JP2010048893A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, improving the maximum throughput even when misprint occurs without lowering the throughput in continuous printing and having high reliability. <P>SOLUTION: The image forming apparatus includes: a first conveying passage for delivering a record medium from an image forming part to a paper delivery device; a second conveying passage for reversing the conveying direction of the record medium and delivering the record medium to the paper delivery device; an image-forming speed-setting part for setting the paper conveying speed of the image forming part; a conveying speed-setting part for setting the reverse conveying speed when reversing the record medium in the second conveying passage; and an inter-paper distance-measuring means for measuring the inter-paper distance between the preceding paper and the subsequent paper before image formation in the process of continuous printing. The inter-paper distance detected by the inter-paper distance measuring means is compared to the inter-paper distance required for reversing the conveying direction in the second conveying passage, and when the inter-paper distance detected by the inter-paper distance measuring means is determined to be shorter, the image forming speed of the image forming speed setting part is set to a second image forming speed lower than the first image forming speed of the preceding paper. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic method or the like is known as an image forming apparatus that forms an image on a recording medium.

  In particular, in a small-sized copying machine, when a plurality of document images are continuously copied on a recording medium (recording paper), the recording medium having an image formed on one side is provided on the side of the image forming apparatus. In general, the sheet is discharged onto the stacking tray with the image forming surface facing up (face up).

  A copying machine that discharges face-up is advantageous in that it can easily recognize an image formed on a recording medium, and it does not have a discharge section at the top of the image forming apparatus. Even if an image reading device for reading a document image is provided at the top of the device, there is an advantage that the overall height of the device can be kept low.

  However, if the recording medium is always ejected face-up, there is a problem that images cannot be ejected in a state in which the images are formed in the output order of the plurality of pages and the page order is aligned.

In view of this, a copying machine is proposed in which a reversing mechanism is provided on a stacking tray provided on the side of the image forming apparatus so that paper can be discharged arbitrarily regardless of whether the image forming surface of the sheet is faced up (face up) or face down (face down). (For example, refer to Patent Document 1).
JP 09-212254 A

  However, in the above-described conventional example, the paper conveyance speed and the throughput that have recently been demanded of printers have been increased. The time required for the reversing operation for face-down paper discharge is limited. That is, the rotation speed of the motor that drives the roller and the like increases as the paper conveyance speed increases. Therefore, more time is required to switch the motor drive direction for the reversing operation, and in order to improve the throughput, the space between the preceding paper and the succeeding paper tends to be shorter. The time tends to be shorter.

  On the other hand, in a paper feed configuration in which paper is fed from a paper feed cassette that stores a plurality of paper (sheets) serving as recording media, the paper feed time varies depending on the behavior of the paper at the time of paper feed. Therefore, the space between the preceding paper and the succeeding paper is widened or narrowed during continuous printing.

  During continuous printing, there is a minimum gap between the preceding paper and the subsequent paper necessary for image formation, and a sensor before image formation detects whether or not this condition is satisfied. When this condition is not satisfied, it is determined that a misprint has occurred without performing image formation on the subsequent sheet, and the sheet is discharged as a blank sheet onto the stacking tray.

  However, as described above, if face-down paper discharge is performed while the distance between the preceding paper and the following paper is short, the trailing edge of the preceding paper and the leading edge of the following paper collide during the reversing operation of the preceding paper. Therefore, there is a possibility that neither paper can be normally discharged out of the machine (loading tray).

  Therefore, if a misprint occurs with a short gap between the preceding paper and the succeeding paper, the paper gap during continuous printing is widened so that the trailing edge of the preceding paper and the leading edge of the succeeding paper do not collide, or It was necessary to reduce the throughput performance somewhat by reducing the paper conveyance speed.

  The invention according to the present application has been made in view of the above-described prior art, and the preceding paper and the succeeding paper are not reversed during the reversing operation for face-down paper discharge even when a misprint occurs without reducing the throughput during continuous printing. An object of the present invention is to provide a highly reliable image forming apparatus while improving the maximum throughput by avoiding a paper jam caused by a collision.

