Patent Application
20220388321
The present invention relates to an ink jet printing apparatus equipped with means for wiping a discharge port surface.
In conventional ink jet printing apparatuses, in which an ink jet print head mounted on a carriage is moved reciprocally for printing, a larger capacity ink tank is necessary to reduce the frequency with which the ink tank is replaced. However, in systems where the ink jet print head and ink tank are integrated, mounting a large ink tank on the carriage increases the inertia of the carriage. Accordingly, ink jet printing apparatuses having ink tanks installed in non-moving positions, rather than on moving objects such as carriages, are known. The ink tank is connected to the print head on the carriage by a supply tube, and ink is supplied from the ink tank to the print head.
In the above-described configuration, it is known that when the ink in the supply tube oscillates as the carriage moves, dynamic pressure is applied to the ink due to inertia. Japanese Patent Laid-Open No. 2013-226738 discloses a configuration which fills a sub-tank with ink by controlling the acceleration of a carriage using dynamic pressure of the ink produced in the tube. “Sub-tank” refers to an ink holding unit provided between a main tank and the print head.
On the other hand, in ink jet printing apparatuses, fine droplets produced by ink ejection, splash-back of ejected ink from the print medium, and the like may adhere to the discharge port surface. Such adhering objects can cause blockage of the discharge port, come into contact with the ejected ink droplets, or the like, reducing the quality of the printed image. In order to suppress such printing defects, a technique is known in which the discharge port surface is wiped with a blade or the like to remove adhering ink droplets and the like. Japanese Patent Laid-Open No. 2000-094701 discloses an ink jet printing apparatus that wipes the discharge port surface of the print head during and after printing (after the print paper is discharged).
When ink flows from the supply tube into the print head due to dynamic pressure applied to the ink within the supply tube, the internal pressure in the print head rises. Japanese Patent Laid-Open No. 2013-226738 states that this dynamic pressure of ink is proportional to the acceleration/deceleration of the carriage, and the same is true for the internal pressure in the print head. In other words, depending on the magnitude of the acceleration/deceleration, the internal pressure in the print head may become a positive pressure after the carriage stops. In Japanese Patent Laid-Open No. 2000-094701, wiping is performed after the carriage stops. In this case, a convex meniscus formed at the discharge port may be broken by the wiping member, and subsequent movement of the carriage may cause ink to drip from the discharge port onto the print medium or the like, reducing the quality of the printed image.
Note that ink leakage can be suppressed by reducing the internal pressure in the print head from a positive pressure to a negative pressure during an operating time, such as raising and lowering the wiper after the carriage stops and before the wiping operations are executed.
On the other hand, if the carriage is moved at a higher speed to improve throughput, the acceleration/deceleration of the carriage must also be increased, and the range over which the internal pressure in the print head rises and falls increases accordingly.
Particularly when printing operations are performed at high speed, it may not be possible to secure time for the internal pressure in the print head to drop from a positive pressure to a negative pressure before the wiping operations are executed.
Having been achieved in light of the above-described issue, the present invention suppresses a drop in image quality caused by ink leakage from a discharge port after wiping.
According to a first aspect of the present invention, there is provided a printing apparatus comprising: a carriage including a print head that discharges ink, the carriage reciprocally moving relative to a print medium; a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed; and a control unit configured to control a movement operation of the carriage and a wiping operation of the wiping unit such that when a deceleration when stopping the carriage is a first deceleration, a time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a first time, and when the deceleration when stopping the carriage is a second deceleration lower than the first deceleration, the time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a second time shorter than the first time.
According to a second aspect of the present invention, there is provided a printing apparatus comprising: a carriage including a print head that discharges ink, the carriage reciprocally moving relative to a print medium; a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed; and a control unit configured to control a movement operation of the carriage and a wiping operation of the wiping unit such that when a movement distance at a constant speed of the carriage before stopping the carriage is a first distance, a time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a first time, and when the movement distance at the constant speed of the carriage is a second distance longer than the first distance, the time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a second time shorter than the first time.
According to a third aspect of the present invention, there is provided a printing apparatus comprising: a carriage including a print head that discharges ink, the carriage reciprocally moving relative to a print medium; a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed; and a control unit configured to control a movement operation of the carriage and a wiping operation of the wiping unit such that when a printing strike density indicating a ratio of ink dots applied to a predetermined region of the print medium during the movement operation of the carriage before the carriage is stopped is a first strike density, a time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a first time, and when the printing strike density is a second strike density higher than the first strike density, the time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a second time shorter than the first time.
