JP4752654B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  As a conventional technique related to an image forming apparatus, Patent Document 1 describes a technique for reducing the sheet conveyance speed before the leading edge of a sheet hits a registration roll.

  Japanese Patent Application Laid-Open No. 2004-228561 describes a technique for reducing the sheet conveyance speed by the reversing roll when the low noise mode is set.

JP 2003-155147 A JP 2004-18195 A

  An object of the present invention is to achieve high productivity and low noise with a single image forming apparatus.

According to the first aspect of the present invention, a first image forming mode for feeding a sheet at a first feeding interval and forming an image on the sheet fed at the first feeding interval, and the first Paper is fed at a second paper feed interval wider than one paper feed interval, and an image is printed on the paper fed at the second paper feed interval at the same image forming speed as in the first image forming mode. A second image forming mode to be formed; a selection unit that selects one of the first image forming mode and the second image forming mode according to a user operation; and a leading end of a sheet as a reference member on the sheet conveyance path And a posture correction unit that corrects the posture of the paper by slackening the paper in a loop shape, and when the second image forming mode is selected by the selection means , the leading edge of the paper is placed on the reference member. The abutting speed when abutting is the first An image forming apparatus, characterized in that it comprises a control means for controlling so as to be slower than the image formation mode.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the first image forming mode is selected by the selection unit, the control unit supplies the paper to be fed and the paper The sheet is controlled to be fed at the minimum first feeding interval that does not contact the succeeding sheet fed next .
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the control unit performs image formation when the second image forming mode is selected by the selection unit. In addition, the control is performed so that the loop amount of the paper abutted against the reference member is larger than that in the first image forming mode.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the control unit performs image formation when the second image forming mode is selected by the selection unit. In addition, the acceleration time and the deceleration time of the paper transport motor are controlled to be longer than those in the first image forming mode.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect , the control unit selects the first image from the user when the second image forming mode is selected by the selection unit. When image formation is performed in response to an instruction for priority for early delivery, the first sheet is transported under the first transport condition, and the second and subsequent sheets have an abutting speed higher than that of the first transport condition. Control is performed so that the sheet is conveyed at a low speed and under a second conveyance condition in which an acceleration time and a deceleration time of the sheet conveyance motor are longer than the first conveyance condition.

  According to the first aspect of the present invention, by performing image formation in the first image forming mode, higher productivity than in the second image forming mode can be obtained. Further, by performing image formation in the second image forming mode, it is possible to reduce the impact sound when the sheet hits the reference member, as compared with the first image forming mode. Therefore, high productivity and low noise can be realized with a single image forming apparatus.

According to the fourth aspect of the present invention, when image formation is performed in the second image formation mode, the amount of paper loop is increased as compared with the first image formation mode, so that the paper striking the reference member is promoted. Since the force increases, it is possible to compensate for a decrease in posture correction force due to a decrease in the abutting speed.

According to the fifth aspect of the present invention, when image formation is performed in the second image formation mode, it is possible to reduce the driving sound of the paper transport motor as compared with the first image formation mode.

According to the third aspect of the present invention, when image formation is performed in the second image formation mode, it is possible to output (discharge) the first sheet as soon as the user desires.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram showing a configuration example of an image forming apparatus to which the present invention is applied. In the figure, two sheet storage portions 1 and 2 are arranged in a vertical positional relationship. Each of the paper storage units 1 and 2 stores a predetermined number of sheets (a plurality of sheets) in a stacked state. The size of the paper stored in the paper storage unit 1 is smaller than the size of the paper stored in the paper storage unit 2.

  In the paper feed portion of the upper paper storage unit 1, a call roll 3 and a feed roll 4 are arranged as paper feed rolls. The call roll 3 is for calling the sheets stored in the sheet storage unit 1 in order from the top sheet. The delivery roll 4 separates and feeds the sheets called up by the calling roll 3 one by one. Similarly, a calling roll 5 and a delivery roll 6 are also arranged as a paper feeding roll in the paper feeding portion of the lower paper storage unit 2.

  A sheet conveyance path is formed in the main body of the image forming apparatus. The paper transport path is formed using a transport path forming member (not shown). A plurality of transport rolls 7 to 19 are provided on the paper transport path. Each of the conveying rolls 7 to 19 conveys a sheet by applying a conveying force to the sheet by rotating with the sheet sandwiched between a pair of rolls.

