JP2010128297A - Belt driving device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve accurate drive control of an intermediate transfer belt by exactly calculating the speed deciding surface of a transfer belt. <P>SOLUTION: Whenever each mark Q is detected by a mark sensor 180, a belt traveling speed calculation part calculates the belt traveling speed of the intermediate transfer belt 20 on the basis of time from timing to start detecting the mark Q until timing to finish detecting the mark Q. A speed deciding surface calculation part calculates the speed deciding surface of a portion of the intermediate transfer belt 20 coming into contact with a pressing roller 23 based on the calculated belt traveling speed, rotational speed of the pressing roller 23 detected by a pressing roller rotational speed detection part and the predetermined diameter of the pressing roller when calculating the belt traveling speed. A controller drives and controls a driving roller on the basis of the calculated speed deciding surface in the entire peripheral area 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, the intermediate transfer belt needs to be controlled after the traveling speed thereof is detected with high accuracy for the purpose of preventing color misregistration when the color toner images are superimposed.

Therefore, as a technique for detecting the running speed of the intermediate transfer belt, (1) a technique for detecting the rotation speed of a roller that stretches the intermediate transfer belt and calculating the speed of the intermediate transfer belt from the rotation speed of the roller has been proposed. ing. (2) As shown in Patent Document 1 and Patent Document 2 below, 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, in the technique (1), 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 (the belt surface that determines the traveling speed of the intermediate transfer belt at the contact point with the roller). ) Is used to calculate the running speed of the intermediate transfer belt. Therefore, it is important to accurately determine the speed determining surface for calculating the speed of the intermediate transfer belt. However, 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 transfer actually running at the time of image formation is caused by the change 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 belt cannot be detected. In the technique (2), when the thickness unevenness component of the intermediate transfer belt does not appear as a sine wave, the speed determining surface cannot be calculated.

  The present invention has been made to solve the above-described problems, and avoids the adverse effect of uneven belt thickness at each position in the transfer belt running direction on the running speed detection of the transfer belt. An object of the present invention is to enable accurate drive control of a transfer belt by accurately calculating a speed determination surface even when the sine wave does not appear as a sin wave.

The invention according to claim 1 of the present invention is a belt-like member that travels endlessly, and has one or more marks on the surface thereof in the traveling direction, and the recording placed on the surface or the surface. A transfer belt on which a toner image is transferred from an image carrier to paper;
A plurality of rollers that stretch the transfer belt so that it can run endlessly;
A driving roller that is one of the plurality of rollers and causes the transfer belt to travel endlessly;
A mark detection unit that is provided at a position facing the mark forming portion of the transfer belt surface and detects the mark on the transfer belt surface when the transfer belt is running;
A belt running speed calculation unit that calculates a belt running speed of the transfer belt based on a time from a detection start timing of the mark by the mark detection unit to a detection end timing;
A first roller rotation speed detector that detects a rotation speed of a first roller that is one of the plurality of rollers;
When the belt running speed is calculated by the belt running speed calculating unit, the calculated belt running speed, the rotation speed of the first roller detected by the first roller rotation speed detecting unit, and the first The belt driving device includes a speed determining surface calculating unit that calculates a speed determining surface of a transfer belt portion in contact with the first roller from a predetermined diameter of the roller.

  The invention according to claim 2 is the belt drive device according to claim 1, wherein the speed determining surface calculating unit is calculated when the belt traveling speed is calculated by the belt traveling speed calculating unit. The belt running speed Vi (t), the first roller rotation speed R (n) detected by the first roller rotation speed detector, the predetermined diameter φ of the first roller, and the circumference From the rate π, the speed of the transfer belt portion in contact with the first roller is determined using the formula L (n) = 1/2 {Vi (t) / (π × R (n)) − φ}. The surface L (n) is calculated.

  In these inventions, the belt running speed calculation unit calculates the belt running speed of the transfer belt based on the time from the mark detection start timing to the detection end timing by the mark detection unit, and the speed determination surface calculation unit When the travel speed is calculated, the calculated belt travel speed, the first roller rotation speed detected by the first roller rotation speed detector, and the predetermined diameter of the first roller The speed determining surface of the transfer belt portion in contact with one roller is calculated.

  Therefore, according to these inventions, since the speed determination surface is calculated by the speed determination surface calculation unit according to the thickness unevenness of the transfer belt of the transfer belt portion that contacts the first roller, the speed fluctuation caused by the belt thickness unevenness Therefore, it is possible to control the running speed of the transfer belt corresponding to the above, and 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 the need for processing to approximate and extract the uneven thickness component of the transfer belt with a sin wave as in the prior art, the uneven thickness component of the transfer belt is the sin wave. Even if it does not appear as, the speed determining surface can be calculated accurately.

