Patent Publication Number: US-2007103497-A1

Title: Driving method of ink-jet printer and its driving apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This is a Continuation-in-Part application of U.S. Pat. No. 1,126,9407, filed Nov. 8, 2005, now abandoned, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a driving method of an ink jet printer and its driving apparatus.  
      2. Description of the Related Art  
      Where a printer head as shown in  FIG. 8B  is driven in three-time division fashion, a printing is made in a predetermined head drive frequency with a relative head/medium speed set to a predetermined speed. By doing so, a positional difference of nozzle groups corresponding to three divisions ceases to exist and, as shown in  FIG. 8A , a printing is made in one line at a predetermined pitch in a nozzle direction.  
      Generally, in a serial printer, a printing is made in one line with the use of a plurality of nozzles and, by doing so, the printer is driven in a fashion less prominent in “print drops” and less “banding” resulting from a head-caused print variation. Here, the “banding” means a nonuniform concentration caused by a white line emerging on a recording medium due to the non-jetting of an ink from some nozzle as well as by the misdirection caused by some nozzle. In this case, it is known that, in the prior art technique, a printing is made by alternately using one half number of nozzles for each column and, by doing so, a printing is made a plurality of numbers as shown in  FIG. 7A .  
      In  FIG. 7B , reference numeral  11  shows a printing head. The nozzles  12  are provided in a zigzag fashion on a nozzle surface of the printing head  11 . Those nozzles  12  are sequentially grouped in an A→B→C order from near the moving direction of the printing head  11 . An Xab pitch is provided between the group A and the group B and an Xbc pitch between the group B and the group C.  
      As shown in  FIG. 7A , a printing is made in an order of n−2, n−1, n, n+1, n+2 columns.  
      This printing is made in a sequential order of groups A, B, C for each column in a state to jet an ink from those nozzles belonging to the group. For the n−2 column, a printing is made at A 1  belonging to group A, with no ink jetted from B 2  due to no print data involved under group B, a printing is made at C 1  under group C. And no ink is jetted at A 2  due to no print data involved under group A and a printing is made at Bl under group B and no ink is jetted at C 2  due to no print data under group C.  
      For the n−1 column, a printing is made at B 11  under group B, at A 12  under group A and at C 12  under group C. In the n−1 column, a printing is made at B 11  under group B, at A 12  under group A and at C 12  under group C. In the n−1 column, no ink is jetted from the rest due to no print data involved.  
      In this case, a printing was done using the relative speed of the head and recording medium as a predetermined speed. Since no half number of nozzles are not used for each column, it may be said that no effective use can be expected for the head.  
      Where a printing is effected at a coarse pitch with the above-mentioned relative speed increased from the state of  FIG. 8A , a matched printing position is not obtained at the nozzle groups of each three divisions. As a result, as shown in  FIG. 9A , a straight printing line is not obtained in the nozzle direction, thus presenting a problem. It is to be noted that  FIG. 9B  shows a printing head.  
