The present invention relates to a dot impact printer having a
recording head that drives recording wires to form dots on recording
paper, and to a method of controlling the printer.
2. Related Art
[0002]
Dot impact printers are used in many industries due to their high
reliabilityandabilityto overprint onmultipart forms. Adot impact
printerhasarecordingheadwithmultiplerecordingwires (wirepins).
The recording head has a head coil (electromagnetic coil) to
individually drive each recording wire, and selectively propels the
recording wires to strike by selectively driving the head coils. A
dotimpactprinterfomsdotsandrecordsinformationontherecording
paper by selectively striking the recording wires of the recording
head against the recording paper through an intervening ink ribbon
while the carriage carrying the recording head scans widthwise over
the recording paper (the head scanning direction).
[0003]
The recording wires are disposedtothe recording headaccording
to the dot density at which the recording head records. For example,
the recording wires are aligned at a standard dot pitch
perpendicularly to the head scanning direction.
Alternatively, the recording wires are disposed in two left and
right rows at twice the standard dot pitch side by side in the paper
width direction with one row off set the standard dot pitch f ram the
other row perpendicularly to the head scanning direction. While the
recording head scans widthwise to the paper, the dot impact printer
energizes the head coils a t a specific drive cycle to print f u l l dots
by forming dots at a standard pitch vertically and horizontally, or
prints half dots by forming dots at 1/2 the standard pitch. This
recording head can adjust the density of dots formed on the recording
paper and the print resolution by appropriately shifting the drive
cycle of the head coils according to the speed of the head and the
alignment of the recording wires.
[00041
If the recording wires of the dot impact printer are driven
continuously, the head coils driving those recording wires can
quickly overheat and become damaged. To prevent damaging the head
coils,thedotimpactprinterdetectsthetemperatureoftherecording
headandeither reducesthe printing speedwhen the temperature rises
toathresholdatwhichheatdamage canoccur, or simplystopsprinting
until the temperature of the headcoil drops. Tomorereliablyprevent
heat damage to the head coil, a dot pattern that can be expected to
produce a sudden temperature r i s e could be determined, and when t h i s
dot p a t t e r n i s d e t e c t e d i n t h e p r i n t d a t a , the dot impact printer could
set the threshold for switching to a low heat output drive mode to
a lower temperature than normal. A dot impact printer that uses t h i s
control method is taught in Japanese Unexamined Patent Appl. Pub.
JP-A-2011-255632.
[0006]
Multiple head coils for drivingthe recording w i r e s are disposed
close together inthe recordingheadof adot impact printer. Adjacent
head coils mutually receive magnetic interference due to the drive
current flowing to each head coil, but the magnetic effect is
cancelled when the coils are synchronously driven because the drive
current waveforms are also synchronized. However, when the drive
cycles of adjacent head coils are out of sync, the magnetic force that
drives the recording wires fluctuates due to the magnetic
interference, andthebehavior ofthe recordingwires canbeaffected.
FIG. 11 describes the change in recording wire behavior due to
magnetic interference, (a) showing recording wire behavior
(recording wire protrusion on the y-axis, time on the x-axis) and (b)
showing the current waveform of the head coil adjacent to the head
coil driving the recording wire. In FIG. 11 (a) , the solid line shows
the original behavior when there is nomagnetic interference, and the
dotted line shows the behavior when there is magnetic interference.
In FIG. 11 (b), the solid line shows the current waveform when the
head coils are driven synchronously, and the dotted line shows the
current waveform when the drive cycles are shifted 1/2 period. As
shown in the figure, when a recording wire is driven and an adjacent
recording wire is driven offset 1/2 period, the return of the
recording wire is delayed by magnetic interference as indicated by
the dotted line in (a), and the next protrusion (drive) operation
startswithoutthewire returning completelytothe original position.
This poor recording wire response can cause problems such as the
recording wire catching on the ink ribbon when the recording head
moves.
[00071
To prevent the ink ribbon from catching due to the poor response
of the recording wire caused by magnetic interference, the drive
frequency could be reduced to reduce the effect of the drive current
of the adjacent head coil, but this reduces the printing speed and
thus reduces printer throughput. The drop in printer throughput is
particularlyaproblemwhencontrolthatincreasesthehead coil drive
interval is simultaneouslyappliedtopreventheat damage tothe head
coil.
SubMARY
[ O O O B ]
A dot impact printer according to the invention can suppress a
drop in printer throughput while preventing the ink ribbon from
catchingonarecordingwire due tomagnetic interferencebetweenhead
coils.
[00091
One aspect of the invention is a dot impact printer including:
a carriage that scans in a direction intersecting the conveyance
direction of a recording medium; a recording head carried on the
carriage; andacontrolunitthatcontrolstherecordinghead; wherein
the recording head has a plurality of recording wires that form dots
on the recording medium, and a plurality of head coils that
respectively drive the plural recording wires selectively; and the
control unit detects in dot line data to be printed a specific dot
patternthat is printedbydrivingadjacentheadcoils with a specific
drive cycle s h i f t , selects a drive mode of the recording head based
on the result of detecting the specific dot pattern, and prints the
dot line datatobeprintedbydrivingthe recordingwires while moving
the carriage in the selected mode.
[OOlOI
This aspect of the invention can determine before starting
printing if there is print data that can result in the behavior of
recording wires being affected by the interaction (magnetic
interf erence) of adjacent head coils. By determining the drive mode
of the recording head based on the result of this decision, the ink
ribbon can then be prevented from catching on a recording wire due
to poor recording w i r e response. For example, by selecting a drive
mode that can reduce overlap of the drive current waveform (such as
by setting a drive mode with a low drive frequency), magnetic
interference can be reduced and the ink ribbon can be prevented from
catchingonarecordingwire due topoor recording wire response. When
the likelihood of affecting recording wire behavior is not detected,
a drive mode with a high drive frequency is selected so that the
printing speed does not drop. A drop in throughput can therefore be
suppressed while preventing the ink ribbon from catching due to the
interaction of adjacent head coils.
[00111
When the plural head coils are aligned in a circle inside the
recording head, and at least part of the plural recording wires are
aligned at a specific pitch in a direction intersecting the scanning
direction of the carriage in the same sequence as the alignment order
ofthe head coils, the specific dot pattern is a zigzagpatternhaving
plural dots aligned in a zigzag offset half the distance of the
standard dot pitch.
In a recording head thus comprised, a zigzag pattern is an
exampleofaspecificdotpatternthatcancausemagnetic interference
between head coils that drive recording wires aligned in a direction
intersectingthe head scanning direction. Bydetectingthis pattern,
a drive mode that can prevent the ink ribbon from catching can be
selected.
[00121
In another aspect of the invention, the control unit
sequentially selects each of the plural recording wires as a target
recording wire and determines if the specific dot pattern is printed
by the target recording wire and an adjacent recording wire at a
predetermined position relative to the target recording wire in each
row from the first row to the last row of the dot line data to be
printed; determines that a preset specific pattern is detected when
the number of rows where the number of recording wires determined to
print the specific dot pattern equals or exceeds a preset reference
number is greater than or equal to a preset consecutive row count;
and selects the drive mode based on the result of detecting the
specific pattern.
