Title: Ink-jet printer
Abstract: There is described an ink-jet printer, which emits ink particles onto a recording medium to prints an image on the recording medium, and in which moving velocities of the ink particles are detected to perform stable emitting actions of the ink particles. The ink-jet printer includes: an ink-jetting head having a plurality of nozzles from which the ink particles are emitted; a velocity detecting section to detect moving velocities of the ink particles by measuring detection times at each of which each of the ink particles is detected; a calculating section to calculate an average value of the detection times measured by the velocity detecting section; and a head-drive controlling section that compares the average value calculated by the calculating section with a target value established in advance, to change a driving condition for the ink-jetting head so that the average value coincides with the target value.
Patent Number: 6,843,548 Issued on 01/18/2005 to Arakawa, et al.
| Inventors:
|
Arakawa; Hiroaki (Uenohara-machi, JP);
Matsui; Yasuhiro (Tokyo, JP)
|
| Assignee:
|
Konica Corporation (Tokyo, JP)
|
| Appl. No.:
|
336989 |
| Filed:
|
January 6, 2003 |
Foreign Application Priority Data
| Jan 11, 2002[JP] | P2002-004708 |
| May 10, 2002[JP] | P2002-136228 |
| Aug 09, 2002[JP] | P2002-233053 |
| Current U.S. Class: |
347/19; 347/14 |
| Intern'l Class: |
B41J 029/393; B41J029/38 |
| Field of Search: |
347/14,19
|
References Cited [Referenced By]
U.S. Patent Documents
| 5517216 | May., 1996 | Stamer et al. | 347/6.
|
| 6568780 | May., 2003 | Schantz et al. | 347/14.
|
| 2002/0070993 | Jun., 2002 | Mantell | 347/19.
|
| 2003/0048331 | Mar., 2003 | Takahashi et al. | 347/57.
|
| Foreign Patent Documents |
| 11-300944 | Nov., 1999 | JP.
| |
Primary Examiner: Meier; Stephen D.
Assistant Examiner: Dudding; Alfred
Attorney, Agent or Firm: Frishauf, Holtz, Goodman & Chick, P.C.
Claims
What is claimed is:
1. An ink-jet printer, comprising:
an ink-jetting head having a plurality of nozzles from which ink particles,
being microscopic droplets of ink, are emitted;
a velocity detecting section to detect moving velocities of said ink
particles, each of which is emitted from each of said plurality of
nozzles, by measuring detection times at each of which each of said ink
particles is detected;
a calculating section to calculate an average value of said detection times
measured by said velocity detecting section; and
a head-drive controlling section that compares said average value
calculated by said calculating section with a target value established in
advance, to change a driving condition for said ink-jetting head so that
said average value coincides with said target value.
2. The ink-jet printer of claim 1, further comprising:
a target-value changing section to change said target value corresponding
to an environmental condition around said ink-jet printer.
3. The ink-jet printer of claim 1,
wherein said head-drive controlling section determines said driving
condition, based on a difference value between said target value and said
average value calculated by said calculating section.
4. The ink-jet printer of claim 1,
wherein said head-drive controlling section determines said driving
condition, by employing a look-up table based on a difference value
between said target value and said average value calculated by said
calculating section.
5. The ink-jet printer of claim 1,
wherein, when said driving condition, determined by said head-drive
controlling section, deviates from a stably-emitting condition of said ink
particles, said head-drive controlling section establishes a specific
value as said driving condition, said specific value being approximately
equal to a marginal value for a stably-emitting action of said ink-jetting
head.
6. The ink-jet printer of claim 1, further comprising:
a determining section to determine whether or not each of said detection
times measured by said velocity detecting section exceeds a predetermined
time value;
wherein, when said determining section determines that a detection time of
a specific nozzle exceeds said predetermined time value, said calculating
section excludes said detection time of said specific nozzle from a group
of detection times objective for calculating said average value.
7. The ink-jet printer of claim 1,
wherein said ink-jet printer comprises a plurality of ink-jetting heads,
each of which corresponds to said ink-jetting head, and said target value
is established for each of said plurality of ink-jetting heads.
8. An ink-jet printer, comprising:
an ink-jetting head having a plurality of nozzles from which ink particles,
being microscopic droplets of ink, are emitted;
a velocity detecting section to detect moving velocities of said ink
particles, each of which is emitted from each of said plurality of
nozzles, by measuring detection times at each of which each of said ink
particles is detected;
a moving device to move said ink-jetting head and/or said velocity
detecting section relative to each other;
an emitting-action controlling section to control said ink-jetting head so
that an action for emitting at least one of said ink particles from at
least one of predetermined plural nozzles, included among all of said
plurality of nozzles, is conducted at a timing when said plurality of
nozzles cross a detectable region of said velocity detecting section in a
relative moving process of said ink-jetting head and said velocity
detecting section; and
a head-drive controlling section that compares a detected value detected by
said velocity detecting section with a target value established in
advance, to change a driving condition for said ink-jetting head so that
said detected value coincides with said target value.
9. The ink-jet printer of claim 8,
wherein said emitting-action controlling section controls said ink-jetting
head so that said action for emitting at least one of said ink particles
from at least one of said predetermined plural nozzles, included among all
of said plurality of nozzles, is repeated plural times at said timing when
said plurality of nozzles cross said detectable region of said velocity
detecting section; and
wherein said detected value to be compared with said target value is an
average value of plural detected values, each of which is detected every
time of said plural times by said velocity detecting section.
