Patent Publication Number: US-8540339-B2

Title: Ink jet printing apparatus with ink stirring operation

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink jet printing apparatus which print an image by moving a carriage that can mount an ink tank. 
     2. Description of the Related Art 
     A pigment ink has higher weatherability than a dye ink and is therefore beginning to be used on ink jet printing apparatus in recent years. The weatherability includes lightfastness, ozone resistance and waterfastness. Pigment particles contained in the pigment ink do not easily lose their color saturation if decomposed by light or ozone and their colors do not fade if exposed to light or ozone for a long period of time. Thus, the pigment ink shows its particularly excellent performance when used for the printing of outdoor advertisements and exhibits that are displayed for long periods or of pictures that need to be stored for long period. Further, since pigment particles are not water-soluble, the pigment ink has better waterfastness than dye ink. Because of these advantages, the oil-based pigment inks are widely used. 
     Generally, ink jet printing apparatus often use water-based ink. To make water-soluble those color materials not soluble in water, such as pigments, requires rendering the pigment particles hydrophilic by using polymer resins or surfactants and dispersing them in water or other solvent components. 
     If a pigment is used as an ink colorant and accommodated in an ink tank or other container and left unused, the pigment will deposit at the bottom of the ink tank, changing an ink concentration which will unavoidably become non-uniform. Solid particles such as pigment are suspended in a liquid as fine particles. If their specific gravity is greater than that of the solvent (medium), it is known from the following equation (1) that the particles will settle.
 
 u= 2 r 2(ρ 2 −ρ 1 ) g /9η  (1)
 
     Where u is a settling rate of particles, r is a radius of particles when the pigment particles are assumed to be spherical, ρ 1  is density of medium (solvent), ρ 2  is density of particles, g is a gravitational acceleration and η is a viscosity coefficient of the medium. The equation (1) is called Navier-Stokes&#39; equation. The equation (1) also shows that the water-based pigment ink with water as a main component of medium has a faster setting rate than that of the oil-based pigment ink. It is noted, however, that the pigment particles are subjected to a thermal motion of medium molecules in addition to the settling action by gravity and therefore are continuously in the Brownian motion. This Brownian motion causes the pigment particles to disperse, an action opposing the settling action, to realize a uniform particle distribution. This means that the pigment particles do not always settle according to the above equation (1). By improving the degree of hydrophilicity of pigment, i.e., the level of pigment diffusion in solvent, a pigment ink can be produced whose pigment particles will not easily deposit. However, the pigment particles still settle gradually in small numbers. 
     When the pigment particles settle, the property of the pigment ink, such as colorant concentration, viscosity and specific gravity, will change. In the ink jet printing apparatus, changes in a colorant concentration of the pigment ink lead directly to a color change in images, and changes in ink viscosity and specific gravity affect an injection volume and an injection speed of ink. 
     Therefore, in the ink jet printing apparatus using pigment inks, it is important to make the pigment ink concentration uniform in the ink tank. 
     As a method for making the pigment ink concentration in an ink tank uniform, it is known to directly stir ink in the ink tank. For example, Japanese Patent Laid-Open No. 4-087250 describes a method in which a reciprocally movable carriage mounting a print head and an ink tank is moved before a printing operation or at specified time intervals to agitate the ink in the ink tank. Another Japanese Patent Laid-Open No. 5-338195 discloses a method which rotates or reverses an ink tank by a motor to change the direction of gravity acting in the ink tank to prevent the sedimentation of pigment particles. Further, to ensure the effectiveness of the ink stirring, Japanese Patent Laid-Open Nos. 4-169240 and 9-309212 disclose a method that uses a steel ball in the ink tank to facilitate the stirring of ink. 
     If left unused for many hours, the color material in the ink in an ink jet printing apparatus settles, causing the ink concentration in an upper part of the ink tank to decrease and that of a lower part to increase, with the result that the ink concentration becomes non-uniform in the ink tank. If a recovery operation to maintain a good ink ejection performance of the print head is performed by discharging an ink, that does not contribute to the image printing, from a print head connected to the lower part of the ink tank, the high concentration ink is discharged from the ink tank. As a result, the colorant concentration in the ink tank gradually falls causing density variations in a printed image, which may lead to image impairments. The stirring operation, such as described in the above-cited references, can indeed alleviate the ink concentration changes in the ink tank or ink supply paths. 
     However, none of the patent documents cited above proposes a shortening of the time for stirring operation performed before the start of the printing operation. 
     SUMMARY OF THE INVENTION 
     The present invention provides an ink jet printing apparatus which can reduce the time for stirring operation performed before the start of the printing operation and stir ink efficiently. 
     In a first aspect of the present invention, there is provided an ink jet printing apparatus for printing an image by a reciprocal movement of a carriage, the carriage being capable of mounting an ink tank to supply ink to an ink ejection portion, the ink jet printing apparatus comprising: means for executing a stir operation of stirring the ink in the ink tank, the stir operation being executed by a reciprocal movement of the carriage during a non-printing operation excluding a print operation accompanied by a reciprocal movement of the carriage, wherein at least a part of the stir operation is executed in parallel with at least one specific operation among a plurality of operations executed by the ink jet printing apparatus. 
     In a second aspect of the present invention, there is provided an ink jet printing apparatus for printing an image by a reciprocal movement of a carriage, the carriage being capable of mounting an ink tank to supply pigment ink to an ink ejection portion, the ink jet printing apparatus comprising: means for executing a stir operation of stirring the pigment ink in the ink tank, the stir operation being executed by a reciprocal movement of the carriage during a non-printing operation excluding a print operation accompanied by a reciprocal movement of the carriage; a cap capable of receiving the pigment ink ejected from the ink ejection portion; and means for executing a discharge operation of discharging the pigment ink received in the cap, wherein the stir operation is executed in parallel with the discharge operation. 
     With this invention, the stirring operation for stirring ink in the ink tank can be executed efficiently in terms of time by performing at least a part of the stirring operation in parallel with processing that the ink jet printing apparatus executes during a non-printing operation. This can render a concentration of ink uniform in the ink tank, assuring a printing of quality images. 
     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 diagram for explaining a flow in which image data are processed in a printing system to which an embodiment of the present invention is applied. 
         FIG. 2  is an explanatory diagram showing an example of a configuration of print data transferred from a printer driver of a host apparatus to a printing apparatus in the printing system shown in  FIG. 1 . 
         FIG. 3  is a diagram showing output patterns which correspond to input levels, and which are obtained by conversion in a dot arrangement patterning process in the printing apparatus used in the embodiment. 
         FIG. 4  is a schematic diagram for explaining a multi-pass printing method which is performed by the printing apparatus used in the embodiment. 
         FIG. 5  is an explanatory diagram showing an example of mask patterns which are applied to the multi-pass printing method which is performed by the printing apparatus used in the embodiment. 
         FIG. 6  is a perspective view of the printing apparatus used in the embodiment, and shows the printing apparatus in an unused condition when viewed from the front. 
         FIG. 7  is another perspective view of the printing apparatus used in the embodiment, and shows the printing apparatus in the unused condition when viewed from the back. 
         FIG. 8  is yet another perspective view of the printing apparatus used in the embodiment, and shows the printing apparatus in a used condition when viewed from the front. 
         FIG. 9  is a diagram for explaining an internal mechanism of the main body of the printing apparatus used in the embodiment, and is a perspective view showing the printing apparatus when viewed from the right above. 
         FIG. 10  is another diagram for explaining the internal mechanism of the main body of the printing apparatus used in the embodiment, and is another perspective view showing the printing apparatus when viewed from the left above. 
         FIG. 11  is a side, cross-sectional view of the main body of the printing apparatus used in the embodiment for the purpose of explaining the internal mechanism of the main body of the printing apparatus. 
         FIG. 12  is yet another perspective view of the printing apparatus used in the embodiment, and shows the printing apparatus in the process of performing a flat-pass printing operation when viewed from the front. 
         FIG. 13  is still another perspective view of the printing apparatus used in the embodiment, and shows the printing apparatus in the process of performing the flat-pass printing operation when viewed from the back. 
         FIG. 14  is a schematic, side, cross-sectional view of the internal mechanism for explaining the flat-pass printing operation performed in the embodiment. 
         FIG. 15  is a perspective view showing a cleaning section in the main body of the printing apparatus used in the embodiment. 
         FIG. 16  is a cross-sectional view of a wiper portion in the cleaning section shown in  FIG. 15  for explaining a configuration and an operation of the wiper portion. 
         FIG. 17  is a cross-sectional view of a wetting liquid transferring unit in the cleaning section for explaining a configuration and an operation of the wetting liquid transferring unit. 
         FIG. 18  is a block diagram schematically showing the entire configuration of an electrical circuit in the embodiment of the present invention. 
         FIG. 19  is a block diagram showing an example of an internal configuration of a main substrate shown in  FIG. 18 . 
         FIG. 20  is a diagram showing an example of a configuration of a multisensor system mounted on a carriage board shown in  FIG. 18 . 
         FIG. 21  is a perspective view of a head cartridge and ink tanks applied in the embodiment, which shows how the ink tanks are attached to the head cartridge. 
         FIG. 22  is a flow chart showing a sequence of steps performed during a printing operation in a first embodiment of this invention; 
         FIG. 23  is a diagram showing a stirring time set in the first embodiment of this invention; 
         FIG. 24  is a diagram showing how the stirring time of  FIG. 23  is determined; 
         FIG. 25  is a flow chart showing a sequence of steps performed when power is turned on in a second embodiment of this invention; 
         FIG. 26  is a flow chart showing a sequence of steps during a normal printing operation of  FIG. 25 ; and 
         FIG. 27  is a flow chart showing a sequence of steps performed during a printing operation in a fourth embodiment of this invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Now, referring to the accompanying drawings, the preferred embodiments of this invention will be described in detail. In this invention, the word “idle scan” means a scan operation of a print head executed without ejecting ink for printing purpose from the print head. 
     1. Basic Configuration 
     1.1 Outline of Printing System 
       FIG. 1  is a diagram for explaining a flow in which image data are processed in a printing system to which an embodiment of the present invention is applied. This printing system J 0011  includes a host apparatus J 0012  which generates image data indicating an image to be printed, and which sets up a user interface (UI) for generating the data and so on. In addition, the printing system J 0011  includes a printing apparatus J 0013  which prints an image on a printing medium on the basis of the image data generated by the host apparatus J 0012 . 
     The printing apparatus J 0013  performs a printing operation by use of 10 color inks of cyan (C), light cyan (Lc), magenta (M), light magenta (Lm), yellow (Y), red (R), green (G), black 1 (K1), black 2 (K2) and gray (Gray). To this end, a printing head H 1001  for ejecting these 10 color inks is used for the printing apparatus J 0013 . These 10 color inks are pigmented inks respectively including ten color pigments as the color materials thereof. 
     Programs operated with an operating system of the host apparatus J 0012  include an application and a printer driver. An application J 0001  executes a process of generating image data with which the printing apparatus makes a print. Personal computers (PC) are capable of receiving these image data or pre-edited data which is yet to process by use of various media. By means of a CF card, the host apparatus according to this embodiment is capable of populating, for example, JPEG-formatted image data associated with a photo taken with a digital camera. In addition, the host apparatus according to this embodiment is capable of populating, for example, TIFF-formatted image data read with a scanner and image data stored in a CD-ROM. Moreover, the host apparatus according to this embodiment is capable of capturing data from the Web through the Internet. These captured data are displayed on a monitor of the host apparatus. Thus, an edit, a process or the like is applied to these captured data by means of the application J 0001 . Thereby, image data R, G and B are generated, for example, in accordance with the sRGB specification. A user sets up a type of printing medium to be used for making a print, a printing quality and the like through a UI screen displayed on the monitor of the host apparatus. The user also issues a print instruction through the UI screen. Depending on this print instruction, the image data R, G and B are transferred to the printer driver. 
