Patent Publication Number: US-8967759-B2

Title: Image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on and claims priority pursuant to 35 U.S.C. §119 to Japanese Patent Application No. 2013-045956, filed on Mar. 7, 2013, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein. 
     BACKGROUND 
     1. Technical Field 
     Embodiments of this disclosure relate to an image forming apparatus. 
     2. Description of the Related Art 
     Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having at least one of the foregoing capabilities. As one type of image forming apparatus employing a liquid-ejection recording method, inkjet recording apparatuses are known that use a recording head (liquid ejection head or liquid-droplet ejection head) for ejecting droplets of ink or other liquid. 
     For example, a liquid-ejection type image forming apparatus has an ejection detector to detect a state of droplet ejection from a recording head. When faulty droplet ejection is detected on a nozzle(s), the image forming apparatus performs maintenance and recovery operation (maintenance operation) on the recording head, such as cleaning of a nozzle face. 
     For example, an ejection detector detects ejection or non-ejection by measuring an electric change when liquid droplets ejected from a recording head land on an electrode plate (see JP-2007-050533-A). 
     In addition, JP-2004-306475-A proposes to clean such an electrode plate by a wiping member to wipe the plate in the same direction as a moving direction of a carriage. 
     For the above-described configuration in which detection or non-detection is detected based on an electric change generated by liquid droplets ejected onto an electrode plate, liquid droplets adhere to the electrode plate in the detection of droplet ejection. Such liquid droplets ejected from nozzles of the recording head in the detection of droplet ejection are a minute amount of droplets. 
     Thus, as described in JP-2004-306475-A, even when a wiping member wipes the electrode plate in the same direction as the moving direction of the carriage, that is, in a direction perpendicular to a nozzle array direction in which nozzles are arrayed in the recording head, droplets may not be collected on the wiping member, thus adhering the wiping member as separate droplets. 
     As a result, waste liquid adhering to the wiping member may solidify, thus reducing the wiping performance of the wiping member and hampering cleaning of the electrode plate and accurate ejection detection. 
     BRIEF SUMMARY 
     In at least one exemplary embodiment of this disclosure, there is provided an image forming apparatus including a recording head, an ejection detection unit, a cleaner, and a holder member. The recording head has a plurality of nozzles to eject droplets and a nozzle face in which the plurality of nozzles is formed. The ejection detection unit detects ejection or non-ejection of the droplets from the plurality of nozzles of the recording head. The ejection detection unit has an electrode member disposed in an area in which the electrode member is opposable to the recording head. The droplets ejected from the plurality of nozzles of the recording head land on the electrode member. The cleaner cleans the electrode member. The cleaner includes a cleaning member to remove droplets adhering to the electrode member. The ejection detection unit detects ejection or non-ejection of the droplets from the plurality of nozzles by detection of electric changes of the electrode member generated when the droplets ejected from the plurality of nozzles of the recording head land on the electrode member in a state in which a potential difference is created between the nozzle face of the recording head and the electrode member and the nozzle face of the recording head is opposed to the electrode member. The holder member supports the electrode member, and holds the cleaning member movable in parallel to a nozzle array direction in which the plurality of nozzles is arrayed in the recording head. 
    
    
     
       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 plan view of a mechanical section of an image forming apparatus according to an exemplary embodiment of this disclosure; 
         FIG. 2  is a partial side view of the mechanical section illustrated in  FIG. 1 ; 
         FIG. 3  is a schematic view of recording heads of the image forming apparatus according to an exemplary embodiment of this disclosure; 
         FIG. 4  is a side view of a mounting structure of an ejection detection unit of the image forming apparatus according to an exemplary embodiment of this disclosure; 
         FIG. 5  is a block diagram of a controller of the image forming apparatus according to an exemplary embodiment of this disclosure; 
         FIG. 6  is a block diagram of an ejection detector of the controller according to an exemplary embodiment of this disclosure; 
         FIG. 7  is a perspective view of an ejection detection unit according to an exemplary embodiment of this disclosure; 
         FIG. 8  is a perspective view of the ejection detection unit of  FIG. 7  seen from an opposite side of  FIG. 7 ; 
         FIG. 9  is a partial front view of the ejection detection unit of  FIG. 7 ; 
         FIG. 10  is a perspective view of an ejection detection unit according to an exemplary embodiment of this disclosure; 
         FIG. 11  is a cross-sectional view of the ejection detection unit cut along A-A line of  FIG. 10 ; 
         FIG. 12  is a perspective view of an ejection detection unit according to an exemplary embodiment of this disclosure; 
         FIG. 13  is a perspective view of an ejection detection unit according to an exemplary embodiment of this disclosure; 
         FIG. 14  is a partial side view of an ejection detection unit according to an exemplary embodiment of this disclosure; 
         FIG. 15  is a perspective view of an ejection detection unit according to an exemplary embodiment of this disclosure; 
         FIG. 16  is a side view of the ejection detection unit of  FIG. 15  during operation of a wiping member; 
         FIG. 17  is a side view of an ejection detection unit during operation of a wiping member according to an embodiment of this disclosure; 
         FIG. 18A  is a plan view of a wiper during wiping operation according to a comparative example of this disclosure; 
         FIG. 18B  is a side view of the wiper of  FIG. 18A  during wiping operation; 
         FIG. 19A  is a plan view of a wiper during wiping operation according to an embodiment of this disclosure; and 
         FIG. 19B  is a side view of the wiper of  FIG. 19A  during wiping operation. 