10. The ink-jet printer of claim 8, further comprising:
a target-value changing section to change said target value corresponding
to an environmental condition around said ink-jet printer.
11. The ink-jet printer of claim 8,
wherein said head-drive controlling section determines said driving
condition, based on a difference value between said target value and
detected value detected by said velocity detecting section.
12. The ink-jet printer of claim 8,
wherein said head-drive controlling section determines said driving
condition, by employing a look-up table based on a difference value
between said target value and said detected value detected by said
velocity detecting section.
13. The ink-jet printer of claim 8,
wherein, when said driving condition, determined by said head-drive
controlling section, deviates from a stably-emitting condition of said ink
particles, said head-drive controlling section establishes a specific
value as said driving condition, said specific value being approximately
equal to a marginal value for a stably-emitting action of said ink-jetting
head.
14. The ink-jet printer of claim 8,
wherein said ink-jet printer comprises a plurality of ink-jetting heads,
each of which corresponds to said ink-jetting head, and said target value
is established for each of said plurality of ink-jetting heads.
15. An ink-jet printer, which prints an image on a recording medium by
emitting ink particles onto said recording medium, comprising:
an ink-jetting head to emit said ink particles from a plurality of nozzles
onto said recording medium; and
a velocity measuring section to measure moving velocity values of said ink
particles emitted from said plurality of nozzles;
wherein a nozzle average value, being an average value of said moving
velocity values measured by said velocity measuring section, is
calculated, and a specific nozzle, which emits an ink particle at a moving
velocity value being different from said nozzle average value by more than
a predetermined value, is detected.
16. The ink-jet printer of claim 15,
wherein, when said specific nozzle is detected, a maintenance operation for
normalizing said specific nozzle is executed.
17. An ink-jet printer, which prints an image on a recording medium by
emitting ink particles onto said recording medium, comprising:
a plurality of ink-jetting heads, each of which emits said ink particles
from a plurality of nozzles onto said recording medium in response to
drive-voltages applied to said plurality of nozzles; and
a velocity measuring section to measure moving velocity values of said ink
particles emitted from said plurality of nozzles;
wherein nozzle average values, each of which is an average value of said
moving velocity measured for each of said plurality of ink-jetting heads
by said velocity measuring section, are calculated, and then, a head
average value, being an average value of said nozzle average values, is
calculated; and
wherein, with respect to a specific ink-jetting head, a nozzle average
value of which is different from said head average value by more than a
predetermined value, said drive-voltages, to be applied to said plurality
of nozzles of said specific ink-jetting head, are compensated for.
18. The ink-jetting head of claim 17, further comprising:
a head-drive controlling section to control said plurality of ink-jetting
heads; and
a head-driving circuit to apply said drive-voltages to said plurality of
nozzles, based on control signals transmitted from said head-drive
controlling section;
wherein said velocity measuring section includes an ink-particle detecting
device, disposed at a predetermined position being apart from said
plurality of nozzles to detect passages of said ink particles, and a
time-measuring circuit to measure time differences between output timings
of said control signals and detected timings of said passages of said ink
particles; and
wherein said moving velocity values of said ink particles emitted from said
plurality of nozzles are equivalent to said time differences.
19. An ink-jet printer, which prints an image on a recording medium by
emitting ink particles onto said recording medium, comprising:
a plurality of ink-jetting heads, each of which emits said ink particles
from a plurality of nozzles onto said recording medium;
a velocity measuring section to measure moving velocity values of said ink
particles emitted from said plurality of nozzles;
a head-drive controlling section to control said plurality of ink-jetting
heads; and
a head-driving circuit to drive said plurality of ink-jetting heads so as
to emit said ink particles from said plurality of nozzles, based on
control signals transmitted from said head-drive controlling section;
wherein said velocity measuring section includes an ink-particle detecting
device, disposed at a predetermined position being apart from said
plurality of nozzles to detect passages of said ink particles, and a
time-measuring circuit to measure time differences between output timings
of said control signals and detected timings of said passages of said ink
particles; and
wherein said moving velocity values of said ink particles emitted from said
plurality of nozzles are equivalent to said time differences.
20. The ink-jet printer of claim 19,
wherein said ink-particle detecting device includes a wave-receiving
section to receive a wave motion; and
wherein said velocity measuring section detects a passage of an ink
particle, based on either a local maximum or a local minimum of an output
value of said wave-receiving section, which varies associating with an
action of shading said wave motion to be arrived at said wave-receiving
section.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an ink-jet printer, which emits ink
particles onto a recording medium to prints an image on the recording
medium, and specifically relates to an ink-jet printer, in which moving
velocities of the ink particles, being micro droplets of ink, are detected
to perform stable emitting actions of the ink particles.
In recent years, a great number of image printing methods using an ink-jet
printer have been employed as convenient methods for forming images at a
reduced cost. The ink-jet printer prints images onto paper or other
recording media by emitting ink as ink particles from a plurality of
emission ports towards the recording media by use of a voltage applied to
a piezoelectric element or heater provided on the ink-jetting head of the
printer, and then scanning the recording media with the ink-jetting head
while fixing the ink onto the recording media.
However, to print images on recording media with stable accuracy, ink
particles emitted from the emission ports of each nozzle are required to
hit the recording media at properly timed intervals according to the
particular operation of the ink-jetting head. It is preferable, therefore,
that the emission velocity of ink from each nozzle of the ink-jetting head
should be kept constant.
According to the prior art practice, however, the velocity of ink particles
emitted may vary according to each emission port if the status of the
emission ports deteriorates due to drying of the ink or the ingress of
dirt, air bubbles or the like.
