JP2010126262A - Paper conveying device and image forming device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress speed fluctuation of paper caused by speed controls (speed increases) for a pair of register rolls prevented from being in time for load fluctuation according to stopping of driving of a pair of feed rolls. <P>SOLUTION: A conveying device includes a paper storing container for storing recording paper, a pair of separation rolls for conveying the recording paper delivered from the paper storing container in a state separated one sheet by one sheet and stopping the conveyance by timing fixed in advance, a pair of register rolls for conveying the recording paper to a downstream side of a paper conveying direction in a registered state of each distal end of the recording paper conveyed in the state separated one sheet by one sheet by the pair of the separation rolls, a driving means for rotating and driving the pair of separation rolls and the pair of register rolls by different timing, and a speed control means for increasing driving speed of the pair of register rolls by the driving means from a time before the pair of separation rolls are stopped. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sheet conveying device and an image forming apparatus using the same.

Japanese Patent No. 3881822 JP 2002-104695 A JP 2002-326741 A JP 2005-330016 A

  Conventional paper transport devices and image forming apparatuses using the same are disclosed in, for example, Japanese Patent No. 3881822, Japanese Patent Application Laid-Open No. 2002-104695, Japanese Patent Application Laid-Open No. 2002-326741, Japanese Patent Application Laid-Open No. 2005-330016, and the like. What has been disclosed has already been proposed.

The image forming apparatus according to the above-mentioned Japanese Patent No. 3881822 discloses a paper feeding unit that stores paper,
A paper feeding unit that is driven to feed the paper in the paper feeding unit to the image forming unit;
Including a registration roller disposed between the image forming unit and the paper feed roller, and a registration unit that is driven after the image formation of the image forming unit is started,
The paper feeding means is driven until a predetermined time determined according to the length of the paper to be fed elapses after the registration means is driven, and stops driving when the predetermined time elapses. Thus, drive control is performed so as to stop when the trailing edge of the paper to be fed reaches the paper feeding means.

  In addition, an image forming apparatus according to Japanese Patent Application Laid-Open No. 2002-104695 includes an image forming unit that forms an image, a transfer unit that transfers an image from the image forming unit to a sheet, and an upstream of the transfer unit in the sheet conveyance direction. The image forming apparatus includes a registration roller disposed on a side and capable of controlling a sheet conveyance speed, and a conveyance unit disposed on an upstream side of the registration roller in a sheet conveyance direction. The sheet is conveyed at a speed higher than the image forming speed for conveying while forming an image on the sheet, and the registration roller is decelerated to the image forming speed before the sheet reaches the transfer unit. is there.

  Further, an image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 2002-326741 includes a plurality of sheet conveying mechanisms on a sheet conveying path, and an image forming apparatus that forms an image on a sheet conveyed by the sheet conveying mechanism. A first sheet conveyance mechanism that can freely change the speed, a second sheet conveyance mechanism that is provided downstream of the first sheet conveyance mechanism, and conveys the sheet at a constant conveyance speed, and the first sheet conveyance mechanism. A sensor for detecting the leading edge and the trailing edge of the sheet being conveyed, a measuring means for measuring a time interval between sheets conveyed continuously based on the detection result of the sensor, and the measurement And an interval adjusting means for adjusting the sheet interval by controlling the conveying speed of the first sheet conveying mechanism based on the time interval measured by the means. It is.

In addition, the paper transport device according to the above-mentioned Japanese Patent Application Laid-Open No. 2005-330016 corrects the skew of the paper by a feed roll pair that transports the paper fed from the paper feed tray every leaf and the abutting of the paper. A pair of registration rolls that operate at a predetermined timing and sandwich and convey the sheet to the subsequent stage, and the feed roll pair and the registration roll pair are arranged side by side on the sheet conveyance path. Because
Corresponding to the timing when driving of the pair of feed rolls for conveying the paper stops, speed control means for performing speed control on the pair of registration rolls so as not to transmit the load fluctuation due to the stop to the paper. It is composed.

  By the way, the problem to be solved by the present invention is that the speed control (acceleration) with respect to the pair of registration rolls is particularly effective in stopping the driving of the pair of feed rolls, as compared with the technique disclosed in the above Japanese Patent Laid-Open No. It is an object of the present invention to provide a paper transport device capable of suppressing paper speed fluctuation caused by not being able to meet the accompanying load fluctuation and an image forming apparatus using the same.

That is, the invention described in claim 1 includes a paper container that stores recording paper,
While conveying the recording paper sent out from the paper storage container one by one, a pair of rolling rolls that stops at a predetermined timing;
A pair of alignment rolls that conveys the leading edge of the recording sheet conveyed in a state of being rolled one by one by the pair of rolling rolls to the downstream side in the sheet conveying direction in an aligned state;
Drive means for rotationally driving the pair of rolling rolls and the pair of matching rolls at different timings;
A sheet transporting apparatus comprising: a speed control unit configured to increase the driving speed of the alignment roll pair by the driving unit before the stopping roll pair is stopped.

