JP4831220B2 - Paper transport apparatus and ink jet recording apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus for conveying a sheet and an ink jet recording apparatus including the same.

  The ink jet printer includes a paper transport device including a pair of drive rollers and an endless transport belt wound around the drive roller. The ink is ejected from the ink jet head onto the paper while the paper is transported by the paper transport device. By doing so, a desired image can be formed on the paper. In this case, the resolution in the paper transport direction in the formed image depends on the transport accuracy of the paper transport device. Therefore, in order to form a highly accurate image, it is necessary to accurately drive the sheet conveying device at a predetermined speed. In such a sheet conveying apparatus, an endless conveying belt wound around a driving roller is opposed to a speed detection roll (encoder roller) to which a rotary encoder is attached and biased in a direction toward the speed detection roll. A technique is known in which driving of a conveyor belt is controlled based on a rotational position of a speed detection roll that is sandwiched between rolls (encoder nip rollers) and detected by a rotary encoder (see Patent Document 1). According to this, since the rotational speed of the conveyor belt can be directly detected by the rotary encoder, the conveyor belt can be accurately driven at a predetermined speed.

JP 05-297737 (FIG. 1)

  In the technique described above, the conveyed paper passes between the speed detection roll and the conveyance belt. For this reason, at the moment when the paper enters between the speed detection roll and the conveyance belt and the moment when the paper is discharged from between these, the conveyance belt is bent in the thickness direction, and the opposing roll is instantaneously displaced. When the opposing roll is displaced momentarily, the urging pressure of the opposing roller with respect to the conveyance belt changes instantaneously, and the contact pressure between the speed detection roll and the conveyance belt changes abruptly. At this time, the speed detection roll may not follow the fluctuation of the conveyor belt, and the rotational speed of the conveyor belt may not be accurately read.

  A main object of the present invention is to provide a paper transport device capable of accurately reading the rotational speed of the transport belt and an ink jet recording apparatus including the paper transport device.

The sheet conveying apparatus of the present invention includes an endless conveying belt whose surface is a sheet placement surface, a driving unit that drives the conveying belt, an encoder roller that is in contact with one surface of the conveying belt, and the conveying belt An encoder nip roller that is in contact with the other surface serving as the mounting surface and sandwiches the conveyor belt together with the encoder roller, and a first bias that biases at least one of the encoder roller and the encoder nip roller toward each other A mechanism, an encoder that detects the rotational position of the encoder roller, and a sensor that detects the slit of the encoder and outputs it to the control unit, and both the encoder roller and the encoder nip roller are transported. in contact with the surface of the conveyor belt in the area but deviated from paper passing region passing Rutotomoni, the length in the axial direction of the encoder nip roller is shorter than the length in the axial direction of the encoder roller, the paper passing region is positioned to correspond to the center in the width direction of the conveyor belt, A pair of the encoder roller and the encoder nip roller is disposed on both sides in the width direction of the transport belt, the encoder and the sensor are provided for each of the two encoder rollers, and the control The unit controls the driving means so as to correct the difference in the rotational position of the encoder roller based on the detection signals output from the two sensors.

  According to the present invention, paper does not pass between one of the encoder roller and encoder nip roller that are in contact with the surface of the conveyor belt and the conveyor belt. For this reason, even when the paper passes through the shaft of the encoder roller, the encoder roller or the encoder nip roller is not instantaneously displaced, and the encoder roller and the encoder nip roller always sandwich the conveyance belt with a constant pressure. Thereby, the encoder roller can be made to follow the conveyance belt stably, and the transfer speed of the conveyance belt can be read accurately. In the present invention, the paper passage area through which the paper to be conveyed passes means an area through which the paper placed on the conveyance belt passes when the conveyance belt is driven.

1 is a schematic configuration diagram of a printer according to a first embodiment of the present invention. FIG. 2 is a plan view of the paper transport device shown in FIG. 1. It is sectional drawing of the III-III line shown in FIG. It is sectional drawing of the IV-IV line shown in FIG. FIG. 2 is a functional block diagram of a control unit depicted in FIG. 1. It is a functional block diagram of the control part shown in FIG. It is a top view of the paper conveyance apparatus which the printer which is 2nd Embodiment concerning this invention has. It is sectional drawing of the VIII-VIII line shown in FIG. It is sectional drawing of the IX-IX line shown in FIG. It is a figure which shows the modification of the conveyance belt shown in FIG. It is a top view of the paper conveying apparatus which the printer which is the 3rd Embodiment concerning this invention has. It is sectional drawing of the XII-XII line | wire shown in FIG.

  Hereinafter, a first embodiment according to the present invention will be described with reference to the drawings.

  First, an ink jet printer according to a first embodiment will be described with reference to FIG. A printer 1 shown in FIG. 1 is a line-type color inkjet printer including four inkjet heads 2 whose outer shape is a rectangle that is long in a direction perpendicular to the paper surface of FIG. The printer 1 is provided with a paper feeding device 14 in the lower part of the figure, a paper receiving part 16 in the upper part of the figure, and a paper conveying apparatus 20 in the central part in the figure. Further, the printer 1 includes a control unit 100 that controls these operations.

