JP6344553B2 - Optical writing head positioning mechanism, process unit, and image forming apparatus - Google Patents

Description

  The present invention relates to an optical writing head positioning mechanism that determines the position of an optical writing head with respect to a latent image carrier, a process unit including the same, and an image forming apparatus.

  As an exposure apparatus that exposes a latent image carrier such as a photosensitive drum to form a latent image, an image forming apparatus using an optical writing head composed of an LED or an organic EL element is known. In such an image forming apparatus, since it is required to determine the position of the optical writing head with respect to the latent image carrier with high accuracy, in general, the optical writing that determines the position of the optical writing head with respect to the latent image carrier is performed. A head positioning mechanism is provided.

  For example, Patent Document 1 describes an optical writing head positioning mechanism using a spacer member provided between a latent image carrier and an optical writing head.

  By the way, in a positioning mechanism using a spacer member, if foreign matter such as toner adhered on the latent image carrier enters between the contact surfaces of the spacer member and the latent image carrier, optical writing to the latent image carrier is performed. There is a problem that the head positioning accuracy cannot be secured.

  With respect to such a problem, in the apparatus described in Patent Document 1, the radius of curvature of the contact surface of the spacer member with the latent image carrier is made smaller than the radius of curvature of the latent image carrier, and the spacer member has elasticity. By doing so, the spacer member is brought into close contact with the surface of the latent image carrier.

  However, it is difficult to effectively prevent the intrusion of foreign matter between the spacer member and the surface of the latent image carrier with no gap therebetween.

In order to solve the above problems, the present invention is provided between a latent image carrier that carries a latent image and an optical writing head that exposes the latent image carrier to form a latent image, and In an optical writing head positioning mechanism comprising a spacer member for determining the position of the optical writing head with respect to the carrier,
A passage blocking agent that prevents foreign matter on the latent image carrier from passing between the contact surfaces of the spacer member and the latent image carrier is attached to the spacer member, and the spacer member A plurality of contact surfaces with the image carrier are provided, and each of the contact surfaces is arranged at least one on each side so as to avoid a boundary of a cleaning area by a cleaning means for cleaning the surface of the latent image carrier. And

  According to the present invention, it is possible to prevent foreign matter from entering between the contact surfaces of the spacer member and the latent image carrier by attaching the passage blocking agent to the spacer member. The position can be maintained with high accuracy.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is a schematic block diagram of the process unit which concerns on this embodiment. It is a schematic block diagram of the optical writing head positioning mechanism which concerns on this embodiment. It is a schematic block diagram of the optical writing head positioning mechanism which concerns on this embodiment. It is a figure which shows the structure of the spacer member which concerns on this embodiment. It is a figure which shows the relationship between a spacer front end width | variety and a load. It is a figure which shows a mode that a passage inhibitor is made to adhere to the spacer member which concerns on this embodiment. It is a figure which shows the experimental result which evaluates the foreign-material sticking property and cleaning property of a passage inhibitor. It is a schematic block diagram of another optical writing head positioning mechanism. It is a figure which shows a mode that a foreign material adheres to the photoreceptor surface.

  Hereinafter, the present invention will be described with reference to the accompanying drawings. In the drawings for explaining the present invention, components such as members and components having the same function or shape are denoted by the same reference numerals as much as possible, and once described, the description will be given. Omitted.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. First, the overall configuration and operation of the image forming apparatus will be described with reference to FIG.

  The image forming apparatus shown in FIG. 1 is a monochrome image forming apparatus. A process unit 1 as an image forming unit is detachably attached to an apparatus main body (image forming apparatus main body) 100 of such an image forming apparatus. The process unit 1 includes a drum-shaped photosensitive member 2 as a latent image carrier that carries an image on the surface, a charging roller 3 as a charging unit that charges the outer peripheral surface of the photosensitive member 2, and an outer peripheral surface of the photosensitive member 2. An optical writing head 4 as an exposure unit that forms an electrostatic latent image by exposure, a developing roller 5 as a developing unit that visualizes the latent image on the photosensitive member 2, and the photosensitive member 2. A cleaning blade 6 as a cleaning means for cleaning the surface of the photosensitive member 2 and a neutralizing device (not shown) for neutralizing the outer peripheral surface of the photoreceptor 2.

  All of the above-described photoreceptor 2, charging roller 3, optical writing head 4, developing roller 5, cleaning blade 6, and static eliminating device are integrally provided on the support of the process unit 1. For this reason, these parts can be replaced at once by attaching and detaching the process unit 1 to and from the apparatus main body 100.

  Further, a transfer roller 7 is disposed at a position facing the photoconductor 2 as transfer means for transferring an image on the photoconductor 2 to a sheet. The transfer roller 7 is disposed at a position where the transfer unit 7 can come into contact with the photoreceptor 2 in a state where the process unit 1 is mounted on the apparatus main body 100, and a transfer nip is formed by the contact portion between the two. Further, the transfer roller 7 is connected to a power source (not shown) so that a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied.

