Patent Publication Number: US-8529055-B2

Title: Printing apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printing apparatus, and particularly relates to a printing apparatus capable of selecting a suitable conveyance path from multiple conveyance paths according to a type of printing medium and/or a selected print quality. 
     2. Description of the Related Art 
     A printing apparatus such as an inkjet printing apparatus forms an image on a printing medium by moving the printing medium and a printing head, which is used to apply a printing agent, relative to each other. If printing media are relatively soft like plain paper, many printing media can be stacked on an inclined sheet feeding tray, and are separately fed one by one by a sheet feeding roller. Then, the printing medium is fed while changing its feeding path by gently bending along the sheet feeding roller, and then is printed and discharged. Instead, such printing media are housed in a cassette disposed at a lower portion of the apparatus, and are fed one by one by a sheet feeding roller. The printing medium thus fed is bent and conveyed in the reverse direction by the sheet feeding roller, turn-over rollers or other similar rollers. After that, the printing medium is printed and further conveyed. 
     In contrast, printing is performed on a printing medium, such as a thick printing medium, a printing medium desired not to bend, and also a printing medium, like a CD-R, practically incapable of bending (in essence, a printing medium having a relatively high stiffness), while the printing medium is conveyed entirely in one plane. To this end, a printing apparatus having a conveyance path in one plane in addition to a conveyance path as described above has been proposed and been put into practical use (For example, see Japanese Patents Laid-open Nos. 2002-192782 and 2007-70105). In this description, such a conveyance path in one plane and printing accompanied by a conveyance operation through the conveyance path are referred to as a flat path and flat path printing, respectively. 
     Japanese Patent Laid-open No. 2002-192782 discloses a configuration including a pair of conveying rollers for conveying a printing medium by nipping the printing medium therebetween from its both sides when printing is performed. With this configuration, a user himself/herself separates and presses together the pair of conveying rollers to set a printing medium. More specifically, in order to perform the flat path printing on a printing medium such as thick paper, the user sets the printing medium by once separating the pair of conveying rollers from each other; horizontally inserting the printing medium into a manual feeding port provided on the back of an apparatus; and then pressing the pair of conveying rollers against each other with the printing medium nipped therebetween. In short, a printing medium is horizontally fed by a user in the sheet feeding operation, whereby the flat path is put into practice without causing the printing medium to bend in the sheet feeding operation. 
     On the other hand, Japanese Patent Laid-open No. 2007-70105 discloses another configuration including a pair of conveying rollers for conveying a printing medium by nipping the medium therebetween from its both sides. In this configuration, the pair of conveying rollers are automatically separated from and pressed against each other. Moreover, an apparatus with this configuration employs a structure allowing a printing medium to be horizontally inserted into the apparatus from the front of the apparatus. Thus, this configuration has an advantage that the operation needed to be performed by a user is easy. 
     The foregoing methods described in Japanese Patents Laid-open Nos. 2002-192782 and 2007-70105, however, have several problems. For example, the configuration in which a user manually separates and presses together the conveying rollers as in Japanese Patent Laid-open No. 2002-192782 requires the user&#39;s manual operation, which may result in an operational error. Moreover, since a printing medium is inserted from the back of the apparatus, this configuration has a problem of poor operability in setting the printing medium. On the other hand, the configuration described in Japanese Patent Laid-open No. 2007-70105 has good operability because the apparatus has the conveying rollers automatically separated and pressed together and allows a printing medium to be inserted from the front of the apparatus. In some cases, however, the flat path printing is desired on a thin printing medium such as plain paper and photo paper, that is, a relatively soft printing medium, as well as a printing medium having relatively high stiffness as described above. When using such a relatively soft printing medium, a user has difficulty in setting the printing medium with high accuracy even with the configuration allowing the printing medium to be set from the front of the apparatus. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in consideration of the foregoing problems, and aims to allow even a relatively soft printing medium to be easily set in a printing apparatus when performing flat path printing. 
     In an aspect of the present invention, there is provided a printing apparatus including a feeder on which a plurality of printing media are stackable, which is capable of feeding the printing media separately one by one, and which includes a feeding path that curves with respect to a conveyance surface where each of the printing media is printed on a print position by a printing unit, the printing apparatus comprising: a conveyance path that is a flat conveyance path continuous with the conveyance surface and is configured to convey the printing medium toward the print position; and a control unit that, without causing the printing unit to perform printing, causes the printing medium to be firstly conveyed from the feeder up to a position where a rear end of the printing medium gets out of the feeding path, and that, after the first conveyance, causes the printing medium to be conveyed reversely in the conveyance path, and that, after the reverse conveyance, causes the printing medium to be conveyed to the print position and then to be printed by the printing unit. 
     In another aspect of the present invention, there is provided a printing apparatus comprising: a flat conveyance path on which a disk-shaped printing medium is conveyable; a printing unit that performs printing on a printing medium conveyed on the conveyance path; a feeder that separates stacked printing media from one to another, and feeds each separated printing medium to the conveyance path through a curving feeding path continuous with the conveyance path; a first mode in which a printing medium fed from the feeder is conveyed until a rear end of the printing medium gets out of the feeding path and then is reversely conveyed, and then in which printing is started under a condition where the printing medium is entirely inside the conveyance path; a second mode in which printing is started under a condition where a part of a printing medium fed from the feeder still remains on the feeding path; and a selector that selects one of the first mode and the second mode. 
