Patent Publication Number: US-7914101-B2

Title: Ink jet printing apparatus with ink stirring by carriage reciprocation

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a so-called serial scan type ink jet printing apparatus. 
     2. Description of the Related Art 
     Known ink jet printing apparatuses print images by using an ink tank that accommodates pigment ink and a print head that ejects the pigment ink fed from the ink tank. The pigment ink tends to have its pigment component precipitated to the bottom of the ink tank. The precipitated pigment component may produce an area with a higher ink concentration and an area with a lower ink concentration in the ink tank. 
     Japanese Patent Laid-Open No. 2005-066520 describes an ink jet printing apparatus that performs printing operations by moving a carriage equipped with a print head and an ink tank. The printing apparatus utilizes the inertia force of the carriage during a printing operation to allow a stirrer in the ink tank to stir the ink. According to Japanese Patent Laid-Open No. 2005-066520, the stirrer is integrated with a case of the ink tank by molding. The stirrer extends in the case of the ink tank so as to hang down from its ceiling to bottom. The stirrer has a cylindrical weight formed at its lower end. The stirrer stirs the ink in the ink tank by swinging around its root on the ceiling of the case in the same direction in which the carriage moves, under an inertia force resulting from operations of the carriage including acceleration, stoppage, and reversal. 
     Japanese Patent Laid-Open No. 2005-066520 describes a stirrer that is freely movable on an inner bottom surface of an ink tank instead of being fixed to its case. The stirrer stirs the ink in the ink tank by moving on the bottom surface of the ink tank under an inertia force resulting from operations of the carriage including acceleration, stoppage, and reversal. 
     Japanese Patent Laid-Open No. 2004-216761 discloses a stirring mechanism comprising a shaft-like weight that swings around a swinging central shaft in a lateral direction under an inertia force resulting from movement of the carriage and a plurality of fins that swing in the lateral direction integrally with the shaft-like weight. The plurality of fins are juxtaposed in the height direction of an ink tank to evenly stir the ink in the ink tank from its upper layer to lower layer. 
     A known method for stirring a pigment component precipitated to the bottom of an ink tank provides a moving object or a space in the ink tank to stir the ink utilizing operations of the carriage in the ink jet printing apparatus. 
     Japanese Patent Laid-Open No. 09-309212 and U.S. Pat. No. 6,062,682 describe a configuration that moves a carriage to stir ink, upon receiving a signal for powering on the printing apparatus, a print signal, or a cleaning signal. A predetermined printing operation and an operation of cleaning a print head are performed after a stirring operation. These documents also describe a configuration that detects the time for which a printing operation is stopped. If the printing operation is stopped for at least a predetermined time (hereinafter referred to as a “stirring operation wait time”)), a stirring operation is performed to prevent the precipitation of a pigment component. 
     As described in Japanese Patent Laid-Open No. 09-309212, if a printing operation is stopped for at least the predetermined time (stirring operation wait time) to keep the ink tank stationary for at least a predetermined time, the ink needs to be sufficiently stirred before the subsequent printing operation or cleaning operation. This is required to achieve favorable printing results and to prevent a pigment component from being fixed in an ink channel. 
     However, the use period of the ink jet printing apparatus varies; the ink jet printing apparatus is often consecutively operated in very short periods. Obviously, a short printing operation may be repeated during the predetermined stirring operation wait time. Thus, with a simple scheme of waiting for at least the stirring operation wait time to pass before a stirring operation is performed, no stirring operation may be performed over a long period. In this case, the precipitation of the pigment component may progress to cause inappropriate printing in spite of the small amount of pigment component precipitated. 
     To prevent this problem, a very small value may be set for the stirring operation wait time, after which a stirring operation or a cleaning operation is performed. However, this increases the frequency at which a stirring operation or a cleaning operation is performed, possibly significantly reducing printing speed. 
     Further, the cleaning operation may include an operation (suction recovering operation) of sucking and discharging ink not contributing to image printing from nozzles in order to avoid blockage in nozzles in the print head and to discharge bubbles mixed into the ink channel. In this case, a suction recovering operation may be performed a predetermined time after the execution of the last suction recovering operation. The suction recovering operation is effective for avoiding the adverse effect of precipitation of the pigment component in areas in the nozzles or ink channel which are not subjected to the stirring operation. However, it is very difficult to discharge all of the pigment component precipitated in the ink tank simply by means of the suction recovering operation. 
