JP2007091415A - Paper sheet inversion device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper sheet inversion device capable of shortening the conveyance time and suppressing jamming with a simple configuration. <P>SOLUTION: The paper sheet inversion device has a first shaft roller 16a provided on a first shaft 16, two kinds of second shaft rollers 17a, 17b having different diameter provided on a second shaft 17, and a third shaft roller 18a provided on a third shaft 18. There are provided a plurality of second shaft rollers 17b of one kind. The second shaft roller 17a of the smaller diameter out of the two kinds of second shaft rollers is pressed against the first shaft roller 16a. The second shaft roller 17b of the larger diameter is pressed against the third shaft roller 18a. A container with an image formed on one side is passed between the first shaft roller 16a and the second shaft roller 17a, and conveyed from its fore-end to the discharge side. When an image is also formed on the other side, the paper sheet is passed between the second shaft roller 17b and the third shaft roller 18a, and returned from its rear end to an image forming means 2 side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet reversing device used in an image forming apparatus such as a copying machine, a printer, and a facsimile.

  2. Description of the Related Art A paper reversing device is disclosed in which an image forming unit of a double-sided image forming apparatus sends a sheet printed on one side to the image forming unit again to print on the other side (for example, a patent) Reference 1).

  FIG. 13 is a side view of a conventional sheet reversing device.

  As shown in FIG. 13, the conventional sheet reversing device includes three roller shafts 124, a roller shaft 125, and a roller shaft 126. Of these roller shafts, the roller shaft 125 is disposed substantially at the center. Further, a conveyance path 100 is formed between the roller shaft 124 and the roller shaft 125, and a reverse conveyance path 101 is formed between the roller shaft 125 and the roller shaft 126. The sheet moves in the direction indicated by the dotted arrow in the conveyance path 100 and in the direction indicated by the one-dot chain arrow in the reverse conveyance path 101.

  FIG. 14 is a front view of the conventional sheet reversing device shown in FIG.

  As shown in FIG. 14, the roller shaft 125 has two rollers 125 a provided so as to be rotatable with respect to the shaft, and two rollers 125 b fixed to the shaft. The roller shaft 124 includes two rollers 124a fixed to the shaft and pressed against the roller 125a, and three rollers 124b having a smaller diameter and fixed to the shaft. is doing. Of these three rollers 124b, two rollers 124b arranged at both ends of the shaft are opposed to the roller 125b with a slight gap. The roller shaft 126 has three rollers 126a fixed to the shaft, and two of the rollers 126a at both ends are in pressure contact with the roller 125b.

  The roller shaft 125 is provided with a reduction gear 102, and the roller shaft 124 is provided with a drive gear 103. The drive gear 103 and the reduction gear 102 are engaged with each other. The reduction gear 102 is provided with driving means (not shown). When the roller shaft 125 is rotated by the driving means, the roller shaft 124 is rotated at a rotational speed slower than the rotation of the roller shaft 125. Become.

  Further, the image forming apparatus includes image forming means (not shown) such as a transfer unit that transfers an image onto a sheet and a fixing unit that fixes toner on the upstream side of the roller shaft 125 of the conveyance path 100 shown in FIG. ing. In addition, two rollers (not shown) are installed on the downstream side of the transport path 100. The two rollers convey the paper along the reverse conveyance path 101 when an image is formed on the other surface of the paper having an image formed on one side, and discharge the paper in other cases.

  Further, a guide 104 for guiding the sheet to the two rollers is provided on the downstream side of the roller shaft 125 of the transport path 100, and the guide 104 has an end 105 a on the upstream side of the roller shaft 125 of the transport path 100. The guide film 105 which is fixed and whose other end 105b is a free end is in contact. A space between the guide 104 and the guide film 105 is a part of the conveyance path 100 and the reverse conveyance path 101.

  In the paper reversing device as described above, the rotation speed of the roller shaft 125 can be made faster than the rotation speed of the roller shaft 124 by the reduction gear 102 and the drive gear 103. The speed can be increased when the paper passes between the roller shaft 125 and the roller shaft 126 of the reverse conveyance path 101 than when the paper passes between the rollers 125. When transporting in the direction of the transport path 100, the toner image that has just been fixed is rubbed on the surfaces of the rollers 125a and 124a. When transporting in the direction, there is no such limitation and the speed can be increased, so the reverse transport time can be shortened.

