Image forming device

Abstract

To achieve both quietness and high productivity by adjusting setting of a paper ejection speed in an image forming device to which a post-processing device is connected.SOLUTION: An image forming device to which a post-processing device can be connected includes a conveyance part that inverts image-formed paper and conveys the inverted paper to the post-processing device and control means for setting a conveyance speed when conveying paper to the post-processing device based on paper length information. The control means (1) sets the conveyance speed for each paper to a first conveyance speed when image formation on paper whose length is a first length is continuously executed, (2) sets the conveyance speed for each paper to a second conveyance speed which is slower than the first conveyance speed when the image formation on paper of a second length shorter than the first length is continuously executed, and (3) sets the conveyance speed for each paper to the first conveyance speed when the image formation on paper having the first length and paper having the second length is continuously executed.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Image forming devices such as copiers and printers are generally equipped with a paper reversing mechanism. In image forming devices equipped with such a reversing mechanism, the paper is conveyed to a desired position, stopped, and then switched back in the opposite direction to reverse the paper's direction. When the paper is switched back, the preceding and succeeding sheets pass each other, so the conveying speed is increased to prevent the trailing edge of the preceding sheet from colliding with the leading edge of the succeeding sheet.

[0003] However, if paper is discharged from the machine while the paper transport speed is kept high, the resulting noise becomes a problem. Quieter operation is highly sought after in today's offices, and standards such as Blue Angel require that product models meet noise standards appropriate for the model. For this reason, the transport speed is slowed down to a level where 100% productivity can be achieved when paper is discharged from the machine, thereby achieving quieter operation.

[0004] Incidentally, image forming apparatuses are often connected to post-processing devices that perform post-processing such as stapling and folding. In such systems, the post-processing device adjusts the conveying speed when receiving paper from the image forming apparatus so that it is the same as the discharge speed of the image forming apparatus. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-182475 [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-102192 Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional image forming devices, the conveyance speed when ejecting paper is determined based on the paper size (particularly the length of the paper in the conveying direction). For example, for large-sized paper such as A3, a high conveyance speed is set to maintain high productivity in order to avoid collisions between the preceding and succeeding sheets when the paper is reversed and ejected. On the other hand, for small-sized paper such as A4, a low conveyance speed is set to achieve both high productivity and quiet operation, since high productivity can be maintained even if the conveyance speed is reduced when ejecting.

[0007] In this way, the paper conveyance speed when ejected from the image forming apparatus is determined by the size of the paper. As a result, when images are formed continuously on paper of different sizes, the conveyance speed when ejecting each paper may differ.

[0008] In an image forming apparatus that is not connected to a post-processing device, there is no particular problem even if the conveying speed during discharge changes for each sheet of paper. However, in an image forming apparatus that is connected to a post-processing device, if the conveying speed during discharge changes for each sheet of paper, the following problems arise.

[0009] As mentioned above, the post-processing device adjusts the conveying speed when receiving paper to be the same as the discharge speed of the image forming device. Because the post-processing device is an independent drive system separate from the image forming device, if the discharge conveying speed is changed every time the paper size is changed in the image forming device, the post-processing device's conveying speed must be changed each time. As a result, downtime occurs when the conveying speed is changed, reducing productivity.

[0010] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a means for improving productivity while realizing quieter operation when performing image formation on paper of different lengths. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, the image forming apparatus of the present invention is an image forming apparatus to which a post-processing device can be connected, and comprises: an image forming unit that forms an image on paper; a transport unit that inverts the paper on which the image has been formed by the image forming unit and transports the inverted paper to the post-processing device; and a control means that sets the transport speed when transporting the paper to the post-processing device based on information about the length in the transport direction of the paper on which the image is formed by the image forming unit, and controls the transport unit so that the paper is transported to the post-processing device at the set transport speed, wherein the control means (1) sets the transport speed for each paper to a first transport speed when image formation is performed continuously on paper having a paper length of a first length in the transport direction; (2) sets the transport speed for each paper to a second transport speed that is slower than the first transport speed when image formation is performed continuously on paper having a paper length of a second length in the transport direction that is shorter than the first length; and (3) sets the transport speed for each paper to the first transport speed when image formation is performed continuously on paper having a paper length of the first length and paper having a paper length of the second length in the transport direction.

[0012] In order to achieve the above object, another image forming apparatus of the present invention is an image forming apparatus to which a post-processing device can be connected, and comprises: an image forming unit that forms an image on a sheet; a transport unit that inverts the sheet on which the image has been formed by the image forming unit and transports the inverted sheet to the post-processing device; and a control means that sets a transport speed when transporting the sheet to the post-processing device based on information about the length in the transport direction of the sheet on which the image is formed by the image forming unit, and controls the transport unit so that the sheet is transported to the post-processing device at the set transport speed, consecutively Image formation is performed Different lengths in the conveying direction When the conveying speed differs between the sheets, consecutively The conveying speed for each sheet on which an image is formed is changed to the fastest speed among the different conveying speeds. [Effects of the Invention]

[0013] According to the present invention, when performing image formation on sheets of paper of different lengths, it is possible to improve productivity while realizing quieter operation. [Brief explanation of the drawings]

[0014] [Figure 1] Cross-sectional view of an image forming apparatus [Figure 2] Block diagram showing the control configuration of the image forming apparatus [Figure 3] Cross-sectional view of an image forming system having a post-processing device [Figure 4] FIG. 10 is a diagram showing an example of passing multiple pages with narrow gaps between them in an image forming system. [Figure 5] FIG. 10 is a diagram showing an example of passing multiple pages with wide gaps between them in an image forming system. [Figure 6] Cross-sectional view of the paper reversing and discharging section of the image forming apparatus [Figure 7] FIG. 10 is a diagram showing a reversing operation of the image forming apparatus; [Figure 8] Diagram showing the difference in ejection speed at the reverse ejection section [Figure 9] Flowchart for explaining the operation of determining the paper discharge speed for each paper [Figure 10] A diagram showing an example of a sequence when three pages are printed consecutively. [Figure 11] A diagram showing an example of a sequence when three pages are printed consecutively. [Figure 12] A diagram showing an example of a sequence when three pages are printed consecutively. [Figure 13] A diagram showing an example of a media table [Figure 14] FIG. 10 is a diagram showing an example of a paper transport interval. [Figure 15] Cross-sectional view showing an example of a paper transport space [Figure 16] A diagram showing the status of QUEs on a page-by-page basis [Figure 17] Flowchart (for configurations that do not have two paper ejection speeds for each paper type) [Figure 18]FIG. 10 is a diagram illustrating an example of a media table according to the second embodiment. [Figure 19] FIG. 10 is a diagram showing an example of a sequence in the second embodiment. [Figure 20] FIG. 10 is a diagram illustrating an example of a paper transport interval in the second embodiment. [Figure 21] FIG. 10 is a diagram showing an example of a sequence in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the image forming apparatus according to the present invention will be specifically described.

[0016] <Image forming device> First, the configuration of an image forming apparatus will be described with reference to FIG. 1. The image forming apparatus 100 shown in FIG. 1 is an example of a color image forming apparatus. In FIG. 1, laser scanners 1Y, 1M, 1C, and 1K are an example of an optical scanning device including a semiconductor laser and a polygon mirror. Also, photosensitive drums 2Y, 2M, 2C, and 2K are an example of an image carrier, and after their outer circumferential surfaces are charged, laser light corresponding to an image signal input to the laser scanners 1Y, 1M, 1C, and 1K is irradiated thereon. For convenience of explanation, photosensitive drum 2 may be used to represent photosensitive drums 2Y, 2M, 2C, and 2K in the description. The same applies to other image forming process units.

[0017] The charging rollers 3Y, 3M, 3C, and 3K are an example of a charging unit that uniformly charges the surface of each photosensitive drum 2. The developing devices 4Y, 4M, 4C, and 4K are developing units that use toner to develop toner images on the photosensitive drums 2Y, 2M, 2C, and 2K. The developing sleeves 5Y, 5M, 5C, and 5K are developer carriers that are rotatably provided within the developing device 4. The developing sleeves 5 transport developer (toner) of each color to the surface of each photosensitive drum 2. The cleaners 6Y, 6M, 6C, and 6K are cleaning units that clean the surface of the photosensitive drum 2. The intermediate transfer belt 7 is an intermediate transfer belt onto which the toner on the photosensitive drum 2 is transferred, and is stretched and rotatable in the clockwise direction in FIG. 1 by a drive roller 9, tension rollers 36a to 36d, and an inner transfer roller 27.