A third aspect of the present invention is the belt driving device according to the first or second aspect, wherein the transfer belt is formed at predetermined intervals on the surface of the entire circumference in the running direction. Having a plurality of marks,
Based on each of the marks, the speed determination surface of the transfer belt portion that contacts the first roller is provided to the belt travel speed calculation unit and the speed determination surface calculation unit in the entire circumference in the travel direction of the transfer belt. It further includes a control unit for calculation.

  In the present invention, the control unit calculates the speed determination surface of the transfer belt portion described above based on each of the marks in the belt traveling speed calculation unit and the speed determination surface calculation unit in the entire circumference region in the traveling direction of the transfer belt. To do. Therefore, in the present invention, for the transfer belt that is actually running endlessly at the time of image formation, a speed determination surface at each position over the entire circumference in the traveling direction is obtained, and from the speed determination surface for each position. 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.

  According to a fourth aspect of the present invention, there is provided the belt driving device according to the third aspect, wherein the driving control unit drives and controls the driving roller based on each speed determining surface calculated in the entire circumferential area of the transfer belt. Is further provided.

  In the present invention, the drive control unit controls the drive roller based on each speed determination surface calculated in the entire circumference of the transfer belt, so that the transfer belt actually running endlessly at the time of image formation. The running speed of the transfer belt can be accurately controlled according to the state.

  According to a fifth aspect of the present invention, in the belt driving device according to the third or fourth aspect, the control unit sets the speed determination surface calculation range as N circumferences of the transfer belt (N = 1 or more). The speed determining surface is calculated in the entire circumference of the transfer belt so that the circumference of the transfer belt is an integral multiple of the circumference of the drive roller.

  According to the present invention, the speed determining surface calculation range is set to the circumference of the transfer belt N (an integer equal to or greater than 1), so that the entire circumference of the transfer belt is determined for each turn regardless of the number of turns of the transfer belt. Thus, the speed determination plane calculation can be performed with high accuracy because the rotation of the driving roller is always completely completed during one rotation of the transfer belt.

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, the speed determining surface is calculated in accordance with the thickness unevenness of the transfer belt in the transfer belt portion facing the mark detection portion, 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, the speed determining surface can be calculated accurately.

  Hereinafter, an image forming apparatus including a belt traveling speed detection device and a belt driving 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 driving device according to an embodiment of the present invention. FIG. 3 is a perspective view showing the intermediate transfer belt and the mark sensor.

  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.

  Further, on the surface of the intermediate transfer belt 20 other than the area where the image is formed by the units 13M, 13C, 13Y, and 13K, as shown in FIG. A plurality of marks Q formed at predetermined intervals are provided over the entire circumference. In this embodiment, an example in which a plurality of marks Q are provided over the entire circumference in the traveling direction of the intermediate transfer belt 20 is described above, but the number of marks Q is not particularly limited as long as it is one or more. Further, the color and size of the mark Q are not particularly limited, but the mark Q is preferably a color that is greatly different from the color of the intermediate transfer belt 20. In the present embodiment, the intermediate transfer belt 20 is black and the mark Q is white.

  Further, a mark sensor 180 is provided at a position facing the mark Q formation region on the surface of the intermediate transfer belt 20. The mark sensor 180 is, for example, a light emitting unit (light source) including an LED (Liquid Crystal Display) that irradiates light to the intermediate transfer belt 20 and light emitted from the light emitting unit to the surface of the intermediate transfer belt 20. And a light receiving unit including a photosensor that receives reflected light. The mark sensor 180 emits light from the light emitting portion to the mark Q forming region on the surface of the intermediate transfer belt 20 during endless running of the intermediate transfer belt 20, and the reflected light from the surface of the intermediate transfer belt 20 received by the light receiving portion. The received light amount is output to a belt traveling speed calculation unit 102 described later.

  Note that the transfer unit 200, which is an example of a belt driving device according to an embodiment of the present invention, includes, for example, an intermediate transfer belt 20, a driving roller 22, a transfer belt driving motor 27, a transfer roller driving motor 135, and a press. A roller 23, a lower driven roller 25, tension rollers 21 and 24, a pressing roller rotation speed detection unit 140, a mark sensor 180, and a control unit 100 are provided. The said structure is only an example of the structure of the transfer unit which concerns on this invention, and the transfer unit which concerns on this invention is not limited to the said structure.

