U.S. patent application number 14/026603 was filed with the patent office on 2014-01-09 for color printer with power saving recording head.
This patent application is currently assigned to CASIO COMPUTER CO., LTD.. The applicant listed for this patent is CASIO COMPUTER CO., LTD., CASIO ELECTRONICS MANUFACTURING CO., LTD.. Invention is credited to Jun Hashimoto.
Application Number | 20140009554 14/026603 |
Document ID | / |
Family ID | 45021880 |
Filed Date | 2014-01-09 |
United States Patent
Application |
20140009554 |
Kind Code |
A1 |
Hashimoto; Jun |
January 9, 2014 |
COLOR PRINTER WITH POWER SAVING RECORDING HEAD
Abstract
The present invention relates to a color printer and
particularly to a color printer reducing power consumption and
complying with international criteria ensuring sustained earth
environment. In a color printer having multiple optical writing
heads for individual recording colors, the activated periods of
individual color recording heads are set to different periods and
one writing period of individual recording heads is divided into
multiple periods, video data for recording one dot line are divided
into multiple blocks in the main scan direction, and the divided
video data are used for emission at different times in the sub-scan
direction, whereby a smaller number of optical writing elements are
simultaneously driven for emission and the peak power consumption
of the entire apparatus is reduced.
Inventors: |
Hashimoto; Jun; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CASIO COMPUTER CO., LTD.
CASIO ELECTRONICS MANUFACTURING CO., LTD. |
Tokyo
Iruma-shi |
|
JP
JP |
|
|
Assignee: |
CASIO COMPUTER CO., LTD.
Tokyo
JP
CASIO ELECTRONICS MANUFACTURING CO., LTD.
Iruma-shi
JP
|
Family ID: |
45021880 |
Appl. No.: |
14/026603 |
Filed: |
September 13, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13113233 |
May 23, 2011 |
8559060 |
|
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14026603 |
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Current U.S.
Class: |
347/232 |
Current CPC
Class: |
G03G 15/5004 20130101;
G03G 15/011 20130101; G03G 2215/0132 20130101; B41J 2/435 20130101;
H04N 1/40 20130101 |
Class at
Publication: |
347/232 |
International
Class: |
B41J 2/435 20060101
B41J002/435 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2010 |
JP |
2010-119178 |
Feb 22, 2011 |
JP |
2011-036303 |
Claims
1. A printer creating video data corresponding to recording colors
based on print information entered from a host machine, supplying
the video data to corresponding recording color optical writing
recording heads comprising an array of light emitting elements
arranged in a main scan direction, and forming images by exposing
image lights consequently emitted on corresponding photoconductive
bodies for recording color, the photoconductive bodies being
provided to face the optical writing recording heads and moving in
a sub-scan direction perpendicular to the main scan direction, and
the printer comprising: a recording head selection/activated unit
activating individual color optical writing recording heads in
sequence to enable optical writing in each of periods equal to one
n-th of one writing period of the optical writing recording heads,
where n represents a number of divisions into which one dot line
image to be recorded is divided in the sub-scan direction; a video
data supply unit supplying video data corresponding to the one dot
line image to be recorded to the optical writing recording heads
during an activated period by the recording head
selection/activated unit; and a divided emission control unit
selectively activating a plurality of blocks comprising a given
number of light emitting elements of the optical writing recording
heads so as to allow the light emitting elements in the plurality
of blocks to selectively emit light based on video data applied to
the optical writing recording heads during the activated period by
the recording head selection/activated unit.
2. The printer according to claim 1, wherein the recording color
optical writing recording heads are provided such that each of the
blocks are shifted in the sub-scan direction by a quantity to
cancel an emission time-lag between the light emitting elements in
different blocks activated with a time-lag by the divided emission
control unit.
3. A printer creating video data corresponding to recording colors
based on print information entered from a host machine, supplying
the video data to corresponding recording color optical writing
recording heads comprising an array of light emitting elements
arranged in a main scan direction, and forming images by exposing
image lights consequently emitted on corresponding photoconductive
bodies for recording color, the photoconductive bodies being
provided to face the optical writing recording heads and moving in
a sub-scan direction perpendicular to the main scan direction, and
the printer comprising: a recording head selection/activated unit
activating individual color optical writing recording heads in
sequence to enable optical writing in each of periods equal to one
n-th of one writing period of the optical writing recording heads,
where n represents a number of divisions into which one dot line
image to be recorded is divided in the sub-scan direction; a video
data dividing/supply unit dividing an activated period by the
recording head selection/activated unit into m periods where m
represents an integer equal to or greater than two, and applying,
to the optical writing recording heads, only video data
corresponding to each piece of one dot line image data divided into
the number m in the main scan direction during each of the m
periods; and a divided emission control unit selectively activating
a specific block of light emitting elements of the optical writing
recording heads so as to allow the light emitting elements in the
block to selectively emit light based on video data applied to the
optical writing recording heads in each of the activated periods by
the selection/activated unit in the m periods.
4. The printer according to claim 3, wherein the individual color
optical writing recording heads are provided such that each of the
blocks are shifted in the sub-scan direction by a quantity to
cancel an emission time-lag between the light emitting elements in
different blocks activated with a time-lag by the divided emission
control unit.
5. A non-transitory computer-readable recording medium having a
program stored thereon for controlling a printer that (i) creates
video data corresponding to recording colors based on print
information entered from a host machine, (ii) supplies the video
data to corresponding recording color optical writing recording
heads comprising an array of light emitting elements arranged in a
main scan direction, and (iii) forms images by exposing image
lights consequently emitted on corresponding photoconductive bodies
for recording color, wherein the photoconductive bodies are
provided to face the optical writing recording heads and move in a
sub-scan direction perpendicular to the main scan direction, and
wherein the program is executable to control the printer to
function as units comprising: a recording head selection/activated
unit activating individual color optical writing recording heads in
sequence to enable optical writing in each of periods equal to one
n-th of one writing period of the optical writing recording heads,
where n represents a number of divisions into which one dot line
image to be recorded is divided in the sub-scan direction; a video
data supply unit supplying video data corresponding to the one dot
line image to be recorded to the optical writing recording heads
during an activated period by the recording head
selection/activated unit; and a divided emission control unit
selectively activating a plurality of blocks comprising a given
number of light emitting elements of the optical writing recording
heads so as to allow the light emitting elements in the plurality
of blocks to selectively emit light based on video data applied to
the optical writing recording heads during the activated period by
the recording head selection/activated unit.