     Further, with a high carriage moving speed and a large printing amount for a printing operation, the ink in the ink tank on the carriage can be expected to be stirred during the printing operation. However, owing to the variation of the printing speed and amount, the ink in the ink tank is not always stirred. 
     SUMMARY OF THE INVENTION 
     The present invention provides a printing apparatus that can print appropriate images by efficiently stirring ink in an ink tank in accordance with its status to homogenize it. 
     In the first aspect of the present invention, there is provided an ink jet printing apparatus including a carriage on which a print head and an ink tank can be mounted, the print head being capable of ejecting ink on the basis of print data, the ink tank supplying ink to the print head, the ink jet printing apparatus performing a printing operation of printing an image on a print medium through reciprocations of the carriage, the apparatus comprising: measuring means for measuring an elapsed time from end of movement of the carriage; acquiring means for acquiring information correlated with the degree of ink stirring involved in the printing operation performed after the carriage movement has been finished; setting means for, if the elapsed time is shorter than a specified time, setting conditions for carriage movement for stirring the ink in the ink tank on the basis of the information acquired; and control means for reciprocating the carriage in accordance with the set movement conditions. 
     In the second aspect of the present invention, there is provided an ink jet printing apparatus including a carriage on which a print head and an ink tank can be mounted, the print head being capable of ejecting ink, the ink tank supplying ink to the print head, the ink jet printing apparatus performing a printing operation of printing an image on a print medium through reciprocations of the carriage, the apparatus comprising: measuring means for measuring an elapsed time from end of movement of the carriage; acquiring means for acquiring information on conditions for carriage movement involved in the printing operation performed after the carriage movement has been finished; setting means for, if the elapsed time is shorter than a specified time, setting the conditions for carriage movement for stirring the ink in the ink tank on the basis of the information acquired; and control means for reciprocating the carriage in accordance with the set movement conditions after the printing operation. 
     The present invention measures the elapsed time from the end of reciprocation of the carriage, on which the print head and ink tank can be mounted. Then, when the measured elapsed time is shorter than a specified time, the condition under which the carriage is reciprocated so as to stir the ink in the ink tank is set in accordance with the printing amount based on a printing operation. Then, the carriage is reciprocated in accordance with the condition for reciprocations to enable the ink in the ink tank to be efficiently stirred in accordance with its status. This enables the ink such as pigment ink in the ink tank to be homogenized, allowing appropriate images to be printed. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flowchart illustrating operations of an ink jet printing apparatus in accordance with a first embodiment of the present invention; 
         FIG. 2  is a perspective view of the appearance of the ink jet printing apparatus in accordance with the first embodiment of the present invention; 
         FIG. 3  is a perspective view illustrating a mechanism inside the main body of the ink jet printing apparatus in  FIG. 2 ; 
         FIG. 4  is a perspective view of an ink tank in  FIG. 3 ; 
         FIG. 5  is a perspective view illustrating the internal configuration of the ink tank in  FIG. 4 ; 
         FIG. 6  is an exploded perspective view of the ink tank in  FIG. 3 ; 
         FIG. 7  is a block diagram of a control system in the ink jet printing apparatus in  FIG. 2 ; and 
         FIG. 8  is a flowchart illustrating operations of an ink jet printing apparatus in accordance with a second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Detailed embodiments of the present invention will be described below with reference to the drawings. 
     First Embodiment 
     First, description will be given of an ink jet printing apparatus provided with an ink tank in accordance with present invention. 
     The ink jet printing apparatus is based on a non-impact printing scheme which enables high-speed printing and printing of various print media and which minimizes noise during printing. As shown in  FIG. 2 , the basic configuration of the ink jet printing apparatus includes an apparatus body M 1000 , a feeding section M 3022  that feeds a print medium such as a sheet, and a sheet discharging tray M 1004 . A printing operation mechanism is constructed inside the apparatus body M 1000  as shown in  FIG. 3 . An ink jet print head  6  and an ink tank T 2000  are releasably mounted on a carriage  1 ; the ink jet print head  6  performs a desired printing operation on a print sheet (print medium)  5  conveyed to a print position and the ink tank T 2000  stores ink to be supplied to the print head  6 . The carriage  1  with the print head  6  and ink tank T 2000  mounted thereon is reciprocated along a guide shaft  4  in a main scanning direction by the driving force of a carriage motor  3  transmitted via a timing belt  2 ; the main scanning direction is shown by an arrow X. The print sheet  5  is conveyed in a sub-scanning direction shown by an arrow Y and which crosses (in the present example, which is orthogonal to) the main scanning direction. 
