JPH0752482A - Image forming equipment - Google Patents

Abstract

PURPOSE:To enable execution of high-speed recording by making a paper feeding speed high even when paper turned over is used, and besides, to enable increase of a recycling effect by selectin recording paper partially usable. CONSTITUTION:In response to the result of detection in a blank paper detecting part 24, rcording paper is conveyed to an image recording part 1 by paper conveying means 36 and 41 when the surface of the recording paper is blank, while it is dischargd to a paper discharging part 45 by paper discharging means 36 and 48 when neither the surface nor the rear rthereof is blank. Moreover, a control means 70 which makes a control so that the recording paper stored in a turned-over paper storage part 44 be sent out to the image recording part 1 and that the recording paper in the blank paper detecting part 24 be turned over and stored in the turned-over paper storage part 44, when the rear of this recording paper is blank while the surface is not blank, is provided.

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 printer or a copying machine. In the image forming apparatus, an image is recorded on a recording sheet, but it is uneconomical to discard the recording sheet without using the back side at all, which is against the social demand for resource saving.

Therefore, for example, an unused sheet is used for recording for clear copy, and recording is performed on the back side of a sheet already recorded on the front side for drafting or document level recording. ing.

[0003]

2. Description of the Related Art Most primitively, there is a method in which unused sheets, both front and back, are placed in a paper feed tray, and when the back side of used paper is used, the sheets are manually fed one by one. . However, not only is it troublesome and troublesome,
There is also the possibility of accidentally overwriting on the recorded surface.

Therefore, during automatic paper feeding, it is detected whether or not the fed recording paper is a blank sheet, and if the front side is recorded and the back side is a blank sheet, the sheet is turned upside down. The recording medium is conveyed to a recording unit and automatically recorded on a blank surface (Japanese Patent Laid-Open Nos. 4-164744 and 2-8).
147).

[0005]

However, if the front and back sides of the recording sheet are reversed and conveyed to the recording section during the sheet feeding, the sheet feeding rate for each sheet becomes slow and the total recording rate becomes extremely high. It will be late.

Further, if recording is carried out even on a small part of the recording paper, it will be judged as unusable even if it can be used, for example, if the paper is cut in half, thus wasting resources. It was.

Therefore, according to the present invention, even when the sheets are used upside down, the feeding speed is high and recording can be performed at high speed, and partially usable recording sheets are selected and collected. It is an object of the present invention to provide an image forming apparatus capable of enhancing the recycling effect.

[0008]

In order to achieve the above object, the image forming apparatus of the present invention determines whether the recording paper 100 is a blank paper as shown in FIG. 1 for explaining the embodiment. Blank sheet detection unit 24 for detecting both front and back sides
A sheet feeding means 22 for feeding the recording sheets 100 to the blank sheet detecting section 24 one by one, and a sheet conveying section 36 for conveying the recording sheet 100 from the blank sheet detecting section 24 to the image recording section 1. 41, sheet discharging means 36 and 48 for discharging the recording sheet 100 from the blank sheet detecting section 24 to the sheet discharging section 45, and the recording sheet 100 from the blank sheet detecting section 24.
And the reverse side of the recording sheet 100 and store the recording sheet 100, and the recording sheet 100 can be sent to the image recording section 1 and the blank sheet detecting section 24.
When the surface of the recording paper 100 is blank, the recording paper 100 is conveyed from the blank paper detecting unit 24 to the image recording unit 1 in response to the detection result of the recording paper 100. When both the front and back sides are not blank sheets, the recording sheet 100 is moved from the blank sheet detection section 24 to the sheet ejection section 4 by the sheet ejection means 36 and 48.
5 and the back side of the recording sheet 100 is not blank and the front side is not blank, the recording sheet 100 stored in the reversal storage section 44 is sent to the image recording section 1 and the recording sheet of the blank sheet detecting section 24. 100 is the reversal storage unit 44
And a control means 70 for controlling so that the sheet is pulled in and inverted and stored.