  Further, in the invention described in claim 2, the speed control means sets the driving speed of the aligning roll pair by the driving means to a steady speed before the trailing edge of the paper passes through the pair of rolling rolls. The sheet conveying device according to claim 1, wherein

  Furthermore, the invention described in claim 3 is characterized in that the speed control means controls the drive speed of the alignment roll pair by the drive means based on a predetermined speed profile. The sheet conveying apparatus according to 1 or 2.

  Further, in the invention described in claim 4, the speed control unit is configured to respond to a time from when the paper roll pair is stopped until the trailing edge of the paper passes through the paper roll pair. The sheet conveying apparatus according to claim 3, wherein the speed profile is changed so that the speed increase amounts are equal.

  Furthermore, the invention described in claim 5 is characterized in that, when the recording paper is thick paper, the maximum value of the speed profile to be accelerated is set smaller than that of plain paper. The sheet conveying device according to claim 1.

According to a sixth aspect of the present invention, there is provided a paper storage container that stores recording paper;
While conveying the recording paper sent out from the paper storage container one by one, a pair of rolling rolls that stops at a predetermined timing;
A pair of alignment rolls that conveys the leading edge of the recording sheet conveyed in a state of being rolled one by one by the pair of rolling rolls to the downstream side in the sheet conveying direction in an aligned state;
Drive means for rotationally driving the pair of rolling rolls and the pair of matching rolls at different timings;
Speed control means for increasing the driving speed of the alignment roll pair by the driving means from before the stopping roll pair is stopped;
An image forming apparatus comprising: an image forming unit that forms an image on a recording sheet conveyed by the alignment roll pair.

  According to the invention described in claim 1, in order to suppress the speed fluctuation of the alignment roll pair due to the stopping of the winding roll pair, the speed control (acceleration) for the alignment roll pair is: It is possible to suppress fluctuations in the speed of the paper due to not being able to meet the load fluctuations associated with the stoppage of the driving of the winding roll pair.

  According to the second aspect of the present invention, it is possible to avoid the influence of increasing the speed of the aligning roll pair from appearing after the trailing edge of the sheet has passed through the separating roll pair. it can.

  Furthermore, according to the invention described in claim 3, it is possible to easily control the driving speed of the alignment roll pair.

  According to the fourth aspect of the present invention, the speed increase amount can be controlled in accordance with the sheet conveyance speed, and the adverse effect of the speed increase of the alignment roll pair can be suppressed.

  Furthermore, according to the fifth aspect of the present invention, when the paper is a thick paper, it is possible to prevent the paper transport speed by the alignment roll pair from becoming too fast.

  According to the invention described in claim 6, in order to suppress the speed fluctuation of the aligning roll pair due to the stopping of the separating roll pair, the speed control (acceleration) for the aligning roll pair is performed. However, it is possible to suppress the speed fluctuation of the sheet due to not being able to keep up with the load fluctuation accompanying the stoppage of the driving of the pair of winding rolls, and it is possible to improve the image quality.

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

Embodiment 1
FIG. 2 shows a tandem type full-color printer as an image forming apparatus to which the paper conveying apparatus according to Embodiment 1 of the present invention is applied.

  In FIG. 2, reference numeral 1 denotes a main body of a tandem-type full-color printer as an image forming apparatus main body. Inside the printer main body 1, an image forming unit 2 is arranged at the upper and lower sides of the printer main body 1. It is arrange | positioned up and down along the perpendicular direction which is a direction. Further, inside the full color printer main body 1, a recording medium onto which toner images of a plurality of colors formed by the image forming unit 2 are transferred is adsorbed to one side (right side in the illustrated example) of the image forming unit 2. The control unit 4 having a control circuit and the like is provided on the other side (left side in the illustrated example) of the image forming unit 2. Power supply circuit units 5 each including a high-voltage power supply circuit and the like are disposed obliquely below 2. A paper feeding device 6 for feeding recording paper 37 or the like as a recording medium is disposed at the bottom of the full color printer main body 1.

  The image forming unit 2 includes four process cartridges 7Y, 7M, 7C, and 7K that form toner images of yellow (Y), magenta (M), cyan (C), and black (K) in order from the bottom. These four process cartridges 7Y, 7M, 7C, and 7K are arranged in parallel at regular intervals along the vertical direction.

