Patent Publication Number: US-10328704-B2

Title: Inkjet printer with ink receptor for receiving ink as waste liquid

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2017-064378, filed on Mar. 29, 2017, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Technical Background 
     The disclosure relates to an inkjet printer which performs printing by ejecting ink from an inkjet head. 
     2. Related Art 
     In an inkjet printer, a maintenance operation of an inkjet head is performed for removal of dust attaching to the inkjet head, stabilization of physical properties of ink in nozzles, and similar purposes. 
     As the maintenance operation of the inkjet head, for example, a series of operations is performed in which so-called purging is performed to forcedly eject the ink from the nozzles, and then a nozzle surface of the inkjet head is wiped with a wiper. 
     The ink ejected in the maintenance operation of the inkjet head as described above is received by an ink receptor. Then, the ink in the ink receptor is sent to a waste liquid tank and stored. 
     As a method of sending the ink from the ink receptor to the waste liquid tank, Japanese Patent No. 4645172 discloses a technique in which the ink is made to flow by its own weight to the waste liquid tank via an ink passage connected to a bottom surface of the ink receptor and extending downward. 
     SUMMARY 
     Among inkjet printers, there is an inkjet printer configured such that the aforementioned ink receptor horizontally moves between a position directly below the inkjet head where the ink receptor is disposed in the maintenance operation and a position retreated from the position directly below the inkjet head. 
     When the aforementioned ink passage is connected to the bottom surface of the ink receptor in such a configuration, the ink passage also moves as the ink receptor moves to perform the wiping. Accordingly, the ink passage with a length corresponding to a movement distance of the ink receptor needs to be provided. Moreover, a standby space for the ink passage with the length corresponding to the movement distance of the ink receptor needs to be provided below the ink receptor. Since many members are disposed below the ink receptor, it is difficult to provide the space for the ink passage and such a configuration may lead to an increase of an apparatus size. 
     The disclosure is directed to an inkjet printer which can suppress an increase of an apparatus size. 
     An inkjet printer in accordance with some embodiments includes: at least one ink receptor having a tray shape with a bottom plate and an opening facing upward, the at least one ink receptor being horizontally movable and configured to receive ink ejected from at least one inkjet head as waste liquid; and a suction unit including at least one suction nozzle arranged above the bottom plate within a movable range of the at least one ink receptor, the suction unit configured to suction the ink in the at least one ink receptor through the opening with the at least one suction nozzle. 
     In the configuration described above, unlike in a configuration in which the ink in the ink receptor flows to a waste liquid tank via an ink passage extending downward from a bottom surface of the ink receptor, a standby space for the ink passage with a length corresponding to the movement distance of the ink receptor does not have to be provided below the ink receptor. As a result, an increase of an apparatus size can be suppressed. 
     The at least one inkjet head may include inkjet heads. The at least one ink receptor may include ink receptors corresponding to the inkjet heads, respectively. The at least one suction nozzle may include suction nozzles corresponding to the ink receptors, respectively. The suction unit may include: a negative pressure tank shared by the suction nozzles and in which a negative pressure is generated for suctioning the ink in the ink receptors by the suction nozzles, the negative pressure tank configured to store the ink suctioned by the suction nozzles; an air pump shared by the suction nozzles and configured to generate the negative pressure in the negative pressure tank; and an ink suction passage connecting the suction nozzles with the negative pressure tank. 
     In the configuration described above, the negative pressure tank and the air pump which are suction force generation mechanisms shared by the suction nozzles can generate the suction force in the suction nozzles and suction the ink from the ink receptor. Accordingly, it is possible to collect the ink from the ink receptors while suppressing the increase of the apparatus size in the inkjet printer including the multiple inkjet heads and the multiple ink receptors. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic configuration diagram of an inkjet printer according to an embodiment. 
         FIG. 2  is a perspective view of a main portion of a maintenance unit and an inkjet head in the inkjet printer illustrated in  FIG. 1 . 
         FIG. 3A  is an explanatory diagram of a deployment position of an ink receptor in the inkjet printer illustrated in  FIG. 1 . 
         FIG. 3B  is an explanatory diagram of a retreat position of the ink receptor. 
         FIG. 4  is a control block diagram of the inkjet printer illustrated in  FIG. 1 . 
         FIG. 5  is a flowchart for explaining a maintenance operation of the inkjet head. 
