JP2013257364A - Developing device, process cartridge, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that securely supplies developer to a supply roller, improves stability of solid density, and supplies a high-quality image.SOLUTION: A developing unit 4 comprises: a developing roller 17; a supply roller 20 that comes into contact with or enters the developing roller at a nip part N, and rotates in a direction E opposite to the surface of the developing roller 17 at the nip part N; a storage part Q arranged above the supply roller 20 to store toner T; a housing chamber 18 arranged below the storage part Q to house the toner T; an agitation member 22 arranged in the housing chamber 18 to convey the toner T from the housing chamber 18 to the storage part Q; and a toner return member 50 that faces, comes into contact with, or enters the supply roller 20 in the vicinity in different phase positions in a cross section thereof in a longitudinal direction Z, and comes close to the supply roller 20 in a downstream region in the rotation direction E of the supply roller 20 with respect to the nip part N.

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 inline 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.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a developing device capable of improving solid density stability and supplying a high-quality image while ensuring supply of a developer to a supply roller. 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 developer returning member that contacts or enters the supply roller across a different phase position in the cross section of the supply roller in the longitudinal direction in a downstream region in the rotation direction of the supply roller with respect to the nip portion. And

  According to the present invention, it is possible to improve the stability of the solid density and supply a high-quality image while securing the supply of the developer to the supply roller.

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 sectional drawing which shows the structure of a developing roller and a supply roller. It is sectional drawing etc. which show the structure of a supply roller and a toner return member. 6 is a cross-sectional view illustrating a configuration of a supply roller and a toner return member included in an image forming apparatus according to Embodiment 2. FIG. 6 is a cross-sectional view illustrating a configuration of a supply roller and a toner return member provided in an image forming apparatus according to Embodiment 3. FIG. It is explanatory drawing etc. which show the measuring method of surface ventilation.

  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.

  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”.

  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 by utilizing the spring elasticity of the thin plate, and the surface thereof is in contact contact with the toner T and the development 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 arrow 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 formed in a space surrounded by the developing roller 17, the supply roller 20, and the toner return member 50 (see FIG. 1).

  FIG. 3 is a cross-sectional view illustrating the configuration of the developing roller 17 and the supply roller 20. The toner returning member 50 will be described below with reference to FIG. FIG. 3 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 drawing is taken into the suction part M, and most of the toner T is conveyed in the direction of the arrow F1 in the drawing. The operation of the toner return member 50 is to rebound 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 drawing, and again has the toner T in the vicinity of the suction portion M. It is to create a continuous toner circulation F (a combined circulation of F1, F2, and F3). 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 51 and 52 described later).

  FIG. 4 is a cross-sectional view showing the configuration of the supply roller 20 and the toner return member 51. FIG. 4A is a cross-sectional view taken along the line AA as viewed from the direction of the arrow K in FIG. 4C, and FIG. 4B is a view taken along the line BB as viewed from the direction of the arrow K in FIG. It is sectional drawing which follows a line. FIG. 4C is a plan view seen from the direction of arrow J in FIGS. 4A and 4B. In FIG. 4A and FIG. 4B, the developing roller 17 is omitted. The toner return member 50, which is a “developer return member”, is supplied to the supply roller 20 in the downstream direction in the rotation direction E of the supply roller 20 with respect to the nip portion N in the longitudinal direction Z across different phase positions in the cross section of the supply roller 20. Opposite, contact or invade in the vicinity. That is, in the case of FIG. 4A and the case of FIG. 4B, the circumferential displacement (L × θ1) of the tip of the toner return member 50 relative to the surface of the supply roller 20 is the axis of the supply roller 20. Are different from each other.

  The toner returning member 50 has a central portion 50a located on the center side in the longitudinal direction Z, and both end portions 50b located on the end side in the longitudinal direction Z. The upstream edge 50c on the upstream side in the rotation direction E of the supply roller 20 included in the both end portions 50b is disposed upstream in the rotation direction E of the supply roller 20 (see FIG. 4A), and the central portion 50a is the supply roller. It arrange | positions downstream in the rotation direction E of 20 (refer FIG.4 (b)). Both end portions 50b and the central portion 50a are formed continuously.

  Both end portions 50b have plate surfaces that go downstream in the rotation direction E of the supply roller 20 as they go from the end portion to the center in the longitudinal direction Z. The central portion 50a has a plate surface along the longitudinal direction Z. The above-described plate surfaces of the both end portions 50b and the above-described plate surface of the central portion 50a face the upstream side in the rotation direction of the supply roller 20. When viewed from the direction orthogonal to the horizontal plane (the direction of arrow J, upward), the length of the central portion 50a is set to be greater than the length of both end portions 50b.

