Patent Grant
9044938
This application claims priority under 35 U.S.C. §119 from Japanese Patent Application No. 2012-093535 filed on Apr. 17, 2012. The entire subject matter of the application is incorporated herein by reference.
1. Technical Field
The following description relates to one or more techniques for an inkjet printer configured to perform printing by discharging ink droplets from nozzles onto a recording medium.
2. Related Art
As an example of inkjet printers that perform printing by discharging ink droplets from nozzles onto a recording medium, an inkjet printer has been known that is configured to perform printing by discharging ink droplets onto a recording sheet (a recording medium) from a recording head (an inkjet head) mounted on a carriage reciprocating along a predetermined scanning direction. Further, the known inkjet printer is configured to cause feed rollers and corrugated holding spur wheels to press the recording sheet against a surface of a platen that has thereon convex portions and concave portions alternately formed along the scanning direction, so as to hold the recording sheet in a predetermined wave shape. The predetermined wave shape has mountain portions protruding toward an ink discharge surface of the recording head, and valley portions recessed in a direction opposite to the direction toward the ink discharge surface, the mountain portions and the valley portions alternately arranged along the scanning direction. In other words, the recording sheet is corrugated in such a corrugated form as to have ridges and grooves (flutes) extending along a sheet feeding direction perpendicular to the predetermined scanning direction and alternating along the predetermined scanning direction.
In the known inkjet printer, a gap (distance) between the ink discharge surface of the recording head and the recording sheet varies depending on portions (locations) on the recording sheet held in the wave shape (hereinafter, which may be referred to as a “wave-shaped recording sheet” or a “corrugated recording sheet”). Therefore, when the known inkjet printer performs printing by discharging ink droplets from the recording head onto the wave-shaped recording sheet with the same ink discharge timing as when performing printing on a recording sheet not held in such a wave shape (a recording sheet having a substantially uniform distance from the ink discharge surface all over the recording sheet), the ink droplets might land in positions deviated from their respective desired positions on the recording sheet. Thus, it might result in a low-quality printed image.
In the meantime, the known inkjet printer is configured to discharge ink droplets from the recording head while reciprocating the carriage. In the reciprocating movement, the carriage decelerates just before turning around its moving direction, and then accelerates in a direction opposite to the previous moving direction. The known inkjet printer may be configured to perform printing by discharging ink droplets from the recording head while accelerating or decelerating the carriage.
However, when the known inkjet printer discharges ink droplets from the recording head while accelerating or decelerating the carriage, the moving velocity of the carriage varies from one ink discharge moment to another. Therefore, when ink discharge timing is determined with no consideration for the change in the moving velocity of the carriage, it leads to positional deviations of the ink droplets landing on the recording sheet and thus to a low-quality printed image.
Aspects of the present invention are advantageous to provide one or more improved techniques for allowing an inkjet printer to land ink droplets in appropriate positions on a wave-shaped recoding sheet even when the inkjet printer performs printing by discharging the ink droplets from an inkjet head while accelerating or decelerating the inkjet head.
According to aspects of the present invention, an inkjet printer is provided that includes an inkjet head configured to discharge ink droplets from nozzles formed in an ink discharge surface thereof while reciprocating relative to a recording sheet along a scanning direction parallel to the ink discharge surface, a wave shape holding mechanism configured to hold the recording sheet in a predetermined wave shape that has top portions of portions protruding in a first direction toward the ink discharge surface and bottom portions of portions recessed in a second direction opposite to the first direction, the top portions and the bottom portions alternately arranged along the scanning direction, and a control device configured to control the inkjet head to move along the scanning direction and discharge the ink droplets from the nozzles, determine ink discharge moments to discharge the ink droplets from the nozzles while the inkjet head is moving within at least one of an acceleration range to accelerate the inkjet head and a deceleration range to decelerate the inkjet head, based on a distance between the ink discharge surface and the recording sheet held in the predetermined wave shape and a moving velocity of the inkjet head.
