Patent Publication Number: US-7901030-B2

Title: Inkjet recording apparatus

Description:
This application is based on Japanese Patent Application No. 2006-301,010 filed on Nov. 6, 2006 with the Japanese Patent Office, the entire content of which is hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     This invention relates to an inkjet recording apparatus, particularly relates to an inkjet recording apparatus including a conveyance device for conveying a recording medium which is placed on the exterior surface of an endless belt, and also a cleaning device for cleaning the ink adhered on the conveyance device. 
     BACKGROUND OF THE INVENTION 
     Known is an inkjet recording apparatus for jetting ink onto a recording medium to record an image thereon while an endless belt conveys the recording medium. The recording medium is in close contact with an exterior surface of the endless belt by electrostatic absorption or an adhesive agent applied to the exterior surface of the endless belt. 
     In the case of conducting a recording operation by conveying a recording medium in the inkjet recording apparatus, there is a case that due to inferior conveyance of the recording medium, ink is jetted onto the belt, not onto the recording medium. Further, in the case of recording, what is known as a borderless image, whereby ink is jetted onto the area which is a little bit wider than the size of the recording medium, so that ink is also jetted onto the belt around the recording medium. 
     If the ink jetted onto the exterior surface of the endless belt is allowed to adhere onto the rear surface of the recording medium, it lowers the recorded image quality. Further, since the ink lowers the surface resistance of the belt, the problem occurs that the belt decreases a force to adhere the recording medium, and conveyance capability of the recording medium deteriorates. Thus, up to now, a cleaning device has been provided to remove the ink adhered on the endless belt. 
     With respect to the method for removing the ink adhered on the endless belt, known is a method of rasping off said ink by sliding on and rubbing the moving belt surface while conveying the belt by contact of an elastic plate member, such as a wiper blade, made of rubber or plastic. In order to stabilize the sliding and rubbing force, the elastic plate member is pressed against the exterior surface of the endless belt at a predetermined force. 
     When the plate member is used as a cleaning means, if the plate member is always in contact with the belt, the conveyance system tends to become deformed by the pressing force of the plate member, which tends to deteriorate the image quality. Further, since the plate member is always forced in a single direction, the plate member can be deformed, which deteriorates its cleaning capability. 
     In order to overcome the above problems, the thickness of the plate member may be increased, or alternatively the elasticity of the plate member may be increased, so that the plate member tends to straighten itself due to its inherent elastic force, but the pressing force becomes greater on the surface of the endless belt, resulting in an effect opposite the desired one. 
     Further, there is a case in which the belt is driven in a direction opposite a normal conveyance direction due to paper jams, and a case in which even when the normal recording operation is conducted, after the recording medium is conveyed for a predetermined distance, the belt is driven in the opposite direction to convey the recording medium for the predetermined distance. In addition, the normal conveyance direction means a recording direction. That is, when the belt is driven in the opposite direction, and if the plate member is always in contact with the surface of the belt, the plate member is forced to bend. Since the plate member has elasticity exhibiting a predetermined pressing force, the plate member receives an unreasonable load, which can result in damage to the plate member and the belt. 
     Due to this, in the conventional art, the plate member is controlled to not always be in contact with the surface of the belt, and is controlled to contact the surface of the belt only when the belt is to be cleaned. 
     For example, by providing a wiper to scratch and drop the ink adhered on the belt surface and an absorbing member to clean the residing ink droplets left on remaining tracks of the wiper edge on the belt so as to be capable of contacting with and separating from the belt, the wiper and the absorbing member are in contact with the belt only when a cleaning sequence is conducted after the jam is detected, which overcomes the problem in the case that the wiper and the absorbing member are always in contact with the belt, which is disclosed in Unexamined Japanese patent Application Publication No. 3-227,648. Further, by providing a wiper to scratch and drop the ink adhered on the belt surface and an absorbing member to clean the residing ink droplets left on tracks of the wiper edge on the belt so as to be capable of contacting with and separating from the belt, the wiper and the absorbing member are made to contact the belt only when the recording operation is not conducted, which overcomes the problem in the case that the wiper and the absorbing member are always in contact with the belt, which is disclosed in Unexamined Japanese patent Application Publication No. 4-31,070. 
     In the case when conducting belt cleaning by contacting a cleaning member with the belt only when conducting a cleaning sequence after having detected a jam as, disclosed in Unexamined Japanese Patent Application Publication No. 03-227,648, since belt cleaning is not executed during normal recording operation, the ink, which has adhered onto the belt during normal operation, such as when recording a borderless image onto the recording material, cannot be cleaned off at all. 
