JP4323848B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus in which an image is formed on both sides of a sheet by reversing a sheet on which an image is formed on one side and then transporting the sheet again to an image forming unit.
[0002]
[Prior art]
Conventionally, in an image forming apparatus such as a copying machine or a laser printer, a sheet is fed from a paper feeding unit to an image forming unit, and image formation is performed by a transfer method (indirect method) or a direct method. The sheet is discharged to the paper discharge unit. The image forming unit in such an image forming apparatus includes various image forming principles and processes such as an electrophotographic mechanism, an electrostatic recording mechanism, a magnetic recording mechanism, a thermal recording mechanism, an ink jet mechanism, and an impact printing mechanism. Are known.
[0003]
Examples of the recording material sheet include a transfer material, photosensitive paper (electrofax paper), electrostatic recording paper, thermal paper, printing paper, printing paper, format paper, card, postcard, envelope, and OHP paper. Furthermore, the material of the sheet is not limited to paper, but may be plastic, metal, leather, cloth, or the like.
[0004]
By the way, in some conventional image forming apparatuses, an image is formed on both sides of a sheet. In such an image forming apparatus, after forming an image on one side (front surface) of the sheet, the sheet is inverted. A sheet reversing device is provided so that the sheet can be conveyed again to the image forming unit and an image can be formed on the back surface of the sheet (see Patent Document 1).
[0005]
Note that such a sheet reversing device is configured to be attached to the image forming apparatus main body in advance or to be detachable.
[0006]
In an image forming apparatus provided with such a sheet reversing device, at the time of single-sided printing in which an image is formed on one side, a sheet fed by a cassette mounted on the main body is conveyed to an image forming unit for printing (image Forming), and after the image is fixed by the fixing unit, the image is discharged to the paper discharge unit.
[0007]
Also, during duplex printing where images are formed on both sides, the sheet on which the image formed on one side has been fixed is conveyed by the forward / reverse rollers of the reversing unit to the same path as the sheet ejected from the paper ejection unit and reversed. Thereafter, the sheet is conveyed again to the image forming unit in a state where the front and back sides are reversed. Then, in the image forming unit, the sheet that has been turned upside down is re-formed on the surface where the image is not formed, the image is fixed by the fixing unit, and then discharged to the paper discharge unit.
[0008]
[Patent Document 1]
JP-A-6-316125
[0009]
[Problems to be solved by the invention]
However, in such a conventional image forming apparatus, when the image forming unit becomes large due to an increase in the amount of toner in the process cartridge due to an increase in the maximum number of prints of the image forming apparatus, or when the image forming apparatus is black, In the case of a color image forming apparatus provided with cyan, magenta, and yellow color process cartridges, the main body height becomes high.
[0010]
When the height of the main body is increased in this way, the sheet conveyance distance is extended, and when the sheet conveyance distance is extended in this way, the image forming operation for the back surface of another sheet, particularly after the image forming operation for the surface of the sheet. In the case of forming an image by so-called alternate paper passing alternately and continuously, the front end of the first sheet that is reversed and re-conveyed to the image forming unit after the surface image formation is completed, The distance to the trailing edge of the second sheet on which the image is formed on the preceding surface is increased.
[0011]
Here, when a double-sided image is formed in this manner, if the interval between sheets (hereinafter referred to as the “inter-paper distance”) is widened, the time required for the double-sided image formation of the image forming apparatus becomes long and the productivity is lowered. In addition, when the distance between the sheets is increased in this way, the inverted first sheet and the second sheet may be slid, and when the sheet is slid in this way, the image quality is deteriorated.
[0012]
Accordingly, the present invention has been made in view of such a current situation, and an object thereof is to provide an image forming apparatus capable of preventing a decrease in productivity and a decrease in image quality during double-sided image formation. It is.