According to aspects of the present invention, further provided is an inkjet printer that includes an inkjet head configured to discharge ink droplets from nozzles formed in an ink discharge surface thereof while reciprocating relative to a recording sheet along a scanning direction parallel to the ink discharge surface, a wave shape holding mechanism configured to hold the recording sheet in a predetermined wave shape that has top portions of portions protruding in a first direction toward the ink discharge surface and bottom portions of portions recessed in a second direction opposite to the first direction, the top portions and the bottom portions alternately arranged along the scanning direction, and a control device configured to control the inkjet head to move along the scanning direction and discharge the ink droplets from the nozzles, and determine ink discharge timing to discharge an ink droplet from the nozzles while the inkjet head is moving within a predetermined printable range including at least one of an acceleration range to accelerate the inkjet head and a deceleration range to decelerate the inkjet head, based on a moving velocity of the inkjet head and a distance between the ink discharge surface and the recording sheet held in the predetermined wave shape, the distance determined depending on a position of the inkjet head in the scanning direction.
According to aspects of the present invention, further provided is an inkjet printer configured to form an image on a sheet, the inkjet printer including an inkjet head configured to discharge an ink droplet from an ink discharge surface thereof, a head moving mechanism configured to reciprocate the inkjet head in a predetermined printable range along a scanning direction, a detector configured to detect a position of the inkjet head in the scanning direction in the printable range, a sheet conveyor configured to convey the sheet in a sheet feeding direction perpendicular to the scanning direction and to corrugate the sheet in such a corrugated form that a flute of the corrugated sheet extends along the sheet feeding direction, and a control device configured to control the head moving mechanism to reciprocate the inkjet head in the printable range along the scanning direction, detect the position of the inkjet head in the scanning direction in the printable range, using the detector, determine a moving velocity of the inkjet head in the scanning direction in accordance with a detection result of the detector, determine a distance between the ink discharge surface and the corrugated sheet in accordance with the position of the inkjet head in the scanning direction and the predetermined corrugated form of the sheet, determine an ink discharge timing to discharge the ink droplet from the ink discharge surface in accordance with the moving velocity of the inkjet head in the scanning direction and the distance between the ink discharge surface and the corrugated sheet, and control the inkjet head to discharge the ink droplet at the determined ink discharge timing.
It is noted that various connections are set forth between elements in the following description. It is noted that these connections in general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. Aspects of the invention may be implemented on circuits (such as application specific integrated circuits) or in computer software as programs storable on computer readable media including but not limited to RAMs, ROMs, flash memories, EEPROMs, CD-media, DVD-media, temporary storage, hard disk drives, floppy drives, permanent storage, and the like.
Hereinafter, an embodiment according to aspects of the present invention will be described in detail with reference to the accompanying drawings.
An inkjet printer 1 of the embodiment is a multi-function peripheral having a plurality of functions such as a printing function to perform printing on a recording sheet P and an image reading function. The inkjet printer 1 includes a printing unit 2 (see
The printing unit 2 is disposed inside the inkjet printer 1. The printing unit 2 is configured to perform printing on the recording sheet P. A detailed configuration of the printing unit 2 will be described later. The sheet feeding unit 3 is configured to feed the recording sheet P to be printed by the printing unit 2. The sheet ejecting unit 4 is configured to eject the recording sheet P printed by the printing unit 2. The reading unit 5 is configured, e.g., as an image scanner, to read images. The operation unit 6 is provided with buttons. A user is allowed to operate the inkjet printer 1 via the buttons of the operation unit 6. The display unit 7 is configured, e.g., as a liquid crystal display, to display information necessary in the use of the inkjet printer 1.
Subsequently, the printing unit 2 will be described. As shown in
The carriage 11 is configured to reciprocate along a scanning direction while guided by a guiderail (not shown). The inkjet head 12 is mounted on the carriage 11. The inkjet head 12 is configured to discharge ink droplets from a plurality of nozzles 10 formed in an ink discharge surface 12a that is a lower surface of the inkjet head 12. The feed rollers 13 are two rollers configured to pinch therebetween the recording sheet P fed by the sheet feeding unit 3 and feed the recording sheet P in a sheet feeding direction perpendicular to the scanning direction. The platen 14 is disposed to face the ink discharge surface 12a. The recording sheet P is fed by the feed rollers 13, along an upper surface of the platen 14.
