JP2008068443A - Inkjet recording apparatus and recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus which can detect a defect of signal connection with the recording head without increasing cost by remarkably adding neither circuits nor signal lines, and can avoid damage to the recording head and can prevent abnormality and failure of the recording head from occurring by stopping to drive the recording head when the defect is detected, and to provide the recording head. <P>SOLUTION: The recording head which is dividedly driven has a latch circuit for storing data of a driving block driven just before and a latch circuit for storing data of a driving block to be driven from now, and has a comparator for comparing outputs of these two latch circuits. When they are judged to be the same by the comparator, by gating heat enabling (corresponding to heat pulse driven), it is prohibited that the same driving block is continuously driven. In addition, by returning the gated heat enabling to a printer main body, the abnormality can be sensed by a printer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that forms an image on a recording medium by ejecting ink from a recording head. In particular, the present invention relates to a technique for preventing malfunction due to an error signal to a recording head.

  Ink jet recording apparatuses generally include serial type recording apparatuses and line type recording apparatuses.

  In a serial type recording apparatus, a recording head attached to a carriage so that a plurality of recording elements (nozzles) arranged in a direction parallel to a recording medium conveyance direction (sub-scanning direction) is arranged is perpendicular to the sub-scanning direction. By scanning in the (main scanning direction) and driving the recording head according to the supplied image data, printing for one band is performed on the recording medium. Then, a desired image is formed on the recording medium by repeating the operation of printing the next one band on the recording medium stopped after the conveyance (pitch conveyance). In a line type recording apparatus, a recording head is arranged so that a plurality of recording elements (nozzles) arranged in a direction perpendicular to the recording medium conveyance direction are arranged, and the recording head is arranged according to image data while conveying the recording medium. Printing is performed by driving, conveyance is stopped, and image printing is also terminated.

  A color image is printed by arranging such a recording head for each ink color and mounting it on a carriage. The recording head may be independent for each ink color, or a plurality of ink colors (for example, four colors of black, cyan, magenta, yellow and six colors of black, cyan, magenta, yellow, light cyan, and light magenta) There is also a recording head in which the recording heads are integrated into one.

  Regardless of serial type or line tie, in order to drive the recording head, it is related to the signal corresponding to the print data from the control unit (electric board composed of CPU, memory, AISC, etc.) and driving of the recording head. A signal needs to be sent to the recording head.

  In particular, in a serial type recording apparatus, since the carriage on which the recording head is mounted moves, the recording head and the control unit are connected by a long transmission path (wire material or FFC). In particular, recently, the transmission path tends to be long in a large recording apparatus that prints on a large sheet.

  In addition, in such an ink jet recording apparatus, there are a type in which the recording head cannot be replaced and can be used up to the product life, and a type in which the recording head can be replaced. In particular, in the case of a type in which the recording head can be exchanged, an electrical joining means (for example, a connector, an electrode, etc.) is provided on the recording head, and an electrical joining means is also provided on the other side to be attached to the recording head.

  In such an ink jet recording apparatus, if the recording head is not connected to the control unit, it may lead to a printing failure or an abnormality or failure of the recording head.

  Therefore, there is a method for checking the connection of the recording head by reading information (serial number, color information) from a memory such as an EEPROM provided in the recording head (for example, see Patent Documents 1 and 2). .

  In addition, there is a method of determining a connection check of the recording head based on a change in head voltage (see, for example, Patent Document 3).

  On the other hand, as a method for detecting an abnormality of the recording head, there is a method of detecting the temperature of the recording head (see, for example, Patent Document 4).

Also, there is a method of detecting an abnormality by checking a printed image using a line sensor (for example, see Patent Document 5).
JP-A-11-115217 JP2002-079685 JP 10-109409 A JP 04-250056 JP 07-047743

  By checking the connection with the EEPROM and the head power supply as in the conventional example, the connection with the recording head cannot be confirmed for all signals, so drive the recording head with an incorrect signal. Therefore, there is a possibility of causing an abnormality or failure in the recording head.

  In addition, as in the conventional example, the abnormality of the recording head is detected by the temperature abnormality or the printing abnormality after the operation in the abnormal state occurs, and there is a possibility of causing the abnormality or failure of the recording head.

  In particular, connection failure (contact failure, disconnection failure, etc.) may increase due to an increase in the number of signals sent to the recording head and an increase in the transmission path due to the increase in the number of colors and the length and speed of the recording head. .

  On the other hand, confirming the connection with the recording head for all signals causes an increase in cost due to the addition of a determination signal line such as a return line and an increase in circuits.

  A detection unit that detects that the information based on the signal transmitted to the recording head does not change and a stop unit that stops the driving of the recording head when it is detected that the information does not change are included.

  Furthermore, it has a notification means for notifying that it has detected no change.

  In particular, as information based on the signal transmitted to the recording head, paying attention to the drive block of divided drive, it is detected whether the drive block driven immediately before is the same as the drive block to be driven from now on. Stop means for detecting and stopping driving is provided.

  It is possible to detect a poor signal connection with the printhead without increasing the cost without adding a significant circuit and without adding a significant signal line, and driving the printhead when a defect is detected. By stopping the operation, damage to the recording head can be eliminated, and an abnormality or failure of the recording head can be prevented.