  A sheet feeding device 8 is disposed at the lower part of the apparatus main body 100. The paper feeding device 8 has a nip between a paper feeding cassette 9 that stores paper as a recording medium, a paper feeding roller 10 that feeds paper stored in the paper feeding cassette 9, and the paper feeding roller 10. A separation pad 11 and the like for separating the formed and overlapped sheets are provided. The paper includes cardboard, postcard, envelope, plain paper, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like. In addition, an OHP sheet, an OHP film, a fabric, or the like can be used as a recording medium other than paper.

  The sheet fed from the sheet feeding device 8 is conveyed in the direction indicated by the dotted arrow in the drawing along the conveyance path provided in the apparatus main body 100. In this transport path, a pair of timing rollers 12 that transport the paper to the transfer nip at a transport timing downstream of the paper feed roller 10 in the paper transport direction and upstream of the transfer roller 7 in the paper transport direction. Is arranged.

  In the transport path, a fixing device 13 for fixing the image transferred to the paper is disposed downstream of the transfer roller 7 in the paper transport direction, and a pair of paper for discharging the paper to the outside of the device is further provided on the downstream side. The paper discharge roller 16 is disposed. The fixing device 13 includes a fixing roller 14 heated by a heat source such as a halogen lamp (not shown), and a pressure roller 15 that rotates while contacting the fixing roller 14 with a predetermined pressure. A fixing nip is formed at the contact points 14 and 15. In addition, a paper discharge tray 17 on which the paper discharged outside the apparatus by the paper discharge roller 16 is placed is provided on the upper portion of the apparatus main body 100.

Next, an image forming operation of the image forming apparatus according to the present embodiment will be described with reference to FIG.
When the image forming operation is started, the photosensitive member 2 is rotationally driven, and the surface of the photosensitive member 2 is uniformly charged to a predetermined polarity by the charging roller 3. Then, based on image information from a reading device or a computer (not shown), light is irradiated from the optical writing head 4 to the surface of the photoreceptor 2, and an electrostatic latent image is formed on the charged surface of the photoreceptor 2. The By supplying toner from the developing roller 5 to the electrostatic latent image on the photoreceptor 2 formed in this way, the electrostatic latent image is visualized (visualized) as a toner image.

  When the image forming operation is started, the paper feed roller 10 starts to rotate, and only the uppermost paper among the papers stored in the paper feed cassette 9 is sent out to the transport path. The fed paper is temporarily stopped by the timing roller 12. Thereafter, rotation of the timing roller 12 is started at a predetermined timing, and the sheet is conveyed to the transfer nip in accordance with the timing at which the toner image on the photoreceptor 2 reaches the transfer nip.

  At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the photoreceptor 2 is applied to the transfer roller 7, thereby forming a transfer electric field in the transfer nip. Then, the toner image on the photoreceptor 2 is transferred onto the paper by this transfer electric field. The residual toner on the photoreceptor 2 that could not be transferred onto the paper is removed by the cleaning blade 6. Thereafter, the surface of the photoreceptor 2 is neutralized by a neutralizing device (not shown).

  The sheet on which the toner image has been transferred is conveyed to the fixing device 13 and is heated and pressurized by passing through the fixing nip between the fixing roller 14 and the pressure roller 15 to fix the toner image on the sheet. Is done. The paper is then discharged out of the apparatus by the paper discharge roller 16 and placed on the paper discharge tray 17.

  Incidentally, the optical writing head 4 uses an LED or an organic EL element as a light emitting element. Since such a light emitting element has a shallow depth of focus (about 100 μm), it is necessary to determine the position of the optical writing head 4 with respect to the photoreceptor 2 with high accuracy. For this reason, the process unit 1 is provided with an optical writing head positioning mechanism for positioning the optical writing head 4 with respect to the photoreceptor 2. Hereinafter, the optical writing head positioning mechanism will be described.

  As shown in FIG. 2, the optical writing head positioning mechanism 20 includes a spacer member 21 that is in contact with the photosensitive member 2 and the optical writing head 4 and is provided therebetween. The spacer member 21 functions as a regulating member that regulates the distance between the photosensitive member 2 and the optical writing head 4 and plays a role of determining the distance between them.

  As shown in FIG. 3, the optical writing head 4 is arranged extending in the axial direction (main scanning direction) of the photoreceptor 2. The optical writing head 4 includes a lens array 4a, a light emitting substrate (not shown), and a head frame 4b as a holding member that holds the lens array 4a and the light emitting substrate. The spacer members 21 are disposed on both ends of the optical writing head 4 in the longitudinal direction or in the axial direction of the photosensitive member 2, and are in contact with the head frame 4 b of the optical writing head 4 and the photosensitive member 2, respectively. Then, in a state where the spacer member 21 is in contact with both the photosensitive member 2 and the optical writing head 4, the spacer member 21 is moved from the optical writing head 4 to the photosensitive member 2 by an urging means (not shown) such as a coil spring. It is configured to receive a load.