     On the other hand, in the case when conducting belt cleaning by contacting the cleaning member with the belt only during a non-recording period, as proposed in Unexamined Japanese Patent Application Publication No. 04-31,070, since belt cleaning is not executed during normal recording operation, in case when continuously recording images onto a long recording material, such as textile outputted from rolled original textile, cleaning is not executed for a long period of time. Thus, since the recording material is conveyed when the belt surface is dirty, it is hard to avoid staining of the recording medium. Further, in case when the non-recording operation period does not coincide with the necessary time period for cleaning, the belt surface cannot be cleaned. When a recording operation is stopped until a cleaning operation is completed, the image recording productivity is reduced. 
     Further when the cleaning member is mechanically contacted with and separated from the belt surface, if the belt is conveyed at a high velocity to raise the recording productivity, the number of contact-separating operation of the cleaning member against the belt per a unit-time becomes large. Thus, there is a problem that mechanical operation sound level of the contact-separating operation becomes high. 
     Further, since a plurality of cleaning members are contacted with and separated from the belt, the maintenance work for stably operating the cleaning device for a long time becomes complicated. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an inkjet recording apparatus including a belt cleaning function, which is capable of stably cleaning a belt surface and rasping off ink adhered on the belt surface, by simple structure, even during recording operations, without mechanical contact with and separation from the belt surface. 
     The other problems to be solved by this invention will be described below. 
     The problems described above can be solved by the following embodiments. 
     The preferred embodiment of this inkjet recording apparatus, includes: 
     a conveyance device including an endless belt which conveys a recording medium placed on an exterior surface of the endless belt, 
     a recording device which jets ink onto the recording medium conveyed by the conveyance device, to record an image, and 
     a cleaning device to clean the exterior surface of the endless belt, including: 
     a flexible sheet member which is mounted more downstream in a conveyance direction of the endless belt than a position where the recording device is mounted, and a top surface of the flexible sheet member comes into slidably contact with the exterior surface of the endless belt, and 
     an elastic supporting member which is mounted to contact the flexible sheet member, 
     wherein when the flexible sheet member bends due to running of the endless belt, the elastic supporting member comes into contact with the flexible sheet member to support, and the elastic supporting member provides a pressing force against the flexible sheet member so that the flexible sheet member presses against the exterior surface of the endless belt. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic side view of an inkjet recording apparatus. 
         FIG. 2  illustrates a front view showing an example of a brush roller. 
         FIG. 3  illustrates a partial side view showing an example of a jetting device. 
         FIG. 4  illustrates a flexible sheet member and an elastic supporting member of a first embodiment, when the endless belt is rotating during the recording state. 
         FIG. 5  illustrates the flexible sheet member and the elastic supporting member of the first embodiment, when the endless belt is during a stand-by state. 
         FIG. 6  illustrates nipping amounts of the flexible sheet member and the elastic supporting member. 
         FIG. 7  illustrates a flexible sheet member and an elastic supporting member of the second embodiment, when the endless belt is rotating in the recording state. 
         FIG. 8  illustrates the flexible sheet member and the elastic supporting member of the second embodiment, when the endless belt is in the stand-by state. 
         FIG. 9  illustrates another example incorporated in the inkjet recording apparatus. 
         FIG. 10  illustrates a side view of another structure including a brush roller and an elastic supporting member. 
     
    
    
     PREFERABLE EMBODIMENTS OF THE INVENTION 
     An embodiment of the present invention will be described below while referring to the drawings. 
       FIG. 1  illustrates a schematic side view of an inkjet recording apparatus. 
     In  FIG. 1 , numeral  1  represents a belt type conveyance device in the present invention, in which drive roller  11  and driven roller  12  are parallel and provided at a predetermined interval, and weight roller  13  is set below and between drive roller  11  and driven roller  12 . Endless belt  14  is entrained about drive roller  11 , driven roller  12  and weight roller  13 . 
     The exterior surface of endless belt  14  is arranged as a conveyance surface of the recording medium. In the normal recording state to record an image on recording medium P, as illustrated in  FIG. 1 , a sub-scanning motor (which is not shown) drives drive roller  11  counterclockwise at a predetermined velocity. Recording medium P, which is in close contact with the exterior surface of endless belt  14 , is intermittently conveyed with a predetermined amount in the direction shown by arrow A, which is the sub-scanning direction. 
     In the present invention, endless belt  14  is driven in the direction shown by arrow A so that recording medium P is conveyed in the normal recording state. 
     With respect to the material of recording medium P, a recording material, which is normally used for inkjet recording, for example, paper, textile, plastic film and glass, may be used. Recording medium P may be a sheet cut to a predetermined size or a long sheet continuously unrolled from a spool, on which sheet is wound in a roll shape. 