This aspect of the invention can determine if there are
consecutive zigzag patterns in the print data that can result in the
ink ribbon catching. Adrivemode that canprevent the ink ribbon from
catching can therefore be selected.
[00131
In another aspect of the invention, drive modes with different
head coil drive frequencies can be set as the drive mode of the
recordinghead forprinting; andthe control unit selects a drivemode
with a head coil drive frequency that is lower when the specific
pattern is detectedthan when the specific pattern is not detected.
and prints the dot line data to be printed in the selected drive mode.
A drop in throughput can therefore be suppressed while
preventingtheinkribbon fromcatchingduetothe interactionof head
coils.
[00141
In another aspect of the invention, the control unit preferably
executes the process detecting the specific dot pattern in the dot
line data to be printed, and selects the recording head drive mode
based on the result of detecting the specific dot pattern, when in
a print mode that prints half dots forming dots at half the standard
dot pitch, and does not execute the process detecting the specific
dot pattern when in a print mode that does not print half dots.
This aspect of the invention can simplify control and shorten
the processing time for setting the drive mode because the detection
process is not applied unnecessarily to dot line data that will not
cause magnetic interference.
[00151
In another aspect of the invention, the control unit detects the
specific dot pattern and a preset high duty dot pattern from dot line
datatobeprinted; the highduty dot patternis a dot pattern inwhich
the consecutive drive count of the same recording wire, or the
consecutive intermittent drive count of the same recording wire
driven every other dot, is greater than or equal to a preset maximum;
and the control unit selects the recording head drive mode based on
the result of detecting the high duty dot pattern or the specific dot
pattern in the dot line data to be printed, and prints the dot line
data to be printed in the selected drive mode.
This aspectoftheinventioncansetadrivemodethatcanprevent
heat damage to the head coils, and can efficiently detect a specific
dot pattern and a high duty dot pattern to prevent the ink ribbon from
catching. The processing time required to select the drive mode can
therefore be shortened.
[00161
In dot impact printer according to another aspect of the
invention, drive modes that produce different amounts of heat can be
set as the drive mode of the recording head when printing; the drive
mode and the temperature of the recording head are related; the
recording head temperatures related to the drive modes include at
least a first temperature and a second temperature that is lower than
the first temperature; and the control unit detects the temperature
ofthe recordingheadbefore printing the dot line datatobeprinted,
selects either the first temperature or the second temperature based
on the result of detecting the specific dot pattern and the high duty
dot pattern in the dot line data to be printed, selects the drive mode
corresponding to the detected temperature of the recording head from
among the drivemodes related tothe selectedtemperature, andprints
the dot line data to be printed in the selected drive mode.
This aspect of the invention can prevent heat damage to the head
coils by using two different reference temperatures to select the
drive mode.
Another aspect of the invention is a control method of a dot
impact printer having a carriage that scans in a direction
intersecting the conveyance direction of a recording medium, a
recording head carried on the carriage, and a control unit that
controls the recording head, the recording head having a plurality
of recording wires that form dots on the recording medium, and a
plurality of head coils that respectively drive the plural recording
wires selectively, the control method having steps executed by the
control unit including: detecting in dot line data to be printed a
specific dot pattern that is printed by driving adjacent head coils
with a specific drive cycle shift; selecting a drive mode - of the
recording head based on the result of detecting the specific dot
pattern; and printing the dot line data to be printed by driving the
recording wires while moving the carriage in the selected mode.
Effect of the invention
[00171
The invention can determine before starting printing if there
is print data that can result in thebehavior of recording wires being
af fected by the interaction (magnetic interference) of adjacent head -
coils. By determining the drive mode of the recording head based on
the result of this decision, a drop in throughput can be suppressed
while preventing the ink ribbon from catching due to the interaction
of head coils.
Other objects and attainments together with a fuller
understanding of the invention will become apparent and appreciated
by referring to the following description and claims taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows main parts of a dot impact printer according to the
invention.
FIG. 2 is a section view of the recording head.
FIG. 3 shows the plane configuration of the head coil.
FIG. 4 shows the configuration of recording wires.
FIG. 5Ais atableshowingcombinationsoftarget recordingwires
and recording wires adjacent thereto.
FIG. 5B describes special bit image Al.
FIG. 5C describes special bit image A2.
FIG. 6 is a flow chart of the special bit image A detection
process.
FIG. 7A describes special bit image B1 (high duty dot pattern) .
FIG. 7B describes special bit image B2 (high duty dot pattern) .
FIG. 8 is a control table for determining the drive mode.
FIG. 9 is a flow chart of the drive mode determination process
and printing process.
FIG. 10 is a flow chart of the special bit image detection
process.
FIG. 11 describes the change in recording wire behavior due to
magnetic interference.
DESCRIPTION OF EMBODIMENTS
too191
A preferred embodiment of a dot impact printer according to the
present invention is described below with reference to the
accompanying figures.
[00201
General configuration
FIG. 1 shows the main parts of a dot impact printer according
to the invention. This dot impact printer 1 has a recording head 2,
and a platen 3 disposed opposite the recording head 2 with the
recording paper (recording medium) therebetween. The recording head
2 is mounted on a carriage 4, and the carriage 4 is mounted slidably
widthwise to the printer (across the paper width) on a carriage guide
shaft 5. The carriage 4 is moved bidirectionally to the printer width
based on the output of a carriage motor 6b through a drive mechanism
6a suchas atimingbelt andpulleys. More specifically, the carriage
moves bidirectionallyinthe head scanning direction. The ends ofthe
carriage guide shaft 5 are supportedonthe left and right side panels
7a, 7b of the printer frame.
[ 0 02 11
The recording head 2 and platen 3 are disposed with a specific
gap therebetween, and an ink ribbon 8 is disposed in this gap. The
ink ribbon 8 is pulled out from an ink ribbon cassette not shown, and
passes in front of the printing face 2a of the recording head 2.
The dot impact printer 1 also has a conveyance mechanism (not
shown in the figure) such as a tractor unit or paper feed roller. The
recording paper is conveyed in a direction intersecting
(substantiallyperpendicularlyto) theheadscanningdirectionbythe
paper feed force of the conveyance mechanism. The recording paper is
conveyed in conjunction with the printing operation of the recording
head 2, and is discharged from the printer when printing ends.
100221
Recording head
F I G . 2 is a section view of the recording head 2, and F I G . 3 shows
the configuration of the head coils 16 in plan view.
The recording head 2 has a cylindrical head body 11, a nose 12
attached at one end of the center axis of the cylindrical head body
11, and a radiator 13 attached so that it covers the side on the other
end and the outside surface of the head body 11. Multiple cores 15
made of a magnetic material are disposed to the frame 14 of the head
body 11 at a specific interval in a circle. A head coil 16 is wound
around each of the cores 15 on a bobbin (not shown in the figure).