  Here, when the paper transport path is divided into a plurality of paper transport paths R1 to R6, the first paper transport path R1 and the second paper transport path R2 are divided between the transport roll 8 and the transport roll 9. Has been. The third paper transport path R3 branches off from the second paper transport path R2 on the downstream side of the transport roll 11. The third paper transport path R3 and the fourth paper transport path R4 are divided between the transport roll 14 and the transport roll 15. The fifth paper transport path R5 branches from the fourth paper transport path R4 between the transport roll 14 and the transport roll 15. The fifth paper transport path R5 joins the second paper transport path R2 on the upstream side of the transport roll 9. The sixth paper transport path R6 branches from the third paper transport path R3 between the transport roll 13 and the transport roll 14. The sixth paper transport path R6 joins the second paper transport path R2 on the upstream side of the transport roll 12.

  The first paper transport path R1 is a paper feed transport path for feeding the paper stored in the paper storage units 1 and 2 toward the image forming means, and the second paper transport path R2 is the image forming means. It becomes an image forming conveyance path that conveys the sheet so as to pass through. Further, the third paper transport path R3 is a relay transport path that relays between the second paper transport path R2 and the fourth paper transport path R4, and the fourth paper transport path R4 reverses the front and back of the paper. Is the reverse conveyance path. The fifth paper transport path R5 is a re-feed paper transport path for feeding the paper reversed in the fourth paper transport path R4 toward the image forming unit again, and the sixth paper transport path R6. Is a reversal discharge conveyance path for reversing and discharging the image-formed paper.

  The transport rolls 7 and 8 are disposed on the first paper transport path R1, and the transport rolls 9 to 12 are disposed on the second paper transport path R2. The transport rolls 13 and 14 are disposed on the third paper transport path R3, and the transport roll 15 is disposed on the fourth paper transport path R4. The transport rolls 16 to 19 are arranged on the fifth paper transport path R5.

  Further, the transport roll 7 is disposed on the upstream side of the transport roll 8 on the first paper transport path R1. The transport roll 8 is disposed on the downstream side of the transport roll 7 on the first paper transport path R1. These transport rolls 7 and 8 respectively receive the paper supplied from the paper storage unit 1 by the paper supply rolls 3 and 4 and the paper supplied from the paper storage unit 2 by the paper supply rolls 5 and 6. It is conveyed along the first paper conveyance path R.

  The transport roll 9 is arranged on the upstream side of the transport roll 10 on the second paper transport path R2. The transport roll 9 transports the paper transported from the first paper transport path R 1 to the second paper transport path R 2 by the transport roll 8 toward the transport roll 10. The transport roll 10 is a roll that feeds the paper transported by the transport roll 9 to the image transfer unit at a predetermined timing. The image transfer unit refers to a portion where an image is transferred to a sheet on a sheet conveyance path. In the following description, the transport roll 10 that feeds paper to the image transfer unit is referred to as a registration roll, and the transport roll 9 that feeds paper to the transport roll 10 is referred to as a pre-registration roll. The pre-registration roll 9 and the registration roll 10 are arranged in a positional relationship adjacent to each other in the paper conveyance direction.

  An attitude correction unit 20 is provided between the pre-registration roll 9 and the registration roll 10 in the paper conveyance direction. The posture correction unit 20 is a portion that corrects the posture (tilt) of the paper on the second paper transport path R2. In the posture correction unit 20, on the upstream side of the registration roll 10, for example, by using the registration roll 10 as a reference member, the leading edge of the paper is abutted against the registration roll 10 to loosen the paper in a loop shape, thereby adjusting the posture of the paper. to correct. The reference member is a member used to align the front end of the sheet in the direction perpendicular to the sheet conveyance direction within the sheet conveyance surface. In the posture correction unit 20, among the conveyance path forming members that form the second paper conveyance path R <b> 2, an arcuate conveyance path forming member disposed outside the conveyance curve between the pre-registration roll 9 and the registration roll 10 is provided. In this configuration, the sheet is pushed by the paper forming the loop by abutting against the resist roll 10 and escapes (displaces) outward.