6. A non-transitory computer-readable recording medium having a
program stored thereon for controlling a printer that (i) creates
video data corresponding to recording colors based on print
information entered from a host machine, (ii) supplies the video
data to corresponding recording color optical writing recording
heads comprising an array of light emitting elements arranged in a
main scan direction, and (iii) forms images by exposing image
lights consequently emitted on corresponding photoconductive bodies
for recording color, wherein the photoconductive bodies are
provided to face the optical writing recording heads and move in a
sub-scan direction perpendicular to the main scan direction, and
wherein the program is executable to control the printer to
function as units comprising: a recording head selection/activated
unit activating individual color optical writing recording heads in
sequence to enable optical writing in each of periods equal to one
n-th of one writing period of the optical writing recording heads,
where n represents a number of divisions into which one dot line
image to be recorded is divided in the sub-scan direction; a video
data dividing/supply unit dividing an activated period by the
recording head selection/activated unit into m periods where m
represents an integer equal to or greater than two, and applying,
to the optical writing recording heads, only video data
corresponding to each piece of one dot line image data divided into
the number m in the main scan direction during each of the m
periods; and a divided emission control unit selectively activating
a specific block of light emitting elements of the optical writing
recording heads so as to allow the light emitting elements in the
block to selectively emit light based on video data applied to the
optical writing recording heads in each of the activated periods by
the selection/activated unit in the m periods.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a Divisional of U.S. application Ser. No.
13/113,233, filed May 23, 2011, which claims the benefit of
priority from Japanese Patent Application No. 2010-119178, filed
May 25, 2010, and Japanese Patent Application No. 2011-036303,
filed Feb. 22, 2011, the entire contents of all of which are
incorporated herein by reference.
FIELD
[0002] This application relates generally to a printer, and more
particularly, to a tandem color printer using
electrophotography.
BACKGROUND
[0003] A tandem printer using electrophotography utilizes, for
example, yellow (Y), magenta (M), cyan (C), and black (K) imaging
units for printing process in which the recording heads in the
imaging units emit light in accordance with print data on the
peripheral surfaces of photoconductor drums for exposure to form
toner images and the toner images are transferred to a printing
medium.
[0004] FIG. 10 is an illustration for explaining a prior art
control, showing a time chart of controlling yellow (Y), magenta
(M), cyan (C), and black (K) stations driving Y, M, C, and K
imaging units. As shown in the figure, in the Y, M, C, and K
stations, load signals are simultaneously output, individual color
print data are supplied, and strobe signals are simultaneously
output to drive the individual recording heads.
[0005] Therefore, as shown in the figure, the recording heads are
equal in power consumption. For example, a current of 500 mA flows
through each recording head at the time of not printing and a
current of 800 mA flows through the same at the time of printing.
In all four imaging units, a total current of 2000 mA flows through
the recording heads at the time of not printing and a total current
of 3200 mA flows through the same at the time of printing.
[0006] A prior art for preventing excessive power consumption is
disclosed in Patent Literature 1, in which, for example, the cyan,
magenta, yellow, and black LED heads are turned on in sequence to
prevent excessive power consumption.
[0007] Patent Literature 2 discloses an invention in which the LED
array chips are shifted in the sub-scan direction for preventing
failure of printed data to be printed on a line because of the LED
array chips driven in a time division manner. [0008] [Patent
Literature 1] Unexamined Japanese Patent Application KOKAI
Publication No. H7-199582 [0009] [Patent Literature 2] Unexamined
Japanese Patent Application KOKAI Publication No. H7-329352
[0010] However, sustained earth environment is called for worldwide
and the global warming conference is playing a pivotal role for
realizing regulations on emission of greenhouse gasses such as CO2
(carbon dioxide). Under such circumstances, criteria for complying
with the "International Energy Star Program" of the ECCJ (Energy
Conservation Center, Japan) are set on electric appliances such as
printers, facsimiles, copiers, personal computers (PCs), and
displays.
[0011] The above-described prior art printers are designed to
supply a large current to the recording heads at the time of
printing, requiring large power consumption. Then, their design
does not comply with the above "International Energy Star
Program."
[0012] The present invention provides a printer reducing power
consumption and complying with the international criteria ensuring
sustained earth environment.
SUMMARY
[0013] In order to achieve the above object, the present invention
provides a color printer creating video data corresponding to n
colors based on print information entered from a host machine,
supplying individual color video data to corresponding recording
color optical writing recording heads comprising an array of many
light emitting elements arranged in a main scan direction, forming
individual color images by exposing the individual color image
lights consequently emitted on corresponding photoconductive bodies
for recording color, the photoconductive bodies being provided to
face the optical writing recording heads and moving in a sub-scan
direction perpendicular to the main scan direction to form
individual color images, and finally merging all color images on a
printing medium to form a color image, wherein the color printer
comprises a recording head selection/activation unit activating
individual color recording heads in sequence to enable optical
writing in each of periods equal to one n-th of one writing period
of the optical writing recording heads; a video data supply unit
applying video data corresponding to one dot line image to be
recorded to the recording heads during an activated period of
individual recording color recording heads; a staggered emission
drive signal generation unit generating x staggered emission drive
signals for each of individual recording color recording heads
during the activated period of individual recording color recording
heads; and a divided emission control unit selectively activating a
block comprising a given number of light emitting elements of the
individual color recording heads so as to allow the light emitting
elements in the block to selectively emit light based on video data
applied to the recording head during each of staggered emission
drive periods, and the individual recording color recording heads
are provided in the manner that the blocks are shifted in the
sub-scan direction by the quantity to cancel the emission time-lag
between the light emitting elements in different blocks activated
with time-lag by the staggered emission drive signals.
