SHEET-CONVEYING DEVICE
A drive roller and the follower roller defines a nip line therebetween. A recording medium has a leading edge provided with a first corner contactable with the drive roller and a second corner contactable with the follower roller at a contact line when the drive roller and the follower roller provide the nip line. A supporting unit supports the follower roller and is capable of retracting the follower roller away from the nip line in a retracting plane. The retracting plane contains the axis of the follower roller. An angle α1 and α2 greater than the angle α1 is defined between the retracting plane and an imaginary plane that contains the axes of the drive roller and follower roller. The supporting unit allows the follower roller to be retracted in a downstream side of the paper conveying direction with respect to the imaginary plane. The angle α1 is greater than an angle β defined between the imaginary plane and a radial plane passing through the second axis and the contact line.
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This application claims priority from Japanese Patent Application No. 2005-376678 filed Dec. 27, 2005. The entire content of the priority application is incorporated herein by reference.
TECHNICAL FIELDThe disclosure relates to a sheet-conveying device for pinching and conveying a sheet-like medium between a drive roller and a follow roller that contacts the drive roller with pressure and follows the rotation of the drive roller. The present invention also relates to an image-recording device equipped with the sheet-conveying device, and particularly to the structure for pressing the follow roller against the drive roller.
BACKGROUNDThe recording paper S is conveyed intermittently by a pair of conveying rollers 103 disposed on the upstream side of the platen 102 in the conveying direction of the recording paper S, and a pair of discharge rollers 104 disposed on the downstream side of the platen 102. A controller (not shown) controls the rotations of the conveying roller 103 and discharge roller 104.
The conveying roller 103 is configured of a drive roller 105 that is driven to rotate by a drive force transmitted from a motor, and a follow roller 106 urged against the drive roller 105 by a coil spring 107. As shown in
After the registration process is completed, the drive roller 105 is driven to rotate in a direction for conveying the recording paper S downstream, that is, a forward rotation. Consequently, the drive roller 105 and follow roller 106 pinch the recording paper S and begin conveying the recording paper S, as shown in
U.S. Pat. No. 5,640,901 discloses a nip roller device that shifts the direction in which the follow roller presses against the drive roller from a radial centerline passing through the point of contact between the follow roller and the drive roller. The pressing direction is shifted by an angle equivalent to an pressure angle in a plurality of engaged gears that transmit a driving force from the drive roller to the follow roller. This construction can prevent variations in nip pressure between the drive roller and follow roller, even when a rotational load is generated in the direction of the pressure angle.
SUMMARYAs shown in
However, at the instant the recording paper S becomes interposed between the conveying rollers 103, the coil spring 107 applies a spring force F1 to the leading edge of the recording paper S, as shown in
In view of the foregoing, it is an object of the invention to provide a sheet-conveying device and an image-recording device capable of reliably pinching the leading edge of a sheet of recording paper or other conveyed medium at the beginning of a conveying process, and capable of preventing skew from being produced in the conveyed medium and variations in the amount of lead allocated on the leading edge of each sheet of conveyed medium.
In order to attain the above and other objects, the invention provides a sheet-conveying device. The sheet-conveying device includes a pair of conveying rollers, a supporting unit, and an urging unit. The pair of conveying rollers includes a drive roller that is driven to rotate about a first axis, and a follower roller that contacts the drive roller with pressure and follows the rotation of the drive roller about a second axis. The conveying rollers convey a recording medium in a sheet-conveying direction when the drive roller rotates in a first rotational direction and the follower roller rotates in a second rotational direction that is reverse to the first rotational direction. The drive roller and the follower roller define a nip line therebetween. The recording medium has a leading edge provided with a first corner contactable with the drive roller and a second corner contactable with the follower roller at a contact line when the drive roller and the follower roller provide the nip line. The supporting unit supports the follower roller and is capable of retracting the follower roller away from the nip line in a retracting plane. The retracting plane contains the second axis. An angle α1 and α2 greater than the angle α1 is defined between the retracting plane and an imaginary plane that contains the first and second axes. The supporting unit allows the follower roller to be retracted in a downstream side of the paper conveying direction with respect to the imaginary plane. The urging unit urges the follower roller to provide the nip line. The angle α1 is greater than an angle β defined between the imaginary plane and a radial plane containing the second axis and the contact line.
An intended direction of the retracting plane is the direction of the line L1 shown in
According to another aspects, the invention provides an image-recording device. The image-recording device includes a sheet-conveying device and an image-recording unit. The sheet-conveying device includes a pair of conveying rollers, a supporting unit, and an urging unit. The pair of conveying rollers includes a drive roller that is driven to rotate about a first axis, and a follower roller that contacts the drive roller with pressure and follows the rotation of the drive roller about a second axis. The conveying rollers conveys a recording medium in a sheet-conveying direction when the drive roller rotates in a first rotational direction and the follower roller rotates in a second rotational direction that is reverse to the first rotational direction. The drive roller and the follower roller define a nip line therebetween. The recording medium has a leading edge provided with a first corner contactable with the drive roller and a second corner contactable with the follower roller at a contact line when the drive roller and the follower roller provide the nip line. The supporting unit supports the follower roller and is capable of retracting the follower roller away from the nip line in a retracting plane. The retracting plane contains the second axis. An angle α1 and α2 greater than the angle α1 is defined between the retracting plane and an imaginary plane that contains the first and second axes. The supporting unit allows the follower roller to be retracted in a downstream side of the paper conveying direction with respect to the imaginary plane. The urging unit urges the follower roller to provide the nip line. The angle α1 is greater than an angle β defined between the imaginary plane and a radial plane containing the second axis and the contact line. The image-recording unit records an image on a sheet-like conveyed medium conveyed by the sheet-conveying device.
