JP3920017B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that can be changed to a configuration that enables double-sided image formation according to a user's request.
[0002]
[Prior art]
In recent years, image forming apparatuses such as copiers and printers have been increasingly equipped with a double-sided printing function for forming images on both sides of paper as part of resource saving and environmental protection, and this tendency is relatively slow. It extends to small models.
On the other hand, for low-speed and small-sized models, there is still a demand for a machine that omits the double-sided function as usual and desires a space-saving and low-cost machine.
In order to meet such market demands, a so-called optional duplex unit that can be added with a duplex function later has been proposed (for example, JP-A-10-268585).
[0003]
[Problems to be solved by the invention]
However, such an optional duplex unit is designed to be attached to the outside of the image forming apparatus with an emphasis on the ease of mounting when mounting it, so when the unit is installed, the entire unit is as much as the duplex unit. However, there was a drawback that the size of the film increased in the width direction.
[0004]
That said, for example, as described in Japanese Patent Publication No. 8-18724, if the double-sided function is installed from the beginning without considering the option, the double-sided function is not required and low cost is desired. There is a problem that an unwilling device is provided to the user.
In addition, since there is no manual sheet feeding in the configuration of this apparatus, there is a case where it is impossible to form an image using an irregular size sheet, OHP, a postcard or the like.
[0005]
The present invention has been made in view of the above-described problems, and can selectively provide a duplex function for forming an image on both sides of a sheet according to a user's request. An object of the present invention is to provide an image forming apparatus capable of minimizing the size of the apparatus in the width direction.
It is another object of the present invention to enable manual paper feeding even when a duplex function is provided.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus having an image forming unit and a paper transport path for transporting paper in the apparatus main body constitutes the paper transport path in the vicinity of the image forming unit. The paired paper transport system is divided into two parts with the paper transport path as a boundary, one of which is provided on the apparatus main body side and the other is provided on a transport unit that can be detached from the apparatus main body, and the paired paper And a refeed path for receiving the paper after passing through the image forming unit and transporting the image forming unit in a state where the front and back sides of the image forming unit are reversed. Instead of this, a double-sided unit that can be attached is provided.
[0007]
In the image forming apparatus, it is preferable that a manual sheet feeding device is provided in each of the transport unit and the duplex unit.
Further, in the image forming apparatus, a reversing unit that receives the sheet after passing through the image forming unit and changes the traveling direction of the sheet and transports it to the refeed path is provided to be removable from the apparatus main body. Good.
[0008]
Each of the transport unit and the duplex unit is provided with a rotational force connection mechanism for connecting the drive system of the manual sheet feeding device to the drive system provided on the apparatus main body side, and the duplex unit includes the refeed sheet. A drive source for driving only the transport system on the path may be provided.
[0009]
Further, the manual paper feed path from the manual paper feed device is merged with the refeed path, and the refeed path after merging with the manual paper feed path is connected to the image forming unit of the paper transport path. The registration rollers provided on the upstream side in the paper transport direction are joined to the upstream side in the paper transport direction, and the paper is detected on the upstream side in the paper transport direction with respect to the point where the refeed path joins the manual feed path. In addition to providing a sensor, it is preferable to provide a control means for stopping the driving of the transport system on the refeed path when the sensor detects a sheet when an interrupt for using the manual sheet feeder occurs during double-sided image formation. .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment when the image forming apparatus according to the present invention is provided with a double-sided image forming function. FIG. 2 is a block diagram showing the configuration when the image forming apparatus is dedicated to single-sided image formation. FIG.
[0011]
As shown in FIG. 2, this image forming apparatus supports a conveyance unit 16 extending in the vertical direction on the right side of the apparatus main body 1 so as to be freely rotatable by a support shaft 23, which can be opened in the direction of arrow A. Yes. As will be described in detail later, the transport unit 16 can be replaced with the duplex unit 26 shown in FIG.