     
    
    
     The accompanying drawings are intended to depict exemplary 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 OF EXEMPLARY EMBODIMENTS 
     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. 
     For example, in this disclosure, the term “sheet” used herein is not limited to a sheet of paper and includes anything such as OHP (overhead projector) sheet, cloth sheet, glass sheet, or substrate on which ink or other liquid droplets can be attached. In other words, the term “sheet” is used as a generic term including a recording medium, a recorded medium, a recording sheet, and a recording sheet of paper. The terms “image formation”, “recording”, “printing”, “image recording” and “image printing” are used herein as synonyms for one another. 
     The term “image forming apparatus” refers to an apparatus that ejects liquid on a medium to form an mage on the medium. The medium is made of, for example, paper, string, fiber, cloth, leather, metal, plastic, glass, timber, and ceramic. The term “image formation” includes providing not only meaningful images such as characters and figures but meaningless images such as patterns to the medium (in other words, the term “image formation” also includes only causing liquid droplets to land on the medium). 
     The term “ink” is not limited to “ink” in a narrow sense, unless specified, but is used as a generic term for any types of liquid usable as targets of image formation. For example, the term “ink” includes recording liquid, fixing solution, DNA sample, resist, pattern material, resin, and so on. 
     The term “image” used herein is not limited to a two-dimensional image and includes, for example, an image applied to a three dimensional object and a three dimensional object itself formed as a three-dimensionally molded image. 
     Although the exemplary embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the invention and all of the components or elements described in the exemplary embodiments of this disclosure are not necessarily indispensable to the present invention. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, exemplary embodiments of the present disclosure are described below. 
     Below, an image forming apparatus according to some exemplary embodiments of this disclosure is described below with reference to  FIGS. 1 and 2 . 
       FIG. 1  is a partial plan view of a mechanical section of an image forming apparatus according to an exemplary embodiment of this disclosure.  FIG. 2  is a partial side view of the mechanical section illustrated in  FIG. 1 . 
     In this embodiment, the image forming apparatus is a serial-type inkjet recording apparatus. In the image forming apparatus, a carriage  3  is supported by a main guide member  1  and a sub guide rod  2  so as to be movable in a direction (main scanning direction) indicated by an arrow MSD in  FIG. 1 . The main guide member  1  and the sub guide member  2  extend between left and right side plates. A main scanning motor  5  reciprocally moves the carriage  3  for scanning in the main scanning direction MSD via a timing belt  8  extending between a driving pulley  6  and a driven pulley  7 . 
     The carriage  3  mounts recording heads  4   a  and  4   b  (collectively referred to as “recording heads  4 ” unless distinguished) serving as liquid ejection heads for ejecting liquid droplets. The recording heads  4  eject, for example, ink droplets of different colors, such as yellow (Y), cyan (C), magenta (M), and black (K). The carriage  3  mounts the recording heads  4  so that nozzle rows, each of which includes multiple nozzles  4   n , are arranged in a sub scanning direction (indicated by an arrow SSD in  FIG. 1 ) perpendicular to the main scanning direction MSD and ink droplets are ejected downward from the nozzles. 
