JP2012012193A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reuse a paper within an image-forming device without ejecting the image-formed paper when an obstacle such as a hand over a paper eject tray is detected.SOLUTION: An image forming device 10 includes a paper feeding section 20 with a paper feed tray 21, an image forming section 30, a paper ejecting section 70 with a paper eject tray 71, a paper path for recirculation 50 where a paper feed path KR and a paper eject path HR are branched and installed in a path for recirculation JR which recirculates paper PA through an image forming section 30, and a control section 13 for controlling each section. The image forming device 10 also includes an optical sensor 73 for detecting an obstacle which approaches a portion over the paper eject tray 71. When the optical sensor 73 finds any obstacle, the control section 13 stops feed and ejection of the paper PA and allows the paper PA not arriving yet at the paper eject path HR to recirculate along the path for recirculation JR.

Description

  According to the present invention, in an image forming apparatus including at least a paper feed unit, an image forming unit, a paper discharge unit, a paper circulation conveyance path unit, and a control unit, the image forming unit enters above a paper discharge tray of the paper discharge unit. The present invention relates to an image forming apparatus configured to detect obstacles such as human hands.

  In general, an image forming apparatus that forms an image on paper by printing or copying is widely used in various fields.

  In this type of image forming apparatus, there is an image forming system apparatus in which an optical sensor for detecting an obstacle at the lower part of the sheet discharge table is provided on the lower surface side of the sheet discharge table that moves up and down with a sheet on which an image is formed. (For example, refer to Patent Document 1).

  In addition, in a printing apparatus, there is a printing apparatus provided with an interruption switch for temporarily stopping printing paper discharge operation in the vicinity of a discharge table (for example, see Patent Document 2).

  Further, the present applicant, when the ink image is color-printed on the paper by discharging each ink of yellow (Y), magenta (M), cyan (C), and black (B) from a plurality of inkjet heads. An image forming apparatus has been proposed in which a drying time is secured for printed paper to suppress paper deformation (curl) and a paper circulation conveyance path is provided for printing on both sides of the paper. (For example, refer to Patent Document 3).

JP-A-8-26570 Japanese Patent Laid-Open No. 11-105383 JP 2009-208364 A

  By the way, following the technical idea of the image forming apparatus disclosed in Patent Document 3 described above, the sheet can be circulated to form images on both sides of the sheet, and an image can be formed with some improvements. There is a demand for a new image forming apparatus capable of detecting an obstacle so that an image-formed paper and an obstacle such as a hand do not come into contact with each other when discharging the paper.

  At this time, when the technical idea of Patent Document 1 described above is applied to a newly developed image forming apparatus, although an obstacle at the lower part of the paper discharge table can be detected, image formation stacked on the paper discharge table is performed. No measures are taken against the problem that jamming occurs due to contact between an image-formed paper and an obstacle such as a hand when removing the used paper.

  On the other hand, when the technical idea of Patent Document 2 described above is applied to a newly developed image forming apparatus, the middle switch provided near the discharge table is manually operated. It is not for obstacle detection that detects an obstacle such as a human hand that has entered the upper side of the paper discharge tray.

  Accordingly, the present invention has a problem that when an image-formed sheet stacked on a sheet discharge tray of a sheet discharge unit is taken out, a jam occurs due to contact between the image-formed sheet and an obstacle such as a hand. An object of the present invention is to provide an image forming apparatus that can solve the above-mentioned problems.

The present invention has been made in view of the above problems, and the invention according to claim 1 is a paper feeding unit that feeds the uppermost sheets stacked on the paper feeding table one by one;
An image forming unit that forms an image on the fed paper;
A paper discharge unit that discharges the paper on which the image is formed on a paper discharge table;
A paper circulation conveyance path unit that has a circulation conveyance path that circulates the paper via the image forming unit, and a paper supply conveyance path and a paper discharge conveyance path are branched in the circulation conveyance path;
An image forming apparatus comprising: a control unit that controls each unit described above;
An obstacle detection optical sensor is provided for detecting an obstacle that has entered the upper side of the paper discharge tray. When the obstacle detection optical sensor detects that there is an obstacle, the control unit supplies the paper. In the image forming apparatus, the paper and the paper discharge are stopped, and the paper before reaching the paper discharge conveyance path is circulated along the circulation conveyance path.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect,
The control unit, when detecting that the obstacle has been removed by the obstacle detection optical sensor, resumes discharging the sheet without disturbing the order of the number of pages of the sheet. Forming device.

