JP5582449B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus having a sheet conveying equipment for conveying the sheet material.

  Conventionally, as shown in FIG. 13, some inkjet printing apparatuses are configured to guide a sheet downward on the downstream side in the sheet conveyance direction of the inkjet printing unit 100 (see Patent Document 1). In the configuration shown in FIG. 13, the sheet on which the image is formed by the inkjet printing unit 100 is conveyed downstream by the conveying belt 200, bent downward by a switching claw 400, a guide plate (not shown), and the like and guided to the conveying path R10. Is done.

  Further, as shown in FIG. 14, there is one configured to guide the paper upward on the downstream side in the paper conveyance direction of the inkjet printing unit 500 (see Patent Document 2). In this case, the sheet on which the image is formed by the inkjet printing unit 500 is conveyed downstream by the conveyance belt 600, bent upward by a guide plate (not shown), and guided to the conveyance path R20.

  By the way, in recent years, with the miniaturization of image forming apparatuses including ink jet printing apparatuses, the bending degree of the bending conveyance part in the paper conveyance path has been increased. In particular, in the image forming apparatus configured as described above, when the sheet is bent and conveyed as shown in FIG. 13, the trailing edge e2 of the sheet P is conveyed as shown in FIG. 15 depending on the rigidity of the sheet. The ink may float from the belt 200 and come into contact with the inkjet printing unit 100. As described above, when the rear end of the paper comes into contact with the ink jet printing unit, the rear end of the paper becomes dirty with ink, and the next ink is not ejected normally from the ink jet printing unit. Further, when the paper is bent upward and conveyed as shown in FIG. 14, the rear end e2 side of the paper P may be lifted from the conveying belt 600 as shown in FIG. There is a possibility that the paper P may be soiled or ink may be discharged due to contact with the inkjet printing unit 500.

  In addition, as shown in FIG. 17, if a conveyance resistance is generated when the front end e1 of the sheet P comes into contact with the switching claw 400 provided in the bending conveyance unit, the conveyance speed of the sheet P may be reduced. . At this time, if image formation is performed on the rear end e2 side of the paper P, there is a possibility that the image formation on the rear end e2 side of the paper P may not be accurately performed due to a decrease in the conveyance speed. Such a problem is likely to occur when the distance from the ink jet printing unit to the bending conveyance unit is shortened or a long sheet is conveyed in order to reduce the size of the image forming apparatus. Note that FIG. 17 shows an example in which the sheet passes through a bending conveyance section bent downward, but the same problem occurs in a configuration in which the bending conveyance section is bent upward.

  The lifting of the trailing edge of the paper and the reduction in the paper speed may occur even with thin paper with low rigidity, but thick paper with high rigidity is more difficult to smoothly convey in the bending conveyance section. The occurrence of the above-mentioned problems becomes remarkable.

Therefore, in view of such circumstances, the present invention raises the rear end of the sheet material as the sheet material such as paper passes through the bending conveyance unit, and the guide provided at the bending conveyance unit with the front end of the sheet material. it is intended to provide an image forming apparatus having a Cie over preparative conveying device can prevent a decrease in transportation speed by coming into contact with the plate or the like.

The invention of claim 1 includes a first straight conveyance unit, a bending conveyance unit continuously provided in a convex curved shape on the downstream side in the conveyance direction of the first straight conveyance unit, and a downstream side in the conveyance direction of the bending conveyance unit. A conveyor belt that conveys a sheet material on a conveyor surface that is provided and has a second straight conveyor section that is inclined with respect to the first straight conveyor section, and sucks air from the back surface side of the conveyor belt. An air adsorbing unit that adsorbs the sheet material to the conveyance belt, and an inkjet head that is disposed to face the first straight conveyance unit and discharges ink to the sheet material to form an image. In the image forming apparatus configured to convey the sheet material from the first straight conveyance unit to the second straight conveyance unit via the bending conveyance unit by a belt, the front end of the sheet material is When the second straight conveying unit reaches a predetermined position, the suction force of the air adsorbing means in the vicinity of the upstream side in the sheet conveying direction of the bending conveying unit is more than the suction force in the upstream side of the sheet conveying direction. Is set to be larger.

  By increasing the suction force in the vicinity of the upstream side in the sheet conveyance direction of the bending conveyance unit (hereinafter, simply referred to as “upstream side vicinity”), the trailing edge of the sheet material passing through the bending conveyance unit is increased. Lifting can be effectively prevented. In addition, by increasing the suction force in the vicinity of the upstream side of the bending conveyance section, the suction force of the sheet material to the conveyance belt at that location increases, so the front end of the sheet material is provided on the bending conveyance section. Even if conveyance resistance occurs due to contact with the sheet, the sheet material can be conveyed without causing slippage (decrease in conveyance speed). On the other hand, since there is no possibility that the above-described problem occurs further upstream near the upstream side of the bending conveyance section, it is possible to reduce noise and power consumption by not increasing the suction force in such a place.

According to a second aspect of the invention, in the image forming apparatus according to claim 1, wherein the air suction means comprises a suction duct having a plurality of suction openings which are disposed opposite to the back surface of the conveyor belt, wherein The opening area ratio of the suction duct in the vicinity of the upstream side in the sheet conveyance direction of the bending conveyance section is set larger than the opening area ratio of the suction duct in the upstream side in the sheet conveyance direction.

  By increasing the opening area ratio of the suction duct in the vicinity of the upstream side of the bending conveyance section to be larger than the opening area ratio of the suction duct in the upstream side of the bending conveyance section, a large suction force is generated in the vicinity of the upstream side of the bending conveyance section. It becomes possible to demonstrate.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect , the width of the suction area in the vicinity of the upstream side in the sheet conveyance direction of the bending conveyance unit of the air adsorption unit corresponds to the width of the sheet material. Thus, it can be changed.

  By configuring the suction area width in the vicinity of the upstream side of the bending conveyance section to be compatible with the width of the sheet material, unnecessary air suction outside the area through which the sheet material passes can be reduced. It is possible to prevent a reduction in suction force due to air leakage. Thereby, the suction force can be effectively increased in the vicinity of the upstream side of the bending conveyance unit.

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the suction force in the vicinity of the upstream side in the sheet conveyance direction of the bending conveyance unit of the air adsorption unit It can be changed according to the type.

  By configuring the suction force in the vicinity of the upstream side of the bending conveyance section of the air adsorbing means to be changeable according to the type of sheet material, it is possible to exert a suction force suitable for each type of sheet material Become. Thereby, it is possible to reliably prevent the trailing edge of the sheet material from being lifted and the sheet material from being lowered in speed.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect , the suction force in the vicinity of the upstream side in the sheet conveying direction of the bending conveying portion of the air adsorbing means is the type of the sheet material having a large rigidity or a thick thickness The sheet material is configured to be large, and the sheet material is configured to be small when the type of the sheet material is small or thin.

