JP2008175912A - Image forming apparatus and method for controlling conveyance of recording material therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus in which a sensor to be used for conveyance interval control is used as a sensor to be used for throughput control, and to provide its control method. <P>SOLUTION: A detection part detects recording paper with size in a direction orthogonal to a conveying direction equal to or above predetermined size. When the recording paper with size equal to or above the predetermined size is detected, a throughput control part sets throughput in the image forming apparatus to a first value. When detecting the passage of recording paper with size under the predetermined size, the throughput control part sets the throughput to a second value smaller than the first value. When the recording paper with size equal to or above the predetermined size is detected, a conveyance interval control part controls so that a conveyance interval between the preceding recording paper and the following recording paper may be within a predetermined range. When the recording paper with size under the predetermined size is detected, the conveyance interval control part does not perform control for the conveyance interval. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a recording material conveyance control method thereof.

  In general, an image forming apparatus increases the number of images formed per unit time by maintaining a conveyance interval (inter-paper distance) between a preceding recording sheet and a succeeding (next line) recording sheet at a minimum interval. Can do. For example, when the conveyance intervals of a plurality of recording sheets are constant between the registration roller pair, the conveyance intervals after the registration roller pair are also kept constant.

  Note that when a plurality of recording sheets are continuously fed, variations in the feeding position of each recording sheet (the leading end position of each recording sheet stored in the storage unit) may be a problem. According to Patent Document 1, a method is proposed in which the pre-registration sensor is arranged upstream of the registration sensor arranged immediately before the registration roller pair, thereby maintaining the conveyance interval constant.

  Incidentally, an electrophotographic image forming apparatus generally employs a film heating type fixing device. The fixing device includes a fixing film and a pressure roller, and an overheater is disposed inside the fixing film. When the recording paper on which the unfixed toner image is placed passes between the fixing film and the pressure roller (nip portion), the toner image is pressurized and heated and fixed on the recording paper.

  There are various widths of the recording paper passing through the fixing device (size in the direction orthogonal to the transport direction), but a problem is likely to occur when a large number of narrow recording papers are passed. Generally, the heat of the fixing device is taken away by the recording paper to be passed. However, when a narrow recording paper is passed, a portion where heat is taken away (paper passing portion) and a portion where paper is not taken away (non-paper passing portion) are generated in the pressure roller and the fixing film. In particular, around the non-sheet passing portion, heat damage is likely to occur in the bearing of the fixing roller, the pressure roller, the fixing film, the film guide stay, and other components.

According to Japanese Patent Laid-Open No. 2003-260260, a method for alleviating the temperature rise of the non-sheet passing portion by reducing the throughput of the image forming apparatus according to the temperature of the non-sheet passing portion and the size of the recording paper is proposed.
JP-A-4-235848 JP 2002-91226 A

  The above-described conveyance interval control and throughput control for preventing the temperature rise of the non-sheet passing portion are executed independently. Therefore, a sensor necessary for controlling the conveyance interval and a sensor for detecting a size necessary for preventing the temperature rise of the non-sheet passing portion are prepared separately.

  Therefore, an object of the present invention is to propose an image forming apparatus and a control method therefor that can share, for example, a sensor used for transport interval control and a sensor used for throughput control. Other purposes can be understood from the entire specification and drawings.

  The present invention is provided, for example, in a storage unit that stores recording paper, a feeding unit that feeds recording paper, and a downstream of the feeding unit in the transport direction, and the transport timing of the leading edge of the recording paper The present invention can be applied to an image forming apparatus including a synchronization unit for synchronizing with timing. The image forming apparatus includes an image forming unit that forms an image on a recording sheet and a fixing unit that fixes an image formed on the recording sheet. In particular, the image forming apparatus includes a detection unit, a throughput control unit, and a conveyance interval control unit. The detection unit is disposed downstream of the feeding unit and upstream of the synchronization unit, and is capable of detecting a recording sheet whose size in a direction orthogonal to the transport direction is a predetermined size or more. When a recording sheet of a predetermined size or larger is detected, the throughput control unit controls the throughput in the image forming apparatus to be the first value, and detects a recording sheet of a size smaller than the predetermined size. Then, the throughput is controlled to be a second value lower than the first value. The conveyance interval control unit controls the conveyance interval between the preceding recording sheet and the succeeding recording sheet to be within a predetermined range when a recording sheet of a predetermined size or more is detected, When a recording sheet having a size smaller than a predetermined size is detected, control of the conveyance interval is omitted.

