Image forming apparatus

Abstract

The image forming apparatus of the present invention includes a developing roller, an image forming section, a housing, a scraper, and an adjusting screw. The developing roller has an outer peripheral surface that carries and conveys developer. The image forming section forms an image using the developer conveyed by the developing roller. The housing rotatably houses the developing roller. The scraper has opposing end edges facing the outer peripheral surface of the developing roller at a constant gap, and its two ends in the longitudinal direction are fixed to the housing. The adjusting screw has, between the two ends of the scraper, a first pressing portion extending in a first direction in which the developing roller and the scraper are arranged, which engages with a nut fixed to the housing, and presses the first pressed surface of the scraper in the first direction by rotating it in the positive direction; and a second pressing portion pressing the second pressed surface of the scraper in a second direction opposite to the first direction by rotating it in the opposite direction.

Description

Technical Field

[0001] Embodiments of the present invention relate to image forming apparatuses such as MFPs (Multifunction Peripheral). Background Technology

[0002] The image forming apparatus includes a blade for controlling the amount of developer delivered from the developing roller to the photosensitive drum to be constant. A constant gap is formed between the blade and the outer peripheral surface of the developing roller, thereby controlling the amount of developer passing through the gap to be constant.

[0003] The scraper is mounted on the housing of the developing roller by pressing its two ends along its length against the bearings of the developing roller through spacers used for gap adjustment.

[0004] The scraper has approximately the same length as the developing roller. Therefore, even if both ends of the scraper are fixed with a constant gap relative to the developing roller along its length, scrapers with low straightness will still have a slight bend near the center, resulting in an uneven gap with the developing roller. This bend in the scraper can cause it to bulge or recede towards the developing roller, making it difficult to control the gap evenly. Summary of the Invention

[0005] The image forming apparatus of this embodiment includes a developing roller, an image forming section, a housing, a scraper, and an adjusting screw. The developing roller has an outer peripheral surface that carries and conveys developer. The image forming section forms an image using the developer conveyed by the developing roller. The housing rotatably houses the developing roller. The scraper has opposing end edges that face the outer periphery of the developing roller at a constant gap, and both ends in the longitudinal direction are fixed to the housing. The adjusting screw extends along a first direction in which the developing roller and the scraper are arranged between the two ends of the scraper, and engages with a nut fixed to the housing. It has a first pressing part and a second pressing part. The first pressing part presses the first pressed surface of the scraper in the first direction by rotating in the forward direction, and the second pressing part presses the second pressed surface of the scraper in a second direction opposite to the first direction by rotating in the reverse direction. Attached Figure Description

[0006] The general architecture for implementing various features of the embodiments will now be described with reference to the accompanying drawings. The drawings and related descriptions are provided to illustrate the embodiments and not to limit the scope of the invention.

[0007] Figure 1 This is a schematic diagram illustrating an image forming apparatus according to an embodiment.

[0008] Figure 2 It is shown Figure 1 A schematic diagram of the image forming part used for black.

[0009] Figure 3 It is used for Figure 2 A partially enlarged perspective view illustrating the fixing structure of the scraper.

[0010] Figure 4 This shows the adjustment Figure 3 A schematic three-dimensional diagram of the structure of the gap between the scrapers.

[0011] Figure 5 It is shown Figure 4 The front view (a), bottom view (b), and top view (c) of the adjusting screw.

[0012] Figure 6 It is used to explain the basis Figure 5 A partially enlarged sectional view of the method for adjusting the gap of the adjusting screw.

[0013] Figure 7 It is used to explain the basis Figure 5 A partially enlarged sectional view of the method for adjusting the gap of the adjusting screw. Detailed Implementation

[0014] The embodiments will now be described using the accompanying drawings.

[0015] like Figure 1 As shown, one embodiment of the image forming apparatus 100 includes a frame 1 constituting the apparatus housing. The image forming apparatus 100 has a display unit 2 and an input unit 3 on the upper part of the front surface side of the frame 1. The frame 1 includes a communication interface 4, a controller 10, a paper tray 5, a transport unit 20, an image forming unit 30, and a fixing unit 40. The image forming apparatus 100 also includes a paper discharge tray 6 for discharging the paper P after image formation into the machine.

