Abstract:
An object of this invention is to provide ink viscosity information of an inkjet printing apparatus at low cost in small space. To achieve this object, the inkjet printing apparatus of this invention serves as an inkjet printing apparatus which performs image printing by using a printhead with a plurality of nozzles from which ink is discharged. This inkjet printing apparatus includes a switching unit which switches to a test print mode for providing the ink viscosity information. The inkjet printing apparatus also includes an image printing unit which prints a predetermined image in response to a plurality of driving pulses with different frequencies to obtain a test print pattern ( 600 ), when the switching unit switches to the test print pattern.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an inkjet printing apparatus and an information processing method for the inkjet printing apparatus.  
       BACKGROUND OF THE INVENTION  
       [0002]     A so-called “inkjet printing apparatus” has been popular, in which heat energy corresponding to a driving pulse is applied to ink to generate bubbles by film boiling, and ink is discharged from printheads onto a print medium such as paper by generated bubbles to print an image.  
         [0003]     In this inkjet printing apparatus, in order to maintain high-quality image printing, it is important for a user to optimally manage ink viscosity. Hence, in order to optimally manage ink viscosity, the inkjet printing apparatus has a function of monitoring a change in ink viscosity, and when ink viscosity falls outside a predetermined allowance, notifying the user of a message indicating this. Since the inkjet printing apparatus has such function, the user can take an appropriate action such as replacing an ink cartridge of a predetermined color, on the basis of this notification (as described above, output information required to take the appropriate action is generally referred to as “ink viscosity information”).  
         [0004]     Most of conventional inkjet printing apparatuses monitor the change in ink viscosity by measuring the electrical conductivity of ink, the pressure in an ink channel, and the like (e.g., see Japanese Patent Laid-Open No. 7-178924).  
         [0005]     However, the method of monitoring the change in ink viscosity by measuring the electrical conductivity and pressure poses the burden of cost, and increases an apparatus size, thus posing a problem. Hence, a demand has arisen for providing ink viscosity information required to take an appropriate action for ink at low cost without an increase in the apparatus size.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention has been made in consideration of the above problems, and has as its object to provide ink viscosity information of an inkjet printing apparatus at low cost in small space.  
         [0007]     In order to achieve the above object, an inkjet printing apparatus according to the present invention comprises the following arrangement. That is,  
         [0008]     an inkjet printing apparatus which prints an image using a printhead having a plurality of nozzles from which ink is discharged, comprising:  
         [0009]     a switching unit configured to switch to a test print mode for providing information about a viscosity of the ink; and  
         [0010]     an image printing unit configured to print predetermined images in response to a plurality of driving pulses with different frequencies when the switching unit switches to the test print mode.  
         [0011]     According to the present invention, ink viscosity information of an inkjet printing apparatus can be provided at low cost in small space.  
         [0012]     Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
         [0014]      FIG. 1  is a view showing the internal arrangement of an inkjet printing apparatus according to an embodiment of the present invention;  
         [0015]      FIG. 2  is a view showing the block arrangement of the inkjet printing apparatus according to the embodiment of the present invention;  
         [0016]      FIG. 3A  is a flowchart showing the processing flow of ink supply operation in the inkjet printing apparatus;  
         [0017]      FIG. 3B  is a flowchart showing the processing flow of ink recovery operation in the inkjet printing apparatus;  
         [0018]      FIG. 4  is a diagram showing an ink flow in the inkjet printing apparatus;  
         [0019]      FIG. 5  is a flowchart of test print mode operation in the inkjet printing apparatus according to the embodiment of the present invention;  
         [0020]      FIG. 6  is a view showing one example of a test print pattern for viscosity check; and  
         [0021]      FIG. 7  is a view showing one example when the test print pattern for viscosity check is not completely printed, and a discharge error occurs. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.  
