JP6977349B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

In recent years, multifunctional image forming devices that also have functions such as printers, scanners, copiers, and fax machines have been widely used. In such image forming devices, the paper length is relatively long with respect to the device configuration. The demand for automatic double-sided printing on paper is increasing.

For example, after the paper after the fixing process in which the image is formed on one side through the transport path is drawn into the drawing path extending to the lower part of the device in the vertical direction of the image forming device, a pair of reversing rollers provided in the drawing path is provided. A technique has been proposed in which the paper is rotated in the reverse direction and re-fed to the transport path via the re-feed path (see, for example, Patent Document 1). In this way, by taking a long distance of the pull-in path from which the paper is drawn, the front and back sides of the paper having a relatively long paper length can be reversed, and double-sided printing is possible.

Japanese Unexamined Patent Publication No. 11-139646

However, according to the above-mentioned conventional technique, if jam occurs in a state where the paper straddles a plurality of units in the pull-in path, there is a problem that the paper is torn by the unit opening operation for jam processing. In order to avoid this, it is conceivable to take a relatively wide lead-in path in the machine so that jam processing can be performed without damaging the paper, but such a configuration makes the housing rigid. It cannot be secured, and the durability of the device may decrease.

On the other hand, instead of providing the pull-in path independently, by connecting the back side of the pull-in path in the pull-in direction to the transport path, the distance of the pull-in path is secured and the front and back of the paper are reversed. It is thought that it is possible. However, in such a configuration, depending on the paper length of the paper, the tip of the paper reaches the image forming portion or the fixing device on the transport path when the paper is pulled in. Since the image forming unit and the fixing device are not configured to be driven in the reverse rotation, if the re-feeding operation is started in such a state, the image forming unit and the fixing device are rotated in the opposite direction and are damaged. There is a problem that the image is damaged or a problem occurs.

Therefore, an object of the present invention is to provide an image forming apparatus capable of performing automatic double-sided printing of paper without causing damage or malfunction of members.

In order to solve the above problems, the invention according to claim 1 is an image forming apparatus.
An image forming apparatus that forms an image on paper transported along a transport path.
A pair of transfer members provided in the transport path to transfer the toner image to the paper,
A pair of fixing members provided in the transport path and fixing the toner image transferred on the paper to form an image,
A lead-in path connecting a first branch point on the downstream side of the fixing member of the transfer path and a confluence point on the upstream side of the transfer member of the transfer path, a second branch point of the lead-in path, and the transport path. A reversal transfer path having a refeed path connecting the refeed points on the upstream side of the transfer member, and a reverse transfer path.
A transport mechanism for transporting paper by a plurality of transport roller pairs provided in the transport path and the reverse transport path, respectively.
The transport mechanism pulls in the paper having an image formed on one side until the rear end of the paper reaches the confluence side of the second branch point of the pull-in path, and after the pull-in operation, the paper is reversed. A control unit that performs a re-feeding operation of feeding in the direction and re-feeding the paper whose front and back are reversed via the re-feeding path from the re-feeding point to the feeding path.
Equipped with
The control unit rotates and drives at least in the positive direction of the transfer member, the fixing member, and the transport roller pair provided on the downstream side of the confluence of the transport path. The paper that has arrived at the end of the operation is separated before the re-feeding operation .
Paper size, when the paper type and basis weight of the predetermined condition is satisfied, before the image forming after the completion and the pull-in operation to one side of the sheet, characterized by Rukoto is separated the transfer member.
Further, in order to solve the above problems, the invention according to claim 2 is an image forming apparatus.
An image forming apparatus that forms an image on paper transported along a transport path.
A pair of transfer members provided in the transport path to transfer the toner image to the paper,
A pair of fixing members provided in the transport path and fixing the toner image transferred on the paper to form an image,
A lead-in path connecting a first branch point on the downstream side of the fixing member of the transfer path and a confluence point on the upstream side of the transfer member of the transfer path, a second branch point of the lead-in path, and the transport path. A reversal transfer path having a refeed path connecting the refeed points on the upstream side of the transfer member, and a reverse transfer path.
A transport mechanism for transporting paper by a plurality of transport roller pairs provided in the transport path and the reverse transport path, respectively.
The transport mechanism pulls in the paper having an image formed on one side until the rear end of the paper reaches the confluence side of the second branch point of the pull-in path, and after the pull-in operation, the paper is reversed. A control unit that performs a re-feeding operation of feeding in the direction and re-feeding the paper whose front and back are reversed via the re-feeding path from the re-feeding point to the feeding path.
A detection unit for detecting the presence or absence of paper in each of the transfer member, the fixing member, and the transfer roller pair provided on the downstream side of the confluence of the transfer path.
Equipped with
The control unit rotates and drives at least in the positive direction of the transfer member, the fixing member, and the transport roller pair provided on the downstream side of the confluence of the transport path. The paper that has arrived at the end of the operation is separated before the re-feeding operation.
Among the transfer roller pairs provided on the downstream side of the transfer member, the fixing member, and the confluence point of the transfer path during the pull-in operation, those in which the detection unit detects that the paper has arrived are sequentially selected. It is characterized by being separated.

The invention according to claim 3 is the image forming apparatus according to claim 1 or 2.
A guide member for guiding the entry of the paper into the fixing member is provided.
The control unit is characterized in that when the fixing member is separated, the paper is supported by the guide member so that the paper does not come into contact with the fixing member.

