Abstract:
A fluid ejecting apparatus includes: a plurality of ejection heads having ejection nozzles through which fluid is ejected; cap members that are provided so as to correspond to the ejection heads and form sealed spaces around the ejection nozzles in the ejection heads when brought into contact with the ejection heads; cap-member moving mechanisms that press the cap members against the corresponding ejection heads; a fluid suction unit that, while the cap members are pressed against the corresponding ejection heads, produces negative pressure in the sealed space of a selected ejection head to suck the fluid in the ejection head; cap-member selective-separation mechanisms that selectively separate the cap member from the corresponding ejection head having undergone suction; and a selective wiping mechanism that selectively wipes off the fluid deposited around the ejection nozzles in the ejection head separated from the corresponding cap member.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to a technique for ejecting fluid from an ejection head. 
         [0003]    2. Related Art 
         [0004]    Ink jet printers can print high-quality images by ejecting a precise amount of ink from fine nozzles onto a precise position. By ejecting various fluids, instead of ink, onto substrates using this technique, it is possible to produce electrodes, sensors, biochip, etc. 
         [0005]    In this technique, a dedicated ejection head is used to enable a precise amount of fluid, such as ink, to be ejected at a precise position. As time passes, the fluid supplied to the ejection head thickens because of the evaporation of moisture or the vaporization of constituent. It is impossible to eject a precise amount of fluid in the ejection head onto a precise position if the fluid is thickened. Therefore, nozzles are covered with a cap to prevent the fluid from becoming thick while they do not eject fluid. Even if the nozzles are covered with the cap, the fluid thickens with time. In such a case, the thickened fluid in the ejection head is sucked and new fluid is supplied (cleaning operation). Although the sucked fluid is of course wasted, it is possible to prevent thickening of the fluid in the ejection head and to allow adequate ejection of the fluid. After the cleaning operation, the fluid sucked from the ejection head is deposited around the nozzles. This causes another problem, such as clogging of the nozzles, if left untreated. Thus, after the cleaning operation, the fluid deposited around the nozzles (wiping operation) is wiped off. 
         [0006]    Fluid ejecting apparatuses, such as ink jet printers, using these techniques typically have a plurality of ejection heads so that they can eject several types of fluid (for example, ink of different colors). Some apparatuses have a plurality of ejection heads so that they can eject a greater amount of fluid in a shorter time. In an apparatus having a plurality of ejection heads, not necessarily all the ejection heads contain thickened fluid. Japanese Unexamined Patent Application Publication No. 6-328727 proposes a technique to reduce the consumption of fluid by performing a cleaning operation only on the ejection head containing thickened fluid. 
         [0007]    However, the proposed technique has a problem in that the consumption of fluid cannot be sufficiently reduced for the following reasons. That is, even if the cleaning operation is performed only on the ejection head containing thickened fluid, the caps of the other ejection heads have to be removed when the wiping operation is performed on the aforementioned ejection head. This evaporates the moisture in the fluid in the nozzles in the ejection heads not to be cleaned and accelerates thickening of the fluid in these ejection heads. Thus, performing the cleaning operation on the ejection head containing thickened fluid accelerates thickening of the fluid in the other ejection heads and shortens the cycle of the cleaning operation. For these reasons, it is difficult to sufficiently reduce the consumption of fluid with the proposed technique. 
       SUMMARY 
       [0008]    An advantage of some aspects of the invention is that it provides a technique for a fluid ejecting apparatus having a plurality of ejection heads to effectively reduce the consumption of fluid due to cleaning operation. 
         [0009]    According to an aspect of the invention, a fluid ejecting apparatus includes: a plurality of ejection heads having ejection nozzles through which fluid is ejected; cap members that are provided so as to correspond to the ejection heads and form sealed spaces around the ejection nozzles in the ejection heads when brought into contact with the ejection heads; cap-member moving mechanisms that press the cap members against the corresponding ejection heads; a fluid suction unit that, while the cap members are pressed against the corresponding ejection heads, produces negative pressure in the sealed space of a selected ejection head to suck the fluid in the ejection head; cap-member selective-separation mechanisms that selectively separate the cap member from the corresponding ejection head having undergone suction; and a selective wiping mechanism that selectively wipes off the fluid deposited around the ejection nozzles in the ejection head separated from the corresponding cap member. 
