JP6834622B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

Generally, in an image forming apparatus, recording materials such as cut paper are laminated on a tray and designed to be fed one by one on a transport path by a paper feed roller or the like.
However, depending on the type of paper, double feeding may occur in which a plurality of sheets are fed at one time. In a state where double feeding occurs, the weight and thickness of the paper are increased, so that the paper may not be conveyed normally.

Conventionally, when double feeding is detected, the paper transport is interrupted and the image forming apparatus is stopped. However, in such a control, the user must take out the double-fed paper by himself / herself, which increases the time and effort of the user and wastes time. In addition, even the paper that was originally capable of forming an image is discarded (spoiled paper).
In the field of production printing, since the productivity of printed matter is directly linked to the profitability of the business, it is strongly desired to reduce downtime as much as possible and to suppress the generation of spoiled paper.

Therefore, Patent Document 1 discloses a technique of performing image formation to suppress a decrease in productivity when image formation is not hindered even during double feeding.
Specifically, if the tip of the paper to be image-formed is retracted from the edge of another paper that overlaps the paper, image formation is stopped, but if it is not retracted, the image formation is stopped. Perform image formation. As a result, it is possible to suppress a decrease in productivity as compared with the case where image formation is stopped immediately when double feeding occurs.

Japanese Unexamined Patent Publication No. 2012-2935

However, as in the invention described in Patent Document 1, when the double-fed paper is controlled to be discharged to the discharge tray installed outside the image forming apparatus, it is downstream depending on the degree of deviation in the transport direction of the overlapping papers. It will be erroneously detected by the JAM detection sensor on the side. That is, if the double-fed paper is significantly deviated in the transport direction, the passing time of the paper measured by the JAM detection sensor becomes long, so that it is determined that JAM has occurred. In this case, the image forming apparatus will execute the JAM processing, which will promote downtime.
On the other hand, if the JAM detection sensor or the like is turned off during double feed transportation in order to prevent erroneous detection of the JAM detection sensor or the like, it cannot be detected when JAM occurs during double feed transportation.

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 suitably eliminating double feeding.

In order to achieve the above object, the image forming apparatus according to claim 1 is
Image formation including a paper feed unit for feeding paper, a transport unit for transporting paper fed from the paper feed unit, and an image forming unit for forming an image on the paper transported by the transport unit. In the device
A double feed detection unit, which is arranged between the paper feed unit and the image forming unit and detects double feed of the paper fed by the paper feed unit,
A paper length calculation unit that calculates the double feed paper length of the double feed paper for which double feed is detected by the double feed detection unit,
A control unit that controls paper transport by the transport unit of the double feed paper based on the double feed paper length calculated by the paper length calculation unit.
It is characterized by having.

The invention according to claim 2 is the image forming apparatus according to claim 1.
A tip position calculation unit that calculates the tip position of the double feed paper from the timing when the double feed detection unit detects the double feed of the paper.
Equipped with an output tray for ejecting paper,
The transport unit
A first transport path for transporting the paper fed from the paper feed section to the image forming section, a second transport path for reversing the paper image-formed by the image forming section, and the first transport. It is provided with a confluence portion where the path and the second transport path merge.
The double feed detection unit is arranged on the first transport path on the upstream side of the confluence unit.
The control unit
When the tip position does not reach the merging portion, the transport of the double-feed paper and the paper upstream of the double-feed paper is stopped, and the first transport path downstream of the merging portion and the first After transporting the paper on the transport path of No. 2 to the output tray, the first mode of transporting the double feed paper and the paper upstream of the double feed paper to the output tray is executed.
When the tip position reaches the merging portion, the paper on the first transport path downstream of the merging portion and the double-feeding paper and the paper upstream of the double-feeding paper are placed in the discharge tray. After the paper is transported, the second mode of transporting the paper on the second transport path to the output tray is executed.

The invention according to claim 3 is the image forming apparatus according to claim 2.
The output tray has at least a first output tray and a second output tray.
The control unit
In the first mode, the paper on the first transport path and the second transport path downstream of the confluence portion is made to form an image by the image forming section, and the first paper ejection tray is formed. It is characterized in that the double-feeding paper and the paper upstream of the double-feeding paper are discharged to the second paper ejection tray without being caused to form an image by the image forming unit.

