JP6051555B2 - Medium conveying apparatus, image forming apparatus, and medium conveying method - Google Patents

Description

  The present invention relates to a medium conveying apparatus, an image forming apparatus, and a medium conveying method.

  In an image forming apparatus, a toner image formed on a photosensitive member is transferred to an intermediate transfer belt, and the toner image is secondarily transferred onto a sheet between the intermediate transfer belt and a secondary transfer roller that is in pressure contact with the intermediate transfer belt. After that, a configuration for printing and outputting an image on paper has been put into practical use.

  When the toner image is secondarily transferred to the paper, if there is a speed difference between the surface speed of the rotating intermediate transfer belt and the secondary transfer roller, the toner image on the intermediate transfer belt is not correctly transferred to the paper and the image is misaligned. Etc., and the image quality deteriorates.

  Therefore, the surface speed of the intermediate transfer belt and the secondary transfer roller is detected by detecting the torque command value for the motor that drives the intermediate transfer belt and controlling the surface speed of the secondary transfer roller based on the detection result of the torque command value. There is a method of controlling so that the speed difference is within a predetermined range (see, for example, Patent Document 1).

  Here, when the surface layer of the secondary transfer roller is formed of an elastic member, the surface speed of the deformed portion according to the amount of deformation of the surface layer elastic member due to the pressure contact between the secondary transfer roller and the intermediate transfer belt. Changes. When the secondary transfer roller is in contact with or separated from the intermediate transfer belt, the surface speed gradually changes according to the amount of deformation of the secondary transfer roller surface layer. Therefore, based on the torque command value as described above. Even if the surface speed of the secondary transfer roller is controlled, a difference in surface speed may actually occur between the intermediate transfer belt and the secondary transfer roller, and the image quality may deteriorate.

  The present invention has been made in view of the above, and an object of the present invention is to provide a medium transport apparatus capable of appropriately controlling the surface speeds of two rotating bodies when the medium is transported between the two rotating bodies. And

According to one aspect of the present invention, there is provided a medium transport device that transports a medium between two rotating bodies, the first rotating body that is rotatably provided, and at least a surface layer that is formed of an elastic material and is rotatable. A second rotating body provided in pressure contact with the first rotating body, driving means for rotating the second rotating body at a target rotational speed, and the first rotating body or the second rotating body. A moving means for moving the body between a position where the first rotating body and the second rotating body are pressed against and a position where they are separated from each other, and a pressing force between the first rotating body and the second rotating body Pressure detecting means for detecting the pressure, storage means for storing a correction amount of the target rotational speed of the driving means according to the pressing force of the first rotating body and the second rotating body, and the pressing force detecting means Based on the pressing force detected by the storage means according to the pressing force stored by the storage means. In the correction amount, the velocity correction means for correcting the target rotational speed of the drive means, and a speed detecting means for detecting a rotational speed of the second rotary member, said speed correction means, said moving means said When the first rotating body or the second rotating body is moved, the storage means stores the difference based on the difference between the rotational speed of the second rotating body detected by the speed detecting means and the target rotational speed. The correction amount according to the pressing force is corrected .

  According to the embodiment of the present invention, when a medium is transported between two rotating bodies, a medium transporting apparatus capable of appropriately controlling the surface speeds of the two rotating bodies can be provided.

1 is a schematic view illustrating the configuration of an image forming apparatus according to a first embodiment. 2 is a schematic view illustrating the configuration of an intermediate transfer belt and a secondary transfer roller according to the first embodiment. FIG. It is a figure which illustrates the composition of the contacting / separating mechanism concerning a 1st embodiment. It is a figure explaining the change of the peripheral speed of the elastic roller pressed by the roller formed with the rigid body. FIG. 6 is a diagram illustrating a relationship between a distance between a center of an opposing roller and a rotation center of a secondary transfer roller and a pressing force of the secondary transfer roller against an intermediate transfer belt in the first embodiment. FIG. 6 is a diagram illustrating a relationship between a pressing force of a secondary transfer roller with respect to an opposing roller and a speed correction amount of a secondary transfer motor in the first embodiment. FIG. 3 is an example of a control block diagram of a secondary transfer motor that rotates a secondary transfer roller in the first embodiment. FIG. 6 is a diagram illustrating a flowchart of a speed control process of a secondary transfer roller in the first embodiment. FIG. 6 is a diagram illustrating a flowchart of a speed control process of a secondary transfer motor in the first embodiment. FIG. 10 is an example of a control block diagram of a secondary transfer motor that rotates a secondary transfer roller according to a second embodiment. It is a figure explaining the method of correct | amending the relationship between a gap and pressing force in 2nd Embodiment. FIG. 10 is a diagram illustrating a flowchart of a speed control process of a secondary transfer motor according to a second embodiment. FIG. 10 is an example of a control block diagram of a secondary transfer motor that rotates a secondary transfer roller according to a third embodiment. It is a figure explaining the method of correct | amending the relationship between pressing force and speed correction amount in 3rd Embodiment. FIG. 10 is a diagram illustrating a flowchart of a secondary transfer motor speed control process according to a third embodiment. It is a figure which illustrates the composition of the pressure sensor in a 1st embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

