JP2010137412A - Inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording apparatus suppressing spoiling of the quality of a recording image caused by shifting of a recording medium in the direction orthogonal to the conveying direction of the recording medium. <P>SOLUTION: Shifting of the recording medium in the carriage scanning direction before and after passing through pinching of the recording medium between a conveying roller and a pinching roller is detected, and a timing of delivery from a recording head is corrected according the result of the detection. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that performs recording by ejecting ink onto a recording medium by recording means.

  Conventionally, in a recording apparatus such as a printer, a copying machine, and a facsimile, as a mechanism for conveying a recording medium, a conveying roller, a pinch roller that generates a conveying force by being pinched with the conveying roller, and an urging force is generated in the pinch roller. There is provided a mechanism comprising a means for making them. Such a transport mechanism transports the recording medium fed from the paper feed unit in a recording area that can receive the ink ejected from the recording head. Generally, two pairs of transport mechanisms are provided before and after the recording area. Thereby, the recording medium can be conveyed with high accuracy in the recording area, and a predetermined tension can be applied to the recording medium during recording to keep a wide area flat.

  FIG. 12 is a cross-sectional view mainly showing a recording medium conveying mechanism in a conventional ink jet recording apparatus. The recording head 11 mounted on the carriage unit 13 scans in a direction perpendicular to the paper surface of the drawing, and performs recording (hereinafter also referred to as printing) by ejecting ink during the scanning. In the recording area in which the recording head 11 can record on the recording medium P, the recording medium P is transported substantially horizontally from the right side to the left side in the figure below the carriage unit 13. That is, on the upstream side and downstream side of the recording area in the conveyance direction of the recording medium P, a pair of a conveyance roller (hereinafter also referred to as an LF roller) 21 and a pinch roller 22, and a paper discharge roller 30 and a spur 32, respectively. A pair is provided as the two pairs of transport mechanisms described above. Among these, the pinch roller 22 is rotatably supported by a rotating shaft provided in the pinch roller holder 23, and the pinch roller holder 23 is urged by a spring to press the pinch roller 22 against the transport roller 21. can do. A pressing force is similarly applied between the paper discharge roller 30 and the spur 32 by a pressing mechanism (not shown). The recording medium P is sandwiched between these two pairs of rollers, and the conveyance roller 21 and the paper discharge roller 30 are rotationally driven by a drive mechanism (not shown), so that the recording medium P is one of the recording heads 11. A predetermined amount is conveyed for each scanning.

  Control of the conveyance amount in conveyance of the recording medium P is normally performed based on a signal generated by an encoder mechanism having an encoder wheel that is directly attached to the conveyance roller 21 and rotates. Specifically, the rotation amount or the rotation position is known by counting signals generated as the encoder wheel rotating coaxially with the conveyance roller 21 rotates, and the conveyance amount of the recording medium P is detected based on this. is doing. Then, when the detected transport amount reaches a predetermined amount, control is performed to stop the rotation of the motor that drives the transport roller and the like.

  Among the recording apparatuses, the serial printer using the dot matrix recording method such as the ink jet method employed in the recording apparatus of the present embodiment is a bidirectional printing method as a method for realizing high-speed or high-quality printing at low cost. There is. As a technique for performing high-quality printing in this bidirectional printing method, for example, there is multi-pass printing. In order to realize high-speed or high-quality printing, it is considered to increase the number of recording elements in a recording head having a plurality of recording elements and to improve the scanning speed of the recording head. Performing bidirectional printing scanning is also an effective method. For example, when recording is performed by transporting a recording medium in a direction perpendicular to the recording scanning (main scanning) direction (for example, the sub-scanning direction that is the feeding direction of the recording medium), the unidirectional printing for bidirectional printing is performed by the recording head. All printing scans are performed only when moving in one direction from a predetermined scan start position. Then, in the reverse direction for returning from the scan end position to the scan start position, the recording head returns to the scan start position without performing printing. Therefore, bi-directional printing can be performed at a speed nearly twice that of unidirectional printing, and can be said to be an effective method for improving the recording speed.

Next, a multi-scan printing method will be described as an example of a high image quality technology.
When printing is performed using a recording head having a plurality of recording elements, the quality of the recorded image largely depends on the performance of the recording head alone. For example, in the case of an ink jet recording head, slight differences that occur in the recording head manufacturing process, such as variations in the shape of the ink discharge port and the elements that generate energy used for ink discharge, such as electrothermal transducers (heaters), are This affects the amount and direction of ink discharge. These differences can cause image quality to deteriorate as density unevenness of the finally formed image.

