Patent Publication Number: US-11396184-B2

Title: Ink jet recording apparatus

Description:
INCORPORATION BY REFERENCE 
     This application claims priority to Japanese Patent Application No. 2019-101518 filed on May 30, 2019, the entire contents of which are incorporated by reference herein. 
     BACKGROUND 
     The present disclosure relates to an ink jet recording apparatus, and in particular to a technique to clean an ink ejection surface of a recording head. 
     Ink jet recording apparatuses are known that eject ink from a nozzle of a recording head, onto a recording medium such as a recording sheet. The ink droplet ejected from the nozzle of the recording head is separated into a main portion and minute droplets, in other words mist. The mist is highly susceptible to air resistance and carrier wind, and is therefore prone to stick to the nozzle surface of the recording head. When water-based ink is used, the mist gradually dries, thereby firmly adhering to the nozzle surface. In such a case, it is difficult to completely remove the mist by an ordinary cleaning method, such as purging the ink from the nozzle and wiping the nozzle surface several times with a rubber wiper. 
     Accordingly, an ink jet recording apparatus has been developed that includes a cleaning liquid supply device, having a cleaning liquid supply surface with a cleaning liquid supply port from which a cleaning liquid is supplied, and located upstream of the nozzle surface of the recording head in the wiping direction of the wiper. In this case, after the ink is purged from the nozzle, the nozzle surface is wiped by the wiper to which the cleaning liquid from the cleaning liquid supply port is applied. Such a mechanism for wiping the nozzle surface, with the wiper to which the cleaning liquid is applied, is useful for removing the mist stuck to nozzle surface. 
     SUMMARY 
     The disclosure proposes further improvement of the foregoing technique. 
     In an aspect, the disclosure provides an ink jet recording apparatus including a recording head, a wiper member, a cleaning liquid supply device, a cleaning liquid flow path, a driving device, and a control device. The recording head includes an ink ejection surface having an ejection port from which ink is ejected. The wiper member wipes the ink ejection surface, by moving in a predetermined wiping direction in contact with the ink ejection surface. The cleaning liquid supply device includes a cleaning liquid supply surface having a cleaning liquid supply port from which cleaning liquid for wiping the ink ejection surface with the wiper member is supplied, and is located upstream of the ink ejection surface in the wiping direction. The cleaning liquid flow path guides the cleaning liquid containing bubbles to the cleaning liquid supply device. The driving device provides force to move the cleaning liquid through the cleaning liquid flow path and squeeze out the cleaning liquid from the cleaning liquid supply port. The control device includes a processor, and acts as a controller when the processor executes a control program. The controller controls a cleaning operation performed by the wiper member to wipe the ink ejection surface with the cleaning liquid, the control of the cleaning operation including squeezing out the cleaning liquid containing bubbles from the cleaning liquid supply port, and moving the wiper member carrying the cleaning liquid containing bubbles, in the wiping direction from a movement start position to an end position ahead of the ink ejection surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front cross-sectional view showing a configuration of an ink jet recording apparatus according to a first embodiment of the disclosure. 
         FIG. 2  is a front cross-sectional view showing a state where a conveying device has been moved to a lower maintenance position, and a cleaning device has been moved to a position right under a recorder. 
         FIG. 3  is a functional block diagram showing an essential internal configuration of the ink jet recording apparatus according to the first embodiment. 
         FIG. 4A  is a schematic front view of the recorder and the conveying device. 
         FIG. 4B  is a plan view of the conveying device and the recorder. 
         FIG. 5A  is a partially seen-through side view showing a state where an ink tray and a wiper member of the cleaning device are located under the recorder. 
         FIG. 5B  is a schematic drawing showing the ink ejection surface of a recording head. 
         FIG. 6  is a schematic perspective view showing a cleaning liquid flow path for supplying a cleaning liquid to a line head. 
         FIG. 7A  is a partial perspective view of a portion of the recording head on the side of a cleaning liquid supply device, seen from an obliquely lower position. 
         FIG. 7B  is a schematic side view of the portion of the recording head on the side of the cleaning liquid supply device. 
         FIG. 8  is a flowchart showing an operation performed by the ink jet recording apparatus according to the first embodiment. 
         FIG. 9A  to  FIG. 9E  are partially seen-through side views, for explaining a cleaning operation according to the first embodiment. 
         FIG. 10  is a functional block diagram showing an essential internal configuration of the ink jet recording apparatus according to a second embodiment. 
         FIG. 11A  is a partial perspective view of the portion of the recording head on the side of the cleaning liquid supply device according to the second embodiment, seen from an obliquely lower position. 
         FIG. 11B  is a partial perspective view of the portion of the recording head on the side of the cleaning liquid supply device according to a variation of the second embodiment, seen from an obliquely lower position. 
         FIG. 12A  is a flowchart showing an operation performed by the ink jet recording apparatus according to the second embodiment. 
         FIG. 12B  is a table showing degasification information stored in a storage device. 
         FIG. 13  is a partial perspective view of the portion of the recording head on the side of the cleaning liquid supply device according to a third embodiment, seen from an obliquely lower position. 
         FIG. 14  is a schematic side view of the portion of the recording head on the side of the cleaning liquid supply device, according to a fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereafter, an ink jet recording apparatus according to a first embodiment of the disclosure will be described, with reference to the drawings.  FIG. 1  is a front cross-sectional view showing a configuration of the ink jet recording apparatus according to the first embodiment of the disclosure.  FIG. 2  is a front cross-sectional view showing a state where a conveying device has been moved to a lower maintenance position, and a cleaning device has been moved to a position right under a recorder. The ink jet recording apparatus  1  is a multifunction peripheral having a plurality of functions, such as copying, printing, scanning, and facsimile transmission, and includes an operation device  47 , a document feeding device  6 , a document reading device  5 , an image recording device  12 , a paper feeding device  14 , a paper conveyance device  19 , a conveying device  125 , and a cleaning device  8 , which are provided on or inside a main body  11 . 
     The operation device  47  is for receiving instructions from the user to execute the functions and operations that the ink jet recording apparatus  1  is configured to perform, for example an image recording operation. The operation device  47  includes a display device  473  for displaying, for example, an operation guide for the user. The display device  473  is set up as a touch panel, so that the user can operate the ink jet recording apparatus  1  by touching buttons and keys displayed on the screen. 
