JP5472782B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, or a printer having a function of adjusting a distance between an image carrier and a facing member that forms a transfer region facing the image carrier.

In this type of image forming apparatus, by adjusting the relative distance between the image carrier and the opposing member, the pressure of the transfer nip due to the contact between the two can be adjusted, or a recording sheet made of thick paper can enter the transfer nip. It is possible to alleviate the fluctuation of the load on the image carrier. As the distance adjusting means for adjusting the relative distance between the image carrier and the opposing member, the opposing member is urged toward the image carrier by the urging means and pushed back to a certain degree against the urging force. Is common. The distance adjusting means of the image forming apparatus described in Patent Document 1 has such a configuration. Specifically, a transfer roller as an opposing member in the image forming apparatus includes a cylindrical roller portion and shaft members that respectively protrude from both end surfaces of the roller portion so as to rotate integrally therewith. ing. Each shaft member is provided with an eccentric cam that can idle. These eccentric cams are directly connected to motors for causing the eccentric cams to idle on the peripheral surface of the shaft member. The eccentric cam that is idled on the peripheral surface of the shaft member by the motor abuts the cam surface against the end of the photosensitive member in the axial direction within a predetermined rotation angle range. By this abutment, the distance between the photosensitive member and the transfer roller is adjusted by moving the transfer roller biased toward the photosensitive member in a direction away from the photosensitive member against the urging force. .
JP-A-10-83124

  However, in this image forming apparatus, in order to drive the eccentric cam that idles on the shaft member on one end side in the axial direction of the transfer roller and the eccentric cam that idles on the shaft member on the other end side, It was necessary to provide drive transmission mechanisms in the vicinity of both ends. Such layout restrictions significantly hinder downsizing of the apparatus.

  In the image forming apparatus disclosed in Patent Document 1, the eccentric cam that idles on the shaft member of the transfer roller is abutted against the photosensitive member. However, the eccentric cam that idles on the shaft member of the photoreceptor is abutted against the transfer roller. A similar problem may occur even in a configuration in which the transfer roller is moved away from the photoreceptor. The same applies to a case in which at least one of the photosensitive member and the opposing member that are in contact with each other to form a transfer nip is configured as a belt member that moves endlessly while being wound around a rotatable support rotating member. Problems can arise.

  The present invention has been made in view of the above background, and an object of the present invention is to improve the degree of layout freedom of the distance adjusting means for adjusting the distance between the image carrier and the facing member. An image forming apparatus is provided.

In order to achieve the above object, according to the first aspect of the present invention, at least one of an image carrier and a facing member that forms a transfer region facing the image carrier is supported by a support rotating body. The distance between the image carrier and the opposing member in the transfer area is adjusted by changing the rotational position of the cam provided on the support rotary body or the shaft of the rotary body. The visible image on the image carrier is transferred to the opposing member, or is transferred to a recording sheet passed between the image carrier and the opposing member , and the cam has a radius with respect to its own rotation center. In the image forming apparatus having a cam surface which is a non-uniform abutting surface, the supporting rotating body or the rotating body provided with the cam on its own shaft portion is at least at the rotation center position in the rotation axis direction. Book with a through-hole penetrating into And a penetrating shaft member as the shaft portion that idles on the surface of the main body portion while penetrating through the through hole of the main body portion. The cams are fixed to both end regions not located in the main body so as to rotate integrally with the penetrating shaft member.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, at least one of the image carrier and the opposing member is constituted by the belt member, and the supporting rotating body supports the belt member. The main body is rotated on the surface of the penetrating shaft member as the belt member moves.
The invention according to claim 3 is the image forming apparatus according to claim 1 or 2, further comprising urging means for urging the opposing member toward the image carrier, and the recording sheet and the opposing member. Prior to entering between the two, the rotation of the through shaft member and the cam is stopped at a predetermined rotation angle, and the opposing member is pushed back against the biasing force of the biasing means. The above-described operation for further expanding the distance is performed.
According to a fourth aspect of the present invention, there is provided the image forming apparatus according to any one of the first to third aspects, wherein the recording sheet is inserted between the image carrier and the opposing member and then discharged from the space. Prior to stopping the rotation of the penetrating shaft member at a predetermined rotation angle, the opposing member is pushed back against the urging force of the urging means to perform the operation of further increasing the distance. It is characterized by this.
According to a fifth aspect of the present invention, in the image forming apparatus of the second aspect, the two cams at both longitudinal ends of the penetrating shaft member are arranged in the longitudinal direction of the penetrating shaft member in the belt width dimension of the belt member. It is characterized by being fixed to the penetrating shaft member at a greater distance.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the image carrier and the opposing member are each constituted by the belt member or the rotating body, and the belt member constituting the image carrier. Alternatively, any one of the rotating body and the belt member or the rotating body constituting the opposing member is configured by at least the main body portion and the penetrating shaft member to which the cam is fixed. The abutting member to be abutted against the cam is provided on the supporting rotating body of the belt member constituting the shaft or the shaft portion of the rotating body so as to be able to idle.
A seventh aspect of the present invention is the image forming apparatus according to any one of the first to sixth aspects, further comprising distance detection means for detecting the distance, and the penetrating shaft member based on a detection result by the distance detection means. The rotation stop position is adjusted.
According to an eighth aspect of the present invention, in the image forming apparatus of the sixth aspect, at least one of the cam and the abutted member is made of an insulating material. Is.
According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, an eccentric cam having no step is used as the cam.
A tenth aspect of the present invention is the image forming apparatus according to any one of the first to ninth aspects, wherein the thickness information acquiring unit acquires the thickness information of the recording sheet supplied between the image carrier and the opposing member. And adjusting the distance based on the detection result by the thickness information detection means.

  In these inventions, the rotating body constituting the image bearing member or the opposing member, or the supporting rotating body of the belt member constituting the image bearing member or the opposing member is a penetrating shaft penetrated through the cylindrical main body. The main body is freely idled on the member. Cams are provided on one end side and the other end side in the axial direction of the penetrating shaft member so as to rotate integrally with the penetrating shaft member. When the penetrating shaft member rotates, cams fixed to both end portions in the axial direction of the penetrating shaft member rotate together, so that a drive transmission mechanism for transmitting drive to the penetrating shaft member is provided in the axial direction. It is possible to rotate these cams only by providing them at either one of the both end sides. Therefore, the layout freedom of the distance adjusting means can be improved as compared with the conventional case where it is necessary to provide drive transmission mechanisms on both ends.

