JP4089471B2 - Recording medium transport device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recording medium conveying apparatus that conveys a recording medium, and a recording apparatus including the recording medium conveying apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, for example, an ink jet printer, which is one of recording apparatuses, has a configuration in which, for example, a sheet, which is one of recording media, is recorded while being sent to a recording unit by a paper transport device and is sent to the outside. In such an ink jet printer, paper is recorded by a recording head while being nipped and fed by a paper feed roller and its driven roller, and is nipped and sent by a paper discharge roller and a spur roller as its driven roller. ing.
[0003]
In an ink jet printer equipped with such a paper transport device, when an image on which a large number of ink droplets are ejected, such as a solid image, is recorded on the paper, the paper absorbs a large amount of ink and is recorded. A so-called cockling that swells later in the recording head side may occur. When this cockling occurs and develops, the gap between the paper and the recording head becomes non-uniform, and the flying distance of ink droplets varies, resulting in uneven recording, or the paper contacts the recording head. There is a problem that gets dirty. Therefore, in recent years, there has been proposed an ink jet printer that punches a plurality of holes in a sheet conveyance surface and sucks the sheet with a suction pump or the like through these holes to suppress the cockling described above (Patent Document 1, Patent Document 1). 2).
[0004]
[Patent Document 1]
JP-A 63-303781 [Patent Document 2]
Japanese Patent Laid-Open No. 3-270
[Problems to be solved by the invention]
In the ink jet printer provided with the above-described conventional suction-type paper conveyance device, since it has a configuration in which a through-hole is just opened in the paper conveyance surface and sucks, the entire area of the paper is printed in the recording unit with an appropriate suction force. It is difficult to suppress the cockling described above. Conversely, if the suction force is too strong, cockling can be suppressed over the entire surface of the paper, but the paper feeding accuracy may be reduced.
[0006]
The present invention has been made in view of the various problems as described above, and an object of the present invention is to provide a recording medium conveying apparatus capable of suppressing the influence of cockling when conveying a recording medium, and the recording medium conveying apparatus. It is to provide a recording apparatus provided.
[0007]
[Means for Solving the Problems]
To achieve the above object, the recording medium conveying apparatus according to the present invention includes a recording medium supporting member that supports the recording medium to be conveyed and has a plurality of suction holes for sucking the recording medium. A recording medium conveyance device of a recording apparatus that discharges ink to the supported recording medium by a recording head, the support surface of the recording medium support member extending from a conveyance upstream side of the recording medium to a conveyance downstream side; And a dimple having a plurality of the suction holes on the bottom surface,
The dimple is characterized in that the depth of the transport downstream end is deeper than the depth of the transport upstream end. As a result, even with an appropriate suction force, it can be sucked into the dimple from the cockling recess that has occurred immediately after recording to the cockling recess that has developed after recording, so that it can be transported by suction. The protrusion from the surface can be suppressed, and the distance between the recording medium and the recording head can be kept uniform.
[0009]
The dimples are formed so as to gradually become deeper from the transport upstream end of the recording medium toward the transport downstream end. The dimples are formed so that the predetermined length gradually increases from the transport upstream end of the recording medium toward the transport downstream end, and thereafter, the dimples are formed to have a constant depth up to the transport downstream end of the recording medium. It is characterized by having. Further, the dimple is formed so that a predetermined length becomes a first depth from the conveyance upstream end of the recording medium toward the conveyance downstream end, and thereafter, from the first depth to the conveyance downstream end of the recording medium. It is characterized by being formed at a deep second depth. Accordingly, since the concave portion of the cock ring that becomes the maximum at the time of drying after recording can be surely drawn into the dimple, the protruding portion of the convex portion of the cock ring from the recording medium conveyance surface can be suppressed almost completely.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a side view showing a recording medium conveying apparatus according to an embodiment of the present invention. The recording medium transport apparatus 100 includes a suction unit 110 that sucks and holds a recording medium during recording, and a recording medium transport unit 150 that transports the recording medium from the upstream side to the downstream side of the suction unit 110. The suction unit 110 is disposed on the lower side of the recording head 231 for recording on a recording medium with the recording medium conveyance path L interposed therebetween. The upper suction part 120 and the lower suction force generation part 130 are formed in a hollow box shape having two upper and lower stages.
