JP2011164351A - Developing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain narrow charge distribution without excessively stressing toner to be subjected to development before development. <P>SOLUTION: The developing device includes: a stirring and conveying member 3 that mixes and stirs and also conveys two-component developer (developer) D containing toner T and carrier C; a developer conveying member 4 that holds and conveys the two-component developer D conveyed from the stirring and conveying member 3; a charge injection member 5 that injects charge having the same polarity as the charge characteristic of toner T of the two-component developer D on the developer conveying member 4 into the toner T by making predetermined electric field for injecting charge act between the developer conveying member 4 and the charge injection member; and a toner conveying member 6 that separates the toner T into which the charge is injected by the charge injection member 5 from the two-component developer D on the developer conveying member 4 by making predetermined electric field for separating toner act between the developer conveying member 4 and the toner conveying member, and also holds and conveys the separated toner T to be subjected to development of a latent image on an image holding body 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus using the developing device.

Japanese Patent Application Laid-Open No. H10-228561 discloses a method in which a charge injection electric field is applied through a charge injection member disposed opposite to a toner carrier that carries conductive toner to inject charges into the toner.
Further, Patent Document 2 includes a charge injection member arranged to face a toner carrier that carries conductive toner, and a method of injecting charge while rubbing the toner between the charge injection member and the toner carrier. Is disclosed.
Further, Patent Document 3 is provided with a supply member that is disposed opposite to a developer carrier that carries a one-component developer and supplies the developer to the developer carrier, and makes light contact with the outer peripheral surface of the supply member. There is disclosed a system in which an electrode member is provided and a developer is charged by applying a DC voltage in a direction in which the developer is pressed against the electrode member between the electrode member and the supply member.

Japanese Patent Laying-Open No. 2005-331780 (Embodiment 1, FIG. 9) JP 2006-091269 A (Embodiment 1, FIG. 4) JP 2007-164026 A (Best Mode for Carrying Out the Invention, FIG. 2)

  The problem to be solved by the present invention is to provide a developing device capable of realizing a narrow charge distribution without giving excessive stress to the toner to be developed before development, and an image forming apparatus using the developing device. is there.

  According to a first aspect of the present invention, there is provided a developing container having an opening facing an image holding body in which a two-component developer containing toner and a carrier is stored and a latent image is held, and the two-component developer is provided in the developing container. An agitating / conveying member that charges the toner by mixing and agitating the developer and conveys the two-component developer, and a two-component that is provided in the developing container opposite to the agitating / conveying member and conveyed from the agitating / conveying member A predetermined electric field for charge injection is applied between the developer conveying member that holds and conveys the developer, and the developer conveying member that is provided in the developer container so as to face the developer conveying member. A charge injection member for injecting a charge of the same polarity as the toner charging characteristics to the toner of the two-component developer on the developer conveying member, an image carrier facing the opening of the developing container, and the developer conveying member To face The toner injected by the charge injecting member is separated from the two-component developer on the developer conveying member by applying a predetermined electric field for toner separation between the developer conveying member and the developer conveying member. And a toner conveying member for holding and conveying the separated toner and for developing the latent image on the image holding member.

According to a second aspect of the present invention, in the developing device according to the first aspect, the charge injection member is disposed so as to face the developer conveying member with an interval through which one developer can pass. Developing device.
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the charge injection member is configured such that a side in contact with the developer has a resistance larger than a resistance of the developer layer on the developer transport member. The developer conveying member is configured to have a resistance smaller than that of the developer layer.
According to a fourth aspect of the present invention, in the aspect in which the carrier is a magnetic carrier in the developing device according to any one of the first to third aspects, the developer conveying member corresponds to a portion facing the toner conveying member. A developing device comprising magnetic field generating means for applying a magnetic field for attracting a carrier toward the developer conveying member.

According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the charge injection member is a developer transport member of the developer transport member rather than a portion where the developer transport member and the toner transport member are opposed to each other. The developing device is provided on the upstream side in the direction.
According to a sixth aspect of the present invention, in the developing device according to the fifth aspect, the charge injection member is provided such that the shape on the developer conveying member side is a curved surface along the outer periphery of the developer conveying member. Developing device.
According to a seventh aspect of the present invention, in the developing device according to the sixth aspect, the charge injection member also serves as a layer thickness regulating member that regulates the layer thickness of the developer on the developer conveying member to one layer. This is a developing device.

