JP2006267704A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus capable of appropriately adjusting the distortion of an image transferred to a recording medium by a secondary transfer belt. <P>SOLUTION: In the image forming apparatus 1, by adjusting the position (a position around a shaft 86) of a cam 84 for a BTB mechanism 70 and adjusting the tilt angle of an idle roll 23 to a driving roll 22, the circumferential length of a secondary transfer/carrying belt 21 on an IN side (inner side vertical to paper surface) is made to differ from that on an OUT side (this side vertical to paper surface), then, the carrying direction of the paper can be intentionally bent. That is, by making a paper carrying velocity by the secondary transfer/carrying belt 21 on the IN side differ from that on the OUT side, a rotating force is applied to the paper. Consequently, the paper carrying direction can be adjusted (reformed) as the appropriate direction, and then, the distortion (image parallelism) of a toner image (image) transferred to the paper is appropriately adjusted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer and a copying machine, and more particularly to an image forming apparatus provided with an intermediate transfer member.

  In image forming apparatuses such as printers and copiers, so-called full-color tandem machines have been proposed for the purpose of forming color images at high speed and high image quality. As such a tandem machine, four image forming units of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in parallel with each other, and each of these image forming units sequentially. The formed toner images of yellow, magenta, cyan, and black are temporarily transferred to an intermediate transfer belt, which is an intermediate transfer body, and then transferred to a recording medium (paper) from the intermediate transfer belt (secondary transfer). A configuration in which a full-color or black-and-white (monochrome) image is formed by fixing the toner image formed on the paper is known.

  In such an image forming apparatus using an intermediate transfer belt, a so-called BTR mechanism, a so-called BTB mechanism, or the like is known as a mechanism used for the secondary transfer unit.

  In the BTR mechanism, the intermediate transfer belt is supported by the backup roll from the inside, and the secondary transfer roll is brought into contact with the surface side of the intermediate transfer belt, and a voltage is applied between the backup roll and the secondary transfer roll. Is configured to perform transfer.

  Further, in such a BTR mechanism, the present applicant adjusts the nip balance (the balance of the nip pressure on the front side of the apparatus and the back side of the apparatus) with respect to the intermediate transfer belt (backup roll) of the secondary transfer roll, A configuration is proposed in which the paper traveling direction (conveying direction) is corrected to an appropriate direction to suppress image distortion in the secondary transfer unit (see, for example, Patent Document 1).

  On the other hand, the BTB mechanism includes a secondary transfer belt formed of an elastic annular belt instead of the secondary transfer roll, and performs transfer by bringing the secondary transfer belt into contact with the surface of the intermediate transfer belt. It has become. The BTB mechanism is an improvement of the poor thin paper releasability, which is a drawback of the BTR mechanism, by adsorbing the sheet to the secondary transfer belt.

  Further, in such a BTB mechanism, the present applicant adjusts the nip balance of the secondary transfer belt with respect to the intermediate transfer belt (backup roll) in the same manner as the BTR mechanism described above, thereby appropriately adjusting the paper traveling direction. A configuration in which the image is corrected in the direction to suppress image distortion in the secondary transfer portion has been proposed (see, for example, Patent Document 2).

However, in the BTB mechanism, the paper traveling direction (conveyance direction) is greatly affected by the contact state with the secondary transfer belt, and therefore, the image distortion cannot be sufficiently suppressed only by adjusting the nip balance as described above. There is. In particular, when duplex printing is continued, oil (so-called fuser oil) adhering to the surface of the paper adheres to the secondary transfer belt, so that the frictional force between the paper and the secondary transfer belt changes partially. However, there is a problem that the paper traveling direction changes.
JP 2003-186318 A JP 2004-246022 A

  In view of the above facts, an object of the present invention is to provide an image forming apparatus capable of suitably adjusting the distortion of an image transferred to a recording medium by a secondary transfer belt.

  According to a first aspect of the present invention, there is provided an image forming apparatus comprising: an intermediate transfer belt on which the toner image is transferred by rotating while abutting an image carrier on which the toner image is carried; And a pair of rolls that are movable in a state in which one axis is inclined on the same plane with respect to the other axis, and an endless shape having elasticity, A portion wound around the other roll is in contact with the intermediate transfer belt, and the recording medium supplied to the contact portion is conveyed while being sandwiched between the intermediate transfer belt. A secondary transfer belt that transfers the toner image transferred to the intermediate transfer belt to the recording medium, and an adjustment unit that can arbitrarily adjust the inclination angle of the one roll with respect to the other roll. It is characterized by a door.

  In the image forming apparatus according to claim 1, the toner image transferred from the image carrier to the intermediate transfer belt has a recording medium supplied to a contact portion between the intermediate transfer belt and the secondary transfer belt. It is transferred to a recording medium by being conveyed while being pinched with the next transfer belt.

