developing member  204  is brought into contact with an image carrier  202  (i.e. the developing member  204  is moved in a direction of an arrow BB in  FIG. 1 ). Accordingly, the image forming apparatus is normally operated to perform printing. 
     However, since the conventional image forming apparatus is not configured to automatically confirm whether the developing member  204  is in contact with or spaced apart from the image carrier  202 , the user needs to visually check whether the developing member  204  is in contact with the image carrier  202  or not. If the user operates the image forming apparatus in a state in which the lever member  210  is not rotated, that is, in a state in which the developing member  204  is not contact with the image carrier  202 , then because the developing member  204  is not contact with the image carrier  202 , an image is not formed. 
     Also, in a case in which the photographing unit  201  or the developing unit  203  needs to be replaced for maintenance of the image forming apparatus, the lever member  210  of  FIG. 1  should be rotated downward. Then, the developing member  204  is spaced apart from the image carrier  202  so that the developing unit  203  and the photographing unit  201  may be separated. If the user separates the photographing unit  201  and developing unit  203  in a state in which the lever member  210  is not rotated downward (in a direction opposite arrow AA in  FIG. 1 ), because the image carrier  202  and the developing member  204  are in contact with each other, the photographing unit  201  and the developing unit  203  may be damaged. For example, if the photographing unit  201  is forcibly removed in a state in which the developing member  204  is in contact with the image carrier  202 , contact regions of the developing member  204  and the image carrier  202  are severely rubbed against each other so that the surface of the image carrier  202  may be damaged. 
     However, since the conventional image forming apparatus is configured so that the user manually rotates the lever member  210  to allow the image carrier  202  to be in contact with or to be separated from the developing member  204 , the user may forget to rotate the lever  210  member. If the photographing unit  201  or the developing unit  203  is separated in a state in which the lever member  210  is not rotated, the image carrier  202  is rubbed against the developing member  204  and may be damaged. Further, after the photographing unit  201  and the developing unit  203  are mounted, if the image forming apparatus is operated in a state in which the lever member  210  is not rotated, the developing member  204  is not in contact with the image carrier  202  so that normal printing may not be performed. 
     Accordingly, it is necessary to provide an image forming apparatus that can prevent problems caused by a user forgetting to rotate the lever member  210 . 
     SUMMARY OF THE INVENTION 
     The present general inventive concept provides an image forming apparatus configured so that, when separation of a photographing unit and a developing unit is required, an image carrier and a developing member are automatically spaced apart from each other, and, after the photographing unit and the developing unit are mounted, a waste developer receptacle may not be mounted if the developing member and the image carrier are not in contact with each other, and a maintenance method of the image forming apparatus. 
     Additional features and utilities of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
     Exemplary embodiments of the present general inventive concept provide an image forming apparatus, including a main body frame, an image forming unit disposed in the main body frame and including an image carrier and a developing member, a gap control unit configured to selectively allow the image carrier and the developing member to be in contact with or to be spaced apart from each other, a lever member disposed at one end of the gap control unit to operate the gap control unit, the lever member configured to be moved between a contact position in which the gap control unit is operated so that the image carrier and the developing member are in contact with each other and a separation position in which the gap control unit is operated so that the image carrier and the developing member are spaced apart from each other, and a waste developer receptacle detachably disposed in the main body frame, the waste developer receptacle provided with a lever member receiving groove that can receive the lever member when the lever member is in the contact position, wherein if the waste developer receptacle is removed from the main body frame, the image carrier and the developing member are spaced apart from each other by the gap control unit. 
     The lever member receiving groove of the waste developer receptacle may include a lever member operating rib to press the lever member towards the separation position. 
     The lever member receiving groove of the waste developer receptacle may further include a stopper to limit rotation of the lever member by the lever member operating rib. 
     The lever member operating rib may include an inclined surface to be in contact with the lever member. 
     The main body frame may include a mounting groove that is formed in a shape corresponding to the waste developer receptacle and in which the waste developer receptacle is detachably disposed. The lever member may be rotatably disposed on a bottom surface of the mounting groove. 
     When the lever member is placed in the separation position, the waste developer receptacle may not be mounted in the mounting groove. 
     The lever member may be formed in an L-shape, the lever member receiving groove of the waste developer receptacle may include a vertical groove and a horizontal groove that are formed in the L-shape to accommodate the lever member inserted therein, and a lever member operating rib configured to press the lever member towards the separation position may be provided on a top surface of the horizontal groove, and a bottom surface of the horizontal groove may be configured to limit rotation of the lever member by the lever member operating rib. 
     The gap control unit may be a link structure having at least two links. 
     The image forming unit may include a developing unit including the developing member, and a photographing unit that is hinge-connected to the developing unit and includes the image carrier. The gap control unit may include a pressing member disposed in the main body frame so that the pressing member can linearly move with respect to a lower portion of the developing unit, a link member having one end connected to the pressing member, a crank arm rotatably connected to other end of the link member, an elastic member disposed around the link member to elastically support the pressing member, and a rotation shaft that is connected to the crank arm, is rotatably disposed in the main body frame, and has one end being protruded in the mounting groove. The lever member may be connected to the one end of the rotation shaft that is protruded in the mounting groove. 
     The pressing member may include an elongate groove that is formed in a direction parallel to a moving direction of the pressing member, and a guide projection may be formed at one end of the link member, may be inserted in the elongate groove, and may be moved inside the elongate groove. 
     If the lever member is placed in the contact position, the elastic member may push the pressing member to allow the developing unit to be rotated by a predetermined angle so that the developing member is brought into contact with the image carrier, and if the lever member is placed in the separation position, a force with which the elastic member pushes the pressing member may be removed to allow the developing unit to be returned to an original position so that the developing member is spaced apart from the image carrier. 
     When the link member and the crank arm make a straight line, the elastic member may be compressed to a maximum. 
     A first stopper may be disposed in the main body frame and may be configured to limit rotational motion of the crank arm, and when the crank arm is in contact with the first stopper, the pressing member may press the developing unit by the elastic force of the elastic member so that the developing member is brought into contact with the image carrier. 