  Further, the information can be effectively used by a notification means for notifying that a defect has been detected. For example, it can be determined that there is a possibility that a printing failure has occurred due to the detection of a failure, and the printing sequence can be stopped to notify the user.

  A recording head that performs divided driving has a latch circuit that stores data of a driving block that has been driven immediately before and a latch circuit that stores data of a driving block that will be driven from now on, and compares the outputs of these two latch circuits. If it is determined that the comparators are the same, the same drive block is prohibited from being continuously driven by gating heat enable (corresponding to a heat pulse to be driven).

  In particular, by having these circuits in the recording head, a signal for gating heat enable is not received from the outside of the recording head, so that the connection reliability of this signal can be secured and the recording head can be Stop driving immediately.

[Outline of recording device main unit]
10 is an external perspective view of an ink jet recording apparatus (hereinafter also referred to as an ink jet printer), and FIG. 11 is a perspective view of the inside of the ink jet recording apparatus of FIG.

  In FIG. 10, the ink jet recording apparatus 2 includes a printer apparatus main body 200, a stand 300 on which the printer apparatus main body 200 is placed, and a stacker 400 on which recording media such as discharged recording paper are stacked. A manual insertion slot 201 is provided on the front surface of the printer apparatus main body 200, and a roll paper cassette 202 that can be opened and closed to the front surface is provided below the main body 200, and a recording medium (not shown) such as recording paper can be used as the manual insertion slot 201 or roll. The paper is supplied from the paper cassette 202 into the printer apparatus main body 200. The printer apparatus main body 200 includes an upper cover 203 that can be opened and closed. On the right side in the figure, an operation panel unit 12 and an ink supply unit 8 (including an ink tank) are disposed.

  Further, in FIG. 11, when the inside of the inkjet recording apparatus 2 is virtually viewed, a conveyance roller 204 for conveying a recording medium such as recording paper in the arrow B direction (sub-scanning direction), and a width direction of the recording medium ( A carriage unit 4 guided and supported so as to be reciprocally movable in the direction of arrow A and the main scanning direction, a carriage motor (not shown) for reciprocating the carriage 4 in the direction of arrow A, belt transmission means 205, and carriage 4 A recording head 11 serving as a recording unit mounted and a suction-type ink recovery unit 9 for supplying ink and for eliminating ink discharge defects due to clogging of the discharge ports of the recording head 11 are provided.

  In the case of the illustrated ink jet recording apparatus, the carriage unit 4 is provided with a recording head 11 for performing color recording on a recording medium. This recording head has, for example, four ink colors corresponding to different colors of ink {for example, Bk (black), C (cyan), M (magenta), Y (yellow)}, and two more ink colors. {For example, it is composed of six colors with light C (light cyan) and light M (light magenta) added.

  Alternatively, the recording head 11 may be a printer including a plurality of recording heads. The plurality of recording heads are, for example, four recording heads corresponding to inks of different colors {for example, Bk (black) head, C (cyan) head, M (magenta) head, Y (yellow) For example, a head for light C (light cyan) and a head for light M (light magenta)}.

  When recording on a recording medium such as recording paper with the above configuration, after the recording medium is conveyed to a predetermined recording start position by the conveying roller 204, the main scanning by the recording head 11 and the sub-scanning by the conveying roller 204 are repeated from here. Thus, recording is performed on the entire recording medium.

  That is, the carriage unit 4 is moved in the direction of arrow A in FIG. 11 by the carriage belt 205 and a carriage motor (not shown), and recording is performed on the recording medium. When the carriage unit is returned to the position before being scanned, the recording medium is conveyed by the conveying roller in the sub-scanning direction (the direction of arrow B in FIG. 3), and then the carriage unit is scanned again in the direction of arrow A in FIG. As a result, images, characters, etc. are recorded on the recording medium. When the above operation is repeated and the recording for one sheet of recording medium is completed, the recording medium is discharged into the stacker 400, and the recording for one sheet is completed. In particular, when the recording medium is roll paper (not shown in FIG. 1, corresponding to 50 in FIGS. 4 to 6), the roll paper is cut with a cutter (not shown) before being discharged. There is a case.

[Internal block diagram of inkjet printer 2]
FIG. 9 is a block diagram showing the main configuration of the ink jet printer of this embodiment.

  In FIG. 9, reference numeral 1 denotes a personal computer (PC) that supplies image data and commands to be printed, and 2 denotes reception of image data, commands, parameters, an image processing LUT (lookup table), etc. from the personal computer. The inkjet printer prints received image data in accordance with commands, parameters, and image processing LUTs.

  The personal computer has a keyboard and a display, and an interface with the user is realized by application software, a printer driver (for the inkjet printer 2), and dedicated printer control software (RIP, etc.).

  The internal configuration of the inkjet printer 2 includes a control unit 20 for controlling the entire printer 2, a carriage unit 4 on which the recording head 11 is mounted, a carriage transport unit 6 for reciprocating the carriage unit 4 in the main scanning direction, paper, and the like. The recording head 11 is improved by performing a paper transport unit 7 for moving the recording medium in the sub-scanning direction, a supply unit 8 for supplying ink to the recording head 11, a surface cleaning of the recording head 11, ink suction, ink droplet ejection, and the like. A recovery unit 9 for recovering to a proper state, a power source 10 for supplying power to the recording head 11, a power source for the control unit 3, and a power source for each unit, and an operation panel unit 12 having a key switch (not shown) and an LCD (not shown). To become the main.

