Abstract:
The efficiency and speed in ink jet printing can be improved by adding a storage register between the shift register and the jet drive logic. By adding the storage register, jet print data that is serially loaded into the shift register can be parallel transferred to the storage register, where it is used by the jet drive logic to fire ink jets. While the jets are being fired new data is loaded and transferred to the storage registers to be used by the jet drive logic. This improves the system efficiency by eliminating the need for two extra pulses that are usually needed to load the first block of data and fire the last block of data.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention is directed to ink jet printers. 
     2. Description of Related Art 
     In operating ink jet printers and other devices that use ink jet technology, print heads that contain ink fire ink onto paper or other printable media through jets located in the print heads. Firing the individual jets of the ink jet print head is determined by the firing pulse of the system that operates the ink jet print head. 
     Data is transferred to the print heads by a control circuit. The control circuit controls the logic that determines how many jets to fire at a time and when to fire the jets. The data is held in the print heads until a fire pulse activates the print heads and the jets are fired. Typically four or eight jets are fired at a time. Each set of jets are fired sequentially until all the jets in the print head have been fired for the current position of the print head. 
     In operating an ink jet printer, smart logic ink jet print heads typically use a serial shift system to clock data into the print head. This information is decoded and used to determine which jets to fire. The first set of data is shifted into a register and then fired by an enable pulse. At the same time this first set is being fired, a second set of data is loaded into the register for the next set of jets to be fired. Once the first set of jets are fired, the second set can be fired using the second set of data loaded into the register, while a third set of data is loaded. This is continued until all the jets in the head have been fired for the current position of the print head. 
     SUMMARY OF THE INVENTION 
     However, in most ink jet printing devices, two extra pulses are needed to operate the jets. The first pulse is used to load the first set of data into the register. The second pulse is used to fire the last set of data. 
     This invention provides ink jet printing systems and methods that improve the efficiency and increase the speed of ink jet printing. 
     This invention separately provides double banking and/or ping-ponging ink jet printing systems and methods that eliminate the two extra pulses needed to operate the jets. 
     In various exemplary embodiments of the systems and methods according to this invention, double banking is used by adding a buffer between the shift register and the firing logic. The buffer or storage register eliminates the need for the two extra pulses. 
     In other exemplary embodiments of the systems and methods according to this invention, alternating, or “ping-ponging”, between two buffers or registers is used to eliminate the need for the two extra pulses. Two different buffers or registers are used to store the data from the shift register. The two registers are alternatively selected. When one buffer or register is being fired using a current set of data, the other is loaded with the next set of data. 
     These and other features and advantages of this invention are described in or are apparent from the following detailed description of the apparatus/systems and methods according to this invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various exemplary embodiments of this invention will be described in detail, with reference to the following figures, wherein: 
     FIG. 1 is a cross sectional view of an ink jet print head; 
     FIG. 2 is a schematic showing the basic principle of an ink jet print head; 
     FIG. 3 is a conventional control system for print heads; 
     FIG. 4 is the timing diagram for the conventional control system shown in FIG. 3; 
     FIG. 5 is one exemplary embodiment of a control system for print heads using the double banking technique according to this invention; 
     FIG. 6 is one exemplary embodiment of a control system for print heads using the ping-ponging technique according to this invention; and 
     FIG. 7 is the timing diagram for the control system shown in FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 shows a cross sectional view of an ink jet print head  100 . The ink jet print head includes a piezoelectric element  120  and a diaphragm  110  mounted on a substrate  130 . The diaphragm  110  is located above the ink chamber  160  and nozzle  150 . A electrode  170  is formed on top of the piezoelectric element  120 . A support  140  is composed of a rigid material such as metal, a high rigidity resin or the like. 
     When voltage is applied to the electrodes  170 , the piezoelectric element  120  changes shape and pushes on the diaphragm  110 . The diaphragm  110  then exerts pressure on the ink, forcing an ink droplet out nozzle  150 . 
     FIG. 2 shows more clearly the general principle of how a print head functions. The print head  200  includes a piezoelectric element  220  attached on a diaphragm  210 , and an ink fountain  270  supplies ink  230  to a pressure chamber  250  via an ink chamber  260 . When a signal source  280  applies a voltage to the piezoelectric element  220 , the corresponding part of the diaphragm  210  is stressed by the piezoelectric element pushing down on it. The diaphragm  210  correspondingly exerts pressure on the pressure chamber  250 . Thus, the ink  230  is expelled, as an ink drop  231 , from the corresponding nozzle  240  onto the paper  300 . After the ink has been expelled, the diaphragm  210  returns to its original state. A negative pressure is generated in the pressure chamber  250  and the same amount of ink  230  that was expelled through nozzle  240  is replaced by this negative pressure. The negative pressure draws the ink  230  from the ink well  270  through the ink chamber  260  and into the ink pressure chamber  250 . The print head is then again ready to be fired. 
