JP2007203629A - Recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain reliability of a recording head and improvement of image quality by suppressing fluctuations in discharging amount of ink without exerting an excessive heat stress on a heating element, considering that a recorder loading a line head in particular is employed for most frequency used high speed continuous printing and a means for improving durability of the recording head is important. <P>SOLUTION: A plurality of preheat pulses can be selected by an input means of a plurality of preheat pulse signals which apply energy to ink to a degree that the ink is not foamed, prior to application of a drive pulse, based on drive information of each heating element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a recording apparatus that ejects ink droplets onto a recording medium such as paper and prints characters and images.

  In an inkjet printer equipped with a line head, in order to prevent the influence of image unevenness due to the decrease in the life of the inkjet head recording and the variation in the ink discharge amount, the load has been concentrated on a specific nozzle in the past, and the inkjet head has a high temperature. In some cases, the ejection of ink is dispersed by shifting the image for each predetermined page so as not to become a problem.

JP 07-047714 A

  However, since the image position on the recording medium is shifted in the horizontal direction in the method of Patent Document 1, even a slight shift may be a problem depending on the image contents. In addition, a slight shift amount cannot be sufficiently shifted, and a heat stress may be generated by heating a certain heating element in a continuous burst. As a result, the heat generating element may be damaged, and the durability may be reduced. Also, the viscosity of the ink may change due to heat, resulting in variations in the amount of ink discharged, which may cause unevenness in the printed image. is there.

In order to solve the above problems, a recording apparatus according to the present invention includes a recording head that selectively heats a heating unit provided for each of a plurality of nozzles to eject ink, and a temperature detection unit that detects a temperature of the recording head. ,
A first application pulse to be supplied to the heating means; and an application pulse supply means to supply a second application pulse to be preliminarily supplied,
It further comprises counter means for counting a value corresponding to the number of heating times of the heating means, and pulse width correcting means for correcting the pulse width of the second applied pulse based on the counting result of the counter means. .

  In a recording apparatus embodying the present invention, a preheat pulse with reduced input energy is applied to a heat generating element with a large number of ejections so that excessive heat stress is not applied to the heat generating element, and variation in ink discharge amount is suppressed. Therefore, it is possible to improve the reliability of the recording head and the image quality.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the relative arrangement, numerical formulas, numerical values, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified.

FIG. 1 is a perspective view schematically illustrating a recording unit of a recording apparatus embodying the present invention.
In the recording unit (100) of the recording apparatus, four recording heads (101K), (101C), (101M), and (101Y) that discharge ink of each color perform a recording operation while still at the recording positions in the drawing.
A plurality of labels (106) temporarily attached on a mount of roll paper (105) wound in a roll shape is fed out in the arrow carrying direction, and the paper is fed at a constant speed by a carry motor (108) to a feed roller (109). After being conveyed and passing under the recording heads (101K), (101C), (101M), and (101Y), the recorded label (107) is continuously discharged. When the leading end of the label (106) is detected by a paper leading end detection sensor 111, each recording head (101K), (101C) is synchronized with the output of the rotary encoder (110) coupled to the motor shaft of the transport motor (108). ), (101M), and (101Y) record each assigned color.
112 is also used for detecting a paper jam by a paper leading edge detection sensor.
FIG. 2 is an electrical block diagram of the recording apparatus embodying the present invention. The recording data on the paper is created by the host PC (200) and transferred to the interface controller (201) of the recording apparatus.
The recording data received by the interface controller (201) is no different from conventional recording data. The memory controller (206) temporarily writes the received data into the image buffer (207) at a high speed according to an instruction from the CPU (202).
After receiving a predetermined amount of recording data, the CPU (202) starts preparation for recording operation of the recording unit (100).

First, the head U / D motor (211) and the cap motor (212) are operated in parallel via the drive unit (210), and the recording head (101K) that has been capped in standby by a cap mechanism (not shown), (101C), (101M), and (101Y) are moved to the recording position. At this time, the recording heads (101K), (101C), (101M), and (101Y) move up and down, and a cap mechanism (not shown) moves back and forth in the sheet conveyance direction.
Subsequently, the roll paper (105) is fed out by a roll paper supply motor (not shown), and the transport motor (108) is also activated via the drive unit (217). The start of the conveyance motor (108) is triggered by the speed instruction value of the conveyance motor (108), which is a servo motor, being written from the CPU (202) to the servo logic circuit (216).

  After that, the output of the rotary encoder (110) is fed back to the servo logic circuit (216), and the feedback loop of the drive unit (217) to the transport motor (108) to the rotary encoder (110) to the servo logic circuit (216). Speed controlled.

