JP2007108587A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accelerate first printing speed, even in an image forming apparatus using motors different in performance among a plurality of ejection ports. <P>SOLUTION: When an instruction to output to a first ejection port is given, a first drive motor for driving a paper ejection roller for the first paper ejection port is increased to a first acceleration speed that is higher than an image forming speed the instant that paper has reached a first acceleration initiating position. When instruction to output to a second ejection port is given, a second drive motor for driving a paper ejection roller for the second ejection port is increased to a second acceleration speed that is higher than the image forming speed the instant that paper has reached a second acceleration initiating position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a multi-function copying machine or a printer, and more particularly to discharge control of the image forming apparatus.

  Conventionally, in an image forming apparatus, there are cases where the speed at which a sheet is conveyed to a sheet discharge port after printing and the sheet discharge speed to the outside of the apparatus are different. The purpose of this is to improve the first print speed of the low-speed engine or improve the stackability of the discharged paper.

  In particular, in the former example, if the paper is accelerated and discharged only after paper discharge after image formation, the time taken to discharge the first page to the outside of the machine can be shortened, so the paper discharge is accelerated (kicked paper discharge). In some cases, the technology is employed (see Patent Document 1). In particular, in recent years, the user's demand for the first print speed is increasing, and therefore, the number of image forming apparatuses adopting the paper discharge acceleration in the low speed engine is increasing.

On the other hand, the image forming apparatus performs a process of switching the paper discharge destination according to the usage application of the user. For example, the destination 1 for copying, the destination 2 for printing, and the destination 3 for fax. Conventionally, by connecting a post-processing device to the image forming apparatus, after the paper is discharged from the same discharge port from the main body of the image forming apparatus, the post-processing device sorts the paper discharge destination. However, when the post-processing apparatus is connected, the installation area of the entire image forming apparatus is increased. Therefore, some of the image forming apparatus main body has a plurality of outlets by providing a discharge destination in the body of the image forming apparatus main body. It is increasing.
JP 2002-278186 A

  In particular, in the case of a low-speed engine that requires an increased discharge speed, the cost of the image forming apparatus is kept as low as possible. For this reason, motors as necessary are installed in the plurality of outlets provided in the main body of the image forming apparatus.

  For example, since the paper discharge destination 1 can discharge thick paper, a motor having a range that can operate even at a half speed of the image forming speed of plain paper is installed. On the other hand, since the thick paper is not transported to the paper discharge destination 2, a low speed range is narrow, but a motor of a range that can operate even at a double speed of the image forming speed of plain paper is installed.

  For this reason, since the type / performance of the motor differs depending on the discharge port, it is not always possible to increase the speed to the same speed with any motor.

  The present invention has been made in view of the above circumstances, and is intended to improve the first print speed even in an image forming apparatus using a motor having different performance at a plurality of discharge ports.

  In order to achieve the above object, an image forming apparatus of the present invention has a plurality of paper discharge ports, and a paper discharge roller provided at each of the plurality of paper discharge ports for discharging paper. And a drive motor for driving the paper discharge roller is provided independently for each paper discharge roller provided at each paper discharge port, and output to the first discharge port among the plurality of paper discharge ports. When the sheet reaches the first acceleration start position, the first drive motor that drives the sheet discharge roller of the first sheet discharge port is set to a first increase that is faster than the image forming speed. When the speed is increased and an output to the second discharge port is instructed among the plurality of sheet discharge ports, the second discharge port is turned on when the sheet reaches the second acceleration start position. The second drive motor that drives the paper discharge roller is increased to a second increase speed that is faster than the image forming speed. .

  In an image forming apparatus that uses different motors for each of the plurality of discharge ports, it is possible to improve the first print speed by switching the optimal acceleration start position and acceleration according to the discharge destination and conveying the paper. Is possible.

  FIG. 1 is a diagram showing a schematic configuration of a full-color image forming apparatus according to an embodiment of the present invention. A basic configuration will be described with reference to FIG.

