JP2002012374A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device allowing miniaturization of the device, attaining high productivity when forming both surface images. SOLUTION: A pair of carrier rollers 28a and 28b are driven and controlled to locate a tip position of a sheet S once stopping and standing by at a position 7d just before the downstream of a joining part 7c with a carrier path from a sheet storing part 1b in the middle of a recarrier path. As a result, standby space corresponding to the carrying direction length of the sheet S can be secured within the carrier path from a termination part 7a of the recarrier path to the direct before position 7d, the sheet S is once stopped and stood by in the recarrier path, a carrying operation for forming both surface images of the sheet S just after the sheet S can be performed, the length of the carrier path from the termination part 7a to the joining part 7c can be made shorter than that in a conventional way and thereby the compact device can be realized.

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 for forming a double-sided image, such as a copying machine, a facsimile, and a printer.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus,
For example, there is one shown in FIGS.

FIG. 3 is a schematic sectional view showing an image forming apparatus main body. In FIG. 3, a sheet S is stored in a sheet feed tray 1 (1
a to 1d), the sheet is fed to the separation roller pair 121 by the pickup roller 120 and fed, and is passed through the conveyance path 8;
The sheet is conveyed in synchronization with the rotation of a photosensitive drum (not shown) by the registration roller pair 130, and the toner image is transferred from the photosensitive drum to the upper surface by the transfer unit 2. Then, the toner on the sheet S passes through the transport unit 3 and is thermally fixed by the fixing unit 4.

[0004] The toner image transferred onto the sheet S by the transfer means 2 is exposed by an exposure means after the photosensitive drum is primarily charged by a charging means, so that an electrostatic latent image is formed on the surface of the photosensitive drum. The electrostatic latent image is visualized and formed by toner supplied from a developing unit (not shown).

[0005] The image forming means performs the steps until the toner image is thermally fixed on the sheet S as described above. The image forming unit may have another configuration such as an inkjet system.

Then, the sheet S after image formation is straight discharged (conveyance path 5a-conveyance path 5f (first conveyance path)),
Reverse discharge (conveyance path 5a-conveyance path 5b (second conveyance path)-conveyance path 5c (third conveyance path)-conveyance path 5e-conveyance path 5f),
Alternatively, for double-sided image formation, the sheet is re-conveyed to the transfer unit 2 again (conveying path 5a-conveying path 5b-conveying path 5d-conveying path 5h as reverse conveying path (fourth conveying path) -conveying path 5j-re-conveying). Transport paths 5g, 6a, 6c, 7).

In FIG. 3, a double-sided reversing unit (U) surrounded by a broken line indicates a transport path (5) for double-sided image formation.
d, 5h, 5j, 5g, 6a, 6c,) are provided, and this double-sided reversing unit (U) is configured to be detachable from the apparatus main body in a drawer type.

[0008] The double-sided reversing unit (U) is provided with an arc transport path (transport path 5h-transport path 5j) which is a transport path on an arc.
A large-diameter roller 25 as a forward / reverse transport roller having the same curvature on the outer peripheral surface as the curvature of the transport path 5g). That is, the large-diameter roller 25 is a transport roller having the inner peripheral surface of the arc transport path as the outer peripheral surface. Driven rollers 26a and 26b are provided around the large-diameter roller 25, and the driven rollers 26a and 26b rotate integrally with the large-diameter roller 25.

The conveyance of the sheet S after the fixing means 4 will be described in detail sequentially along the flow of the sheet S with reference to FIG.

The switching between the straight discharge and the reverse discharge is performed by switching the first discharge flapper 51.
The switching of the first discharge flapper 51 is performed using a driving means such as a solenoid (not shown).

In the case of reverse discharge, the sheet S is guided to the transport path 5c via the transport path 5b by switching the first discharge flapper 51, and by switching the double-sided first flapper 21 as switching means. Switching of the double-sided first flapper 21 is performed by using a driving means such as a solenoid (not shown).

The conveyed sheet S is applied to a large-diameter roller 2.
The rotation of the roller 5 in the counterclockwise direction and the rotation of the driven roller 26a cause the sheet 5 to be drawn into the transport path 5g. At this time, the arrival of the sheet S is detected by the sheet detecting means 27a provided downstream of the driven roller 26a.

The CPU of the apparatus main body uses the large-diameter roller 2 based on the signal of the arrival of the sheet S and the information on the length of the sheet S in the conveying direction.
The drive of the large-diameter roller 25 is controlled by judging the timing of the stop and reversal (clockwise rotation) of the roller 5.

