Patent Publication Number: US-8118423-B2

Title: Image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Division of application Ser. No. 11/619,717 filed Jan. 4, 2007 now U.S. Pat. No. 7,850,300, the entire contents of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image forming apparatus for printing an image on a medium such as, for example, a printing sheet, and particularly to an image forming apparatus having a recording head of an ink-jet system. 
     2. Description of the Related Art 
     As this type of image forming apparatus, for example, as disclosed in JP-A-2006-219235, there is known one in which a transport path for transporting a sheet is included in an apparatus main body, and an image is formed by discharging ink from a recording head to the sheet transported through this transport path. 
     In general, a sheet guide (medium guide) is provided to be separate from and opposite to a recording head, and ink is discharged to a sheet guided along this sheet guide. 
     At the time of a printing operation, an ink mist is generated around the recording head, and especially the sheet guide is soiled with this ink mist. When the sheet guide is soiled with the ink mist, there is a fear that when a subsequent sheet is guided, the sheet is soiled. 
     Then, in the related art, the sheet guide is periodically cleaned. 
     However, in the related art, since the sheet guide is fixedly provided in the apparatus main body, in the case where the sheet guide is cleaned, it has been necessary that a cleaning tool is inserted in the apparatus main body and the work is performed in a narrow space. Thus, there has been a problem that the workability is poor, and the confirmation of a cleaning effect becomes difficult. 
     Incidentally, as another means for cleaning a sheet guide, a paper for cleaning (for example, a white paper) is made to pass a sheet guide, and the soil of the sheet guide is removed by this paper. 
     However, in this case, there is a problem that since the paper is wastefully used, this is uneconomical. 
     BRIEF SUMMARY OF THE INVENTION 
     An aspect of the invention has been made in view of such circumstances, and it is an object to provide an image forming apparatus in which a medium guide is taken out to the outside of an apparatus main body and its cleaning can be performed. 
     An image forming apparatus according to an aspect of the invention includes an apparatus main body, a transport device that is provided in the apparatus main body and transports a medium, a recording device to record an image by discharging ink to the medium transported by the transport device, a medium guide that is provided to be opposite to the recording device and guides the medium, a transport roller provided at an upstream side of the medium guide in a medium transport direction, an ejection roller provided at a downstream side thereof, and a transport unit that integrates the medium guide, the transport roller and the ejection roller and is provided to freely come in and out of the apparatus main body. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is an outer appearance perspective view showing an image forming apparatus of a first embodiment of the invention; 
         FIG. 2  is an inner structure view showing the image forming apparatus of  FIG. 1 ; 
         FIG. 3  is a perspective view showing a movement mechanism and a cleaning mechanism of a recording head of  FIG. 2 ; 
         FIG. 4  is a perspective view showing a drive mechanism of a transport roller of  FIG. 2 ; 
         FIG. 5  is a plan view showing a sheet guide of  FIG. 2 ; 
         FIG. 6  is a view showing a state in which an opening and closing cover of an ink absorption member of  FIG. 5  is opened; 
         FIG. 7  is a view showing a state in which the opening and closing cover of the ink absorption member of  FIG. 5  is closed; 
         FIG. 8  is a view showing a state in which a transport unit of  FIG. 2  is taken out from an apparatus main body; 
         FIG. 9  is a view showing an image forming apparatus of a second embodiment of the invention; 
         FIG. 10  is a view showing a state in which a transport unit of  FIG. 9  is pulled down in a path unit; and 
         FIG. 11  is a view showing a state in which the path unit of  FIG. 10  is pulled out from an apparatus main body. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. 
       FIG. 1  is an outer appearance perspective view showing an image forming apparatus of a first embodiment of the invention. 
     An image forming apparatus  10  includes an apparatus main body  11 , and a first supply tray  13  is provided at a rear side of the apparatus main body  11 , an ejection tray  14  is provided at a front side thereof, and a second supply tray  15  is provided at a lower side of the apparatus main body. 
       FIG. 2  schematically shows the inner structure of the image forming apparatus  10 . 
     The apparatus main body  11  includes a sheet transport mechanism  21  as a transport device, a sheet guide  22  as a medium guide having a guide surface  22   a  in the horizontal direction, a head cleaning mechanism  24  shown in  FIG. 3 , and the like. The sheet guide  22  and the head cleaning mechanism  24  will be described later in detail. 
     A carriage  30 , a carriage drive mechanism  31  to drive the carriage  30 , a recording head  32  as a recording device of an ink-jet system mounted on the carriage  30  and the like are disposed at the upper side of the sheet guide  22 . An exchangeable ink cartridge (not shown) is received in the recording head  32 . 