  First, the configuration of the color reader unit 1 will be described. Reference numeral 101 denotes a platen glass (platen), and 102 denotes an automatic document feeder (ADF). In place of the automatic document feeder 102, a specular pressure plate or a white pressure plate (not shown) may be mounted. Reference numerals 103 and 104 denote light sources for illuminating the original, and light sources such as halogen lamps, fluorescent lamps, and xenon tube lamps are used. Reference numerals 105 and 106 denote reflection umbrellas that condense light from the light sources 103 and 104 onto the original. Reference numerals 107 to 109 denote mirrors, and 110 denotes a lens that collects reflected light or projection light from a document on a CCD (charge coupled device) image sensor (hereinafter referred to as CCD) 111. Reference numeral 112 denotes a substrate on which the CCD 111 is mounted, 100 denotes a control unit that controls the entire image forming apparatus, 113 denotes a printer processing unit that includes portions excluding the image processing unit 111 in FIG. 4 and 401 and 402 in FIG. (Reader scanner control unit). A carriage 114 accommodates the light sources 103 and 104, the reflectors 105 and 106, and the mirror 107. A carriage 115 accommodates the mirrors 108 and 109. The carriage 114 is moved at a speed V and the carriage 115 is moved at a speed V / 2 in the sub-scanning direction Y orthogonal to the electrical scanning direction (main scanning direction X) of the CCD 111. Scan the entire surface. Reference numeral 116 denotes an external interface (I / F) with another device.

  The control unit 100 includes a CPU having an I / F that exchanges information for performing control with respect to the digital image processing unit and the printer control unit, an operation unit, and a memory. The operation unit is configured by a liquid crystal with a touch panel for inputting processing execution contents by the operator, notification of processing information to the operator, warnings, and the like.

  Next, the configuration 2 of the color printer unit will be described. In FIG. 1, reference numeral 250 denotes a printer control unit, which serves as a control signal receiving port from a CPU on the control unit 100 which is a control unit of the entire image forming apparatus. The control unit 100 temporarily stores the read image data in the memory on the control unit by performing the above-described image reading control on the color reader unit 1, and stores the read image data on the memory in accordance with the reference timing from the printer control unit 250. The image data is transmitted to the printer control unit 250 as an image data signal in synchronization with the video clock.

  The image forming unit forms a yellow image, an image forming unit 1Y that forms a yellow image, an image forming unit 1M that forms a magenta image, an image forming unit 1C that forms a cyan image, and a black image The image forming unit 1Bk includes four image forming units (image forming units), and these four image forming units 1Y, 1M, 1C, and 1Bk are arranged in a line at regular intervals.

  Each of the image forming units 1Y, 1M, 1C, and 1Bk is provided with drum-type electrophotographic photosensitive members (hereinafter referred to as photosensitive drums) 2a, 2b, 2c, and 2d as image carriers. Around each photosensitive drum 2a, 2b, 2c, 2d, there are primary chargers 3a, 3b, 3c, 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d as transfer means, Drum cleaner devices 6a, 6b, 6c, and 6d are arranged, respectively. Below the primary chargers 3a, 3b, 3c, and 3d and the developing devices 4a, 4b, 4c, and 4d, a laser exposure device 7 is provided. is set up.

  Each developing device 4a, 4b, 4c, 4d contains yellow toner, cyan toner, magenta toner, and black toner, respectively.

  Each of the photosensitive drums 2a, 2b, 2c, and 2d is a negatively charged OPC photosensitive member having a photoconductive layer on an aluminum drum base, and is driven in a direction indicated by an arrow (counterclockwise in FIG. 1) by a driving device (not shown). Rotation drive at a predetermined process speed.

  Primary chargers 3a, 3b, 3c, and 3d as primary charging means make the surface of each photosensitive drum 2a, 2b, 2c, and 2d have a predetermined negative potential by a charging bias applied from a charging bias power source (not shown). Charge uniformly.

