JP2009198596A - Transfer device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of shock jitter and transfer failure caused by a change in the diameter or elastic modulus of a secondary transfer roller, with the result that a distance between the surface of an intermediate transfer belt and the rotation shaft of the secondary transfer roller deviates from an appropriate distance. <P>SOLUTION: A transfer device includes: a thickness sensor 38 that detects the thickness of a recording sheet P; and a distance sensor 81 that detects the position of the secondary transfer roller 72. The control section is configured such that based on a detection result obtained by the distance sensor 81 when an eccentric cam 80 is not pressed against a rocking arm 76 holding the secondary transfer roller 72 so that it is rockable and based on a detection result obtained by the thickness sensor 38, the position of the secondary transfer roller 72 with the eccentric cam 80 pressed against the rocking arm 76 is adjusted. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transfer device for transferring a visible image carried on the surface of an image carrier onto a recording sheet sandwiched between the rotatable carrier or a belt member stretched around the rotary member and the image carrier. It is about. The present invention also relates to an image forming apparatus using such a transfer device.

Conventionally, in this type of image forming apparatus, when a relatively thick sheet such as cardboard or paperboard is used as a recording sheet, linear density unevenness called shock jitter may occur. This density unevenness is caused by a sudden increase in the load on the drive source of the image carrier when the thick recording sheet enters between the image carrier and the rotating body in contact with or close to the image carrier. This is caused by greatly reducing the surface moving speed instantaneously. The paperboard is a general term for thick paper containing wood chemical pulp, waste paper, and the like, and generally refers to paper having a basis weight of generally 160 [g / m ² ] or more.

  On the other hand, Patent Document 1 describes the following image forming apparatus. That is, this image forming apparatus transfers a toner image, which is a visible image on a latent image carrier, to a recording sheet sandwiched between a pressure roller, which is a rotating body, and a rotatable drum-shaped image carrier. It has a transfer device. In the transfer device, the pressure roller is swingably held by a swing arm that can swing about a swing shaft. The pressure roller and the image carrier are brought into contact with each other by pressing the pressure roller on the rocking arm against the image carrier while urging the swing arm as a holding member toward the image carrier with a spring. A contact nip is formed. The recording sheet that has entered the transfer nip pushes back the pressure roller on the swing arm in the direction opposite to the spring biasing direction. Thereby, the pressure roller is moved together with the swing arm in the direction opposite to the spring biasing direction by the thickness of the recording sheet. When a relatively thin sheet is used as the recording sheet, a sudden load increase at the time of entering the sheet is avoided by the movement of the pressure roller due to pushing back as described above. However, when thick paper such as cardboard or paperboard is used, it is impossible to avoid a sudden load increase at the time of entering the sheet only by moving the pressure roller by pushing back. Therefore, in the image forming apparatus described in Patent Document 1, a thickness sensor that detects the thickness of the recording sheet, an eccentric cam that abuts against a swinging arm that is biased by a spring, and a mechanism for rotating the cam. A motor and a motor drive circuit are provided. When the thickness sensor detects a thickness equivalent to thick paper, the eccentric cam is forced to push down the swinging arm by a predetermined amount in the direction opposite to the biasing direction, thereby adding to the surface of the image carrier. The distance from the rotating shaft of the pressure roller is made larger than before. In such a configuration, when using thick paper, the swing arm is pushed down with an eccentric cam to weaken the transfer nip pressure, or the thick paper is passed through the gap obtained by separating the pressure roller from the image carrier. It is possible to suppress the occurrence of shock jitter due to a sudden load increase.

JP-A-4-242276

  However, even in such a configuration, if the diameter of the rotating body changes, the occurrence of shock jitter may not be sufficiently suppressed, or a transfer failure may occur. Specifically, when the swinging arm is not pushed down by the eccentric cam, the pressure roller abuts against the image carrier by the biasing force of the spring to form a transfer nip. The transfer nip has an appropriate transfer nip pressure when the spring exerts an appropriate biasing force. In this state, if the diameter of the pressure roller changes as the temperature changes, or if the elastic modulus (hardness) of the elastic body of the pressure roller changes over time, the pressure on the surface of the image carrier is increased accordingly. Although the distance from the rotation axis of the roller changes, an appropriate value is maintained for the transfer nip pressure. That is, when the swing arm is not pushed down by the eccentric cam, the transfer nip pressure is maintained at an appropriate value even if the diameter and elastic modulus of the pressure roller change. The distance between the surface of the image carrier at that time and the rotation shaft of the pressure roller is a distance at which an appropriate transfer nip pressure can be exerted. In addition, when using thick paper, a value obtained by adding a value corresponding to the thickness of the thick paper to the above-mentioned distance is an appropriate distance that does not cause shock jitter or transfer failure when the thick paper enters the transfer nip. However, in the conventional image forming apparatus, when the thick paper is detected, the rotary member is simply pushed down to a predetermined position, so that the surface of the image carrier after being pushed down and the rotary shaft of the rotary member are The distance was constant regardless of changes in the diameter and elastic modulus of the rotating body. For this reason, depending on the amount of change in the diameter and elastic modulus of the rotator, the distance between the surface of the image carrier and the rotation axis of the rotator is smaller than the appropriate distance, causing shock jitter, or larger than the proper distance. This may cause a transfer failure.

  The present invention has been made in view of the above background, and the object of the present invention is to ensure that the distance between the surface of the image carrier and the rotation axis of the rotator is appropriate as the diameter and elastic modulus of the rotator change. It is an object of the present invention to provide a transfer device and an image forming apparatus capable of suppressing the occurrence of shock jitter and transfer failure due to deviation from the distance.