Illustrative aspects in accordance with the invention will be described in detail with reference to the following figures wherein:
A sheet-conveying device according to some aspects of the invention will be described while referring to the accompanying drawings wherein like parts and components are designated by the same reference numerals to avoid duplicating description.
The printer section 2 of the multifunction device 1 is primarily connected to a computer or other external information device for recording text and images on a recording paper based on print data including text or image data transmitted from the computer. The multifunction device 1 may also be connected to a digital camera and may record image data inputted from the digital camera on recording paper. Also, the multifunction device 1 may be loaded with a memory card or other storage medium and may be capable of recording image data stored on the storage medium on recording paper.
As shown in
The scanner section 3 disposed in the upper section of the multifunction device 1 is a flatbed scanner. As shown in
A control panel 4 is provided on the top front surface of the multifunction device 1 for operating the printer section 2 and the scanner section 3. The control panel 4 is configured of various operating buttons and a liquid crystal display. The multifunction device 1 operates based on operating instructions inputted through the control panel 4 and, when connected to an external computer, operates based on instructions that the computer transmits through a printer driver or a scanner driver. As shown in
Next, the internal structure of the multifunction device 1, and particularly the structure of the printer section 2, will be described with reference to
The feeding arm 26 is rotatably supported on a base end 26a. When the feeding arm 26 pivots about the base end 26a, the feeding roller 25 moves vertically so as to contact and separate from the feeding tray 20. As shown in
Excluding the section in which the image-recording unit 24 are provided, the paper-conveying path 23 is configured of an outer guide surface and an inner guide surface that oppose each other with a prescribed gap formed therebetween. For example, a curved section 17 of the paper-conveying path 23 may be configured near the rear side of the multifunction device 1 by fixing an outer guide member 18 and an inner guide member 19 to a frame of the multifunction device 1. Rollers 16 are provided along the paper-conveying path 23, and particularly in the curved section of the paper-conveying path 23. The rollers 16 are rotatably provided on axes extending in the width direction of the paper-conveying path 23. The surfaces of the rollers 16 are exposed from the outer guide surface. These rollers 16 facilitate the smooth conveyance of recording paper in the curved section of the paper-conveying path 23.
As shown in
The guide rail 43 disposed on the upstream side of the guide rail 44 in the paper-conveying direction is plate-shaped with a dimension in the width direction (left-to-right direction) of the paper-conveying path 23 greater than the reciprocating range of the carriage 38. The guide rail 44 disposed on the downstream side is also plate-shaped with a dimension in the width direction of the paper-conveying path 23 substantially the same as that of the guide rail 43. The carriage 38 is capable of sliding in the longitudinal direction of the guide rails 43 and 44 with an upstream end of the carriage 38 supported on the guide rail 43 and a downstream end supported on the guide rail 44. The guide rail 44 has an edge part 45 bent upward at substantially a right angle from the upstream side of the guide rail 44. The carriage 38 supported on the guide rails 43 and 44 has a pair of rollers or other gripping members for slidably gripping the edge part 45. Hence, the carriage 38 can slide in a direction orthogonal to the paper-conveying direction, while being positioned in the paper-conveying direction. In other words, the carriage 38 is slidably supported on the guide rails 43 and 44 and is capable of reciprocating in a direction orthogonal to the paper-conveying direction with the edge part 45 of the guide rail 44 serving as a positional reference. Although not shown in the drawings, a lubricating agent such as grease is applied to the edge part 45 to facilitate sliding of the carriage 38.
A belt drive mechanism 46 is provided on the top surface of the guide rail 44. The belt drive mechanism 46 is configured of a drive pulley 47 and a follow pulley 48 disposed near widthwise ends of the paper-conveying path 23, and an endless timing belt 49 stretched around the drive pulley 47 and follow pulley 48 and having teeth on the inside surface thereof. A carriage motor 73 (see
The bottom surface of the carriage 38 is fixed to the timing belt 49 so that the circuitous movement of the timing belt 49 causes the carriage 38 to reciprocate over the guide rails 43 and 44 while the edge part 45 maintains the position of the carriage 38 relative to the paper-conveying direction. The inkjet recording head 39 is mounted in the carriage 38 having this construction so that the inkjet recording head 39 also reciprocates in the width direction. Here, the width direction is the main scanning direction.