  A photosensitive drum 22 is disposed on the downstream side of the registration roll 10 in the second paper transport path R2. The photosensitive drum 22 is rotationally driven in the counterclockwise direction in the figure. Around the photosensitive drum 22, as a means for forming an image (toner image) to be transferred onto a sheet, for example, a charger (not shown) that charges the surface of the photosensitive drum 22 to a predetermined potential level. The surface of the photosensitive drum 22 charged by the charger is exposed and scanned with a laser beam (laser beam) to write an electrostatic latent image, and the electrostatic latent image written by the image writing unit 23 is written. A developing unit (not shown) for developing the image with toner, a transfer roll 24 for transferring the toner image developed by the developing unit to a sheet, and a toner remaining on the surface of the photosensitive drum 22 without being transferred to the sheet. A drum cleaner (not shown) to be removed and a static eliminator (not shown) to remove the surface of the photosensitive drum 22 are sequentially arranged in the rotation direction of the photosensitive drum 22.

  The photoconductive drum 22 and the transfer roll 24 are arranged to face each other via the second paper transport path R2. The photosensitive drum 22 and the transfer roll 24 are in contact with each other at a predetermined pressure when the sheet passes through at least the opposing portion. Then, the sheet fed by the resist roll 10 passes through a facing portion between the photoconductive drum 22 and the transfer roll 24 which are in contact with each other with a predetermined pressure. At this time, the transfer roller 24 applies a charge having a polarity opposite to that of the toner to the sheet, whereby the toner image is transferred from the photosensitive drum 22 to the sheet. Therefore, the facing portion between the photosensitive drum 22 and the transfer roll 24 corresponds to the image transfer portion.

  The vacuum transport unit 25 includes an endless transport belt 26 and two rolls 27 and 28 that support the transport bell 26. The vacuum conveyance unit 25 places a sheet on the conveyance belt 26 and sucks the lower surface of the sheet (the surface opposite to the surface on which the toner image is transferred) by a vacuum method, and the sheet is conveyed according to the traveling of the conveyance belt 26. It is to be transported.

  A fixing device 29 is disposed on the downstream side of the vacuum transport unit 25. The fixing device 29 fixes the toner image transferred onto the paper by the image transfer unit on the paper surface of the paper by a heating and pressurizing method. The heating roller 30 is heated to a predetermined temperature (fixing temperature) by a heater or the like, A pressure roll 31 that contacts the heating roll 30 at a predetermined pressure is provided. The fixing device 29 constitutes an image forming unit together with the above-described photosensitive drum 22, charger, image writing unit 23, developing device, transfer roll 24, and the like. However, the configuration of the image forming unit is not limited to this, and may be, for example, a configuration using an intermediate transfer body (intermediate transfer belt or the like) or a configuration employing a tandem system in which a plurality of photosensitive drums are arranged.

  The transport roll 11 is disposed on the downstream side of the fixing device 29 on the second paper transport path R2. On the downstream side of the transport roll 11, the third paper transport path R3 branches obliquely downward from the middle of the second paper transport path R2, and a transport switching member (not shown) is provided at this branched portion. The conveyance switching member is configured so that the traveling direction of the sheet conveyed by the conveyance roll 1 is a first direction toward the conveyance roll 12 (a direction along the second sheet conveyance path R2) and a second direction toward the conveyance roll 13. The direction is switched to one of the three directions (the direction of branching to the third paper transport path R3).

  The transport roll 12 is disposed at the end portion of the second paper transport path R2. The transport roll 12 is a roll (hereinafter also referred to as a “discharge roll”) that discharges an image-formed sheet to a sheet discharge storage unit (for example, a discharge tray) (not shown).

  The transport roll 13 transports the paper transported by the transport roll 11 toward the transport roll 14 disposed on the downstream side of the transport roll 13. The transport roll 14 is disposed on the downstream side of the transport roll 13 on the third paper transport path R3. The transport roll 14 is provided so as to be rotatable (forward / reverse) in both directions.

  The transport roll 15 is disposed on the downstream side of the transport roll 14 in the paper transport direction. Similarly to the transport roll 14, the transport roll 15 is provided so as to be rotatable (forward / reverse) in both directions. Each of the transport roll 14 and the transport roll 15 is a roll (hereinafter, also referred to as “reversing roll”) that reverses the paper being transported by the switchback method. The leading edge of the sheet refers to the end of the sheet that is arranged on the sheet conveying path so as to face the downstream side in the sheet conveying direction. The rear end of the paper refers to the end of the paper that is arranged on the paper transport path so as to face the upstream side in the paper transport direction.

  The transport rolls 16 to 19 are arranged in order from the upstream side to the downstream side in the paper transport direction. That is, in the fifth paper transport path R5, the transport roll 17 is disposed on the downstream side of the transport roll 16, the transport roll 18 is disposed on the downstream side of the transport roll 17, and the transport roll 19 is on the downstream side of the transport roll 18. Has been placed.