In the image forming apparatus of the present invention, the blank sheet detecting section 24, which detects whether the recording sheet 100 is a blank sheet by dividing it into front and back sides, and records the blank sheet detecting section 24. Paper feeding means 22 for feeding the paper 100 one by one, and paper conveying means 36, 41 for conveying the recording paper 100 from the blank paper detecting section 24 to the image recording section 1.
And sheet discharging means 36 and 48 for discharging the recording sheet 100 from the blank sheet detecting section 24 to the sheet discharging section 45, and for discharging the recording sheet 100 from the blank sheet detecting section 24 to the second sheet discharging section 46. It is possible to draw the recording paper 100 from the second paper discharge means 54 and the blank paper detection unit 24, store the recording paper 100 with its front and back reversed, and send the recording paper 100 to the image recording unit 1. In response to the detection results of the reversal storage unit 44 and the blank sheet detection unit 24, when the surface of the recording sheet 100 is blank, the recording sheet 100 is transferred from the blank sheet detection unit 24 to the image by the sheet conveying means 36 and 41. When the recording paper 100 is conveyed to the recording unit 1 and all the front and back surfaces of the recording paper 100 are not blank, the recording paper 10 is discharged by the paper discharge means 36 and 48.
0 is discharged from the blank paper detection unit 24 to the paper discharge unit 45,
When part of both the front and back sides of the recording paper 100 is blank, the recording paper 100 is discharged by the second paper discharging means 54.
Is discharged to the second paper discharge section 46, and the recording paper 100 is discharged.
When the back side of the sheet is blank and the front side is not blank, the recording sheet 100 stored in the reversal storing section 44 is sent to the image recording section 1 and the recording sheet 1 of the blank sheet detecting section 24 is discharged.
And a control unit 70 for controlling so that 00 is drawn into the reversal storage unit 44 and inverted and stored.

In addition, in response to the detection result of the blank sheet detecting section 24, when the back surface of the recording sheet 100 conveyed to the image recording section 1 is not a blank sheet, a marking means 60 for marking a mark on the surface is provided. May be.

[0011]

The blank detecting section 24 is controlled by the control means 70.
When the front surface of the recording paper 100 is a blank paper, the paper transporting means 36, 41 transports the recording paper 100 from the blank paper detection unit 24 to the image recording unit 1, and when both the front and back surfaces of the recording paper 100 are not blank paper. The paper ejecting means 36 and 48 eject the recording paper 100 from the blank paper detecting unit 24 to the paper ejecting unit 45. When the back surface of the recording paper 100 is blank and the front surface is not blank, it is stored in the reversal storage unit 44. Recording paper 10
0 is sent to the image recording unit 1 and the recording paper 100 of the blank paper detection unit 24 is pulled into the reversal storage unit 44 and reversed and stored.

If part of the front and back surfaces of the recording paper 100 is blank, the recording paper 100 is ejected to the second paper ejection section 46. And the marking means 60 is
When the back surface of the recording paper 100 conveyed to the image recording unit 1 is not blank, a mark is printed on the back surface.

[0013]

Embodiments will be described with reference to the drawings. Figure 1
1 illustrates an electrophotographic full-color printer device to which the present invention is applied. However, the present invention can be applied to various image forming apparatuses such as a monochrome printer and a copying machine.

The left half of the apparatus is an image recording section 1 which forms and records an image on the recording sheet 100, and the right half is automatically set to the image recording section 1 one by one. It is an automatic paper feeding unit 2 that feeds paper to.

When recording in the image recording unit 1,
First, the charger 4 charges the surface of the photosensitive drum 5 to a negative potential. Then, the surface of the photosensitive drum 5 is exposed by the laser optical unit 6 to form an electrostatic latent image of an image to be recorded on the surface of the photosensitive drum 5.