As shown in
Light-transmitting parts allowing the passage of light and light-blocking parts preventing the passage of light are alternately disposed along the length of the encoder strip 50 at a prescribed pitch. An optical sensor 35 configured of a transmission sensor is disposed on the top surface of the carriage 38 at a position opposing the encoder strip 50. The optical sensor 35 reciprocates together with the carriage 38 along the length of the encoder strip 50 and detects the pattern formed on the encoder strip 50. A head controlling circuit board is provided in the inkjet recording head 39 for controlling ink ejection. The head controlling circuit board outputs a pulse signal based on detection signals from the optical sensor 35. By determining the position of the carriage 38 based on this pulse signal, it is possible to control the reciprocating motion of the carriage 38. The head controlling circuit board is covered by a head cover of the carriage 38 and is therefore not visible in
As shown in
As shown in
The waste ink tray 84 is disposed on the top surface of the platen 42 outside of the image-recording range, but within the reciprocating range of the carriage 38 for receiving ink that has been flushed out of the inkjet recording head 39. The inside of the waste ink tray 84 is lined with felt for absorbing and holding the flushed ink. The maintenance unit having this construction can perform such maintenance as removing air bubbles and mixed ink of different colors from the inkjet recording head 39, and preventing the inkjet recording head 39 from drying out.
As shown in
The ink tubes 41 are tubes formed of synthetic resin and are flexible so as to be able to bend when the carriage 38 reciprocates. As shown in
Specifically, the section of the ink tubes 41 between the fixing clip 36 and carriage 38 leads in one direction along the reciprocating path of the carriage 38 and subsequently reverses directions, forming a curved section. In other words, this section of the ink tubes 41 is substantially U-shaped in a plan view. At the carriage 38, the four ink tubes 41 are horizontally juxtaposed along the paper-conveying direction and extend in the reciprocating direction of the carriage 38. However, the four ink tubes 41 are arranged vertically at the fixing clip 36 to facilitate fixation. The fixing clip 36 has a U-shaped cross-section open on the top. The vertically stacked ink tubes 41 are inserted through this opening and are integrally held by the fixing clip 36. In this way, the four ink tubes 41 curve along a U-shaped path from the carriage 38 to the fixing clip 36 while twisting from a horizontally juxtaposed relationship to a vertically juxtaposed relationship.
The four ink tubes 41 have substantially the same length from the carriage 38 to the fixing clip 36. The ink tube 41 positioned farthest upstream in the paper-conveying direction at the carriage 38 is positioned on the top at the fixing clip 36. The ink tube 41 disposed next in order from the upstream side at the carriage 38 is disposed next in order vertically at the fixing clip 36. This process is repeated so that the ink tubes 41 arranged from the upstream side to the downstream side in the paper-conveying direction at the carriage 38 are arranged in order from top to bottom at the fixing clip 36. Being substantially equivalent in length, the ink tubes 41 curve so that the center of the curved section of each ink tube 41 is offset in the paper-conveying direction according to the order in which the ink tubes 41 are juxtaposed in the paper-conveying direction. As a result, the four ink tubes 41 have a vertically sloped arrangement in the curved section, thereby minimizing interference among the ink tubes 41 as the ink tubes 41 change shape to follow the reciprocating motion of the carriage 38. In the multifunction device 1, four of the ink tubes 41 are provided. However, even if the number of the ink tubes 41 is increased, the ink tubes 41 can be arranged in the same juxtaposed relationship, with the ink tube 41 disposed farthest upstream in the paper-conveying direction at the carriage 38 positioned on top at the fixing clip 36.
A flat cable 85 transfers recording signals from a main circuit board constituting a controller 64 (see
The flat cable 85 is flexible and bends in response to the reciprocation of the carriage 38. As shown in
The end of the flat cable 85 fixed to the carriage 38 is electrically connected to the head control circuit board mounted in the carriage 38. The other end of the flat cable 85 fixed to the fixing clip 86 extends to and is electrically connected to the main circuit board. The section of the flat cable 85 curved in a U shape is not fixed to any member, but changes in shape as the carriage 38 reciprocates, similar to the ink tubes 41. A rotating support member 90 is provided for supporting the ink tubes 41 and flat cable 85 as these components change in shape when the carriage 38 reciprocates. The rotating support member 100 supports the ink tubes 41 and the flat cable 85.
A restricting wall 37 is provided on the front surface of the printer section 2 extending in the width direction (left-to-right direction). The restricting wall 37 has a vertical surface that is contacted by the ink tubes 41 and extends along a straight line following the reciprocating direction of the carriage 38. The restricting wall 37 is disposed in the area that the ink tubes 41 extend from the fixing clip 36 and is set to a height sufficient for all four ink tubes 41 juxtaposed vertically to contact. The ink tubes 41 extend from the fixing clip 36 along the restricting wall 37.
By contacting the inside surface of the restricting wall 37, the ink tubes 41 are restricted from expanding in a direction toward the front surface of the printer section 2, that is, away from the carriage 38. A section of the ink tubes 41 from the fixing clip 36 to the curved section is maintained in a vertically juxtaposed relationship at the fixing clip 36 with the ink tubes 41 contacting the restricting wall 37. Therefore, the ink tubes 41 are reliably maintained in a desired sloping arrangement within the U-shaped curved section.