[0014] In order to achieve the above object, the present invention
provides a color printer creating video data corresponding to n
colors based on print information entered from a host machine,
supplying individual color video data to corresponding recording
color optical writing recording heads comprising an array of many
light emitting elements arranged in a main scan direction, forming
individual color images by exposing the individual color image
lights consequently emitted on corresponding photoconductive bodies
for recording color, the photoconductive bodies being provided to
face the optical writing recording heads and moving in a sub-scan
direction perpendicular to the main scan direction to form
individual color images, and finally merging all color images on a
printing medium to form a color image, wherein the color printer
comprises a recording head selection/activation unit activating
individual color recording heads in sequence to enable optical
writing in each of periods equal to one n-th of one writing period
of the optical writing recording heads; a video data
dividing/supply unit dividing an activated period of individual
recording color recording heads into a first half period and a
second half period and applying only video data corresponding to
the first half in the main scan direction of one dot line data to
the print heads in the first half period and only video data
corresponding to the second half in the main scan direction of the
one dot line data to the recording heads in the second half period;
a staggered emission drive signal generation unit generating x
staggered emission drive signals for each of individual recording
color recording heads in each of the first half period and second
half period of individual recording color recording heads; and a
divided emission control unit selectively activating a specific
block of light emitting elements of the individual color recording
heads so as to allow the light emitting elements in the block to
selectively emit light based on video data applied to the recording
head during each of staggered emission drive periods, and the
individual color recording heads are provided in the manner that
the blocks are shifted in the sub-scan direction by the quantity to
cancel the emission time-lag between the light emitting elements in
different blocks activated with time-lag by the staggered emission
drive signals.
[0015] The present invention can provide a printer reducing the
maximum power consumption of the entire apparatus compared with the
prior art and complying with the international criteria ensuring
sustained earth environment.
BRIEF DESCRIPTION I/F THE DRAWINGS
[0016] A more complete understanding of this application can be
obtained when the following detailed description is considered in
conjunction with the following drawings, in which:
[0017] FIG. 1 is an Illustration for explaining the configuration
of the head control unit in detail;
[0018] FIG. 2 is a schematic illustration showing the entire
structure of a color printer of this embodiment;
[0019] FIG. 3 is an illustration for explaining the control system
of the color printer of this embodiment;
[0020] FIG. 4 is an Illustration for explaining the structure of a
recording head of Embodiment 1;
[0021] FIG. 5 is an Illustration for explaining the structure of a
recording head of Embodiment 2;
[0022] FIG. 6 is a time chart showing by means of strobe signals
emission timing of the four color recording heads during recording
of a dot line in Embodiment 1;
[0023] FIG. 7 is a time chart showing by means of strobe signals
emission timing of the four color recording heads during recording
of a dot line in Embodiment 2;
[0024] FIG. 8 is a time chart for explaining the operation in
Embodiment 1 and an Illustration showing head current consumption
data;
[0025] FIG. 9 is a time chart for explaining the operation in
Embodiment 2 and an Illustration showing head current consumption
data; and
[0026] FIG. 10 is a time chart for explaining a prior art
operation.
DETAILED DESCRIPTION
[0027] Embodiments of the present invention will be described
hereafter with reference to the drawings.
[0028] FIG. 2 is a schematic illustration showing the entire
structure of a color printer 1 of the present invention.
[0029] The color printer 1 of the present invention comprises an
imaging unit 1a forming four, yellow (Y), magenta (M), cyan (C),
and black (K), print color toner images on photoconductor drums, a
primary transfer unit 1b transferring the toner images formed on
the photoconductor drums to a transfer belt, a secondary transfer
unit 1c further transferring the toner images transferred to the
transfer belt to a paper P, and a heat fixing unit 1d heat-fixing
the toner image transferred to the paper P on the paper P.
[0030] More specifically, the imaging unit 1a comprises individual
color recording heads 20Y, 20M, 20C, and 20K, photoconductor drums
DY, DM, DC, and DK to be exposed to image light emitted by the
recording heads 20Y, 20M, 20C, and 20K based on print data, and
developers GY, GM, GC, and GK developing latent images formed on
the exposed individual photoconductor drums DY, DM, DC, and DK
using individual color toners.
[0031] The primary transfer unit 1b comprises transfer units TY,
TM, TC, and TK transferring the individual color toner images to a
transfer belt B to form a merged image from the individual color
toner images developed on the photoconductor drums DY, DM, DC, and
DK.
[0032] The secondary transfer unit 1c comprises a secondary
transfer roll TR. The transfer belt B on which all color toner
images are transferred and merged is conveyed to the secondary
transfer unit 1c, where the image is transferred to a paper P or a
printing medium by the secondary transfer roller TR. The toner
image secondary-transferred on the paper P is further heat-fixed by
a heat-fixing unit FU at the heat fixing unit 1d.
[0033] The recording heads 20Y, 20M, 20C, and 20K facing the
surfaces of the photoconductor drums 20DY, 20DM, 20DC, and 20DK
rotating in the sub-scan direction consist of an array of many
small LED (light emitting diode) elements lined up in the axial
direction of the photoconductor drums 20DY, 20DM, 20DC, and 20DK
(the main scan direction perpendicular to the sub-scan direction).
The LED elements are selectively driven based on print data. The
uniformly charged photoconductor drums 20DY, 20DM, 20DC, and 20DK
are exposed to the light emitted by the LED elements so as to
discharge the surfaces of the photoconductor drums 20DY, 20DM,
20DC, and 20DK. Then, electrostatic latent images corresponding to
the exposure light images are formed on the photoconductor drums
20DY, 20DM, 20DC, and 20DK and the electrostatic latent images are
developed by toner absorbed from the corresponding developers 20GY,
20GM, 20GC, and 20GK by electrostatic force to form visible
images.
