Ink jet recording device and method of conveying recording medium in the same

An ink jet recording device includes a recording head, a conveying member, a platen, a supporting member, and a driving member. The recording head ejects ink droplets onto a recording medium. The conveying member conveys the recording medium in a conveying direction. The recording medium has a leading edge and a trailing edge in the conveying direction. The platen is disposed in confrontation with the recording head to support the recording medium while keeping a predetermined distance from the recording head. The supporting member is disposed in the platen to slide in the conveying direction while supporting the recording medium. The driving member drives the supporting member to start sliding in the conveying direction at a starting timing corresponding to a position of at least one of the leading edge and the trailing edge.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink jet recording device.

2. Description of Related Art

An ink jet recording device has a recording head in which a lot of nozzles are arrayed. A recording medium (typically, recording sheet) on which an image is recorded is conveyed below the recording head. The recording head ejects ink drops from the nozzles at a predetermined timing while moving in a main scanning direction (a direction orthogonal to a recording sheet conveyance direction), thereby recording the image on the recording sheet. In recent years, the ink jet recording device has a function of recording the image on the recording sheet without forming a blank space in the border of the recording sheet as in photo printing. Thus, such image recording is called as “borderless recording”.

In the borderless recording, when an image is recorded, ink is ejected to the outside of the recording sheet beyond the border of the recording sheet as well as the recording sheet. For example, in the borderless recording at the front end and the rear end of the recording sheet, the recording sheet is positioned relative to the recording head so that some nozzles of the lot of nozzles may be located outside of the border of the recording sheet and eject ink drops on a platen disposed under the recording sheet. A groove extending in the main scanning direction is provided on an upper surface of the platen. The groove has an ink absorption therein. Thus, ink drops which are not adhered to the recording sheet are adsorbed in the ink absorption material. In Unexamined Patent Application Publication No. 2000-118058, in this manner, the image is recorded all over the recording sheet without forming a blank space in the border of the recording sheet and furthermore, a back surface of the recording sheet is prevented from being smeared with the ink ejected on the platen.

In these years, speeding-up of image recording by the ink jet recording device has been requested. To achieve speeding-up of image recording, upsizing of the recording head has been conventionally attempted. As the recording head is upsized, the number of nozzles aligned in the recording sheet conveyance direction is increased, thereby enabling high-speed recording. However, to perform the above-mentioned borderless recording satisfactorily, as the recording head is upsized, the width dimension (dimension in the recording sheet conveyance direction) of the groove formed on the platen need to be made larger.

When the above-mentioned borderless recording is performed, the recording sheet is disposed on the groove formed on the platen. Thus, when the width of the groove in the recording sheet conveyance direction is increased, the recording sheet is bent downward in the vertical direction and deformed to fall into the groove. When the recording sheet is bent, a distance between the nozzles of the recording head and the surface of the recording sheet is changed, thereby possibly causing defective recording.

In Unexamined Patent Application Publications No. 2001-80145 and No. 2002-307769, to eliminate such disadvantages, a sheet support member is provided in the groove on the platen so as to rotate in connection with conveyance of the recording sheet. Thus, the sheet support member supports the recording sheet advancing on the groove and a region of the sheet support member which supports the recording sheet moves in the groove width direction. Accordingly, even when the recording sheet is conveyed above the groove on the platen, the recording sheet is supported by the sheet support member.

SUMMARY OF THE INVENTION

However, since the sheet support member disclosed in Unexamined Patent Application Publication No. 2001-80145 is rotated around a predetermined rotational center axis, a front end of the sheet support member (a part which contacts against the recording sheet) comes closer to the recording head and then, is separated. For this reason, the recording sheet is not always supported in parallel to the recording head.

To solve this problem, a sufficient rotational radius only needs to be assured. However, this causes a new problem that the ink jet recording device is upsized. Further, a surface of the sheet support member disclosed in Unexamined Patent Application Publication No. 2001-80145 is formed in the shape of an arc extending about the rotational center axis. In this case, a point at the recording sheet is supported is fixed and thus, the end of the conveyed recording sheet is not necessarily supported at all times. That is, when the surface which supports the recording sheet is formed in the shape of an arc, the recording sheet is supported only at the above-mentioned support point and regions other than the support point (regions in front of and in the rear of the support point) are bent. As a result, as mentioned above, defective recording may occur.

Furthermore, the sheet support member disclosed in Unexamined Patent Application Publication No. 2001-80145 needs to be rotated at any time in connection with conveyance of the recording sheet. In addition, to hold the conveyed recording sheet on the groove in a flatter state, the sheet support member needs to swing at all times in the forward and reverse directions of conveyance of the recording sheet. Accordingly, since a motor for driving the sheet support member needs to rotate in the normal and reverse directions, electric power consumption of the ink jet recording device is disadvantageously increased.

In view of the above-described drawbacks, it is an objective of the present invention to provide an ink jet recording device capable of performing high-speed borderless recording by supporting the end of the conveyed recording sheet on the platen at all times.

Another object of the present invention is to provide a compact power-saving ink jet recording device capable of performing satisfactory borderless recording.

In order to attain the above and other objects, the present invention provides an ink jet recording device including a recording head, a conveying member, a platen, a supporting member, and a driving member. The recording head ejects ink droplets onto a recording medium. The conveying member conveys the recording medium in a conveying direction. The recording medium has a leading edge and a trailing edge in the conveying direction. The platen is disposed in confrontation with the recording head to support the recording medium while keeping a predetermined distance from the recording head. The supporting member is disposed in the platen to slide in the conveying direction while supporting the recording medium. The driving member drives the supporting member to start sliding in the conveying direction at a starting timing corresponding to a position of at least one of the leading edge and the trailing edge.

Another aspect of the present invention provides a method of conveying a recording medium in an ink jet recording device. The ink jet recording device includes a recording head, conveying member, a platen, and a supporting member. The recording head ejects ink droplets onto a recording medium. The conveying member conveys the recording medium in a conveying direction. The recording medium has a leading edge and a trailing edge in the conveying direction. The platen is disposed in confrontation with the recording head to support the recording medium while keeping a predetermined distance from the recording head. The supporting member is disposed in the platen to slide in the conveying direction while supporting the recording medium. The platen has a printing region over which the recording head can eject ink droplets. The supporting member slides in printing region. The method includes (a) conveying the recording medium; and (b) driving the supporting member to start sliding in the conveying direction after the leading edge of the recording medium starts sliding in the printing region.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An ink jet recording device according to preferred embodiments of the present invention will be described while referring to the accompanying drawings wherein like parts and components are designated by the same reference numerals to avoid duplicating description.

In the following description, the expressions “front”, “rear”, “upper”, “lower”, “right”, and “left” are used to define the various parts when the ink jet recording device is disposed in an orientation in which it is intended to be used.

FIG. 1is an outline perspective view of a compound machine1(ink jet recording device) in accordance with a first embodiment of the present invention andFIG. 2is a sectional view of the compound machine1.

The compound machine1is a multi function product (MFP) which is provided with a printer unit2in an upper portion thereof and a scanner unit3in a lower portion thereof in an integral manner and has printing, scanning, copying and faxing functions.

As shown inFIG. 1, an opening2ais formed on a front surface of the printer unit2. A sheet feed tray20and a sheet discharge tray21are provided inner of the opening2ain two vertical stages. The sheet feed tray20has a slide tray20a. By pulling out the slide tray20a, the tray surface is enlarged (refer toFIG. 2).

The scanner unit3is provided in the upper portion of the compound machine1. As shown inFIG. 1andFIG. 2, a platen glass31and an image sensor32are provided below a manuscript cover30which is openably formed as a top board of the compound machine1. A manuscript, an image of which is read, is mounted on the platen glass31. The depth direction of the compound machine1(crosswise direction inFIG. 2) is defined as the main scanning direction. The image sensor32is provided below the platen glass31so as to reciprocate in the width direction of the compound machine1(direction perpendicular to the sheet ofFIG. 2).

