JP6112855B2 - Developing device, process cartridge, image forming apparatus - Google Patents

Description

  The present invention relates to a developing device that develops an object to be developed. More specifically, the present invention relates to a one-component development type contact development device that develops in contact with an object to be developed.

  Further, a process cartridge using the developing device as a developing processing means for an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric, and a copying machine or a printer using the developing device as a developing processing means for the image carrier. The present invention relates to an image recording apparatus (image forming apparatus).

In the electrophotographic image forming apparatus, an electrostatic latent image formed on an electrophotographic photosensitive member as an object to be developed (image carrier) is developed with a one-component developer. Is widely used (see, for example, Patent Document 1 and Patent Document 2).
Here, the magnetic non-contact development method will be briefly described.

(Magnetic non-contact development method)
In the magnetic non-contact development method, a developer is carried on a development sleeve (developer carrier) containing a magnet. Then, development is performed by causing the photosensitive member to face the developing sleeve with a predetermined minute gap from the surface and causing the developer to fly from the developing sleeve toward the photosensitive member. The developer in the developing device is conveyed to the developing sleeve by a mechanical stirring mechanism or gravity. Further, the magnetic one-component developer is supplied to the developing sleeve under a certain magnetic force by a magnet contained in the developing sleeve.

  In the magnetic non-contact developing system as described above, the magnetic seal member is attached to the end of the developing sleeve in order to prevent the toner from leaking out of the developer container from the gap between the developing container and the longitudinal end of the developing sleeve. There has been proposed a method of arranging so as to face the part (see Patent Document 3). This is a system in which the magnetic seal member is disposed at a predetermined distance from the end of the developing sleeve, and the toner is held on the magnetic seal member by the magnetic force of the magnetic seal member. That is, the toner that moves to the outside of the developer container is held by the magnetic seal member, thereby suppressing the leakage of the toner.

  Here, in the developing device, a regulating blade is disposed as a developer regulating member that regulates the amount of toner carried on the developing sleeve to be constant. And the magnetic seal member as described in patent document 3 will be arrange | positioned on the outer side of a control blade.

  At this time, since it is difficult to completely contact the end face of the regulating blade and the side surface of the magnetic seal member without a gap, a slight gap may be formed between the end face of the regulating blade and the magnetic seal member. . Since the toner carried on the developing sleeve in this gap is positioned outside the regulating blade, it is not regulated by the regulating blade. That is, if a gap is formed between the end face of the regulating blade and the magnetic seal member, the toner amount (developer amount) carried on the developing sleeve becomes larger in the gap portion than in other regions. Further, the toner located outside the regulating blade is not easily charged because it is not subjected to friction by the regulating blade, and the charge amount is low. Therefore, if the toner is carried on the developing sleeve in the area between the end face of the regulating blade and the magnetic seal member, the toner easily moves from this area to the photoreceptor. Such a toner may move to a region of the photoreceptor where a developed image should not be formed, and may cause a so-called fog.

  Therefore, another seal member (hot melt) is newly provided in the gap between the magnetic seal member and the restriction blade end portion, and the gap between the magnetic seal member and the restriction blade end portion is filled so as to be outside the end portion of the restriction blade. A method for preventing the toner from being carried on the developing sleeve has been proposed (see Patent Document 4).

JP 54-43027 A Japanese Patent Laid-Open No. 55-18656 Japanese Patent Laid-Open No. 10-39630 JP 2006-208552 A

  However, the configuration of the above-described Patent Document 4 is complicated, and there is a concern that the cost increases as another seal (hot melt) is newly provided in the gap between the magnetic seal and the end of the regulating blade.

  In view of the above problems, the present invention is characterized by adopting a magnetic contact development system instead of the magnetic non-contact development system. Accordingly, an object is to suppress the occurrence of a defective image by suppressing the developer from being carried on the developer carrier outside the developer regulating member with a simple configuration.

A typical configuration of an image forming apparatus for achieving the above object includes an image carrier, a developer, a developer container that contains the developer, and the developer supplied from the developer container. Provided in the developer container, a magnetic field generating member that is provided inside the developer carrier and generates a magnetic field for attracting the developer to the developer carrier from a magnetic field generation region, and the developer container. A seal member for restricting leakage of the developer from a gap between a longitudinal end portion of the developer carrier and the developer container, and regulating an amount of the developer carried on the developer carrier. A developer regulating member to be supplied, and an opening for supplying the developer from the inside of the developer container to the developer carrying member, wherein the developer is a magnetic one-component developer, and the developer In the longitudinal direction of the carrier, the magnetic field An end portion of the magnetic field generation region of the raw member is disposed on an inner side than an end portion of the developer regulating member, and the developer carrier is formed in the latent image formed on the image carrier while being in contact with the image carrier. In the image forming apparatus, the image is developed with the developer, and the length of the magnetic field generation region is shorter than the length of the opening in the longitudinal direction.

