JP5237766B2 - Belt meandering speed detection device, belt unit provided with this belt meandering speed detection device, and image forming apparatus provided with this belt unit - Google Patents

Description

  The present invention relates to a belt meandering speed detecting device for detecting a meandering speed of an endless belt, a belt unit including the belt meandering speed detecting device, and an image forming apparatus including the belt unit.

    In an image forming apparatus capable of color printing, such as a printer, a copying machine, and a facsimile machine, four color (magenta, cyan, yellow, black) image forming stations are arranged at predetermined intervals along the moving direction of the intermediate transfer belt. In some cases, a toner image is superimposed and transferred onto an intermediate transfer belt moving at each of these image forming stations, and the toner image is printed on a sheet (copy paper, plastic film, etc.). The intermediate transfer belt is an endless belt wound around a plurality of rollers, and is rotated by the plurality of rollers.

  In such an image forming apparatus, when the intermediate transfer belt meanders, the transfer position shifts in a direction perpendicular to the rotational direction of the intermediate transfer belt, and the toner images of the respective colors superimposed on the intermediate transfer belt are displaced. A color shift occurs in the color image printed on the sheet.

  In order to prevent such color misregistration, a technique for accurately detecting meandering of the intermediate transfer belt and controlling meandering of the intermediate transfer belt based on the detection result is already known (see Patent Document 1).

  13 and 14 show a belt device 111 in which a technique for controlling the meandering of the intermediate transfer belt 110 is incorporated. In the belt device 111 shown in these drawings, detection flanges 114 and 114 are rotatably attached to roller shafts 113 and 113 protruding from both shaft end portions of the roller 112 around which the transfer belt 110 is wound. The detection flange 114 includes a cylindrical belt contact portion 115 having the same diameter as the outer diameter of the roller 112, and a disk-shaped encoder disk portion 116 fixed to the end of the belt contact portion 115. . The detection flange 114 is disposed adjacent to both end surfaces of the roller 112 having the same axial length as the widthwise dimension of the intermediate transfer belt 110, so that the roller shaft 113 does not fall off the roller shaft 113. 113 is prevented from coming off. A plurality of slits 117 are formed in the encoder disk portion 116 at equal intervals along the circumferential direction. Further, a photo interrupter 118 is disposed in a portion of the encoder disk portion 116 where the slit 117 is formed. The rotation of the encoder disk unit 116 is detected by the photo interrupter 118.

In such a belt device 111, when the intermediate transfer belt 110 meanders and the end portion in the width direction of the intermediate transfer belt 110 is disengaged from the axial end portion of the roller 112, the detection flanges 114 arranged on both sides of the roller 112 are detected. , 114 is in contact with the intermediate transfer belt 110, the belt contact portion 115 is rotated by the intermediate transfer belt 110, and the rotation of the belt contact portion 115 is detected by the photo interrupter 118. As a result, meandering of the intermediate transfer belt 110 is detected.
JP 2000-281233 A

  However, in the belt device 111 shown in FIGS. 13 and 14, when the detection flange 114 rotates with the roller 112, the intermediate transfer belt 110 rotates without causing meandering. If the intermediate transfer belt 110 meanders by the interrupter 118, it will be erroneously detected. In order to prevent such erroneous detection, it is necessary to provide a gap between the roller 112 and the belt contact portion 115 of the detection flange 114 to prevent the roller 112 and the detection flange 114 from rotating together. For this reason, in the belt device 111 of FIGS. 13 and 14, even if the intermediate transfer belt 110 meanders and the end of the intermediate transfer belt 110 in the width direction is disengaged from the roller 112, the end of the intermediate transfer belt 110 in the width direction. Until the belt 112 reaches the belt contact portion 115 beyond the gap between the roller 112 and the belt contact portion 115, the meandering of the intermediate transfer belt 110 cannot be detected, and the detection of the meandering of the intermediate transfer belt 110 is delayed.

  13 and 14, the intermediate transfer belt 110 meanders, the intermediate transfer belt 110 contacts the belt contact portion 115 of the detection flange 114, and the detection flange 114 is rotated by the intermediate transfer belt 110. Even if the meandering of the intermediate transfer belt 110 is detected by the photo interrupter 118, the meandering amount of the intermediate transfer belt 110 cannot be detected, so that it is difficult to correct the meandering of the intermediate transfer belt 110 with high accuracy.

  Accordingly, the present invention provides a belt meandering speed detection device capable of quickly detecting the meandering of the belt and performing correction of the meandering of the belt with high accuracy, and a belt unit including the belt meandering speed detection device, An object of the present invention is to provide an image forming apparatus including the belt unit.

  The invention according to claim 1 relates to a belt meandering speed detecting device for detecting the meandering speed of an endless belt wound around a plurality of rollers and rotated. The belt meandering speed detecting device according to the present invention detects a belt meandering amount by using a belt turning speed detecting means for detecting the turning speed of the belt and a detection result of the belt turning speed detecting means. Belt meandering amount detecting means; and belt meandering speed calculating means for calculating the meandering speed of the belt based on the detection result of the belt meandering amount detecting means. The belt has endless ridges extending along the circumferential direction on at least one of the inner circumferential surface and the outer circumferential surface thereof and on a portion that does not contact the plurality of rollers. The belt rotation speed detecting means has a cylindrical roller that is always in contact with the belt and is rotated by the belt, and a first sensor that measures the rotational speed of the cylindrical roller within a predetermined time. The rotation speed of the belt is detected from the detection result of the first sensor. The belt meandering amount detecting means includes (1) a conical roller that is always in contact with the belt and is rotated by the belt, and a second sensor that measures the rotational speed of the conical roller within a predetermined time. (2) The tapered outer peripheral surface of the conical roller is always in contact with the convex strip of the belt, and the generatrix direction of the outer peripheral surface of the conical roller contacting the convex strip is in the width direction of the belt. (3) The meandering amount of the belt is detected using the detection result from the second sensor and the detection result of the belt rotation speed detection means.

  The invention of claim 2 relates to a belt meandering speed detecting device for detecting the meandering speed of an endless belt wound around a plurality of rollers and rotated. The belt meandering speed detecting device according to the present invention detects a belt meandering amount by using a belt turning speed detecting means for detecting the turning speed of the belt and a detection result of the belt turning speed detecting means. Belt meandering amount detecting means; and belt meandering speed calculating means for calculating the meandering speed of the belt based on the detection result of the belt meandering amount detecting means. The belt has endless ridges extending along the circumferential direction at one end in the width direction on the inner peripheral surface and at one end not contacting the plurality of rollers. The belt rotation speed detecting means has a cylindrical roller that is always in contact with the belt and is rotated by the belt, and a first sensor that measures the rotational speed of the cylindrical roller within a predetermined time. The rotation speed of the belt is detected from the detection result of the first sensor. The belt meandering amount detecting means includes (1) a conical roller that is always in contact with the belt and is rotated by the belt, and a second sensor that measures the rotational speed of the conical roller within a predetermined time. (2) The tapered outer peripheral surface of the conical roller is always in contact with the convex strip of the belt, and the generatrix direction of the outer peripheral surface of the conical roller contacting the convex strip is in the width direction of the belt. (3) The meandering amount of the belt is detected using the detection result from the second sensor and the detection result of the belt rotation speed detection means.

  The invention of claim 3 relates to a belt meandering speed detecting device for detecting the meandering speed of an endless belt that is wound around a plurality of rollers and rotated. The belt meandering speed detecting device according to the present invention comprises a belt turning speed detecting means for detecting the turning speed of the belt, a belt meandering amount detecting means for detecting the meandering amount of the belt, and the belt turning speed detecting means. And a belt meandering speed calculating means for calculating the meandering speed of the belt based on a detection result of the belt meandering amount detecting means. The belt has endless ridges extending along the circumferential direction on at least one of the inner circumferential surface and the outer circumferential surface thereof and on a portion that does not contact the plurality of rollers. The belt rotation speed detecting means includes a cylindrical roller that is always in contact with the belt and is rotated by the belt, and a first sensor that measures the number of rotations of the cylindrical roller within a predetermined time. The detection result of the first sensor is output to the belt meandering speed calculation means. The belt meandering amount detecting means includes (1) a conical roller that is always in contact with the belt and is rotated by the belt, and a second sensor that measures the rotational speed of the conical roller within a predetermined time. (2) The tapered outer peripheral surface of the conical roller is always in contact with the convex strip of the belt, and the generatrix direction of the outer peripheral surface of the conical roller contacting the convex strip is in the width direction of the belt. (3) The detection result from the second sensor is output to the belt meandering speed calculation means.