     To perform the document reading operation, the ink jet recording apparatus  1  operates as follows. The document reading device  5  optically reads the image on a source document delivered from the document feeding device  6  or placed on a platen glass  161 , and generates image data. The image data generated by the document reading device  5  is stored, for example, in a non-illustrated image memory. 
     The document reading device  5  includes a reading mechanism  163  having a light emitter and a charge coupled device (CDC) sensor, to illuminate a source document with the light emitter having a light source, and receive the reflected light with the CCD sensor, thereby reading the image from the source document. 
     To perform the image forming operation, the ink jet recording apparatus  1  operates as follows. The image recording device  12  forms an image on a recording sheet P, delivered from the paper feeding device  14  and transported by the paper conveyance device  19 , on the basis of the image data generated through the document reading operation, stored in the image memory, or received from a computer connected via a network. 
     The paper feeding device  14  includes a paper cassette  141 . A feed roller  145  is provided on the upper side of the paper cassette  141 , to feed the recording sheet P stored in the paper cassette  141  toward a transport route  190 . 
     The paper feeding device  14  also includes a manual bypass tray  142 , attached to a wall face of the main body  11  so as to be opened and closed. The recording sheet P set on the manual bypass tray  142  is delivered to the transport route  190  by a feed roller  146 . 
     The paper conveyance device  19  includes the transport route  190  through which the recording sheet P is transported from the paper feeding device  14  to an output tray  151 , a transport roller pair  191  located at a predetermined position on the transport route  190 , and a discharge roller pair  192 . 
     The recording sheet P delivered from the paper feeding device  14  is introduced into the transport route  190  by the transport roller pair  191 . The recording sheet P, on which an image has been formed by the image recording device  12 , is transported along an outgoing transport route  193  (part of the transport route  190 ) in a face-up orientation, and then discharged to the output tray  151  by the discharge roller pair  192 . 
     The paper conveyance device  19  also includes a non-illustrated offset mechanism, configured to displace the discharge roller pair  192  in a right angle direction with respect to the recording sheet transport direction, to shift the recording sheet P to be discharged to the output tray  151  in the width direction of the recording sheet. 
     The image recording device  12 , configured to record the image based on the document image data, on the recording sheet P delivered from the paper feeding device  14  and transported along the transport route  190 , includes a conveying device  125 , an adsorption roller  126 , a recorder  3 , and an ink tank  122 . 
     The conveying device  125  includes a drive roller  125 A, a follower roller  125 B, a tension roller  127 , and a conveyor belt  128 . The conveyor belt  128  is an endless belt, wound over the drive roller  125 A, the follower roller  125 B, and the tension roller  127 . The drive roller  125 A is driven to rotate counterclockwise by a non-illustrated motor, so that, when the drive roller  125 A is driven, the conveyor belt  128  runs counterclockwise, and the follower roller  125 B and the tension roller  127  are made to also rotate counterclockwise. 
     The tension roller  127  serves to maintain the tension of the conveyor belt  128  at an appropriate level. The adsorption roller  126  is opposed, in contact with the conveyor belt  128 , to the follower roller  125 B, and charges the conveyor belt  128  so as to electrostatically adsorb the recording sheet P, delivered from the paper feeding device  14 , to the conveyor belt  128 . 
     The recorder  3  ejects ink droplets of four different colors (black, cyan, magenta, and yellow) onto the recording sheet P being transported by the paper conveyance device  19 , thereby sequentially recording an image. In the ink tank  122 , ink of the corresponding color is loaded. 
     To be more detailed, the recorder  3  includes line heads  31 ,  32 ,  33 , and  34 , respectively corresponding to black, cyan, magenta, and yellow. Thus, the ink jet recording apparatus  1  is a line-head ink jet recording apparatus. The recorder  3  also includes a head frame  35  (see  FIG. 4A  and  FIG. 4B ) supporting the line heads  31  to  34 . The head frame  35  is supported by the main body  11 . 
     The conveying device  125  is supported by an elevation mechanism  129  from below, and moved up and downward with respect to the line heads  31  to  34 . In other words, the elevation mechanism  129  relatively moves the conveying device  125  with respect to the line heads  31  to  34 , so as to locate the conveying device  125  close to and away from the line heads  31  to  34 . More specifically, the elevation mechanism  129  moves the conveying device  125  between a recording position that enables the recorder  3  to execute printing (position shown in  FIG. 1 ), and a maintenance position displaced downward from the recording position by a predetermined distance (position shown in  FIG. 2 ). 
       FIG. 3  is a functional block diagram showing an essential internal configuration of the ink jet recording apparatus according to the first embodiment. The ink jet recording apparatus  1  includes the control device  10 , the document feeding device  6 , the document reading device  5 , the image recording device  12 , the paper feeding device  14 , the paper conveyance device  19 , the operation device  47 , the conveying device  125 , the elevation mechanism  129 , a cleaning liquid pump  130 , and the cleaning device  8 . The same components as those of the ink jet recording apparatus  1  illustrated in  FIG. 1  are denoted by the same reference numerals, and detailed description thereof will be omitted. 
     The paper feeding device  14  and the paper conveyance device  19  respectively include roller drivers  14 A and  19 A. The roller drivers  14 A and  19 A each include a motor, gears, and a driver. The roller driver  14 A serves as an energy source that gives rotative force to the feed rollers  145  and  146 . The roller driver  19 A serves as an energy source that gives rotative force to the respective drive rollers of the transport roller pair  191  and the discharge roller pair  192 . 
     The control device  10  includes a processor, a random-access memory (RAM), a read-only memory (ROM), and an exclusive hardware circuit. The processor is, for example, a central processing device (CPU), an application specific integrated circuit (ASIC), or a micro processing device (MPU). The control device  10  includes a controller  100 . 
     The control device  10  acts as the controller  100 , when the processor operates according to a control program stored in a built-in non-volatile memory. Here, the controller  100  may be constituted in the form of a hardware circuit, instead of being realized by the operation of the control device  10  according to the control program. This also applies to other embodiments, unless otherwise specifically noted. 
     The controller  100  controls the overall operation of the ink jet recording apparatus  1 . The controller  100  is connected to the document feeding device  6 , the document reading device  5 , the image recording device  12 , the paper feeding device  14 , the paper conveyance device  19 , the cleaning device  8 , the operation device  47 , the conveying device  125 , the elevation mechanism  129 , the cleaning liquid pump  130 , and the heating element  874 , to control the operation of the mentioned components. 