     When the lever member is in contact with a stopper of the waste developer receptacle, an angle between the crank arm and the link member may be the same as or similar to an angle between the crank arm and the link member when the crank arm is in contact with the first stopper. 
     Exemplary embodiments of the present general inventive concept also provide a maintenance method of an image forming apparatus, the method including separating a waste developer receptacle from a main body frame, allowing, if the waste developer receptacle is separated, a lever member to be automatically moved to a separation position so that a developing member of a developing unit is spaced apart from an image carrier of a photographing unit, allowing the lever member to be moved to a contact position so that the developing member of the developing unit is in contact with the image carrier of the photographing unit, mounting the waste developer receptacle in the main body frame in order for the lever member in the contact position to be inserted into a lever member receiving groove of the waste developer receptacle, and allowing, when the waste developer receptacle is mounted in the main body frame, a lever member operating rib of the lever member receiving groove to press the lever member towards the separation position so that the lever member is brought into contact with a stopper of the lever member receiving groove. 
     When the lever member is in contact with the stopper of the lever member receiving groove, a force that is applied to the developing unit may be the same as or similar to a force that is applied to the developing unit when the lever member is placed in the contact position. 
     If the waste developer receptacle is separated from the main body frame, the lever member may be moved to the separation position by an elastic force of a gap control unit pressing the developing unit so that the developing member of the developing unit is spaced apart from the image carrier of the photographing unit. 
     Exemplary embodiments of the present general inventive concept also provide an image forming apparatus including a gap control unit disposed to control a gap between an image carrier and a developing member, the gap control unit being configured to narrow the gap when disposed in a first position, and a lever member disposed to move the gap control unit to a second position opposite to the first position with respect to a reference line, according to a force transmitted from an external unit to the lever member when the external unit is installed in the image forming apparatus. 
     The external unit may be a waste developer receptacle. 
     The gap control unit may include an arm forming an angle with the reference line according to the position of the gap control unit. 
     The angle formed by the arm with the reference line may control the gap between the image carrier and the developing member. 
     The absolute value of the angle formed by the arm with the reference line when the gap control unit is in the first position may be approximately equal to the absolute value of the angle formed by the arm with the reference line when the gap control unit is in the second position. 
     The gap control unit may further include a link to form an angle with the arm, the angle between the arm and the link varying according to a movement of the lever member. 
     The angle between the arm and the link may control the gap between the image carrier and the developing member. 
     The absolute value of the angle between the arm and the link when the gap control unit is in the first position may be approximately equal to the absolute value of the angle between the arm and the link when the gap control unit is in the second position. 
     The link may include an elastic member to move the gap control unit according to the movement of the lever member. 
     The gap control unit may further include a shaft connected to the lever member at one end of the gap control unit, and a distance between the shaft and an opposite end of the gap control unit may control the gap between the image carrier and the developing member. 
     When the external unit is removed from the image forming apparatus, the gap control unit may move in a direction towards a third position. The gap control unit may be configured to widen the gap between the image carrier and the developing member when the gap control unit is moved towards the third position. 
     The lever member may move in the same direction when the gap control unit moves from the first position to the second position as when the gap control unit moves from the second position to the third position. 
     Exemplary embodiments of the present general inventive concept further provide a maintenance method of an image forming apparatus, the method including narrowing a gap between an image carrier and a developing member when a gap control unit is disposed in a first position, and using a lever member to move the gap control unit to a second position opposite to the first position with respect to a reference line, according to a force transmitted from an external unit to the lever member when the external unit is installed in the image forming apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other features and utilities of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a partial view illustrating a state in which a developing member is in contact with an image carrier in a conventional image forming apparatus; 
         FIG. 2  is an exploded perspective view illustrating an image forming apparatus according to an embodiment of the present general inventive concept; 
         FIG. 3  is a cross-sectional view schematically illustrating a configuration of the image forming apparatus of  FIG. 2 ; 
         FIG. 4  is a perspective view illustrating a waste developer receptacle that is used in the image forming apparatus of  FIG. 2 ; 
         FIG. 5  is a view illustrating a state of a lever member when a waste developer receptacle is mounted in the image forming apparatus of  FIG. 2 ; 
         FIG. 6  is a view illustrating a posture of a lever member when a waste developer receptacle is removed from a mounting groove of an image forming apparatus; 
         FIG. 7  is a partial perspective view illustrating a gap control unit of an image forming apparatus according to an embodiment of the present general inventive concept; 
         FIG. 8  is a view illustrating a state in which a developing unit is not pressurized by the gap control unit of  FIG. 7 ; 
         FIG. 9  is a view illustrating a state of a gap control unit when a lever member is placed in a separation position; 
         FIG. 10  is a view illustrating a state of a gap control unit when a lever member is placed in a contact position; 
         FIG. 11  is a view illustrating a state of a gap control unit when a lever member is inserted into a lever member receiving groove of a waste developer receptacle; 
         FIG. 12  is a view illustrating a state in which a developing member of a developing unit is in contact with an image carrier of a photographing unit by a gap control unit when a lever member is inserted into a lever member receiving groove of a waste developer receptacle; 
         FIG. 13A  is a view illustrating a state just before a lever member operating rib of a waste developer receptacle is in contact with a lever member when the lever member is placed in a contact position; 
         FIG. 13B  is a view illustrating a case in which a lever member is rotated to be a state of  FIG. 11  by a lever member operating rib when a waste developer receptacle is inserted; 
         FIG. 14  is a view illustrating a state in which a lever member interferes with a waste developer receptacle when the lever member is placed in a separation position; 
         FIG. 15  is a flowchart illustrating a maintenance method of an image forming apparatus according to an embodiment of the present general inventive concept; and 
         FIG. 16  is a flowchart illustrating one type of maintenance which may be performed according to the maintenance method of  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept while referring to the figures. 
