Abstract:
An inkjet recording apparatus includes a first unit, a second unit and a third unit. Each of the first to third units includes monochrome section and a different primary color section. The first to third units are integrated such that the monochrome sections are placed side-by-side and the primary color sections are placed side-by-side in a direction orthogonal to the line.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus employing an inkjet recording method, and more particularly to a recording apparatus for use in a printer for ejecting droplets from a nozzle to a recording medium. 
     2. Description of the Related Art 
     There has recently been a growing interest in non-impact printers, because noise while recording is extremely small to such a degree that it can be neglected. Particularly, inkjet printers are extremely effective in that they are structurally simple and that they can perform high-speed recording directly onto ordinary medium. 
     Inkjet printers fall into three broad categories: continuous type, on-demand (or impulse) type and electrostatic type. Among these types, the on-demand inkjet printer is provided with a lot of piezoelectric actuators which are selectively driven to eject ink droplets. Since a piezoelectric actuator ejects ink droplets on demand, it is possible to avoid needless ink consumption. Further, since the on-demand inkjet printer is structurally simple, it is expected to be widely used. 
     Recently, a color printer has been commercially available and the quality of color print is becoming increasingly higher. For a color inkjet head for use in such a color printer, it is very important to eliminate bleeding due to a combination of black and color nozzles. 
     In Japanese Patent Unexamined Publication No. 7-205454, an inkjet printer has been disclosed in which, to eliminate the bleeding when printing, an array of black nozzles is provided at a distance from other arrays of color nozzles. More specifically, the black nozzle array is placed such that it performs ink ejection in a scan line preceding that of the color nozzle arrays. 
     Since the black nozzle array and the color nozzle arrays are separately provided within a single head, however, it is difficult to miniaturize the inkjet head and further accurate positioning and high integration techniques are needed. 
     As another example of prior art, there has been disclosed an inkjet head in Japanese Patent Unexamined Publication No. 7-256874. This conventional inkjet head is provided with a plurality of arrays of nozzles wherein the upper half of a specific array is used for black ink and the respective lower halves of other arrays are used for different color inks; Yellow (Y), Magenta (M) and Cyan (Cy). 
     However, the lower half of the specific array and the respective upper halves of the other arrays are not used at all. Therefore, unused nozzles are easily clogged, resulting in deteriorated quality of printing. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide an inkjet recording apparatus which can achieve enhanced miniaturization and high reliability of printing. 
     According to the present invention, the apparatus includes first to third units which are integrated. 
     The first unit has a first monochrome section comprising a plurality of first monochrome nozzles and a first primary color section comprising a plurality of first primary color nozzles, wherein the first monochrome nozzles and the first primary color nozzles are arranged in a line. 
     The second unit has a second monochrome section comprising a plurality of second monochrome nozzles and a second primary color section comprising a plurality of second primary color nozzles, wherein the second monochrome nozzles and the second primary color nozzles are arranged in a line. 
     The third unit has a third monochrome section comprising a plurality of third monochrome nozzles and a third primary color section comprising a plurality of third primary color nozzles, wherein the third monochrome nozzles and the third primary color nozzles are arranged in a line. 
     The first to third units are integrated such that the first to third monochrome sections are placed side-by-side and the first to third primary color sections are placed side-by-side in a direction orthogonal to the line. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and advantages will become apparent from the following detailed description when read in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a front view of an inkjet head according to an embodiment of the present invention; 
     FIG. 2A is a perspective and partial cutaway view of a head chip of the inkjet head as shown in FIG. 1; 
     FIG. 2B is a cross-sectional view taken on line A—A of FIG. 2A; and 
     FIG. 3 is a block diagram showing a circuit configuration of an inkjet printer employing the embodiment of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, an inkjet head according to an embodiment of the present invention is comprised of three head chips  101 - 103  each having a predetermined number (N+M) of nozzles which are arranged in a line. More specifically, the first head chip  101  has N+M nozzles arranged in a line C 1  which consist of N black nozzles NB 11 -NB 1N  spaced uniformly and M yellow (Y) nozzles NC 11 -NC 1M  spaced uniformly. The second head chip  102  has N+M nozzles arranged in a line C 2 , which consist of N black nozzles NB 21 -NB 2N  spaced uniformly and M magenta (M) nozzles NC 21 -NC 2M  spaced uniformly. The third head chip  103  has N+M nozzles arranged in a line C 3 , which consist of N black nozzles NB 31 -NB 3N  spaced uniformly and M cyan (Cy) nozzles NC 31 -NC 3M  spaced uniformly. The lines C 1 -C 3  are spaced uniformly and parallel to each other. 
