JP2015089623A - Inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording device capable of outputting an image in which both density unevenness depending on driving order and density unevenness associated with a flow channel direction are less noticeable while using a long recording head composed of a plurality of chips.SOLUTION: Wiring is made so that impedances corresponding to chips of a plurality of chips 101 are different from each other between a chip in which a moving direction of ink in a flow channel matches a delay direction of driving and a chip in which the moving direction of the ink in the flow channel is an opposite direction to the delay direction.

Description

  The present invention relates to an ink jet recording apparatus. In particular, in a long inkjet head configured by arranging a plurality of chips on which a plurality of recording elements are arranged, in order to reduce variations in the ejection amount in the recording head due to temperature rise and electrical noise. Concerning configuration.

  An ink jet recording apparatus that applies a voltage pulse to a heating resistor provided in each recording element and ejects ink using the generated thermal energy is widely used because it can output an image with high definition and high speed. Yes. In particular, a full-line type ink jet head in which a plurality of recording elements are arranged at a high density by a distance corresponding to the width of the recording paper has rapidly become popular in recent years because it enables higher-speed output. In such a long inkjet head, in order to improve the manufacturing yield, a plurality of chips each having a smaller number of recording elements are arranged in the width direction of the paper. There are many.

  By the way, in a long inkjet head (recording head) in which ink is ejected by driving a heating resistor, a large voltage drop occurs when a large number of heating resistors are energized at once. Such a voltage drop can be mitigated by preparing a capacitor, but considering the case of a large number of simultaneous drives, such as recording a high density image, a large capacity capacitor is required and the cost increases. . For this reason, in general, a plurality of recording elements arranged on one chip are divided into a plurality of groups and time-division driving is performed, and a stable voltage application to the heating resistor is realized while suppressing a current flowing in a unit time. doing.

  Furthermore, even when such block driving is performed, if the heating resistors in the same block are driven simultaneously, electromagnetic noise due to inductive coupling is generated at the rise and fall of the current flowing through the drive power supply wiring and ground wiring. There is. Such electromagnetic noise is superimposed on the logic signal flowing through the logic signal wiring, and may cause malfunction in the logic circuit. On the other hand, in Patent Documents 1 and 2, when the heating resistors of the same block are driven, the current flowing per unit time is reduced by further shifting the timing of each heating resistor in units of nanoseconds. A configuration for suppressing the generation of electromagnetic noise is disclosed.

  On the other hand, in Patent Document 3, an ink inlet and an outlet are provided to the inkjet head in order to suppress an increase in discharge amount due to the temperature rise of the inkjet head, and each recording element is directed from the inlet to the outlet. In other words, a configuration in which ink is supplied from ink that flows in this manner is disclosed. Usually, the discharge amount of each recording element tends to increase according to the temperature of ink in the vicinity of the heating element. As in Patent Document 2, if the ink supplied to the heat generating element is constantly flowing, the temperature rise of the ink in the vicinity of the heat generating element can be suppressed, and the increase in the discharge amount can also be suppressed.

Japanese Patent No. 03333597 JP 2008-114378 A JP 2009-961 A

  By the way, in a full-line type ink jet recording apparatus using a recording head in which a large number of chips are arranged, the apparatus is relatively large, so that the wiring length from the power supply circuit to each chip in the apparatus is long, and the parasitic inductance is large. Sometimes it cannot be ignored. Specifically, when a certain amount of current flows, ringing occurs due to the influence of parasitic inductance, and the voltage applied to the heating resistor becomes unstable. When the time-division driving between blocks as described in the background section is performed, the voltage drop is suppressed, but the voltage pulse waveform becomes unstable between the blocks and is applied to each heating resistor. As a result, the ejection amount of each recording element varies. As a result, density unevenness is also confirmed in the image recorded on the paper. More specifically, the energy applied to the block driven slightly later tends to be larger than the block driven earlier, and the direction according to the drive order of the blocks in the chip is increased. Density unevenness occurs.

On the other hand, the configuration employing Patent Document 3 has an effect of suppressing the temperature rise of each individual heating element and the entire inkjet head, but the ink temperature tends to gradually increase in the path from the inlet to the outlet. It is in. Therefore, the temperature of the supplied ink varies depending on the position of the chip disposed in the ink jet head and the position where the individual recording elements are disposed in the same chip. Specifically, the discharge amount of the recording element arranged on the downstream side of the recording element upstream of the ink flow path is larger, and the image density tends to be higher on the downstream side than on the upstream side of the chip. There is.

  Such density unevenness in accordance with the driving order and density unevenness in the direction of the flow path may be emphasized by overlapping each other even if they do not cause a significant adverse effect. And since both have directionality, if the combination of the direction of the driving order and the direction of the flow path varies depending on the chip, there are a mixture of chips that cancel each other's density unevenness and chips that grow, and the same Large density unevenness occurs in the inkjet head.

  The present invention has been made to solve the above problems. Therefore, the object is to output an image in which density unevenness according to the driving order and density unevenness due to the direction of the flow path are not noticeable while using a long recording head composed of a plurality of chips. An ink jet recording apparatus is provided.

  For this purpose, the present invention provides a recording element that ejects ink by applying a predetermined voltage pulse to the heating resistor in a predetermined direction, and the position of the recording element in the predetermined direction when an equal voltage pulse is applied. An image is recorded using a recording head having a plurality of chips whose ejection amount changes with a certain tendency in accordance with a flow path for moving ink while sequentially supplying ink to the plurality of chips. An ink jet recording apparatus for recording, wherein among the plurality of chips, a chip in which the direction of ink movement in the flow path coincides with the predetermined direction, and a direction of ink movement in the flow path is opposite to the predetermined direction Wiring is performed so that the impedance corresponding to the chip is different from that of the chip in the direction.

