JP2008122935A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out image formation suppressing deterioration in productivity even when size of recording material is not known. <P>SOLUTION: An image forming apparatus includes; a paper cassette feeding the recording material, an image forming unit forming an image, a primary transfer part transferring the image onto an intermediate transfer belt, a secondary transfer part for transferring the image transferred on the intermediate transfer belt onto the fed recording material, and a sensor detecting the size of the recording material. When image formation on the recording material is started, until the sensor detects the size of the recording material, a plurality of the images are formed on the intermediate transfer belt at a first interval according to a predetermined recording material size, and after the sensor detects the size of the recording material, a plurality of images are formed on the intermediate transfer belt at a second interval according to the detected recording material size. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic or electrostatic storage type copying machine or printer.

  An outline of the configuration of a color laser printer as an image forming apparatus will be described with reference to FIG.

  As shown in FIG. 1, the color laser printer forms an electrostatic latent image on a photosensitive member by light emitted based on an image signal transmitted from a controller unit (not shown) in an image forming unit. The electrostatic latent image formed on the photosensitive member is developed, and the visible image is superimposed and transferred to the intermediate transfer member to form a color visible image. Then, this color visible image is transferred to the recording material 2 and the color visible image on the recording material 2 is fixed.

  The image forming units are arranged side by side for the colors to be developed (here, four colors of yellow, magenta, cyan, and black), and each image forming unit has a photoreceptor (5Y, 5M, 5C, 5K). Further, each image forming unit includes a charger (7Y, 7M, 7C, 7K) as a primary charging unit and a developing unit (8Y, 8M, 8C, 8K). In addition, other toner cartridges (11Y, 11M, 11C, 11K) for supplying toner, intermediate transfer body 12, paper feeding unit 1, primary transfer unit (29Y, 29M, 29C, 29K), secondary transfer unit 9 and The fixing unit 13 is configured.

  The photoreceptor (5Y, 5M, 5C, 5K), the charger (7Y, 7M, 7C, 7K) as the primary charging unit, and the developing unit (8Y, 8M, 8C, 8K) are detachable from the main body of the image forming apparatus. It is configured as an integrated process cartridge (22Y, 22M, 22C, 22K).

  The photosensitive drums (also referred to as photoconductors) 5Y, 5M, 5C, and 5K are configured by applying an organic photoconductive layer to the outer periphery of an aluminum cylinder. Then, the driving force of a driving motor (not shown) is transmitted to rotate, and the driving motor rotates the photosensitive drums 5Y, 5M, 5C, and 5K in the counterclockwise direction in the drawing according to the image forming operation. Light irradiated onto the photosensitive drums 5Y, 5M, 5C, and 5K is emitted from the scanner units 10Y, 10M, 10C, and 10K. An electrostatic latent image is formed by selectively irradiating light on the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K according to an image signal.

  As primary charging means, four chargers 7Y, 7M, 7C, and 7K for charging the photoreceptors of yellow (Y), magenta (M), cyan (C), and black (K) are provided for each image forming unit. Each charger is provided with a charging roller (also referred to as a charging sleeve) 7YS, 7MS, 7CS, 7KS.

  As developing means, in order to visualize the electrostatic latent image, four developing devices 8Y for developing yellow (Y), magenta (M), cyan (C), and black (K) in each image forming unit, Each developing device is provided with a developing roller (also referred to as a developing sleeve) 8YS, 8MS, 8CS, and 8CK. Each developing device is detachably attached.

  The intermediate transfer body 12 is in contact with the photosensitive drums 5Y, 5M, 5C, and 5K, and rotates in the clockwise direction in the drawing at the time of image formation. Then, the visible images on the rotating photosensitive drums 5Y, 5M, 5C, and 5K are transferred to the intermediate transfer body 12. Further, the intermediate transfer member 12 is contacted by a transfer roller 9a (to be described later) at the time of image formation, and the recording material 2 is nipped and conveyed, whereby the color visible image formed on the intermediate transfer member 12 by the respective image forming units on the recording material 2. Transcript. The transfer roller 9a is brought into contact with the intermediate transfer body while the color visible image is superimposed and transferred onto the recording material 2, but is separated to a position 9b when the printing process is completed.

