Patent Publication Number: US-7914112-B2

Title: Printing apparatus with switchover section that switches over patterns of velocity data

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a printing apparatus. 
     2. Related Art 
     A dot impact printer is known as one example of various kinds of conventional printing apparatuses. As disclosed in JP-A-2004-322463, a dot impact printer prints images by striking a number of recording wires onto a sheet of print target medium so as to record dot pattern thereon while scanning (i.e., moving) a carriage, which has recording heads mounted thereon, in the axial direction of a carriage axis. 
     The dot impact printer described in JP-A-2004-322463 (refer to abstract thereof) changes the accelerated velocity of the carriage during acceleration and deceleration thereof depending on the characteristic value of its operating environment. That is, in accordance with the environmental characteristic value, the disclosed dot impact printer changes the accelerated velocity of the carriage that is applied during acceleration up to the point at which the moving speed of the carriage reaches a predetermined value and the accelerated velocity thereof that is applied during deceleration from the point at which the carriage moves at the predetermined speed till it stops. By this means, the related-art dot impact printer described in the above publication achieves high-precision printing depending on use environment. 
     As described above, the related-art dot impact printer disclosed in the above publication changes the accelerated velocity of the carriage during acceleration and deceleration thereof depending on the characteristic value of its operating environment. Therefore, under a given set of circumstances, the carriage moves in a main scan direction constantly with the same accelerated velocity. For this reason, disadvantageously, the carriage is susceptible to intense vibration always at the same time after the start of its scanning movement, that is, when the forced vibration frequency of a carriage driving motor coincides with the resonance frequency of the dot impact printer. It is desired to provide a technical solution to the problem of uneven printing, which could occur when the carriage is vibrated intensely during the execution of printing. One conceivable solution for prevention of uneven printing is, for example, to accelerate and decelerate the carriage in a “no-ink-discharge” state. However, if such an approach is taken, a sufficiently wide space is required to secure the scanning range of the carriage. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide a printing apparatus that does not form “rainbow unevenness” in a print target medium. 
     In order to address the above-identified problems without any limitation thereto, the invention provides, as a first aspect thereof, a printing apparatus that performs printing by scanning a carriage that has a print head in a main scan direction, the printing apparatus including: a carriage motor that drives the carriage; a control section that controls the driving of the carriage motor; a memory section that stores a plurality of patterns of velocity data regarding at least either one of scanning speeds of the carriage after start of the scanning and driving speeds of the carriage motor corresponding to the scanning speeds of the carriage; and a driving mode switchover section that switches over the patterns of the velocity data, wherein the control section controls the driving of the carriage motor in such a manner that the carriage is scanned on the basis of the velocity data selected by the driving mode switchover section. 
     With such a configuration, since the carriage is scanned on the basis of velocity data selected, as a result of switchover, by the driving mode switchover section, it is possible to switch over to velocity data that is suited for the operating environment or the like among the plurality of patterns of velocity data. Therefore, the invention makes it possible to respond flexibly to the operating environment, which achieves printing with high precision. In addition thereto, the above-mentioned switchover makes it possible to stagger points in time at which the carriage is affected by vibrations. Therefore, it is possible to spread uneven printing points caused by the vibrations of the carriage. Thus, the invention makes it possible to effectively avoid the generation of rainbow unevenness on the print target medium after completion of printing. 
     In the configuration of the printing apparatus according to the first aspect of the invention, it is preferable that the plurality of patterns of the velocity data are provided for at least either one of acceleration and deceleration of the carriage that is to be scanned. 
     According to the above configuration, the velocity data have a plurality of acceleration inclinations or a plurality of deceleration inclinations. Therefore, the above-mentioned switchover performed by the driving mode switchover section makes it possible to stagger points in time at which the carriage is affected by vibrations during at least either one of acceleration and deceleration of the carriage. 
     In the configuration of the printing apparatus according to the first aspect of the invention, it is preferable that the driving mode switchover section switches over the plurality of patterns of the velocity data stored in the memory section so as to select a pattern of the velocity data to be used in a sequential manner among the plurality of patterns of the velocity data. 
     With such a configuration, the carriage is scanned in accordance with the velocity data having patterns different from one another that are switched therebetween in a sequential manner. Therefore, the above-mentioned switchover makes it possible to stagger points in time at which the carriage is affected by vibrations without fault. Therefore, it is possible to spread uneven printing points caused by the vibrations of the carriage without fault. Thus, the invention makes it possible to effectively avoid the generation of rainbow unevenness on the print target medium after completion of printing. 
     In the configuration of the printing apparatus according to the first aspect of the invention, it is preferable that the driving mode switchover section switches over the patterns of the velocity data either for each outward movement or for each set of outward and homeward movements of the carriage. 
     With such a configuration, it is possible to perform the switchover of the scanning speeds of the carriage both for bidirectional printing and unidirectional printing. Therefore, the above-mentioned switchover makes it possible to stagger points in time at which the carriage is affected by vibrations for each scanning. 
     In the configuration of the printing apparatus according to the first aspect of the invention, it is preferable that the printing apparatus further includes a print target medium recognition section that detects the size or the type of a print target medium, wherein the driving mode switchover section switches over the patterns of the velocity data on the basis of a result of detection that is performed by the print target medium recognition section. 
     With such a configuration, it is possible to scan the carriage at the scanning speed suited for the size or the type of the print target medium. 
     In the configuration of the printing apparatus according to the first aspect of the invention, it is preferable that the driving mode switchover section switches over the patterns of the velocity data on the basis of ink discharge amount. 
     With such a configuration, it is possible to scan the carriage on the basis of a predetermined velocity data depending on required printing precision. 
     In order to address the above-identified problems without any limitation thereto, the invention provides, as a second aspect thereof, a printing apparatus that performs printing by scanning a carriage that has a print head in a main scan direction, the printing apparatus including: a carriage motor that drives the carriage; a control section that controls the driving of the carriage motor; a memory section that stores a plurality of pieces of data regarding at least either one of movement start positions of the carriage and movement stop positions of the carriage; and a movement position switchover section that switches over at least either one of the movement start positions of the carriage and the movement stop positions of the carriage, wherein the control section controls the driving of the carriage motor in such a manner that the carriage is scanned on the basis of the movement start position and/or the movement stop position selected by the movement position switchover section. 
     With such a configuration, since the carriage is scanned on the basis of movement start positions and movement stop positions selected, as a result of switchover, by the movement position switchover section, it is possible to switch over to a movement start position and a movement stop position that is suited for the operating environment or the like among the plurality of movement start positions and movement stop positions. Therefore, the invention makes it possible to respond flexibly to the operating environment, which achieves printing with high precision. In addition thereto, the above-mentioned switchover makes it possible to stagger points in time at which the carriage is affected by vibrations. Therefore, it is possible to spread uneven printing points caused by the vibrations of the carriage. Thus, the invention makes it possible to effectively avoid the generation of rainbow unevenness on the print target medium after completion of printing. 
     In the configuration of the printing apparatus according to the second aspect of the invention, it is preferable that the movement position switchover section switches over at least either one of the movement start positions and the movement stop positions either for each outward movement or for each set of outward and homeward movements of the carriage. 
     With such a configuration, it is possible to perform the switchover of at least either one of the movement start positions and the movement stop positions of the carriage both for bidirectional printing and unidirectional printing. Therefore, the above-mentioned switchover makes it possible to stagger points in time at which the carriage is affected by vibrations for each scanning. 
     In the configuration of the printing apparatus according to the second aspect of the invention, it is preferable that the printing apparatus further includes a print target medium recognition section that detects the size or the type of a print target medium, wherein the movement position switchover section switches over at least either one of the movement start positions and the movement stop positions on the basis of a result of detection that is performed by the print target medium recognition section. 
     With such a configuration, it is possible to scan the carriage at the movement start position and/or the movement stop position suited for the size or the type of the print target medium. 
     In the configuration of the printing apparatus according to the second aspect of the invention, it is preferable that the movement position switchover section switches over at least either one of the movement start positions and the movement stop positions on the basis of ink discharge amount. 
     With such a configuration, it is possible to scan the carriage on the basis of a predetermined movement start position and/or movement stop position depending on required printing precision. 
     In the configuration of the printing apparatus according to the second aspect of the invention, it is preferable that printing is started during acceleration of the carriage, or the started printing is continued until the carriage decelerates. 
     With such a configuration, it is possible to provide a “marginless” printing, that is, printing with no margin left at edges of the printing paper, or printing with relatively narrow margins left thereat. Thus, the invention makes it possible to offer high-quality printing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a perspective view that schematically illustrates an example of the overall configuration of a printing apparatus according to a first exemplary embodiment of the invention. 
         FIG. 2  is a side view that schematically illustrates an example of the partial configuration of the printing apparatus illustrated in  FIG. 1 , focusing on the paper feeding structure thereof. 
         FIG. 3  is a diagram that schematically illustrates an example of the control mechanism of the printing apparatus illustrated in  FIG. 1 . 
         FIG. 4  is a block diagram that schematically illustrates an example of the configuration of a control unit according to the first exemplary embodiment of the invention. 
         FIG. 5  is a set of diagrams that illustrates the scanning speeds of a carriage that correspond to a plurality of velocity curves switched over therebetween. 
         FIG. 6  is a flowchart that illustrates the operational flow of switchover processing performed by a driving mode switchover section. 
         FIG. 7  is a set of explanatory diagrams that illustrates the comparative print results that appear on a paper P after printing performed by means of the driving mode switchover section. 
         FIG. 8  is a block diagram that schematically illustrates an example of the configuration of a control unit according to the second exemplary embodiment of the invention. 
         FIG. 9  is a flowchart that illustrates the operational flow of switchover processing performed by a movement position switchover section. 
         FIG. 10  is a set of diagrams that illustrates the scanning speeds of a carriage that correspond to a plurality of movement positions switched over therebetween. 
         FIG. 11  is a block diagram that schematically illustrates an example of the configuration of a control unit according to the third exemplary embodiment of the invention. 
         FIG. 12  is a flowchart that illustrates the operational flow of switchover processing performed by a switchover judgment section. 
         FIG. 13  is a flowchart that illustrates the operational flow of switchover processing performed on the basis of the size of a print target paper. 
         FIG. 14  is a block diagram that schematically illustrates an example of the configuration of a control unit according to the fourth exemplary embodiment of the invention. 
         FIG. 15  is a flowchart that illustrates the operational flow of switchover processing performed by a velocity mode switchover section. 
         FIG. 16  is a set of diagrams that illustrates the scanning speeds of a carriage under velocity (i.e., reduced speed) mode. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     First Embodiment 
     With reference to accompanying drawings, a printing apparatus  1  according to a first exemplary embodiment of the invention is described below. 
       FIG. 1  is a perspective view that schematically illustrates an example of the overall configuration of a printing apparatus  1  according to the first exemplary embodiment of the invention.  FIG. 2  is a side view that schematically illustrates an example of the partial configuration of the printing apparatus  1  illustrated in  FIG. 1 , focusing on the paper feeding structure thereof.  FIG. 3  is a diagram that schematically illustrates an example of the control mechanism of the printing apparatus  1  illustrated in  FIG. 1 . 
