JP2007119112A - Ink jet recording apparatus and control method of ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording apparatus capable of recording a high quality image by simple control.
The recording medium conveying means includes an upstream conveying means arranged on the upstream side of the recording means and downstream conveying means 40, 41, 42, 43 arranged on the downstream side of the recording means. The The upstream-side conveying unit records a pair of rollers 36 and 37 disposed so as to oppose each other so as to sandwich and release the recording medium, and record at least one of the pair of rollers 36 and 37 from the sandwiching position where the recording medium is sandwiched. Roller moving means for moving the medium to a release position for releasing the medium. The roller moving unit is controlled so as to release the nipping state between the pair of rollers before the trailing end of the recording medium reaches between the pair of rollers of the upstream conveying unit.
[Selection] Figure 5

Description

  The present invention relates to an inkjet recording apparatus that performs a recording operation while transporting a recording medium to a recording unit, and a method for controlling the inkjet recording apparatus.

  2. Description of the Related Art Conventionally, printing applications for photographic images have been increasing in recording devices such as printers. In particular, an ink jet recording apparatus can form an image with a quality equal to or better than that of a silver salt photograph by reducing the size of ink droplets and improving image processing technology. In this ink jet recording apparatus, an ink droplet is ejected from a recording head kept in a non-contact state with respect to the recording medium conveyed by the conveying means, and the ink droplet is landed on the recording medium to form an image. For this reason, the quality of the image is greatly influenced by the conveyance accuracy of the recording medium. In general, the ink jet recording apparatus is provided with conveying means for conveying a recording medium respectively on the upstream side and the downstream side of a recording head that is a recording means. The upstream conveying means includes a conveying roller as a driving roller that rotates intermittently and a pinch roller as a driven roller provided opposite to the conveying roller. By rotating while pinching with a roller, it sends out to the downstream side. Accordingly, a conveying force is applied by the upstream conveying means until the trailing edge of the recording medium passes between both rollers.

  The recording medium sent to the downstream side by the upstream conveying unit is recorded by the recording head, and then intermittently conveyed further downstream by the downstream conveying unit, and finally to the paper discharge unit. It is supposed to be discharged.

  In this intermittent conveyance operation of the recording medium, when the conveyance roller stops intermittently just before the trailing edge of the recording medium comes out of the nip formed by the conveyance roller and the pinch roller, that is, the trailing edge of the recording medium is the nip. If the conveyance roller stops in a state where the recording medium remains, the pinch roller urged toward the conveyance roller is rotated by the urging force, and the recording medium is pushed out from between the two rollers to the downstream side. was there. In this case, the recording medium is transported by a transport amount larger than a preset transport pitch, which causes a disadvantage that unevenness occurs in the image.

  In order to eliminate such an inconvenience, Japanese Patent Application Laid-Open No. H10-228561 discloses a technique for controlling the rear end conveyance and suppressing the recording deviation in combination with the used nozzle shift of the recording head.

  This patent document mainly discloses the following contents.

  (A) The rear end position of the recording medium is detected by a sensor so that the rear end of the recording medium does not remain in the nip portion of the upstream conveying unit.

  (B) Until the conveyance of the recording medium is stopped at a position where the recording medium does not remain in the nip portion, the nozzles on the downstream side in the recording medium conveyance direction are throttled, and an image is formed using only the upstream nozzles.

  (C) The recording medium is conveyed to a downstream position from the nip so that the rear end portion of the recording medium does not remain in the nip.

(D) The used nozzle is shifted downstream in the recording medium conveyance direction to form an image.
JP 2002-254736 A

  However, in the technique disclosed in Patent Document 1, the following problems have not been solved yet.

  (1) In order to transport a recording medium as in (c) above, it is necessary to make the transport amount longer than a preset transport pitch, and as a result, more transport errors such as transport means are accumulated. As a result, there arises a problem that the conveyance accuracy is lowered.

  For this reason, when carrying out the technique disclosed in Patent Document 1, the accuracy of conveyance is improved by increasing the accuracy of components of the downstream conveyance unit that manages the conveyance operation after passing through the upstream conveyance unit. It is necessary to secure the manufacturing cost.

  (2) Since a process for controlling the conveyance amount of the recording medium when the trailing end of the recording medium passes through the nip of the upstream conveying unit and a process for shifting the nozzles used in the recording head are required, normal recording is performed. The recording time is increased compared to the operation. In particular, when so-called full-surface printing (also referred to as borderless printing) is performed in which an image is recorded on the entire surface of the recording medium without providing a margin at the end of the recording medium, the increase in recording time becomes more remarkable. .

  The present invention has been made paying attention to the above-mentioned problems, and does not require complicated control such as shifting the nozzles used for the recording means or changing the conveyance amount of the recording medium, and increasing the accuracy of the conveyance means. An object of the present invention is to provide a recording apparatus capable of recording a high-quality image with simple control.

  In order to achieve the above object, the present invention has the following configuration.

  That is, the first aspect of the present invention controls the conveying means for conveying the recording medium, the recording means for recording an image by discharging ink onto the recording medium conveyed by the conveying means, and the both means. An ink jet recording apparatus comprising: a control unit; and an upstream transport unit disposed upstream of the pre-recording unit, and a downstream transport unit disposed downstream of the recording unit. The upstream conveying means includes a pair of rollers arranged to oppose each other so as to sandwich and release the recording medium, and at least one of the pair of rollers from the sandwiching position for sandwiching the recording medium. Moving means to move to a release position for releasing the recording medium, and the control means is held by the pair of rollers before the trailing end of the recording medium reaches between the pair of rollers of the upstream conveying means. The And controlling said moving means so as to release.

  According to a second aspect of the present invention, there is provided an inkjet recording apparatus comprising: a conveying unit that conveys a recording medium; and a recording unit that records an image by discharging ink onto the recording medium conveyed by the conveying unit. The conveying means comprises an upstream conveying means arranged upstream of the recording means and a downstream conveying means arranged downstream of the recording means, and the upstream means The pair of rollers arranged opposite to each other so that the recording medium is sandwiched and released, and at least one of the pair of rollers is moved from a sandwiching position for sandwiching the recording medium to a release position for releasing the recording medium. And the moving means for moving, and the moving means is controlled so as to release the clamping state by the pair of rollers before the trailing edge of the recording medium reaches between the pair of rollers of the upstream conveying means. Characterized in that it.

  According to the above configuration, it is possible to obtain good recording quality by simple control of separating the driven roller of the conveying unit from the driving roller without requiring complicated control such as nozzle shift of the recording head. . Therefore, a decrease in throughput can be suppressed. In addition, since it is not necessary to use particularly high-precision parts for the conveying means, it can be configured at low cost.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  A first embodiment of the present invention will be described with reference to the drawings. 1 is a perspective view of a recording apparatus according to each embodiment of the present invention, FIG. 2 is a perspective view of a mechanism portion of the recording apparatus according to each embodiment of the present invention, and FIG. 3 is a vertical side view of each embodiment of the present invention. 4 is a perspective view showing a pinch roller raising / lowering mechanism in each embodiment of the present invention, and FIG. 5 is an explanatory longitudinal sectional side view showing a recording operation state with respect to the rear end portion of the recording medium in the first embodiment of the present invention.

  The recording apparatus of the present invention includes a recording apparatus 1, a paper feeding apparatus 2, a paper feeding section 3, a carriage section 5, a paper discharge section 4, a U-turn / automatic double-sided conveyance section 8, and a recording head 7. Then, these are divided into items and the outline is described sequentially.

(A) Paper Feed Unit In FIGS. 1 to 3, the paper feed unit 2 includes a pressure plate 21 on which the recording medium P is stacked, a paper feed roller 28 for feeding the recording medium P, a separation roller 24 for separating the recording medium P, and recording. A return lever 22 or the like for returning the medium P to the loading position is attached to the base 20.

  A paper feed tray 26 for holding the stacked recording media P is attached to the base 20 or the exterior. The paper feed tray 26 is a multi-stage type and is pulled out for use.