The CPU stops and reverses the large-diameter roller 25 when the rear end of the sheet S is located before passing through the second sheet discharging flapper 52 and reaching the double-side reversing unit (U).

The second paper discharge flapper 52 is urged leftward in the figure by a spring force, its own weight, or the like, to prevent the sheet S from flowing upward in the figure in the direction of the conveying path 5b after reversing, and Sheet S is in the conveying path (conveying path 5e-conveying path 5f)
It is provided to be guided to.

When the sheet S to be reversed and discharged has a long length in the conveying direction, the conveying rollers 28a and 28b are
And drives the sheet S in synchronization with the length of the sheet S.

In the case of double-sided image formation, the sheet S is guided through the transport path 5b by switching the first discharge flapper 51, and guided to the transport path 5d by switching the first double-side flapper 21.

The conveyed sheet S is applied to a large-diameter roller 2.
Due to the clockwise rotation of 5 and the rotation of the driven roller 26b, the sheet 5 is drawn into the transport path 5h. At this time, the arrival of the sheet S is detected by the sheet detecting means 27b provided downstream of the driven roller 26b.

Based on the arrival signal of the sheet S and the information on the length of the sheet S in the conveying direction, the CPU of the apparatus main body determines the large-diameter roller 25.
, And the drive of the large diameter roller 25 is controlled.

The CPU stops and reverses the large-diameter roller 25 when the rear end of the sheet S is located before passing through the second-side second flapper 22 and reaching the driven roller 26b.

The double-sided second flapper 22 is urged downward in the drawing by a spring force, its own weight, or the like, similarly to the second paper discharge flapper 52, and after reversing, in the direction of the transport path 5d of the sheet S going leftward in the drawing. Is provided so that the sheet S after the reversal is guided to the conveyance path 5j.

The sheet S conveyed along an arc conveying path (conveying path 5j-conveying path 5g) along the outer peripheral surface of the large-diameter roller 25.
Are transport roller pairs 28a, 28b, 28e arranged in order,
28c, the transfer path from the transfer path 5g to the transfer path (the transfer path 6a-
The sheet is conveyed along the conveyance path 6c), merges again into the conveyance path 8, and is conveyed to the transfer unit 2 to form the second image.

The image forming apparatus performing the above operation is
In recent years, for example, copiers have also been digitized, and have become multifunction peripherals that also have functions such as a printer and a facsimile. In recent years, these multifunction devices have been required to have higher speed in order to improve productivity.

In order to realize such a high speed, conventionally, as one method for realizing the high speed, when the sheet S is conveyed to the transfer unit 2, the sheet S in the conveyance path to the transfer unit 2 is used. Is performed at high speed.
The high-speed transport control will be described below with reference to FIGS.

The sheet S is separated from the sheet storage sections 1 (ad) by a pickup roller 120 by a separation roller pair 121.
Sent to The separation roller pair 121 conveys only one uppermost sheet S among the sheets S picked up by the pickup roller 120 to the conveyance roller pair 122 or 28d.

A sensor 113 for detecting the leading end of the sheet S is provided immediately before or immediately after the pair of conveying rollers 122 and 28d, and the sheet S whose leading end is detected by the sensor 113 is held between the pair of conveying rollers 122 and 28d. Once stopped, it stops and waits at a predetermined position.

Thereafter, the sheet is conveyed again at a timing at which the sheet S conveyed immediately before is at a predetermined conveying interval.

This is because during high-speed transport control, the transport speed of the sheet S can be increased by optimizing the transport interval with the immediately preceding transported sheet S. If this control is omitted, the next sheet S conveyed at an increased speed to the immediately preceding sheet S being conveyed at a predetermined speed by the registration roller pair 130 toward the transfer means 2 catches up, and the sheet S is damaged. This is because there is a possibility that the sheet will be fed or overlapped.

After the correction of the conveyance interval as described above, the sheet S is transferred from the transfer unit 2 to the registration roller pair 130.
It is conveyed at a speed higher than the above conveying speed. Thereafter, this control is repeatedly performed.

When performing double-sided image formation, a re-conveying path (conveying path 5g-conveying path 6a-
The leading end of the sheet S is detected by the sensor 115 arranged in the middle of the conveying path 6c), and the sheet S is temporarily stopped and waits at a predetermined position in a state where the sheet S is held between the conveying roller pair 28b. The conveyance is started again at a timing at which the sheet S to be conveyed has a predetermined interval.