  These four process cartridges 7Y, 7M, 7C, and 7K are configured in the same manner except for the color of the image to be formed. As shown in FIG. 2, at a predetermined rotational speed along the direction of the arrow. The surface of the photosensitive drum 8 is rotated by a photosensitive drum 8 as an image bearing member that is driven to rotate, a charging roll 9 for primary charging that uniformly charges the surface of the photosensitive drum 8, and an image exposure device 21 described later. An image exposure passage 10 for performing image exposure corresponding to each color to form an electrostatic latent image, and developing means for developing the electrostatic latent image formed on the photosensitive drum 8 with a corresponding color toner. Developing device 11 and a cleaning device 12 for cleaning residual toner remaining on the photosensitive drum 8.

  As shown in FIG. 2, the image exposure device 21 is configured in common to four process cartridges 7Y, 7M, 7C, and 7K of yellow (Y), magenta (M), cyan (C), and black (K). Four semiconductor lasers 14 that emit laser beams LB based on image data of each color of yellow (Y), magenta (M), cyan (C), and black (K), and the four semiconductor lasers 14 A collimator lens 15 that collimates the four laser beams LB emitted from each other, a reflection mirror 16 that reflects the laser beam LB emitted from the semiconductor laser 14, and a laser beam LB reflected by the reflection mirror 16. The rotary polygon mirror 17 that deflects and scans the laser beam LB reflected by the rotary polygon mirror 17 and the image forming units 7Y, 7M, 7C, and 7K. A plurality of reflecting mirrors 18, 19 for scanning exposure on the photosensitive drum 8, and is configured with a transparent glass 20 that transmits the laser beam LB. The reflection mirrors 18 and 19 have a function of changing the focal length (f) according to the deflection angle (θ) of the laser beam LB.

  On the other hand, as shown in FIG. 2, a control unit 4 is disposed inside the full-color printer main body 1, and the control unit 4 includes, for example, an image for performing predetermined image processing on image data. A processing device 30 is provided. The image processing apparatus 30 sequentially outputs image data of each color of yellow (Y), magenta (M), cyan (C), and black (K) to the image exposure apparatus 10, and the image exposure apparatus 10 outputs the image data. The four laser beams LB emitted according to the above are scanned and exposed on the respective photosensitive drums 8Y, 8M, 8C, and 8K to form electrostatic latent images. The electrostatic latent images formed on the photosensitive drums 8Y, 8M, 8C, and 8K are respectively yellow (Y), magenta (M), cyan (C), and cyan by developing devices 11Y, 11M, 11C, and 11K. The toner image is developed as a black (K) color toner image.

  Further, as shown in FIG. 2, the paper transport belt unit 3 is provided with a paper transport belt 31 that circulates and moves without a break as an endless belt, and the paper transport belt 31 includes each process cartridge 7Y, Recording paper 37 as a recording medium to which toner images of each color of yellow (Y), magenta (M), cyan (C), and black (K) formed by 7M, 7C, and 7K are electrostatically adsorbed It is comprised so that it may convey in the state which carried out. The paper transport belt unit 3 is integrally formed with a transport roll 49 provided in a reversing paper transport path 50 (to be described later). When a jam or the like of the recording paper 37 occurs, the printer body By opening the front cover 32, it is possible to move to a retracted position rotated clockwise with respect to the printer body 1.

  As shown in FIG. 2, the paper transport belt 31 includes a drive roll 33, a follower roll 34, a first idler roll 35, and a second idler, which are arranged as a stretch roll arranged vertically along the vertical direction. It is stretched between the roll 36 with a predetermined tension. For example, the drive roll 33 is rotationally driven through a gear or the like by a drive motor (not shown) and circulates in a clockwise direction at a predetermined speed. Is configured to do. For example, the distance between the driving roll 33 and the driven roll 34 is set to be substantially equal to the length of the A3 size recording sheet 37, but is not limited thereto, and the distance between the driving roll 33 and the driven roll 34 is not limited thereto. Of course, it may be set arbitrarily. As the paper transport belt 31, for example, a flexible synthetic resin film such as polyimide or polyimide amide formed in an endless belt shape is used.

  Further, an image quality adjustment pattern is transferred onto the paper transport belt 31 at a predetermined timing, and yellow (Y), magenta (M), cyan (C) of the paper transport belt 31 is configured. ), The non-transfer running area 31b on the opposite side of the running area 31a where the black (K) process cartridges 7Y, 7M, 7C, and 7K are disposed is used for adjusting the image quality transferred onto the paper conveying belt 31. A pattern detection device 38 for optically detecting the pattern is disposed, and the toner constituting the image quality adjustment pattern on the paper transport belt 31 is disposed downstream of the pattern detection device 38 in the belt movement direction. A cleaning device 40 having a cleaning blade 39 for removing foreign substances such as the like is disposed.

  Further, on the surface of the driven roll 34, as shown in FIG. 2, a suction roll 41 for electrostatically attracting the recording paper 37 to the surface of the paper transport belt 31 is applied via the paper transport belt 31. It arrange | positions so that it may contact | connect. For example, the suction roll 41 is configured by covering the surface of a metal core bar with a conductive rubber similarly to the charging roll 9 of the process cartridges 7Y, 7M, 7C, and 7K. A bias voltage for adsorption is applied. The suction roll 41 is configured to electrostatically charge the recording paper 37 sent from the paper feeding device 6 and suck it onto the surface of the paper transport belt 31.