  The fixing unit 13 fixes the color visible image transferred onto the recording material 2 while transporting the recording material 2. The fixing roller 14 that heats the recording material 2 and the recording material 2 are pressed against the fixing roller 14. And a pressure roller 15 is provided. The fixing roller 14 and the pressure roller 15 are formed in a hollow shape, and heaters 16 and 17 are incorporated therein. That is, the recording material 2 holding the color visible image is conveyed by the fixing roller 14 and the pressure roller 15, and the toner is fixed on the surface by applying heat and pressure. The recording material 2 after fixing the visible image is discharged to the paper discharge unit and the image forming operation is completed.

  In the color laser printer, the sensors 23, 24, 25, 26, and 19, the pre-fixing sensor 27, the fixing paper discharge sensor 20, and the paper discharge sensor 28 on the recording material conveyance path detect the conveyance position and grasp the conveyance state. . Sensors A23 and B25 are sensors for detecting the recording material supplied from the upper cassette, and sensors A24 and B26 are sensors for detecting the recording material supplied from the lower cassette.

  A cleaner 21 as a cleaning unit cleans the toner remaining on the intermediate transfer body 12. For example, after the color visible image formed on the intermediate transfer body 9 is transferred to the recording material 2, the toner remaining on the intermediate transfer body is cleaned and stored in the cleaner container.

  Further, a color misregistration measuring sensor 6 for detecting a positional deviation of an image formed on the intermediate transfer member and a density measuring sensor 4 for detecting the density of the image are provided. Color misregistration correction and density correction are performed according to the results of inspection by these sensors.

  FIG. 2 is a block diagram for explaining the system configuration of the image forming apparatus.

  The controller unit 201 can bidirectionally communicate with the host computer 200 and the engine control unit 202 (220 and 222 in FIG. 2).

  The controller unit 201 receives image information and printing conditions from the host computer 200. The controller unit 201 sends to the engine control unit 202 a print reservation command for reserving a print operation to which print information (paper feed unit, recording material size, print mode, etc.) for each recording material is added based on the received printing conditions. Send. Then, the received image information is analyzed and converted into bitmap data (print data). When the analysis of the image information is completed, the controller control unit 201 transmits a print start command and print data for instructing the engine control unit 202 to start a printing operation.

  When the engine control unit 202 receives the print start command, the engine control unit 202 outputs a / TOP signal (221 in FIG. 2) serving as a reference timing for outputting an image signal to the first image forming unit, and starts a paper feeding operation. After the recording material that has been fed is temporarily held by the registration roller 3, the recording material is moved from the position of the registration roller 3 as the toner image formed on the intermediate transfer member reaches the secondary transfer position. Refeed.

  This / TOP signal is a signal for instructing to write an image on the photosensitive drum of the image forming unit, and the engine control unit 202 outputs this / TOP signal to form a latent image on the photosensitive drum.

  In the image forming apparatus described above, a configuration in which the distance from the image formation start position of the first image forming unit to the secondary transfer position is longer than the distance from the paper feed position to the secondary transfer position may be employed. That is, in the image forming apparatus of FIG. 1, the distance A from the image formation start position (development position) of the yellow first image forming unit to the secondary transfer position is longer than the distance B from the paper feed position to the secondary transfer position. This is a case where a configuration is adopted.

  In this configuration, when a recording material is fed or when paper is re-fed from the registration roller 3, an image for a plurality of pages is formed on the intermediate transfer member (hereinafter referred to as throughput). Can be made faster. Therefore, conventionally, control for forming an image on the intermediate transfer member is performed before the recording material is fed or re-fed.

  Here, the first image forming unit is a yellow image forming unit, and the image formation start position is a position at which development is disclosed on the photosensitive drum. In FIG. 1, this corresponds to the position where the toner image is developed on the yellow photosensitive drum.

  FIG. 3 is a timing chart in the case where a plurality of pages of images are formed on the intermediate transfer member to increase the throughput. Throughput means the number of images formed per unit time.