LO0231
A through-hole 14a is formed in the radial center of the frame
14 circle, and a plurality of recording wires 17 pass through the
through-hole 14a. Note that only one recording wire 17 is shown in
F I G . 2, and the other recording wires 17 are not shown.
The distal end of each recording wire 17 is guided to the distal
end of the nose 12 through a wire guide 18 disposed in the nose 12.
The back (base) end of the recording wire 17 is fastened to one end
of a wire lever 19 that is driven by the energizing operation of the
head coil 16. The same number of wire levers 19 as head coils 16 are
disposed in a radiating pattern inside the head body 11, each wire
lever 19 extending radially across the end face of a core 15. The
radial end 19a of the wire lever 19 a t the outside of the c i r c l e of
wire levers 19 is pressed to the outside of the frame 14 by a pivot
pressure spring 20. The radial inside end of each wire lever 19 is
urged to the opposite side as the d i s t a l end of the nose 12 by a
compression spring (not shown in the figure) held by a spring holder
21 disposed inside the through-hole 14a.
[00241
A circuit board 22 for supplying current to the head coils 16
is disposed between the frame 14 and nose 12. When current is supplied
to aheadcoi.116, thewire l e v e r 1 9 i s p u l l e d t o t h e core 15 andpivots
on the end 19a. As a r e s u l t , the recording wire 17 moves in the
direction toward the d i s t a l end of the nose 12, and the d i s t a l end
of the recording wire 17 protrudes from an end guide 12a disposed in
the distal end of the nose 12. When the current supply to the head
coil 16 stops, the urging force of the compression spring held by the
spring holder 21 causes the wire lever 19 to pivot so that the d i s t a l
end of the recording wire 17 is pulled inside the nose 12.
When the distal end of the recording wire 17 protruding from the
end guide 12a strikes the ink ribbon 8 against the recording paper
on the platen 3 , a dot is formed by the ink of the ink ribbon 8 on
the recording paper. When carbonless copy paper and plain paper are
conveyed together, a dot is also formed a t the same position on the
carbonless copy paper.
roo251
When a head coil 16 is energized, the head coil 16 heats and the
temperatureofthe headbodyllrises. The radiator13 o f t h e recording
head 2 is made from aluminum or other material with good heat
conductivity, takes andradiates heat fromtheheadbodyll, andcools
the head body 11.
A temperature detector 23 is also disposed to the frame 14 of
the head body 11. A thermistor of which the resistance changes
according to the temperature is used as the temperature detector 23
in this embodiment.
[00261
Recording wire and head coil configuration
FIG. 4 describes the configuration of the recording wires 17.
The recording wires 17 are wire pins that are round in section, and
the end face of one recording wire 17 forms one dot. The recording
head 2 in this embodiment of the invention has 24 recording wires 17.
The head face 2a from which the recording wires 17 protrude is formed
in the end guide 12a at the distal end of the nose 12. The 24 recording
wires 17 protrude from the head face 2a in an alignment determined
by the print density of the recording head 2.
In this embodiment as shown in FIG. 4, the 24 recording wires
17 are disposed in two rows of 12 wires. In FIG. 4, X indicates the
scanning direction of the carriage 4 that carries the recording head
2 (the head scanning direction). The rows of recording wires 17 are
substantially perpendicular to the scanning direction X. If the
reference dot pitch is dl the pitch of the recording wires 17 in each
row is twice d (2d), and the distance between the two recording wire
rows 17A, 17B is six times the reference dot pitch d (6d). The
recording wire rows 17A, 17B are also offset reference dot pitch d
in the direction substantially perpendicular to the scanning
direction X.
[00271
The recording head 2 has 24 pairs (#1 to #24) of recording wires
17 and head coils 16. These 24 pairs labelled #1 to #24 are arranged
as shown in FIG. 3 and FIG. 4. More specifically, the 24 head coils
16 are disposed in a circle to the recording head 2, but the group
of head coils 16 that drive recording wire row 17A are disposed in
a semicircle in the same order as the recording wires 17 in the
recordingwirerow17A. Thegroupofheadcoils16thatdriverecording
wire row 17B are likewise disposed in a semicircle in the same order
as the recording wires 17 in the recording wire row 17B.
More specifically, recording wire row 17A contains recording
wires 17 #I, #3, #5, #7, #9, #Ill #13, #IS. #17. #19. #21. #23, and
the head coils 16 corresponding to these recording wires 17 are
disposedinthe same order in one half-circle. Recording wire row 17B
contains recording wires 17 #2, #4, #6, #8, #lo, #12, #14, #16, #18.
#20, #22. #24. and the head coils 16 corresponding to these recording
wires 17 are disposed in the same order in the other half-circle.
The special bit images A (All A2) used to determine the drive
mode of the recording head 2 as described below are constructed
according to this configuration of recording wires 17 and head coils
16.
[00281
Control system
The dot impact printer 1 has a control unit 9 that centrally
controls parts of the dot impact printer 1. Print data and control
commands from a host device are input through a communication line,
for example, to the control unit 9. Based on the input print data and
control commands, the control unit 9 outputs control signals to the
carriage motor 6b and conveyance mechanism, and controls the
conveyance position of the recording paper and the position of the
carriage 4. Also based on the print data and control commands, the
control unit9 outputs controlsignalsthroughaheaddrivernot shown
to the head coils 16 of the recording head 2, and controls energizing
individual head coils.
[0029]
The detection signal from the temperature detector 23 is also
input to the control unit 9. When printing, the control unit 9
determines based on the detection signal from the temperature
detector 23 if the recording head 2 exceeds a preset reference
temperature. Based on this decision, the control unit 9 determines
the drive mode of the recording head 2 when printing, that is,
determines the settings (drive mode) related to controlling
energizing the head coils 16 to drive specific recording wires 17.
The control unit 9 has a storage unit 10 that stores data used to
determine the drive mode and control operation in each drive mode.
[O 03 0 I
The control unit 9 prints line by line by energizing the
necessary head coils 16 based on the print data while moving the
carriage 4, and selectively driving the recording wires 17 at the
necessary time. The print data for one line printed by the recording
head2 is composedof dot line data containingthe arrangement of dots
(dot pattern) indicatingwhether or not adot is formedat aparticular
position in one line on the recording medium.
Because the recording head 2 has 24 recording wires 17 in two
rows of 12 wires each, the dot line data contains information about
each of the 24 dots in the row direction (the number of dots in the
direction substantially perpendicular to the head scanning
direction). The dot line data describes where the 24 dots are formed
at the reference dot pitch d in the scanning direction X and the
reference dot pitch d in the direction substantially perpendicular
to the scanning direction X when the recording wires 17 are driven
to print each time the recording head 2 moves the reference dot pitch
d in the scanning direction X. More specifically, full dots are
printed by driving the recording wires 17 synchronized to a preset
standard drive cycle.
Half dots can also be printed at a dot interval of 1/2 the
reference dot pitch d. In this event, the recording wire 17 forming
a dot at a position off set a half dot from the standard dot position
is driven at a timing off set 1/2 of the standard drive cycle from the
drive timing of a recording wire 17 forming a dot at the standard dot
position.