According to a fourth aspect of the present invention, there is provided a printing apparatus comprising: a carriage including a print head that discharges ink, the carriage reciprocally moving relative to a print medium; a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed; and a control unit configured to control a movement operation of the carriage and a wiping operation of the wiping unit such that when the carriage is stopped without wiping the discharge port surface, a deceleration of the carriage is set to a first deceleration, and when the carriage is stopped in order to wipe the discharge port surface, the deceleration of the carriage is set to a second deceleration lower than the first deceleration.
According to a fifth aspect of the present invention, there is provided a printing apparatus comprising: a carriage including a print head that discharges ink, the carriage reciprocally moving relative to a print medium; a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed; and a control unit configured to control a movement operation of the carriage and a wiping operation of the wiping unit such that when a deceleration when stopping the carriage is a first deceleration, a time from when the wiping unit finishes wiping the discharge port surface to when a next movement operation of the carriage starts is set to a first time, and when the deceleration when stopping the carriage is a second deceleration lower than the first deceleration, the time from when the wiping unit finishes wiping the discharge port surface to when the next movement operation of the carriage starts is set to a second time shorter than the first time.
According to a sixth aspect of the present invention, there is provided a printing apparatus comprising: a carriage including a print head that discharges ink, the carriage reciprocally moving relative to a print medium; a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed; and a control unit configured to control a movement operation of the carriage and a wiping operation of the wiping unit such that when a movement distance at a constant speed of the carriage before stopping the carriage is a first distance, a time from when the wiping unit finishes wiping the discharge port surface to when a next movement operation of the carriage starts is set to a first time, and when the movement distance at the constant speed of the carriage is a second distance longer than the first distance, the time from when the wiping unit finishes wiping the discharge port surface to when the next movement operation of the carriage starts is set to a second time shorter than the first time.
According to a seventh aspect of the present invention, there is provided a printing apparatus comprising: a carriage including a print head that discharges ink, the carriage reciprocally moving relative to a print medium; a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed; and a control unit configured to control a movement operation of the carriage and a wiping operation of the wiping unit such that when a printing strike density indicating a ratio of ink dots applied to a predetermined region of the print medium during the movement operation of the carriage before the carriage is stopped is a first strike density, a time from when the wiping unit finishes wiping the discharge port surface to when a next movement operation of the carriage starts next is set to a first time, and when the printing strike density is a second strike density higher than the first strike density, the time from when the wiping unit finishes wiping the discharge port surface to when the next movement operation of the carriage starts is set to a second time shorter than the first time.
According to an eighth aspect of the present invention, there is provided a method of controlling a printing apparatus, the printing apparatus including a carriage which has a print head that discharges ink and which reciprocally moves relative to a print medium and a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed, the method comprising: controlling a movement operation of the carriage and a wiping operation of the wiping unit such that when a deceleration when stopping the carriage is a first deceleration, a time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a first time, and when the deceleration when stopping the carriage is a second deceleration lower than the first deceleration, the time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a second time shorter than the first time.
According to a ninth aspect of the present invention, there is provided a method of controlling a printing apparatus, the printing apparatus including a carriage which has a print head that discharges ink and which reciprocally moves relative to a print medium and a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed, the method comprising: controlling a movement operation of the carriage and a wiping operation of the wiping unit such that when a movement distance at a constant speed of the carriage before stopping the carriage is a first distance, a time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a first time, and when the movement distance at the constant speed of the carriage is a second distance longer than the first distance, the time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a second time shorter than the first time.
According to a 10th aspect of the present invention, there is provided a method of controlling a printing apparatus, the printing apparatus including a carriage which has a print head that discharges ink and which reciprocally moves relative to a print medium and a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed, the method comprising: controlling a movement operation of the carriage and a wiping operation of the wiping unit such that when a printing strike density indicating a ratio of ink dots applied to a predetermined region of the print medium during the movement operation of the carriage before the carriage is stopped is a first strike density, a time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a first time, and when the printing strike density is a second strike density higher than the first strike density, the time from when the carriage stops to when the wiping unit starts wiping the discharge port surface is set to a second time shorter than the first time.
According to an 11th aspect of the present invention, there is provided a method of controlling a printing apparatus, the printing apparatus including a carriage which has a print head that discharges ink and which reciprocally moves relative to a print medium and a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed, the method comprising: controlling a movement operation of the carriage and a wiping operation of the wiping unit such that when the carriage is stopped without wiping the discharge port surface, a deceleration of the carriage is set to a first deceleration, and when the carriage is stopped in order to wipe the discharge port surface, the deceleration of the carriage is set to a second deceleration lower than the first deceleration.