The photosensitive drum 5 is driven to rotate in the arrow direction,
In the developing unit 7, color toner is selectively attached to the latent image on the photosensitive drum 5. The developing unit 7 has four sets of developing units 7a, 7b, 7c and 7d for recording four colors including black of three primary colors yellow, magenta and cyan.
Is provided, and development with yellow toner is first performed.

In the transfer section 8, the toner image on the photosensitive drum 5 is transferred to the transfer drum 9. After the transfer, the cleaner unit 10 cleans the photosensitive drum 5 to remove the residual toner, and the image forming process on the photosensitive drum 5 is repeated.

In the next step, a magenta developing unit 7b is used instead of yellow for development, and the magenta toner image is superposed on the transfer drum 9 while being aligned with the yellow toner image. . In the same manner, a cyan toner image and a black toner image are sequentially superposed on the transfer drum 9 to obtain a full color image.

When the four color toner images are overlaid,
The toner image is collectively transferred from the transfer drum 9 onto the recording paper 100 by the transfer device 13 arranged in the second transfer unit 12. Thereafter, the fixing device 14 heats and presses the recording paper 100 to fix the toner image on the recording paper 100.

After the transfer drum 9 is transferred to the recording paper 100, the cleaner 15 removes the residual toner, and the transfer drum 9 is used again for superimposing and transferring the toner images. The above operation is repeated to record a full-color image on the recording paper 100.

The automatic paper feeder 2 is shown enlarged in FIG. Reference numeral 21 denotes a paper feed tray for storing a large number of recording papers 100 in a stacked state and preparing them. The pickup roller 22 allows the recording papers 100 at the top to be stored.
Independently from the inside of the paper feed tray 21, the white paper detection unit 24
It is rolled out.

The blank paper detection unit 24 includes a back surface sensor 2 for detecting whether the back surface of the recording paper 100 is blank paper.
5 and a surface sensor 26 for detecting whether or not the surface of the recording paper 100 is blank.

FIG. 3 shows the back surface sensor 25. The light source 28 is provided so as to illuminate the back surface of the recording paper 100 over the entire width, the photoelectric element 29 for receiving the reflected light from the recording paper 100, and the recording paper. In order that the recording state on the front surface side of 100 does not affect the reflected light, the recording paper 100
And a back plate 30 for preventing the light transmitted therethrough from returning. Back plate 30
For this, it is preferable to use a black plate having an OD value (optical density) of 1.5 or more.

As the light source 28, as shown in FIG. 4, a part other than the irradiation direction is irradiated so that the light of the fluorescent lamp 28a having the width of A4 size is irradiated in only one direction. The one with the light-shielding cover 28b attached to
As shown in Fig. 6, a large number of light emitting diodes (LEDs) arranged in an A4 width, or, as shown in Fig. 6,
A4 width electroluminescent plate for one line 28d
Various light sources can be used, such as those using.

As the photoelectric element 29, as shown in FIG. 7, it is possible to use one in which the photoelectric elements 29 are arranged so that one photoelectric element 29 covers 2-3 dots. Is lower, it means that the amount of reflected light has decreased, and it can be seen that recording has been completed on the back surface of the recording paper 100.

Returning to FIG. 2, the front surface sensor 26 detects the state of the back surface of the recording paper 100 from below while the above-mentioned back surface sensor 25 detects the recording paper 1 from above.
00 for detecting the state of the front surface, and the configuration may be the same as that of the back surface sensor 25.

In the blank sheet detecting section 24, the recording sheet 100 is conveyed by the sheet conveying rollers 31 and 32, while the front surface sensor 25 and the rear surface sensor 26 sequentially detect the recording state of both the front and back sides.

The exit portion of the blank sheet detecting section 24 is a step having a step lower than the exit point, and a guide cover 34 for guiding the recording sheet 100 is provided above the step section 33. .

A paper conveyance roller (conveyance direction switching roller) 36 is provided in the middle of the paper conveyance path 35 beyond that.
Further, a stop position sensor 37 for detecting the recording sheet 100 and stopping the conveyance thereof is provided further ahead.

