U.S. patent application number 12/963089 was filed with the patent office on 2011-11-17 for printing apparatus and printing method.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Hisatsugu Naito.
Application Number | 20110279508 12/963089 |
Document ID | / |
Family ID | 44911411 |
Filed Date | 2011-11-17 |
United States Patent
Application |
20110279508 |
Kind Code |
A1 |
Naito; Hisatsugu |
November 17, 2011 |
PRINTING APPARATUS AND PRINTING METHOD
Abstract
When a splice of a continuous sheet is detected, a printing
apparatus defines an unprintable area including the splice on the
continuous sheet and continues printing by changing the order in
which unit images and maintenance patterns are printed so that the
unprintable area is not used for the print operation and a
maintenance pattern is printed in an area subsequent to the
unprintable area.
Inventors: |
Naito; Hisatsugu;
(Yokohama-shi, JP) |
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
44911411 |
Appl. No.: |
12/963089 |
Filed: |
December 8, 2010 |
Current U.S.
Class: |
347/16 |
Current CPC
Class: |
B41J 11/0095 20130101;
B41J 15/04 20130101; G06K 15/022 20130101; B41J 29/38 20130101;
B41J 11/008 20130101; B41J 2/16526 20130101 |
Class at
Publication: |
347/16 |
International
Class: |
B41J 29/38 20060101
B41J029/38 |
Foreign Application Data
Date |
Code |
Application Number |
May 13, 2010 |
JP |
2010-111535 |
Claims
1. An apparatus comprising: a sheet feeding unit configured to feed
a continuous sheet along a path; a printing unit configured to
perform a print operation to print unit images and maintenance
patterns in a determined order on the continuous sheet fed from the
sheet feeding unit; a detection unit, disposed between the sheet
feeding unit and the printing unit in the path, configured to
detect a splice of the continuous sheet; and a control unit
configured to control so as to define an unprintable area,
including the splice, where the unit image is not to be printed on
the continuous sheet when the detection unit detects the splice,
and change the determined order so that a maintenance pattern is
printed in an area subsequent to the unprintable area and the print
operation continues while avoiding the unprintable area.
2. The apparatus according to claim 1, wherein the control unit
performs control so as to change the determined order so that the
maintenance pattern is additionally printed in an area preceding
the unprintable area.
3. The apparatus according to claim 1, wherein the control unit
performs rescheduling to change the determined order so that
maintenance patterns are formed at intervals from the maintenance
pattern formed in the area subsequent to the unprintable area.
4. The apparatus according to claim 1, wherein, when the splice
passes through a position at which the splice faces a print head of
the printing unit, the print head temporarily moves away from the
continuous sheet.
5. The apparatus according to claim 1, further comprising a reverse
unit configured to reverse the continuous sheet for duplex
printing, wherein the control unit controls so that, in the duplex
printing, the printing unit performs printing a plurality of the
unit images and the maintenance patterns in the determined order on
a first surface of the sheet fed from the sheet feeding unit, the
printed sheet is reversed by the reversed unit to feed the reversed
sheet to the printing unit, and the printing unit performs printing
a plurality of the unit images and the maintenance patterns in the
determined order on a second surface, which is the back of the
first surface, of the sheet fed from the reverse unit.
6. The apparatus according to claim 5, wherein the printing unit
includes a plurality of inkjet print head.
7. A method comprising the steps of: feeding a continuous sheet;
printing unit images and maintenance patterns in a determined order
on the fed continuous sheet; detecting an unsuitable area that is
not suitable for printing on the fed continuous sheet; and defining
an unprintable area, including the unsuitable area, where the unit
image is not to be printed on the continuous sheet when the
unsuitable area is detected, and changing the determined order so
that a maintenance pattern is printed in an area subsequent to the
unprintable area and continuing the printing while avoiding the
unprintable area.
8. The method according to claim 7, wherein the unsuitable area
represents one of a splice, a portion having a stain, and a preset
marking portion of the continuous sheet.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a printing apparatus that
performs printing using a continuous sheet.
[0003] 2. Description of the Related Art
[0004] For high volume printing, such as print labs, a rolled
continuous sheet is used. When manufacturing a rolled continuous
sheet, a plurality of continuous sheets each having a length
smaller than a required length may be connected with a fixing
member, such as a splicing tape, (hereinafter simply referred to as
a "tape") in order to increase the yield ratio. In this way, the
sheet having a required length is rolled. Such a rolled continuous
sheet has one or more splices (connecting portions) at random
positions at which two sheets are connected with a tape.
[0005] An apparatus described in Japanese Patent Laid-Open No.
2001-239715 detects the position of a splice by detecting a tape
using an optical sensor. The apparatus performs control so that a
certain area including the splice is defined as an unrecordable
area and printing is not performed on the unrecordable area. In
addition, if an area ahead of the splice cannot contain the
entirety of an image of a large size (a second print size), the
apparatus changes the sequence of images to be printed so that an
image having a smaller size (a first print size) is printed in the
area first.