     Numeral  2  represents a recording head provided above endless belt  14  entrained about drive roller  11  and driven roller  12 . Recording head  2  is installed onto a carriage (which is not shown) and is able to reciprocally move along the main scanning direction (which is the depth direction of  FIG. 1 ), which is perpendicular to arrow A. On the moving process along the main scanning direction, numerous nozzles formed on a nozzle surface are arranged to jet ink droplets of a specific color in response to image data onto recording medium P set below recording head  2 . Based on this arrangement, recording head  2  is structured of an on-demand type inkjet head which forms a necessary image together with intermittent conveyance of recording medium P by the rotation of endless belt  14 . 
     Further, recording head  2  is not limited to a shuttle type recording head, which reciprocally moves along the main scanning direction as described above. Recording head  2  may be a line type recording head, which is fixedly provided across the width of the recording medium formed into a long roll. In this case, endless belt  14  is driven so that recording medium P is continuously conveyed at a constant rate. 
     Numeral  3  represents a cleaning device, which is provided adjacent to weight roller  13 , more downstream in the conveyance direction of endless belt  14  than the position where recording head  2 . Cleaning device  3  includes brush roller  31 , flexible sheet member  32 , elastic supporting member  33  and water absorbing member  34 . 
     Brush roller  31  serves as a cleaning device, and preferably equipped in the present invention. Said brush roller  31  is formed as a roller so that brush bristles  31   b  are planted along the circumferential surface of brush shaft  31   a . The length of brush shaft  31   a  is formed so as to be the same or a little bit longer than the width of endless belt  14 . The brush shaft  31   a  is bridged over the width direction of endless belt  14  and the edge of brush bristles  31  are always in contact with the exterior surface of endless belt  14 . 
     In cases when endless belt  14  is in the recording state, brush roller  31  slides on and rubs against the exterior surface of endless belt  14  to remove any adhered ink, dust and foreign matter, such as dirt (hereinafter referred to as remaining ink). 
     In order to improve the removing effect, it is preferable that brush roller  31  is capable of reverse rotation (counterclockwise as shown in  FIG. 1 ) against the conveyance direction of endless belt  14  by a driving device (which is not shown), to slide on and rub the exterior surface of the endless belt  14 . The rotation rate of brush roller  31  is preferably set at 50-250 rpm. 
     With respect to the material of brush bristle  31   b , any appropriate type of natural bristle and artificial bristle may be used. From the viewpoint of cost, durability and capability for removing remaining ink, etc., it is particularly preferable to use Nylon as the material for brush bristle  31   b.    
     It is also preferable that the bristle diameter is set 0.05-0.3 mm. 
     With respect to the examples of planting brush bristle  31   b , listed are methods 1-3: 
     method 1: planting brush bristle  31   b  over the full circumference of brush shaft  31   a  at a high density, 
     method 2: arranging several rows of brush bristles  31   b  planted along the longitudinal direction of brush shaft  31   a  at a high density, and the rows to be separated from each other at a uniform interval around the circumference of brush shaft  31   a , and 
     method 3: spirally planting brush bristles  31   b  around the circumferential surface of brush shaft  31   a.    
     In the three methods described above, it is preferable to use method 3 of spirally planting brush bristles  31   b  from the viewpoints of cost. Even though brush bristles  31   b  are planted with high density, any adverse effect to endless belt  14  is little, and it is possible to slide on and rub the exterior surface of endless belt  14  across its full width without unevenness by brush bristles  31   b.    
     If brush bristles  31   b , spirally planted in a single direction against the circumferential surface of brush shaft  31   a , are used, shifting force may be generated which shifts endless belt  14  in one direction with respect to the width of endless belt  14  while endless belt  14  is driven, and thereby, there is the tendency to cause the shift of endless belt  14  in one direction. Thus in the case of spirally planting brush bristle  31   b , as shown in  FIG. 2 , it is preferable that brush bristles  31   b  are planted so that the spiral shape is symmetrical at the center of the brush shaft length. Based on this arrangement, no shifting force to shift endless belt  14  in one direction of its width is generated, and the possibility of causing endless belt  14  to shift becomes extremely low. 
     As long as after recording medium P has been separated from the exterior surface of endless belt  14 , the setting position of brush roller  31  may be determined anywhere downstream of a setting position of recording head  2  in the conveyance direction of endless belt  14 . However, as shown in  FIG. 1 , it is preferable that the position of brush roller  31  is adjacent to the roller section, such as weight roller  13 . Since in such position, the interior surface of endless belt  14  is supported by weight rollers  13 , vibration and fluttering of endless belt  14  can be prevented. Further, since chatter vibration nor fluttering occur, the contact force of brush roller  31  against endless belt  14  can be stabilized to increase removable effect of remaining ink. 
     Below brush roller  31  serving as a washing device, water receiving section  35 , in which washing water  35   a  is stored, is provided and a part of the ends of brush bristles  31   b  dip into washing water  35   a . Thus, when brush roller  31  rotates, brush bristles  31   b  transfer washing water  35   a  out of water receiving section  35  so that washing water  35   a  washes the exterior surface of endless belt  14 . 