         [0010]    The fluid ejecting apparatus of the invention can eject fluid from the ejection heads having the ejection nozzles. The cap members are provided so as to correspond to the ejection heads. When the ejection heads do not eject fluid, the cap members are pressed against the ejection heads to form the sealed spaces around the ejection nozzles. Thus, thickening or degradation of the fluid due to evaporation of moisture can be prevented. Even if the nozzles are covered with the cap members, fluid in some ejection heads may thicken or degrade. In such a case, while the cap members are pressed against the ejection heads, negative pressure is applied to the sealed space formed between a selected ejection head and the corresponding cap member. Thus, the fluid in the ejection head is sucked. Then, the cap member corresponding to the ejection head after suction is selectively separated from the ejection head, and fluid deposited around the ejection nozzles in the aforementioned ejection head can be wiped off. 
         [0011]    Thus, when fluid in some ejection heads thickens or degrades, suction of the fluid and wiping of the fluid deposited around the ejection nozzles can be performed only on these ejection heads. Because the other ejection heads can be kept capped, thickening or degradation of fluid in these ejection heads is not accelerated. As a result, in the fluid ejecting apparatus, thickening or degradation of fluid in the ejection head can be suppressed. Accordingly, the number of suction operations to recover the property of fluid is reduced, and thus, the total amount of sucked fluid can be reduced. 
         [0012]    In this case, the cap members may be pressed against or separated from the ejection heads independently, and the fluid deposited around the ejection nozzles may be simultaneously wiped off from the ejection heads that are separated from the corresponding cap members. 
         [0013]    Since thickening or degradation of fluid in the ejection heads may occur in any of the ejection heads, it is preferable that the cap members can be pressed against or separated from the ejection heads individually. In contrast, to wipe off the fluid deposited around the ejection nozzles, the cap members have to be separated from the ejection heads. That is, only fluid deposited on the ejection heads that are separated from the cap members needs to be wiped off, and the ejection heads do not need to be wiped individually. Accordingly, by simultaneously wiping the ejection heads separated from the corresponding cap members, the structure of the fluid ejecting apparatus can be simplified. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
           [0015]      FIG. 1  is a schematic diagram showing the structure of a fluid ejecting apparatus according to this embodiment, using an ink jet printer as an example. 
           [0016]      FIG. 2  is a bottom view of a carriage case having a plurality of ejection heads. 
           [0017]      FIG. 3  shows the structure of a maintenance mechanism installed in the ink jet printer according to this embodiment. 
           [0018]      FIG. 4  is a flowchart of maintenance processing performed in a maintenance operation. 
           [0019]      FIGS. 5A and 5B  show suction of ink by applying negative pressure produced by a suction pump to a specified ejection head. 
           [0020]      FIGS. 6A to 6D  show that the ejection head after cleaning operation is wiped and capped. 
           [0021]      FIGS. 7A and 7B  show a modification in which wiping operation is performed simultaneously on ejection heads whose cap units are lowered. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0022]    To clarify the invention, embodiments will be described below in the following order.
   A. Structure of Apparatus   
 
         [0024]    A-1. Structure of Fluid Ejecting Apparatus 
         [0025]    A-2. Structure of Maintenance Mechanism
   B. Maintenance Operation According to This Embodiment   C. Modification   
 
       A. Structure of Apparatus 
     A-1. Structure of Fluid Ejecting Apparatus 
       [0028]      FIG. 1  is a schematic diagram showing the structure of a fluid ejecting apparatus according to this embodiment, using an ink jet printer as an example. As shown in  FIG. 1 , an ink jet printer  10  includes a carriage  20  that forms ink dots on a printing medium  2  while reciprocating in a main scanning direction, a driving mechanism  30  that reciprocates the carriage  20 , a platen roller  40  that feeds the printing medium  2 , and a maintenance mechanism  50  that performs maintenance to enable proper printing. The carriage  20  includes ink cartridges  26  containing ink, a carriage case  22  to which the ink cartridges  26  are mounted, and ejection heads  24  for ejecting ink mounted on the bottom surface (the surface facing the printing medium  2 ) of the carriage case  22 . Ink in the ink cartridges  26  is guided to the ejection heads  24 , and the ejection heads  24  eject a precise amount of ink onto the printing medium  2 . Thus, an image is printed. 
         [0029]    The driving mechanism  30  that reciprocates the carriage  20  includes a guide rail  38  extending in the main scanning direction, a timing belt  32  having teeth formed inside thereof, a driving pulley  34  that engages with the teeth of the timing belt  32 , a stepping motor  36  for driving the driving pulley  34 . Part of the timing belt  32  is fixed to the carriage case  22 . By driving the timing belt  32 , the carriage case  22  can be moved along the guide rail  38 . Because the timing belt  32  and the driving pulley  34  are engaged with each other by the teeth, driving of the driving pulley  34  by the stepping motor  36  can precisely move the carriage case  22  according to the drive amount. 
