JP5626071B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including an image forming unit that performs uniform initialization charging on a photosensitive drum with a mechanically simple configuration.

  Conventionally, a toner image is formed on an image carrier by electrophotography using toner, the toner image is directly or indirectly transferred to a sheet, and the transferred toner image is fixed on a sheet by a fixing device to form an image. An image forming apparatus is known.

  Such an image forming apparatus includes, for example, a plurality of internal devices such as a paper feeding unit, a belt unit, a toner supply unit, an image forming unit, and a fixing unit. In particular, in an image forming unit, it is an important issue to develop a toner image faithful to image data by uniformly charging and initializing the peripheral surface potential of the photosensitive drum.

  As an example, in order to remove the reversely charged toner that hinders uniform charging of the surface potential of the photosensitive drum from the charging roller, the application of the negative voltage to the charging roller is stopped at each rotation of the photosensitive drum, and charging is performed. There has been proposed a method in which a reversely charged toner is moved from a roller to the surface of a photosensitive drum and scraped off by a cleaning blade. (For example, refer to Patent Document 1.)

  FIG. 5 is a perspective view showing a structural relationship between a general photosensitive drum and a charging roller of such a conventional image forming unit. The figure shows a photosensitive drum 1, a charging roller 2, a charging cleaner 3, a mylar sheet 4 for preventing toner leakage, a drum kit casing 5, a shaft pressing plate spring 6, a charging bearing 7, and a bearing in the image forming unit. The end of the holder 8 on the drum gear 9 side is shown.

  Note that the other end has the same mirror symmetry as that shown in FIG. 5 except that the drum gear 9 is not provided. As shown in FIG. 5, the charging roller 2 is pressed against the peripheral surface of the photosensitive drum 1 by shaft pressing plate springs 6 at both ends of the rotating shaft.

  In particular, image forming apparatuses in recent years have been reduced in size, the internal image forming unit has also been reduced in size, and the diameter of the photosensitive drum and the diameter of the charging roller have been reduced. Since the photosensitive drum is made of metal and is not easily affected by downsizing, the charging roller is made of a sponge with a flexible surface, so that the charging roller is bent by the pressing force from the shaft pressing plate spring 6 applied to both ends of the shaft. It is easy to get up.

JP 2000-259057 A

  By the way, when the charging roller bends, the pressure on the photosensitive drum tends to be strong at both ends of the shaft, and the pressure tends to be weak at the center. Where the pressure is strong, the charging function to the photosensitive drum is strong, and when the pressure is weak, the charging function to the photosensitive drum is weak.

  The change in the strength of pressing from the shaft end to the shaft center appears as the strength of the charging function of the charging roller with respect to the photosensitive drum. If there is unevenness in the charge on the photosensitive drum, the unevenness appears in the density of the toner image developed on the peripheral surface of the photosensitive drum, and the image quality deteriorates.

  In the technique described in Patent Document 1 above, there is a description about the removal of the reversely charged toner that prevents the uniform charging of the surface potential of the photosensitive drum, but similarly the uniform charging of the surface potential of the photosensitive drum is prevented. There is no description of a solution for the bending of the charging roller.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems and to provide an image forming apparatus including an image forming unit that performs uniform initialization charging on a photosensitive drum with a simple mechanical structure. To do.

  In order to solve the above problems, an image forming apparatus according to the present invention is provided in the cleaning unit in an image forming apparatus including at least a toner developing device, a photosensitive drum, and a cleaning unit in an image forming unit frame. A charging roller that is brought into pressure contact with the circumferential surface of the photosensitive drum along the axial direction of the photosensitive drum to initialize and charge the photosensitive drum, and provided in the cleaning unit, along the axial direction of the charging roller. A charging roller cleaner for cleaning the charging roller in pressure contact with the charging roller on the opposite side of the photosensitive drum, and a long leaf spring member having a U-shaped cross section. A cleaner holding member having a side surface fixed to the image forming unit frame and holding the charging roller cleaner by the other side surface of the U-shape; Further, the cleaner holding member linearly holds the charging roller cleaner from one end to the other end by the other side surface of the U-shape so as to press the charging roller against the charging roller. The charging roller is biased against the peripheral surface of the photosensitive drum by a biasing force that is linearly and uniformly applied from the cleaner holding member to the other shaft end from the cleaner holding member via the charging roller cleaner. Further, it is configured such that it is pressed with a linear and uniform pressing force from one axial end to the other axial end along the axial direction of the photosensitive drum.