  According to the present invention, it is possible to suppress variation in the ejection amount over the entire area of the ink jet head and output an image having a uniform density.

It is sectional drawing of the inkjet recording device which can be used for this invention. FIG. 6 is a plan view when the recording head 17 for one color is observed from the ejection port surface. FIG. 2 is a side sectional view of a recording head. It is a perspective view which shows a mode that the base substrate was laminated | stacked on the lower base substrate. FIG. 6 is a cross-sectional view of a recording head for explaining a path of a flow path. (A) And (b) is the perspective view and sectional drawing of a chip | tip. (A) And (b) is a figure for demonstrating an ink circulation system. FIG. 9 is an equivalent circuit diagram corresponding to FIG. 8. (A) And (b) is a figure which shows the discharge amount fluctuation | variation in a chip | tip. (A) And (b) is the wiring block diagram which provided the capacitor | condenser in the middle of the cable. FIG. 11 is an equivalent circuit diagram corresponding to FIG. 10. It is the schematic for demonstrating the wiring structure in a chip | tip. FIG. 4 is a diagram illustrating an arrangement state of dots formed on a recording sheet. (A)-(c) is a timing chart of various signals. (A) And (b) is a figure which compares the magnitude | size of a dot according to the position of a capacitor | condenser. It is a figure which shows the mode of the discharge amount fluctuation | variation accompanying the arrangement | positioning state of a chip | tip, and the heat storage of a flow path. It is a figure which shows the mode of the discharge amount fluctuation | variation accompanying a chip | tip arrangement state and ringing. It is a figure which shows the discharge amount fluctuation | variation which combined the discharge amount fluctuation | variation accompanying the heat storage of a flow path, and the discharge amount fluctuation | variation accompanying ringing. (A) And (b) is a wiring block diagram and the comparison figure of a capacitor | condenser. It is a figure which shows the discharge amount fluctuation | variation at the time of employ | adopting the wiring structure of this invention.

(First embodiment)
FIG. 1 is a cross-sectional view for explaining the internal configuration of an ink jet recording apparatus 18 (hereinafter simply referred to as a recording apparatus) that can be used in the present invention. The recording device 18 is connected to a host device 16 such as a personal computer, and records an image by an inkjet method according to image data supplied from the host device 16. In the recording apparatus 18, the control unit 13 includes a controller 15 that controls the entire recording apparatus.

  The sheet supply unit 1 stores two rolls R1 and R2, and alternatively draws out a sheet (paper) and supplies it to the conveyance path. The number of rolls that can be stored is not limited to two, and may be one, or three or more.

  The decurling unit 2 is a unit that reduces curling (warping) of a sheet supplied from the sheet supply unit 1 or a reversing unit 9 described later. In the decurling unit 2, two pinch rollers are pressed against one driving roller to give a warp in a direction opposite to the curl to the sheet. By passing through the decurling unit 2, curl wrinkles in the sheet supply unit 1 and the reversing unit 9 are reduced, and the sheet is conveyed smoothly.

  The skew correction unit 3 is a unit that corrects skew (inclination with respect to the traveling direction) of the sheet that has passed through the decurling unit 2. By pressing the sheet end on the reference side against the guide member, the sheet is oriented so as to advance straight.

  The printing unit 4 records an image by ejecting ink from the recording head unit 14 on the conveyed sheet. The recording head unit 14 of the present embodiment is configured by preparing a full-line type recording head 17 described in FIG. 2 for each ink color and arranging the plurality of recording heads 17 in parallel in the X direction. In this example, there are four recording heads corresponding to four colors of C (cyan), M (magenta), Y (yellow), and K (black). The number of colors and the number of recording heads are not limited to four. Each color ink is supplied from an ink tank, which will be described later, to the recording head unit 14 via an ink tube. The printing unit 4 is provided with a plurality of conveyance rollers for conveying the sheet, a platen for supporting the sheet from below, and the like so that the sheet in the area facing each recording head 17 is smoothed.

  The inspection unit 5 includes a CCD image sensor and a CMOS image sensor, and is a unit that optically reads an inspection pattern and an image on a sheet recorded by the print unit 4. The read information is transferred to the control unit 13 to determine the state of the nozzles of the recording head 17, the sheet conveyance state, the position of the image, and the like.

  The cutter unit 6 is a unit that cuts an image in accordance with a cut mark recorded on a sheet. However, when performing double-sided recording, the cutter unit 6 only cuts the trailing edge of the last image on the first side, and the continuous sheet is conveyed to the information recording unit 7 without being cut. The information recording unit 7 records information such as a serial number and date related to the recorded image as characters and codes in the blank area of the image sheet. The drying unit 8 is a unit for drying the applied ink in a short time.

  The reversing unit 9 is a unit that temporarily winds a continuous sheet on which recording on the first side is completed when performing double-sided recording. The continuous sheet on which the recording on the first surface has been completed is gradually wound around a rotating body (drum) 9a that rotates counterclockwise. The rotating body 9a stops when it is wound up to the rear end of the continuous sheet, and then rotates in the opposite direction, that is, clockwise. As a result, the continuous sheet is sent to the decurling unit 2. In the decurling unit 2, the sheet is corrected in a direction that reduces the warp when it is wound up by the rotating body 9 a.

  In the path from the decurling unit 2 to the printing unit 4, the continuous sheet is in a state where the front and back and the front and rear end portions are reversed. That is, the second surface faces the recording head 17, and the rear end portion during the first surface recording is conveyed as the leading end portion.