The fixing clip 36 is disposed near the widthwise center of the printer section 2. The fixing clip 36 fixes the ink tubes 41 so that the ink tubes 41 extend toward the restricting wall 37′. More specifically, the vertical surface of the restricting wall 37 and the direction in which the ink tubes 41 extend from the fixing clip 36 forms an obtuse angle less than 180 degrees in a plan view. The ink tubes 41 are flexible, but have a degree of stiffness (flexural rigidity). Hence, the ink tubes 41 press against the surface of the restricting wall 37 when extending at the angle from the fixing clip 36 to the restricting wall 37. Consequently, the range in which the ink tubes 41 follow the restricting wall 37 expands within the reciprocating range of the carriage 38, thereby reducing the area in the section from the curved section of the ink tubes 41 to the carriage 38 that expands toward the carriage 38.
The fixing clip 86 is disposed near the widthwise center of the printer section 2 further inside than the fixing clip 36. The fixing clip 86 fixes the flat cable 85 so that the flat cable 85 expands toward the restricting wall 37. Hence, the vertical surface of the restricting wall 37 and the direction in which the flat cable 85 extends from the fixing clip 86 forms an obtuse angle smaller than 180 degrees in a plan view. The flat cable 85 is flexible, but has a degree of stiffness (flexural rigidity). Hence, the flat cable 85 presses against the surface of the restricting wall 37 when extending at the angle from the fixing clip 86 to the restricting wall 37. Consequently, the range in which the flat cable 85 follows the restricting wall 37 expands within the reciprocating range of the carriage 38, thereby reducing the area in the section from the curved section of the flat cable 85 to the carriage 38 that expands toward the carriage 38.
As shown in
The pinch roller 88 is rotatably supported in a pinch roller holder 96 while contacting the drive roller 87 with a prescribed urging force. The pinch roller holder 96 is rollingly supported on a holder support member 97 (
As shown in
The drive roller 87 and drive roller 90 are driven to rotate by a drive force transmitted from the linefeed motor 71 (see
After the registration process has been performed for a prescribed time, the drive roller 87 is driven in a forward rotation for conveying the recording paper downstream. Consequently, the recording paper is pinched by the drive roller 87 and pinch roller 88 and conveyed downstream. Rotation of the drive roller 87 and drive roller 90 is synchronized. Further, a rotary encoder 76 (see
The drive roller 87 is driven intermittently at prescribed linefeed widths. Accordingly, recording paper pinched by the drive roller 87 and pinch roller 88 is conveyed intermittently over the platen 42 at the prescribed linefeed widths. The inkjet recording head 39 is scanned after each linefeed and records an image beginning from the leading edge side of the recording paper. The drive roller 90 and spur roller 91 pinch the leading edge side of the recording paper after an image has been recorded thereon. Hence, the recording paper is conveyed intermittently at prescribed linefeed widths, with the leading edge side of the paper pinched between the drive roller 90 and spur roller 91 and with the trailing edge side pinched between the drive roller 87 and pinch roller 88, while the inkjet recording head 39 records an image after each linefeed. As the recording paper is conveyed further, the trailing edge of the paper separates from the drive roller 87 and pinch roller 88 so that the conveying rollers 89 no longer grip the paper. At this time, the recording paper is conveyed intermittently at the prescribed linefeed widths while gripped only by the drive roller 90 and spur roller 91, and the inkjet recording head 39 continues to record an image after each linefeed. After an image has been completed in the prescribed region of the recording paper, the drive roller 90 is driven to rotate continuously, and the paper gripped by the drive roller 90 and spur roller 91 is discharged onto the discharge tray 21.
The ROM 66 stores programs for controlling various operations of the multifunction device 1. The RAM 67 functions as a storage area or a work area for temporarily saving various data used by the CPU 65 in executing the programs. The EEPROM 68 stores settings, flags, that must be preserved when the power is turned off.
As shown in
The drive circuit 72 drives the linefeed motor 71, which is connected to the feeding roller 25, and purge mechanism 51. Upon receiving an output signal from the ASIC 70, the drive circuit 72 generates an electric signal for rotating the linefeed motor 71. When the linefeed motor 71 rotates, the rotational force of the linefeed motor 71 is transferred to the feeding roller 25, conveying roller 60, discharge rollers 62, and purge mechanism 51 via a drive mechanism well known in the art that includes gears, drive shafts. In other words, in addition to feeding recording paper from the feeding tray 20, the linefeed motor 71 in the multifunction device 1 functions to convey recording paper to a position over the platen 42 and to discharge recording paper onto the discharge tray 21 after recording is completed.
Similarly, upon receiving a command from the CPU 65, the ASIC 70 generates a phase excitation signal and the like for supplying electricity to the carriage motor 73 and applies this signal to a drive circuit 74 of the carriage motor 73. By supplying a drive signal to the carriage motor 73 via the drive circuit 74, the ASIC 70 can control the rotation of the carriage motor 73.
The drive circuit 74 functions to drive the carriage motor 73. Upon receiving an output signal from the ASIC 70, the drive circuit 74 generates an electric signal for rotating the carriage motor 73. When the carriage motor 73 rotates, the rotational force of the carriage motor 73 is transferred to the carriage 38 via the belt drive mechanism 46, thereby scanning the carriage 38 in a reciprocating motion. In this way, the controller 64 can control the reciprocation of the carriage 38.