  Here, the image forming apparatus includes an adjusting unit that can arbitrarily adjust an inclination angle of one roll with respect to the other of the pair of rolls around which the secondary transfer belt is wound. Therefore, when the transfer direction of the recording medium is bent during the transfer by the secondary transfer belt (the recording medium rotates), and the transferred toner image (image) is distorted, the adjustment unit adjusts the other of the one roll. By appropriately adjusting the tilt angle with respect to the roll, a difference is generated between the circumference of one end of the secondary transfer belt and the circumference of the other end, and the conveyance direction of the recording medium is adjusted (corrected) to an appropriate direction. can do. Thereby, the distortion of an image can be adjusted suitably.

  An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the adjusting means is provided between the one axial end portions of the pair of rolls and the other axial end portion of the pair of rolls. A cam that is rotatably provided in at least one of the gaps and inclines the one roll with respect to the other roll by rotating in a state of directly or indirectly contacting the pair of rolls. It is characterized by that.

  The image forming apparatus according to claim 2, wherein cams provided at least one of the pair of rolls between one axial end portion and the pair of roll axial other end portions rotate while contacting the pair of rolls. Thus, the inclination angle of one roll with respect to the other roll is adjusted.

  According to a third aspect of the present invention, there is provided the image forming apparatus according to the second aspect, wherein the adjusting means has a drive source for rotating the cam with a driving force.

  In the image forming apparatus according to the third aspect, since the cam can be rotated by driving the drive source, for example, the parallelism of the pair of rolls can be easily adjusted even during printing.

  An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the third aspect, wherein the adjusting means includes the type of the recording medium, the difference between the front and back of the recording medium when performing duplex printing, the position of the output tray, A plurality of inclination angles set in advance based on both various image forming conditions including at least one image forming condition among the number of printed sheets and continuous printing time and the degree of distortion of the toner image transferred to the recording medium. A storage unit that stores the correction data, and the correction data corresponding to the image forming condition selected from among the various image forming conditions is selected from a plurality of the correction data, and based on the selected correction data And a control unit for controlling the drive of the drive source.

  The image forming apparatus according to claim 4, wherein the tilt angle (based on one roll with respect to the other roll) set in advance based on both the various image forming conditions and the degree of distortion of the toner image transferred to the recording medium is used. A plurality of correction data (tilt angle) is stored in the storage unit. When the user selects a desired image forming condition from various image forming conditions, the control unit selects correction data corresponding to the selected image forming condition from a plurality of correction data, and The drive of the drive source is controlled based on the selected correction data. Thereby, the cam is rotated, and the inclination angle of one roll with respect to the other roll is adjusted based on the correction data corresponding to the selected image forming condition.

  An image forming apparatus according to a fifth aspect of the present invention is the image forming apparatus according to the fourth aspect, wherein the adjusting means includes a display unit capable of displaying an image of a toner image whose distortion is adjusted by driving the driving source. It is characterized by having.

  In the image forming apparatus according to the fifth aspect, the image of the toner image on the recording medium whose distortion is adjusted by driving the drive source can be displayed on the display unit. Therefore, the user can easily confirm the adjustment state of the distortion visually by using the displayed image, thereby facilitating the adjustment work.

  An image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to the first aspect, wherein the adjusting means is arranged between one axial end portions of the pair of rolls and the other axial end portion of the pair of rolls. It is characterized by being inserted into at least one of the gaps to serve as a spacer that inclines the one roll with respect to the other roll.

  The image forming apparatus according to claim 6, wherein a spacer is inserted between at least one of the axial ends of the pair of rolls and between the other axial ends of the pair of rolls, so that the other of the one rolls. The tilt angle with respect to the roll is adjusted.

  As described above, according to the image forming apparatus of the present invention, it is possible to suitably adjust the distortion of the image transferred to the recording medium by the secondary transfer belt.

<First Embodiment>
FIG. 1 is a schematic configuration diagram of an image forming apparatus 1 according to the first embodiment of the present invention.

  The image forming apparatus 1 is an intermediate transfer type image forming apparatus adopting a so-called tandem type, and includes a plurality of image forming units 10 (10Y, 10M, 10C, 10K), an intermediate transfer belt 15 as a carrier for sequentially transferring (primary transfer) and holding each color component toner image formed in each image forming unit 10, and a superimposed toner image transferred onto the intermediate transfer belt 15 A secondary transfer unit 20 that performs batch transfer (secondary transfer) onto a sheet P that is a recording medium, and a fixing unit 60 that fixes an image secondarily transferred onto the sheet P are provided. Moreover, it has the control apparatus 40 which controls operation | movement of each apparatus (each part).

  In the first embodiment, each of the image forming units 10 (10Y, 10M, 10C, and 10K) is for charging the photosensitive drums 11 around the photosensitive drums 11 that rotate in the arrow A direction. A charging device 12, a laser exposure device 13 for writing an electrostatic latent image on the photosensitive drum 11 (exposure beam is indicated by a symbol Bm in the drawing), each color component toner is accommodated, and the electrostatic latent image on the photosensitive drum 11 is stored. The developing device 14 that visualizes the image with toner, the primary transfer roll 16 that transfers the toner image of each color component formed on the photosensitive drum 11 to the intermediate transfer belt 15, and the residual toner on the photosensitive drum 11 are removed. The electrophotographic devices such as the drum cleaner 17 are sequentially arranged. These image forming units 10 are arranged substantially linearly in the order of yellow (Y color), magenta (M color), cyan (C color), and black (K color) from the upstream side of the intermediate transfer belt 15. Yes.

