JP6164884B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including an intermediate transfer belt or a conveyance belt.

An electrophotographic image forming apparatus that outputs a color image is provided with a mechanism called a belt conveyance device or a sheet conveyance device as a mechanism for conveying a toner image or a sheet as a recording paper using an endless flat belt. In the belt conveyance device, a belt called an intermediate transfer belt is used. An image forming apparatus provided with a belt conveying device does not directly transfer toner images of different colors carried on a plurality of photosensitive drums onto a sheet, but instead from each photosensitive drum to the surface of an intermediate transfer belt. Transfer and transfer the transferred image to a sheet. In the sheet conveying apparatus, a belt called a conveying belt is used. An image forming apparatus including a sheet conveying device is configured to directly transfer a toner image on each photosensitive drum to a sheet, and a conveying belt transfers the toner image to the sheet and conveys the sheet. Used for.
In the belt conveyance device and the sheet conveyance device, correction of color deviation, density, chromaticity, and the like of an image transferred to a transfer material is performed by detecting the surface state of the belt using an optical sensor or the like. In Patent Document 1, when detecting a toner image mark or the like transferred to the belt by an optical sensor arranged opposite to the belt surface, a backing member is provided on the back side of the belt at the detection location to correct the deformation of the belt. A configuration for realizing accurate optical sensor detection is described.

JP 2007-148197 A

  However, since the backing member is a rubbing member that rubs against the rotating belt, a frictional force is generated at a contact portion with the belt. Depending on the relationship between the contact pressure between the belt and the rubbing member and the frictional force, there is a concern that the rubbing member vibrates and abnormal noise is generated.

  An object of the present invention is to provide an image forming apparatus capable of suppressing the generation of abnormal noise due to vibration of a rubbing member in a configuration in which a belt and a rubbing member are rubbed.

To achieve the above SL is provided an image forming apparatus of the present invention,
A belt that is movable to convey a toner image to be transferred to the recording material or a recording material to which the toner image is transferred;
Detecting means facing the outer peripheral surface of the belt;
Pressed against the inner peripheral surface of the belt, and a rubbing member for rubbing against the moving belt,
A support member for supporting the rubbing member;
In an image forming apparatus comprising:
The support member includes a first support portion that supports a surface of the rubbing member opposite to the contact surface with the belt, and a side of the first support portion that is opposite to the side that supports the rubbing member. A second support portion extending in parallel with the outer peripheral surface,
Area of the projected shape with respect to the virtual plane parallel to the outer peripheral surface may be smaller than the area of the projected shape with respect to an imaginary plane perpendicular to the vertical and the transport direction on the outer peripheral surface.

  According to the present invention, in the configuration in which the belt and the rubbing member are rubbed, generation of abnormal noise due to vibration of the rubbing member can be suppressed.

1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. Main cross-sectional view of photosensitive drum cartridge and intermediate transfer belt unit Cross-sectional view of photosensitive drum cartridge and intermediate transfer belt unit Conceptual diagram of force acting on rubbing member Cross-sectional shape of conventional rubbing member A arrow view of a conventional rubbing member B arrow view of a conventional rubbing member Relationship between the cross-sectional shape of the rubbing member and the secondary moment of the cross-section Sectional shape of a rubbing member according to Embodiment 1 of the present invention The arrow A view of the rubbing member which concerns on Example 1 of this invention B arrow figure of the rubbing member which concerns on Example 1 of this invention Cross-sectional shape of conventional support member A arrow view of a conventional support member B arrow view of a conventional support member Relationship between the cross-sectional shape of the support member and the moment of inertia of the cross-section Sectional shape of support member according to embodiment 2 of the present invention The A arrow directional view of the support member which concerns on Example 2 of this invention B arrow view of a support member according to Example 2 of the present invention

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

Example 1
FIG. 1 is a schematic view of an electrophotographic image forming apparatus according to this embodiment, and FIG. 2 is a schematic sectional view of the electrophotographic image forming apparatus according to this embodiment. In this embodiment, as an electrophotographic image forming apparatus, a rotary (developer rotating) type four-cycle full-color laser printer will be described as an example.