[0016] Display unit 2 displays an image, for example, based on an image signal input from a display control unit (not shown). Display unit 2 displays, for example, various operation instructions for the image forming apparatus 100, various setting screens for the image forming apparatus 100, and status information such as toner balance.

[0017] The input unit 3 includes a power button, a paper feed button, various function keys, numeric keys, and a keyboard. The input unit 3 provides the controller 10 with operation signals input by the operator. The input unit 3 can also be configured as a touch panel integrated with the display unit 2.

[0018] Communication interface 4 is, for example, an interface used for communication with a host device (external device). Communication interface 4 can also be, for example, a LAN connector. Communication interface 4 can also communicate wirelessly with other devices.

[0019] The controller 10 controls the operation of the image forming apparatus 100. The controller 10 controls the transport unit 20 to transport the paper P, the image forming unit 30 to form an image on the paper P, and the fixing unit 40 to fix the image on the paper P by executing a program stored in the memory.

[0020] The controller 10 performs various information processing tasks by executing programs stored in memory. For example, the controller 10 generates a print job based on image data acquired from an external device via communication interface 4. The controller 10 stores the generated print job in memory. The print job includes image data formed on paper P. The image data can be data used to form an image on a single sheet of paper P, or data used to form an image on multiple sheets of paper P. The print job includes information indicating whether it is a color print or a monochrome print.

[0021] The image forming apparatus 100 includes a plurality of paper trays 5 (two in this embodiment). The paper trays 5 are capable of stacking and storing multiple sheets of paper P of a specified size, and can be inserted and removed from the front surface of the frame 1.

[0022] The transport unit 20 transports paper P within the image forming apparatus 100. The transport unit 20 includes, for example, a paper supply transport path 21 and a paper discharge transport path 22. The transport unit 20 has multiple pairs of transport rollers 23 that apply a transport force to the paper P by clamping and rotating it. The transport unit 20 also has multiple transport guides (not shown).

[0023] Paper feed path 21 conveys the paper P taken from the paper tray 5 by the pick-up roller 24 to the image forming unit 30. Paper discharge path 22 conveys the paper P that has passed through the image forming unit 30 via the fixing unit 40. At the end of paper discharge path 22 is a paper discharge tray 6.

[0024] The image forming unit 30 forms an image on paper P conveyed via the paper feed path 21 based on a print job generated by the controller 10. The image forming unit 30 has multiple (four in this embodiment) processing units 31. The multiple processing units 31 respectively form cyan, magenta, yellow, and black developer images. The image forming unit 30 has a ring-shaped transfer belt 38 that overlaps, transfers, and conveys the four color developer images. The four processing units 31 have substantially the same structure; therefore, they are referred to here as... Figure 1 The processing unit 31, which forms a black developer image and is located on the far right, will be used as an example for explanation.

[0025] like Figure 2 As shown, the black processing unit 31 includes an exposure device 32, a developing device 50, a primary transfer roller 33, a cleaner 34, a charger 35, and a photosensitive drum 36.

[0026] Exposure device 32 exposes the surface of photosensitive drum 36, which is charged at a specified potential by charged charger 35, to form an electrostatic latent image of a black image.

[0027] The developing apparatus 50 includes a toner cartridge 51 for storing black toner T and a developer 53. The developer 53 has a housing 54 that rotatably houses the developing roller 52 and the two-component developer G. Within the housing 54 are two agitator screws 55 extending in a direction parallel to the central axis of the photosensitive drum 36 (hereinafter referred to as the axial direction). The housing 54 is fixed to both ends of a scraper 60 opposite the developing roller 52 along its axial direction.

[0028] The developing unit 50 rotates the screw conveyor 56 of the toner cartridge 51 to feed black toner T into the housing 54 of the developing unit 53. Two stirring screws 55 within the housing 54 agitate the carrier housed within the housing 54 and the black toner T fed from the toner cartridge 51. The developing roller 52 has a developing sleeve that magnetically attracts a two-component developing agent G containing the black toner T, which becomes charged through agitation, creating a magnetic field that forms magnetic brushes of black toner T on the outer circumferential surface of the developing sleeve. A scraper 60 limits the thickness of the magnetic brushes formed on the outer circumferential surface of the developing sleeve to a constant thickness.

[0029] The developing apparatus 50 delivers a constant amount of black toner T, limited by the scraper 60, to the surface of the photosensitive drum 36 by rotating the developing roller 52, thereby developing the electrostatic latent image formed on the surface of the photosensitive drum 36.

