JP2013178305A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device which effectively supplies a developer to a supply roller, improves the stability of a solid density, and produces a good quality image.SOLUTION: A developing unit 4 comprises: a developing roller 17; a supply roller 20 which rotates in a rotation direction E opposite to a surface of the developing roller 17 at a nip part N; an accumulation part Q which is provided upward the supply roller 20, and accumulates toner T; a storage chamber 18 which is provided downward the accumulation part Q, and stores the toner T; an agitation member 22 which is provided inside the storage chamber 18, and conveys the toner T from the storage chamber 18 to the accumulation part Q; and a toner return member 50 including a close part 59 which is a close side to the supply roller 20 opposite to the supply roller 20 in the vicinity of the supply roller 20 in an area downstream the nip part N in the rotation direction E of the supply roller 20, and upper edge parts 51a, 58a which are formed on the far side from the supply roller 20, and have different positions from the close part 59 in the longitudinal direction Z.

Description

  The present invention relates to a developing device including a developer carrier and a supply roller, a process cartridge including the same, and an image forming apparatus.

  Conventionally, as an invention related to an in-line image forming apparatus, an image forming apparatus described in Patent Document 1 has been disclosed. In the invention described in Patent Document 1, a plurality of photosensitive drums are disposed below the intermediate transfer member and the recording material transport member. In such a configuration, for example, the fixing device and the developing device (or the exposure device) can be arranged at positions separated from each other, with the intermediate transfer member and the recording material conveyance member sandwiched therebetween. For this reason, there are obtained advantages such that the developing device (exposure device) is hardly affected by the heat of the fixing device.

  On the other hand, in such a configuration, it is necessary to supply the developer to the developing roller and the supply roller in the developing device against gravity. At this time, it is most efficient to supply the developer to the supply roller by transporting the developer to a portion immediately downstream of the nip portion between the development roller and the supply roller on the downstream side in the rotation direction of the supply roller. That is, in the supply roller provided with an elastic layer having a plurality of cells on the outer peripheral portion, the elastic portion coming out from the nip portion is released from the pressure immediately after the nip portion, and the cell opens accordingly. At this time, intake is performed and developer is sucked. Therefore, in order to efficiently hold the developer on the supply roller, it is preferable to feed the toner directly into the suction portion.

  However, in a developing device that supplies developer against gravity, it is difficult to feed a large amount of developer to the suction portion with a simple configuration. Even if the developer is sent to the vicinity of the suction portion, a part of the developer is sucked, but most of the developer is returned to the storage chamber or the like with the rotation of the supply roller.

  Therefore, in the developing device of Patent Document 1, a technique for supplying the developer at the lower portion of the supply roller has been proposed. In Patent Document 1, the supply roller rotates from below to above at the contact portion between the developing roller (developer carrier) and the supply roller. A toner receiving member is provided below the supply roller, and a base end portion of the receiving sheet is attached to the toner receiving member, and the receiving sheet contacts the supply roller with an appropriate linear pressure. According to such a configuration, the developer adhering to the supply roller is received by the receiving sheet, and the phenomenon of dropping due to gravity is suppressed, and the decrease in the developer that can be supplied to the development roller is suppressed, and the solid density is reduced. Is suppressed.

JP 2003-173083 A

  However, in the developer supply mechanism described in Patent Document 1, when durability is performed with an image pattern having a low printing rate, since the amount of developer to be developed is small, the developer is circulated between the supply roller and the receiving sheet. There may be a large amount of developer that does not. That is, although the developer is accumulated below the supply roller, the consumption of the accumulated developer does not progress in the durability of the image pattern with a low printing rate. Therefore, as the supply roller rotates, the developer is supplied one after another, the developer aggregates and packs, and the image quality deteriorates such as density unevenness due to uneven supply of the developer to the supply roller. May be caused.

  In view of the above circumstances, an object of the present invention is to provide a developing device that can efficiently supply a developer to a supply roller, improve solid density stability, and supply a high-quality image. To do.

  In order to achieve the above object, a developing device according to the present invention includes a developer carrying member that is rotatable while carrying a developer, and contacts or enters the developer carrying member at a nip portion. A supply roller that is rotatable in the opposite direction with respect to the surface of the developer carrier and contains developer to supply the developer to the developer carrier, and is disposed above the supply roller to store the developer. A storage section that is disposed below the storage section and stores the developer; a transport member that is disposed inside the storage chamber and transports the developer from the storage chamber to the storage section; A first edge that faces, contacts or enters the supply roller in the vicinity of the supply roller in the downstream region in the rotation direction of the supply roller with respect to the nip portion, and a side far from the supply roller. Being said in the longitudinal direction Characterized in that it comprises a developer flashing member position from the edge portion has a different second edge portion.

  According to the present invention, the developer can be efficiently supplied to the supply roller, the solid density stability can be improved, and a high-quality image can be supplied.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to Embodiment 1 of the present invention. It is sectional drawing which shows the structure of a cartridge. It is explanatory drawing etc. which show the measuring method of "surface air flow" It is sectional drawing which shows the structure of a developing roller and a supply roller. It is a figure which shows the structure of a toner return member and a supply roller. FIG. 10 is a cross-sectional view illustrating a configuration of a toner return member and a supply roller included in a developing unit according to Embodiment 2. FIG. 10 is a cross-sectional view illustrating a configuration of a toner return member and a supply roller included in a developing unit according to Embodiment 3. FIG. 6 is a cross-sectional view illustrating a trajectory of toner transported by a stirring member.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, since the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, there is no specific description. As long as the scope of the invention is not limited to these, it is not intended. Further, the technical ideas described in the first to third embodiments can be appropriately combined.

  FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus 100 according to Embodiment 1 of the present invention. The image forming apparatus 100 is an image forming apparatus such as a full-color laser printer that employs an inline method or an intermediate transfer method using an electrophotographic image forming process. The image forming apparatus 100 can form a full-color image on the recording material 12 (for example, recording paper, plastic sheet, cloth, etc.) according to the image information.