     As shown in  FIG. 2 , the recording head  32  includes a nozzle unit  32   a  opposite to the guide surface  22   a  of the sheet guide  22 , and an ink discharge mechanism (not shown) to discharge ink from the nozzle unit  32   a . The recording head  32  forms an image on a sheet S (shown in  FIG. 3 ) by this ink. An arrow A in  FIG. 3  indicates a transport direction of the sheet S. 
     An example of the ink discharge mechanism includes a thermal type. In the thermal type, heat is applied to ink by a heater incorporated in the recording head  32 , so that the ink is film-boiled. A change in pressure occurs in the ink by the growth or contraction of a bubble by this film-boiling. The ink is discharged from the nozzle unit  32   a  by this change in pressure, so that an image is formed on the sheet S. Other than the thermal type, an ink discharge mechanism using, for example, an element having a piezoelectric effect (for example, a piezoelectric element) may be adopted. For example, the piezoelectric element is deformed by an electric current, and ink is discharged from the nozzle unit by the pumping action based on the deformation. 
     As shown in  FIG. 3 , the carriage drive mechanism  31  includes a carriage guide  40  extending in the horizontal direction, a motor  41  such as a stepping motor, power transmission members such as a timing belt  42  and sprockets  43  and  44 , a sensor unit  45  for controlling the position of the carriage  30 , and the like. The carriage guide  40  extends in a direction B orthogonal to the transport direction of the sheet S. The carriage guide  40  is supported by a frame of the apparatus main body  11 . The recording head  32 , together with the carriage  30 , can be reciprocated in the direction (arrow B direction) orthogonal to the transport direction of the sheet S along the carriage guide  40 . 
     The rotation of the motor  41  is transmitted to the carriage  30  through the timing belt  42 . Thus, the recording head  32  reciprocates along the carriage guide  40 . The sensor unit  45  for controlling the position of the carriage  30  includes, for example, an encoder sensor  46  and a ladder plate  47  as a unit to be detected. The ladder plate  47  extends in the direction parallel to the carriage guide  40 . The ladder plate  47  has a ladder pattern formed at an equal pitch. The ladder pattern of the ladder plate  47  is optically detected by the encoder sensor  46  according to the position of the carriage  30 , so that the position of the carriage  30  is detected. A signal of the detected position is inputted to a control unit  50  through a flexible harness  48 . 
     As shown in  FIG. 2 , the sheet transport mechanism  21  includes a first transport unit  61 , a second transport unit  62 , a two-sided printing transport unit  63  used when two-sided printing is performed, an ejection mechanism  64  and the like. 
     The first transport unit  61  transports the sheet taken out from the first supply tray  13  to the recording head  32 . The second transport unit  62  transports the sheet taken out from the second supply tray  15  to the recording head  32 . The ejection mechanism  64  has a function to eject the printed sheet onto the ejection tray  14 . 
     Plural sheets (for example, printing sheets) are stacked in the thickness direction and can be placed on the first supply tray  13 . As shown in  FIG. 1 , a movable guide  65  is provided on the first supply tray  13 . The movable guide  65  can be moved in the width direction of the sheet S according to the size of the sheet S. The movable guide  65  is moved in the width direction of the sheet S, so that the position of the sheet S in the width direction on the first supply tray  13  can be regulated. 
     The first transport unit  61  includes a supply roller  70 , a separation roller  71  positioned below the supply roller  70 , a separation unit  72  including a separation pad, and the like. The supply roller  70  supplies the sheet taken out from the lower end of the first supply tray  13  to the recording head  32 . 
     A torque limiter is provided on the separation roller  71 . The separation roller  71  rotates in the same direction as the supply roller  70  by the function of the torque limiter in the case where only one sheet exists between the supply roller  70  and itself. In the case where two or more sheets exist between the supply roller  70  and the separation roller  71 , the separation roller  71  rotates in the reverse direction to the supply roller  70 . Accordingly, in the case where plural sheets are taken out from the first supply tray  13  and are sent to between the supply roller  70  and the separation roller  71 , the sheet at the uppermost part and the other sheets are separated from each other, and only the sheet at the uppermost part is supplied to the recording head  32 . The supply roller  70 , the separation roller  71 , the separation unit  72  and the like constitute a sheet separation mechanism to take out the sheet one by one from the first supply tray  13 . 
     The separation roller  71  is held by a holder  73 . The holder  73  can move in the up-and-down direction around a shaft  74  extending in the horizontal direction. The separation roller  71  is brought into contact with the supply roller  70  at a specified load by a spring and is separated from the supply roller  70  by a not-shown cam. The separation unit  72  can be moved by the not-shown cam in the direction of approaching or separating from the supply roller  70 . 