In order to achieve the above object, a first aspect of the present invention is a rotatable rotating body, and an urging means for urging the rotating body or a holding body holding the rotating body toward an image carrier of an image forming apparatus. An abutting member that abuts against the rotating body or the holding body urged by the urging means, a moving unit that moves the abutting member, and a thickness information acquisition unit that acquires thickness information of a recording sheet on which an image is formed. By controlling the driving of the moving means based on the thickness information, the distance between the surface of the image carrier and the rotation axis of the rotator when the abutting member is abutted against the rotator or holder A visible image carried on the surface of the image carrier, and sandwiching the visible image between the rotary body or a belt member stretched around the rotary body and the image carrier. In a transfer device that transfers to a recording sheet By the position detection means provided in a state where the position detection means for detecting the position of the rotation axis of the rotation body with respect to the surface of the image carrier is provided and the abutting member is not abutted against the rotation body or the holding body. Based on the detection result and the thickness information, the control means is configured to adjust the position of the rotating body in a state where the abutting member is abutted against the rotating body or the holding body. Is.
According to a second aspect of the present invention, in the transfer device according to the first aspect, the position-detecting member is obtained in a state where the abutting member is not abutted against the rotating body or the holding body. Based on the detection result, after performing an analysis process for analyzing the position variation of the rotating body per integer rotation, based on the analysis result and the thickness information, the abutting member is pushed against the rotating body or the holding body. The control means is configured to adjust the position of the rotating body in the applied state.
According to a third aspect of the present invention, in the transfer device according to the second aspect, in the state where the abutting member is abutted against the rotating body or the holding body, the abutting amount of the abutting member against the rotating body or the holding body is set. The control means is configured to perform control to vary the phase according to the phase of the position variation.
According to a fourth aspect of the present invention, in the transfer apparatus according to any one of the first to third aspects of the present invention, as the moving means, a device that moves the abutting member by driving a motor or an actuator and adjusting the driving amount of the motor or actuator is used. The control means is configured to adjust the position of the rotating body in a state where the abutting member is in contact with the rotating body or the holding body.
According to a fifth aspect of the present invention, in the transfer device according to the fourth aspect, the urging means, the abutting member, and the moving means are respectively provided at one end side and the other end side of the rotating body in the rotation axis direction. The position detecting means is provided, and the motor or actuator is provided with one for one end and the other for the other end, and the abutting member is not in contact with the rotating body or the holding body. The control means is configured to individually adjust the position of the rotating body at the one end side and the other end side.
According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising: a visible image forming unit that forms a visible image on the surface of the image carrier; and a transfer unit that transfers the visible image on the surface to a recording sheet. The transfer device according to any one of claims 1 to 5 is used as the transfer means.

  In these inventions, the occurrence of shock jitter and transfer failure due to the change in the diameter of the rotating body can be suppressed as follows. That is, when the diameter and elastic modulus of the rotating body change, the position detecting means detects the position of the rotating body in a state where the abutting member is not in contact with the rotating body or the holding body. This position indicates the distance between the reference position such as the rotation axis of the image carrier and the rotation axis of the rotation body. This distance is the distance between the surface of the image carrier and the rotation axis of the rotator that provides an appropriate transfer nip pressure when the rotator is freely brought into contact with the image carrier by the urging means. is there. When thick paper is detected based on the thickness information, the distance is increased by an amount corresponding to the thickness of the recording sheet by the movement of the abutting member by the moving means, so that the increased distance is set to the thickness of the recording sheet and It is possible to make the value suitable for the diameter and elastic modulus of the rotating body. By increasing the distance in this way, shock jitter and transfer due to the distance between the surface of the image carrier and the rotating shaft of the rotating body deviating from the appropriate distance as the diameter and elastic modulus of the rotating body change. The occurrence of defects can be suppressed.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of a copying machine that forms an image by an electrophotographic method will be described.
First, a basic configuration of the copying machine according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram showing a copying machine according to the present embodiment. The copying machine includes a printer unit 1, a blank paper supply device 100, and a document conveyance reading unit 150. The document conveyance reading unit 150 includes a scanner 160 as a document reading device fixed on the printer unit 1 and an ADF 170 as a document conveyance device supported by the scanner 160.

  The blank paper supply apparatus 100 includes two paper feed cassettes 102 and 103, two pairs of separation roller pairs 104 and 105, a paper feed path 106, a plurality of transport roller pairs 107, and the like arranged in multiple stages in the paper bank 101. is doing. Each of the two paper feed cassettes 102 and 103 is housed in the form of a paper bundle in which a plurality of recording sheets (not shown) are stacked. Based on the control signal from the printer unit 1, the sending rollers 102 a and 103 a are driven to rotate, and the uppermost recording sheet in the paper bundle is sent out toward the paper feed path 106. The fed recording sheet is separated into one sheet by the pair of separation rollers 104 and 105 and then reaches the sheet feeding path 106. Then, the sheet is fed to the first receiving branch path 30 of the printer unit 1 through the conveyance nips of the plurality of conveyance roller pairs 107 provided in the sheet feeding path 106.

  The printer unit 1 includes four process units 2Y, 2M, 2C, and 2K for forming yellow (Y), magenta (M), cyan (C), and black (K) toner images. Further, the first receiving branch path 30, the receiving conveyance roller pair 31, the manual feed tray 32, the pickup roller 33, the second receiving branch path 34, the separation roller 35, the pre-transfer conveyance path 36, the registration roller pair 37, the conveyance belt unit 39, A fixing unit 43, a switchback device 46, a discharge roller pair 47, a discharge tray 48, a switching claw 49, an optical writing unit 50, a transfer unit 60, and the like are also provided. The process units 2Y, 2M, 2C, and 2K have drum-shaped photoreceptors 3Y, 3M, 3C, and 3K that are latent image carriers.

  A pre-transfer conveyance path 36 for conveying a recording sheet immediately before a secondary transfer nip described later is branched into a first reception branch path 30 and a second reception branch path 34 on the upstream side in the paper conveyance direction. After the recording sheet sent out from the paper feed path 106 of the blank paper supply device 100 is received by the first receiving branch path 30, the recording sheet passes through the transport nip of the receiving transport roller pair 31 disposed in the first receiving branch path 30. Then, it is sent to the pre-transfer conveyance path 36.

  A manual feed tray 32 is disposed on the side surface of the housing of the printer unit 1 so as to be openable and closable with respect to the housing. The uppermost recording sheet in the manually fed paper bundle is picked up by the pickup roller 33, separated one by one by the separation roller 35, and sent to the second receiving branch path 34. Thereafter, the sheet is sent to the pre-transfer conveyance path 36 via the registration nip of the registration roller pair 37.

  The optical writing unit 50 includes a laser diode, a polygon mirror, various lenses (not shown), etc., and is based on image information read by a scanner 160 described later or image information sent from an external personal computer. Drive the laser diode. Then, the photoconductors 3Y, M, C, and K of the process units 2Y, M, C, and K are optically scanned. Specifically, the photoconductors 3Y, 3M, 3C, and 3K of the process units 2Y, 2M, 2C, and 2K are rotated in the counterclockwise direction in the drawing by driving means (not shown). The optical writing unit 50 irradiates the driven photosensitive members 3Y, 3M, 3C, and 3K with laser light (L in FIG. 2 to be described later) while deflecting them in the direction of the rotation axis, thereby performing optical scanning processing. I do. Thereby, electrostatic latent images based on Y, M, C, and K image information are formed on the photoreceptors 3Y, 3M, 3C, and 3K.

  FIG. 2 is a partially enlarged configuration diagram illustrating a part of the internal configuration of the printer unit 1 in an enlarged manner. The process units 2Y, 2M, 2C, and 2K of the respective colors support the photosensitive member as a latent image carrier and various devices arranged around it on a common support as a unit. It is detachable from the printer unit main body. The configuration is the same except that the colors of the toners used are different. Taking the process unit 2Y for Y as an example, this has a developing device 4Y for developing an electrostatic latent image formed on the surface of the photoreceptor 3Y into a Y toner image in addition to the photoreceptor 3Y. This copying machine has a so-called tandem configuration in which four process units 2Y, 2M, 2C, and 2K are arranged along an endless movement direction with respect to an intermediate transfer belt 61 described later.