Further, by passing the sheet between the guide 104 and the guide film 105, curling generated on the fixed sheet can be reduced, and the sheet is placed between the roller 125b and the roller 126a in the reverse conveyance path 101. Since it becomes easy to insert, paper jam can be suppressed.
JP-A-5-11527

  However, since the conventional paper reversing apparatus employs a mechanism including the drive gear 103 and the reduction gear 102 combined therewith in order to shorten the conveyance time, the drive mechanism is complicated and the number of parts is large. Therefore, there was a problem that the cost was high.

  Further, a guide film 105 is provided to suppress the influence of curled curves α and β (see FIG. 7) generated by the fixing process. The guide film 105 is composed of a roller shaft 125 and a roller shaft 126. They are arranged throughout, complicating the configuration, and working time is long during maintenance and the like.

  An object of the present invention is to provide a reversing apparatus or an image forming apparatus capable of reducing the reverse conveyance time and suppressing paper jam with a simpler configuration in consideration of the above-described conventional problems. .

In order to achieve the above object, the first present invention provides:
When a sheet on which an image is formed on one side by the image forming means is transported with its leading edge directed toward the discharge side and an image is also formed on the other side of the sheet, the sheet is formed from the trailing edge. A paper reversing device for returning to the means side,
A first shaft roller provided on the first shaft;
At least two types of second shaft rollers provided on the second shaft and having different diameters;
A third shaft roller provided on the third shaft,
The first axis, the second axis, and the third axis are substantially parallel to each other;
Of the two types, one type of the second shaft roller is plural, and the other type of the second shaft roller is one or plural,
Of the two types of second shaft rollers, the smaller second shaft roller is in pressure contact with the first shaft roller, and the larger diameter second shaft roller is in pressure contact with the third shaft roller. Has been
Passing between the first shaft roller and the second shaft roller, the paper is conveyed from the leading edge,
The sheet reversing device is configured to pass between the second shaft roller and the third shaft roller and return the sheet from the rear end to the image forming unit side.

The second aspect of the present invention is
Drive means coupled to the second shaft;
The second shaft roller is fixed to the second shaft;
The first shaft roller and the third shaft roller are the sheet reversing device according to the first aspect of the present invention, which is driven by the second shaft roller.

The third aspect of the present invention
The plurality of second shaft rollers are the sheet reversing device according to the first aspect of the present invention, which is disposed so as to be bilaterally symmetric with respect to substantially the center in the length direction of the second shaft.

The fourth aspect of the present invention is
The one type of second shaft roller is an even number,
The sheet reversing device according to the third aspect of the present invention, wherein the second shaft roller of the one type is disposed on both sides of the second shaft roller of the other type.

The fifth aspect of the present invention is
The one type of second shaft roller is the second shaft roller having the larger diameter,
The other type of second shaft roller is the paper reversing device according to the fourth aspect of the present invention, which is the second shaft roller having the smaller diameter.

The sixth aspect of the present invention
The one type of second shaft roller is the second shaft roller having the smaller diameter,
The other type of second shaft roller is the sheet reversing device according to the fourth aspect of the present invention, which is the second shaft roller having the larger diameter.

The seventh aspect of the present invention
The number of the second type of the second shaft roller is two,
In the paper reversing device of the fifth or sixth aspect of the present invention, the number of the second type of second shaft rollers is two.

Further, the eighth aspect of the present invention is
The number of the second type of the second shaft roller is two,
In the paper reversing device of the fifth or sixth aspect of the present invention, the number of the second type of second shaft rollers is one.

The ninth aspect of the present invention provides
Image forming means for forming an image on paper;
A sheet reversing device of the first invention;
A discharge means for discharging the paper conveyed by the paper reversing device;
Reverse conveying means for reversely conveying the paper conveyed by the paper reversing device from the rear end of the paper to the paper reversing device;
An image forming apparatus comprising: a control unit configured to operate the reverse conveying unit when forming an image on the other surface of the sheet; otherwise, the discharge unit discharges the sheet. is there.