The intermediate transfer belt 15 that is an intermediate transfer member (toner image carrier) is made of a resin such as polyimide or polyamide containing a suitable amount of a conductive agent such as carbon black, and has a volume resistivity of 10 ⁶ to 10. It is formed so as to be 10 ¹⁴ Ω · cm, and the thickness thereof is constituted by, for example, a film-like endless belt of about 0.1 mm. The intermediate transfer belt 15 is circulated and driven (rotated) at a predetermined speed in the direction B shown in the figure by various rolls. As these various rolls, a drive roll 31 that is driven by a motor (not shown) having excellent constant speed and circulates and drives the intermediate transfer belt 15, and an intermediate that extends substantially linearly along the arrangement direction of the photosensitive drums 11. A support roll 32 that supports the transfer belt 15, a tension roll 33 that functions as a correction roll that applies a constant tension to the intermediate transfer belt 15 and prevents meandering of the intermediate transfer belt 15, and a backup provided in the secondary transfer unit 20. A cleaning backup roll 34 provided in a cleaning unit for scraping off residual toner on the roll 25 and the intermediate transfer belt 15 is provided.

  A voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roll 16 provided inside the intermediate transfer belt 15 facing the respective photosensitive drums 11 and extending substantially linearly. As a result, the toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15 so that the toner images superimposed on the intermediate transfer belt 15 are formed.

  The secondary transfer unit 20 includes a BTB mechanism 70 disposed on the toner image carrying surface side of the intermediate transfer belt 15, a backup roll 25, and the like. The backup roll 25 is a tube of EPDM and NBR blend rubber with carbon dispersed on the surface, and the inside is made of EPDM rubber. The surface roll efficiency is 7 to 10 logΩ / □, and the roll diameter is 28 mm. Is set to 70 degrees (Asker C), for example. The backup roll 25 is disposed on the back side of the intermediate transfer belt 15 and serves as a counter electrode of the secondary transfer conveyance belt (secondary transfer belt) 21 of the BTB mechanism 70 to stably apply the secondary transfer bias. A metal power supply roll 26 is disposed in contact therewith.

On the other hand, the secondary transfer conveyance belt (secondary transfer belt) 21 is a semiconductive material wound around a drive roll 22 and an idle roll 23 as a pair of rolls, for example, having a volumetric efficiency of 10 ⁶ to 10 ¹⁰ Ωcm. A material having a 100% elongation modulus of 3.8 MPa is used. The secondary transfer conveyance belt 21 is conveyed at a predetermined speed by a driving roll 22 made of, for example, a rubber roll, and given a predetermined tension by an idle roll 23 made of, for example, SUS. The drive roll 22 is disposed in pressure contact with the backup roll 25 with the secondary transfer conveyance belt 12 and the intermediate transfer belt 15 interposed therebetween, and performs secondary transfer on the paper P conveyed on the secondary transfer conveyance belt 21. It functions as a secondary transfer roll. In addition, a cleaner 27 made of a rubber plate-like member that scrapes off the toner on the secondary transfer conveyance belt 21 is applied to the secondary transfer conveyance belt 21 in the vicinity of the upstream side of the secondary transfer portion in contact with the intermediate transfer belt 15. It touches.

  Further, on the downstream side of the secondary transfer portion 20 of the intermediate transfer belt 15, a belt cleaner 35 that removes residual toner and paper dust on the intermediate transfer belt 15 after the secondary transfer and cleans the surface of the intermediate transfer belt 15. Is provided so as to be freely contacted and separated. On the other hand, on the upstream side of the yellow image forming unit 10Y, a reference sensor (home position sensor) that generates a reference signal serving as a reference for taking the image forming timing in each image forming unit 10 (10Y, 10M, 10C, 10K). ) 42 and an image density sensor 43 for adjusting image quality is disposed downstream of the black image forming unit 10K. The reference sensor 42 recognizes a predetermined mark provided on the intermediate transfer belt 15 and generates a reference signal. In response to an instruction from the control device 40 based on the recognition of the reference signal, each image forming unit 10 ( 10Y, 10M, 10C, and 10K) are configured to start image formation.

  Further, in the first embodiment, as the paper transport system, the paper trays 50A and 50B that store the paper P, and the paper feed that takes out and transports the paper P collected in the paper trays 50A and 50B at a predetermined timing. A roll 51, a transport roll 52 that transports the paper P fed by the paper feed roll, a transport chute 53 that feeds the paper P transported by the transport roll 52 to the secondary transfer unit 20, and the secondary transfer transport belt 21. A belt 55 is provided for transporting the paper P transported after the next transfer to the fixing unit 60.