[0018] Primary transfer rollers 8Y, 8M, 8C, and 8K are provided on the inner peripheral surface of the intermediate transfer belt 7, facing the surfaces of the photosensitive drums 2. A cleaner 10 is a cleaning unit that cleans the outer peripheral surface of the intermediate transfer belt 7. A secondary transfer roller 11 is a secondary transfer unit that is provided on the outer peripheral surface of the intermediate transfer belt 7, facing the inner transfer roller 27. A fixing device 12 is a fixing unit that thermally fixes the toner image formed on the paper. A fixing roller 13 is a fixing roller that is rotatably provided within the fixing device 12. A pressure roller 14 is rotatably provided within the fixing device 12, facing the fixing roller 13.

[0019] Paper feed cassettes 15a to 15d are detachably provided within the image forming apparatus 100 body and are storage units for storing recording paper 16a to 16d. In this embodiment, paper feed cassette 15a is assigned the identification number of "paper feed stage 1" and stores A4-sized plain paper. Paper feed cassette 15b is assigned the identification number of "paper feed stage 2" and stores A4R-sized plain paper. Paper feed cassette 15c is assigned the identification number of "paper feed stage 3" and stores A3-sized plain paper. Paper feed cassette 15d is assigned the identification number of "paper feed stage 4" and stores A3-sized plain paper. In this embodiment, A3 paper is an example of paper whose paper length in the transport direction is a first length. A4 paper and A4R paper are examples of paper whose paper length in the transport direction is a second length that is shorter than the first length.

[0020] In some cases, the paper feed cassettes 15a to 15d are represented by the paper feed cassette 15. In some cases, an optional paper feed cassette (not shown) may be provided outside the image forming apparatus 100 main body.

[0021] Feeding rollers 17a to 17d are feeding rollers that feed paper toward the image forming unit. Note that in some cases, feeding roller 17 will be used to represent feeding rollers 17a to 17d. Reference numeral 18 is a registration roller (hereinafter referred to as a registration roller). Reference numeral 19 is a pre-registration roller. Reference numerals 20a to 20d are intermediate conveying rollers. Note that in some cases, intermediate conveying roller 20 will be used to represent intermediate conveying rollers 20a to 20d.

[0022] The external discharge roller 21a and the external discharge front roller 21b are a pair of rollers that discharge the paper, whose traveling direction has been reversed by the upper and lower inversion rollers 22a and 22b, outside the apparatus. Furthermore, if a post-processing device is connected to the image forming apparatus 100, the received paper is passed to the post-processing device. The upper inversion roller 22a and the lower inversion roller 22b are reversible rollers that reverse the traveling direction of the paper on which the toner image has been fixed by the fixing device 12 (fixing unit). 23a to 23d are double-sided conveying rollers. In this embodiment, the upper inversion roller 22a, the lower inversion roller 22b, the external discharge roller 21a, and the external discharge front roller 21b are an example of a conveying unit that inverts the front and back of the paper on which an image has been formed and conveys the inverted paper.

[0023] <Image formation operation> An image forming operation in the image forming unit of the image forming apparatus 100 shown in Fig. 1 will now be described. Each photosensitive drum 2 is constructed by coating an organic photoconductive layer on the outer periphery of an aluminum cylinder, and rotates counterclockwise in Fig. 1 by the rotational driving force of a motor (not shown) serving as a drive source. The motor rotates each photosensitive drum 2 counterclockwise in Fig. 1 in accordance with the image forming operation. The surface of each photosensitive drum 2 rotating counterclockwise in Fig. 1 is uniformly charged by each charging roller 3.

[0024] 2, a laser beam 1a is emitted from each laser scanner 1 to the surface of each photosensitive drum 2 that has been uniformly charged by each charging roller 3, in accordance with image data for each color of yellow Y, magenta M, cyan C, and black K. The laser beam 1a is irradiated onto the surface of each photosensitive drum 2, selectively exposing the surface to light, and an electrostatic latent image is formed.

[0025] The electrostatic latent image formed on the surface of each photosensitive drum 2 is supplied with a developer (toner) of each color carried on the surface of each developing sleeve 5, and is developed into a toner image, making it visible.

[0026] Meanwhile, the outer peripheral surface of the intermediate transfer belt 7 is in contact with the surface of each photosensitive drum 2, and is driven to rotate by a drive roller 9 during image formation, rotating in the clockwise direction in Fig. 1. At this time, a primary transfer voltage is applied to each primary transfer roller 8, and the toner images formed on the surface of each photosensitive drum 2 are sequentially primarily transferred onto the outer peripheral surface of the intermediate transfer belt 7 and superimposed thereon.

[0027] During image formation, a secondary transfer roller 11 comes into contact with the outer circumferential surface of the intermediate transfer belt 7, and a secondary transfer voltage is applied to the secondary transfer roller 11. As a result, the toner images that have been primarily transferred onto the outer circumferential surface of the intermediate transfer belt 7 are secondarily transferred en bloc onto a sheet of paper that has been conveyed to a secondary transfer nip portion N1 between the outer circumferential surface of the intermediate transfer belt 7 and the secondary transfer roller 11.

[0028] The secondary transfer roller 11 is in contact with the outer surface of the intermediate transfer belt 7 while the toner image that has been primarily transferred onto the outer surface of the intermediate transfer belt 7 is being secondarily transferred onto paper, but is separated from the outer surface of the intermediate transfer belt 7 when image formation is completed.

[0029] The paper onto which the toner image has been secondarily transferred is transported by a transport belt 28 with the toner image facing up to a fixing device 12. The fixing device 12 thermally melts the transferred toner image and fixes it to the paper as the paper is transported. As shown in FIG. 1, the fixing device 12 includes a fixing roller 13 that heats the paper and a pressure roller 14 that presses the paper against the fixing roller 13. The fixing roller 13 is hollow and has a heater (not shown) built in. That is, the paper carrying the toner image is heated and pressurized as it is nipped and transported between the fixing roller 13 and the pressure roller 14, so that the toner image is thermally melted and thermally fixed to the surface of the paper.

[0030] When the image forming operation is completed, the cleaners 6 clean the residual toner remaining on the surface of each photosensitive drum 2. In addition, the cleaner 10 cleans the residual toner remaining on the outer peripheral surface of the intermediate transfer belt 7. This residual toner is collected in a collection container (not shown).

[0031] <Paper transport operation> Next, a paper transport operation in the image forming apparatus 100 will be described. Paper sheets selectively fed from each of the paper feed cassettes 15a to 15d are unwound by each feed roller 17 and separated and fed one by one in cooperation with a separation unit (not shown). The fed paper sheets are nipped and transported by each transport roller 29 and merge into the transport path 31. Thereafter, the paper sheets are transported toward the pre-registration rollers 19 by each intermediate transport roller 20 provided on the transport path 31, and further nipped and transported by the pre-registration rollers 19 until the leading edge of the paper abuts against the nip of the registration rollers 18, which are temporarily stopped. The paper sheets are then handled by their stiffness, and any skew is corrected.

[0032] The registration rollers 18 rotate in synchronization with the timing at which the laser beams 1a emitted from the laser scanners 1 are irradiated onto and exposed to the surfaces of the photosensitive drums 2. The registration rollers 18 then sandwich and transport the paper, sending it to the secondary transfer nip N1 between the outer circumferential surface of the intermediate transfer belt 7 and the secondary transfer roller 11.

[0033] The paper is sandwiched and transported between the outer circumferential surface of the intermediate transfer belt 7 and the secondary transfer roller 11. As a result, the toner image on the outer circumferential surface of the intermediate transfer belt 7 is transferred all at once onto the paper. Thereafter, the paper carrying the toner image is transported by the transport belt 28 to the fixing device 12. The toner image transferred to the paper is thermally fixed by the fixing device 12.