  The invention according to claim 4 relates to a belt meandering speed detecting device for detecting the meandering speed of an endless belt that is wound around a plurality of rollers and rotated. The belt meandering speed detecting device according to the present invention comprises a belt turning speed detecting means for detecting the turning speed of the belt, a belt meandering amount detecting means for detecting the meandering amount of the belt, and the belt turning speed detecting means. And a belt meandering speed calculating means for calculating the meandering speed of the belt based on a detection result of the belt meandering amount detecting means. The belt has endless ridges extending along the circumferential direction at one end in the width direction on the inner peripheral surface and at one end not contacting the plurality of rollers. The belt rotation speed detecting means includes a cylindrical roller that is always in contact with the belt and is rotated by the belt, and a first sensor that measures the number of rotations of the cylindrical roller within a predetermined time. The detection result of the first sensor is output to the belt meandering speed calculation means. The belt meandering amount detecting means includes (1) a conical roller that is always in contact with the belt and is rotated by the belt, and a second sensor that measures the rotational speed of the conical roller within a predetermined time. (2) The tapered outer peripheral surface of the conical roller is always in contact with the convex strip of the belt, and the generatrix direction of the outer peripheral surface of the conical roller contacting the convex strip is in the width direction of the belt. (3) The detection result from the second sensor is output to the belt meandering speed calculation means.

  According to a fifth aspect of the present invention, in the belt meandering speed detection device according to any one of the first to fourth aspects, the cylindrical roller and the conical roller are arranged so as to sandwich the belt. Yes.

  A sixth aspect of the present invention is a plurality of rollers, an endless belt wound around the plurality of rollers, a belt meandering speed detecting device according to any one of the first to fifth aspects, and a meandering of the belt. A belt meandering correction mechanism for correcting the belt meander, and drive means for controlling the belt meandering correction mechanism based on the meandering speed of the belt detected by the belt meandering speed detection device. It is about.

  A seventh aspect of the present invention relates to an image forming apparatus comprising: the belt unit according to the sixth aspect of the present invention; and an image forming unit that forms an image on a sheet conveyed by the belt unit. It is.

  According to the belt meandering speed detecting device according to the first and second aspects of the invention, the belt rotation speed detecting means is configured so that the cylindrical roller is always in contact with the belt and is rotated by the belt. And can be detected accurately. Further, the belt meandering amount detecting means is configured such that the conical roller is always in contact with the belt and is rotated by the belt, the belt meanders, the belt protrusion and the tapered outer peripheral surface of the conical roller. If the contact position of the roller is displaced along the generatrix direction of the outer peripheral surface of the conical roller, the meandering of the belt is quickly detected as a change in the rotational speed of the conical roller, and based on this detection result and the detection result of the belt rotation speed detecting means. Since the meandering amount of the belt is calculated, the meandering amount of the belt can be accurately detected even if the rotation speed of the belt varies. The belt meandering speed calculation means can calculate the meandering speed of the belt quickly and with high accuracy based on the result detected by the belt meandering amount detection means. Therefore, according to the first and second aspects of the invention, the meandering amount of the belt can be detected quickly and accurately as the meandering speed of the belt.

  According to the belt meandering speed detecting device according to the third and fourth aspects of the invention, the belt rotation speed detecting means is configured so that the cylindrical roller is always in contact with the belt and is rotated by the belt. And can be detected accurately. Further, the belt meandering amount detecting means is configured such that the conical roller is always in contact with the belt and is rotated by the belt, the belt meanders, the belt protrusion and the tapered outer peripheral surface of the conical roller. When the contact position is shifted along the generatrix direction of the outer peripheral surface of the conical roller, the meandering of the belt can be quickly detected as a change in the rotational speed of the conical roller. The belt meandering speed calculation means calculates the belt meandering speed based on the detection results of the belt rotation speed detection means and the belt meandering amount detection means, and therefore the belt rotation speed varies. Even so, the meandering speed of the belt can be calculated quickly and with high accuracy. Therefore, according to the third and fourth aspects of the present invention, the meandering amount of the belt can be detected quickly and accurately as the meandering speed of the belt.

  According to the belt meandering speed detection device of the fifth aspect of the invention, since the belt is sandwiched between the cylindrical roller and the conical roller, an appropriate pressing force (contact pressure) can be applied to the cylindrical roller, the conical roller and the belt. The cylindrical roller and the conical roller are less likely to slip with the belt, and the cylindrical roller and the conical roller are accurately rotated by the belt (the rotation of the cylindrical roller and the conical roller is stabilized). The speed can be detected quickly and accurately.

  According to the belt unit of the sixth aspect of the invention, the drive means is a belt meandering correction mechanism based on the detection result (belt meandering speed) of the belt meandering speed detecting device according to any one of the first to fifth aspects of the invention. Therefore, the meandering of the belt can be corrected quickly and with high accuracy, and the meandering of the belt can be suppressed quickly.

  According to the invention of claim 7, since the belt unit according to the invention of claim 6 is provided, high-quality image formation is possible without causing image formation defects such as color misregistration due to meandering of the belt. become.

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

(Image forming device)
FIG. 1 is a schematic structural diagram for explaining an example of an image forming apparatus 1 according to the present invention. The image forming apparatus 1 shown in FIG. 1 is an electrophotographic four-color full-color printer, and employs a tandem method and an intermediate transfer method. In the image forming apparatus 1, a sheet feeding unit 3, an image forming unit 4, a fixing unit 5, and a sheet refeeding unit 6 are provided in the image forming apparatus main body 2.

  The sheet feeding unit 3 includes a plurality of sheet feeding cassettes 7, a pickup roller 8 disposed corresponding to each sheet feeding cassette 7, a feeding roller 10, a retard roller 11, and a registration roller pair 12. Is arranged. In each paper feed cassette 7, a plurality of sheets P are stored in a stacked state. The sheet P in the sheet feeding cassette 7 is sent out from the sheet feeding cassette 7 by the pickup roller 8, and is then prevented from being double fed by the feeding roller 10 and the retard roller 11. It is. The sheet P sent to the sheet conveyance path 13 is brought into contact with the nip of the resist roller pair 12 that is stopped, and the skew is corrected and temporarily stopped. Thereafter, the temporarily stopped sheet P is synchronized with the transfer of the toner image on the intermediate transfer belt (belt) 14 to the secondary transfer portion T2 as the intermediate transfer belt 14 rotates in the direction of arrow R14. The toner is supplied toward the secondary transfer portion T2 by the rotation of the registration roller pair 12 so as to be positioned at the next transfer portion T2. A conveyance roller (not shown) is arranged in the sheet conveyance path 13, and the conveyance roller conveys the sheet P along the sheet conveyance path 13.

  The image forming unit 4 is provided with four image forming stations and an intermediate transfer unit (belt unit) 15. The four image forming stations sequentially form magenta (M), cyan (C), yellow (Y), and black (BK) image forming stations 16M, 16C, 16Y, in order from the upstream side in the rotation direction of the intermediate transfer belt. 16BK is arranged. These four color image forming stations 16M, 16C, 16Y, and 16BK are configured in the same manner except for the developer to be used. The magenta image forming station 16M will be described as an example. The image forming station 16M includes a photosensitive drum (image carrier) 17, a charger 18, an exposure device 20, a developing device 21, and a cleaning device 22. On the other hand, the intermediate transfer unit 15 includes a transfer frame 23 and a plurality of rollers rotatably supported by the transfer frame 23 (that is, a driving roller 24, a driven roller 25, a primary transfer roller 26, and a secondary transfer counter roller 27). , A plurality of tension rollers, etc.) and an endless intermediate transfer belt 14 stretched around these rollers (wound in a tensioned state). The intermediate transfer belt 14 rotates in the arrow R14 direction by the rotation of the driving roller 24 in the arrow direction (clockwise in FIG. 1). The entire intermediate transfer unit 15 is configured to be detachable from the image forming apparatus body 2 from the front side of the image forming apparatus body 2.

  In the magenta image forming station 16M, the photosensitive drum 17 is rotationally driven by a driving means (not shown) at a predetermined process speed (circumferential speed) in an arrow direction (counterclockwise in FIG. 1), and its surface (outer peripheral surface). ) Are uniformly charged to a predetermined polarity and potential by the charger 18. The surface of the photosensitive drum 17 after charging is exposed according to image information by the exposure device 20, and the charge of the exposed portion is removed to form an electrostatic latent image. This electrostatic latent image is developed as a magenta toner image by the developing device 21 with magenta toner attached thereto. The magenta toner image is transferred onto the intermediate transfer belt 14 by the primary transfer roller 26 at the primary transfer portion T1. After the toner image is transferred, the transfer residual toner remaining on the surface of the photosensitive drum 17 is removed by the cleaning device 22 and used for the next image formation.