  According to the present invention, it is possible to provide a reversing device or an image forming apparatus capable of reducing the reverse conveyance time and suppressing paper jam with a simpler configuration.

  Embodiments of the present invention will be described below with reference to the drawings. A printer capable of duplex printing will be described as an example of the image forming apparatus of the present invention. Here, the image forming apparatus according to the present invention will be described, and an example of the reversing apparatus of the present invention will be described at the same time.

(Embodiment 1)
FIG. 1 is an external view of a printer according to an embodiment of the present invention. FIG. 2 is a schematic side view of the printer according to the first embodiment.

  As shown in FIG. 2, the printer according to the first embodiment includes a paper tray 1 that stores paper for printing, an image forming unit 2 that forms an image on the paper supplied from the paper tray 1, and an image is formed. A discharge means 4 for discharging the discharged paper, and a discharge tray 23 on which the paper discharged from the discharge means 4 is placed. In addition, a sheet reversing unit 3 is provided for conveying the sheet on which one side of the image is formed by the image forming unit 2 to the discharge unit 4 side, and conveying the sheet conveyed to the discharge unit 4 side to the image forming unit 2 side again. Has been. The paper tray 1 is provided with a paper feeding means 26 configured by rollers for supplying paper to the image forming means 2.

  The paper tray 1 is disposed at the bottom of the printer of the present embodiment, and the image forming means 2 is disposed above the paper tray 1. The discharge means 4 is arranged on the upper part on the back side of the printer, and the discharge tray 23 is arranged on the upper surface of the printer.

  Next, the image forming unit 2 will be described.

  The image forming unit 2 includes an image transfer unit 5 that transfers toner to a sheet, and a fixing unit 6 that fixes the toner to the sheet by increasing the temperature.

  The image transfer unit 5 removes the charged charges by irradiating the surface of the photosensitive drum 7 other than the photosensitive drum 7, the charger 8 for charging the surface of the photosensitive drum 7, and the portion where the image is formed. The exposure unit 9 forms an electrostatic latent image, and the developing unit 10 attaches toner to the electrostatic latent image formed on the surface of the photosensitive drum 7 to form a visible image. Further, the image transfer unit 5 applies a charge opposite to the toner from the opposite side of the photosensitive drum 7 to the conveyed sheet, and transfers the toner to the sheet by electrostatic force, and the surface of the photosensitive drum 7 is charged. And a cleaner 13 for removing toner remaining on the photosensitive drum 7 without being transferred.

  The fixing unit 6 includes a fixing roller 14 having a heater and a pressure roller 15 in pressure contact with the fixing roller 14.

  Next, the paper reversing means 3 as an example of the paper reversing device of the present invention will be described.

  As shown in FIG. 2, the paper reversing means 3 has a first shaft 16, a second shaft 17, and a third shaft 18 each having a roller. These three axes are arranged in parallel to each other, and the second axis 17 is arranged between the first axis 16 and the third axis 18.

  FIG. 3 is a perspective view of the sheet reversing unit 3 according to the present embodiment as viewed from the arrow S side in FIG. Further, FIG. 4 is a front view from S schematically showing the sheet reversing means 3 shown in FIG. The first shaft 16 and the third shaft 18 are fixed to the frame 30 of the printer, and the second shaft 17 is rotatably attached to the frame 30. The second shaft 17 is connected to driving means (not shown). In FIG. 3, the third shaft 18 is omitted in the middle of reaching the frame 30.

  As shown in FIGS. 3 and 4, the first shaft 16 is covered with a cover 24, and the two first shaft rollers 16 a arranged on the first shaft 16 are exposed from the cover 24. . The two first shaft rollers 16 a are installed so as to be rotatable with respect to the first shaft 16.