     Further, instead of the structure for transferring washing water from water receiving section  35 , washing water supplying device  36 , which supplies washing water to the exterior surface of endless belt  14  by using spraying nozzle  36   a , is provided adjacent to brush roller  31 , as shown in  FIG. 3 . In  FIG. 3 , alpha-numeric designation  36   b  represents a storage tank for washing water, and alpha-numeric designation  36   c  represents a pump for jetting washing water in storage tank  36   b  from spraying nozzle  36   a . In this case, water receiving section  35  stores any dripped washing water jetted from spraying nozzle  36   a . The washing water may be supplied not only to the exterior surface of endless belt  14  but also directly onto brush roller  31 . 
     Flexible sheet member  32  is provided more downstream in the conveyance direction of endless belt  14  than brush roller  31 . 
     Further, elastic supporting member  33  serves as an elastic supporting member of the present invention, which is provided more downstream in the conveyance direction of endless belt  14  than flexible sheet member  32 , and is adjacent to and parallel to flexible sheet member  32 . 
     First Embodiment 
     A first embodiment relating to flexible sheet member  32  and elastic supporting member  33  will be further detailed while referring to  FIGS. 4-6 . 
     While endless belt  14  is driven, flexible sheet member  32  scrapes and removes any water droplets, including ink, adhered on the exterior surface of endless belt  14  passed through brush roller  31 , the ink being diluted by washing water  35   a.    
     Flexible sheet member  32  is formed of a single sheet material, to be the same as or slightly wider than the width of endless belt  14 . Back end  322  of this flexible sheet member  32 , which is positioned opposite the exterior surface of endless belt  14 , is mounted on bracket  32   a  and positioned at a predetermined distance from the exterior surface of endless belt  14 , whereby said flexible sheet member  32  is arranged across the full width of endless belt  14 . 
     Since flexible sheet member  32  is mounted so that the distance from the bracket  32   a  to the exterior surface of endless belt  14  is arranged to be less than the free length of flexible sheet member  32  (the length extended from bracket  32   a ) as shown in  FIG. 4 . Accordingly, leading top edge  321  of flexible sheet member  32  bends in the same direction as the rotation of endless belt  14 , and elastically contacts the exterior surface of endless belt  14 . 
     The contact angle of flexible sheet member  32  against the exterior surface of endless belt  14  is preferably set in the range of −45°˜+45° against the vertical direction so that the water droplets scraped by brush bristles  31   b  easily drop from back end  322 . 
     Elastic supporting member  33  is provided so that a leading end  331  of the elastic supporting member  33  elastically comes into contact with the exterior surface of endless belt  14 . When endless belt  14  is driven, leading end  331  elastically bends due to the rotation of endless belt  14 . Intermediate portion  332  of elastic supporting member  33  convexly curves toward flexible sheet member  32  to come into contact with the concave surface of flexible sheet member  32 . Accordingly, flexible sheet member  32  can be supported by elastic supporting member  33 . That is, while using its elasticity, elastic supporting member  33  functions to apply contact-pressing force to the exterior surface of endless belt  14 , through flexible sheet member  32 . 
     Accordingly, said contact-pressing force is applied to the exterior surface of endless belt  14  by elastic supporting member  33 . That is, since flexible sheet member  32  and elastic supporting member  33  work together, the contact-pressing force is generated, by which leading top edge  321  of flexible sheet member  32  can scrape off the remaining ink on the exterior surface of endless belt  14 . 
     Since this structure, including flexible sheet member  32  and elastic supporting member  33 , defers to a conventional rigid plate member, both flexible sheet member  32  and elastic supporting member  33  can easily bend while following not only the sheet conveyance movement but also the reverse movement of endless belt  14 . That is, it is only necessary that flexible sheet member  32  and elastic supporting member  33  have flexibility to slidably contact the exterior surface of endless belt  14 . As long as flexible sheet member  32  and elastic supporting member  33  are flexible enough to rub the surface of endless belt  14 , they are not to be so elastic as to be rigid to scrape off any remaining ink by themselves, while elastically contacting the exterior surface of endless belt  14 . 
     Due to this structure, though flexible sheet member  32  and elastic supporting member  33  are always in contact with the exterior surface of endless belt  14  during the sheet conveyance operation, no undesirable load is applied on rotating endless belt  14 . 
     In order to satisfy the function of flexible sheet member  32  and elastic supporting member  33 , the elasticity of elastic supporting member  33  was compared with that of flexible sheet member  32 . As a result, it is found that each material can be preferably selected so that the elasticity of elastic supporting member  33  is greater than that of flexible sheet member  32 . 
     Flexible sheet member  32  can be formed of a flexible rubber sheet or a resin sheet. In more detail, from the view-point of appropriate flexibility and inherent elastic force, a flexible sheet member is preferably formed of 0.05-0.3 mm polyethylene terephthalate (PET) sheet. 
