Inkjet recording device

Abstract

To improve accuracy of preliminary ejection control on an inkjet recording head.SOLUTION: The time from the previous recording timing signal input for each nozzle array is measured and, when the measured time is smaller than a predetermined threshold, preliminary discharge control is executed only to the nozzles while excluding the nozzles used in the latest recording operation.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an inkjet recording apparatus. [Background technology]

[0002] In inkjet recording devices, when the nozzles of the recording head are generally exposed to the atmosphere, the ink solvent evaporates from the nozzles, and to prevent the ink components from condensing and solidifying inside the nozzles, the ink ejection surface of the recording head is covered with a cap-like member when recording operations are not being performed to prevent the ink solvent from evaporating.

[0003] However, because the cap members are removed during printing, nozzles that are not used for printing, i.e., nozzles that do not eject ink, are exposed to the atmosphere for a long period of time. As a result, the ink solution in the nozzles that do not eject ink evaporates, and ink may harden inside the nozzles. If the ink hardens, the nozzles may become clogged, preventing ink from being ejected, which may result in defective printed images.

[0004] To prevent this, inkjet recording devices generally perform nozzle clogging prevention control (hereafter referred to as preliminary ejection) by periodically discharging old ink from all nozzles. However, periodically ejecting ink from all nozzles in this way poses the problem of a decrease in the throughput of the recording device.

[0005] Patent Document 1 describes a configuration in which the number of ink ejections is measured individually by multiple counters for some of the multiple printing elements, and preliminary ejection is appropriately controlled according to the count values.

[0006] Furthermore, Patent Document 2 describes a configuration in which, as a way to reduce the circuit scale, the number of times the printing element is driven is periodically acquired for each time-divided block unit, stored in a temporary memory, and the printable time, i.e., the time during which preliminary ejection is not required, is adjusted according to the stored number of times the printing element is driven. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2004-58528 [Patent Document 2] Patent Publication No. 2009-12186 Summary of the Invention [Problem to be solved by the invention]

[0008] The printing devices in Patent Documents 1 and 2 determine the ejection status of all nozzles by observing the number of ejections of some nozzles in a nozzle row or by obtaining the number of times the nozzles are driven in time-divided blocks. Based on the results of this determination, the time when preliminary ejection is not required is adjusted, thereby reducing the number of times preliminary ejection control is executed as much as possible.

[0009] However, in a configuration in which the nozzle length is longer, the number of nozzles that are not used for printing increases, and the number of states that do not meet the conditions for adjusting the time when preliminary ejection is not required increases, which may make it difficult to achieve the effect of reducing the number of times preliminary ejection control is performed. [Means for solving the problem]

[0010] An inkjet recording device has a recording head that ejects ink, and performs preliminary ejection control to eject ink from the recording head separately from the recording operation. The inkjet recording device has a recording data generation unit that generates recording data from data input from outside, a nozzle selection unit that generates nozzle selection data for allocating the recording data to each nozzle in the recording head, and a temporary storage memory for temporarily storing the data generated by the recording data generation unit and the nozzle selection unit, and is characterized in that the device extracts multiple columns of the nozzle selection data from the temporary storage memory, counts the number of ejections from each nozzle, and performs control not to perform preliminary ejection for nozzles whose number of ejections is equal to or greater than a predetermined number. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing a main mechanism of an inkjet recording apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing a hardware configuration for operating the inkjet printing apparatus according to the present embodiment. [Figure 3] FIG. 2 is a block diagram showing a configuration related to printing and preliminary ejection control according to the embodiment. [Figure 4] 10A to 10C are diagrams illustrating an example of generation of ejection nozzle mask data in this embodiment. [Figure 5] 10A and 10B are diagrams illustrating an example of a division method when dot counting is performed in multiple steps in this embodiment. [Figure 6] 4 is a flowchart of preliminary ejection control in the first embodiment. [Figure 7] 10 is a flowchart of preliminary ejection control in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the members, numerical values, materials, etc. used in the description are merely examples for the purpose of aiding understanding, and are not intended to limit the present invention.