  The lift of the rear end of the sheet material and the decrease in the conveyance speed of the sheet material tend to become more prominent as the sheet material becomes thicker or the rigidity becomes higher. Therefore, in the case of a sheet material having a large rigidity or a thick material, by increasing the suction force, it is possible to exert a strong adsorption force toward the conveyance belt with respect to the sheet material, and effectively suppress the above-described problems. It is possible. On the other hand, in the case of a sheet material having a low rigidity or a thin sheet material, a large suction force is not necessary to suppress the above-described problems. Therefore, it is possible to reduce noise and power consumption by reducing the suction force.

  According to the present invention, by increasing the suction force in the vicinity of the upstream side of the bending conveyance unit, the trailing edge is lifted as the sheet material passes through the bending conveyance unit, and the front end of the sheet material is added to the bending conveyance unit. It is possible to effectively prevent the sheet material from slipping due to contact with the provided guide plate or the like. Thereby, a conveyance property can be improved and it becomes possible to convey a sheet material smoothly and stably. On the other hand, since there is no possibility that the above-mentioned problem occurs on the upstream side in the vicinity of the upstream side of the bending conveyance section, noise and power consumption can be reduced by not increasing the suction force in such a place.

1 is a schematic configuration diagram of an ink jet printer equipped with a sheet conveying device of the present invention. It is a schematic block diagram of the characteristic part of the said sheet conveying apparatus. It is a top view at the time of seeing the 1st suction duct and the 2nd suction duct with which the sheet conveyance device is provided from the upper part. It is a block diagram showing a control system of the sheet conveying apparatus. It is a figure which shows the display part of the paper type selection mode of the operation panel provided in the said printer. It is the top view which looked at the paper feed tray provided in the printer from the upper part. 6 is a flowchart of the operation of the sheet conveying apparatus. It is a figure which shows a mode that a sheet | seat is conveyed with the said sheet conveying apparatus. It is a schematic diagram of the sheet conveying equipment according to a reference example. It is a flowchart of operation | movement of the sheet conveying apparatus which concerns on the said reference example . It is a figure which shows a mode that a sheet | seat is conveyed with the sheet conveying apparatus which concerns on the said reference example . It is a schematic diagram of a sheet conveying apparatus to which the present invention can be applied. It is a schematic block diagram of the conventional sheet conveying apparatus. It is a schematic block diagram of another conventional sheet conveying apparatus. It is a figure for demonstrating the subject of the conventional sheet conveying apparatus. It is a figure for demonstrating the subject of the conventional sheet conveying apparatus. It is a figure for demonstrating the subject of the conventional sheet conveying apparatus.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the overall configuration of an image forming apparatus equipped with the sheet conveying apparatus of the present invention will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of an ink jet printer as an image forming apparatus according to the present invention. The apparatus main body 1 is provided with an image reading unit 2, an image forming unit 3, a paper feeding unit 4, and the like.

  The image reading unit 2 feeds a document placed on a document table to a reading position where a contact image sensor (not shown) is arranged, and after reading an image by the contact image sensor, a document discharge tray (not shown). ) To discharge the original. The image forming unit 3 includes an image forming head unit 11 having line-type inkjet heads 10Y, 10M, 10C, and 10K of four colors of yellow, magenta, cyan, and black. In the paper feed unit 4, a plurality of paper feed cassettes 12 that contain paper P as a sheet material are disposed. Each paper feed cassette 12 is provided with a supply roller 13 for sending out the stored paper P. A pair of feed reverse rollers 50a, 50b, 51a, 51b for separating the sheets P one by one are disposed on the downstream side of each supply roller 13 in the sheet conveying direction. In the present embodiment, a sheet feeding device 6 as another sheet feeding unit is disposed on the right side of the drawing of the apparatus main body 1. The sheet supplied from the sheet feeding device 6 or the sheet feeding cassette 12 is finally discharged to a sheet discharge tray 20 provided on the left side of the apparatus main body 1 in the drawing after an image is formed by the image forming unit 3. It is like that. Further, a post-processing device (finisher) that performs so-called post-processing such as stapling, folding, punching, and bookbinding on the paper after image formation may be provided.

  In FIG. 1, an alternate long and two short dashes line is a conveyance path through which a sheet is conveyed. The direction of the arrow attached to the two-dot chain line indicates the sheet conveyance direction. In the present embodiment, the transport path is configured by first to fifth transport paths A to E.

  The first transport path A is a transport path for guiding the paper supplied from the paper feed cassette 12 or the paper feed device 6 to the image forming unit 3. Specifically, the first transport path A is a transport path in the vertical and horizontal directions for guiding the paper fed from the paper feed cassette 12 to the image forming unit 3, and the paper fed from the paper feed device 6. And a horizontal conveyance path for guiding the image to the image forming unit 3 are formed by joining in the middle. In the first transport path A, registration roller pairs 25a and 25b that perform paper skew correction and transport timing adjustment are disposed on the upstream side in the transport direction of the junction.

  The second conveyance path B is a conveyance path for discharging the sheet after image formation to the outside of the apparatus, and is arranged so as to go straight from the first conveyance path A in the horizontal direction. Discharge roller pairs 26a and 26b for discharging the sheet to the outside of the apparatus are disposed on the downstream end side in the transport direction of the second transport path B. Further, a decurler unit 90 for removing the curl of the paper is provided on the upstream side in the transport direction from the pair of discharge rollers 26a and 26b. As the decurler unit 90, for example, three rollers are opposed to each other and a curving path for curl correction is formed between them, or a hard roller is brought into contact with a soft roller and the contact portion is subjected to curl correction. For example, an existing conventional technique such as a curved path may be employed.

  The third transport path C extends downward from the downstream side in the transport direction of the first transport path A, is pulled back upward at the lower part of the apparatus main body 1, and joins upstream of the decurler unit 90 of the second transport path B. . In addition, in order to select and guide the paper to either the second transport path B or the third transport path C, at a location separated from the second transport path B on the upstream side in the transport direction of the third transport path C. Switching claw 28 is provided. Further, in the middle of the third transport path C, a pair of reverse transport rollers 27a and 27b capable of forward and reverse rotation are disposed. When the reverse conveying roller pair 27a, 27b rotates in the forward direction, the paper is conveyed in the lower discharge direction in the figure, and when the reverse conveyance roller pair 27a, 27b rotates in the reverse direction, the paper is in the direction opposite to the discharge direction. It is conveyed (upward in the figure). Further, a detection sensor 95 for detecting the rear end of the sheet is disposed on the upstream side in the transport direction (discharge direction) during the forward rotation of the pair of reverse transport rollers 27a and 27b.

  The fourth transport path D branches from the reverse transport roller pair 27a, 27b of the third transport path C on the upstream side in the transport direction (discharge direction) during normal rotation, and is arranged so as to join the first transport path A. It is installed. Further, a switching claw 29 for guiding the sheet fed back from the third transport path C to the fourth transport path D is provided at a location where the fourth transport path D branches from the third transport path C. Yes.

  The fifth transport path E branches on the upstream side in the transport direction (discharge direction) during forward rotation with respect to the reverse transport roller pair 27a and 27b of the third transport path C, and joins on the downstream side of the third transport path C. It is arranged like this. Further, a switching claw 30 for guiding a sheet fed back from the third transport path C to the fifth transport path E is disposed at a location where the fifth transport path E branches from the third transport path C. Yes.