Further, a plurality of ink-jetting heads are used to implement color
printing according to the prior art. In this case, however, the velocity
of the ink particles emitted may also differ depending on the ink-jetting
heads because of idiosyncrasies of each recording head and the type of ink
used in each ink-jetting head.
If the velocity of the ink particles emitted differs depending on according
to each emission port of the ink-jetting head or each ink-jetting head,
image-printing accuracy may deteriorated, as described above.
For example, if the emission velocity of ink particles changes at some
emission ports, the status of the emission ports may have been
deteriorated, as described above. If this trouble is left unprepared, ink
may not be emitted from some of the nozzles.
Further, the ink-jet recorder emits ink particles in the form of minute
liquid droplets from a multitude of nozzles formed on the ink-jetting head
so that they will hit the recording media arranged so as to face the
nozzle surfaces of the ink-jetting head. Then a desired image is recorded
and formed on the recording media during main scanning of the ink-jetting
head in both directions.
To achieve high-quality image recording with such an ink-jet recorder, it
is necessary to keep track of how the ink particles are emitted from each
nozzle of the ink-jetting head. If the ink particles emitted from each
nozzle of the ink-jetting head are kept in a constant status, there will
be deviations in the position of ink particles reaching the recording
media during main scanning of the recording media in both directions by
the ink-jetting head. For example, if the velocity of ink particles
emitted from each nozzle of the ink-jetting head is lower than the
intended velocity, the ink particle "a" that should hit a target line X on
the recording media reaches a position deviated from the target line X by
the distance corresponding to the lower velocity, as shown in FIG. 18.
This is repeated for each main-scanning operation of the ink-jetting head
in both directions (indicated by the arrow). Deviations in the position
hit by ink particles in both directions will cause disturbances in the
image recorded, thus reducing resolution significantly.
Since changes in the velocity of ink particles appear as changes in the
amount of particles, the density of the recorded image will change, and
the color balance of the image will also be changed.
Further, when the stable driving conditions for ink particle emission of
the ink-jetting head are not met, air will be entrapped into the ink
chamber to prevent ink particles from being emitted correctly, or ink
particles will take a curved course, resulting in stripe-like
irregularities. This will cause image quality to deteriorate
significantly.
When the ink-jetting head consists of a plurality of ink-jetting heads that
records images using ink of different colors such as yellow (Y), magenta
(M), cyan (C), and black (K), the position hit by ink particles varies
from color to color due to the difference in the distance between the
recording medium of each ink-jetting head and the head surface.
The prior art of detecting the velocities of the minute ink particles
emitted from the ink-jetting head, and modifying and controlling the
ink-jetting head driving conditions based on the detection is disclosed in
the Official Gazette of Japanese Application Patent Laid-Open Publication
No. Hei 11-300944. According to this prior art, however, the velocities of
the particles emitted from the multiple nozzles formed on the ink-jetting
heads are detected for each nozzle. To detect the velocities of the
particles emitted from all nozzles, more time is required. Namely, each
ink-jetting head must be stopped to ensure that ink particles emitted from
each nozzle of the ink-jetting head will match the detection position (an
optical path of detecting beam or detecting range) of velocity detection
means. This requires a very high positioning accuracy when the ink-jetting
head is positioned at the detection position. Thus, a lot of time must be
consumed in the control of stop position, hence velocity detection,
according to the aforementioned prior art. Especially when the recording
mechanism has a plurality of ink-jetting heads for ink of different
colors, a great deal of time is required since each ink-jetting head must
be stopped to detect velocities.
SUMMARY OF THE INVENTION
To overcome the abovementioned drawbacks in conventional ink-jet printers,
it is a first object of the present invention to provide an ink-jet
printer that can print images with stable accuracy.
Further, it is a second object of the present invention to minimize the
causes of image deterioration and to ensure high-quality image recording,
by keeping track of the velocities of the ink particles emitted from
ink-jetting heads and modifying the driving conditions of the ink-jetting
heads based on the aforementioned velocities.
Still further, it is a third object of the present invention to provide an
ink-jet printer that is capable of quick measurement of the moving
velocities of ink particles through detection of the velocities of ink
particles emitted from the nozzles during the moving process, without
having to stop each of the ink-jetting heads at a predetermined detection
position as in the prior art, and capable of compensating for changes in
the moving velocities of ink due to environmental changes or due to rise
in the temperatures of the ink-jetting heads based on measurement results.
Accordingly, to overcome the cited shortcomings, the abovementioned objects
of the present invention can be attained by ink-jet printers described as
follow.
(1) An ink-jet printer, comprising: an ink-jetting head having a plurality
of nozzles from which ink particles, being microscopic droplets of ink,
are emitted; a velocity detecting section to detect moving velocities of
the ink particles, each of which is emitted from each of the plurality of
nozzles, by measuring detection times at each of which each of the ink
particles is detected; a calculating section to calculate an average value
of the detection times measured by the velocity detecting section; and a
head-drive controlling section that compares the average value calculated
by the calculating section with a target value established in advance, to
change a driving condition for the ink-jetting head so that the average
value coincides with the target value.
(2) The ink-jet printer of item 1, further comprising: a target-value
changing section to change the target value corresponding to an
environmental condition around the ink-jet printer.
(3) The ink-jet printer of item 1, wherein the head-drive controlling
section determines the driving condition, based on a difference value
between the target value and the average value calculated by the
calculating section.
