Image forming device

Abstract

To prevent the generation of image noise caused by a local recess in an application brush included in a lubricant application device in an image forming apparatus.SOLUTION: An image forming apparatus comprises: an image carrier 1 that rotates and has a cylindrical shape; solid lubricant; and a roller-shaped application brush 72 that includes brush fibers 722 on its outer peripheral surface and is arranged to rotate so as to scrape off lubricant from the solid lubricant and apply it to the image carrier 1 with the brush fibers 722. The direction of rotation of the application brush 72 is a direction in which an outer peripheral surface 723 of the application brush 72 travels in the same direction as the direction of travel of an outer peripheral surface of the image carrier 1 at a contact portion of the image carrier 1 and the application brush 72. When a cross section cut on a surface perpendicular to the rotation axis of the application brush 72 is seen, at an uppermost stream position 51 in an area where the image carrier 1 and the application brush 72 are in contact, the leading ends of the brush fibers 722 are directed to the center side of the application brush 72 compared with a tangent line 42 of the outer periphery of the image carrier 1.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Generally, in an image forming apparatus using electrophotographic process technology, a photoconductor is disposed on the surface of a photoconductor drum, and an electrostatic latent image is formed by irradiating the charged surface of the photoconductor with laser light based on image data. A toner image is formed by supplying toner to the photoconductor drum on which the electrostatic latent image is formed. Generally, a cleaning blade is provided to scrape off the transfer residual toner adhering to the surface of the photoconductor drum. However, as the cleaning blade wears out, the cleaning performance deteriorates, so a lubricant is applied to the surface of the photoconductor drum. A roller-shaped application brush is used for this application. The configuration of such an image forming apparatus is described in JP 2017-187638 A (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-187638 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, a mechanism that uses an application brush to apply lubricant to a photoconductor drum serving as an image carrier is referred to as a "lubricant application device." Two types of lubricant application devices have been put to practical use: a "counter type" in which the application brush rotates in the opposite direction to the image carrier, and a "with type" in which the application brush rotates in the same direction as the image carrier. In a with type lubricant application device, the application brush and the image carrier are each rotated.

[0005] In an image forming apparatus equipped with such a With-type lubricant applicator, repeated printing may cause a localized dent in the outer diameter of the application brush of the lubricant applicator. The application brush has a long cylindrical shape, and a dent occurs at a location along its length. When such a localized dent occurs, an image defect occurs corresponding to the location of the dent. That is, a band-shaped image noise extending in the direction of passage of the recording medium, such as paper, appears on the surface of the recording medium.

[0006] Therefore, an object of the present invention is to suppress the occurrence of image noise caused by localized depressions in the application brush. [Means for solving the problem]

[0007] In order to achieve the above object, an image forming apparatus according to the present invention includes a cylindrical image carrier that rotates, a solid lubricant, and a roller-shaped application brush that includes brush fibers on its outer circumferential surface and is arranged to rotate so as to scrape the lubricant from the solid lubricant and apply it to the image carrier. The direction of rotation of the application brush is a direction in which the outer circumferential surface of the application brush advances in the same direction as the outer circumferential surface of the image carrier advances at a contact point between the image carrier and the application brush. When a cross section of the application brush cut along a plane perpendicular to the rotation axis of the application brush is viewed, at the most upstream position of the contact area between the image carrier and the application brush, assuming the attitude of the brush fibers when the image carrier is not present, the tips of the brush fibers face toward the center of the application brush rather than the tangent to the outer circumferential surface of the image carrier. Effect of the Invention

[0008] According to the present invention, the brush fibers of the application brush are less likely to curl up, making it less likely that localized dents will occur in the application brush, and as a result, image noise caused by localized dents in the application brush can be reduced. [Brief description of the drawings]

[0009] [Figure 1]1 is a schematic diagram of an image forming apparatus in a first embodiment according to the present invention. [Diagram 2] 1 is an enlarged view of an image carrier and its vicinity provided in an image forming apparatus in a first embodiment according to the present invention. [Diagram 3] 1 is a perspective view of an application brush provided in an image forming apparatus in accordance with a first embodiment of the present invention. [Figure 4] FIG. 3 is an enlarged view of a portion of the configuration shown in FIG. 2, illustrating the positional relationship around the most upstream position. [Diagram 5] FIG. 5 is an enlarged view of a portion of the configuration shown in FIG. 4. [Figure 6] FIG. 3 is an enlarged view of a portion of the configuration shown in FIG. 2, illustrating the positional relationship around the most downstream position. [Figure 7] FIG. 7 is an enlarged view of a portion of the configuration shown in FIG. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The dimensional ratios shown in the drawings do not necessarily represent the actual ratios, and may be exaggerated for the convenience of explanation. In the following description, when the concept of up or down is mentioned, it does not necessarily mean absolute up or down, but may mean relative up or down in the illustrated position.

