U.S. patent application number 11/690411 was filed with the patent office on 2007-10-04 for printing device that controls discharge roller based on thickness of recording medium.
This patent application is currently assigned to BROTHER KOGYO KABUSHIKI KAISHA. Invention is credited to Shunsuke MIZUTANI, Yoichi SHIKAI.
Application Number | 20070228649 11/690411 |
Document ID | / |
Family ID | 38557656 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070228649 |
Kind Code |
A1 |
MIZUTANI; Shunsuke ; et
al. |
October 4, 2007 |
Printing Device that Controls Discharge Roller Based on Thickness
of Recording Medium
Abstract
A printing device includes a printing unit, a discharge roller,
and a roller controller. The printing unit performs printing on a
recording medium at a printing position. The discharge roller is
configured to rotatably contact the recording medium on which the
printing unit has performed printing, thereby discharging the
recording medium. The roller controller controls the discharge
roller to rotate such that the discharge roller discharges a
recording medium having thickness greater than or equal to a
predetermined threshold value at a first speed and that the
discharge roller discharges a recording medium having thickness
less than the predetermined threshold value at a second speed
higher than the first speed.
Inventors: |
MIZUTANI; Shunsuke;
(Nagoya-shi, JP) ; SHIKAI; Yoichi; (Nagoya-shi,
JP) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.;ATTORNEYS FOR CLIENT NOS. 0166889, 006760
1100 13th STREET, N.W., SUITE 1200
WASHINGTON
DC
20005-4051
US
|
Assignee: |
BROTHER KOGYO KABUSHIKI
KAISHA
Nagoya-shi
JP
|
Family ID: |
38557656 |
Appl. No.: |
11/690411 |
Filed: |
March 23, 2007 |
Current U.S.
Class: |
271/314 |
Current CPC
Class: |
B65H 29/14 20130101;
B65H 2511/13 20130101; B65H 2513/108 20130101; B65H 2801/12
20130101; B65H 2511/13 20130101; B65H 2513/108 20130101; B65H
2220/02 20130101; B65H 2404/14 20130101; B65H 2220/01 20130101 |
Class at
Publication: |
271/314 |
International
Class: |
B65H 29/20 20060101
B65H029/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2006 |
JP |
2006-096625 |
Claims
1. A printing device comprising: a printing unit that performs
printing on a recording medium at a printing position; a discharge
roller that is configured to rotatably contact the recording medium
on which the printing unit has performed printing, thereby
discharging the recording medium; and a roller controller that
controls the discharge roller to rotate such that the discharge
roller discharges a recording medium having thickness greater than
or equal to a predetermined threshold value at a first speed and
that the discharge roller discharges a recording medium having
thickness less than the predetermined threshold value at a second
speed higher than the first speed.
2. The printing device according to claim 1, further comprising: a
feeding cassette that is configured to accommodate at least one
sheet of the recording medium; a feeding roller that feeds the
recording medium from the feeding cassette; a conveying roller that
is configured to contact the recording medium fed by the feeding
roller and to rotate in a conveying direction for conveying the
recording medium to the printing position; and a motor that rotates
the discharge roller and the conveying roller in synchronicity with
each other, such that the conveying roller rotates in the conveying
direction when the discharge roller rotates in a direction for
discharging the recording medium, wherein the roller controller
controls the motor to rotate the conveying roller and the feeding
roller such that the conveying roller rotates in a direction
opposite the conveying direction while the feeding roller rotates
in a direction for feeding the recording medium.
3. The printing device according to claim 2, wherein the motor is
configured to rotate all of the discharge roller, the conveying
roller, and the feeding roller.
4. The printing device according to claim 1, wherein the roller
controller controls the discharge roller to rotate such that the
discharge roller conveys the recording medium up to a predetermined
position at a third speed higher than the second speed and that,
from the predetermined position, the discharge roller discharges
the recording medium at either the first speed or the second speed
depending on the thickness of the recording medium.
5. The printing device according to claim 4, further comprising: a
thickness determining section that determines whether the thickness
of the recording medium is greater than or equal to the
predetermined threshold value; and a size comparing section that
compares a size of the recording medium with a reference size that
is either one of an A4 size and a letter size, wherein the roller
controller controls the discharge roller to rotate such that the
discharge roller conveys the recording medium up to the
predetermined position at the third speed and that, from the
predetermined position, the discharge roller discharges the
recording medium at a discharge speed higher than or equal to 12
inches per second and lower than or equal to 14 inches per second,
when the thickness determining section that determines that the
thickness of the recording medium is less than the predetermined
threshold value and the size comparing section determines that the
size of the recording medium is the reference size.
6. The printing device according to claim 5, wherein the roller
controller controls the discharge roller to rotate such that the
discharge roller conveys the recording medium up to the
predetermined position at the third speed and that, from the
predetermined position, the discharge roller discharges the
recording medium at a discharge speed higher than or equal to 4
inches per second and lower than or equal to 6 inches per second,
when the thickness determining section that determines that the
thickness of the recording medium is greater than or equal to the
predetermined threshold value or when the size comparing section
determines that the size of the recording medium is smaller than
the reference size.
7. The printing device according to claim 4, wherein the
predetermined position is a position at which a trailing edge of
the recording medium is 15 millimeters upstream from the discharge
roller in a direction in which the recording medium is discharged.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from Japanese Patent
Application No. 2006-096625 filed Mar. 31, 2006. The entire
contents of the priority application are incorporated herein by
reference.