  Further, two third shaft rollers 18a are installed on the third shaft 18 so as to be rotatable with respect to the shaft. The second shaft 17 is provided with two rollers having two different diameters. The smaller one of the two types is a small-diameter second shaft roller 17a, and the larger-diameter roller. Is a large-diameter second shaft roller 17b. The small-diameter second shaft roller 17a and the large-diameter second shaft roller 17b are fixed to the second shaft 17, and the two small-diameter second shaft rollers 17a are pressed against the two first shaft rollers 16a. The two large-diameter second shaft rollers 17b are in pressure contact with the two third shaft rollers 18a.

  Further, these rollers are arranged substantially symmetrically with respect to the center of the second shaft 17 in the length direction. The small-diameter second shaft roller 17a is not in contact with the third shaft 18 and the third shaft roller 18a. The large-diameter second shaft roller 17b is not in contact with the cover 24 and the first shaft roller 16a.

  Next, the discharging means 4 will be described.

  The discharge means 4 has two sets of roller pairs 19 and 20 arranged in the vertical direction between the paper reversing means 3 and the discharge tray 23. Each of the roller pairs 19 and 20 is composed of two rollers. In addition, one of the two rollers of the roller pair 19 and 20 is connected to the driving means, and can rotate in the forward direction and the reverse direction. Here, the forward direction is a direction in which the sheet is conveyed from the sheet reversing unit 2 side to the discharge tray 23 side, and the reverse direction is a direction in which the sheet is returned to the sheet reversing unit 2 side. The roller pair 20 forms a paper discharge port, and the discharge tray 23 is provided on the upper surface of the printer adjacent to the roller pair 20.

  Although not shown, a control unit for controlling the sheet feeding unit 25, the image forming unit 2, the sheet reversing unit 3, and the discharging unit 4 is provided.

  Next, the paper conveyance path through which the paper is conveyed will be described.

  The printer according to the present embodiment includes a paper tray 1, a photosensitive drum 7 and a transfer device 11, a fixing roller 14 and a pressure roller 15, a first shaft roller 16 a and a small-diameter second shaft roller 17 a, and a roller pair 19. And a sheet conveyance path 21 through which sheets are conveyed in the order between the roller pair 20. Further, the printer according to the present embodiment has a paper reverse conveyance path 22 through which the paper is conveyed in the order between the roller pair 20, the roller pair 19, and the large-diameter second shaft roller 17b and the third shaft roller 18a. I have. This sheet reverse conveyance path 22 is further formed between the large-diameter second-axis roller 17b and the third-axis roller 18a through the position between the sheet tray 1 and the image forming means 2, and is shown in FIG. At the point P shown, it joins the paper transport path 21. In FIG. 2, the paper transport path 21 is indicated by a solid arrow, and the paper reverse transport path 22 is indicated by a dotted arrow.

  Next, after describing the outline of the operation of the printer of the present embodiment having the above-described configuration, the operation of the sheet reversing unit 3 will be described in detail.

  In the printer of this embodiment, when print data is transmitted from a connected computer or the like (not shown), the print data is stored in a memory (not shown).

  A part of the surface of the photosensitive drum 7 is uniformly charged by the charger 8 and is exposed by the exposure device 9 based on the print data, and the charge of the portion other than the image is removed to form an electrostatic latent image. In the developing unit 10, toner that is colored fine particles charged with a polarity opposite to that of the electrostatic latent image is attached to the electrostatic latent image to form a visible image. Along with this operation, the sheet is conveyed from the sheet tray 1 at the bottom of the image forming apparatus to the photosensitive drum 7 and the transfer unit 11 located above the sheet tray 1.

  Then, the toner attached to the surface of the photosensitive drum 7 is transferred onto the sheet by the transfer unit 11. The charge on the surface of the photosensitive drum 7 transferred to the sheet is removed by the slow current device 12, and the remaining toner is removed by the cleaner 13. The portion where the toner has been removed is charged again and the above-described operation is repeated.

  Next, the sheet on which the image is transferred passes between the heated fixing roller 14 and the pressure roller 15, whereby the toner adhering to the sheet surface is fixed on the sheet. Then, the sheet is conveyed to the sheet reversing unit 3 side.