[0011] (Embodiment 1) (Configuration of Image Forming Apparatus) An image forming apparatus in a first embodiment according to the present invention will be described with reference to Fig. 1 to Fig. 5. An overall outline of an image forming apparatus 101 in this embodiment is shown in Fig. 1. Image forming apparatus 101 includes an operation display unit 20, an image reading unit 21, an image processing unit 22, a paper transport unit 23, a paper feed unit 24, a fixing unit 27, and a paper discharge unit 28.

[0012] The operation display unit 20 may be, for example, a liquid crystal display with a touch panel. The image reading unit 21 includes an automatic document feeder 211 and an original image scanning device 212. The automatic document feeder 211 conveys an original placed on an original tray by a conveying mechanism and sends it to the original image scanning device 212. The original image scanning device 212 optically scans and reads the original. The image processing unit 22 performs predetermined image processing on data generated based on the reading result.

[0013] A paper feed unit 24 is disposed at the bottom of the image forming apparatus 101. An image forming unit is disposed between the paper feed unit 24 and the image reading unit 21. The paper feed unit 24 includes tray units 241, 242, and 243. Paper sheets are stored in each of the tray units 241, 242, and 243 as recording media. In each of the tray units 241, 242, and 243, paper sheets are taken out one by one from the top. The taken-out paper sheets are transported to the image forming unit by the paper transport unit 23.

[0014] The image forming unit includes an intermediate transfer belt 6 arranged in a loop shape. The intermediate transfer belt 6 travels in the direction of an arrow 91. Four image carriers 1 are arranged in the middle of the travel path of the intermediate transfer belt 6 so as to contact the outer surface of the intermediate transfer belt 6. The image carriers 1 are photosensitive drums. The four image carriers 1 correspond to toner images of each color, for example, Y (yellow), M (magenta), C (cyan), and K (black). At the locations where the image carriers 1 contact the intermediate transfer belt 6, primary transfer rollers 5 are arranged on the opposite side of the image carriers 1. The intermediate transfer belt 6 is sandwiched between the image carriers 1 and the primary transfer roller 5. In the middle of the travel path of the intermediate transfer belt 6, a secondary transfer roller 25 is arranged so as to contact the outer surface of the intermediate transfer belt 6. At this position, the intermediate transfer belt 6 is sandwiched between the secondary transfer roller 25 and a backup roller 26. When the paper conveyed by paper conveying section 23 passes between secondary transfer roller 25 and intermediate transfer belt 6, the paper passes between secondary transfer roller 25 and backup roller 26, so that the toner image is transferred from the outer surface of intermediate transfer belt 6 to the surface of the paper. The paper onto which the image has been transferred in this manner is further conveyed and subjected to a fixing process in fixing section 27, and then discharged from paper discharge section 28.

[0015] FIG. 2 shows an enlarged view of the image carrier 1 and its vicinity. The intermediate transfer belt 6 travels in the direction of an arrow 91. The image carrier 1 rotates in the direction of an arrow 92. A charging device 2 is arranged to face the outer peripheral surface of the image carrier 1. An exposure device 3 is arranged downstream of the charging device 2 so that the outer peripheral surface of the image carrier 1 can be irradiated with a laser beam 8. A developing device 4 is arranged downstream of the irradiation position of the laser beam 8 so as to contact the outer peripheral surface of the image carrier 1. The location where the image carrier 1 contacts the intermediate transfer belt 6 is downstream of the developing device 4. A cleaning device 7 is arranged downstream of the location where the image carrier 1 contacts the intermediate transfer belt 6 so as to contact the outer peripheral surface of the image carrier 1. The cleaning device 7 includes a cleaning blade 71, a roller-shaped application brush 72, a solid lubricant 73, and a blade 74. The toner remaining on the outer peripheral surface of the image carrier 1 after the primary transfer is removed by the cleaning blade 71. Cleaning blade 71 may be made of, for example, urethane rubber. Application brush 72 applies the lubricant scraped off from solid lubricant 73 to the outer circumferential surface of image carrier 1. The lubricant may be made of, for example, zinc stearate. The lubricant applied to the outer circumferential surface of image carrier 1 by application brush 72 is pressed by blade 74.