  Further, the apparatus main body 1 is equipped with a sheet conveying apparatus having various conveying means for conveying the paper along the conveying path. This sheet conveying apparatus includes a conveying belt 18 disposed below the image forming unit 3 as one of conveying means. The conveyor belt 18 is an endless belt, and is stretched by one drive roller 14 and three driven rollers 15, 16, and 17. A predetermined tension is applied to the transport belt 18 by a tension roller 19. The driving roller 14 can be driven to rotate by a driving device (not shown). When the driving roller 14 rotates, the conveying belt 18 rotates in the arrow direction in the figure. Further, on the downstream side of the driven roller 15 and the driven roller 17 in the paper transport direction, paper detection sensors 35 and 36 for detecting the paper are provided, respectively.

  Here, the conveyance surface (conveyance path) for carrying and conveying the paper on the conveyance belt 18 has a first straight conveyance portion S1 arranged horizontally and an arc shape continuously provided downstream in the conveyance direction. The first bending conveyance section M1, the second straight conveyance section S2 that is inclined and connected downstream in the conveyance direction, and the arc-shaped second bending conveyance section M2 that is arranged downstream in the conveyance direction. The third straight transport unit S3 is connected to the downstream side in the transport direction so as to be inclined.

  Further, the sheet conveying apparatus includes an air adsorbing unit that sucks air from the back side of the conveying belt 18 and adsorbs the sheet to the conveying belt 18. The air suction means includes first to fourth suction ducts 21 to 24 as air guide paths disposed on the back side of the conveyor belt 18, and air suction for sucking air independently from the suction ducts 21 to 24. As a means, a suction fan (not shown) is provided. The conveyor belt 18 is formed with a large number of small holes for sucking air. By sucking air from these small holes through the suction ducts 21, 22, 23, and 24, the conveyor belt 18 is provided. It has a mechanism for adsorbing paper on top.

  The arrangement positions of the respective suction ducts will be described in detail. The first suction duct 21 is disposed below the image forming unit 3 so as to face the first straight conveyance unit S1. The second suction duct 22 is disposed opposite to the first straight transport unit S1 in the vicinity of the upstream side of the first bending transport unit M1 in the paper transport direction. The third suction duct 23 is disposed at a position facing the second straight transport unit S2. The fourth suction duct 24 is disposed at a position facing the third straight transport unit S3.

  A first air blowing device 31 and a second air blowing device 32 are provided on the outer peripheral side of the conveying belt 18 as air blowing means for blowing air onto the paper conveyed by the conveying belt 18. The first air blowing device 31 is disposed on the downstream side in the paper conveyance direction from the first bending conveyance unit M1 (or the position of the driven roller 16). The second air blowing device 32 is disposed on the downstream side in the paper conveyance direction from the second bending conveyance unit M2 (or the position of the driven roller 17).

  Further, a transport belt 39 as another transport means is disposed in the second transport path B. The conveyor belt 39 is also an endless belt having a large number of small holes, and is stretched by a driving roller 37 and a driven roller 38. A suction duct 40 for sucking air from a small hole formed in the transport belt 39 is disposed below the transport belt 39. The suction duct 40 is also provided with a suction fan (not shown). By driving the suction fan, air is sucked from the small holes of the transport belt 39 so that the paper can be sucked onto the transport belt 39.

  Further, as other transport means, a plurality of transport rollers 52a, 52b to 61a, 61b are provided. Among the conveying rollers, the roller (the roller indicated by reference numerals 56a, 57a, 58a, 59a, 60a, 61a, 61b in FIG. 1) that contacts the image forming surface side of the sheet is in contact with the image forming surface. A roller with a small area is used. Specifically, these rollers are configured by adhering a large number of abrasive grains such as ceramics to the surface of a plastic or rubber roller member. Accordingly, the roller can make point contact with the image forming surface, and the image forming surface is less likely to be disturbed. Further, the roller that contacts the image forming surface side of the sheet may be a spur roller formed of a thin metal or the like. Also in this case, since the roller is in point contact with the image forming surface, similarly, the image forming surface is hardly disturbed. Similarly, both the rollers of the discharge roller pair 26a and 26b and the roller 27a that is in contact with the image forming surface side of the sheet of the reverse conveying roller pair 27a and 27b also have a contact area with the image forming surface. Consists of small rollers, making it difficult to disturb the image forming surface.

  Furthermore, in this embodiment, in order to prevent the disturbance of the image forming surface of the paper, the linear velocity difference between the upstream and downstream rollers is minimized. As a result, the sheet is bent between the upstream side roller and the downstream side roller so that the image forming surface comes into contact with the conveyance guide plate, or the sheet is pulled and the image forming surface is rubbed against the roller. It becomes possible to prevent. In order to make the linear velocity between the upstream and downstream rollers substantially constant, for example, a one-way clutch is provided on the upstream roller, or the upstream and downstream rollers are driven by the same drive motor. Is possible.

Hereinafter, the basic operation of the ink jet printer according to the present invention will be described with reference to FIG.
When there is an instruction to start printing, the paper P is sent out from the paper feed cassette 12 or the paper feed device 6. The fed paper P abuts against the registration roller pair 25a, 25b and is temporarily stopped. Thereby, the skew of the paper is corrected. Thereafter, the pair of registration rollers 25a and 25b starts to rotate at a predetermined timing, and the paper P is transported onto the transport belt 18. The paper P is adsorbed onto the transport belt 18 by air suction of the first suction duct 21, and the transport belt 18 rotates in this state, so that the paper P is transported below the image forming head unit 11. At this time, the leading edge of the paper P is detected by the paper detection sensor 35. Based on the detection of the paper detection sensor 35, the image forming head unit 11 is driven at a predetermined timing. , 10K nozzles eject ink onto paper P. Thus, a full color image is formed on the paper P.

  Also, a monochrome image is formed using any one of the four inkjet heads 10Y, 10M, 10C, and 10K, and a two-color or three-color image is formed using two or three inkjet heads. It is also possible to do. In addition, the speed of the conveyor belt 18 during this period is controlled so as not to fluctuate as much as possible. Actually, the speed fluctuation is detected by a detection device (not shown) so that ink is ejected at an accurate timing according to the paper position. Is called.