  The discharge conveyance unit 10 conveys the cut sheet cut by the cutter unit 6 and dried by the drying unit 8 to the sorter unit 11. The sorter unit 11 sorts the recorded cut sheets into groups such as by size and discharges them to the respective discharge ports. A tray 12 for receiving cut sheets is prepared at each discharge port, and the cut sheets are stacked on one of the trays 12.

  FIG. 2 is a plan view when the recording head 17 for one color is observed from the ejection port surface. In each of the chips 101 formed of silicon, a plurality of recording element arrays 102 in which a plurality of recording elements are arranged at a predetermined pitch in a predetermined direction (here, the x direction) are arranged in four lines in the y direction intersecting this. Has been placed. Eight such chips 101 are arranged on the lower base substrate 118 so that the recording elements are continuous in the x direction while being alternately displaced in the y direction. In the present embodiment, it is assumed that Chip0 to Chip7 are arranged as illustrated. The ink ejected from one recording head 17 is the same ink. With such a recording head 17 fixed to the recording head unit 14, a desired image can be recorded on the recording paper by conveying the sheet serving as the recording paper in the y direction. Each chip 101 has an effective width of 1 inch in the x direction, and eight chips can cope with a paper width of up to 8 inches. Electrode units 100 are provided at both ends of each chip 101 in the x direction, and are electrically connected to the flexible wiring board 106 extending from the control unit 13 by wire bonding. Such a recording head 17 is fixed to the recording head portion 14 of the apparatus main body through a fixing hole 150.

  FIG. 3 is a side sectional view of the recording head 17. In the position where the chip 101 is arranged on the lower base substrate 118 described with reference to FIG. 2, the common liquid chamber 110 for supplying ink in common to the printing elements in the chip 101 and the four printing element rows 102 are respectively provided. A slit 104 for distributing ink is formed. A base substrate 111 is laminated on the lower base substrate 118, and the common liquid chamber 110 is expanded.

  FIG. 4 is a perspective view showing a state in which the base substrate 111 is stacked on the lower base substrate 118. It can be seen that the eight common liquid chambers 110 are formed in accordance with the positions of the eight chips 101.

  Referring to FIG. 3 again, a head liquid chamber member 112 is further laminated on the base substrate 111. The head liquid chamber member 112 is a member in which a flow path 109 for supplying ink cyclically to each of the eight chips is formed.

  FIG. 5 is a cross-sectional view of the recording head 17 for explaining the path of the flow path 109. The ink supplied from the main tank of the apparatus main body is received in the recording head from the ink inlet 113 formed in the head liquid chamber member 112, and then the surface parallel to the discharge port surface (xy) along the flow path 109. Move the plane. Then, while being sequentially supplied to each of the eight chips 101 arranged in the x direction, ink that has not been used for recording is discharged from the ink outlet 114 to the outside of the recording head. At this time, as can be seen from FIG. 3, the ink flow path 102 from the ink inlet 113 to the ink outlet 114 has two paths. Both of them are fed from two ink inlets 113 installed in the center of the recording head 17 in the x direction, separated in the opposite direction of the x direction, and supplied to each of the four chips. It is discharged from the outlet 114. In the path from the ink inlet 113 to the ink outlet 114, no resistance member such as a filter is provided. Therefore, the ink in the flow path 109 can move from the ink inlet 113 to the ink outlet 114 without pressure loss.

  Returning to FIG. The ink moving through the flow path 109 flows into the common liquid chamber 110 corresponding to each chip 101 via the filter 151 supported by the filter support member 150 on the base substrate 111. The filter member 151 is formed by weaving stainless steel fine wires, and foreign matters that cause clogging in the recording element are blocked here. In addition, in each chip 101, a sufficiently large size is prepared so as not to impair the required flow rate even when the maximum number of printing elements simultaneously perform the ejection operation.

  The lower base substrate 118, the base substrate 111, and the head liquid chamber member 112 described above are integrated by a fixed shaft 120 that passes through them. Further, a flexible wiring substrate 106 is disposed from the discharge port surface side of the lower base substrate 118 to the side surface of the head liquid chamber member 112 so as to cover them, and drive signals and electric power necessary for the discharge operation of individual recording elements are provided. Supply.

  6A and 6B are a perspective view and a cross-sectional view of the chip 101. FIG. Referring to FIG. 6A, on the surface of the chip 101, recording element arrays 102 in which a plurality of recording elements 20 are arranged so as to be continuous at a predetermined pitch in the x direction are further arranged in four lines in the y direction. They are arranged in parallel. The chip 101 has a configuration in which the nozzle member 21 is stacked on the element substrate 22. An alignment mark 23 is formed on the surface end of the chip 101 as a mark when the chip 101 is positioned on the lower base substrate 118.

  FIG. 6B is a cross-sectional view taken along the line AA in FIG. In the element substrate 22, slits 104 for supplying the ink supplied from the common liquid chamber 110 to each recording element array 102 are formed for each recording element array 102. Individual recording elements 20 are formed on the nozzle member 21. In the present embodiment, one recording element 20 includes an ink path 211, a foaming chamber 212, and a heating resistor 221. The ink supplied from each slit 104 is guided to the ink path 211 from the foaming chamber 212 corresponding to each recording element, and forms a meniscus in the vicinity of the ejection port. When the heating resistor 221 is applied according to the recording data, film boiling occurs in the ink in the foaming chamber 212, and the ink in the ink path is ejected from the ejection port by the growth energy of the generated bubbles. The ink consumed for the ejection is newly replenished from the slit 104.