[0031]
Each time one line of print data is printed, the control unit
9 determines before printing the line if the dot line data to be
printed contains a dot pattern matching a preset special bit image
A (special dot pattern). The control unit 9 also determines if the
dot line data contains a dot pattern matching a preset special bit
image B (highduty dot pattern). Basedon this decision, the detection
signal from the temperature detector 23, and specific parameters
specified by the print data, the control unit 9 determines the drive
mode of the recording head 2. The control unit 9 then prints the dot
line data to be printed in the selected drive mode.
[00321
Special bit image A and detection process
Special bit image A is a dot pattern for determining the
likelihood of poor response by each of the 24 recording wires 17 due
to magnetic interference from the head coils 16 of the adjacent
recording wires 17. FIG. 5A to FIG. 5C describe special bit images
A, FIG. 5A being a table showing the combinations of recording wires
adjacent to each of the 24 recording wires 17 (target recording wires
17) , FIG. 5B describing a special bit image Al, and FIG. 5C describing
another special bit image A2. A black dot in the figures indicates
a dot (black dot) that is formed on the recording medium, and a white
white dot indicates where a dot is notprintedonthe recordingmedium
(a white dot).
[00331
Anadjacent recording wire is a recordingwire17 whose head coil
16 is adjacent to the head coil 16 of the target recording wire 17.
For example, as shown in FIG. 4, if the target recording wire 17 (17a)
is #I, the adjacent recording wires 17 (17b, 17c) are #2 and #3. If
the target recording wire 17 (17a) is #13, the adjacent recording
wires 17 (17b, 17c) are #11 and #15. The 24 combinations of target
recording wire 17 (17a) and adjacent recording wires 17 (17b, 17c)
can be defined from the alignments shown in FIG. 3 and FIG. 4. The
special bit images A (Al, A2) are set to include dot patterns that
are formed when the target recording wire 17 (17a) is driven and the
adjacent recordingwires17 (17b, 17c) are drivenoffset1/2 reference
drive cycle to print a half dot.
[00341
FIG. 5B shows an example of the special b i t image A ( A l ) when
the target recording wire 17 (17a) and the adjacent recording w i r e s
17 (17b, 17c) are in the same row. FIG. 5C shows an example of the
special b i t image A (A2) when one adjacent recording wire 17 (17c)
is in a different row than the target recording wire 17 (17a).
Special b i t image A1 is a zigzag pattern C (specific dot pattern)
of dots formed in a zigzag comprising the dot formation positions of
the reference recordingwire 17 (17a), andthe dot formationpositions
of the adjacent recording wires 17 (17b, 17c) shifted a half dot (that
is, dot formation positions shiftedone dot in the scanning direction
X of the recording head 2) . When the target recording wire 17 (17a)
and both adjacent recording wires 17 (17b, 17c) are i n the same row,
that i s , when recording wires 17 #3 to #22 are the target recording
wire 17, a zigzag pattern C such as included in special b i t image A1
is detected. This zigzag pattern C is a dot pattern formed by driving
adjacent head coils 16 a t a specific drive period o f f s e t (1/2
reference drive cycle i n t h i s embodiment).
[00351
Special b i t image A2 r e s u l t s when the target recording wire 17
and the adjacent recording wire 17 (17c) are in d i f f e r e n t rows. In
t h i s instance, the special b i t image A2 is set with reference t o the
dot density (print resolution) and the distance between the recording
wire rows 17A, 17B so that the special b i t image A2 includes a dot
patternthat forms azigzagpatterncwhenthedotdataofthe adjacent
recording wires is shifted in the scanning direction X of the
recording head 2 a number of dots (Nd dots in FIG. 5C) equal to the
distance between the l i n e s . For example, when half dots are printed
with a recording wire 17 configuration having a l i n e gap of 6d as in
t h i s embodiment, Nd = 12. In t h i s configuration, therefore, special
bit image A2 is set to include a dot pattern forming a zigzag pattern
C when the dot positions are shifted12 dots in the scanning direction
X. With the configuration of recording wires 17 and head coils 16 in
this embodiment, the zigzag pattern C included in special bit image
A2 is detected when the target recording wire 17 is #I, #2, #23, or
#24.
[0036]
FIG. 6 is a flow chart of a process for detecting special bit
image A. The control unit 9 detects if special bit image A is found
anywhere in the print data for one line (24 rows of dot line data)
according to this flow chart. More specifically, the control unit 9
applies this process to each row from the first to the last row of
the dot line data to be printed, sequentially using each of the 24
recording wires 17 as the target recording wire 17 to determine if
dots are formed at positions forming a zigzag pattern C as described
above. If detection of a zigzag pattern C in the print data of the
line to be printed matches preset conditions, the special bit image
A is considered detected.
More specifically, the special bit image A is determined
detected if the number of rows in which the number of recording wires
17 forming a zigzag pattern C at either of two consecutive dot
positions equals or exceeds a preset reference number (2 in this
embodiment) is greater than or equal to a preset consecutive row count
(12 in this embodiment) .
LO0371
The control unit 9 has a zigzag pattern counter, a wire counter,
andadetectednumbercounteras countersusedinthe specialbit image
A detection process. Before starting to apply the special bit image
A detection process to one line of print data, the control unit 9
initializes the zigzag pattern counter to 0. The control unit 9 then
starts the process of steps S1 to Sll from the first row in the print
data for one line.
At step S1, the control unit 9 initializes the detected number
counter and sets the count (PinCnt) to 0, and initializes the wire
counterthatspecifiesthetargetrecordingwire17 and sets the count
(i) to 1.
[0038]
Next, in step S2, the control unit 9 gets dot data for three dots
(first dot data set) : the dot data (data indicating if the recording
wire prints a dot on the recording medium) for the recording wire 17a
targeted in row i (that is, recording wire 17 #1 in this instance) ;
the dot data for the adjacent recording wire 17b (recording wire #3
in this instance) at a position shifted a half dot (1 dot); and the
dot data for adjacent recording wire 17c (recording wire #2 in this
instance) at a position shifted a half dot (1 dot) plus the distance
between the recording wire rows (Nd dots, 12 dots with the wire
con£ iguration shown in FIG. 4) . The control unit 9 then goes to step
S3.
If i = 1, 2, 23, or 24 in step S2, the control unit 9 looks for
the zigzag pattern C of special bit image A2, and acquires dot data
at the position shifted a half dot plus the recording wire row gap
as the dot data for adjacent recording wire 17c. If i = 3 to 22, the
control unit 9 looks for the zigzag pattern C of special bit image
All and gets the dot data for the position shifted a half dot as the
dot data for adjacent recording wire 17c.
[00391
In step 53, the control unit 9 determines if the three acquired
dot data form a zigzag pattern C (that is, if all three dot data
indicate a dot is printed on the recording medium) . If the data form
a zigzag pattern C (step 53 returns YES), control goes to step S4.
If a zigzag pattern C is not formed (step S3 returns NO) , control goes
to step S5.