         FIG. 6  is a flowchart for explaining the maintenance operation of the inkjet head. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
     Description will be hereinbelow provided for an embodiment of the present invention by referring to the drawings. It should be noted that the same or similar parts and components throughout the drawings will be denoted by the same or similar reference signs, and that descriptions for such parts and components will be omitted or simplified. In addition, it should be noted that the drawings are schematic and therefore different from the actual ones. 
       FIG. 1  is a schematic configuration diagram of an inkjet printer  1  according to an embodiment of the present invention.  FIG. 2  is a perspective view of a main portion of a maintenance unit  3  and inkjet heads  11 A to  11 D of the inkjet printer  1  illustrated in  FIG. 1 .  FIG. 3A  is an explanatory view of deployment positions of wiping units  21 A to  21 D in the inkjet printer  1  illustrated in  FIG. 1 .  FIG. 3B  is an explanatory view of retreat positions of the wiping units  21 A to  21 D.  FIG. 4  is a control block diagram of the inkjet printer  1  illustrated in  FIG. 1 . In the following description, a direction orthogonal to the sheet surface of  FIG. 1  is referred to as front-rear direction and direction toward the viewer is referred to as front direction. Moreover, up, down, left, and right in the sheet surface of  FIG. 1  are referred to as up, down, left, and right directions. In  FIGS. 1, 3A, and 3B , the right, left, up, down, front, and rear directions are denoted by RT, LT, UP, DN, FR, and RR. Note that  FIGS. 1 and 2  are views illustrating a state where ink receptors  26  are disposed at the deployment positions. 
     As illustrated in  FIGS. 1 and 4 , the inkjet printer  1  includes a printing unit  2 , a maintenance unit  3 , and a controller  4 . 
     The printing unit  2  prints an image on a print medium (not illustrated). The printing unit  2  includes the inkjet heads  11 A to  11 D and lifting-lowering motors  12 A to  12 D. Note that the inkjet heads  11 A to  11 D and the like are sometimes collectively referred to by omitting the alphabets attached to the reference numerals. 
     The inkjet heads  11  print an image on a print medium conveyed in a left-right direction (sub-scanning direction) by ejecting inks. The inkjet heads  11 A to  11 D eject inks of different colors (for example, black, cyan, magenta, and yellow), respectively. The inkjet heads  11  are configured to be capable being lifted and lowered. 
     As illustrated in  FIG. 2 , each inkjet head  11  includes ten head modules  16 . In the inkjet head  11 , the ten head modules  16  are arranged in a zigzag pattern. Specifically, in the inkjet head  11 , the ten head modules  16  are arranged in the front-rear direction (main scanning direction) with the positions thereof in the left-right direction (sub-scanning direction) being alternately shifted. 
     Each of the head modules  16  has multiple nozzles (not illustrated) arranged in the main scanning direction and ejects the ink from the nozzles. The nozzles are open on a nozzle surface  16   a  which is a lower surface of the head module  16 . 
     The lifting-lowering motors  12 A to  12 D lift and lower the inkjet heads  11 A to  11 D, respectively. 
     The maintenance unit  3  performs maintenance of the inkjet heads  11 . The maintenance unit  3  includes the wiping units  21 A to  21 D, movement motors  22 A to  22 D, a suction unit  23 , and a waste liquid collector  24 . 
     The wiping units  21 A to  21 D are provided to correspond to the inkjet heads  11 A to  11 D, respectively. The wiping units  21 A to  21 D wipe the nozzles surfaces  16   a  of the head modules  16  in the inkjet heads  11 A to  11 D, respectively. As illustrated in  FIG. 2 , each of the wiping units  21  ( 21 A to  21 D) includes an ink receptor  26 , a wiper attachment base  27 , and two wipers  28 . 
     The ink receptor  26  is a member which receives the ink ejected from the inkjet head  11  by purging in the maintenance as waste liquid. The ink receptor  26  has a tray shape whose upper side is open. Specifically, the ink receptor  26  includes a rectangular bottom plate  31  and a surrounding wall  32  standing upright in a periphery of the bottom plate, and an upper end of the surrounding wall  32  defines an opening  26   a . The ink receptor  26  is horizontally movable between the deployment position and the retreat position. As illustrated in  FIG. 3A , the deployment position of the ink receptor  26  is directly below the inkjet head  11 . As illustrated in  FIG. 3B , the retreat position of the ink receptor  26  is a position retreated rearward from the position directly below the inkjet head  11 . The retreat position and the deployment position are at the same height. 