  The developing devices 4a, 4b, 4c, and 4d contain toner, and are developed as toner images by attaching toners of respective colors to the electrostatic latent images formed on the photosensitive drums 2a, 2b, 2c, and 2d, respectively ( Visualization).

  Transfer rollers 5a, 5b, 5c, and 5d as primary transfer means are disposed so as to be in contact with the respective photosensitive drums 2a, 2b, 2c, and 2d via the intermediate transfer belt 8 in the respective primary transfer portions 32a to 32d. Yes.

  Each of the drum cleaners 6a, 6b, 6c, and 6d includes a cleaning blade for removing, from the photosensitive drum 2, transfer residual toner remaining on the photosensitive drum 2 during the primary transfer.

  The intermediate transfer belt 8 is disposed on the upper surface side of each photosensitive drum 2a, 2b, 2c, 2d and is stretched between the secondary transfer counter roller 10 and the tension roller 11, and the secondary transfer counter roller 10 is In the secondary transfer portion, the secondary transfer roller 206 is disposed so as to be in contact with the intermediate transfer belt 8. The intermediate transfer belt 8 is made of a dielectric resin such as polycarbonate, polyethylene terephthalate resin film, polyvinylidene fluoride resin film, or the like.

  Further, the intermediate transfer belt 8 is movably disposed on the upper surface of the photosensitive drums 2a, 2b, 2c, and 2d, and has a primary transfer surface formed on the surface facing the photosensitive drum 2, that is, a lower flat surface. The second transfer roller 206 is inclined so that the side is the lower side. Specifically, this inclination angle is set to about 15 °. Further, the intermediate transfer belt 8 is arranged on the side opposite to the secondary transfer counter roller 10 that is arranged on the secondary transfer roller 206 side and applies a driving force to the intermediate transfer belt 8, and the primary transfer portions 32a to 32d are interposed therebetween. The intermediate transfer belt 8 is stretched with two tension rollers 11 for applying tension.

  The secondary transfer counter roller 10 is disposed so as to be in contact with the secondary transfer roller 206 via the intermediate transfer belt 8. In addition, a belt cleaning device 13 that removes and collects transfer residual toner remaining on the surface of the intermediate transfer belt 8 is installed outside the endless intermediate transfer belt 8 and in the vicinity of the tension roller 11. Further, a fixing device 207 having a fixing roller and a pressure roller is installed in a vertical path configuration on the downstream side of the transfer direction of the transfer material P from the secondary transfer unit.

  The exposure device 7 is composed of laser light emitting means that emits light corresponding to time-series electric digital pixel signals of given image information, a polygon lens, a reflection mirror, and the like, and exposes each photosensitive drum 2a, 2b, 2c, 2d. As a result, an electrostatic latent image of each color corresponding to the image information is formed on the surface of each photosensitive drum 2a, 2b, 2c, 2d charged by each primary charger 3a, 3b, 3c, 3d. The laser light emitting means can change the laser power to 15 levels by switching the output current of the laser.

  Next, an image forming operation by the above-described image forming apparatus will be described.

  When an image formation start signal is issued, the photosensitive drums 2a, 2b, 2c, and 2d of the image forming units 1Y, 1M, 1C, and 1Bk that are rotationally driven at a predetermined process speed are respectively connected to primary chargers 3a, 3b, 3c and 3d are uniformly negatively charged. Then, the exposure apparatus 7 irradiates an image signal, which is color-separated from the outside, from the laser light-emitting element, and passes each color on each photosensitive drum 2a, 2b, 2c, 2d via a polygon lens, a reflection mirror, etc. An electrostatic latent image is formed.

  First, yellow toner is adhered to the electrostatic latent image formed on the photosensitive drum 2a by the developing device 4a to which a developing bias having the same polarity as the charging polarity (negative polarity) of the photosensitive drum 2a is applied. Visualize as an image. This yellow toner image is driven by a transfer roller 5a to which a primary transfer bias (a reverse polarity (positive polarity) to toner) is applied in a primary transfer portion 32a between the photosensitive drum 2a and the transfer roller 5a. Primary transfer is performed on the intermediate transfer belt 8.