[Outline of image forming operation of color image forming apparatus]
The intermediate transfer belt 5a is stretched around a driving roller 40, a first driven roller (tension roller) 41, and a second driven roller (idler roller) 42 as stretching members, and the driving roller 40 rotates. 2 is configured to be rotatable in the direction of the arrow (clockwise) in FIG. The photosensitive drum 1 rotates the photosensitive drum 1 in a direction opposite to the arrow direction in FIG. 2 (counterclockwise) in synchronization with the rotation of the intermediate transfer belt 5a.

  The surface of the photosensitive drum 1 is uniformly charged by the charging device 2 and a yellow image is exposed by the exposure unit 3 to form a yellow electrostatic latent image on the photosensitive drum 1. Simultaneously with the formation of the electrostatic latent image, the rotary developing device 4 is driven to place the yellow developing device 4Y at the developing position, and a voltage having the same polarity as the charging polarity on the photosensitive drum 1 is applied. As a result, yellow toner adheres to the electrostatic latent image on the photosensitive drum 1, and the yellow toner image is developed. Thereafter, a voltage having a polarity opposite to that of the toner is applied to the primary transfer roller 5j in the intermediate transfer belt unit to primarily transfer the yellow toner image on the photosensitive drum 1 onto the intermediate transfer belt 5a.

  When the primary transfer of the yellow toner image is completed, the rotary developing device 4 rotates and the developing devices (4M, 4C, 4Bk) of other colors are positioned at the developing positions facing the photosensitive drum 1, and in the case of yellow Similarly to the above, formation of an electrostatic latent image, development of a toner image, and primary transfer are performed. In this way, for each color of magenta, cyan, and black, electrostatic latent image formation, development, and primary transfer are sequentially performed, and four color toner images are superimposed on the intermediate transfer belt 5a. During this time, the secondary transfer roller 11 is not in contact with the intermediate transfer belt 5a. At this time, the charging brush 22 and the charging roller 23 as the cleaning unit are also in a non-contact state with the intermediate transfer belt 5a.

  After the four color toner images are formed on the intermediate transfer belt 5a, the secondary transfer roller 11 is brought into contact with the intermediate transfer belt 5a (the state shown in FIG. 2). In synchronism with the rotation of the intermediate transfer belt 5a, recording paper as a transfer medium (recording material) is separated and fed one by one from the stacking means 19 by the pickup roller 18. The recording paper that has been waiting at a predetermined position is fed into the nip portion between the intermediate transfer belt 5 a and the secondary transfer roller 11 by a pair of conveying rollers 7 d that are refeeding means.

  Here, immediately before the conveying roller pair 7d, there is provided a registration sensor (not shown) that detects the leading edge of the recording paper, temporarily interrupts the rotational driving force of the conveying roller pair 7d, and waits the recording paper at a predetermined position. Yes. Further, a voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller 11, and the toner image on the intermediate transfer belt 5a is secondarily transferred collectively onto the surface of the conveyed recording paper. The recording sheet on which the toner images of a plurality of colors are secondarily transferred is fixed on the toner image by the fixing device 8 and then discharged onto the discharge tray 10 above the color image forming apparatus A by the discharge roller pair 9. The Thus, image formation is completed.

  On the other hand, after the primary transfer, the cleaning charging brush 22 and the charging roller 23 are brought into contact with the intermediate transfer belt 5a, and the residual toner remaining on the intermediate transfer belt 5a is given a charge opposite to that at the time of transfer. The residual toner to which the reverse charge is applied is electrostatically attached to the photosensitive drum 1 and then collected by the cleaning blade 6 for the photosensitive drum 1. Here, the drive roller 40 is wider than the secondary transfer roller 11 in the width direction, and wider than the cleaning charging brush 22 and the charging roller 23. The driving roller 40 is coated with a rubber having a low electrical resistance, and functions as a counter electrode for the secondary transfer roller 11, the cleaning charging brush 22, and the charging roller 23.

[Intermediate transfer belt unit and photosensitive drum unit]
3 is a schematic main cross-sectional view of the intermediate transfer belt unit 21 and the photosensitive drum unit 20, and FIG. 4 is a schematic cross-sectional view of the intermediate transfer belt unit 21 and the photosensitive drum unit 20 of FIG. .

  The photosensitive drum unit 20 is disposed above the intermediate transfer belt 5a of the intermediate transfer belt unit 21, and a waste toner box 16 is disposed on the front (front) side of the apparatus. In the photosensitive drum unit 20, both ends of the photosensitive drum 1 are rotatably held by the right bearing 202 and the left bearing 206, and a predetermined rotational driving force is transmitted from the apparatus main body via the coupling 49 at the right end. It has become. The charging roller 2 is pressed against the photosensitive drum 1 with a predetermined force by a compression spring 26 via bearings 25 at both ends, and is driven to rotate with respect to the photosensitive drum 1.