     The printing apparatus  1  according to the present embodiment of the invention is configured as an ink-jet printer. An ink-jet printer performs printing by discharging ink in the form of a liquid onto a sheet of printing paper P that is taken as an example of various kinds of recording target media herein. In the following description, the printing apparatus according to the present embodiment of the invention is simply referred to as printer. As illustrated in  FIGS. 1 and 2 , a printer  1  according to the present embodiment of the invention is provided with a carriage  3 , a carriage motor (CR motor)  4 , a paper feed motor (PF motor)  5 , a PF driving roller  6 , a platen  7 , and a printer body chassis  8 . A print head  2 , which discharges ink drops, is mounted on the carriage  3 . The CR motor  4  drives the carriage  3  so that it moves in the main scan (MS) direction. The PF motor  5  provides a driving force for transportation of the printing paper P in the sub scan (SS) direction. The PF driving roller  6  is interlocked with the PF motor  5 . The platen  7  is arranged so as to be opposed to the nozzle surface of the print head  2  (i.e., the lower surface thereof according to  FIG. 2 ). These components are housed in the printer body chassis  8 . In the present embodiment of the invention, both of the CR motor  4  and the PF motor  5  are configured as direct-current (DC) motors. 
     As illustrated in  FIG. 2 , the printer  1  is further provided with a hopper (feeder)  11 , a paper feed roller  12 , a detachment pad  13 , a paper detector  14 , and a paper ejection drive roller  15 . The printing papers P that are waiting to be print-processed are placed on the hopper  11 . The paper feed roller  12  and the detachment pad  13  work in combination with each other so as to take the printing paper P placed on the hopper  11  into the printer  1 . The paper detector  14  detects the printing paper P that is taken from the hopper  11  into the printer  1  as it passes through a detection area thereof. The paper ejection drive roller  15  ejects the printed paper P (i.e., printing paper P after completion of printing) out of the printer  1 . 
     In the configuration of the printer  1 , the carriage  3  has its home position at the right end of its scanning range according to  FIG. 1  (i.e., near end according to  FIG. 2 ). Accordingly, the carriage  3  has its “away” position at the other end opposite to the home position end (i.e., left end according to  FIG. 1 , and far end according to  FIG. 2 ). The carriage  3  moves within the scanning range, which is defined as a region from the home position to the away position. 
     The carriage  3  is configured so that it can travel in the main scan MS direction along a guide shaft  17 , which is supported by a supporting frame  16  that is fixed to the printer body chassis  8 , by means of a timing belt  18 . As illustrated in  FIG. 2 , the timing belt  18 , a part of which is fixed to the carriage  3 , is wound around pulleys  19  and  20  in such a manner that it has a certain belt tension therebetween. The pulley  19  is attached to the output axis of the CR motor  4 , whereas the pulley  20  is attached to the supporting frame  16  in a rotatable manner. The guide shaft  17  supports and guides the carriage  3  in such a manner that it can slide thereon in the MS direction. In addition to the print head  2 , ink cartridges  21  are detachably attached to the carriage  3 . The ink cartridges  21  contain various kinds of ink to be supplied to the print head  2 . 
     The paper feed roller  12  is coupled to the PF motor  5  by means of interlocking gears that are not shown in the drawing. Accordingly, the PF motor  5  drives the paper feed roller  12  by communicating its driving force through the interlocking gears. As illustrated in  FIG. 2 , the hopper  11  is configured as a plate member on which the printing papers P can be placed. By means of a cam mechanism that is not shown in the drawing, the hopper  11  can oscillate around a turn axis  22  that is provided at the upper portion thereof. As the hopper  11  shakes through the working of the cam mechanism, the lower end of the hopper  11  is pressed resiliently against the paper feed roller  12  at one time and moves away from the paper feed roller  12  at another time. The detachment pad  13  is provided at a position opposed to the paper feed roller  12 . As the paper feed roller  12  rotates, the surface of the paper feed roller  12  contacts the detachment pad  13 . With such a structure, when the paper feed roller  12  rotates, the uppermost one of the printing papers P placed on the hopper  11  passes through the contact region between the surface of the paper feed roller  12  and the detachment pad  13  to be fed toward the paper-ejection side of the printer  1 . In contrast, the second printing paper P counted from the top and the remaining sheets of the printing papers P thereunder placed on the hopper  11  are prevented from being transported toward the paper-ejection side thereof thanks to the functioning of the detachment pad  13 . 
     The PF driving roller  6  is coupled to the PF motor  5  either directly or by means of interlocking gears that are not shown in the drawing. As illustrated in  FIG. 2 , the printer  1  has a PF slave roller (i.e., driven roller)  23  that cooperates with the PF driving roller  6  so as to transport the printing paper P. The PF slave roller  23  is provided at the paper-ejection side of a slave roller holder (i.e., driven roller holder)  24  in a rotatable manner. The slave roller holder  24  is configured in such a manner that it can oscillate (i.e., turn) around a turn axis  25 . The slave roller holder  24  is urged counter clockwise in  FIG. 2  by a spring that is not shown in the drawing in such a manner that the PF slave roller  23  is constantly urged toward the PF driving roller  6 . With such a structure, when the PF driving roller  6  is driven, the PF slave roller  23  turns as the PF driving roller  6  turns. 
     As illustrated in  FIG. 2 , the paper detector  14 , which is made up of a detection lever  26  and a paper detection sensor  27 , is provided in the proximity of the slave roller holder  24 . The detection lever  26  can oscillate around a turn axis  28 . When the printing paper P transitions from a “paper-passing” state illustrated in  FIG. 2  to a next state, that is, after the printing paper P has passed through a region under the detection lever  26 , the detection lever  26  turns counterclockwise. As the detection lever  26  turns, light propagating from the light emission portion of the paper detection sensor  27  toward the light reception portion thereof is shut off. By this means, the paper detector  14  is able to detect the passing of the printing paper P. 
     The paper ejection drive roller  15 , which is provided at the paper-ejection side of the printer  1 , is coupled to the PF motor  5  by means of interlocking gears that are not shown in the drawing. As illustrated in  FIG. 2 , the printer  1  has a paper ejection slave roller  29  that cooperates with the paper ejection drive roller  15  so as to eject the printing paper P. In the same way as the PF slave roller  23  is done, the paper ejection slave roller  29  is urged by a spring that is not shown in the drawing in such a manner that it is constantly urged toward the paper ejection drive roller  15 . With such a structure, when the paper ejection drive roller  15  is driven, the paper ejection slave roller  29  turns as the paper ejection drive roller  15  turns. 
     As illustrated in  FIGS. 2 and 3 , the printer  1  is provided with a linear encoder  33 , which is made up of a linear scale  31  and a photo sensor  32 , as a positional detection device that detects the position of the carriage  3  in the MS direction. The linear encoder  33  further detects the moving speed of the carriage  3  in the MS direction and/or similar parameters thereof. In addition, as illustrated in  FIG. 3 , the printer  1  is further provided with a rotary encoder  36 , which is made up of a rotary scale  34  and a photo sensor  35 , as another positional detection device that detects the position of the printing paper P in the SS direction. The rotary encoder  36  further detects the transportation speed of the printing paper P in the SS direction and/or similar parameters thereof. Specifically, the rotary encoder  36  detects the rotation position, the rotation speed, and the like, of the PF driving roller  6 . Signals outputted from the linear encoder  33  and the rotary encoder  36  are, as illustrated in  FIG. 3 , inputted into a control unit  37 , which functions as a control section (as recited in the appended claims), so that the control unit  37  can perform various kinds of control on the printer  1 . 
     In the printer  1  configured as described above, the printing paper P, which has been taken from the hopper  11  into the printer  1  by means of the paper feed roller  12  and the detachment pad  13 , is transported in the SS direction by the PF driving roller  6 , which is driven and turned by the PF motor  5 . While the printing paper P is being fed in the SS direction, the carriage  3 , which is driven by the CR motor  4 , reciprocates (i.e., moves in a reciprocatory manner) in the MS direction. When the carriage  3  reciprocates, ink drops are discharged from the print head  2 . By this means, printing is performed on the printing paper P. For the purpose of shortening the distance in the MS direction of the printer  1  so as to achieve a smaller body configuration thereof, the discharge of ink drops from the print head  2  is started during the acceleration of the carriage  3 , whereas the discharge of ink drops from the print head  2  is finished during the deceleration thereof. After print processing on the printing paper P is completed, the printing paper P is ejected out of the printer  1  by means of the paper ejection drive roller  15  and the paper ejection slave roller  29 . 
     The printer  1  has its inherent (i.e., natural) resonance frequency. When the resonance frequency of the printer  1  coincides with the forced vibration frequency of the CR motor  4 , which drives the carriage  3 , the printer  1  vibrates in resonance therewith. When the resonance vibration is generated, the vibration is communicated to the carriage  3 , which causes uneven printing. In order to avoid such a problem, it is necessary to control the driving speed of the CR motor  4  so that the resonance vibration does not occur in the printer  1 . In the present embodiment of the invention, it is assumed that the resonance vibration is generated when the scanning speed of the carriage  3  reaches 22 ips. It should be noted that the above scanning speed of the carriage  3  that causes the resonance vibration, that is, 22 ips, according to the present embodiment of the invention is nothing more than an example given solely for the purpose of illustrative explanation. In actual implementation of the invention, the scanning speed thereof could vary depending on the type, size, and/or similar factors of a printer. It should be further noted that, when the forced vibration frequency of the CR motor  4  reaches two resonance frequencies of the printer  1 , that is, the secondary resonance frequency and the tertiary resonance frequency thereof, the printer  1  vibrates in resonance therewith twice each at the time of acceleration of the carriage  3  and at the time of deceleration thereof. 
       FIG. 4  is a block diagram that schematically illustrates an example of the configuration of the control unit  37 , which controls the CR motor  4  illustrated in  FIG. 1 .  FIG. 5  is a set of diagrams that illustrates velocity curves in the scanning of the carriage  3 . Specifically,  FIG. 5A  illustrates the velocity curves that apply during acceleration of the carriage  3 . On the other hand,  FIG. 5B  illustrates the velocity curves that apply during deceleration thereof. In each of  FIGS. 5A and 5B , the horizontal axis represents time where the driving start of the carriage  3  is taken as zero. The vertical axis in each of  FIGS. 5A and 5B  represents the scanning speed of the carriage  3 . 
     As has already been described, the control unit  37  functions to perform various kinds of control on the printer  1 . As one of its functions, the control unit  37  controls the CR motor  4  as illustrated in  FIG. 3 . Various kinds of signals are inputted into the control unit  37 , including, though not limited thereto, signals coming from various kinds of sensors such as the paper detection sensor  27 , the linear encoder  33 , the rotary encoder  36 , etc., and a power signal coming from a power switch, which turns the power of the printer  1  ON/OFF. In addition, printing signals are inputted from a control instruction unit  40  of an external device such as a computer or the like that is connected to the printer  1  so as to specify various kinds of printing parameters such as paper size, paper type, resolution, MicroWeave, bidirectional printing, color adjustment, and so on. 
     In the present embodiment of the invention, when the carriage  3  is moved in the MS direction, the control unit  37  controls the accelerated velocity of the carriage  3  that is applied during acceleration up to the point at which the moving speed of the carriage  3  reaches a predetermined value (hereafter referred to as “steady-state velocity”) and the accelerated velocity thereof that is applied during deceleration from the point at which the carriage  3  moves at the steady-state velocity till it stops. That is, the control unit  37  controls the driving speed of the CR motor  4  during acceleration and deceleration of the carriage  3 . 
