JPH1144976A - Image forming device - Google Patents

Abstract

(57) [Summary] (Modifications required) [Problem] If back paper is mixed, or if back and back is mixed in the back paper, only the back paper or only the inverted back paper is used. To provide an image forming apparatus that separates the paper from the recording paper and does not perform recording on them, and also provides an image forming apparatus that can reversely feed the reverse side of the back paper and record on a blank paper in some circumstances. I do. SOLUTION: A back paper detecting unit 3 for detecting whether or not the recording paper fed from the paper feeding storage unit 1 is a back paper or an inverted back paper, and the back paper detecting unit detects whether the recording paper is back paper. Image forming control means 6 for controlling not to perform a recording operation on recording paper when it is detected that the paper is a back paper or a reverse back paper, and paper discharge storage means 9, 10 having at least two storage locations
When the backing paper detection unit detects that the recording paper is a backing paper or a reversed backing paper, the recording paper is discharged to one storage location of the paper discharge storing means, and the backing paper or the reversed backing paper. And a discharge destination switching means 11 for discharging the paper to the other storage location when it is not detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to a method for determining whether or not a supplied recording sheet is a back sheet or whether or not the supplied recording sheet is an inverted back sheet. The present invention relates to an image forming apparatus that can execute appropriate processing based on a result.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine,
In recent years, as part of the recycling campaign, instead of discarding used recording paper that has been recorded on one side only (hereinafter referred to as backing paper), image formation (recording) using the blank side of the other side There is more to do. However, when using such backing paper, the wrong side of the backing paper was mistakenly recorded on the recording surface side, or it was intended to copy on unused ordinary recording paper. There is a problem such as copying. Conventionally, as a means for solving such a problem, it is automatically determined whether or not a sheet is a back sheet at the time of feeding, and if the sheet is a back sheet, it is determined whether or not the front and back are reversed. An image forming apparatus having a configuration for feeding paper to an image unit has also been proposed. Japanese Patent Laid-Open No. 6-255842 discloses a paper feed tray 1 as shown in the schematic external view of FIG.
And a means for determining whether the recording paper supplied from the paper supply tray 1 is a backing paper in the image forming apparatus provided with the paper discharging tray 10 and, if the recording paper is a backing paper, a display unit indicating the fact. , It is possible to prevent the occurrence of a situation in which recording is performed on a backing sheet even though the front and back sides are intended to be recorded on a plain recording sheet.

[0003]

However, as in the prior art described above, when it is determined that the back and front sides of the back paper to be fed are reversed, the recording paper is automatically inverted and used. The method is problematic when the back paper has a mix of reverse back paper. That is, if the front and back of a part of the plurality of back papers to be fed are reversed, the back side (the already recorded side) of the back paper is misunderstood as an effective side, and This is because it may be recorded. Further, in the case of the prior art disclosed in Japanese Patent Application Laid-Open No. 6-255842, if back paper is mixed in ordinary recording paper, if the back paper is detected, There is a problem that recording is not performed on recording paper. An object of the present invention is to solve the above-described problems of the related art, and in a case where back paper is mixed in ordinary recording paper, or in a case where reverse back paper is mixed in back paper. In some cases, an image forming apparatus is provided in which only the back paper or only the reverse back paper is separated so that recording is not performed on them, and depending on the situation, the reverse back paper is reversed and white is supplied. An object of the present invention is to provide an image forming apparatus capable of recording on paper.

[0004]