  Here, when the maximum image forming area on which the toner image is formed on the photoreceptor 2 is A, the contact of the spacer member 21 with the photoreceptor 2 is suppressed in order to suppress wear of the photoreceptor 2 in the maximum image forming area A. The surface 21a is disposed outside the maximum image forming area A.

  Further, in the present embodiment, each spacer member 21 is in contact with the photosensitive member 2 at two locations separated from each other in the axial direction. That is, each spacer member 21 has two contact surfaces 21a that contact the photoreceptor 2 at positions separated from each other. These two contact surfaces 21a are arranged on both sides of the photosensitive member 2 so as to avoid the boundary (cleaning region end) of the cleaning region B where the cleaning blade 6 contacts.

  As described above, by arranging the contact surfaces 21a on both sides of the boundary of the cleaning region B, streaky residual toner generated in the vicinity of the boundary of the cleaning region B is transferred to the photoreceptor 2 and the spacer member 21 (contact surface 21a). To prevent intrusion between. This prevents a decrease in the positional accuracy of the optical writing head 4 with respect to the photosensitive member 2 due to the residual toner entering between the photosensitive member 2 and the spacer member 21.

  In addition to the arrangement of the present embodiment as described above, in order to arrange the contact surface 21a of the spacer member 21 while avoiding the boundary of the cleaning region B, for example, two contact surfaces 21a are provided as shown in FIG. It is also conceivable to arrange them inside the boundary of the cleaning region B without dividing them. However, in this case, the length Lb of the cleaning area B in the photoconductor axis direction is equal to the length La of the maximum image forming area A in the photoconductor axis direction and the photoconductor axis direction of the contact surfaces 21a of both spacer members 21. It becomes longer than the total with the length Lc (Lb> La + 2Lc). As a result, the length of the cleaning blade 6 becomes long.

  Further, when the contact surface 21 a of the spacer member 21 is disposed outside the boundary of the cleaning region B, the axial length Ld of the photosensitive member 2 outside the cleaning region B is set to the photosensitive surface 21 a of the spacer member 21. It is necessary to make it longer than the length Lc in the body axis direction. Therefore, in this case, the entire axial length of the photosensitive member 2 becomes long.

  As described above, when the contact surface 21a is arranged inside or outside the cleaning region B without being divided into two, the length of the cleaning blade 6 and the total length of the photosensitive member 2 are increased, and in both cases, the size is reduced. Disadvantageous.

  On the other hand, when the contact surface 21a is arranged separately on both sides of the boundary of the cleaning region B as in this embodiment, the length of the spacer member 21 in the photosensitive member axial direction is the same as the example shown in FIG. Even in such a case, the length of the cleaning blade 6 and the entire length of the photosensitive member 2 can be shortened. As a result, in this embodiment, both prevention of a decrease in the positional accuracy of the optical writing head 4 due to intrusion of residual toner between the photosensitive member 2 and the spacer member 21 and a reduction in the size of the apparatus are realized. Can do. In addition, the contact surface 21a which contacts the photoconductor 2 in one spacer member 21 may be three or more. Even in such a case, the same effect as described above can be obtained by disposing at least one contact surface 21a on each side of the contact surface 21a avoiding the boundary of the cleaning region B.

FIG. 10 is a view of the configuration shown in FIG. 9 as viewed from the optical writing head side.
As shown in FIG. 10A, also in this example, a cleaning blade 6 as a cleaning unit is provided so as to contact the photoreceptor 2 as in the present embodiment. Accordingly, residual toner or the like remaining on the photoreceptor 2 after image transfer is basically removed from the photoreceptor 2 by the cleaning blade 6. However, a free substance such as silica that has been peeled off from the toner has a size of several nanometers and is particularly small, and thus may pass through the cleaning blade 6 without being removed. The free substance that has passed through remains on the photoreceptor 2 and becomes a cleaning residue.

  As shown in FIG. 10B, the cleaning residue G that has passed through the cleaning blade 6 contacts the spacer member 21 that is downstream of the cleaning blade 6 in the photosensitive member rotation direction (latent image carrier rotation direction). , Deposited on the upstream side in the rotation direction of the photosensitive member. Thereafter, as shown in FIG. 10C, a part of the accumulated cleaning residue G moves into the maximum image forming area A at a certain timing due to vibration or the like. Then, as shown in FIG. 10D, the cleaning residue G that has moved into the maximum image forming area A is pressed against the photoconductor 2 by the developing roller 5 and the cleaning blade 6 and is fixed on the photoconductor 2. Further, as shown in FIG. 10E, when residual toner or the like adheres from the fixed cleaning residue G as a starting point and the fixed matter becomes large, an image defect may occur due to this.

