JP3769002B2 - Paper transfer device for image forming apparatus - Google Patents

Description

  The present invention relates to a sheet transfer device of an image forming apparatus, and in particular, an image forming apparatus having a reverse rotation roller that rotates forward or backward in contact with a transfer roller so as to prevent double feeding of picked up sheets. The present invention relates to a paper transport apparatus.

  In general, the electrophotographic image forming apparatus 1 is supplied with paper P by a knock-up plate type paper feeding device 2. As shown in FIG. 1, the paper P is picked up by the pickup roller 3, and in order to prevent double feeding of the picked up paper P, a paper transporting device 10 including a pair of rollers is provided.

  As shown in FIG. 2, the sheet transfer device 10 includes a transfer roller 11 and a reverse rotation roller 12. A torque limiter 13 is coaxially mounted on the reverse rotation roller 12 to rotate the reverse rotation roller 12 in the reverse direction. A possible reverse motor (not shown) is provided separately from the driving device for driving the transfer roller 11.

  The reverse rotation roller 12 rotates in the opposite direction to the transfer roller 11, and when the paper P is double-fed, it prevents the doubled paper from being fed due to the difference in frictional force. When the paper P is not double-fed, the frictional force with the transfer roller 11 is coaxially connected to the reverse rotation roller 12 and becomes larger than the torque of the torque limiter 13 having a constant size torque. It rotates in the same direction as the transfer roller 11. The reverse rotation roller 12 is coaxially installed with a reverse rotation gear 14 for transmitting the power of the reverse rotation motor. The reverse rotation gear 14 rotates in the opposite direction together with the torque limiter 13 and moves independently of the transfer roller 11.

  The transfer roller 11 and the reverse roller 12 according to the related art configured as described above are made of a rubber material having a constant friction coefficient on the surface. As the rubber, a material having a certain hardness, a friction coefficient, durability, and the like, such as NR, NBR, EPDM, urethane, and silicon, is used according to the application.

  However, since the reverse rotation roller 12 rotates in the direction opposite to the paper entering direction, its surface is heavily worn. Due to such wear, the transfer roller shaft S1 and the reverse roller shaft S2 cannot maintain the initial parallel state as the reverse roller 12 is worn, and gradually incline as shown in FIG. Changes to the state.

  This is because the position of the reverse gear 14 is fixed. As described above, when the transfer roller shaft S1 and the reverse roller shaft S2 are not parallel, the contact between the transfer roller 11 and the reverse roller 12 is not smooth. The prevention function and the sheet transfer function cannot be performed, which may cause malfunction of the image apparatus.

  Accordingly, the present invention has been made in view of such problems, and the object of the present invention is to prevent double feed when the reverse rotation roller is worn by forward and reverse rotation in contact with the transfer roller. It is an object of the present invention to provide a sheet transfer device for an image forming apparatus that can prevent a decrease in performance.

  In order to solve the above-described problems, according to one aspect of the present invention, a transfer roller for transferring a sheet, a reverse roller disposed in contact with the transfer roller, a drive motor for providing power to the reverse roller, An idle gear that couples the reverse rotation roller and the drive motor to transmit power, and the idle gear transmits the power of the drive motor to the reverse rotation roller while the rotation center moves in accordance with wear of the reverse rotation roller. A sheet transport device for an image forming apparatus is provided.

  In other words, the transfer roller and the reverse roller serve to prevent the double feeding of the paper by transferring the paper to the image forming unit while rotating forward and backward while being in contact with each other. In this case, the reverse rotation roller is transmitted with power by a drive motor which is a separate power source separated from the transfer roller, but a gear train including an idle gear is used for power transmission. In this case, the idle gear is configured such that the center of rotation thereof moves so that the transfer roller and the reverse rotation roller can always maintain a constant contact force when the reverse rotation roller is worn.

  Thus, even if the reverse roller is worn and the distance between the central axes of the transfer roller and the reverse roller changes, the distance at which the rotation center changes while the idle gear that transmits power to the reverse roller moves. The shafts of the transfer roller and the reverse rotation roller are kept parallel, and the reverse rotation roller and the transfer roller can maintain a constant contact force.

  At this time, it is desirable that the idle gear moves on a trajectory that overlaps a virtual circle having a radius from the center of the idle gear with the center of the drive gear of the drive motor as the center. Therefore, the idle gear can be configured such that the central axis swings along a swing slot formed on one side of the image forming apparatus corresponding to the movement track of the idle gear.