According to a 12th aspect of the present invention, there is provided a method of controlling a printing apparatus, the printing apparatus including a carriage which has a print head that discharges ink and which reciprocally moves relative to a print medium and a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed, the method comprising: controlling a movement operation of the carriage and a wiping operation of the wiping unit such that when a deceleration when stopping the carriage is a first deceleration, a time from when the wiping unit finishes wiping the discharge port surface to when a next movement operation of the carriage starts is set to a first time, and when the deceleration when stopping the carriage is a second deceleration lower than the first deceleration, the time from when the wiping unit finishes wiping the discharge port surface to when the next movement operation of the carriage starts is set to a second time shorter than the first time.
According to a 13th aspect of the present invention, there is provided a method of controlling a printing apparatus, the printing apparatus including a carriage which has a print head that discharges ink and which reciprocally moves relative to a print medium and a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed, the method comprising: controlling a movement operation of the carriage and a wiping operation of the wiping unit such that when a movement distance at a constant speed of the carriage before stopping the carriage is a first distance, a time from when the wiping unit finishes wiping the discharge port surface to when a next movement operation of the carriage starts is set to a first time, and when the movement distance at the constant speed of the carriage is a second distance longer than the first distance, the time from when the wiping unit finishes wiping the discharge port surface to when the next movement operation of the carriage starts is set to a second time shorter than the first time.
According to a 14th aspect of the present invention, there is provided a method of controlling a printing apparatus, the printing apparatus including a carriage which has a print head that discharges ink and which reciprocally moves relative to a print medium and a wiping unit configured to wipe a discharge port surface in which an ink discharge port of the print head is formed, the method comprising: controlling a movement operation of the carriage and a wiping operation of the wiping unit such that when a printing strike density indicating a ratio of ink dots applied to a predetermined region of the print medium during the movement operation of the carriage before the carriage is stopped is a first strike density, a time from when the wiping unit finishes wiping the discharge port surface to when a next movement operation of the carriage starts next is set to a first time, and when the printing strike density is a second strike density higher than the first strike density, the time from when the wiping unit finishes wiping the discharge port surface to when the next movement operation of the carriage starts is set to a second time shorter than the first time.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but limitation is not made to an invention that requires all such features, and multiple such features may be combined as appropriate. Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted.
In this specification, “print” refers not only to forming meaningful information such as text, diagrams, and the like, but also to information which is not meaningful. “Printing” refers broadly to forming an image, a design, a pattern, or the like on a print medium or the processing of a medium, regardless of whether or not the image or the like is manifested in a way that can be perceived visually by humans. “Print medium” refers not only to paper used in general printing apparatuses, but also to a wide range of media that can accept ink, including cloth, plastic film, metal plates, glass, ceramics, wood, leather, and the like. Furthermore, “ink” (sometimes referred to as “liquid”) should be interpreted as broadly as the definition of “print” above. Accordingly, “ink” represents a liquid that can be supplied to a print medium to form an image, a design, a pattern, or the like, the processing of the print medium, or processing of the ink (e.g., solidifying or insolubilizing the coloring material in the ink applied to the print medium). Furthermore, unless otherwise specified, “nozzle” refers collectively to a discharge port, a liquid channel connected thereto, and an element that generates the energy used for ink discharge.
Hereinafter, an ink jet printing apparatus according to a first embodiment of the present invention will be described in detail with reference to the appended drawings.
A recovery unit 107 is installed outside a printing region in the movement direction of the carriage 104. The carriage 104 stops at a home position outside the printing region before the start of the printing operations, as needed during the printing operations, and the like. “Home position” means the rightmost position in the diagram with respect to the main scanning direction of the carriage. The leftmost position in the diagram with respect to the main scanning direction of the carriage will be called a “back position”. The recovery unit 107 is provided in a position opposite the print head 101 when the carriage 104 stops at the home position. The recovery unit 107 performs cleaning operations by sucking ink and air from a plurality of discharge ports provided on a discharge port surface 200 of the print head 101, wiping operations for removing ink, foreign objects, and the like adhering to the discharge port surface, and the like as necessary.
The cap 302 is positioned in the lowered position during printing operations to avoid interference with the print head 101, which moves with the carriage 104. With the cap 302 in the lowered position, the print head 101 can pre-discharge against the cap 302 upon moving to a position opposite the cap 302. The wiper 301 contacts and retracts from the discharge port surface 200 by reciprocally moving between a wiping position and a retracted position in the direction of the arrow Z, using a well-known means, in order to remove foreign objects such as ink residues that adhere to the discharge port surface 200. In other words, the wiper 301 is in the retracted position, as illustrated in
The suction pump 303 is driven when the cap 302 covers the discharge port surface 200 of the print head 101 and the interior thereof is a substantially airtight space, and performs suction operations to suck ink from the print head 101 by generating negative pressure within the airtight space. The suction operations are performed when the print head 101 is filled with ink from the ink tank 103 (during initial filling), when dust, adhering matter, air bubbles, and the like in the discharge ports are suctioned and removed (during suction recovery), and the like. The cap 302 is connected to a waste ink absorber (not shown) by a flexible tube 304.