Hereinafter, an embodiment in which the present invention is applied to a tandem type color copying machine (hereinafter simply referred to as a copying machine) as an image forming apparatus will be described.
FIG. 1 is a schematic configuration diagram illustrating a copying machine according to an embodiment. The copier includes a printer unit 100, a paper feeding unit 200, a scanner unit 300 attached on the printer unit 100, and an automatic document feeder (ADF) 400 attached on the scanner unit 300. ing.

  The printer unit 100 includes an endless belt-shaped intermediate transfer belt 21 as an image carrier. The intermediate transfer belt 21 is wound around the driving roller 22, the driven roller 23, and the secondary transfer counter roller 24 in a posture in which the side view is an inverted triangular shape, and is driven by rotation of the driving roller 22. It can be moved endlessly in the clockwise direction in the figure. Above the intermediate transfer belt 21, there are four image forming units 1C, M, Y, and K for forming C (cyan), M (magenta), Y (yellow), and K (black) toner images. Arranged along the belt moving direction.

  The image forming units 1C, M, Y, and K include photoreceptors 2C, M, Y, and K, developing units 3C, M, Y, and K, and photoreceptor cleaning devices 4C, M, Y, and K. Yes. The photoreceptors 2C, M, Y, and K abut on the intermediate transfer belt 21 to form primary transfer nips for C, M, Y, and K, respectively, and are driven in a counterclockwise direction in FIG. It can be driven to rotate. The developing units 3C, M, Y, and K are for developing the electrostatic latent image formed on the photoreceptors 2C, M, Y, and K with C, M, Y, and K toners. Further, the photoconductor cleaning devices 4C, M, Y, and K clean the transfer residual toner attached to the photoconductors 2C, M, Y, and K after passing through the primary transfer nip. In this printer, a tandem image forming unit 10 is configured by four image forming units 1C, M, Y, and K arranged in the belt moving direction.

  In the printer unit 100, an optical writing unit 15 is disposed above the tandem image forming unit 10. The optical writing unit 15 performs an optical writing process by optical scanning on the surfaces of the photoreceptors 2C, M, Y, and K that are rotationally driven counterclockwise in the drawing to form an electrostatic latent image. Is. Prior to the optical writing process, the surfaces of the photoreceptors 2C, M, Y, and K are uniformly charged by the uniform charging means of the image forming units 1C, M, Y, and K, respectively.

  The transfer unit 20 including the intermediate transfer belt 21 has primary transfer rollers 25C, M, Y, and K inside the loop of the intermediate transfer belt 21. These primary transfer rollers 25C, M, Y, and K press the intermediate transfer belt 21 toward the photoreceptors 2C, M, Y, and K on the back side of the primary transfer nip for C, M, Y, and K. Yes.

  A secondary transfer roller 30 is disposed below the intermediate transfer belt 21. The secondary transfer roller 30 abuts on the intermediate transfer belt 21 around the secondary transfer counter roller 24 from the belt front surface side to form a secondary transfer nip. A recording sheet is fed into the secondary transfer nip at a predetermined timing. Then, the four-color superimposed toner image on the intermediate transfer belt 21 is secondarily transferred collectively onto the recording sheet at the secondary transfer nip.

  The scanner unit 300 reads image information of a document placed on the contact glass 301 by the reading sensor 302 and sends the read image information to the control unit of the printer unit 100. A control unit (not shown) controls a light source such as a laser diode or an LED in the optical writing unit 15 of the printer unit 100 based on the image information received from the scanner unit 300, and lasers for C, M, Y, and K. Writing light is emitted to optically scan the photoreceptors 2C, M, Y, and K. By this optical scanning, electrostatic latent images are formed on the surfaces of the photoreceptors 2C, M, Y, and K, and the latent images are developed into C, M, Y, and K toner images through a predetermined development process.

  A paper feed unit 200 includes paper cassettes 202 arranged in multiple stages in the paper bank 201, a paper feed roller 203 that feeds out recording sheets from the paper feed cassette 202, and separates the sent out recording sheets into a paper feed path 204. A separation roller 205 that guides the sheet, and a conveyance roller 206 that conveys the recording sheet to the sheet feeding path 99 of the printer unit 100 are provided.

  In addition to the paper feed unit 200, manual paper feed is also possible, and the manual feed tray 98 for manual feed and the recording sheets on the manual feed tray 98 are separated one by one toward the manual feed path 97. A separating roller 96 is also provided. In the printer unit 100, the manual paper feed path 97 joins the paper feed path 99.

  Near the end of the paper feed path 99, a registration roller pair 95 is disposed. The registration roller pair 95 sandwiches the recording sheet conveyed in the paper feed path 99 between the rollers and then feeds it toward the secondary transfer nip at a predetermined timing.

  In the copying machine according to the embodiment, when copying a color image, an original is set on the original table 401 of the ADF 400, or the ADF 400 is opened and the original is set on the contact glass 301 of the scanner unit 300. Hold the document by closing it. Then, a start switch (not shown) is pressed. Then, when the document is set on the ADF 400, the document is conveyed onto the contact glass 301. Thereafter, the scanner unit 300 starts driving, and the first traveling body 303 and the second traveling body 304 start traveling along the document surface. Then, the light emitted from the light source by the first traveling body 303 is emitted on the document surface, and the obtained reflected light is folded and directed to the second traveling body 304. The folded light is further folded by the mirror of the second traveling body 304 and then enters the reading sensor 302 through the imaging lens 305. Thereby, the content of the original is read.

  When the printer unit 100 receives the image information from the scanner unit 300, the printer unit 100 feeds a recording sheet having a size corresponding to the image information to the paper feed path 99. Along with this, the drive roller 22 is rotationally driven by a drive motor (not shown) to move the intermediate transfer belt 21 endlessly in the clockwise direction in the drawing. At the same time, after starting rotation of the photosensitive members 2C, M, Y, and K of the image forming units 1C, M, Y, and K, uniform charging processing, optical writing processing, and the like for the photosensitive members 2C, M, Y, and K are performed. Perform development processing. The C, M, Y, and K toner images formed on the surfaces of the photoreceptors 2C, M, Y, and K by these processes are sequentially overlapped at the C, M, Y, and K primary transfer nips to be intermediate. Primary transfer is performed on the transfer belt 21 to form a four-color superimposed toner image.

