JP6981066B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

Conventionally, an image forming unit that forms an image on paper by transferring a toner image formed on a photoconductor drum to paper via an intermediate transfer belt and heating and pressurizing the paper to fix the toner image on the paper. An image forming apparatus provided is known.
In such a device, it is common to invert the front and back of the image-formed paper on one side, pass it through the image-forming portion again, and provide an inversion path capable of forming an image on both sides of the paper. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-298605

In recent years, there has been a demand for such an image forming apparatus to perform a process of passing through an image forming portion a plurality of times without inverting the front and back of the paper, aiming at further image quality. For example, when it is desired to form an image by superimposing it on the same surface of paper.
However, in order to pass the image forming portion a plurality of times without inverting the front and back of the paper, it is necessary to set the paper passing through the image forming portion in the apparatus again.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of passing through an image forming portion a plurality of times without inverting the front and back of the paper.

In order to solve the above problems, the invention according to claim 1 is used in an image forming apparatus.
An image forming part that forms an image on paper,
An image forming path for transporting paper to the image forming section, and an image forming path.
A switchback unit that branches from the image forming path downstream of the image forming unit in the paper transport direction, sequentially feeds until the rear end of the paper reaches a predetermined position, and then reversely feeds the paper, and the switchback portion feeds back. An inversion path having a refeeding section for joining the paper to be fed to the image forming path upstream of the image forming section in the paper transport direction.
A shortcut path that branches from the switchback section upstream of the predetermined position in the paper transport direction during sequential paper feeding and transports the paper to the refeeding section without backfeeding.
A control unit that executes a process of transporting the paper to the refeeding unit via the shortcut path so that the paper is passed through the image forming unit a plurality of times so that the image forming surfaces are on the same surface.
It is continuously provided from the downstream end portion in the paper transport direction when the paper in the switchback portion is sequentially fed, and is upstream in the paper transport direction from the image forming section without causing the paper on the switchback portion to be fed backward. In the second refeeding unit that merges with the image forming path,
Equipped with
When the control unit executes the process, the control unit transfers the paper to the re-feeding unit via the shortcut path or the paper to the second re-feeding unit according to the length of the paper in the conveying direction. It is characterized by selecting whether to transport the paper.

Further, the invention according to claim 2 is the image forming apparatus according to claim 1.
A first switching unit that switches the paper transfer destination on the image forming path to the switchback unit, and
The second switching section and the third switching section provided from the upstream side to the downstream side in the paper transport direction at the time of progressive paper feeding in the switchback section, and the third switching section.
Equipped with
The second switching unit switches the transport destination of the paper sequentially fed on the switchback unit to the shortcut path.
The third switching unit is characterized in that the transfer destination of the paper back-fed on the switchback unit is switched to the re-feeding unit.

Further, the invention according to claim 3 is the image forming apparatus according to claim 1 or 2.
The second refeeding unit is characterized in that the paper is provided so as to run near the bottom surface of the image forming apparatus.
Further, the invention according to claim 4 is the image forming apparatus according to any one of claims 1 to 3.
Equipped with multiple paper trays for storing paper
The plurality of paper feed trays are characterized in that they are located between the image forming path and the second re-feeding unit.

According to the present invention, it is possible to pass the image forming portion a plurality of times without inverting the front and back of the paper.

It is a block diagram which shows typically the image forming apparatus which concerns on this embodiment. It is a block diagram schematically showing the structure of the control system of the image forming apparatus of FIG. It is a flowchart which shows the image formation process which is executed in the image formation apparatus of FIG. It is a block diagram which shows the modification of the image forming apparatus schematically. It is a flowchart which shows the image formation process which is executed in the image formation apparatus of FIG.