  In general, it is ideal that ink is ejected from each ink ejection port (hereinafter also simply referred to as ejection port) in a substantially uniform ejection amount and in a uniform direction. If ideal ejection is performed, ink dots of uniform size land on the recording medium, and a uniform image without density unevenness can be obtained as a whole. However, in actuality, as described above, the recording head has variations in each discharge port. For this reason, when printing is performed as it is, the size and direction of ink droplets ejected from the respective ink ejection ports vary, and the blank portion of the recording medium periodically exists in the main scanning direction of the recording head. Or, conversely, dots overlap more than necessary. A collection of dots that have landed in such a state has a density distribution with respect to the direction in which the ejection ports are arranged, and as a result, is normally perceived as density unevenness by the human eye.

  Therefore, a multi-scan printing method has been devised as a measure against density unevenness. In this method, printing is completed by performing a plurality of scans with respect to the recording width recorded in one recording scan. The ejection ports of the recording head are divided into a plurality of groups in the vertical direction (sub-scanning direction), and image data is thinned and recorded according to a predetermined image data array. Then, the recording medium is conveyed, and similarly, dots are embedded in the remaining image data during the second and subsequent scans, thereby completing a pixel unit area. Since the influence on the recorded image due to such a variation in each nozzle is halved, density unevenness is considerably reduced.

  When performing such printing, the first and second scans divide the image data according to a predetermined arrangement (mask) so as to make up for each other. In general, this image data array (thinning pattern) is most commonly used in the form of a staggered pattern for each vertical and horizontal pixel. In the unit printing area (4 pixel unit here). Recording is completed by the first scan that forms dots in a zigzag pattern and the second scan that forms dots in a reverse zigzag pattern. Further, the moving amount (sub-scanning amount) of the recording medium between each scanning is normally set to be constant and is moved evenly by the divided nozzles.

  In some cases, density unevenness is caused by factors of the recording apparatus as a cause of density unevenness. In the transport mechanism as described above, the recording medium P is transported more than the intended transport amount when the trailing end of the transport of the recording medium P comes out of the nipping by the transport roller 21 and the pinch roller 22. There is a case. As a result, it is known that the relative position of the recording head with respect to the recording medium sheet P deviates from the normal position. As a result, the positions (image positions) of the ink dots formed on the recording medium P are shifted by the ink ejection from the recording head at the recording positions before and after the recording medium P is nipped by the conveying roller 21 and the pinch roller 22. The quality of the recorded image is impaired. Therefore, Patent Document 1 discloses a configuration in which the recording medium P detects the amount of rotation of the paper discharge roller 30 immediately before and after the nipping by the conveying roller 21 and the pinch roller 22 and corrects the recording.

JP 2002-361958 A

  However, the correction in the transport mechanism as in Patent Document 1 is correction only in the transport direction (sub-scanning direction) of the recording medium. Actually, even in the main scanning direction intersecting with the transport direction, the recording medium may deviate from the normal position when the rear end portion of the recording medium P comes out of the nipping by the transport roller 21 and the pinch roller 22. As a result, the overlapping of the arrangement of the ink dots printed before and after the nipping by the conveying roller 21 and the pinch roller 22 may deviate from the normal position, and the quality of the recorded image may be impaired.

  Therefore, the present invention has been made to solve the above problems, and provides a recording apparatus that suppresses the deterioration of the quality of a recorded image due to the displacement of the recording medium in a direction orthogonal to the recording medium conveyance direction. The purpose is to do.

  Therefore, the ink jet recording apparatus of the present invention includes a recording head that discharges ink to a recording medium, a carriage that mounts and scans the recording head, and the recording medium is narrowed by a first roller and a second roller. An inkjet recording apparatus comprising: a conveying unit configured to convey the recording medium in a scanning direction of the carriage before and after being released from the nipping between the first roller and the second roller; Detection means for detecting a positional deviation is provided, and the ejection timing of the recording head is corrected according to the detection result of the detection means.

  The ink jet recording apparatus of the present invention includes a recording head that discharges ink to a recording medium, a carriage that mounts and scans the recording head, and the recording medium includes a first roller and a second roller. First conveying means for conveying by holding, and second conveying for conveying the recording medium conveyed by the first conveying means by nipping between the third roller and the fourth roller A detecting means for detecting a positional deviation of the third roller before and after the recording medium is released from the nipping between the first roller and the second roller. And the ejection timing of the recording head is corrected according to the detection result of the detection means.

  The ink jet recording apparatus of the present invention comprises a detecting means for detecting a positional deviation in the scanning direction of the carriage of the recording medium before and after being released from the nipping between the first roller and the second roller. According to the detection result, the ejection timing of the recording head is corrected. Accordingly, it is possible to realize a recording apparatus that suppresses the deterioration of the quality of the recorded image due to the displacement of the recording medium in the direction orthogonal to the recording medium conveyance direction.