     The separation roller  71  and the separation unit  72  are respectively separated from the supply roller  70  after the sheet is supplied, are moved to a standby position and are on standby until the time of next sheet supply. A return lever  75  is rotatably arranged in the vicinity of the lower end of the first supply tray  13 . The return lever  75  is retracted by a spring to a position where the transport of the sheet is not prevented when the sheet taken out from the first supply tray  13  is transported to the supply roller  70 . The return lever  75  is rotated in synchronization with the movement of the separation roller  71  and the separation unit  72  to the standby position, and returns the remaining sheet to the first supply tray  13 . 
     The first transport unit  61  includes a transport roller  80 , a pinch roller  81  opposite to the transport roller  80 , a sheet sensor  82 , a media sensor  83 , a switching member  84  and the like. The transport roller  80  supplies the sheet to between the sheet guide member  22  and the recording head  32 . The sheet sensor  82  includes a sensor arm capable of detecting the positions of the front end and the rear end of the sheet. 
     The media sensor  83  has a function to detect the quality (for example, paper quality) of the sheet. For example, in the case where the surface of the sheet is made of a hygroscopic substance, a signal to increase the amount of ink to be discharged from the recording head  32  is outputted to the control unit  50 . In the case of the sheet the surface of which is glossy, for example, a coat paper, control is performed so that a signal to decrease the amount of ink to be discharged from the recording head  32  is outputted to the control unit  50 . In the case of color printing, based on the signal from the media sensor  83 , the discharge ratio of plural color components may be adjusted. 
     As shown in  FIG. 4 , the transport roller  80  is attached to a shaft  90 . The shaft  90  is rotated by a controllable motor  91  such as a stepping motor. The pinch roller  81  opposite to the transport roller  80  is in contact with the transport roller  80  by a not-shown spring. A disk-like ladder wheel  92  is attached to the shaft  90  of the transport roller  80 . A ladder pattern is formed on the ladder wheel  92  in the circumferential direction at a constant pitch. The ladder wheel  92  is detected by a sensor  93 , and the input is made to the control unit  50 . By this, the rotation of the transport roller  80  is controlled, and the transport of the sheet is controlled at the time of image formation. 
     The sheet taken out from the first supply tray  13  by the supply roller  70  passes through the first transport unit  61  as indicated by an arrow F 1  in  FIG. 2  and is transported to between the transport roller  80  and the pinch roller  81 . The leading end of the sheet is detected by the sheet sensor  82 , and positioning for the image formation is performed. This sheet passes between the upper surface (guide surface  22   a ) of the sheet guide  22  and the recording head  32  by the rotation of the transport roller  80 . At that time, the image formation is performed on the sheet S by the recording head  32 . Ribs functioning as the transport reference surface are formed on the guide unit  22   a  of the sheet guide  22 . These ribs hold the height of the sheet suitably and prevents the sheet from corrugating. The sheet on which an image has been formed is transported to the ejection mechanism  64 . 
     The second transport unit  62  includes rollers  100  and  101  to take out the sheet from the cassette type second supply tray  15 , a switching member  102 , guide members  103  and  104  to guide the taken-out sheet, a transport roller  105  provided at the midway of the guide members  103  and  104 , and a pinch roller  106  opposite to the transport roller  105 . The pinch roller  106  is pressed to the transport roller  105  by a spring. Plural sheets (for example, printing sheets) are stacked in the thickness direction and can be contained in the second supply tray  15 . The rollers  100  and  101  of the second transport unit  62  function as a sheet separation mechanism to take out the sheet one by one from the second supply tray  15 . 
     The sheet taken out from the second supply tray  15  passes through the switching member  102  and passes the guide members  103  and  104  of the second transport unit  62  as indicated by an arrow F 2  in  FIG. 2 . Further, this sheet is transported to the transport roller  80  by the rollers  105  and  106 , and is supplied to between the recording head  32  and the sheet guide  22 . 
     The two-sided printing transport unit  63  includes guide members  110  and  111 , a transport roller  112  provided at the midway of the guide members  110  and  111 , a pinch roller  113  opposite to the transport roller  112 , and the like. The pinch roller  113  is pressed to the transport roller  112  by a spring. The guide members  110  and  111  are arranged between the switching member  84  of the first transport unit  61  and the switching member  102  of the second transport unit  62 . At the time of two-sided printing, the sheet is made to pass in an arrow F 3  direction in  FIG. 2 . The transport rollers  80 ,  105  and  112  are such that a rubber resin such as EPDM (ethylene propylene diene rubber) is provided on a metal shaft, and have a function to transport the sheet S by friction. 