  In the intermediate transfer belt unit 21, the intermediate transfer belt 5 a is stretched around a driving roller 40, a tension roller 41, and an idler roller 42. The driving roller 40 of the intermediate transfer belt unit 21 is provided with a cleaning charging brush 22 and a charging roller 23 for applying a charge having a polarity opposite to that at the time of transfer to the residual toner on the intermediate transfer belt 5a. Both ends of the drive roller 40 are rotatably supported by the right bearing 201 and the left bearing 205, and a predetermined rotational drive is transmitted from the apparatus main body via the drive gear 48 of the right bearing portion. The bearings at both ends of the tension roller 41 are provided with compression springs 44 so as to apply a predetermined tension to the intermediate transfer belt 5a. A primary transfer roller 5j is provided at a position facing the photosensitive drum 1 with the intermediate transfer belt 5a interposed therebetween, and a predetermined force is applied to the intermediate transfer belt 5a by a compression spring 47 via bearings 46 at both ends. The roller is pressed against the photosensitive drum 1 and is driven to rotate. At least one of the bearings is formed of a conductive member, and the toner on the surface of the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5a by applying a predetermined bias to the primary transfer roller 5j. .

[Alignment and density adjustment of each color toner image of full color image]
The intermediate transfer belt 5a is provided with detection means for detecting the position of the intermediate transfer belt 5a in the transport direction and adjusting the position and density of each color toner image superimposed on the intermediate transfer belt 5a.

  A light reflecting marker 71 is stuck outside the image forming area in the width direction of the intermediate transfer belt 5a. A reflection type photosensor (photosensor) 70 is arranged at a predetermined position so as to face this. Here, the width direction of the intermediate transfer belt 5a is a direction orthogonal to the moving direction of the intermediate transfer belt 5a. The image forming region in the width direction of the intermediate transfer belt 5a (width direction image forming region) is a region where a toner image can be transferred from the photosensitive drum 1 on the intermediate transfer belt 5a. By detecting the reflected light from the marker 71 of the light reflector, the image writing reference position in the transport direction of the intermediate transfer belt 5a is detected, and the image on the photosensitive drum 1 by the exposure means 3 is synchronized with this detection signal. The data write timing is controlled. Therefore, the conveyance speed of the intermediate transfer belt 5a must be stable in order to synchronize the image writing timing. When the conveyance speed becomes unstable, the image writing timing cannot be synchronized and a color misregistration image is generated.

The optical sensor 70 also performs density adjustment correction by detecting the detection patch based on the toner image of each color formed on the intermediate transfer belt 5a and the reflected light intensity on the surface of the intermediate transfer belt 5a. Accordingly, the deformation of the belt at the detection position of the intermediate transfer belt 5a leads to a detection error, resulting in a density adjustment error. Therefore, it is necessary to suppress the deformation of the intermediate transfer belt 5a as much as possible. A rubbing member 72 that abuts against the back surface of the intermediate transfer belt 5a is disposed at a position facing the optical sensor 70 in order to suppress deformation of the intermediate transfer belt 5a. The rubbing member 72 is a plate-like member having a substantially rectangular cross section extending in the belt width direction, and both ends thereof are fixed to a frame member of the intermediate transfer belt unit 21 (not shown). The rubbing member 72 is pressed against the intermediate transfer belt 5a in the width direction of the intermediate transfer belt 5a with a width equal to or larger than the width of the image forming area of the intermediate transfer belt 5a. Further, the area pressed by the rubbing member 72 includes an area corresponding to an area in the intermediate transfer belt 5a that reflects light from the optical sensor.

  FIG. 5 is a schematic diagram showing the concept of the force acting on the rubbing member 72 in contact with the back surface of the intermediate transfer belt 5a. The force N (vertical drag) generated on the rubbing member 72 due to the tension of the intermediate transfer belt 5a, the friction coefficient μ between the intermediate transfer belt 5a and the rubbing member 72, and the force generated in the conveying direction of the intermediate transfer belt 5a are F (tangential). Force), it is expressed as F = μ · N. Accordingly, the tangential force F increases as the vertical drag N or the friction coefficient μ between the intermediate transfer belt 5a and the rubbing member 72 increases. In particular, if the friction coefficient μ is large, stick slip is likely to occur, and if stick slip occurs, the tangential force F fluctuates, causing the rubbing member 72 to vibrate.

