JP2010151956A - Belt driving device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately calculate the speed determination surface of a transfer belt and accurately control to drive the intermediate transfer belt. <P>SOLUTION: A belt traveling speed calculation part calculates the belt traveling speed of the intermediate transfer belt 20 from the rotating speed per unit time of a pressure roller 23 detected by a pressure roller rotating speed detection part, the speed determination surface of the intermediate transfer belt 20 at a contact point with the pressure roller 23 and the diameter of the pressure roller 23. A speed determination surface calculation part calculates the speed determination surface of the intermediate transfer belt 20 at the contact point with a lower part driven roller 25 from the calculated belt traveling speed, the rotating speed per unit time of the lower part driven roller 25 detected by a lower part roller rotating speed detection part and the diameter of the lower part driven roller 25. A control part controls to drive a driving roller 22 based on the speed determination surfaces calculated in the whole circumference of the intermediate transfer belt 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a belt driving device and an image forming apparatus, and more particularly to a technique for controlling driving of a transfer belt that travels endlessly.

  Conventionally, a plurality of image carriers (photoreceptor drums) on which toner images of different colors are carried, and the toner images on the respective image carriers are sequentially transferred in a state of being overlaid by rotating between a plurality of rollers. After the color image formed on the surface of the intermediate transfer belt is transferred as a color image from the intermediate transfer belt to the recording paper, and the recording paper on which the color image is transferred is subjected to a fixing process. An image forming apparatus that discharges the recording paper is known. In the image forming apparatus, it is necessary to control the intermediate transfer belt after detecting its traveling speed with high accuracy for the purpose of preventing color misregistration at the time of superimposing the color toner images.

Therefore, as a technique for detecting the running speed of the intermediate transfer belt, (1) a technique for detecting the marking on the surface of the intermediate transfer belt with an optical sensor and calculating the speed of the intermediate transfer belt from the moving speed of the marking, (2 There is a technique for detecting the rotational speed of a roller that stretches the intermediate transfer belt and calculating the speed of the intermediate transfer belt from the rotational speed of the roller. (3) As shown in the following Patent Document 1 and Patent Document 2, the rotational speed of the driving roller or the driven roller that stretches the intermediate transfer belt is detected, and the thickness unevenness component of the intermediate transfer belt is detected as a sin wave. There has also been proposed a technique for calculating the speed determining surface by approximating and extracting at.
JP 2007-147735 A JP 2006-227192 A

  However, since the technique of (1) is difficult to mark on the intermediate transfer belt, the marking must be applied with a sticker or the like, and this sticker affects the original operation of the intermediate transfer belt. There is also a possibility that the life of the intermediate transfer belt may be reduced due to the sticking of the seal. In the technique (2), in addition to the rotational speed of the driving roller or the driven roller, a speed determining surface based on the thickness of the intermediate transfer belt (a belt surface that determines the traveling speed of the intermediate transfer belt at the contact point with the roller). Since the intermediate transfer belt is used to calculate the running speed of the intermediate transfer belt, it is important to accurately determine the speed determining surface for calculating the speed of the intermediate transfer belt, but the intermediate transfer belt has uneven thickness at each position in the running direction. Since the thickness unevenness changes the speed determining surface, the intermediate portion actually running in the image forming embodiment is caused by the variation of the speed determining surface at the contact position between the driving roller or the driven roller and the intermediate transfer belt. There is a possibility that the running speed of each part of the transfer belt cannot be detected. In the technique (3), when the thickness unevenness component of the intermediate transfer belt does not appear as a sin wave, the speed determining surface cannot be calculated.

  The present invention has been made to solve the above-described problems, and eliminates the adverse effects on the transfer belt operation and the reduction in the belt life due to the sticking of the seal described above, and uneven belt thickness at each position in the transfer belt running direction. This also avoids the adverse effect of the transfer belt on the running speed detection.In addition, even when the transfer belt thickness unevenness component does not appear as a sine wave, the speed determination surface can be calculated accurately, so that the transfer belt can be driven accurately. The purpose is to enable control.

The invention according to claim 1 of the present invention includes a transfer belt on which a toner image of an image carrier carried in accordance with image information is transferred to a surface or a recording paper placed on the surface;
A plurality of rollers that stretch the transfer belt so that it can run endlessly;
A drive roller for running the transfer belt endlessly;
A first roller rotation speed detector that detects the number of rotations per unit time of a first roller that is one of the plurality of rollers;
A predetermined speed determining surface serving as a belt surface that determines the rotational speed of the first roller detected by the first roller rotational speed detecting unit and the traveling speed of the transfer belt at a contact point with the first roller. A belt running speed calculating unit that calculates a belt running speed of the transfer belt from a predetermined diameter of the first roller;
A second roller rotation speed detection unit that detects the number of rotations per unit time of a second roller that is one of the plurality of rollers and disposed at a position different from the first roller in the transfer belt traveling direction;
From the belt running speed calculated by the belt running speed calculating unit, the rotation speed of the second roller detected by the second roller rotation speed detecting unit, and a predetermined diameter of the second roller, A speed determining surface calculating unit that calculates a speed determining surface of the transfer belt at a contact point with the second roller;
The belt traveling speed calculation by the belt traveling speed calculation unit and the speed determination surface calculation by the speed determination surface calculation unit are performed every predetermined time, and the entire area in the traveling direction of the transfer belt is performed. And a control unit that calculates a speed determining surface of the transfer belt at a contact point with the second roller.