  When the engine control unit 202 receives a print start command from the controller control unit 201, the engine control unit 202 performs a preparation operation for printing. When the preparation operation is completed, the / TOP signal for the first recording material is output, and the / TOP signal for the subsequent recording material is output so that the distance between the recording materials becomes a desired interval (311, 321, 322). ). The engine control unit 202 starts the paper feeding operation after a predetermined timing after outputting the / TOP signal for each recording material (312, 322, 332). The engine control unit 202 temporarily stops the conveyance of the recording material by conveying the leading end of the recording material to a desired position on the basis of the time when the fed recording material reaches the registration roller 3 (313, 323, 333). (314, 324, 334), the conveyance of the recording material is resumed in accordance with the conveyance of the toner image formed on the intermediate transfer member (315, 325, 335), and the toner image is transferred to the recording material. At this time, when the first sheet is fed again, image formation for the third sheet is started.

  In order to perform the above operation, it is necessary to form an image so that the distance between the recording materials becomes a desired interval, and for this purpose, the engine control unit 202 needs to know the recording material size in advance. Here, the size of the recording material means the length in the direction in which the recording material is conveyed.

Therefore, when the recording material size is not known in advance, the size of the first recording material is detected by detecting the size of the first recording material fed using the sensor on the recording material conveyance path. Thereafter, a paper feeding operation is proposed that is performed at intervals based on the detected size of the recording material. (For example, it is disclosed in Patent Document 1.)
FIG. 4 shows a configuration in which the distance from the start position of the first image forming unit to the secondary transfer position is longer than the distance from the paper feed position to the secondary transfer position, and the recording material size is unknown. It is a timing chart which shows operation in the case of (size indefinite state).

  The engine control 202 outputs a / TOP signal for the first sheet (411), and starts a paper feeding operation after a predetermined time (412). The engine control unit 202 transports the leading end of the recording material to a desired position and temporarily stops the conveyance of the recording material on the basis of the time when the fed recording material reaches the registration roller 3 (413) (414). Thereafter, the conveyance of the recording material is resumed (415) in accordance with the conveyance of the toner image formed on the intermediate transfer member, whereby the toner image is transferred to the recording material. At this time, the engine control unit 202 determines the length in the conveyance direction of the first recording material from the time from when the leading edge of the first recording material reaches the sensor 19 until the trailing edge of the recording material passes through the registration sensor. (Also referred to as the actual length of the recording material) is determined (416).

  The engine control unit 202 starts the printing operation for the second sheet when the trailing edge of the first recording material passes through the sensor 19, and outputs the / TOP signal for the second sheet (421). Here, the / TOP signal for the second and subsequent sheets is output so as to realize an optimum throughput according to the detected recording material length (431).

Reference numeral 422 indicates the start of the second sheet feeding operation, and reference numeral 423 indicates the time when the second recording material reaches the registration roller. Reference numerals 424 and 425 are registration roller driving timings for the second recording material. Further, reference numeral 431 denotes the third / TOP signal, reference numeral 432 denotes the start of the third sheet feeding operation, and reference numeral 433 denotes the time when the third recording material reaches the registration roller. Reference numerals 434 and 435 denote registration roller driving timings for the third recording material.
Japanese Unexamined Patent Publication No. 2000-272781

  However, in the printing operation in the case where the size of the recording material is unknown, the second / TOP signal is detected until the detection of the size of the first recording material is completed (that is, until the first sheet passes through the sensor 19). Is not output. Therefore, compared with the case where the size of the recording material is known in advance, the print interval between the first sheet and the second sheet becomes wider, the throughput of the image forming apparatus is lowered, and the performance is lowered.

  This decrease in performance increases as the distance from the image formation start position of the first image forming unit on the intermediate transfer member to the secondary transfer position increases.

  SUMMARY An advantage of some aspects of the invention is that an image forming operation is performed so that performance is not degraded as much as possible even when the size of a recording material is unknown.

  In the image forming apparatus having a configuration in which the distance from the image formation start position of the image forming unit to the secondary transfer position is longer than the distance from the paper feed position to the secondary transfer position, Even if you don't know, you can prevent performance degradation.

  In order to achieve the above object, an image forming apparatus of the present invention is formed on a sheet feeding unit for feeding the recording material, an image forming unit for forming an image on an image bearing member, and the image bearing member. A primary transfer unit that transfers the transferred image to the intermediate transfer member, a secondary transfer unit that transfers the image transferred to the intermediate transfer member to the recording material fed from the paper feeding unit, and the recording material A size detection unit that detects a size; and a setting unit that sets an interval between image formations of a plurality of images formed on the intermediate transfer member, and starts feeding the recording material from the paper feeding unit. The timing for starting image formation by the image forming unit is set earlier than the timing, and the setting unit is set in advance until the size detection unit detects the size of the recording material. At a first interval according to the size of the recording material After forming a plurality of images on the intermediate transfer member and detecting the size of the recording material by the size detection unit, the plurality of images are formed on the intermediate transfer member at a second interval according to the detected size of the recording material. The interval of image formation is set so as to form.