[0012]
This image forming apparatus is provided with a paper feed cassette 14 at the lower part of the apparatus body 1, and the paper P set in the paper feed cassette 14 is separated into one sheet by a paper feed roller 15 and a friction pad 10, The paper is sent to the paper conveyance path 2.
A drum-shaped photoconductor 9 is provided in the image forming section on the paper conveyance path 2 so as to be rotatable in the direction indicated by an arrow B. Around the photoconductor 9, a charging roller 11, a developing roller 19, and a spring are provided. The transfer roller 13 and the cleaning blade 12 that are in contact with the photosensitive member 9 are provided.
[0013]
A fixing device including a fixing roller 6 and a pressure roller 7 that are in pressure contact with each other is provided on the downstream side (upper side in FIG. 2) in the sheet conveyance direction with respect to the photoreceptor 9. A discharge roller 8 including a pair of rollers and a paper discharge tray 25 that receives the paper P discharged by the discharge roller 8 are provided on the downstream side of the fixing device in the paper conveyance direction.
[0014]
The sheet conveying system of the sheet conveying path 2 includes a plurality of pairs of guide plates 5a, 5b and 5c, 5d and 5e, 5f and 5g, 5h and 5i, and 5j and pairs of registration rollers 3a and 3b. Consists of conveying rollers 4a, 4b and the like.
Of the sheet conveying path 2, guide plates 5a, 5b and 5c, which form a pair constituting the sheet conveying system constituting the sheet conveying path in the vicinity of the image forming portion of the photoconductor 9, are formed. 5d and 5e, 5f and 5g and 5h, and paired transport rollers 3a and 3b and 4a and 4b are divided into two parts with the sheet transport path 2 as a boundary.
[0015]
That is, one guide plate 5b, 5d, 5f, 5h among the pair of guide plates 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h is fixed to the apparatus main body 1 side.
Of the registration rollers 3a and 3b and the conveyance rollers 4a and 4b that form a pair, one registration roller 3a and one conveyance roller 4a are rotatably attached to the apparatus main body 1 side.
[0016]
On the other hand, the other guide plates 5a, 5c, 5e, and 5g are fixed to the side of the transport unit 16 that can be detached from the apparatus body 1, and among the pair of registration rollers 3a, 3b and transport rollers 4a, 4b The registration roller 3b and the conveyance roller 4b, which are the other side and the driven side, are rotatably attached to each other.
In addition, a transfer roller 13 is rotatably attached to the transport unit 16 and a manual paper feeder 17 is also provided.
[0017]
The transfer roller 13 and the other registration roller 3b may be provided on the apparatus main body 1 side. Further, the other guide plates 5a, 5c, 5e, and 5g may be fixed to the apparatus main body 1 as long as they do not interfere with the jam processing.
[0018]
The manual paper feeding device 17 is provided with a manual paper feeding roller 18 and a friction pad 34 on the upper side of the paper feed end side of the manual feeding table 17a, thereby separating the paper set on the manual feeding table 17a into one sheet, It can be conveyed to the sheet conveying path 2 via the manual sheet feeding path 36.
The manual paper feed path 36 from the manual paper feeder 17 is joined to the paper transport path 2, and the junction is upstream of the registration rollers 3a and 3b in the paper transport direction.
When the manual sheet feeder 17 is used, the manual feed base 17a is opened in the direction indicated by the arrow C in FIG.
[0019]
As described above, the transport unit 16 can be rotated with respect to the apparatus body 1 with the support shaft 23 as a fulcrum. When the transport unit 16 is opened, its position is made of resin at a predetermined opening angle as shown in FIG. The band 41 is regulated by extending (no sagging).
Further, the conveyance unit 16 is fixed to the apparatus main body 1 by a lock lever 21 swingably attached to the conveyance unit 16 side and engaged with a stay 22 on the apparatus main body 1 side as shown by a solid line in FIG. Is done.