  The carriage unit 4 has a mechanism that allows the recording head 11 to be removed and attached. The carriage unit 4 includes an electrical contact, a joint portion such as a tube that supplies ink, a member that supports and fixes the recording head 11, and the carriage transport unit 6. It has a connection (not shown) and is supported by a rail (not shown) of the carriage transport unit 6 and connected to a motor (not shown) of the carriage transport unit 6 by a timing belt (not shown) of the carriage transport unit 6. Thus, the carriage unit reciprocates in the main scanning direction by the rotation of the motor. An encoder sensor (not shown) is mounted on the carriage unit 4, and a linear scale (not shown) for the encoder is stretched in the main scanning direction on the carriage transport unit 6, and the recording head 11 mounted on the carriage unit 4. The movement speed can also be controlled.

  The paper transport unit 7 also performs rotation control of the transport roller with a motor (not shown) and a rotary encoder (not shown) in order to move a recording medium such as paper in the sub-scanning direction.

  The supply unit 8 connects the ink tank unit (not shown) and the recording head 11 with an ink tube (not shown) or the like, supplies ink, and has a valve mechanism (not shown) in the middle of the ink tube. Ink replacement from the ink tube or the recording head is prevented by closing the valve when replacing the ink tank or the ink tank. A motor (not shown) and a photo interrupter (not shown), which is a position sensor for detecting the open / closed state of the valve, are used as a drive source for moving the valve mechanism.

  The recovery unit 9 includes a wiping mechanism (not shown) for wiping the surface of the recording head 11, a capping mechanism (not shown) for sealing the surface of the recording head with a member, and a suction pump mechanism for sucking ink from the nozzles of the recording head 11. (Not shown), a motor (not shown) for driving them, a drive transmission mechanism (not shown), and a position sensor (not shown) for detecting the state of each mechanical mechanism.

  The power supply unit 10 is turned on / off by an AC switch (not shown) or a soft switch (not shown) on the operation panel 12, and the control unit 3 is supplied with a voltage of 3.3V or 5V as a logic power supply. Is supplied to the actuator (motor, etc.) via the I / O control unit & driver unit 26 in the control unit, and the head power supply to the recording head 11 is supplied to the head power control unit in the control unit. (Not shown) is supplied at a voltage value set via

  Functionally, the control unit 20 has an I / F unit 22 that interfaces with the personal computer 1, a sequence control unit 21 that manages the overall operation, and an image that performs conversion processing from image data to print data. A processing unit 23, a timing control unit 24 that adjusts the timing of print data in accordance with the operation of the printer 2, a head drive unit 25 that controls drive data, a drive pulse, a drive voltage, and the like of the recording head 11, a sensor of an internal unit of the printer 2 And an I / O control unit & driver unit 26 for performing an interface with an actuator (motor or the like) and driving.

  Here, the control unit 20 is physically an electric board, and in particular, the sequence control unit 21 is a CPU (not shown) such as a microprocessor, and a ROM (not shown) storing a CPU control program and various data. A RAM (not shown) used as a work area for the CPU and storing various data, an I / F unit (appended) for controlling an interface with the host computer 1, and the like, an image processing unit 23, a timing control unit 24, The head drive unit 25 and the tag information access unit 27 are mainly composed of an ASIC (not shown) and a memory (not shown), and the I / O control unit & driver unit 26 is constituted by an electric circuit such as a general-purpose LSI or a transistor. The

  The inside of the image processing unit 23 uses image data (here: red: R, green: G, blue: B) from the personal computer as ink colors of the printer (here, black: Bk, cyan: C, magenta: M, yellow). : Y, light cyan: LM, light magenta) based on the output γ characteristic of the printer. The color conversion processing unit 41 converts the ink color image data into ink color image data based on the image processing LUT. An output γ processing unit 42 that converts the data, and a binarization processing unit 43 that converts ink color image data (multi-value data) from the output γ processing unit 42 into binary ink color print data.

  The timing control unit 24 includes an HV conversion unit that converts the order (raster direction order) of the ink color print data (binary) processed by the image processing unit 23 to the nozzle order (column direction order) of the recording head 11. 44, a memory unit 45 for storing the print data converted in the column direction, and the read timing from the memory unit 45 is controlled for each print data of each ink color according to the position and moving direction of the recording head 11, etc. The registration adjustment unit 46 is configured to adjust so that printing does not shift.

  The head control unit 25 generates a signal in which the print data from the timing control unit 24 is matched with the data format for driving the recording head 11, generates a driving signal under the control of the sequence control unit 21, and outputs these signals to the recording head. 11 to send. The recording head 11 is driven by a signal from the head control unit 25 and forms an image by ejecting ink.

  The I / O control unit & driver unit 26 is driven by a signal whose timing is controlled by the sequence control unit 21, and drives and controls each connected unit (6 to 10, 12).

[Outline of recording head]
An outline of the outer shape of the recording head 11 will be described with reference to FIG.