[0034] <Straight discharge and reverse discharge> The paper that has passed through the fixing device 12 may be discharged straight via the conveying path 32a, or may be discharged in an inverted state via the conveying path 32b, the inverting conveying path 33, and the conveying path 33a.

[0035] When the paper that has passed through the fixing device 12 is to be discharged straight, the paper that has passed through the fixing device 12 is handed over to the outer discharge rollers 21a via the conveying path 32a. On the other hand, when the paper is to be discharged upside down, the paper that has passed through the fixing device 12 is handed over to the upper reversing rollers 22a provided on the reversing conveying path 33 via the conveying path 32b.

[0036] <Straight discharge> When conveying path 32a is selected by rotation of a flapper (not shown), the paper that has passed through fixing device 12 passes through conveying path 32a, is pinched by external discharge rollers 21a, and is discharged to the outside of the image forming apparatus 100 body with the side on which the toner image has been fixed facing upward. Alternatively, if a post-processing device is connected, the paper that has been discharged to the outside of the image forming apparatus 100 body by external discharge rollers 21a is passed to the post-processing device, where predetermined post-processing such as binding and hole punching is performed. After that, the image forming operation ends.

[0037] <Reverse discharge> On the other hand, when the paper is inverted and discharged outside the apparatus, the paper 16 that has passed through the fixing device 12 passes through the conveying path 32b and is guided to the reversing conveying path 33. The upper reversing roller 22a is rotatable forward and backward. The paper 16 that has passed through the fixing device 12 passes through the conveying path 32b and reaches the upper reversing roller 22a provided on the reversing conveying path 33. The upper reversing roller 22a then rotates forward while holding the paper, and the end 16, which is the trailing end in the paper's traveling direction, is conveyed along the reversing conveying path 33 downward in FIG. 1 until it reaches the vicinity upstream of the upper reversing roller 22a.

[0038] Thereafter, the upper reversing roller 22a is driven to rotate in the reverse direction while clamping the end 16A2, which is the rear end in the traveling direction of the paper. Then, the paper reverses its conveying direction on the reversing conveying path 33, is guided to the conveying path 33a, and is delivered to the outer discharge rollers 21a and the outer pre-discharge rollers 21b.

[0039] The sheet of paper conveyed from the reversing conveying path 33 along the conveying path 33a while being held between the upper reversing roller 22a, the outer discharge roller 21a, and the front outer discharge roller 21b is discharged out of the main body of the image forming apparatus 100 with the side on which the toner image has been fixed facing downward. Alternatively, the sheet of paper discharged out of the main body of the image forming apparatus 100 by the outer discharge roller 21a and the front outer discharge roller 21b is delivered to a post-processing device (not shown) where predetermined post-processing such as binding and hole punching is performed. After that, the image forming operation is completed.

[0040] <Double-sided printing> When printing on both sides of a sheet of paper, the sheet of paper with an image formed on its first side passes through the fixing device 12, then passes through the conveying path 32b and is guided to the reversing conveying path 33. The sheet is then handed over to the upper reversing roller 22a and the lower reversing roller 22b provided on the reversing conveying path 33. The upper and lower reversing rollers 22a and 22b are capable of rotating forward and backward.

[0041] During double-sided printing, the trailing edge of the paper guided to the reversing conveyance path 33 is conveyed to the vicinity of the lower reversing roller 22b. Thereafter, the lower reversing roller 22b is driven to rotate in the reverse direction, and the paper is guided to the double-sided conveyance path 35 by a flapper (not shown). The paper is then handed over to the double-sided conveyance rollers 23a to 23d provided in the double-sided conveyance path 35. At this time, the paper on which the image has been formed is conveyed through the double-sided conveyance path 35 with the first side facing upward.

[0042] The paper conveyed by the double-sided conveying rollers 23a to 23d provided on the double-sided conveying path 35 rejoins the conveying path 31 and is sent to the pre-registration rollers 19 and the registration rollers 18. When the paper is handed over from the double-sided conveying rollers 23d to the pre-registration rollers 19, the paper is turned over so that the second side faces upward.

[0043] The paper is then sandwiched between registration rollers 18 and transported at a predetermined timing to secondary transfer nip N1 between the outer circumferential surface of intermediate transfer belt 7 and secondary transfer roller 11. At secondary transfer nip N1, the toner image carried on the outer circumferential surface of intermediate transfer belt 7 is secondarily transferred to the paper, and then the toner image is thermally fixed to the paper by fixing device 12. The paper is then guided to transport path 32a, sandwiched and transported by external discharge rollers 21a, and discharged outside image forming apparatus 100. Alternatively, the paper is handed over to a post-processing device, where predetermined post-processing is performed, and then the double-sided printing operation is completed.

[0044] 3 is a cross-sectional view of an image forming system having an image forming apparatus 100 and a post-processing device. This image forming system is configured so that an A3 inserter, an A2 folder, and an A1 finisher, which are examples of post-processing devices, are connected to the paper discharge port of the image forming apparatus 100. When paper is to be fed separately from the inserter, it is possible to feed paper by placing the paper on the A30 insert paper stacking section above the A3 inserter.

[0045] In an image forming system to which a post-processing device is connected, the paper on which an image is formed is discharged to one of the discharge outlets (A10 discharge outlet 1, A11 discharge outlet 2, A12 discharge outlet 3) of the A1 finisher.

[0046] FIG. 4 illustrates a case in which an A4 sheet (P1) and an A4R sheet (P2) are sequentially ejected. The transport rollers A26 and A27 of the A2 folder are driven by a motor A25. The transport rollers A36 and A37 of the A3 inserter are driven by a motor A35. Therefore, when the A4 sheet (P1) passes through the transport rollers A36, the next sheet, the A4R sheet (P2), has already reached the transport rollers A37, so the drive speed of the motor A35 cannot be changed. This is because the transport rollers A36 and A37 must be running at the same speed as the external ejection rollers 21 of the image forming apparatus 100, and the post-processing device and the image forming apparatus are controlled by separate CPUs. In a system controlled by separate CPUs like this, the motor speeds cannot be changed simultaneously because data is exchanged between the CPUs via communication.

[0047] When changing the paper discharge speed on a paper-by-paper (page-by-page) basis, the post-processing device must receive the paper at the same speed as the paper discharge speed of the external discharge rollers 21 of the image forming device 100. The example in FIG. 4 shows a pattern in which the gap between the paper sheets (P1) and (P2) is narrow, making it impossible to change the speed between the sheets. On the other hand, the example in FIG. 5 shows an example in which there is a gap between the paper sheets (P1) and (P2) (an example in which continuous image formation is not performed). In the example in FIG. 5, when the paper sheet (P1) passes through the conveyance rollers A36, the next paper sheet (P2) has not yet reached the conveyance rollers A37. In other words, by changing the speed of the motor A35 when the paper sheet (P1) passes through the conveyance rollers A36, it becomes possible to receive the next paper sheet (P2). While an A3 inserter is used in this example, the same applies to A2 folders and A1 finishers. The image forming device 100 enables continuous printing by conveying the paper sheets with the necessary gap between each post-processing device. Image forming apparatus 100 acquires information about the sheet spacing required by the post-processing device via ACC communication unit 171, which will be described later.

[0048] Next, the paper discharge section of image forming apparatus 100 will be described using the cross-sectional view of the main body paper discharge section in Fig. 6. As described in Fig. 1, when reverse discharge is performed, the paper is accelerated when it passes through fuser 318, and is pulled into reverse conveyance path 33 by upper reverse roller 22a and lower reverse roller 22b, and the trailing edge of the paper is stopped at the reverse stop position. When the trailing edge of the paper stops at the reverse stop position, a motor (not shown) drives upper reverse roller 22a and lower reverse roller 22b in the reverse direction, and the paper is conveyed to external paper discharge rollers 21a and 21b.