     The matters defined herein, such as a detailed construction and elements thereof, are provided to assist in a comprehensive understanding of this description. Thus, it is apparent that exemplary embodiments of the present general inventive concept may be carried out without those defined matters. Also, well-known functions or constructions are omitted to provide a clear and concise description of exemplary embodiments of the present general inventive concept. Further, dimensions of various elements in the accompanying drawings may be arbitrarily increased or decreased to assist in a comprehensive understanding. 
       FIG. 2  is an exploded perspective view illustrating an image forming apparatus  1  according to an exemplary embodiment of the present general inventive concept, and  FIG. 3  is a cross-sectional view schematically illustrating a configuration of the image forming apparatus  1  of  FIG. 2 .  FIG. 4  is a perspective view illustrating a waste developer receptacle  80  that is used in the image forming apparatus  1  of  FIG. 2 . 
     Referring to  FIGS. 2 and 3 , the image forming apparatus  1  according to an exemplary embodiment of the present general inventive concept includes a main body frame  10 , a paper feeding unit  20 , an image forming unit  30 , an exposure unit  40 , a fixing unit  50 , a paper discharging unit  60 , and a controller  70 . 
     The paper feeding unit  20  stores a predetermined number of sheets of print media P, and feeds the print media P one by one. The paper feeding unit  20  includes a pickup roller  21  that picks up the print media P one by one and feeds it to the image forming unit  30 . 
     The image forming unit  30  is to form a certain developer image on the print medium P fed from the paper feeding unit  20 , and includes a photographing unit  31 , a developing unit  33 , and a gap control unit  100 . The photographing unit  31  includes an image carrier  32  on which a predetermined electrostatic latent image is formed, and the developing unit  33  includes a developing member  34  to supply developer to the image carrier  32  to thereby form the certain developer image on the image carrier  32 . The developer image formed on the image carrier  32  is transferred onto the print medium P by a transfer roller  36 . The developing unit  33  is hinge-connected to the photographing unit  31  to be rotated by a predetermined angle on a hinge shaft  35  about the photographing unit  31 . The photographing unit  31  and the developing unit  33  are detachably disposed in the main body frame  10 . 
     The gap control unit  100  is disposed below the photographing unit  31 , and is formed to selectively apply a force to at least one of the image carrier  32  and the developing member  34  to control a gap G (illustrated for example in  FIGS. 8 and 12 ) between the image carrier  32  and the developing member  34 . For the purposes of the exemplary embodiment of the present general inventive concept illustrated in the figures, the gap control unit  100  applies the force to a lower portion of the developing unit  33 , and by extension the developing member  34 . If the gap control unit  100  applies the force to the lower portion of the developing unit  33 , the developing member  34  of the developing unit  33  is in contact with the image carrier  32  of the photographing unit  31 . If the force being applied by the gap control unit  100  is removed, the developing unit  33  is rotated by a predetermined angle so that the developing member  34  is spaced apart from the image carrier  32 . A gap maintaining member (not illustrated) is disposed between the developing unit  33  and the photographing unit  31  so that the developing member  34  is spaced apart from the image carrier  32 . The gap maintaining member may be formed as an elastic member such as a spring. The gap control unit  100  may be formed as a link structure including at least two links. A detailed description about the structure of the gap control unit  100  will be described later with reference to  FIGS. 7-12 . When the gap control unit  100  does not apply a force to the developing unit  33 , the developing unit  33  and the photographing unit  31  can be separated through an opening  15  that is formed in a side surface of the main body frame  10 . The opening  15  may correspond to the shape of the waste developer receptacle  80 . 
     The exposure unit  40  is disposed below the image forming unit  30 , and forms electrostatic latent images corresponding to printing data that are transmitted from the controller  70  onto a surface of the image carrier  32 . 
     The fixing unit  50  includes a pressure roller and a heating roller, and applies heat and pressure to the print medium P to allow the developer image transferred on the print medium P when passing through the image forming unit  30  to be fixed on the print medium P. 
     The paper discharging unit  60  discharges the print medium P on which fixing of the image is completed out of the main body frame  10 . 
     The controller  70  receives the printing data from the outside, for example a computer (not illustrated) connected to the image forming apparatus  1 . The controller then controls the paper feeding unit  20 , the image forming unit  30 , the exposure unit  40 , the fixing unit  50 , and the paper discharging unit  60  to form images corresponding to the received printing data on the print medium P. 
     The paper feeding unit  20 , the exposure unit  40 , the fixing unit  50 , the paper discharging unit  60 , and the controller  70  as described above are similar to or the same as the paper feeding unit, the exposure unit, the fixing unit, the paper discharging unit and the controller of a conventional image forming apparatus. Therefore, detailed descriptions thereof are omitted. 
     Also, the paper feeding unit  20 , the image forming unit  30 , the exposure unit  40 , the fixing unit  50 , and the paper discharging unit  60  are fixed inside the main body frame  10 . As illustrated in  FIG. 2 , a mounting groove  11  in which the waste developer receptacle  80  is inserted and mounted may be provided in a side surface of the main body frame  10 . The mounting groove  11  is concavely formed in a shape corresponding to the shape of the waste developer receptacle  80  in the side surface of the main body frame  10 . A lever member  160  of the gap control unit  100  is rotatably disposed in a bottom surface of the mounting groove  11 . A cover  17  is detachably disposed on the side surface of the main body frame  10  in which the mounting groove  11  is provided. Accordingly, in order to mount or remove the waste developer receptacle  80 , the cover  17  should be separated from the main body frame  10 . In an exemplary embodiment as illustrated in  FIG. 2 , the waste developer receptacle  80  is mounted in the recessed mounting groove  11 . However, the waste developer receptacle  80  does not have to be disposed in the mounting groove  11 . In an exemplary embodiment of the present general inventive concept, the waste developer receptacle  80  may be disposed in a state in which the waste developer receptacle  80  is fixed to the main body frame  10  and protrudes from the side surface of the main body frame  10 . 
