JP2001139219A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of forming images on both sides without paper jamming by a simplified constitution. SOLUTION: By normally rotating a both-side carrier means 8 provided on a paper discharging passage so as to be rotatable forward and backward, a sheet S formed with images on one side at the time of a one-side mode and a sheet S formed with images on both-sides at the time of a both-side mode are carried to a paper discharging part 9 and are discharged. By reversely rotating the both-side carrier means 8 after the means 8 is normally rotated for prescribed time at the time of the both-side mode, the sheet S formed with images on one side is reversed and carried to the both-side carrier part 2 after a part of the sheet S formed with images on one side is discharged to the paper discharging part 9. At the time of the both-side mode, when a control means determines that the paper discharging part 9 is a in full state based on a full detection signal from a full detection means 7 for detecting the full state of the paper discharging part 9, rotation of both-side carrier means 8 is controlled to prevent a reversal carrier of the sheet S.

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 laser printer capable of forming images on the front and back of a sheet, and more particularly, to a two-sided conveying unit after reversing a sheet having an image formed on one side. And transporting the image to an image forming unit.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, a sheet on which an image is formed on one side by an image forming unit is turned over, conveyed again to the image forming unit, and an image is formed on the back surface of the sheet. is there.

[0003] In an image recording apparatus such as a laser printer, which is an example of a conventional image forming apparatus, a double-sided conveying method in which a sheet is turned over and conveyed to an image forming section by a relatively large-sized, high-speed, and high-cost apparatus. 2. Description of the Related Art In some cases, an image is recorded on both sides of a sheet by installing a duplex conveying unit having a path as an option. In recent years, companies have been increasing the number of companies that instruct employees to print on both sides of sheets for environmental protection, and there is a growing desire to use a double-sided printing mechanism even for small, low-speed, low-cost laser printers. It is getting.

[0004]

In a conventional image forming apparatus such as a small-sized, low-speed, and low-cost laser printer, a low-cost double-sided printing mechanism is indispensable. Is configured to perform a reversal operation of double-sided printing by using a paper discharge unit for stacking discharged sheets after printing. That is, when performing double-sided printing, there is a type in which a part of a sheet printed on one side is discharged to a paper discharge unit, and then the sheet is turned over.

However, in the case of such a configuration, if the reversing operation is performed while the sheet discharge unit is in the full state, the stacked sheets may be pulled in together with the sheet to be reversed. When the other sheet is pulled in, the sheet to be reversely conveyed is jammed together with the other sheet. In this case, the operation of removing the jammed sheet by the user is very troublesome.
Further, when another sheet is jammed in this way, the page corresponding to this sheet must be printed again, which not only wastes paper but also requires time and labor for reprinting.

Accordingly, the present invention has been made in view of such a situation, and it is an object of the present invention to provide an image forming apparatus capable of forming an image on both sides without a paper jam with a simplified configuration. It is the purpose.

[0007]

According to the present invention, there is provided a single-sided mode in which an image is formed on one side of a sheet, and a sheet on which an image is formed on one side is turned over and then conveyed to an image forming section by a double-sided conveying section. An image forming apparatus having a double-sided mode for forming an image on the back surface of the sheet, wherein the sheet discharge unit stores the sheet discharged after an image is formed on one side or both sides of the one side and the back side A double-sided conveyance means provided in a paper discharge path for conveying the sheet having an image formed on one or both sides thereof to the paper discharge section so as to be able to rotate forward and reverse, and a full load detection for detecting a full load state of the paper discharge section Means for transporting a sheet having an image formed on one side thereof in the one-sided mode, and a sheet having an image formed on both sides thereof in the two-sided mode to the paper discharge unit. While rotating forward, the double-sided At this time, after a part of the sheet having an image formed on one side is discharged to the paper discharge unit, the double-sided conveying unit is rotated forward for a predetermined time so that the sheet is reversely conveyed to the double-sided conveying unit, and then the reverse rotation is performed. Control means for rotating,
In the duplex mode, when the control unit determines that the paper discharge unit is in a full load state based on a full load detection signal from the full load detection unit, the control unit does not perform reverse conveyance of the sheet. It is characterized in that the rotation of the double-sided conveying means is controlled.