Hereinafter, the present embodiment will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

[Structure of image forming apparatus 100]
First, the configuration of the image forming apparatus 100 in the present embodiment will be described.
FIG. 1 is a configuration diagram schematically showing an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 is an electrophotographic image forming apparatus 100 such as a copying machine, and forms a full-color image by arranging a plurality of photoconductors in a vertical direction facing a single intermediate transfer belt. This is a so-called tandem type color image forming apparatus.

The image forming apparatus 100 is mainly composed of a document reading apparatus SC, an image forming unit 10, a paper conveying unit 20, and a control unit 11, and these are housed in one housing.

The document reading device SC scans and exposes an image of a document by the optical system of the scanning exposure device, reads the reflected light by a line image sensor, and obtains an image signal. This image signal is input to the control unit 11 as image data after being subjected to processing such as A / D conversion, shading correction, and compression. The image data input to the control unit 11 is not limited to the image data read by the document reading device SC, and is received from, for example, a personal computer or another image forming device connected to the image forming device 100 by the communication unit 13. It may be the one that has been used.

The image forming unit 10 includes four sets of normal color image forming units 10Y, 10M, 10C, 10K, one set of special color image forming units 10W, an intermediate transfer belt 6, a secondary transfer roller 8, a fixing device 9, and the like. It is composed of.
The image forming units 10Y, 10M, 10C, and 10K are an image forming unit 10Y that forms an image of yellow (Y), an image forming unit 10M that forms an image of magenta (M), and an image that forms an image of cyan (C). It is composed of a forming unit 10C and an image forming unit 10K that forms an image of black (K).
Further, the image forming unit 10W is composed of an image forming unit 10W that forms a white (W) image.

The image forming unit 10Y is composed of a photoconductor drum 1Y and a charging unit 2Y arranged around the photoconductor drum 1Y, an optical writing unit 3Y, a developing device 4Y, and a drum cleaner 5Y. Similarly, the image forming units 10M, 10C, 10K, 10W include the photoconductor drums 1M, 1C, 1K, 1W and the charging units 2M, 2C, 2K, 2W and the optical writing units 3M, 3C arranged around them. It is composed of 3K, 3W, a developing device 4M, 4C, 4K, 4W and a drum cleaner 5M, 5C, 5K, 5W.

The surface of the photoconductor drums 1Y to 1W is uniformly charged by the charging portions 2Y to 2W, and a latent image is formed on the photoconductor drums 1Y to 1W by scanning exposure by the optical writing units 3Y to 3W. Will be done. Further, the developing devices 4Y to 4W visualize the latent image on the photoconductor drums 1Y to 1W by developing with toner. As a result, a toner image of a predetermined color corresponding to any of yellow, magenta, cyan, black, and white is formed on the photoconductor drums 1Y to 1W. The toner image formed on the photoconductor drums 1Y to 1W is sequentially transferred to a predetermined position on the rotating intermediate transfer belt 6 by the primary transfer rollers 7Y, 7M, 7C, 7K, 7W.

The toner image composed of each color transferred on the intermediate transfer belt 6 is transferred by the secondary transfer roller 8 to the paper P transferred at a predetermined timing by the paper transport unit 20 described later. The secondary transfer roller 8 is a pressure contact member that forms a nip portion (hereinafter referred to as “transfer nip portion”) by being placed in pressure contact with the intermediate transfer belt 6.

The fixing device 9 is a device that performs a fixing process on the paper P on which the toner image is transferred, that is, the paper P sent out from the transfer nip portion, and is, for example, a pair of fixing members (for example, a pair of rollers) and the fixing. It is composed of a heater that heats one or both of the members. In the process of transporting the paper P, the fixing device 9 fixes the toner image on the paper P through the action of the pressure of the pair of fixing members and the heat of the fixing member.

