Patent Publication Number: US-7708374-B2

Title: Inkjet image forming apparatus including cap member

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority under 35 U.S.C. §119(a) from Korean Patent Application No. 10-2005-0128706, filed on Dec. 23, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present general inventive concept relates to an inkjet image forming apparatus, and more particularly, to an inkjet image forming apparatus including an inkjet head having a nozzle portion, a length of which in a main scanning direction corresponds to a width of a printing medium, and a cap member to cap the nozzle portion. 
   2. Description of the Related Art 
   In general, an inkjet image forming apparatus forms images by ejecting ink from an inkjet head, which reciprocates in a main scanning direction (shuttle type inkjet head), onto a sheet of paper conveyed in a sub-scanning direction. The inkjet head includes a nozzle portion including a plurality of nozzles through which ink is ejected. Ink droplets that are not ejected remain around the nozzle portion. When the nozzle portion is exposed to air when a printing operation is not performed, the ink droplets around the nozzle portion may harden, and impurities, such as fine dust in the air, may attach to the nozzle portion. The hardened ink or impurities may change an ink ejecting direction, thereby degrading printing quality. In addition, since a humidity of the ink in the nozzles evaporates, the nozzles portion may become clogged with ink. 
   Recently, high speed printing has been performed using an inkjet head (array inkjet head) including a nozzle portion having a length in a main scanning direction corresponding to a width of a sheet of paper. In the inkjet image forming apparatus, the inkjet head is fixed, and sheets of paper are conveyed in a sub-scanning direction. Therefore, a driving unit for the inkjet image forming apparatus has a simple structure, and a printing operation can be performed at a high speed. In the inkjet image forming apparatus, the length of the nozzle portion corresponding to A4 paper is about 210 mm, without considering a printing margin in a width direction of the paper. Since the array inkjet head ejects ink in a fixed position unlike the shuttle type inkjet head reciprocating in the main scanning direction, it is difficult to fix operational problems when some of the nozzles are clogged or when an ejecting direction of the ink is changed due to impurities. 
   Therefore, when the printing operation is not performed, the nozzle portion should be isolated from the outside (e.g., an environment surrounding the nozzle portion). 
   SUMMARY OF THE INVENTION 
   The present general inventive concept provides an inkjet image forming apparatus having a nozzle portion of an array inkjet head that can be capped in order to isolate the nozzle portion from the outside (e.g., an environment surrounding the nozzle portion). 
   Additional aspects and advantages 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. 
   The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing an inkjet image forming apparatus, including an inkjet head including a nozzle portion having a length in a main scanning direction that is at least equal to a width of a printing medium, a conveying unit to convey the printing medium, a driving motor to drive the conveying unit, a cap member to cap the nozzle portion, a cap driving unit to move the cap member to a capping position where the nozzle portion is capped and an uncapping position where the cap member is separated from the nozzle portion when the driving motor rotates in a first direction and in a second direction, and a first clutch to block a driving force of the driving motor to the cap driving unit when the cap member is located at the uncapping position, in which the driving motor moves the cap member to the uncapping position by rotating in the first direction, the conveying unit conveys the paper in the sub-scanning direction to perform a printing operation, and the driving motor moves the cap member to the capping position by rotating in the second direction. 
   The apparatus may further include a second clutch to block the driving force of the driving motor to the cap driving unit when the cap member is located at the capping position. The first clutch may include a clutch gear connected to the cap driving unit and including gear teeth, the clutch gear including a first idle portion on which the gear teeth are not formed, the first idle portion being formed in a portion of the clutch gear corresponding to the uncapping position, and a first swing gear to connect with the clutch gear when the driving motor rotates in the first direction. The second clutch may include a second swing gear to connect with the clutch gear when the driving gear rotates in the second direction, and a second idle portion formed in a portion of the clutch gear corresponding to the capping position by omitting some of the gear teeth of the clutch gear. 
   The inkjet image forming apparatus may further include a loading unit in which the printing medium is loaded, a pickup roller to pick up the printing medium from the loading unit, and a pickup motor to drive the pickup roller. 
