JP5325391B2 - Developer conveying screw device - Google Patents

Description

  The present invention stores a developing device that develops an electrostatic latent image formed on an image carrier with a developer into a visible image, and a replenishing developer for supplying toner (developer) to the developing device. The present invention relates to a developer conveying screw device having a screw body that is used in a toner container, a toner conveying device that conveys toner from the toner container to a developing device, and the like, and a screw body that rotates to convey the developer along an axial direction.

  Conventionally, a developing device for developing an electrostatic latent image formed on an image carrier with a developer to make a visible image, and a replenishment developer for supplying toner (developer) to the developing device are stored. As a toner container, a toner conveying device that conveys toner from a toner container to a developing device, and the like, a developer conveying screw device including a screw body that rotates to convey the developer along an axial direction is known. (For example, refer to Patent Document 1).

  Moreover, as a screw main body used for the developer conveying screw device, for example, as shown in FIG. 7, a screw main body in which a spiral blade portion 2 is integrally formed around a rotation shaft 1 having a rotation center Q. 3 is well known.

  At this time, the blade portion 2 has a larger developer conveying force when the inclination angle θ5 from the apex of the developer conveying surface to the rotation center Q with respect to the developer conveying direction (see the thick arrow in the drawing) is closer to the vertical. Therefore, in general, the inclination angle θ5 is often set to a steep slope of about 70 to 80 ° in consideration of the draft angle of the screw mold.

  However, when such an inclination angle θ5 is set to be steep, the developer T is in the blade portion 2 as the screw body 3 rotates, as shown in FIG. Since the developer T receives a force pushed in the traveling direction by the toner, the developer T is shifted to the developer conveyance surface side of the blade part 2 and the toner conveyance amount decreases as the distance from the blade part 2 increases, and the pitch of each blade part 2 is reduced. When the developer conveyance distribution in the cross-sectional direction between them is viewed, a large portion and a small portion are formed according to the pitch of the blade portion 2, and there is a problem that toner conveyance unevenness is caused.

Therefore, as shown in FIG. 9, the inclination angle θ6 from the apex of the developer conveyance surface with reference to the developer conveyance direction (see thick arrow in the figure) toward the rotation center Q is set to a gentle slope of 60 ° or less, and It is considered to suppress conveyance unevenness.
JP 2004-117507 A

  However, in the developer transport screw device configured as described above, if the inclination angle θ6 from the apex of the developer transport surface toward the rotation center Q is set to a gentle slope of 60 ° or less, for example, FIG. 9 is the same between the pitches of adjacent ones of the blades 2 shown in FIG. 9 and the pitch between adjacent ones of the blades 2 shown in FIG. 9, and the diameter of the rotating shaft 1 and the diameter of the blades 2. In any case, the amount of toner transport between the pitches of the blade portions 2 is extremely reduced, and the cross-section of the blade portion 2 is increased due to the gentle slope. Since the depth in the direction (vertical direction in the figure) is different, it has been difficult to say that it can contribute to substantial toner flattening in the developer transport distribution in the cross-sectional direction.

  In view of the above circumstances, the present invention provides a developer transport screw device that can contribute to the uniform distribution of developer transport in the cross-sectional direction perpendicular to the transport direction during developer transport. Objective.

  The developer conveying screw device of the present invention is a developer conveying screw device including a screw body that rotates to convey the developer along the axial direction, and the screw body protrudes spirally around the rotation axis. A large-diameter blade portion, and a small-diameter blade portion that is positioned between the pitches of the large-diameter blade portion and that has a smaller diameter than the large-diameter blade portion and protrudes spirally around the rotation axis. It is characterized in that it is located downstream of the developer conveying surface of the diameter blade portion in the developer conveying direction.

  At this time, the inclination angle of the developer conveying surface from the apex of the large-diameter blade portion toward the rotation axis center is θ1, and the inclination angle of the developer conveying surface from the apex of the small-diameter blade portion toward the rotation axis center is θ2. Then, it is desirable that θ1 <θ2 is set.

  The developer transport screw device of the present invention can contribute to uniform developer transport distribution in the cross-sectional direction perpendicular to the transport direction during developer transport.

  Next, a developer conveying screw device according to an embodiment of the present invention is applied to a color printer using a two-component developer as an image forming apparatus, and will be described with reference to the drawings.