  Next, a basic image forming process of the image forming apparatus 1 according to the first embodiment will be described. Image data output from an image reading device (IIT) (not shown), a personal computer (PC) (not shown) or the like is input to the image forming apparatus 1 shown in FIG. In the image forming apparatus 1, after predetermined image processing is performed by an image processing apparatus (IPS) (not shown), an image forming operation is performed by the image forming unit 10 or the like. In the image processing apparatus (IPS), the input reflectance data is subjected to predetermined image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, and movement editing. Is done. The image data subjected to the image processing is converted into color material gradation data of four colors of yellow (Y), magenta (M), cyan (C), and black (K), and is output to the laser exposure unit 13. .

  The laser exposure unit 13 irradiates each photosensitive drum 11 of the image forming units 10Y, 10M, 10C, and 10K with, for example, an exposure beam Bm emitted from a semiconductor laser according to the input color material gradation data. Yes. In the photosensitive drums 11 of the image forming units 10Y, 10M, 10C, and 10K, the surface is charged by the charger 12, and then the surface is scanned and exposed by the laser exposure unit 13 to form an electrostatic latent image. The formed electrostatic latent images are developed as yellow (Y), magenta (M), cyan (C), and black (K) toner images in the respective image forming units 10Y, 10M, 10C, and 10K. The

  The toner images formed on the photosensitive drums 11 of the image forming units 10Y, 10M, 10C, and 10K are transferred onto the intermediate transfer belt 15 at the primary transfer portion where the photosensitive drums 11 and the intermediate transfer belt 15 are in contact with each other. Transcribed. More specifically, in the primary transfer portion, the primary transfer roll 16 applies a voltage having a polarity opposite to the charged polarity of the toner to the base material of the intermediate transfer belt 15, and the unfixed toner image is transferred to the surface of the intermediate transfer belt 15. Are sequentially superposed on each other and primary transfer is performed. The unfixed toner image primarily transferred in this way is conveyed to the secondary transfer unit 20 as the intermediate transfer belt 15 rotates.

  On the other hand, in the paper transport system, the paper feed roll 51 rotates in synchronization with the image formation timing, and the paper P of a predetermined size is supplied from the paper tray 50A or the paper tray 50B. The paper P supplied by the paper feed roll 51 is transported by the transport roll 52 and reaches the secondary transfer unit 20 via the transport chute 53. Before reaching the secondary transfer portion 20, the paper P is temporarily stopped, and the registration roll (not shown) rotates in accordance with the movement timing of the intermediate transfer belt 15 carrying the toner image as described above. Thus, the position of the paper P and the position of the toner image are aligned.

  In the secondary transfer unit 20, the driving roll 22 is moved to the backup roll 25 with the semiconductive secondary transfer conveyance belt 21 and the intermediate transfer belt 15 being sandwiched therebetween in accordance with the timing of the secondary transfer onto the paper P. Pressed. At this time, the sheet P transported at the same timing is sandwiched between the intermediate transfer belt 15 and the secondary transfer transport belt 21. At this time, when a voltage (normal transfer bias) having the same polarity as the toner charging polarity is applied to the power supply roll 26, a transfer electric field is formed on the secondary transfer conveyance belt 21 as a counter electrode, and the drive roll 22 and the backup roll 22 are backed up. The unfixed toner image carried on the intermediate transfer belt 15 is electrostatically transferred onto the paper P at the secondary transfer position pressed by the roll 25.

  Thereafter, the sheet P on which the toner image has been electrostatically transferred is conveyed as it is while being peeled off from the intermediate transfer belt 15 by the secondary transfer conveyance belt 21, and is provided downstream of the secondary transfer conveyance belt 21 in the sheet conveyance direction. It is conveyed to the conveyor belt 55. The conveyance belt 55 conveys the paper P to the fixing unit 60 in accordance with the optimum conveyance speed in the fixing unit 60. The unfixed toner image on the paper P is fixed on the paper P by being subjected to fixing processing by heat and pressure by the fixing unit 60, and the paper P on which the fixed image is formed is discharged by a discharge roll (not shown). Is discharged outside. On the other hand, after the transfer onto the paper P is completed, the residual toner remaining on the intermediate transfer belt 15 is conveyed to the cleaning unit as the intermediate transfer belt 15 rotates, and is intermediately transferred by the cleaning backup roll 34 and the belt cleaner 35. It is removed from the belt 15.

  Next, the configuration of the BTB mechanism 70 according to the first embodiment will be described with reference to FIGS. In FIG. 2, the left side corresponds to the OUT side (front side, front side) of the device, and the right side corresponds to the IN side (back side, rear side) of the device.

  The secondary transfer conveyance belt 21 of the BTB mechanism 70 is wound around the drive roll 22 and the idle roll 23 as described above. The drive roll 22 and the idle roll 23 are arranged so that their axes are opposed to each other on the same plane, and a pair of support members 71 and 72 formed in a rectangular flat plate shape are provided on both sides in the axial direction. They are arranged facing each other in a parallel state.