  In addition, the ink jet recording apparatus of the present invention includes a detecting unit that detects a positional deviation of the third roller before and after the recording medium is released from the nipping between the first roller and the second roller. The ejection timing of the recording head is corrected according to the detection result. Accordingly, it is possible to realize a recording apparatus that suppresses the deterioration of the quality of the recorded image due to the displacement of the recording medium in the direction orthogonal to the recording medium conveyance direction.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic perspective view showing the overall configuration of a recording apparatus to which the present invention is applicable. FIG. 2 is a schematic side sectional view showing the overall configuration of the recording apparatus as seen from the direction of arrow A in FIG. A chassis 10 supports the structure of the recording unit main body 1. The ink tank 12 stores ink to be supplied to the recording head 11, and the recording head 11 performs recording by discharging the ink supplied from the ink tank 12. The guide shaft 14 supports the carriage, and the guide rail 15 supports the carriage 13 in parallel with the guide shaft 14. The carriage 13 holds the recording head 11 and the ink tank 12 and scans along the guide rail 15.

  The carriage motor 17 drives the carriage belt 16 via a pulley, and the code strip 18 detects the position of the carriage 13. The idler pulley 20 stretches the carriage belt 16 facing the pulley of the carriage motor 17. The pinch roller 22 is a conveyance roller that conveys the recording medium, and is pressed and driven by the conveyance roller 21. The pinch roller holder 23 rotatably holds the pinch roller 22, and the pinch roller spring 24 is a pinch roller 22 that conveys the conveyance roller. Press contact. The conveyance roller pulley 25 is fixed to the conveyance roller, and the LF motor 26 drives the conveyance roller. The code wheel 27 detects the rotation angle of the conveying roller, and the platen 29 faces the recording head 11 and supports a recording medium (hereinafter also referred to as a sheet). The first paper discharge roller 30 cooperates with the conveyance roller 21 to convey the recording medium P. The second paper discharge roller 31 is provided on the downstream side of the first paper discharge roller 30, and the first spur train 32 faces the first paper discharge roller 30 and holds the recording medium. The second spur train 33 holds the recording medium facing the second paper discharge roller. The spur base 34 rotatably holds the first spur train 32 and the second spur train 33, and the maintenance unit 36 is used for preventing nozzle clogging of the recording head 11 and replacing the ink tank 12. The main ASF 37 is loaded with recording media and supplied one by one during the recording operation, and the ASF base 38 is a base of the main ASF 37. The paper feed roller 39 contacts and conveys the stacked recording media, and the separation roller 40 separates a plurality of recording media one by one when they are simultaneously conveyed. The pressure plate 41 is loaded with a recording medium and urged toward the paper feed roller 39, and the side guide 42 is provided on the pressure plate 41 so that the recording medium can be fixed with an arbitrary width. The return claw 43 returns the leading end of the recording medium that has advanced beyond the nip portion between the paper supply roller 39 and the separation roller 40 to a predetermined position during the paper supply operation. The ASF flap 44 restricts the recording medium feeding direction from the main ASF 37 to one direction. The lift input gear 50 engages with the ASF planetary gear 49, and the lift reduction gear train 51 transmits the power from the lift input gear 50 while decelerating. The lift cam gear 52 is directly connected to the lift cam shaft, and the guide shaft spring 55 urges the guide shaft to be biased. The guide slope 56 is a surface on which the cam of the guide shaft gear 53 slides, and the lift cam shaft 58 lifts the pinch roller holder 23 and the like. The sheet passing guide 70 guides the leading edge of the recording medium to the nip portion between the conveying roller 21 and the pinch roller 22. The base 72 supports the entire recording unit main body 1, and the control board 301 collects the control unit.

  FIG. 3 is a block diagram illustrating a driving unit that drives a recording apparatus to which the present embodiment is applicable. The CR encoder sensor 19 is mounted on the carriage 13 and reads the code strip 18. The LF encoder sensor 28 is attached to the chassis 1 and reads the code wheel 27. The ASF motor 46 drives the main ASF 37, and the PE sensor 67 detects the operation of the PE sensor lever. The lift cam sensor 69 detects the operation of the lift cam shaft 58, and the duplex unit sensor 130 detects the attachment / detachment of the automatic duplex unit 2. The PG motor 302 drives the maintenance unit 36, and the PG sensor 303 detects the operation of the maintenance unit 36. The ASF sensor 305 detects the operation of the main ASF 37, and the head driver 307 drives the recording head 11. The host device 308 sends the recording data to the recording device, and the I / F 309 mediates the electrical connection between the host device and the recording device. The CPU 310 controls the recording apparatus and issues a control command. The ROM 311 is an area where control data and the like are written, and the RAM 312 is an area where the recording data and the like are expanded.