     The printer driver includes a precedent process J 0002 , a subsequent process J 0003 , a γ correction process J 0004 , a half-toning process J 0005  and a print data creation process J 0006  as processes performed by itself. Brief descriptions will be provided below for these processes J 0002  to J 0006 . 
     (A) Precedent Process 
     The precedent process J 0002  performs mapping of a gamut. In this embodiment, data are converted for the purpose of mapping the gamut reproduced by image data R, G and B in accordance with the sRGB specification onto a gamut to be produced by the printing apparatus. Specifically, a respective one of image data R, G and B deal with 256 gradations of the respective one of colors which are represented by 8 bits. These image data R, G and B are respectively converted to 8-bit data R, G and B in the gamut of the printing apparatus J 0013  by use of a three-dimensional LUT. 
     (B) Subsequent Process 
     On the basis of the 8-bit data R, G and B obtained by mapping the gamut, the subsequent process J 0003  obtains 8-bit color separation data on each of the 10 colors. The 8-bit color separation data correspond to a combination of inks which are used for reproducing a color represented by the 8-bit data R, G and B. In other words, the subsequent process J 0003  obtains color separation data on each of Y, M, Lm, C, Lc, K1, K2, R, G, and Gray. In this embodiment, like the precedent process, the subsequent process is carried out by using the three dimensional LUT, simultaneously using an interpolating operation. 
     (C) γ Correction Process 
     The γ correction J 0004  converts the color separation data on each of the 10 colors which have been obtained by the subsequent process J 0003  to a tone value (gradation value) representing the color. Specifically, a one-dimensional LUT corresponding to the gradation characteristic of each of the color inks in the printing apparatus J 0013  is used, and thereby a conversion is carried so that the color separation data on the 10 colors can be linearly associated with the gradation characteristics of the printer. 
     (D) Half-Toning Process 
     The half-toning process J 0005  quantizes the 8-bit color separation data on each of Y, M, Lm, C, Lc, K1, K2, R, G and Gray to which the γ correction process has been applied so as to convert the 8-bit separation data to 4-bit data. In this embodiment, the 8-bit data dealing with the 256 gradations of each of the 10 colors are converted to 4-bit data dealing with 9 gradations by use of the error diffusion method. The 4-bit data are data which serve as indices each for indicating a dot arrangement pattern in a dot arrangement patterning process in the printing apparatus. 
     (E) Print Data Creation Process 
     The last process performed by the printer driver is the print data creation process J 0006 . This process adds information on print control to data on an image to be printed whose contents are the 4-bit index data, and thus creates print data. 
       FIG. 2  is a diagram showing an example of a configuration of the print data. The print data are configured of the information on print control and the data on an image to be printed. The information on print control is in charge of controlling a printing operation. The data on an image to be printed indicates an image to be printed (the data are the foregoing 4-bit index data). The information on print control is configured of “information on printing media,” “information on print qualities,” and “information on miscellaneous controls” including information on paper feeding methods or the like. Types of printing media on which to make a print are described in the information on printing media. One type of printing medium selected out of a group of plain paper, glossy paper, a post card, a printable disc and the like is specified in the information on printing media. Print qualities to be sought are described in the information on print qualities. One type of print quality selected out of a group of “fine (high-quality print),” “normal,” “fast (high-speed print)” and the like is specified in the information on print qualities. Note that these pieces of information on print control are formed on the basis of contents which a user designates through the UI screen in the monitor of the host apparatus J 0012 . In addition, image data originated in the half-toning process J 0005  are described in the data on an image to be printed. The print data thus generated are supplied to the printing apparatus J 0013 . 
     The printing apparatus J 0013  performs a dot arrangement patterning process J 0007  and a mask data converting process J 0008  on the print data which have been supplied from the host apparatus J 0012 . Descriptions will be provided next for the dot arrangement patterning process J 0007  and the mask data converting process J 0008 . 
     (F) Dot Arrangement Patterning Process 
     In the above-described half-toning process J 0005 , the number of gradation levels is reduced from the 256 tone values dealt with by multi-valued tone information (8-bit data) to the 9 tone values dealt with by information (4-bit data). However, data with which the printing apparatus J 0013  is actually capable of making a print are binary data (1-bit) data on whether or not an ink dot should be printed. Taken this into consideration, the dot arrangement patterning process J 0007  assigns a dot arrangement pattern to each pixel represented by 4-bit data dealing with gradation levels  0  to  8  which are an outputted value from the half-toning process J 0005 . The dot arrangement pattern corresponds to the tone value (one of the levels  0  to  8 ) of the pixel. Thereby, whether or not an ink dot should be printed (whether a dot should be on or off) is defined for each of a plurality of areas in each pixel. Thus, 1-bit binary data indicating “1 (one)” or “0 (zero)” are assigned to each of the areas of the pixel. In this respect, “1 (one)” is binary data indicating that a dot should be printed. “0 (zero)” is binary data indicating that a dot should not be printed. 
       FIG. 3  shows output patterns corresponding to input levels  0  to  8 . These output patterns are obtained through the conversion performed in the dot arrangement patterning process of the embodiment. Level numbers in the left column in the diagram correspond respectively to the levels  0  to  8  which are the outputted values from the half-toning process in the host apparatus. Regions each configured of 2 vertical areas×4 horizontal areas are shown to the right of this column. Each of the regions corresponds to a region occupied by one pixel receiving an output from the half-toning process. In addition, each of the areas in one pixel corresponds to a minimum unit for which it is specified whether the dot thereof should be on or off. Note that, in this description, a “pixel” means a minimum unit which is capable of representing a gradation, and also means a minimum unit to which the image processes (the precedent process, the subsequent process, the γ correction process, the half-toning process and the like) are applied using multi-valued data represented by the plurality of bits. 
     In this figure, an area in which a circle is drawn denotes an area where a dot is printed. As the level number increases, the number of dots to be printed increases one-by-one. In this embodiment, information on density of an original image is finally reflected in this manner. 
     From the left to the right, (4n) to (4n+3) denotes horizontal positions of pixels, each of which receives data on an image to be printed. An integer not smaller than 1 (one) is substituted for n in the expression (4n) to (4n+3). The patterns listed under the expression indicate that a plurality of mutually-different patterns are available depending on a position where a pixel is located even though the pixel receives an input at the same level. In other words, the configuration is that, even in a case where a pixel receives an input at one level, the four types of dot arrangement patterns under the expression (4n) to (4n+3) at the same level are assigned to the pixel in an alternating manner. 
     In  FIG. 3 , the vertical direction is a direction in which the ejection openings of the printing head are arrayed, and the horizontal direction is a direction in which the printing head moves. The configuration enabling a print to be made using the plurality of different dot arrangement patterns for one level brings about the following two effects. First, the number of times that ejection is performed can be equalized between two nozzles in which one nozzle is in charge of the patterns located in the upper row of the dot arrangement patterns at one level, and the other nozzle is in charge of the patterns located in the lower row of the dot arrangement patterns at the same level. Secondly, various noises unique to the printing apparatus can be disaggregated. 
     When the above-described dot arrangement patterning process is completed, the assignment of dot arrangement patterns to the entire printing medium is completed. 
     (G) Mask Data Converting Process 
     In the foregoing dot arrangement patterning process J 0007 , whether or not a dot should be printed is determined for each of the areas on the printing medium. As a result, if binary data indicating the dot arrangement are inputted to a drive circuit J 0009  of the printing head H 1001 , a desired image can be printed. In this case, what is termed as a one-pass print can be made. The one-pass print means that a print to be made for a single scan region on a printing medium is completed by the printing head H 1001  moving once. Alternatively, what is termed as a multi-pass print can be made. The multi-pass print means that a print to be made for a single scan region on the printing medium is completed by the printing head moving a plurality of times. Here, descriptions will be provided for a mask data converting process, taking an example of the multi-pass print. 
       FIG. 4  is a schematic diagram showing the printing head and print patterns for the purpose of describing the multi-pass printing method. The print head H 1001  applied to this embodiment actually has 768 nozzles. For the sake of convenience, however, descriptions will be provided for the printing head and the print patterns, supposing that the printing head H 1001  has 16 nozzles. The nozzles are divided into a first to a fourth nozzle groups. Each of the four nozzle groups includes four nozzles. Mask P 0002  are configured of a first to a fourth mask patterns P 0002 ( a ) to P 0002 ( d ). The first to the fourth mask patterns P 0002 ( a ) to P 0002 ( d ) define the respective areas in which the first to the fourth nozzle groups are capable of making a print. Blackened areas in the mask patterns indicate printable areas, whereas whitened areas in the mask patterns indicate unprinted areas. The first to the fourth mask patterns are complementary to one another. The configuration is that, when these four mask patterns are superposed over one another, a print to be made in a region corresponding to a 4×4 area is completed. 
     Patterns denoted by reference numerals P 0003  to P 0006  show how an image is going to be completed by repeating a print scan. Each time a print scan is completed, the printing medium is transferred by a width of the nozzle group (a width of four nozzles in this figure) in a direction indicated by an arrow in the figure. In other words, the configuration is that an image in any same region (a region corresponding to the width of each nozzle region) on the printing medium is completed by repeating the print scan four times. Formation of an image in any same region on the printing medium by use of multiple nozzle groups by repeating the scan the plurality of times in the afore-mentioned manner makes it possible to bring about an effect of reducing variations characteristic of the nozzles, and an effect of reducing variations in accuracy in transferring the printing medium. 
       FIG. 5  shows an example of mask which is capable of being actually applied to this embodiment. The printing head H 1001  to which this embodiment is applied has 768 nozzles, and 192 nozzles belong to each of the four nozzle groups. As for the size of the mask, the mask has 768 areas in the vertical direction, and this number is equal to the number of nozzles. The mask has 256 areas in the horizontal direction. The mask has a configuration that the four mask patterns respectively corresponding to the four nozzle groups maintain a complementary relationship among themselves. 
     In the case of the ink jet printing head applied to this embodiment, which ejects a large number of fine ink droplets by means of a high frequency, it has been known that an air flow occurs in a neighborhood of the printing part during printing operation. In addition, it has been proven that this air flow particularly affects a direction in which ink droplets are ejected from nozzles located in the end portions of the printing head. For this reason, in the case of the mask patterns of this embodiment, a distribution of printable ratios is biased depending on which nozzle group a region belongs to, and on where a region is located in each of the nozzle groups, as seen from  FIG. 5 . As shown in  FIG. 5 , by employing the mask patterns having a configuration which makes the printable ratios of the nozzles in the end portions of the printing head smaller than those of nozzles in a central portion thereof, it is possible to make inconspicuous an adverse effect stemming from variations in positions where ink droplets ejected from the nozzles in the end portions of the printing head are landed. 
     Note that a printable ratio specified by a mask pattern is as follows. A printable ratio of a mask pattern is a percentage denomination of a ratio of the number of printable areas constituting the mask pattern (blackened areas in the mask pattern P 0002 ( a ) to P 0002 ( d ) of  FIG. 4 ) to the sum of the number of printable areas and the number of unprintable areas constituting the mask pattern (the whitened areas in the mask patterns P 0002 ( a ) to P 0002 ( d ) of  FIG. 4 ). In other words, a printable ratio (%) of a mask pattern is expressed by
 
 M ÷( M+N )×100
 
     where M denotes the number of printable areas constituting the mask pattern and N denotes the number of unprintable areas constituting the mask pattern. 