According to a third aspect of the present invention, in the image forming apparatus of the first aspect,
When the controller detects that the obstacle is present with the obstacle detection light sensor and determines that the obstacle has not been removed after a certain period of time, the controller issues a warning and forces the job. An image forming apparatus characterized in that the image forming apparatus is terminated.

  According to the image forming apparatus of claim 1, particularly, when an obstacle detection optical sensor for detecting an obstacle that has entered the upper side of the sheet discharge table is provided, and the obstacle detection optical sensor detects that there is an obstacle, In addition, the control unit stops feeding and discharging the paper and circulates the paper before reaching the paper discharge conveyance path along the circulation conveyance path, so that the image formation stacked on the paper discharge table is formed. When the used paper is taken out, the obstacle detection light sensor detects that there is an obstacle such as a hand above the paper output tray. Can be prevented from coming into contact with obstacles such as human hands. In addition, when an obstacle such as a hand is detected by the obstacle detection optical sensor, it is possible to return to normal operation immediately after removing the obstacle by maintaining a part of the idling state without stopping all parts in the apparatus. Therefore, the throughput of the apparatus can be improved.

  According to the image forming apparatus of the second aspect, in particular, when the control unit detects that the obstacle is removed by the obstacle detection optical sensor, the control unit discharges the sheet without disturbing the order of the page number of the sheet. Since the paper is resumed, the number of pages can be made uniform without counting the number of pages for the image-formed paper ejected on the paper ejection tray after the paper ejection is resumed.

  According to the image forming apparatus of claim 3, in particular, the control unit determines that the obstacle has not been removed even after a predetermined time has elapsed after detecting the obstacle with the obstacle detection optical sensor. In this case, a warning is issued and the job is forcibly terminated, which can contribute to improvement of the reliability of the apparatus.

1 is a block diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a longitudinal sectional view showing an overall configuration of an image forming apparatus according to an embodiment of the present invention. (A), (b) is an enlarged plan view and a front view showing a first example when a light-reflective obstacle detecting optical sensor is installed on the side surface of a housing in the vicinity of a paper discharge table. . (A), (b) is the top view and front view which expanded and showed the 2nd example at the time of installing the light reflection type obstacle detection optical sensor on a paper discharge stand. FIG. 5 is a diagram illustrating operation timing for explaining an operation when a light reflection type obstacle detecting optical sensor is installed in the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a flowchart for explaining an operation when a light reflection type obstacle detecting optical sensor is installed in the image forming apparatus according to the embodiment of the present invention.

  Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described in detail with reference to FIGS.

  An image forming apparatus according to the present invention includes a paper feed unit that feeds paper, an image forming unit that forms an image on the fed paper, a paper discharge unit that discharges the paper on which the image is formed, A paper circulation conveyance path for circulating the paper as necessary to form images on both sides of the paper and a control unit for controlling each part in the apparatus are provided. A light reflection type obstacle detecting optical sensor for detecting an obstacle such as a hand is installed in the vicinity of the paper table or on the paper discharge table.

  In the image forming apparatus according to the present invention, the image forming unit that forms an image on a sheet may be a printing unit that prints an image by an inkjet printing method, a laser printing method, a thermal transfer printing method, or the like, or a copy of the image. However, it is a necessary condition that the apparatus has a paper circulation transport path.

  In the following embodiments, an example in which an inkjet printing method is applied as an image forming unit will be described.