[First Embodiment]
<Configuration of image forming apparatus>
FIG. 1 is a schematic view illustrating the configuration of an image forming apparatus 100 according to the first embodiment.

  The image forming apparatus 100 includes a photoconductor 10, a charging device 11, an exposure device 12, a developing device 13, an intermediate transfer belt 20, a secondary transfer roller 30, a fixing device 40, an automatic document feeder (ADF) 50, a reading device 51, and the like. And a multifunction machine that prints and outputs an image on the paper P stored in the paper tray 60.

  When printing an image on the paper P in the image forming apparatus 100, first, the charging device 11 uniformly charges the surface of the rotating photoreceptor 10, and the image read by the reading device 1 on the original set on the ADF 50. Based on the data and the like, the exposure device 12 exposes the surface of the photoreceptor 10 to form an electrostatic latent image. Next, the developing device 13 containing a developer containing toner therein develops the electrostatic latent image on the surface of the photoreceptor 10 to form a toner image. The image forming apparatus 100 includes a plurality of photoconductors 10, a developing device 13, and the like. After forming toner images of different colors, the toner images are transferred onto the rotating intermediate transfer belt 20 in a superimposed manner.

  The toner image transferred to the intermediate transfer belt 20 is secondarily transferred to the paper P conveyed from the paper tray 60 at the secondary transfer portion between the intermediate transfer belt 20 and the secondary transfer roller 30. The sheet P onto which the toner image has been transferred is further conveyed, heated and pressed by the fixing device 40 to fix the toner image, and is discharged to the paper discharge tray 70.

  After the toner image is transferred to the intermediate transfer belt 20, the toner remaining on the surface is removed by the cleaning device 14 to prepare for the next image formation.

<Configuration of intermediate transfer belt and secondary transfer roller>
FIG. 2 is a schematic view illustrating the configuration of the intermediate transfer belt 20 and the secondary transfer roller 30 according to the first embodiment.

  The intermediate transfer belt 20 is stretched over rollers 21, 22, 24 and the like, and is rotated in the direction of the arrow in the drawing by following the roller 21 rotated by the intermediate transfer motor 25. A toner image formed on the surface of the photoconductor 10 is transferred between the photoconductor 10 and the primary transfer roller 15 on the intermediate transfer belt 20.

  The secondary transfer roller 30 is an example of a second rotating body, and is configured, for example, by covering an outer periphery of a metal core such as SUS with an elastic material such as urethane whose resistance value is adjusted by a conductive material. ing. The secondary transfer roller 30 is rotatably provided and can be moved between a position where the roller 24 as an example of the first rotating body is pressed via the intermediate transfer belt 20 and a position where the roller 24 is separated from the roller 24. Is provided.

  The secondary transfer roller 30 is rotated in the direction of the arrow in the figure by a secondary transfer motor 31 as an example of a driving unit. The secondary transfer roller 30 is rotationally driven at a predetermined rotational speed by a secondary transfer motor 31 whose rotational speed is feedback controlled by the control unit A. A secondary transfer encoder 32 is provided on the rotation shaft of the secondary transfer motor 31, and the control unit A can obtain the rotational speed of the secondary transfer roller 30 from the detection result of the secondary transfer encoder 32.

  The contact / separation mechanism 35 is a moving unit that moves the secondary transfer roller 30 between a position where the roller 24 is pressed against the intermediate transfer belt 20 and a position where the roller 24 is separated from the intermediate transfer belt 20.