  The feed roller 28 has a bar shape with a circular arc in cross section. One paper feed roller rubber is provided based on the paper standard, and this feeds the recording medium. Driving to the paper feed roller 28 is transmitted from a motor shared with a cleaning unit (not shown) provided in the paper feed unit 2.

  A movable side guide 23 is movably provided on the pressure plate 21 to regulate the loading position of the recording medium P. The pressure plate 21 can rotate around a rotation shaft coupled to the base 20, and is urged by the pressure plate spring 212 to the paper feed roller 28. A separation sheet (not shown) made of a material having a large coefficient of friction such as artificial leather for preventing double feeding of the recording medium P near the end of the stack is provided at a portion of the pressure plate 21 facing the paper feed roller 28. The pressure plate 21 is configured to be able to contact and separate from the paper feed roller 28.

  Further, a separation roller 24 for separating the recording media P one by one is attached to a separation roller holder (not shown), is provided on the base 20, and is urged against the paper feed roller 28 by a spring or the like. The separation roller 24 has a structure in which a clutch spring is attached, and a portion to which the separation roller 24 is attached can rotate when a load exceeding a predetermined value is applied. The separation roller 24 is configured to be able to contact and separate from the paper feed roller 28. The positions of the pressure plate 21, the return lever 22, and the separation roller 24 are detected by an ASF sensor.

  A return lever 22 for returning the recording medium P to the loading position is rotatably attached to the base 20 and is urged by a return lever spring in the release direction. When the recording medium P is returned, the recording medium P is rotated by a control cam (not shown).

  In the normal standby state, the pressure plate 28 is released, the separation roller 24 is released by the control cam, the return lever 22 returns the recording medium P, and closes the stacking port so that the recording medium P does not enter the back during loading. It is provided at a proper loading position. When paper feeding starts from this state, first, the separation roller roller 24 contacts the paper feeding roller 28 by driving the motor. Then, the return lever 22 is released, and the pressure plate 21 comes into contact with the paper feed roller 28. In this state, feeding of the recording medium P is started. The recording medium P is limited by a pre-stage separation unit provided on the base 20, and only a predetermined number of the recording media P is sent to a nip part composed of a paper feed roller 28 and a separation roller 24. The sent recording medium P is separated at the nip portion, and only the uppermost recording medium P is conveyed.

  When the recording medium P reaches a later-described conveying roller 36 and pinch roller 37, the pressure plate 21 is released by the pressure plate cam and the separation roller 28 is released by the control cam. The return lever 22 is returned to the loading position by the control cam. At this time, the recording medium P that has reached the nip portion constituted by the paper feed roller 28 and the separation roller 24 can be returned to the stacking position.

(B) Paper feeding part The paper feeding part 3 is attached to the chassis 11 made of a bent metal sheet. The paper feeding unit 3 includes a conveyance roller 36 that conveys the recording medium P and a PE sensor 213. The transport roller 36 has a configuration in which ceramic fine particles are coated on the surface of a metal shaft, and the metal portions of both shafts are received by a bearing 38 and attached to the chassis 11. A conveyance roller tension spring 381 is provided between the bearing 38 and the conveyance roller 36 to bias the conveyance roller 36 in the thrust direction, thereby preventing the displacement of the conveyance roller 36 in the thrust direction.

  A plurality of driven pinch rollers 37 are provided in contact with the conveying roller 36. The pinch roller 37 is held by the pinch roller holder 30 shown in FIG. 4 and is urged by the pinch roller spring 31 shown in FIG. 4 so that the pinch roller 37 is pressed against the transport roller 36 and generates the transport force of the recording medium P. ing. At this time, the rotation fulcrum shaft 30a of the pinch roller holder 30 is attached to the bearing of the chassis 11 and rotates around the shaft. Further, a paper guide flapper 33 and a platen (support member) 34 for guiding the recording medium P are disposed at the entrance of the paper feeding unit 3 to which the recording medium P is conveyed. Further, the pinch roller holder 30 is provided with a PE sensor lever 32 that transmits the leading edge and trailing edge detection of the sheet P to the PE sensor 213. The platen 34 is attached to the chassis 11 and positioned. The paper guide flapper 33 can be rotated around a bearing portion 331 that fits and slides on the conveyance roller 36, and is positioned by contacting the chassis 11.

  In the above configuration, the recording medium P sent to the paper feeding unit 3 is guided by the pinch roller holder 30 and the paper guide flapper 33 and sent to the roller pair of the transport roller 36 and the pinch roller 37. At this time, the leading end of the recording medium P conveyed to the PE sensor lever 32 is detected, and thereby the recording position of the recording medium P is obtained. The recording medium P is transported on the platen 34 as the roller pairs 36 and 37 are rotated by a transport motor (not shown). On the platen 34, a rib serving as a conveyance reference surface is formed. The gap with the recording head 7 is managed, and the corrugation of the recording medium P is controlled together with a later-described paper discharge unit. And it is configured so that the undulation does not become large.

  The drive to the transport roller 36 is transmitted to the pulley 361 provided on the shaft of the transport roller 36 by a timing bell or the like using the rotational force of the transport motor 35 formed of a DC motor. A code wheel 362 on which markings are formed at a pitch of 150 lpi to 300 lpi for detecting a conveyance amount by the conveyance roller 36 is provided on the axis of the conveyance roller 36, and an encoder sensor 363 that reads the code wheel 362 is a code wheel. It is attached to the chassis 11 at a position adjacent to 362.

  Further, a recording head 7 that forms an image based on image information is provided on the downstream side of the conveying roller 36 in the recording medium conveying direction. As the recording head 7, an ink jet recording head equipped with replaceable ink tanks 71 for each color is used. The recording head 7 can apply heat to the ink by a heater or the like. Then, the film of the ink is boiled by this heat, and the ink is ejected from the nozzles of the recording head 7 by the pressure change caused by the growth or contraction of the bubbles due to the film boiling, and an image is formed on the recording medium P.

(C) Carriage unit The carriage unit 5 includes a carriage 50 to which the recording head 7 (see FIG. 5) is attached. The carriage 50 holds the guide shaft 52 for reciprocating scanning in the direction intersecting the conveyance direction of the recording medium P and the rear end of the carriage 50 to maintain a gap between the recording head 7 and the recording medium P. It is supported by rails 111. The guide shaft 52 is attached to the chassis 11. The guide rail 111 is formed integrally with the chassis 11.

  The carriage 50 is driven via a timing belt 541 by a carriage motor 54 attached to the chassis 11. The timing belt 541 is stretched and supported by an idle pulley 542. The timing belt 541 is coupled to the carriage 50 via a damper 55 made of rubber or the like, and reduces image unevenness by attenuating vibration of the carriage motor 54 or the like. A code strip 561 in which markings are formed at a pitch of 150 lpi to 300 lpi for detecting the position of the carriage 50 is provided in parallel with the timing belt 541. In addition, an encoder sensor for reading it is provided on a carriage substrate mounted on the carriage 50. The carriage substrate is also provided with contacts for electrical connection with the recording head 7. Further, the carriage 50 is provided with a flexible substrate 57 for transmitting a recording head 7 head signal from the electric substrate 9.

  In order to fix the recording head 7 to the carriage 50, the carriage 50 is provided with positioning means and pressing means. The pressing means is mounted on the head set lever 51 and is configured to act on the recording head 7 when the head set lever 51 is turned around the rotation fulcrum and set.

  In addition, eccentric cams are provided at both ends of the guide shaft 52, and the guide shaft 52 is transmitted to the eccentric cam via the gear train 581 by the main cam 63 of the cleaning unit 6 that performs the cleaning process of the recording head. Can be moved up and down. As a result, the carriage 50 can be moved up and down to form an optimum gap for the recording media P having different thicknesses. The driving force of the main cam 63 is transmitted from a motor shared with the cleaning unit described above.