  The paper feeding device 14 is a paper storage unit 15 that can store a plurality of stacked printing papers P, and a feeding unit that feeds the uppermost printing paper P in the paper storage unit 15 toward the paper transport device 20 one by one. And a paper roller 45. The paper storage unit 15 stores the printing paper P so that it is fed in a direction parallel to the long side. Feed rollers 18a, 18b, 19a, and 19b are disposed between the paper storage unit 15 and the paper transport device 20 along the transport path. The printing paper P discharged from the paper feeding device 14 is sandwiched by the feed rollers 18a and 18b and fed upward in FIG. 1 with one short side as the leading edge, and is then sandwiched by the feed rollers 19a and 19b. It is sent to the left side in FIG.

  The paper transport device 20 includes an endless transport belt 11 and two belt rollers 6 and 7 around which the transport belt 11 is wound. The length of the conveyor belt 11 is adjusted so that a predetermined tension is generated in the conveyor belt 11 wound between the two belt rollers 6 and 7. By being wound around the two belt rollers 6 and 7, the transport belt 11 is formed with two parallel planes each including a common tangent of the belt rollers 6 and 7. Of these two planes, the surface facing the inkjet head 2 is the surface on which the printing paper P is placed. When the printing paper P sent out from the paper feeding device 14 is placed on the transport belt 11 and transported, the upper surface thereof is printed by the ink jet head 2 and reaches the paper receiving section 16. In the paper receiving unit 16, a plurality of printed printing papers P are placed so as to overlap each other. Details of the sheet conveying device 20 will be described later.

  Each of the four inkjet heads 2 has a head body 13 at the lower end thereof. The head main body 13 has a rectangular parallelepiped shape elongated in a direction orthogonal to the paper surface of FIG. The four head bodies 13 are arranged close to each other along the transport direction of the printing paper P by the paper transport device 20 (the left-right direction in FIG. 1). A large number of nozzles having minute diameters are provided on the bottom surfaces (ink ejection surfaces) of the four head main bodies 13. The four head bodies 13 are different in the color of the ejected ink, and each head body 13 has one of the colors of magenta (M), yellow (Y), cyan (C), and black (K). Ink is ejected. That is, the ink colors ejected from a large number of nozzles belonging to one head body 13 are the same.

  A slight gap is formed between the bottom surface of the head body 13 and the conveyor belt 11. The printing paper P is conveyed from right to left in FIG. 1 through this gap. When the printing paper P sequentially passes under the four head bodies 13, ink is ejected from the nozzles toward the upper surface of the printing paper P, so that a desired color image is formed on the printing paper P.

  As shown on the left side in FIG. 1, a peeling plate 40 is provided on the downstream side of the paper transport device 20 in the paper transport direction. The peeling plate 40 peels the printing paper P adhered to the placement surface of the conveying belt 11 from the paper passing area 27 by the leading end of the peeling plate 40 entering between the printing paper P and the conveying belt 11.

  Feed rollers 21 a, 21 b, 22 a, and 22 b are disposed between the paper transport device 20 and the paper receiver 16. The printing paper P discharged from the paper transporting device 20 is sandwiched between the feed rollers 21a and 21b with the short side of one of the leading ends as the leading edge, and is fed upward in FIG. 1, and is sandwiched between the feed rollers 22a and 22b to receive the paper. Sent to section 16.

  As shown in FIG. 1, a paper surface sensor 33, which is an optical sensor composed of a light emitting element and a light receiving element, is disposed on the upstream side of the transport belt 11 in the paper transport direction. The paper surface sensor 33 irradiates light from the light emitting element toward the detection position on the conveyor belt 11 and receives the reflected light by the light receiving element. The output signal level from the paper surface sensor 33 reflects the difference in the intensity of reflected light depending on the presence or absence of the printing paper P on the detection position. That is, the leading edge of the printing paper P has reached the detection position at the time when the output signal level suddenly increases. Since the output signal from the paper surface sensor 33 indicates that the leading edge of the print paper P has reached the detection position, a print start signal is supplied to the inkjet head 2 accordingly.

  Next, the details of the sheet conveying device 20 will be described with reference to FIGS. FIG. 2 is a plan view of the sheet conveying device 20 as viewed from the inkjet head 2 side. 3 is a cross-sectional view taken along line III-III shown in FIG. FIG. 4 is a cross-sectional view taken along line IV-IV shown in FIG.

  As shown in FIGS. 1 to 4, the sheet conveying device 20 includes the conveying belt 11 and the belt rollers 6 and 7, a conveying motor 74 that drives the belt roller 6 via a transmission belt 74 a, an encoder roller 39, and the like. A rotary encoder 41 for detecting the rotational position of the encoder roller 39, an encoder nip roller 51, and an encoder nip urging mechanism 50 that urges the encoder nip roller 51 in a direction close to the encoder roller 39 while rotatably supporting the encoder nip roller 51; The sheet nip roller 61 and a sheet nip urging mechanism 60 that urges the sheet nip roller 61 in a direction close to the encoder roller 39 while rotatably supporting the sheet nip roller 61. The conveyor belt 11 is formed by covering the entire outer periphery of the base material layer 35 with an adhesive layer 36 made of adhesive silicone rubber (see FIG. 10). The surface of the adhesive layer 36 becomes the outer peripheral surface 11a of the transport belt 11 on which the printing paper P is placed, and the surface of the base material layer 35 that is not covered with the adhesive layer 36 is the inner peripheral surface 11b of the transport belt 11. It becomes. Further, a region through which the transport belt 11 is driven and the printing paper P placed on the transport belt 11 is transported is a paper passage region 27. As shown in FIG. 2, the paper passage area 27 is a rectangular area that is line symmetric with respect to the center line in the width direction of the transport belt 11. The outer periphery of the paper passage area 27 is a paper non-passage area 28 through which the printing paper P does not pass.