(4) The ink-jet printer of item 1, wherein the head-drive controlling
section determines the driving condition, by employing a look-up table
based on a difference value between the target value and the average value
calculated by the calculating section.
(5) The ink-jet printer of item 1, wherein, when the driving condition,
determined by the head-drive controlling section, deviates from a
stably-emitting condition of the ink particles, the head-drive controlling
section establishes a specific value as the driving condition, the
specific value being approximately equal to a marginal value for a
stably-emitting action of the ink-jetting head.
(6) The ink-jet printer of item 1, further comprising: a determining
section to determine whether or not each of the detection times measured
by the velocity detecting section exceeds a predetermined time value;
wherein, when the determining section determines that a detection time of
a specific nozzle exceeds the predetermined time value, the calculating
section excludes the detection time of the specific nozzle from a group of
detection times objective for calculating the average value.
(7) The ink-jet printer of item 1, wherein the ink-jet printer comprises a
plurality of ink-jetting heads, each of which corresponds to the
ink-jetting head, and the target value is established for each of the
plurality of ink-jetting heads
(8) An ink-jet printer, comprising: an ink-jetting head having a plurality
of nozzles from which ink particles, being microscopic droplets of ink,
are emitted; a velocity detecting section to detect moving velocities of
the ink particles, each of which is emitted from each of the plurality of
nozzles, by measuring detection times at each of which each of the ink
particles is detected; a moving device to move the ink-jetting head and/or
the velocity detecting section relative to each other; an emitting-action
controlling section to control the ink-jetting head so that an action for
emitting at least one of the ink particles from at least one of
predetermined plural nozzles, included among all of the plurality of
nozzles, is conducted at a timing when the plurality of nozzles cross a
detectable region of the velocity detecting section in a relative moving
process of the ink-jetting head and the velocity detecting section; and a
head-drive controlling section that compares a detected value detected by
the velocity detecting section with a target value established in advance,
to change a driving condition for the ink-jetting head so that the
detected value coincides with the target value.
(9) The ink-jet printer of item 8, wherein the emitting-action controlling
section controls the ink-jetting head so that the action for emitting at
least one of the ink particles from at least one of the predetermined
plural nozzles, included among all of the plurality of nozzles, is
repeated plural times at the timing when the plurality of nozzles cross
the detectable region of the velocity detecting section; and wherein the
detected value to be compared with the target value is an average value of
plural detected values, each of which is detected every time of the plural
times by the velocity detecting section.
(10) The ink-jet printer of item 8, further comprising: a target-value
changing section to change the target value corresponding to an
environmental condition around the ink-jet printer.
(11) The ink-jet printer of item 8, wherein the head-drive controlling
section determines the driving condition, based on a difference value
between the target value and detected value detected by the velocity
detecting section.
(12) The ink-jet printer of item 8, wherein the head-drive controlling
section determines the driving condition, by employing a look-up table
based on a difference value between the target value and the detected
value detected by the velocity detecting section.
(13) The ink-jet printer of item 8, wherein, when the driving condition,
determined by the head-drive controlling section, deviates from a
stably-emitting condition of the ink particles, the head-drive controlling
section establishes a specific value as the driving condition, the
specific value being approximately equal to a marginal value for a
stably-emitting action of the ink-jetting head.
(14) The ink-jet printer of item 8, wherein the ink-jet printer comprises a
plurality of ink-jetting heads, each of which corresponds to the
ink-jetting head, and the target value is established for each of the
plurality of ink-jetting heads.
(15) An ink-jet printer, which prints an image on a recording medium by
emitting ink particles onto the recording medium, comprising: an
ink-jetting head to emit the ink particles from a plurality of nozzles
onto the recording medium; and a velocity measuring section to measure
moving velocity values of the ink particles emitted from the plurality of
nozzles; wherein a nozzle average value, being an average value of the
moving velocity values measured by the velocity measuring section, is
calculated, and a specific nozzle, which emits an ink particle at a moving
velocity value being different from the nozzle average value by more than
a predetermined value, is detected.
(16) The ink-jet printer of item 15, wherein, when the specific nozzle is
detected, a maintenance operation for normalizing the specific nozzle is
executed.
(17) An ink-jet printer, which prints an image on a recording medium by
emitting ink particles onto the recording medium, comprising: a plurality
of ink-jetting heads, each of which emits the ink particles from a
plurality of nozzles onto the recording medium in response to
drive-voltages applied to the plurality of nozzles; and a velocity
measuring section to measure moving velocity values of the ink particles
emitted from the plurality of nozzles; wherein nozzle average values, each
of which is an average value of the moving velocity measured for each of
the plurality of ink-jetting heads by the velocity measuring section, are
calculated, and then, a head average value, being an average value of the
nozzle average values, is calculated; and wherein, with respect to a
specific ink-jetting head, a nozzle average value of which is different
from the head average value by more than a predetermined value, the
drive-voltages, to be applied to the plurality of nozzles of the specific
ink-jetting head, are compensated for.
(18) The ink-jetting head of item 17, further comprising: a head-drive
controlling section to control the plurality of ink-jetting heads; and a
head-driving circuit to apply the drive-voltages to the plurality of
nozzles, based on control signals transmitted from the head-drive
controlling section; wherein the velocity measuring section includes an
ink-particle detecting device, disposed at a predetermined position being
apart from the plurality of nozzles to detect passages of the ink
particles, and a time-measuring circuit to measure time differences
between output timings of the control signals and detected timings of the
passages of the ink particles; and wherein the moving velocity values of
the ink particles emitted from the plurality of nozzles are equivalent to
the time differences.