  As shown in FIG. 1, the image forming apparatus 100 includes an image forming apparatus main body (hereinafter simply referred to as “apparatus main body”) 100A. Inside the apparatus main body 100A, an image forming unit SY that forms an image, SM, SC, and SK are provided. The image forming units SY, SM, SC, and SK include photosensitive drums 1Y, 1M, 1C, and 1K that are “image carriers”, and transfer rollers 8Y, 8M, 8C, and 8K that are “transfer devices”.

  The image forming apparatus 100 includes, as a plurality of image forming units, first, second, and third images for forming yellow (Y), magenta (M), cyan (C), and black (K) images, respectively. And fourth image forming units SY, SM, SC, and SK. In the present embodiment, the first to fourth image forming units SY, SM, SC, and SK are arranged in a line in a direction that intersects the vertical direction.

  In the present embodiment, the configurations and operations of the first to fourth image forming units SY, SM, SC, and SK are substantially the same except that the colors of images to be formed are different. Therefore, in the following, unless there is a particular distinction, the subscripts Y, M, C, and K given to the reference numerals to indicate that they are elements provided for any color are omitted, and generally explain.

  The image forming apparatus 100 includes four drum-type electrophotographic photosensitive members arranged in a direction intersecting the vertical direction, that is, the photosensitive drums 1, as a plurality of “image carriers” that carry electrostatic images. Have. The photosensitive drum 1 is rotationally driven by a driving means (driving source) (not shown) in the direction indicated by an arrow A (clockwise).

  Around the photosensitive drum 1, a charging roller 2 as a charging means for uniformly charging the surface of the photosensitive drum 1, a laser is irradiated based on image information, and an electrostatic image (electrostatic) is formed on the photosensitive drum 1. A scanner unit (exposure device) 3 is disposed as exposure means for forming (image). Around the photosensitive drum 1, a developing unit 4 as a “developing device” that develops an electrostatic image as a toner image, and a toner T (transferred) remaining on the surface of the photosensitive drum 1 after transfer. A cleaning member 6 is disposed as a cleaning means for removing (remaining toner). Further, an intermediate transfer belt 5 as an intermediate transfer body for transferring the toner image on the photosensitive drum 1 to the recording material 12 is disposed opposite to the four photosensitive drums 1.

  Here, the photosensitive drum 1 and the charging roller 2, the developing unit 4 and the cleaning member 6 as process means acting on the photosensitive drum 1 are integrally formed into a cartridge. Then, a cartridge 7 which is a “process cartridge” detachably attached to the apparatus main body 100A is formed.

  The intermediate transfer belt 5 formed of an endless belt as an intermediate transfer member abuts on all the photosensitive drums 1 and circulates (rotates) in the direction of arrow B (counterclockwise) in the figure. The intermediate transfer belt 5 is wound around a driving roller 61, a secondary transfer counter roller 62, and a driven roller 63 as a plurality of support members.

  On the inner peripheral surface side of the intermediate transfer belt 5, four primary transfer rollers 8 as primary transfer means are arranged in parallel so as to face the respective photosensitive drums 1, and the toner on the photosensitive drum 1 is arranged. The image is transferred (primary transfer) onto the intermediate transfer belt 5. A secondary transfer roller 9 as a secondary transfer unit is disposed at a position facing the secondary transfer counter roller 62 on the outer peripheral surface side of the intermediate transfer belt 5, and the toner image on the intermediate transfer belt 5 is transferred to the intermediate transfer belt 5. Transfer (secondary transfer) is performed on the recording material 12.

  The recording material 12 onto which the toner image has been transferred is conveyed to a fixing device 10 as a fixing unit. The toner image is fixed on the recording material 12 by applying heat and pressure to the recording material 12 in the fixing device 10. Further, the primary transfer residual toner remaining on the photosensitive drum 1 after the primary transfer process is removed and collected by the cleaning member 6. The secondary transfer residual toner remaining on the intermediate transfer belt 5 after the secondary transfer process is cleaned by the intermediate transfer belt cleaning device 11. The photosensitive drum 1 and the primary transfer roller 8 form a nip N1, and the secondary transfer counter roller 62 and the secondary transfer roller 9 form a nip N2.

  FIG. 2 is a cross-sectional view showing the configuration of the cartridge 7 and corresponds to a cross-sectional view seen from the direction along the longitudinal direction (rotational axis direction) of the photosensitive drum 1. Here, except for the type (color) of the developer stored therein, the configuration and operation of the cartridge 7 for each color are substantially the same. The cartridge 7 includes a photoconductor unit 13 including the photoconductor drum 1 and the like, and a developing unit 4 including a developing roller 17 and the like.

  The photoconductor unit 13 has a cleaning frame 14 as a frame that supports various elements in the photoconductor unit 13. The photosensitive drum 1 is rotatably attached to the cleaning frame 14 via a bearing (not shown). The photosensitive drum 1 is rotated in the direction indicated by the arrow A (clockwise) in accordance with the image forming operation by transmitting the driving force of a driving motor (not shown) as a driving means (driving source) to the photosensitive unit 13. Driven.

  In the photoconductor unit 13, a cleaning member 6 and a charging roller 2 are disposed so as to contact the circumferential surface of the photoconductor drum 1. The transfer residual toner removed from the surface of the photosensitive drum 1 by the cleaning member 6 falls into the cleaning frame 14 and is accommodated.

  The charging roller 2 as charging means is driven to rotate by bringing the roller portion of conductive rubber into pressure contact with the photosensitive drum 1. Here, a predetermined DC voltage is applied to the core of the charging roller 2 with respect to the photosensitive drum 1 as a charging step, whereby a uniform dark portion potential (Vd) is applied to the surface of the photosensitive drum 1. ) Is formed. The photosensitive drum 1 is exposed by the laser beam from the scanner unit 3 described above, and the surface of the exposed portion is lost by the carrier from the carrier generation layer, and the potential is lowered. As a result, an electrostatic image having a predetermined light portion potential (Vl) in the exposed portion and a predetermined dark portion potential (Vd) in the unexposed portion is formed on the photosensitive drum 1.