  FIG. 1 is an explanatory view of a color printer as an image forming apparatus provided with a developer conveying screw device according to an embodiment of the present invention, and FIG. 2 is a development including a developer conveying screw device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of a part of a screw main body in a developer conveying screw device according to an embodiment of the present invention, and FIG. 4 is a screw main body in the developer conveying screw device according to an embodiment of the present invention. FIG. 5 is an explanatory view of a developer conveying state in a developer conveying screw main body according to an embodiment of the present invention, and FIG. 6 is a screw in a developer conveying screw device according to an embodiment of the present invention. It is a chart of the relationship of each inclined surface of a main part.

  As shown in FIG. 1, a color printer 11 according to an embodiment of the present invention includes a paper feed cassette 13 that stores transfer paper (not shown) in a printer main body 12, and a transfer paper from the paper feed cassette 13. A sheet feeding unit 14 for taking out the image, an image forming processing unit 15 for performing an image forming process on a transfer sheet supplied from a sheet feeding cassette 13 or a manual feed tray (not shown), and a paper feeding cassette 13 or a manual feed tray. A transfer unit 17 that transfers the toner image that has undergone image formation processing by the image formation processing unit 15 while guiding the transferred transfer paper through the transfer paper conveyance path 16, and a fixing unit 18 that fixes the toner image after transfer.

  For example, the image forming processing unit 15 employs a tandem method in which image forming is performed using toner (developer) of four colors of yellow (Y), magenta (M), cyan (C), and black (K). And a plurality of toner containers 19 that store the replenishment toners for the respective colors, and a photoreceptor that forms toner images based on the image data included in the print data transmitted from a personal computer (not shown). 20, a developing device 21 that supplies toner to the photoconductor 20, and an endless intermediate transfer belt 22 to which a toner image formed on the photoconductor 20 is transferred.

  Each photoconductor 20 carries a toner image of each color based on the laser beam emitted from the exposure device 23 on its surface and transfers the toner image to the intermediate transfer belt 22. It is disposed below the transfer belt 22. Further, around the drum-shaped photoconductor 20, a charger 24, an exposure device 23, a developing device 21, an intermediate transfer belt 22, a cleaning device 25, and a static eliminator 26 are arranged along the rotation direction (see arrows). ing.

  Each developing device 21 basically has the same configuration and is arranged adjacent to the lower side of the intermediate transfer belt 22 along the rotational movement direction. The developing device 21 includes a casing 27, a pair of stirring screws 28 and 29, a magnetic roller 30, a developing roller 31, and a toner concentration sensor 32.

  The intermediate transfer belt 22 is an endless belt disposed in the printer main body 12 so as to extend in the horizontal direction, and is circulated and driven in accordance with an image forming operation. The toner image transferred onto the intermediate transfer belt 22 is transferred by the transfer unit 17 to the transfer paper conveyed through the transfer paper conveyance path 16 from the paper feed cassette 13 or the manual feed tray.

  Further, the transfer paper on which the toner image is transferred by the transfer unit 17 is fixed by the fixing unit 18 through the transfer paper transport path 16, and then guided to the end of the transfer paper transport path 16 to be transferred to the upper surface of the printer main body 12. As shown in FIG.

  Each of the stirring screws 28 and 29 has substantially the same configuration, and the toner is conveyed along the axial direction so that the developer is circulated and conveyed in the casing 27 through the partition wall 27a of the casing 27. It arrange | positions so that a direction may become reverse direction. In addition, each of the stirring screws 28 and 29 is formed with spiral blade portions 28b and 28c and blade portions 29b and 29c having large and small diameters on the outer circumferences of the rotation shafts 28a and 29a.

  Hereinafter, a specific configuration of each of the stirring screws 28 and 29 will be described with the stirring screw 28 as a representative. As shown in FIG. 3, each stirring screw 28 has alternately formed large-diameter blade portions 28 b and small-diameter blade portions 28 c that protrude from the rotation shaft 28 a. At this time, the pitch (inter-vertex distance) L1 of the large-diameter blade portion 28b and the pitch L2 of the small-diameter blade portion 28c are the same (for example, 20 mm). Further, here, the diameter D2 (for example, φ17 mm) of the large-diameter blade portion 28b and the diameter D3 (for example, φ9 mm) of the small-diameter blade portion 28c with respect to the diameter D1 (for example, φ5 mm) of the rotating shaft 28a are the diameters. The diameter D3 is set to about twice the diameter D1, and the diameter D2 is set to about twice the diameter D3. In addition, the rotation center Q with reference to the inclination angle θ1 of the developer conveyance surface toward the rotation center Q with reference to the toner conveyance direction of the large-diameter blade portion 28b (see the thick arrow in FIG. 4) and the toner conveyance direction of the small-diameter blade portion 28c. The inclination angle θ2 of the developer transport surface facing the direction is set so that θ1 <θ2. When the diameter D1 of the rotary shaft 28a is 5 mm, the protruding height of the large-diameter blade portion 28b is 12 mm when the diameter D2 is 17 mm, and the protruding height of the small-diameter blade portion 28c is 4 mm when the diameter D3 is 9 mm. The protruding height of the large-diameter blade portion 28b is about three times the protruding height of the small-diameter blade portion 28c.