     As illustrated in  FIG. 4 , the control unit  37  is provided with a CPU  39 , a ROM  41 , a RAM  43 , an output port  49 , an interface  51 , and a motor driver  53 . These components are interconnected with one another via a bus  55 , which is a group of signal lines. 
     The CPU  39  functions as the central unit that handles data computation/processing among these components. Specifically, the CPU  39  executes programs that are stored in the ROM  41 , which serves as a memory section (as recited in the appended claims), and stored in the RAM  43 , which serves as another memory section. In addition, the CPU  39  receives data from an input unit (i.e., input means), the ROM  41 , and the RAM  43  to perform computation on the basis of the received data and processes the received data. Then, the CPU  39  outputs the computed/processed data to the motor driver  53  via the interface  51 , which is an output unit (i.e., output means). The CPU  39  receives the above-described signals coming from various kinds of sensors such as the paper detection sensor  27 , the linear encoder  33 , the rotary encoder  36 , etc., the power signal coming from the power switch, which turns the power of the printer  1  ON/OFF, and/or the printing signal supplied from the control instruction unit  40 . The CPU  39  functions as a driving mode switchover section (as recited in the appended claims) that switches over velocity data patterns in accordance with velocity curves A 1 -A 4  stored in the ROM  41 . The CR motor  4  is driven on the basis of the velocity data that is selected (i.e., switched over) by the CPU  39  so as to move the carriage  3 . 
     The ROM  41  memorizes control programs that are used for controlling the printer  1  and other data that are required for print processing. In the present embodiment of the invention, specifically, the ROM  41  memorizes control programs that are used for acceleration/deceleration control. In addition to such acceleration/deceleration control programs, data pertaining to the driving speed of the CR motor  4  that correspond to the plurality of acceleration curves A 1 -A 4  illustrated in  FIG. 5A  and the plurality of deceleration curves A 1 -A 4  illustrated in  FIG. 5B  (i.e., velocity data corresponding to time) are stored in the ROM  41 . Each of the deceleration curves A 1 -A 4  constitutes a “mirror-pattern” curve of the corresponding one of the acceleration curves A 1 -A 4 . When both of the acceleration curves A 1 -A 4  and the deceleration curves A 1 -A 4  are used in accordance with the selection (i.e., switchover) done by the CPU  39 , each of the acceleration curves A 1 -A 4  and the corresponding one of the deceleration curves A 1 -A 4  are used as a pair. In the following description, when each of the acceleration curves A 1 -A 4  and the corresponding one of the deceleration curves A 1 -A 4  are used as a pair, it is simply referred to as a velocity curve A 1 -A 4 . The RAM  43  serves as a temporary memory in which programs, data, and the like that are required for the CPU  39  to perform print execution and print computation are stored. 
     The output port  49  takes out necessary data only in a selective manner from the CPU  39 , the RAM  43 , etc., and supplies the extracted data to the interface  51 . The interface  51  is responsible for ensuring various kinds of electric and temporal (i.e., timing) matching. Specifically, for example, the interface  51  performs signal level conversion on a signal that is inputted from the output port  49 . In addition, the interface  51  performs data interface timing control. On the basis of an input signal supplied from the interface  51 , the motor driver  53  supplies a current to each phase of the CR motor  4  so as to drive the CR motor  4  for rotation thereof. 
     The driving speed of the CR motor  4  is controlled on the basis of various kinds of signals that are inputted from the control instruction unit  40  and/or on the basis of the result of computation performed by the CPU  39 . Specifically, the CPU  39  performs arithmetic processing on the basis of the velocity data and/or the programs stored in the ROM  41  or the RAM  43 . The result of the computation thereof is inputted into the motor driver  53  via the output port  49  and the interface  51 . Then, the motor driver  53  supplies the driving power to the CR motor  4 . In addition to the above, the driving speed of the CR motor  4  is also controlled on the basis of printing signals that are inputted from the control instruction unit  40 , which specify various kinds of printing parameters such as paper size, paper type, resolution, printing mode, bidirectional printing, color adjustment, and so on. It should be noted that such printing parameters including but not limited to paper size, paper type, resolution, printing mode, (unidirectional printing or) bidirectional printing, and color adjustment may be arbitrarily set depending on the operating environment of the printer  1 . 
     Next, a printing operation that is performed when the CPU  39  switches driving modes is explained below. 
       FIG. 6  is a flowchart that illustrates the operational flow of mode switchover processing, which is performed by the CPU  39  (driving mode switchover section).  FIG. 7  is a set of explanatory diagrams that illustrates the comparative print results that appear on the printed paper P so as to show a distinctive advantage that is gained when the CPU  39  switches driving modes according to the invention. 
     When printing is performed, as the first step, the control instruction unit  40  receives print-related data such as paper size, paper type, resolution, printing mode, unidirectional printing or bidirectional printing, color adjustment, and so on. Upon reception of these data, the control instruction unit  40  supplies a signal based on the received data to the CPU  39 . As the next step, the CPU  39  reads out velocity data stored in the ROM  41  or the RAM  43  on the basis of the input signal supplied from the control instruction unit  40 . In the present embodiment of the invention, it is assumed that printing is performed under a MicroWeave printing mode. Herein, the term “MicroWeave” refers to a printing function/method where a print head having a plurality of nozzles is used to scan the same single line by means of different nozzles so as to form each one dot in a superposed manner. The MicroWeave printing ensures high quality in printed images. 
     In the present embodiment of the invention, it is assumed that so-called unidirectional printing is performed. In the unidirectional printing, ink drops are discharged from the print head  2  onto the printing paper P during a time period in which the carriage  3  travels along the MS direction from the home position to the away position thereof, which is referred to as “outward movement” (i.e., defined as the opposite word of “homeward movement” herein) hereafter as long as the context allows. The discharging of ink drops starts at the point in time E 1  shown in  FIG. 5A , and ends at the point in time E 2  shown in  FIG. 5B . This means that the print target area, at which printing is performed, is defined as a region where the carriage  3  travels during a time period between the point in time E 1  and the point in time E 2 . The CPU  39  performs computation for driving mode switchover when the carriage  3  reaches the away position after traveling along the MS direction. In the unidirectional printing, the printing paper P is fed in the SS direction during the homeward movement of the carriage  3 , that is, during a time period in which the carriage  3  travels along the MS direction from the away position to the home position thereof. Printing is not performed on the printing paper P during the homeward movement of the carriage  3 . Printing is carried out through the repetitions of these outward and homeward movements of the carriage  3  as well as the feeding of the printing paper P in the SS direction meanwhile. Upon completion of printing, the printing paper P is ejected out of the printer  1  by means of the paper ejection drive roller  15  and the paper ejection slave roller  29 . 
     When the CPU  39  receives various kinds of signals, it performs pattern switchover. In the present embodiment of the invention, it is assumed that four velocity curves A 1 -A 4  are stored in the ROM  41 . Accordingly, the pattern switchover is carried out by means of these four velocity curves. As illustrated in  FIG. 6 , as the first step shown in the flowchart thereof, the CPU  39  judges whether the dot size version is “VSD3” or not (step S 101 ). Herein, the term “VSD3” is defined as a specific dot size version for high-quality printing. If the dot size version is “VSD3”, it is possible to reduce dot size because the discharge amount of ink for VSD3 is relatively small. Since the dot size is made smaller, it is possible to print images with a higher resolution, featuring the output resolution of “2,880 dpi (V) times 720 dpi (H)”. The control instruction unit  40  transmits the information on the dot size version as a signal related to resolution to the CPU  39 . If it is judged as NO in the step S 101 , the driving modes are switched over to select the velocity data corresponding to the velocity curve A 1  (step S 108 ). Then, a signal for scanning the carriage  3  in accordance with the velocity curve A 1  is transmitted to the motor driver  53 . Accordingly, the carriage  3  reciprocates in the MS direction on the basis of the velocity curve A 1 . That is, the carriage  3  travels at the scanning speed based on the velocity curve A 1  during both of its outward movement and homeward movement. During the outward movement, the carriage  3  performs printing (step S 112 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (i.e., addition of “1” to the value of BB) (step S 113 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next velocity data switchover processing is started. In addition thereto, the carriage  3  moves to its home position. It should be noted that the default value of BB is set as “0”. This value is reset to “0” each time when a paper is fed. 
     It is assumed that the result of judgment made at the step S 101  is, again, NO after returning to the start of this switchover loop. If so, the velocity curve A 1  is selected (step S 108 ). Accordingly, the carriage  3  travels at the scanning speed based on the velocity curve A 1  during both of its outward movement and homeward movement, while performing printing during its outward movement (step S 112 ). If decisions made at the step S 101  continue to be NO, in other words, if the dot size version is not “VSD3”, it means that images with high resolution are not required. In such a case, printing is performed on the basis of the same velocity curve without requiring (switchover among) a plurality of velocity curves. 