The invention according to claim 4 is the image forming apparatus according to any one of claims 1 to 3.
The control unit is one of the transport roller pairs provided on the downstream side of the confluence of the transport path and can be rotationally driven in the forward and reverse directions, and the paper arrives at the completion of the pull-in operation. It is characterized in that the paper is conveyed by being driven in a reverse rotation during the re-feeding operation.

According to the present invention, it is possible to provide an image forming apparatus capable of performing automatic double-sided printing of paper without causing damage or malfunction of members.

It is a block diagram which shows typically the image forming apparatus which concerns on 1st Embodiment. It is explanatory drawing which shows the operation of the member which comprises the fixing device. It is a schematic diagram which shows the position of the long paper at the time of pulling-in operation. It is a schematic diagram which shows the position of the long paper at the time of completion of a pulling operation. It is a schematic diagram which shows the position of the long paper at the time of a re-feeding operation. 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 long paper reversal control process which is executed by the control part of FIG. 6 in 1st Embodiment. It is a flowchart which shows the long paper reversal control process which is executed by the control part of FIG. 6 in the 2nd Embodiment. It is a flowchart which shows the long paper reversal control process which is executed by the control part of FIG. 6 in the 3rd Embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, although the embodiments described below are provided with various technically preferable limitations for carrying out the present invention, the scope of the invention is not limited to the following embodiments and illustrated examples.

<< First Embodiment >>
[Structure of image forming apparatus 100]
First, the configuration of the image forming apparatus 100 in the first 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. Further, the image forming apparatus 100 can form an image not only on the standard size paper P2 but also on the long paper P1 which is a paper having a longer paper length than the standard size paper P2. The standard paper P2 is housed in a paper feed tray 21 or the like as described later, and the long paper P1 is fed into the device from a long paper tray 41 or a manual feed tray 42 externally connected to the image forming device 100. .. In the following description, image formation on the long paper P1 will be mainly described, but images can be formed on the standard paper P2 in the same manner.

The image forming apparatus 100 is mainly composed of a document reading device SC, an image forming unit 10, a fixing device 50, 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 was done.

The image forming unit 10 includes four sets of image forming units 10Y, 10M, 10C, 10K, an intermediate transfer belt 6, a secondary transfer roller 9, and the like. 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).

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

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

The toner image composed of each color transferred on the intermediate transfer belt 6 is transferred by the secondary transfer roller 9 to the long paper P1 conveyed at a predetermined timing by the paper conveying unit (conveying mechanism) 20 described later. Toner. The secondary transfer roller 9 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, and is in a pressure contact state under the control of the control unit 11. It is configured to be switchable to the separated state. Therefore, in the present embodiment, the intermediate transfer belt 6 and the secondary transfer roller 9 form a pair of transfer members.

Next, the fixing device 50 will be described with reference to FIGS. 1 and 2. FIG. 2 is a schematic view showing the operation of the members constituting the fixing device 50.

The fixing device 50 is a device that performs fixing processing on the long paper P1 on which the toner image is transferred, that is, the long paper P1 sent out from the transfer nip portion, and is, for example, a pair of fixing members 51, 52 and the said fixing device 50. It is composed of a heater 53 that heats one or both of the fixing members 51 and 52, and a guide member 54. In the transfer process of the long paper P1, the fixing device 50 fixes the toner image on the long paper P1 through the action of the pressure by the pair of fixing members 51 and 52 and the heat of the fixing members 51 and 52. conduct. Further, the fixing member 51 and the fixing member 52 are pressure contact members that form a nip portion (hereinafter referred to as “fixing nip portion”) by being pressed and arranged, and the pressure contact state is separated under the control of the control unit 11. It is configured to be switchable to.
In addition to being composed of a pair of rollers, the fixing members 51 and 52 can be widely adopted in a configuration composed of a pair of rotating members, such as a combination of belts and a combination of belts and rollers.

Further, as shown in FIG. 2A, the guide member 54 supports the long paper P1 and guides the long paper P1 to enter the fixing nip portion. Further, the guide member 54 is configured to be movable under the control of the control unit 11, and moves in the direction of the arrow in FIG. 2B when the fixing members 51 and 52 are switched to the separated state. As a result, the guide member 54 is moved to a position that supports the long paper P1 and can prevent the long paper P1 from coming into contact with the fixing members 51 and 52 while the fixing members 51 and 52 are separated from each other.

The long paper P1 that has been fixed by the fixing device 50 is discharged to the paper ejection tray 29 attached to the outer side surface of the housing by the paper ejection roller 28.

As shown in FIG. 1, the paper transport unit 20 transports the long paper P1 or the standard paper P2 along the transport path R1 and the reverse transport path R2 including the lead-in path R21 and the refeed path R22. The transport path R1 is a path from the long paper tray 41 or the manual feed tray 42 or the paper feed tray 21 to the paper output tray 29 through the transfer nip portion and the fixing nip portion of the image forming unit 10. The long paper P1 is housed in a long paper tray 41 connected to the image forming apparatus 100 or placed on the manual feed tray 42, and the image forming apparatus is placed on the long paper tray 41 or the manual feed tray 42. It is supplied into 100 and sent out to the transport path R1. Further, the standard paper P2 is housed in the paper feed tray 21, is taken in by the paper feed unit 22, and is sent out to the transport path R1.