  The recording head 11 is provided with mechanical support portions 71, 72, and 73 as mechanical connection portions in a state where the nozzle surface that is an ink discharge port faces downward (the lower left diagram in FIG. 6), and the carriage unit 4 is mechanically connected. The left and right sides (main scanning direction) are fixed by mechanical support portions 71 and 72 by a portion (not shown) and supported downward, and the pressure from the front side and the upper side is applied by the mechanical support portion 73 to thereby apply the recording head 11. Is fixed in the carriage unit 4. An electrical contact 75 is provided as an electrical connection, and a signal and power are supplied by holding the contact with the pressure applied to the mechanical contact portion 73 to a spring connector (not shown) in the carriage unit 4. I do. By pressing an ink joint portion (not shown) in the carriage unit 4 from the front to the ink joint portion 74, the ink joint portion 74 is connected to the ink joint portion 74 so that ink can be supplied.

  The recording head 11 has a structure in which the nozzle rows of each ink are integrated. When the nozzle surface 76 is enlarged, black Bk, light cyan PC, cyan C, light magenta PM, magenta M, Yellow Y and each ink are arranged, and the nozzles of each ink color are arranged in the same structure. The nozzles of each ink color are arranged in a staggered arrangement of 1280, and in two rows, 640 even nozzles (0, 2, ... 1278) and 64 odd nozzles (1, 3, ... 1279). . The even nozzles and odd nozzles are 1/600 inch apart, and the odd and even nozzles are 1/1200 inch apart. The interval between the even nozzle row and the odd nozzle row is 5/600 inch. The distance of the nozzle row between the ink colors is 82/600 inches (however, the difference between C and PM is wide).

(Split drive)
Divided drive divides a recording head composed of a plurality of nozzles into a unit (referred to as a block), reduces the number of simultaneously driven nozzles to one block, and sequentially changes the blocks to be driven. The nozzle is driven.

  The divided drive will be described with reference to FIGS.

  FIG. 7 is an internal block diagram of the recording head 11 that performs split driving, FIG. 2 is a driver internal circuit, and FIG. 8 is a timing diagram of split driving.

  However, the case will be described where the number of nozzles is 80 instead of 1280 for one ink color as shown in FIG. 7 and 8, the number of blocks is 10 and the maximum number of nozzles that can be ejected simultaneously is 8. Further, here, in order to simplify the description, 80 nozzles are not arranged in a staggered manner as shown in FIG. 6 for one ink color, but nozzles 0, 2, 4,. . . It will be described in the case of a single column. In order to simplify the description, the signal logic is described as positive logic (the active state is high).

  In FIG. 7, the internal block of the recording head 11 includes a 12-bit shift register 101, an 8-bit latch circuit 102, a 4-bit latch circuit 103, and an AND circuit group 104 (internally eight 2-input ANDs (not shown)). And 4 bit input 10 output decoder 105 and drivers 110-117.

  As shown in FIG. 2, each of the drivers 110 to 117 is mainly composed of 2-input AND circuits 120 to 129, switching circuits 130 to 139, and heaters 140 to 149 in each nozzle. Corresponds to 10 nozzles, 8 of the drivers 110 to 117 are similar circuits, and the number of AND circuits, switching circuits, heaters, and nozzles is 10 × 8 = 80.

  Here, the driver 110 corresponds to nozzles 1 to 10, the driver 111 corresponds to nozzles 11 to 20, ... (omitted) .... the driver 116 corresponds to nozzles 61 to 70, and the driver 117 corresponds to nozzles. It corresponds to 71-80.

  The shift register 101 is connected by a clock signal CLK, which is a signal from the head control unit 25, and a data signal DT_IN, and sequentially takes DT_IN into the shift register in synchronization with the rising edge of CLK. As shown in the timing chart of FIG. 8, image data signals DT0 to DT7 and block enable signals BE0 to BE3 are superimposed on DT_IN serially and transferred by CLK. The image data signals DT0 to DT7 and the block enable signals BE0 to BE3 stored in the shift register 101 are stored in the latch circuits 102 and 103, respectively, at the rising edge of the latch signal LAT that is a signal from the head controller 25. In FIG. 8, as the first block drive, DT0 to DT7 are 10001011 and BE0 to 3 are 0100, and 10001011 is stored in the latch circuit 102 and 0100 is stored in the latch circuit 103 at the rising edge of the LAT signal.

  The output DT (0 to 7) of the latch circuit 102 is connected to the AND circuit group 104, and the other input of the AND circuit group 104 is connected to a head enable signal HE (so-called heat pulse). Combined with the signal, HT0 to HT7 are output, and HT0 to HT7 are connected to drivers 110 to 117, respectively. The HE signal is also sent from the head controller 25.

  On the other hand, the output of the latch circuit 103 is connected to the decoder 105. The decoder 105 decodes the input BE (0-3) and outputs BLK (0-9), and BLK (0-9) Connected to 117.

  In FIG. 8, as the driving of the first block, the output DT (0 to 7) of the latch circuit 102 is 10001011 and is combined with the HE signal by the AND circuit group 104 to output HT (0 to 7). , HT0, HT4, HT6, HT7 are active. On the other hand, the output BE (0-3) of the latch circuit 103 is 0100, the decoder 105 outputs BLK (0-9), and only BLK2 is in the active state.