     If it is judged as YES in the step S 101 , the CPU  39  further judges whether to perform so-called unidirectional printing or not, that is, whether to discharge ink during the outward movement of the carriage  3  only or not (step S 102 ). A signal indicating whether to perform unidirectional printing or not is transmitted from the control instruction unit  40  to the CPU  39 . If it is judged as NO in the step S 102 , the driving modes are switched over to select the velocity data corresponding to the velocity curve A 1  (step S 108 ). Then, a signal for scanning the carriage  3  in accordance with the velocity curve A 1  is transmitted to the motor driver  53 . Accordingly, the carriage  3  reciprocates in the MS direction on the basis of the velocity curve A 1 . The carriage  3  travels at the scanning speed based on the velocity curve A 1  during both of its outward movement and homeward movement. Herein, since the decision made at the step S 102  is NO, the carriage  3  performs so-called bidirectional printing; that is, the carriage  3  discharges ink both during the outward movement and the homeward movement thereof (step S 112 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 113 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next velocity data switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     On the other hand, if the decision made at the step S 102  is YES, the CPU  39  divides the value of the variable BB by 4 to calculate a local variable CC, which is the value of the remainder of such a division (step S 103 ). Thereafter, the CPU  39  judges whether the value of the variable CC is “0” or not (step S 104 ). If the value of the variable CC is “0”, the CPU  39  switches the driving modes so as to select the velocity data corresponding to the velocity curve A 1  (step S 109 ), and then transmits a signal for scanning the carriage  3  in accordance with the velocity curve A 1  to the motor driver  53 . Then, the carriage  3  performs printing at the scanning speed based on the velocity curve A 1  during its outward movement (step S 112 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 113 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next velocity data switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     If the results of judgment made both at the step S 101  and the step S 102  are YES after returning to the start of this switchover loop, then, the value of the variable CC is calculated in the step S 103 . It should be noted that the value of the variable BB is incremented by “1” in the previous flow processing in this switchover loop. If the value of the variable CC calculated in the previous flow processing is “0”, it is judged as “1” this time. Then, the CPU  39  judges whether the value of the variable CC is “1” or not (step S 105 ). If the value of the variable CC is judged as “1”, the CPU  39  switches the driving modes so as to select the velocity data corresponding to the velocity curve A 2  (step S 110 ), and then transmits a signal for scanning the carriage  3  in accordance with the velocity curve A 2  to the motor driver  53 . Then, the carriage  3  performs printing at the scanning speed based on the velocity curve A 2  during its outward movement (step S 112 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 113 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next velocity data switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     Next, if the results of judgment made both at the step S 101  and the step S 102  are YES again after returning to the start of this switchover loop, then, the value of the variable CC is calculated in the step S 103 . It should be noted that the value of the variable BB is incremented by “1” in the previous flow processing in this switchover loop. If the value of the variable CC calculated in the previous flow processing is “1”, it is judged as “2” this time. Then, the CPU  39  judges whether the value of the variable CC is “2” or not (step S 106 ). If the value of the variable CC is judged as “2”, the CPU  39  switches the driving modes so as to select the velocity data corresponding to the velocity curve A 3  (step S 111 ), and then transmits a signal for scanning the carriage  3  in accordance with the velocity curve A 3  to the motor driver  53 . Then, the carriage  3  performs printing at the scanning speed based on the velocity curve A 3  during its outward movement (step S 112 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 113 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next velocity data switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     Next, if the results of judgment made both at the step S 101  and the step S 102  are YES again after returning to the start of this switchover loop, then, the value of the variable CC is calculated in the step S 103 . It should be noted that the value of the variable BB is incremented by “1” in the previous flow processing in this switchover loop. If the value of the variable CC calculated in the previous flow processing is “2”, it is judged as “3” this time. Consequently, the CPU  39  switches the driving modes so as to select the velocity data corresponding to the velocity curve A 4  (step S 107 ), and then transmits a signal for scanning the carriage  3  in accordance with the velocity curve A 4  to the motor driver  53 . Then, the carriage  3  performs printing at the scanning speed based on the velocity curve A 4  during its outward movement (step S 112 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 113 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next velocity data switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     As described above, if it is decided YES successively in the steps S 101  and S 102 , the velocity patterns for respective travels of the carriage  3  are switched over in such a manner that four times of reciprocating movements constitute one unit of operation. In addition, when the decisions made at the steps S 101  and S 102  are successive YES, the velocity curves are switched over among A 1 , A 2 , A 3 , and A 4 , in the order of appearance herein, in a sequential manner for respective travels (i.e., corresponding to the above-mentioned four times of reciprocating movements) in the unit of operation. The above series of operations is repeated until printing is completed. When the velocity curves are switched over sequentially in the order of A 1 , A 2 , A 3 , and A 4  as described above, resonance vibrations occur at D 1 , D 2 , D 3 , and D 4  during acceleration as illustrated in  FIG. 5A  and at D 5 , D 6 , D 7 , and D 8  during deceleration as illustrated in  FIG. 5B , that is, four different points in time each for acceleration and deceleration after the start of scanning (i.e., movement or travel) of the carriage  3 . 
     As described above, each of D 1 -D 4  and D 5 -D 8  is a point at which the printer  1  vibrates in resonance. For this reason, the carriage  3  vibrates at each of D 1 -D 4  and D 5 -D 8 , which might cause uneven printing. If the same velocity curve is used, resonance vibrations are generated at the same points in time. Therefore, as illustrated in  FIG. 7A , each set of the points D 1 -D 4  and the points D 5 -D 8  is aligned in the SS direction on the printing paper P, which is recognized (i.e., observed or perceived) as “rainbow unevenness”. In contrast, if the CPU  39  switches over the velocity curves among A 1 , A 2 , A 3 , and A 4  for print execution, as illustrated in  FIG. 7B , the points D 1 -D 4  and the points D 5 -D 8  are staggered with respect to one another (i.e., spread or scattered) in the MS direction of the printing paper P. Therefore, these points do not form two lines along the SS direction. Thus, no rainbow unevenness appears on the paper P after completion of printing. 
     In the printer  1  configured as above, a driving mode switchover section  45  switches over among four velocity curves A 1 -A 4 , which have four acceleration inclinations and four deceleration inclinations that vary from one another, so as to move the carriage  3 . With such a structure, it is possible to shift (i.e., stagger) points in time at which the carriage  3  is affected by vibrations, that is, points in time at which unevenness in printing occurs. As a consequence thereof, as illustrated in  FIG. 7B , the points D 1 -D 4  and the points D 5 -D 8  at which unevenness in printing could occur are staggered with respect to one another in the MS direction of the printed paper P (i.e., the printing paper P after completion of printing). Therefore, uneven points will never be aligned (in two lines) along the SS direction. Thus, the invention makes it possible to effectively avoid the generation of rainbow unevenness on the printed paper P (i.e., after completion of printing). 
     According to the exemplary configuration of the printer  1  described above, the pattern switchover is carried out in accordance with printing direction, that is, either bidirectional printing or unidirectional printing, as well as printing resolution. Specifically, the pattern switchover is executed by means of the velocity curves A 1 -A 4  if high-resolution unidirectional printing is performed. Therefore, it is possible to adjust printing precision (i.e., actual print quality) depending on required print quality. The pattern switchover is carried out either for each outward movement or for each set of outward and homeward movements of the carriage  3 . Therefore, it is possible to apply the switchover (technique) of the scanning speeds of the carriage  3  according to the invention to both of bidirectional printing and unidirectional printing. Thus, the invention increases the diversification of printing that is performed by the printer  1 . 
     According to the exemplary configuration of the printer  1  described above, printing is started during acceleration of the carriage  3 . After the start of printing, it is continued until the carriage  3  decelerates. Therefore, the invention makes it possible to provide a “marginless” printing, that is, printing with no margin left at edges of the printing paper P, or printing with relatively narrow margins left thereat. Thus, the invention makes it possible to offer high-quality printing. 
     Second Embodiment 
     With reference to accompanying drawings, a printing apparatus  70  according to a second exemplary embodiment of the invention is described below. It should be noted that, in the following description of the printer  70  according to the second exemplary embodiment of the invention, the same reference numerals are consistently used for the same components as those of the printer  1  according to the first exemplary embodiment of the invention so as to omit any redundant explanation or simplify explanation thereof. 
       FIG. 8  is a block diagram that schematically illustrates an example of the configuration of a control unit  72 , which controls the CR motor  4  in the printer  70 . 
     Note that the configuration of the printer  70  is the same as that of the counterpart illustrated in the first embodiment of the invention described above. In the configuration of the printer  70 , the control unit  72 , which functions as a control section, is in charge of controlling the driving speed of the CR motor  4 . As illustrated in  FIG. 8 , the control unit  72  is provided with the CPU  39 , the ROM  41 , the RAM  43 , the output port  49 , the interface  51 , and the motor driver  53 . These components are interconnected with one another via the bus  55 , which is a group of signal lines. The CPU  39  serves as a movement position switchover section (as recited in the appended claims), which switches over “movement start positions” in the MS direction of the carriage  3 . In the present embodiment of the invention, data of velocity curve A 1  (i.e., velocity data corresponding to time) is stored in the ROM  41 . 
     In the following description, a printing operation that is performed when the CPU  39  switches movement start positions is explained. 
       FIG. 9  is a flowchart that illustrates the operational flow of movement start position switchover processing, which is performed by the CPU  39  (move position switchover section).  FIG. 10  is a set of diagrams that illustrates velocity curves in the scanning of the carriage  3 ; specifically, it illustrates the velocity curves that are used when the movement start positions of the carriage  3  are switched over.  FIG. 10A  illustrates the velocity curves that apply during acceleration of the carriage  3 . On the other hand,  FIG. 10B  illustrates the velocity curve (i.e., a single curve) that applies during deceleration thereof. In each of  FIGS. 10A and 10B , the horizontal axis represents time where the driving start of the carriage  3  is taken as zero. The vertical axis in each of  FIGS. 10A and 10B  represents the scanning speed of the carriage  3 . 
     When printing is performed, as the first step, the control instruction unit  40  receives print-related data such as paper size, paper type, resolution, printing mode, unidirectional printing or bidirectional printing, color adjustment, and so on. Upon reception of these data, the control instruction unit  40  supplies a signal based on the received data to the CPU  39 . As the next step, the CPU  39  reads out movement-start-position data as well as velocity data stored in the ROM  41  or the RAM  43  on the basis of the input signal supplied from the control instruction unit  40 . In the present embodiment of the invention, it is assumed that printing is performed under a MicroWeave printing mode. 
     In the present embodiment of the invention, it is assumed that so-called unidirectional printing is performed. As has already been described, in the unidirectional printing, ink drops are discharged from the print head  2  onto the printing paper P during a time period in which the carriage  3  travels along the MS direction from the home position to the away position thereof, which is referred to as outward movement and defined as the opposite word of homeward movement in this specification. The discharging of ink drops starts at the point in time E 3  shown in  FIG. 10A , and ends at the point in time E 4  shown in  FIG. 10B . This means that the print target area, at which printing is performed, is defined as a region where the carriage  3  travels during a time period between the point in time E 3  and the point in time E 4 . The CPU  39  performs computation for movement start position switchover when the carriage  3  reaches the away position after traveling along the MS direction. 
     When the CPU  39  receives various kinds of signals, it performs pattern switchover. As has already been described, in the present embodiment of the invention, the velocity data stored in the ROM  41  includes data pertaining to the velocity curve A 1  only. Therefore, the carriage  3  is moved on the basis of the velocity curve A 1 . As illustrated in  FIG. 9 , as the first step of the pattern switchover shown in the flowchart thereof, the CPU  39  judges whether the dot size version is “VSD3” or not (step S 201 ). The definition of the term “VSD3” in this embodiment is the same as that of the first embodiment of the invention described above. If the dot size version is not “VSD3”, that is, if the decision made at the step S 201  is NO, the CPU  39  reads, out of the ROM  41 , data that specifies G 1  as the position at which the movement of the carriage  3  is started, and effects a switchover so as to set the movement start position of the carriage  3  at G 1  as illustrated in  FIG. 10A  (step S 208 ). That is, a signal that causes the carriage  3  to start its outward movement at the position G 1  on the basis of the velocity curve A 1  is transmitted to the motor driver  53 . It should be noted that the movement stop position of the carriage  3  is not switched over in this pattern switchover processing. Accordingly, as illustrated in  FIG. 10B , the movement stop position of the carriage  3  is constantly set at a position F 1 . By this means, the carriage  3  starts its outward movement at the position G 1 , and travels along the MS direction to stop its movement at the position F 1 . That is, printing is performed at the scanning speed based on the velocity curve A 1  in such a manner that the carriage  3  starts its outward movement at the movement start position G 1  and ends its outward movement at the movement stop position F 1  (step S 212 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 213 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing is started. In addition thereto, the carriage  3  moves to its home position. It should be noted that the default value of BB is set as “0”. This value is reset to “0” each time when a paper is fed. 
     It is assumed that the result of judgment made at the step S 201  is, again, NO after returning to the start of this switchover loop. If so, the movement start position G 1  is selected (step S 208 ). Accordingly, the carriage  3  travels at the scanning speed based on the velocity curve A 1  so as to perform its outward movement, which starts at the movement start position G 1  and ends at the movement stop position F 1 , while performing printing during the above-mentioned outward movement (step S 212 ). If decisions made at the step S 201  continue to be NO in this switchover loop, in other words, if the dot size version is not “VSD3”, it means that images with high resolution are not required. In such a case, the carriage  3  continues to start its outward movements at the same movement start position, that is, the position G 1 , so as to perform printing. 