TECHNICAL FIELD
[0002] The invention relates to a printing device, and more
particularly to a printing device having a discharge roller for
discharging a printed recording medium.
BACKGROUND
[0003] Printing devices for performing printing on recording paper
(recording medium) have been widely used. In such printing devices,
the recorded paper is discharged by a discharge roller and stacked
on, for example, a discharge tray. When the speed of discharging
the recording paper (discharge speed) is increased, the recording
paper bursts onto the discharge tray at a high speed. Hence, there
is a possibility that the recording paper is not neatly stacked on
the discharge tray. Japanese Publication of Patent Application No.
2000-198600 discloses improving stack performance of the recording
paper by decreasing the discharge speed.
SUMMARY
[0004] However, if the discharge speed is simply decreased, the
following problem will occur. That is, when the thickness of the
recording paper is small or the size of the recording paper is
large, the trailing edge of the recording paper is not separated
from the discharge roller and thus the recording paper may not be
discharged.
[0005] More specifically, when a recording paper is thin and
flexible (small flexural rigidity), the leading edge of the
recording paper passing through the discharge roller hangs down and
contacts the recording paper stacked on a discharge tray. As a
result, friction occurs between the recording paper in the
discharge tray and the newly discharged recording paper. Since the
recording paper needs to be discharged against the frictional
force, the thin and flexible recording paper requires a larger
amount of energy for discharging, in comparison with a thick or
less flexible recording paper which generates less friction.
[0006] Further, when the recording paper is fed from a paper
cassette (not shown) to a conveying roller, the fed recording paper
and the recording paper in the paper cassette rub against each
other, so that the recording paper takes on static electricity. As
the size of the recording paper is larger, the recording paper
becomes charged with static electricity more easily. A larger
amount of energy is required to discharge the recording paper
against the static electricity. Due to such frictional force and
static electricity, the large recording paper or the thin recording
paper is hard to be discharged. When the recording paper is not
discharged onto the discharge tray, the user has to remove a cover
of the printing device and pull out the printed recording paper by
himself or herself, which is bothersome.
[0007] To reliably discharge the recording paper against the
above-mentioned frictional force and static electricity, the
discharge speed should be increased. However, if the discharge
speed of the recording paper is uniformly increased, the stack
performance of the recording paper deteriorates. Especially when
the thickness of the recording paper is large or the size of the
recording paper is small, the above-mentioned frictional force and
static electricity have less effect on the recording paper. Thus,
the recording paper is discharged onto the discharge tray with
great force, leading to poor stack performance.
[0008] In view of the foregoing, it is an object of the invention
to provide a printing device capable of reliably discharging a
recording medium while improving stack performance of the recording
medium.
[0009] In order to attain the above and other objects, the
invention provides a printing device. The printing device includes
a printing unit, a discharge roller, and a roller controller. The
printing unit performs printing on a recording medium at a printing
position. The discharge roller is configured to rotatably contact
the recording medium on which the printing unit has performed
printing, thereby discharging the recording medium. The roller
controller controls the discharge roller to rotate such that the
discharge roller discharges a recording medium having thickness
greater than or equal to a predetermined threshold value at a first
speed and that the discharge roller discharges a recording medium
having thickness less than the predetermined threshold value at a
second speed higher than the first speed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Illustrative aspects in accordance with the invention will
be described in detail with reference to the following figures
wherein:
[0011] FIG. 1 is a perspective view of a printing device according
to an embodiment of the invention;
[0012] FIG. 2 is a schematic side view showing an internal
configuration of the printing device;
[0013] FIG. 3 is a block diagram showing an electric configuration
of the printing device;
[0014] FIG. 4 is a flow chart showing a printing process according
to the embodiment;
[0015] FIG. 5 is an explanatory diagram showing a testing method
for measuring paper discharge positions;
[0016] FIG. 6A is a table showing averages and standard deviations
which were calculated in a first test;
[0017] FIG. 6B is a graph in which a thin line connects each point
of calculated standard deviations and a thick curve is a polynomial
approximation showing relationship between discharge speeds and the
standard deviations, where the standard deviations are shown in a
vertical axis and the discharge speeds are shown in a horizontal
axis;
[0018] FIG. 6C is a graph in which a thin line connects each point
of calculated averages and a thick curve is a polynomial
approximation showing relationship between discharge speeds and the
averages, where the averages are shown in a vertical axis and the
discharge speeds are shown in a horizontal axis;
[0019] FIG. 7A is a table showing averages and standard deviations
which were calculated in a second test;
[0020] FIG. 7B is a graph in which a thin line connects each point
of calculated standard deviations and a thick curve is a polynomial
approximation showing relationship between discharge speeds and the
standard deviations, where the standard deviations are shown in a
vertical axis and the discharge speeds are shown in a horizontal
axis;
[0021] FIG. 7C is a graph in which a thin line connects each point
of calculated averages and a thick curve is a polynomial
approximation showing relationship between discharge speeds and the
averages, where the averages are shown in a vertical axis and the
discharge speeds are shown in a horizontal axis; and
[0022] FIG. 8 is an explanatory diagram showing a paper discharge
mechanism according to a comparative example.