   The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet image forming apparatus, including an inkjet head including a nozzle portion having a length in a main scanning direction that is at least equal to a width of a printing medium, a conveying unit to convey the printing medium, a driving motor to drive the conveying unit, a cap member moveable to a capping position where the nozzle portion is capped and to an uncapping position where the cap member is separated from the nozzle portion, a clutch gear connected to the cap member and including gear teeth, the clutch gear including a first idle portion and a second idle portion in portions of the clutch gear corresponding to the capping position and the uncapping position by omitting some of the gear teeth of the clutch gear, and a first swing gear and a second swing gear to connect with the clutch gear when the driving motor rotates in a first direction and a second direction, respectively, in which the conveying unit and the cap member are driven simultaneously by the driving motor. 
   The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an image forming apparatus, including a print head unit including a nozzle unit having a plurality of nozzles to eject ink to form an image on a printing medium, a conveying unit to convey the printing medium along a conveying path to the print head unit, a capping unit comprising a capping member to separate the nozzle unit from an environment surrounding the nozzle unit, the capping unit being movable between a capping position at which the nozzle unit is capped by the cap member and an uncapping position at which the nozzle unit is uncapped, a driving unit to generate a driving force to drive the conveying unit to convey the print medium along the conveying path to the print head unit, and to drive the capping unit to move to the capping position and the uncapping position, and a clutch unit to prevent the driving force from driving the capping unit when the capping unit is at the uncapping position. 
   The clutch unit may prevent the driving force from driving the capping unit when the capping unit is at the capping position. The clutch unit may include a first clutch part to prevent the driving force from driving the capping unit when the capping unit is in the uncapping position, and a second clutch part to prevent the driving force from driving the capping unit when the capping unit is in the capping position. The image forming apparatus may further include a detection unit to detect a position of the capping unit. 
   The driving unit may include a driving motor to generate the driving force, the driving motor being rotatable in a first direction to drive the conveying unit to convey the print medium along the conveying path to the print head unit and to drive the capping unit to move to the uncapping position, and a second direction to drive the capping unit to move to the capping position. The clutch unit may include a clutch gear to rotate the capping unit to move the capping unit to the capping position and the uncapping position, the conveying unit may include a roller to convey the printing medium and a conveying gear to rotate the roller, and the driving unit may include a pulley to transmit the driving force generated by the driving motor to the clutch gear and the conveying gear. The clutch unit may further include a first clutch part to prevent the driving force from driving the capping unit when the capping unit is in the uncapping position, the first clutch part comprising a first idle portion corresponding to the uncapping position and a first swing gear to communicate with the clutch gear, and a second clutch part to prevent the driving force from driving the capping unit when the capping unit is in the capping position, the second clutch part comprising a second idle portion corresponding to the capping position and a second swing gear to communicate with the clutch gear. 
   The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing a method of separating a nozzle unit of a print head unit from an environment surrounding the nozzle unit, the method including conveying a printing medium along a conveying path to the print head unit by rotating a driving unit in a first direction to form an image on the printing medium, preventing the driving unit rotating in the first direction from driving a movement of a capping unit using a clutch unit when the capping unit is at an uncapping position spaced apart from the nozzle unit, moving the capping unit towards the nozzle by rotating the driving unit in a second direction to cap the nozzle unit, and preventing the driving unit rotating in the second direction from driving a movement of the capping unit using the clutch unit when the capping unit is at a capping position at which the nozzle unit is capped by the capping unit. 