In this transport path R1, a plurality of transport roller pairs 23 to 27 for transporting the long paper P1 are provided on the upstream side of the transfer nip portion. The individual transport roller pairs 23 to 27 are composed of a pair of pressure-welded rollers, and at least one of the rollers is rotationally driven in the positive direction through a drive mechanism mainly composed of an electric motor to transport the long paper P1. do. Here, the forward direction is the rotation direction for transporting the long paper P1 to the downstream side, and the reverse direction is the rotation direction opposite to the forward direction. Further, the pair of rollers constituting the individual transport roller pairs 23 to 27 are configured so that the state between the rollers can be switched between the pressure contact state and the separated state under the control of the control unit 11.
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.

Further, the transport roller pair 26 functions as a loop roller pair, and the transport roller pair 27 functions as a resist roller pair. That is, in the transport path R1, the long paper P1 to be fed is sequentially transported by a plurality of transport roller pairs 23 to 26 provided from the upstream side to the downstream side and proceeds. When the tip of the long paper P1 approaches the transport roller pair 27, the long paper P1 transported by the transport roller pair 26 or the like is abutted against the transport roller pair 27 in the stopped rotation state, and the transport roller pair 26 is abutted against the transport roller pair 27. Continues to rotate for a predetermined time, so that a loop is formed on the long paper P1. By the action of this loop formation, the bending of the tip of the long paper P1 is corrected. Next, the transfer roller pair 27 starts rotating at a predetermined timing so as to synchronize with the toner image carried by the intermediate transfer belt 6, so that the long paper P1 is transferred to the transfer nip portion.

The transport path R1 is provided with a detection unit SE, and the detection unit SE is composed of position detection sensors SE1 to SE5. The operation of the paper transport unit 20 is controlled by the control unit 11 based on the detection results of the position detection sensors SE1 to SE5.

The position detection sensors SE1 to SE5 are arranged in the vicinity of the transfer roller pairs 25 to 27, the secondary transfer rollers 9 and the fixing members 51 and 52 in the transfer path R1, respectively, and the detection positions of the position detection sensors SE1 to SE5 (respectively). The arrival of the tip of the long paper P1 to the transport roller pairs 25 to 27, the secondary transfer roller 9 and the positions near the fixing members 51 and 52) is detected. The detection results of these position detection sensors SE1 to SE5 are used for determining the separation timing of the transfer roller pairs 25 to 27, the secondary transfer roller 9, and the fixing members 51 and 52.

Here, with reference to FIGS. 3 to 5, the movement of the long paper P1 when double-sided printing is performed on the long paper P1 will be described. FIG. 3 shows a state when the long paper P1 is pulled into the pull-in path R21 after image formation is performed on one side, and FIG. 4 shows a state when the long paper P1 is pulled in completely. FIG. 5 shows a state when the inverted long paper P1 is re-fed into the transport path R1. In FIGS. 3 to 5, the position of the long paper P1 is indicated by a thick line portion on the transport path R1 or the reverse transport path R2.

When image formation is also performed on the back surface of the long paper P1, the long paper P1 that has finished image formation on the front surface is introduced into the lead-in path R21 by the switching gate (first branch point) 30 as shown in FIG. Be transported. The lead-in path R21 is a path connecting the switching gate 30 on the downstream side of the fixing device 50 of the transfer path R1 and the confluence point A1 on the upstream side of the secondary transfer roller 9 of the transfer path R1. Further, the lead-in path R21 branches to the re-feed path R22 at the second branch point A2. The re-feeding path R22 is a path connecting the second branch point A2 of the lead-in path R21 and the re-feeding point A3 on the upstream side of the secondary transfer roller 9 of the transport path R1.

In the lead-in path R21, the transfer roller pairs 31 and 32 are provided on the switching gate 30 side of the second branch point A2, and in the lead-in path R21, the transfer roller pair 33 is provided on the confluence point A1 side of the second branch point A2. , 34 are provided. The transport roller pairs 31 and 32 are configured in the same manner as the transport roller pairs 23 to 27. Further, the transport roller pairs 33 and 34 are configured in substantially the same manner as the transport roller pairs 23 to 27, and are further configured to be rotatable in the opposite direction. The long paper P1 conveyed into the drawing path R21 by the switching gate 30 is conveyed in the direction of the arrow in FIG. 3 by these transport roller pairs 31 to 34 and is drawn to the confluence point A1 side (pulling operation). Then, based on the detection result of the sensor (not shown) provided at the second branch point A2, as shown in FIG. 4, the rear end of the long paper P1 is behind the second branch point A2 (that is, the confluence point A1 side). ) Is reached, the transport of the long paper P1 is stopped, and the pulling operation is completed. At this time, depending on the paper length of the long paper P1, as shown in FIG. 4, the tip of the long paper P1 enters the transport path R1 from the confluence point A1 and reaches the secondary transfer roller 9 and the fixing device 50. In some cases.

