Patent Publication Number: US-10759172-B2

Title: Head cleaning device and liquid discharge apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2018-033011, filed on Feb. 27, 2018, in the Japan Patent Office, the entire disclosure of which is incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     Aspects of the present disclosure relate to a head cleaning device and an liquid discharge apparatus. 
     Related Art 
     In general, an inkjet recording apparatus can perform a cleaning operation (suction cleaning) for forcibly suctioning ink from a nozzle of a liquid spray head into a cap and discharging the ink in a capping state where the cap is brought into contact with a nozzle forming surface so as to surround the nozzle of the liquid spray head. When the suction cleaning is repeatedly performed, a nip at a cap front end is gradually contaminated with ink, and the ink attached to the nip of the cap at the time of capping such as the suction cleaning is transferred on the nozzle surface. The ink is dried and thickened to be fixed so as to surround the nozzle of the nozzle surface. As deposition of adhered ink on the nozzle surface is progressed, a conveyance object is scraped with the deposition at the time of printing and an image defect occurs, and a gap is generated between the nozzle surface and the nip of the cap at the time of capping, and moisture retention and suction of the nozzle surface are not normally performed. Therefore, it is necessary to sufficiently remove the adhered ink at the time of wiping the nozzle surface. 
     As a method for wiping the nozzle surface of the recording head of the inkjet recording apparatus, a method has been known for removing ink on the nozzle surface using a wiping sheet which is provided in the apparatus body and is a wiping member for wipe the ink on the nozzle surface. 
     SUMMARY 
     In an aspect of the present disclosure, there is provided a head cleaning device that includes a liquid discharge head, a wiping member, a rotatable pressing member, and a moving assembly. The liquid discharge head includes a nozzle, which discharges liquid, on a nozzle surface. The wiping member wipes the nozzle surface. The rotatable pressing member presses the wiping member against the nozzle surface. The moving assembly contacts the wiping member with the nozzle surface and relatively moves the liquid discharge head and the wiping member to perform a wiping operation. The pressing member includes a recess corresponding to a nozzle forming portion of the nozzle surface on a part of a surface of the pressing member. 
     In another aspect of the present disclosure, there is provided a head cleaning device that a liquid discharge head, a wiping member, a rotatable pressing member, and a moving assembly. The liquid discharge head includes a nozzle, which discharges liquid, on a nozzle surface. The wiping member wipes the nozzle surface. The rotatable pressing member presses the wiping member against the nozzle surface. The moving assembly contacts the wiping member with the nozzle surface and relatively moves the liquid discharge head and the wiping member to perform a wiping operation. A hardness of a part of a peripheral surface of the pressing member is lower than a hardness of another part of the peripheral surface. 
     In still another aspect of the present disclosure, there is provided a liquid discharge apparatus including the above-described head cleaning device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The aforementioned and other aspects, features, and advantages of the present disclosure would be better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a perspective explanatory view of an inkjet recording apparatus viewed from a front side; 
         FIG. 2  is a schematic side view for explaining a general arrangement of a mechanical unit of the inkjet recording apparatus; 
         FIG. 3  is a plan explanatory view of a main part of the mechanical unit; 
         FIG. 4  is a block explanatory diagram of an outline of a controller of the inkjet recording apparatus; 
         FIGS. 5A to 5E  are diagrams of a deposition mechanism of adhered ink from a cap to a nozzle surface; 
         FIG. 6  is a diagram of the deposition mechanism of the adhered ink from the cap to the nozzle surface  37 ; 
         FIG. 7  is a diagram of a wiping unit according to an embodiment of the present disclosure; 
         FIGS. 8A to 8D  are diagrams of a wiping operation of the wiping unit; 
         FIG. 9  is a diagram of a cleaning liquid applicator according to an embodiment of the present disclosure; 
         FIGS. 10A and 10B  are diagrams of a comparative example of a pressing member; 
         FIGS. 11A and 11B  are diagrams of a pressing member according to a first embodiment of the present disclosure; and 
         FIGS. 12A and 12B  are diagrams of a pressing member according to a second embodiment of the present disclosure. 
     
    
    
     The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. 
     DETAILED DESCRIPTION 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve similar results. 
     Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and all of the components or elements described in the embodiments of this disclosure are not necessarily indispensable. 
     Referring now to the drawings, embodiments of the present disclosure are described below. In the drawings for explaining the following embodiments, the same reference codes are allocated to elements (members or components) having the same function or shape and redundant descriptions thereof are omitted below. 
       FIG. 1  is a perspective explanatory view of an inkjet recording apparatus  600  as an liquid discharge apparatus according to an embodiment of the present disclosure viewed from a front side. 
     The inkjet recording apparatus  600  includes an apparatus body  1 , a supply tray  2  which is mounted in the apparatus body  1  and loads a conveyance object, and an ejection tray  3  which is removably attached to the apparatus body  1  and stocks the conveyance object on which an image is recorded (formed). In addition, on one end portion side of a front surface of the apparatus body  1  (side of supply and ejection tray), a cartridge loading unit  4  to load an ink cartridge is included, and an upper surface of the cartridge loading unit  4  is an operation/display unit  5  in which operation buttons, a display, and the like are provided. 