  Similarly, cyan, yellow, and black toner images respectively formed on the respective photosensitive drums 17 in the primary transfer portions of the cyan, yellow, and black image forming stations 16C, 16Y, and 16BK are respectively transferred by the primary transfer roller 26. Primary transfer is performed so as to be sequentially superimposed on a magenta toner image on the intermediate transfer belt 14. The four color toner images superimposed on the intermediate transfer belt 14 in this way are conveyed to the secondary transfer portion T2 by the rotation of the intermediate transfer belt 14. In parallel with this, the sheet P is supplied to the secondary transfer portion T2 by rotating the pair of registration rollers 12. The four color toner images on the intermediate transfer belt 14 are secondarily transferred collectively onto the sheet P by the secondary transfer roller 28. The transfer residual toner remaining on the surface of the intermediate transfer belt 14 after the secondary transfer is removed by the belt cleaner 30. On the other hand, the sheet P after the toner image transfer is conveyed to the fixing unit 5 by the conveyance belt 31.

  The fixing unit 5 includes a fixing device 34 having a fixing roller 32 and a pressure roller 33 that is pressed against the fixing roller 32 and constitutes a fixing nip N. When the sheet P conveyed to the fixing device 34 passes through the fixing nip portion N, it is heated and pressed to fix the toner image on the surface. The sheet P after the toner image is fixed is discharged onto a paper discharge tray 36 by a paper discharge roller pair 35. Thereby, the four-color full-color image formation on one side of one sheet P is completed.

  When image formation is performed also on the back surface (unprinted surface) of the sheet P on which one side has been printed, the sheet is reversed by the flappers 37 and 38 disposed in the sheet refeed unit 6, the reversing path 40, and the like. P is supplied again to the image forming unit 4 through the refeed path 41 and the like, and after the toner image is transferred and fixed on the back surface (unprinted surface) in the same manner as described above, the paper discharge tray 36 is discharged.

(Belt meander correction mechanism)
FIG. 2 is a diagram schematically showing the belt meandering correction mechanism 42 attached to the intermediate transfer unit 15 of the image forming apparatus, and shows the intermediate transfer unit 15 as viewed from the direction A in FIG.

  As shown in FIG. 2, the belt meandering correction mechanism 42 protrudes outward from one end side of the roller shaft 43 of the driven roller 25 constituting the intermediate transfer unit 15 and from the widthwise end of the intermediate transfer belt 14. A driven roller 25 supported by the transfer frame 23 of the intermediate transfer unit 15 so that the roller shaft 43 can be swung by an angle of 2δ with the other end side of the roller shaft 43 as a rocking fulcrum 43a. Can be swung based on a control signal from the controller 44 (see FIG. 1).

  The belt meandering correction mechanism 42 swings the roller shaft 43 based on the rotation of the motor 45 and the motor 45 such as a stepping motor capable of rotating by a minute angle based on a control signal from the controller 44. A power transmission mechanism 46. The power transmission mechanism 46 includes a cam (not shown) rotated by a motor 45, a lever (not shown) swung by the cam, and a gear train (not shown) rotated by the motor 45. As long as the follower roller 25 is swung with a minute angle with high accuracy, it may be any combination.

  Here, in the driven roller 25, the intermediate transfer belt 14 is wound around the outer surface of the roller body 25a, and one end portion side (the right end portion 25b side in the drawing) of the roller body 25a is one end in the width direction of the intermediate transfer belt 14. The length of the roller body 25a in the axial direction is intermediate transfer belt so as to be located on the inner side of the portion side (the protrusion 47, which is an endless protrusion formed continuously protruding along the circumferential direction of the inner peripheral surface). 14 is formed shorter than the dimension in the width direction. The driven roller 25 is supported by the transfer frame 23 of the intermediate transfer unit 15 at the other end side of the roller shaft 43 via a bearing 48. The roller shaft support point of the bearing 48 is used as a swinging fulcrum 43a in a counterclockwise direction. Oscillated in the direction or clockwise.

  Such a belt meandering correction mechanism 42 can suppress meandering of the intermediate transfer belt 14 by swinging the driven roller 25.

(Belt meandering speed detection device)
3 to 4 are diagrams schematically showing the intermediate transfer unit 15 in which the belt meandering speed detection device 50 is installed. Among these, FIG. 3 is a perspective view schematically showing the intermediate transfer unit 15 as viewed from the lower front side. 4 is a cross-sectional view of the intermediate transfer unit 15 schematically shown by cutting along the line X1-X1 in FIG. Here, as shown in FIG. 5, the belt meandering speed detection device 50 includes a belt rotation speed detecting means 51, a belt meandering amount detecting means 52, and a belt meandering speed calculating means 53, which will be described in detail later. .

  As shown in FIGS. 3 to 4, the space between the driving roller 24 and the driven roller 25 of the intermediate transfer unit 15 and between peripheral devices such as an image forming station is on the outer surface of the intermediate transfer belt 14. A cylindrical roller 54 that rolls is disposed, and a conical roller 55 that is disposed so as to face the cylindrical roller 54 and rolls on the ridge 47 on the inner surface of the intermediate transfer belt 14 is disposed. The cylindrical roller 54 and the conical roller 55 are always in contact with the intermediate transfer belt 14, and the intermediate transfer belt 14 is sandwiched between the cylindrical roller 54 and the conical roller 55.

  The cylindrical roller 54 is rotatably attached to a frame (not shown) of the intermediate transfer unit 15 via a support shaft 56, and the axial direction of the support shaft 56 extends along the width direction of the outer surface of the intermediate transfer belt 14. It extends parallel to the outer surface of the transfer belt 14, and a partial region (the right end region in FIG. 4) of the outer peripheral surface contacts the outer surface of the intermediate transfer belt 14 and is rotated by the rotating intermediate transfer belt 14. It is supposed to be. The cylindrical roller 54 rotates with the intermediate transfer belt 14 without causing a slip. The cylindrical roller 54 has one end in the axial direction and a first encoder disk 57 in which a thin film-like member having a disc shape is fixed at a position away from the intermediate transfer belt 14. Yes.

  The first encoder disk 57 has a plurality of light shielding portions 58 formed at equal intervals along the circumferential direction, and the portions other than the light shielding portions 58 transmit light. A first photo interrupter 60 is disposed at a position facing the light shielding portion 58 of the first encoder disk 57. Here, the first encoder disk 57 and the first photo interrupter 60 constitute a first sensor 61 that detects the rotational speed of the cylindrical roller 54. The first sensor 61 outputs a detection pulse to the controller 44 every time the light-shielding portion 58 of the first encoder disk 57 passes between the light-emitting portion and the light-receiving portion facing each other of the first photo interrupter 60. ing. The controller 44 is housed in the image forming apparatus main body 2 shown in FIG. 1 and calculates the rotational speed of the intermediate transfer belt 14 based on the number of detected pulses from the first sensor 61 within a predetermined time. A rotation speed calculation unit 62 is included. The cylindrical roller 54, the first sensor 61, and the belt rotation speed calculation unit 62 constitute a belt rotation speed detector 51 (see FIG. 5).

  Here, the diameter of the cylindrical roller 54 is D (mm), the number of pulses (the number of encoder pulses) output from the first photo interrupter 60 during one rotation of the first encoder disk 57 is fa, and the cylindrical roller 54 is If the number of pulses (number of detected pulses) output from the first photo interrupter 60 when rotating for a predetermined measurement time (t seconds) is Fa and the rotation speed of the intermediate transfer belt 14 is V (mm / s), the intermediate The rotation speed V (mm / s) of the transfer belt 14 is expressed as follows.

この数１の計算式に基づいて、制御コントローラ４４内のベルト回動速度算出部６２が中間転写ベルト１４の回動速度を算出し、その算出結果が記憶手段６３内に記憶される（図５参照）。

Based on the formula (1), the belt rotation speed calculator 62 in the controller 44 calculates the rotation speed of the intermediate transfer belt 14, and the calculation result is stored in the storage means 63 (FIG. 5). reference).

  As shown in FIGS. 4 and 6, the conical roller 55 is rotatably attached to a frame (not shown) of the intermediate transfer unit 15 via a support shaft 64. The conical roller 55 has a frustoconical outer shape, and a shaft hole 65 formed in the center of rotation is fitted to the support shaft 64 in a relatively rotatable state, and the tapered outer peripheral surface 66 is intermediate. It contacts with the ridges 47 formed on the inner peripheral surface of the transfer belt 14 and is rotated by the intermediate transfer belt 14. Here, the conical roller 55 is configured such that the generatrix of the outer peripheral surface 66 extends in parallel with the inner peripheral surface 14a of the intermediate transfer belt 14 at a position where the tapered outer peripheral surface 66 contacts the protrusion 47, and the intermediate transfer belt. 14 are arranged so as to extend along the width direction. The conical roller 55 is configured to rotate without causing slippage with the protrusion 47 of the intermediate transfer belt 14. The conical roller 55 has one end in the axial direction and a second encoder disk 67 fixed to the end on the large diameter side. The conical roller 55 is formed so that the angle formed by the axis 64a of the support shaft 64 and the generatrix of the outer peripheral surface 66 is θ when the taper angle of the outer peripheral surface 66 is 2θ. The belt 14 is positioned on the inner side in the width direction, the large diameter portion is positioned on the outer side in the width direction of the intermediate transfer belt 14, and the shaft center 64 a of the support shaft 64 is θ relative to the width direction of the intermediate transfer belt 14. It is attached at an angle.