According to an eighth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, at least a part of the toner conveying member also serves as a charge injecting member, and the charge injecting member is provided to the developer conveying member. The developing device is characterized by being opposed to each other.
According to a ninth aspect of the present invention, in the developing device according to the eighth aspect, the toner conveying member is an upstream toner conveying member that also serves as a charge injection member and faces the developer conveying member, and the upstream toner conveying member. And a downstream conveying member facing the different side from the developer conveying member.
According to a tenth aspect of the present invention, in the developing device according to the ninth aspect, the rotational speed of the upstream toner conveying member is set to be higher than the rotational speed of the downstream toner conveying member. It is a developing device.
According to an eleventh aspect of the present invention, in the developing device according to any one of the eighth to tenth aspects, the developer transport member is located upstream of the developer transport direction in the developer transport member with respect to a portion where the toner transport member and the developer transport member are opposed to each other. The developing device includes a layer thickness regulating member that is provided and regulates the layer thickness of the developer on the developer conveying member to one layer.
According to a twelfth aspect of the present invention, in the developing device according to the eleventh aspect, the developing device is characterized in that a leveling member for leveling the toner layer on the charge injection member is provided at a position facing the charge injection member. Device.
According to a thirteenth aspect of the invention, there is provided an image carrier that holds a latent image, and the developing device according to any one of the first to twelfth aspects that is provided to face the image carrier. An image forming apparatus.

According to the first aspect of the present invention, compared to the case where charge injection is performed on a one-component toner, a narrow charge distribution is realized without applying excessive stress to the toner used for development before development. it can.
According to the second aspect of the present invention, the charged charge of the toner can be made to have a narrower charge distribution while stably maintaining the charge injection to the toner as compared with the case without this configuration.
According to the third aspect of the present invention, charge injection into the toner can be performed more stably than in the case where this configuration is not provided.
According to the fourth aspect of the present invention, the toner can be more easily separated from the developer than in the case where this configuration is not provided.
According to the fifth aspect of the present invention, the charge injection into the toner is more stable than in the case where the present configuration is not provided.
According to the sixth aspect of the present invention, stable charge injection can be maintained as compared with the case without this configuration.
According to the invention which concerns on Claim 7, compared with the case where it does not have this structure, an apparatus structure is simplified.
According to the invention which concerns on Claim 8, compared with the case where it does not have this structure, an apparatus structure is simplified.
According to the ninth aspect of the present invention, it is possible to secure the toner amount during development while ensuring stable toner conveyance as compared with the case where this configuration is not provided.
According to the tenth aspect of the present invention, it is possible to secure a sufficient amount of toner during development as compared with the case where this configuration is not provided.
According to the eleventh aspect of the present invention, the charged charge of the toner can be made to have a narrower charge distribution while maintaining stable charge injection into the toner as compared with the case without this configuration.
According to the twelfth aspect of the present invention, a toner layer free from carrier contamination is maintained.
According to the thirteenth aspect of the present invention, compared to a case where charge injection is performed on a one-component toner, a narrow charge distribution is realized without excessive stress applied to the toner to be developed before development. Can ensure stable image quality.

It is explanatory drawing which shows the outline | summary of embodiment of the developing device to which this invention was applied. (A) (b) is explanatory drawing which shows the aspect which actualized the outline | summary of embodiment of the developing device more, respectively. FIG. 5 is an explanatory diagram showing a state in which charge injection is performed on toner and developer, where (a) is a toner that is not a single layer, (b) is a toner restricted to a single layer, and (c) is a developer. Shows the case. 1 is an explanatory diagram illustrating an outline of an overall configuration of an image forming apparatus according to a first embodiment. FIG. 2 is an explanatory diagram illustrating an outline of the developing device according to the first embodiment. FIG. 6 is an explanatory diagram illustrating an outline of a developing device according to a second embodiment. (A) and (b) are graphs showing the results of Example 1. It is explanatory drawing which shows the charging condition with respect to the toner in a steady state, (a) is a schematic diagram, (b) is an equivalent circuit, (c) is a calculation formula. FIG. 6 is a schematic diagram illustrating a charging state with respect to a toner when a steady state is not reached. It is explanatory drawing which shows the charging condition with respect to the toner which became a pair in a steady state, (a) is a schematic diagram, (b) is an equivalent circuit, (c) is a calculation formula. FIG. 6 is a schematic diagram illustrating a charging state for a pair of toners when a steady state is not reached. (A) and (b) are graphs showing the results of Example 2. It is explanatory drawing which shows the outline | summary of the apparatus A used for the comparative example. It is explanatory drawing which shows the outline | summary of the apparatus B used for the comparative example. (A) (b) is a graph which shows the result in the high temperature, high humidity environment of a comparative example. (A) (b) is a graph which shows the result in the low temperature low humidity environment of a comparative example. 10 is a graph showing the results of Example 3. It is a graph which shows the result of Example 4.