  Further, an automatic registration adjustment sensor 59 for automatically correcting the landing deviation of the ejected ink from the recording head 7 on the recording medium P is attached to the carriage 50. The sensor 59 is a reflection type optical sensor, and an optimum registration adjustment value can be obtained by receiving light reflected from a light emitting element and receiving a reflected light on a predetermined recording pattern on the recording medium P.

  In the above configuration, when an image is formed on the recording medium P, the roller pairs 36 and 37 convey the recording medium P to the row position (position in the conveyance direction of the recording medium P) where the image is formed, and the carriage 50 is moved by the carriage motor 54. The recording head 7 is moved to the row position for image formation (position perpendicular to the conveyance direction of the recording medium P) and the recording head 7 is opposed to the image formation position. Thereafter, as described above, an image is formed by the recording head 7 ejecting ink toward the recording medium P in response to a signal from the electric substrate 9.

(D) Paper Discharge Unit The paper discharge unit 4 is provided with two paper discharge rollers 40 and 41, paper discharge rollers 40 and 41 at a predetermined pressure, and spurs 42 and 43 configured to be rotated by being driven. It is composed of a gear train for transmitting the driving of the conveying roller to the paper discharge rollers 40 and 41, and the like.

  The paper discharge rollers 40 and 41 are attached to the platen 34. The discharge roller 40 on the downstream side in the conveyance direction of the recording medium P is provided with a plurality of rubber portions on the metal shaft. The drive from the transport roller 36 is driven by being transmitted to the paper discharge roller 40 via the idler gear. The paper discharge roller 41 provided on the upstream side of the paper discharge roller 40 has a structure in which a plurality of elastomer elastic bodies are attached to a resin shaft. Drive to the paper discharge roller 41 is transmitted from the paper discharge roller 40 via an idler gear.

  The spur 42 is a thin stainless steel plate, and a plurality of convex shapes are formed integrally with the resin portion and attached to the spur holder 43. A spur spring 44 provided with a coil spring in a rod shape causes the spur 42 to be attached to the spur holder 43 and pressed against the discharge rollers 40 and 41 and the like. A spur is provided at a position corresponding to the rubber part and the elastic body part of the paper discharge rollers 40 and 41, and mainly serves to generate the conveyance force of the recording medium P, and the rubber of the paper discharge rollers 40 and 41 therebetween. The part 401 is provided at a position where the elastic body part is not present, and mainly serves to suppress the lifting when the recording medium P is recorded.

  By lifting both ends of the recording medium P between the paper discharge rollers 40 and 41, holding the recording medium P at the tip of the paper discharge rollers 40 and 41, and rubbing the recording on the previous recording medium P. Paper edge support is provided to prevent damage. A resin member provided with a roller at the tip is urged by a paper end support spring, and the roller is pressed against the recording medium P with a predetermined pressure, so that both ends of the recording medium P can be lifted and can be held by making a strainer. It is configured.

  With the above configuration, the recording medium P on which an image is formed by the carriage unit 5 is sandwiched by the nip between the paper discharge roller 41 and the spur 42, conveyed, and discharged to the paper discharge tray 46. The paper discharge tray 46 is configured to be housed in the front cover 95. When used, pull out. The discharge tray 46 increases in height toward the leading end, and both ends thereof are configured to be high in height so that the stackability of the discharged recording medium P can be improved and the recording surface can be prevented from rubbing.

(E) U-turn / automatic double-sided portion The recording medium P is stored in a cassette 81 provided on the front surface of the apparatus. In order to separate and feed the recording medium P, the cassette 81 is provided with a pressure plate 822 on which the recording medium P is stacked and brought into contact with the paper feed roller 821. A sheet feeding roller 821 that feeds the recording medium P, a separation roller 831 that separates the recording medium P, a return lever 824 for returning the recording medium P to the stacking position, a pressurizing / controlling unit for the pressure plate 822, etc. It is configured to be attached to the UT base 84.

  The cassette 81 has a two-stage contraction configuration, and can be selectively used depending on the size of the recording medium P. When the small size paper or the cassette is not used, the cassette 81 contracts and can be stored inside the main body exterior portion 9.

  The paper feed roller 821 has a bar shape with a circular arc in cross section. One paper feed roller rubber is provided based on the paper standard, and this feeds the recording medium. The drive to the paper feed roller 821 is transmitted from a U-turn / automatic double-side motor (not shown) provided in the U-turn / automatic double-sided section 5.

  A movable side guide 827 is movably provided on the pressure plate 822 to regulate the loading position of the recording medium P. The pressure plate 822 is rotatable about a rotation shaft coupled to the cassette 81, and is urged to the paper feed roller 821 by a pressure / control unit including a pressure plate spring 828 provided on the UT base 84. A separation sheet (not shown) made of a material having a large friction coefficient such as artificial leather for preventing double feeding of the recording medium P near the end of the stack is provided at a portion of the pressure plate 822 facing the paper feed roller 821. The pressure plate 822 is configured to be able to contact and separate from the paper feed roller 821 by a pressure plate cam (not shown).

  Further, a separation roller (not shown) for separating the recording media P one by one is attached to a separation roller holder (not shown), attached to the UT base 84, and biased by the paper feed roller 821. The separation roller is attached to a clutch spring, and is configured to be able to rotate a portion to which the separation roller is attached when a predetermined load or more is applied. The separation roller is configured to be able to contact and separate from the paper feed roller 821. The positions of the pressure plate 822, the return lever 824, and the separation roller are detected by a UT sensor.

  A return lever 824 for returning the recording medium P to the loading position is rotatably attached to the UT base 83 and is biased by a return lever spring in the release direction. When the recording medium P is returned, it is configured to rotate by a control cam.

  In a normal standby state, the pressure plate 822 is released, the separation roller 831 is also released, and the return lever 824 returns the recording medium P, and the loading position closes the loading port so that the recording medium P does not enter the back during loading. Is provided. When paper feeding starts from this state, the separation roller 831 first comes into contact with the paper feeding roller 821 by driving the motor. Then, the return lever 824 is released, and the pressure plate 822 contacts the paper feed roller 821. In this state, feeding of the recording medium P is started. The recording medium P is limited by the pre-stage restricting means provided on the UT base 84, and only a predetermined number of the recording medium P is sent to the nip portion constituted by the paper feed roller 821 and the separation roller 831. The sent recording medium P is separated at the nip portion, and only the uppermost recording medium P is conveyed.

  Two transport rollers, a first U-turn intermediate roller 86 and a second U-turn intermediate roller 87, are configured on the downstream side of the paper feed portion to transport the fed recording medium. In these, EPDM having a rubber hardness of 40 ° to 80 ° is attached to 4 to 6 locations on the metal core of the metal shaft. U-turn pinch rollers 861 and 871 for sandwiching the recording medium P at positions corresponding to the rubber portions are attached to the spring shaft, and are attached to the first U-turn intermediate roller 86 and the second U-turn intermediate roller 87. It is energized. In order to form a transport path, an inner guide 881 that forms the inner side and an outer guide (not shown) that forms the outer side are configured.

  When the separated / conveyed recording medium P reaches a first U-turn intermediate roller 86 and a U-turn pinch roller 861 described later, the pressure plate 822 and the separation roller 831 are released by the control cam. The return lever 824 is returned to the loading position by the control cam. At this time, the recording medium P that has reached the nip formed by the paper feed roller 821 and the separation roller 831 can be returned to the stacking position.

  The junction point of the paper path with the paper feed unit 2 described above is configured by a flapper 883 so that the mutual path merges smoothly. When the leading edge of the recording medium P is fed to the above-described conveyance roller 36 and pinch roller 37, the recording medium P is brought into contact with the nip of the stopped roller pair, and the registration removing operation is performed.

  The recording medium P on which recording has been performed while being transported by the transport roller 36 and the pinch roller 37 passes between the transport roller 36 and the pinch roller 37. At the time of automatic double-sided recording, the trailing edge of the recording medium P is again sandwiched between the conveyance roller 36 and the pinch roller 37 and conveyed. At this time, the pinch roller 37 can be smoothly conveyed because the recording medium P is sent to the rising portion by the lifting mechanism.