     The waste developer receptacle  80  is detachably mounted in the main body frame  10 , and stores waste developer that remains in the image forming unit  30  after printing. Accordingly, after the developer image is transferred onto the print medium P, the waste developer remaining on the image carrier  32  is collected into the waste developer receptacle  80 . Referring to  FIG. 4 , a rear surface of the waste developer receptacle  80  is provided with an inlet  81  through which the collected waste developer comes from the image forming unit  30  through a waste developer path (not illustrated) and a lever member receiving groove  83  in which the lever member  160  of the gap control unit  100  is accommodated. 
     With further reference to  FIG. 4 , the lever member receiving groove  83  includes a lever member operating rib  84  that operates the lever member  160  and a stopper  85  that limits rotation of the lever member  160  by the lever member operating rib  84 . The lever member receiving groove  83  is formed in a shape corresponding to the lever member  160 . In an exemplary embodiment of the present general inventive concept, the lever member  160  is formed in a substantially L-shape as illustrated in  FIG. 7 , so the lever member receiving groove  83  is also formed in the substantially L-shape to accommodate the lever member  160 . Accordingly, when the lever member  160  is placed in a contact position, the lever member  160  is inserted into the lever member receiving groove  83  of the waste developer receptacle  80  so that the waste developer receptacle  80  may be inserted in the mounting groove  11  of the main body frame  10  as illustrated in  FIG. 5 . In this state, if the waste developer receptacle  80  is separated from the mounting groove  11  of the main body frame  10 , the lever member  160  is automatically moved to a separation position as illustrated in  FIG. 6 . The image forming unit  30 , including both the photographing unit  31  and the developing unit  33  are omitted from  FIGS. 5 and 6  for simplicity of illustration. However, it will be understood that the image forming unit  30  may be located in the same location relative to the gap control unit  100  as illustrated in  FIG. 3 . 
     The gap control unit  100  according to the present general inventive concept controls the spacing of a gap G between the image carrier  32  and the developing member  34 . Depending on the configuration of a particular embodiment of the present general inventive concept, the gap control unit  100  may control the gap G according to a distance D between two ends of the gap control unit (described in detail below with reference to  FIGS. 8 and 10 ), an angle between two components (described in detail below with reference to  FIGS. 8 and 10 ), or a combination thereof. 
       FIG. 7  is a partial perspective view illustrating a gap control unit  100  of an image forming apparatus  1  according to an exemplary embodiment of the present general inventive concept.  FIG. 8  is a view illustrating a state in which the developing unit  33  is not pressurized by the gap control unit  100  of  FIG. 7 .  FIG. 9  is a view illustrating a state of the gap control unit  100  when the lever member  160  is placed in a separation position, and  FIG. 10  is a view illustrating a state of the gap control unit  100  when the lever member  160  is placed in a contact position.  FIG. 11  is a view illustrating a state of the gap control unit  100  when the lever member  160  is inserted into the lever member receiving groove  83  of the waste developer receptacle  80 .  FIG. 12  is a view illustrating a state in which a developing member  34  of the developing unit  33  is in contact with the image carrier  32  of the photographing unit  31  by the gap control unit  100  when the lever member  160  is inserted into the lever member receiving groove  83  of the waste developer receptacle  80 . More specifically, when the lever member  160  is placed in the contact position, the image carrier  32  and the developing member  34  are separated by the gap G having a first spacing. Depending on the particular embodiment of the present general inventive concept, the first spacing may be zero, in the case that the image carrier  32  and developing member  34  are physically contacting each other as illustrated for example in  FIG. 12 . Alternatively, the first spacing may be a non-zero distance less than that of a second spacing of the gap G between the image carrier  32  and the developing member  34  when the lever  160  is in the separation position (illustrated for example in  FIG. 8 ). 
     Referring to  FIGS. 7 to 12 , the gap control unit  100  that rotates the developing unit  33  of the image forming unit  30  of the image forming apparatus  1  according to an exemplary embodiment of the present general inventive concept by a certain angle includes a rotation shaft  110 , a crank arm  120 , a link member  130 , a pressing member  140 , an elastic member  150 , and the lever member  160 . 
     The rotation shaft  110  is rotatably disposed in the main body frame  10 . One end of the rotation shaft  110  is protruded from the side surface of the main body frame  10 . The lever member  160  that can rotate the rotation shaft  110  is disposed in the protruded one end of the rotation shaft  110 . In a case of the present exemplary embodiment, the one end of the rotation shaft  110  is protruded from the bottom surface of the mounting groove  11 . Accordingly, the lever member  160  is rotatably disposed in the bottom surface of the mounting groove  11  of the main body frame  10 . If the lever member  160  is rotated, the rotation shaft  110  is rotated integrally with the lever member  160 . 
     The crank arm  120  is disposed in the rotation shaft  110 . Since the crank arm  120  is fixed to the rotation shaft  110 , if the rotation shaft  110  is rotated, the crank arm  120  is also rotated integrally with the rotation shaft  110 . Accordingly, if the lever member  160  is rotated by a certain angle, the crank arm  120  is also rotated at the same angle in the same direction as the lever member  160 . An angle the crank arm  120  makes with a center line CL (described in detail below with reference to  FIG. 10 ) may control the spacing of the gap G. 
     The rotation of the crank arm  120  is limited by a supporting member  13  of the main body frame  10 . For example, in the case of the gap control unit  100  as illustrated in  FIG. 10 , if the crank arm  120  is rotated by a certain angle in the counterclockwise direction (a direction of an arrow A, illustrated in  FIG. 9 ), one end of the crank arm  120  interferes with the supporting member  13  so that the crank arm  120  cannot be further rotated. In other words, the supporting member  13  performs a function of a first stopper that limits an angle by which the crank arm  120  can be rotated in the counterclockwise direction. 