At this time, the leading end of the sheet S, which temporarily stops and waits, is positioned upstream (in the left direction in the drawing) in the transport direction from the junction 7c where the transport path from the sheet storage section 1b merges in the middle of the re-transport path. I was trying to make it.

[0032]

However, in the case of the above-described prior art, the following problems have occurred.

In the double-sided reversing unit (U) shown in FIG. 4, high-speed conveyance control is performed in order to secure high productivity. Transports the sheet S to be subsequently imaged on both sides without affecting the temporarily stopped and waiting sheet S.
Need to be transported to

For this reason, the front end position of the sheet S to be temporarily stopped and waited is set to be on the upstream side in the conveyance direction from the merging portion 7c where the conveyance path from the sheet storage section 1b joins the middle of the re-conveyance path, and is temporarily stopped and waited. Sheet S to be rolled is a large diameter roller 25
It is necessary to secure a standby space corresponding to the length of the sheet S in the transport direction in the transport path from the terminal end 7a of the arc transport path (5c-5g) to the merging section 7c so as not to be affected by the above. However, the length of the transport path from the terminal end 7a to the junction 7c must be sufficiently long.

Since a transport path from the long end portion 7a to the merging portion 7c is required, it is not possible to reduce the size and space of the image forming apparatus main body.

The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to achieve high productivity in forming a double-sided image and reduce the size of the image forming apparatus. It is to provide a device.

[0037]

According to the present invention, there is provided an image forming means for forming an image on one side of a conveyed sheet, and an image forming means for forming an image on both sides of the sheet by the image forming means. An image forming apparatus comprising: a re-conveying path that conveys a sheet on which a single-sided image has been formed to the image forming unit again; and a sheet storage unit that feeds the sheet to a conveying path that joins in the middle of the re-conveying path. In the forming apparatus, the sheet on which the one-sided image is formed is temporarily stopped in the re-conveying path, and when the sheet is temporarily stopped, the tip of the sheet on which the single-sided image is formed is temporarily stopped and waited. The transport path from the sheet storage unit is located downstream from a merging position where the conveying path merges.

Therefore, the sheet newly fed from the sheet storage unit and the sheet temporarily stopped and waited by the high-speed conveyance control share the re-conveyance path downstream of the merging position. A standby space corresponding to the length of the standby sheet in the transport direction may be secured in the re-conveyance path, and the image forming apparatus body can be made compact and space-saving. That is, the size of the apparatus can be reduced while achieving high productivity by performing high-speed conveyance control during double-sided image formation.

A reversing conveyance path provided upstream of the re-conveying path for reversing the sheet on which the single-sided image has been formed, an arc conveying path communicating the reversing conveyance path with the re-conveying path; It is preferable to include a transport roller having an inner peripheral side surface as an outer peripheral surface of the transport path.

As a result, the sheet on which the single-sided image has been formed is inverted before being conveyed to the re-conveying path, and time loss caused by reversing the sheet during the subsequent high-speed conveyance control can be prevented. In addition, since the front end of the sheet to be temporarily stopped and waited is positioned downstream from the merging position,
It is possible to prevent a sheet that temporarily stops and waits in the re-conveyance path from being affected by a conveyance roller provided upstream of the re-conveyance path.

[0041]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The materials, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

FIG. 1 is a schematic sectional view showing the image forming apparatus main body. In FIG. 1, a sheet S is stored in a sheet feed tray 1 (1
a to 1d), the sheet is fed to the separation roller pair 121 by the pickup roller 120 and fed, and is passed through the conveyance path 8;
The sheet is conveyed in synchronization with the rotation of a photosensitive drum (not shown) by the registration roller pair 130, and the toner image is transferred from the photosensitive drum to the upper surface by the transfer unit 2. Then, the toner on the sheet S passes through the transport unit 3 and is thermally fixed by the fixing unit 4.

The toner image transferred onto the sheet S by the transfer means 2 is exposed by an exposure means after the photosensitive drum is primarily charged by a charging means to form an electrostatic latent image on the surface of the photosensitive drum. The electrostatic latent image is visualized and formed by toner supplied from a developing unit (not shown).

The structure for performing the steps until the toner image is thermally fixed on the sheet S is an image forming means. The image forming unit may have another configuration such as an inkjet system.