       First Embodiment  
       [0000]     &lt;Device Arrangement of Inkjet Printing Apparatus&gt; 
         [0023]      FIG. 1  is a view showing the device arrangement of an inkjet printing apparatus ( 100 ) according to an embodiment of the present invention. In  FIG. 1 , reference numeral  101  denotes a rolled label paper sheet (print medium) on which a plurality of labels are temporarily stuck. The label paper sheet is conveyed in a “paper sheet conveyance direction” indicated by an arrow in  FIG. 1 , at a constant speed using a conveyance belt  102  driven by a conveyance motor  103 .  
         [0024]     Reference numerals  104 K,  104 C,  104 M, and  104 Y denote printheads. When a leading edge sensor  105  senses the leading edge of each label on the label paper sheet  101 , image printing is performed on each label at a predetermined printing timing by using the printheads ( 104 K,  104 C,  104 M, and  104 Y), with reference to the sensed label position.  
         [0025]     Color image printing is performed by using the printheads, e.g., printheads  104 K (black ink printhead),  104 C (cyan ink printhead),  104 M (magenta ink printhead), and  104 Y (yellow ink printhead) corresponding to four color inks. Note that in the first embodiment, each printhead ( 104 K,  104 C,  104 M, or  104 Y) serves as a line head having a printing width corresponding to the maximum width of the label to be used.  
         [0026]     In the lower portion of the inkjet printing apparatus  100 , ink cartridges  106 K,  106 C,  106 M, and  106 Y, subtanks  107 K,  107 C,  107 M, and  107 Y, and waste ink tanks  108 K,  108 C,  108 M, and  108 Y are arranged in correspondence with the respective printheads  104 K,  104 C,  104 M, and  104 Y.  
         [0027]     Also, in the lower portions of the printheads  104 K,  104 C,  104 M, and  104 Y, capping mechanisms  109 K,  109 C,  109 M, and  109 Y are respectively arranged. Note that six capping mechanisms are shown in  FIG. 1 , which include preliminary mechanisms for additional ink, e.g., pale cyan, pale magenta, or special color ink.  
         [0028]     The ink cartridges  106 K,  106 C,  106 M, and  106 Y, subtanks  107 K,  107 C,  107 M, and  107 Y, printheads  104 K,  104 C,  104 M, and  104 Y, waste ink tanks  108 K,  108 C,  108 M, and  108 Y, and capping mechanisms  109 K,  109 C,  109 M, and  109 Y are connected via ink tubes each of which is separated for each ink color (to be described later in detail).  
         [0000]     &lt;Hardware Arrangement of Inkjet Printing Apparatus&gt; 
         [0029]     The hardware arrangement of the inkjet printing apparatus  100  will be described next with reference to  FIG. 2 . Note that the same reference numerals as in  FIG. 1  denote the same parts in  FIG. 2 .  
         [0030]     Reference numeral  220  denotes a host computer. Print data transmitted from the host computer  220  is received by an interface controller  202  of the inkjet printing apparatus  100 .  
         [0031]     The interface controller  202  also receives and analyzes various commands including data (e.g., the number, type, and size of the label) of the label paper sheet  101  serving as the print medium on which an image is to be printed, and an identification result obtained based on a test print pattern (ink viscosity information) read by an image reading apparatus  230  (to be described later in detail).  
         [0032]     Reference numeral  201  denotes a CPU (Central Processing Unit), which controls the overall operations such as command analysis, print data reception, image printing operation, and print medium handling in the inkjet printing apparatus  100 .  
         [0033]     The print data received via the interface controller  202  is analyzed by the CPU  201 , and then bitmapped to an image memory  204  as image data for each color component.  
         [0034]     As operation processing prior to image printing, the CPU  201  drives both a capping motor (not shown) and head motor (not shown) via an input/output port (I/O)  210  and motor driving unit  211 , and moves each of the printheads  104 K,  104 C,  104 M, and  104 Y from a capping position (standby position) to a print position (position of each printhead in image printing).  
         [0035]     The CPU  201  substantially simultaneously drives a paper feed motor (not shown) and the conveyance motor  103  for feeding the label paper sheet  101  serving as the print medium, and continuously conveys the label paper sheet  101 .  