     According to the present invention, the flat path printing can be performed even when printing media are set on the feeder that is disposed in the printing apparatus and is configured to feed the printing media separately one by one. Accordingly, even when the flat path printing is to be performed on a relatively soft printing medium, the printing medium can be set easily and surely on the printing apparatus. Consequently, printing quality can be enhanced. 
     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 perspective view of the printing apparatus used in one embodiment of the present invention, and shows the printing apparatus in an unused condition when viewed from the front; 
         FIG. 2  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. 3  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. 4  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. 5  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. 6  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. 7  is a perspective view for explaining a construction of a head cartridge employed in the embodiment; 
         FIG. 8  is a block diagram schematically showing the entire configuration of an electrical circuit in the embodiment of the present invention; 
         FIG. 9  is a block diagram showing an example of an internal configuration of a main substrate shown in  FIG. 8 ; 
         FIG. 10  is a perspective view of the printing apparatus used in an embodiment, showing the printing apparatus during flat path printing when viewed from the front; 
         FIG. 11  is a perspective view of the printing apparatus used in the embodiment, showing the printing apparatus during the flat path printing when viewed from the back; 
         FIG. 12  is a schematic side cross sectional view for explaining the flat path printing performed in the embodiment; 
         FIGS. 13A and 13B  are views for explaining a configuration and operation of a FPPE sensor lever that operates a sensor (FPPE sensor) for detecting an end of a printing medium in the flat path printing; 
         FIGS. 14A and 14B  are perspective views showing a schematic configuration of a mechanism related to conveyance in the flat path printing; 
         FIG. 14A  is a perspective view of the mechanism from the back side when the upper case is detached from the printing apparatus main body; and  FIG. 14B  is a perspective view of the mechanism when the sheet feeding section is further detached from the printing apparatus main body in  FIG. 14A ; 
         FIGS. 15A and 15B  are partial cross-sectional views for schematically showing an operation of a sheet guide flapper for controlling a conveyance path.  FIG. 15A  is a view showing that the sheet guide flapper is lifted, and  FIG. 15B  is a view showing that the sheet guide flapper is lowered; 
         FIG. 16  is a flowchart showing the relationship of  FIGS. 16A and 16B ; 
         FIG. 16A  is a flowchart for explaining an operational sequence performed by the printing apparatus of the embodiment; 
         FIG. 16B  is a flowchart for explaining an operational sequence performed by the printing apparatus of the embodiment; 
         FIG. 17  is a cross-sectional view of  FIG. 14A ; 
         FIGS. 18A and 18B  are cross-sectional views showing a conveyance path of a printing medium; 
         FIG. 18A  shows the conveyance path continued from the sheet feeding section; and  FIG. 18B  shows the conveyance path switched to the flat path; 
         FIG. 19  is a cross sectional view of a printing apparatus showing another embodiment of the flat path section; and 
         FIGS. 20A and 20B  are cross sectional views of a main part of the printing apparatus for explaining flat path printing in the configuration shown in  FIG. 19 . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Descriptions will be provided below for embodiments of the present invention by referring to the drawings. 
     1 Basic 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 sheet feeding section (feeder), a sheet conveying section, a sheet discharging section, a carriage section, a flat path printing section and the like from a viewpoint of functions performed by the mechanisms. These mechanisms are contained in an outer case. 
       FIGS. 1 ,  2 , and  3  are perspective views respectively showing appearances of the printing apparatus to which this embodiment is applied.  FIG. 1  shows the printing apparatus in an unused condition when viewed from the front.  FIG. 2  shows the printing apparatus in an unused condition when viewed from the back.  FIG. 3  shows the printing apparatus in a used condition when viewed from the front. In addition,  FIGS. 4 to 6  are diagrams for describing internal mechanisms in a main body of the printing apparatus. In this respect,  FIG. 4  is a perspective view showing the printing apparatus when viewed from the right above.  FIG. 5  is a perspective view showing the printing apparatus when viewed from the left above.  FIG. 6  is a side, cross-sectional view of the main body of the printing apparatus. 
     Descriptions will be provided for each of the sections by referring to these figures whenever deemed necessary. 
     (A) Outer Case (Refer to  FIGS. 1 and 2 ) 
     The outer case is attached to the main body of the printing apparatus in order to cover the sheet feeding section, the sheet conveying section, the sheet discharging section, the carriage section, and the flat path section. 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 . 
     Sheet 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 sheet discharging tray M 3160  is capable of being contained therein. In addition, the front cover M 7010  is configured to close the sheet 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  (described later) 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 path 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 sheet feeding tray M 2060  is turnably attached to the upper case M 7040 . While the sheet feeding section is not used, the sheet 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 sheet feeding section. 