  FIG. 3 is a diagram illustrating the configuration of the contact / separation mechanism 35 according to the first embodiment. FIG. 3A illustrates a state in which the secondary transfer roller 30 is separated from the roller 24, and FIG. FIG. 7B shows a state where the secondary transfer roller 30 is in contact with the roller 24. An intermediate transfer belt 20 exists between the secondary transfer roller 30 and the roller 24.

  As shown in FIG. 3, the secondary transfer roller 30 is urged in the direction of the opposed roller 24 by a spring 64. An eccentric cam 62 is provided on the rotating shaft of the roller 24, and the contact / separation motor 61 connected to the eccentric cam 62 via a gear rotates, so that the roller 24 and the secondary transfer roller 30 come in contact with and separate from each other.

  For example, as shown in FIG. 3A, the eccentric cam 62 of the roller 24 is rotated by the contact / separation motor 61 to press the eccentric cam support member 63 provided on the secondary transfer roller 30, so that the roller 24 And the secondary transfer roller 30 are separated from each other. 3B, when the eccentric cam 62 of the roller 24 is rotated by the contact / separation motor 61 and is separated from the eccentric cam support member 63 of the secondary transfer roller 30, it is biased by the spring 64. Then, the secondary transfer roller 30 contacts the roller 24. The position of the secondary transfer roller 35 with respect to the surface of the intermediate transfer belt 20 is obtained by the control unit B based on the rotation amount of the contact / separation motor 61.

  In this embodiment, the secondary transfer roller 30 is provided so as to move with respect to the roller 24. However, by moving the roller 24, the roller 24 comes into contact with and separates from the secondary transfer roller 30. It may be configured.

  The control unit A and the control unit B are connected to a memory 34 as a storage unit. The control unit A controls the rotational speed of the secondary transfer motor 31 based on data stored in the memory 34, and the control unit B The position of the secondary transfer roller 30 by the contact / separation mechanism 35 is controlled. Note that the functions of the control unit A and the control unit B are realized by, for example, a CPU (not illustrated) included in the image forming apparatus 100 executing a program stored in a ROM, a RAM, or the like.

<Relationship between pressing force of secondary transfer roller against intermediate transfer belt and peripheral speed>
FIG. 4 is a diagram for explaining a change in the peripheral speed of the elastic roller 2 pressed against the rigid roller 1. 4A shows a state where the elastic roller 2 is pressed against the roller 1 by the pressing force P1, and FIG. 4B shows a state where the elastic roller 2 is pressed against the roller 1 by P2 larger than the pressing force P1. Represents the state.

  It is assumed that the elastic roller 2 has an elastic layer 2a formed around the cored bar 2b and is driven to rotate at a constant rotational speed. Moreover, each symbol described in the figure represents the following.

r: inner diameter of elastic layer 2a of elastic roller 2 R: outer diameter of elastic roller 2 AB: outer peripheral length of contact area between roller 1 and elastic roller 2 A'B ': contact area between roller 1 and elastic roller 2 inner peripheral length V r of the elastic layer _2a: the inner periphery of the angular velocity V R of the elastic layer 2a of the elastic roller _2: as shown in the outer periphery of the angular velocity Figure 4 of the elastic roller 2, the pressing force P to the roller 1 of the elastic roller 2 Is increased, the amount of strain of the elastic layer 2a of the elastic roller 2 increases, and the contact range (AB) between the roller 1 and the elastic roller 2 increases. However, since the influence of the strain of the elastic layer 2a is small on the inner peripheral side of the elastic layer 2a of the elastic roller 2, the strain amount AB / A'B '(peripheral length ratio between the inner periphery and the outer periphery of the contact region) is the pressing force P. It grows with. Speed ratio V _C of the angular velocity V _R of the inner periphery of the angular velocity V _r and the outer periphery of the elastic roller 2 at this time is represented by the following formula (1).