  At both ends in the axial direction of the drive roll 22, circular shaft portions 22 </ b> A are coaxially and integrally projected, and these shaft portions 22 </ b> A penetrate through the support members 71 and 72. These are rotatably supported by a pair of bearings 74 and 76 attached to the support members 71 and 72, respectively.

  Similarly to the drive roll 22, both circular axial support shaft portions 23A are coaxially and integrally projected at both axial ends of the idle roll 23. These support shaft portions 23A are The support members 71 and 72 pass through the support members 71 and 72 and are rotatably supported by a pair of bearings 78 and 80 attached to the support members 71 and 72, respectively.

  However, the bearings 74 and 76 that support the respective support shaft portions 22A of the drive roll 22 are fixed to the support members 71 and 72, respectively, whereas the bearings 78 that support the respective support shaft portions 23A of the idle roll 23, 80 is movably fitted in long holes 71A and 72A formed in the support members 71 and 72, respectively. The long holes 71A and 72A are formed in a long shape along the opposing direction of the axis of the drive roll 22 and the axis of the idle roll 23, whereby the idle roll 23 has a pair of bearings 78 and 80. At the same time, it can move toward and away from the drive roll 22 (see arrow C in FIG. 2).

  Moreover, in this case, the pair of bearings 78 and 80 can move independently, and the idle roll 23 moves in a state where its own axis is inclined on the same plane as described above with respect to the axis of the drive roll 22. It is possible (the tilt angle of the idle roll 23 with respect to the drive roll 22 is adjustable).

  In addition, between the bearing 74 and the bearing 78 attached to the support member 71 on the IN side and between the bearing 76 and the bearing 80 attached to the support member 72 on the OUT side, the axis lines having an elliptical cross section are respectively provided. A cam 82 and a cam 84 formed in a columnar shape having a short directional dimension are arranged. These cams 82 and 84 are circular shafts 86 (FIGS. 3A and 3B) that project coaxially and integrally from the respective axial portions toward the support members 71 and 72, respectively. )), And these shafts 86 are fitted into circular holes (not shown) formed in the support members 71 and 72, so that the shafts 86 are rotatably supported around the shafts 86 with respect to the support members 71 and 72, respectively. Yes.

  In addition, the bearing 74 of the drive roll 22 and the bearing 78 of the idle roll 23 are always pressed against the cam 82 by the elastic force of the secondary transfer conveyance belt 21, and the IN side ( The inter-axis distance (one axial side) is defined by the rotational position of the cam 82.

  Similarly, the bearing 84 of the drive roll 22 and the bearing 80 of the idle roll 23 are always pressed against the cam 84 by the elastic force of the secondary transfer conveyance belt 21, and the OUT side between the drive roll 22 and the idle roll 23 is pressed. The inter-axis distance (on the other end side in the axial direction) is defined by the rotational position of the cam 84.

  Further, as shown in FIGS. 3A and 3B, a plurality of the cams 84 on the OUT side (the end surface opposite to the support member 72) arranged at equal intervals along the circumferential direction are provided. The scale 88 is formed, and the support member 72 has one scale 90 corresponding to the plurality of scales 88. For this reason, the position of the cam 84 (that is, the distance between the shafts on the OUT side between the drive roll 22 and the idle roll 23) can be specified by the correspondence between the plurality of scales 88 of the cam 84 and the scale 90 of the support member 72. ing. In addition, a screw (not shown) is screwed onto the shaft center portion of the cam 84, and the cam 84 can be fixed (rotation restricted) by tightening the screw.

  Although not shown, the IN-side cam 82 and the IN-side support member 71 have the same configuration as the OUT-side cam 84 and the OUT-side support member 72, and usually the IN-side cam 82. The correspondence relationship between the plurality of scales 88 and the scale 90 of the IN-side support member 71 and the correspondence relationship between the plurality of scales 88 of the OUT-side cam 84 and the scale 84 of the OUT-side support member 72 are the same. (Normally, the cam 82 and the cam 84 are fixed with screws at the same position in the circumferential direction). For this reason, normally, the drive roll 22 and the idle roll 23 are arranged in a state in which the axes of each other are parallel.

  Next, the operation of the first exemplary embodiment of the present invention will be described.

  In the image forming apparatus 1 configured as described above, when image data output from an image reading device (not shown) or the like is input, a predetermined image processing is performed by an image processing device (not shown) and then the image forming unit 10 or the like. An image forming operation is performed, and a toner image is formed on the photosensitive drum 11. The toner image formed on each photoconductor drum 11 is transferred onto the intermediate transfer belt 15 at a primary transfer portion where each photoconductor drum 11 and the intermediate transfer belt 15 come into contact with each other, and is further transferred to the secondary transfer position. The supplied paper P is transferred to the paper P by being conveyed while being sandwiched between the intermediate transfer belt 15 and the secondary transfer conveyance belt 21. The sheet P on which the toner image has been transferred is conveyed to the fixing unit 60 by the secondary transfer conveying belt 21 and the conveying belt 55, and the unfixed toner image on the sheet P is fixed by heat and pressure by the fixing unit 60. The paper P on which the fixed image is formed is discharged to the outside of the apparatus by a discharge roll (not shown).