  The recording medium P sent in again is sandwiched between the double-sided roller 891 and the pinch roller 892 and conveyed. The recording medium P is guided by the guide 893 and conveyed. The double-sided paper conveyance path is configured to merge with the paper path at the time of U-turn conveyance after a predetermined amount. Therefore, the subsequent configuration and operation of the paper path are the same as those described above.

Schematic Configuration of Control System FIG. 6 is a block diagram showing the main configuration of the control system in the embodiment of the present invention.

  In FIG. 6, reference numeral 101 denotes a host computer connected to the recording apparatus 1 via an interface 114. In the host computer 101, a printer driver for generating image information and control information for causing the recording apparatus 1 to execute a recording operation is input and stored from a predetermined storage medium. The printer driver and the host computer Image information is generated by the hardware resources.

  On the other hand, 201 is a control unit as a control means for controlling the overall operation of the recording apparatus 1. This control unit stores a CPU 210 such as a microprocessor, a control program executed by the CPU 210, and various data. ROM 211 and RAM 212 that is used as a work area when various processes are executed by CPU 210 and temporarily stores various data. In the RAM 212, recording heads 7Y, 7M, 7C, 7Bk, and 7CL for recording with ink of each color such as the above-described reception buffer 115 and Y, M, C, Bk, and CL (in the present specification, these recording heads are collectively shown). Corresponding to the recording head 7), Y, M, C, Bk, CL recording buffers (image information storage means) for storing recording data are provided.

  Reference numeral 202 denotes a head driver, which corresponds to the recording data of each color output from the control unit 201. The yellow recording head 45Y, the magenta recording head 45M, the cyan recording head 45C, the black recording head 45Bk, and the light cyan recording head. 45CL is driven. Each of 203, 204, 206 and 207 is a motor driver, and drives a corresponding carriage motor 6, paper feed motor 205, AP motor 70, and a lift drive motor that rotates a pinch roller release gear 303 described later. Yes.

  Further, the medium edge detection sensor 213 reaches the recording head from a confluence of a transport path (first transport path) from the paper feed unit of the inkjet recording apparatus and a transport path (second transport path) from the cassette. It is a sensor provided at a predetermined reference position in the transport path. The medium end detection sensor 213 switches the output from on to off when the end of the recording medium conveyed from the first path or the second path reaches the reference position. Based on the output result, the CPU 210 determines whether or not the end of the recording medium has reached the reference position.

  Further, a pulse signal from the encoder sensor 363 is input to the CPU 210, whereby the CPU 210 can detect the movement position of the carriage.

FIG. 5 is a diagram illustrating a conveyance operation state at the time of recording the trailing edge in the first embodiment of the present invention.

  When the recording start command is received, the recording medium P is fed from the paper feeding unit 2 or the front cassette 81 as described above. The fed recording medium P is fed by a predetermined amount by the transport roller 36 and predetermined recording is performed by the recording head 7 mounted on the carriage 50. When full-surface printing (marginless recording) is performed, the ink that protrudes from the end of the recording medium P lands on the platen absorber 344 provided on the platen 34 and is absorbed therein. That is, all the ink that protrudes from the four side edges of the recording medium P is absorbed here.

  FIG. 7 is an explanatory diagram showing the conveyance operation of the recording medium P and the state of multi-pass recording. As shown in the figure, in the first embodiment, four-pass printing is performed in which each row of the image to be formed is scanned four times by the print head to complete the image of each row. Further, the centers of the transport roller 36 and the pinch roller 37 are slightly offset in the direction of transport of the recording medium P, and the nip between the transport roller 36 and the pinch roller 37 is slightly downward. As a result, the recording medium P sent between the conveying roller 36 and the pinch roller 37 is sent out toward the platen 34. For this reason, even if the recording medium is a thin recording medium such as plain paper, the recording medium can always be conveyed while being in contact with the platen 34, and the recording medium is prevented from bending or floating on the platen. can do. As a result, the contact between the recording head 7 and the recording medium can be avoided, and the distance between the recording head and the recording medium (also referred to as a sheet interval) can be kept constant.

  As the recording operation proceeds, the rear end of the recording medium P passes through the position detected by the PE sensor 213. Then, a rear end detection signal is output from the PE sensor 213, and the CPU recognizes the position of the rear end of the recording medium in response to the detection signal (see FIG. 5A). Upon receiving the trailing edge detection signal, the CPU conveys the recording medium P by a predetermined amount. When the trailing edge of the recording medium P approaches the nip between the conveying roller 36 and the pinch roller 37, the CPU stops the conveying motor, and the conveying roller 36. And the pinch roller 37 are stopped (see FIG. 5B). At this point, the leading end of the recording medium P passes through the recording head 7 and enters the nips of the discharge roller 40 and the pinch roller 42 and the discharge roller 41 and the pinch roller 43 as downstream conveying means. It is in a clamped state.

  When the conveyance operation of the recording medium P is stopped in the state of FIG. 5B, the CPU 210 next moves the pinch roller 37 away from the recording medium P and the conveyance roller 36 by a predetermined amount (see FIG. 5C). . This is performed by the CPU 210 controlling a lifting drive motor 80 that is a drive source of the pinch roller lifting mechanism.

  FIG. 4 shows the main configuration of the pinch roller lifting mechanism 300.

  As described above, the pinch roller 37 is supported by the front end portion of the pinch roller holder 30, and the rear end portion of the pinch roller holder 30 is rotatably attached to the chassis 11 by the rotation fulcrum shaft 30a. Yes. Further, the pinch roller holder 30 is biased so as to be pressed against the conveying roller 36 by a pinch roller spring 31. A pinch roller release shaft 302 formed by bending a sheet metal into a U shape is attached to the chassis 11. A plurality of pinch roller release cams 301 for pressing and releasing the rear end portion of the pinch roller holder 30 are attached to the pinch roller release shaft 302.

  Further, a pinch roller release gear 303 is fixed to an end portion of the pinch roller release shaft 302 to transmit a driving force of a lifting drive motor 80 (not shown) to the pinch roller release shaft 302.

  In the pinch roller lifting mechanism 300 configured as described above, when the pinch roller release gear 303 rotates due to the rotation of the lifting drive motor 80, the pinch roller release shaft 302 and the pinch roller release cam 301 rotate together, and the pinch roller release cam is rotated. 301 presses the rear end of the pinch roller holder 30. As a result, the pinch roller holder 30 rotates about the fulcrum shaft 30 a against the urging force of the pinch roller spring 31 in the direction indicated by the arrow a, and the pinch roller 37 is separated from the conveying roller 36. When the elevating drive motor 80 further rotates to a predetermined position, the pinch roller release cam 301 releases the pressure against the pinch roller holder 30, and the pinch roller holder 30 rotates in the direction of arrow b by the urging force of the pinch roller spring 31. The pinch roller 37 presses the transport roller 36 again.

  When the pinch roller 37 is moved away from the conveying roller 36 by the pinch roller lifting mechanism 300, the CPU 210 then restarts the recording operation on the recording medium. At this time, the recording medium P is intermittently conveyed as before, but the conveyance is performed by the rotational force of the paper discharge rollers 40 and 41. The transported recording medium P may stop on the transport roller 36, but the pinch roller 37 is in the raised position, so that it is pushed out by the nip between the pinch roller 37 and the transport roller 36 as in the prior art. It is not conveyed and is accurately conveyed at a preset conveyance pitch.

  Therefore, in the first embodiment, as shown in FIG. 7, after the pinch roller 37 is separated, four-pass recording is performed in the same manner as before the separation. When the rear end portion passes through the nip between the conveyance roller and the pinch roller 37, it is not necessary to increase the conveyance distance or shift the nozzles of the recording head 7. When the rear end of the recording medium P has advanced to a position beyond the nip position between the conveying roller 36 and the pinch roller 37, the CPU 210 rotates the lifting drive motor to release the separation of the pinch roller 37. Then, the recording medium P and the conveying roller 36 are pressed again (see FIG. 5D). Thereafter, when printing of the lowermost end portion at the rear end of the recording medium P is completed, the paper discharge operation is started, and the recording medium P is discharged onto the paper discharge tray 46.