Then, the sheet S after image formation is straight discharged (conveyance path 5a-conveyance path 5f (first conveyance path)),
Reverse discharge (conveyance path 5a-conveyance path 5b (second conveyance path)-conveyance path 5c (third conveyance path)-conveyance path 5e-conveyance path 5f),
Alternatively, for double-sided image formation, the sheet is re-conveyed to the transfer unit 2 again (conveying path 5a-conveying path 5b-conveying path 5d-conveying path 5h as reverse conveying path (fourth conveying path) -conveying path 5j-re-conveying). Transport paths 5g, 6a, 6c, 7).

In FIG. 1, a double-sided reversing unit (U) surrounded by a broken line indicates a conveying path (5) for double-sided image formation.
d, 5h, 5j, 5g, 6a, 6c,) are provided, and this double-sided reversing unit (U) is configured to be detachable from the apparatus main body in a drawer type.

The double-sided reversing unit (U) is provided with an arc transport path (transport path 5h-transport path 5j) which is a transport path on an arc.
A large-diameter roller 25 as a forward / reverse transport roller having the same curvature on the outer peripheral surface as the curvature of the transport path 5g). That is, the large-diameter roller 25 is a transport roller having the inner peripheral surface of the arc transport path as the outer peripheral surface. Driven rollers 26a and 26b are provided around the large-diameter roller 25, and the driven rollers 26a and 26b rotate integrally with the large-diameter roller 25.

The conveyance of the sheet S after the fixing means 4 will be described in detail sequentially along the flow of the sheet S with reference to FIG.

The path of the straight discharge and the reverse discharge is switched by switching the first discharge flapper 51.
The switching of the first discharge flapper 51 is performed using a driving means such as a solenoid (not shown).

In the case of the reverse discharge, the sheet S is guided to the transport path 5c through the transport path 5b by switching the first discharge flapper 51 and by switching the double-sided first flapper 21 as a switching means. Switching of the double-sided first flapper 21 is performed by using a driving means such as a solenoid (not shown).

The conveyed sheet S is applied to the large-diameter roller 2
The rotation of the roller 5 in the counterclockwise direction and the rotation of the driven roller 26a cause the sheet 5 to be drawn into the transport path 5g. At this time, the arrival of the sheet S is detected by the sheet detecting means 27a provided downstream of the driven roller 26a.

Although the sheet detecting means 27a is not shown in detail, for example, a flag protruding on the transport path and having a center of rotation outside the transport path is rotated by contact of the leading end of the sheet S, and provided in this flag. There is one that senses that the shielded plate shields between the light emitting and receiving parts of the photo interrupter.

The CPU of the main body of the apparatus uses the large-diameter roller 2 based on the arrival signal of the sheet S and information on the length of the sheet S in the conveying direction.
The drive of the large-diameter roller 25 is controlled by judging the timing of the stop and reversal (clockwise rotation) of the roller 5.

The CPU stops and reverses the large-diameter roller 25 when the rear end of the sheet S is positioned before passing through the second sheet discharge flapper 52 and reaching the double-side reversing unit (U).

The second paper discharge flapper 52 is urged leftward in the figure by a spring force, its own weight, or the like, to prevent the sheet S from flowing upward in the figure in the direction of the conveying path 5b after reversing, and after reversing. Sheet S is in the conveying path (conveying path 5e-conveying path 5f)
It is provided to be guided to.

When the sheet S to be reversed and discharged has a long length in the conveying direction, the conveying rollers 28a and 28b are
And drives the sheet S in synchronization with the length of the sheet S.

In the case of double-sided image formation, the sheet S is guided through the transport path 5b by switching the first discharge flapper 51, and to the transport path 5d by switching the first double flapper 21.

The conveyed sheet S is applied to the large-diameter roller 2
Due to the clockwise rotation of 5 and the rotation of the driven roller 26b, the sheet 5 is drawn into the transport path 5h. At this time, the arrival of the sheet S is detected by the sheet detecting means 27b provided downstream of the driven roller 26b. The configuration of the sheet detecting means 27b is the same as that of the sheet detecting means 27a.

Based on the arrival signal of the sheet S and the information on the length of the sheet S in the transport direction, the CPU of the apparatus main body determines the large-diameter roller 25.
, And the drive of the large diameter roller 25 is controlled.

The CPU stops and reverses the large-diameter roller 25 when the rear end of the sheet S is positioned before passing through the second-side second flapper 22 and reaching the driven roller 26b.

The double-sided second flapper 22 is urged downward in the figure by a spring force, its own weight, or the like, similarly to the second sheet discharge flapper 52, and after reversing, in the direction of the transport path 5d of the sheet S going leftward in the figure. Is provided so that the sheet S after the reversal is guided to the conveyance path 5j.