  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 at a slightly left position in FIG. 2 of the primary transfer roller 136 of the magenta unit 13M, 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. The belt is stretched around the pressing 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. Each 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. 4 is a block diagram illustrating an example of a schematic configuration of the printer 1. FIG. 5 shows an example of a mark detection signal output from the mark sensor. FIG. 6 shows the intermediate transfer belt 20 and marks formed on the surface thereof.

  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. 4, each image forming unit for yellow, magenta, cyan, and black is shown as one image forming unit, but actually, as shown in FIG. 1, each image forming unit is used for each color. 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 secondary transfer roller drive motor 148 is a drive source that rotationally drives the secondary transfer roller 138 and is controlled by the control unit 101. Therefore, the rotation speed of the secondary transfer roller drive motor 148 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.

  In addition, the printer 1 is provided with a pressure roller rotation speed detection unit 140 that detects the rotation speed (angular speed) of the pressure roller 23. 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 pressing roller rotation speed detection unit 140. For example, the pressure roller rotation speed detection unit 140 sets the number of detection pulses per unit time (predetermined fixed time) as the number of rotations R (n) of the pressure roller 23 based on the number of detection pulses obtained from the sensor. The rotation speed R (n) of the pressure roller 23 is set as the rotation speed of the pressure roller 23 by sequentially calculating at arbitrary moments.

  The mark sensor 180 is also controlled by the control unit 101. As described above, the mark sensor 180 irradiates light from the light emitting portion to the mark Q forming region on the surface of the intermediate transfer belt 20 when the intermediate transfer belt 20 is running endlessly, and the surface of the intermediate transfer belt 20 that the light receiving portion receives. The amount of received reflected light from is output to the belt running speed calculation unit 102.

  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 intermediate transfer belt 20 is driven so as to run at a speed for image formation, for example, when the printer 1 is warmed up or adjusted, the belt running speed calculation unit 102 is moved on the surface of the intermediate transfer belt 20 by the mark sensor 180. Each time the mark Q is detected, the belt running speed of the intermediate transfer belt 20 is calculated based on the time from the detection start timing of the mark Q to the detection end timing. As shown in FIG. 5, for example, the output that the belt traveling speed calculation unit 102 receives from the mark sensor 180 includes a relatively high value obtained by voltage-converting the amount of reflected light from the white mark Q, and the mark Q. The amount of reflected light from the black intermediate transfer belt 20 which is not a portion is constituted by a relatively low value obtained by voltage conversion. The distances d indicating the widths of the marks Q on the surface of the intermediate transfer belt 20 in the running direction of the transfer belt 20 are all the same as indicated by d1, d2, d3... In FIG. The time during which the width of Q is detected (the time interval from the detection start timing of the mark Q to the detection end timing) t is shown in FIG. 5 as, for example, t1, t2, t3. It varies according to the running speed fluctuation. For this reason, the belt running speed calculation unit 102 measures the time t for all the marks Q provided on the surface of the intermediate transfer belt 20, and for example, the width d of each mark Q is determined for each mark Q. By dividing by the corresponding time t, the belt running speed Vi (t) at each part in the running direction of the intermediate transfer belt 20 (the part where the mark Q is provided) is calculated. The belt running speed Vi (t) is the same on all speed determining surfaces (described later) at each position in the running direction of the intermediate transfer belt 20 at the time of calculation.

  The distance d (the width of the mark Q) 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.

  On the other hand, when the belt travel speed Vi (t) of the intermediate transfer belt 20 is calculated by the belt travel speed calculation unit 102, the speed determination surface calculation unit 103 calculates the belt travel speed Vi (t) of the intermediate transfer belt 20 and the belt travel speed Vi (t). The speed of the intermediate transfer belt 20 at the point of contact with the pressure roller 23 is determined from the rotation speed of the pressure roller 23 detected by the pressure roller rotation speed detection unit 140, the diameter of the pressure roller 23, and the circumference. Calculate the surface.

  The speed determination surface 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. 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.

A method for calculating the belt speed determination surface by the speed determination surface calculation unit 103 will be described. First, when the circumference ratio π, the diameter φ of the pressure roller 23, the speed determining surface L (n), and the rotation speed R (n) of the pressure roller 23, the pressure roller 23 is in contact with the inner side of the intermediate transfer belt 20. Therefore, regarding the speed Vr (t) of the surface of the intermediate transfer belt 20 on which the toner image is formed by the image forming units 13M, 13C, 13Y, and 13K at the position where the intermediate transfer belt 20 contacts the pressing roller 23,
Vr (t) = π (φ + 2L (n)) × R (n) (1)
Equation (1) is established. The rotation speed R (n) of the pressing roller 23 is the rotation speed per unit time.