  The servo logic circuit (216) converts the conveyance position pulse from the output of the rotary encoder (110) and outputs it, and the recording heads (101K), (101C), (101M), and (101Y) cut out each for recording. Signal.

  Then, the leading end of the label (106) is detected by the leading end detection sensor (111) on the upstream side in the transport direction, and each of the recording heads (101K), (101C), (101M), (101Y) is detected from the leading end detection sensor (111). Is received by the memory controller (206), the image buffer (207) is read out and transferred to the recording head control circuit (208). In the recording head control circuit (208), the data is sequentially transferred to the recording head corresponding to the read image data.

  A mounting space for the recording heads (101K), (101C), (101M), and (101Y) may have a spare mounting space. The recording heads (Preliminary 1 and 2) in FIG. 2 are shown for reference.

  The processing of the CPU (202) depends on the control program written in the ROM (203), but the RAM (204) is also used as a working memory. The EEPROM (205) is a non-volatile memory that stores numerical values unique to the apparatus such as an adjustment value for electrically adjusting a minute recording position (registration) between the recording heads. The recording device is provided with an operation panel (219) including a display device such as an LCD and a pause / resume / emergency stop key for the recording operation, and writing of display data and key ON / OFF via the input / output port (209). The status can be read out.

  The analog output values of the paper leading edge detection sensors (111) and (112) and the internal temperature sensor (210) can be read out almost in real time via the AD converter (218).

  Next, the configuration of a cell forming a heater board of a conventional recording head will be described with reference to FIG. In the case of the recording apparatus of the present invention, the heater board of each recording head is equipped with four cells shown in FIG. 7 and has 640 [bit] (for 640 nozzles) heating elements per cell. It has a nozzle drive circuit.

  FIG. 9 shows a conceptual diagram of the recording heads 101K, C, M, and 101Y composed of four cells (Cells 1 to 4).

  In order to monitor the temperature of the recording head, the cell incorporates two diode-type temperature sensors (304), a total of eight, but as described above, for example, two at both ends and one at the center, a total of 3 The temperature sensor 304 output at the location is read.

Next, the circuit configuration of one cell will be described with reference to FIG. VH is a driving power source for driving the heating element (401), HGND is a GND for the heating element driving power source, and 402 is a driving transistor for the heating element (401). ODD is a signal for instructing energization of the odd-numbered heating elements (401), and EVEN is a signal for instructing energization of the even-numbered heating elements (401). Reference numeral 403 denotes a 3-input-8-output decoder. In this embodiment, 640 heating elements (401) are divided into 8 blocks (80 nozzles / block) and are driven to generate heat according to block selection signals (BENB0 to 2). The block of the heating element (401) is selected. For example, the nozzle numbers corresponding to each block are as follows (n = 0 to 9).
Block 0: (1 + 64n), (2 + 64n), (3 + 64n), (4 + 64n), (8 + 64n)
Block 1: (9 + 64n), (10 + 64n), (11 + 64n), (12 + 64n), (16 + 64n)
Block 2: (17 + 64n), (18 + 64n), (19 + 64n), (20 + 64n), (24 + 64n)
Block 3: (25 + 64n), (26 + 64n), (27 + 64n), (28 + 64n), (32 + 64n)
Block 4: (33 + 64n), (34 + 64n), (35 + 64n), (36 + 64n), (40 + 64n)
Block 5: (41 + 64n), (42 + 64n), (43 + 64n), (44 + 64n), (48 + 64n)
Block 6: (49 + 64n), (50 + 64n), (51 + 64n), (52 + 64n), (56 + 64n)
Block 7: (57 + 64n), (58 + 64n), (59 + 64n), (60 + 64n), (64 + 64n)
The above ODD, EVEN and block selection signals are called time-division signals. In order to suppress the voltage drop in the drive power supply path and the influence (crosstalk) on the vicinity of the movement of ink simultaneously ejected from the nozzles, In this embodiment, the driving is divided into 16 times in total by multiplying 2 divisions by ODD and EVEN and 8 divisions by the block selection signal.

  Also, when applying a drive voltage to the heating element (401), it is better to apply a short pulse (preheat pulse) first and then apply a long pulse (main pulse) than to apply one pulse for a long time. It is known that it is easy to correct the discharge amount. This method is a known technique called double pulse control.

  FIG. 5 shows a timing chart for driving the nozzle heater by double pulse control and 16-time time-division driving. Pulse width: T1 portion is a preheat pulse (PH_A), and T3 portion is a main pulse (MH). In order to correct manufacturing variations, the main heat pulse signal (MH) is arbitrarily selected for each cell from four types of pulse widths (MH1, MH2, MH3, MH4).

  The preheat pulse signal can be selected from two types of pulse widths (PL_A, PL_B) by the control described later, and the optimum preheat pulse signal for each heating element, that is, for each nozzle heater.