     Elastic supporting member  33  can be formed of an appropriate material exhibiting greater elasticity compared to flexible sheet member  32 . 
     In  FIGS. 4-6 , a straight strip brush, serving as elastic supporting member  33 , is illustrated, on which brush bristles are planted across the width of the endless belt, which is a preferable example as elastic supporting member  33 . 
     Said straight strip brush  33  is formed of a large number of brush bristles  33   b  planted on a straight strip brush base  33   a  arranged across the width of endless belt  14 . The width of brush base  33   a  is at least as great as the width of endless belt  14 , and brush base  33   a  is arranged along the width of endless belt  14 . 
     Leading top edge  331  of brush bristles  33   b  is slightly bent and elastically contacts the exterior surface of endless belt  14 , due to the inherent elasticity of brush bristles  33   b . That is, straight strip brush  33  is mounted in such a way that the distance between brush base  33   a  and the exterior surface of endless belt  14  is less than the free length of brush bristles  33   b  (which is the length extending from brush base  33   a ), whereby straight strip brush  33  is bent in the conveyance direction of endless belt  14 , and elastically contacts the exterior surface of endless belt  14 . 
     In the first embodiment, since straight strip brush  33  is always in close contact with the exterior surface of endless belt  14 , the ink droplets, remaining on the exterior surface of endless belt  14  cleaned by brush roller  31  and flexible sheet member  32 , are diluted by washing water  35   a , whereby the water droplets including remaining ink droplets are scraped and removed from the exterior surface of endless belt  14 . 
     Additionally, each brush bristle  33   b  of straight strip brush  33  follows to rub any small irregularity on the exterior surface of endless belt  14 , which increases the cleaning effect on endless belt  14 . 
     The contact angle of straight strip brush  33  against the exterior surface of endless belt  14  is preferably set in a range of −45°˜+45° against the vertical direction so that the water droplets scratched by brush bristle  32   b  easily drop from brush bristle  32   b.    
     Natural bristle or artificial bristle can be used as a material for brush bristle. From the viewpoint of lower cost and high removable capability against ink, etc., Nylon is preferably used as a material for brush bristle  33   b . The diameter of brush bristle  33   b  is preferably 0.05-0.3 mm, and the free length of brush bristle  33   b  is preferably 20-50 mm. 
     Nip forming amount L 1  of flexible sheet member  32  against endless belt  14  and nip forming amount L 2  of straight strip brush  33  against endless belt  14  (see  FIG. 6 ), can be accordingly set at optimal values, respectively, based on the free lengths of flexible sheet member  32  and straight strip brush  33 , as well as the attaching angle against endless belt  14 . When endless belt  14  is rotating, as shown in  FIG. 4 , leading top edge  321  of flexible sheet member  32  is set so as to bend due to the rotation of endless belt  14 , and leading top edge  331  of brush bristles  33   b  of straight strip brush  33 , exhibiting elastic force, is also set so as to bend due to the rotation of endless belt  14 . 
     When endless belt  14  is temporarily stopped for the conveyance, and then is rotated in the opposite direction (which is the clockwise direction in  FIG. 5 ), brush bristles  33   b  of straight strip brush  33  are bent in the opposite direction due to the clockwise rotation of endless belt  14 , and at the same time, flexible sheet member  32  is also bent in the opposite direction due to the clockwise rotation of endless belt  14 , and further, leading top edge  331  of straight strip brush  33  pushes leading top edge  321  of flexible sheet member  32  to bend, whereby leading top edge  321  of flexible sheet member  32  is separated from the exterior surface of endless belt  14 , that is, leading top edge  331  of straight strip brush  33  is supported between flexible sheet member  32  and the exterior surface of endless belt  14 . 
     As an example, it is preferable that nip forming amount L 1  of flexible sheet member  32  is set to be 0.5-19.5 mm, while nip forming amount L 2  of straight strip brush  33  is set to be 1-20 mm. In addition, L 1 &lt;L 2  is essential. 
     It is preferable that a supporting member to support endless belt  14  from the rear is provided on the interior surface of endless belt  14 , opposite both flexible sheet member  32  and straight strip brush  33  (being the elastic supporting member). Since in such position, even though leading top edge  321  of flexible sheet member  32  and leading top edge  331  of elastic supporting member  33  are in elastic contact with endless belt  14 , it is possible to prevent the exterior surface of endless belt  14  from separating from both flexible sheet member  32  and elastic supporting member  33 . Accordingly, the contact force of both flexible sheet member  32  and elastic supporting member  33  against endless belt  14  can be stabilized, and removal of the water droplets on the exterior surface of endless belt  14  can be improved. 