  According to the present invention, it is possible to suppress the occurrence of a defective image by suppressing the developer from being carried on the developer carrier outside the developer regulating member with a simple configuration.

Schematic configuration diagram of an image forming apparatus using a developing device Schematic configuration diagram of the developing device Schematic configuration diagram of the developing device The figure showing the positional relationship between the longitudinal position of each part of the developing device and the magnetic flux density in Example 1. The figure showing the positional relationship of the longitudinal position of each part of a developing device and magnetic flux density in a comparative example FIG. 10 is a diagram illustrating the positional relationship between the longitudinal position of each part of the developing device and the magnetic flux density in Example 2. Schematic configuration diagram of the developing device in Embodiment 3

<Example 1>
1 and 2 are schematic configuration diagrams of an image forming apparatus (image recording apparatus) 100 using a developing device applied to the present invention. This image forming apparatus is a laser printer using an electrophotographic process. Although details will be described later, the image forming apparatus 100 of the present embodiment uses a magnetic contact development system as a development system.

  Reference numeral 1 denotes an image carrier, which is a rotating drum type negative-polarity OPC photosensitive member (negative photosensitive member, hereinafter referred to as a photosensitive drum) having a diameter of 24 mm in this example. The photosensitive drum 1 is rotationally driven in a clockwise direction indicated by an arrow at a constant speed of 85 mm / sec (= process speed PS, printing speed).

  Reference numeral 2 denotes a charging roller as charging means for the photosensitive drum 1. The charging roller 2 is a conductive elastic roller. In this example, the charging roller 2 rotates following the rotation of the photosensitive drum 1.

  A DC voltage of -1300V is applied to the charging roller 2 as a charging bias to uniformly contact and charge the surface of the photosensitive drum 1 to a charging potential (dark portion potential) of -700V.

  Reference numeral 4 denotes a laser beam scanner (exposure device) including a laser diode, a polygon mirror, and the like. When the uniformly charged surface of the photosensitive drum 1 is exposed entirely with laser light, the laser power is adjusted so that the potential of the photosensitive drum surface becomes −150V.

  An electrostatic latent image corresponding to target image information is formed on the surface of the photosensitive drum 1 rotated by the scanning exposure L.

  Reference numeral 3 denotes a developing device (developer). The toner t is a developer for developing the latent image, and has a constant charge due to frictional charging. Here, a developing bias voltage is applied between the developing roller sleeve 3 b as a developer carrying member (developer carrying member, toner carrying member) and the photosensitive drum 1 by a developing bias applying power source (not shown). The developing roller sleeve 3b is a roller in which an elastic layer is formed on the surface of a hollow aluminum cylinder (aluminum sleeve). Hereinafter, the developing roller sleeve 3b is simply referred to as a developing sleeve 3b.

  The toner t is moved from the developing sleeve 3b to the photosensitive drum 1 in the developing portion (developing area) a by this developing bias, and the electrostatic latent image on the photosensitive drum 1 is visualized. The developing device 3 will be described later.

  Reference numeral 6 denotes a transfer roller as a contact transfer hand throw, which is pressed against the photosensitive drum 1 with a predetermined force. A transfer material P as a recording medium is fed to the transfer portion from a paper feed portion (not shown) at a predetermined timing, and a predetermined transfer bias voltage is applied to the transfer roller 6. Accordingly, the toner image (developer image) on the photosensitive drum 1 side is sequentially transferred onto the surface of the transfer material P fed to the transfer nip portion.

  Reference numeral 7 denotes a fixing device such as a heat fixing method. The transfer material P that has received the transfer of the toner image at the transfer portion is separated from the surface of the rotating photosensitive drum 1 and introduced into the fixing device 7, and the toner image is fixed to form an image formed product (print copy). It is discharged outside.

  A photosensitive drum cleaning device (drum cleaner) 8 scrapes off the transfer residual toner remaining on the photosensitive drum 1 with a cleaning blade 8a and collects it in a waste toner container 8b.