(19) An ink-jet printer, which prints an image on a recording medium by
emitting ink particles onto the recording medium, comprising: a plurality
of ink-jetting heads, each of which emits the ink particles from a
plurality of nozzles onto the recording medium; a velocity measuring
section to measure moving velocity values of the ink particles emitted
from the plurality of nozzles; a head-drive controlling section to control
the plurality of ink-jetting heads; and a head-driving circuit to drive
the plurality of ink-jetting heads so as to emit the ink particles from
the plurality of nozzles, based on control signals transmitted from the
head-drive controlling section; wherein the velocity measuring section
includes an ink-particle detecting device, disposed at a predetermined
position being apart from the plurality of nozzles to detect passages of
the ink particles, and a time-measuring circuit to measure time
differences between output timings of the control signals and detected
timings of the passages of the ink particles; and wherein the moving
velocity values of the ink particles emitted from the plurality of nozzles
are equivalent to the time differences.
(20) The ink-jet printer of item 19, wherein the ink-particle detecting
device includes a wave-receiving section to receive a wave motion; and
wherein the velocity measuring section detects a passage of an ink
particle, based on either a local maximum or a local minimum of an output
value of the wave-receiving section, which varies associating with an
action of shading the wave motion to be arrived at the wave-receiving
section.
Further, to overcome the abovementioned problems, other ink-jet printers,
embodied in the present invention, will be described as follow:
(21) An ink-jet printer that prints images by emitting ink onto recording
media, characterized by comprising;
an ink-jetting head for emitting ink as particles from a plurality of
nozzles onto a recording medium, and
velocity measuring means for measuring the values for the velocity of the
ink emitted from the aforementioned nozzles;
the aforementioned ink-jet printer being further characterized in that the
velocity measuring means measures the values for the velocity of the ink
emitted from each nozzle, calculates the average nozzle value as the
average value for these velocities, and detects the nozzle that emits ink
particles at a velocity differing from the aforementioned average nozzle
value by more than a predetermined value.
The velocity of the ink emitted from each nozzle of the ink-jetting head is
compared with the average nozzle value for all nozzle emission velocities,
whereby the nozzle that causes image printing accuracy to be deteriorated
by timing error of the ink hitting the recording medium is detected as a
nozzle where the velocity of the emitted ink is lower or higher than that
of other nozzles.
(22) An ink-jet printer according to Item (21) further characterized in
that, when a nozzle has been detected that emits ink particles at the
velocity differing from the aforementioned average nozzle value by more
than the predetermined value, maintenance is performed on the ink-jetting
head of the detected nozzle.
When the nozzle has been detected that causes the image printing accuracy
to deteriorate, maintenance is carried out on the ink-jetting head
provided with that nozzle. Cleaning operation such as ink absorption is
carried out to remove clogging or other troubles from that nozzle. This
step ensures that ink particles emitted from each nozzle always hit the
recording medium at the same timed intervals. It allows the ink-jetting
head to print images with stable accuracy at all times, and makes it
possible to provide an ink-jet printer capable of printing images with
more stabilized accuracy (23) An ink-jet printer that prints images by
emitting ink onto recording media, characterized by comprising;
a plurality of ink-jetting heads for emitting ink as ink particles from a
plurality of nozzles onto a recording medium by applying a voltage, and
velocity measuring means for measuring the values for the velocity of the
ink emitted from the aforementioned nozzles, and characterized in that,
the average nozzle value is calculated as the average value for the
velocities of ink particles emitted from the nozzle for each of the
aforementioned ink-jetting heads, and the average head value is to
calculated as the average of the average nozzle values of each of the
aforementioned ink-jetting heads, and then, the applied voltage for the
aforementioned ink-jetting head, where the aforementioned average nozzle
value differs from the average head value by more than a predetermined
value, is corrected.
The average head value as an average of the values for velocities of ink
particles emitted from the nozzles equipped in the ink-jetting heads is
calculated, and this average head value is compared with the average
nozzle value of each ink-jetting head, thereby detecting a ink-jetting
head where the velocity of ink particles significantly differs from those
of other ink-jetting heads. The voltage to be applied to the ink-jetting
heads detected in this manner is corrected, and the value denoting the
velocity of ink particles is matched with the values of other ink-jetting
heads. This ensures that ink particles emitted from each nozzle always hit
the recording medium at the same timed intervals. This removes the factors
that cause deterioration in image printing accuracy, with the result that
it is possible to provide an ink-jet printer capable of printing images
with more stabilized accuracy.
(24) An ink-jet printer according to any one of Items (21), (22) and (23)
characterized by further comprising;
controlling means for controlling the aforementioned ink-jetting head, and
an ink-jetting head driving circuit for emitting ink from the
aforementioned nozzles in accordance with the control signals sent from
the aforementioned controlling means; and characterized in that,
the aforementioned velocity measuring means further comprises;
an ink particle detector for detecting the passage of ink particles at a
predetermined position away from the aforementioned nozzles, and
a time counting circuit for measuring the difference in time between the
output of the aforementioned control signal and the detection of the ink
particles by the aforementioned ink particles detector;
wherein the value for the aforementioned velocity is within the
aforementioned time difference.
The value representing the velocity of the ink particles emitted from the
nozzle is calculated from the difference in time between the output of the
control signal for emitting ink particles from the nozzle, and the
detection of the ink particles by the aforementioned ink particle
detector. This ensures easy creation of velocity measuring means that
detects the value for the velocity of ink particles with sufficient
accuracy for comparison between a plurality of nozzles. This makes it
possible to create an ink-jet printer capable of printing images with
stable accuracy at a low cost.