[0016] FIG. 3 shows the application brush 72 taken out by itself. The application brush 72 includes a shaft 721 and brush fibers 722. The application brush 72 has an outer circumferential surface 723. The brush fibers 722 are not straight but are curved. The brush fibers 722 may be made of acrylic, for example. The image carrier 1, the application brush 72, and the solid lubricant 73 in FIG. 2 are taken out and shown in detail in FIG. 4. The lubricant application device includes the application brush 72 and the solid lubricant 73.

[0017] (Considerations on the cause of dents) The inventors have considered the phenomenon in which localized dents occur in the roller-shaped application brush of a lubricant application device of a With-type lubricant application device during continued use of the image forming apparatus as follows.

[0018] In a With-type lubricant applicator, if the brush fibers of the application brush do not always fall in the same direction, the tips of the brush fibers will become distorted, resulting in image noise. Therefore, in order to ensure that the brush fibers of the application brush always fall in the same direction, the rotation speed of the application brush is generally set to be faster than the rotation speed of the image carrier.

[0019] If the application brush is always rotating while the image carrier is rotating, the brush fibers of the application brush will fall in a consistent and stable direction. However, it is known that the operation of the lubricant application device is stopped to reduce the consumption of lubricant at the start and end of an image forming operation, or when an optional device is connected to the image forming apparatus and the image forming operation is interrupted and the optional device is operating. In this state, the image carrier continues to rotate, and the application brush stops rotating.

[0020] In this case, at the point where the application brush contacts the image carrier, a force is applied in the direction of rotation of the image carrier to the bristles of the application brush, i.e., the tips of the brush fibers, which may cause the bristles to turn over. When image formation operations are repeated, in some places on the application brush, the bristles alternate between being turned over and not being turned over, so the bristles gradually become tangled and the outer diameter of the application brush becomes smaller. This results in a localized dent in the application brush.

[0021] When the tip of the application brush is in contact with the image carrier at its very tip, the frictional force between the tip and the surface of the image carrier is large, so that when the application brush is stopped rotating and the image carrier is rotating, the tip of the brush is likely to be dragged by the surface of the image carrier and turn over. However, when the tip of the application brush is in contact with the image carrier at a point slightly away from the tip, rather than at the very tip, that is, when the tip is in a so-called belly contact state, the frictional force is small, and as a result, the tip of the brush is less likely to turn over. Furthermore, when the tip of the brush is in belly contact, the contact point with the image carrier is closer to the base of the brush fiber, so the resistance to turning over is increased. This also makes the tip of the brush less likely to turn over.

[0022] The inventors noticed that curling of the bristles often starts from the most upstream position of the contact point between the application brush and the image carrier and spreads downstream. Therefore, the inventors thought that curling of the bristles could be effectively suppressed by making the brush fibers contact the belly at the most upstream position, and as a result, localized dents in the application brush could be prevented.

[0023] Furthermore, if there is a location within the contact area between the application brush and the image carrier where the direction of the bristles switches from facing upstream of the normal to the outer periphery of the image carrier to facing downstream of the normal, the bristles may curl up downstream of this switching location. Therefore, the inventors thought that if the direction of the bristles is aligned so that it faces upstream of the normal to the outer periphery of the image carrier throughout the entire contact area between the application brush and the image carrier, the bristles will be less likely to curl up.

[0024] (Image forming device configuration (continued)) Fig. 4 shows in detail the image carrier 1, the application brush 72, and the solid lubricant 73 taken out from the portion shown in Fig. 2. Fig. 5 shows an enlarged view of a portion of Fig. 4.

[0025] The image forming apparatus 101 includes a cylindrical rotating image carrier 1, a solid lubricant 73, and a roller-shaped application brush 72. The application brush 72 includes brush fibers 722 on its outer circumferential surface, and is arranged and rotated so that the brush fibers 722 scrape off the lubricant from the solid lubricant 73 and apply it to the image carrier 1. The rotation direction of the application brush 72 is the same as the movement direction of the outer circumferential surface of the image carrier 1 at the contact point between the image carrier 1 and the application brush 72. In the example shown here, the movement direction of the outer circumferential surface of the image carrier 1 is indicated by an arrow 92. The rotation direction of the application brush 72 is indicated by an arrow 93. The arrows 92 and 93 are in the same direction at the contact point between the image carrier 1 and the application brush 72. That is, this lubricant application device is a with-type.