  In FIG. 4, reference numeral 405 denotes a shift register that captures and temporarily holds print data for 640 nozzles that are serially input in synchronization with the clock DCLK.

  The held print data is latched in the data latch circuit (404) by the data latch signal DLT_N.

  If the latched data is “1” (printing), the preheat pulse signal and the double pulse signal of the main pulse signal are valid.

Next, a print control sequence for correcting the drive pulse width based on the reading result of the temperature sensor (304) will be described.
When the recording data is transferred from the host PC, etc., this print control sequence is started, and the temperature of each recording head is read every time a predetermined amount of printing is performed, such as every page, and the temperature is lower than the maximum rated temperature of the recording head. If the maximum rated temperature is exceeded, control is performed such as temporarily stopping the recording operation.

  In addition, in order to improve image unevenness due to a change in ink discharge amount depending on temperature, control is performed so as to correct the drive pulse of the recording head.

  However, as described above, the temperature sensor (304) is controlled based on outputs from only a total of three locations near both ends and the center of the recording head, for example.

  If an image as shown in FIG. 3 is continuously printed, the nozzle area 305 in charge of a portion where pixels are relatively concentrated, such as portions 302 and 303, on the recording medium (301), and 304 that is not the case. A peak temperature difference occurs between the nozzle region 306 in charge of the portion, and thermal stress is applied to the nozzle heater in the nozzle region 305 portion.

  Therefore, the connection between the printhead control circuit 208 and the printhead 101, which is a characteristic part of the present invention, and the detailed signal flow will be described with reference to FIG.

  Inside the recording head control circuit 208, the ejection number counter 601 is provided in the same number as the number of nozzles of the recording head 101.

  The output of 2560 ejection number counters is selected one by one by a selector 602 at the end of printing for a predetermined area, for example, one page, and compared with the value of the register 604 storing the predetermined value, and the comparison result is obtained. If it is larger than the predetermined value, “1” is output, and if it is smaller than the predetermined value, “0” is output and temporarily set in the prepulse selection data generation circuit 605. When the prepulse selection data corresponding to all nozzles is set, the transfer data line and the transfer clock line that are originally used to transfer the recording data are temporarily set in the prepulse selection data generation circuit. The setting data contents are transferred to the shift register 405 of the recording head 101. Immediately after the transfer is completed, the latch signal HLT_N to the prepulse selection signal latch circuit is operated (falling operation), and the prepulse selection data is taken into the prepulse selection signal latch circuit 606 from the shift register 405. These contents are immediately output to the pre-pulse selection logic 607, and either PH_A or PH_B is selected for each nozzle. That is, a pre-pulse: PH_B having a smaller pulse width is selected for a nozzle having a large number of ejections within a page, while a pre-pulse: PH_A having a larger pulse is selected for a nozzle having a small number of ejections within the page.

  As already explained, it is necessary and sufficient that the number of ejection number counters used is the maximum, the recording width, and a thinned number such as every 4 nozzles, every 8 nozzles or every 16 nozzles is sufficient. An effect will be obtained.

  Next, the configuration of the heater board circuit in the ink jet recording head according to the present invention will be described with reference to FIG. In this circuit configuration, a pre-pulse signal B (PH_B) in which the width of the pre-pulse signal is reduced is added, and a pre-pulse is generated for each heating element so that an excessive pulse is not applied when energization is concentrated on some heating elements (401). Can be switched.

  First, data 64 [bit] of which pre-pulse signal (PH_A, PH_B) is selected for each heating element is temporarily stored in the shift register (405) in the same manner as the print data.

  This pre-pulse selection data may be stored by adding another shift register, but it is preferably shared with the recording data transfer circuit in order to reduce the circuit scale inside the head. The prepulse selection data held in this way is latched in the prepulse selection latch circuit (701) by the newly added prepulse selection latch signal (HLT_N). Then, an independent prepulse selection signal is output from the prepulse selection latch circuit 701 for each heating element for 640 nozzles.

  For nozzles with prepulse selection data set to '0', the conventional prepulse (PH_A) is selected. For nozzles with prepulse selection data set to 1 ', that is, nozzles with high ejection frequency, the pulse width is set. The pre-pulse selection logic circuit 702 determines to select the reduced pre-pulse (PH_B), and the double pulse driving of the selected pre-pulse signal and the main pulse signal does not give excessive thermal stress to the nozzle heater, and the ink Variations in the discharge amount can be suppressed.

  Next, the printing sequence of the recording apparatus embodying the present invention will be described with reference to the flowchart of FIG. This sequence is a sequence for adjusting the width of the preheat pulse of each heating element for each page.

  When the print command is generated (801), the preheat selection data of all the nozzles is cleared to zero in advance.

