JP2015191150A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce rubbing noise which is generated when an intermediate transfer belt and a transfer member rub on each other.SOLUTION: An image forming apparatus includes: an intermediate transfer belt 11 which circulates; a photoreceptor drum 7 arranged on the side of an outer peripheral surface of the intermediate transfer belt 11, and carrying a toner image; and a brush-like transfer member 20 that comprises a brush bristling section 24 extended in a position facing the photoreceptor drum 7 toward an inner peripheral surface of the intermediate transfer belt 11, and having a tip rubbing on the inner peripheral surface by circulating the intermediate transfer belt 11, and transfers the toner image carried on the photoreceptor drum 7 to the side of the outer peripheral surface of the intermediate transfer belt 11. The image forming apparatus includes a contact angle changing mechanism 30 for changing a direction of the tip of the bristling section 24 with respect to the inner peripheral surface of the intermediate transfer belt 11.

Description

  The present invention relates to an image forming apparatus.

  Conventionally, as an image forming apparatus such as a copying machine or a printer using an electrophotographic system, there is a system using an intermediate transfer belt. In an image forming apparatus using this intermediate transfer belt, a full color image is formed through a primary transfer process and a secondary transfer process. As the primary transfer member of the image forming apparatus, a transfer member such as a roller shape, a blade shape, or a brush shape is used. These transfer members are in contact with the inner peripheral surface of the intermediate transfer belt at a position facing the photoconductor, and are used by applying a primary transfer voltage. In particular, the brush-like transfer member is composed of a group of conductive fibers, and each fiber can abut against the back surface of the intermediate transfer belt independently. Therefore, there is a feature that uneven contact that occurs when a roller-like or blade-like transfer member is used is improved, and a more uniform contact with the inner peripheral surface of the intermediate transfer belt is obtained. As a result, image defects such as density unevenness that occur in the primary transfer step are satisfactorily suppressed.

  As a method for contacting the brush-shaped transfer member with the inner peripheral surface of the intermediate transfer belt, for example, there is a method disclosed in Patent Document 1. This method is a contact method in which the transfer member is inclined so that the fibers are in contact with the inner peripheral surface of the intermediate transfer belt in a state where the fibers are tilted downstream in the moving direction of the intermediate transfer belt. By this contact method, it is possible to prevent the fibers from randomly falling upstream and downstream in the moving direction of the intermediate transfer belt, and to limit the falling direction to the downstream side. As a result, abnormal discharge occurring on the upstream side of the primary transfer portion is prevented, and image defects such as vertical stripes are also satisfactorily suppressed.

JP 2001-134115 A

  As described above, the use of the brush-like transfer member as the primary transfer member has an advantage that image defects are suppressed. However, when a brush-shaped transfer member is used, the fiber tip of the brush-shaped transfer member is scraped off according to the number of sheets passing through the image forming apparatus as shown in FIG. The contact surface with the surface spreads. FIG. 8A shows a state of the brushed brush tip in the initial state, and FIG. 8B shows a state where the brushed brush tip is scraped after the paper is passed. By scraping the brush raising tip, the brush raising tip continues to slide with the belt in a state where the contact surface with the belt is widened, and the sliding force between the brush and the belt increases. This increases the possibility of generating a sliding noise during the circulation of the belt.

  SUMMARY An advantage of some aspects of the invention is that it reduces sliding noise generated when an intermediate transfer belt and a transfer member slide.

In order to achieve the above object, an image forming apparatus according to the present invention includes:
An endless belt that circulates,
An image carrier provided on the outer peripheral surface side of the belt and carrying a developer image;
A brushed portion that extends toward the inner circumferential surface of the belt at a position facing the image bearing member and has a tip portion that slides on the inner circumferential surface by the circulating movement of the belt; A transfer member for transferring the developer image carried thereon to the outer peripheral surface side of the belt;
An image forming apparatus having
It has a change means which changes the direction of the said front-end | tip part with respect to the said internal peripheral surface, It is characterized by the above-mentioned.

An image forming apparatus according to the present invention is
An endless belt that circulates,
An image carrier provided on the outer peripheral surface side of the belt and carrying a developer image;
A transfer member that contacts the inner peripheral surface of the belt at a position facing the image carrier, and transfers the developer image carried by the image carrier to the outer peripheral surface of the belt;
An image forming apparatus having
The transfer member has a first contact portion that can contact the inner peripheral surface of the belt, and a second contact portion different from the first contact portion,
It has a change means which changes the contact part with respect to the said internal peripheral surface from the said 1st contact part to the said 2nd contact part.