The paper transport unit 20 transports the paper P according to the transport path of the paper P.
The paper transport unit 20 has an image forming path R1 for transporting the paper P to the image forming unit 10, a paper ejection path R2 for discharging the image-formed paper P to the outside, and an inversion path R3 for inverting the front and back of the paper P. And a shortcut path R4 used to circulate the front and back of the paper P without inverting it.
Further, in the image forming path R1, a switching gate G1 (first switching section) is provided on the downstream side of the fixing device 9 in the paper transport direction, and the switching back section R31 (described later) of the reversing path R3 is provided with a switching gate G2. (Second switching unit) and switching gate G3 (third switching unit) are provided.

Each transport path is provided with a plurality of transport means for transporting the paper P. Each of the conveying means is composed of a pair of pressure-welded rollers, and the paper P is conveyed by rotationally driving at least one of the rollers through a drive mechanism mainly composed of an electric motor.
Further, the pair of rollers constituting the individual transport means are configured so that the state between the rollers can be switched between the pressure contact state and the separated state.
In addition to being composed of a pair of rollers, the transporting means can be widely adopted as a configuration composed of a pair of rotating members, such as a combination of belts and a combination of belts and rollers.

The image forming path R1 is a path for transporting the paper P from the paper feed tray to the switching gate G1.
The paper P is housed in a paper feed tray 21 located at the bottom of the image forming apparatus 100, and the paper P housed in the paper feed tray 21 is taken in by the paper feeding unit 22 and enters the image forming path R1. Be sent out.
Alternatively, the paper P is housed in a paper feed tray of a paper feed device (not shown) connected to the image forming device 100, and the paper P held by the paper feed device forms an image from the paper feed device. It is supplied to the device 100 and sent out to the image forming path R1.
Further, the paper P may be placed on a manual feed tray provided in the image forming apparatus 100 and sent out to the image forming path R1.

An image forming unit 10 is provided on the image forming path R1. Further, the image forming path R1 is provided with an intermediate transport roller 23, a loop roller 24, and a resist roller 25 as transport means from the upstream side to the downstream side in the paper transport direction.

The paper P is sequentially conveyed by the intermediate transfer roller 23 and the loop roller 24, and advances along the image forming path R1. When the tip of the paper P approaches the resist roller 25, the paper P conveyed by the loop roller 24 or the like is abutted against the resist roller 25 in the stopped rotation state, and the loop roller 24 continues to rotate for a predetermined time. As a result, a loop is formed on the paper P. By the action of this loop formation, the bending of the tip of the paper P is corrected (skew correction).
Next, when the resist roller 25 starts rotating at a predetermined timing so as to synchronize with the toner image carried by the intermediate transfer belt 6, the intermediate transfer roller 23 and the loop roller 24 are switched from the pressure contact state to the separated state. The paper P is conveyed to the transfer nip portion of the image forming unit 10 only by the resist roller 25, and then transferred to the fixing device 9 by the secondary transfer roller 8. The paper P that has been subjected to the fixing process in the fixing device 9 is conveyed to the switching gate G1 and proceeds to the paper ejection path R2 or the inversion path R3 according to the guidance of the switching gate G1.

The paper ejection path R2 is a transport path for ejecting the paper P, which has been fixed by the fixing device 9, to the paper ejection tray 26 attached to the outer side surface of the housing.

The inversion path R3 is a transport path for reversing the front and back of the paper P that has been fixed by the fixing device 9 and returning it to the image forming path R1.
The reversing path R3 has a switchback unit R31 for inverting the front and back of the paper P, and a refeeding unit R32 for transporting the paper P inverted by the switchback unit R31 to the image forming path R1.

The switchback portion R31 branches from the position of the switching gate G1 in the image forming path R1 and is arranged so as to extend downward.
The switchback portion R31 is provided with a switching gate G2, a switching gate G3, and a reversing roller 27 from the upstream side to the downstream side (from the upper side to the lower side of the apparatus) in the paper transport direction when the paper P is sequentially fed. There is.
Then, when the front and back sides of the paper P are reversed and the paper P is returned to the image forming path R1, the paper P conveyed from the image forming path R1 reaches the reversing roller 27 (predetermined position) at the trailing end. The reversing roller 27 is sequentially fed, and the reversing roller 27 reverses at the timing when the rear end of the paper P is sandwiched, so that the reverse feeding is started. The back-fed paper P advances from the rear end to the re-feeding unit R32 according to the guidance of the switching gate G3.
For example, when it is assumed that the paper P is a long paper having a length longer in the paper transport direction than the standard paper, the switchback portion R31 is shown by the chain line L in FIG. It is also preferable to provide the image forming apparatus 100 up to a position reaching the vicinity of the bottom surface.