  Yellow (Y), magenta (M), cyan (C), and black (K) toners formed on the photosensitive drums 8Y, 8M, 8C, and 8K of the process cartridges 7Y, 7M, 7C, and 7K. As shown in FIG. 2, the images are transferred onto the recording paper 37 conveyed while being attracted to the surface of the paper conveying belt 31 in a superimposed manner by the transfer rolls 42Y, 42M, 42C, and 42K. Is done. The transfer rolls 42Y, 42M, 42C, and 42K are integrally attached to the paper transport belt unit 3 side.

  As shown in FIG. 2, the recording sheet 37 is fed from the sheet feeding device 6 disposed at the bottom of the printer main body 1 via the sheet conveying device according to the present embodiment. The paper feeding device 6 includes a paper tray 43 that stores recording paper 37 of a desired size and material.

  As shown in FIG. 1, the paper transport device according to this embodiment feeds a recording paper 37 of a desired size and material from a paper tray 43, and the paper tray 43 by the feeding roll 44. The recording paper 37 fed from the paper is conveyed one by one by the supply roll 45 and the separation roll 46 which are conveyed separately in a separated state, and the supply roll 45 and the separation roll 46 are conveyed one by one. The recording sheet 37 is configured to include a registration roll pair 43 that conveys the recording sheet 37 to the surface of the sheet conveying belt 31 at a predetermined timing.

  The recording paper 37 is a sheet-like member, for example, various sizes such as A4 size, A3 size, B5 size and B4 size, and thick paper such as plain paper and coated paper, an OHP sheet, etc. Various materials are used.

  Then, as shown in FIG. 2, the recording paper 37 on which the toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) are transferred in a multiple manner are recorded on the recording paper 37 itself. After being separated from the paper conveyance belt 31 by the rigidity (so-called stiffness), it is conveyed to the fixing device 47, and the toner image of each color is fixed on the recording paper 37 by heat and pressure by the fixing device 47. The fixing device 47 includes a heating roll 48 and a pressure belt 49 or a pressure roll that is in pressure contact with the heating roll 48, and is transferred onto the recording paper 37 by the heating roll 48 and the pressure belt 49. An unfixed toner image is configured to be fixed on the recording paper 37. Thereafter, the recording paper 37 on which the toner images of the respective colors are fixed is discharged from the discharge port 53 by the discharge roll 52 onto the discharge tray 54 provided at the upper part of the full-color printer main body 1 with the print surface facing down. The printing operation is finished.

  The full-color printer is capable of printing not only full-color images but also desired color images such as monochrome, and yellow (Y) and magenta (M) depending on the color of the image to be printed. , Cyan (C), black (K), or some of the process cartridges 7Y, 7M, 7C, and 7K form a toner image.

  Further, when images are formed on both sides of the recording paper 37 by the full-color printer, the recording paper 37 on which the image is fixed on one side by the fixing device 44 is not directly discharged onto the discharge tray 46 by the discharge roll 45. In the state where the trailing edge of the recording sheet 37 is held by the discharge roll 52, the discharge roll 52 is reversed, and the transfer path of the recording sheet 37 is switched to the upper transfer path 55 by a switching gate (not shown). 1 is conveyed to a reversing paper conveyance path 50 provided with conveyance rolls 56 and 57 provided along one side surface. The recording sheet 37 conveyed to the reversing sheet conveying path 50 is conveyed again to the adsorption position of the sheet conveying belt 31 by the registration roll pair 43 with the front and back sides reversed, and a toner image is formed on the back surface. After the toner image is transferred, the fixing device 47 performs fixing processing with heat and pressure, and the discharge roller 52 discharges the toner onto a discharge tray 54 provided on the upper portion of the printer main body 1.

  In FIG. 2, reference numeral 58 denotes a paper feed roll for feeding a transfer material of a desired size and material from a manual feed tray 59 provided on the side surface of the printer body 1, and reference numeral 60 denotes a paper feed roll 58. Each of the conveyance rolls that convey the paper-recorded recording medium to the registration roll 43 is shown.

  Furthermore, in this embodiment, as shown in FIG. 3, the yellow (Y), magenta (M), cyan (C), and black (K) process cartridges 7Y, 7M, 7C, and 7K are rotationally driven. The upper first unit 121 having the photosensitive drum 8 and the charging roll 9 and the cleaning device 12, and the lower second unit having the developing device 11 for developing the electrostatic latent image formed on the photosensitive drum 8. Unit 122.