  At this time, in the drivers 110 to 117, the outputs of the AND circuit 122 that receives BLK2 among the AND circuits 120 to 129 in the drivers 110, 114, 116, and 117 that receive HT0, HT4, HT6, and HT7 in the active state are in the active state. Then, the switching circuit 132 is turned on, and the current from the head power supply Vh flows through the heater 142, so that ink droplets are ejected from the nozzles 3, 43, 63, 73.

  During this discharge, 0101100 and 1100 are sent to DT0-7 and BE0-3 to the DT_IN signal of the next block, respectively, and similarly stored in the latch circuits 102 and 103 by the LAT signal, the next HE is active During the state period, the nozzles 14, 34, and 44 are discharged by setting the HT1, HT3, and HT4 of the AND circuit 104 to the active state and setting only the output BLK3 of the decoder 105 to the active state.

  Similarly, by sending DT0 ~ 7 and BE0 ~ 3 to the DT_IN signal for the next block, controlled by the latch signal LAT and the heat enable signal HE from the head controller 25, the ejection of the corresponding nozzle is performed. Is called.

  In FIG. 8, the order of division driving is described in the order of blocks 2, 3, and 4, but this is not restrictive. It is possible for the head controller 25 to generate various orders. For example, it can be realized by providing a memory unit in the head control unit 25, storing data in a table of BE0 to 3, and sequentially reading the data.

  In this way, the DT_IN signal, the CLK signal, the LAT signal, and the HE signal are sent to the recording head 11 from the head control unit 25. When these signals are in an open state such as a contact failure or a disconnection of the transmission path, Pull-down or the like is performed inside the recording head 11 so that each signal does not become active.

[Abnormality detection circuit and protection circuit]
An example of the abnormality detection circuit and the protection circuit when the signal to the recording head 11 is stopped will be described with reference to FIGS.

  FIG. 1 is an internal block diagram of a recording head 11 that performs divided driving. FIG. 7 is a diagram in which a detection circuit and a protection circuit are added. FIG. 2 is a driver internal circuit (the same as that used in the description of FIG. 7), FIG. 3 is a timing diagram of divided driving at normal time, and FIG. 4 is a timing diagram of divided driving at abnormal time.

  In FIG. 1, what is added to FIG. 7 (the same number is the same function) is a 4-bit latch circuit 106, a 4-bit 2-input comparator 107, and a 2-input AND circuit 108.

  The difference from FIG. 7 is that the output of the latch circuit 103 is connected not only to the decoder 105 but also to one input of the latch circuit 106 and the comparator 107, and the output of the latch circuit 106 is connected to one of the inputs of the comparator 107. The output NEQ of the comparator 107 is connected to one input of the AND circuit 108, the head enable signal HE is input to the other input of the AND circuit 108, and the output signal ENB of the AND circuit 108 is input to the AND circuit group 104. Is connected to one input (terminal to which HE is connected in FIG. 7). Note that the same latch signal LAT as that of the latch circuits 102 and 103 is input to the latch signal of the latch circuit 106.

  Normal operation division driving will be described with reference to the timing chart of FIG.

  First, when the transfer to the recording head 11 is started for the first time, the transfer for initialization is performed. Specifically, since 00000000 is set to DT0-7 and 0000 is set to BE0-3 on DT_IN signal, the DT_IN signal becomes 00000000000 (all low level), and the shift register 101 is sent to the recording head by the clock signal CLK. , DT (0 to 7) and BE (0 to 3) 00000000 and 0000 are taken into the latch circuits 102 and 103 by the latch signal LAT. Subsequently, 1001011 is set in DT0 to DT7 and 0100 is set in BE0 to 3, and the data is sent to the shift register 101 in the recording head by the clock signal CLK. During this period, the head enable signal HE is different from that shown in FIG. Since the initial value of the latch circuit 106 is indeterminate, the comparator 107 may activate the NEQ, so that the ENB is not activated. Set to Low. When the latch circuit 102, the latch circuit 103, and the latch circuit 106 are updated to 1001011, 0100, and 000, respectively, with the LAT signal, the comparator 107 receives 000 as the previous block data and 0100 as the current block data. When the inputs are not equal, the output NEQ signal is activated, the output ENB signal of the AND circuit 108 to which the HE signal and the NEQ signal are input is also activated, and the AND circuit group 104 receives the image data signal DT. AND with (0 ~ 7) and ENB signal and output HT (0 ~ 7). In this case, HT0, HT4, and HT7 are in an active state, BLK2 in the decoder output BLK (0 to 9) is in an active state, and the nozzles 3, 43, 63, and 73 eject ink droplets.

  Similarly, during this discharge, 0101100 is sent to DT0-7 for the next block drive, 1100 is sent to BE0-3 to CLK in shift register 101, and 0101000, 1100, to latch circuits 102, 103, 106 are sent by LAT signal, respectively. When the comparator 107 compares 110 and 010 with the output 0100, the output NEQ is also in the active state, so that the nozzles 14, 34, and 44 are discharged by the next HE.

  Similarly, the continuous division drive is performed for 80 nozzles (10 blocks), and when the 80 nozzles are driven, one row of images is formed. When printing for one row is completed, the next row is printed in the same way. A serial scan type printer drives and forms a single scan image by printing multiple rows.

  Next, the operation at the time of abnormality will be described with reference to the timing chart of FIG.