[Generation of abnormal noise due to vibration of rubbing member]
With reference to FIGS. 6-9, the vibration direction in the conventional-shaped rubbing member is demonstrated. 6 is a cross-sectional shape of the rubbing member 72 in contact with the back surface of the intermediate transfer belt 5a, FIG. 7 is a view taken along the arrow A of the rubbing member 72 in FIG. 6, and FIG. An arrow view is shown. Here, the conveyance direction of the intermediate transfer belt 5a is defined as the x-axis, the height direction is defined as the z-axis, and the width direction of the intermediate transfer belt 5a is defined as the y-axis.

  In the cross-sectional shape of the rubbing member 72 of FIG. 6, W1 indicates the width in the conveyance direction of the intermediate transfer belt 5a, H1 indicates the height, and the height H1 is smaller than the width W1. D1 in FIGS. 7 and 8 indicates the length of the rubbing member 72 in the width direction of the intermediate transfer belt 5a. The shape of the rubbing member 72 having this cross-sectional shape is such that the projected area (W1 × D1) of the shape projected on the virtual surface parallel to the image forming surface of the intermediate transfer belt 5a is on the image forming surface of the intermediate transfer belt 5a. It becomes larger than the projected area (H1 × D1) of the shape projected on the vertical virtual plane.

  Y1 in FIG. 7 indicates the maximum amount of deformation in the height direction when the rubbing member 72 is deformed into an arc shape by receiving the vertical drag N, and x1 in FIG. 8 indicates that the rubbing member 72 is tangent. The maximum value of the amount of deformation in the conveyance direction when deformed into an arc shape by receiving the force F is shown.

  FIG. 9 shows the relationship between the cross-sectional secondary moment and the ratio between the width W1 and the height H1 in the rubbing member 72 having a rectangular cross section with the width W1 and the height H1 as shown in FIG. The cross-sectional secondary moment on the vertical axis and the ratio between the width W1 and the height H1 on the horizontal axis are logarithmically displayed. Here, the ratio of the width W1 to the height H1 is such that the projected area of the shape projected on the virtual plane parallel to the image forming surface of the intermediate transfer belt 5a and the virtual plane perpendicular to the image forming surface of the intermediate transfer belt 5a. It is equal to the ratio of the projected area of the shape projected onto.

  In FIG. 9, Ix1 is a cross-sectional secondary moment around the x-axis calculated from the cross-sectional shape of the rubbing member 73 (cross-sectional secondary moment with respect to the x-axis in a cross section perpendicular to the x-axis), and Iz1 is around the z-axis. The moment of inertia is shown. Dx1 is the value of the cross-sectional secondary moment around the x axis required for the rubbing member 72 in design, and Dz1 is the value of the cross-sectional secondary moment around the z axis required in the design for the rubbing member 72. Each is determined by the material of the rubbing member 72 itself and the allowable value of the detection error of the optical sensor.

  For example, when the width W1 and the height H1 are the same value, that is, when the cross section is a square, Ix1 and Iz1 have the same value. The ease of deformation is the same. When the height H1 is smaller than the width W1 (FIG. 6), Iz1 is larger than Ix1, and the rubbing member 72 has higher rigidity with respect to the force in the transport direction than the force in the height direction. Represents. That is, when the height H1 is smaller than the width W1 as shown in FIG. 6, assuming that the tangential force F and the vertical drag N are the same value, the maximum deformation amount y1 of the rubbing member 72 in the height direction. (FIG. 7) is larger than the maximum value x1 (FIG. 8) of the deformation amount of the rubbing member 72 in the transport direction.

  Therefore, when the rubbing member 72 has a rectangular cross section in which the height H1 is smaller than the width W1 as shown in FIG. 6, when the resultant force of the tangential force F and the normal force N is applied, the height is higher than the conveying direction. It can be said that it is easy to deform in the direction. That is, when stick-slip occurs and the tangential force F fluctuates, it largely vibrates mainly in the height direction. When the rubbing member 72 mainly vibrates in the height direction, the image forming surface having a large surface area of the intermediate transfer belt 5a vibrates up and down, so that the sound pressure is proportional to the surface area in the vibrating direction. , Easy to generate abnormal noise.