[0049] The mechanism for switching the transport path during reversal will be explained using Figure 7. First, when a sheet is pulled in, the leading edge of sheet 407 enters flapper 409 (Figure 7(a)). As the leading edge of sheet 407 enters flapper 409, flapper presser spring 406 is pushed up to the left (Figure 7(b)). Then, as sheet 407 passes through flapper 409 and the trailing edge of the sheet reaches reversal stop position 400, flapper 409 is pushed back to the right by flapper presser spring 406 (Figure 7(c)). Thereafter, transport rollers 320 and reversal rollers 321 are driven in the reverse direction, switching the transport path and the sheet is transported to external discharge rollers 21 (Figure 7(d)).

[0050] Next, using Figure 8, we will explain the movement of paper when the reversing discharge speed for A4R is different. The examples in Figures 8(a) to 8(c) show the case where A4R paper (4) is reversed and discharged at a speed of 380 mm / s, and then A4 paper enters the reversing section at (5). Conversely, the examples in Figures 8(d) to 8(f) show the case where A4R paper (4) is reversed and discharged at a speed of 500 mm / s, and then A4 paper enters the reversing section at (5).

[0051] In Figure 8(a), the reversing drive speed starts at 380 mm / s from the reversing stop position 400. Then, at the point in Figure 8(b), even though the sheet (4) has not come out, the next A4 sheet (5) has entered the reversing conveyance path 33. Then, in Figure 8(c), the sheet (5) cannot be pulled in and has buckled at the conveyance roller 320.

[0052] Conversely, in Fig. 8(d), the reversing drive speed from the reversing stop position 400 is 500 mm / s. Then, at the time of Fig. 8(e), the sheet (4) has passed through the conveying rollers 320, and the next A4 sheet (5) is conveyed to the reversing conveying path 33. Then, in Fig. 8(f), the conveying rollers 320 are ready to receive the sheet (5).

[0053] This is because the time it takes for a sheet to pass through the reverse conveyance path 33 varies depending on the sheet length during reverse discharge. For example, for large-size sheets such as A3, a high conveyance speed is set to maintain high productivity in order to avoid collisions between the preceding and succeeding sheets during reverse discharge. On the other hand, for small-size sheets such as A4, a low conveyance speed is set to achieve both high productivity and quiet operation because high productivity can be maintained even if the conveyance speed is reduced during discharge. In this way, the sheet conveyance speed when discharged from the image forming apparatus is determined by the sheet length. To achieve 100% productivity with reverse discharge, in this embodiment, the system controller 151 refers to FIG. 13 to acquire information about the paper feed tray and paper size information, and can set different discharge speeds (conveyance speeds) depending on the paper basis weight and size.

[0054] In the example of Figure 13, the first paper feed stage (paper feed cassette 15a) is loaded with A4 plain paper, and when using low-speed paper ejection, 100% productivity can be achieved at a speed of 380 mm / s. The second paper feed stage (paper feed cassette 15b) is loaded with A4R plain paper, and when using low-speed paper ejection, 100% productivity can be achieved at a speed of 500 mm / s. The third paper feed stage (paper feed cassette 15c) is loaded with A3 plain paper, and both the low-speed and high-speed paper ejection speeds are the same, 642 mm / s, and 100% productivity can be achieved at this speed.

[0055] In the case of the image forming apparatus 100 of this embodiment, 100% productivity is 70 ppm (ppm = number of sheets output per minute) for A4 paper, 49.5 ppm for A4R paper, and 35 ppm for A3 paper. Thus, in this embodiment, productivity is determined by the paper length.

[0056] 2 is a block diagram showing an example of the control configuration of the image forming apparatus 100. The system controller 151 includes a CPU 151a, a ROM 151b, and a RAM 151c. The system controller 151 is also connected to the image processing unit 112, an operation unit 152, an analog-to-digital (A / D) converter 153, a high-voltage control unit 155, motor control devices 157 and 158, sensors 159, an AC driver 160, and an ACC communication unit 171. The system controller 151 can send and receive data and commands to and from each connected unit. The image processing unit 112 stores and reads image data, and is responsible for storing scanned document data during the COPY operation and receiving and outputting image data such as FAX and PDL.

[0057] CPU 151a reads and executes programs stored in ROM 151b. RAM 151c is a volatile memory that stores various data, such as setting values ​​for high-voltage control unit 155, command values ​​for motor control device 157, and information received from operation unit 152. System controller 151 transmits setting data required for image processing in image processing unit 112 to image processing unit 112. Furthermore, system controller 151 receives signals from sensors 159 and sets setting values ​​for high-voltage control unit 155 based on the received signals. High-voltage control unit 155 supplies the required voltage to high-voltage unit 156 (charger, developer, transfer charger, etc.) in accordance with the setting values ​​set by system controller 151.

[0058] The motor control device 157 drives and controls each motor in response to commands output from the CPU 151a. The A / D converter 153 receives a detection signal detected by a thermistor 154 for detecting the temperature of the fixing heater 161, converts the detection signal from an analog signal to a digital signal, and sends it to the system controller 151. The system controller 151 controls the AC driver 160 based on the digital signal received from the A / D converter 153. The AC driver 160 controls the fixing heater 161 so that the temperature of the fixing heater 161 reaches a temperature required for fixing processing. The fixing heater 161 is a heater used in fixing processing, and is included in the fixing unit 318.

[0059] The system controller 151 displays an operation screen on a display unit provided in the operation unit 152, which allows the user to set the type of paper to be used (hereinafter referred to as paper type), etc. The system controller 151 receives information set by the user from the operation unit 152, and controls the operation sequence of the image forming apparatus 100 based on the information set by the user. The system controller 151 also transmits information indicating the status of the image forming apparatus to the operation unit 152. The operation unit 152 displays the information received from the system controller 151 on the display unit.

[0060] The system controller 151 is also communicably connected to post-processing devices such as an A1 finisher, an A2 folder, and an A3 inserter via an ACC communication unit 171, and exchanges data on a sheet-by-sheet (page-by-page) basis. This data exchange notifies the image forming apparatus 100 of the sheet-by-sheet (page-by-page) paper discharge speed.

[0061] The post-processing device receives notification of the paper discharge speed from the image forming device 100 and notifies the required paper interval in response. The image forming device 100 determines the image creation timing by comparing the received paper interval notification information with the paper interval at 100% productivity. The image creation timing is determined so that the required paper interval for the preceding page is ensured during continuous printing. If the required paper interval notified by the post-processing device is longer than that at 100% productivity, the post-processing device waits until that time is reached before starting image creation, thereby guaranteeing the required paper interval for the post-processing device.

[0062] <Determining the paper ejection speed> The operation of determining the paper discharge speed for each sheet (page), which is a characteristic feature of this embodiment, will be described below. The operation of determining the paper discharge speed differs between an image forming apparatus configured to have two paper discharge speeds (low speed / high speed) for each sheet and an image forming apparatus configured not to have two speeds. Therefore, the embodiment will be described in two parts.

[0063] [1] Example 1 (Determining the paper ejection speed in a configuration with two paper ejection speeds for each paper) The operation of determining a paper discharge speed in a configuration with two paper discharge speeds for each paper sheet will be described using the flowchart of FIG. 9. The explanation will also be provided with reference to an event sequence diagram. The event sequence diagram of FIG. 10 illustrates the process of printing three pages consecutively. When an image is stored in the image processing unit 112, the image processing unit 112 notifies the system controller 151 of a page-by-page advance notification event (hereinafter referred to as an advance information notification). The advance information notification also includes information about the paper feed source, i.e., information about which paper feed tray the paper will be fed from. The system controller 151 sets the paper discharge speed when the paper is discharged from the image forming apparatus 100 to the outside of the apparatus, based on the paper feed tray information included in the received advance information notification, by referring to the table of FIG. 13. After the advance information notification, the image processing unit 112 notifies the system controller 151 of a page determination notification, page by page, when the image data can be transferred as print data. Since the image memory (not shown) only holds one page, being able to transfer it as print data means that image data is being expanded in the image memory, and once image transfer is complete, the next image data is expanded.