  FIG. 3 is an enlarged configuration diagram showing the Y process unit 2Y. As shown in the figure, the process unit 2Y includes a developing device 4Y, a drum cleaning device 18Y, a charge eliminating lamp 17Y, a charging roller 16Y, and the like around the photoreceptor 3Y.

  As the photoreceptor 3 </ b> Y, a drum-like member is used in which a photosensitive layer is formed by applying a photosensitive organic photosensitive material to a raw tube such as aluminum. However, an endless belt may be used.

  The developing device 4Y develops a latent image using a two-component developer (hereinafter simply referred to as developer) containing a magnetic carrier (not shown) and non-magnetic Y toner. And it has the stirring part 5Y which conveys the developer accommodated in the inside while stirring, and the developing part 9Y which develops the electrostatic latent image on the photoreceptor 3Y. As the developing device 4Y, a type that performs development with a one-component developer that does not include a magnetic carrier may be used instead of the two-component developer.

  The agitating unit 5Y is provided at a position lower than the developing unit 9Y. The first conveying screw 6Y and the second conveying screw 7Y are arranged in parallel to each other, a partition plate provided between these screws, and the bottom surface of the casing. The toner density sensor 8Y and the like provided in the printer.

  The developing unit 9Y includes a developing roll 10Y that faces the photoreceptor 3Y through the opening of the casing, a doctor blade 13Y that makes its tip close to the developing roll 10Y, and the like. The developing roll 10Y includes a cylindrical developing sleeve 11Y made of a nonmagnetic material, and a magnet roller 12Y provided inside the developing roll 11Y so as not to rotate. The magnet roller 12Y has a plurality of magnetic poles arranged in the circumferential direction. Each of these magnetic poles applies a magnetic force to the developer on the sleeve at a predetermined position in the rotational direction. As a result, the developer sent from the stirring unit 5Y is attracted and carried on the surface of the developing sleeve 11Y, and a magnetic brush along the magnetic field lines is formed on the sleeve surface.

  The magnetic brush is transported to a developing region facing the photoreceptor 3Y after being regulated to an appropriate layer thickness when passing through a position facing the doctor blade 13Y as the developing sleeve 11Y rotates. Then, Y toner is transferred onto the electrostatic latent image by the potential difference between the developing bias applied to the developing sleeve 11Y and the electrostatic latent image on the photoreceptor 3Y, thereby contributing to development. Further, as the developing sleeve 11Y rotates, the developing sleeve 9Y returns to the developing portion 9Y again, and after the release from the sleeve surface due to the influence of the repulsive magnetic field formed between the magnetic poles of the magnet roller 12Y, the developing sleeve 11Y returns to the stirring portion 5Y. An appropriate amount of toner is supplied to the developer in the stirring unit 5Y based on the detection result of the toner density sensor 8Y.

  As the drum cleaning device 18Y, a system that presses the cleaning blade 20Y made of polyurethane rubber against the photoreceptor 3Y is used, but another system may be used. For the purpose of improving the cleaning property, this copying machine employs a system having a fur brush 19Y whose outer peripheral surface is in contact with the photoreceptor 3Y so as to be rotatable in the direction of the arrow in the figure. The fur brush 19Y also serves to apply the lubricant to the surface of the photoreceptor 3Y while scraping the lubricant from a solid lubricant (not shown) into a fine powder.

  The toner attached to the fur brush 19Y is transferred to the electric field roller 21Y to which a bias is applied while rotating in contact with the fur brush 19Y in the counter direction. And after scraping off from the electric field roller 21Y by the scraper 22Y, it falls on the collection | recovery screw 23Y.

  The collection screw 23Y conveys the collected toner toward the end of the drum cleaning device 18Y in the direction perpendicular to the drawing surface, and delivers it to an external recycling conveyance device. A recycle conveyance device (not shown) sends the delivered toner to the developing device 4Y for recycling.

  The neutralization lamp 17Y neutralizes the photoreceptor 3Y by light irradiation. The surface of the photoreceptor 3Y that has been neutralized is uniformly charged by the charging roller 16Y, and then subjected to optical scanning by the optical writing unit described above. The charging roller 16Y is rotationally driven while receiving a charging bias from a power source (not shown). Instead of the charging method using the charging roller 16Y, a scorotron charger method in which charging processing is performed in a non-contact manner on the photoreceptor 3Y may be employed.

  In FIG. 2 described above, Y, M, C, and K toner images are formed on the surfaces of the photoreceptors 3Y, M, C, and K of the four process units 2Y, 2M, 2C, and 2K by the processes described above. Is formed.

  A transfer unit 60 is disposed below the four process units 2Y, 2M, 2C, and 2K. The transfer unit 60 rotates the drive roller 67 in the clockwise direction in the drawing while the intermediate transfer belt, which is an image carrier stretched by a plurality of rollers, is brought into contact with the photoreceptors 3Y, 3M, 3C, and 3K. Move endlessly. As a result, primary transfer nips for Y, M, C, and K in which the photoreceptors 3Y, 3M, 3C, and 3K contact the intermediate transfer belt 61 are formed.

  In the vicinity of the primary transfer nips for Y, M, C, and K, the intermediate transfer belt 61 is moved to the photosensitive members 3YY, M, C, and K by primary transfer rollers 62Y, M, C, and K disposed inside the belt loop. Pressing toward K. A primary transfer bias is applied to the primary transfer rollers 62Y, 62M, 62C, 62K by a power source (not shown). As a result, a primary transfer electric field for electrostatically moving the toner images on the photoreceptors 3Y, 3M, 3C, and 3K toward the intermediate transfer belt 61 is formed in the primary transfer nips for Y, M, C, and K. Has been.

  In the drawing, a toner image is formed on each of the primary transfer nips on the front surface of the intermediate transfer belt 61 that sequentially passes through the primary transfer nips for Y, M, C, and K with endless movement in the clockwise direction. Are sequentially superimposed and primarily transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) is formed on the front surface of the intermediate transfer belt 61.

  A secondary transfer roller 72, which is a rotating body, is disposed below the intermediate transfer belt 61 in the drawing, and this abuts from the belt front surface to a portion where the intermediate transfer belt 61 is wound around the transfer counter roller 68. To form a secondary transfer nip. As a result, a secondary transfer nip where the front surface of the intermediate transfer belt 61 and the secondary transfer roller 72 abut is formed.

  A secondary transfer bias is applied to either one of the transfer counter roller 68 in the belt loop and the secondary transfer roller 72 outside the belt loop by a power source (not shown). The other is electrically grounded. Thereby, a secondary transfer electric field is formed in the secondary transfer nip.