         [0030]    The platen roller  40  that feeds the printing medium  2  is driven by a driving motor and a gear mechanism (not shown) so that it can feed the printing medium  2  in the sub-scanning direction by a predetermined amount. 
         [0031]    The maintenance mechanism  50  is provided in an area called “home position” located outside a printing area. The maintenance mechanism  50  basically consists of cap units  100  and a pump unit  150 . The cap units  100  are provided so as to correspond to the ejection heads  24 . The cap units  100  can be raised and lowered individually. The structure of the maintenance mechanism  50  will be described below in detail. 
         [0032]      FIG. 2  is a bottom view of the carriage case  22  (viewed from the printing medium  2  side). As shown in  FIG. 2 , a plurality of ejection heads  24  are provided on the bottom surface of the carriage case  22 . The carriage case  22  according to this embodiment has four ejection heads  24 . This is because the ink jet printer  10  according to this embodiment can eject four types of ink, namely, cyan ink, magenta ink, yellow ink, and black ink, and the ejection heads  24  are provided so as to correspond to these four types of ink. Each ejection head  24  has a plurality of ejection nozzles arranged in a staggered manner at a predetermined interval. These ejection heads  24  can print an image on the printing medium  2  by ejecting ink from the ejection nozzles. 
       A-2. Structure of Maintenance Mechanism 
       [0033]      FIG. 3  shows the structure of the maintenance mechanism  50  installed in the ink jet printer  10  according to this embodiment. As described above, the maintenance mechanism  50  basically consists of the cap units  100  and the pump unit  150 . The cap units  100  are provided so as to correspond to the ejection heads  24 . As shown in  FIG. 2 , in this embodiment, the number of ejection heads  24  is four. Thus, the number of cap units  100  is also four. 
         [0034]    As shown in  FIG. 3 , each cap unit  100  includes a substantially rectangular cap plate  116 , a rectangular frame-shaped cap  114  that is formed of an elastic resin material, such as rubber, and is disposed on substantially the center of the top surface of the cap plate  116 , and a plate-like wiper blade  112  projected from an end of the top surface of the cap plate  116 . The four cap units  100  can be raised and lowered individually by actuators (not shown). By moving the carriage  20  to the home position and raising the cap units  100 , the caps  114  are pressed against the ejection heads  24 . Thus, thickening of ink in the ejection nozzles can be prevented. 
         [0035]    Small discharge ports are provided inside the rectangular frame-shaped caps  114 . The discharge ports are connected to the pump unit  150  through tubes  130  made of resin. 
         [0036]    The pump unit  150  accommodates a switching unit  152  to which the tubes  130  extending from the cap units  100  are connected and a suction pump  156  that produces negative pressure to suck the liquid. The tubes  130  extending from the cap units  100  are integrated into one path in the switching unit  152  and is connected to the suction pump  156  via a connecting tube  154  made of resin. Paths in the switching unit  152  to which the tubes  130  are connected are provided with open/close valves. These open/close valves are normally closed. By selecting an open/close valve and opening it, negative pressure from the suction pump  156  is guided to the corresponding cap unit  100 . Thus, the cleaning operation to suck the ink in the ejection head  24  can be performed. 
         [0037]    Furthermore, the cap units  100  according to this embodiment, in a lowered state, can be moved forward and backward. That is, actuators (not shown) for moving the cap units  100  forward and backward are provided separately from the actuators for moving the cap units  100  in the vertical direction. When one of the cap units  100  is lowered to a predetermined position, the cap unit  100  can be moved in the forward and backward. As described above, the cap units  100  have the wiper blades  112  projecting from one end thereof. Therefore, by moving the cap units  100  in a lowered state forward and backward, ink deposited around the ejection nozzles can be wiped off with the wiper blades  112  (wiping operation). 
         [0038]    Typically, sucked ink is deposited around the ejection nozzles right after the cleaning operation. If left untreated, the deposited ink becomes solid, possibly causing failure such as clogging of the ejection nozzles. Therefore, after the cleaning operation, the wiping operation has to be performed to wipe off the ink deposited around the ejection nozzles. In the ink jet printer  10  according to this embodiment, to reduce the consumption of ink associated with the maintenance operation (the cleaning operation and the subsequent wiping operation), the maintenance operation is performed as follows. 