   The method may further include uncapping the nozzle unit and moving the nozzle unit to the uncapping position by rotating the driving unit in the first direction, and preventing the driving unit rotating in the first direction from driving a movement of the capping unit using the clutch unit when the capping unit is at the uncapping position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and advantages 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 block diagram illustrating an inkjet image forming apparatus according to an embodiment of the present general inventive concept; 
       FIG. 2  is a view illustrating a nozzle portion of the inkjet image forming apparatus of  FIG. 1  according to an embodiment of the present general inventive concept; 
       FIG. 3  is a side view illustrating the inkjet image forming apparatus of  FIG. 1 ; 
       FIG. 4  is an exploded perspective view illustrating a platen and a wiping unit of the inkjet image forming apparatus of  FIG. 1  according to an embodiment of the present general inventive concept; 
       FIG. 5  is an exploded perspective view illustrating the inkjet image forming apparatus of  FIG. 1 ; 
       FIG. 6  is a detailed view illustrating a guide slot and a wiping trace of the image forming apparatus illustrated in  FIG. 5  according to an embodiment of the present general inventive concept; 
       FIG. 7  is an exploded perspective view illustrating a structure to drive a cap member and a conveying unit using a driving motor in the image forming apparatus of  FIG. 1  according to an embodiment of the present general inventive concept; 
       FIG. 8A  is a perspective view illustrating an example of a first clutch and a second clutch according to an embodiment of the present general inventive concept; 
       FIG. 8B  is a perspective view illustrating another example of the first clutch and the second clutch according to an embodiment of the present general inventive concept; 
       FIGS. 9A through 9F  are views illustrating processes of moving a cap member to an uncapping position and a capping position according to an embodiment of the present general inventive concept; and 
       FIG. 10  is a view illustrating the wiping unit and the platen of  FIG. 4  in a maintenance position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED 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 by referring to the figures. 
     FIG. 1  is a block diagram illustrating an inkjet image forming apparatus according to an embodiment of the present general inventive concept. Referring to  FIG. 1 , a printing medium, such as a sheet of paper (P), picked from a paper cassette (loading unit)  50  by a pickup roller  40  is conveyed in a sub-scanning direction (S) by a feed roller  20 . An inkjet head  10  is installed above the paper (P). The inkjet head  10  ejects ink onto the paper P at a fixed position to print an image on the paper P. A discharge roller  30  is installed in an outlet portion of the inkjet head  10  to discharge the paper P on which the image is printed. 
   The inkjet head  10  is an array inkjet head. In addition, a length of a nozzle portion  11  in a main scanning direction (M) is at least equal to a width of the paper P.  FIG. 2  illustrates an example of the nozzle portion  11 . Referring to  FIG. 2 , the nozzle portion  11  includes a plurality of nozzle plates  12  arranged in zigzag in the main scanning direction M. Each of the nozzle plates  12  includes a plurality of nozzles  13  to eject ink. The nozzle plate  12  may include a plurality of nozzle rows  12 - 1 ,  12 - 2 ,  12 - 3 , and  12 - 4 . In addition, the nozzle rows  12 - 1 ,  12 - 2 ,  12 - 3 , and  12 - 4  may eject ink of the same color or may eject ink of different colors (for example, cyan, magenta, yellow, and black).  FIG. 2  illustrates an example of the nozzle portion  11 ; however, the present general inventive concept is not limited thereto. The inkjet head  10  may include a chamber (not illustrated) having a discharge unit (for example, a piezoelectric device or a heater) connected to the nozzle to provide a driving force to discharge ink, and a flowing path to supply ink to the chamber. The chamber, the discharge unit, and the flowing path (not illustrated) are well known to those who skilled in the art, and thus, detailed descriptions are omitted. 
   A platen  60  faces the nozzle portion  11  and supports a rear surface of the paper P, thereby forming a paper conveying path  100 . The platen  60  is positioned so that the nozzle portion  11  of the inkjet head  10  is kept at a predetermined distance, for example, about 0.5 mm to about 2 mm, from the paper P. 
   If the nozzle portion  11  is exposed to air when a printing operation is not performed, ink droplets around the nozzle portion  11  may harden, and impurities (such as fine dust in the air) can attach to the nozzle portion  11 . The hardened ink or the impurities may change an ink ejecting direction of the nozzles  13 , and may degrade the printing quality. In addition, since a humidity of the ink in the nozzles  13  evaporates continuously, a viscosity of the ink in the nozzles  13  increases. Further, the ink in the nozzles  13  may be hardened. Thus, the nozzle portion  11  may be clogged by the ink of high viscosity or the hardened ink. Since the inkjet head  10  prints the image at a fixed position, if some of the nozzles  13  are clogged with ink, a white line appears in the printed image at a portion corresponding to the nozzle that is clogged. 