  The two belt rollers 6 and 7 extend along the width direction of the conveyor belt 11 so as to cross the conveyor belt 11 and are in contact with the inner peripheral surface 11 b of the conveyor belt 11. The transport motor 74 is driven to rotate under the control of the control unit 100. When the conveyance motor 74 is driven to move the belt roller 6 counterclockwise in the figure (in the direction of arrow A in FIG. 1), the printing paper P conveyed by the feed rollers 18a, 18b, 19a, 19b is conveyed. It is placed on the outer peripheral surface 11a of the belt 11 and conveyed. The belt roller 7 is a driven roller that is rotated by a rotational force applied from the transport belt 11 as the belt roller 6 rotates.

  As shown in FIGS. 3 and 4, the encoder roller 39 extends across the conveyance belt 11 along the width direction of the conveyance belt 11 and is in contact with the inner peripheral surface 11 b of the conveyance belt 11. A rotary encoder 41 is provided at one end of the encoder roller 39. The rotary encoder 41 is attached to one end of an encoder roller 39, and has a disc-shaped slit plate 41a in which a large number of slits are formed along the outer edge, and an optical sensor 41b that detects the slits of the slit plate 41a. Yes. When the encoder roller 39 rotates, the slit plate 41a fixed to the encoder roller 39 also rotates. When the slit plate 41 a rotates by a predetermined angle, the optical sensor 41 b detects the passage of the slit of the slit plate 41 a and outputs a detection signal to the control unit 100. As will be described later, the control unit 100 detects the transport speed of the transport belt 11 based on the detection signal output from the encoder roller 39 and controls the transport motor 74 and the inkjet head 2.

  As shown in FIGS. 2 and 3, the two encoder nip biasing mechanisms 50 are arranged so that the encoder nip roller 51 faces the encoder roller 39 through the conveyance belt 11 in a state where the encoder nip roller 51 is positioned in the paper non-passing area 28. I support it. The encoder nip biasing mechanism 50 includes a roller support member 52 that supports the encoder nip roller 51 and a release mechanism 55 that releases the contact between the encoder nip roller 51 and the transport belt 11. The roller support member 52 can swing about a swing shaft 53 whose both ends are fixed to the frame so as to be along the width direction of the conveyor belt 11, and both ends of the encoder nip roller 51 can be rotated at its ends. It has a pair of holding arms 52a to support, and a connecting portion 52b provided between the pair of holding arms 52a to connect them. A biasing spring 54 is attached between the connecting portion 52b and the frame (not shown) so that the encoder nip roller 51 is biased in the direction approaching the encoder roller 39. When the roller support member 52 swings in a direction in which the encoder nip roller 51 is brought close to the encoder roller 39, the encoder nip roller 51 comes into contact with the conveyance belt 11 in the paper non-passing area 28 and sandwiches the conveyance belt 11 together with the encoder roller 39 (FIG. 5). reference).

  The release mechanism 55 is for releasing the contact between the encoder nip roller 51 and the conveyor belt 11. The eccentric cam 55 a is attached to the rotation shaft 56 a of the cam motor 56, and the eccentric cam 55 a is rotated by driving the cam motor 56. It is what The eccentric cam 55a is disposed so that its outer peripheral surface (cam surface) faces the opposite side of the biasing spring 54 with respect to the swing shaft 53 in the connecting portion 52b of the roller support member 52. The operation of the release mechanism 55 will be described with reference to FIG. FIG. 5A shows a state when the release mechanism 55 does not release the contact between the encoder nip roller 51 and the transport belt 11, and FIG. 5B shows the contact between the encoder nip roller 51 and the transport belt 11. Shows the states when is released by the release mechanism 55.

  As shown in FIG. 5A, when the eccentric cam 55a stops at a rotational position where it does not contact the roller support member 52, the urging force of the urging spring 54 causes the encoder nip roller 51 to approach the encoder roller 39. The roller support member 52 swings. As a result, the encoder nip roller 51 comes into contact with the conveyance belt 11 and sandwiches the conveyance belt 11 together with the encoder roller 39. As shown in FIG. 5B, when the eccentric cam 55a stops at the rotational position where it comes into contact with the roller support member 52, the eccentric cam 55a pushes down the roller support member 52 and the encoder nip roller 51 moves away from the encoder roller 39. Then, the roller support member 52 swings. As a result, the encoder nip roller 51 is separated from the transport belt 11.

  2 and 3, the paper nip urging mechanism 60 supports the paper nip roller 61 so as to face the encoder roller 39 through the transport belt 11 in a state where the paper nip roller 61 is positioned in the paper passage region 27. . The sheet nip urging mechanism 60 includes a roller support member 62 that supports the sheet nip roller 61 and a release mechanism 65 that releases the contact between the sheet nip roller 61 and the conveyance belt 11. The roller support member 62 is swingable about the swing shaft 53, and between the pair of holding arms 62a and a pair of holding arms 62a that supports both ends of the paper nip roller 61 to be rotatable at the ends thereof. It has a connecting part 62b that is provided and connects them. A biasing spring 64 is attached between the connecting portion 62b and the frame (not shown) so that the paper nip roller 61 is biased in the direction approaching the encoder roller 39. When the roller support member 62 swings in the direction in which the paper nip roller 61 is brought close to the encoder roller 39, the paper nip roller 61 abuts the transport belt 11 in the paper passage region 27 and sandwiches the transport belt 11 together with the encoder roller 39 (see FIG. 5). . As a result, when the paper nip roller 61 and the encoder roller 39 sandwich the printing paper P together with the conveying belt 11, the printing paper P is securely adhered to the adhesive layer 36. Further, the paper nip roller 61 in contact with the transport belt 11 is coaxial with the pair of encoder nip rollers 51 in contact with the transport belt 11 (the central axis of the paper nip roller 61 and the central axis of the encoder nip roller 51 are collinear. In the state of Note that the biasing force of the biasing spring 64 of the paper nip biasing mechanism 60 is smaller than the biasing force of the biasing spring 54 of the encoder nip biasing mechanism 50.