As shown inFIG. 1andFIG. 2, an operation panel4operating the printer unit2and the scanner unit3is provided on the upper end of the front surface of the compound machine1is provided. A slot unit5is provided in a left upper portion of the front surface of the compound machine1(refer toFIG. 1).

Hereinafter, internal configuration of the compound machine1, especially, configuration of the printer unit2will be described.

As shown inFIG. 2, the sheet feed tray20is provided on the bottom of the compound machine1and a separation inclined plate22is provided in the back of the sheet feed tray20. A sheet conveyance path23extends upward from the separation inclined plate22, turns to the front surface side, extends from the back surface to the front surface of the compound machine1and leads to the sheet discharge tray21through an image recording unit24.

FIG. 3is a partial enlarged sectional view showing main configuration of the printer unit2. As shown inFIG. 3, a sheet feed tray25is provided above the sheet feed tray20. The sheet feed tray25is axially supported at a front end of a sheet feed arm26. The sheet feed tray25is rotationally driven by an LF motor71as a drive source (refer toFIG. 5) via a drive transmission mechanism27. The sheet feed arm26is supported by the base shaft26a.

A curved part17of the sheet conveyance path23on the back surface side of the compound machine1is formed by fixing an outer guide member18and an inner guide member19to a frame. Rotational rollers16are provided at curved places on the sheet conveyance path23.

As shown inFIG. 3, the image recording unit24is disposed on the sheet conveyance path23. The image recording unit24has a carriage38which mounts an ink jet recording head39thereon and reciprocates in the main scanning direction. Ink of colors of cyan (C), magenta (M), yellow (Y) and black (Bk) is supplied to the ink jet recording head39from ink cartridges which is disposed in the compound machine1independently from the ink jet recording head39through ink tubes41(refer toFIG. 4).

FIG. 4is a plan view showing main configuration of the printer unit2, mainly, configuration of a part from a substantially center of the printer unit2to the back surface side of the device.FIG. 5is a perspective view showing main configuration of the printer unit2, that is, configuration of the image recording unit24.

As shown inFIG. 4andFIG. 5, a pair of guide rails43,44are disposed above the sheet conveyance path23. The carriage38extends between the guide rails43,44so as to be slidable in the direction perpendicular to the recording sheet conveyance direction.

An edge45upstream of the guide rail44in the conveyance direction is bent upward at almost right angles. The carriage38carried by the guide rails43,44slidably holds the edge45with holding members such as a pair of rollers.

As shown inFIG. 4, a belt drive mechanism46is disposed on the upper surface of the guide rail44. The belt drive mechanism46is formed by stretching an endless circular timing belt49having teeth on an inner side thereof between a driving pulley47and a driven pulley48. A drive force is transmitted from a CR motor73to a shaft of the driving pulley47(refer toFIG. 5). With rotation of the driving pulley47, the timing belt49is circulated.

As shown inFIG. 4, an encoder strip50of a linear encoder77(refer toFIG. 8) is disposed at the guide rail44. A pair of support parts33,34are formed on both ends of the guide rail44in the width direction (reciprocation direction of the carriage38) so as to rise from the upper surface of the guide rail44.

A pattern in which light-transmitting parts letting light therethrough and light-shielding parts shielding light are alternatively disposed at regular pitches in the longitudinal direction is inscribed on the encoder strip50. An optical sensor35as a transmission sensor is provided at a position corresponding to the encoder strip50on the upper surface of the carriage38.

As shown inFIG. 3andFIG. 4, the platen42is disposed below the sheet conveyance path23as opposed to the ink jet recording head39. The platen42is disposed over a central region of a reciprocation range of the carriage38where the recording sheet passes. The width of the platen42is much larger than a maximum width of the conveyable recording sheet and thus, both ends of the recording sheet certainly pass on the platen42. As described in detail later, the platen42is provided with movable support parts104having movable ribs121(refer toFIG. 8toFIG. 12). The movable support parts104are slidably driven by a drive mechanism105(an example of slide drive means) described later according to a conveyance position of the recording sheet conveyed on the platen42.

As shown inFIG. 4, a maintenance unit such as a purge mechanism51and a waste ink tray84are disposed in a region where the recording sheet does not pass, that is, beyond the range of image recording by the ink jet recording head39. The purge mechanism51serves to suck and remove air bubbles and foreign matters which are generated from nozzles53of the ink jet recording head39(refer toFIG. 6). The purge mechanism51is formed of a cap52which covers the nozzles53of the ink jet recording head39, a pump mechanism connected to the ink jet recording head39through the cap52and a moving mechanism for bringing the cap52into contact with the nozzles53of the ink jet recording head39or separating the cap52from the nozzles53of the ink jet recording head39. InFIG. 4, since the pump mechanism and the moving mechanism are located below the guide frame44, the mechanisms are invisible.

As shown inFIG. 1, a door7is openably formed on the front surface of a housing of the printer unit2. As shown inFIG. 4, the above-mentioned four ink tubes41corresponding to four colors, respectively, are drawn from a cartridge attachment part to the carriage38.

Each ink tube41derived from the cartridge attachment part is drawn to the almost center of the device along the width direction, and as shown inFIG. 4, is fixed at a fixing clip36of the device main unit. InFIG. 4, portions of the ink tubes41which extend from the fixing clip36toward the cartridge attachment part are not shown.

A record signal or other signals are transmitted from a main substrate forming a control unit64(refer toFIG. 15) to a head control substrate of the ink jet recording head39through a flat cable85. The main substrate is disposed on the front surface side of the device (near side inFIG. 4) and is not shown inFIG. 4.

FIG. 6is a bottom view of a nozzle forming surface of the ink jet recording head39. As shown inFIG. 6, the nozzles53are provided on the lower surface of the ink jet recording head39. The nozzles53corresponding to the ink colors of cyan (C), magenta (M), yellow (Y) and black (Bk), respectively, are arranged in the recording sheet conveyance direction. InFIG. 6, the vertical direction represents the recording sheet conveyance direction and the horizontal direction represents the reciprocation direction of the carriage38.

FIG. 7is a partial enlarged sectional view showing internal configuration of the ink jet recording head39. As shown inFIG. 7, a cavity55having a piezoelectric element54is formed upstream of the nozzles53formed on the lower surface of the ink jet recording head39.

A manifold56is formed in the cavity55. A buffer tank57is disposed upstream of the manifold56. Ink flowing through the ink tubes41is supplied from an ink feed port58into the buffer tank57. Air bubbles captured in the buffer tank57are sucked and removed from an air bubble discharge port59by the pump mechanism.

As shown inFIG. 3andFIG. 5, a pair of conveyance rollers89having a conveyance roller87and a pinch roller88are provided upstream of the image recording unit24. The pinch roller88is disposed under the conveyance roller87so as to be pressed against each other. The conveyance roller87and the pinch roller88hold the recording sheet conveyed on the sheet conveyance path23therebetween and convey the recording sheet onto the platen42. The pinch roller88is rotatably supported by a pinch roller holder96with being pressed against the conveyance roller87with a predetermined urging force.