  The intermediate transfer belt 8 onto which the yellow toner image has been transferred is moved to the image forming unit 1M side. In the image forming unit 1M, in the same manner as described above, the magenta toner image formed on the photosensitive drum 2b is superimposed on the yellow toner image on the intermediate transfer belt 8, and the primary transfer unit 32b Transcribed.

  At this time, the transfer residual toner remaining on each photosensitive drum 2 is scraped off and collected by a cleaner blade or the like provided in the drum cleaner devices 6a, 6b, 6c, and 6d.

  Similarly, cyan and black toner images formed by the photosensitive drums 2c and 2d of the image forming units 1C and 1Bk on the yellow and magenta toner images superimposed and transferred on the intermediate transfer belt 8 are respectively transferred in the primary manner. A full-color toner image is formed on the intermediate transfer belt 8 by sequentially superposing the portions 32a to 32d.

  On the other hand, each cassette stage is picked up by each pickup roller 212/213/214/215 from each cassette stage (upper stage cassette 208 / lower stage cassette 209 / 3rd stage cassette 210 / 4th stage cassette 211). The recording paper conveyed by the paper rollers 216/217/218/219 is conveyed to the registration roller 221 by the vertical path conveying rollers 222/223/224/225. In the case of manual feed, the recording paper loaded on the manual feed tray 240 is conveyed to the registration roller 221 by the manual feed roller 220. Then, at the timing when the transfer to the intermediate transfer belt 8 is completed, the recording paper is conveyed between the intermediate transfer belt 8 and the secondary transfer roller 206. Thereafter, the recording paper is conveyed in the direction of the fixing device while being sandwiched between the secondary transfer roller 206 and the intermediate transfer belt 8 and is pressed against the intermediate transfer belt 8, and the toner image on the intermediate transfer belt 8 is transferred to the recording paper. Next is transferred. The toner image transferred to the recording paper is heated and pressed by the fixing roller and the pressure roller 207 and fixed on the recording paper.

  In the case of the first paper discharge, the recording paper on which the image is fixed is discharged toward the paper discharge roller 233 by switching the first paper discharge flapper 237 toward the first paper discharge roller. In the case of the second paper discharge, the first paper discharge flapper 237 and the second paper discharge flapper 238 are switched toward the second paper discharge roller, and the paper is discharged toward the paper discharge roller 234. In the case of the third discharge, the first discharge flapper and the second discharge flapper are switched in the direction of the reverse roller 235 and reversed by the reverse roller 235 in order to perform the reverse operation once by the reverse roller 235. After being reversed by the reverse roller 235, the third paper discharge flapper is switched to the third paper discharge direction, and the paper is discharged toward the third paper discharge roller 236. In the case of double-sided discharge, the reverse roller portion 235 once performs a reverse operation similarly to the case of the third discharge, and the third discharge flapper is switched to the double-sided unit direction and conveyed to the double-sided unit. After the recording paper is detected by the double-sided sensor, the recording paper is temporarily stopped after a predetermined time, and is fed again as soon as the image preparation is completed, and the second side image is formed.

  FIG. 2 is a control block diagram in the image forming apparatus. A CPU 171 performs basic control of the image forming apparatus, and a ROM 174 in which a control program is written, a work RAM 175 for processing, and an input / output port 173 are connected by an address bus and a data bus. The input / output port 173 is connected to various loads (not shown) such as a motor and a clutch for controlling the image forming apparatus, and an input (not shown) such as a sensor for detecting the position of the paper.