  The release mechanism 65 has the same configuration as the release mechanism 55, and an eccentric cam 65 a is attached to the rotation shaft 56 a of the cam motor 56. The eccentric cam 65a is disposed so that its outer peripheral surface (cam surface) faces the opposite surface of the sheet nip roller 61 with respect to the swing shaft 63 in the roller support member 62. Since the operation of the release mechanism 65 is substantially the same as the operation of the release mechanism 55, description thereof is omitted.

Next, the details of the control unit 100 will be described with reference to FIG. FIG. 6 is a functional block diagram of the control unit 100. The control unit 100 includes a CPU (Central Processing Unit) that is an arithmetic processing unit, a ROM (Read Only Memory) in which a program executed by the CPU and data used in the program are stored, and data temporarily stored when the program is executed. A random access memory (RAM) and other logic circuits are included, and these function together to construct a functional unit described below.

As shown in FIG. 6, the control unit 100 includes a head control unit 101 that controls ejection of ink from the inkjet head 2, a motor control unit 104 that controls driving of the carry motor 74, an encoder nip biasing mechanism 50, And an urging mechanism control unit 107 that controls the sheet nip urging mechanism 60. Each of these functional units is hardware configured with an ASIC (Application Specific Integrated Circuit) or the like, but all or a part of the functional units may be configured with software.

  The head control unit 101 includes an ejection timing determination unit 102 and a pulse generation unit 103. The ejection timing determination unit 102 controls the ejection timing of ink to be ejected by the inkjet head 2 based on image data to be formed on the printing paper P. Further, the discharge timing determination unit 102 changes the ink discharge timing in order to correct the positional deviation of the transport belt 11 based on the rotation position of the encoder roller 39 detected by the encoder roller rotation position detection unit 105 described later. The pulse generation unit 103 generates a drive pulse for driving the head main body 13 according to the ink discharge timing determined by the discharge timing determination unit 102, and supplies the generated drive pulse to the head main body 13. . The head body 13 ejects ink onto the printing paper P every time a driving pulse is supplied from the pulse generator 103.

  The motor control unit 104 includes an encoder roller rotation position detection unit 105 and a motor drive unit 106. The encoder roller rotation position detector 105 detects the rotation position of the encoder roller 39 based on the detection result of the optical sensor 41 b of the rotary encoder 41. By detecting the rotational position of the encoder roller 39, the position and rotational speed of the conveyor belt 11 can be detected. The motor drive unit 106 drives the carry motor 74 based on the rotation position of the encoder roller 39 detected by the encoder roller rotation position detection unit 105.

  The urging mechanism control unit 107 drives the release mechanism 55 of the encoder nip urging mechanism 50 and the release mechanism 65 of the paper nip urging mechanism 60 by controlling the driving of the cam motor 56. Specifically, in conjunction with the motor control unit 104 and the paper surface sensor 33, the encoder nip roller 51, the paper nip roller 61, and the conveyance belt 11 are brought into contact only when the printing paper P is not placed on the conveyance belt 11. The release mechanism 55 and the release mechanism 65 are controlled so as to be released. That is, when the biasing mechanism control unit 107 controls the release mechanism 55 and the release mechanism 65 so that the encoder nip roller 51 and the paper nip roller 61 are in contact with the conveyance belt 11, the eccentric cam 55 a of the release mechanism 55 is connected to the roller support member 52. The cam motor 56 is driven so that the eccentric cam 65a of the release mechanism 65 does not contact the roller support member 62 so as not to contact. Further, when the release mechanism 55 and the release mechanism 65 are controlled so as to release the contact between the encoder nip roller 51 and the paper nip roller 61 and the conveying belt 11, the eccentric cam 55 a of the release mechanism 55 comes into contact with the roller support member 52. In addition, the cam motor 56 is driven so that the eccentric cam 65a of the release mechanism 65 contacts the roller support member 62 (see FIGS. 5A and 5B).

  In the first embodiment described above, the encoder nip roller 51 is configured to come into contact with the conveyance belt 11 only in the paper non-passing area 28, so that the printing paper P is interposed between the encoder nip roller 51 and the conveyance belt 11. Never pass. Therefore, regardless of whether or not the printing paper P is placed on the transport belt 11, the transport belt 11 can be pressed against the encoder roller 39 with the encoder nip roller 51 always at a constant pressure. Thereby, the accurate transfer speed of the conveyor belt 11 can be detected from the rotational position of the encoder roller 39. Further, the ejection timing determination unit 102 of the head control unit 101 corrects the positional deviation of the conveyor belt 11 by controlling the ink ejection timing based on the rotation position of the encoder roller 39 detected by the encoder roller rotation position detection unit 105. By doing so, it is possible to quickly and accurately correct the deviation caused by the unique fluctuations that occur in the conveyor belt 11.