  The overall configuration of the image forming apparatus 10 according to the embodiment of the present invention will be described with reference to FIGS.

  The image forming apparatus 10 according to the above-described embodiment includes a power source 11, an interface 12 to which print data D is input from a personal computer PC or a LAN cable (not shown), and the print data D is input via the interface 12. A control unit 13 that controls the entire apparatus, an operation panel unit 15 that operates the entire apparatus, a sheet feeding unit 20 that feeds paper PA, and a plurality of colors that are fixedly installed on the sheet conveyance downstream side of the sheet feeding unit 20 An image forming unit (hereinafter, referred to as a printing unit) that has a plurality of line-type inkjet heads 31 that eject ink IK and forms (prints) a color image with a plurality of colors of ink IK on paper PA according to print data D ) 30, the belt platen mechanism unit 40 that is rotatably disposed below the printing unit 30, and the paper PA fed by the paper feeding unit 20 through the printing unit 30. A paper circulation conveyance path section 50 that conveys in the paper direction and switches back to the paper PA to be printed on both sides and conveys again in the direction of the printing section 30, and a paper circulation conveyance path section 50 on the downstream side of the printing section 30. A drying furnace 60 that blows dry air to suppress deformation (curl) of the printed paper PA installed therein, and a switch for the paper PA that discharges the printed paper PA and wants to perform duplex printing. By including the paper discharge unit 70 for backing, an ink jet printing method is applied.

  Here, the main components provided in the image forming apparatus 10 of the embodiment will be described in order.

  First, as shown in FIG. 1, the control unit 13 described above is changed during operation of the image forming apparatus 10, an arithmetic unit (CPU) 13 a, a ROM 13 b that stores an operation program of the image forming apparatus 10, and the like. It has a RAM 13c for temporarily storing possible information and a timer 13d for measuring time.

  In addition, the control unit 13 includes an operation panel unit 15, a paper feeding unit 20, a printing unit (image forming unit) 30 to which an inkjet printing method is applied, a belt platen mechanism unit 40, and first and second conveyances described later. A paper circulation conveyance path 50 having path switching levers 52 and 53 and first to fourth paper detection optical sensors 54 to 57, a drying furnace 60, and a paper discharge having an obstacle detection optical sensor 73 described later. The unit 70 is controlled.

  At this time, as shown in FIG. 2, the control unit 13 is installed at an appropriate location in the housing 14 that forms the exterior of the image forming apparatus 10.

  Next, as shown in FIG. 2, the above-described operation panel unit 15 is installed on the upper surface (or front surface) of the housing 14 so that the user can perform a desired operation on the image forming apparatus 10. ing.

  Next, as shown in FIG. 2, the above-described paper feeding unit 20 is arranged at the side paper feed table 21 disposed at the lower left side portion 14 a of the housing 14 and the lower left portion of the housing 14. A plurality of paper feed trays 22 and 23 are provided, and the side paper feed tray 21 can stack paper PAs of appropriate sizes while detecting the size of the paper PA. The bases 22 and 23 are capable of laminating sheets PA of specific sizes such as A4 size and A3 size, respectively.

  After the uppermost paper PA among the unprinted papers PA stacked on the side paper feed tray 21 or the plurality of paper feed trays 22 and 23 is fed one by one by each paper feed roller 24. A leading portion of the paper PA conveyed along the paper feed conveyance path KR by a driving mechanism such as a roller is guided to a registration roller pair 51 provided in the paper circulation conveyance path 50, and this registration roller The timing is adjusted so that the top positions of the paper PA are aligned in the pair 51.

  Next, the printing unit 30 described above is fixedly installed on the downstream side of the paper feeding unit 20 and the upstream side of the paper circulation conveyance path unit 50, and is positioned at a substantially central portion in the housing 14.

  In the printing unit 30, a plurality of line-type inkjet heads 31 corresponding to a plurality of color inks IK are used for C (cyan), K (black), M (magenta), and Y from upstream to downstream. They are arranged in the order for (yellow).