A pair of discharge rollers92having a sheet discharge roller90and a spur roller91provided above the sheet discharge roller90are provided downstream of the image recording unit24. The sheet discharge roller90and the spur roller91hold the recording sheet on which the image is recorded therebetween and convey the recording sheet to the sheet discharge tray21. Since the spur roller91contacts against the recording sheet on which the image is recorded, the roller surface is irregular in the shape of a spur so that the image recorded on the recording sheet may not deteriorate. The spur roller91is provided so as to be slidable in the direction of getting closer to or separating from the sheet discharge roller90, and is urged to contact against the sheet discharge roller90by a coil spring not shown. When the recording sheet enters between the sheet discharge roller90and the spur roller91, the spur roller91retreats against the urging force by the thickness of the recording sheet and holds the recording sheet so as to bring the recording sheet into contact with the sheet discharge roller90. Thereby, a rotational force of the sheet discharge roller90is reliably transmitted to the recording sheet.

A driving force is transmitted from the LF motor71connected to one end of the conveyance roller87in the axial direction (refer toFIG. 5) to the conveyance roller87, thereby intermittently driving the conveyance roller87with a predetermined line feed width. The conveyance roller87is coupled to the sheet discharge roller90with a transmission mechanism such as a gear. A driving force is transmitted from the conveyance roller87to the sheet discharge roller90through the transmission mechanism. Consequently, rotation of the conveyance roller87is synchronized with rotation of the sheet discharge roller90. A rotary encoder76provided at the conveyance roller87(refer toFIG. 15) detects a pattern of an encoder disk61rotating with the conveyance roller87. By controlling the LF motor71on the basis of this detection signal, the conveyance roller87and the sheet discharge roller90are rotationally driven. A rib motor93not shown for sliding the above-mentioned movable support parts104(refer toFIG. 15) is also controlled on the basis of the detection signal. Thereby, the movable support parts104are slidably moved in a predetermined direction at a predetermined timing. A method for driving the movable support parts104will be described by using a flow chart ofFIG. 16.

The recording sheet held between the conveyance roller87and the pinch roller88is intermittently conveyed on the platen42with a predetermined line feed width. The ink jet recording head39is scanned for each line feed to perform image recording starting from the front end side of the recording sheet. The front end of the recording sheet on which the image is recorded is held between the sheet discharge roller90and the spur roller91. That is, the front end of the recording sheet is held between the sheet discharge roller90and the spur roller91and the rear end of the recording sheet is held between the conveyance roller87and the pinch roller88. In this state, the recording sheet is intermittently conveyed with the predetermined line feed width and image recording is performed by the ink jet recording head39for each line feed. When the recording sheet is further conveyed, the rear end of the recording sheet escapes from between the conveyance roller87and the pinch roller88and is released from the pair of conveyance rollers89. That is, the recording sheet is held only between the sheet discharge roller90and the spur roller91and intermittently conveyed. Image recording is performed by the ink jet recording head39for each line feed. After image recording is performed on a predetermined region of the recording sheet, the sheet discharge roller90is rotationally driven continuously. Thereby, the recording sheet held between the sheet discharge roller90and the spur roller91is discharged to the sheet discharge tray21.

A regi-sensor95is located upstream of the pair of conveyance rollers89on the sheet conveyance path23. The regi-sensor95has a sensor inFIG. 3and an optical sensor not shown. The sensor is disposed so as to appear or disappear on the sheet conveyance path23. The sensor is elastically urged to protrude from the sheet conveyance path23at all times. The sensor is rotated so as to disappear on the sheet conveyance path23by contacting against the conveyed recording sheet. Depending on appearance or disappearance of the sensor, the above-mentioned optical sensor is turned ON or OFF. By allowing the sensor to appear by the recording sheet in this manner, the front end or the rear end of the recording sheet on the sheet conveyance path23is detected.

In the compound machine1in accordance with this embodiment, as described above, the LF motor71is a driving source for feeding of the recording sheet from the sheet feed tray20, conveyance of the recording sheet on the platen42and discharge of the recording sheet on which the image is recorded to the sheet discharge tray21. That is, the LF motor71drives drive shafts of the conveyance roller87and the sheet discharge roller90through a predetermined power transmission mechanism formed of a gear train and a timing belt (refer toFIG. 5) and drives the sheet feed tray25through the drive transmission mechanism27.

FIG. 8is an enlarged perspective view of a main part inFIG. 5, that is, the platen42.FIG. 9is a plan view of the platen42. TheFIG. 10is a view of the platen42viewed from the direction of an arrow X inFIG. 9.FIG. 11is a bottom view of the platen42.FIG. 12is a perspective view of the platen42viewed from a bottom surface.

As described above, the platen42is located as opposed to the recording head39(below the recording head39inFIG. 3) and supports the conveyed recording sheet (refer toFIG. 3andFIG. 5). As shown inFIG. 8, the platen42is shaped like an elongated rectangular thin plate as a whole. The platen42is located so that the longitudinal direction extends along the main scanning direction. In the figure, a direction represented by an arrow101is the conveyance direction. The recording sheet is conveyed in the direction of the arrow101by the pair of conveyance rollers89and the pair of sheet discharge rollers92.

The platen42has a frame100, first fixing ribs102and second fixing ribs103which are provided on the frame100, the movable support parts104slidably provided on the frame100and the drive mechanism105which slidably drives the movable support parts104as described below.

The frame100is made of, for example, synthetic resin or steel plate and constitutes a framework of the platen42. The frame100is formed so as to a substantially C-like cross section (so-called channel type). As shown inFIG. 8toFIG. 12, brackets106,107are formed at the bottom end and the front end of the frame100, respectively. These brackets106,107are formed integrally with the frame100. The frame100is fixed to the compound machine1via the brackets106,107(refer toFIG. 3andFIG. 5). InFIG. 9, the right side represents the front end of the frame100and the left side represents the bottom end of the frame100.

A drive mechanism attachment part108is provided at the bottom end of the frame100. As shown inFIG. 8toFIG. 12, especially,FIG. 8andFIG. 12, the drive mechanism attachment part108extends from the bottom end of the frame100and has a top plate110provided on the side of an upper surface109of the frame100and a bottom plate111provided on the side of a lower surface of the frame100. Both the top plate110and the bottom plate111are rectangular and formed integrally with the frame100. The bottom plate111supports the drive mechanism105described in detail later.

The first fixing ribs102and the second fixing ribs103are formed on the upper surface109of the frame100. Specifically, the first fixing ribs102are provided near the upstream end of the upper surface109in the conveyance direction and protrude upward (toward the recording head39). The second fixing ribs103are provided near the downstream end of the upper surface109in the conveyance direction and protrude upward. As shown inFIG. 8, the first fixing ribs102and the second fixing ribs103each are formed of a rectangular thin plate-like member and vertically provided on the upper surface109.

In this embodiment, the plurality of first fixing ribs102are formed on the upper surface109and aligned in the main scanning direction. Similarly, the plurality of second fixing ribs103are formed on the upper surface109and aligned in the main scanning direction. In the figures, a part of the fixing ribs are given reference numerals. By providing the plurality of first fixing ribs102and second fixing ribs103, a groove116are formed between the first fixing rib102and the second fixing rib103. As shown inFIG. 8andFIG. 9, the groove116extends in the main scanning direction as well as spread in the conveyance direction.

The width dimension (dimension in the conveyance direction) of the groove116corresponds to size of the recording head39. Specifically, the width dimension (dimension in the conveyance direction) W of the groove116(refer toFIG. 9) is set to be larger than an ink ejection region118of the recording head39(refer toFIG. 6). The width dimension (dimension in the conveyance direction) W of the groove116corresponds to size of the ink jet recording head39and is set to be larger than a maximum use region118of the ink jet recording head39(refer toFIG. 6). Effects obtained by setting the width dimension W of the groove116to be larger than the maximum use region118will be described in detail later.