[0034] The individual color toner images formed at the individual
color imaging units 1a are transferred to the transfer belt B by
the primary transfer unit 1b as described above and further
transferred to a paper P by the secondary transfer unit 1c. The
heat fixing unit 1d heat-fixes the color image to the paper P,
which is discharged on a not-shown catch tray.
[0035] FIG. 3 is an illustration for explaining the control system
of the color printer 1 having the above basic structure. In the
figure, the color printer 1 comprises an interface controller ("I/F
controller" hereafter) 2 and an engine control unit 3. The I/F
controller 2 comprises a reception control unit 4, an ROM 5, a font
ROM 6, a display control unit 7, a video I/F control unit 8, a
memory 9 (standard RAM 9a and extended RAM 9b), a
reduction/enlargement control unit 10, and an MPU 11.
[0036] The engine control unit 3 comprises a head control unit 13,
a motor control unit 14, an MPU 15, a fixing control unit 16, and a
high voltage control unit 17. The head control unit 13 sends video
data to the above-described recording head 20 (20Y, 20M, 20C, and
20K). The motor control unit 14 outputs drive signals to multiple
main motors 21. Various loads 22 are driven/controlled by the
engine control unit 3. Detection signals of a sensor 23 such as a
paper ejection sensor are supplied to the engine control unit
3.
[0037] The MPU 15 receives information on detected temperature of a
not-shown fixing roller from a fixing thermistor 24 provided in the
above-described heat fixing unit FU and outputs temperature control
signals to a fixing heater 25 provided to the fixing roller.
Furthermore, the high voltage control unit 17 outputs high voltage
control signals to the high voltage unit 26.
[0038] The color printer 1 having the above configuration is
supplied with print data from a host machine 28 such as a personal
computer (PC) and printer server via a Centronics interface and LAN
(local area network).
[0039] The print data supplied from the host machine 28 are
transferred to the reception control unit 4. After a specific
amount of print data are transferred to the reception control unit
4, the print data are transferred to the memory 9 (for example, the
standard RAM 9a). The print data transferred to the memory 9 are
analyzed under the control of the MPU 11, reduced/enlarged by the
reduction/enlargement control unit 10, and then output to the
engine control unit 3 from the video I/F control unit 8.
[0040] FIG. 1 is an illustration for explaining the configuration
of the head control unit 13 in detail. The head control unit 13
comprises a video I/F control unit 30, a head I/F control unit 31,
a basic timing creation unit 32, and a CPU I/F unit 33. The video
I/F control unit 30, head I/F control unit 31, basic timing
creation unit 32, and CPU I/F control unit 33 are each connected by
a CPU bus. The video I/F control unit 30 exchanges vertical
synchronizing signals (VSYNC), horizontal synchronizing signals
(HSYNC), video data (Video), and synchronizing signals (VCLK),
which will be described later, with the I/F controller 2.
Furthermore, the video I/F control unit 30 is also connected to the
video RAM 34 and exchanges video data with the video RAM 34.
[0041] The head I/F control unit 31 comprises a dot pattern
creation unit 35, a head data transmission unit 36, a head control
signal generation unit 37, a strobe signal generation unit 38, a
head correction data control unit 39, a RAM 40, and a line buffer
control unit 41. The dot pattern creation unit 35 creates four or
eight staggered light emission video data, which will be described
later, based on video data supplied from the video I/F control unit
30 and transfers dot pattern data to the recording head 20 (20Y,
20M, 20C, and 20K) via the head data transmission unit 36.
[0042] The head control signal generation unit 37 generates
horizontal synchronizing signals (HSYNC) and synchronizing signals
(DCLK) for transferring the dot pattern data to the recording head
20 and outputs them to the recording head 20. The strobe signal
generation unit 38 generates strobe signals and outputs the strobe
signals to the recording head 20. The CPU I/F unit 33 communicates
with the MPU 15.
[0043] The basic timing creation unit 32 divides video data to be
recorded according to predetermined information in the sub-scan
direction and creates basic timing according to the throughputs of
the individual color recording heads. Signals such as the
above-described horizontal synchronizing signals (HSYNC) and dot
clock (DCLK) are generated according to various timing signals.
Here, for example, the strobe signal generation unit 38 outputs
four strobe signals in one writing period TW of recording one dot
line image for performing four-step staggered light emission in the
sub-scan direction for recording one dot line image as in
Embodiment 1 described later. On the other hand, for example, the
strobe signal generation unit 38 outputs eight strobe signals in
one writing period TW of recording one dot line image for
performing eight-step staggered light emission in the sub-scan
direction for recording one dot line image as in Embodiment 2
described later.
[0044] The head correction data control unit 39 comprises a serial
interface control unit ("the serial I/F control unit" hereafter)
39a and receives light amount correction data from a head
information ROM 44 within the recording head 20. Here, the light
amount correction data stored in the head information ROM 44 are
correction data obtained by measuring variation in light amount of
the light emitting elements constituting the recording head 20 and
stored as light amount correction data.
[0045] Furthermore, the head correction data control unit 39 writes
light amount correction data read from the head information ROM 44
in a correction table 40b of the RAM 40 when the recording head 20
makes transition from the power saving mode to the print mode. The
RAM 40 also comprises a line buffer 40a. The light amount
correction data written in the correction table 40b are sent to the
recording head 20 via the line buffer 40a.
[0046] The line buffer control unit 41 comprises a power saving
mode setting unit 41a and is used for dividing video data as
described later. Furthermore, drive timing of yellow (Y), magenta
(M), cyan (C), and black (K) video data in the power saving mode
and the number by which video data are divided are set in the power
saving mode setting unit 41a.
[0047] The structure and drive control method of the recording head
20 will be described in detail hereafter.