In step S5, the control unit 9 shifts to the next row adjacent
to the current row, and acquires dot data for the target recording
wire 17a. and the adjacent recording wires 17b. 17c as described in
S2.
In step 56, the control unit 9 then determines if the acquired
three dot data (second dot data set) form a zigzag pattern C. If a
zigzag pattern C is formed (step S6 returns YES). control goes to step
S4.
In step S4 the detected number counter PinCnt is incremented 1.
Control then goes to step S7.
If the second dot data set does not form a zigzag pattern C (step
56 returns NO), control goes to step 57 without incrementing the
detected number counter PinCnt.
[O 04 01
The control unit 9 adds 1 to the wire counter count in step 57,
and then goes to step 58 to determine if the current count of the wire
counter is greater than or equal to 24. that is. if all 24 recording
wires 17 have been inspected. If the count is less than 24 (step 58
returns NO), control returns to step 52. Steps S2 to 58 then repeat
until the count (i) of the wire counter reaches 24.
[0041]
When the wire counter ireaches 24 (step 58 returns YES), control
goes to step S9, and the control unit 9 determines if the detected
number counter PinCnt is greater than or equal to 2. If greater than
or equal to 2 (step S9 returns YES), control goes to step S10, and
the count ofthe zigzag pattern counter is incrementedl. Control then
goes to step S12. If the detected number counter PinCnt is less than
Or equal to 1 (step S9 returns NO), control goes to step S11 and the
zigzag pattern counter is reinitialized to 0. Control then goes to
step S12.
[0042]
Whether the count of the zigzag pattern counter is 12 or more
is determined in step 512. If the count is 12 or more. that is, if
there are 12 or consecutive rows where are 2 or more recording wires
17 that form a zigzag pattern C (step S12 returns YES) , the control
unit 9 determines that the line to be printed contains special bit
image A, and ends this process. However, if the count of the zigzag
pattern counter is less than 12 (step S12 returns NO), control goes
to step S13.
In step 513 the control unit 9 determines if the row tested is
the last row in the line to be printed. If not (step S13 returns NO),
the control unit 9 moves to the next adjacent row, returns to step
S1, and repeats the process (steps S1 to S12) on the next row. If it
is the last row (step 513 returns YES), the control unit 9 determines
the line to be printed does not contain the special bit image A, and
ends the process.
[0043]
Special bit images B and detection process
FIG. 7 describes another type of special bit image B (high duty
dot pattern) usedto determine the drive mode, FIG. 7Ashowing a first
dot pattern B1 of consecutive dots formed by the same recording wire
17, and FIG. 7B showing a second dot pattern B2 with every other
consecutive dot formed by the same recording wire 17. In this
embodiment, one line of print data consists of dot line data for a
maximum 136 columns (1 column equals the width of one character) of
24 dots in the row (column) direction. These special bit images B are
detected by detecting the number of consecutive dots in the dot
patterns shown in FIG. 7A or FIG. 7B. and determining if the maximum
consecutivenumber is greaterthanorequaltoathreshold count (such
[0044]
Beforeprintingeachline, the control unit 9 detectsthe special
bit images B parallel to detecting special bit images A described
above. Both special bit image A, B detection processes are applied
to all dot line data tobe printed. More specifically, the consecutive
count of first dot pattern B1 and second dot pattern B2 is detected
in all 24 rows of dot line data on the line to be printed. Whether
firstdotpatternB1orseconddotpatternB2is detectedis determined
based on whether half dot printing is selected. The consecutive count
of first dot pattern B1 is detected if the half dot printing mode is
not selected, and the consecutive count of second dot pattern B2 is
detected if half dot printing is selected. Whether the maximum
consecutive count in the print data for one line exceeds a reference
count is determined, and if the reference count is exceeded, detection
of a special bit image B is confirmed.
[00451
Other parameters for determining the drive mode
In addition to the results of detecting special bit images A and
B described above, the control unit 9 also uses the temperature of
the recording head 2 (the value detected by the temperature detector
23), and the print quality specified for the dot data to be printed,
as parameters for determining the drive mode of the recording head
2 (the settings related to energizing control of the head coils 16).
The print quality is specified by a combination of two parameters,
the print mode and character quality. The print mode is either NORMAL
or COPY. Thecharacterqualityis eitherDRAFTorLQ (letterquality).
The draft mode is for print data at a lower resolution than a preset
standard resolution, and letter quality is set for print data at a
resolution equal to or exceeding the standard resolution.
[0046]
FIG. 8 shows a control table for determining the drive mode. The
control unit 9 determines based on the detection signal from the
temperature detector 23 if the recording head 2 exceeds a preset
reference temperature, and based on the decision adjusts energizing
the head coils 16 when printing each line. This embodiment of the
invention uses three reference temperatures.
In FIG. 8, the column labelled special bit image A sets the
reference temperature and other parameters when special bit image A
is detected. The column labelled special bit image B sets the
reference temperature and other parameters used when special bit
image A is not detected and the number of areas containing a special
bit image B is greater than or equal to reference count N.
The column labelled special bit image A also has the label "no
special bit image, which means that when neither special bit image
A or B is detected, the same settings are used as when special bit
image A is detected. In this embodiment as shown in FIG. 8, three
reference temperatures are preset for a total of eight patterns
including four print quality levels combining the print mode
(normal/copy) and character quality (draft/letter quality), and two
variations, special bit image A or no special bit image, and special
bit image B. Note that the control table in FIG. 8 does not show the
actualreferencetemperatures, andonly showsthe output values (Rin,
Rhh, Rst) of the temperature detector 23 corresponding to the
reference temperatures.
LOO471
FIG. 8 shows the output values of the temperature detector 23
(such as thermistor) at the set reference temperatures. The lowest
of the three reference temperatures is the interval printing
condition (Rin) for setting the time interval (head coil drive
interval) from the end of energizing to form one dot and the start
of energizing for the next dot.
The next lowest reference temperature after the interval
printing condition (Rin) is the Uni-D printing condition (Rhh) for
setting whether to use a bidirectional printing mode that forms dots
on both the outbound and return passes of the bidirectional movement
of the carriage 4, or a unidirectional printing mode that forms dots
only on the outbound or the return pass.
Thehighestreferencetemperatureisthe stopprinting condition
(Rst) used to determine whether or not to stop printing. The control
unit 9 determines whether to use a default interval time (Tinl) or
a high temperature interval time (Tina) by comparing the output value
of the temperature detector 23 and Rin. The control unit 9 also
determines whether to use bidirectional or unidirectional printing
by comparing the output value of the temperature detector 23 and Rhh.
The control unit 9 also determines whether to stop printing by
comparing the output value of the temperature detector 23 and Rst.
100481
Controlling the recording head when printing
FIG. 9 is a flow chart of the drive mode selection process and
printing process using the control table shown in FIG. 8. FIG. 10 is
a flow chart of the special bit image detection process executed as
step S24 in FIG. 9. The printing process when printing print data one
line at a time is described below with reference to the flow charts.