In this embodiment, as shown inFIG. 9, one first fixing rib102is opposed to one second fixing rib103across the groove116in the conveyance direction (direction of the arrow101). As shown inFIG. 8, corners112,113of each first fixing ribs102are chamfered to form a pair of inclined planes. In this embodiment, the inclined planes of the corners112,113are formed on the both sides of the first fixing ribs102in the conveyance direction. However, the inclined planes only need to be formed on at least the corners112on the upstream side in the conveyance direction. Similarly, the corners114,115of each second fixing ribs103are chamfered to form a pair of inclined planes. In this embodiment, the inclined planes of the corners114,115on the both sides of the second fixing ribs103in the conveyance direction. However, the inclined planes only need to be formed on at least the corners114on the upstream side in the conveyance direction. Effects obtained by chamfering the corners112to115of the first fixing ribs102and the second fixing ribs103will be described later.

A plurality of slits119are formed on the upper surface109of the frame100. As shown inFIG. 8, the slits119extend from the upstream end to the downstream end of the upper surface109in the conveyance direction. Each slit119is formed continuously between the adjacent first fixing ribs102and between the adjacent second fixing ribs103. The movable ribs121of the movable support parts104are fitted into the slits119from the lower surface to the upper surface109of the frame100and protrude upward from the slits119.

Specifically, each movable support part104is, as shown inFIG. 12, formed of a box-like base120and the movable rib121made of a rectangular thin plate-like member. The movable support parts104may be made of synthetic resin or metal. The base120is formed of a channel member having a C-like cross section and fitted into the inner side of the frame100. Although not shown, both ends of the base120in the main scanning direction are slidably supported by the frame100. Accordingly, the base120can smoothly slide inside of the frame100in the conveyance direction (the direction of an arrow147inFIG. 11).

The movable ribs121are formed on the upper surfaces of the bases120. The movable ribs121are formed integrally with the base120. The movable ribs121are rectangular and protrude upward from the upper surface109of the frame100through the slits119. The plurality of movable ribs121are provided on the upper surface of the base120. Specifically, the plurality of movable ribs121are aligned on the upper surface of the base120with a predetermined distance therebetween along main scanning direction. The predetermined distance corresponds to the pitch of the slits119. Thus, the plurality of movable ribs121protrude upward from the slits119. In the figures, a part of the movable ribs121are given reference numerals.

FIG. 13is an enlarged view of the main part inFIG. 9.FIG. 14is a view showing positional relationship among the movable ribs121, the recording sheet146and the ink jet recording head39when borderless recording is performed, taken along a line XIV-XIV inFIG. 13.

As shown inFIG. 14, when ink drops are ejected to the recording sheet146conveyed on the platen42from the ink jet recording head39, an use region99of the ink jet recording head39is set to overhang from the front end of the recording sheet146in the conveyance direction by a distance f. The distance f is determined by controlling the nozzles53used by the control unit64(refer toFIG. 7). In this figure, the distance f is set on the front end side of the recording sheet146. However, the distance f may be similarly set on the rear end side of the recording sheet146. The distance f is set to about 0.5 mm to 7 mm. In this embodiment, the distance f is set to about 3.5 mm on both the front end side and the rear end side of the recording sheet146.

When the borderless recording is performed, the recording sheet146is positioned so that the front end may overhang from the movable ribs104in the conveyance direction (specifically, from the movable ribs121in the conveyance direction) by a predetermined distance p1. The position of the recording sheet146is adjusted by controlling rotation of the LF motor71by use of the control unit64(refer toFIG. 15). The distance p1is an allowable distance by which the recording sheet146overhangs on the downstream side in the conveyance direction so as to be supported by the movable ribs121without hanging down. The distance p1is determined depending on the type of the recording sheet146and generally set to 0.5 mm to 8 mm. For example, when the recording sheet146is plain paper of A4 size, p1is set to 3.5 mm. In this figure, the distance p1is set on the front end side of the recording sheet146. However, similarly, a distance p2is set on the rear end side of the recording sheet146. In this embodiment, the distance p1and the distance p2are set to the same value.

Here, a distance E1obtained by adding the distance p1to the distance f is defined on the front end side of the recording sheet146and a distance E2obtained by adding the distance p2to the distance f is defined on the rear end side of the recording sheet146. That is, these distances E1, E2each are set to about 1 mm to 13 mm. In this embodiment, both the distances E1and E2are set to 7.0 mm. As shown inFIG. 13andFIG. 14, a length R of the movable ribs104(more specifically, the movable ribs121) in the conveyance direction is set to be smaller than the width dimension W of the groove116. Given that a length of the maximum use region118of the ink jet recording head39in the conveyance direction when borderless recording is performed is H, R is set so as to satisfy R=H−(E1+E2). In this embodiment, since the length H of the maximum use region118in the conveyance direction is set to 24.9 mm, the length of the movable ribs121in the conveyance direction is set to 10.9 mm. The length H may be the size in the case where all of the nozzles53provided at the ink jet recording head39are used or the size in the case where the nozzle53located at the border is eliminated in consideration of accuracy of ejecting ink drops of the nozzle53located at the border. Furthermore, in this embodiment, the width dimension W of the groove116is set to 30.9 mm. However, if the width dimension W of the groove116may be set to another size as long as W>R+E1+E2is satisfied.

Like the first fixing ribs102and the second fixing ribs103, corners122,123of the movable ribs121are chamfered to form a pair of inclined planes. In this embodiment, the inclined planes of the corners122,123are formed on the both sides of the movable ribs121in the conveyance direction. However, the inclined planes only need to be formed on at least the corners122on the upstream side in the conveyance direction. Since the corners122,123of the movable ribs121are chamfered in this manner, even when the end of the recording sheet146which passes through the first fixing rib102comes into contact with the corner122of the movable support part104, the end of the recording sheet146is smoothly guided to the upper surface of the movable support part104. Thus, the movable support parts104do not prevent smooth conveyance of the recording sheet146. Similarly, as described above, since the corners112to115of the first fixing ribs102and the second fixing ribs103are chamfered to form inclined planes, even when the recording sheet146during conveyance comes into contact with the corners112to115, smooth conveyance of the recording sheet146is not prevented.

The drive mechanism105serves to slide the movable support parts104in the recording sheet conveyance direction and has, as shown inFIG. 11andFIG. 12, a pulley125and a swing member126. A timing belt not shown for transmitting a rotational force to the pulley125and the rib motor93, an output shaft of which is connected to the timing belt (refer toFIG. 15), is further provided. In this embodiment, a stepping motor which requires no feedback control is used as the rib motor93. By controlling the rib motor93as described below, a driving force of the rib motor93is transmitted to the pulley125through the timing belt and then, from the pulley125to the swing member126. Thereby, the swing member126is moved in the recording sheet conveyance direction. In this embodiment, the driving force of the rib motor93is transmitted to the swing member126by the timing belt and the pulley125. However, as a matter of course, a transmission mechanism such as a gear may be used in place of the timing belt and the pulley125.

The pulley125is shaped like a disc and is rotatably supported by a rotational center shaft134. The rotational center shaft134is fixed to the frame100(specifically, the bottom plate111) and inserted into the center of the pulley125. The pulley125has a circular groove136. The circular groove136is shaped like a ring and the center of the circular groove136does not correspond to the center of the pulley125. That is, the circular groove136is eccentric to the center of the pulley125. The circular groove136is engaged with a bottom end126aof the swing member126.

The swing member126has a main body137formed of an elongated flat plate, an engaging pin138provided at the bottom end126aof the swing member126(the bottom end126aof the main body137) (refer toFIG. 12) and an engaging rod139provided at a front end126b. The swing member126is also made of synthetic resin or metal. The main body137is rotatably supported by a swing center shaft140. The swing center shaft140is fixed to the bottom plate111of the drive mechanism attachment part108and inserted into a predetermined position of the bottom end126afrom the center of the main body137. The engaging pin138is formed so as to protrude upward from the main body137(refer toFIG. 11) and fitted into the circular groove136of the pulley125. An outer diameter of the engaging pin138corresponds to the groove width dimension of the circular groove136. The engaging pin138can slide relatively along the circular groove136without rattling A publicly known slide mechanism may be used as such configuration.