     While the above-outlined description of FIGS. 1 and 2 is directed to piezoelectric ink jet printers, any other known or later developed type of ink jet printer, including thermal ink jet printers and acoustic ink jet printers, that use the data signals and firing pulses described below can incorporate either of the fire control systems according to this invention. Because the structure and general operation of such other ink jet printers are well known to those of ordinary skill in the art, or are easily understandable from the description of the conventional piezoelectric ink jet printer shown in FIGS. 1 and 2, a detailed description of these other types of ink jet printers is omitted. 
     FIGS. 3 and 4 show a conventional ink jet fire control system  300  and the timing diagram  350  for this conventional ink jet fire control system  300 , respectively. The data is serially loaded into a shift register  310  through a data connection  314 . The data is then loaded in parallel from the shift register  310  over the connections  312  to the jet drive logic  320 . A data signal  360  on the signal line  314  is used to load data into the shift register  310 . A first signal  370  on the fire line  322  is used to fire the print head jets in accordance with the data contained in the shift register  310 . 
     As shown in FIG. 4, during a first cycle  361  of the data signal  360 , a first set of the print data contained in a first cycle  361  of the data signal line  361  is loaded into the shift register  310 . At this time, in a first cycle  371  of the fire signal  370 , the fire signal  370  is not enabled. During a second cycle  362  of the data signal  360 , the second set of data  362  is loaded into shift register  310 . 
     At the same time, in a second cycle  372  of the fire signal  370 , the fire signal is enabled. As a result, the jet drive logic  320  fires the print head jets in accordance with the first set of data contained in the first cycle  361  of the data signal  360  and stored in the shift register  310 . During the next to last cycle  364  of the data signal  360 , the last set of data  364  is loaded into shift register  310 . The fire signal  373  of the fire signal  370  is enabled, while data  364  is loaded into shift register  310  and the print head jets are fired by the jet drive logic  320  using the previously stored set of data. This continues in the print section, until a last cycle. 
     During the last cycle of the data signal  360 , no additional data is received at the shift register  310 , therefore the last cycle  365  of the data signal  360  does not contain any data. At this time, however, during a last cycle  374  of the fire signal  370 , the fire signal  370  is enabled to fire the jets using the last set of data received during the next to last cycle  364  of the data signal. Because shift register  310  already contains data from the previous cycle, the jet drive logic must use the data  364  to fire the jets to clear shift register  310  so that new data of the next print section can be received by shift register  310 . That is, during this last cycle  374  of the fire signal  370 , the print head jets are fired in accordance with the set of data  364  loaded into shift register  310  during the next to last cycle  364  using the fire pulse  374 . After the last cycle of the data and fire signal  360  and  370  is complete, the next print section continues in the same manner as described above, with the first cycles of the data signal  360  and the fire signal  370 . 
     FIGS. 5 shows one exemplary embodiment of an ink jet fire control system  400  according to this invention for transferring print data to be used in the firing of ink jets by the jet drive logic  420 . In particular, FIG. 5 shows a double banking ink jet fire control system  400 . The double banking system  400  serially loads print data, of a print section, into shift register  410  received over a connection  414 . Once the data is loaded into the shift register  410 , the data is then transferred in parallel from the shift register  410  to a storage register  430  over the connections  412 . The data is then transferred to the jet fire logic  420  over the connections  432 . The data is used by the jet fire logic  420  to fire the print head jets. At the same time that the print head jets are fired by the jet drive logic  420 , using the print data stored in the storage register  430 , a new set of print data is loaded into the shift register  410 . This process is continued until all print sections are completed. 
     FIG. 6 shows an exemplary embodiment of a ping-ponging ink jet fire control system  500  according to this invention. The ping-ponging ink jet fire control  500  shown in FIG. 6 uses two shift registers  510  and  520  to store the print data. The transfer logic  530  alternately selects the data from one of the two shift registers  510  and  520  and transfers the data through the transfer logic  530  to the jet drive logic  540 . The data is serially loaded into the shift registers  510  and  520  over the connections  514 . The shift registers  510  and  520  are alternately loaded with the print data. In other words, if the shift register  510  is loaded with the first set of data, then the shift register  520  is loaded with the second set of data. Therefore, the shift registers  510  and  520  alternate loading each set of data. 
     After the print data is loaded into either the shift register  510  or the shift register  520 , the print data in that shift register  510  or  520  is then transferred through the transfer logic  530 , over the connections  512  or  522  and over the connections  532 , to the jet drive logic  540 . A select signal on a signal line  536  controls the alternate loading of the data into the shift registers  510  and  520 . The select signal is also provided to the transfer logic  530 , through the signal line  536 . The transfer logic  530  is controlled by the select signal to select the print data contained in either the shift register  510  or the shift register  520  to send to the jet drive logic  540 . The transfer logic  530  can be any known or later developed logic circuit, such as a multiplexer, that can alternately connect the two shift registers  510  and  520  to the jet drive logic  540  under control of a select signal. 