The present invention further comprises mode designation means for designating the one-sided mode and the two-sided mode, wherein the control means controls the rotation of the two-sided conveyance means in accordance with the mode designated by the mode designation means. When the two-sided mode is designated, if it is determined that the paper discharge unit is in a full load state, the rotation of the two-sided conveying unit is controlled so that the sheet is not reversely conveyed. Is what you do.

Further, according to the present invention, the control means determines whether or not the sheet discharge section is fully loaded before performing the reverse conveyance of the sheet, and the sheet discharge section is fully loaded. When the determination is made, the rotation of the double-sided conveying means is controlled so that the sheet is not reversed and conveyed.

Further, according to the present invention, when the sheet is reversed and conveyed, it is determined whether or not the paper discharge unit is in a full load state, and the paper discharge unit is in a full load state. When the determination is made, the rotation of the double-sided conveying means is controlled so that the sheet is not reversed and conveyed.

Further, according to the present invention, when the sheet is reversed and conveyed, it is determined whether or not the paper discharge unit is in a full load state, and the paper discharge unit is in a full load state. After the determination, the rotation of the double-sided conveyance means is controlled so that the sheet is not reversed and conveyed when the paper discharge section remains in the full load state even after a predetermined time has elapsed.

Further, in the present invention, the control means rotates the double-sided conveying means in a forward direction so as to discharge the sheet on which an image is formed on one side to the discharge section when the reverse conveyance of the sheet is not performed. It is characterized by the following.

Further, the present invention is characterized in that the control means, when it is determined that the paper discharge unit is in a full load state, notifies the full load of the paper discharge unit.

Further, by configuring as in the present invention,
The control unit rotates the double-sided conveying unit provided in the paper discharge path so as to be capable of normal and reverse rotation, so that the sheet on which an image is formed on one side is used in the single-sided mode, and the sheet is printed on both sides in the double-sided mode. The sheet on which the image has been formed is conveyed to the paper discharge unit and discharged. Further, in the double-sided mode, after rotating the double-sided conveying unit in the normal direction for a predetermined time and then rotating the double-sided conveying unit in reverse, a part of the sheet having an image formed on one side is discharged to the sheet discharging unit, and then inverted to the double-sided conveying unit Transport. Then, in the duplex mode, when it is determined that the paper discharge unit is in the full load state based on the full load detection signal from the full load detection unit that detects the full load state of the paper discharge unit, the rotation of the double-sided conveyance unit is stopped. Control so that the sheet is not reversed and conveyed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram illustrating a schematic configuration of a laser beam printer as an example of an image forming apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 1A denotes a laser beam printer. This laser beam printer 1A forms a single-sided mode in which an image is formed on one side of a sheet of paper, and forms an image on the back side of the sheet having an image formed on one side. And a double-sided mode. Reference numeral 1 denotes a laser beam printer main body (hereinafter, referred to as a main body); 2, a double-sided conveyance unit having a double-sided conveyance path R2 and detachably attached to the main body 1; and 3, a paper cassette for storing sheets.

The paper stored in the paper cassette 3 is fed in the direction of L1 by driving the cassette feeding roller 3a and the pair of conveying rollers 3b, and thereafter driven in the direction of L2 by driving the pair of conveying rollers 3c. Transported to

Reference numeral 4 denotes a laser scanner unit which raster-scans a laser beam based on image data from a host computer or the like, which will be described later, and turns a mirror on a photosensitive drum 5a which is charged in advance by a charger 5b. 4a forms an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 5a is developed by a developing unit 5c with toner, and then transferred to a sheet conveyed by a pair of conveying rollers 3c in a transfer unit 5d. Reference numeral 5 denotes an image forming unit including a laser scanner unit 4, a photosensitive drum 5a, a charger 5b, a developing unit 5c, and a transfer unit 5d.