     If the decision made at the step S 201  is YES after returning to the start of this switchover loop, the CPU  39  further judges whether to perform unidirectional printing or not, that is, whether to discharge ink during the outward movement of the carriage  3  only or not (step S 202 ). If the decision made at the step S 202  is NO, the CPU  39  effects a switchover so that the movement start position of the carriage  3  is set at G 1  (step S 208 ). That is, a signal that causes the carriage  3  to start its outward movement at the position G 1  and end its outward movement at the position F 1  on the basis of the velocity curve A 1  and causes the carriage  3  to start its homeward movement at the position F 1  and end its homeward movement at the position G 1  on the basis thereof is transmitted to the motor driver  53 . Accordingly, so-called bidirectional printing is performed at the scanning speed based on the velocity curve A 1  during both of the outward movement and the homeward movement of the carriage  3  in such a manner that the carriage  3  starts its outward movement at the movement start position G 1  and ends its outward movement at the movement stop position F 1  and that the carriage  3  starts its homeward movement at the movement start position F 1  and ends its homeward movement at the movement stop position G 1  (step S 212 ). In the bidirectional printing, the carriage  3  discharges ink both during the outward movement and the homeward movement thereof. Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 213 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement position switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     On the other hand, if the decision made at the step S 202  is YES, the CPU  39  divides the value of the variable BB by 4 to calculate a local variable CC, which is the value of the remainder of such a division (step S 203 ). Then, the CPU  39  judges whether the value of the variable CC is “0” or not (step S 204 ). If it is judged that the value of the variable CC is “0” (step S 204 ), the CPU  39  effects a switchover so that the movement start position of the carriage  3  is set at G 1  (step S 209 ). That is, a signal that causes the carriage  3  to start its outward movement at the position G 1  and end its outward movement at the position F 1  on the basis of the velocity curve A 1  is transmitted to the motor driver  53 . Then, printing is performed at the scanning speed based on the velocity curve A 1  in such a manner that the carriage  3  starts its outward movement at the movement start position G 1  and ends its outward movement at the movement stop position F 1  (step S 212 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 213 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     If the results of judgment made both at the step S 201  and the step S 202  are YES after returning to the start of this switchover loop, then, the value of the variable CC is calculated in the step S 203 . It should be noted that the value of the variable BB is incremented by “1” in the previous flow processing in this switchover loop. If the value of the variable CC calculated in the previous flow processing is “0”, it is judged as “1” this time. Then, the CPU  39  judges whether the value of the variable CC is “1” or not (step S 205 ). If it is judged that the value of the variable CC is “1”, the CPU  39  effects a switchover so that the movement start position of the carriage  3  is set at G 2  (step S 210 ). That is, a signal that causes the carriage  3  to start its outward movement at the position G 2  and end its outward movement at the position F 1  on the basis of the velocity curve A 1  is transmitted to the motor driver  53 . Accordingly, printing is performed during the outward movement of the carriage  3  at the scanning speed based on the velocity curve A 1  in such a manner that the carriage  3  starts the above-mentioned outward movement at the movement start position G 2  and ends the above-mentioned outward movement at the movement stop position F 1  (step S 212 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 213 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     Next, if the results of judgment made both at the step S 201  and the step S 202  are YES again after returning to the start of this switchover loop, then, the value of the variable CC is calculated in the step S 203 . It should be noted that the value of the variable BB is incremented by “1” in the previous flow processing in this switchover loop. If the value of the variable CC calculated in the previous flow processing is “1”, it is judged as “2” this time. Then, the CPU  39  judges whether the value of the variable CC is “2” or not (step S 206 ). If it is judged that the value of the variable CC is “2”, the CPU  39  effects a switchover so that the movement start position of the carriage  3  is set at G 3  (step S 211 ). That is, a signal that causes the carriage  3  to start its outward movement at the position G 3  and end its outward movement at the position F 1  on the basis of the velocity curve A 1  is transmitted to the motor driver  53 . Accordingly, printing is performed during the outward movement of the carriage  3  at the scanning speed based on the velocity curve A 1  in such a manner that the carriage  3  starts the above-mentioned outward movement at the movement start position G 3  and ends the above-mentioned outward movement at the movement stop position F 1  (step S 212 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 213 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     Next, if the results of judgment made both at the step S 201  and the step S 202  are YES again after returning to the start of this switchover loop, then, the value of the variable CC is calculated in the step S 203 . It should be noted that the value of the variable BB is incremented by “1” in the previous flow processing in this switchover loop. If the value of the variable CC calculated in the previous flow processing is “2”, it is judged as “3” this time. If it is judged that the value of the variable CC is “3”, the CPU  39  effects a switchover so that the movement start position of the carriage  3  is set at G 4  (step S 207 ). That is, a signal that causes the carriage  3  to start its outward movement at the position G 4  and end its outward movement at the position F 1  on the basis of the velocity curve A 1  is transmitted to the motor driver  53 . Accordingly, printing is performed during the outward movement of the carriage  3  at the scanning speed based on the velocity curve A 1  in such a manner that the carriage  3  starts the above-mentioned outward movement at the movement start position G 4  and ends the above-mentioned outward movement at the movement stop position F 1  (step S 212 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 213 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     As described above, if it is decided YES each in the steps S 201  and S 202  by the CPU  39 , the movement positions for respective travels of the carriage  3  are switched over in such a manner that four times of reciprocating movements constitute one unit of operation. In addition, when the decisions made at the steps S 201  and S 202  are successive YES, the movement start positions are switched over among G 1 , G 2 , G 3 , and G 4 , in the order of appearance herein, in a sequential manner for respective travels (i.e., corresponding to the above-mentioned four times of reciprocating movements) in the unit of operation. The above series of operations is repeated until printing is completed. When the movement start positions are switched over sequentially in the order of G 1 , G 2 , G 3 , and G 4  as described above, resonance vibrations occur at J 1 , J 2 , J 3 , and J 4  during acceleration as illustrated in  FIG. 10A , that is, four different points in time. 
     As described above, each of J 1 -J 4  is a point at which the carriage  3  is affected by vibration. Therefore, if the CPU  39  performs a switchover according to the present embodiment of the invention, it is possible to stagger points in time at which the printer  70  vibrates in resonance, in other words, points in time at which unevenness in printing occurs. As a consequence thereof, in the same (or similar) manner as the first embodiment of the invention described above does, the present embodiment thereof offers advantageous effects in that the points J 1 -J 4  at which unevenness in printing could occur are staggered with respect to one another in the MS direction of the paper P after completion of printing. Therefore, uneven points will never be aligned along the SS direction. Thus, no rainbow unevenness appears on the paper P after completion of printing. 
     In the printer  70  configured as above, the CPU  39  causes the carriage  3  to travel while switching over the movement start positions thereof among G 1 , G 2 , G 3 , and G 4  in a sequential manner. With such a structure, it is possible to shift (i.e., stagger) points in time at which the carriage  3  is affected by vibrations, that is, points in time at which unevenness in printing occurs. As a consequence thereof, the points J 1 -J 4  shown in  FIG. 10A  at which unevenness in printing could occur are staggered (i.e., shifted) with respect to one another. Therefore, uneven points will never be aligned along the SS direction but will be spread in the MS direction of the printing paper P after completion of printing. Thus, the invention makes it possible to effectively avoid the generation of rainbow unevenness on the printing paper P after completion of printing. 
     According to the exemplary configuration of the printer  70  described above, the pattern switchover is carried out in accordance with printing direction, that is, either bidirectional printing or unidirectional printing, as well as printing resolution. Specifically, the movement start position pattern switchover is executed if high-resolution unidirectional printing is performed. Therefore, it is possible to adjust actual print quality, that is, printing precision, depending on required print quality. The pattern switchover is carried out either for each outward movement or for each set of outward and homeward movements of the carriage  3 . Therefore, it is possible to apply the switchover (technique) of the scanning positions of the carriage  3  according to the invention to both of bidirectional printing and unidirectional printing. Thus, the invention increases the diversification of printing that is performed by the printer  70 . 
     According to the exemplary configuration of the printer  70  described above, printing is started during acceleration of the carriage  3 . After the start of printing, it is continued until the carriage  3  decelerates. Therefore, the invention makes it possible to provide a marginless printing, that is, printing with no margin left at edges of the printing paper P, or printing with relatively narrow margins left thereat. Thus, the invention makes it possible to offer high-quality printing. 
     Third Embodiment 
     With reference to accompanying drawings, a printing apparatus  80  according to a third exemplary embodiment of the invention is described below. It should be noted that, in the following description of the printer  80  according to the third exemplary embodiment of the invention, the same reference numerals are consistently used for the same components as those of the printer  1  according to the first exemplary embodiment of the invention so as to omit any redundant explanation or simplify explanation thereof. 
       FIG. 11  is a block diagram that schematically illustrates an example of the configuration of a control unit  82 , which controls the CR motor  4  in the printer  80 . 
     Note that the configuration of the printer  80  is the same as that of the counterpart illustrated in the first embodiment of the invention described above. In the configuration of the printer  80 , the control unit  82 , which functions as a control section, is in charge of controlling the driving speed of the CR motor  4 . As illustrated in  FIG. 8 , the control unit  82  is provided with the CPU  39 , the ROM  41 , the RAM  43 , the output port  49 , the interface  51 , and the motor driver  53 . These components are interconnected with one another via the bus  55 , which is a group of signal lines. The CPU  39  functions as a switchover judgment section (as recited in the appended claims) that makes a proper decision as to which one of the switchover methods described in the foregoing exemplary embodiments of the invention, that is, either the driving mode switchover or the movement start position switchover, should be used, and performs a switchover as a result of the decision made in accordance with a signal indicating paper size and paper type. 
     In the present embodiment of the invention, the CPU  39  makes a decision to selectively use the driving mode switchover or the movement start position switchover so as to perform the pattern switchover (in an illustrated example which is described below, the CPU  39  makes a decision to selectively use either the driving mode switchover or the movement start position switchover for acceleration, while using the driving mode switchover consistently for deceleration). Such a selection is made based on, for example, paper size. Data pertaining to paper size can be received at the control instruction unit  40 . The control instruction unit  40  supplies the set paper size data to the CPU  39 . The CPU  39 , which serves as a print target medium recognition section (as recited in the appended claims), detects the size of the print target paper. Next, the CPU  39 , which further functions as the switchover judgment section, makes a decision as to which one of the above should be used, that is, either the driving mode switchover or the movement start position switchover. Among a variety of paper sizes, “A3”, “A4”, and “B5” are known as popular ones. On the basis of the input signal that is supplied from the control instruction unit  40 , the CPU  39  reads out either the velocity data or the movement start position data stored in the ROM  41  or the RAM  43 . Next, the CPU  30  performs arithmetic processing in accordance with the program. 
     In the following example, an explanation is given of how the CPU  39  makes a decision to selectively use the driving mode switchover or the movement start position switchover on the basis of paper sizes. In the present embodiment of the invention, a set of the above-mentioned popular paper sizes, that is, “A3”, “A4”, and “B5”, is taken as an example for the purpose of explanation. 
       FIG. 12  is a flowchart that illustrates the operational flow of driving mode switchover processing and the movement start position switchover processing performed on the basis of paper sizes. 