The invention according to claim 4 is the image forming apparatus according to claim 2 or 3.
The output tray has at least a first output tray and a second output tray.
The control unit
In the second mode, the paper on the second transport path is made to form an image by the image forming unit, and the paper is conveyed to the first paper ejection tray and is conveyed to the first paper ejection tray, and the first one downstream of the merging portion. It is characterized in that the paper on the transport path, the double-feed paper, and the paper upstream of the double-feed paper are discharged to the second output tray without causing the image forming unit to form an image.

The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4.
A determination unit for determining whether or not the double feed paper length is larger than the maximum paper length that can be conveyed by the image forming apparatus is provided.
The control unit is characterized in that when the determination unit determines that the double feed paper length is larger than the maximum paper length, the transport of the double feed paper is stopped.

The invention according to claim 6 is the image forming apparatus according to any one of claims 1 to 5.
Equipped with a passing time detection unit that detects the passing time of paper
The control unit determines the occurrence of JAM based on the length of the double-feeding paper and the passing time, and when it is determined that the JAM has occurred, the control unit stops the transport of the double-feeding paper.

According to the present invention, it is possible to provide an image forming apparatus capable of preferably eliminating double feeding.

It is a figure which shows the schematic structure of the image forming apparatus which concerns on this invention. It is a block diagram which shows the functional structure of the image forming apparatus which concerns on this invention. It is a figure explaining the calculation method of the double feed paper tip position and the double feed paper length. It is a flowchart which shows the paper transport operation which concerns on 1st Embodiment. It is a figure which shows the transport state of the double feed paper and other papers when the tip of the double feed paper does not reach a confluence part. It is a figure which shows the transport state of a double feed paper and other papers when the tip of the double feed paper reaches a confluence part. It is a flowchart which shows the paper transport operation which concerns on 2nd Embodiment. It is a flowchart which shows the paper transport operation at the time when the tip of the double feed paper which concerns on 2nd Embodiment reaches a confluence part. It is a flowchart which shows the paper transport operation at the time when the tip of the double-feeding paper which concerns on 2nd Embodiment does not reach a merging part.

[First Embodiment]
First, a first embodiment of the image forming apparatus 1 according to the present invention will be described. The present invention is not limited to the illustrated examples.

FIG. 1 is a schematic configuration diagram of the image forming apparatus 1. FIG. 2 is a block diagram showing a functional configuration of the image forming apparatus 1.
The image forming apparatus 1 is composed of a main body 100 and a post-processing apparatus 200.

The main body 100 includes a control unit 110, a storage unit 111, a communication unit 112, an operation panel 120, an image reading unit 130, an image forming unit 140, a paper feeding unit 150, and a paper conveying unit 160.

The control unit 110 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU reads various processing programs stored in the ROM in response to an operation signal input from the operation unit 121 or an instruction signal received by the communication unit 112, expands the RAM, and follows the expanded program to the main body. Centrally control the operation of each part of 100.
When a print instruction is received via the communication unit 112, the storage unit 111 stores image data, paper size, double feed paper length, and other paper information.

The storage unit 111 is configured by a storage means such as a DRAM (Dynamic Random Access Memory) or an HDD (Hard Disk Drive) which is a semiconductor memory, and the image data acquired by the image reading unit 130 or external via the communication unit 112. Image data input from, and paper information such as paper size and double feed paper length are stored.

The communication unit 112 transmits / receives data to / from an external device connected to a communication network such as a LAN (Local Area Network).

The operation panel 120 includes an operation unit 121 and a display unit 122.
The operation unit 121 includes a touch panel formed so as to cover the display screen of the display unit 122, various operation buttons such as a number button and a start button, and outputs an operation signal based on the user's operation to the control unit 110.
The display unit 122 is composed of an LCD (Liquid Crystal Display), and displays various screens according to an instruction of a display signal input from the control unit 110.

The image reading unit 130 includes an ADF (automatic document feeding device), a scanner, and the like, and outputs the image data obtained by reading the image of the document to the control unit 110.

The image forming unit 140 forms an image on the paper fed from the paper feeding unit 150 based on the image data read by the image reading unit 130 or the image data received from the external device.
The image forming unit 140 is a photoconductor drum 141Y, 141M, 141C, 141K, an intermediate transfer belt 142, and a secondary transfer roller corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K). It is provided with 143, a fixing portion 144, a resist roller 145, and the like.