According to the present invention, since the entire lengthwise direction of the charging roller can be uniformly brought into pressure contact with the photosensitive drum, there is an effect that a better image can be formed.
Moreover, since the structure which consists of several components of two shaft pressing leaf | plate springs and one mylar sheet | seat conventionally can be made into one component, there exists an effect that it is effective in cost reduction.

1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (printer) according to Embodiment 1 of the invention. 3 is an enlarged cross-sectional view of an image forming unit of the printer according to Embodiment 1. FIG. FIG. 3 is a perspective view illustrating a configuration around a charging roller disposed in a cleaner portion of the image forming unit of the printer according to the first exemplary embodiment. FIG. 5A is a diagram illustrating a configuration of a waste toner bottle of a printer according to a second embodiment, and FIG. 5B is a diagram illustrating a configuration of a waste toner conveyance device that sends waste toner to the waste toner bottle. FIG. 10 is a perspective view illustrating a configuration relationship between a general photosensitive drum and a charging roller in an image forming unit of a conventional printer.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, a two-component developer including a toner and a carrier is used. In the following description, the two-component developer is simply referred to as a developer or a toner.

  FIG. 1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (hereinafter simply referred to as a printer) 10 according to a first embodiment of the present invention.

  A printer 10 shown in FIG. 1 is an electrophotographic secondary transfer tandem type color image forming apparatus, and includes an image forming unit 12, a transfer belt unit 13, a toner supply unit 14, a paper feeding unit 15, a belt type fixing. It comprises a unit 16 and a transport unit 17 for duplex printing.

  The image forming unit 12 is in contact with the lower running portion surface 18a of the transfer belt 18 of the transfer belt unit 13 so that four image forming units 19 (19y, 19m, 19c, 19k) are multistaged from left to right in FIG. It consists of the structure arranged in parallel. The image forming unit 12 is held on the frame of the main body of the printer 10 so as to be movable up and down from the printing execution position shown in FIG. 1 to a maintenance position below the printing execution position.

  Of the four image forming units 19, three image forming units 19y, 19m, and 19c on the upstream side (the left side in the figure) are subtractive mixed primary colors yellow (Y), magenta (M), cyan ( A mono-color image is formed with the color toner C), and the image forming unit 19k forms a monochrome image with black (K) toner mainly used for dark portions of characters and images.

  Each of the image forming units 19 has the same configuration except for the color of the toner for developing the image. Accordingly, the configuration of the image forming unit 19y for yellow (Y) toner will be described below as an example.

  The image forming unit 19 includes a photosensitive drum 20 at the top. The photosensitive drum 20 has a peripheral surface made of, for example, an organic photoconductive material. A cleaner 21, a charging roller 22, an optical writing head 23, and a developing roller 25 of a developing device 24 are disposed around the periphery of the photosensitive drum 20.

  The developing device 24 includes a housing 26 that covers the outside, a partition wall 27 provided inside, a developing roller 25, a first stirring and conveying screw 28, and a second stirring and conveying screw 29. Although not specifically shown, the first and second agitating and conveying screws 28 and 29 include a screw shaft and a fin that is integrally formed with the screw shaft and rotates.

  The transfer belt unit 13 has an endless transfer belt 18 that extends in the shape of a flat loop in the left-right direction in the figure at the approximate center of the main body device, and the transfer belt 18 is stretched over the transfer belt 18. A driving roller 31 and a driven roller 32 that circulate in a counterclockwise direction indicated by an arrow a in the figure are provided.