  Next, the paper passes between the first shaft roller 16a provided on the first shaft 16 and the small-diameter second shaft roller 17a provided on the second shaft 17 from the tip, and is discharged. It is conveyed to the means 4. The first shaft 16 is driven by the driving means clockwise in FIG.

  Here, when the printer according to the present embodiment has not received a double-sided printing instruction from a computer or the like, the control unit drives the roller pair 19 and the roller pair 20 in the forward direction, and the sheet is discharged from the leading end of the discharge tray 23. Discharged to the top.

  On the other hand, when the printer is instructed to perform double-sided printing, after the trailing edge of the paper passes between the first shaft roller 16a and the second shaft roller 17a, the control means reversely sets the roller pair 19 in the reverse direction. And the roller pair 20 is driven.

  By driving the roller pairs 19 and 20 in the reverse direction, the sheet is conveyed from the rear end side through the sheet reverse conveyance path 22 to the sheet reversing unit 3 side. The sheet is then inserted between the large-diameter second shaft roller 17 b provided on the second shaft 17 and the third shaft roller 18 a provided on the third shaft 18. That is, when the paper is conveyed in reverse, it is inserted between the large-diameter second shaft roller 17b and the third shaft roller 18a from the rear end of the paper.

  Next, the sheet is conveyed from the sheet reversing unit 3 through the sheet reverse conveyance path 22, joins the sheet conveyance path 21, and is conveyed through the sheet conveyance path 21. Subsequently, as in the case where an image is formed on one side, an image is formed on the other side by the image forming unit 2 on the sheet. Then, the sheet sequentially passes between the first shaft roller 16 a and the small-diameter second shaft roller 17 a of the sheet reversing unit 3 and between the pair of rollers 19 and 20 of the discharging unit 4 and is discharged onto the discharge tray 23.

  Next, the operation of the sheet reversing unit 3 in the above-described printer operation will be described in more detail.

  The operation of the sheet reversing unit 3 when the sheet 25 is conveyed from the image forming unit 2 side to the discharge unit 4 side through the sheet conveyance path 21 will be described.

  FIG. 5 is a diagram showing a state in which the paper 25 passes between the first shaft roller 16a and the small-diameter second shaft roller 17a in the paper reversing unit 3 shown in FIG. In FIG. 5, the paper 25 is conveyed from the back of the paper toward the front.

  Here, as shown in FIG. 5, since the two large-diameter second shaft rollers 17b are arranged on the second shaft 17 outside the two small-diameter second shaft rollers 17a, the paper 25 When passing between the first shaft 16 and the second shaft 17, the central portion 25 a of the paper 25 is curved toward the second shaft 17 side with respect to both end portions 25 b in the width direction of the paper 25. Power will be applied.

  FIG. 6 is a diagram for explaining the state of the paper 25 that has passed between the first shaft 16 and the second shaft 17 of the paper reversing means 3. An arrow T indicates the paper conveyance direction. Further, the width of the paper 25 perpendicular to the transport direction T is 25 w, and the length of the paper 25 parallel to the transport direction T is 25 L. A dotted line shown in FIG. 6 indicates a line separating the central portion 25a and both end portions 25b in the width 25w of the paper 25, and substantially corresponds to a portion where the paper 25 in FIG. 5 contacts the large-diameter second shaft roller 17b.

  In FIG. 6, the wavy irregularities are clearly formed on the paper 25. However, actually, the wavy irregularities that can be clearly recognized visually are not formed on the paper, as shown in FIG. This shows that the correction force is applied to the paper 25 in the direction in which the wavy irregularities are formed.

  Such correction force causes the paper 25 to have a waist with respect to the conveyance direction. This eliminates the curled curves α and β (see FIG. 7).

  As described above, when the sheet is conveyed through the sheet reversing unit of the present embodiment, the curled curves α and β in the direction of the length 25L of the sheet are corrected, and double-sided printing is performed. When the sheet is conveyed from the discharge unit 4 side to the sheet reversing unit 3 side, the sheet 25 can be smoothly inserted between the large-diameter second shaft roller 17b and the third shaft roller 18a.