  According to the present invention, it is possible to realize an image forming apparatus capable of sharing a sensor used for transport interval control and a sensor used for throughput control, and a control method thereof. Thereby, while suppressing thermal damage to the fixing unit or the like due to the difference in the size of the recording paper, it is possible to maintain the throughput and further reduce the number of sensors.

[Example 1]
FIG. 1 is a schematic cross-sectional view showing an example of a color image forming apparatus. Here, an electrophotographic image forming apparatus will be described as an example. Note that the image forming apparatus is realized as, for example, a printing apparatus, a printer, a copier, a multifunction peripheral, a facsimile, or the like.

  The storage unit 1 stores a large number of recording sheets 2 such that the center of the recording sheet coincides with the center of the transport path. Note that the recording paper may be called, for example, a recording material, a recording medium, a paper, a sheet, a transfer paper, or a transfer material. A paper feed roller 4 for feeding and transporting (feeding) recording paper is provided in the paper feed port 3 of the storage unit 1. The paper feed roller 4 is an example of a feeding unit that feeds recording paper. A pre-registration sensor 5 that is an example of a first sheet sensor is disposed downstream of the feeding unit in the transport direction. The pre-registration sensor 5 is a sheet sensor that detects passage of a recording sheet having a predetermined size or larger. “Register” and “resist” are abbreviations for registration.

  In the transport path, a registration roller pair 6 is provided further downstream than the pre-registration sensor 5. The registration roller pair 6 is an example of a synchronization unit that is disposed downstream of the feeding unit in the conveyance direction and that synchronizes the conveyance timing of the leading edge of the recording paper with the timing of image formation. A registration sensor 7, which is an example of a second sheet sensor, is provided upstream of the registration roller pair 6 and further downstream of the pre-registration sensor 5 in the conveyance path. For example, the registration roller pair 6 conveys the recording paper 2 only for a predetermined time after the registration sensor 7 detects the leading edge of the recording paper 2. Thereby, since the recording paper 2 is looped, the skew of the recording paper 2 is corrected.

  The image forming unit 20 is a unit that forms an image on a recording sheet. In this example, four stations that use different colors of developer (toner) are provided. The basic configuration of each station is the same. The surface of the photoreceptor 8 as an image carrier is uniformly charged by a charging device 9. Next, the photoconductor 8 is exposed by a beam output from the scanner unit 10 and modulated by an image signal. As a result, an electrostatic latent image is formed on the surface of the photoconductor 8. The electrostatic latent image is developed by the developing device 11 and becomes a developer image. Developer images of different colors from each station are primarily transferred to an intermediate transfer belt 12 as an intermediate transfer member. Thus, a color visible image is formed by multiple transfer of developer images of different colors. Finally, the color visible image is secondarily transferred from the intermediate transfer belt 12 to the recording paper in the transfer unit 13 including the transfer roller. Note that the synchronization unit by the registration roller pair 6 synchronizes the timing at which the color visible image arrives at the transfer unit 13 and the timing at which the leading edge of the recording paper arrives at the transfer unit 13.

  The fixing unit 14 is a unit that fixes a color visible image while conveying the recording paper 2. The fixing unit 14 includes a fixing roller 15 that heats the recording paper 2 and a pressure roller 16 that presses the recording paper 2 against the fixing roller 15. The fixing roller 15 is formed in a hollow shape and includes a heater 17 and a temperature detection sensor 18 inside. The temperature of the fixing roller 15 is adjusted according to the temperature detected by the temperature detection sensor 18. The recording paper 2 holding the color visible image is conveyed by the fixing roller 15 and the pressure roller 16, and the toner is fixed on the surface by applying heat and pressure. The recording paper 2 after fixing the visible image is discharged to the outside.