The re-feeding unit R32 branches from the position of the switching gate G3 in the switchback unit R31, and is arranged so as to reach a confluence 51 provided in the middle of the image forming path R1.
The re-feeding unit R32 is provided with an intermediate transport roller 28 as a transport means from the upstream side to the downstream side in the paper transport direction. The intermediate transport rollers 28 are arranged so as to have an interval shorter than the length of the minimum paper P to pass in the paper transport direction.
Then, the paper P back-fed by the switchback unit R31 is conveyed from the rear end by the re-feeding unit R32, and the confluence 51 provided in the image forming path R1 upstream of the image forming unit 10 in the paper conveying direction. To reach. The paper P that has reached the confluence 51 will be sent out to the image forming path R1 again.

The shortcut path R4 is a transport path used to return the paper P, which has been fixed by the fixing device 9, to the image forming path R1 without inverting the front and back (without changing the image forming surface). be.
The shortcut path R4 branches from the position of the switching gate G2 in the switchback section R31 of the inversion path R3, and is arranged so as to reach the refeed section R32.
Then, when the paper P is returned to the image forming path R1 without inverting the front and back of the paper P, the paper P conveyed from the image forming path R1 is switched without reaching the switching gate G3 or the inverting roller 27. According to the guidance of the gate G2, the process proceeds to the shortcut path R4, and is conveyed to the re-feeding unit R32 by the shortcut path R4.
The paper P that has reached the refeeding unit R32 by the shortcut path R4 is conveyed by the refeeding unit R32, passes through the confluence 51 provided in the image forming path R1, and is sent out to the image forming path R1 again. It becomes.

The switching gate G1 is provided on the downstream side of the fixing device 9 in the paper transporting direction in the image forming path R1, and switches the feeding destination of the paper P that has passed through the fixing device 9. Specifically, the switching gate G1 guides the paper P downward when the paper P that has passed through the fixing device 9 is conveyed to the reversing path R3. Further, the switching gate G1 causes the paper P to go straight when the paper P is conveyed to the paper ejection path R2.
The switching gate G1 is normally in a state of sending the paper P to the paper ejection path R2. Then, when the paper P is sent to the reversing path R3, it is driven by a drive unit (not shown), and after the paper P is conveyed downward, it returns to the original state.

The switching gate G2 is provided in the switchback portion R31 of the reversing path R3, and switches the transfer destination of the paper P guided downward by the switching gate G1. Specifically, the switching gate G2 guides the paper P downward when the front and back of the paper P are reversed. Further, the switching gate G2 guides the paper P diagonally downward to the right in FIG. 1 when the front and back sides of the paper P are not reversed, that is, when the paper P is conveyed to the shortcut path R4.
The switching gate G2 is usually in a state of guiding the paper P downward. Then, when the paper P is sent to the shortcut path R4, it is driven by a drive unit (not shown), and after the paper P is conveyed diagonally downward to the right, it returns to the original state.

The switching gate G3 is provided in the switchback unit R31 downstream of the switching gate G2 in the paper transporting direction when the paper P is sequentially fed, and switches the transport destination of the paper P back-fed by the switchback section R31. Specifically, the switching gate G3 guides the paper P diagonally upward to the right in FIG. 1 when the paper P for back-feeding the switchback unit R31 is conveyed to the re-feeding unit R32. Further, the switching gate G3 guides the paper P downward when the paper P conveyed from the image forming path R1 is sequentially fed.
The switching gate G3 is normally in a state of guiding the paper P downward (a state in which the paper P is sequentially fed). Then, when the paper P is conveyed (reversely fed) to the re-feeding unit R32, it is driven by a drive unit (not shown), and after the paper P is conveyed diagonally upward to the right, it returns to the original state.