  When the sheet P on which the image is formed by the image forming unit 3 is discharged as it is, the switching claw 28 is disposed at a position indicated by a dotted line in the drawing, and the sheet P is moved straight in the horizontal direction. The paper P is transported onto the transport belt 39 disposed in the second transport path B, and the paper P is adsorbed onto the transport belt 39 by air suction of the suction duct 40. When the conveying belt 39 rotates in this state, the sheet P is conveyed downstream, and after the curl of the sheet is removed by the decurler unit 90, the sheet P is discharged out of the apparatus by the discharge roller pairs 26a and 26b. The

  Further, when the paper P after the image formation passes through the third conveyance path C and is discharged outside the apparatus, the switching claw 28 is disposed at a position indicated by a solid line in the drawing, and the paper P is conveyed in the first conveyance. The route A can be guided to the third transport route C. When the transport belt 18 rotates in this state, the paper P is transported to the third transport path C while being attracted to the transport belt 18 by air suction of the first to fourth suction ducts 21 to 24. Since the conveyance path (or the conveyance belt 18) is bent in the bending conveyance unit M1, the front end of the sheet P is lifted on the downstream side in the conveyance direction of the first bending conveyance unit M1 depending on the thickness, rigidity, and other conditions of the sheet. There is a possibility that the image forming surface strongly contacts peripheral members such as the switching claw 28.

  Therefore, the first air blowing device 31 disposed on the downstream side of the first bending conveyance unit M1 in the conveyance direction blows air onto the paper P so that the paper P is bent in a direction along the conveyance belt 18 (or conveyance path). I have to. As a result, the leading edge of the paper P can be conveyed without strongly contacting the switching claw 28 or the like. Then, the paper P bent by the air is adsorbed to the transport belt 18 by the air suction of the third suction duct 23. In particular, when the rigidity of the paper P is large, when the leading edge of the paper P is bent by the first air blowing device 31, the trailing edge of the paper P is conversely upstream of the first bending conveying portion M1 in the conveying direction. May float from. In such a case, air suction is performed by the second suction duct 22 so that the trailing edge of the paper P does not rise. As described above, since each suction duct is configured to be capable of being sucked independently, the air suction operation of the second suction duct 22 can be controlled without being affected by the operation of other suction ducts. it can.

  When the paper P is transported to the position of the second bending transport section M2, the transport path (or transport belt 18) is also bent at this position, so that the paper P is transported by the transport belt 18 similarly to the first bending transport section M1. There is a possibility of floating from. Therefore, here, the second air blowing device 32 blows air onto the paper P so that the paper P is bent in the direction along the transport belt 18 (or the transport path). Thus, the paper P bent by the blowing air is adsorbed to the transport belt 18 by the air suction of the fourth suction duct 24.

  Thereafter, the sheet P is separated from the conveying belt 18 at the position of the driving roller 14 and conveyed to the pair of reverse conveying rollers 27a and 27b. Further, the switching claw 29 and the switching claw 30 are arranged at positions indicated by solid lines in the figure so as not to prevent the passage of the paper P. The sheet P that has reached the pair of reverse conveyance rollers 27a and 27b is conveyed to the second conveyance path B by the pair of reverse conveyance rollers 27a and 27b that rotate in the forward direction and a plurality of conveyance rollers disposed on the downstream side in the conveyance direction. . Then, after the curl is removed by the decurler unit 90, the paper P is discharged out of the apparatus by the discharge roller pairs 26a and 26b.

  As described above, the third transport path C functions as a discharge path that guides the paper in the discharge direction when the pair of reverse transport rollers 27a and 27b is rotated forward. Further, in this case, since the sheet passes through the third conveyance path C and is detoured downward and guided to the second conveyance path B, the conveyance path until the sheet P is discharged can be lengthened. The paper P can be discharged after the ink is sufficiently dried.

  When performing duplex printing, the paper P on which an image is formed in the image forming unit 3 is transported from the first transport path A to the third transport path C. Also in this case, the paper P is transported obliquely downward by the transport belt 18, but the transport operation here is performed in the same manner as when the paper P is discharged through the third transport path C. In this case, when the trailing edge of the paper P is detected by the detection sensor 95, the normal rotation of the pair of reverse conveying rollers 27a and 27b is stopped based on the detection signal. Thereafter, the switching claw 29 at the branch point of the fourth transport path D is switched to the position indicated by the dotted line in the drawing so that the paper P can be guided to the fourth transport path D. In this state, the pair of reverse conveying rollers 27a and 27b are rotated in the reverse direction, whereby the paper P is fed back and guided to the fourth conveying path D. As a result, the paper P is transported to the fourth transport path D in a state where the front and back are reversed. In this case, the third transport path C functions as a reversing path for transporting the sheet by reversing the front and back.

  Then, the paper P is guided to the first transport path A through the fourth transport path D, and is transported to the image forming unit 3 again with the front and back sides reversed. As described above, the fourth transport path D functions as a double-sided transport path that guides the paper P that has been fed back from the third transport path C to the first transport path A again in order to perform double-sided printing. Then, an image is formed on the back side of the paper P in the image forming unit 3 in the same manner as in the case of the front side.

  The sheet P on which images are formed on both sides is transported in the horizontal direction from the first transport path A to the second transport path B. At this time, the switching claw 28 between the first transport path A and the second transport path B is switched to the position of the dotted line in the figure. Further, when the paper P is transported from the first transport path A to the second transport path B, the air blowing from the first air spraying device 31 is not performed. The paper P is transported downstream by the transport belt 39 disposed in the second transport path B in the same manner as described above, and after the curl of the paper is removed by the decurler unit 90, the paper P is removed from the outside by the discharge roller pairs 26a and 26b. Is discharged.

  Further, when performing page sequential stacking by single-sided printing, the paper P on which an image is formed in the image forming unit 3 is transported from the first transport path A to the third transport path C. The conveyance operation by the conveyance belt 18 here is also the same as the case where the sheet P is discharged through the third conveyance path C. In this case, when the trailing edge of the paper P reaches the position of the reverse conveying roller pair 27a, 27b, the normal rotation of the reverse conveying roller pair 27a, 27b is stopped. Thereafter, the switching claw 30 at the branch point of the fifth transport path E is switched to the position indicated by the dotted line in the drawing so that the paper P can be guided to the fifth transport path E. In this state, the pair of reverse conveying rollers 27a and 27b are reversely rotated to reversely feed the sheet P, and the sheet P is conveyed to the fifth conveying path E. Then, the sheet P is sent to the second transport path B through the fifth transport path E. As described above, the fifth transport path E is a transport path for guiding the paper P, which is reversely transported in the third transport path C, to the second transport path B without being guided to the image forming unit 3. Function. Thereafter, after the curl is removed by the decurler unit 90, the paper P is discharged out of the apparatus by the discharge roller pairs 26a and 26b. As a result, the paper P is discharged in a state where the front and back sides and the front and back sides are reversed, and is stacked on the paper discharge tray 20 in a state where the papers are aligned in the page order.

Hereinafter, the configuration of the sheet conveying apparatus will be described in detail.
FIG. 2 is a view showing the first suction duct 21 and the second suction duct 22 provided on the conveyor belt 18 and their peripheral members. As shown in FIG. 2, the first suction duct 21 and the second suction duct 22 are each provided with two suction fans 41a, 41b, 42a, and 42b as air suction means. However, the way of arranging the suction fans in the suction ducts 21 and 22 is different. The first suction duct 21 is provided with two suction fans 41a and 41b in parallel, while the second suction duct 22 is provided with two suction fans 42a and 42b in series. Thus, by providing the suction fans in series in the second suction duct 22, a negative pressure can be generated larger than in the first suction duct 21 in which the suction fans are provided in parallel. In the present embodiment, the negative pressure (static pressure) generated in the first suction duct 21 is about 500 Pa, whereas the negative pressure (static pressure) generated in the second suction duct 22 is about the first suction duct 21. It is about 800 Pa which is larger than that.