[0020]
The lock lever 21 is urged to rotate clockwise in FIG. 2 by a spring (not shown), and the rotation is restricted to the position indicated by the solid line in FIG. Therefore, when the transport unit 16 is closed from the open position, the upper left hook portion of the lock lever 21 in FIG. 2 contacts the stay 22 in the process and once rotates slightly in the counterclockwise direction, then the solid line is illustrated. The position is engaged and fixed.
[0021]
In this image forming apparatus, when the image forming operation is started, the photoconductor 9 rotates in the direction indicated by the arrow B, the surface thereof is uniformly charged by the charging roller 11, and the charged surface is light from an exposure device (not shown). L is exposed, and an electrostatic latent image is formed there.
The electrostatic latent image is visualized by attaching toner to the developing roller 19.
[0022]
In addition, the sheet P is fed from a sheet feeding cassette 14 provided in the lower part of the apparatus main body 1, and after it is temporarily stopped by the pair of registration rollers 3a and 3b, it matches the image on the photoconductor 9. The sheet is conveyed toward a transfer position where the transfer roller 13 is located at an accurate timing.
Then, the toner image on the photoconductor 9 is transferred onto the paper P by the transfer roller 13, and the paper P is conveyed to a fixing device composed of a fixing roller 6 and a pressure roller 7, where the toner image is heated and heated. It is fixed by pressure.
[0023]
The paper P is stacked on the paper discharge tray 25 by the discharge roller 8.
Further, residual toner is removed by the cleaning blade 12 on the surface of the photosensitive member 9 after the transfer and separation are completed, and it is prepared for the next image formation.
[0024]
By the way, this image forming apparatus is provided with the duplex unit 26 shown in FIG.
The duplex unit 26 includes a paper refeeding path 20 that receives the paper after passing through the image forming unit provided with the photoconductor 9 and conveys the paper again to the image forming unit with the front and back sides reversed. Yes.
[0025]
Then, the duplex unit 26 opens to a position where the resin band 41 is fully extended and regulated as shown by the phantom line in the drawing, with the support shaft 23 as a fulcrum as shown by the phantom line in FIG. Be able to.
[0026]
In the duplex unit 26, a plurality of pairs of refeed rollers 27, 28, and 29 are rotatably provided on the refeed path 20, and the reversal guide plate 32a is rotated by the refeed rollers. And 32b are sent again to the paper transport path 2.
The duplex unit 26 is also provided with a manual sheet feeder 17 so that the sheet set on the manual table 17a can be separated into a single sheet and fed toward the refeed roller pair 29.
[0027]
The manual paper feed path 43 from the manual paper feeder 17 is joined to the refeed path 20, and the refeed path 20 after joining the manual paper feed path 43 is connected to the paper transport path 2. The pair of registration rollers 3a and 3b provided on the upstream side in the paper conveyance direction of the image forming unit are joined to the upstream side in the paper conveyance direction.
When the sheet is fed from the manual feed table 17a using the manual sheet feeder 17 of the duplex unit 26, the sheet is relayed by the refeed roller pair 29, and the pair of registration rollers 3a, It is conveyed to 3b.
[0028]
In this way, by using the re-feed roller pair 29 as a relay roller, even if the distance from the manual feed roller 18 to the registration rollers 3a and 3b is some distance away, the conveyance failure of small-size paper is prevented. Can be prevented. Further, by using the re-feed roller pair 29 provided for the re-feed path 20 as a relay roller at the time of manual feeding as described above, it becomes unnecessary to provide a new relay roller. An increase in cost can be suppressed and an increase in space can be prevented.
[0029]
In this image forming apparatus, a reversing unit 24 that accepts a sheet after passing through the image forming unit, changes the traveling direction of the sheet (switchback conveyance), and can convey the sheet to the refeed path 20 with respect to the apparatus main body 1. It is provided so that it can be removed.