To solve the above problem,
(1) An image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording medium,
A first conveyance path for discharging a recording medium from the image forming unit to a paper discharge device;
A second transport path that is longer than the first transport path for discharging the recording medium from the image forming unit to the paper discharge apparatus, and reverses the transport direction of the recording medium to the paper discharge apparatus. A second transport path for discharging paper;
A transport path switching unit that switches whether the recording medium is transported to the first transport path or the second transport path;
An image forming speed setting unit for setting a paper conveyance speed of the image forming unit;
A transport speed setting unit for setting a reverse transport speed when reversing the recording medium in the second transport path;
A paper gap measuring means for measuring a gap between the preceding paper and the succeeding paper before the image formation during continuous printing;
The paper gap detected by the paper gap measuring means is shorter by comparing the paper gap detected by the paper gap measuring means with the paper gap necessary for reversing the conveyance direction in the second conveyance path. The image forming speed setting unit sets the image forming speed of the succeeding sheet to the second image forming speed that is lower than the first image forming speed of the preceding sheet.

In order to solve the above problems,
(2) An image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording medium,
A first conveyance path for discharging a recording medium from the image forming unit to a paper discharge device;
A second transport path that is longer than the first transport path for discharging the recording medium from the image forming unit to the paper discharge apparatus, and reverses the transport direction of the recording medium to the paper discharge apparatus. A second transport path for discharging paper;
A transport path switching unit that switches whether the recording medium is transported to the first transport path or the second transport path;
An image forming speed setting unit for setting a paper conveyance speed of the image forming unit;
A transport speed setting unit for setting a reverse transport speed when reversing the recording medium in the second transport path;
A paper gap measuring means for measuring a gap between the preceding paper and the succeeding paper before the image formation during continuous printing;
The paper gap detected by the paper gap measuring means is shorter by comparing the paper gap detected by the paper gap measuring means with the paper gap necessary for reversing the conveyance direction in the second conveyance path. When the determination is made, the conveyance path switching unit conveys the recording medium to the paper discharge device via the first conveyance path.

As explained above,
(1) An image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording medium,
A first conveyance path for discharging a recording medium from the image forming unit to a paper discharge device;
A second transport path that is longer than the first transport path for discharging the recording medium from the image forming unit to the paper discharge apparatus, and reverses the transport direction of the recording medium to the paper discharge apparatus. A second transport path for discharging paper;
A transport path switching unit that switches whether the recording medium is transported to the first transport path or the second transport path;
An image forming speed setting unit for setting a paper conveyance speed of the image forming unit;
A transport speed setting unit for setting a reverse transport speed when reversing the recording medium in the second transport path;
A paper gap measuring means for measuring a gap between the preceding paper and the succeeding paper before the image formation during continuous printing;
Comparing the paper interval detected by the paper interval measuring means with the paper interval necessary for reversing the conveying direction in the second conveying path, the paper interval detected by the paper interval measuring means is shorter. If the image forming speed setting unit determines that the image forming speed of the succeeding sheet is set to the second image forming speed that is lower than the first image forming speed of the preceding sheet, the maximum throughput is increased. This achieves the effect of improving the reliability of the image forming system.

(2) An image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording medium,
A first conveyance path for discharging a recording medium from the image forming unit to a paper discharge device;
A second transport path that is longer than the first transport path for discharging the recording medium from the image forming unit to the paper discharge apparatus, and reverses the transport direction of the recording medium to the paper discharge apparatus. A second transport path for discharging paper;
A transport path switching unit that switches whether the recording medium is transported to the first transport path or the second transport path;
An image forming speed setting unit for setting a paper conveyance speed of the image forming unit;
A transport speed setting unit for setting a reverse transport speed when reversing the recording medium in the second transport path;
A paper gap measuring means for measuring a gap between the preceding paper and the succeeding paper before the image formation during continuous printing;
Comparing the paper interval detected by the paper interval measuring means with the paper interval necessary for reversing the conveying direction in the second conveying path, the paper interval detected by the paper interval measuring means is shorter. When the determination is made, the conveyance path switching unit conveys the succeeding sheet to the paper discharge device via the first conveyance path, thereby achieving the maximum throughput and the image forming system. As a result, there is an effect of improving reliability.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first exemplary embodiment of the present invention. In FIG. 1, reference numeral 100 denotes a printer engine body. 101 is a toner cartridge that can be attached to and detached from the printer engine, 102 is a photosensitive drum as an electrostatic carrier, 103 is a semiconductor laser as a light source, 105 is a rotating polygon mirror that is rotated by a scanner motor 104, and 106 is a semiconductor laser 103. Is a laser beam which is emitted from the laser beam and scans on the photosensitive drum 101.