Outline of Embodiment First, an outline of an embodiment of a developing device to which the present invention is applied will be described.
FIG. 1 shows an outline of a developing device according to an embodiment model embodying the present invention, in which a two-component developer (developer) D including a toner T and a carrier C is accommodated and a latent image is stored. A developer container 2 having an opening 2a facing the held image carrier 1 and a developer container 2 provided in the developer container 2 to charge the toner T by mixing and stirring the two-component developer D and the two-component developer An agitating and conveying member 3 that conveys D, and a developer conveying member that is provided in the developing container 2 so as to face the agitating and conveying member 3 and that holds and conveys the two-component developer D conveyed from the agitating and conveying member 3 4 and an electric field for charge injection that is provided in the developing container 2 so as to be opposed to the developer conveying member 4 and between the developer conveying member 4 and the developer conveying member 4. Toner for toner T of two-component developer D A charge injection member 5 for injecting a charge having the same polarity as the charging characteristics of the toner container, and facing the opening of the developing container 2 so as to face the image carrier 1 and the developer transport member 4. The toner T injected by the charge injection member 5 is separated from the two-component developer D on the developer conveying member 4 by applying a predetermined electric field for toner separation between the toner and the separated toner. A toner conveying member 6 that conveys the toner holding the T and is used to visualize the latent image on the image holding member 1.

Here, the developer D to be used may be a two-component developer D including the toner T and the carrier C. However, the developer D is stably transported and the toner T is easily separated from the carrier C. From the viewpoint, it is preferable to use a magnetic carrier as the carrier C.
The agitating / conveying member 3 agitates the two-component developer D containing the carrier C and the toner T to charge the toner T, and the charged toner T is adhered to the carrier C, so that the toner T is held on the carrier C. Any developer can be used as long as it can transport the developer D in a state, and a typical example is an auger. However, the present invention is not limited to this. For example, a paddle or the like may be used.

The developer conveying member 4 only needs to be capable of holding and conveying the developer D conveyed by the agitating and conveying member 3, and the surface thereof has a predetermined roughness so that the developer D can be conveyed satisfactorily. For example, it may be provided with a groove having a predetermined size.
Further, the charge injection member 5 is disposed opposite to the developer transport member 4, and an electric field for charge injection is applied between the charge injection member 5 and the developer transport member 4, thereby injecting charge into the developer D at the site. The shape and the like are not limited as long as it is performed, and it is only necessary to have a surface property that does not impair the transportability of the developer D transported on the developer transport member 4.
Further, the toner conveying member 6 separates charged toner T from the developer D on the developer conveying member 4 by applying an electric field for toner separation between the toner conveying member 4 and the developer conveying member 4, and then the separation. Any toner can be used as long as the toner T can be held and conveyed.

In such a developing device, from the viewpoint of stably maintaining the charge injection state, it is preferable that the charge injection member 5 is disposed to face the developer transport member 4 with a space through which one layer of the developer D can pass. . In this way, the charge state in the toner T is further stabilized by charge injection in a single layer state.
Further, from the viewpoint of more effectively injecting charge into the developer D, the charge injecting member 5 has a resistance whose side in contact with the developer D is higher than the resistivity of the developer layer on the developer conveying member 4. It is preferable that it is composed of a body. According to this, local electric field concentration is suppressed when an electric field for charge injection is applied to the developer D between the developer conveying member 4 and the charge injection member 5, and a wider range is achieved. A substantially uniform electric field for charge injection acts on the developer D over the entire time.