The reversing unit 24 includes a branching claw 33, a pair of reversing rollers 31, a pair of guide plates, a reversing sensor 42, and the like, which are detachably attached to the apparatus body 1 immediately after the fixing roller 6. . Therefore, in the case of a user who does not need the double-sided function, if the reversing unit 24 is not attached as shown in FIG. 2, the cost can be reduced accordingly.
[0030]
Even if the reversing unit 24 is fixed integrally to the apparatus main body 1 side, it does not interfere with the single-sided image formation. Therefore, the reversing unit 24 is configured to be fixed integrally to the apparatus main body 1 from the beginning. Also good. In this case, when the double-sided image can be formed, it is only necessary to replace the transport unit 16 with the double-sided unit 26, so that the recombination work is simplified.
[0031]
The branching claw 33 is driven by an electromagnetic solenoid (not shown) and rotated between a position indicated by a solid line and a position indicated by a virtual line in FIG. 1, and is moved to a position indicated by a solid line in FIG. Sometimes moves to the position indicated by the virtual line.
[0032]
The reversing roller 31 can be rotated in both forward and reverse directions by a motor (not shown). When the sheet is conveyed upward in FIG. 1 by the fixing roller 6 and the pressure roller 7, the sheet is moved in the direction of arrow E. The paper rotates in the transport direction. However, when the reverse sensor 42 disposed between the reverse roller 31 and the branch claw 33 detects the trailing edge of the paper, the reverse sensor 42 rotates in the reverse direction.
Accordingly, the sheet is conveyed to the refeed path 20 of the duplex unit 26 with the rear end side up to that leading side.
[0033]
The sheet P is conveyed to the pair of registration rollers 3a and 3b by the re-feed roller pairs 27, 28, and 29, with the front and back being reversed, and the image on the photoconductor 9 of the image forming unit is transferred by the transfer roller 13. This time it is transferred to the back side.
Then, the image of the paper P is fixed by the fixing roller 6 and the pressure roller 7, guided to the branch claw 33 whose rotational position is switched to the position indicated by the phantom line in FIG. The paper is discharged onto the paper discharge tray 25.
[0034]
As described above, this image forming apparatus is provided with the conveyance unit 16 dedicated to single-sided image formation and the double-sided unit 26 that enables double-sided image formation so that they are interchangeable.
Therefore, for example, if the duplex unit 26 is a normal option, the duplex function can be easily added by replacing the transport unit 16 with the duplex unit 26 and attaching the reversing unit 24 at the user's site.
[0035]
As a factory option, if the duplex unit 26 and the reversing unit 24 are assembled at the factory shipment, the duplex function can be easily added and shipped.
In this image forming apparatus, even when the duplex function is added, one of the pair of sheet conveyance systems constituting the sheet conveyance path 2 of the duplex unit 26, that is, the guide plates 5b, 5d, 5f, and 5h is paired. One registration roller 3a and one pair of conveyance rollers 4a are provided on the apparatus main body 1 side, and the sheet conveyance system is a conveyance unit 16 (see FIG. 2) dedicated to one side and a duplex unit having a duplex function. 26 can be shared by both.
[0036]
Therefore, compared with the case where the duplex unit 26 is simply added to the outside of the transport unit 16, the size of the entire apparatus in the width direction can be reduced, thus saving space.
Further, even when the duplex function is added, the manual paper feeding device 17 can be used for manual paper feeding.
[0037]
The double-sided unit 26 is also provided with a lock lever 21 'that performs the same function as the lock lever 21 described with reference to FIG. 2, but when the double-sided unit 26 is closed from the open position, In the process, the hook portion at the upper left in FIG. 1 of the lock lever 21 'comes into contact with the stay 22 and once rotates a little in the counterclockwise direction, and then is engaged and fixed at the position shown by the solid line.
[0038]
Next, the drive system of the manual sheet feeder provided in the transport unit 16 will be described with reference to FIGS.