  On the other hand, the developing unit 4 includes a developing chamber 17, a developing blade 21, a supply roller 20, toner T, and a storage chamber 18 that stores toner T that contributes to development, in addition to the toner return member 50 that is a feature of the present embodiment. Have The developing roller 17 that is a “developer carrying member” is a roller that is rotatable while carrying the toner T that is a “developer”. A developing roller 17 is rotatably supported in the opening of the storage chamber 18.

  Inside the storage chamber 18, a stirring member 22, which is a “transport member” that transports the toner T from the storage chamber 18 to the storage portion Q, is disposed. In other words, the agitating member 22 agitates the toner T stored in the storage chamber 18 and also conveys the toner T toward the upper portion of the supply roller 20 in the direction of arrow G in the figure.

  The developing blade 21 is in contact with the developing roller 17 at a counter, and regulates the coating amount of the toner T supplied by the supply roller 20 and applies a charge. The developing blade 21 is made of a thin plate-like member, forms contact pressure using the spring elasticity of the thin plate, and the surface thereof is in contact with the toner T and the developing roller 17. The toner T is triboelectrically charged by sliding between the developing blade 21 and the developing roller 17 to be charged, and at the same time the layer thickness is regulated. In this embodiment, a predetermined voltage is applied to the developing blade 21 from a blade bias power source (not shown) to stabilize the toner coat.

  In the present embodiment, the toner T, which is negatively charged by frictional charging with respect to a predetermined DC bias applied to the developing roller 17, has a bright portion potential at the developing portion where the photosensitive drum 1 contacts the photosensitive drum 1. The electrostatic image is visualized by transferring only to the part.

  The supply roller 20 is contacted or intruded by the developing roller 17 on the peripheral surface of the developing roller 17 at a nip portion N that forms a predetermined nip. This roller is rotatable in a rotation direction E (counterclockwise) that is an “opposite direction” with respect to the surface of the developing roller 17 at the nip portion N, and includes toner T for supplying the toner T to the developing roller 17. . The supply roller 20 is an elastic sponge roller in which a foamed urethane layer 20b that is a foam is formed on the outer periphery of the conductive core metal 20a. The supply roller 20 and the developing roller 17 are in contact with each other with a predetermined penetration amount. The contact portions rotate so as to move in opposite directions (the supply roller 20 rotates in the direction of rotation E and the developing roller 17 rotates in the direction of arrow D).

  By this operation, the undeveloped toner T on the developing roller 17 that has not been used for visualization at the contact portion between the photosensitive drum 1 and the developing roller 17 is returned to the inside of the developing unit 4 by the rotation of the developing roller 17. Then, the development residual toner T on the developing roller 17 is peeled off from the developing roller 17 by the supply roller 20. At the same time, new toner T is supplied onto the developing roller 17 by the rotation of the supply roller 20 and is conveyed again to the contact portion between the developing blade 21 and the developing roller 17.

  Further, since both end portions in the axial direction of the supply roller 20 are non-image forming regions, the amount of the development residual toner T is always large. Therefore, the supply roller 20 repeatedly peels and supplies, and is easily affected by a frictional load or thermal stress continuously. If the toner deterioration is promoted by these influences, the toner T may be fused to the developing roller 17 or the developing blade 21 to cause an image defect. Therefore, when the life of the developing device is long, it is necessary to reduce the toner deterioration at the end portion.

  A storage portion Q that stores the toner T is disposed above the supply roller 20. A storage chamber 18 for storing the toner T is disposed below the storage portion Q. The storage portion Q is a space surrounded by the developing roller 17, the supply roller 20, and the toner return member 50 (see FIG. 1) (in Examples 2 and 3, the toner return members 70 and 80 and FIGS. 6 and 7). Formed with.

Here, the details of the supply roller 20 used in the first to third embodiments will be described below. The supply roller 20 in the present embodiment includes a conductive support and a foam layer supported by the conductive support. Specifically, a foam composed of a conductive metal core 20a, which is a core metal electrode having an outer diameter of φ5 (mm), which is a conductive support, and an open cell body (open cells) in which bubbles are connected to each other. A urethane foam layer 20b as a layer is provided and rotates in the rotation direction E. Further, the longitudinal width of the supply roller 20 used in this embodiment is 220 mm. By making the urethane of the surface layer into an open cell body, a large amount of toner T can enter the supply roller 20. Further, the resistance of the supply roller 20 in this embodiment is 1 × 10 ⁹ (Ω). Next, a method for measuring the surface full-time amount of the supply roller 20 according to the first to third embodiments will be described with reference to FIG.

  FIG. 3A is an explanatory diagram showing a method of measuring “surface ventilation”. FIG. 3B is a perspective view showing the configuration of the measurement jig 41. FIG. 3C is a perspective view showing the configuration of the ventilation holder 42. Hereinafter, a method for measuring the resistance of the supply roller 20 will be described with reference to FIGS. 3 (a) to 3 (c). The supply roller 20 is brought into contact with an aluminum sleeve having a diameter of 30 mm so that an intrusion amount described later becomes 1.5 mm. By rotating the aluminum sleeve, the supply roller 20 is driven to rotate with respect to the aluminum sleeve at 30 rpm.

  Next, a DC voltage of −50 V is applied to the developing roller 17. At that time, a resistance of 10 kΩ is provided on the ground side, the current is calculated by measuring the voltage at both ends, and the resistance of the supply roller 20 is calculated. Here, the surface cell diameter of the supply roller 20 is 50 μm to 1000 μm, and the porosity is 0.6.

  Here, the cell diameter means the average diameter of the foamed cells having an arbitrary cross section. First, the area of the foamed cell that is the maximum is measured from the enlarged image of the arbitrary cross section, and the maximum cell diameter is converted from this area by converting the equivalent circle diameter. Get. And after deleting the foam cell which is 1/2 or less of this maximum cell diameter as noise, it points out the average value of each cell diameter converted similarly from the remaining individual cell area. The porosity means the ratio of foam cells in an arbitrary cross section. First, the area of each foam cell is measured from an enlarged image of the arbitrary cross section, and the total area of the foam cells is obtained. And the ratio for which the total area of this foaming cell occupied in arbitrary cross sections was calculated | required, and the value was made into the porosity.

  The supply air flow rate of the supply roller 20 was 1.8 (liters / minute). Here, the “surface ventilation amount” of the supply roller 20 will be described in detail.