式（１）から、内周の角速度Ｖ_ｒが一定の場合、押圧力Ｐが大きくなる程ひずみ量ＡＢ／Ａ'Ｂ'が大きくなるため、外周の角速度Ｖ_Ｒは速くなる。したがって、例えば弾性ローラ２を回転駆動するモータの回転速度を一定に制御すると、弾性ローラ２の弾性層２ａの内周の角速度Ｖ_ｒは一定に制御可能であるが、弾性ローラ２の弾性層２ａが押圧されてひずむため、弾性ローラ２の外周の角速度Ｖ_Ｒは押圧力Ｐに応じて変化することになる。

From equation (1), when the angular velocity V _r of the inner periphery is constant, since the extent strain amount AB / A'B pressing force P increases' increases, the angular velocity V _R of the outer periphery becomes faster. Therefore, for example, when the rotational speed of the motor that rotationally drives the elastic roller 2 is controlled to be constant, the angular velocity V _r of the inner circumference of the elastic layer 2a of the elastic roller 2 can be controlled to be constant, but the elastic layer 2a of the elastic roller 2 There because distorted is pressed, the angular velocity V _R of the outer periphery of the elastic roller 2 will vary in response to the pressing force P.

  In the first embodiment, the pressing force to the intermediate transfer belt 20 changes according to the position at which the secondary transfer roller 30 moves by the contact / separation mechanism 35. When the secondary transfer roller 30 is pressed against the intermediate transfer belt 20, the elastic layer of the secondary transfer roller 30 is distorted. Therefore, even if the rotation speed of the secondary transfer motor 31 is controlled to be constant, The speed changes according to the pressing force. Therefore, the peripheral speed of the secondary transfer roller 30 changes according to the position where the secondary transfer roller 30 moves by the contact / separation mechanism 35.

<Secondary transfer roller speed control>
Next, a method for controlling the peripheral speed of the secondary transfer roller 30 that changes according to the pressing force applied to the intermediate transfer belt 20 will be described.

  First, FIG. 5 illustrates the relationship between the distance between the center of the opposing roller 24 and the rotation center of the secondary transfer roller 30 and the pressing force of the secondary transfer roller 30 against the opposing roller 24 in the first embodiment. FIG. Hereinafter, the distance between the center of the roller 24 and the rotation center of the secondary transfer roller 30 is referred to as a “gap”.

  As shown in FIG. 5, when the gap is equal to or larger than the sum R of the radius of the roller 24 and the radius of the secondary transfer roller 30, the pressing force of the secondary transfer roller 30 against the intermediate transfer belt 20 is zero, and the gap is smaller than R. As it is, the pressing force of the secondary transfer roller 30 against the intermediate transfer belt 20 gradually increases.

  Since the relationship between the gap and the pressing force depends on the elastic material constituting the secondary transfer roller 30, the configuration of the contact / separation mechanism 35, and the like, those measured in advance are stored in the memory 34.

  Further, as shown in Expression (1), as the pressing force of the secondary transfer roller 30 against the intermediate transfer belt 20 increases, the outer peripheral length AB of the contact area increases and the peripheral speed of the secondary transfer roller 30 increases. Therefore, in order to keep the peripheral speed of the secondary transfer roller 30 constant, it is necessary to decrease the rotational speed of the secondary transfer motor 31 as the pressing force increases.

The speed correction amount necessary for the secondary transfer motor 31 is calculated in advance by measuring the strain amount AB / A′B ′ corresponding to the pressing force of the secondary transfer roller 30 against the intermediate transfer belt 20 and using the equation (1). From the speed ratio V _C , the following formula (2) is used for calculation.

Speed correction amount = (1−V _C ) × target speed (2)
FIG. 6 is a diagram exemplifying the relationship between the pressing force of the secondary transfer roller 30 against the opposing roller obtained based on the formula (2) and the speed correction amount of the secondary transfer motor 31. The relationship between the pressure and the speed correction amount is obtained in advance and stored in the memory 34.

Note that the peripheral speed of the secondary transfer roller 30 is measured while changing the pressing force of the secondary transfer roller 30 against the roller 24, and the ratio with the peripheral speed when the pressing force is 0 is the speed ratio V in the equation (2). _C may also be used.

  As described above, the secondary transfer roller 30 is controlled by controlling the rotational speed of the secondary transfer motor 31 based on the relationship between the gap and the pressing force stored in the memory 34 and the relationship between the pressing force and the speed correction amount. The peripheral speed can be kept constant.

  FIG. 7 is an example of a control block diagram of the secondary transfer motor 31 that rotates the secondary transfer roller 30 in the first embodiment.