(25) An ink-jet printer that prints images by emitting ink onto recording
media, characterized by comprising;
an ink-jetting head for emitting ink as in particles from a plurality of
nozzles onto a recording medium,
velocity measuring means for measuring the velocity of the ink particles
emitted from the aforementioned nozzles,
controlling means for controlling the aforementioned ink-jetting head, and
an ink-jetting head driving circuit for emitting ink from the
aforementioned nozzles in accordance with the control signals sent from
the aforementioned controlling means; and characterized in that,
the aforementioned velocity measuring means further comprises a ink
particle detector for detecting the passage of ink particles at a
predetermined position away from the aforementioned nozzles, and a time
counting circuit for measuring the difference in time between the output
of the aforementioned control signals and the detection of the ink
particles by the aforementioned ink particle detector; the value for the
aforementioned velocity being within the aforementioned time difference.
An effect similar to that described in Item (24) can be yielded.
(26) An ink-jet printer according to Item (24) or (25), characterized in
that,
the aforementioned ink-jet printer further comprises a wave receiver for
receiving incident waves, and the aforementioned velocity measuring means
detects the passage of the ink particles by determining whether the output
of the aforementioned wave receiver that is changed according to the
interception of the wave entering the wave receiver takes the maximum or
minimum value.
The ink particle detection sensitivity of the ink particle detector can be
further improved by detecting the passage of the ink particles by
determining whether the output signal from the ink particle detector takes
a maximum or minimum value, than by detecting it from the amount of
variation with respect to the base line of the signal. This ensures the
image printing accuracy of the ink-jet printer to be stabilized in a more
reliable manner.
(27) An ink-jet recorder, characterized by comprising;
an ink-jetting head for emitting minute ink particles from nozzles,
velocity detection means for detecting the velocity of the ink particles
from the detection time of its particles emitted from each nozzle of the
aforementioned ink-jetting head,
calculation means for calculating the average value of the detection time
of the ink particles emitted from each the aforementioned nozzle, and
driving controlling means for comparison between a predetermined target
value and the average value which has been calculated by the
aforementioned calculation means, and modifying the driving conditions of
the ink-jetting head so that the average value agrees with the target
value.
(28) An ink-jet recorder according to Item (27), characterized by further
comprising:
target value changing means for changing the aforementioned target value
according to the ambient environmental conditions.
(29) An ink-jet recorder according to Item (27) or (28), characterized in
that,
the aforementioned driving controlling means determines the driving
conditions of the aforementioned ink-jetting head by the value which has
been calculated from the difference between the aforementioned target
value and the average value that was calculated by the aforementioned
calculation means.
(30) The ink-jet recorder according to Item (27) or (28), characterized in
that,
the aforementioned driving controlling means uses a look-up table to
determine the driving conditions of the aforementioned ink-jetting head,
based on the difference between the aforementioned target value and the
average value calculated by the aforementioned calculation means.
(31) An ink-jet recorder according to Item (29) or (30), characterized in
that,
when the driving conditions determined in the above-mentioned manner
deviate from the conditions for stable emission of ink particles, the
aforementioned driving controlling means establishes a specified value as
the driving conditions, this specific condition being approximately equal
to a marginal value for stable emission.
(32) An ink-jet recorder according to any one of items from (27) to (31),
characterized by further comprising:
determining means for determining whether or not the detection time of the
ink particles emitted from each nozzle detected by the aforementioned
velocity detection means exceeds a predetermined value; and characterized
in that
the aforementioned calculation means does not include in the calculation of
the average value the detection time of ink particles emitted from the
nozzle that has been determined to exceed the predetermined value.
(33) An ink-jet recorder according to any one of the items from (27) to
(32) above, characterized in that,
the aforementioned ink-jet recorder comprises a plurality of the
aforementioned ink-jetting heads, and the aforementioned target value is
established for each of a plurality of ink-jetting heads.
(34) An ink-jet recorder, characterized by comprising;
an ink-jetting head for emitting minute ink particles from a plurality of
nozzles,
velocity detection means for detecting the velocity of the ink particles
based on the detection time of ink particles from each nozzle of the
aforementioned ink-jetting head,
movement means for relative movement of the aforementioned ink-jetting head
and velocity detection means, an emission controlling means by which,
whenever the nozzles of the aforementioned ink-jetting head traverse the
velocity detection zone of the aforementioned velocity detection means in
the process of relative movement between the ink-jetting head and the
velocity detection means by the aforementioned movement means, control is
provided so that ink particles are emitted from one or more of all nozzles
of the ink-jetting head at the same timed intervals, and
a driving controlling means by which the value that has been detected by
the aforementioned velocity detection means regarding the emission of each
particle of the ink by the aforementioned emission controlling means is
compared with a predetermined target value, and the aforementioned driving
conditions of the ink-jetting head are modified so that the detected value
agrees with the target value.
(35) An ink-jet recorder according to Item (34), characterized in that,
the aforementioned emission controlling means provides control so that the
emission of ink particles is repeated a plurality of times whenever the
nozzles of the aforementioned ink-jetting head traverse the velocity
detection zone of the aforementioned velocity detection means, and the
detected value compared with the aforementioned target value is an average
value based on the value when the emission of ink particles is repeated a
plurality of times.