  As shown in FIGS. 3, 4 and 6, the second encoder disk 67 is configured in substantially the same manner as the first encoder disk 57, and a plurality of light shielding portions 68 are formed at equal intervals along the circumferential direction. ing. A second photo interrupter 70 is disposed at a position facing the light shielding portion 68 of the second encoder disk 67. The second photo interrupter 70 is configured in the same manner as the first photo interrupter 60. Here, the second encoder disk 67 and the second photo interrupter 70 constitute a second sensor 71 that measures the meandering amount of the intermediate transfer belt 14. The second sensor 71 outputs a detection pulse to the control controller 44 every time the light shielding portion 68 of the second encoder disk 67 passes between the light emitting portion and the light receiving portion facing each other of the second photo interrupter 70. ing.

  Therefore, in the second sensor 71, the intermediate transfer belt 14 meanders, and the contact position between the protrusion 47 of the intermediate transfer belt 14 and the conical roller 55 is changed from the home position (reference position) to the large diameter portion side (a in FIG. 4). As the rotational speed of the intermediate transfer belt 14 is constant, the rotational speed of the conical roller 55 decreases, and the number of detection pulses output to the controller 44 decreases. On the other hand, in the second sensor 71, when the intermediate transfer belt 14 meanders and the contact position between the protrusion 47 of the intermediate transfer belt 14 and the conical roller 55 moves from the home position to the small diameter side (b direction side in FIG. 4). Even if the rotational speed of the intermediate transfer belt 14 is constant, the number of rotations of the conical roller 55 increases, and the number of detection pulses output to the controller 44 increases. As shown in FIG. 5, the controller 44 includes a belt meandering amount calculation unit 72 that calculates the meandering amount of the intermediate transfer belt 14 from the amount of change in the number of detected pulses from the second sensor 71 within a predetermined time. . The conical roller 55, the second sensor 71, and the belt meandering amount calculation unit 72 constitute the belt meandering amount detecting means 52 (see FIG. 5). Note that the home position of the conical roller 55 at the contact position with the intermediate transfer belt 14 (the ridge 47) is substantially the intermediate position between the small diameter portion and the large diameter portion of the conical roller 55.

  Here, the diameter at the contact position between the conical roller 55 and the intermediate transfer belt 14 (projection 47) is Φ (mm), and the pulses output from the second photo interrupter 70 during one rotation of the second encoder disk 67. The number (encoder pulse number) is fb, the pulse number (detection pulse number) output from the second photo interrupter 70 when the conical roller 55 rotates for a predetermined measurement time (t seconds) is Fb, and the intermediate transfer belt 14 When the rotation speed is V (mm / s), the number of detected pulses Fb can be expressed as the following equation (Equation 2).

この数２の式は、次式（数３）のように変形すると、円錐コロ５５の中間転写ベルト１４（凸条４７）に接触している位置における直径Φ（ｍｍ）を求める式に書き換えることができる。なお、凸条４７は、図６に示すように、中間転写ベルト１４の幅方向に沿った断面形状が略三角形状であり、その頂点部が円錐コロ５５の外周面６６に弾性変形した状態で接触してニップを形成する。したがって、凸条４７と円錐コロ５５との接触位置は、突条４７と円錐コロ５５との接触部に形成されるニップの中心位置（中間転写ベルト１４の幅方向における中心位置）とする。

When the equation (2) is transformed as the following equation (Equation 3), the equation (2) is rewritten into an equation for obtaining the diameter Φ (mm) at the position where the conical roller 55 is in contact with the intermediate transfer belt 14 (protrusion 47). Can do. As shown in FIG. 6, the protrusion 47 has a substantially triangular cross-sectional shape along the width direction of the intermediate transfer belt 14, and its apex is elastically deformed to the outer peripheral surface 66 of the conical roller 55. Contact to form a nip. Therefore, the contact position between the protrusion 47 and the conical roller 55 is the center position of the nip formed at the contact portion between the protrusion 47 and the conical roller 55 (the center position in the width direction of the intermediate transfer belt 14).

この数３における中間転写ベルト１４の回動速度Ｖの値として、円筒コロ５４に関する数１の式で求めた計測値（ベルト回動速度検出手段５１の検出結果）を使用すれば、円錐コロ５５の中間転写ベルト１４（凸条４７）に接触している位置における直径（以下、ベルト接触位置直径と略称する）Φ（ｍｍ）を、中間転写ベルト１４の速度変動に影響されることなく、正確に算出することが可能になる。一方、数３の式において、中間転写ベルト１４の回動速度Ｖとして、工場出荷時における初期値（Ｖ₀）を使用し、円錐コロ５５のみによって円錐コロ５５のベルト接触位置直径Φを求めようとすると、中間転写ベルト１４の周長が経時変化によって長くなった（伸びた）ような場合や、中間転写ベルト１４とこれを回動させる駆動ローラ２４との間に滑りを生じたような場合には、中間転写ベルト１４の速度変動（ΔＶ）分だけ誤差を生じてしまう。しかし、本実施形態によれば、中間転写ベルト１４の回動速度Ｖを円筒コロ５４及び第１センサ６１によって正確に計測し、その計測値を使用して円錐コロ５５のベルト接触位置直径Φを計算することになるため、円錐コロ５５のベルト接触位置直径Φを正確に求めることができる。この円錐コロ５５のベルト接触位置直径Φは、この数３の計算式に基づいて、制御コントローラ４４内のベルト蛇行量算出部７２によって算出され、その算出結果が記憶手段６３内に記憶される（図５参照）。

As the value of the rotational speed V of the intermediate transfer belt 14 in Equation 3, if the measured value (the detection result of the belt rotational speed detecting means 51) obtained by Equation 1 regarding the cylindrical roller 54 is used, the conical roller 55 is obtained. The diameter (hereinafter abbreviated as belt contact position diameter) Φ (mm) at the position in contact with the intermediate transfer belt 14 (projection 47) is accurate without being affected by the speed fluctuation of the intermediate transfer belt 14. Can be calculated. On the other hand, in the equation ( ₃ ), the initial value (V ₀ ) at the time of shipment from the factory is used as the rotation speed V of the intermediate transfer belt 14, and the belt contact position diameter Φ of the conical roller 55 is obtained only by the conical roller 55. Then, when the peripheral length of the intermediate transfer belt 14 becomes longer (elongated) due to a change with time, or when the intermediate transfer belt 14 slips between the intermediate transfer belt 14 and the driving roller 24 that rotates the intermediate transfer belt 14. In this case, an error is generated by the speed variation (ΔV) of the intermediate transfer belt 14. However, according to the present embodiment, the rotational speed V of the intermediate transfer belt 14 is accurately measured by the cylindrical roller 54 and the first sensor 61, and the belt contact position diameter Φ of the conical roller 55 is determined using the measured value. Since the calculation is performed, the belt contact position diameter Φ of the conical roller 55 can be accurately obtained. The belt contact position diameter Φ of the conical roller 55 is calculated by the belt meandering amount calculation unit 72 in the controller 44 based on the equation (3), and the calculation result is stored in the storage means 63 ( (See FIG. 5).

FIG. 7 is a diagram showing the relationship between the sampling time (predetermined measurement time) and the sampling interval when measuring the meandering amount of the intermediate transfer belt 14. Here, the sampling time is a time for measuring the rotation speed V of the intermediate transfer belt 14 by the cylindrical roller 54 and the first sensor 61, and the contact of the conical roller 55 by the conical roller 55 and the second sensor 71. This is the time (t seconds) for measuring the position diameter Φ (see FIGS. 3 and 4). The sampling interval refers to the time (t ₁ second) from the first sampling start (measurement start) to the second sampling start (measurement start). Thus, the meandering amount of the intermediate transfer belt 14 can be obtained by measuring the contact position diameter Φ of the conical roller 55 twice at a predetermined sampling interval.