  In the case of the agitating screw 28 as the screw body shown in FIG. 4, the large-diameter blade portion 28b and the small-diameter blade portion 28c have right-angled triangles whose cross sections are perpendicular to each other. The side inclination angle θ1 is set to 30 °, and the inclination angle θ2 is set to 60 °. Accordingly, the diagonal angle θ3 of the inclination angle θ1 of the large-diameter blade portion 28b is 60 °, and the diagonal angle θ4 of the inclination angle θ2 of the small-diameter blade portion 28c is 30 °. In addition, it is preferable that the distances L3 and L4 of the surface portion of the rotating shaft 28a located between the large-diameter blade portion 28b and the small-diameter blade portion 28c are substantially the same (for example, 2 mm).

  Further, the inclination angles θ1 and θ2 are preferably combined as shown in FIG. 5. By adopting such a configuration, the toner (developer) T is conveyed as shown in FIG. At this time, when the developer transport distribution in the cross-sectional direction between the pitches of the large-diameter blade portions 28b constituting the substantial developer transport surface is viewed, the surface side can be made substantially flat and the depth in the cross-sectional direction can be made. In addition, as compared with the case where there is almost no part of the same depth as described in the prior art (see FIGS. 8 and 9), the toner transport is substantially flattened without extremely different developer transport distribution. In particular, when θ1 = 30 ° and θ2 = 75 °, a high level of toner conveyance can be realized.

  In FIG. 5, × is an unfavorable condition at a level at which it appears to be completely uneven on the transfer paper after the image forming process, Δ is an unfavorable condition at a level at which an unevenness is apparently visible, and ○ is the same Preferable conditions at a level where it is difficult to visually confirm unevenness, and ◎ means the best conditions where virtually no unevenness is apparent.

  By the way, in the above embodiment, the developer conveying screw device of the present invention is applied to the stirring screw 28 (29) for the developing device 21. However, for example, it is arranged in a toner container or other conveying path. Needless to say, the present invention can be applied to stirring screws and conveying screws in general.

  Moreover, in the said embodiment, although disclosed by the case where one small diameter blade | wing part 28c has been arrange | positioned between adjacent large diameter blade | wing parts 28b (between pitches), this small diameter blade | wing part 28c is provided with two or more between the same pitches. Also good.

FIG. 3 is an explanatory diagram of a color printer as an image forming apparatus including a developer conveying screw device according to an embodiment of the present invention. It is explanatory drawing of the developing device provided with the developer conveyance screw device which concerns on one Embodiment of this invention. FIG. 4 is a partial cross-sectional view of a screw body in the developer conveying screw device according to an embodiment of the present invention. It is explanatory drawing of the principal part of the screw main body in the developer conveyance screw apparatus which concerns on one Embodiment of this invention. It is explanatory drawing of the developer conveyance state in the developer conveyance screw main body which concerns on one Embodiment of this invention. It is a chart of the relationship of each inclined surface of the screw main body in the developer conveyance screw device concerning one embodiment of the present invention. It is a front view of the principal part of the screw main body in the conventional developer conveyance screw device. It is sectional drawing of the principal part of the screw main body in the conventional developer conveyance screw apparatus. It is sectional drawing of the principal part of the other screw main body in the conventional developer conveyance screw apparatus.

Explanation of symbols

T ... Toner (Developer)
28 ... Stir screw (screw body)
28a ... Rotating shaft 28b ... Large-diameter blade portion 28c ... Small-diameter blade portion

Claims (1)

In the developer transport screw device having a screw body that rotates to transport the developer along the axial direction,
The screw main body is located between the large-diameter blades that project spirally around the rotation axis and the pitch between the large-diameter blades, and is smaller than the large-diameter blades and projects spirally around the rotation axis. A small-diameter blade portion, and an inclination angle of the developer transport surface from the top of the large- diameter blade portion toward the rotation axis center in the developer transport direction is θ1, and from the top of the small-diameter blade portion in the developer transport direction. A developer conveying screw device , wherein θ1 <θ2 is set, where θ2 is an inclination angle of the developer conveying surface toward the rotation axis center .

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