  FIG. 2 is a diagram for explaining a mounting position of the pre-registration sensor according to the embodiment. In the present embodiment, the pre-registration sensor 5 can be used for transport interval control and throughput reduction control by devising the mounting position of the pre-registration sensor 5 in the main scanning direction. Conventionally, individual sensors have been used for these controls. However, in this embodiment, one sensor can be shared, which is advantageous in terms of cost. FIG. 2 schematically shows a conveyance path from the paper feed roller 4 to the registration roller pair 6. The main scanning direction is a direction orthogonal to the conveyance direction (conveyance direction) of the recording paper 2. Note that the conveyance interval may be referred to as a feeding interval, a sheet feeding interval, a sheet interval, or a sheet interval.

  The pre-registration sensor 5 is disposed offset from the center of the conveyance path by a predetermined distance d in a direction orthogonal to the conveyance direction. The predetermined distance d is, for example, a distance corresponding to half of a predetermined recording paper size. In general, the recording paper 2 is stored in the storage unit 1 so as to pass near the center of the transport path. Therefore, the conventional pre-registration sensor is arranged at the center of the conveyance path. However, the pre-registration sensor 5 of this embodiment is offset from the center because it is sufficient to detect only recording paper of a size that does not require a reduction in throughput. As a result, the recording sheet 2 can detect a recording sheet whose length in the main scanning direction is less than 2d without detecting a recording sheet whose length in the main scanning direction is less than 2d. Note that the throughput is sometimes referred to as the image forming speed and the number of images formed per unit time value. The throughput in this embodiment is an image forming speed, and the throughput down control means that the rotation speed of the registration roller pair 6 and the rotation speed of the fixing roller are set to be low.

  FIG. 3 is a diagram illustrating a method for determining whether or not the conveyance interval control and the throughput reduction control can be performed. First, a determination method for a large size will be described. The large size is a size that can be detected by the pre-registration sensor 5.

  At t1, the image forming apparatus drives the paper feed roller 4 to pick up the recording paper, and feeds the recording paper. When the pre-registration sensor 5 detects the leading edge of the recording paper at t2, the image forming apparatus starts control of the conveyance interval. The conveyance interval is controlled by decelerating or accelerating the speed of the paper feed roller 4 so that the distance between the trailing edge of the preceding recording sheet and the leading edge of the succeeding (next line) recording sheet becomes a desired distance. It is a process to adjust. Since a recording sheet of a predetermined size or more is detected, the image forming apparatus does not decrease the throughput from the first value to the second value, that is, keeps the throughput at the first value. To do.

  When the registration sensor 7 detects the leading edge of the recording paper at t3, the image forming apparatus ends the control of the conveyance interval. Further, the image forming apparatus stops the conveyance by the sheet feeding roller by stopping the sheet feeding motor at t4 after a predetermined time from t3. Thereby, a loop is formed on the recording paper. Further, at t5 synchronized with the arrival timing of the developer image, the image forming apparatus re-feeds the recording paper by the registration roller pair 6 by driving the registration motor.

  Next, a determination method for a small size will be described. The small size is a size that cannot be detected by the pre-registration sensor 5. At t11, the image forming apparatus drives the paper feed roller 4 to pick up the recording paper, and feeds the recording paper. At t12, the recording paper passes near the pre-registration sensor 5, but the pre-registration sensor 5 cannot detect the recording paper because the size is small. As described with reference to FIG. 2, the recording paper passes through the center of the transport path, but the pre-registration sensor 5 is offset from the center.

  When the registration sensor 7 detects the leading edge of the recording paper at t13, the image forming apparatus determines that the small-size recording paper has been fed because the pre-registration sensor 5 has not been detected, and the throughput exceeds the first value. Reduce to a low second value. Further, since the pre-registration sensor 5 could not be detected, control on the conveyance interval between the preceding recording sheet and the succeeding recording sheet is omitted.

  The image forming apparatus stops the conveyance by the sheet feeding roller by stopping the sheet feeding motor at t4 after a predetermined time from t13. Thereby, a loop is formed on the recording paper. Further, at t15 after a predetermined time from t14, the image forming apparatus re-feeds the recording paper. Since the throughput is reduced, the time interval between t14 and t15 is longer than the time interval between t4 and t5. Thereby, the temperature rise of the non-sheet passing portion is alleviated.