     As illustrated in  FIG. 3 , each recording head  4  has two nozzle rows Na and Nb, each of which is formed of multiple nozzles  4   n . For example, one (nozzle row Na) of the nozzle rows of the recording head  4   a  ejects droplets of black (K), and the other (nozzle row Nb) ejects droplets of cyan (C). One (nozzle row Na) of the nozzle rows of the recording head  4   a  ejects droplets of magenta (M), and the other (nozzle row Nb) ejects droplets of yellow (Y). 
     For example, piezoelectric actuators such as piezoelectric elements or thermal actuators that generate film boiling of liquid (ink) using electro/thermal converting elements, such as heat-generation resistant, to cause a phase change may be employed as the liquid ejection heads forming the recording heads  4 . 
     The carriage  3  mounts head tanks  40  to temporarily store ink to be supplied to the recording heads  4 . Different color inks are supplied from ink cartridges (main tanks) to the head tanks  40 . 
     The image forming apparatus has a conveyance belt  12  serving as a conveyance device to convey a sheet  10  at a position opposing the recording heads  4  while adhering the sheet  10  thereon by static electricity. The conveyance belt  12  is an endless belt that is looped between a conveyance roller  13  and a tension roller  14 . 
     The conveyance roller  13  is rotated by a sub-scanning motor  16  via a timing belt  17  and a timing pulley  18  to circulate the conveyance belt  12  in the sub-scanning direction SSD illustrated in  FIG. 1 . A charging roller  31  charges (supplies electric charges to) the conveyance belt  12  during circulation of the conveyance belt  12 . 
     At one end in the main scanning direction MSD of the carriage  3 , a maintenance assembly (maintenance-and-recovery assembly)  20  is disposed near a lateral side of the conveyance belt  12  to perform maintenance and recovery on the recording heads  4 . At the opposite end in the main scanning direction MSD, a first dummy ejection receptacle  21  is disposed at the opposite lateral side of the conveyance belt  12  to receive liquid droplets ejected from the recording heads  4  by dummy ejection in which liquid droplets not contributing to image formation are ejected for maintenance, e.g., removal of viscosity-increased liquid or bubbles. 
     The maintenance assembly  20  includes cap members  20   a  to cap, for example, nozzle faces (nozzle formed faces)  41  of the recording heads  4 , a wiper member  20   b  to wipe the nozzle faces  41 , and a second dummy ejection receptacle to store liquid droplets not contributing to image formation. 
     An ejection detection unit  100  includes an ejection detector to detect ejection and non-ejection of droplets and a cleaner according to an exemplary embodiment of this disclosure. The ejection detection unit  100  is disposed in an area outside a recording region between the conveyance belt  12  and the maintenance assembly  20 , in which the ejection detection unit  100  can oppose the recording heads  4 . 
     An encoder scale  23  having a predetermined pattern extends between the side plates along the main scanning direction MSD of the carriage  3 , and the carriage  3  has a main-scanning encoder sensor  24  serving as a transmissive photosensor to read the pattern of the encoder scale  23 . The encoder scale  23  and the main-scanning encoder sensor  24  form a linear encoder (main scanning encoder) to detect movement of the carriage  3 . 
     A code wheel  25  is mounted on a shaft of the conveyance roller  13 , and a sub-scanning encoder sensor  26  serving as a transmissive photosensor is provided to detect a pattern of the code wheel  25 . The code wheel  25  and the sub-scanning encoder sensor  26  form a rotary encoder (sub scanning encoder) to detect the movement amount and movement position of the conveyance belt  12 . 
     In addition, as illustrated in  FIG. 2 , a discharge roller  51  and a spur roller  52  are disposed at a downstream side of the conveyance belt  12  from the driven roller  14 . The discharge roller  51  and the spur roller  52  feed, to an output tray, a sheet  10  having an image formed thereon. 
     In the image forming apparatus having the above-described configuration, a sheet  10  is fed from a sheet feed tray, attached on the conveyance belt  12  charged, and conveyed in the sub-scanning direction SSD with the circulation of the conveyance belt  12 . 
     By driving the recording heads  4  in response to image signals while moving the carriage  3  in the main scanning direction MSD, ink droplets are ejected onto the sheet  10  stopped to form one line of a desired image. Then, the sheet  10  is fed by a certain distance to prepare for the next operation to record another line of the image. Receiving a signal indicating that the image recording has been completed or a rear end of the sheet  10  has arrived at the recording region, the image forming apparatus finishes the recording operation and outputs the sheet  10  to a sheet output tray. 