  The CPU 171 sequentially performs input / output control via the input / output port 173 in accordance with the contents of the ROM 174 to execute an image forming operation. An operation unit 172 is connected to the CPU 171 and controls display means and key input means of the operation unit 172. The operator instructs the CPU 171 to switch the image forming operation mode and display through the key input means, and the CPU 171 displays the state of the image forming apparatus 100 and the operation mode setting by key input. The CPU 171 includes an external I / F processing unit 400 that transmits and receives image data and processing data from an external device such as a PC, an image memory unit 300 that performs image expansion processing and temporary storage processing, and an image memory unit 300. An image forming unit 200 is connected to perform processing to expose the transferred line image data to the exposure device 7.

  Next, details of the image memory unit 300 will be described with reference to FIG. The image memory unit 300 writes the image data received from the external I / F processing unit 400 via the memory controller unit 302 to the page memory 301 configured by a memory such as a DRAM, and reads the image to the image forming unit 2. Access image input / output.

  The memory controller unit 302 determines whether the image data from the external device received from the external I / F processing unit 400 is compressed data. If it is determined that the image data is compressed data, the compressed data expansion processing unit After the decompression process is performed using 303, a write process is performed on the page memory 301 via the memory controller unit 302.

  The memory controller unit 302 generates a DRAM refresh signal for the page memory 301, and arbitrates access to the page memory 301 for writing from the image I / F processing unit 400 and reading to the image forming unit 200. Further, in accordance with an instruction from the CPU 171, a write address to the page memory 301, a read address from the page memory 301, a read direction, and the like are controlled.

  The configuration of the external I / F processing unit 400 will be described with reference to FIG.

  The external I / F processing unit 400 receives image data and print command data transmitted from the external device 500 via any of the USB I / F unit 401, the Centro I / F unit 402, and the network I / F unit 403. Or the status information of the image forming apparatus determined by the CPU 171 is transmitted to the external apparatus 500. Here, the external device 500 is a computer, a workstation, or the like.

  The print command data received from the external device 500 via the USB I / F unit 401, the Centro I / F unit 402, or the network I / F unit 403 is processed by the CPU 171 and the print operation is performed by the image forming unit 200 or A setting and timing for executing a printing operation using the I / O 173 in FIG. 2 and the like are generated.

  Image data received from the external device 500 via the USB I / F unit 401, the Centro I / F unit 402, or the network I / F unit 403 is transferred to the image memory unit 300 according to the timing based on the print command data. Sent and processed by the image forming unit 200 to form an image.

  Next, details of the sheet conveyance control in the image forming apparatus of this embodiment will be described with reference to FIG.

  The sheet conveyance is controlled by a total of seven motors 501 to 507.

  The registration motor 501 controls the driving of the registration roller 221. The main motor 502 controls driving of the intermediate transfer belt 8 and the secondary transfer roller 206 facing the intermediate transfer belt. The fixing motor 503 controls the driving of the fixing roller 207. The first paper discharge motor 504 controls the driving of the first transport roller 511 and the first paper discharge roller 233. The second paper discharge motor 505 controls the driving of the second transport roller 512 and the second paper discharge roller 234. The third paper discharge motor 506 controls driving of the reverse roller 235, the third paper discharge roller 236, and the third transport roller 513. A double-sided motor 507 controls driving of the first double-sided roller 514 and the second double-sided roller 515.

  When the paper fed from the paper feeding unit is transported from 520 and discharged to the first paper discharge port 521 via the registration roller 221, the secondary transfer roller 206, the fixing roller 207, and the first transport roller 511. Is discharged to the outside of the image forming apparatus via the first paper discharge roller 233. Similarly, when discharging to the second sheet discharge port 522, the sheet is discharged from the first conveyance roller 511 to the outside of the image forming apparatus via the second conveyance roller 512 and the second sheet discharge roller 234. In the case of discharging to the third paper discharge port 524, the second conveyance roller 512 passes through the reverse roller 235 and reverses at the reverse port 523 and then passes through the third paper discharge roller 236 to the outside of the image forming apparatus. Is discharged. When performing duplex printing, the sheet is reversed at the reversing port 523 and then conveyed again from the registration roller 221 via the third conveyance roller 513, the first duplex roller 514, and the second duplex roller 515.