The photosensitive drum 1 is charged again by the charging device 2 and repeatedly used for image formation.
Reference numeral 9 denotes a process cartridge in which the photosensitive drum 1, the charging roller 2, the developing device 3, and the drum cleaner 8 are integrally formed, and is configured to be detachable from the apparatus main body 100 </ b> A of the image forming apparatus 100.

  The developing device 3 of this embodiment will be described. The developing sleeve 3b is a developer carrying member (developer carrying / conveying member) that encloses a magnet roller 3a as a magnetic field generating member and carries toner (developer) t on the surface thereof. The developing sleeve 3b is formed by forming a nonmagnetic conductive elastic layer 3b2 with a thickness of 1.0 mm on an φ12 mm aluminum cylinder (aluminum sleeve) 3b1.

  If the conductive elastic layer 3b2 is too thick, the effect of the magnetic force of the included magnet roller 3a is weakened. Therefore, it is desirable to design the conductive elastic layer 3b2 in consideration of the balance with the magnetic force. The developing sleeve 3b is disposed in the opening 3g of the developer container 3e, faces the photosensitive drum 1, and is in contact with the photosensitive drum 1 with a certain amount of pressure. The opening of the developer container 3e extends along the longitudinal direction of the developing sleeve 3b.

  The longitudinal direction of the developing sleeve 3b is a direction in which the rotation axis of the developing sleeve 3b extends or a direction parallel to this direction. Hereinafter, when there is no notice, the longitudinal direction is simply the longitudinal direction of the developing sleeve 3b.

  The magnet roller 3a is a magnetic field generating member for generating a magnetic force at each location on the developing sleeve 3b, and is a roller made of a fixed magnet fixed to the developer container 3e. The magnet roller 3a has four magnetic poles arranged along the circumferential direction. This magnetic pole generates a magnetic force at a predetermined peak density at each location of the developing unit a, the conveying unit, the supplying unit, and the collecting unit.

  Specifically, the magnet roller 3a has magnetic poles of S pole, N pole, S pole, and N pole along the downstream direction of the rotation direction of the developing sleeve 3b from the developing section a. The peak density of the magnetic field is generated in the section, supply section, and transport section. Part of the toner t reaching the developing section a moves from the developing sleeve 3b to the photosensitive drum 1, and develops the latent image formed on the photosensitive drum 1. The toner t that is not consumed in the developing unit a moves to the collecting unit located downstream of the developing unit a in the rotation direction of the developing sleeve 3b, and is collected in the developer container 3e. In this collection part, the peak density of the magnetic field is generated, so that the toner t in the developing device 3e is prevented from being blown out.

  In this way, the toner t that has reached the collection unit is conveyed downstream of the collection unit to a supply unit located in the developer container 3e. The magnetic field formed by the magnet roller 3b in the supply unit attracts the toner t in the developer container 3e to the developing sleeve 3b. As a result, the toner t that has not been consumed by the developing unit a and has reached the collecting unit is mixed with the toner t that is newly supplied by the supply unit. The toner t mixed in this manner and carried on the developing sleeve 3b is conveyed to a conveying unit located downstream of the supply unit and reaches the developing unit again. This realizes continuous supply of toner t to the developing unit a.

  The toner t used as the developer is a one-component magnetic toner (magnetic one-component developer), and is produced by a suspension polymerization method in this embodiment, and has an average circularity of 0.976.

  The toner t has a constant layer thickness by passing between the regulating blade (developer regulating member) 3c and the developing sleeve 3b in the process of being conveyed on the developing sleeve 3b while receiving the magnetic force from the magnet roller 3a. That is, the regulating blade (developer regulating member) 3c is a developer layer thickness regulating member that regulates the thickness of the toner layer formed on the developing sleeve 3b at a constant level. The amount of the toner t carried by the developing sleeve 3b is adjusted. This is a developer amount regulating member that regulates the amount constant. In addition, the toner t is charged by receiving a charge from the regulating blade 3c.

  A stirring member 3d circulates the toner t in the developer container 3e and sequentially conveys the toner t within a magnetic force reachable range around the sleeve.

  The toner t coated on the developing sleeve 3b is conveyed to a developing portion (developing region portion) a that is a portion opposite to the photosensitive drum 1 and the developing sleeve 3b by the rotation of the developing sleeve 3b. A developing bias voltage (DC voltage -450 V) is applied to the developing sleeve 3b from a developing bias applying power source (not shown). The developing sleeve 3b is driven with respect to the photosensitive drum 1 at a predetermined peripheral speed. As a result, the electrostatic latent image on the photosensitive drum 1 side is reversely developed with the toner t.