     The controller  100  controls, as will be subsequently described, a cleaning operation including causing a wiper member  821  to wipe an ink ejection surface  361  with cleaning liquid  831  containing bubbles. 
     As shown in  FIG. 3 , the image recording device  12  further includes a heater H 1  that heats the ink on the ink supply path leading to a recording head  36  of each of the line heads  31  to  34  shown in  FIG. 4B , and an ink temperature sensor TS 1  that detects the temperature of the ink heated by the heater H 1 . 
     The controller  100  decides whether the ink temperature detected by the ink temperature sensor TS 1  is a printable temperature, and permits, upon deciding that the ink temperature is the printable temperature, the recorder  3  to execute printing. Here, since the heater H 1  heats the ink, the ink temperature can be efficiently raised before the ink is ejected. Accordingly, an increase in viscosity of the ink can be prevented, even under a low-temperature environment. As result, the ink ejection performance can be prevented from falling below an expected level. In addition, since the printing is executed only when the ink temperature is the printable temperature, expected printing quality can be secured. Thus, the “printable temperature” refers the temperature at which the expected ink ejection performance can be realized, in other words the temperature at which the printing may be permitted. 
     The configuration of the recorder  3  will be described in detail hereunder, with reference to the drawings.  FIG. 4A  illustrates the recorder and the conveying device.  FIG. 4B  illustrates the conveying device and the recorder viewed from above. 
     As shown in  FIG. 4A , the conveying device  125  is located under the line heads  31  to  34 . The conveying device  125  conveys the recording sheet P opposed to the ink ejection surface  361 . The gap between the conveyor belt  128  and the ink ejection surface  361  is adjusted such that the gap between the surface of the recording sheet P and the ink ejection surface  361  during the printing operation becomes, for example, 1 mm. 
     The recorder  3  includes the line heads  31  to  34 , as shown in  FIG. 4B . The line heads  31  to  34  are elongate in a width direction D 2  (width direction of recording sheet P), orthogonal to the transport direction D 1  of the recording sheet P. The line heads  31  to  34  each have a width corresponding to the width of the widest recording sheet P that can be transported. The line heads  31  to  34  are fixed to the head frame  35 , at predetermined intervals along the transport direction D 1  of the recording sheet P The line heads  31  to  34  each include a plurality (e.g., three) of recording heads  36 . Accordingly, the recorder  3  has twelve recording heads  36 . 
     The recording head  36  includes a plurality of ink nozzles  37  each having an ink ejection port  371 , from which the ink is ejected. Here, although the plurality of ink nozzles  37  are simply illustrated in a single row in  FIG. 4B , actually the nozzles  37  are aligned in three rows in a checkerboard pattern, as shown in  FIG. 5B  to be subsequently referred to. The lower face of the recording head  36  is configured as the ink ejection surface  361  having the ink ejection port  371 . In this embodiment, the line head  31  includes three recording heads  36 , arranged in a checkerboard pattern along the width direction D 2 . Likewise, the remaining line heads  32  to  34  each include three recording heads  36 , arranged in a checkerboard pattern along the width direction D 2 . 
     The recorder  3  is configured to eject the ink from the ink nozzles  37  of the respective recording heads  36  onto the recording sheet P being transported by the conveying device  125 , to thereby record an image on the recording sheet P The ink may be ejected from the line heads  31  to  34  by, for example, a piezoelectric method using a piezoelectric element, or a thermal method including generating bubbles by heat. 
     As shown in  FIG. 1 , the ink tank  122  includes ink tanks  41 ,  42 ,  43 , and  44  in which black, cyan, magenta, and yellow ink is respectively stored. The ink tanks  41  to  44  are respectively connected to the line heads  31  to  34  of the corresponding color, via a non-illustrated ink tube. Thus, the ink is supplied from the ink tanks  41  to  44  to the line heads  31  to  34 , respectively. The ink employed in the ink jet recording apparatus  1  is normally formed of a solvent or water, containing a color material corresponding to each color. 
     The cleaning device  8  performs the cleaning operation (purging inclusive) when the conveying device  125  is located at the maintenance position as shown in  FIG. 2 , to thereby recover the function of the respective recording heads  36  of the line heads  31  to  34 . The cleaning device  8  includes an ink tray  81  and a wiper unit  82 , as shown in  FIG. 1  and  FIG. 5A .  FIG. 5A  is a partially seen-through side view showing a state where the ink tray and the wiper members of the cleaning device are located under the recorder.  FIG. 5B  illustrates the ink ejection surface of the recording head. 
     The ink tray  81  is for receiving the ink discharged from the ink nozzles  37  of the respective recording heads  36 . The ink tray  81  is supported by a non-illustrated first moving mechanism, so as to move in a horizontal direction (left-right direction in  FIG. 1 ). The first moving mechanism is a known drive mechanism, for example including a rack and pinion mechanism that converts the rotary motion of a gear coupled to a rotary shaft of a motor into a linear motion, to horizontally move the ink tray  81 . The ink tray  81  is usually (e.g., during the printing operation) located at a retracted position downstream of the recorder  3  in the transport direction D 1  (indicated by dash-dot lines in  FIG. 2 ). 
     When an instruction to perform the cleaning operation is inputted, the ink tray  81  is moved by the first moving mechanism, to a space opposite the line heads  31  to  34  created when the conveying device  125  is moved to the maintenance position by the elevation mechanism  129  (indicated by solid lines in  FIG. 2 ). The ink tray  81  is also supported so as to move in a vertical direction (up-down direction in  FIG. 1 ). Upon reaching the position opposite the line heads  31  to  34 , the ink tray  81  is moved upward, by the operation of the elevation mechanism  129  to move the conveying device  125  upward from the maintenance position by a predetermined distance. 
     The wiper unit  82  includes a plurality of wiper members  821  for cleaning the ink stuck to the ink ejection surface  361 , each supported by a pair of side frames  823  via a stay  822 . The wiper unit  82  is movable along the width direction D 2 . More specifically, the plurality of wiper members  821  are movable in a wiping direction D 21  from a cleaning liquid supply device  83 , in contact with the ink ejection surface  361  (see  FIG. 9  to be subsequently referred to). 
     The plurality of wiper members  821  each clean the ink ejection surface  361  with the cleaning liquid  831  (see  FIG. 9 ) supplied from the cleaning liquid supply device  83 , by moving in the wiping direction D 21 . 