When the engaging pin138is relatively displaced along the circular groove136, the main body137is rotated about the swing center shaft140. That is, the swing member126swings about the swing center shaft140. Thereby, the engaging rod139provided at the front end126bof the main body137slides in the form of an arc around the swing center shaft140. The engaging rod139is coupled to the base120of the movable support parts104. The base120has a long hole141extending in the longitudinal direction (that is, the main scanning direction) and the engaging rod139is fitted into the long hole141. The outer diameter of the engaging rod120corresponds to the inner diameter of the long hole141. No rattling between the engaging rod139and the long hole141occurs in directions other than the scanning direction.

Thus, as described above, when the main body137swings and the engaging rod139slides in the form of an arc around the swing center shaft140, the engaging rod139slides along the long hole141in the main scanning direction and the base120is moved in the recording sheet conveyance direction. As described above, since the both ends of the base120in the main scanning direction are slidably supported by the frame100, the base120smoothly slides within the frame100and on a virtual plane which is parallel to the upper surface109of the frame100in the conveyance direction (the direction of the arrow inFIG. 11). In other words, by swinging the swing member126, the movable support parts104slide in the conveyance direction.

In this embodiment, the circular groove136is formed so that the movable support parts104may slide between a position T1(refer toFIG. 17) and a position T4(refer toFIG. 19) described below. The slide range of the movable support parts104is not necessarily a range between the position T1and the position T4. The slide range should be at least a range between a position T3at which the end of the first fixing rib102on the side of the groove116substantially coincides with the upstream end of the movable rib121(refer toFIG. 18,FIG. 19) and a position T2at which the end of the second fixing rib103on the side of the groove116substantially coincides with the downstream end of the movable rib121.

FIG. 15is a block diagram showing configuration of the control unit64of the compound machine1.

The control unit64controls an overall operation of the compound machine1including the printer unit3as well as the scanner unit2and is formed of a main substrate connected to the flat cable85. Since configuration of the scanner unit3is not main configuration according to the present invention, detailed description thereof is omitted.

As shown inFIG. 15, the control unit64is formed of a micro computer33mainly having a CPU (Central Processing Unit)65, a ROM (Read Only Memory)66, a RAM (Random Access Memory)67and an EEPROM (Electrically Erasable and Programmable ROM)68and is connected to an ASIC (Application Specific Integrated Circuit)70via a bus69.

The ROM66stores a program for controlling various operations of the compound machine1and table data used for control therein. The RAM67is used as a storage area or a work area for temporarily storing various data used when the CPU65executes the above-mentioned program therein. The EEPROM68stores setting and flags which should be held after power-off.

In response to an instruction of the CPU65, the ASIC70generates a phase excitation signal for passing an electric current to the LF motor71, the CR motor73and the rib motor93. This signal is given to drive circuits72,74,94for driving the motors71,73,94. The drive signal is passed to the motors71,73,94through the drive circuits72,74,94. In this manner, rotation of the motors71,73,94is controlled.

The drive circuit72drives the LF motor71connected to the sheet feed tray25, the conveyance roller87, the sheet discharge roller90and the purge mechanism51and generates an electric signal for rotating the LF motor71in response to an output signal sent from the ASIC70. In response to the electric signal, the LF motor71is rotated. A rotational force of the LF motor71is transmitted to the sheet feed tray25, the conveyance roller87, the sheet discharge roller90and the purge mechanism51through the publicly known drive transmission mechanism formed of a gear and a drive shaft. That is, as described above, in the compound machine1in accordance with this embodiment, the LF motor71acts as a drive source for feeding of the recording sheet from the sheet feed tray20, conveyance of the recording sheet located on the platen42and discharge of the recording sheet on which the image is recorded to the sheet discharge tray21.

The drive circuit74drives the CR motor73and in response to the output signal sent from the ASIC70, generates an electric signal for rotating the CR motor73. In response to the electric signal, the CR motor73is rotated. A rotational force of the CR motor73is transmitted to the carriage38through the belt drive mechanism46, thereby reciprocating the carriage38. In this manner, the reciprocating motion of the carriage38is controlled by the control unit64.

The drive circuit94drives the rib motor93and in response to the output signal sent from the ASIC70, generates an electric signal for rotating the rib motor93. In response to the electric signal, the rib motor93is rotated. A rotational force of the rib motor93is transmitted to the swing member126through the drive mechanism105(refer toFIG. 12). When the rotational force is transmitted to the movable support parts104, the movable support parts104are slid in the recording sheet width direction. Thereby, the movable ribs121are slidingly moved on the platen42in the conveyance direction. Sliding of the movable support parts104by the control unit64will be described below with reference to a flow chart ofFIG. 16.

The drive circuit75drives the ink jet recording head39at a predetermined timing. On the basis of a drive control procedure output from the CPU65, the drive circuit75receives the output signal generated by the ASIC70and controls driving of the ink jet recording head39. The drive circuit75is mounted in the head control substrate to transmit a signal from a main substrate forming the control unit64to the head control substrate through the flat cable85. Thereby, the ink jet recording head39selectively ejects ink of each color to the recording sheet at a predetermined timing.

The ASIC70is connected to the rotary encoder76for detecting rotation of the conveyance roller87, the linear encoder77for detecting position of the carriage38and the regi-sensor95for detecting the front end and the rear end of the recording sheet (refer toFIG. 3). On turning on the compound machine1, the carriage38is moved to ends of the guide rails43,44to initiate detection position of the linear encoder77. When the carriage38is moved on the guide rails43,44from the initial position, the optical sensor35provided on the carriage38detects the pattern of the encoder strip50. The number of pulse signals based on the pattern is grasped by the control unit64as movement of the carriage38. On the basis of the movement, to control the reciprocating motion of the carriage38, the control unit64control rotation of the CR motor73. The control unit64grasps position of the front end and the rear end of the recording sheet on the basis of a signal of the regi-sensor95and encoded quantity detected by the rotary encoder76and when the front end of the recording sheet reaches a predetermined position of the platen42, controls rotation of the LF motor71to intermittently convey the recording sheet for each predetermined line feed width. The line feed width is set based on resolution or the like input as a record condition. When borderless recording on the recording sheet is performed, the control unit64controls rotation of the LF motor71so that the use region99of the ink jet recording head39overhang from the recording sheet by the distance f in the conveyance direction. The overhang distance f can be set to 0.5 mm to 7 mm.

The ASIC70is connected to the scanner unit3, the operation panel4for instructing operations of the compound machine1, the slot unit5for inserting various small-sized memory cards thereinto, and a parallel interface78and an USB interface79for receiving/transmitting data from/to an external information device such as a personal computer through a parallel cable or an USB cable. The ASIC70is further connected to an NCU (Network Control Unit)80and a modem81for performing a faxing function.

Referring to a flow chart ofFIG. 16and schematic views ofFIG. 17toFIG. 19, an example of the slide control processing procedure and example of the slide operation of the movable support parts104which are executed by the control unit64, respectively, will be described.FIG. 16is the flow chart for illustrating the example of the slide control processing procedure.FIG. 17toFIG. 19are the schematic views for illustrating the slide operation of the movable support parts104. S1, S2in the figures represent processing procedure (step) numbers. The processing starts from a step S1.

In the compound machine1, the user performs setting of enabling a borderless recording function with the operation panel4in advance. Then, after inputting of an instruction to start image recording, processing after the step S1is started. When determination is made that borderless recording is not set, that is, normal image recording is performed, image recording is performed in the state where the movable support parts104are stationary at a reference position set around the center of the groove116.