     The wiper attachment base  27  is a member to which the wipers  28  are attached. The wiper attachment base  27  is fixed to a front wall  32   a  which is a portion of the surrounding wall  32  of the ink receptor  26  extending along the front side of the bottom plate  31 . 
     The wipers  28  are members which wipe the nozzle surfaces  16   a . The wipers  28  are made of elastically-deformable material such as rubber and are formed in a plate shape. The wipers  28  are fixed to the wiper attachment base  27 . Upper ends of the wipers  28  are located above the upper end of the surrounding wall  32 . The two wipers  28  are arranged side by side in a left-right direction. The left wiper  28  wipes the nozzle surfaces  16   a  of the five head modules  16  arranged on the left side out of the ten head modules  16  arranged in zigzag. The right wiper  28  wipes the nozzle surfaces  16   a  of the five head modules  16  arranged on the right side. 
     The movement motors  22 A to  22 D horizontally move the wiping units  21 A to  21 D, respectively, in the front-rear direction between the deployment positions and the retreat positions. In this description, horizontally moving each wiping unit  21  between the deployment position and the retreat position is the same meaning as horizontally moving the ink receptor  26  between the deployment position and the retreat position. 
     The suction unit  23  suctions the ink in the ink receptors  26  of the wiping units  21 A to  21 D through the openings  26   a  of the ink receptors  26 . The suction unit  23  includes suction nozzles  41 A to  41 D, a negative pressure tank  42 , a negative pressure tank liquid level sensor  43 , an ink suction passage  44 , suction nozzle valves  45 A to  45 D, an air pump  46 , an air pump pipe  47 , an atmospheric release valve  48 , and an atmospheric release pipe  49 . 
     The suction nozzles  41 A to  41 D are provided to correspond to the ink receptors  26  of the wiping units  21 A to  21 D, respectively. The suction nozzles  41 A to  41 D are nozzles which suction the ink in the ink receptors  26  of the wiping units  21 A to  21 D through the openings  26   a.    
     Each of the suction nozzles  41  ( 41 A to  41 D) are arranged to be fixed above the bottom plate  31  of the corresponding ink receptor  26 , within a movable range of the ink receptor  26 . Specifically, as illustrated in  FIGS. 2, 3A, and 3B , in the front-rear direction, the suction nozzle  41  is installed to be located in a rear end portion of the ink receptor  26  at the deployment position and in a front end portion of the ink receptor  26  at the retreat position. In the up-down direction, the suction nozzle  41  is installed above the bottom plate  31  of the ink receptor  26  such that a front end (lower end) of the suction nozzle  41  where a suction opening is opened is away from the bottom plate  31  by a predetermined distance. In the left-right direction, the suction nozzle  41  is installed in a center portion of the ink receptor  26 . 
     The negative pressure tank  42  is a tank in which a negative pressure is generated for suctioning the ink in the ink receptors  26  by the suction nozzles  41  and which stores the ink suctioned by the suction nozzles  41 . 
     The negative pressure tank liquid level sensor  43  detects whether the liquid level of the ink stored in the negative pressure tank  42  is a specified height or more. 
     The ink suction passage  44  is a passage connecting the suction nozzles  41 A to  41 D with the negative pressure tank  42 . The ink suction passage  44  includes a main suction pipe  51  and branching suction pipes  52  to  54 . 
     The main suction pipe  51  forms an ink flow passage from the suction nozzle  41 D to the negative pressure tank. Moreover, the main suction pipe  51  forms part of ink flow passages from the suction nozzles  41 A to  41 C to the negative pressure tank. One end of the main suction pipe  51  is connected to the suction nozzle  41 D and the other end thereof is connected to the negative pressure tank  42 . 
     The branching suction pipes  52  to  54  form ink flow passages from the suction nozzles  41 A to  41 C to the main suction pipe  51 , respectively. One end of the branching suction pipe  52  is connected to the suction nozzle  41 A and the other end thereof is connected to the main suction pipe  51 . One end of the branching suction pipe  53  is connected to the suction nozzle  41 B and the other end thereof is connected to the main suction pipe  51 . One end of the branching suction pipe  54  is connected to the suction nozzle  41 C and the other end thereof is connected to the main suction pipe  51 . 