         [0036]     When the leading edge sensor  105  detects the leading edge of the label in order to determine a timing at which printing is performed on the label paper sheet  101  conveyed at a constant speed, the detected signal is input to the CPU  201  via an I/O  208 .  
         [0037]     In synchronism with conveyance of the label paper sheet  101  by the conveyance motor  103 , the CPU  201  sequentially reads out image data of corresponding colors from the image memory  204 , and transfers the readout image data to the respective printheads  104 K,  104 C,  104 M, and  104 Y via a printhead control circuit  209  to perform color printing.  
         [0038]     The CPU  201  operates based on various control programs stored in a program ROM  203  to control the overall inkjet printing apparatus  100 .  
         [0039]     Such control programs include, e.g., a control program corresponding to the procedure shown in the flowchart ( FIGS. 3A and 3B ) to be described later, and a control program for generating the test print pattern in a test print mode to be describe later (these control programs use a work RAM  205  as a working memory in execution).  
         [0040]     Note that  FIG. 6  is a view showing one example of a test print pattern  600  generated by executing the control programs which are stored in the program ROM  203  to generate the test print pattern. As shown in  FIG. 6 , in accordance with the control programs, each of the printheads ( 104 K,  104 C,  104 M, and  104 Y) is driven in response to a driving pulse with a frequency of 2 kHz (see reference numeral  601 ) to form each image  602 Y- 1 ,  602 M- 1 ,  602 C- 1 , or  602 Bk- 1  with a predetermined shape. Each of the printheads ( 104 K,  104 C,  104 M, and  104 Y) is also driven in response to a driving pulse with a frequency of 3 kHz to form each image  602 Y- 2 ,  602 M- 2 ,  602 C- 2 , or  602 Bk- 2  with a predetermined shape. After that, the frequency of the driving pulse changes by 1 kHz to form images with predetermined shapes at each frequency by using each printhead. With this operation, in accordance with the control programs for generating the test print pattern, an image print result can be obtained at each frequency using the printheads by printing the images with predetermined shapes in response to the plurality of driving pulses with different frequencies.  
         [0041]     Referring to  FIG. 2 , an EEPROM  206  serves as a rewritable nonvolatile memory for storing the time of a previous head recovery operation (to be described later in detail), storing a correction valve and the like for finely adjusting (registering) the widths of the plurality of printheads and the print position in the paper sheet conveyance direction, or storing a parameter unique to the inkjet printing apparatus  100 .  
         [0042]     Note that in ink supply operation or recovery operation of the printhead  104 K,  104 C,  104 M, or  104 Y, the CPU  201  receives a detection result from an ink sensor  216  via an A/D converter  207 , and drives and controls a pressure pump motor  212  and subpump motor  213  (to be described later) via the input/output port (I/O)  210  and the motor driving unit  211 . The CPU  201  also processes, via an input/output port (I/O)  214 , various pieces of information input from an operation panel  215 . The various pieces of information processed by the CPU  201  are displayed on the operation panel  215  via the I/O  214 .  
         [0000]     &lt;Ink Flow in Inkjet Printing Apparatus&gt; 
         [0043]     A main ink flow in the inkjet printing apparatus  100  will be described next. More specifically, (1) an ink flow in supplying ink from the ink cartridge to the subtank when a new ink cartridge is mounted to replace the old ink cartridge, and (2) an ink flow in operation (head recovery operation) for recovering printhead discharge nozzles to a preferable condition will be described with reference to  FIGS. 3A, 3B , and  4 .  
         [0044]      FIG. 3A  is a flowchart showing the operation flow in supplying ink from the ink cartridge to the subtank in the inkjet printing apparatus  100 , and  FIG. 3B  is a flowchart showing the operation flow (head recovery operation) in recovering the printhead discharge nozzle to the preferable condition.  FIG. 4  is a diagram showing the ink flow. As described above, the inkjet printing apparatus  100  according to the first embodiment mounts the four color ink cartridges ( 106 K,  106 C,  106 M, and  106 Y). In the diagram of  FIG. 4 , a specific one of these ink cartridges is exemplified. Each of the remaining ink cartridges has a similar arrangement.  
