Patent Document

BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to an inkjet printer for emitting ink droplets to record letters and images.  
           [0003]    2. Description of the Related Art  
           [0004]    The ink jet printer is a type of printer for recording letters and images formed from ink dots arriving on a recording medium such as paper after being emitted as droplets of ink from fine nozzles arrayed in the printer head. The ink-jet printer is characterized in having a high recording speed, a low recording cost and further can easily perform color printing.  
           [0005]    Printer heads in the ink-jet printer of the related art come in two types: a so-called serial head shorter than the page width of printing paper, and a so-called line head having almost the same length dimensions as the page width of printing paper. As methods for emitting the ink droplets there are the piezo method utilizing a piezoelectric element, and a thermal method utilizing a thermal (or heat-emitting) element.  
           [0006]    The line head method mentioned above, unlike the serial head, is characterized in not requiring a drive means such as a motor, to move in the direction of the page width when recording, so the printer chassis can be made compact and costs can be reduced.  
           [0007]    Compared to the piezo method, the thermal method is characterized in that increasing the number of drive elements and placement density in order to emit the ink droplets is relatively easy, so the thermal method is ideal for use with the line head method. This invention therefore proposes an ink-jet printer comprising a thermal type line head.  
           [0008]    Compared to the piezo method, the thermal method has the disadvantages of low energy efficiency and large power consumption during recording. To eliminate these disadvantages, the plurality of thermal elements such as employed in thermal type serial heads must be apportioned into a certain number of blocks, and a time-division drive method for sequentially driving each thermal element in a block on shared time must also be applied to each block.  
           [0009]    The ink-jet printer of the related art also generally utilized digital image processing such as the so-called dither method and error diffusion method to express print tones. However, these methods essentially utilize a plurality of dots to express the print tones so that the actual resolution of the print is low, and the dots have a grainy, rough appearance to the human eye that reduces the image quality. The dot size must therefore be made smaller and the dot placement density increased in order to improve the printing resolution and image quality. of these problems, the dot size in both the thermal type line head and the serial head can be made smaller by reducing the size of the thermal elements, the diameter of the nozzles and the volume of the chamber to reduce the volume of the ink particles being emitted.  
           [0010]    However, compared to serial heads, the problem of dot placement density is difficult to eliminate in thermal type line heads. This problem is due to the fact that while the serial head will have several hundred nozzles, the line head will require several thousand nozzles in the case for instance of an A4 sheet of paper. The large number of nozzles not only greatly reduces the production pace of nozzle manufacture, but also creates problems because of the large scale increased in head driver circuits and the related higher costs and reliability.  
           [0011]    Therefore a method using the so-called tiling method is utilized which employs an array of a plurality of head chips containing a specified number of nozzles.  
           [0012]    Line heads utilizing this tiling method are comprised for instance as shown in FIG. 19.  
           [0013]    In FIG. 19, a line head  1  is comprised of a plurality of head chips  2  (Five head chips  2  are shown in the figure.) each installed with a specified number of nozzles (not shown in drawing) are connected so as to be arrayed in a straight line.  
           [0014]    As also shown in FIG. 19, the nozzles arrayed in a straight line and the head chips  2  comprising the nozzle  1  are subdivided into blocks  3  and the nozzle of each block is driven in sequence by time-division. Each head chip  2  is therefore also comprised of a drive circuit  4  containing drive elements such as the aforementioned thermal elements. These drive circuits  4  respectively correspond to a time-division driven block  3 .  
           [0015]    Here, each drive circuit  4  is comprised of a thermal element  4   a  and a switching element  4   b  as shown in FIG. 21. When the switching element  4   b  is turned on by the drive signal, drive current flows in the thermal element  4   a  so that the thermal element  4   a  emits heat and emits ink from the corresponding nozzle.  
           [0016]    The plurality of nozzle units of each block  3  are in this way sequentially time-division driven by the corresponding drive circuit  4  so that ink is emitted.  
           [0017]    However, in a line head  1  configured by tiling of this kind, the above described number of time-division drive phases or in other words, the number of nozzles for each block is set regardless of the number of nozzles for each head chip  2 .  