     BRIEF SUMMARY OF THE INVENTION  
      In one aspect of the present invention, there is provided a printing head driving method using a printer head configured to effect a three time division so as not to simultaneously print an adjacent channel and means for receiving print data corresponding to each time division and printing it, the printer head being so constructed that, with the respective time division groups given as A, B, C, the head and printing medium are moved at predetermined speeds and, with the sequential drive order given as A, B, C, a printing result emerges as one row in a nozzle direction at a predetermined pitch to a relative moving direction of the head and printing medium, the method comprising a step of effecting a driving in a sequential drive order including C, B, A with the relative driving speed of the head and printing medium set double its speed and a step of receiving print data corresponding to each division and making a printing so that a printing result in a relative moving direction emerges at a pitch double that predetermined pitch and a printing result of the group A, C nozzles and B nozzles emerges in a state displace by a predetermined pitch. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
      The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
       FIG. 1  is a block diagram showing an ink jet printer according to one embodiment of the present invention;  
       FIG. 2  is a block diagram showing a controller of the ink jet printer;  
       FIG. 3  is a block diagram showing a head drive circuit of the ink jet printer;  
       FIG. 4  is a view showing a memory map of the present embodiment;  
       FIG. 5A  is a timing chart for explaining an operation of the embodiment;  
       FIG. 5B  is a timing chart for explaining an operation of the embodiment;  
       FIG. 5C  is a timing chart for explaining an operation of the embodiment;  
       FIG. 5D  is a timing chart for explaining an operation of the embodiment;  
       FIG. 5E  is a timing chart for explaining an operation of the embodiment;  
       FIG. 6A  is a view showing a printing example printed by a driving method of an ink jet printer of the embodiment;  
       FIG. 6B  is a front view showing a printing head of the ink jet printer of the embodiment;  
       FIG. 7A  is a view showing a printing example printed by a driving method of a conventional ink jet printer;  
       FIG. 7B  is a front view showing a print head of this ink jet printer;  
       FIG. 8A  is a view showing a printing example printed by a driving method of a conventional ink jet printer;  
       FIG. 8B  is a front view showing a printing head of this ink jet printer;  
       FIG. 9A  is a view showing a printing example printed in a drive order of ABC at a speed set as fast as double its predetermined speed; and  
       FIG. 9B  is a front view showing a printing head of this ink jet printer. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      With reference to the drawing an explanation will be made below about one embodiment of the present invention.  
      In  FIG. 1 , reference numeral  21  shows a printing head allowing three time divisions to be achieved without any simultaneous printing on an adjacent channel. The printing head  21  is mounted on a carriage  22 . The control of the printing head  21  and carriage  22  is done by a controller  23 .  
      Under the control of the controller  23 , the carriage  22  is moved in right and left directions as indicated by an arrow a and a printing medium  24 , while being conveyed in a direction (arrow b) perpendicular to the operation direction of the carriage  22 , is printed so that an image is formed on it.  
      With reference to  FIG. 2  an explanation will be made below in more detail about a block diagram of the controller  23 . In  FIG. 2 , reference numeral  31  shows a host computer. To this host computer  31  is connected the controller  23 .  
      The controller  23  comprises a CPU  41 , a memory  42 , a FIFO memory  43  and a GA (gate array)  44 . From the FIFO memory  43  and GA  44 , a head control signal and print data are sent to a head driving circuit  45 . The head driving circuit  45  is provided in the controller  23 . A detailed arrangement of the head driving circuit  45  is shown in  FIG. 3 .  
      With reference to  FIGS. 5A  to  5 E, an explanation will be made below about a flow of the print data. The print data is such as to allow data corresponding to a few lines to be sent from the host computer  31  to a printer  32 . The thus sent print data is written into a memory  42  through the CPU  41  and GA  44 .  
      Before a printing is started, the print data written into the memory  42  is converted to a form shown in  FIG. 4  and stored into the FIFO memory  43 . Here, as shown in  FIG. 7 , nozzles are provided in a zigzag array on the printing head  21 . As shown in  FIG. 7 , the nozzles are divided into three groups (A, B, C) and driven in a divided way.  
      That is, (n+1)st line data is stored for the group A data, (n)th line data for the group B data, and (n−1)th line data for the group C data (See  FIG. 4 ).  
      It is to be noted that the print data, which is output from the FIFO memory  43 , as shown in  FIG. 5C  is stored in the shift register (S/R)  51  shown in  FIG. 3  by a shift clock shown in  FIG. 5B . When the data is output from the FIFO memory  43 , the next print data is converted and stored in the FIFO memory  43 . Then when a latch signal shown in  FIG. 5A  is input to a latch circuit  52 , the data of the shift register  51  is latched to the latch circuit  52 . After this, the data stored in the FIFO memory  43  is stored in the shift register  51  by a shift clock.  
      Then after the inputting of the latch signal, a first timing signal ( FIG. 5D ) is input to an output control circuit  53 . When the first timing signal is input to the output control circuit  53 , if the group C print data ( FIG. 5C ) stored in the latch circuit  52  is 1, a drive waveform generating circuit  54  outputs a drive waveform ( FIG. 5E ) to a corresponding group C nozzle. By doing so, an ink is jetted from the group C nozzle to effect a printing.  