  The above-described registration roller pair (not shown) is disposed on the right side of the secondary transfer nip in the drawing, and the recording sheet sandwiched between the rollers can be synchronized with the four-color toner image on the intermediate transfer belt 61. Send to the secondary transfer nip. In the secondary transfer nip, the four-color toner images on the intermediate transfer belt 61 are secondarily transferred onto the recording sheet under the influence of the secondary transfer electric field and the nip pressure, and become a full color image combined with the white color of the recording sheet.

  The transfer residual toner that has not been transferred to the recording sheet at the secondary transfer nip is attached to the front surface of the intermediate transfer belt 61 that has passed through the secondary transfer nip. This transfer residual toner is cleaned by a belt cleaning device 73 that contacts the intermediate transfer belt 61.

  In FIG. 1 described above, the recording sheet that has passed through the secondary transfer nip is separated from the intermediate transfer belt 61 and transferred to the transport belt unit 39. The transport belt unit 39 moves the endless transport belt 40 endlessly in the counterclockwise direction in the figure by the rotational drive of the drive roller 41 while being stretched by the drive roller 41 and the driven roller 42. The recording sheet delivered from the secondary transfer nip is conveyed along with the endless movement of the belt while being held on the belt upper tension surface, and delivered to the fixing unit 43.

  In the fixing unit 43, a fixing belt stretched by a driving roller and a heating roller containing a heat generation source is moved endlessly in the clockwise direction in the drawing as the driving roller is driven to rotate. The pressure roller 45 disposed below the fixing belt is brought into contact with the lower tension surface of the fixing belt to form a fixing nip. The recording sheet received by the fixing unit 43 is pressed or heated in the fixing nip, whereby the full-color image on the surface is fixed. Then, it is sent out from the fixing unit 43 toward the switching claw 49.

  The switching claw 49 is swung by a solenoid (not shown), and the recording sheet conveyance path is switched between the discharge path and the reversing path in accordance with the swing. When the paper discharge path is selected by the switching claw 49, the recording sheet sent out from the fixing unit 43 passes through the paper discharge path and the paper discharge roller pair 47, and is then discharged to the outside of the apparatus to be a paper discharge tray. 48 is stacked.

  A switchback device 46 is disposed below the fixing unit 43 and the conveyor belt unit 39. When the switchback path is selected by the switching claw 49, the recording sheet sent out from the fixing unit 43 is turned upside down via the reversing path and then sent to the switchback device 46. Then, the image enters the secondary transfer nip again, and the image is subjected to secondary transfer processing and fixing processing on the other side.

  The scanner 160 fixed on the printer unit 1 has a fixed reading unit 161 and a moving reading unit 162 as reading means for reading an image of a document (not shown). A fixed reading unit 161 having a light source, a reflection mirror, an image reading sensor such as a CCD, and the like is disposed immediately below a first contact glass (not shown) fixed to the upper wall of the casing of the scanner 160 so as to contact the document. . Then, when the document conveyed by the ADF 170 passes over the first contact glass, the light emitted from the light source is sequentially reflected by the document surface and is received by the image reading sensor via the plurality of reflection mirrors. Thus, the original is scanned without moving the optical system including the light source and the reflecting mirror.

  On the other hand, the moving reading unit 162 is disposed directly below a second contact glass (not shown) fixed to the upper wall of the casing of the scanner 160 so as to come into contact with the document, and an optical system including a light source, a reflection mirror, and the like. It can be moved in the left-right direction in the figure. Then, in the process of moving the optical system from the left side to the right side in the figure, the light emitted from the light source is reflected by a document (not shown) placed on the second contact glass and then passed through a plurality of reflecting mirrors. The image is received by an image reading sensor fixed to the scanner body. Accordingly, the original is scanned while moving the optical system.

  FIG. 4 is a configuration diagram showing the transfer unit 60 and its surrounding configuration. In the drawing, a drive receiving gear 74 is fixed to a rotary shaft member 67a of a drive roller 67 that moves the intermediate transfer belt 61 endlessly while stretching. The drive receiving gear 74 is meshed with an output gear 75 a fixed to the rotating shaft of the belt drive motor 75. In this mechanism, the rotational driving force of the output gear 75 a of the belt driving motor 75 is transmitted to the intermediate transfer belt 61 via the driving receiving gear 74 and the driving roller 67.

  FIG. 5 is a perspective view showing the secondary transfer nip and the surrounding configuration. The secondary transfer roller 72 as a rotating body is in contact with a portion where the intermediate transfer belt 61 is wound around the transfer counter roller 68 to form a secondary transfer nip. The secondary transfer roller 72 is rotatably received by a bearing 77 fixed to a swing arm 76 as a holding body. The secondary transfer roller 72 and the transfer counter roller 68 are each arranged in such a posture that the axial direction is along the longitudinal direction of the copying machine. The printer unit of the copying machine includes a front support side plate 56 and a rear support side plate 57 that face each other at a predetermined distance in the front-rear direction of the copying machine (axial direction of the roller). , Located between these support side plates. And it is supported so that it may rock | fluctuate centering | focusing on the rocking | fluctuation shaft 76a by the rocking | fluctuation shaft 76a provided so that these support side plates might be penetrated.

  One end of an urging coil spring 78 as urging means is fixed to the front support side plate 56 and the rear support side plate 57. The other end sides of the urging coil springs 78 are fixed to the lower surface of the swing arm 76, respectively. As a result, a force that rotates counterclockwise in the figure about the swing shaft 76a is applied to the swing arm 76.

  On the downstream side of the swing arm 76 in the rotational direction, a place where the intermediate transfer belt 61 is wound around the transfer counter roller 68 is located. That is, the swing arm 76 and the secondary transfer roller 72 held by the swing arm 76 are urged by the urging coil spring 78 toward the intermediate transfer belt 61 as an image carrier. Due to this urging, the secondary transfer roller 72 is brought into contact with the portion where the intermediate transfer belt 61 is wound around the transfer counter roller 68 to form a secondary transfer nip.

  Since the swing arm 76 swings about the swing shaft 76a as described above, the secondary transfer roller 72 held by the swing arm 76 has a predetermined swing centered on the swing shaft 76a. Oscillates with a radius (hereinafter referred to as a roller oscillation radius). A cam motor 79 is opposed to a portion of the swing arm 76 that swings at a swing radius larger than the roller swing radius. The cam motor 79 is supported by a support bracket (not shown) provided in the printer unit. An eccentric cam 80 is fixed to the rotating shaft of the cam motor 79. In the illustrated state, the rotation shaft of the cam motor 79 is stopped at a rotation angle that extends the eccentric cam 80 in the 9 o'clock direction in the figure. From this state, when the rotating shaft starts to rotate counterclockwise in the figure by driving the cam motor 79, the eccentric cam 80 starts to abut against the swing arm 76 as shown in FIG. It begins to push down against the biasing force of the coil spring 78.