The load torque when manually feeding paper from the manual feed table 17a of the manual paper feeder 17 shown in FIG. 2 is about 2 Kgf · cm due to the paper feed pressure and the separation friction force by the friction pad 34.
[0039]
Therefore, the motor that drives the manual sheet feeding roller 18 needs to have a large output that can overcome the load torque and enable sheet feeding.
Therefore, when a motor having such a large output is provided in the transport unit 16, the transport unit 16 is increased in size, and the weight of the transport unit 16 that can be attached to and detached from the apparatus main body 1 is increased.
[0040]
Therefore, this image forming apparatus is configured to drive the manual sheet feeding roller 18 by using the driving force of a motor that drives various drive systems provided on the apparatus main body 1 side.
That is, as shown in FIGS. 3 and 4, the electromagnetic clutch 37 is attached to the apparatus body 1, and the gear 45 is fixed to the clutch shaft 37 a of the electromagnetic clutch 37, and the swing gear 38 is engaged with the gear 45. Is supported rotatably.
[0041]
A clutch gear 46 (see FIG. 4 because it appears to overlap with the gear 45 in FIG. 3) is attached to the clutch shaft 37a so as to be relatively rotatable. The clutch gear 46 is connected to various drive systems in the apparatus main body 1. The gear 44 is engaged with the gear 44 rotated by the rotational force from the motor to be driven.
[0042]
Therefore, when the electromagnetic clutch 37 is off, the clutch gear 46 is idle with respect to the clutch shaft 37a by the rotating gear 44. However, when the electromagnetic clutch 37 is turned on, the clutch gear 46 is connected to the clutch shaft 37a. As a result, the clutch shaft 37 a rotates integrally with the gear 45.
[0043]
As a result, the swing gear 38 rotates, and when the drive gear 47 on the transport unit 16 side is engaged with the swing gear 38, the drive gear 47 is rotated to rotate manually. The paper feed roller 18 (see FIG. 2) rotates in the paper feed direction.
[0044]
The swing gear 38 is supported by a support member (not shown) so as to swing in the direction indicated by the arrow G in FIG. 3 about the clutch shaft 37a of the electromagnetic clutch 37. Therefore, when the transport unit 16 is rotated counterclockwise from the open position shown in FIG. 3 and closed to a predetermined position, the drive gear 47 on the transport unit 16 side comes into contact with the swing gear 38 to drive the transport unit 16. The gear 47 is slightly rotated counterclockwise in the figure, and the drive gear 47 and the swing gear 38 are engaged with each other.
[0045]
In this embodiment, the electromagnetic clutch 37, the gear 44, the gear 45, the clutch gear 46, the swinging gear 38, and the drive gear 47 constitute the drive system of the manual sheet feeding device 17 of the transport unit 16 on the apparatus main body 1 side. It functions as a rotational force connection mechanism that connects to the drive system provided in the system.
[0046]
Next, the drive system of the manual sheet feeder provided in the duplex unit 26 will be described with reference to FIG. In FIG. 5, parts corresponding to those in FIG. 3 are denoted by the same reference numerals.
In the duplex unit 26, similarly to the transport unit 16, the manual paper supply roller 18 of the manual paper supply device 17 is rotated by the driving force from the apparatus main body side.
[0047]
However, since the position of the manual sheet feeding roller 18 is slightly different from the position of the manual sheet feeding roller 18 of the transport unit 16, the duplex unit 26 is transported with the duplex unit 26 by adding two idler gears 39a and 39b. The unit 16 is compatible with each other. An idler gear 39 a on the swing gear 38 side meshes with the swing gear 38.
The other configuration of the apparatus main body is the same as that described with reference to FIG.
[0048]
Therefore, when the duplex unit 26 is attached and closed at a predetermined position of the apparatus main body 1 (the position indicated by the solid line in FIG. 1), the rotational force from the motor that drives the various drive systems in the apparatus main body 1 is changed to the gear. 44, the clutch gear 46 (FIG. 4), the clutch shaft 37a, the gear 45, and the swing gear 38 are sequentially transmitted in this order.