A drive circuit 75 is provided for driving the inkjet recording head 39 at a prescribed timing. The ASIC 70 generates and outputs a signal to the drive circuit 75 based on a drive control procedure received from the CPU 65. The drive circuit 75 drives the inkjet recording head 39 based on the output signal received from the ASIC 70. The drive circuit 75 is mounted in the head control circuit board. When an output signal is transferred from the main circuit board constituting the controller 64 to the head control circuit board via the flat cable 85, the drive circuit 75 drives the inkjet recording head 39 to selectively eject ink of each color onto the recording paper at a prescribed timing.
The ASIC 70 is also connected to the rotary encoder 76 for detecting the rotated amount of the conveying roller 60, the linear encoder 77 for detecting the position of the carriage 38. When the power of the multifunction device 1 is turned on, the carriage 38 is moved to one end of the guide rails 43 and 44 and the detection position of the linear encoder 77 is initialized. When the carriage 38 moves from this initial position over the guide rails 43 and 44, the optical sensor 35 provided on the carriage 38 detects the pattern on the encoder strip 50 and outputs a pulse signal based on these detections. The controller 64 determines the distance that the carriage 38 has moved based on the number of pulse signals. According to this detected movement, the controller 64 controls the rotation of the carriage motor 73 in order to control the reciprocating motion of the carriage 38.
The ASIC 70 is also connected to the scanner section 3; the control panel 4 for specifying operations of the multifunction device 1; the slot section 5 in which various small memory cards can be inserted; a parallel interface 78, and a USB interface 79 for exchanging data with a personal computer or other external device via a parallel cable or USB cable; and a NCU (network control unit) 80 and a modem 81 for implementing a facsimile function.
Next, the structure of the holder support member 97 and the pinch roller holder 96, and the support structure of the pinch roller holder 96 will be described in detail with reference to
The pinch roller holder 96 has an elongated shape, as shown in
The pinch rollers 88 are accommodated in the spring-accommodating compartments 99 and have rotational shafts 130 aligned with the longitudinal direction of the pinch roller holder 96. The spring-accommodating compartments 99 are formed adjacent to and on both ends of the roller-accommodating compartments 98. Coil springs 131 are accommodated in the spring-accommodating compartments 99 in a compressed state. This construction is one example, but it should be apparent that the number of the pinch rollers 88 and coil springs 131 and the accommodating method may be modified as appropriate.
The spring-accommodating compartments 99 are defined by partitioning plates 132 erected on both longitudinal sides of the spring-accommodating compartments 99. A bearing 133 is formed in each partitioning plate 132 for supporting the rotational shaft 130 of the respective pinch roller 88. The bearings 133 are formed as long vertical grooves in the opposing partitioning plates 132. The upper end of the groove constituting the bearings 133 is formed slightly smaller than the diameter of the rotational shaft 130. When the rotational shaft 130 is pressed into the bearings 133, the upper end of the groove widens elastically to allow insertion of the rotational shaft 130. After the rotational shaft 130 is completely inserted, the upper ends of the grooves are restored to their original shape so that the rotational shaft 130 cannot easily come out of the bearings 133. In this way, the rotational shaft 130 is supported in the bearings 133, while being capable of moving vertically within the grooves. By extension, the pinch rollers 88 are supported so as to be capable of moving vertically along the depth direction of the bearings 133.
The spring-accommodating compartments 99 are formed as recessed parts that are recessed in the depth direction of the bearings 133 formed in the partitioning plates 132. The coil springs 131 are housed in the spring-accommodating compartments 99, and the rotational shafts 130 of the pinch rollers 88 are inserted into the bearings 133, compressing the coil springs 131. As a result, the elastic force of the compressed coil springs 131 urges the pinch rollers 88 upward, in other words, an urging force toward the drive roller 87 is applied to the pinch rollers 88. Hence, the pinch rollers 88 are rotatably supported in the bearings 133 and urged toward the drive roller 87 by the coil springs 131. When recording paper of a prescribed thickness is conveyed to the drive roller 87 and pinch rollers 88, the paper pushes the pinch rollers 88 downward against the urging force of the coil springs 131 by a distance corresponding to the paper thickness.
As described above, the spring-accommodating compartments 99 are formed as recessions that are recessed in the depth direction of the bearings 133. Therefore, the expanding and contracting direction of the coil spring 131 matches the direction in which the pinch rollers 88 move up and down. Accordingly, the entire urging force of the coil springs 131 is applied to the pinch rollers 88 fox pressing the pinch rollers 88 against the drive roller 87. Of course the expanding/contracting direction of the coil spring 131 need not match the moving direction of the pinch rollers 88, provided the structure applies a pressure force toward the drive roller 87 to the pinch rollers 88. Here, the coil spring 131 may be configured of a plate spring or other type of spring. It is also possible to use another type of urging means for applying a pressure force to the pinch roller 88, such as an elastic member formed of rubber.