         [0000]     (1) Ink Flow in Supplying Ink to Subtank when Replacing Ink  
         [0045]     First, the ink flow in supplying ink from a newly mounted ink cartridge  400  to a subtank  404  when replacing the old ink cartridge will be described with reference to  FIGS. 3A and 4 .  
         [0046]     The CPU  201  executes ink supply operation based on the control programs stored in the program ROM  203 , as follows.  
         [0047]     First, a recycle valve  415  is closed in step S 301 . An ink supply valve  402  is then opened (step S 302 ), and a subpump  403  is driven (step S 303 ).  
         [0048]     The ink in the ink cartridge  400  is supplied to the subtank  404  through an ink supply filter  401 , the ink supply valve  402 , and the subpump  403 . When the ink sensors  216  in the subtanks  404  sense that all the subtanks of the respective colors are filled with inks (step S 304 ), the CPU  201  stops driving the subpumps  403  (step S 305 ). Note that a timer is used to monitor whether all the subtanks of the respective colors are filled with inks. If not all the subtanks are filled with inks within a predetermined period of time (“YES” in step S 308 ), an alarm is output (step S 309 ), and processing ends.  
         [0049]     Next, the ink supply valve  402  is closed (step S 306 ). The recycle valve  415  is then opened (step S 307 ), and processing ends. Note that opening/closing operation of each valve is controlled by applying a current to a solenoid coil (not shown).  
         [0000]     (2) Ink Flow in Head Recovery Operation  
         [0050]     Next, the ink flow in the head recovery operation in recovering the discharge nozzles of a printhead  406  to the preferable condition will be described with reference to  FIGS. 3B and 4 .  
         [0051]     First, the ink supply valve  402  is closed (step S 351 ) to start driving the subpump  403  (step S 352 ). Then, ink is started to be sucked from an ink pool  413  in a capping mechanism  409  through a recycle filter  414 , a recycle valve  415 , and the subpump  403 .  
         [0052]     After that, a recovery valve  411  is closed (step S 353 ) to drive a pressure pump  405  (step S 354 ). Accordingly, the ink in the subtank  404  is supplied to a common ink chamber  407  of the printhead  406  through the pressure pump  405  and a tube  418 . Since the recovery valve  411  is closed, the pressure in the common ink chamber  407  is increased. Thus, a relatively large amount of ink is ejected from each of the discharge nozzles of the printhead  406 , and the discharge nozzles can be recovered to the preferable condition.  
         [0053]     The ink ejected on a discharge nozzle surface  408  tends to temporarily stay in the ink pool  413  in the capping mechanism  409 . However, since the subpump  403  is driven while the recycle valve  415  is open and the ink supply valve  402  is closed, the ink in the ink pool  413  is filtered through the recycle filter  414 , and forced to return to the subtank  404  through the recycle valve  415  and subpump  403 . That is, the ink used in the recovery operation is recycled without any waste.  
         [0054]     When a predetermined period of time has elapsed in the above pressure state (step S 355 ), the pressure pump  405  stops (step S 356 ), and the recovery valve is opened (step S 357 ). After that, when a predetermined period of time has elapsed (step S 358 ), the subpump  403  also stops (step S 359 ), and processing ends.  
         [0000]     &lt;Mode in Inkjet Printing Apparatus&gt; 
         [0055]     The inkjet printing apparatus  100  according to the first embodiment is used in a print mode in which the print data image received by the host computer  220  is printed, or a test print mode in which the test print pattern is generated (ink viscosity information is provided) to take an appropriate action for ink as needed. The processing flow in the test print mode will be described below.  