Further, the toner image transferred onto the sheet is fixed on the sheet by the heat fixing device 6. The heat fixing device 6 includes a heating element (not shown) and a thermistor for detecting the temperature of the heating element, and applies heat and pressure to the sheet after the transfer process to fix the toner image on the sheet. Is configured.

Reference numeral 7 denotes a paper discharge roller pair, and the paper that has passed through the heat fixing device 6 is discharged by the paper discharge roller pair 7 to the face-up tray 10 or a paper discharge unit provided on the upper surface of the main body 2. The paper is discharged to a face-down paper discharge unit 9. Here, the face-up tray 10
The face-up tray 10 is provided so as to be openable and closable on the main body 1, and when the paper is discharged in a face-up state, the face-up tray 10 is opened as shown in FIG.

On the other hand, when the paper is to be discharged face down, the face-up tray 10 is closed as shown in FIG. A paper discharge path R1 for carrying the sheet to the down paper discharge unit 9 is secured.

When the paper discharge path R1 is secured in this way, the paper disposed on the downstream side of the paper discharge path R1 and having an image formed on one or both sides is transferred to the face-down paper discharge section 9. By rotating the face-down discharge roller pair 8 in the direction of arrow a (forward rotation), which is a double-sided transporting means capable of transporting the paper forward and reverse, the paper on which an image is formed on one side is used in the single-sided mode, and The sheet on which images are formed on both sides can be discharged to the face-down sheet discharge section 9.

In the duplex mode, the face-up tray 10 is closed, and the face-down discharge roller pair 8 is rotated forward for a predetermined time so that the paper printed on the first face (front face) is face-down. After the paper is conveyed in the direction of the paper discharge unit 9 and a part of the paper is discharged to the face-down paper discharge unit 9, the face-down paper discharge roller pair 8 is rotated in the reverse direction so as to face the double-sided conveyance unit 2.

The sheet thus directed to the two-sided conveyance section 2 is conveyed to the two-sided conveyance path R2 shown in FIG. 1 by the reversing sheet guide roller 11, and the sheet conveyed to the two-sided conveyance path R2 is turned over. L4 by paper transport roller pair 12
Is stopped in front of the pair of reversing paper re-feed rollers 13 and stands by until the paper is re-fed as the paper for the second side (back side) of the double-sided printing.

In FIG. 1, S6 is a re-feed sensor provided in the double-sided conveyance section 2, and the re-feed sensor S6 detects that the sheet conveyed to the double-sided conveyance path R2 is at a predetermined re-feed position. Is detected, the detection signal is output to the CPU 14A of the engine controller 14 which is a control means shown in FIG.

Then, C of the engine controller 14
The PU 14A stops the reversing sheet transport roller pair 12 based on the detection signal from the re-feeding sensor S6 and causes the sheet to wait at a predetermined re-feeding position. 13 is driven. As a result, the sheet waiting in the double-sided conveyance path R2 is re-fed to the image forming unit 5 via the conveyance roller pair 3c, and then is transferred on the same conveyance path as the printing operation from the paper cassette 3 described above. The printing operation on the second side (back side) of the printing is performed, and then the sheet is discharged to the face-down sheet discharge section 9.

In FIG. 3, reference numeral S3 denotes a paper discharge sensor for detecting that the paper has passed through the thermal fixing device 6, and S4 denotes a face-up tray open / close detection sensor for detecting opening / closing of the face-up tray 10. Face-up tray 1 by up-tray open / close detection sensor S4
CPU 14A when it is detected that
Performs the face-down sheet ejection and the sheet conveyance to the two-sided conveyance path R2 described above.