  Reference numeral 107 denotes a charging roller for uniformly charging the surface of the photosensitive drum 102, and reference numeral 108 denotes a developing unit for developing the electrostatic latent image formed on the photosensitive drum 102 with toner. Reference numeral 109 denotes a transfer roller for transferring the toner image developed by the developing roller 108 to a predetermined recording sheet. Reference numeral 110 denotes a fixing heater for a fixing device for fusing the toner transferred to the recording sheet by heat. 111 Is a fixing film.

  112 is a paper feed cassette 格納 for storing paper, 113 is a cassette size sensor for detecting the paper size of the cassette stored in the cassette 、, 114 is a cassette mounting sensor for checking whether the cassette 桶 112 is stored, 115 is A cassette paper presence / absence sensor 116 for detecting whether or not paper is stacked on the cassette 、, the pickup roller 116 feeds the paper from the paper feed cassette 桶 112 by one rotation, and sends it out to the conveyance path, and 117 is the pickup roller 116. When the paper picked up in (2) is a paper bundle, it is a pair of rollers for separating the paper into one and sending it out to the transport path.

  118 is an intermediate roller for conveying the sheet fed from the cassette to the image forming unit, 119 is a pre-feed sensor for detecting the leading edge and the trailing edge of the sheet conveyed by the intermediate roller 118, and 120 is conveyed. A pre-transfer roller 121 for feeding the printed paper to the photosensitive drum 102 synchronizes image writing (recording / printing) on the photosensitive drum 102 and paper conveyance with respect to the fed paper, and also feeds the fed paper. It is a top sensor for measuring the length of the conveyance direction. 122 is a fixing sensor for detecting the presence or absence of a sheet after fixing, 123 is a conveying roller for discharging the fixed sheet to the discharge conveying path, and 124 is for conveying the sheet conveyed from the conveying roller 123 to the face-up conveying path. A face-up conveyance path switching flapper for switching between conveying to the face-down sheet discharge conveyance path, 125 conveys the sheet guided to the face-down sheet discharge conveyance path to a reversing unit for switching back and upside down. A reversing sensor 126 for detecting the leading and trailing edges of the paper guided on the paper discharge conveyance path and generating a normal rotation timing and a reverse rotation timing for the reversing roller 127. The reverse flapper 129 for switching the conveyance path at the front end of the paper whose front and rear ends are reversed by switching back is switched back. A sheet discharge intermediate roller that conveys the sheet, 130 a sheet discharge sensor that detects the leading and trailing edges of the sheet passing through the face-down sheet discharge conveyance path and the face-up sheet discharge conveyance path, and 131 stacks the sheet discharge sheet. A paper discharge roller that discharges paper to the paper discharge tray 132.

  FIG. 2 shows a block diagram of a circuit configuration of a control system that controls such a mechanism unit. In FIG. 2, reference numeral 201 denotes a printer controller for expanding image code data sent from an external device such as a host computer (not shown) into bit data necessary for printing by the printer, and reading printer internal information and displaying it. .

  A printer engine control unit 202 controls the printing operation of each unit of the printer engine in accordance with an instruction from the printer controller 201 and notifies the printer controller 201 of printer internal information. A high-voltage control unit 203 performs high-voltage output control in each process such as charging, development, and transfer in accordance with an instruction from the printer engine control unit 202. An optical system control unit 204 controls driving / stopping of the scanner motor 104 and lighting of the laser beam in accordance with instructions from the engine control unit 202. Reference numeral 205 denotes a fixing device controller that drives / stops energization of the fixing heater in accordance with an instruction from the printer engine controller 202.