[0013] (First embodiment) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0014] FIG. 1 is a perspective view showing the external configuration of an inkjet recording apparatus equipped with an inkjet recording head (hereinafter referred to as a recording head) that ejects ink droplets according to an inkjet method, which is a typical embodiment of the present invention.

[0015] A carriage 3 carrying a recording head 27 is slidably supported by a guide shaft 4 and moves back and forth over a recording medium (sheet) 1. A carriage motor (DC motor) 5 with a pulley is located at one end of the movement range of the carriage 3, and an idle pulley 6 is located at the other end. A timing belt 7 is wound around these, connecting the carriage 3 and the timing belt 7.

[0016] In addition, in order to prevent the carriage 3 from rotating around the guide shaft 4, a support member 8 is installed extending parallel to the guide shaft 4, and the carriage 3 is also supported by the support member 8 so that it can slide freely.

[0017] The print head 27 is provided with a large number of print elements (hereinafter referred to as nozzles), and the nozzles are arranged in rows for each ink color. The number of nozzles and the number of ink colors, i.e., the number of nozzle rows, is not a factor in the configuration of the present invention. An FFC (flexible flat cable) 11 is provided to the print head 27 to supply drive signals to each nozzle from the main body of the inkjet printing device. The FFC 11 is an elongated, thin film with a conductor pattern formed inside or on its surface for transmitting drive signals. It is flexible enough to bend as the carriage 3 moves, and the center of bending moves.

[0018] Furthermore, an ink tank (not shown) is disposed outside the carriage 3, and a tube 12 is disposed therein to supply ink stored in the ink tank to the recording head 27. The tube 12 is flexible so that it bends as the carriage 3 moves, and the center position of the bend moves. A connecting member 10 consisting of the FFC 11 and the tube 12 is connected between the carriage 3 and a fixed part 9 of the inkjet recording device main body.

[0019] Furthermore, a linear scale 16 used to acquire position information of the carriage 3 is arranged parallel to the carriage movement direction (main scanning direction) and is configured to be read by an encoder sensor 15 attached to the carriage 3. The read position information can be used to generate the ink ejection timing of the recording head.

[0020] Furthermore, ink recovery ports 14a and 14b are provided on both outer sides of the width of the recording medium 1 to recover ink when the recording head 27 performs preliminary ejection, so that preliminary ejection control can be performed before the start of recording operation or during recording operation at a position that does not affect the recording medium 1.

[0021] With this configuration, the carriage 3 moves back and forth in the direction of arrow A (main scanning direction). The recording medium 1 is also transported by a transport motor (not shown) in the direction of arrow B (sub-scanning direction) that perpendicularly intersects with the carriage 3.

[0022] Figure 2 is a schematic diagram of the hardware configuration for operating the inkjet recording apparatus shown in Figure 1. Note that Figure 2 does not show all of the components of the inkjet recording apparatus.

[0023] When the inkjet recording device operates, a recording command including image data is input to the communication unit 21 from an external data input device (PC 20 in Figure 2). The inkjet recording device begins recording operations upon receiving the image data via the communication unit 21. The operation panel 22 is used for various settings of the inkjet recording device, such as issuing a command to start copy recording. The CPU 23 is an arithmetic processing unit that loads programs stored in the ROM 24 onto the RAM 26 and performs various control and arithmetic processing. The ASIC 25 is an arithmetic processing unit comprised of integrated circuits for image processing and actuator operation, and executes arithmetic processing upon receiving commands from the CPU 23. Note that the CPU 23 may be incorporated within the ASIC 25 or mounted on a separate chip. Externally input image data is expanded within the ASIC 25 into print data (hereinafter referred to as print data) that can be printed by the print head 27, and then transferred to the print head 27, enabling the printing operation. In addition to expanding the input image data, the ASIC 25 also generates preliminary ejection data for preliminary ejection control.

[0024] FIG. 3 is a block diagram showing an example of a hardware configuration for implementing the printing control and preliminary ejection control of the present invention.

[0025] First, the function of each module for recording operation will be explained. When image data is input from the PC 20, the data is received by the data receiving unit 30, which receives external data within the ASIC 25, and the image data is loaded into the DRAM 31 via a DMA controller (not shown). At this time, the data receiving unit may convert the data into a format that is easy to handle in subsequent control, or the data may be converted by another module.