In FIG. 1, S1 is a paper sensor for detecting the presence or absence of paper in the paper cassette 3, and S2 is a paper feed sensor for detecting the leading edge and the trailing edge of the paper transported by driving the transport roller pair 3c. The CPU 14A determines the image writing timing based on the detection signal from the paper feed sensor S2. S5 is a reverse paper introduction detection sensor that detects the timing at which the paper is transported to the duplex transport path R2 and the leading and trailing edges of the paper.

FIG. 3 is a block diagram of a printer controller for controlling the above-mentioned series of printing operations. The printer controller includes an engine controller 14 and an image controller 15.

Here, after receiving the coded image information (code data) from the host computer 17 or the like via the external interface 16, the image controller unit 15 converts the code data into dot image video data, A print command is sent to the CPU 14A of the engine controller 14 via the video interface 18, and video data is sequentially sent to the engine controller 14 in synchronization with the main scan and sub-scan synchronization signals from the engine controller 14. It is composed.

The CP of the engine controller 14
The U14A monitors the drive of the sheet discharge roller 7, the face-down sheet discharge roller pair 8, the other transport roller pairs, and the like, and monitors the input from the face-up tray open / close detection sensor S4 and other sensors to thereby control the laser scanner unit 4,
The printer controller controls the printer engine such as the heat fixing device 6 and prints the video data from the image controller 15 on paper.

In the figure, reference numeral 20 denotes a print mode designating unit which is a mode designating means for designating a single-sided mode and a double-sided mode. Is specified.

Reference numeral 21 denotes a timer, which is a CPU 14A
For example, after a detection signal is input from a paper discharge sensor S3 that detects that a sheet has passed through the heat fixing device 6, the face-down discharge roller pair 8 is rotated forward in the direction of arrow a for a predetermined time to perform face-down discharge. The paper is conveyed in the direction of the paper section 9 and the timer 21 starts counting time. The CPU 14A reverses the face-down sheet discharge roller pair 8 based on the timing information from the timer 21.

In FIG. 1 and FIG. 1, reference numeral S7 denotes a full load detecting sensor which is a full load detecting means for detecting whether or not the paper S discharged to the face-down discharge section 9 is in a full load state. The full-load detection sensor S7 outputs a full-load detection signal to the CPU 14A when detecting that the face-down paper discharge section 9 is in a full-load state.

Here, when the full load detection signal is input from the full load detection sensor S7 as described above, the CPU 14A determines that the paper S is in the full load state based on the full load detection signal, and issues a print request in the duplex mode. In addition to not accepting the information, the fact that it is full is notified to a host computer or the like.

When the paper S becomes full, the print request in the double-sided mode is not accepted, thereby preventing the sheet from being reversed and conveyed. Paper jams can be prevented. In this embodiment, when the sheet S is fully loaded, the sheet is not reversed and the one-sided printing operation is performed from the next page onward.

Next, the control operation of the CPU 14A will be described with reference to the flowchart of FIG.

First, the CPU 14A sets the print mode designating section 2
It is determined whether or not the single-sided mode is designated as the print mode by F. 0 (F401). If the single-sided mode is designated (Y of F401), the full load detection sensor S7 then determines whether the face-down discharge unit 9 is full. It is determined whether or not it has been detected (F403). If the full load sensor S7 has not detected a full load (N in F403), a print request is accepted and a one-sided printing operation is started (F404).

If the single-sided mode is not specified as the print mode (N in F401) and the double-sided mode is specified (Y in F402), then it is determined whether or not the full load sensor S7 detects full load. A judgment is made (F403). And
If the full load detection sensor S7 has not detected full load (F
In N) of 402, the print request is accepted and the double-sided printing operation is started (F404). If the one-sided mode is not specified (N in F401) and the two-sided mode is not specified (N in F402), the process returns to F401 and waits for a print request.

On the other hand, if the full load sensor S7 detects full load (Y in F403), the full load information is notified to the host computer 17 or the like without accepting the print request (F).
405). Further, the process returns to F401, and waits for the input of the next print request and the state where the full load detection sensor S7 does not detect the full load.