SUMMARY OF THE INVENTION
[0006] A nozzle of an inkjet print head that is infrequently used
may have an ink ejection error. To prevent the occurrence of such
an ink ejection error, periodical head maintenance is needed. Even
when a plurality of images are sequentially printed on a continuous
sheet, it is desirable that periodical head maintenance be
performed by ejecting ink from all of the nozzles and forming a
maintenance pattern on the sheet each time a predetermined number
of images have been printed.
[0007] However, the apparatus described in Japanese Patent
Laid-Open No. 2001-239715 does not take into account such head
maintenance. The apparatus only defines a splice as an unrecordable
area. For an unrecordable area, all of the nozzles of the print
head do not eject ink and the operation of the print head stops.
Thus, a nozzle may become clogged due to ink drying during the
inoperable period. If a nozzle becomes clogged, an image artifact
occurs in an image printed in an area subsequent to the
unrecordable area.
[0008] Accordingly, the present invention provides a technique for,
when sequentially printing a plurality of images on a continuous
sheet including an unsuitable area that is not suitable for image
printing, avoiding an image from being printed in the unsuitable
area and excellently printing an image in an area subsequent to the
unsuitable area.
[0009] According to an embodiment of the present invention, an
apparatus includes a sheet feeding unit configured to feed a
continuous sheet along a path, a printing unit configured to
perform a print operation to print unit images and maintenance
patterns in a determined order on the continuous sheet fed from the
sheet feeding unit, a detection unit disposed between the sheet
feeding unit and the printing unit in the path and configured to
detect a splice of the continuous sheet, and a control unit
configured to control so as to define an unprintable area including
the splice, where the unit image is not to be printed on the
continuous sheet when the detection unit detects the splice, and
change the determined order so that a maintenance pattern is
printed in an area subsequent to the unprintable area and the print
operation continues while avoiding the unprintable area.
[0010] According to the present invention, printing an image onto
an unsuitable area, such as a splice, can be prevented. In
addition, a maintenance pattern is formed in an area subsequent to
the unsuitable area, and maintenance of a print head is performed
using the maintenance pattern. As a result, printing an image onto
an area subsequent to an unsuitable area can be excellently
performed.
[0011] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic illustration of the internal
configuration of a printing apparatus.
[0013] FIG. 2 is a block diagram of a control unit.
[0014] FIG. 3 is a flowchart illustrating all of the sequences of a
printing operation controlled by the control unit.
[0015] FIGS. 4A and 4B illustrate the order in which unit images
are printed in accordance with information in a print instruction
table.
[0016] FIG. 5 illustrates the procedure for updating the print
sequence defined in the print instruction table.
[0017] FIG. 6 is a flowchart of the procedure for updating the
print instruction table.
[0018] FIGS. 7A and 7B illustrate an example of a modification of
FIGS. 4A and 4B.
[0019] FIG. 8 illustrates an example of a modification of FIG.
5.
[0020] FIG. 9 is a flowchart of the procedure of a process
performed in the modification.
DESCRIPTION OF THE EMBODIMENTS
[0021] A printing apparatus using an inkjet printing method
according to an embodiment of the present invention is described
below. According to the present embodiment, a printing apparatus
employs a long continuous sheet (a long continuous sheet that is
longer than repeated units of printing in the conveying direction
(the unit is referred to as a "page" or a "unit image")). The
printing apparatus is a high-speed line printer that is operable in
either one of a simplex print mode and a duplex print mode. The
printing apparatus is suitable for a high-volume printing market,
such as print labs. As used herein, even when a plurality of small
images, characters, and white spaces are present in an area of a
unit of printing (a page), the small images, characters, and white
spaces are collectively referred to as a "unit image". That is, the
term "unit image" refers to a unit of printing (a page) when a
plurality of pages are sequentially printed on a continuous sheet.
Note that a unit image is also simply referred to as an "image".
The length of a unit image varies in accordance with the image size
to be printed. For example, the length of an L size photo in the
conveying direction is 135 mm, and the length of an A4 size photo
in the conveying direction is 297 mm. The present invention is
widely applicable to a printing apparatus that uses ink and
requires an ink drying process, such as a printer, a multi function
peripheral, a copier, a facsimile, or equipment used for
manufacturing a variety of devices.
[0022] FIG. 1 is a cross-sectional view schematically illustrating
the internal configuration of the printing apparatus. According to
the present embodiment, the printing apparatus can perform duplex
printing on the first surface of a rolled sheet and the second
surface of the sheet which is a back face of the first surface. The
printing apparatus includes a sheet feeding unit 1, a decurl unit
2, a skew correction unit 3, a printing unit 4, an inspection unit
5, a cutter unit 6, an information recording unit 7, a drying unit
8, an reverse unit 9, an ejection conveying unit 10, a sorter unit
11, an ejection unit 12, and a control unit 13. The ejection unit
12 includes the sorter unit 11. The ejection unit 12 ejects the
sheet. The sheet is conveyed by a conveying mechanism including
rollers and a belt along a sheet conveying path shown as a solid
line in FIG. 1 and is processed by the units. At any point in the
sheet conveying path, the side adjacent to the sheet feeding unit 1
is referred to as "upstream", and the side opposite to the side
adjacent to the sheet feeding unit 1 is referred to as
"downstream".