The photoconductor drum 141Y is uniformly charged and then scanned and exposed by a laser beam based on the yellow image data to form an electrostatic latent image. Then, yellow toner is adhered to the electrostatic latent image on the photoconductor drum 141Y, and development is performed.
The photoconductor drums 141M, 141C, and 141K are the same as the photoconductor drum 141Y except that the colors to be handled are different, and thus the description thereof will be omitted.

The toner images of each color formed on the photoconductor drums 141Y, 141M, 141C, and 141K are sequentially transferred onto the rotating intermediate transfer belt 142 (primary transfer). That is, a color toner image in which four color toner images are superimposed is formed on the intermediate transfer belt 142.
The color toner image on the intermediate transfer belt 142 is collectively transferred onto the paper by the secondary transfer roller 143 (secondary transfer).

The fixing unit 144 includes a heating roller that heats the paper on which the color toner image is transferred, and a pressure roller that pressurizes the paper, and fixes the color toner image on the paper by heating and pressurizing.

The paper feed unit 150 includes a paper feed tray Ta and Tb and a plurality of paper feed trays Tc to Th arranged in two paper feed devices connected in series, and any one of the paper feed trays Ta to Th. Paper is fed from the paper feed tray of. Each of the paper feed trays Ta to Th stores a predetermined type (size, paper type, basis weight, etc.) of paper for each paper feed tray. The paper stored in each of the paper feed trays Ta to Th is sent out to the image forming unit 140 by driving the paper feed motor.
The paper feed trays Ta to Th are provided so that they can be pulled out, and paper is replenished in a state where the paper feed trays Ta to Th are pulled out.

The paper transport unit 160 includes a transport roller or the like for transporting paper on the paper transport path, and transports the paper.
The paper transport unit 160 includes a paper feed transport path R1 (each paper feed tray to the resist roller 145: the first transport path) and an image formation path R2 (resist roller 145 to the fixing section 144: the first transport path) as paper transport paths. Path), reversing mechanism R3 (path for reversing the paper that has passed through the fixing portion 144: second transport route), discharge path R4 (path for transporting the paper that has passed through the fixing portion 144 to the aftertreatment device), and an image. It includes a merging portion J in which the forming path R2 and the reversing mechanism R3 merge and the paper passing through the reversing mechanism R3 is returned onto the image forming path R2.

The paper feed unit 150 feeds paper from any of the paper feed trays Tc to Th onto the paper feed transfer path R1, and conveys the paper to the image forming unit 140 of the main body 100 by the paper transfer unit 160. Alternatively, the paper feed unit 150 may feed paper from either the paper feed tray Ta or Tb onto the paper feed transport path R1 and transport the paper to the image forming unit 140 by the paper transport unit 160.

When the paper is conveyed to the image forming unit 140, the paper is conveyed on the image forming path R2, and the image forming unit 140 forms an image on the surface of the paper.
Further, when forming an image on both sides of the paper, the paper printed on the front surface is conveyed to the reversing mechanism R3 and inverted, and then conveyed again to the image forming path R2 by the confluence J to form an image on the back surface. After that, the paper is conveyed to the post-processing device 300.
When the image is formed on only one side of the paper, the paper having the image formed on one side through the discharge path R4 is conveyed to the post-processing device 200 without the paper being inverted by the reversing mechanism R3. Will be done.

Further, the paper transport unit 160 has double feed detection sensors SE1 and SE2 on the paper transport paths on the downstream side of the paper feed trays Tc to Te and Tf to Th, respectively. The double feed detection sensors SE1 and SE2 are composed of sensors such as an ultrasonic sensor that can detect double feed, and detect the presence or absence of double feed of the paper conveyed from each paper feed tray.
Further, the paper transport unit 160 has a JAM detection sensor SE3 on the paper transport path downstream of the fixing unit 144. The JAM detection sensor SE3 detects the presence or absence of JAM on the paper that has passed through the fixing portion 144.

The post-processing device 200 includes a control unit 210, a paper transport unit 260, and a post-processing unit 270.

The control unit 210 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU reads various processing programs stored in the ROM, expands them in the RAM, and centrally controls the operation of each part of the post-processing apparatus 200 according to the expanded programs.