  A second aspect of the present invention is the belt drive device according to the first aspect, wherein the drive control unit drives and controls the drive roller based on each speed determination surface calculated in the entire circumference of the transfer belt. Is further provided.

A third aspect of the present invention is the belt driving device according to the first or second aspect, wherein the belt running speed calculating unit is detected by the first roller rotation speed detecting unit. The rotation speed R1 (0), a predetermined speed determination surface L (0) which is a belt surface for determining the traveling speed of the transfer belt at a contact point with the first roller, and a predetermined speed of the first roller. When the diameter φ1, the circumference ratio π, and the belt running speed V (0) of the transfer belt,
Calculate the belt running speed based on the equation of V (0) = π (φ1 + 2L (0)) × R1 (0),
The speed determining surface calculating unit includes a belt running speed V (0) calculated by the belt running speed calculating unit, a second roller rotation speed R2 (n) detected by the second roller rotation speed detecting unit, When the predetermined diameter φ2 of the second roller, the circumference ratio π, and the speed determining surface L (n) of the transfer belt at the point of contact with the second roller,
The speed determination plane is calculated based on the equation L (n) = {V (0) / (R2 (n) × π) −φ2} / 2.

  In these inventions, the belt running speed calculation unit determines the number of rotations of the first roller detected by the first roller rotation speed detection unit per unit time and the transfer belt at a contact point with the first roller in advance. Based on the speed determining surface and the diameter of the first roller, the belt traveling speed of the transfer belt is calculated, and the speed determining surface calculating unit detects the detected belt traveling speed and the first roller in the transfer belt traveling direction. Is determined from the rotation number of the second roller per unit time detected by the second roller rotation speed detector for the second roller disposed at a different position and the diameter of the second roller. The speed determining surface of the transfer belt at the contact point is calculated.

  For this reason, in the present invention, for the transfer belt that is actually running endlessly at the time of image formation, a speed determining surface is obtained at each position over the entire circumference in the traveling direction, and the speed determining surface for each position is obtained. Since it is possible to accurately detect the running speed at each position in the running direction of the transfer belt, it is possible to accurately control the running speed of the transfer belt according to the state of the transfer belt that is actually running endlessly during image formation. become.

  Further, in the case of the present invention, since the sticking of the seal to the transfer belt as in the prior art is unnecessary for the running speed control of the transfer belt, there is no possibility of adverse effects on the transfer belt operation due to the sticking of the seal or a decrease in the belt life. . Further, according to the present invention, the speed determining surface is calculated according to the thickness unevenness of the transfer belt at the contact point with the second roller, and the transfer belt traveling speed can be controlled according to the belt thickness unevenness. Therefore, it is possible to prevent the belt thickness unevenness from adversely affecting the running speed detection and running control of the transfer belt. In addition, since the present invention calculates the speed determining surface without requiring processing for approximating and extracting the thickness unevenness component of the transfer belt with sin waves as in the prior art, the thickness unevenness component of the transfer belt becomes sin waves. Even if it does not appear as, it is possible to accurately calculate the speed determination surface and to accurately control the running speed of the transfer belt.

  According to a fourth aspect of the present invention, there is provided the belt driving device according to any one of the first to third aspects, wherein the control unit is based on the speed determining surface calculation unit in the entire circumference of the transfer belt. When the calculation number N of the speed determination surface and the calculation numbers n and M of the speed determination surface by the speed determination surface calculation unit between the first and second rollers are integers, the condition of N / n ≠ M In addition, the speed determining surface of the transfer belt is calculated.

  In the present invention, since the cycle of the rotation of the driving roller and the speed determination surface calculation timing at the contact point between the second roller and the transfer belt are not synchronized, even if the driving roller is eccentric, the eccentricity The speed determining surface at each position of the transfer belt is calculated after accurately grasping the drive roller surface speed fluctuation due to the above.

  The invention according to claim 5 is the belt drive device according to any one of claims 1 to 4, wherein the first and second rollers have the same diameter.

  According to this invention, since the diameters of the first and second rollers are the same, it is possible to simplify the speed determination surface calculation process by the belt traveling speed calculation unit and the speed determination surface calculation unit.

According to a sixth aspect of the present invention, an image forming unit that forms an image of a toner image according to image information on the surface of the transfer belt or a recording medium placed on the surface;
An image forming apparatus comprising the belt driving device according to claim 1.

  According to the present invention, the same operation as that of any of the first to fifth aspects can be obtained.

  According to the present invention, since the sticking of the seal to the transfer belt as in the prior art is unnecessary for the running speed control of the transfer belt, there is no possibility of adverse effects on the operation of the transfer belt due to the sticking of the seal and a decrease in the belt life. Further, according to the present invention, the speed determining surface is calculated according to the thickness unevenness of the transfer belt at the contact point with the second roller, and the running speed of the transfer belt can be controlled according to the belt thickness unevenness. Therefore, it is possible to prevent the belt thickness unevenness from adversely affecting the running speed detection and running control of the transfer belt. In addition, since the present invention calculates the speed determining surface without requiring processing for approximating and extracting the thickness unevenness component of the transfer belt with sin waves as in the prior art, the thickness unevenness component of the transfer belt becomes sin waves. Even if it does not appear as, it is possible to accurately calculate the speed determination surface and to accurately control the running speed of the transfer belt.

  Hereinafter, a belt running speed detection device and an image forming apparatus including a belt device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional explanatory diagram for explaining the internal structure of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a diagram showing an extracted belt device according to an embodiment of the present invention.