  Further, since the paper nip roller 61 is configured to come into contact with the transport belt 11 in the paper passage area 27, when the print paper P passes between the paper nip roller 61 and the transport belt 11, the paper nip roller 61 and the encoder roller 39. However, it is possible to sandwich the printing paper P together with the transport belt 11 and to securely adhere the printing paper P to the adhesive layer 36 and prevent the printing paper P from floating from the transport belt 11.

  Further, since the paper passage area 27 is located corresponding to the center of the conveyance belt 11 in the width direction, when the printing paper P is conveyed, the conveyance belt 11 is uniformly weighted. Thereby, it becomes difficult for the conveyor belt 11 to meander, and a more accurate transfer speed of the conveyor belt 11 can be obtained.

  In addition, the pair of encoder nip rollers 51 and the paper nip roller 61 that are in contact with the transport belt 11 are coaxially arranged, and the encoder roller 39 is configured to face not only the encoder nip roller 51 but also the paper nip roller 61. The number of rollers can be reduced and the cost can be reduced. In addition, the encoder nip roller 51 efficiently performs the unique fluctuation that occurs in the conveyance belt 11 at the moment when the printing paper P enters between the paper nip roller 61 and the conveyance belt 11 and at the moment when the printing paper P is discharged from between them. It can be reduced well. Furthermore, since the encoder nip roller 51 applies an even weight to both sides in the width direction of the transport belt 11 (direction orthogonal to the paper transport direction), the transport belt 11 becomes difficult to meander.

  Further, when the printing paper P is not placed on the conveyance belt 11, the urging mechanism control unit 107 releases the contact between the encoder nip roller 51 and the paper nip roller 61 and the conveyance belt 11. Therefore, an excessive frictional force is not applied, and the load applied to the conveyor belt 11 is reduced.

  Further, since the biasing force of the biasing spring 64 of the paper nip biasing mechanism 60 is smaller than the biasing force of the biasing spring 54 of the encoder nip biasing mechanism 50, there is a gap between the paper nip roller 61 and the transport belt 11. At the moment when the printing paper P enters and at the moment when the printing paper P is discharged from between the two, it is possible to relatively reduce the peculiar fluctuation generated in the transport belt 11. Further, if the urging force of the urging spring 54 is sufficiently large, the followability of the encoder roller 39 is unlikely to be impaired even if there is such a specific fluctuation, and a more accurate rotation speed of the conveyor belt 11 can be obtained. become.

  Furthermore, since the inkjet head 2 is a line-type inkjet head extending in a direction orthogonal to the paper conveyance direction, the printing paper P can be compared with a serial inkjet head that scans in a direction orthogonal to the paper conveyance direction. The conveyance speed can be increased. Thereby, the printing speed can be improved.

  Next, a second embodiment according to the present invention will be described with reference to the drawings. In addition, about the same member as 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted. FIG. 7 is a plan view of the paper transport device 220 included in the ink jet printer according to the second embodiment. 8 is a cross-sectional view taken along line VIII-VIII shown in FIG. 9 is a cross-sectional view taken along line IX-IX shown in FIG.

  As shown in FIGS. 7 to 9, the sheet conveying device 220 includes the conveying belt 11 formed by covering the entire outer periphery of the base material layer 35 with the adhesive layer 36 as in the first embodiment, and the belt roller 6. 7, while supporting the conveyance motor 74, the two encoder rollers 239, the two rotary encoders 241 for detecting the respective rotational positions of the two encoder rollers 239, the encoder nip roller 251, and the encoder nip roller 251. Two encoder nip urging mechanisms 250 that urge in the direction close to the encoder roller 239, the paper roller 238, the paper nip roller 261, and the paper that urges in the direction close to the paper roller 238 while supporting the paper nip roller 261. And a nip urging mechanism 260. Further, in the present embodiment, a load nip roller 271 and two load nip urging mechanisms 270 that urge the load nip roller 271 in a direction close to the paper roller 238 are newly provided.

  As shown in FIGS. 7 and 8, the two encoder rollers 239 have axial lengths that contact only the inner peripheral surface 11 b corresponding to the paper non-passing regions 28 on both sides in the width direction of the transport belt 11. A rotary encoder 241 is provided at each end of each encoder roller 239. The rotary encoder 241 includes a disc-shaped slit plate 241a in which a large number of slits are formed along the outer edge, and an optical sensor 241b that detects the slits of the slit plate 241a. When the encoder roller 239 rotates, the slit plate 241a fixed to the encoder roller 239 also rotates. When the slit plate 241a rotates by a predetermined angle, the optical sensor 241b detects the passage of the slit and outputs a detection signal to the control unit 100. The control unit 100 controls the ejection timing of ink from the transport motor 74 and the inkjet head 2 so as to correct the difference in the rotational position of the encoder roller 239 based on the detection signals output from the two optical sensors 241b.

  The paper roller 238 extends so as to cross the conveyance belt 11 along the width direction of the conveyance belt 11 and is in contact with the inner peripheral surface 11 b of the conveyance belt 11.

