JP2005335343A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that landing positions are varied and image quality is deteriorated since inclination amounts of a carriage are different in a forward operation and a backward operation in bidirectional printing. <P>SOLUTION: This device is configured in the following manner. When sub-scanning feeding control is to be performed, the row to be printed in the scan is determined to be a forward printing or not. If it is determined to be the forward printing, a sheet 15 is fed by a predetermined feeding amount X. If it is not the forward printing (if it is a backward printing), the sheet 15 is fed by a feeding amount (X+a) in which a correction value a of the backward printing obtained in accordance with the misalignment amount of the landing positions due to the inclination of the carriage is added to the predetermined feeding amount (transportation amount) X. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus capable of bidirectional printing by bidirectionally scanning a carriage in both directions.

  2. Related Art As an image forming apparatus such as a printer, a facsimile machine, a copying machine, or a multifunction machine of these, for example, an ink jet recording apparatus using a droplet discharge head as a recording head is known. An ink jet recording apparatus performs recording by ejecting a recording liquid (ink) from an ink recording head onto a recording medium (also referred to as paper, recording medium, recording paper, or printing medium). Color images can be recorded at high speed.

  In such an ink jet recording apparatus, the recording head is mounted on the carriage and reciprocated in the main scanning direction, the recording medium is intermittently sent (transferred) in the sub scanning direction, and printing is performed on the forward and return paths of the carriage. There are known ones that can perform two-way printing.

However, when bi-directional printing is performed by the serial type image forming apparatus as described above, there is a problem that the recording position in the main scanning direction in the forward path and the backward path is shifted due to backlash of the driving mechanism in the main scanning direction. easy. Therefore, in order to solve such a positional deviation in the main scanning direction, for example, as described in Patent Document 1, a positional deviation amount (printing deviation) in the main scanning direction is registered in advance, and this positional deviation amount is recorded. Based on the above, the dot recording position in the forward path and the backward path is corrected, or as described in Patent Document 2, the correction value is converted into a positional deviation inspection pattern actually printed on the print medium. What is determined based on this is known.
Japanese Patent Laid-Open No. 5-69625 Japanese Patent No. 3480374

  Further, in such a serial type image forming apparatus, since the recording head is mounted on the carriage so that the nozzle row is in the direction along the sub-scanning direction, landing also occurs when the nozzle row of the recording head is inclined. The position will vary and the image quality will deteriorate.

Therefore, as described in Patent Document 3, an evaluation chart that includes an inclination correction unit that corrects the inclination of the nozzle row, and as described in Patent Document 4, an evaluation chart that can easily determine the inclination of the head. Is used to evaluate the tilt.
JP 2001-129983 A JP 2002-103576 A

  The inclination of the recording head in the serial type image forming apparatus described above occurs not only in the initial state but also when the carriage moves. In other words, the carriage on which the recording head is mounted is slidably supported (held) by a carriage support member having a length in the carriage movement direction, and the carriage support member normally passes through the slide member of the carriage. The carriage is supported by. In this case, a clearance necessary for the operation of the mechanical parts must be provided between the carriage support member and the sliding member of the carriage.

  However, if there is a clearance, when the carriage moves, the carriage tilts from a predetermined state due to the action of the rotational moment. The fulcrum when tilting is the carriage support member, but the nozzle row for ejecting the recording liquid (nozzle row) is away from the carriage support member, so the nozzle row rotates around the carriage support member. As a result, a displacement occurs in the position of the nozzle row in the sub-scanning direction.

  In particular, during bidirectional printing, the amount of tilt of the carriage may differ between the carriage forward operation and the carriage return operation, so that the recording liquid ejected from the nozzle row during the carriage forward operation reaches the recording medium. The relative position in the sub-scanning direction is shifted between the position and the landing position of the recording liquid ejected from the nozzle row on the recording medium during the backward operation of the carriage, which causes deterioration in image quality such as banding. There is.