  With respect to such a problem, in the present embodiment, as shown in FIG. 3, of the two contact surfaces 21 a with the photosensitive member 2 included in the spacer member 21, a contact surface 21 a 1 (hereinafter referred to as the contact surface 21 a 1) disposed inside the cleaning region B , The width W1 in the direction of the photoconductor axis of the photoconductor axis of the photoconductor axis of the contact surface 21a2 (hereinafter referred to as the “outside photoconductor contact surface”) disposed outside the cleaning region B. It is smaller than the width W2 in the direction. By configuring in this way, even if free substances that have been peeled off from the toner pass through the cleaning blade 6, accumulation of cleaning residues on the inner photoreceptor contact surface 21a1 can be suppressed. As a result, it is possible to reduce the chance or amount of the accumulated cleaning residue to move into the maximum image forming area A and fix it, and to suppress the occurrence of image defects due to the fixing of the cleaning residue. Become.

  Furthermore, as shown in FIG. 4, in the present embodiment, the inner photoconductor contact surface 21a1 is inclined with respect to the photoconductor axis direction. Specifically, the inner photoconductor contact surface 21a1 is inclined so as to be separated from the maximum image forming area A from the upstream side to the downstream side in the photoconductor rotation direction. Accordingly, the cleaning residue can be moved along the inclination of the inner photoconductor contact surface 21a1, and the cleaning residue can be moved away from the maximum image forming area A. Therefore, the cleaning residue is fixed to the maximum image forming area A. It becomes possible to suppress more effectively. In the present embodiment, the entire inner photoconductor contact surface 21a1 is inclined, but the edge 210 (facing the upstream side in the photoconductor rotation direction on which the cleaning residue in particular accumulates on the inner photoconductor contact surface 21a1. Hereinafter, only the “upstream side edge portion”) may be inclined.

FIG. 5 is a diagram showing a configuration of the spacer member 21 according to the present embodiment.
Hereinafter, the configuration of the spacer member 21 will be described in detail with reference to FIGS.
Both spacer members 21 have one contact surface 21b in contact with the optical writing head 4, one (the right spacer member 21 in FIG. 4) and the other (the left spacer member 21 in FIG. 4). Except for the point, the configuration is almost the same with the shape symmetrical to each other. Therefore, in the following description, the spacer member 21 having two contact surfaces 21b with the optical writing head 4 will be described as an example.

  The spacer member 21 includes a plate-like portion 25, two leg portions 24 provided on the photosensitive member 2 side of the plate-like portion 25 {the lower surface in FIG. 5A}, and the optical writing head 4 of the plate-like portion 25. It is comprised with the two columnar parts 26 provided in the side {upper surface in Fig.5 (a)}. The plate-shaped part 25, the leg part 24, and the columnar part 26 may be integrally molded, or may be molded separately. The leg portions 24 are arranged at both ends in the width direction of the plate-like portion 25 corresponding to the axial direction of the photoconductor 2 with a space therebetween. On the other hand, each columnar portion 26 is disposed in the intermediate portion in the width direction where the leg portion 24 in the plate-like portion 25 is not provided. Further, the columnar portions 26 are arranged at intervals from each other in the direction orthogonal to the width direction of the plate-like portion 25, in other words, in the circumferential direction of the photoreceptor 2.

  Each columnar portion 26 contacts the optical writing head 4 in a state where the spacer member 21 is disposed between the optical writing head 4 and the photosensitive member 2. Accordingly, each columnar portion 26 has a contact surface 21 b that contacts the optical writing head 4. Each columnar portion 26 may be fixed to the optical writing head 4 or may be configured to be able to contact and separate.

  On the other hand, each leg portion 24 comes into contact with the photosensitive member 2 in a state where the spacer member 21 is disposed between the optical writing head 4 and the photosensitive member 2. The contact surface 21 a of each leg 24 with the photoreceptor 2 is formed in an arc shape following the surface shape of the photoreceptor 2. As a result, each leg portion 24 can come into contact with the photoreceptor 2 in a stable posture.

  Further, each leg portion 24 is formed in a rib-shaped portion extending in the photoconductor rotation direction. For this reason, each leg portion 24 is easily elastically deformed along the surface of the photosensitive member 2, and a gap is hardly generated between the leg portion 24 and the photosensitive member 2.