     The plurality of wiper members  821  are each formed of, for example, an elastomer, in a plate shape in a thickness of 1 mm to 2 mm, and thus possess elasticity. Examples of the suitable elastomer include urethane rubber, ethylene propylene diene monomer (EPDM), nitrile rubber (NBR), styrene rubber (SBR), chloroprene rubber, silicone rubber, and fluororubber. Thus, the wiper member  821  is formed of a material that does not absorb the cleaning liquid  831 . 
     A plurality of stays  822  are arranged so as to extend in the transport direction D 1 , and coupled to the pair of side frames  823 . In this embodiment, three stays  822  are provided, and four wiper members  821  are fixed to each of the stays  822 . Thus, twelve wiper members  821  are provided, in accordance with the number of recording heads  36 . 
     The pair of side frames  823  can be moved in the width direction D 2 , by a non-illustrated second moving mechanism. The second moving mechanism is a known drive mechanism, such as a rack and pinion mechanism. For example, when rotating force is applied to a non-illustrated pinion gear, the side frame  823  acting as the rack is caused to reciprocate along the width direction D 2 . Accordingly, the entirety of the wiper unit  82 , the plurality of wiper members  821  inclusive, is caused to reciprocate along the width direction D 2 . 
     The recording head  36  includes a cleaning liquid supply device  83 , located upstream of the ink ejection surface  361  in the wiping direction D 21 , as shown in  FIG. 5A  and  FIG. 5B . The cleaning liquid supply device  83  includes a cleaning liquid supply surface  865  having a cleaning liquid supply port  834 , from which the cleaning liquid  831  for wiping the ink ejection surface is supplied to the wiper member  821 , and is located upstream of the ink ejection surface  361 , in the wiping direction D 21 . 
     The cleaning liquid supply device  83  also includes an inclined surface  866 , continuously extending from the cleaning liquid supply surface  865  to the upstream side in the wiping direction D 21 , and inclined upward with respect to the cleaning liquid supply surface  865 , toward the upstream side in the wiping direction D 21 . 
     The recorder  3  includes twelve cleaning liquid supply devices  83 , because of having twelve recording heads  36  as shown in  FIG. 4B . The twelve cleaning liquid supply devices  83  each supply the cleaning liquid  831  for cleaning the ink ejection surface  361 . The cleaning liquid supply device  83  supplies, when cleaning the ink ejection surface  361  with the wiper member  821 , the cleaning liquid  831  stored in a space  832 , through a cleaning liquid nozzle  833  communicating with the space  832 . 
     As shown in  FIG. 9A  to be subsequently referred to, the cleaning liquid  831  protrudes in a semispherical shape from the cleaning liquid supply port  834  of the cleaning liquid nozzle  833 , when supplied to clean the ink ejection surface  361 . In contrast, in occasions other than the cleaning of the ink ejection surface  361 , the cleaning liquid  831  forms a concave meniscus inside the cleaning liquid nozzle  833 . The concave meniscus can be formed by appropriately adjusting the inner diameter of the cleaning liquid nozzle  833 , and the negative pressure applied by the space  832  to the inside of the cleaning liquid nozzle  833 . 
     Further, the recording head  36  includes, as shown in  FIG. 5A  and  FIG. 5B , a scattering prevention member  84  located downstream of the ink ejection surface  361  in the wiping direction D 21 . The scattering prevention member  84  includes an inclined surface  841 , to be contacted by the wiper member  821 , after the wiper member  821  has wiped the ink ejection surface  361 . The inclined surface  841  continuously extends from the ink ejection surface  361  to the downstream side in the wiping direction D 21 , and is inclined upward with respect to the ink ejection surface  361 , toward the downstream side in the wiping direction D 21 . Accordingly, the distortion of the wiper member  821  is gradually reduced while the wiper member  821  advances in the wiping direction D 21  in contact with the inclined surface  841  of the scattering prevention member  84 , and finally the wiper member  821  is gently parted from the inclined surface  841 . Accordingly, the scattering of the liquid can be minimized, compared with the case where the scattering prevention member  84  is not provided. In addition, the scattering prevention member  84  is, for example, formed of a polyacetal resin (POM). The ink ejection surface  361  of the recording head  36  is provided with, for example, a fluorine-based water-repellent film. Therefore, the scattering prevention member  84  is less water-repellent than the ink ejection surface  361 . As result, even though the cleaning liquid remains on the scattering prevention member  84 , the droplet of the cleaning liquid is prevented from contacting the recording sheet, since the droplet has a lower height. 
     A cleaning liquid tank  85  is provided to accommodate the cleaning liquid  831 , as shown in  FIG. 5A . Here, a material obtained by eliminating the color material from the ink may be employed as the cleaning liquid  831 . In other words, a material predominantly composed of a solvent or water may be employed as the cleaning liquid  831 . A surfactant, and/or preservative and fungicide may be added to the cleaning liquid  831 , if need be. 
       FIG. 6  schematically illustrates a cleaning liquid flow path, through which the cleaning liquid is supplied to one of the line heads.  FIG. 6  shows the cleaning liquid flow path  87  for the line head  31 . The cleaning liquid flow path  87  includes pipes for conducting the cleaning liquid  831  from the cleaning liquid tank  85  to the respective cleaning liquid supply devices  83  of the three recording heads  36 . The cleaning liquid flow path  87  is provided for each of the line heads  31  to  34 . In other words, one cleaning liquid flow path  87  is provided for each color. The configuration of the cleaning liquid flow path  87  for the remaining line heads  32  to  34  is the same as that for the line head  31 . 
     The cleaning liquid flow path  87  includes vertical tubular members  871  and horizontal tubular members  872 . The vertical tubular members  871 , which are hatched in  FIG. 6 , each have one end connected to the cleaning liquid supply device  83 , and extend upward therefrom to the other end. The horizontal tubular members  872  each have one end connected to the upper end of the vertical tubular member  871 , and horizontally extend to the other end. The capacity of the horizontal tubular member  872  is, for example, five times the total capacity of the cleaning liquid supply device  83  and the vertical tubular member  871 . 
     The horizontal tubular member  872  also includes a check valve  873  that guides the cleaning liquid  831  toward the vertical tubular member  871 . The check valve  873  restricts the cleaning liquid  831  from reversely flowing toward the cleaning liquid tank  85 , thereby allowing the cleaning liquid  831  to be stably supplied. 