  Next, the operation (image forming operation) of the image forming apparatus according to the embodiment of the present invention will be described. First, when starting an image forming operation, a sheet to be subjected to image formation is fed from a sheet container designated by a user or automatically selected sheet container. For example, assuming that the user-specified paper storage unit or the automatically selected paper storage unit is the upper paper storage unit 1, the paper storage unit 1 can store the paper by rotating the calling roll 3 and the delivery roll 4 corresponding to the paper storage unit 1. The sheet is sent out from the section 1 to the first sheet conveyance path R1.

  At this time, when the number of print pages specified by the user is multiple pages or the number of print copies specified by the user is multiple copies, and a plurality of sheets are continuously fed from the sheet storage unit 1 The paper is fed with a predetermined interval (hereinafter referred to as “paper feeding interval”) between the preceding paper and the succeeding paper adjacent in the paper conveyance direction.

  For example, a paper detection sensor is provided in the vicinity (downstream side) of the delivery roll 4 so that the trailing edge of the paper conveyed downstream in the paper conveyance direction by the rotation of the delivery roll 4 or the conveyance roll 8 is the paper feeding interval. When the paper roll passes through the detection position of the paper detection sensor (the paper detection sensor is turned off), the rotation of the feed roll 4 is stopped, and then, when the rotation of the feed roll 4 is resumed to feed the next paper, the feed roll 4 This corresponds to the time interval from when the rotation of the motor is stopped until it is restarted. Therefore, if the time interval from when the rotation of the feed roll 4 is stopped to when it is restarted is increased, the paper feed interval (inter-paper distance) is increased accordingly. Further, if the time interval from when the rotation of the feed roll 4 is stopped to when it is restarted is shortened, the paper feed interval (inter-paper distance) is shortened accordingly.

  Thus, the sheet fed from the sheet storage unit 1 is transported to the downstream side in the sheet transport direction by the rotation of the transport roll 8 and sent to the pre-registration roll 9. Next, the sheet is fed into the registration roll 10 according to the rotation of the pre-registration roll 9. At this time, the posture correction unit 20 corrects the posture of the paper by abutting against the resist roll 10. The registration roll 10 is brought into a rotation stopped state prior to feeding of the paper by the pre-registration roll 9. Therefore, the leading edge of the sheet fed by the pre-registration roll 9 is abutted against the registration roll 10 in a rotation stopped state. Further, by feeding a predetermined amount of paper by the pre-registration roll 9 in this abutting state, the paper is slacked in a loop shape by the posture correction unit 20 provided on the upstream side of the registration roll 10, that is, the posture of the paper ( In this state, the paper is temporarily stopped.

  On the other hand, on the downstream side of the resist roll 10, the photosensitive drum 22 rotates at a constant speed, and an electrostatic latent image is written on the surface of the photosensitive drum 22 by the image writing unit 23 during this rotation. The electrostatic latent image thus written on the surface of the photosensitive drum 22 is developed into a toner image by a developing device (not shown) and sent to the image transfer unit.

  On the other hand, the registration roll 10 starts rotating at a predetermined timing so that the paper reaches the image transfer unit at the timing when the toner image reaches the image transfer unit. As a result, the sheet is fed to the image transfer unit according to the rotation of the registration roll 10. In the image transfer section, the paper moves so as to pass through the facing portion (contact portion) of the photosensitive drum 22 and the transfer roll 24, and the transfer roll 24 imparts a charge having a reverse polarity to the toner to the paper. As a result, the toner image on the photosensitive drum 22 is transferred to the first surface of the paper.

  Thereafter, the sheet is sent to the fixing device 29 by the vacuum conveyance unit 25. The paper sent to the fixing device 29 moves so as to pass between the heating roll 30 and the pressure roll 31 (contact portion), and the paper is applied by the heating action and pressure action applied by the rolls 30 and 31. A toner image is fixed on the first side of the sheet. Next, the paper sent out from the fixing device 29 is sent from the transport roll 11 to the discharge roll 12 along the second paper transport path R2, and then discharged to the paper discharge storage portion (not shown) by the discharge roll 12. Is done. The above operation is applied in single-sided image forming processing for forming an image on one side of a sheet.