  Of the two legs 24, the leg 24 having the inner photoconductor contact surface 21a1 inclined with respect to the photoconductor rotation direction is narrower than the other leg 24, so that it is more elastically deformed. It is easy to come into contact with the photoreceptor 2 more easily. In addition, since the tip width t1 of the leg portion 24, which is the width of the inner photoconductor contact surface 21a1, is formed smaller than the width t2 on the root side {see FIG. 5 (d)}, the tip width t1 and the root The side t2 is more elastically deformed than the same width t2. As described above, the leg portion 24 having the inner photoconductor contact surface 21a1 is particularly easily elastically deformed, so that a gap is hardly formed between the leg portion 24 and the photoconductor 2. Accordingly, the cleaning residue hardly passes between the contact surfaces of the leg portion 24 and the photosensitive member 2 and moves along the inclination of the leg portion 24, so that the cleaning residue adheres to the maximum image forming area A. Can be suppressed.

  FIG. 6 shows the effect of removing cleaning residues by changing the tip width t1 of the leg 24, which is the width of the inner photoconductor contact surface 21a1, and the load condition that the spacer member 21 receives from the optical writing head 4. It is a figure which shows the experimental result which verifies the change of durability of the photoreceptor 2 and the spacer member 21. This experiment was performed under the following conditions.

<Experimental conditions>
-Photoconductor linear velocity: 240 [mm / s]
-Photoconductor diameter: φ30 [mm]
-Spacer member pressing method: Pressing two contact surfaces against the optical writing head-Inclining angle of the inner photosensitive member contact surface with respect to the rotation direction of the photosensitive member: 23 [°]
The length in the direction perpendicular to the photosensitive member axial direction of the projection area when the inner photosensitive member contact surface is projected onto the surface (plane) on the photosensitive member side of the plate-like portion: 12.8 [mm]
-Width in the photoconductor axial direction of the outer photoconductor contact surface: 2.0 [mm]
The length of the arc of the portion of the outer photoreceptor contact surface that is in contact with the photoreceptor: 9.7 [mm]

  The smaller the tip width t1 of the leg 24 that is the width of the inner photoconductor contact surface 21a1, the easier it is for the inner photoconductor contact surface 21a1 to come into contact with the photoconductor 2. It becomes difficult. On the other hand, if the tip width t1 is made too small, there will be a problem that the tip of the leg portion 24 having the inner photoreceptor contact surface 21a1 is cut off due to the cleaning residue on the photoreceptor 2. If the tip portion of the leg portion 24 is chipped, the cleaning residue on the photoreceptor 2 may slip through after the chipping and the cleaning residue cannot be removed suitably. In order to suppress the occurrence of such chipping at the tip, it is desirable to set the tip width t1 to 0.1 [mm] or more as shown in FIG.

  On the other hand, if the tip width t1 of the leg 24, which is the width of the inner photoconductor contact surface 21a1, is increased, the manufacture of the parts is facilitated, but the inner photoconductor contact surface 21a1 is less likely to contact the photoconductor 2. As a result, a gap is formed between the inner photoconductor contact surface 21a1 and the photoconductor 2, so that the cleaning residue on the photoconductor 2 slips through, and the cleaning residue cannot be removed suitably. In order to suppress the occurrence of such a gap between the inner photoreceptor contact surface 21a1 and the photoreceptor 2, it is desirable to set the tip width t1 to 0.6 [mm] or less as shown in FIG. .

  The larger the load that the spacer member 21 receives from the optical writing head 4, the easier the inner photoreceptor contact surface 21a1 comes into contact with the photoreceptor 2, but if it is too large, the photoreceptor 2 and spacer Wear of the member 21 is promoted. As a result, the distance between the optical writing head 4 and the photosensitive member 2 becomes too close, and defocusing of the optical writing head 4 occurs. In order to suppress such abrasion of the photoreceptor 2 and the spacer member 21, it is desirable to set the load on the spacer member 21 to 8 [N] or less as shown in FIG.

  On the other hand, if the load on the spacer member 21 is reduced, the wear of the photoconductor 2 and the spacer member 21 can be suppressed, but the inner photoconductor contact surface 21a1 is less likely to contact the photoconductor 2. As a result, a gap is formed between the inner photoconductor contact surface 21a1 and the photoconductor 2, so that the cleaning residue on the photoconductor 2 slips through, and the cleaning residue cannot be removed suitably. In order to suppress the occurrence of such a gap between the inner photoreceptor contact surface 21a1 and the photoreceptor 2, the load on the spacer member 21 should be set to 3 [N] or more as shown in FIG. desirable.

  Based on the above results, in the configuration of the present embodiment, the tip width t1 of the leg 24, which is the width of the inner photoconductor contact surface 21a1, is in the range of 0.1 [mm] to 0.6 [mm]. It can be said that it is desirable to set the load on the spacer member 21 within the range of 3 [N] or more and 8 [N] or less.

  However, in the region where the tip width t1 of the leg portion 24 is 0.4 [mm] or more, the inner photoconductor contact surface 21a1 and the photoconductor 2 are caused by variations in the shape of the spacer member 21 and variations in the roughness of the photoconductor 2. The cleaning residue may slip through between the two. Therefore, in order to prevent such cleaning residue from slipping through, the following measures are taken in the present embodiment.