  As described above, in the first embodiment, the recording medium is preliminarily controlled by performing very simple control that only raises the pinch roller 37 when the rear end portion of the recording medium passes over the pinch roller 37. The sheet can be accurately conveyed at the set conveyance pitch, and recording can be performed at an appropriate position with respect to the recording medium in each scan of the recording head. For this reason, it is possible to prevent recording unevenness from occurring between images formed by each recording scan. Even when borderless recording is performed, the recording medium is accurately conveyed, so that recording can be reliably performed on the rear end portion of the recording medium, and an image of good quality can be formed. .

  However, in the first embodiment, when the pinch roller 37 is moved away from the recording medium P by the pinch roller lifting mechanism 300, the rear end of the recording medium P may be slightly lifted. Accordingly, there is a possibility that the landing position of the ink droplet from the recording head is slightly shifted in the paper feeding direction and the carriage scanning direction. For this reason, in the first embodiment, the conveyance amount of the recording medium is also corrected in consideration of landing errors caused by the floating of the recording medium.

  FIG. 8 is a diagram illustrating a state in which the recording medium P is lifted when the pinch roller 31 is raised, and a state in which landing deviation of ink droplets is generated due to the lifting, and FIG. 8A is a diagram illustrating the recording medium that has been lifted. FIG. 5B is a diagram viewed from a direction (carriage movement direction) orthogonal to the conveyance direction of FIG. 5, and FIG. 9B is a diagram viewed from the direction perpendicular to the carriage movement direction.

  When the recording medium P is lifted, the recording medium P is inclined obliquely in the transport direction as shown in FIG. 8A, so that a slight shift α occurs in the ink droplet landing position. Further, as shown in FIG. 8B, in the carriage 50 scanning direction, the scanning speed of the carriage 50 is added to the ink droplets ejected from the recording head 7, so that the recording head 7 and the recording medium are When the distance between the two (the distance between the sheets) changes, a deviation β occurs in the landing position of the carriage.

  Therefore, the conveyance amount set in advance is corrected by an amount corresponding to the deviation α of the landing position to optimize the recording medium conveyance direction. In this case, the landing position on the paper surface can be corrected in units of 6000 dpi (4.2 μm) by controlling the conveyance motor based on the code wheel 362 and the encoder sensor 363 directly connected to the conveyance roller 36. As for the landing position deviation β in the scanning direction of the carriage 50, the ink discharge timing from the recording head 7 is controlled based on the code strip 561 and the encoder sensor 56 mounted on the carriage 50, so that the landing position on the paper surface is 9600 dpi. It is possible to correct in units of (2.6 μm). These correction values are set in advance and stored in the ROM 211 of the control unit 201. By this conveyance correction and ink ejection timing correction, it is possible to correct for the change between the papers accompanying the floating of the recording medium P when the pinch roller 37 is separated, and to secure a better image. it can.

  As described above, according to the first embodiment, there is no need to perform a special control such as selecting a use area in the nozzle group of the recording head or shifting the use nozzle, and the driven roller of the conveying unit. By performing simple controls such as raising the (pinch roller 37), delaying the ink ejection timing of the recording head, and shortening the conveyance pitch of the recording medium, an image of good quality can be obtained.

  Further, when the trailing edge of the recording medium P approaches the nip formed by the conveying roller 36 and the pinch roller 37, the recording medium conveying distance is not increased as in the conventional case. There is no need to increase the mechanical accuracy, and it can be configured at low cost.

  In the above-described embodiment, the recording medium P is transported in all four passes regardless of whether the pinch roller 37 is lifted or not. However, as shown in FIG. After the increase, the carry amount may be half of the carry amount so far, and 8-pass multi-pass printing may be performed.

  Thus, by doubling the number of passes of multi-pass printing after the pinch roller 37 is raised, the effect of improving the image quality by multi-pass is increased, the landing of the recording head is disturbed, and the recording medium P conveyance accuracy is lowered. Etc. can be made inconspicuous, and image quality can be further improved. In this case, the throughput is reduced, but the recording accuracy is also improved by reducing the nozzles in half and performing 4-pass multi-pass printing.

  Further, in the first and second embodiments described above, after the trailing end of the recording medium P passes through the nip portion between the conveyance roller 36 and the pinch roller 37, the pinch roller 37 is pressed against the conveyance roller 36 during the recording operation. However, the pinch roller 37 may be returned after the recording on the recording medium P is completely completed. In this case, in each of the above-described embodiments, the return time of the pinch roller 37 is added during recording, which leads to a decrease in throughput. However, when the pinch roller 37 is returned after recording, Since the operation can be performed using another operation period accompanying the recording operation, the throughput can be improved. Other configurations and operations are the same as those of the first embodiment described above.

  In each of the above-described embodiments, the center position of the pinch roller 37 is slightly offset from the center position of the transport roller 36 in the transport direction of the recording medium P. However, as shown in FIGS. A configuration not offset may be used.

  That is, FIG. 10A shows that the center position of the pinch roller is offset from the center position of the transport roller in the transport direction with the pinch roller 37 and the transport roller 36 in contact with each other as in the above-described embodiments. (Hereinafter, this state is referred to as a state where the pinch roller 37 is offset). FIG. 10B shows a state in which the pinch roller 37 is separated from the conveying roller 36 from the state shown in FIG.

  As shown in FIG. 10A, when the pinch roller 37 is lowered, the recording medium is in contact with the platen 34 by the pressing force of the pinch roller 37. As shown in FIG. When 37 is raised, the recording medium comes into contact with the top of the conveying roller 36 by its waist, and is slightly lifted above the platen 34.

  On the other hand, in the third embodiment, as shown in FIG. 10C, the conveying roller 36 is at the same position as the height of the upper surface of the platen 34, and the center position of the pinch roller 37 and the conveying roller 36 are The center position coincides with the conveyance direction of the recording medium.

  In the state where the pinch roller 37 is lowered as shown in FIG. 10C, the recording medium P is sandwiched between the uppermost position of the transport roller 36 and the lowermost position of the pinch roller, and the sandwiched position is the platen 34. The upper surface position coincides with the height direction. For this reason, even when the pinch roller 37 is nipped and raised, the recording medium P is held at the uppermost position of the transport roller and the upper surface of the platen 34 as before the ascent (FIG. 10C). It has become. That is, the position of the recording medium P does not change before and after the pinch roller 37 is raised, and the gap between the sheets is kept constant. Therefore, even if the pinch roller 37 is raised, landing deviation does not occur as in the above-described embodiments, and processing such as adjustment of ink ejection twing and correction of transport amount becomes unnecessary. As a result, an image of good quality can be obtained with simpler control.

  In the fourth embodiment of the present invention, the center position of the pinch roller 37 is transported as shown in FIG. 11A with respect to the center position of the transport roller 36 depending on whether or not the pinch roller 37 is raised. In this configuration, it is possible to selectively switch between a state offset in the direction (hereinafter referred to as a state where the pinch roller 37 is offset) and a state where it is not offset as shown in FIG. is there.

  That is, the third embodiment includes a pinch roller moving mechanism that switches between a state in which the pinch roller 37 is offset and a state in which the pinch roller 37 is offset, and a recording unit lifting mechanism that moves the carriage 50 and the recording head 7 up and down. ing.

  Here, the roller position selection mechanism rotates the side plate 304 around the conveyance roller 36 and moves the pinch roller 37 along the outer periphery of the conveyance roller 36 together with the pinch roller holder 30 held by the side plate 304. Thus, it is possible to set the position without offset and the offset position.