  In the paper supply unit 200, one of the paper supply rollers 203 is selectively rotated according to the recording sheet size, and the recording sheet is sent out from one of the three paper supply cassettes 202. The fed recording sheets are separated one by one by the separation roller 4205 and introduced into the paper feed path 206, and then sent to the paper feed path 99 in the printer unit 100 via the transport roller 206. When the manual feed tray 98 is used, the paper feed roller of the tray is driven to rotate, and the recording sheet on the tray is fed to the manual paper feed path 97 while being separated by the separation roller 96 and is fed to the end of the paper feed path 99. To the vicinity. In the vicinity of the end of the paper feed path 99, the recording sheet stops by abutting the leading edge against the registration roller pair 95. Thereafter, when the registration roller pair 95 is rotationally driven at a timing that can synchronize with the four-color superimposed toner image on the intermediate transfer belt 21, it is fed into the secondary transfer nip and is in close contact with the four-color superimposed toner image on the belt. . Then, the secondary transfer is performed collectively on the recording sheet due to the influence of the nip pressure and the transfer electric field.

  The recording sheet on which the four-color superimposed toner image has been secondarily transferred at the secondary transfer nip is fed into the fixing device 71 by the paper transport belt 70. Then, when the fixing device 71 is sandwiched in the fixing nip between the pressure roller 72 and the fixing belt 73, the four-color superimposed toner image is fixed on the surface by pressure or heat treatment. The recording sheet on which the color image has been formed in this manner is stacked on a discharge tray 75 outside the apparatus via a discharge roller pair 74. When an image is also formed on the other side of the recording sheet, the recording sheet is discharged from the fixing device 71 and then sent to the sheet reversing device 75 by the path switching by the switching claw 76. Then, after being turned upside down, it is returned to the registration roller pair 95 again, and then goes through the secondary transfer nip and the fixing device 71 again.

  After passing through the secondary transfer nip, the belt cleaning device 26 contacts the surface of the intermediate transfer belt 21 before entering the C primary transfer nip where the primary transfer process is the most upstream of the four colors. ing. This belt cleaning device 26 cleans the transfer residual toner adhering to the belt surface.

  FIG. 2 is an enlarged schematic diagram illustrating the secondary transfer nip and the surrounding configuration in the printer unit 100 of the copying machine according to the embodiment. In the figure, a secondary transfer counter roller 24 that partially wraps the belt around its peripheral surface inside the loop of the intermediate transfer belt 21 backs up the deformable intermediate transfer belt 21 on its peripheral surface. It plays the role of maintaining the shape along a certain curvature. A secondary transfer roller 30 is in contact with the secondary transfer counter roller 24 on the intermediate transfer belt 21 from the belt front surface side to form a secondary transfer nip.

  The secondary transfer roller 30 is rotatably held by the roller unit holder 40 via a bearing (not shown). The roller unit holding body 40 is configured to be rotatable about a rotation shaft 40 a disposed so as to take a posture parallel to the rotation axis of the secondary transfer roller 30. When the roller unit holder 40 rotates counterclockwise in the figure around the rotation shaft 40a, the secondary transfer roller 30 held by the roller unit holder 40 is pressed against the intermediate transfer belt 21 and 2 A next transfer nip is formed. Further, when the roller unit holder 40 rotates in the clockwise direction in the drawing around the rotation shaft 40a, the secondary transfer roller 30 held by the roller unit holder 40 is separated from the intermediate transfer belt 21. In the copying machine according to the embodiment, the biasing coil spring 45 always biases the end of the roller unit holding body 40 opposite to the rotation shaft 40 a toward the intermediate transfer belt 21. The urging coil spring 45 always applies a force to the roller unit holder 40 to rotate counterclockwise in the drawing around the rotation shaft 40a, thereby causing the secondary transfer roller 30 to move to the intermediate transfer belt 21. It is energizing towards.

  The secondary transfer roller 30 is rotationally driven in the counterclockwise direction in the figure by transmitting the rotational driving force of a roller driving motor (not shown) via a drive transmission means such as a gear (not shown). These roller drive motors and drive transmission means are also held by the roller unit holder 40 and rotated together with the secondary transfer roller 30 and the roller unit holder 40. The roller unit holder 40 also holds a cleaning blade 39, a solid lubricant 41, a lubricant pushing device 43, and the like.

  The toner on the belt adheres to the surface of the secondary transfer roller 30 that is in contact with the front surface of the intermediate transfer belt 21 that carries the toner image. If this adhering toner is left as it is, it is transferred to the back surface of the recording sheet at the secondary transfer nip, and so-called back dirt is generated. Therefore, in this copying machine, the toner is mechanically removed from the surface of the secondary transfer roller 30 by bringing the edge of the cleaning blade 39 into contact with the surface of the secondary transfer roller 30. In such a configuration, a load impeding the rotation is applied to the secondary transfer roller 30 due to the contact of the cleaning blade 39, so that the secondary transfer roller 30 is driven to rotate along with the intermediate transfer belt 21. I can't. For this reason, the secondary transfer roller 30 is rotationally driven by the roller driving motor described above.

  The lubricant pressing device 43 applies the lubricant powder to the secondary transfer roller 30 by pressing the solid lubricant 41 made of a zinc stearate block or the like against the secondary transfer roller 30 by the biasing coil spring 42. By applying the lubricant in this way, an increase in rotational load due to contact between the cleaning blade 39 and the secondary transfer roller 30 is suppressed. In addition, occurrence of blade edge entrainment is also suppressed. Instead of pressing the solid lubricant 41 against the secondary transfer roller 30, a rotary application brush for applying the lubricant to the secondary transfer roller 30 while scraping the lubricant from the solid lubricant 41 may be provided.

Next, a characteristic configuration of the copier according to the embodiment will be described. FIG. 3 is an enlarged cross-sectional view showing a configuration around the secondary transfer nip. FIG. 4 is a perspective view showing a configuration around the secondary transfer nip.
In these drawings, the secondary transfer roller 30 includes a roller portion 31, first and second shaft members 32 and 33 that protrude from both end surfaces in the axial direction of the roller portion 31 and extend in the rotational axis direction, and will be described later. A first idling roller 34 and a second idling roller 35 are provided. The roller unit 31 includes a cylindrical hollow core 31a, an elastic layer 31b made of an elastic material fixed to the peripheral surface thereof, and a surface layer 31c fixed to the peripheral surface thereof. .