  A registration roller pair 37 for feeding the recording sheet P toward the secondary transfer nip is provided on the right side of the secondary transfer nip in the drawing. In the vicinity of the registration roller pair 37, a registration sensor 55 and a thickness sensor 38 as thickness information acquisition means are disposed.

  The thickness sensor 38 detects the thickness of the recording sheet P sent to the registration roller pair 37 and outputs the detection result to the control unit 82 as a control means. Further, the control unit 82 includes a CPU (Central Processing Unit) as a calculation means (not shown), a RAM (Random Access Memory) as a data storage means, a ROM (Read Only Memory) as a data storage means, and the like. Is used to control driving and to set operating conditions.

  The thickness sensor 38 detects the thickness of the recording sheet P based on the amount of displacement of the recording sheet P when the recording sheet P is sandwiched between the rollers of the registration roller pair 37, or the thickness sensor 38 itself and the surface of the recording sheet P. What detects the thickness of the recording sheet P based on the distance can be used.

  The registration sensor 55 includes a reflective photosensor and the like, detects the leading edge of the recording sheet P that has passed between the rollers of the registration roller pair 37, and outputs a detection signal to the control unit 82. The controller 82 causes the recording sheet P to wait at the position of the registration roller pair 37 by temporarily stopping the driving of the registration roller pair 37 based on the detection signal.

  In this copying machine, the secondary transfer roller 72 has a lower hardness than the transfer counter roller 68. Then, the secondary transfer roller 72 having a certain length in the roller rotation direction is deformed by deforming a roller portion made of an elastic body of the secondary transfer roller 72 by contact with the transfer counter roller 68 via the intermediate transfer belt 61. A nip is formed. When the secondary transfer roller 72 and the transfer counter roller 68 are both made of non-deformable metal rollers, the secondary transfer nip cannot be formed, and the secondary transfer roller 72 is lined with respect to the intermediate transfer belt 61. Will be in contact. When the distance between the axes of the secondary transfer roller 72 and the transfer counter roller 68 when such a line contact occurs is L1, the distance L2 between the axes when forming the secondary transfer nip as in this copying machine is It becomes shorter than that. A value obtained by subtracting the inter-axis distance L 2 from the inter-axis distance L 1 is the amount of biting into the secondary transfer roller 72 in the transfer counter roller 68.

  In this copying machine, three image forming operation modes for forming an image on the recording sheet P are prepared: a plain paper mode, a thick paper mode, and a paperboard mode. The plain paper mode is an image forming operation mode when a recording sheet P having a thickness of less than 200 [μm] is used. In this plain paper mode, the rotating shaft of the cam motor 80 is stopped in a posture in which the eccentric cam 80 extends in the 9 o'clock direction in the drawing, so that the image forming operation is performed without the eccentric cam 80 abutting against the swing arm 76. . The amount of biting of the transfer facing roller 68 with respect to the secondary transfer roller 72 in the plain paper mode is 0.5 [mm].

  The thick paper mode is an image forming operation mode when a recording sheet P having a thickness of 200 [μm] or more and less than 400 [μm] is used. In this thick paper mode, the image forming operation is performed by pushing down the swing arm 76 by the eccentric cam 80 until the biting amount of the transfer counter roller 68 with respect to the secondary transfer roller 72 becomes approximately 0.2 [mm].

  The paperboard mode is an image forming mode when a recording sheet P having a thickness of 400 [μm] or more is used. In this paperboard mode, the eccentric cam 80 moves to the position where the secondary transfer roller 72 is soft-touched to the intermediate transfer belt 61 while the amount of biting of the transfer counter roller 68 with respect to the secondary transfer roller 72 is approximately 0 [mm]. The swing arm 76 is pushed down to perform an image forming operation.

  A mode in which the secondary transfer roller 72 is separated from the intermediate transfer belt 61 and the swing arm 76 is pushed down by the eccentric cam 80 to a position where a predetermined gap is formed between them may be provided.

  In the present copying machine having the above basic configuration, the four process units 2Y, M, C, and K, the optical writing unit 50, the transfer unit 60, and the like can be applied to the surface of the intermediate transfer belt 61 as an image carrier. Visible image forming means for forming a visible toner image is configured. The transfer unit 60 functions as a transfer unit that transfers the toner image on the surface of the intermediate transfer belt 61 to a recording sheet.

Next, a characteristic configuration of the copying machine will be described.
A distance sensor 81 serving as a position detecting unit is disposed below the swing arm 76 at a position facing the eccentric cam 80 via the swing arm 76. The distance sensor 81 detects the distance between itself and the test object while emitting ultrasonic waves, infrared rays, magnetism, and the like, and outputs the detection result to the control unit 82. The control unit 82 grasps the distance between the intermediate transfer belt 61 and the rotation shaft of the secondary transfer roller 72 and the position of the rotation shaft of the secondary transfer roller 72 in the machine based on the detection result by the distance sensor 81. More specifically, on the surface of the intermediate transfer belt 61, the distance between the location where the secondary transfer roller 72 is most strongly in contact with the rotation axis of the secondary transfer roller 72 (hereinafter referred to as the belt-axis distance), the rotation axis. Know the position of the. On the surface of the intermediate transfer belt 61, the portion where the secondary transfer roller 72 comes into contact most strongly intersects a straight line connecting the center of the rotation shaft member of the transfer counter roller 68 and the center of the rotation shaft member of the secondary transfer roller 72. It is a place to do.

  As shown in the figure, the distance sensor 81 uses a portion to be pressed by the eccentric cam 80 in the swing arm 76 as a test target. The pressed down portion is a portion where the swing radius around the swing shaft 76 a is larger than that of the secondary transfer roller 72. Therefore, when the secondary transfer roller 72 is moved by the distance La due to the pressing of the swing arm 76 by the eccentric cam 80, the above-described pressed down portion to be tested by the distance sensor 81 is a distance La ′ larger than the distance La ′. Become. Since the ratio between the distance La and the distance La ′ is constant, the control unit 82 can grasp the distance La based on the distance La ′ based on the detection result of the distance sensor 81. Since the distance La is detected after being amplified to a larger distance La ′, the secondary transfer roller 72 is compared with the case where the distance La is detected as it is or the distance La is reduced and detected. Can be detected with high accuracy.