The paper transport unit 260 includes a transport roller or the like for transporting paper on the paper transport path, transports the paper in the post-processing device 200, and discharges the paper tray T11 or T12 installed outside the post-processing device 200. Discharge the paper.
The paper transport unit 260 discharges the image-formed effective paper to the output tray T11 (first output tray) and the invalid paper that has not been image-formed to the T12 (second output tray).

The post-processing unit 270 performs paper processing such as sorting processing, staple processing, punching hole processing, folding processing, and bookbinding processing on the paper on which the image is formed by the image forming unit 140, if necessary.

Next, the paper transport control in the image forming apparatus 1 according to the first embodiment will be described. The present embodiment is characterized in that paper transport control is performed according to the length of the double-fed paper in the transport direction (double-feed paper length).
FIG. 3 shows an example of a method for calculating the double feed paper length in the present embodiment. Here, it is assumed that the paper is fed from the paper feed tray Tc and the paper Y is double-fed under the paper X that should be originally conveyed.

First, the double feed detection sensor SE1 (double feed detection means) detects the double feed.
The double feed detection sensor SE1 detects whether or not the double feed state is in the double feed state at a cycle of 1 ms, with the point a advanced by a predetermined distance from the tip of the paper X as the detection start point. The reason why the paper is detected at a cycle of 1 ms in this way is to improve the calculation accuracy of the tip position of the paper. For example, when the paper transport speed is 1000 mm / s, 1 ms corresponds to the distance traveled by the paper of 1 mm, and if it is 1 ms, the double feed position can be detected with an accuracy of 1 mm.

Next, the tip position of the double feed paper is calculated.
The position of the tip of the double feed in the paper transport direction (double feed tip position A) is, for example, a detection start point a of 5 mm, a paper transport speed V of 1000 mm / s, and double feed after 300 ms (detection timing time T). When is detected, it is determined that the position is 305 mm upstream from the position where the double feed detection sensor SE1 detects double feed.
That is,
A = V * T + a ... (1)
The double feed sheet tip position Amm is calculated by.

Next, the double feed paper length is calculated based on the equation (1).
The total length (double feed paper length D mm) of the double feed paper in the paper transport direction is the size of the paper to be fed C mm.
Then
D = C + A ... (2)
Calculated by.

When transporting the paper fed from any of the paper feed trays Tc to Te, the double feed detection sensor SE1 is used when transporting the paper fed from any of the paper feed trays Tf to Th. Can perform the same control using the double feed detection sensors SE1 and / or SE2.

That is, in the present embodiment, when double feed is detected, the double feed paper length D is used to control downstream from the double feed detection position.
For example, a JAM detection sensor SE3 or the like that detects the passage of paper is arranged downstream of the fixing unit 144 in the paper transport direction. The JAM detection sensor SE3 determines that JAM has occurred when the ON time of the JAM detection sensor SE3 is longer than the paper passing time obtained based on the paper size and the paper transport speed. However, when the paper is double-fed and the double-feed paper length is larger than the paper size, the ON time of the JAM detection sensor SE3 becomes longer than usual, and it is erroneously detected that JAM has occurred. There is a risk of
Therefore, in the present embodiment, when double feed is detected, the above-mentioned double feed paper length D is stored as the paper size and used for control after double feed detection.

Further, in the present embodiment, when the double feed paper length exceeds the maximum paper length that can be conveyed by the image forming apparatus 1, the paper transfer is stopped and the paper ejection operation is not performed.

In the case of long paper, if the double-fed paper deviates significantly in the transport direction, the length of the paper that can be conveyed by the image forming apparatus 1 (maximum paper length) may be exceeded. In such a case, if the paper transport is continued, JAM or the like may be generated. Therefore, control is performed to stop the transport of the double feed paper and its upstream paper.
That is, in FIG. 3, assuming that the maximum paper length that can be conveyed by the image forming apparatus 1 is E mm and the length that can be conveyed beyond the maximum paper length E is β mm.
D> E + β ・ ・ ・ (3)
If the condition is satisfied, the transport of the double feed paper and its upstream paper is stopped.

Next, the paper transport control according to the first embodiment will be described with reference to the flowchart of FIG. Here, a case where paper is fed from the paper feed tray Tc will be described.
Upon receiving the print instruction, the control unit 110 controls the paper feed tray Tc to feed the paper and start the transfer (step S401). Subsequently, the control unit 110 determines whether or not the double feed detection sensor SE1 (double feed detection unit) has detected the double feed (step S402).