  According to another aspect of the present invention, there is provided an image forming apparatus that feeds the recording material, an image forming unit that forms an image on an image carrier, and an image formed on the image carrier. A primary transfer portion for transferring to a transfer body, a secondary transfer portion for transferring an image transferred to the intermediate transfer body to a recording material fed from the paper feeding portion, and detecting the size of the recording material A size detection unit; a designation unit that designates the size of the recording material; and a setting unit that sets image formation intervals of a plurality of images formed on the intermediate transfer member. The timing for starting image formation by the image forming unit is set to be earlier than the timing for starting the feeding of the recording material, and the setting unit sets the size of the recording material designated by the designation unit. A plurality of intermediate transfer members at a first interval according to After forming an image and detecting the size of the recording material by the size detection unit, the image is formed so that a plurality of images are formed on the intermediate transfer body at a second interval according to the detected size of the recording material. Set the formation interval.

  As described above, according to the present invention, it is possible to perform an image forming operation while suppressing a decrease in productivity.

  Further, according to the present invention, the distance from the image formation start position of the image forming unit to the secondary transfer position is longer than the distance from the paper feed position to the secondary transfer position, and in the paper transport direction. Even when the size is unknown, it is possible to perform an image forming operation capable of suppressing a decrease in performance.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
This embodiment is based on the premise that the distance from the image formation start position of the first image forming unit to the secondary transfer position is longer than the distance from the paper feed position to the secondary transfer position. A method for performing an image forming operation without degrading performance even when the size of the recording material (hereinafter referred to as “paper”) is unknown will be described.

  The configuration and operation of the color laser printer as the image forming apparatus are the same as those in FIG. 1 described above, and thus detailed description thereof is omitted.

  The system configuration of the image forming apparatus is the same as that described with reference to FIG.

  The first image forming unit is a yellow image forming unit, and the image formation start position is a position at which development is disclosed on a photosensitive drum as an image carrier, and is the same as described above. is there.

  In the present embodiment, until the engine control unit 202 detects the length of the recording material, at a printing interval that allows printing of the maximum size paper among the recording materials that may be set in the paper feeding unit. The TOP signal is output. Thereafter, after detecting the length of the sheet, the / TOP signal is output at an interval that can realize an optimum throughput according to the detected sheet length.

  In the following description, the maximum size of paper that can be set in the paper feed unit is the legal size (paper size in the transport direction: 355.6 mm), and the paper actually set in the paper feed unit is the letter size ( The case of a paper size in the transport direction: 279.4 mm) will be described as an example.

  FIG. 5 is a timing chart during the printing operation in the present embodiment.

  The following engine control unit 202 functions as a setting unit that sets the time interval of the / TOP signal.

  Since the paper size is unknown (also referred to as an undefined paper size state), the engine control unit 202 outputs the first / TOP signal and assumes that the paper is a legal size. A signal is output (511, 521). The time interval of the / TOP signal is assumed to be the maximum size of the legal size Tmax. That is, Tmax = legal size + margin. The margin is a value set as appropriate according to the paper feed interval and the like.

  Then, the engine control unit 202 starts the paper feeding operation after a predetermined timing after outputting the first / TOP signal (512), and determines when the fed paper reaches the registration roller 3 (513). Based on the reference, the front end of the sheet is conveyed to a desired position, and the conveyance of the sheet is temporarily stopped (514). Then, in accordance with the toner image formed on the intermediate transfer member, paper conveyance is resumed (515), and the toner image is transferred to the paper. At this time, the engine control unit 202 measures the time from when the leading edge of the first sheet reaches the sensor 19 until the trailing edge of the sheet passes through the sensor 19, and based on the result, The actual size is determined (516). Here, the engine control unit 202 monitors the detection result of the sensor 19 to determine the size. The sensor 19 and the engine control unit 202 function as a size detection unit.