  FIG. 7 is a graph showing the relationship between the output voltage from the distance sensor 81 and the belt-axis distance. The control unit 82 stores the graph, an algorithm corresponding to the graph, or a data table corresponding to the graph in a ROM (not shown) in advance. In this copying machine, as the distance sensor 81, a sensor that increases the output voltage as the distance between the object to be examined (the above-mentioned pressed portion) and itself decreases. When the secondary transfer roller 72 is moved away from the intermediate transfer belt 61 by the depression of the swing arm 76 by the eccentric cam 80, the belt-to-axis distance becomes larger and the secondary transfer nip pressure becomes smaller. At this time, since the distance between the distance sensor 81 and the pressed down portion becomes smaller, the output voltage of the distance sensor 81 increases. That is, in this copying machine, when the swing arm 76 is pushed down by the eccentric cam 80 (when the distance between the belt and the shaft increases), the output voltage of the distance sensor 81 increases according to the amount of the push down. Yes.

  FIG. 8 is a graph showing fluctuations in the output voltage of the distance sensor 81 when the plain paper mode is not passed (when the recording sheet is not fed into the nip). As described above, since the eccentric cam 80 is not abutted against the swing arm 76 in the plain paper mode, the pressed down portion of the swing arm 76 is under the condition of the diameter of the secondary transfer roller 72 at that time. It settles at a position where a predetermined transfer nip pressure can be obtained. The relationship between the output voltage and time becomes a sinusoidal characteristic as shown in the figure. The belt-shaft distance varies depending on the rotation angle of the secondary transfer roller 72 due to the eccentricity of the secondary transfer roller 72. Because it does. A portion above the center line in the sine curve indicates that a portion rotating at a radius larger than the normal rotation radius on the peripheral surface of the secondary transfer roller has entered the transfer nip.

  When the eccentric cam 80 is rotated a little, as shown in FIG. 9, instead of the portion below the center line in the sine curve disappearing partially, the graph portion corresponding to the disappearing portion becomes a horizontal straight line. This is because when the small-diameter region of the secondary transfer roller 72 enters the secondary transfer nip and the swing arm 76 tries to move to the intermediate transfer belt 61 side, it strikes the eccentric cam 80 when it moves to some extent. It is. Such a horizontal straight line corresponds to a contact position between the eccentric cam 80 and the swing arm 76. Hereinafter, this horizontal straight line is referred to as a “butting straight line”.

  When the eccentric cam 80 is further rotated a little, as shown in FIG. 10, the position of the “butting straight line” is shifted slightly upward. This is because the abutting position between the eccentric cam 80 and the swing arm 76 has shifted to the biasing coil spring 78 side.

  When the eccentric cam 80 is further rotated a little, as shown in FIG. 11, the position of the “butting straight line” is shifted to the position of the center value of the sine curve. This indicates that the abutting position between the eccentric cam 80 and the swing arm 76 has reached the following position. That is, it is a position where an appropriate transfer nip pressure is exerted in a state in which a roller peripheral surface portion rotating at a normal rotation radius enters the secondary transfer nip. Hereinafter, this position is referred to as a “normal radius position”.

  In FIG. 7 described above, the output voltage value V1 indicates that the swing arm 76 is in the “normal radius position” (belt-axis distance = Lx1). The output voltage value V2 indicates that the swing arm 76 is at a position where the amount of biting of the transfer facing roller 68 with respect to the secondary transfer roller 72 is 0.2 [mm] corresponding to the thick paper mode ( Belt-shaft distance = Lx2). The output voltage value V3 indicates that the swing arm 76 is in a position where the amount of biting of the transfer counter roller 68 with respect to the secondary transfer roller 72 is 0 [mm] corresponding to the plate thickness mode (belt). -Interaxial distance = Lx3).

  When the eccentric cam 80 is further rotated a little, the “butting straight line” is further shifted downward as shown in FIG. 12, but at this time, the graph behaves differently. Specifically, from FIG. 9 to FIG. 11, the position of the upper half of the sine curve did not change even when the “butting straight line” moved upward. On the other hand, in FIG. 12, in addition to the “butting straight line” being moved upward, the upper half of the sine curve is also moved upward by the same shift amount as compared to FIG. This is for the reason described below. That is, in the state shown in FIGS. 9 to 11, although the “butting straight line” appears due to the contact between the eccentric cam 80 and the swing arm 76, the eccentric cam 80 substantially pushes down the swing arm 76. Absent. This substantial depression means that the eccentric cam 80 is rotated to an angle at which the eccentric cam 80 always abuts against the swing arm 76 regardless of the rotation angle of the secondary transfer roller 72. Therefore, the reason why the eccentric cam 80 substantially pushes down the swing arm 76 is that the contact position between the two is after the “butting straight line” is shifted to the “normal radius position”. That is, the substantial push-down of the swing arm 76 by the eccentric cam 80 is started after the “butting straight line” is shifted to the “normal radius position”. Then, the upper half of the sine curve starts to move upward together with the “butting straight line”.

  In FIG. 8 described above, the center value of the sine curve (the center value of the wave height) is the surface of the intermediate transfer belt 61 and the secondary transfer roller 72 in a state where the eccentric cam 80 is not in contact with the swing arm 76. The average value of distance with a rotating shaft is shown. When the diameter and the elastic modulus of the secondary transfer roller 72 change with the temperature change, the position of the center value goes up and down with it, and the position at that time is an appropriate value for obtaining an appropriate transfer nip pressure. In a state where the eccentric cam 80 is not in contact with the swing arm 76, the distance between the surface of the intermediate transfer belt 61 and the rotation shaft of the secondary transfer roller 72 is naturally adjusted to an appropriate value.

  When the diameter and elastic modulus of the secondary transfer roller 72 change with temperature change, the center value of the sine curve shifts up and down accordingly. This means that the position of V1 is shifted up and down by that amount in FIG. Then, if the positions of V2 and V3 are also shifted up and down by that amount, the distance between the belt surface and the rotation shaft of the secondary transfer roller 72 can be set to the diameter and elasticity of the secondary transfer roller 72 even in the thick paper mode and the paperboard mode. A value commensurate with the rate (a distance at which an appropriate transfer nip can be obtained with the sheet sandwiched between the nips) can be obtained.

  Therefore, the control unit 82 performs the following processing at regular timing such as every predetermined time. That is, first, the distance per integer rotation of the secondary transfer roller 72 while the secondary transfer roller 72 is rotated once or more in a state where the eccentric cam 80 is positioned at the home position extending in the 9 o'clock direction in the drawing. The output voltage value from the sensor 81 is sampled at a predetermined time interval such as 20 [msec] and stored in the RAM. As a result, the fluctuation of the belt-axis distance per integer rotation of the secondary transfer roller 72 is analyzed. That is, an analysis process for analyzing the distance between the belt and the shaft is performed. By this analysis, even if the secondary transfer roller 72 is eccentric, an appropriate belt-axis distance can be accurately obtained.