  The primary role of the magnet roller 3a in the developing system of this embodiment is a supply unit and a collection unit. The toner t is supplied to the surface of the developing sleeve 3b by the magnetic force of the magnet roller acting on the magnetic toner t. The toner t supplied to the developing sleeve 3b passes through the regulating blade and is held on the developing sleeve 3b when an electric charge is applied.

  The magnetic pole arrangement of the magnet roller 3a described above is an example, and the present invention is not limited to this. There is no problem even if the magnetic roller magnetic poles do not have a peak density in the developing unit and the transport unit.

  In order to prevent leakage of toner t from the vicinity of the end of the developing sleeve 3b to the outside, that is, so-called toner leakage, a magnetic seal member 3h is provided in the vicinity of the end of the developing sleeve. The magnetic seal member 3h is a seal member (end seal member) that seals the gap so that toner does not leak from the gap between the end of the developing sleeve and the developer container. The magnetic seal member 3h is disposed with a predetermined gap h from the developing sleeve 3b.

  Here, the end of the opening of the developer container will be further described with reference to FIG. However, since the following description is about the end of the opening of the developing device, the developing sleeve is omitted in the drawings shown in FIGS. FIG. 3C shows a diagram in which the developing sleeve 3b is arranged.

  As shown in FIG. 3A, the developing device 3 includes an opening 3g, and the toner t is conveyed by the magnetic force of the magnet roller and the stirring member as described above. A magnetic seal member 3h is disposed at the end of the opening 3g as shown in FIG. Between the magnetic seal member 3h and the surface of the developing sleeve 3b, toner t, which is a magnetic toner, is held by the magnetic seal member 3h by a magnetic force generated from the magnetic seal member 3h. As a result, the sealing property of the developer is ensured so that the toner t does not leak out of the developer container. Further, the side surface portion of the magnetic seal member 3h is disposed close to the side surface portions on both ends of the regulation blade 3c, but between the side surface portion (inner end portion) of the magnetic seal member 3h and the end portion of the regulation blade 3c. Not a little gap B occurs.

(Explanation regarding dimensions and arrangement of each member in this embodiment)
Next, FIGS. 4A and 4B are diagrams showing the positional relationship between the longitudinal position and the magnetic force in this embodiment. FIG. 4A shows the positional relationship among the lengths in the longitudinal direction of the opening 3g, the magnetic seal member 3h, the developing sleeve 3b, the magnet roller 3a, and the regulating blade 3c. In the figure, reference numeral 3j denotes a shaft portion of the magnet roller 3a, which is a support portion for supporting the magnet roller 3a inside the developer container 3e (see FIG. 1). That is, the magnet roller 3a is fixed to the developer container by fixing the shaft portion 3j to the developer container 3e.

  FIG. 4B shows the positional relationship with the longitudinal distribution of the magnitude (unit: Tesla) of the magnetic flux density of the magnet roller. In the developing part a (see FIG. 1), the magnitude of the magnetic flux density generated on the surface of the developing sleeve 3b is measured.

  In the present embodiment, in the longitudinal direction of the developing sleeve 3b, the length of the magnet roller 3a is made shorter than the length of the regulating blade 3c, so that the end of the magnet roller 3a is arranged inside the end of the regulating blade 3c. It is characterized by that. As a result, the toner t is prevented from being excessively carried on the end portion of the developing sleeve 3b, and the occurrence of defective images is suppressed, which will be described below.

  In the area outside the longitudinal end (A in the figure) of the magnet roller 3a, the distribution of magnetic force is small. This characteristic is the same in the longitudinal magnetic force distribution in each place of the developing unit a, the conveyance unit, the supply unit, and the collection unit. As described above, the toner t is conveyed on the developing sleeve 3b while receiving a magnetic force from the magnet roller 3a. Therefore, the amount of toner t on the developing sleeve 3b also depends on the magnitude of the magnetic force. If the magnetic force is small, the amount of toner t is also reduced.