     The ink tank T 2000  is releasable from the print head  6 . The print head  6  ejects ink droplets from ejection ports using electrothermal conversion elements (heaters) formed of heating resistors, piezo elements, or the like. With electrothermal conversion element, ink in nozzle is heated by the element to cause bubbling so that the resulting bubbling energy can be used to eject ink droplet from the ejection port. 
     A capping device  8  is provided at a home position of the print head  6 . The capping device  8  has a cap that covers nozzles in the print head  6  having moved to its home position. This prevents the possible evaporation of ink from the nozzles and the fixation of ink in the nozzles. A suction pump (not shown) is connected to the cap through a tube to introduce a negative pressure into the cap covering the nozzles. This enable ink not contributing to image printing to be sucked and discharged from the nozzles (suction recovering operation). Reference numeral  9  denotes a blade that moves relative to the print head  6  to wipe off a surface of the print head  6  in which ejection ports are formed. The ink not contributing to image printing can also be ejected from the nozzles toward the interior of the cap (preliminary ejection). A cleaning operation for cleaning the nozzles and ink channels in the print head  6  may include the suction recovering operation, the wiping operation, and the preliminary ejecting operation. 
     To print an image, a printing scan performed by the print head  6  and an operation of conveying the print sheet  5  are repeated. In the printing scan, the print head  6  ejects ink from the ejection ports on the basis of image data while moving in the main scanning direction together with the carriage  1 . In the conveying operation, the print sheet  5  is conveyed in the sub-scanning direction by a predetermined amount. 
       FIG. 7  is a block diagram of a control system in the printing apparatus M 1000 . A CPU  100  executes a process for controlling a stirring operation described below, data processing, and the like. A ROM  101  stores programs for the procedures of the above processes. A RAM  102  is used as a work area in which the processes are executed. Ink ejection from the print head  6  is performed by the CPU  100  by supplying a head driver  6 A with driving data (image data) and driving control signals (heat pulse signals) for the electrothermal converters or the like. The CPU  100  controls, via a motor driver  3 A, the carriage motor  3 , which drives the carriage  1  in the main scanning direction. The CPU  100  also controls, via a motor driver  104 A, a P. F motor  104  that conveys the print sheet  5  in the sub-scanning direction. 
       FIG. 4  is a perspective view of the appearance of the ink tank T 2000 .  FIG. 5  is a perspective view illustrating the internal configuration of the ink tank T 2000 .  FIG. 6  is an exploded perspective view of the ink tank T 2000 . 
     The ink tank T 2000  is a liquid housing container that houses liquid ink. As shown in  FIG. 4 , the ink tank T 2000  includes a container body T 2017  and a cover T 2018 , with an ink housing chamber formed inside the container body T 2017  and cover T 2018 . The ink tank T 2000  has an ink supply port T 2002  formed in a bottom surface thereof to supply ink to the print head  6 . The ink tank T 2000  further includes a spring T 2005 , a plate T 2022 , a flexible film T 2004 , a meniscus former T 2020 , a retainer plate  2021 , and a stirrer (stirring member) T 2015  as shown in  FIG. 6 . 
     The container body T 2017  is formed of, for example, polypropylene. As shown in  FIG. 6 , the meniscus former T 2020  is provided at the ink supply port T 2002  at the bottom of the container body T 2017 . The retainer plate T 2021  is fitted around the meniscus former T 2020 . The meniscus former T 2020  comprises, for example, a capillary formed of a fibrous material such as polypropylene or a combination of the capillary and a filter. The filter has a permeation size of about 15 to 30 μm and is made of, for example, a stainless material or polypropylene. The interiors of the meniscus former T 2020  and container body T 2017  are in communication with each other through an ink channel T 2019 . This allows ink meniscus to be formed so as to prevent the possible entry of bubbles into an ink housing chamber described below. 