           [0018]    The wiring of the drive circuit  4  corresponding to the drive element for emitting ink from each nozzle is therefore different and the wiring for each head chip  2  in the entire line head  1  becomes complicated, and the configuration of the drive circuits  4  for each head chip  2  is therefore different.  
           [0019]    One block is comprised of 16 nozzles as shown in FIG. 20, and each head chip  2  has 15 nozzles. When the number of time-division drive phases is  8 , the first head chip  2 A is comprised of a drive circuit  4  for driving nozzles from phase No. 1 through 15 as shown in FIG. 21A. A second head chip  2 B contains a drive circuit  4  for driving the nozzle for phase No. 16 of the first block, and nozzles for phase No. 2 through 14 of the second block, as shown in FIG. 21B.  
           [0020]    However, the above configuration requires fabricating multiple types of head chips  2 A,  2 B containing different types of circuits, and creates the problem that efficient mass production is difficult so that the manufacturing cost of the head chip  2  and the line chip  1  is high.  
         SUMMARY OF THE INVENTION  
         [0021]    In view of the above problems with the related art, this invention has the object of providing a line head ink-jet printer having lower manufacturing costs because of more efficient mass production due to a simple head chip configuration, and further having high resolution and image quality along with reduced power consumption.  
           [0022]    To attain the above objectives, according to one aspect of the present invention, there is provided an ink-jet printer emitting droplets of ink arriving as ink dots forming images and letters recorded onto a recording medium from a line head having a plurality of nozzles arrayed in the width direction of the recording medium which is almost perpendicular to the feed direction of the recording medium comprising head chips having a specified number of nozzles and a drive circuit to drive each nozzle, wherein a plurality of the head chips are arrayed in the width direction thereof to form the line head so that the nozzles each head chip has and the nozzles the neighboring head chips have are not arrayed in the feed direction of the recording medium.  
           [0023]    To also attain the above objectives, according to another aspect of the present invention, there is provided an ink-jet printer, wherein the nozzles each head chip has are sequentially time-series driven by separate driving, and the number of the nozzles each head chip has is an integer multiple of the number of phases for the separate driving of the nozzles.  
           [0024]    To also attain the above objectives, according to still another aspect of the present invention, there is provided an ink-jet printer emitting droplets of ink arriving as ink dots forming images and letters recorded onto a recording medium from a line head having a plurality of nozzles arrayed in the width direction of the recording medium which is almost perpendicular to the feed direction of the recording medium comprising head chips having a specified number of nozzles and a drive circuit to drive each nozzle, in which a plurality of the head chips are arrayed in the width direction thereof to form the line head so that the nozzles each head chip has and part of the nozzles the neighboring head chips have are arrayed in the feed direction of the recording medium.  
           [0025]    To also attain the above objectives, according to still another aspect of the present invention, there is provided an ink-jet printer, wherein said nozzles each head chip has are sequentially time-series driven by separate driving, and the number of the nozzles each head chip has is the number of the part of the nozzles the neighboring head chips have and the number of nozzles arrayed in the feed direction of the recording medium added to the integer multiple of the number of phases for the separate driving of the nozzles.  
           [0026]    In the above structure, the nozzles for each head chip are set as an integer multiple of the number of phases for separate driving of the nozzles or set as this figure added with the number of overlapping nozzles, so that when a plurality of head chips are arrayed by tiling to comprise a line head, the block of time-shared driven nozzles are matched in a coordinated manner with the head chips.  
           [0027]    Therefore, by arraying a plurality of head chips each having a small number of nozzles, a line head can be configured by so-called tiling, so that along with obtaining high image resolution and high image quality by a higher dot placement density, the power consumption can be reduced by time-division driving of the nozzles.  
           [0028]    Further, the structure of the drive circuit containing the drive elements for driving each nozzle is the same for each head chip so that a line head can be comprised by arraying a plurality of head chips each containing an identical drive circuit, and since only one type of head chip is being produced, efficient mass production can be achieved. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    [0029]FIG. 1 is a fragmentary perspective view of showing a cross section of the overall structure of the embodiment of the ink-jet, printer of this invention.  