  Incidentally, since the recording head 17 of the present embodiment performs the ejection operation using the thermal energy applied to the heating resistor 221, the temperature of the chip 101 rises as the ejection operation continues. At this time, such a temperature rise is suppressed to some extent by the ink supplied from the flow path 109, but at the same time, heat from the chip 101 is conducted to the ink flowing through the flow path 109. That is, as the number of ejections on the chip 101 increases, the amount of heat increases, and the temperature of ink flowing while supplying ink to each chip in order increases gradually from upstream to downstream. Usually, even when the same drive voltage is applied to the heating resistor 221, it is known that bubbles grow larger and the ejection amount increases as the ink temperature increases. That is, the discharge amount of the chip located on the downstream side is larger than the discharge amount of the chip located on the upstream side with respect to the flow path 109.

  However, if a plurality of channels 109 having the same channel length, that is, the number of chips for supplying ink, are prepared as in this embodiment, such a temperature rise can be suppressed as small as possible. Further, there is a concern that the temperature difference between the two flow paths and the difference in the discharge amount will increase as the flow proceeds downstream, but the position of the ink inlet to which ink of substantially the same temperature is supplied as in the present embodiment is set in the x direction. If it is provided at the center of the image, it is possible to prevent an extreme density difference from being adjacent on the image.

  FIGS. 7A and 7B are diagrams for explaining the ink circulation system in the recording apparatus 18 in the present embodiment. Basically, the ink is circulated between the recording head 17 and the sub-tank 201 having a relatively small capacity installed in the apparatus. When replenishing the ink in the sub tank that is consumed by the recording operation, the ink stored in the large-capacity main tank 161 installed in the apparatus is supplied to the sub tank 201 through the pump 200.

  The ink in the sub tank 201 is sent to the ink inlet 113 of the recording head 17 via the pump 202 and is collected from the ink outlet 114 via the pump 203. At this time, in order to prevent inadvertent ink leakage from the recording element 20, the flow path 109 in the recording head 17 is set slightly negative by adjusting the driving force of the pump 202 and the pump 203. It is preferable. The ink that has flowed out of the ink outlet 114 is adjusted to a predetermined temperature by passing through the temperature adjusting device 133, and is then collected again in the sub tank 201.

  FIG. 7B is a schematic diagram for explaining the structure of the temperature adjustment device 133. The temperature adjusting device 133 contains a liquid L maintained at 30 degrees, and a stainless steel ink path 140 for guiding the ink is spirally held therein. The ink flowing out from the ink outlet 114 of the recording head 17 enters the ink path 140 via the inlet 144 and is adjusted to 30 degrees by passing through the spiral path regardless of whether the temperature is high or low. Then, it is discharged from the outlet 145.

  FIG. 8 is a diagram for explaining a wiring configuration for the recording head 17. The flexible wiring board 106 electrically connected to each chip 101 is connected to the head control board 300 of the apparatus main body by two cables 301 and 302. Cables 301 corresponding to Chip 0 to Chip 3 are connected to the head control board 300 by the first connector 303. Cables 302 corresponding to Chip 4 to Chip 7 are connected to the head control board 300 by the second connector 304.

  A voltage (VH) and a ground (GNDH) for driving the recording element 20 of each chip 101 are generated by the power supply circuit 305 of the head control board 300, and the individual power supply circuit 306 and the ground wiring 307 are used for the individual power supply circuit 305. It is supplied to the chip 101. Here, the drive power supply wiring 306 is classified into a drive power supply wiring 306-1 on the head control board 300, a drive power supply wiring 306-2 on the cable 301, and a drive power supply wiring 306-3 on the flexible wiring board 106. I can think of it. The ground wiring 307 can be classified into a ground wiring 307-1 on the head control board 300, a ground wiring 307-2 of the cable 301, and a flexible wiring board 307-3.

  The head control board 300 is provided with a capacitor 308 for stabilizing the drive voltage (VH). Since the capacitor 308 is relatively thick, a certain amount of space is required above the installation area. Therefore, it is difficult to provide in the vicinity of the chip whose distance to the recording paper is about 1 mm. In the example of FIG.

  FIG. 9 is an equivalent circuit diagram of the drive power supply wirings 306-1 to 306-3 and the ground wirings 307-1 to 307-3 corresponding to one chip 101 in FIG. In each of the drive power supply wirings 306-1 to 306-3 and the ground wirings 307-1 to 307-3, there are a parasitic resistance 309 and a parasitic inductance 310 proportional to the respective wiring lengths. In the figure, the parasitic resistance in the drive power supply wiring 306-1 and the ground wiring 307-1 is 309-1, and the parasitic inductance is 310-1. Further, the parasitic resistance in the drive power supply wiring 306-2 and the ground wiring 307-2 is 309-2, and the parasitic inductance is 310-2. Further, the parasitic resistance in the drive power supply wiring 306-3 and the ground wiring 307-3 is shown as 309-3, and the parasitic inductance is shown as 310-3.

  In the wiring for the full-line type ink jet head as in the present embodiment, the length of the drive power supply wiring 306-3 and the ground wiring 307-3 disposed on the flexible wiring board 106 is 100 mm or more. Further, due to restrictions on the arrangement of the head control board 300 and the recording head unit 14 in the recording apparatus, the wiring lengths of the drive power supply wiring 308-2 and the ground wiring 309-2 arranged in the cable 301 are 200 mm or more. Therefore, the wiring length from the capacitor 308 disposed on the head control board 300 to the chip 101 becomes 300 mm or more, and there is a concern about the influence of parasitic inductance in this region. Specifically, the sum of the parasitic inductances 310-2 and 310-3 from the capacitor 308 to the chip 101 is a value on the order of several hundreds nH. When a large current flows through the parasitic inductance of several hundreds of nH, large ringing occurs, and the voltage applied to the heating resistor becomes unstable.