The plurality of corrugated plates 15 are disposed to face an upper surface of an upstream end of the platen 14 in the sheet feeding direction. The plurality of corrugated plates 15 are arranged at substantially regular intervals along the scanning direction. The recording sheet P, fed by the feed rollers 13, passes between the platen 14 and the corrugated plates 15. At this time, the recording sheet P is pressed from above by pressing surfaces 15a that are lower surfaces of the plurality of corrugated plates 15. Each individual rib 16 is disposed between corresponding two mutually-adjacent corrugated plates 15 in the scanning direction, on the upper surface of the platen 14. The plurality of ribs 16 are arranged at substantially regular intervals along the scanning direction. Each rib 16 protrudes from the upper surface of the platen 14 up to a level higher than the pressing surfaces 15a of the corrugated plates 15. Each rib 16 extends from an upstream end of the platen 14 toward a downstream side in the sheet feeding direction. Thereby, the recording sheet P on the platen 14 is supported from underneath by the plurality of ribs 16.
The ejection rollers 17 are two rollers configured to pinch therebetween portions of the recording sheet P that are located in the same positions as the plurality of ribs 16 in the scanning direction and feed the recording sheet P toward the sheet ejecting unit 4. An upper one of the ejection rollers 17 is provided with spur wheels so as to prevent the ink attached onto the recording sheet P from transferring to the upper ejection roller 17. The plurality of corrugated spur wheels 18 are disposed substantially in the same positions as the corrugated plates 15 in the scanning direction, at a downstream side relative to the ejection rollers 17 in the sheet feeding direction. The plurality of corrugated spur wheels 19 are disposed substantially in the same positions as the corrugated plates 15 in the scanning direction, at a downstream side relative to the corrugated spur wheels 18 in the sheet feeding direction. In addition, the plurality of corrugated spur wheels 18 and 19 are placed at a level lower than a position where the ejection rollers 17 pinch the recording sheet P therebetween, in the vertical direction. The plurality of corrugated spur wheels 18 and 19 are configured to press the recording sheet P from above at the level. Further, each of the plurality of corrugated spur wheels 18 and 19 is not a roller having a flat outer circumferential surface but a spur wheel. Therefore, it is possible to prevent the ink attached onto the recording sheet P from transferring to the plurality of corrugated spur wheels 18 and 19.
Thus, the recording sheet P on the platen 14 is pressed from above by the plurality of corrugated plates 15 and the plurality of corrugated spur wheels 18 and 19, and is supported from underneath by the plurality of ribs 16. Thereby, as shown in
Further, outmost corrugated plates 15 in the scanning direction are positionally adjusted so as to press the recording sheet P more strongly than the other corrugated plates 15. Thereby, the both ends of the recording sheet P in the scanning direction are more strongly pressed, and thus it is possible to put the recording sheet P in a stable state. Further, thereby, as shown in
An encoder sensor 20 is mounted on the carriage 11. The encoder sensor 20, together with an encoder belt (not shown) extending along the scanning direction, forms a linear encoder. The encoder sensor 20 is configured to detect slits formed in the encoder belt and thereby detect a position of the inkjet head 12 moving together with the carriage 11 along the scanning direction.
The printing unit 2 configured as above performs printing on the recording sheet P, by discharging ink droplets from the inkjet head 12 reciprocating together with the carriage 11 along the scanning direction while feeding the recording sheet P in the sheet feeding direction by the feed rollers 13 and the ejection rollers 17.
At this time, when moving rightward along the scanning direction, the carriage 11 accelerates up to a predetermined velocity in a range R1 (an acceleration range) facing a left end area of the recording sheet P. Subsequently, the carriage 11 moves at the predetermined velocity in a range R2 (a constant-velocity range) that is located on a right side of the range R1 and faces an intermediate area other than both end areas of the recording sheet P in the scanning direction. Then, the carriage 11 decelerates in a range R3 (a deceleration range) that is located on a right side of the range R2 and faces a right end area of the recording sheet P. On the contrary, when moving leftward along the scanning direction, the carriage 11 accelerates up to the predetermined velocity in the range R3 (the acceleration range), moves at the predetermined velocity in the range R2 (the constant-velocity range), and decelerates in the range R1 (the deceleration range).
In the embodiment, a printing operation is performed all over the areas of the recording sheet P that face the ranges R1, R2, and R3. In other words, all the ranges R1, R2, and R3 are included in a printable range Rp for the recording sheet P. Ink droplets, discharged from the nozzles 10 when the carriage 11 is within the ranges R1 and R3 where the carriage 11 accelerates or decelerates, land on two acceleration-deceleration print areas Pc that correspond to the both end areas of the recording sheet P in the scanning direction, respectively. Further, ink droplets, discharged from the nozzles 10 when the carriage 11 is within the range R2 where the carriage 11 moves at the predetermined velocity, land on a constant-velocity print area Pe between the two acceleration-deceleration print areas Pc. The aforementioned mountain portions Pm1 and valley portions Pv1 are included in the acceleration-deceleration print areas Pc.
