Image forming device

Abstract

To suppress occurrence of an image defect in an image-forming device having a brush member that can at least partially abut on a rotating member.SOLUTION: An image-forming device includes a rotatable rotating member, and a tabular brush member having a fiber thread, the rotating member and the brush member can relatively move to a first position in which the tip of the fiber thread separates from the surface of the rotating member and a second position in which the tip of the fiber thread abuts on the surface of the rotating member, and a relative approach direction to the rotating member of the brush member is a direction from a downstream side to an upstream side in a rotation direction of the rotation member in a relative movement from the first position to the second position.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] In an electrophotographic image forming apparatus, rotating members such as a photosensitive drum, a charging roller, and a transfer roller are used. In addition, a technique is also common in which a brush member having fiber threads is brought into contact with the surface of a rotating member to perform cleaning or other processing on the surface of the rotating member. For example, Patent Document 1 discloses a technique in which a brush member is provided that contacts the surface of the photosensitive drum at a position downstream of a transfer section and upstream of a charging section in the rotation direction of the photosensitive drum, and the polarity of the transfer residual toner on the photosensitive drum surface is controlled (see Patent Document 1). The transfer residual toner is scattered by the brush member and charged to the normal polarity by the discharge of the charging roller. After this, the toner is collected by a developing device due to the potential difference between the photosensitive drum and the developing roller, and the photosensitive drum surface is refreshed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-183905 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to clean the surface of the rotating member and control the charge of the residual toner, it is considered effective to increase the contact pressure of the brush member against the photosensitive drum. However, the brush member described in Patent Document 1 is fixed to the device body in contact with the surface of the photosensitive drum. Therefore, the orientation of the fiber threads constituting the brush may become uneven due to the attachment state of the brush member during manufacturing or changes in state over time due to contact with the photosensitive drum, and as shown in FIG. 10, the fiber density at the contact position may vary. FIG. 10 shows a schematic diagram of a state in which the fiber density is sparse at position A. When the fiber density varies, the toner that invades the dense fiber density area is blocked, and the toner flows into the sparse fiber density area, so that more toner invades the sparse fiber density area. The difference in the amount of toner that invades in the longitudinal direction causes vertical streak-like unevenness in passing through, and vertical streak-like image defects such as poor charging and poor transfer may occur downstream in the rotation direction of the rotating member.

[0005] SUMMARY OF THE DISCLOSURE An object of the present invention is to prevent the occurrence of image defects in an image forming apparatus having a brush member, at least a portion of which can come into contact with a rotating member. [Means for solving the problem]

[0006] The present invention relates to a rotatable Photosensitive drum and, A support member contacts the surface of the photosensitive drum. Fiber Yarn and, Have The fiber yarn is supported by the support member in a non-rotatable manner. Brush member 、 Support the support member; The fibers Thread The above Photosensitive drum a first location spaced from the surface of the fiber; Thread The above Photosensitive drum a second position abutting the surface of the a third position different from the first position where the fiber yarn is entirely separated from the surface of the photosensitive drum; To The brush member move A moving mechanism for , having From the first position to the second position The brush member is move If you do In the brush member Photosensitive drum fart Connection The near direction is Photosensitive drum The direction of rotation is from the downstream side to the upstream side. When the brush member moves from the second position to the third position, the brush member separates from the photosensitive drum in a direction from the downstream side to the upstream side in a rotation direction of the photosensitive drum. The image forming apparatus is characterized in that

[0008] The present invention relates to a rotatable Photosensitive drum and, A support member contacts the surface of the photosensitive drum. Fiber Yarn and, Have The fiber yarn is supported by the support member in a non-rotatable manner. Brush member 、 Support the support member; The fibers Thread The above Photosensitive drum a first location spaced from the surface of the fiber; Thread The above Photosensitive drum a second position abutting the surface of the fiber; Thread The above Photosensitive drum From the surface all a third position different from the first position, The brush member move A moving mechanism for , having The above Photosensitive drum In the rotation direction, the position of the brush member at the first position is downstream of the position of the brush member at the second position, and the position of the brush member at the third position is upstream of the position of the brush member at the second position. Effect of the Invention

[0013] According to the present invention, in an image forming apparatus having a brush member at least a portion of which can come into contact with a rotating member, the occurrence of image defects can be suppressed. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is an explanatory diagram of the contact and separation operation of the brush member in the first embodiment. [Diagram 2] FIG. 1 shows an image forming apparatus according to a first embodiment of the present invention. [Diagram 3]Cartridge diagram of the first embodiment [Figure 4] FIG. 1 is an explanatory diagram of a brush member according to a first embodiment of the present invention; [Diagram 5] Clark-Evans Index Measurement Method for the Brush Member of Example 1 [Figure 6] FIG. 1 is an explanatory diagram of a contact pressure measurement method according to the first embodiment. [Figure 7] FIG. 11 is an explanatory diagram of a photosensitive drum unit according to a second embodiment of the present invention; [Figure 8] FIG. 11 is an explanatory diagram of the contact / separation operation of the photosensitive drum in the second embodiment; [Figure 9] FIG. 11 is an explanatory diagram of a photosensitive drum separation operation according to the second embodiment; [Figure 10] Diagram of the problem to be solved by the invention [Figure 11] FIG. 1 shows an image forming apparatus according to a third embodiment of the present invention. [Figure 12] FIG. 11 is an explanatory diagram of the contact / separation operation of the photosensitive drum in the third embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Exemplary embodiments for carrying out the present invention will be described with reference to the drawings.

[0016] Example 1 In Example 1, a photosensitive drum serving as an image carrier is used as the rotatable member, and a brush member is used as the cleaning member. Preferred embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiments can be changed as appropriate depending on the configuration and various conditions of the device to which the invention is applied, and the scope of the present invention is not limited to the following embodiments.

[0017] (Configuration of Image Forming Apparatus) 2, the electrophotographic image forming apparatus 100 is a laser beam printer using electrophotographic technology in which a cartridge B is detachably attached to an apparatus main body A. When the cartridge B is attached to the apparatus main body A, an exposure device 1 (laser scanner unit) is disposed above the cartridge B.

[0018] Further, below the cartridge B, there is disposed a sheet tray 2 that accommodates a recording medium (hereinafter, referred to as recording material P) on which an image is to be formed.

[0019] Furthermore, in the apparatus main body A, a pickup roller 3, a pair of conveying rollers 4, a transfer roller 5, a fixing device 6, a pair of discharge rollers 8, a discharge tray 9, etc. are arranged in this order along the conveying direction D of the recording material P. The fixing device 6 has a heating roller 7a and a pressure roller 7b.