     In the case where the two-sided printing is performed, after one side of a sheet is printed by the recording head  32 , the rear end of this sheet is detected by the sheet sensor  82 . Immediately after that, the transport roller  80  is reversely rotated, and the position of the switching member  84  is switched. By this, the sheet is sent to the two-sided printing transport unit  63  as indicated by the arrow F 3  in  FIG. 2 . Further, this sheet is transported by the rollers  112  and  113 , passes through the switching member  102 , and passes the guide members  103  and  104  of the second transport unit  62 . In this way, the sheet turns over, and this sheet is again sent to the recording head  32  by the transport roller  80 , so that the other side of the sheet is printed. 
     The ejection mechanism  64  includes an ejection roller  120 , a star wheel  121 , a transmission mechanism (not shown) to transmit the rotation of the transport roller  80  to the ejection roller  120  and the star wheel  121 , and the like. The star wheel  121  is a gear-like wheel made of a thin plate of stainless steel or the like. The sheet printed by the recording head  32  is pressed to the ejection roller  120  by the star wheel  121  and is transported in a direction indicated by an arrow F 4  toward the ejection tray  14 . The star wheel  121  prevents the sheet after printing from rising from the ejection roller  120 . 
     As shown in  FIG. 5 , an ink absorption unit  130  is formed on the upper side of the sheet guide member  22 . The ink absorption unit  130  is opposite to the nozzle unit  32   a  (shown in  FIG. 2 ) of the recording head  32 , and is formed at a position lower than the guide surface  22   a . The width of the ink absorption unit  130  is larger than the width of the sheet S, and the ink absorption unit  130  contains, for example, a sponge-like ink absorption member  131 . In the case where frameless printing of a sheet is performed, surplus ink protruding from the edge of the sheet is absorbed by this ink absorption member  131 , so that it is prevented that a subsequent sheet is soiled. 
     The head cleaning mechanism  24  shown in  FIG. 3  includes a suction pump  140  for cleaning the recording head  32 , a cap  141  for preventing drying of the recording head  32 , a blade member  142  for cleaning the nozzle unit  32   a  of the recording head  32 , and the like. In an example of the suction pump  140 , a tube  144  is squeezed in a direction indicated by an arrow C by a rotator  143 , so that a negative pressure is generated inside the cap  141 . 
     The cap  141  can be moved in the up-and-down direction (an arrow D direction in  FIG. 3 ) by a drive unit  145 . In the drive unit  145 , for example, an electric actuator such as, a solenoid is used as a drive source, and the cap  141  is moved up and down. Incidentally, the cap  141  may be moved up and down by converting the rotation of the motor into a linear movement by a cam or a link mechanism. When the recording head  32  is maintained, the cap  141  is raised to the recording head  32 , so that the cap  141  is brought into close contact with the recording head  32 . The suction pump  140  is actuated in this state, so that surplus ink attached to the nozzle unit  32   a  of the recording head  32  is sucked. The sucked waste ink is ejected into a waste ink tank  146 . Thereafter, the cap  141  is separated from the recording head  32 , and further, the nozzle unit  32   a  of the recording head  32  is cleaned by the blade member  142 . 
     As shown in  FIG. 2 , the sheet guide  22 , the transport roller  80  and the pinch roller  81  disposed at the upstream side of the sheet guide  22  in the sheet transport direction, and the ejection roller  120  and the star wheel  121  disposed at the downstream side thereof are integrated to constitute a transport unit  151 . This transport unit  151  is provided to be freely come in and out of the apparatus main body  11 . 
     The transport unit  151  comes in and out along the transport direction of the sheet. However, there is a fear that when being merely pulled out along the transport direction of the sheet, the transport unit  151  comes in contact with the recording head  32  and damages it. 
     Then, the transport unit  151  is once moved downward to go away from the recording head  32 , and can be pulled out along the transport direction of the sheet. 
     That is, a horizontal guide unit  153  is provided in a lower part of the transport unit  151 , and the transport unit  151  is guided in the up-and-down direction along a not-shown vertical guide unit between the home position and the horizontal guide unit  153 . An opening  11   a  through which the transport unit  151  comes in and out is formed at the front side of the apparatus main body  11 . 
     As shown in  FIG. 6 , an opening and closing cover  156  for opening and closing the ink absorption unit  130  is provided in the transport unit  151 . This opening and closing cover  156  is provided to be slidable in the transport direction of the sheet, and an end at its upper side is connected to a spring member  157  and is urged in the direction of closing the ink absorption unit  130  as shown in  FIG. 7 . 