The outline of the recording apparatus will be described with reference to FIG. 1 and FIG. 2, and then the operation of each unit will be described. First, an outline of the configuration of a general serial scanning recording apparatus will be described.
The recording apparatus according to the present embodiment is roughly divided into a sheet feeding unit, a sheet conveying unit, a recording unit, and a recording head maintenance unit. When recording data is sent from the host device 308 and stored in the RAM 312 via the I / F 309, the CPU 310 issues a recording operation start command to start the recording operation. When the recording operation starts, a paper feeding operation is first performed.

  The paper feeding unit is a main ASF (Automatic Sheet Feeder) 37, which plays a role of pulling out one recording medium for each recording operation from a plurality of recording media (not shown) stacked on the pressure plate 41 and sending it to the paper transport unit. Have. At the start of the paper feeding operation, the ASF motor 46 rotates in the forward direction, and the power rotates the cam holding the pressure plate 41 via the gear train. When the cam is removed by rotation, the pressure plate 41 is urged toward the paper feed roller 39 by the action of a pressure plate spring (not shown). At the same time, the paper feed roller 39 rotates in the direction in which the paper is transported, so that transport of the uppermost recording medium loaded is started. At that time, a plurality of recording media may be simultaneously conveyed depending on the conditions of the frictional force between the paper feed roller 39 and the recording medium and the frictional force between the recording media. In that case, the separation roller 40 is pressed against the paper feed roller 39 and has a predetermined return rotational torque in the direction opposite to the recording medium conveyance direction, and the recording medium other than the recording medium closest to the paper feed roller 39 is used. It works to push back onto the pressure plate. At the end of the ASF paper feeding operation, the separation roller 40 is released from the pressure contact state with the paper feeding roller 39 by the operation of the cam and is separated by a predetermined distance. At that time, the recording medium is surely reached to a predetermined position on the pressure plate. In order to push back, the return claw 43 rotates and plays a role. By the operation as described above, only one recording medium is conveyed to the sheet conveying unit. When one recording medium is transported from the main ASF 37, the leading edge of the recording medium comes into contact with the ASF flap 44 that is urged by the ASF flap spring in a direction that obstructs the sheet passing path. Push away and pass. When the recording operation of the recording medium is completed and the trailing edge of the recording medium passes through the ASF flap 44, the ASF flap 44 returns to the original biased state and the sheet passing path is closed, so that the recording medium is conveyed in the reverse direction. However, it does not return to the main ASF 37 side.

  The recording medium conveyed from the paper supply unit is held in a nipping portion (hereinafter also simply referred to as a nip portion) between a conveyance roller (first roller) 21 and a pinch roller (second roller) 22 as a sheet conveyance unit. It is conveyed toward. Since the center of the pinch roller 22 is attached with a slight offset in the direction approaching the first paper discharge roller 30 with respect to the center of the transport roller 21, the tangential angle at which the recording medium is inserted is slightly inclined from the horizontal. ing. Accordingly, the sheet is conveyed at an angle in the sheet passing path formed by the pinch roller holder 23 and the sheet passing guide 70 so that the leading end of the sheet is accurately guided to the nip portion. The sheet conveyed by the ASF 37 is abutted against the nip portion of the conveyance roller 21 in a stopped state. At this time, a paper loop is formed between the paper feed roller 39 and the transport roller 21 by transporting the main ASF 37 for a distance slightly longer than the predetermined sheet passing path length. When the leading edge of the sheet is pressed against the nip of the conveying roller 21 by the force that the loop returns straight, the leading edge of the sheet becomes parallel to the conveying roller 21 and the so-called registration removing operation is completed.

  After completing the registration removing operation, the LF motor 26 starts to rotate in the direction in which the recording medium moves in the forward direction (the direction in which the recording medium advances toward the first paper discharge roller 30). After that, the driving force of the paper feed roller 39 is cut, and the paper feed roller 39 rotates with the recording medium. At this time, the recording medium is transported only by the transport roller 21 and the pinch roller 22. The paper advances in the positive direction every predetermined line feed amount, and advances along the rib provided on the platen 29. The leading edge of the sheet is gradually applied to the first paper discharge roller (third roller) 30 and the first spur train (fourth roller) 32, and the second paper discharge roller 31 and second spur train 33. In the present embodiment, the first discharge roller and the first spur train, or the second discharge roller and the second spur train are used as the discharge unit. The peripheral speeds of the first paper discharge roller 30 and the second paper discharge roller 31 are set substantially equal to the peripheral speed of the transport roller 21, and the first paper discharge roller 30 and the second paper discharge roller 31 from the transport roller 21 are set. Are connected by a gear train. For this reason, these rollers rotate synchronously, so that the paper is conveyed without being slackened or pulled.