[0020] (Image formation process) Next, an outline of the image forming process will be described with reference to Figs. 2 and 3. Based on a print start signal, the photosensitive drum 10, which is an image carrier of φ24, is rotated in the direction of the arrow R at a predetermined peripheral speed (process speed 100 mm / sec). The charging roller 12, which is applied with a bias voltage and rotates in the direction of the arrow R', comes into contact with the outer peripheral surface of the photosensitive drum 10 and uniformly charges the outer peripheral surface of the photosensitive drum 10. The charging roller 12 may be configured to rotate at the same speed as the photosensitive drum 10 by following the rotation of the photosensitive drum 10, or may be configured to rotate at a speed different from that of the photosensitive drum 10 by providing a driving means for rotating the charging roller 12. The applied bias at this time is a DC voltage of -1100V, and charges the photosensitive drum 10 to -500V. The exposure device 1 outputs a laser beam L according to image information. The laser beam L passes through an exposure window 13 on the top surface of the cartridge B and scans and exposes the outer peripheral surface of the photosensitive drum 10. As a result, an electrostatic latent image corresponding to the image information is formed on the outer circumferential surface of the photosensitive drum 10 .

[0021] On the other hand, as shown in the cross-sectional view of the cartridge in FIG. 3, in the developing unit 20 as a developing device, the toner T in the toner chamber 21 is made of a non-magnetic one-component developer whose normal polarity is negative, and is stirred and conveyed by the rotation of the conveying member 22, and is sent out to the toner supply chamber 23. Thereafter, the toner T is carried and conveyed by the sponge-like supply roller 24 having a diameter of φ10, and is carried on the surface of the developing roller 25 made of an elastic conductive rubber having a diameter of φ12. The developing roller 25 is driven to rotate in the direction of the arrow R'' at a speed of 140 mm / sec, which is a peripheral speed ratio of 140% to the photosensitive drum, via a driving gear from the main body. Then, the toner T is frictionally charged to a negative polarity by the developing blade 26, while the layer thickness on the peripheral surface of the developing roller 25 is regulated. A developing bias (−350 V) is applied to the developing roller 25, and the toner T is transferred to the photosensitive drum 10 according to the electrostatic latent image, and is visualized as a toner image.

[0022] 2, in synchronization with the output timing of the laser light L, the recording material P stored in the lower part of the apparatus main body A is fed from the sheet tray 2 by the pickup roller 3 and the conveying roller pair 4. Then, the recording material P is supplied to a transfer position between the photosensitive drum 10 and the transfer roller 5. At this transfer position, the toner image is sequentially transferred from the photosensitive drum 10 to the recording material P. The recording material P to which the toner image has been transferred is separated from the photosensitive drum 10 and conveyed to the fixing device 6. Then, the recording material P passes through a nip portion between the heating roller 7a and the pressure roller 7b constituting the fixing device 6. At this nip portion, a pressure / heat fixing process is performed, and the toner image is fixed to the recording material P. The recording material P to which the toner image has been fixed is conveyed to the discharge roller pair 8 and discharged to the discharge tray 9.

[0023] On the other hand, the transfer residual toner remaining on the photosensitive drum 10 after transfer is toner that has become positive, the polarity opposite to the normal polarity, due to the discharge of the transfer bias (+1 kV) applied to the transfer roller 5, and negative transfer residual toner that could not be transferred. The transfer residual toner is sent to the contact position of the brush member 11 as the photosensitive drum 10 rotates. A brush member bias (-350 V) is applied to the brush member 11 by a power source (not shown), and the brush member 11 retains the positive toner inside while allowing the negative toner to pass through, and sends it to the contact position of the charging roller 12. The positive toner that was not retained by the brush member 11 becomes negative toner T due to discharge caused by the charging bias (-1100 V) applied to the charging roller 12 near the contact position of the charging roller 12. Then, as the photosensitive drum 10 rotates, the developing roller 25 and the photosensitive drum 10 face each other in the development area. In the development area G, the negative polarity toner T is collected from the photosensitive drum 10 to the development roller 25 side due to the potential difference between the photosensitive drum 10 and the development roller 25 and is reused.

[0024] (Cartridge B Configuration) Next, the overall structure of cartridge B will be described with reference to Figure 3. Cartridge B has at least a latent image unit B1 for forming a latent image consisting of a photosensitive drum 10 and a charging roller 12, and a developing unit B2 for developing the latent image consisting of toner T, a developing roller 25, a developing blade 26, etc. Cartridge B is constructed by inserting and positioning the latent image unit B1 and the developing unit B2 into the main body A of the apparatus. The latent image unit B1 may include a brush member 11.

[0025] The driven members of the latent image unit B1 and the developing unit B2 are rotationally driven by a driving force input from the driving means of the main assembly A of the apparatus.

[0026] (Configuration of brush member 11) Fig. 4(a) is a schematic diagram of the brush member 11 in a standalone state, as viewed along its longitudinal direction (substantially parallel to the direction of the rotation axis of the photosensitive drum 10). Fig. 4(b) is a schematic diagram of the brush member 11 in contact with the photosensitive drum 10, as viewed along its longitudinal direction.

[0027] The brush portion of the brush member 11 is made up of a flat fixed brush. A flat fixed brush is less expensive than a rotatable brush roller and requires less installation space, which has the advantage of allowing the cartridge B to be made smaller and at lower cost.

[0028] 4, the brush member 11 is composed of pile yarns 11a made of nylon 6, which are a plurality of bristles that rub against the surface of the photosensitive drum 10, and a base fabric 11b that supports the pile yarns 11a. Note that the pile yarns 11a may be made of materials other than nylon, such as rayon, acrylic, or polyester.

[0029] 4(a), when the brush member 11 is in a single state, i.e., when no external force is being applied to bend the pile yarns 11a, the distance from the base fabric 11b to the tip of the pile yarns 11a exposed from the base fabric 11b is taken as L1. In the first embodiment, L1 is 5.75 mm. The brush member 11 is arranged such that the base fabric 11b is fixed to a support member (not shown) installed at a predetermined position on the container frame by a fixing means such as double-sided tape, and the tip of the pile yarns 11a penetrates the photosensitive drum 10.

[0030] As shown in Fig. 4(b), the shortest distance from the base fabric 11b of the brush member 11 fixed to the support member to the photosensitive drum 10 is defined as L2. In Fig. 4(b), the surface of the photosensitive drum 10 and the base fabric 11b are shown to be substantially parallel to each other, but they do not have to be parallel to each other and may be disposed at an angle. In this case, the shortest distance from the base fabric 11b to the photosensitive drum 10 is also defined as L2.

[0031] Also, the difference between L2 and L1 is defined as the penetration amount of the brush member 11 into the photosensitive drum 10. In Example 1, as shown in Fig. 4(a), when the brush member 11 is in a standalone state, the length L3 of the brush member 11 in the circumferential direction of the photosensitive drum 10 (hereinafter referred to as the "short direction") is 4 mm. Also, in Example 1, the length in the longitudinal direction of the brush member 11 is 216 mm. The length in the longitudinal direction of the brush member 11 is equal to or greater than the length of an image forming area (area where a toner image can be formed) on the photosensitive drum 10 with respect to the direction of the rotation axis of the photosensitive drum 10, so that the brush member 11 can contact the entire image forming area.