  As shown in FIGS. 7 and 9, the two encoder nip urging mechanisms 250 are arranged so that the encoder nip roller 251 faces the encoder roller 239 via the transport belt 11 in a state where the encoder nip roller 251 is positioned in the paper non-passing area 28. I support it. The encoder nip urging mechanism 250 includes a roller support member 252 that supports the encoder nip roller 251. The axial length of the encoder nip roller 251 is shorter than the axial length of the encoder roller 239. The roller support member 252 can swing about a swing shaft 253 whose one end is fixed to the frame along the width direction of the transport belt 11, and both ends of the encoder nip roller 251 can be rotated at its end. A pair of holding arms 252a to be supported and a connecting portion 252b provided between the pair of holding arms 252a and connecting them are provided. A biasing spring 254 is attached between the connecting portion 252b and the frame (not shown) so that the encoder nip roller 251 is biased in the direction approaching the encoder roller 239. When the roller support member 252 swings in a direction in which the encoder nip roller 251 is brought close to the encoder roller 239, the encoder nip roller 251 contacts the conveyance belt 11 in the paper non-passing area 28 and sandwiches the conveyance belt 11 together with the encoder roller 239. That is, the two encoder nip rollers 251 are independently in contact with both sides in the width direction of the transport belt 11 corresponding to the paper non-passing area 28.

  The paper nip urging mechanism 260 supports the paper nip roller 261 so as to face the paper roller 238 through the transport belt 11 while being positioned in the paper passage region 27. The sheet nip urging mechanism 260 includes a roller support member 262 that supports the sheet nip roller 261 and a release mechanism 65 that releases the contact between the sheet nip roller 261 and the conveyance belt 11. The roller support member 262 can swing about a swing shaft 263 whose both ends are fixed to the frame along the width direction of the transport belt 11, and both ends of the paper nip roller 261 can be rotated at the end. A pair of holding arms 262a to be supported and a connecting portion 262b provided between the pair of holding arms 262a to connect them. A biasing spring 264 is attached between the connecting portion 262b and the frame (not shown) so that the paper nip roller 261 is biased in the direction approaching the paper roller 238. When the roller support member 262 swings in the direction in which the paper nip roller 261 is brought close to the paper roller 238, the paper nip roller 261 contacts the transport belt 11 in the paper passage region 27 and sandwiches the transport belt 11 together with the paper roller 238. As a result, the paper nip roller 261 and the paper roller 238 sandwich the printing paper P together with the transport belt 11, and the printing paper P is securely adhered to the adhesive layer 36.

  The two load nip urging mechanisms 270 support the load nip roller 271 so as to face the paper roller 238 via the transport belt 11 in a state where the load nip roller 271 is positioned in the paper non-passing area 28. The load nip biasing mechanism 270 includes a roller support member 272 that supports the load nip roller 271. The roller support member 272 can swing about the swing shaft 263, and has a pair of holding arms 272 a that rotatably support both ends of the load nip roller 271 at its end, and a pair of holding arms 272 a. A connecting portion 272b that is provided and connects them. A biasing spring 274 is attached between the connecting portion 272b and the frame (not shown) so that the load nip roller 271 is biased in the direction approaching the paper roller 238. When the roller support member 272 swings in the direction in which the load nip roller 271 is brought close to the paper roller 238, the load nip roller 271 contacts the transport belt 11 in the paper non-passing area 28 and sandwiches the transport belt 11 together with the paper roller 238. That is, the two load nip rollers 271 are in contact with the conveyance belt 11 independently in the paper non-passing area 28. At this time, the two load nip rollers 271 that are in contact with the conveyance belt 11 are arranged coaxially with the paper nip roller 261 that is also in contact with the conveyance belt 11.

  In the second embodiment described above, the encoder nip roller 251 is configured to come into contact with the transport belt 11 in the paper non-passing area 28, so that the printing paper P is between the encoder nip roller 251 and the transport belt 11. Never pass. Therefore, regardless of whether or not the printing paper P is placed on the transport belt 11, the transport belt 11 can be pressed against the encoder roller 239 with the encoder nip roller 251 always at a constant pressure. Thereby, the accurate transfer speed of the conveyor belt 11 can be detected from the rotational position of the encoder roller 239.

  Further, since the length of the encoder nip roller 251 in the axial direction is shorter than the length of the encoder roller 239 in the axial direction, the inertia of the encoder nip roller 251 is reduced, and the response to the behavior of the conveyor belt is improved. Furthermore, since the length of the encoder roller 239 in the axial direction is a length that contacts only the inner peripheral surface 11b corresponding to the paper non-passing regions 28 on both sides in the width direction of the transport belt 11, the inertia of the encoder roller 239 is also reduced. It becomes small and the responsiveness with respect to the behavior of a conveyance belt improves further.

  In addition, the sheet nip roller 261 is disposed coaxially between the pair of load nip rollers 271, and the sheet roller 238 faces not only the sheet nip roller 261 but also the load nip roller 271. The cost can be reduced by reducing the number of points. In addition, the load nip roller 271 is efficient for the unique fluctuation that occurs in the transport belt 11 at the moment when the print paper P enters between the paper nip roller 261 and the transport belt 11 and when the print paper P is discharged from between these. It can be reduced well. Further, since the load nip roller 271 applies an even weight to both sides in the width direction of the conveying belt 11 (direction orthogonal to the sheet conveying direction), the conveying belt 11 is difficult to meander.

  In addition, since a pair of the encoder roller 239 and the encoder nip roller 251 is disposed on both sides in the width direction of the transport belt 11, a load is equally applied to both sides of the transport belt 11 in the width direction. It becomes more difficult to meander.

  Further, a rotary encoder 241 is provided corresponding to each of the two encoder rollers 239, and the control unit 100 calculates a difference between the rotational positions of the two encoder rollers 239 based on the detection results output by the two optical sensors 241b. Since correction is performed, a more accurate transfer speed of the conveyor belt 11 can be obtained.