  Next, a center value that bisects the area of the sine curve is obtained by a well-known analysis method, and the output voltage from the distance sensor 81 corresponding to the center value is set as an appropriate value in the plain paper mode. Then, after obtaining the shift amount from V1 in FIG. 7 at the appropriate value, V2 and V3 in FIG. 7 are shifted up and down by the shift amount. Accordingly, the belt-axis distance in the thick paper mode or the paperboard mode is corrected to a value corresponding to the diameter of the secondary transfer roller 72. Thereafter, when the thick paper mode or the paperboard mode is executed, the swing arm 76 is pushed down to the position of V2 or V3.

  As the cam motor 79, a rotary motor mounted type is used, and the control unit 82 can accurately grasp the rotation angle of the rotation shaft of the cam motor 79 based on a signal sent from the rotary encoder. . The rotation angle of the rotation shaft of the cam motor 79 and the push-down position of the swing arm 76 show a good correlation. The control unit 82 stores in the ROM a data table indicating the relationship between the rotation angle and the push-down position of the swing arm 76 (output voltage value in FIG. 7). Then, the rotation angle corresponding to the corrected V2 and V3 is specified from this data table, and the cam motor 79 is rotated to the same rotation angle position as the specification result, thereby pushing down the swing arm 76 to the target position.

  In the present copying machine, a rotary encoder (not shown) as a rotation angle detecting means for detecting the rotation angle of the secondary transfer roller 72 is provided in the vicinity of the rotation shaft of the secondary transfer roller 72. Based on the detection result by the rotary encoder, the control unit grasps what radius portion of the secondary transfer roller 72 is entering the secondary transfer nip. For example, when the upper peak in the sine curve of FIG. 8 is obtained, the maximum radius portion of the secondary transfer roller 72 has entered the secondary transfer nip, so that the belt-axis distance is furthest away. It is. If the angle information (phase pulse) from the rotary encoder at this time is Pa, when the angle information from the rotary encoder is Pa, the maximum radius portion of the secondary transfer roller 72 has entered the secondary transfer nip. It will be. Further, when the center value in the sine curve of FIG. 8 is obtained, the normal radius portion of the secondary transfer roller 72 enters the secondary transfer nip. Assuming that the angle information from the rotary encoder at this time is Pb, when the angle information from the rotary encoder is Pb, the regular radius portion of the secondary transfer roller 72 has entered the secondary transfer nip. Further, the lower peak in the sine curve of FIG. 8 is obtained when the minimum radius portion of the secondary transfer roller 72 enters the secondary transfer nip. If the angle information from the rotary encoder at this time is Pc, when the angle information from the rotary encoder is Pc, the minimum radius portion of the secondary transfer roller 72 has entered the secondary transfer nip. In this manner, the control unit can grasp what radius portion of the secondary transfer roller 72 has entered the secondary transfer nip based on the detection result of the rotary encoder.

  When the control unit pushes down the swing arm 76 to the target position described above, first, the rotation of the secondary transfer roller 72 is stopped at a timing when the detection result by the rotary encoder becomes Vb. That is, the rotation of the secondary transfer roller 72 is stopped in a state where the regular radius portion of the secondary transfer roller 72 is entered into the secondary transfer nip. Thereafter, the swing arm 76 is pushed down to the target position described above. Accordingly, the belt-shaft distance is set to an appropriate distance when the regular radius portion of the secondary transfer roller 72 is entered into the secondary transfer nip.

  Thereafter, when performing a print job based on the image information, the control unit first obtains the eccentric transfer cam 80 with respect to the integer rotation of the secondary transfer roller 72 acquired in a state where the eccentric cam 80 is not in contact with the swing arm 76. Read belt-axis distance fluctuation data. When the rotation of the secondary transfer roller 72 is started, the rotation angle of the eccentric cam 80 is changed every moment based on the data and the output value from the rotary encoder that detects the rotation angle of the secondary transfer roller 72. Let Specifically, the amount of push-down of the swing arm 76 by the eccentric cam 80 (abutting amount) is changed so that the phase of the eccentric cam 80 varies in a phase opposite to the phase of the sine curve in the fluctuation data of the belt-shaft distance. Change the rotation angle. As a result, the belt-shaft distance due to the eccentricity of the secondary transfer roller 72 as shown in the sensor output change waveform of FIG. Counteract with fluctuations in distance. For this reason, during the print job, the belt-to-axis distance is minimized due to the eccentricity of the roller by making the belt-to-axis distance constant regardless of the rotation angle of the secondary transfer roller 72. It is possible to avoid the occurrence of shock jitter due to the cardboard or paperboard entering the secondary transfer nip at the timing. Further, it is possible to avoid the occurrence of transfer failure and image collapse due to the transfer nip pressure being changed due to the change in the belt-axis distance.

  Note that the control for changing the push-down amount in a phase opposite to the phase of the sine curve in the fluctuation data of the belt-axis distance is also executed in the plain paper mode. Therefore, even in the plain paper mode, it is possible to avoid the occurrence of transfer failure and image collapse due to the transfer nip pressure being changed due to the change in the belt-axis distance.

  Instead of using the rotary encoder mounted type as the cam motor 79, a stepping motor may be used as the cam motor 79, and the rotation angle of the cam motor 79 may be grasped based on the number of step pulses when driving the stepping motor.

  Further, when the eccentric cam 80 is worn, the rotation angle of the rotating shaft of the cam motor 79 and the push-down position of the swing arm 76 do not show a good correlation. In order to cope with such a case, the cam motor 79 may be driven until the output voltage value from the distance sensor 81 becomes V2 or V3 after correction.

  In the copying machine configured as described above, even if the secondary transfer roller 72 changes its diameter and elastic modulus as the temperature changes, in the thick paper mode and the paperboard mode, it swings to an appropriate position corresponding to the diameter. The moving arm 76 can be pushed down. As a result, it is possible to suppress the occurrence of shock jitter and transfer failure in the thick paper mode or the paperboard mode due to the diameter change of the secondary transfer roller 72.

  Next, an example copier in which a more characteristic configuration is added to the copier according to the embodiment will be described. Unless otherwise specified, the configuration of the copying machine according to the example is the same as that of the embodiment.

  FIG. 13 is a perspective view illustrating the secondary transfer nip and the surrounding configuration of the copying machine according to the embodiment. In the figure, the secondary transfer roller 72 holds the rotating shaft members respectively protruding from both ends in the axial direction of the roller portion by different swing arms. Specifically, the front support side plate 56 of the printer unit supports the front swing arm 83F so as to be swingable about the swing shaft 84. The front swing arm 83F rotatably holds the front-side rotary shaft member of the secondary transfer roller 72. Further, the rear support side plate 57 of the printer unit supports the rear swing arm 83R so as to be swingable about the swing shaft 85. The rear swing arm 83R rotatably holds the rear-side rotation shaft member of the secondary transfer roller 72.

  The front swing arm 83F that is a swing body is pushed down by a front eccentric cam 80F that is rotationally driven by a front cam motor 79F. The belt-axis distance on the front side of the secondary transfer roller 72 is grasped based on the detection result by the front distance sensor 81F disposed below the front swing arm 83F.