     Further, as shown in  FIG. 5A  and  FIG. 6 , a heating element  874  is provided on the cleaning liquid flow path  87 , to apply heat to the cleaning liquid flow path  87 . The heating element  874  is, for example, provided on each of the three vertical tubular members  871  in the cleaning liquid flow path  87 . 
       FIG. 7A  is a partial perspective view of a portion of the recording head on the side of the cleaning liquid supply device, seen from an obliquely lower position. The heating element  874  is attached to the outer circumferential portion of the vertical tubular member  871  as shown in  FIG. 5A  and  FIG. 7A , to heat the vertical tubular member  871 . The heating element  874  is, for example, a ceramic heater. The ceramic heater generates heat, when a current is supplied thereto. Here, the heating element  874  may be of a different type, such as an electric heater or a pipe heater. 
     The cleaning liquid pump  130  serves to provide the force to cause the cleaning liquid  831  to move through the cleaning liquid flow path  87 , and come out from the cleaning liquid supply port  834 . The cleaning liquid flow path  87  is connected to the output side of the cleaning liquid pump  130 , and an input side flow path connected to the cleaning liquid tank  85  is connected to the input side of the cleaning liquid pump  130 . One cleaning liquid pump  130  is provided for each cleaning liquid flow path  87 , in other words one for each color. The cleaning liquid pump  130  exemplifies the driving device in What is claimed is. 
     As shown in  FIG. 6 , flow path lengths L 1 , L 2  and L 3  from the cleaning liquid pump  130 , to the respective cleaning liquid supply devices  83  of the three recording heads  36  of the same color, are the same as each other. Accordingly, in the cleaning liquid flow path  87  composed of the vertical tubular members  871  and the horizontal tubular members  872 , the same amount of the cleaning liquid can be supplied, from each of the cleaning liquid supply devices  83 . 
     Referring to  FIG. 7A , when the cleaning liquid pump  130  applies the force to squeeze out the cleaning liquid  831  from the cleaning liquid supply port  834 , while bubbles are generated in the vertical tubular member  871  by the heat from the heating element  874 , the cleaning liquid  831  containing the bubbles in the vertical tubular member  871  is moved toward the cleaning liquid supply port  834 , and the cleaning liquid  831  containing the bubbles is squeezed out from the cleaning liquid supply port  834 .  FIG. 7B  is a schematic side view of the portion of the recording head on the side of the cleaning liquid supply device. As shown in  FIG. 7B , the controller  100  controls the cleaning operation, including causing the wiper member  821  to wipe the ink ejection surface  361  with the cleaning liquid  831  containing the bubbles. 
     Hereunder, an exemplary operation performed by the control device  10  of the ink jet recording apparatus  1  according to the first embodiment will be described, with reference to the drawings.  FIG. 8  is a flowchart showing the operation performed by the ink jet recording apparatus according to the first embodiment. 
     Referring to  FIG. 8 , the controller  100  of the control device  10  decides whether maintenance is to be started (S 1 ). More specifically, for example, when a predetermined time has elapsed after the ink jet recording apparatus  1  is turned on, without the printing operation having been started, the controller  100  decides that the maintenance is to be started (YES at S 1 ). Then the controller  100  moves the conveying device  125  to the maintenance position, and moves the cleaning device  8  to the position right under the recorder  3 , as shown in  FIG. 2 . The timing to start the maintenance is not limited to the above, but may be specified as, for example, when an instruction to turn off the ink jet recording apparatus  1  is inputted, when the operation time of the ink jet recording apparatus  1  has reached a predetermined time, or when the number of sheets printed by the ink jet recording apparatus  1  has exceeded a predetermined cumulative number of sheets. 
     Upon deciding that the maintenance is to be started (YES at S 1 ), the controller  100  executes the control of the cleaning operation (S 2 ).  FIG. 9A  to  FIG. 9E  are partially seen-through side views for explaining the cleaning operation according to the first embodiment. 
     In  FIG. 9A , the controller  100  supplies purge ink  45  to the recording head  36 , so that the purge ink  45  is discharged from the ink ejection port  371  of the ink nozzle  37 . Accordingly, thickened ink, foreign matters, and bubbles inside the ink nozzle  37  are discharged toward the ink tray  81 , together with the purge ink  45  supplied to the ink nozzle  37 . Such a purging operation eliminates clogging of the ink nozzle  37 . The ink and other substances discharged to the ink tray  81  are discharged to a predetermined waste ink deposit, from a drain port provided on the bottom portion of the ink tray  81 , through a non-illustrated ink tube. 
     When the purging operation is finished, the cleaning device  8  performs the cleaning operation, using the cleaning liquid  831  containing the bubbles. The cleaning operation is performed to wipe off the purge ink  45  stuck to the ink ejection surface  361 , and ink stuck to the proximity of the ink ejection port  371 , with the wiper member  821 . 
     In the cleaning operation, the controller  100  supplies power to the heating element  874  for a predetermined period, to cause the heating element  874  to generate heat. When the heating element  874  heats the vertical tubular member  871 , bubbles are generated in the cleaning liquid  831  in the vertical tubular member  871 . The controller  100  then squeezes out a predetermined amount (e.g., 1.5 mL) of cleaning liquid  831  containing the bubbles, so that the cleaning liquid  831  containing bubbles is made to protrude in a semispherical shape from the cleaning liquid supply port  834  of the cleaning liquid supply device  83  (see  FIG. 7A  and  FIG. 9A ). 
     Here, the predetermined amount (e.g., 1.5 mL) refers to the total dispensing amount of the line heads  31  to  34 , in other words the total for all the four colors. The cleaning liquid  831  containing bubbles may be supplied at the same time as the discharging of the purge ink  45 , or before or after the discharging of the purge ink  45 . 
     The controller  100  disconnects the power to the heating element  874 , when a predetermined time has elapsed. Alternatively, the controller  100  may control the power supply to the heating element  874 , so as to maintain the heating temperature of the heating element  874  at a predetermined level. 