  A primary transfer roller 33 is integrated with the transfer belt unit 13 in the transfer belt 18. The primary transfer roller 33 is pressed against the photosensitive drum 20 via the transfer belt 18 and directly transfers (primary transfer) the toner image to the belt surface that circulates below. The transfer belt 18 conveys the toner image to a secondary transfer unit 34 to the paper to further transfer (secondary transfer) to the paper.

  The toner supply unit 14 is detachably disposed on four reserve tanks 35 (35k, 35c, 35m, and 35y) disposed above the upper running unit of the transfer belt 18 and these reserve tanks 35, respectively. And a toner cartridge 36 (36k, 36c, 36m, 36y) for toner replenishment.

  The four toner cartridges 36k, 36c, 36m, and 36y contain black (K), cyan (C), magenta (M), and yellow (Y) toners, respectively, and four reserve tanks 35 (35k, 35c). , 35m, and 35y) are replenished with toner from the toner cartridge 36 mounted thereon.

  These four reserve tanks 35 are hidden behind the opposite side of the transfer belt unit 13 in FIG. 1, but are connected to the corresponding developing devices 24 of the image forming unit 19 through toner supply paths.

  The developing device 24 includes a reserve tank 35 (35k, 35c, 35m, 35y) of the toner supply unit 14, and black (K), cyan (C), and black as indicated by K, C, M, and Y in FIG. Either magenta (M) or yellow (Y) toner is supplied.

  Two electrical parts 37 are disposed on the left side of the toner supply unit 14 from the upper side to the left side of the drive roller 31. The electrical unit 37 includes a circuit board on which a control device including a plurality of electronic components is mounted.

  The paper feed unit 15 includes two paper feed cassettes 38 (38a, 38b) arranged in two upper and lower stages. A paper take-out roller 39, a feed roller 41, a separating roller 42, and a standby conveyance roller pair 43 are arranged near the paper feed opening (right side in the drawing) of the two paper feed cassettes 38, respectively.

  A secondary transfer roller 44 that is in pressure contact with the driven roller 32 via the transfer belt 18 is disposed in the paper transport direction of the standby transport roller pair 43 (vertically upward in the drawing), and secondary transfer onto the paper described above. A portion 34 is formed.

  A belt-type thermal fixing unit 16 is disposed downstream (upward in the drawing) of the secondary transfer portion 34. On the further downstream side of the belt-type heat fixing unit 16, a pair of carry-out rollers 45 for carrying out the paper after fixing from the belt-type heat fixing unit 16, and a paper discharge tray 46 formed on the upper surface of the apparatus. A paper discharge roller pair 47 for discharging the paper is disposed.

  The duplex printing conveyance unit 17 has an outer surface (right outer surface in the drawing) serving as an opening / closing member that opens or shields the inside of the printer 10 from the side surface to the outside.

  The duplex printing transport unit 17 has a return start path 48a that branches rightward in the figure from just before the paper discharge roller pair 47, a return intermediate path 48b that bends downward, and a left lateral direction opposite to the above. Thus, a return path 48 including a return end path 48c for finally inverting the return sheet is provided.

  Further, five pairs of return rollers 49 (49a, 49b, 49c, 49d, 49e) are arranged in the return path 48. The exit of the end return path 48 c joins the conveyance path to the pair of standby conveyance rollers 43 corresponding to the sheet feeding cassette 38 b below the sheet feeding section 15.

  Further, a rectangular waste toner bottle 51 extending in the depth direction of the drawing is disposed between the image forming unit 12 below the two electrical components 37 and the left inner wall of the printer main body. In the waste toner bottle 51, the waste toner removed from the photosensitive drum 20 by the cleaner 21 is collected through a waste toner transport pipe 52 disposed below the image forming unit 12.