  A sensor input unit 206 notifies the engine control unit 202 of the presence / absence of paper in the pre-feed sensor 119, the top sensor 121, the fixing sensor 122, the reverse sensor 126, and the paper discharge sensor 130, and 207 is in accordance with an instruction from the printer engine control unit 202. 1 is a paper conveyance control unit that drives / stops a motor / roller or the like for conveyance of recording paper, and includes a pickup roller 116, a conveyance roller pair 117, a pre-transfer roller 120, a photosensitive drum 102, a fixing film 111, and conveyance in FIG. It controls the driving / stopping of the roller 123, the merging roller 125, the reverse roller 127, the intermediate roller 129, and the paper discharge roller 131.

  FIG. 3 is a flowchart showing typical face-down paper discharge printing and paper conveyance control of the engine control unit 202 in the printer configuration of this embodiment. In FIG. 3, when an instruction to start printing is received from the printer controller 201, reference numeral 301 starts driving the scanner motor 104, starts temperature control of the fixing heater 110, and charges the contact between the fixing film 111 and the photosensitive drum 102. Driving of the roller 107, the developing roller 108, the transfer roller 109, the intermediate roller 118 for feeding and conveying, the pre-transfer roller 120 and the like at a speed (V1) for forming an image is started. Further, a predetermined high voltage is applied to the charging roller 107, the developing roller 108, and the transfer roller 109 to start an electrophotographic process necessary for printing.

  At 302, the start of the electrophotographic process, the start of the scanner motor 104 is completed, and it is confirmed that the temperature adjustment temperature of the fixing heater 111 reaches a predetermined temperature. The paper is fed from the beginning. In the paper feeding operation, the pickup roller 116 is rotated once to pick up the paper. At this time, the second and lower sheets below the uppermost surface electrostatically attached to the uppermost paper loaded in the cassette are also moved simultaneously. There is a case. The roller pair 117 separates only the uppermost sheet from such a sheet bundle and rotates so as to be guided to the intermediate roller 118.

  304 monitors whether the leading edge of the sheet fed at 303 reaches the top sensor 121. When the top sensor detects the leading edge of the sheet at 304, the printing operation is started at 305.

  Reference numeral 306 indicates that the fixing sensor 122 monitors the arrival of the leading edge of the sheet. When the fixing sensor 122 detects the leading edge of the sheet at 306, it starts driving the joining roller 125 at the transport speed (V 1). At 308, the fixing sensor 122 monitors the passage of the trailing edge of the sheet. When the fixing sensor 122 detects the trailing edge of the sheet, the conveyance speed of the merging roller is increased to (V2) faster than (V1) and the reverse roller 127 is turned on. Driving is started at the conveyance speed (V2).

  The leading edge of the paper lifts the reverse flapper 128 by its own weight and proceeds toward the reverse roller 127. When the reverse sensor 126 monitored at 309 detects the rear edge of the paper, the speed of the converging roller 125 is set at 310 (V1). The reverse roller 127 is rotated reversely at the timing when the trailing edge of the sheet passes the leading edge of the reverse flapper 128. The reversely rotated sheet pushes down the reverse flapper 128 from above and starts to advance in the direction of the sheet discharge intermediate roller 129.

  In 311, the paper discharge sensor 130 monitors the trailing edge of the paper, and when the paper discharge sensor 130 detects the paper trailing edge, it is determined that the paper discharge is completed in 312.

  After the paper conveyance speed of the merging roller 125 is increased from (V1) to (V2) in 308, the pickup roller 116 is moved at a timing such that the preceding paper and the succeeding paper have a predetermined paper distance L1 during continuous printing. Driving. This is a process for preventing the trailing edge of the preceding paper (which switches to the leading edge when switched back) and the leading edge of the succeeding paper from colliding with the reverse flapper 128 in the vicinity of the preceding paper conveyed to the reversing unit at such timing. The conveying speed (V2) is determined so that this is possible.