  In this case, if the clearance between the support member and the sliding member of the carriage is close to zero, the inclination of the carriage can be reduced and the amount of inclination of the carriage can be reduced. This increases the load and causes problems in operation. In addition, when the width is increased in the operation direction of the carriage, the span of the support member that supports the carriage is widened, so that the carriage is difficult to tilt, but there is a problem that the entire apparatus becomes large.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus in which landing position deviation due to a tilt of a carriage is reduced and image quality is improved.

  In order to solve the above-described problems, the image forming apparatus according to the present invention has a configuration in which the transfer amount of the recording medium is different between forward printing and return printing for a predetermined transfer amount.

  Here, a configuration having individual correction values for forward printing and return printing for a predetermined transfer amount, or a correction value for either forward printing or return printing for a predetermined transfer amount. It can be set as the structure which has.

  The carriage preferably has an elastic body. In this case, it is preferable that the carriage is held so as to be movable in the main scanning direction at at least two positions of the lower end position and a position above the lower end position.

  Further, it has at least a head including a nozzle array for ejecting an achromatic recording liquid and a head including a nozzle array for ejecting a chromatic recording liquid, and is covered during achromatic printing and chromatic printing. It is preferable to individually correct the transfer amount of the recording medium.

  According to the image forming apparatus of the present invention, since the transport amount of the recording medium is different between the forward printing and the backward printing for a predetermined transport amount, the landing position and the carriage backward printing at the carriage forward printing due to the inclination of the carriage are configured. The landing position at the same time can be made the same, and the impact of landing deviation in the sub-scanning direction during bidirectional printing due to the tilt of the carriage can be reduced without causing an increase in load or upsizing of the device. Will improve.

  Hereinafter, embodiments of the present invention will be described. First, an example of an ink jet recording apparatus as an image forming apparatus to which the present invention is applied will be described with reference to FIGS. 1 is a schematic perspective view of the mechanism of the recording apparatus, FIG. 2 is a plan view of the main part of the recording apparatus, and FIG. 3 is a side view of the main part of the recording apparatus.

  In this ink jet recording apparatus, the carriage 5 can be moved in the main scanning direction (arrow A direction) by a guide shaft 3 and a stay 4 which are carriage support members that are horizontally mounted between the left and right side plates 1 and 2 constituting the frame member. I support it. That is, the carriage 5 is held so as to be movable in the main scanning direction at at least two positions, ie, at least one lower end position and a position above the lower end position.

  Then, a timing belt 9 is stretched between a driving roller 7 and a driven roller 8 provided on the rotation shaft of the main scanning motor 6, and the timing belt 9 and a part 5a of the carriage 5 are connected as shown in FIG. By coupling, the carriage 5 is moved and scanned in the main scanning direction by rotationally driving the main scanning motor 6.

  As shown in FIG. 2, the carriage 5 has a recording head 11A composed of a droplet discharge head having a nozzle row in which a plurality of nozzles are arranged in a direction along the sub-scanning direction (the arrow B direction in FIG. 1). 11B (referred to as recording head 11 when not distinguished).

  The recording head 11A has, for example, a nozzle row that ejects yellow (Y) ink droplets (recording droplets) and a nozzle row that ejects magenta (M) ink droplets (recording droplets), and the recording head 11B is cyan. (C) a nozzle row for ejecting ink droplets (recording droplets) and a nozzle row for ejecting black (Bk) ink droplets (recording droplets). It should be noted that an independent head may be used for each color, and the number of colors and the arrangement order are not limited to this.

  As a droplet discharge head constituting the recording head 11, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a metal phase caused by temperature change. A shape memory alloy actuator using a change, an electrostatic actuator using an electrostatic force, or the like as an energy generating means for discharging a liquid can be used.

  Further, as shown in FIG. 3, the carriage 5 is also equipped with a sub tank 12 for supplying ink of each color to the recording head 11, and the sub tank 12 is replenished and supplied with ink of each color from the ink cartridge on the apparatus main body side. An ink supply tube 13 is connected for this purpose. The ink supply tube 13 is made of a soft resin tube, and the tube 13 is also used as an elastic body provided in the carriage 5. The elastic body provided in the carriage 5 may be other springs or rubber. Examples include a leaf spring, a coil spring, and a helical spring.