  The recording unit mainly includes a recording head 11 and a carriage 13 that mounts the recording head 11 and scans in a direction (main scanning direction) orthogonal to the recording medium conveyance direction. The carriage 13 is supported by a guide shaft 14 and a guide rail 15 that is a part of the chassis 10. Between the carriage 13 and the guide rail 15, a slider 9 that is rotatably attached to the carriage 13 is provided and slides on the guide rail. The carriage 13 is reciprocally scanned by transmitting the driving force of the carriage motor 17 via the carriage belt 16 stretched between the carriage motor 17 and the idler pulley 20. The recording head 11 has a plurality of ink flow paths connected to the ink tank 12, and the ink flow paths are connected to the ejection nozzle rows arranged on the surface facing the platen 29. In the vicinity of the ejection nozzle row, an ink ejection actuator provided for each ejection nozzle is arranged. As the discharge actuator, an actuator utilizing a liquid film boiling pressure by an electrothermal transducer, an electrical pressure transducer such as a piezo element, or the like is used.

  By transmitting the signal of the head driver 307 to the recording head 11 via the flexible flat cable 73, it is possible to eject ink droplets according to the recording data. Further, by reading the code strip 18 stretched on the chassis 10 by the CR encoder sensor 19 mounted on the carriage 13, ink droplets can be ejected toward the recording medium at an appropriate timing. In this way, when the recording for one line is completed, the recording medium is conveyed by a necessary amount by the paper conveying unit. By repeating this operation, the recording operation over the entire surface of the recording medium becomes possible.

  The recording head maintenance unit plays a role of preventing ink clogging of the ink discharge nozzles of the recording head 11 and eliminating dirt due to paper dust or the like, or for sucking ink when the ink tank 12 is replaced. For this reason, the maintenance unit 36 installed so as to face the recording head 11 at the standby position of the carriage 13 generates a cap that protects the ink discharge port, a wiper that wipes the surface of the ink discharge port, and negative pressure in the cap. It is composed of a pump and the like. When the ink in the ejection port of the recording head 11 is sucked out, the cap is pressed against the ejection port surface of the recording head 11 and the pump is driven to make the inside of the cap have a negative pressure, thereby sucking the ink. In addition, when ink is attached to the discharge port surface after ink suction or when foreign matter such as paper dust adheres to the discharge port surface, the wiper is brought into contact with the discharge port surface and moved in parallel. It also has a mechanism. The above is the outline of the recording apparatus.

  Here, the recording range at the time of surface recording will be described. The recording head 11 is provided such that an ink discharge nozzle region N (see FIG. 2) is provided between the transport roller 21 and the first paper discharge roller 30. However, it is usually difficult to arrange the ink discharge nozzle region N in the vicinity of the nip portion of the transport roller 21 due to the arrangement of the ink flow path to the nozzle and the wiring to the actuator that discharges ink. Therefore, in a range where the recording medium is nipped by the conveyance roller 21 and the pinch roller 22 (hereinafter, also simply referred to as nipping by the conveyance roller), recording is performed only up to a range separated by a length L1 downstream from the nip of the conveyance roller. I can't do it. In order to reduce the lower end margin area of the front surface, in the recording apparatus provided in the present embodiment, the recording medium is detached from the nip portion of the transport roller 21, and the first discharge roller 30 (second transport unit) and the second discharge unit are removed. The recording operation is continued until the portion that is nipped and conveyed only by the paper roller 31. As a result, a recording operation until the bottom margin at the front surface becomes zero is possible.

  FIG. 4 is a bottom view of the carriage portion as seen from the direction of arrow B in FIG. The positional relationship between the printing unit and the optical characteristic measuring unit in the configuration of the recording apparatus provided in the present embodiment will be described. In printing that normally forms an image, printing is performed by conveying the recording medium in the direction of the arrow. The recording head 11 is provided with ejection ports composed of 11A, 11B, 11C, 11D, 11E, and 11F communicating with the respective ink tanks 12. The carriage 13 is provided with a reflective optical sensor 200 on the upstream side in the transport direction from the ejection port of the mounted recording head 11. The recording head 11 is an ink jet recording head that ejects ink using thermal energy, and includes an electrothermal transducer for generating thermal energy. In other words, printing is performed by ejecting ink from the ejection port using the pressure of bubbles generated by film boiling caused by thermal energy applied by the heat converter. The reflective sensor 200 is configured to detect the light reflection density with respect to the light irradiation region.