  In this embodiment, an example in which four line-type inkjet heads 31 are installed corresponding to four color (CKMY) inks IK will be described. For example, when printing only characters, one color (K) is used. Therefore, it is sufficient that at least one line type inkjet head 31 is installed.

  Here, the plurality of line-type ink jet heads 31 provided for each color are all formed in the same structure, and detailed illustration is omitted, but one line-type ink jet head 31 has a plurality of nozzles perpendicular to the paper surface. A plurality of head blocks arranged along the main scanning direction are arranged along one line along the main scanning direction, and are divided into two lines in the sub scanning direction perpendicular to the main scanning direction. In the adjacent lines 1 and 2, the head blocks are alternately arranged in a staggered pattern so as to partially overlap each other.

  Next, as shown in FIG. 2, the belt platen mechanism 40 described above is disposed below the plurality of line-type inkjet heads 31 so as to face the printing unit 30.

  The belt platen mechanism unit 40 has a plurality of unprinted papers PA fed by the paper feeding unit 20 or a single side transported by a circulation transport path JK to be described later while transporting a plurality of printed papers PA. A belt-like belt platen 41 formed by penetrating air suction holes (not shown) at substantially equal intervals is stretched between a drive pulley 42 and a driven pulley 43 that are driven to rotate by a drive source (not shown). In addition, an air suction portion (suction box) 44 that sucks the paper PA onto the belt platen 41 is provided between the drive pulley 42 and the driven pulley 43.

  When the paper PA is mounted on the belt-like belt platen 41, the paper PA is fixed onto the belt platen 41 by sucking air from the plurality of air suction holes formed in the belt platen 41. Thus, a color image is printed on the basis of the print data D (FIG. 1) by the plurality of line-type ink-jet heads 31 while conveying the paper PA in the sub-scanning direction (arrow X direction) by the rotation of the belt platen 41.

  Next, as shown in FIG. 2, the paper circulation conveyance path unit 50 prints the paper PA to the printing unit 30 in order to perform single-sided printing or double-sided printing on the paper PA fed by the paper feeding unit 20. A circulation conveyance path JR that circulates through the sheet, and a paper conveyance path KR that conveys an unprinted paper PA from the paper feed table 21 side in the circulation conveyance path JR, and printing on the paper discharge table 71 side. A paper discharge conveyance path HR for conveying the finished paper PA is branched and installed.

  In addition, the above-described circulation transport path JR has a normal transport path CR that transports the printed paper PA printed on one side (front surface) of the paper PA by the printing unit 30 in the direction in which it is discharged as it is, and one side (front surface). Printed paper PA is printed on both sides (front and back) by switching the transport direction by switching the transport direction with the first and second transport path switching levers 52 and 53 using a solenoid valve or the like from the middle of the normal transport path CR. And a switchback transport path SR for performing the above operation.

  Then, the paper PA desired to be printed on both sides can be circulated through the printing unit (image forming unit) 30 by the circulation conveyance path JR.

  At this time, the normal conveyance path CR in the circulation conveyance path JR passes below the printing unit 30, and thereafter, above the printing unit 30 in order to secure time for drying the ink IK on the printed paper PA. The printed paper PA to be discharged is transported from the normal transport path CR to the discharge tray 71 of the discharge section 70 through the discharge transport path HR. .

  On the other hand, the switchback transport path SR in the circulation transport path JR changes the transport direction of the paper PA by switching the front of the normal transport path CR toward the paper discharge unit 70 with the first transport path switching lever 52. The paper PA moves toward the inside of the paper guide frame 72 formed on the back surface of the paper discharge tray 71 of the unit 70. After the head position of the paper PA is reversed in the paper guide frame 72, the second paper path switching lever 53 is used to switch the paper PA. The conveying direction is changed to again face the registration roller pair 51, and thereafter, the printing unit 30 and the belt platen mechanism 40 are connected.