     In the cartridge loading unit  4 , recording liquid (ink) which is color materials having different colors, for example, ink cartridges (main tank)  10   k ,  10   c ,  10   m , and  10   y  (referred to as “ink cartridge  10 ” when colors are not distinguished from each other) which are recording liquid cartridges for storing black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink can be inserted to be loaded from the front side toward the rear side of the apparatus body  1 . On the front side of the cartridge loading unit  4 , a front cover (cartridge cover)  6  which opens when the ink cartridge  10  is attached/detached is openably and closably provided. In addition, the ink cartridges  10   k ,  10   c ,  10   m , and  10   y  are loaded in a state of being arranged to be vertically placed and aligned in the lateral direction. 
     In the operation/display unit  5 , at arrangement positions corresponding to attaching positions (arrangement position) of the respective ink cartridges  10   k ,  10   c ,  10   m , and  10   y , remaining amount display units  11   k ,  11   c ,  11   m , and  11   y  of the colors to display that the remaining amount of each of the ink cartridges  10   k ,  10   c ,  10   m , and  10   y  reaches near end or to the end are arranged. In addition, in the operation/display unit  5 , a power button  12 , a conveyance object feed/print restart button  13 , and a cancel button  14  are arranged. 
     Next, a mechanical unit of the inkjet recording apparatus  600  will be described with reference to  FIGS. 2 and 3 .  FIG. 2  is a schematic explanatory side view of an outline of the mechanical unit, and  FIG. 3  is a plan explanatory view of a main part. 
     A main guide rod  31  and a guided rod  32  which are main guide members for laterally bridging on right and left side plates  21 A and  21 B forming a frame  21  slidably hold a carriage  33  in a main scanning direction, and a main scanning motor  500  moves and scans the carriage  33  via a timing belt  502  in an arrow direction in  FIG. 3  (carriage main scanning direction). 
     As described above, on the carriage  33 , four recording heads  34  including liquid droplet discharge heads to discharge ink droplets of colors of yellow (Y), cyan (C), magenta (M), and black (Bk) are arranged in a state where a plurality of ink discharge ports is arranged in a direction intersecting with the main-scanning direction (conveyance object conveying direction), and the recording head  34  is attached to the carriage  33  so that the ink droplet is discharged downward. A configuration including a single or a plurality of heads including a row of nozzles to discharge liquid of the respective colors can be employed. 
     As an inkjet head configuring the recording head  34 , an inkjet head including a pressure generator which generates a pressure to discharge the liquid such as a piezoelectric actuator such as a piezoelectric element, a thermal actuator which uses a phase change caused by film boiling of the liquid by using an electrothermal conversion element such as a heating resistor, a shape-memory alloy actuator using a metal phase change caused by a temperature change, and an electrostatic actuator using electrostatic power can be used. 
     A head tank  35  of each color to supply ink of each color to each recording head  34  is mounted on the carriage  33 . As described above, the ink of each color is supplemented and supplied from the ink cartridge  10  of each color attached to the cartridge loading unit  4  to the head tank  35  of each color via a flexible supply tube  36  of each color. In the cartridge loading unit  4 , a supply pump  24  which is a liquid supply unit to supply the ink in the ink cartridge  10  is provided. 
     On the other hand, as a supply unit for supplying a conveyance object  42  stacked on a conveyance object stacking unit (pressure plate)  41  of the supply tray  2 , a semicircular roller (supply roller)  43  which separately feeds the conveyance object  42  from the conveyance object stacking unit  41  one by one and a separating pad  44  which faces the supply roller  43  and includes a material with a large coefficient of friction are included, and the separating pad  44  is biased toward the supply roller  43 . 
     To feed the conveyance object  42  supplied from the supply unit below the recording head  34 , a guide  45  for guiding the conveyance object  42 , a counter roller  46 , a conveyance guide member  47 , a holding member  48  including a front end pressurizing roller  49  are included, and in addition, a conveyance belt  51  which is a conveyer for electrostatically attracting the fed conveyance object  42  to convey the conveyance object  42  at a position facing the recording head  34  is included. 
     The conveyance belt  51  is an endless belt and is stretched around a conveyance roller  52  and a tension roller  53  to rotate in a belt conveyance direction (sub-scanning direction). Furthermore, a charging roller  56  which is a charger for charging a surface of the conveyance belt  51  is included. The charging roller  56  is arranged so as to have contact with the surface layer of the conveyance belt  51  and rotate by following the rotation of the conveyance belt  51 . In addition, on a rear side of the conveyance belt  51 , a guide member  57  is arranged in correspondence with a printing area printed by the recording head  34 . 
     The conveyance roller  52  rotates and drives via a timing by a sub-scanning motor  504  to rotate and move the conveyance belt  51  in the belt conveyance direction in  FIG. 3 . 
     In addition, as an ejector to eject the conveyance object  42  recorded by the recording head  34 , a separation claw  61  which separates the conveyance object  42  from the conveyance belt  51 , an ejection roller  62 , and an ejection roller  63  are included, and the ejection tray  3  is provided below the ejection roller  62 . 
     A duplex unit  71  is removably attached to the back surface portion of the apparatus body  1 . The duplex unit  71  takes in and inverts the conveyance object  42  which is returned in an against rotation of the conveyance belt  51  and supplies the conveyance object  42  between the counter roller  46  and the conveyance belt  51  again. An upper surface of the duplex unit  71  serves as a manual sheet feeding tray  72 . 
     In addition, as illustrated in  FIG. 3 , in a non-printing area on one side of the carriage  33  in the scanning direction, a maintenance and recovery mechanism  81  which includes a recovery unit for maintaining and recovering a state of the nozzle of the recording head  34  is arranged. 