  As shown in FIG. 4C, the toner T stored on the upper side in the gravity direction of the developing roller 17 and the supply roller 20 moves to the downstream direction of the rotation direction E of the supply roller 20 by the both end portions 50b (arrows). F1). Then, the toner T is bounced back by the central portion 50a and moves in the upstream direction of the rotation direction E of the supply roller 20 (see arrow F3). By such an action, the toner T moves from the both end portions 50b to the central portion 50a, so that the phenomenon of staying at both end portions 50b is suppressed, and the phenomenon of being continuously subjected to a sliding load or thermal stress is suppressed. As a result, the circulation of the toner T in the storage portion Q suppresses the deterioration of the toner T at the longitudinal end portion of the supply roller 20 and suppresses the fusion of the toner T even when the development life is long.

  In the present embodiment, both the developing roller 17 and the supply roller 20 have an outer diameter φ20. As for the arrangement of the toner return member 50, the above-described embodiment may be a state in which the toner return member 50 has entered the supply roller 20, but may be disposed in the vicinity of the supply roller 20 in a non-contact manner. Instead, if the toner return member 50 is too far from the supply roller 20, the toner T that has flowed in the direction of the arrow F1 cannot be sufficiently blocked, and the amount of rebound is reduced. Therefore, 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 toner return member 50 has the same material as that of the developing container and has a thickness of 1.0 mm and a length of 5.5 mm from the end, and is set to an angle θ of 0.18 ° / mm with respect to the supply roller 20. have. The angle θ is an amount indicating the rate of increase in the longitudinal direction of the phase angle of the cross section of the supply roller 20. The angle θ may be an angle at which the toner T reflects in the longitudinal direction, and is preferably 0.045 ° / mm or more and 2.0 ° / mm or less. This θ is described as θ1, θ2, and θ3 in FIGS. 4, 5, and 6.

  As described above, in the present invention, the toner T can be efficiently supplied to the supply roller 20 by disposing the toner return member 50 at an appropriate position. Therefore, it is possible to improve the stability of the solid density, prevent the toner fused image due to the toner deterioration, and supply a high-quality image.

  FIG. 5 is a cross-sectional view illustrating configurations of the supply roller 20 and the toner return member 51 provided in the image forming apparatus according to the second embodiment. 5A is a cross-sectional view taken along the line AA as viewed from the direction of the arrow K in FIG. 5C, and FIG. 5B is a cross-sectional view from the direction of the arrow K in FIG. It is sectional drawing which follows a line. FIG. 5C is a plan view seen from the direction of arrow J in FIGS. 5A and 5B. In FIG. 5A and FIG. 5B, the developing roller 17 is omitted. Among the configurations of the second embodiment, the same configurations and effects as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate. Since the second embodiment can be applied to the same image forming apparatus 100 as that of the first embodiment, the description of the image forming apparatus is omitted. The second embodiment is different from the first embodiment in that the shape of the toner return member 51 is different. Details will be described below.

  The toner return member 51, which is a “developer return member”, is in the downstream region in the rotation direction E of the supply roller 20 with respect to the nip portion N and in the vicinity of the supply roller 20 at a different phase position in the cross section of the supply roller 20 in the longitudinal direction Z. Opposite, touch or invade. That is, in the case of FIG. 5A and FIG. 5B, the circumferential displacement (L × θ2) of the tip of the toner return member 51 relative to the surface of the supply roller 20 is the axis of the supply roller 20. Are different from each other.

  Both end portions 51 b have plate surfaces that go downstream in the rotation direction E of the supply roller 20 in the longitudinal direction Z from the end portion toward the center. The central portion 51a has a plate surface along the longitudinal direction Z. The aforementioned plate surfaces of the both end portions 51b and the aforementioned plate surface of the central portion 51a are directed to the upstream side in the rotation direction E of the supply roller 20. When viewed from a direction orthogonal to the horizontal plane, the length of both end portions 51b is set to be larger than the length of the central portion 51a.

  The toner returning member 51 has a central portion 51a located on the center side in the longitudinal direction Z and both end portions 51b located on the end side in the longitudinal direction Z. The upstream edge portion 51c on the upstream side in the rotation direction E of the supply roller 20 included in the both end portions 51b is disposed upstream in the rotation direction E of the supply roller 20 (see FIG. 5B), and the central portion 51a is the supply roller. It arrange | positions downstream in the rotation direction E of 20 (refer Fig.5 (a)). Both end portions 51b and the central portion 51a are formed continuously.

  Further, as shown in FIG. 5C, the toner return member 51 is formed in a convex shape from the both end portions 51b to the central portion 51a in the downstream direction of the rotation direction E of the supply roller 20. . In this state, the tip of the toner return member 51 is disposed close to the supply roller 20.