[0026] The control timing after image data input is generated by the timing generation unit 33 from position information read by the encoder sensor 15 attached to the carriage 3 shown in Fig. 1 or from arbitrary timing generated by firmware control. When performing a recording operation, after a predetermined amount of input data is loaded into the DRAM 31, the timing signal (recording timing signal) generated by the timing generation unit 33 starts generating recording data in the recording data generation unit 34.

[0027] Generally, image data size increases in proportion to the size of the recording medium, so it is often stored in DRAM with a large storage capacity and retrieved from the DRAM using a DMA module that can access data without going through the CPU, and therefore a configuration using a DMA controller is shown in Figure 3. The data expanded in DRAM 31 is taken into print data generator 34 via DMA controller 32, and print data generator 34 generates print pattern data 36 by converting the image data into a format that can be printed by the print head, and temporarily stores this in temporary storage memory 29.

[0028] Next, upon receiving data from the print data generation unit 34, or at a predetermined timing, the nozzle selection unit 35 acquires the print pattern data 36 from the temporary storage memory 29, and generates nozzle selection data 37 including information on which nozzle on the print head to eject ink from, and stores this in the temporary storage memory 29.

[0029] Next, when the print data generation unit 34 or the nozzle selection unit 35 has completed generating a predetermined amount of data, the head control unit 38 generates data for ejecting ink from the print head from the print pattern data 36 and the nozzle selection data 37, and transfers the data to the print head to perform the printing operation.

[0030] As described above, the recording operation requires a preliminary ejection operation to be performed periodically after the start of the recording operation to prevent ink from adhering to the nozzles of the recording head. The preliminary ejection operation is initiated at an arbitrary timing (preliminary ejection timing signal) generated by the timing generation unit 33 after image data is input from the outside. In conventional control, preliminary ejection pattern data 40 is generated by the preliminary ejection data generation unit 39 upon receiving the preliminary ejection timing signal, and is stored in the temporary storage memory 29. The data is then transferred to the recording head by the head control unit 38, where preliminary ejection control is performed. The preliminary ejection pattern data 40 generated here is configured to be ejected from all the nozzles in the recording head.

[0031] Therefore, this invention proposes a configuration for controlling preliminary discharge on a nozzle-by-nozzle basis. This configuration includes a counter 41 for measuring the time elapsed since the start of the previous printing operation, i.e., since the input of a print timing signal, and a total preliminary discharge cycle setting unit 42 that can arbitrarily set the cycle for performing preliminary discharge for all nozzles (hereinafter referred to as total preliminary discharge), and an total preliminary discharge execution determination unit 43 determines whether the time elapsed since the input of the print timing signal is within the total preliminary discharge cycle. The total preliminary discharge execution determination unit 43 is provided for each nozzle row of the print head, and determines whether or not to perform total preliminary discharge for each nozzle row, and passes the determination result to the preliminary discharge data generation unit 39.

[0032] If the determination result of the full preliminary ejection execution determination unit 43 indicates that full preliminary ejection is required, the preliminary ejection data generation unit 39 generates preliminary ejection data so that preliminary ejection is performed from all nozzles in the nozzle row, as in conventional control.

[0033] On the other hand, if the result of the determination by the all preliminary discharge execution determination unit 43 is that preliminary discharge for all of the nozzle rows in question is not necessary, a process for identifying the nozzles that have discharged ink within a predetermined period is required.

[0034] The nozzle selection data 37 generated during a printing operation is generated in column units (hereinafter referred to as column) that match the nozzle length of the print head, and a certain number of columns of data are stored in temporary storage memory 29. Next, a configuration for identifying the nozzles that have ejected ink from the nozzle selection data 37 for multiple columns that has already been generated will be described.