After the pulling operation is completed, the transport roller pairs 33 and 34 are driven in reverse rotation to reversely feed the long paper P1 drawn into the pulling path R21 and convey it from the second branch point A2 into the refeeding path R22 (. Refeed operation). The refeed path R22 is provided with a transport roller pair 35 to 39. These transport roller pairs 35 to 39 are configured in the same manner as the above transport roller pairs 23 to 27. As shown in FIG. 5, the long paper P1 conveyed in the re-feeding path R22 is transferred from the second branch point A2 toward the re-feeding point A3 by the conveying roller pair 35 to 39 in the direction of the arrow in FIG. It is conveyed and is conveyed from the re-feeding point A3 into the transfer path R1. As a result, inversion of the long paper P1 is achieved.
The paper ejection roller 28, the switching gate 30, and the transport roller pairs 31 to 39 also constitute the paper transport unit 20 described above.

FIG. 6 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. 6, the control unit 11 includes a storage unit 12, a communication unit 13, an operation unit 14, a document reading device SC, an image forming unit 10, a paper transport unit 20, a fixing device 50, and position detection sensors SE1 to SE5. It is connected. 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 displays the toner image on the long paper P1 based on the image data input by the document reading device SC and the communication unit 13. Control to form. Further, when the job execution command is input by the operation unit 14, the control unit 11 executes the long paper reversal control process described later, and the transport rollers 25 to 27 during the job execution, the secondary transfer roller 9, and the fixing are fixed. Pressure welding / separation control of members 51 and 52 is performed.

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 can use the printing conditions, that is, the type of long paper P1 (for example, size, paper type, basis weight, etc.), the paper feed tray to be used, the density of the image, the magnification, the presence or absence of double-sided printing, and the like. Can be set. Further, the user can input a job execution command and an operation instruction in the adjustment mode 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 the first embodiment will be described.
The image forming apparatus 100 performs the long paper inversion control process as shown in FIG. FIG. 7 is a flowchart showing an example of the long paper inversion control process. 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.

As shown in FIG. 7, after the job is started, the control unit 11 is based on the size of the long paper P1 input in advance by the user, the image data input by the document reading device SC, the communication unit 13, and the like. , It is determined whether or not the image formation on one side of the long paper P1 is completed (step S101).

When it is determined that the image formation is not completed (step S101; NO), the control unit 11 performs the process of step S101 again.

When it is determined that the image formation is completed (step S101; NO), the control unit 11 starts the pull-in operation (step S102). Specifically, the control unit 11 guides the long paper P1 having an image formed on one side by the switching gate 30 into the pull-in path R21, and further, by means of a transport roller pair 31 to 34 provided in the pull-in path R21. The long paper P1 is conveyed toward the confluence point A1. As a result, the long paper P1 is conveyed from the confluence point A1 into the transfer path R1 and reaches the transfer roller pairs 25 to 27, the secondary transfer roller 9, the fixing device 50, and the like in sequence.

Next, the control unit 11 detects the arrival of the long paper P1 among the transport roller pairs 25 to 27, the secondary transfer rollers 9 and the fixing members 51 and 52, based on the detection results of the position detection sensors SE1 to SE5. It is determined whether or not there is a member (step S103).

When it is determined that there is a member in which the arrival of the long paper P1 is detected (step S103; YES), the control unit 11 puts the member in which the arrival of the long paper P1 is detected in a separated state (step S104). .. For example, when the position detection sensors SE1 and SE2 detect the long paper P1, the control unit 11 sets the transport roller pairs 25 and 26 in a separated state. Further, for example, when all of the position detection sensors SE1 to SE5 detect the long paper P1, the control unit 11 is a transfer roller pair 25 to 27, an intermediate transfer belt 6 and a secondary transfer roller 9, and a fixing member. Both 51 and 52 are separated from each other. Further, when the fixing members 51 and 52 are separated from each other, the control unit 11 moves the guide member 54 so that the long paper P1 does not come into contact with the fixing members 51 and 52, and supports the long paper P1. .. As a result, it is possible to suppress the occurrence of image defects in the image formed on one side of the long paper P1.

If it is determined that there is no member for which the arrival of the long paper P1 is detected (step S103; NO), the control unit 11 omits the process of step S104.

Next, the control unit 11 determines whether or not the pulling operation is completed (step S105). Specifically, a sensor (not shown) provided at the second branch point A2 detects whether or not the rear end of the long paper P1 has crossed the second branch point A2 and reached the confluence point A1 side, and the control unit 11 Determines whether or not the pull-in operation is completed based on the detection result.

When it is determined that the pulling operation is not completed (step S105; NO), the control unit 11 performs the process of step S103 again.

When it is determined that the pull-in operation is completed (step S105; YES), the control unit 11 performs a re-feeding operation (step S106). Specifically, the control unit 11 drives the transport roller pairs 33 and 34 in a reverse rotation drive, reverse-feeds the long paper P1, and feeds the long paper P1 from the second branch point A2 into the re-feeding path R22. Then, the control unit 11 conveys the long paper P1 by the transfer roller pair 35 to 39 provided in the refeed path R22, and conveys the long paper P1 from the refeed point A3 into the transfer path R1. As a result, the inversion of the long paper P1 is achieved.
As described above, the long paper inversion control process is performed.