     In this embodiment, data for the mask as shown in  FIG. 5  are stored in memory in the main body of the printing apparatus. The mask data converting process J 0008  performs the AND process on the mask data with the binary data obtained in the foregoing dot arrangement patterning process. Thereby, binary data to be a print object in each print scan are determined. Subsequently, the binary data are transferred to the driving circuit J 0009 . Thus, the printing head H 1001  is driven, and hence inks are ejected in accordance with the binary data. 
       FIG. 1  shows that the host apparatus J 0012  is configured to perform the precedent process J 0002 , the subsequent process J 0003 , the γ correction process J 0004 , the half-toning process J 0005  and the print data creation process J 0006 . In addition,  FIG. 1  shows that the printing apparatus J 0013  is designed to perform the dot arrangement patterning process J 0007  and the mask data converting process J 0008 . However, the present invention is not limited to this embodiment. For example, the present invention may be carried out as an embodiment in which parts of the processes J 0002  to J 0005  are designed to be performed by the printing apparatus J 0013  instead of by the host apparatus J 0012 . Otherwise, the present invention may be carried out as an embodiment in which all of these processes are designed to be performed by the host apparatus J 0012 . Alternately, the present invention may be carried out as an embodiment in which the processes J 0002  to J 0008  are designed to be performed by the printing apparatus J 0013 . 
     1.2 Configuration of Mechanisms 
     Descriptions will be provided for a configuration of the mechanisms in the printing apparatus to which this embodiment is applied. The main body of the printing apparatus of this embodiment is divided into a paper feeding section, a paper conveying section, a paper discharging section, a carriage section, a flat-pass printing section and a cleaning section from a viewpoint of functions performed by the mechanisms. These mechanisms are contained in an outer case. 
       FIGS. 6 ,  7 ,  8 ,  12  and  13  are perspective views respectively showing appearances of the printing apparatus to which this embodiment is applied.  FIG. 6  shows the printing apparatus in an unused condition when viewed from the front.  FIG. 7  shows the printing apparatus in an unused condition when viewed from the back.  FIG. 8  shows the printing apparatus in a used condition when viewed from the front.  FIG. 12  shows the printing apparatus during flat-pass printing when viewed from the front.  FIG. 13  shows the printing apparatus during flat-pass printing when viewed from the back. In addition,  FIGS. 9 to 11  and  14  to  16  are diagrams for describing internal mechanisms in the main body of the printing apparatus. In this respect,  FIG. 9  is a perspective view showing the printing apparatus when viewed from the right above.  FIG. 10  is a perspective view showing the printing apparatus when viewed from the left above.  FIG. 11  is a side, cross-sectional view of the main body of the printing apparatus.  FIG. 14  is a cross-sectional view of the printing apparatus during flat-pass printing.  FIG. 15  is a perspective view of the cleaning section.  FIG. 16  is a cross-sectional view for describing a configuration and an operation of a wiping mechanism in the cleaning section.  FIG. 17  is a cross-sectional view of a wetting liquid transferring unit in the cleaning section. 
     Descriptions will be provided for each of the sections by referring to these figures whenever deemed necessary. 
     (A) Outer Case (Refer to  FIGS. 6 and 7 ) 
     The outer case is attached to the main body of the printing apparatus in order to cover the paper feeding section, the paper conveying section, the paper discharging section, the carriage section, the cleaning section, the flat-pass section and the wetting liquid transferring unit. The outer case is configured chiefly of a lower case M 7080 , an upper case M 7040 , an access cover M 7030 , a connector cover, and a front cover M 7010 . 
     Paper discharging tray rails (not illustrated) are provided under the lower case M 7080 , and thus the lower case M 7080  has a configuration in which a divided paper discharging tray M 3160  is capable of being contained therein. In addition, the front cover M 7010  is configured to close the paper discharging port while the printing apparatus is not used. 
     An access cover M 7030  is attached to the upper case M 7040 , and is configured to be turnable. A part of the top surface of the upper case has an opening portion. The printing apparatus has a configuration in which each of ink tanks H 1900  or the printing head H 1001  (refer to  FIG. 21 ) is replaced with a new one in this position. Incidentally, in the printing apparatus of this embodiment, the printing head H 1001  has a configuration in which a plurality of ejecting portions are formed integrally into one unit. The plurality of ejecting portions corresponding respectively to a plurality of mutually different colors, and each of the plurality of ejecting portions is capable of ejecting an ink of one color. In addition, the printing head is configured as a printing head cartridge H 1000  which the ink tanks H 1900  are capable of being attached to, and detached from, independently of one another depending on the respective colors. The upper case M 7040  is provided with a door switch lever (not illustrated), LED guides M 7060 , a power supply key E 0018 , a resume key E 0019 , a flat-pass key E 3004  and the like. The door switch lever detects whether the access cover M 7030  is opened or closed. Each of the LED guides M 7060  transmits, and displays, light from the respective LEDs. Furthermore, a multi-stage paper feeding tray M 2060  is turnably attached to the upper case M 7040 . While the paper feeding section is not used, the paper feeding tray M 2060  is contained within the upper case M 7040 . Thus, the upper case M 7040  is configured to function as a cover for the paper feeding section. 
     The upper case M 7040  and the lower case M 7040  are attached to each other by elastic fitting claws. A part provided with a connector portion therebetween is covered with a connector cover (not illustrated). 
     (B) Paper Feeding Section (Refer to  FIGS. 8 and 11 ) 
     As shown in  FIGS. 8 and 11 , the paper feeding section is configured as follows. A pressure plate M 2010 , a paper feeding roller M 2080 , a separation roller M 2041 , a return lever M 2020  and the like are attached to a base M 2000 . The pressure plate M 2010  is that on which printing media are stacked. The paper feeding roller M 2080  feeds the printing media sheet by sheet. The separation roller M 2041  separates a printing medium. The return lever M 2020  is used for returning the printing medium to a stacking position. 
     (C) Paper Conveying Section (Refer to  FIGS. 8 to 11 ) 
     A conveying roller M 3060  for conveying a printing medium is rotatably attached to a chassis M 1010  made of an upwardly bent plate. The conveying roller M 3060  has a configuration in which the surface of a metal shaft is coated with ceramic fine particles. The conveying roller M 3060  is attached to the chassis M 1010  in a state in which metallic parts respectively of the two ends of the shaft are received by bearings (not illustrated). The conveying roller M 3060  is provided with a roller tension spring (not illustrated). The roller tension spring pushes the conveying roller M 3060 , and thereby applies an appropriate amount of load to the conveying roller M 3060  while the conveying roller M 3060  is rotating. Accordingly, the conveying roller M 3060  is capable of conveying printing medium stably. 
     The conveying roller M 3060  is provided with a plurality of pinch rollers M 3070  in a way that the plurality of pinch rollers M 3070  abut on the conveying roller M 3060 . The plurality of pinch rollers M 3070  are driven by the conveying roller M 3060 . The pinch rollers M 3070  are held by a pinch roller holder M 3000 . The pinch rollers M 3070  are pushed respectively by pinch roller springs (not illustrated), and thus are brought into contact with the conveying roller M 3060  with the pressure. This generates a force for conveying printing medium. At this time, since the rotation shaft of the pinch roller holder M 3000  is attached to the bearings of the chassis M 1010 , the rotation shaft rotates thereabout. 
     A paper guide flapper M 3030  and a platen M 3040  are disposed in an inlet to which a printing medium is conveyed. The paper guide flapper M 3030  and the platen M 3040  guide the printing medium. In addition, the pinch roller holder M 3000  is provided with a PE sensor lever M 3021 . The PE sensor lever M 3021  transmits a result of detecting the front end or the rear end of each of the printing medium to a paper end sensor (hereinafter referred to as a “PE sensor”) E 0007  fixed to the chassis M 1010 . The platen M 3040  is attached to the chassis M 1010 , and is positioned thereto. The paper guide flapper M 3030  is capable of rotating about a bearing unit (not illustrated), and is positioned to the chassis M 1010  by abutting on the chassis M 1010 . 
     The printing head H 1001  (refer to  FIG. 21 ) is provided at a side downstream in a direction in which the conveying roller M 3060  conveys the printing medium. 
     Descriptions will be provided for a process of conveying printing medium in the printing apparatus with the foregoing configuration. A printing medium sent to the paper conveying section is guided by the pinch roller holder M 3000  and the paper guide flapper M 3030 , and thus is sent to a pair of rollers which are the conveying roller  3060  and the pinch roller M 3070 . At this time, the PE sensor lever M 3021  detects an edge of the printing medium. Thereby, a position in which a print is made on the printing medium is obtained. The pair of rollers which are the conveying roller M 3060  and the pinch roller M 3070  are driven by an LF motor E 0002 , and are rotated. This rotation causes the printing medium to be conveyed over the platen M 3040 . A rib is formed in the platen M 3040 , and the rib serves as a conveyance datum surface. A gap between the printing head H 1001  and the surface of the printing medium is controlled by this rib. Simultaneously, the rib also suppresses flapping of the printing medium in cooperation with the paper discharging section which will be described later. 
     A driving force with which the conveying roller M 3060  rotates is obtained by transmitting a torque of the LF motor E 0002  consisting, for example, of a DC motor to a pulley M 3061  disposed on the shaft of the conveying roller M 3060  through a timing belt (not illustrated). A code wheel M 3062  for detecting an amount of conveyance performed by the conveying roller M 3060  is provided on the shaft of the conveying roller M 3060 . In addition, an encode sensor M 3090  for reading a marking formed in the code wheel M 3062  is disposed in the chassis M 1010  adjacent to the code wheel M 3062 . Incidentally, the marking formed in the code wheel M 3062  is assumed to be formed at a pitch of 150 to 300 lpi (line/inch) (an example value). 
     (D) Paper Discharging Section (Refer to  FIGS. 8 to 11 ) 
     The paper discharging section is configured of a first paper discharging roller M 3100 , a second paper discharging roller M 3110 , a plurality of spurs M 3120  and a gear train. 
     The first paper discharging roller M 3100  is configured of a plurality of rubber portions provided around the metal shaft thereof. The first paper discharging roller M 3100  is driven by transmitting the driving force of the conveying roller M 3060  to the first paper discharging roller M 3100  through an idler gear. 
     The second paper discharging roller M 3110  is configured of a plurality of elastic elements M 3111 , which are made of elastomer, attached to the resin-made shaft thereof. The second paper discharging roller M 3110  is driven by transmitting the driving force of the first paper discharging roller M 3100  to the second paper discharging roller M 3110  through an idler gear. 
     Each of the spurs M 3120  is formed by integrating a circular thin plate and a resin part into one unit. A plurality of convex portions are provided to the circumference of each of the spurs M 3120 . Each of the spurs M 3120  is made, for example, of SUS. The plurality of spurs M 3120  are attached to a spur holder M 3130 . This attachment is performed by use of a spur spring obtained by forming a coiled spring in the form of a stick. Simultaneously, a spring force of the spur spring causes the spurs M 3120  to abut respectively on the paper discharging rollers M 3100  and M 3110  at predetermined pressures. This configuration enables the spurs  3120  to rotate to follow the two paper discharging rollers M 3100  and M 3110 . Some of the spurs M 3120  are provided at the same positions as corresponding ones of the rubber portions of the first paper discharging roller M 3110  are disposed, or at the same positions as corresponding ones of the elastic elements M 3111  are disposed. These spurs chiefly generates a force for conveying printing medium. In addition, others of the spurs M 3120  are provided at positions where none of the rubber portions and the elastic elements M 3111  is provided. These spurs M 3120  chiefly suppresses lift of a printing medium while a print is being made on the printing medium. 