DETAILED DESCRIPTION
[0023] A printing device according to an embodiment of the
invention will be described while referring to FIGS. 1 through
7C.
[0024] FIG. 1 is a perspective view showing a printing device 1
according to the embodiment. The printing device 1 (multifunction
device) shown in FIG. 1 has a facsimile function, printer function,
copier function, scanner function, and the like. The printing
device 1 is configured of a main case 2 that is substantially
box-shaped and open on the top, and an upper case 3 disposed on top
of the main case 2 and capable of swinging open and closed about
the swing axis of hinges or the like (not shown) provided on one
side of the main case 2. In the following description, the
left-to-right direction (main scanning direction and Y direction),
front-to-rear direction (subscanning direction and X direction),
and vertical direction will be based on the orientation of the
printing device 1 shown in FIG. 1. The main case 2 and upper case 3
are formed of a synthetic resin according to an injection molding
process.
[0025] A control panel 30 is provided on the top surface of the
upper case 3 and the front end thereof. The control panel 30
includes various buttons, including numerical buttons, a Start
button, and functional buttons. The user manipulates these buttons
to perform various operations. The control panel 30 also includes a
liquid crystal display (LCD) 31 for displaying the settings and
status of the printing device 1 and various operational messages as
needed.
[0026] A scanner 33 is disposed in the upper case 3 to the rear of
the control panel 30. The scanner 33 has a flatbed scanning unit
with a large glass plate on which an original to be scanned is
placed, and a cover 34 capable of rotating over the flatbed
scanning unit to cover or expose the top surface thereof. The
scanner 33 functions to read images from a facsimile original to be
transferred to another facsimile device with the facsimile function
or an original to be copied with the copy function.
[0027] While not shown in the drawings, a line-type contact image
sensor is disposed beneath the glass plate of the flatbed scanning
unit. The contact image sensor is one example of a photoelectric
conversion device for scanning the image surface of an original
placed on the glass plate. The cover 34 is capable of swinging open
and closed about hinges provided on the rear side of the printing
device 1 (far side in FIG. 1).
[0028] As shown in FIG. 1, a paper cassette 5 is provided in the
left-to-right center of the main case 2. The paper cassette 5 can
accommodate a plurality of sheets of a recording paper P in a
stacked and substantially level state on the bottom surface
thereof. The paper cassette 5 can be pulled out through an opening
2a formed in the front surface of the main case 2. A discharge tray
10 is provided above the paper cassette 5. The printed recording
paper P is discharged onto the discharge tray 10 in a direction
indicated by an arrow B, with its printed surface oriented upward.
The opening 2a is also in communication with the discharge tray
10.
[0029] FIG. 2 is a side view conceptually illustrating the internal
structure of the printing device 1. In FIGS. 1 and 2, an arrow B
indicates the conveying (feeding) direction of the recording paper
P. As shown in FIG. 2, a feeding unit 6 is accommodated in the main
case 2. The feeding unit 6 includes a feeding roller 7 disposed
above the paper cassette 5. The feeding unit 6 is configured to
feed sheets of the recording paper P along a conveying path formed
in a U-shape in the rear end of the main case 2 so that the sheet
is conveyed upward, inverted, and conveyed back in the forward
direction (left in FIG. 2).
[0030] Positioned downstream of the U-shaped section of the
conveying path with respect to the conveying direction of the
recording paper P (B direction) are provided a conveying roller 20a
for conveying the recording paper P, and a pinch roller 20b for
pressing the recording paper against the conveying roller 20a.
Working together, the conveying roller 20a and pinch roller 20b
pinch convey the sheets of recording paper P. A flat platen 11 is
disposed downstream of the conveying roller 20a and pinch roller
20b for supporting the sheets of recording paper P conveyed by the
conveying roller 20a and pinch roller 20b.
[0031] Further downstream of the platen 11 in the conveying
direction of the recording paper P are provided a discharge roller
21a for receiving sheets of recording paper P conveyed from the
conveying roller 20a and for discharging the sheets from the main
case 2, and a pinch roller 21b for pressing the recording paper P
against the discharge roller 21a. The discharge tray 10 is provided
downstream of the discharge roller 21a and pinch roller 21b for
discharging the printed recording paper P. Further, a recording
head 12 is positioned above the platen 11 between the conveying
roller 20a and discharge roller 21a and above the conveying path
along which the recording paper P is conveyed.
[0032] The recording head 12 is mounted in a carriage 13 that can
reciprocate in the main scanning direction (direction orthogonal to
the plane of the drawing in FIG. 2). Nozzles (not shown) are formed
in the recording head 12 on the recording paper P side for ejecting
ink toward the recording paper P pinched by the conveying roller
20a and the like. The position on the platen 11 that confronts the
nozzles of the recording head 12 serves as a printing position
14.
[0033] Ink tanks for supplying ink to the recording head 12 are
detachably mounted in an accommodating section (not shown) of the
main case 2 from an upper side. In the present embodiment, the
recording head 12 is configured to perform color printing, and the
accommodating section accommodates ink tanks in the four colors
black, cyan, magenta, and yellow. However, the accommodating
section may be configured to accommodate ink tanks for a greater or
smaller number of colors. Flexible ink tubes connect the ink tanks
to the recording head 12 for supplying ink thereto.