Next, an explanation will be provided about the control device 50 for controlling the operations of the inkjet printer 1. The control device 50 includes a control unit 51 and an application specific integrated circuit (ASIC) 52. The control unit 51 includes a central processing unit (CPU) 56, a read only memory (ROM) 57, and a random access memory (RAM) 58 interconnected via a bus. The CPU 56 is configured to issue instructions to the ASIC 52 and determine a below-mentioned discharge mode in accordance with data values and control programs stored on the ROM 57 and RAM 58.
The ASIC 52 includes various control circuits such as a carriage control circuit 61 configured to control a carriage motor 41 for driving the carriage 11, a head control circuit 62 configured to control a driver IC 42 for driving the inkjet head 12, a sheet feeding control circuit 63 configured to control a feed motor 43 for driving the feed rollers 13 and the ejection rollers 17, and a discharge timing determining circuit 64 configured to determine ink discharge timings (moments) to discharge ink droplets from the nozzles 10. It is noted that the term “timing,” which will frequently be referred to in the following description, may have the same meaning as “a moment” or “a time.” The ASIC 52 is configured to, in response to receiving instructions from the control unit 51, control the elements included in the inkjet printer 1 such that the inkjet printer 1 performs printing.
The discharge timing determining circuit 64 will be described in detail. As shown in
The counters 71a, 71b, and 71c are configured to count the number of slits of the encoder belt (not shown) detected by the encoder sensor 20. The resolution converting circuit 72 is configured to determine a position, corresponding to a resolution of printing, of the inkjet head 12 in the scanning direction, based on the number of the slits counted by the counter 71a.
The acceleration-deceleration delay generating circuit 73 is configured to determine a delay time ΔT1 depending on the moving velocity of the inkjet head 12, in a below-mentioned manner, from the number of slits counted per unit time by the counter 71b. The acceleration-deceleration corrected discharge timing generating circuit 74 is configured to determine the ink discharge timing based on a reference discharge position (an ink discharge position in the case of no delay time) determined by the resolution converting circuit 72, and on the delay time ΔT1 determined by the acceleration-deceleration delay generating circuit 73. Specifically, the acceleration-deceleration corrected discharge timing generating circuit 74 determines, as the ink discharge timing, a time delayed by the delay time ΔT1 determined by the acceleration-deceleration delay generating circuit 73 with respect to a reference discharge timing (moment) for discharging ink in the reference discharge position determined by the resolution converting circuit 72.
As will be described, the corrugated-surface delay generating circuit 75 is configured to determine a delay time ΔT2 required for attaining regular intervals of ink landing positions on the wave-shaped recording sheet P in the scanning direction. Specifically, when the corrugated plates 15, the ribs 16, and the corrugated spur wheels 18 and 19 are disposed as described above, the recording sheet P has a height varying depending on a position thereof in the scanning direction. The corrugated-surface delay generating circuit 75 acquires the position of the inkjet head 12 in the scanning direction based on the number of the slits counted by the counter 71c, and acquires the height of a corresponding portion of the recording sheet P based on the acquired position of the inkjet head 12 in the scanning direction. Then, the corrugated-surface delay generating circuit 75 determines the delay time ΔT2 depending on the acquired height of the recording sheet P in a below-mentioned manner.
The corrugated-surface corrected discharge timing generating circuit 76 is configured to further adjust the ink discharge timing determined by the acceleration-deceleration corrected discharge timing generating circuit 74 and determine final ink discharge timing. Specifically, the corrugated-surface corrected discharge timing generating circuit 76 determines, as the final ink discharge timing, a time delayed by the delay time ΔT2 with respect to the ink discharge timing determined by the acceleration-deceleration corrected discharge timing generating circuit 74. Namely, the final ink discharge timing is determined as a time delayed, with respect to the reference discharge timing, by the delay time ΔT1 determined depending on the moving velocity of the inkjet head 12 and the delay time ΔT2 determined depending on the height of the wave-shaped recording sheet P.