  In the double-sided image forming process for forming images on both sides of a sheet, the sheet conveyed by the conveying roll 11 is guided from the second sheet conveying path R2 to the third sheet conveying path R3 by a conveyance switching member (not shown). And fed into the transport roll 13. Next, the sheet is sent to the reverse roll 14 by the transport roll 13 and further sent to the reverse roll 15 by the normal rotation of the reverse roll 14. Next, the sheet is taken into the fourth sheet conveyance path R <b> 4 by the forward rotation of the reverse roll 15. When the trailing edge of the sheet passes the branch position to the fifth sheet conveyance path R5, the reversing roll 15 stops rotating in a state where the sheet is sandwiched, and then starts reverse rotation. Thus, the sheet is fed from the fourth sheet transport path R4 to the fifth sheet transport path R5 according to the reverse rotation of the reversing roll 15.

  Thereafter, the sheet is conveyed from the upstream side to the downstream side along the fifth sheet conveyance path R5 according to the rotation of the plurality of conveyance rolls 16 to 19 provided in the fifth sheet conveyance path R5. Then, at the most downstream portion of the fifth paper transport path R5, the paper is transported by the transport roll 19 so as to merge from the terminal end of the fifth paper transport path R5 to the start end of the second paper transport path R2. . As a result, the sheet is again fed into the pre-registration roll 9 on the second sheet conveyance path R2. Thereafter, an image is formed (transferred and fixed) on the second surface of the sheet in the same procedure as described above.

  Also, the paper on which image formation on the second surface has been completed is sent from the transport roll 11 to the discharge roll 12 along the second paper transport path R2, and then the paper discharge accommodating portion (not shown) by the discharge roll 12. ).

  On the other hand, when the paper on which image formation on the second surface has been completed is reversed and discharged, the paper conveyed by the discharge roll 11 is transferred from the second paper conveyance path R2 by the conveyance switching member (not shown). 3 is guided to the third sheet transport path R3 and sent to the transport roll 13. Next, the paper is sent to the reverse roll 14 by the transport roll 13, and further sent downstream by the reverse roll 14 in the paper transport direction. When the trailing edge of the sheet passes through the branch position to the sixth sheet conveyance path R6, the reversing roll 14 stops rotating with the sheet sandwiched therebetween, and then starts reverse rotation. As a result, the paper is fed from the third paper transport path R3 to the sixth paper transport path R6 according to the reverse rotation of the reversing roll 14. Next, the sheet is fed from the sixth sheet conveyance path R6 to the discharge roll 12 so as to join the second sheet conveyance path R2, and then discharged to a sheet discharge container (not shown) by the discharge roll 12. The

  As an image forming mode for forming an image on a sheet in such a procedure, the image forming apparatus according to the embodiment of the present invention includes two image forming modes having the same image forming speed and different paper feed intervals. One is a first image forming mode in which image forming productivity is emphasized, and the other is a second image forming mode in which noise reduction is emphasized.

  The productivity of image formation is defined by the number of processed sheets per unit time (sheets / minute). For this reason, the productivity of image formation depends on the paper feed interval when the paper to be image-formed is fed. That is, if the paper feed interval is narrowed, the number of processed sheets per unit time increases accordingly, and the productivity of image formation increases. Further, if the paper feed interval is widened, the number of processed sheets per unit time is reduced by that amount, so that the image forming productivity is lowered. Accordingly, in the first image forming mode in which productivity is emphasized, paper is fed at a first paper feeding interval that is as narrow as possible within the range allowed for control, and in the second image forming mode in which low noise is emphasized, the first paper feeding is performed. Paper is fed at a second paper feed interval that is wider than the interval.

  However, the image forming speed is common (same speed) in the first image forming mode and the second image forming mode. In the case of an electrophotographic image forming apparatus, the image forming speed is a processing speed for transferring an image onto a sheet. More specifically, for example, when a toner image is transferred from the photosensitive drum 22 to a sheet as described above. Means the moving speed of the paper (peripheral speed of the photosensitive drum 22) passing through the opposite portion (image transfer portion) between the photosensitive drum 22 and the transfer roll 24. Therefore, the image forming speed in this case corresponds to the rotational speed of the photosensitive drum 22 that rotates at a constant speed. Therefore, the rotational speed of the photosensitive drum 22 does not change regardless of whether the first image forming mode or the second image forming mode is applied.