The rotational force of the swing gear 38 is transmitted in the order of the idler gear 39a, the idler gear 39b, and the drive gear 47, and the manual feed roller 18 (see FIG. 1) is rotated in the paper feed direction by the drive gear 47.
[0049]
As described above, the duplex unit 26 obtains the driving force of the manual sheet feeding roller 18 from the motor on the apparatus body 1 side, and therefore the duplex unit 26 is provided with only the pair of refeed rollers 27, 28, and 29. It is only necessary to provide a motor to be driven.
In this embodiment, the electromagnetic clutch 37, the gear 44, the gear 45, the clutch gear 46, the swing gear 38, the idler gears 39a and 39b, and the drive gear 47 are connected to the drive system of the manual sheet feeder 17 of the duplex unit 26. Functions as a rotational force connection mechanism that connects the motor to the drive system provided on the apparatus main body 1 side.
[0050]
By the way, in a normal double-sided unit, paying attention to a motor that operates a drive system provided in the double-sided unit, loads applied to the motor include a plurality of conveyance systems provided on a refeed path. There are a load for driving the refeed roller pair and a load for driving the manual sheet feed roller of the manual sheet feeder.
If one of these loads is driven by a single motor that is provided in the duplex unit, there is generally about 2 kgf · cm only with the manual feed load torque described above, so the motor to be used has a fairly large torque capacity. Will have to use.
[0051]
Therefore, for example, in the case of a stepping motor, a low-cost PM (permanent magnet) type cannot be used in capacity, and a high-cost HB (hybrid) type motor must be used. Therefore, the cost becomes high.
However, in the image forming apparatus according to this embodiment, the motor provided in the duplex unit 26 has a small output as long as the refeed roller pair 27, 28, and 29 can obtain a conveyance force sufficient to convey one sheet. Since the manual feed roller 18 with a large load torque is driven by a driving force from a motor provided on the apparatus main body 1 side, a motor on the duplex unit 26 side is used. Can be a motor with a very small torque (output).
[0052]
Therefore, the duplex unit 26 can be reduced in size and weight, and the cost can be reduced. Moreover, workability at the time of attaching the double-sided unit 26 to the apparatus main body 1 is improved as much as the weight is reduced.
[0053]
FIG. 6 is a block diagram similar to FIG. 1 showing another embodiment of the image forming apparatus according to the present invention, and portions corresponding to those in FIG.
The image forming apparatus according to this embodiment is provided with a sensor 40 that detects a sheet on the upstream side in the sheet conveyance direction with respect to a point a that joins the manual sheet feeding path 43 of the refeed path 20 and is manually fed during double-sided image formation. When an interrupt for using the paper feeding device 17 occurs, if the sensor 40 detects the leading edge of the paper, the drive of the pair of paper feeding rollers 27, 28 and 29, which is a transport system on the paper feeding path 20, is rotated by the motor 51. A control device 50 is provided which functions as a control means for stopping each by stopping.
[0054]
The control device 50 includes a central processing unit (CPU) having various determination and processing functions, a ROM storing each processing program and fixed data, a RAM serving as a data memory storing processing data, and an input / output circuit (I / O).
[0055]
The control device 50 outputs an interrupt signal that is output when an interrupt key 52 on an operation panel provided in the apparatus main body 1 of the image forming apparatus is pressed, and when various other keys are pressed. Various operation command signals are input, and various mode signals such as a single-sided image forming mode or a double-sided image forming mode, and a manual feed mode are input.
In addition, various sensor signals and the like are input at predetermined timing from various sensors provided in the apparatus main body 1.
Further, the sensor 40 receives a paper detection signal that is output when the paper is detected.