     A peripheral edge of the flexible film T 2004  is soldered to an opening periphery T 2016  of the container body T 2017 . This forms an ink housing chamber that houses ink, between an inner wall of the container body T 2017  and the flexible film T 2004 . The flexible film T 2004  comprises, for example, a film including a thin polypropylene film (thickness: about 20 to 100 μm). The flexible film T 2004  is urged outward by the spring T 2005  via the plate T 2022 . This generates a negative pressure in the ink housing chamber. Both the spring T 2005  and plate T 2022  are formed of, for example, a stainless material. The cover T 2018  is set in the opening of the container body T 2017  to protect the flexible film T 2004 , which projects outward. The cover T 2018  has an air communicating portion (not shown) that sets the inside of the cover T 2018 , separated from the ink housing chamber by the flexible film T 2004 , at the atmospheric pressure. 
     The ink in the ink housing chamber is fed to the print head  6  through the ink supply port T 2002 . Consumption of the ink contracts the spring T 2005  while flexing the flexible film T 2004 , to reduce the volume of the ink housing chamber. The plate T 2022  has an opening T 2027  to avoid interference with the support T 2023  described below. Thus, the ink in the ink housing chamber can be consumed until the plate T 2022  comes into contact with the container body T 2017 . 
     The stirrer T 2015  is provided with a supported end supported by the support T 2023  and a moving end that can be freely swung. The stirrer T 2015  can thus be swung in the main scanning direction, which is shown by an arrow X and in which the carriage  1  moves. The stirrer T 2015  is composed of a material (for example, SUS) having a specific gravity greater than that of ink. During a printing operation described below and a stirring operation, the stirrer T 2015  is swung by an inertia force resulting from the reciprocation of the carriage  1  to stir the ink in the ink housing chamber. The support T 2023  has a retainer T 2024  at a tip thereof to prevent the stirrer T 2015  from slipping out. 
       FIG. 1  is a flowchart illustrating operations performed by the ink jet printing apparatus M 1000  in order to stir the ink in the ink tank T 2000 . 
     An external apparatus (host apparatus) such as a personal computer (PC) inputs a print signal to the ink jet printing apparatus M 1000  (step S 1 ). When the print signal is input, the ink jet printing apparatus M 1000  loads the elapsed time T from the end of the last reciprocation of the carriage  1 , that is, the elapsed time T from the last stirring of the ink in the ink tank T 2000  (step S 2 ). The ink is stirred by the printing operation or the stirring operation, described below. The printing apparatus M 1000  or print head comprises a timer that measures the elapsed time T. 
     If the elapsed time T is shorter than a specified time T 1 , the printing operation is performed on the basis of the input print signal (step S 3 ). In the printing operation, an image is printed on the print sheet  5  in conjunction with the reciprocation of the carriage on the basis of the input print signal. In this case, the stirrer T 2015  swings to stir the ink in the ink housing chamber. The printing operation is repeated on print signals sequentially input by the host apparatus (steps S 3  and S 4 ). Once the series of printing operations are finished, the process shifts to step S 5  to acquire information correlated with the degree of ink stirring involved in the printing operations. The degree of ink stirring depends on the printing amount of the printing operations. Thus, in this case, the information correlated with the degree of ink stirring involved in the printing operations is information corresponding to the printing amount of the printing operations. Specifically, to obtain the information corresponding to the printing amount of the printing operations, the number of carriage reciprocations, that is, the number of scans, is read. The number of scans may be sequentially counted during the printing operation in step S 4  and stored in a storage element provided in the print head. In this case, the printing apparatus can load the contents stored in the storage element. 
     In step S 5 , a condition (in this case, the number of carriage movements) for the movement of the carriage made to stir the ink in the ink tank is set in accordance with the number of scans as the printing amount during the printing operation. That is, with a large number of scans, that is, a large printing amount during the printing operation (step S 3 ), the ink stirring during the printing operation is at a relatively high degree. Thus, in this case, the number of reciprocations of the carriage during a stirring operation (step S 6 ) is set at a relatively small value. For example, the number of reciprocations of the carriage during the stirring operation is set at 20. A sufficiently large printing amount eliminates the need for stirring. Thus, in this case, the number of reciprocations of the carriage during the stirring operation is set at 0. 
     On the other hand, with a small number of scans, that is, a small printing amount during the printing operation (step S 3 ), the ink stirring during the printing operation is at a relatively low degree. Thus, in this case, the number of reciprocations of the carriage during the stirring operation (step S 6 ) is set at a relatively large value. For example, the number of reciprocations of the carriage during the stirring operation is set at 50. 