  As described above, when both the pre-registration sensor 5 and the registration sensor 7 detect recording paper, the image forming apparatus can determine that recording paper of a predetermined size or more has passed. Therefore, the image forming apparatus controls the throughput so as to be the first value, and controls the conveyance interval between the preceding recording sheet and the succeeding recording sheet to be within a predetermined range. On the other hand, when the pre-registration sensor 5 cannot be detected and only the registration sensor 7 detects the recording paper, it can be determined that the recording paper having a size smaller than a predetermined size has passed. Therefore, the image forming apparatus controls the throughput to be a second value lower than the first value, and omits control of the conveyance interval between the preceding recording sheet and the succeeding recording sheet. The second value may occur in a portion (non-sheet passing portion) other than a part of the fixing unit 14 when a recording sheet having a size less than a predetermined size passes through a part (sheet passing unit) of the fixing unit 14. This value is determined from the viewpoint of mitigating the rise in temperature. The sheet passing portion is generally near the center of the fixing roller 15 and the pressure roller 16, and the non-sheet passing portion is near the ends of the fixing roller 15 and the pressure roller 16. This is because all the recording sheets are transported while being centered with respect to the transport path.

  4 and 5 are diagrams for explaining the control of the conveyance interval. In general, it is desirable that the conveyance interval between the preceding recording sheet and the succeeding recording sheet be constant. However, the leading edge position of each recording sheet stored in the storage unit may be different. This is one of the causes that the conveyance interval between the preceding recording sheet and the succeeding recording sheet is not constant when a plurality of recording sheets are continuously fed.

  Here, in the transport path from the paper feed roller 4 to the registration roller pair 6, the actual transport interval between the preceding recording paper 2a and the succeeding recording paper 2b is Xm. The conveyance interval Xm is calculated by multiplying the time difference between the time when the pre-registration sensor 5 detects the trailing edge of the preceding recording paper 2a and the time when the leading edge of the succeeding recording paper 2b is detected by the conveyance speed. The If the actual conveyance interval Xm is longer than the ideal conveyance interval Xa, the paper feed roller 4 may be temporarily stopped until the conveyance interval is extended to Xa. As shown in FIG. 5, if the actual conveyance interval Xn is longer than the ideal conveyance interval Xa, the paper feed roller 4 may be temporarily accelerated until the conveyance interval is reduced to Xa.

  FIG. 6 is a block diagram illustrating an example of a control unit according to the embodiment. FIG. 6 shows only units directly related to the present embodiment, and other units are omitted. Each unit can be configured by, for example, a CPU, ROM, RAM, ASIC, logic circuit, and the like.

  The main control unit 600 includes a throughput control unit 601 and a conveyance interval control unit 602. The throughput control unit 601 controls the throughput of the image forming apparatus to be the first value when the passage of a recording sheet having a predetermined size or more is detected. In this case, the rotational speed of the registration motor 621 that rotates the registration roller pair 6 and the fixing motor 623 that rotates the fixing roller are relatively high.

  The throughput control unit 601 controls the throughput in the image forming apparatus to be a second value lower than the first value when the passage of a recording sheet having a size smaller than a predetermined size is detected. In this case, the rotational speed of the registration motor 621 that rotates the registration roller pair 6 and the fixing motor 623 that rotates the fixing roller are relatively low.

  The conveyance interval control unit 602 detects the passage of a recording sheet of a predetermined size or larger so that the conveyance interval between the preceding recording sheet and the succeeding recording sheet is within a predetermined range. Control. For example, according to the time difference between the timing at which the pre-registration sensor 5 detects the passage of the preceding recording paper and the timing at which the subsequent recording paper is detected, the conveyance interval control unit 602 performs the conveyance speed of the subsequent recording paper. Is decelerated or accelerated. Deceleration and acceleration of the conveyance speed are realized by adjusting the rotation speed of the paper feed motor 622 that rotates the paper feed roller. On the other hand, the conveyance interval control unit 602 omits control of the conveyance interval between the preceding recording sheet and the succeeding recording sheet when the passage of the recording sheet having a size smaller than the predetermined size is detected.