  When the engine control unit outputs the second / TOP signal (521) and the detection of the length of the first sheet is completed, the engine control unit sets the detected sheet length (sheet size). Based on this, the interval between the third and subsequent / TOP signal outputs is determined. If the detection of the length of the first sheet is not completed, it is the maximum size (legal size) that may be set in the paper feed unit, as with the second sheet / TOP. Output a / TOP signal.

  In the case of FIG. 5 of the present embodiment, the detection of the length of the first sheet ends after the second / TOP signal, so the second and third / TOP signals are output. The interval Tmax is determined on the assumption of the legal size. After the third / TOP signal is output, the first sheet length detection has already been completed (517), so the / TOP signal output interval T (541) for the third and subsequent sheets is detected. It is set based on the paper length (letter size).

  Reference numeral 522 indicates the start of the second sheet feeding operation, 523 indicates the time when the second recording material reaches the registration roller, and 526 indicates the time when the second recording material passes the sensor 19. Reference numerals 524 and 525 denote registration roller driving timings for the second recording material. Reference numeral 532 denotes the start of the third sheet feeding operation, 533 denotes the time when the third recording material reaches the registration roller, and 536 denotes the time when the third recording material passes the sensor 19. . Reference numerals 534 and 535 are registration roller driving timings for the third recording material.

  FIG. 6 is a flowchart for explaining the operation timing in this embodiment.

  The engine control 202 outputs the first / TOP signal, and sets the output timing of the second / TOP signal at the maximum size (legal size) (601, 602).

  Then, the engine control unit outputs the second / TOP signal at the output timing of the second / TOP signal (604, 605). The engine control unit 202 confirms whether the detection of the length of the first sheet has been completed after the second / TOP signal is output (606).

  When the detection of the length of the first sheet has been completed, a setting is made based on the detected sheet length (letter size) (letter size) of the / TOP signal of the next page (1 sheet). When the detection of the length of the eye sheet is not completed, the timing of outputting the third / TOP signal is set on the premise of the maximum size (legal size) as in the case of the second sheet.

  Thereafter, at the time of / TOP output, the output timing of the / TOP signal of the next page is determined depending on whether or not the detection of the length of the first sheet has been completed.

  As described above, until the engine control unit 202 detects the sheet length, the maximum size (in this embodiment, the legal size) of the sheets that may be set in the sheet feeding unit is set. The / TOP signal is output at an interval that allows printing.

  In other words, the / TOP signal is output based on the maximum size before the detection of the paper length is completed, so that the / TOP signal is output after the detection of the paper length is completed. The distance between the first and second sheets does not increase.

  Conventionally, the second image is not formed until the detection of the length of the first sheet is completed after the first image is formed on the intermediate transfer member. On the other hand, in the method of this embodiment, the second image can be formed without waiting for the end of detection of the length of the first sheet. Referring to the figure, the interval between / TOP signals # 1 and # 2 in FIG. 5 in this embodiment is shorter than the interval between / TOP signals # 1 and # 2 in FIG. Therefore, a decrease in throughput can be suppressed as compared with the conventional method.

  After the paper length is detected, a printing operation is performed so that an optimum throughput can be realized according to the detected paper length. As a result, it is possible to perform a printing operation with minimal performance degradation.

(Embodiment 2)
In the first embodiment, when the / TOP signal is output, the next / TOP signal output timing is determined based on the maximum size (legal size).

  In the second embodiment, when the detection of the length of the first sheet is completed, the next / TOP output timing is changed according to the detected length of the sheet.

  The configuration and operation of the color laser printer as the image forming apparatus are the same as those in FIG. 1 described above, and thus detailed description thereof is omitted.

  The system configuration of the image forming apparatus is the same as that described with reference to FIG.

  The first image forming unit is a yellow image forming unit, and the image formation start position is a position at which development is disclosed on the photosensitive drum, and is the same as described above.

  Hereinafter, in this embodiment, the maximum size of paper that can be set in the paper feeding unit is the legal size (paper size in the transport direction: 355.6 mm), and the paper actually set in the paper feeding unit is a letter. A case of a size (paper size in the transport direction: 279.4 mm) will be described as an example.

  FIG. 7 is a timing chart during the printing operation of this embodiment.