     Further, the color nozzles NC 11 -NC 31  over three head chips  101 - 103  are arranged in a line L C1  orthogonal to the lines C 1 -C 3 . Similarly, color nozzles NC 12 -NC 32 , NC 13 -NC 33 , . . . , and NC 1M -NC 3M  are arranged in lines L C2 -L CM , respectively. The lines L C1 -L CM  are spaced uniformly and parallel to each other. 
     Furthermore, the black nozzles NB 11 -NB 31  over three head chips  101 - 103  are arranged in a line L B1  crossing each of the lines C 1 -C 3  at an angle. Similarly, black nozzles NB 12 -NB 32 , NB 13 -NB 33 , . . . , and NB 1N -NB 3N  are arranged in lines L B2 -L BN , respectively. The lines L B1 -L BN  are spaced uniformly and parallel to each other. The angle of tilt of lines L B1 -L BN  is determined such that a combination of black nozzles of three head chips  101 - 103  provides three times as high as the black resolution of each head chip. Therefore, in the case of monochrome printing, only one scan of the inkjet head in the direction orthogonal to the lines C 1 -C 3  causes the monochrome image to be provided with the predetermined resolution. 
     Referring to FIGS. 2A and 2B, there is shown an example of a single head chip of the inkjet head. A substrate  201  is provided with black and color ink chambers  202  and black and color ink-flowing grooves  203 . In this embodiment, the ink chambers  202  consist of black ink chamber and color ink chamber (yellow, magenta or cyan) and the black and color ink-flowing grooves  203  extend from the corresponding ink chamber to the front end of the substrate  201  on the substrate  201 . Therefore, ink flows through the corresponding ink-flowing grooves  203 . A nozzle plate  204  is placed at the front end of the substrate  201  and has N+M nozzles  205  corresponding to the ink-flowing grooves  203 , respectively. 
     The surface of the substrate  201  having the grooves  203  formed thereon is covered with a seal plate  206  on which N+M piezoelectric actuators  207  are placed corresponding to the ink-flowing grooves  203 . The piezoelectric actuators  207  are fixed to a fixing plate  208 . In such a structure, when a selected piezoelectric actuator  207  is driven, the corresponding ink-flowing groove is compressed to push the ink to the corresponding nozzle from which droplets are jetted. 
     The inkjet head as shown in FIG. 1 is formed with a combination of three head chips  101 - 103  each having the structure as shown in FIGS. 2A and 2B. Another type of head chip may be employed which has the ink-flowing grooves formed within an piezoelectric device. 
     Referring to FIG. 3, an inkjet printer is provided with the inkjet head including the head chips  101 - 103 . The head chip  101  has piezoelectric actuators  301  corresponding to the nozzles, respectively. As described above, the nozzles of the head chip  101  consist of N black nozzles NB 11 -NB 1N  and M yellow (Y) nozzles NC 11 -NC 1M . Similarly, the head chip  102  has piezoelectric actuators  302  corresponding to the black and magenta nozzles, respectively, and the head chip  103  has piezoelectric actuators  303  corresponding to the black and cyan nozzles, respectively. The piezoelectric actuators  301  are driven by a driver  304 , and similarly, other piezoelectric actuators  302  and  303  are driven by drivers  305  and  304 , respectively. 
     When receiving control data and print data from a host computer (not shown), a microprocessor  307  analyzes the data to produce nozzle selection data. The selection data for black nozzle, S BLK1 -S BLK3 , are output to the drivers  304 - 306 , respectively. The selection data for Y, M and Cy nozzles, S Y , S M , and S Cy , are output to the drivers  304 - 306 , respectively. 
     In the case of monochrome printing, the microprocessor  307  uses the black nozzles of all head chips by providing black nozzle selection data S BLK1 -S BLK3  to the driver  304 - 306 , respectively. 
     In the case of color printing, the microprocessor  307  uses the black nozzles of a selected head chip and selected color nozzles by providing black nozzle selection data and color nozzle selection data to the driver  304 - 306 , respectively.