  The detection unit 610 can detect the passage of a recording sheet whose size in the direction orthogonal to the conveyance direction is equal to or larger than a predetermined size among the recording sheets fed from the storage unit 1. On the contrary, the detection unit 610 detects the passage of a recording sheet having a size smaller than a predetermined size when it has not detected the passage of a recording sheet having a predetermined size or more. For example, the detection unit 610 is realized by including a determination unit 611 and a holding unit 612 that determine the size of the recording paper based on the detection results of the pre-registration sensor 5 and the registration sensor 7 described above. When a job for forming an image on a plurality of recording sheets is input, the holding unit 612 holds the detection result of the detection unit for the first recording sheet related to the job. Accordingly, at least one of the throughput control unit 601 and the conveyance interval control unit 602 can control the second and subsequent recording papers using the detection result held in the holding unit 612.

  When the pre-registration sensor 5 detects the passage of the recording sheet, the determination unit 611 determines that a recording sheet of a predetermined size or more has passed. On the other hand, when the pre-registration sensor 5 cannot detect the passage of the recording paper and the registration sensor 7 can detect the passage of the recording paper, the determination unit 611 passes the recording paper having a size smaller than a predetermined size. It is determined that

  FIG. 7 is a flowchart illustrating the control method according to the embodiment. In step S701, the detection unit 610 reads the detection signal of the pre-registration sensor 5. In step S702, the determination unit 611 determines whether the detection signal of the pre-registration sensor 5 means the passage of the recording paper. Since the pre-registration sensor 5 can detect the passage of the recording paper of a predetermined size or more, the detection of the passage of the recording paper means the passage of the recording paper of the predetermined size or more. In this case, the process proceeds to step S710, and the conveyance interval control unit 602 executes control of the conveyance interval. On the other hand, the throughput control unit 601 sets the throughput at a high speed.

  On the other hand, when the pre-registration sensor 5 cannot detect the passage of the recording paper, the process proceeds to step S703. In step S703, the detection unit 610 reads a detection signal from the registration sensor 7. In step S704, the determination unit 611 determines whether the detection signal of the registration sensor 7 means the passage of the recording paper. Here, if the registration sensor 7 can detect the passage of the recording sheet, the determination unit 611 determines that the recording sheet having a size less than the predetermined size is passing. Accordingly, the process proceeds to step S705, and the throughput control unit 601 sets the throughput to a low speed. The conveyance interval control unit 602 does not execute the conveyance interval control. Note that if the registration sensor 7 cannot detect the passage of the recording paper even after a certain period of time, it is considered that a jam has occurred, and therefore the image forming apparatus executes jam processing.

  FIG. 8 is a flowchart illustrating a more detailed control method according to the embodiment. In step S <b> 801, the main control unit 600 activates the paper feed roller 4. As a result, the picked-up recording paper 2 is fed from the paper feed port to the transport path.

  In step S802, the determination unit 611 determines whether the pre-registration sensor 5 has detected a recording sheet. If the recording paper is detected, it is understood that the fed recording paper is large. Therefore, the process proceeds to step S806 in order to form an image while executing the conveyance interval control. On the other hand, when the recording paper cannot be detected by the pre-registration sensor, the process proceeds to step S803. In step S803, the determination unit 611 determines whether the registration sensor 7 has detected a recording sheet. If the registration sensor 7 can detect the recording sheet even though the recording sheet cannot be detected by the pre-registration sensor, it is understood that the fed recording sheet is a small size. Therefore, in order to form an image with a reduced throughput, the process proceeds to step S819. If the registration sensor 7 cannot detect the recording paper, the process advances to step S804, and the determination unit 611 determines whether a predetermined time specified for detecting the occurrence of a jam has elapsed. If the predetermined time has not elapsed, the process returns to step S802. When the predetermined time has elapsed, the process proceeds to step S805, and the main control unit 600 executes jam processing (eg, stopping of the image forming operation).

[Recording paper larger than a predetermined size]
When a recording paper of a predetermined size or more is detected, the processing is executed as follows. In step S806, the determination unit 611 determines whether the registration sensor 7 has detected a recording sheet. If not detected, the process proceeds to step S807, and the determination unit 611 determines whether a predetermined time specified for detecting the occurrence of a jam has elapsed. If the predetermined time has elapsed, the process proceeds to step S805. If not, the process returns to step S806. If a recording sheet is detected in step S806, the process advances to step S809, and the determination unit 611 determines whether a loop has been created on the recording sheet. This determination is performed based on whether or not the time necessary for creating a loop on the recording paper has elapsed. When the loop is formed, the process proceeds to step S810, and the main control unit 600 stops the paper feed roller 4.