     The link member  130  is disposed between the crank arm  120  and the pressing member  140 . One end of the link member  130  is connected to the pressing member  140 , and the other end of the link member  130  is connected to the one end of the crank arm  120 . The other end of the link member  130  is rotatably connected to the one end of the crank arm  120 . In the case of the present exemplary embodiment, the other end of the link member  130  and the one end of the crank arm  120  are connected by a rotation pin  121  so that the link member  130  and the crank arm  120  can be freely rotated with respect to each other. The link member  130  and the crank arm  120  therefore form an angle α therebetween (illustrated for example in  FIG. 8 ), which may control the spacing of the gap G between the image carrier  32  and the developing member  34 . When the lever member  160  is in the separation position (illustrated for example in  FIG. 8 ), the angle α has a first size β, while when the lever member  160  is in the contact position (illustrated for example in  FIG. 10 ), the angle α has a second size γ, described in greater detail below. 
     A guide projection  131  that can be inserted in an elongate groove  141  of the pressing member  140  is provided in the one end of the link member  130 . The guide projection  131  may be formed in a cylindrical shape. The link member  130  is connected to perform a rotational motion and a linear motion with respect to the pressing member  140 . The link member  130  plays a role to convert the rotation of the crank arm  120  into the linear motion of the pressing member  140 . 
     The pressing member  140  is configured to apply a force to a lower portion of the developing unit  33  to push the developing unit  33  in a direction. The pressing member  140  may be disposed to move linearly in the supporting member  13 . Accordingly, the supporting member  13  may be provided with a pair of guide rails  13   a  to guide the pressing member  140 . The distance D between the shaft  110  and the leading end of the pressing member  140  may control the spacing of the gap G between the image carrier  32  and the developing member  34  When the lever member  160  is in the separation position (illustrated for example in  FIGS. 8 and 9 ), the distance D is a first distance shorter than a second distance formed when the lever member  160  is in the contact position (illustrated for example in  FIG. 10 ). 
     The pressing member  140  is formed in a hollow substantially rectangular parallelepiped shape, and each of opposite inner side surfaces of the pressing member  140  is provided with the elongate groove  141 . The pair of elongate grooves  141  is formed parallel to a moving direction of the pressing member  140  so that opposite ends of the guide projection  131  of the link member  130  can be inserted and moved in the pair of elongate grooves  141 . The length of the elongate grooves  141  is determined so that the rotational motion of the crank arm  120  can be converted into the linear motion. The pressing member  140  is moved toward the developing unit  33  by an elastic force of the elastic member  150  that is applied to the pressing member  140 . The developing unit  33  is rotated on the hinge shaft  35  (illustrated in  FIG. 8 ) by the movement of the pressing member  140 . This widens the gap G between the image carrier  32  and developing member  34 , such that the gap G has the second spacing defined by the separation position illustrated in  FIGS. 8 and 9 . 
     A pair of guide grooves  143  may be provided on opposite outer side surfaces of the pressing member  140 . The pair of guide grooves  143  is formed to be inserted in the pair of guide rails  13   a  that is provided in the supporting member  13 . The pair of guide rails  13   a  provided in the supporting member  13  is formed in the form of square bars facing each other. Accordingly, each of the pair of guide grooves  143  may be formed in a groove having a square cross-section corresponding to the square bar. If the pair of guide rails  13   a  of the supporting member  13  is inserted in the pair of guide grooves  143  of the pressing member  140 , the pressing member  140  can linearly move along the pair of guide rails  13   a  of the supporting member  13 .  FIG. 7  illustrates only one of the pair of guide rails  13   a  formed in the supporting member  13 , for simplicity of illustration. 
     A second stopper  13   b  that limits one direction movement of the pressing member  140  may be provided in an end of at least one of the pair of guide rails  13   a  of the supporting member  13 . The second stopper  13   b  limits the moving distance of the pressing member  140  in a direction away from the developing unit  33 . As illustrated in  FIGS. 7 and 8 , the second stopper  13   b  is provided in a direction perpendicular to the guide rail  13   a  in one end of the guide rail  13   a  of the supporting member  13 . Accordingly, when the lever member  160  is moved to the separation position, the second stopper  13   b  limits the movement of the pressing member  140 . 
     A leading end of the pressing member  140  is brought into contact with the lower portion of the developing unit  33  by the elastic member  150 , as illustrated for example in  FIGS. 9-10 . At this time, the leading end of the pressing member  140  and the lower portion of the developing unit  33  may be formed to be in surface contact or point contact with each other. 
     The elastic member  150  is disposed around the link member  130 , and elastically supports the pressing member  140 . In detail, the link member  130  is inserted in the elastic member  150 . Accordingly, if the link member  130  is disposed between the pressing member  140  and the crank arm  120 , the elastic member  150  applies a force to the pressing member  140 . In other words, one end of the elastic member  150  is supported by the one end of the crank arm  120 , and the other end of the elastic member  150  is supported by a rear end of the pressing member  140 , in detail, by a rear end of an elongate groove portion  142  in which the elongate grooves  141  are formed. The one end of the crank arm  120  and the rear end of the elongate groove portion  142  are formed in a curved surface so that, when the link member  130  is rotated by the crank arm  120 , the link member  130  does not interfere with the elastic member  150 . 
     Since the one end of elastic member  150  is supported by the crank arm  120  and the elastic member  150  is guided by the link member  130 , the elastic member  150  pushes the pressing member  140  toward the developing unit  33 . Accordingly, a coil spring may be used as the elastic member  150 . At this time, the coil spring  150  has an elastic force that allows the pressing member  140  to press the lower portion of the developing unit  33  so that the developing unit  33  is rotated on the hinge shaft  35  so that the developing member  34  is brought into contact with the image carrier  32  of the photographing unit  31 , as illustrated for example in  FIG. 12 . In other words, by only the elastic force of the coil spring  150 , the developing unit  33  may be rotated so that the developing member  34  is brought into contact with the image carrier  32 , thereby forming a proper developing nip between the developing member  34  and the image carrier  32 . 
     The force which the elastic member  150  applies to the pressing member  140  varies depending on the rotation of the crank arm  120 . As illustrated in  FIG. 9 , when the lever member  160  is placed in the separation position, the rear end of the pressing member  140  is in contact with the second stopper  13   b  so that the elastic member  150  is a state to receive no force or a minimum force. At this time, the elastic member  150  may be in an uncompressed or minimally compressed state. Accordingly, when the lever member  160  is placed in the separation position, no force is applied to the developing unit  33  by the gap control unit  100 . 