     The suction nozzle valves  45 A to  45 D are provided in the ink suction passage  44  to correspond to the suction nozzles  41 A to  41 D, respectively, and each switch the corresponding suction nozzle  41  between a state communicating with the negative pressure tank  42  and a state disconnected from the negative pressure tank  42 . 
     Specifically, the suction nozzle valve  45 A is disposed in the branching suction pipe  52  and switches the ink flow passage in the branching suction pipe  52  between an open state and a closed state. The suction nozzle valve  45 B is disposed in the branching suction pipe  53  and switches the ink flow passage in the branching suction pipe  53  between the open state and the closed state. The suction nozzle valve  45 C is disposed in the branching suction pipe  54  and switches the ink flow passage in the branching suction pipe  54  between the open state and the closed state. The suction nozzle valve  45 D is disposed in the main suction pipe  51  between the suction nozzle  41 D and a point where the branching suction pipe  54  is connected, and switches the ink flow passage in the main suction pipe  51  between the open state and the closed state. 
     The air pump  46  suctions air from the negative pressure tank  42  to generate a negative pressure in the negative pressure tank  42 . The air pump  46  is disposed in the air pump pipe  47 . 
     The air pump pipe  47  forms a passage for air suctioned by the air pump  46  from the negative pressure tank  42 . One end of the air pump pipe  47  is connected to the negative pressure tank  42  and the other end (atmosphere communication end) thereof communicates with the atmosphere. 
     The atmospheric release valve  48  opens and closes an air flow passage in the atmospheric release pipe  49  to switch the negative pressure tank  42  between a sealed state and an atmospheric release state. 
     The atmospheric release pipe  49  forms the air flow passage for opening the negative pressure tank  42  to the atmosphere. One end of the atmospheric release pipe  49  is connected to the negative pressure tank  42  and the other end thereof is connected to a portion of the air pump pipe  47  between the air pump  46  and the atmosphere communication end. 
     The waste liquid collector  24  collects the ink from the negative pressure tank  42  as the waste liquid and stores it. The waste liquid collector  24  includes a waste liquid tank  61 , an ink pump  62 , a waste liquid collection pipe  63 , and a waste liquid collection valve  64 . 
     The waste liquid tank  61  stores the ink sent from the negative pressure tank  42  as the waste liquid. 
     The ink pump  62  sends the ink from the negative pressure tank  42  to the waste liquid tank  61 . The ink pump  62  is disposed in the waste liquid collection pipe  63 . 
     The waste liquid collection pipe  63  forms a flow passage for the ink sent from the negative pressure tank  42  to the waste liquid tank  61 . One end of the waste liquid collection pipe  63  is connected to the negative pressure tank  42  and the other end thereof is connected to the waste liquid tank  61 . 
     The waste liquid collection valve  64  switches the ink flow passage in the waste liquid collection pipe  63  between an open state and a closed state. 
     The controller  4  controls operations of units in the inkjet printer  1 . The controller  4  includes a CPU, a RAM, a ROM, a hard disk drive, and the like. 
     Next, a maintenance operation of the inkjet heads  11  in the inkjet printer  1  is described. 
     The maintenance operation of the inkjet heads  11  is performed, for example, before start of printing in the case where the inkjet printer  1  is instructed to start the printing. Here, description is given of the case where the maintenance operation is performed before the start of printing.  FIGS. 5 and 6  are flowcharts for explaining the maintenance operation of the inkjet heads  11 . 
     In a standby state before the start of printing in the inkjet printer  1 , as illustrated in  FIG. 3A , the wiping units  21  (ink receptors  26 ) are disposed at the deployment positions. In this case, the inkjet heads  11  are disposed at standby positions (maintenance positions). The standby positions of the inkjet heads  11  are above print positions which are the height positions of the inkjet heads  11  in the printing. When the inkjet heads  11  are disposed at the standby positions and the wiping units  21  are disposed at the deployment positions, the upper ends of the wipers  28  are located above the nozzle surfaces  16   a  of the inkjet heads  11 . Moreover, in the standby state before the start of printing in the inkjet printer  1 , the suction nozzle valves  45 A to  45 D and the waste liquid collection valve  64  are closed and the atmospheric release valve  48  is open. 
     In step S 1  of  FIG. 5 , the controller  4  closes the atmospheric release valve  48 . The negative pressure tank  42  is thereby set to the sealed state. 