     The upper case M 7040  and the lower case M 7080  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). 
     Sheet Feeding Section (Refer to  FIGS. 3 and 6 ) 
     As shown in  FIGS. 3 and 6 , the sheet feeding section is configured as follows. A pressure plate M 2010 , a sheet 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 sheet 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. 
     Sheet Conveying Section (Refer to  FIGS. 3 to 6 ) 
     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 sheet guide flapper M 3030  and a platen M 3040  are disposed in an inlet to which a printing medium is conveyed. The sheet 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-sheet 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 sheet 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  as a printing unit is moved 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 sheet conveying section is guided by the pinch roller holder M 3000  and the sheet 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 sheet 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 (lines/inch). 
     Sheet Discharging Section (Refer to  FIGS. 3 to 6 ) 
     The sheet discharging section is configured of a first sheet discharging roller M 3100 , a second sheet discharging roller M 3110 , a plurality of spurs M 3120  and a gear train. 
     The first sheet discharging roller M 3100  is configured of a plurality of rubber portions provided around the metal shaft thereof. The first sheet discharging roller M 3100  is driven by transmitting the driving force of the conveying roller M 3060  to the first sheet discharging roller M 3100  through an idler gear. 
     The second sheet 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 sheet discharging roller M 3110  is driven by transmitting the driving force of the first sheet discharging roller M 3100  to the second sheet 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 sheet discharging rollers M 3100  and M 3110  at predetermined pressures. This configuration enables the spurs  3120  to rotate to follow the two sheet 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 sheet 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 generate 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 sheet 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 sheet discharging roller M 3110  and the spurs M 3120 , and thus is conveyed. Accordingly, the printing medium is delivered to the sheet discharging tray M 3160  and supported thereon. The sheet discharging tray M 3160  is divided into a plurality of parts, and has a configuration in which the sheet discharging tray M 3160  is capable of being contained under the lower case M 7080  which will be described later. When used, the sheet discharging tray M 3160  is drawn out from under the lower case M 7080 . In addition, the sheet 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. 
     Carriage Section (Refer to  FIGS. 4 to 6 ) 
     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 010 , and guides and supports the carriage M 4000  so as to cause the carriage M 4000  to perform reciprocating 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. 8 ). 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. 8 ). 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. 8 ). 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 disc 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 first and second operations. During the first operation, the carriage M 4000  moves in the row direction while the printing head H 1001  is making a print. During the second operation, 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. 
     Head Cartridge 
     The head cartridge H 1000  is detachably mounted on the carriage M 4000 . The head cartridge H 1000  in this embodiment includes the printing head H 1001 , a unit for mounting the ink tanks H 1900  on the printing head H 1001 , and a unit for supplying inks from the respective ink tanks H 1900  to the printing head H 1001 . 
     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 colors, and each of the plurality of ejecting portions is capable of ejecting an ink of one color. Each of the plurality of ejecting portions has  768  nozzles arranged in a direction crossing to the carriage moving direction to allow printing with a density of 1200 dpi (dots/inch) per one color. 
       FIG. 7  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  (K 1 ), black  2  (K 2 ), 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. 7 , 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 . 
     Other Mechanisms 
     In addition to the above mechanisms, the printing apparatus of the present embodiment is provided with an ejection recovery unit as a mechanism to be used to maintain or recover an ejection performance of the printing head H 1001 . The ejection recovery unit may have a cap for capping an ejection-opening forming face of the printing head, a pump operable to apply suction force onto the ejection openings to forcibly discharge ink therefrom in the capping state, and a mechanism for contacting/disparting the cap with/from the ejection-opening forming face. Further, the ejection recovery unit may have a wiper to wipe the ejection-opening forming face thereby wiping off ink and dust remained thereon. 
     Further, the printing apparatus is provided with a flat path section as a substantial unit of the present invention. This flat path section will be described later. 
     1 Configuration of Electrical Circuit 
     Descriptions will be provided next for a configuration of an electrical circuit of this embodiment. 
       FIG. 8  is a block diagram for schematically describing the entire configuration of the electrical circuit in the printing apparatus J 0013 . The printing apparatus of this embodiment 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 (CRFEC) 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 . 
     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 a host apparatus J 0012 . 
     The host apparatus J 0012  is in the form of a computer which generates image data indicating an image to be printed, and which sets up a user interface (UI) for generating the data. Programs operated with an operating system of the host apparatus J 0012  include an application and a printer driver. An application 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. These received data are displayed on a monitor of the host apparatus. Thus, an edit, a process or the like is applied to these received data by means of the application. Thereby, image data are generated. 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 are processed by the printer driver and then transferred to the printing apparatus. 