     Then, if the lever member  160  is rotated in the counterclockwise direction (a direction of arrow A) as illustrated in  FIG. 9 , the crank arm  120  is also rotated in the counterclockwise direction. When the crank arm  120  is rotated in the counterclockwise direction, the elastic member  150  receives a force by the crank arm  120 , thereby being compressed. When the link member  130  and the crank arm  120  makes a straight line (namely, when the lever member  160  reaches an inflection point), the elastic member  150  is compressed to the maximum. After that, if the lever member  160 , and by extension the crank arm  120 , is rotated over the inflection point, the force which is applied to the elastic member  150  is again decreased. When the lever member  160  is rotated by a predetermined angle over the inflection point in the counterclockwise direction, as illustrated in  FIG. 10 , the crank arm  120  is brought into contact with the supporting member  13  of the first stopper so that crank arm  120  may not be further rotated. When the crank arm  120  is in contact with the first stopper  13 , because the pressing member  140  that receives the force by the elastic force of the elastic member  150  presses the lower portion of the developing unit  33 , the developing unit  33  is rotated on the hinge shaft  35  so that the developing member  34  is brought into contact with the image carrier  32 . This configuration is illustrated in  FIG. 12 . 
     The lever member  160  is disposed at one end of the gap control unit  100 , in detail, at the one end of the rotation shaft  110  so that the lever member  160  can operate the gap control unit  100 . The lever member  160  may move between the contact position illustrated in  FIG. 10 , in which the gap control unit  100  is operated so that the image carrier  32  and the developing member  34  are in contact with each other, and the separation position illustrated in  FIG. 9 , in which the gap control unit  100  is operated so that the image carrier  32  and the developing member  34  are spaced apart from each other. 
     In the exemplary embodiment of the present general inventive concept illustrated in  FIGS. 7-12 , the lever member  160  is formed in a substantially L-shape. In detail, the lever member  160  is configured of two arms  161  and  162  that are connected substantially at 90 degrees as illustrated in  FIG. 7 , and bottom surfaces of the two arms  161  and  162  are connected by a bottom plate  163  of a fan shape. A user may rotate the lever member  160  by hand so that the lever member  160  is placed in the contact position or the separation position. It will be understood that in this exemplary embodiment of the present general inventive concept, if the user moves the lever member  160  to the contact position the elastic member  150  may maintain the lever member  160  in the contact position. That is, moving the lever member  160  away from the contact position would move the lever member  160  clockwise (in the direction of an arrow B in  FIG. 10 ) towards the inflection point, which would compress the elastic member  150  and therefore generate a force urging the lever member  160  counterclockwise, towards the contact position. Therefore, once the user has moved the lever member  160  to the contact position, the lever member  160  will remain in the contact position without a need for further user interaction. Also, the lever member  160  may be rotated by mounting or removing of the waste developer receptacle  80 . Furthermore, the lever member  160  as illustrated in  FIG. 7  is only one example; the shape of the lever member  160  is not limited to just the L-shape illustrated therein. It will be understood that the lever member  160  may be formed in any shape capable of moving between the contact position and the separation position, depending on the particular configuration of an embodiment of the present general inventive concept. As another example, the lever member  160  may be formed in a bar shape. 
     The waste developer receptacle  80  is detachably disposed in the main body frame  10 . However, only when the lever member  160  is placed in the contact position (illustrated in  FIG. 10 ), the waste developer receptacle  80  may be mounted in the main body frame  10 . When the lever member  160  is placed in the separation position (illustrated in  FIG. 9 ), the waste developer receptacle  80  may not be mounted in the main body frame  10 . For this, the lever member receiving groove  83  that can receive the lever member  160  which is placed in the contact position is provided in the rear surface of the waste developer receptacle  80  (see  FIG. 4 ). 
     The lever member receiving groove  83  of the waste developer receptacle  80  is configured of a vertical groove  83   a  and a horizontal groove  83   b  that are formed in the substantially L-shape corresponding to the lever member  160  so that the lever member  160  can be inserted into the lever member receiving groove  83 . Each of the vertical groove  83   a  and horizontal groove  83   b  of the lever member receiving groove  83  is formed to have a width wider than the width of each of the arms  161  and  162  of the lever member  160  so that the lever member  160  can be rotated by a predetermined angle within the lever member receiving groove  83 . The lever member operating rib  84  that presses the lever member  160  in a clockwise direction (direction B in  FIG. 11 ), in detail, that presses the arm  161  of the lever member  160  in the clockwise direction, is provided on a top surface of the horizontal groove  83   b . The lever member operating rib  84  is formed to include an inclined surface  84   a  (see  FIG. 13A ) that is in contact with the lever member  160 . Accordingly, when the waste developer receptacle  80  is mounted, the lever member  160  receives a force by the inclined surface  84   a  of the lever member operating rib  84  provided in the lever member receiving groove  83  of the waste developer receptacle  80  so as to be rotated clockwise. 
     Rotating operation of the lever member  160  by the lever member operating rib  84  will be described in detail with reference to  FIGS. 13A and 13B .  FIGS. 13A and 13B  are partial views illustrating the lever member receiving groove  83  and the lever member  160  by cutting a portion of the waste developer receptacle  80  in order to illustrate that the lever member  160  is rotated by the lever member operating rib  84 .  FIG. 13A  is a view illustrating a state just before the lever member operating rib  84  of the waste developer receptacle  80  is in contact with the lever member  160  when the lever member  160  is placed in the contact position, and  FIG. 13B  is a view illustrating a state in which, when the waste developer receptacle  80  is completely inserted, the lever member  160  is rotated by the lever member operating rib  84  so that the lever member  160  is supported by the bottom surface  85  of the lever member receiving groove  83 . 