FIG. 3 is a plan view of the first suction duct 21 and the second suction duct 22 as viewed from above.
As shown in FIG. 3, the conveying belt 18 has a number of small holes 18a from which air is sucked. Although the conveyor belt 18 is stretched by the driven roller 16 and the like, the conveyor belt 18 is partially broken in FIG. A face plate 43 in which a plurality of suction openings 43 a are formed is disposed below the transport belt 18 and above the first suction duct 21. Similarly, a face plate 44 in which a plurality of suction openings 44 a are formed is disposed below the transport belt 18 and above the second suction duct 22. Air is sucked from the suction openings 43a, 44a formed in the face plates 43, 44 by driving the suction fans 41a, 41b, 42a, 42b (see FIG. 2). In FIG. 3, the face plates 43 and 44 are partially broken, but the face plates 43 and 44 are arranged in the width direction of the conveyor belt 18.

  Further, the opening area ratio occupied by the suction openings 43a and 44a per unit area of the face plates 43 and 44 is configured to be larger on the second suction duct 22 side than on the first suction duct 21 side. In this embodiment, the opening area ratio is about 20 to 30% on the first suction duct 21 side and about 60 to 70% on the second suction duct 22 side. Further, the suction opening 43a on the first suction duct 21 side is a round hole, and the suction opening 44a on the second suction duct 22 side is a square hole or a hexagonal hole, but the shapes of the suction openings 43a and 44a are these. It is not limited to.

  As shown in FIG. 3, a pair of movable partition plates 45 and 46 are disposed in the second suction duct 22. Slide members 47 and 48 provided with rack teeth 47a and 48a are integrally attached to the movable partition plates 45 and 46, respectively. Further, as moving means for moving the slide members 47 and 48, two motors 49 and 62 as drive means, and two pinion gears as transmission means for transmitting the driving force of the motors 49 and 62 to the slide members 47 and 48, respectively. 91 and 92 are provided. The two pinion gears 91 and 92 mesh with the rack teeth 47a and 48a of the slide members 47 and 48, respectively. When the pinion gears 91 and 92 are rotated forward or backward by driving the motors 49 and 62, the slide guide members 47 and 48 are moved in the width direction of the transport belt 18, and the pair of movable partition plates 45 and 46 approach each other. Alternatively, they are separated. As a result, the distance between the movable partition plates 45 and 46 changes, and the width (width in the direction perpendicular to the paper transport direction) W of the suction area where the suction force is exerted in the second suction duct 22 can be changed. Yes.

FIG. 4 is a block diagram showing a control system of the second suction duct 22 and the suction fans 42a and 42b provided thereon.
As shown in FIG. 4, motors 49 and 62 (hereinafter referred to as “suction area width adjusting motor”) for moving the movable partition plates 45 and 46, and a suction fan provided in the second suction duct 22. 42a and 42b are controllable by the control part 9 comprised from CPU etc. which were mounted in the apparatus main body. Specifically, the driving of the suction area width adjusting motors 49 and 62 is controlled based on detection information of the sheet width detecting means 80 that detects the width of the sheet (sheet material). The outputs of the suction fans 42a and 42b are input information of the sheet type input means 8 for inputting the type of sheet (sheet material), and detection by the rear end position detection sensor 96 for detecting the rear end position of the sheet. It is controlled based on information.

  The rear end position detection sensor 96 is disposed at a predetermined position on the first straight transport portion S1 of the transport belt 18 (see FIG. 2). When the trailing edge of the sheet is detected by the trailing edge position detection sensor 96, the outputs of the suction fans 42a and 42b provided in the second suction duct 22 are increased.

  The sheet type input means 8 is constituted by an operation panel provided in the main body of the ink jet printer. In addition, a personal computer or the like connected to the printer can be used as a sheet type input unit for inputting the type of sheet material (paper type). Alternatively, the sheet type detection means 70 for detecting the type (sheet type) of the sheet material by a unique sensor is provided, and the outputs of the suction fans 42a and 42b are controlled based on the detection information of the sheet type detection means 70. Good. In that case, it is possible to eliminate the input work by the user on the operation panel 8.

FIG. 5 shows a display section of the paper type selection mode of the operation panel 8.
The operation panel 8 includes a touch panel type liquid crystal display unit, and in this embodiment, any one of “standard paper”, “thin paper”, and “thick paper” can be selected and input. For example, “standard paper” is about 55-70K paper, “thin paper” is less than 45K paper, and “thick paper” is about 110-135K paper. In addition, other paper types can be arbitrarily set. In the present embodiment, the outputs of the suction fans 42a and 42b are preset for each paper type by a control table (not shown) or the like.

  The sheet width detecting means 80 is provided in each of the paper feeding unit 4 and the paper feeding device 6 shown in FIG. Hereinafter, a specific configuration of the sheet width detection unit 80 will be described in detail with reference to FIG.

FIG. 6 is a plan view of the paper feed tray 73 provided in the paper feed unit 4 and the paper feed device 6 as viewed from above.
As shown in FIG. 6, a pair of side fences 74 and 75 that guide both side portions of the paper P are erected on the paper feed tray 73. Moving members 76 and 77 that move in a direction orthogonal to the sheet conveying direction are attached to the side fences 74 and 75, and a rotatable pinion gear 78 is disposed between the moving members 76 and 77. ing. Further, rack teeth 76 a and 77 a that mesh with the pinion gear 78 are formed on the surfaces of the moving members 76 and 77 that face the pinion gear 78. As a result, when one of the side fences 74 and 75 approaches or separates from the other, the pinion gear 78 rotates, so that the other also moves in a direction that approaches or separates in conjunction with the other. In this manner, the pair of side fences 74 and 75 are configured to be able to approach and separate from each other, and the interval Y between the side fences 74 and 75 can be matched with the width of the paper P.

  The paper feed tray 73 is provided with a plurality of side fence position detection sensors 79 that detect the positions of the side fences 74 and 75. These sensors 79 detect the positions of the side fences 74 and 75 so that the width of the paper P can be indirectly known. That is, in the present embodiment, the side fence position detection sensor 79 functions as the sheet width detection unit 80 that detects the width of the paper P. Then, based on the sheet width detected by the side fence position detection sensor 79, the control unit 9 drives the suction area width adjustment motors 49 and 62 to adjust the positions of the movable partition plates 45 and 46, The width W of the suction area matches the width of the detected paper.