The protruding pieces 135 engage in engaging grooves 134 formed in the holder support member 97. The protruding pieces 135 are plate-shaped members that protrude downward from the bottom surface of the pinch roller holder 96 and extend along the shorter dimension of the pinch roller holder 96. The protruding pieces 135 fit into the engaging grooves 134 with a prescribed degree of play. With this construction, the holder support member 97 supports the pinch roller holder 96 so that the pinch roller holder 96 can move along the shorter direction of the holder support member 97, that is, the paper-conveying direction, while restricting the movement of the pinch roller holder 96 to a prescribed range.
The holder support member 97 has an elongated shape similar to the pinch roller holder 96 and is arranged on the internal frame 95 (see
As shown in
As shown in
Ribs 138 extending upward from the curved surface 136 of the holder support member 97 are formed on the rear ends of the engaging grooves 134, continuing upward from the inner wall and rear side of the engaging grooves 134. The ribs 138 function to restrict rearward movement of the pinch roller holder 96. When the pinch roller holder 96 is supported on the holder support member 97 so as to be capable of moving in the short dimension of the holder support member 97 while the protruding pieces 135 are engaged with the engaging grooves 134, forward movement of the pinch roller holder 96 is restricted when the front ends of the protruding pieces 135 contact the inner wall on the front sides of the engaging grooves 134, and rearward movement of the pinch roller holder 96 is restricted when the rear ends of the protruding piece 135 contact the ribs 138.
As shown in
In this example, the movable range of the pinch roller holder 96 in the short dimension of the holder support member 97 (front-to-rear direction) is restricted between a conveying position and a retracted position. As shown in
With this configuration of the pinch roller holder 96 and holder support member 97, the pinch roller holder 96 moves from the retracted position (see
Next, the rolling principle of the pinch roller holder 96 will be described in detail.
As shown in
More specifically, the angle α is set by the angle β defined by a recording paper that can be used in a recording mode in which a page margins are minimum size or borderless printing mode, and that has a maximum thickness. In other words, the maximum thickness recording paper defines the contact points G1 and G2. The point G1 defines the angle β. The angle α is set such that α>β when the pinch roller 88 is in the retracted position E.
When the printer section 2 completes the registration process on the recording paper S and begins driving the drive roller 87 to rotate clockwise in
At the moment the conveying rollers 89 pinch the recording paper S, a spring force F11 of the coil spring 131 is applied to the leading edge of the recording paper S, as shown in
The angle β can be derived from the following equation (1), where h is the thickness of the recording paper, R is the radius of the drive roller 87, and r is the radius of the pinch roller 88. In the multifunction device 1, the angle α is set greater than the smallest positive solution in equation (1).
h+r cos β+R cos(r/R·β)=R+r (1)
From equation (1), a threshold value for the angle β can be easily found to satisfy the condition α>β, facilitating the positioning of the pinch roller 88.
In other words, the points G1 and G2 are a point on the pinch roller 88 and a point on the drive roller 87 respectively, satisfying that the distance between the point G1 and G2 is a prescribed length h, and that the line G1-G2 passing through the points G1 and G2 is parallel to a line O-A. Where the line O-A passes through the center of revolution O and the rotational centers A. The angle β is the angle between a line A-B2 and a line G1-B2. Here, the line A-B2 passes through the rotational centers A and B2. The line G1-B2 passes through the rotational center B2 and the point G1. That is, the angle β is decided by the length h, the radius R of the drive roller 87, and the radius r of the pinch roller 87 by solving the equation (1). The depth direction of the bearing 133 is inclined by the angle α in a clockwise direction from the line A-B2 when the pinch roller 8 is in the retracted position E, satisfying the condition α>β.
Next, the rolling principle of the pinch roller holder 96 will be described with reference to
In this description, an angle formed by line segments OA and OB when the pinch rollers 88 are moved to an arbitrary position will be referred to as θ, where the angle θ may fall within the range θ1≦θ≦θ2. The coil springs 131 accommodated in the pinch roller holder 96 in a compressed state urge the pinch rollers 88 toward the drive roller 87 (along the line segment AB).
As shown in the drawings, when θ>0, the center O of the arc DE does not match the center A of the drive roller 87 about which the pinch roller 88 revolves. Therefore, as θ grows larger, the pinch roller holder 96 separates from the drive roller 87, forcing the coil springs 131 to expand. Hence, an elastic energy E1 in the coil springs 131 decreases as θ grows larger. At this time, a moment M1 acts on the pinch rollers 88 in the counterclockwise direction about the center point A, that is, a direction orthogonal to the line segment AB. The magnitude of the moment M1 is proportional to a decrease dE1/dθ in the elastic energy E1.