Next, detection of a recording medium positional deviation before and after releasing the conveyance roller nipping, which is a characteristic configuration of this embodiment, will be described.
FIGS. 5A to 5D show the conveyance state before and after the nip in the conveyance of the recording medium P in each stage. FIG. 5A is a diagram showing a recording medium leading edge detection step, in which the PE sensor lever 66 is in a free state. The PE sensor lever 66 is rotatably supported by the bearing portion of the chassis 10. In this state, the PE sensor lever 66 is biased to the position shown in the figure by the action of the PE sensor lever spring 68, and the shielding plate portion of the PE sensor lever 66 shields the PE sensor 67. From this state, when the recording medium P passes through the PE sensor lever 66, the PE sensor lever 66 rotates clockwise, and the PE sensor 67 is in a transmissive state to detect the presence of the recording medium.

  FIG. 5B shows the conveyance roller nip state, and the PE sensor 67 is in the transmissive state to detect the presence of the recording medium. The recording medium P is sandwiched and conveyed synchronously between the conveying roller 21 and the pinch roller 22 and between the discharge rollers 30 and 31 and the spurs 32 and 33.

  FIG. 5C is a rear end detection and conveyance roller nipping release determination step, and shows a state immediately after the PE sensor 67 enters the shielding state from the transmission state. Here, the distance between the conveyance roller 21 and the rear end of the recording medium is ΔL, and the conveyance amount by one driving of the conveyance roller 21 is ΔY. In this case, the recording medium P is held between the conveyance rollers 21 up to an integral number of conveyance roller feeding times of (ΔL / ΔY) value, and the recording medium P is conveyed to the conveyance rollers by the next conveyance roller 21. 21 is released from clamping.

  FIG. 5D shows a state in which the recording medium P is released from the conveyance roller 21, and the recording medium P released from the conveyance roller 21 is recorded while being conveyed by the discharge rollers 30 and 31. You can continue.

  FIG. 6 shows a recording medium in the carriage scanning direction in which the recording medium P is nipped between the conveyance rollers 21 and the state immediately before nipping is released (FIG. 5C) and the recording medium is just after nipping is released (FIG. 5D). It is the figure which showed the position of. The recording medium P <b> 1 indicates a recording medium that is sandwiched between the transport rollers 21, and the recording medium P <b> 2 indicates a recording medium that is transported only by the paper discharge rollers 30 with the transport rollers 21 being released.

  In the recording medium P1 and the recording medium P2, relative displacement of the displacement amount ΔX occurs in the recording medium with respect to the carriage scanning direction (arrow X direction) due to the conveyance roller 21 being nipped and released. The reason why such a relative shift occurs is as follows. The conveyance direction by the conveyance roller 21 and the paper discharge roller 30 is not necessarily the same conveyance direction due to dimensional tolerances. For this reason, the state in which the recording medium is being transported by the transport roller 21 and the paper discharge roller 30 is a state in which the paper discharge roller 30 is generally affected by the transport direction of the transport roller 21 and has a certain charging force. The recording medium is conveyed while maintaining the above. Therefore, at the moment when the recording medium is released from the nipping by the conveying roller 21 and changed to the nipping state of only the paper discharge roller 30, the charging force of the paper discharge roller 30 is released and moves in the carriage scanning direction. Also move together.

Next, a method for detecting the positional deviation amount ΔX of the recording medium will be described.
In each state of the recording medium P1 and the recording medium P2 in FIG. 6, the carriage is scanned at a constant speed in the scanning direction (the arrow X direction in FIG. 6). At this time, scanning is performed until the optical sensor 200 detects the absence of the recording medium after detecting the recording medium.

  FIG. 7 is a graph showing the result of detecting the presence or absence of a recording medium as described above using the reflective sensor 200. The vertical axis represents output and the horizontal axis represents detection position. The detection result Vp1 indicates the state of the recording medium P1 in FIG. 6 as the recording medium, and the detection result Vp2 indicates the state of the recording medium P2 in FIG. The output value Vp indicates a detection value when the recording medium is detected by a sensor, and the output value Vn indicates a detection value in an area where there is no recording medium. Although the detection result Vp1 and the detection result Vp2 indicate the same output value, the detection position is different from the detection position X1 and the detection position X2 at the same output V in the scanning direction.

Therefore, it is possible to detect the amount of movement of the recording medium in the scanning direction by detecting the presence or absence of the recording medium and calculating the shift amount ΔX from the respective scanning detection positions X1 and X2 at which the output V is substantially the same. It becomes possible. That is, the deviation amount ΔX can be expressed by the following equation.
ΔX = X2−X1

  Next, a method for correcting the recording position of the recording data due to the positional deviation of the recording medium P will be described. The recording position of the recording data is corrected by correcting the driving timing of the recording head. The correction value E1 of this drive timing control is obtained by the following calculation.

When the drive timing unit is Ddpi, the correction value E1 for correcting the shift amount ΔX of the recording medium can be expressed by the following equation.
E1 = ΔX / D

  Therefore, after obtaining the correction value E1 by calculation, the print head driving timing is shifted by the correction value E1 with respect to the print data, so that the image correction corresponding to the positional deviation of the print medium P can be performed.