  However, when the sheet bundle fed by the pickup roller 116 cannot be separated normally by the roller pair 117, the interval between the preceding paper and the succeeding paper may be shorter than L1. At this time, there is a possibility that the trailing edge of the preceding sheet conveyed to the reversing unit (switching to the leading edge when switched back) and the leading edge of the succeeding sheet collide with the reversing flapper 128 in the vicinity, thereby preventing normal conveyance. In order to avoid such a situation, a sheet interval detection method and an avoidance control method during continuous printing in this embodiment are described in the flowchart of FIG.

  In FIG. 4, 401 monitors the leading edge of the paper reaching the top sensor 121. When the top sensor detects the leading edge of the sheet in 401, the printing operation is started in 402. Reference numeral 403 indicates that the top sensor 121 monitors passage of the trailing edge of the sheet. When the top sensor 121 detects the trailing edge of the sheet at 403, the printing operation is terminated at 404, and a timer for measuring the gap between the following sheets is started. Reference numeral 405 monitors whether the leading edge of the succeeding sheet reaches the top sensor 121. When 405 detects the leading edge of the succeeding sheet, the timer is stopped at 406, and it is confirmed at 407 whether it is longer or shorter than the assumed sheet interval (L1). If it is longer than (L1), it is determined that the paper interval is normal, and the process returns to 402. If the paper interval is shorter than (L1), it is determined at 408 that the paper interval is defective, and the printing operation for that paper is stopped. In 409, the conveying speed of the photosensitive drum 102, the charging roller 107, the developing roller 108, the pre-transfer roller 120, the intermediate roller 118, and the conveying roller pair 117 is changed to (V3), which is slower than (V1).

  The conveyance speed of V3 is set so that the following formula is established.

V3 ≦ v
(L1-L2): L3 = v: V1
The above (L2) is obtained by the counted timer value × V1, and L3 is the distance from the top sensor 121 to the fixing sensor 122.

  In 410 of the flowchart, the fixing sensor monitors the trailing edge of the preceding sheet. When the fixing sensor 122 detects the trailing edge of the preceding sheet, the sheet conveyance speed of the fixing film 111 is also changed from (V1) to (V3) at 411.

  Thereafter, at 412, the fixing sensor monitors the leading edge of the succeeding sheet. When the fixing sensor 122 detects the leading edge of the succeeding sheet, the conveyance speed control is terminated at 413, and the conveyance speeds of all the rollers driven at the conveyance speed (V3) are returned to (V1).

  As described above, even when the paper interval when the top sensor 121 detects is shorter than (L1) by the sequence, when reaching the fixing sensor 122, the state is equal to or longer than (L1). Can do.

  Accordingly, it is possible to avoid a collision that may occur in the vicinity of the reverse flapper 128 between the trailing edge of the preceding sheet conveyed to the reversing unit (switching to the leading edge when switched back) and the leading edge of the succeeding sheet. Therefore, unnecessary paper jams in the machine can be prevented and all the paper in the machine can be discharged out of the machine, so that a user-friendly and reliable image forming apparatus can be provided.

  In the first exemplary embodiment, when it is determined that the interval between the sheets is short, the trailing edge of the preceding sheet conveyed to the reversing unit is reduced by slowing the sheet conveying speed of the succeeding sheet (switching to the leading end of the sheet when switched back). And a collision that could occur in the vicinity of the reverse flapper 128 at the leading edge of the succeeding paper was avoided. This embodiment is characterized in that a collision is avoided by switching the conveyance path. This will be described below.

  FIG. 1 is a schematic diagram showing the configuration of the image forming apparatus in the present embodiment, FIG. 2 is a block diagram of a circuit configuration of a control system, and FIG. 3 is a flowchart regarding printing of face-down paper discharge and paper conveyance control. Since these descriptions are made in the first embodiment, the details are omitted. FIG. 5 shows a paper gap detection method and avoidance control method during continuous printing in this embodiment.