  In the present embodiment, the printer 1 is employed as the image forming apparatus. As shown in FIG. 1, the printer 1 includes a paper feeding unit 12 that stores a bundle of paper P, an image forming unit 13 that transfers a toner image onto the paper P conveyed from the paper feeding unit 12, and the image The printer main body 11 includes a fixing unit 14 that performs a fixing process on the toner image transferred to the paper P by the forming unit 13 and a paper discharge unit 15 that discharges the paper P subjected to the fixing process by the fixing unit 14. It is configured by being attached.

  The paper feed unit 12 includes a paper cassette 121 capable of storing a plurality of papers P that are detachably attached to the lower part of the printer main body 11, and a pickup provided at an upper right position of the paper cassette 121 in FIG. 1. And a roller 122. The sheets P stored in the sheet cassette 121 are picked up one by one by driving the pickup roller 122 and sent out toward the image forming unit 13.

  The image forming unit 13 forms a toner image on the paper P fed from the paper feeding unit 12. In the present embodiment, the image forming unit 13 sequentially arranges from the upstream side (left side of the paper surface in FIG. 1) to the downstream side. A magenta unit 13M that uses magenta toner, a cyan unit 13C that uses cyan toner, a yellow unit 13Y that uses yellow toner, and a black unit 13K that uses black toner. And are provided.

  Each of the units 13M, 13C, 13Y, and 13K has an electrostatic latent image on the peripheral surface and a front-rear direction in which a toner image is formed along the electrostatic latent image (a direction perpendicular to the paper surface of FIG. 1). A photosensitive drum (image carrier) 131 that can rotate around the extended axis, and a charging wire that forms a uniform charge on the peripheral surface of the photosensitive drum 131 by performing a charging process on the peripheral surface. A charging device 132, and an exposure device 133 that forms an electrostatic latent image by irradiating a laser beam based on image information onto the peripheral surface of the photosensitive drum 131 to which a uniform charge is applied by the charging device 132; A developing device 134 that forms a toner image on the peripheral surface of the photosensitive drum 131 on which the electrostatic latent image is formed by supplying toner, and each developing device that supplies toner to the developing device 134 To 134 Then, a toner container 135 that is detachably mounted, and a primary transfer roller 136 that electrostatically peels off the toner image on the photosensitive drum 131 and transfers it onto the surface of an intermediate transfer belt (an example of a transfer belt) 20 described later. And a drum cleaning device 137 for cleaning the peripheral surface of the photosensitive drum 131 after the transfer process to the intermediate transfer belt 20 is provided.

  Further, in the image forming unit 13, as a member common to the units 13M, 13C, 13Y, and 13K, a photosensitive drum whose upper side is in contact with the photosensitive drum 131 at a position below the photosensitive drum 131 is provided. The intermediate transfer belt 20 onto which the toner image on the peripheral surface 131 is transferred, and the secondary transfer in which the toner image on the intermediate transfer belt 20 is electrostatically peeled off and transferred to the paper P fed from the paper feeding unit 12. A roller 138 is provided.

  The photosensitive drum 131 is for forming an electrostatic latent image and a toner image along the electrostatic latent image on the peripheral surface, and is an extremely smooth amorphous silicon layer having tough and excellent wear resistance on the peripheral surface. Are made suitable for forming these images. Each of the photosensitive drums 131 is supplied with toner from the corresponding developing device 134 while rotating counterclockwise in FIG.

  In the charger 132, a high voltage is applied to the charging wire from a power source (not shown), and a uniform charge is formed on the peripheral surface of the photosensitive drum 131 by corona discharge. Instead of the charger 132, a charging roller to which a high voltage is applied may be brought into contact with the peripheral surface of the photosensitive drum 131, thereby forming a charge on the peripheral surface of the photosensitive drum 131. Good.

  The exposure device 133 irradiates the peripheral surface of the photosensitive drum 131 uniformly charged by the charger 132 with laser light based on image data input from a computer (not shown). The electrostatic latent image is formed on the peripheral surface of the photoconductive drum 131 by the irradiation of. By supplying toner from the developing device 134 to the electrostatic latent image, a toner image is formed on the peripheral surface of the photosensitive drum 131, and this toner image is transferred to the rotating intermediate transfer belt 20. It has become.

  The developing device 134 is provided with an agitating / conveying member inside, and is provided with a developing roller having a peripheral surface facing the peripheral surface of the photosensitive drum 131 at the lowest position, and toner is transferred to the photosensitive member by the rotation of the developing roller. The drum 131 is supplied to the peripheral surface.

  The toner images formed on the peripheral surfaces of the photosensitive drums 131 in the units 13M, 13C, 13Y, and 13K are sequentially transferred onto the surface of the intermediate transfer belt 20 while being overlaid, thereby forming a color image on the surface. Is done.

  Note that the transfer unit 200, which is an example of a belt driving device according to an embodiment of the present invention, includes image forming units 13M, 13C, 13Y, and 13K (part of an image forming unit in claims) and an intermediate transfer belt. 20, a drive roller 22, a transfer belt drive motor 27, a secondary transfer roller 138 (a part of an image forming unit in claims), a transfer belt drive motor 125, a pressing roller 23, and a lower driven roller. 25, a driven roller 21, a pressing roller rotation speed detection unit 140, a lower roller rotation speed detection unit 150, and a control unit 100. This is an example of the configuration of the transfer unit 200, and is not limited thereto.