[0013]
[Means for Solving the Problems]
In the present invention, when an image is formed on a sheet by an image forming unit, and an image is formed on both sides of the sheet, the sheet on which the image is formed on one side is used. By reversing part In the image forming apparatus that is reversed and then conveyed again to the image forming unit, A discharge roller that discharges a sheet on which an image is formed to a discharge unit; and a reversing conveyance unit that is provided in the reversing unit and conveys the sheet in one direction and then in the reverse direction; Above Reverse transfer means By The direction of conveyance A reconveying passage through which a sheet conveyed again to the image forming unit passes after reversing, a reconveying unit provided in the reconveying passage and reconveying the inverted sheet to the image forming unit, A switching unit that selectively moves between a first position for guiding the sheet fed by the discharge roller to the reverse conveying unit and a second position for discharging the sheet to the discharge unit by the discharge roller; With In the second position, the switching unit moves the sheet conveyed in the reverse direction by the reversing conveying unit to the reconveying path by the same surface as the surface for guiding the sheet fed by the discharge roller to the reversing conveying unit. Guiding, Above By reversing part The sheet reversing speed of the reversing unit and the sheet conveying speed of the re-conveying means are controlled so that the sheet conveying speed when the reversed sheet is conveyed again to the image forming unit is higher than the image forming speed. It is what.
[0014]
Further, according to the present invention, the reversing unit is detachably attached to the apparatus main body and has a sheet reversing unit for reversing the sheet on which the image is formed on one side. Deadline Replacement means and before Reprint And a rolling and conveying means.
[0015]
Further, the present invention is characterized in that driving means for driving the re-conveying means and the reverse conveying means is provided in the apparatus main body or the reversing unit.
[0016]
Further, the present invention is characterized in that control means for controlling the sheet reversing speed of the reversing unit and the sheet conveying speed of the re-conveying unit is provided in the apparatus main body or the reversing unit via the driving unit. It is.
[0017]
In the present invention, when an image is formed on a sheet by the image forming unit, and an image is formed on both sides of the sheet, the sheet on which the image is formed on one side is used. By reversing part In the image forming apparatus that is reversed and then conveyed again to the image forming unit, A discharge roller that discharges a sheet on which an image is formed to a discharge unit; and a reversing conveyance unit that is provided in the reversing unit and conveys the sheet in one direction and then in the reverse direction; Above Reverse transfer means By The direction of conveyance After reversing, a re-conveying passage through which a sheet conveyed again to the image forming unit passes, The reversing unit is selectively moved to a first position where the sheet fed by the discharge roller is guided to the reversing conveyance unit and a second position when the sheet is discharged to the discharge unit by the discharge roller. Switching means for With In the second position, the switching unit moves the sheet conveyed in the reverse direction by the reversing conveying unit to the reconveying path by the same surface as the surface for guiding the sheet fed by the discharge roller to the reversing conveying unit. Lead It is characterized by this.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0019]
FIG. 1 is an overall configuration diagram of a color laser printer as an example of an image forming apparatus according to an embodiment of the present invention.
[0020]
In the figure, reference numeral 50 denotes a color laser printer, and 51 denotes a color laser printer main body (hereinafter referred to as a printer main body). The printer main body 51 has an image forming unit 52 for forming an image on a sheet, and a sheet feeding unit. A paper unit 8, a sheet conveying device 9 that conveys a sheet fed from the paper feeding unit 8 to the image forming unit 52, and a fixing unit 10 that fixes an image formed on the sheet are provided.
[0021]
Here, the image forming unit 52 is arranged in the vertical direction, and each of the photosensitive drums 1a to 1d and the photosensitive drums 1a to 1d, which are image carriers that support toner images of four colors of yellow, magenta, cyan, and black. Charging means 2a to 2d, which are arranged around 1d along the rotation direction and uniformly charge the surface of the photosensitive drum, and irradiate a laser beam based on image information to form an electrostatic latent image on the photosensitive drum. Exposing means 3a to 3d for forming the toner, developing means 4a to 4d for making the toner image adhere to the electrostatic latent image and developing the toner image, and cleaning means 6a to 6a for removing the toner remaining on the surface of the photosensitive drum after transfer. 6d etc. are provided.
[0022]
In this embodiment, the photosensitive drums 1a to 1d, the charging units 2a to 2d, the developing units 4a to 4d, and the cleaning units 6a to 6d are integrally formed as a cartridge to form process cartridges 7a to 7d. Yes.