  As an abnormality, it is assumed that the CLK signal stops midway. In FIG. 4, the stop of the CLK signal and the abnormal signal associated therewith are indicated by asterisks.

  3 is the same as in Fig. 3, from DT_IN signal with 00000000 of DT0 to 7 and 000 of BE0 to 3 being transmitted to the shift register with CLK until the nozzles 3, 43, 63, 73 ejecting, CLK signal Is stopped when driving nozzles 3, 43, 63, 73, since the data is not taken into the shift register 101, the LAT signal latches 102, 103 with the same value 1001011 as before, On the other hand, 0100 is stored in the latch circuit 106, the same value 0100 is input to the two inputs of the comparator 106, and the output NEQ of the comparator 106 is in the low state. Therefore, the HE signal is gated by the AND circuit 108, the ENB signal is set to the low state, and all HT (0T to 7) are set to the low state. In this block, control is performed so that no nozzle is ejected. Thereafter, if the state where CLK is not input continues, the NEQ signal is similarly maintained at the low state, and no nozzles are ejected.

  Here, the explanation was made assuming that CLK stopped halfway, but when CLK stops from the beginning, the data is determined by the LAT signal in latch circuits 103 and 106 (by the LAT signal rising twice) Similarly, no nozzles are ejected to bring the NEQ signal to a low state.

  When the CLK signal stops from a half-finished state, the shift register 101 operates, so there is a possibility of ejection for that block drive, but ejection is similarly stopped in the next block drive.

  By returning the output signal ENB of the AND circuit 108 to the control unit 20, the control unit 20 detects that a head abnormality has occurred when the ENB signal goes low while the HE signal is being output. it can.

  Next, another abnormal operation will be described with reference to the timing chart of FIG.

  As an abnormality, BE0 to 3 are assumed to stop halfway. In FIG. 5, the stop of BE0 to 3 and the abnormal signal associated therewith are indicated by asterisks.

  In FIG. 5, in the second DT_IN, BE0-3 becomes 000 which is the same as the previous value. Since the outputs of the latch circuits 103 and 106 are the same as 000, as in FIG. The output NEQ of the comparator 107 goes to a low state, the HE signal is gated by the AND circuit 108, and the ENB signal goes low, thereby stopping ejection. Next, when BE0 to 3 change, ejection can be resumed.

  Such an abnormality corresponds to a case where there is a mistake in the circuit, program, or register setting that generates BE0 to BE3, or a defect in the substrate.

  When the DT_IN signal is disconnected or poorly contacted, not only BE0 to BE3 but also DT0 to DT7 are all 0 (low state), and therefore, no ejection is performed even if ENB is not set to the low state. However, the ENB signal indicates that an abnormality has occurred. Also, if disconnection or contact failure occurs in the middle of the DT_IN signal, it is detected that there is no change in BE (0 to 3) for continuous ejection while remaining in the shift register 101, and the ENB signal is By setting it to Low, discharge can be prevented and abnormality can be detected.

[When there are two DT_IN]
The problem of stoppage due to disconnection or poor contact of the DT_IN signal becomes prominent when there are two or more DT_IN signals. The reason why the number of DT_IN signals is set to two or more is to increase the number of nozzles, shorten the time required for image data transfer, and absorb the increase in ejection frequency.

  FIG. 12 shows a block diagram in the recording head when there are two DT_IN signals.

  FIG. 13 is a timing chart for explaining the operation of the abnormality detection and protection circuit in FIG.

  The difference from Fig. 1 is that there are two DT_IN signals, DT_IN0 signal and DT_IN1 signal, DT_IN0 is assigned DT0 ~ 5, DT_IN1 is assigned DT6, 7 and BE0 ~ 3, DT_IN0 signal is 6bit shift The CLK signal is transferred to the register 91, the DT_IN1 signal is input to the 4-bit shift register 93, and further connected to the 2-bit shift register 92 of the 4-bit shift register 93, and transferred to the shift registers 93 and 92 by the CLK signal. . Shift register 93 stores BE0-3 and outputs to latch circuit 103, shift register 91 stores DT0-5, shift register 92 stores DT6-7, and outputs to latch circuit 102 as DT0-7 Is done. The following operations are the same as those in FIG.

  In FIG. 13, as in FIG. 3, instead of setting 00000000 to DT0-7 and 000 to BE0-3 and sending in DT_IN, DT_IN0 is DT0-5 and DT_IN1 is DT6,7 and BE0-3 000000 is sent to the shift registers 91, 92, 93 with six CLK signals. The operation in FIG. 12 is the same as that in FIG. 3 until the nozzles 3, 43, 63, 73 are discharged in the timing chart of FIG.

  The case where DT_IN1 becomes abnormal during the third block transfer (from the asterisk of the DT_IN1 signal in FIG. 13) will be described. DT_IN1 is stuck in the Low state by pull-down inside the recording head 11 when the contact state or the disconnection of the transmission line is in an open state. Therefore, since 0000 is stored as BE (0-3) in the latch circuit 103 and 0100 is stored in the latch circuit 106 by the LAT signal, the output NEQ signal of the comparator 107 becomes active and DT_IN0 In the latch circuit 10, 01011000 is stored in the latch circuit 10 as DT0 to DT7, and the nozzles 11, 31, and 41 are discharged, but in the next block cycle, the latch circuit 106 also becomes 0000, and the comparator 107 The output NEQ signal is in a low state and no longer discharges. Without such protection, BLK0 is always in an active state, and the same block is continuously driven according to the image data signals DT0 to DT5 sent by DT_IN0, which may damage the recording head 11. .