  As shown in FIG. 3, the first unit 121 and the second unit 122 are connected to the photosensitive drum 8 and the developing roll 116 via a fulcrum 123 provided at the end opposite to the photosensitive drum 8. Are connected to each other so as to be swingable in the direction in which they are separated from each other, and are provided at both end portions along the axial direction of the photosensitive drum 8 of the first unit 121 and the developing roll 116 of the second unit 122. The urging means 124 such as a coil spring is urged so as to come into contact with the non-tracking roll.

  The process cartridges 7Y, 7M, 7C, and 7K configured as described above are individually provided by opening a front cover 32 that is openable and closable on the front surface of the printer body 1, as shown in FIG. It is configured to be detachable with respect to the printer main body 1, and when the photosensitive drum 8 is deteriorated or when the developer stored in the developing device 11 becomes empty, the process cartridge 7Y, The user can easily perform maintenance by removing it from the printer body 1 every 7M, 7C, and 7K and replacing it with new process cartridges 7Y, 7M, 7C, and 7K.

  Further, in the developer accommodating chamber 13 of the developing device 11 of the process cartridges 7Y, 7M, 7C, and 7K, as shown in FIG. 4, a one-component developer 110 consisting only of toner, or two consisting of toner and carrier. The developer 110 of the component is accommodated, and the developer 110 is agitated in the developer accommodating chamber 13, and is an end portion on the developing device 11 side in the longitudinal direction of the developer accommodating chamber 13. Two film-shaped agitators 112 as a developer agitating member for discharging the developer 110 from the developer discharge port 111 formed at one end of the developer are arranged in parallel.

  As shown in FIGS. 4 and 5, these two film-like agitators 112 discharge the developer 110 from the developer discharge port 111 while stirring the developer 110 stored in the developer storage chamber 13. For this purpose, a synthetic resin film 112b made of a Mylar film or the like is provided so as to protrude toward the outer periphery in the radial direction of the rotating shaft 112a made of synthetic resin. The synthetic resin film 112b is set to have such a length that the tip thereof is in contact with one side surface from the bottom surface of the developer storage chamber 13, and the developer 110 adheres to the bottom surface and one side surface of the developer storage chamber 13. In this way, the developer 110 is scraped into the developer discharge port 111.

  In addition, the developer 110 transports the developer 110 from the developer accommodating chamber 13 to the developing chamber 113 of the developing device 11 between the developer accommodating chamber 13 and the developing chamber 113 communicating with the developer discharging port 111. An agent transport device 130 is provided.

  In this embodiment, a one-component developer 110 made only of toner is accommodated in the developer accommodating chamber 13, and the developer accommodating chamber 13 is a toner accommodating chamber.

  As shown in FIG. 4, an agitation auger 114 that conveys the developer 110 supplied into the developing chamber 113 along the direction of the arrow while being agitated is rotatably disposed in the developing chamber 113. In addition, a supply auger 115 for supplying development to a developing roll 116 as a developer carrying member while agitating and conveying the developer 110 is disposed in parallel with the agitating auger 114. Further, the partition wall 117 provided between the stirring auger 114 and the supply auger 115 has a developer at both end portions along the axial direction of the stirring auger 114 and the supply auger 115 as shown in FIG. Passages 118 and 119 for delivering 110 are provided.

  In the developing device 11, as shown in FIGS. 4 and 5, the layer thickness of the developer 110 supplied to the developing roll 116 by the supply auger 115 is regulated to a predetermined value by the layer thickness regulating roll 120. On the other hand, the photosensitive drum 8 is conveyed to a developing area facing the photosensitive drum 8, and the electrostatic latent image formed on the surface of the photosensitive drum 8 is developed with toner of a predetermined color.

  As the developer 110 accommodated in the developing device 11, a two-component developer 110 composed of toner and carrier is used, but a one-component developer composed only of toner may be used. Of course it is good.

  Further, as shown in FIG. 3, the cleaning device 12 removes the transfer residual toner remaining on the surface of the photosensitive drum 8 by the cleaning blade 26, and the removed transfer residual toner is put inside the cleaning device 12. It is comprised so that it may collect | recover and accommodate.

  Incidentally, as shown in FIG. 1, the sheet conveying apparatus 70 according to this embodiment includes a drive motor 71 that rotationally drives both the supply roll 45 and the registration roll pair 43. The force is transmitted to the supply roll 45 via the feed clutch 72 and is also transmitted to the registration roll pair 43 via the registration clutch 73.

  As the drive motor 70, for example, a stepping motor is used. Based on a signal from the CPU 100 as a control means, the speed control circuit 102 refers to a speed profile stored in advance in the ROM 101 and turns on / off rotation. The rotation speed is controlled.

  In this embodiment, the drive motor 71, the feed clutch 72, and the registration clutch 73 are used as drive means for rotationally driving both the supply roll 45 and the registration roll pair 43, but the supply roll 45 and the registration clutch 73 are used. The roll pair 43 may be driven by a drive motor provided individually.