In the present embodiment, the wiper 301 is constituted by an elastic material such as rubber, but the wiper 301 may also be a member constituted by a sheet of porous material that absorbs ink. Compared to elastic materials, porous materials are more likely to absorb and draw ink from the discharge ports during wiping, which enhances the effect of the present embodiment.
The wiping unit 309 includes a liquid-impregnated member (wiping member) 305, which is constituted by a porous material formed in the shape of an elongated sheet and is pre-impregnated with a wiping liquid having a low-volatility solvent, such as polyethylene glycol or the like, as a main component. This liquid-impregnated member (wiping member) 305 will also be referred to as a “sheet member” hereinafter.
The sheet member 305, formed in the shape of an elongated sheet, is wound into a roll shape around a first core member 307 at one end and a second core member 308 at the other end. The sheet member 305 is disposed such that the part that is not wound into a roll shape (called a “non-rolled part” hereinafter) faces the ink discharge port surface 200 while the print head 101 reciprocally moves. In other words, the non-rolled part of the sheet member 305 is positioned higher in the vertical direction than the first core member 307 and the second core member 308.
The sheet member 305 is supported by a support member 306, constituted by an elastic material, on the back surface of the non-rolled part (the surface on the opposite side from the surface facing the ink discharge port surface 200). The support member 306 contacts and retracts from the discharge port surface 200 by reciprocally moving between a wiping position and a retracted position in the direction of the arrow Z, using a well-known means, in order to remove foreign objects such as ink residues that adhere to the discharge port surface 200. In other words, the support member 306 is in the retracted position, as illustrated in
The first core member 307 is driven by a transport motor of the sheet member 305, and is configured to rotate in a direction R indicated in
In the present embodiment, the wiping direction is the direction in which the discharge port rows are arranged in the print head, but the configuration may be such that the movement is in a direction that intersects (is orthogonal to) the stated direction (the direction in which the discharge ports are arranged).
In the present embodiment, two wipers 310 and 311 are provided for wiping three discharge port rows (201 to 203 and 204 to 206), respectively, in
In the configuration illustrated in
In the present embodiment, the configuration is such that the wiping is performed only when the wiper moves in one direction, but the configuration may be such that the wiping is performed when the wiper moves in both the forward and backward directions.
The ink supply system 108 is held and fixed in a predetermined position in the body of the printing apparatus. In the present embodiment, a sub-tank 407 is provided vertically below the ink tank 103, and the sub-tank 407 includes a first hollow pipe 404 and a second hollow pipe 405 that extend vertically upward. The sub-tank 407 is also provided with an atmospheric communication port 406. The ink tank 103 has, in its bottom, a first joint part 402 and a second joint part 403. By inserting the first hollow pipe 404 into the first joint part 402 and the second hollow pipe 405 into the second joint part 403, the ink tank 103 and the atmosphere communicate through the atmospheric communication port 406.
The print head 101 is connected by the supply tube 102 to the sub-tank 407, which holds ink inside. During printing operations, ink is supplied from the sub-tank 407 through the supply tube 102 as needed as ink in the print head 101 is consumed by the ink being discharged from each discharge port. When ink in the sub-tank 407 is consumed, the liquid level in the sub-tank 407 first drops. Then, the ink level in the sub-tank 407 is separated from the bottom end of the first hollow pipe 404, and the ink tank 103 communicates with the atmosphere through the first hollow pipe 404. By communicating with the atmosphere, air is discharged from the atmospheric communication port 406 and the ink level in the ink tank 103 drops, causing the sub-tank 407 to be filled with ink again. When the liquid level rises to the same position as a vertical position indicated by B in
In addition, the vertical position and the like of the sub-tank 407 are set such that the ink level in the sub-tank 407 is below the discharge port surface 200 of the print head 101 in the direction of gravity. Accordingly, the pressure in the print head 101 is maintained at a negative pressure due to what is known as the “water head difference”. The vertical position and the like of the sub-tank 407 are set such that a meniscus formed at the ink discharge port is not broken by this negative pressure. Note that in the present embodiment, a height difference between the discharge port surface 200 and the ink level in the sub-tank 407, i.e., a water head difference H, is about 80 mm. An on/off valve 408 is provided in the supply tube 102 adjacent to the sub-tank 407, and opens and closes the ink channel constituted by the supply tube 102. When the ink jet printing apparatus is transported, the on/off valve 408 is closed to prevent ink from leaking and dripping from the discharge port. The foregoing has been an overview of the ink supply system using the water head difference method according to the present embodiment.