     The maintenance and recovery mechanism  81  includes cap members (referred to as “cap” below)  82   a  to  82   d  (referred to as “cap  82 ” when not distinguished) for respectively capping the nozzle surfaces of the recording heads  34 , an dummy discharge receptacle  84  which receives droplets generated when dummy discharge for discharging droplets which do not contribute to record is performed to discharge thickened recording liquid, and a suction pump  508 . Here, the cap  82   a  is used as a suction and moisture cap, and the other caps  82   b  to  82   d  are used as moisture caps. 
     Waste liquid of the recording liquid generated by a maintenance and recovery operation of the maintenance and recovery mechanism  81 , ink discharged to the cap  82 , ink dummy-discharged to the dummy discharge receptacle  84  are discharged to and stored in a waste liquid tank  506 . 
     The inkjet recording apparatus  600  includes a wiping unit  100  between the maintenance and recovery mechanism  81  and the conveyance belt  51  in the scanning direction of the carriage  33 . The wiping unit  100  makes a cloth-like wiping sheet  101  have contact with the nozzle surface  37  of the recording head  34  to wipe and clean the nozzle surface  37 . The wiping unit  100  moves in the sub-scanning direction when wiping the nozzle surface  37  of the recording head  34 . 
     Furthermore, as illustrated in  FIG. 3 , in a non-printing area on the other side of the carriage  33  in the scanning direction, a dummy discharge receptacle  88  which receives droplets generated when dummy discharge for discharging droplets which do not contribute to record is performed to discharge thickened recording liquid during recording and the like is arranged, and the dummy discharge receptacle  88  includes an opening  89  along a nozzle row direction of the recording heads  34 . 
     In the inkjet recording apparatus  600  configured as described above, the conveyance objects  42  are separated and supplied from the supply tray  2  one by one, and the conveyance object  42  which has been supplied substantially vertically upward is guided by the guide  45 , sandwiched between the conveyance belt  51  and the counter roller  46  and conveyed, and in addition, the front end of the conveyance object  42  is guided by the conveyance guide member  47  and pressed against the conveyance belt  51  by the front end pressurizing roller  49 , and accordingly, the conveyance direction of the conveyance object  42  is changed by substantially 90°. 
     At this time, to alternately repeat plus outputs and minus outputs from an alternating current (AC) bias supply unit of the controller provided in the apparatus to the charging roller  56 , a charging voltage pattern in which an alternating voltage is applied and the conveyance belt  51  is alternately charged is used, that is, plus and minus voltages are alternately charged in a band shape in the sub-scanning direction which is a rounding direction. When the conveyance object  42  is fed on the conveyance belt  51  which has been alternately charged to plus and minus, the conveyance object  42  is attracted by the conveyance belt  51  and conveyed in the sub-scanning direction according to the rotation movement of the conveyance belt  51 . 
     Therefore, by driving the recording heads  34  according to an image signal while moving the carriage  33 , ink droplets are discharged to the stopped conveyance object  42  to record one line, and the next line is recorded after the conveyance object  42  has been conveyed by a predetermined amount. Upon receiving a recording end signal or a signal indicating that the rear end of the conveyance object  42  has reached a recording area, a recording operation is terminated, and the conveyance object  42  is ejected to the ejection tray  3 . 
     Furthermore, the carriage  33  is moved to the side of the maintenance and recovery mechanism  81  when waiting printing (recording), the cap  82  caps the recording head  34 , and the nozzle is maintained to be moist so that a discharge failure due to ink drying is prevented. In a state where the cap  82  caps the recording head  34 , the recovery operation is performed for suctioning the recording liquid from the nozzle (referred to as “nozzle suction” or “head suction”) by the suction pump  508  and discharging the thickened recording liquid and bubbles. In addition, before the start of recording, dummy discharge operation for discharging ink which is not related to recording is performed in the middle of the recording. With this operation, a stable discharging performance of the recording head  34  is maintained. 
     Next, an outline of a controller of the liquid discharge apparatus will be described with reference to  FIG. 4 . Note that  FIG. 4  is a block explanatory diagram of the entire controller. 
     The controller includes a main controller  301  as circuitry which performs control of the entire liquid discharge apparatus and includes a microcomputer which also functions as a unit for performing control according to an embodiment of the present disclosure and a print controller  302  including a microcomputer which controls printing. 
     Then, the main controller  301  controls the driving of the main scanning motor  500  for moving the carriage  33  in the main scanning direction via a main scanning motor driving circuit  303  and the sub-scanning motor  504  for feeding the conveyance object  42  via a sub-scanning motor driving circuit  304  to form an image on the conveyance object  42  based on print processing information input from a communication circuit  300  and controls to transmit printing data to the print controller  302 . 
     Furthermore, a detection signal is input from a carriage position detection circuit  305  which detects the position of the carriage  33  to the main controller  301 , and the main controller  301  controls a moving position and a moving speed of the carriage  33  based on the detection signal. Furthermore, the main controller  301  controls a moving position and a moving speed of the wiping unit  100  to be described later, a rotation amount of a winding roller  103 , a rotation fixing position of a pressing member  104 . Furthermore, the main controller  301  controls opening and closing of a valve  403  of a cleaning liquid applicator  400  illustrated in  FIG. 9 . The carriage position detection circuit  305 , for example, reads and counts the number of slits of an encoder sheet  512  arranged along the scanning direction of the carriage  33  by a photosensor  510  mounted on the carriage  33  to detect the position of the carriage  33 . The main scanning motor driving circuit  303  rotates and drives the main scanning motor  500  according to a moving amount of the carriage input from the main controller  301  and moves the carriage  33  to a predetermined position at a predetermined speed. 