     Subsequently, the carriage is reciprocated a set number of times to allow the stirrer T 2015  to stir the ink in the ink housing chamber (step S 6 ). At this time, since no image printing operation is performed, the reciprocation of the carriage in step S 6  is called a stirring operation. 
     Thus, the number of reciprocations of the carriage for the stirring operation (step S 6 ) is set in accordance with the degree of ink stirring during the printing operation (step S 3 ). This enables the ink in the ink housing chamber to be stirred using the stirrer T 2015 . As previously described, if a large number of scans are performed to sufficiently stir the ink during the printing operation (step S 3 ), the stirring operation (step S 6 ) need not be performed. 
     Now, description will be given of the significance of the stirring operation in steps S 5  and S 6 . If steps S 5  and S 6  are not provided, then after the printing operation in step S 3 , the process shifts to a standby state (step S 8 ) without performing any stirring operation. Then, if a printing operation with a very low degree of ink stirring which lasts for a time shorter than a specified time T 1 , precipitation of pigment in the ink tank gradually progresses. If the use state is repeated without performing any ink stirring operation, then when the ink is used up, dense ink deposited at the bottom of the ink tank is rapidly supplied to the print head to cause inappropriate printing. On the other hand, providing steps S 5  and S 6  allows a resetting operation to be performed, that is, makes the density of the pigment in the ink tank uniform, every time a printing operation is finished. This enables the ink in the ink tank to be used up without causing inappropriate printing in the above use environment. 
     After the stirring operation (step S 6 ) is finished, a timer is reset to measure the elapsed time T (step S 7 ). The timer starts measuring the elapsed time T at that point of time. Subsequently, to prevent the evaporation of the ink from the nozzles in the print head  6  and the fixation of the ink in the nozzles, the nozzles are covered by the capping device  8  of the ink jet printing apparatus M 1000  (step S 8 ). 
     On the other hand, if the elapsed time T is longer than the specified time T 1  in step S 2 , then in step S 9 , the carriage is reciprocated a predetermined number of times to stir the ink in the ink tank (stirring operation) before a printing operation. The nozzles are subsequently cleaned (step S 10 ). During the cleaning operation, a negative pressure is introduced into the cap covering the nozzles of the print head to suck and discharge the ink not contributing to image printing (suction recovering operation) as described above. The suction recovering operation allows a predetermined amount of ink in the ink channel and ink tank to be discharged. 
     Subsequently, a printing operation (steps S 11  and S 12 ) is performed as in the case of steps S 3  and S 4 , previously described. Timer resetting (step S 13 ) and capping (step S 14 ) are then performed as in the case of steps S 7  and S 8 , previously described. 
     If the elapsed time T from the end of the last carriage movement is short, the precipitation of a pigment component in the ink tank is at a relatively low degree and printing results are thus not virtually affected. Accordingly, if the elapsed time T is shorter than the specified time T 1 , then as in the case of step S 3 , a printing operation may be performed without a stirring operation, without posing any problem. In particular, with a large printing operation amount, the ink in the ink tank is sufficiently stirred to enable the inhibition of progress of the precipitation of the pigment component without the need for the stirring operation. On the other hand, with a short elapsed time T and a small printing operation amount, the stirring operation (step S 6 ) is performed after the printing operation (step S 3 ). Thus, the time from the input of a print signal until the end of printing does not include the time required for the stirring operation. Therefore, precipitation of the pigment component of the ink in the ink tank can be alleviated without sacrificing the printing speed. 
     Further, in place of the number of scans (the number of movements) of the carriage, a dot count value may be used as information corresponding to the printing amount. That is, ink jet printing apparatuses print images by ejecting ink droplets from the print head on the basis of input print signals. Accordingly, the number of ink droplets ejected, that is, the number of dots formed by the ink droplets, corresponds to the printing amount. Thus, the number of ink droplets is counted on the basis of print signals (print data) to obtain a dot count value, which can be used as information corresponding to the printing amount. That is, the number of reciprocations of the carriage during the stirring operation in step S 6  can be set in accordance with the dot count value. 
     Further, the present embodiment adopts information corresponding to the printing amount of printing operations as information correlated with the degree of ink stirring involved in the printing operations. However, the present invention is not limited to this. For example, carriage movement duration, which affects the degree of stirring, may be adopted as information correlated with the degree of ink stirring involved in the printing operations. 