     Referring to  FIG. 9B  to  FIG. 9D , upon supplying the cleaning liquid  831  containing the bubbles, the controller  100  drives the non-illustrated second moving mechanism to horizontally move the wiper unit  82  in the wiping direction D 21 . To be more detailed, the controller  100  locates the wiper member  821  at a movement start position (see  FIG. 9B ), and then moves the wiper member  821  from the movement start position as far as an end position where the wiper member  821  contacts the scattering prevention member  84  (see  FIG. 9C  and  FIG. 9D ). In this process, the wiper member  821  moves through the inclined surface  866 , the cleaning liquid supply surface  865 , and the ink ejection surface  361 , in contact therewith, until contacting the scattering prevention member  84 . 
     As shown in  FIG. 7B  and  FIG. 9D , the wiper member  821  wipes off the purge ink  45  stuck to the ink ejection surface  361 , and ink stuck to the proximity of the ink ejection port  371 , while moving along the ink ejection surface  361  in contact therewith. The residual ink and other substances wiped off by the wiper member  821  move downward together with the cleaning liquid  831  along the surface of the wiper member  821 , and then drop to the ink tray  81 . 
     Thereafter, the controller  100  drives the elevation mechanism  129  to cause the conveying device  125  to descend by a predetermined distance and return to the maintenance position, thereby moving the wiper member  821  away from the scattering prevention member  84 , as shown in  FIG. 9E . 
     The controller  100  then drives the elevation mechanism  129  to cause the conveying device  125  to descend to the maintenance position (see  FIG. 2 ), and drives the first moving mechanism to cause the ink tray  81  of the cleaning device  8  to return to the retracted position (see  FIG. 1 ). Further, the controller  100  drives the elevation mechanism  129  to cause the conveying device  125  to the recording position (position shown in  FIG. 1 ). At this point, the controller  100  finishes the operation shown in  FIG. 8 . 
     With the configuration according to the first embodiment, the heating element  874  applies heat to the cleaning liquid flow path  87 , thereby generating bubbles in the cleaning liquid flow path  87 . The controller  100  controls the cleaning operation, including wiping the ink ejection surface  361  of the recording head  36  with the wiper member  821 , using the cleaning liquid  831  containing the bubbles. Accordingly, the gas-liquid interface of the bubbles can be made to pass over the ink stuck to the proximity of the ink ejection port  371 , so that mist stuck to the nozzle surface, and the ink stuck to the proximity of the ink ejection port  371  can be effectively removed. 
     Here, with the ink jet recording apparatus according to the foregoing background art, although the mechanism for wiping the nozzle surface with the wiper carrying the cleaning liquid can effectively remove mist stuck to the nozzle surface, the mist may still remain unremoved. In addition, the ink stuck to the proximity of the ink ejection port is unable to be removed, and therefore the adhered ink is unable to be effectively removed. 
     With the configuration according to this embodiment, unlike the above, the adhered ink and other substances can be effectively removed. 
     The heating element  874  is provided in contact with the outer circumferential portion of the cleaning liquid flow path  87 , to heat the same. Therefore, the cleaning liquid flow path  87  can be directly heated, and bubbles can be efficiently and stably generated in the cleaning liquid flow path  87 . As result, the cleaning operation with the cleaning liquid  831  containing bubbles can be stably performed. 
     In addition, the heating element  874  is provided in contact with the outer circumferential portion of the vertical tubular member  871 , at a position close to the cleaning liquid supply device  83 , to heat the vertical tubular member  871 . Therefore, the vertical tubular member  871  can be directly heated, and bubbles can be efficiently and stably generated in the vertical tubular member  871 . As result, the cleaning operation with the cleaning liquid  831  containing bubbles can be stably performed. Further, the bubbles generated in the vertical tubular member  871  at the position adjacent to the cleaning liquid supply device  83  are immediately supplied thereto, and therefore the flow path of the bubbles between the position of generation and the position of use is sufficiently short, which prevents the bubbles from residing in the horizontal tubular member  872  distant from the cleaning liquid supply device  83 . 
     To control the cleaning operation, the controller  100  squeezes out the cleaning liquid  831  containing bubbles from the cleaning liquid supply port  834 , moves the wiper member  821  carrying the cleaning liquid  831  containing bubbles in the wiping direction D 21 , from the movement start position as far as the end position ahead of the ink ejection surface  361 , and then moves the wiper member  821  away from the end position. Thus, the ink ejection surface  361  of the recording head  36  is wiped by the wiper member  821  carrying the cleaning liquid  831  containing bubbles. Accordingly, the gas-liquid interface of the bubbles can be made to pass over the ink stuck to the proximity of the ink ejection port  371 , so that the mist stuck to the nozzle surface and the ink stuck to the proximity of the ink ejection port  371  can be effectively removed. In other words, when the cleaning liquid  831  containing bubbles is used for the wiping, higher cleaning performance can be attained compared with the case of wiping with the cleaning liquid  831  without the bubbles, and therefore the adhered ink and mist can be effectively removed. 
     The wiper member  821  is formed of a material that is non-absorptive of the cleaning liquid  831 , and therefore the cleaning liquid  831  containing bubbles remains on the surface of the wiper member  821 . Then the wiper member  821 , carrying the cleaning liquid  831  containing bubbles stuck to the surface, moves in the wiping direction D 21  in contact with the ink ejection surface  361 . Accordingly, the ink stuck to the proximity of the ink ejection port  371  of the ink ejection surface  361  can be effectively removed. 
     To control the cleaning operation, the controller  100  squeezes out the purge ink from the ink ejection port  371  of the recording head  36 , and also the cleaning liquid  831  containing bubbles from the cleaning liquid supply port  834 , moves the wiper member  821  carrying the cleaning liquid  831  containing bubbles in the wiping direction D 21 , from the movement start position as far as the end position ahead of the ink ejection surface  361 , and then moves the wiper member  821  away from the end position. Squeezing out the purge ink from the ink ejection port  371  contributes to eliminating clogging of the ink ejection port  371 . Then the ink ejection surface  361  of the recording head  36  is wiped by the wiper member  821  carrying the cleaning liquid  831  containing bubbles. Accordingly, the gas-liquid interface of the bubbles can be made to pass over the ink stuck to the proximity of the ink ejection port  371 , so that the mist stuck to the nozzle surface and the ink stuck to the proximity of the ink ejection port  371  can be effectively removed. 
     The inclined surface  866  of the cleaning liquid supply device  83  continuously extends from the cleaning liquid supply surface  865  toward the upstream side in the wiping direction D 21 , and is inclined upward with respect to the cleaning liquid supply surface  865 , toward the upstream side in the wiping direction D 21 . The movement start position is set to a predetermined position where the tip portion of the wiper member  821  is located right under the inclined surface  866 , and in an upper region of a plane including the cleaning liquid supply surface  865 . Such a setting allows the wiper member  821  to properly contact the cleaning liquid supply surface  865  and the ink ejection surface  361 . 