  When printing an image by transferring a toner image onto the paper P in the image forming apparatus 100, the secondary transfer motor 30 is first rotated at a target speed that is input, whereby the secondary transfer roller 30 is moved at a constant speed. Rotate with Next, the contact / separation mechanism 35 drives the contact / separation motor 61 by the contact / separation controller 51 that controls the contact / separation mechanism 35 based on the input target position of the secondary transfer roller 30 to transfer the secondary transfer roller 30. It is moved in a direction in which it is pressed against or separated from the roller 24 via the belt 20.

  The pressing force detection means 52 obtains a gap that is a distance between the center of the roller 24 and the rotation center of the secondary transfer roller 30 based on, for example, the rotation amount of the motor of the contact / separation mechanism 35, and the gap stored in the memory 34. The pressure of the secondary transfer roller 30 against the roller 24 is detected from the relationship between the pressure and the pressure.

  Next, the speed correction unit 53 acquires the speed correction amount from the relationship between the pressing force stored in the memory 34 and the speed correction amount based on the pressing force detected by the pressing force detection unit 52, and performs secondary transfer. The target speed input to the motor controller 54 that controls the motor 31 is corrected.

  The contact / separation controller 51 and the pressing force detection means 52 are functions of the control unit B shown in FIG. 2, and the speed correction means 53 and the motor controller 54 are functions of the control unit A shown in FIG.

  In this way, by controlling the rotational speed of the secondary transfer motor 31 during the press-contact / separation operation between the secondary transfer roller 30 and the roller 24, the secondary transfer roller 30 is in contact with and pressed against the transfer belt 20. The peripheral speed can be kept constant, and a difference in speed from the surface speed of the transfer belt 20 can be prevented.

<Flowchart of Secondary Transfer Roller Speed Control Process>
FIG. 8 is a diagram illustrating a flowchart of the speed control process of the secondary transfer roller 30 in the first embodiment.

  First, with the secondary transfer motor 31 activated in step S1, speed control of the secondary transfer motor 31 is started in step S2.

  Next, a speed correction process of the secondary transfer motor 31 is performed in step S3.

  FIG. 9 illustrates a flowchart of the speed correction process of the secondary transfer motor 31.

  As shown in FIG. 9, in the speed correction process of the secondary transfer motor 31, first, in step S401, the pressing force detection means 52 obtains a gap from the motor rotation amount of the contact / separation mechanism 35, and the step S402 stores it in the memory 34. The pressing force is detected from the relationship between the gap and the pressing force.

  In step S403, the speed correction unit 53 obtains a speed correction amount from the relationship between the pressing force stored in the memory 34 and the speed correction amount, and the speed is set to the target speed of the secondary transfer motor 31 in step S404. The correction amount is added, and the speed correction process of the secondary transfer motor 31 is completed.

  Returning to the flowchart shown in FIG. 8, when the speed correction process of the secondary transfer motor 31 is completed in step S3, if the secondary transfer motor 31 is continuously driven in step S4, the secondary transfer motor 31 is continued in step S3. A speed correction process of the transfer motor 31 is performed. When the drive of the secondary transfer motor 31 is stopped in step S4, the secondary transfer motor 31 is stopped in step S5, and the speed control of the secondary transfer roller 30 is finished.

  In this way, using the relationship between the gap and the pressing force stored in the memory 34 and the relationship between the pressing force and the speed correction amount, the pressing force and the speed correction are performed based on the gap obtained from the operation of the contact / separation mechanism 35. By obtaining the amount and correcting the rotational speed of the secondary transfer motor 31, it is possible to keep the peripheral speed of the secondary transfer roller 30 constant when the secondary transfer roller 30 is pressed / separated. Therefore, there is no speed difference between the transfer belt 20 and the toner image on the transfer belt 20 can be transferred to the paper P without causing a positional shift and a high quality image can be obtained.

  Note that a pressure sensor that measures the pressing force of the secondary transfer roller 30 against the transfer belt 20 may be provided as the pressing force detection unit 52. When the pressure sensor is provided, for example, as shown in FIG. 16, a pressure sensor 65 is provided on the eccentric cam support member 63 so that pressure is applied to the pressure sensor 65 when the secondary transfer roller 30 contacts the roller 24. In addition, a counter member 66 having the same diameter as the roller 24 is provided on the rotation shaft of the roller 24. At this time, the eccentric cam support member 63 is provided coaxially with the secondary transfer roller 30, but is fixed so as not to rotate.