  In this embodiment, in order to prevent foreign matters such as cleaning residues on the photoconductor 2 from passing between the inner photoconductor contact surface 21a1 of the spacer member 21 and the contact surface of the photoconductor 2, FIG. As shown in FIG. 5, silica 30 as a passage blocking agent is attached to the upstream edge 210 of the inner photoreceptor contact surface 21 a 1 of the spacer member 21.

  Specifically, in attaching the silica 30 to the upstream side edge portion 210, first, as shown in FIG. 7A, the silica 30 is attached to the contact surface of the spacer member 21 with the photoreceptor 2 (inner photoreceptor contact). It is applied to the surface of the photoconductor upstream of the surface 21a1) in the photoconductor rotation direction. Next, the photoreceptor 2 is rotated. As a result, the silica 30 moves to the downstream side in the rotation direction of the photosensitive member, and adheres to the upstream edge portion 210 of the inner photosensitive member contact surface 21a1, as shown in FIG. 7B. Further, the silica 30 is not applied to the surface of the photoreceptor 2, but is directly applied (attached) to the upstream edge 210 of the inner photoreceptor contact surface 21 a 1, and then the spacer member 21 is attached to the photoreceptor 2. It may be assembled.

  In this way, by attaching the silica 30 to the upstream side edge portion 210 of the inner photoconductor contact surface 21a1, a minute gap between the inner photoconductor contact surface 21a1 and the photoconductor 2 is blocked by the silica 30, It is possible to prevent foreign matter on the photoconductor 2 from passing through the gap. Accordingly, it is possible to prevent foreign matter from sticking to the surface of the photoconductor 2, and the photoconductor 2 caused by the stuck foreign matter entering between the inner photoconductor contact surface 21 a 1 of the spacer member 21 and the contact surface of the photoconductor 2. Accordingly, it is possible to prevent the positioning accuracy of the optical writing head 4 from being lowered.

  Here, in this embodiment, silica used as an external additive of toner is used as a passage inhibitor, but silica as an external additive of toner passes between the contact surfaces of the spacer member and the photoreceptor. On the other hand, silica as a passage inhibitor is difficult to pass between the contact surfaces. The reason for this is considered to be the difference in the presence or absence of the influence of the wax on the silica. That is, silica as an external toner additive is likely to pass between the contact surfaces of the spacer member and the photosensitive member because it is difficult to adhere to and peel off from the photosensitive member due to the influence of the wax contained in the toner base material. . In addition, there is a silica mixed with wax, which has high viscosity and very low fluidity. On the other hand, since silica as a passage inhibitor contains no wax and is a single silica, it has a very high fluidity and is easily filled in a minute gap between the spacer member and the photosensitive member. For this reason, it is considered that silica as a passage blocking agent stays in a minute gap between the spacer member and the photosensitive member and hardly passes between the contact surfaces of both.

  FIG. 8 shows the silica used as a passage inhibitor, the number average particle diameter (average particle diameter of primary particles when fine particles are monodispersed) and the presence or absence of silicone oil treatment of various silicas. The experimental result which evaluates foreign material adhesivity and cleaning property is shown.

  In this experiment, various types of silica shown in FIG. 8 were attached to the spacer member in the same manner as in the above embodiment, and a predetermined number of images were formed. Then, the presence / absence of foreign matter adhering to the surface of the photoconductor and the presence / absence of cleaning failure due to the passage of the passage inhibitor were confirmed. In FIG. 8, regarding the evaluation of the anti-adhesion property, “◯” indicates that no foreign matter is fixed on the surface of the photosensitive member, and “X” indicates that the foreign matter is fixed. In addition, the evaluation of the cleaning property is “X” when the passage inhibitor passes through the contact surface between the spacer member and the photosensitive member, and the cleaning blade also slips, resulting in poor cleaning. Thereafter, “Δ” indicates that the cleaning failure is eliminated within 10 sheets of image formation, and “◯” indicates that the passage of the passage inhibitor does not occur.

  The number average particle diameter of silica can be measured by a particle size distribution measuring device using dynamic light scattering, for example, DLS-700 manufactured by Otsuka Electronics Co., Ltd. or Coulter N4 manufactured by Coulter Electronics. However, since it is difficult to dissociate the secondary agglomeration of the particles after the silicone oil treatment, it is preferable to directly determine the particle diameter from a photograph obtained by a scanning electron microscope or a transmission electron microscope. More preferably, it is preferable to observe silica at a magnification of 100,000 times by FE-SEM (field emission scanning electron microscope). In this case, at least 100 fine particles are observed, and the average value of the major axis is obtained. In addition, when silica has an aggregate structure, the major axis of single primary particles constituting the aggregate is also obtained.