According to a first aspect of the present invention, there is provided a paper feeding and storing means for storing a plurality of sheets of recording paper to be recorded, and a plurality of sheets having completed recording. Backing paper for detecting whether or not the recording paper fed from the paper feeding and storing means is a back paper, or an inverted back paper, in an image forming apparatus provided with a paper discharge storage means for storing the recording paper A detection unit, an image forming control unit that controls not to perform a recording operation on the recording paper when the recording paper is detected by the back paper detection unit to be a back paper or an inverted back paper, Paper discharge storage means having two storage locations, and storage of the recording paper in one of the discharge storage means when the back paper detection unit detects that the recording paper is a back paper or a reverse back paper Drain to the location and make it the backing paper or the upside-down backing paper When not detected it is characterized in that a discharge destination switching means for discharging to the other storage place. According to a second aspect of the present invention, in the image forming apparatus of the first aspect, when the back paper detecting unit determines that the recording paper is the reverse back paper, the image forming unit reverses the recording paper. Reversing transporting means for transporting the paper to the front and back, and when it is determined that the paper is reversed, whether the reversal transporting is performed by the reversing transporting means or the discharging destination is switched by the discharging destination switching means. And selecting means for selecting. According to a third aspect of the present invention, there is provided an image forming apparatus provided with a paper supply storing unit for storing a plurality of recording papers to be recorded, wherein the supplied recording paper is a back paper, A back sheet detecting unit for detecting whether or not the sheet is paper; and a direction reversing means for reversing the transport direction of the recording sheet when the back sheet detecting unit detects that the recording sheet is a back sheet or a reverse back sheet. And return paper storage means for storing the recording paper whose direction has been inverted and conveyed by the direction inversion means. According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, when the back paper detecting unit determines that the recording paper is the reverse back paper, the recording paper is turned over to the image forming unit. When it is determined that the paper is the reverse back and forth transporting means to be transported, and if the reverse side is determined to be the reverse side, the front and back reverse transporting means may perform the reverse side transporting, or the transport direction may be reversed by the direction reversing means, and the recording paper may be returned. Selecting means for selecting whether to store in the storage means.

[0005]

According to the first aspect of the present invention, when the fed recording paper is a back paper or an inverted back paper, the recording paper has at least two storage locations. The paper is discharged to one storage location of the paper storage means, and is discharged to the other storage location when the paper is not a back paper or a reverse back paper. According to the second aspect of the present invention, when it is determined that the reverse side of the paper is reversed, it is possible to select whether to perform reverse transport or to switch the discharge destination. According to the third aspect of the present invention, when it is detected that the recording paper is the back paper or the reverse back paper, the transport direction of the recording paper is reversed, and the recording paper is returned and stored to the paper supply side. . According to the fourth aspect of the invention, when it is determined that the sheet is the reverse side, the user can select whether to carry out the reverse side transport or reverse the transport direction and return and store the recording paper to the paper supply side. Can be.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration block diagram of an image forming apparatus showing a first embodiment of the present invention, and FIG. 2 is a schematic external view thereof. As shown in the figure, the image forming apparatus according to this embodiment includes a paper feed tray (paper feed storage unit) 1 for storing recording paper to be recorded from now on, and one recording paper from the paper feed tray 1. The paper feed unit 2 that separates and sends out the recording paper, and detects whether or not there is a black image on both sides of the recording paper sent from the paper supply unit 2 and detects whether or not it is a back paper, or detects whether or not it is a reverse back and back paper. An operation display panel 4 for displaying that the recording paper is a back paper or an inverted back paper according to the detection result of the paper detection unit 3 and the back paper detection unit 3, and a display for controlling the operation display panel 4. A controller 5, an image forming controller (image forming controller) for performing image forming control in accordance with a detection result of the backing sheet detector 3, an image forming unit 7, which forms an image on recording paper under the control of the image forming controller 6, A first paper transport unit 8 for transporting the recording paper sent from the paper feed unit 2 to the image forming unit 7; It was backing paper or the front and back paper discharge tray for backing paper for containing the reverse of the backing paper (discharge and storage means =
Storage location) 9, a paper output tray for storing other discharged recording paper (paper output storage means = storage location) 10, backing paper detection unit 3
If it is detected that the recording paper is a back paper or an inverted back paper, the recording paper after image formation is stored in the paper discharge tray 9 for the back paper, otherwise, it is stored in the paper discharge tray 10. A discharge tray switching unit (discharge destination switching means) 11 for switching, the first for discharging the recording paper to the back paper discharge tray 9
Paper transport unit 1 that transports the recording paper sent from the paper output unit 12 and the paper output tray switching unit 11 to the first paper output unit 12
3. Second paper discharge unit 1 for discharging recording paper to paper discharge tray 10
4, a third paper transport unit 15 for transporting the recording paper sent from the paper output tray switching unit 11 to the second paper output unit 14, and the like. In each figure, the shaded portions are new components added in the present invention.