[0023] The sheet feeding unit 1 holds a rolled continuous sheet and
feeds the continuous sheet. The sheet feeding unit 1 can contain
two rolls R1 and R2. The sheet feeding unit 1 selects one of the
rolls R1 and R2 and draws a sheet from the selected roll and feeds
the sheet. Note that the number of rolls contained in the sheet
feeding unit 1 is not limited to two. For example, the number of
contained rolls may be one or three or more. Alternatively, a
continuous sheet that is not rolled can be used. For example, a
continuous sheet having perforations at predetermined intervals may
be folded at the perforations and stacked in the sheet feeding unit
1.
[0024] The continuous sheet used in the present embodiment has at
least one splice (a connecting portion) in which two sheets are
connected using an adhesive tape or a glue at a random position.
The splice is considered as an unsuitable area that is not suitable
for image printing. A splice sensor 17 is disposed in the vicinity
of the exit of the sheet feeding unit 1. The splice sensor 17
detects a splice of the continuous sheet fed from the sheet feeding
unit 1. The splice sensor 17 is described in more detail below.
[0025] The decurl unit 2 reduces the curl of the sheet fed from the
sheet feeding unit 1. The decurl unit 2 allows the sheet to pass
therethrough using two pinch rollers corresponding to one driving
roller in order to curve the sheet so that an inverse curl is fed
to the sheet. In this way, a decurling force is applied to the
sheet and, therefore, the curl is reduced.
[0026] The skew correction unit 3 corrects the skew of the sheet
that has passed through the decurl unit 2 (the inclination of the
sheet with respect to the designed feed direction). By urging the
end of the sheet on the reference side against a guide member, the
skew can be corrected. In the skew correction unit 3, a loop of the
conveyed sheet is formed.
[0027] The printing unit 4 performs a printing operation on the
sheet and forms an image on the sheet using a print head assembly
14 disposed above the conveyed sheet. That is, the printing unit 4
serves as a processing unit that performs a predetermined
processing on the sheet. The printing unit 4 includes a plurality
of conveying rollers that convey the sheet. The print head assembly
14 includes a line print head having an inkjet nozzle row that
covers the maximum width of the sheet to be used. In the print head
assembly 14, a plurality of print heads are arranged in parallel
along the conveying direction. In this example, the print head
assembly 14 includes seven print heads corresponding to the
following seven colors: cyan (C), magenta (M), yellow (Y), light
cyan (LC), light magenta (LM), grey (G), and black (K). However, it
should be noted that the number of colors and the number of print
heads are not limited to seven. Examples of the inkjet method
include a method using a heater element, a method using a
piezoelectric element, a method using an electrostatic element, and
a method using a microelectromechanical system (MEMS) element. The
ink of each color is supplied from an ink tank to the print head
assembly 14 via an ink tube.
[0028] The inspection unit 5 optically scans, using a scanner, an
inspection pattern or an image printed on a sheet by the printing
unit 4 and inspects the state of a nozzle of the print head, the
conveying state of a sheet, and the position of an image. In this
way, the inspection unit 5 determines whether an image has been
correctly printed. The scanner includes a charge-coupled device
(CCD) image sensor or a complementary metal-oxide semiconductor
(CMOS) image sensor.
[0029] The cutter unit 6 includes a mechanical cutter 18 that cuts
the printed sheet into predetermined lengths. The cutter unit 6
further includes a cut mark sensor that optically detects a cut
mark recorded on the sheet and a plurality of conveying rollers
that convey the sheet to the next processing stage. A trash can 19
is disposed in the vicinity of the cutter unit 6. The trash can 19
contains small sheet tips generated by and output from the cutter
unit 6 as trash. The cutter unit 6 includes a dispatching mechanism
that determines whether the cut sheet is output to the trash can 19
or the original conveying path.
[0030] The information recording unit 7 records print information
(unique information), such as the serial number of the printout and
the date and time, in the non-print area of the cut sheet. The
information is recorded by printing characters and code using, for
example, an inkjet method or a thermal transfer method.
[0031] The drying unit 8 heats the sheet printed by the printing
unit 4 so as to dry the applied ink in a short time. In the drying
unit 8, heated air is applied to the sheet that passes through the
drying unit 8 in at least the upward direction. Note that instead
of applying heated air, the drying unit 8 can dry the ink by
irradiating the surface of the sheet with electromagnetic waves
(e.g., ultraviolet rays or infrared rays).
[0032] As used herein, the above-described sheet conveying path
from the sheet feeding unit 1 to the drying unit 8 is referred to
as a "first path". The first path has a shape so as to perform a
U-turn between the printing unit 4 and the drying unit 8. The
cutter unit 6 is located in the U-turn.
[0033] The reverse unit 9 temporarily winds the printed continuous
sheet and turns over the sheet when duplex printing is performed.