[0056]
The control device 50 outputs various drive signals for driving the various drive systems provided in the apparatus main body 1 to the drive system at predetermined timings, and the refeed roller pair. A signal for rotating or stopping the motor 51 for rotating the motors 27, 28 and 29 is output.
[0057]
When the double-sided image forming mode is selected and double-sided image formation is being performed, the image forming apparatus is controlled when the interrupt key 52 is pressed to manually feed paper and an interrupt occurs. When the sensor 40 detects the leading edge of the paper conveyed on the refeed path 20, the motor 51 immediately stops rotating, thereby stopping the conveyance of the paper by the refeed roller pairs 27, 28 and 29.
[0058]
Accordingly, the sheet on the refeed path 20 stops at the sensor 40 and enters a standby state. Therefore, the sheet fed on the refeed path 20 during double-sided image formation and the manual sheet feeder 17 are fed. Interference with the paper that has been printed can be prevented, and manual paper feeding can be reliably performed.
Therefore, even if there is a person who wants to manually form an image during double-sided image formation, there is no need to wait until the double-sided image formation is completed.
[0059]
In particular, when the image forming apparatus is a digital multi-function peripheral, if there are people who want to make a manual copy while multiple duplex printing is being performed with the printer function, the printer waits until all the duplex printing is completed. However, in the image forming apparatus according to this embodiment, if the interrupt key 52 is pressed in such a case, the sheet during double-sided printing is located at a position of the sensor 40 on the refeed path 20. Since it is temporarily stopped, it is possible to copy by manual feeding immediately.
[0060]
Note that the control device 50 determines the distance L from the sensor 40 to the branch position of the conveyance path of the reversing unit 24. ₁ And length L in the paper transport direction ₂ Is L ₁ > L ₂ The manual feed interruption described above is allowed at the time of ₁ <L ₂ When the above relationship is satisfied, control is performed not to allow the above interruption, but to allow the interruption of manual sheet feeding after the sheet is discharged to the discharge tray 25 without stopping the conveyance of the sheet during double-sided printing. To do.
[0061]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
According to the image forming apparatus of the first aspect, if the user who performs only single-sided image formation attaches the transport unit to the apparatus main body, the unit necessary for double-sided image formation is not attached, and thus the configuration of the apparatus is simplified accordingly. Can be downsized and cheap.
[0062]
For users who also perform double-sided image formation, a double-sided image can be easily formed by attaching a double-sided unit instead of the transport unit. In addition, a pair of paper conveyance systems constituting a paper conveyance path in the vicinity of the image forming unit is divided into two, and one of them is provided on the apparatus main body side, so that only the other of the paper conveyance systems is provided in the duplex unit. Therefore, the size in the width direction of the apparatus can be minimized as compared with the case where all of the paired sheet transport systems are provided on the duplex unit side.
[0063]
According to the image forming apparatus of the second aspect, since the manual paper feeder is provided in each of the transport unit and the duplex unit, the manual paper feeder is used regardless of whether the transport unit or the duplex unit is attached. It is possible to manually feed irregular-size paper, OHP, postcards, and the like.
[0064]
According to the image forming apparatus of the third aspect, the reversing unit capable of receiving the sheet after passing through the image forming unit and changing the traveling direction of the sheet and transporting it to the refeed path can be detached from the apparatus main body. In the case of an apparatus for a user who only performs single-sided image formation, if the reversing unit is not mounted, the apparatus can be made cheaper by that amount.
[0065]
According to the image forming apparatus of the fourth aspect, the conveying unit and the duplex unit are not provided with a driving source for driving the driving system of the manual sheet feeding device, and the driving force from the driving system provided on the apparatus main body side is provided. Since the drive system of the manual sheet feeder is used to drive the double-side unit, the drive source for driving only the transport system for transporting the paper on the refeed path is provided. Since a small output is sufficient, the apparatus can be reduced in size and can be made inexpensive.