[Configuration to reduce the occurrence of abnormal noise]
With reference to FIGS. 9-12, the structure which reduces the noise generated by the vibration of the rubbing member which is the characteristics of this invention is demonstrated. 10 is a cross-sectional shape of the rubbing member 73 in contact with the back surface of the intermediate transfer belt 5a, FIG. 11 is a view taken along the arrow A of the rubbing member 73 in FIG. 10, and FIG. An arrow view is shown. Here, the conveyance direction of the intermediate transfer belt 5a is defined as the x-axis, the height direction is defined as the z-axis, and the width direction of the intermediate transfer belt 5a is defined as the y-axis.

  In the cross-sectional shape of the rubbing member 73 in FIG. 10, W1 indicates the width in the transport direction of the intermediate transfer belt 5a, and H1 indicates the height. The height H1 is larger than the width W1. D1 in FIGS. 11 and 12 indicates the length of the rubbing member 73 in the width direction of the intermediate transfer belt 5a. The shape of the rubbing member 73 having this cross-sectional shape is such that the projection area (W1 × D1) of the projection shape of the virtual surface parallel to the image forming surface of the intermediate transfer belt 5a is perpendicular to the image forming surface of the intermediate transfer belt 5a. It becomes smaller than the projected area (H1 × D1) of the projected shape of the virtual plane.

  11 indicates the maximum value of the amount of deformation in the height direction when the rubbing member 73 is deformed into an arc shape by receiving the vertical drag N, and x2 in FIG. 12 indicates that the rubbing member 73 is tangent. The maximum value of the amount of deformation in the conveyance direction when deformed into an arc shape by receiving the force F is shown.

  As can be seen from FIG. 9, when the height H1 is larger than the width W1, Iz1 is smaller than Ix1, indicating that the rigidity with respect to the force in the conveying direction is lower than the force in the height direction. In this embodiment, the width W1 and the height H1 are determined in a range where H1 / W1 exceeds 1 and Ix1 and Iz1 are larger than Dx1 and Dz1, that is, smaller than A1 in FIG. . Assuming that the tangential force F and the vertical drag N have the same value, the maximum deformation amount y2 (FIG. 10) of the rubbing member 73 in the height direction is the maximum value x2 of the deformation amount of the rubbing member 73 in the transport direction. FIG. 8) a smaller value.

  Therefore, when the rubbing member 73 as shown in FIG. 10 has a rectangular cross section in which the height H1 is larger than the width W1, when the resultant force of the tangential force F and the normal force N is applied, the conveyance is performed in the height direction. It can be said that it is easy to deform in the direction. That is, when stick slip occurs and the tangential force F fluctuates, it largely vibrates mainly in the transport direction. When the rubbing member 73 mainly vibrates in the transport direction, the image forming surface having a large surface area of the intermediate transfer belt 5a vibrates in the front-rear direction in the transport direction, and noise is hardly generated.

  Up to this point, the configuration in which the rubbing member 73 directly contacts the back surface of the intermediate transfer belt 5a has been described. However, a conductive sheet or the like is disposed on the abutting surface of the rubbing member 73 with the intermediate transfer belt 5a. Also good.

As described above, in the image forming apparatus according to the present embodiment, the surface on which the rubbing member 73 is pressed against the intermediate transfer belt 5a is smaller than the surface that is perpendicular to the image forming surface and extends in the width direction. Features. That is, with respect to the shape of the rubbing member 73, the area within the width of the image forming area of the projected shape with respect to the virtual plane parallel to the image forming surface of the intermediate transfer belt 5a is set to a virtual plane perpendicular to the image forming surface and perpendicular to the transport direction. Is smaller than the area within the width of the image forming area of the projected shape. Therefore, the cross-sectional secondary moment with respect to the axis perpendicular to the image forming surface of the rubbing member 73 is larger than the cross-sectional secondary moment with respect to the axis parallel to the transport direction. According to such a configuration, even when the tangential force F applied to the rubbing member 73 fluctuates, the surface area in the vibrating direction of the intermediate transfer belt 5a is reduced by vibrating the intermediate transfer belt 5a in the front-rear direction. It is possible to make it difficult to generate abnormal noise. As a result, even when the back surface of the intermediate transfer belt 5a and the rubbing member 73 are rubbed and the friction coefficient μ increases to cause stick slip and the rubbing member 73 vibrates, noise can be reduced with a simple configuration. Can do. That is, it is possible to realize a color electrophotographic image forming apparatus that is compact and prevents abnormal noise.