  The intermediate transfer belt 20 includes a primary transfer roller 136 of each of the units 13M, 13C, 13Y, and 13K, a tension roller 21 provided slightly to the left of the primary transfer roller 136 of the magenta unit 13M in FIG. The drive roller 22 provided slightly to the right in FIG. 1 of the primary transfer roller 136 in FIG. 1 for the black unit 13K, and in this embodiment, substantially directly below the primary transfer roller 136 in the cyan unit 13C on the right side of the tension roller 21. A bending roller 30 for bending the intermediate transfer belt 20 disposed at a position, and a substantially intermediate position between the bending roller 30 and the driving roller 22, and disposed below the bending roller 30. It is stretched around a pressing roller (an example of a first roller) 23.

  The pressing roller (an example of a first roller) 23 is for pressing the intermediate transfer belt 20 toward the secondary transfer roller 138, and thereby the color image on the surface of the intermediate transfer belt 20 is transferred to the intermediate transfer belt 20. And the secondary transfer roller 138 are reliably transferred to the sheet P being conveyed. The pressure roller 23 rotates following the traveling of the intermediate transfer belt 20.

  The drive roller 22 is driven by a transfer belt drive motor (roller drive source) 220. The transfer belt drive motor 220 is provided concentrically with the drive roller 22 and on the rear side of the drive roller 22 (the back side of the sheet of FIG. 1). The drive roller 22 is externally fitted to the drive shaft 221 of the transfer belt drive motor 220 so as to be integrally rotatable. Therefore, the drive roller 22 rotates integrally around the drive shaft 221 by driving the transfer belt drive motor 220.

  The driving roller 22, the tension roller 21, the pressing roller 23, and the primary transfer roller 136 are all in contact with the back surface side of the intermediate transfer belt 20, whereas the bending roller 30 has its peripheral surface. Is in contact with the surface side of the intermediate transfer belt 20.

  The secondary transfer roller 138 is pressed by the pressing roller 23 via the intermediate transfer belt 20 at a position directly below the pressing roller 23. A bias voltage for electrostatically peeling off the toner image on the intermediate transfer belt 20 is applied to the secondary transfer roller 138 from a power supply (not shown). Therefore, the toner image on the intermediate transfer belt 20 is transferred onto the paper P that passes between the intermediate transfer belt 20 and the secondary transfer roller 138.

  Further, an upper driven roller 24 is provided at the left position of each primary transfer roller 136, and a lower driven roller is provided between the bending roller 30 and the pressing roller 23 and between the driving roller 22 and the pressing roller 23. A roller (an example of a second roller) 25 is provided. These upper and lower driven rollers 24 and 25 are for maintaining a tension state so that the intermediate transfer belt 20 is not loosened.

  The fixing unit 14 performs a fixing process on the transfer image transferred to the paper P by the image forming unit 13. The fixing unit 141 is heated by an energizing heating element such as a halogen lamp, and the fixing roller 141 at the lower part. The pressure roller 142 is disposed so as to face the peripheral surface of the fixing roller 141 so that the peripheral surface thereof is pressed against the peripheral surface of the fixing roller 141. As shown in FIG. 1, the fixing unit 14 is disposed in a space formed by pressing the intermediate transfer belt 20 by the bending roller 30.

The sheet P on which the toner image is transferred from the intermediate transfer belt 20 by the secondary transfer roller 138 is
In the state of being sandwiched between the intermediate transfer belt 20 and the secondary transfer roller 138 and introduced into the fixing unit 14 while being guided by the circumference of the intermediate transfer belt 20 and passing between the fixing roller 141 and the pressure roller 142. The toner image is fixed on the paper P by heating.

  The sheet P after the fixing process is lifted up the discharge conveyance path 108 by driving the discharge roller pair 143, and is discharged to the discharge tray 151 provided at the top of the printer main body 11 through the discharge outlet 152.

  FIG. 3 is a block diagram illustrating an example of a schematic configuration of the printer 1. The printer 1 is provided with a control unit 100 for controlling the entire printer 1. Connected to the control unit 100 is a ROM 112 that stores an operation program and the like of the entire apparatus, and is connected to a RAM 113 that temporarily stores image data and functions as a work area. The control unit 100 is connected to image forming units 13K, 13Y, 13M, and 13C for each color, and the control unit 101 in the control unit 100 is provided in each of the image forming units 13K, 13Y, 13M, and 13C. A charger 132, an exposure device 133, a developing device 134, a transfer bias unit 114 that applies a transfer bias to the transfer roller 136 in order to transfer the toner image on the photosensitive drum 131 to a recording sheet, and a photosensitive member. The drum motor 115 which is a driving source of the drum 131 is controlled.

  The fixing motor 1401 rotates the pair of fixing rollers of the fixing unit 14 and is controlled by the control unit 101. The fixing heater 1402 is provided in a heat roller that constitutes one of the fixing roller pair, and is turned on / off by the control unit 101. In FIG. 3, each of the image forming units for yellow, magenta, cyan, and black is shown as one image forming unit, but actually, as shown in FIG. 1, each image forming unit for each color is provided. It is connected to the control unit 101 and controlled.

  The transfer belt drive motor 125 is a drive source of the drive roller 22 that causes the intermediate transfer belt 20 to travel, and is controlled by the control unit 101. Therefore, the rotation speed of the transfer belt drive motor 125 can be controlled by changing the frequency of the clock signal sent from the control unit 101 to a driver (not shown).

  The operation unit 127 includes an operation panel for inputting various operation instructions from the user and a display unit for displaying various messages. The control unit 101 is connected to a PC (personal computer) 130 via an interface 129. The printer 1 forms an image based on the image data input from the PC 130.

  The registration motor 190 rotates the registration roller 17 (FIG. 1) and is controlled by the control unit 101.