  However, the first image forming mode and the second image forming mode have different transport conditions (paper transport conditions) applied when transporting the paper on which the image is to be formed. That is, the first transport condition is applied to the first image forming mode, and the second transport condition is applied in principle to the second image forming mode. In the first transport condition, the sheet transport speed is set to be higher than the second transport condition at a stage before the image is transferred to the sheet. In the second conveyance condition, the abutting speed when the leading edge of the sheet is abutted against the registration roll 10 is set to be lower than that in the first conveyance condition. In addition, the second transport condition is set such that the acceleration time and the deceleration time of the paper transport motor are longer than the first transport condition.

  FIG. 2 shows the speed profile of the paper transport motor (stepping motor). In FIG. 2, (A) is the speed profile of the paper transport motor based on the first transport condition, and (B) is the paper based on the second transport condition. The speed profile of a conveyance motor is shown. In FIG. 2, the vertical axis represents the drive frequency (pps: pulses / second) of the paper transport motor, and the horizontal axis represents time (T). The sheet conveyance speed increases as the drive frequency of the sheet conveyance motor increases.

  Among the timings Tm1 to Tm8 attached on the time axis, the paper transport motor driven during the period of timings Tm1 to Tm5 serves as a driving source for rotating the pre-registration roll 9, and is driven during the period of timings Tm6 to Tm8. The sheet transport motor is a drive source for rotating the registration roll 10. In the following description, the paper conveyance motor that is the drive source of the pre-registration roll 9 is referred to as a pre-registration motor, and the paper conveyance motor that is the drive source of the registration roll 10 is referred to as a registration motor.

  On the time axis, the timing Tm1 indicates the timing at which the rotation of the pre-registration roll 9 is started as shown in FIG. 3A, and the timing Tm2 is the paper on the pre-registration roll 9 as shown in FIG. The timing of conveying at a constant speed is shown. Further, the timing Tm3 indicates the timing at which the abutting speed starts decreasing as shown in FIG. 4A, and the timing Tm4 indicates the timing at which the leading edge of the sheet hits the registration roll 10 as shown in FIG. 4B. Is shown.

  The timing Tm5 indicates the timing when the paper loop formation is completed as shown in FIG. 5A, and the timing Tm6 indicates the timing when the rotation of the registration roll 9 is started as shown in FIG. 5B. ing. Timing Tm7 indicates the timing at which the sheet is conveyed at a constant speed by the registration roll 10 as shown in FIG. 6A, and timing Tm8 indicates the rotation of the registration roll 10 as shown in FIG. 6B. The timing to stop is shown.

  As can be seen from the figure, in the first transport condition, the acceleration time of the pre-registration motor is T1 (msec), the deceleration time of the pre-registration motor is T2 + T3 (msec), the acceleration time of the registration motor is T4 (msec), The motor deceleration time is set to T5 (msec). In the first transport condition, the driving frequency of the pre-registration motor at timing Tm2 is P1 (pps), the driving frequency of the pre-registration motor at timing Tm4 is P2 (pps), and the driving frequency of the registration motor at timing Tm7 is P3. (pps) is set.

  On the other hand, under the second transport condition, the acceleration time of the pre-registration motor is T6 (msec), the deceleration time of the pre-registration motor is T7 + T8 (msec), the acceleration time of the registration motor is T9 (msec), and the deceleration time of the registration motor Is set to T10 (msec). In the second transport condition, the driving frequency of the pre-registration motor at timing Tm2 is P4 (pps), the driving frequency of the pre-registration motor at timing Tm4 is P5 (pps), and the driving frequency of the registration motor at timing Tm7 is P6. (pps) is set.

  Here, when the first transport condition and the second transport condition are relatively compared, the acceleration time of the pre-registration motor is a relationship of T1 <T6, and the deceleration time of the pre-registration motor is a relationship of T2 <T7 and T3 <T8. The acceleration time of the registration motor is set to a relationship of T4 <T9, and the deceleration time of the registration motor is set to a relationship of T5 <T10. Further, the driving frequency of the pre-registration motor at timing Tm2 is set to a relationship of P1> P4, the driving frequency of the pre-registration motor at timing Tm4 is set to a relationship of P2> P5, and the driving frequency of the registration motor at timing Tm7 is set to a relationship of P3> P6. Has been.

  FIG. 7 is a block diagram showing a configuration example of a control system of the image forming apparatus according to the embodiment of the present invention. The operation panel 32 serves as a user interface for a user who uses the image forming apparatus to input various information and display various information to the user. The operation panel 32 includes, for example, an input unit having various buttons, switches, keys, and the like, and a display unit including a liquid crystal display with a touch panel.