For example, as shown in FIG. 6, the contact position diameter (diameter at the contact position L ₁ ) of the conical roller 55 obtained by the first measurement is Φ ₁ and the conical roller obtained by the second measurement is obtained. When the contact position diameter (diameter at the contact position L ₂ ) is Φ ₂ , the meandering amount ΔL (ΔL = L ₂ −L ₁ ) of the intermediate transfer belt can be expressed by the following equation (Equation 4). It is assumed that the conical roller 55 is positioned so that the taper angle of the outer peripheral surface 66 is 2θ and the axis 64a divides the taper angle into two. Further, the contact position between the conical roller 55 and the intermediate transfer belt 14 is expressed by a distance from the reference position L ₀ with the minimum diameter portion of the conical roller 55 as the reference position L ₀ . In FIG. 6, the contact position between the conical roller 55 and the intermediate transfer belt 14 at the time of the first measurement is represented by L ₁ , and the contact position between the conical roller 55 and the intermediate transfer belt 14 at the time of the second measurement. Is represented by L ₂ .

この数４を書き換えると、次式（数５）のようになる。

When this equation 4 is rewritten, the following equation (equation 5) is obtained.

図５に示した制御コントローラ４４のベルト蛇行量算出部７２は、第１回目の計測において算出した円錐コロ５５の接触位置直径Φ₁と第２回目の計測において算出した円錐コロ５５の接触位置直径Φ₂を使用し、数４の計算式にしたがって中間転写ベルト１４の蛇行量ΔＬを算出する。

The belt meandering amount calculator 72 of the controller 44 shown in FIG. 5 calculates the contact position diameter Φ ₁ of the conical roller 55 calculated in the first measurement and the contact position diameter of the conical roller 55 calculated in the second measurement. Using Φ ₂ , the meandering amount ΔL of the intermediate transfer belt 14 is calculated according to the equation (4).

The belt meandering speed calculation means 53 of the controller 44 shown in FIG. 5 determines the meandering speed v of the intermediate transfer belt 14 based on the calculation result of the belt meandering amount calculation unit 72 (detection result by the belt meandering amount detection means 52). calculate. The following equation (Equation 6) is an equation for obtaining the meandering speed v of the intermediate transfer belt 14. That is, the contact position between the conical roller 55 and the intermediate transfer belt 14 moves from L ₁ to L ₂ during the sampling interval (t ₁ ), and the amount of movement becomes ΔL (ΔL = L ₂ −L ₁ ). (See FIG. 6). Therefore, the meandering speed v of the intermediate transfer belt 14 can be obtained by dividing the moving amount ΔL of the contact position between the conical roller 55 and the intermediate transfer belt 14 by the sampling interval (t ₁ ).

次に、この中間転写ベルト１４の蛇行を抑えるため、中間転写ベルト１４の蛇行速度ｖを零にするように、制御コントローラ４４によってベルト蛇行補正機構４２を作動制御する方法について説明する（図２及び図５参照）。

Next, in order to suppress the meandering of the intermediate transfer belt 14, a method for controlling the belt meandering correction mechanism 42 by the controller 44 so that the meandering speed v of the intermediate transfer belt 14 is zero will be described (FIG. 2 and FIG. 2). (See FIG. 5).

  In the belt meandering correction mechanism 42 shown in FIG. 2, the power transmission mechanism unit 46 is configured such that the relationship between the rotation angle of the motor 45 and the meandering speed v of the intermediate transfer belt 14 is a desired relationship. For example, in this embodiment, as shown in FIG. 8, the belt meandering correction mechanism 42 is configured so that the relationship between the rotation angle of the motor 45 and the meandering speed v of the intermediate transfer belt 14 is a linear relationship. ing. FIG. 8 shows a mode in which the meandering speed v of the intermediate transfer belt 14 changes by −50 μm / second by one rotation of the motor 45.

  As shown in FIG. 5, the controller 44 calculates the rotation angle of the motor 45 based on the meandering speed v of the intermediate transfer belt 14 calculated by the belt meandering speed calculation means 53, and rotates the motor 45. The motor drive means 73 which controls is provided. The motor driving means 73 functions as a driving means for the belt meandering correction mechanism 42 and controls the overall operation of the belt meandering correction mechanism 42 by controlling the rotation of the motor 45.

  When the motor 45 is rotated by a predetermined angle by the motor driving means 73, the meandering speed v of the intermediate transfer belt 14 becomes substantially zero, and the meandering of the intermediate transfer belt 14 is suppressed. Note that the control accuracy (deviation amount from v = 0) of the meandering speed v of the intermediate transfer belt 14 is determined by the performance (step angle) of the motor 45 and the like. Therefore, the control range of the meandering speed v of the intermediate transfer belt 14 (range of v≈0) is determined in advance with a range of v≈0 (v≈0 = ± Δv) in consideration of the performance of the motor 45. The numerical value of Δv is recorded in a readable state in the storage means 63 of the controller 44, and the numerical value of ± Δv is appropriately read from the storage means 63 and compared with the calculated value of the belt meandering speed calculating means 53. (Step S4 in FIG. 9).

  In the present embodiment as described above, the belt rotation speed detector 51 is configured so that the cylindrical roller 54 is always in contact with the intermediate transfer belt 14 and is rotated by the intermediate transfer belt 14. Can be detected quickly and accurately. Further, the belt meandering amount detecting means 52 is configured such that the conical roller 55 is always in contact with the intermediate transfer belt 14 and is rotated by the intermediate transfer belt 14, and the intermediate transfer belt 14 meanders and the intermediate transfer belt 14 is rotated. 14 is shifted along the generatrix direction of the outer peripheral surface 66 of the conical roller 55, the meander belt of the intermediate transfer belt 14 is rotated at the rotational speed of the conical roller 55. Since the meandering amount of the intermediate transfer belt 14 is calculated based on the detection result and the detection result of the belt rotation speed detecting means 51, the rotation speed of the intermediate transfer belt 14 is calculated. Even if there is a fluctuation, the meandering amount of the intermediate transfer belt 14 can be accurately detected. The belt meandering speed calculating means 53 can calculate the meandering speed v of the intermediate transfer belt 14 quickly and accurately based on the result detected by the belt meandering amount detecting means 52. Therefore, the belt meandering speed detection device 50 according to this embodiment can quickly and accurately detect the meandering amount of the intermediate transfer belt 14 as the meandering speed of the intermediate transfer belt 14.

  Further, according to the belt meandering speed detecting device 50 according to the present embodiment, the intermediate transfer belt 14 is sandwiched between the cylindrical roller 54 and the conical roller 55. An appropriate pressing force (contact pressure) can be applied to the belt 14, and the cylindrical roller 54 and the conical roller 55 are less likely to slip with the intermediate transfer belt 14, and the cylindrical roller 54 and the conical roller 55 are accurately moved by the intermediate transfer belt 14. (The rotation of the cylindrical roller 54 and the conical roller 55 is stabilized), and the meandering amount of the intermediate transfer belt 14 can be detected rapidly and with high accuracy as the meandering speed v of the intermediate transfer belt 14.

  In addition, according to the intermediate transfer unit 15 including the belt meandering speed detection device 50 according to the present embodiment, the motor driving unit 73 determines the detection result of the belt meandering speed detection device 50 (meandering speed v of the intermediate transfer belt 14). Based on this, the belt meandering correction mechanism 42 is controlled so that the meandering of the intermediate transfer belt 14 can be corrected quickly and with high accuracy, and the meandering of the intermediate transfer belt 14 can be suppressed quickly.

  Further, the image forming apparatus 1 including the intermediate transfer unit 15 according to the present embodiment does not cause image formation defects such as color misregistration due to the meandering of the intermediate transfer belt 14, and enables high-quality image formation. Become.

(Modification of belt meandering speed detection device)
Hereinafter, modifications of the belt meandering speed detection device 50 according to the present invention will be described. In addition, the overlapping description is abbreviate | omitted about the same structure as the said embodiment.

  By substituting Equation 1 into Equation 3 above, it can be expressed as the following equation (Equation 7).

また、円筒コロ５４側のエンコーダパルス数ｆａと円錐コロ５５側のエンコーダパルス数ｆｂが等しい（ｆａ＝ｆｂ）場合、数７は次式（数８）のように表すことができる。

When the number of encoder pulses fa on the cylindrical roller 54 side and the number of encoder pulses fb on the conical roller 55 side are equal (fa = fb), Equation 7 can be expressed as the following equation (Equation 8).

次に、第１回目の計測において算出した円錐コロ５５の接触位置直径Φ₁と、第２回目の計測において算出した円錐コロ５５の接触位置直径Φ₂は、次式（数９）のように表すことができる。

Next, the contact position diameter Φ _{1 of} the conical roller 55 calculated in the first measurement and the contact position diameter Φ ₂ of the conical roller 55 calculated in the second measurement are expressed by the following equation (Equation 9). Can be represented.