  Then, an electrostatic conveyance belt 16 for conveying the paper 15 as a recording medium is provided in an image forming area by the recording head 11, and the sub-scanning is performed by electrostatically adsorbing the paper 15 fed from a paper feeding unit (not shown). It is conveyed (transferred) in the direction (the direction of arrow B in FIG. 1).

  As shown in FIG. 3, the electrostatic conveyance belt 16 is an endless belt (either an endless belt in molding or a belt made endless by connecting both ends), and a conveyance roller 17 and a tension roller 18. And the conveying roller 17 is rotated from the sub-scanning motor 21 via the timing belt 22 and the timing roller 23, so that it is circulated in the sub-scanning direction. A guide member 25 is disposed on the back side of the conveying belt 16 in correspondence with the image forming area formed by the recording head 12. Further, a charging roller 19 as charging means is provided in contact with the conveying belt 16 so as to face the conveying roller 17.

  Further, as a paper discharge unit for discharging the paper 15 recorded by the recording head 11, a separation claw 31 for separating the paper 15 from the conveying belt 16, a paper discharge roller 32, and a paper discharge roller 33 are provided. The paper 12 is discharged to a paper discharge tray (not shown).

  In this apparatus configured as described above, the transported belt 15 is electrostatically attracted onto the transport belt 16 by being charged by contact with the charging roller 19 to which a high voltage is applied while rotating. And hold.

  Therefore, the recording belt 11 is moved by rotating the conveyance belt 16, the recording head 11 is driven in accordance with the image signal while the carriage 5 is moved and scanned in both directions, and droplets are ejected (jetted) from the recording head 11. Then, ink droplets, which are droplets, are landed on the stopped paper 15 to form dots, so that one line is recorded, and after the paper 15 is conveyed by a predetermined amount, the next line is recorded. When the recording end signal or the signal that the rear end of the paper 15 reaches the recording area is received, the recording operation is ended.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. This figure is an overall block diagram of the control unit.
The control unit 100 includes a CPU 101 that controls the entire apparatus, a ROM 102 that stores programs executed by the CPU 101 and other fixed data, a RAM 103 that temporarily stores image data, and the like, while the apparatus is powered off. Also, a non-volatile memory (NVRAM) 104 for holding data and an ASIC 105 for processing image processing for performing various signal processing and rearrangement and other input / output signals for controlling the entire apparatus are provided.

  The control unit 100 also controls the drive of the I / F 106 for transmitting and receiving data and signals to and from the host, which is an image processing apparatus (or data processing apparatus) such as a personal computer, and the recording head 11. The head drive control unit 107 and the head driver 108, the main scanning motor driving unit 111 for driving the main scanning motor 6, the sub scanning motor driving unit 113 for driving the sub scanning motor 21, and the charging roller 19 are high. An AC bias supply unit 114 that supplies a voltage, an encoder 26 that detects the rotation amount of the sub-scanning motor 21, an I / O 116 that inputs detection signals from various sensors 118, and the like are provided. The control unit 100 is connected to an operation panel 117 for inputting and displaying information necessary for the apparatus.

  Here, the control unit 100 cable print data (print data) including image data from the host 90 side such as an image processing device such as a personal computer, an image reading device such as an image scanner, and an imaging device such as a digital camera. Alternatively, it is received by the I / F 106 via the net. In the present embodiment, print data is generated and output to the control unit 100 by a printer driver on the host side.

  Then, the CPU 101 reads and analyzes the print data in the reception buffer included in the I / F 106, performs data rearrangement processing by the ASIC 105, and transfers the image data to the head drive control unit 107. Note that the print data for image output is converted into bitmap data, as described above, the image data is developed into bitmap data by the host-side printer driver and transferred to this apparatus.

  When the head drive control unit 107 receives image data (dot pattern data) corresponding to one row of the recording head 11, the dot pattern data for one row is serialized to the head driver 108 in synchronization with the clock signal. Data is sent out, and a latch signal is sent to the head driver 108 at a predetermined timing.