  In addition, since the load nip urging mechanism 270 is provided, when the printing paper P passes between the paper nip roller 261 and the conveyance belt 11, the load fluctuation ratio with respect to the conveyance belt 11 is reduced, and the accuracy is further increased. A transfer speed of the transport belt 11 can be obtained.

  Next, a modification of the second embodiment will be described with reference to FIG. FIG. 10 is a diagram illustrating a modified example of the transport belt 11. In the present embodiment, all of the outer peripheral surface 11a of the conveyor belt 11 is the adhesive layer 36, but as shown in FIG. 10, both end portions of the conveyor belt 211 corresponding to the sheet non-passing area 28 are provided. Alternatively, the adhesive layer 36 may not be covered and the base material layer 35 may be exposed. According to this configuration, the encoder nip roller 251 comes into contact with the base material layer 35 that is less likely to be deformed compared to the adhesive layer 36. Therefore, the urging force from the encoder nip roller 251 is efficiently transmitted to the encoder roller 239, and is more accurate. The position of the correct conveyor belt 211 can be obtained.

  Next, a third embodiment according to the present invention will be described with reference to the drawings. In addition, about the same member as 1st Embodiment and 2nd Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted. FIG. 11 is a plan view of a sheet transport device 320 included in the printer according to the third embodiment. 12 is a cross-sectional view taken along line XII-XII shown in FIG.

  As shown in FIGS. 11 and 12, the sheet conveying device 320 is a rotary for detecting the rotation position of the conveying belt 11, the belt rollers 6 and 7, the conveying motor 74, the encoder roller 339, and the encoder roller 339. An encoder 341, an encoder nip roller 351, an encoder nip biasing mechanism 350 that supports the encoder nip roller 351 and biases in the direction approaching the encoder roller 339, a paper roller 238, a paper nip biasing mechanism 260, and a load nip roller 371 and two load nip urging mechanisms 370 that urge the load nip roller 371 in a direction approaching the encoder roller 339 while supporting the load nip roller 371.

  In the present embodiment, the encoder nip roller 351 is in contact with the central portion in the width direction of the transport belt 11, and the printing paper P is transported from a position slightly downstream in the paper transport direction from the encoder nip roller 351. It is placed on the belt 11. Therefore, the position where the placement of the printing paper P is started corresponds to the most upstream position of the paper passage area 327, and the portion upstream of the encoder nip roller 351 of the transport belt 11 corresponds to the paper non-passage area 328. . The configuration of the encoder nip roller 351 will be described later.

  The encoder roller 339 extends across the conveyor belt 11 along the width direction of the conveyor belt 11 and corresponds to the sheet non-passing area 328 further upstream from the most upstream position of the sheet passing area 327. It is in contact with the inner peripheral surface 11b. A rotary encoder 341 is provided at the end of the encoder roller 339. The rotary encoder 341 includes a disc-shaped slit plate 341a in which a large number of slits are formed along the outer edge, and an optical sensor 341b that detects the slit of the slit plate 341a. Since the operation of the rotary encoder 341 is substantially the same as that of the rotary encoder 41 of the first embodiment, the description thereof is omitted.

  The encoder nip urging mechanism 350 supports the encoder nip roller 351 so as to face the encoder roller 339 via the conveyance belt 11, and the encoder nip roller 351 is further upstream than the most upstream position in the paper passage region 327. The sheet non-passage area 328 is positioned at the center in the width direction of the conveyor belt 11. The encoder nip biasing mechanism 350 includes a roller support member 352 that supports the encoder nip roller 351. The roller support member 352 can swing about a swing shaft 353 whose both ends are fixed to the frame so as to follow the width direction of the transport belt 11, and both ends of the encoder nip roller 351 can be rotated at its end. A pair of holding arms 352a to be supported and a connecting portion 352b provided between the pair of holding arms 352a and connecting these lower ends are provided. An urging spring 354 is attached between the pair of holding arms 352a and a frame (not shown) so that the encoder nip roller 351 is urged in a direction approaching the encoder roller 339. When the roller support member 352 swings in the direction in which the encoder nip roller 351 is brought close to the encoder roller 339, the encoder nip roller 351 contacts the conveyance belt 11 in the paper non-passing region 328 further upstream from the paper passing region 327. At the same time, the conveyor belt 11 is sandwiched. The connecting portion 352b serves as a guide introduction portion for introducing the printing paper P conveyed by the feed rollers 18a, 18b, 19a, and 19b onto the conveying belt 11 at the most upstream position of the paper passage region 327. (See arrow B in FIG. 12).

  The two load nip urging mechanisms 370 support the load nip rollers 371 so as to face the encoder rollers 339 via the conveyor belt 11 while being positioned in the paper non-passing area 328. Since the configuration of the load nip urging mechanism 370 is substantially the same as that of the load nip urging mechanism 270 of the second embodiment, detailed description thereof is omitted.

  In the third embodiment described above, the encoder nip roller 351 is configured to come into contact with the transport belt 11 in the paper non-passage area 328, so the printing paper P is between the encoder nip roller 351 and the transport belt 11. Never pass. Therefore, regardless of whether or not the printing paper P is placed on the transport belt 11, the transport belt 11 can be pressed against the encoder roller 339 with the encoder nip roller 351 always at a constant pressure. Thereby, the accurate transfer speed of the conveyor belt 11 can be detected from the rotational position of the encoder roller 339.