In order to feed the sheet that has passed through the drying unit
8 to the printing unit 4 again, the reverse unit 9 is disposed in a
path from the drying unit 8 to the printing unit 4 via the decurl
unit 2 (a loop path, hereinafter referred to as a "second path").
The reverse unit 9 includes a winding rotary member (a drum) that
rotates to reel in the sheet. The printed continuous sheet before
being cut is temporarily wound around the winding rotary member.
After the continuous sheet is wound, the winding rotary member
rotates in the opposite direction and, therefore, the continuous
sheet is fed in a direction opposite that when the continuous sheet
is wound. The continuous sheet is fed to the decurl unit 2 and is
delivered to the printing unit 4. Since the sheet is turned over,
the printing unit 4 can perform a printing operation on the back
surface of the sheet. If the sheet feeding unit 1 is referred to as
a "first sheet feeding unit", the reverse unit 9 can be referred to
as a "second sheet feeding unit." Such duplex printing is described
in more detail below.
[0034] The ejection conveying unit 10 conveys the sheet cut by the
cutter unit 6 and dried by the drying unit 8 and delivers the sheet
to the sorter unit 11. The ejection conveying unit 10 is disposed
in a path that is different from the second path having the reverse
unit 9 thereon (hereinafter, referred to as a "third path"). In
order to selectively deliver the sheet that has been conveyed along
the first path to the second path or the third path, a path
switching mechanism including a movable flapper is disposed at a
branch position in the path (also referred to as an "ejection
branch position").
[0035] The ejection unit 12 including the sorter unit 11 is
disposed at the end of the third path so as to be adjacent to the
sheet feeding unit 1. The sorter unit 11 sorts the printed sheets
into groups as needed. The sorted sheets are ejected onto a
plurality of trays of the ejection unit 12. In this way, the third
path has a layout that allows a sheet to pass beneath the sheet
feeding unit 1 and allows the sheet to be ejected to the opposite
side of the sheet feeding unit 1 from the printing unit 4 and the
drying unit 8.
[0036] As described above, the units from the sheet feeding unit 1
to the drying unit 8 are sequentially arranged along the first
path. Downstream of the drying unit 8, the first path branches into
the second path and the third path. The reverse unit 9 is disposed
in the middle of the second path. Downstream of the reverse unit 9,
the second path merges with the first path. The ejection unit 12 is
disposed at the end of the third path.
[0037] The control unit 13 performs overall control of the printing
apparatus. The control unit 13 includes a controller having a
central processing unit (CPU), a storage unit, and a variety of
control sub-units, an external interface, and an operation unit 15
used by the user when the user inputs data and receives output
data. The operation performed by the printing apparatus is
controlled using instructions received from the controller or a
host apparatus 16, such as a host computer, connected to the
controller via the external interface.
[0038] FIG. 2 is a block diagram schematically illustrating the
control unit 13. The controller (a block enclosed by a dashed line)
included in the control unit 13 includes a CPU 201, a read only
memory (ROM) 202, a random access memory (RAM) 203, a hard disk
drive (HDD) 204, an image processing unit 207, an engine control
unit 208, an individual unit controller 209. The CPU 201 performs
overall control of the printing apparatus. The ROM 202 stores
programs executed by the CPU 201 and fixed data necessary for the
printing apparatus to perform a variety of operations. The RAM 203
is used as a work area of the CPU 201 and a temporary storage area
for a variety of received data items. In addition, the RAM 203
stores a variety of setting data items. The HDD 204 can store and
deliver programs executed by the CPU 201, print data, and setting
information necessary for the operation performed by the printing
apparatus. The operation unit 15 serves as an input/output
interface with the user. The operation unit 15 includes hard keys,
an input unit of a touch-sensitive panel, and a display and a sound
generator for outputting information.
[0039] The units that are required to perform a high-speed
operation include dedicated processing unit. The image processing
unit 207 performs image processing on print data manipulated by the
printing apparatus. The image processing unit 207 converts the
color space of the input image data (e.g., YCbCr) into a standard
RGB color space (e.g., sRGB). In addition, the image processing
unit 207 performs a variety of image processing, such as resolution
conversion, image analysis, and image correction, on the image data
as needed. Print data obtained through such image processing is
stored in the RAM 203 or the HDD 204. In response to a control
command received from the CPU 201, the engine control unit 208
controls driving of the print head assembly 14 of the printing unit
4 using the print data. The engine control unit 208 further
controls a conveying mechanism of each of the units in the printing
apparatus. The individual unit controller 209 is a sub-controller
that individually controls the sheet feeding unit 1, the decurl
unit 2, the skew correction unit 3, the inspection unit 5, the
cutter unit 6, the information recording unit 7, the drying unit 8,
the reverse unit 9, the ejection conveying unit 10, the sorter unit
11, and the ejection unit 12. In response to an instruction
received from the CPU 201, the individual unit controller 209
controls the operation of each of the units. An external interface
205 is an interface (I/F) used for connecting the controller to the
host apparatus 16. The external interface 205 is a local I/F or a
network I/F. The above-described components of the printing
apparatus are connected to one another via a system bus 210.