FIG. 2 is an enlarged view of the image forming unit 12 shown in FIG.
FIG. 3 is an enlarged perspective view of the cleaner 21 shown in FIG. 2 and 3, the same components as those shown in FIG. 1 are denoted by the same reference numerals as those in FIG.

  In FIG. 2, the doctor blade 53, the waste toner conveying screw 54, and the cleaning blade 55, which are not described in FIG. Further, FIG. 2 or 3 shows toner scattering prevention sheets A56 and B57, a charging roller cleaner 58, and a cleaner pressing plate spring 59, which are not shown in FIG.

  3 shows a charging roller casing 61, a charging roller bearing 62, a bearing holder 63, and a drum gear 64, which are not described or illustrated in FIG. The drum gear 64 is provided at one end (the right end in the figure) and is not provided at the left end outside the figure.

  The doctor blade 53 uniformly regulates the toner layer formed on the peripheral surface of the developing roller 25 to a predetermined thickness. The waste toner conveying screw 54 sends the waste toner removed by the cleaning blade 55 and the charging roller cleaner 58 and staying in the cleaner 21 to the waste toner conveying pipe 52 shown in FIG.

  The cleaning blade 55 removes toner remaining on the peripheral surface of the photosensitive drum 20. The toner scattering prevention sheet A56 shields the gap between the inside and the outside of the developing device 24 and prevents the toner inside from scattering to the outside.

  The toner scattering prevention sheet B57 shields the gap between the inside and the outside of the cleaner 1 and prevents the toner inside from scattering to the outside. The charging roller 22 is in sliding contact with the peripheral surface of the photosensitive drum 20 to initialize and charge the photosensitive drum 20, and scrapes and removes remaining toner and the like that cannot be removed by the cleaning blade 55.

  The charging roller cleaner 58 cleans waste toner, dust, and the like attached to the peripheral surface of the charging roller 22 as the charging roller 22 is scraped and removed from the photosensitive drum 20. The cleaner pressing leaf spring 59 is made of a long leaf spring member having a U-shaped cross section.

  The cleaner pressing plate spring 59 serves as a cleaner holding member and a charging roller urging member, and one side surface of the U-shape is used as an image forming unit frame (specifically, the cleaning unit housing frame 50 of the image forming unit). The charging roller cleaner 58 is held by the other side face of the U-shape.

  The cleaner pressing plate spring 59 holds the charging roller cleaner 58 linearly and uniformly from one end to the other end by the other side of the U-shape holding the charging roller cleaner 58. Energize to press against.

  The charging roller 22 is linearly and uniformly applied from the cleaner pressing plate spring 59 that also serves as a cleaner holding member via the charging roller cleaner 58 from one shaft end to the other shaft end. Is pressed with a linear and uniform pressing force from one axial end to the other axial end along the axial direction of the photosensitive drum 20.

As described above, in the first embodiment of the present invention, the entire lengthwise direction of the charging roller can be uniformly brought into pressure contact with the photosensitive drum, so that an effect that a better image can be formed is achieved. Further, one that is established between the conventional and two-axis pressing plate spring biasing the both ends of the charging roller shaft toward the photosensitive drum direction, and an open mouth end portions of the charging roller cleaner and the cleaning section housing frame of a structure comprising a plurality of parts of Mylar sheets, cleaner presser plate as the cleaner holding member arranged elongated toward the apertures direction of the housing frame of the cleaning unit the bending portion of the U-shaped cross section in U-shaped Since it can be replaced with a spring to form a single component, it is effective in reducing costs.

  4A is a side view of the waste toner bottle 51 shown in FIG. 1 of the printer according to the second embodiment. FIG. 4B is a waste toner that feeds the waste toner into the waste toner bottle 51. FIG. FIG. 2 is a diagram illustrating a detailed configuration of a waste toner conveyance pipe 52 illustrated in FIG. 1 as a conveyance device.