         [0000]     &lt;Processing Flow in Test Print Mode&gt; 
         [0056]     The processing flow in the test print mode will be described with reference to the flowchart ( FIG. 5 ). When the test print mode starts, the ink in the head channel is kept at a predetermined temperature by a heater (heating means) (not shown), and head recovery operation is then executed (in step S 501 , see  FIGS. 3B and 4  for head recovery operation in detail). The mode may be switched to the test print mode in accordance with a user&#39;s instruction, or automatically switched by the timer in the inkjet printing apparatus  100 . Note that the user&#39;s instruction to switch to the test print mode may be issued via the operation panel  215  or host computer  220 .  
         [0057]     In step S 502 , test print operation is executed in accordance with the control programs for generating the test print pattern. The viscosity of the printed test print pattern image is visually identified by the user, or automatically identified by the host computer  220  on the basis of the read result from the image reading apparatus  230 . More specifically, the viscosity of the test print pattern is identified based on 1) whether all the pattern images are printed, and 2) whether the viscosity value of the test print pattern exceeds the viscosity bodying limit of the inkjet printing apparatus  100 . Note that whether the viscosity value of the test print pattern exceeds the viscosity bodying limit is determined based on whether the test print pattern images can be printed at up to a defined frequency (e.g., 7 kHz).  
         [0058]      FIG. 6  shows a state wherein image printing can be completely performed for each color at each frequency denoted by reference numeral  601 .  FIG. 7  shows an example when the test print pattern image is not completely printed, and ink is not discharged. As shown in  FIG. 7 , image printing is completely performed for each color at frequencies of 2 to 5 kHz. However, when the frequency is set equal to or higher than 6 kHz, Bk (black ink) is not discharged as a result of an increase in viscosity. When the frequency is set equal to or higher than 8 kHz, Y (yellow ink), M (magenta ink), and C (cyan ink) are not discharged (see  702 Y,  702 M,  702 C, and  702 Bk).  
         [0059]     In step S 503 , the user receives the input of the identification result of the test print pattern obtained by the host computer  220 . More specifically, the user receives information indicating whether all the pattern images can be printed, and information indicating whether image printing can be performed up to the defined frequency. Note that the user may directly input these pieces of information to the inkjet printing apparatus  100  via the operation panel  215 , or may input these pieces of information to the host computer  220 , and transmit them from the host computer  220  to the inkjet printing apparatus  100 .  
         [0060]     In step S 504 , processing is switched in accordance with the identification result input in step S 503 . That is, when information indicating that all pattern images can be printed is input in step S 503 , the test print mode ends. Alternatively, information indicating that all pattern images cannot be printed is input in step S 503 , the flow advances to step S 505 .  
         [0061]     In step S 505 , processing is also switched in accordance with the identification result input in step S 503 . That is, information indicating that image printing can be performed up to the defined frequency is input in step S 503 , the flow advances to step S 506 . Alternatively, information indicating that image printing cannot be performed up to the defined frequency is input in step S 503 , the flow advances to step S 508  to display, on the operation panel  215 , a message to replace the ink cartridge with a new one. This message may be displayed not only on the operation panel  215  but also, e.g., on the host computer  220  via the interface controller  202 .  
         [0062]     The user who receives the message display inputs an instruction to replace the ink cartridge  400 . Upon reception of this instruction, the inkjet printing apparatus  100  executes a series of ink replace processes (step S 509 ). More specifically, a valve  420  in the channel between the subtank  404  and a waste ink tank  421  is opened to remove ink into the waste ink tank  421  by water head pressures of the subtank  404  and waste ink tank  421 . When ink has been removed to the waste ink tank  421 , a message indicating this is displayed on the operation panel  215  or the host computer  220 . When the user sets a new ink cartridge  400  in accordance with this display, the inkjet printing apparatus  100  performs ink supply operation (see  FIGS. 3A and 4  in detail). With this operation, ink cartridge replacement is completed, and the flow returns to step S 501 . Note that at this time, various recovery operations such as wiping operation of the nozzle surface  408  of the printhead using a wiper blade are also executed.  