  Here, in the image forming apparatus 1 according to the first embodiment, the drive roll 22 and the idle roll 23 are usually arranged in parallel with each other, and the peripheral length on the IN side of the secondary transfer conveyance belt 21 is The circumference on the OUT side is set to the same length. Therefore, as shown in FIG. 4A, the conveyance speed of the paper P by the secondary transfer conveyance belt 21 is set to the same speed on the IN side and the OUT side (see arrows S1 and S2). The paper P is basically conveyed straight. As a result, an undistorted image G is formed on the paper P at the secondary transfer position.

  However, for example, there is a difference between the IN side and the OUT side in the frictional force (conveyance resistance) between the secondary transfer conveyance belt 21 and the paper P for some reason, and the conveyance direction of the paper P by the secondary transfer conveyance belt 21 Is bent (when the paper P rotates), the image G formed on the paper P is distorted (the parallelism of the image G deteriorates).

  In such a case, in the image forming apparatus 1 according to the first embodiment, at least one position (position around the shaft 86) of the IN side cam 82 and the OUT side cam 84 of the BTB mechanism 70 is adjusted. (Change) and adjusting the inclination angle of the idle roll 23 with respect to the drive roll 22 causes a difference between the peripheral length on the IN side and the peripheral side on the OUT side of the secondary transfer transport belt 21, and transports the paper P. The direction can be bent intentionally. That is, as shown in FIG. 4B, the rotational speed of the paper P by the secondary transfer transport belt 21 is made different between the IN side and the OUT side (see arrows S3 and S4), thereby canceling the rotational force described above. Another rotational force can be applied to the paper P. Therefore, the conveyance direction of the paper P can be adjusted (corrected) in an appropriate direction, and the distortion (image parallelism) of the image G can be suitably adjusted.

  In addition, in the image forming apparatus 1 according to the first embodiment, the cams 82 and 84 are arranged using the plurality of scales 88 formed on the cams 82 and 84 and the scale 90 formed on the support members 71 and 72 as a guide. Since the position can be adjusted, the adjustment work is easy.

  As described above, in the image forming apparatus 1 according to the first embodiment of the present invention, the distortion of the image G transferred onto the paper P by the secondary transfer conveyance belt 21 can be suitably adjusted.

Next, another embodiment of the present invention will be described. Note that configurations and operations that are basically the same as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.
<Second Embodiment>
FIG. 5 is a plan view showing the configuration of the BTB mechanism 101 constituting the image forming apparatus 100 (see FIG. 1) according to the second embodiment of the present invention.

  The BTB mechanism 101 is applied to the image forming apparatus 100 having basically the same configuration as the image forming apparatus 1 according to the first embodiment, instead of the BTB mechanism 70 according to the first embodiment. The configuration is basically the same as that of the BTB mechanism 70.

  However, motors 102 and 104 (for example, stepping motors) as drive sources are mechanically connected to the cams 82 and 84 of the BTB mechanism 101, respectively, and the cams 82 and 104 are driven by the driving force of the motors 102 and 104. 84 is rotated. In the BTB mechanism 101, the screws for fixing the cams 82 and 84 are omitted. Further, when the motors 102 and 104 cannot be mounted inside the apparatus due to space restrictions, the shafts 86 of the cams 82 and 84 are protruded to the outside of the apparatus, and the motors 102 and 104 are connected thereto. It is good.

  In the image forming apparatus 100, the control device 40 includes a CPU 106 and a driver 108 as control units, and the motors 102 and 104 are electrically connected to a power source (not shown) via the driver 108. The CPU 106 controls whether power is supplied to the motors 102 and 104 via the driver 108, the direction and magnitude of the supply current, and the like.

  Further, an NVM memory 110 as a storage unit is electrically connected to the CPU 106. The NVM memory 110 stores image forming conditions (such as the type of the paper P, the difference between the front and back of the paper P when performing double-sided printing, the position of the output tray, the number of prints, and the continuous printing time) in the image forming apparatus 100. In this case, the amount of toner image transferred to the paper P by the BTB mechanism 101 is distorted (how much the image parallelism changes), which is confirmed in advance by tests and stored as various change data. Has been.

  For example, when double-sided printing is performed continuously, oil (so-called “fuser oil”) adhering to the surface of the paper adheres to the surface of the secondary transfer conveyance belt 21, and the paper P and the secondary transfer conveyance belt 21 gradually move. Since the friction between the sheets changes and the conveyance resistance of the sheet P differs between the IN side and the OUT side, the sheet P rotates during conveyance by the secondary transfer conveyance belt 21 and the image parallelism changes. However (see FIG. 6), the NVM memory 110 stores such change data of the image parallelism.