  Further, in a mode in which a magnetic carrier is used as the carrier C of the developer D, the developer transport member 4 sucks the carrier C toward the developer transport member 4 corresponding to a portion facing the toner transport member 6. It is preferable to provide magnetic field generating means 7 (see FIG. 1) for applying a magnetic field. A typical embodiment of the magnetic field generating means 7 includes a magnetic pole provided in the developer conveying member 4, but the magnetic pole is not limited to one, and a combination of a plurality of magnetic poles may be used. It suffices that the magnetic carrier C can be attracted to the developer conveying member 4 side corresponding to the facing portion between the toner conveying member 4 and the toner conveying member 6.

  As a first aspect of such a developing device, there is an aspect in which the charge injection member 5 is provided separately from the toner conveying member 6 as shown in FIG. That is, the charge injection member 5 is provided on the upstream side of the developer transport member 4 in the developer transport direction with respect to the portion where the developer transport member 4 and the toner transport member 6 are opposed to each other. Here, the charge injection member 5 may be a non-rotating mode or a rotating mode, but from the viewpoint of causing a stable electric field for charge injection to act on the developer D, An embodiment that does not rotate is preferred.

  In addition, as a preferable shape of the charge injection member 5 in the first aspect, the charge injection member 5 has a curved shape along the outer periphery of the developer transport member 4 on the developer transport member 4 side. What is provided is mentioned. In other words, for example, when the developer conveying member 4 has a roll shape, it is sufficient that the developer conveying member 4 has an arc shape that matches the roll shape, and the belt shape has a curved surface shape (curved shape). Just do it. Furthermore, from the viewpoint of simplifying the apparatus configuration, the charge injection member 5 is preferably used also as a layer thickness regulating member that regulates the layer thickness of the developer D on the developer transport member 4 to one layer. At this time, when a magnetic carrier is used as the carrier C, the layer thickness may be further restricted by making the developer D stand up by utilizing the action of the magnetic pole on the developer conveying member 4 side.

  On the other hand, as a second mode of the developing device, as shown in FIG. 2B, a mode in which the toner conveying member 6 also serves as the charge injection member 5 can be cited. In other words, at least a part of the toner transport member 6 also serves as the charge injection member 5 (6a), and the charge injection member 5 (6a) is disposed opposite to the developer transport member 4. In this case, a part of the toner transport member 6 has a function as the charge injection member 5 (6 a), and an electric field for charge injection acts between the charge injection member 5 (6 a) and the developer transport member 4. By injecting the electric charge into the developer D on the developer conveying member 4, and further applying an electric field for toner separation between the developer conveying member 4 and the developer on the developer conveying member 4. It is only necessary to have a function of separating the charged toner T from D and holding and transporting the separated toner T. In this way, an electric field for charge injection is applied between the toner conveying member 6 (part of which is the charge injecting member 5 and part of which corresponds to the toner conveying member 6 (6b)) and the developer conveying member 4. Thus, the developer D on the developer transport member 4 moves the toner T in the developer D to the toner transport member 6 side by the mirror image effect while the charge is injected.

  Further, from the viewpoint of maintaining good transportability of the toner T in the second embodiment, the toner transport member 6 includes an upstream toner transport member 6a that also serves as the charge injection member 5 and faces the developer transport member 4, and It is preferable to include a downstream conveying member 6b that faces a different side of the upstream toner conveying member 6a from the developer conveying member 4 (see FIG. 2B). In this case, the rotational speed of the upstream toner transport member 6a is preferably set to be higher than the rotational speed of the downstream toner transport member 6b. According to this, the amount of toner per unit area on the downstream toner conveying member 6b is increased, and for example, the developing density when the latent image on the image carrier 1 is visualized is increased.

  Further, from the viewpoint of stabilizing the charge injection action to the developer D, the developer is provided on the upstream side of the developer conveying direction of the developer conveying member 4 with respect to the toner conveying member 6 and the developer conveying member 4 in the developer conveying direction. It is preferable to include a layer thickness regulating member 8 that regulates the layer thickness of the developer D on the agent conveying member 4 to one layer. In the second aspect, a leveling member 9 for leveling the toner layer on the charge injection member 5 is provided at a position facing the charge injection member 5 (corresponding to a part of the toner conveying member 6). It is preferable. According to this, even if the carrier C is transported to the charge injection member 5 side, the leveling member 9 can prevent the carrier C from entering.