  In the recording unit lifting mechanism, the platen 34 can be lifted and lowered by rotating the platen stopper 305 provided on the side plate 304 to move the pinch roller as described above. The carriage 50 and the recording head 7 can be moved up and down by rotating the main cam 63 and moving the guide shaft 52 up and down. Here, the carriage 50 and the recording head 7 are moved up and down by the main cam 63 according to the movement of the pinch roller holder 30, that is, the movement of the pinch roller 36 and the platen 34. Further, the movement amount of the carriage 50 and the recording head 7 and the movement amount of the platen 34 are set to be the same.

  In the third embodiment configured as described above, if the recording medium to be used is easily deformed after recording, such as plain paper, it is used with the pinch roller 37 being offset. In this case, the recording medium can be brought into contact with the platen as described above, and the recorded recording medium is smoothly fed to the paper discharge roller while being slightly bent.

  On the other hand, in the case of a photographic medium having a thick recording medium and little deformation after recording, if the pinch roller 37 is used in an offset state, the recording medium may be tilted or wrinkled. May occur, and the recording medium may not be easily fed between the discharge roller and the pinch roller. Therefore, when the recording medium is thick and stiff, the side plate 304 is rotated to move the pinch roller 37 to a position where it is not offset, and the platen stopper 305 is raised to move the platen 34 to the pinch roller. 37 and move to almost the same height. At the same time, the main cam 63 rotates to raise the carriage 50 and the recording head 7 by the same amount as the platen 34. As a result, the nip formed by the conveying roller 36 and the pinch roller 37, the upper surface of the platen, and the nip formed by the paper discharge roller 41 and the pinch roller 42 are positioned on the same plane. The recording medium is smoothly guided from the conveying roller 36 onto the platen 34 to the paper discharge roller 40 without being bent. Further, when the rear end of the recording medium P reaches the vicinity of the nip formed between the conveying roller 36 and the pinch roller 37, the pinch roller 37 is raised in the same manner as in each of the above embodiments. Since the conveyance pitch does not change carelessly and a constant sheet interval can be maintained, an image of good quality can be formed even on a thick and stiff recording medium. Further, since the gap between the sheets is kept constant, the recording medium and the recording head do not come into contact with each other.

  In the third embodiment, even when a flexible recording medium such as plain paper is used, the pinch roller 37 is raised and the platen and recording head are shown in FIG. As shown in FIG. 9A, the gap between the sheets is not changed as shown in FIG. 9A, and the apex of the transport roller 36 and the discharge roller 41 and the upper surface of the platen 34 as shown in FIG. It becomes possible to support the recording medium P, and before and after the pinch roller 37 is moved up and down, it is possible to perform a recording operation while maintaining a certain interval between sheets, and a higher quality image can be obtained.

  The fifth embodiment of the present invention is configured to improve the recording medium conveyance accuracy when the pinch roller 37 is moved up and down and in the raised state.

  As shown in FIG. 12, the pressing roller 1201 is rotatably held at the tip of the pressing holder 1202, and the rear end portion of the pressing holder 1202 is rotatably attached to the chassis 11 by a rotation support shaft 1202a. Further, the pressing roller 1201 is pressed against the conveying roller 36 by the pressing spring 1203 through the pressing holder 1202. Here, one end of the pressing spring 1203 is hung on the chassis 11 and always generates a pressing force.

  As a result, the conveying roller 36 is reliably grounded to the bearing 38 by the pressing force of the pressing roller 1201 even though the pressing force to the conveying roller 36 by the pinch roller spring 31 is lost as the pinch roller 37 moves up. Further, it is possible to prevent the displacement of the conveying roller 36.

  Here, the positional deviation of the conveyance roller 36 is greatly involved in the conveyance by the paper discharge roller 40. This is because the positions of the transport roller 36 and the paper discharge roller 40 are determined by reading the rotation amount of the code wheel 362 attached to the transport roller 36 with the encoder sensor 363. This is because, of course, the position of the paper discharge roller 40 located downstream of the drive transmission is also shifted.

  As shown in FIGS. 13 to 15, various forces are applied to the transport roller 36 when the recording medium P is transported. In FIG. 13, the pinch roller 37 and the pressing roller 1201 are pressed against the transport roller 36 by the transport before the rear end of the recording medium P, and mainly the transport roller 36 (the discharge roller 40 (which is transported even though not shown). ) Shows the rotation operation (FIG. 13-a) and the stop operation (FIG. 13-b) of the conveying roller 36 in the state of conveying the recording medium P. FIG. In the conveyance of the rear end of P, the pinch roller 37 is separated from the conveyance roller 36, the pressing roller 1201 is pressed against the conveyance roller 36, and the conveyance roller is in a state where the recording medium 40 is conveyed by the paper discharge roller 40. 14A and 14B show the rotation operation (FIG. 14-a) and the stop operation (FIG. 14-b) of Fig. 15. Fig. 15 shows the conveyance of the rear end portion of the recording medium P not adopting this embodiment, and the pinch roller 37 conveys it. Carrying in a state where the recording medium 40 is conveyed by the paper discharge roller 40 while being separated from the roller 36. It shows the time of rotating the feed roller (FIG. 15-a) and the time of stopping (FIG. 15-b).

  13A, Fg is the gravity of the conveying roller 36, 1301 is a timing belt for transmitting driving force from the conveying motor 35 to the pulley 361 provided on the axis of the conveying roller 36, and 1302 is a gear portion provided on the pulley 361. An idler gear that transmits a driving force from 361-a to the paper discharge roller 40 (not shown). Fm is a driving force by which the timing belt 1301 rotates the pulley by the rotation of the conveyance motor 35, and T is a torque generated in the conveyance roller 36. Ff is the resistance force on the discharge roller 40 side, Fp is the pressing force of the pinch roller 37, Fk is the pressing force of the pressing roller 1201, Fb is the conveyance resistance (back tension) of the recording medium P, and N1 and N2 are two-plane grounding shapes The vertical drags μN1 and μN2 of the bearing 38 are frictional forces generated between the bearing 38 and the conveying roller 36. Here, the conveying roller 36 is pressed against the bearing 38 by the pressing force Fp + Fk of the pinch roller 37 and the pressing roller 1201, and the conveying roller 36 is displaced due to generation of a force such as a resistance force Ff and a frictional force μN2. (N1 and N2 are not 0).

  In FIG. 13B, Ft1 and Ft2 are static belt tensions by the timing belt 1301. In this case as well, the roller 38 is pressed against the bearing 38 by the pressing force Fp + Fk of the pinch roller 37 and the pressing roller 1201, and the transport roller 36 is not displaced (N1 and N2 do not become zero).

  On the other hand, in the configuration in which the pinch roller 37 is raised and the pressing roller 1201 is not provided, the force for pressing the transport roller 36 in the gravity direction is insufficient during the rotation operation of the transport roller 36 in FIG. When the resistance force Ff generated by applying the driving force Fm is large, or due to the occurrence of stick-slip or the like between the transport roller 36 and the bearing 38, N1 or N2 temporarily becomes 0 (the transport roller 36 is Floating).

  In FIG. 15B, N2 becomes 0 depending on the direction and size of the belt tensions Ft1 and Ft2. This explanatory diagram shows the relationship between the conveying roller 36 on the side having the drive train (left side as viewed from the front of the recording apparatus) and the bearing 38, but on the opposite side (right side as viewed from the front of the recording apparatus). In this case, the driving force Fm, resistance force Ff, and belt tension Ft1, Ft2 cause a moment force with the bearing 38 on the side having the driving train as a fulcrum, so that N1, N2 on the opposite side is more likely to be zero. (Conveyor roller 36 is in a floating state).

  On the other hand, in FIGS. 14A and 14B, which are explanatory diagrams of the present embodiment, the force Fk (pressing force of the pressing roller 1201) for suppressing the conveying roller 36 as in FIGS. 13A and 13B. Thus, the conveying roller 36 is pressed against the bearing 38, and the conveying roller 36 does not cause a positional shift (N1 and N2 do not become zero). That is, the conveyance state before the rear end portion of the recording medium P shown in FIG. 13 and the conveyance state of the rear end portion of the recording medium P where the pinch roller 37 shown in FIG. It is possible to prevent the deterioration of accuracy due to.