[0035] A nozzle selection data acquisition unit 44 acquires nozzle selection data for a desired number of columns from temporary storage memory 29, and a dot number measurement counter 46 counts how many times ejection has been performed for each nozzle within the acquired number of columns. An ejection nozzle mask data generation unit 47 determines whether the counted number of dots is equal to or greater than a threshold predetermined by a duty determination threshold setting unit 45, and generates ejection nozzle mask data 48 to mask nozzles that have ejected a predetermined number of times within a predetermined period in accordance with the determination result, so as not to perform preliminary ejection. The ejection nozzle mask data 48 is expanded in temporary storage memory 29, and by reading it from temporary storage memory 29 and applying it when preliminary ejection pattern data generation unit 39 generates preliminary ejection pattern data, it is possible to control nozzles that do not require preliminary ejection not to perform preliminary ejection.

[0036] Alternatively, when the ejection nozzle mask data generating unit 47 determines that preliminary ejection is unnecessary for all nozzles in all nozzle rows, preliminary ejection control itself is not performed.

[0037] Next, the generation of the ejection nozzle mask data will be described in detail with reference to FIG.

[0038] Figure 4(a) shows an example in which nozzle selection data for a total of four columns is acquired, going back three columns from the data for the Nth column used in the previous printing operation. Nozzle number 0 ejected ink from columns N and N-1, but not from columns N-2 and N-3, so the dot count counter counts 2. Here, if the ink ejection rate from each nozzle (hereinafter referred to as "duty") required to determine that preliminary ejection is unnecessary is set to 50%, nozzle number 0 ejected ink twice out of four columns, so the duty is 50%. Therefore, preliminary ejection is determined to be unnecessary for nozzle number 0, and ejecting nozzle mask data is generated so that the mask is enabled. Performing the same process for nozzle numbers 1 and onward results in ejecting nozzle mask data in which nozzle number 1 has two dots, so the mask is enabled at 50% duty; nozzle number 2 has four dots, so the mask is enabled at 100% duty; and nozzle number 3 has one dot, so the mask is disabled at 25% duty.

[0039] As another embodiment, an example is shown in Figure 4(b) in which ejection nozzle mask data is generated without measuring the number of dots using only the nozzle selection data for the previous column. Because it is data for one column, the ejection nozzle mask data is the inverse of the nozzle selection data without calculating the duty.

[0040] 4(c) shows an example of another embodiment in which the number of dots in the nozzle selection data is not measured, but ejecting nozzle mask data is generated by performing a logical OR on multiple columns of nozzle selection data on a nozzle-by-nozzle basis. In the figure, nozzle numbers 5 and 11 have never ejected, so ejecting nozzle mask data is generated assuming that all nozzles other than these two dots do not require preliminary ejection.

[0041] The generation of ejection nozzle mask data has been described above, but if the circuit has dot number measurement counters shown in Figure 4(a) that match the nozzle length of the print head, the number of counters will increase as the nozzle length becomes longer, so the following configuration will allow for efficient use of the counters.

[0042] Figure 5 shows an example of a configuration with 16 dot number measurement counters within the circuit. The number of counters should be set appropriately depending on the hardware configuration, making processing easier. In the first process, the number of dots is counted for nozzle numbers 0 to 15, and the duty is calculated to generate ejection nozzle mask data. In the second process, the number of dots is counted for nozzle numbers 16 to 31, and the duty is calculated to generate ejection nozzle mask data. By performing the same process for nozzle numbers 32 and onwards, ejection nozzle mask data can be generated. Because these processes can be performed in parallel with the printing operation process within the hardware circuit, generating ejection nozzle mask data multiple times does not affect the throughput of the printing operation.

[0043] Next, the preliminary discharge control performed by the printing apparatus having the above-described configuration will be described with reference to the flowchart of Fig. 6. In this embodiment, this flow is a process performed by the ASIC 25.

[0044] First, in step S101, a cycle Ty at which preliminary discharge control is required from the start of the printing operation is set in the total preliminary discharge cycle setting unit 42. The cycle to be set may be given as an initial value in a register inside the ASIC, or may be rewritten at any timing.