  The “aeration amount” is defined so that the toner T in and out of the supply roller 20 is smoothly sucked and discharged, and the inside of the supply roller 20 and the outside of the supply roller 20 are in an equilibrium state. Since the discharge and suction of the toner T mixed with air and turned into a powder fluid is performed through the “surface layer surface” of the supply roller 20, it is important to directly define the “aeration amount passing through the surface layer surface”. is there.

  First, the supply roller 20 is inserted into a measurement jig 41 as shown in FIG. The measurement jig 41 has a φ10 (mm) through-hole 41a passed through the side surface of a hollow cylindrical body, and is made so that the central axis of the through-hole 41a and the cylindrical axis of the cylindrical hole 41b are orthogonal to each other.

  Since the supply roller 20 has an outer diameter of φ20 (mm), the inner diameter of the measuring jig 41 is φ19 (mm). The measuring jig 41 into which the supply roller 20 is inserted is attached to a ventilation holder 42 as shown in FIG.

  The inner diameter of the connection pipe 42 b is set to be larger than the through hole 41 a of the measurement jig 41. In this embodiment, the inner diameter of the connecting pipe 42b is φ12 (mm). The inner diameter of the hollow cylindrical body 42a of the ventilation holder 42 is substantially the same as the outer diameter of the measuring jig 41, so that the measuring jig 41 can be inserted into the hollow cylindrical body 42a. As shown in FIG. 3 (a), one of the through holes 41a of the measuring jig 41 is fully exposed in the cutout portion 42c of the hollow cylindrical body 42a, and the other of the through holes 41a is substantially opposed to the inner diameter of the connecting pipe 42b. Install in.

  As shown in FIG. 3A, acrylic pipes 45a and 45b having one end connected to the hollow cylindrical body 42a are installed on the left and right sides of the hollow cylindrical body 42a of the ventilation holder 42. In the middle of the vent pipe 44, a flow meter 46 (KZ type vent flow measuring device: Daiei Chemical Seiki Seisakusho) and a differential pressure adjusting valve 47 are installed.

  The “surface aeration” is measured as follows. First, in FIG. 3A, the decompression pump 43 is operated without the supply roller 20 installed, and the measured value of the flowmeter 46 is stabilized at 10.8 (liters / minute) by the differential pressure adjusting valve 47. Adjust so that Thereafter, the supply roller 20 to be measured is installed, and the measured value of the flow meter 46 is measured as “surface ventilation” under the same exhaust conditions as described above.

  The air flow passing through the supply roller 20 flows in from the surface of the urethane foam layer 20b located in the exposed through hole 41a of the measurement jig 41, passes through the inside of the urethane foam layer 20b, and passes through the other side of the measurement jig 41. Flows out from the surface of the urethane foam layer 20b located in the through hole 41a.

  It may be influenced by the above-mentioned surface condition, and the behavior cannot be captured only by measuring the bulk air flow rate as in JIS-L1096. Therefore, in the present invention, the above-described air flow measurement method for measuring the air flow flowing in / out from the surface of the urethane foam layer 20b is adopted, and the above-described equilibrium state (or a state close thereto) of the toner powder fluid is used. Was the main parameter for the appearance.

  By using the supply roller 20 having a large surface ventilation amount as described above, the toner T can be smoothly exchanged into and out of the supply roller 20, so that the specific toner T does not stay in the supply roller 20, and the toner Deterioration of T is suppressed.

  FIG. 4 is a cross-sectional view illustrating the configuration of the developing roller 17 and the supply roller 20. The toner return member 50 will be described below with reference to FIG. FIG. 4 shows a configuration in the vicinity of the suction portion M of the supply roller 20, and the toner T is conveyed to the supply roller 20 by the stirring member 22, and the subsequent movement of the toner T is shown. It is efficient that the toner T is transported by the stirring member 22 toward the suction portion M of the supply roller 20. Therefore, in the present invention, by installing the toner return member 50, the toner T is efficiently taken into the supply roller 20, and the amount of toner transported to the developing roller 17 by the supply roller 20 is increased.

  A part of the toner T conveyed to the vicinity of the suction part M by the agitating member 22 along the path of the arrow G in the figure is taken into the suction part M, and most of the toner T is conveyed in the direction of the arrow F1 in the figure. The operation of the toner return member 50 rebounds the toner T that is not taken into the supply roller 20 in the vicinity of the suction portion M but flows in the direction of the arrow F1 in the figure, and brings the toner T in the vicinity of the suction portion M again. Toner circulation F (circulation combining F1, F2, and F3) is created. With this action, the toner T can be efficiently taken into the supply roller 20. Note that the amount of depression of the supply roller 20 that is recessed by the developing roller 17 is ΔE in the drawing. The toner return member 50 is attached to the storage chamber 18 (the same applies to toner return members 70 and 80 described later).

  FIG. 5 is a diagram illustrating the configuration of the toner return member 50 and the supply roller 20. FIG. 5A is a plan view of the configuration of the toner return member 50, the developing roller 17, and the supply roller 20 as viewed from above. FIG. 5B is a side view of the configuration of the toner return member 50 and the supply roller 20 viewed from the horizontal direction. 5C to 5E are cross-sectional views showing the configurations of the toner return member 50 and the supply roller 20. In particular, FIG. 5C is a cross-sectional view taken along the line AA in FIG. FIG.5 (d) is sectional drawing which follows the BB line in FIG.5 (b) seen from the arrow K direction. FIG.5 (e) is sectional drawing which follows the CC line | wire in FIG.5 (b) seen from the arrow K direction.

  The supply roller 20 is in contact with the developing roller 17 by forming a nip portion N, and rotates in a rotation direction E that is opposite to the surface of the developing roller 17 at the nip portion N (see FIG. 4). The toner return member 50 that is a “developer return member” is disposed in a downstream region in the rotation direction E of the supply roller 20 with respect to the nip portion N, and is close to the supply roller 20 (see FIG. 4).