On the other hand, when determination is made that the borderless recording function is set, first, the movable support parts104are moved to the reference position. The sensor124(refer toFIG. 8) is provided at one end on the side of the main scanning direction of the movable support parts104. A photo interrupter not shown for detecting the sensor124is provided at a guide member on the sheet conveyance path23. The sensor124and the photo interrupter are located at the position where the sensor124can be detected by the photo interrupter when the movable support parts104are moved to the reference position. Thus, by driving the rib motor93while monitoring a detection signal sent from the photo interrupter, movement of the movable support parts104to the reference position is achieved.

When the movable support parts104are moved to the reference position, at the step S1, the movable support parts104are slid to the position T1shown inFIG. 17. The position T1is a predetermined position between adjacent first fixing ribs102. In this processing, specifically, as described above, in response to the instruction of the CPU65, the ASIC70generates the phase excitation signal for passing the electric current to the rib motor93. Then, the electric signal generated by the drive circuit94in response to the output signal of the ASIC70is sent to the rib motor93, thereby sliding the movable support parts104. The instruction of the CPU65contains the number of steps which is required to slide the movable support parts104from the reference position (around the center of the groove116) to the position T1as positional information. Based on the number of steps, the rib motor93is rotationally driven. Since the below-mentioned sliding of the movable support parts104to the positions T2, T3, T4is performed according to the same control procedure as that in the sliding to the position T1, the slide processing procedure to each position will be omitted in the following description.

In this embodiment, the movable support parts104are slid from the reference position to the position T1prior to the below-mentioned feeding of the recording sheet. However, the movable support parts104may be moved to the image recording position to the position T1before the recording sheet reaches to the position on the platen42. Alternatively, even after the recording sheet reaches to the image recording position, the movable support parts104may be moved to the position T1before image recording on the recording sheet is performed.

When the movable support parts104are slid to the position T1, at a step S2, the recording sheet146accommodated in the sheet feed tray20(refer toFIG. 17) is conveyed toward the platen42. Describing in detail, first, by controlling driving of the LF motor71by the control unit64to rotate the sheet feed tray25, a uppermost recording sheet146in the sheet feed tray20is sent to the sheet conveyance path23. When the recording sheet146reaches the pair of conveyance rollers89, a resist operation is performed. By the resist operation, the front end of the recording sheet146is adjusted to correct inclination of the recording sheet146. Specifically, advance of the recording sheet146is inhibited by the pair of conveyance rollers89rotated by the LF motor71in the direction of returning the recording sheet146upstream in the conveyance direction (reverse rotation). The resist operation is continued until a predetermined time period has elapsed since the front end of the recording sheet146is detected by the regi-sensor95. When the resist operation is finished, the pair of conveyance rollers89rotates in the direction of conveying the recording sheet146downstream in the conveyance direction (normal rotation). At this time, the front end of the recording sheet146is conveyed by the pair of conveyance rollers89to the position where the image is recorded by the image recording unit24(specifically, the ink jet recording head39) (image recording position). That is, head-finding conveyance of the recording sheet146is performed. The head-finding conveyance is performed by controlling driving of the LF motor71on the basis of the number of steps corresponding to the distance between the resist position where the resist operation is performed and the image recording position. By the head-finding conveyance, the front end of the recording sheet146is conveyed to the position at which the recording sheet146protrudes on the groove116by the width p1and is made stationary in this state. When the recording sheet146is conveyed to the image recording position, as shown inFIG. 17A, the front end of the recording sheet146is supported by the first fixing ribs102and the movable ribs121. At this time, the movable ribs121are completely covered with the recording sheet146in a plan view.

When head-finding conveyance of the recording sheet146is performed, at a step S3, image recording on a region for one line feed is performed. That is, the scanning carriage38is slidingly reciprocated once in the main scanning direction while ink drops are selectively ejected from the ink jet recording head39. Since the movable ribs121is completely covered with the recording sheet146in a plan view, even when the ink drops are blown to the front end of the recording sheet146, the movable ribs121are not smeared with ink.

Subsequently, at a step S4, it is determined whether or not the front end of the recording sheet146is located at the position where image recording is performed. Specifically, it is determined whether or not the front end of the recording sheet146falls within a range between the image recording position and the downstream end of the frame100in the conveyance direction (hereinafter referred to as an “end printing range”). Such determination is made, for example, by allowing the CPU64to monitor the number of steps of the LF motor71from the resist position or the number of steps of the LF motor71after head-finding conveyance and calculating the conveyance position of the recording sheet146from the number of steps. As a matter of course, a determination method is not limited to the above-mentioned method and determination may be made by detecting the conveyance position of the recording sheet146using a plurality of optical sensors. The above-mentioned end printing range is merely an example. The range may be appropriately set and, for example, a range where the front end of the recording sheet146is located on the groove116.

When it is determined that the front end of the recording sheet146falls within the end printing range at the step S4, the movable support parts104are slid at the timing (slide start timing) according to the conveyance position of the front end of the recording sheet146. Specifically, first, the recording sheet146is intermittently conveyed by one line feed (S5) and then, the movable support parts104are slid downstream in the conveyance direction by one line feed (S6). That is, sliding of the movable support parts104is performed at a timing later than conveyance of the recording sheet146. At this time, the movable support parts104are slid in the state where the front ends of the movable ribs121in the conveyance direction are shifted upstream from the front end of the recording sheet146in the conveyance direction by the width p1. As a result, the movable ribs121are covered with the recording sheet146at all times.

Here, intermittent conveyance of the recording sheet146is achieved by controlling driving of the LF motor71by the control unit64on the basis of the number of steps corresponding to one line feed width. Sliding of the movable support parts104is also achieved by controlling driving of the rib motor93by the control unit64on the basis of the number of steps corresponding to one line feed width. In this embodiment, when it is determined that the front end of the recording sheet146falls within the end printing range at the step S4, as described above, first, the recording sheet146is conveyed and then, the movable support parts104are slid. Thus, the problem does not occur that undried ink ejected to the front end of the recording sheet146is adhered to the movable ribs121. Furthermore, the back surface of the recording sheet146is not smeared with ink.

In this embodiment, the movable support parts104are slid after intermittent conveyance of the recording sheet146is finished. However, intermittent conveyance of the recording sheet146needs only to be started ahead of the sliding. Thus, sliding of the movable support parts104may be started during intermittent conveyance of the recording sheet146. In this case, for example, it is necessary to assure that the movable ribs121slid later may not pass the conveyance position of the front end of the recording sheet146by setting the conveyance speed of the recording sheet146and the moving speed of the movable ribs121to the same speed. Intermittent conveyance of the recording sheet146and sliding of the movable support parts104may be started simultaneously by bringing the operations in sync with each other. In either case, the problem does not occur that ink is adhered to the movable ribs121and smears the movable ribs121.

When movement of the movable support parts104is finished, at a step S7, it is determined whether or not image recording for 1 page is finished. Such determination can be made, for example, by allowing the CPU64to monitor the number of steps of the LF motor71or the number of times of scanning of the carriage38and determining whether or not the monitored value reaches a predetermined value. Here, when it is determined that image recording for 1 page is finished (Yes at S7), the recording sheet146on which the image is recorded is discharged to the sheet discharge tray21. On the other hand, when it is determined that image recording for 1 page is not finished (No at S7), the processing at the step S3and the subsequent steps is repeated. By repeating conveyance of the recording sheet146(S5) and sliding of the movable support parts104(S6) by repeating processing at the step S3to the step S6in this manner, the movable support parts104are slid from the position T1shown inFIG. 17Aso as to follow conveyance of the recording sheet146as shown inFIGS. 17B and 17C. Sliding of the movable support parts104at this time is stopped at the point when the movable support parts104reaches the position T2where the downstream ends of the movable ribs121in the conveyance direction substantially coincide with the ends of the second fixing ribs103on the side of the groove116. At the position T2, the movable support parts104remain at rest for a while. The position T2may be any position as long as the recording sheet146can be guided to the second fixing ribs103without hanging-down of the front end of the recording sheet146toward the groove116and damage of the front end. Thus, a gap of the width p1between the movable ribs121and the second fixing ribs103causes no problem.