     Further, the printing apparatus is provided with various motors such as the carriage motor E 0001 , the LF motor E 0002 , an AP motor E 3005  and a PR motor E 3006  which are appropriately controlled. The carriage motor E 0001  is a motor being a driving source for moving the carriage M 4000 . The LF motor E 0002  is a motor being a driving source for conveying the printing medium. The AP motor E 3005  is a motor being a driving source for recovery operation of the printing head H 1001  and for feeding operation of the printing medium. The PR motor E 3006  is a motor being a driving source for flat path printing operation. Further, various sensors such as the PE sensor, a CR lift sensor, LF encoder sensor, a PG sensor and the like are connected to sensor signals E 0104  for transmitting control signals thereto or receiving detection signals therefrom. A printing medium type detection sensor E 0105  is provided as one of such sensors. This sensor is disposed between the sheet feeding roller M 2080  and the PE sensor lever M 3021  for irradiating light on the surface of the printing medium thereby detecting a material of the printing medium based on the light reflected from the printing medium. The main substrate E 0014  is connected to the CREEC E 0012  and a power supply unit E 0015 . The main substrate E 0014  has an interface for transmitting information to, and receiving signals from, the 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 M 0020 , the power supply key E 0018  ( FIG. 1 ). 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. 9  is a block diagram showing an internal configuration of the main substrate E 1004 . 
     In  FIG. 9 , 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 or receives sensor signals E 0104  concerning the various sensors including the printing medium type detection sensor E 0105 . 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 path 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 . 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. 
     3. Characteristic Configuration 
     Descriptions will be provided next for a configuration and operation of a flat path section constituting a characteristic configuration of this embodiment. 
     3.1 Flat-Path Section 
       FIGS. 10 and 11  show the printing apparatus of this embodiment during the flat path printing, viewed from the front and back thereof, respectively.  FIG. 12  is a cross section view for explaining an internal mechanism of the main body of the printing apparatus that performs the flat path printing. 
     A printing medium is fed from the sheet feeding section while being bent, because the path for conveying the printing medium curves up to the pinch rollers M 3070  as shown in  FIG. 6 . For this reason, a reaction force is generated once in the printing medium due to this bent state, and then disappears when the rear end of the printing medium gets out of this curve portion. This causes a conveyance load on the printing medium to largely vary during printing. Such variation in the conveyance load may deteriorate print quality. 
     To avoid such a problem, in the flat path printing of this embodiment, a printing medium is fed from the sheet feeding section, and then is further conveyed without being printed until the rear end of the printing medium gets out of the curve portion. After being conveyed to the position described above, the printing medium is reversely conveyed along the flat and horizontal conveyance path and is set in a predetermined position. Then, the printing medium is printed by being further conveyed from the predetermined position to the print position. 
     The front cover M 7010  is usually located below the sheet delivery section, because the front cover M 7010  is also used as a tray on which several tens of printing media already printed are stacked (refer to  FIG. 3 ). In the fiat path printing, however, the front cover M 7010  is lifted up to the position of the sheet discharging port so as to convey the printing medium horizontally ( FIG. 10 ). An unillustrated hook or the like is provided to the front cover M 7010  and is used to fix the front cover M 7010  to a flat path sheet feeding position. A sensor can detect that the front cover M 7010  is in the flat path sheet feeding position. Thus, according to the detection, it can be determined that the current mode is the flat path printing mode. 
     Moreover, A rear tray M 7090  can be opened by pressing a rear tray button M 7110 . Further, a rear sub-tray M 7091  can be opened in the form of the letter V (refer to  FIG. 11 ). The rear tray M 7090  and the rear sub-tray M 7091  are trays for supporting a long printing medium on the back side of the main body of the printing apparatus in the case where the long printing medium juts out from the back side of the main body while being conveyed reversely. Unless a thick printing medium is kept flat during printing, the conveyance load may vary. This is likely to adversely affect the print quality. For this reason, the provision of these trays is effective. However, if a printing medium is short enough not to jut out of the back side of the main body of the printing apparatus, the rear tray M 7090  and the like do not need to be opened. 
     The flat path conveyance of a printing medium is ready to start by setting the front cover M 7010  in the up position (and also by opening the rear tray M 7090 , if needed), as described above. At this time, the flat path is approximately horizontal as shown in  FIG. 12 . 
       FIGS. 13A and 13B  are views for providing detailed descriptions of an FPPE sensor lever M 3041  that operates a sensor E 9001  (FPPE sensor) for detecting a rear end of a printing medium in the flat path printing. The FPPE sensor lever M 3041  is configured to be rotatable about the second sheet delivery roller M 3110 . When no printing medium is conveyed, the FPPE sensor lever M 3041  is biased to a position shown in  FIG. 13A  by the action of an FPPE sensor lever spring M 3042 . When the FPPE sensor lever M 3041  is located in this position, a light shield plate of the FPPE sensor lever M 3041  does not block a light path of the FPPE sensor E 9001  in the form of a transmissive-type optical sensor. 
     In this embodiment, a printing medium is conveyed in a direction F shown in  FIG. 13B  when being fed from the sheet feeding section and when being fed in the flat path printing. When the printing medium is conveyed from the platen M 3040  in the F direction, a leading end of the printing medium rotates the FPPE sensor lever M 3041  about the second sheet delivery roller M 3110  in the counterclockwise direction in  FIG. 13B . With this rotation, the light shield plate of the FPPE sensor lever M 3041  comes to a position where the light path of the FPPE sensor E 9001  is blocked. At a timing of being blocked, the FPPE sensor E 9001  detects the end of the printing medium. On the other hand, when a printing medium is again drawn back to the inside of the main body for the flat path printing, the printing medium is conveyed in a direction B in  FIG. 13B . Also, in this case, a leading end of the printing medium rotates the FPPE sensor lever M 3041  and thereby the FPPE sensor E 9001  detects the end of the printing medium. 