[0040] The host apparatus 16 serves as a supply source of image
data to be printed by the printing apparatus. The host apparatus 16
may be a general-purpose computer or a dedicated computer.
Alternatively, the host apparatus 16 may be a dedicated imaging
device, such as an image capturing device including an image reader
unit, a digital camera, or a photo storage device. When the host
apparatus 16 is a computer, a storage unit of the computer stores
an operating system (OS), application software that generates image
data, and a printer driver for the printing apparatus installed
therein. However, it should be noted that all of the
above-described processes are not necessarily realized by software.
Some or all of the processes may be realized by hardware.
[0041] The basic operation performed during a printing operation is
described next. The operation in a simplex print mode differs from
that in a duplex print mode. Accordingly, both the operations are
described below.
[0042] In a simplex print mode, a sheet is fed from the sheet
feeding unit 1 and is subjected to the processing performed by the
decurl unit 2 and the skew correction unit 3. Thereafter, printing
is performed on the front surface (the first surface) of the sheet
in the printing unit 4. Printing of an image having a predetermined
unit length in the conveying direction (a unit image) is
sequentially performed on the continuous sheet. Thus, a plurality
of images are formed so as to be sequentially arranged on the
continuous sheet. The printed sheet passes through the inspection
unit 5 and is cut into the unit images by the cutter unit 6. The
print information is printed on the back surfaces of the cut sheets
in the information recording unit 7 as needed. Subsequently, the
cut sheets are conveyed to the drying unit 8 one by one, where each
of the sheets is dried. Thereafter, each of the sheets passes
through the ejection conveying unit 10 and is sequentially ejected
and stacked on the ejection unit 12 of the sorter unit 11. In
contrast, the sheet remaining on the side of the printing unit 4
after the last unit image is cut out is delivered back to the sheet
feeding unit 1. The sheet is wound around the roll R1 or R2. In
this way, in a simplex print mode, the sheet passes through the
first path and the third path. The sheet does not pass through the
second path.
[0043] In contrast, in a duplex print mode, after first print
sequences on the front surface (the first surface) are completed,
second print sequences on the back surface (the second surface) are
performed. In the first print sequences, the operations performed
by the sheet feeding unit 1 to the inspection unit 5 are the same
as those in the simplex print mode. However, the cutting operation
is not performed by the cutter unit 6. The continuous sheet is
conveyed to the drying unit 8. The drying unit 8 dries the ink on
the front surface of the continuous sheet. Thereafter, the sheet is
led to the path on the side of the reverse unit 9 (the second
path), not the path on the side of the ejection conveying unit 10
(the third path). In the second path, the sheet is reeled in around
the winding rotary member of the reverse unit 9 that rotates in the
forward direction (the counterclockwise direction in FIG. 1). After
the printing on planned area of the front surface is completed in
the printing unit 4, the trailing edge of the printed area of the
continuous sheet is cut by the cutter unit 6. The entirety of the
portion of the continuous sheet downstream of the cut position (on
the side of the printed area) in the conveying direction is rewound
by the reverse unit 9 via the drying unit 8. In contrast, at the
same time as the rewinding operation performed by the reverse unit
9, the portion of the continuous sheet remaining upstream of the
cut position (on the side of the printing unit 4) in the conveying
direction is fed back to the sheet feeding unit 1 and reeled in
around the roll R1 or R2 so that the leading edge of the portion
(the cut edge) does not remain in the decurl unit 2. Through such
rewinding operation (feedback), the sheet does not collide with the
sheet that is subsequently fed for the back surface printing
described below.
[0044] After the above-described front surface printing sequences
are completed, the processing is switched to the back surface
printing sequences. The winding rotary member of the reverse unit 9
rotates in a direction (a clockwise direction in FIG. 1) that is
the reverse of the direction when the sheet was reeled in. The edge
of the wound sheet (the trailing edge of the sheet when reeled is
changed to the leading edge when fed) is conveyed into the decurl
unit 2 along the path shown as a dashed line in FIG. 2. A curl of
the sheet given by the winding rotary member is decurled in the
decurl unit 2. That is, the decurl unit 2 is disposed between the
sheet feeding unit 1 and the printing unit 4 in the first path and
is disposed between the reverse unit 9 and the printing unit 4 in
the second path. In either path, the decurl unit 2 serves as a
shared unit for decurling. The turned-over sheet is advanced to the
printing unit 4 via the skew correction unit 3, and printing on the
back surface of the sheet is performed. The printed sheet passes
through the inspection unit 5 and is cut into sheets each having a
preset unit length by the cutter unit 6. Since either side of each
of the cut sheets is printed, recording is not performed by the
information recording unit 7. The cut sheets are conveyed to the
drying unit 8 one by one. Thereafter, the cut sheets are
sequentially ejected to the sorter unit 11 of the ejection unit 12
via the ejection conveying unit 10. In this way, in the duplex
print mode, the sheet passes through the first path, the second
path, the first path, and the third path and is processed.