FIG. 2 is a block diagram schematically showing the configuration of the control system of the image forming apparatus 100 according to the present embodiment.
As shown in FIG. 2, the control unit 11 is connected to a storage unit 12, a communication unit 13, an operation unit 14, a document reading device SC, an image forming unit 10, and a paper transport unit 20.

The control unit 11 is composed of a CPU (Central Processing Unit), a RAM (Random Access Memory), and the like. The CPU of the control unit 11 reads out the system program and various processing programs stored in the storage unit 12 and expands them in the RAM, and centrally controls the operation of each unit of the image forming apparatus 100 according to the expanded program.
For example, when the job execution command is input by the operation unit 14, the control unit 11 executes the job and causes the paper P to form a toner image based on the image data input by the document reading device SC and the communication unit 13. Take control.
Further, in the present embodiment, the control unit 11 circulates the paper P on which the image is formed by the image forming unit 10 without inverting the front and back sides, and the image forming unit 10 forms an image on the image forming surface. It is possible to execute overwriting processing.

The storage unit 12 is composed of a non-volatile semiconductor memory, an HDD (Hard Disk Drive), or the like, and stores various programs executed by the control unit 11 as well as parameters and data required by each unit.

The communication unit 13 is provided with various interfaces such as NIC (Network Interface Card), MODEM (Modulator-DEModulator), and USB (Universal Serial Bus), and connects to an external device.

The operation unit 14 outputs various information set by the user to the control unit 11. As the operation unit 14, for example, a touch panel capable of performing an input operation according to the information displayed on the display can be used. Through the operation unit 14, the user sets image formation conditions, that is, the type of paper P (for example, basis weight, size, paper quality, etc.), paper feed tray to be used, image density, magnification, image formation mode, and the like. be able to. Further, the user can input a job execution command and an operation instruction in various modes through the operation unit 14. Further, by controlling the operation unit 14, the control unit 11 can display various messages to the user via the operation unit 14.

[Operation of image forming apparatus 100]
Next, the operation of the image forming apparatus 100 in this embodiment will be described.
FIG. 3 is a flowchart showing an image forming process executed by the image forming apparatus 100. The process shown in this flowchart is executed in collaboration with the program stored in the control unit 11 and the storage unit 12 in response to a job execution command from the user.

First, the control unit 11 acquires job information transmitted from an external device via the communication unit 13 (step S1).
The job information includes various information related to the image forming process, for example, mode information, image data of the image to be formed, and the like.
As the mode information, for example, any one of a normal mode, a double-sided mode, and an overwriting mode is set. The normal mode is a mode in which an image is formed once on one side of the paper P. Further, the double-sided mode is a mode in which an image is formed on both sides of the paper P. Further, the overwriting mode is a mode in which an image is formed a plurality of times on one surface of the paper P.
The image data includes one or a plurality of image data according to the image forming mode, and information such as which side of the paper P is formed on the front and back sides and the number of times the image data is formed is added.

Next, the control unit 11 executes the highest priority image formation among the unprocessed image formations by the image forming unit 10 (step S2).
For example, in the normal mode, the control unit 11 forms an image on one side (front surface) of the paper P.
Further, for example, in the overwriting mode, the control unit 11 executes this when the first image formation is not processed, the first image formation is completed, and the second image formation is not processed. In some cases, a second image formation is performed.
Further, for example, in the double-sided mode, the control unit 11 executes this when the image formation on the front surface is not processed, and when the image formation on the front surface is completed and the image formation on the back surface is not processed, the back surface is not processed. Perform image formation.