     Furthermore, the gear train transmits the driving force of the conveying roller M 3060  to the paper discharging rollers M 3100  and M 3110 . 
     With the foregoing configuration, a printing medium on which an image is formed is pinched with nips between the first paper discharging roller M 3110  and the spurs M 3120 , and thus is conveyed. Accordingly, the printing medium is delivered to the paper discharging tray M 3160 . The paper discharging tray M 3160  is divided into a plurality of parts, and has a configuration in which the paper discharging tray M 3160  is capable of being contained under the lower case M 7080  which will be described later. When used, the paper discharging tray M 3160  is drawn out from under the lower case M 7080 . In addition, the paper discharging tray M 3160  is designed to be elevated toward the front end thereof, and is also designed so that the two side ends thereof are held at a higher position. The design enhances the stackability of printing media, and prevents the printing surface of each of the printing media from being rubbed. 
     (E) Carriage Section (Refer to  FIGS. 9 to 11 ) 
     The carriage section includes a carriage M 4000  to which the printing head H 1001  is attached. The carriage M 4000  is supported with a guide shaft M 4020  and a guide rail M 1011 . The guide shaft M 4020  is attached to the chassis M 1010 , and guides and supports the carriage M 4000  so as to cause the carriage M 4000  to perform reciprocating scan in a direction perpendicular to a direction in which a printing medium is conveyed. The guide rail M 1011  is formed in a way that the guide rail M 1011  and the chassis M 1010  are integrated into one unit. The guide rail M 1011  holds the rear end of the carriage M 4000 , and thus maintains the space between the printing head H 1001  and the printing medium. A slide sheet M 4030  formed of a thin plate made of stainless steel or the like is stretched on a side of the guide rail M 1011 , on which side the carriage M 4000  slides. This makes it possible to reduce sliding noises of the printing apparatus. 
     The carriage M 4000  is driven by a carriage motor E 0001  through a timing belt M 4041 . The carriage motor E 0001  is attached to the chassis M 1010 . In addition, the timing belt M 4041  is stretched and supported by an idle pulley M 4042 . Furthermore, the timing belt M 4041  is connected to the carriage M 4000  through a carriage damper made of rubber. Thus, image unevenness is reduced by damping the vibration of the carriage motor E 0001  and the like. 
     An encoder scale E 0005  for detecting the position of the carriage M 4000  is provided in parallel with the timing belt M 4041  (the encoder scale E 0005  will be described later by referring to  FIG. 18 ). Markings are formed on the encoder scale E 0005  at pitches in a range of 150 lpi to 300 lpi. An encoder sensor E 0004  for reading the markings is provided on a carriage board E 0013  installed in the carriage M 4000  (the encoder sensor E 0004  and the carriage board E 0013  will be described later by referring to  FIG. 18 ). A head contact E 0101  for electrically connecting the carriage board E 0013  to the printing head H 1001  is also provided to the carriage board E 0013 . Moreover, a flexible cable E 0012  (not illustrated) is connected to the carriage M 4000  (the flexible cable E 0012  will be described later by referring to  FIG. 18 ). The flexible cable E 0012  is that through which a drive signal is transmitted from an electric substrate E 0014  to the printing head H 1001 . 
     As for components for fixing the printing head H 1001  to the carriage M 4000 , the following components are provided to the carriage M 4000 . An abutting part (not illustrated) and pressing means (not illustrated) are provided on the carriage M 4000 . The abutting part is with which the printing head H 1001  positioned to the carriage M 4000  while pushing the printing head H 1001  against the carriage M 4000 . The pressing means is with which the printing head H 1001  is fixed at a predetermined position. The pressing means is mounted on a headset lever M 4010 . The pressing means is configured to act on the printing head H 1001  when the headset lever M 4010  is turned about the rotation support thereof in a case where the printing head H 1001  is intended to be set up. 
     Moreover, a position detection sensor M 4090  including a reflection-type optical sensor is attached to the carriage M 4000 . The position detection sensor is used while a print is being made on a special medium such as a CD-R, or when a print result or the position of an edge of a sheet of paper is being detected. The position detection sensor M 4090  is capable of detecting the current position of the carriage M 4000  by causing a light emitting device to emit light and by thus receiving the emitted light after reflecting off the carriage M 4000 . 
     In a case where an image is formed on a printing medium in the printing apparatus, the set of the conveying roller M 3060  and the pinch rollers M 3070  transfers the printing medium, and thereby the printing medium is positioned in terms of a position in a column direction. In terms of a position in a row direction, by using the carriage motor E 0001  to move the carriage M 4000  in a direction perpendicular to the direction in which the printing medium is conveyed, the printing head H 1001  is located at a target position where an image is formed. The printing head H 1001  thus positioned ejects inks onto the printing medium in accordance with a signal transmitted from the electric substrate E 0014 . Descriptions will be provided later for details of the configuration of the printing head H 1001  and a printing system. The printing apparatus of this embodiment alternately repeats a printing main scan and a sub-scan. During the printing main scan, the carriage M 4000  scans in the row direction while the printing head H 1001  is making a print. During the sub-scan, the printing medium is conveyed in the column direction by conveying roller M 3060 . Thereby, the printing apparatus is configured to form an image on the printing medium. 
     (F) Flat-Pass Printing Section (Refer to  FIGS. 12 to 14 ) 
     A printing medium is fed from the paper feed section in a state where the printing medium is bent, because the passage through which the printing medium passes continues curving up to the pinch rollers as shown in  FIG. 11 . For this reason, if a thicker printing medium with a thickness of approximately 0.5 mm or more, for example, is attempted to be fed from the paper feeding section, a reaction force of the bent printing medium occurs, and thus resistance to the paper feeding increases. As a result, it is likely that the printing medium cannot be fed. Otherwise, even if the printing medium can be fed, the delivered printing medium remains bent, or is folded. 
     A flat-pass print is made on printing media, such as thicker printing media, which a user does not wish to fold, and on printing media, such as CD-Rs, which cannot be bent. 
     Types of flat-pass prints include a type of print made by manually supplying a printing medium from a slit-shaped opening portion (under a paper feeding unit) in the back of the main body of a printing apparatus, and by thus causing pinch rollers of the main body to nip the printing medium. However, the flat-pass print of this embodiment employs the following mode. A printing medium is fed from the paper discharging port located in the front side of the main body of the printing apparatus to a position where a print is going to be made, and the print is made on the printing medium by switching back the printing medium. 
     The front cover M 7010  is usually located below the paper discharging section, because the front cover M 7010  is also used as a tray in which several tens of printing media on which prints have been made are stacked (refer to  FIG. 8 ). When a flat-pass print is going to be made, the front tray M 7010  is elevated up to a position where the paper discharging port is located (refer to  FIG. 12 ) for the purpose of supplying a printing medium from the paper discharging port horizontally in a direction reverse to the direction in which a printing medium is usually conveyed. Hooks and the like (not illustrated) are provided to the front cover M 7010 . Thus, the front cover M 7010  is capable of being fixed to a position where the printing medium is supplied for the purpose of the flat-pass print. It can be detected by a sensor whether or not the front cover M 7010  is located at the position where the printing medium is supplied for the purpose of the flat-pass print. Depending on this detection, it can be determined whether the printing apparatus is in a flat-pass printing mode. 
     In the case of the flat-pass printing mode, first of all, a flat-pass key E 3004  is operated for the purpose of placing a printing medium on the front tray M 7010  and inserting the printing medium from the paper discharging port. Thereby, a mechanism (not illustrated) lifts the spur holder M 3130  and the pinch roller holder M 3000  respectively up to positions higher than a presumed thickness of the printing medium. In addition, in a case where the carriage M 4000  exists in an area through which the printing medium is going to pass, a lifting mechanism (not illustrated) lifts the carriage M 4000  up. This makes it easy to insert the printing medium therein. Moreover, by pressing a rear tray button M 7110 , a rear tray M 7090  can be opened. Furthermore, a rear sub-tray M 7091  can be opened in the form of the letter V (refer to  FIG. 13 ). The rear tray M 7090  and the rear sub-tray M 7091  are trays with which a long printing medium is supported in the back of the main body of the printing apparatus. This is because, if the long printing medium is inserted from the front of the main body of the printing apparatus, the long printing medium juts out of the back of the main body of the printing apparatus. If a thicker printing medium is not kept flat while a print is being made on the thicker printing medium, the thicker printing medium may be rubbed against the head ejection face, or the conveyance load may change. This is likely to adversely affect the print quality. For this reason, the disposition of these trays is effective. However, if a printing medium is not long enough to jut out of the back of the main body of the printing apparatus, the rear tray M 7090  and the like need not be opened. 
     In the foregoing manner, a printing medium can be inserted from the paper discharging port to the inside of the main body of the printing apparatus. A printing medium is positioned on the front tray M 7010  by aligning the rear edge (an edge at the side located closest to a user) and the right edge of the printing medium to a position in the front tray M 7010  where a marker is formed. 
     At this time, if the flat-pass key E 3004  is operated once again, the spur holder M 3130  comes down, and thus the paper discharging rollers M 3100 , M 3110  and the spurs M 3120  jointly nip the printing medium. Thereafter, the paper discharging rollers M 3100  and M 3110  draw the printing medium into the main body of the printing apparatus by a predetermined amount thereof (in a direction reverse to the direction in which the printing medium is conveyed during normal printing). Because the edge at the side closest to the user (the rear edge) of a printing medium is aligned to the marker when the printing medium is set up at the beginning, it is likely that the front edge (the edge located farthest from a user) of the printing medium may not reach the conveying roller M 3060 , if the printing medium is shorter. With this taken into consideration, the predetermined amount is defined as a distance between the rear edge of a printing medium with the presumably shortest length and the conveying roller M 3060 . Once a printing medium is transferred by the predetermined amount, the rear edge of the printing medium reaches the conveying roller M 3060 . Thus, the pinch roller holder M 3000  is lowered at the position, and the conveying roller M 3060  and the pinch rollers M 3070  are caused to nip the printing medium. Subsequently, the printing medium is further transferred so that the rear edge of the printing medium is nipped by the conveying roller M 3060  and the pinch rollers M 3070 . Thereby, the supplying of the printing medium for the purpose of the flat-pass print is completed (at a position where the printing medium waits for a print to be made thereon). 
     A nip force with which the paper discharging roller M 3100  and M 3110  as well as the spurs M 3120  nip a printing medium is set relatively weak lest the force should adversely affect image formation while the printing medium is being delivered during a normal print. For this reason, in the case where a flat-pass print is going to be made, it is likely that the position of the printing medium shifts before the print starts. In this embodiment, however, a printing medium is nipped by the conveying roller M 3060  and the pinch rollers M 3070  which have a relatively stronger nip force. This secures a position where a printing medium should be set. In addition, while a printing medium is being conveyed into the inside of the main body by the predetermined amount, a flat-pass paper detection sensor lever (hereinafter referred to as an “FPPE sensor lever”) M 3170  blocks or forms a light path of an FPPE sensor E 9001  which is an infrared-ray sensor, and which is not illustrated here. Thereby, the position of the rear edge (the position of the front edge during the print) of the printing medium can be detected. Incidentally, the FPPE sensor lever may be rotatably provided between the platen M 3040  and the spur holder M 3130 . 