     Next, a mounting structure of an ejection detection unit according to an exemplary embodiment is described with reference to  FIG. 4 . 
       FIG. 4  is a side view of an ejection detection unit  100  according to an exemplary embodiment of this disclosure. 
     The ejection detection unit  100  includes an electrode plate  101  and a holder member  103 . The electrode plate  101  serves as an electrode member on which liquid droplets from the recording heads  4  for ejection detection adhere. The holder member  103  serves as a holding member to hold the electrode plate  101  thereon, and is made of an insulation material, such as plastic. 
     The electrode plate  101  is preferably, for example, a conductive metal plate made of a material which is rustproof and resistant to ink. The electrode plate  101  may be, for example, stainless steel (SUS)  304  or copper alloy plated with nickel (Ni) or palladium (Pd). A surface of the electrode plate  101  on which liquid droplets adhere is preferably finished to be water repellent. 
     Here, to detect droplet ejection at stable detection accuracy, a clearance H between the nozzle face  41  of each recording head  4  and the electrode plate  101  is preferably maintained constant regardless of the positions of the nozzles. 
     Hence, in this embodiment, the holder member  103  is fastened to the main guide member  1  and the sub guide member  2 , which support the carriage  3 , with screws  81  and  82 , respectively. 
     Such a configuration allows the clearance H between the nozzle face  41  of each recording head  4  and the electrode plate  101  to be maintained constant regardless of the positions of the nozzles, thus stabilizing detection accuracy. 
     Next, an outline of a controller of an image forming apparatus according to an exemplary embodiment is described with reference to  FIG. 5 . 
       FIG. 5  is a block diagram of a controller  500  of an image forming apparatus according to an exemplary embodiment. 
     The controller  500  includes a main control unit  500 A including a central processing unit (CPU)  501 , a read-only memory (ROM)  502 , and a random access memory (RAM)  503 . The CPU  501  controls the entire image forming apparatus. The ROM  502  stores programs executed by the CPU  501  and other Fixed data. The RAM  503  temporarily stores image data and other data. 
     The controller  500  has a host interface (IT)  506  to transmit and receive data to and from a host (information processing device)  600 , such as a personal computer (PC), an image output control unit  511  to control driving of the recording heads  4 , and an encoder analyzer  512 . The encoder analyzer  512  receives and analyzes detection signals from the main-scanning encoder sensor  24  and the sub-scanning encoder sensor  26 . 
     The controller  500  includes a main-scanning motor driver  513  to drive the main scan motor  5 , a sub scanning motor driver  514  to drive the sub-scanning motor  16 , and an input/output (I/O) unit  516  between various sensors and actuators  517 . 
     The controller  500  also includes an ejection detector  531  to measure (detect) electric changes caused when liquid droplets land on the electrode plate  101  of the ejection detection unit  100  to determine ejection or non-ejection. The controller  500  further includes a cleaner driver  532  to drive a driving motor  210  to move a cleaner  200 . The cleaner  200  cleans the electrode plate  101  of the ejection detection unit  100 . 
     The image output control unit  511  includes a data generator to generate print data, a driving waveform generator to generate driving waveforms to control driving of the recording heads  4 , and a data transmitter to transmit print data and head control signals for selecting desired driving signals from the driving waveforms. The image output control unit  511  outputs the driving waveforms, the head control signals, print data and so on to a head driver  51 , which is a head driving circuit for driving the recording heads  4  mounted on the carriage  3 , to eject liquid droplets from nozzles of the recording heads  4  in accordance with print data. 
     The encoder analyzer  512  includes a direction detector  520  to detect a movement direction of the carriage  3  from detection signals and a counter  521  to detect a movement amount of the carriage  3 . 
     Based on analysis results transmitted from the encoder analyzer  512 , the controller  500  controls driving of the main scanning motor  5  via a the main scanning motor driver  513  to control movement of the carriage  3 . The controller  500  also controls driving of the sub-scanning motor  16  via a sub scanning motor driver  514  to control feeding of the sheet  10 . 
     In detection of ejection of droplets from the recording heads  4 , the main control unit  500 A of the controller  500  controls the recording heads  4  to move and eject droplets from desired nozzles of the recording heads  4 , and determines droplet ejection states based on detection signals from the ejection detector  531 . 