  The swing slot for moving the idle gear can be formed, for example, so that the curvature of the inner peripheral surface is parallel to the movement locus of the idle gear, and this causes the shaft position of the reverse rotation roller to move. However, the meshing of the reverse gear and the idle gear can be maintained.

  In addition, the swing slot for moving the idle gear can be formed in the tangential direction of a virtual circle centered on the center of the drive gear of the drive motor and having a radius from the center of the idle gear. The swing slot at this time preferably includes an elastic member that elastically supports the central axis of the idle gear. The elastic member pressurizes the central axis of the idle gear and applies an elastic restoring force to the reverse gear side so that the meshed state of the reverse gear and the idle gear can be maintained.

  According to the sheet transfer device of the image forming apparatus according to the present invention as described above, even if the reverse roller is worn and the distance between the central axes between the transfer roller and the reverse roller changes, The idle gear that transmits power moves so as to correspond to the distance that the center of rotation has changed, and the reverse rotation roller and the transfer roller can maintain a constant contact force, thus maintaining double feed prevention performance and product reliability. Can be secured.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 3 is an explanatory diagram showing an operation state of the sheet transport device of the image forming apparatus according to the preferred embodiment of the present invention. As shown in the drawing, the sheet transfer device 100 of the image forming apparatus according to the present embodiment is arranged so that the transfer roller 110 and the reverse rotation roller 120 face each other at a constant pressure. Each of the transfer roller 110 and the reverse rotation roller 120 includes a transfer gear 112 and a reverse rotation gear 122 to which power is transmitted by separate drive sources. The reverse rotation roller 120 is rotated by receiving power from the drive motor 130 (see FIG. 4).

  Further, the reverse rotation roller 120 includes load means including a torque limiter T that is coaxially installed on the reverse rotation roller shaft 121. The torque limiter T senses whether or not the frictional force between the transfer roller 110 and the reverse rotation roller 120 has dropped below a certain value when a sheet enters between the transfer roller 110 and the reverse rotation roller 120.

  According to the detection signal of the torque limiter T, the reversing roller 120 transfers the paper while rotating in the same direction as the transfer roller 110 when the paper is supplied one by one, and transfers the paper when the paper is double fed. The paper that has been multi-fed while rotating in the direction opposite to the roller 110 is separated so that only one paper can enter the image forming unit (not shown).

  More specifically, the sheet picked up by the sheet feeding unit passes through the transfer roller 110 and the reverse rotation roller 120 installed so as to come into contact with each other, and proceeds to the image forming unit. The reverse roller 120 rotates in the same direction as the transfer roller 110 when the friction force with the transfer roller 110 is greater than a certain value, and when the friction force with the transfer roller 110 is small, the reverse roller 120 It rotates in the direction opposite to the rotation direction.

  However, since the reverse rotation roller 120 is continuously rubbed with the paper, the wear amount gradually increases as the usage time increases. As wear of the reverse roller 120 proceeds, the axial position of the reverse roller shaft 121 moves in parallel to the transfer roller 110 side by a distance d as shown in FIGS.

  Accordingly, in order for the reverse rotation gear 122 to continuously transmit power from the drive motor 130 (see FIG. 4) even when the axial position of the reverse rotation roller shaft 121 is moved, it is interlocked with the position change of the reverse rotation gear 122. Thus, the idle gear 140 that can maintain the meshing is required. Such an idle gear 140 must be configured so that its central axis Ci can move, as shown in FIG.

  Thereby, the center axis Ci of the idle gear 140 can maintain the meshing between the reverse gear 122 and the idle gear 140 while moving along the predetermined swing locus A shown in FIG.

  The idle gear 140 is installed such that its central axis Ci is movable on one side wall surface W (see FIGS. 5 and 6) of the image forming apparatus, and the reverse roller shaft 121 is moved to the transfer roller 110 side by wear of the reverse roller 120. Even when moving to the center, the center axis Ci can move along the swing path A, so that the meshing between the idle gear 140 and the reverse gear 122 is maintained.

  The swing trajectory A preferably overlaps with the circumferential direction of a virtual circle whose radius is the distance between the center axis Ci of the idle gear 140 and the center axis Cm of the drive gear 131. 5 and 6 are diagrams schematically illustrating a preferred embodiment in which the central axis Ci of the idle gear 140 can move along the swing path A. FIG.

  For example, as shown in FIG. 5, the central axis Ci of the idle gear 140 is slidably installed on one side wall surface W of the image forming apparatus. The curved swing slot 141 is provided with a width corresponding to the diameter of the central axis Ci so as to overlap the swing locus A on the wall surface W on which the central axis Ci is installed.