  As shown in FIG. 4 (a), the waste toner bottle 51 is a long rectangular container having a gear 65 that engages with the drive system of the printer main body on the front, and a waste toner receiving port 66 on the front upper surface. An auger roller 67 connected to the rotation shaft of the gear 65 is provided in the container.

  In FIG. 4 (a), the auger roller 67 is indicated by a broken line. The auger roller 67 is a stirring and conveying member having a rotating shaft and a spiral blade fixed to the rotating shaft. The auger roller 67 packs the waste toner fed from the waste toner receiving port 66 as shown by the arrow c into the container as shown by the arrow d while stirring.

  As shown in FIG. 4 (b), the waste toner transport pipe 52 has a lower horizontal portion 52a and an upper horizontal portion 52b that are horizontally disposed, both of which are pipes made of a hard member, and inside the waste toner transport coil 68. It has. A waste toner discharge port 69 is formed at the end of the upper horizontal portion 52b.

  Further, the waste toner conveying pipe 52 includes a tube 52c made of a flexible bending member at a portion rising from the lower horizontal portion 52a to the upper horizontal portion 52b. A guide 71 made of a hard plate member is in close contact with the outer side of the bent portion of the tube 52c that is bent in an arc of approximately 90 degrees.

  Inside the bent portion, there are eight rotating arms 73 that rotate counterclockwise as indicated by an arrow e around the rotating shaft 72, and presses disposed at the tips of the rotating arms 73, respectively. A roller 74 is provided.

  Waste toner that has been conveyed by the waste toner conveyance coil 68 as shown by the arrow f in the lower horizontal portion 52a of the waste toner conveyance pipe 52 is fed into the tube 52c. The waste toner 75 sent to the tube 52c is sequentially pressed by the pressing roller 74, thereby forming a lump state between the adjacent pressing rollers 74. The tube 52c is rotated by the rotating arm 73 as indicated by an arrow g. Move in the direction.

  Then, the waste toner 75 that has reached the upper horizontal portion 52b of the waste toner transport pipe 52 is transported again by the waste toner transport coil 68, and from the waste toner discharge port 69 of the upper horizontal portion 52b, as shown in FIGS. As shown by an arrow c, the toner is fed into the waste toner receiving port 66 of the waste toner bottle 51.

  As described above, in the second embodiment of the present invention, by using the tube and the rotation pressing roller, it is possible to convey the ink upward at a right angle, which is almost impossible with a conventional waste toner conveying device using a coil spring or the like. Therefore, a highly reliable waste toner conveyance mechanism can be provided, design restrictions on the arrangement of waste toner bottles can be eliminated, the degree of freedom in layout of printer components can be increased, and the entire printer can be reduced in size.

Although several embodiments of the present invention have been described, the present invention is included in the invention described in the claims and the equivalents thereof. Hereinafter, the invention described in the scope of claims of the present application will be appended.
[Appendix 1]

In an image forming apparatus including at least a toner developing device, a photosensitive drum, and a cleaning unit in an image forming unit frame,
A charging roller that is provided in the cleaning unit, presses the circumferential surface of the photosensitive drum along the axial direction of the photosensitive drum, and initializes the photosensitive drum;
A charging roller cleaner that is provided in the cleaning unit, presses against the charging roller on the opposite side of the photosensitive drum along the axial direction of the charging roller, and cleans the charging roller;
A cleaner comprising a long leaf spring member having a U-shaped cross section, one side of the U-shaped being fixed to the image forming unit frame, and the charging roller cleaner being held by the other side of the U-shaped A holding member;
With
The cleaner holding member is urged by the other side surface of the U-shape to hold the charging roller cleaner linearly from one end to the other end and press the charging roller against the charging roller. And
The charging roller is configured to apply a linear and uniform biasing force from the cleaner holding member to the other shaft end from the cleaner holding member via the charging roller cleaner with respect to the circumferential surface of the photosensitive drum. Abutting with a linear and uniform pressing force from one shaft end to the other shaft end along the axial direction of the drum,
An image forming apparatus.
[Appendix 2]

  The image forming apparatus according to claim 1, wherein the cleaner holding member is configured to be arranged in place of a mylar sheet that prevents leakage of waste toner to the outside.