[0045] Next, in step S102, a print timing signal for each nozzle array is input to the all-preliminary-fire execution determination unit 43, which starts counting the cycles to determine whether all preliminary fire is to be executed. In step S103, it is determined whether the cycle count value is equal to or greater than the set cycle Ty. Note that while FIG. 6 illustrates only the process for nozzle array n when there are 0 to n nozzle arrays, the same process is performed for all nozzle arrays 0 to n. If the cycle count value is less than Ty, it is determined in step S104 that preliminary fire is unnecessary (can be skipped) for all nozzles in nozzle array n. However, here, this control is performed as a flag that is easy to handle as a hardware circuit. Therefore, in step S104, the all-preliminary-fire execution determination unit 43 outputs an all-preliminary-fire skip flag for nozzle array n as ON. On the other hand, if the cycle count value is equal to or greater than Ty, the all-preliminary-fire skip flag for nozzle array n is output as OFF in step S105.

[0046] Next, in step S106, it is determined whether the all preliminaryfire skip flag for nozzle array n is OFF in the preliminaryfire data generation unit 39. If the all preliminaryfire skip flag for nozzle array n is OFF, in step 107, preliminaryfire data is generated within the preliminaryfire data generation unit 39 without using mask data for the nozzles of nozzle array n. In other words, if a predetermined time or more has passed since the immediately preceding printing operation, preliminaryfire is performed from all nozzles, as was done in the conventional control.

[0047] If the all preliminary fire skip flag for nozzle array n is ON, a determination is made for each nozzle in nozzle array n as to whether preliminary fire is necessary (not shown), as described above in FIG. 4, and in step S108, the preliminary fire data generation unit 39 determines whether all nozzles in nozzle array n have fired. If it is determined that all nozzles in nozzle array n have fired, in step S109, it is further determined whether all nozzles in nozzle arrays 0 to n have fired. If it is determined that all nozzles in all nozzle arrays have fired, the preliminary fire control itself is not performed, and a flag (preliminary fire not performed flag) in the preliminary fire data generation unit 39 is turned ON (step S110). Here, the flag is held within the preliminary fire data generation unit 39, but it may be configured to be managed by a separate hardware circuit module.

[0048] If the determination result in either step S108 or S109 is negative, the preliminary-ejection-data generating unit 39 generates preliminary-ejection data by applying the mask data to each nozzle (step S111). If the preliminary-ejection data is generated in step S107 or step S111, the preliminary-ejection-not-performed flag in the preliminary-ejection-data generating unit 39 is turned OFF to perform preliminary ejection (step S112).

[0049] In the first embodiment, a configuration is shown in which the processing up to step S112 is performed by a hardware circuit, and step S200 and thereafter are performed by firmware control.

[0050] When the firmware is about to perform preliminary discharge, it is first determined whether a preliminary discharge not yet performed flag in the hardware circuit is ON (step S200). If the preliminary discharge not yet performed flag is ON, preliminary discharge start control is not performed, and all flags in the hardware circuit are cleared (step S203), and preliminary discharge control is terminated.

[0051] On the other hand, if the preliminary-ejection-not-executed flag is OFF at the timing when preliminary-ejection is to be executed under firmware control, processing to start preliminary-ejection control is executed (step S201). Because preliminary-ejection control is configured to issue an interrupt when it is completed within the hardware circuit, firmware control monitors until a preliminary-ejection completion interrupt is issued (step S202). When the interrupt is issued, preliminary-ejection control is completed, and in step S203 all flags within the hardware circuit are cleared, thereby completing preliminary-ejection control.

[0052] As in the configuration described above, by identifying the nozzles in the print head that have been used in the printing operation within a specified time period and generating preliminary ejection pattern data to mask the target nozzles, it is possible to increase the accuracy of preliminary ejection control and to reduce the consumption of ink used in preliminary ejection control.

[0053] (Second embodiment) In the second embodiment, steps S101 to S112 are the same as those in the first embodiment, but FIG. 7 shows a configuration in which the determination of whether the preliminary ejection unexecuted flag is ON is performed within a hardware circuit.

[0054] The processing in the hardware circuit determines whether the pre-ejection not yet performed flag is ON (step S113), and if the pre-ejection not yet performed flag is ON, the processing continues up to issuing a pre-ejection end interrupt (step S114) in the timing generation unit 33. In this embodiment, the timing generation unit 33 is configured to issue the pre-ejection end interrupt, but a separate hardware circuit module may be configured to manage the interrupt.