When the full load detection sensor S7 detects the full load state as described above, by not accepting the double-sided mode designation, that is, by not performing the reverse conveyance of the sheet, In the duplex mode, after a part of the paper is discharged to the face-down paper discharge unit 9 in a full load state, when the paper is reversed and conveyed, the face-down paper discharge unit 9 is used.
Other already printed paper loaded on the printer can be prevented from being pulled in.

Thus, paper jam can be prevented, and waste of paper caused by performing printing again can be eliminated. Also, as described above, the full load detection sensor S
When the full load state is detected, the apparatus can be simplified by not performing the reverse conveyance of the double-sided printing. Further, when the full load detection sensor S7 detects the full load state, the full load information is reported to the host computer to inform the user of the removal of the full load paper, and the full load state can be eliminated more quickly.

By the way, the case where the face-down discharge unit 9 is determined to be full when the duplex mode is designated has been described above. Even when the paper unit 9 is fully loaded, the face-down paper discharge unit 9 is not used until the reverse conveyance by the face-down paper discharge roller pair 8 is started for the paper on which the transfer of the image to the first surface and the fixing have been completed. The paper may be removed from the paper.

When the sheet is removed from the face-down sheet discharging section 9 as described above, even if the sheet is reversed and conveyed, other sheets stacked on the face-down sheet discharging section 9 are not pulled in. Therefore, double-sided printing can be performed.

Then, in such a two-sided mode, after the transfer and fixing of the image on the first side are completed, the face-down discharge rollers 8 start reversing the face of the sheet. A description will be given of a second embodiment of the present invention in which the full loading state of the down sheet discharging section 9 is determined.

FIG. 5 is a flowchart showing the control operation of the CPU 14A of the image forming apparatus according to this embodiment. If the print mode designating section 20 designates the duplex mode, the CPU 14A first prints on the first side. Then, the sheet passing through the heat fixing device 6 is directed to the sheet discharge path R1, and thereafter, the face-down sheet discharge roller pair 8 is moved in the direction of arrow a.
The paper is conveyed in the direction of the face-down paper discharge unit 9 while being rotated forward in the direction for a predetermined time, and a part of the paper is discharged to the face-down paper discharge unit 9.

At the same time, the timer 21 is operated based on a detection signal from the sheet discharge sensor S3 for detecting that the sheet has passed the thermal fixing device 6, and the reversing operation is performed based on the time measurement information from the timer 21. Is determined (F501), and if it is an inversion timing (F501)
Next, it is determined whether the full load detection sensor S7 detects the full load state (F502). Here, if the full load detection sensor S7 has not detected the full load state (F50
2N), the face-down discharge roller pair 8 is inverted,
The reverse transport of the sheet is started (F503). This allows
The printing operation on the second side (back side) of the double-sided printing is performed.

On the other hand, if the full load detection sensor S7 detects the full load state (Y in F502), the face-down discharge roller pair 8 is not inverted, the discharge operation is started, and the one-side printed sheet is left as it is. The sheet is discharged to the face-down sheet discharge section 9 (F504). After this, while the full load detection sensor S7 is detecting the full load state, that is, until the paper is removed from the face-down discharge unit 9, the one-sided printing reception of the next page is permitted, and the printing operation on one side is enabled. (F
505).

By detecting the full loading state when the reverse transport is started, the face-down discharge section 9 is fully loaded by the timing when the reverse transport is started for the sheet on which printing on the first side is completed. Even in the state, the full load detection sensor S
When it is detected that the sheet 7 is not in the full load state, the sheet is reversely conveyed to the double-sided conveyance path as it is, and the double-side mode operation on the sheet can be continued.

When the full load sensor S7 detects that the paper is full, the discharge of the paper to the face-down paper discharge section 9 is completed, and the duplex mode operation for the paper is terminated. A single-sided printing operation can be accepted.

In this embodiment, the case where the full loading state is detected at the time of starting the reverse conveyance has been described. However, the present invention is not limited to this.
For example, when a sheet passes through the heat fixing device 6, the sheet ejection sensor S
3, the full load state may be detected based on the detection signal.