     Once a printing medium is set at the position where the printing medium waits for a print to be made thereon, a print command is executed. Specifically, the conveying roller M 3060  conveys the printing medium to a position where the printing head H 1001  is going to make a print on the printing medium. Thereafter, the print is made in the same manner as a normal printing operation is performed. After the print, the printing medium is discharged to the front tray M 7010 . 
     In a case where the flat-pass print is intended to be made successively, the printing medium on which the print has been made is removed from the front tray M 7010 , and the next printing medium is set thereon. After that, it is sufficient that the foregoing processes are repeated. Specifically, the subsequent print starts with the setting of a printing medium after the spur holder M 3130  and the pinch roller holder M 3000  are lifted up by pressing the flat-pass key E 3004 . 
     On the other hand, in a case where the flat-pass print is intended to be completed, the printing apparatus is returned to the normal printing mode by returning the front tray M 7010  to the normal print position. 
     (G) Cleaning Section (Refer to  FIGS. 15 and 16 ) 
     The cleaning section is a mechanism for cleaning the printing head H 1001 . The cleaning section is configured of a pump M 5000 , caps M 5010 , a wiper portion M 5020  and the like. The caps M 5010  are those which prevent the printing head H 1001  from being dried out. The wiper portion M 5020  is used for cleaning the surface of the printing head H 1001  on which the ejection openings are formed. 
     In the case of this embodiment, a chief driving force of the cleaning section is transmitted from an AP motor E 3005  (see  FIG. 18 ). The pump M 5000  is designed to be operated by rotation in one direction which is generated by means of a one-way clutch (not illustrated). The wiper portion M 5020  and the caps M 5010  are designed to ascend and descend by rotation in the other direction which is generated by the one-way clutch Incidentally, the AP motor E 3005  is also used as a driving power supply for an operation of feeding printing medium, but a motor specialized for operating the cleaning section may be provided to the cleaning section instead. 
     The motor E 0003  drives the caps M 5010  so as for the caps M 5010  to be capable of ascending and descending by means of an ascending/descending mechanism (not illustrated). When the caps M 5010  go up to an ascending position, the caps M 5010  cap each of the ejection faces of several ejecting portions provided to the printing head H 1001 . While no print operation is being performed, the caps M 5010  can protect the printing head H 1001 . Otherwise, the caps M 5010  can recover the printing head H 1001  by suction. While a print operation is being performed, the caps M 5010  can be placed in a descending position which prevents the caps M 5010  from interfering with the printing head H 1001 . In addition, by opposing the caps M 5010  to the ejection face, the caps M 5010  are capable of receiving preliminary ejections. In a case where, for instance, the printing head H 1001  is provided with ten ejecting portions, two caps M 5010  are provided to the cleaning section in the illustrated example so that the ejection face corresponding to each five ejecting portions can be capped collectively by corresponding one of the two caps M 5010 . 
     A wiper portion M 5020  made of an elastic member such as rubber is fixed to a wiper holder (not illustrated) The wiper holder is capable of moving in directions indicated by −Y and +Y in  FIG. 16  (−Y and +Y are directions in which the ejection openings in the ejecting portions are arranged). When the printing head H 1001  gets to the home position, the wiper holder moves in the direction indicated by an arrow −Y. Thereby, a surface of the printing head H 1001  can be wiped. Once the wiping operation is completed, the carriage is caused to escape out of the range where the wiping operation is designed to be performed, and thus the wiper is returned to a position which prevents the wiper from interfering with the ejection face and the like. Incidentally, the wiper portion M 5020  of this example is provided with a wiper blade M 5020 A for wiping the entire surface of the printing head H 1001  including all of the ejection faces of the ejecting portions. In addition, the wiper portion M 5020  is provided with the other two wiper blades M 5020 B and M 5020 C. The wiper blade M 5020 B wipes vicinities of nozzles for ejection faces of five of the ten ejecting portions, whereas the wiper blade M 5020 C wipes vicinities of nozzles for ejection faces of the other five of the ten ejecting portions. 
     After wiping, the wiper portion M 5020  abuts on a blade cleaner M 5060 . Thereby, the wiper blades M 5020 A to M 5020 C are configured to be cleaned of inks and the like which have been adhered to themselves. In addition, the wiper portion M 5020  has the following configuration (a wetting liquid transferring unit). A wetting liquid is transferred onto the wiper blades M 5020 A to M 5020 C before wiping. This enhances cleaning performance of the wiping operation. Descriptions will be provided later for a configuration of this wetting liquid transferring unit and the wiping operation. 
     The suction pump M 5000  is capable of generating negative pressure in a state where an airtight space is formed inside the cap M 5010  by connecting the cap M 5010  to the ejection faces. Thereby, inks can be filled in the ejecting portions from the ink tanks H 1900 . In addition, dust, adhering matter, bubbles and the like which exist in the ejection openings and the internal ink passage leading to the ejection openings can be removed by suction. 
     What is used for the suction pump M 5000  is, for example, a tube pump. This includes a member having a curved surface which is formed by squeezing and holding at least part of a flexible tube; a roller being capable of pressing the flexible tube towards the member; and a roller supporting part which supports the roller, and which is capable of rotating. Specifically, the roller supporting part is rotated in a predetermined direction, and thereby the roller is rolled on the member in which the curved surface has been formed, while pressing the flexible tube. In response to this, the negative pressure is generated in the airtight space formed by the cap M 5010 . This negative pressure sucks inks from the ejection openings, and subsequently sucks up the inks into the tube or the suction pump from the cap M 5010 . Thereafter, the sucked inks are further transferred to a suitable member (a waste ink absorbing member) provided inside the lower case M 7080 . 
     Note that an absorbing member M 5011  is provided to the inside portion of the cap M 5010  for the purpose of reducing the amount of inks remaining on the ejection faces of the printing head H 1001  after the suction. In addition, consideration is made for sucking inks, which remain in the cap M 5010  and the absorbing member M 5011 , in a state where the cap M 5010  is opened, and for thus precluding the ink residue from coagulating and for accordingly preventing an adverse affect from occurring subsequently by sucking. It is desirable that no abrupt negative pressure should work on the ejection faces by providing an open-to-atmosphere valve (not illustrated) in a middle of the ink suction passage, and by thus beforehand opening the valve when the cap M 5010  is intended to be detached from the ejection faces. 
     Furthermore, the suction pump M 5000  can be operated not only for the purpose of the recovery by suction, but also for the purpose of discharging inks which have been received by the cap M 5010  by the preliminary ejection operation performed in the state where the cap M 5010  is opposite to the ejection faces. Specifically, when an amount of inks held in the cap M 5010  after preliminary ejection reaches a predetermined amount, the inks held in the cap M 5010  can be transferred to the waste ink absorbing member through the tube by operating the suction pump M 5000 . 
     The series of operations performed successively, such as the operations of the wiper portion M 5020 , the ascent/descent of the cap M 5010  and the opening/closing of the valve, can be controlled by means of a main cam (not illustrated) provided on the output axle of the motor E 0003 , and a plurality of cams and arms and like which move so as to follow the main cam. Specifically, rotation of the main cam in response to a direction in which the motor E 0003  rotates operates cams, arms and the like in each of the units and parts. Thereby, the predetermined operations can be performed. The position of the main cam can be detected with a position detection sensor such as a photo-interrupter. 
     (H) Wetting Liquid Transferring Unit (Refer to  FIGS. 16 and 17 ) 
     Recently, inks containing pigment components as color materials (pigmented inks) are increasingly used for the purpose of enhancing the printing density, water resistance, light resistance of printed materials. Pigmented inks are produced through dispersing color materials themselves, which are originally solids, into water by adding dispersants thereto, or by introducing functional groups to pigment surfaces. Consequently, dried matter of pigmented inks resulting from drying the inks through evaporating moisture from the inks on the ejection faces damages the ejection faces more than dried coagulated matter of dyed inks in which the color materials are dissolved at molecular level. In addition, polymer compounds used for dispersing the pigments into the solvent are apt to be adsorbed to the ejection faces. This type of problem occurs in matter other than pigmented inks in a case where polymer compounds exist in the inks as a result of adding reactive liquids to the inks for the purpose of administering the viscosities of the inks, for the purpose of enhancing the light resistance of the inks, or for other purposes. 
     In this embodiment, a liquid is transferred onto, and adhered to, the blades of the wiper portion M 5020 , and thus the wiping operation is performed with the wetted blades M 5020 , in order to solve the foregoing problem. Thereby, the present embodiment attempts at preventing the ejection faces from deteriorating due to the pigmented inks, at reducing the abrasion of the wiper, and at removing the accumulated matter by dissolving the ink residue accumulated on the ejection faces. Such a liquid is termed as the wetting liquid from the viewpoint of its function in the description. The wiping by use of this liquid is termed as the wet wiping. 
     This embedment adopts a configuration in which the wetting liquid is stored inside the main body of the printing apparatus. Reference numeral M 5090  denotes a wetting liquid tank. As the wetting liquid, a glycerin solution or the like is contained in the wetting liquid tank M 5090 . Reference numeral M 5100  denotes a wetting liquid holding member, which is fibrous member or the like. The wetting liquid holding member M 5100  has an adequate surface tension for the purpose of preventing the wetting liquid from leaking from the wetting liquid tank M 5090 . The wetting liquid holding member M 5100  is impregnated with, and holds, the wetting liquid. Reference numeral M 5080  denotes a wetting liquid transferring member, which is made, for example, of a porous material having an adequate capillary force. The wetting liquid transferring member M 5080  includes a wetting liquid transferring part M 5081  which is in contact with the wiper blade. The wetting liquid transferring member M 5080  is also in contact with the wetting liquid holding member M 5100  infiltrated with the wetting liquid. As a result, the wetting liquid transferring member M 5080  is also infiltrated with the wetting liquid. The wetting liquid transferring member M 5080  is made of the material having the capillary force which enables the wetting liquid to be supplied to the wetting liquid transferring part M 5081  even if a smaller amount of wetting liquid remains 
     Descriptions will be provided for operations of the wetting liquid transferring unit and the wiper portion. 
     First of all, the cap M 5010  is set at the descending position, and thus is escaped to a position where the carriage M 4000  does not contact the blades M 5020 A to M 5020 C, In this state, the wiper portion M 5020  is moved in the −Y direction, and is caused to pass through the part of the blade cleaner M 5060 . Accordingly, the wiper portion M 5020  is caused to abut on the wetting liquid transferring part M 5081  (refer to  FIG. 17 ). By keeping the wiper portion M 5020  in contact with the wetting liquid transferring part M 5081  for an adequate length of time, an adequate amount of wetting liquid is transferred onto the wiper portion M 5020 . 
     Subsequently, the wiper portion M 5020  is moved in the +Y direction. The blade contacts the blade cleaner M 5060  only in a part of the surface of the blade cleaner M 5060 , and no wetting liquid is adhered to the part. For this reason, the wetting liquid remains to be held on the blade. 
     The blade is returned to the position where the wiping operation has been started. Thereafter, the carriage M 4000  is moved to the position where the wiping operation is designed to be performed. Subsequently, the wiper portion M 5020  is moved in the −Y direction. Thereby, the ejection faces of the printing head H 1001  can be wiped with the surface to which the wetting liquid is adhered. 
     1.3 Configuration of Electrical Circuit 
     Descriptions will be provided next for a configuration of an electrical circuit of this embodiment. 