[0030] The primary transfer roller 33 forms a predetermined electric field with the photosensitive drum, transferring the developer image of the black toner T formed on the surface of the photosensitive drum 36 onto the surface of the transfer belt 38. The primary transfer rollers 33 of each color processing unit 31 overlap and transfer the developer images of each color onto the surface of the transfer belt 38 at timings consistent with the travel of the transfer belt 38.

[0031] The cleaner 34 presses the cleaning scraper onto the surface of the photosensitive drum 36 to remove various colors of toner remaining on the surface of the photosensitive drum 36.

[0032] The charged charger 35 uniformly charges the surface of the photosensitive drum 36 to, for example, a negative potential.

[0033] The photosensitive drum 36 has a cylindrical drum and a photosensitive layer disposed on the outer peripheral surface of the drum.

[0034] The image forming unit 30 includes a drive roller 37 on which a transfer belt 38 is wound, and a secondary transfer roller 39 opposite to the drive roller 37, which clamps the transfer belt 38 in between. The drive roller 37 is driven by a motor (not shown), causing the transfer belt 38 to... Figure 1The transfer belt 38 travels counterclockwise at a specified speed. It conveys the four-color developer image, which has been superimposed and transferred by the color processing units 31, to the space between the drive roller 37 and the secondary transfer roller 39.

[0035] The conveying unit 20 conveys the paper P taken from the paper tray 5 via the paper feed conveying path 21 and feeds it between the secondary transfer roller 39 and the drive roller 37. A predetermined electric field is formed between the secondary transfer roller 39 and the drive roller 37, which transfers the 4-color developer image conveyed by the transfer belt 38 onto the paper P.

[0036] The fixing unit 40 includes a heating roller 41 and a pressure roller 42. The heating roller 41 and the pressure roller 42 are positioned opposite each other, sandwiching the paper conveying path 22 in the middle. The heating roller 41 heats the paper P, which has been printed with an image of various colors of developer, to melt the developer. The pressure roller 42 presses the molten developer of various colors onto the paper P and fixes it. The paper conveying path 22 transports the paper P, after the image has been formed by the fixing unit 40, to the paper tray 6.

[0037] like Figure 3 As shown, the scraper 60 of the developing apparatus 50 is installed between the housing 54 of the developer 53 and the developing roller 52. The developing apparatus 50 of each color processing unit 31 has the same structure, and the fixing structures at both ends of the scraper 60 of the developing apparatus 50 are roughly the same. Therefore, the fixing structure of the front side of the scraper 60 of the developing apparatus 50 of the black processing unit 31 will be used as an example for explanation.

[0038] The developing apparatus 50 has two mounting fittings 57 for mounting the two ends of the scraper 60 along its length to the housing 54. Figure 3 (Only the front side is shown in the diagram). The mounting accessory 57 integrally comprises: a first leaf spring portion 571, which presses the front end of the scraper 60 toward the developing roller 52; a second leaf spring portion 572, which presses the front end of the scraper 60 toward the housing 54; and a fixing portion 573, which is fixed to the housing 54 continuously disposed with the base ends of the first and second leaf spring portions 571 and 572. The mounting accessory 57 is, for example, formed by shaping and bending a metal plate.

[0039] The fixing part 573 has two mounting holes 574 and 575 for receiving two bosses 541 and 542 protruding from the housing 54. The fixing part 573 also has through holes for inserting fixing screws 58 to secure the mounting accessory 57 to the housing 54. The fixing part 573 is then fixed to the housing 54 by the fixing screws 58. Figure 3In the state shown, the first leaf spring portion 571 of the mounting accessory 57 generates a restoring force in the direction (first direction) that presses the scraper 60 toward the developing roller 52, and the second leaf spring portion 572 of the mounting accessory 57 generates a restoring force in a direction (third direction) that is approximately orthogonal to the first leaf spring portion 571, thereby pressing the scraper 60 toward the housing 54.

[0040] like Figure 4 As shown, the scraper 60 has: a generally rectangular plate-shaped body 602 having an opposing end edge 601 facing the outer periphery of the developing roller 52 at a predetermined gap in the longitudinal direction; and a generally rectangular plate-shaped reinforcing rib 603, which is integrally continuous with respect to the end edge of the plate body 602 opposite to the opposing end edge 601. The scraper 60 is a component made by bending a metal plate into an L-shaped strip with a cross-section at approximately a right angle along a line in the longitudinal direction. The width of the reinforcing rib 603 in the direction orthogonal to the longitudinal direction is shorter than the width of the scraper body 602 in the direction orthogonal to the longitudinal direction.