As the stop position sensor 37, a light source 38 and a photoelectric element 39 facing each other, an infrared transmitter / receiver and a reflecting plate facing each other can be used.

A sheet conveying roller (registration roller) 41 for conveying the recording sheet 100 to the image recording unit 1 is provided further on the sheet conveying path 35, and the recording sheet 100 is imaged at the same timing. It is conveyed to the recording unit 1.

As shown in FIG. 8, the step portion 33 has an opening to the entrance of the paper retreat path 43 that obliquely descends rearward. The roller 31 that sends out the recording sheet 100 from the blank sheet detection unit 24 is rotated at the same time, and the sheet retracting path 4 is provided on the lower surface.
The paper in 3 is conveyed.

In the middle of the paper evacuation path 43, the recording paper 10
A switching plate 48 for selectively switching the destination of 0 to either the direction of the reversing storage unit 44 or the direction of the first and second sheet discharge trays 45 and 46 is provided, and the first and second destinations ahead thereof are provided. A passage sensor 49 for detecting passage of the recording paper 100 is provided in front of the second paper discharge trays 45 and 46.

As the passage sensor 49, for example, as shown in FIG. 9, a conductive chain line 52 between electrodes 50 and 51 is provided.
It is possible to use, for example, a device in which the recording paper 100 is suspended and the electrodes 50 and 51 are insulated by passing the recording paper 100 between them, thereby detecting the passage of the recording paper 100.

A sorting roller 54 is disposed between the passage sensor 49 and the first and second sheet discharge trays 45 and 46 to select which tray the recording sheet 100 is to be discharged. In addition, recording paper 1 that has been recorded on both front and back
If 00 is to be uniformly discharged, only one sheet discharge tray is required and the sorting roller 54 is not necessary.

The reversal storage unit 44 is formed in a fan shape below the paper conveyance path 35, and the recording paper 100 that reaches the slope 56 of the reversal storage unit 44 from the paper retraction path 43 through the switching plate 48 is a natural paper sheet. The front and back of the recording paper 100 on the transport path 35 are reversed.

A sheet conveying roller (lower conveying roller) 57 is provided in the middle of the slope 56, the upper end portion of the slope 56 is opened to the sheet conveying path 35, and the recording sheet 100 is placed above the portion. Guide cover 58 for guiding
Is provided.

The stop position sensor 37 is disposed immediately before the upper end of the slope 56. The stop position sensor 37 is provided for the recording sheet 1 on the sheet conveyance path 35.
00 and the recording sheet 100 on the slope 56 of the reversal storage unit 44 are also used as stop position sensors, and also a sensor for detecting whether or not the recording sheet is in a standby position for being conveyed by the registration rollers 41. Also serves as.

Reference numeral 60 denotes a marking portion for printing a mark on the back surface side of the recording paper 100 conveyed to the image recording portion 1. The ink in the ink tank 61 is pushed out by the piezoelectric element 62 of the ink head. As shown in FIG. 16, the ink adheres to the surface of the transfer roller 64 through the nozzle 63, and the ink is transferred to the back surface of the recording paper 100 as shown in FIG.

The ink remaining on the surface of the transfer roller 64 without being transferred to the back surface of the recording paper 100 is removed by the cleaner 65. In addition, the content of the marking is, for example, a character such as “back side”, and the marking unit 60 may be omitted and not provided in some cases.

FIG. 10 is a block diagram of the configuration of the control system of the above embodiment. The control unit 70 includes a central processing unit (CP).
U) 71, a memory 72 and the like are included. And
The control unit 70 includes a detection signal from the stop position sensor 37, a detection signal from the passage sensor 49, and a back surface sensor 25.
Also, a detection signal from the surface sensor 26 is input.

The control signal output from the control unit 70 is, via the motor driver 74, the first motor 75 for driving the paper transport rollers (duplex transport rollers) 31, 32 and the first for driving the transport direction switching roller 36. Two motors 76,
The operations of the third motor 77 that drives the switching plate 48, the fourth motor 78 that drives the selection roller 78, and the fifth motor 79 that drives the lower conveyance roller 57 are controlled. The rotation of the pickup roller 22 is transmitted from the dual-purpose transport rollers 31 and 32 via the clutch 80.