  As shown in FIGS. 5B to 5E, the toner return member 50 is a proximity portion that is a “first edge” that faces, contacts, or enters the supply roller 20 in the vicinity on the side close to the supply roller 20. 59 (proximity part). Further, the toner return member 50 is formed on the side far from the supply roller 20 and is a “second edge” that is different in position in the longitudinal direction Z from the proximity portion 59, and is an upper edge portion 51a and an upper edge portion 58a (a separated portion). Have Here, the proximity portion 59 is a portion facing in the vicinity of the supply roller 20. The upper edge portion 51a is an upper edge portion of the both end portions 51 that are separated from the proximity portion 59 by the dimension H1. The upper edge portion 58a is an upper edge portion of the central portion 58 that is separated from the proximity portion 59 by the dimension H2. Moreover, it forms with the plate-shaped member along a perpendicular direction ranging from the proximity part 59 (both ends 51 and the center part 58).

  As described above, the both end portions 51 and 58 are partitioned on the upper edge portion 51a which is the “upper edge portion on both ends” of the both end portions 51 which are partitioned on both end sides in the longitudinal direction Z, and on the center side in the longitudinal direction Z. It has an upper edge 58 a that is a “center upper edge” of the center 58. The upper edge portion 51a is set at a position closer to the proximity portion 59 than the upper edge portion 58a. Specifically, in the central portion (BB cross section) of the supply roller 20, the upper edge portion 58a of the central portion 58 of the toner return member 50 is high (extends longer in the direction of gravity) (height H2). On the other hand, at both end portions (AA cross section and CC cross section) of the supply roller 20, the upper edge portions 51a of both end portions 51 of the toner returning member 50 are low (extends shortly upward in the gravity direction) ( Height H1).

  For this reason, as described above, the toner return member 50 has a shape having different heights in the direction orthogonal to the axis of the supply roller 20 such as the upper edge 51a and the upper edge 58a at each portion in the longitudinal direction Z. Will have.

  As shown in FIG. 5A, the toner T is moving in the storage portion Q between the developing roller 17 and the supply roller 20. FIG. 5A corresponds to a view of the movement of the toner T stored in the storage unit Q as viewed from the upper side in the gravity direction. The toner T is transported from the storage chamber 18 to the storage portion Q by the stirring member 22, proceeds in the direction of arrow F <b> 4 inside the storage portion Q and then transported in the direction of arrow F <b> 5, and passes through the upper edge portions 51 a of both end portions 51. Get over and return to storage room 18.

  As shown in FIG. 5D, the toner T advances in the direction of arrow F <b> 4 along with the rotation of the supply roller 20 and is rebounded by the central portion 58 inside the storage portion Q. Since the height H2 of the central portion 58 is larger than the height H1 of the both end portions 51, the toner T is rebounded.

  As shown in FIGS. 5C and 5E, the toner T advances in the direction of the arrow F5 along with the rotation of the supply roller 20 inside the storage portion Q and gets over the upper edge portions 51a of both end portions 51. . Since the upper edge portion 51 a of the both end portions 51 is smaller than the upper edge portion 58 a of the central portion 58, the toner T gets over and is conveyed to the storage chamber 18.

  By these actions, the toner T inside the storage portion Q flows from the central portion of the supply roller 20 toward both ends and flows into the storage chamber 18 without staying at both ends. As a result, the amount of toner T inside the storage portion Q staying at both ends of the supply roller 20 is reduced while continuously circulating in the longitudinal direction Z inside the storage portion Q, and continuously rubbed. The phenomenon of receiving load and heat stress is suppressed. Thus, the deterioration of the toner T at both ends of the supply roller 20 is suppressed, and the toner T is hardly fused even if the development life is long.

  Here, both the developing roller 17 and the supply roller 20 have an outer diameter φ20. The toner returning member 50 is disposed in the vicinity of the supply roller 20 in a non-contact manner. This is because if the toner return member 50 is too far from the supply roller 20, the toner flowing in the direction of the arrow F4 cannot be sufficiently blocked, and the amount of rebound is reduced. The distance between the toner return member 50 and the supply roller 20 is preferably 2 mm or less, and more preferably 1 mm or less. In this example, it was set to 1.0 mm.

  Further, the height of the central portions 58 and 51 of the toner return member 50 is preferably higher than the suction portion M. That is, in this embodiment, the central portion 58 of the longitudinal center is set to 5.0 mm in height X with respect to the height of the suction portion M, and both end portions 51 in the region 5.0 mm from both longitudinal ends are the suction portions. The height X was set to 1.0 mm with respect to the height of M. The toner return member 50 is made of the same material as the developing container (housing chamber 18) and has a thickness of 1.0 mm.

  As long as it is a means for making a gradient in the toner agent surface height in the storage portion Q such that the height of the second edge portion remote from the supply roller 20 in the toner return member 50 is lowered in a part of the longitudinal direction Z, The configuration of the embodiment is not necessarily limited. For example, as shown in FIGS. 8C to 8E, the upper edge portion 58a, which is the “second edge portion”, is formed on the side far from the proximity portion 59, and is defined as “both ends in the longitudinal direction”. It is assumed that the upper edge portions of the both end portions 51 and the central portion 58 "defined on the central side in the longitudinal direction. In this case, a hole 71 is formed in a part of both ends 51 (see FIG. 8C), or an upper portion 151 (or a part on both ends) of both ends 51 is in the rotation direction E of the supply roller 20. It may be configured to be bent toward the downstream side (to the storage chamber 18 side) (see FIGS. 8D and 8E). These configurations are also means for creating a gradient in the toner agent surface height in the storage portion Q. Even with such a configuration, it is possible to obtain the effect of returning the toner to the storage chamber 18 and moving the toner T in the longitudinal direction Z in the storage portion Q to form circulation in the longitudinal direction Z.

  In addition, FIG.8 (c) is a side view which shows the modification of Example 1 corresponding to FIG.5 (b). FIG.8 (d) is sectional drawing which shows the modification of Example 1 corresponding to FIG.5 (d). FIG.8 (e) is sectional drawing which shows the modification of Example 1 corresponding to FIG.5 (e). According to the configuration of the first embodiment described above, by arranging the toner return member 50 in a suitable shape, the toner T can be efficiently supplied to the supply roller 20, and the solid density stability can be improved. A toner fused image due to toner deterioration can be prevented, and a high-quality image can be supplied.