[0034] In the present embodiment, a linefeed motor 42 configured of
a DC motor produces a rotational force for rotating the conveying
roller 20a. The rotational force of the linefeed motor 42 is also
transmitted to the discharge roller 21a and the feeding roller 7
via a drive gear 101 that rotates together with the conveying
roller 20a. The mechanism for transmitting the drive force from the
conveying roller 20a to the discharge roller 21a is well known, and
is not shown in the drawings and will not be described herein. The
conveying roller 20a and the discharge roller 21a are driven to
rotate in synchronicity with each other.
[0035] As shown in FIG. 2, the driving force of the conveying
roller 20a is transmitted via the drive gear 101 to a gear train 43
configured of a plurality of mating gears 43a, 43b, 43c, and 43d.
The drive force is in turn transmitted via the gear train 43 to a
drive shaft 14 of the feeding unit 6. Next, the driving force of
the drive shaft 14 is transmitted to the feeding roller 7 via a
gear train 50 configured of a plurality of mating gears.
[0036] In the present embodiment, rotation of the linefeed motor 42
in a direction driving the conveying roller 20a and the discharge
roller 21a to convey the recording paper P in the conveying
direction B is called a forward rotation, and rotation of the
linefeed motor 42 in a direction driving the conveying roller 20a
and the discharge roller 21a to convey the recording paper P in the
direction opposite the conveying direction B (the direction for
returning the recording paper P toward the paper cassette 5) is
called a reverse rotation. In FIG. 2 arrows formed of solid lines
(arrows F) indicate the rotational direction of each roller and
gear during a forward rotation of the linefeed motor 42, while
arrows formed of dotted lines (arrows R) indicate the rotational
direction during a reverse rotation of the linefeed motor 42.
[0037] When the linefeed motor 42 rotates in reverse, the conveying
roller 20a rotates counterclockwise in FIG. 2. Accordingly, the
feeding roller 7 is driven to rotate in the feeding direction
(counterclockwise in FIG. 2) through the gear train 50 of the
feeding unit 6. In this way, the feeding roller 7 begins to feed
the topmost sheet of the recording paper P stacked in the paper
cassette 5. At this time, the conveying roller 20a rotates in the
direction opposite from the direction for conveying the recording
paper P in the conveying direction B. Thus, even when the recording
paper P is slanted, the leading edge of the recording paper P is
temporarily stopped at the conveying roller 20a to correct the
slant.
[0038] After the sheet of recording paper P fed from the paper
cassette 5 reaches the conveying roller 20a, the linefeed motor 42
rotates forward a prescribed amount. This is a cueing operation in
which the recording paper P becomes pinched between the conveying
roller 20a and pinch roller 20b and is conveyed below the recording
head 12. The cueing operation is an operation for setting the
recording paper P in a position where printing can begin by
advancing the leading edge of the recording paper P to a prescribed
position over the platen 11. During the cueing operation, the
feeding roller 7 rotates in the direction opposite the feeding
direction (clockwise in FIG. 2). However, since the nip force
between the conveying roller 20a and pinch roller 20b is set
greater than the conveying force of the feeding roller 7, the
feeding roller 7 does not return the recording paper P to the paper
cassette 5, but rather the conveying roller 20a and pinch roller
20b gripping the leading edge of the recording paper P convey the
recording paper P forward as the recording paper P slips over the
outer surface of the feeding roller 7.
[0039] Next, the conveying roller 20a begins advancing the
recording paper P intermittently, while the recording head 12
mounted on the carriage 13 begins printing by ejecting ink through
the nozzles onto one surface of the recording paper P as the
carriage 13 reciprocates in the main scanning direction. As shown
in FIG. 2, both the conveying roller 20a and the discharge roller
21a rotate in the conveying direction of the recording paper P when
advancing the recording paper P intermittently.
[0040] After printing is complete for one sheet of the recording
paper P, the printing device 1 begins to discharge the printed
sheet of recording paper P. At this time, the linefeed motor 42
rotates forward a prescribed amount sufficiently for continuously
rotating the conveying roller 20a and discharge roller 21a in the
discharging direction, after which the linefeed motor 42 is
halted.
[0041] A rotary encoder 44 is also provided on one end of the
conveying roller 20a. The rotary encoder 44 is configured of a slit
plate 44a having slits (not shown) formed at prescribed intervals
along the circumferential direction of the plate, and an optical
sensor 44b. The optical sensor 44b converts light passing through
the slits in the slit plate 44a to an electric signal and outputs
the signal. Hence, the slits in the slit plate 44a can be detected
based on the electric signal outputted from the optical sensor
44b.
[0042] The slit plate 44a rotates coaxially with the conveying
roller 20a. As described above, the linefeed motor 42 rotates the
conveying roller 20a. Hence, by counting the number of slits
detected by the rotary encoder 44, it is possible to calculate not
only the rotational amount of the conveying roller 20a, but also
the rotational amounts of the linefeed motor 42.
[0043] A paper sensor 117 is also disposed upstream of the
conveying roller 20a in the conveying direction B. The paper sensor
117 detects the leading and trailing edges of the recording paper P
when the recording paper P passes through the U-shaped section of
the conveying path and approaches the printing position 14. The
position of the recording paper P along the conveying path can be
determined based on detections by the paper sensor 117.