FIG. 3 shows an operation flow of this embodiment.
The operation of this embodiment will be described below with reference to FIG.
First, a plurality of recording sheets to be recorded are stored in the paper feed tray 1. It is assumed that among these recording papers, in addition to ordinary recording papers whose both sides are blank, back papers whose only one side is blank are mixed. At the time of image formation on the recording paper, the recording paper stored in the paper feed tray 1 is fed out one by one by the paper feed unit 2. Paper feed unit 2
As shown in FIG. 4, the recording paper transport path located on the downstream side (downstream side of the paper flow)
1, a plurality of reflective photosensors (light emitting element and light receiving element) are provided on the inner surface of each of the transport guide plates 40 and 41 at a predetermined interval and arrangement along a direction orthogonal to the moving direction of the recording paper. 21), and these reflection-type photosensors constitute the backing paper detection unit 3. The arrangement and number of the reflective photosensors 21 are as follows.
What is shown is only an example. The upper reflective photosensor group 21A detects the black pixels on the upper surface of the recording paper passing therethrough, and the lower reflective photosensor group 21B detects the black pixels on the lower surface of the recording paper passing therethrough. For example, among the plurality of photosensors 21 constituting the upper reflective photosensor group 21A, a photosensor having a predetermined number A or more detects a black pixel,
When only a predetermined number B or less of the plurality of photosensors 21 constituting the lower photosensor group 21B detect a black pixel, a normal backside paper (one side is blank and the other side is dirty) If the determination result is upside down, it is determined that the backside is upside down, and the photo sensor that detects a black pixel among the photosensors constituting both photosensor groups 21A and 21B is also determined. If the number of sensors is less than the predetermined number B, both sides are determined to be blank ordinary recording sheets (S1 NO). Instead of arranging a plurality of reflective light emitting and receiving elements 21 on the transport guide plates 40 and 41 facing the both sides of the recording paper, a CCD line sensor having a coarse pixel density may be provided on each surface. .

In the above-described determination, if the back paper detecting unit 3 determines that the recording paper to be conveyed is a back paper or an upside-down back paper (YES in S 1), the back paper detecting unit 3 sets the display control unit 5. Through the operation display panel 4 to indicate that the recording paper is the back paper or that the recording paper is the reverse paper. Also, the fact is notified to the image forming control unit 6. On the other hand, the recording paper sent out by the paper supply unit 2 is sent to the first paper conveyance unit 8 (S
2) The sheet is conveyed to the image forming unit 7 by the sheet conveying unit 8. Since the image forming control unit 6 is notified that the sheet is a back sheet or a reverse sheet, the image forming on the recording sheet is performed. The image forming unit 7 is controlled so as not to perform the operation. In this way, the recording paper in the same state as when it was fed reaches the discharge tray switching unit 11. As shown in FIG. 5, the paper discharge tray switching unit 11 includes a shaft 24, an S-shaped plate member 22 integrated with the shaft 24, and rotating around the shaft 24 by the rotation of the shaft 24, and a shaft 24. It comprises a drive unit (not shown) for rotating, a conveying roller 23, and control means (not shown) for the same. The back paper detecting unit 3 detects that the recording paper is a back paper or an inverted back paper. By the notification, the driving unit rotates the shaft 24, and the S-shaped plate member
22 is positioned in the state shown by the solid line in FIG. 5 (S3). That is, when the S-shaped plate member 22 is at the raised position indicated by the broken line, the recording paper P conveyed by the conveyance roller 23 is conveyed to the paper discharge tray side, and the S-shaped plate member 22 is moved to the lowered position indicated by the solid line. , The recording paper P is conveyed through the S-shaped plate member 22 in the direction of the backing paper discharge tray.

As a result, the recording paper P, which is the backing paper, advances to the position of the transport roller 25 constituting the second paper transport section 13 (S4), and is transported by the transport roller 25 to the first paper discharge section. Then, the paper is further discharged into the back paper discharge tray 9 by the first paper discharge unit 12 (S5). If the next sheet is not determined by the back sheet detection unit 3 to be a back sheet or an upside-down back sheet, the preceding back sheet has passed the position of the transport roller 25. At this time, the S-shaped plate-like member 22 is positioned at a position indicated by a chain line. If the formation of a plurality of sheets has not been completed, the next recording sheet is conveyed and the image is formed without interruption. On the other hand, if it is determined in step S1 that the sheet is not a back sheet or an upside-down back sheet (NO in S1), the recording sheet sent by the sheet feeding unit 2 is sent to the first sheet conveying unit 8 (S6). ), The sheet is conveyed to the image forming unit 7 by the sheet conveying unit 8, and the image forming unit 7 forms an image on a recording sheet (S).
7). Then, the recording sheet on which the image has been formed reaches the discharge tray switching unit 11. In the paper discharge tray switching unit 11, an S-shaped plate member 22 is usually positioned as shown by a dashed line in FIG. 5, whereby the recording paper P constitutes a third paper transport unit 15. (S8), and is transported by the transport roller 26 to the second position.
Then, the paper is discharged into the paper discharge tray 10 by the second paper discharge unit 14 (S9). As described above, according to the first embodiment, if it is determined that the supplied recording paper is a back paper or an inverted back paper as a result of the determination for each supplied recording paper, the recording paper is replaced with another paper. Since the paper is discharged to the paper discharge tray, there is no need to sort back paper or reverse paper. Further, since the front and back sides of the discharged back side are uniform, normal results can be obtained even if the front and back sides are not manually aligned in the next image forming operation. In addition, since there is no interruption during the image forming operation for a plurality of sheets, the operation efficiency is improved.