  Examples of the metal constituting the hollow core 31a include stainless steel and aluminum, but are not limited to these materials. The elastic layer 31b is preferably 70 [°] or less in terms of JIS-A hardness. However, since the cleaning blade 39 is in contact with the roller portion 31, various problems are caused if the elastic layer 31b is too soft. Therefore, it is desirable that the elastic layer 31b has a JIS-A hardness of 40 [°] or more. An elastic layer 31b having a JIS-A hardness of about 50 [°] is formed of epichlorohydrin rubber exhibiting a certain degree of conductivity. As a rubber material exhibiting conductivity, EPDM or Si rubber in which carbon is dispersed, NBR having an ionic conductivity function, urethane rubber, or the like may be used instead of the above-described conductive epichlorohydrin rubber. Since many rubber materials exhibit good chemical affinity for the toner or exhibit a relatively large coefficient of friction, the surface of the elastic layer 31b made of rubber is covered with the surface layer 31c. ing. As a result, toner adhesion to the surface of the roller unit 31 is suppressed, and the frictional load with the blade is reduced. As a material for the surface layer 31c, a material in which a resistance adjusting material such as carbon or an ionic conductive agent is contained in a fluororesin resin that exhibits a low coefficient of friction and good toner releasability is suitable.

  When the secondary transfer roller 30 rotates in contact with the intermediate transfer belt 21, it may have a slight linear velocity difference from the belt. The friction coefficient of the surface layer 31c is adjusted to 0.3 or less so that the belt does not slip due to this linear speed difference. The intermediate transfer belt 21 is required to be driven at a constant speed in order to transfer the images of each color in a superimposed manner without color misregistration. Therefore, it is necessary to reduce the surface friction resistance of the surface layer 31c of the secondary transfer roller 30. is important.

  The secondary transfer roller 30 having such a configuration is biased toward the intermediate transfer belt 21 that is wound around the secondary transfer counter roller 24. The secondary transfer counter roller 24 that is wound around the intermediate transfer belt 21 passes through the roller portion 24b, which is a cylindrical main body portion, and the rotation center of the roller portion 24b in the rotation axis direction, and the roller portion 24b. And a through shaft member 24a that idles on its surface. The penetrating shaft member 24a is made of metal, and freely rotates the roller portion 24b freely on its peripheral surface. The roller part 24b as the main body part is composed of a drum-shaped hollow cored bar 24c, an elastic layer 24d made of an elastic material fixed on the peripheral surface of the drum-shaped hollow cored bar 24c, and balls press-fitted to both ends in the axial direction of the hollow cored bar 24c. And a bearing 24e. The ball bearing 24e rotates on the penetrating shaft member 24a together with the hollow core metal 24c while supporting the hollow core metal 24c. The elastic layer 24d is press-fitted into the outer peripheral surface of the hollow cored bar 24c.

  The through shaft member 24a is rotatably supported by a first bearing 52 fixed to the first side plate 28 of the transfer unit that stretches the intermediate transfer belt 21 and a second ball bearing 53 fixed to the second side plate. Has been. However, most of the time during the print job is stopped without being driven to rotate. Then, the roller portion 24b that is to be rotated along with the endless movement of the intermediate transfer belt 21 is freely idled on its own peripheral surface.

  The elastic layer 24d fixed on the peripheral surface of the hollow core metal 24c is composed of a conductive rubber material whose resistance value is adjusted by adding an ionic conductive agent so as to exhibit a resistance of 7.5 [LogΩ] or more. Has been. The reason why the electric resistance of the elastic layer 24d is adjusted within a predetermined range is that when a recording sheet having a relatively small size in the roller axial direction, such as A5 size, is used, the recording sheet is moved in the secondary transfer nip. This is because the transfer current is prevented from being concentrated at a position where the belt and the roller are in direct contact without intervention. By setting the electric resistance of the elastic layer 24d to a value larger than the resistance of the recording sheet, it is possible to suppress such transfer current concentration.

  In addition, as the conductive rubber material constituting the elastic layer 16c, foamed rubber is used so as to exhibit elasticity of about 40 [°] in Asker-C hardness. By forming the elastic layer 16c with such foamed rubber, the elastic layer 16c is flexibly deformed in the thickness direction in the secondary transfer nip to form a secondary transfer nip having a certain size in the sheet conveying direction. can do. In this copying machine, as described above, for the convenience of bringing the cleaning blade 39 into contact with the secondary transfer roller 30, it is possible to use an elastic material as the material of the roller portion of the secondary transfer roller 30. Have difficulty. Therefore, instead of the secondary transfer roller 30, the roller portion 24b of the secondary transfer counter roller 24 is elastically deformed.

  In the penetrating shaft member 24a of the secondary transfer counter roller 24, the two end regions that are not located in the roller portion 24b in the entire longitudinal direction are respectively abutted against the secondary transfer roller 30. An eccentric cam as a member is fixed so as to rotate integrally with the through shaft member 24a. Specifically, the first eccentric cam 50 is fixed to one end region in the longitudinal direction of the penetrating shaft member 24a. In the first eccentric cam 50, an eccentric cam portion 50a and a true circular roller portion 50b are integrally formed side by side in the axial direction. The first eccentric cam 50 is fixed to the penetrating shaft member 24a by screwing the screw 80 penetrating the roller portion 50b into the penetrating shaft member 24a. A second eccentric cam 51 having the same configuration as that of the first eccentric cam 50 is fixed to the other end region in the longitudinal direction of the through shaft member 24a.

  A drive receiving gear 54 is fixed to a region outside the second eccentric cam 51 in the axial direction of the penetrating shaft member 24a. In addition, a detected disk 59 is fixed on the further outside of the drive receiving gear 54.

  On the other hand, a cam drive motor 58 is fixed to the second side plate 29 of the transfer unit, and an input / output gear unit is rotatably fixed. This input / output gear unit meshes with the input gear portion 55 that meshes with the motor gear 57 of the cam drive motor 58 and receives the driving force, and the drive receiving gear 54 that is fixed to the through-shaft member 24a. The output gear portion 56 to be transmitted is integrally formed side by side in the axial direction. By driving the cam drive motor 58, the through shaft member 24a can be rotated. At this time, even if the through-shaft member 24a is rotated, the roller portion 24b can be freely idled on the through-shaft member 24a, so that the rotation of the roller portion 24b by the belt is not hindered.

  When the penetrating shaft member 24a stops rotating within a predetermined rotation angle range, the first eccentric cam 50 and the second eccentric cam 51 abut each of the cam portions against the secondary transfer roller 30, and the secondary transfer roller 30. Is pushed back against the biasing force of the biasing coil spring (45) of the roller unit holder. As a result, the distance between the secondary transfer counter roller 24 and the secondary transfer roller 30 is adjusted by moving the secondary transfer roller 30 away from the secondary transfer counter roller 24 (and thus the intermediate transfer belt 21). To do. In such a configuration, the inter-axial distance between the secondary transfer counter roller 24 and the secondary transfer roller 30 by the first eccentric cam 50, the second eccentric cam 51, the cam drive motor 58, various gears, the roller unit holder described above, and the like. A distance adjusting means for adjusting the distance is configured. Then, the secondary transfer counter roller 24 as a rotatable support rotating body freely idles the roller portion 24b on the penetrating shaft member 24a penetrating the cylindrical roller portion 24b. When the penetrating shaft member 24a rotates, the eccentric cams (50, 51) respectively fixed to both end portions in the axial direction of the penetrating shaft member 24a rotate together, so that the drive is transmitted to the penetrating shaft member 24a. It is possible to rotate the eccentric cams at both ends only by providing the drive transmission mechanism at one end in the axial direction. Therefore, the layout freedom of the distance adjusting means can be improved as compared with the conventional case where it is necessary to provide drive transmission mechanisms on both ends.