Further, since the double-sided unit is lightened by the size of the drive source, the workability when the double-sided unit is attached to the apparatus main body is improved accordingly.
[0066]
According to the image forming apparatus of the fifth aspect, when an interruption to use the manual sheet feeding device occurs during double-sided image formation, if the sensor detects a sheet conveyed on the sheet refeeding path, the sheet refeeding is performed. Since the paper on the refeed path is stopped when the path transport system is stopped, interference between the paper during double-sided image formation and the manually fed paper is prevented, and manual paper feeding is ensured. It can be performed.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment when an image forming apparatus according to the present invention has a double-sided image forming function.
FIG. 2 is a configuration diagram showing a configuration when the image forming apparatus is also dedicated to single-sided image formation.
FIG. 3 is a schematic diagram for explaining a drive system of a manual sheet feeding device provided in a transport unit that is mounted when the image forming apparatus is dedicated to single-sided image formation.
FIG. 4 is a plan view showing gear meshing in the drive system of the manual sheet feeder.
FIG. 5 is a schematic diagram for explaining a drive system of a manual sheet feeder provided in a duplex unit that is mounted when the image forming apparatus can also form a duplex image.
FIG. 6 is a configuration diagram similar to FIG. 1 showing another embodiment of the image forming apparatus according to the present invention.
[Explanation of symbols]
1: Device body 2: Paper transport path
3a, 3b: Registration roller
4a, 4b: Conveying rollers (paper conveying system)
5a to 5j: Guide plates (paper transport system)
16: Transport unit 17: Manual paper feeder
20: Re-feed path 24: Reversing unit
26: Duplex unit
36, 43: Manual feed path 37: Electromagnetic clutch
38: Oscillating gear
39a, 39b: idler gear 40: sensor
45: Gear 46: Clutch gear
47: Drive gear 50: Control device
51: Motor 52: Interrupt key

Claims (5)

In an image forming apparatus provided with an image forming unit and a paper conveyance path for conveying paper in the apparatus main body,
A pair of paper conveyance systems constituting the paper conveyance path in the vicinity of the image forming unit is divided into two with the paper conveyance path as a boundary, one of which is provided on the apparatus main body side, and the other is disposed on the apparatus main body It is installed in the transport unit that can be removed and
The apparatus main body, comprising: the other of the paired sheet conveying systems; and a sheet refeeding path that accepts the sheet after passing through the image forming unit and conveys the sheet again to the image forming unit with the front and back reversed. An image forming apparatus comprising a double-sided unit that can be attached instead of the transport unit. 2. The image forming apparatus according to claim 1, wherein a manual sheet feeder is provided in each of the transport unit and the duplex unit. 3. The image forming apparatus according to claim 1 or 2, wherein a reversing unit capable of receiving a sheet after passing through the image forming unit and changing a traveling direction of the sheet and transporting the sheet to the refeeding path with respect to the apparatus main body. An image forming apparatus provided so as to be removable. 3. The image forming apparatus according to claim 2, further comprising a rotational force connection mechanism that connects a drive system of the manual sheet feeding device of each of the transport unit and the duplex unit to a drive system provided on the apparatus body side, The image forming apparatus, wherein the duplex unit is provided with a drive source for driving only a transport system on the refeed path. 3. The image forming apparatus according to claim 2, wherein the manual paper feed path from the manual paper feed apparatus is merged with the refeed path, and the refeed path after joining the manual paper feed path is the paper. The registration roller provided on the upstream side in the sheet conveyance direction of the image forming unit in the conveyance path is merged to the upstream side in the sheet conveyance direction, and the sheet is conveyed to a point where the refeed path meets the manual sheet feeding path. In addition to providing a sensor to detect the paper upstream in the direction,
An image is provided, wherein a control unit is provided for stopping driving of the transport system on the refeed path when the sensor detects a sheet when an interrupt for using the manual sheet feeder occurs during double-sided image formation. Forming equipment.

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