The control signal output from the control unit 70 is sent to the registration roller 41 via the motor driver 81.
The operation of the sixth motor 82 for driving the ink jet head and the operation of the seventh motor 83 for driving the transfer roller 64 are controlled, and the operation of the piezoelectric element 62 is controlled via the ink head driver 84.

Next, the operation of the above embodiment will be described. The recording paper 100 is first taken out from the paper feed tray 21 by the pickup roller 22. Then, in order to grasp the printing state, while the recording sheet 100 is being conveyed by the conveyance rollers 31 and 32 in the blank sheet detection unit 24, the back surface sensor 25 and the front surface sensor 26 scan the back surface and the front surface in this order to detect the presence or absence of printing. It

When the surface sensor 26 determines that the recording is not performed (entire blank surface), the recording sheet 100 is conveyed by the conveying roller 36 as it is toward the image recording section 1 and is sent by the registration roller 41 at the same timing.

When the front surface sensor 26 determines that printing has been completed and the back surface sensor 25 determines that no recording has been performed (entire blank surface), the switching plate 48 is raised. Then, when the recording paper 100 is sent to the stop position sensor 37 by the transport roller 36, the transport roller 36 starts rotating in the opposite direction.

As a result, the recording paper 100 is conveyed in the opposite direction, and the front end of the recording paper 100 in the advancing direction has the step 3
3 to the paper retreat path 43 with the switching plate 48 automatically. Then, the leading edge of the recording sheet 100 is guided to the switching plate 48 and is conveyed to the slope 56 for holding the reversal sheet via the conveying rollers 32 and 57.

Recording paper 100 stored on slope 56
Is sent to the image recording unit 1 prior to that. Therefore, apparently, the paper is fed to the image recording unit 1 without taking time to reverse the recording paper 100.

When the back surface sensor 25 determines that printing has been completed,
The switching plate 48 is lowered, the transport roller 36 is rotated in the opposite direction, and the recording paper 100 is discharged onto the discharge trays 45 and 46.
Sent in the direction of.

When at least one of the front and back surfaces is a partially usable recording sheet, the sorting roller 54 is rotated in the forward direction with respect to the conveying direction so that the recording sheet 100 is transferred to the second discharge tray 46. Is discharged.

In the case of the recording paper 100 that cannot be partially used, the sorting roller 54 rotates in the direction opposite to the conveying direction, the leading end of the recording paper 100 is pushed downward, and the first discharge tray 45 is ejected. The recording paper 100 is ejected onto the sheet.

Whether or not the recording sheet 100 can be partially used is determined from the output changes of the front surface sensor 26 and the back surface sensor 25. FIG. 11 shows such a state, and when the detection output is at a high level over the entire range as shown in FIG.

Then, as shown in (B) to (D), when the detection output is at a low level, it is understood that the position has been recorded. Therefore, in the case of (B), only the second half can be reused, in the case of (C) only the first half can be reused, and in the case of (D), it cannot be reused.

12 to 15 are flow charts showing the control processing contents of the control unit 70, and S shows a processing step. Here, first, the recording paper 100 is fed from the paper feed tray 21 to the blank paper detection unit 24 by the pickup roller 22 (S1), and the blank paper detection unit 24 determines whether the entire surface of the recording paper 100 is blank paper. (S2).

When the entire surface of the recording paper 100 is blank, the recording paper 1 reaches the stop position sensors 38 and 39.
When the recording paper 100 starts to be conveyed from the registration roller 41 to the image recording unit 1, the next recording paper 100 is taken out from the paper feed tray 21. However, when the back side is not blank, the marking section 60 prints a mark on the back side (S
4, S5).