[0064] The image forming apparatus 100 also notifies the post-processing devices (A1, A2, A3) of the set paper discharge speed using a PaperLatch signal. Upon receiving the notification, the post-processing devices determine whether additional paper gaps are required for receiving sheets on a page-by-page basis. The PaperLatch signal is a signal for notifying the post-processing devices of the paper information to be discharged, and is capable of notifying the post-processing devices of the paper discharge speed. The post-processing devices determine whether additional paper gaps are required, and if no waiting time is required, they send a response notification to the system controller 151 with a parameter of 0. If a waiting time is required, they send a parameter containing the required time (usually in the order of milliseconds). The system controller 151 receives a response signal from the post-processing device in response to the PaperLatch signal. If the waiting time is 0, the system controller 151 immediately sends an image transfer start event to the image processing unit 112. If a waiting time is required, the system controller 151 sends an image transfer start event to the image processing unit 112 after the required time has elapsed.

[0065] Upon receiving the image transfer start event, the image processing unit 112 inputs the image data as print data to the optical scanning device 311, which includes a semiconductor laser and a polygon mirror, as described in Fig. 1. As a result, image creation processing is performed on a page-by-page basis in accordance with instructions from the system controller 151.

[0066] When the system controller 151 receives the advance information notification, it generates page-by-page data (hereinafter referred to as QUE) in the RAM 151c, as shown in FIG. 16. FIG. 16(A) shows the state in which QUE P1 is registered. From this state, the state transitions to FIGS. 16(B) and 16(C), with QUE P2 and P3 connected after QUE P1, making it possible to understand the context. A number indicating the state is updated for each QUE. S=1 indicates the state in which the advance information notification is received and the QUE is generated. S=2 indicates the state in which page confirmation information is received. S=3 indicates the state in which the image transfer start event is notified to the image processing unit 112 on a page-by-page basis, as shown in FIGS. 16(D), 16(E), and 16(F). Each QUE is deleted as shown in (G) and (H) when the paper is completely ejected.

[0067] Based on the above, the flowchart in Fig. 9 will be described. The flowchart in Fig. 9 is a flowchart showing the operation when information on the sheets on which images are to be formed is received and the discharge speed of each sheet is set based on that information. Each step in this flowchart is executed by the system controller 151.

[0068] First, in S11, the system controller 151 determines whether there is an unprocessed advance information notification. Specifically, the system controller 151 determines that there is an unprocessed advance information notification if there is a page for which a QUE has not been generated, as shown in FIG. 16, despite having received an advance information notification event. If it is determined in S11 that there is an unprocessed advance information notification page, the process proceeds to S12, where the system controller 151 generates a QUE and sets the status to S=1. The system controller 151 also acquires a paper discharge speed corresponding to paper size information from the table shown in FIG. 13 for that QUE, and sets the transport speed for low-speed paper discharge. Note that the transport speed information set here is a temporary setting, and the setting may be changed by executing the processes of S14 to S22, which will be described later.

[0069] In the case of FIG. 10, the first advance information notification indicates that the paper feed tray is cassette 1 (hereinafter referred to as CST) and therefore 380 mm / s is set. Similarly, the second and third advance information notifications indicate that CST2 is the paper feed tray, and therefore 500 mm / s is set. After S12, the process proceeds to S13, where it is determined whether there is a confirmed page. As described above, the system controller 151 determines whether a page confirmation notification has been received from the image processing unit 112. If the system controller 151 determines in S13 that it has received a page confirmation notification from the image processing unit 112, it proceeds to S14. In S14, the system controller 151 checks the connection status of the post-processing device (any or all of A1, A2, and A3) and determines whether the post-processing device is connected to the paper discharge port of the image forming apparatus. If it determines in S14 that the post-processing device (any or all of A1, A2, and A3) is connected, it proceeds to S15.

[0070] In S15, the system controller 151 determines whether there is a preceding page for the QUE whose page was confirmed in S13. In the example of FIG. 16, in the case of P1 in (A), it is determined that there is no preceding page, and in the case of P2 in (B), it is determined that there is a preceding page because P1 is the preceding page. If it is determined in S15 that there is a preceding page, the process proceeds to S16, where the system controller 151 compares the paper discharge speed of the preceding page with the paper discharge speed of the current target page. If it is determined in S16 that the paper discharge speed of the preceding page differs from the paper discharge speed of the current target page, the process proceeds to S17, where the system controller 151 changes and sets the paper discharge speed of the QUE to a high-speed paper discharge speed. In the case of the QUE of P2 (page confirmation notification 2) in FIG. 10, the high-speed paper discharge speed is set to 642 mm / s by referring to the table in FIG. 13. After S17, the process proceeds to S18, where the system controller 151 determines whether there is a paper gap between the preceding page (previous paper) and the current target page (target paper). Here, the case where it is determined that there is no paper interval corresponds to the case where image formation is performed successively on the preceding paper and the succeeding paper, which will be described later.

[0071] There are two possible patterns for determining whether there is a gap between sheets. The first pattern is when the submission of a job is delayed. If a job is submitted while a preceding job is being printed, the printing operation is generally performed as a continuous job. However, depending on the printing status of the preceding job, the printing operation may not be performed as a continuous job. This occurs when the final image formation of the preceding job has already begun when the subsequent job is submitted. In such a case, even if printing of the subsequent job that has been submitted begins immediately, there will be a gap between the last sheet of the preceding job and the first sheet of the subsequent job, and continuous image formation will not occur. This case will be explained using the sequence diagram in Figure 12 and the conceptual diagrams of paper position in Figures 14 and 15.

[0072] In FIG. 12, after receiving the preliminary information notification 1, the page confirmation notification 1 and the image transfer start 1 are subsequently executed. Before the completion of the paper ejection of P1, the next job is submitted, and the image processing unit 112 notifies the system controller 151 of the preliminary information notification 2 and the preliminary information notification 3. The preliminary information notification 2 is received when time has elapsed since the image transfer start 1 of the previous page 1. In this case, there is a gap between the paper ejection of pages 1 and 2 to the post-processing device. Therefore, even if the paper ejection speed is changed on the post-processing device side after the ejection of page 1, it can be accommodated within the gap. In this case, the determination in S18 for page 2 is that the speed change is possible. This is because the response to the page confirmation notification 2, PaperLatch2 to the post-processing device, has a waiting time of 0. Since page 3 is ejected at the same speed as page 2, the waiting time is also 0. At this time, the positional relationship of the paper in Figure 14 indicates that there is space between P1 and P2, so it is determined that the paper discharge speed of P2 should be 500 mm / s. Also, the paper positional relationship in the cross-sectional view of Figure 15 indicates that P1 has started to be discharged to the post-processing device, but P2 is physically far away before it reaches the post-processing device.

[0073] The second pattern will be explained using the sequence diagram in Figure 11. Figure 11 illustrates a case in which a paper gap adjustment is performed for page 2. In this case in Figure 11, when page confirmation notification 1 is received, the high-speed paper ejection speed of 642 mm / s is set in the processing of S22, which will be described later. Subsequently, when page confirmation notification 2 is received, the paper gap is adjusted by an interrupt. After the adjustment is completed, a gap occurs between the pages of page 1 because the adjustment time has elapsed. Because of this gap, the PaperLatch response for page 2 indicates a wait time of 0, and it is determined in S18 that a speed change is possible. In this case, even if the paper is ejected at a low paper ejection speed, or even if the paper ejection speed is changed after page 1 is ejected, it is possible to accommodate the gap within the gap. This pattern is described assuming that the paper gap adjustment time is longer than the speed change time in the post-processing device. However, it is also possible to determine whether a wait time is required for the speed change in the post-processing device through PaperLatch communication. In this case, a protocol can be used in which multiple candidate paper discharge speeds are notified in the PaperLatch exchange, and the waiting time for each is informed in the PaperLatch response. In this case, the protocol will also notify the post-processing device of the confirmed paper discharge speed.

[0074] In the above two cases, the system controller 151 determines in S18 that the speed can be changed, and proceeds to S19. In S19, the system controller 151 changes the setting of the current target page to a slow paper ejection speed. Taking the example of FIG. 11, the paper ejection speed for page 2 is changed to 642 mm / s in S17, but then changed to 500 mm / s in S19. After S19, the system controller 151 proceeds to S20, where it determines whether there are subsequent pages. Whether there are subsequent pages can be determined by referring to the state of QUE in FIG. 16 described above. For example, in the case of (C) in FIG. 16, when viewed from P2, P3 is set as the subsequent page, so it can be determined that there are subsequent pages, but when viewed from P3, it can be determined that there are no subsequent pages. If the system controller 151 determines in S20 that there is a subsequent page, it proceeds to S21, where it compares the discharge speed of the subsequent paper (subsequent page) with the discharge speed of the target paper (current page). If the system controller 151 determines in S21 that the discharge speed of the subsequent page is different from the discharge speed of the current page, it proceeds to S22, where it sets the current target page to a high discharge speed. After S22, it returns to S11.