  The engine control unit 202 outputs the first / TOP signal (711), and sets the output interval Tmax of the / TOP signal for subsequent sheets on the assumption that the sheet is legal size. The engine control unit 202 starts the paper feeding operation after a predetermined timing after outputting the first / TOP signal (712), and the time point when the fed paper reaches the registration roller 3 (713) as a reference. Then, the leading edge of the sheet is conveyed to a desired position, and the conveyance of the sheet is temporarily stopped (714). Then, in accordance with the toner image formed on the intermediate transfer member, paper conveyance is resumed (715), and the toner image is transferred to the paper. At this time, the engine control unit measures the time from when the leading edge of the first sheet reaches the sensor 19 until the trailing edge of the sheet passes through the sensor 19, and from the measured time, the first sheet Is determined (716).

  During the printing operation, the engine control unit 202 monitors the end of the detection of the length of the first sheet, and when the detection ends, the elapsed time T1 from the output of the / TOP signal output last time. And the output interval T of the / TOP signal for the next sheet is calculated based on the detected sheet length.

  Specifically, the / TOP signal output interval T is calculated from the detected sheet length, and when T time has already passed since the previous / TOP signal was output, the current sheet is the next sheet. The / TOP signal is output. If T has not elapsed since the previous / TOP signal was output, the / TOP signal is output after T1 time has elapsed from the previous / TOP signal.

  Until the detection of the length of the first sheet is completed, the engine control unit 202 is calculated at the / TOP interval calculated based on the maximum size (legal size) of the sheet that may be set in the sheet feeding unit. Control to output a / TOP signal.

  In the case of FIG. 7 in the present embodiment, since the detection of the length of the first sheet is completed after the output of the second / TOP signal, the engine control unit 202 determines the length of the first sheet. When the detection is finished, the third / TOP signal output timing is calculated and the third / TOP signal is output (717, 731).

  In FIG. 7, the output interval T of the / TOP signal is calculated by counting the time T1 from the previous / TOP signal 721 to the time point 716 when the detection of the paper length is completed, and detecting the detected paper length (this embodiment). In the case of the example, it is detected that the letter size is used). That is, for example, if α is a preset time, T = T1 (time from the previous / TOP signal until the end of paper length detection) + α. This time α may be set as appropriate for each paper size.

  The / TOP interval between the first sheet and the second sheet is a timing calculated based on the maximum size (legal size) of a sheet that may be set in the sheet feeding unit.

  Note that reference numeral 722 indicates the start of the second sheet feeding operation, reference numeral 723 indicates the time when the second recording material reaches the registration roller, and reference numeral 726 indicates the time when the second recording material passes the sensor 19. Reference numerals 724 and 725 are registration roller driving timings for the second recording material. Reference numeral 732 denotes the start of the third sheet feeding operation, reference numeral 733 denotes the time when the third recording material reaches the registration roller, and reference numeral 736 denotes the time when the third recording material passes the sensor 19. . Reference numerals 734 and 735 are registration roller driving timings for the third recording material.

  FIG. 8 is a flowchart for explaining the operation of this embodiment.

  The engine control 202 outputs the / TOP signal of the first sheet, and determines the / TOP signal output timing of the next sheet with the legal size which is the maximum size (801, 802).

  During the printing operation, the engine control unit 202 always monitors the end of the detection of the length of the first sheet, and when the detection of the length of the sheet is completed, the elapsed time from the previously output / TOP signal and Based on the detected paper length, the output timing of the / TOP signal for the next paper is calculated (804, 805).

  If the detection of the length of the first sheet has been completed, the engine control unit 202 outputs / TOP for the next sheet at the output interval of the / TOP signal calculated and calculated under the above conditions. It sets so that a signal may be output (807).

  Once the detection of the paper length is completed, the / TOP signal output timing of the next paper is determined based on the detected paper length (809). If the detection of the paper length has not been completed, the / TOP signal output timing is determined based on the maximum size (legal size) of the paper that may be set in the paper feed unit (802).

  As described above, until the engine control unit 202 detects the length of the paper, the paper of the maximum size (in this embodiment, the legal size) among the papers that may be set in the paper feeding unit. The / TOP signal is output at an interval that allows printing. When the detection of the length of the first sheet is completed, the / TOP signal output timing of the next sheet is calculated. Therefore, even when the paper size is unknown, it is possible to perform the printing operation without degrading the performance.

  In this embodiment, the / TOP signal interval can be changed more quickly than in the first embodiment, so that the throughput can be further improved.