  The surface speed Vr (t) of the intermediate transfer belt 20 at the position where the intermediate transfer belt 20 contacts the pressing roller 23 is equal to the belt running speed Vi (t) of the intermediate transfer belt 20 calculated at the time of the contact.

For this reason, the speed determination plane calculation unit 103
L (n) = 1/2 {Vi (t) / (π × R (n)) − φ} (2)
Based on the equation (2), the speed determining surface of the intermediate transfer belt 20 at the contact point of the intermediate transfer belt 20 with the pressing roller 23 is calculated.

  Then, the control unit 101 causes the belt traveling speed calculation by the belt traveling speed calculation unit 102 and the speed determination surface calculation by the speed determination surface calculation unit 103 to be performed every time each mark Q is detected by the mark sensor 180. The transfer belt 20 is caused to calculate a speed determining surface at a point of contact with the pressing roller 23 in the entire circumferential direction of the transfer belt 20.

  The interval number Q1 between the marks Q formed on the intermediate transfer belt 20 is the number of rotations M of the driving roller required for the drive roller 22 to make the intermediate transfer belt 20 make one round in the belt traveling direction (M = It is preferable that Q1 ≠ M when an integer of 1 or more.

  That is, the control unit 101 sets the belt traveling speed calculation by the belt traveling speed calculation unit 102 and the speed determination surface calculation range by the speed determination surface calculation unit 103 as N circumferences of the intermediate transfer belt 20 (N = 1 or more). (Integer), it is preferable to perform the speed determination surface calculation in the entire peripheral region of the intermediate transfer belt 20 so that the peripheral length of the intermediate transfer belt 20 is an integral multiple of the peripheral length of the pressure roller 23.

  Next, the speed determination surface calculation process of the intermediate transfer belt 20 by the printer 1 will be described. FIG. 7 is a flowchart showing the speed determination surface calculation process of the intermediate transfer belt 20 by the printer 1.

  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 control unit 101 drives the driving roller 22 to drive the intermediate transfer belt 20 at the above-described traveling speed for image formation when the printer 1 is warmed up, the control unit 101 performs intermediate transfer to the mark sensor 180. The mark on the belt 20 is detected, and the mark sensor 180 outputs a detection signal to the belt traveling speed calculation unit 102 every time a mark is detected (S1).

  Upon receiving the belt detection signal from the mark sensor 180, the belt traveling speed calculation unit 102 calculates a time t for one mark Q1, and divides the distance d indicating the width of the mark Q1 by the time t. Thus, the running speed Vi (t) of the intermediate transfer belt 20 at this time is calculated (S2).

  Then, the pressing roller rotation speed detector 140 detects the number of rotations R (n) of the pressing roller 23 at this time (S3).

  The speed determining surface calculating unit 103 calculates the belt traveling speed Vi (t) of the intermediate transfer belt 20 calculated by the belt traveling speed calculating unit 102 and the rotation of the pressing roller 23 calculated by the pressing roller rotation speed detecting unit 140. From the number R (n), the circumferential ratio π, and the diameter φ of the pressure roller 23, the intermediate transfer belt at the contact point pt (n) with the pressure roller 23 at this time is obtained using the above equation (2). A speed determination plane L (n) at 20 specific points p (n) is calculated (S4).

  After the processes of S1 to S4, the control unit 101 determines that the specific point p (n) on the surface of the intermediate transfer belt 20 that was at the position pt (0) at the time when the speed determination surface calculation process was started is the intermediate transfer belt 20. Whether or not the belt has returned to the position pt (0) after having made one turn, the running time (predetermined value) assumed to be required for the intermediate transfer belt 20 to make one turn by the counter is the speed. Judgment is made based on whether or not it has been measured that the decision plane calculation process has been disclosed (S5).

  The control unit 101 determines that the specific point p (n) 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 this is the case (NO in S5), the process returns to S1, and based on the mark Q2 detected next and the mark Q3 detected next, the belt running speed calculation process and speed in S1 to S4 The determination plane calculation process is repeated. Then, the control unit 101 performs the calculation process of the speed determination surface L (n) once for the part that was the specific part p (n) on the surface of the intermediate transfer belt 20 at the time of disclosure of the speed determination surface calculation process. Repeat until it returns to position pt (0) (YES in S5).