A pressurized method using a regulator and the like can be given as other ink supply methods, and the effects of the present embodiment can be achieved regardless of the supply method. In particular, in the water head difference method, the internal pressure in the print head is controlled only by the water head difference, and because the pressure fluctuation effect exerted by the ink dynamic pressure caused by carriage movement is large, the effects of the present embodiment are even more pronounced.
A control configuration for executing printing control of the ink jet printing apparatus will be described next.
In
A CPU 508, an input/output port 509, a storage device (ROM 510) that stores control programs and the like, RAM 511 that serves as a work area when performing various type of image processing, and non-volatile memory NVRAM 512 are provided in a printing control unit 507. The ROM 510 stores various types of data such as control programs for the CPU 508 and parameters necessary for printing operations. The RAM 511 is used as a work area for the CPU 508, and also temporarily stores various types of data such as image data received from the image input unit 502 and generated printing data. An image is formed by applying ink to the print medium from each discharge port of the print head 101 based on the image data converted in the printing control unit 507.
In addition, various types of motors 518 for operating the carriage and an LF (line feed), a suction operation motor 519, the print head 101, and corresponding drive circuits 513, 514, and 515, are connected to the printing control unit 507 through the input/output port 509. The suction operation motor 519 is a drive source for operating the suction pump 303 in order to suction and discharge ink from the print head 101 described with reference to
Internal pressure fluctuations in the print head 101 due to the movement of the carriage 104 will be described next.
In period A in
Next, in period B, the carriage 104 moves at a constant speed V1. At this time, no inertia acts on the ink, and thus the internal pressure in the print head 101 gradually decreases toward a reference pressure P0. Here, “reference pressure P0” is the internal pressure in the print head 101 when the carriage 104 is stationary, which in the present embodiment is −80 mmaq. Because the internal pressure in the print head 101 has increased in period A, the internal pressure in the print head 101 decreases toward the reference pressure P0 in period B in
Next, in periods C and D, the carriage 104 decelerates on the back position side, reverses direction, and then accelerates, moving in the opposite direction at a speed V2. In the present embodiment, the speed V2 is also set to 60 inches/sec.
Next, in period E, the carriage 104 moves at a constant speed, similar to period B. Because the internal pressure in the print head 101 is decreasing in period D, the internal pressure in the print head 101 increases toward the reference pressure P0 in period E in
Finally, in period F, deceleration is performed to stop the carriage 104 at a position above the recovery unit 107. The arrangement of the supply tube 102 at time TF (when the carriage stops) in
As described above, the internal pressure in the print head 101 is likely to be a positive pressure on the home position side where the recovery unit 107 is disposed. Accordingly, the effect of the present embodiment is greater if the supply tube 102 is connected from the back position side.
Here, the dynamic pressure of the ink in the tube can be expressed as follows:
Pn=(mn·an)/S . . . Formula (1)
mn: mass of ink subject to acceleration
S: cross-sectional area of supply tube
an: carriage acceleration
In this case, the ink mass at the time of maximum dynamic pressure can be expressed as follows:
mn=k·S·Ln . . . Formula (2)
k: relative density of ink
S: cross-sectional area of supply tube
Ln: maximum length of supply tube subject to inertia due to acceleration
By substituting Formula (2) into Formula (1), the following relationship is established:
Pn=k·Ln·an . . . Formula (3)
Here, “acceleration” is a difference between the carriage speed at the start of acceleration and the carriage speed at the end of acceleration, divided by an acceleration time. Similarly, “deceleration” is a difference between the carriage speed at the start of deceleration and the carriage speed at the end of deceleration, divided by a deceleration time. Both take the positive direction in the X axis in
From Formula (3), it can be seen that the ink dynamic pressure is proportional to the acceleration/deceleration. The acceleration/deceleration is affected mainly by the carriage speed during printing. If the carriage speed is increased to improve throughput, the acceleration/deceleration will also increase, and conversely, if the carriage speed is reduced to improve image quality, the acceleration/deceleration will also decrease.
From Formula (3), it can also be seen that the ink dynamic pressure is proportional to the maximum length of the tube subjected to inertia due to acceleration. Accordingly, when the carriage 104 accelerates or decelerates on the home position side in an ink jet printing apparatus having a tube arrangement such as that illustrated in
Based on the foregoing, the range of the increase in the internal pressure in the print head due to carriage acceleration/deceleration on the home position side may be greater than the range of the decrease in the internal pressure in the print head due to carriage acceleration/deceleration on the back position side and the range of the increase in the internal pressure in the print head during movement at a constant speed. At this time, the internal pressure in the print head due to carriage acceleration/deceleration on the home position side remains at least the reference pressure P0.