  According to the present invention, it is possible to reduce the sliding noise generated when the intermediate transfer belt and the transfer member slide.

Schematic sectional view of the overall configuration of the image forming apparatus according to the present embodiment The figure for demonstrating the primary transfer of Example 1 The perspective view which shows the structure of the brush-shaped transfer member of Example 1. FIG. Schematic sectional view showing the configuration of the brush-like transfer member of Example 1 The perspective view which shows the structure of the contact angle change mechanism of Example 1. FIG. The figure which shows the structure of the contact angle change mechanism of Example 1. FIG. The figure explaining the structure of the contact angle change mechanism of Example 1. The enlarged view of the brush raising front-end | tip part of the brush transfer member in Example 1 The figure explaining the structure of the contact angle change mechanism of Example 2. FIG. The figure explaining the structure of the contact angle change mechanism of Example 3.

  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.

<Overall configuration of image forming apparatus>
First, with reference to FIG. 1, an outline of the overall configuration of the image forming apparatus according to the present embodiment will be described. FIG. 1 is a schematic cross-sectional view of the overall configuration of the image forming apparatus according to the present embodiment. In this embodiment, a laser beam printer will be described as an example of the image forming apparatus. Further, as an image forming apparatus according to the present embodiment, a toner image as a developer image on the photosensitive drum 7 is sequentially transferred to an intermediate transfer belt (hereinafter also simply referred to as a belt) 11, and then the toner image on the belt 11 is transferred. A description will be given of a configuration that employs a configuration in which the recording material is collectively transferred. In this embodiment, image formation is performed using toner for forming images of each color of yellow Y, magenta M, cyan C, and black K. Hereinafter, in the case where it is not particularly necessary to distinguish, the subscripts Y, M, C, and K given to the reference numerals in order to indicate the elements provided for any color will be omitted.

As shown in FIG. 1, the image forming apparatus according to the present embodiment includes a feeding tray 1 as main components,
A secondary transfer roller 6, a photosensitive drum 7 as an image carrier, an exposure device 8, a developing roller 9, an intermediate transfer belt 11, a fixing film 13, a pressure roller 14, and a primary transfer member 20 are included. The feeding tray 1 is loaded with a recording material 2 such as paper. The photosensitive drum 7 is provided on the outer peripheral surface side of the intermediate transfer belt 11 so as to be rotatable in the counterclockwise direction in FIG. 1 (the direction of arrow A in FIG. 2 described later). The exposure device 8 forms an electrostatic latent image on the photosensitive drum 7 by irradiating laser light. The developing roller 9 supplies toner onto the photosensitive drum 7 to visualize the electrostatic latent image and forms a toner image on the photosensitive drum 7. The primary transfer member 20 primarily transfers the toner image formed on the photosensitive drum 7 to the outer peripheral surface of the intermediate transfer belt 11. The intermediate transfer belt 11 is a cylindrical and endless belt-like film, and is stretched by two rollers, an in-belt driving roller 5 and a tension roller 12. The intermediate transfer belt 11 circulates and moves in the direction of arrow B in FIG. 1 at approximately the same speed as the movement speed of the surface of the photosensitive drum 7 when the in-belt driving roller 5 is rotationally driven in the clockwise direction in FIG. The secondary transfer roller 6 secondarily transfers the toner image primarily transferred onto the intermediate transfer belt 11 onto the recording material 2. The fixing film 13 and the pressure roller 14 fix the toner image secondarily transferred onto the recording material 2 by heating and pressing the recording material 2 conveyed to the nip portion thereof.

  Further, an outline of an image forming operation of the image forming apparatus according to the present embodiment will be described. First, the recording material 2 loaded and stored in the feeding tray 1 is fed by a feeding roller 3 that rotates in the clockwise direction in the drawing, is sent to a conveying roller 4, and is subjected to secondary transfer with an in-belt driving roller 5. It is sent to the nip portion of the roller 6. On the other hand, in each image forming unit, electrostatic latent images are sequentially formed on the outer peripheral surfaces of the photosensitive drums 7Y, 7M, 7C, and 7K by the laser light from the exposure device 8, and the electrostatic latent images are subsequently formed on the developing rollers 9Y, The toner image is formed by developing with 9M, 9C, and 9K.