  Further, with the above configuration, the curled curves α and β can be corrected without providing a guide film as in the prior art, so it is possible to suppress paper jam with a simple configuration.

  Further, when the paper is transported through the paper transport path 21, the paper 25 is transported by the small-diameter second shaft roller 17 a installed on the second shaft 17, and when the paper is transported through the paper reverse transport path 22, The sheet 25 is conveyed by the large-diameter second shaft roller 17b. As a result, the speed of the sheet 25 conveyed by the sheet reversing unit 3 can be higher when the sheet 25 is conveyed reversely along the sheet reverse conveyance path 22 than when it is conveyed along the sheet conveyance path 21. Become.

  For this reason, it is possible to increase the paper conveyance speed during double-sided printing while keeping the speed after fixing at a predetermined speed, and it is possible to reduce the conveyance speed.

  Further, since the sheet conveying speed in the sheet conveying path 21 and the sheet reverse conveying path 22 is changed by two types of rollers having different diameters provided on the second axis 17, the driving means is provided only for the second axis 17. And a reduction gear mechanism is not required, and the conveyance time can be shortened with a simpler structure than in the prior art.

  In the paper reversing means of the present embodiment, the first shaft roller 16a and the third shaft roller 18a are configured to be rotatable with respect to the shaft, but the first shaft 16 and the third shaft 18 are the frame. If it is rotatable with respect to 30, it may be fixed with respect to the shaft.

  In the sheet reversing means of the present embodiment, the small-diameter second shaft roller 17 a and the large-diameter second shaft roller 17 b are fixed to the second shaft 17, and the first shaft roller is driven according to the driving of the second shaft 17. 16a and the third shaft roller 18a are driven, but not only the second shaft 17, but the first shaft 16 or the third shaft 18 is driven and the other shaft is driven. There may be.

  For example, when the driving means is coupled to the first shaft 16 and the small-diameter second shaft roller 17a, the large-diameter second shaft roller 17b, and the third shaft roller 18a are driven according to the driving of the first shaft 16, the first shaft 16 The shaft roller 16a, the small-diameter second shaft roller 17a, and the large-diameter second shaft roller 17b are fixed with respect to the shaft, and the first shaft 16 and the second shaft 17 are rotatably installed on the frame 30 of the printer. Need to be. Further, when the third shaft 18 is rotatably attached to the frame 30, the third shaft roller 18a may be fixed to the shaft, but the third shaft 18 is fixed to the frame 30. In the case where the third shaft roller 18a is fixed to the shaft, the third shaft roller 18a needs to be installed so as to be rotatable with respect to the shaft.

  In addition, when the driving means is connected to the third shaft 18 and the small-diameter second shaft roller 17a, the large-diameter second shaft roller 17b, and the first shaft roller 16a are driven according to the driving of the third shaft 18, the third shaft 18 The shaft roller 18a, the small-diameter second shaft roller 17a, and the large-diameter second shaft roller 17b are fixed with respect to the shaft, and the third shaft 18 and the second shaft 17 are rotatably installed on the printer frame 30. Need to be. Further, when the first shaft 16 is rotatably attached to the frame 30, the first shaft roller 16a may be fixed to the shaft, but the first shaft 16 is fixed to the frame 30. In the case where the first shaft roller 16a is fixed to the shaft, the first shaft roller 16a needs to be rotatably installed with respect to the shaft.

  Alternatively, the first shaft 16 and the third shaft 18 may be provided with driving means, and the small-diameter second shaft roller 17a and the large-diameter second shaft roller 17b may be driven according to the driving of these shafts. However, in this case, although there is an effect of correcting the curled curves α and β, the configuration is complicated because the number of driving means is two, and thus the configuration having one driving means as described in the present embodiment. Is more preferable.

  An example of one type of the second shaft roller of the present invention corresponds to the large-diameter second shaft roller 17b of the present embodiment, and an example of the other type of second shaft roller of the present invention is the present embodiment. The sheet reversing means 3, which is an example of the sheet reversing device of the present invention, has the number and arrangement of rollers as shown in FIG. 4, but is not limited to this configuration. It does not have to be, and can be changed as appropriate. Hereinafter, modified examples of the sheet reversing unit shown in the present embodiment will be described with reference to the drawings.