ここで、第１回目の計測における検出パルス数Ｆａ，ＦｂをＦａ₁，Ｆｂ₁とし、第２回目の計測における検出パルス数Ｆａ，ＦｂをＦａ₂，Ｆｂ₂とすれば、Φ₂−Φ₁は、次式（数１０）のように表すことができる。

Here, if the detected pulse numbers Fa and Fb in the _first measurement are Fa ₁ and Fb ₁ and the detected pulse numbers Fa and Fb in the second measurement are Fa ₂ and Fb ₂ , then Φ ₂ −Φ ₁ Can be expressed as the following equation (Equation 10).

そして、中間転写ベルトの蛇行速度ｖは、数５，数６，数１０より、次式（数１１）のように表すことができる。

The meandering speed v of the intermediate transfer belt can be expressed by the following equation (Equation 11) from Equation 5, Equation 6, and Equation 10.

したがって、制御コントローラ４４のベルト蛇行速度算出手段５３は、第１回目の計測における第１センサ６１から出力された検出パルスＦａ₁と第２センサ７１から出力された検出パルスＦｂ₁、及び第２回目の計測における第１センサ６１から出力された検出パルスＦａ₂と第２センサ７１から出力された検出パルスＦｂ₂とに基づいて、中間転写ベルト１４の蛇行速度ｖを算出することができる（図５参照）。すなわち、本変形例によれば、ベルト蛇行速度検出装置５０は、図５に示すように、ベルト回動速度算出部６２及びベルト蛇行量算出部７２を省略することが可能になり、制御コントローラ４４の構成を簡略化することが可能になる。

Therefore, the belt meandering speed calculating means 53 of the controller 44 detects the detection pulse Fa ₁ output from the first sensor 61 and the detection pulse Fb ₁ output from the second sensor 71 in the first measurement, and the second time. The meandering speed v of the intermediate transfer belt 14 can be calculated based on the detection pulse Fa ₂ output from the first sensor 61 and the detection pulse Fb ₂ output from the second sensor 71 in this measurement (FIG. 5). reference). That is, according to the present modification, the belt meandering speed detection device 50 can omit the belt rotation speed calculation unit 62 and the belt meandering amount calculation unit 72 as shown in FIG. The configuration can be simplified.

  The motor drive unit 73 of the controller 44 calculates the rotation angle of the motor 45 based on the meandering speed v of the intermediate transfer belt 14 calculated by the belt meandering speed calculation unit 53, and the motor 45 based on the calculated value. Is rotated by a predetermined angle so that the meandering speed v of the intermediate transfer belt 14 becomes substantially zero, and the meandering of the intermediate transfer belt 14 is suppressed.

  According to the belt meandering speed detecting device 50 according to the present modification as described above, the belt meandering speed calculating means 53 includes the number of detected pulses from the first sensor 61 of the belt rotation speed detecting means 51 and the belt meandering amount detecting means. Since the meandering speed v of the intermediate transfer belt 14 is calculated based on the number of detected pulses from the second sensor 71 of 52, even if the rotational speed of the intermediate transfer belt 14 fluctuates, The meandering speed v of the transfer belt 14 can be calculated quickly and with high accuracy. Therefore, the belt meandering speed detection device 50 according to this modification can quickly and accurately detect the meandering amount of the intermediate transfer belt 14 as the meandering speed v of the intermediate transfer belt 14.

  Further, according to the intermediate transfer unit 15 including the belt meandering speed detection device 50 according to the present modification, the meandering of the intermediate transfer belt 14 is corrected quickly and with high accuracy, as in the above-described embodiment, and the fitting transfer belt. 14 meandering can be quickly suppressed.

  In addition, the image forming apparatus 1 including the intermediate transfer unit 15 according to this modification does not cause image formation defects such as color misregistration due to meandering of the intermediate transfer belt 14 as in the above-described embodiment. High quality image formation becomes possible.

(Example of belt meandering speed detection device)
Next, an embodiment of the belt meandering speed detection device 50 will be described with reference to the flowchart of FIG. Here, the belt rotation speed V of the intermediate transfer belt 14 was 200 mm / second during the first measurement and 202 mm / second during the second measurement. The sampling time was 5 seconds for both the first time and the second time. The sampling interval was 5.05 seconds. The number of detected pulses on the cylindrical roller 54 side (first sensor 61) was Fa1 = 6366 (pulse) during the first measurement, and Fa2 = 6494 (pulse) during the second measurement (FIG. 9 steps S11, S12). The number of detected pulses on the conical roller 55 side (second sensor 71) was Fb1 = 5945 (pulse) during the first measurement and Fb2 = 6272 (pulse) during the second measurement (FIG. 9 steps S21, S22). The outer diameter of the cylindrical roller 54 is D = 10 mm. The taper angle of the conical roller 55 is 2θ = 90 °. The second encoder pulse number fb is 200 (pulse / rev). The taper angle 2θ of the conical roller 55 is 90 °, and 2 · sin 45 ° is 1.414.

  By substituting these numerical values into Equation 11, the meandering speed v of the intermediate transfer belt 14 is obtained. That is, v = 10 (mm) × (6494 / 6272-6366 / 5945) /1.414/5.05=−0.049 (mm / second). This meandering speed v is calculated by the belt meandering speed calculating means 53 (step S3 in FIG. 9).

  Since the meandering speed v of the intermediate transfer belt 14 calculated by the belt meandering speed calculating means 53 is not v≈0 (step S4 in FIG. 9), the motor driving means 73 is driven by the motor based on the meandering speed v of the intermediate transfer belt 14. The rotation angle 55 is calculated, and the motor drive means 73 drives the motor 45 to rotate (step S5 in FIG. 9). Here, when the rotation angle of the motor 45 is obtained using FIG. 8, it is + 360 °. Therefore, by rotating the motor 45 by + 360 °, the meandering speed v of the intermediate transfer belt 14 can be made zero, and the meandering of the intermediate transfer belt 14 can be suppressed.

  If the printing is not finished, the control for further suppressing the meandering of the intermediate transfer belt 14 is continued. When the printing is finished, the control for suppressing the meandering of the intermediate transfer belt 14 is finished (step S6 in FIG. 9).

  In addition, according to the aspect (comparative example) in which the meandering speed v of the intermediate transfer belt 14 is obtained using only the conical roller 55 without using the cylindrical roller 54, the meandering speed of the intermediate transfer belt 14 is obtained from Equations 3, 5, and 6. v is calculated. That is, in the comparative example, v = 200 (mm / second) × 200 (pulse / rev) / π × (1 / 6272-1 / 5945) /1.414=−0.079 (mm / second). The numerical value (v = −0.079 (mm / second)) according to this comparative example and the calculated value (v = −0.049 (mm / second)) by the belt meandering speed calculating means 53 of the present invention are compared and clarified. As described above, there is a large difference in the calculated value of the meandering speed v of the intermediate transfer belt 14 between the comparative example and the present invention. This is because, in the comparative example, the fluctuation of the rotation speed V of the intermediate transfer belt 14 becomes an error in the calculated value of the meandering speed v of the intermediate transfer belt 14.

(Example of belt meandering correction mechanism)
10 to 12 show an embodiment of the belt meandering correction mechanism 42 shown in FIG. In these drawings, FIG. 10A is a front view of the belt meandering correction mechanism 42. FIG. 10B is a plan view of the belt meandering correction mechanism. FIG. 11 is a perspective view of the belt meandering correction mechanism 42 as viewed from the lower right side on the front side. FIG. 12 is a perspective view of the solid cam.

  As shown in these drawings, the meandering correction mechanism 42 includes a motor 45, a solid cam 80, a cam follower 81, a compression spring 82 as a cam urging member, and a tension spring 83 as a pressing means. . Note that the three-dimensional cam 80, the cam follower 81, the compression spring 82, and the tension spring 83 constitute the power transmission mechanism 46 (see FIG. 2).

  The motor 45 is supported by the transfer frame 23 so that its output shaft 84 is substantially parallel to the roller shaft 43 of the driven roller 25. As the motor 45, a stepping motor capable of obtaining a rotation angle corresponding to the number of input pulses can be used. A solid cam 80 is attached to the output shaft 84 of the motor 45. Note that a servo motor can be used as the motor.