[0044] FIG. 3 is a block diagram showing the primary electrical
structure of the printing device 1 described above. As shown in
FIG. 3, the printing device 1 includes a CPU 300, a ROM 301, a RAM
302, and a EEPROM 303 that are all connected to an ASIC
(application specific integrated circuit) 306 via a bus 305. The
printing device 1 also includes the paper sensor 117, the rotary
encoder 44, a linear encoder 37, the recording head 12, a drive
circuit 314 for driving the recording head 12, a carriage motor 24,
a drive circuit 312 for driving the carriage motor 24, the linefeed
motor 42, a drive circuit 311 for driving the linefeed motor 42, a
keyboard 30a, the LCD 31, a panel interface 313 connected to the
keyboard 30a and the LCD 31, a parallel interface 315, a USB
interface 316, and a NCU (network control unit) 317.
[0045] The CPU 300 is a central processing unit that controls
overall operations of the printing device 1. The CPU 300 executes
various programs, including a program for implementing the
processes shown in FIG. 4. The ROM 301 is a non-rewritable memory
storing various control programs, including a program for
implementing the operations in FIG. 4, and data required by the CPU
300 when executing the control programs.
[0046] The RAM 302 temporarily stores programs and data required
for various processes executed by the CPU 300. The RAM 302 includes
a paper size memory 302a and a paper thickness memory 302b. The
paper size memory 302a is a memory for storing the size of the
recording paper P used in a printing process described later (FIG.
4). The paper thickness memory 302b is a memory for storing the
thickness of the recording paper P used in the printing
process.
[0047] The ASIC 306 is also connected to the NCU 317 having a modem
318. A communication signal received by the NCU 317 from a public
network is first demodulated by the modem 318 and then inputted
into the ASIC 306. Further, when the ASIC 306 transmits image data
externally for a facsimile transmission or the like, the modem 318
modulates the image data to produce a communication signal and
outputs this signal to the public network via the NCU 317.
[0048] In addition, the ASIC 306 generates a phase excitation
signal or the like for energizing the linefeed motor 42, for
example, based on commands from the CPU 300 and applies this signal
to the drive circuit 311 of the linefeed motor 42 and the drive
circuit 312 of the carriage motor 24, thereby supplying a drive
signal to the linefeed motor 42 and carriage motor 24 via the drive
circuit 311 and drive circuit 312 for controlling the forward and
reverse rotations of the linefeed motor 42 and carriage motor 24,
halting the motors, and the like. The ASIC 306 is also connected to
the drive circuit 314 that drives the recording head 12 to
selectively eject ink onto the recording paper P at a prescribed
timing. The ASIC 306 generates and outputs a signal based on a
drive control procedure received from the CPU 300, and the drive
circuit 314 controls the recording head 12 based on the signal
outputted from the ASIC 306.
[0049] The ASIC 306 is also connected to the panel interface 313
for facilitating transmission and reception operations with the
keyboard 30a and the LCD 31 of the control panel 30, and the
parallel interface 315 and USB interface 316 for exchanging data
with a personal computer or other external device via a parallel
cable or USB cable, respectively.
[0050] Further, the ASIC 306 is connected to the paper sensor 117
positioned upstream of the conveying roller 20a in the conveying
direction for detecting the leading and trailing edges of the
recording paper P as the recording paper P is fed toward the
printing position 14 (FIG. 2), the rotary encoder 44 for detecting
rotational amounts of the conveying roller 20a and the feeding
roller 7, and the linear encoder 37 for detecting the amount that
the carriage 13 moves in the main scanning direction and the
current position of the carriage 13.
[0051] Next, processes executed on the printing device 1 of the
present embodiment will be described with reference to the
flowchart in FIG. 4. FIG. 4 is a flowchart illustrating steps in a
printing process initiated when a print command is issued from an
external device or the like (not shown).
[0052] In S2 the CPU 300 acquires the paper size selected by the
user and stores the paper size in the paper size memory 302a. In S4
the CPU 300 acquires the paper thickness selected by the user and
stores the paper thickness in the paper thickness memory 302b. For
example, the user selects the paper size and the paper thickness on
a printing setting screen of a personal computer. When the user
gives a printing instruction from the personal computer, the paper
size and the paper thickness are included in printing data. Thus,
the CPU 300 stores the paper size and the paper thickness in the
paper size memory 302a and the paper thickness memory 302b,
respectively.
[0053] In S6 the CPU 300 controls the linefeed motor 42 to rotate
reverse to rotate the sheet feeding roller 7 to separate only an
uppermost recording paper P from a plurality of sheets of the
recording paper P stacked in the paper cassette 5 and to feed the
uppermost recording paper P until the leading edge of the recording
paper P reaches the conveying roller 20a.
[0054] In S8 the CPU 300 controls the linefeed motor 42 to rotate
forward by a predetermined amount to rotate the conveying roller
20a to convey the recording paper P nipped at a nip part between
the pinch roller 20b and the conveying roller 20a to the printing
position 14.
[0055] In S10 the CPU 300 controls the carriage motor 24 and the
recording head 12 to perform printing for one line on the recording
paper P while the carriage 13 is reciprocated. In S12 the CPU 300
controls the linefeed motor 42 to rotate forward by a predetermined
amount to rotate the conveying roller 20a for conveying the
recording paper P by one linefeed in the conveying direction B. In
S14 the CPU 300 determines whether printing for one page is
completed. When printing for one page is not completed (S14: No),
the CPU 300 drives the recording head 12 and the carriage 13 again
to repeat printing for one linefeed and conveying for one linefeed
(S10, S12).