[0023]
In addition, the photosensitive drums 1a to 1d as image carriers are configured by applying an organic photoconductor layer (OPC) to the outer peripheral surface of an aluminum cylinder. Further, both end portions of the photosensitive drums 1a to 1d are rotatably supported by flanges, and are driven to rotate counterclockwise by transmitting a driving force from a driving motor (not shown) to one end portion. It is like that.
[0024]
The charging means 2a to 2d are conductive rollers that abut on the surface of the photosensitive drum and uniformly charge the surface of the photosensitive drum by applying a charging bias voltage by a power source (not shown). It is. The exposure means 3a to 3d have a polygon mirror, and image light corresponding to an image signal is irradiated to the polygon mirror from a laser diode (not shown).
[0025]
The developing means 4a to 4d are adjacent to the toner storage portions 4a1 to 4d1 storing toners of black, cyan, magenta, and yellow, respectively, and are driven to rotate by a driving unit (not shown) and are not shown. It is composed of developing rollers 4a2 to 4d2 that perform development by applying a developing bias voltage from a bias power source.
[0026]
In addition, transfer rollers 5a to 5d that sandwich the transfer conveyance belt 9a together with the four photosensitive drums 1a to 1d are provided inside the transfer conveyance belt 9a that is an endless sheet conveyance member that conveys a sheet, which will be described later. Has been.
[0027]
Here, the transfer rollers 5a to 5d are connected to a transfer bias power source (not shown), and positive charges are applied to the sheet from the transfer rollers 5a to 5d via the transfer conveyance belt 9a. Yes. By applying the transfer bias in this manner, the negative color toner images on the photosensitive drum 1 are sequentially transferred to the sheet in contact with the photosensitive drum 1 so that a multicolor image is formed. It has become.
[0028]
The paper feed unit 8 includes a paper feed cassette 8a, a multi-feed tray 8b, a multi-feed unit 8c, a registration roller pair 8d, and the like. Here, the paper feed cassette 8a stores a plurality of sheets and is loaded on the bottom of the printer main body, and the multi-feed tray 8b is usually stored in the front of the printer main body, but when used, FIG. It is opened as shown in Fig. 2 and a plurality of sheets are stacked.
[0029]
When forming an image, the sheet is separated and fed one by one from the sheet feeding cassette 8a by the pickup roller 8a1, and the sheet conveying device 9 is conveyed by the intermediate conveying roller 8a2 and the registration roller pair 8d that conveys the sheet at a predetermined timing. It is designed to be conveyed.
[0030]
When feeding sheets from the multi-feed tray 8b, the sheets stored in the multi-feed tray 8b are separated and fed one by one by the multi-pickup roller 8c1, and the multi-conveying roller 8c2 and the registration roller pair 8d are fed. Is conveyed to the sheet conveying device 9. Note that separation and conveyance of sheets in the paper feed cassette 8a and the multi-feed unit 8c are performed by a feed motor (not shown) provided in the paper feed unit 8 via a gear drive train.
[0031]
The sheet conveying apparatus 9 is provided with a transfer conveying belt 9a as a sheet carrier that is stretched and supported by a driving roller 9b and driven rollers 9c and 9d, and is disposed to face all the photosensitive drums 1a to 1d. ing. Here, the transfer conveyance belt 9a electrostatically attracts the sheet to the outer peripheral surface facing the photosensitive drums 1a to 1d, and circulates and moves by the driving roller 9b so that the sheet contacts the photosensitive drums 1a to 1d. It is like that. The sheet is conveyed to the transfer position by the transfer conveyance belt 9a by being electrostatically attracted to the transfer conveyance belt 9a that circulates in this way, and the toner image on the photosensitive drum 1 is transferred.
[0032]
Reference numeral 9e denotes an adsorption roller that is disposed at the most upstream position of the transfer conveyance belt 9a, holds the sheet together with the transfer conveyance belt 9a, and adsorbs the sheet to the transfer conveyance belt 9a. By applying a voltage to the roller 9e, an electric field is formed between the opposed driven roller 9c and a dielectric polarization is generated between the transfer conveyance belt 9a and the sheet, thereby electrostatically attracting both. It is supposed to give rise to.