  Further, the printer 1 is provided with a pressure roller rotational speed detector 140 that detects the rotational speed (angular speed) of the pressure roller 23 and a lower roller rotational speed detector 150 that detects the rotational speed (angular speed) of the lower driven roller 25. It has been. The pressing roller rotation speed detection unit 140 is composed of, for example, a rotary encoder. For example, the encoder includes a sensor wheel provided on the rotational drive shaft of the pressure roller 23 so as to rotate concentrically with the pressure roller 23, and a light detector having a light emitting portion and a light receiving portion provided at a part of the periphery of the sensor wheel. An optical sensor. A large number of slits are formed at regular intervals along the circumferential direction of the sensor wheel in the sensing target region by the optical sensor, which is the periphery of the sensor wheel. The sensor has a light emitting unit (light source) and a light receiving unit provided facing the sensor wheel at a position sandwiching the row of slits, and when the light receiving unit receives light interrupted by the row of slits, Each time, a detection pulse is output to the belt running speed calculation unit 102. For example, the pressing roller rotation speed detection unit 140 sets the number of detection pulses per unit time (predetermined fixed time) as the rotation number R1 (n) of the pressing roller 23 based on the number of detection pulses obtained from the sensor. The rotation speed R1 (n) of the pressing roller 23 is set as the rotation speed of the pressing roller 23 by sequentially calculating at arbitrary moments.

  The lower roller rotation speed detection unit 150 also includes a sensor wheel and an optical sensor similar to the pressure roller rotation speed detection unit 140, but the sensor wheel of the lower roller rotation speed detection unit 150 is connected to the rotation drive shaft of the lower driven roller 25. The lower driven roller 25 is provided so as to rotate concentrically. When the light receiving unit receives light interrupted by the slit row of the sensor wheel, the sensor outputs a detection pulse to the speed determination surface calculation unit 103 each time the light is received. For example, the lower roller rotation speed detector 150 determines the number of detected pulses per unit time (predetermined fixed time) based on the number of detected pulses obtained from the sensor as the number of rotations R2 (n) of the lower driven roller 25. As a result, the rotational speed R2 (n) of the lower driven roller 25 is set as the rotational speed of the lower driven roller 25.

  The control unit 100 includes a control unit 101, a belt traveling speed calculation unit 102, and a speed determination surface calculation unit 103.

  The control unit 101 controls the overall operation of the printer 1 by using the RAM 113 as a work area in accordance with the operation program stored in the ROM 112. In this respect, the control unit 101 functions as a drive control unit that drives and controls each mechanism of the printer 1 during the image forming operation. Further, the control unit 101 causes a belt traveling speed calculation by a belt traveling speed calculation unit 102, which will be described later, and a speed determination surface calculation by a speed determination surface calculation unit 103 to be performed every elapse of a predetermined time.

  When the printer 1 is warmed up or adjusted, the belt running speed calculation unit 102 is provided in the intermediate transfer belt 20 when the intermediate transfer belt 20 is driven to run at a speed for image formation, for example. The intermediate transfer belt 20 travels from the rotational speed of the pressing roller 23, which is one of the driven rollers, a predetermined speed determining surface at the contact point with the pressing roller 23, and the diameter of the pressing roller 23. Calculate the speed.

  The belt running speed calculation unit 102 uses the number of detection pulses sent from the pressing roller rotation speed detection unit 140 within a certain time as rotation speed information of the pressing roller 23.

  The speed determination surface used by the belt traveling speed calculation unit 102 to calculate the belt traveling speed of the intermediate transfer belt 20 is a belt surface that determines the traveling speed of the intermediate transfer belt 20. That is, the speed determining surface is such that the intermediate transfer belt 20 is in a position where the intermediate transfer belt 20 contacts the pressing roller 23 when the driving roller 22 is driven at a predetermined rotational speed for image forming operation. The position in the thickness direction (the surface at the position) indicates which position is traveling at the traveling speed of the intermediate transfer belt 20, and the speed determination surface is a distance from the inner surface of the intermediate transfer belt 20. (Thickness) In the present embodiment, the speed determination surface varies for each position according to the thickness at each position in the running direction of the intermediate transfer belt 20.

  Note that the speed determining surface varies depending on the composition of the intermediate transfer belt, such as when the intermediate transfer belt is formed of a plurality of layers or when the composition is different.

  The speed determination surface at the position where the intermediate transfer belt 20 contacts the pressing roller 23 is measured in advance by the manufacturer of the printer 1 and stored in the belt traveling speed calculation unit 102 as a fixed value.

  The diameter of the pressing roller 23 is also measured in advance by the manufacturer of the printer 1 and stored in the belt traveling speed calculation unit 102 as a fixed value.

The belt traveling speed calculation unit 102 is configured to include a belt traveling speed V (0) on the surface of the intermediate transfer belt 20, a circumferential ratio π, a diameter φ1 of the pressure roller 23, a speed determination surface L (0), and a rotational speed R1 ( 0), the pressing roller 23 is in contact with the inner side of the intermediate transfer belt 20, so
V (0) = π (φ1 + 2L (0)) × R1 (0)… (1)
Based on the equation (1), the belt running speed of the intermediate transfer belt 20 is calculated. The belt running speed V (0) is the same for all speed determination surfaces at each position in the running direction of the intermediate transfer belt 20 at the time of calculation.

  On the other hand, the speed determination surface calculation unit 103 is one of a plurality of driven rollers provided on the intermediate transfer belt 20 and the belt traveling speed of the intermediate transfer belt 20 calculated by the belt traveling speed calculation unit 102. From the rotational speed of the lower driven roller 25 disposed at a position downstream of the pressing roller 23 in the traveling direction of the transfer belt 20 and the diameter of the lower driven roller 25, The speed determining surface of the intermediate transfer belt 20 at the contact point is calculated.