Next, the delay times ΔT1 and ΔT2 will be described. When the recording sheet P is held in a wave shape as shown in
In the embodiment, as shown in
Further, in the embodiment, as shown in
Specifically, for instance, when the inkjet head 12 moves rightward, as shown in
On the contrary, the inkjet head 12, which is within the range R1 or the range R3, moves at a velocity that is lower than when the inkjet head 12 is within the range R2 and varies depending on the position of the inkjet head 12 in the scanning direction. Therefore, a component in the scanning direction of an ink discharge velocity varies depending on each reference discharge position of the inkjet head 12. Hence, an ink droplet, when discharged from the nozzles 10 each time the inkjet head 12 moves by the distance D3, sequentially lands on the recording sheet P while changing the ink landing position relative to a corresponding ink discharge position of the inkjet head 12, as indicated by a dashed line in
Accordingly, in order to land the ink droplets at regular intervals in the scanning direction on the recording sheet P, when the inkjet head 12 is within the range R1 or the range R3, it is required to displace the ink discharge positions in the scanning direction with respect to the respective reference discharge positions (see dashed arrows in
In the embodiment, under the assumption that the recording sheet P is not held in the wave shape, when “Ta” represents a time period from a time when an ink droplet is disposed from the nozzles 10 to a time when the discharged ink droplet lands on the recording sheet P, “Tx” represents a count period that is a reciprocal of the number of slits counted per a unit time by the counter 71b, and “Ts” represents a minimum count period previously set as a minimum value of the count period T, the delay time ΔT1 is determined as the following expression 1. It is noted that the minimum count period Ts is set based on design values of factors such as the moving velocity of the inkjet head 12 in the range R2 (a maximum moving velocity of the inkjet head 12) and the interval of the slit, and is the same as the count period when the inkjet head 12 moves in the range R2.
At this time, the count period Tx is shorter, as the moving velocity of the inkjet head 12 is higher when the inkjet head 12 is within the range R1 or the range R3 (while the inkjet head 12 is accelerating or decelerating). Further, the count period Tx is identical to the minimum count period Ts when the inkjet head 12 is within the range R2 (while the inkjet head 12 is moving at the constant velocity). Accordingly, as shown in
Thus, in the case where the ink discharge positions are displaced in the ranges R1 and R3, for instance, as shown in
By delaying the ink discharge timing by a delay time resulting from adding the delay time ΔT2 to the delay time ΔT1 determined in the aforementioned manner, it is possible to land ink droplets in respective appropriate positions on the wave-shaped recording sheet P in the printing operation, regardless of whether the inkjet head 12 discharges the ink droplets from the nozzles 10 while moving at the constant velocity or while accelerating or decelerating.
Subsequently, an explanation will be provided bout a relationship between a change in the moving velocity of the inkjet head 12 and time intervals of the ink discharge timings (moments).
Under the assumption that (the surface of) the recording sheet P is as high as the lowest bottom portions Pb1, in order to land ink droplets at regular intervals in the scanning direction on the recording sheet P while the inkjet head 12 is moving at the constant velocity in the range R2, the ink droplets are discharged in the reference discharge positions, as shown in
On the contrary, while the inkjet head 12 is accelerating, the moving velocity of the inkjet head 12 becomes gradually higher, and is lower than when the inkjet head 12 is moving at the constant velocity. Accordingly, while the inkjet head 12 is accelerating, as shown in
Meanwhile, while the inkjet head 12 is decelerating, the moving velocity of the inkjet head 12 becomes gradually lower, and is lower than when the inkjet head 12 is moving at the constant velocity. Accordingly, while the inkjet head 12 is decelerating, as shown in
In the inkjet printer 1, the moving velocity of the inkjet head 12 and the heights of the platen 14, the corrugated plates 15, the ribs 16, and the corrugated spur wheels 18 and 19, which heights are factors for determining the distance between the ink discharge surface 12a and each individual portion of the recording sheet P, are determined in such a manner that the time intervals Tk1 are longer than a minimum time interval Tm required for stably discharging an ink droplet from a nozzle 10 again after discharging an ink droplet from the same nozzle 10.