       B. Maintenance Operation According to This Embodiment 
       [0039]      FIG. 4  is a flowchart of maintenance processing performed during the maintenance operation by the ink jet printer  10  according to this embodiment. This maintenance processing is started when the carriage  20  is located at the home position and the cap units  100  are pressed against the ejection heads  24 . 
         [0040]    When the maintenance processing starts, first, the ejection head  24  to be subjected to the cleaning operation is specified (step S 100 ). That is, as described above with reference to  FIG. 3 , the ink jet printer  10  according to this embodiment has the switching unit  152  having the open/close valves, and it is possible to apply negative pressure only to the ejection head  24  corresponding to the opened valve to suck the ink. Thus, the ejection head  24  to be subjected to the cleaning operation to suck the ink is specified among four ejection heads  24 . The ejection head  24  to be subjected to the cleaning operation is preliminarily identified by an operator by, for example, printing a predetermined test pattern and is specified via an operation panel (not shown) provided on the ink jet printer  10 . 
         [0041]    When the ejection head  24  to be subjected to the cleaning operation is specified, negative pressure produced by the suction pump  156  is applied to the specified ejection head  24  to suck the ink in the ejection head  24  (step S 102 ).  FIGS. 5A and 5B  show suction of ink by applying negative pressure produced by the suction pump  156  to the specified ejection head  24 .  FIG. 5A  shows that the cap units  100  are raised and pressed against the ejection heads  24  to seal the ejection nozzles in the ejection heads  24 . The operation in which the cap units  100  are pressed against the ejection heads  24  to seal the ejection nozzles is sometimes referred to as “capping operation”. 
         [0042]    The cap units  100  are connected to the switching unit  152  via the tubes  130  extending from the bottom portions thereof. Dashed lines in the switching unit  152  represent paths formed in the switching unit  152 . The paths have the open/close valves  153 . Before ink suction, the open/close valves  153  in the paths are closed, and the suction pump  156  is stopped. 
         [0043]    When the ejection head  24  to be subjected to the cleaning operation is specified in this state (step S 100  in  FIG. 4 ), first, the corresponding open/close valve  153  in the switching unit  152  is opened, and the suction pump  156  is activated. Then, ink is selectively sucked from the specified ejection head  24 , and thus, the cleaning operation can be performed.  FIG. 5B  shows that the cleaning operation is selectively performed on the second ejection head  24  from the left. After the open/close valve  153  corresponding to the specified ejection head  24  is opened while those corresponding to the non-specified ejection heads  24  are kept closed, the suction pump  156  is activated. This causes negative pressure produced by the suction pump  156  to act only on the specified ejection head  24  to suck the ink.  FIG. 5B  shows that the ink sucked from the specified ejection head  24  is discharged from the suction pump  156  through the path in the switching unit  152 . Thus, in step S 102  in  FIG. 4 , a predetermined amount of ink is sucked from the specified ejection head  24 . 
         [0044]    When the cleaning operation on the specified ejection head  24  is completed, the suction pump  156  is stopped, and the open/close valve  153  in the switching unit  152  is closed again. Then, only the corresponding cap unit  100  is lowered and separated from the ejection head  24  (step S 104 ). At this time, the ejection heads  24  not having undergone the cleaning operation are covered with the cap units  100 . As described above with reference to  FIG. 3 , the cap units  100  are provided so as to correspond to the ejection heads  24  and can be pressed against or separated from the ejection heads  24  individually. 
         [0045]    When the cap unit  100  is lowered by a predetermined amount, the cap unit  100  is moved forward and backward (step S 106 ). This causes the wiper blade  112  of the cap unit  100  to move while being pressed against a nozzle surface (the surface having the ejection nozzles) of the ejection head  24 . Thus, ink deposited on the nozzle surface can be wiped off (wiping operation). 
         [0046]    After the wiping operation, the cap unit  100  in a lowered state is returned to where it was just before starting the wiping operation. Then, the cap unit  100  is raised and pressed against the ejection head  24  again (step S 108 ). 
         [0047]      FIGS. 6A to 6D  show that the ejection head  24  after the cleaning operation is wiped and capped.  FIG. 6A  shows that only the cap unit  100  corresponding to the ejection head  24  having undergone the cleaning operation is lowered (step S 104  in  FIG. 4 ). In the example shown in  FIG. 6A , only the cap unit  100  corresponding to the second ejection head  24  from the left is lowered, and the cap units  100  corresponding to the other ejection heads  24  are pressed against the ejection heads  24 . 