  In addition, the encoder nip roller 351 and the encoder roller 339 are disposed at the center in the width direction of the transport belt 11 in the paper non-passing region 328 located further upstream than the paper passing region 27. Compared to the second embodiment, the encoder nip roller 351 can be formed longer. As a result, the contact area of the encoder nip roller 351 with the conveyor belt 11 can be increased, and the conveyor belt 11 is reliably pressed against the encoder roller 339. For this reason, a more accurate transfer speed of the conveyor belt 11 can be obtained.

  Furthermore, the connecting portion 352b of the roller support member 352 also serves as a guide introduction portion that guides the printing paper P conveyed by the feed rollers 18a, 18b, 19a, 19b so as to be placed on the conveying belt 11. Therefore, the number of parts can be reduced, and the cost of the sheet conveying device 320 can be reduced.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various design changes can be made as long as they are described in the claims. For example, in the first embodiment, the encoder nip biasing mechanism 50 biases the encoder nip roller 51 in the direction approaching the encoder roller 39, but is not limited to such a configuration. The encoder roller 39 may be biased in the direction approaching the encoder nip roller 51, or the encoder roller 39 and the encoder nip roller 51 may be biased together.

  Furthermore, in the first embodiment, the encoder roller 39 is in contact with the inner peripheral surface 11 b of the transport belt 11 and the encoder nip roller 51 is in contact with the outer peripheral surface 11 a of the transport belt 11. The encoder nip roller 51 may be in contact with the inner peripheral surface 11 b of the conveyor belt 11.

  In addition, in the first embodiment, the sheet conveying device 20 may be configured by omitting the sheet nip roller and the sheet nip roller urging mechanism.

  Further, in the first embodiment, the sheet passing area 27 corresponds to an area that is line-symmetric with respect to the center line in the width direction of the transport belt 11. The structure corresponding to the area | region biased to any one side on the basis of the centerline of 11 width directions may be sufficient.

  In addition, the first embodiment includes a release mechanism 55 that releases the contact between the encoder nip roller 51 and the transport belt 11 and a release mechanism 65 that releases the contact between the paper nip roller 61 and the transport belt 11. However, a configuration in which at least one of the release mechanism 55 and the release mechanism 65 is omitted may be employed.

In the first embodiment, the urging force of the urging spring 64 of the paper nip urging mechanism 60 is smaller than the urging force of the urging spring 54 of the encoder nip urging mechanism 50. The biasing force of the biasing spring 54 and the biasing spring 64 may be the same, or the biasing force of the biasing spring 54 may be smaller than the biasing force of the biasing spring 64.

  In addition, in the first embodiment, the inkjet head 2 has the configuration of the line-type inkjet printer 1, but the serial-type inkjet in which the inkjet head scans in a direction orthogonal to the conveyance direction of the printing paper P. The printer may be configured.

  In the second embodiment, the rotary encoder 241 is attached to each of the two encoder rollers 239. However, the rotary encoder 241 may be attached to only one of the two encoder rollers 239. . At this time, the other encoder roller 239 functions as an auxiliary roller.

  Furthermore, in the second embodiment, the axial length of the encoder nip roller 251 is shorter than the axial length of the encoder roller 239. However, the axial length of the encoder nip roller is the axis of the encoder roller. It may be longer than the length in the direction.

  In addition, in the second embodiment, the paper nip urging mechanism 260 urges the paper nip roller 261 in the direction approaching the paper roller 238. However, the present invention is not limited to such a configuration. The paper nip biasing mechanism may bias the paper roller 238 in the direction approaching the paper nip roller 261, or may bias both the paper roller 238 and the paper nip roller 261.

  Furthermore, in the first to third embodiments, the sheet conveying devices 20, 220, and 320 are configured to be applied to an ink jet printer. However, the present invention is not limited to such a configuration. The apparatuses 20, 220, and 320 may be applied to other apparatuses including a mechanism for conveying paper, such as a laser-type printer and a copying machine.

DESCRIPTION OF SYMBOLS 1 Printer 2 Inkjet head 11 Conveying belt 20 Paper conveying apparatus 27 Paper passing area 28 Paper non-passing area 39 Encoder roller 41 Rotary encoder 50 Encoder nip urging mechanism 51 Encoder nip rollers 52 and 62 Roller supporting members 54 and 64 Energizing spring 55, 65 Release mechanism 60 Paper nip urging mechanism 61 Paper nip roller 74 Conveyance motor 100 Control unit

Claims (1)

Surface and endless conveyance belt serving as the mounting surface of the sheet, and driving means for driving the conveyor belt, and an encoder roller in contact with one surface of the conveyor belt, while serving as the mounting surface of the conveyor belt An encoder nip roller that is in contact with the surface of the roller and sandwiches the conveying belt together with the encoder roller, a first urging mechanism that urges at least one of the encoder roller and the encoder nip roller toward each other, and rotation of the encoder roller An encoder for detecting the position, and a sensor for detecting the slit of the encoder and outputting it to the control unit, and both the encoder roller and the encoder nip roller are out of the paper passage area through which the conveyed paper passes. together are in contact with the surface of the conveyor belt in the region, the diene The axial length of the Danippurora is shorter than the axial length of the encoder roller, the paper passing region is positioned to correspond to the center in the width direction of the conveyor belt, wherein the encoder roller and A pair of the encoder nip rollers is disposed on both sides in the width direction of the conveyor belt, the encoder and the sensor are provided for each of the two encoder rollers, A paper conveying apparatus that controls the driving means so as to correct a difference in rotational position of an encoder roller based on detection signals output from two sensors .

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