As described above, while the inkjet head 12 is accelerating, each individual time interval Ty of the ink discharge timing is shorter than the corresponding time interval Tk2. However, the inkjet head 12, while accelerating, moves at a lower velocity than when the inkjet head 12 moves at the constant velocity. Therefore, the time intervals Tk2 are longer than the time interval Tk1. Accordingly, each individual time interval Ty has a certain degree of length even though it is shorter than the corresponding time interval Tk2. Therefore, a problem is less likely to be caused that after a nozzle 10 discharges an ink droplet therefrom, a next ink discharge timing (moment) might come before the nozzle 10 is ready to stably discharge another ink droplet again, and thus the nozzle 10 is not able to adequately discharge an ink droplet.
Further, in consideration of the delay time ΔT2 depending on the height of the recording sheet P, as will be described below, there may be a situation where a time interval of the ink discharge timing is shortened in response to a change in the delay time ΔT2. However, as described above, each individual time interval Ty has a certain degree of length. Therefore, even though the time interval of the ink discharge timing is rendered shorter in response to the change in the delay time ΔT2, the aforementioned problem is less likely to be caused.
Meanwhile, while the inkjet head 12 is decelerating, as described above, each individual time interval Tz of the ink discharge timing is longer than the corresponding time interval Tk3. Further, the inkjet head 12, while decelerating, moves at a lower velocity than when the inkjet head 12 moves at the constant velocity. Therefore, the time intervals Tk3 are longer than the time interval Tk1. Accordingly, under an assumption that the delay time ΔT2 depending on the height of the recording sheet P is zero, it is certain that after a nozzle 10 discharges an ink droplet therefrom, a next ink discharge timing (moment) comes after the nozzle 10 is ready to stably discharge another ink droplet again.
Further, as described above, the time intervals Tk3 are longer than the time interval Tk1. Therefore, as described above, even though the time interval of the ink discharge timing is rendered shorter in response to a change in the delay time ΔT2, the aforementioned problem is less likely to be caused.
Additionally, in the embodiment, in the mountain portions Pm1 that have a greater amplitude than the amplitude of the other mountain portions Pm and the valley portions Pv1 that have a greater amplitude than the amplitude of the other valley portions Pv, the heights of the portions Pm1 and Pv1 greatly vary depending on the position in the scanning direction. Further, in the mountain portions Pm1 and the valley portions Pv1, the delay time ΔT2 greatly varies depending on the position in the scanning direction. Therefore, in the mountain portions Pm1 and the valley portions Pv1, when the time interval of the ink discharge timing is shortened in response to the change in the delay time ΔT2, the change in the time interval of the ink discharge timing is great.
However, when the inkjet head 12 is within the range R1 or R3 in which the inkjet head 12 discharges and lands ink droplets on the mountain portions Pm1 and the valley portions Pv1, as described above, the time intervals Tk2 and Tk3 are longer than the time interval Tk1. Therefore, when the time interval of the ink discharge timing is shortened, the change in the time interval of the ink discharge timing is somewhat great. Nonetheless, the time interval of the ink discharge timing is not shortened as much as when the inkjet head 12 moves at the constant velocity. Thus, the aforementioned problem is less likely to be caused.
Subsequently, an explanation will be provided about an ink discharge mode in the inkjet printer 1. In the inkjet printer 1, the control device 50 is configured to, in the printing operation, control the nozzles 10 to discharge ink therefrom in a selected one of a first discharge mode and a second discharge mode.
As described above, in the printing operation, the inkjet printer 1 discharges ink from the nozzles 10 while moving the inkjet head 12 together with the carriage 11 in the scanning direction. At this time, the recording sheet P is divided into an ascending area where the recording sheet P has a surface ascending in the moving direction of the inkjet head 12 and a descending area where the recording sheet P has a surface descending in the moving direction of the inkjet head 12.
Specifically, on the wave-shaped recording sheet P, areas S1 and areas S2 are alternately arranged along the scanning direction. Each area S1 has a bottom portion Pb at the left end thereof and an adjacent top portion Pt at the right end thereof. Meanwhile, each area S2 has a top portion Pt at the left end thereof and an adjacent bottom portion Pb at the right end thereof. When the inkjet head 12 moves rightward in
In the first discharge mode, as shown in
Meanwhile, in the second discharge mode, as shown in
Here, an explanation will be provided about a difference in the time interval of the ink discharge timing between when ink droplets are discharged onto the ascending areas and when ink droplets are discharged onto the descending areas.