  In the present embodiment, as shown in FIG. 4A, the longitudinal end portion of the magnet roller 3a is located inside the end portion of the regulating blade 3c. Since the position of the gap B between the side surface portion of the magnetic seal member 3h and the end of the regulating blade 3c and the magnet roller 3a do not overlap, the magnet roller 3a generated on the developing sleeve in this gap B portion. Magnetic force becomes small. By reducing the magnetic force, the force for holding the toner t on the developing sleeve is reduced. Further, since the toner is attracted toward a stronger magnetic force, the toner t is difficult to go to this gap B portion. That is, in the region corresponding to the gap B, the toner t supplied from the developer container to the developing sleeve 6b decreases.

  As described above, in the region corresponding to the gap B, the regulating blade 3c does not exist, and the amount of toner carried on the developing sleeve 6b cannot be regulated by the regulating blade 3c. For this reason, in this embodiment, the magnet roller 3a is not arranged in the region corresponding to the gap B, and the amount of toner t supplied to the developing sleeve 6b is reduced in this region.

  Therefore, it is possible to suppress an excessive amount of toner t carried on the developing sleeve 6b even in the gap B area where the regulating blade 3c is not disposed.

  If the amount of toner carried on the developing sleeve 6b is excessive outside the regulating blade 3c, the toner is transferred to a non-image portion (a portion that originally does not form an image) of the photosensitive drum 1. So-called fogging may occur. However, in this embodiment, there is no such fear, and the fogging of the toner t can be suppressed in this gap B portion.

(Difference between this example and non-contact development method)
In the present embodiment, the contact development method was adopted, so that the relationship between the longitudinal length of the magnet roller 3a and the arrangement of the magnetic seal member 3h could be as described above. This will be described in detail below.

  Conventionally, in the non-contact developing method often used as a developing method using magnetic toner, the developing sleeve and the photosensitive member are separated from each other, so that the toner is caused to fly from the developing sleeve toward the photosensitive member. At this time, the flying of the toner is controlled by the balance between the magnitude of the magnetic force acting on the surface of the developing sleeve and the voltage (developing bias) applied to the developing sleeve.

  More specifically, in the non-contact development method, a development bias in which an AC bias is superimposed on a DC bias is applied to the development sleeve, and an electric field is formed between the development sleeve and the photosensitive drum. A force is applied to the toner charged by this electric field. When this force exceeds the magnetic force of the magnet contained in the developing sleeve, the toner held on the developing sleeve will fly to the photosensitive drum. That is, the toner (developer) can fly toward the latent image formed on the photosensitive drum, thereby developing the latent image.

  Therefore, in the non-contact developing method, if there is a portion where the magnetic force by the magnet is weak on the surface of the developing sleeve, the force with which the toner is held by the developing sleeve becomes weak. As a result, more toner than the desired amount will fly from the developing sleeve to the photosensitive drum. As a result, a defective image such as fog (toner adheres to a portion where an image is not originally formed) is generated. That is, in the non-contact development method, it is necessary to lengthen the magnet roller disposed inside the developing sleeve so that a portion where the magnetic force by the magnet roller is weakened is not formed on the developing sleeve. Therefore, unlike the present embodiment, the end of the magnet roller cannot be arranged inside the end of the regulating blade.

  In contrast, in this embodiment, although magnetic toner is used, a contact development method is used instead of the conventional non-contact development method. In this contact development method, the developing sleeve 3b is in contact with the photosensitive drum 1 as described above, and only the DC bias is applied to the developing sleeve 3b. Since the photosensitive drum 1 and the developing sleeve 3b are in contact with each other, a very large electric field acts between the photosensitive drum 1 and the developing sleeve 3b as compared with the non-contact developing method.

  That is, in the contact development method, the force when the toner t is developed on the photosensitive drum 1 is dominated by the electric field, and the magnetic force by the magnet roller 3a is small. Therefore, the difference in the force applied to the toner t is small where there is a magnetic force action by the magnet roller 3a, and the difference in the effect on the fog is very small.

  If a developing bias or the like is appropriately set so that a fogging image does not occur in the central portion in the longitudinal direction of the developing sleeve 3b, the region of the gap B where the magnetic force by the magnet roller 3a is small (outside the end of the regulating blade 3c). In this area, the possibility that a fogging image is generated is small.

  That is, in this embodiment, by adopting the magnetic contact development method instead of the conventional magnetic non-contact development method, the end of the magnet roller 3a can be arranged inside the end of the regulating blade 3c. It has become. As a result, the amount of toner carried outside the end of the regulating blade 3c is reduced, and the transfer of the toner positioned outside the end of the regulating blade 3c from the developing sleeve 3b to the photosensitive drum 1 is suppressed. Is possible.