     Second Embodiment 
       FIG. 8  is a flowchart illustrating a second embodiment of the present invention. Step S 5 A of determining the degree of ink stirring involved in printing operations in accordance with the present embodiment is different from step S 5  of the first embodiment. In  FIG. 8 , the same steps as those shown in  FIG. 1  are denoted by the same reference numerals and will not be described. 
     The stirrer T 2015 , provided in the ink tank, moves through the ink tank to stir the ink under an inertia force resulting from the reciprocation of the carriage. Thus, the movement range and moving speed of the stirrer T 2015  increase consistently with the magnitude of the inertia force acting on the stirrer T 2015 . Ink stirring efficiency increases consistently with the movement range and moving speed of the stirrer T 2015 . Accordingly, if the carriage moves at a high speed, the degree of ink stirring can be increased even with a small number of carriage movements during a printing operation. Thus, the ink stirring efficiency varies depending on the condition for carriage movements. 
     Thus, in the present embodiment, at step S 5 A, the ink jet printing apparatus loads a printing amount corresponding to a print signal and a print mode set on a driver (program) that controls the ink jet printing apparatus. Then, on the basis of this information, the number of reciprocations of the carriage during the stirring operation in step S 6  is set. That is, the present embodiment acquires information corresponding to the printing amount and information on the print mode, as information correlated with the degree of ink stirring involved in printing operations. 
     The print mode is set by selecting one of, for example, a high-speed print mode in which the carriage moves at a high speed, a normal print mode in which the carriage moves at a normal speed, and a high-quality print mode in which the carriage moves at a low speed. The moving speeds of the carriage in the high-speed print mode, normal print mode, and high-quality print mode are defined as Va, Vb, and Vc, respectively, and are in the relationship Va&gt;Vb&gt;Vc. The stirring operation amount required after a printing operation in the high-speed print mode (step S 3 ), that is, the number of reciprocations of the carriage during the stirring operation (step S 6 ), is defined as N(a). Similarly, the stirring operation amount required after a printing operation in the normal print mode (step S 3 ) and the stirring operation amount required after a printing operation in the high-quality print mode (step S 3 ) are defined as N(b) and N(c), respectively. The stirring operation amounts are set to be in the relationship N(c)&gt;N(b)&gt;N(a). 
     Thus, the stirring operation (step S 6 ) can be more efficiently performed by setting the stirring operation amount in accordance with the moving speed of the carriage during the printing operation (carriage moving condition). That is, a sufficient stirring effect can be exerted even with a small value set for the number of reciprocations required to stir the ink. 
     The present embodiment acquires information corresponding to the printing amount and information on the print mode, as information correlated with the degree of ink stirring involved in printing operations. However, it is possible that with the acquisition of the information corresponding to the printing amount avoided, only the information on the print mode, that is, the information on carriage movement conditions, is acquired. 
     Other Embodiments 
     In the description of the first and second embodiments, the number of carriage movements is set as the condition for carriage movements for the stirring operation. However, in the present invention, the movement condition for the carriage for the stirring operation is not limited to this. The degree of ink stirring varies depending on the moving distance, moving speed, acceleration, and moving time of the carriage. Thus, one of the moving distances, moving speed, acceleration, and moving time of the carriage may be set as the movement condition for the carriage for the stirring operation. 
     The first and second embodiments adopts the information corresponding to the printing amount of printing operations or the information on the carriage movement conditions (movement count and movement speed), as information correlated with the degree of ink stirring involved in the printing operations. However, the present invention is not limited to this example. For example, if the carriage movement conditions vary depending on the type of the print medium used to print images, the number of carriage reciprocations for ink stirring may be set on the basis of the type of the print medium. That is, information on the type of the print medium is used as information correlated with the degree of ink stirring involved in the printing operation. Moreover, the information on the type of the print medium may be combined with the printing amount, carriage movement conditions, print mode, or the like for the printing operation. 
     The information correlated with the degree of ink stirring involved in the printing operation includes at least one of the printing amount of the printing operation, the information on the carriage movement condition for the printing operation, the information on the print mode, and the information on the type of the print medium. 
     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. 2006-130794, filed May 9, 2006, which is hereby incorporated by reference herein in its entirety.