  According to the evaluation results shown in FIG. 8, with respect to the anti-adhesion property, only Example 1 was evaluated as “x”, and other examples were evaluated as “◯”. In addition, with regard to the cleaning property, Example 1 and Example 7 were evaluated as “×”, Example 2 was evaluated as “Δ”, and other than that was evaluated as “◯”. Considering the above results, the number average particle diameter of the silica is preferably in the range of 0.05 μm or more and less than 0.3 μm in order to ensure both the foreign matter fixing property and the cleaning property. By setting the number average particle size within such a range, it is possible to prevent the passage of foreign matter on the photoconductor, and even if silica passes through the contact surface between the spacer member and the photoconductor, the downstream side It is possible to remove the silica that slips through the cleaning blade.

  In addition, when Example 2 and Example 3 are compared, the number average particle diameter is 0.05 μm, which is the same, but there is a difference between “△” and “◯” in the evaluation of the cleaning property. This difference in cleaning properties is considered to be caused by the presence or absence of the silicone oil treatment. That is, it is considered that the silica treated with the silicone oil of Example 3 is more easily removed by the cleaning blade than the silica not treated with the silicone oil of Example 2. Therefore, it is preferable to use silica treated with silicone oil in order to further improve the cleaning property.

  In addition to silica, examples of the passage inhibitor include alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, iron oxide, copper oxide, zinc oxide, tin oxide, and silica sand. , Clay, mica, wollastonite, diatomaceous earth, chromium oxide, cerium oxide, bengara, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, silicon nitride, etc. can be used .

  Silicone oils used in the silicone oil treatment of the passage blocking agent include dimethyl silicone oil, methylphenyl silicone oil, chlorophenyl silicone oil, methyl hydrogen silicone oil, alkyl modified silicone oil, fluorine modified silicone oil, polyether modified silicone. Oil, alcohol-modified silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, epoxy-polyether-modified silicone oil, phenol-modified silicone oil, carboxyl-modified silicone oil, mercapto-modified silicone oil, acrylic, methacryl-modified silicone oil, α-methylstyrene Examples include modified silicone oil. These silicone oils can be used alone or in a mixture of two or more.

  In order to treat the passage inhibitor with silicone oil, the passage inhibitor and silicone oil which have been sufficiently dehydrated and dried in an oven of several hundred degrees Celsius are brought into uniform contact with each other to adhere the silicone oil to the surface of the passage inhibitor. In order to adhere the silicone oil, the passage inhibitor powder and the silicone oil are sufficiently mixed with the powder using a mixer such as a rotary blade. Alternatively, the silicone oil may be dissolved in a solvent having a relatively low boiling point capable of diluting the silicone oil, impregnated with the passage inhibitor powder in the liquid, and the solvent may be removed and dried. When the viscosity of the silicone oil is high, the treatment is preferably performed in a liquid. Thereafter, the passage inhibitor powder to which the silicone oil is adhered is subjected to heat treatment in an oven at 100 ° C. to several hundred ° C. (usually about 400 ° C.), thereby using the hydroxyl group on the surface of the passage inhibitor powder to form metal and silicone oil. And form a siloxane bond. Further, the silicone oil itself can be further polymerized and crosslinked. In addition, a catalyst such as acid, alkali, metal salt, zinc octylate, tin octylate, dibutyltin dilaurate or the like may be included in the silicone oil in advance to promote the reaction. By transferring the silicone oil to the electrostatic latent image carrier, the frictional force with the cleaning blade can be reduced over a long period of time, and wear can be significantly suppressed.

  Further, the passage inhibitor may be previously treated with a hydrophobizing agent of a silane coupling agent before the silicone oil treatment. The amount of silicone oil adsorbed increases if it is hydrophobized in advance.

  Note that the embodiment of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

  In the above-described embodiment, as illustrated in FIG. 7, the case where the passage blocking agent is attached to the spacer member 21 in which the contact surfaces 21 a are arranged on both sides of the boundary of the cleaning region B has been described as an example. Similarly, the present invention can be applied to the spacer member 21 configured as shown in FIG.

  The image forming apparatus to which the present invention is applicable is not limited to a monochrome image forming apparatus as shown in FIG. The present invention provides an indirect transfer type color image forming apparatus that indirectly transfers images on a plurality of photoreceptors 2 to a sheet via an intermediate transfer belt (intermediate transfer body), and images on a plurality of photoreceptors 2. The present invention can also be applied to a color image forming apparatus of a direct transfer system that directly transfers the image to a sheet conveyed by a conveyance belt (conveyance body). Further, the image forming apparatus to which the present invention can be applied includes a printer, a copying machine, a facsimile, or a complex machine thereof.