  Here, it goes without saying that the pressing force of Fk is set to such a magnitude that the conveying roller 36 does not float up from the bearing 38 in any case (no misalignment).

  13 to 15 are not provided with an offset in the pinch roller 37 for simplification of description, but the case where the offset is provided does not change at all. Further, the bearing 38 has been described as a two-plane contact shape in which the positional deviation with respect to the conveying roller 36 is suppressed as much as possible. However, in a general round hole-shaped bearing, it is caused by a change in the direction of the acting force on the conveying roller 36. The positional deviation of the conveying roller 36 becomes more remarkable.

  Further, as shown in FIGS. 13 and 14, the pressing position of the pressing roller 1201 is equal to the pressing position of the pinch roller 37 in the transport cross section. Accordingly, the pressing force can be applied without changing in the pressing direction of the conveying roller 36 regardless of the presence or absence of the pressing force of the pinch roller 37, and the change in the positional stability of the conveying roller 36 due to the change in the pressing state of the pinch roller 37. Is kept to a minimum. The above-described general round hole bearing is more effective.

  As described above, by pressing the pressing roller 1201 against the transport roller 36, the position of the transport roller 36 is stabilized regardless of the elevation of the pinch roller 37 and the rotation accuracy of the paper discharge roller 40 is maintained. The recording operation can be performed without deterioration of the image quality, and a higher quality image can be obtained.

(Sixth embodiment)
In this embodiment, as shown in FIG. 16, as compared with the fifth embodiment, a press cam 1601 that presses and releases the rear end of the press holder 1202 is attached to the pinch roller release shaft 302, One end is hung on the pressing cam 1601. With this configuration, the pressing roller 1201 is pressed and separated according to the lifting and lowering operation of the pinch roller 37. In the figure, the pinch roller 37 presses the transport roller 36 and the pressing roller 1201 is raised.

  As shown in FIG. 17, when the pinch roller 37 is pressed, the pressing roller 1201 is separated when the pinch roller 37 is pressed (FIG. 17A), and when the pinch roller 37 is separated, the pressing roller 1201 is pressed (FIG. 17). -c) Configuration. Here, the separation and pressing timing of the pinch roller 37 and the pressing roller 1201 have both pressing overlap operation regions so that both the pinch roller 37 and the pressing roller 1201 are not simultaneously separated from the conveying roller 36. (FIG. 17-b). This is because the transport roller 36 is pressed against the bearing 38 in any case. That is, the upward movement of the pinch roller 37 operates as shown in FIG. 17-a → FIG. 17-b → FIG. 17-c, and conversely, the downward movement of the pinch roller 37 occurs as shown in FIG. 17-c → FIG. 17-b → FIG. Works with a.

  Here, the force of the pressing spring 1203 is determined so that the total pressure of the pressing force (F3) applied to the conveying roller 36 by the pressing roller 1201 and the pressing force (F1) applied to the conveying roller 36 by the pinch roller 37 is constant. (Here, it is ideal that the pressing force F2 in the pressing overlap operation region of the pinch roller 37 and the pressing roller 1201 is equal to F1 or F3. However, if the conveying roller 36 is not conveyed in this state, the conveying roller 36 (It may be a pressing force that does not cause misalignment). The rotation operation of the conveying roller 36 is performed in FIG. 17A or 17C, and is not performed in FIG. 17B. However, if the pressing force applied to the conveying roller 36 can be kept equal to the pressing force (F1) and the pressing force (F3) in FIG. 17-b and other states, the rotating operation of the conveying roller 36 may be performed. . Further, the pressing direction by the pinch roller 37 and the pressing direction by the pressing roller 1201 are made equal as in the fifth embodiment. That is, the conveying roller 36 is always subjected to the same pressing force in the same direction by the pinch roller 37 and the pressing roller 1201, and the action force state becomes equal, so that the mechanical load can be stabilized. In the explanatory view here, for simplification, no offset is provided in the pressing direction of the pinch roller 37 and the pressing roller 1201, but the case where the offset is provided does not change at all.

  In this case, the DC motor 35 is used as a drive source for the conveyance roller 36, the rotation amount (position) of the conveyance roller 36 is detected by the encoder sensor 363, and the position and speed information is feedback-controlled to control the operation of the conveyance roller 36. Yes. Immediately before the stop, the actuator is operated at a controllable slow speed, the power is turned off at the target position (encoder slit), and the actuator is stopped by the frictional force of the mechanism.

  Here, two important points in securing the conveyance stop accuracy are the stability of the speed immediately before the stop and the stability of the frictional force of the mechanism.

  With respect to the stability of the speed immediately before the first stop, the state of the controlled object needs to be constant in order to stabilize the servo control. When the operation is about to stop, the amount of rotation of the code wheel 362 is reduced, and the number of output signals from the encoder sensor 363 is reduced. Therefore, the control stability is deteriorated. This is because the stability of the controlled object becomes important in such a state.

  FIG. 18 shows the influence on stopping accuracy when the speed before stopping changes due to deterioration of control stability or the like. In the figure, the vertical axis indicates speed, the horizontal axis indicates position, P0 is the target stop position, and the arrow indicates the operation until stop. When the speed before stoppage is slow (1801) changes to Vs1 when it is fast (1802), the power is turned off at the moment when the target stop position P0 is reached in these states, and the mechanical load (mainly the transport roller 36 and the bearing) If the target position P0 is used as a reference, the positions to stop at (38 frictional force) are ΔPs0 and ΔPs1, and a difference of ΔPs1−ΔPs0 occurs. If the pre-stop speed for each transport is the same, the deviation amount based on P0 becomes equal for each transport and the transport pitch is maintained, so that the transport accuracy is maintained. If the speed before stopping changes as described above and the shift amount changes, the transport pitch changes for each transport, which deteriorates the transport accuracy.

  In this embodiment, as described above, regardless of whether the pinch roller 37 is pressed or separated, the load (torque) and the load direction to the conveyance roller 36 to be controlled are made constant so that the state of the control object is equalized. Therefore, the stability of the control is achieved and the speed before the stop is stabilized (the same result can be obtained with the same control and the same gain).

  Regarding the stability of the frictional force of the second mechanical point, the idling rotation amount of the conveying roller 36 from the moment when the power is turned off until it stops is always kept constant. The idling rotation amount greatly depends on the braking force received by the conveying roller 38 in addition to the speed (including acceleration) at the moment of turning off the power.

As shown in FIG. 19, for example, even if the speed v at the moment when the power is turned off by the control is kept constant, if the rotational load of the transport roller 36 is small (1901), the braking force is insufficient and the engine overruns. The position shifts from the target position in the transport direction and stops (position of ΔPf1). Furthermore, since the braking force is insufficient, it becomes sensitive to the speed shift at the moment of turning off the power, and the variation in the stop position becomes large. On the other hand, if the rotational load of the transport roller 36 is large (1902), the braking force is large, so that the position where the power is turned off and stopped at the target stop position comes to the front (position of ΔPf0). Conversely, if the speed v and the braking force at the moment of turning off the power are kept constant, the stop position can be stabilized. (In the same figure, as in FIG. 18, the vertical axis indicates speed, the horizontal axis indicates position, P0 is the target stop position, and the arrow indicates the operation until stop.)
In other words, it is important to keep the braking force (load) applied to the conveyance roller 36 to be controlled constant regardless of whether the pinch roller 37 is pressed or separated. The mileage can be stabilized and stopping accuracy can be improved.

(For the sake of clarity, FIGS. 18 and 19 show an example in which when the power is turned off at the target stop position, the machine stops before the target stop position. Actually, when the power is turned off at a sufficiently slow speed, the mechanism is stopped. (Because of elasticity etc., it stops before the transport direction from the target stop position.)
As described above, the pressing roller 1201 is moved up and down in accordance with the lifting and lowering operation of the pinch roller 37, and the braking force received by the conveying roller 36 is made constant, so that the stopping accuracy of the conveying roller 36 and the discharging roller 40 is stopped. And a higher quality image can be obtained even in the rear end region.