  FIG. 8 is a flowchart for correcting a displacement in the carriage conveyance direction of the recording medium of the present embodiment. Hereinafter, a printing correction method for the positional deviation of the recording medium in the carriage conveyance direction will be described with reference to this flowchart.

  When recording is started, it is determined in step S1 whether or not the conveyance is just before the conveyance roller nipping is released. If the conveyance immediately before the conveyance roller nipping is not released, the process proceeds to step S10, recording is performed without correcting the drive timing, and the recording medium P is conveyed by the rotation of the conveyance roller 21. In step S1, in the case of conveyance just before the conveyance roller nipping is released, the process proceeds to step S2. In step S2, one end (detection position X1) of the recording medium P is detected by a reflective sensor (optical sensor 200) mounted on the carriage. Thereafter, the process proceeds to step S3, and the carriage is scanned to execute printing (recording) of print data. In step S4, the transport roller is rotated to execute the next printing. At this time, the recording medium is released from the holding roller. In step S5, the carriage is scanned in a state where the recording medium is released from the holding roller, and one end (detection position X2) of the recording medium is detected by the reflective sensor. When the detection of the one end portion (detection position X2) of the recording medium is completed, a correction value E1 that determines the recording head drive timing when printing is calculated in step S6. After calculating the correction value E1, in step S7, the recording head drive timing is shifted by the correction value E1, and printing of the recording data is executed. In step S8, it is determined whether there is recording data that has not been recorded. If recording data still exists, the paper discharge roller is rotated in step S9. This operation is repeated until there is no recording data, and printing is terminated when there is no recording data.

  As described above, the deviation in the carriage scanning direction of the recording medium before and after the recording medium comes out of the nipping between the conveyance roller and the pinch roller is detected, and the ejection timing from the recording head is corrected according to the detection result. As a result, it is possible to realize a recording apparatus that suppresses the deterioration of the quality of the recorded image due to the displacement of the recording medium in the direction orthogonal to the conveyance direction of the recording medium.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 9 is a simplified diagram showing a part of a recording apparatus to which the present embodiment is applied. The transport roller 21 is provided with a paper feed roller pulley 25 so that the drive from the paper discharge roller 30 is transmitted. The paper discharge roller 30 is provided with a paper discharge roller gear 30a, and an idler gear 35 is provided therebetween. . Further, a position sensor 201 for detecting the behavior of the paper discharge roller 30 in the carriage scanning direction is provided so as to face the side surface of the paper discharge roller 30.

  In this embodiment, the position sensor 201 is configured to use an eddy current sensor. At the moment when the recording medium P is released from the state of being held between the conveyance rollers 21 and changed to the state of holding only the discharge roller 30, the force charged in the discharge roller 30 is released and the discharge roller 30 is recorded. It moves in the carriage scanning direction integrally with the medium P. Therefore, in this embodiment, the positional deviation of the recording medium P is indirectly detected by the positional deviation of the paper discharge roller 30.

Next, a method for detecting the shift amount ΔX of the recording medium will be described.
FIG. 10 shows the output of the position sensor 201 when the recording medium P shifts from the state where the recording medium P is sandwiched from the conveying roller 21 to the state where the sandwiching is released. When the recording medium P is held between the conveyance rollers 21, the output of the position sensor 201 indicates V1, and when the recording medium P is released from the conveyance rollers 21, the output of the position sensor 201 indicates V2. Therefore, the scanning direction movement amount ΔX of the recording medium P can be detected from the difference between the detection values V1 and V2 by the displacement conversion constant K. That is, the deviation amount ΔX is expressed by the following equation.
ΔX = K (V2−V1)

Next, a method for correcting the recording position of the recording data due to the displacement of the recording medium P will be described. The recording position of the recording data is corrected by correcting the driving timing of the recording head. The correction value for the print head drive timing control is obtained by the following calculation. When the drive timing unit is Ddpi, the correction value E2 for correcting the positional deviation ΔX of the recording medium is expressed by the following equation.
E2 = ΔX / D

  Therefore, after the correction value is determined by calculation, the image correction corresponding to the displacement of the recording medium can be performed by shifting the recording head drive timing by the correction value E with respect to the recording data.

  FIG. 11 is a flowchart for correcting the displacement in the carriage conveyance direction of the recording medium of the present embodiment. Hereinafter, a printing correction method for the positional deviation of the recording medium in the carriage conveyance direction will be described with reference to this flowchart.