In the process of step S103, whether or not the control unit 11 has detected the arrival of the long paper P1 among the transfer roller pairs 25 to 27, the secondary transfer rollers 9, and the fixing members 51 and 52. However, it is not limited to this. For example, when the transport roller pairs 25 to 27 are configured to be rotatable in the forward direction and the reverse direction, the control unit 11 is the long paper P1 of the secondary transfer roller 9 and the fixing members 51 and 52. It may be determined whether or not there is a member for which the arrival of is detected. Further, in this case, the detection unit SE may not have the position detection sensors SE1 to SE3.

[Technical effect of this embodiment]
As described above, according to the first embodiment, the image forming apparatus 100 that forms an image on the paper conveyed on the conveying path R1 is provided in the conveying path R1 and is an intermediate transfer that transfers the toner image to the paper. The belt 6 and the secondary transfer roller 9, the pair of fixing members 51 and 52 provided on the transfer path R1 to fix the toner image transferred on the paper to form an image, and the fixing member 51 of the transfer path R1. The lead-in path R21 connecting the switching gate 30 on the downstream side of 52 and the confluence point A1 on the upstream side of the secondary transfer roller 9 on the transfer path R1, and the second branch point A2 and the transfer path R1 on the lead-in path R21. A reversing transfer path R2 having a refeed path R22 connecting the refeed point A3 on the upstream side of the next transfer roller 9, and a plurality of transfer roller pairs provided in the transfer path R1 and the reverse transfer path R2, respectively. ~ 27, the paper transport section 20 that transports the paper by 31 to 39, and the paper transport section 20 that draws the paper with the image formed on one side into the paper, and the confluence point A1 from the second branch point A2 of the path R21. The pull-in operation of pulling in until it reaches the side, and after the pull-in operation, the paper is conveyed in the opposite direction and the paper whose front and back sides are reversed via the re-feeding path R22 is re-fed from the re-feeding point A3 to the conveying path R1. A control unit 11 for performing a re-feeding operation is provided, and the control unit 11 is downstream from the confluence point A1 of the intermediate transfer belt 6, the secondary transfer rollers 9, the fixing members 51 and 52, and the transfer path R1. Of the transport roller pairs 25 to 27 provided in the above, at least those that are rotationally driven only in the positive direction and that the paper has reached when the pulling operation is completed are separated before the refeeding operation, so that image formation is performed. Automatic double-sided printing of paper having a relatively long paper length with respect to the device configuration of the device 100 can be performed. Further, even if the paper reaches a member on the transport path R1 that cannot be driven in the reverse rotation by the pulling operation, by separating them, damage or malfunction due to the reverse rotation of the paper by the refeeding operation can be caused. The occurrence can be suppressed.

Further, a guide member 54 for guiding the entry of the paper into the fixing members 51 and 52 is provided so that the paper does not come into contact with the fixing members 51 and 52 when the control unit 11 separates the fixing members 51 and 52. Since the paper is supported by the guide member 54, it is possible to prevent the paper having an image formed on one side from coming into contact with the fixing members 51 and 52, and to suppress the occurrence of image defects due to this.

Further, detection for detecting the presence or absence of paper in each of the intermediate transfer belt 6, the secondary transfer roller 9, the fixing members 51 and 52, and the transfer roller pairs 25 to 27 provided on the downstream side of the confluence point A1 of the transfer path R1. The transfer roller pair 25 is provided with a section SE, and the control section 11 is provided on the downstream side of the confluence point A1 of the intermediate transfer belt 6, the secondary transfer rollers 9, the fixing members 51 and 52, and the transfer path R1 during the pull-in operation. Of ~ 27, those detected by the detection unit SE that the paper has arrived are sequentially separated from each other, so that it is possible to more reliably suppress the occurrence of damage or malfunction of each component. Further, since each member is separated at the same time as the pulling operation, it is possible to prevent the drawn paper from coming into contact with the secondary transfer roller 9 and the fixing device 50, and it is possible to more reliably suppress the occurrence of image defects.

<< Second Embodiment >>
Next, the second embodiment will be described. The points other than those described below shall be configured in the same manner as in the first embodiment.

The image forming apparatus 100 of the second embodiment is different from the first embodiment in that the long paper inversion control process is performed as shown in FIG. FIG. 8 is a flowchart showing an example of the long paper inversion control process according to the second embodiment. 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.

As shown in FIG. 8, after the job is started, the control unit 11 is based on the size of the long paper P1 input in advance by the user, the image data input by the document reading device SC, the communication unit 13, and the like. , It is determined whether or not the image formation on one side of the long paper P1 is completed (step S201).

When it is determined that the image formation is not completed (step S201; NO), the control unit 11 performs the process of step S201 again.

When it is determined that the image formation is completed (step S201; NO), the control unit 11 determines that the transfer rollers 25 to 27, the secondary transfer rollers 9 and the secondary transfer rollers 9 are based on the size of the long paper P1 input in advance by the user. Among the fixing members 51 and 52, the member to which the long paper P1 reaches when the pulling operation with respect to the long paper P1 is completed is specified (step S202).