  When DT_IN1 is stuck to 0 (Low state) from the beginning, 0000 is set in the latch circuit 103 and the latch circuit 102 twice in the LAT signal, so the output NEQ signal of the comparator 107 is It becomes Low state and does not discharge at all.

[Other Examples]
[Special treatment for BLK0]
In FIGS. 12 and 13, the ejection cannot be stopped in the block cycle immediately after the abnormality of DT_IN1 occurs, but the drive block is different from BLK2 and BLK0, and therefore the recording head 11 is not damaged.

  However, in order to stop such discharge of BLK0, the output of the decoder 105 is increased by one from BLK0-9 to BLK0-10, and BLK1-10 is assigned to the drivers 110-117 without assigning BLK0 to the drivers 110-117. By connecting each, DT_IN1 can be attached to 0.

  When pulling down inside the recording head 11, the assignment of BLK0 is prohibited, but when it is pulled up, it sticks to 1, so it can be dealt with by making BLK15 unused.

[DT_IN0 error detection]
If the DT_IN0 signal is in an open state such as a contact failure or transmission line disconnection, and stuck to a low state due to a pull-down inside the recording head 11, it cannot be detected and protected by the block of FIG. 12, but the DT_IN1 signal As long as is normal, BE0 to 3 are changed, so that the same block is not continuously ejected by the block drive, and the recording head 11 is not damaged. However, since there is no discharge from the nozzle corresponding to the DT_IN0 signal, an image defect occurs.

  To detect abnormalities in the DT_INT0 signal, a circuit (latch 106, comparator 107) that detects changes in BE0 to 3 used for DT_INT1 is introduced by adding data that changes between blocks to the DT_INT0 signal. Thus, it can be detected. For example, by adding BE0 ~ 3 to DT_IN0, sending DT0 ~ 3, sending BE0 ~ 3 and DT4 ~ 7 to DT_IN1, and receiving them by 6-bit shift register, and seeing the change of BE0 ~ 3 Detect anomalies. Since information is duplicated, one BE0-3 can be used for decoding 105. Two comparators 107 and two latch circuits 106 may be provided, and the outputs of the two comparators and the HE signal may be put into a 3-input AND circuit to be an ENB signal.

  In order to simplify the circuit, it is also possible to cope with DT_IN0 by disabling 1 bit changing between blocks.

[Abnormality detection circuit and protection circuit layout]
Although the embodiment having the abnormality detection circuit and the protection circuit in the recording head 11 has been described, the present invention is not limited to this. For example, by providing it on the output side of the head control unit 25 in the control unit 20, it can be used for abnormality detection and recording head protection when the control unit 20 performs an abnormal operation. In addition, a sub unit such as a relay board is provided in the carriage unit in the middle from the control unit 20 to the recording head 11, and an abnormality detection circuit and a protection circuit are mounted in the sub unit, thereby detecting an abnormality in a long transmission path. can do. This subunit can also be an electric board having a connector that contacts the recording head 11.

[1280 nozzles when nozzle count increases]
It is possible to cope with the case where the number of nozzles is 1280 as shown in FIG. 6 and the even nozzles and odd nozzles are arranged in a staggered manner.

  Even number nozzles and odd number nozzles can be divided into two and 640 can be implemented in one configuration.

  When the number of divisions is 20 (the number of nozzles in the driver is 20) and the image data is 32 bits for 640 nozzles, the shift registers 91, 92, and 93 in FIG. 12 are 19 bits, 14 bits, 5 bits, and latches, respectively. The circuit 102 and the AND circuit group 104 have 32 bits, the latch circuits 103 and 106 have 5 bits, and the decoder 105 has 5 bits and 20 bits.

  DT_IN0 is assigned DT0-17 and flag bit, and DT_IN1 is assigned DT18-31 and BE0-4. The flag bit is changed between blocks. Since BE0 to 4 and 5 bits can be coded with 32, 20 are necessary, so that BLK0 can not be assigned if decoder 105 outputs 5 bits and 21 bits.

  By providing the same circuit as the above for 640 even nozzles and 640 odd nozzles, 1280 nozzles can be handled. At this time, the control unit 20 (particularly the head controller 25) reduces the number of signal lines by making the CLK signal and the LAT signal common to the even nozzles and the odd nozzles.

  The DT_IN0 signal, DT_IN1 signal, and HE signal are handled separately for even nozzles and odd nozzles.

[When there are multiple ink colors]
When there are six ink colors as shown in FIG. 6, it can be realized by having the circuit described above for each ink color based on the same idea as the odd nozzle and the even nozzle.

  Also at this time, the number of signal lines is reduced by making the CLK signal and the LAT signal common. The DT_IN0 signal, the DT_IN1 signal, and the HE signal are independent for each color and every even odd number. Therefore, the number of signals sent from the head controller 25 is 3 × 2 (odd number / even number) × 6 colors + 2 = 38. However, head power supply VH and logic power supply are excluded. By increasing the DT_IN signal in this way, even if the problem of stoppage due to disconnection or poor contact becomes significant, abnormality detection and protection (discharge stop) can be performed in this embodiment.