     With the foregoing configuration, the front or the rear end of the printing medium can be detected. Note that, the aforementioned PE sensor lever M 3021  is also rotated by an end of the printing medium, and the PE sensor E 0007  is enabled to detect the front or rear end of a printing medium in the direction F and in the direction B shown in  FIG. 13B , according to a detection that the light path of the PE sensor E 0007  is in the light blocked state or in the light passing state. 
       FIGS. 14A and 14B  are perspective views showing a schematic configuration of a mechanism related to conveyance in the flat path printing.  FIG. 14A  is a perspective view of the mechanism from the back side when the upper case M 7040  is detached from the printing apparatus main body, and  FIG. 14B  is a perspective view of the mechanism when the sheet feeding section is further detached from the printing apparatus main body in  FIG. 14A . 
       FIG. 14A  shows that a flat conveyance path (flat path) for a printing medium is formed by the sheet delivery tray M 3160 , the front cover M 7010 , the platen M 3040 , the sheet guide flapper M 3030 , the flat path guide M 3050 , the rear tray M 7090  and the rear sub-tray M 7091 . In  FIG. 14B , a PGF input gear M 9210  is pivotally and rotatably supported by the chassis M 1010  with a sheet guide flapper rotation shaft (hereinafter, referred to as a PGF rotation shaft) M 9200 . 
     Moreover, a cam-shaped portion M 9211  for pressing down one end of the sheet guide flapper M 3030  is integrally formed on the PGF input gear M 9210  located at one end of the PGF rotation shaft M 9200 . In addition, a sheet guide flapper release cam (hereinafter, referred to as a PGF release cam) M 9240  for pressing down the other end of the sheet guide flapper M 3030  is provided at the other end of the PGF rotation shaft M 9200 . These two cam-shaped portions have symmetrical shapes, and press down the sheet guide flapper M 3030  at the same timing. Thus, a surface of the sheet guide flapper M 3030  on which a printing medium is conveyed is positioned approximately horizontal, whereby the flat path is formed. 
     The PGF input gear M 9210  is further provided with an unillustrated rib with a cylindrical shape. With the rotation of the PGF rotation shaft M 9200 , the rib covers and uncovers an unillustrated sheet guide flapper sensor being an infrared sensor, whereby the rotation angle of the PGF rotation shaft M 9200  can be detected. 
       FIGS. 15A and 15B  are partial cross-sectional views for schematically showing an evading operation of the sheet guide flapper M 3030 .  FIG. 15A  shows that the sheet guide flapper M 3030  is lifted to guide a printing medium conveyed from the sheet feeding section. The sheet guide flapper M 3030  is biased by an unillustrated spring member in a direction in which the sheet guide flapper M 3030  is lifted. In addition, since the sheet guide flapper M 3030  is capable of rotating about the unillustrated bearing unit as described above, the sheet guide flapper M 3030  is positioned by abutting on the chassis M 1010 . 
       FIG. 15B  is a partial cross-sectional view showing that the sheet guide flapper M 3030  is lowered. The cam-shaped portion M 9211  formed on the PGF input gear M 9210 , and the PGF release cam M 9240  (see  FIG. 14 ) are symmetrically formed respectively at both ends of the PGF rotation shaft M 9200 , as described above, and come into contact with arm portions M 3031  of the sheet guide flapper M 3030 . With the rotations of these two cam-shaped portions, the arm portions M 3031  are pressed down in a direction shown by an arrow M 3030   a , and thereby the lifted side of the sheet guide flapper M 3030  is also pressed down. Consequently, the printing medium conveying surface is made approximately horizontal. During the flat path printing, a printing medium is conveyed from the sheet discharging port with the conveying surface thus made horizontal. 
     With the mechanism described above, the sheet guide flapper M 3030  of this embodiment can change its state between the state for the sheet feeding from the sheet feeding section as shown in  FIG. 15A , and the state for the flat path conveyance as shown in  FIG. 15B . Such a change is made by transmission of power from the foregoing PR motor E 3006 . 
     3.2 Flat Path Printing Control 
       FIG. 16  is a flowchart for explaining an operational sequence performed by the printing apparatus of this embodiment.  FIG. 17  is a cross-sectional view of  FIG. 14A .  FIGS. 18A and 18B  are cross-sectional views for explaining characteristic operational states in the flowchart in  FIG. 16 . 