Next, the control unit 11 determines whether or not the overwriting mode or the double-sided mode is set (step S3), and if the setting is not made (normal mode), this process is performed. finish.

On the other hand, when the overwriting mode or the double-sided mode is set (step S3: YES), the control unit 11 determines whether or not there is unprocessed image formation (step S4), and when there is no such setting (step S4). S4: NO), this process is terminated.

On the other hand, when there is unprocessed image formation (step S4: YES), the control unit 11 switches the switching gate G1 and conveys the paper P to the switchback unit R31 of the reversal path R3 (step S5).

Next, the control unit 11 determines whether or not the overwriting mode is set (step S6), and if the overwriting mode is set (step S6: YES), switches the switching gate G2 (step S6). S7), after that, the process proceeds to step S2, and the subsequent processes are repeated.
As a result, the paper P is conveyed to the re-feeding unit R32 via the shortcut path R4, returns to the image forming path R1 by the re-feeding unit R32, and reaches the image forming unit 10.

On the other hand, when the overwriting mode is not set (step S6: NO), the control unit 11 determines whether or not the rear end of the paper P has reached the reversing roller 27 (step S8), and has not reached it. In the case (step S8: NO), the process of this step S8 is repeated.
On the other hand, when the rear end of the paper P reaches the reversing roller 27 (step S8: YES), the control unit 11 switches the switching gate G3 (step S9), and then shifts to the above step S2, and thereafter. Repeat the process.
As a result, the paper P is back-fed and conveyed to the re-feeding unit R32, returns to the image forming path R1 by the re-feeding unit R32, and reaches the image forming unit 10.

As described above, according to the present embodiment, the image forming unit 10 that forms an image on the paper P, the image forming path R1 that conveys the paper P to the image forming unit 10, and the paper conveying rather than the image forming unit 10. The switchback unit R31, which branches from the image forming path R1 downstream in the direction, sequentially feeds until the rear end of the paper P reaches a predetermined position, and then reversely feeds the paper P, and the paper P which is back-fed by the switchback portion R31. An inversion path R3 having a refeeding section R32 that merges with the image forming path R1 upstream of the image forming section 10 in the paper transport direction, and a switchback section R31 upstream of the predetermined position in the paper transport direction during progressive feeding of the paper P. It is characterized by including a shortcut path R4 that branches from the paper P and conveys the paper P to the re-feeding unit R32 without back-feeding.
Therefore, by advancing the paper P that has progressed to the switchback unit R31 to the refeeding unit R32 via the shortcut path R4, it is possible to return the paper P to the image forming unit 10 without inverting the front and back sides of the paper P. It will be possible.
That is, it is possible to pass the image forming unit 10 a plurality of times without inverting the front and back of the paper P.

Further, according to the present embodiment, the switching gate G1 that switches the transport destination of the paper P on the image forming path R1 to the switchback portion R31 and the upstream of the paper transport direction when the paper P is sequentially fed in the switchback portion R31. The switching gate G2 and the switching gate G3 provided from the side to the downstream side are provided, and the switching gate G2 switches the transport destination of the paper P sequentially fed on the switchback portion R31 to the shortcut path R4, and the switching gate G3 , The transfer destination of the paper P back-fed on the switchback unit R31 is switched to the re-feeding unit R32.
Therefore, before the paper P that has advanced to the switchback unit R31 is reversed, it can be advanced to the refeeding unit R32 via the shortcut path R4.

Further, according to the present embodiment, by transporting the paper P to the refeeding unit R32 via the shortcut path R4, the image forming unit 10 is performed a plurality of times so that the image forming surfaces of the paper P are the same surface. A control unit 11 for executing a process of passing the paper is provided.
Therefore, for example, it is possible to perform processing such as forming an image on the same surface of the paper P.