The sheet S conveyed along the arc conveying path (conveying path 5j-conveying path 5g) along the outer peripheral surface of the large-diameter roller 25.
Are transport roller pairs 28a, 28b, 28e arranged in order,
28c, the transfer path from the transfer path 5g to the transfer path (the transfer path 6a-
The sheet is conveyed along the conveyance path 6c), merges again into the conveyance path 8, and is conveyed to the transfer unit 2 to form the second image.

In this image forming apparatus, the transfer means 2
When the sheet S is conveyed to the transfer device 2, high-speed conveyance control of the sheet S in the conveyance path to the transfer unit 2 is performed, thereby enabling high productivity. The high-speed transfer control is described below with reference to FIGS.
This will be described with reference to FIG.

The sheet S is separated from the sheet storage section 1 (ad) by a pickup roller 120 by a separation roller pair 121.
Sent to The separation roller pair 121 conveys only one uppermost sheet S among the sheets S picked up by the pickup roller 120 to the conveyance roller pair 122 or 28d.

A sensor 113 for detecting the leading end of the sheet S is provided immediately before or immediately after the pair of conveying rollers 122 and 28d, and the sheet S whose leading end is detected by the sensor 113 is held between the pair of conveying rollers 122 and 28d. Once stopped, it stops and waits at a predetermined position.

Thereafter, the sheet is conveyed again at a timing at which the sheet S conveyed immediately before is at a predetermined conveying interval.

This is because, during high-speed transport control, the transport speed of the sheet S can be increased by making the transport interval with the sheet S transported immediately before appropriate. If this control is omitted, the next sheet S conveyed at an increased speed to the immediately preceding sheet S being conveyed at a predetermined speed by the registration roller pair 130 toward the transfer means 2 catches up, and the sheet S is damaged. This is because there is a possibility that the sheet will be fed or overlapped.

After the above-described correction of the conveyance interval is performed, the sheet S is transferred to the registration roller pair 130 by the transfer unit 2.
It is conveyed at a speed higher than the above conveying speed. Thereafter, this control is repeatedly performed.

When performing double-sided image formation, the re-transport path (transport path 5g-transport path 6a-
The leading end of the sheet S is detected by the sensor 115 arranged in the middle of the conveying path 6c), and the sheet S is temporarily stopped and waits at a predetermined position in a state where the sheet S is held between the conveying roller pair 28b. The conveyance is started again at a timing at which the sheet S to be conveyed has a predetermined interval.

Here, in this image forming apparatus, an arc transport path (5c
-5g) Distance of the transport path from the terminal end 7a to a position 7d immediately before the first transport roller pair 28e downstream of the junction 7c where the transport path from the sheet storage unit 1b joins the middle of the re-transport path. However, for example, the length of the small-size sheet usable in the apparatus is longer than the length in the longitudinal direction, and the distance of the conveyance path from the terminal end 7a to the junction 7c is less than the length of the small-size sheet in the longitudinal direction. Is configured.

The distance of the conveying path from the position 7b immediately after the first conveying roller pair 28a past the terminal end portion 7a to the position immediately before 7d is equal to or more than the length of the small-sized sheet in the width direction, and It is configured such that the distance of the conveyance path from the to the merging portion 7c is less than the length of the small size sheet in the width direction.

In the image forming apparatus having the above structure, when forming a double-sided image of a sheet (for example, A4R size),
To perform high-speed conveyance control, detect the leading end of the single-sided image-formed sheet S conveyed to the re-conveying path by the large-diameter roller 25 with the sensor 115, and correct the conveyance interval with the immediately preceding sheet S. When the sheet S temporarily stops and waits, the leading end position of the temporarily stopped and waiting sheet S is positioned at the immediately preceding position 7d on the downstream side of the junction 7c with the conveyance path from the sheet storage unit 1b in the middle of the re-conveyance path. Conveying roller pair 2
8a and 28b are drive-controlled.

As a result, a standby space for the length of the sheet S in the transport direction can be secured in the transport path from the terminal end portion 7a of the re-transport path to the immediately preceding position 7d. The transport operation for forming the double-sided image of the sheet S immediately after stopping, waiting, and conveying the sheet S to the transport path 5d by rotating the large-diameter roller 25, or the transport path 5
The sheet S is turned over at h and conveyed to the conveying path 5g. )
Can be performed, the length of the transport path from the terminal end 7a to the junction 7c can be shortened, and the apparatus can be made more compact.