  FIG. 6 shows the driving speed of each conveyance motor in this embodiment. In this embodiment, the registration motor 501, the main motor 503, and the fixing motor 503 are controlled so as to be always driven at the same speed. If the speed of any one of the motors changes during image formation, problems such as the image not being formed correctly, the paper and the image not matching, and the image not being properly fixed occur. It is.

  In this embodiment, the paper having a basis weight of 105 g or less is image-formed at a constant speed, the paper having a thickness larger than that is formed at a half-speed, and the OHP sheet is formed at a quarter-speed. Perform image formation.

  Here, the first paper discharge motor 504 needs to correspond to all image forming speeds because the front end of the paper reaches the first transport roller 511 while the rear end of the paper is driven by the fixing roller 207. . On the other hand, the speed increase possible speed of the first paper discharge motor 504 itself is 337 mm / s.

  Similarly, for the second paper discharge motor 505, depending on the size of the paper, the leading edge of the paper reaches the second conveying roller 512 while the trailing edge of the paper is driven by the fixing roller 207. It is necessary to respond. On the other hand, the speed increase possible speed of the second paper discharge motor 505 itself is 460 mm / s.

  Similarly, for the third paper discharge motor 506, when the paper size is large, the leading edge of the paper reaches the reverse roller 235 while the trailing edge of the paper is driven by the fixing roller 207. There is a need to. However, since the OHP sheet cannot be reversed due to the configuration of the apparatus, it is not necessary to correspond to the 1/4 speed that is the image forming speed of the OHP sheet. Further, the speed increase possible speed of the third paper discharge motor 506 itself is 460 mm / s.

  Regarding the double-sided motor 507, since the leading edge of the paper reaches the registration roller 221 in a state where the trailing edge of the paper is driven by the first double-sided roller 514 or the second double-sided roller 515, it is necessary to cope with the image forming speed. However, since the OHP sheet does not perform double-sided printing, it is not necessary to correspond to the 1/4 speed that is the image forming speed of the OHP sheet. Further, the speed increase possible speed of the double-sided motor 507 itself is 460 mm / s.

  Next, the switching timing of the driving speed of the first paper discharge motor 504 will be described based on the flowchart of FIG.

  When image formation is started (S701), driving of the first paper discharge motor 504 is started at the image formation speed (S702). While the trailing edge of the sheet is driven by the fixing roller 207, the first paper discharge motor 504 needs to be driven at the same speed as the fixing roller 207. Thereafter, when the rear end of the sheet reaches the position (first acceleration position 530) that has passed through the fixing roller 207 (S703), the sheet is conveyed at an increased speed up to 337 mm / s, which is a speed increase possible speed. (S704). Thereafter, immediately before the sheet passes through the first paper discharge roller 233, when the rear end of the paper reaches a position (first deceleration position 533) where 10 mm remains upstream from the first paper discharge roller 233 (S705), the image The speed is reduced to the forming speed (S707), and the sheet is discharged to the outside of the image forming apparatus. This is because if the sheet is discharged to the outside of the image forming apparatus at the increased speed, the alignment of the sheet on the sheet discharge tray is deteriorated. On the other hand, even if the trailing edge of the sheet has not reached the first deceleration position in S705, if the leading edge of the next sheet reaches the first acceleration position 530 (S706), the image forming speed is reached. Is decelerated (S707). This is to prevent the leading edge of the sheet from reaching the first transport roller 511 that is driven at a high speed while the trailing edge of the next sheet is driven by the fixing roller 207. After discharging the paper to the outside of the image forming apparatus at the image forming speed, if there is a next paper, the control from S703 is repeated again, and if there is no next paper, the driving of the first paper discharge motor 504 is stopped. Then, the image formation is finished (S710).

  Similarly, the switching timing of the driving speed of the second paper discharge motor 505 will be described based on the flowchart of FIG.