[0048] The individual color recording heads 20Y, 20M. 20C, and 20K
each consist of, for example, eight LED chips lined up in the main
scan direction. One LED chip consists of an array of, for example,
960 LED elements (a set of light emitting elements) lined up also
in the main scan direction. A total of 7680 LED elements are lined
up overall. The recording head 20 used in this embodiment is
subject to emission control in which the LED chips are driven
individually (staggered emission control), which will be described
in detail later. The chips are shifted and tiered in the sub-scan
direction in accordance with staggered drive timing in order to
cancel the driving time-lag.
[0049] More specifically, as shown in FIGS. 4 and 5, the recording
head 20 is driven in eight separate blocks in the main scan
direction on the basis of a LED chip including a given number of
LED elements. As described above, the chips are subject to emission
drive control using four or eight staggered strobe signals
generated in one writing period TW. Only the LED elements of two
chips (1920 elements) or one chip (960 elements) emit light
simultaneously.
[0050] Here, FIG. 4 shows the structure of the recording head 20
according to Embodiment 1. For example, the K color recording head
20K is supplied with four staggered emission strobe signals (c1 to
c4) in one writing period TW of recording one dot line. The LED
chips in blocks "1" and "5" are simultaneously driven by the strobe
signals c-1. The LED chips in blocks "2" and "6" are simultaneously
driven by the strobe signals c-2. The LED chips in blocks "3" and
"7" are simultaneously driven by the strobe signals c-3. The LED
chips in blocks "4" and "8" are simultaneously driven by the strobe
signals c-4.
[0051] The strobe signals are generated with a small time-lag in
one writing period TW. However, the LED chips are provided in the
manner that the time-lag in staggered emission of the chips in the
sub-scan direction is cancelled as shown in the chip layout in the
upper part of FIG. 4. Therefore, the dot light images exposed on
the corresponding photoconductor drums DY, DM, DC, and DK are
formed on one line in the main scan direction.
[0052] In Embodiment 1 shown in FIG. 4, eight chips are driven at
four staggered times. One strobe signal is used to drive two chips.
Then, the blocks "1" and "5," blocks "2" and "4," blocks "3" and
"5," and blocks "4" and "8" are provided on the same line,
respectively, with respect to the sub-scan direction.
[0053] On the other hand, FIG. 5 shows the structure of the
recording head 20 according to Embodiment 2. Eight blocks ("1" to
"8") of LED chips are driven at eight staggered times in one
writing period TW of recording one dot line. One strobe signal
supplies a drive timing signal to one LED chip. Therefore, all
eight LED chips are shifted in the sub-scan direction. More than
one chip is not driven simultaneously. Then, the peak current
required for driving the recording head for emission can be reduced
to a half of that in Embodiment 1.
[0054] FIG. 6 is a time chart showing by means of strobe (Strb)
signals emission timing of four color recording heads (20Y, 20M,
20C, and 20K) in Embodiment 1 while recording one dot line. On the
other hand, FIG. 7 is a time chart showing by means of strobe
(Strb) signals emission timing of four color recording heads (20Y,
20M, 20C, and 20K) in Embodiment 2 while recording one dot
line.
[0055] As shown in these figures, the recording head of the present
invention repeats a procedure to form one dot line image in one
writing period TW three times in the sub-scan direction so as to
form one pixel line image.
[0056] In the above explanation, the K color recording head 20K is
described in detail. The other recording heads 20Y, 20M, and 20C
have the same configuration although they are supplied with
different data and driven at different timing for exposure.
Therefore, the other color recording heads are not explained
here.
[0057] Operation in this embodiment having the above configuration
will be described hereafter.
Embodiment 1
[0058] FIG. 8 is a time chart for explaining the operation in
Embodiment 1 and an illustration showing head current consumption
data.
[0059] First, print data created by an application in the host
machine 28 is sent to the reception control unit 4 from the host
machine 28 via an LAN or USB, and further transferred to the memory
9 (standard RAM 9a). The print data are analyzed on commands under
the control of the MPU 11 to create drawing data.
[0060] The drawing data are subject to page start processing at the
time a vertical synchronizing signal (VSYNC) is output (at a low
level) and printed at the times shown in FIG. 8. First, a load
signal is output from the head control signal generation unit 37 at
a time a shown in the figure. The load signal is output
simultaneously at the Y, M, C, and K stations. After the load
signal is output, yellow (Y), magenta (M), cyan (C), and black (K)
print data are supplied to the corresponding recording heads 20Y,
20M, 20C, and 20 K at a time b.
[0061] Then, individual color strobe signals are output at
different times in accordance with yellow (Y), magenta (M), cyan
(C), and black (K) drive timing set in the power saving mode
setting unit 41a of the line buffer control unit 41. More
specifically, at a time c shown in the figure, a strobe signal is
output from the strobe signal generation unit 38 to the black (K)
recording head 20K, the black (K) recording head 20K is driven,
black print in accordance with the black (K) print data is made on
a printing medium. During that time, the recording head 20K
undergoes a power consumption of 800 mA and the other, cyan,
magenta, and yellow, recording heads 20C, 20M, and 20Y undergo a
power consumption of 500 mA.
[0062] Furthermore, the strobe signal c given to the K color
recording head microscopically consists of four staggered strobe
signals as shown in FIG. 4. The strobe signals each selectively
drive two blocks of LED chips to emit light simultaneously among
the eight separate blocks in the main scan direction, whereby the
number of LED elements actively driven in one strobe period is
limited to one quarter of the entire heads. Therefore, the current
amount required for emission is reduced to one quarter.
[0063] Then, at a time d, a strobe signal is output from the strobe
signal generation unit 38 to the cyan (C) recording head 20C, the
cyan (C) recording head 20C is driven, print in accordance with the
cyan (C) print data is made on the printing medium. During that
time, the recording head 20C undergoes a power consumption of 800
mA and the other, black, magenta, and yellow, recording heads 20K,
20M, and 20Y undergo a power consumption of 500 mA.