When the control unit 110 determines that the double feed has been detected (step S402: Yes), the control unit 110 (tip position calculation unit) calculates the double feed tip position A (step S403). Subsequently, the control unit 110 (paper length calculation unit) calculates the double feed paper length D (step S404).

Next, when the control unit 110 (determination unit) determines whether D> E + β (step S405) and determines that D> E + β (step S405: No), the control unit 110 is double-fed. The transfer of the paper and the paper upstream thereof is stopped (step S406), and the control is terminated.
When the control unit 110 determines that D> E + β is not satisfied (step S405: Yes), the control unit 110 changes the paper size stored in the storage unit 111 to D (step S407).

Here, when the control unit 110 receives a print instruction, the storage unit 111 stores the paper size to be printed, and the control unit 110 performs paper transport control including JAM detection and the like based on the paper size information stored in the storage unit 111. .. By updating the paper size information stored in the storage unit 111 in step S407 to the double feed paper length D, the subsequent paper transport control can be executed as the paper having the paper size D.

Subsequently, when the double feed paper is conveyed downstream of the image forming unit 140, the control unit 110 determines whether or not JAM has occurred based on the paper passing time by the JAM detection sensor SE3 (passing time detecting unit). Determine (step S409). Here, as described above, the control unit 110 determines the occurrence of JAM by using the passing time based on the double feed paper length D.

When the control unit 110 determines that JAM has occurred (step S409: Yes), the control unit 110 executes the JAM process (step S410). Here, the JAM processing means that the control unit 110 displays on the display unit 122 that an error has occurred, and in order to prevent the subsequent paper from hitting the JAM, a load such as a motor upstream of the fixing unit 144 is used. Refers to the process of stopping the image forming apparatus 1 by stopping the image forming apparatus 1.

If it is determined in step S409 that JAM has not occurred (step S409: No), the control unit 210 (control unit) determines whether or not the double feed paper has been discharged to the output tray T12 (step S411). When the control unit 110 determines that the ejection is not completed (step S411: No), the process returns to step S409, but when it is determined that the ejection is completed (step S411: Yes), the paper stored in the storage unit 111 is stored. The size information is returned from the double feed paper length D to the initial value (step S412), returned to step S402, and paper transport is continued.

In step S402, when it is determined that the control unit 110 has not detected double feeding (step S402: No), it is determined whether or not all the sheets have been ejected (step S413), and it is determined that all the sheets have been ejected. Then (step S413: Yes), the control is terminated, but if it is determined that the control is not completed (step S413: No), the process returns to step S402 and the paper transport is continued.

As described above, the image forming apparatus 1 according to the first embodiment includes the double feed detection sensors SE1 and SE2 for detecting the double feed of the conveyed paper and the double feed paper in the upstream of the image forming unit 140. The control unit 110 includes a control unit 110 that calculates the double feed paper length in the transport direction and controls the feed of the paper based on the double feed paper length when the double feed of the paper is detected. The JAM detection by the JAM detection sensor SE3 downstream of the fixing unit 44 is controlled by the paper feed length.
Therefore, when the length of the paper in the transport direction changes due to the double feed, the double feed is appropriately discharged to the outside of the image forming apparatus without erroneously detecting the occurrence of JAM, so that the double feed is preferably released. it can. Further, since the double-fed paper is automatically transported and printing on other paper is continued, downtime and occurrence of spoiled paper can be suppressed.

Further, the image forming apparatus 1 according to the first embodiment stops the conveying of the double feeding paper and its upstream paper when the double feeding paper length exceeds the maximum transferable paper length of the image forming apparatus 1. Therefore, it is possible to prevent the occurrence of JAM or the like due to the transport of the double-feed paper.

In the above embodiment, JAM is detected on the double-feeding paper on which JAM is likely to occur, but of course, JAM may be detected not only on the double-feeding paper but also on all the papers. ..

[Second Embodiment]
Next, a second embodiment of the image forming apparatus according to the present invention will be described. Compared with the image forming apparatus 1 according to the first embodiment, the image forming apparatus 1 according to the second embodiment controls the transfer of paper depending on whether or not the tip of the double-fed paper reaches the merging portion J. It differs in that it changes.
For the sake of simplification of the description, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 3, it is assumed that the paper Y is double-fed under the paper X that is fed from the paper feed tray Tc and should be originally conveyed.
Whether or not the tip of the double feed sheet has reached the confluence J of the image forming path R2 and the reversing mechanism R3 is determined by using the following equation.
That is, assuming that the distance between the double feed detection sensor SE1 and the merging portion J is the distance between the merging points B mm and the maximum assumed distance that the paper advances due to inertia is α mm.
B ≤ A + α
In the case of, it can be determined that the tip of the double-feed paper reaches the merging portion J.