  As shown in FIG. 8, the arrangement of the small-diameter second shaft roller 17a and the large-diameter second shaft roller 17b may be reversed. According to the arrangement of the rollers of the second shaft 17, the position of the first shaft roller 16a moves outward and the position of the third shaft roller 18a moves inward.

  Further, in the paper reversing means 3 shown in FIG. 4, the two small-diameter second shaft rollers 17a are arranged, but may be one small-diameter second shaft roller 17c. In this case, as shown in FIG. 9, from the viewpoint of stability when transporting the sheet, one small-diameter second shaft roller 17c is disposed substantially at the center in the length direction of the second shaft 17, It is preferable that the width is wider than the width of the small-diameter second shaft roller 17a in FIG. In FIG. 9, the first shaft 16 is provided with two first shaft rollers 16a. However, the first shaft 16 may be provided with one roller having the same width as the small-diameter second shaft roller 17a. Good (not shown). Furthermore, the arrangement of the small-diameter second shaft roller 17c and the large-diameter second shaft roller 17b in FIG. 9 may be reversed (not shown). That is, a wide large-diameter second shaft roller may be disposed at the center of the second shaft 17, and a small-diameter second shaft roller 17a may be disposed on both sides thereof.

  Further, in the sheet reversing means 3 shown in FIG. 4, the number of the small diameter second shaft rollers 17a disposed between the two large diameter second shaft rollers 17b may be increased, or the small diameter second shaft rollers 17a. You may increase the number of the two large diameter 2nd axis | shaft rollers 17b arrange | positioned at the both sides. As an example of this, FIG. 10 shows a state in which three small-diameter second shaft rollers 17a are arranged at the center of the second shaft 17, and two large-diameter second shaft rollers 17b are arranged on both sides thereof. Note that the number of the first shaft rollers 16 a and the third shaft rollers 18 a increases corresponding to the rollers disposed on the second shaft 17.

  In short, there are an even number of rollers arranged outside either the small-diameter second shaft roller 17a or the large-diameter second shaft roller 17b so that the second shaft 17 is symmetrical with respect to the center in the length direction. It is only necessary to be arranged in.

  In addition to the above-described configuration, as shown in FIG. 11, a large-diameter second shaft roller 17b may be further disposed between the two small-diameter second shaft rollers 17a of the sheet reversing means 3 shown in FIG. Good. In short, it is only necessary that the small-diameter second shaft roller 17a and the large-diameter second shaft roller 17b are arranged so as to be bilaterally symmetric with respect to the center in the length direction of the second shaft 17.

  Further, from the viewpoint of applying a force so as to form a wave-like unevenness on the paper and causing the paper to be stiff with respect to the conveyance direction, the small-diameter second shaft roller 17a and the large-diameter second shaft roller 17b are the second shaft. It is not necessary to arrange them symmetrically with respect to the center of 17. As shown in FIG. 12, only the large-diameter second shaft roller 17 b is disposed on one side and only the small-diameter second shaft roller 17 a is disposed on the opposite side. You may arrange. Also in this case, wave-like irregularities are formed on the paper 25 passing through the paper reversing means between the small-diameter second shaft roller 17a and the large-diameter second shaft roller 17b adjacent thereto.

  However, with reference to the center in the width 25w direction of the paper 25, in FIG. 12, only the right side of the paper 25 is in contact with the first shaft roller 16a and the small-diameter second shaft roller 17a, and the paper 25 is conveyed. From the viewpoint of stability during conveyance, the large-diameter second shaft roller 17b and the small-diameter second shaft roller 17a are more preferably arranged so as to be symmetrical with respect to the center of the second shaft 17. preferable.

  According to the paper reversing device of the present invention, it is possible to shorten the conveyance time and suppress paper jamming, and it is useful for image forming apparatuses such as copying machines, printers, and facsimiles.