[0064] Similarly to the above, the strobe signal d given to the C
color recording head 20C microscopically consists of four staggered
strobe signals. The strobe signals each selectively drive two
blocks of LED chips to emit light simultaneously among the eight
separate blocks in the main scan direction, whereby the number of
LED elements actively driven in one strobe period is limited to one
quarter of the entire heads. Therefore, the current amount required
for emission is reduced to one quarter.
[0065] Then, at a time e, a strobe signal is output from the strobe
signal generation unit 38 to the magenta (M) recording head 20M,
the magenta (M) recording head 20M is driven, print in accordance
with the magenta (M) print data is made on the printing medium.
During that time, the magenta recording head 20M undergoes a power
consumption of 800 mA and the other, black, cyan, and yellow,
recording heads 20K, 20C, and 20Y undergo a power consumption of
500 mA.
[0066] Similarly to the above, the strobe signal e given to the M
color recording head microscopically consists of four staggered
strobe signals. The strobe signals each selectively drive two
blocks of LED chips to emit light simultaneously among the eight
separate blocks in the main scan direction, whereby the number of
LED elements actively driven in one strobe period is limited to one
quarter of the entire heads. Therefore, the current amount required
for emission is reduced to one quarter.
[0067] Then, at a next time f, a strobe signal is output to the
yellow (Y) recording head 20Y, the yellow (Y) recording head 20Y is
driven, print in accordance with the yellow (Y) print data is made
on the printing medium. During that time, the yellow recording head
20Y undergoes a power consumption of 800 mA and the other, black,
cyan, and magenta, recording heads 20K, 20C, and 20M undergo a
power consumption of 500 mA.
[0068] Similarly to the above, the strobe signal f given to the Y
color recording head microscopically consists of four staggered
strobe signals. The strobe signals each selectively drive two
blocks of LED chips to emit light simultaneously among the eight
separate blocks in the main scan direction, whereby the number of
LED elements actively driven in one strobe period is limited to one
quarter of the entire heads. Therefore, the current amount required
for emission is reduced to one quarter.
[0069] In the above operation, the multiple color recording heads
do not perform exposure simultaneously and all LED elements are not
activated simultaneously. The current flowing through all four
imaging units is 2000 mA.fwdarw.2300 mA.fwdarw.2300 mA.fwdarw. . .
. 2000 mA. A large current (for example, the above-described
current of 3200 mA) does not flow as in a prior art system in which
the multiple color recording heads perform exposure simultaneously.
In this case, the power consumption during printing can be reduced
by 28% compared with the prior art. Consequently, the process in
this embodiment can provide a color printer reducing power
consumption required by the entire apparatus at the same time and
complying with international criteria ensuring sustained earth
environment.
Embodiment 2
[0070] FIG. 9 is a time chart for explaining the operation in
Embodiment 2 and an illustration showing head current consumption
data.
[0071] Also in the explanation of this embodiment, the control
system of the color printer 1 shown in FIG. 2 and the basic
configuration of the head control unit shown in FIG. 1 are the same
as those in Embodiment 1.
[0072] As described above, first, print data created by an
application in the host machine 28 is sent to the reception control
unit 4 from the host machine 28 via an LAN or USB, and further
transferred to the memory 9 (standard RAM 9a). The print data are
analyzed on commands under the control of the MPU 11 to create
drawing data.
[0073] The drawing data are subject to page start processing at the
time a vertical synchronizing signal (VSYNC) is output (at a low
level) and one dot line image is divided and printed in the first
half and in the second half of one writing period TW at the times
shown in FIG. 9. First, a load signal for first half data An is
output from the head control signal generation unit 37 at a time g1
shown in the figure.
[0074] Here, the first half data An consist of image data of only
the first half of one dot line image data. The second half of the
data consists of all invalid data that are not recorded. The first
half load signal g1 is output simultaneously at the Y, M, C, and K
stations. After the first half load signal g1 is output, yellow
(Y), magenta (M), cyan (C), and black (K) print data An are
supplied to the corresponding recording heads 20Y, 20M, 20C, and 20
K at a time h1.
[0075] Furthermore, a load signal for second half data Bn is output
from the head control signal generation unit 37 at a time g2. Here,
the second half data Bn consist of image data of only the second
half of one dot line image data. The first half of the data
consists of all invalid data that are not recorded. The second half
load signal g2 is output also simultaneously at the Y, M, C, and K
stations. After the second half load signal g2 is output, yellow
(Y), magenta (M), cyan (C), and black (K) print data Bn are
supplied to the corresponding recording heads 20Y, 20M, 20C, and
20K at a time h2.
[0076] In this embodiment, video data supplied to the recording
head 20 for recording one dot line image are divided into two,
first half and second half, regions in the main scan direction and
supplied in halves at different times. The data An supplied as the
first half are half the data for printing one dot line in
Embodiment 1. The data Bn supplied as the second half are also half
the data for printing one dot line in Embodiment 1.
[0077] After the load signal g1 is output, at a time i1 shown in
the figure, a first half strobe signal i1 for the first half data
An is output from the strobe signal generation unit 38 to the black
(K) recording head 20K, the black (K) recording head 20K is driven,
print in accordance with the black (K) first half data An is made
on a printing medium. Furthermore, at a time i2 shown in the
figure, a second half strobe signal for the second half data Bn is
output from the strobe signal generation unit 38 to the black (K)
recording head 20K, the black (K) recording head 20K is driven,
print in accordance with the black (K) second half data Bn is made
on the printing medium. Because valid data only for a half of one
dot line image data are included whichever strobe signal it is
driven by, the recording head 20K undergoes a power consumption of
650 mA and the other recording heads 20C, 20M, and 20Y undergo a
power consumption of 500 mA. In other words, only half the amount
of current in Embodiment 1 flows through the recording head 20K at
this time, reducing power consumption. Here, 500 mA is basic
current consumption. A current amount of 300 mA while driven can be
reduced by half. In other words, the current flowing through the
recording head 20K is reduced to 650 mA as described above.