  In step S811, the determination unit 611 determines whether a predetermined time has passed. The predetermined time here is, for example, a waiting time for matching the timing at which the developer image arrives at the transfer unit 13 and the arrival timing of the recording paper. When the predetermined time has elapsed, the process advances to step S812, and the main control unit 600 starts refeeding the recording paper by activating the paper feed roller 4 and the registration roller pair 6. In step S813, the main control unit 600 temporarily stops the paper feed roller 4 and the registration roller pair 6.

  In step S814, the main control unit 600 determines whether a print continuation request has arrived from a print controller (not shown). If it is not necessary to continue printing, this process is terminated. On the other hand, if it is necessary to continue printing, the process proceeds to step S815, and the main control unit 600 starts feeding the recording paper of the next item by activating the paper feed roller 4. In step S816, the determination unit 611 determines whether the pre-registration sensor 5 has detected a recording sheet. If detected, the process returns to step S806. If not detected, the process proceeds to step S817, and the determination unit 611 determines whether a predetermined time defined for detecting the occurrence of a jam has elapsed. If the predetermined time has not elapsed, the process returns to step S816. When the predetermined time has elapsed, the process proceeds to step S805.

[Recording paper less than a predetermined size]
When a recording sheet having a size smaller than a predetermined size is detected, the processing is executed as follows. In this case, the throughput control unit 601 performs throughput reduction. In step S819, the determination unit 611 determines whether a loop is created on the recording paper. This determination is performed based on whether or not the time necessary for creating a loop on the recording paper has elapsed. When the loop is formed, the process proceeds to step S820, and the main control unit 600 stops the paper feed roller 4.

  In step S821, the determination unit 611 determines whether a predetermined time has passed. The predetermined time here is, for example, a waiting time for matching the timing at which the developer image arrives at the transfer unit 13 and the arrival timing of the recording paper. When the predetermined time has elapsed, the process proceeds to step S822, and the main control unit 600 starts refeeding the recording paper by activating the paper feed roller 4 and the registration roller pair 6. In step S823, the determination unit 611 determines whether the registration sensor 7 has detected passage of the trailing edge of the recording paper. Normally, the output of the registration sensor 7 is ON when the recording paper is passing, and OFF when the recording paper is not passing. Therefore, when the rear end passes, the detection signal changes from ON to OFF. After waiting for the trailing edge of the recording paper to pass, the process proceeds to step S824.

  In step S824, the main control unit 600 temporarily stops the paper feed roller 4 and the registration roller pair 6. In step S825, the main control unit 600 determines whether a print continuation request has arrived from a print controller (not shown). If it is not necessary to continue printing, this process is terminated. On the other hand, if it is necessary to continue printing, the process advances to step S826, and the main control unit 600 starts feeding the recording paper of the next item by activating the paper feed roller 4. In step S827, the determination unit 611 determines whether or not the registration sensor 7 recording paper has been detected. If detected, the process returns to step S819. If not detected, the process proceeds to step S828, and the determination unit 611 determines whether or not a predetermined time specified for detecting the occurrence of a jam has elapsed. If the predetermined time has not elapsed, the process returns to step S827. When the predetermined time has elapsed, the process proceeds to step S805.

  As described above, according to the present embodiment, it is possible to realize an image forming apparatus and a control method thereof that can share a sensor used for transport interval control and a sensor used for throughput control. This can be realized by providing a detection unit capable of detecting the passage of the recording paper when the size in the main scanning direction is equal to or larger than a predetermined size. Therefore, it is possible to maintain the throughput while suppressing thermal damage to the fixing unit due to the difference in the size of the recording paper, and to reduce the number of sensors. It goes without saying that the volume and cost of the image forming apparatus can be reduced by reducing the number of sensors.