   The nozzle portion  11  should maintain an optimal condition to perform the printing operation in order to obtain high printing quality. To do this, maintenance operations, such as a preliminary spitting process, a wiping process, and a capping operation, can be performed. If the printing operation is not performed for a predetermined period of time, or if there are nozzles  13  that are not used for a predetermined period of time during the printing operation, the ink in the nozzles  13  and around the nozzles  13  is dried and a viscosity of the ink increases, and thus, a defective ejecting operation may occur. The preliminary spitting is an operation of spitting ink a few times in a predetermined time period in order to remove the ink having the increased viscosity. In the wiping process, a surface of the nozzle portion  11  is wiped in order to remove the hardened ink and impurities around the nozzles  13 . The capping process is performed in order to separate the nozzle portion  11  from the outer air (e.g., an environment surrounding the nozzle portion  11 ) and to prevent the nozzles  13  from drying by capping the nozzle portion  11  when the printing operation is not performed for a predetermined period of time. 
   To maintain the nozzle portion  11  in a suitable condition to perform the printing operation, the inkjet image forming apparatus according to the present embodiment includes a cap member  90  to cap the nozzle portion  11  to isolate the nozzle portion  11  from the outer air (e.g., the environment surrounding the nozzle portion  11 ), and a wiping unit  80  to clean the nozzle portion  11 , as illustrated in  FIG. 3 . In the image forming apparatus according to the present embodiment, the platen  60  can move between a printing position (refer to  FIG. 3 ) along the paper conveying path  100  and a maintenance position (refer to  FIG. 10 ) where the platen  60  moves away from a lower portion of the nozzle portion  11  so that the cap member  90  can access the nozzle portion  11 . A conveying unit including the feed roller  20  and the discharge roller  30  to convey the paper P does not move. The wiping unit  80  is installed on the platen  60  to be moved with the platen  60  while cleaning the nozzle portion  11 . 
   Referring to  FIG. 4 , the platen  60  includes a plurality of ribs  65  supporting the rear surface of the paper P. In addition, the platen  60  includes a plurality of receiving portions  66  corresponding to the plurality of nozzle plates  12  illustrated in  FIG. 2  in order to receive the preliminarily spitted ink. The platen  60  includes a coupling portion  64  on a side portion thereof. The wiping unit  80  includes a supporting member  86  and a wiper  81 . The wiper  81  of the present embodiment is a roller that rotates while contacting the nozzle portion  11 . An axis  82  of the wiper  81  is coupled to the supporting member  86 . The supporting member  86  includes a first protrusion  83  that is inserted into a wiping trace  150  (see  FIGS. 5 and 6 ) that will be described later together with the axis  82  of the wiper  81 , and a second protrusion  85  coupled to the coupling portion  64 . A front edge portion  63  of the platen  60  pushes the axis  82  of the wiper  81  when the platen  60  moves to the printing position from the maintenance position. The coupling portion  64  pulls the wiping unit  80  when the platen  60  moves to the maintenance position from the printing position. 
   Referring to  FIG. 5 , the platen  60  is coupled to side walls  101  and  102 . The side walls  101  and  102  respectively include guide slots  120  illustrated in  FIGS. 5 and 6 . Protrusions  61  are formed on both sides of the platen  60 . The protrusions  61  are inserted into the guide slots  120 . The platen  60  moves to the printing position or the maintenance position along the guide slots  120 . Each of the guide slots  120  includes parallel sections  121  that are parallel to the paper conveying path  100 , and slant sections  122  that are inclined. A connection arm  542  includes an elongated slot  543 . The slot  543  is inserted into a guide pole  62  formed on the platen  60 . A shaft  530  is rotatably supported by the side walls  101  and  102 . D-cut portions  531  and  532  are formed on both ends of the shaft  530 . A pair of connection arms  541  are coupled to the D-cut portions  531  and  532  of the shaft  530 , and are respectively connected to the pair of connection arms  542  to be rotated. A gear  401  is coupled to the D-cut portion  532 . A maintenance motor  301  rotates the gear  401  to move the platen  60  to the printing position or to the maintenance position. 