     As illustrated in  FIG. 13A , before the inclined surface  84   a  of the lever member operating rib  84  of the waste developer receptacle  80  is in contact with the lever member  160 , the lever member  160  remains in the contact position. If the waste developer receptacle  80  is inserted, the lever member  160  is inserted in the lever member receiving groove  83 . At this time, the lever member  160  is urged clockwise by the inclined surface  84   a  of the lever member operating rib  84  provided on the top surface of the lever member receiving groove  83  so that the lever member  160  is rotated clockwise, i.e., towards the separation position. However, the rotation of the lever member  160  is limited by the bottom surface  85  of the horizontal groove  83   b  of the lever member receiving groove  83 . 
     In other words, the bottom surface  85  of the horizontal groove  83   b  of the lever member receiving groove  83  serves as a stopper to limit the rotation of the lever member  160  that is rotated by the lever member operating rib  84 . At this time, the bottom surface  85  of the horizontal groove  83   b  is provided in a position in which the gap control unit  100  presses the developing unit  33  with a force that is the same as to or similar to the force with which the gap control unit  100  presses the developing unit  33  when the lever member  160  is in the contact position. In other words, the bottom surface  85  of the horizontal groove  83   b  is formed so that, when the arm  161  of the lever member  160  is in contact with the bottom surface  85  of the horizontal groove  83   b  of the lever member receiving groove  83 , the angle of the crank arm  120  is the same as or similar to the angle of the crank arm  120  when the lever member  160  is placed in the contact position. In detail, when the lever member  160  is in the contact position, as illustrated in  FIG. 10 , the crank arm  120  forms a certain angle θ about the center line CL that is formed when the crank arm  120  and the link member  130  makes a straight line, i.e., when the lever member  160  is at the inflection point. Accordingly, as illustrated in  FIG. 11 , the bottom surface  85  of the horizontal groove  83   b  is formed so that, when the arm  161  of the lever member  160  is in contact with the bottom surface  85  of the horizontal groove  83   b , the crank arm  120  forms the same or similar angle θ about the center line CL (the center line formed when the crank arm  120  and the link member  130  makes a straight line). However, when the lever member  160  is supported by the horizontal groove  83   b  of the lever member receiving groove  83 , the angle of the crank arm  120  is in the opposite direction about the center line CL from the angle of the crank arm  120  when the lever member  160  is in the contact position. For example, if, when the lever member  160  is in the contact position, the crank arm  120  is placed in a position where the crank arm  120  forms an angle of +θ against the center line CL as illustrated for example in  FIG. 10 , then when the lever member  160  is supported by the waste developer receptacle  80 , the crank arm  120  is placed in a position where the crank arm  120  forms an angle of −θ against the center line CL, as illustrated for example in  FIG. 11 . Accordingly, when the lever member  160  is in contact with the bottom surface  85  of the horizontal groove  83   b  of the lever member receiving groove  83  of the waste developer receptacle  80 , namely, the stopper  85  as illustrated in  FIG. 11 , the angle α between the crank arm  120  and the link member  130  has a size that is the same as or similar to that of the size γ of the angle α between the crank arm  120  and the link member  130  when the crank arm  120  is in contact with the first stopper  13  as illustrated in  FIG. 10 . Hereinafter, the position in which the lever member  160  is supported by the horizontal groove  83   b  of the waste developer receptacle  80  to press the developing unit  33  so that the developing member  34  and the image carrier  32  are brought into contact with each other will be referred to as a support position. 
     Accordingly, when the lever member  160  is in the contact position as illustrated in  FIG. 10 , if the waste developer receptacle  80  is inserted into the mounting groove  11  of the main body frame  10 , the lever member  160  is rotated by a predetermined angle by the lever member operating rib  84 , thereby being placed in the support position, as illustrated in  FIG. 11 . When the lever member  160  is in the support position, then as illustrated in  FIG. 12  the developing member  34  is in contact with the image carrier  32  so that a proper developing nip is formed between the developing member  34  and the image carrier  32 . 
     When the lever member  160  is in the support position where the lever member  160  is supported by the waste developer receptacle  80 , if the waste developer receptacle  80  is removed from the main body frame  10 , the lever member  160  is moved to the separation position by the elastic member  150  of the gap control unit  100 . That is, the elastic member  150  exerts a force against the lever member  160  to rotate the lever member  160  clockwise. If the lever member  160  is moved to the separation position, the developing unit  33  is rotated on the hinge shaft  35  by the gap maintaining member (not illustrated) so that the developing member  34  is spaced apart from the image carrier  32  by the gap G having the second spacing (illustrated in  FIG. 8 ). 
     When the lever member  160  is in the separation position, the waste developer receptacle  80  cannot be mounted in the mounting groove  11  of the main body frame  10 . This is because the lever member  160  interferes with the lever member receiving groove  83  of the waste developer receptacle  80 . When the lever member  160  is in the separation position, as illustrated in  FIG. 14 , the arm  162  of the lever member  160  is placed in the opposite direction against the horizontal groove  83   b  of the lever member receiving groove  83  of the waste developer receptacle  80  so that the lever member  160  interferes with the waste developer receptacle  80 .  FIG. 14  illustrates only the rear surface of the waste developer receptacle  80  and the lever member  160  in order to explain interference between the lever member  160  and the waste developer receptacle  80 . As described above, when the lever member  160  is in the separation position, the waste developer receptacle  80  may not be mounted in the main body frame  10 , and as a result the image forming apparatus  1  cannot operate normally. 
     Generally, if the waste developer receptacle  80  is not mounted, the controller  70  of the image forming apparatus  1  notifies a user that the waste developer receptacle  80  is not mounted, and controls the image forming apparatus  1  not to perform printing. Accordingly, with the image forming apparatus  1  according to an exemplary embodiment of the present general inventive concept, if the lever member  160  is not placed in the contact position, the waste developer receptacle  80  may not be mounted, and if the waste developer receptacle  80  is not mounted, the image forming apparatus  1  may not perform printing. Therefore, operation of the image forming apparatus  1  while the developing member  34  is not contact with the image carrier  32  may be prevented. 