  The head drive control unit 107 includes a ROM (can be configured by the ROM 102) storing pattern data of a drive waveform (drive signal) and D / A-converted D of drive waveform data read from the ROM. A waveform generation circuit including an A converter and a drive waveform generation circuit including an amplifier and the like are included.

  The head driver 108 also receives a clock signal from the head drive control unit 107 and serial data as image data, and a latch circuit that latches the register value of the shift register using a latch signal from the head drive control unit 107. A level conversion circuit (level shifter) that changes the output value of the latch circuit, an analog switch array (switch means) that is controlled to be turned on / off by the level shifter, and the like, and controls on / off of the analog switch array. In this way, a required drive waveform included in the drive waveform is selectively applied to the actuator means of the recording head 11 to drive the head.

  Further, the control unit 100 performs sub-scanning motors with a feed amount obtained by adding (adding or subtracting) a different correction value for a predetermined paper feed amount (transfer amount) during forward printing and during backward printing during bidirectional printing. The driving unit 113 is controlled to drive the sub-scanning motor 31 to control the feed amount of the paper 15 by the transport belt 21. The correction value is a value including “0”.

Therefore, paper feed control during bidirectional printing in the inkjet recording apparatus will be described with reference to FIG.
First, as shown in FIG. 2, it is necessary to provide a predetermined clearance C between the sliding member of the carriage 5 (not shown, but a bush or the like) and the guide rod 3 which is a carriage supporting member. is there. For this reason, as shown in FIG. 5, the carriage 5 may be inclined in the opposite direction during forward printing and backward printing.

  FIG. 5 is an explanatory diagram for explaining the landing position deviation due to the inclination of the carriage. In the figure, the angle “θ” indicates the tilt angle of the carriage 5, the point D indicates the fulcrum of the tilt of the carriage 5, and the line “E” indicates the axis in the sub-scanning direction passing through the fulcrum of the tilt of the carriage 5. ing. At this time, the head 11A is arranged on one side with respect to the axis E, and the head 11B is arranged on the other side.

  Here, as shown in FIG. 5A, when the carriage 5 is scanned in the forward direction (scanning in the direction of arrow A1), the carriage 5 is centered on the fulcrum D and the downstream side of the carriage 5 is in the sub-scanning direction. With respect to the axis E along the sub-scanning direction passing through the rotation fulcrum D, the inclination is inclined in the direction opposite to the moving direction (arrow A1 direction) on the forward path by an inclination angle θ.

  Further, as shown in FIG. 5B, when the carriage 5 performs backward scanning (when scanning in the direction of arrow A2), the carriage 5 rotates around the fulcrum D on the downstream side in the sub scanning direction. With respect to the axis E along the sub-scanning direction passing through the fulcrum D, the inclination angle −θ is inclined in the direction opposite to the moving direction (arrow A2 direction) on the return path.

  Therefore, as shown in FIG. 5, for example, when an image (line) Y is printed by forward printing, and when an image (line) Z is printed by backward printing, landing on the paper 14 as a recording medium is possible. A shift amount a1 or a2 in the bidirectional sub-scanning direction of the generated image is generated.

  For example, in the forward printing, the line Y2 is printed by the recording head 11A and the line Y1 is printed by the recording head 11B. In the backward printing, the line Z2 is printed by the recording head 11A and the line Z1 is printed by the recording head 11B. For the recording head 11A, even if the nozzles are the same, a deviation amount a2 is generated (the backward path is shifted upstream in the sub-scanning direction), and for the recording head 11B, the deviation amount a1 is generated (return path). Is shifted to the downstream side in the sub-scanning direction). That is, during bidirectional printing, a deviation due to the carriage tilt occurs in the forward path and the backward path, but the phase of the deviation is reversed depending on the position of the recording head.

  Therefore, in this ink jet recording apparatus, the landing positions in the forward printing and the backward printing are made the same by making the paper feed amount (transfer amount) different between the forward printing and the backward printing.