Next, the control unit 11 puts the member specified in the process of step S202 into a separated state (step S203). For example, when it is specified that the long paper P1 reaches the transport roller pairs 25 and 26 when the pulling operation is completed, the control unit 11 sets the transport roller pairs 25 and 26 in a separated state. Further, for example, when it is specified that the long paper P1 reaches the transfer roller pairs 25 to 27, the intermediate transfer belt 6 and the secondary transfer roller 9, and the fixing members 51 and 52 when the pulling operation is completed, the control unit 11 determines. The transport roller pairs 25 to 27, the secondary transfer roller 9, and the fixing members 51 and 52 are all separated from each other. Further, when the fixing members 51 and 52 are separated from each other, the control unit 11 moves the guide member 54 so that the long paper P1 does not come into contact with the fixing members 51 and 52, and supports the long paper P1. .. As a result, it is possible to suppress the occurrence of image defects in the image formed on one side of the long paper P1.

Next, the control unit 11 performs a pull-in operation (step S204) and a re-feeding operation (step S205).
As described above, the long paper inversion control process is performed.

In the process of step S202, the control unit 11 reaches the long paper P1 when the pulling operation with respect to the long paper P1 is completed among the transport roller pairs 25 to 27, the secondary transfer rollers 9, and the fixing members 51 and 52. Although it is intended to specify the member to be used, the present invention is not limited to this. For example, when the transport roller pairs 25 to 27 are configured to be rotatable in the forward direction and the reverse direction, the control unit 11 is the long paper P1 of the secondary transfer roller 9 and the fixing members 51 and 52. The member to which the long paper P1 reaches when the pulling operation is completed may be specified.

As described above, according to the second embodiment, as in the first embodiment, automatic double-sided printing of paper having a relatively long paper length with respect to the apparatus configuration of the image forming apparatus 100 can be performed.
Further, the control unit 11 is provided on the downstream side of the confluence point A1 of the intermediate transfer belt 6, the secondary transfer rollers 9, the fixing members 51 and 52, and the transfer path R1 based on the size of the paper. Of the 27, the one that the paper has reached when the pulling operation is completed is separated after forming an image on one side of the paper, so that each member can be separated before the pulling operation is performed. .. Therefore, even if the paper reaches a member on the transport path R1 that cannot be driven in the reverse rotation by the pulling operation, by separating them, damage or malfunction due to the reverse rotation of the paper by the refeeding operation can be caused. The occurrence can be suppressed. Further, since the members are separated from each other before the pulling operation, it is possible to prevent the drawn paper from coming into contact with the secondary transfer roller 9 and the fixing device 50, and it is possible to more reliably suppress the occurrence of image defects.

<< Third Embodiment >>
Next, a third embodiment will be described. The points other than those described below shall be configured in the same manner as in the first embodiment.

In the image forming apparatus 100 of the third embodiment, the transfer roller pairs 25 to 27 are configured to be rotatable in the forward direction and the reverse direction, and the long paper inversion control process is performed as shown in FIG. It differs from the first embodiment in that it is performed. FIG. 9 is a flowchart showing an example of the long paper inversion control process according to the third embodiment. 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.

As shown in FIG. 9, after the job is started, the control unit 11 is based on the size of the long paper P1 input in advance by the user, the image data input by the document reading device SC, the communication unit 13, and the like. , It is determined whether or not the image formation on one side of the long paper P1 is completed (step S301).

When it is determined that the image formation is not completed (step S301; NO), the control unit 11 performs the process of step S301 again.

When it is determined that the image formation is completed (step S301; YES), the control unit 11 satisfies a predetermined condition based on the size, paper type, and basis weight of the long paper P1 input in advance by the user. Whether or not it is determined (step S302). Specifically, the paper length of the long paper P1 is the length at which the tip of the long paper P1 reaches the secondary transfer roller 9 when the pulling operation is completed, and the paper type and basis weight of the long paper P1 are different. The control unit 11 determines that the condition is satisfied when the secondary transfer roller 9 is rigid enough to be conveyed to the downstream side even if it is not in the pressure contact state during the pull-in operation.

When it is determined that the long paper P1 satisfies a predetermined condition (step S302; YES), the control unit 11 separates the intermediate transfer belt 6 and the secondary transfer roller 9 (step S303).
Here, an image is formed on one side, and the long paper P1 transported from the confluence point A1 into the transport path R1 by the pull-in operation has a high temperature because it has just passed through the fixing device 50. Therefore, when the long paper P1 in a high temperature state reaches the secondary transfer roller 9 by the pulling operation, the temperature of the secondary transfer roller 9 and the intermediate transfer belt 6 rises, and an image defect occurs in the image formed on the back surface. There is a risk of Therefore, when the long paper P1 satisfies a predetermined condition, the intermediate transfer belt 6 and the secondary transfer roller 9 are separated from each other before the pulling operation is performed to suppress the occurrence of the image defect. Can be done.

If it is determined that the long paper P1 does not satisfy the predetermined condition (step S302; NO), the control unit 11 omits the process of step S303.

Next, the control unit 11 performs a pull-in operation (step S304).

Next, the control unit 11 separates the intermediate transfer belt 6, the secondary transfer roller 9, and the fixing members 51 and 52, and sets the guide member 54 so that the long paper P1 does not come into contact with the fixing members 51 and 52. Move (step S305). When the intermediate transfer belt 6 and the secondary transfer roller 9 are already separated by the processing of step S303, only the fixing members 51 and 52 are separated.