[0013]
The suction unit 120 includes a decompression chamber 121 formed therein, and a plurality of suction chambers 123 that are characteristic portions of the present invention and are formed in the recording medium transport surface 122 as rectangular recesses that are long in the recording medium transport direction. And a plurality of suction holes 124 having a circular cross-sectional area smaller than the suction chamber 123 extending in the vertical direction so that the suction chambers 123 communicate with the decompression chamber 121, respectively.
[0014]
2A and 2B are a plan view and a cross-sectional side view taken along the line AA of the suction unit 120, respectively. The suction chamber 123 is formed so that the short side has a predetermined length and the long side extends from the vicinity of the upstream end of the recording medium conveyance surface 122 to the vicinity of the downstream end. That is, the suction chambers 123 are formed so as to communicate with each other in the recording medium conveyance direction and to be arranged with the partition wall 125 in between in a direction orthogonal to the recording medium conveyance direction. The suction holes 124 are formed at a predetermined pitch in the recording medium conveyance direction on the bottom surface of the suction chamber 123. That is, the suction holes 124 are formed in one row for each suction chamber 123.
[0015]
The suction force generation unit 130 is communicated with the decompression chamber 121 of the suction unit 120 via the communication hole 131 and includes a pump 132 having a centrifugal fan therein. The pump 132 is attached to a predetermined position below the decompression chamber 121 so as to communicate with the decompression chamber 121 via the communication hole 131, and the centrifugal fan rotates during recording.
[0016]
The recording medium conveying means 150 includes a feeding roller 151 that feeds the recording medium between the recording head 231 and the suction unit 110, a driven roller 152 that is pressed against the feeding roller 151 from above, and the recording medium to the outside. A discharge roller 153 for discharging, and a spur roller 154 that comes into contact with the discharge roller 153 from above are provided. It should be noted that the discharge roller 153 and the spur roller 154 can be omitted by making the suction unit 110 movable in the discharge direction.
[0017]
As described above, the suction hole is constituted by the suction hole 124 and the suction chamber 123, and the suction hole 124 is formed by a small-diameter through hole, thereby increasing the utilization rate of the negative pressure that can be used for the characteristics of the pump 132. At the same time, by forming the suction chamber 123 as a substantially rectangular recess having a larger area than the suction hole 124, a large suction force can be generated with respect to the recording medium.
[0018]
Here, conventionally, the recording medium floats and protrudes on the recording medium conveyance surface due to the occurrence of cockling undulating in the direction orthogonal to the recording medium conveyance direction. However, in the present invention, the recording medium is orthogonal to the recording medium conveyance direction. Since the dimple-shaped suction chamber 123 is formed on the recording medium conveyance surface 122 so as to be lined up with the partition wall 125 in the direction, the concave portion of the cock ring is drawn into the dimple-shaped suction chamber 123 and the convex portion of the cock ring is The portion can be along the top of the partition wall 125. Therefore, the protrusion of the recording medium from the recording medium conveyance surface 122 can be suppressed, and the recording accuracy can be improved by making the interval between the recording medium and the recording head 231 uniform. However, it has been found that the uneven state of the cockling of the recording medium changes as time elapses from the start of recording.
[0019]
FIG. 3 is a diagram illustrating the uneven state of cockling of the recording medium after a predetermined time has elapsed since the start of recording. Note that the solid line in the drawing indicates the uneven state of the recording medium conveyance surface 122 in the main scanning direction, and the depth of the suction chamber 123 in this example is about 0.5 mm. As shown by the dashed line in the figure, the amplitude of the concave and convex portions of the cockling of the recording medium after about 3.6 seconds from the start of recording is about 0.46 mm, and the protrusion of the recording medium from the recording medium conveying surface 122 is It can be completely prevented. However, as shown by the two-dot chain line in the figure, the amplitude of the concave and convex portions of the cockling of the recording medium after 22.4 seconds has elapsed since the start of recording has developed to about 0.7 mm. Projecting from the surface 122.