  When sending the ENB signal to the control unit 20, the signal lines can be reduced by sending each ENB signal from each ink color and even nozzle / odd nozzle to one by the OR circuit.

[Including LAT signal abnormality detection]
An embodiment in which LAT signal abnormality detection is also taken into account will be described with reference to FIGS.

  14 adds an inverter 95 and an OR circuit 96 to FIG. 1, inverts the HE signal by the inverter 95, outputs HE *, puts it in one input of the OR circuit 96, and inputs the other input of the OR circuit 96. The LAT signal is input to, and the output of the OR circuit 96 is input as the latch signal of the latch circuit 106.

  FIG. 15 is a timing chart of FIG. 14, and the LAT signal causes an abnormality at the time of the third block transfer, and is stuck in the Low state. The same control as in FIG. 3 is performed until the nozzles 3, 43, 63, and 73 discharge, but 0100 which is the output BE (0 to 3) of the latch circuit 103 is supplied to the latch circuit 106 by the inverted signal HE * of the HE signal. By taking in, the output NEQ of the comparator 107 is set to the low state, but since the subsequent LAT signal does not change, the NEQ signal continues to be in the low state, the ENB signal also goes to the low state, and ejection from all nozzles stops. After that, the latch circuit 106 operates by HE *, but the contents of the latch circuit 103 are not rewritten because there is no LAT signal, and therefore the contents of the latch circuit 106 do not change, so the output NEQ of the comparator 107 is Low. The state continues.

  The HE * signal has a delay time with respect to the HE signal, and the time of the ENB signal is ensured by delaying the transition time of the NEQ signal to Low from the fall of the HE signal.

  When the latch signal LAT is stopped from the beginning, the data held in the latch circuits 102 and 103 does not change. Therefore, both BLK (0 to 9) and HT (0 to 7) are fixed and discharged by the first HE signal. However, since the value of the latch circuit 103 is copied to the latch circuit 106 by the inverted signal HE * of the ejected HE, the output NEQ of the comparator 107 is in the low state, and the next and subsequent HEs do not eject.

  When HE stops (HE sticks to the low state), all of HT0 to HT7 become inactive, and no discharge occurs, so there is no damage to the recording head. However, since the ENB signal does not change by returning the ENB signal to the control unit 20, an abnormality due to the stop of the HE signal can be detected.

  Note that when the head power supply VH is stopped, no discharge is performed, so there is no damage to the recording head.

FIG. 3 is an internal block diagram of a recording head having an abnormality detection unit. Internal circuit of the driver of the print head internal block. FIG. 6 is a timing chart during normal operation of the recording head having an abnormality detection unit. FIG. 6 is a timing chart when the CLK signal is abnormally operated in the recording head having the abnormality detection means. FIG. 4 is a timing chart when a BE signal is abnormally operated in a recording head having abnormality detection means. FIG. FIG. 3 is an internal block diagram of a recording head that performs divided driving. FIG. 6 is a timing chart of a recording head that performs divided driving. 1 is a block diagram illustrating a main configuration of an ink jet printer according to an embodiment. 1 is an external perspective view of an inkjet printer. The perspective view which looked at the inside of the ink jet recording device of Drawing 10 virtually. The internal block diagram which has an abnormality detection means with the recording head of data 2 input type. FIG. 13 is a timing chart for explaining an abnormal operation of input data in FIG. 12. Internal block diagram of the recording head with LAT signal error detection taken into account. The timing diagram explaining the LAT signal abnormal operation in FIG.

Explanation of symbols

1 PC 2 Inkjet recording device (inkjet printer)
4 Carriage unit
11 Recording head
20 Control unit
21 Sequence controller
25 Head controller
101 Shift register
102, 103, 106 Latch circuit
104 AND circuit group
105 Decoder
107 comparator
108 AND circuit
110 to 117 Driver in the recording head
120-129 AND circuit
130 to 139 switching circuit
140 ~ 149 Heater

Claims (8)

  An ink jet recording apparatus comprising: detecting means for detecting that information based on a signal transmitted to the recording head does not change; and stopping means for stopping driving of the recording head when it is detected that the information does not change.   2. An ink jet recording apparatus according to claim 1, further comprising notification means for notifying that said detection means has not changed.   The detection means pays attention to a drive block of divided drive, detects whether the drive block driven immediately before is the same as the drive block to be driven from now on, and detects the abnormality in the case of being the same. 1, 2 inkjet recording devices.   3. An ink jet recording apparatus according to claim 1, wherein said stop means gates a drive pulse of the recording head based on a detection result of said detection means.   A recording head comprising: detecting means for detecting that information based on a signal transmitted to the recording head does not change; and stopping means for stopping driving of the recording head when it is detected that no change has occurred.   6. A recording head according to claim 5, further comprising notification means for notifying that said detection means has not changed.   The detection means pays attention to a drive block of divided drive, detects whether the drive block driven immediately before is the same as the drive block to be driven from now on, and detects the abnormality in the case of being the same. 5 and 6 recording heads.   7. The recording head according to claim 5, wherein the stopping means gates a driving pulse of the recording head based on a detection result of the detecting means.

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