  When recording is started, it is determined in step S11 whether or not the recording medium is immediately before the conveyance roller is released. If the conveyance roller just before the nipping is not released, the process proceeds to step S110, recording is performed without correcting the drive timing, and the recording medium P is conveyed by the rotation of the conveyance roller 21. In step S11, in the case of conveyance just before the conveyance roller nipping is released, the process proceeds to step S12. In step S12, the position of the paper discharge roller 31 is detected by the position sensor 201 mounted on the carriage. Thereafter, the process proceeds to step S13, and the carriage is scanned to print (record) the recording data. In step S14, the transport roller is rotated to execute the next printing. At this time, the recording medium is released from the holding roller. Then, the process proceeds to step S15, and the position of the paper discharge roller 31 is detected in a state where the recording medium is released from the nipping of the conveyance roller 21. When the position detection of the discharge roller 31 is completed, a correction value E that determines the recording head drive timing when printing is calculated in step S16. After calculating the correction value E2, in step S17, the recording head drive timing is shifted by the correction value E2, and printing of the recording data is executed. In step S18, it is determined whether there is recording data that has not been recorded. If recording data still exists, the paper discharge roller is rotated in step S19. This operation is repeated until there is no recording data, and recording ends when there is no recording data.

  In the present embodiment, an eddy current sensor is used as a position sensor, but a laser position sensor can also be used. In FIG. 9, the position sensor 201 for detecting the behavior is provided on the side surface of the paper discharge roller 20. However, the position sensor for detecting the behavior of any component of the paper discharge means may be provided. I do not care.

  As described above, the displacement of the discharge roller before and after the recording medium comes out of the nipping between the conveyance roller and the pinch roller is detected, and the ejection timing from the recording head is corrected according to the detection result. As a result, it is possible to realize a recording apparatus that suppresses the deterioration of the quality of the recorded image due to the displacement of the recording medium in the direction orthogonal to the conveyance direction of the recording medium.

1 is a schematic perspective view illustrating an overall configuration of a recording apparatus to which the present invention can be applied. FIG. 2 is a schematic side cross-sectional view showing the overall configuration of the recording apparatus as seen from the direction of arrow A in FIG. FIG. 2 is a block diagram illustrating a driving unit that drives a recording apparatus to which the first embodiment can be applied. It is the bottom view which looked at the carriage part from the arrow B direction of FIG. (A) to (d) are diagrams showing the conveyance state before and after the nip in the conveyance of the recording medium divided into stages. FIG. 4 is a diagram illustrating a position of a recording medium in a carriage scanning direction when a recording medium is nipped by a conveyance roller and immediately before nipping is released and when the recording medium is immediately after nipping is released. It is the graph which showed the result of having detected the presence or absence of a recording medium as mentioned above using a reflection type sensor. 6 is a flowchart for correcting a positional deviation in the carriage conveyance direction of the recording medium according to the first embodiment. It is the simplified diagram which showed a part of recording device to which the 2nd Embodiment of this invention is applied. FIG. 6 is a diagram illustrating an output of a position sensor when the recording medium is shifted from a state in which the recording medium is sandwiched from a conveyance roller to a state in which the recording medium is released. 10 is a flowchart for correcting a positional deviation in a carriage conveyance direction of a recording medium according to a second embodiment. FIG. 6 is a cross-sectional view mainly showing a recording medium transport mechanism in a conventional ink jet recording apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Recording head 12 Ink tank 13 Carriage 21 Carrying roller 22 Pinch roller 30 Paper discharge roller 31 Paper discharge roller 37 ASF
39 Feed roller 66 PE sensor lever 200 Optical sensor 201 Position sensor

Claims (5)

A recording head that discharges ink to the recording medium; a carriage that mounts and scans the recording head; and a conveying unit that conveys the recording medium by sandwiching the recording medium between a first roller and a second roller. In an ink jet recording apparatus comprising a paper discharge means for transporting the recording medium transported by the transport means by being sandwiched between a third roller and a fourth roller,
Detecting means for detecting a displacement of the recording medium in the scanning direction of the carriage before and after being released from the nipping between the first roller and the second roller;
An ink jet recording apparatus, wherein the ejection timing of the recording head is corrected according to a detection result of the detecting means.   The ink jet recording apparatus according to claim 1, wherein the detection unit is provided in the carriage.   The inkjet recording apparatus according to claim 1, wherein the detection unit is an optical sensor. A recording head that discharges ink to the recording medium; a carriage that mounts and scans the recording head; and a conveying unit that conveys the recording medium by sandwiching the recording medium between a first roller and a second roller. A paper discharge means for transporting the recording medium transported by the transport means by sandwiching the recording medium between a third roller and a fourth roller;
Detecting means for detecting a positional deviation of the paper discharge means before and after the recording medium is released from the nipping between the first roller and the second roller;
An ink jet recording apparatus, wherein the ejection timing of the recording head is corrected according to a detection result of the detecting means.   The inkjet recording apparatus according to claim 4, wherein the detection unit is an eddy current sensor.

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