       FIG. 18  is a block diagram for schematically describing the entire configuration of the electrical circuit in the printing apparatus J 0013 . The printing apparatus to which this embodiment is applied is configured chiefly of the carriage board E 0013 , the main substrate E 0014 , a power supply unit E 0015 , a front panel E 0106  and the like. 
     The power supply unit E 0015  is connected to the main substrate E 0014 , and thus supplies various types of drive power. 
     The carriage board E 0013  is a printed circuit board unit mounted on the carriage M 4000 . The carriage board E 0013  functions as an interface for transmitting signals to, and receiving signals from, the printing head H 1001  and for supplying head driving power through the head connector E 0101 . The carriage board E 0013  includes a head driving voltage modulation circuit E 3001  with a plurality of channels to the respective ejecting portions of the printing head H 1001 . The plurality of ejecting portions corresponding respectively to the plurality of mutually different colors. In addition, the head driving voltage modulation circuit E 3001  generates head driving power supply voltages in accordance with conditions specified by the main substrate E 0014  through the flexible flat cable (CRFFC) E 0012 . In addition, change in a positional relationship between the encoder scale E 0005  and the encoder sensor E 0004  is detected on the basis of a pulse signal outputted from the encoder sensor E 0004  in conjunction with the movement of the carriage M 4000 . Moreover, the outputted signal is supplied to the main substrate E 0014  through the flexible flat cable (CRFFC) E 0012 . 
     An optical sensor E 3010  and a thermistor E 3020  are connected to the carriage board E 0013 , as shown in  FIG. 20 . The optical sensor E 3010  is configured of two light emitting devices (LEDs) E 3011  and a light receiving element E 3013 . The thermistor E 3020  is that with which an ambient temperature is detected. Hereinafter, these sensors are referred to as a multisensor system E 3000 . Information obtained by the multisensor system E 3000  is outputted to the main substrate E 00014  through the flexible flat cable (CRFFC) E 0012 . 
     The main substrate E 0014  is a printed circuit board unit which drives and controls each of the sections of the ink jet printing apparatus of this embodiment. The main substrate E 0014  includes a host interface (host I/F) E 0017  thereon. The main substrate E 0014  controls print operations on the basis of data received from the host apparatus J 0012  ( FIG. 1 ). The main substrate E 0014  is connected to and controls various types of motors including the carriage motor E 0001 , the LF motor E 0002 , the AP motor E 3005  and the PR motor E 3006 . The carriage motor E 0001  is a motor serving as a driving power supply for causing the carriage M 4000  to perform main scan. The LF motor E 0002  is a motor serving as a driving power supply for conveying printing medium. The AP motor E 3005  is a motor serving as a driving power supply for causing the printing head H 1001  to perform recovery operations. The PR motor E 3006  is a motor serving as a driving power supply for performing a flat-pass print operation; and the main substrate E 0014  thus controls drive of each of the functions. Moreover, the main substrate E 0014  is connected to sensor signals E 0104  which are used for transmitting control signals to, and receiving detection signals from, the various sensors such as a PF sensor, a CR lift sensor, an LF encoder sensor, and a PG sensor for detecting operating conditions of each of the sections in the printer. The main substrate E 0014  is connected to the CRFFC E 0012  and the power supply unit E 0015 . Furthermore, the main substrate E 0014  includes an interface for transmitting information to, and receiving information from a front panel E 0106  through panel signals E 0107 . 
     The front panel E 0106  is a unit provided to the front of the main body of the printing apparatus for the sake of convenience of user&#39;s operations. The front panel E 0106  includes the resume key E 0019 , the LED guides M 7060 , the power supply key E 0018 , and the flat-pass key E 3004  (refer to  FIG. 6 ). The front panel E 0106  further includes a device I/F E 0100  which is used for connecting peripheral devices, such as a digital camera, to the printing apparatus. 
       FIG. 19  is a block diagram showing an internal configuration of the main substrate E 1004 . 
     In  FIG. 19 , reference numeral E 1102  denotes an ASIC (Application Specific Integrated Circuit). The ASIC E 1102  is connected to a ROM E 1004  through a control bus E 1014 , and thus performs various controls in accordance with programs stored in the ROM E 1004 . For example, the ASIC E 1102  transmits sensor signals E 0104  concerning the various sensors and multisensor signals E 4003  concerning the multisensor system E 3000 . In addition, the ASIC E 1102  receives sensor signals E 0104  concerning the various sensors and multisensor signals E 4003  concerning the multisensor system. Furthermore, the ASIC E 1102  detects encoder signals E 1020  as well as conditions of outputs from the power supply key E 0018 , the resume key E 0019  and the flat-pass key E 3004  on the front panel E 0106 . In addition, the ASIC E 1102  performs various logical operations, and makes decisions on the basis of conditions, depending on conditions in which the host I/F E 0017  and the device I/F E 0100  on the front panel are connected to the ASIC E 1102 , and on conditions in which data are inputted. Thus, the ASIC E 1102  controls the various components, and accordingly drives and controls the ink jet printing apparatus. 
     Reference E 1103  denotes a driver reset circuit. In accordance with motor controlling signals E 1106  from the ASIC E 1102 , the driver reset circuit E 1103  generates CR motor driving signals E 1037 , LF motor driving signals E 1035 , AP motor driving signals E 4001  and PR motor driving signals  4002 , and thus drives the motors. In addition, the driver reset circuit E 1103  includes a power supply circuit, and thus supplies necessary power to each of the main substrate E 0014 , the carriage board E 0013 , the front panel E 0106  and the like. Moreover, once the driver reset circuit E 1103  detects drop of the power supply voltage, the driver reset circuit E 1103  generates reset signals E 1015 , and thus performs initialization. 
     Reference numeral E 1010  denotes a power supply control circuit. In accordance with power supply controlling signals E 1024  outputted from the ASIC E 1102 , the power supply control circuit E 1010  controls the supply of power to each of the sensors which include light emitting devices. The host I/F E 0017  transmits host I/F signals E 1028 , which are outputted from the ASIC E 1102 , to a host I/F cable E 1029  connected to the outside. In addition, the host I/F E 0017  transmits signals, which come in through this cable E 1029 , to the ASIC E 1102 . 
     Meanwhile, the power supply unit E 0015  supplies power. The supplied power is supplied to each of the components inside and outside the main substrate E 0014  after voltage conversion depending on the necessity. Furthermore, power supply unit controlling signals E 4000  outputted from the ASIC E 1102  are connected to the power supply unit E 0015 , and thus a lower power consumption mode or the like of the main body of the printing apparatus is controlled. 
     The ASIC E 1102  is a single-chip semiconductor integrated circuit incorporating an arithmetic processing unit. The ASIC E 1102  outputs the motor controlling signals E 1106 , the power supply controlling signals E 1024 , the power supply unit controlling signals E 4000  and the like. In addition, the ASIC E 1102  transmits signals to, and receives signals from, the host I/F E 0017 . Furthermore, the ASIC E 1102  transmits signals to, and receives signals from, the device I/F E 0100  on the front panel by use of the panel signals E 0107 . As well, the ASIC E 1102  detects conditions by means of the sensors such as the PE sensor and an ASF sensor with the sensor signals E 0104 . Moreover, the ASIC E 1102  controls the multisensor system E 3000  with the multisensor signals E 4003 , and thus detects conditions. In addition, the ASIC E 1102  detects conditions of the panels signals E 0107 , and thus controls the drive of the panel signals E 0107 . Accordingly, the ASIC E 1102  turns on/off the LEDs E 0020  on the front panel. 
     The ASIC E 1102  detects conditions of the encoder signals (ENC) E 1020 , and thus generates timing signals. The ASIC E 1102  interfaces with the printing head H 1001  with head controlling signals E 1021 , and thus controls print operations. In this respect, the encoder signals (ENC) E 1020  are signals which are receives from the CRFFC E 0012 , and which have been outputted from the encoder sensor E 0004 . In addition, the head controlling signals E 1021  are connected to the carriage board E 0013  through the flexible flat cable E 0012 . Subsequently, the head controlling signals E 1021  are supplied to the printing head H 1001  through the head driving voltage modulation circuit E 3001  and the head connector E 0101 . Various types of information from the printing head H 1001  are transmitted to the ASIC E 1102 . Signals representing information on head temperature of each of the ejecting portions among the types of information are amplified by a head temperature detecting circuit E  3002  on the main substrate, and thereafter the signals are inputted into the ASIC E 1102 . Thus, the signals are used for various decisions on controls. 
     In the figure, reference numeral E 3007  denotes a DRAM. The DRAM E 3007  is used as a data buffer for a print, a buffer for data received from the host computer, and the like. In addition, the DRAM is used as work areas needed for various control operations. 
     1.4 Configuration of Printing Head 
     Descriptions will be provided below for a configuration of the head cartridge H 1000  to which this embodiment is applied. 
     The head cartridge H 1000  in this embodiment includes the printing head H 1001 , means for mounting the ink tanks H 1900  on the printing head H 1001 , and means for supplying inks from the respective ink tanks H 1900  to the printing head H 1001 . The head cartridge H 1000  is detachably mounted on the carriage M 4000 . 
       FIG. 21  is a diagram showing how the ink tanks H 1900  are attached to the head cartridge H 1000  to which this embodiment is applied. The printing apparatus of this embodiment forms an image by use of the pigmented inks corresponding respectively to the ten colors. The ten colors are cyan (C), light cyan (Lc), magenta (M), light magenta (Lm), yellow (Y), black 1 (K1), black 2 (K2), red (R), green (G) and gray (Gray). For this reason, the ink tanks H 1900  are prepared respectively for the ten colors. As shown in  FIG. 21 , each of the ink tanks can be attached to, and detached from, the head cartridge H 1000 . Incidentally, the ink tanks H 1900  are designed to be attached to, and detached from, the head cartridge H 1000  in a state where the head cartridge H 1000  is mounted on the carriage M 4000 . 
     1.5 Configuration of Inks 
     Descriptions will be provided below for the ten color inks used in the present invention. 
     The ten colors used in the present invention are cyan (C), light cyan (Lc), magenta (M), light magenta (Lm), yellow (Y), black 1 (K1), black 2 (K2), gray (Gray), red (R) and green (G). It is desirable that all of the color materials used respectively for the ten colors should be pigments. In this respect, for the purpose of dispersing the pigments, publicly known dispersants may be used. Otherwise, for the purpose, it is sufficient that pigments surfaces are modified by use of a publicly known method, and that self-dispersants are added thereto. In addition, color materials used for at least some of the colors may be dyes as long as the use agrees with the spirit and scope of the present invention. Furthermore, color materials used for at least some of the colors may be what are obtained by harmonizing pigments and dyes in color, and a plurality of kinds of pigments may be included therein. Moreover, as for the ten colors of the present invention at least one kind of substance selected from the group consisting of an aqueous organic solvent, an additive, a surfactant, a binder and an antiseptic may be included in therein as long as the inclusion is within the spirit and the scope of the present invention. 
     Next, preferred constitutional materials for 10 color inks used in this embodiment will be described specifically. (Pigment) 
     As color pigments, organic pigments may be used. More specifically, they may include dye lake-based pigments, such as acid dye lake and basic dye lake; insoluble azo pigments, condensed azo pigments and azo lake pigments, such as mono azo yellow, disazo yellow, β-naphthal, naphthal AS, pyrazolone and benzimidazolone; and multiple condensed ring pigments, such as phthalocyanine, quinacridone, anthraquinone, perylene, indigo, dioxazines, quinophthalone, isoindolinone and diketopyroropyrole. Color pigments are not limited to these and other organic pigments may be used. 