   Referring to  FIGS. 5 and 6 , the wiping trace  150  is formed on the side walls  101  and  102 . The axis  82  and the first protrusion  83  of the wiping unit  80  are inserted into the wiping trace  150 . When the platen  60  moves from the printing position to the maintenance position and from the maintenance position to the printing position, the axis  82  and the first protrusion  83  are guided by the wiping trace  150  in an arrow direction  151 , as illustrated in  FIG. 6 . Therefore, the wiping unit  80  wipes the nozzle portion  11  when the platen  60  moves from the maintenance position to the printing position. 
     FIGS. 3 and 5  illustrate a cap driving unit  500  to move the cap member  90  to a capping position and an uncapping position. The cap driving unit  500  includes a cap arm  520 , a shaft  550 , and connection arms  561  and  562 . An end  521  of the cap arm  520  is coupled to a rotary shaft  71  formed on a guide member  70 . The cap member  90  is installed on the other end of the cap arm  520 , opposite to the end  521  coupled to the rotary shaft  71 . The shaft  550  is rotatably supported by the side walls  101  and  102 . D-cut portions  551  are disposed on both ends of the shaft  530  (one D-cut portion  551  is illustrated in  FIG. 5 ). The pair of connection arms  561  (one connection arm  561  of the pair is illustrated in  FIG. 5 ) is coupled to the D-cut portion  551  of the shaft  550 , and is rotatably connected to the pair of connection arms  562  (one connection arm  562  of the pair is illustrated in  FIG. 5 ). The pair of connection arms  562  are rotatably connected to the pair of cap arms  520  (one cap arm  520  of the pair is illustrated in  FIG. 5 ). 
   According to the image forming apparatus of the present embodiment, the cap member  90  is moved to the capping and uncapping positions using a driving motor  302  (refer to  FIG. 7 ) driving the conveying unit. In this case, the pickup roller  40  picking a sheet of paper P from the paper cassette  50  can be driven by a driving force generated by a pickup motor  303  illustrated in  FIG. 3 . Otherwise, the pickup roller  40  can be driven by the driving motor  302 . In this case, a clutch unit (not illustrated) may be used to selectively transmit the driving force of the driving motor  302  to the pickup roller  40 . A detailed description of the clutch unit is omitted since it is well known in the art. 
     FIG. 7  illustrates a driving bracket  103 . The driving bracket  103  is coupled to the side wall  101 . A first pulley  201  and a second pulley  202  are coupled to the driving bracket  103 . The first pulley  201  is rotated by the driving motor  302 . The first and second pulleys  201  and  202  are connected to each other through a belt  206 . In addition, the first and second pulleys  201  and  202  include gear portions  203  and  204 , respectively. The gear portions  203  and  204  are connected to a conveying gear  21  (refer to  FIG. 5 ) that is coupled to the feed roller  20  and to a discharge gear  31  (refer to  FIG. 5 ) that is coupled to the discharge roller  30 , respectively. 
   The cap driving unit  500  is connected to the driving motor  302  through a gear portion  205  of the first pulley  201 . When the image is printed onto the paper P, the cap member  90  should be located at the uncapping position. When the paper P is not picked from the paper cassette  50  by the pickup motor  303 , the paper P is not conveyed even if the driving motor  302  rotates in a first direction, that is, a direction to convey the paper P in the sub-scanning direction S by the feed roller  20  and the discharge roller  30 . Therefore, before driving the pickup motor  303 , the driving motor  302  can be rotated in the first direction to move the cap member  90  to the uncapping position. When the cap member  90  is located at the uncapping position, the driving motor  302  rotates in the first direction to perform the printing operation. The image forming apparatus of the present embodiment includes a first clutch (see  FIGS. 8A and 8B ) so that the driving force of the driving motor  302  is not transmitted to the cap driving unit  500  even when the driving motor  302  rotates in the first direction when the cap member  90  is located at the uncapping position. 