  The image forming mode selection unit 33 selects an image forming mode applied to the above-described image forming operation. The image forming mode selection unit 33 selects one of the first image forming mode and the second image forming mode described above.

  The image formation control unit 34 controls the image formation operation according to the image formation mode selected by the image formation mode selection unit 33. The image forming operation includes a photosensitive drum 22, a charger (not shown), an image writing unit 23, a developing device (not shown), a transfer roll 24, a drum cleaner (not shown), a static eliminator (not shown), and fixing. An image forming operation by the device 29 or the like.

  The paper transport control unit 35 controls the paper transport operation in accordance with the image forming mode selected by the image forming mode selection unit 33. The paper transport operation refers to a paper transport operation by the paper feed rolls 3 to 6, the transport rolls 7 to 19, the vacuum transport unit 25, and the like.

  FIG. 8 is a flowchart illustrating an example of an image forming job performed by the image forming apparatus according to the embodiment of the present invention.

  First, when an image forming job of the image forming apparatus is started, for example, when a user presses a start button provided on the operation panel 32, the image forming mode selection unit 33 is applied to the current image forming job. An image forming mode is selected (step S1). In this case, the image formation mode selection unit 33 may select an image formation mode instructed by the user in advance using the operation panel 32, or image formation according to the image formation conditions set by the user using the operation panel 32. A mode may be selected.

  In the former case, when a selection screen for selecting an image formation mode is displayed on the operation panel 32, the image formation mode selection unit 33 selects an image formation mode instructed by the user on the selection screen. That is, when the user has instructed the selection of the first image forming mode on the selection screen, the image forming mode selection unit 33 selects the first image forming mode in accordance with this instruction, and the user on the selection screen Is instructing the selection of the second image forming mode, the image forming mode selecting unit 33 selects the second image forming mode in accordance with this instruction.

  In the latter case, when the setting screen for setting the image forming conditions is displayed on the operation panel 32, the image forming mode selection unit 33 performs the first image forming according to the image forming conditions set by the user on the setting screen. The mode or the second image forming mode is selected. For example, if the user selects the paper type as one of the image forming conditions, the first image forming mode is selected if the paper type is thin paper or plain paper, and the first type is selected if the paper type is thick paper. 2 image forming mode is selected. The first image forming mode is selected if the paper length in the paper transport direction is shorter than the predetermined length, and the second image forming mode is selected if the paper length is longer than the predetermined length.

  Next, if the image formation mode selected by the image formation mode selection unit 33 in step S1 is the first image formation mode, the process proceeds from step S2 to step S3. In step S3, the paper transport control unit 35 controls the paper transport operation so that the paper is fed at the first paper feed interval. Next, in step S4, the sheet conveyance control unit 35 controls the sheet conveyance operation so that all sheets fed at the first sheet feeding interval are conveyed under the first conveyance condition.

  If the image forming mode selected by the image forming mode selection unit 33 in step S1 is the second image forming mode, the process proceeds from step S2 to step S5. In step S5, the sheet conveyance control unit 35 controls the sheet conveyance operation so that the sheet is fed at the second sheet feeding interval.

  Next, in step S6, it is confirmed whether or not an instruction to prioritize the first sheet is received. The instruction to give priority to the first sheet is issued by the user using the operation panel 32 before starting the image forming job.

  If the user does not receive an instruction to give priority to the first sheet early, the sheet conveyance control unit 35 causes the sheet conveyance control unit 35 to convey all sheets fed at the second sheet feeding interval under the second conveyance condition. Is controlled (step S7). Further, the sheet conveyance control unit 35 controls the sheet conveyance operation so that the loop amount of the sheet abutted against the registration roll 10 by the posture correction unit 20 is larger than that in the first image forming mode. The paper loop amount is determined by the paper feed amount from when the leading edge of the paper hits the registration roll 10 until the rotation of the pre-registration roll 9 is stopped. Therefore, this feed amount is larger than that in the first image forming mode. The sheet conveyance control unit 35 controls the rotation operation of the pre-registration roll 9 so that the number of image forming modes of 2 is increased.