  For example, by arranging the pre-registration sensor 5 at a position offset in the main scanning direction by a half of a predetermined size from the center of the conveyance path, and using the registration sensor 7, such a detection unit can be Realized. In this case, when the pre-registration sensor 5 detects the passage of the recording paper, the determination unit can determine that the recording paper of a predetermined size or more has passed. Further, when the pre-registration sensor 5 cannot detect the passage of the recording paper, but the registration sensor 7 can detect the passage of the recording paper, it can be determined that the recording paper having a size smaller than a predetermined size has passed.

  Depending on the time difference between the timing at which the pre-registration sensor 5 detects the passage of the preceding recording paper and the timing at which the subsequent recording paper is detected, the transport interval control unit 602 sets the transport speed of the subsequent recording paper. Decelerate or accelerate. As a result, it is easy to improve the throughput by absorbing variations in the conveyance interval.

  Note that the second value for the throughput is a value determined from the viewpoint of mitigating the temperature rise that may occur in the non-sheet passing portion. Thereby, the temperature rise that can occur in the non-sheet passing portion can be reduced.

  As shown in FIG. 8, the throughput control unit 601 and the conveyance interval control unit 602 control the second and subsequent recording sheets using the first detection result held in the holding unit 612. May be performed. In this case, since detection and determination for the second and subsequent recording sheets can be omitted, the throughput can be easily improved.

[Example 2]
In the first embodiment, the size of the recording paper is determined for each job (that is, only the first sheet of the job). Therefore, in the second embodiment, it is assumed that at least one of the throughput control unit 601 and the conveyance interval control unit 602 performs control using the detection result detected for each recording sheet by the detection unit 610.

  FIG. 9 is a flowchart of the control method according to the second embodiment. Steps common to the first embodiment are given the same reference numerals. As can be seen from comparison with FIG. 8, steps S814 to S817 are replaced with S914, and S825 to S828 are replaced with S925.

  In step S914, the main control unit 600 determines whether a print continuation request has arrived from a print controller (not shown). If it is not necessary to continue printing, this process is terminated. On the other hand, if it is necessary to continue printing, the process returns to step S802. In step S925, the determination is performed in the same manner as in step S914.

  As described above, in the second embodiment, the size of the recording paper is detected every time. Therefore, even in the case where recording sheets of different sizes are mixed in one job, the second embodiment can execute the conveyance interval control and the throughput reduction control more suitably than the first embodiment.

[Example 3]
In the first and second embodiments, the image forming apparatus having only one storage unit has been described. However, the present invention is not limited by the number of storage units. Therefore, in an embodiment 3, an image forming apparatus having a plurality of storage units will be described.

  FIG. 10 is a schematic sectional view of the image forming apparatus according to the third embodiment. Parts that are common to the parts already described are given the same reference numerals to simplify the description. According to FIG. 10, in addition to the first storage unit 1A and the first paper feed roller 4A, a second storage unit 1B and a second paper feed roller 4B are added. The conveyance path 19A extending from the storage unit 1A to the registration roller pair 6 and the conveyance path 19B extending from the storage unit 1B to the registration roller pair 6 are joined together to form one conveyance path.

  Here, the above-described pre-registration sensors may be provided for both the storage units 1A and 1B. However, in the third embodiment, a device is provided that does not increase the number of pre-registration sensors. That is, as shown in FIG. 10, the pre-registration sensor 5 ', which is an example of the detection unit 610, is disposed downstream of the junction of the conveyance path extending from each storage unit. The control method may be the one described in the first embodiment or the one described in the second embodiment.

  As described above, according to the third exemplary embodiment, even when the image forming apparatus includes a plurality of storage units, it is possible to realize conveyance interval control and throughput reduction control only by providing one pre-registration sensor. is there.

  In the above-described embodiment, an example of controlling the image forming speed is shown as an example of controlling the throughput. However, the present invention is not limited to this, and the image forming speed is kept constant, and the sheet feeding timing is changed to change the unit time value image. You may control to make the number of formation variable.

It is a schematic sectional drawing which shows an example of a color image forming apparatus. It is a figure for demonstrating the attachment position of the sensor before registration which concerns on an Example. It is the figure shown about the determination method of the feasibility of carrying interval control and throughput down control. It is a figure for demonstrating control of a conveyance space | interval. It is a figure for demonstrating control of a conveyance space | interval. It is a block diagram which shows an example of the control part which concerns on an Example. It is a flowchart which shows the control method which concerns on an Example. It is a flowchart which shows the more detailed control method based on an Example. 6 is a flowchart of a control method according to a second embodiment. FIG. 10 is a schematic cross-sectional view of an image forming apparatus according to a third embodiment.