Even in a system in which the print head and ink tank are integrated, this effect can be achieved if part of the ink channel has a section that is substantially parallel to the movement direction of the carriage. However, the effect of the present embodiment is greater in systems where ink is supplied from the ink tank to the print head by a supply tube.
Control for setting a wait time from the carriage stop to the start of the wiping operations, which is a characteristic part of the present embodiment, will be described next.
As illustrated in
Accordingly, in the present embodiment, a wait time is provided in a state where the carriage is stopped, until the internal pressure in the print head drops from a positive pressure to a negative pressure, and the wiping operations are shifted to after the wait time. If a wait time of T802 (sec) or longer from time T802a to time T802b in
As illustrated in
Furthermore, this wait time can be optimized according to the scan width and the printing strike density (also called “duty” hereinafter). “Printing strike density” refers to the ratio (%) of ink dots applied to a predetermined region during the movement of the carriage in the present embodiment, and applying one ink dot to a region of 1/1200 inch square (a 1200-dpi square) is defined as a duty of 100%.
While the carriage moves at a constant speed, the internal pressure in the print head converges on the reference pressure P0. Here, “reference pressure P0” is the pressure in the print head 101 when the carriage is at rest (−80 (mmaq)). When the internal pressure in the print head in period D illustrated in
On the other hand, the shorter the scan width is immediately before the wiping operations and the shorter the period E in which the carriage moves at a constant speed is, the smaller the range of the drop in the internal pressure in the print head becomes, and the internal pressure does not converge on the reference pressure P0. Accordingly, the carriage starts decelerating in period F without the internal pressure in the print head having dropped sufficiently, and the internal pressure in the print head after the carriage stops is high. Accordingly, in the present embodiment, control is performed such that the shorter the scan width is immediately before the wiping operations, the longer the wait time is before the wiping operations.
In addition, a higher duty during printing means that more ink is discharged from the print head. In other words, not only is ink returned from inside the print head to the tank side through the supply tube while the carriage is moving at a constant speed, but ink in the print head also decreases as a result of the discharge. The internal pressure in the print head is therefore more likely to decrease when the duty is high. Accordingly, in the present embodiment, when the carriage is stopped for wiping operations, control is performed such that the higher the duty is in the scan, the shorter the wait time is until the wiping operations.
In the present embodiment, the wait time is determined by all the factors of carriage deceleration, scan width, and printing strike volume.
In step S901, at the start of printing, a carriage deceleration a, a scan width w, and a printing strike density (duty) d in that printing mode are obtained. In step S902, a wait time Tw during the stop before wiping is determined from these values based on the table in
In the present embodiment, for example, when the carriage deceleration is 400 (inches/sec2) or more, the scan width is 36 (inches), and the duty is 50 (%), the wait time is set to 2.9 (sec).
After printing starts in step S903, the carriage is accelerated in step S904.
In step S905, it is determined whether wiping is to be performed after the scan is completed. Specifically, the number of dots discharged from the print head in the printing operations is counted as a dot count value, and when this count value exceeds a predetermined value, it is determined that wiping is to be performed. Alternatively, the time since the last time wiping was performed is counted as a timer count value, and when this count value exceeds a predetermined value, it is determined that wiping is to be performed. The dot count value or the timer count value is cleared (set to 0) after the wiping. If wiping is determined to be performed through the above determination method, the carriage is stopped in step S906, the apparatus waits for the wait time Tw to pass in step S908, and the wiping is performed in step S909.
On the other hand, if it is determined in step S905 that wiping is not to be performed after the end of scanning, the carriage is stopped at the deceleration a in step S907.
In step S910, it is determined whether to end the printing. If not, the sequence returns to step S904, and if so, the operations of this flow end.
As described thus far, according to the present embodiment, a wait time until the internal pressure in the print head drops from a positive pressure to a negative pressure is provided in a carriage stopped state according to the deceleration for stopping the carriage, the scan width, and the printing strike density, and wiping is performed after the wait time. This makes it possible to suppress situations where ink leaks and drips from the discharge ports onto the print medium or the like, even if the carriage starts moving again after the wiping.
Although a specific time has been given for the wait time, the wait time is not limited to the above value, as long as the wait time is longer than the time required for the internal pressure in the print head to drop from a positive pressure to a negative pressure.