[0078] Furthermore, the strobe signals i1 and i2 given to the K
color recording head at two separate times microscopically consist
of eight staggered strobe signals as shown in FIG. 5. The strobe
signals each selectively drive one block of LED chip to emit light
among the eight separate blocks in the main scan direction, whereby
the number of LED elements actively driven in one strobe period is
limited to one eighth of the entire heads. Therefore, the current
amount required for emission is reduced to one eighth.
[0079] Then, at a time j1, a first half strobe signal for the first
half data An is output from the head control signal generation unit
38 to the cyan (C) recording head 20C, the cyan (C) recording head
20C is driven, and print in accordance with the cyan (C) first half
data An is made on the printing medium. Then, at a time j2 shown in
the figure, a second half strobe signal for the second half data Bn
is output from the head control signal generation unit 38 to the
cyan (C) recording head 20C, the cyan (C) recording head 20C is
driven, and print in accordance with the cyan (C) second half data
Bn is made on the printing medium. Also here, the recording head
20C undergoes a power consumption of 650 mA and the other recording
heads 20K, 20M, and 20Y undergo a power consumption of 500 mA.
[0080] Similarly to the above, the strobe signals j1 and j2 given
to the C color recording head at two separate times microscopically
consist of eight staggered strobe signals. The strobe signals each
selectively drive one block of LED chip to emit light among the
eight separate blocks in the main scan direction, whereby the
number of LED elements actively driven in one strobe period is
limited to one eighth of the entire heads. Therefore, the current
amount required for emission is reduced to one eighth.
[0081] Then, at a time k1, a first half strobe signal for the first
half data An is output from the head control signal generation unit
38 to the magenta (M) recording head 20M, the magenta (M) recording
head 20M is driven, and print in accordance with the magenta (M)
first half data An is made on the printing medium.
[0082] Then, at a time k2 shown in the figure, a second half strobe
signal for the second half data Bn is output from the head control
signal generation unit 38 to the magenta (M) recording head 20M,
the magenta (M) recording head 20M is driven, and print in
accordance with the magenta (M) second half data Bn is made on the
printing medium. Also here, the recording head 20M undergoes a
power consumption of 650 mA and the other recording heads 20K, 20C,
and 20Y undergo a power consumption of 500 mA.
[0083] Similarly to the above, the strobe signals k1 and k2 given
to the M color recording head at two separate times microscopically
consist of eight staggered strobe signals. The strobe signals each
selectively drive one block of LED chip to emit light among the
eight separate blocks in the main scan direction, whereby the
number of LED elements actively driven in one strobe period is
limited to one eighth of the entire heads. Therefore, the current
amount required for emission is reduced to one eighth.
[0084] Then, at a next time m1, a first half strobe signal for the
first half data An is output to the yellow (Y) recording head 20Y,
the yellow (Y) recording head 20Y is driven, and print in
accordance with the yellow (Y) first half data An is made on the
printing medium. Then, at a time m2 shown in the figure, a second
half strobe signal for the second half data Bn is output from the
head control signal generation unit 38 to the yellow (Y) recording
head 20Y, the yellow (Y) recording head 20Y is driven, and print in
accordance with the yellow (Y) second half data Bn is made on the
printing medium. During that time, the recording head 20Y undergoes
a power consumption of 650 mA and the other recording heads 20K,
20C, and 20M undergo a power consumption of 500 mA.
[0085] Furthermore, the strobe signals m1 and m2 given to the Y
color recording head at two separate times microscopically consist
of eight staggered strobe signals. The strobe signals each
selectively drive one block of LED chip to emit light among the
eight separate blocks in the main scan direction, whereby the
number of LED elements actively driven in one strobe period is
limited to one eighth of the entire heads. Therefore, the current
amount required for emission is reduced to one eighth.
[0086] In the above operation, the current flowing through all four
imaging units is 2000 mA.fwdarw.2150 mA.fwdarw.2000 mA.fwdarw.2150
mA.fwdarw. . . . . A large current (for example, the
above-described 3200 mA) does not flow as in the prior art. In
other words, the power consumption can be reduced more in the above
operation than in Embodiment 1. In this case, the power consumption
during printing can further be reduced by 7% compared with in
Embodiment 1.
[0087] Video data are transferred two times faster in the operation
in Embodiment 2 shown in FIG. 9 than in Embodiment 1 shown in FIG.
8. Video data are transferred in halves as described above.
Therefore, one dot line image data are transferred at a time in the
time chart of Embodiment 1 without dividing them into An and Bn.
One dot line image data are divided into An and Bn and transferred
and the corresponding recording head 20 is driven according to the
strobe signals in the time chart of Embodiment 2.
[0088] The above operation is based on a half-split setting set in
the power saving mode setting unit 41a of the line buffer control
unit 41. Therefore, although four strobe signals are output in one
writing period TW as shown in the time chart of FIG. 8 for
recording one dot line image in Embodiment 1, eight strobe signals
are output in one writing period (TW) as shown in the time chart of
FIG. 9 and divided video data are transferred to the corresponding
recording head 20 in Embodiment 2.
[0089] For example, with respect to video data An, four strobe
signals are output in the first half n1 of one writing period TW
shown in FIG. 9 and divided video data are transferred to the
corresponding color recording head 20, whereby the recording head
20 is driven by half the power. On the other hand, with respect to
video data Bn, four strobe signals are output in the second half p1
of one writing period TW shown in FIG. 9 and divided video data are
transferred to the corresponding color recording head 20, whereby
the recording head 20 is driven by half the power.
[0090] In the same manner, with respect to the next video data An+1
and Bn+1, four strobe signals are output in the first half n2 of
one writing period TW shown in FIG. 9 and divided video data An+1
are transferred to the corresponding color recording head 20, four
strobe signals are output in the second half p2 of one writing
period TW and divided video data Bn+1 are transferred to the
corresponding color recording head 20, whereby the recording head
20 is driven each time by half the power.