     Upon reception of a signal indicating the paper size of the printing paper P, the CPU  39  judges whether the indicated paper size is “B5” or not (step S 301 ). If the CPU  39  judges that the indicated paper size is “B5” (step S 301 : YES), it determines that the movement start position switchover should be used for acceleration of the carriage  3  whereas the driving mode switchover should be used for deceleration thereof (step S 304 ). When the indicated paper size is “B5”, which is relatively small, there is a relatively wide space between the home position of the carriage  3  and the “home-position-side” end of the print target paper. Therefore, in such a case, it is possible to perform a pattern switchover by switching the movement start position of the carriage  3  while utilizing the above-mentioned relatively wide space between the home position of the carriage  3  and the home-position-side end of the print target paper. 
     On the other hand, if the CPU  39  judges that the indicated paper size is not “B5” (step S 301 : NO), the CPU  39  further judges whether the indicated paper size is “A4” or not (step S 302 ). If the CPU  39  judges that the indicated paper size is “A4” (step S 302 : YES), it determines that the movement start position switchover should be used for acceleration of the carriage  3  whereas the driving mode switchover should be used for deceleration thereof (step S 305 ). When the indicated paper size is “A4”, which is the middle size at least in this example, there is a sufficient space between the home position of the carriage  3  and the home-position-side end of the print target paper. Therefore, in such a case, it is possible to perform a pattern switchover by switching the movement start position of the carriage  3  while utilizing the above-mentioned sufficient space between the home position of the carriage  3  and the home-position-side end of the print target paper. 
     On the other hand, if the CPU  39  judges that the indicated paper size is not “A4” (step S 302 : NO), the CPU  39  further judges whether the indicated paper size is “A3” or not (step S 303 ). If the CPU  39  judges that the indicated paper size is “A3” (step S 303 : YES), it determines that the driving mode switchover should be used for both acceleration and deceleration of the carriage  3  (step S 306 ). When the indicated paper size is “A3”, which is relatively large, there is not sufficient space between the home position of the carriage  3  and the home-position-side end of the print target paper. Therefore, in such a case, it is not possible to perform a pattern switchover by switching the movement start position of the carriage  3  because of the above-mentioned insufficient space between the home position of the carriage  3  and the home-position-side end of the print target paper. 
     If the CPU  39  judges that the indicated paper size is not “A3” (step S 303 : NO), it determines that the driving mode switchover should be used for both acceleration and deceleration of the carriage  3  (step S 307 ). 
     Next, a printing operation that is performed for each paper size is explained. 
       FIG. 13  is a flowchart that illustrates the operational flow of a pattern switchover that is performed when the paper size is either “B5” or “A4”. 
     When printing is performed, as the first step, the control instruction unit  40  receives print-related data such as paper size, paper type, resolution, printing mode, unidirectional printing or bidirectional printing, color adjustment, and so on. Next, the control instruction unit  40  supplies the received data to the CPU  39 . On the basis of the input data that is supplied from the control instruction unit  40 , the CPU  39  reads out either the velocity data or the movement start position data stored in the ROM  41  or the RAM  43 . Next, the CPU  30  performs arithmetic processing in accordance with the program. In the present embodiment of the invention, it is assumed that printing is performed under a MicroWeave printing mode. 
     In the present embodiment of the invention, it is assumed that so-called unidirectional printing is performed. As has already been described, in the unidirectional printing, ink drops are discharged from the print head  2  onto the printing paper P during a time period in which the carriage  3  travels along the MS direction from the home position to the away position thereof, which is referred to as outward movement and defined as the opposite word of homeward movement in this specification. The CPU  39  performs computation for the driving mode switchover and the movement start position switchover when the carriage  3  reaches the away position after traveling along the MS direction. 
     As has already been described, if the CPU  39  receives a signal indicating that the paper size of the print target paper is either “B5” or “A4”, the movement start position switchover is used for acceleration of the carriage  3  whereas the driving mode switchover is used for deceleration thereof. In the present embodiment of the invention, data pertaining to the velocity curves A 1 -A 4  as well as movement start positions is stored in the ROM  41 . As illustrated in  FIG. 13 , as the first step of the pattern switchover shown in the flowchart thereof, if the indicated paper size is either “B5” or “A4”, the CPU  39  judges whether the dot size version is “VSD3” or not (step S 401 ). If the dot size version is not “VSD3”, that is, if the decision made at the step S 401  is NO, the CPU  39  reads data out of the ROM  41  so as to select G 1  as the position at which the movement of the carriage  3  is started (refer to  FIG. 10A ) and A 1  as the deceleration curve to be applied therefor (refer to  FIG. 5B ) (step S 408 ). Accordingly, the CPU  39  transmits a signal for scanning the carriage  3  in accordance with the acceleration curve A 1  from the movement start position G 1  and scanning the carriage  3  in accordance with the deceleration curve A 1  for its outward movement to the motor driver  53 . Consequently, the carriage  3  travels in accordance with the velocity curve A 1  during its acceleration from the movement start position G 1  and in accordance with the velocity curve A 1  during its deceleration in the outward movement thereof in the MS direction so as to perform printing (step S 412 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 413 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing/velocity data (deceleration curve) switchover processing is started. In addition thereto, the carriage  3  moves to its home position. It should be noted that the default value of BB is set as “0”. This value is reset to “0” each time when a paper is fed. 
     It is assumed that the result of judgment made at the step S 401  is, again, NO after returning to the start of this switchover loop. If so, the CPU  39  selects G 1  as the position at which the movement of the carriage  3  is started (refer to  FIG. 10A ) and A 1  as the deceleration curve to be applied therefor (refer to  FIG. 5B ) (step S 408 ). Accordingly, the carriage  3  travels in accordance with the velocity curve (i.e., acceleration curve) A 1  during its acceleration from the movement start position G 1  and in accordance with the velocity curve (i.e., deceleration curve) A 1  during its deceleration in the outward movement thereof so as to perform printing (step S 412 ). If decisions made at the step S 401  continue to be NO in this switchover loop, in other words, if the dot size version is not “VSD3”, it means that images with high resolution are not required. In such a case, the carriage  3  continues to start its outward movements at the same movement start position, that is, the position G 1 , so as to perform printing. 
     If the decision made at the step S 401  is YES after returning to the start of this switchover loop, the CPU  39  further judges whether to perform unidirectional printing or not, that is, whether to discharge ink during the outward movement of the carriage  3  only or not (step S 402 ). If the decision made at the step S 402  is NO, the CPU  39  reads data out of the ROM  41  so as to select G 1  as the position at which the movement of the carriage  3  is started (refer to  FIG. 10A ) and A 1  as the deceleration curve to be applied therefor (refer to  FIG. 5B ) (step S 408 ). Then, the CPU  39  transmits a signal for accelerating the carriage  3  in accordance with the acceleration curve A 1  from the position G 1  and decelerating the carriage  3  in accordance with the deceleration curve A 1  in its outward movement while accelerating the carriage  3  in accordance with the deceleration curve A 1  and decelerating the carriage  3  in accordance with the acceleration curve A 1  so as to make the carriage  3  stop at the position G 1  in its homeward movement to the motor driver  53 . Accordingly, the carriage  3  accelerates in accordance with the acceleration curve A 1  after starting its travel from the movement start position G 1  and decelerates in accordance with the deceleration curve A 1  in the outward movement thereof. On the other hand, in its homeward movement, the carriage  3  accelerates in accordance with the deceleration curve A 1  and decelerates in accordance with the acceleration curve A 1  so as to stop its travel at the movement stop position G 1 . While traveling at the above scanning speeds, the carriage  3  performs so-called bidirectional printing in which it discharges ink both during the outward movement and the homeward movement thereof (step S 412 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 413 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing/velocity data (deceleration curve) switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     On the other hand, if the decision made at the step S 402  is YES, the CPU  39  divides the value of the variable BB by 4 to calculate a local variable CC, which is the value of the remainder of such a division (step S 403 ). Thereafter, the CPU  39  judges whether the value of the variable CC is “0” or not (step S 404 ). If it is judged that the value of the variable CC is “0”, the CPU  39  effects a switchover so that the movement start position of the carriage  3  is set at G 1 , and that the acceleration curve A 1  and the deceleration curve A 1  are selected (step S 409 ). Accordingly, the CPU  39  transmits, to the motor driver  53 , a signal for scanning the carriage  3  in accordance with the acceleration curve A 1  from the movement start position G 1  and scanning the carriage  3  in accordance with the deceleration curve A 1  for its outward movement. Consequently, the carriage  3  travels in accordance with the velocity curve A 1  during its acceleration from the movement start position G 1  and in accordance with the velocity curve A 1  during its deceleration in the outward movement thereof in the MS direction so as to perform printing (step S 412 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 413 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing/velocity data (deceleration curve) switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     If the results of judgment made both at the step S 401  and the step S 402  are YES after returning to the start of this switchover loop, then, the value of the variable CC is calculated in the step S 403 . It should be noted that the value of the variable BB is incremented by “1” in the previous flow processing in this switchover loop. If the value of the variable CC calculated in the previous flow processing is “0”, it is judged as “1” this time. Then, the CPU  39  judges whether the value of the variable CC is “1” or not (step S 405 ). If the CPU  39  judges that the value of the variable CC is “1”, the CPU  39  selects G 2  as the position at which the movement of the carriage  3  is started (refer to  FIG. 10A ); and in addition thereto, the CPU  39  selects A 1  as the acceleration curve to be applied therefor and further selects A 2  as the deceleration curve to be applied therefor (refer to  FIG. 5B ) (step S 410 ). Accordingly, the CPU  39  transmits, to the motor driver  53 , a signal for scanning the carriage  3  in accordance with the acceleration curve A 1  from the movement start position G 2  and scanning the carriage  3  in accordance with the deceleration curve A 2  for its outward movement. Consequently, the carriage  3  travels in accordance with the velocity curve A 1  during its acceleration from the movement start position G 2  and in accordance with the velocity curve A 2  during its deceleration in the outward movement thereof in the MS direction so as to perform printing (step S 412 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 413 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing/velocity data (deceleration curve) switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     Next, if the results of judgment made both at the step S 401  and the step S 402  are YES again after returning to the start of this switchover loop, then, the value of the variable CC is calculated in the step S 403 . It should be noted that the value of the variable BB is incremented by “1” in the previous flow processing in this switchover loop. If the value of the variable CC calculated in the previous flow processing is “1”, it is judged as “2” this time. Then, the CPU  39  judges whether the value of the variable CC is “2” or not (step S 406 ). If the CPU  39  judges that the value of the variable CC is “2”, the CPU  39  selects G 3  as the position at which the movement of the carriage  3  is started (refer to  FIG. 10A ); and in addition thereto, the CPU  39  selects A 1  as the acceleration curve to be applied therefor and further selects A 3  as the deceleration curve to be applied therefor (refer to  FIG. 5B ) (step S 411 ). Accordingly, the CPU  39  transmits, to the motor driver  53 , a signal for scanning the carriage  3  in accordance with the acceleration curve A 1  from the movement start position G 3  and scanning the carriage  3  in accordance with the deceleration curve A 3  for its outward movement. Consequently, the carriage  3  travels in accordance with the velocity curve A 1  during its acceleration from the movement start position G 3  and in accordance with the velocity curve A 3  during its deceleration in the outward movement thereof in the MS direction so as to perform printing (step S 412 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 413 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing/velocity data (deceleration curve) switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     Next, if the results of judgment made both at the step S 401  and the step S 402  are YES again after returning to the start of this switchover loop, then, the value of the variable CC is calculated in the step S 403 . It should be noted that the value of the variable BB is incremented by “1” in the previous flow processing in this switchover loop. If the value of the variable CC calculated in the previous flow processing is “2”, it is judged as “3” this time. If the CPU  39  judges that the value of the variable CC is “3”, the CPU  39  selects G 4  as the position at which the movement of the carriage  3  is started (refer to  FIG. 10A ); and in addition thereto, the CPU  39  selects A 1  as the acceleration curve to be applied therefor and further selects A 4  as the deceleration curve to be applied therefor (refer to  FIG. 5B ) (step S 407 ). Accordingly, the CPU  39  transmits, to the motor driver  53 , a signal for scanning the carriage  3  in accordance with the acceleration curve A 1  from the movement start position G 4  and scanning the carriage  3  in accordance with the deceleration curve A 4  for its outward movement. Consequently, the carriage  3  travels in accordance with the velocity curve A 1  during its acceleration from the movement start position G 4  and in accordance with the velocity curve A 4  during its deceleration in the outward movement thereof in the MS direction so as to perform printing (step S 412 ). Subsequently, the value of BB, which indicates a global variable, is incremented by “1” (step S 413 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next movement start position switchover processing/velocity data (deceleration curve) switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     As described above, if it is decided YES each in the steps S 401  and S 402  by the CPU  39  in this switchover loop, the movement positions for respective travels of the carriage  3  are switched over in such a manner that four times of reciprocating movements constitute one unit of operation. In addition, when the decisions made at the steps S 401  and S 402  are successive YES, the movement start positions and the deceleration curves are switched over among G 1 , G 2 , G 3 , and G 4 , and A 1 , A 2 , A 3 , and A 4 , respectively, in the order of appearance herein, in a sequential manner for respective travels (i.e., corresponding to the above-mentioned four times of reciprocating movements) in the unit of operation. The above series of operations is repeated until printing is completed. When the movement start positions and the deceleration curves are switched over sequentially in the order of G 1 , G 2 , G 3 , and G 4 , and A 1 , A 2 , A 3 , and A 4 , respectively, as described above, the vibrations of the carriage  3  occur at J 1 , J 2 , J 3 , and J 4  during acceleration as illustrated in  FIG. 10A  and at D 5 , D 6 , D 7 , and D 8  during deceleration as illustrated in  FIG. 5B , that is, four different points in time each for acceleration and deceleration. 