(36) An ink-jet recorder according to Item (34) or (35), characterized by
further comprising:
target value changing means for changing the aforementioned target value
according to the ambient environmental conditions.
(37) An ink-jet recorder according to any one of Items (34), (35) and (36),
characterized in that,
the aforementioned ink-jet recorder is characterized in that the
aforementioned driving controlling means determines the driving conditions
of the aforementioned ink-jetting head according to the value calculated
from the difference between the aforementioned target value and the
detected value.
(38) An ink-jet recorder according to any one of Items (34), (35)
(36), characterized in that, the aforementioned driving controlling means
uses a look-up table to determine the driving conditions changed by the
aforementioned ink-jetting head based on the difference between the
aforementioned target value and the detected value.
(39) An ink-jet recorder according to any one of Items from (34) to (38),
characterized in that,
when the driving conditions to be changed deviate from the conditions for
stable emission of ink particles, the aforementioned driving controlling
means establishes a specified value as the driving conditions, this
specific condition being approximately equal to a marginal value for
stable emission.
(40) An ink-jet recorder according to any one of items from (34) to (39),
characterized by further comprising a plurality of the aforementioned
ink-jetting heads, and characterized in that,
the aforementioned target value is established for each of the multiple
ink-jetting heads.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the present invention will become apparent
upon reading the following detailed description and upon reference to the
drawings in which:
FIG. 1 is a major component perspective view showing the structure of an
ink-jet printer pertaining to the present invention;
FIG. 2 is a major component perspective view showing the ink-jetting head
and velocity measuring means applied to the ink-jet printer in partial
perspective form;
FIG. 3 is a major component block diagram showing the composition of the
ink-jet printer;
FIG. 4(a) and FIG. 4(b) are major component block diagrams showing the
composition of the velocity measuring means applied to the ink-jet
printer;
FIG. 5 is a diagram showing examples of the waveforms of the signals
processed by the ink-jet printer;
FIG. 6 is a flow hart showing the procedure of measuring the emission
velocity in the ink-jet printer;
FIG. 7 is a schematic view showing the structure of the main component
blocks in the ink-jet recorder pertaining to the present invention;
FIG. 8 is a front view showing the shape of a light-receiving opening;
FIG. 9 is a view showing how ink particles are emitted during the detection
operation of velocity detection means;
FIG. 10 is a control flow diagram showing the detection operation of the
velocity detection means;
FIG. 11 is a block diagram showing the composition of the velocity
detection means;
FIG. 12 is a timing chart of an emission starting signal and detection
signal;
FIG. 13 is a timing chart of an emission starting signal and detection
signal;
FIGS. 14(a) and (b) are diagrams showing the composition of controlling
means equipped with a limiters;
FIG. 15 is a schematic perspective view of the ink-jetting heads provided
for each color;
FIG. 16 is a diagram explaining the relationship between the ink-jetting
heads provided for each color and a recording medium;
FIG. 17 is a schematic block diagram showing another example of the
velocity detection means;
FIG. 18 is an explanatory diagram showing deviations in the positions hit
by ink particles emitted from the ink-jetting heads;
FIG. 19 is a schematic view of the main components in the ink-jet recorder
pertaining to the present invention;
FIG. 20 is a control flow diagram showing the detection operation of
velocity detection means;
FIG. 21 is a diagram explaining the relationship between ink-jetting heads
and an ink-receiving pan;
FIG. 22 is a timing chart of an emission starting signal and detection
signal; and
FIG. 23 is a perspective view showing another example of the ink-jetting
head.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The ink-jet printer 100 pertaining to a first embodiment of the present
invention is described below using figures:
The ink-jet printer 100 pertaining to a first embodiment of the present
invention comprises a head carriage 2, maintenance means 3, ink-jetting
heads 4, controlling means 5, velocity measuring means 6, head
moisture-retaining means 7, a carriage rail 11, a guide member 12, and
other components.
When the recording medium M for printing images is carried by carriage
means not shown in FIG. 1, the guide member 12 guides the recording medium
in the direction of an arrow X in FIG. 1 (in the X-axis direction). The
carriage rail 11 is installed in parallel to the direction of an arrow Y
in FIG. 1, namely, in the lateral direction of the recording medium M (in
the Y-axis direction). The carriage rail 11 is provided with the head
carriage 2 described below, and the head carriage 2 is guided in the
Y-axis direction.
Depending on the number of colors to be used to print images on the
recording medium M, the head carriage 2 contains a plurality of
ink-jetting heads 4, 4, . . . (described later), and a plurality of
nozzles 41, 41, . . . arranged under the ink-jetting heads. The head
carriage 2 is installed to be freely movable in the Y-axis direction with
respect to the carriage rail 11 and is moved in the Y-axis direction by
the operation of head carriage moving means (not illustrated).
Each ink-jetting head 4 comprises an emission means (not illustrated) and a
nozzle 41. The ink-jetting head 4 is connected to the controlling means 5
via an ink-jetting head driving circuit 42. The ink-jetting head driving
circuit 42 applies voltage to the emission means in accordance with the
control signals T0, T1, . . . that are transmitted from the controlling
means 5. One emission means is installed for one nozzle 41 in the form
connected thereto, and comprises, for example, a piezo-element.
A plurality of nozzles 41, 41, . . . are installed on the bottom of the
ink-jetting head 4 to form a linear bank of nozzles (nozzle line). Voltage
is applied to the emission means according to the control signals
transmitted from the controlling means 5 based on the image data of the
recording medium M, with the result that ink is emitted as particles P
from the nozzles 41 connected to the emission means.