[0045] FIG. 3 is a flowchart illustrating all of the sequences of a
printing operation controlled by the control unit 13. In step S101,
an initial print instruction table is generated in a memory in
response to a print instruction. The print instruction table is
used for sequentially printing unit images and maintenance patterns
in a predetermined order. The print instruction table is described
in more detail below.
[0046] In step S102, unit images and maintenance patterns are
sequentially printed in the predetermined order indicated by the
generated print instruction table. In step S103, it is determined
whether printing indicated by the print instruction table is
completed (Yes) or not (No). If the determination is "Yes", the
sequence is completed. However, if the determination is "No", the
processing proceeds to step S104, where it is determined whether a
splice of the continuous sheet is detected by the splice sensor 17
during the printing operation (Yes) or not (No). If the
determination is "Yes", the processing proceeds to step S105.
However, if the determination is "No", the processing returns to
step S103 and the processing is repeated. In step S105, the print
instruction table is updated in accordance with the detected
position of the splice (the detected timing). In order to update
the print instruction table, a merge table of a pattern group
including an unprintable area (a white space) and two maintenance
patterns that sandwich the unprintable area is used. Thereafter,
the processing returns to step S103 and the processing is repeated.
The procedure for updating the print instruction table is described
in more detail below.
[0047] The splice of the sheet is thicker than the other original
portion of the sheet. Accordingly, if a narrow gap is employed, the
splice may be in contact with the print head. Therefore, when the
splice passes through the position that faces the print head during
a printing operation, the print head assembly 14 is temporarily
moved away from a surface of the sheet so that the gap increases
and the splice is not in contact with the nozzle of the print head.
After the splice has passed through the gap, the increased gap size
returns to the original size that is suitable for a print
operation.
[0048] In step S104, when a splice of a fed continuous sheet S
passes through a detection position (immediately beneath the splice
sensor 17), the signal level of the splice sensor 17 varies and,
thus, passing of the splice is detected. The splice sensor 17 is
formed from a reflective photosensor, which detects a difference
between the surface reflectivities of the sheet and the splice (the
tape) or the stepped edge of the splice using the amount of the
reflected light. Note that the splice sensor 17 may be formed from
a transmissive photosensor that can detect a splice using a
difference between the light transmissivities of the sheet and the
splice. Still alternatively, the splice sensor 17 may be formed
from a contact sensor, not an optical sensor. The contact sensor
can detect a splice by detecting a variation in the thickness of
the splice using a variation in an amount of movement of a contact
tip that is in contact with the continuous sheet S.
[0049] FIGS. 4A and 4B illustrate the order in which unit images
and maintenance patterns are sequentially printed on the continuous
sheet S in accordance with the information in the print instruction
table. FIG. 4A illustrates the order indicated by the initial print
instruction table generated in step S101. FIG. 4B illustrates the
order indicated by the print instruction table updated in step
S105. In FIG. 4B, a splice 20 appears during a print operation. In
FIGS. 4A and 4B, in addition to a unit image, examples of the
patterns include a white space, a maintenance image (e.g., a clog
monitor pattern or a preliminary ejection pattern), and a cut mark
(a margin area). In the example shown in FIGS. 4A and 4B, the
following patterns are arranged from the leading edge of the sheet:
a white space a, a maintenance pattern b, a white space a, a clog
monitor pattern c, a preliminary ejection pattern d, a cut mark e,
a preliminary ejection pattern d, a unit image x1, a cut mark f, a
unit image x2, . . . , and a unit image x13. In general, the
maintenance pattern is formed at predetermined intervals. The
predetermined intervals vary in accordance with the size of the
unit image (the number of print lines) in the conveying direction.
In this example, as shown in FIG. 4A, each time four unit images or
a set of three unit images and one clog monitor pattern are printed
in accordance with the initial print instruction table, a
preliminary ejection operation is performed and a preliminary
ejection pattern is repeatedly formed. The reference symbol "A"
shown in FIG. 4B represents the predetermined pattern sequence that
is inserted into the pattern due to an update operation. The splice
20 is located in the middle of the predetermined pattern
sequence.
[0050] FIG. 5 illustrates the procedure for updating the initial
print instruction table. The data used for updating includes
entries each including a table number, the type of pattern, and the
number of print lines (corresponding to the length in the conveying
direction). Such data is stored in the memory in the form of a
table. A merge table A is inserted into a point corresponding to
the detection position (the detection timing) of the splice 20
(i.e., an additional instruction group is inserted into the initial
print instruction table). In this example, a merge table having
table numbers 20' to 24' is inserted into a point between the entry
having a table number of 19 and the entry having a table number of
20. The table number 20' indicates a clog monitor pattern. The
table number 21' indicates a preliminary ejection pattern. The
table number 22' indicates a white space. The table number 23'
indicates a clog monitor pattern. The table number 24' indicates a
preliminary ejection pattern. The table numbers 20' and 21'
indicate maintenance patterns located downstream of an unprintable
area (the white space indicated by the table number 22') including
the splice 20. The table numbers 23' to 26' indicate maintenance
patterns (including a cut mark) located upstream of an unprintable
area (the white space indicated by the table number 22') including
the splice 20. That is, maintenance of the print head is performed
before and after the unprintable area has passed.