     As described above, each of J 1 -J 4  and D 5 -D 8  is a point at which the carriage  3  is affected by vibration. Therefore, if the driving modes/movement start positions are switched over as described above, it is possible to shift (i.e., stagger) points in time at which the carriage  3  is affected by vibrations, that is, points in time at which unevenness in printing occurs. As a consequence thereof, in the same (or similar) manner as the first embodiment of the invention described above does, the present embodiment thereof offers advantageous effects in that the points J 1 -J 4  and D 5 -D 8  at which unevenness in printing could occur are staggered with respect to one another in the MS direction of the paper P after completion of printing. Therefore, uneven points will never be aligned along the SS direction. Thus, no rainbow unevenness appears on the paper P after completion of printing (refer to  FIG. 7 ). 
     If the CPU  39  receives a signal that indicates that the paper size of the print target paper is “A3”, driving modes are switched over for both acceleration and deceleration of the carriage  3  (refer to  FIG. 12 ). Note that the printing operation based on such a switchover is the same as that of the counterpart illustrated in the first embodiment of the invention described above. 
     When scanning the carriage  3 , the printer  80  having the configuration described above makes a decision to selectively use either the driving mode switchover or the movement start position switchover on the basis of paper size. With such a configuration, if there is a space that is sufficiently wide between the home position of the carriage  3  and the home-position-side end of the printing paper P, it is possible to perform a pattern switchover by switching the movement start positions of the carriage  3  at the home-position side. Therefore, in such a case, it is not necessary to achieve acceleration on the basis of a plurality of velocity curves for each printing path. As a result thereof, since it is not necessary to use a velocity curve having a relatively low degree of acceleration (i.e., low accelerated velocity), it is possible to offer high-speed printing. In addition, it is possible to shift (i.e., stagger) points in time at which the carriage  3  is affected by vibrations, that is, points in time at which unevenness in printing occurs because the driving modes/movement start positions are switched over as described above. As a consequence thereof, the points J 1 -J 4  and the points D 5 -D 8  at which unevenness in printing could occur are staggered with respect to one another in the MS direction of the printed paper P (i.e., the printing paper P after completion of printing). Therefore, uneven points will never be aligned along the SS direction on the printed paper P. Thus, the invention makes it possible to effectively avoid the generation of rainbow unevenness on the printing paper P after completion of printing. 
     According to the exemplary configuration of the printer  80  described above, the pattern switchover is carried out in accordance with printing direction, that is, either bidirectional printing or unidirectional printing, as well as printing resolution. Specifically, the movement start position pattern switchover/velocity data (deceleration curve) switchover is executed if high-resolution unidirectional printing is performed. Therefore, it is possible to adjust actual print quality, that is, printing precision, depending on required print quality. The pattern switchover is carried out either for each outward movement or for each set of outward and homeward movements of the carriage  3 . Therefore, it is possible to apply the switchover (technique) of the scanning positions/scanning speeds of the carriage  3  according to the invention to both of bidirectional printing and unidirectional printing. Thus, the invention increases the diversification of printing that is performed by the printer according to embodiment thereof. 
     According to the exemplary configuration of the printer  80  described above, printing is started during acceleration of the carriage  3 . After the start of printing, it is continued until the carriage  3  decelerates. Therefore, the invention makes it possible to provide a marginless printing, that is, printing with no margin left at edges of the printing paper P, or printing with relatively narrow margins left thereat. Thus, the invention makes it possible to offer high-quality printing. 
     Fourth Embodiment 
     With reference to accompanying drawings, a printing apparatus  90  according to a fourth exemplary embodiment of the invention is described below. It should be noted that, in the following description of the printer  90  according to the fourth exemplary embodiment of the invention, the same reference numerals are consistently used for the same components as those of the printer  1  according to the first exemplary embodiment of the invention so as to omit any redundant explanation or simplify explanation thereof. 
       FIG. 14  is a block diagram that schematically illustrates an example of the configuration of a control unit  92 , which controls the CR motor  4  in the printer  90 . 
     Note that the configuration of the printer  90  is the same as that of the counterpart illustrated in the first embodiment of the invention described above. In the configuration of the printer  90 , the control unit  92 , which functions as a control section, is in charge of controlling the driving speed of the CR motor  4 . As illustrated in  FIG. 14 , the control unit  92  is provided with the CPU  39 , the ROM  41 , the RAM  43 , the output port  49 , the interface  51 , and the motor driver  53 . These components are interconnected with one another via the bus  55 , which is a group of signal lines. In the present embodiment of the invention, the ROM  41  memorizes data of a velocity curve  5  in addition to that of the velocity curve A 1 . The velocity curve  5  is characteristic in that it does not reach the scanning speed at which the printer  90  vibrates in resonance therewith, that is, 22 ips according to this specification. The CPU  39 , which functions as a velocity mode switchover section, switches over to a velocity data pattern in accordance with the velocity curve A 5  stored in the ROM  41 . 
     In the following description, a printing operation that is performed when the CPU  39  effects the switchover described above is explained. 
       FIG. 15  is a flowchart that illustrates the operational flow of the switchover processing performed by the CPU  39  according to the present embodiment of the invention.  FIG. 16  is a set of diagrams that illustrates velocity curves in the scanning of the carriage  3 . Specifically,  FIG. 16A  illustrates the velocity curves (i.e., acceleration curves) that apply during acceleration of the carriage  3 . On the other hand,  FIG. 16B  illustrates the velocity curves (i.e., deceleration curves) that apply during deceleration thereof. In each of  FIGS. 16A and 16B , the horizontal axis represents time where the driving start of the carriage  3  is taken as zero. The vertical axis in each of  FIGS. 16A and 16B  represents the scanning speed of the carriage  3 . 
     When printing is performed, as the first step, the control instruction unit  40  receives print-related data such as paper size, paper type, resolution, printing mode, unidirectional printing or bidirectional printing, color adjustment, and so on. Next, the control instruction unit  40  supplies the received data to the CPU  39 . On the basis of the input data that is supplied from the control instruction unit  40 , the CPU  39  reads out the velocity data stored in the ROM  41  or the RAM  43 . Next, the CPU  30  performs arithmetic processing in accordance with the program. In the present embodiment of the invention, it is assumed that printing is performed under a MicroWeave printing mode. 
     In the present embodiment of the invention, it is assumed that so-called unidirectional printing is performed. As has already been described, in the unidirectional printing, ink drops are discharged from the print head  2  onto the printing paper P during a time period in which the carriage  3  travels along the MS direction from the home position to the away position thereof, which is referred to as outward movement and defined as the opposite word of homeward movement in this specification. The discharging of ink drops starts at the point in time E 5  shown in  FIG. 16A , and ends at the point in time E 6  shown in  FIG. 16B . This means that the print target area, at which printing is performed, is defined as a region where the carriage  3  travels during a time period between the point in time E 5  and the point in time E 6 . The CPU  39  performs computation for the switchover according to the present embodiment of the invention when the carriage  3  reaches the away position after traveling along the MS direction. 
     When the CPU  39  receives various kinds of signals, it performs the velocity mode switchover so that printing is performed in the selected velocity mode. As illustrated in  FIG. 15 , as the first step of the velocity mode switchover shown in the flowchart thereof, the CPU  39  judges whether the dot size version is “VSD3” or not (step S 501 ). If the dot size version is not “VSD3”, that is, if the decision made at the step S 501  is NO, the CPU  39  reads, out of the ROM  41 , velocity data that corresponds to the velocity curve A 1 , and effects a switchover so as to select the velocity data corresponding to the velocity curve A 1  (step S 504 ). Next, the CPU  39  transmits a signal for scanning the carriage  3  in accordance with the velocity curve A 1  to the motor driver  53 . Accordingly, the carriage  3  reciprocates in the MS direction on the basis of the velocity curve A 1 . That is, the carriage  3  travels at the scanning speed based on the velocity curve A 1  during both of its outward movement and homeward movement. During the outward movement, the carriage  3  performs printing (step S 505 ). Thereafter, at the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next velocity data switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     It is assumed that the result of judgment made at the step S 501  is, again, NO after returning to the start of this switchover loop. If so, the velocity curve A 1  is selected (step S 504 ). Accordingly, the carriage  3  travels at the scanning speed based on the velocity curve A 1  during both of its outward movement and homeward movement, while performing printing during its outward movement (step S 505 ). As described above, if decisions made at the step S 501  continue to be NO, in other words, if the dot size version is not “VSD3”, printing continues to be performed on the basis of the same velocity curve (that is, velocity curve A 1 ). 