In the present embodiment, the full-load state of the face-down sheet discharge section 9 is detected not when the double-sided mode is designated but when the reverse conveyance is started. The paper may be removed from the face-down paper discharge unit 9 when the operation is started.

When the sheet is removed from the face-down sheet discharge section 9 when the reverse conveyance is started, the sheet is stacked on the face-down sheet discharge section 9 even when the sheet is reversed and conveyed. Since no other paper is drawn in, double-sided printing can be performed.

Therefore, the next time the sheet is reversed and conveyed, the full state of the face-down sheet discharging section 9 is determined after waiting for the sheet to be removed from the face-down sheet discharging section 9 for a predetermined time. The third embodiment will be described.

FIG. 6 is a flowchart showing the control operation of the CPU 14A of the image forming apparatus according to the present embodiment. If the double-sided mode is specified by the print mode specifying unit 20, the CPU 14A first prints on the first side. Then, the sheet passing through the heat fixing device 6 is directed to the sheet discharge path R1, and thereafter, the face-down sheet discharge roller pair 8 is moved in the direction of arrow a.
The paper is rotated in the positive direction for a predetermined time, and is conveyed in the direction of the face-down paper discharge unit 9.

Next, it is determined whether or not it is the inversion operation timing based on the time information of the timer 21 (F501). Here, if it is the reversing evening (Y in F601), the face-down discharge roller pair 8 is not immediately reversed, and a new time measurement is started by the timer 21 from this timing (F602), and the full load detection sensor It is determined whether the full load is detected in S7 (F603).

If the full load sensor S7 has not detected full load (N in F603), the timing is ended (F604), and the reverse conveyance is started (F605).
Continue the back side printing operation of double sided printing.

On the other hand, when the full load detection sensor S7 detects a full load (Y in F603), it is determined whether or not the standby time for newly starting time measurement by the timer 21 has timed out (F606). Until the time is over (Y in F606), the process waits until the full load state is removed.

If the user removes the sheet from the face-down sheet discharge section 9 before the waiting time expires (N in F606) and the full load detecting sensor S7 stops detecting the full load (N in F603). The timing is ended (F604), and the reverse conveyance is started (F60).
5) Continue the back side printing operation of double sided printing.

When the standby time has elapsed without removing the sheet from the face-down sheet discharge section 9 (Y in F606), the time measurement is terminated (F607), and the face-down sheet discharge roller pair 8 is not inverted. Then, the paper discharge operation is started, and the paper printed on one side is directly discharged to the face-down paper discharge unit 9 (F608). After that, the reception of the single-sided printing of the next page is permitted, and the printing operation is enabled (F609).

When the full load detecting sensor S7 detects that the full load is in the full load state at the timing when the reverse conveyance is started, the standby state is waited for the full load state to be released. Then, it is possible to continue the double-sided mode operation on the sheet.

After waiting for a certain period of time, the discharge of the sheet to the face-up tray is completed, the duplex mode operation on the sheet is completed, and the one-side printing operation of the next page can be accepted.

[0064]

As described above, according to the present invention, in the double-sided mode, when it is determined that the paper discharge section is full, the rotation of the double-sided conveying means is controlled to reverse the sheet. Since conveyance can be prevented, images can be formed on both sides without paper jam. Further, this can save paper waste and trouble of reprinting. Further, even when the paper discharge unit is in the full load state, by performing the single-sided printing operation of the next page, it is possible to provide a user-friendly image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a laser beam printer as an example of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the laser beam printer.

FIG. 3 is a control block diagram of a printer controller of the laser beam printer.

FIG. 4 is a flowchart illustrating a control operation of a CPU of the printer controller.

FIG. 5 is a flowchart illustrating a control operation of the image forming apparatus according to the second embodiment of the present invention.