  The toner images formed on the photosensitive drums 7 </ b> Y, 7 </ b> M, 7 </ b> C, 7 </ b> K are pressed and applied with voltages by the primary transfer members 20 </ b> Y, 20 </ b> M, 20 </ b> C, 20 </ b> K, and are sequentially primary transferred onto the outer peripheral surface of the intermediate transfer belt 11. Next, the toner image primarily transferred to the intermediate transfer belt 11 is collectively transferred to the recording material 2 sent to the nip portion between the in-belt driving roller 5 and the secondary transfer roller 6. Further, the recording material 2 onto which the toner image has been transferred is sent to the nip portion between the fixing film 13 and the pressure roller 14 where it is heated and pressurized to fix the toner image on the recording material 2. The recording material 2 on which the toner image is fixed is discharged out of the image forming apparatus by a discharge roller 15 and a discharge roller 16.

(Example 1)
<Primary transfer>
Next, with reference to FIG. 2, the details of the operation until the primary transfer is performed in the image forming operation of Embodiment 1 will be described. FIG. 2 is a diagram for explaining the primary transfer in the first embodiment.

  The photosensitive drum 7 is rotationally driven in a counterclockwise direction in FIG. 2 by a driving unit (not shown). The surface of the photosensitive drum 7 is uniformly charged by the charging roller 17. Then, a laser beam according to the image information is irradiated from the exposure device 8 to the photosensitive drum 7, and an electrostatic latent image is formed on the photosensitive drum 7. Further, when the surface of the photosensitive drum 7 advances in the direction of arrow A (counterclockwise direction) in FIG. 2, toner is supplied to the surface of the photosensitive drum 7 according to the image information by the developing roller 9, and the electrostatic latent image is developed. As a result, a toner image is formed on the photosensitive drum 7. The developing roller 9 develops the latent image on the photosensitive drum 7 by a reversal developing method. That is, the developing roller 9 causes the toner (negative polarity) charged with the same polarity as the charging polarity (negative polarity) of the photosensitive drum 7 to adhere to the image portion (exposure portion) on the uniformly charged photosensitive drum 7. Develop.

In the direction of arrow A (counterclockwise direction) in FIG. 2 of the photosensitive drum 7, the surface of the photosensitive drum 7 is positioned downstream of a position facing the developing roller 9 (hereinafter referred to as a developing position) as an intermediate transfer member. An intermediate transfer belt 11 is disposed. The intermediate transfer belt 11 circulates in the direction of arrow B in FIGS. A brush-like transfer member 20 as a primary transfer member is disposed at a position facing the photosensitive drum 7 via the intermediate transfer belt 11.

  The brush-like transfer member 20 is bonded to a holding member 31 that holds the brush-like transfer member 20 with a double-sided tape 21. The brush-like transfer member 20 is pressed against the photosensitive drum 7 and the intermediate transfer belt 11 by a pressing force from the holding member 31 in a direction substantially perpendicular to the inner peripheral surface of the intermediate transfer belt 11. By this pressing, a primary transfer nip 22 that is a contact portion between the photosensitive drum 7 and the intermediate transfer belt 11 is formed. As the intermediate transfer belt 11 circulates, the inner peripheral surface of the intermediate transfer belt 11 and a brush raising portion (raising portion) 24 of the brush-like transfer member 20 described later slide.

  As the photosensitive drum 7 rotates and the intermediate transfer belt 11 circulates, the toner image formed on the photosensitive drum 7 is primarily transferred onto the outer peripheral surface of the intermediate transfer belt 11 by the action of the brush-like transfer member 20. At this time, a primary transfer voltage having a polarity (positive polarity) opposite to the toner charging polarity (negative polarity) is applied to the brush-like transfer member 20 by a primary transfer power source (not shown).

  The charging, exposure, development, and primary transfer processes as described above are performed for each color of yellow, magenta, cyan, and black sequentially from the upstream side in the moving direction of the surface of the intermediate transfer belt 11. As a result, a full-color image in which toner images of four colors of yellow, magenta, cyan, and black are superimposed on the outer peripheral surface of the intermediate transfer belt 11 is formed.

(Configuration of brush-like transfer member)
Next, the configuration of the brush-like transfer member of Example 1 will be described with reference to FIGS. FIG. 3 is a perspective view illustrating a configuration of the brush-shaped transfer member of the first embodiment. FIG. 4 is a schematic cross-sectional view showing the configuration of the brush-like transfer member of Example 1. Note that the left side in FIG. 4 is the upstream side in the circulating movement direction of the intermediate transfer belt 11, and the right side is the downstream side.

  As shown in FIG. 3, the brush-like transfer member 20 includes a brush raising portion 24 made of conductive fibers, a base cloth portion 23 made of non-conductive fibers, and a double-sided tape 21. The brush raising portions 24 are densely arranged with raising in a substantially vertical direction with respect to the base cloth portion 23. The brush raising portion 24 is disposed so as to extend toward the inner peripheral surface of the intermediate transfer belt 11, and a tip portion in the extending direction is referred to as a brush raising tip portion 25.