1 is a perspective view of a printer according to a first embodiment of the present invention. 1 is a configuration diagram of a main part of a printer according to a first embodiment of the present invention. The perspective view of the paper inversion means in Embodiment 1 concerning this invention FIG. 2 is a plan view schematically showing a sheet reversing unit according to the first embodiment of the present invention. The top view which showed typically the state through which the paper passes the paper inversion means in Embodiment 1 concerning this invention The figure for demonstrating the state of the paper which passed the paper inversion means in Embodiment 1 concerning this invention. FIG. 7 is a diagram for explaining a state of a sheet after passing through a fixing unit in the image forming apparatus according to the first embodiment of the present invention. The top view which represented typically the paper inversion means in the modification of Embodiment 1 concerning this invention The top view which represented typically the paper inversion means in the modification of Embodiment 1 concerning this invention The top view which represented typically the paper inversion means in the modification of Embodiment 1 concerning this invention The top view which represented typically the paper inversion means in the modification of Embodiment 1 concerning this invention The top view which represented typically the paper inversion means in the modification of Embodiment 1 concerning this invention Side view of a conventional paper reversing device Front view of a conventional paper reversing device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper tray 2 Image forming means 3 Paper reversing means 4 Discharge means 5 Image transfer part 6 Fixing part 7 Photosensitive drum 8 Charger 9 Exposure device 10 Developer 11 Transfer device 12 Gradual charger 13 Cleaner 14 Fixing roller 15 Pressure roller 16 First Shaft 17 second shaft 18 third shaft 19 roller pair 20 roller pair 21 paper transport path 22 paper reverse transport path 23 discharge tray 24 cover 25 paper 30 frame

Claims (9)

When a sheet on which an image is formed on one side by the image forming unit is conveyed toward the discharge side and an image is formed on the other side of the sheet, the sheet is formed from the rear end. A paper reversing device for returning to the means side,
A first shaft roller provided on the first shaft;
At least two types of second shaft rollers provided on the second shaft and having different diameters;
A third shaft roller provided on the third shaft,
The first axis, the second axis, and the third axis are substantially parallel to each other;
Of the two types, one type of the second shaft roller is plural, and the other type of the second shaft roller is one or plural,
Of the two types of second shaft rollers, the smaller second shaft roller is in pressure contact with the first shaft roller, and the larger diameter second shaft roller is in pressure contact with the third shaft roller. Has been
Passing between the first shaft roller and the second shaft roller, the paper is conveyed from the leading edge,
A sheet reversing device in which the sheet is returned to the image forming unit side from the rear end through the second axis roller and the third axis roller. Drive means coupled to the second shaft;
The second shaft roller is fixed to the second shaft;
The sheet reversing device according to claim 1, wherein the first shaft roller and the third shaft roller are driven by the second shaft roller.   3. The sheet reversing device according to claim 1, wherein the plurality of second shaft rollers are arranged to be bilaterally symmetric with respect to a substantially center in a length direction of the second shaft. The one type of second shaft roller is an even number,
The sheet reversing device according to claim 3, wherein the one type of second axis roller is disposed on both sides of the other type of second axis roller. The one type of second shaft roller is the second shaft roller having the larger diameter,
The sheet reversing device according to claim 4, wherein the other type of second shaft roller is a second shaft roller having a smaller diameter. The one type of second shaft roller is the second shaft roller having the smaller diameter,
The sheet reversing device according to claim 4, wherein the second shaft roller of the other type is a second shaft roller having a larger diameter. The number of the second type of the second shaft roller is two,
The sheet reversing device according to claim 5 or 6, wherein the number of the second type of second shaft rollers is two. The number of the second type of the second shaft roller is two,
The sheet reversing device according to claim 5 or 6, wherein the number of the second type of second shaft rollers is one. Image forming means for forming an image on paper;
A sheet reversing device according to claim 1;
A discharge means for discharging the paper conveyed by the paper reversing device;
Reverse conveying means for reversely conveying the paper conveyed by the paper reversing device from the rear end of the paper to the paper reversing device;
An image forming apparatus comprising: a control unit that operates the reverse conveying unit when an image is formed on the other surface of the sheet; otherwise, the discharge unit discharges the sheet.

Images