[0091] The above operation is repeated with respect to divided data
An+2 and Bn+2, divided data An+3 and Bn+3, . . . ; four strobe
signals are output in the first half n2 of one writing period TW,
in the second half p2 of one writing period TW, in the first half
n3 of one writing period TW, in the second half p3 of one writing
period TW, . . . , and divided video data are transferred to the
corresponding color recording head 20 in sequence, whereby the
recording head 20 is driven each time by half the power.
[0092] Here, video data are transferred two times faster in
Embodiment 2 than in Embodiment 1. Strobe signals are output in
correspondence with a print density of 7200 DPI in Embodiment 1.
They are output in correspondence with a doubled print density of
14400 DPI in Embodiment 2.
[0093] Furthermore, the power saving mode setting unit 41a is set
for half-split in Embodiment 2. The power saving mode setting unit
41a is not restricted to half-split and can be set for three-way or
four-way split for further power saving.
[0094] In the above embodiments, the LED recording heads are driven
in separate blocks on the basis of a LED chip. It is unnecessary
that a block consists of a LED chip. A block can consist of any
number LED elements that are selectively driven.
[0095] Several embodiments of the present invention are described.
The present invention includes the invention described in the scope
of claims and in the scope equivalent thereto. The invention
described in the scope of claims of the original application of
this patent application will be described in the following
subjunction.
[0096] Subjunction 1
[0097] A color printer creating video data corresponding to n
colors based on print information entered from a host machine,
supplying individual color video data to corresponding recording
color optical writing recording heads comprising an array of many
light emitting elements arranged in a main scan direction, forming
individual color images by exposing the individual color image
lights consequently emitted on corresponding photoconductive bodies
for recording color, the photoconductive bodies being provided to
face the optical writing recording heads and moving in a sub-scan
direction perpendicular to the main scan direction to form
individual color images, and finally merging all color images on a
printing medium to form a color image, wherein the color printer
comprises:
[0098] a recording head selection/activation unit activating
individual color recording heads in sequence to enable optical
writing in each of periods equal to one n-th of one writing period
of the optical writing recording heads;
[0099] a video data supply unit applying video data corresponding
to one dot line image to be recorded to the recording heads during
an activated period of individual recording color recording
heads;
[0100] a staggered emission drive signal generation unit generating
x staggered emission drive signals for each of individual recording
color recording heads during the activated period of individual
recording color recording heads; and
[0101] a divided emission control unit selectively activating a
block comprising a given number of light emitting elements of the
individual color recording heads so as to allow the light emitting
elements in the block to selectively emit light based on video data
applied to the recording head during each of staggered emission
drive periods, and
[0102] the individual recording color recording heads are provided
in the manner that the blocks are shifted in the sub-scan direction
by the quantity to cancel the emission time-lag between the light
emitting elements in different blocks activated with time-lag by
the staggered emission drive signals.
[0103] Subjunction 2
[0104] The color printer according to Subjunction 1, wherein a
plurality of the given blocks that are selectively activated by the
divided emission control unit in the staggered emission drive
period are provided.
[0105] Subjunction 3
[0106] The color printer according to Subjunction 1, wherein the
light emitting elements are light emitting diodes.
[0107] Subjunction 4
[0108] The color printer according to Subjunction 1, wherein the
color printer is of a tandem type in which imaging units including
a yellow recording optical writing head, a magenta recording
optical writing head, a cyan recording optical writing head, and a
black recording optical writing head, respectively, are arranged in
the moving direction of a printing medium.
[0109] Subjunction 5
[0110] A color printer creating video data corresponding to n
colors based on print information entered from a host machine,
supplying individual color video data to corresponding recording
color optical writing recording heads comprising an array of many
light emitting elements arranged in a main scan direction, forming
individual color images by exposing the individual color image
lights consequently emitted on corresponding photoconductive bodies
for recording color, the photoconductive bodies being provided to
face the optical writing recording heads and moving in a sub-scan
direction perpendicular to the main scan direction to form
individual color images, and finally merging all color images on a
printing medium to form a color image, wherein the color printer
comprises:
[0111] a recording head selection/activation unit activating
individual color recording heads in sequence to enable optical
writing in each of periods equal to one n-th of one writing period
of the optical writing recording heads;
[0112] a video data dividing/supply unit dividing an activated
period of individual recording color recording heads into a first
half period and a second half period and applying only video data
corresponding to the first half in the main scan direction of one
dot line data to the print heads in the first half period and only
video data corresponding to the second half in the main scan
direction of the one dot line data to the recording heads in the
second half period;
[0113] a staggered emission drive signal generation unit generating
x staggered emission drive signals for each of individual recording
color recording heads in each of the first half period and second
half period of individual recording color recording heads; and
[0114] a divided emission control unit selectively activating a
specific block of light emitting elements of the individual color
recording heads so as to allow the light emitting elements in the
block to selectively emit light based on video data applied to the
recording head during each of staggered emission drive periods,
and
[0115] the individual color recording heads are provided in the
manner that the blocks are shifted in the sub-scan direction by the
quantity to cancel the emission time-lag between the light emitting
elements in different blocks activated with time-lag by the
staggered emission drive signals.
[0116] Subjunction 6
[0117] The color printer according to Subjunction 5, wherein a
plurality of the given blocks that are selectively activated by the
divided emission control unit in the staggered emission drive
period are provided.
[0118] Subjunction 7
[0119] The color printer according to Subjunction 5, wherein the
light emitting elements are light emitting diodes.
[0120] Subjunction 8
[0121] The color printer according to Subjunction 5, wherein the
color printer is of a tandem type in which imaging units including
a yellow recording optical writing head, a magenta recording
optical writing head, a cyan recording optical writing head, and a
black recording optical writing head, respectively, are arranged in
the moving direction of a printing medium.
[0122] Having described and illustrated the principles of this
application by reference to one (or more) preferred embodiment(s),
it should be apparent that the preferred embodiments may be
modified in arrangement and detail without departing from the
principles disclosed herein and that it is intended that the
application be construed as including all such modifications and
variations insofar as they come within the spirit and scope of the
subject matter disclosed herein.
* * * * *