  The size of the brush-like transfer member 20 in the longitudinal direction (the direction in which the intermediate transfer belt 11 is installed substantially perpendicularly to the circulating movement direction) is sufficiently wide with respect to the width of the recording material that can be printed by the image forming apparatus. The length can be formed. The size of the brush-like transfer member 20 in the short direction (circulation movement direction of the intermediate transfer belt 11, the left-right direction in FIG. 3) is wide enough to form a sufficient primary transfer nip 22 with the intermediate transfer belt 11. Is taking. The upstream end portion 24A of the brush raising portion 24 of the brush-like transfer member 20 in the circulating movement direction of the intermediate transfer belt 11 is arranged so as to be substantially straight in the longitudinal direction in order to obtain stable image formation. .

(Contact angle change mechanism)
With reference to FIGS. 5 to 8, by changing the angle of the brush-like transfer member 20 with respect to the inner peripheral surface of the intermediate transfer belt 11 of Example 1, the brush raising tip portion 25 of the brush raising tip portion 25 with respect to the inner peripheral surface of the intermediate transfer belt 11 is changed. The contact angle changing mechanism 30 that changes the direction will be described. FIG. 5 is a perspective view illustrating a configuration of a contact angle changing mechanism as a changing unit according to the first embodiment. FIG. 6 is a diagram illustrating a configuration of the contact angle changing mechanism according to the first embodiment. FIG. 7 is a diagram illustrating the configuration of the contact angle changing mechanism according to the first embodiment. 6 is a view seen from the direction of arrow X in FIG. 5, and FIG. 7 is a view seen from the direction of arrow Y in FIG.

  As shown in FIGS. 5 to 7, the contact angle changing mechanism 30 of the brush-like transfer member 20 in the first embodiment includes a holding member 31, a pressing member 32, a pressing spring 33, a rotating member 34, and a slide member 35. doing. For convenience of explanation, the intermediate transfer belt 11 is omitted in FIGS. 5 and 6, and the pressing member 32 and the pressing spring 33 are omitted in FIG. 7.

  As shown in FIG. 7A, the rotating member 34 is sandwiched and fixed between holding portions 31 a at both ends of the holding member 31. The rotating member 34 is provided so as to be rotatable with respect to the pressing member 32 with a round shaft 32A provided on the pressing member 32 as a rotation center. The pressing member 32 is controlled by a guide (not shown) to operate and rotate in the same direction as the circulating movement direction of the intermediate transfer belt 11, and operates only in a direction substantially perpendicular to the inner peripheral surface of the intermediate transfer belt 11. The pressing member 32 is urged in the direction of arrow C in FIG. 5 by the pressing spring 33, so that the brush-shaped transfer member 20 is pressed against the inner peripheral surface of the intermediate transfer belt 11 and the photosensitive drum 7 via the pressing member 32. Pressed.

  The slide member 35 is configured to linearly move in substantially the same direction as the circulating movement direction of the intermediate transfer belt 11 by a drive motor (not shown), a drive gear train, and a rack and pinion gear. As shown in FIG. 7, the round shaft 35 </ b> A provided on the slide member 35 engages with the elongated round hole 34 </ b> B provided on the rotating member 34, and slides in the same direction as the circulating movement direction of the intermediate transfer belt 11. The rectilinear motion of the member 35 is converted into a rotational motion around the round hole 34 </ b> A of the rotating member 34.

  FIG. 7A is a diagram illustrating a state in which the contact angle of the brush-like transfer member 20 with respect to the intermediate transfer belt 11 in the first embodiment is in an initial state. FIG. 7B is a diagram illustrating a state where the brush-like transfer member 20 according to the first embodiment is rotated in the clockwise direction in the drawing from the initial state. FIG. 7C is a diagram illustrating a state in which the brush-like transfer member 20 according to the first exemplary embodiment is rotated counterclockwise in the drawing from the initial state.

  As shown in FIG. 7B, the slide member 35 linearly moves from the state shown in FIG. 7A in the direction opposite to the circulating movement direction (arrow B direction) of the intermediate transfer belt (arrow D1 direction). The rotating member 34 rotates in the clockwise direction (arrow E1 direction) around the round hole 34A. As a result, the contact angle of the brush-like transfer member 20 to the belt is changed to the angle shown in FIG. On the other hand, as shown in FIG. 7C, the slide member 35 rotates straight from the state of FIG. 7A in the same direction as the circulating movement direction of the intermediate transfer belt 11 (in the direction of arrow D2). The member 34 rotates counterclockwise (arrow E2 direction) around the round hole 34A. As a result, the contact angle of the brush-like transfer member 20 to the belt is changed to the angle shown in FIG.