[0026] 4 shows a normal line 41 to the outer periphery of application brush 72 at the most upstream position 51, a tangent line 42 to image carrier 1 at the most upstream position 51, a straight line 43 indicating the direction of the tips of brush fibers 722 at the most upstream position 51, and a normal line 44 to the outer periphery of image carrier 1 at the most upstream position 51. In Fig. 4, the shape of brush fibers 722 is shown in the absence of image carrier 1. In reality, brush fibers 722 are deformed by being pressed against image carrier 1.

[0027] When looking at a cross section cut perpendicular to the axis of rotation of application brush 72, at most upstream position 51 of the contact area between image carrier 1 and application brush 72, assuming the orientation that brush fibers 722 would assume if image carrier 1 were not present, the tips of brush fibers 722 point toward the center of application brush 72 relative to tangent 42 to the outer periphery of image carrier 1. In other words, angle A in Figure 5 is sufficiently large, and as a result, angle B>0.

[0028] (Action and effect) In this embodiment, at the most upstream position 51, the tips of the brush fibers 722 face toward the center of the application brush 72 rather than the tangent line 42 to the outer periphery of the image carrier 1, so the brush fibers 722 of the application brush 72 are less likely to turn up. Therefore, localized depressions in the application brush 72 are less likely to occur. As a result, it is possible to suppress the occurrence of image noise caused by localized depressions in the application brush. An experiment verifying this effect will be described later as "Experiment 1."

[0029] (Preferred configuration) Furthermore, the following can be said about the most downstream position 52 of the contact area between the image carrier 1 and the application brush 72. While Figures 4 and 5 show in detail the positional relationship around the most upstream position 51 of the contact area between the image carrier 1 and the application brush 72, Figure 6 shows in detail the positional relationship around the most downstream position 52 of the contact area between the image carrier 1 and the application brush 72. Furthermore, Figure 7 shows an enlarged view of a portion of Figure 6.

[0030] When viewing a cross section cut along a plane perpendicular to the rotation axis of the application brush 72, it is preferable that the tip of the brush fiber 722 is parallel to the normal line 62 of the outer periphery of the image carrier 1 or faces the upstream side of the normal line 62 with respect to the rotation of the application brush 72 at the most downstream position 52 of the region where the image carrier 1 and the application brush 72 contact each other. That is, it is preferable that the angle C in FIG. 6 is sufficiently large, and as a result, the angle D>0. By adopting this configuration, the brush fiber 722 of the application brush 72 is less likely to be turned up. Therefore, localized depressions in the application brush 72 are less likely to occur. As a result, it is possible to suppress the occurrence of image noise caused by localized depressions in the application brush. An experiment verifying this effect will be described later as "Experiment 2".

[0031] It is preferable that the speed of the outer peripheral surface of the application brush 72 caused by the rotation of the application brush 72 is faster than the speed of the outer peripheral surface of the image carrier 1 caused by the rotation of the image carrier 1. By employing this configuration, curling of the bristles of the application brush 72 can be more reliably prevented.

[0032] The following describes the experiments that the inventors conducted to confirm the effects. (Experiment 1) Experiment 1 was conducted with the following configuration. The solid lubricant 73 is made of zinc stearate. The application brush 72 includes a shaft 721 and brush fibers 722 planted on the outer circumferential surface of the shaft 721. The brush fibers 722 are made of acrylic. The density of the brush fibers 722 is 150 kF per square inch (6.45 square cm). The application brush 72 is connected to a driving source (not shown) so as to rotate in a with-type manner. The rotation speed of the application brush 72 is set to be faster than the rotation speed of the image carrier 1. As an example, in this experiment, the speed of the outer circumferential surface of the image carrier 1 is set to 300 mm / sec, and the speed of the outer circumferential surface of the application brush 72 is set to 400 mm / sec. In this experiment, three types of application brushes 72 with different inclination angles of the bristles were prepared as samples 1 to 3. The "inclination angle of the bristles" refers to the angle between the normal line 41 and the straight line 43, that is, angle A in FIG. 5. Furthermore, attention was paid to whether or not the tip of the brush fiber 722 at the most upstream position 51 faces toward the center of the application brush 72 relative to the tangent 42 to the outer periphery of the image carrier 1, that is, whether or not the angle B in Figure 5 is positive. The results of this experiment are shown in Table 1.