  FIG. 6 is a cross-sectional view illustrating the configuration of the toner return member 70 and the supply roller 20 included in the developing unit according to the second embodiment. FIG. 6A is a plan view of the configuration of the toner return member 70, the developing roller 17, and the supply roller 20 as viewed from above. FIG. 6B is a side view of the configuration of the toner return member 70 and the supply roller 20 as viewed from the horizontal direction. 6C to 6E are cross-sectional views showing the configurations of the toner return member 70 and the supply roller 20. In particular, FIG. 6C is a cross-sectional view taken along the line AA in FIG. FIG. 6D is a cross-sectional view taken along the line BB in FIG. FIG. 6E is a cross-sectional view taken along the line CC in FIG.

  Of the configuration of the developing unit of the second embodiment, the same configurations and effects as those of the developing unit 4 of the first embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate. Since the second embodiment can be applied to the same image forming apparatus as that of the first embodiment, the description of the image forming apparatus is omitted. In the developing unit according to the second embodiment, the upper edge portions 52a and 158a include an upper edge portion 52a that is an “upper edge portion on both ends” of the both end portions 52 that are partitioned on both ends in the longitudinal direction Z, and a center in the longitudinal direction Z. An upper edge portion 158a which is a “center upper edge portion” of the center portion 158 divided on the side is provided. The end portions 52 are characteristically bent toward the nip portion N between the supply roller 20 and the developing roller 17 and toward the center in the longitudinal direction Z rather than the center portion 158. Such a toner return member 70 is disposed close to the supply roller 20. Details will be described below.

  As a premise of the second embodiment, the internal configuration of the apparatus main body 100A other than the toner return member 70 and the image forming conditions are the same as those of the first embodiment. The toner return member 70 includes a proximity portion 59 (proximity portion) that is close to the supply roller 20, and both end portions 52 and a central portion 158 (space portion) that are separated from the supply roller 20. The proximity portion 59 is a portion facing the supply roller 20. The central portion 158 is a plate-like portion along the vertical direction (the trapezoidal portion in FIG. 6B). Both end portions 52 are bent toward the nip portion N between the supply roller 20 and the developing roller 17 and toward the center in the longitudinal direction Z (non-proximal bent portions) (triangles in FIG. 6B). Shaped part). For this reason, the toner return member 70 which is a “developer return member” has an upper edge portion 52a which is a “second edge portion” on the side far from the supply roller 20 at a position different from the proximity portion 59 in the longitudinal direction Z. 158a.

  According to such a configuration, when the supply roller 20 rotates, the toner T at both ends of the supply roller 20 in the storage portion Q can be conveyed toward the center in the longitudinal direction Z. Therefore, the toner T circulates over a wide range in the longitudinal direction Z of the storage portion Q. In particular, when the stirring member 22 is formed in a sheet shape, the way in which the stirring member 22 bends in the longitudinal direction Z may differ, and uneven supply of the toner T to the storage portion Q is likely to occur. Even in such a case, the toner T circulates inside the storage part Q, so that the supply roller 20 can suck the toner T with little unevenness of stirring in the suction part M.

  As shown in FIGS. 6B to 6E, in the central portion (BB cross section) of the supply roller 20, the central portion 158 (non-proximity portion) (non-proximity portion) of the toner return member 70 is It extends linearly. On the other hand, at both end portions (AA cross section and CC cross section) of the supply roller 20, both end portions 52 (non-proximity portions) (non-proximity portions) of the toner return member 70 are between the supply roller 20 and the developing roller 17. The angle bent toward the nip portion N is set to an angle R1. This part can also be expressed as a non-proximal bent part.

  Here, for example, at the position of 5.0 mm from both ends of the supply roller 20 (AA cross section and CC cross section), both end portions 52 of the toner return member 70 are nip portions N between the supply roller 20 and the developing roller 17. It is bent so that the angle R1 = 30 degrees.

  As shown in FIG. 6A, the toner T moves in the storage portion Q between the developing roller 17 and the supply roller 20. FIG. 6A corresponds to a view of the movement of the toner T stored in the storage unit Q as viewed from the upper side in the gravity direction. The toner T is transported to the central side in the longitudinal direction Z of the supply roller 20 in the storage portion Q, and rebounds from the central portion 158 to move from the arrow F6 direction to the arrow F7 direction (that is, from the longitudinal center of the supply roller 20 to both longitudinal ends). The direction toward the club).

  As described above, at both end portions of the supply roller 20 in the storage portion Q, the both end portions 52 of the toner return member 70 are in the direction of the nip portion N between the supply roller 20 and the developing roller 17 and the central direction in the longitudinal direction Z. It is bent to the back. Therefore, the toner T is bounced back by the both end portions 52 toward the center of the longitudinal direction Z in the direction of the nip portion N as indicated by the arrow F7. Thereafter, it merges with the toner T conveyed from the suction portion M, and reaches the toner return member 70 again as indicated by the arrow F6.

  In this way, by circulating the toner in the longitudinal direction Z inside the storage portion Q, the toner T circulates even when the toner supply unevenness of the stirring member 22 occurs, so that the supply roller 20 supplies the uniform toner T. It becomes possible to inhale.

  In addition, even when a large number of image patterns having different printing ratios are output in the longitudinal direction Z as in the first embodiment, since the toner T circulates inside the storage portion Q, local deterioration is reduced and toner deterioration is reduced. This makes it possible to prevent toner fusion and the like. As described above, according to the configuration of the second embodiment, the toner T can be efficiently supplied to the supply roller 20, the solid density stability can be improved, and a high-quality image can be supplied.

  FIG. 7 is a cross-sectional view illustrating the configuration of the toner return member 80 and the supply roller 20 included in the developing unit according to the third embodiment. FIG. 7A is a plan view of the configuration of the toner return member 80, the developing roller 17, and the supply roller 20 as viewed from above. FIG. 7B is a side view of the configuration of the toner return member 80 and the supply roller 20 as viewed from the horizontal direction. 7C to 7E are cross-sectional views showing configurations of the toner return member 80 and the supply roller 20. In particular, FIG. 7C is a cross-sectional view taken along the line AA in FIG. FIG.7 (d) is sectional drawing which follows the BB line in FIG.7 (b) seen from the arrow K direction. FIG.7 (e) is sectional drawing which follows the CC line | wire in FIG.7 (b) seen from the arrow K direction.