  When image formation is started (S801) and the leading edge of the paper reaches the second acceleration position 531 (S802), the driving of the second paper discharge motor 505 is started at the image formation speed (S803). While the trailing edge of the paper is being driven by the fixing roller 207, the second paper discharge motor 505 needs to be driven at the same speed as the fixing roller 207. Further, even after the trailing edge of the sheet passes through the fixing roller 207, the second discharge motor 505 is driven at the image forming speed while the trailing edge of the sheet is driven by the first transport roller 511. This is because the speed increase possible speed of the first paper discharge motor 504 and the speed increase possible speed of the second paper discharge motor 505 are different. Thereafter, when the trailing edge of the sheet reaches the position (second acceleration position 531) that has passed through the first conveying roller 511 (S804), the sheet is increased to a speed that can be increased to 460 mm / s, and the sheet is conveyed. (S805). Thereafter, immediately before the paper exits the second paper discharge roller 234, when the rear end of the paper reaches 10 mm upstream from the second paper discharge roller 234 (second deceleration position 534) (S806), the image The speed is reduced to the forming speed (S808), and the paper is discharged to the outside of the image forming apparatus. This is because if the sheet is discharged to the outside of the image forming apparatus at the increased speed, the alignment of the sheet on the sheet discharge tray is deteriorated. On the other hand, even if the trailing edge of the sheet does not reach the second deceleration position in S806, if the leading edge of the next sheet reaches the second acceleration position 531 (S807), the image forming speed is reached. Is decelerated (S808). This is to prevent the leading edge of the sheet from reaching the second conveying roller 512 that is driven at an increased speed while the trailing edge of the next sheet is driven by the fixing roller 207 or the first conveying roller 511. . After discharging the sheet to the outside of the image forming apparatus at the image forming speed, if there is a next sheet, the control from S802 is repeated again. If there is no next sheet, the driving of the second sheet discharge motor 505 is stopped. Then, the image formation is completed (S811).

  Similarly, switching timing of the driving speed of the third paper discharge motor 506 will be described based on the flowchart of FIG.

  When image formation is started (S901) and the leading edge of the paper reaches the third acceleration position 532 (S902), driving of the third paper discharge motor 506 is started at the image formation speed (S903). While the trailing edge of the paper is being driven by the fixing roller 207, the third paper discharge motor 506 needs to be driven at the same speed as the fixing roller 207. Further, even after the trailing edge of the sheet passes through the fixing roller 207, the third paper discharge motor 505 is driven at the image forming speed while the trailing edge of the sheet is driven by the first conveying roller 511. This is because the speed increase possible speed of the first paper discharge motor 504 and the speed increase possible speed of the third paper discharge motor 506 are different. Thereafter, when the trailing edge of the sheet reaches the position (second acceleration position 531) that has passed through the first conveyance roller 511 (S904), the sheet is increased to a speed that can be increased to 460 mm / s, and the sheet is conveyed. (S905). The speed increase is started at this time because the speed increase possible speed of the second paper discharge motor 505 and the speed increase possible speed of the third paper discharge motor 506 are the same. Thereafter, when the sheet reaches the reverse position, the sheet is temporarily stopped (S906), and the driving is started again toward the third sheet discharge port 524 (S907). Thereafter, immediately before the paper exits the third paper discharge roller 236, when the rear end of the paper reaches 10 mm upstream from the third paper discharge roller 236 (third deceleration position 535), the image is reached (S908). The speed is reduced to the forming speed (S910), and the paper is discharged to the outside of the image forming apparatus. This is because if the sheet is discharged to the outside of the image forming apparatus at the increased speed, the alignment of the sheet on the sheet discharge tray is deteriorated. On the other hand, even if the trailing edge of the sheet has not reached the third deceleration position in S908, if the leading edge of the next sheet reaches the third acceleration position 532 (S909), the image forming speed is reached. Is decelerated (S910). This is to prevent the leading edge of the paper from reaching the reversing roller 235 that is driven to increase the speed while the trailing edge of the next paper is driven by the fixing roller 207 or the first conveying roller 511. After discharging the paper to the outside of the image forming apparatus at the image forming speed, if there is a next paper, the control from S902 is repeated again. If there is no next paper, the driving of the third paper discharge motor 506 is stopped. Then, the image formation is completed (S913).