FIG. 5 shows an image forming apparatus 1 in a state where the tip of the double feed paper does not reach the merging portion J.
Double-sided printing is completed on the paper a in the drawing, single-sided printing is completed on the paper b and the paper c, and the paper d is being conveyed in the reversing mechanism R3, and the paper d is executing the single-sided printing. Further, the paper e is fed in a state of being double-fed from the paper feed tray Tc, and the paper f is fed from the paper feed tray Tc after the paper e is fed.
Here, since the tip of the paper e has not reached the confluence J, the papers b, c, and d are continued to be conveyed, and after passing through the reversing mechanism R3, printing on the back surface is executed on the image forming path R2. However, there is no possibility of collision with the double-fed paper e at the merging portion J and occurrence of jam or the like. Therefore, in the case of FIG. 5, the first mode is implemented. That is, in the first mode, after discharging the paper a to the output tray T11, printing using the papers b, c and d as effective paper and discharging the paper to the output tray T11, the double-fed paper e and the paper f are ejected. It is discharged to the paper feed tray T12 as invalid paper.

FIG. 6 shows an image forming apparatus 1 in a state where the tip of the double-feed paper reaches the confluence J.
When the paper b, c, and d are conveyed into the reversing mechanism R3 and printed on the back surface while the paper e is at the position shown in FIG. 6, the tips of the paper collide with each other at the confluence J, causing jams and the like. There is a risk. Therefore, in the case of FIG. 6, the second mode is implemented. That is, in the second mode, after the paper a is ejected to the output tray T11, the paper d on the image forming path R2 and the double-fed paper e and the paper f are regarded as invalid papers and then sent to the output tray T12. After discharging, printing is performed on the back surface using the papers b and c as effective paper, and the paper is discharged to the paper ejection tray T11.

Further, also in the present embodiment, as in the first embodiment, when the double feed paper length exceeds the maximum paper length that can be conveyed by the image forming apparatus 1, the paper transfer is stopped and the paper ejection operation is performed. It shall not be.

Next, the paper transport operation in the second embodiment will be described with reference to the flowcharts of FIGS. 7, 8 and 9. Here, a case where paper is fed from the paper feed tray Tc will be described.
Since the processes of steps S701 to S704 and steps S706 are the same as the processes of steps S401 to S404 and step S413 in FIG. 4, the description thereof will be omitted.

In step S705, the control unit 110 determines whether or not B ≦ A + α, that is, whether or not the double paper tip position A has reached the confluence portion J. When the control unit 110 determines that B ≦ A + α (step S705: Yes) and has reached the merging unit J, the control unit 110 proceeds to step S801 of FIG. 8 and starts the second mode. When the control unit 110 determines that the merging unit J has not been reached instead of B ≦ A + α (step S705: No), the control unit 110 proceeds to step S901 of FIG. 9 and starts the first mode.

The paper transport operation in the second mode will be described.
In the second mode, the transfer of the paper (paper b and paper c in FIG. 6) in the reversing mechanism R3 is stopped (step S801).
Subsequently, the control unit 210 ejects the paper for which double-sided printing has been completed (paper a in FIG. 6) to the output tray T11 (step S802), and the unprinted paper downstream from the merging unit J (paper d in FIG. 6). ) Is discharged to the output tray T12 as invalid paper (step S803).

In step S804, the control unit 110 (judgment unit) determines whether D> E + β, and if it determines that D> E + β is not (step S804: Yes), the process proceeds to step S805, and D> E + β. If it is determined that there is (step S804: No), the process proceeds to step S811.

In step S805, the control unit 110 updates the paper size stored in the storage unit 111 to D. Subsequently, the control unit 210 ejects the double-fed paper (paper e in FIG. 6) and the paper upstream thereof (paper f in FIG. 6) to the output tray T12 (step S806), and the control unit 110 is the most upstream. It is determined whether or not the rear end of the paper (paper f in FIG. 6) has passed the confluence J (step S807).