     In order to start the flat path printing mode, whether or not printing is currently ongoing is determined in step S 1 . If it is determined that the printing is ongoing, the processing moves to step S 2  and the printing is continuously performed on a page whose printing is ongoing. If there is print data following data of the current page, the data is cancelled in step S 3 . In the printing apparatus of this embodiment, the front cover M 7010  is made approximately horizontal in the flat path printing, while the front cover M 7010  is configured to have its one end elevated to improve the capacity of stacking printing media discharged in the normal printing mode. If the posture of the front cover M 7010  is changed during printing, such a change adversely affects the printing medium conveyance, and thereby deteriorates the print quality. To avoid this, only a single printing medium whose printing is ongoing is completely printed and then discharged in this embodiment. 
     If it is determined in step S 1  that the printing is not ongoing, the processing moves to step S 4  and both outputs of the PE sensor E 0007  and the FPPE sensor E 9001  are checked. Even when it is determined in step S 1  that the printing is not ongoing, a printing medium previously printed may remain in the sheet conveying section. For this reason, in this embodiment, a final confirmation as to the presence of a printing medium is made by use of the two sensors just in case. If any one of the sensors detects the presence of a printing medium (ON state), the processing goes to step S 5  and the discharge processing of the printing medium is performed. Upon completion of all these steps, it is definitely sure that no sheet remains in the printing medium conveyance path. 
     In step S 6 , a designated print quality and printing medium type are checked in reference to a print control signal from a host apparatus J 0012 . When the designated print quality is high or when the designated printing medium type is photo paper, the processing goes to step S 7 . Otherwise, the processing goes to step S 29 . This embodiment employs the sequence in which the processing goes to step S 7  if any one of the designated print quality and printing medium type is determined as matching a predetermined condition for the flat path printing in step S 6 . Instead, the processing may go to step S 7  only if both of them match their respective predetermined conditions for the flat path printing. 
     Step  7  to step  28  are for a flat path printing operation, while step  29  to step  36  are for a normal printing operation. 
     When the processing goes to step  7 , the position of the front cover M 7010  is detected based on a sensor output in order to perform the flat path printing. Moreover, whether the rear tray M 7090  is open or close is detected based on a sensor output in step S 8 . After confirming that the front cover M 7010  is in the flat path position in step S 7  and confirming that rear tray M 7090  is open in step S 8 , the processing goes to step S 9 . 
     In step S 9 , the sheet guide flapper M 3030  is rotated to a sheet feeding position in order to receive a printing medium fed from the sheet feeding section.  FIG. 18A  shows a state in which the sheet guide flapper M 3030  is located in the sheet feeding position after rotation in step S 8 . In this state, the printing medium conveyance path from the sheet feeding section to the sheet conveying section is continuously formed in a direction of an arrow A in  FIG. 18A . 
     In subsequent step S 10 , a printing medium stacked on the sheet feeding section is fed. In step S 11 , the front end of the fed printing medium is detected based on the output from the PE sensor E 0007 . A failure in detecting the front end of the printing medium in step S 11  means that no printing medium is set on the sheet feeding section. Thus, the processing goes to step S 12 , and the operation is terminated as a SHEET EMPTY error. 
     If the front end of the printing medium is detected in step S 11 , the printing medium is conveyed by a predetermined distance up to a nip portion between the conveying roller M 3060  for generating a force of conveying the printing medium, and the pinch rollers M 3070 . Then, in step S 13 , the front end of the printing medium comes into contact with the nip portion between the conveying roller M 3060  and the pinch rollers M 3070  (these rollers are not rotated at this time), whereby the front end of the printing medium is aligned in a direction perpendicular to the conveyance direction. In this way, an operation for correcting oblique conveyance of the printing medium (also called “a registration operation”) is performed herein, the oblique conveyance mainly being attributed to the sheet feeding section. The printer apparatus for the conventional flat path printing is configured to require a user to set a printing medium on the flat path, and thereby is incapable of performing such an oblique conveyance correction operation by itself. In this embodiment, however, the printer apparatus feeds a printing medium from the sheet feeding section, and thus is enabled to perform the oblique conveyance correction operation. Consequently, highly accurate conveyance of printing media can be achieved. 
     In subsequent step S 14 , the printing medium is further conveyed until the rear end of the printing medium gets out of the sheet feeding section. When the rear end of the printing medium is out of the sheet feeding section, the printing medium can be guided onto the flat path by rotating the sheet guide flapper M 3030 . In this embodiment, the printing medium is conveyed until the output from the PE sensor E 0007  turns into the OFF state (a SHEET ABSENT STATE) in step S 15 . This prevents the printing medium from returning to the sheet feeding section when the printing medium is conveyed reversely in step S 20 . Otherwise, the rear end of the printing medium may be still in the sheet feeding section, and the printing medium may return to the sheet feeding section. Instead, if the PE sensor E 0007  is in the ON state in step S 15 , this means that a sheet jam occurs in the course of sheet feeding. In this case, the processing goes to step S 16 , and the operation is terminated as a sheet jam error. 
     In step S 17 , the output from the FPPE sensor E 9001  is similarly determined. If the FPPE sensor E 9001  is in the OFF state (SHEET ABSENT STATE), it is determined that a sheet jam occurs between the roller pair of the conveying roller M 3060  and the pinch rollers M 3070  and the processing goes to step S 18 . Then, the operation is terminated as a sheet jam error. 