Hereinafter, the operation of the sheet conveying apparatus will be described with reference to the flowchart of FIG.
First, when the user inputs a paper type using the operation panel (STEP 1), the width W (see FIG. 3) of the suction area of the second suction duct 22 matches the paper width before starting the paper transport operation. (STEP 2). Thereafter, the conveyance of the sheet is started (STEP 3), and when the sheet is conveyed onto the conveyance belt 18, the sheet P is adsorbed onto the conveyance belt 18 by air suction from the first suction duct 21 shown in FIG. (STEP4). Then, the sheet is conveyed by the conveying belt 18 to the lower part of the image forming unit 3 where an image is formed. After the image is formed on the paper, the paper is transported above the second suction duct 22 and is sucked onto the transport belt 18 by air suction from the second suction duct 22 (STEP 5).

When the sheet is further conveyed downstream and the trailing edge of the sheet is detected by the trailing edge position detection sensor 96 shown in FIG. 2 (STEP 6), suction fans 42a and 42b provided in the second suction duct 22 are detected. And the suction force increases (STEP 7). Thereby, the suction force of the second suction duct 22 becomes larger than the suction force of the first suction duct 21. In the present embodiment, for example, the suction force of the first suction duct 21 is about 10 to 30 N / m ² , while the suction force of the second suction duct 22 after the suction force is increased is 100 to 150 N / m ^2. It will be about. Further, the amount of increase in the suction force at this time is performed based on the input sheet type information and a preset control table. When the trailing edge of the paper passes the predetermined position X on the first bending conveyance section M1 shown in FIG. 2 (STEP 8), the suction fans 42a and 42b provided in the second suction duct 22 are reduced in output and sucked. The force is restored (STEP 9). Whether or not the trailing edge of the sheet has passed the predetermined position X can be detected based on, for example, the detection timing of the trailing edge position detection sensor 96 and the conveyance speed of the conveyance belt 18.

  In the ink jet printer of the present embodiment, as shown in FIG. 8, the paper P is bent and transported downward in the first bending transport section M1, and the front end e1 of the paper P is at a position downstream of the first bending transport section M1. Is reached, the rear end e2 of the paper P is likely to be lifted from the conveyance belt 18 in the vicinity of the upstream side of the first bending conveyance unit M1. If the trailing edge e2 of the paper P is lifted, the image forming surface of the paper P may come into contact with a peripheral member or the like to disturb the image. Further, as shown in FIG. 8, in particular, when image formation is performed at the rear end e2 of the paper P, if the rear end e2 of the paper P is lifted, there is a possibility that image formation may not be performed satisfactorily. Further, the rear end e2 may come into contact with the nozzles of the ink jet head of the image forming unit 3 to cause contamination of the paper P, ink ejection failure, or the like.

  Therefore, as described above, the second suction duct 22 is provided when the rear end of the sheet is in the transport range Y from the position of the rear end position detection sensor 96 to the predetermined position X on the first bending transport unit M1. The suction force in the second suction duct 22 is increased by increasing the output of the suction fans 42a and 42b. Accordingly, a large suction force can be applied to the sheet in the vicinity of the upstream side of the first bending conveyance unit M1, and the trailing edge of the sheet can be prevented from being lifted.

  Further, as described above, by detecting the position of the trailing edge e2 of the sheet P, the suction force in the second suction duct 22 is increased when the sheet is being conveyed in a range in which the trailing edge is easily lifted. Therefore, it is possible to reliably prevent the rear end from being lifted. In the present embodiment, the timing at which the output of the suction fans 42a and 42b is increased is higher than the timing at which the trailing edge of the sheet reaches a position where the trailing edge is likely to be lifted in consideration of the rise time of the suction fans 42a and 42b. It is set to be the front.

  On the other hand, when the trailing edge e2 of the paper P is outside the transport range Y from the position of the trailing edge position detection sensor 96 to the predetermined position X, the trailing edge e2 hardly rises. For this reason, when the trailing edge e2 of the paper P is in a range where no lifting occurs, the suction force of the second suction duct 22 is not increased, so that the noise and power consumption of the suction fan can be reduced.

  In the present embodiment, the air suction from the first suction duct 21 and the air suction from the second suction duct 22 are performed independently by separate suction fans. As a result, in the first suction duct 21 and the like disposed at a position where the trailing edge of the sheet is not likely to be lifted, there is no unnecessary increase in suction force, so the noise and power consumption of the suction fan can be reduced. Can be reduced.

  On the other hand, the second suction duct 22 is required to generate a suction force larger than that of the first suction duct 21, and is thus devised. Specifically, as described above, two suction fans 42a and 42b are arranged in series (see FIG. 2), or the opening area ratio of the suction opening 44a formed in the face plate 44 is increased. (See FIG. 3). Further, by changing the width W of the suction area of the second suction duct 22 to coincide with the sheet width, unnecessary air suction outside the area through which the sheet passes is eliminated, and the suction force is reduced due to air leakage. It is preventing. Even if the width W of the suction area is not completely matched with the paper width, it is possible to reduce unnecessary air suction and suppress a decrease in suction force.

  Further, the lifting of the trailing edge of the paper tends to become more prominent as the paper becomes thicker or the rigidity becomes higher. Thus, as described above, the suction force in the second suction duct 72 is adjusted to a value suitable for the paper type by changing the amount of increase in the suction force of the second suction duct 22 according to the type of paper. doing. Specifically, when the paper is a thick paper with high rigidity, it is possible to suppress the lifting of the trailing edge of the paper by increasing the amount of increase in the suction force and applying a strong suction force. On the other hand, when the paper is a thin paper with low rigidity, a strong suction force is not necessary to suppress the trailing edge of the paper from rising, and therefore the amount of increase in the suction force may be small. Further, depending on the paper type, there is a case where the suction force in the second suction duct 22 may not be increased at all. In this way, when transporting thin paper or the like, it is possible to reduce the noise and power consumption of the suction fan by minimizing the amount of increase in suction force.

FIG. 9 is a schematic configuration diagram illustrating a part of an inkjet printer according to a reference example .
The ink jet printer shown in FIG. 9 is also provided with the image forming unit 3 including the image forming head unit 11 having the ink jet heads 10Y, 10M, 10C, and 10K for the respective colors, as in the embodiment of the present invention. In FIG. 9, a two-dot chain line is a conveyance path through which a sheet as a sheet material is conveyed, and an arrow attached to the two-dot chain line indicates a sheet conveyance direction. The ink jet printer is provided with a sheet conveying device that conveys the paper along its conveying path. The sheet conveying device serves as a conveying unit such as a conveying belt 63 disposed below the image forming unit 3 and the sheet conveying device. A pair of conveyance rollers 64a and 64b and the like disposed on the downstream side in the sheet conveyance direction are provided.

  Further, the conveyance path includes a first straight conveyance unit S1 in which the sheet is conveyed in the horizontal direction by the conveyance belt 63, and a bent conveyance that is connected to the downstream side in the conveyance direction and is bent and conveyed upward by the switching claw 68. It has a section M1 and a second straight transport section S2 that is connected to the downstream side in the transport direction and transported vertically upward by the transport roller pairs 64a and 64b.