When the control unit 110 determines that the rear end of the most upstream paper has not passed through the merging portion J (step S807: No), the control unit 110 repeats the process of step S807, but determines that it has passed (step S807: Yes). The paper size stored in the storage unit 111 is returned to the initial value (step S808). Subsequently, the control unit 110 prints on the back surface of the paper (paper b and paper c in FIG. 6) in the reversing mechanism R3 (step S809), and the control unit 210 ejects the paper to the output tray T11 (step S810). ..

When the control unit 110 determines in step S804 that D> E + β (step S804: No), the control unit 81 performs the double-fed paper (paper e in FIG. 6) and the paper upstream thereof (paper in FIG. 6). The transport of f) is stopped (step S811), and the control is terminated.

The paper transport operation in the first mode will be described.
In the first mode, the control unit 110 stops the transport of the double-fed paper (paper e in FIG. 6) and the paper upstream thereof (paper f in FIG. 6) (step S901).
Subsequently, the control unit 210 ejects the paper for which double-sided printing has been completed (paper a in FIG. 6) to the output tray T11 (step S902), and the unprinted paper downstream from the merging unit J (paper d in FIG. 6). Printing is continued (step S903), and the paper for which double-sided printing is completed is ejected to the output tray T11 (step S904).

Next, the control unit 110 determines whether or not all the paper downstream from the merging unit J has been ejected (step S905). When the control unit 110 determines that the product has not been discharged (step S905: No), the process of step S905 is repeated, but when it is determined that the product has been discharged (step S905: Yes), the process proceeds to step S906.

In step S906, the control unit 110 (judgment unit) determines whether D> E + β, and if it determines that D> E + β is not (step S906: Yes), the process proceeds to step S907, and D> E + β. If it is determined that there is (step S906: No), the control is terminated.

In step S907, the control unit 110 updates the paper size stored in the storage unit 111 to D.
Subsequently, the control unit 210 ejects the double-fed paper (paper e in FIG. 6) and the paper upstream thereof (paper f in FIG. 6) to the output tray T12 (step S908).
When all the paper has been ejected, the control unit 110 returns the paper size stored in the storage unit 111 to the initial value (step S909), and ends the control.

As described above, in the image forming apparatus 1 according to the second embodiment, the control unit 110 of the double-fed paper at the time when the double-feed detection sensor SE1 or SE2 detects the double-feed of the paper. When the tip position is calculated and the tip position does not reach the confluence J of the image forming path R2 and the reversing mechanism R3, an image is formed on the paper on the image forming path R2 and the reversing mechanism R3 downstream of the confluence J. Is performed, and after the paper is conveyed to the output tray T11, the first mode of conveying the double-fed paper and its upstream paper to the output tray T12 is executed.
Therefore, since image formation is executed on all the papers downstream of the merging portion J and only the double feed paper and the upstream papers thereof are discharged as invalid papers, it is possible to suppress the occurrence of spoiled papers.

Further, in the image forming apparatus 1 according to the second embodiment, when the tip position reaches the merging portion J, the control unit 110 ejects the paper on the image forming path R2 and the double-fed paper. After transporting to the tray T12, an image is formed on the paper on the image forming path R2, and a second mode of transporting to the output tray T11 is executed.
Therefore, since the image is formed on the paper on the reversing mechanism R3 after the double-feed paper and its upstream paper are discharged, it is possible to suppress the occurrence of jam at the merging portion J. Further, since image formation is executed on all the papers downstream of the merging portion J and only the double feed paper and the upstream papers thereof are discharged as invalid papers, it is possible to suppress the occurrence of spoiled papers.

Further, in the image forming apparatus 1 according to the second embodiment, a paper ejection tray for ejecting the image-formed paper and a paper ejection tray for ejecting the image-forming paper including the double-feed paper are provided. It is a separate item. That is, since the invalid paper and the valid paper are separated, it is not necessary for the user to separate them, which saves time and effort.

Further, the image forming apparatus 1 according to the second embodiment stops the conveying of the double feeding paper and its upstream paper when the double feeding paper length exceeds the maximum transferable paper length of the image forming apparatus 1. Therefore, it is possible to prevent the occurrence of JAM or the like due to the transport of the double-feed paper.