[0033] [Table 1]

[0034] In sample 1, the outer diameter of application brush 72 was reduced. In samples 2 and 3, the outer diameter of application brush 72 was not reduced. In other words, samples 2 and 3, in which angle B>0, showed good results. From this, it was confirmed that in the configuration of the image forming apparatus in this embodiment, localized dents in application brush 72 are less likely to occur.

[0035] (Experiment 2) Experiment 2 was conducted with the following configuration. The parts common to Experiment 1 will not be described again. In this experiment, three types of application brushes 72 with different inclination angles of the bristles were prepared as samples 4 to 6. The "inclination angle of the bristles" refers to the angle between the normal line 41 and the straight line 43, that is, angle A in FIG. 5 and angle C in FIG. 7. Furthermore, as in Experiment 1, attention was paid to whether or not the tip of the brush fiber 722 faces toward the center of the application brush 72 more than the tangent line 42 of the outer periphery of the image carrier 1 at the most upstream position 51, that is, whether or not angle B in FIG. 5 is positive. Furthermore, attention was paid to the positional relationship of the tip of the brush fiber 722 with respect to the normal line 62 of the outer periphery of the image carrier 1 at the most downstream position 52, that is, whether or not angle D in FIG. 7 is 0 or more. The results of this experiment are shown in Table 2.

[0036] [Table 2]

[0037] In sample 4, the outer diameter of the application brush 72 was locally reduced. In samples 5 and 6, the outer diameter of the application brush 72 was not reduced. In other words, samples 5 and 6, in which angle D≧0, showed good results. From this, it was confirmed that in the configuration of the image forming apparatus in which angle D≧0, localized dents in the application brush 72 are less likely to occur.

[0038] In addition, two or more of the above-described embodiments may be appropriately combined and adopted. The above-described embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0039] 1 image carrier, 2 charging device, 3 exposure device, 4 developing device, 5 primary transfer roller, 6 intermediate transfer belt, 7 cleaning device, 8 laser light, 20 operation display unit, 21 image reading unit, 22 image processing unit, 23 paper transport unit, 24 paper feed unit, 25 secondary transfer roller, 26 backup roller, 27 fixing unit, 28 paper discharge unit, 41 normal (of outer circumference of application brush at most upstream position), 42 tangent (of image carrier at most upstream position), 43 tip direction (of brush fiber at most upstream position), 44 normal (of outer circumference of image carrier at most upstream position), 51 most upstream position, 52 most downstream position, 61 normal (of outer circumference of application brush at most downstream position), 62 normal (of outer circumference of image carrier at most downstream position), 63 tip direction (of brush fiber at most downstream position), 71 cleaning blade, 72 application brush, 73 Solid lubricant, 74 blade, 91 arrow (indicating the direction in which the intermediate transfer belt runs), 92 arrow (indicating the direction in which the image carrier rotates), 93 arrow (indicating the direction in which the application brush rotates), 101 image forming apparatus, 211 automatic document feeder, 212 document image scanning apparatus, 241, 242, 243 tray unit, 721 shaft, 722 brush fiber, 723 outer circumferential surface.

Claims

1. a cylindrical rotating image carrier; A solid lubricant; a roller-shaped application brush that includes brush fibers on an outer circumferential surface and is disposed and rotated so as to scrape off the lubricant from the solid lubricant with the brush fibers and apply the lubricant to the image carrier; a rotation direction of the application brush such that an outer peripheral surface of the application brush moves in the same direction as a moving direction of an outer peripheral surface of the image carrier at a contact point between the application brush and the image carrier; When the cross section of the application brush is cut on a plane perpendicular to the rotation axis, An image forming device in which, at the most upstream position of the area where the image carrier and the application brush contact, when assuming the posture that the brush fibers would take if the image carrier were not present, the tips of the brush fibers point toward the center of the application brush rather than the tangent to the outer periphery of the image carrier.

2. When the cross section of the application brush is cut on a plane perpendicular to the rotation axis, 2. An image forming apparatus as described in claim 1, wherein at the most downstream position of the area where the image carrier and the application brush contact each other, the tips of the brush fibers are parallel to a normal to the outer periphery of the image carrier, or point upstream of the normal in terms of the rotation of the application brush.

3. 3. The image forming apparatus according to claim 1, wherein a speed of the outer peripheral surface of the application brush caused by the rotation of the application brush is faster than a speed of the outer peripheral surface of the image carrier caused by the rotation of the image carrier.

Images