         [0063]     On the other hand, in step S 506 , various pieces of information obtained from the printed test pattern image are input. The various pieces of information obtained from the printed test print pattern image include, for example, information about the frequency at which ink is not discharged, and information about the discharge error occurrence rate at the frequency at which ink is not discharged.  
         [0064]     In step S 507 , an image printing sequence or recovery sequence is changed by collating the various pieces of information input in step S 506  with the information stored in the program ROM  203 . Note that a “change in image printing sequence” means a change in various pieces of information such as ink discharge amount in image printing processing. Also, a “change in recovery sequence” means a change in various pieces of information such as ink circulation time (see  FIG. 4  in detail) in ink processing other than image printing.  
         [0065]     Upon completion of sequence change processing in step S 507 , the test print mode ends, and the mode shifts to the print mode.  
         [0066]     As is apparent from the above description, in the first embodiment, since ink is discharged in response to the driving pulses with the different frequencies in the test print mode, ink viscosity information (test print pattern) can be provided. In this method, the ink viscosity information can be provided without a specific device such as a sensor, and the information can be provided at lower cost in smaller space than a conventional one.  
         [0067]     Note that the first embodiment has been described by exemplifying an apparatus which employs an ink recycling scheme, in which evaporation of ink components is considerable. However, the present invention is not limited to this. The present invention can also be applied to an apparatus which employs a non-recycling scheme.  
       Second Embodiment  
       [0068]     In the first embodiment, an ink discharge amount changes as a change in an image printing sequence. However, the present invention is not limited to this. For example, stable discharge corresponding to a change in ink viscosity may be implemented by adjusting an ink temperature in a channel of a printhead  406  using a heater (heating means).  
       Third Embodiment  
       [0069]     In the first embodiment, an ink discharge amount changes as a change in an image printing sequence. However, the present invention is not limited to this. For example, stable discharge corresponding to a change in ink viscosity may be implemented by adjusting discharge energy of a printhead  406 .  
       Fourth Embodiment  
       [0070]     In the first embodiment, an ink discharge amount changes as a change in an image printing sequence. However, the present invention is not limited to this. For example, stable discharge corresponding to a change in ink viscosity may be implemented by adjusting the interval (time) between discharge processes (i.e., adjusting the frequency of a driving pulse) of a printhead  406 .  
       Fifth Embodiment  
       [0071]     In the first embodiment, an ink circulation time changes as a change in an image recovery sequence. However, the present invention is not limited to this. Stable discharge corresponding to a change in ink viscosity may be implemented by adjusting the amount of the ink circulating in the channel of a printhead  406 .  
       Sixth Embodiment  
       [0072]     In the first embodiment, an ink circulation time changes as a change in an image recovery sequence. However, the present invention is not limited to this. Stable discharge corresponding to a change in ink viscosity may be implemented by adjusting the pressure in a channel when ink circulates in the channel of a printhead  406 .  
       Other Embodiment  
       [0073]     The object of the present invention is realized even by supplying a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or an apparatus, and causing the computer (or a CPU or an MPU) of the system or the apparatus to read out and execute the program codes stored in the storage medium.  
         [0074]     In this case, the program codes read out from the storage medium realize the functions of the above-described embodiments by themselves, and the storage medium storing the program codes constitutes the present invention.  
         [0075]     As a storage medium for supplying the program codes, a floppy® disk, a hard disk, an optical disk, a magnetooptical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.  
         [0076]     The functions of the above-described embodiments are realized not only when the readout program codes are executed by the computer but also when the OS (Operating System) running on the computer performs part or all of actual processing on the basis of the instructions of the program codes.  
         [0077]     The functions of the above-described embodiments are also realized when the program codes read out from the storage medium are written in the memory of a function expansion board inserted into the computer or a function expansion unit connected to the computer, and the CPU of the function expansion board or function expansion unit performs part or all of actual processing on the basis of the instructions of the program codes.  
         [0078]     The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention, the following claims are made.  
         [0079]     This application claims the benefit of Japanese Application No. 2005-030567 filed on Feb. 7, 2005, which is hereby incorporated by reference herein in its entirety.