Claims (7)

An image forming apparatus,
A storage section for storing recording paper;
A feeding unit that feeds the recording paper from the storage unit;
A synchronization unit that is arranged downstream of the feeding unit in the conveyance direction, and synchronizes the conveyance timing of the leading edge of the recording paper with the timing of image formation;
A detection unit that is disposed downstream of the feeding unit and upstream of the synchronization unit, and capable of detecting a recording sheet having a size in a direction orthogonal to the conveyance direction that is greater than or equal to a predetermined size;
When a recording paper of a predetermined size or more is detected, the throughput in the image forming apparatus is controlled to be a first value, and when a recording paper of a size less than a predetermined size is detected, the throughput A throughput control unit that controls the second value to be a second value lower than the first value;
When a recording paper of a predetermined size or more is detected, the conveyance interval between the preceding recording paper and the succeeding recording paper is controlled to be within a predetermined range, and less than the predetermined size. When the recording paper is detected, a conveyance interval control unit that omits control of the conveyance interval;
An image forming unit that forms an image on the recording paper;
An image forming apparatus comprising: a fixing unit that fixes an image formed on the recording paper. The storage unit stores the recording paper so that the center of the recording paper coincides with the center of the transport path for transporting the recording paper,
The detector is
It is a conveyance path between the feeding section and the synchronization section, and is disposed at a position offset in a direction perpendicular to the conveyance direction at a predetermined distance from the center of the conveyance path. A first sheet sensor that detects the passage of recording paper of a size or larger;
A second sheet sensor that is provided downstream of the first sheet sensor and upstream of the synchronization unit and detects the passage of the leading edge of the recording paper;
When the first sheet sensor detects the passage of the recording paper, it is determined that the recording paper of a predetermined size or more has passed, the first sheet sensor cannot detect the passage of the recording paper, and And a determination unit that determines that recording paper having a size less than a predetermined size is passing when the second sheet sensor can detect the passage of the recording paper. Image forming apparatus. The conveyance interval controller
The first sheet sensor decelerates or accelerates the conveyance speed of the subsequent recording sheet in accordance with the time difference between the timing at which the preceding recording sheet is detected and the timing at which the subsequent recording sheet is detected. The image forming apparatus according to claim 2. When a job for forming an image on a plurality of recording sheets is input, the image forming apparatus further includes a holding unit that holds a detection result in the detection unit for the first recording sheet related to the job,
The at least one of the throughput control unit and the conveyance interval control unit controls the second and subsequent recording papers using a detection result held in the holding unit. The image forming apparatus according to any one of the above.   4. The control unit according to claim 1, wherein at least one of the throughput control unit and the conveyance interval control unit performs control using a detection result detected for each recording sheet by the detection unit. The image forming apparatus described in 1.   The said detection part is arrange | positioned downstream from the confluence | merging location of the conveyance path each extended | stretched from each storage part, when the said storage part is plural, The any one of Claim 1 thru | or 5 characterized by the above-mentioned. The image forming apparatus described in 1. At least a storage section storing recording paper;
A feeding section for feeding the recording paper;
A recording material conveyance control method for an image forming apparatus, including a synchronization unit that is arranged downstream of the feeding unit in the conveyance direction and synchronizes the conveyance timing of the leading edge of the recording paper with the timing of image formation,
A detection step of detecting a recording sheet having a size equal to or larger than a predetermined size in a direction downstream of the feeding unit and upstream of the synchronization unit and orthogonal to the conveyance direction;
When a recording paper of a predetermined size or more is detected, the throughput in the image forming apparatus is controlled to be a first value, and when a recording paper of a size less than a predetermined size is detected, the throughput A throughput control step for controlling the second value to be a second value lower than the first value;
When a recording paper of a predetermined size or more is detected, the conveyance interval between the preceding recording paper and the succeeding recording paper is controlled to be within a predetermined range, and less than the predetermined size. A control method for an image forming apparatus, comprising: a transport interval control step that omits control of the transport interval when a recording sheet is detected.

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