  That is, as shown in FIG. 6, when performing the sub-scan feed control, it is determined whether or not the line to be printed in the scan is forward pass printing, and if it is forward pass printing, a predetermined feed amount (predetermined transport amount) is determined. If the paper 15 is fed by X and is not forward printing, that is, if it is backward printing, the paper is fed by a feeding amount (X + a) obtained by adding a correction value a of the feeding amount of the backward printing to a predetermined feeding amount (transfer amount) X. 15 is sent. It should be noted that a separate correction value can be added to the predetermined printing amount for both the forward printing and the backward printing, or the forward printing amount is set as the predetermined printing amount. An amount obtained by adding a correction value to the predetermined feed amount (subtracted here) can also be used.

  In other words, when the predetermined feed amount is X, the forward printing amount X and the backward printing feed amount (X + a) are different for this predetermined feed amount X (both the forward pass and the return pass are the same). It does not mean that it is different from the predetermined feed amount X).

  This will be specifically described with reference to FIG. FIG. 7 is an explanatory diagram for correction of sub-scan feed, and shows a state in the case of performing half-interlaced bi-directional printing, and a line image formed with a predetermined interval width of two dots of landed ink droplets. It is explanation about.

  At this time, FIG. 7A shows a situation in which a line image is formed during the carriage forward movement during the first scan, and FIG. 7B shows a situation in which a line image is formed during the carriage backward movement during the second scan. 7 (c) shows a situation in which a line image is formed during the forward operation during the third scan.

  In this example, since the line image is formed by the recording head 11B, the shift amount a2 is generated on the downstream side in the sub-scanning in the backward printing with respect to the forward printing. Therefore, the landing position deviation due to the deviation amount a2 can be eliminated by increasing the feeding amount of the sheet 15 by an amount corresponding to the deviation amount a2 with respect to the predetermined feeding amount.

  First, the line image Y1 is formed by the recording head 11B in the first scan (outward printing). Thereafter, in order to print the next line on the return path, the value when the carriage 5 is tilted is added as the correction value a to the predetermined transport amount X of the sub-scan feed, and the paper 15 is fed by the feed amount of (X + a). The recording head 11B forms an image Z1 at a predetermined interval h adjacent to the line image Y1 formed during the first scan in the second scan (return printing).

  At this time, the landing is shifted due to the inclination of the carriage 5, but as described above, the sheet 15 is fed by the feed amount of (X + a) obtained by adding the value when the carriage 5 is tilted to the predetermined transfer amount X as the correction value a. Therefore, when the ink ejected from the nozzles of the recording head 11B lands, the line image at the second scan can be formed with a predetermined interval h adjacent to the line image formed at the first scan.

  After the second scan is completed, printing is performed on the forward path in the next third scan, so the paper 15 is fed with a predetermined feed amount X (that is, without adding the correction value a). In the third scan with respect to the second scan, landing deviation corresponding to the inclination of the carriage 5 occurs. However, since the sheet 15 is fed by a predetermined feed amount X without adding the correction value a, landing deviation caused by the inclination of the carriage 5 is prevented. It will be corrected. Therefore, a line image formed at the time of the third scan is formed at a predetermined interval h adjacent to the line images Z1, Z2 formed at the time of the second scan.

  As described above, the correction during the series of operations can be performed during the carriage forward operation and not performed during the carriage backward operation. Further, the correction amount (correction value) can be individually provided for the carriage forward operation (forward printing) and the carriage return operation (return printing).

  As described above, in order to correct the deviation of the landing on the recording medium in the sub-scanning direction in the forward path and the backward path, the feed amount of the recording medium in the forward path printing and the recording medium in the backward path printing are corrected. The feed amount is corrected using the same difference as the difference between the landing position in the sub-scanning direction caused by the inclination during the forward movement of the carriage and the landing position in the sub-scanning direction caused by the inclination during the backward movement of the carriage. In addition, even if the carriage is tilted, the landing positions in the sub-scanning direction in the forward printing and the backward printing can be made the same, the clearance of the carriage support member is reduced, and the load is not increased. Without increasing the size, the influence of landing deviation in the sub-scanning direction during bidirectional printing due to the inclination of the carriage can be reduced, and the image quality can be improved.