FIG. 6 is a flowchart illustrating a control operation of the image forming apparatus according to the third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1A Laser beam printer 1 Laser beam printer main body 2 Double-sided conveyance section 5 Image forming section 8 Face-down discharge roller pair 9 Face-down discharge section 10 Face-up tray 14A CPU 20 Print mode designation section 21 Timer S3 Discharge sensor S7 Full load detection Sensor R1 Paper discharge path R2 Double-sided conveyance path S Paper

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) 9A001 F term (Reference) 2H027 DA38 DC12 ED16 FA11 FA13 GA30 GB05 2H028 BA06 BA09 BA16 BB04 3F048 AA03 AA05 BA04 BB02 DA03 EA14 EB22 3F053 BA03 BA14 LA03 LA07 LB01 3F100 AA02 CA12 CA13 EA02 EA03 9A001 HZ34 JJ35 KK32 KK42 KZ29

Claims (7)

[Claims] 1. A single-sided mode in which an image is formed on one side of a sheet, and after the sheet on which an image is formed on one side is inverted, the sheet is conveyed to an image forming unit by a double-sided conveying unit, and the image is formed on the back side of the sheet. An image forming apparatus having a double-sided mode for forming, wherein an image is formed on one side or both sides of one side and the back side, and then a sheet discharge unit for storing the sheet to be discharged, and the one side or both sides Double-sided conveyance means provided in a paper discharge path for conveying a sheet on which an image is formed to the paper discharge section so as to be able to rotate forward and backward; full load detection means for detecting a full load state of the paper discharge section; In the double-sided mode, the double-sided conveying means rotates the double-sided conveying means so as to convey the sheet on which an image is formed on one side, and in the double-sided mode, the sheet on which the image is formed on both sides. At the time, the image on one side Control means for, after discharging a part of the formed sheet to the paper discharge section, rotating the double-sided conveying means forward for a predetermined time so as to reversely convey the sheet to the double-sided conveying section, and then rotating the sheet reversely. The control unit does not perform reverse conveyance of the sheet when the control unit determines that the discharge unit is in the full load state based on the full load detection signal from the full load detection unit in the double-sided mode. An image forming apparatus, wherein the rotation of the double-sided conveying means is controlled. 2. A mode designation means for designating the one-sided mode and the two-sided mode, wherein the control means controls the rotation of the two-sided conveyance means in accordance with the mode designated by the mode designation means, and When a mode is designated, when it is determined that the paper discharge unit is in a full load state, the rotation of the double-sided conveyance unit is controlled so as not to perform reverse conveyance of the sheet. 2. The image forming apparatus according to 1. 3. The control unit determines whether or not the sheet discharge unit is fully loaded before performing reverse conveyance of the sheet, and determines that the sheet discharge unit is fully loaded. 2. The image forming apparatus according to claim 1, wherein the rotation of the double-sided conveyance unit is controlled so as not to perform the reverse conveyance of the sheet. 4. The control unit determines whether or not the sheet discharge unit is full when the sheet is reversed and conveyed, and determines that the sheet discharge unit is fully loaded. 2. The image forming apparatus according to claim 1, wherein the rotation of the double-sided conveyance unit is controlled so as not to perform the reverse conveyance of the sheet. 5. The control unit determines whether or not the sheet discharge unit is fully loaded when performing the reverse conveyance of the sheet, and determines that the sheet discharge unit is fully loaded. 2. The method according to claim 1, further comprising: controlling rotation of the double-sided conveyance unit so that the sheet is not reversely conveyed when the discharge unit remains in the full load state even after a predetermined time has elapsed.
The image forming apparatus as described in the above. 6. The control device according to claim 1, wherein when the sheet is not reversely conveyed, the double-sided conveyance device is rotated forward so as to discharge the sheet having an image formed on one side to the sheet discharge unit. The image forming apparatus according to claim 1, wherein: 7. The apparatus according to claim 1, wherein the control unit notifies a full load of the paper discharge unit when the control unit determines that the paper discharge unit is full. The image forming apparatus as described in the above.