  In FIG. 5, reference numeral 501 monitors that the leading edge of the sheet reaches the top sensor 121. When the top sensor detects the leading edge of the sheet at 501, a printing operation is started at 502. Reference numeral 503 indicates that the top sensor 121 monitors the passage of the trailing edge of the sheet. When the top sensor 121 detects the trailing edge of the sheet at 503, the printing operation is terminated at 504, and a timer for measuring the gap between the succeeding sheets is started. Reference numeral 505 monitors whether the leading edge of the succeeding sheet reaches the top sensor 121. When 505 detects the leading edge of the succeeding sheet, the timer is stopped at 506 and it is confirmed at 507 whether it is longer or shorter than the assumed sheet interval (L1). If it is longer than (L 1), it is determined that the paper interval is normal, and the process returns to 502. If the paper interval is shorter than (L1), it is determined at 508 that the paper interval is defective, and the printing operation for that paper is stopped.

  Thereafter, at 509, the fixing sensor 122 monitors the arrival of the leading edge of the succeeding paper. When the fixing sensor 122 detects the leading edge of the succeeding paper, the trailing edge of the preceding paper causes the face-up conveyance path switching flapper 124 to be detected at 510. The face-up transport path switching flapper 124 is driven at the passing timing to guide the succeeding sheet to the face-up transport path. By such a sequence, it is possible to avoid a collision that may occur in the vicinity of the reverse flapper 128 between the trailing edge of the preceding paper conveyed to the reversing unit (switching to the leading edge when switched back) and the leading edge of the succeeding paper. . Therefore, unnecessary paper jams in the machine can be prevented and all the paper in the machine can be discharged out of the machine, so that a user-friendly and reliable image forming apparatus can be provided.

It is a block diagram explaining the mechanism which concerns on the 1st Example of this invention. 1 is a block diagram illustrating a circuit configuration according to a first embodiment of the present invention. 3 is a flowchart regarding print control according to the first exemplary embodiment of the present invention. It is a flowchart regarding the control method which concerns on 1st Example of this invention. It is a flowchart regarding the control method which concerns on 2nd Example of this invention.

Claims (2)

An image forming unit for forming an image on a recording medium;
A first conveyance path for discharging a recording medium from the image forming unit to a paper discharge device;
A second transport path that is longer than the first transport path for discharging the recording medium from the image forming unit to the paper discharge apparatus, and reverses the transport direction of the recording medium to the paper discharge apparatus. A second transport path for discharging paper;
A transport path switching unit that switches whether the recording medium is transported to the first transport path or the second transport path;
An image forming speed setting unit for setting a paper conveyance speed of the image forming unit;
A transport speed setting unit for setting a reverse transport speed when reversing the recording medium in the second transport path;
A paper gap measuring means for measuring a gap between the preceding paper and the succeeding paper before the image formation during continuous printing;
The paper gap detected by the paper gap measuring means is shorter by comparing the paper gap detected by the paper gap measuring means with the paper gap necessary for reversing the conveyance direction in the second conveyance path. The image forming speed setting unit sets the image forming speed of the succeeding sheet to a second image forming speed that is lower than the first image forming speed of the preceding sheet. An image forming unit for forming an image on a recording medium;
A first conveyance path for discharging a recording medium from the image forming unit to a paper discharge device;
A second transport path that is longer than the first transport path for discharging the recording medium from the image forming unit to the paper discharge apparatus, and reverses the transport direction of the recording medium to the paper discharge apparatus. A second transport path for discharging paper;
A transport path switching unit that switches whether the recording medium is transported to the first transport path or the second transport path;
An image forming speed setting unit for setting a paper conveyance speed of the image forming unit;
A transport speed setting unit for setting a reverse transport speed when reversing the recording medium in the second transport path;
A paper gap measuring means for measuring a gap between the preceding paper and the succeeding paper before the image formation during continuous printing;
Comparing the paper interval detected by the paper interval measuring means with the paper interval necessary for reversing the conveying direction in the second conveying path, the paper interval detected by the paper interval measuring means is shorter. In the image forming apparatus, the conveyance path switching unit conveys the recording medium to the paper discharge apparatus via the first conveyance path when the determination is made.

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