     Furthermore, a detection signal is input from a conveyance amount detection circuit  306  which detects a movement amount of the conveyance belt  51  to the main controller  301 , and the main controller  301  controls a moving amount and a moving speed of the conveyance belt  51  based on the detection signal. The conveyance amount detection circuit  306 , for example, reads and counts the number of slits of a rotation encoder sheet  516  attached to a rotation shaft of the conveyance roller  52  by a photosensor  518  to detect a conveyance amount. The sub-scanning motor driving circuit  304  rotates and drives the sub-scanning motor  504  according to the conveyance amount input from the main controller  301  and rotates and drives the conveyance roller  52  to move the conveyance belt  51  to a predetermined position at a predetermined speed. 
     The main controller  301  issues a sheet feeding roller driving command to a sheet feeding roller driving circuit  307  to drive the supply roller  43  once. The main controller  301  rotates and drives a motor of the maintenance and recovery mechanism  81  via a motor driving circuit for driving the maintenance and recovery mechanism  308  so as to raise and lower the cap  82  and to drive the suction pump  508  as described above. 
     The main controller  301  controls the driving of a driving motor (supply motor)  514  for driving a pump of a supply pump  24  via a supply pump driving circuit  311  and supplements and supplies (fills) ink from the ink cartridge  10  loaded to the cartridge loading unit  4  to the head tank  35 . At this time, the main controller  301  controls supplement and supply (filling operation) based on a detection signal from a head tank full-state sensor  312  which detects that the head tank  35  is full. In this case, there are atmospheric release filling in which the head tank  35  is filled in a state where an atmospheric release mechanism is opened and normal filling in which the head tank  35  is filled while closing the atmospheric release mechanism. 
     In addition, the main controller  301  takes in information stored in a non-volatile memory (for example, a cartridge electrically erasable programmable read-only memory (cartridge EEPROM))  316  which is a storage provided in each ink cartridge  10  attached to the cartridge loading unit  4  via a cartridge communication circuit  314 , performs predetermined processing, and stores and holds the information in a non-volatile memory (for example, an EEPROM)  315  which is a main body storage. 
     In addition, a detection signal from an environmental sensor  313  which detects an environmental temperature and an environmental humidity is input to the main controller  301 . 
     The print controller  302  generates data to drive the pressure generator for discharging the droplets of the recording head  34  based on the signal from the main controller  301  and the position and the conveyance amount of the carriage from the carriage position detection circuit  305 , the conveyance amount detection circuit  306 , and the like. Furthermore, the print controller  302  transfers the image data described above as serial data to a head driving circuit  310  and outputs a transfer clock and a latch signal necessary for transferring the image data, determining the transfer, and the like, a droplet control signal (mask signal), and the like to the head driving circuit  310 . Furthermore, the print controller  302  includes a digital to analog (D/A) converter which D/A converts pattern data of a driving signal stored in a ROM, a driving waveform generation unit including a voltage amplifier, a current amplifier, and the like, and a driving waveform selection unit which selects a driving waveform to be applied to a head driver. Then, the print controller  302  generates a driving waveform including a single driving pulse (driving signal) or a plurality of driving pulses (driving signal) and outputs the generated signal to the head driving circuit  310 . 
     The head driving circuit  310  applies a driving signal forming the driving waveform applied from the print controller  302  to a driving element (for example, piezoelectric element described above) which generates energy for selectively discharge the droplets of the recording head  34  based on image data corresponding to one line of the recording head  34  which is serially input to drive the recording head  34 . At this time, by selecting the driving pulse forming the driving waveform, for example, it is possible to separately record dots with different sizes, for example, a large droplet (large dot), a medium droplet (medium dot), and a small droplet (small dot). 
     Next, an example of the present embodiment will be described in detail. 
     First, a deposition mechanism of adhered ink from the cap  82  to the nozzle surface  37  will be described with reference to  FIGS. 5A to 5E and 6 . In  FIGS. 5A to 5E , description will be made as assuming that the cap  82  move toward the recording head  34 . However, either one of the cap  82  or the recording head  34  may move. Furthermore, under the cap  82 , the suction pump  508  for suctioning ink from a nozzle  38  of the recording head  34  is arranged. 
     At the time of maintenance and recovery operation (maintenance) of the recording head, after the cap  82  away from the nozzle surface  37  of the recording head  34  is raised, has contact with the nozzle surface  37 , and performs capping ( FIG. 5A ), ink  90  is suctioned from the nozzle  38  by the suction pump  508  ( FIG. 5B ). Next, after the cap  82  has moved down to a position away from the nozzle surface  37  and the nozzle surface  37  has been wiped by the wiping sheet  101 , the ink  90  in the cap is discharged ( FIG. 5C ). After the ink  90  is discharged, the ink  90  is attached to a nip  83  which is a part of the cap  82  having contact with the nozzle surface  37 . If capping is performed in this state, the ink  90  has contact with the nozzle surface  37  again ( FIG. 5D ), and the ink  90  is transferred on the nozzle surface  37  after the cap  82  has been separated from the nozzle surface  37  ( FIG. 5E ). 
     With the deposition mechanism described above, the ink  90  is attached on the nozzle surface  37  so as to surround the nozzle  38  ( FIG. 6 ).  FIG. 6  is a bottom view of the recording head  34 , and it can be seen that the ink  90  is deposited on the nozzle surface  37  in a rectangular shape. This is because the nip  83  of the cap  82  has a rectangular shape so as to surround the nozzle  38 . However, the shape of the nip  83  is not limited to a rectangle and may have another shape. 