[0020]
Therefore, as a result of repeated measurement of the cockling behavior in various recording media and various environments, the deformation of the recording medium is small if the recording medium is only wetted by the adhesion of the ink. It has been found that the growth starts, and that the deformation of the recording medium tends to shrink as the ink dries further. The deformation peak of the recording medium is usually when the recorded area of the recording medium moves to the downstream side of the conveyance, and the main scanning direction of the carriage on which the recording head 231 is mounted (the conveyance direction of the recording medium). This may be achieved when in a moving region (in the orthogonal direction).
[0021]
Therefore, by setting the depth of the suction chamber 123 in the area downstream from the deformation peak portion of the recording medium to be deeper than the depth of the suction chamber 123 in the area upstream of the deformation peak portion, recording on the recording medium is performed. Protrusion from the medium conveyance surface 122 can be completely prevented, and the recording accuracy can be further increased by making the distance between the recording medium and the recording head 231 more uniform. Therefore, in order to identify the deformation peak portion of the recording medium, the following examination was performed.
[0022]
FIG. 4 is a diagram showing the change over time of the amplitude of the cockling unevenness of the recording medium after the start of recording. As is apparent from FIG. 4, the amplitude of the cockling unevenness of the recording medium increases rapidly immediately after the start of recording, but maintains a constant value (approximately 0.7 mm) after a lapse of a certain time. The deformation peak of the recording medium occurs most rapidly when high duty recording is performed in a high-temperature and low-humidity environment, and when about 10 seconds have elapsed since recording in that portion.
[0023]
Accordingly, the branch point between the upstream depth of the suction chamber 123 and the downstream depth of the suction chamber 123 is set based on the time from the start of recording, and this reference time is preferably about 10 seconds or more. Then, the distance from the recording start point on the recording medium conveying surface 122 to the deformation peak point is obtained by integrating the reference time and the medium conveying speed, and the distance from the upstream end of conveyance on the recording medium conveying surface 122 to the recording start point is calculated as the distance. The suction chamber 123 is formed by adding the distances to obtain a branch point between the depth on the upstream side of the suction chamber 123 and the depth on the downstream side of the transport.
[0024]
5A, 5 </ b> B, and 5 </ b> C are cross-sectional side views taken along the line B-B in FIG. 2, illustrating an exemplary cross-sectional shape of the suction chamber 123. The suction chamber 123 shown in FIG. 5A is transported so that the depth d of the branch point A between the depth upstream of the suction chamber 123 and the depth downstream of the transport becomes the peak value of deformation of the recording medium. It is formed so as to gradually become deeper from the upstream side toward the conveyance downstream side. Further, in the suction chamber 123 shown in FIG. 5B, the depth d of the branch point A between the depth upstream of the suction chamber 123 and the depth downstream of the transport is the peak value of the deformation of the recording medium. From the upstream side of the conveyance to the branch point A, the depth is gradually increased, and from the branch point A toward the downstream side of the conveyance, the depth d is constant. Further, the suction chamber 123 shown in FIG. 5C is formed uniformly from the upstream side of the conveyance to the branch point A at a depth d1 that is a peak value of deformation of the recording medium, and from the branch point A toward the downstream side of the conveyance. In other words, it is formed constant at a depth d2 deeper than the depth d1. Thereby, the concave portion of the cock ring that becomes the largest at the time of drying after recording can be surely drawn into the dimple-shaped suction chamber 123, and the convex portion of the cock ring can be along the top of the partition wall 125. Therefore, the protrusion of the recording medium from the recording medium conveyance surface 122 can be suppressed almost completely, and the interval between the recording medium and the recording head 231 can be made more uniform to further improve the recording accuracy.
[0025]
The recording medium transport apparatus 100 having such a configuration operates as follows. The feed roller 151 and the like are rotationally driven to feed the recording medium between the recording head 231 and the suction unit 110. On the other hand, the pump 132 is driven to apply a suction force to the suction hole 124 and the suction chamber 123 through the communication hole 131 and the decompression chamber 121. As a result, the recording medium is conveyed while being sucked and adsorbed on the recording medium conveying surface 122. At the same time, the recording head 231 performs recording by ejecting ink particles onto the recording medium while moving in the main scanning direction above the recording medium.