  The speed determination surface calculation unit 103 uses the number of detection pulses sent from the lower roller rotation speed detection unit 150 within a predetermined time as rotation number information of the lower driven roller 25.

  The diameter of the lower driven roller 25 is measured in advance by the manufacturer of the printer 1 and stored in the speed determination surface calculation unit 103 as a fixed value.

The speed determining surface calculation unit 103 is configured to detect the belt running speed V (0) of the intermediate transfer belt 20, the circumferential ratio π, the diameter φ 2 of the lower driven roller 25, and the speed of the intermediate transfer belt 20 at the contact point with the lower driven roller 25. When the determination surface L (n) and the rotational speed R2 (n) of the lower driven roller 25 are set,
Since V (0) = π (φ2 + 2L (n)) x R2 (n) holds,
L (n) = {V (0) / (R2 (n) × π) −φ2} / 2 (2)
Based on the equation (2), the speed determining surface of the intermediate transfer belt 20 at the contact point with the lower driven roller 25 is calculated. The belt running speed of the intermediate transfer belt 20 is calculated.

  Then, the control unit 101 causes the belt traveling speed calculation unit 102 to calculate the belt traveling speed and the speed determination surface calculation unit 103 to calculate the speed determination surface every time a predetermined time elapses. The speed determining surface of the intermediate transfer belt 20 at the contact point with the lower driven roller 25 is calculated in the entire circumferential area in the traveling direction. Note that the predetermined time is, for example, a time when a specific portion of the surface of the intermediate transfer belt 20 starts to circulate from a specific position in the belt traveling direction and returns to the specific position by endless traveling. The time (the time required for the intermediate transfer belt 20 to make one revolution in the belt traveling direction) is divided into N equal parts (N is an integer of 2 or more).

  In addition, the control unit 101 performs the speed determination surface calculation in the entire circumference area of the intermediate transfer belt 20 in a range in which the intermediate transfer belt 20 travels n (n = 1 or more). As a result, the intermediate transfer belt 20 acquires the speed determination surface at each of the above positions in the entire circumferential direction of the intermediate transfer belt 20, and the calculation target region of the speed determination surface is the intermediate transfer belt 20 with the entire peripheral surface of the drive roller 22 as the calculation target region. Therefore, even if the drive roller 22 is eccentric, all surface speed fluctuations of the drive roller 22 due to the eccentricity of the drive roller 22 appear uniformly on the intermediate transfer belt 20. Thus, it can be accurately reflected in the calculation of the speed determination surface.

  Next, the speed determination surface calculation process of the intermediate transfer belt 20 by the printer 1 will be described. FIG. 4 is a flowchart showing the speed determination surface calculation process of the intermediate transfer belt 20 by the printer 1. Hereinafter, the speed determination surface calculation process will be described with reference to FIGS. 4 and 2.

  The speed determining surface calculation process of the intermediate transfer belt 20 by the printer 1 is performed when the intermediate transfer belt 20 is driven during warm-up or adjustment of the printer 1.

  For example, when the printer 101 is warmed up, when the control unit 101 drives the drive roller 22 to drive the intermediate transfer belt 20 at the travel speed for image formation, the rotation is driven by the intermediate transfer belt 20. The rotation speed R1 (0) of the pressure roller 23 to be detected is detected by the pressure roller rotation speed detector 140 (S1).

  The belt running speed calculation unit 102 calculates the detected rotation speed R1 (0) of the pressure roller 23, the speed determination surface L (0) at the contact point with the pressure roller 23, and the diameter φ1 of the pressure roller 23. From this, the belt running speed V (0) of the intermediate transfer belt 20 is calculated using the above equation (1) (S2).

  The lower roller rotational speed detector 150 also detects the rotational speed of the lower driven roller 25 that rotates following the intermediate transfer belt 20 when the rotational speed R1 (0) of the pressure roller 23 is detected by the pressure roller rotational speed detector 140. R2 (n) is detected (S3).

  The speed determination surface calculation unit 103 includes the belt travel speed V (0) of the intermediate transfer belt 20 calculated by the belt travel speed calculation unit 102 and the lower driven roller 25 detected by the lower roller rotation speed detection unit 150. From the rotation speed R2 (n) and the diameter φ2 of the lower driven roller 25, the intermediate transfer belt 20 at the contact point pt (n) with the lower driven roller 25 at this time is calculated using the above equation (2). The speed determining plane L (n) at the specific location p (n) is calculated (S4).

  After the processing of S1 to S4, the control unit 101 determines that the specific point p (0) on the surface of the intermediate transfer belt 20 that was at the position pt (0) in contact with the pressing roller 23 at the time of performing the processing of S1 to S4. The fact that the intermediate transfer belt 20 has moved to the position pt (n) in contact with the lower driven roller 25 is detected at a specific point p (0) of the intermediate transfer belt 20 by a counter built in the control unit 101, for example. Is determined by measuring that the traveling time (predetermined value) that is assumed to be necessary for moving from position pt (0) to position pt (n) has elapsed (S5).

  Here, when the control unit 101 determines that the specific point p (0) on the surface of the intermediate transfer belt 20 has moved from the position pt (0) to the position pt (n) (YES in S5), the speed determination is further performed. It is determined whether or not the specific point p (0) on the surface of the intermediate transfer belt 20 that was at the position pt (0) at the time of disclosure of the surface calculation process has returned to the position pt (0) after one turn of the intermediate transfer belt 20. Judgment is made based on whether the travel time (predetermined value) assumed to be required for the intermediate transfer belt 20 to make one revolution by the counter is measured to have elapsed since the speed determination surface calculation process was disclosed. (S6).