  The control unit 101 uses the information on the speed determination surface L (n) at each position 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 detected. The traveling speed of the intermediate transfer belt 20 when it moves to the position pt (0) that contacts the pressing roller 23 is calculated and accumulated for the entire circumferential area of the intermediate transfer belt 20 in the traveling direction. The intermediate transfer belt 20 is driven at a constant speed by increasing or decreasing the rotational speed of the transfer belt drive motor 125 according to the running speed information at each position of the intermediate transfer belt 20 (S6).

  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.

  In the speed determination surface calculation process, the speed determination surface is calculated in each part of the intermediate transfer belt 20 in the entire travel direction. However, the speed determination surface is calculated in the travel direction of the intermediate transfer belt 20. If only one mark Q is provided, it is possible to calculate the speed determination surface at the one place. Further, in the case where the speed determination surface is calculated at a plurality of arbitrary positions in the traveling direction of the intermediate transfer belt 20, if the mark Q is provided in an arbitrary number on the surface of the intermediate transfer belt 20, the speed determination surface is calculated. It is possible to calculate speed determining surfaces at a plurality of locations.

  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.

  Moreover, in the said embodiment, although the example of the 1st roller in a claim is demonstrated as the press roller 23, it replaces with this, the lower driven roller 25, the tension roller 21, the drive roller 22, and the upper driven roller It is also possible to calculate the speed determining surface at each position in the running direction of the intermediate transfer belt 20 using 24 as the first roller.

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 drive device concerning one Embodiment of this invention. FIG. 4 is a perspective view showing an intermediate transfer belt and a mark sensor. FIG. 2 is a block diagram illustrating an example of a schematic configuration of a printer. It is an example of the mark detection signal output from a mark sensor. It is a figure which shows the mark formed on the intermediate transfer belt and its surface. 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 13K, 13Y, 13M, 13C Image formation unit 13 Image formation part 20 Intermediate transfer belt 21 Tension roller 22 Drive roller 23 Press roller 24 Upper driven roller 25 Lower driven roller 100 Control unit 101 Control part 102 Belt running speed calculation part 103 Speed determination surface calculation unit 125 Transfer belt drive motor 140 Press roller rotation speed detection unit 180 Mark sensor 200 Transfer unit 220 Transfer belt drive motor

Claims (6)

A belt-like member that travels endlessly, and has one or more marks on its surface in the traveling direction, and a toner image is transferred from the image carrier to the surface or a recording sheet placed on the surface. A transfer belt;
A plurality of rollers that stretch the transfer belt so that it can run endlessly;
A driving roller that is one of the plurality of rollers and causes the transfer belt to travel endlessly;
A mark detection unit that is provided at a position facing the mark forming portion of the transfer belt surface and detects the mark on the transfer belt surface when the transfer belt is running;
A belt running speed calculation unit that calculates a belt running speed of the transfer belt based on a time from a detection start timing of the mark by the mark detection unit to a detection end timing;
A first roller rotation speed detector that detects a rotation speed of a first roller that is one of the plurality of rollers;
When the belt running speed is calculated by the belt running speed calculating unit, the calculated belt running speed, the rotation speed of the first roller detected by the first roller rotation speed detecting unit, and the first A belt driving device comprising: a speed determining surface calculating unit that calculates a speed determining surface of a transfer belt portion in contact with the first roller from a predetermined diameter of the roller.   The speed determination surface calculation unit is detected by the calculated belt travel speed Vi (t) and the first roller rotation speed detection unit when the belt travel speed is calculated by the belt travel speed calculation unit. From the rotation speed R (n) of the first roller, the predetermined diameter φ of the first roller, and the circumferential ratio π, L (n) = 1/2 {Vi (t) / (π × 2. The belt driving device according to claim 1, wherein a speed determining surface L (n) of the transfer belt portion in contact with the first roller is calculated using an equation of R (n)) − φ}. The transfer belt has a plurality of marks formed at predetermined intervals on the surface of the entire circumference in the running direction,
Based on each of the marks, the speed determination surface of the transfer belt portion that contacts the first roller is provided to the belt travel speed calculation unit and the speed determination surface calculation unit in the entire circumference in the travel direction of the transfer belt. The belt driving device according to claim 1, further comprising a control unit for calculation.   The belt drive device according to claim 3, 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 control unit sets the speed determining surface calculation range to N circumferences of the transfer belt (N = 1 or greater integer) so that the circumference of the transfer belt is an integral multiple of the circumference of the drive roller. The belt driving device according to claim 3, wherein the speed determining surface is calculated in the entire circumference of the transfer belt. 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.

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