         [0030]    [0030]FIG. 2 is a cross sectional view of the ink-jet printer of FIG. 1.  
         [0031]    [0031]FIG. 3 is a block diagram showing the recording and control system of the electrical circuit section in the ink-jet printer of FIG. 1.  
         [0032]    [0032]FIG. 4 is a block diagram showing in more detail the line head and the head drive circuit of FIG. 3.  
         [0033]    [0033]FIG. 5 is a first drawing showing the PNM processing by the head drive circuit of FIG. 4.  
         [0034]    [0034]FIG. 6 is a second drawing showing the PNM processing by the head drive circuit of FIG. 4.  
         [0035]    [0035]FIG. 7A and 7B are respectively a flat view and a bottom view showing the structure of a one color portion line head for the ink-jet printer of FIG. 1.  
         [0036]    [0036]FIG. 8A is a side view showing a cross section taken along lines A-A in the line head of FIG. 7A.  
         [0037]    [0037]FIG. 8B is a side view showing a cross section taken along lines B-B in the line head of FIG. 7B.  
         [0038]    [0038]FIG. 9 is a perspective view of the line head of FIG. 7 seen from the bottom side.  
         [0039]    [0039]FIG. 10 is a flat view showing the detailed structure of the head chips of the line head of FIG. 7.  
         [0040]    [0040]FIG. 11 is a perspective view showing the detailed structure of the nozzles in proximity on the head chip of FIG. 7 as seen from the bottom side.  
         [0041]    [0041]FIGS. 12A to  12 C are schematic diagrams showing the relation of the drive circuits and the structure of each head chip in the line head of FIG. 7.  
         [0042]    [0042]FIG. 13 is a schematic diagram showing the nozzle arrangement in the line head of FIG. 12B.  
         [0043]    [0043]FIG. 14 is a timing chart showing the drive signals for one block of nozzles in the line head of FIG. 13.  
         [0044]    [0044]FIG. 15 is a circuit diagram showing the drive circuits for one block of nozzles in the line head of FIG. 12B.  
         [0045]    [0045]FIGS. 16A and 16B are schematic drawings showing the structure of the line head of the second embodiment of the ink-jet printer of this invention.  
         [0046]    [0046]FIG. 17 is a schematic diagram showing the nozzle array in the line head of FIG. 16.  
         [0047]    [0047]FIG. 18 is a timing chart showing the drive signals for one block of nozzles in the line head of FIG. 17.  
         [0048]    [0048]FIG. 19 is a schematic drawing showing the interrelation of the drive circuits with the line head in an example of time-division drive of the line head structured by tiling in an ink-jet printer of the related art.  
         [0049]    [0049]FIG. 20 is a schematic drawing showing the nozzle array in the line head of FIG. 19.  
         [0050]    [0050]FIGS. 21A and 21B are circuit diagrams showing the drive circuits for one block of nozzles in the line head of FIG. 19. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0051]    Hereafter, the preferred embodiments of the invention are described in detail while referring to FIG. 1 through FIG. 18.  
         [0052]    The following described embodiments are preferred working examples of the invention and so are preferably limited in regards to their technical aspects, however unless otherwise stated, the scope of the invention is not limited by the following description and not limited by these aspects of the invention.  
         [0053]    (Printer Overall Structure)  
         [0054]    The overall structure of the ink-jet printer of the embodiment of this invention is shown in FIG. 1 and FIG. 2.  
         [0055]    In FIG. 1 and FIG. 2, an ink-jet printer  100  is comprised of a line head  120  having thermal elements not shown in the drawing, as drive elements for emitting droplets of ink, and having a PNM (pulse number modulation) function for modulating the number of dots form the ink droplets in a recording range having a width largely equal to a paper P.  
         [0056]    The ink-jet printer  100  is comprised of a line head  120 , a paper feed section  130 , a line feed section  140 , a paper tray  150 , and an electrical circuit section  160  installed in a cabinet  110 .  