Next, the control unit 11 performs a re-feeding operation (step S306). Specifically, the control unit 11 drives the transport roller pairs 25 to 27, 33, and 34 in a reverse rotation drive, reverse-feeds the long paper P1, and feeds the long paper P1 from the second branch point A2 into the re-feeding path R22. Then, the control unit 11 conveys the long paper P1 by the transfer roller pair 35 to 39 provided in the refeed path R22, and conveys the long paper P1 from the refeed point A3 into the transfer path R1. As a result, the inversion of the long paper P1 is achieved.
As described above, the long paper inversion control process is performed.

In the long paper inversion control process, the processes of steps S302 and S303 are performed, but the present invention is not limited to this, and the processes of steps S302 and S303 may not be performed.

Further, in the long paper reversal control process, the transport roller pairs 25 to 27 are configured to be rotatable in the forward direction and the reverse direction, and in the process of step S305, the intermediate transfer belt 6 and the secondary transfer roller 9 and the fixing are performed. The members 51 and 52 are separated from each other, and the long paper P1 is back-fed by the transport roller pairs 25 to 27, 33, 34 in the process of step S306, but the present invention is not limited to this. That is, the transport roller pairs 25 to 27 are configured to be rotatable and driven only in the positive direction, and in the process of step S305, the transport roller pairs 25 to 27, the intermediate transfer belt 6 and the secondary transfer roller 9, and the fixing members 51 and 52. The long paper P1 may be back-fed by the transport roller pairs 33 and 34 in the process of step S306.

Further, in the process of step S306, the transport roller pairs 25 to 27 are driven in reverse rotation, but the present invention is not limited to this. For example, the control unit 11 may drive the transport roller pairs 25 to 27 in which the long paper P1 is detected by the position detection sensors SE1 to SE3 when the pulling operation is completed in the reverse rotation.

As described above, according to the third embodiment, as in the first embodiment, automatic double-sided printing of paper having a relatively long paper length with respect to the apparatus configuration of the image forming apparatus 100 can be performed.
Further, among the transport roller pairs 25 to 27 provided on the downstream side of the confluence point A1 of the transport path R1, the control unit 11 can be rotationally driven in the forward and reverse directions, and the paper arrives when the pulling operation is completed. Since the paper is conveyed by rotating it in the reverse direction during the re-feeding operation, the re-feeding operation can be performed more reliably when the paper is thick or has a large basis weight. ..

Further, when the paper size, the paper type, and the basis weight satisfy the predetermined conditions, the control unit 11 separates the intermediate transfer belt 6 and the secondary transfer roller 9 before the pulling operation, so that an image is formed on one side. As a result, the heated paper comes into contact with the intermediate transfer belt 6 and the secondary transfer roller 9, and the temperature rise of them can be suppressed. As a result, it is possible to suppress the occurrence of image defects due to the temperature rise of the intermediate transfer belt 6 and the secondary transfer roller 9.

Further, at least one of the transfer roller pairs 25 to 27 provided on the downstream side of the confluence point A1 of the intermediate transfer belt 6, the secondary transfer rollers 9, the fixing members 51 and 52, and the transfer path R1 by the control unit 11. When the paper is driven to rotate only in the positive direction and the paper has reached when the pulling operation is completed, and the paper is separated after the pulling operation is completed and before the refeeding operation, the paper is moved on the transport path R1 by the pulling operation. Even if the members that cannot be driven in the reverse rotation of the above are reached, by keeping them apart from each other, it is possible to suppress the occurrence of damage or malfunction due to the reverse rotation of the members due to the refeeding operation. Further, since the members are separated from each other after the pulling operation is completed, the occurrence of jam during the pulling operation can be more reliably suppressed, and the paper can be more reliably drawn into the transport path R1.

"others"
The description in the above embodiment shows a suitable example of the image forming apparatus according to the present invention, and is not limited thereto.

For example, in the first to third embodiments described above, the image formed on the photoconductor drums 1Y to 1K is primarily transferred to the intermediate transfer belt 6, and the image is transferred from the intermediate transfer belt 6 to the paper by the secondary transfer roller 9. Although the description has been given by taking a color image forming apparatus for transferring the image as an example, the present invention can also be applied to a monochrome image forming apparatus for transferring an image directly from a photoconductor drum to paper by a transfer roller.

Further, in the first to third embodiments described above, the fixing device 50 is configured to have the guide member 54, but the guide member 54 may not be provided. In this case, for example, an air separation fan (not shown) for blowing air to the fixing nip portion is provided in order to efficiently separate the paper passing through the fixing nip portion from the fixing members 51 and 52, and the fixing members 51 and 52 are provided. The control unit 11 may adjust the amount of air blown by the air separation fan so that the paper does not come into contact with the fixing members 51 and 52.

Further, in the first to third embodiments described above, the guide member 54 is configured to be movable under the control of the control unit 11, but the present invention is not limited to this. For example, the guide member 54 may not move and may be configured to be able to support the paper by projecting a protrusion from the guide member 54 under the control of the control unit 11.

Further, in the first to third embodiments described above, the standard paper P2 is fed from the paper feed tray 21, but the present invention is not limited to this, and the paper is fed from the manual feed tray 42. It is also good.

Further, in the first to third embodiments described above, it is assumed that the paper transport unit 20 has transport roller pairs 23 to 27, 31 to 39 provided in the transport path R1 or the reverse transport path R2. , Not limited to this. That is, the number of transport roller pairs possessed by the paper transport unit 20 may be larger or smaller than this, so that the distance between the transport roller pairs is shorter than the paper length of the paper to be transported. It suffices if it is arranged.