[0033]
The fixing unit 10 applies heat and pressure to the image formed on the sheet to fix the toner image, and includes a fixing belt 10a and an elastic pressure roller 10b. Here, the fixing belt 10a is a cylindrical belt having an electromagnetic induction heat generating layer, and is guided by a belt guide member 10c having a built-in magnetic field generating means including an exciting coil and a T-shaped magnetic core.
[0034]
The elastic pressure roller 10b sandwiches the fixing belt 10a and forms a fixing nip portion N having a predetermined width with a predetermined pressure contact force with the belt guide member 10c. Then, the elastic pressure roller 10b is driven to rotate by a driving means (not shown), and the cylindrical fixing belt 10a is rotated accordingly, and electromagnetic induction heat generation of the fixing belt 10a is performed by feeding power from an excitation circuit (not shown) to the excitation coil. It has become so.
[0035]
Next, an image forming operation of the color laser printer 50 configured as described above will be described.
[0036]
First, when the surface of the photosensitive drums 1a to 1d uniformly charged by the charging units 2a to 2d is scanned with a laser beam corresponding to the image information irradiated from the exposure units 3a to 3d, A latent image is formed, and this latent image is further developed by developing means 4a to 4d, whereby toner images of four colors of yellow, magenta, cyan and black are formed on the surface of the photosensitive drum.
[0037]
In parallel with this toner image forming operation, the sheet accommodated in the paper feed cassette 8a is picked up by the pickup roller 8a1, or the sheet accommodated in the multi-feed tray 8b is fed by the multi-pickup roller 8c1. After being separated and fed one by one, after being guided to the registration roller pair 8d, the registration roller pair 8d is attracted to the transfer conveyance belt 9a in synchronism with the image forming operation, and is transferred to the photosensitive drums 1a to 1d. The belt 9a is conveyed to the transfer portion T where it is in pressure contact.
[0038]
Next, on the sheet conveyed to the transfer unit T in this manner, the transfer rollers 5a to 5d disposed on the transfer units T and applied with a voltage having a polarity opposite to that of the toner are applied to the photosensitive drums 1a to 1d. The toner images of the respective colors are sequentially transferred on the sheet. The sheet on which the four color toner images are transferred in this way is separated from the transfer conveyance belt 9a and conveyed to the fixing device 10.
[0039]
Next, the sheet on which the unfixed toner image conveyed from the image forming unit 52 is formed is elastic with the fixing belt 10a of the fixing nip N in a state where the temperature of the fixing nip N rises to a predetermined temperature. It is introduced between the pressure roller 10b and the image surface facing upward, that is, facing the fixing belt surface. Thereafter, the image surface is brought into close contact with the outer surface of the fixing belt 10a at the fixing nip portion N and together with the fixing belt 10a. The fixing nip portion N is nipped and conveyed.
[0040]
In the process of being conveyed along the fixing nip N together with the fixing belt 10a in this way, the sheet is heated by electromagnetic induction heat generated by the fixing belt 10a, and the unfixed toner image on the sheet is heated and fixed. As a result, a full-color print image is fixed on the sheet as a permanent image. Next, after the full-color print image is fixed as a permanent image in this way, the sheet S is discharged and stacked on the discharge unit 13 by the discharge roller pairs 11 and 12.
[0041]
By the way, the color laser printer 50 of the present embodiment can form images on both sides of the sheet S. When images are formed on both sides of the sheet S, as shown in FIG. The sheet reversing device 53 constituting the reversing unit is detachably attached to the discharge port 51a (see FIG. 1) of the printer main body 51.
[0042]
Here, when forming images on both sides of the sheet S, the sheet reversing device 53 is configured to reverse the sheet S discharged from the discharge roller pair 11, 12 and downstream of the discharge roller pair 11, 12. , A pair of reversing rollers 20 and 21, and a pair of re-conveying rollers 22 and 23.