In general, ringing depends on impedance characteristics in a series circuit of LCRs. For example, R is a parasitic resistance, ω is an AC frequency, L is a parasitic inductance, i is a current, C is a capacitor capacitance, and Z is an impedance characteristic. In this case, the impedance characteristic Z of this circuit is Z = R + iωL + 1 / iωC
Can be expressed as That is, if the capacitor capacitance C can be increased, the impedance characteristic Z can be reduced and ringing can be suppressed. In other words, it can be said that it is effective to place a capacitor at a position close to a place where the ringing is most desirably suppressed.

  10A and 10B are wiring configuration diagrams in a state where the capacitor 308 (the collective substrate 311 in this example) is moved from the head control substrate 300 to the middle of the cable 301 with respect to the wiring configuration of FIG. . FIG. 10A is an overall view, and FIG. 10B is a wiring configuration diagram showing details of the collective substrate 311. Four capacitors 308 are provided on each of the two aggregate substrates 311, and one capacitor 308 corresponds to one chip.

  FIG. 11 is an equivalent circuit diagram of the drive power supply wirings 306-1 to 306-3 and the ground wirings 307-1 to 307-3 corresponding to one chip 101 in FIG. Compared to FIG. 9, the parasitic inductance from the capacitor 308 to the chip 101 is reduced by the amount the capacitor 308 is closer to the chip 101, and the influence of ringing can be suppressed.

  Thus, by providing the capacitor 308 near the chip on the cable 301, the influence of ringing due to parasitic inductance can be suppressed, and the energy applied to the chip 101 can be stabilized. However, it is difficult to dispose the capacitor 308 in the middle of the cable 301 as a single unit, and in fact, a new member such as the collective substrate 311 is disposed as shown in FIG. As a result, there is a concern that the manufacturing cost increases.

  FIG. 12 is a schematic diagram for explaining a wiring configuration in one chip 101. Here, the 256 heat generating resistors are divided into 32 groups of 32 groups, group 0 to group 31. In the drawing, the heating resistors included in group 0 are indicated by reference numerals 400-0 to 400-31, and the heating resistors included in group 1 are indicated by reference numerals 401-0 to 401-31. The current to each of the heating resistors 400-0 to 431-31 is supplied by energizing the electrode pad VH maintaining a predetermined voltage and the ground electrode pad GNDH. At this time, the timing of energization, that is, the timing of switching ON / OFF of the transistors 500-0 to 531-31 corresponding to the individual heating resistors is made different between the groups 0 to 31.

  Specifically, the heat enable signal HE generated by a HE generation circuit (not shown) is delayed by 32 nanoseconds in 32 stages in the order of HE-31 to HE-0 by the delay circuit 501, and the first control is performed. Input to gates 600-0 to 631-31. In addition to the heat enable signal (HE), the recording data latched by the data latch circuit is input to the first control gates 600-0 to 631-31, and becomes active when both of these signals are turned on. . In addition to the active signal from the first control gates 600-0 to 631-31, the signals ENB0 to ENB31 output from the decoder 503 are input to the second control gates 700-0 to 731-31. In the present embodiment, ENB signals are output from the decoder 503 at intervals of about 10 microseconds in the order of ENB31 → ENB0. Then, at the timing when both of these signals are input, a voltage pulse is applied to the heating resistors 400-0 to 431-31 via the transistors 500-0 to 531-31, and a current flows. Note that the delay signals HE-0 to HE-31 generated by the delay circuit 501 are reset at the timing when the decoder 503 outputs a new ENB, and return to HE-31.

  Based on the above configuration, a specific driving order will be described. When the decoder 503 outputs ENB signals at intervals of about 10 microseconds in the order of ENB31 → ENB30 →... → ENB0, the second control gates 700-0 to 731-31 have 7 **-31 in each group. → 7 **-30 ... → 7 **-0 becomes active at the same interval in this order. On the other hand, when the delay circuit 501 outputs HE signals at intervals of several nanoseconds in the order of HE-31 → HE-30 →... → HE-0, the first control gates 600-0 to 600-31 are It becomes active in the order of group 31 → group 30 ... → group 0. Therefore, among the 256 second control gates, the second control gate 631-31 to which the ENB 31 of the group 31 is input is activated first, and the corresponding heating resistor 431-31 is driven first. The Thereafter, at intervals of several nanoseconds, the heating resistors 4 **-31 included in different groups are sequentially driven in the order of 430-31 → 429-31, 428-31... 400-31. .

  As described above, when the driving of the heating resistors 4 **-31 is completed for all the groups, the decoder 503 ends the output of the ENB 31 and starts the output of the ENB 30. At the same time, the delay circuit 501 also resets the output and returns to the HE-31 output again. Accordingly, the heating resistors 4 **-30 included in different groups are sequentially driven at intervals of several nanoseconds in the order of 431-30 → 430-30 → 429-30... → 400-30. By repeating the above-described steps for all ENB signals, all of the heating resistors 400-0 to 431-31 are driven in sequence, so that the ejection operation for one line in the chip 101 is performed.