  In this way, the pressure sensor 65 measures the pressing force during the pressing / separating operation between the secondary transfer roller 30 and the roller 24, and the speed correcting means 53 stores the pressing force stored in the memory 34 based on the measured pressing force. It is also possible to obtain the speed correction amount from the relationship with the speed correction amount.

[Second Embodiment]
Next, a second embodiment will be described based on the drawings. Note that a description of the same components as those of the above-described embodiment will be omitted.

  According to the second embodiment, by appropriately correcting the relationship between the gap and the pressing force stored in the memory 34, it is possible to keep the peripheral speed of the secondary transfer roller 30 accurately and constant over time. become.

  FIG. 10 is an example of a control block diagram of the secondary transfer motor that rotates the secondary transfer roller in the second embodiment.

  As shown in FIG. 10, the pressing force detection unit 52 detects the target speed input to the secondary transfer motor 31 and the rotation detected by the secondary transfer encoder 32 provided on the rotation shaft of the secondary transfer motor 31. Find the speed deviation from the speed. The pressing force detection unit 52 corrects the relationship between the gap and the pressing force stored in the memory 34 based on the detected speed deviation.

  For example, when the outer diameter of the secondary transfer roller 30 increases due to thermal expansion over time, the secondary transfer roller 30 is initially contacted and pressed at a position where it does not contact the transfer belt 20. Since the speed correction of the secondary transfer motor 31 is performed based on the gap, an appropriate speed correction control is not performed at such a position, so that a speed deviation occurs between the transfer belt 20 and the secondary transfer roller 30. .

  Therefore, for example, when the outer diameter of the secondary transfer roller 30 is increased due to thermal expansion, the pressing force detecting means 52 is stored in the memory 34 based on the gap in which the speed deviation occurs as shown in FIG. The relationship between the gap and the pressing force is corrected to shift. Specifically, the relationship between the gap and the pressing force stored in the memory 34 is slid in parallel so that the gap position where the value of the pressing force rises matches the gap position where the speed deviation occurs.

  Further, for example, even when there is an error in the relationship between the gap and the pressing force stored in advance in the memory 34, it can be similarly corrected by acquiring the speed deviation.

  FIG. 12 illustrates a flowchart of the speed control process of the secondary transfer motor 31 in the second embodiment, and a process for correcting the relationship between the gap and the pressing force stored in the memory 34 will be described.

  As shown in FIG. 12, the speed control process of the secondary transfer motor 31 is performed by detecting the pressing force from the motor rotation amount of the contact / separation mechanism 35 in step S411 during the pressure contact / separation operation between the secondary transfer roller 30 and the roller 24. The means 52 obtains the gap, and detects the pressing force from the relationship between the gap in the memory 34 and the pressing force in step S412.

  In step S413, the speed correction unit 53 obtains a speed correction amount from the relationship between the pressing force stored in the memory 34 and the speed correction amount. In step S414, the speed correction unit 53 corrects the speed to the target speed of the secondary transfer motor 31. Add the amount.

  If the roller 24 and the secondary transfer roller 30 are in pressure contact or separation operation in step S415, the pressing force detection means 52 detects the target speed and the secondary transfer encoder 32 in step S416. The speed deviation from the rotational speed of the secondary transfer motor 31 is obtained, and the speed deviation with respect to the gap is stored in the memory 34. Next, when the pressing or separating operation is completed in step S417, the pressing force detecting means 52 corrects the relationship between the gap and the pressing force based on the speed deviation stored in the memory 34 in step S418. The process is terminated.

  Instead of correcting the relationship between the gap and the pressing force every time the secondary transfer roller 30 is operated, for example, the correction may be periodically performed at regular time intervals.

  As described above, according to the second embodiment, even when a change occurs in the outer diameter due to thermal expansion or the like of the secondary transfer roller 30, for example, the gap and the pressing force stored in the memory 34 are changed. By appropriately correcting this relationship, the rotational speed of the secondary transfer motor 31 can be controlled in accordance with changes in the secondary transfer roller 30. In the press-contact / separation operation of the roller 24 and the secondary transfer roller 30, the peripheral speed of the secondary transfer roller 30 can always be kept constant over time, and a speed difference is generated between the surface speed of the transfer belt 20. There is nothing. Accordingly, the toner image on the transfer belt 20 can be transferred to the paper P without causing a positional deviation and the like, and a high quality image can be obtained over time.