(Embodiment 3)
In the first and second embodiments, until the detection of the length of the first sheet is completed, the / TOP signal is based on the maximum sheet size (legal size) that may be set in the sheet feeding unit. Was to determine the interval.

  In particular, in this embodiment, the output interval of the / TOP signal until the detection of the paper length is completed is not determined based on the maximum size (legal size), but the paper size designated by the controller control unit 201. It is characterized by a point determined based on

  Since the timing chart is the same as that of the first embodiment, description thereof is omitted. In other words, the present embodiment is different in that the value of Tmax in the first embodiment is set to the value of Tcont designated by the controller.

  In this embodiment, a method for setting the output interval of the / TOP signal until the detection of the paper length is completed based on the paper size designated by the controller control unit 201 will be described.

  In the following description, a case where the next / TOP signal output timing is set when the / TOP signal is output and a case where the / TOP signal output timing is calculated when the detection of the length of the first sheet is completed will be described. .

  FIG. 9 is a flowchart for determining the next / TOP signal output timing when the / TOP signal is output. The engine control 202 outputs the first / TOP signal, and sets the output timing of the second / TOP signal based on the paper size designated by the controller control unit 201 (901, 902).

  The engine control unit outputs the second / TOP signal when the second / TOP signal is output (904, 905). The engine control unit 202 confirms whether the detection of the length of the first sheet has been completed after the second / TOP signal is output (906). If the detection of the length of the first sheet has been completed, the setting is made (907) based on the detected length of the / TOP signal output timing of the next page. If the detection of the length of the first sheet is not completed, the output timing of the third / TOP signal is determined based on the sheet size designated by the controller control unit 201 as in the second sheet. Set. Thereafter, at the time of / TOP output, the / TOP signal output timing of the next page is determined depending on whether or not the detection of the length of the first sheet has been completed.

  FIG. 10 is a flowchart in the case where the / TOP signal output timing is recalculated when the detection of the length of the first sheet is completed.

  The engine control 202 outputs the / TOP signal of the first sheet, and sets the / TOP signal output timing of the next sheet based on the sheet size designated by the controller control unit 201 (1001, 1002). During printing, the engine control unit 202 always monitors the end of the detection of the length of the first sheet, and when the detection ends, the time from the previously output / TOP signal and the detected length of the sheet. To calculate the / TOP signal output timing for the next sheet (1004, 1005).

  When the detection of the length of the first sheet has been completed, the engine control unit 202 outputs the / TOP signal for the next sheet at the calculated / TOP signal output timing ( 1007). Once the detection of the paper length is completed, the / TOP signal output timing of the next paper is determined based on the detected paper length (1009). If the detection of the paper length has not ended, the / TOP signal timing is set based on the paper size designated by the controller control unit (1002).

  Here, the specification of the paper size from the controller control unit may be, for example, a specific paper size or a free size specification.

  The free size designation is a designation to set an interval for outputting the / TOP signal so that printing can be reliably performed on a sheet having a size equal to or smaller than a certain sheet size.

  For example, when the free size 1 is designated, the / TOP signal is output based on the length of the legal size paper. When the free size 2 is designated, the / TOP signal is based on the length of the letter size paper. Is set to output.

  In recent years, a paper feed cassette that can store free-size paper is also provided as a paper feed unit in which a user can freely set the paper size. In that case, a printing operation can be performed without degrading the performance by designating the maximum size of the paper supported by the free size paper cassette from the controller control unit as the free size. Note that an operation panel can be used as a designating unit for designating the size.

  As described above, until the engine control unit 202 finishes detecting the paper length, the / TOP signal is output at an interval at which printing can be performed with the paper size designated by the controller control unit 201. After the detection of the length of the first sheet is completed, performance is degraded even if the sheet size is unknown by setting the / TOP signal output timing based on the detected sheet length. It is possible to perform a printing operation without causing it to occur.