  In this embodiment, the projection shape of the rubbing member is defined based on the image forming surface as the conveying surface for conveying the image on the intermediate transfer belt. However, in the case of the belt conveying device, the recording material is recorded on the conveying belt. What is necessary is just to use the conveyance surface which conveys as a reference. Further, in this embodiment, the case where the present invention is applied to a rotary type image forming apparatus has been described. However, a tandem type image forming apparatus provided with an image forming unit including a photosensitive drum and a developing device for each toner color, or a single color Needless to say, the present invention can also be applied to a monocolor image forming apparatus.

(Example 2)
An image forming apparatus according to a second embodiment of the present invention will be described with reference to FIGS. Here, differences from the first embodiment will be mainly described, and the same reference numerals are given to common configurations, and description thereof will be omitted as appropriate. Matters not specifically described here are the same as those in the first embodiment.

  The image forming apparatus according to the present embodiment includes a rubbing unit that includes a rubbing member that rubs against the back surface of the intermediate transfer belt 5a and a support member that supports the rubbing member. In the first embodiment, the shape of the sliding member is configured to reduce the occurrence of abnormal noise. However, in this embodiment, the shape of the support member that supports the sliding member is configured to reduce the occurrence of abnormal noise. It is said.

[Generation of abnormal noise due to vibration of rubbing member]
With reference to FIGS. 13-16, the vibration direction in the conventional-shaped rubbing means is demonstrated. 13 is a cross-sectional shape of the rubbing member 74 and the support member 75 that are in contact with the back surface of the intermediate transfer belt 5a, FIG. . Here, the conveyance direction of the intermediate transfer belt 5a is defined as the x-axis, the height direction is defined as the z-axis, and the width direction of the intermediate transfer belt 5a is defined as the y-axis.

  In the cross-sectional shape of the support member 75 in FIG. 13, W2 indicates the width in the conveyance direction of the intermediate transfer belt 5a, H2 indicates the height, and t indicates the thickness. The height H2 is smaller than the width W2. 14 and 15 indicate the length of the support member 75 in the width direction of the intermediate transfer belt 5a. The shape of the support member 75 having this cross-sectional shape is such that the projection area (W2 × D2) of the projection shape of the virtual surface parallel to the image forming surface of the intermediate transfer belt 5a is perpendicular to the image forming surface of the intermediate transfer belt 5a. It becomes larger than the projected area (H2 × D2) of the projected shape of the surface.

  The rubbing member 74 is a flat plate member having a small thickness in the height direction, the upper surface is pressed against the intermediate transfer belt 5 a, and the lower surface is fixed to the support member 75. The support member 75 is a member having a substantially L-shaped cross section extending in the belt width direction, and both ends thereof are fixed to a frame member of the intermediate transfer belt unit 21 (not shown).

14 indicates the maximum value of the deformation amount in the height direction when the support member 75 receives the vertical drag N via the rubbing member 74 and deforms into an arc shape. Further, x3 in FIG. 15 indicates the maximum value of the deformation amount in the transport direction when the support member 75 receives the tangential force F via the rubbing member 74 and deforms into an arc shape. Here, when considering the deformation amount of the support member 75, the rigidity of the rubbing member 74 is sufficiently lower than the rigidity of the support member 75, and the rigidity of the rubbing member 74 is negligible.

  FIG. 16 shows the relationship between the cross-sectional secondary moment and the ratio of the width W2 to the height H2 in the support member 75 having the L-shaped cross section with the width W2 and the height H2 as shown in FIG. The cross-sectional secondary moment on the vertical axis and the ratio between the width W2 and the height H2 on the horizontal axis are respectively logarithmically displayed.

  In FIG. 16, Ix2 represents a cross-sectional secondary moment about the x-axis calculated from the cross-sectional shape of the support member 75, and Iz2 represents a cross-sectional secondary moment about the z-axis. Dx2 is a value of the cross-sectional secondary moment around the x axis necessary for the support member 75 in design, and Dz2 is a value of the cross-sectional secondary moment around the z axis required in the design of the support member 75. Each is determined by the material of the support member 75 itself and the allowable value of the detection error of the optical sensor.