  In the above description, the influence of the ink supply tube 12 connected to the carriage 5 has been ignored. Next, an elastic body such as the ink supply tube 12 is connected to or coupled to the carriage 5, so that the carriage A case where an urging force in a predetermined direction is applied to 5 will be described with reference to FIG.

  As shown in FIG. 8, when an elastic body (in this case, the tube 12) is attached to the carriage 5, the carriage 5 is stably brought into contact with the elastic body from the left to the right in FIG. Since the moment acts, the difference between the inclination α1 of the carriage 5 during the carriage outward movement and the inclination α2 of the carriage 5 during the carriage backward movement becomes small, and if a certain force or more is applied to the carriage 5 from the elastic body, the carriage The inclination direction 5 is the same in the carriage forward operation and in the backward operation.

  In this case, the amount of deviation in the sub-scanning direction during bidirectional printing is the same as the amount of deviation a3 in the recording head 11A and the amount of deviation a4 in the recording head 11B.

  Further, as shown in FIG. 9, the fulcrum supporting the carriage 5 is set at a lower position M (support position by the guide rod 3) near the end of the carriage 5 and an upper position N (support position by the stay 4). Place each one. As a result, the force applied to the position M is stably in the f2 direction, so that the carriage 5 is stably applied to the guide rod 3 from the f2 direction.

  Thus, the inclination of the carriage 5 is reduced during the backward operation, and the position of the carriage 5 in the sub-scanning direction is prevented from becoming unstable due to the clearance between the sliding member of the carriage 5 and the carriage support member (guide rod 3). it can.

  By these actions, the landing deviation in the sub-scanning direction during bidirectional printing of the carriage forward scanning and the carriage backward scanning is stable and the difference in the amount of landing deviation in the sub-scanning direction during the carriage forward and backward passes is also reduced. Therefore, the correction value of the feed amount (transfer amount) of the sub-scan feed in the carriage forward path and the carriage return path is not recorded even when the head is arranged so as to sandwich the axis line in the sub-scan direction passing through the fulcrum of the tilt of the carriage. Even when the head is driven, the same correction value can be used.

  In other words, if there is a phase difference between the slopes in the forward path and the backward path, the left and right heads will land with different phases, so it is necessary to have a correction value, but if there is no phase difference between the forward path and the backward path, it will be corrected. Since the values are in the same direction, the same correction value can be used. This is because the elastic body makes the forward and backward carriages tilt in the same direction as described above, the elastic body reduces the difference between the forward and backward carriage inclinations, and the carriage support structure (method). By pressing the carriage in one direction, the carriage scans a stable position, so there is less variation in landing, so there is little difference in landing between the left and right heads, and minute landing deviation due to left and right heads. The influence on the image quality due to the image quality can be ignored, and the same correction value can be used for the left and right sides of the head. As a result, bidirectional printing in which the left and right heads are simultaneously driven can be performed.

  Here, it demonstrates concretely with reference to FIG. This figure shows a state by half-interlaced bidirectional printing, and is an explanation of a line image formed with a width of 2 dots of landed ink droplets. Here, FIG. 10A shows the first scan (forward pass printing), FIG. 10B shows the second scan (return pass printing), and FIG. 10C shows the third scan (outward pass print). Yes.

  As can be seen from FIG. 8 described above, if the forward printing and the backward printing have the same inclination direction and the backward printing has a small inclination angle, the backward printing feed amount is set to a predetermined feed amount x (x includes the corrected amount). Then, the difference (a3−a4) in the amount of deviation between the forward printing and the backward printing is set as the correction value a, so that when the line to be printed is the forward printing, the sub-scan feed amount is (x + a). Sometimes the sub-scan feed amount may be set to a predetermined feed amount x.