     Next, a wiping unit according to an embodiment of the present disclosure will be described with reference to  FIG. 7 . 
     The wiping unit  100  wipes the ink  90 , a foreign matter, and the like attached on the nozzle surface  37  of the recording head  34  by the wiping sheet  101  at the time of maintenance. 
     The wiping unit  100  includes the wiping sheet  101  which is a planar and roll-shaped wiping member to wipe the nozzle surface  37  of the recording head  34 , a supply roller  102  which supplies the wiping sheet  101 , the pressing member  104  which presses the wiping sheet  101  against the nozzle surface  37 , the winding roller  103  which is a winding member for winding the supplied wiping sheet  101 , a compression spring  106  which presses the pressing member  104 , a base  105  for fixing the compression spring, and the like. A width of the wiping sheet  101  perpendicular to a wiping direction is set so as to wipe the nozzle surface  37  of the recording head  34  at one time. The pressing member  104  is coupled to the base  105  with the compression spring  106  so as to be pressed against the nozzle surface  37  of the recording head  34  with a constant pressure. The recording head  34  and the wiping unit  100  can be relatively moved to each other. The inkjet recording apparatus  600  includes the recording head  34  including the nozzle  38  for discharging the ink which is a droplet, the cap  82  including the nip  83  which can be abut on the recording head  34  so as to surround the nozzle  38 , and the wiping unit  100 . 
     It is preferable to provide an elastic member such as rubber on the surface of the pressing member  104  so as not to damage the nozzle surface  37  of the recording head  34 . Furthermore, the pressing member  104  is a rotatable roller member. 
     The inkjet recording apparatus  600  includes a moving assembly  530  as a mover to move the wiping unit  100  in the sub-scanning direction. The moving assembly  530  is connected to a connection portion  532  of the wiping unit  100  and includes a belt  520  stretched around rollers  526  and a motor  524  for driving the roller  526 . By rotating and driving the roller  526  by driving the motor  524 , the belt  520  and the wiping unit  100  connected to the belt  520  are moved in the sub-scanning direction. 
     The wiping unit  100  has contact with a cam  534  via an engaging portion  536 . By rotating and driving the cam  534 , the wiping unit  100  can be vertically moved. 
     A rotary encoder  109  is attached to the winding roller  103 , and a photosensor  107  of the rotary encoder  109  can measure a wound distance of the wiping sheet  101 . The wiping unit  100  includes a driving motor  108  which rotates and drives the winding roller  103 , and the main controller  301  controls a rotation speed of the driving motor  108 . 
     In  FIG. 7 , a head cleaning device  200  according to an embodiment of the present disclosure includes the recording head  34  as a liquid discharge head having the nozzle  38  to discharge liquid on the nozzle surface  37 , the wiping sheet  101  as a wiping member which wipes the nozzle surface  37 , the rotatable pressing member  104  which presses the wiping sheet  101  against the nozzle surface  37 , the main controller  301  as circuitry which rotates the pressing member  104  and fixes the pressing member  104  at an arbitrary position, and the moving assembly  530  as a mover to contact the wiping sheet  101  with the nozzle surface  37  and perform the wiping operation for relatively moving the recording head  34  and the wiping sheet  101 . As will be described later, the pressing member  104  includes a recess  115  corresponding to a nozzle forming portion of the nozzle surface  37  on a part of the surface of the pressing member  104  or a hardness of a part of a peripheral surface of the pressing member  104  is lower than a hardness of other parts of the peripheral surface. 
     Next, the wiping operation of the wiping unit  100  will be described with reference to  FIGS. 8A to 8D . 
     Here, first, a wiping operation in a case where the adhered ink is deposited on the nozzle surface  37  so as to surround the nozzle  38  of the nozzle surface  37  by the transfer from the nip  83  will be described with reference to  FIGS. 8A to 8D . An upper view of  FIG. 8A  is a bottom view of the recording head  34 , and a side view of the recording head  34  and the wiping unit  100  is illustrated below the upper view of  FIG. 8A . 
     After the wiping operation has been requested, under the control of the main controller  301  ( FIG. 4 ), the wiping unit  100  is raised until the upper end of the pressing member  104  is positioned to be upper than the nozzle surface  37  of the recording head  34  to be wiped ( FIG. 8A ). A vertical distance A between a height position of the upper end of the pressing member  104  and a height position of the nozzle surface of the recording head  34  is equal to a contraction amount of the compression spring  106  which couples the pressing member  104  at the time of wiping the nozzle surface with the base  105 . Therefore, it is necessary for the vertical distance A to be a raise amount to obtain a desired pressing pressure. Furthermore, by changing a spring constant or a natural length of the compression spring  106 , it is possible to wipe the nozzle surface  37  of the recording head  34  by the wiping sheet  101  by an arbitrary pressing load. At this time, the recording head  34  and the wiping unit  100  are relatively moved in a state where the winding roller  103  is fixed to wipe the nozzle surface  37  of the recording head  34 . 
     Specifically, by moving the wiping unit  100  in the sub-scanning direction in a state where the wiping sheet  101  has contact with and is pressed against the nozzle surface  37  of the recording head  34 , the nozzle surface  37  is wiped by the wiping sheet  101  ( FIG. 8B ). At this point, a short side position B perpendicular to the wiping direction of the adhered ink  90  surrounding the nozzle  38  has been already wiped. 
     Thereafter, the wiping operation and the relative movement are continued for a while in a state where the winding roller  103  is fixed ( FIG. 8C ), and the adhered ink on the two sides along the long side which are attached on both sides of two lines of the nozzles  38  of the rectangular adhered ink  90  attached on the nozzle surface  37  is wiped by the wiping sheet  101 . 