  The CPU 100 controls the image forming operation of the entire full-color printer, and based on a print instruction from a personal computer (not shown) or the like, yellow (Y), magenta (M), cyan (C), black (K) The image forming operation of toner images on the photosensitive drums 8Y, 8M, 8C, and 8K of the process cartridges 7Y, 7M, 7C, and 7K, and the feeding of the recording paper 37 by the paper transport device 70 from the paper feeding device 6 It controls various image forming operations such as operations.

  In the paper transport device 70, as shown in FIG. 1, a desired size such as A4 size, A3 size, B5 size, B4 size, letter size, etc. stored in the paper tray 43 of the paper feeding device 6, or plain paper or Of the recording paper 37 that is a recording medium of a desired material such as a thick paper or an OHP sheet, the uppermost recording paper 37 is intermittently driven along the arrow direction at a predetermined timing. It is fed by the feed roll 33.

  At this time, when the recording paper 37 accommodated in the paper tray 43 of the paper feeding device 6 is fed by the feeding roll 33, the uppermost recording paper 37 and about one or two sheets positioned below the uppermost recording paper 37 are provided. Recording paper 37 may be simultaneously fed by the frictional force between the recording papers 37. The recording paper 37 fed from the paper tray 43 is driven to rotate in opposite directions, that is, in a direction opposite to the supply roll 45 in a direction opposite to the feed roll 45, or The paper is conveyed to the downstream side in the paper conveyance direction in a state where the paper is separated and wound one by one by the rolling roll 46 to which driving torque in the opposite direction is applied. Accordingly, only one recording sheet 37 that has passed through the supply roll 45 and the separation roll 46 as the pair of separation rolls is conveyed downstream in the sheet conveyance direction.

  On the downstream side in the paper conveyance direction of the supply roll 45 and the separating roll 46, a paper conveyance path 74 that is curved upward and conveys the recording paper 37 to a pair of registration rolls 43 disposed obliquely above is provided. The recording paper 37 is conveyed to the registration roll pair 43 along the paper conveyance path 74. In addition, a first paper sensor 75 is disposed in the paper conveyance path 74 at the outlets of the supply roll 45 and the separating roll 46, and in front of the registration roll pair 43 as an alignment roll pair, Two paper sensors 76 are provided.

  When the leading edge of the recording paper 37 reaches the registration roll pair 43, as shown in FIG. 6, the registration clutch is OFF and the registration roll pair 43 is stopped, and the leading edge of the recording paper 43 is registered. In a state of being in contact with the roll pair 43, the leading edge of the recording paper 37 is aligned with a slight loop. The registration roll 43 is provided with toner on the photosensitive drums 8Y, 8M, 8C, and 8K for the yellow (Y), magenta (M), cyan (C), and black (K) process cartridges 7Y, 7M, 7C, and 7K. At a timing synchronized with the image, as shown in FIG. 1, the recording motor 37 is driven to rotate by a drive motor 71 via a registration roll clutch, and is transported to the suction position of the paper transport belt 31.

  The recording sheet 37 conveyed by the resist roll pair 43 is conveyed while being attracted to the surface of the sheet conveying belt 31, and each of yellow (Y), magenta (M), cyan (C), and black (K) is conveyed. When forming a full-color image from the photosensitive drums 8Y, 8M, 8C, and 8K of the process cartridges 7Y, 7M, 7C, and 7K, toner images of each color are transferred.

  At this time, the feed clutch that transmits the rotational driving force of the drive motor 71 to the supply roll 45 is turned off at a predetermined timing in order to prevent jamming of the recording paper 37, as shown in FIG. The driving of the supply roll 45 is stopped. Thereafter, the recording paper 37 is sequentially transported to the paper transport belt 31 only by the transport force of the registration roll pair 43.

  As described above, in this embodiment, when the feed clutch 72 is turned off at a predetermined timing and the driving of the supply roll 45 is stopped, a load is applied to the resist roll pair 43 at that moment. The drive speed of the drive motor 71 starts to increase from a time point before a predetermined time when the drive is stopped, and the maximum value of the drive motor 71 is positioned slightly before the center of the acceleration profile. It is set to be. As shown in FIG. 6, the speed increasing profile is set to have a maximum value when a predetermined time, for example, about 10 to 20 msec elapses from the drive stop timing of the supply roll 45, and then gradually. By reducing the speed increase rate so that the normal speed is reached, before the trailing edge of the recording paper 37 exits the supply roll 45, the normal speed is restored to the previous speed, and the trailing edge of the recording paper 37 exits the supply roll 45. By reducing the load, the resist roll pair 43 is prevented from being accelerated unnecessarily.