In advance of the explanation on the difference in the time interval of the ink discharge timing, an explanation will be provided about a case where the recording sheet P has an even height. Under an assumption that the recording sheet P has an even height, while the inkjet head 12 is moving at the constant velocity, as shown in
Meanwhile, when ink droplets are discharged to land on an ascending area, a portion of the recording sheet P on which a later-discharged ink droplet lands is closer to the ink discharge surface 12a. Therefore, under an assumption that the inkjet head 12 moves at the constant velocity, as shown in
Meanwhile, when ink droplets are discharged to land on a descending area, a portion of the recording sheet P on which a later-discharged ink droplet lands is further away from the ink discharge surface 12a. Therefore, under the assumption that the inkjet head 12 moves at the constant velocity, as shown in
Next, an explanation will be provided about a selection between the first discharge mode and the second discharge mode in the inkjet printer 1, with reference to
Then, as shown in
In the inkjet printer 1 of the embodiment, as described above, the time interval Tk1 is generally longer than the minimum time interval Tm. Nonetheless, in the low-resolution printing, the moving velocity of the inkjet head 12 is higher than that in the high-resolution printing, and the time interval Tk1 is short.
Meanwhile, when ink droplets are discharged to land on an ascending area, as described above, the ink droplets are discharged from the nozzles 10 at the time intervals Ti longer than the time interval Tk1. Accordingly, in each of the high-resolution printing and the low-resolution printing, the aforementioned problem is less likely to be caused that after an ink droplet is discharged from a nozzle 10, a next ink discharge timing (moment) might come before the nozzle 10 is ready to stably discharge another ink droplet again.
On the contrary, when ink droplets are discharged to land on a descending area, as described above, the ink droplets are discharged from the nozzles 10 at the time intervals Tj shorter than the time interval Tk1. At this time, in the high-resolution printing, the time interval Tk1 is longer than when in the low-resolution printing. Hence, even though the time intervals Tj are somewhat shorter than the time interval Tk1, the aforementioned problem is less likely to be caused.
At this time, in the low-resolution printing, the time interval Tk1 is shorter than when in the high-resolution printing. Hence, the time intervals Tj shorter than the time interval Tk1 might be shorter than the minimum time interval Tm, and thus the aforementioned problem might be caused.
In the embodiment, as described above, in the high-resolution printing, the first discharge mode is selected in which the inkjet head 12 is controlled to discharge ink droplets onto both the ascending areas and the descending areas, regardless of whether the inkjet head 12 moves rightward or leftward. Meanwhile, in the low-resolution printing, the second discharge mode is selected in which the inkjet head 12 is controlled to discharge ink droplets onto only the ascending areas when the inkjet head 12 moves rightward and as well moves leftward. Thereby, it is possible to prevent the aforementioned problem that after an ink droplet is discharged from a nozzle 10, a next ink discharge timing (moment) might come before the nozzle 10 is ready to stably discharge another ink droplet again.
Hereinabove, the embodiment according to aspects of the present invention has been described. The present invention can be practiced by employing conventional materials, methodology and equipment. Accordingly, the details of such materials, equipment and methodology are not set forth herein in detail. In the previous descriptions, numerous specific details are set forth, such as specific materials, structures, chemicals, processes, etc., in order to provide a thorough understanding of the present invention. However, it should be recognized that the present invention can be practiced without reapportioning to the details specifically set forth. In other instances, well known processing structures have not been described in detail, in order not to unnecessarily obscure the present invention.
Only an exemplary embodiment of the present invention and but a few examples of their versatility are shown and described in the present disclosure. It is to be understood that the present invention is capable of use in various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein. For example, the following modifications are possible. It is noted that, in the following modifications, explanations about the same configurations as exemplified in the aforementioned embodiment will be omitted.
[Modifications]
In the aforementioned embodiment, the selection between the first discharge mode and the second discharge mode is made depending on whether to perform the high-resolution printing or the low-resolution printing. However, the selection between the first discharge mode and the second discharge mode may be made in a different manner.
For instance, in the aforementioned embodiment, the delay times ΔT1 and ΔT2 are determined based on detection results of the encoder sensor 20. However, in advance of being actually determined in such a manner, the delay times ΔT1 and ΔT2 may be estimated based on factors such as the height of the ink discharge surface 12a, the heights of the mountain portions Pm and the valley portions Pv on the recording sheet P, the moving velocity of the inkjet head 12, and the ink discharge velocity for discharging ink droplets from the nozzles 10.