         [0057]    The cabinet  110  is formed in the shape of a right-angled parallelepiped. A paper ejection slot  111  for the paper P is formed in one end of the cabinet  150 , and a tray inlet/outlet  112  for the paper tray  150  is formed in the other end of the cabinet  150 . The line head  120  contains four color CMYK (cyan, magenta, yellow, black) and nozzles not shown in the drawing are installed above the end of the paper ejection slot  111  to face downward.  
         [0058]    The paper feed section  130  is comprised of a paper feed guide  131 , paper feed roller  132 ,  133 , a paper feed motor  134 , pulleys  135 ,  136 , and belts  137 ,  138 , and is installed below the edge of the paper ejection slot  111 . The paper feed guide  131  is formed a level plate shape and installed with specified open gaps below the line head  120 . The paper feed rollers  132  and  133  form a pair of rollers in mutual contact, and are installed on both sides of the paper feed guide  131 , namely on the side of the tray inlet/outlet  112  and the side of the paper ejection slot  111 . The paper feed motor  134  as shown in FIG. 2 is installed below the paper feed guide  131 , and is linked to the paper feed rollers  132 ,  133  by way of the pulleys  135 ,  136  and the belts  137 ,  137 .  
         [0059]    The line feed section  140  is comprised of the line feed roller  141 , line feed motor  142  and gear  143 , and is installed on the tray inlet/outlet  112  opposite the paper feed section  130 . The line feed roller  141  is formed in a roughly semicircular tubular shape and installed in proximity to the paper feed roller  132  on the tray inlet/outlet  112  side. The line feed motor  142  is installed above the line feed roller  141 , and is linked to the line feed roller  141  by the gear  143 .  
         [0060]    The paper tray  150  is formed in a box shape capable of storing a plurality of sheets of paper P for instance of A 4  size, and has a paper clamp  152  engaged with a spring  151 . The paper tray  150  is installed from below the line feed section  140  to the tray inlet/outlet  112 . The electrical circuit section  160  controls the driving of each section and is installed above the paper tray  150 .  
         [0061]    Therefore, when using this type of ink-jet printer  100 , the user, after turning on the power to the ink-jet printer  100 , pulls out the paper tray  150  from the tray inlet/outlet  112  and presses a specified number of sheets of paper P inside the paper tray  150 . When the sheets of paper P are pressed in, the paper clamp  152  raises up the end portion of the paper P by means of the action of the spring  151 , and presses the paper P against the line feed roller  141 . The line feed motor  142  then drives and rotates the line feed roller  141 , and one sheet of paper P is fed to the paper feed roller  132  from the paper tray  150 .  
         [0062]    Next, the paper feed rollers  132 ,  133  are rotated by the driving action of the paper feed motor  134 , and the paper P fed from the paper feed roller  132  is fed to the paper feed guide  131 . The line head  120  then operating at a specified timing, emits droplets of ink from a nozzle to impact on the paper P and record characters and images formed of dots from the ink droplets. Then, the paper P fed out from the paper feed roller  133 , is ejected from the paper ejection slot  111 . This process is repeated until the recording is complete.  
         [0063]    A block diagram showing the electrical circuit section  160  for recording and control in the ink-jet printer  100  of FIG. 1 of this invention is shown in FIG. 3.  
         [0064]    A correction circuit  162  stored with pre-established correction data in a ROM map method, a head drive circuit  163  for driving a line head  120 , a control circuit  164  for controlling motor drive and other control as well as a memory  165  constituted by a line buffer memory and a one screen memory are connected in a signal processing control circuit  161  for software processing by means of a CPU and DSP configuration.  
         [0065]    Signals such as record data, are input from the signal input section  166  to the signal processor-control circuit  161  arranged in a record sequence, and sent to a correction circuit  162  for correction processing such as correcting irregularities in each nozzle, color correction, and γ correction. Then signals such as for record data after correction are extracted from the signal processor-control circuit  161  according to external conditions, such as the nozzle No., temperature, and input signal, and sent as drive signals to the head drive circuit  163  and each control circuit  164 .  