  In order to apply such a developing device to an image forming apparatus, the image carrier 1 that holds a latent image and the above-described developing device may be provided so as to face the image carrier 1.

Next, an operation when charge is injected into the developer D using negatively charged toner as the toner T will be described.
First, assuming that charge injection is performed on the one-component toner T instead of charge injection on the two-component developer D, the charge injection member 5 is used and the resistor 5a of the charge injection member 5 (see FIG. 3). An electric field for charge injection is applied by the voltage V ′ with the side in contact with the toner T. At this time, as shown in FIG. 3A, if the toner layer when the charge is injected is not a single layer, the electric field for charge injection acting on the toner layer is partially different, and the charge of the toner A large amount of toner of reverse polarity different from the charge is generated, or the charged toner T has a wide distribution of charge. Therefore, when development is performed using the toner T charged by such charge injection, image quality deterioration such as background fog tends to occur.

  On the other hand, as shown in FIG. 3B, when the toner layer is a single layer at the time of charge injection, unlike the case of FIG. 3A, the generation of reverse polarity toner is small and the charge distribution is charged with a narrow distribution. Therefore, the occurrence of image quality deterioration such as background fog due to development can be suppressed. However, in order to arrange the toner layer into a single layer so that such stable charging is performed, it is necessary to make the toner layer of a certain thickness thin, for example, by squeezing, and the toner layer is likely to be uneven, Further, the mechanical stress on the toner T is increased, and as a result, the toner T itself is deteriorated by peeling or embedding the external additive of the toner T, for example. For this reason, there is a risk of causing problems in transfer performance and the like.

Accordingly, the present inventors have focused on charge injection in the state of the two-component developer D so that charge injection without mechanical stress is performed on the toner T.
FIG. 3C shows a state in which charge injection is performed in the state of the two-component developer D, and the developer D is in a substantially single layer state between the developer transport member 4 and the charge injection member 5. It is sandwiched. When at least the developer conveying member 4 is moved in the direction of the arrow in such a state, the carrier C in the developer D is appropriately rotated, and the toner T held on the carrier C as the carrier C rotates. However, the contact with the surfaces of the developer conveying member 4 and the charge injection member 5 is appropriately repeated. When an electric field for charge injection is applied by the voltage V while the appropriate contact is repeated in this manner, the toner T in the developer D is stably charged to the original polarity of the toner (in this example, negatively charged), and the carrier C maintains the opposite charge to the toner T.

In this case, since the developer D is sandwiched between the developer transport member 4 and the charge injection member 5, the developer D has a substantially single layer due to the large particle diameter of the carrier C compared to the case where only the toner T is sandwiched. In addition, since the mechanical stress on the toner T is reduced, the toner T after the charge injection is less likely to generate reverse polarity toner and has a narrow charge distribution.
In such a charge injection method, if the carrier surface coverage of the toner T with the developer D (the coverage of the toner T with respect to the carrier C) is too high, the charge distribution of the injected and charged toner varies. The carrier surface coverage of toner T is preferably a value that allows toner T to maintain a single layer on the surface of carrier C (100%).

Next, the present invention will be described in more detail based on embodiments shown in the drawings.
Embodiment 1
FIG. 4 is an explanatory diagram showing a schematic configuration of the image forming apparatus 10 according to the first embodiment to which the present invention is applied as an example.
In the figure, an image forming apparatus 10 according to the present embodiment uses, for example, an electrophotographic system, and a recording material supply unit 12 that supplies a recording material is provided in the apparatus housing 11, and this recording material supply unit. An image forming unit 20 that forms an image (toner image) on the recording material supplied from 12, a fixing device 14 that fixes an unfixed toner image formed on the recording material by the image forming unit 20, and the like. The recording material that has been fixed is discharged and accommodated in a discharge accommodating portion 11 a provided on the surface of the apparatus housing 11.
In the recording material conveyance path, the recording material supplied from the recording material supply unit 12 is positioned and fixed by a positioning member 13 and a fixing device 14 which are conveyed toward the image forming unit 20 at a predetermined timing. A discharge member 15 or the like for discharging the recording material to the discharge accommodating portion 11a is provided.