[0032] The length L3 of the brush member 11 in the lateral direction of the photosensitive drum 10 in the first embodiment is It is not limited thereto. For example, it may be changed as appropriate depending on the life of the image forming apparatus 100 or the process cartridge. Furthermore, the longitudinal length of the brush member 11 in the first embodiment is not limited to the above example. For example, it may be changed as appropriate depending on the maximum paper passing width of the image forming apparatus 100. It is preferable that the lateral length of the brush member 11 is 3 mm or more from the viewpoint of long life. Furthermore, in the first embodiment, the thickness of the pile yarn 11a is 2 denier, and the density is 240 kF / inch. 2 where kF / inch 2 is a unit of brush density, and indicates the number of filaments per square inch. The thickness and density of the pile yarn 11a may be appropriately determined in consideration of the passage of toner. Specifically, if the pile yarn 11a is too thick, it will hinder the passage of the yarn, and the yarn will tend to come out in streaks, while if the density of the pile yarn 11a is too high, the yarn will not allow the toner to pass through, and the toner held back by the brush member 11 will scatter, causing dirt inside the machine. Therefore, the thickness and density of the pile yarn 11a should be set to 1 to 6 denier and 150 to 350 kF / inch, respectively, in consideration of the passage of toner. 2 It is preferable that:

[0033] In addition, the Clark-Evans index is used as a numerical value representing the degree of density of the brush of the brush member 11. If the distance from point i to the nearest point is di, the number of points is n, and the average value W of the distances from each point to the nearest point is W, the average value W is expressed by the following formula 1.

number

number

number

[0034] (Contact pressure of brush member 11) A method for determining the maximum contact pressure, which is a parameter that controls the contact state of the brush member 11 at this time, will now be described. As shown in Fig. 6(a), a compression test fixture 71 for Shimadzu small tabletop testing machine EZTest (manufactured by Shimadzu Corporation) is used to measure the normal force corresponding to the amount of penetration of the brush member 11 into the photosensitive drum 10. Also, as shown in Fig. 6(b), the brush member 11 is pressed against a transparent glass drum 72 moving in the moving direction D, and the contact width 73 in the short direction is measured by observing from the glass drum 72 side. Here, the average pressure is Average pressure = normal force / (contact width x longitudinal width)(gf / mm 2 ) (Equation 4) The portion where the amount of penetration of the brush member 11 into the photosensitive drum 10 is the largest is the portion where the contact pressure is the maximum. The average amount of penetration obtained from the maximum amount of penetration and the minimum amount of penetration is expressed as follows: Average amount of intrusion = (maximum amount of intrusion + minimum amount of intrusion) / 2 (Formula 5) The maximum contact pressure of the brush member 11 on the photosensitive drum 10 is Maximum contact pressure = average pressure x maximum penetration amount / average penetration amount (gf / mm 2 ) (Equation 6) The maximum contact pressure can be calculated using the conversion formulas 4, 5, and 6. This conversion formula can be used when the density and thickness of the brush member 11 are uniform. However, when the density and thickness of the brush member 11 are not uniform in the short direction, the brush member 11 is cut into unit lengths in the short direction, and the average pressure obtained using formula 4 becomes the maximum contact pressure. The maximum contact pressure is 0.7 to 3.5 gf / mm 2 is preferred.

[0035] Next, the arrangement of the brush member 11 relative to the photosensitive drum 10 in the first embodiment will be described with reference to FIG. 1. The brush member 11 is supported by a base member 11c bonded to a base cloth 11b. The base member 11c is supported by a moving mechanism 110 provided in the main body A of the image forming apparatus 100, and the moving mechanism 110 can move the brush member 11 relative to the photosensitive drum 10. The brush member 11 and the photosensitive drum 10 can move relatively to a first position where the tip of the pile yarn 11a is separated from the surface of the photosensitive drum 10, a third position different from the first position, and a second position where the tip of the pile yarn 11a abuts against the surface of the photosensitive drum 10. FIG. 1(a) shows a state where the relative positions of the photosensitive drum 10 and the brush member 11 are in the first position. FIG. 1(b) shows a state where the relative positions of the photosensitive drum 10 and the brush member 11 are in the second position. FIG. 1C shows a state in which the relative positions of the photosensitive drum 10 and the brush member 11 are in a third position.

[0036] As shown in FIG. 1, the moving mechanism 110 is capable of moving the photosensitive drum 10 and the brush member 11 relative to each other so that the relative positions of the photosensitive drum 10 and the brush member 11 move from a first position to a second position and from the second position to a third position.

[0037] (Contact between the brush member 11 and the photosensitive drum 10) When at rest, as shown in Fig. 1(a), the brush member 11 and the photosensitive drum 10 are separated, and the brush member 11 is located at a retracted position. During image formation, the base member 11c is pressed in the direction of arrow N1 (see Fig. 1(b)) by a pressing mechanism of the moving mechanism 110. This causes the brush member 11 to move from the retracted position in Fig. 1(a) to a contact position against the photosensitive drum 10 in Fig. 1(b) and apply a predetermined contact pressure (the above-mentioned maximum contact pressure = 0.7 to 3.5 g). f / mm 2 ) is brought into contact with the photosensitive drum 10.

[0038] As shown in Figure 1(b), during the relative movement of the photosensitive drum 10 and the brush member 11 from the first position to the second position, the relative approach direction N1 of the brush member 11 to the photosensitive drum 10 is a direction from the downstream side to the upstream side of the rotation direction R of the photosensitive drum 10.

[0039] In a virtual plane perpendicular to the rotation axis 10d of the photosensitive drum 10, point T is within the contact range (indicated by 11e) between the tip of the pile yarn 11a and the surface of the photosensitive drum 10 when the relative positions of the photosensitive drum 10 and the brush member 11 are in the second position. Here, point T is a point in the center of the short side direction of the contact range 11e. Also, the direction parallel to the tangent S of the photosensitive drum 10 surface at point T is defined as the X direction. In this case, the direction of the X direction component N1x of the approach direction N1 is opposite to the rotation direction R of the photosensitive drum 10 at point T. In other words, the dot product of the approach direction vector (indicated by arrow N1) and the rotation direction vector (indicated by arrow R) of the photosensitive drum 10 at point T is a negative value.