[0026]
At this time, the concave portion of the cock ring that becomes the maximum at the time of drying after recording is surely drawn into the deeply formed dimple-shaped suction chamber 123, and the convex portion of the cock ring is along the top of the partition wall 125. The interval between the recording medium and the recording head 231 is uniform. Therefore, it is possible to prevent uneven recording due to variations in the flying distance of ink droplets and contamination due to the recording medium coming into contact with the recording head 231. Then, the discharge roller 153 and the like are driven to rotate, and the recording medium on which recording is completed is discharged to the outside.
[0027]
FIG. 6 is a perspective view showing an ink jet printer as a recording apparatus including the recording medium conveying apparatus 100, and FIGS. 7 to 9 are a plan view, a front view, and a side view showing the main part. The ink jet printer 200 includes an automatic paper feed (ASF) unit 220 that is obliquely attached to the rear upper part of the printer main body 210, a recording unit 230 and a recording medium transport device 100 built in the printer main body 210. As the recording medium, various kinds of paper such as OHP film, tracing paper, postcard, etc. can be used in addition to the dedicated paper and plain paper of the ink jet printer 200.
[0028]
The ASF unit 220 includes a tray 221 that stores the paper 1, a paper feed roller 222 that pulls out and supplies the paper 1 from the tray 221, and the like. The recording unit 230 includes a carriage 233 on which the recording head 231 and the ink cartridge 232 are mounted, a DC motor 235 that moves the carriage 233 along a guide shaft 234 disposed in the main scanning direction, and the like. The recording head 231 has a nozzle row composed of a plurality of nozzles such as 96 for each color of cyan, magenta, yellow, light cyan, light magenta, light yellow, and black, for example.
[0029]
The recording medium conveyance device 100 conveys the recording medium from the upstream side to the downstream side of the suction unit 110, and the suction unit 110 including an upper suction unit 120 and a lower suction force generation unit 130 that suck and hold the recording medium during recording. Recording medium conveying means 150. The suction unit 120 includes a decompression chamber 121 formed therein, a plurality of suction chambers 123 formed as rectangular recesses long in the recording medium transport direction on the recording medium transport surface 122, and the suction chambers 123 respectively decompressed. A plurality of suction holes 124 communicating with the chamber 121 are provided. In the suction chamber 123, as shown in FIG. 5A, the depth d of the branch point A between the depth upstream of the suction chamber 123 and the depth downstream of the transfer is the peak value of the deformation of the recording medium. In addition, it is formed so as to gradually become deeper from the transport upstream side toward the transport downstream side.
[0030]
The suction force generation unit 130 is communicated with the decompression chamber 121 of the suction unit 120 via the communication hole 131 and includes a pump 132 having a centrifugal fan therein. The pump 132 is attached to a predetermined position below the decompression chamber 121 so as to communicate with the decompression chamber 121 via the communication hole 131, and the centrifugal fan rotates during recording.
[0031]
The recording medium transport unit 150 includes a feeding roller 151 that feeds the recording medium between the recording head 231 and the suction unit 110, and a driven roller 152 that is pressed against the feeding roller 151 from above. In this embodiment, the discharge unit 153 that discharges the recording medium to the outside and the spur roller 154 that is in contact with the discharge roller 153 from above are unnecessary, and the suction unit 110 that can move in the discharge direction is provided. Although the inkjet printer 200 is used, an inkjet printer having a discharge roller 153 and a spur roller 154 may be used.
[0032]
The ink jet printer 200 having such a configuration operates as follows. When a recording command for the paper 1 stored in the tray 221 is input by a host computer or the like (not shown), the paper feed roller 222 is rotated to pick up the paper 1 stored in the tray 221 one by one. Feed paper. Further, the feed roller 152 and the like are rotationally driven to feed the paper 1 between the recording head 231 and the suction unit 110.