[Modification example]
Next, a modified example of the image forming apparatus 100 of the above embodiment will be described.
FIG. 4 is a configuration diagram schematically showing the image forming apparatus 100A of the modified example. The same components as those of the image forming apparatus 100 of FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.
As shown in FIG. 4, the image forming apparatus 100A has a configuration in which the inversion path R3 includes a switchback unit R31, a re-feeding unit R32, and a second re-feeding unit R33.
The second refeeding unit R33 is continuously provided in the switchback unit R31 from the downstream end in the paper transport direction when the paper P is sequentially fed, and reaches the confluence 52 provided in the middle of the image forming path R1. It is arranged like this.
Further, the second re-feeding unit R33 is provided so that the paper P runs below the paper feed tray 21, that is, near the bottom surface of the image forming apparatus 100A.
The second re-feeding unit R33 can be used, for example, when the paper P is circulated when the paper P is a long paper having a length longer in the paper transport direction than the standard paper.
When the paper P is a long paper, the paper P is image-formed by, for example, a paper feeding device (not shown) connected to the image forming apparatus 100A or a manual feed tray provided in the image forming apparatus 100A. It can be sent to the route R1.

Hereinafter, the operation of the image forming apparatus 100A will be described.
FIG. 5 is a flowchart showing an image forming process executed by the image forming apparatus 100A. The same processing as the image forming processing of FIG. 3 is designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 5, the control unit 11 executes the same processing as the image forming processing of FIG. 3 from step S1 to step S6.
Then, when the overwriting mode is set in step S6 (step S6: YES), the control unit 11 determines whether or not the paper P is a long paper (step S10), and the long paper is used. If (step S10: YES), the process proceeds to step S2.
That is, in the case of long paper, the switching gate G2 cannot be switched, and the paper P is sequentially fed by the switchback section R31, reaches the second refeed section R33, and is conveyed by the second refeed section R33. It leads to the image formation path R1.

On the other hand, when the paper is not long paper (step S10: NO), the control unit 11 switches the switching gate G2 (step S7), and then returns to step S2 to repeat the subsequent processing.

As described above, according to the present modification, the inversion path R3 is continuously provided from the downstream end portion of the switchback portion R31 in the paper transport direction when the paper P is forwardly fed, and is provided on the switchback portion R31. When the control unit 11 includes a second re-feeding unit R33 that merges the paper P with the image forming path R1 upstream of the image forming unit 10 in the paper transport direction without causing the paper P to be fed backward, the control unit 11 executes the overwriting process. Depending on the length of the paper P in the transport direction, the paper P is transported to the refeed unit R32 via the shortcut path R4, or the paper P is transported to the second refeed unit R33 via the switchback unit R31. Select whether to do it.
Therefore, an appropriate transport route can be selected according to the length of the paper P in the paper transport direction.

Further, according to the present modification, the second refeeding unit R33 is provided so that the paper P runs near the bottom surface of the image forming apparatus 100A.
Therefore, since the straight line portion of the second refeeding unit R33 can be lengthened, jamming of the paper P can be suppressed.

Further, as a method of using the second re-feeding unit R33, in addition to the above, processing such as changing the transport order of a plurality of sheets P by retaining the paper P in the second re-feeding unit R33. It can also be used for.

According to the above-described embodiment and modification, as the process executed by the control unit 11, the overwriting process of forming an image a plurality of times on the same surface of the paper P has been described as an example, but the overwriting process has been described. In addition to this, for example, it is also possible to execute a process of controlling gloss by circulating the image-formed paper P and passing it through the fixing device 9 without forming an image from the second time onward.

Further, in the above-described embodiments and modifications, a configuration including an image forming unit 10W for forming a white (W) toner image has been exemplified as a feature, but the feature is not limited to white. In addition to this, for example, it may be clear (transparent) or the like.
Further, although the number of image forming units forming the spot color is one, the configuration may include two or more sets of image forming units forming the spot color of two or more colors.
Of course, the configuration may not include an image forming unit that forms a spot color.