     As a black pigment, carbon black is preferably used. For example, furnace black, lamp black, acetylene black and channel black may be used. Further, carbon black that is newly prepared for this invention may be used. This invention, however, is not limited to these pigments and can use the conventionally known carbon black. Rather than using carbon black, it is possible to use, as black pigments, magnetic fine particles such as magnetite and ferrite, or titanium black. 
     For dispersion of pigments, commonly known dispersants may be used, or pigment surfaces may be modified by generally known methods to provide a self dispersion capability. 
     To the ink may be added water-soluble organic solvents, additives, surfactants and antiseptics. For these, commonly available materials may be used. 
     2. Characteristic Construction 
     Now, examples of constructions characteristic of this invention will be described in the following. 
     First Embodiment 
       FIG. 22  is a flow chart showing a sequence of steps executed in a printing operation according to a first embodiment. 
     In the printing sequence, after a print signal is received, the cap M 5010  (see  FIG. 15 ) is opened (step S 1 ). More specifically, the cap M 5010  is moved to a lowered position, as described above, to part it from the print head H 1500  situated at the home position. 
     Then, a stir sequence is executed as required (step S 2 ).  FIG. 22  is a flow chart for the stir sequence. Whether or not to execute the stir sequence depends on whether it is necessary to stir ink in the ink tank before a print operation described later is started. This decision is made by the ASIC E 1102 . For example, the decision making may involve storing the time of execution of the previous stir operation in an EEPROM not shown and, if an elapsed time from the previous stir operation execution until the print signal is received is more than a predetermined length of time, deciding to execute the stir operation. 
     When a decision is made to perform the stir operation as shown in  FIG. 22 , the operation to stir ink in the ink tank is executed at step S 2  and step S 14 . That is, as described later, the carriage M 4000  mounting the print head and the ink tank is reciprocally moved in the main scan direction to stir the ink in the ink tank by an acceleration of the carriage motion. The reciprocal motion of the carriage M 4000  performed to stir ink is different from the reciprocal motion of the carriage M 4000  performed to print an image (step S 4 ), which is described later. In the following, the reciprocal motion of the carriage M 4000  performed at step S 2  and S 14  is referred to as a “stir operation”. When a decision is made to execute the stir sequence as shown in  FIG. 22 , the stir operation is executed at step S 2  and S 14 . When a decision is made not to execute the stir sequence, the stir operation in at least step S 2  is not executed. The stir operations in these steps S 2  and S 14  will be detailed later. 
     Then, prior to the print operation, a preliminary ejection is performed (step S 3 ). The preliminary ejection is a recovery operation which involves ejecting ink, that does not contribute to image printing, from nozzles of the print head H 1001  toward the cap M 5010  in order to maintain the ink ejection performance of the print head H 1001  in good condition. 
     Then, the printing operation is performed by reciprocally moving the carriage M 4000  in the main scan direction (step S 4 ). That is, an operation to eject ink from the print head H 1001  toward the print medium in synchronism with the reciprocal motion of the carriage M 4000  as described above and an operation to feed the print medium in the subscan direction by the transport roller M 3060  are alternated repetitively. As a result of this printing operation, an image according to print data is formed. 
     After the image is formed based on the print data, the carriage M 4000  is returned to the home position (i.e., a capping position in this case) (step S 5 ). 
     Then, a check is made as to whether the next print signal is received (step S 6 ). If it is decided that the next print signal is received, the processing returns to the previous step S 3  to repeat the sequence of steps to perform the preliminary ejection prior to printing (step S 3 ), the print operation (step S 4 ) and the moving of the carriage M 4000  to the home position (step S 5 ). If it is decided that the next print signal is not received, a preliminary ejection is executed during standby by ejecting the ink not contributing to the image printing toward the cap M 5010  situated at the home position (step S 7 ). 
     Then, when the next print signal is received, the processing returns to the previous step S 3  as described above (step S 8 ). As long as the next print signal is not received, the preliminary ejection during standby is repeated at step S 7  until a predetermined time elapses (step S 9 ). When the predetermined time passes, the processing proceeds to step S 10 . 
     Since at the point in time of step S 10  it is not known when the next print signal will be received, wiping on the print head H 1001  is performed in step  10  so that there will be no problem if the print head is left unused for a long period without receiving the next print signal. That is, as described above, the print head H 1001  has its face (nozzle opening forming surface) wiped clean with the blade M 5020 . During the wiping operation, when it contacts the face of the print head, the blade M 5020  may press the residual ink adhering to it into nozzles that are adapted to eject ink of a different color, resulting in a mixing of different color inks. To prevent this, after such a wiping, a preliminary ejection is performed to eject the mixed inks from the nozzles (step S 11 ). This preliminary ejection, as in the preliminary ejection described earlier, ejects ink not contributing to the image printing toward the cap M 5010  situated at the home position. 
     With the preliminary ejection into the cap M 5010  performed, there is ink in the cap M 5010 . If the cap is left standing for a long period, the ink in the cap M 5010  becomes viscous and thereafter may impair the function of the cap M 5010 . That is, the viscous ink may become a hindrance to the normal performance of the capping operation of the cap M 5010 , the suction-based recovery operation, the pressurization-based recovery operation and the preliminary ejection operation. Among them the suction-based recovery operation is most likely to be affected. 
     Therefore, in the next step S 12  the ink in the cap M 5010  is sucked out. That is, as described above, the suction pump M 5000  is operated to transfer the ink from the cap M 5010  into the waste ink absorbent. This operation to suck out ink from the cap M 5010  is also called a “suction-based discharge operation”. 
     Then, the cap M 5010  is closed (step S 13 ). That is, as described above, the cap M 5010  is moved to the raised position to cap the print head H 1500 . 
     During the suction-based discharge operation by step S 12 , the stir operation is also performed at the same time (step S 14 ). The stir operation is done by reciprocally moving the carriage M 4000  but is different from the reciprocal motion of the carriage M 4000  performed during the printing operation (step S 4 ). Since, during the suction-based discharge operation by step S 12 , the cap M 5010  is open, retracted from the print head, the suction-based discharge operation and the stir operation of reciprocally moving the carriage M 4000  can be performed independently and in parallel of each other. 
     In this embodiment the stir operation (step S 14 ) is carried out in parallel with the suction-based discharge operation (step S 12 ) prior to the closing of the cap (step S 13 ). Therefore, there are two kinds of stir operations to stir ink: one performed in the stir sequence (step S 2 ) prior to the print operation and one performed in parallel with the suction-based discharge operation (step S 14 ). 
     Next, the advantage gained by providing two kinds of stir operations will be explained. 
     Normally, the time required to stir ink before starting the print operation increases as the elapsed time from the previous stir operation becomes long. This is because the longer the elapsed time, the more facilitated the deposition of pigment component in the ink will be. For example, as indicated by dashed line in  FIG. 23 , if the elapsed time from the previous stir operation is from one to five days, 20 seconds of stirring is required. Similarly, if the elapsed time is five to 14 days, 40 seconds is required; if the elapsed time is 14 to 30 days, 60 seconds is required; if the elapsed time is 30 to 60 days, 90 seconds is required; and if the elapsed time is more than 60 days, 120 seconds of stirring is required. 
     In this embodiment, the required stirring time is divided and assigned to two stir operations (step S 2 , S 14 ). Therefore, when the stir sequence is executed prior to the print operation, i.e., when it is decided that a stir operation (step S 2 ) needs to be done before the print operation, a part of the time required for the ink stirring at that point in time can be allocated to the subsequent stir operation (step S 14 ). As a result, the stirring time of the stir operation (step S 2 ) performed prior to the print operation can be shortened to the minimum required, thus reducing the time the user has to wait before the print operation starts. On the other hand, the second stir operation (step S 14 ) is performed in parallel with the suction-based discharge operation (step S 12 ). So, the time it takes to complete the post processing after the print operation is finished (post-processing time) does not increase at all. Therefore, the post processing can be completed in the same time as before. 
     In this example, the stirring time required prior to the print operation and indicated by the dashed line in  FIG. 23  is reduced by 10 seconds and this reduced time (i.e., the required stirring time minus 10 seconds) is taken as the stirring time for the first stir operation (step S 2 ). Then, the duration of 10 seconds (by which the stirring time for the first stir operation is reduced) is allocated to the second stir operation (step S 14 ). That is, the stirring time for the second stir operation (step S 14 ) is set to 10 seconds. 
     The stirring times for the two stir operations (step S 2 , S 14 ) are basically set as follows. 
     First, the stirring time corresponding to the dashed line in  FIG. 23 , i.e., the stirring time required to stir ink, is determined. More specifically, the ink tank is actually left standing or put in an accelerated test condition, after which it is mounted to the ink jet printing apparatus. The accelerated test is a high-temperature storage test in which the ink tank is placed in an elevated temperature bath. With the ink tank put in an elevated temperature environment, the ink rises in temperature, reducing its viscosity, which in turn accelerates the sedimentation of pigment component according to the settling equation of Stokes&#39; described above. Further, under the high-temperature environment, a probability of pigment particles impinging on one another increases, accelerating the aggregation of the pigment particles. The acceleration of aggregation is considered to also speed up the sedimentation. It is only necessary to verify how long the ink in the ink tank needs to be stirred to recover its initial state as good as a fresh ink (with no colorant sedimentation). That is, when an ink tank that has been left standing for a predetermined period of time is mounted on an ink jet printer and used for a printing operation without being stirred, a printed image will have a higher density than normal. It is only necessary therefore to determine how long the ink tank needs to be stirred to prevent this phenomenon. 
     The ratio of stirring times allocated to the two stir operations (step S 2 , S 14 ) can be set from the result of investigation described as follows. 
     For example, two or more ink tanks left standing for 14 days as indicated by a dashed line in  FIG. 23  are used. These ink tanks are stirred for different durations of time before they are used to print images. Chromaticities of the printed images are then measured. These chromaticities of the printed images are compared with those of images printed using fresh inks (hereinafter referred to as “reference chromaticities”). 
     An abscissa in  FIG. 24  represents a stirring time in which the ink in the ink tank was stirred after the ink tank that had been left standing for 14 days was mounted in an ink jet printing apparatus. An ordinate in  FIG. 24  represent a difference (color difference) ΔE between a chromaticity of an image printed with an ink in the ink tank that was stirred for the stirring time and a chromaticity of an image printed with a fresh ink. From  FIG. 24  it is seen that 40 seconds of stirring is enough for the ink tank that was left standing for 14 days and that the effect of stirring is saturated if the ink tank is stirred for more than 40 seconds. Here, the color difference ΔE is based on CIE1976 color system. 
     Normally, if the color difference ΔE in the image is less than 2, there is no problem when viewed visually. So, it is seen from  FIG. 24  that setting the stirring time to 30 seconds results in the color difference in the image ΔE of less than 2 and thus poses no practical problem. In this embodiment therefore, for the ink tank that was left standing for 14 days, the stirring time of the stir operation (step S 2 ) prior to the print operation is set to 30 seconds, rather than 40 seconds required to return the pigment ink in the ink tank to the state as good as a fresh ink. That is, the stirring time of the stir operation (step S 2 ) prior to the print operation is allocated 30 seconds which allows the ink to be stirred to a level that does not pose any practical problem. The remaining 10 seconds is allotted to the second stir operation (step S 14 ). 