     Next, in step S 2 , the controller  4  generates the negative pressure in the negative pressure tank  42 . Specifically, first, the controller  4  starts drive of the air pump  46 . Air is thereby suctioned from the negative pressure tank  42  and the inside of the negative pressure tank  42  starts to be depressurized. Then, when a not-illustrated pressure sensor detects that the pressure inside the negative pressure tank  42  reaches a certain preset pressure which is the negative pressure, the controller  4  stops the air pump  46 . 
     Then, in step S 3 , the controller  4  sets a variable n indicating the number of the maintenance of the inkjet heads  11  in the order of execution to “1”. In this case, the maintenance is executed in the order of the inkjet head  11 A to  11 D. 
     Next, in step S 4 , the controller  4  causes the n-th inkjet head  11  to eject the ink from the nozzles by performing purging. The ink ejected from the nozzles thereby attaches to the nozzle surfaces  16   a . Moreover, the ink not attaching to the nozzle surfaces  16   a  drops from the nozzle surfaces  16   a  and is received by the ink receptor  26 . 
     Then, in step S 5 , the controller  4  opens the suction nozzle valve  45  corresponding to the n-th inkjet head  11 . The suction nozzle  41  corresponding to the n-th inkjet head  11  thereby starts suction of the ink in the ink receptor  26  by means of the negative pressure in the negative pressure tank  42 . 
     Then, in step S 6 , the controller  4  moves the wiping unit  21  corresponding to the n-th inkjet head  11  from the deployment position to the retreat position. 
     In this case, as described above, since the inkjet head  11  is at the standby position, the upper ends of the wipers  28  are located above the nozzle surface  16   a . Thus, when the wiping unit  21  moves from the deployment position to the retreat position, the wipers  28  come into contact with the head modules  16 . When coming into contact with the head modules  16 , the wipers  28  are pressed against the head modules  16  and elastically deform. Then, upper end portions of the wipers  28  slide on (wipe) the nozzle surfaces  16   a  as the wiping unit  21  moves. 
     The ink attaching onto the nozzle surfaces  16   a  is thereby removed. Together with the ink, dust and the like on the nozzle surfaces  16   a  are removed and the nozzle surfaces  16   a  are thereby cleaned. The ink removed from the nozzle surfaces  16   a  by the wipers  28  flows to the ink receptor  26 . 
     While the wiping unit  21  is moving from the deployment position to the retreat position, the suction nozzle  41  suctions the ink in the ink receptor  26 . The ink suctioned from the ink receptor  26  by the suction nozzle  41  flows into the negative pressure tank  42  through the ink suction passage  44 . 
     Next, in step S 7 , the controller  4  determines whether the variable n is “4” which is the last number of maintenance in the order of execution. 
     When the controller  4  determines that n is not 4 (step S 7 : NO), in step S 8 , the controller  4  closes the suction nozzle valve  45  corresponding to the n-th inkjet head  11 . The suction of ink by the suction nozzle  41  corresponding to the n-th inkjet head  11  is thereby stopped. 
     Then, in step S 9 , the controller  4  determines whether the negative pressure tank liquid level sensor  43  is on. Note that the negative pressure tank liquid level sensor  43  is on when the liquid level of the ink in the negative pressure tank  42  is the specified height or more. 
     When the controller  4  determines that the negative pressure tank liquid level sensor  43  is on (step S 9 : YES), in step S 10 , the controller  4  opens the atmospheric release valve  48 . The negative pressure tank  42  is thereby set to the atmospheric release state. 
     Next, in step S 11 , the controller  4  performs control such that the waste liquid collector  24  collects the ink from the negative pressure tank  42  and sends it to the waste liquid tank  61 . Specifically, the controller  4  opens the waste liquid collection valve  64  and drives the ink pump  62  for specified time. The ink is thereby sent from the negative pressure tank  42  to the waste liquid tank  61  and the negative pressure tank liquid level sensor  43  is turned off. 
     Next, in step S 12 , the controller  4  closes the atmospheric release valve  48 . The negative pressure tank  42  is thereby set to the sealed state. 
     Then, in step S 13 , the controller  4  generates the negative pressure in the negative pressure tank  42  as in step S 2  described above. 
     Next, in step S 14 , the controller  4  increments the variable n by “1.” Thereafter, the controller  4  returns to step S 4 . 