     Further, to control the cleaning operation, the controller  100  squeezes out the purge ink from the ink ejection port  371  of the recording head  36 , and also the cleaning liquid  831  from the cleaning liquid supply port  834 , moves the wiper member  821  in the wiping direction D 21  from the movement start position and through the ink ejection surface  361 , until reaching the end position where the wiper member  821  contacts the scattering prevention member  84 , and then moves the wiper member  821  away from the end position. Since the wiper member  821  is moved away from the scattering prevention member  84 , the liquid (ink and/or cleaning liquid) is kept from remaining on the ink ejection surface  361 . In addition, the scattering prevention member  84  prevents the liquid from splashing around, when the wiper member  821  is parted from the end position. 
     Hereunder, the ink jet recording apparatus  1  according to a second embodiment will be described.  FIG. 10  is a functional block diagram showing an essential internal configuration of the ink jet recording apparatus according to the second embodiment.  FIG. 11A  is a partial perspective view of the portion of the recording head on the side of the cleaning liquid supply device according to the second embodiment, seen from an obliquely lower position. 
     In the first embodiment, the single-purpose heating element  874  for generating bubbles (see  FIG. 3 ) is provided on the cleaning liquid flow path  87 . In the second embodiment, however, the heater H 1  of the recording head  36  is utilized to generate bubbles in the cleaning liquid flow path  87  as shown in  FIG. 11A , instead of providing the heating element  874  as in the first embodiment. 
     The heater H 1  is provided, as shown in  FIG. 11A , on the face of the recording head  36  opposed to the vertical tubular member  871 . The heater H 1  serves, as in the first embodiment, to heat the ink on the ink supply path leading to the recording head  36 . The cleaning liquid flow path  87  is installed such that the vertical tubular member  871 , a part thereof, is located within a range where the heat from the heater H 1  can reach. Accordingly, the heat of the heater H 1  is transmitted by the convection of gas (air) present between the heater H 1  and the cleaning liquid flow path  87  (more accurately, vertical tubular member  871 ), so that the vertical tubular member  871  is heated. In other words, the vertical tubular member  871  can be heated because of the transmission of the hot air from the heater H 1  to the vertical tubular member  871 . 
     Here, the recording head  36  may further include an enclosure member CV for conducting the hot air from the heater H 1  toward the vertical tubular member  871 , as shown in  FIG. 11B .  FIG. 11B  is a partial perspective view of the portion of the recording head on the side of the cleaning liquid supply device according to a variation of the second embodiment, seen from an obliquely lower position. The enclosure member CV is located so as to enclose the space between the heater H 1  and the vertical tubular member  871 , and therefore a larger portion of the hot air from the heater H 1  can be transmitted to the vertical tubular member  871 . 
     Further, the control device  10  acts also as a storage device  101 , in addition to the controller  100 , when the processor executes the control program, for example stored in a built-in non-volatile memory. The storage device  101  may be a storage device such as a HDD. 
     Hereunder, an operation performed by the control device  10  of the ink jet recording apparatus  1  according to the second embodiment will be described, with reference to the drawings.  FIG. 12A  is a flowchart showing an operation performed by the ink jet recording apparatus according to the second embodiment.  FIG. 12B  is a table showing degasification information stored in a storage device. 
     The degasification information shown in  FIG. 12B , indicating whether the cleaning liquid  831  stored in the cleaning liquid tank  85  is degassed, is stored in advance in the storage device  101 . More specifically, the storage device  101  contains the degasification information that indicates “undegassed” when the cleaning liquid  831  in the cleaning liquid tank  85  has not been degassed, and the degasification information that indicates “degassed” when the cleaning liquid  831  in the cleaning liquid tank  85  has been degassed. 
     The steps S 1  and S 2  in  FIG. 12A  are the same as those of the first embodiment, and therefore the steps S 31  to S 33  in  FIG. 12A  will be described hereunder. 
     Upon deciding that the maintenance is to be started (YES at S 1 ), the controller  100  decides whether the cleaning liquid has been degassed (S 31 ). More specifically, the controller  100  reads out the degasification information stored in the storage device  101  (see  FIG. 12B ), and decides that the cleaning liquid has not been degassed, when the degasification information indicates “undegassed” (NO at S 31 ). 
     When the storage device  101  indicates that the cleaning liquid has not been degassed, the controller  100  decides whether the ink temperature detected by the ink temperature sensor TS 1  accords with the printable temperature (S 32 ). Upon deciding that the ink temperature accords with the printable temperature (YES at S 32 ), the controller  100  performs the control of the cleaning operation (S 2 ). Upon deciding that the ink temperature does not accord with the printable temperature (NO at S 32 ), the operation returns to S 32 , and the controller  100  stands by for the decision that the ink temperature accords with the printable temperature, before starting the control of the cleaning operation. 
     In contrast, when the degasification information stored in the storage device  101  (see  FIG. 12B ), read out at S 31 , indicates that the cleaning liquid has been degassed, the controller  100  decides that the cleaning liquid has been degassed (YES at S 31 ). 
     When the storage device  101  indicates that the cleaning liquid has been degassed (YES at S 31 ), the controller  100  decides whether the ink temperature detected by the ink temperature sensor TS 1  accords with a specified temperature higher than the printable temperature (S 33 ). Upon deciding that the ink temperature accords with the specified temperature higher than the printable temperature (YES at S 33 ), the controller  100  performs the control of the cleaning operation (S 2 ). Upon deciding that the ink temperature does not accord with the specified temperature (NO at S 33 ), the operation returns to S 33 , and the controller  100  stands by for the decision that the ink temperature accords with the specified temperature, before starting the control of the cleaning operation. 
     With the configuration according to the second embodiment, the heat of the heater H 1  is transmitted by the convection of the gas present between the heater H 1  and the cleaning liquid flow path  87  (more accurately, vertical tubular member  871 ), and thus heats the vertical tubular member  871 . Therefore, the heater H 1  of the recording head  36  can be effectively utilized, because the heat of the heater H 1  is also used to generate bubbles in the cleaning liquid flow path  87 . Further, the mentioned configuration eliminates the need to additionally provide the heating element  874  exclusively for the cleaning liquid flow path  87 , thereby suppressing an increase in number of parts. 