[0043]
Here, when an image is formed only on one side of the sheet S, the flapper 18 serving as a switching unit does not hinder the discharge of the sheet S discharged from the discharge roller pairs 11 and 12 as shown in FIG. However, when double-sided image formation is performed to form images on both sides of the sheet S, as shown in FIG. 3, the discharged sheet S is moved to a first position for guiding it to the sheet reversing unit 19. . The flapper 18 is configured to return to the second position shown in FIG. 4 after the sheet S is completely guided to the sheet reversing unit 19, whereby the sheet S is transferred to the re-conveying roller pairs 22 and 23. The conveyance path 24 to be directed can be secured.
[0044]
Further, the pair of reverse rollers 20 and 21 as the reverse conveying means can be rotated forward and backward, and when the flapper 18 moves to the first position shown in FIG. 3, the sheet S is rotated forward so as to be drawn into the sheet reverse portion, After the sheet S is completely guided to the sheet reversing unit 19, the sheet S is conveyed to the re-conveying roller pair 22 and 23 by reverse rotation.
[0045]
In FIG. 2, reference numeral 15 denotes a re-conveying path to which the sheet S conveyed by the reversing roller pairs 20 and 21 and the re-conveying roller pairs 22 and 23 is fed after being reversed. The sheet S passes through the oblique feed rollers 16a and 16b attached to the front of the image forming apparatus main body, and is then conveyed to the U-turn roller 17 and is conveyed again to the image forming unit 52 by the U-turn roller 17 and the registration roller 8d. It has come to be.
[0046]
5 is a control block diagram of such a sheet reversing device 53. In FIG. 5, 100 is a control unit, 101 is a sensor for detecting that the sheet S is conveyed to the sheet reversing unit 19, and 102 is a sheet. A drive motor 103 provided in the reversing device 53 is a solenoid for controlling the position of the flapper 18. The controller 100 may be provided in the sheet reversing device 53 or in the printer main body 51.
[0047]
Here, the drive motor 102 drives the reversing roller pairs 20 and 21, the re-conveying roller pairs 22 and 23, the skew feeding roller 16, and the U-turn roller 17, and thus the reversing roller pairs 20, 21, By driving the re-conveying roller pair 22, 23, the skew feeding roller 16, and the U-turn roller 17 by the drive motor 102, it is possible to perform control different from the image forming operation of the printer main body 51. As a result, the sheet conveyance speed can be changed according to the distance between the sheets and the reverse conveyance distance.
[0048]
In the color laser printer 50 having the sheet reversing device 53 configured as described above, when forming images on both sides of the sheet S, the control unit 100 first shows the flapper 18 by the solenoid 103 as shown in FIG. While switching to the first position, normal rotation of the motor 102 is started.
[0049]
As a result, the sheet S that has passed through the fixing unit 10 is guided to the sheet reversing unit 19 along the flapper 18 and then rotated in the direction in which the sheet S is pulled into the sheet reversing unit 19 by the normal rotation of the motor 102. 20 and 21 are pulled into the sheet reversing unit 19, and then a part of the sheet reversing device 53 protrudes outward.
[0050]
In addition, by projecting a part of the sheet S to the outside of the sheet reversing device 53 in this way, one or both surfaces of the sheet S are exposed to the outside air to be cooled. Even when S is transported to the re-transport path 15, the temperature rise of the printer main body 51 can be suppressed.
[0051]
Next, when the sensor 101 detects that the trailing edge of the sheet has been reliably conveyed downstream from the flapper 18, the solenoid 103 causes the flapper 18 to be reversed as shown in FIG. Returning to the second position, the conveyance path 24 to the re-conveyance roller pair 22, 23 is secured. And after ensuring the conveyance path 24 to the re-conveyance roller pair 22 and 23 reliably in this way, the motor 102 is reversely rotated and the reverse roller pair 20 and 21 is reversely rotated.
[0052]
As a result, the sheet S is conveyed along the conveying path 24 secured by the flapper 18 to the re-conveying roller pair 22 and 23 which are other re-conveying means, and the re-conveying rollers 22 and 23 enter the re-conveying path 15. Be transported. Thereafter, the sheet S passes through the oblique feeding rollers 16a and 16b and is conveyed to the U-turn roller 17, and is further conveyed again to the image forming unit 52 by the U-turn roller 17 and the registration roller 8d.