[0040] In the first embodiment, the pressing direction N1 of the pressing mechanism against the brush member 11 faces upstream in the rotation direction R of the photosensitive drum 10 from a straight line P connecting the rotation center 10d of the photosensitive drum 10 and the short-side center 11d of the brush member 11 at the abutment position. By pressing the brush member 11 in this pressing direction N1, the pile yarns 11a start to abut against the surface of the photosensitive drum 10 while receiving a force in the rotation direction R of the photosensitive drum 10. In this state, the pile yarns 11a move to a predetermined abutment position while being further pressed in the same direction, as a result, the pile yarns 11a fall down in unison in the rotation direction R of the photosensitive drum 10.

[0041] In a virtual plane perpendicular to the rotation axis 10d of the photosensitive drum 10, an angle θ1 is formed between a line passing through the point T and parallel to the approach direction N1, and a line (tangent S) passing through the point T and parallel to the rotation direction R at the point T. The smaller θ1 is, the more the pile yarns 11a are likely to receive a force in the rotation direction of the photosensitive drum 10. Therefore, the pile yarns 11a are more likely to fall in unison with the rotation direction R of the photosensitive drum 10. Conversely, the larger θ1 is, the more the orientation of the pile yarns 11a is likely to become random, and the smaller the effect of the pile yarns 11a falling in unison with the rotation direction R of the photosensitive drum 10 is. According to the inventors' study, a range of 0°≦θ1≦60° is preferable.

[0042] In addition, with regard to the time relationship between the timing at which the brush member 11 starts contacting the photosensitive drum 10 and the timing at which the photosensitive drum 10 starts rotating, the above-mentioned effect is more easily obtained by having the brush member 11 contact the photosensitive drum 10 after the photosensitive drum 10 starts rotating.

[0043] (Separation of the brush member 11 and the photosensitive drum 10) When image formation is completed, the brush member 11 starts to separate from the photosensitive drum 10. By separating and lowering the contact pressure, creep deformation of the pile yarn 11a can be suppressed. In addition, toner and other foreign matter that was attached to the pile yarn 11a when it was in contact with the pile yarn 11a no longer remains in the same place on the pile yarn 11a due to the release of the pressure, so that the toner and foreign matter can be suppressed from adhering to the pile yarn 11a.

[0044] Furthermore, if the brush member 11 moves in the opposite direction to the pressing direction N1 along the same trajectory as when it was pressed (when moving from the first position to the second position) when the pressure is released, the pile yarns 11a are released from the pressure while receiving a force in the opposite direction to the rotation direction of the photosensitive drum 10. In this case, the direction in which the pile yarns 11a fall may become irregular, and the density of the tips of the pile yarns 11a may vary. Therefore, in the first embodiment, when the pressure on the brush member 11 is released, it moves from the second position to a third position different from the first position, as shown in FIG. 1(c).

[0045] As shown in FIG. 1C, the photosensitive drum 10 and the brush member 11 are moved from the second position to the third position. In the relative movement to the photosensitive drum 10, a relative separation direction N2 of the brush member 11 from the photosensitive drum 10 is a direction from the downstream side to the upstream side of the rotation direction R of the photosensitive drum 10. In other words, the direction of the X-direction component N2x of the separation direction N2 is the opposite direction to the rotation direction R of the photosensitive drum 10. In further other words, the dot product of the separation direction vector (indicated by arrow N2) and the rotation direction vector (indicated by arrow R) of the photosensitive drum 10 is a negative value.

[0046] The angle θ2 is defined as the angle between a line passing through point T and parallel to the separation direction N2 and a line passing through point T and parallel to the rotation direction R at point T. θ2 is a right angle or an obtuse angle, and preferably 90°≦θ2≦180°. In other words, in the first embodiment, the separation operation is performed in the same direction as the pressing direction N1 when the brush member 11 is in contact with the brush member 11. In this way, the pile yarn 11a continues to receive a force in the same direction as the rotation direction R of the photosensitive drum 10 even during the pressure release operation, so that the direction of the pile yarn 11a is maintained uniform. After the pressure release operation is completed, the brush member 11 returns to the retracted position (first position) and waits for the next image forming operation.

[0047] When the pressure is released, if the brush member 11 and the photosensitive drum 10 are separated from each other in such a manner that there is no contact between them, the effect of maintaining the direction of the pile yarns 11a aligned can be more effectively obtained. Note that the above effect can be obtained even if the brush member 11 and the photosensitive drum 10 are separated even partially.

[0048] 1, in the first embodiment, in the rotation direction R of the photosensitive drum 10, the position of the brush member 11 at the first position (FIG. 1(a)) is downstream of the position of the brush member 11 at the second position (FIG. 1(b)). Also, the position of the brush member 11 at the third position (FIG. 1(c)) is upstream of the position of the brush member 11 at the second position (FIG. 1(b)).

[0049] In the first embodiment, the moving mechanism 110 moves the brush member 11 relative to the photosensitive drum 10 to relatively move the photosensitive drum 10 and the brush member 11, but is not limited to this. The moving mechanism 110 may be configured to move the photosensitive drum 10 relative to the brush member 11, or may be configured to move both the photosensitive drum 10 and the brush member 11.

[0050] The moving mechanism 110 may be configured to be able to move the relative positions of the photosensitive drum 10 and the brush member 11 from the third position to the first position. Thereby, when the photosensitive drum 10 and the brush member 11 are once moved from the second position to the third position and separated from each other, and then the photosensitive drum 10 and the brush member 11 are brought into contact with each other again, the moving mechanism 110 can return to the first position and then move to the second position. Therefore, when the brush member 11 is brought into contact with the photosensitive drum 10, the brush member 11 can always be brought into contact with the photosensitive drum 10 while approaching the photosensitive drum 10 in the approach direction N1. This allows the pile yarn 11a to be brought into contact with the photosensitive drum 10 more reliably and uniformly inclined in a certain direction, and the density of the pile yarn 11a at the contact position can be suppressed from varying. This allows the occurrence of image defects downstream in the rotation direction of the photosensitive drum 10 from the contact position to be more reliably suppressed.

[0051] Example 2 In the second embodiment, the brush member 11 is fixed and does not move with respect to the contact and separation between the brush member 11 and the photosensitive drum 10, and the photosensitive drum 10 moves in response to pressure from the developing unit 20 to contact and separate with the brush member 11. The basic configurations of the apparatus main body A and the cartridge B, and the configuration of the brush member 11 that are the same as those in the first embodiment are given the same reference numerals and names, and detailed explanations are omitted. In the second embodiment, the configuration related to contact and separation will be mainly explained.

[0052] (Configuration of the photosensitive drum) The support structure of the photosensitive drum 10 will be described. As shown in FIG. 7, the photosensitive drum 10 is made up of a cylinder 10a on which a photosensitive layer is applied, and a support member provided at one end side and the other end side in the longitudinal direction of the cylinder 10a. The cylinder 10a is supported by a shaft 10b.