  FIG. 13 is a diagram illustrating an arrangement state of dots formed on a recording sheet when ink is ejected in the order described above. In the figure, the discharge ports corresponding to the heating resistors 400-0 to 431-31 are divided into groups 0 to 31 and shown in one row. In the figure, since the paper is transported at a constant speed in the y direction, dots formed by ink ejected later are landed on the right side. During the driving of the first block ENB31 by the decoder 501, 32 dots are recorded while shifting slightly from the left end to the right in the order of 431-31 → 430-31 →... → 400-31. On the right side, dots recorded during driving of the next block ENB31 are arranged in the order of 431-30 → 430-30 →... → 400-30.

  14A to 14C are timing charts of various signals. FIG. 14A is a diagram showing a latch signal LT for sequentially switching the driving of 32 blocks and an HE signal as a driving pulse for one column. Note that the column indicates a time that is secured for recording all dots by the recording elements arranged on the chip 101 one by one.

  FIGS. 14B and 14C show the driving pulses HE-31 to HE-0 delayed by the delay circuit 501 in 32 stages, and the waveforms of the current and voltage that flow along with this. 14B shows a case where the capacitor 308 is arranged on the head control board 300 as shown in FIGS. 8 and 9, and FIG. 14C shows a collective board provided in the middle of the cable 301 as shown in FIGS. A case where a capacitor 308 is arranged on 311 is shown. In the present embodiment, delay signals are generated in the order of HE-31 → HE-30 →... → HE-0 with respect to the HE signal generated by the HE generation circuit, and the energization to the power generation element is performed in this order. And the discharge operation is executed. In the figure, VH represents a voltage waveform of VH, GNDH represents a voltage waveform of GNDH, and IH represents a current waveform of a current flowing through VH.

  Here, the period t1 is a period in which energization to the 32 heating resistors having different groups is started in order, and the value of IH gradually increases. In the configuration in which the capacitor 308 is disposed on the head control board 300 at the time of the rise of the IH, the ringing as shown in FIG. 14B is caused in the VH and GNDH due to the influence of the parasitic inductance caused by the IH flowing through the drive power supply wiring. Occurs. Specifically, undershoot occurs in the VH voltage waveform, and overshoot ringing occurs in the GNDH voltage waveform. For this reason, the voltage applied to both ends of the heating resistor in the period t1 is lower than that in the period t2, and the current flowing through the heating resistor is also reduced.

  On the other hand, in the configuration in which the capacitor 308 is arranged on the collective substrate 311 provided in the middle of the cable 301, as shown in FIG. 14C, ringing of overshoot and undershoot is suppressed. Therefore, fluctuations in the voltage applied to both ends of the heating resistor during the period t1 are stabilized, and variations in the current flowing through the heating resistor are suppressed.

  The period t3 is a period in which energization of the 32 heating resistors is sequentially terminated, and the value of IH gradually decreases. Even when this IH falls, in the configuration in which the capacitor 308 is arranged on the head control board 300, as shown in FIG. 14B, VH and GNDH are affected by the parasitic inductance caused by the IH flowing through the drive power supply wiring. Ringing occurs. Specifically, undershoot occurs in the VH voltage waveform, and overshoot ringing occurs in the GNDH voltage waveform. For this reason, the voltage applied to both ends of the heating resistor in the period t3 is higher than that in the period t2, and the current flowing through the heating resistor is also increased.

  On the other hand, in the configuration in which the capacitor 308 is arranged on the collective substrate 311 provided in the middle of the cable 301, as shown in FIG. 14C, ringing of overshoot and undershoot is suppressed. Therefore, also in the period t3, the fluctuation of the voltage applied to both ends of the heating resistor is stable, and the variation of the current flowing through the heating resistor can be suppressed.

  As described above, when the capacitor 308 is arranged on the head control board 300, the energy generated by the heating resistor 431-31 that is driven first among the heating resistors 400-31 to 431-31 is the smallest. Become. The energy generated by the heating resistor 400-31 that is driven last is the largest. As a result, even within the same block (that is, within the same ENB signal), the ink ejection amount of the recording element including the heating resistor 431-31 driven first is the smallest, and the heating resistor 400- driven last. The ink discharge amount of the recording element having 31 is the largest. Such a magnitude relationship between the discharge amounts can occur equally in all ENBs. Therefore, in the entire chip 101, the discharge amount gradually increases from one end (group 31) to the other end (group 0). On the other hand, in the configuration in which the capacitor 308 is arranged on the collective substrate 311 provided in the middle of the cable 301, the overshoot and undershoot ringing can be suppressed for all the heating resistors. Is stable.

  FIGS. 15A and 15B show a configuration in which the capacitor 308 is disposed on the head control board 300 and a configuration in which the capacitor 308 is disposed on the collective substrate 311 provided in the middle of the cable 301. It is a figure which compares the magnitude | size of the dot made. When the capacitor 308 is arranged on the head control board 300, as shown in FIG. 15A, the size of dots recorded in the same group is substantially equal, but the size of dots recorded in different groups is They are different from each other. In the recording head 17 of the present embodiment, the recording heads 17 are grouped into 32 groups with respect to the arrangement direction (x direction) of the recording elements, and the individual heating resistors are driven in the order from the group 31 to the group 0. Therefore, the dot recorded in the group 31 recorded on the right side of the figure is the smallest, and the dot increases as it moves to the left. As a result, the area recorded at the left end of the chip has a higher density than the area recorded at the right end of the chip.

  On the other hand, in the configuration in which the capacitor 308 is arranged on the collective substrate 311 provided in the middle of the cable 301, as shown in FIG. 15B, the sizes of the dots are uniform in all the groups. Therefore, there is no difference in density at both ends of the chip 101, and a uniform density can be obtained over the entire area.

  Hereinafter, the fluctuation state of the ejection amount of the entire recording head configured by arranging eight chips will be described.