Further, in the above-described embodiments and modifications, an example in which a non-volatile memory, a hard disk, or the like is used as a computer-readable medium for the program according to the present invention has been disclosed, but the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. Further, a carrier wave is also applied as a medium for providing the data of the program according to the present invention via a communication line.

Further, in the above-described embodiments and modifications, the electrophotographic image forming apparatus has been described as an example, but the present invention can also be applied to other image forming methods such as an inkjet method. Further, the transfer method is not limited to that of the above-described embodiment and modification.

In addition, the detailed configuration and detailed operation of the image forming apparatus can be appropriately changed without departing from the spirit of the present invention.

100, 100A Image forming device SC Original reading device 10 Image forming unit 10Y, 10M, 10C, 10K, 10W Image forming unit 1Y, 1M, 1C, 1K, 1W Photoreceptor drum 2Y, 2M, 2C, 2K, 2W Charging part 3Y, 3M, 3C, 3K, 3W Optical writing unit 4Y, 4M, 4C, 4K, 4W Developer 5Y, 5M, 5C, 5K, 5W Drum cleaner 6 Intermediate transfer belt 7Y, 7M, 7C, 7K, 7W Primary transfer Roller 8 Secondary transfer roller 9 Fixing device 20 Paper transport section 21 Paper feed tray 22 Feed feed section 23 Intermediate transport roller 24 Loop roller 25 Resist roller 26 Paper discharge tray 27 Reversing roller 28 Intermediate transport roller 51 Confluence point R1 Image formation path R2 Paper ejection path R3 Reverse path R31 Switchback section R32 Refeed section R33 Second refeed section R4 Shortcut path G1 Switching gate (first switching section)
G2 switching gate (second switching section)
G3 switching gate (3rd switching section)
11 Control unit 12 Storage unit 13 Communication unit 14 Operation unit P Paper

Claims (4)

An image forming part that forms an image on paper,
An image forming path for transporting paper to the image forming section, and an image forming path.
A switchback unit that branches from the image forming path downstream of the image forming unit in the paper transport direction, sequentially feeds until the rear end of the paper reaches a predetermined position, and then reversely feeds the paper, and the switchback portion feeds back. An inversion path having a refeeding section for joining the paper to be fed to the image forming path upstream of the image forming section in the paper transport direction.
A shortcut path that branches from the switchback section upstream of the predetermined position in the paper transport direction during sequential paper feeding and transports the paper to the refeeding section without backfeeding.
A control unit that executes a process of transporting the paper to the refeeding unit via the shortcut path so that the paper is passed through the image forming unit a plurality of times so that the image forming surfaces are on the same surface.
It is continuously provided from the downstream end portion in the paper transport direction when the paper in the switchback portion is sequentially fed, and is upstream in the paper transport direction from the image forming section without causing the paper on the switchback portion to be fed backward. In the second refeeding unit that merges with the image forming path,
Equipped with
When the control unit executes the process, the control unit transfers the paper to the re-feeding unit via the shortcut path or the paper to the second re-feeding unit according to the length of the paper in the conveying direction. An image forming apparatus characterized in that it selects whether to transport a paper. A first switching unit that switches the paper transfer destination on the image forming path to the switchback unit, and
The second switching section and the third switching section provided from the upstream side to the downstream side in the paper transport direction at the time of progressive paper feeding in the switchback section, and the third switching section.
Equipped with
The second switching unit switches the transport destination of the paper sequentially fed on the switchback unit to the shortcut path.
The image forming apparatus according to claim 1, wherein the third switching unit switches the destination of the paper to be fed back on the switchback unit to the re-feeding unit. The image forming apparatus according to claim 1 or 2 , wherein the second refeeding unit is provided so that the paper runs near the bottom surface of the image forming apparatus. Equipped with multiple paper trays for storing paper
The image forming apparatus according to any one of claims 1 to 3, wherein the plurality of paper feed trays are located between the image forming path and the second re-feeding unit.

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