FIG. 6 is a structural block diagram of an image forming apparatus showing a second embodiment of the present invention, and FIG. 7 is a schematic external view thereof. As shown in the figure, the image forming apparatus of this embodiment includes a back paper discharge tray 9, a discharge tray switching unit 11, a first paper discharge unit 12, and a second paper transport unit 13 of the first embodiment. Instead, a return tray (return paper storage means) 16 provided on the paper feed tray side, a paper reversing section (direction reversing means, front / reverse reversing conveyance means) 17 for reversing the conveyance direction, and recording in which the conveyance direction is reversed A selection unit for controlling the operation of the fourth paper transport unit 18 for transporting the paper to the return tray 16 and the paper reversing unit 17; Hereinafter, the operation of this embodiment will be described in accordance with the operation flow shown in FIG. However, step S11
Is the same as step S1 of the first embodiment, and a description thereof will be omitted. In step S12, it is determined that the recording sheet is a back sheet or a reverse sheet, and the sheet reversing unit 17 reverses the transport direction of the recording sheet. FIG. 9 shows details of the sheet reversing unit 17 and the like. FIG. 9A is a side view, and FIG. 9B is a top view. The sheet reversing unit 17 includes a pair of reversing rollers 28 and 29, as shown in FIG.
It is composed of a drive unit (not shown) for moving 28 and 29, a drive control unit (not shown) for controlling the drive unit, etc., and the recording paper is back paper or reverse back paper Is notified from the backing paper detection unit 3, the pair of the reversing rollers 28 and the pair of the reversing rollers 29 (shown by the dotted lines) which have been retracted to both sides of the path of the recording paper P are shown in FIG.
And the two reversing rollers 28 and 29 are rotated (reversing rollers ON).

Thus, the recording paper is reversed in its traveling direction by the two rotating reversing rollers 28 and 29, and proceeds to the fourth paper transport section 18 (S13). Then, the sheet is stored in the return tray 16 by the fourth sheet transport section 18 (S1).
Four). On the other hand, if it is determined in step S11 that the sheet is not the back sheet or the reverse sheet,
NO), the two reversing rollers 28 and 29 shown in FIG. 9 remain on both sides (the position shown by the dotted line) of the recording paper path (reversing roller OFF) (S15), so that the recording paper goes straight. Then, the process proceeds to the position of the transport roller 27 constituting the first paper transport unit 8 (S16). Hereinafter, steps S17 to S19 are the first
The description is omitted because it is the same as S7 to S9 of the embodiment. The selecting means, when it is determined that the paper is the reverse of the reverse side, causes the above-mentioned reverse side transporting means to perform the reverse side transporting, or reverses the transport direction by the direction reversing means, and returns the recording paper to the return paper storing means. This is a means for selecting whether to store the data in the storage area. As described above, according to the second embodiment, mixed back paper or reversed back paper is separated and returned to the paper feeding side, so that in addition to the effect of the first embodiment, the back paper or the inverted paper is added. The time required to discharge the backing paper can be shortened. In FIG. 6, a paper discharge tray 9 and a paper discharge tray 10 for back paper, a paper discharge tray switching unit (discharge destination switching means) 11, and the above-mentioned paper reversing unit (direction reversing means, front and back reversing conveyance means) 17 to cause the sheet to be turned over,
The selection range may be expanded by adding a selection means for selecting whether to switch the paper discharge destination.