  For example, when the width W2 and the height H2 have the same value, that is, when the cross section has the same length of the short side and the long side, Ix2 and Iz2 have the same value. The ease of bending in the height direction and the ease of deformation in the transport direction are the same. Further, when the height H2 is smaller than the width W2 (FIG. 13), Iz2 is larger than Ix2, and the support member 75 has higher rigidity with respect to the force in the transport direction than the force in the height direction. Represents. That is, when the height H2 is smaller than the width W2 as shown in FIG. 13, assuming that the tangential force F and the vertical drag N are the same value, the maximum deformation amount y3 (in the height direction of the support member 75) 14) is larger than the maximum value x3 (FIG. 15) of the deformation amount of the support member 75 in the transport direction.

  Therefore, when the support member 75 has an L-shaped cross section whose height H2 is smaller than the width W2 as shown in FIG. 13, when the resultant force of the tangential force F and the normal force N is applied, the height is higher than the conveying direction. It can be said that it is easy to deform in the direction. That is, when stick-slip occurs and the tangential force F fluctuates, it largely vibrates mainly in the height direction. When the support member 75 mainly vibrates in the height direction, the image forming surface having a large surface area of the intermediate transfer belt 5a vibrates up and down, so that the sound pressure is proportional to the surface area in the vibrating direction. Abnormal noise is likely to occur.

[Configuration to reduce the occurrence of abnormal noise]
The structure which reduces the abnormal noise which generate | occur | produces by the vibration of the supporting member which is the characteristics of this invention is demonstrated using FIGS. 17 is a cross-sectional shape of the rubbing member 76 and the support member 77 that are in contact with the back surface of the intermediate transfer belt 5a, FIG. 18 is a view as viewed from an arrow A in FIG. 17, and FIG. . Here, the conveyance direction of the intermediate transfer belt 5a is defined as the x-axis, the height direction is defined as the z-axis, and the width direction of the intermediate transfer belt 5a is defined as the y-axis.

  In the cross-sectional shape of the support member 77 in FIG. 17, W2 indicates the width in the transport direction of the intermediate transfer belt 5a, and H2 indicates the height. The height H2 is larger than the width W2. D1 in FIGS. 18 and 19 indicates the length of the support member 77 in the width direction of the intermediate transfer belt 5a. The shape of the support member 77 having this cross-sectional shape is such that the projection area (W2 × D2) of the projection shape of the virtual surface parallel to the image forming surface of the intermediate transfer belt 5a is perpendicular to the image forming surface of the intermediate transfer belt 5a. It becomes smaller than the projected area (H2 × D2) of the projected shape of the surface.

  The rubbing member 76 is a flat plate member having a small thickness in the height direction, the upper surface is pressed against the intermediate transfer belt 5 a, and the lower surface is fixed to the support member 77. The support member 77 is a member having a substantially L-shaped cross section extending in the belt width direction, and both ends thereof are fixed to a frame member of the intermediate transfer belt unit 21 (not shown). The support member 77 extends substantially perpendicularly to the image forming surface and supports a surface of the rubbing member 76 opposite to the belt contact surface, and a side of the first support portion that supports the rubbing member 76. And a second support portion extending substantially parallel to the image forming surface from the opposite side.

  18 indicates the maximum value of the amount of deformation in the height direction when the support member 77 receives the vertical drag N via the rubbing member 76 and deforms into an arc shape. Further, x4 in FIG. 19 indicates the maximum value of the deformation amount in the transport direction when the support member 77 receives the tangential force F via the rubbing member 76 and deforms into an arc shape. Here, when considering the deformation of the support member 77, the rigidity of the rubbing member 76 is sufficiently lower than the rigidity of the support member 77, and the rigidity of the rubbing member 76 is negligible.

  As can be seen from FIG. 16, when the height H2 is larger than the width W2, Iz2 is smaller than Ix2, indicating that the rigidity with respect to the force in the conveying direction is lower than the force in the height direction. In this embodiment, the width W2 and the height H2 are determined in a range where H2 / W2 exceeds 1 and Ix2 and Iz2 are larger than Dx2 and Dz2, that is, smaller than A2 in FIG. . Assuming that the tangential force F and the vertical drag N have the same value, the maximum deformation amount y4 (FIG. 18) of the support member 77 in the height direction is the maximum deformation amount x4 of the support member 77 in the transport direction. FIG. 19) a smaller value.