     The vertical tubular member  871 , a part of the cleaning liquid flow path  87 , is located within the reach of the heat from the heater H 1 , thus to be heated thereby. It was confirmed that, in the case where the cleaning liquid  831  in the cleaning liquid flow path  87  has not been degassed, bubbles were generated in the cleaning liquid  831  in the vertical tubular member  871 , when the ink temperature detected by the ink temperature sensor TS 1  reaches the printable temperature. When the storage device  101  indicates that the cleaning liquid has not been degassed, the controller  100  decides whether the ink temperature detected by the ink temperature sensor TS 1  accords with the printable temperature, and upon deciding that the ink temperature accords with the printable temperature, the controller  100  performs the control of the cleaning operation. Accordingly, the ink ejection surface  361  can be cleaned with the cleaning liquid  831  containing bubbles, and the ink stuck to the proximity of the ink ejection port  371  can be effectively removed. On the other hand, upon deciding that the ink temperature does not accord with the printable temperature, the controller  100  stands by for the decision that the ink temperature accords with the printable temperature, before starting the control of the cleaning operation. Such an arrangement prevents the cleaning liquid  831  without bubbles from being used to clean the ink ejection surface  361 , thereby ensuring that the cleaning liquid  831  containing bubbles is utilized for the cleaning operation. 
     It was also confirmed that, in the case where the cleaning liquid  831  in the cleaning liquid flow path  87  has been degassed, bubbles were not generated despite the ink temperature detected by the ink temperature sensor TS 1  having reached the printable temperature, but that bubbles were generated in the cleaning liquid  831  in the vertical tubular member  871 , when the ink temperature reaches the specified temperature higher than the printable temperature. Accordingly, when the storage device  101  indicates that the cleaning liquid has been degassed, the controller  100  decides whether the ink temperature detected by the ink temperature sensor TS 1  accords with the specified temperature higher than the printable temperature, and upon deciding that the ink temperature accords with the specified temperature, the controller  100  performs the control of the cleaning operation. Therefore, the ink ejection surface  361  can be cleaned with the cleaning liquid  831  containing bubbles, and the ink stuck to the proximity of the ink ejection port  371  can be effectively removed. On the other hand, upon deciding that the ink temperature does not accord with the specified temperature, the controller  100  stands by for the decision that the ink temperature accords with the specified temperature, before starting the control of the cleaning operation. Such an arrangement prevents the cleaning liquid  831  without bubbles from being used to clean the ink ejection surface  361 , thereby ensuring that the cleaning liquid  831  containing bubbles is utilized for the cleaning operation. 
     Hereunder, the ink jet recording apparatus  1  according to a third embodiment will be described.  FIG. 13  is a partial perspective view of the portion of the recording head on the side of the cleaning liquid supply device according to the third embodiment, seen from an obliquely lower position. 
     In the first embodiment, the check valve  873  is provided on the horizontal tubular member  872  (see  FIG. 6 ), to conduct the cleaning liquid  831  toward the cleaning liquid supply device  83 . The third embodiment is different from the first embodiment, in that the check valve  873  is located upstream of the heating element  874  attached to the vertical tubular member  871 , as shown in  FIG. 13 . 
     According to the third embodiment, the check valve  873  is located upstream of the heating element  874  attached to the vertical tubular member  871 . In other words, the check valve  873  is located upstream of the position where the cleaning liquid flow path  87  is heated by the heating element  874 . Such a configuration prevents the bubbles generated in the vertical tubular member  871  from reaching the horizontal tubular member  872 , in other words from reversely flowing. 
     Although the check valve  873  is only provided on the vertical tubular member  871  in the third embodiment, the check valve  873  may be provided on each of the horizontal tubular member  872  and the vertical tubular member  871 . 
     Hereunder, the ink jet recording apparatus  1  according to a fourth embodiment will be described.  FIG. 14  is a schematic side view of the portion of the recording head on the side of the cleaning liquid supply device, according to the fourth embodiment. 
     Although the wiper member  821  according to the first embodiment is formed of a material that is non-absorptive of the cleaning liquid  831 , the fourth embodiment is different from the first embodiment in that a wiper member  821 A formed of a material absorptive of the cleaning liquid  831  is employed, as shown in  FIG. 14 . 
     The wiper member  821 A is, for example, formed of an absorptive non-woven cloth, such as a wipe cloth. Here, it suffices that the wiper member  821 A includes the absorptive non-woven cloth, at least around an outer portion. 
     Further, the wiper member  821 A may include a rotary shaft oriented in the direction orthogonal to the wiping direction D 21  (e.g., transport direction D 1  of the recording sheet P shown in  FIG. 4B ), and the absorptive non-woven cloth may be attached to the outer circumferential surface of the rotary shaft. In this case, the wiper member  821 A wipes the ink ejection surface  361  by rotating about the rotary shaft, while moving in the wiping direction D 21 . Alternatively, the wiper member  821 A may be configured to wipe the ink ejection surface  361 , without rotating. 
     Since the wiper member  821 A is formed of a material absorptive of the cleaning liquid  831  according to the fourth embodiment, the cleaning liquid  831  containing bubbles is absorbed into the wiper member  821 A. Then the cleaning liquid  831  containing bubbles is continuously squeezed out toward the ink ejection surface  361 , from inside of the wiper member  821 A (i.e., the non-woven cloth in which the cleaning liquid  831  has been absorbed), while the wiper member  821 A carrying the cleaning liquid  831  containing bubbles moves in the wiping direction D 21  in contact with the ink ejection surface  361 . Therefore, the cleaning capability can be maintained during the travel in the wiping direction D 21 , and resultantly the cleaning performance can be improved. 
     The disclosure may be modified in various manners, without limitation to the foregoing embodiments. For example, although the MFP is taken up in the foregoing embodiments as an example of the ink jet recording apparatus according to the disclosure, the disclosure is also applicable to various other ink jet recording apparatuses having a printing function. 
     Further, the configurations and processings described in the foregoing embodiments with reference to  FIG. 1  and  FIG. 14  are merely exemplary, and in no way intended to limit the disclosure to those configurations and processings. 
     While the present disclosure has been described in detail with reference to the embodiments thereof, it would be apparent to those skilled in the art the various changes and modifications may be made therein within the scope defined by the appended claims.