At step S21, the control unit 9 gets and comparesthe output value
R of the temperature detector 23 with the output value corresponding
to a preset reference temperature. The reference temperature used
here is lower thanthevalue ofthe interval printing condition (Rin),
which is the lowest of the three reference temperatures, and in this
embodiment is the temperature corresponding tothe outputvalue13.62
kR of detector 23. If the temperature of the recording head 2 is less
than or equal to the reference temperature, that is, if R >= 13.62
kR, (step S21 returns YES), the control unit 9 goes to step S22 and
sets the drive mode.
[00491
InstepS22,the controlunit9 sets theheadcoil drive frequency
f to f c= 780Hz (0.78 kHz), and sets the head coil energizing time
to Pwn + 10 (s in the normal mode, and to Pwc + 10 Is in the copy mode.
Pwn is the preset standard energizing time in the normal mode,
and Pwc is the preset standard energizing time in the copy mode.
Note that the default interval (Tinl) corresponding to the print
quality can be selected from the no special bit image column for the
head coil drive interval, for example. A different interval can also
be set set.
Control then goes to step S23, the current line to be printed
is printed in the set drive mode, and the process then ends.
[0050]
If in step S21thetemperature ofthe recordinghead2 is greater
than the reference temperature (that is, R c 13.62 kQ) (step 521
returns NO), the control unit 9 goes to step S24.
Steps24 consistsofthe three steps S24a, S24b, andS24cinwhich
the control unit 9 looks for the special bit images A and B in the
dot line data to be printed as described above and shown in FIG. 10.
[00511
More specifically, in step S24a, the control unit 9 determines
if the print data is data for printing half dots. If the data is for
printing half dots (step S24a returns YES) , control goes to step S24b.
If the data is not for printing half dots (step S24a returns NO),
control goes to step S24c, skipping step S24b.
In step S24b1 the control unit 9 looks for a special bit image
A in the dot line data to be printed as described in the flow chart
in FIG. 6. In step S24c, the control unit 9 looks for a special bit
image B in the dot line data to be printed.
If the control unit determines in step S24a that the data is for
half dot printing, it determines in step S24c if the maximum
consecutivecount ofthe seconddotpatternB2 isgreaterthanorequal
to the reference count. If the control unit determines in step S24a
that the data is not for half dot printing, the control unit 9
determines in step S24c if the maximum consecutive count of the first
dot pattern B1 is greater than or equal to the reference count.
[00521
If special bit image A is found in step S24b of step S24 (that
is, if there are 12 or consecutive rows where are 2 or more recording
wires 17 that form a zigzag pattern C) (step 524 returns YES (I)),
control goes to step S25.
In step S25, the control unit 9 references the control table in
FIG. 8, and of the three reference temperatures, selects the
temperature (first temperature) in the special bit image A column of
the print quality set for the current print data. The control unit
9 also sets the output value Rin, Rhh, Rst of the temperature detector
23 corresponding to the selected reference temperature as the
evaluation value for determining the drive mode.
[00531
If in step S24 the special bit image A is not detected (is not
detected in step S24b or step S24b is skipped), and special bit image
B is detected in step S24c (step S24 returns YES (2)), control goes
to step S26.
In step S26, the control unit 9 references the control table in
FIG. 8, and of the three reference temperatures, selects the
temperature (second temperature) in the special bit image B column
of the print quality set for the current print data. The control unit
9 also sets the output value Rin, Rhh, Rst of the temperature detector
23 corresponding to the selected reference temperature as the
evaluation value for determining the drive mode.
[0054]
If in step S24 the special bit image A is not detected (is not
detected in step S24b or step S24b is skipped), and special bit image
B is not detected in step S24c (step S24 returns NO), control goes
to step S27.
In step S27, the control unit 9 references the control table in
FIG. 8, and of the three reference temperatures, selects the
temperature (first temperature) in the no special bit image column
of the print quality set for the current print data. The control unit
9 also sets the output value Rin, Rhh, Rst of the temperature detector
23 corresponding to the selected reference temperature as the
evaluation value for determining the drive mode.
LO0551
If control goes to step S25 (special bit image A is detected) ,
the output value R of the temperature detector 23 is compared with
Rin, Rhh, and Rst, and the drive mode is set based on the result of
these comparisons, in steps S28 to 533. In step 525, the three
reference temperatures are set to TI, T2C, T3 (0.90 kQ, 0.52 kQ, 0.51
kS2) when the character quality is set to draft, and to TI, T4, T5 (0.90
kQ, 0.57 kQ, 0.53 kQ) when the character quality is set to letter
quality.
In step 528, the output value R is compared with the output value
Rin corresponding tothe interval printing condition (TI) that is the
lowest reference temperature. If R > Rin (temperature T of the
recording head 2 c= TI) (step 528 returns NO) , control goes to step
S29, the head coil drive frequency f is set to f c= 0.78 kHz, and the
head coil energizing time Pw is set to Pwn in the normal mode, and
Pwc in the copy mode. The head coil drive interval is set to Tinl.
[00561
If in step 528 R c= Rin (temperature T of the recording head 2
> TI) (step S28 returns YES), control goes to step 530, and the output
value R is compared with the output value Rhh corresponding to the
Uni-D printing condition (T2, T4). If R z Rhh (temperature T of the
recording head 2 c= 124 degC) (step 53 0 returns NO) , control goes to
step S31, andthe headcoil drive frequency f andheadcoil energizing
time are set as shown in step S31 in FIG. 9.
100571
If in step 530 R c= Rhh (temperature T of the recording head 2
sT2 T4) (step 530 returns YES), control goes to step 532, and output
value R is compared with the output value Rst corresponding to the
stop printing condition (T3, T5) .
If R > Rst (temperature T of the recording head 2 c= T3, T5) (step
S32 returns NO), control goes to step S33, and the head coil drive
frequency f and head coil energizing time are set as shown in step
533 in FIG. 9.
[0058]
When the drive mode is set in step S29, S31, or S33, control goes
to stepS23, the current linetobeprintedisprintedinthe set drive
mode, and the process ends.
However, if in step S32 R <= Rst (temperature T of the recording
head 2 >T3 ,T5) (step S32 returns YES) , control goes to step S34, and
printing stops.
In step S34, the control unit 9 stops printing for apreset delay
time (time for dissipating the heat of the recording head 2) . Control
then returns to step S21, and the process resumes.
LOO591
If controlproceedsto steps26 (special bit image Bis detected),
the output value R of the temperature detector 23 is compared with
Rin, Rhh, and Rst, and the drive mode is set based on the result of
these comparisons, in steps 535 to S40. In step S26, the three
reference temperatures are set to T6, T7, T5 (5.82 kQ, 4.16 kQ, 0.53
kQ) . In this instance, the reference temperature is the same whether
the character quality is set to draft or letter quality.
The process of steps S35 to S40 is the same as steps S28 to S33
except that the three reference temperatures are lower than in steps
S28 to S33 (the second temperature is selected as the reference
temperature), and the head coil drive frequency f is a higher drive
frequency (f <= 1.56 kHz in the normal mode, f <= 1.26 kHz in the copy
mode) than the frequency f <= 0.78 kHz set in steps S29, S31, and S33.