[0041] The scraper 60 has two pressing protrusions 600 at both ends of its opposing end edge 601 along its length. Each pressing protrusion 600 has a front end protruding from the opposing end edge 601 in a direction away from the reinforcing rib 603. The protruding length of the front end of the pressing protrusion 600 relative to the opposing end edge 601 determines the gap between the scraper 60 and the developing roller 52. That is, as... Figure 3 As shown, the scraper 60 is fixed to the housing 54 by two mounting fittings 57 with the two pressing protrusions 600 located at both ends of its length abutting against the outer peripheral surfaces 591 of the bearings 59 provided at both ends of the developing roller 52. This ensures that the gap between the opposing end edges 601 of the scraper 60 and the outer peripheral surfaces of the developing roller 52 remains constant.

[0042] The scraper 60 is formed from a long strip of metal plate having approximately the same length as the developing roller 52, making it difficult to improve straightness and form the opposing end edge 601 perfectly straight. Therefore, when the two ends of the scraper 60 are fixed to the housing 54 along its length as in this embodiment, if the scraper 60 has low straightness, an uneven gap will occur near the center of the scraper 60 between the opposing end edge 601 and the outer peripheral surface of the developing roller 52. A scraper 60 with low straightness requires additional processing to make the opposing end edge 601 straight, or it must be discarded. Therefore, in this embodiment, an adjusting screw 70 for adjusting the gap between the opposing end edge 601 and the outer peripheral surface of the developing roller 52 is provided near the center of the long scraper 60.

[0043] like Figure 5As shown, the adjusting screw 70 is an integral and coaxial screw having a threaded portion 71 that engages with a nut 80 embedded in the housing 54, an annular flange portion 72 located at the rear end of the threaded portion 71, a cylindrical shaft portion 73 located on the side of the flange portion 72 opposite to the threaded portion 71, and a circular plate-shaped head 74 located on the side of the shaft portion 73 opposite to the flange portion 72. The pitch of the threaded portion 71 of the adjusting screw 70 is approximately 0.2 mm to 0.5 mm. The head 74 of the adjusting screw 70 serves as a surface capable of pressing against the outer surface 6031 of the scraper 60. Figure 6 The first pressing part functions as the head 74. The head 74 has a Phillips head groove 75 for engaging the tip of a screwdriver (not shown). The flange portion 72 serves as the inner surface 6032 of the scraper 60, which can press down. Figure 7 The second pressing part of the unit functions.

[0044] The scraper 60 has a U-shaped notch 61 at its center along its length, formed by cutting the end edge opposite to the plate body 602 of the reinforcing rib 603. The notch 61 functions as a fitting part for the shaft portion 73 of the adjusting screw 70. The nut 80 is an embedded nut embedded in the housing 54. The nut 80 is embedded in the housing 54 with the adjusting screw 70, to which the threaded portion 71 is screwed, extending along the direction (first direction) in which the scraper 60 and the developing roller 52 are arranged.

[0045] The following is mainly based on Figure 6 , Figure 7 The method for adjusting scraper 60 is explained.

[0046] When the scraper 60, whose two ends are fixed to the housing 54, is bent in a direction that is recessed toward the outer peripheral surface of the developing roller 52, that is, when the gap between the opposing end edge 601 at the center of the scraper 60 in the longitudinal direction and the outer peripheral surface of the developing roller 52 is larger than the design value, such as Figure 6 As shown, the adjusting screw 70 is rotated in the positive direction to adjust towards the direction of tightening the screw. When the adjusting screw 70 is tightened, the annular flat surface 741 on the shaft portion 73 side of the head 74 presses the outer surface 6031 (first pressed surface) of the reinforcing rib 603 of the scraper 60 towards the developing roller 52 (first direction), so that the center of the scraper 60 can approach the developing roller 52, reducing the central gap.