  Other apparatus configurations and image forming conditions are set to the same conditions as in the first embodiment. The toner returning member 51 is set to a shape in which the angle θ indicating the rate of increase in the longitudinal direction Z of the phase angle of the cross section of the supply roller 20 is 0.045 ° / mm or more in the region from both ends 51b to the inside of 75 mm. doing. With this shape, the toner T circulates over a wide range of the length of the storage portion Q. In particular, when the stirring member 22 of the toner T is in the form of a sheet, the unevenness of the supply of the toner T to the storage portion Q is likely to occur because the recording material 12 bends differently in the longitudinal direction Z. Even in such a case, since the toner T circulates inside the storage portion Q, the supply roller 20 can suck the toner T uniformly in the longitudinal direction.

  As shown in FIG. 5C, the toner T staying on the upper side in the gravity direction of the developing roller 17 and the supply roller 20 moves to the downstream direction of the rotation direction E of the supply roller 20 by the both ends 51b (arrows). F1). Then, the toner T merges at the central portion 51a and spreads toward the both end portions 51b while facing the upstream direction of the rotation direction E of the supply roller 20 (see arrow F3). Then, the toner T merges with the toner T conveyed from the toner suction portion, and reaches the toner return member 51 again.

  Due to such an action, in addition to the actions described in the first embodiment, the following actions are obtained. That is, the toner T circulates in the longitudinal direction Z in the storage portion Q of the toner T, so that the supply roller 20 sucks the toner T uniformly in the longitudinal direction Z even when the supply unevenness of the toner T of the stirring member 22 occurs. It becomes possible.

  Similarly to the first embodiment, even when a large number of image patterns having different print ratios are output in the longitudinal direction Z, the toner T circulates in the storage portion Q. T fusion or the like is suppressed.

  FIG. 6 is a cross-sectional view illustrating the configuration of the supply roller 20 and the toner return member 52 provided in the image forming apparatus according to the third embodiment. 6A is a cross-sectional view taken along the line AA as seen from the direction of the arrow K in FIG. 6C, and FIG. 6B is a view taken along the line BB as seen from the direction of the arrow K in FIG. It is sectional drawing which follows a line. FIG. 6C is a plan view seen from the direction of the arrow J in FIGS. 6A and 6B. In FIG. 6A and FIG. 6B, the developing roller 17 is omitted. Of the configurations of the third embodiment, the same configurations and effects as those of the first embodiment are denoted by the same reference numerals, and the 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 third embodiment is different from the first embodiment in that the shape of the toner return member 52 is different. The toner return member 52, which is a “developer return member”, is in the downstream region in the rotation direction E of the supply roller 20 with respect to the nip portion N and in the vicinity of the supply roller 20 at a different phase position in the cross section of the supply roller 20 in the longitudinal direction Z. Opposite, contact, invade. That is, in the case of FIG. 6A and the case of FIG. 6B, the circumferential displacement of the tip of the toner return member 52 with respect to the surface of the supply roller 20 is seen from the axis of the supply roller 20. Is different. That is, one end portion 52b positioned on one end side in the axial direction of the toner return member 52 is disposed on the upstream side in the rotation direction E of the supply roller 20 (see FIG. 6B). The other end 52a located on the other end side is disposed on the downstream side in the rotation direction E of the supply roller 20 (see FIG. 6A).

  Further, the toner return member 52 has a plate surface that goes downstream in the rotation direction E of the supply roller 20 from the one end portion 52b in the longitudinal direction Z toward the other end portion 52a. This plate surface is directed to the upstream side in the rotation direction E of the supply roller 20. Details will be described below.

  Other apparatus configurations and image forming conditions are set to the same conditions as in the first embodiment. The penetration amount of the toner return member 52 into the supply roller 20 is 1.5 mm, and the crossing angle is set to an angle θ of 0.18 ° / mm with respect to the supply roller 20.

  As described above with reference to FIG. 3, the toner T conveyed by the stirring member 22 in the vicinity of the suction portion M along the path of the arrow G in the drawing is partially taken into the suction portion M, and many of them are shown in the drawing. Is conveyed in the direction of arrow F1. The toner returning member 52 has two actions.

  One is a toner circulation F (F1) that bounces off the toner that has not been taken in by the supply roller 20 in the vicinity of the suction portion M and flows in the direction of the arrow F1 in the drawing, and brings the toner T in the vicinity of the suction portion M again. , F2, and F3 combined).

  The other is to discharge the excess toner T in the supply roller 20 and to keep the amount of toner in the supply roller 20 constant. At this time, the toner T discharged from the supply roller 20 holds a constant amount of charge, and is circulated in the storage portion Q temporarily surrounded by the supply roller 20, the developing roller 17, the toner return member 52, and the developing unit 4. To do. As a result, the toner T can be supplied to the developing roller 17 as much as necessary, and unnecessary portions can be temporarily stored in the storage portion Q, so that the pumping of the toner T by the stirring member 22 is minimized. Can do.