     In addition, the wiping operation and the relative movement are continued for a while in a state where the winding roller  103  is fixed ( FIG. 8D ), and the adhered ink on the two sides along the long side which are attached on both sides of two lines of the nozzles  38  and the short side position D perpendicular to the wiping direction of the rectangular adhered ink  90  attached on the nozzle surface  37  are wiped by the wiping sheet  101 . 
     At this point, the entire adhered ink surrounding the nozzle  38  has been already wiped. Finally, by lowering the wiping unit  100  and returning relative positions of the recording head  34  and the wiping unit  100  to the original positions, the wiping operation is completed. 
     Next, the cleaning liquid applicator according to an embodiment of the present disclosure will be described with reference to  FIG. 9 . 
     In addition to the wiping unit  100 , the head cleaning device  200  according to the present embodiment includes the cleaning liquid applicator  400  which applies cleaning liquid  401  to the supplied wiping sheet  101 . The cleaning liquid applicator  400  includes the cleaning liquid  401  stored in a storage tank  402 , a nozzle  404  which extends from the storage tank  402  to above the pressing member  104 , the valve  403  provided in the nozzle  404 , and the like. The valve  403  is opened and closed in response to a request from the main controller  301  ( FIG. 4 ) to drop the cleaning liquid  401  on the wiping sheet  101  via the nozzle  404 . The front end of the nozzle  404  is positioned at an upper position so as not to have contact with the wiping sheet  101 . 
     Solution having high volatility is used for the cleaning liquid  401 , and the solution can effectively remove the ink  90  and foreign matters attached on the nozzle surface  37  of the recording head  34 . It is preferably to use solution having an action for dissolving ink as the cleaning liquid  401 . It is desirable that the cleaning liquid  401  is covered with a cover and the like so that the cleaning liquid  401  having high volatility does not come into contact with atmosphere. If a state where the cleaning liquid  401  is hardly volatilized by covering the cleaning liquid  401  with the cover is maintained, it is not necessary to provide the cleaning liquid applicator  400  in the inkjet recording apparatus  600  or the wiping unit  100 , and it is preferable that the cleaning liquid  401  be impregnated into the wiping sheet  101  before the wiping sheet  101  is set in the wiping unit  100 . 
     By the cleaning liquid applicator  400  or impregnating the wiping sheet  101  with the cleaning liquid  401  in advance, the nozzle surface  37  can be wet-wiped by using the cleaning liquid  401  with the wiping sheet  101 . Therefore, by wiping the nozzle surface  37  in a state where the cleaning liquid is applied to the wiping sheet  101 , the adhered ink  90  attached on the nozzle surface  37  can be more efficiently removed. 
     In a case where the cleaning liquid applicator  400  is provided in the head cleaning device  200  or the inkjet recording apparatus  600  as illustrated in  FIG. 9 , a configuration is preferable in which the cleaning liquid applicator  400  is fixed at a position which does not prevent the movement of the wiping unit  100  above the wiping unit  100  and the cleaning liquid  401  is dripped on the wiping sheet  101  from the nozzle  404  to apply the cleaning liquid  401  to the wiping sheet  101 . A timing when the cleaning liquid  401  is applied to the wiping sheet  101  is preferably immediately before the wiping unit  100  performs the wiping operation. Furthermore, it is preferable that a range in which the cleaning liquid  401  is applied to the wiping sheet  101  be an entire area of the wiping sheet  101  to be used in the following wiping operation. Therefore, in a case where the relative positions of the wiping unit  100  and the cleaning liquid applicator  400  are fixed, in an application process of the cleaning liquid  401  to the wiping sheet  101 , it is necessary to apply an amount of the cleaning liquid  401  enough for wet the entire area to be used in the following wiping operation. Alternatively, by relatively moving the wiping unit  100  and the cleaning liquid applicator  400  when the cleaning liquid  401  is applied to the wiping sheet  101 , cleaning liquid may be applied to the entire area to be used in the following wiping operation. Furthermore, as a unit for controlling the amount of the cleaning liquid to be applied to the wiping sheet  101 , a method is preferable for controlling an opening time of the openable/closable valve  403  provided in the cleaning liquid applicator  400  by the main controller  301  ( FIG. 4 ) as described above. Alternatively, in a case where an electric pump and the like is used to apply the cleaning liquid  401 , an apply voltage may be controlled. 
     Next, a method for selectively changing a pressure acting on the nozzle surface at the time of wiping the nozzle surface will be described with reference to  FIGS. 10A to 12B .  FIG. 10A  is a schematic perspective view of a comparative example of a pressing member, and  FIG. 10B  is a schematic side view of the comparative example of the pressing member.  FIG. 11A  is a schematic perspective view of a pressing member according to a first embodiment of the present disclosure, and  FIG. 11B  is a schematic side view of the pressing member.  FIG. 12A  is a schematic perspective view of a pressing member according to a second embodiment of the present disclosure, and  FIG. 12B  is a schematic side view of the pressing member. 
     A first method is to change the shape of the pressing member  104  as illustrated in  FIGS. 10A to 11B . As described above, the wiping sheet  101  is pressed against the nozzle surface  37  by the pressing member  104  illustrated in  FIGS. 11A and 11B , and the ink  90  attached on the nozzle surface  37  is removed. 