     Next, an outline of the ejection detector  531  according to an exemplary embodiment of this disclosure is described with reference to  FIG. 6 . 
     The electrode plate  101  onto which liquid droplets for ejection detection are ejected from the recording heads  4  is connected to the ejection detector  531 . The ejection detector  531  has a high-voltage power source  701  to supply a high voltage VE (e.g., 750V) to the electrode plate  101 . The main control unit  500 A control on and off states of the high-voltage power source  701 . 
     The ejection detector  531  also has a band pass filter (BPF)  702  to input signals involving electric changes when liquid droplets land on the electrode plate  101 , an amplification (AMP) circuit  703  to amplify the signals, and an analog-digital converter (ADC)  704  to convert the amplified signals from analog format to digital format. Resultant converted signals of the ADC  704  are input to the main control unit  500 A. 
     When ejection detection is performed, the nozzle face  41  of one of the recording heads  4  is placed to oppose the electrode plate  101 . A high voltage VE is supplied to the electrode plate  101  to generate a potential difference between the nozzle face  41  and the electrode plate  101 . At this time, the nozzle face  41  of the recording head  4  is negatively charged while the electrode plate  101  is positively charged. 
     In such a state, a liquid droplet(s) for ejection detection is (are) ejected from each nozzle of the recording heads  4 . 
     At this time, since liquid droplets are ejected from the nozzle face  41  negatively charged, the liquid droplets are also negatively charged. When the liquid droplets negatively charged land on the electrode plate  101 , the voltage of the high voltage VE supplied to the electrode plate  101  slightly changes. 
     The band-pass filter  702  extracts the voltage change (alternative current (AC) component) and the amplification circuit  703  amplifies the AC component. The ADC  704  converts the amplified component from analog format to digital format and inputs the converted data as a measurement result (detection result) to the main control unit  500 A. 
     The main control unit  500 A determines whether the measurement result (voltage change) is greater than a preset threshold value, and if the measurement result is greater than the threshold value, the main control unit  500 A determines that a detected nozzle of the recording heads  4  has ejected a liquid droplet(s). By contrast, if the measurement result is not greater than the threshold value, the main control unit  500 A determines that a detected nozzle of the recording heads  4  has not ejected a liquid droplet(s). 
     In this embodiment, since a liquid droplet(s) is (are) ejected from each nozzle of the recording heads  4  to land on the electrode plate  101 , it takes approximately 0.5 milliseconds (msec) to approximately 10 msec to determine ejection or non-ejection of a single nozzle. After ejection or non-ejection of all nozzles is determined, the high voltage VE supplied to the electrode plate  101  is turned into off state. 
     Next, an ejection detection unit according to an exemplary embodiment of this disclosure is described with reference to  FIGS. 7 to 9 . 
       FIG. 7  is a perspective view of an ejection detection unit according to an exemplary embodiment of this disclosure.  FIG. 5  is a perspective view of the ejection detection unit of  FIG. 7  seen from the opposite side of  FIG. 7 .  FIG. 9  is a front view of the ejection detection unit of  FIG. 7 . 
     In this embodiment, the cleaner  200  includes a cleaning member  202  to contact a surface of an electrode plate  101  and remove droplets (waste liquid) adhering to the surface of the electrode plate  101  while scraping the droplets off. 
     The cleaning member  202  has a cleaning portion  203  and a guide portion  204 . The cleaning portion  203  contacts a surface of the electrode plate  101 . The guide portion  204  supports the cleaning portion  203  and movably engages a guide groove  110  formed at each side face of a holder member  103  in a nozzle array direction (sub-scanning direction) in which nozzles of a recording head are arrayed in line. In this embodiment, the cleaning portion  203  and the guide portion  204  are integrally molded as a single member. 
     A driving assembly to move the cleaning member  202  includes, e.g., a driving motor  210 , a pulley  211 , a pulley  212 , and a driving belt  213 . The driving motor  210  is disposed at an end of the holder member  103  in the sub-scanning direction. The pulley  211  is disposed on a motor shaft of the driving motor  210 . The pulley  212  is disposed at the other end of the holder member  103  in the sub-scanning direction. The driving belt  213  is wound around and between the pulley  211  and the pulley  212 . 
     The cleaning member  202  has a clamp portion  202   a  to sandwich and clamp the driving belt  213 . 