   When the driving motor  302  rotates in a second direction, that is, the opposite direction to the first direction, the paper P is not conveyed. Therefore, the cap member  90  can be moved to the capping position by rotating the driving motor  302  in the second direction. When the cap member  90  reaches the capping position, the driving motor  302  stops operating. A detecting unit (not illustrated) to detect the position of the cap member  90  may be included in order to determine when the driving motor  302  stops operating. However, the image forming apparatus of the present embodiment can include a second clutch (see  FIGS. 8A and 8B ) so that the driving force from the driving motor  302  is not transmitted to the cap driving unit  500  when the driving motor  302  rotates in the second direction when the cap member  90  is located at the capping position. According to the above structure, the detecting unit to detect the position of the cap member  90  is not necessary. 
   Referring to  FIG. 7 , a clutch gear  403  includes a first gear portion  403   a  and a second gear portion  403   b . The first gear portion  403   a  is connected to a cap gear  402  that is coupled to the d-cut portion  551  of the shaft  550 . A first swing gear  405  and a second swing gear  406  are coupled to a swing arm  407 , and are engaged with a gear  404  that is located on a swing shaft  407   a  of the swing arm  407 . The gear  404  is connected to the gear portion  203  of the first pulley  201  via gears  408  and  409 . 
   Referring to  FIG. 8A , the second gear portion  403   b  of the clutch gear  403  includes a first idle portion  411  and a second idle portion  412 , having no teeth. The first and second idle portions  411  and  412  correspond to the uncapping position and the capping position, respectively. In addition, the first and second idle portions  411  and  412  correspond to the first swing gear  405  and  406 , respectively. The first and second idle portions  411  and  412  are staggered in an axial direction of the clutch gear  403 , and the first and second swing gears  405  and  406  are also staggered in the axial direction of the clutch gear  403 . In addition, as illustrated in  FIG. 8B , the first and second idle portions  411  and  412  can be formed at the same portion of the clutch gear  403 . In this case, the clutch gear  403  may be larger than the clutch gear  403  of  FIG. 8A . 
   The first swing gear  405  and the first idle portion  411  perform as the first clutch that blocks the driving force of the driving motor  302  transmitting to the cap driving unit  500 , when the cap member  90  is located at the uncapping position. In addition, the second swing gear  406  and the second idle portion  412  perform as the second clutch such that the driving force of the driving motor  302  is not transmitted to the cap driving unit  500 , when the cap member  90  is located at the capping position. 
   Maintenance operations will be described using the above structure. Referring to  FIG. 3 , the platen  60  is located at the printing position and supports the rear surface of the paper P. The protrusion  61  of the platen  60  is supported by the parallel section  121  of the guide slot  120  (see  FIG. 6 ). Therefore, even if the position accuracy of the platen  60  at the printing position is low, a distance between the nozzle portion  11  and the upper surface of the paper P can be maintained accurately as long as the protrusion  61  is supported by the parallel section  121 . The wiping unit  80  and the cap member  90  are disposed under the platen  60 . The wiping unit  80  is separated from the nozzle portion  11 . As illustrated in  FIGS. 3 and 9A , the cap member  90  is located at the uncapping position. 
   When the pickup motor  303  (see  FIG. 1 ) rotates, the paper P is picked from the paper cassette and is conveyed to the feed roller  20 . When the paper P reaches the feed roller  20 , the pickup motor  303  stops operating. When the driving motor  302  rotates in the first direction, the conveying roller (feed roller)  20  conveys the paper P in the sub-scanning direction S. Referring to  FIG. 9A , since the first swing gear  405  is located at the first idle portion  411 , the clutch gear  403  is not rotated even if the driving motor  302  rotates in the first direction. The driving force of the driving motor  302  is not transmitted to the cap driving unit  500 . Therefore, the cap member  90  does not move. The nozzle portion  11  spits the ink onto the paper P to print the image. The discharge roller  30  discharges the printed paper P. 