     A projection  159  is provided to protrude at the apparatus main body  11  side, and as described later, when the transport unit  151  is inserted into the apparatus main body  11 , the lower end of the opening and closing cover  156  comes in contact with the projection  159 . By this, as shown in  FIG. 6 , the opening and closing cover  156  is moved against the urging force of the spring member  157 , and the ink absorption body  130  is made open. 
     When the transport unit  151  is pulled out from the apparatus main body  11 , as shown in  FIG. 7 , the lower end of the opening and closing cover  156  is separated from the projection  159 . By this, the opening and closing cover  156  is moved by the urging force of the spring member  157  and closes the ink absorption body  130 . 
     At the time of printing, an ink mist is generated around the recording head  32 , and especially the sheet guide  22  is soiled with this ink mist. When the sheet guide  22  is soiled with the ink mist, since a subsequent sheet is soiled when the sheet is guided, it is necessary to periodically clean the sheet guide  22 . 
     Next, a cleaning method of the sheet guide  22  will be described. 
     In this case, first, as shown in  FIG. 8 , the transport unit  151  is moved downward along the not-shown vertical guide, is moved away from the recording head  32  and is placed on the horizontal guide  153 . Next, the transport unit  151  is pulled out along the horizontal guide unit  153  and is taken out through the opening unit  11   a  of the apparatus main body  11 . At the time of taking out, as shown in  FIG. 7 , the lower end of the opening and closing cover  156  is separated from the projection  159 , the opening and closing cover  156  is moved by the urging force of the spring member  157 , and the ink absorption unit  130  is closed. After the transport unit  151  is taken out to the outside in this way, the cleaning of the sheet guide  22  is performed, and further, the cleaning of the transport roller  80 , the pinch roller  81 , the ejection roller  120  and the star wheel  121  is also performed at the same time. 
     After the cleaning is ended, the transport unit  151  is inserted through the opening  11   a  of the apparatus main body  11 , and then it is raised and is returned to the home position. 
     According to this embodiment, since the cleaning of the sheet guide  22  and the rollers  80 ,  81 ,  120  and  121  can be performed in the outside of the apparatus main body  11 , there is a merit that the cleaning can be easily and certainly performed. 
     Besides, at the time of taking out the transport unit  151 , as shown in  FIG. 7 , since the ink absorption unit  130  is closed by the opening and closing cover  156 , a hand does not touch the ink absorption member  131  at the time of cleaning, and soil can be certainly prevented. 
       FIG. 9  shows a second embodiment of the invention. 
     Incidentally, portions similar to those shown in the first embodiment are denoted by the same reference numerals and their description will be omitted. 
     In this second embodiment, a first supply tray  13 , a first transport unit  61  (except a transport roller  80  and a pinch roller  81 ), a second transport unit  62 , and a two-sided printing transport unit  63  are integrated to constitute a paper feed unit  161 . The paper feed unit  161  is integrated with a transport unit  151  to constitute a path unit  162 . This path unit  162  is provided to be freely come in and out of an apparatus main body  11 . The transport unit  151  can be moved in the up-and-down direction along a not-shown vertical guide in the paper feed unit  161 . 
     Next, a cleaning method of a sheet guide  22  will be described. 
     In this case, first, as shown in  FIG. 10 , the transport unit  151  is moved downward along the not-shown vertical guide in the path unit  162  and is moved away from the recording head  32 . Next, the path unit  162  is pulled out in the horizontal direction as shown in  FIG. 11 , and is taken out through an opening  11   b  of the apparatus main body  11 . After the path unit  162  is taken out to the outside in this way, the cleaning of the sheet guide  22  of the transport unit  151  is performed, and further, the cleaning of the transport roller  80  and the pinch roller  81 , and an ejection roller  120  and a star wheel  121  is also performed at the same time. 
     Besides, at this time, since the first transport unit  61 , the second transport unit  62  and the two-sided printing transport unit  63  of the paper feed unit  161  are also taken out to the outside, the cleaning of the rollers in those units is also performed at the same time. 
     According to this second embodiment, since the cleaning of the sheet guide  22  and the rollers  80 ,  81 ,  120  and  121 , and the first transport unit  61 , the second transport unit  62  and the two-sided printing transport unit  63  can be performed outside a housing  20  of the main body unit  11 , there is a merit that the cleaning becomes easy and certain. 
     Besides, also in the case where a sheet is jammed in the transport unit  151  or the paper feed unit  161 , the path unit  162  is taken out to the outside, and the removal work can be performed outside the apparatus main body  11 , and accordingly, the workability can be improved. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.