Additionally, although the determination as to whether to perform wiping is made in step S905, the number of scans the carriage makes before wiping may be set in advance, such as every time or every several times the carriage is moved to the home position.
Additionally, if the internal pressure in the print head does not become positive immediately after the carriage stops at less than a predetermined carriage deceleration (e.g., less than 100 (inches/sec2)), the wait time may be set to 0 (sec).
In the present embodiment, as illustrated in
Additionally, in the present embodiment, the wait time is determined by referring to all three factors of carriage deceleration, scan width, and duty, but it is sufficient to determine the wait time based on at least one of these factors.
Here, the “carriage deceleration” may be obtained by referring to a signal for carriage speed control, or by referring to the results of real-time measurements using an accelerometer or the like.
A second embodiment will be described next. The second embodiment will describe a method for controlling the carriage deceleration when the carriage is stopped to perform wiping operations.
The following will describe a case where printing is performed using a printing mode having the carriage speed profile indicated by data 1001 in
Because it is necessary for the carriage to move to the recovery unit in order to shift to the wiping operations, the carriage movement distance is longer in scans 7 and 9 than in scans 1, 3, and 5. If the deceleration in scan 7 is, for example, the same as the deceleration in
Accordingly, in the present embodiment, when the carriage deceleration is such that the internal pressure in the print head after the carriage stops becomes a positive pressure, the carriage deceleration is switched to a smaller value when performing the wiping operations than the carriage deceleration when the wiping operations are not performed. In addition, as described in the first embodiment, the shorter the scan width is or the lower the duty is, the higher the internal pressure in the print head becomes when the carriage stops. Accordingly, furthermore, in the present embodiment, control is performed such that the shorter the scan width is or the lower the duty is in the printing operations, the lower the carriage deceleration is after the switch.
Whether to switch the carriage deceleration at which the carriage is stopped when performing the wiping operations is determined according to whether a predetermined carriage deceleration is exceeded. The predetermined carriage deceleration is a carriage deceleration at which the internal pressure in the print head does not become a positive pressure when the carriage stops.
Data 1101 in
In
After printing starts in step S1203, the carriage is accelerated in step S1204.
In step S1205, it is determined whether wiping is to be performed after the scan is completed. Whether wiping is needed is determined by a similar method as in the first embodiment. If it is determined that wiping is to be performed, the carriage is stopped at the carriage deceleration aw in step S1206, and wiping is then performed in step S1208.
On the other hand, if it is determined in step S1205 that wiping is not to be performed after the end of scanning, the carriage is stopped at the deceleration a in step S1207.
In step S1209, it is determined whether to end the printing. If not, the sequence returns to step S1204, and if so, the operations of this flow end.
As described thus far, according to the present embodiment, if the deceleration of the carriage during normal printing is such that the internal pressure in the print head after the carriage stops is a positive pressure, the following operations are performed. That is, the carriage deceleration when wiping operations are performed is switched to a lower value than the carriage deceleration when the wiping operations are not performed. This makes it possible to suppress situations where ink leaks and drips from the discharge ports onto the print medium or the like, even if the carriage starts moving again after the wiping.
Although a specific deceleration is indicated for the carriage deceleration when the wiping operations are performed, the deceleration is not limited to the above value, as long as the carriage deceleration does not cause the internal pressure in the head to become a positive pressure after the carriage stops.
Additionally, although the descriptions of the present embodiment assume that the carriage speed is constant, the carriage speed may also be switched during a scan when the carriage is stopped for wiping operations.
Additionally, in the present embodiment, the carriage speed profile is switched for a scan in which the carriage is stopped for wiping operations. However, the carriage speed profile may be switched for a plurality of scans including a scan in which the carriage is stopped for wiping operations.
Additionally, in the present embodiment, the carriage deceleration immediately before wiping is determined by referring to all three factors of carriage deceleration, scan width, and duty, but it is sufficient to determine the carriage deceleration aw based on at least one of these factors.
In the present embodiment, the carriage deceleration immediately before wiping is determined by providing two levels each for the carriage deceleration, the scan width, and the duty, but each of these may be divided into a greater number of levels.
Although the present embodiment describes a case of shifting to wiping operations in the middle of printing, the same applies to a case of shifting to wiping operations after the end of carriage movement outside of the printing operations.
A third embodiment will be described next. The third embodiment will describe control for setting a carriage stop time after wiping operations are performed following the carriage stopping.
Assume that the time when the carriage, which had been moving at a speed V803, decelerates at a deceleration a803 and stops above the recovery unit is T803. Assume also that a time from when wiping is performed to when the wiping ends is T803y, and a time from a time T803a when wiping ends to a time T803b when the internal pressure in the print head reaches 0 is T803c.