  FIG. 16 is a diagram illustrating an arrangement state of the eight chips Chip0 to Chip7 and how the discharge amount varies with heat storage in the flow path 109. As described above, the ink adjusted to 30 degrees flows in from the center of the chip and gradually rises in temperature while proceeding separately on the left and right. Therefore, the discharge amount is also the smallest in the two central chips (Chip 3 and Chip 4) and increases as it goes outward.

  Further, such a deviation in the discharge amount with respect to the flow path direction (x direction) also exists in each of the chips 101. Even in the same chip, the recording element located on the downstream side with respect to the recording element located on the upstream side with respect to the flow path 109 is supplied with higher temperature ink and the discharge amount is also increased. However, in any of the chips, the discharge amount fluctuation in the chip has a similar tendency that the discharge amount at the center is large and the discharge amount at the end is small. This is because heat is more easily transmitted to the alumina member located behind the tip end than the center. As a result of synthesizing the elements described above, the discharge amount variation accompanying heat storage in the flow path 109 has a symmetrical shape as shown in FIG.

  On the other hand, FIG. 17 is a diagram illustrating an arrangement state of eight chips Chip0 to Chip7 and a state of a discharge amount variation accompanying ringing in the configuration in which the capacitor 308 is disposed on the head control board 300. As shown in FIG. 15A, since the discharge amount increases according to the driving order of the heating resistors, the discharge amount changes with a predetermined inclination in each chip.

  18 is a diagram illustrating the discharge amount fluctuation in a state in which the discharge amount fluctuation accompanying the ringing shown in FIG. 17 is combined with the discharge amount fluctuation accompanying the heat storage of the flow path 109 shown in FIG. In the figure, the broken line indicates the discharge amount fluctuation when only the heat storage in the flow path 109 is taken into account, and this coincides with the discharge amount fluctuation accompanying the heat storage in the flow path 109 shown in FIG. On the other hand, the solid line shows the output amount fluctuation when the discharge amount fluctuation accompanying ringing shown in FIG. 17 is added to the discharge amount fluctuation shown by the broken line.

  About the discharge amount fluctuation | variation (broken line) accompanying the thermal storage of the flow path 109, it has changed substantially symmetrically. In more detail about each chip, the discharge amount on the left side is larger than that on the right side in Chip 0 to Chip 3 on the left side from the center, but the discharge amount on the right side is larger than that on the right side in Chip 4 to Chip 7 on the right side than the center. It has become. On the other hand, the discharge amount fluctuation accompanying ringing is such that the discharge amount on the Chip 0 side is larger than that on the Chip 7 side in all the chips. As a result, in Chip 0 to Chip 3 on the left side of the center, the discharge amount fluctuation accompanying heat accumulation in the flow path 109 and the discharge amount fluctuation accompanying ringing increase, and the discharge amount fluctuation becomes larger than the broken line. On the other hand, in Chip 4 to Chip 7 on the right side of the center, the discharge amount fluctuation accompanying heat accumulation in the flow path 109 and the discharge amount fluctuation accompanying ringing cancel each other out, and the discharge amount fluctuation is suppressed as compared with the broken line, so that there is almost no problem. Yes. In other words, with respect to Chip 4 to Chip 7 on the right side of the center, ringing occurs, so that the discharge amount fluctuation accompanying heat accumulation in the flow path 109 is suitably suppressed.

  In view of the above situation and the influence on the cost, the present inventors are in the middle of the cable 301 only for the left four chips where the discharge amount fluctuation accompanying heat accumulation in the flow path and the discharge amount fluctuation accompanying ringing increase. The inventor has found that it is effective to dispose the collective substrate 311 on the surface.

FIGS. 19A and 19B are diagrams comparing the wiring configuration diagram employed in the present embodiment with the types of capacitors employed and their effects. Referring to FIG. 19A, the collective substrate 311 on which the capacitor 308 is mounted is arranged in the middle of the cable 301 only for the four chips of Chip0 to Chp3. Moreover, in FIG.19 (b), the impedance characteristic with respect to alternating frequency is shown for every kind of capacitor | condenser. In the figure, curve A shows the characteristics when no capacitor is provided. A curve B indicates characteristics when a general electrolytic capacitor such as an aluminum electrolytic capacitor or a tantalum electrolytic capacitor is used as the capacitor. Furthermore, curve C shows the case where a multilayer ceramic chip capacitor is used as the capacitor. In the circuit of this embodiment, the frequency band in which ringing occurs is in the range of 2.0 × 10 ^{6 to} 2.5 × 10 ⁶ [hz] surrounded by a broken line. Focusing on this area, the curve A (when no capacitor is provided) has the highest impedance characteristic, the curve B (when an electrolytic capacitor is used) is the next, and the curve C (chip) has the lowest impedance characteristic. When using a capacitor). Therefore, in this embodiment, it is assumed that the collective substrate 311 on which chip capacitors are mounted is arranged in the middle of the cable 301.

  FIG. 20 is a diagram showing the discharge amount fluctuation when the wiring configuration shown in FIG. 19 is adopted. Compared with FIG. 18 in which the collective substrate 311 is not arranged in the middle of the cable 301, it can be seen that in the four chips on the right side, the influence due to ringing is suppressed and only the discharge amount fluctuation due to heat accumulation in the flow path remains. On the other hand, in the four chips on the left side, similarly to FIG. 18, the discharge amount fluctuation (broken line) accompanying the heat accumulation in the flow path is further suppressed. As a result, it is possible to suppress fluctuations in the discharge amount over the entire area of the inkjet head and output an image having a uniform density.