[0060]
If control proceeds to step S27 (neither special bit image A or
B is detected), the output value R of the temperature detector 23 is
compared with Rin, Rhh, and Rst, and the drive mode is set based on
the result of these comparisons, in steps S41 to S46. In step S27,
Rin, Rhh, and Rst are set to the same values as in step S25.
The process of steps S41 to S46 is the same as steps S28 to S33
except t h a t theheadcoil drive frequencyf is ahigherdrive frequency
(f c= 1.56 kHz in the normal mode, f <= 1.26 kHz in the copy mode)
than the frequency f <= 0.78 kHz s e t in steps S29, S31, and S33.
[00611
The invention thus controls setting the drive mode with
consideration for magnetic interference between adjacent head c o i l s
16.More specifically, the drivemode selectedinstepS25 setsalower
head coil drive frequency f than the drive modes selected i n steps
S26 and S27. More specifically, when a special b i t image A containing
more than a threshold number of zigzag patterns C that are printed
by adjacent head coils 16 being driven with a specific s h i f t in the
drive cycle is detected from the dot l i n e data to be printed, that
i s , when magnetic interference between head coils is expected t o
result in the ink ribbon being caught on one or more wire pins, the
head coil drive frequency f is set lower than when the special b i t
image A is not detected.
roo621
As a r e s u l t , while t h i s reduces the printing speed, poor
recording wire 17 response due to magnetic interference between
adjacent headcoils16 canbe suppreqsed. The inkribboncantherefore
be prevented from being caught on a recording wire. Furthermore,
because the printing speed drops only when the special b i t image A
is detected, the printing speed is not reduced u n t i l the p o s s i b i l i t y
of the ink ribbon being caught is detected. Throughput is therefore
notreducedmorethannecessary. Furthermore, because the special b i t
image A detection process executes only when printing half dots, that
i s , only when printing with the head c o i l drive timing shifted 1 / 2
the standard drive cycle, unnecessary detection processes can be
eliminated. Control can therefore be simplified, and the processing
time shortened.
LO0631
Whenprintingahighdutydotpatternthatcausesthetemperature
of the recording head 2 to exceed the heat damage threshold
temperature of the head coil 16, the invention controls switching to
a drive mode that produces less heat while the temperature of the head
coils 16 is already low. More specifically, when control goes to step
S25 or S27, the reference temperature for setting the drive mode is
set to TI, T2, T3 or TI, T4, T5 (first temperature) . When control goes
to step S26, the reference temperature is set to T6, T7, T4 (second
temperature). Whencontrolgoesto step S25 or S27, thehead coil drive
intervalTin1, Tin2 corresponding tothe reference temperature is set
lower than when control goes to step S26. More specifically, when
special bit imaqes B are contained in the dot line data to be printed
(that is, when the temperature of the recording head 2 is expected
to exceed the heat damage threshold temperature of the head coil),
the reference temperature of the recording head 2 for changing the
drive mode is reduced and the printing speed is slowed more than when
no special bit imaqes B are detected in the dot line data (that is,
when the temperature ofthe recording head2 is notexpectedtoexceed
the heat damage threshold temperature of the head coil).
LO0641
By thus lowering the reference temperature, a drive mode that
produces less heat is set eventhoughthe temperature ofthe recording
head 2 is the same. A drive mode that produces little heat and has
a slow printing speed is therefore set only when there is the
possibility that the temperature of the recording head 2 will exceed
the heat damage threshold temperature of the head coil. Heat damage
to the head coils can therefore be prevented, and printer throughput
is not reduced more than necessary.
[00651
Furthermore, because special bit images A and B can be detected
at the same time in step S24, detection can be controlled efficiently
and processing time can be shortened.
100661
Other embodiments
(1) A special bit image A is detected in the foregoing embodiment
if thenumber of rows inwhichthenumber of recordingwires17 forming
a zigzag pattern C at either of two consecutive dot positions equals
or exceed sapreset referencenumber (2 wires) is greaterthanorequal
to a preset consecutive row count (12 rows) , but the reference number
of wires and the consecutive row count are respectively not limited
to 2 wires and 12 rows. The reference number of wires and the
consecutive row count can be set appropriately by testing and
verifyingtheprintdata conditions that may result in the ink ribbon
being caught.
[00671
(2) Special bit images A and B are detected in step 524 in the
foregoing embodiment, but the special bit image B detection process
can be omitted. In this implementation the data shown in the special
bit image B column in the control table in FIG. 8 is unnecessary, and
steps S25 to S30 in the flow chart in FIG. 9 are unnecessary.
[0068]
(3) The special bit images A (Al, A2) and process for detecting them
in the foregoing embodiment are based on the head coil 16
configurationandrecordingwire 17 alignment shown inFIG. 3 andFIG.
4, but the invention can also be applied to head coil and recording
wire conf igurations different from those shown in FIG. 3 and FIG. 4.
For example, similar combinations of recording wires 17a to target
and adjacent recording wires 17b. 17c can be defined if at least part
of the recording wires 17 are aligned in a row and the head coils 16
that drive the recordingwires 17 are alignedina corresponding order
in one row or a circle. Whether or not the print data may result in
the ink ribbon being caught can then be determined by determining if
the recording wires 17 will form a zigzag pattern C.
[0069]
The invention can thus be applied to various configurations
having a plurality of adjacent head coils 16. More specifically, a
specific dot pattern that is printed by adjacent head coils 16 being
driven ata specific drive cycle shift that could cause poor recording
wire 17 response due to magnetic interference can be determined in
advance, and a suitable drive mode can be selected based on the result
of this detection process.
[0070]
(4) The process ofdetectingthe special bit image Bin the foregoing
embodiment focuses on the maximum consecutive number of first dot
patterns B1 and second dot patterns B2 in the print data on one line,
and determines that the special bit image B was detected if this
maximumconsecutive number exceeds athresholdnumber. Alternatively,
the number (count) of first dot patterns B1 or second dot patterns
B2 with a consecutive count exceeding a reference number could be
counted, and the special bit image B considered tobe detectedif this
count is greater than or equal to a reference number (the reference
number can be set appropriately to 2, 3, 4 or other number).
The invention being thus described, it will be obvious that it
may be varied in many ways. Such variations are not to be regarded
as a departure from the spirit and scope of the invention, and all
such modifications as would be obvious to one skilled in the art are
intended to be included within the scope of the following claims.

What is claimed is:
1. A dot impact printer comprising:
a carriage that scans in a direction intersectingthe conveyance
direction of a recording medium;
a recording head carried on the carriage; and
a control unit that controls the recording head;
wherein the recording head has a p l u r a l i t y of recording wires
that form dots on the recording medium, and
a plurality of head coils that respectively drive the
plural recording wires selectively; and
t h e c o n t r o l u n i t d e t e c t s i n d o t l i n e d a t a t o b e p r i n t e d a s p e c i f i c
dot pattern that is printed by driving adjacent head c o i l s with a
specific drive cycle s h i f t ,
selects a drive mode of the recording head based on the
result of detecting the specific dot pattern, and
prints the dot l i n e data t o be printed by driving the
recording wires while moving the carriage in the selected mode.