When the recording sheet146is further conveyed, for example, as shown inFIG. 18A, it is determined that the front end of the recording sheet146does not fall within the end printing range at the step S4(No at S4). Such determination can be easily made by grasping the conveyance position of the recording sheet146on the basis of the number of steps monitored by the CPU64. When it is determined as described above, the procedure proceeds to a step S9. At the step S9, it is determined whether or not the rear end of the recording sheet146is located at the position where image recording is performed. Specifically, it is determined whether or not the rear end of the recording sheet146is located in the end printing range. Such determination is made by calculating the conveyance position of the recording sheet146on the basis of the number of steps of the LF motor71from the resist position or the number of steps of the LF motor71after head-finding conveyance. Here, when determination is made that the rear end of the recording sheet146is not located in the end printing range (No at S9), the procedure proceeds to a step S12.

At the step S12, it is determined whether or not the conveyance position of the recording sheet146is a center record position. Here, the center record position is a conveyance position of the recording sheet146where image recording is performed in the state where the recording sheet146is conveyed while being held between both the pair of conveyance rollers89and the pair of sheet discharge rollers92. The determination at the step S12is also made by calculating the conveyance position of the recording sheet146on the basis of the number of steps of the LF motor71from the resist position or the number of steps of the LF motor71after head-finding conveyance. Needless to say, the determination is made on the basis of detection signals of the regi-sensor95and a sensor not shown which is provided downstream of the pair of sheet discharge rollers92.

When the recording sheet146is further conveyed, the front end of the recording sheet146escapes from the end printing range and then determination is made that the conveyance position of the recording sheet146is the center record position at the step S12(Yes at S12), it is determined whether or not the movable support parts104are located at the position T3shown inFIG. 18Cat a step S13. Here, the position T3is a position where the upstream ends of the movable ribs121in the conveyance direction substantially coincide with the ends of the first fixing ribs103on the side of the groove116. At the present time, since the movable support parts104are rest at the position T2shown inFIG. 17C, the movable support parts104are not located at the position T3. The position T3may be any position as long as the end of the recording sheet146can be guided from the first fixing ribs102to the movable ribs121without hanging-down of the end (the front end or the rear end) of the recording sheet146toward the groove116and damage of the end. Thus, a gap of the width p1between the movable ribs121and the first fixing ribs102causes no problem.

When it is determined that the movable support parts104are not located at the position T3at the step S13(No at s13), the movable support parts104are slid to the position T3at a next step S14(refer toFIG. 18C). That is, the movable support parts104are slid from the position T2shown inFIG. 18Ain the direction opposite to the conveyance direction of the recording sheet146as shown inFIGS. 18B and 18C, that is, from the position T2to the upstream side in the conveyance direction. Then, after sliding in the reverse direction, the recording sheet146on which the image is recorded is intermittently conveyed downstream in the conveyance direction (S15). After that, the procedure proceeds to the step S7.

On the other hand, when it is determined that the movable support parts104are located at the position T3at the step S13(Yes at S13), sliding of the movable support parts104in the reverse direction is stopped and only intermittent conveyance of the recording sheet146is performed (S15).

When it is determined that the conveyance position of the recording sheet146is not the center record position at the step S12, that is, recording sheet146are not held by both the pair of conveyance rollers89and the pair of sheet discharge rollers92, the movable support parts104are not slid in the direction opposite to the conveyance direction and the recording sheet146on which the image is recorded is intermittently conveyed downstream in the conveyance direction (S15). As described above, in this embodiment, only when the recording sheet146is conveyed while being held by both the pair of conveyance rollers89and the pair of sheet discharge rollers92, that is, the recording sheet146is in a stable state without being pulled due to the frictional force with the movable ribs121, the movable support parts104are slid in the reverse direction. Thus, bending of the recording sheet146is prevented, thereby achieving satisfactory image recording.

When the recording sheet146is conveyed while being held only by the pair of sheet discharge rollers92, the movable support parts104may be slid in the reverse direction. This is due to that even when the recording sheet146is pulled and bent once by sliding of the movable support parts104in the reverse direction, the bending is removed by subsequent intermittent conveyance of the recording sheet146.

When the recording sheet146is further conveyed as shown inFIG. 19A, determination is made that the rear end of the recording sheet146is located in the end printing range at the step S9(Yes at S9). Such determination can be easily made by grasping the conveyance position of the recording sheet146on the basis of the number of steps monitored by the CPU64. When it is determined as described above, the movable support parts104are slid at a timing (slide start timing) according to the conveyance position of the rear end of the recording sheet146. Specifically, first, the movable support parts104are slid downstream in the conveyance direction by one line feed at the step S10. Then, the recording sheet146is intermittently conveyed by one line feed (S11). At this time, the movable support parts104are slid in the state where the rear ends of the movable ribs121in the conveyance direction are shifted downstream from the rear end of the recording sheet146in the conveyance direction by at least the width p1(corresponding to the predetermined width). Thus, the movable ribs121are covered with the recording sheet146at all times. When the recording sheet146is intermittently conveyed by one line feed, the procedure proceeds to the step S7. That is, sliding of the movable support parts104is performed at an earlier timing of conveyance of the recording sheet146. Accordingly, in this case, the recording sheet146is conveyed so as to follow sliding of the movable support parts104. In this embodiment, after the image is recorded on the rear end of the recording sheet146, the movable support parts104are, as shown inFIG. 19, slid to the position T4downstream of the position T2in the conveyance direction. The position T4is a predetermined position between the adjacent second fixing ribs102.

In this embodiment, as described in the case at the steps S10and S11, after the movable support parts104are slid by the predetermined width, the recording sheet146is intermittently conveyed. However, for example, when the conveyance speed of the recording sheet146and the moving speed of the movable ribs121are the same speed or the rear end of the recording sheet146cannot catch the movable ribs121, sliding of the movable support parts141needs only to be started ahead of the intermittent conveyance. Thus, intermittent conveyance of the recording sheet146may be started during sliding of the movable support parts104. Sliding of the movable support parts104and intermittent conveyance of the recording sheet146may be started simultaneously by bringing the operations in sync with each other. In either case, the problem does not occur that ink is adhered to the movable ribs121and smears the movable ribs121.

As described above, in this embodiment, when it is determined that the rear end of the recording sheet146is located in the end printing range at the step S9, as described above, first, the movable support parts104are slid and then, the recording sheet146is conveyed. Thus, immediately after recording, the rear end of the recording sheet146does not move on the movable ribs121. Accordingly, the problem does not occur that undried ink ejected to the rear end of the recording sheet146is adhered to the movable ribs121and the back surface of the recording sheet146is not smeared with the ink. In this embodiment, the movable support parts104are slid in the state where the rear ends of the movable ribs121in the conveyance direction are shifted downstream in the conveyance direction from the rear end of the recording sheet146in the conveyance direction by the width p1(corresponding to the predetermined width). Thus, since the movable ribs121are covered with the recording sheet146at all times, ink is not adhered to the movable ribs121.