     Using the above method, the stirring time of the stir operation (step S 2 ) prior to the print operation is set according to the number of days that the ink tank has been left standing, as shown at a solid line in  FIG. 23 . That is, as described above, the time indicated by the dashed line in  FIG. 23  minus 10 seconds is set as the stirring time of the stir operation (step S 2 ) prior to the print operation. More specifically, if the ink tank is left standing for 1 to 5 days, the stirring time is set to 10 seconds; for 5 to 14 days, it is set to 30 seconds; for 14 to 30 days, it is set to 50 seconds; for 30 to 60 days, it is set to 80 seconds; and for 60 or more days, it is set to 110 seconds. 
     Then the second stir operation (step S 14 ) is allotted a stirring time of 10 seconds. When the second stir operation (step S 14 ) is finished, the ink is stirred enough to regain its initial condition, a condition as good as the fresh ink. Although the ink is not completely stirred by the first stir operation (step S 2 ) prior to the print operation, the print operation (step S 4 ) can print an image with no problem in terms of hue. 
     For example, when the period in which the ink tank was left standing is one to five days, the stirring time of the stir operation (step S 2 ) that was set to 20 seconds can be halved to 10 seconds. This can reduce the stress on the user. Further, this embodiment carries out the stir operation (step S 14 ) in parallel with the suction-based discharge operation (step S 12 ) as described above. That is, after the ink jet printing apparatus has received a print signal, the stir operation (step S 14 ) is executed while performing other operations than the print operation. This can shorten the stirring time of the stir operation (step S 2 ) prior to the print operation, reducing the user stress without impairing the quality of the printed image. 
     Further, a stirring means to enhance the efficiency of the stir operation is preferably installed in the ink tank. For example, a conventionally known steel ball may be used that can move on a bottom of the ink tank. It is also possible to suspend a stir plate in the ink tank that will oscillate by an acceleration of the carriage during the stir operation. In either case, the cooperation with the stirring means installed in the ink tank is preferable in enhancing the efficiency of the stir operation (i.e., reducing the stirring time). 
     The speed at which the carriage moves during the stir operation (also called an “idle scan”) should preferably be set faster than the carriage moving speed during the print operation. The carriage moving width (distance moved by the carriage) during the stir operation should preferably be set shorter than that during the print operation. Setting the carriage moving condition during the stir operation in this way is preferable in enhancing the stirring efficiency. 
     That is, to more efficiently stir the ink in the ink tank requires an acceleration of the carriage produced during its acceleration and deceleration. The stirring effect is small when the carriage is moved at a constant speed. In the case of an ordinary ink jet printing apparatus, the moving speed of the carriage during the print operation is set to around 20 inches/second, considering a limit of the frequency of continuously ejecting ink from the print head. To increase the stirring efficiency, it is preferable to set the carriage moving speed during the print operation faster to apply a strong acceleration to the ink. 
     During the print operation it is required that the moving width of the carriage (distance traveled by the carriage) almost corresponding to the print width be scanned at a constant speed. During the stir operation, on the other hand, since the stirring effect produced is small if the carriage is moved at a constant speed, it is preferred that the distance the carriage travels at a constant speed be set as short as possible in order to reduce the stirring time and at the same time enhance the stirring efficiency. That is, the moving width of the carriage (idle scan width) during the stir operation is preferably set shorter than the moving width of the carriage (scan width) during the print operation. 
     For example, a stir plate may be installed oscillatable in the ink tank and the moving speed and moving width of the carriage during the stir operation (idle scan) set to 40 inches/second and to 120 mm. In that case, since one reciprocal movement of the carriage takes about 0.5 seconds including a ramp-up and a ramp-down, the carriage can be reciprocally moved about 60 times in 30 seconds, for example. The carriage moving speed during the normal print operation is 18-24 inches/second. The carriage moving width during the normal print operation is about 230 mm for A4 size paper. 
     In this embodiment as described above, when it is decided that an ink stir operation is necessary, the time required for the stirring is divided and allotted to two stir operations (step S 2 , S 14 ). In that case, the stir operation to eliminate the deposited pigment components in the ink to a level where adverse affects of the settled pigment will not show in a printed image is the one executed prior to the print operation (step S 2 ). In this example, therefore, to allow the ASIC E 1102  to decide whether or not the stir sequence (stir operation (step S 2 )) needs to be carried out, the time that the stir operation (step S 2 ) was last executed is stored in an EEPROM not shown. If the elapsed time from the last execution time (stored in the EEPROM) of the stir operation (step S 2 ) exceeds a predetermine length of time, it is decided that the stir sequence (stir operation (step S 2 )) needs to be executed. 
     If the first stir operation (step S 2 ) is performed, the second stir operation (step S 14 ) is always executed after the printing apparatus has performed a print operation (step S 4 ). So, there is no need to store the final stirring time of the second stir operation (step S 14 ) in the EEPROM. In this example, therefore, the time when the first stir operation (step S 2 ) was executed is taken as the final stirring time. 
     The EEPROM to store the final stirring time may be provided on the ink tank side or on the printing apparatus side. If the EEPROM is installed in the ink tank, an appropriate stir operation condition can be set by considering the final stirring times for individual ink tanks mountable in the printing apparatus. 
     Second Embodiment 
     If it is decided that the stir operation prior to the print operation is not required, the sequence of  FIG. 25  may be executed when the power of the printing apparatus is turned on. When a print signal is received, the normal print sequence of  FIG. 26  may be executed. In  FIG. 25  and  FIG. 26 , steps similar to those of  FIG. 22  are given the same step numbers and their explanations are omitted. 
     In this example, if, after the power of the printing apparatus is turned on, a print signal fails to be received for a predetermined time, the step S 14  in  FIG. 25  performs a stir operation in parallel with the suction-based discharge operation (step S 12 ). If the print signal is received within the predetermined time, the processing moves from step S 8  to step S 20  in  FIG. 25  to execute the normal print sequence of  FIG. 26 . The print sequence in  FIG. 26  is similar to that of  FIG. 22  except that it does not have a stir sequence of step S 2 . In  FIG. 26  the step S 14  executes the stir operation in parallel with the suction-based discharge operation (step S 12 ). As described above, in both  FIG. 25  and  FIG. 26  the stir operation (step S 14 ) is executed in parallel with the suction-based discharge operation (step S 12 ) prior to the cap closing operation (step S 13 ). Therefore, the operation time and the printing time of the printing apparatus are not prolonged because of the stir operation (step S 14 ). 
     When the stir operation prior to the print operation is not required, the stir operation (step S 14 ) is executed during a time period after a printing apparatus power-on operation signal or a print signal is received until a cap is closed (step S 13 ). The stir operation (step S 14 ) to stir ink by reciprocally moving the carriage is separate from the print operation (step S 4 ) and performed in parallel with other operations such as the suction-based discharge operation (step S 12 ). As described above, by closing the cap (step S 13 ) after executing the stir operation (step S 14 ), it is possible to reduce the amount of the next stir operation that is executed when the next operation signal or print signal is received. 
     Third Embodiment 
     In the first embodiment described above, if the number of days that have passed after the print sequence (see  FIG. 22 ) including the stir operation prior to the print operation is finished is within one day, it is decided that the stir operation prior to the print operation is not needed (see  FIG. 23 ). Therefore, in the second embodiment described above, if the number of days that have passed after the print sequence of  FIG. 22  is finished is within one day, the normal print sequence of  FIG. 26  is applied. If in that one day the normal print sequence of  FIG. 26  has been repeated three times to execute a total of three stir operations (step S 14 ) and a fourth print sequence is performed, the fourth stir operation (step S 14 ) may no longer be necessary. That is, when the print sequence of  FIG. 26  is repeated a plurality of times and if the number of repetitions exceeds a predetermined number, the ink is stirred enough and the stir operation (step S 14 ) of  FIG. 26  may no longer be required. 
     This embodiment counts the number of times that the normal print sequence of  FIG. 26  is repeated, i.e., the number of times that the stir operation (step S 14 ) in the figure is repeated. Based on the count, it is decided whether or not to execute the stir operation (step S 14 ) in the figure. For example, it may be decided not to execute the stir operation (step S 14 ) if the number of repetitions of the normal print sequence of  FIG. 26  is four times or more. 
     Fourth Embodiment 
     This embodiment executes a stir operation (step S 2 ) and a suction sequence (step S 30 ) for a suction-based recovery operation, prior to the print operation, as shown in  FIG. 27 . As described later, the time required by the stir operation (step S 2 ) is shortened to reduce the stresses on the user caused by the time the user has to wait until the print operation starts. The suction-based recovery operation is, as described earlier, to suck out ink not contributing to the image printing from the nozzles of the print head into the cap. The ink discharged by suction is the ink supplied from the ink tank. 
     If the pigment component settles in ink, performing the suction-based recovery operation normally renders less noticeable the hue problem that an image is printed more densely than normal. In this embodiment, therefore, when executing the stir operation (step S 2 ) and the suction-based recovery operation (step S 30 ), a ratio of stirring times of the two stir operations (step S 2 , S 14 ) is differentiated from that of the first embodiment. That is, compared with the first embodiment, the ratio of the stirring time for the stir operation (step S 2 ) is reduced whereas the ratio of the stirring time for the stir operation (step S 14 ) is increased. 
     For example, the stirring time of the second stir operation (step S 14 ) is set to 20 seconds and the stirring time of the first stir operation (step S 2 ) is set to 20 seconds less than the time indicated by the dashed line in  FIG. 23 . In this way, if the suction-based recovery operation (step S 30 ) and the stir operation (step S 2 ) are required prior to the print operation, the stirring time of the stir operation (step S 2 ) is shortened by a certain amount and the stirring time of the stir operation (step S 14 ) following the print operation is increased by that same amount. This can further reduce the user stresses while maintaining the printed image quality without losing the ink stirring effect. 
     The timing to execute the stir operation and the suction-based recovery operation may be set at a predetermined time after the last print operation, stir operation or suction-based recovery operation has been executed. It is also possible to increase the degree of the stir operation and suction-based recovery operation (e.g., the stirring time and suction force) as the elapsed time increases. 
     Other Embodiments 
     The operation executed in parallel with the stir operation (also referred to as a “specific operation”) is not limited to the suction-based ink discharge from the cap (step S 12 ). The specific operation needs only to include at least one of a plurality of operations executed by the ink jet printing apparatus during a non-printing operation excluding a print operation involving the reciprocal motion of the carriage. The specific operation can include at least mechanical operations or electrical information processing, such as initialize operation to initialize the ink jet printing apparatus. The stir operation needs only to have at least one part thereof executed in parallel with the specific operation. Therefore, if the stir operation is dividedly executed before and after the print operation, a part of at least one of the divided stir operations must be able to be executed in parallel with the specific operation. 
     Further, based at least on the execution interval of the stir operations or the number of stir operations executed in a defined period, a decision may be made as to whether the recovery operation should be executed and a control may be performed on a carriage moving time, speed and distance during the recovery operation. 
     It is preferred that a stirring means to stir ink in the ink tank by the moving force of the carriage during the stir operation be installed in the ink tank. The stirring means may include a variety of stirring members that can be moved or oscillated in the ink tank. It is, however, not necessary to provide the stirring means in the ink tank. 
     At least a part of the control functions to control the stir operation may be provided in a host device that sends a print signal to the printing apparatus. 
     Further, the ink tank and the print head may be constructed separately, or integrally constructed to realize a head-tank integral configuration. 
     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. 2006-169086, filed Jun. 19, 2006, which is hereby incorporated by reference herein in its entirety.