  The image forming unit 20 is charged by a charging device (not shown) or a charging device that charges the photosensitive member 21 to a predetermined potential around a drum-like or belt-like photosensitive member 21 as an image holding member. An exposure device (not shown) that performs selective exposure to form a latent image on the photoreceptor 21, a development device 30 that develops the latent image formed by the exposure device using toner, and development by the development device 30 A transfer device 22 that transfers the toner image on the photosensitive member 21 onto a recording material, a cleaning device (not shown) that cleans residual toner on the photosensitive member 21 after transfer, and the like are provided.

Next, the developing device 30 of the present embodiment will be described in detail with reference to FIG.
In this figure, in the present embodiment, the charge injection member is provided separately from the toner conveying member. In other words, the developing device 30 is provided with a developing roller 32 as a toner conveying member that holds and rotates toner at an opening position facing the photosensitive member 21 in the developing container 31, and the photosensitive member 21 and the developing roller 32. A developing area for developing the latent image on the photosensitive member 21 with toner on the developing roll 32 is formed at a portion opposite to. Further, a magnet roll 33 as a developer conveying member that holds and conveys the developer is provided at a position facing the developing roll 32 behind the developing roll 32 in the developing container 31. The magnet roll 33 has a plurality of magnetic poles 34 (in this example, five, 34 a to 34 e) fixed therein, and has a developing sleeve 35 that can rotate on the surface, and the developer is supplied by the rotation of the developing sleeve 35. Transport.
The developing sleeve 35 of the present embodiment has a surface with a 10-point average roughness Rz of 5 to 15 μm, for example, in consideration of developer transportability. The developing sleeve 35 may have any shape that allows the developer to be conveyed by the rotation of the developing sleeve 35. For example, the developer may be conveyed in a grooved surface shape.

In addition, a charge injection member 36 facing the magnet roll 33 with the developer interposed therebetween is provided on the upstream side in the rotation direction of the magnet roll 33 with respect to the facing portion between the magnet roll 33 and the developing roll 32, and the shape thereof is the magnet roll 33. The side has a surface arc shape substantially along the outer periphery of the magnet roll 33. The charge injection member 36 has a resistor 36a having a volume resistivity of 10 ⁴ to 10 ¹² Ω · cm on the magnet roll 33 side, for example, by mixing carbon or metal particles as a conductive agent into urethane rubber, silicone rubber, acrylic resin, or the like. The opposite side is an electrode part 36b that supports the resistor 36a, and the electrode part 36b is fixed to the developing container 31 so that the charge injection member 36 is disposed at a stable position. Further, when the charge injection member 36 is transported by the rotation of the developing sleeve 35 with respect to the developer sandwiched between the charge injection member 36 and the developing sleeve 35, the contact surface with the developer is kept smooth. On the charge injection member 36 side, the mechanical stress applied to the developer is further reduced by preventing the transportability from being impaired.
In this embodiment, if the resistance of the charge injection member 36 is Rin, the resistance of the developing sleeve 35 is Rs1, and the resistance of the developer layer is Rdeve, it is necessary to satisfy Rs1 <Rdeve <Rin.

Here, the resistivity of the charge injection member 36 and the developer is calculated as follows.
A metal member having the same type as that of the charge injection member 36 is used, and the surface material (corresponding to the developing sleeve 35) of the magnet roll 33 is made of a metal such as an aluminum alloy or SUS. The resistance Rdeve of the developer layer is calculated from the current value when a voltage is applied with a gap interposed therebetween. In this state, the total resistance R1 is calculated from the current value when a voltage is applied by switching the metal member to the charge injection member. Next, the resistance of the charge injection member 36 is calculated by dividing the resistance Rdeve of the developer layer from the total resistance R1. Further, when a material other than metal is used as the surface material of the developing sleeve 35, the resistance can be obtained by subtracting R1 from the total resistance R2 when the material is used.