  In the above-described embodiment, the image forming apparatus using the drum-shaped photoconductor 2 as the latent image carrier has been described. However, the present invention is not limited to such a configuration. The present invention is also applicable to an image forming apparatus using a so-called photoreceptor belt. More specifically, a spacer member is brought into contact with the stretching roller (backup roller) of the photosensitive belt via the photosensitive belt, and light that determines the position of the optical writing head with respect to the photosensitive belt by the spacer member. The present invention is also applicable to an image forming apparatus provided with a write head positioning mechanism.

  As described above, according to the present invention, the passage of foreign matter between the contact surfaces of the spacer member and the latent image carrier can be prevented by attaching the passage blocking agent to the spacer member. In addition, since it is only necessary to attach the passage blocking agent to the spacer member, it is possible to prevent the passage of foreign substances by a simple method without requiring a design change or addition of a new member. As a result, foreign matter can be prevented from intervening between the contact surfaces of the spacer member and the latent image carrier, and the positional accuracy of the optical writing head relative to the latent image carrier can be reduced by the presence of foreign matter between the contact surfaces. It is possible to prevent the decrease. In addition, it is possible to prevent foreign matter that has passed between the contact surfaces of the spacer member and the latent image carrier from remaining as a fixed substance on the surface of the latent image carrier, so that the fixed substance is a latent image. It is also possible to prevent a decrease in the positional accuracy of the optical writing head with respect to the latent image carrier due to passing between the contact surfaces as the carrier rotates. Thus, according to the present invention, it is possible to prevent foreign matter from entering between the contact surfaces of the spacer member and the latent image carrier with a simple configuration in which the passage blocking agent is attached to the spacer member. It is possible to maintain the position of the optical writing head with respect to the body with high accuracy.

1 process unit 2 photoconductor (latent image carrier)
4 Optical writing head 6 Cleaning blade (cleaning means)
20 Optical writing head positioning mechanism 21 Spacer member 21a Contact surface 210 Upstream edge (edge facing upstream in the rotation direction of the latent image carrier)
A Maximum image forming area B Cleaning area

Japanese Patent No. 4073234

Claims (9)

Provided between a latent image carrier that carries a latent image and an optical writing head that exposes the latent image carrier to form a latent image, and positions the optical writing head with respect to the latent image carrier. In an optical writing head positioning mechanism comprising a spacer member for determining,
A passage blocking agent that prevents foreign matter on the latent image carrier from passing between contact surfaces of the spacer member and the latent image carrier is attached to the spacer member ;
The spacer member has a plurality of contact surfaces with the latent image carrier, and at least one of the contact surfaces is provided on both sides of the contact surface so as to avoid the boundary of the cleaning area by the cleaning means for cleaning the surface of the latent image carrier. An optical writing head positioning mechanism characterized by being arranged one by one . Provided between a latent image carrier that carries a latent image and an optical writing head that exposes the latent image carrier to form a latent image, and positions the optical writing head with respect to the latent image carrier. In an optical writing head positioning mechanism comprising a spacer member for determining,
A passage blocking agent that prevents foreign matter on the latent image carrier from passing between contact surfaces of the spacer member and the latent image carrier is attached to the spacer member;
The edge of the contact surface of the spacer member with the latent image carrier facing the upstream side in the latent image carrier rotation direction is arranged on the latent image carrier from the upstream side to the downstream side in the latent image carrier rotation direction. An optical writing head positioning mechanism that is inclined so as to be separated from the image forming area . 3. The optical writing head positioning according to claim 1, wherein the passage blocking agent is attached to an edge of the contact surface of the spacer member with the latent image carrier that faces the upstream side in the latent image carrier rotation direction. mechanism. Applying the passage blocking agent to the surface of the latent image carrier upstream of the contact surface of the spacer member with the latent image carrier in the rotation direction of the latent image carrier, and rotating the latent image carrier. The optical writing head positioning mechanism according to claim 3, wherein the optical writing head positioning mechanism is attached to the spacer member . The rib member according to any one of claims 1 to 4, wherein a rib-shaped portion extending in the rotation direction of the latent image carrier is provided on the spacer member, and a leading end surface of the rib-shaped portion is brought into contact with the latent image carrier. Optical writing head positioning mechanism. The optical writing head positioning mechanism according to claim 5, wherein the width of the leading end surface of the rib-shaped portion is set within a range of 0.1 mm to 0.6 mm . The optical writing head positioning mechanism according to claim 1, wherein a load that the spacer member receives from the optical writing head is set in a range of 3N or more and 8N or less . In a process unit comprising a latent image carrier on which a latent image is formed by exposure of an optical writing head, and an optical writing head positioning mechanism that determines the position of the optical writing head with respect to the latent image carrier,
A process unit comprising the optical writing head positioning mechanism according to claim 1 as the optical writing head positioning mechanism. An image forming apparatus comprising the optical writing head positioning mechanism according to claim 1.

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