  In the first embodiment, in order to change the contact angle of the brush-like transfer member 20 with respect to the intermediate transfer belt 11, a system in which the rotation drive of the drive motor is transmitted to the rotation member 34 by the rack and pinion gear is used. However, the present invention is not limited to this, and in order to change the contact angle with respect to the intermediate transfer belt 11, for example, a gear (the central axis of the round hole 34 </ b> A) is attached to the rotating member 34 by a gear train. It is also possible to use a method of transmitting to the above. Or you may use the system which transmits the rotational drive of a drive motor to the rotation member 34 by a link mechanism. In the first embodiment, the rotation center of the brush-like transfer member 20 is disposed below the holding member 31 as described above. However, a configuration in which the rotation center is disposed in the vicinity of the primary transfer nip 22 may be used. Good. When the rotation center is arranged in the vicinity of the primary transfer nip 22, the pressing member 32 and the rotating member 34 are arranged outside the intermediate transfer belt 11 and the photosensitive drum 7 in the longitudinal direction. In this way, a configuration is conceivable in which the round shaft 32A of the pressing member 32 and the central shaft of the round hole 34A of the rotating member 34 are disposed so as to pass through the vicinity of the primary transfer nip 22.

<Brush brushed tip wear and timing of contact angle change>
Next, with reference to FIG. 7 and FIG. 8, the timing for changing the contact angle of the brush transfer member with respect to the intermediate transfer belt and the abrasion of the brush raising tip in Example 1 will be described. FIG. 8 is an enlarged view of the brush raising tip portion of the brush transfer member according to the first embodiment. 8A is an initial state of the brushed brush tip, FIG. 8B is a worn state of the brushed brush tip, and FIG. 8C is a counterclockwise direction (arrow E2 direction) from FIG. 8B. FIG. 6 is a diagram illustrating a state in which the direction of the brushed brush front end portion with respect to the inner peripheral surface of the intermediate transfer belt is changed. Here, as shown in FIG. 8, in the brush raising tip 25, the upstream corner of the intermediate transfer belt 11 in the circulating movement direction (arrow B direction) is the brush raising tip 25A, and the downstream corner is the brush raising. The tip portion is 25C, and the tip surface is a brushed brush tip portion 25B.

  As shown in FIG. 8A, in the initial state, the brush raising tip portion 25 </ b> A of the brush raising portion 24 is in contact with the intermediate transfer belt 11. The contact state of the brush raising tip portion 25 is as shown in FIG. 8A because the brush raising tip portion 25 is caused by sliding with the intermediate transfer belt 11 due to the circulation movement of the intermediate transfer belt 11. This is because it falls in the circulating movement direction (arrow B direction). Then, as the number of printed sheets increases, the brush raising tip 25 of the brush raising portion 24 is worn, and the brush raising tip 25B in FIG. 8B comes into contact with the intermediate transfer belt 11, and the intermediate transfer belt. The contact surface with 11 spreads. When the contact surface is widened, the frictional force (tangential force) between the brush raising portion 24 and the intermediate transfer belt 11 is increased. When the frictional force increases, a sliding sound due to sliding between the intermediate transfer belt 11 and the brush raising portion 24 increases.

  Therefore, in the first embodiment, the number of printed sheets is counted, and it is determined that the brushed brush tip 25 is worn at the timing when the predetermined number of prints is exceeded, and the brushed brush tip with respect to the inner peripheral surface of the intermediate transfer belt 11 is determined. Change the direction of 25. As shown in FIG. 8C, by changing the orientation of the brush raising tip portion 25 with respect to the inner peripheral surface of the intermediate transfer belt 11, the contact portion of the brush raising portion 24 with the inner peripheral surface of the intermediate transfer belt 11 is changed. Can be changed from the brush raising tip 25B to the brush raising tip 25C. Thereby, the contact area between the brush raising tip portion 25 of the brush raising portion 24 and the intermediate transfer belt 11 can be reduced, and the frictional force (tangential force) between the brush raising portion 24 and the intermediate transfer belt 11 is increased. Can be suppressed.