[0053] A cylindrical shaft portion 10b having a diameter smaller than the outer diameter of the cylinder 10a protrudes from both ends of the cylinder 10a. The shaft portion 10b of the photosensitive drum 10 is supported slidably on the inner surface of a hole portion (not shown) provided in a bearing member (not shown) serving as a support member. The bearing member is provided in a frame that constitutes the latent image unit B1.

[0054] The arrangement of the brush member 11 relative to the photosensitive drum 10 in the second embodiment will be described.

[0055] In the following description, the rotation center of the photosensitive drum 10 when the photosensitive drum 10 is positioned during image formation is set as the origin O, and the short-side center 11d of the brush member 11 is at the 12 o'clock position with respect to the origin O. The regions on the same side as the brush member 11 with respect to the origin O are set as the first and second quadrants, and the opposite sides are set as the third and fourth quadrants. The directions from the first quadrant to the fourth quadrant, from the fourth quadrant to the third quadrant, from the third quadrant to the second quadrant, and from the second quadrant to the first quadrant are set as the same direction as the rotation direction R of the photosensitive drum 10. In the second embodiment, the brush member 11 is fixed to the device body A of the image forming device 100, and the photosensitive drum 10 is configured to be movable relative to the brush member 11. In the second embodiment, a moving mechanism 110 is provided that is configured to move the photosensitive drum 10 relative to the brush member 11 by abutting and pressing the developing roller 25 against the surface of the photosensitive drum 10. The specific configuration of the moving mechanism 110 for moving the developing roller 25 against and away from the surface of the photosensitive drum 10 and pressing it against the photosensitive drum 10 can appropriately use a known drive transmission mechanism or biasing mechanism using gears, elastic members, etc., and therefore a detailed description thereof will be omitted here.

[0056] The brush member 11 and the photosensitive drum 10 are relatively movable between a first position where the tip of the pile yarn 11a is separated from the surface of the photosensitive drum 10, a third position different from the first position, and a second position where the tip of the pile yarn 11a abuts against the surface of the photosensitive drum 10. Figures 8(a) and 8(b) show a state where the relative positions of the photosensitive drum 10 and the brush member 11 are in the first position. Figure 8(c) shows a state where the relative positions of the photosensitive drum 10 and the brush member 11 are in the second position. Figure 8(d) shows a state where the relative positions of the photosensitive drum 10 and the brush member 11 are in the third position.

[0057] (Contact between the photosensitive drum 10 and the brush member 11) 8(a), when at rest, the relative positions of the brush member 11 and the photosensitive drum 10 are in a first position (retracted position) where the tip of the pile yarn 11a of the brush member 11 is separated from the surface of the photosensitive drum 10. At this time, the photosensitive drum 10 and the developing roller 25 located in the fourth quadrant are separated from each other.

[0058] During image formation, as shown in FIG. 8B, the developing roller 25 is first pressed in the direction of the arrow M1 by the moving mechanism 110 and comes into contact with the photosensitive drum 10. The photosensitive drum 10 moves in the first direction M1 (pressing direction) by this pressing force, whereby the shaft portion 10b of the photosensitive drum 10 comes into contact with the first abutment surface 30 located in the second quadrant. In a virtual plane perpendicular to the rotation axis O of the photosensitive drum 10, the first direction M1 is a direction from the fourth quadrant to the second quadrant, and the angle θ between the first direction M1 and the first abutment surface 30 that comes into contact with the shaft portion 10b of the photosensitive drum 10 in the second quadrant is 90 degrees or more. In other words, the component M1a of the first direction M1 parallel to the first abutment surface 30 is a direction toward the brush member 11, that is, a direction away from the origin O. Due to this contact, the moving direction of the photosensitive drum 10, which is pressed in the first direction M1 by the moving mechanism 110 via the developing roller 25, changes to a second direction (the direction of the arrow M2) that is not parallel to the first direction M1, as shown in Fig. 8(c). The second direction M2 is a direction parallel to a component M1a of the first direction M1 that is parallel to the first abutting surface 30.

[0059] When the photosensitive drum 10 is further pressed in the first direction M1 by the moving mechanism 110 via the developing roller 25, the photosensitive drum 10 moves further in the second direction M2, and the surface of the photosensitive drum 10 comes into contact with the brush member 11. At this time, the relative positions of the photosensitive drum 10 and the brush member 11 are at a second position (contact position) where the tip of the pile yarn 11a comes into contact with the surface of the photosensitive drum 10. As shown in FIG. 8(c), in the relative movement from the first position to the second position, the relative approach direction M20 of the brush member 11 to the photosensitive drum 10 is opposite to the second direction M2 in which the photosensitive drum 10 approaches the brush member 11. This approach direction M20 is a direction from the downstream side to the upstream side of the rotation direction R of the photosensitive drum 10. Here, in a virtual plane perpendicular to the rotation axis O of the photosensitive drum 10, point I is defined as a contact range between the tip of the pile yarn 11a and the surface of the photosensitive drum 10 when the relative positions of the photosensitive drum 10 and the brush member 11 are in the second position. Here, point I is defined as a point in the center of the short side direction of the contact range. Also, a direction parallel to the tangent H of the surface of the photosensitive drum 10 at point I is referred to as a tangential direction. In this case, the direction of the tangential component M20a of the approach direction M20 is opposite to the rotation direction R of the photosensitive drum 10 at point I. In other words, the dot product of the vector of the approach direction M20 and the vector of the rotation direction R of the photosensitive drum 10 at point I is a negative value.

[0060] The moving direction M2 of the photosensitive drum 10 at the time of contact faces the downstream side of the rotation direction R of the photosensitive drum 10 with respect to the straight line L connecting the origin O of the photosensitive drum 10 and the short-side center 11d of the brush member 11. As a result, the direction of the pile yarn 11a is aligned with the rotation direction R of the photosensitive drum 10. After the photosensitive drum 10 contacts the brush member 11, the shaft portion 10b of the photosensitive drum 10 contacts the second abutment surface 31 located in the first quadrant, and the contact operation ends. In this way, when the relative position between the photosensitive drum 10 and the brush member 11 moves from the first position (retracted position) to the second position (contact position), the relative approach direction M20 of the brush member 11 to the photosensitive drum 10 always faces from the downstream side to the upstream side of the rotation direction R. As a result, the falling direction of the pile yarn 11a is uniformly the same direction, so that the occurrence of sparse and dense pile yarns 11a can be suppressed.