(Description of comparative example)
Next, a comparative example in which the length in the longitudinal direction of the magnet roller and the positional relationship of the gap B between the side surface portion of the magnetic seal member 3h and the end portion of the regulating blade 3c will be described with reference to FIG. .

  5A and 5B are diagrams showing the positional relationship between the longitudinal position and the magnetic force in the comparative example. FIG. 5A shows the positional relationship among the lengths in the longitudinal direction of the opening 3g, the magnetic seal member 3h, the developing sleeve 3b, the magnet roller 103a, and the regulating blade 3c. FIG. 5B shows the magnitude of magnetic flux density (unit: Tesla) of the magnet roller along the longitudinal direction of the developing sleeve 3b.

  In this comparative example, unlike the example, the end of the magnet roller 103a is arranged outside the end of the regulating blade 3c. That is, the length of the magnet roller 103a is longer than the length of the regulating blade 3c.

  In the region outside the longitudinal end portion (C in the figure) of the magnet roller 103a, the distribution of magnetic force is small. This characteristic is the same in each place of the developing unit a, the transport unit, the supply unit, and the collection unit. As described above, the toner t is conveyed on the developing sleeve 3b while receiving a magnetic force from the magnet roller 103a. The toner t conveyed on the developing sleeve 3b is regulated by the regulating blade 3c.

  In the comparative example, since the magnet roller 103a is also disposed in the gap B, the toner is supplied to the developing sleeve 3b also in this region. However, in the gap B portion, there are no members (regulating blade 3c or magnetic seal member 3h) that regulate the amount of toner t on the developing sleeve 3b. Therefore, the developing sleeve 3b may carry the toner t excessively in the gap B. As a result, the toner easily transfers from the developing sleeve 3b toward the photosensitive drum 1 in this portion, and a defective image such as a fog may occur.

  From the above, it can be seen that the present example is more preferable than the comparative example in suppressing defective images.

(Summary)
In summary, in this embodiment, by adopting the magnetic contact development method, the end of the magnet roller 3a can be arranged inside the end of the regulating blade 3c, which is a problem in the magnetic non-contact development method. Could be solved. That is, it is possible to suppress the toner from being excessively carried on the developing sleeve 3b outside the end portion of the regulating blade 3c.

  In particular, when the magnetic seal member 3h is used as an end seal member, there may be a gap B between the regulating blade 3c and the magnetic seal member 3h. Since the amount of toner on the developing sleeve 3b cannot be regulated in the gap B, it is effective to reduce the amount of toner supplied to the developing sleeve 3b by adopting the configuration of this embodiment.

  In some cases, the magnet roller 3a and the shaft portion 3j (see FIG. 4A) are integrated. In such a case, the shaft portion 3j may also generate a magnetic field. However, the influence of the magnetic field generated by the shaft portion 3j having a smaller diameter than the magnet roller 3a is very small on the surface of the developing sleeve 3b. It may be considered that the part that actually generates an effective magnetic field (magnetic field generation region) is only the magnet roller 3a. That is, in this embodiment, when the magnet roller 3a is integrated with the shaft 3j, or when the shaft 3j generates a magnetic field, the end of the magnetic field generating member or the end of the magnetic field generating region is used. Point to the end of the magnet roller 3a. The end of the magnetic field generating member and the end of the magnetic field generating region do not indicate the end of the support portion (shaft portion 3j) of the magnet roller 3a.

  In the present embodiment, the magnetic field generating member (magnet roller 3a) is a cylindrical member, but the shape of the magnetic field generating member is not limited to a cylindrical shape.

  Increasing the length of the longitudinal end of the magnet roller 3a away from the gap B portion is effective in suppressing the amount of toner carried on the developing sleeve 3b in the gap B portion. Therefore, in this embodiment, the length of the magnet roller 3a is made shorter than the length of the opening 3g of the developer container 3e. In other words, in the longitudinal direction of the developing sleeve 3b, the end of the magnet roller 3a is arranged more inside than the end of the opening 3g.

  Alternatively, the length of the regulating blade 3c may be sufficiently longer than the length of the magnet roller 3a. However, in this case, since the size of the developing device becomes large, it is desirable to appropriately determine the dimensional arrangement of the magnet roller 3a, the regulating blade 3c, etc. in consideration of functions required for the developing device.

<Example 2>
In this embodiment, another method for reducing the magnetic force of the magnet roller included in the developing sleeve 3b in the gap B between the side surface portion of the magnetic seal member 3h and the end portion of the regulating blade 3c will be described. The magnet roller 3a used in the first embodiment has an almost entire region which is a region for generating a magnetic field (magnetic field generation region). In this embodiment, only a part of the magnet roller 3a is a magnetic field generation region. 3i is used.

  As the magnet roller 3i, a material mainly composed of magnetic powder and a resin binder is used. By injecting these molten materials into a production mold in which magnets are arranged, the magnet roller 3i is manufactured, and the magnet roller 3i is further magnetized and oriented.

  It is possible to change the longitudinal range (width) magnetized by the magnet roller 3i by shortening the magnet for magnetizing and orienting the production mold with respect to the longitudinal length of the magnet roller 3i.

  FIGS. 6A and 6B show the positional relationship between the longitudinal position and the magnetic force in this embodiment. There is no correlation between the longitudinal length of the magnet roller 3i and the longitudinal distribution of the magnetic flux density. The longitudinal region (magnetic field generation region i) where the magnet roller 3i is magnetized is changed so that the longitudinal distribution of the magnetic flux density becomes smaller in the gap B between the side surface portion of the magnetic seal member 3h and the end portion of the regulating blade 3c. Is set in When the magnitude of the magnetic flux density generated by the magnet roller 3i is measured on the surface of the developing sleeve 3b, the maximum value is Bp, and a magnetic field is generated in a region where the magnitude of the magnetic flux density is within 50% of the maximum value Bp. Region i was defined. That is, the position (half position) Bi where the magnitude of the magnetic flux density is halved to 50% of the maximum value Bp is defined as the end of the magnetic field generation region i.

  In this embodiment, the end of the magnetic field generation region i is arranged inside the gap B portion. That is, in the longitudinal direction of the developing sleeve 3b, the end portion of the magnetic field generation region i is disposed inside the end portion of the regulating blade 3c.

  Since the magnetic force generated by the magnet roller 3i is reduced in the vicinity of the magnetic seal member 3h, the force for holding the toner t on the developing sleeve is reduced. Further, since the toner is attracted toward a stronger magnetic force, the toner t is less likely to go to the gap B portion. As a result, the toner fog in the gap B can be suppressed.

  Thereby, it is possible to suppress the toner t from moving outside the regulating blade 3c. Note that the end of the magnetic field generation region i may be disposed further inside than the end of the opening 3g in order to more reliably suppress the toner t from moving outside the regulating blade 3c.

<Example 3>
In the first and second embodiments, the magnetic seal member 3h that does not contact the developing sleeve 3b is used as the end seal member. However, even when a contact seal member such as a wool felt that contacts the developing sleeve 3b is used as the end seal member instead of the magnetic seal member 3h, the configuration of the magnet roller 3a or magnet roller 3i of the first and second embodiments is employed. Is possible.

  FIG. 7 shows the developing device of this embodiment. As the seal member, a wool felt contact end seal 3f that contacts the developing sleeve 3b was used. Also in this case, if the end portion of the magnet roller 3a is arranged inside the end portion of the regulating blade 3c as in the first embodiment, it is possible to suppress the toner from moving to the outside of the regulating blade 3c. Or after using the magnet roller 3i instead of the magnet roller 3a like Example 2, you may arrange | position the edge part of the magnetic field generation | occurrence | production area | region i inside the edge part of the control blade 3c.

  Note that the contact seal member 3f used in this embodiment is generally softer than the magnetic seal member 3h, and can be arranged so that the end of the contact seal member 3f and the end of the regulating blade 3c overlap each other. In this case, it is possible to suppress the formation of a gap between the end portion of the contact seal member 3f and the end portion of the regulating blade 3c. Therefore, it is possible to more reliably suppress toner from being carried on the developing sleeve 3b at a position outside the regulating blade 3c.

  On the other hand, when the contact seal member 3f comes into contact with the developing sleeve 3b, there is a possibility that a torque required to rotate the developing sleeve 3b becomes large. Therefore, it is only necessary to appropriately determine whether to use the magnetic seal member 3h or the contact seal member 3f as the end seal member in accordance with the configuration of the developing device. When the magnetic seal member 3h is used as the end seal member, there is a gap between the magnetic seal member 3h and the developing sleeve 3b, so that the magnetic seal member 3h does not hinder the rotation of the developing sleeve 3b.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Developing device 3a Magnet roller 3b Developing sleeve 3c Restriction blade 3d Stirring member 3e Developer container 3h Magnetic seal member 3g Opening part 4 Laser beam scanner 6 Transfer roller 7 Fixing device 8 Cleaning device 9 Process cartridge

Claims (18)

An image carrier;
Developer,
A developer container for accommodating the developer,
A developer carrying member for carrying the developer supplied from said developer container,
Provided inside the developer carrying member, and the magnetic field generating member for generating a magnetic field for attracting the developer on the developer carrier from the magnetic field generating region,
Wherein provided on the developer container, a seal member for regulating a from the gap between the longitudinal end portion and the developer container of the developing agent carrier of the developer from leaking,
A developer regulating member for regulating an amount of the developer carried on said developer carrying member,
An opening for supplying the developer from the inside of the developer container to the developer carrier;
With
The developer is a magnetic one-component developer;
In the longitudinal direction of the developer carrying member, an end portion of the magnetic field generating region of the magnetic field generating member, wherein disposed on the inner side of the end portion of the developer regulating member, the developer carrying member, said image bearing member the latent image formed on the image bearing member while contacting developed with the developer,
In the longitudinal direction, the length of the magnetic field generating region of the image forming apparatus characterized by less than the length of the opening. The image forming apparatus according to claim 1, wherein a length of the magnetic field generation region is shorter than the developer regulating member in the longitudinal direction. In the longitudinal direction, the length of the magnetic field generating member image forming apparatus according to claim 1 or 2, characterized in that less than the length of the opening. 4. The image forming apparatus according to claim 1, wherein a length of the developer regulating member is shorter than a length of the opening in the longitudinal direction. 5. In the longitudinal direction, an inner end portion of the seal member is disposed outside an end portion of the developer regulating member, and a gap is formed between the seal member and the developer regulating member. The image forming apparatus according to any one of claims 1 to 4. The seal member is spaced said developer carrying member with a gap, according to claim 1 which attracts the developer by the magnetic force, the developer is characterized in that to regulate the leakage to the outside of the developer container 6. The image forming apparatus according to any one of items 1 to 5. The sealing member, by contact with the longitudinal end of said developer carrying member, any one of claims 1 to 5, characterized in that said developer is regulated from leaking to the outside of the developer container 2. The image forming apparatus according to item 1. The image forming apparatus according to claim 7, wherein the seal member is in contact with the developer regulating member. When developing the latent image formed on said image bearing member, an image forming apparatus according to any one of claims 1 to 8 wherein the developer carrying member, characterized in that only the DC voltage is applied . Wherein the magnetic field generating member, an image forming apparatus according to any one of claims 1 to 9, characterized in that a cylindrical shape. The image forming apparatus according to claim 1, wherein the developer carrying member has a conductive elastic layer on a surface thereof. Developer,
A developer container for accommodating the developer,
A developer carrying member for carrying the developer supplied from said developer container,
It provided inside the developer carrying member, and the magnetic field generating member for generating a magnetic field for attracting the developer to the developer carrying member,
Wherein provided on the developer container, a seal member for regulating a from the gap between the longitudinal end portion and the developer container of the developing agent carrier of the developer from leaking,
A developer regulating member for regulating an amount of the developer carried on said developer carrying member,
An opening for supplying the developer from the inside of the developer container to the developer carrier;
With
The developer is a magnetic one-component developer;
In the longitudinal direction of the developer carrier, the end of the magnetic field generating member is disposed inside the end of the developer regulating member,
The developer carrier develops a latent image formed on the image carrier with a developer while in contact with the image carrier ,
The developing device according to claim 1 , wherein in the longitudinal direction, the length of the magnetic field generating member is shorter than the length of the opening . The developing device according to claim 12, wherein in the longitudinal direction, the length of the developer regulating member is shorter than the length of the opening. 14. The seal member according to claim 12 or 13, wherein the seal member regulates leakage of the developer to the outside of the developer container by contacting a longitudinal end portion of the developer carrier. Development device. The developing device according to claim 14, wherein the seal member is in contact with the developer regulating member. 16. The developing device according to claim 12, wherein when developing a latent image formed on the image carrier, only a DC voltage is applied to the developer carrier. The developing device according to claim 12, wherein the developer carrying member has a conductive elastic layer on a surface thereof. The image carrier;
A developing device according to any one of claims 12 to 17 ,
A process cartridge that is detachable from the main body of the image forming apparatus.

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