  Further, the arrangement of the magnetic pole 34 of the magnet roll 33 of the present embodiment is such that the magnetic pole 34a is provided corresponding to the entrance of the charge injection member 36 (upstream end along the rotation direction of the magnet roll 33), and the magnetic pole 34b is charged. A magnetic pole 34 c is provided at a position facing the developing roll 32, corresponding to the outlet of the injection member 36 (downstream end along the rotation direction of the magnet roll 33). Further, a repulsive magnetic field is applied between the magnetic pole 34d and the magnetic pole 34e, and the developer on the developing roll 32 is easily peeled off by the repelling magnetic field. The arrangement of the magnetic pole 34 is not limited to this, and may be selected as appropriate.

  Behind the magnet roll 33, the toner is charged by mixing and stirring the two-component developer containing the toner and the magnetic carrier, and the developer with the toner held on the carrier is supplied and conveyed to the magnet roll 33. At the same time, a pair of agitating and conveying members 37 and 38 for again agitating and conveying the developer peeled off from the magnet roll 33 is provided with a partition wall 31 a formed of a part of the developing container 31 interposed therebetween. The stirring and conveying member 37 closer to the magnet roll 33 is a supply auger that mainly supplies the developer to the magnet roll 33, and the other is an admixing auger that mainly mixes and stirs the developer. Therefore, the developer is circulated along the developer circulation path formed between the supply auger 37 and the admix auger 38 and is supplied to the magnet roll 33 as appropriate.

  In addition, a toner replenishing device 41 that replenishes toner in the developing container 31 is provided above the admixing auger 38 of the present embodiment, and replenishing toner is appropriately supplied to the admixing auger 38 side. It is like that. Further, in the present embodiment, the density sensor 42 is provided on the path side where the admix auger 38 is provided for detecting the toner density of the developer.

  In order to apply various electric fields in the developing device 30 as described above, an injection bias 43 for applying an injection electric field to the developer between the magnet roll 33 and the charge injection member 36 is provided in the present embodiment. The developing roll 32 is provided with a developing bias 44 for applying a developing electric field for developing the latent image on the photosensitive member 21 with toner. In this embodiment, the magnitude of the DC component of these biases 43 and 44 is affected by an electric field for toner separation that can separate and move the toner from the developer from the magnet roll 33 toward the developing roll 32. It is a size.

Next, the operation of such a developing device will be described.
The developer mixed and stirred by the admix auger 38 and the supply auger 37 has a structure in which the toner is held by the electrostatic force on the carrier. For example, if the toner is a negatively charged toner, the carrier is positively charged. Become. Then, the developer sufficiently mixed and stirred in this way is supplied from the supply auger 37 toward the magnet roll 33. The developer supplied to the magnet roll 33 is regulated in a state where the layer thickness is regulated in a state where the head is raised by the magnetic pole 34a at the entrance of the charge injection member 36, and the developer whose layer thickness is regulated to substantially one developer layer is a magnet. As the magnet roll 33 rotates, it moves between the roll 33 and the charge injection member 36. That is, the charge injection member 36 also serves as a developer layer thickness regulating member on the magnet roll 33.

The developer on the magnet roll 33 becomes a developer layer for one developer at the entrance of the charge injection member 36, and is then conveyed along with the rotation of the magnet roll 33. At this time, because the rotation of the magnet roll 33 and the ears are laid down between the magnetic pole 34 a and the magnetic pole 34 b, the developer passes through the gap between the charge injection member 36 and the magnet roll 33 satisfactorily. Further, at this time, since the developer is appropriately rotated and an electric field for charge injection by the injection bias 43 acts, the toner in the developer is appropriately charged and charged in advance. Is charged. In addition, since charge injection is performed in such a manner, excessive mechanical stress is not applied to the toner, and the charge distribution of the charged toner becomes narrow.
Note that the toner charged by the charge injection while passing through the portion facing the charge injection member 36 is a toner in contact with the surface of the charge injection member 36, so that the developer easily moves at the portion facing the charge injection member 36. For example, in the configuration of FIG. 5, the magnetic pole 34 a and the magnetic pole 34 b are set to have the same polarity.