  The maximum value of the driving speed of the driving motor 71 is set to increase by about 2.5% when the process speed is set to 155 mm / s, for example, but is not limited thereto. Although it may be 2 to 3%, it has been found by the inventor's experiment that about 5% is too large.

  Further, the time from when the feed clutch 72 is turned off to stop the driving of the supply roll 45 until the trailing edge of the recording paper 37 exits the supply roll 45 includes, for example, the speed increasing profile of the drive motor 71. 240 msec, the recording paper conveyance distance is set to 37.2 mm.

  The speed increasing profile of the drive motor 71 is also controlled according to the steady-state conveyance speed of the recording paper 37, from when the supply roll 45 is stopped until the trailing edge of the recording paper 37 passes the supply roll 45. It is desirable to change the speed profile so that the speed increase amount (a value obtained by integrating the speed with time) becomes equal according to time.

  In the above configuration, in the full-color printer to which the paper conveying device according to this embodiment is applied, the speed control (acceleration) for the registration roll pair is in time for the load fluctuation accompanying the stoppage of driving of the feed roll pair as follows. It is possible to suppress the speed fluctuation of the paper due to the absence.

  That is, in the above-described full-color printer, when the printing operation is started as shown in FIG. 2, the drive motor 71 is driven to rotate at a predetermined timing as shown in FIG. At the same time or a little later, the feed clutch 72 is turned on, and the supply roll 45 and the separating roll 46 are driven to rotate. Next, in the paper transport device 70, as shown in FIG. 6, the feed roll 44 is intermittently rotated to feed the recording paper 37 from the paper tray 43 of the paper feed device 6. The recording paper 37 fed from the paper tray 43 of the paper feeding device 6 is separated and fed one by one by a supply roll 45 and a rolling roll 46 that rotate in opposite directions, and is passed through the paper transport path 74. To the resist roll pair 43. At this time, the registration clutch 73 is in an OFF state, and the registration roll pair 43 is stopped. Therefore, the recording paper 37 conveyed to the registration roll pair 43 while being fed one by one by the supply roll 45 and the separation roll 46 abuts against the nip portion of the registration roll pair 43 and stops, and is predetermined. Form a loop.

  Thereafter, the registration clutch 73 is turned on at a predetermined timing as shown in FIG. 6, the registration roll pair 43 is driven to rotate, and the recording paper 37 is transferred to the registration roll pair as shown in FIG. 43 is conveyed to the sheet conveying belt 31.

  Then, as shown in FIG. 6, the feed clutch 73 is turned off at a predetermined timing T1, and the supply roll 45 and the separating roll 46 are stopped. However, when the supply roll 45 and the separating roll 46 are stopped, the registration roll The conveyance load of the recording paper 37 by the pair 43 is increased, and the registration roll pair 43 is conveyed to the paper conveyance belt 31 and is conveyed by the paper conveyance belt 31 while being yellow (Y), magenta (M), cyan ( C), the moving speed of the recording paper 37 onto which the toner image of each color is transferred from the photosensitive drums 8Y, 8M, 8C, 8K of the process cartridges 7Y, 7M, 7C, 7K of black (K). Become.

  Therefore, in this embodiment, as shown in FIG. 6, immediately before the feed clutch 72 is turned off, the drive motor 71 is gradually increased so as to be faster than the normal drive speed faster by a predetermined time t1. The drive speed of the drive motor 71 is based on a speed profile stored in advance in the ROM so that the maximum speed is reached after a predetermined time (10 to 20 ms) has elapsed since the feed clutch 73 is turned off. And controlled by the speed control circuit 102.

  As a result, even when the feed clutch 72 is turned off and the load on the registration roll pair 43 increases, the drive speed of the drive motor 71 that drives the registration roll pair 43 is increased in advance. It can be suppressed that the pair 43 is rapidly decelerated and the vibration speed fluctuation is generated in the recording sheet 37 conveyed by the resist roll pair 43. Accordingly, the yellow (Y), magenta (M), cyan (C), and black (K) process cartridges 7Y, 7M, 7C, and 7K photosensitive drums 8Y while being transported by the paper transport belt 31 as described above. , 8M, 8C, and 8K, the moving speed of the recording paper 37 onto which the toner image of each color is transferred can be controlled to a substantially constant speed, and the occurrence of color misregistration due to the fluctuation of the moving speed of the recording paper 37 can be prevented. Can be suppressed.

  Thereafter, the drive speed of the drive motor 71 is gradually decelerated from the maximum value until the trailing edge of the recording paper 37 exits the supply roll 45, and before the trailing edge of the recording paper 37 exits the supply roll 45. In addition, the normal speed is restored.