  In the above, as shown in FIG. 19, among the two cables 301, the collective substrate 311 is only applied to Chip 0 to Chip 3 in which the discharge amount fluctuation accompanying heat accumulation in the flow path and the discharge amount fluctuation accompanying ringing increase. It was explained in a form that is arranged on the other side. However, the present invention is not limited to such a form. A second capacitor having a smaller capacity than the first capacitor for Chip 0 to Chip 3 is installed on the aggregate substrate 311 for Chip 4 to Chip 7 while the aggregate substrate 311 is arranged on either side. It is good also as a form to do. In addition, it is possible to adjust the impedance characteristics of the power transmission path by making the frequency characteristics of both capacitors different. Furthermore, while preparing the collective substrate 311 having the same form, it is possible to adjust the influence of the parasitic inductance by changing the installation position in the cable 301 and appropriately set the impedance characteristics of both. In this case, a position closer to the chip than the collective substrate 311 for Chip 4 to Chip 7 in which Chip 0 to Chip 3 where the discharge amount variation accompanying heat accumulation in the flow path and the discharge amount variation accompanying ringing increase increases. Will be distributed. Furthermore, in the above description, the impedances of the two are made different depending on the position and type of the capacitor. However, by appropriately providing the first resistor and the second resistor having different resistance values in each path, these can be appropriately set. It can be adjusted. In any case, the wiring is different so that different impedance is obtained on the side where the discharge amount fluctuation accompanying heat accumulation in the flow path and the discharge amount fluctuation accompanying ringing increase and cancel each other, resulting in the recording head It is within the scope of the present invention if the variation in the discharge amount over the entire area can be suppressed.

  In the above description, the full-line type ink jet head as shown in FIG. 1 has been described as an example. However, the present invention is not limited to such a configuration. If a relatively long ink jet head is used by combining a plurality of chips, the effects of the present invention can be obtained even when mounted on a serial type recording apparatus.

17 Recording head
18 Inkjet recording device
20 recording elements
101 chips
109 flow path
221 Heating resistor
301 cable
308 capacitor

Claims (10)

Recording elements for ejecting ink by applying a predetermined voltage pulse to the heating resistor are arranged in a predetermined direction, and when an equal voltage pulse is applied, the recording element has a certain tendency according to the position in the predetermined direction With a plurality of chips whose discharge amount changes with
A flow path for moving ink while sequentially supplying ink to the plurality of chips;
An inkjet recording apparatus that records an image using a recording head having
Of the plurality of chips, a chip in which the direction of ink movement in the flow path coincides with the predetermined direction, and a chip in which the direction of ink movement in the flow path is opposite to the predetermined direction, An inkjet recording apparatus, wherein wiring is performed so that impedances corresponding to chips are different.   With the ringing generated by sequentially shifting the timing of applying the voltage pulse to the plurality of heating resistors arranged on the chip with respect to the predetermined direction, the ejection amount of the recording element is brought to a position in the predetermined direction. 2. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus changes with a certain tendency. In the recording head,
The flow path is composed of two flow paths that move ink in opposite directions to the predetermined direction while sequentially supplying ink to the same number of chips among the plurality of chips.
Of the two flow paths, the chip to which ink is supplied from one flow path and the chip to which ink is supplied from the other flow path are wired so as to have different impedances. The ink jet recording apparatus according to claim 1 or 2.   A capacitor is provided for the wiring corresponding to the chip in which the direction of ink movement in the flow path coincides with the predetermined direction, and it corresponds to the chip in which the direction of ink movement in the flow path is opposite to the predetermined direction. 4. The ink jet recording apparatus according to claim 1, wherein the wiring impedance is made different by not providing the capacitor.   A first capacitor is provided for the wiring corresponding to the chip whose ink movement direction matches the predetermined direction, and the ink movement direction in the flow path is opposite to the predetermined direction. 4. The wiring according to claim 1, wherein the wiring corresponding to the chip is provided with a second capacitor having a capacitance different from that of the first capacitor, whereby the impedance of the wiring is made different. 5. The ink jet recording apparatus described.   A first capacitor is provided for the wiring corresponding to the chip whose ink movement direction matches the predetermined direction, and the ink movement direction in the flow path is opposite to the predetermined direction. 4. The wiring according to claim 1, wherein the wiring corresponding to the chip has a wiring impedance different by arranging a second capacitor having a frequency characteristic different from that of the first capacitor. 5. Inkjet recording apparatus.   A first capacitor is provided for the wiring corresponding to the chip whose ink movement direction matches the predetermined direction, and the ink movement direction in the flow path is opposite to the predetermined direction. 4. The wiring corresponding to a chip has a wiring impedance different by disposing a second capacitor at a position farther from the chip than the first capacitor. 2. An ink jet recording apparatus according to item 1.   8. The capacitor according to claim 4, wherein the capacitor is disposed on a substrate provided in the middle of a cable positioned between the chip and a head control substrate provided in a main body of the ink jet recording apparatus. The inkjet recording apparatus according to any one of the above.   For the wiring corresponding to the chip whose ink movement direction in the flow path coincides with the predetermined direction, a first resistor is provided, and the ink movement direction in the flow path is opposite to the predetermined direction. 4. The ink jet recording according to claim 1, wherein the wiring corresponding to the chip is provided with a second resistance different from the first resistance, whereby the impedance of the wiring is made different. 5. apparatus.   10. The recording head according to claim 1, wherein the recording head is a full-line recording head, and records an image by conveying a sheet in a direction intersecting the predetermined direction with respect to the recording head. 2. An ink jet recording apparatus according to item 1.