  The conveyor belt 63 is an endless belt, and is stretched by a plurality of rollers 65, 66, 67 and the like including at least one drive roller. Further, as the driving roller rotates, the conveyance belt 63 rotates in the direction of the arrow in the figure. The sheet conveying apparatus according to the present embodiment also includes an air adsorbing unit that sucks air from the back side of the conveying belt 63 and adsorbs the sheet to the conveying belt 63. The air suction means is a first and second suction ducts 71 and 72 as air guide paths disposed on the back side of the conveyor belt 63, and an air suction means for sucking air independently from the suction ducts 71 and 72. A plurality of suction fans 81a, 81b, 82a, 82b.

The arrangement positions of the suction ducts 71 and 72 and the suction fans 81a, 81b, 82a and 82b will be described in detail.
The first suction duct 71 is disposed below the image forming unit 3 so as to face the first straight transport unit S1, and the second suction duct 72 is located near the upstream side of the bending transport unit M1 in the paper transport direction. One straight conveying portion S1 is arranged to face. The two suction fans 81a and 81b provided in the first suction duct 71 are disposed in parallel, but the two suction fans 82a and 82b provided in the second suction duct 72 are disposed in series. ing. As described above, by disposing the suction fan in a different manner, it is possible to generate a larger negative pressure in the second suction duct 72 than in the first suction duct 71 as in the above embodiment. I have to.

Further, the second suction duct 72 is devised in the same manner as the embodiment of the present invention in order to generate a suction force larger than that of the first suction duct 71. That is, the opening area ratio of the suction opening formed in the face plate (not shown) provided in the second suction duct 72 is made larger than that of the first suction duct 71. Further, in the second suction duct 22, the width W of the suction area (see FIG. 3) can be changed so as to match the paper width, and unnecessary air suction outside the area through which the paper passes is eliminated. Prevents a decrease in suction force due to leakage. Also, the suction mechanism width W variable mechanism and paper width detection mechanism in this reference example can be the same as those described with reference to FIGS.

In addition, a front end position detection sensor 97 that detects the front end position of the sheet is disposed at a predetermined position on the transport belt 63. When the front edge of the sheet is detected by the front edge position detection sensor 97, the output of the suction fans 82a and 82b provided in the second suction duct 72 is controlled to increase. Also in this reference example , the outputs of the suction fans 82a and 82b provided in the second suction duct 72 are input information of sheet type input means (operation panel or the like) for inputting the type of paper (sheet material). It is controlled based on. Alternatively, as in the above-described embodiment, a sheet type detection unit that detects the type (sheet type) of the sheet material is provided, and the outputs of the suction fans 82a and 82b are controlled based on the detection information of the sheet type detection unit. Is also possible. The control system for the outputs of the suction fans 82a and 82b and the width W of the suction area in the present reference example can be the same as that described with reference to FIGS.

The operation of the sheet conveying apparatus according to the reference example shown in FIG. 9 will be described below with reference to the flowchart of FIG.
First, when the user inputs a paper type through the operation panel (STEP 1), the width W of the suction area of the second suction duct 72 is adjusted to coincide with the paper width before starting the paper transport operation ( (Step 2). Thereafter, the conveyance of the sheet is started (STEP 3), and when the sheet is conveyed onto the conveyance belt 63, the sheet P is adsorbed onto the conveyance belt 63 by air suction from the first suction duct 71 shown in FIG. (STEP4). Then, after the sheet P is conveyed to the lower part of the image forming unit 3 by the conveying belt 63 and an image is formed there, the sheet is further conveyed downstream, and the sheet is conveyed to the conveying belt 63 by air suction from the second suction duct 72. Adsorbed (STEP 5).

  Thereafter, when the front end of the sheet is detected by the front end position detection sensor 97 (STEP 6), the outputs of the suction fans 82a and 82b provided in the second suction duct 72 are increased and the suction force is increased (STEP 7). As a result, the suction force of the second suction duct 72 is greater than the suction force of the first suction duct 71. Further, the amount of increase in the suction force at this time is performed based on the input sheet type information and a preset control table. Then, when the trailing edge of the paper passes the predetermined position V on the bending conveyance section M1 shown in FIG. 9 (STEP 8), the output of the suction fans 82a and 82b provided in the second suction duct 72 is reduced and suction force is reduced. It is restored (STEP 9).

  FIG. 11 shows a state in which the leading edge e1 of the sheet P conveyed by the conveying belt 63 is in contact with the switching claw 68 provided in the bending conveying unit M1 in the ink jet printer shown in FIG. In this way, when the paper P enters the bending conveyance section M1, if the leading edge e1 of the paper P contacts the switching claw 68 or the like, conveyance resistance is generated by the contact. Then, as shown in FIG. 11, when the sheet P slides backward with respect to the conveyance belt 63 due to the conveyance resistance generated by the contact in a state where the image is formed on the rear end e2 side of the sheet, There is a possibility that the conveyance speed of the paper P changes, and the image formation on the rear end e2 side of the paper P is not accurately performed.

  Therefore, as described above, when the front end e1 of the sheet P is in the transport range Z from the position of the front end position detection sensor 97 to the predetermined position V on the bending transport unit M1, the suction duct provided in the second suction duct 72 is used. The output of the fans 82a and 82b is increased to increase the suction force in the second suction duct 72. As a result, the suction force becomes stronger in the vicinity of the upstream side of the bending conveyance section M1, so that the conveyance force can be sufficiently applied to the paper P, and even if conveyance resistance occurs due to the contact of the front end e1 of the paper P. Thus, the paper P can be transported without causing slippage.

Further, in this reference example , when the paper P is being transported within a range in which the transport resistance due to the contact of the front end e1 is likely to occur by detecting the position of the front end e1 of the paper P, the suction in the second suction duct 72 is performed. The force can be increased and the paper P can be reliably conveyed. In this reference example , the timing of increasing the output of the suction fans 82a and 82b is set before the timing at which the front edge of the sheet contacts the switching claw 68 in consideration of the rise time of the suction fans 82a and 82b. It is set to become.

  On the other hand, when the front end e1 of the sheet P is outside the transport range Z from the position of the front end position detection sensor 97 to the predetermined position V, there is no problem due to the contact of the front end e1. For this reason, when the front end e1 of the paper P is in a range where no trouble occurs due to contact, the suction force of the second suction duct 72 is not increased, thereby reducing the noise and power consumption of the suction fan. .

Also in this reference example , the air suction from each of the suction ducts 71 and 72 is configured to be performed independently, so that the first suction duct disposed at a position where no trouble occurs due to the contact. In 71 and the like, useless suction force is not increased, and noise and power consumption of the suction fan can be reduced.

  Further, the conveyance resistance due to the contact of the front end of the sheet tends to increase as the sheet becomes thicker or the rigidity increases. Therefore, as described above, the suction force in the second suction duct 72 is adjusted to a value suitable for the paper type by changing the amount of increase in the suction force of the second suction duct 72 according to the type of paper. doing. Specifically, when the paper is thick paper with high rigidity, the amount of increase in the suction force is increased and a strong suction force is applied so that the paper does not slip even if a large transport resistance occurs. It can be transported. On the other hand, when the paper is a thin paper or the like having a low rigidity, the amount of increase in the suction force may be small because the generated transport resistance is small and no strong suction force is required. Further, depending on the paper type, there is a case where the suction force in the second suction duct 72 may not be increased at all. In this way, when transporting thin paper or the like, it is possible to reduce the noise and power consumption of the suction fan by minimizing the amount of increase in suction force.