[0056] When printing for one page is completed in this manner (S14:
Yes), in S16 the CPU 300 controls the linefeed motor 42 to rotate
forward by a predetermined amount to rotate the conveying roller
20a and the discharge roller 21a, thereby conveying the recording
paper P at a discharge speed of 20 inches/second (ips) in the
conveying direction B until the trailing edge of the printed
recording paper P reaches a position which is 15 mm (millimeters)
upstream from the discharge roller 21a (more specifically, a
position which is 15 mm upstream from a nip position between the
discharge roller 21a and the pinch roller 21b in the conveying
direction B).
[0057] In S18, referring to the paper thickness memory 302b, the
CPU 300 determines whether the thickness of the recording paper P
is greater than or equal to a predetermined threshold (0.21 mm in
the present embodiment). When the thickness of the recording paper
P is greater than or equal to 0.21 mm, that is, the recording paper
P is thick (S18: Yes), in S22 the CPU 300 controls the linefeed
motor 42 to rotate forward by a predetermined amount so that the
discharge roller 21a discharges the recording paper P onto the
discharge tray 10 at a discharge speed of 4 inches/second.
[0058] On the other hands when the thickness of the recording paper
P is less than 0.21 mm (S18: No), referring to the paper size
memory 302a, in S20 the CPU 300 compares the size of the recording
paper P with DIN A4 size. In other words, the CPU 300 determines
whether the paper size stored in the paper size memory 302a is less
than A4 size. When the size of the recording paper P is less than
A4 size (S20: Yes), in S22 the CPU 300 controls the linefeed motor
42 to rotate forward and controls the discharge roller 21a to
rotate so that the recording paper P is discharged onto the
discharge tray 10 at a discharge speed of 4 inches/second.
[0059] On the other hand, when the thickness of the recording paper
P is less than 0.21 mm (SIB: No) and the paper size is A4 size
(S20: No), in S24 the CPU 300 controls the linefeed motor 42 to
rotate forward and controls the discharge roller 21a to rotate so
that the recording paper P is discharged onto the discharge tray 10
at a discharge speed of 13 inches/second. The thin or large
recording paper P is hard to be separated from the discharge roller
21a due to frictional force and static electricity. However, the
recording paper P can be reliably separated by discharging the
recording paper P at such a high speed.
[0060] In S26 the CPU 300 determines whether data exists for the
recording paper P of next page. When data exists (S26: Yes), the
process returns to S6 and feeding of the next recording paper P is
started. In this case, since the linefeed motor 42 is rotated
reverse, the discharge roller 21a is also rotated in the direction
opposite the direction in which the recording paper P is
discharged. However, since the recording paper P is reliably
separated from the discharge roller 21a and discharged, it can be
prevented that the recording paper P caught by the discharge roller
21a is fed back. When all data is printed by repeating the
above-mentioned process (S26: No), the process ends.
[0061] According to the printing process in the present embodiment,
rotation of the discharge roller 21a is controlled so that the thin
and large recording paper P of A4 size having a thickness less than
0.21 mm is discharged at a higher speed than the thick recording
paper P having a thickness greater than or equal to 0.21 mm or the
recording paper P smaller than A4 size. Accordingly, even the thin
or large recording paper P which is greatly affected by static
electricity and frictional force can be reliably discharged. On the
other hand, since the thick or small recording paper P which is
less affected by static electricity and frictional force is
discharged at a low speed, stack performance after discharging is
improved.
[0062] Referring to FIGS. 5 through 7C, results of tests of
discharging the recording paper P at different discharge speeds
using a conveying mechanism and a discharge mechanism in the
printing device 1 will be described.
[0063] As shown in FIG. 5, in the tests, the discharge tray 10 was
provided with a stopper 10a. One hundred (100) sheets of the
recording paper P were stacked on the discharge tray 10 beforehand
such that the discharged recording paper P would not hit the
stopper 10.
[0064] First, a test of discharging a golden copy sheet
(manufactured by Optima Corp., thickness of 0.1 mm) of A4 size was
carried out as a first test. In the first test, the recording paper
P was conveyed at 20 inches/second until the trailing edge of the
recording paper P is at a position which is 15 mm upstream from the
discharge roller 21a. Then, the discharge speed was changed after
the trailing edge of the recording paper P passed the position
which is 15 mm upstream from the discharge roller 21a, and a paper
discharge position was measured. Here, a position Q1 of the stopper
10a is referred to as a reference position O. A direction in which
the recording paper P moves away from the discharge roller 21a (the
same direction as the conveying direction B) is referred to as a
plus (+) direction. A direction in which the recording paper P gets
closer to the discharge roller 21a (the direction opposite the
conveying direction B) is referred to as a minus (-) direction.
Specifically, using the left and right end positions of the leading
edge of the discharged recording paper P as measurement points,
distances between the measurement points and the reference position
O were measured and an average of the distances was determined as
the paper discharge position of the recording paper P.
[0065] Ten (10) tests were carried out for each of different
discharge speeds. An average and a standard deviation .sigma. of
the paper discharge positions obtained through the ten tests were
calculated.