  Furthermore, not only the positional deviation of the transport roller 36 is prevented, but the rotational load of the transport roller 36 does not increase even though the pressing function of the pressing roller 1201 is added, so the load of the transport motor is increased. The advantage that the performance of the conveyance motor 35 can be utilized to the maximum is also obtained.

1 is a perspective view of a recording apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view of a mechanism unit of the recording apparatus according to the embodiment of the invention. It is a vertical side view in embodiment of this invention. It is a perspective view which shows the pinch roller raising / lowering mechanism in embodiment of this invention. FIG. 5 is an explanatory longitudinal sectional side view showing a recording operation state with respect to the rear end portion of the recording medium in the embodiment of the present invention. It is a block diagram which shows schematic structure of the control system in embodiment of this invention. FIG. 6 is an explanatory diagram illustrating a recording medium conveyance operation and a 4-pass multi-pass recording state according to the first embodiment of the present invention. FIG. 7 is a diagram showing a state in which the recording medium P is lifted when the pinch roller 31 is raised, and a state in which landing deviation of ink droplets has occurred due to the lifting, and (a) shows the lifted recording medium in the conveyance direction of the recording medium. FIG. 4B is a diagram viewed from a direction perpendicular to the carriage (moving direction of the carriage), and FIG. 5B is a diagram illustrating the floating recording medium viewed from a direction orthogonal to the carriage moving direction. FIG. 10 is an explanatory diagram illustrating a state in which the recording medium conveyance operation and the number of passes of multi-pass recording are switched in the second embodiment of the present invention. It is a description vertical side view of the conveyance part in the 3rd Embodiment of this invention, and a recording part. It is an explanatory vertical section side view showing the state of a conveyance part and a recording part in a 4th embodiment of the present invention. It is a perspective view which shows the press roller mechanism in the 5th Embodiment of this invention. It is a description cut-away side view of the conveyance roller part in the 5th Embodiment of this invention. It is a description cut-away side view of the conveyance roller part in the 5th Embodiment of this invention. It is a description cut-away side view of the conveyance roller part in the 5th Embodiment of this invention. It is a perspective view which shows the press roller raising / lowering mechanism in the 6th Embodiment of this invention. It is a description sectional side view which shows operation | movement of the press roller raising / lowering mechanism in the 6th Embodiment of this invention. It is explanatory drawing of the conveyance stop vicinity operation | movement in the 6th Embodiment of this invention. It is explanatory drawing of the conveyance stop vicinity operation | movement in the 6th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Paper feeding part 4 Paper discharge part 7 Recording head 31 Pinch roller spring 32 PE sensor lever 34 Platen 36 Conveyance roller 37 Pinch roller 30 Pinch roller holder 301 Pinch roller release cam 302 Pinch roller release shaft 303 Pinch roller release gear 304 Side plate 305 Platen stopper 381 Roller tension spring 40 Discharge roller 1
41 Paper discharge roller 2
42 Spur 50 Carriage 1201 Press roller

Claims (16)

An inkjet recording apparatus comprising: a conveying unit that conveys a recording medium; a recording unit that records an image by ejecting ink onto the recording medium conveyed by the conveying unit; and a control unit that controls the two units. There,
The conveying means is composed of an upstream conveying means arranged on the upstream side of the recording means, and a downstream conveying means arranged on the downstream side of the recording means,
The upstream conveying means includes a pair of rollers arranged to oppose each other so as to sandwich and release the recording medium,
Moving means for moving at least one of the pair of rollers from a holding position for holding the recording medium to a release position for releasing the recording medium;
The control means controls the moving means to release the sandwiched state by the pair of rollers before the trailing end of the recording medium reaches between the pair of rollers of the upstream side conveying means. apparatus.   The upstream conveying unit includes a driving roller that is rotated by a driving force of a predetermined driving source, and a driven roller that is provided to face the driving roller, and the driven roller records between the driving roller. 2. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is movable to a holding position for holding the medium and a release position separated from the recording medium.   The conveying means intermittently conveys the recording medium, and the recording means discharges and records ink while scanning in a direction crossing the conveying direction according to the intermittent conveying operation of the recording medium. The inkjet recording apparatus according to claim 1 or 2, wherein   The control unit is configured to carry the intermittent conveyance operation for each intermittent conveyance operation by each of the conveyance units before, when the driven roller of the upstream conveyance unit is separated from the recording medium, and after the separation. The recording apparatus according to claim 2, wherein the recording apparatus is changed. The recording means has a nozzle group composed of a plurality of nozzles arranged along a direction intersecting with the conveyance direction of the recording medium,
The control means completes an image by executing a plurality of scans using different nozzles for the same recording area of the recording medium, and separates the driven roller of the upstream conveying means from the driving roller. 5. The recording apparatus according to claim 1, wherein after that, the number of scans required to complete an image in each recording area is increased.   6. The control unit according to claim 2, wherein the control unit changes ink ejection timing in the scanning direction of the recording unit before and after the driven roller of the upstream conveying unit is separated from the driving roller. An ink jet recording apparatus according to claim 1.   3. The control device according to claim 2, wherein the control unit changes a transport amount of one time in an intermittent transport operation by the transport unit before and after the driven roller of the upstream transport unit is separated from the recording medium. The inkjet recording apparatus according to any one of 5.   8. The ink jet recording apparatus according to claim 2, wherein the driven roller of the upstream side conveying unit abuts on the driving roller after the recording operation for the entire recording medium is finished after being separated from the recording medium. .   3. The nip position between the driven roller and the driving roller of the upstream side conveying unit is set to the apex position of the driving roller, and the nip position is located on the same plane as the conveyance path of the recording medium. The ink jet recording apparatus according to any one of Items 8 to 8.   The upstream conveying unit is configured such that the nip position between the driven roller and the driving roller is movable on the driving roller, and is provided at the recording unit and a position facing the recording unit according to the position of the nip position. 9. The ink jet recording apparatus according to claim 2, wherein the position of the supporting member of the recording medium is configured to be movable.   The said upstream conveyance means has a press means which presses the drive roller of the said upstream conveyance means with respect to the bearing which supports this drive roller in addition to the said driven roller. 2. An ink jet recording apparatus according to 1.   When the recording medium is transported, the pressing means does not press the driving roller when the driven roller presses the driving roller, and the pressing means when the driven roller is separated from the driving roller. The inkjet recording apparatus according to claim 11, wherein the drive roller is pressed.   13. The ink jet recording apparatus according to claim 12, wherein a total pressing force applied to the driving roller by the driven roller is equal to a total pressing force applied to the driving roller by the pressing unit.   14. The ink jet recording apparatus according to claim 11, wherein a pressing direction given to the driving roller by the driven roller is equal to a pressing direction given to the driving roller by the pressing means.   The driving means for driving the two conveying means includes a DC motor and a rotational position detecting means for the driving roller of the upstream conveying means, and the DC motor is feedback-controlled based on information from the position detecting means for the driving. 15. The ink jet recording apparatus according to claim 1, wherein the roller is positioned. A control method for an ink jet recording apparatus comprising: a transport unit that transports a recording medium; and a recording unit that records an image by ejecting ink onto the recording medium transported by the transport unit,
The conveying means is composed of an upstream conveying means arranged on the upstream side of the recording means and a downstream conveying means arranged on the downstream side of the recording means,
The upstream conveying means is configured to release a recording medium from a clamping position where the recording medium is sandwiched between a pair of rollers arranged to oppose each other so as to sandwich and release the recording medium, and at least one of the pair of rollers. And moving means for moving to a position,
A control method for an ink jet recording apparatus, wherein the moving means is controlled so as to release a sandwiched state by the pair of rollers before the trailing end of the recording medium reaches between the pair of rollers of the upstream transport means.

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