In this embodiment, when borderless recording is performed, image recording on the end of the recording sheet becomes possible while ink drops are ejected from all nozzles of the recording head39. That is, borderless recording is performed at high speed and complicated control in relation to ejection of ink drops from an ink ejection port53becomes unnecessary. Furthermore, the cross section of the ink ejection port53is not necessarily a perfect circle. Minute dusts may be adhered to inner surface of the ink ejection port53. Accordingly, ink drops may be ejected in a slight oblique direction, not directly below the ink ejection port53. In this case, since the width W of the groove116is set to be larger than the ink ejection region118of the recording head39, the ink drops are not adhered to the outside of the groove116. As a result, it is possible to reliably prevent the back surface of the recording medium from being smeared with ink, (Effect of B0105)

Next, a second embodiment of the present invention will be described with reference toFIG. 20toFIG. 22. In the second embodiment, description of elements which are same as those in the first embodiment is omitted.

Referring to a flow chart ofFIG. 20and schematic views ofFIG. 21toFIG. 22, an example of slide control processing procedure and an example of a slide operation of movable support parts104in accordance with the second embodiment, respectively, will be described.FIG. 20is the flow chart for illustrating the example of the slide control processing procedure in the second embodiment.FIG. 21toFIG. 22are the schematic views for illustrating the slide operation of the movable support parts104.

In the second embodiment (FIG. 20), processing at a step20is performed in place of the processing at the step S5and the step S6in the first embodiment (FIG. 16) and processing at a step S21is performed in place of the processing at the step S10and the step S11in the first embodiment. Here, only the step S20and the step S11are described and description of the other steps is omitted.

By the head-finding conveyance performed at the step S2, as described above, the front end of the recording sheet146overhangs from the movable ribs104by the distance p1and the use region99of the ink jet recording head39overhangs from the front end of the recording sheet146in the conveyance direction by the distance f (refer toFIG. 18). When the main scanning recording for one line feed is performed, the procedure proceeds to the step S4.

In this embodiment, when the front end of the recording sheet146is in the end printing range (Yes at S4), the procedure proceeds to the step S20. At the step S20, conveyance of the recording sheet146and movement of the movable ribs104are performed simultaneously. Specifically, as shown inFIGS. 21A and 21B, the movable ribs104are slid downstream in the conveyance direction following conveyance of the recording sheet146while supporting the front end of the recording sheet146. That is, the movable ribs104follows the recording sheet146as the overhang distances f and p1are maintained. At this time, since the area where the recording sheet146covers the platen42becomes larger as the recording sheet146is conveyed, the use region99of the ink jet recording head39also becomes larger with conveyance of the recording sheet146. As shown inFIG. 21C, the movable ribs104returns to the initial position T3(the center of the groove116) and the use region99of the ink jet recording head39becomes maximum. As in the first embodiment, the procedure proceeds to the step S7.

When the recording sheet146is further conveyed, at the step S4and it is determined that the front end of the recording sheet146is not located in the recording range (No at S4), the procedure proceeds to the step S9. When determination is made that the rear end of the recording sheet146is located in the end printing range at the step S9(Yes at S9), the procedure proceeds to the step S21.

At the step S21, the movable ribs104follow the recording sheet146again and moves in the conveyance direction. Specifically, when the rear end of the recording sheet146passes the regi-sensor95(refer toFIG. 3), the control unit64grasps that the rear end passes the regi-sensor95on the basis of a signal output from the regi-sensor95(FIG. 22A). On the basis of encoder quantity detected by the rotary encoder76, position of the rear end of the recording sheet146is grasped by the control unit64. When the rear end of the recording sheet146gets closer to the movable ribs104and overhangs upstream in the conveyance direction from the movable ribs104by the distance p2and the use region99of the ink jet recording head39overhangs upstream in the conveyance direction from the rear end of the recording sheet146by the distance f, the movable ribs104which stops at the initial position are slid in the conveyance direction.

As shown inFIG. 22C, the movable ribs104are slid downstream in the conveyance direction following the recording sheet146while supporting the rear end of the recording sheet146. Specifically, the rib motor93is driven by the control unit64, thereby rotating a rotational plate125to the right inFIG. 12. Then, the movable ribs104reach the position shown inFIG. 22Dand stops. At this time, as described above, the rear end of the recording sheet146overhangs from the movable ribs104by the distance p2and the use region99of the ink jet recording head39overhangs from the front end of the recording sheet146in the conveyance direction by the distance f.

In the compound machine1in accordance with this embodiment, especially when borderless recording is performed, the above-mentioned overhang distance f is set. Thus, the ink drops ejected from the ink jet recording head39are reliably ejected to the border of the recording sheet146, thereby preventing defective recording such as so-called printing in white. When the recording sheet146is conveyed on the platen42, the movable ribs104are slid while supporting the recording sheet146. Thus, the front end and the rear end of the recording sheet146are supported at all times. Consequently, even when the recording sheet146is plain paper or the other high visible paper, the recording sheet146never hangs down and the distance between the recording sheet146and the ink jet recording head39is kept constant. As a result, high-image quality borderless printing is achieved.

Since the length R of the movable ribs104in the conveyance direction is set as described above, even when the movable ribs104are stopped in the center of the platen42during conveyance of the recording sheet146, the front end and the rear end of the conveyed recording sheet146do not hang down. That is, by setting the length R of the movable ribs104as described above, the movable ribs104are designed to have necessary and sufficient size. Thus, the movable ribs104need not be slid in the direction opposite to the conveyance direction during printing to prevent hanging-down of the end of the recording sheet146and support the recording sheet146. Consequently, the compound machine1can be made compact and the motion of the movable ribs104in image recording is simplified. As a result, control of the movable ribs104by the control unit64is simplified and electric power for driving the movable ribs104is reduced.

In addition, since the conveyed recording sheet146is supported by the movable ribs104, the width dimension W of the groove116provided on the platen42can be set large. Thus, the use region99of the ink jet recording head39is set large, thereby enabling high-speed recording. In this embodiment, since the distance E1obtained by adding the overhang distance f to the overhang distance p1and the distance E2obtained by adding the overhang distance f to the overhang distance p2are each set to 1 mm to 13 mm, even when the recording sheet146is any of plain water, photo L-size paper or the other various recording media, hanging-down of the recording sheet146is prevented. Thus, irrespective of the type of the recording medium, satisfactory borderless recording is advantageously performed.

In this embodiment, since the width dimension W in the conveyance direction of the groove116provided on the platen42is set so as to satisfy W>R+E1+E2, even when the use region99of the ink jet recording head39varies in any way during borderless recording, ink drops ejected beyond the border of the recording sheet146are reliably received in the groove116. Thus, it is possible to reliably prevent the platen42and the recording sheet146from being smeared with the ink drops ejected from the ink jet recording head39.

In this embodiment, since the conveyed recording sheet146is supported by the first fixing ribs102, the second fixing ribs103and the movable ribs104, a contact area between the recording sheet146and each of the ribs102to104becomes smaller and thus, smooth conveyance of the recording sheet146is achieved. Moreover, since configuration of the first fixing ribs102, the second fixing ribs103and the movable ribs104becomes extremely simple, increase in manufacturing costs of the compound machine1is advantageously suppressed.

While the invention has been described in detail with reference to the specific embodiment thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention. For example, the drive source for the movable ribs104is not specifically limited. The movable ribs104may be driven by the CR motor73as a drive source. Specifically, the movable ribs104may be driven by power which is generated by the carriage38slid by CR motor73and transmitted through the drive mechanism.

The above-mentioned embodiments are merely examples of the present invention. Thus, as a matter of course, the embodiments may be modified as necessary so as not to change the subject matter of present invention. For example, unlike the above-mentioned embodiments, a drive mechanism described in Japanese Patent Application Publication No. 2006-326990, which are previously filed by this Applicant, may be adopted as the drive mechanism.