  Since the change data shows different tendencies depending on the individual image forming apparatuses 100, it is preferable to set the change data by performing a test for each apparatus.

  Further, in the NVM memory 110, the drive amounts and drive timings (cams 82 and 84) of the motors 102 and 104 in which the degree of distortion of the toner image (image parallelism) is in a suitable state based on each of the various change data. (Adjustment amount and adjustment timing) set in advance by tests are stored as various correction data (adjustment amount data).

  That is, in the NVM memory 112, for example, when performing double-sided printing continuously, the scale 88 of the IN-side cam 82 is moved by 1/2 pitch with respect to the scale 90 of the IN-side support member 71 every 25 sheets. Correction data for moving the cam 82 or the cam 84 by a predetermined amount in accordance with a continuous printing time such as every 30 minutes or every hour is stored.

  Furthermore, a user interface unit (UI unit) 112 as a display unit is electrically connected to the CPU 106. The UI unit 112 includes a button for selecting an image forming condition, a button for independently driving the motors 102 and 104, and driving of the motors 102 and 104 (rotation of the cams 82 and 84). An image of a toner image on the paper P whose distortion is adjusted is displayed.

  Here, in the image forming apparatus 100, the CPU 106 selects correction data corresponding to the image forming conditions input to the UI unit 112 from among a plurality of correction data stored in the NVM memory 110, and the selected correction is performed. The driving of the motors 102 and 104 is controlled based on the data. Thereby, the cam is rotated, and the inclination angle of one roll with respect to the other roll is adjusted based on the correction data corresponding to the selected image forming condition.

  Next, the operation of the second exemplary embodiment of the present invention will be described.

  In the image forming apparatus 100 having the above-described configuration, the motors 102 and 104 can be driven independently only by operating the buttons displayed on the UI unit 112, and thus the positions of the cams 82 and 84 can be freely adjusted. The user can easily adjust the image parallelism according to the type and size of the paper P. Moreover, since the adjustment can be performed electrically as described above, the positions of the cams 82 and 84 can be arbitrarily adjusted even during printing. Therefore, for example, when performing double-sided printing, the positions of the cams 82 and 84 (that is, image parallelism) can be adjusted corresponding to the front and back sides of the paper P, respectively.

  Moreover, since the toner image image whose distortion is adjusted by driving the motors 102 and 104 can be displayed on the UI unit 112, the adjustment state of the image parallelism can be easily confirmed visually by the displayed image image. it can. Therefore, the adjustment work is further facilitated and accurate adjustment can be performed.

  Further, in this image forming apparatus 100, when a desired image forming condition is input to the UI unit 112, the CPU 106 selects correction data corresponding to the input image forming condition from the plurality of correction data in the NVM memory 110. The driving of the motors 102 and 104 is controlled based on the selected correction data. As a result, the positions of the cams 82 and 84 are automatically adjusted to a suitable state, so that adjustment work can be performed very easily and uniform image quality can be ensured for various image forming conditions.

As described above, the image forming apparatus 100 according to the second embodiment of the present invention has basically the same operations and effects as the image forming apparatus 1 according to the first embodiment. In addition, the image forming apparatus 100 can perform adjustment work more easily. For example, it is preferable to call a service engineer to change the image parallelism each time the type of the paper P is changed. Yes (the user can easily perform adjustment work).
<Third Embodiment>
FIGS. 7A and 7B are side views showing the configuration of the BTB mechanism 121 constituting the image forming apparatus 120 (see FIG. 1) according to the third embodiment of the present invention. Yes.

  The BTB mechanism 121 is applied to the image forming apparatus 120 having basically the same configuration as the image forming apparatus 1 according to the first embodiment, instead of the BTB mechanism 70 according to the first embodiment. The configuration is basically the same as that of the BTB mechanism 70.

  However, a columnar fixing member 122 fixed to the support member 72 is provided between the bearings 76 and 80 on the OUT side of the BTB mechanism 121 instead of the cam 84 according to the first embodiment. ing. Although not shown, between the bearings 74 and 78 on the IN side of the BTB mechanism 121, the same size and shape as the fixing member 122 are formed instead of the cam 82 according to the first embodiment. The fixed member 122 is arranged in a state of being fixed to the support member 71. The bearings 76 and 80 or the bearings 74 and 78 are always pressed against the fixing member 122 by the elastic force of the secondary transfer conveyance belt 21. Normally, the drive roll 22 and the idle roll 23 have mutually parallel axes. It is arranged in the state.

  Further, the BTB mechanism 121 is provided on a plurality of plate-like spacers 124 formed in a predetermined thickness dimension (for example, 0.01 mm) provided in the main body of the image forming apparatus so that an engineer can adjust the site. (See FIG. 7B). One or a plurality of these spacers 124 can be inserted between the IN-side fixing member 122 and the bearing 78 or between the OUT-side fixing member 122 and the bearing 80. The tilt angle of the idle roll 23 with respect to the drive roll 22 is adjusted according to the state.