[0051] FIG. 6 is a flowchart of the procedure for updating a print
instruction table in step S105. In step S201, when the splice 20 is
detected, it is determined at which point of the print instruction
table the merge table is merged. The point is determined by
performing computation using the point (the timing) at which the
splice sensor 17 detects the splice 20 and the number of print
lines in the print instruction table. In step S202, it is
determined whether the last pattern before merge is a clog monitor
pattern (Yes) or not (No) by referring to the print instruction
table. If the determination is "Yes", the processing proceeds to
step S204. However, if the determination is "No", the processing
proceeds to step S203, where a clog monitor pattern (refer to the
table number 20' shown in FIG. 5) is set at the top of the merge
table. In step S204, it is determined whether a preliminary
ejection operation is needed (Yes) or not (No) using the print
pattern before merge. The preliminary ejection operation is needed
for the maintenance of the print head at predetermined time
intervals (for each conveying distance). If the case in which the
preliminary ejection operation is needed in an unprintable area
(described in more detail below) occurs, it is determined that the
preliminary ejection operation is needed in advance. If the
determination is "Yes", the processing proceeds to step S205.
However, if the determination is "No", the processing proceeds to
step S206. In step S205, a preliminary ejection pattern (refer to
the table number 21' shown in FIG. 5) is set in the merge
table.
[0052] In step S206, a white space pattern (refer to the table
number 22' shown in FIG. 5) is set in a predetermined area, at the
center of which is the splice 20. This white space represents an
unprintable area in which printing is not performed. In step S207,
it is determined whether the first pattern subsequent to the white
space is a clog monitor pattern (Yes) or not (No) by referring to
the print instruction table. If the determination is "Yes", the
processing proceeds to step S208. However, if the determination is
"No", the processing proceeds to step S209. In step S208, a clog
monitor pattern (refer to the table number 23' shown in FIG. 5) is
set immediately after the while space in the merge table. In step
S209, it is determined whether a preliminary ejection operation is
needed (Yes) or not (No) immediately after the white space. If the
determination is "Yes", the processing proceeds to step S210.
However, if the determination is "No", the sequences are completed.
In step S210, preliminary ejection patterns and a cut mark (refer
to the table numbers 24' to 26' shown in FIG. 5) are set at the end
of the merge table.
[0053] After the merge table is generated, the control unit
performs control so that processing next to the processing based on
the table number 19 is performed using the merge table (refer to
the table numbers 20' to 26'). Subsequently, the processing returns
to that based on the table number 20. In this way, the printing
operation continues. As described above, the print instruction
table is updated and the predefined print sequence is changed so
that if a splice is detected by the splice sensor 17, the
unprintable area including the splice is defined as a white space.
In addition, a maintenance pattern is printed in an area after the
unprintable area. Thus, the printing operation continues while
avoiding the unprintable area so that the unprintable area is not
used. Even when the nozzle is clogged due to dried ink while the
unprintable area is passing beneath the print head, the maintenance
of the print head is performed immediately after the unprintable
area has passed. Thus, the occurrence of an artifact of the
subsequent images can be prevented. Furthermore, when a maintenance
pattern is needed in an unprintable area, the maintenance of the
print head is performed in advance before the unprintable area is
reached. Thus, the print head can be maintained in an excellent
state.
[0054] Still furthermore, even when the merge table is merged and
an interruption process is performed, the order in which unit
images are arranged remains unchanged. In some cases (e.g., the
case of printing of a photo album), the order in which images are
continuously printed (the order in which pages are arranged) is
important. In such cases, if the order in which images are printed
is changed, the user needs to rearrange the printed images. The
present embodiment can prevent such a troublesome operation.
[0055] A modification of the above-described embodiment is
described next. In the above-described example, if a splice is
detected, a merge table is merged. Thereafter, a printing operation
continues without changing the subsequent print order. In contrast,
according to the modification, if a splice is detected, a merge
table is merged. In addition, the subsequent print order is changed
so that the position at which a maintenance pattern is inserted is
more appropriate.
[0056] Like FIGS. 4A and 4B, FIGS. 7A and 7B illustrate the order
in which unit images and maintenance patterns are sequentially
printed on the continuous sheet S in accordance with the
information in a print instruction table. Like FIG. 5, FIG. 8
illustrates the procedure for updating an initial print instruction
table. The same numbering will be used in describing FIG. 8 as was
utilized above in describing FIG. 5, where appropriate. In this
example, the order of data items subsequent to the data item having
the table number 19 in the initial print instruction table is
changed. Thus, the data items subsequent to the data item having
the table number 20 are replaced with new data items. As used
herein, this operation is referred to as "rescheduling".