[0075] Furthermore, in the determination of S21, if the system controller 151 determines that the discharge speed of the subsequent page is the same as the discharge speed of the current page, the process returns to S11, as after S22.

[0076] Furthermore, in the determination in S20, if the system controller 151 determines that there is no subsequent page, the process returns to S11, as after S22.

[0077] Furthermore, in the determination of S18, if the system controller 151 determines that there is no gap between the preceding page and the current target page that allows for speed change, the process proceeds to S20.

[0078] Furthermore, in the determination of S16, if the system controller 151 determines that the paper discharge speed of the preceding page is the same as the paper discharge speed of the current target page, the process proceeds to S18.

[0079] Furthermore, if the system controller 151 determines in S15 that there is no preceding page, the process proceeds to S20.

[0080] Furthermore, if the system controller 151 determines in S13 that it has not received a page confirmation notification from the image processing unit 112, it proceeds to S30 and determines whether there are any pages to be ejected. The presence or absence of ejected pages can be determined by whether a notification of paper ejection completion has been received from the post-processing device. Paper ejection completion is notified for each page, making it possible to determine whether each page has been ejected normally. If the system controller 151 determines in S30 that there are any pages to be ejected, it proceeds to S31 and deletes the QUE data, as in the example of (G) in FIG. 16. In the example of G, page 1 has been deleted. After S31, it proceeds to S32 and determines whether all pages have been ejected. Whether all pages have been ejected can be determined by the fact that all the QUE data in FIG. 16 has disappeared. If the system controller 151 determines in S32 that all pages have been ejected, it ends the job.

[0081] Conversely, if the system controller 151 determines in step S32 that all pages have not been ejected, the process returns to step S11.

[0082] Furthermore, in the determination of S11, if the system controller 151 determines that there is no unprocessed advance information notification page, the process proceeds to S13.

[0083] Furthermore, if the system controller 151 determines in S14 that the post-processing devices (any or all of A1, A2, and A3) are not attached, the process returns to S11.

[0084] As shown in the flowchart of FIG. 9, in this embodiment, the paper discharge speed (the transport speed when the paper is transported outside the image forming apparatus 100 by the external discharge rollers 21) is determined as follows: First, in S14, it is determined whether or not a post-processing device is connected. If a post-processing device is not connected (NO in S14), the paper discharge speed is determined based on the paper information set for each paper sheet, with reference to the table in FIG. 13. The paper discharge speed determined here is the slowest of the multiple transport speeds corresponding to that paper sheet. In this embodiment, when a post-processing device is not connected, the transport speed is slowed to a level at which 100% productivity can be achieved, thereby reducing operating noise. Therefore, quiet operation can be achieved.

[0085] On the other hand, when a post-processing device (A1 to A3) is connected (YES in S14) and image formation is performed continuously on multiple sheets, if the discharge speed is switched for each sheet, the post-processing device will have to switch the conveying speed, which will reduce overall productivity. Therefore, in this embodiment, if the discharge speed of the target sheet is different from the discharge speed of the preceding or succeeding sheet, the control is performed to match the discharge speed of the target sheet to the discharge speed of the preceding or succeeding sheet (S16, S17, S21, S22). Specifically, if it is determined in S15 that the discharge speed of the target sheet is different from the discharge speed of the preceding sheet, the discharge speed of the target sheet is set to a high-speed conveying speed that is the same as the discharge speed of the preceding sheet (S17). Similarly, if it is determined that the discharge speed of the target sheet is different from the discharge speed of the succeeding sheet, the discharge speed of the target sheet is set to a high-speed conveying speed that is the same as the discharge speed of the succeeding sheet (S22).

[0086] In this way, by controlling the discharge speed to be the same high speed as that of the preceding and succeeding sheets, when continuously printing sheets of different lengths, there is no need to perform speed change processing on the post-processing device side, and a decrease in productivity of the entire system can be prevented.

[0087] For example, in an image forming apparatus connected to a post-processing device, when continuously printing only A3 paper, which is an example of paper of a first length, the first conveying speed is set to 642 mm / s. When continuously printing only A4 paper, which is an example of paper of a second length, the second conveying speed is set to 380 mm / s. When continuously printing only A4R paper, another example of paper of the second length, the second conveying speed is set to 500 mm / s.

[0088] On the other hand, when printing multiple sheets of paper, including both A3 and A4 paper, consecutively, the ejection speed for all of those sheets is set to the first conveyance speed of 642 mm. Similarly, when printing multiple sheets of paper, including both A4 and A4R paper, consecutively, the ejection speed for those sheets is also set to the first conveyance speed of 642 mm / s. When printing multiple image formation jobs of mixed sizes consecutively, the conveyance speed for each sheet is set to the same, but faster, conveyance speed to prevent speed changes in the post-processing device. As a result, high productivity can be achieved when consecutively forming images on sheets of different sizes. On the other hand, when a post-processing device is not connected, the optimal ejection speed for each sheet is set, enabling quieter operation without sacrificing productivity.

[0089] [2] Example 2 (Determining the paper ejection speed in a configuration that does not have two ejection speeds for each paper) Next, a second embodiment will be described. In the second embodiment, a configuration is not provided with two paper ejection speeds for each paper sheet. Using the flowchart of FIG. 17, a paper ejection speed determination operation in a configuration is not provided with two paper ejection speeds for each paper sheet. The explanation will also be made with reference to an event sequence diagram. The event sequence diagram of FIG. 21 illustrates the case where three pages are printed consecutively. When an image is stored in the image processing unit 112, the image processing unit 112 notifies the system controller 151 of an advance notification event (hereinafter referred to as an advance information notification) of page information on a page-by-page basis. The advance information notification also includes information on the paper feed source, i.e., information on which paper feed tray the paper will be fed from. The system controller 151 sets the paper ejection speed when the paper is ejected from the image forming apparatus 100 to the outside of the apparatus, based on the paper feed tray information included in the received advance information notification, by referring to the table of FIG. 18. After the advance information notification, the image processing unit 112 notifies the system controller 151 of a page determination notification on a page-by-page basis when the image data can be transferred as print data. Since the image memory (not shown) only holds one page, being able to transfer it as print data means that image data is being expanded in the image memory, and once image transfer is complete, the next image data is expanded.

[0090] The image forming apparatus 100 also notifies the post-processing devices (A1, A2, A3) of the set paper discharge speed using a PaperLatch signal. Upon receiving the notification, the post-processing devices determine whether additional paper gaps are required for receiving sheets on a page-by-page basis. The PaperLatch signal is a signal for notifying the post-processing devices of the paper information to be discharged, and is capable of notifying the post-processing devices of the paper discharge speed. The post-processing devices determine whether additional paper gaps are required, and if no waiting time is required, they send a response notification to the system controller 151 with a parameter of 0. If a waiting time is required, they send a parameter containing the required time (usually in the order of milliseconds). The system controller 151 receives a response signal from the post-processing device in response to the PaperLatch signal. If the waiting time is 0, the system controller 151 immediately sends an image transfer start event to the image processing unit 112. If a waiting time is required, the system controller 151 sends an image transfer start event to the image processing unit 112 after the required time has elapsed.

[0091] Upon receiving the image transfer start event, the image processing unit 112 inputs the image data as print data to the optical scanning device 311, which includes a semiconductor laser and a polygon mirror, as described in Fig. 1. As a result, image creation processing is performed on a page-by-page basis in accordance with instructions from the system controller 151.