  In this copying machine, the hollow cored bar 31a of the secondary transfer roller 30 is grounded, and a secondary transfer bias having the same polarity as the toner is applied to the hollow cored bar 24c of the secondary transfer counter roller 24. As a result, a secondary transfer electric field for electrostatically moving the toner from the secondary transfer counter roller 24 side to the secondary transfer roller 30 side is formed in the secondary transfer nip between the two rollers.

  The first bearing 52 that rotatably receives the metal penetrating shaft member 24a of the secondary transfer counter roller 30 includes a conductive sliding bearing. A high voltage power supply 61 that outputs a secondary transfer bias is connected to the conductive first bearing 52. The secondary transfer bias output from the high voltage power supply 61 is guided to the secondary transfer counter roller 30 via the conductive first bearing 52. In the secondary transfer counter roller 30, a metal penetrating shaft member 24a, a metal ball bearing 24e, a metal hollow cored bar 24c, and a conductive elastic layer 24d are sequentially transmitted.

  The detected disk 59 fixed to one end of the penetrating shaft member 24a has a test portion 59a that rises in the axial direction at a predetermined position in the rotation direction of the penetrating shaft member 24a. On the other hand, an optical sensor 60 is fixed to the motor bracket that supports the cam drive motor 58. In the process of rotating the through shaft member 24a, when the through shaft member 24a is positioned within a predetermined rotation angle range, the test portion 59a of the detected disk 59 enters between the light emitting element and the light receiving element of the optical sensor 60. The optical path between the two is blocked. When the light receiving element of the optical sensor 60 receives light from the light emitting element, it transmits a light receiving signal to a control unit (not shown). Based on the timing at which the light receiving signal from the light receiving element is interrupted and the amount of drive of the cam drive motor 58 from that timing, the control unit determines the cam portion of the eccentric cam (50, 51) fixed to the through shaft member 24a. Know the rotation angle position.

  As described above, the eccentric cam (50, 51) abuts against the secondary transfer roller 30 within a predetermined rotation angle range, causing the secondary transfer roller 30 to resist the biasing force of the biasing coil spring (45). Pushing back in a direction away from the transfer counter roller 24 (hereinafter, this pushing back is referred to as “pressing down”). The amount of pushing back (hereinafter referred to as the amount of pushing down) at this time is determined by the rotational angle position of the eccentric cam (50, 51). Note that the distance between the axes of the secondary transfer counter roller 24 and the secondary transfer roller 30 increases as the amount of depression of the secondary transfer roller 30 increases.

  In the secondary transfer roller 30, a first idling roller 34 is provided on the first shaft member 32 that rotates integrally with the roller portion 31 so as to be idling. The first idling roller 34 has a donut disk shape whose outer diameter is slightly larger than that of the roller portion 31. And it has a function as a ball bearing itself, and can idle | slide on the surrounding surface of the 1st shaft member 32. FIG. A second idling roller 35 having the same configuration as the first idling roller 34 is provided on the second shaft member 33 of the secondary transfer roller 30 so as to be idling.

  As described above, in the secondary transfer counter roller 24, the eccentric cam (50, 51) fixed to the through shaft member 24a hits the secondary transfer roller 30 at a predetermined rotational angle position. It hits against the above-mentioned idling roller (34, 35). Specifically, the first eccentric cam 50 fixed to one end side of the penetrating shaft member 24 a abuts on the first idling roller 34 of the secondary transfer roller 24. At the same time, the second eccentric cam 51 fixed to the other end side of the penetrating shaft member 24 a comes into contact with the second idling roller 35 of the secondary transfer roller 24. The idling rollers (34, 35) abutted against the eccentric cam (50, 51) of the secondary transfer counter roller 24 are prevented from rotating along with the abutment, and thereby the rotation of the secondary transfer roller 30 is prevented. Will not be disturbed. Even if the idling rollers (34, 35) stop rotating, the idling rollers are ball bearings, so the shaft members (32, 33) of the secondary transfer roller 30 can rotate freely independently from the idling rollers. Because it can be done. By stopping the rotation of the idle rollers (34, 35) with the abutment of the eccentric cam (50, 51), the occurrence of friction between the two is avoided, and a belt drive motor or secondary transfer roller due to the friction is avoided. It is also possible to avoid an increase in the torque of 30 drive motors.

Figure 5 is an enlarged schematic view showing a state of the secondary transfer nip immediately before advancing the plain paper P ₁ as a recording sheet. In this copying machine, when the plain paper P ₁ enters the secondary transfer nip, the eccentric cams (50, 51) of the secondary transfer counter roller 24 are idled on the secondary transfer roller 30 as shown in the figure. The rotation of the penetrating shaft member 24a of the secondary transfer counter roller 24 is stopped at a position where it does not hit (34, 35). That is, when using plain paper _{P 1} does not implement the depression of the secondary transfer roller 30 by the eccentric cam (50, 51). This is because the plain paper P _{1 having} a relatively small thickness does not cause a large load fluctuation on the belt and the secondary transfer roller 30 when entering the secondary transfer nip even if the secondary transfer roller 30 is not pushed down.

Figure 6 is an enlarged schematic view showing a state of the secondary transfer nip immediately before advancing the cardboard P ₂ as a recording sheet. In the copying machine, when advancing the cardboard P ₂ to the secondary transfer nip, as shown, the eccentric cam of the secondary transfer opposing roller 24 (50, 51), idling roller of the secondary transfer roller 30 ( 34, 35), the rotation of the through shaft member 24a of the secondary transfer counter roller 24 is stopped. That is, when using the thick paper _{P 2} performs a depression of the secondary transfer roller 30 by the eccentric cam (50, 51). In relatively large cardboard P ₂ of thickness, not performed the depression of the secondary transfer roller 30 when, because thus generate a large load fluctuation during the secondary transfer nip enters the belt and the secondary transfer roller 30.