     As the print data is transferred from one of the shift registers  510  or  520  through the transfer logic  530  to the jet drive logic  540 , new print data is loaded into the other shift register  510  or  520 . For example, a first set of data is loaded into shift register  510 . The first set of data is then transferred through the transfer logic  530  to the jet drive  540 . The first set of print data is used by the jet drive logic  540  to fire the print head jets. At the same time that this first set of data is used by the jet drive logic  540 , a second set of data is loaded into the shift register  520 . The second set of print data is then provided to jet drive logic  540  through the transfer logic  530 , where it is used by the jet drive logic  540 , while a third set of print data is loaded into the first shift register  510 . This process is repeated until all print sections have been printed. 
     Because the shift registers  510  and  520  transfer their print data directly to the jet drive logic  540 , the last data that is used to fire the print head jets is accomplished with one of the shift registers  510  and  520  already cleared and ready to store the print data on the first cycle of the next print section. Therefore, as with the ink jet fire control system  400  shown in FIG. 5, the ink jet fire control system  500  does not require an extra pulse at the beginning and end of each print section. This increases the speed and efficiency of the entire system. 
     FIG. 7 is a timing diagram  450  for the ink jet fire control system  400  shown in FIG.  5 . During a load cycle  451 , the data contained in a first data cycle  461  of the data signal  460  is loaded into the shift register  410 . At this time, the transfer signal  480  is not enabled. Once all the data of the first data cycle  461  is loaded into the shift register  410 , on an enable pulse contained on a first cycle  481  of the transfer signal  480  is then provided to the storage register  430 . As a result, the data of the first data cycle  461  is transferred from the shift register  420  to the storage register  430 . At this time, the first cycle  471  of the fire signal  470  does not enable the jet fire logic  420 . 
     During the first cycle  452  of the first section of the timing diagram  450 , the fire pulse in the first cycle  472  of the fire signal  470  is enabled. This causes the jet drive logic  420  to fire the first set of ink jets based on the print data in the first cycle  461  of the data signal  460  that is stored in the storage register  430 . At the same time as the fire pulse  472  is enabled, data contained in the second data cycle  462  of the data signal  460  is loaded into the shift register  410 . The transfer pulse in a second cycle  482  of the transfer signal  480  is then enabled to transfer the print data contained in the second cycle  462  to the storage register  430 . 
     During the last cycle  453  of the first section of the timing diagram  450 , the fire pulse for the last cycle  474  of the fire signal  470  is enabled and the print data of a next-to-last data cycle of the data signal  460  is used to fire the print head jets. The print data contained in the last cycle  464  of the data signal  460  received during the last cycle  453  of the first section of the timing diagram  450  is loaded into the shift register  410 . The transfer pulse  481  in the last cycle  484  of the transfer signal  480  received during the last cycle  453  of the timing diagram  450  is enabled. In response, the print data contained in the last cycle  464  of the data signal  460  is transferred to the storage register  430 . Once the print data contained in the last cycle  464  of the data signal  460  of the last cycle  453  of the first section of the timing diagram  450  is transferred to the storage register  430 , the shift register  410  is cleared and the print data contained in the first cycle  461  of the data signal  460  on the first cycle  452  of the next section of the timing diagram  450  can be loaded into the shift register  410 . Therefore, the transition from one print section to another is continuous. This process is continued in subsequent cycles and print sections. The last cycle in the print section therefore does not require an extra beginning or end pulse for the new print section. 
     The systems of FIG. 5 and 6 only require a full extra load cycle at the beginning or end of a print section. A print section can be a line, a portion of a page, a whole page or whatever is specified. Since a single line is greater than the number of jets in a print head, the efficiency is increased. To fire an entire print section, the total number of cycles: 
     
       
         Total number of cycles=(total number of jets)/(total number of jets to be fired at one time) 
       
     
     In the conventional systems that include the two extra pulses to fire an entire set of the ink jets for each position of the print head, the total number of cycles is: 
     
       
         Total number of cycles=2+((total number of jets)/(total number of jets to be fired at one time)) 
       
     
     Therefore, if there are 128 jets in the print head and 8 jets are fired at one time, the total number of cycles per print head location for the conventional system is equal to 18. For just a single location of the print head, the total number of cycles such a print head, when using the systems and methods, of this invention, is equal to 16. This is an improvement of 12.5%. The exemplary embodiments of the invention decrease the number of cycles, while increasing the overall efficiency of the ink jet control system. The added chip area is also not significant, since the registers require low power and do not take up a lot of chip space. Thus, the overall performance is increased, while decreasing the size and power consumption of the chip. 
     While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention may be made without departing from the spirit and scope of the invention.