[0033]
On the other hand, the pump 132 is driven to apply a suction force to the suction hole 124 and the suction chamber 123 through the communication hole 131 and the decompression chamber 121. Then, the sheet 1 is conveyed while being sucked and adsorbed to the recording medium conveying surface 125. At the same time, the DC motor 235 is driven to move the carriage 233 along the guide shaft 234 via the timing belt. At this time, the recording head 231 records the ink supplied from the ink cartridge 232 for each color by ejecting the ink on the paper 1 as fine ink droplets from all or a part of the plurality of nozzles according to the recording data. . As a result, cockling may occur in the paper 1 after recording. However, the concave portion of the cock ring is drawn into the dimple-shaped suction chamber 123, and the convex portion of the cock ring is along the top of the partition wall 125. Therefore, the interval between the recording medium and the recording head 231 is uniform, and recording can be maintained with high accuracy. Then, the discharge roller 153 and the like are driven to rotate, and the recording-completed sheet 1 is discharged from the discharge port 201 to the outside.
[0034]
As described above, even with an appropriate suction force, it can be completely drawn into the dimple-shaped suction chamber 123 from the cockling recess generated immediately after recording to the cockling recess developed after the recording, and can be sucked and conveyed. Further, the protrusion of the cockling convex portion from the recording medium conveying surface 122 can be reliably suppressed, and the interval between the recording medium and the recording head 231 can be kept more uniform. Therefore, since the recording head 231 can be brought closer to the recording medium, the recording accuracy can be further improved. In the above-described embodiment, the recording apparatus including the apparatus for transporting the recording medium has been described. However, the present invention can also be applied to a liquid ejecting apparatus including an apparatus for transporting a material to be ejected including, for example, an ink jet printer. Has the effect of.
[Brief description of the drawings]
FIG. 1 is a side view showing a recording medium conveying apparatus according to an embodiment of the present invention.
FIG. 2 is a plan view and a cross-sectional side view taken along the line AA showing the suction part of FIG. 1;
FIG. 3 is a diagram showing an uneven state of cockling of a recording medium after a predetermined time has elapsed from the start of recording.
FIG. 4 is a diagram showing a change with time of amplitude of cockling unevenness of a recording medium after starting recording.
5 is a cross-sectional side view taken along the line BB showing an example of a cross-sectional shape of the suction chamber of FIG. 2;
FIG. 6 is a perspective view showing an ink jet printer as a recording apparatus including the recording medium conveying apparatus of the present invention.
7 is a plan view showing a main part of the ink jet printer shown in FIG. 6. FIG.
8 is a front view showing a main part of the ink jet printer shown in FIG. 6;
9 is a side view showing a main part of the ink jet printer shown in FIG. 6;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Paper, 100 Recording medium conveyance apparatus, 110 Suction unit, 120 Suction part, 121 Decompression chamber, 122 Recording medium conveyance surface, 123 Suction chamber, 124 Suction hole, 125 Partition wall, 130 Suction force generation part, 131 Communication hole, 132 Pump, 150 Recording medium conveying means, 151 Feed roller, 152 Drive roller, 153 Discharge roller, 154 Spur roller, 200 Inkjet printer, 210 Printer main body, 220 ASF unit, 221 Tray, 222 Paper feed roller, 230 Recording unit, 231 Recording head, 232 ink cartridge, 233 carriage, 234 guide shaft, 235 DC motor

Claims (4)

A recording medium supporting member that supports the recording medium to be conveyed and has a plurality of suction holes for sucking the recording medium;
A recording medium conveying apparatus of a recording apparatus for ejecting ink to the recording medium supported by the recording medium support member by a recording head,
The support surface of the recording medium support member is provided with dimples extending from the transport upstream side of the recording medium to the transport downstream side and having a plurality of the suction holes on the bottom surface,
In the dimple, the recording medium transport device, characterized in that the depth of the conveyed downstream end is formed to be deeper than the depth of the conveyor upstream end. 2. The recording medium conveying apparatus according to claim 1, wherein the dimple is formed so as to gradually become deeper from the conveying upstream end to the conveying downstream end of the recording medium. The dimple is formed so that a predetermined length gradually becomes deeper from the conveyance upstream end of the recording medium toward the conveyance downstream side, and thereafter, the dimple is formed to have a constant depth to the conveyance downstream end. The recording medium carrying device according to claim 1.   The dimple is formed so that the predetermined length becomes the first depth from the conveyance upstream side to the conveyance downstream side of the recording medium, and thereafter, the second depth deeper than the first depth to the conveyance downstream end. The recording medium conveying apparatus according to claim 1, wherein the recording medium conveying apparatus is formed as described above.

Images