  The control unit 101 determines that the specific point p (0) on the surface of the intermediate transfer belt 20 at the time when the speed determination surface calculation process is disclosed has not yet returned to the position pt (0) after the intermediate transfer belt 20 has made one round. If so (NO in S6), the process returns to S1, and the rotation speed R1 (0) of the pressing roller 23 at this time is newly detected by the pressing roller rotation speed detection unit 140 (S1).

  Then, the belt running speed calculation unit 102 calculates the newly detected rotation speed R1 (0) of the pressure roller 23, the predetermined speed determination surface L (0), and the diameter φ1 of the pressure roller 23. From this, the belt running speed V (0) of the intermediate transfer belt 20 at the time is newly calculated using the above equation (1) (S2).

  The lower roller rotational speed detector 150 newly detects the rotational speed R2 (n) of the lower driven roller 25 when detecting the rotational speed R1 (0) of the new pressing roller 23 (S3), and calculates the speed determination surface. The unit 103 determines the intermediate transfer belt 20 based on the newly calculated belt running speed V (0), the new rotational speed R2 (n) of the lower driven roller 25, and the diameter φ2 of the lower driven roller 25. As the vehicle travels, the speed determining surface L (n) is calculated for a location that is newly moved to the position pt (n) at this time and becomes a new specific location p (n) on the surface of the intermediate transfer belt 20. (S4).

  That is, the control unit 101 moves the specific point p (0) on the surface of the intermediate transfer belt 20 that was at the position pt (0) in contact with the pressing roller 23 to the position pt (n) in contact with the lower driven roller 25. The process of S1 to S4 is repeated every time a new specific position p (n) is reached, and at this time, the surface position p (n of the intermediate transfer belt 20 located at the contact point pt (n) with the lower driven roller 25 is reached. ) For the speed determination plane L (n). Then, the control unit 101 performs the calculation process of the speed determination surface L (n) once for the portion that has been the specific location p (0) on the surface of the intermediate transfer belt 20 at the time when the speed determination surface calculation processing is disclosed. Repeat until it returns to position pt (0).

  The control unit 101 uses the information on the speed determination surface L (n) obtained at each position in the entire traveling direction of the intermediate transfer belt 20 as described above, so that each location on the surface of the intermediate transfer belt 20 is transferred to the lower driven roller 25. The traveling speed of the intermediate transfer belt 20 when moving to the contact position pt (n) is calculated and accumulated for the entire circumferential area of the intermediate transfer belt 20 in the traveling direction, and the accumulated intermediate transfer is performed at the time of image formation. The intermediate transfer belt 20 is caused to travel at a constant speed by increasing or decreasing the rotational speed of the transfer belt drive motor 125 according to the travel speed information at each position of the belt 20 (S7).

  That is, the control unit 101 performs intermediate transfer according to the state of the intermediate transfer belt 20 that is actually running (the intermediate transfer belt 20 that is running while varying the surface speed at a specific location with uneven thickness). It is possible to accurately control the traveling speed of the intermediate transfer belt 20 so that the traveling speed of the belt 20 is constant.

  However, the control unit 101 uses the speed determination surface calculation unit 103 between the pressure roller 23 and the lower driven roller 25 to calculate the number N of the speed determination surfaces by the speed determination surface calculation unit in the entire circumference of the intermediate transfer belt 20. The condition of N / n ≠ M when the calculated number n of speed determination surfaces (n = 1 in the present embodiment) and the driving roller 22 is the driving roller rotational speed M that makes the intermediate transfer belt 20 make one round in the belt traveling direction. It is preferable to perform the speed determination surface calculation after satisfying the above.

  In this case, since the cycle in which the drive roller 22 rotates once and the speed determination surface calculation timing at the contact point between the lower driven roller 25 and the intermediate transfer belt 20 are not synchronized, even if the drive roller 22 is eccentric, The speed determining surface at each of the above-mentioned portions of the intermediate transfer belt 20 is calculated after accurately grasping the fluctuation of the driving roller surface speed due to eccentricity or the like. For example, when the driving roller 22 is coated with a rubber layer for avoiding slipping, the surface speed fluctuation of the eccentric driving roller 22 greatly affects the traveling speed of the intermediate transfer belt 20. According to the process, even in such a case, it is possible to prevent the traveling speed detection and drive control of the intermediate transfer belt 20 from being adversely affected.

The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above embodiment, the belt traveling speed calculation unit 102 calculates the belt traveling speed, and the speed determination surface calculation unit 103 calculates the speed determination surface using the calculated belt traveling speed. However, the speed determination plane L (n) can also be calculated using the following formula (3).
L (n) = {(φ1−φ2 + 2L (0)) × (R1 (0) / R2 (n))} / 2 (3)
That is, in the above-described embodiment, a mode in which the calculation processing by the belt traveling speed calculation unit 102 and the speed determination surface calculation unit 103 is performed separately is shown. The calculation process includes a case where the calculation process is performed at once using the equation (3).

  Further, in the above embodiment, the relationship between the pressing roller 23 diameter φ1 and the lower driven roller 25 diameter φ2 is not particularly defined, but when calculating the speed determining surface L (n) using the above equation (3), By making the diameter φ1 of the pressing roller 23 and the diameter φ2 of the lower driven roller 25 the same, it is possible to simplify the equation (3), that is, the speed determination surface calculation process by the speed determination surface calculation unit.