     In the embodiment illustrated in  FIG. 1 , flexible sheet member  32  and elastic supporting member  33  are arranged at the place where weight roller  13  is bridged over endless belt  14 . Weight roller  13  functions as a member to support the surface opposed to both flexible sheet member  32  and elastic supporting member  33 . Thus, it is not necessary to provide a separate support member. 
     As illustrated in  FIG. 1 , flexible sheet member  32  and elastic supporting member  33  are set so that back end  322  of flexible sheet member  32  and the base of elastic supporting member  33  are positioned inside water receiving section  35  to receive water from brush roller  31 . Thus, any water droplets, which have been removed and dropped by flexible sheet member  32  and elastic support member  33 , can be stored in water receiving section  35 . 
     Liquid absorbing member  34  is provided more downstream in the conveyance direction of endless belt  14 , than elastic supporting member  33 , and contacts the exterior surface of endless belt  14 . Liquid absorbing member  33  is not a necessary element in this embodiment, however, since liquid absorbing member  34  can absorb the water droplets on the exterior surface of endless belt  14 , which have not been removed by flexible sheet member  32  and elastic supporting member  33  from the exterior surface of endless belt  14 , the cleaning effect can be improved. 
     The material of liquid absorbing member  34  is preferably formed by porous absorbing material. Concretely, sponge can be utilized as the porous absorbing material. 
     Liquid absorbing member  34  can be structured so as to be in sliding contact with the exterior surface of endless belt  14 , without moving. However, in order not to give unnecessary deviation of the conveyance function of endless belt  14 , as illustrated in  FIG. 1 , liquid absorbing member  34  is preferably structured as a roller, which is driven due to contact with endless belt  14 . The rotation of liquid absorbing member  34  improves its durability. 
     Below liquid absorbing member  34 , waste ink receiver  37  is provided to store the liquid droplets, which were absorbed and dropped from rotated liquid absorbing member  34 . 
     Next, the operation of cleaning device  3 , incorporating flexible sheet member  32  and straight strip brush  33  as the elastic supporting member, relating to the first embodiment, will be detailed. 
     In the case that conveyance device  1  starts operation by turning the apparatus power switch on, brush roller  31  rotates in the reverse direction against the conveyance direction of endless belt  14 . Brush roller  31  starts wiping and sliding against the exterior surface of endless belt  14 , and both flexible sheet member  32  and straight strip brush  33  wipe and slide against the exterior surface of endless belt  14 , while both flexible sheet member  32  and straight strip brush  33  also bend in the conveyance direction based on the conveyance of endless belt  14 . 
     The ink jetted from recording head  2  forms a predetermined image onto intermittently conveyed recording medium P, which is placed on the exterior surface of endless belt  14 . When endless belt  14  is further conveyed, the exterior surface of endless belt  14 , from which recording medium P has been separated, approaches the setting place of brush roller  31 . Rotating brush roller  31  slides on and wipes the exterior surface of endless belt  14  and removes any remaining ink by washing water  35   a  applied by brush roller  31 . 
     After brush roller  31  washes the exterior surface of the endless belt  14 , some water droplets, including diluted ink, are adhered onto the exterior surface of endless belt  14 , and some of the water droplets do not run off and reside on the surface of endless belt  14 . 
     As endless belt  14  is further conveyed and passes through the setting place of flexible sheet member  32 , the water droplets on the exterior surface of endless belt  14  are wiped and dropped by flexible sheet member  32 , which is forced against the exterior surface of endless belt  14  by straight strip brush  33 . Wiped and dropped water droplets are stored in water receiving section  35  after passing flexible sheet member  32 . 
     Further, brush bristles  33   b  of straight strip brush  33  also contact the exterior surface of endless belt  14 , so that all residual water droplets on the exterior surface of endless belt  14  are wiped and dropped by straight strip brush  33 . The wiped water is received in water receiving section  35  through brush bristles  33   b . A water replenishing section and a drain section are provided in water receiving section  35 , neither of which is illustrated. 
     After passing through straight strip brush  33 , even though water droplets exist on the exterior surface of endless belt  14 , the water droplets are absorbed by liquid absorbing member  34 , driven by endless belt  14 , and completely removed from the exterior surface of endless belt  14 . At this moment, since flexible sheet member  32  and straight strip brush  33  remove almost of the water droplets, the water droplets absorbed by the liquid absorbing member  34  is an extremely small amount. Thus the frequency of the exchange of liquid absorbing member  34  due to staining decreases very much. 
     Since brush roller  31 , flexible sheet member  32  and liquid absorbing member  34  are normally in contact with the exterior surface of endless belt  14 , the overall cleaning operation by cleaning device  3  is continuous while conveyance device  1  is in the recording state. Accordingly, even in a case that a borderless image is recorded under normal recording operation and any ink is adhered on the exterior surface of endless belt  14 , cleaning can be conducted in the recording state. Thus, it is not necessary to pay attention to the stains on recording medium P. 