  When the print start (801) command is received, the preheat pulse selection data for each nozzle is transferred to each recording head before printing, and the preheat pulse latch signal (HLT_N) is validated to the preheat pulse selection latch circuit (601). Store (803).

  Since the value of the preheat pulse selection data has been cleared to zero in advance, ('0') is set for all the nozzles. These are performed by the print head control circuit 208 and the hardware inside the print head 101 as described above.

  Subsequently, the temperature of each recording head 101 is read out, and printing is started on the condition that the temperature is equal to or lower than a predetermined temperature (802-Yes) (803).

  If it is not within the predetermined temperature (802-No), the preheat selection data of all nozzles is cleared to zero (804), and the operation is interrupted (805).

  When printing is started, print data is transferred to each recording head, and a double pulse signal is applied to the corresponding nozzle and ink is ejected. The ejection number counter for each nozzle during printing increments by one each time “printing is performed” and holds a cumulative value. These are performed by hardware as described above.

If printing of one page is finished (806-Yes) and printing of all pages is finished (807-Yes), the preheat selection data is cleared to zero (815), and the process is finished, but still If printing is not completed (807-No), the average number of ejections per nozzle (average number of pixels): N _Ave : N _Ave is determined from the total number of ejections (total number of pixels) in the corresponding page (808). If the discharge count value is smaller than the average discharge count value (809-No), the preheat pulse selection data value corresponding to the nozzle is set to “0” (810), and the discharge count value is compared with the discharge count value. Is larger than the average discharge count value (809-Yes), the value of the preheat pulse selection data corresponding to the nozzle is set to '1' (811).

  That is, the preheat pulse signal B (PH_B) in which the pulse width of the preheat pulse signal is reduced is applied to nozzles larger than the average number of ejections.

  The nozzle number is advanced (812), and after setting preheat selection data for all nozzles in the print area (813-Yes), the setting result is transferred to the recording head (814), and the process returns to 802.

  This flow is repeated until the designated number of prints are completed, and when completed (807-Yes), the preheat selection data is cleared to zero (815), and the process ends.

  In this embodiment, the preheat pulse selection information for each nozzle is 1 [bit] data, but the selection information is increased to a plurality of bits, and the types of pulse widths that can be selected are increased accordingly, thereby performing more delicate adjustments. Things are possible.

  The average number of ejections described in this embodiment is not simply the average value of the total number of ejections (total number of pixels), but is an average value depending on factors such as the temperature and humidity of the print head and the type of ink. A correction may be added.

  The recording apparatus of the present invention can significantly improve the operation reliability of the recording apparatus when used in a line printer such as a high-speed and heavy-duty label printer or a large color printer.

1 is a perspective view showing a schematic configuration of an ink jet printing apparatus as an embodiment according to the present invention. 1 is an electrical block diagram of a recording apparatus embodying the present invention. FIG. 6 is a diagram illustrating a printed image that is likely to generate thermal stress in a recording head. It is a figure which shows the heater board circuit structure of the conventional recording head. 3 is a drive timing chart of a recording head of the recording apparatus embodying the present invention. 1 is a diagram illustrating a configuration of a drive circuit of a recording apparatus embodying the present invention. FIG. 3 is a diagram illustrating a configuration of a heater board circuit of a recording head. 6 is a flowchart at the time of printing of the recording apparatus embodying the present invention. FIG. 3 is a diagram illustrating a configuration of a recording head according to the present invention.

Explanation of symbols

101K recording head (black)
101C print head (cyan)
101M print head (magenta)
101Y recording head (yellow)
106 Label 111 Tip detection sensor

200 host PC
202 CPU
203 ROM
208 Printhead control circuit

601 Discharge counter 603 Comparator 606 Prepulse selection signal latch circuit 607 Prepulse selection logic

Claims (5)

A recording head that selectively heats a heating unit provided for each of a plurality of nozzles to eject ink; a temperature detection unit that detects a temperature of the recording head;
In a recording apparatus comprising a first application pulse to be supplied to the heating means and an application pulse supply means for supplying a second application pulse to be supplied preliminarily.
It further comprises counter means for counting a value corresponding to the number of heating times of the heating means, and pulse width correcting means for correcting the pulse width of the second applied pulse based on the counting result of the counter means. Recording device. The recording apparatus according to claim 1, wherein a pulse width of the second applied pulse is smaller than a pulse width of the first applied pulse. The recording apparatus according to claim 1, wherein the pulse width correction amount by the pulse width correction unit is changed based on a detection result by the temperature detection unit. The recording apparatus according to claim 1, wherein the counter unit counts the number of times of heating for each predetermined recording range. The recording apparatus according to claim 1, wherein the counter unit is provided for each heating unit.

Images