[0053]
Here, the conveying speed of the sheet S by the reversing roller pair 20, 21, the re-conveying roller pair 22, 23, the skew feeding roller 16, and the U-turn roller 17 is a motor that is a drive source provided in the sheet reversing device 53. 102 can be changed according to the distance between sheets and the reverse conveyance distance.
[0054]
In the present embodiment, the speed increase is performed when the pair of reversing rollers 20 and 21 performs the reverse rotation, and accordingly, when the sheet S is reversed in the sheet reversing device 53, the time required for the reversal is determined. I try to reduce the distance between papers.
[0055]
Note that after the speed is increased in this manner, the speed is reduced before reaching the registration roller 8d conveyed at the conveyance speed of the printer main body 51, and the sheet S reversed thereby is re-conveyed to the image forming unit 52. The sheet conveying speed at that time is equal to the image forming speed of the image forming unit 52 (the conveying speed of the transfer conveying belt 9a and the rotational speed of the photosensitive drums 1a to 1d).
[0056]
By performing such speed control, the image formation on the front surface of the sheet S and the image formation on the back surface of the other sheet S are alternately alternately performed regardless of the change in the conveyance distance due to the height of the printer main body 51 or the like. In so-called alternate sheet feeding, the distance between sheets when forming a single-sided image and the distance between sheets when forming a double-sided image can be made equal. As a result, image formation when an image is formed on one side of a sheet S can be performed. The speed and the image forming speed when images are formed on both sides of the sheet S are equal.
[0057]
That is, when images are formed on both sides of the sheet S, the sheet of the reversing rollers 20 and 21 is set so that the sheet conveying speed when the reversed sheet S is conveyed again to the image forming unit 52 is higher than the image forming speed. By controlling the conveyance speed (reversing speed), the distance between sheets in single-sided printing and double-sided printing can be made equal. Thereby, it is possible to prevent a decrease in productivity when images are formed on both sides of the sheet S, and it is possible to prevent the second sheet S and the first sheet S from slipping. Quality can be improved.
[0058]
Further, since the electric parts such as the flapper 18 and the solenoid 103 are arranged in the sheet reversing device 53, it is not necessary to provide the printer main body 51 with unnecessary parts such as the flapper 18 and the electric parts. Cost increase can be prevented.
[0059]
Further, since the sheet reversing device 53 is mounted on the upper part of the printer main body, it is possible to add a double-sided function without increasing the installation area of the entire printer and the area required for various operations. In addition, since all operations such as jam handling, cartridge replacement, transfer material replacement, etc. can be performed from one direction, usability is not impaired.
[0060]
In the description so far, when images are formed on both sides of the sheet S, the sheet conveying speed when the inverted sheet S is conveyed again to the image forming unit 52 is reversed so as to be faster than the image forming speed. Although the case where the conveying speed of the roller pair 20 and 21 is controlled has been described, the present invention is not limited to this, and the reversing roller pair 22 and 23, the reconveying rollers 22 and 23, and the oblique feeding constituting the reconveying means. By controlling the sheet conveyance speed of the roller 16 and the U-turn roller 17, the distance between the sheets can be made equal when the single-sided image is formed and when the double-sided image is formed.
[0061]
In the above description, the case where the motor 102 as a driving source is provided in the sheet reversing device 53 has been described. However, the present invention is not limited to this, and the motor 102 may be provided in the printer main body 51. .
[0062]
Furthermore, in the above description, the color laser printer as shown in FIG. 1 has been described as an example of the image forming apparatus. However, the present invention is not limited to this, and when an image is formed on both sides of a sheet, the image forming apparatus may be on one side. Needless to say, the present invention can be applied to an image forming apparatus in which a sheet on which an image is formed is reversed and then conveyed again to an image forming unit.