  In addition, in the paper circulation conveyance path section 50, light reflection type (or light transmission type) first to fourth paper detection optical sensors 54 to 57 are installed. The second paper detection optical sensor 55 is disposed downstream of the registration roller pair 51 in the paper feed conveyance path KR and functions as a paper feed sensor for detecting the paper feed state of the paper PA. It functions as a transport path pre-switching sensor that detects the state before reaching the transport path HR or the switchback transport path SR, and the third paper detection optical sensor 56 is installed along the paper discharge transport path HR and discharged. The fourth paper detection optical sensor 57 functions as a paper discharge sensor that detects the paper discharge state of the paper PA heading to the paper base 71. Further, the fourth paper detection optical sensor 57 is provided between the first transport path switching lever 52 and the second transport path switching lever 53. Of paper PA installed and circulated Functions as the circulating paper detection sensor for detecting the free state.

  Next, as shown in FIG. 2, the drying furnace 60 described above is disposed downstream of the printing unit 30 and above the printing unit 30 in the normal conveyance path CR provided in the paper circulation conveyance path unit 50. Has been.

  The drying furnace 60 includes a long duct 61 and a dryer 62 that is provided on the upstream side of the duct 61 and blows the drying air toward the downstream side, and is printed by the printing unit 30. By forcibly drying the ink IK on the printed paper PA by the drying air blown from the dryer 62, the ink on the printed paper PA is quickly dried, and the ink IK on the printed paper PA is used. Curling is suppressed.

  When the ink IK on the printed paper PA is naturally dried, the dried paper PA may be naturally dried in the middle of being conveyed along the normal conveyance path CR without providing the drying furnace 60. good.

  Next, in the paper discharge unit 70 described above, a paper discharge stand 71 provided here is installed obliquely with respect to the upper portion 14 b on the left side surface of the housing 14.

  At this time, the paper discharge table 71 has a function of storing the printed paper PA conveyed by the normal conveyance path CR and the paper discharge conveyance path HR provided in the paper circulation conveyance path unit 50, and the paper discharge table 71. The paper guide frame 72 formed on the back surface has a function of switching back and reversing the leading position of the paper PA in order to print the back surface of the paper PA printed on one side (front surface).

  In addition, a light reflection type obstacle detecting optical sensor 73 which is a main part of the present invention is disposed on the left side upper portion 14 b of the housing 14 so as to face the paper discharge table 71.

  As described above, the light reflection type obstacle detecting optical sensor 73 installed in the upper portion 14b on the left side surface of the housing 14 is as shown in the first example enlarged in FIGS. 3 (a) and 3 (b). Light is emitted in a substantially horizontal direction from the upper portion 14 b on the left side surface of the housing 14 toward the paper discharge table 71, and this light is blocked and reflected by an obstacle O such as a human hand that has entered the paper discharge table 71. By detecting the reflected light, it can be detected that there is an obstacle O via the control unit 13, and a warning is displayed on the operation panel unit 15 when the obstacle O is detected.

  In this embodiment, the light reflection type obstacle detecting optical sensor 73 is installed in the upper portion 14b on the left side surface of the casing 14, but the present invention is not limited to this, and FIGS. As shown in the second example enlarged in FIG. 2, the light reflection type obstacle detecting optical sensor 73 is placed on the upper surface 71a of the paper discharge table 71 so as not to interfere with the printed paper PA stacked thereon. You may install in the side of.

  In the case of this second example, the obstacle detection optical sensor 73 emits light upward, so that when an obstacle O such as a human hand enters above the upper surface 71a of the paper discharge table 71, the obstacle is detected. The obstacle O can be detected by the obstacle detection optical sensor 73 based on the reflected light reflected by the object O.

  Here, the operation of the light reflection type obstacle detecting optical sensor 73 will be described with reference to FIGS. 1 to 4 and the new FIGS.