[0066] FIG. 6A is a table showing averages and standard deviations
.sigma. which are calculated in the first test. FIG. 6B is a graph
in which a thin line connects each point of calculated standard
deviations .sigma. and a thick curve is a polynomial approximation
showing relationship between discharge speeds and the standard
deviations .sigma., where the standard deviations .sigma. are shown
in a vertical axis and the discharge speeds are shown in a
horizontal axis. FIG. 6C is a graph in which a thin line connects
each point of calculated averages and a thick curve is a polynomial
approximation showing relationship between discharge speeds and the
averages, where the averages are shown in a vertical axis and the
discharge speeds are shown in a horizontal axis.
[0067] The standard deviation .sigma. in FIG. 6B is a value
representing variation in the paper discharge positions, and thus
indicates stack performance of the recording paper P (whether the
sheets of the recording paper P are stacked neatly). As the
standard deviation .sigma. becomes larger, variation in the paper
discharge position is larger, which indicates that stack
performance is worse. FIG. 6B shows that the standard deviation
.sigma. rapidly increases when the discharge speed exceeds 14
inches/second (ips). The reason is as follows: when the discharge
speed is high, kinetic energy of the recording paper P during
discharge is large. Thus, the recording paper P is easily affected
by various factors (attitude or direction of the recording paper
during discharge, static electricity, frictional force, and the
like), resulting in large variation. In the first test, the stack
performance is determined as OK when .sigma. is less than 4.5 mm
and as NG when .sigma. is greater than or equal to 4.5 mm.
[0068] The average in FIG. 6C is an average of leading edge
positions of the recording paper P discharged at the different
discharge speeds. When the average is large, the recording paper P
is discharged to a position sufficiently away from the discharge
roller 21a. When the average is small, the recording paper P is
discharged to a position in vicinity of the discharge roller 21a.
Especially the thin (0.1 mm) A4 golden copy sheet used in the first
test is easily affected by static electricity and frictional force
and cannot be easily separated from the discharge roller 21a. Thus,
when the discharge speed is low, there are cases where the
recording paper P cannot be separated from the discharge roller
21a. If the linefeed motor 42 is rotated reverse to feed the next
recording paper P in the state where the recording paper P is not
separated from the discharge roller 21a, the recording paper P
caught by the discharge roller 21a is fed back, thereby leading to
a paper jam.
[0069] The longitudinal length of the A4 recording paper P used in
the first test is 297 mm. A distance L between a position Q2 of the
discharge roller 21a and the position Q1 of the stopper 10a was set
to 322 mm which was obtained by adding 25 mm to the length of the
A4 recording paper P. Thus, when the leading edge of the discharged
recording paper P is located upstream (at the discharge roller 21a
side) than -25 mm position, the recording paper P is caught by the
discharge roller 21a and fed back. Further, as described above, the
discharge positions of the recording papers P vary around the
average. Hence, in the first test, in consideration of the
variation of 20 mm, if the average of the paper discharge positions
is greater than or equal to -5 mm (that is, the trailing edge of
the recording paper P is separated from the discharge roller 21a by
greater than or equal to 20 mm on the average), it is determined as
"no backward feed (backward feed OK)". On the other hand, if the
average of the paper discharge positions is less than -5 mm, it is
determined as "possible backward feed (backward feed NG)".
[0070] As described above, determination results on stack
performance and backward feed for each discharge speed are
summarized in FIG. 6A. As shown in FIG. 6A, the discharge speed
from 12 inches/second to 14 inches/second is suitable for the A4
golden copy sheet. As shown in FIG. 6A, since the discharge speed
greater than or equal to 12 inches/second results in the average of
the paper discharge positions greater than or equal to -5 mm, the
recording paper P can be reliably separated from the discharge
roller 21a and discharged irrespective of static electricity and
frictional force. In addition, by setting the discharge speed to
less than 14 inches/second, stack performance of the recording
paper P can be prevented from being impaired.
[0071] Next, a test of discharging an L size sheet (89 mm.times.127
mm, thickness of 0.21 mm) was carried out as a second test. In the
second test, the recording paper P was conveyed at 20 inches/second
until the trailing edge of the recording paper P is at a position
which is 15 mm upstream from the discharge roller 21a. Then, after
the trailing edge of the recording paper P passed the position
which is 15 mm upstream from the discharge roller 21a, the
discharge speed was changed and a paper discharge position was
measured. Here, the position Q2 of the discharge roller 21a is
referred to as a reference position O (refer to FIG. 5). A
direction in which the recording paper P moves away from the
discharge roller 21a (the same direction as the conveying direction
B) is referred to as a plus (+) direction. A direction in which the
recording paper P gets closer to the discharge roller 21a (the
direction opposite the conveying direction B) is referred to as a
minus (-) direction. Specifically, the left and right end positions
of the trailing edge of the discharged recording paper P from the
reference position O in the conveying direction B were measured,
and an average of the measured positions was determined as the
paper discharge position of the recording paper P.
[0072] Ten (10) tests were carried out for each discharge speed of
different discharge speeds. An average and a standard deviation
.sigma. of the paper discharge positions obtained through the 10
tests were calculated.