     Thus, by driving the driving motor  210 , the cleaning member  202  is reciprocally moved in the sub-scanning direction (i.e., a direction parallel to the nozzle array direction) to remove ink droplets landed on the surface of the electrode plate  101 . 
     In this embodiment, the positions of a wiping surface (contact surface) of the cleaning portion  203  of the cleaning member  202  and the surface of the electrode plate  101  are defined by a distance L between an upper surface of the guide groove  110 , which is formed at each side face of the holder member  103  in the nozzle array direction, and the wiping surface of the cleaning portion  203 , which contacts the surface of the electrode plate  101 . Here, the upper surface of the guide groove  110  serves as a reference surface RS. In other words, the positions of the wiping surface (contact surface) of the cleaning portion  203  of the cleaning member  202  and the surface of the electrode plate  101  are defined by only a dimension L of the cleaning member  202  and a dimension L of the holder member  103  including the electrode plate  101 . 
     Such a configuration allows simple and accurate positioning of the distance between the cleaning member  202  and the electrode plate  101 . 
     As a result, ink droplets ejected on the electrode plate  101  can be reliably removed, thus allowing ejection detecting performance to be maintained in good condition over a long period of time. 
     Next, an ejection detection unit according to an embodiment of this disclosure is described with reference to  FIGS. 10 and 11 . 
       FIG. 10  is a perspective view of an ejection detection unit according to an embodiment of this disclosure.  FIG. 11  is a cross-sectional view of the ejection detection unit cut along A-A line of  FIG. 10 . 
     In this embodiment, an electrode plate  101  is a pillar-shaped member. The electrode plate  101  serving as a shaft is fitted in a hole of the cleaning member  202 . 
     Such a shaft-hole configuration can position the cleaning member  202  without using the holder member  103 , thus allowing more accurate positioning than the above-described embodiment. 
     Next, an ejection detection unit according to an embodiment of this disclosure is described with reference to  FIG. 12 . 
       FIG. 12  is a perspective view of an ejection detection unit according to an embodiment of this disclosure. 
     For this embodiment, in the configuration of the above-described embodiment illustrated in  FIGS. 7 to 9 , an absorbing member  208  to absorb ink is disposed at a cleaning terminal side at which the cleaning member  202  finishes cleaning the electrode member  101 . 
     The absorbing member  208  absorbs ink scraped off from the electrode plate  101  by the cleaning member  202 , thus allowing the cleaning member  202  to be maintained in clear condition. Such a configuration can maintain cleaning performance in good condition over a longer period of time. 
     Next, an ejection detection unit according to an embodiment of this disclosure is described with reference to  FIG. 13 . 
       FIG. 13  is a perspective view of an ejection detection unit according to an embodiment of this disclosure. 
     In this embodiment, a cleaner  200  has a cleaning portion  203  and a guide portion  204 . The cleaning portion  203  contacts a surface of an electrode plate  101 . The guide portion  204  supports the cleaning portion  203  and movably engages a guide groove  110  formed at each side face of a holder member  103  in a nozzle array direction (sub-scanning direction) in which nozzles of a recording head are arrayed in line. In this embodiment, the cleaning portion  203  and the guide portion  204  are formed as separate members. 
     The cleaning portion  203  has a slant surface  203   a  gradually rising upward from a leading edge to an opposite side of the leading edge in a cleaning direction of the cleaning member  202  in which the cleaning member  202  moves to remove ink droplets on the electrode plate  101 . 
     Such a configuration can more reliably remove ink from the electrode plate  101 . 
     Next, an ejection detection unit according to an embodiment of this disclosure is described with reference to  FIG. 14 . 
       FIG. 14  is a partial side view of an ejection detection unit according to an embodiment of this disclosure. 
     In this embodiment, in the configuration of the above-described embodiment illustrated in  FIG. 13 , an absorbing member  209  to absorb ink in disposed on an upper side of a slant surface  203   a  of a cleaning member  202 . 
     Such a configuration can absorb ink, which is scraped upward along the slant surface  203   a , with the absorbing member  209  and retain the ink in the absorbing member  209 , thus allowing cleaning performance to be maintained over a longer period of time. 
     In any of the above-described embodiments, the surface of the cleaning member  202  opposing the electrode plate  101  is formed of an elastic member, such as rubber or elastomer. Even if the flatness of the electrode plate  101  is low to some degree, such a configuration allows the surface of the cleaning member  202  to follow and closely contact the surface of the electrode plate  101 , thus allowing ink to be more reliably removed from on the electrode plate  101 . 