         [0066]    The head drive circuit  163  controls driving of the line heads  120  based on the drive signal. The control circuits  164  controls driving of the paper feed motor  134 , the line feed motor  142 , and the line head  120  for cleaning etc., based on the drive signal. Signals such as for record data are temporarily recorded in the memory  165  and extracted as needed.  
         [0067]    A block diagram showing a detailed view of the line head  120  and the head drive circuit of FIG. 3, is shown in FIG. 4.  
         [0068]    The head drive circuit  163  is configured to perform time-shared driving and PNM modulation. The head drive circuit  163  is comprised of a tone counter  163   a , a converter  163   b , a serial-parallel converter  163   c  and a data loader  163   d .  
         [0069]    As shown in FIG. 5, the tone counter  163   a , is a counter for counting up the PNM (pulse number modulation) pulses. The converter  163   b  compares the count value with the record data from the data loader  163   d , and outputs an “H” when the record data is higher than the count value. The serial-parallel converter  163   c , as shown in FIG. 6, after processing in serial data the thermal element data to simultaneously drive nozzles at a certain number of time-drive divisions during one tone, converts the serial data into parallel data.  
         [0070]    The line head  120  is comprised by tiling of a plurality of head chips  121  each having one time-division driven block. A time-division driven phase generator circuit  121   a , holds the output for the total number of phases, and forms one sub-unit with the thermal element  121   b , the switching element  121   c , and the gate circuit  121   d . The gate circuit  121   d  forms a logic “AND gate” input with the signal from the time-division driven phase generator circuit  121   a  and the data from the serial/parallel converter  163   c , and when the phase and data input to the AND gate are both “H”, the switching element  121   c  is turned on to drive the thermo element  121   b  and emit the ink.  
         [0071]    (Head Structure)  
         [0072]    A flat view and a bottom view showing the structure for a line head  120  for one color portion in the ink-jet printer  100  of FIG. 1 are respectively shown in FIG. 7A and FIG. 7B. FIG. 8A is a cross sectional view taken along the lines A-A, and FIG. 8B is a cross sectional view taken along the lines B-B of FIG. 7B. A fragmentary, perspective view as seen from the bottom side is shown in FIG. 9.  
         [0073]    As these figures show, an ink supply hole  122   a  is formed in a slit shape in the center of the line-shaped head frame  122  of the line head  120 . A plurality of head chips  121  formed of silicon plate are attached on the other side of the head frame  122 . The head chips  121  are formed in a staggered formation on both sides of the ink supply hole  122   a  on the head frame  122 . As shown also in FIG. 10, a plurality of thermal elements  121   a  are arrayed in a row on the ink supply hole  122   a  side on the head chip  121 , and on the opposite side, a row of connecting elements  121   b  are arrayed in a row paired with the thermal elements  121   a.    
         [0074]    In this example, the thermal elements  121   a  are arrayed at 600 dpi. A switching circuit  121   c  for performing time-division drive of the head chip  121  (thermal element  121   a ) and (logic) gate circuits  121   d  are respectively laid out between the connecting elements  121   b  and the thermal elements  121   a . The temperature of the head chip  121  rises due to the (ink) emission operation but the top surface and side surface of the head chip  121  are immersed in ink so that the head chip  121  is directly cooled by the ink.  
         [0075]    A nozzle plate  124  having a plurality of nozzles  124   a  are formed on the head chip  121  by way of a member  123  forming the flow path  123   b  and the plurality of fluid compartments  123   a  as shown in FIG. 11. In the member  123 , each fluid compartment  123   a  houses thermal elements  121   a  arrayed in the head chip  121 , and further, each flow path  123   b  extends from the fluid compartments  123   a  to the edge of the head chip  121  by means of light-sensitive plastic such as so-called dry photoresist.  