[0061] FIG. 9(a) shows a state where the photosensitive drum 10 and the brush member 11 are in the second position (contact position). As shown in FIG. 9(a), in a virtual plane perpendicular to the rotation axis O of the photosensitive drum 10, an angle θ3 is formed between a line passing through point I and parallel to the approach direction M20 and a line (tangent H) passing through point I and parallel to the rotation direction R at point I. The smaller θ3 is, the more likely the pile yarns 11a are to receive a force in the rotation direction of the photosensitive drum 10. Therefore, the pile yarns 11a are more likely to fall in unison in the rotation direction R of the photosensitive drum 10. Conversely, the larger θ is, the more likely the direction of the pile yarns 11a is to become random, so the effect of the pile yarns 11a falling in unison in the rotation direction R of the photosensitive drum 10 is reduced. According to the inventors' study, a range of 0°≦θ3≦60° is preferable.

[0062] (Separation of the photosensitive drum 10 and the brush member 11) When the image formation is completed, as shown in FIG. 9B, the brush member 11 starts to separate from the photosensitive drum 10. At this time, if the photosensitive drum 10 moves in the opposite direction along the same path as when it moves from the first position (separated position) to the second position (contact position), the pile yarn 11a is released from the pressure while receiving a force in the opposite direction to the rotation direction R of the photosensitive drum 10. In this case, the direction of the pile yarn 11a may be disturbed. Therefore, in the second embodiment, when the brush member 11 is released from the second position, it moves from the second position to the third position (separated position different from the first position) along a path different from the path from the first position to the second position. As shown in FIG. 9B, in the relative movement of the photosensitive drum 10 and the brush member 11 from the second position to the third position, the moving mechanism 110 moves the photosensitive drum 10 so that the photosensitive drum 10 is separated from the brush member 11 in the third direction M3. In the relative movement from the second position shown in FIG. 9A to the third position shown in FIG. 9B, a relative separation direction M30 of the brush member 11 from the photosensitive drum 10 is opposite to a third direction M3 in which the photosensitive drum 10 separates from the brush member 11. The separation direction M30 is a direction from the downstream side to the upstream side of the rotation direction R of the photosensitive drum 10. In other words, the direction of the tangential component M30a of the separation direction M30 is opposite to the rotation direction R at the point I of the photosensitive drum 10. In other words, the dot product of the vector of the separation direction M30 and the vector of the rotation direction R at the point I of the photosensitive drum 10 is a negative value.

[0063] 9(a), the position of the brush member 11 corresponding to point I, which was in contact with the photosensitive drum 10 at point I in the second position (contact position), is designated as point U. As shown in FIG. 9(b), in a virtual plane perpendicular to the rotation axis O of the photosensitive drum 10, if an angle θ4 between a line passing through point U and parallel to the separation direction M30 and a line passing through point U and parallel to the tangent line H is designated as 90°≦θ4≦180°, it is preferable. In this way, the pile yarns 11a continue to receive a force in the same direction as the rotation direction R of the photosensitive drum 10 even during the pressure release operation, so that the direction of the pile yarns 11a is maintained uniform.

[0064] In the second embodiment, when moving from the first position in FIG. 8(a) to the second position in FIG. 8(c), the photosensitive drum 10 moves along a path where the photosensitive drum 10 abuts against the first abutment surface 30 as shown in FIG. 8(b). In contrast, in the separation operation from the second position in FIG. 8(c) to the third position in FIG. 8(d), the photosensitive drum 10 is released from the brush member 11 along a path where the photosensitive drum 10 does not abut against the first abutment surface 30. Specifically, when image formation is completed, the moving mechanism 110 operates to separate the developing roller 25 from the photosensitive drum 10. This separation operation removes the pressure on the photosensitive drum 10, so the photosensitive drum 10 is released from the brush member 11 by its own weight. In this case, θ4=90°. By adopting this configuration, the configuration of the moving mechanism 110 can be simplified compared to the configuration of the moving mechanism 110 required to realize the separation operation shown in FIG. 9. In this configuration, the third position in FIG. 8(d) and the first position in FIG. 8(a) may be the same position. In this case, the moving mechanism 110 performs relative movement so that the path of the relative position between the photosensitive drum 10 and the brush member 11 when moving from the first position to the second position is different from the path when moving from the second position to the third position (=first position). Specifically, as described above, the approach direction M20 when the brush member 11 approaches the photosensitive drum 10 relatively is directed toward the upstream side of the rotation direction R of the photosensitive drum 10. And, the separation direction M30 when the brush member 11 relatively separates from the photosensitive drum 10 is at least not directed toward the downstream side of the rotation direction R of the photosensitive drum 10. By doing so, the pile yarn 11a does not continue to receive a force in the same direction as the rotation direction R of the photosensitive drum 10 during the pressing release operation, but does not receive a force in the opposite direction to the rotation direction R, so that the pile yarn 11a can be prevented from being disturbed. Therefore, it is possible to prevent the pile yarns 11a from varying in density.

[0065] After the pressure release operation is completed, the photosensitive drum 10 returns to the retreat position and waits for the next image forming operation. After that, the same operation is repeated.

[0066] Example 3 In the first and second embodiments, the contact and separation method has been described using the photosensitive drum 10 and the brush member 11 as examples of a rotatable rotating member and a brush member that is movable relative to the rotating member, but the rotatable rotating member is not limited to the photosensitive drum 10. As the rotatable rotating member, the present invention can be similarly applied to other rotating members (transfer roller, charging roller (charging member)) in an electrophotographic system to obtain the above-mentioned effects. In addition, the present invention can be applied to a contact and separation method of a movable moving member and a brush member that is movable relative to the moving member to obtain the same effects as those in the first and second embodiments. Examples of such moving members include a photosensitive belt and a transfer belt (transfer member). Below, an embodiment in which the present invention is applied to a contact and separation method of a transfer belt and a brush member will be described.

[0067] Figure 11 shows the transfer of the toner image from the photosensitive drum to the transfer belt, followed by the transfer of the toner image from the transfer belt. An embodiment in which the present invention is applied to an image forming apparatus configured to perform secondary transfer of a toner image onto a recording material is shown. In FIG. 11, the same components as those in the first embodiment are given the same reference numerals, and detailed description is omitted. The image forming apparatus 200 shown in FIG. 11 has four image forming units that transfer toner images made of toners (developers) of four colors, yellow (Y), magenta (M), cyan (C), and black (K), onto a transfer belt 15. In FIG. 11, each image forming unit is distinguished by the reference numerals Y, M, C, and K representing the color. For example, an image forming unit that forms and transfers a yellow toner image has a photosensitive drum 10Y, a charging roller 12Y, a developing roller 25Y, and a transfer roller 5Y. An electrostatic latent image corresponding to a yellow image is formed on the surface of the photosensitive drum 10Y, and a yellow toner image is developed onto the photosensitive drum 10Y (on the image carrier) by a developing device including the developing roller 25Y. The image forming apparatus 200 has a transfer belt 15, which is an endless belt that is wound around a plurality of rollers and rotatably supported. The transfer belt 15 moves in the direction of the arrow R. A yellow toner image formed on the photosensitive drum 10Y is primarily transferred to the transfer belt 15 at a primary transfer portion formed between the transfer roller 5Y and the photosensitive drum 10Y. Similarly, a magenta toner image, a cyan toner image, and a black toner image are sequentially primarily transferred onto the transfer belt 15 to form a full-color toner image. The full-color toner image formed on the transfer belt 15 is secondarily transferred to a recording material P at a secondary transfer portion formed of secondary transfer rollers 50 and 51. The process after the secondary transfer is the same as in the first embodiment. The transfer residual toner remaining on the transfer belt 15 after the secondary transfer is cleaned by a brush member 11 that can contact the transfer belt 15. The configuration of the brush member 11 is the same as in the first embodiment.