At this time, the recording medium M is carried along the surface of the
guide member 12 to change the relative positions of the ink heads 4 in the
X-axis direction with respect to the recording medium M. Further, the head
carriage 2 containing the ink heads 41 is driven by carriage driving means
to move along the surface of the carriage rail 11 and thus to change the
Y-axis relative positions of the ink heads 4 with respect to the recording
medium M. Ink particles P, P, . . . are emitted from the ink-jetting heads
4, 4, . . . in synchronization with the above-mentioned guide member 12
and carriage driving means, and consequently, an image consisting of a set
of UV ink particles P, P, . . . is formed on the recording medium M.
As shown in FIG. 1, maintenance means 3 is provided in the proximity to the
guide member 12 near the underside of one end of the carriage rail 11, and
comprises a suction caps 31, idle emission/collection means 34 and a blade
portion 35. Ink suction, idle emission, and other maintenance operations
for cleaning are performed on each ink-jetting head 4 by the maintenance
means 3 to remove air bubbles, dry ink, dirt, and other potential clogging
substances from the nozzles 41, and thus to ensure that each ink-jetting
head 4 is capable of emitting ink particles P exactly as designed, thereby
allowing a clear image to be printed on the recording medium M with stable
accuracy.
Ink emitted from the nozzles 41 is absorbed by the suction caps 31 using
the suction force generated by a suction pump (not illustrated). After the
suction by the suction caps 31, 31, the blade portion 35 wipes off the ink
and other substances sticking in the vicinity of the nozzles 41, 41, . . .
.
After the above-mentioned operations, the emission means is filled with
clean ink by idle emission of ink particles P from the nozzles 41, 41, . .
. to complete the entire step of emission status maintenance. When the
idle emission is conducted, the idle-emission/collection means 34 collects
the ink idle-emitted from the nozzles 41, 41, . . . . The
idle-emission/collection means 34 is, for example, a box-like body with an
opening on top, and an ink particle detector 61 (described later) is
provided on the inner side of the idle-emission/collection means 34.
The velocity measuring means 6 comprises an ink particle detector 61 and a
circuit section 63. In addition to detecting the passage of the ink
particles P, P, . . . emitted from the nozzles 41, 41, . . . , the
velocity measuring means 6 measures the time differences t1, t2, . . .
between the output of control signals T1, T2, . . . from the controlling
means 5, and the detection of the ink particles P.
The ink particle detector 61 comprises a light-emitting section 61a and a
light-receiving section (wave receiving section) 61b. The light-emitting
section 61a and the light-receiving section 61b are arranged to face one
another on the inner side of, for example, the idle-emission/collection
means 34. The light-emitting section 61a is, for example, light-emitting
diode (LED), and emits light towards the light-receiving section 61b. The
light-receiving section 61b is, for example, a photodiode, and receives
light from the light-emitting section 61a and then transmits it wherein
this light-receiving state is assumed as form a light-receiving signal
(wave receiving signal).
The circuit section 63 comprises a current amplification circuit 63a, an
alternating-current (AC) amplification circuit 63b, a peak detection
circuit 63c, a time counting circuit 63d, and an amplitude feedback
circuit 63e. The circuit section 63 generates detection signals Q0, Q1, .
. . based on the changes in the current values of the light-receiving
signals which change when the passage of the ink particles P, P, . . . is
detected by the light-receiving section 61b, and measures the time
differences between the output of control signals T0, T1, . . . and the
output of detection signals Q0, Q1, . . . .
The current amplification circuit 63a amplifies the light-receiving signals
sent from the light-receiving section 61b. The AC amplification circuit
63b further AC-amplifies the light-receiving signals that have been
amplified by the current amplification circuit 63a. The peak detection
circuit 63c generates detection signals Q0, Q1, . . . as pulses based on
the changes in the current values of the light-receiving signals sent via
the AC amplification circuit 63b. The time counting circuit 63d measures
the time differences between the output of control signals T0, T1, . . .
and the output of detection signals Q0, Q1, . . . . The amplitude feedback
circuit 63e adjusts the current and voltage of the electric power supplied
to the light-emitting section 61a to optimize the current values of the
light-receiving signals that are sent from the light-receiving section 61b
both when ink particles P are detected and when they are not detected.
The head moisture-retaining means 7 comprises moisture-retentive caps 71,
71, . . . in the same number as the ink-jetting heads 4 arranged on the
head carriage 2. The head moisture-retaining means 7 humidifies the
ink-jetting heads 4 by covering the nozzles 41 with the moisture-retentive
caps 71 when the ink-jetting heads 4 are placed in the stand-by mode.
The controlling means 5 controls the, UV ink-jet printer 100. The
controlling means 5 comprises a central processing unit (CPU) 51, a
read-only memory (ROM) 52, a random access memory (RAM) 53, an interface
54 and other elements, and controls the components of the UV ink-jet
printer 1. The controlling means 5 is connected to the ink-jetting heads
4, 4, . . . , the velocity measuring means 6, the maintenance means 3 and
other components of the printer via the interface 54.
The CPU 51 performs various computations and judgments based on the
information stored in the ROM 52 and the RAM 53, and the information sent
from the velocity measuring means 6, and controls components such as the
ink-jetting heads 4, 4, . . . . The ROM 52 contains such data as a
calculation procedure for the average nozzle values (described later) and
average nozzle values, and a method for calculating a predetermined data
as the basis for comparison between the average nozzle values and average
time differences t'1, t'2, . . . (described later) and between the av