         [0076]    The nozzle plate  124  is made for example by electrotyping and receives anti-corrosive plating such as of gold or palladium to prevent corrosion caused by the ink and formed to prevent clogging of the ink supply holes  122   a  and also so the nozzles  124  form one-to-one pairs with the thermal elements  121   b . In other words, the fluid compartments  123   a  are connected by the flow paths  123   b  formed in the member  123  and to the nozzles  124   a  formed in the nozzle plate  124 .  
         [0077]    An ink tank  126  is attached to the other surface of the head frame  122  by way of the filter  125 . The filter  125  is formed to cover the ink supply holes  122   a  and fulfills the job of preventing debris and clusters of ink material from the ink tank  126  from penetrating into the nozzle side  124 . The ink tank  126  is formed in a double layer by the bag  126   a  and the outer cabinet  126   b.    
         [0078]    A spring member  126   c  is placed between the bag  126   a  and the outer cabinet  126   b  to make the bag  126   a  widen to the outer side. The ink is in this way subjected to a negative pressure, and the ink is prevented from naturally leaking away from the nozzle  124 . This negative pressure is further set to reduce the capillary action of the nozzle  124   a  so that the ink can be prevented from being pulled in to the nozzle  124   a.    
         [0079]    An electrical wiring  127 madeof so-called FPC (flexible printed circuit board) is attached from above the head chip  121 , along the outer side of the head frame  122  to the outer circumferential surface of the ink tank  126 . The electrical wiring  127  is for supplying electrical power and electrical signals to the head chip  121 , and is connected to the connection terminal  121  of the head chip  121 .  
         [0080]    In the above structure, the ink is supplied from the ink tank  126  to the ink supply holes  122   a , and supplied by way of the flow path  123   b  to the fluid compartment  123   a . Here, the nozzles  124   a  are formed in a circular shape, and the center of the ink surface is concave due to the negative pressure of the ink at the tip of the nozzle, creating the so-called meniscus effect. A drive voltage is applied to the thermal elements  121   b , and when air bubbles occur on the thermal element  121   b  surface, ink particles are emitted from the nozzle  124   a.    
         [0081]    In the line head  120 , each head chip  121  has a specified number of first phase time-driven nozzles  124   a  as shown in FIG. 12A, and contains a drive circuit  128  (switching circuit  121   c  and logic circuit  121   d  explained in FIG. 4) for driving these first phase nozzles. The first phase nozzles  124   a  contained in each head chip  121  comprise one time-division driven block  129 .  
         [0082]    The head chip  121  of FIG. 13 may also be comprised of a specified number of second phase or third phase nozzles  124   a  shown as shown in FIG. 12B or FIG. 12C, and a drive circuit  128  for driving these nozzles.  
         [0083]    More specifically, besides each block  129 , being comprised of the second phase or in other words 16 nozzles on one head chip  121  as shown for example in FIG. 13, each head chip  121  contains a drive circuit  128  for 16 nozzles for nozzles from phase No. 1 through 16 or in other words for two blocks  129 .  
         [0084]    In the drive circuit  128 , phase Nos. from 1 through 16 are assigned in sequence in the drive circuit  128 , the first phase is comprised of phase No. 1 through 8, and a second phase is comprised of phase No. 9 through 16. As shown in FIG. 15, the signal lines A 1  through A 8  are respectively connected to each phase of the drive circuit  128 , and each phase is connected to the control signal lines B 1  or B 2 . The nozzles  124   a  for each phase are sequentially driven as shown in FIG. 14.  
         [0085]    In this way, the nozzle  124   a  for each phase is sequentially driven and the power consumption can be reduced.  
         [0086]    In this case, each head chip  121  can be provided with the same, double or three times the number of nozzles per the number of phases as described above, and the nozzles for each block for one time-division driven phase, are driven by drive circuits  128  with identical structures on identical head chips  121  so that each head chip  121  including the drive circuit has an identical structure.  
         [0087]    A line head  120  can therefore be tiling structured, by arraying a plurality of head chips  121  of a single type, comprised of drive circuits  128  having identical circuit structures, so that the head chips  121  can be manufactured at low cost by being mass produced in large numbers, and the cost of the line head  120  and the ink-jet printer  10  is therefore reduced.  