  In the first embodiment, when determining the timing for changing the contact angle of the brush-like transfer member 20 with respect to the intermediate transfer belt 11, the number of printed sheets (the number of recording materials 2 on which toner images have been formed) is used as information regarding the wear state. ) A method using information was adopted. However, the present invention is not limited to this, and when determining the timing of changing the contact angle with respect to the intermediate transfer belt 11, for example, a method of determining the timing by counting the amount of circulation movement of the intermediate transfer belt 11 may be adopted. Good. Alternatively, a method may be adopted in which a load torque detector is attached to a drive motor that rotates the intermediate transfer belt 11 to detect the load and determine the timing. Alternatively, a method may be used in which a consumption current amount detector is attached to a drive motor that rotates the intermediate transfer belt 11, and the timing is determined by detecting the consumption current amount.

  Further, the contact angle of the brush-like transfer member 20 with respect to the belt is changed every predetermined number of prints or every predetermined circulation movement amount of the intermediate transfer belt 11, and the contact angle is alternately changed between the initial state and the changed state. A method that can be switched to (changeable) may be used. By switching repeatedly, the timing for changing the contact angle with respect to the belt is earlier than in the above-described method, and an increase in the contact area of the brush raising tip 25 can be suppressed. Thereby, it is possible to keep the contact area between the brush raising tip 25 and the intermediate transfer belt 11 relatively small, and to reduce the sliding noise. As a result, the brush-like transfer member 20 can have a long life.

(Example 2)
Next, Example 2 will be described with reference to FIG. FIG. 9 is a diagram illustrating the configuration of the contact angle changing mechanism according to the second embodiment. In FIG. 9, the pressing member 32 and the pressing spring 33 are omitted as in FIG. 7 described in the first embodiment, but also in the second embodiment, the inner peripheral surface of the intermediate transfer belt 11 by the pressing member 32. The brush-like transfer member 20 is biased in a substantially vertical direction. In addition, about the structure similar to Example 1, the description is abbreviate | omitted using the same code | symbol.

  FIG. 9A shows an initial state of the contact angle of the brush-like transfer member 20 with respect to the belt. As shown in FIG. 9A, the holding member 31 includes a plurality of surfaces, and the brush-like transfer member 20 is bonded to the plurality of surfaces. Since the holding member 31 is composed of a plurality of surfaces, the brush raising portion also has a plurality of surfaces such as 24D, 24E, and 24F. That is, the brush-like transfer member 20 as the transfer member in Example 2 has three different contact portions. The configuration of each contact portion is the same as the configuration of the brush-like transfer member described in the first embodiment (see FIGS. 3 and 4). Although not shown, also in Example 2, the tip portions of the brush raising portions 24D, 24E, and 24F that contact the inner peripheral surface of the intermediate transfer belt 11 are referred to as brush raising tip portions 25D, 25E, and 25F, respectively. And these brush raising front-end | tip parts 25D-25F become a shape with the part used as the corner | angular of an upstream, the part used as a corner | angular of a downstream, and a front end surface similarly to what was shown in FIG. Yes.

  As shown in FIG. 9A, when the contact angle of the brush-like transfer member 20 to the belt is in the initial state, the brush raising portion 24D (first contact portion) contacts the inner peripheral surface of the intermediate transfer belt 11. . As the number of printed sheets increases, the brush raising tip portion 25D of the brush raising portion 24D is worn by sliding between the inner peripheral surface of the intermediate transfer belt 11 and the brush raising tip portion 25D of the brush raising portion 24D. Then, as described in the first embodiment with reference to FIG. 8B, the brush raising tip portion 25D is worn and the contact surface of the brush raising tip portion 25D with the intermediate transfer belt 11 is widened. As the contact surface widens, the frictional force (tangential force) between the brush raising portion 24D and the intermediate transfer belt 11 increases.

  FIG. 9B shows a state where the contact angle of the brush-like transfer member 20 with respect to the belt is changed from the initial state shown in FIG. As shown in FIG. 9B, when the slide member 35 moves straight from the state of FIG. 9A in the direction opposite to the belt conveyance direction (arrow B direction) (arrow D1 direction), the rotation member 34 is moved. Rotates around the round hole 34A in the direction of arrow E1 in the figure. As a result, the surface (part) that contacts the inner peripheral surface of the intermediate transfer belt 11 of the brush-like transfer member 20 is changed. That is, the brush raising portion 24 that contacts the intermediate transfer belt 11 is changed from the brush raising portion (first contact portion) 24D to the brush raising portion (second contact portion) 24E. The intermediate transfer belt 11 is brought into contact with the brush raising tip portion 25E of the brush raising portion 24E that is not worn, and an increase in frictional force (tangential force) between the brush raising portion 24 and the intermediate transfer belt 11 can be suppressed. it can.