[0068] The image forming apparatus 200 has a moving mechanism 110 that moves the brush member 11 and the transfer belt 15, which is a moving member, relatively. FIG. 11 shows a state in which the relative position between the brush member 11 and the transfer belt 15 is at a second position where the tip of the fiber thread of the brush member 11 abuts against the surface of the transfer belt 15. In addition, the relative position between the transfer belt 15 and the brush member 11 can be a first position where the tip of the fiber thread of the brush member 11 is separated from the surface of the transfer belt 15, and a third position different from the first position where the tip of the fiber thread of the brush member 11 is separated from the surface of the transfer belt 15. FIG. 12(a) shows a state in which the relative position between the transfer belt 15 and the brush member 11 is at the first position. FIG. 12(b) shows a state in which the relative position between the transfer belt 15 and the brush member 11 is at the second position. FIG. 12(c) shows a state in which the relative position between the transfer belt 15 and the brush member 11 is at the third position.

[0069] The moving mechanism 110 is capable of moving the transfer belt 15 and the brush member 11 relative to each other so that the relative positions of the transfer belt 15 and the brush member 11 move from a first position to a second position and from the second position to a third position, as shown in FIG.

[0070] 12(b), in the relative movement of the transfer belt 15 and the brush member 11 from the first position to the second position, the approach direction N1 of the brush member 11 to the transfer belt 15 is a direction from the downstream side to the upstream side of the movement direction R of the transfer belt 15. In other words, when the direction parallel to the surface of the transfer belt 15 and perpendicular to the rotation axis direction of the secondary transfer rollers 5, 51, etc. (see FIG. 11) that movably support the transfer belt 15 is defined as the X direction, the direction of the X-direction component N1x of the approach direction N1 is opposite to the movement direction R of the transfer belt 15. In other words, the dot product of the approach direction vector (represented by the arrow N1) and the movement direction vector of the transfer belt 15 (represented by the arrow R) is a negative value. The angle between a line passing through point 11f within contact range 11e between the tip of the pile yarn 11a and the surface of the transfer belt 15 when the relative position between the transfer belt 15 and the brush member 11 is at the second position and parallel to the approach direction N1, and a line passing through point 11f and parallel to the movement direction R, is defined as θ1. θ1 is an acute angle, and preferably satisfies 0°≦θ1≦60°.

[0071] As shown in FIG. 12C, in the relative movement of the transfer belt 15 and the brush member 11 from the second position to the third position, the separation direction N2 of the brush member 11 from the transfer belt 15 is a direction from the downstream side to the upstream side of the moving direction R of the transfer belt 15. The direction of the X-direction component N2x of the removal direction N2 is opposite to the moving direction R of the transfer belt 15. In other words, the inner product of the vector of the removal direction (indicated by the arrow N2) and the vector of the moving direction of the transfer belt 15 (indicated by the arrow R) is a negative value. In other words, the angle θ2 between a line passing through the point 11f and parallel to the removal direction N2 and a line passing through the point 11f and parallel to the moving direction R is a right angle or an obtuse angle, and is preferably 90°≦θ2≦180°.

[0072] In the third embodiment, the moving mechanism 110 moves the brush member 11 relative to the transfer belt 15 to relatively move the transfer belt 15 and the brush member 11, but is not limited thereto. The moving mechanism 110 may be configured to move the transfer belt 15 relative to the brush member 11, or may be configured to move both the transfer belt 15 and the brush member 11.

[0073] Also, the relative positions of the transfer belt 15 and the brush member 11 may be configured to be movable from the third position to the first position. As a result, when the transfer belt 15 and the brush member 11 are once moved from the second position to the third position and separated from each other, and then the transfer belt 15 and the brush member 11 are brought into contact with each other again, the transfer belt 15 and the brush member 11 can be returned to the first position and then moved to the second position. Therefore, when the brush member 11 is brought into contact with the transfer belt 15, the brush member 11 can always be brought into contact with the transfer belt 15 while approaching the transfer belt 15 in the approach direction N1. This allows the pile yarn 11a to be brought into contact with the transfer belt 15 more reliably and uniformly inclined in a certain direction, and the density of the pile yarn 11a at the contact position can be prevented from varying. This allows the occurrence of image defects downstream in the movement direction of the transfer belt 15 from the contact position to be more reliably prevented.