FIG. 10 is a configuration block diagram of an image forming apparatus showing a third embodiment of the present invention. The image forming apparatus of this embodiment has a configuration in which the configuration of the first embodiment and the configuration of the second embodiment are combined, and further includes a sheet reversing unit (direction reversing unit,
A reversing switching unit 19 that re-conveys the recording paper whose conveying direction and the front and back are reversed by the front and back reverse conveying means 17 and conveys the recording paper in the same direction again. Select and set a desired mode from among multiple modes, such as a mode for discharging to a paper output tray, a mode for discharging to a return tray, and a mode for performing front / reverse / image formation and discharging to a normal paper output tray. The configuration is such that a mode setting unit 20 is added. Hereinafter, the operation of this embodiment will be described according to the operation flow shown in FIG. It is assumed that a desired mode is set in the mode setting unit 20 in advance. First, the recording paper is sent out by the paper supply unit 2, and at this time, the back paper detection unit 3 is set in the mode setting unit.
It is determined whether or not the back sheet detection mode is set to 20 (S21). If the back sheet detection mode is set (YES in S21), it is determined whether or not the sent recording sheet is a back sheet. Or, it is determined whether or not the sheet is the reverse side of the sheet (S22). And
If it is a back paper or a reverse back paper (YES in S22),
It is determined whether the mode setting is the front / back / transport direction reversal mode (S23).

As a result, if it is determined that the mode is the reversing mode (YES in S23), the sheet reversing section 17 reverses the recording paper conveyance direction and the front and back (S24) (see S12 in FIG. 8). Subsequently, it is determined whether or not the mode setting is image formation after reversal (S2).
5) If the image is an image after inversion (YES in S25), FIG.
The rear end of the recording paper P is monitored by a sensor 30 (which constitutes a post-reversal switching section together with the control means) provided near the reversing rollers 28 and 29 (see FIG. 12A). When the rear end reaches the position of the sensor 30 (see FIG. 12B), the reversing rollers 28 and 29 are reversely rotated (S26). Thus, the recording paper is conveyed in the direction of the arrow in FIG. In this way, the rear end of the recording paper that has been turned upside down becomes the leading end, and the recording paper advances to the first paper conveyance unit 8 (the conveyance roller 27 shown in FIG. 9) (S27), and the reversing roller Two
8 and 29 are turned off (S28). Hereinafter, steps S29 to S33 are executed. However, since these steps are the same as steps S6 to S9 of the first embodiment, description thereof will be omitted.

On the other hand, if it is determined in step S25 that the image is not formed after reversing (NO in S25), the reversing switching unit 19 does not switch the transport direction even if the sensor 30 detects the trailing edge of the recording paper. (S34), the recording paper is stored in the fourth paper transport unit 18
(S35), the reversing rollers 28 and 29 are turned off (S36), and the recording paper is stored in the return tray 16 (S37). Further, in the case where the setting of not performing the back sheet detection in step S21 (NO in S21), and
If no back paper or upside down back paper is detected in step 22 (NO in S22), the process proceeds to steps S29 and S30 to receive an image. If it is determined in step S23 that the sheet is not to be reversed (NO in step S23), the reversing rollers 28 and 29 are avoided and are kept in the OFF state (step S38). Sent to the paper transport unit 8,
The process proceeds to the discharge tray switching unit 11 without performing image formation. If the setting mode is to discharge to the back paper discharge tray (YES in S39), steps S40 to S42 are executed. Steps S40 to S42 are the same as steps S3 to S5 of the first embodiment, and a description thereof will be omitted. If the discharge to the back paper discharge tray 9 is not set in step S39 (NO in S39), the process proceeds to step S31, where the paper is discharged to the normal paper discharge tray 10. According to this embodiment, since the user can select and set various modes, it is possible to take an appropriate action according to the situation when detecting the back paper or the reverse back paper. Note that a configuration in which some of the above modes are not provided is also possible.

[0015]

As described above, according to the first aspect of the present invention, as a result of detecting each of the fed recording sheets one by one, when the recording sheet is a back sheet or a reverse back sheet,
The recording paper is discharged to one storage location of the paper discharge storage means having at least two storage locations, and is discharged to the other storage location when it is not a back paper or a reverse back and back paper. When performing continuous printing, even if recording paper contains back paper or reversed back paper, image formation can be performed without interrupting the operation, and back paper or reversed back paper can be formed. The paper can be separated. According to the second aspect of the present invention, when it is determined that the sheet is a reverse sheet, it is possible to select whether to perform reverse / image formation or to switch the discharge destination without forming an image. Because it is possible, the handling of the backside upside down can be appropriately selected according to the situation. According to the third aspect of the present invention, when it is detected that the paper is a back paper or an inverted back paper, the transport direction of the back paper is reversed, and the recording paper is returned and stored to the paper supply side. In addition to the effects of the first aspect, the discharge time of the back paper or the back paper upside down can be shortened. According to the fourth aspect of the present invention, when it is determined that the back sheet is the reverse side, whether to reverse the image and form the image or to reverse the transport direction and return the recording paper to the paper supply side for storage. Can be selected, so that the same effects as those of the second and third aspects can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic external view of an image forming apparatus according to a first embodiment of the present invention.