Further, the sheet S is temporarily stopped during the re-conveying path,
When a new sheet S is fed from the sheet storage unit 1b in the standby state, the downstream of the re-conveying path merging portion 7c is temporarily stopped, and the standby sheet S and the new sheet S are shared. can do.

That is, a new sheet S fed from the sheet storage unit 1b is transported between the sheet S, which has been stopped and waited, and one side surface of the re-conveying path, by a pair of conveying rollers 28d, 28.
e and 28c.

Therefore, the sheet S temporarily stopped and waited
A standby space corresponding to the length in the transport direction may be secured in the transport path from the terminal end portion 7a to the immediately preceding position 7d in the re-transport path, and the image forming apparatus body can be made compact and space-saving. . That is, the size of the apparatus can be reduced while achieving high productivity by performing high-speed conveyance control during double-sided image formation.

[0077]

As described above, according to the present invention, when a single-sided image-formed sheet is temporarily stopped and waited in the re-conveying path, the one-sided image-formed sheet to be temporarily stopped and waited is By being located downstream from the merging position where the conveyance path from the sheet storage section in the middle of the re-conveyance path merges, the sheet newly fed from the sheet storage section temporarily stops and waits by high-speed conveyance control. Since the sheet and the sheet jointly use the re-conveying path downstream of the merging position, it is sufficient to secure a standby space in the re-conveying path corresponding to the length of the sheet to be temporarily stopped and waiting in the conveying direction. The main body can be made compact and space can be saved. That is, the size of the apparatus can be reduced while achieving high productivity by performing high-speed conveyance control during double-sided image formation.

A reversing conveyance path provided upstream of the re-conveying path for reversing a sheet on which a single-sided image has been formed, an arc conveying path communicating the reversing conveying path with the re-conveying path, and an inner diameter side surface of the arc conveying path And a conveying roller having an outer peripheral surface, the sheet on which a single-sided image is formed is inverted before being conveyed to the re-conveying path, and the sheet is inverted during high-speed conveying control thereafter. Time loss can be prevented. In addition, since the leading end of the sheet to be temporarily stopped and waited is located downstream of the merging position, the sheet to be temporarily stopped and waited in the re-conveyance path is affected by the conveyance roller provided upstream of the re-conveyance path. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an image forming apparatus according to an embodiment.

FIG. 2 is a schematic sectional view showing a double-sided reversing unit according to the embodiment.

FIG. 3 is a schematic sectional view showing a conventional image forming apparatus.

FIG. 4 is a schematic sectional view showing a conventional double-sided reversing unit.

[Explanation of symbols]

1 (1a, 1b, 1c, 1d) Sheet storage unit 2 Transfer unit 3 Transport unit 4 Fixing unit 5 (5a, 5b, 5c, 5d, 5e, 5f, 5g, 5)
h, 5j) Conveying path 6 (6a, 6c) Conveying path 7c Converging part 7a End part 7b Immediate position 7d Immediate position 8 Conveying path 25 Large diameter roller 26 (26a, 26b) Followed roller 27 (27a, 27b) Sheet detecting means 28 (28a, 28b, 28c, 28e) Transport Roller Pair 113 Sensor 115 Sensor 120 Pickup Roller 121 Separation Roller Pair 122 Transport Roller Pair 130 Registration Roller Pair

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H028 BA05 BA09 BA14 3F053 BA03 BA12 LA02 LA05 LA07 LB01 3F100 AA02 CA12 CA14 DA01 EA02 EA06

Claims (2)

[Claims] An image forming means for forming an image on one side of a conveyed sheet, and an image forming means for forming an image on both sides of the sheet with the image forming means.
A re-conveying path that re-conveys the sheet on which the single-sided image has been formed to the image forming unit, and a sheet storage unit that feeds the sheet to a conveying path that merges in the middle of the re-conveying path. When temporarily stopping the sheet on which the single-sided image has been formed in the re-conveying path, and temporarily stopping the sheet, the leading end of the single-sided image-formed sheet to be temporarily stopped and waited from the sheet storage portion in the middle of the re-conveying path. An image forming apparatus which is located downstream of a merging position where the conveying paths merge. 2. A reversing conveyance path provided upstream of the re-conveying path and for reversing the sheet on which the single-sided image has been formed, an arc conveying path communicating the reversing conveyance path with the re-conveying path, A transport roller having an inner peripheral side surface as an outer peripheral surface of the arc transport path,
The image forming apparatus according to claim 1, further comprising: