JP5403988B2 - Development device - Google Patents

Description

  The present invention relates to a developing device in which a first developer carrying body and a second developer carrying body perform development in parallel while transferring the developer from the upstream side to the downstream side, and more specifically, the first developer carrying body. The developer is unlikely to leak out to the photosensitive member side from the interval between the first developer carrier and the second developer carrier.

  2. Description of the Related Art Image forming apparatuses in which a plurality of photoconductors are arranged along a belt member and a developing device that develops an electrostatic image formed on the photoconductor with toner are arranged on each photoconductor. In recent years, development devices that perform development in a plurality of stages using a plurality of developer carriers including a pair of developer carriers have been put into practical use due to an increase in the process speed of image formation.

  Patent Document 1 discloses a double sleeve type developing device that develops an electrostatic image in two stages using a first developer carrier and a second developer carrier. Here, in the developer container, a belt-like magnet member, which is an example of an upstream regulating member, is opposed to the end of the developer carrier, so that the two-component developer carrying region is set in the longitudinal direction of the developer carrier. It is limited to. The band-shaped magnet member forms magnetic spikes of the two-component developer and slides the developer-carrying member on the surface, so that the two-component developer in the developer container is rotated around the developer-carrying member from the end. Prevent leakage.

In Patent Document 2, two components are formed from the first developer carrier on the upstream side to the second developer carrier on the downstream side by arranging the magnetic poles of the magnetic member arranged non-rotatingly inside the developer carrier. A developing device for delivering the developer is shown. Here, a belt-like magnet member, which is an example of a downstream regulating member in which a magnetic pole having the same polarity as the magnetic pole for delivering the two-component developer on the magnetic member of the second developer carrier, is disposed in the developer container. 2 opposite the end of the developer carrier. The strip-shaped magnet member is rotated around the second developer carrier while the two-component developer in the developer container diffuses outside the two-component developer carrying region, and the second developer carrier and the second developer carrier. This prevents leakage from the developer carrier.
JP 2003-15410 A JP 2007-72222 A

  In the case of the developing device disclosed in Patent Document 2, the following configuration prevents the developer from scattering from the end of the developer carrying member. That is, by the magnetic pole arrangement of the non-rotating magnetic member arranged inside the first developer carrier and the second developer carrier, the first developer carrier and the second developer carrier are separated from each other. In the interval, the magnetic spikes of the two-component developer continuously form a shielding wall (seal). For this reason, regarding the two-component developer carrying region, the two-component developer does not leak from the interval between the first developer carrying member and the second developer carrying member, but outside the carrying region, There is a possibility that the two-component developer in the developing container leaks out. Outside the two-component developer carrying region, no magnetic spikes are formed in the space between the first developer carrying member and the second developer carrying member, so that the downstream development rotating toward the outside of the developing container is performed. This is because it is not possible to prevent leakage of the two-component developer brought along with the agent carrier. Therefore, in the developing device disclosed in Patent Document 2, as described above, a band-shaped magnet member is disposed at the end of the second developer carrier, and the two-component developer is applied to the second developer carrier. It is magnetically blocked from reaching the distance between the pair of developer carrying members.

  However, even if the two-component developer leaking out of the developer container is eliminated in this way, the first developer carrier and the first developer carrier at the end portions of the first developer carrier and the second developer carrier. It has been found that the two-component developer leaking through the gap between the two developer carriers is not completely eliminated. In other words, even in the developing devices to which the countermeasures disclosed in Patent Documents 1 and 2 are applied, a very small amount of the two-component developer may leak from the interval between the first developer carrier and the second developer carrier. found.

  As will be described later, a part of the two-component developer delivered from the first developer carrier to the second developer carrier also includes the first developer carrier and the second developer carrier. It was confirmed that it leaked through the interval.

  Then, the two-component developer that leaks from the space between the first developer-carrying member and the second developer-carrying member outside the two-component developer carrying region falls and accumulates under the end of the developing device. . In addition, the toner in the two-component developer adheres to the end of the photosensitive drum and rotates around, and contamination of the end of the cleaning device, the end of the intermediate transfer belt, the end of the secondary transfer roller, etc. There is a possibility of staining the extra white part. There is also a possibility that density unevenness is formed in the image by reducing the charging performance at the end of the charging device.

  Therefore, it is possible to collect the leaked two-component developer by arranging magnets and suction devices at both ends of the gap formed by the first developer carrier, the second developer carrier and the photosensitive drum. was suggested. However, it is not possible to arrange a structure that can provide a sufficient effect in a narrow space between the first developer carrier, the second developer carrier, and the photosensitive drum. The magnet and the suction device affect the carrying area of the two-component developer on the first developer carrying body and the second developer carrying body, and conversely, the amount of scattering of the two-component developer may increase. .

In the present invention, the two-component developer leaking through the gap between the first developer carrier and the second developer carrier is collected in the developer container without affecting the developer carrying region, and the outside. An object of the present invention is to provide a developing device that does not leak.

The developing device according to the present invention supplies a developer to a developing position that stores at least a developer having magnetic particles and a developing position that is rotatably provided in an opening provided in the developer container and faces the image carrier. a first developer carrying member for the opening in the rotating capable provided, together passed the developer at a position facing the first developer carrying member, opposed to said image bearing member developing A second developer carrier for supplying a developer to a position; and the first developer carrier disposed in a non-rotating manner inside the first developer carrier and the second developer carrier. A magnetic member for supporting the developer on the surfaces of the first and second developer carriers, and the first developer carrier and the second developer carrier on the outside of the developer bearing region of the first developer carrier and the second developer carrier. From the distance between the developer carrier and the second developer carrier, the Arranged on a path towards the carrier, but to obtain Bei and a cover member for guiding said developing container with shielding the developer from scattering to the outside of the developer container. The cover member is sandwiched between the first developer carrier and the second developer carrier along the peripheral surfaces of the first developer carrier and the second developer carrier. It is provided so as to enter the space.

In the developing device of the present invention, the developer leaking through the gap between the first developer carrier and the second developer carrier is captured by the cover member. The captured developer is transported through the gap between the second developer carrier and the cover member using the rotational force of the second developer carrier and is collected in the developer container. For this reason, the amount of the developer leaking out of the developing device through the end regions of the first developer carrier and the second developer carrier is reduced. Since the cover member is disposed outside the developer carrying area, the cover member does not interfere with the developer in the carrying area and is not scattered, and no magnetic force or air current that affects the developer in the carrying area is generated.

  Accordingly, the developer leaking through the space between the first developer carrying member and the second developer carrying member can be quickly collected in the developing container without affecting the developer in the carrying region with a simple structure. And do not leak outside.

  Hereinafter, some embodiments of the present invention will be described in detail with reference to the drawings. The present invention can also be implemented in another embodiment in which a part or all of the configuration of each embodiment is replaced with the alternative configuration as long as both ends of the developer carrier are covered with thin cover members. .

  Therefore, the developing device can be implemented not only in a double sleeve type having two developing sleeves but also in a developing device having three or more developing sleeves. Not only the intermediate transfer type, but also a recording material conveyance method using a recording material conveyance belt as a belt member, and a sheet-fed image forming apparatus that transfers a toner image from a photosensitive drum to each recording material.

  In the present embodiment, only main parts related to toner image formation / transfer will be described. However, the present invention includes a printer, various printing machines, a copier, a fax machine, a composite machine, in addition to necessary equipment, equipment, and a housing structure. It can be implemented in various applications such as a machine.

  In addition, about the general matter regarding the image forming apparatus and the developing device disclosed in Patent Documents 1 and 2, the illustration is omitted and redundant description is omitted. In the description, the reference symbols in parentheses attached to the configuration names used in the claims are examples for assisting understanding of the invention, and the configuration is limited to the corresponding members in the embodiments. Is not.

<Image forming apparatus>
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus.

  As shown in FIG. 1, the image forming apparatus 100 according to the first embodiment includes a tandem type in which a plurality of image forming portions PY, PM, PC, and PK of yellow, magenta, cyan, and black are arranged along an intermediate transfer belt 25. It is a full color printer.

  In the image forming unit PY, a yellow toner image is formed on the photosensitive drum 1Y and is primarily transferred to the intermediate transfer belt 25 that passes through the primary transfer unit TY. In the image forming unit PM, a magenta toner image is formed on the photosensitive drum 1M, and is primarily transferred to the yellow toner image on the intermediate transfer belt 25 passing through the primary transfer unit TM. In the image forming units PC and PK, cyan toner images and black toner images are formed on the photosensitive drums 1C and 1K, respectively, and are primarily transferred onto the intermediate transfer belt 25 that passes through the primary transfer units TC and TK.

  A plurality of four-color toner images, which are examples, are transported to the secondary transfer portion T2 as the intermediate transfer belt 25 rotates, fed to the secondary transfer portion T2, and sandwiched and transported over the toner image. Batch secondary transfer to the material P is performed.

  The recording material P on which the four-color toner images, which are a plurality of examples, are secondarily transferred, is sent to the fixing device 7 in which the pressure roller 72 is pressed against the fixing roller 71 heated from the inside by the heater 73 to be heated. By receiving the pressure, the toner image is fixed.

  The separating device 12 separates the recording material P drawn from the recording material cassette 10 by the pickup roller 11 one by one and sends it to the registration roller 13. The registration roller 13 receives and waits for the recording material P in the stopped state, and sends the recording material P to the secondary transfer portion T2 in time with the toner image carried on the intermediate transfer belt 25.

  The intermediate transfer belt 25, which is an example of a belt member, is supported around the tension roller 21, the driving roller 22, and the opposing roller 23, and is driven by the driving roller 22 to rotate in the direction of the arrow R <b> 2.

  The belt cleaning device 26 rubs the intermediate transfer belt 25 with a cleaning blade to remove the transfer residual toner attached to the intermediate transfer belt 25 that has passed through the secondary transfer portion T2.

  The image forming units PY, PM, PC, and PK are configured substantially the same except that the color of toner used in the attached developing devices 4Y, 4M, 4C, and 4K is different from yellow, magenta, cyan, and black. In the following, the image forming unit PY will be described, and the other image forming units PM, PC, and PK will be described by replacing Y at the end of the code in the description with M, C, and K.

  The image forming unit PY includes a charging device 2Y, an exposure device 3Y, a developing device 4Y, a primary transfer transfer roller 5Y, and a cleaning device 6Y around the photosensitive drum 1Y.

  The photosensitive drum 1Y is configured by applying an organic photoconductor (OPC) having a negative charge property to the outer peripheral surface of an aluminum cylinder having an outer diameter of 80 mm, and a process speed of 300 mm / sec centering on the central support shaft. It rotates in the direction of arrow R1.

  The charging device 2Y applies a high voltage to the wire electrode to generate corona discharge, and irradiates the photosensitive drum 1Y with charged particles associated with the corona discharge, thereby uniformly uniforming the negative surface potential of the negative polarity on the surface of the photosensitive drum 1Y. Charge to VD (eg -700V).

  The exposure device 3Y scans the scanning line image data obtained by developing the yellow separated color image with a rotating mirror, and writes an electrostatic image of the image on the surface of the charged photosensitive drum 1Y. In the exposed portion, the dark portion potential VD is discharged, and the light portion potential VL (eg, −100 V) is lowered.

  The developing device 4Y develops the electrostatic image written on the photosensitive drum 1Y by the exposure device 3Y with yellow toner to form a yellow toner image on the photosensitive drum 1Y.

  The primary transfer roller 5Y is urged toward the photosensitive drum 1Y and presses against the intermediate transfer belt 25 to form a transfer portion TY between the intermediate transfer belt 25 and the photosensitive drum 1Y. The power source D1 applies a positive DC voltage V1 (for example, −2200V) to the primary transfer roller 5Y, and negatively charges the toner image carried on the photosensitive drum 1Y to the intermediate transfer belt 25 for primary transfer.

  The cleaning device 6Y brings a cleaning blade into contact with the photosensitive drum 1Y to remove the transfer residual toner remaining on the surface of the photosensitive drum 1Y that has passed through the primary transfer portion TY.

<Developing device>
FIG. 2 is an explanatory view of the delivery of the two-component developer between a pair of developer carriers of the developing device, and FIG. 3 is an explanatory view of a magnet member arranged at the end of the developer carrier.

  As shown in FIG. 2, the developing device 4 </ b> Y exposes the two-component developer carrying surface of the rotating developing sleeves 41 and 43 from the opening provided in the developing container 40 to the photosensitive drum 1 </ b> Y side. The developing container 40 contains a two-component developer in which yellow non-magnetic toner and a magnetic carrier are mixed as a developer having at least magnetic particles. The developer supply chamber 47 through which the supply screw 45 is arranged and the developer agitation chamber 48 through which the agitation screw 46 is arranged communicate with each other to constitute a circulation path for the two-component developer. doing.

  A replenishment two-component developer having an increased toner ratio is supplied to the developer stirring chamber 48 through the developer supply port 50 disposed at the end of the developing container 40 positioned upstream in the transport direction of the stirring screw 46. . The agitating screw 46 is a process for transporting the two-component developer in the axial direction and circulating it to the developer supply chamber 47 in the course of circulating the two-component developer to the developer supply chamber 47. Mix the agent. At the same time, the two-component developer separated from the developing sleeve 43 to the developer stirring chamber 48 is taken into the circulating two-component developer and mixed.

  The supply screw 45 uniformly supplies the charged two-component developer along the longitudinal direction of the developing sleeve 41 in the process of conveying the two-component developer in the axial direction and circulating it to the developer stirring chamber 48. Part of the circulated two-component developer overflows and is removed as having deteriorated charging performance through the developer discharge port 49 disposed at the end of the developing container 40 located on the downstream side in the conveyance direction of the supply screw 45. Is done.

  The developing device 4Y stirs the two-component developer in the direction perpendicular to the paper surface by the supply screw 46 and the stirring screw 45, and charges the nonmagnetic toner to negative polarity and the magnetic carrier to positive polarity. The charged two-component developer is carried on the developing sleeves 41 and 43 rotating around the magnets 42 and 44 as an example of a magnetic member, and rubs against the photosensitive drum 1Y.

  The power source D4 applies to the developing sleeves 41 and 43 an oscillating voltage obtained by superimposing a rectangular AC voltage having a frequency of 8.0 kHz and a peak-to-peak voltage Vpp of 1.8 kV on a negative DC voltage Vdc (for example, −350 V). . As a result, the negatively charged toner moves to the electrostatic image of the photosensitive drum 1Y that has a positive polarity relative to the developing sleeves 41 and 43 by the DC voltage Vdc, and the electrostatic image of the photosensitive drum 1Y is changed. Reversal developed.

  The two-component developer is attracted to the developing sleeve 41 by the cut pole N1 of the magnet 42, and the layer thickness carried by the coating amount regulating member 54 is made uniform. In the two-component developer, the cut pole N 1, the transport poles S 1 and N 1, the development pole S 2, and the transfer pole N 3 of the magnet 42 are constrained by a magnetic field generated along the surface of the development sleeve 41. The toner in the two-component developer conveyed to the developing position facing the photosensitive drum 1Y by the developing sleeve 41 receives an electric force due to the potential difference between the electrostatic image on the photosensitive drum 1Y and the developing sleeve 41, and the photosensitive material is developed from the developing sleeve 41. Fly toward drum 1Y.

  More specifically, the toner reciprocates in the facing distance between the developing sleeve 41 and the photosensitive drum 1Y by the alternating voltage applied to the developing sleeve 41. The negatively charged toner moves according to the potential difference between the DC voltage Vdc applied to the developing sleeve 41 and the electrostatic image while reciprocating. As a result, the toner returns to the developing sleeve 41 in the dark portion potential VD region, and an amount of toner corresponding to the potential difference adheres to the photosensitive drum 1Y in the bright portion potential VL region.

  The two-component developer carried on the developing sleeve 41 moves to the developing sleeve 43 along the magnetic lines of force of the magnets 42 and 44 formed in the opposing region between the developing sleeve 41 and the developing sleeve 43. Since there is no magnetic pole downstream in the rotational direction from the transfer pole N3 magnetic pole of the magnet 42, the two-component developer is peeled off from the developing sleeve 41, and is attracted to the transfer pole S1 of the magnet 44 and transferred to the developing sleeve 43. It is done. In the two-component developer, the transfer pole S 1, the development pole N 1, the transport poles S 2 and N 3, and the stripping pole S 3 of the magnet 44 are constrained by a magnetic field generated along the surface of the development sleeve 43.

  The toner of the two-component developer transported again to the developing position facing the photosensitive drum 1Y by the developing sleeve 43 receives an electric force due to the potential difference between the electrostatic image on the photosensitive drum 1Y and the developing sleeve 43, and the photosensitive material is developed from the developing sleeve 43. Fly toward drum 1Y. The toner reciprocates at the interval facing the photosensitive drum 1Y by the AC voltage applied to the developing sleeve 43, and an amount corresponding to the potential difference between the DC voltage Vdc applied to the developing sleeve 43 and the electrostatic image is applied to the photosensitive drum 1Y. Adhere to.

  The two-component developer, in which a part of the toner is consumed by the development, is carried on the developing sleeve 43 and rotates, and is collected again in the developing container 40 and returned to the developer stirring chamber 48. Since there is no magnetic pole downstream in the rotation direction from the stripping pole S3 of the magnet 44, the magnetic force is lost and the binding force becomes zero, and the two-component developer that has passed through the stripping pole S3 is blown away by centrifugal force. It is separated from the developing sleeve 43 by dropping by gravity.

  As shown in FIG. 3A, a belt-like magnetic seal 51 having a magnetic pole disposed on the surface is disposed at the end of the developing sleeve 41. The magnetic seal 51 fills the gap between the magnetic seal 51 and the developing sleeve 41 by forming magnetic spikes H of a two-component developer on the surface. As a result, the two-component developer moves in the axial direction through the gap between the magnetic seal 51 and the developing sleeve 41 so that the two-component developer does not adhere to the end of the developing sleeve 41 or leak from the developing container 40. I have to.

  The two-component developer carrying area A1 in the developing sleeve 41 is limited in the longitudinal direction by the magnetic spike H formed on the magnetic seal 51 which is an example of the upstream regulating member. Thereafter, the carrying area A1 is conveyed to the gap G1 between the developing sleeve 41 and the developing sleeve 43 through the developing area A2 facing the photosensitive drum. At the interval G1, the two-component developer moves so that the magnetic spike H formed on the developing sleeve 41 is pulled out and transferred to the developing sleeve 43. At this time, since the two-component developer moves with a rapid change of direction between the developing sleeve 41 and the developing sleeve 43 whose surface moves in the counter direction, the distance G1 between the developing sleeve 41 and the developing sleeve 43 is two. Component developer diffuses slightly outward. Therefore, the two-component developer carrying area A3 in the developing sleeve 43 is wider outward in the longitudinal direction than the two-component developer carrying area A1 in the developing sleeve 41.

  At the interval G1, the two-component developer moves with a sudden change of direction, so a very small amount of the two-component developer is scattered along the interval G1 to the interval G2 outside the two-component developer carrying area. . Then, a part of the scattered two-component developer is driven by the developing sleeve 43 that rotates outward, and is scattered from the gap G2 to the photosensitive drum 1Y side.

  At the end of the developing sleeve 43, a belt-like magnetic seal 52 is disposed in which a magnetic pole is disposed on the surface facing the developing sleeve 43. The magnetic seal 52 forms a magnetic spike H of the two-component developer on the surface, and removes the two-component developer that rotates around the developing sleeve 43 by rubbing the area where the magnet 44 does not have a magnetic pole. Further, the gap between the magnetic seal 52 and the developing sleeve 43 is filled with the magnetic spike H to prevent the two-component developer from moving in the axial direction toward the end of the developing sleeve 43.

  As shown in FIG. 3B, the ends of the magnetic seals 51 and 52 on the side close to the gap G2 between the developing sleeves 41 and 43 are formed to have the same polarity as the S3 magnetic pole of the magnet 44 on the downstream side. is there. A repulsive magnetic field is formed between the end of the magnetic seal 52, which is an example of a downstream regulating member, and the S3 magnetic pole of the magnet 44, so that the two-component developer that rotates around the developing sleeve 43 has a gap G2 between the developing sleeves 41, 43. It is blocked from being transported to.

  As shown in FIG. 3A, this prevents the two-component developer from leaking from the inside of the developing container through the gap G2 outside the carrying area A1, as shown in Patent Document 2. . However, as shown in Patent Document 2, the magnetic countermeasure for preventing the two-component developer from entering the gap G2 from the inside of the developing container is not limited to such a magnetic pole arrangement.

  However, it has been found that even if the magnetic poles of the magnetic seals 51 and 52 are set in this way, the two-component developer leaking from the gap G2 between the developing sleeves 41 and 43 outside the carrying areas A1 and A3 cannot be completely prevented. did.

  As shown in FIG. 2, when a large amount of image is formed over a long period of time, on the guide member 11 on which the developing device 4Y is mounted, the developing sleeves 41 and 43 are positioned immediately below the carrying areas A2 and A4. The two-component developer ni is deposited like an anthill. The deposited two-component developer ni is separated into a non-magnetic toner and a magnetic carrier when the charged charge is attenuated, so that the fine non-magnetic toner is scattered around by a slight wind when the developing device 4Y is pulled out to the front side. End up.

  Then, the deposited two-component developer spreads inward in the longitudinal direction, falls on the intermediate transfer belt 25 and stains the image. Further, the toner carried along with the rotation of the photosensitive drum 1Y reaches the cleaning device 6Y shown in FIG. 1, and stains the area outside in the longitudinal direction from the cleaning blade. For this reason. It is dammed by a side seal installed outside the cleaning blade, falls, and accumulates like a anthill on a guide member on which the cleaning device 6Y is mounted. Also in this case, the image is spread on the inner side of the longitudinal direction on the guide member and falls on the intermediate transfer belt 25 to contaminate the image.

  Further, a part of the toner passes through the cleaning device 6Y and reaches the charging device 2Y, and the shielding plate and grid of the charging device 2Y are soiled, resulting in an increase in maintenance frequency.

  As shown in FIG. 3A, the distance G2 outside the carrying areas A1 and A3 is larger than the distance G1 between the carrying areas A1 and A2, and the two-component developer is more sensitive to the photosensitive drum (1: FIG. 2). It is scattered to the side. Then, the non-magnetic toner resulting from the leakage of the two-component developer rotates around the photosensitive drum 1 and causes unnecessary toner contamination around the end of the photosensitive drum 1.

  Accordingly, in the developing device 4Y, the two-component developer leaking from the gap G2 is covered by covering the outer side of the two-component developer carrying area A4 of the developing sleeve 43 with an end cover sheet of sheet material which is an example of an outer cover member. It was confined in the developing device 4Y. After the two-component developer leaking from the gap G2 is captured by the end cover sheet, it is collected into the developing container 40 by utilizing the rotation of the developing sleeve 43.

<Outer cover member>
FIG. 4 is an explanatory view of the arrangement of the end cover sheet.

  As shown in FIG. 4A, the end cover sheet 70 is located outside the developer carrying area of the first developer carrying body and the second developer carrying body in the developer carrying area (A3). It is provided on a path from the gap (G2) between the developer carrying members (41, 43) to the photoconductor on the outside. By doing this, outside the developer carrying region, the developer scattered outside the developer container from the gap (G2) between the developer carrying bodies (41, 43) is blocked, and the two-component developer that leaks is removed from the developer. The developer is guided to the developer container (40) along the rotation direction of the carrier (43).

  As shown in FIG. 4B, the end cover sheet 70 has a cross-sectional shape that enters and exits along the contour of the cross section perpendicular to the longitudinal direction of the developer carrier (41, 43). The end cover sheet 70 integrally covers the outside of the two-component developer carrying area (A1, A3) in the developer carrying body (41, 43).

  As shown in FIG. 4A, the end cover sheet 70 is attached with the upper portion 70 c and the lower portion 70 d fixed to the developing container 40. The center of the end cover sheet 70 is pressed by the guide pin 71, and the side part 70b of the end cover sheet 70 is brought into close contact with the developing container 40 so that a gap through which the two-component developer leaks out is not formed. . The inner edge 70a of the end cover sheet 70 is positioned as close as possible within a range that does not come into contact with the two-component developer carrying area A3 that has diffused outward as the developer sleeve 41 is transferred to the developing sleeve 43. .

<Example 1>
5 is a cross-sectional view perpendicular to the rotation direction of the developing device in the first embodiment, FIG. 6 is a perspective view of the developing device without an end cover, and FIG. 7 is a perspective view of the developing device with the end cover attached. FIG. 8 is an explanatory diagram of the peripheral configuration of the developing sleeve in Example 1, and FIG. 9 is an explanatory diagram of the end cover sheet.

  As shown in FIG. 5B, in Example 1, the end cover sheet 80 has a maximum particle diameter of the two-component developer that is larger than the facing distance between the developer carrier (43) and the photoreceptor (1Y). It is formed of a thinner sheet material. And it arrange | positions so that it may rub against the surface of a developer carrier (43) by the opposing space | interval of a developer carrier (43) and a photoreceptor (1Y). This prevents the photosensitive member (1Y) from being damaged by dragging the two-component developer between the end cover sheet 80 and the photosensitive member (1Y).

  The end cover sheet 80 is formed of a stretchable sheet material having a uniform thickness, and is arranged in a state where tension is applied in the rotation direction of the developer carrier (43). As a result, the end cover sheet 80 is drawn toward the developer carrier (43) side and slid against the surface at the facing distance between the developer carrier (43) and the photoreceptor (1Y).

As shown in FIG. 9, the outer cover member (80) has a portion covering the developer carrier (43) on the downstream side rather than a portion covering the developer carrier (41) on the upstream side. 43), a step is formed in the outline of the edge so as to be located outward in the longitudinal direction. The steps are positioned at intervals between the development regions (A2, A4) where the pair of developer carriers (41, 43) develop the photosensitive member (1Y), respectively, and the pair of developer carriers (41, 43). Arranged so as to be shifted to the developer carrier side (43) downstream of the interval. The step has a rounded recess in which the edge is slanted backward.
Diameter of developing sleeves 41 and 43: 20 mm
Development sleeve 41, 43 length: 350 mm
Distance between developing sleeves 41 and 43: 1 mm
Peripheral speed of developing sleeves 41 and 43: 400 mm / sec
Diameter of photosensitive drum 4Y: 80mm
Peripheral speed of photosensitive drum 4Y: 300 mm / sec
Opposite distance between the photosensitive drum 4Y and the developing sleeves 41 and 43: 300 μm
Material of end cover sheet 80: Urethane sheet Dimension of end cover sheet 80: length 80 mm × width 25 mm × thickness 100 μm
Level difference: 1.5mm
Inclination angle of the step: 45 degrees Earl of the bottom of the step: 2 mm
Toner ratio of two-component developer: 8% by weight
Maximum diameter of magnetic carrier: 70 μm
Average particle diameter of toner: 5.5 μm

  As shown in FIG. 5A, at the central portion in the longitudinal direction of the developing device 4Y, the two-component developer carried on the developing sleeves 41 and 42 circulates to develop the electrostatic image on the photosensitive drum 1Y. The developing sleeves 41 and 43 rotate in the directions of arrows R3 and R4, respectively, so that the surface moves in the same direction as the surface of the photosensitive drum 1Y that rotates in the direction of arrow R1.

  The two-component developer is supplied from the supply screw 45 to the developing sleeve 41, and the coating amount is regulated by the coating amount regulating member 54. The two-component developer is developed for the first time by the developing sleeve 41, and only the toner is transferred to the photosensitive drum 1Y. Thereafter, the two-component developer is transferred from the developing sleeve 41 to the developing sleeve 43 at an interval between the developing sleeves 41 and 43, the second development is performed on the developing sleeve 43, and only the toner is transferred to the photosensitive drum 1Y. Thereafter, the two-component developer carried on the developing sleeve 43 enters the developing container 40 and returns to the stirring screw 46.

  As shown in FIG. 5B, magnetic seals 51 and 52 are installed in an arc shape at the end portions of the developing sleeves 41 and 43 with a predetermined gap from the developing sleeves 41 and 43.

  As shown in FIG. 8, the cylinder surfaces of the developing sleeves 41 and 43 are subjected to a blasting process so that the two-component developer can be easily coated. The lengths of the magnets 42 and 44 arranged non-rotatingly inside the developing sleeves 41 and 43 are slightly the same length as the blasted region, or slightly (1 to 2 mm) in consideration of mounting play and component tolerance. Degree) is longer. In order to reliably coat the blasted area with the two-component developer, it is better to make the area slightly longer.

  Magnetic seals 51 and 52 are disposed in the non-blasting region at the ends of the developing sleeves 41 and 43. The magnetic seals 51 and 52 prevent the two-component developer coated on the developing sleeves 41 and 43 from leaking from the end during rotation.

  However, since the developing sleeves 41 and 43 are close to each other, the magnetic seals 51 and 52 cannot be disposed in the vicinity of the interval between the developing sleeves 41 and 43. For this reason, the two-component developer floating around the interval between the developing sleeves 41 and 43 leaks out in the direction of the photosensitive drum 1 </ b> Y by the rotational force of the developing sleeve 43.

  Therefore, in Example 1, an end cover sheet 80 is provided as shown in FIG. 7 in order to block the two-component developer leaking from the interval between the non-blast regions at the ends of the developing sleeves 41 and 43.

  As shown in FIG. 9, since the end cover sheet 80 is disposed between the developing sleeve 43 and the photosensitive drum 1Y, the end cover sheet 80 has a thickness thinner than the facing interval between the developing sleeve 43 and the photosensitive drum 1Y.

  In many cases, the developing gap between the developing sleeve and the photosensitive member is 200 to 500 μm, but in Example 1, the developing gap is 300 μm, and the thickness of the end cover sheet 80 is 100 μm.

  Since the end cover sheet 80 is rubbed against the surfaces of the developing sleeves 41 and 43 and the photosensitive drum 1Y, the material is preferably a soft and slidable urethane or a fluorine-based resin material. Further, considering that the slack is reduced and the arrangement is made along the contours of the developing sleeves 41 and 43, a stretchable material is preferable. If the surface of the end cover sheet 80 is textured, it is preferable that it is not attached to the developing sleeves 41 and 43 and the photosensitive drum 1Y.

The end cover sheet 80 was attached by the following procedure.
(1) With the drum seal 53 removed, the upper portion of the end cover sheet 80 is sandwiched by a holding plate (not shown), and the holding plate is fixed to the developing container 40 with screws. The upper portion of the end cover sheet 80 may be fixed to the developing container 40 with a double-sided tape.
(2) In a state where the end cover sheet 80 is lightly tensioned, the lower part of the end cover sheet 80 is fixed with screws of a press plate or double-sided tape, and then the drum seal 53 is attached.
(3) Finally, the edge of the end cover sheet 80 is attached so as to follow the curvature of the side surface of the developing container 40 in which the bearing that rotatably supports the developing sleeves 41 and 43 is stored.
(4) At this time, the end cover sheet 80 is attached while being slightly stretched. For this reason, if only the central recess is fixed with double-sided tape or screws, the entire area of the edge of the end cover sheet 80 is in intimate contact with the side surface of the developing container 40, and the two components further outward from the end cover sheet 80. It is possible to prevent the developer from leaking.

  Note that the side surface of the developing container 40 is configured to follow the contour of the developing sleeves 41 and 43, and is attached along the curved surface of the side surface of the developing container 40 to end along the developing sleeves 41 and 43. The part cover sheet 80 can be fixed.

  It is desirable that the attachment position in the longitudinal direction of the end cover sheet 80 does not interfere with the two-component developer carrying area. This is because when the end cover sheet 80 comes into contact with the magnetic spikes of the two-component developer rotating at high speed, the two-component developer is scattered.

  Here, the carrying area of the two-component developer in the upstream developing sleeve 41 is a blast area of the developing sleeve 41 as shown in FIG. However, in the developing sleeve 43 on the downstream side, the two-component developer carrying region tends to expand slightly outward in the longitudinal direction. In other words, even if the blast areas and magnet lengths of the developing sleeves 41 and 43 are equal, the developing sleeve 43 has a slightly wider length of the two-component developer carrying area. The position of the inner edge of the end cover sheet 80 is not in contact with the two-component developer, and the marginal position is more effective against leakage.

  Therefore, in the first embodiment, as shown in FIG. 9, the inner edge of the end cover sheet 80 is shifted to the outer side in the vicinity of the developing sleeve 43 by the extent of the carrying region, rather than in the vicinity of the developing sleeve 41.

  A stepped shape 81 (a marking line is also acceptable) is taken into the side surface portion 40b of the developing container 40 to which the upper and lower portions of the end cover sheet 80 are attached. Therefore, the end cover sheet 80 can be accurately positioned and attached in the longitudinal direction of the developing sleeves 41 and 43 at the time of assembly in which the two-component developer is not carried by abutting against the stepped shape 81.

  In the first embodiment, the end cover sheet 80 is attached to the end portions of the pair of developing sleeves 41 and 43, thereby preventing the two-component developer from leaking from the interval between the developing sleeves 41 and 43 to the photosensitive drum 1Y side. The By providing the end cover sheet 80, the two-component developer leaking from the interval between the developing sleeves 41 and 43 is damped, and various problems caused by the leakage are avoided. By preventing the leakage of the two-component developer, not only the toner scattering in the housing is reduced, but also a ripple effect such as extending the life of the regular replacement parts such as the charging device and the photosensitive drum.

  Then, the blocked two-component developer is guided to the end cover sheet 80 and returned into the developing container 40, so that the two-component developer may accumulate in the end cover sheet 80 and overflow. Absent. The end cover sheet 80 has produced a good developer circulation in which the two-component developer that is likely to leak from the end portions of the developing sleeves 41 and 43 is returned to the developing container 40 again.

  Further, since the end cover sheet 80 is attached along the side surface of the developing container 40 that rotatably supports the developing sleeves 41 and 43, the thin flexible end cover sheet 80 does not sag and the side surface is curved. Installed in close contact. As a result, leakage of the two-component developer to the outside through under the edge of the end cover sheet 80 can be prevented. Since the contact area between the photosensitive drum 1Y and the end cover sheet 80 is reduced, the thin flexible end cover sheet 80 is not pulled by the rotating photosensitive drum 1Y and does not continue to be unstablely deformed.

<Example 2>
FIG. 10 is an explanatory diagram of the arrangement of the end cover sheet according to the second embodiment.

  As shown in FIG. 10A, in the second embodiment, the end cover sheet 85 covers the developing sleeve 43 side on the downstream side from the vicinity of the distance between the developing sleeves 41 and 43.

  In the side surface portion 40b of the developing container 40 in which the bearing Be that rotatably supports the developing sleeves 41 and 43 is stored, an end cover sheet fixing member 86 is fixed to a recess corresponding to an intermediate position between the two bearings Be. Yes. The upper part of the end cover sheet 85 is fixed to the end cover sheet fixing member 86. Since the end cover sheet fixing member 86 is very close to the developing sleeves 41 and 43 and the photosensitive drum 1Y to which a high voltage is applied, the end cover sheet fixing member 86 is like a highly insulating resin material (or a material coated with an insulating material on a metal material). An insulating member is used.

  Here, after attaching the upper part of the end cover sheet 85 to the end cover sheet fixing member 86, the lower part is fixed in a state where the end cover sheet 85 is lightly tensioned. At this time, the outer edge of the end cover sheet 85 is brought into close contact with the unevenness on the side surface of the developing container 49, and leakage of the two-component developer from the end can be prevented.

  As shown in FIG. 3B, the leakage of the two-component developer is caused by the rotational force of the developing sleeve 43 from the interval between the developing sleeves 41 and 43. That is, since it flies to a position lower than the interval between the developing sleeves 41 and 43, if the lower side is covered from the interval between the developing sleeves 41 and 43, a sufficient effect can be exhibited with respect to leakage of the two-component developer.

  Further, similarly to the first embodiment, the two-component developer blocked is returned into the developing container 40 by the end cover sheet 85, and therefore, the two-component developer accumulates in the end cover sheet 85 and overflows. There is nothing.

<Example 3>
FIG. 11 is an explanatory diagram of the arrangement of the end cover sheet according to the third embodiment.

  As shown to (a) of FIG. 11, Example 3 has the characteristic in the lower part to which the edge part cover sheet 90 is attached.

  As shown in FIG. 11B, first, the tip of the lower jaw portion 91 of the developing container 40 has an acute angle. Second, an end cover guide 92 that urges the end cover sheet 90 toward the developing sleeve 43 is fixed to the developing container 40 with screws 93 so as to sandwich the end cover sheet 90. The two-component developer dammed by the end cover sheet 90 by the above two configurations. It is easier to return to the developing container 40.

<Example 4>
FIG. 12 is an explanatory diagram of the arrangement of the end cover sheet of Example 4.

  As shown in FIG. 12A, in the fourth embodiment, the rotation direction of the photosensitive drum 1Y is counterclockwise as in the first to third embodiments, but the rotation direction of the developing sleeves 41 and 43 is the third embodiment. It is the opposite of 1-3. That is, since the developing sleeves 41 and 43 rotate counterclockwise as the counter direction with respect to the surface of the photosensitive drum 1Y, the circulation direction of the two-component developer is opposite to that in the first to third embodiments. Yes. Although not shown, the rotation direction of the agitation screw 46 and the supply screw 45 shown in FIG. 3 and the arrangement of the coating amount regulating member (54: FIG. 5) are also changed for the reverse circulation. Yes.

  That is, the two-component developer is carried from the agitating screw (46: FIG. 3) to the developing sleeve 43 with a regulated layer thickness, and is carried on the developing sleeve 43 and rotated from the bottom to the top to electrostatically charge the photosensitive drum 1Y. After the image is developed, the image is transferred to the developing sleeve 41.

  Thereafter, the two-component developer is carried on the developing sleeve 41 and rotated from the bottom to the top, and the electrostatic image on the photosensitive drum 1Y is developed again, and then collected in the developing container 40.

  In Embodiment 4, since the upper developing sleeve 41 is on the downstream side, the length of the two-component developer carrying region in the longitudinal direction of the developing sleeve 41 is longer than that in the developing sleeve 43.

  Therefore, the edge of the end cover 95 located on the inner side in the longitudinal direction of the developing sleeve 41 is opposite to that of the first embodiment, and is more outward in the vicinity of the developing sleeve 43 than in the vicinity of the developing sleeve 43. There is a shift. In other words, since the length of the carrying region on the downstream side is increased by 1 to 2 mm in the transport direction of the two-component developer, the end cover sheet 95 also has an inner line corresponding to the downstream developing sleeve 41 corresponding to the inner line 1 to 1 mm. A step is formed so as to shift outward by 2 mm.

1 is an explanatory diagram of a configuration of an image forming apparatus. FIG. 6 is an explanatory diagram of delivery of a two-component developer in a pair of developer carrying members of a developing device. It is explanatory drawing of the magnet member arrange | positioned at the edge part of a developing material carrier. It is explanatory drawing of arrangement | positioning of an edge part cover sheet. 3 is a cross-sectional view perpendicular to the rotation direction of the developing device in Embodiment 1. FIG. FIG. 6 is a perspective view of a developing device without an end cover. It is a perspective view of the developing device with an end cover attached. 3 is an explanatory diagram of a peripheral configuration of a developing sleeve in Embodiment 1. FIG. It is explanatory drawing of an edge part cover sheet. 6 is an explanatory diagram of an arrangement of an end cover sheet of Example 2. FIG. FIG. 10 is an explanatory diagram of an arrangement of an end cover sheet of Example 3. It is explanatory drawing of arrangement | positioning of the edge part cover sheet of Example 4. FIG.

Explanation of symbols

1Y, 1M, 1C, 1K photoconductor (photosensitive drum)
2Y, 2M, 2C, 2K Charging device 3Y, 3M, 3C, 3K Exposure device 4Y, 4M, 4C, 4K Developing device 5Y, 5M, 5C, 5K Primary transfer roller 6Y, 6M, 6C, 6K Cleaning device 25 Intermediate transfer belt 41, 43 Developer carrier (developing sleeve)
42, 44 Magnetic member (magnet)
45 Supply screw 46 Stir screw 51, 52 Magnetic seal 70, 80, 85, 90, 95 Outer cover member (end cover sheet)

Claims (5)

A developer container containing a developer having at least magnetic particles;
A first developer carrier that is rotatably provided at an opening provided in the developer container, and that supplies a developer to a development position facing the image carrier;
The opening in the rotating capable provided, the first with passed the developer with a developer carrying member opposite to the position, the second supplying developer to the developing position facing the image bearing member A developer carrier;
The first developer carrier and the second developer carrier are arranged non-rotatingly inside the first developer carrier and the developer is carried on the surfaces of the first developer carrier and the second developer carrier, respectively. A magnetic member to be
Outside the developer carrying area of the first developer carrying body and the second developer carrying body, the image carrying body is spaced from the distance between the first developer carrying body and the second developer carrying body. provided in a path over toward, Bei give a, a cover member for guiding said developing container with shielding the developer from scattering to the outside of the developer container,
The cover member is in a space sandwiched between the first developer carrier and the second developer carrier along the peripheral surfaces of the first developer carrier and the second developer carrier. A developing device provided to invade . A developer container containing a developer having at least magnetic particles;
A first developer carrier that is rotatably provided at an opening provided in the developer container, and that supplies a developer to a development position facing the image carrier;
The opening in the rotating capable provided, the first with passed the developer with a developer carrying member opposite to the position, the second supplying developer to the developing position facing the image bearing member A developer carrier;
The first developer carrier and the second developer carrier are arranged non-rotatingly inside the first developer carrier and the developer is carried on the surfaces of the first developer carrier and the second developer carrier, respectively. A magnetic member to be
Outside the developer carrying area of the first developer carrying body and the second developer carrying body, the image carrying body is spaced from the distance between the first developer carrying body and the second developer carrying body. provided in a path over toward, Bei give a, a cover member for guiding said developing container with shielding the developer from scattering to the outside of the developer container,
Than the inner edge of the cover member provided at a position corresponding to the first development region where the first developer carrier is opposed to the image carrier in the circumferential direction of the first developer carrier, In the circumferential direction of the second developer carrier, the inner edge of the cover member provided at a position corresponding to the second development region where the second developer carrier is opposed to the image carrier. The developing device is arranged outside in the longitudinal direction of the first developer carrier . A developer container containing a developer having at least magnetic particles;
A first developer carrier that is rotatably provided at an opening provided in the developer container, and that supplies a developer to a development position facing the image carrier;
The opening in the rotating capable provided, the first with passed the developer with a developer carrying member opposite to the position, the second supplying developer to the developing position facing the image bearing member A developer carrier;
The first developer carrier and the second developer carrier are arranged non-rotatingly inside the first developer carrier and the developer is carried on the surfaces of the first developer carrier and the second developer carrier, respectively. A magnetic member to be
Outside the developer carrying area of the first developer carrying body and the second developer carrying body, the image carrying body is spaced from the distance between the first developer carrying body and the second developer carrying body. provided in a path over toward, Bei give a, a cover member for guiding said developing container with shielding the developer from scattering to the outside of the developer container,
The cover member is arranged such that a portion corresponding to the second developer carrier is positioned more outward in a longitudinal direction of the developer carrier than a portion corresponding to the first developer carrier. A step is formed in the outline of the edge of the cover member,
The step is located between a first development area where the first developer carrier develops the image carrier and a second development area where the second developer carrier develops the image carrier. In addition, the developing device is arranged so as to be shifted toward the second developer carrying body with respect to the gap between the first developer carrying body and the second developer carrying body . The distance between the inner edge of the cover member that covers one end of the first developer carrier and the inner edge of the cover member that covers the other end of the first developer carrier is The developing device according to claim 1, wherein the developing device is substantially constant in an area corresponding to one developer carrier . (1) a developer carrying region end of the first developer carrying member;
(2) With respect to the circumferential direction of the first developer carrier, the first developer carrier is located on the inner side of the cover member provided at a position corresponding to the first development region facing the image carrier. Edge,
(3) a developer carrying region end of the second developer carrying member;
(4) With respect to the circumferential direction of the second developer carrier, the second developer carrier is located on the inner side of the cover member provided at a position corresponding to the second development region facing the image carrier. Edge,
5. The developing device according to claim 1, wherein the developing devices are arranged in this order from the inside toward the outside .

Images