     In this embodiment, the distance of the printing medium conveyance is set to be such a length that the rear end of the printing medium cannot reach the nip portion between the conveying roller M 3060  and the pinch rollers M 3070  after the PE sensor E 0007  turns into the OFF state. This setting keeps the printing medium nipped between the roller pair of the conveying roller M 3060  and the pinch rollers M 3070 . Thus, the effect of the oblique conveyance correction operation in step S 13  is also maintained. 
     After it is confirmed that the printing medium is normally conveyed in step S 15  and S 17 , the sheet guide flapper M 3030  is rotated in step S 19  to switch the printing medium conveyance path to the flat path as shown in  FIG. 18B . 
     In subsequent step S 20 , the printing medium is conveyed reversely in a direction shown by an arrow B in  FIG. 18B  up to the flat path formed by the bottom surface of the sheet feeding section, the flat path guide M 3050  and the rear tray M 7090 . Also, during this reverse conveyance, the outputs from the PE sensor E 0007  and the FPPE sensor E 9001  are checked in step S 21  and step S 23 , respectively If a sheet jam is determined as occurring, the processing goes to step S 22  or S 24  where the operation is terminated as a sheet jam error. 
     The distance of the printing medium reverse conveyance in step  20  is set to be such a length that the front end of the printing medium cannot reach the nip portion between the conveyance roller M 3060  and the pinch rollers M 3070  after the front end of the printing medium is detected by the FPPE sensor E 9001 . This setting keeps the printing medium nipped between the roller pair of the conveying roller M 3060  and the pinch rollers M 3070 . Thus, the effect of the oblique conveyance correction operation in step S 13  is also maintained. 
     In step S 25 , the printing medium M 9900  is set in a position ready to print, that is, a print start position thereof is detected, prior to the printing operation. After that, the printing operation is normally performed in step S 26  and the sheet discharge operation after the printing is performed in step S 27 . Then, this series of printing operation is terminated in step S 28 . The printing medium conveying direction in step S 25  to step S 28  is a direction shown by an arrow F in  FIG. 18B . 
     On the other hand, if it is found, as a result of checking in step S 6 , that neither of the designated print quality nor the printing medium matches the predetermined condition, the processing goes to step S 29  and the normal printing operation is performed. In this case, firstly in step S 29 , the sheet guide flapper M 3030  is rotated to the sheet feeding position, whereby the printing medium conveyance path from the sheet feeding section to the sheet conveying section is continuously formed. Then, if the OFF state (SHEET ABSENT STATE) is detected by the PE sensor in step S 31 , this means that a sheet jam occurs during the sheet feeding. Accordingly, the processing goes to step S 32 , and the operation is terminated as a sheet jam error. 
     If the ON state (SHEET PRESENT STATE) is detected in step S 31 , the processing goes to step S 31 - 2 . In aforementioned step S 6 , the flat path printing operation is selected according to a signal being included in a print control signal from the host apparatus J 0012 , and indicating the printing medium type and printing mode. In contrast, in step S 31 - 2 , which type of printing medium is actually used as a print target is determined based on a detection result from the printing medium type detection sensor E 0105 , under the situation where the flat path printing is not selected as a result of step S 6 . Then, if the printing medium is determined as a photo paper sheet or a thick paper sheet, the processing goes to step S 13  and the flat path printing is performed. 
     If the printing medium is determined as neither the photo paper sheet nor the thick paper sheet in step S 31 - 2 , the processing goes to step S 31 - 3 . In step S 31 - 3 , whether or not a time t is longer than a usual time is determined, under the situation where the flat path printing is not selected based on the detection result from printing medium type detection sensor E 0105 . Here, the time t is a time required by the PE sensor E 0007  to detect the frond end of the printing medium after the sheet feeding roller M 2080  starts sheet feeding. In other words, a determination is made as to whether or not the time t is longer than a predetermined time T. Then, if the determination result is affirmative, the processing goes to step S 13  and the flat path printing is performed. Here, a case where the time t required until the front end of the printing medium is detected after the sheet feeding starts is longer than the usual time is considered to occur for the following reason. When a printing medium is thick and accordingly has large conveyance resistance, the printing medium may slip on the sheet feeding roller M 2080  due to the large conveyance resistance. Thereby, in such a case, the flat path printing is performed. This switching to the flat path printing is effective for the case where the printing medium type detection sensor E 0105  fails to detect that a printing medium is a thick paper sheet even though the printing medium is actually the thick paper sheet. 
     If the determination result is negative in step S 31 - 3 , that is, if the time t is equal to or shorter than the predetermined time T, the processing goes to step S 32  and the foregoing oblique conveyance correction operation is performed. Thereafter, in step S 34  to step S 37 , the same operation as in step S 25  to step S 28  in the flat path printing is performed and the normal printing operation is terminated. In other words, in the course of step S 29  to step S 37 , the sheet guide flapper M 3030  is constantly located in the position as shown in  FIG. 18A  without any rotation. 
     Herein, any one of or both of foregoing steps S 31 - 1  and S 31 - 3  can be omitted. 