      Then, a second timing signal is input to the output control circuit  53 . When the second timing signal ( FIG. 5D ) is input to the output control circuit  53 , if the print data is  1  based on the group B print data ( FIG. 5C ) stored in the latch circuit  52 , the drive waveform generating circuit  54  outputs a drive waveform ( FIG. 5E ) to a corresponding group B nozzle. By doing so, an ink is jetted from the group B nozzle to effect a printing.  
      Finally, a third timing signal is input to an output control circuit  53 . When the third timing signal ( FIG. 5D ) is input to the output control circuit  53 , if group A print data stored in the latch circuit  52  is 1, the drive waveform generating circuit  54  outputs a drive waveform ( FIG. 5E ) to a corresponding group A nozzle. By doing so, an ink is jetted from the group A nozzle to effect a printing.  
      In this way, the jetting of the ink from the nozzles of the groups A, B, C is completed. By repeating these operations, a printing is done.  
      For a printing example as shown in  FIGS. 6A and 8A , an ink is jetted in a sequential order of group A nozzle→group B nozzle→group C nozzle. At this time, it is given that the relative speed of the printing medium  24  and printing head  21  is  16  ips (406 mm/s), the image resolution of the printing head  21  in a moving direction is 300 dpi and the dot-to-dot drive frequency is 4800 Hz.  
      From such a state, with the relative speed of the printing medium  24  and printing head  21  given as a double speed (32 ips), an ink is jet-driven in the sequential order of group C nozzle→group B nozzle→group A nozzle.  
      And with the group A nozzle-group B nozzle and group B nozzle-group C nozzle intervals given as 1/900 inch (⅓ of 1/300 inch) image resolution, a printer is driven at 4800×14400 Hz at the respective group nozzle intervals and, by doing so, respective dots are deposited on a 300 dpi grid array.  
      That is, under the control of the following procedure with the use of the printing head  21  it is possible to, while moving the printing head  21  at a speed double its relative speed normally using all the nozzles, construct one line with a plurality of nozzles and to realize an accurate printing with a desired printing image resolution.  
      It is given that the printer is driven at a reverse order of the groups C→B→A instead of the order of A→B→C.  
      By driving the printer in this way, the printing interval between respective nozzles of the groups A, B, C becomes 150 dpi and a printing is made with the groups A and B and the groups C and B displaced 300 dpi in a moving direction.  
      In this case, for the groups A, B, C, a printing needs be effected at different columns and their corresponding print data may be transmitted to the head drive circuit  45 .  
      An explanation will now be made in more detail while paying attention to a restricted area  51 . A printing is effected in a sequence of a dot C 10  at the group C nozzle, a dot B 30  at the group B nozzle and a dot A 40  at the group A nozzle.  
      A printing is made with a group B nozzle dot B 20  at an n−1 column, and a group A nozzle dot A 10  and group C nozzle dot C 10  at the n−1 column.  
      By the above-mentioned control, it is possible to make a printing as shown in  FIG. 6A . That is, in the case of  FIG. 6A , it is possible to make a printing with a desired image resolution by twice printing operations. Here, the second printing is made by shifting the printing head  21  by an interval of 3Y×m(m is an integer not less than 0) (dpi) toward a direction perpendicular to a moving direction of the printing head  21 . Printing is performed with the nozzles shifted by a pitch x in the conveying direction with respect to the first printing.  
      That is, one line can be comprised of different nozzles.  
      In this way, a 100% nozzle use efficiency can be achieved on the head and there is no unavailable area when compared with that of  FIG. 7A .  
      Further, it is possible to set the moving speed of the head double its speed and to effect an accurate printing on a grid array of a desired image resolution and to construct one line with a plurality of nozzles. It is thus possible to obtain a better printing result compared to that of  FIG. 7A .  
      Although, in the above-mentioned embodiment, an explanation has been made about a shared mode system, the present invention is not restricted to this system. If, for example, nozzles are arranged in a displaced fashion as shown in  FIG. 7B  and respective nozzle groups are driven in a time division fashion, the present invention can be applied to it.  
      Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.