Image forming apparatus

Abstract

By overlapping the rear end of the preceding sheet of paper PA and the front end of the subsequent sheet of paper PA, a collision between the preceding sheet of paper PA and the subsequent sheet of paper PA is avoided, and the occurrence of a paper discharge jam is prevented.SOLUTION: The image forming apparatus includes the first conveying section 3 for conveying the sheet P at the first conveying speed V1 which is the printing speed of the image forming section 2, and the second conveying section 4 for conveying the sheet PA at the second conveying speed V1 slower than the first conveying speed V2 and discharging the sheet PA to the sheet discharge tray 51, wherein the second conveying speed V2 is a conveying speed at which the rear end of the preceding sheet PA and the front end of the subsequent sheet PA overlap when the front end of the sheet PA conveyed in advance by the second conveying section 4 reaches the end fence 52 of the sheet discharge tray 51.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus that prevents collision of sheets discharged onto a sheet receiving tray and prevents deterioration of alignment of sheets discharged onto the sheet receiving tray even when the printing speed is increased. [Background technology]

[0002] A known paper discharge device that discharges and stacks paper from an image forming unit onto a paper discharge tray is configured to include a discharge conveying section that transports the paper to the paper discharge tray, and a paper discharge tray equipped with an end fence that abuts the leading edge of the paper discharged from the discharge conveying section, and the paper that abuts against the end fence falls freely and is stacked on the paper discharge tray.

[0003] Patent Document 1 discloses a paper discharge device that is provided near the discharge port of an image forming device through which print paper is discharged and has a collision avoidance means that pushes down the rear end of the print paper when it is discharged. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-62156 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the technology described in Patent Document 1, as printing speeds increase, the paper discharge speed also increases, making it easier for paper to become out of position during transport, and the time interval between subsequent sheets becomes shorter, resulting in an increased incidence of paper discharge jams caused by the rear end of the preceding sheet colliding with the front end of the succeeding sheet.Furthermore, as paper discharge speeds increase, the impact when the paper hits the end fence cannot be fully absorbed, causing a large rebound, which causes the paper to lose its position, disrupting the alignment of the discharged paper stack and causing collisions.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an image forming apparatus that can prevent the collision of paper discharged onto the paper discharge tray and prevent deterioration of the alignment of paper discharged onto the paper discharge tray, even when the printing speed is increased. [Means for solving the problem]

[0007] In order to achieve the above object, the image forming apparatus according to the present invention is characterized by: a first conveying unit that conveys paper at a first conveying speed that is a printing speed by the image forming unit; a second conveying unit that conveys the paper at a second conveying speed that is slower than the first conveying speed and discharges the paper onto a paper discharge tray; The second conveying speed is set to a conveying speed at which the rear end of the preceding paper sheet overlaps with the leading end of the succeeding paper sheet when the leading end of the preceding paper sheet being conveyed by the second conveying section reaches the end fence of the paper output tray. [Effects of the Invention]

[0008] According to the features of the image forming apparatus of the present invention, even if the printing speed is increased, it is possible to prevent the sheets discharged onto the sheet receiving tray from colliding with each other and to prevent the alignment of the sheets discharged onto the sheet receiving tray from deteriorating. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of an inkjet printing apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a schematic configuration diagram of an inkjet printing apparatus according to a second embodiment of the present invention. [Figure 3] 10 is a timing chart showing the detection state of a paper sensor provided in an inkjet printing device according to a second embodiment of the present invention, the conveying speed by the second conveying unit, the paper rear end speed before discharge, the paper rear end speed after discharge, the paper front end speed before discharge, and the paper front end speed after discharge. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components are designated by the same or equivalent reference numerals throughout the drawings. However, it should be noted that the drawings are schematic and may differ from the actual product. Furthermore, the drawings may include parts with different dimensional relationships and ratios.

[0011] Furthermore, the embodiments shown below are merely examples of devices that embody the technical concept of the present invention, and the technical concept of the present invention does not limit the arrangement of each component to that shown below. Various modifications can be made to the technical concept of the present invention within the scope of the claims.

[0012] Example 1 An embodiment of an inkjet printing apparatus 1 to which an image forming apparatus according to the present invention is applied will be described in detail below with reference to the accompanying drawings.

[0013] FIG. 1 is a schematic diagram of an inkjet printing apparatus 1 according to a first embodiment of the present invention.

[0014] In the following description, the front side of the paper in Figure 1 where the user is positioned is referred to as the right side, and the back side of the paper is referred to as the left side. Also, in Figure 1, up and down as seen from the user is referred to as the up and down direction. Also, the path indicated by the dashed line in Figure 1 is the path of the leading edge of the paper PA after it is released, within the transport path. The transport direction of the paper PA is referred to as the front-to-rear direction. In the following description, upstream means the front direction, and downstream means the rear direction.