1 is a side sectional view of an image forming apparatus to which the present invention is applied. 1 is a control block diagram of an image forming apparatus to which the present invention is applied. 1 is a configuration diagram of an image memory unit of an image forming apparatus to which the present invention is applied. 1 is a configuration diagram of an external I / F processing unit of an image forming apparatus to which the present invention is applied. FIG. 3 is a schematic diagram of a paper conveyance path in the present embodiment. Driving speed of the conveyance motor in this embodiment. 6 is a flowchart of a switching operation of the driving speed of the first paper discharge motor in the present embodiment. 9 is a flowchart of a switching operation of the driving speed of the second paper discharge motor in the present embodiment. 9 is a flowchart of a switching operation of a driving speed of a third paper discharge motor in the present embodiment.

Explanation of symbols

1Y, 1M, 1C, 1Bk Image forming section
2a, 2b, 2c, 2d Photosensitive drum (image carrier)
3a, 3b, 3c, 3d Primary charger (charging means)
4a, 4b, 4c, 4d Developing device (developing means)
5a, 5b, 5c, 5d Transfer roller (primary transfer means)
6a, 6b, 6c, 6d Drum cleaner device (cleaner means)
7 Exposure equipment (exposure means)
7a Bottom surface
7b Bottom edge
8 Intermediate transfer belt
10 Secondary transfer counter roller
11 Tension roller
13 Cleaning device
206 Secondary transfer roller (secondary transfer means)
207 Fixing roller
208 to 211 Paper cassette
21 Paper discharge roller (discharge means)
32a, 32b, 32c, 32d Primary transfer part

Claims (5)

In an image forming apparatus having a plurality of paper discharge ports, and a paper discharge roller provided at each of the plurality of paper discharge ports for discharging paper,
A drive motor for driving the paper discharge roller is provided independently for each paper discharge roller provided at each paper discharge port;
When output to the first discharge port is instructed among the plurality of sheet discharge ports, the discharge roller of the first sheet discharge port is driven when the sheet reaches the first acceleration start position. Increasing the first drive motor to a first increase speed faster than the image forming speed,
When the output to the second discharge port is instructed among the plurality of sheet discharge ports, the discharge roller of the second discharge port is driven when the sheet reaches the second acceleration start position. An image forming apparatus, wherein the second drive motor is accelerated to a second acceleration that is faster than the image forming speed.   The first or second acceleration start position is determined by the most upstream roller driven by the first or second drive motor and the most downstream roller driven by a motor upstream of the first or second drive motor. The image forming apparatus according to claim 1, wherein the image forming apparatus is a time point when the trailing edge of the sheet reaches in between. When the output to the first discharge port is instructed and the sheet is conveyed at the first speed increase, the first drive motor forms an image when the sheet reaches the first deceleration start position. Decelerate to speed,
When the output to the second discharge port is instructed and the paper is being conveyed at the second speed increase, the second drive motor forms an image when the paper reaches the second deceleration start position. The image forming apparatus according to claim 1, wherein the image forming apparatus is decelerated to a speed.   4. The image forming apparatus according to claim 3, wherein the first or second deceleration start position is immediately before a rear end of the sheet passes through a most downstream roller driven by the first or second drive motor. . In the case where the output to the first discharge port is instructed and the sheet is conveyed at the first acceleration, and the next sheet reaches the first acceleration start position, the first Reduce the drive motor to the image forming speed,
When the output to the second discharge port is instructed and the sheet is being conveyed at the second acceleration, and the next sheet reaches the second acceleration start position, the second The image forming apparatus according to claim 1, wherein the drive motor is decelerated to an image forming speed.

Images