The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention. For example, in the embodiment shown in FIG. 2 and the like, similarly to the reference example shown in FIG. 9 and the like, the front end position of the sheet is detected and the suction force is changed, and the front end of the sheet comes into contact with the bending conveyance unit. This may prevent a decrease in the conveyance speed (see FIG. 17). Further, in the reference example shown in FIG. 9 and the like, similarly to the embodiment shown in FIG. 2 and the like, the rear end position of the paper is detected and the suction force is changed, and the paper on the rear end side is lifted (see FIG. 9). 16) may be prevented. Moreover, the 1st suction duct 21 and the 2nd suction duct 22 which are shown in FIG. 2 are comprised integrally, and the upstream vicinity of a bending conveyance part (1st bending conveyance part M1) in the suction duct comprised integrally. The suction force at may be set to be larger than the suction force at the upstream side. That is, the number of air suction means for sucking air in the straight transport unit (first straight transport unit S1) may be one.

  Moreover, the bending direction of the said bending conveyance part (1st bending conveyance part) is not limited to upper direction or the downward direction. That is, as shown in FIG. 12, according to the present invention, the bending conveyance unit M or M ′ continuously provided on the downstream side in the conveyance direction of the straight conveyance unit S has a conveyance belt 85 with respect to the extension line L of the straight conveyance unit S. If it is the structure arrange | positioned so that it may bend to the arrangement | positioning side or the other side, it is applicable.

  In addition to the ink jet printer shown in FIG. 1, the sheet conveying apparatus according to the present invention forms an image such as a printer provided with an electrophotographic image forming unit, other copiers, facsimiles, or composite machines thereof. It can also be installed in equipment.

  As described above, according to the present invention, by increasing the suction force in the vicinity of the upstream side of the bending conveyance unit, it is possible to effectively lift the rear end associated with the sheet material such as paper passing through the bending conveyance unit. Can be prevented. In addition, by increasing the suction force in the vicinity of the upstream side of the bending conveyance section, the suction force of the sheet material to the conveyance belt at that location increases, so the front end of the sheet material is provided on the bending conveyance section. Even if conveyance resistance occurs due to contact with the sheet, the sheet material can be conveyed without causing slippage (decrease in conveyance speed). As described above, in the present invention, it is possible to effectively prevent the trailing edge of the sheet material from being lifted and the sheet material from slipping (decrease in the conveyance speed) with respect to the conveyance belt, so that the sheet material can be conveyed smoothly and stably. It becomes. On the other hand, since there is no possibility that the above-mentioned problem occurs further upstream near the upstream side of the bending conveyance section, noise and power consumption can be reduced by not increasing the suction force in such a place.

  In addition, by configuring the suction force in the vicinity of the upstream side of the bending conveyance section of the air adsorbing means to be changeable according to the type of the sheet material, it is possible to exhibit a suction force suitable for each type of sheet material. It becomes like this. Specifically, when the sheet material is highly rigid or thick, by increasing the suction force, it is possible to exert a strong adsorption force toward the conveyance belt with respect to the sheet material. Can be suppressed. On the other hand, in the case of a sheet material having a low rigidity or a thin sheet material, a large suction force is not necessary to suppress the above-described problems, and thus it is possible to reduce noise and power consumption by reducing the suction force. Become.

  Further, when the rear end of the sheet material passes at least a predetermined range in the vicinity of the upstream side of the bending conveyance unit (for example, the conveyance range Y shown in FIG. 8), the bending conveyance unit of the air adsorbing means is compared with other times. By increasing the suction force in the vicinity of the upstream side of the sheet material, it is possible to reliably prevent the trailing edge of the sheet material from being lifted. On the other hand, while the rear end of the sheet material passes through other locations, there is no possibility that the rear end will be lifted, so noise and power consumption can be reduced by not increasing the suction force.

  Further, when the front end of the sheet material passes at least a predetermined range (for example, the conveyance range Z shown in FIG. 12) in the bending conveyance unit, the upstream side of the bending conveyance unit of the air adsorbing unit is compared with other times. By increasing the suction force in the vicinity of the side, the sheet material can be reliably conveyed without causing a decrease in the conveyance speed of the sheet material. On the other hand, while the front end of the sheet material passes through other locations, there is no risk of a decrease in the sheet material conveyance speed, so noise and power consumption can be reduced by not increasing the suction force. It is.

8 Operation panel (sheet type input means)
18 Conveying belts 21 to 24 Suction duct 43a Suction opening 44a Suction opening 63 Conveying belt 85 Conveying belt A to E First to fifth conveying paths M1 and M2 Bending and conveying unit P Paper (sheet material)
S1 to S3 Straight conveyance part W Suction area width

JP 2009-274368 A JP 2009-1113935 A

Claims (5)

A first straight conveying unit; a bending conveying unit continuously provided in a convex curved shape downstream in the conveying direction of the first straight conveying unit; and the first straight conveying unit provided continuously on the downstream side in the conveying direction of the bending conveying unit. A conveyance belt that carries and conveys a sheet material on a conveyance surface having a second straight conveyance unit that is inclined with respect to the straight conveyance unit, and sucks air from the back side of the conveyance belt to transfer the sheet material to the conveyance belt An air adsorbing means for adsorbing to the first straight conveying section, and an ink jet head disposed to face the first straight conveying portion and ejecting ink onto the sheet material to form an image. In an image forming apparatus configured to convey from one straight conveyance unit to the second straight conveyance unit via the bending conveyance unit,
When the front end of the sheet material reaches a predetermined position of the second straight conveyance unit, the suction force in the vicinity of the upstream side in the sheet conveyance direction of the bending conveyance unit by the air adsorbing unit is more upstream in the sheet conveyance direction than that An image forming apparatus characterized in that it is set to be larger than the suction force in the case. The air adsorbing means includes a suction duct having a plurality of suction openings disposed to face the back surface of the transport belt, and the opening area of the suction duct in the vicinity of the upstream side in the sheet transport direction of the bending transport section The image forming apparatus according to claim 1, wherein the rate is larger than the opening area rate of the suction duct on the upstream side in the sheet conveyance direction . 3. The image forming apparatus according to claim 1 , wherein the width of the suction area in the vicinity of the upstream side of the bending conveyance unit of the air adsorbing unit in the sheet conveyance direction can be changed according to the width of the sheet material . 4. The image forming apparatus according to claim 1 , wherein the suction force of the air adsorbing unit in the vicinity of the upstream side in the sheet conveyance direction of the bending conveyance unit can be changed according to the type of sheet material. 5. . The suction force in the vicinity of the upstream side in the sheet conveyance direction of the bending conveyance unit of the air adsorbing means is increased when the sheet material type is a rigid or thick sheet material, and the sheet material type is small or The image forming apparatus according to claim 4 , wherein the thin sheet material is configured to be small .

Images