[0063]
【The invention's effect】
As described above, according to the present invention, the sheet conveyance speed when the sheet reversed by the reversing section is conveyed again to the image forming section is controlled so as to be higher than the image forming speed. By equalizing the inter-paper distance during image formation, it is possible to prevent a decrease in productivity and a decrease in image quality during double-sided image formation.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a color laser printer as an example of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram illustrating a state in which a sheet reversing device is mounted on the color laser printer.
FIG. 3 is a diagram illustrating a state in which a sheet is conveyed to the sheet reversing device.
FIG. 4 is a diagram illustrating a state when a sheet reversed by the sheet reversing device is conveyed.
FIG. 5 is a control block diagram of the sheet inverting device.
[Explanation of symbols]
15 Re-transfer passage
16 Skew roller
17 U-turn roller
18 Flapper
19 Sheet reversing part
20, 21 Reverse roller pair
22, 23 Re-conveying roller pair
50 color laser printer
51 Color laser printer body
52 Image forming unit
53 Sheet reversing device
100 Control unit
102 Drive motor
S sheet

Claims (7)

When an image is formed on a sheet by the image forming unit and the image is formed on both sides of the sheet, the sheet on which the image is formed on one side is reversed by the reversing unit and then conveyed to the image forming unit again. In the image forming apparatus,
A discharge roller for discharging the sheet on which the image is formed to a discharge unit;
A reversing conveyance unit that is provided in the reversing unit and conveys the sheet in one direction and then in the reverse direction;
A re-conveying path through which a sheet conveyed again to the image forming unit passes after reversing the conveying direction by the reversing conveying unit ;
A re-conveying means that is provided in the re-conveying path and conveys the inverted sheet to the image forming unit again;
And a switching unit that selectively moves to a first position for guiding the sheet fed by the discharge roller to the reverse conveying unit and a second position for discharging the sheet to the discharge unit by the discharge roller. ,
In the second position, the switching unit moves the sheet conveyed in the reverse direction by the reversing conveying unit to the reconveying path by the same surface as the surface for guiding the sheet fed by the discharge roller to the reversing conveying unit. guided, the sheet conveying speed of the sheet transport speed, the sheet reversing speed and the re-conveying means of the reversing portion to be faster than the image formation speed when transporting the sheets inverted by the inverting unit again to the image forming section And an image forming apparatus. The inverting section is provided with a detachably attached to the main body, and said sheet reversing unit on one side to the image reverses the formed sheet, and pre-Symbol changeover means, before and Kihan rolling conveying means, The image forming apparatus according to claim 1, wherein:   The image forming apparatus according to claim 2, wherein a driving unit that drives the re-conveying unit and the reverse conveying unit is provided in the apparatus main body or the reversing unit.   The image according to claim 3, wherein a control unit that controls a sheet reversing speed of the reversing unit and a sheet conveying speed of the re-conveying unit via the driving unit is provided in the apparatus main body or the reversing unit. Forming equipment. When an image is formed on a sheet by the image forming unit and the image is formed on both sides of the sheet, the sheet on which the image is formed on one side is reversed by the reversing unit and then conveyed to the image forming unit again. In the image forming apparatus,
A discharge roller for discharging the sheet on which the image is formed to a discharge unit;
A reversing conveyance unit that is provided in the reversing unit and conveys the sheet in one direction and then in the reverse direction;
A re-conveying passage through which a sheet conveyed again to the image forming unit passes after reversing the conveying direction by the reversing conveying unit ;
The reversing unit is selectively moved to a first position where the sheet fed by the discharge roller is guided to the reversing conveyance unit and a second position when the sheet is discharged to the discharge unit by the discharge roller. Switching means ,
In the second position, the switching unit moves the sheet conveyed in the reverse direction by the reversing conveying unit to the reconveying path by the same surface as the surface for guiding the sheet fed by the discharge roller to the reversing conveying unit. An image forming apparatus characterized by being guided .   The image forming apparatus according to claim 5, wherein the reversing unit is detachably attached to a sheet discharge port of the apparatus main body. The image forming apparatus according to claim 1, wherein a sheet that is reversed by the reversing unit and a sheet that is discharged to the discharge unit by the discharge roller are alternately conveyed by the image forming unit. apparatus.

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