[0015] As shown in FIG. 1, the inkjet printing apparatus 1 includes an image forming unit 2, a first conveying unit 3, a second conveying unit 4, a paper ejection unit 5, and a control unit 6.

[0016] The image forming unit 2 forms an image by ejecting black (K), cyan (C), magenta (M), and yellow (Y) inks from the nozzles of the inkjet head while transporting the paper PA (PA3) at a first transport speed. The nozzles form a nozzle row arranged linearly in the left-right direction (main scanning direction).

[0017] The first conveying section 3 conveys the paper PA, which has been conveyed from the image forming section 2 at the first conveying speed, to the second conveying section 4 at the first conveying speed. The first conveying section 3 has a conveying belt 31, a pair of belt pulleys 32, a suction fan 33, and a wing 34.

[0018] The conveyor belt 31 is an endless circular belt stretched over a pair of belt pulleys 32. The conveyor belt 31 has intake holes, which are through holes for suction-holding the paper sheets PA, formed at predetermined intervals along the conveying direction of the conveyor belt 31. The conveyor belt 31 suctions and holds the paper sheets PA on the conveyor belt 31 by the negative pressure (adsorption force) generated in the intake holes by the driving of the suction fan 33.

[0019] 1 by the rotational drive of the pair of belt pulleys 32. As a result, the conveyor belt 31 moves endlessly to convey the paper PA to the right.

[0020] The wings 34 are provided above the first conveying section 3 and lift up both ends of the paper PA in the paper width direction, bending the paper PA into a U-shape. This gives stiffness to the paper PA conveyed by the conveyor belt 21 and conveys it to the second conveying section 4.

[0021] The second conveying unit 4 conveys the paper PA, which has been conveyed from the first conveying unit 3 at the first conveying speed V1, at a second conveying speed V2 that is slower than the first conveying speed V1, and discharges the paper onto a paper discharge tray of the paper discharge unit 5. The second conveying unit 4 has a conveying belt 41, a pair of belt pulleys 42, a suction fan 43, a wing 44, and a paper sensor 45.

[0022] The conveyor belt 41 is an endless circular belt stretched over a pair of belt pulleys 42. The conveyor belt 41 has intake holes, which are through holes for attracting and holding the paper sheets PA, formed at predetermined intervals along the conveying direction of the conveyor belt 41. The conveyor belt 41 attracts and holds the paper sheets PA on the conveyor belt 41 by a negative pressure (adsorption force) generated in the intake holes by driving the suction fan 43.

[0023] 1 by the rotational drive of the pair of belt pulleys 42. As a result, the conveyor belt 41 moves endlessly to convey the paper PA to the right.

[0024] The wings 44 are provided above the second conveying unit 4 and lift up both ends of the paper PA in the paper width direction, bending the paper PA into a U-shape. This gives stiffness to the paper PA conveyed by the conveying belt 41 and allows it to be discharged onto the paper discharge tray of the paper discharge unit 5.

[0025] The paper sensor 45 detects the paper PA conveyed from the first conveying section 3.

[0026] The paper discharge unit 5 has a paper discharge tray 51. The paper discharge tray 51 places the paper PA transported by the second transport unit 4 at the second transport speed V2.

[0027] An end fence 52 is provided on the paper receiving tray 51 so as to be slidable in the front-rear direction, and a side fence 53 is provided so as to be slidable in the left-right direction.

[0028] The control unit 6 controls the first conveying unit 3 to convey the paper PA conveyed from the image forming unit 2 at the first conveying speed to the second conveying unit 4 at the first conveying speed, and also controls the second conveying unit 4 to convey the paper PA conveyed from the first conveying unit 3 at the first conveying speed V1 at a second conveying speed V2 slower than the first conveying speed V1 and discharge the paper onto the paper discharge tray of the paper discharge unit 5.

[0029] Here, the second conveying speed V2 is the conveying speed at which the rear end of the preceding paper PA (PA1) overlaps with the leading end of the succeeding paper PA (PA2) when the leading end of the preceding paper PA (PA1) being conveyed in advance by the second conveying section 4 reaches the end fence 52 of the paper output tray 51.

[0030] Specifically, the second conveying speed V2 is determined so as to satisfy the following (Equation 1).

[0031]

number

[0032] Here, V1 is the first conveying section conveying speed (=image forming section conveying speed), V2 is the second conveying section conveying speed, L2 is the second conveying section conveying distance + flying distance, D1 is the distance between the printing section and the paper discharge section, and D3 is the overlap amount during discharge.