     Next, an ejection detection unit according to an embodiment of this disclosure is described with reference to  FIGS. 15 and 16 . 
       FIG. 15  is a perspective view of an ejection detection unit according to an embodiment of this disclosure.  FIG. 16  is a side view of the ejection detection unit during operation of a wiping member. 
     In this embodiment, an electrode plate  101  is fixedly mounted on a holder member  103  with a step between the electrode plate  101  and a surface of the holder member  103 . 
     A cleaner  200  includes a wiper  222  to wipe and clean a surface of the electrode plate  101  and a wiper holder  221  to hold the wiper  222 . 
     Here, for example, the wiper holder  221  is moved in parallel to the nozzle array direction along a guide groove  110  formed at each lateral side face of the holder member  103  in the nozzle array direction, as in the cleaning member  202  in any of the above-described embodiments. 
     As illustrated in  FIG. 16 , when the wiper  222  moves wiping direction WD, the wiper  222  is bent and an edge of the wiper  222  moves while sliding over the surface of the electrode plate  101  in contact with the surface of the electrode plate  101 . Thus, the wiper  222  cleans the electrode plate  101  while scraping and collecting ink ejected on the electrode plate  101 . 
     Next, an ejection detection unit according to an embodiment of this disclosure is described with reference to  FIG. 17 . 
       FIG. 17  is a side view of an ejection detection unit during operation of a wiping member according to an embodiment of this disclosure. 
     In this embodiment, in the configuration of the above-described embodiment illustrated in  FIGS. 15 and 16 , an absorbing member  223  is disposed at a position at which a wiper  222  arrives after the wiper  222  wipes out the surface of an electrode plate  101 . 
     Accordingly, the absorbing member  223  absorbs and cleans ink adhering to the wiper  222  during wiping. Such a configuration allows the wiper  222  to be maintained in clean condition over a long period of time, thus allowing cleaning performance for the electrode plate  101  to be maintained in good condition. 
     It is to be noted that, in the above-described embodiments illustrated in  FIGS. 15 and 16  and  FIG. 17 , the wiper  222  may wipe the electrode plate  101  in a direction opposite the wiping direction WD, or in both of the wiping direction WD and the opposite direction. 
     Next, a wiping direction WD of a wiper is described with reference to  FIGs. 18A and 18B  and  FIGS. 19A and 19B . 
       FIGS. 18A and 18B  show a wiping direction WD1 of a wiper  1202  according to a comparative example of this disclosure.  FIGS. 19A and 1913  show a wiping direction WD2 of a wiper  202  according to an embodiment of this disclosure. 
     Here, a configuration is described in which the wiper cleaner (cleaning member) wipes off waste liquid adhering to the wiper. 
     In the comparative example illustrated in  FIGS. 18A and 18B , the wiper  1202  is formed so that the wiper  1202  has a longitudinal direction parallel to a nozzle array direction NAD in which nozzles of a recording head are arrayed in line. Droplets  800  for ejection detection are ejected onto an electrode plate  101 , and the wiper  1202  is moved in a wiping direction WD1 perpendicular to the nozzle array direction NAD to wipe the droplets  800  on the electrode plate  101 . 
     At this time, the droplets  800  are an extremely small amount of droplets. Accordingly, when the droplets  800  are wiped in the wiping direction WD1 perpendicular to the nozzle array direction NAD, the liquid droplets  800  on the electrode plate  1101  are not collected together. 
     As a result, waste liquid adhering to the wiper  1202  may not be fully removed and may firmly adhere to the wiper  1202 , resulting in a reduction in wiping performance. 
     By contrast, in this embodiment, as illustrated in  FIGS. 19A and 19B , droplets  800  for ejection detection are ejected onto the wiper  222 , and the wiper  222  is moved in a wiping direction WD2 parallel to the nozzle array direction NAD to wipe the droplets  800  on the electrode plate  101 . 
     As described above, when the wiper  222  is moved in the wiping direction WD2 parallel to the nozzle array direction NAD to wipe the droplets  800  on the electrode plate  101 , the droplets  800  are collected as waste liquid, thus allowing the waste liquid adhering to the wiper  222  to be easily removed from the wiper  222 . 
     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.