[0055] The firmware control does not determine whether to perform preliminary discharge control, but instead performs processing to start preliminary discharge control when preliminary discharge is about to be performed (step S201), and monitors until a preliminary discharge end interrupt is issued, as in normal preliminary discharge control (step S202). However, if the preliminary discharge not yet performed flag is ON, the preliminary discharge end interrupt is immediately issued, so preliminary discharge control is not performed, and in the next step S203, all flags in the hardware circuit are cleared and preliminary discharge control is terminated. By performing the preliminary discharge not yet performed flag determination within the hardware circuit, there is an advantage that the firmware control processing from step S201 onwards can be configured with the same program regardless of whether preliminary discharge control is being performed or not.

[0056] (Third embodiment) As a third embodiment, in addition to the configurations shown in the first and second embodiments, there is a technique for correcting, using print data, misalignment between nozzles that occurs during the manufacture of the print head chip on which the ink ejection nozzles in the print head are mounted, and misalignment and tilt that occurs when the print head is installed in an inkjet printing apparatus, and a configuration can be proposed in which the correction data used in this case is also applied to the preliminary ejection data. By doing so, it is possible to generate ejection nozzle mask data that has been corrected for tilt and is synchronized with the nozzle information actually used for printing.

Claims

1. It has a recording head that ejects ink, In an inkjet recording apparatus, a preliminary ejection control is performed to eject ink from the recording head separately from a recording operation, a recording data generating unit that generates recording data from data input from an external device; a nozzle selection unit that generates nozzle selection data for allocating print data to each nozzle in the print head; a temporary storage memory for temporarily storing data generated by the print data generating unit and the nozzle selecting unit; extracting the nozzle selection data for multiple columns from the temporary storage memory and counting the number of ejections from each nozzle; An inkjet recording apparatus characterized in that it performs control not to perform preliminary ejection of a nozzle when the number of ejections reaches a predetermined number or more.

2. 2. The inkjet recording apparatus according to claim 1, wherein a preliminary ejection data generation unit that generates an ejection pattern for preliminary ejection at a predetermined cycle or at an arbitrary timing counts a predetermined number of ejections from each nozzle based on the nozzle selection data, and when the number of ejections from each nozzle reaches a predetermined threshold, the inkjet recording apparatus determines that preliminary ejection is unnecessary and generates mask data that is applied to the preliminary ejection data, thereby performing preliminary ejection control in accordance with the ratio of ink ejection amounts from each nozzle.

3. 3. The inkjet printing apparatus according to claim 2, wherein the preliminary ejection control measures the elapsed time from the timing when the previous printing was performed for each nozzle row, and when the elapsed time is shorter than a predetermined time, performs preliminary ejection control by applying the mask data to the preliminary ejection data.

4. An inkjet printing apparatus according to claim 1, characterized in that when correcting the tilt of the nozzle array that occurs during the manufacture of the print head chip or installation of the device when generating print data, similar tilt correction data is also applied to the nozzle selection data, thereby synchronizing the nozzle information used for printing.

5. an ejection nozzle mask data generation unit that determines whether or not the number of ejected dots among the acquired number of columns is equal to or greater than a threshold value for each nozzle in the nozzle selection data for a predetermined number of columns acquired from the nozzle selection data generated by the nozzle selection unit; 2. The inkjet recording apparatus according to claim 1, wherein the ejection nozzle mask data generating unit performs control such that a preliminary ejection operation is skipped when it is determined that ink has been ejected from all the nozzles.

6. an ejection nozzle mask data generation unit that determines whether or not the number of ejected dots among the acquired number of columns is equal to or greater than a threshold value for each nozzle in the nozzle selection data for a predetermined number of columns acquired from the nozzle selection data generated by the nozzle selection unit; 2. The inkjet recording apparatus according to claim 1, wherein the ejection nozzle mask data generation unit acquires nozzle selection data for multiple columns generated by the nozzle selection unit, and generates ejection nozzle mask data from the logical sum of the acquired nozzle selection data for multiple columns.

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