Holding device of recording medium, image forming apparatus, and conveying method of recording medium

Abstract

According to one embodiment, the image forming apparatus includes, an endless device having a plurality of suction holes, and a negative pressure chamber which communicates with the suction holes, a rotation mechanism which rotates the endless device, a suction mechanism which discharges air in the negative pressure chamber, an opening and closing mechanism which has a switching blade which opens and closes the suction holes, a driving mechanism which moves the switching blade to a first position and a second position, a recording head unit, a supply mechanism which supplies the recording medium to the endless device, and a controller. If the switching blade moves to the first position, the suction holes are shut. If the switching blade moves to the second position, the suction holes communicate with the negative pressure chamber. The controller drives the opening and closing mechanism according to the size of the recording medium.

What is claimed is: 
     
         1 . A holding device of a recording medium comprising:
 an endless device which includes a circumferential surface which holds the recording medium, a plurality of suction holes which is formed on the circumferential surface, and a negative pressure chamber which communicates with the suction holes, and rotates in a predetermined direction;   a suction mechanism which discharges air in the negative pressure chamber;   a switching blade which is provided in the endless device, and moves between a first position at which the suction holes are closed and a second position at which the suction holes are opened; and   a driving mechanism which moves the switching blade to the first position and the second position.   
     
     
         2 . The device according to  claim 1 ,
 wherein the endless device includes the front side hole row which is formed such that a plurality of the suction holes is formed to have a interval in a width direction of the endless device, in a position which corresponds to a leading end of the recording medium in a movement direction, which is held by the endless device.   
     
     
         3 . The device according to  claim 2 ,
 wherein the endless device includes the rear side hole row which is formed such that a plurality of the suction holes is formed to have a internal in a width direction of the endless device, in a position which corresponds to a trailing end of the recording medium in a movement direction, which is held by the endless device.   
     
     
         4 . The device according to  claim 2 ,
 wherein the endless device includes a first rear side hole row which is formed such that a plurality of the suction holes is formed in a position which corresponds to a trailing end of the recording medium of a first size, in a movement direction, and a second rear side hole row which is formed such that a plurality of the suction holes is formed in a position which corresponds to a trailing end of the recording medium of a second size in the movement direction.   
     
     
         5 . The device according to  claim 4 ,
 wherein the front side hole row is always open, and the switching blade is disposed at the first and second rear side hole rows.   
     
     
         6 . The device according to  claim 1 ,
 wherein the endless device is a drum, and the switching blade moves in an axial direction of the drum.   
     
     
         7 . The device according to  claim 6  comprising:
 an engaging portion in which the switching blade extends in the axial direction of the drum, 
 wherein the driving mechanism includes a driving member which has the driving unit engaging with the engaging portion, and an actuator which moves the switching blade to the first position and the second position if the engaging portion and the driving unit engage with each other. 
 
     
     
         8 . The device according to  claim 1 ,
 wherein a dielectric layer to which a charge for electrostatically adsorbing the recording medium is applied is provided on the circumferential surface of the endless device.   
     
     
         9 . The device according to  claim 3 ,
 wherein the endless device further includes a plurality of intermediate suction holes which communicates with the negative pressure chamber between the front side hole row and the rear side hole row.   
     
     
         10 . The device according to  claim 9 ,
 wherein the intermediate suction holes are smaller than those of the front and rear side hole rows.   
     
     
         11 . An image forming apparatus comprising:
 an endless device which includes a circumferential surface which holds the recording medium, a plurality of suction holes which is formed on the circumferential surface, and a negative pressure chamber which communicates with the suction holes;   a rotation mechanism which rotates the endless device in a predetermined direction;   a suction mechanism which discharges air in the negative pressure chamber;   a opening and closing mechanism which has a switching blade which is provided in the endless device, and moves between a first position at which the suction holes are closed and a second position at which the suction holes are opened;   a driving mechanism which moves the switching blade to the first position and the second position;   a recording head unit which is arranged to face a circumferential surface of the endless device, and forms images on the recording medium;   a supplying mechanism which supplies the recording medium to the circumferential surface of the endless device; and   a controller which drives the opening and closing mechanism according to a size of the recording medium.   
     
     
         12 . The apparatus according to  claim 11 ,
 wherein the endless device includes hole rows which are formed such that the plurality of suction holes is formed to have a interval in a width direction of the endless device, and   wherein the controller controls the supply mechanism so that the leading end of the recording medium which is supplied to the endless device is positioned on the hole rows.   
     
     
         13 . The apparatus according to  claim 11  further comprising:
 a dielectric layer which is provided on the circumferential surface of the endless device, and to which a charge for electrostatically adsorbing the recording medium, is applied; 
 a charging roller which applies the charge to the dielectric layer; and 
 a neutralizing charger which neutralizes the charge from the recording medium on which the image is formed. 
 
     
     
         14 . The apparatus according to  claim 11 ,
 wherein the endless device is a drum, and the switching blade moves in the axial direction of the drum.   
     
     
         15 . The apparatus according to  claim 11 ,
 wherein the endless device includes the front side hole row which is formed in a position which corresponds to the leading end of the recording medium in a movement direction which is held to the endless device; the rear side hole row which is formed in a position which corresponds to the trailing end of the recording medium in the movement direction; and a plurality of intermediate suction holes which communicates with the negative pressure chamber and which is formed between the front side hole row and the rear side hole row.   
     
     
         16 . The apparatus according to  claim 15 ,
 wherein the intermediate suction holes are smaller than those of the front side hole row and the rear side hole row.   
     
     
         17 . A conveying method of a recording medium comprising:
 generating a negative pressure in a negative pressure chamber of an endless device including a plurality of suction holes on a circumferential surface;   opening suction holes in a position which corresponds to a size of the recording medium, among the plurality of suction holes;   closing at least a part of the suction holes in a position which is not covered by the recording medium, among, the plurality of suction holes;   adsorbing the recording medium to the circumferential surface of the endless device, by allowing the negative pressure to act on the recording medium through the opened suction holes; and   conveying the recording medium to the recording head unit by rotating the endless device.   
     
     
         18 . The method according to  claim 17 ,
 wherein the recording medium is supplied to the circumferential surface of the endless device such that the leading end and the trailing end are supposed to position at the opened suction holes.   
     
     
         19 . The method according to  claim 17 ,
 wherein a charge is applied to the circumferential surface of the endless device, in order to electrostatically adsorb the recording medium, using the charge, and   wherein the recording medium is adsorbed in the electrostatic manner to the circumferential surface of the endless device, and the leading end and the trailing end of the recording medium are adsorbed to the endless device using the negative pressure.   
     
     
         20 . The method according to  claim 17 ,
 wherein the leading end and the trailing end of the recording medium in the movement direction, are adsorbed to the endless device using the negative pressure which acts through the suction holes, and portions between the leading end and the trailing end of the recording medium are adsorbed to the endless device using the negative pressure which acts through suction holes smaller than the above suction holes.