  The three-dimensional cam 80 has an external shape such that the outer peripheral surface (outer peripheral portion) of the truncated cone is stepped. A cam surface 85 having a predetermined width is spirally formed on the outer peripheral surface of the three-dimensional cam 80. Here, the predetermined width refers to a width that allows the roller (abutting portion) 86 of the cam follower 81 to roll effectively without detachment. Specifically, for example, the width is equal to or slightly wider than the width of the roller 86. Of the two end surfaces in the direction of the output shaft 84 in the three-dimensional cam 80, when the side with the smaller end surface is the small diameter portion 87 and the side with the larger end surface is the large diameter portion 88, the cam surface 85 is: From the small diameter part 87 to the large diameter part 88, it is formed in a spiral shape so that the distance from the output shaft 84 gradually increases. The cam surface 85 includes an end edge 90 on the small diameter portion 87 side and an end edge 91 on the large diameter portion 88 side. The end edge 90 on the small diameter portion 87 side is substantially perpendicular to the cam surface 85. A guide surface 92 is erected. The guide surface 92 is formed in a spiral shape along the cam surface 85 in the same manner as the cam surface 85. As shown in FIG. 12, in this embodiment, the cam surface 85 and the guide surface 92 are formed over almost three rounds of the three-dimensional cam 80. Of the cam surface 85, the end located closest to the small diameter portion 87 is the start end portion 93, the end located closest to the large diameter portion 88 is the end portion 94, and further from the center of the output shaft 84 to the start end portion 93. If the distance from the center of the output shaft 84 to the end portion 94 is d2, the cam surface 85 makes three rounds, that is, by rotating 1080 degrees (= 360 degrees × 3), the lift amount is It will increase by d2-d1. In this embodiment, the cam surface 85 is viewed from the direction in which the first and second rounds 85 a and 85 b and the second and third rounds 85 b and 85 c are orthogonal to the output shaft 84. Appear to be adjacent. That is, the first round 85a and the second round 85b are connected by the guide surface 92 while forming a step. The same applies to the second round 85b and the third round 85c. The height of the guide surface 92 as a step, that is, the height in the radial direction of the guide surface 92 is such that when the guide surface 92 is pressed against the roller 86 of the cam follower 81 by a compression spring 82 described later, the roller 86 is The height is set so as not to deviate from 92. In the present embodiment, the three-dimensional cam 80 is movable in the direction along the output shaft 84 with the large diameter portion 88 facing the output shaft 84 of the motor 45 in the circumferential direction. It is attached non-rotatably. That is, the solid cam 80 rotates in the same direction as the output shaft 84 rotates, and can move in the direction of the output shaft 84.

  As shown in FIG. 10A, the cam follower 81 is formed in a plate shape and is supported so as to be swingable. The cam follower 81 is formed in a rectangular plate shape whose dimension in the left-right direction is longer than the dimension in the vertical direction. A shaft (oscillation fulcrum) 95 is penetrated in the front-rear direction at the approximate center of the cam follower 81 in the vertical direction and the horizontal direction. The shaft 95 is supported on the base end side by the transfer frame 23 and is arranged substantially in parallel with the roller shaft 43 described above, and the tip end side penetrates the cam follower 81 and is attached with a stopper (not shown). The cam follower 81 is prevented from moving unnecessarily in the front-rear direction. The shaft 95 serves as the swing center of the cam follower 81.

  One end portion (left end portion in FIG. 2) of the cam follower 81 is a bearing portion 97 that rotatably supports one end portion 96 of the roller shaft 43. That is, the one end portion 96 of the roller shaft 43 passes through one end portion of the cam follower 81 from the rear to the front, and the stopper 98 is attached. As a result, when the cam follower 81 swings about the above-described shaft 95, the one end portion 96 of the roller shaft 43 moves up and down (up and down) substantially in the vertical direction, that is, in a direction substantially perpendicular to the tension applying direction to the intermediate transfer belt 14. ) The other end portion of the roller shaft 43 is rotatably supported by a normal bearing (not shown), and when the one end portion 96 of the roller shaft 43 moves up and down, the roller shaft 43 is inclined. The inclination angle of the roller shaft 43 is approximately 1 degree in the vertical direction, and the length of the roller shaft 43 is sufficiently long (for example, about 350 mm) with respect to the inclination angle.

  A roller 86 serving as a contact portion is rotatably supported at the other end portion (right end portion in FIG. 10) of the cam follower 81. The roller 86 is pressed substantially from above with respect to the cam surface 85 of the three-dimensional cam 80 and from the front side with respect to the guide surface 92. In the present embodiment, the center of the shaft 95 is configured so as to be located between the center of the roller shaft 43 and the rotation center of the roller 86. That is, when the roller 86 rolls following the cam surface 85 due to the rotation of the three-dimensional cam 80, the vertical movement amount of the rotation center of the roller 86 is the same as the vertical movement amount of the center of the roller shaft 43. It is supposed to be. However, the moving direction in the vertical direction is reversed.

  A compression spring 82 as a cam urging member is interposed between the motor 45 and the three-dimensional cam 80 and is externally fitted to the output shaft 84. The solid cam 80 is urged toward the distal end side of the output shaft 84 by the compression spring 82. Thereby, the guide surface 92 of the three-dimensional cam 80 is pressed against the roller 86 of the cam follower 81. That is, the roller 86 is prevented from being detached from the cam surface 85 when the biased guide surface 92 presses the roller 86.

  In this embodiment, the tension spring 83 as the pressing means is attached to a part (not shown) of the transfer frame 23 on the base end side (upper end side), and on the left end side of the cam follower 81 on the front end side (lower end side). It is attached to the upper end. As a result, the cam follower 81 is biased upward on the left end side with the bearing portion 96 around the shaft 95, and as a result, the right end side with the roller 86 is biased downward, and the roller 86 is moderately applied to the cam surface 85. It is pressed with an appropriate pressing force.

  In the belt meandering correction mechanism 42 according to this embodiment, the solid cam 80 is disposed at the home position in a state where the driven roller 25 is disposed at the home position, that is, the roller shaft 43 of the driven roller 25 is disposed horizontally. The roller 86 of the cam follower 81 comes into contact with the cam surface 85 of the three-dimensional cam 80 in which the home position is arranged. Here, the home position of the three-dimensional cam 80 is 1.5 when the three-dimensional cam 80 is in the direction of the arrow (counterclockwise) in FIG. Rotate. That is, the state in which the roller 86 is in contact with the intermediate point of the second turn 85b on the spiral cam surface 85 having a total of three turns is defined as the home position of the three-dimensional cam 80. From this state, when the three-dimensional cam 80 rotates in the arrow direction (clockwise) in FIG. 10B, the distance from the output shaft 84 of the contact portion of the roller 86 on the cam surface 85 decreases. The right end side of the cam follower 81 is lowered about the shaft 95, the left end side of the cam follower 81 is raised, and the one end portion 96 of the roller shaft 43 is raised. Conversely, when the three-dimensional cam 80 rotates in the direction of the arrow in FIG. 10B (counterclockwise), the distance from the output shaft 84 at the contact portion between the cam surface 85 and the roller 86 increases. The right end side of the cam follower 81 is raised around the shaft 95, the left end side of the cam follower 81 is lowered, and the one end portion 96 of the roller shaft 43 is lowered. By repeating the forward / reverse rotation of the motor 45 as appropriate based on the output of the motor driving means 73, the one end portion 96 of the roller shaft 43 can be raised and lowered to suppress meandering of the intermediate transfer belt 14.

  The belt meandering correction mechanism 42 is not limited to the present embodiment, and may be a mechanism that causes the driven roller 25 to swing at a minute angle with high accuracy by operating the power transmission mechanism 46 by the motor 45. That's fine.

(Other variations)
The present invention is not limited to the embodiment shown in FIGS. 2 to 3, and an endless ridge 47 is formed on the outer peripheral surface of the intermediate transfer belt 14 and at one end in the width direction of the intermediate transfer belt 14. The conical roller 55 that rolls on the ridge 47 may be arranged on the outer peripheral surface side of the intermediate transfer belt 14, and the cylindrical roller 54 may be arranged to roll on the inner peripheral surface of the intermediate transfer belt 14.

  Further, the belt meandering speed detecting device 50 of the present invention is not limited to the case where the belt is applied to the intermediate transfer unit 15 in which the belt is the intermediate transfer belt 14 as described above. The present invention can be applied to a belt unit such as a conveyance belt that conveys to each image station (tandem four-color image station) or a photosensitive belt that is a belt-shaped photosensitive member. The same effect as the above embodiment can be obtained.

  Further, the belt meandering speed detecting device 50 according to the present invention is an electrophotographic image forming apparatus, which has been described as an example applied to the intermediate transfer type four-color full-color image forming apparatus 1. The present invention is not limited, and the present invention can be widely applied to various image forming apparatuses having an endless belt, for example, an image forming apparatus using an inkjet recording method and an image forming apparatus for monochrome printing.

  Further, the belt unit such as the intermediate transfer unit 15 to which the belt meandering speed detection device 50 according to the present invention is applied is not limited to the mode of FIGS. 3, 4, and 6, and the belt is wound thereon. If a plurality of rollers (driving roller 24, driven roller 25, etc.) can be provided with grooves or spaces that can avoid interference with the ridge 47, the ridge 47 is not an end in the width direction of the belt. The strip 47 may be formed near the center in the width direction of the belt, and the conical roller 55 may be rolled on the convex strip 47.