[0074] The disclosure of this embodiment includes the following configuration. (Configuration 1) A rotatable rotating member; A flat brush member having fiber yarns; having The rotating member and the brush member are relatively movable between a first position where the tip of the fiber yarn is separated from the surface of the rotating member and a second position where the tip of the fiber yarn is in contact with the surface of the rotating member, An image forming apparatus characterized in that, during the relative movement from the first position to the second position, the direction of approach of the brush member relative to the rotating member is from the downstream side to the upstream side of the rotation direction of the rotating member. (Configuration 2) In a virtual plane perpendicular to the rotation axis of the rotating member, When the relative position of the rotating member and the brush member is in the second position, an angle θ1 between a line passing through a point within a contact range between the tip of the fiber yarn and the surface of the rotating member and parallel to the approach direction, and a line passing through the point and parallel to the rotation direction at the point is 0°≦θ1≦60° 2. The image forming apparatus according to claim 1, (Configuration 3) A rotatable rotating member; A flat brush member having fiber yarns; having The rotating member and the brush member are relatively movable between a second position where the tip of the fiber yarn abuts against the surface of the rotating member and a third position where the tip of the fiber yarn is separated from the surface of the rotating member, An image forming apparatus characterized in that, during the relative movement from the second position to the third position, the direction in which the brush member moves relatively away from the rotating member is from the downstream side to the upstream side in the rotation direction of the rotating member. (Configuration 4) In a virtual plane perpendicular to the rotation axis of the rotating member, When the relative position of the rotating member and the brush member is in the second position, an angle θ2 is formed between a line passing through a point within a contact range between the tip of the fiber yarn and the surface of the rotating member and parallel to the separation direction, and a line passing through the point and parallel to the rotation direction at the point, 90°≦θ2≦180° 4. The image forming apparatus according to claim 3, wherein (Configuration 5) A rotatable rotating member; A flat brush member having fiber yarns; having the rotating member and the brush member are relatively movable among a first position where the tip of the fiber yarn is separated from the surface of the rotating member, a second position where the tip of the fiber yarn is in contact with the surface of the rotating member, and a third position different from the first position where the tip of the fiber yarn is separated from the surface of the rotating member; an image forming apparatus characterized in that, in a rotation direction of the rotating member, a position of the brush member at the first position is downstream of a position of the brush member at the second position, and a position of the brush member at the third position is upstream of a position of the brush member at the second position. (Configuration 6) A rotatable rotating member; A flat brush member having fiber yarns; having the rotating member and the brush member are relatively movable among a first position where the tip of the fiber yarn is separated from the surface of the rotating member, a second position where the tip of the fiber yarn is in contact with the surface of the rotating member, and a third position different from the first position where the tip of the fiber yarn is separated from the surface of the rotating member; an image forming apparatus characterized in that a direction in which the brush member approaches the rotating member relatively during the relative movement from the first position to the second position, and a direction in which the brush member moves relatively away from the rotating member during the relative movement from the second position to the third position, are both directions from the downstream side to the upstream side of the rotation direction of the rotating member. (Configuration 7) 7. The image forming apparatus according to any one of configurations 1 to 6, wherein the rotating member is an image carrier on which an electrostatic latent image is formed. (Configuration 8) 8. The image forming apparatus according to any one of configurations 1 to 7, wherein the rotating member is a charging member that charges an image bearing member on which an electrostatic latent image is formed. (Configuration 9) A movable moving member; A flat brush member having fiber yarns; having the moving member and the brush member are relatively movable between a first position where the tip of the fiber yarn is separated from the surface of the moving member and a second position where the tip of the fiber yarn is in contact with the surface of the moving member; An image forming apparatus characterized in that, during the relative movement from the first position to the second position, the direction of approach of the brush member relative to the movable member is from the downstream side to the upstream side of the movement direction of the movable member. (Configuration 10) A movable moving member; A flat brush member having fiber yarns; having the moving member and the brush member are relatively movable among a first position where the tip of the fiber yarn is separated from the surface of the moving member, a second position where the tip of the fiber yarn is in contact with the surface of the moving member, and a third position different from the first position where the tip of the fiber yarn is separated from the surface of the moving member; An image forming apparatus characterized in that, in the movement direction of the movable member, the position of the brush member at the first position is downstream of the position of the brush member at the second position, and the position of the brush member at the third position is upstream of the position of the brush member at the second position. (Configuration 11) A movable moving member; A flat brush member having fiber yarns; having the moving member and the brush member are relatively movable among a first position where the tip of the fiber yarn is separated from the surface of the moving member, a second position where the tip of the fiber yarn is in contact with the surface of the moving member, and a third position different from the first position where the tip of the fiber yarn is separated from the surface of the moving member; An image forming apparatus characterized in that the direction of relative approach of the brush member to the movable member during the relative movement from the first position to the second position, and the direction of relative departure of the brush member from the movable member during the relative movement from the second position to the third position, are both directions from the downstream side to the upstream side of the movement direction of the movable member. (Configuration 12) 12. The image forming apparatus according to any one of configurations 9 to 11, wherein the moving member is a transfer member onto which a developer on an image carrier on which an electrostatic latent image is formed is transferred. [Explanation of symbols]

[0075] 10: photosensitive drum, 11: brush member, 11a: pile yarn, 100: image forming apparatus

Claims

1. A rotatable photosensitive drum; a non-rotatable brush member having a support member and a fiber yarn contacting the surface of the photosensitive drum, the non-rotatable brush member supporting the fiber yarn on the support member; a moving mechanism that supports the support member and moves the brush member to a first position where the fiber yarn is separated from the surface of the photosensitive drum, a second position where the fiber yarn is in contact with the surface of the photosensitive drum, and a third position different from the first position where the fiber yarn is completely separated from the surface of the photosensitive drum; having An image forming apparatus characterized in that, when the brush member moves from the first position to the second position, the direction in which the brush member approaches the photosensitive drum is a direction from the downstream side to the upstream side in the rotation direction of the photosensitive drum, and, when the brush member moves from the second position to the third position, the direction in which the brush member leaves the photosensitive drum is a direction from the downstream side to the upstream side in the rotation direction of the photosensitive drum.

2. In a virtual plane perpendicular to the rotation axis of the photosensitive drum, The angle θ1 between a line passing through a point within the contact range between the fiber yarn and the surface of the photosensitive drum when the brush member is in the second position and parallel to the approach direction, and a line passing through the point and parallel to the rotation direction at the point, is 0°≦θ1≦60° The image forming apparatus according to claim 1 , wherein the above-mentioned condition is satisfied.

3. In a virtual plane perpendicular to the rotation axis of the photosensitive drum, The angle θ2 between a line passing through a point within the contact range between the fiber yarn and the surface of the photosensitive drum when the brush member is in the second position and parallel to the separation direction, and a line passing through the point and parallel to the rotation direction at the point, is 90°≦θ2≦180° The image forming apparatus according to claim 1 , wherein the above-mentioned condition is satisfied.

4. A rotatable photosensitive drum; a non-rotatable brush member having a support member and a fiber yarn contacting the surface of the photosensitive drum, the non-rotatable brush member supporting the fiber yarn on the support member; a moving mechanism that supports the support member and moves the brush member to a first position where the fiber yarn is separated from the surface of the photosensitive drum, a second position where the fiber yarn is in contact with the surface of the photosensitive drum, and a third position different from the first position where the fiber yarn is completely separated from the surface of the photosensitive drum; having An image forming apparatus characterized in that, in the rotation direction of the photosensitive drum, the position of the brush member at the first position is downstream of the position of the brush member at the second position, and the position of the brush member at the third position is upstream of the position of the brush member at the second position.

5. In a virtual plane perpendicular to the rotation axis of the photosensitive drum, The angle θ1 between a straight line that passes through a point within the contact range between the fiber yarn and the surface of the photosensitive drum when the brush member is at the second position and is parallel to the approach direction of the brush member to the photosensitive drum when the brush member moves from the first position to the second position, and a straight line that passes through the point and is parallel to the rotation direction at the point is given by: 0°≦θ1≦60° The image forming apparatus according to claim 4 , which satisfies the above condition.

6. In a virtual plane perpendicular to the rotation axis of the photosensitive drum, The angle θ2 between a straight line that passes through a point within the contact range between the fiber yarn and the surface of the photosensitive drum when the brush member is at the second position and is parallel to the direction in which the brush member separates from the photosensitive drum when the brush member moves from the second position to the third position, and a straight line that passes through the point and is parallel to the direction of rotation at the point is given by: 90°≦θ2≦180° The image forming apparatus according to claim 4 , which satisfies the above condition.

Images