FIG. 3 is an operation flowchart of the image forming apparatus according to the first embodiment of the present invention;

FIG. 4 is an explanatory diagram of a main part of the image forming apparatus (a backing paper detection unit) according to the first embodiment of the present invention;

FIG. 5 is another explanatory diagram of a main part of the image forming apparatus (discharge tray switching unit) according to the first embodiment of the present invention.

FIG. 6 is a configuration block diagram of an image forming apparatus according to a second embodiment of the present invention.

FIG. 7 is a schematic external view of an image forming apparatus according to a second embodiment of the present invention.

FIG. 8 is an operation flowchart of the image forming apparatus according to the second embodiment of the present invention.

FIGS. 9A and 9B are explanatory diagrams of a main part (sheet reversing unit) of an image forming apparatus according to a second embodiment of the present invention.

FIG. 10 is a configuration block diagram of an image forming apparatus according to a third embodiment of the present invention.

FIG. 11 is an operation flowchart of the image forming apparatus according to the third embodiment of the present invention.

FIGS. 12A and 12B are explanatory diagrams of a main part (sheet reversing unit) of an image forming apparatus according to a third embodiment of the present invention.

FIG. 13 is a schematic external view of an image forming apparatus showing an example of a conventional technique.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 paper feed tray, 2 paper feed section, 3 back paper detection section, 4 operation display panel, 6 image formation control section, 7 image formation section, 8 first paper transport section, 9 back paper discharge tray, 10 Discharge tray, 11 discharge tray switching unit, 13 second paper transport unit, 15 third paper transport unit, 16 return tray, 17 paper reversing unit, 18 fourth paper transport unit, 20 mode setting unit,
21 Reflective light emitting and receiving element, 22 S-shaped plate member, 28 reversing roller, 29 reversing roller, 30 sensor

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B65H 29/60 B65H 29/60 A G03G 21/00 378 G03G 21/00 378

Claims (4)

[Claims] 1. An image forming apparatus comprising: a paper feed storage unit that stores a plurality of recording sheets to be printed; and a paper discharge storage unit that stores a plurality of printed recording sheets. Whether the recording paper fed from the paper feed storage means is backing paper,
Or, a back paper detection unit for detecting whether or not the paper is reversed, and a recording operation on the recording paper when the back paper detection unit detects that the recording paper is a back paper or a reversed back paper. Image forming control means for controlling so as not to perform, a paper discharge storage means having at least two storage locations, and the back paper detecting section has detected that the recording paper is a back paper or a reverse back and back paper. A discharge destination switching unit that discharges the recording paper to one storage location of the paper discharge storage unit, and discharges the recording paper to the other storage location when it is not detected that the recording paper is a back paper or a reverse back paper. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein when the recording paper is determined by the back paper detecting unit to be the reverse of the recording paper, the recording paper is reversed and conveyed to the image forming unit. When it is determined that the paper is the reverse side, the sheet is turned over by the above-mentioned reverse side transfer means, or the sheet discharge destination is switched by the sheet discharge destination switching means. An image forming apparatus comprising: 3. An image forming apparatus provided with a paper feeding and storing means for storing a plurality of recording papers to be recorded, wherein whether the fed recording paper is a back paper, or whether the fed recording paper is a reverse back paper or not. A back paper detecting unit for detecting whether or not the recording paper is a back paper or a reverse back paper by the back paper detecting unit, a direction reversing means for reversing the transport direction of the recording paper,
An image forming apparatus, comprising: return paper storage means for storing the recording paper whose direction has been inverted and conveyed by the direction inversion means. 4. The image forming apparatus according to claim 3, wherein when the back paper detecting unit determines that the recording paper is the reverse back paper, the recording paper is turned over and conveyed to the image forming unit. When it is determined that the paper is reversed, the recording paper is stored by returning the recording paper by reversing the transport direction by the reversing transport means. An image forming apparatus comprising: a selection unit that selects whether to store the image in the unit.