[0073] FIG. 7A is a table showing averages and standard deviations
.sigma. which are calculated in the second test. FIG. 7B is a graph
in which a thin line connects each point of calculated standard
deviations .sigma. and a thick curve is a polynomial approximation
showing relationship between discharge speeds and the standard
deviations .sigma., where the standard deviations .sigma. are shown
in a vertical axis and the discharge speeds are shown in a
horizontal axis. FIG. 7C is a graph in which a thin line connects
each point of calculated averages and a thick curve is a polynomial
approximation showing relationship between discharge speeds and the
averages, where the averages are shown in a vertical axis and the
discharge speeds are shown in a horizontal axis.
[0074] FIG. 7B shows that the standard deviation .sigma. rapidly
increases when the discharge speed exceeds 6 inches/second. In the
second test, the stack performance is determined as OK when .sigma.
is less than 4.5 mm and as NG when .sigma. is greater than or equal
to 4.5 mm.
[0075] The average in FIG. 7C is an average of trailing edge
positions of the recording paper P discharged at each discharge
speed. As in the first test, in consideration of the variation, if
the trailing edge of the recording paper P is separated from the
position Q2 by greater than or equal to 20 mm on the average, it is
determined as "no backward feed (backward feed OK)". On the other
hand, if the trailing edge of the recording paper 2 is separated
from the position Q2 by less than 20 mm on the average, it is
determined as "possible backward feed (backward feed NG)".
[0076] As a result of the second test, it was revealed that the
discharge speed from 4 inches/second to 6 inches/second is suitable
for the recording paper P of L-size. By setting the discharge speed
to greater than or equal to 4 inches/second, the printing rate can
be prevented from decreasing. In addition, by setting the discharge
speed to 6 inches/second or less, stack performance can be
improved.
[0077] While the invention has been described in detail with
reference to the above aspects thereof, it would be apparent to
those skilled in the art that various changes and modifications may
be made therein without departing from the spirit of the
invention.
[0078] For example, in the above-described embodiment, size and
thickness are acquired based on user settings. However, the method
for acquiring size and thickness of the recording paper P is not
limited to this. For example, the printing device 1 may be
configured so that a sensor is provided on the carriage 13, size
and thickness of the recording paper P is detected by the sensor
prior to printing by the recording head 12, and the discharge speed
is determined based on the detection results.
[0079] In the above-described embodiment, the discharge speed is
determined based on size and thickness of the recording paper P.
However, the discharge speed may be determined based on only the
thickness.
[0080] In the above-described embodiment, using 0.21 mm as a single
threshold of thickness, the discharge speed is determined from two
kinds of discharge speeds based on whether the thickness is greater
than or equal to the threshold, or less than the threshold.
However, a plurality of thresholds may be set so as to determine
the discharge speed in greater number of segments.
[0081] In the above-described embodiment, using A4 size as a
standard size, the recording paper smaller than A4 size is
discharged at the discharge speed from 4 inches/second to 6
inches/second. However, the discharge speed may be changed using
letter size as a reference size, for example. Although description
of detailed test results is omitted, even when the recording paper
P of letter size having a thickness less than 0.21 mm is used, the
same effects as in the above-described A4 recording paper P having
a thickness less than 0.21 mm can be obtained by setting the
discharge speed from 12 inches/second to 14 inches/second.
[0082] The printing device 1 may be configured such that the
recording paper P larger than A4 size is discharged at a higher
discharge speed than that of the recording paper P in A4 size.
COMPARATIVE EXAMPLE
[0083] A printing device according to a comparative example will be
described with reference to FIG. 8. In FIG. 8, a recording head 112
mounted on a carriage 113 ejects ink on a recording paper P on a
platen 111 while reciprocating in a main scanning direction (the
direction perpendicular to the sheet of FIG. 8) to perform
printing. A position between the recording head 112 and the platen
111 is referred to as a printing position 114. As shown in FIG. 8,
the recording paper P held between a conveying roller 120a and a
pressing roller 120b opposed to the conveying roller 120a is fed to
the printing position 114 by rotation of the conveying roller 120a
and reaches a discharge roller 121a. Here, the recording paper P is
held between the discharge roller 121a and a pressing roller 121b
opposed to the discharge roller 121a and discharged to a discharge
tray 122 by rotation of the discharge roller 121a.
[0084] When the recording paper P is thin and flexible (small
flexural rigidity), the leading edge of the recording paper P
passing through the discharge roller 11a hangs down and contacts
the recording paper stacked in the discharge tray 122. As a result,
friction occurs between the recording paper in the discharge tray
122 and the newly discharged recording paper P. Since the recording
paper P needs to be discharged against the frictional force, the
thin and flexible recording paper P requires a larger amount of
energy for discharging, in comparison with a thick or less flexible
recording paper P which generates less friction.
[0085] Further, when the recording paper P is fed from a feeding
tray (not shown) to the conveying roller 120a, the fed recording
paper P and the recording paper in the feeding tray rub against
each other, so that the recording paper P takes on static
electricity. As the size of the recording paper P is larger, the
recording paper P becomes charged with static electricity more
easily. A larger amount of energy is required to discharge the
recording paper P against the static electricity. Due to such
frictional force and static electricity, the large recording paper
P or the thin recording paper P is hard to be discharged. When the
recording paper P is not discharged onto the discharge tray, the
user has to remove a cover of the printing device and pull out the
printed recording paper P by himself or herself, which is
bothersome. However, these problems do not occur in the printing
device 1 in the above-described embodiment.
* * * * *