  Accordingly, when the position of the reverse roller shaft 121 moves due to wear of the reverse roller 120, the central axis Ci can slide along the curved swing slot 141, and the meshing between the reverse gear 122 and the idle gear 140 is continuously maintained. be able to.

  As shown in FIG. 5, the curved swing slot 141 is preferably formed so that its width corresponds to the diameter of the central axis Ci of the idle gear 140 and has a circumferential curvature corresponding to the swing locus A. It is good to form.

  FIG. 6 shows another embodiment of the structure in which the idle gear can move along the swing path A. A center axis Ci of the idle gear 140 is slidably installed on one side wall surface W of the image forming apparatus, and a width corresponding to the diameter of the center axis Ci in the tangential direction of the swing path A is formed on the wall surface W on which the center axis Ci is installed. A linear swing slot 142 is provided.

  In this case, a predetermined elastic member 143 such as a compression spring is installed in the linear swing slot 142. The elastic member 143 applies an elastic restoring force toward the reverse gear 122 to the idle gear 140 so that the idle gear 140 can be kept in mesh with the reverse gear 122.

  According to the sheet transfer device 100 of the image forming apparatus as described above, when the reverse rotation roller 120 is worn, the reverse rotation roller shaft 121 moves toward the transfer roller 110 by the amount of wear of the reverse rotation roller 120. Since the meshing is maintained in conjunction with the position change of the reverse rotation gear 122, malfunction such as the reverse rotation roller 120 being worn away by one side or being separated from the transfer roller 110 and the paper double feed prevention function does not operate is prevented. be able to.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are of course within the technical scope of the present invention. Understood.

  The present invention can be applied to a paper transport device of an image forming apparatus, and can be applied to a paper transport device of all image forming apparatuses including a laser printer, a copying machine, a multifunction peripheral, and the like.

FIG. 2 is an explanatory diagram schematically illustrating a structure of a normal image forming apparatus. It is explanatory drawing which shows the state from which the transfer roller which concerns on a prior art, and a reverse roller became non-parallel by abrasion of the reverse roller. It is explanatory drawing which shows the state to which the rotating shaft of a reverse roller moves the transfer roller and reverse roller which concern on this Embodiment at the time of abrasion of a reverse roller. FIG. 4 is an explanatory diagram illustrating an idle gear that moves along a swing path in the sheet transfer device of the image forming apparatus according to the embodiment. FIG. 4 is an explanatory diagram illustrating a structure example in which an idle gear can move along a swing path in the sheet transport device of the image forming apparatus according to the embodiment. FIG. 10 is an explanatory diagram illustrating another example of the structure in which the idle gear can move along a swing path in the sheet transport device of the image forming apparatus according to the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Paper transfer apparatus 110 Transfer roller 111 Transfer roller shaft 112 Transfer gear 120 Reverse rotation roller 121 Reverse rotation roller shaft 122 Reverse rotation gear 130 Drive motor 131 Drive gear 140 Idle gear A Swing locus Cm Central axis Ci Central axis d Distance

Claims (6)

A transfer roller for transferring paper;
A reverse rotation roller disposed in contact with the transfer roller;
A drive motor that provides power to the reverse roller;
An idle gear for connecting the reverse roller and the drive motor to transmit power;
Including
The sheet transfer device of the image forming apparatus, wherein the idle gear transmits the power of the drive motor to the reverse rotation roller while the rotation center moves in accordance with wear of the reverse rotation roller. The idle gear is
2. The sheet of the image forming apparatus according to claim 1, wherein the sheet moves on a trajectory overlapping a virtual circle whose radius is the distance from the center of the idle gear with the center of the drive gear of the drive motor as a center. Transfer device. The idle gear is
The sheet transporting device for an image forming apparatus according to claim 2, wherein the central axis swings along a swing slot formed on one side of the image forming apparatus corresponding to the movement path of the idle gear. The swing slot is
4. The sheet transfer device for an image forming apparatus according to claim 3, wherein a curvature of an inner peripheral surface is formed in parallel with a movement locus of the idle gear. The swing slot is
The sheet of the image forming apparatus according to claim 3, wherein the sheet is formed in a tangential direction of an imaginary circle having a radius from a center of the drive gear of the drive motor as a radius. Transfer device. The swing slot is
6. The sheet transport device for an image forming apparatus according to claim 5, further comprising an elastic member that elastically supports a central axis of the idle gear.

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