As can be seen from a comparison between FIG. 5 and FIG. 6, the length Wb of the secondary transfer nip in the belt moving direction when the secondary transfer roller 30 is pushed down by the eccentric cam (50, 51) is pushed down. It becomes shorter than length Wa when not implementing. On the other hand, the inter-axis distance Lb between the secondary transfer counter roller 24 and the secondary transfer roller 30 when the pressing is performed is larger than the inter-axis distance La when the pressing is performed. When the distance between the shafts is increased, the pressing force of the secondary transfer roller 30 against the intermediate transfer belt 21 is weakened, and the secondary transfer nip pressure is reduced. Thus, it is possible to suppress the occurrence of a sudden load increase on the secondary transfer nip the belt and rollers when the thick paper P ₂ enters.

The present inventors conducted an experiment to investigate the relationship between the interaxial distance and the dot diameter variation using a copying tester having the same configuration as the copying machine shown in FIG. Specifically, when the intermediate transfer belt 21 is traveling stably at the designed speed, the linear velocity between the photosensitive member and the belt in the primary transfer nip for transferring the toner image from the photosensitive member to the belt. There is almost no difference. In this state, the dots constituting the toner image are primarily transferred onto the belt in the same shape (circular shape). On the other hand, when the running speed of the intermediate transfer belt 21 decreases instantaneously due to a sudden torque increase when the thick paper enters the secondary transfer nip, a linear speed difference between the photosensitive member and the belt occurs at that moment. . Then, due to the difference in linear velocity, each dot is primarily transferred to the belt in an elliptical shape stretched in the direction of movement of the photoreceptor surface, so that the dot diameter becomes larger than usual. In order to investigate the relationship between such a difference in dot diameter and the amount by which the secondary transfer roller 30 is pushed down by the eccentric cam, a predetermined dot pattern image was output under various conditions of the amount of depression in the copying test machine. . As the recording sheet, cardboard having a basis weight of 300 [g / m ² ] was used.

  FIG. 7 is a graph showing the relationship between the dot diameter and the dot sub-scanning position when a dot pattern image is output under the condition that the secondary transfer roller 30 is not pushed down. The dot sub-scanning position means the position of the dot in the sheet conveyance direction on the recording sheet. In the same figure, the moment when the dots formed at the sub-scanning position xa are primarily transferred from the photosensitive member to the belt is also the moment when the leading edge of the thick paper enters the secondary transfer nip (hereinafter referred to as the leading edge of the sheet). . Under the condition that the pressing amount of the secondary transfer roller 30 is set to zero, as shown in the figure, the diameter of the dot at the sub-scanning position xa is considerably larger than the diameter of the dot at the other position. This is because, under the above-described conditions, a sudden load increase occurs on the belt when the sheet leading edge approaches, and the moving speed of the belt decreases instantaneously.

  FIG. 8 is a graph showing the relationship between the dot diameter and the dot sub-scanning position when a dot pattern image is output under the condition that the pressing amount of the secondary transfer roller 30 is set to 0.5 [mm]. Under this condition, an increase in the dot diameter when entering the leading end of the sheet is suppressed as compared with a condition where the amount of pressing down is zero, but the dot diameter when entering the leading end of the sheet is still larger than usual. This is because the instantaneous belt speed drop at the time of entering the leading edge of the sheet is not completely eliminated.

  FIG. 9 is a graph showing the relationship between the dot diameter and the dot sub-scanning position when a dot pattern image is output under the condition that the pressing amount of the secondary transfer roller 30 is set to 1.0 [mm]. Under this condition, the increase in the dot diameter when entering the leading edge of the sheet is completely eliminated. This is because the momentary belt speed drop at the time of entering the leading edge of the sheet is completely eliminated. From this result, it was proved that an instantaneous belt speed decrease at the time of entering the leading end of the sheet can be eliminated if the pressing amount is appropriately set.

Next, the inventors conducted an experiment to investigate the relationship between the secondary transfer nip pressure when the recording sheet is interposed in the nip, the amount by which the secondary transfer roller 30 is pushed down, and the thickness of the recording sheet. It was. The recording sheet, cardboard (thickness about 320 .mu.m) with a basis weight 300 [g / ^{m 2],} basis weight 200 [g / ^{m 2]} (approximately 200μm thick) cardboard in the basis weight 80 [g / ^{m 2} ] Of plain paper (thickness is about 90 μm). The result is shown in FIG. As shown in the drawing, it can be seen that the secondary transfer nip pressure when the sheet is interposed decreases as the thickness of the recording sheet decreases under the condition of the same pressing amount. In order to achieve good secondary transfer, the secondary transfer nip pressure needs to be in a certain range regardless of the thickness of the recording sheet, and the amount of pressing down needs to be set according to the thickness of the recording sheet. There is. If the same pressing amount is set for thick paper and plain paper, even if the increase in dot diameter when entering the leading edge of the sheet can be avoided, the plain paper may cause a transfer failure due to insufficient nip pressure, and vice versa. Instead of being able to avoid the occurrence of transfer failure, for the thick paper, the dot diameter at the time of entering the leading edge of the sheet is remarkably increased.

  Therefore, this copying machine is provided with thickness information acquisition means for acquiring thickness information of the recording sheet supplied to the secondary transfer nip. And the control part which is a part of distance adjustment means is comprised so that the depression amount of the secondary transfer roller 30 may be adjusted according to the acquisition result by the thickness information acquisition means. Specifically, a data storage means such as a ROM in the control unit stores a data table indicating the relationship between the thickness of the recording sheet and the corresponding rotation stop position (agreement with the amount of depression) of the through shaft member 24a. ing. Then, the rotation stop position corresponding to the recording sheet thickness acquisition result is specified from the data table, and the process of causing the recording sheet to enter the secondary transfer nip is performed after the through shaft member 24a is rotated to the rotation stop position. Thus, the control unit is configured. Thereby, it is possible to set an interaxial distance suitable for the thickness of the recording sheet, and to suppress both a transfer failure due to insufficient nip pressure and an increase in the dot diameter when entering the leading end of the sheet.

  As described above, the rotation stop position of the through shaft member 24a is based on the timing at which the optical sensor 60 detects the detected portion 59a of the detected disk 59 and the drive amount of the cam drive motor 58 from the timing. The control unit is configured to grasp.

  As the thickness information acquisition means, a thickness detection sensor that actually detects the thickness of the recording sheet conveyed in the paper feed path 99 may be used, or a data input means that receives data input of thickness information from the operator. It may be used. Examples of the thickness detection sensor include an optical sensor that detects light transmittance in the thickness direction, a sensor that detects the amount of roller movement when a recording sheet is sandwiched between a pair of conveyance rollers, and the like.