     As illustrated in  FIGS. 10A and 10B , in the comparative example of the pressing member  104 , a diameter of the pressing member at a position facing a nozzle forming portion of the nozzle surface is smaller than a non-nozzle forming portion on the outer side of the nozzle forming portion. With this structure, at the time of wiping the nozzle surface, a pressure acting on the nozzle forming portion from the wiping sheet is reduced. Therefore, the ink attached to the nozzle forming portion is more hardly removed than the other parts. 
     On the other hand, according to the first embodiment, as illustrated in  FIGS. 11A and 11B , a part of the surface of the pressing member  104  has a recess  115  corresponding to the width of the nozzle forming portion of the nozzle surface  37 . In other words, the surface of the pressing member  104  at the position facing the nozzle forming portion of the nozzle surface  37  is locally formed in a recess-like shape (only a part in circumferential direction). On the nozzle surface  37 , the two rows of nozzles  38  on the nozzle surface  37  are positioned in the range of the nozzle forming portion, and the non-nozzle forming portion is positioned outside the nozzles  38 . A part of the pressing member  104  in the circumferential direction other than the recess  115  is formed as a projection  117 . In this example, since the pressing member  104  has a cylindrical shape, the shape of the projection  117  corresponds to the side surface of the cylinder. Therefore, a pressure generated when the wiping sheet  101  is pressed against the nozzle surface  37  by the projection  117  is larger than a pressure generated when the wiping sheet  101  is pressed against the nozzle surface  37  by the recess  115 . As a material of the pressing member  104 , an elastic member such as resin and rubber can be used. 
     Furthermore, the pressing member  104  is rotatable, and the pressing member  104  is rotated by power transmission from the driving motor  108  which is controlled by the main controller  301  and is fixed at an arbitrary position. The pressing member  104  is supported with respect to the moving assembly  530  by a shaft  121 . Therefore, the rotation fixing position of the pressing member  104  is changed so that the pressure acting on the nozzle surface  37  from the wiping sheet  101  can be selectively changed. For example, in a case where the nozzle forming portion is further worn and water repellency is deteriorated, by changing the rotation fixing position of the pressing member  104  and pressing the wiping sheet  101  against the nozzle surface  37  by using the projection  117  of the pressing member  104  to wipe the nozzle surface  37 , it is possible to sufficiently remove the ink attached to the nozzle forming portion and the non-nozzle forming portion of the nozzle surface  37 . In a case where the nozzle forming portion is not worn (for example, when recording head  34  is new), by changing the rotation fixing position of the pressing member  104  and pressing the wiping sheet  101  against the nozzle surface  37  by using the recess  115  of the pressing member  104  to wipe the nozzle surface  37 , it is possible to remove the ink attached to the nozzle forming portion of the nozzle surface  37  using a weak pressure. The degree of the wear of the nozzle forming portion may be determined by the main controller  301 , for example, based on the number of wipes of the recording head  34  and an elapsed time after exchanging the recording head  34 . In this way, the main controller  301  changes the rotation fixing position of the pressing member  104  according to the degree of the wear of the nozzle forming portion. 
     Even in a case where the recess  115  is used, the non-nozzle forming portion of the nozzle surface  37  is wiped by the projection  117 . In addition, for example, after several times of wiping operations using the recess  115 , the main controller  301  may perform the wiping operation using the projection  117  once. With this operation, normal discharge of the nozzle surface can be maintained without excessively wearing the nozzle surface  37 . 
     As described above, since the surface of the pressing member  104  locally has the recess  115  and the projection  117  and can be rotated to an arbitrary position and can be fixed, the position of the pressing member  104  facing the nozzle surface  37  can be by rotation so that the pressure acting on the nozzle surface  37  can be selectively changed by changing. Therefore, by selectively changing the wiping pressure acting on the nozzle forming portion and wipes the nozzle forming portion with an appropriate pressure, normal ink discharge can be maintained. In a case where it is desired to sufficiently remove the ink attached to the nozzle forming portion, the pressing member  104  is rotated, the projection  117  is used, and the pressure acting on the nozzle forming portion is temporarily increased so that the residual ink on the nozzle forming portion can be reduced. 
     A pressure which acts on the nozzle surface  37  from the wiping sheet  101  and is generated by the recess  115  of the pressing member  104  is smaller than a pressure which acts on the nozzle surface  37  from the wiping sheet  101  and is generated by the projection  117  other than the recess  115 . Accordingly, deterioration of the nozzle forming surface caused by wiping by the wiping sheet  101  can be prevented, and normal ink discharge can be maintained. 
     In the first embodiment illustrated in  FIGS. 11A and 11B , the recess  115  is formed in a part of the surface of the pressing member  104  in the circumferential direction (one location). However, by providing a plurality of recesses  115  in the circumferential direction and the width direction of the pressing member  104 , it is possible that the rotation fixing position of the pressing member  104  is changed to adjust the pressure acting on the nozzle surface  37  in multiple stages. For example, the recesses  115  having different depths are formed at three positions in the circumferential direction of the pressing member  104  and the recesses  115  are used so that the three different pressures can be applied on the nozzle surface  37 . Here, the depth of the recess corresponds to the height from the side surface (projection  117 ) of the pressing member  104  to the bottom portion of the recess. 