  By the way, in the second image forming mode, paper is fed at a wider interval than in the first image forming mode, so that there is a wider interval (a gap between the papers) between the preceding paper and the succeeding paper in that direction. Secured. Therefore, even if the abutting speed on the registration roll 10 is lower than that in the first image forming mode or the acceleration time and the deceleration time of the paper conveyance motor are set longer than the first conveyance condition, the sheet conveyance is performed. Only the interval between the preceding sheet and the succeeding sheet is temporarily reduced, and no control problem occurs.

  When receiving an instruction to give priority to the first sheet early from the user, the first sheet is transported under the first transport condition, and the second and subsequent sheets are transported under the second transport condition. The paper transport control unit 35 controls the paper transport operation (steps S8 and S9). Further, the sheet conveyance control unit 35 controls the sheet conveyance operation so that the loop amount of the first sheet is the same as that in the first image forming mode, and the second and subsequent sheets are controlled. The paper transport operation is controlled so that the paper loop amount is larger than that in the first image forming mode.

  In the above-described embodiment, the posture correction unit 20 causes the leading edge of the sheet to abut against the registration roll 10. However, the present invention is not limited to this, and for example, a solenoid is provided in front of the registration roll 10 (upstream side). A gate member (not shown) that protrudes or retreats from the paper conveyance path by driving such as is provided, and this gate member is projected on the paper conveyance path so that the leading edge of the paper abuts against the gate member It is good.

  The present invention can be widely applied to image forming apparatuses such as copying machines, printers, facsimile machines, and multifunction machines.

1 is a schematic diagram illustrating a configuration example of an image forming apparatus to which the present invention is applied. FIG. 6 is a diagram illustrating a speed profile of a paper transport motor. It is a state transition diagram (the 1) when a paper passes a posture correction part. It is a state transition diagram (the 2) when a paper passes a posture correction part. FIG. 10 is a state transition diagram (part 3) when a sheet passes through the posture correction unit. FIG. 11 is a state transition diagram (part 4) when a sheet passes through the posture correction unit. FIG. 2 is a block diagram illustrating a configuration example of a control system of the image forming apparatus according to the embodiment of the present invention. 6 is a flowchart illustrating an example of an image forming job performed by the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,2 ... Paper accommodating part, 3,5 ... Call roll, 4,6 ... Sending roll, 7-19 ... Conveyance roll, 20 ... Attitude correction part, 22 ... Photoconductor drum, 23 ... Image writing part, 24 ... Transfer Roll, 29 ... Fixer, 32 ... Operation panel, 33 ... Image formation mode selection section, 34 ... Image formation control section, 35 ... Paper transport control section, R1-R6 ... Paper transport path

Claims (5)

A first image forming mode for feeding paper at a first paper feed interval and forming an image on the paper fed at the first paper feed interval;
Paper is fed at a second paper feed interval that is wider than the first paper feed interval, and is fed to the paper fed at the second paper feed interval at the same image forming speed as in the first image forming mode. A second image forming mode for forming an image;
Selecting means for selecting either the first image forming mode or the second image forming mode in accordance with a user operation;
A posture correction unit that corrects the posture of the paper by slacking the paper into a loop shape by hitting the tip of the paper against the reference member on the paper conveyance path;
When the second image forming mode is selected by the selection unit, the abutting speed when the leading edge of the sheet is abutted against the reference member is controlled to be lower than that in the first image forming mode. And an image forming apparatus. When the first image forming mode is selected by the selection unit, the control unit includes a minimum first supply that does not contact a sheet to be fed and a succeeding sheet to be fed next to the sheet. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled to feed a sheet at a sheet interval . When the second image forming mode is selected by the selecting unit and an image formation is performed in response to an instruction to give priority to the first sheet fast-forwarding by the user, the control unit sets the first sheet as the first sheet. The second and subsequent sheets are transported under the first transport condition, and the abutting speed is lower than the first transport condition, and the acceleration time and the deceleration time of the paper transport motor are longer than the first transport condition. the image forming apparatus according to claim 1 or 2, characterized in that control to convey in the second transport conditions. When the second image forming mode is selected by the selecting unit and the image forming is performed, the control unit has a larger loop amount of the paper abutted against the reference member than the first image forming mode. The image forming apparatus according to claim 1 , wherein the image forming apparatus is controlled to be When the second image forming mode is selected by the selecting unit and the image forming is performed, the control unit causes the acceleration time and the deceleration time of the paper transport motor to be longer than those in the first image forming mode. The image forming apparatus according to claim 1 , wherein the image forming apparatus is controlled as follows.

Images