         [0088]    A drawing showing the overall structure of the line head in the second embodiment of the ink-jet printer of this invention is shown in FIGS. 16A and 16B.  
         [0089]    The line head  120  comprised of head chips  121  shown in FIGS. 16A and 16B has nozzle regions that mutually overlap on both sides of each head chip  121 . This design is intended to prevent problems that typically occur in structures having no nozzle overlap as shown in FIGS. 12A and 12B, where irregularities in ink emission amounts between head chips and errors in the impact position are brought about by characteristics of the no overlap nozzle structure and positioning errors, and are causes of the so-called banding noise.  
         [0090]    In other words, each head chip  121  in FIG. 16A, has a number of nozzles  124   a  consisting of a number equal to an overlap portion added to the time-division drive first phase portion of nozzles, and contains drive circuits  128  for driving these nozzles.  
         [0091]    The nozzle  124   a  of the head chip  121 A and the nozzle  124   a  of the head chip  121 B on the other side are thus alternately used in sideways or vertical directions in the overlap region. In this way, the banding noise prone to occur between the two adjacent head chips  121 A and  121 B, is reduced and alleviated.  
         [0092]    The head chip  121 , as shown in FIG. 16B, may be comprised of a number of nozzles  124   a  consisting of a number equal to an overlap portion added to a specified number in the time-division drive second phase portion and, drive circuits  128  to drive these nozzles.  
         [0093]    More specifically, besides each block  129  as shown for example in FIG. 17, being comprised of a number of nozzles consisting of an overlap portion (3 pieces) of nozzles added to a first phase portion (6 pieces) of nozzles contained on one head chip  121  or in other words being comprised of nine nozzles, each head chip  121  is further comprised of nine drive circuits (not shown in the drawing) for driving the nine nozzles.  
         [0094]    Phase No. 1 through 6 are attached in sequence to each nozzle  124   a  as shown in FIG. 17, and in that case the overlapping nozzles are assigned with phase No. from 1 through 3 the same as the overlapped nozzles. Besides phase No. from 1 through 6 constituting the first phase, the respective signal lines A 1  through A 6  are connected to the corresponding drive circuits  128  for each phase, so that the nozzle  124   a  for each phase is sequentially driven based on the signals shown in FIG. 18 from the drive signal lines A 1  through A 6 .  
         [0095]    Therefore, the nozzles  124   a  that make up each phase are driven in sequence, and the power consumption can be reduced In this way, by each head chip  121  has a number of nozzles consisting of a number of overlap nozzles added to one or two times the phase number as described above, and each block nozzle comprising a time-division one phase portion, is driven by a drive circuit  128  contained on the same head chip  121 , so that each head chip  121  is comprised of identical drive circuits  128 .  
         [0096]    Therefore, a line head  120  can therefore be tiling structured, by arraying a plurality of head chips  121  of a single type, comprised of drive circuits  128  having identical circuit structures, so that the head chips  121  can be manufactured at low cost by being mass produced in large numbers, and the cost of the line head  120  and the ink-jet printer  10  is therefore reduced.  
         [0097]    In the above described embodiment, the head chips  121  are comprised of a specified number of nozzles for a time-division driven one phase, two-phase or three phase portion, such as 16 nozzles for example for a two-phase portion, or may be comprised a specified number of nozzles of a time-division drive first phase portion or second phase portion, for example nine nozzle consisting of three overlap portion nozzles added to six nozzles of a first phase portion. However, this invention is not limited to the above examples, and each head chip may comprise a number of nozzles consisting of an integer multiple of the time-division driven number of phases or an integer multiple of the time-division driven number of phases added to the overlap portion of nozzles, and a line head may be configured by arraying a plurality of head chips of a single type comprised of identical type drive circuits.  
         [0098]    Further, in the above embodiment, the drive circuit  128  on each head chip  121  was comprised of thermal elements as drive elements however this invention is not limited by this example and may for instance contain piezoelectric elements as drive elements.

Technology Category: b