If the front surface of the recording paper 100 is not blank in S2, it is determined whether the back surface of the recording paper 100 is blank (S6). Therefore, if the entire back surface is blank, it is determined whether or not the recording paper 100 is stored in the reversal storage unit 44 (S7).

Then, the recording paper 100 is stored in the reversal storage unit 44.
If the recording paper 100 is not stored, after the recording paper 100 is conveyed to the stop position sensor 37, the conveyance roller 36 is reversed and the recording paper 100 is sent to the paper retreat path 43.

By raising the switching plate 48, the recording paper 100 is stored on the slope 56 of the reversal storage unit 44 with its front and back reversed, and the stop position sensor 38,
It waits at the position of 39 (S8). After this, one sheet of recording paper 100 is always in the reversal storage unit 44. Then, the next recording paper 100 is taken out from the paper feed tray 21.

When the recording paper 100 is stored in the reversal storage unit 44, the stored recording paper 100 is conveyed from the reversal storage unit 44 to the registration roller 41 (S
9), a mark is printed on the back surface (S10), and then the recording paper 100 on the paper transport path 35 is reversed to reverse the storage unit 4
It is stored on the slope 56 of No. 4 (S8).

If it is determined in step S6 that both the front and back sides of the recording paper 100 are not blank, the recording paper 100 is conveyed to the stop position sensor 37, and then the conveyance rollers 36, 32.
Is reversed and the recording sheet 100 is sent to the sheet retreat path 43. By lowering the switching plate 48, the recording paper 100 passes through the passage sensor 49 in the paper discharge direction and is sent to the selection roller 54 (S11).

As soon as the passage sensor 49 detects the discharge of the recording paper 100, the next recording paper 1 is removed from the paper feed tray 21.
The feeding of 00 is started. Further, when the back surface sensor 25 and the front surface sensor 26 can reuse at least one of the front and back surfaces of the recording sheet 100 as a blank sheet (S12), the sorting roller 54 can be used.
Is rotated in the forward direction to discharge the recording paper 100 to the second discharge tray 46 (S13). If there is no half blank paper, the selection roller 54 is rotated in the reverse direction to perform recording. The paper 100 is discharged to the first discharge tray 45 (S14). In this way, the reusable recording paper 100 is selected by cutting and discharged to the second discharge tray 46.

At the time of the mark printing in S5 and S10, as shown in the flow chart of FIG. 15, the mark printing is performed on the already recorded portion while avoiding the partially printable portion (S21- S25).

[0063]

According to the image forming apparatus of the present invention, it is possible to correctly perform recording on a blank surface without paying attention to the used state of the front and back sides of the recording sheets which are stacked and set on the sheet feeding tray or the like. When the back side of the recording sheet is blank and the front side is not blank, the recording sheet 100 that has been reversed in the reversing storage section and stored in advance is sent to the image recording section, so that the recording sheet is apparently turned upside down. It is possible to feed paper to the image recording unit at high speed without taking time to perform the operation.

If a part of both the front and back sides of the recording paper is blank, the recording paper is discharged to the second paper discharge unit, and therefore, it is separated from the discarded recording paper and is left blank. The part can be cut and reused easily.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment.

FIG. 2 is a configuration diagram of an embodiment.

FIG. 3 is a partial configuration diagram of an embodiment.

FIG. 4 is a partial configuration diagram of an embodiment.

FIG. 5 is a partial configuration diagram of an embodiment.

FIG. 6 is a partial configuration diagram of an example.

FIG. 7 is a partial configuration diagram of an example.

FIG. 8 is a partial configuration diagram of an example.

FIG. 9 is a partial configuration diagram of an example.

FIG. 10 is a block diagram of a control system of the embodiment.

FIG. 11 is a blank sheet detection output diagram of the embodiment.

FIG. 12 is a control processing flowchart of the embodiment.

FIG. 13 is a control processing flowchart of the embodiment.

FIG. 14 is a control processing flowchart of the embodiment.

FIG. 15 is a control processing flowchart of the embodiment.

FIG. 16 is an explanatory diagram of a marking unit according to the embodiment.