Overall configuration diagram of a laser printer as an image forming apparatus Schematic system diagram of a laser printer as an image forming apparatus Timing chart for improving throughput of conventional example Timing chart at the time of printing when the paper size of the conventional example is unknown Timing chart at the time of printing operation according to the first embodiment Flowchart during printing operation according to the first embodiment Timing chart at the time of printing operation according to the second embodiment Flowchart during printing operation according to the second embodiment Flowchart 1 at the time of printing operation according to the third embodiment Flowchart 2 at the time of printing operation according to the third embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper feed part 2 Recording material 3 Registration roller 4 Density measuring sensor 5Y, 5M, 5C, 5K Photosensitive drum 6 Color shift measuring sensor 7Y, 7M, 7C, 7K, 21 Cleaner 8Y, 8M, 8C, 8K Developer 9 Secondary Transfer unit 10Y, 10M, 10C, 10K Scanner unit 11Y, 11M, 11C, 11K Toner cartridge 12 Intermediate transfer member 13 Fixing unit 18 Drive roller 19, 23, 24, 25, 26 Sensor 20 Fixing discharge sensor 27 Pre-fixing sensor 28 Paper discharge sensor 29Y, 29M, 29C, 29K Primary transfer unit

Claims (11)

An image forming apparatus,
A paper feed unit for feeding recording material;
An image forming unit that forms an image on an image carrier;
A primary transfer portion for transferring an image formed on the image carrier to an intermediate transfer member;
A secondary transfer unit that transfers an image transferred to the intermediate transfer member to a recording material fed from the paper feeding unit;
A size detector for detecting the size of the recording material;
A setting unit for setting intervals of image formation of a plurality of images formed on the intermediate transfer member,
The timing for starting image formation by the image forming unit is set earlier than the timing for starting feeding of the recording material from the paper feeding unit,
The setting unit forms a plurality of images on the intermediate transfer body at a first interval according to a preset size of the recording material until the size detection unit detects the size of the recording material, After the size detection unit detects the size of the recording material, the image formation interval is set so that a plurality of images are formed on the intermediate transfer body at a second interval corresponding to the detected size of the recording material. An image forming apparatus.   The distance from the position at which the recording material starts to be fed from the paper feeding section to the position at which the image is transferred to the recording material by the secondary transfer section starts to form an image on the image carrier by the image forming section. The image forming apparatus according to claim 1, wherein the distance is shorter than a distance from a position where the image is transferred to the recording material by the secondary transfer unit.   The image forming apparatus according to claim 1, wherein the second interval is smaller than the first interval.   2. The preset size of the recording material is a length in a conveyance direction of the recording material, and is a maximum length of the recording material set in the paper feeding unit. 4. The image forming apparatus according to any one of items 1 to 3.   The said setting part calculates the said 2nd space | interval according to the size of the detected recording material, after detecting the size of the said recording material in the said size detection part. The image forming apparatus according to any one of the items. An image forming apparatus,
A paper feed unit for feeding recording material;
An image forming unit that forms an image on an image carrier;
A primary transfer portion for transferring an image formed on the image carrier to an intermediate transfer member;
A secondary transfer unit that transfers an image transferred to the intermediate transfer member to a recording material fed from the paper feeding unit;
A size detector for detecting the size of the recording material;
A designation unit for designating the size of the recording material;
A setting unit for setting intervals of image formation of a plurality of images formed on the intermediate transfer member,
The timing for starting image formation by the image forming unit is set earlier than the timing for starting feeding of the recording material from the paper feeding unit,
The setting unit forms a plurality of images on the intermediate transfer body at a first interval corresponding to the size of the recording material specified by the specifying unit, and detects the size of the recording material by the size detection unit. The image forming apparatus is characterized in that an image forming interval is set so that a plurality of images are formed on the intermediate transfer body at a second interval corresponding to the detected size of the recording material.   The distance from the position at which the recording material starts to be fed from the paper feeding section to the position at which the image is transferred to the recording material by the secondary transfer section starts to form an image on the image carrier by the image forming section. The image forming apparatus according to claim 6, wherein the distance is shorter than a distance from a position where the image is transferred to the recording material by the secondary transfer unit.   The image forming apparatus according to claim 6, wherein the paper feeding unit is a paper feeding unit capable of supplying a free-size recording material.   7. The preset size of the recording material is a length in the conveyance direction of the recording material, and is a maximum length of the recording material supplied to the paper feeding unit. The image forming apparatus according to any one of Items 8 to 8.   The said setting part calculates the said 2nd space | interval according to the size of the detected recording material, after detecting the size of the said recording material in the said size detection part. The image forming apparatus according to the item.   The image forming apparatus according to claim 6, wherein the size designation unit can designate a plurality of paper sizes.

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