  Therefore, an increase in the load of the resist roll pair 43 due to the feed clutch being turned off acts as an impulse (force × time) that is an increase in load generated in a short time. The increase in the load of 43 starts to increase immediately before the feed clutch 73 is turned off. When the feed clutch 72 is turned off, the increase in the speed of the drive motor 71 already increased and the subsequent increase The conveyance speed determined by the speed profile cancels out and cancels, and the conveyance speed of the recording paper 37 by the resist roll pair 43 before and after the feed clutch 72 is turned off can be maintained substantially constant.

  Further, as shown in FIG. 6, the speed increasing profile of the drive motor 71 is set so that the rear end of the recording paper 37 is returned to the normal speed before it exits the supply roll 45. After the rear end passes through the supply roll 45, the influence of the speed increasing profile of the drive motor 71 does not appear in the conveyance speed of the recording paper 37.

  Note that the maximum value of the speed profile is suppressed to an acceleration value of about 1.5% which is smaller than that of plain paper when the recording paper 37 is thick paper.

Experimental Example The inventor makes a prototype of a printer as shown in FIG. 2, controls the speed profile of the drive motor 71 as shown in FIG. 6A, and drives the drive motor 71 before and after the timing to turn off the feed clutch. An experiment was conducted to measure the amount of positional deviation based on the black color of the toner image of each color of the color image transferred and fixed on the recording paper 37.

  7 and 8 show experimental examples of the present invention.

  As can be seen from these figures, as shown in FIG. 6A, it was found that by controlling the speed profile of the drive motor 71, torque fluctuations and color misregistration of the drive motor 17 can be reduced.

Comparative Example The inventor makes a prototype of a printer as shown in FIG. 2, controls the speed profile of the drive motor 71 as shown in FIG. 6B, and drives the drive motor 71 before and after the timing to turn off the feed clutch. An experiment was conducted to measure the amount of positional deviation based on the black color of the toner image of each color of the color image transferred and fixed on the recording paper 37.

  9 and 10 show a comparative example of the present invention.

  As can be seen from these figures, as shown in FIG. 6B, when the speed profile of the drive motor 71 is controlled, the torque fluctuation of the drive motor 17 becomes excessive, and the effect appears as a large color misregistration amount. It was.

FIG. 1 is a configuration diagram showing a main part of a tandem full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram showing a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a block diagram showing a process cartridge of a tandem type full color printer as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 4 is a block diagram showing the developing device. FIG. 5 is a perspective configuration diagram showing the internal structure of the developing device. FIG. 6 is a timing chart showing the operation of the tandem full-color printer as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 7 is a graph showing control characteristics. FIG. 8 is a graph showing the registration misalignment amount of an image. FIG. 9 is a graph showing conventional control characteristics. FIG. 10 is a graph showing a registration shift amount of a conventional image.

Explanation of symbols

  6: paper feeder, 43: paper tray, 37: recording paper, 33: feed roll, 43: registration roll, 45: supply roll, 46: paper roll, 70: paper transport device, 71: drive motor, 72: Feed clutch, 73: registration clutch, 100: CPU (speed control means).

Claims (6)

A paper container containing recording paper;
While conveying the recording paper sent out from the paper storage container one by one, a pair of rolling rolls that stops at a predetermined timing;
A pair of alignment rolls that conveys the leading edge of the recording sheet conveyed in a state of being rolled one by one by the pair of rolling rolls to the downstream side in the sheet conveying direction in an aligned state;
Drive means for rotationally driving the pair of rolling rolls and the pair of matching rolls at different timings;
A sheet conveying apparatus comprising: a speed control unit configured to increase a driving speed of the alignment roll pair by the driving unit from before the stopping roll pair is stopped. The speed control means returns the driving speed of the alignment roll pair by the driving means to a steady speed before the trailing edge of the sheet passes through the pair of rolling rolls. Paper transport device. 3. The sheet conveying device according to claim 1, wherein the speed control unit controls a driving speed of the alignment roll pair by the driving unit based on a predetermined speed profile. The speed control unit changes the speed profile so that the speed increase amount becomes equal according to the time from when the pair of the winding rolls is stopped until the trailing edge of the sheet passes through the pair of the rolling rolls. The paper conveying apparatus according to claim 3, wherein 5. The sheet conveying apparatus according to claim 3, wherein when the recording sheet is a thick sheet, the maximum value of the speed profile to be accelerated is set smaller than that of the plain sheet. A paper container containing recording paper;
While conveying the recording paper sent out from the paper storage container one by one, a pair of rolling rolls that stops at a predetermined timing;
A pair of alignment rolls that conveys the leading edge of the recording sheet conveyed in a state of being rolled one by one by the pair of rolling rolls to the downstream side in the sheet conveying direction in an aligned state;
Drive means for rotationally driving the pair of rolling rolls and the pair of matching rolls at different timings;
Speed control means for increasing the driving speed of the alignment roll pair by the driving means from before the stopping roll pair is stopped;
An image forming apparatus comprising: an image forming unit that forms an image on a recording sheet conveyed by the alignment roll pair.

Images