  As shown in FIGS. 5A to 5E, the obstacle detection optical sensor 73 detects an obstacle O such as a human hand that has entered the upper side of the paper discharge tray 71 via the control unit 13, and the obstacle is detected. The output of the detection light sensor 73 is turned on, the output of the first paper detection light sensor (paper feed sensor) 54 is turned off, and further, the second paper detection light sensor (sensor before transport path switching). When the output of the third paper detection optical sensor (paper discharge sensor) 56 is turned off even if the output of 55 is on, the paper feed operation of the unprinted paper PA by the paper feed unit 20 and the paper discharge unit 70, the paper discharge operation of the printed paper PA is stopped, and the paper transport PA including the paper PA that is being printed by the printing unit 30 before the paper PA reaching the paper discharge transport path HR is discharged without being discharged. Circulating along JR (normal transport path CR and switchback transport path SR)

  On the other hand, if the output of the first paper detection light sensor (paper feed sensor) 54 is on when the output of the obstacle detection light sensor 73 is turned on, only the paper PA being fed is supplied. The paper feeding operation may be stopped after the paper feeding is completed, and the paper PA may be circulated after the paper feeding operation is stopped.

  Further, if the output of the third paper detection light sensor (paper discharge sensor) 56 is turned on when the output of the obstacle detection light sensor 73 is turned on, only the paper PA during paper discharge is output. The paper discharge operation may be stopped after the paper discharge is completed, and the paper PA may be circulated after the paper discharge operation is stopped.

  If the obstacle O such as a human hand that has entered the upper side of the paper discharge tray 71 is removed, and the output of the obstacle detection light sensor 73 is turned off and the obstacle detection is released, the control unit 13 determines that the device 10 is resumed and the normal operation is controlled, so that the paper discharge operation can be resumed without disturbing the order of the number of pages of the printed paper PA. The number of pages can be made uniform without counting the number of pages for the printed paper PA.

  Further, the control unit 13 measures the time with a timer 13d provided in the control unit 13 after a certain period of time has elapsed after detecting that the output of the obstacle detection optical sensor 73 is turned on and there is an obstruction O. If it is determined that the obstacle O above the paper discharge tray 71 has not been removed, a warning is displayed on the operation panel unit 15 and the job is forcibly terminated. It can contribute to improvement.

  Here, as shown in FIG. 6, when the operation flow of the obstacle detection optical sensor 73 is started, first, in step S1, it is asked whether or not the obstacle detection optical sensor 73 is turned on. When the detection light sensor 73 is not on (in the case of NO), there is no obstacle O above the paper discharge table 71, so the normal operation is continued in step S2, and this flow is ended when the normal operation is completed. .

  On the other hand, when the obstacle detection light sensor 73 is on (YES) in step S1, there is an obstacle O above the paper discharge table 71, so in step S3 the paper feed sensor (first paper detection). Whether or not the light sensor 54 is off. If the paper feed sensor 54 is not off (in the case of NO), the paper feeding is stopped after feeding only the paper PA being fed in step S4, Return to step S3.

  On the other hand, when the paper feed sensor 54 is off in step S3 (in the case of YES), it is asked whether or not the paper ejection sensor (third paper detection optical sensor) 56 is off in step S5. If the sensor 56 is not off (in the case of NO), the paper discharge is stopped after discharging only the paper PA being discharged in step S6, and the process returns to step S5.

  On the other hand, if the paper discharge sensor 56 is OFF in step S5 (YES), the paper PA before reaching the paper discharge conveyance path HR is circulated without being discharged in step S7.

  Next, the obstacle O above the paper discharge table 71 is removed in step S8.

  Next, the flow returns to the normal operation in step S9, and when this normal operation is completed, this flow is finished.

  As described above, by installing the obstacle detection optical sensor 73 for detecting the obstacle O such as a human hand that has entered the upper side of the sheet discharge table 71, the printed (image formation) layered on the sheet discharge table 71 is performed. When the obstacle detection light sensor 73 detects that there is an obstacle O above the paper discharge table 71 when the paper is taken out, the paper PA is not discharged onto the paper discharge table 71. It is possible to prevent jamming caused by contact between printed (image-formed) paper and an obstacle O such as a manpower.