  Of the configuration of the developing unit of the third embodiment, the same configurations and effects as those of the developing unit 4 of the first embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate. Since the third embodiment can be applied to the same image forming apparatus as that of the first embodiment, the description of the image forming apparatus is omitted. The developing unit of the third embodiment is characterized in that not only both end portions 54 but also the central portion 53 are bent toward the nip portion N of the supply roller 20 and the developing roller 17. Such a toner return member 80 is disposed so as to enter the supply roller 20. Details will be described below.

  As a premise of the third embodiment, the internal configuration of the apparatus main body 100A other than the toner return member 80 and the image forming conditions are the same as those in the first embodiment. The toner return member 80 includes an intrusion portion 159 (intrusion portion) that enters the supply roller 20, a non-intrusion portion 258 (non-intrusion portion) that is not the supply roller 20, a central portion 53 (separation portion), and both end portions 54. (Separating portion).

  Here, as shown in FIG. 7C to FIG. 7E, the non-intruding portion 258 is arranged to have a surface along the vertical direction. As shown in FIG. 7D, the central portion 53 is formed continuously with the upper end of the non-intruding portion 258, and is bent so as to have a surface inclined by an angle R1 with respect to the vertical direction. As shown in FIGS. 7C and 7E, both end portions 54 are continuously formed on both end sides of the upper end of the central portion 53, and have surfaces that are inclined by an angle R2 with respect to the vertical direction. It is bent like this. With such a configuration, the shape of the toner return member 80 is different in a wide area in the longitudinal direction Z of the supply roller 20 (particularly, the shape of the upper edge portion 53a of the central portion 53 and the upper edge portion 54a of the both end portions 54). It has become. The amount of penetration of the toner return member 80 into the supply roller 20 was 1.5 mm.

  As shown in FIGS. 7B to 7E, in the central portion (BB cross section) of the supply roller 20, the central portion 53 of the toner return member 80 is a nip portion between the supply roller 20 and the developing roller 17. It is bent once in the direction of N (non-intrusion bent portion, angle R1). At both end portions of the supply roller 20 (AA cross section and CC cross section), both end portions 54 of the toner returning member 80 are in the direction of the nip portion N between the supply roller 20 and the developing roller 17 and in the longitudinal direction Z. It is bent one more time toward the center of. Both end portions 54 can also be expressed as non-intrusion bent portions, and are set at an angle R2.

  In summary, the toner return member 80 that is a “developer return member” has an intrusion portion 159 that is a “first edge” that faces, contacts, or intrudes in the vicinity of the supply roller 20 on the side close to the supply roller 20. Further, the toner return member 80 has an upper edge portion 53a and an upper edge portion 54a which are “second edge portions” which are different in the longitudinal direction Z from the proximity portion 59 and are far from the supply roller 20.

  Here, for example, at the central portion (BB cross section) of the supply roller 20, the central portion 53 is bent in the direction of the nip portion N between the supply roller 20 and the developing roller 17 so that the angle R1 = 30 degrees. . Further, at a position of 5.0 mm from both end portions of the supply roller 20 (AA cross section and CC cross section), the both end portions 54 have an angle R2 = 60 degrees in the direction of the nip portion N between the supply roller 20 and the developing roller 17. It is bent one more time so that

  As shown in FIG. 7A, the toner T moves in the storage portion Q between the developing roller 17 and the supply roller 20. FIG. 7A corresponds to a view of the movement of the toner T stored in the storage unit Q as viewed from the upper side in the gravity direction. The toner T is transported toward the central side in the longitudinal direction Z of the supply roller 20 in the storage portion Q, rebounds from the non-intrusion portion 258 and the central portion 53, and from the arrow F8 direction to the arrow F9 direction (that is, the supply roller 20 It spreads in the direction from the longitudinal center to both longitudinal ends.

  As described above, at both end portions of the supply roller 20 in the storage portion Q, the both end portions 54 of the toner return member 80 are in the direction of the nip portion N between the supply roller 20 and the developing roller 17 and in the center in the longitudinal direction Z. It is bent toward Therefore, the toner T is bounced back by the both end portions 54 in the direction of the nip portion N and in the central direction of the longitudinal direction Z as indicated by the arrow F9. Thereafter, it merges with the toner T conveyed from the suction portion M, and reaches the toner return member 80 again as indicated by the arrow F8.

  In this way, by circulating the toner in the longitudinal direction Z inside the storage portion Q, the toner T circulates even when the toner supply unevenness of the agitating member 22 occurs, so the supply roller 20 sucks the uniform toner. It becomes possible.

  Further, even when a large number of image patterns having different printing ratios are output in the longitudinal direction Z as in the first or second embodiment, the toner T circulates inside the storage portion Q, so that local deterioration is reduced and toner deterioration is reduced. This makes it possible to prevent toner fusion and the like.

  Further, the entire length of the central portion 53 of the toner return member 80 is bent in the direction of the nip portion N between the supply roller 20 and the developing roller 17 (non-intrusion bent portion, angle R1), so that the toner return member 80 is conveyed from the stirring member 22. The transported toner T can be easily transported.

  FIG. 8 is a cross-sectional view illustrating a trajectory in which the toner T transported by the stirring member 22 is transported. FIG. 8A is a cross-sectional view showing a configuration in which the toner return member 90 is bent. FIG. 8B is a cross-sectional view showing a configuration in which the toner return member 90 is not bent. As shown in FIG. 8B, in the case where the proximity portion 59 (non-intrusion portion) and the central portion 58 of the toner return member 90 are linearly extended integrally, the toner locus G1 has the storage portion Q. Therefore, the toner T cannot be transported, and a higher toner locus G2 that requires a greater transport capability is required. If it is not the toner locus G2, the toner T cannot exceed the toner return member 91.