[0092] When the system controller 151 receives the advance information notification, it generates page-by-page data (hereinafter referred to as QUE) in the RAM 151c, as shown in FIG. 16. FIG. 16(A) shows the state in which QUE P1 is registered. From this state, the state transitions to FIGS. 16(B) and 16(C), with QUE P2 and P3 connected after QUE P1, making it possible to understand the context. A number indicating the state is updated for each QUE. S=1 indicates the state in which the advance information notification is received and the QUE is generated. S=2 indicates the state in which page confirmation information is received. S=3 indicates the state in which the image transfer start event is notified to the image processing unit 112 on a page-by-page basis, as shown in FIGS. 16(D), 16(E), and 16(F). Each QUE is deleted as shown in (G) and (H) when the paper is completely ejected.

[0093] Based on the above, the flowchart in Fig. 17 will be explained. The flowchart in Fig. 17 is a flowchart showing the operation when information on the sheets on which images are to be formed is received and the discharge speed of each sheet is set based on that information. Each step in this flowchart is executed by the system controller 151.

[0094] First, in S41, the system controller 151 determines whether there is an unprocessed advance information notification. Specifically, the system controller 151 determines that there is an unprocessed advance information notification if there is a page for which a QUE has not been generated, as shown in FIG. 16, despite having received an advance information notification event. If it is determined in S41 that there is an unprocessed advance information notification page, the process proceeds to S42, where the system controller 151 generates a QUE and sets the status to S=1. The system controller 151 also acquires a paper discharge speed corresponding to paper size information from the table shown in FIG. 18 for that QUE, and sets the conveyance speed. Note that the conveyance speed information set here is a temporary setting, and the setting may be changed by executing the processes of S44 to S52, which will be described later.

[0095] In the case of FIG. 21, the first item in the advance information notification indicates that the paper feed tray is cassette 1 (hereinafter referred to as CST) and therefore 380 mm / s is set. Similarly, the second and third items in the advance information notification indicate that CST2 is the paper feed tray, and therefore 500 mm / s is set. After S42, the process proceeds to S43, where it is determined whether there is a confirmed page. As described above, the system controller 151 determines whether a page confirmation notification has been received from the image processing unit 112. If the system controller 151 determines in S43 that it has received a page confirmation notification from the image processing unit 112, it proceeds to S44. In S44, the system controller 151 checks the connection status of the post-processing device (any or all of A1, A2, and A3) and determines whether the post-processing device is connected to the paper discharge port of the image forming apparatus. If it determines in S44 that the post-processing device (any or all of A1, A2, and A3) is connected, it proceeds to S45.

[0096] In S45, the system controller 151 determines whether there is a preceding page for the QUE whose page was confirmed in S43. In the example of FIG. 16, in the case of P1 in (A), it is determined that there is no preceding page, and in the case of P2 in (B), it is determined that there is a preceding page because P1 is the preceding page. If it is determined in S45 that there is a preceding page, the process proceeds to S46, where the system controller 151 compares the paper discharge speed of the preceding page with the paper discharge speed of the current target page. If it is determined in S46 that the paper discharge speed of the preceding page differs from the paper discharge speed of the current target page, the process proceeds to S47. In S47, the system controller 151 changes and sets the paper discharge speed of the QUE to the faster of the paper discharge speed of the paper of the preceding page and the paper discharge speed of the paper of the current target page. If P2 (QUE for page confirmation notification 2) in FIG. 21 is the current target page and P1 (QUE for page confirmation notification 1) is the preceding page, the paper discharge speed of 500 mm / s, which is the paper discharge speed of the paper of CST2, is set from the table in FIG. 18. After S47, the process proceeds to S48, where the system controller 151 determines whether there is a paper gap between the preceding page (preceding sheet) and the current target page (target sheet). If it is determined that there is no paper gap, this corresponds to the case where image formation is performed consecutively on the preceding sheet and the following sheet, as will be described later.

[0097] There are two possible patterns for determining whether there is a gap between sheets. The first pattern is when the submission of a job is delayed. If a job is submitted while a preceding job is being printed, the printing operation is generally performed as a continuous job. However, depending on the printing status of the preceding job, the printing operation may not be performed as a continuous job. This occurs when the final image formation of the preceding job has already begun when the subsequent job is submitted. In such a case, even if printing of the subsequent job that has been submitted begins immediately, there will be a gap between the last sheet of the preceding job and the first sheet of the subsequent job, and continuous image formation will not occur. This case will be explained using the sequence diagram in Figure 12 and the conceptual diagrams of paper position in Figures 14 and 15.

[0098] In FIG. 12, after receiving the preliminary information notification 1, the page confirmation notification 1 and the image transfer start 1 are subsequently executed. Before the completion of the paper ejection of P1, the next job is submitted, and the image processing unit 112 notifies the system controller 151 of the preliminary information notification 2 and the preliminary information notification 3. The preliminary information notification 2 is received when time has elapsed since the image transfer start 1 of the previous page 1. In this case, there is a gap between the paper ejection of pages 1 and 2 to the post-processing device. Therefore, even if the paper ejection speed is changed on the post-processing device side after the ejection of page 1, it can be accommodated within the gap. In this case, the determination in S48 for page 2 is that the speed change is possible. This is because the response to the page confirmation notification 2 to the post-processing device via PaperLatch2 has a waiting time of 0. Since page 3 is ejected at the same speed as page 2, the waiting time is also 0. At this time, the positional relationship of the paper in Figure 14 indicates that there is space between P1 and P2, so it is determined that the paper discharge speed of P2 should be 500 mm / s. Also, the paper positional relationship in the cross-sectional view of Figure 15 indicates that P1 has started to be discharged to the post-processing device, but P2 is physically far away before it reaches the post-processing device.

[0099] The second pattern will be explained using the sequence diagram in Figure 19. Figure 19 describes a case in which paper gap adjustment is performed for page 2. In this case in Figure 19, when page confirmation notification 1 is received, the processing in S52, described below, sets the paper ejection speed to 500 mm / s, which is the faster of the paper ejection speeds for CST1 and CST2. Subsequently, when page confirmation notification 2 is received, the paper gap is adjusted by interruption, and after the adjustment is completed, a gap occurs between the pages for page 1 because the adjustment time has elapsed. Because of this gap, the PaperLatch response for page 2 indicates a wait time of 0, and S48 determines that the speed can be changed. In this case, even if the paper is ejected at the paper ejection speed provided for each paper, or even if the paper ejection speed is changed after page 1 is ejected, it is possible to accommodate the gap within the gap. This pattern is described on the assumption that the time required to adjust the paper gap is longer than the time required to change the speed in the post-processing device, but it is also possible to determine through PaperLatch communication whether a wait time is required for speed changes in the post-processing device. In this case, the protocol can be such that multiple candidate paper ejection speeds are notified through PaperLatch communication, and the PaperLatch response informs the wait time for each. In that case, the protocol will also notify the post-processing device of the confirmed paper ejection speed.

[0100] In the above two cases, the system controller 151 determines in S48 that the speed can be changed, and proceeds to S49. In S49, the system controller 151 changes the setting of the current target page to the discharge speed of that paper. Taking the example of FIG. 20 as an example, the discharge speed for page 2 is changed to 642 mm / s in S47, but is then changed to 500 mm / s in S49. After S49, the system controller 151 proceeds to S50, where it determines whether there are subsequent pages. Whether there are subsequent pages can be determined by referring to the state of QUE in FIG. 16 described above. For example, in the case of FIG. 16(C), when viewed from P2, P3 is set as the subsequent page, so it can be determined that there are subsequent pages, but when viewed from P3, it can be determined that there are no subsequent pages. If the system controller 151 determines in S50 that there is a subsequent page, it proceeds to S51, where it compares the discharge speed of the subsequent paper (subsequent page) with the discharge speed of the target paper (current page). If the system controller 151 determines in S51 that the discharge speed of the subsequent page is different from the discharge speed of the current page, it proceeds to S52. In S52, the system controller 151 sets the discharge speed of the current target page to the faster of the discharge speed of the paper of the current target page and the discharge speed of the paper of the subsequent page. Then, it returns to S41.

[0101] If the system controller 151 determines in step S51 that the discharge speed of the subsequent page is the same as the discharge speed of the current page, it returns to step S41, just as it did after step S52. If the system controller 151 determines in step S50 that there are no subsequent pages, it returns to step S41, just as it did after step S52.