     A second method is to change the hardness (elasticity) of the pressing member  104  as illustrated in  FIGS. 12A and 12B . In the pressing member  104  according to the second embodiment illustrated in  FIGS. 12A and 12B , the hardness of a part of the peripheral surface of the pressing member  104  is lower than the hardness of the other parts of the peripheral surface. In other words, the material of the pressing member  104  at a position facing the nozzle forming portion of the nozzle surface  37  locally (only a part in circumferential direction) includes a material with a smaller hardness. Specifically, as the material of the pressing member  104 , an elastic member such as resin and rubber is used. On a part of the pressing member  104  in the circumferential direction and the width direction, an elastic member  119  such as rubber having a hardness smaller than that of the material of the pressing member  104  is provided. For example, the elastic member  119  may be provided on the recess  115  ( FIGS. 11A and 11B ) in a part of the surface of the pressing member  104  in the circumferential direction. The surface of the elastic member  119  coincides with the shape of the side surface (projection  117 ) of the pressing member  104  having a cylindrical shape and is formed to be smoothly connected to the pressing member  104  with no step. 
     In a case where the wiping sheet  101  is pressed against the nozzle surface  37  by the pressing member  104 , a material with a smaller hardness has a smaller pressure acting on the nozzle surface than a material with a high hardness. Accordingly, the rotation fixing position of the pressing member  104  is changed so that the pressure acting on the nozzle surface  37  from the wiping sheet  101  can be selectively changed. Therefore, for example, in a case where the nozzle forming portion is further worn and water repellency is deteriorated, by changing the rotation fixing position of the pressing member  104  and pressing the wiping sheet  101  against the nozzle surface  37  by using the projection  117  of the pressing member  104  to wipe the nozzle surface  37 , it is possible to sufficiently remove the ink attached to the nozzle forming portion and the non-nozzle forming portion of the nozzle surface  37 . On the other hand, in a case where the nozzle forming portion is not worn (for example, when recording head  34  is new), by changing the rotation fixing position of the pressing member  104  and pressing the wiping sheet  101  against the nozzle surface  37  by using the elastic member  119  of the pressing member  104  to wipe the nozzle surface  37 , it is possible to remove the ink attached to the nozzle forming portion of the nozzle surface  37  using a weak pressure. 
     In a case of the pressing member  104  illustrated in  FIGS. 12A and 12B , the surface of the pressing member  104  does not have a local recess. Therefore, there is no possibility to lose a function caused by inserting ink and the like into the recess and drying the recess to generate a weak pressure. 
     As an image forming apparatus such as a printer, a facsimile, a copying machine, a plotter, and a multifunction peripheral having these functions, for example, a liquid discharge recording type image forming apparatus using a recording head to discharge ink droplets (droplets) (inkjet recording apparatus) has been known. Such an inkjet recording apparatus discharges ink droplets on the conveyance object from the nozzle of the recording head and forms an image (recording, printing, transferring, printing are also synonymous, including an action for not only applying an image having meaning such as a character and a figure on a medium but also applying an image with no meaning such as a pattern on a medium (action referred to as droplet discharge and liquid discharge for simply landing droplets on medium), and target includes two-dimensional image and three-dimensional image (stereoscopic image)). A liquid discharge head (liquid droplet discharge head) used as a recording head is a functional component which discharges and sprays liquid from the nozzle. A piezoelectric head which displaces a diaphragm by a piezoelectric actuator and the like and changes a volume in a liquid chamber to increase a pressure to discharge droplets and a thermal head which provides a heating element for generating heat by energization in a liquid chamber and increase a pressure in the liquid chamber by bubbles generated by the heating element to discharge droplets have been known. 
     In the present application, the material of the “conveyance object” is not limited to paper and includes fabric, leather, metal, plastic, glass, wood, ceramics, and the like. The term “conveyance object” is collectively used for a material referred to as a recording medium, a paper sheet, a recording sheet, and the like to which droplets are attached. Furthermore, the “liquid” discharged from the liquid discharge head is preferably liquid having viscosity and surface tension which can be discharged from the head and is not particularly limited. However, liquid is preferable which has a viscosity which becomes equal to or less than 30 mPa:s under an ordinary temperature and a normal pressure or by being heated or cooled. More specifically, the “liquid” includes a solvent such as water or an organic solvent, solution, suspension liquid, an emulsion, and the like including a coloring agent such as a dye or a pigment, a functionalizing material such as a polymerizable compound, a resin or a surfactant, a biocompatible material such as DNA, an amino acid, a protein, calcium, and the like, an edible material such as a natural colorant, and the like. For example, these kinds of liquid can be used for inkjet ink, surface treatment liquid, liquid for forming a component such as an electronic element and a light emitting element and an electronic circuit resist pattern, material liquid for three-dimensional shaping, and the like. The “liquid discharger” is an assembly of components related to liquid discharge including the liquid discharge head and other functional components and mechanisms integrated together, and includes, for example, at least one of the carriage, the head tank, the liquid supply mechanism, and the maintenance and recovery mechanism. Furthermore, the “liquid discharge apparatus” is a device for driving the liquid discharge head to discharge liquid. The liquid discharge apparatus includes not only a device which can discharge liquid to an object to which liquid can be attached but also a device for discharging liquid towards air and liquid and includes a stereoscopic modeling device, a processing liquid applying device, an injection granulating device, in addition to an image forming apparatus. 
     Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the above teachings, the present disclosure may be practiced otherwise than as specifically described herein. With some embodiments having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the present disclosure and appended claims, and all such modifications are intended to be included within the scope of the present disclosure and appended claims. 
     Each of the functions of the described embodiments may be implemented by one or more processing circuits or circuitry. Processing circuitry includes a programmed processor, as a processor includes circuitry. A processing circuit also includes devices such as an application specific integrated circuit (ASIC), digital signal processor (DSP), field programmable gate array (FPGA), and conventional circuit components arranged to perform the recited functions.