  On the other hand, as shown in FIG. 8A, the proximity portion 59 (non-intrusion portion) and the central portion 58 of the toner return member 90 are bent toward the nip portion N between the supply roller 20 and the developing roller 17. In the case of the configuration, the toner T can be conveyed to the storage portion Q even with the toner locus G1. By the way, here, the angle R1 with respect to the vertical direction of the central portion 53 is set. For this reason, the pumping ability of the toner T by the stirring member 22 is minimized.

  Further, the entire length of the central portion 53 of the toner return member is bent in the direction of the nip portion N between the supply roller 20 and the developing roller 17 (non-intrusion bent portion, angle R1), and thus stored in the storage portion Q. The toner is difficult to return to the storage chamber 18. In other words, even when the rotation speed of the supply roller 20 increases when the process speed is changed, or when the cartridge is tilted when the cartridge is inserted or removed when the printer is jammed, the following occurs. That is, the toner T stored in the storage unit Q is unlikely to return to the storage chamber 18, and the toner T conveyed by the stirring member 22 can be efficiently held in the storage unit Q and supplied to the supply roller 20.

  As a result, the necessary amount of toner can be supplied to the developing roller 17 and the unnecessary amount can be temporarily stored in the storage portion Q, so that the pumping up of the toner by the stirring member 22 can be minimized.

  As described above, according to the configuration of the third embodiment, the toner T can be efficiently supplied to the supply roller 20, the solid density stability can be improved, and a high-quality image can be supplied.

  The toner return members 50 and 70 of the first and second embodiments are configured to face the supply roller 20 in the vicinity, and the toner return member 80 of the third embodiment is configured to enter the supply roller 20. However, the present invention is not limited to this configuration. In other words, the toner return members 50, 70, and 80 may be configured to face each other, contact, or enter in the vicinity of the supply roller 20.

  The examples 1 to 3 have been described above. In the first to third embodiments described above, an image forming apparatus capable of forming a color image is illustrated, but the present invention is not limited to this. An image forming apparatus capable of forming a monochrome image may be used, and the same effect can be obtained by applying the present invention to the developing device in the image forming apparatus.

  In the first to third embodiments, the printer is exemplified as the image forming apparatus. However, the present invention is not limited to this. That is, for example, another image forming apparatus such as a copying machine or a facsimile machine, another image forming apparatus such as a combined machine combining these functions, or a recording agent carrier is used and is carried on the recording agent carrier. Further, the image forming apparatus may sequentially transfer the toner images of the respective colors onto the recording material. In this case, the same effect can be obtained by applying the present invention to the developing device in the image forming apparatus.

DESCRIPTION OF SYMBOLS 4 ... Developing unit (developing device), 17 ... Developing roller (developer carrier), 20 ... Supply roller, 18 ... Storage chamber, 22 ... Stirring member (conveying member)
51 ... Both ends, 51a ... Upper edge (second end), 58 ... Center, 58a ... Upper edge (second end)
52 ... Both ends, 52a ... Upper edge (second end), 158 ... Center, 158a ... Upper edge (second end)
54 ... Both ends, 54a ... Upper edge (second end), 53 ... Center, 53a ... Upper edge (second end)
59 ... Proximity part (first end part), 159 ... Intrusion part (first end part)
E: rotational direction (opposite direction), N: nip, T: toner, Q: reservoir, Z: longitudinal direction

Claims (7)

A developer carrying member that is rotatable while carrying the developer;
A developer that contacts or intrudes into the developer carrying member at a nip portion and is rotatable in the opposite direction with respect to the surface of the developer carrying member at the nip portion to supply the developer to the developer carrying member. A supply roller containing
A storage unit disposed above the supply roller for storing the developer;
A storage chamber that is disposed below the reservoir and stores the developer;
A transport member disposed inside the storage chamber and transporting the developer from the storage chamber to the reservoir;
In the downstream region in the rotation direction of the supply roller with respect to the nip portion, a first edge that opposes, contacts, or enters the supply roller in the vicinity of the supply roller on the side close to the supply roller, and a side far from the supply roller is formed. And a developer return member having a second edge that is different in position from the first edge in the longitudinal direction;
A developing device comprising: The second edge portion includes upper edge portions at both ends of the both end portions defined on both ends in the longitudinal direction of the developer returning member, and a center portion defined on the center side in the longitudinal direction of the developer returning member. Having a central upper edge,
The developing device according to claim 1, wherein the upper edge portions of both ends are set closer to the first edge portion than the central upper edge portion. The second edge portion includes upper edge portions at both ends of the both end portions defined on both ends in the longitudinal direction of the developer returning member, and a center portion defined on the center side in the longitudinal direction of the developer returning member. Having a central upper edge,
The both end portions are bent toward the nip portion of the supply roller and the developer carrier and toward the center in the longitudinal direction from the center portion. Development device.   The developing device according to claim 3, wherein the central portion is bent toward a nip portion of the supply roller and the developer carrying member. A developer carrying member that is rotatable while carrying the developer;
A developer that contacts or intrudes into the developer carrying member at a nip portion and is rotatable in the opposite direction with respect to the surface of the developer carrying member at the nip portion to supply the developer to the developer carrying member. A supply roller containing
A storage unit disposed above the supply roller for storing the developer;
A storage chamber that is disposed below the reservoir and stores the developer;
A transport member disposed inside the storage chamber and transporting the developer from the storage chamber to the reservoir;
In the downstream region in the rotation direction of the supply roller with respect to the nip portion, a first edge that opposes, contacts or enters the supply roller in the vicinity of the supply roller on the side close to the supply roller, and a side far from the supply roller is formed. A developer return member having a second edge;
With
The second edge part is an upper edge part of a center part partitioned at both ends of the developer return member in the longitudinal direction and a center part of the developer return member in the longitudinal direction. ,
The developing device according to claim 1, wherein a hole is formed in a part of the both end portions, or an upper portion of the both end portions is bent toward a downstream side in a rotation direction of the supply roller. A developing device according to any one of claims 1 to 5,
A process cartridge that is detachable from the main body of the image forming apparatus. An image carrier for carrying an electrostatic image;
A developing device according to any one of claims 1 to 5,
An image forming apparatus comprising:

Images