[Third embodiment]
Next, a third embodiment will be described based on the drawings. Note that a description of the same components as those of the above-described embodiment will be omitted.

  According to the third embodiment, the peripheral speed of the secondary transfer roller 30 can be maintained accurately and constant over time by appropriately correcting the relationship between the pressing force stored in the memory 34 and the speed correction amount. Is possible.

  FIG. 13 is an example of a control block diagram of the secondary transfer motor that rotates the secondary transfer roller in the third embodiment.

  As shown in FIG. 13, the speed correction means 53 has a target speed input to the secondary transfer motor 31 and a rotation speed detected by the secondary transfer encoder 32 provided on the rotation shaft of the secondary transfer motor 31. And get the speed deviation. The speed correction unit 53 corrects the relationship between the pressing force stored in the memory 34 and the speed correction amount based on the acquired speed deviation.

  For example, when the secondary transfer roller 30 deteriorates with time and the strain amount with respect to the same pressing force changes, the peripheral speed is kept constant even if the speed control of the secondary transfer roller 30 is performed with the same speed correction amount as the initial stage. There is a possibility that a speed difference may occur with the transfer belt 20.

  Therefore, as shown in FIG. 14, for example, when the characteristics of the secondary transfer roller 30 change over time, the speed acquired by the speed correction unit 53 during the contact / separation operation between the secondary transfer roller 30 and the roller 24. Based on the deviation, the relationship between the pressing force stored in the memory 34 and the speed correction amount is corrected.

  Specifically, when the speed correction unit 53 makes contact / separation between the secondary transfer roller 30 and the roller 24, a speed deviation caused by a change with time of the secondary transfer roller 30 is acquired and stored in the memory 34. The obtained speed deviation is subtracted from the speed correction amount for the pressing force.

  Further, for example, even when there is an error in the relationship between the gap and the pressing force stored in advance in the memory 34, or when the outer diameter of the secondary transfer roller 30 changes with time, the speed deviation is acquired and similarly. It can be corrected.

  FIG. 15 illustrates a flowchart of the speed control process of the secondary transfer motor 31 in the third embodiment, and a process for correcting the relationship between the pressing force stored in the memory 34 and the speed correction amount will be described.

  As shown in FIG. 15, the speed control process of the secondary transfer motor 31 is performed in step S421 to detect the pressing force from the motor rotation amount of the contact / separation mechanism 35 at the time of the pressure contact / separation operation between the secondary transfer roller 30 and the roller 24. The means 52 acquires the gap, and acquires the pressing force from the relationship between the gap in the memory 34 and the pressing force in step S422.

  In step S423, the speed correction unit 53 acquires a speed correction amount from the relationship between the pressing force stored in the memory 34 and the speed correction amount. In step S424, the speed correction unit 53 sets the speed to the target speed of the secondary transfer motor 31. Add the correction amount.

  Here, if the roller 24 and the secondary transfer roller 30 are in pressure contact or separation operation in step S425, the speed correction means 53 is detected by the target speed and the secondary transfer encoder 32 in step S426. A speed deviation from the rotation speed of the secondary transfer motor 31 is acquired, and the speed deviation with respect to the pressing force is stored in the memory 34. Next, when the pressure contact or separation operation is completed in step S427, the relationship between the pressing force and the speed correction amount in the memory 34 is corrected based on the speed deviation acquired by the speed correction means 53 in step S428. The process is terminated.

  Instead of correcting the relationship between the gap and the pressing force every time the secondary transfer roller 30 is operated, for example, the correction may be periodically performed at regular time intervals.

  Further, as described in the second embodiment, the pressing force detection unit 52 acquires the speed deviation, corrects the relationship between the gap and the pressing force stored in the memory 34, and the speed correction unit 53 simultaneously presses the pressing force. Control may be performed so as to correct the relationship between the pressure and the speed correction amount.