     When the controller  4  determines that the negative pressure tank liquid level sensor  43  is off in step S 9  (step S 9 : NO), the controller  4  skips steps S 10  to S 13  and proceeds to step S 14 . 
     When the controller determines that n is 4 in step S 7  (step S 7 : YES), in step S 15  of  FIG. 6 , the controller  4  lowers the inkjet heads  11 A to  11 D from the standby positions to the print positions. Note that, lowering of each of the inkjet heads  11 A to  11 C from the standby position to the print position may be performed at timing depending on a moment when the corresponding one of the suction nozzles  41 A to  41 C stops suctioning the ink. 
     Next, in step S 16 , the controller  4  starts printing of an image by using the inkjet heads  11 A to  11 D. 
     Then, in step S 17 , after a predetermined time elapses from the start of printing, the controller  4  closes the suction nozzle valve  45 D corresponding to the fourth inkjet head  11 D. The suction of the ink by the suction nozzle  41 D corresponding to the fourth inkjet head  11 D is thereby stopped. 
     Next, in step S 18 , the controller  4  opens the atmospheric release valve  48 . The negative pressure tank  42  is thereby set to the atmospheric release state. 
     Then, in step S 19 , the controller  4  determines whether the negative pressure tank liquid level sensor  43  is on. 
     When the controller  4  determines that the negative pressure tank liquid level sensor  43  is on (step S 19 : YES), in step S 20 , the controller  4  performs control such that the waste liquid collector  24  collects the ink from the negative pressure tank  42  and sends it to the waste liquid tank  61  as in step S 11  described above. A series of operations is thereby completed. 
     When the controller  4  determines that the negative pressure tank liquid level sensor  43  is off in step S 19  (step S 19 : NO), step S 20  is skipped and the series of operations is completed. 
     As described above, in the inkjet printer  1 , the suction nozzles  41  disposed above the bottom plates  31  within the movable ranges of the ink receptors  26  suction the ink in the ink receptors  26  through the openings  26   a  on the upper sides of the ink receptors  26 . 
     Thus, unlike in a configuration in which the ink in the ink receptor flows to the waste liquid tank via an ink passage extending downward from a bottom surface of the ink receptor, a standby space for the ink passage with a length corresponding to the movement distance of the ink receptor does not have to be provided below the ink receptor. As a result, the inkjet printer  1  can suppress an increase of an apparatus size. 
     Since there is no ink passage which moves together with the ink receptor, complex routing of the ink passage is avoided. 
     In the inkjet printer  1 , the suction unit  23  includes the negative pressure tank  42  in which the negative pressure is generated for suctioning the ink by the suction nozzles  41 A to  41 D, the air pump  46  which generates the negative pressure in the negative pressure tank  42 , and the ink suction passage  44  which connects the suction nozzles  41 A to  41 D with the negative pressure tank  42 . 
     The negative pressure tank  42  and the air pump  46  which are suction force generation mechanisms shared by the suction nozzles  41  can thereby generate the suction force in the suction nozzles  41  and suction the ink from the ink receptors  26 . Accordingly, it is possible to collect the ink from the ink receptors  26  while suppressing the increase of the apparatus size in the inkjet printer  1  including the multiple inkjet heads  11  and the multiple ink receptors  26 . 
     Note that, in the embodiment described above, the suction nozzle valves  45 A to  45 D are provided in the ink suction passage  44  and the ink is suctioned sequentially from each of the ink receptors  26  by opening and closing the suction nozzle valves  45 A to  45 D. However, the configuration may be such that the suction nozzle valves  45 A to  45 D are omitted and the wiping by the wiping units  21  and the suction of ink from the ink receptors  26  may be performed in parallel for all inkjet heads  11 . 
     In the embodiment described above, the suction force is generated in the suction nozzles  41  by using the negative pressure generated in the negative pressure tank  42  by the air pump  46 . However, the configuration for generating the suction force in the suction nozzles  41  is not limited to this. For example, the configuration may be such that ink pumps corresponding to the respective ink suction nozzles are provided to generate the suction force in the suction nozzles. 
     In the embodiment described above, description is given of the inkjet printer including four inkjet heads and four wiping units. However, the numbers of inkjet heads and the number of wiping units are not limited to this. 
     Embodiments of the present invention have been described above. However, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. 
     Moreover, the effects described in the embodiments of the present invention are only a list of optimum effects achieved by the present invention. Hence, the effects of the present invention are not limited to those described in the embodiment of the present invention.