In the second embodiment as well, as in the first embodiment, JAM may be detected by the JAM detection sensor SE3 on all the papers including the double feed paper. At this time, the double feed paper can perform JAM detection using the double feed paper length D.

[Other Embodiments]
Although the above embodiments have been specifically described based on the embodiment of the present invention, the above-described embodiment is a preferable example of the present invention and is not limited thereto.

For example, in the above embodiment, the double feed detection sensors SE1 and SE2 are arranged downstream of the paper feed trays Tc to Te or the paper feed trays Tf to h, respectively, and are fed from the paper feed trays Tc to Th. On the other hand, double feed detection is performed, but the present invention is not limited to this. By arranging the double feed detection sensor on the paper feed transport path R1 of the main body 100, the same control can be performed on the paper fed from the paper feed tray Ta or Tb.

Further, in the above embodiment, the control of JAM detection by the JAM detection sensor SE3 arranged downstream of the fixing portion 144 has been described, but the present invention is not limited to this. The present invention can also be applied to a JAM detection sensor installed at an arbitrary location in the image forming apparatus 1, such as in the vicinity of the resist roller 145.

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

1 Image forming apparatus 100 Main body 110 Control unit (paper length calculation unit, tip position calculation unit, control unit, judgment unit)
140 Image forming section 144 Fixing section 145 Resist roller 150 Feeding section 160 Paper transport section (transport section)
200 Post-processing device 210 Control unit (control unit)
260 paper transport section (conveyor section)
270 Post-processing unit J Confluence unit R1 Paper feed transfer path (first transfer path)
R2 image formation path (first transport path)
R3 reversing mechanism (second transport path)
R4 discharge path SE1, SE2 double feed detection sensor (double feed detection unit)
SE3 JAM detection sensor (passing time detection unit)
T11 output tray (first output tray)
T12 output tray (second output tray)

Claims (3)

Image formation including a paper feed unit for feeding paper, a transport unit for transporting paper fed from the paper feed unit, and an image forming unit for forming an image on the paper transported by the transport unit. In the device
A double feed detection unit, which is arranged between the paper feed unit and the image forming unit and detects double feed of the paper fed by the paper feed unit,
A paper length calculation unit that calculates the double feed paper length of the double feed paper for which double feed is detected by the double feed detection unit,
A tip position calculation unit that calculates the tip position of the double feed paper from the timing when the double feed detection unit detects the double feed of the paper.
An output tray for ejecting paper and
A control unit that controls paper transport by the transport unit of the double feed paper based on the double feed paper length calculated by the paper length calculation unit.
Equipped with a,
The transport unit
A first transport path for transporting the paper fed from the paper feed section to the image forming section, a second transport path for reversing the paper image-formed by the image forming section, and the first transport. It is provided with a confluence portion where the path and the second transport path merge.
The double feed detection unit is arranged on the first transport path on the upstream side of the confluence unit.
The control unit
When the tip position does not reach the merging portion, the transport of the double-feed paper and the paper upstream of the double-feed paper is stopped, and the first transport path downstream of the merging portion and the first After transporting the paper on the transport path of No. 2 to the output tray, the first mode of transporting the double feed paper and the paper upstream of the double feed paper to the output tray is executed.
When the tip position reaches the merging portion, the paper on the first transport path downstream of the merging portion and the double-feeding paper and the paper upstream of the double-feeding paper are placed in the discharge tray. An image forming apparatus, characterized in that a second mode of transporting the paper on the second transport path to the output tray is executed after the transport. The output tray has at least a first output tray and a second output tray.
The control unit
In the first mode, the paper on the first transport path and the second transport path downstream of the confluence portion is made to form an image by the image forming section, and the first paper ejection tray is formed. The first aspect of the present invention is characterized in that the double-feeding paper and the paper upstream of the double-feeding paper are discharged to the second paper ejection tray without being caused to form an image by the image forming unit. The image forming apparatus described. The output tray has at least a first output tray and a second output tray.
The control unit
In the second mode, the paper on the second transport path is made to form an image by the image forming unit, and the paper is conveyed to the first paper ejection tray and is conveyed to the first paper ejection tray, and the first one downstream of the merging portion. The claim is characterized in that the paper on the transport path, the double-feed paper, and the paper upstream of the double-feed paper are discharged to the second paper ejection tray without causing the image forming unit to form an image. The image forming apparatus according to 1 or 2.

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