  Therefore, the line image Y1 is formed by the recording head 11A in the first scan (outward printing). Thereafter, in order to print the next line in the backward path, the sheet 15 is fed by a predetermined transport amount x of the sub-scan feed, and the line image Y1 formed at the first scan by the recording head 11A in the second scan (return path printing). An image Z1 is formed at a predetermined interval h next to the image Z1.

  At this time, the landing is shifted due to the inclination of the carriage 5, but since the correction value includes the value when the carriage 5 is inclined to the predetermined transfer amount x as described above, the ink ejected from the nozzles of the recording head 11A has landed. Sometimes, a line image for the second scan can be formed with a predetermined interval h adjacent to the line image formed for the first scan.

  After the second scan is completed, printing is performed in the forward path in the next third scan. Therefore, the correction value a corresponding to the inclination of the carriage 5 generated in the forward path printing is added to the predetermined feed amount x (x + a). The paper 15 is fed by the feed amount. In the third scan, a landing deviation corresponding to the inclination of the carriage 5 occurs in the third scan, but since the correction value a is added, the landing deviation due to the inclination of the carriage 5 is corrected. Therefore, a line image formed at the time of the third scan is formed at a predetermined interval h adjacent to the line images Z1, Z2 formed at the time of the second scan.

  In this way, by providing an elastic body that applies a force to the carriage, a force in one direction is applied to the carriage by the elastic body, and the moment of inertia that acts on the carriage during the forward movement of the carriage and the carriage during the backward movement of the carriage. The difference in inertia moment can be reduced, and the difference between the inclination during the carriage forward movement and the inclination during the carriage backward movement can be reduced.

  In addition, the direction of inclination of the carriage during the forward movement of the carriage and the direction of inclination of the carriage during the backward movement of the carriage can be made to coincide with the axis passing through the fulcrum of the carriage inclination. It is also possible to prevent the phase of the landing position deviation direction during the return path operation from being reversed.

  Further, by configuring the fulcrum supporting the carriage to be above and below the end of the carriage, the load direction works stably in a certain direction in the sub-scanning direction, so the carriage moves in a certain direction in the sub-scanning direction. It can be supported stably, and variation in the position of the carriage in the sub-scanning direction can be reduced.

Next, another embodiment of the present invention will be described with reference to FIGS.
In this embodiment, one recording head 51B has a nozzle row for ejecting achromatic ink, and the other recording head 51A has a nozzle row for ejecting chromatic ink.

  Here, when only the achromatic recording head 51B is driven, the feed amount in the sub-scanning direction of the achromatic recording head 51B is corrected. For example, as shown in FIG. 11A, the line drawing Y11 is formed by the forward movement of the carriage 5 during the first scan. Since the second scan is a return pass, the first scan is performed as shown in FIG. 5B by feeding the paper 15 with the feed amount of (X + a) obtained by adding the correction value a5 to the predetermined feed amount X. The line image Z11 can be formed by backward printing at a predetermined interval h adjacent to the line image Y11 at the time.

  Thereafter, since the third scan is forward printing, by feeding the paper 15 with a predetermined feed amount X, as shown in FIG. 5C, a predetermined interval h is adjacent to the line image Z12 at the time of the second scan. A line image Y12 can be formed by placing.

  Further, when an image is formed by driving only the chromatic recording head 51A, as shown in FIG. 12, it is ejected from the nozzles of the chromatic recording head 51A by tilting on the carriage 5 during forward printing. The sheet is fed by a feed amount that is added to a predetermined feed amount X, using a deviation amount a6 in the sub-scanning direction at the time of bidirectional printing at the landing position of the droplet as a correction value.

  For example, as shown in FIG. 12A, the line drawing Y21 is formed by the forward movement of the carriage 5 during the first scan. Since the second scan is a return path, by feeding the paper 15 with a predetermined feed amount X, a predetermined interval h is set next to the line image Y21 during the first scan, as shown in FIG. Then, the line image Z21 can be formed by return printing.

  Thereafter, since the third scan is forward printing, the sheet 15 is fed by a feed amount obtained by adding the correction value a6 to the predetermined feed amount X, and as shown in FIG. A line image Y22 can be formed at a predetermined interval h next to the image Z22.