     If it is judged as YES in the step S 501 , the CPU  39  further judges whether to perform so-called unidirectional printing or not, that is, whether to discharge ink during the outward movement of the carriage  3  only or not (step S 502 ). If it is judged as NO in the step S 502 , the velocity data corresponding to the velocity curve A 1  is read out; and the driving modes are switched over to select the velocity data corresponding to the velocity curve A 1  (step S 504 ). Then, a signal for scanning the carriage  3  in accordance with the velocity curve A 1  is transmitted to the motor driver  53 . Accordingly, the carriage  3  reciprocates in the MS direction on the basis of the velocity curve A 1 . The carriage  3  travels at the scanning speed based on the velocity curve A 1  during both of its outward movement and homeward movement. Herein, since the decision made at the step S 502  is NO, the carriage  3  performs so-called bidirectional printing; that is, the carriage  3  discharges ink both during the outward movement and the homeward movement thereof (step S 505 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next velocity data switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     If the decision made at the step S 502  is YES, the CPU  39  reads, out of the ROM  41 , velocity data that corresponds to the velocity curve A 5  shown in the  FIGS. 16A and 16B , and effects a switchover so as to select the velocity data corresponding to the velocity curve A 5  (step S 503 ). Then, the CPU  39  transmits a signal for scanning the carriage  3  in accordance with the velocity curve A 5  to the motor driver  53 . Accordingly, the carriage  3  performs printing at the scanning speed based on the velocity curve A 5  during its outward movement (step S 505 ). At the point in time at which the carriage  3  reaches its away position, the processing flow returns to the start of the switchover loop described herein. Then, next velocity data switchover processing is started. In addition thereto, the carriage  3  moves to its home position. 
     If it is decided YES successively in the steps S 501  and S 502  in a repetitive manner in this switchover loop, the carriage  3  is repeatedly scanned at the scanning speed that is in accordance with the velocity curve A 5 . If the carriage  3  is repeatedly scanned at the scanning speed that is in accordance with the velocity curve A 5 , the traveling speed of the carriage  3  will be lower than a speed at which the printer  90  vibrates in resonance therewith, that is, 22 ips according to this specification. This means that the carriage  3  never vibrates during printing. Thus, no rainbow unevenness appears on the paper P after completion of printing. 
     According to the configuration of the printer  90  described above, it is possible to control the carriage  3  so that it travels at the scanning speed that is lower than the speed at which the printer  90  vibrates in resonance therewith. Therefore, it is possible to prevent the carriage  3  from vibrating intensely due to the resonance vibration of the printer  90 . Thus, it is possible to effectively prevent a decrease in printing precision (i.e., degradation in print quality) due to vibrations of the carriage  3  during printing. As a result thereof, it is possible to prevent the occurrence of rainbow unevenness on the paper P after completion of printing. 
     In addition, since the velocity data corresponding to the velocity curve A 5  is stored in the ROM  41  of the printer  90 , the invention makes it possible to read the velocity data corresponding to the velocity curve A 5  out of the ROM  41  and to control the scanning speed of the carriage  3  on the basis of the read velocity data corresponding to the velocity curve A 5 . Therefore, it becomes easier to scan the carriage  3  with the same velocity pattern in a repetitive manner. 
     According to the exemplary configuration of the printer  90  described above, the pattern switchover is carried out in accordance with printing direction, that is, either bidirectional printing or unidirectional printing, as well as printing resolution. Specifically, the velocity data pattern switchover is executed if high-resolution unidirectional printing is performed. Therefore, it is possible to adjust actual print quality, that is, printing precision, depending on required print quality. The pattern switchover is carried out either for each outward movement or for each set of outward and homeward movements of the carriage  3 . Therefore, it is possible to apply the switchover (technique) of the scanning speeds of the carriage  3  according to the invention to both of bidirectional printing and unidirectional printing. Thus, the invention increases the diversification of printing that is performed by the printer  90 . 
     According to the exemplary configuration of the printer  90  described above, printing is started during acceleration of the carriage  3 . After the start of printing, it is continued until the carriage  3  decelerates. Therefore, the invention makes it possible to provide a marginless printing, that is, printing with no margin left at edges of the printing paper P, or printing with relatively narrow margins left thereat. Thus, the invention makes it possible to offer high-quality printing. 
     Although various exemplary embodiments of the present invention are described above, needless to say, the invention is in no case restricted to these exemplary embodiments described herein; the invention may be configured and/or implemented in an adaptable manner in a variety of variations without departing from the spirit thereof. 
     In the first, second, and third exemplary embodiments of the invention described above, the velocity data corresponding to four velocity curves A 1 -A 4  are stored in the ROM  41 . However, the number of velocity curves, and thus the number of velocity data, is not limited to four. As an alternative configuration of the invention, the number of the velocity curves and thus the number of velocity data that are stored in the ROM  41  may be five or greater, or three or less. 
     Although the CPU  39 , which functions as the driving mode switchover section, performs switchover by means of the velocity data corresponding to four velocity curves A 1 -A 4  according to the first exemplary embodiment of the invention described above, it may be alternatively configured that the CPU  39  performs the switchover by means of the velocity data corresponding to three velocity curves or less. On the other hand, if the ROM  41  memorizes five pieces of velocity data corresponding to five velocity curves or greater, it may be alternatively configured that the CPU  39  performs the switchover by means of the above-mentioned five pieces of velocity data corresponding to five velocity curves or greater. 
     Similarly, although the CPU  39 , which functions as the movement position switchover section, performs switchover by means of the movement start positions G 1 -G 4  according to the second exemplary embodiment of the invention described above, the number of the movement start positions according to the invention is in no case limited to four. That is, it may be alternatively configured that the CPU  39  performs the switchover by means of five movement start positions or greater, or three movement start positions or less. In addition, the invention may be modified in such a manner that the movement stop positions are switched over so that they correspond to the movement start positions G 1 -G 4 . Moreover, the invention may be modified in such a manner that, when the movement stop positions are switched over, the number of the movement stop positions is not the same as that of the movement start positions. 
     The CPU  39 , which functions as the movement position switchover section, uses the velocity curve A 1  according to the second and third exemplary embodiments of the invention described above. However, the invention is in no case limited to such a configuration. That is, it may be alternatively configured that the CPU  39  uses either the velocity curve A 2  or the velocity curve A 3 . 
     The CPU  39 , which serves as the print target medium recognition section, recognizes (i.e., detects) the size of the print target paper according to the third exemplary embodiment of the invention described above. Then, on the basis of the recognition result, the CPU  39 , which further serves as the switchover judgment section, makes a decision as to which one of the switchover methods should be used, that is, either the driving mode switchover or the movement start position switchover. However, the invention is in no case limited to such a configuration. For example, the invention may be modified in such a manner that the print target medium recognition section recognizes the paper type of the print target paper (for example, whether it is a “normal plain paper” or a “special glossy paper”). As another alternative example, it may be modified in such a manner that the print target medium recognition section recognizes the color type of the print target paper (for example, whether it is a “monochrome paper” or a “sepia-toned paper”). As still another alternative example, it may be modified in such a manner that the print target medium recognition section recognizes which one of the “edged printing” and “edgeless printing” is demanded. In the foregoing exemplary embodiment of the invention, the CPU  39 , the switchover judgment section, makes a decision as to which one of the switchover methods should be used, that is, either the driving mode switchover or the movement start position switchover. However, the invention is in no case limited to such a configuration. For example, the invention may be modified in such a manner that the CPU  39  functioning as the switchover judgment section makes a decision so as to selectively use the velocity curves, the movement start positions, or the movement stop positions for effecting a switchover. 
     According to the fourth exemplary embodiment of the invention described above, the CPU  39 , which functions as the velocity mode switchover section, uses only the velocity curve A 5  if both of the decisions made at the steps S 501  and S 502  are YES. However, the invention is in no case limited to such a configuration. That is, it may be alternatively configured that the velocity curve A 5  is used in combination with any one or more of the velocity curves A 1 -A 4 . In addition to the velocity data corresponding to the velocity curve A 5  described in the fourth exemplary embodiment of the invention described above, another velocity data which corresponds to another velocity curve having a steady-state velocity that is less than 22 ips may be stored in the ROM  41 . In such an alternative configuration, the above-mentioned another velocity curve having a steady-state velocity that is less than 22 ips may be used in place of the velocity curve A 5 , or it may be used in combination thereof. 
     In each of the foregoing exemplary embodiments of the invention, in a case where the dot size version is not “VSD3”, the switchover section causes the carriage  3  to travel at the scanning speed based on the velocity curve A 1  during both of its outward movement and homeward movement. However, the invention is in no case limited to such a configuration. For example, the invention may be modified in such a manner that the carriage  3  is scanned at the scanning speed in accordance with the velocity curve A 1  during its outward movement only, whereas it is scanned during its homeward movement at another scanning speed in accordance with any one of the velocity curves A 2 -A 4  or any other alternative curve that is not A 1 . Although it is assumed that unidirectional printing is performed if the dot size version is not “VSD3” in the foregoing exemplary embodiments of the invention, the invention may be modified so that bidirectional printing is performed in such a case in place of the unidirectional printing. 
     In the exemplary embodiments of the invention described above, the control instruction unit  40  receives input information on paper size and paper type. Herein, information on paper size and paper type may be obtained as user-input data, or alternatively, may be obtained through optical detection by means of a sensor. 
     According to the third exemplary embodiment of the invention described above, if the paper size is judged as “A4”, the movement position switchover section performs a pattern switchover for acceleration of the carriage  3 , whereas the driving mode switchover section performs a pattern switchover for deceleration thereof. However, the invention may be modified in such a manner that, if the size of the print target paper is judged as “A4”, the driving mode switchover section performs a pattern switchover for both of acceleration and deceleration of the carriage  3 . According to the third exemplary embodiment of the invention described above, if it is judged that the paper size is not “B5”, “A4”, nor “A3”, the driving mode switchover section performs a pattern switchover for both of acceleration and deceleration of the carriage  3 . However, the invention is not restricted to such a configuration. For example, the invention may be modified in such a manner that the movement position switchover section performs a pattern switchover for acceleration of the carriage  3 , whereas the driving mode switchover section performs a pattern switchover for deceleration thereof for any paper size that is not “B5”, “A4”, nor “A3”. Alternatively, if it is judged that the paper size is not “B5”, “A4”, nor “A3”, a decision may be made so as to make selection between the driving mode switchover and the movement position switchover depending on the paper size thereof. 
     According to the first, second, and fourth exemplary embodiments of the invention described above, the print target medium recognition section is not provided. However, the invention described in these exemplary embodiments may be modified so that the velocity curve pattern switchover and either one or both of the movement start position switchover and the movement stop position switchover are performed on the basis of the detection result of the print target medium recognition section. 
     In each of the exemplary embodiments of the invention described above, the ROM  41  memorizes velocity data regarding the driving speed of the CR motor  4 , which corresponds to the scanning speed of the carriage  3 . However, the invention is in no case limited to such a configuration. For example, it may be modified in such a manner that velocity data of the scanning speed of the carriage  3  may be stored in the ROM  41 . As another example, the velocity data regarding the driving speed of the CR motor  4  that corresponds to the scanning speed of the carriage  3  may be stored in the ROM  41  in addition to the velocity data of the scanning speed of the carriage  3 . 
     In each of the exemplary embodiments of the invention described above, the carriage  3  is configured to accommodate the ink cartridges  21 . However, the invention is in no case limited to such a configuration. As an example of alternative configurations, the ink cartridges  21  may be mounted not on the carriage  3  but on or in the body chassis of the printer  1 ,  70 ,  80 , or  90 . In such an alternative configuration, ink contained therein is fed to the print head  2  provided on the carriage  3  via, for example, ink tubes.