  Here, FIG. 8 shows the relationship between the thickness dimension (number of sheets) of the spacer 124 inserted between the fixing member 122 and the bearing 78 and between the fixing member 122 and the bearing 80 and the image parallelism. The measurement results measured in two different image forming apparatuses 120 (BTB # 1 and BTB # 2) are shown in a graph. In FIG. 8, the positive side of the horizontal axis corresponds to the OUT side of the apparatus, and the negative side of the horizontal axis corresponds to the IN side of the apparatus.

  8 represents the adjustment sensitivity, but the magnitude of the sensitivity is affected by the peripheral length of the secondary transfer conveyance belt 21. Although the sensitivity becomes higher as the peripheral length of the secondary transfer conveyance belt 21 is shorter, even a slight change in the distance between the axes of the drive roll 22 and the idle roll 23 greatly changes the image parallelism and is difficult to control. Therefore, it is preferable to consider in the system so that the necessary adjustment amount can be secured even if the circumferential length of the secondary transfer conveyance belt 21 is increased to some extent and the sensitivity is lowered.

  The image forming apparatus 120 having the above configuration also has basically the same operations and effects as the image forming apparatus 1 according to the first embodiment. In addition, since the image forming apparatus 120 has a simple configuration in which the inclination angle of the idle roll 23 with respect to the drive roll 22 is adjusted using a plurality of spacers 124, the configuration of the apparatus can be simplified.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a schematic plan view illustrating a configuration of a peripheral member including a secondary transfer belt of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a schematic side view showing the configuration of a peripheral member including a secondary transfer belt of the image forming apparatus according to the first embodiment of the present invention. 1 shows a secondary transfer belt and a recording medium of an image forming apparatus according to a first embodiment of the present invention, wherein (A) is a plane showing a state in which a pair of rolls are arranged in parallel and the recording medium is conveyed straight. (B) is a plan view showing a state in which one roll is inclined with respect to the other roll and the recording medium is rotated. FIG. 6 is a schematic plan view showing a configuration of a peripheral member including a secondary transfer belt of an image forming apparatus according to a second embodiment of the present invention. It is a graph which shows the relationship between the number of printed sheets and image parallelism. FIG. 10 is a schematic side view illustrating a configuration of a peripheral member including a secondary transfer belt of an image forming apparatus according to a third embodiment of the present invention. It is a graph which shows the measurement result which measured the relationship between the thickness (number of sheets) of a spacer, and image parallelism in two different image forming apparatuses.

Explanation of symbols

1 Image forming apparatus 11 Photosensitive drum (image carrier)
15 Intermediate transfer belt 21 Secondary transfer conveyor belt (secondary transfer belt)
22 Drive roll (the other roll)
23 idle roll (one roll)
82 Cam 84 Cam 100 Image forming apparatus 102 Motor (drive source)
104 Motor (drive source)
106 CPU (control unit)
108 Driver (control unit)
110 NVM memory (storage unit)
112 User interface part (display part)
120 Image forming device 124 Spacer

Claims (6)

An intermediate transfer belt to which the toner image is transferred by rotating while abutting on an image carrier on which the toner image is carried;
A pair of rolls arranged such that their axes are opposed to each other on the same plane, and one axis is movable in a state of being inclined on the same plane with respect to the other axis,
An elastic endless shape is wound around the pair of rolls, and a portion wound around the other roll is in contact with the intermediate transfer belt, and a recording medium supplied to the contact portion is provided. A secondary transfer belt that transfers the toner image transferred to the intermediate transfer belt to the recording medium by being conveyed while being sandwiched between the intermediate transfer belt;
An adjusting means capable of arbitrarily adjusting the inclination angle of the one roll with respect to the other roll;
An image forming apparatus. The adjusting means is rotatably provided between at least one axial end of the pair of rolls and between the other axial end of the pair of rolls, and is directly or indirectly attached to the pair of rolls. A cam that tilts the one roll with respect to the other roll by rotating in contact with the other roll,
The image forming apparatus according to claim 1.   The image forming apparatus according to claim 2, wherein the adjusting unit includes a driving source that rotates the cam with a driving force. The adjusting means includes
Various image forming conditions including at least one image forming condition among the types of the recording medium, the difference between the front and back of the recording medium when performing duplex printing, the position of the output tray, the number of printed sheets, and the continuous printing time, and the recording medium A storage unit that stores a plurality of correction data of the inclination angle set in advance based on both the degree of distortion of the transferred toner image;
Control for selecting the correction data corresponding to the selected image forming condition from among the various image forming conditions from a plurality of the correction data, and controlling driving of the drive source based on the selected correction data And
The image forming apparatus according to claim 3, further comprising:   The image forming apparatus according to claim 4, wherein the adjusting unit includes a display unit capable of displaying an image of a toner image whose distortion is adjusted by driving the driving source.   The adjusting means is inserted into at least one of the axial ends of the pair of rolls and between the axial other ends of the pair of rolls, whereby the one roll is made to the other roll. The image forming apparatus according to claim 1, wherein the spacer is inclined.

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