  In this case, since the timing for applying the correction is changed in the forward path (example in FIG. 11) and the return path (example in FIG. 12), the heads are different and the phase is reversed, but the correction timing is changed in this way. Therefore, both corrections are configured to add the correction value a5 or a6 to the predetermined amount X.

  In this way, the carriage is provided with a recording head having a nozzle array that discharges achromatic recording liquid on one side of the axis in the sub-scanning direction passing through the carriage tilt fulcrum, and on the carriage tilt fulcrum. A recording head having a nozzle row that discharges a chromatic recording liquid on the other side across the axis line in the sub-scanning direction that passes therethrough is used as a correction value for the feed amount of the recording medium. Only the side is driven to use the correction value at the time of achromatic color printing, and at the time of chromatic color printing including the achromatic color, only the chromatic color head is driven to use the correction value at the time of chromatic color printing. This makes it possible to change the landing position during the forward operation during bidirectional printing and the correction value during the backward printing depending on the position of the head with respect to the carriage, thus eliminating the positional deviation in the sub-scanning direction in both directions. Image quality is improved.

  In the above-described embodiment, the present invention has been described with an example in which an inkjet recording apparatus as an image forming apparatus is configured as a printer. However, the present invention may be applied to a facsimile apparatus, a copying apparatus, a printer / fax / copier multifunction machine, and the like. it can. The present invention can also be applied to an image forming apparatus using a recording liquid (liquid) other than ink.

1 is a schematic perspective explanatory view of a mechanism portion of an ink jet recording apparatus as an embodiment of an image forming apparatus to which the present invention is applied. It is principal part plane explanatory drawing of the mechanism part. It is principal part side explanatory drawing of the mechanism part. It is a block diagram which shows the outline | summary of the control part of the apparatus. FIG. 6 is an explanatory diagram for explaining occurrence of landing position deviation due to a tilt of a carriage in forward printing and backward printing. FIG. 6 is a flowchart for explaining sheet feed control in the apparatus. FIG. 6 is an explanatory diagram for explaining a specific example of the paper feed control. FIG. 10 is an explanatory diagram for explaining the occurrence of landing position deviation due to the inclination of the carriage in the forward printing and the backward printing when the carriage has an elastic body. It is explanatory drawing with which it uses for description of the acting force which acts on the support point and carriage of a carriage. FIG. 10 is an explanatory diagram for explaining another specific example of sheet feeding control. It is explanatory drawing with which it uses for description of the paper feed at the time of printing by the achromatic head in other embodiment of this invention. It is explanatory drawing with which it uses for description of the paper feed at the time of printing by a chromatic head similarly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Guide shaft 5 ... Carriage 11A, 11B ... Recording head 12 ... Ink supply tube 15 ... Paper (recording medium)
16 ... Conveying belt 21 ... Sub-scanning motor

Claims (6)

  An image capable of bidirectional printing in which a recording head for discharging a recording liquid is reciprocated in the main scanning direction, the recording medium is transferred in the sub-scanning direction orthogonal to the main scanning direction, and an image is formed on the recording medium. The image forming apparatus according to claim 1, wherein the transfer amount of the recording medium is different between forward printing and return printing for a predetermined transfer amount.   The image forming apparatus according to claim 1, wherein each of the correction values for the forward pass printing and the return pass printing is set for a predetermined transfer amount.   The image forming apparatus according to claim 1, wherein the image forming apparatus has a correction value for either the forward printing or the backward printing for a predetermined transfer amount.   The image forming apparatus according to claim 1, wherein the carriage includes an elastic body.   5. The image forming apparatus according to claim 4, wherein the carriage is held so as to be movable in the main scanning direction at two or more positions, at least at one lower end position and above the lower end position. Image forming apparatus.   6. The image forming apparatus according to claim 1, wherein at least a head including a nozzle array for ejecting an achromatic recording liquid and a head including a nozzle array for ejecting a chromatic recording liquid. And an image forming apparatus that individually corrects the transfer amount of the recording medium during achromatic printing and during chromatic printing.

Images