[0047] Conversely, when the scraper 60, which is fixed at both ends to the housing 54, bends in the direction protruding towards the outer peripheral surface of the developing roller 52, that is, when the gap between the opposing end edge 601 at the center of the scraper 60 in the length direction and the outer peripheral surface of the developing roller 52 is less than the design value, such as Figure 7As shown, the adjusting screw 70 is rotated in the opposite direction to loosen the screw. When the adjusting screw 70 is loosened, the annular flat surface 721 on the shaft portion 73 side of the flange portion 72 presses the inner surface 6032 (second pressed surface) of the reinforcing rib 603 of the scraper 60 away from the developing roller 52 (second direction), and the center of the scraper 60 can deform away from the developing roller 52 to increase the central gap.

[0048] Furthermore, since the adjustment range of the adjusting screw 70 for the clearance is approximately ±0.05mm, it is preferable that the pitch of the threaded portion 71 of the adjusting screw 70 is approximately 0.2mm to 0.5mm. The threaded portion 71 can be, for example, a fine thread or a coarse thread. Additionally, the clearance adjustment position performed by the adjusting screw 70 does not need to be constantly at the exact center along the length of the scraper 60; it can be anywhere between the two ends of the scraper 60, preferably near the center.

[0049] As described above, according to this embodiment, by using a non-circular adjusting screw 70 with a flange portion 72, the gap between the opposing end edge 601 at the center of the scraper 60 along its length and the outer peripheral surface of the developing roller 52 can be adjusted in both the positive and negative directions, making the gap between the scraper 60 and the developing roller 52 uniform throughout the entire length of the developing roller 52. Therefore, according to this embodiment, a scraper 60 that is subject to additional processing or discard due to low straightness can be used, reducing additional processing and discarding, thereby lowering manufacturing costs.

[0050] While certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. In fact, the novel embodiments described herein may also be embodied in various other forms. Furthermore, various omissions, substitutions, and changes may be made to the forms of the embodiments described herein without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover these forms or modifications that fall within the scope and spirit of the invention.

Claims

1. An image forming apparatus comprising: A developing roller having an outer peripheral surface that carries and transports the developer; An image forming unit uses a developer supplied by the developing roller to form an image; A housing that rotatably houses the developing roller; A scraper has opposing end edges that are positioned opposite the outer periphery of the developing roller with a constant gap, and its two ends in the longitudinal direction are fixed to the housing. An adjusting screw extends between the two ends of the scraper along a first direction in which the developing roller and the scraper are arranged, and is screwed into a nut fixed to the housing. The screw has a first pressing part and a second pressing part. The first pressing part presses the first pressing surface of the scraper in the first direction by rotating in the positive direction, and the second pressing part presses the second pressing surface of the scraper in a second direction opposite to the first direction by rotating in the opposite direction.

2. The image forming apparatus as claimed in claim 1, wherein, The first pressing part is the head of the adjusting screw, and the second pressing part is an annular flange that is separate from the head and integrally formed on the shaft of the adjusting screw.

3. The image forming apparatus as claimed in claim 1, wherein, The adjusting screw is positioned at the center of the scraper along its length.

4. The image forming apparatus as claimed in claim 1, wherein, The scraper has: a generally rectangular plate-shaped body including the opposing end edge; and a generally rectangular plate-shaped reinforcing rib that extends integrally from the end edge of the plate body opposite to the opposing end edge in a third direction intersecting the first direction, and has a first pressed surface and a second pressed surface.

5. The image forming apparatus as claimed in claim 4, wherein, The adjusting screw is positioned at the center of the scraper along its length.

6. The image forming apparatus as claimed in claim 2, wherein, The scraper has: a generally rectangular plate-shaped main body including the opposing end edge; a generally rectangular plate-shaped reinforcing rib extending integrally from the end edge of the main body opposite to the opposing end edge in a third direction intersecting the first direction, and having a first pressed surface, a second pressed surface, and a fitting portion that engages with the shaft portion of the adjusting screw.

7. The image forming apparatus as claimed in claim 6, wherein, The adjusting screw is positioned at the center of the scraper along its length.

8. The image forming apparatus as claimed in claim 7, wherein, The fitting portion is a U-shaped notch cut from the end edge opposite to the plate body of the reinforcing rib.

9. The image forming apparatus as claimed in claim 1, wherein, The spacing between the adjusting screws is approximately 0.2mm to 0.5mm.

10. The image forming apparatus as claimed in claim 9, wherein, The nut is an embedded nut embedded in the housing.

Images