     Further, as illustrated in  FIG. 5 , in a state in which the waste developer receptacle  80  is mounted in the main body frame  10 , the lever member  160  is placed in the support position in which the lever member  160  is supported by the lever member receiving groove  83  of the waste developer receptacle  80 . When the lever member  160  is in the support position, the crank arm  120  of the gap control unit  100  is placed below the inflection point. Therefore, if the waste developer receptacle  80  is separated, the crank arm  120  is further rotated in the clockwise direction by the elastic member  150  of the gap control unit  100  so that the force which the pressing member  140  of the gap control unit  100  applies to the developing unit  33  is removed. Accordingly, the developing unit  33  is rotated by a predetermined angle against the photographing unit  31  by the gap maintaining member (not illustrated) to be returned to an original position so that the developing member  34  is spaced apart from the image carrier  32 . Accordingly, with the image forming apparatus  1  according to an exemplary embodiment of the present general inventive concept, by separating the waste developer receptacle  80  from the main body frame  10 , the developing member  34  is automatically spaced apart from the image carrier  32 , so a case in which the user does not place the lever member  160  in the separation position and separates the developing unit  33  and the photographing unit  31  may not occur. 
     Hereinafter, a maintenance method of an image forming apparatus  1  with the structure as described above according to an exemplary embodiment of the present general inventive concept will be described with reference to accompanying drawings. 
       FIG. 15  is a flowchart illustrating a maintenance method of an image forming apparatus  1  according to an exemplary embodiment of the present general inventive concept.  FIG. 16  is a flowchart illustrating one type of maintenance which may be performed according to the maintenance method of  FIG. 15 . 
     First, in order to remove the developing unit  33  or the photographing unit  31 , a user or a service staff separates the waste developer receptacle  80  from the main body frame  10  (operation S 1510 ). For this, the cover  17  that is provided to cover the waste developer receptacle  80  is removed, and then the waste developer receptacle  80  is removed from the mounting groove  11 . 
     After the waste developer receptacle  80  is removed, the lever member  160  is automatically moved to the separation position so that the developing member  34  of the developing unit  33  is spaced apart from the image carrier  32  of the photographing unit  31  (operation S 1520 ). In detail, if the waste developer receptacle  80  blocking the rotation of the lever member  160  is removed, the crank arm  120  is rotated in the counterclockwise direction (a direction of arrow B) of  FIG. 11  by the elastic force of the elastic member  150  of the gap control unit  100  to be a state as illustrated in  FIG. 9  so that a force pressing the developing unit  33  is removed. Then, by the gap maintaining member (not illustrated) between the developing unit  33  and the photographing unit  31 , the developing unit  33  is rotated by a predetermined angle to be returned to the original position so that the developing member  34  and the image carrier  32  are spaced apart from each other by the gap G having the second spacing as illustrated in  FIG. 8 . 
     In a state in which the developing member  34  is spaced apart from the image carrier  32 , the user may perform maintenance on the developing unit  33  and the photographing unit  31  without danger of damaging the image carrier  32  and the developing member  34 . The type of maintenance depends on the immediate embodiment of the present general inventive concept and the desire of the user. In the exemplary embodiment of the present general inventive concept illustrated in  FIG. 16 , after operation S 1520  the user separates the developing unit  33  and the photographing unit  31  from the main body frame  10  (operation S 1521 ). 
     As further illustrated in  FIG. 16 , the user inspects the developing unit  33  and the photographing unit  31 . If there is a problem, the user replaces the developing unit  33  or the photographing unit  31  with a new one (operation S 1522 ). 
     After that, the user again mounts the developing unit  33  and the photographing unit  31  in the main body frame  10  (operation S 1523 ). At this time, if at least one of the photographing unit  31  and developing unit  33  is replaced with new one, the new one is mounted in the main body frame  10 . If the both the photographing unit  31  and the developing unit  33  are not replaced, the separated photographing unit  31  and developing unit  33  are again mounted in the main body frame  10 . 
     Returning to  FIG. 15 , after maintenance of the photographing unit  31  and the developing unit  33  is completed, in operation S 1530  the user rotates the lever member  160  to the contact position. When the lever member  160  is moved to the contact position, the developing unit  33  is rotated by the gap control unit  100  so that the developing member  34  of the developing unit  33  is brought into contact with the image carrier  32  of the photographing unit  31 . 
     After that, in order for the lever member  160  in the contact position to be inserted into the lever member receiving groove  83  of the waste developer receptacle  80 , the user mounts the waste developer receptacle  80  in the mounting groove  11  of the main body frame  10  (operation S 1540 ). 
     If the waste developer receptacle  80  is mounted in the main body frame  10 , the lever member operating rib  84  of the lever member receiving groove  83  presses the lever member  160  downwards so that the lever member  160  is brought into contact with the stopper, or the lower surface  85  of the lever member receiving groove  83  (operation S 1550 ). 
     Since the state in which the lever member  160  is supported by the lever member receiving groove  83  of the waste developer receptacle  80  is the state in which the gap control unit  100  presses the developing unit  33 , the developing member  34  of the developing unit  33  remains to be in contact with the image carrier  32  of the photographing unit  31 . When the lever member  160  is in contact with the stopper  85  of the lever member receiving groove  83  of the waste developer receptacle  80 , a force that is applied to the developing unit  33  by the gap control unit  100  is the same as or similar to a force that is applied to the developing unit  33  by the gap control unit  100  when the lever member  160  is in the contact position. 
     As described above, with a maintenance method of an image forming apparatus  1  according to an exemplary embodiment of the present general inventive concept, only by separation of the waste developer receptacle  80 , the developing member  34  and image carrier  32  are automatically spaced apart from each other. Therefore, a case in which the developing unit  33  and the photographing unit  31  are separated in a state in which the developing member  34  and the image carrier  32  are in contact with each other may not occur. 
     Also, with a maintenance method of an image forming apparatus  1  according to an exemplary embodiment of the present general inventive concept, only when the lever member  160  is in the contact position, the waste developer receptacle  80  can be mounted in the main body frame  10 . Therefore, to operate the image forming apparatus  1  in a state in which the developing member  34  is not in contact with the image carrier  32  may be prevented. 
     Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.