     At this time, brush roller  31  and straight strip brush  33  are in contact with the exterior surface of endless belt  14  due to the inherent elastic force of brush bristles  31   b  and  33   b . Further, since flexible sheet member  32  has lower elasticity than straight strip brush  33 , and liquid absorbing member  34  is driven by endless belt  14 , even though endless belt  14  is conveyed at a high rate, vibration and fluttering of endless belt  14  do not occur, and no vibration causing bad interference with the image formation occurs. Yet further, even though brush roller  31  and straight strip brush  33  are arranged to always contact the exterior surface of endless belt  14  during the normal operation, contact resistance is extremely low so that no tracking deviation is caused on conveyance device  1 . 
     In the cases of adjusting the position of recording medium P, due to paper jams or conducting maintenance operation, even though endless belt  14  is conveyed in a reversed direction, brush roller  31 , flexible sheet member  32  and straight strip brush  33  can remain in a contact state with endless belt  14 . Thus, no problem is expected. 
     Further, since flexible sheet member  32  and straight strip brush  33  are always in contact with the exterior surface of endless belt  14 , it is not necessary to conduct a contact-withdrawal operation of cleaning device  3  against endless belt  14  for cleaning operations, there is no operation sound, the structure can be easily configured and the maintenance work is reduced. 
     Since flexible sheet member  32  and straight strip brush  33  are kept in contact with the exterior surface of endless belt  14  for a long time, there is a possibility that flexible sheet member  32  and straight strip brush  33  are deformed to curve toward one side. To overcome this problem, it is preferable that when the recording operation finishes, conveyance device  1  stops the rotation of endless belt  14  at once and rotates endless belt  14  for a predetermined distance in the reverse direction against the normal conveyance direction of recording medium P. 
     Based on this operation, since flexible sheet member  32  and straight strip brush  33  are bent as shown in  FIG. 5 , which is a reversing direction against the direction of the cleaning operation and rests in the stand-by mode, whereby straight strip brush  33  is held between flexible sheet member  32  and endless belt  14  so that the deformation of flexible sheet member  32  and brush bristle  33   b  of straight strip brush  33  into wavy bristle curved in one side can be prevented. 
     Specifically, when flexible sheet member  32 , exhibiting lower elasticity, is used, it tends to deform. During the stand-by state of endless belt  14 , the operation of conveyance device  1  as described above is extremely effective in preventing flexible sheet member  32  to be bent in only one direction by contact with endless belt  14 . 
     Further, each flexible sheet member  32  and straight strip brush  33  can easily follow the rotational direction of endless belt  14 , being either clockwise or counterclockwise, and tend to bend in either direction, endless belt  14  as well as flexible sheet member  32  and straight strip brush  33  are less likely to be damaged. 
     The operation of conveyance device  1  as described above is more preferable when the exterior surface of endless belt  14  exhibits some adherence to recording medium P when it is in close contact with the exterior surface for the conveyance. That is, while endless belt  14  is in the stand-by state, if flexible sheet member  32  continues to be in contact with the exterior surface of endless belt  14 , flexible sheet member  32  tends to somewhat adhere to the exterior surface of endless belt  14 . However, in such a stand-by state, if endless belt  14  is rotated in the opposite direction (being the clockwise direction) for the predetermined direction, leading top edge  321  of flexible sheet member  32  is separated from the exterior surface of endless belt  14 . Accordingly, flexible sheet member  32  cannot adhere to the exterior surface of endless belt  14  under the stand-by state. 
     In the stand-by state, straight strip brush  33  is always in contact with the exterior surface of endless belt  14 . Since straight strip brush  33  is not facially in contact with the exterior surface of endless belt  14 , but each brush bristle  32   b  having a very small diameter is linearly in contact with the exterior belt surface, the adhesive force is so small that straight strip brush  33  can follow the counter-clockwise rotation when normal conveyance operation starts. Thus, if the exterior surface of the endless belt exhibits the adherence, straight strip brush  33 , serving as an elastic supporting member, is preferably utilized. 
     In this case, the opposite direction conveyance distance depends to the free length of flexible sheet member  32  and straight strip brush  32 , and is typically set at 10-100 mm. 
     “Stand-by” state means a fairly long deactivated condition such as when the recording apparatus is switched off, but can also mean a condition while the apparatus is in an active state, for example, when changing recording medium P, changing recording head  2 , cleaning, maintenance work due to non-jetting of ink from a nozzle, changing ink, and paper jams. 
     Second Embodiment 
       FIGS. 7 and 8  show flexible sheet member  32  and elastic supporting member  33  as a second embodiment. 