  Further, when the obstacle detection optical sensor 73 detects an obstacle O such as a hand, a part of the apparatus 10 is kept in an idling state without stopping all the parts, thereby immediately after removing the obstacle O. Since the normal operation can be restored, the throughput of the apparatus 10 can be improved.

  At this time, a specific example in the apparatus 10 regarding the throughput indicating the processing capacity per unit time will be described. A job is started for a paper PA of A3 size or A4 size, and printing processing is performed from paper feeding. Although it takes about 7 to 8 seconds to discharge the printed paper PA, the time required to circulate the paper PA when the obstacle detection light sensor 73 detects an obstacle O such as a hand is required. It is about 2 to 3 seconds, and by keeping the idling state without stopping all jobs, the time of about 5 seconds can be shortened when the job is resumed, so that the throughput of the apparatus 10 is improved. Can do.

  In the present invention, when an obstacle such as a human hand that has entered the upper side of the paper discharge tray is detected, the paper supply and paper discharge are stopped, and the paper before reaching the paper discharge conveyance path is circulated and conveyed. When the operator who uses the image forming apparatus checks the amount of paper to be discharged to the paper discharge tray and loads a desired amount on the paper discharge tray. In addition, in order to remove the desired amount of paper from the paper discharge tray, the user arbitrarily touches the upper side of the paper discharge tray to stop paper feeding and paper discharge, and remove the paper before reaching the paper discharge conveyance path. It can also be used when circulating along the circulation conveyance path.

10 Image forming apparatus,
DESCRIPTION OF SYMBOLS 13 ... Control part, 14 ... Housing | casing, 14b ... Left side upper part, 15 ... Operation panel part 20 ... Paper feed part, 21 ... Side paper feed stand, 22, 23 ... Paper feed stand, 24 ... Paper feed roller,
30 ... Image forming section (printing section), 31 ... Line-type inkjet head,
40 ... belt platen mechanism,
50: Paper circulation conveyance path, KR: Paper feed conveyance path, HR: Paper discharge conveyance path,
JR ... circulation conveyance path, CR ... normal conveyance path, SR ... switchback conveyance path,
52, 53 ... first and second transport path switching levers,
54. First paper detection optical sensor (paper feed sensor),
55. Second sheet detection optical sensor (pre-transport path sensor),
56... Third sheet detection optical sensor (paper discharge sensor),
57. Fourth sheet detection optical sensor (circulation sheet presence / absence detection sensor),
60... Drying oven, 70... Discharge section, 71... Discharge tray, 71 a.
73. Optical sensor for obstacle detection,
D ... print data, IK ... ink, O ... obstacle, PA ... paper.

Claims (3)

A paper feed unit that feeds the uppermost sheets stacked on the paper feed tray one by one;
An image forming unit that forms an image on the fed paper;
A paper discharge unit that discharges the paper on which the image is formed on a paper discharge table;
A paper circulation conveyance path unit that has a circulation conveyance path that circulates the paper via the image forming unit, and a paper supply conveyance path and a paper discharge conveyance path are branched in the circulation conveyance path;
An image forming apparatus comprising: a control unit that controls each unit described above;
An obstacle detection optical sensor is provided for detecting an obstacle that has entered above the paper discharge tray. When the obstacle detection optical sensor detects that there is an obstacle, the control unit supplies the paper. An image forming apparatus that stops paper and paper discharge and circulates the paper before reaching the paper discharge conveyance path along the circulation conveyance path.   The control unit, when detecting that the obstacle has been removed by the obstacle detection optical sensor, resumes discharging the paper without disturbing the order of the number of pages of the paper. Item 2. The image forming apparatus according to Item 1.   When the controller detects that the obstacle is present with the obstacle detection light sensor and determines that the obstacle has not been removed after a certain period of time, the controller issues a warning and forces the job. The image forming apparatus according to claim 1, wherein the image forming apparatus is terminated.

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