  The present invention can be used in an image forming apparatus including an image forming unit that performs uniform initialization charging on a photosensitive drum.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Charging cleaner 4 Mylar sheet for toner leakage prevention 5 Drum kit casing 6 Shaft pressing plate spring 7 Charging bearing 8 Bearing holder 9 Drum gear 10 Image forming apparatus (printer)
DESCRIPTION OF SYMBOLS 12 Image formation part 13 Transfer belt unit 14 Toner supply part 15 Paper feed part 16 Belt type fixing unit 17 Duplex printing conveyance unit 18 Transfer belt 18a Lower running part surface 19 (19y, 19m, 19c, 19k) Image formation unit 20 Photosensitive Body drum 21 Cleaner 22 Charging roller 23 Optical writing head 24 Developer 25 Developing roller 26 Housing 27 Partition 28 First stirring and conveying screw 29 Second stirring and conveying screw 31 Driving roller 32 Followed roller 33 Primary transfer roller 34 Secondary transfer roller Transfer section 35 (35 m, 35 c, 35 y, 35 k) Reserve tank 36 (36 m, 36 c, 36 y, 36 k) Toner cartridge 37 Electrical section 38 (38 a, 38 b) Paper feed cassette 39 Paper take-out roller 41 Feeding roller 42 Rolling roller 43 Standby transport Roller pair 44 Secondary transfer roller 45 Unload roller pair 46 Paper discharge tray 47 Paper discharge roller pair 48 Return path 48a Return start path 48b Return intermediate path 48c Return end path 49 (49a, 49b, 49c, 49d, 49e) Return roller 50 Cleaning unit housing frame 51 Waste toner bottle 52 Waste toner transport pipe 52a Lower horizontal part 52b Upper horizontal part 52c Tube 53 Doctor blade 54 Waste toner transport screw 55 Cleaning blade 56 Toner scattering prevention sheet A
57 Toner scattering prevention sheet B
58 Charging roller cleaner 59 Cleaner presser plate spring 61 Charging roller casing 62 Charging roller bearing 63 Bearing holder 64 Drum gear 65 Gear 66 Waste toner receiving port 67 Auger roller 68 Waste toner transport coil 69 Waste toner discharge port 71 Guide 72 Rotating shaft 73 Rotating arm 74 Pressure roller

Claims (2)

In an image forming apparatus including at least a toner developing device, a photosensitive drum, and a cleaning unit in an image forming unit frame,
A charging roller that is provided in the cleaning unit, presses the circumferential surface of the photosensitive drum along the axial direction of the photosensitive drum, and initializes the photosensitive drum;
A charging roller cleaner that is provided in the cleaning unit, presses against the charging roller on the opposite side of the photosensitive drum along the axial direction of the charging roller, and cleans the charging roller;
A cleaner comprising a long leaf spring member having a U-shaped cross section, one side of the U-shaped being fixed to the image forming unit frame, and the charging roller cleaner being held by the other side of the U-shaped A holding member;
With
The cleaner holding member is urged by the other side surface of the U-shape to hold the charging roller cleaner linearly from one end to the other end and press the charging roller against the charging roller. And
The charging roller is configured to apply a linear and uniform biasing force from the cleaner holding member to the other shaft end from the cleaner holding member via the charging roller cleaner with respect to the circumferential surface of the photosensitive drum. Abutting with a linear and uniform pressing force from one shaft end to the other shaft end along the axial direction of the drum,
An image forming apparatus. The cleaner holding member according to claim 1, wherein toward the bent portion of the shape of U to the outside is disposed between the charging roller cleaner and the opening lower end of the housing frame of the cleaning unit, it is characterized by The image forming apparatus described.