  As described above, according to the third embodiment, for example, even when a change occurs in the secondary transfer roller 30, the relationship between the pressing force stored in the memory 34 and the speed correction amount is appropriately corrected. By doing so, the rotational speed of the secondary transfer motor 31 can be controlled in accordance with the change of the secondary transfer roller 30. In the press-contact / separation operation between the secondary transfer roller 30 and the roller 24, the peripheral speed of the secondary transfer roller 30 can always be kept constant over time, and a speed difference is generated with the surface speed of the transfer belt 20. I will not let you. Accordingly, the toner image on the transfer belt 20 can be accurately transferred to the paper P without causing misalignment even with time, and a high-quality image can be obtained.

  In the first to third embodiments, in the configuration in which the sheet is transferred between the intermediate transfer belt 20 and the secondary transfer roller 30 in the image forming apparatus 100 and the toner image is transferred, the secondary transfer roller 30 The case where the peripheral speed is controlled to be constant has been described. However, the embodiment of the present invention is not limited to this, and can be applied to a case where a support roller of a photosensitive belt is used as the first rotating body or a case where a photosensitive body is used. For example, the present invention can be applied to speed control of a sheet conveying path in the image forming apparatus 100, a pair of conveying rollers provided in an ADF, and the like. Further, the present invention is not limited to an image forming apparatus, and can be used for speed control of a rotating body in a medium conveying apparatus that conveys a medium such as a sheet with two rotating bodies.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations shown here, such as combinations with other elements, etc., in the configurations described in the above embodiments. These points can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form.

20 Intermediate transfer belt 24 Roller (first rotating body)
30 Secondary transfer roller (second rotating body)
31 Secondary transfer motor (drive means)
32 Secondary transfer encoder (speed detection means)
34 Memory (storage means)
35 Contact / separation mechanism (moving means)
52 pressure detection means 53 speed correction means 100 image forming apparatus

JP 2009-9103 A

Claims (5)

A medium conveying apparatus for conveying a medium between two rotating bodies,
A first rotating body provided rotatably,
A second rotating body having at least a surface layer formed of an elastic material, rotatably provided, and capable of being pressed against the first rotating body;
Drive means for rotating the second rotating body at a target rotational speed;
Moving means for moving the first rotating body or the second rotating body between a position where the first rotating body and the second rotating body are pressed against each other and a position where they are separated from each other;
A pressing force detecting means for detecting a pressing force between the first rotating body and the second rotating body;
Storage means for storing a correction amount of the target rotational speed of the driving means according to the pressing force of the first rotating body and the second rotating body;
Speed correcting means for correcting the target rotational speed of the driving means with a correction amount corresponding to the pressing force stored in the storage means based on the pressing force detected by the pressing force detecting means ;
Speed detecting means for detecting the rotational speed of the second rotating body,
The speed correction unit is configured to obtain a rotation speed between the rotation speed of the second rotation body detected by the speed detection means and the target rotation speed when the movement means moves the first rotation body or the second rotation body. The medium transporting apparatus , wherein the correction amount corresponding to the pressing force stored in the storage unit is corrected based on the difference . The medium conveying apparatus according to claim 1, wherein the pressing force detection unit detects the pressing force based on a distance between a center of the first rotating body and a center of the second rotating body. The medium conveying apparatus according to claim 1, wherein the pressing force detecting unit is a pressure sensor that detects a pressing force between the first rotating body and the second rotating body. An image forming apparatus comprising: a medium conveying device according to any one of claims 1 to 3. A first rotating body provided rotatably,
A second rotating body having at least a surface layer formed of an elastic material, rotatably provided, and capable of being pressed against the first rotating body;
Storage means for storing a correction amount according to the pressing force of the first rotating body and the second rotating body;
A medium conveying method in a medium conveying apparatus comprising:
A driving step of rotating the second rotating body at a target rotational speed;
A moving step of moving the first rotating body or the second rotating body between a position where the first rotating body and the second rotating body are pressed against each other and a position where they are separated from each other;
A pressing force detecting step for detecting a pressing force between the first rotating body and the second rotating body;
A speed correction step of correcting the target rotational speed of the driving step with a correction amount corresponding to the pressing force stored in the storage unit based on the pressing force detected in the pressing force detection step ;
A speed detection step of detecting a rotation speed of the second rotating body,
In the speed correction step, when the first rotating body or the second rotating body is moved by the moving step, the rotational speed of the second rotating body detected by the speed detecting step and the target rotational speed are calculated. The medium transporting method according to claim 1, wherein the correction amount corresponding to the pressing force stored in the storage unit is corrected based on the difference .

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