  In this embodiment, the angle θ indicating the rate of increase in the longitudinal direction of the phase angle of the cross section of the supply roller 20 by the toner return member 52 is set to 0.045 ° / mm. When the toner return member 52 comes into contact with the supply roller 20 at different phases, a force that twists the surface of the supply roller 20 works, and it becomes possible to remove excess toner T with a small force.

  As a result, the toner T can be supplied to the developing roller 17 as much as necessary, and unnecessary portions can be temporarily stored in the storage portion Q, so that the pumping of the toner T by the stirring member 22 is minimized. Can do. Furthermore, since the toner return member 52 can reduce the amount of intrusion into the supply roller 20, the friction between the toner return member 52 and the supply roller 20 can be suppressed, and the drive torque can be suppressed. it can.

  As described above, by using the toner returning member 52 according to the third embodiment, it is possible to efficiently hold the toner T conveyed from the stirring member 22 on the supply roller 20 while suppressing the driving torque. . Therefore, it is possible to improve the stability of the solid density and supply a high-quality image.

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 of Examples 1 to 3 will be described with reference to FIG.

  FIG. 7A is an explanatory diagram showing a method of measuring “surface ventilation”. FIG. 7B is a perspective view showing the configuration of the measurement jig 41. FIG. 7C 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. 7 (a) to 7 (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 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. 7 (a), one of the through holes of the measuring jig 41 is completely 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.

  As shown in FIG. 7 (a), 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. 7A, the decompression pump 43 is operated without the supply roller 20 installed, and the measured value of the flow meter 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 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. It flows out from the surface of the urethane foam layer 20b located in the through hole.

  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.

  As described above, according to the configurations of the first to third embodiments described above, it is possible to improve the stability of the solid density and supply a high-quality image while ensuring the supply of the toner T to the supply roller 20. .

  The tip portions of the toner return members 50, 51, 52 may be close to the surface of the supply roller 20 or may be in contact with the surface of the supply roller 20.

  In the above-described embodiments, 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 a developing device in a monochrome image forming apparatus.

  In the above-described embodiment, the printer is exemplified as the image forming apparatus, but the present invention is not limited to this. For example, another image forming apparatus such as a copying machine or a facsimile machine, or another image forming apparatus such as a combined machine combining these functions, or a recording agent carrier is used and is supported on the recording agent carrier. An image forming apparatus that sequentially superimposes and transfers toner images of respective colors on a recording material may be used. The same effect can be obtained by applying the present invention to the developing device in such an image forming apparatus.

4 Development unit (developing device)
17 Development roller (developer carrier)
18 Storage chamber 20 Supply roller 22 Stirring member (conveying member)
50, 51, 52 ... Toner return member (developer return member)
N Nip part Q Storage part T Toner (developer)

Claims (10)

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;
A developer return member that faces, contacts, or enters the supply roller in the vicinity of the supply roller in the longitudinal direction in a downstream region in the rotation direction of the supply roller with respect to the nip portion over a different phase position in the cross section of the supply roller in the longitudinal direction;
A developing device comprising: The developer returning member has a central portion located on the center side in the longitudinal direction, and both end portions located on the end side in the longitudinal direction,
An upstream edge portion upstream of the supply roller in the rotation direction of the both ends is disposed upstream in the rotation direction of the supply roller, and the central portion is disposed downstream in the rotation direction of the supply roller. The developing device according to claim 1.   3. The developing device according to claim 2, wherein the both end portions have plate surfaces that go downstream in the rotation direction of the supply roller as they go from the end portion toward the center in the longitudinal direction.   The developing device according to claim 3, wherein when viewed from a direction orthogonal to a horizontal plane, the length of the central portion is set larger than the lengths of the both end portions.   The developing device according to claim 3, wherein when viewed from a direction orthogonal to a horizontal plane, the length of the both end portions is set larger than the length of the central portion. The developer return member has one end located on one end in the longitudinal direction and the other end located on the other end in the longitudinal direction,
The developing device according to claim 1, wherein the one end portion is disposed upstream in the rotation direction of the supply roller, and the other end portion is disposed downstream in the rotation direction of the supply roller.   The developing device according to claim 6, wherein the developer return member has a plate surface that goes downstream in the rotation direction of the supply roller as it goes from one end to the other end in the longitudinal direction.   The said storage part is formed in the space enclosed by the said developer carrier, the said supply roller, and the said developer return member, The Claim 1 thru | or 7 characterized by the above-mentioned. Development device.   A process cartridge comprising the developing device according to claim 1 and detachable from an image forming apparatus main body. An image carrier for carrying an electrostatic image;
A developing device according to any one of claims 1 to 8,
An image forming apparatus comprising:

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