  In addition, the belt meandering speed detection device 50 according to the present invention is exemplified by a truncated cone shape in which the tip end side of the cone is cut off as the conical roller 55, but is not limited thereto, and the conical roller and the support shaft are integrated. As long as the support shaft is rotatably supported by a bearing, a conical shape can be used.

  Further, the belt meandering speed detection device 50 according to the present invention exemplifies an embodiment in which the taper angle 2θ of the conical roller 55 is 90 °, but is not limited thereto, and is optimal according to the arrangement space of the conical roller 55 and the like. A taper angle 2θ can be selected.

  In the belt meandering speed detection device 50 according to the present invention, both the cylindrical roller 54 and the conical roller 55 may be disposed on the inner peripheral surface side or the outer peripheral surface side of the intermediate transfer belt 14.

1 is a schematic structural diagram for explaining an example of an image forming apparatus according to the present invention, and shows a schematic structure showing an internal configuration of the image forming apparatus as viewed from the front side (side where a user is located when using the image forming apparatus). FIG. FIG. 2 is a diagram schematically illustrating a belt meandering correction mechanism attached to an intermediate transfer unit of the image forming apparatus according to the present invention, and is a diagram illustrating the intermediate transfer unit as viewed from a direction A in FIG. 1. FIG. 3 is a perspective view schematically showing an intermediate transfer unit provided with a belt meandering speed detection device as viewed from the lower front side. FIG. 4 is a partial cross-sectional view of an intermediate transfer unit schematically shown by cutting along a line X1-X1 in FIG. 3. It is a control block diagram of the belt meandering speed detection device according to the present invention. It is a figure which shows the contact state of the protruding item | line of an intermediate transfer belt, and a conical roller. It is a figure which shows the relationship between sampling time and a sampling interval. It is a figure which shows the relationship between the rotation angle (degree) of a motor, and belt meandering speed v (micrometer / sec). It is a flowchart figure explaining the flow of control which rotates a motor according to a sampling result. FIG. 10A is a front view of the belt meandering correction mechanism, and FIG. 10B is a plan view of the belt meandering correction mechanism. It is the perspective view which looked at the belt meandering correction mechanism from the diagonally lower right side on the front side. It is a perspective view of a solid cam. It is an external appearance perspective view which shows the conventional belt apparatus partially. It is a top view which shows the conventional belt apparatus partially.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 4 ... Image forming part, 14 ... Intermediate transfer belt (belt), 14a ... Inner peripheral surface, 15 ... Intermediate transfer unit (belt unit), 24 ... Drive roller (roller) , 25 ... driven roller (roller), 42 ... belt meandering correction mechanism, 47 ... ridge, 50 ... belt meandering speed detection device, 51 ... belt rotation speed detecting means, 52 ... belt meandering amount detection Means 53... Belt meandering speed calculation means 54... Cylindrical roller 55. Conical roller 61. First sensor 66. Outer peripheral surface 71. Second sensor 73. Driving means)

Claims (7)

A belt meandering speed detecting device for detecting a meandering speed of an endless belt that is wound around a plurality of rollers and rotated.
Belt rotation speed detecting means for detecting the rotation speed of the belt;
Belt meandering amount detection means for detecting the meandering amount of the belt using the detection result of the belt rotation speed detection means;
Belt meandering speed calculating means for calculating the meandering speed of the belt based on the detection result of the belt meandering amount detecting means,
In the belt, an endless ridge extending along the circumferential direction is formed in at least one of the inner circumferential surface and the outer circumferential surface and in a portion that does not contact the plurality of rollers,
The belt rotation speed detecting means has a cylindrical roller that is always in contact with the belt and rotated by the belt, and a first sensor that measures the number of rotations of the cylindrical roller within a predetermined time. The rotation speed of the belt is detected from the detection result of the sensor,
The belt meandering amount detecting means includes (1) a conical roller that is always in contact with the belt and is rotated by the belt, and a second sensor that measures the rotational speed of the conical roller within a predetermined time period. 2) The tapered outer peripheral surface of the conical roller is always in contact with the convex strip of the belt, and the generatrix direction of the outer peripheral surface of the conical roller in contact with the convex strip is along the width direction of the belt. (3) The meandering amount of the belt is detected using the detection result from the second sensor and the detection result of the belt rotation speed detection means.
A belt meandering speed detecting device. A belt meandering speed detecting device for detecting a meandering speed of an endless belt that is wound around a plurality of rollers and rotated.
Belt rotation speed detecting means for detecting the rotation speed of the belt;
Belt meandering amount detection means for detecting the meandering amount of the belt using the detection result of the belt rotation speed detection means;
Belt meandering speed calculating means for calculating the meandering speed of the belt based on the detection result of the belt meandering amount detecting means,
The belt is formed with an endless ridge extending along the circumferential direction at one end in the width direction on the inner circumferential surface thereof and at one end not contacting the plurality of rollers.
The belt rotation speed detecting means has a cylindrical roller that is always in contact with the belt and rotated by the belt, and a first sensor that measures the number of rotations of the cylindrical roller within a predetermined time. The rotation speed of the belt is detected from the detection result of the sensor,
The belt meandering amount detecting means includes (1) a conical roller that is always in contact with the belt and is rotated by the belt, and a second sensor that measures the rotational speed of the conical roller within a predetermined time period. 2) The tapered outer peripheral surface of the conical roller is always in contact with the convex strip of the belt, and the generatrix direction of the outer peripheral surface of the conical roller in contact with the convex strip is along the width direction of the belt. (3) The meandering amount of the belt is detected using the detection result from the second sensor and the detection result of the belt rotation speed detection means.
A belt meandering speed detecting device. A belt meandering speed detecting device for detecting a meandering speed of an endless belt that is wound around a plurality of rollers and rotated.
Belt rotation speed detecting means for detecting the rotation speed of the belt;
Belt meandering amount detecting means for detecting the meandering amount of the belt;
Belt meandering speed calculating means for calculating the meandering speed of the belt based on the detection results of the belt rotation speed detecting means and the belt meandering amount detecting means,
In the belt, an endless ridge extending along the circumferential direction is formed in at least one of the inner circumferential surface and the outer circumferential surface and in a portion that does not contact the plurality of rollers,
The belt rotation speed detecting means has a cylindrical roller that is always in contact with the belt and rotated by the belt, and a first sensor that measures the number of rotations of the cylindrical roller within a predetermined time. The detection result of the sensor is output to the belt meandering speed calculation means,
The belt meandering amount detecting means includes (1) a conical roller that is always in contact with the belt and is rotated by the belt, and a second sensor that measures the rotational speed of the conical roller within a predetermined time period. 2) The tapered outer peripheral surface of the conical roller is always in contact with the convex strip of the belt, and the generatrix direction of the outer peripheral surface of the conical roller in contact with the convex strip is along the width direction of the belt. (3) outputting the detection result from the second sensor to the belt meandering speed calculating means,
A belt meandering speed detecting device. A belt meandering speed detecting device for detecting a meandering speed of an endless belt that is wound around a plurality of rollers and rotated.
Belt rotation speed detecting means for detecting the rotation speed of the belt;
Belt meandering amount detecting means for detecting the meandering amount of the belt;
Belt meandering speed calculating means for calculating the meandering speed of the belt based on the detection results of the belt rotation speed detecting means and the belt meandering amount detecting means,
The belt is formed with an endless ridge extending along the circumferential direction at one end in the width direction on the inner circumferential surface thereof and at one end not contacting the plurality of rollers.
The belt rotation speed detecting means has a cylindrical roller that is always in contact with the belt and rotated by the belt, and a first sensor that measures the number of rotations of the cylindrical roller within a predetermined time. The detection result of the sensor is output to the belt meandering speed calculation means,
The belt meandering amount detecting means includes (1) a conical roller that is always in contact with the belt and is rotated by the belt, and a second sensor that measures the rotational speed of the conical roller within a predetermined time period. 2) The tapered outer peripheral surface of the conical roller is always in contact with the convex strip of the belt, and the generatrix direction of the outer peripheral surface of the conical roller in contact with the convex strip is along the width direction of the belt. (3) outputting the detection result from the second sensor to the belt meandering speed calculating means,
A belt meandering speed detecting device.   The belt meandering speed detection device according to any one of claims 1 to 4, wherein the cylindrical roller and the conical roller are arranged so as to sandwich the belt.   A plurality of rollers, an endless belt wound around the plurality of rollers, the belt meandering speed detection device according to any one of claims 1 to 5, and a belt meandering correction mechanism for correcting the meandering of the belt. A belt unit comprising: drive means for controlling the operation of the belt meandering correction mechanism based on the meandering speed of the belt detected by the belt meandering speed detection device.   An image forming apparatus comprising: the belt unit according to claim 6; and an image forming unit that forms an image on a sheet conveyed by the belt unit.

Images