     In the second embodiment, leading top edge  331  of elastic supporting member  33  is provided not in contact with the exterior surface of endless belt  14 , which differs to the first embodiment.  FIG. 7  shows endless belt  14  is in the recording state, while  FIG. 8  shows endless belt  14  is in the stand-by state. 
     Flexible sheet member  32  is provided to always be in contact with the exterior surface of endless belt  14 , which is the same as the first embodiment, while elastic supporting member  33  exhibits shorter free length than that of the first embodiment so that it is provided never in contact with the exterior surface of endless belt  14 . 
     Due to the above structure, when endless belt  14  rotates for normal sheet conveyance operation, leading top edge  321  of flexible sheet member  32  bends toward the rotating direction of endless belt  14  and wipes the exterior surface of endless belt  14 . In that time, elastic supporting member  33  prevents flexible sheet member  32  from bending excessively, and intermediate section  332  elastically supports flexible sheet member  32 , so that moderate elastic force is applied to flexible sheet member  32 , which is the same as in the first embodiment. 
     Elastic supporting member  33  in the second embodiment can be represented by the straight strip brush the same as in the first embodiment, but since elastic supporting member  33  does not come into contact with the exterior surface of endless belt  14 , elastic supporting member  33  can be formed of a sheet member, such as rubber and resin, as long as the degree of elasticity meets the condition described above. 
     The second embodiment can be used when the exterior surface of endless belt  14  exhibits no adhesion. The endless belt exhibiting no adhesion can be listed by a belt which electro-statistically attracts recording medium P. 
     While not illustrated, in each first and second embodiments structured of flexible sheet member  32  and elastic supporting member  33 , by arranging a plurality of sets, structured of flexible sheet member  32  and elastic supporting member  33 , along the conveyance path of endless belt  14 , it is possible to improve the cleaning effects. 
       FIG. 9  illustrates another embodiment of the inkjet recording apparatus. Since, the same symbols used in  FIG. 1  have the same structure and function, their detailed description will be omitted. 
     In this embodiment, instead of brush roller  31  illustrated in  FIG. 1 , washing water jetting device  38  to spray washing water against the exterior surface of endless belt  14  is provided. In  FIG. 9 , alpha-numeric designation  38   a  represents a washing water jetting nozzle, alpha-numeric designation  38   b  represents a washing water storage tank, alpha-numeric designation  38   c  represents a pump for feeding the washing water from storage tank  38   b  through jetting nozzle  38   a , and alpha-numeric designation  38   d  represents a waste water receiver. 
     Washing water jetting device  38  is arranged more downstream of the conveyance direction of endless belt  14  than the setting position of recording head  2 , and washes any ink adhered on the exterior surface of endless belt  14 , by jetting washing water. 
     In order to increase the ink removing effect, washing water jetting device  38  is preferably a high pressure spraying device which jets washing water with fairly high pressure. 
     A plurality of spraying nozzles  38   a  may be provided across the width of endless belt  14  to wash endless belt  14  across the total width direction at once. Or a single jetting nozzle  38   a  may be provided so as to be capable of moving across the width of endless belt  14  to wash the total width of endless belt  14  in a reciprocal motion. 
     After the washing water, jetted from jetting nozzle, washes the ink remaining on the exterior surface of endless belt  14 , the washing water and diluted ink are removed and stored in water receiver  38   d.    
     Even in this structure, while conveyance device  1  is operated, the cleaning operation can be continued, and the same effect described above can be obtained. 
     In the respective embodiments described above, cleaning device  3  is provided adjacent to weight roller  13 . Particularly when using a liquid, such as washing water, to conduct cleaning, when the washing water on the exterior surface of endless belt  14  can naturally drip, this structure is preferable. However, as long as the location of cleaning device  3  is more downstream in the conveyance direction of endless belt  14  than recording head  2 , and as long as cleaning is conducted after recording medium P has been removed, the setting place of cleaning device  3  is not limited. 
     Further, cleaning device  3  can also be provided in the place where endless belt  14  forms a flat surface.  FIG. 10  illustrates an embodiment where brush roller  31 , flexible sheet member  32  and elastic supporting member  33  are provided on the flat surface, which formed by endless belt  14 . In this case, in order to assure a contact state between endless belt  14  and brush roller  31 , flexible sheet member  32  and elastic supporting member  33 , it is preferable that support member  39  to support the rear surface of endless belt  14  is preferably provided at a position opposed to brush roller  31 , flexible sheet member  32  and elastic supporting member  33 , while sandwiching endless belt  14 . 
     In this embodiment, the same as  FIG. 9 , instead of the structure of brush roller  31 , washing water jetting device  38  may be provided. 
     Based on the present invention, the inkjet recording apparatus can be provided, in which, while the endless belt does not vibrate even in the recording state, any ink adhered to the exterior surface of the endless belt is easily scraped off, and no contact-separating mechanism is used, being capable of cleaning the endless belt with a simple structure.