At the same time, a frictional force (frictional moment) M2′ is produced in the pinch rollers 88 in the direction opposite this rotational direction about the center point B as the pinch rollers 88 follow the rotation of the drive roller 87. Here, M2 will designate the moment found by converting the frictional force M2′ to a force about the point A, that is, a direction orthogonal to the line segment AB. The frictional force M2′ generated at this time is a static frictional force produced on the sliding surfaces of the pinch rollers 88 and rotational shafts 130 as the pinch rollers 88 rotate. The moment M2 is not indicated in
Further, a rolling frictional force (frictional moment) M3′ is generated when the pinch roller holder 96 rolls over the curved surface 136 of the holder support member 97. This tolling frictional force M3′ acts about the center of revolution O, that is, in a direction orthogonal to the line segment OB. M3 will be used to designate a moment obtained by converting the frictional force M3′ to a force about the point A, that is, in a direction orthogonal to the line segment AB. The moment M3 is not shown in
As shown in
Further, the length of the springs 131 change by the thickness h of the recording paper when the leading edge of the paper arrives at the nip part between the drive roller 87 and pinch roller 88 or when the trailing edge of the recording paper leaves this nip part. Specifically, the coil springs 131 contract by the thickness h in the former case and expand by the thickness h in the latter case. Consequently, the elastic energy of the coil springs 131 also fluctuates at this time, producing a moment M5 about the point A of a magnitude proportional to dE1/dθ, similar to the moment M1 described above.
Since the angle θ (θ1≦0≦θ2), the thickness h of the recording paper, and the stiffness EI of the recording paper are variables, the moment M1 can be expressed by a function of θ and h, the moment M4 by a function of θ and EI, and the moment M5 as a function of h. While the moments M2 and M3 are also strictly speaking a function of θ and h, these values are much smaller than the moments M1, M4, and M5. Thus, the moment M2 and M3 are considered to be constant. Hereinafter, functions of the angle θ will be expressed as M1(θ) and M4(θ).
In the multifunction device 1, the moments M1-M5 must satisfy the equations described below, assuming that no slippage occurs between the drive roller 87 and pinch roller 88 and that the frictional forces between the drive roller 87 and pinch roller 88 and the pinch roller 88 and the recording paper are sufficiently large.
An equation (2) below is satisfied when the drive roller 87 and pinch roller 88 are not conveying the recording paper. Here, the moment M2 acts in the clockwise direction around the point A, while the moment M3 acts counterclockwise around the point A.
M1(θ)+M3>M2 (2)
In this case, the pinch roller holder 96 retracts rearward while rolling upstream in the paper-conveying direction, and is maintained in the retracted position of θ =θ2.
When the recording paper arrives at the nip part between the drive roller 87 and pinch roller 88 and the leading edge of the recording paper is gripped by the rotating drive roller 87, an equation (3) below is satisfied. At this time, the moment M3 acts counterclockwise around the point A. On the other hand, the moment M5 acts clockwise around the point A.
M1(θ)+M3<M4(θ)+M5 (3)
At this time, the pinch roller holder 96 rolls downstream in the paper-conveying direction and is maintained in the conveying position of θ=θ1. In other words, the distance between the drive roller 87 and the pinch roller 88 grows larger by the paper thickness h in the case when the pinch roller 88 rotates clockwise around the point A with the movement of the pinch roller holder 96 than the case when the pinch roller 88 does not move, that is, the elastic energy E1 becomes smaller when the pinch roller 88 rotates clockwise.
An equation (4) below is satisfied when the recording paper is being conveyed. At this time, the moment M2 acts clockwise around the point A, while the moment M3 also acts clockwise around the point A.
M1(θ)<M2+M3+M4(θ) (4)
Hence, the pinch roller holder 96 continues to be maintained in the conveying position D of θ=θ1.
When the trailing edge of the recording paper comes out of the nip part between the drive roller 87 and pinch roller 88, a following equation (5) is satisfied. At this time, the moment M3 acts clockwise around the point. A, while the moment M5 acts counterclockwise around the point A, as with the moment M1
M1(θ)+M5>M3 (5)
As can be seen from the equation (5), only the moment M3 acts as a frictional force to the moment M1(θ)+M5 produced when the trailing edge of the recording paper leaves the nip part between the drive roller 87 and pinch roller 88. However, since the moment M3 is a very slight frictional force produced by the rolling bearings 125, the moment M3 does not act as a force that pushes the recording paper in the conveying direction. Therefore, nearly all of the moment M1(θ)+M5 acts to rotate the pinch roller holder 96 upstream in the paper-conveying direction. Accordingly, the pinch roller holder 96 is retracted and maintained in the retracted position E of θ=θ2.
A following equation (6) is satisfied when rotating the drive roller 87 in reverse after the trailing edge of the recording paper has left the nip part between the drive roller 87 and pinch roller 88. Thus, even during abnormal cases in which the pinch roller holder 96 does not return to the retracted position E of θ=θ2, the pinch roller holder 96 is enable to roll toward the retracted position E of θ=θ2 by rotating the drive roller 87 in reverse.
M1(θ)+M2>M3 (6)
In this case, the moment M2 acts counterclockwise around the point A, and the moment M3 acts clockwise around the center O.
In the multifunction device 1 described above, the pinch roller holder 96 is rotatably supported via the rolling bearings 125. By providing the pinch roller 88, and pinch roller holder 96, holder support member 97, springs 131 to satisfy equations (2)-(6), it is possible to reduce the amount of force pushing the recording paper in the paper-conveying direction. Further, by positioning the pinch rollers 88 such that the angle α is greater than the angle β in
By setting the inclination angle α greater than the angle β, the force of pressure applied to the recording paper S when the recording paper S is pinched by the pair of conveying rollers 89 and the corresponding reaction force generate a rotating force in the direction for rotating the pinch roller 88 forward. Accordingly, the recording paper S is easily drawn in to the point of contact between the conveying rollers 89 and reliably pinched thereby. As a result, the structure of the multifunction device 1 reduces skew in the recording paper S occurring after conveying begins and produces a uniform amount of lead in the recording paper, in other words, the structure of the multifunction device 1 cues the recording paper uniformly.