  The rear swing arm 83R, which is a swing body, is pushed down by a rear eccentric cam 80R that is rotationally driven by a rear cam motor 79R. The distance between the belt and the shaft on the rear side of the secondary transfer roller 72 is grasped based on the detection result by the rear distance sensor 81R disposed below the rear swing arm 83R.

  In other words, the copying machine according to the embodiment has the following on each of one end side (front side) and the other end side (rear side) of the secondary transfer roller 72 as a rotating body in the rotation axis direction. . That is, an urging coil spring 78 as an urging means, an eccentric cam (80F, 80R) as an abutting member, a cam motor (79F, 79R) as a moving means, and a distance sensor (81F, 81R) as a position detecting means. The control unit 82 individually adjusts the distance between the belt and the shaft on the front side and the rear side by separately performing the same processing as the copying machine according to the embodiment on the front side and the rear side. To do.

  In such a configuration, in the thick paper mode and the paperboard mode, the front side and the rear side can be adjusted by appropriately adjusting the belt-shaft distance to a value corresponding to the diameter of the secondary transfer roller 72. Thus, it is possible to satisfactorily suppress the occurrence of shock jitter and transfer defects.

  So far, a copying machine has been described in which a toner image on a belt is transferred to a recording sheet P sandwiched between an intermediate transfer belt 61 as an image carrier and a secondary transfer roller 72 as a rotating body. The present invention can also be applied to a configuration in which a visible image on an image carrier is transferred to a recording sheet P sandwiched between a transfer roller and a drum-shaped image carrier. In addition, the belt member is stretched by a roller that is a rotating body, and the visible image on the image bearing member is transferred to a recording sheet that is sandwiched between the belt holding portion around the roller and the image bearing member. The application of the present invention is possible.

  In addition, although an example using the thickness sensor 38 as the thickness information acquisition unit has been described, an input unit such as a numeric keypad that accepts an input operation of thickness information by the operator is used as the thickness information acquisition unit, and an image is formed based on the input result. The operation mode may be switched.

1 is a schematic configuration diagram showing a copier according to an embodiment. FIG. 3 is a partially enlarged configuration diagram illustrating a part of an internal configuration of a printer unit in the copier. FIG. 3 is an enlarged configuration diagram showing a process unit for Y of the printer unit. FIG. 2 is a configuration diagram showing a transfer unit and its peripheral configuration in the copier. FIG. 3 is a perspective view showing a secondary transfer nip and surrounding configuration in the copier. The block diagram which shows the same surrounding structure of the state which has pushed down the rocking | fluctuation arm with the eccentric transfer cam and the secondary transfer nip. 3 is a graph showing a relationship between an output voltage from a distance sensor and a belt-axis distance in the copier. The graph which shows the fluctuation curve of the output voltage from the same distance sensor at the time of non-sheet passing of plain paper mode. The graph which shows the same variation curve in the state where the butting straight line began to appear. The graph which shows the same fluctuation curve in the state where the butting straight line shifted slightly upward from FIG. The graph which shows the same fluctuation curve of the state which the butt straight line shifted to the balance position. The graph which shows the same fluctuation curve when substantial push-down of the rocking | fluctuation arm by an eccentric cam starts. FIG. 3 is a perspective view illustrating a secondary transfer nip and a surrounding configuration of the copying machine according to the embodiment.

Explanation of symbols

2Y, M, C, K: Process unit (part of visible image forming means)
38: Thickness sensor (thickness information acquisition means)
50: Optical writing unit (part of visible image forming means)
60: Transfer unit (transfer means, part of visible image forming means)
61: Intermediate transfer belt (image carrier)
72: Secondary transfer roller (rotating body)
78: Energizing coil spring (urging means)
79: Cam motor: moving means 79F: Front cam motor (moving means)
79R: Rear cam motor (moving means)
80: Eccentric cam (butting member)
80F: Front eccentric cam (butting member)
80R: Rear eccentric cam (butting member)
81: Distance sensor (position detection means)
82: Control unit (control means)
P: Recording sheet

Claims (6)

Rotating rotator, urging means for urging the rotator or holding body holding the rotating body toward the image carrier of the image forming apparatus, and the rotator or holding urged by the urging means An abutting member that abuts against the body, a moving unit that moves the abutting member, a thickness information acquisition unit that acquires thickness information of a recording sheet on which an image is formed, and controls the driving of the moving unit based on the thickness information And a control means for adjusting the distance between the surface of the image carrier and the rotation axis of the rotor in a state where the abutting member is abutted against the rotor or the holding body. In a transfer device for transferring a visible image carried on the surface to a recording sheet sandwiched between the rotating body or a belt member stretched around the rotating body and the image bearing body,
While providing a position detection means for detecting the position of the rotating body,
The abutting member is abutted against the rotating body or the holding body based on the detection result by the position detecting means and the thickness information obtained in a state where the abutting member is not abutting against the rotating body or the holding body. A transfer apparatus characterized in that the control means is configured to adjust the position of the rotating body in a closed state. The transfer device according to claim 1.
Based on the detection result per integer rotation of the rotating body by the position detection means obtained in a state where the abutting member is not in contact with the rotating body or the holding body, the position variation per integer rotation of the rotating body After performing the analysis processing for analyzing the control, the control is performed so as to adjust the position of the rotating body in a state where the abutting member is abutted against the rotating body or the holding body based on the analysis result and the thickness information. A transfer device comprising means. The transfer device according to claim 2.
A rotation angle detecting means for detecting the rotation angle of the rotating body is provided,
In the state where the abutting member is abutted against the rotating body or the holding body, the abutting amount of the abutting member with respect to the rotating body or the holding body is calculated based on the detection result by the rotation angle detecting means. A transfer apparatus characterized in that the control means is configured to carry out control to vary the phase according to the control. The transfer device according to any one of claims 1 to 3,
As the moving means, one that moves the abutting member by driving a motor or actuator, and
The transfer means characterized in that the control means is configured to adjust the position of the rotating body in a state where the abutting member is abutted against the rotating body or the holding body by adjusting the driving amount of the motor or actuator. apparatus. The transfer device according to claim 4.
The urging means, the abutting member, the moving means, and the position detecting means are provided on one end side and the other end side of the rotating body in the rotation axis direction, respectively. The one for the other side and the one for the other end are provided, and the position of the rotating body in a state in which the abutting member is not abutted against the rotating body or the holding body is at the one end side and the other end side. A transfer apparatus characterized in that the control means is configured to individually adjust each. In an image forming apparatus comprising: a visible image forming unit that forms a visible image on the surface of an image carrier; and a transfer unit that transfers the visible image on the surface to a recording sheet.
An image forming apparatus using the transfer device according to claim 1 as the transfer unit.

Images