   When the printing operation is completed, the platen  60  is moved to the maintenance position and the nozzle portion  11  is capped. When the maintenance motor  301  rotates the gear  401 , the shaft  530  and the connection arms  541  and  542  connected to the shaft  530  are rotated. The slot  543  of the connection arm  542  pulls the guide pole  62 . The protrusion  61  of the platen  60  is guided by the slant section  122  after escaping from the parallel section  121 . The platen  60  is guided to the maintenance position, as illustrated in  FIG. 10 . In addition, the wiping unit  80  moves together with the platen  60 . The wiping unit  80  does not contact the nozzle portion  11  as the platen  60  moves to the maintenance position. 
   In order to cap the nozzle portion  11 , the driving motor  302  is driven. At this time, the paper P is not picked from the paper cassette  50 , and thus, the paper P is not conveyed even when the driving motor  302  is rotated in the first or second direction. When the driving motor  302  rotates in the second direction, the gear  404  rotates in a direction denoted as A 2  in  FIG. 9B . The swing arm  407  swings in the A 2  direction, and thus, the second swing gear  406  is engaged with the second gear portion  403   b  of the clutch gear  403 . Accordingly, the driving force of the driving motor  302  is transmitted to the cap driving unit  500 . The connection arms  561  and  562  push the cap arm  520 . 
   Referring to  FIG. 9C , the cap arm  520  rotates about the rotary shaft  71 , and the cap member  90  approaches the nozzle portion  11 . Referring to  FIG. 9D , when the cap member  90  reaches the capping position, the second swing gear  406  is located at the second idle portion  412  of the clutch gear  403 . The driving force of the driving motor  302  in not transmitted to the cap driving unit  500 . Therefore, even though the driving motor  302  rotates in the second direction, the cap member  90  does not move. When the printing operation is not performed for a time longer than a predetermined period time, the cap member  90  covers the nozzle portion  11  to prevent the nozzles  13  from drying. 
   When a printing command is input again, the nozzle portion  11  is uncapped and the platen  60  is moved to the printing position before driving the pickup motor  303 . To perform the uncapping operation, the driving motor  302  rotates in the first direction. Since the paper P is not picked yet from the paper cassette  50 , the paper P is not conveyed when the driving motor  302  rotates in the first direction for performing the uncapping operation. 
   Referring to  FIG. 9E , when the driving motor  302  rotates in the first direction, the gear  404  rotates in a direction A 1 . Then, the swing arm  407  swings in the direction A 1 , and thus, the second swing gear  406  is separated from the second gear portion  403   b  of the clutch gear  403 , and the first swing gear  405  is engaged with the second gear portion  403   b  of the clutch gear  403 . The connection arms  561  and  562  pull the cap arm  520 . 
   Referring to  FIG. 9F , the cap arm  520  rotates about the rotary shaft  71 , and the cap member  90  is separated from the nozzle portion  11 . Referring to  FIG. 9A , when the cap member  90  reaches the uncapping position, the first swing gear  405  is located at the first idle portion  411  of the clutch gear  403 . Therefore, when the driving motor  302  rotates, the cap member  90  does not move. 
   Next, when the maintenance  301  rotates the gear  401 , the platen  60  is moved to the printing position. As illustrated by a dashed dot line in  FIG. 10 , the wiping unit  80  contacts the nozzle portion  11  and removes impurities from the nozzle portion  11 . In addition, the platen  60  reaches the printing position. The printing operation is performed in this state. 
   According to the inkjet image forming apparatus according to embodiments of the present general inventive concept, a cap member is moved to capping and uncapping positions using a driving motor that drives a conveying unit, and thus, a nozzle portion can be capped using a simple structure and at low costs. 
   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.