Additionally, assume that the time when the carriage, which had been moving at a speed V804, decelerates at a deceleration a804 (a804>a803) and stops above the recovery unit is T804. Assume also that a time from when wiping is performed to when the wiping ends is T804y, and a time from a time T804a when wiping ends to a time T804b when the internal pressure in the print head reaches 0 is T804c.
As illustrated in
Accordingly, in the present embodiment, a wait time is provided in a state where the carriage is stopped, from after the wiping is performed following the carriage stopping until the internal pressure in the print head drops from a positive pressure to a negative pressure.
Additionally, as illustrated in
Furthermore, this wait time can be optimized according to the scan width and the printing strike density.
In
In the present embodiment, for example, when the carriage deceleration is 400 (inches/sec2) or more, the scan width is 36 (inches), and the duty is 50 (%), the wait time is set to 2.9 (sec).
After printing starts in step S1403, the carriage is accelerated in step S1404.
In step S1405, it is determined whether wiping is to be performed after the scan is completed. Specifically, the number of dots discharged from the print head in the printing operations is counted as a dot count value, and when this count value exceeds a predetermined value, it is determined that wiping is to be performed. Alternatively, the time since the last time wiping was performed is counted as a timer count value, and when this count value exceeds a predetermined value, it is determined that wiping is to be performed. The dot count value or the timer count value is cleared (set to 0) after the wiping. If wiping is determined to be performed through the above determination method, the carriage is stopped in step S1406, the wiping is performed in step S1408, and the movement of the carriage is stopped during the wait time Tw in step S1409.
On the other hand, if it is determined in step S1405 that wiping is not to be performed after the end of scanning, the carriage is stopped at the deceleration a in step S1407.
In step S1410, it is determined whether to end the printing. If not, the sequence returns to step S1404, and if so, the operations of this flow end.
As described thus far, according to the present embodiment, a wait time for putting the carriage into a stopped state until the internal pressure in the print head drops from a positive pressure to a negative pressure is provided after wiping is performed following the carriage stopping, according to the deceleration at which the carriage is stopped. This makes it possible to suppress situations where ink leaks and drips from the discharge ports onto the print medium or the like, even if the carriage starts moving again after the wiping. Although a specific time has been given for the wait time, the wait time is not limited to the above value, as long as the wait time is longer than the time required for the internal pressure in the print head to drop from a positive pressure to a negative pressure.
Additionally, although the determination as to whether to perform wiping is made in step S1405, the number of scans the carriage makes before wiping may be set in advance, such as every time or every several times the carriage is moved to the home position.
A fourth embodiment will be described next. The fourth embodiment will describe control for setting a carriage stop time after wiping operations are performed at a low speed immediately before the carriage stops.
Assume that a time when wiping is started at low speed, immediately before the carriage, which had been moving at a speed V805, decelerates at a deceleration a805 and stops above the recovery unit, is T805. Assume also that a time from when wiping is performed to when the wiping ends is T805y, and the time from a time T805a when the wiping ends to a time T805b when the internal pressure in the print head reaches 0 is T805c.
Additionally, assume that a time when wiping is started at low speed, immediately before the carriage, which had been moving at a speed V806, decelerates at a deceleration a806 (a806>a805) and stops above the recovery unit, is T806. Assume also that a time from when wiping is performed to when the wiping ends is T806y, and the time from a time T806a when the wiping ends to a time T806b when the internal pressure in the print head reaches 0 is T806c.
As illustrated in
Accordingly, in the present embodiment, a wait time is provided in a state where the carriage is stopped, from after the wiping is performed at low speed immediately before the carriage stops until the internal pressure in the print head drops from a positive pressure to a negative pressure. As in the third embodiment,
Additionally, as illustrated in
Furthermore, this wait time can be optimized according to the scan width and the printing strike density, similar to the first and third embodiments.
As described thus far, according to the present embodiment, a wait time in a carriage stopped state until the internal pressure in the print head drops from a positive pressure to a negative pressure is provided after wiping is performed at low speed immediately before the carriage stops, according to the deceleration at which the carriage is stopped. This makes it possible to suppress situations where ink leaks and drips from the discharge ports onto the print medium or the like, even if the carriage starts moving again after the wiping. Furthermore, because wiping is performed before the carriage stops, the time required for the carriage to start decelerating and then accelerate again after the wiping is performed is shorter than in the foregoing embodiments, which improves throughput. Accordingly, this is particularly desirable when wiping is performed frequently, such as every time or every several times the carriage is moved to the home position.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2021-094575, filed Jun. 4, 2021, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-094575 | Jun 2021 | JP | national |