  As described above, when the support member 77 as shown in FIG. 17 has an L-shaped cross section in which the height H2 is larger than the width W2, when the resultant force of the tangential force F and the normal force N is applied, Can be said to be easily deformed in the transport direction. That is, when stick slip occurs and the tangential force F fluctuates, it largely vibrates mainly in the transport direction. When the support member 77 mainly vibrates in the transport direction, the image forming surface having a large surface area of the intermediate transfer belt 5a vibrates mainly in the front-rear direction, and noise is hardly generated.

  Up to this point, the configuration in which the rubbing member 76 directly contacts the back surface of the intermediate transfer belt 5a has been described. However, a conductive sheet or the like is disposed on the abutting surface of the rubbing member 76 with the intermediate transfer belt 5a. Also good.

  As described above, the image forming apparatus according to the present embodiment is characterized in that the height of the support member 77 in the direction perpendicular to the image forming surface is larger than the width in the direction parallel to the image forming surface. To do. That is, with respect to the shape of the support member 77, the area within the width of the image forming region of the projected shape with respect to the virtual plane parallel to the image forming surface of the intermediate transfer belt 5a is set to the virtual plane perpendicular to the image forming surface and perpendicular to the transport direction The area is smaller than the area within the width of the projected image forming area. Therefore, the secondary moment of inertia related to the axis perpendicular to the image forming surface of the support member 77 is larger than the secondary moment of inertia related to the axis parallel to the transport direction. According to such a configuration, even when the tangential force F applied to the support member 77 fluctuates, the surface area in the vibrating direction of the intermediate transfer belt 5a is reduced by vibrating the intermediate transfer belt 5a in the front-rear direction. It is possible to make it difficult to generate sound. Thereby, even when the back surface of the intermediate transfer belt 5a and the rubbing member 76 are rubbed and the friction coefficient μ increases to cause stick slip and the support member 77 vibrates, noise can be reduced with a simple configuration. it can. That is, it is possible to realize a color electrophotographic image forming apparatus that is compact and prevents abnormal noise.

  A ... Image forming apparatus, 5a ... Intermediate transfer belt, 70 ... Optical sensor (detection means), 73, 76 ... Rub member, 77 ... Support member

Claims (9)

A belt that is movable to convey a toner image to be transferred to the recording material or a recording material to which the toner image is transferred;
Detecting means facing the outer peripheral surface of the belt;
Pressed against the inner peripheral surface of the belt, and a rubbing member for rubbing against the moving belt,
A support member for supporting the rubbing member;
In an image forming apparatus comprising:
The support member includes a first support portion that supports a surface of the rubbing member opposite to the contact surface with the belt, and a side of the first support portion that is opposite to the side that supports the rubbing member. A second support portion extending in parallel with the outer peripheral surface,
Wherein the area of the projected shape with respect to the virtual plane parallel to the outer peripheral surface, an image forming apparatus and is smaller than the area of the projected shape with respect to an imaginary plane perpendicular to the vertical and the transport direction on the outer peripheral surface. In the belt width direction, the rubbing member has an image forming area in which a toner image on the outer peripheral surface can be transferred, or an image forming area in which a toner image on a conveyed recording material can be transferred. The image forming apparatus according to claim 1 , wherein the image forming apparatus is pressed against the inner peripheral surface of the belt with a width equal to or greater than the width of the belt. Wherein the support member, the image forming apparatus according to claim 1 or claim 2, characterized in that it is secured at both ends to a frame member for supporting the tension member for stretching the belt. 4. The support member according to any one of claims 1 to 3 , wherein a second moment of section with respect to an axis perpendicular to the outer peripheral surface is greater than a second moment of section with respect to an axis parallel to the conveying direction. The image forming apparatus described. Wherein the support member, the height of a direction perpendicular to the conveying surface, the image of any one of claims 1 to 4, characterized in that greater than a width in a direction parallel to the conveying surface Forming equipment. The rubbing member is an image forming apparatus according to any one of claims 1 to 5 via the conductive sheet, characterized in that it is pressed against the belt. The image forming apparatus according to claim 1, wherein the detection unit includes a reflective optical sensor. The image forming apparatus according to claim 1, wherein the detection unit detects a reference position included in the belt. The image forming apparatus according to claim 1, wherein the detection unit detects a detection patch formed by toner formed on the belt.

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