[0102] If the system controller 151 determines in S48 that there is no gap between the preceding page and the current target page that allows for speed change, the process proceeds to S50. If the system controller 151 determines in S46 that the paper discharge speed of the preceding page and the paper discharge speed of the current target page are the same, the process proceeds to S48.

[0103] Furthermore, if the system controller 151 determines in S45 that there is no preceding page, it proceeds to S50. If the system controller 151 determines in S43 that it has not received a page confirmation notification from the image processing unit 112, it proceeds to S60, where it determines whether there are any ejected pages. The presence or absence of ejected pages can be determined by whether a notification of paper ejection completion has been received from the post-processing device. Paper ejection completion is notified for each page, making it possible to determine whether each page has been ejected successfully. If the system controller 151 determines in S60 that there are any ejected pages, it proceeds to S61, where it deletes the QUE data, as in the example of FIG. 16(G). In the example of FIG. 16(G), page 1 has been deleted. After S61, it proceeds to S62, where it determines whether all pages have been ejected. Whether all pages have been ejected can be determined by the fact that all the QUE data in FIG. 16 has been deleted. If the system controller 151 determines in step S62 that all pages have been ejected, it ends the job.

[0104] Conversely, if the system controller 151 determines in S62 that all pages have not been ejected, the process returns to S41.

[0105] Furthermore, in the determination in S41, if the system controller 151 determines that there is no unprocessed advance information notification page, the process proceeds to S43.

[0106] Furthermore, if the system controller 151 determines in S44 that the post-processing devices (any or all of A1, A2, and A3) are not attached, the process returns to S41.

[0107] As shown in the flowchart of FIG. 17, in this embodiment, the paper discharge speed (the transport speed when the paper is transported outside the image forming apparatus 100 by the external discharge rollers 21) is determined as follows: First, in S44, it is determined whether or not a post-processing device is connected. If a post-processing device is not connected (NO in S44), the paper discharge speed is determined based on the paper information set for each paper type with reference to the table in FIG. 18. The paper discharge speed determined here is the transport speed provided for each paper type. This transport speed is the minimum speed required to achieve 100% productivity. In this embodiment, when a post-processing device is not connected, the transport speed is slowed down to a level at which 100% productivity can be achieved, thereby reducing operating noise. Therefore, quiet operation can be achieved.

[0108] On the other hand, if a post-processing device (A1 to A3) is connected (YES in S44) and image formation is performed continuously on multiple sheets, switching the sheet discharge speed for each sheet would require switching the conveying speed in the post-processing device, resulting in a decrease in overall productivity. Therefore, in this embodiment, if the sheet discharge speed of the target sheet differs from the sheet discharge speed of the preceding or succeeding sheet, the control is performed to match the sheet discharge speed to the sheet discharge speed of the preceding or succeeding sheet (S46, S47, S51, S52). Specifically, if it is determined in S45 that the sheet discharge speed of the target sheet differs from the sheet discharge speed of the preceding sheet, the sheet discharge speed of the target sheet is set to the faster of the sheet discharge speed of the target sheet and the sheet discharge speed of the preceding sheet (S47). Similarly, if it is determined that the sheet discharge speed of the target sheet differs from the sheet discharge speed of the succeeding sheet, the sheet discharge speed of the target sheet is set to the faster of the sheet discharge speed of the target sheet and the sheet discharge speed of the succeeding sheet (S52).

[0109] In this way, by controlling the discharge speed to be the same high speed as that of the preceding and succeeding sheets, when continuously printing sheets of different lengths, there is no need to perform speed change processing on the post-processing device side, and a decrease in productivity of the entire system can be prevented.

[0110] For example, in an image forming apparatus connected to a post-processing device, if you are printing only A3 paper continuously, set the speed to 642 mm / s. If you are printing only A4 paper continuously, set the speed to 380 mm / s. If you are printing only A4R paper continuously, set the speed to 500 mm / s.

[0111] On the other hand, when printing multiple sheets of paper containing a mixture of A3 and A4 paper continuously, the ejection speed for those sheets is set to 642 mm, which is the faster of the ejection speeds for A3 and A4 paper. Similarly, when printing multiple sheets of paper containing a mixture of A4 and A4R paper continuously, the ejection speed for those sheets is set to 500 mm / s, which is the faster of the ejection speeds for A4 and A4R paper. When printing multiple image formation jobs of mixed sizes continuously, the conveyance speed for each sheet is set to the same, but faster, conveyance speed to prevent speed changes in the post-processing device. This results in high productivity when forming images on multiple sheets of paper continuously. On the other hand, when a post-processing device is not connected, the optimal ejection speed for each sheet is set, achieving quieter operation without sacrificing productivity.

[0112] (Other Examples) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0113] 12 Fixing device 28 Conveyor belt 21a External paper ejection roller 21b External paper ejection front roller 22a Reversing upper roller 22b Reversing lower roller 100 Image forming device 151 System Controller 151a CPU 156 High voltage unit (charger, developer, transfer charger, etc.) 311 Optical scanning device including semiconductor laser and polygon mirror 318 Fixing unit

Claims

1. An image forming apparatus to which a post-processing device can be connected, an image forming unit that forms an image on a sheet; a conveying unit that turns over the paper on which the image has been formed by the image forming unit and conveys the turned over paper to the post-processing device; a control means for setting a transport speed when transporting the paper to the post-processing device based on information about the length of the paper on which the image is formed by the image forming unit in the transport direction, and for controlling the transport unit so that the paper is transported to the post-processing device at the set transport speed; and The control means (1) When image formation is continuously performed on sheets of paper having a first length in the conveying direction, the conveying speed for each sheet of paper is set to a first conveying speed; (2) When image formation is continuously performed on sheets of paper having a second length in the conveying direction that is shorter than the first length, the conveying speed for each sheet of paper is set to a second conveying speed that is slower than the first conveying speed, (3) An image forming apparatus characterized in that when image formation is performed consecutively on paper having a paper length in the transport direction of the first length and paper having a paper length in the second length, the transport speed for each paper is set to the first transport speed.

2. The control means determines the connection status of the post-processing device, and when it determines that the post-processing device is not connected, when image formation is performed continuously on paper of the first length and paper of the second length, sets the conveying speed for paper of the first length to the first conveying speed and sets the conveying speed for paper of the second length to the second conveying speed.

3. An image forming apparatus as described in claim 1 or 2, characterized in that when the transport section is transporting a sheet of paper of the second length at the first transport speed, if the gap between the sheet of paper of the first length and the subsequent sheet of paper becomes larger than a predetermined amount, the transport speed of the subsequent sheet of paper is changed to the second transport speed.

4. An image forming apparatus to which a post-processing device can be connected, an image forming unit that forms an image on a sheet; a conveying unit that turns over the paper on which the image has been formed by the image forming unit and conveys the turned over paper to the post-processing device; a control means for setting a transport speed when transporting the paper to the post-processing device based on information about the length of the paper on which the image is formed by the image forming unit in the transport direction, and for controlling the transport unit so that the paper is transported to the post-processing device at the set transport speed; and The control means An image forming apparatus characterized in that, when the conveying speed differs between sheets of paper having different lengths in the conveying direction on which images are continuously formed, the conveying speed for each sheet of paper on which images are continuously formed is changed to the fastest speed among the different conveying speeds.

5. 5. The image forming apparatus according to claim 4, wherein the control means determines the connection status of the post-processing device, and when it determines that the post-processing device is not connected, does not change to the fastest speed when image formation on paper is performed continuously.

6. An image forming apparatus as described in claim 4 or 5, characterized in that when the transport section is transporting paper at the transport speed changed to the fastest speed, if the gap between the paper and the subsequent paper becomes larger than a predetermined amount, the transport speed of the subsequent paper is changed to the original transport speed.

7. 7. The image forming apparatus according to claim 1, wherein the image forming unit has a fixing unit that fixes a toner image to the paper, and the transport unit has a reversible reversing roller that reverses the direction of travel of the paper that has passed through the fixing unit, and a paper discharge roller that transports the paper whose direction of travel has been reversed by the reversing roller at the set transport speed.

Images