     As has been described above, according to this embodiment, the flat path printing can be performed by use of a sheet fed from the sheet feeding section. Thus, a conveyance load is prevented from varying, thereby not leading to deterioration in print quality. Moreover, since the apparatus itself performs the entire operation from feeding to discharging a stacked printing medium, the apparatus can eliminate the necessity for a user to do troublesome work by himself/herself for setting a printing medium on the flat path, and also eliminate the possibility that oblique conveyance or the like occurs. Furthermore, since printing media are fed from the sheet feeding section, the flat path printing can be performed continuously on multiple sheets. 
     3.3 Another Embodiment of Flat-Path Section 
       FIG. 19  is a cross sectional view of a printing apparatus showing another embodiment of the flat-path section.  FIGS. 20A and 20B  are cross sectional views of a main part of the printing apparatus for explaining flat path printing in the configuration shown in  FIG. 19 . 
     The foregoing embodiment is basically suitable for a configuration in which a printing medium stacked on the inclined sheet feeding tray is fed by the sheet feeding roller and is conveyed along the sheet feeding roller while curving gently. In contrast, this embodiment is suitable for a configuration in which a printing medium housed in a cassette disposed in a lower part of the apparatus is fed by a sheet feeding roller and is conveyed in the reverse direction after being bent largely in a U-shape and being turned over by the sheet feeding roller, a turn-over roller or other similar rollers. Such a path will be referred as a U-turn path. 
     In  FIG. 19 , a plurality of unillustrated printing media stacked in a cassette M 8000  are separately fed by a pickup roller M 8010 , and are each guided to a nip portion between a first U-turn roller M 8020  and a first driven roller M 8021 . Then, while being guided by a U-turn inner guide M 8040  and a Upturn outer guide M 8050 , the printing medium is nipped and conveyed between a second U-turn roller M 8030  and a second driven roller M 3081  and then is conveyed to the sheet guide flapper M 3030  being already on standby in the sheet feeding position after rotation. 
     The printing medium conveyance path after that is equivalent to that described with reference to  FIGS. 17 ,  18 A and  18 B. More specifically, after sheet feeding starts, the printing medium is firstly conveyed from the U-turn inner guide M 8040  to the sheet guide flapper M 3030  as shown by an arrow A′ in  FIG. 20A . Then, when the rear end of the printing medium is conveyed to just before the nip portion between the conveying roller M 3060  and the pinch rollers M 3070  after passing by the PE sensor lever M 3000 , the sheet guide flapper M 3030  is rotated to a position shown in  FIG. 20B . The printing medium is reversely conveyed along an arrow B′ in  FIG. 20 . At this time, since the sheet guide flapper M 3030  is located in the flat path position, the printing medium is conveyed on the flat path guide M 3050  disposed below the U-turn inner guide M 8040 . 
     A sequence in this embodiment is equivalent to that explained with reference to  FIG. 16 , and is different from that only in the conveyance path in the sheet feeding operation in step S 10  and step S 30 . Accordingly, this embodiment can produce the same effects as the foregoing embodiment. 
     4. Others 
     In the aforementioned embodiments, the flat path printing is enabled by elevating the front cover M 7010  and also by opening the rear tray M 7090 . However, as described above, the flat path printing can also be performed in a different manner, for example, when a printing medium has a length small enough to be accommodated inside the main body of the apparatus. 
     In addition, the descriptions have been provided for the embodiments in which the present invention is applied to the configuration having the gently curving conveyance path from the sheet feeding section, and the configuration having the largely curving U-turn path. Obviously, the present invention is also applicable to a printing apparatus including both the configurations. 
     In the aforementioned embodiments, the conveyance path (flat path) from the rear tray M 7090  to the sheet delivery tray M 3160  is made flat and horizontal. However, the term “flat” in this description of the invention does not necessarily mean flat in a strict sense. The conveyance path in the flat path state can be curving or concavo-convex to such an extent that a variation of the conveyance load does not deteriorates the print quality, although it depends on a type of printing medium to be used. In addition, this is also applicable to the term “horizontal”. Thus, the conveyance path can be inclined from the horizontal plane to some extent. 
     Additionally, in the foregoing embodiments, whether or not to perform the flat path printing is determined depending on the printing quality and/or the type of printing medium set on a printer driver running in the computer-type host apparatus J 0012 . However, a user may designate whether or not to perform the flat path printing. Moreover, instead of the printer driver, the printer apparatus itself may be configured to be settable for designating whether or not to perform the flat path printing. 
     Moreover, it is apparent that the aforementioned number of tones (colors and densities) of inks and the aforementioned kinds of inks have been described only as examples. 
     Furthermore, although the foregoing embodiments have been described in connection with the printing method using the inkjet printing head that ejects ink as droplets, the printing method to which the present invention is applicable to produce the effects is not limited to this type of printing method. The present invention is applicable to any type of printing method if the method uses a printing head including an array of multiple printing elements such as nozzles or other types. 
     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. 2008-155246, filed Jun. 13, 2008, which is hereby incorporated by reference herein in its entirety.