[0033] As a result, the rear end of the preceding paper PA (PA1) and the front end of the succeeding paper PA (PA2) overlap by D3, so that the preceding paper PA (PA1) and the succeeding paper PA (PA2) do not collide with each other, thereby preventing the occurrence of paper discharge jams.

[0034] <Example 2> The optimal speed range for the transport speed of the paper sheet PA is experimentally determined based on the configuration, such as the angle and positional relationship between the second transport unit 4 and the paper ejection tray 51, and the type of paper sheet PA. Here, the second transport speed V2 calculated by the above (Equation 1) may not reach that range.

[0035] Therefore, in the second embodiment, the second conveying section 4 is provided with a second conveying speed V2 and a discharge speed V3, and the average speed of the conveying section L2 is set to V2. AVE By controlling the conveying speed of the second conveying section 4 so that V3 = V2, the discharge speed V3 is maintained at an optimum speed, and rear-end collisions due to overlapping are prevented.

[0036] FIG. 2 is a schematic diagram of an inkjet printing apparatus 1 according to a second embodiment of the present invention.

[0037] The hardware configuration shown in FIG. 2 is the same as the hardware configuration shown in FIG. 1, and therefore a description thereof will be omitted.

[0038] In the diagram shown in FIG. 2, V1: first conveying section conveying speed (= image forming section conveying speed), V2: second conveying section conveying speed, V3: second conveying section discharge speed, V2 AVE : average transport speed at the rear end of the paper, L2: transport distance of the second transport section + flight distance, D1: distance between the paper in the print section and the ejection section, D3: overlap amount at ejection.

[0039] Figure 3 is a timing chart showing the detection state S01 of the paper sensor 45 provided in the inkjet printing device 1 of Example 2 of the present invention, the conveying speed R01 by the second conveying section 4, the paper rear end speed PS01 before discharge, the paper rear end speed PS02 after discharge, the paper front end speed PS11 before discharge, and the paper front end speed PS12 after discharge.

[0040] As shown in the detection state S01 of the paper sensor 45 in Figure 3, at time t01, when the rear end of the preceding paper PA1 passes and the paper sensor 45 becomes non-detecting, the paper PA1 is transported at the second transport speed V2 of the second transport section 4, as shown in the paper rear end speed PS01 before discharge.

[0041] Then, at time t05, the sheet of paper PA1 is discharged from the second conveying section 4 and begins to fly. As shown by the post-discharge sheet rear end speed PS02, at time t07, the leading edge of the sheet of paper PA1 collides with the end fence 52, so the speed becomes zero.

[0042] In this way, when the preceding paper PA1 reaches the end fence 52, the leading edge of the following paper PA2 is transported a distance indicated by (L2+D1+D3) starting from the paper sensor 45, and is transported overlapping the trailing edge of the preceding paper PA by an overlap amount D3.

[0043] This prevents the preceding sheet PA (PA1) from colliding with the succeeding sheet PA (PA2), thereby preventing the occurrence of a paper discharge jam.

[0044] (Addendum) The present application discloses the following inventions.

[0045] (Appendix 1) a first conveying unit that conveys paper at a first conveying speed that is a printing speed by the image forming unit; a second conveying unit that conveys the paper at a second conveying speed that is slower than the first conveying speed and discharges the paper onto a paper discharge tray; The second conveying speed is a conveying speed at which the rear end of the preceding sheet and the leading end of the succeeding sheet overlap when the leading end of the preceding sheet conveyed by the second conveying unit reaches the end fence of the sheet receiving tray. An image forming apparatus characterized by:

[0046] As a result, the rear end of the preceding paper PA (PA1) and the front end of the succeeding paper PA (PA2) overlap by D3, so that the preceding paper PA (PA1) and the succeeding paper PA (PA2) do not collide with each other, thereby preventing the occurrence of paper discharge jams. [Explanation of symbols]

[0047] 1. Inkjet printing device 2 Image forming unit 3 First conveying section 4 Second conveying section 5 Paper output section 6 Control Unit 21 Conveyor belt 31 Conveyor belt 32 Belt pulley 33 Suction fan 34 Wing 41 Conveyor belt 42 Belt pulley 43 Suction fan 44 Wing 45 Paper sensor 51 Paper receiving tray 52 End Fence 53 Side Fence

Claims

[Claim 1] a first conveying unit that conveys paper at a first conveying speed that is a printing speed by the image forming unit; a second conveying unit that conveys the paper at a second conveying speed that is slower than the first conveying speed and discharges the paper onto a paper discharge tray; The second transport speed is set to a transport speed at which the rear end of the preceding sheet and the leading end of the succeeding sheet overlap when the leading end of the preceding sheet transported by the second transport unit reaches an end fence of the sheet receiving tray. An image forming apparatus characterized by:

Images