2. The dot impact printer described in claim 1, wherein:
the plural head c o i l s are aligned in a circle inside the
recording head;
a t least part of the plural recording wires are aligned a t a
specific pitch in a directionintersectingthe scanning direction of
the carriage in the same sequence as the alignment order of the head
coils; and
the specific dot pattern is a zigzag pattern having plural dots
alignedinazigzagoffsethalfthedistanceofthe standarddotpitch.
3 . The dot impact printer described in claim 1, wherein:
the control unit sequentially selects each of the plural
recording wires as a target recording wire and determines i f the
specific dot pattern is printed by the target recording wire and an
adjacent recording wire at a predetermined position relative to the
target recording wire in each row from the first row to the last row
of the dot line data to be printed,
determines that a preset specific pattern is detected when
the number of rows where the number of recording wires determined to
print the specific dot pattern equals or exceeds a preset reference
number is greater than or equal to a preset consecutive row count,
and
selects the drive mode based on the result of detecting the
specific pattern.
4. The dot impact printer described in claim 3, wherein:
drive modes with different head coil drive frequencies can be
set as the drive mode of the recording head for printing; and
the control unit selects a drive mode with a head coil drive
frequency that is lower when the specific pattern is detected than
when the specific pattern is not detected, and prints the dot line
data to be printed in the selected drive mode.
5. The dot impact printer described in claim 1, wherein:
the control unit execute st he process detectingthe specific dot
pattern in the dot line data to be printed, and selects the recording
head drive mode based on the result of detecting the specific dot
pattern, when in a print mode that prints half dots forming dots at
half the standard dot pitch, and
does not execute the process detecting the specific dot
pattern when in a print mode that does not print half dots.
6. The dot impact printer described in claim 1, wherein:
the control unit detects the specific dot pattern and a preset
high duty dot pattern from dot line data to be printed;
the high duty dot pattern is a dot pattern in which the
consecutive drive count of the same recordingwire, or the consecutive
intermittent drivecount o f t h e same recordingwire driveneveryother
dot, is greater than or equal to a preset maximum; and
the control unit selects the recording head drive mode based on
the result of detecting the high duty dot pattern ox the specific dot
pattern in the dot line data to be printed, and prints the dot line
data to be printed in the selected drive mode.
7 . The dot impact printer described in claim 6, wherein:
drive modes that produce different amounts of heat can be s e t
as the drive mode of the recording head when printing;
the drive mode and the temperature of the recording head are
related;
the recording head temperatures related to the drive modes
include a t least a f i r s t temperature and a second temperature that
is lower than the f i r s t temperature;
the control unit detects t h e temperature of the recording head
before printing the dot l i n e data to be printed;
selects either the f i r s t temperature or the second temperature
based on the result of detecting t h e s p e c i f i c dot pattern and the high
duty dot pattern in the dot line data to be printed;
s e l e c t s t h e drivemode corresponding t o t h e detectedtemperature
of the recording head from among the drive modes related t o the
selected temperature; and
printsthe dot line d a t a t o b e p r i n t e d i n t h e selecteddrivemode.
8. A control method of a dot impact printer having a carriage that
scans in a direction i n t e r s e c t i n g t h e conveyance direction of a
recording medium, a recording head carried on the carriage, and a
control unit that controls the recording head,
the recording head having a p l u r a l i t y of recording wires
that f om dots on the recording medium, and a p l u r a l i t y of head coils
that respectively drive the plural recording wires selectively,
the controlmethodcomprising steps executedbythe control unit
including:
detecting in dot line data to be printed a specific dot pattern
that is printed by driving adjacent head coils with a specific drive
cycle shift;
selecting a drive mode of the recording head based on the result
of detecting the specific dot pattern; and
printing thedot line data tobe printedbydrivingthe recording
wires while moving the carriage in the selected mode.
9. The control method of a dot impact printer described in claim
8, wherein:
the plural head coils are aligned in a circle inside the
recording head;
at least part of the plural recording wires are aligned at a
specific pitch in a direction intersecting the scanning direction of
the carriage in the same sequence as the alignment order of the head
coils; and
the specific dot pattern is a zigzag pattern having plural dots
alignedinazigzagoffsethalfthedistanceofthe standarddot pitch.
10. The control method of a dot impact printer described in claim
8, further comprising steps of the control unit:
sequentially selecting each of the plural recording wires as a
target recording wire and determines if the specific dot pattern is
printed by the target recording wire and an adjacent recording wire
at a predetermined position relative to the target recording wire in
each row from the first row to the last row of the dot line data to
be printed;
determining that a preset specific pattern is detected when the
number of rowswherethenurnber of recordingwires determinedtoprint
the specific dot pattern equals or exceeds a preset reference number
is greater than or equal to a preset consecutive row count; and
selecting the drive mode based on the result of detecting the
specific pattern.
11. The control method of a dot impact printer described in claim
10, wherein:
drive modes with different head coil drive frequencies can be
set as the drive mode of the recording head for printing; and
the control unit selects a drive mode with a head coil drive
frequency that is lower when the specific pattern is detected than
when the specific pattern is not detected, and prints the dot line
data to be printed in the selected drive mode.
12. The control method of a dot impact printer described in claim
8, wherein :
the control unit execute st he process detectingthe specific dot
pattern in the dot line data to be printed, and selects the recording
head drive mode based on the result of detecting the specific dot
pattern, when in a print mode that prints half dots forming dots at
half the standard dot pitch, and
does not execute the process detecting the specific dot
pattern when in a print mode that does not print half dots.
13. The control method of a dot impact printer described in claim
8, wherein :
the control unit detects the specific dot pattern and a preset
high duty dot pattern from dot line data to be printed;
the high duty dot pattern is a dot pattern in which the
consecutivedrive count ofthe same recordingwire, ortheconsecutive
intermittent drive count ofthe samerecordingwiredriveneveryother
dot, is greater than or equal to a preset maximum; and
the control unit selects the recording head drive mode based on
the result of detecting the high duty dot pattern or the specific dot
pattern in the dot line data to be printed, and prints the dot line
data to be printed in the selected drive mode.
1 4 . The control method of a dot impact printer described in claim
13, wherein:
drive modes that produce different amounts of heat can be set
as the drive mode of the recording head when printing;
the drive mode and the temperature of the recording head are
related;
the recording head temperatures related to the drive modes
include at least a first temperature and a second temperature that
is lower than the first temperature;
the control unit detects the temperature of the recording head
before printing the dot line data to be printed;
selects either the first temperature or the second temperature
based on the result of detectingthe specific dot pattern and the high
duty dot pattern in the dot line data to be printed;
selectsthedrivemode correspondingtothedetectedtemperature
of the recording head from among the drive modes related to the
selected temperature; and
printsthe dot line datatobeprintedinthe selecteddrivemode.
Dated this September,
ROBI@RK GROSER
of GRO R & GROSER
AGENT FOR THE APPLICANTS