  In the present copying machine, since the roller portion 24a is idled on the peripheral surface of the through shaft member 24a in the secondary transfer counter roller 24, an eccentric cam (50 as an abutting member fixed to the through shaft member 24a). , 51) does not affect the rotation of the roller portion 24a. Further, in the secondary transfer roller 30, the idle rollers (34, 35) as the abutting members are idled on the shaft members (32, 33), so that the contact state of the idle rollers is secondary transferred. The rotation of the roller 30 is not affected. As a result, even in a print job, the amount by which the secondary transfer roller 30 is pushed down can be changed corresponding to the continuous passage of recording sheets having different thicknesses.

  In FIG. 3 described above, when the eccentric cam (50, 51) of the secondary transfer counter roller 24 is abutted against the idling roller (34, 35) of the secondary transfer roller 30, the former is passed through the abutting portion. If the secondary transfer current leaks from the first roller to the latter roller, a secondary transfer electric field having an appropriate strength cannot be formed in the secondary transfer nip. Therefore, it is desirable that at least one of the eccentric cam and the idling roller is made of an insulating material. In this copying machine, the occurrence of the above-described leakage is prevented by using an eccentric cam (50, 51) made of polyacetal resin which is an insulating material.

  The idling rollers (34, 35) may be made of resin, but are preferably made of a material having high rigidity so as not to be deformed even when pressed from the eccentric cam (50, 51). Therefore, in the present copying machine, as the idling roller, one made of a metal ball bearing is used. Such idling rollers are not deformed even by the pressing of the eccentric cam, and the rotational position accuracy of the secondary transfer roller 30 is not affected. Moreover, since it is excellent in slidability, wear of the eccentric cam can be reduced.

  So far, a copying machine has been described that uses an endless belt-shaped intermediate transfer belt 21 that is wound around a secondary transfer counter roller 24 that is a rotatable support rotating body as an image carrier, and is moved endlessly. However, the present invention can be applied if at least one of an image carrier such as an intermediate transfer belt and a counter member such as a transfer roller is constituted by a belt member supported by a support rotating body or a rotating body. It is.

  For example, in a configuration in which a transfer nip is formed by pressing a drum-shaped photosensitive member as a rotating member and a stationary transfer member that does not move on the surface, the following may be performed. That is, a rotatable drum-shaped photoconductor is constituted by at least a main body portion and a penetrating shaft member, and an eccentric cam integrally formed with the penetrating shaft member may be abutted against a transfer member biased by a biasing means. .

  Further, in the configuration in which the transfer nip is formed by pressing the immovable transfer member that does not move the surface against the photosensitive belt or the intermediate transfer belt that is wound around the rotatable support rotating body and moved endlessly, as follows. do it. That is, the support roller for winding the photosensitive belt and the intermediate transfer belt is composed of at least the main body and the through shaft member, and the eccentric cam integrally formed with the through shaft member is pushed against the transfer member biased by the biasing means. Just guess.

  In addition, a sheet conveying belt as a nip forming member, which is hung around a support roller and moved endlessly, is pressed against a photosensitive belt or an intermediate transfer belt that is hung around a support roller and moved endlessly. The configuration to be formed may be as follows. That is, one of the two support rollers is composed of at least a main body portion and a through shaft member, and an eccentric cam integrally formed with the through shaft member is used as the other support roller biased by the biasing means. Just hit it.

  As described above, in the copying machine according to the embodiment, the endless belt-shaped intermediate transfer belt 21 that is wound around the secondary transfer counter roller 24 that is a support rotating body is used as the image carrier, and the secondary transfer counter roller 24 is The roller portion 24b, which is at least the main body portion, and the through-shaft member 24a are configured so that the roller portion 24b is driven to rotate on the surface of the through-shaft member 24a as the intermediate transfer belt 21 moves endlessly. Yes. With such a configuration, the degree of freedom of layout of the distance adjusting means for adjusting the relative distance between the endless belt-like intermediate transfer belt 21 and the secondary transfer roller 30 can be improved as compared with the related art.

  In the copying machine according to the embodiment, prior to the recording sheet entering between the intermediate transfer belt 21 and the secondary transfer roller 30, the secondary transfer roller is brought into contact with the eccentric cam (50, 51). It consists of a control part, an eccentric cam, etc. so that 30 may be forced back in the direction farther from the belt against the biasing force of the biasing coil spring 45 to further increase the relative distance between the belt and the roller. It constitutes a distance adjusting means. In this configuration, as described above, it is possible to suppress an increase in the dot diameter due to a momentary decrease in the moving speed of the belt when entering the leading end of the sheet.

  Note that, in the copying machine according to the embodiment, prior to discharging the recording sheet entering between the intermediate transfer belt 21 and the secondary transfer roller 30 from both, the secondary sheet is pressed by the eccentric cam. From the control unit or the eccentric cam, the transfer roller is forcibly pushed back in the direction away from the belt against the urging force of the urging coil spring 45 to further increase the relative distance between the belt and the roller. This constitutes a distance adjusting means. In this configuration, when the recording sheet is interposed between the belt and the roller at the secondary transfer nip, the roller is pressed toward the belt with a sufficient force to secure the necessary secondary transfer nip pressure, and the rear end of the sheet. When discharging the belt, it is possible to suppress the occurrence of an instantaneous speed increase of the belt due to a rapid load drop during discharging by increasing the relative distance in advance.

  In the copying machine according to the embodiment, the first eccentric cam 50 and the second eccentric cam 51 at both longitudinal ends of the through shaft member 24a are connected to the belt of the intermediate transfer belt 21 in the longitudinal direction of the through shaft member 24a. The penetrating shaft member 24a is fixed at a distance larger than the width dimension. With this configuration, the intermediate transfer belt 21 can be moved endlessly between the first eccentric cam 50 and the second eccentric cam 51.

  Further, in the copying machine according to the embodiment, the idling rollers (34, 34) serving as members to be abutted against the eccentric cams (50, 51) at both ends in the longitudinal direction of the rotation shaft member of the secondary transfer roller 30. 35) is provided on the surface of the rotary shaft member (32.33) so as to be idle. In such a configuration, the idling roller (34, 35) is idled on the shaft member (32, 33), so that the rotation of the idling roller with the eccentric cam abutting is stopped while performing the secondary transfer. The roller 30 is rotated well. As a result, friction between the eccentric cam and the idling roller can be avoided, and an increase in the torque of the belt or roller due to the friction can be avoided.