Then, each time interval between an ink discharge timing (moment) to discharge an ink droplet from a nozzle 10 and a next ink discharge timing (moment) to discharge another ink droplet from the nozzle 10 may be determined based on the estimated delay times ΔT1 and ΔT2. Further, the first discharge mode may be selected when all the determined time intervals are longer than the minimum time interval Tm. Meanwhile, the second mode may be selected when at least one of the determined time intervals is equal to or shorter than the minimum time interval Tm.
In the aforementioned embodiment, from a viewpoint of the time interval of the ink discharge timing, the first discharge mode is selected for the high-resolution printing, and the second discharge mode is selected for the low-resolution printing. However, the selection between the first discharge mode and the second discharge mode may be made from a different viewpoint.
For example, when an ink droplet is discharged to land on an ascending area, as shown in
Thus, for instance, in a modification according to aspects of the present invention, the second discharge mode may be selected for the high-resolution printing. In the modification, it takes a longer period of time for execution of the high-resolution printing than in the aforementioned embodiment. However, since ink droplets are discharged onto only the ascending areas, it is possible to stabilize the shapes of dots on the recording sheets P and improve the quality of a printed image. Meanwhile, in the low-resolution printing, when the time interval of the ink discharge timing is always longer than the minimum time interval Tm, the first discharge mode may be selected from a viewpoint of speed-up of the printing.
In the aforementioned embodiment, it is possible to switch between the first discharge mode and the second discharge mode. However, a specific one of the first and second discharge modes may be applied to all printing operations.
When an ink droplet is discharged to land on an ascending area, as shown in FIG. 12A, the angle α between the flying direction of the ink droplet and the extending direction of the ascending area on the recording sheet P in the scanning direction is close to 90 degrees. Therefore, the dot to be formed by the ink droplet landing on the ascending area is less likely to extend in the scanning direction. On the contrary, when an ink droplet is discharged to land on a descending area, as shown in
Thus, for instance, in a modification according to aspects of the present invention, the second discharge mode may always be applied to discharge ink droplets from the nozzles 10 in, without the selection between the first discharge mode and the second discharge mode. In the modification, it takes a longer period of time for execution of the high-resolution printing than in the aforementioned embodiment. Nonetheless, since ink droplets are discharged onto only the ascending areas, it is possible to stabilize the shapes of dots on the recording sheets P and improve the quality of a printed image.
In the aforementioned embodiment, the printable range Rp includes all the ranges R1, R2, and R3. However, for example, when printing is performed by discharging ink droplets from the nozzles 10 only in a specific one of the rightward movement and the leftward movement of the inkjet head 12, the printable range Rp may include only the range R2 and one of the ranges R2 and R3.
In this case, as described above, when the inkjet head 12 is within the deceleration range (while the inkjet head 12 is decelerating), the time intervals of the ink discharge timing are longer than when the inkjet head 12 is within the acceleration range (and the constant-velocity range). Accordingly, when it is required to select only one of the ranges R1 and R3 as a range to be included in the printable range Rp, it is advantageous to select a range corresponding to the deceleration range from the ranges R1 and R3.
In the aforementioned embodiment, the range R2 is provided in which the inkjet head 12 moves at the constant velocity. However, for instance, the inkjet head 12 may be configured to begin to decelerate immediately after accelerating up to a maximum velocity.
In the aforementioned embodiment, the outmost top portions Pt1 are higher than the other top portions Pt, and the outmost bottom portions Pb1 are lower than the other bottom portions Pb. However, all the top portions Pt (including the top portions Pt1) may have the same height. Further, all the bottom portions Pb (including the bottom portions Pb1) may have the same height.
In the aforementioned embodiment, an ink droplet is discharged from a nozzle 10 at an ink discharge timing (moment) delayed by the delay times ΔT1 and ΔT2 with respect to the reference discharge timing. However, unlike the aforementioned embodiment in which the ink discharge timing is determined based on the detection result of the encoder sensor 20, all the ink discharge timings (moments) may previously be determined before execution of a printing operation. In this modification, each ink discharge timing (moment) may be determined to be earlier than the reference discharge timing.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-093535 | Apr 2012 | JP | national |
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| 20130271518 A1 | Oct 2013 | US |