While the invention has been described in detail with reference to specific aspects thereof, it would be apparent to those skilled in the art that many modifications and variations may be made therein without departing from the spirit of the invention, the scope of which is defined by the attached claims. For example, the image-recording device of the invention is not limited to a support structure for rolling the pinch rollers 88 with the pinch roller holder 96 supported on the holder support member 97, but may apply the sliding mechanism disclosed in Japanese unexamined patent application publication No. 2004-168451. The sliding mechanism disclosed in this publication supports a follow roller so that the follow roller can rotate and can slidingly move in the paper-conveying direction. When the trailing edge of the recording paper leaves the nip part between the drive roller and the follow roller, the follow roller retracts upstream in the paper-conveying direction due to the reaction force from the recording paper. More detail regarding this mechanism can in the above publication. The multifunction device 1 can also be applied to a pair of conveying rollers 89 that are constantly fixed to prescribed positions before and after conveying the recording paper, without moving the pinch rollers 88 by rolling or sliding.
Claims
1. A sheet-conveying device comprising:
- a pair of conveying rollers including a drive roller that is driven to rotate about a first axis, and a follower roller that contacts the drive roller with pressure and follows the rotation of the drive roller about a second axis, the conveying rollers conveying a recording medium in a sheet-conveying direction when the drive roller rotates in a first rotational direction and the follower roller rotates in a second rotational direction that is reverse to the first rotational direction, the drive roller and the follower roller defining a nip line therebetween, the recording medium having a leading edge provided with a first corner contactable with the drive roller and a second corner contactable with the follower roller at a contact line when the drive roller and the follower roller provide the nip line;
- a supporting unit that supports the follower roller and is capable of retracting the follower roller away from the nip line in a retracting plane, the retracting plane being containing the second axis, an angle α1 and α2 greater than the angle α1 being defined between the retracting plane and an imaginary plane that contains the first and second axes, the supporting unit allowing the follower roller to be retracted in a downstream side of the paper conveying direction with respect to the imaginary plane; and
- an urging unit that urges the follower roller to provide the nip line,
- wherein the angle α1 is greater than an angle β defined between the imaginary plane and a radial plane containing the second axis and the contact line.
2. The sheet-conveying device as claimed in claim 1, wherein the angle β is the smallest positive solution to the following equation, where h is a thickness of the conveyed medium and is equal to a distance between the first corner and the second corner, R is a radius of the drive roller, and r is a radius of the follower roller;
- h+r cos β+R cos(r/R·β)=R+r
3. The sheet-conveying device as claimed in claim 1, wherein the urging unit urges the follower roller in a direction along the retracting plane.
4. The sheet-conveying device as claimed in claim 1, wherein the drive roller executes at least one of a holding process in which the drive roller is halted for a prescribed time and a reverse process in which the drive roller is driven to rotate in the second rotating direction when the conveyed medium is about to be contacted with the conveying rollers.
5. An image-recording device comprising:
- a sheet-conveying device comprising: a pair of conveying rollers including a drive roller that is driven to rotate about a first axis, and a follower roller that contacts the drive roller with pressure and follows the rotation of the drive roller about a second axis, the conveying rollers conveying a recording medium in a sheet-conveying direction when the drive roller rotates in a first rotational direction and the follower roller rotates in a second rotational direction that is reverse to the first rotational direction, the drive roller and the follower roller defining a nip line therebetween, the recording medium having a leading edge provided with a first corner contactable with the drive roller and a second corner contactable with the follower roller at a contact line when the drive roller and the follower roller provide the nip line; a supporting unit that supports the follower roller and is capable of retracting the follower roller away from the nip line in a retracting plane, the retracting plane being containing the second axis, an angle α1 and α2 greater than the angle α1 being defined between the retracting plane and an imaginary plane that contains the first and second axes, the supporting unit allowing the follower roller to be retracted in a downstream side of the paper conveying direction with respect to the imaginary plane; and an urging unit that urges the follower roller to provide the nip line, wherein the angle α1 is greater than an angle β defined between the imaginary plane and a radial plane containing the second axis and the contact line; and
- an image-recording unit that records an image on a sheet-like conveyed medium conveyed by the sheet-conveying device.
6. The image-recording device as claimed in claim 5, wherein the image-recording unit comprises an ejecting unit that ejects micro-droplets of ink on the conveyed medium.
Type: Application
Filed: Dec 14, 2006
Publication Date: Jun 28, 2007
Applicant: BROTHER KOGYO KABUSHIKI KAISHA (Nagoya-shi)
Inventor: Kohei Terada (Nagoya-shi)
Application Number: 11/610,590
International Classification: B65H 5/02 (20060101); B65H 5/04 (20060101);