  In the copying machine according to the embodiment, distance detection means (consisting of a non-detection disk 59, an optical sensor 60, a control unit, etc.) for detecting the relative distance between the belt and the secondary transfer roller 30 is provided, and the distance detection means. The control unit which is a part of the distance adjusting means is configured to adjust the rotation stop position of the through shaft member 24a based on the detection result obtained by the above. In such a configuration, the amount by which the secondary transfer roller 30 is pushed down can be freely adjusted to a desired value based on the rotation stop position of the through shaft member 24a.

  In the copying machine according to the embodiment, at least one of the eccentric cam (50, 51) and the idling roller (34, 35) is made of an insulating material. In such a configuration, it is possible to avoid the occurrence of leakage of the transfer current through the both abutting portions.

  In the copying machine according to the embodiment, since the eccentric cam (50, 51) is used as the abutting member, the cam surface with no step is abutted and pushed down as a relative distance between the belt and the roller. The amount can be freely adjusted steplessly.

  In the copying machine according to the embodiment, a distance information acquisition unit that acquires thickness information of the recording sheet supplied to the secondary transfer nip is provided, and the pressing amount is adjusted based on the detection result thereby. Since the control part which is a part of adjustment means is comprised, the amount of pushing down can be adjusted to the appropriate value according to sheet | seat thickness.

1 is a schematic configuration diagram showing a copier according to an embodiment. FIG. 3 is an enlarged schematic diagram illustrating a secondary transfer nip and a surrounding configuration in a printer unit of the copier. FIG. 3 is an enlarged cross-sectional view showing a configuration around the secondary transfer nip. The perspective view which shows the surrounding structure. FIG. 3 is an enlarged schematic diagram illustrating a state of a secondary transfer nip immediately before entering plain paper. FIG. 3 is an enlarged schematic diagram illustrating a state of a secondary transfer nip immediately before entering a thick paper. 6 is a graph showing a relationship between a dot diameter and a dot sub-scanning position when a dot pattern image is output under a condition where the secondary transfer roller is not pushed down. 6 is a graph showing a relationship between a dot diameter and a dot sub-scanning position when a dot pattern image is output under a condition in which a pressing amount of a secondary transfer roller is set to 0.5 [mm]. 6 is a graph showing a relationship between a dot diameter and a dot sub-scanning position when a dot pattern image is output under a condition in which a pressing amount of a secondary transfer roller is set to 1.0 [mm]. 6 is a graph showing the relationship between the secondary transfer nip pressure when the recording sheet is interposed in the nip, the amount by which the secondary transfer roller is pushed down, and the thickness of the recording sheet.

Explanation of symbols

21: Intermediate transfer belt (image carrier)
24: Secondary transfer counter roller (supporting rotating body)
24a: Through shaft member 24b: Roller part (main body part)
24c: hollow core metal 24d: elastic layer 30: secondary transfer roller (opposing member)
32: First shaft member (shaft portion)
33: Second shaft member (shaft portion)
34: First idling roller (abutting member)
35: Second idling roller (member to be abutted)
45: Energizing coil spring (urging means)
50: First eccentric cam 51: Second eccentric cam 59: Detected disk (part of distance detecting means)
60: Optical sensor (part of distance detection means)

Claims (10)

At least one of the image bearing member and the facing member that forms a transfer region facing the image bearing member is configured by a belt member or a rotating member supported by a supporting rotating member, and the supporting rotating member or the rotating member By changing the rotational position of the cam provided on the shaft of the body, the distance between the image carrier and the opposing member in the transfer area is adjusted, and the visible image on the image carrier is transferred to the opposing member in the transfer area. Or having a cam surface that is an abutting surface that is transferred to a recording sheet passed between the image carrier and the opposing member , and the cam has a non-uniform radius with respect to its rotation center In the image forming apparatus,
While passing through the through hole of the main body part, the main body part having a through hole penetrating the supporting rotary body or the rotary body provided with the cam on its own shaft part at least in the rotational axis direction at the rotation center position The main body is constituted by a through shaft member as the shaft that idles on its surface,
The cam is fixed so as to rotate integrally with the through-shaft member in each of both end regions that are not located in the main body portion in the entire longitudinal region of the through-shaft member. Image forming apparatus. The image forming apparatus according to claim 1.
At least one of the image carrier and the opposing member is configured by the belt member, and the main body of the support rotating body that supports the belt member is moved along the movement of the belt member. An image forming apparatus characterized by being driven to rotate on a surface. The image forming apparatus according to claim 1, wherein:
A biasing means for biasing the opposing member toward the image carrier;
Prior to causing the recording sheet to enter between the image carrier and the opposing member, the opposing member is moved by the biasing means when the rotational drive of the through shaft member and the cam is stopped at a predetermined rotational angle. An image forming apparatus that performs an operation of further expanding the distance by pushing back against an urging force. The image forming apparatus according to any one of claims 1 to 3,
After the recording sheet has entered between the image carrier and the counter member, and before the recording sheet is discharged from the recording sheet, the counter member is stopped by stopping the rotational drive of the through shaft member at a predetermined rotation angle. An image forming apparatus that performs an operation of further increasing the distance by pushing back against the urging force of the urging means. The image forming apparatus according to claim 2.
Two cams at both longitudinal ends of the through shaft member are fixed to the through shaft member at a distance larger than the belt width dimension of the belt member in the longitudinal direction of the through shaft member. Image forming apparatus. The image forming apparatus according to claim 1,
Each of the image carrier and the counter member is configured by the belt member or the rotary body, and either the belt member or the rotary body constituting the image carrier, or the belt member or the rotary body constituting the counter member, At least the main body portion and the penetrating shaft member to which the cam is fixed are configured, and the other is abutted against the cam on the supporting rotating body of the belt member constituting the same or the shaft portion of the rotating body. An image forming apparatus characterized in that an abutted member to be driven is provided so as to be idled. The image forming apparatus according to any one of claims 1 to 6,
An image forming apparatus comprising: a distance detection unit configured to detect the distance; and adjusting a rotation stop position of the through shaft member based on a detection result of the distance detection unit. The image forming apparatus according to claim 6.
An image forming apparatus, wherein at least one of the cam and the abutted member is made of an insulating material. The image forming apparatus according to claim 1,
An image forming apparatus using an eccentric cam having no step as the cam. The image forming apparatus according to any one of claims 1 to 9,
An image characterized by comprising thickness information acquisition means for acquiring thickness information of a recording sheet supplied between the image carrier and the opposing member, and adjusting the distance based on a detection result by the thickness information detection means. Forming equipment.

Images