  Moreover, in the said embodiment, although the calculation number n of the speed determination surface by the belt traveling speed calculation part 102 and the speed determination surface calculation part 103 between the press roller 23 and the lower driven roller 25 is set to 1, the said calculation number n is set to 2. It is good also as above.

  In the above-described embodiment, the intermediate transfer belt 20 that forms a color image in a state of being overcoated on the surface of the belt is employed as the transfer belt. However, the intermediate transfer belt 20 is being conveyed by the belt instead of the intermediate transfer belt 20. A so-called paper conveying belt that forms a color image on paper may be employed as the transfer belt according to the present invention. The image forming apparatus according to the present invention is not limited to the one for color printing, and may be for monochrome printing. In this case, as a matter of course, only one image forming unit (photosensitive drum or the like) is employed.

  In the above-described embodiment, the example of the first roller in the claims is described as the pressing roller 23. Instead, the lower driven roller 25, the tension roller 21, the upper driven roller 24, and the like are replaced with the first roller. It is also possible to calculate the speed determining surface at each position in the running direction of the intermediate transfer belt 20 as one roller.

  Moreover, in the said embodiment, although the example of the 2nd roller in a claim is demonstrated as the lower driven roller 25, if the said 2nd roller is a driven roller different from a 1st roller, the tension roller 21, It is also possible to calculate the speed determining surface at each position in the running direction of the intermediate transfer belt 20 using the upper driven roller 24, the pressing roller 23, and the like as the second rollers.

FIG. 3 is a cross-sectional view for explaining the internal structure of an embodiment of the image forming apparatus according to the present invention. It is the figure which extracted and showed the belt apparatus which concerns on one Embodiment of this invention. FIG. 2 is a block diagram illustrating an example of a schematic configuration of a printer. 6 is a flowchart illustrating a speed determination surface calculation process of an intermediate transfer belt by a printer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 13 Image formation part 13M, 13C, 13Y, 13K Image formation unit 20 Intermediate transfer belt 22 Drive roller 23 Press roller 25 Lower driven roller 100 Control unit 101 Control part 102 Belt running speed calculation part 103 Speed determination surface calculation part 138 2 Next transfer roller 140 Press roller rotational speed detector 150 Lower roller rotational speed detector 200 Transfer unit

Claims (6)

A transfer belt on which a toner image of an image carrier carried in accordance with image information is transferred to the surface or a recording paper placed on the surface;
A plurality of rollers that stretch the transfer belt so that it can run endlessly;
A drive roller for running the transfer belt endlessly;
A first roller rotation speed detector that detects the number of rotations per unit time of a first roller that is one of the plurality of rollers;
A predetermined speed determining surface serving as a belt surface that determines the rotational speed of the first roller detected by the first roller rotational speed detecting unit and the running speed of the transfer belt at a contact point with the first roller. A belt running speed calculating unit that calculates a belt running speed of the transfer belt from a predetermined diameter of the first roller;
A second roller rotation speed detection unit that detects the number of rotations per unit time of a second roller that is one of the plurality of rollers and is disposed at a position different from the first roller in the transfer belt traveling direction;
From the belt running speed calculated by the belt running speed calculating unit, the rotation speed of the second roller detected by the second roller rotation speed detecting unit, and a predetermined diameter of the second roller, A speed determining surface calculating unit that calculates a speed determining surface of the transfer belt at a contact point with the second roller;
The belt traveling speed calculation by the belt traveling speed calculation unit and the speed determination surface calculation by the speed determination surface calculation unit are performed every predetermined time, and the entire belt in the traveling direction of the transfer belt. A belt driving device comprising: a control unit that calculates a speed determining surface of the transfer belt at a contact point with the second roller.   The belt drive device according to claim 1, further comprising a drive control unit that drives and controls the drive roller based on each speed determination surface calculated in the entire circumference of the transfer belt. The belt travel speed calculation unit determines the rotation speed R1 (0) of the first roller detected by the first roller rotation speed detection unit and the travel speed of the transfer belt at a contact point with the first roller. When a predetermined speed determining surface L (0) serving as a belt surface, a predetermined diameter φ1 of the first roller, a circumferential ratio π, and a belt running speed V (0) of the transfer belt are obtained.
Calculate the belt running speed based on the equation of V (0) = π (φ1 + 2L (0)) × R1 (0),
The speed determining surface calculating unit includes a belt running speed V (0) calculated by the belt running speed calculating unit, a second roller rotation speed R2 (n) detected by the second roller rotation speed detecting unit, When the predetermined diameter φ2 of the second roller, the circumference ratio π, and the speed determining surface L (n) of the transfer belt at the point of contact with the second roller,
The belt driving device according to claim 1, wherein the speed determining surface is calculated based on an expression of L (n) = {V (0) / (R2 (n) × π) −φ2} / 2.   The controller is configured to calculate the speed determining surface N by the speed determining surface calculating unit in the entire circumference of the transfer belt, and the speed determining surface by the speed determining surface calculating unit between the first and second rollers. 4. The speed determining surface of the transfer belt is calculated when the calculated numbers n and M are integers, and the condition of N / n ≠ M is satisfied. Belt drive device.   The belt driving device according to any one of claims 1 to 4, wherein the first and second rollers have the same diameter. An image forming unit that forms an image of a toner image according to image information on the surface of the transfer belt or a recording medium placed on the surface;
An image forming apparatus comprising the belt driving device according to claim 1.

Images