  FIG. 9C shows a state where the contact angle of the brush-like transfer member 20 with respect to the belt is changed from the state shown in FIG. 9B. As shown in FIG. 9C, when the slide member 35 moves straight from the state of FIG. 9A in the same direction as the belt conveyance direction (arrow D2 direction), the rotation member 34 moves the round hole 34A. It rotates counterclockwise (arrow E2) about the center. As a result, the surface (part) that contacts the inner peripheral surface of the intermediate transfer belt 11 of the brush-like transfer member 20 is changed. That is, the brush raising portion 24 that contacts the intermediate transfer belt 11 is changed from the brush raising portion 24E to the brush raising portion 24F. The intermediate transfer belt 11 is brought into contact with the brush raising tip portion 25F of the brush raising portion 24F that is not worn, and an increase in frictional force (tangential force) between the brush raising portion 24 and the intermediate transfer belt 11 can be suppressed. it can.

The timing for changing the surface of the brush-like transfer member 20 that contacts the intermediate transfer belt 11 may be the same as in the first embodiment. A method in which the contact surface of the brush-like transfer member 20 can be repeatedly switched (changed) every predetermined number of printed sheets or every predetermined amount of movement of the intermediate transfer belt 11 may be used. By repeatedly switching, not only a part of the brush raised portion 24 (abutment surface) is worn, but a plurality of the abutments are worn little by little. Accordingly, the wear state of the plurality of contact surfaces is homogenized, and the increase speed of the frictional force (tangential force) between the brush raising portion 24 and the intermediate transfer belt 11 can be suppressed.

(Example 3)
Next, Example 3 will be described with reference to FIG. FIG. 10 is a diagram illustrating the configuration of the contact angle changing mechanism according to the third embodiment. In FIG. 10, the pressing member 32 and the pressing spring 33 are omitted as in FIG. 7 described in the first embodiment. In addition, about the structure similar to Example 1, 2, the description is abbreviate | omitted using the same code | symbol.

  FIG. 10A shows an initial state of the contact angle of the brush-like transfer member 20 with respect to the belt. As shown in FIG. 10A, the holding member 31 has a curved surface, and the brush-like transfer member 20 is bonded to the curved surface. Since the holding member 31 is formed of a curved surface, the brush raising portion 24G is also a curved surface. That is, the brush-like transfer member 20 as the transfer member in the third embodiment has a curved surface portion that can contact the inner peripheral surface of the intermediate transfer belt 11. Although not shown, also in Example 3, the tip portion of the brush raising portion 24G that contacts the inner peripheral surface of the intermediate transfer belt 11 is referred to as a brush raising tip portion 25G.

  In the state shown in FIG. 10A, the portion that contacts the inner peripheral surface of the intermediate transfer belt 11 is the first contact portion in the present invention. In the state shown in FIG. The portion that contacts the peripheral surface is the second contact portion in the present invention. That is, the brush-like transfer member 20 of Example 3 has a curved surface portion including a first contact portion and a second contact portion. As described above, in the brush-like transfer member 20 according to the third embodiment, in a certain state, not all of the brush raising portions 24G are in contact with the inner peripheral surface of the intermediate transfer belt 11, but only a part of the brush raising portions 24G. It is comprised so that it may contact | abut.

  When the contact angle of the brush-like transfer member 20 with respect to the belt is in the initial state, a part of the brush raising portion 24G comes into contact with the inner peripheral surface of the intermediate transfer belt 11. As the number of printed sheets increases, the brushed tip 25G of the brushed portion 24G wears out. Then, as described in the first embodiment with reference to FIG. 8B, the brush raising tip portion 25G is worn, and the contact surface of the brush raising tip portion 25G with the intermediate transfer belt 11 is widened. When the contact surface is widened, the frictional force (tangential force) between the brush raising portion 24 and the intermediate transfer belt 11 is increased.