[0057] In the example shown in FIGS. 4A and 4B, the arrangement of
the data items subsequent to the merged data item A after updating
is exactly the same as that before updating. In the arrangement of
unit images, the position at which a maintenance pattern is
inserted remains unchanged before and after the updating.
Accordingly, as shown in FIG. 4B, the case in which a maintenance
operation (refer to the clog monitor pattern and the preliminary
ejection pattern immediately after a unit image 7) is performed
again immediately after a maintenance operation defined by the
merge table has been performed may occur. In contrast, in the
example shown in FIGS. 7A and 7B, rescheduling is performed as
illustrated in FIG. 7B so that after the merge data A is printed,
four unit images are printed and a preliminary ejection operation
is performed. Accordingly, unlike the case shown in FIG. 4B, an
excessive maintenance operation is not performed. Since the
possibility of an excessive maintenance operation being performed
in the print operation subsequent to the splice 20 is reduced,
wastage of the continuous sheet can be reduced. In addition, the
total throughput can be increased.
[0058] FIG. 9 is a flowchart of the procedure for updating the
print instruction table in step S105 according to the modification.
In step S301, when the splice 20 is detected, it is determined at
which point of the print instruction table the merge table is
merged. The point is determined by performing computation using the
point (the timing) at which the splice sensor 17 detects the splice
20 and the number of print lines in the print instruction table. In
step S302, it is determined whether the last pattern before merge
is a clog monitor pattern (Yes) or not (No) by referring to the
print instruction table. If the determination is "Yes", the
processing proceeds to step S304. However, if the determination is
"No", the processing proceeds to step S303, where a clog monitor
pattern (refer to the table number 20 shown in FIG. 8) is set at
the top of the merge table. In step S304, it is determined whether
a preliminary ejection operation is needed (Yes) or not (No) using
the print pattern before merge. If the determination is "Yes", the
processing proceeds to step S305. However, if the determination is
"No", the processing proceeds to step S306. In step S305, a
preliminary ejection pattern (refer to the table number 21 shown in
FIG. 8) is set in the merge table. In step S306, a white space
pattern (refer to the table number 22 shown in FIG. 8) is set in a
predetermined area, at the center of which is the splice 20. The
white space pattern indicates an unprintable area in which image
printing is not suitable. In step S307, maintenance patterns and a
cut mark are set immediately after the white space in the merge
table (refer to the table numbers 23 to 26 shown in FIG. 8).
[0059] The following processing procedure differs from that
illustrated in FIG. 6. In step S308, rescheduling is performed on
the basis of the number of unit images to be printed in an area
after the splice 20. The point in the arrangement of the unit
images at which a maintenance pattern is inserted is optimized.
Since the maintenance pattern is printed in an area immediately
after the unprintable area, a maintenance operation is not needed
for a certain period of time after that. A maintenance pattern is
formed at predetermined intervals after the end of the merge table
(the maintenance pattern immediately after the unprintable area:
the table number 26). The predetermined intervals vary in
accordance with the size of the unit image in the conveying
direction (the number of print lines). In this example, the point
at which a maintenance pattern is inserted is re-defined so that a
preliminary ejection operation is performed each time four unit
images or a set of three unit images and one clog monitor pattern
are printed.
[0060] According to the above-described embodiments, since the
maintenance of the print head is performed by avoiding an image
from being printed in a splice and forming a maintenance pattern in
an area subsequent to the splice, an image artifact does not occur.
Thus, images are excellently printed in an area subsequent to the
splice. In addition, in rescheduling, only the timing of a
maintenance operation is changed, and the order in which the unit
images are arranged remains unchanged. Accordingly, even when the
order in which images are continuously printed (the order in which
pages are arranged) is important, the user need not perform a
troublesome operation to rearrange the unit images.
[0061] In the above-described examples, since a splice of a
continuous sheet is not suitable for image printing, the splice is
defined as an unprintable area. However, in addition to a splice,
an area of a continuous sheet that is not suitable for image
printing is present. Examples of the area that is not suitable for
image printing include damage, a fold line, a break, a large dust
particle, and a stain (water-based or oil-based) that are partially
attached to a continuous sheet during manufacture and that are not
suitable for image printing. As used herein, these defects are
correctively referred to as a "stain on a continuous sheet". The
examples of the area that is not suitable for image printing
further include a marking portion of a continuous sheet that are
intentionally marked on the sheet, such as a symbol or a mark. If
printing is performed for such an area that is not suitable for
image printing, the print quality is significantly degraded, and
the printout becomes defective. Accordingly, control may be
performed as follows: such an area that is not suitable for image
printing is detected using a detection unit, an unprintable area is
defined in the above-described manner, and the order in which unit
images are printed is changed in order to print a maintenance
pattern in an area subsequent to the unprintable area. Since an
area that is not suitable for image printing is optically
detectable, the above-described splice sensor can be employed as
the detection unit.
[0062] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0063] This application claims the benefit of Japanese Patent
Application No. 2010-111535 filed May 13, 2010, which is hereby
incorporated by reference herein in its entirety.
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