Further, in the second and third embodiments described above, the image forming apparatus 100 is provided with the detection unit SE, but the present invention is not limited to this, and the image forming apparatus 100 may not be provided with the detection unit SE. good.

Further, in the first to third embodiments described above, it is assumed that the image forming apparatus 100 is configured to be able to execute different long paper inversion control processes, but the present invention is not limited to this. That is, one image forming apparatus 100 may be configured to be able to execute any two or three of these long paper inversion control processes. In that case, which long paper inversion control process to be executed may be determined based on the user's operation input, or the control unit 11 determines according to the configuration inside the device, the type of paper, and the like. It may be a thing.

Further, in the first to third embodiments described above, any one of the intermediate transfer belt 6, the secondary transfer roller 9, the fixing members 51 and 52, and the transfer roller pair 25 to 27 is separated at a predetermined timing. However, it is not limited to this. For example, if the transport roller pair provided on the downstream side of the fixing device 50 in the transport path R1 is rotationally driven only in the positive direction and the paper reaches when the pulling operation is completed, the transport roller pair is used. May also be separated.

Further, in the above description, 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.

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.

6 Intermediate transfer belt (transfer member)
9 Secondary transfer roller (transfer member)
11 Control unit 20 Paper transport unit (conveyance mechanism)
25-27, 31-39 Conveying roller vs. 30 switching gate (first branch point)
51, 52 Fixing member 54 Guide member 100 Image forming device A1 Confluence point A2 Second branch point A3 Refeeding point R1 Transfer path R2 Reverse transfer path R21 Pull-in path R22 Refeed path SE detector

Claims (4)

An image forming apparatus that forms an image on paper transported along a transport path.
A pair of transfer members provided in the transport path to transfer the toner image to the paper,
A pair of fixing members provided in the transport path and fixing the toner image transferred on the paper to form an image,
A lead-in path connecting a first branch point on the downstream side of the fixing member of the transfer path and a confluence point on the upstream side of the transfer member of the transfer path, a second branch point of the lead-in path, and the transport path. A reversal transfer path having a refeed path connecting the refeed points on the upstream side of the transfer member, and a reverse transfer path.
A transport mechanism for transporting paper by a plurality of transport roller pairs provided in the transport path and the reverse transport path, respectively.
The transport mechanism pulls in the paper having an image formed on one side until the rear end of the paper reaches the confluence side of the second branch point of the pull-in path, and after the pull-in operation, the paper is reversed. A control unit that performs a re-feeding operation of feeding in the direction and re-feeding the paper whose front and back are reversed via the re-feeding path from the re-feeding point to the feeding path.
Equipped with
The control unit rotates and drives at least in the positive direction of the transfer member, the fixing member, and the transport roller pair provided on the downstream side of the confluence of the transport path. The paper that has arrived at the end of the operation is separated before the re-feeding operation .
Paper size, when the paper type and basis weight of the predetermined condition is satisfied, before the image forming after the completion and the pull-in operation to one side of the paper, the image forming apparatus according to claim Rukoto is separated the transfer member. An image forming apparatus that forms an image on paper transported along a transport path.
A pair of transfer members provided in the transport path to transfer the toner image to the paper,
A pair of fixing members provided in the transport path and fixing the toner image transferred on the paper to form an image,
A lead-in path connecting a first branch point on the downstream side of the fixing member of the transfer path and a confluence point on the upstream side of the transfer member of the transfer path, a second branch point of the lead-in path, and the transport path. A reversal transfer path having a refeed path connecting the refeed points on the upstream side of the transfer member, and a reverse transfer path.
A transport mechanism for transporting paper by a plurality of transport roller pairs provided in the transport path and the reverse transport path, respectively.
The transport mechanism pulls in the paper having an image formed on one side until the rear end of the paper reaches the confluence side of the second branch point of the pull-in path, and after the pull-in operation, the paper is reversed. A control unit that performs a re-feeding operation of feeding in the direction and re-feeding the paper whose front and back are reversed via the re-feeding path from the re-feeding point to the feeding path.
A detection unit for detecting the presence or absence of paper in each of the transfer member, the fixing member, and the transfer roller pair provided on the downstream side of the confluence of the transfer path.
Equipped with
The control unit rotates and drives at least in the positive direction of the transfer member, the fixing member, and the transport roller pair provided on the downstream side of the confluence of the transport path. The paper that has arrived at the end of the operation is separated before the re-feeding operation.
Among the transfer roller pairs provided on the downstream side of the transfer member, the fixing member, and the confluence point of the transfer path during the pull-in operation, those in which the detection unit detects that the paper has arrived are sequentially selected. An image forming apparatus characterized by being separated. A guide member for guiding the entry of the paper into the fixing member is provided.
The image forming apparatus according to claim 1 or 2 , wherein the control unit supports the paper by the guide member so that the paper does not come into contact with the fixing member when the fixing member is separated. .. The control unit is one of the transport roller pairs provided on the downstream side of the confluence of the transport path and can be rotationally driven in the forward and reverse directions, and the paper arrives at the completion of the pull-in operation. The image forming apparatus according to any one of claims 1 to 3, wherein the paper is conveyed in a reverse rotation drive during the re-feeding operation.

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