  FIG. 10B shows a state where the contact angle of the brush-like transfer member 20 to the belt is changed from the initial state shown in FIG. As shown in FIG. 10B, when the slide member 35 linearly moves from the state of FIG. 10A in the direction opposite to the belt conveyance direction (arrow B direction) (arrow D1 direction), the rotation member 34 is moved. Rotates around the round hole 34A in the direction of arrow E1 in the figure. As a result, the portion of the brush-like transfer member 20 that contacts the inner peripheral surface of the intermediate transfer belt 11 is changed. That is, the contact portion with respect to the intermediate transfer belt 11 is changed from the worn portion of the brush raising portion 24G to the non-weared portion. The intermediate transfer belt 11 comes into contact with the brush raising portion 24G that is not worn, and an increase in frictional force (tangential force) between the brush raising portion 24G and the intermediate transfer belt 11 can be suppressed. Although not shown in the figure, the brush for the belt 11 is obtained by rotating the slide member 35 in the direction opposite to the arrow E1 direction by moving the slide member 35 straight in the direction opposite to the direction shown in FIG. The contact portion of the raised portion 24G can also be changed. Note that it is conceivable to use the same method as in the first and second embodiments for changing the contact angle (contact portion) of the brush-like transfer member 20 to the belt.

  In the first to third embodiments, the tandem color image forming apparatus having a plurality of photosensitive drums has been described. However, the present invention is not limited to this, and can also be applied to a rotary color image forming apparatus having one photosensitive drum.

DESCRIPTION OF SYMBOLS 7 ... Photosensitive drum (image carrier), 11 ... Intermediate transfer belt (belt), 20 ... Brush-like transfer member (transfer member), 24 ... Brush raising part (raising part), 25 ... Brush raising tip part (tip part) 30 ... Contact angle changing mechanism (changing means)

Claims (14)

An endless belt that circulates,
An image carrier provided on the outer peripheral surface side of the belt and carrying a developer image;
A brushed portion that extends toward the inner circumferential surface of the belt at a position facing the image bearing member and has a tip portion that slides on the inner circumferential surface by the circulating movement of the belt; A transfer member for transferring the developer image carried thereon to the outer peripheral surface side of the belt;
An image forming apparatus having
An image forming apparatus comprising: changing means for changing a direction of the tip portion with respect to the inner peripheral surface.   The changing means includes a holding member that holds the transfer member, and changes an orientation of the tip portion with respect to the inner peripheral surface by changing an angle of the holding member with respect to the inner peripheral surface. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the changing unit changes a direction of the tip portion with respect to the inner peripheral surface based on information on a wear state of the tip portion.   The information on the wear state is the number of recording materials on which the developer image has been formed, the amount of movement due to the circulating movement of the belt, or the amount of current consumed by the motor that circulates and moves the belt. The image forming apparatus according to claim 3.   The image forming apparatus according to claim 1, further comprising a pressing member that presses the transfer member against the inner peripheral surface.   The pressing member presses the transfer member against the inner peripheral surface in a direction substantially perpendicular to the circulating movement direction of the belt regardless of the direction of the tip portion with respect to the inner peripheral surface. The image forming apparatus according to 5. An endless belt that circulates,
An image carrier provided on the outer peripheral surface side of the belt and carrying a developer image;
A transfer member that contacts the inner peripheral surface of the belt at a position facing the image carrier, and transfers the developer image carried by the image carrier to the outer peripheral surface of the belt;
An image forming apparatus having
The transfer member has a first contact portion that can contact the inner peripheral surface of the belt, and a second contact portion different from the first contact portion,
An image forming apparatus comprising: changing means for changing a contact portion with respect to the inner peripheral surface from the first contact portion to the second contact portion.   The changing unit includes a holding member that holds the transfer member, and changes an angle of the holding member with respect to the inner peripheral surface, thereby changing a contact portion with respect to the inner peripheral surface from the first contact portion. The image forming apparatus according to claim 7, wherein the image forming apparatus is changed to a second contact portion.   9. The transfer member according to claim 7, wherein the transfer member has a raised portion whose tip is slid on the inner peripheral surface by circulation movement of the belt provided to extend toward the inner peripheral surface of the belt. The image forming apparatus described.   The said change means can change the contact part with respect to the said internal peripheral surface repeatedly between the said 1st contact part and the said 2nd contact part, The any one of Claim 7 thru | or 9 characterized by the above-mentioned. The image forming apparatus described in the item.   The image forming apparatus according to claim 7, wherein the transfer member includes a curved surface portion including the first contact portion and the second contact portion.   The said changing means changes the contact part of the said transfer member with respect to the said internal peripheral surface based on the information regarding the abrasion state of the said front-end | tip part, The Claim 1 characterized by the above-mentioned. Image forming apparatus.   The information on the wear state is the number of recording materials on which the developer image has been formed, the amount of movement due to the circulating movement of the belt, or the amount of current consumed by the motor that circulates and moves the belt. The image forming apparatus according to claim 12.   14. The image forming apparatus according to claim 7, further comprising a pressing member that presses the transfer member against the inner peripheral surface in a direction substantially perpendicular to a circulation movement direction of the belt.

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