FIG. 17 is an explanatory diagram of a marking unit according to the embodiment.

[Explanation of symbols]

 1 Image Recording Section 2 Automatic Paper Feeding Section 22 Pickup Roller (Paper Feeding Section) 24 Blank Sheet Detection Section 36 Paper Conveying Roller 41 Registration Roller 44 Reversal Storage Section 45 Ejection Tray 48 Switching Plate 70 Control Section

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tomohisa Mikami 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Within Fujitsu Limited

Claims (3)

[Claims] 1. A blank sheet detection unit (24) for detecting whether the recording sheet (100) is a blank sheet or not, and one sheet of recording sheet (100) in the blank sheet detection unit (24). Paper feeding means (22) for feeding the recording paper (100) to the image recording portion (1) from the blank paper detection portion (24).
1) and a paper ejection means (36, 36) for ejecting the recording paper (100) from the blank paper detection portion (24) to the paper ejection portion (45).
48) and the recording sheet (100) is pulled in from the blank sheet detection section (24), the recording sheet (100) is reversed and stored, and the recording sheet (100) is stored in the image recording section (1). In response to the result of detection by the reversal storage unit (44) that can be sent out and the blank sheet detection unit (24),
When the surface of the recording paper (100) is blank, the recording paper (100) is transported from the blank paper detection unit (24) to the image recording unit (1) by the paper transport means (36, 41), and the recording paper (100) is transported. When both the front and back sides of (100) are not blank, the recording sheet (100) is discharged from the blank sheet detecting section (24) to the sheet discharging section (45) by the sheet discharging means (36, 48), and the recording sheet is discharged. When the back side of (100) is blank and the front side is not blank, the reversal storage section (4
The recording paper (100) stored in 4) is sent to the image recording unit (1), and the recording paper (100) of the blank paper detection unit (24) is drawn into the reversal storage unit (44) to turn it over. Control means (7)
0) and 0) are provided. 2. A blank sheet detecting section (24) for detecting whether the recording sheet (100) is a blank sheet by dividing it into front and back sides, and a recording sheet (100) in the blank sheet detecting section (24). A sheet feeding unit (22) for feeding the sheets one by one, and a sheet feeding unit (36, 4) for feeding the recording sheet (100) from the blank sheet detection unit (24) to the image recording unit (1).
1) and a paper ejection means (36, 36) for ejecting the recording paper (100) from the blank paper detection portion (24) to the paper ejection portion (45).
48), and the second paper output unit (46) from the blank paper detection unit (24).
A second sheet discharging means (54) for discharging the recording sheet (100) to the first sheet, and pulling the recording sheet (100) from the blank sheet detecting section (24) to reverse the front and back sides of the recording sheet (100). In response to the detection result of the reversal storage unit (44) that can store and send the recording paper (100) to the image recording unit (1),
When the surface of the recording paper (100) is blank, the recording paper (100) is transported from the blank paper detection unit (24) to the image recording unit (1) by the paper transport means (36, 41), and the recording paper (100) is transported. If all the front and back surfaces of (100) are not blank, the recording paper (100) is discharged from the blank paper detection unit (24) to the paper discharge unit (45) by the paper discharge unit (36, 48). When part of both the front and back sides of the recording paper (100) is blank, the recording paper (100) is removed by the second paper discharging means (54).
When the back surface of the recording paper (100) is blank and the front surface is not blank, the recording paper (100) stored in the reversal storage unit (44) is discharged to the image recording unit. The paper is sent to (1) and the blank sheet detection unit (2
An image forming apparatus comprising: a control unit (70) for controlling so that the recording paper (100) of 4) is drawn into the reversal storage unit (44) and inverted and stored. 3. In response to the detection result of the blank sheet detecting section (24), when the back side of the recording sheet (100) conveyed to the image recording section (1) is not a blank sheet, a mark is printed on that side. An image forming apparatus according to claim 1 or 2, further comprising marking means (60).