         [0048]      FIG. 6B  shows the cap unit  100  in a lowered state, viewed in the direction shown by an arrow Q in  FIG. 6A . As shown in  FIG. 6B , when the cap unit  100  is lowered, the tip of the wiper blade  112  is positioned at the same level as the nozzle surface of the ejection head  24 . The cap unit  100  is then moved in a direction shown by a white arrow in  FIG. 6B . This causes the tip of the wiper blade  112  to move while being in contact with the nozzle surface of the ejection head  24 , wiping off the ink deposited on the nozzle surface.  FIG. 6C  shows that the cap unit  100  is reciprocated while the wiper blade  112  wipes off the ink (step S 106  in  FIG. 4 ). This wiping operation is performed only on the ejection head  24  having undergone the cleaning operation and whose cap unit  100  is lowered. The ejection heads  24  not having undergone the cleaning operation are covered with the corresponding cap units  100 . 
         [0049]    When the wiping operation is finished, the cap unit  100  is returned to where it was just before starting the wiping operation. Then, the cap unit  100  is raised again and is pressed against the ejection head  24  (step S 108  in  FIG. 4 ). With the capping operation, the maintenance processing shown in  FIG. 4  is finished. 
         [0050]    As has been described, the ink jet printer  10  according to this embodiment has the cap units  100  corresponding to the ejection heads  24 . The cleaning operation can be performed only on the ejection head  24  containing thickened ink by switching the cap unit  100  to which the switching unit  152  applies negative pressure. Furthermore, in this embodiment, the wiping operation can be individually performed by individually raising and lowering the cap units  100 . Thus, the wiping operation can be performed only on the ejection head  24  having undergone the cleaning operation. As a result, the ejection heads  24  not having undergone the cleaning operation can be kept capped. Because the cleaning operation can be performed only on the ejection head  24  containing thickened ink without thickening ink in the other ejection heads  24 , the consumption of ink due to cleaning operation can be reduced. 
         [0051]    In addition, because the ejection heads  24  not having undergone the cleaning operation can be kept capped during the wiping operation of the ejection head  24  having undergone the cleaning operation, ink droplets scattered by the wiping operation can be prevented from being deposited on the other ejection heads  24 . 
       C. Modification 
       [0052]    As has been described, in the ink jet printer  10  according to this embodiment, the cap units  100  can be individually raised and lowered, and the cleaning operation and the wiping operation can be performed on the ejection heads  24  individually. Since thickening of ink in the ejection heads  24  may occur in any of the ejection heads  24 , it is necessary that the cleaning operation can be performed on the ejection heads  24  individually. In contrast, the wiping operation should be performed only on the ejection head  24  having undergone the cleaning operation and does not need to be performed on all the ejection heads  24  individually. Accordingly, by performing the wiping operation simultaneously on the ejection heads  24  separated from the corresponding cap units  100 , the structure of the maintenance mechanism  50  can be simplified. 
         [0053]      FIGS. 7A and 7B  show an ink jet printer  10  according to the modification, in which the wiping operation is performed simultaneously on the ejection heads  24  whose cap units  100  are lowered.  FIG. 7A  shows that only the cap units  100  corresponding to two ejection heads  24  having undergone the cleaning operation are lowered. In this modification, the lowered cap units  100  are attached to a driving frame  200  for wiping operation. The wiping operation is performed not by driving the cap units  100  individually, but by driving the driving frame  200 . 
         [0054]      FIG. 7B  shows that the wiping operation is performed by driving the driving frame  200 . In the example shown in  FIG. 7B , two cap units  100  are lowered and attached to the driving frame  200 . By driving the driving frame  200 , the wiping operation can be performed simultaneously on the two ejection heads  24  corresponding to these cap units  100 . In this structure, although a mechanism for raising and lowering the cap unit  100  has to be provided for each ejection head  24 , the number of mechanisms for moving the cap units  100  forward and backward may be one. Accordingly, the structure of the maintenance mechanism  50  can be simplified. 
         [0055]    Although the printing apparatus according to this embodiment has been described above, the invention is not limited to the above-described embodiments. The invention can be variously embodied within the scope not departing from the gist thereof. 
         [0056]    For example, in the above-described embodiment, the wiper blades  112  are provided as part of the cap units  100 . However, the wiper blades  112  may be provided separately from the cap units  100 , and the wiping operation may be performed by driving only the wiper blades  112  after the cap units  100  are lowered. 
         [0057]    The entire disclosure of Japanese Patent Application No. 2008-156298, filed Jun. 16, 2008 is expressly incorporated by reference herein.