In such charge injection, the toner that does not contact the charge injection member 36 may have a reverse polarity, but the moving electric field (injection bias 43 and development) from the magnet roll 33 (specifically, the developing sleeve 35) to the developing roll 32. Due to the difference of the bias 44, the reverse polarity toner is prevented from moving, and the forward polarity toner is selected and adhered to the developing roll 32.
Furthermore, there is a concern that the toner in contact with the surface of the charge injection member 36 may wrap around the surface of the developing sleeve 35 and the injected charge may be erased. However, by reducing the carrier resistance by about an order of magnitude compared to the toner, Erasure can be avoided. This is presumably because by making the resistance of the carrier sufficiently lower than that of the toner, a charge flows mainly through the carrier in the developer layer, and a large electric field does not act on the toner in the developer layer. On the other hand, when the toner is sandwiched on the charge injection member 36 side, it is blocked by the high resistance charge injection member 36 and there is no way for the charge to escape, so that a high electric field acts on the toner and the charge is injected. Conceivable.

The developer into which the charge has been injected proceeds directly to the facing portion between the magnet roll 33 and the developing roll 32, and electrostatic force acts on the facing portion due to the difference between the magnetic field by the magnetic pole 34 c and the injection bias 43 and the developing bias 44. The toner in the developer is separated from the carrier, flies to the developing roll 32 side, and is held on the developing roll 32. On the other hand, the carrier from which the toner has been separated is held and conveyed by the magnet roll 33, and then separated from the magnet roll 33 by the repulsive magnetic field formed by the magnetic pole 34 d and the magnetic pole 34 e, and is added via a part of the supply auger 37. It is returned to the mix auger 38 side.
The toner that has moved to the developing roll 32 is transported to a developing region that is a portion facing the photoconductor 21 as the developing roll 32 rotates, and the latent image on the photoconductor 21 is transferred by the toner on the developing roll 32. Developed.
On the admix auger 38 side, toner for replenishment is appropriately supplied from the toner replenishing device 41 by detecting that the density sensor 42 has a low density with respect to the developer whose density has been lowered by returning the carrier. The

In this embodiment, the leveling member is not provided for the developing roll 32. However, a leveling member for leveling the toner layer on the developing roll 32 may be newly provided. Even if the carrier is transported in addition to the toner, this leveling member prevents the carrier from being mixed. The leveling member may be disposed so as to face the developing roll 32 with a gap that prevents the carrier from passing therethrough.
In this embodiment, since the charge is injected into the toner not in the toner alone but in the developer, the mechanical stress applied to the toner is reduced. If it is too large, the toner charge distribution varies. Therefore, it is preferable that the coverage is not too large. In this case, however, the amount of toner conveyed per unit area of the magnet roll 33 may be reduced. For this, a desired toner amount may be ensured by appropriately selecting the rotation speed of the magnet roll 33 and the developing roll 32. A sufficient developing density can be secured by selecting the rotational speed of the photosensitive member 21 together.
Furthermore, in this embodiment, the rotation direction of the developing roll 32 and the photoconductor 21 is not particularly limited to the direction shown in FIG. 5 and may be selected as appropriate. Furthermore, although a monochromatic image forming apparatus is shown in the present embodiment, it goes without saying that the present invention is also applicable to a multicolor image forming apparatus.

Embodiment 2
FIG. 6 is an explanatory diagram showing an outline of the developing device 30 according to the second embodiment. Unlike the developing device 30 (see FIG. 5) of the first embodiment, the developing device 30 of the present embodiment has a configuration in which a part of the toner conveying member also serves as a charge injection member. That is, the toner conveying member also serves as the charge injection member, and the toner conveying member serves as the upstream toner conveying member (corresponding to the charge injecting member also used) and the downstream toner conveying member. Components similar to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

In the drawing, the developing device 30 of the present embodiment is provided with a rotatable charge injection member 39 disposed opposite to the developing roll 32 behind the developing roll 32 corresponding to the downstream toner conveying member. The charge injection member 39 corresponds to an upstream toner transport member.
The charge injection member 39 has a resistance layer on the surface, and this resistance layer (not shown) has the same function as the resistor 36a (see FIG. 5) of the charge injection member 36 of the first embodiment. Further, a leveling member 47 for leveling the toner layer on the charge injection member 39 is provided on the upstream side in the rotation direction of the charge injection member 39 from the portion where the charge injection member 39 faces the developing roll 32. If the carrier in the developer is transported to the charge injection member 39, the leveling member 47 prevents the carrier from being mixed.

  A magnet roll 33 disposed opposite to the charge injection member 39 is provided behind the charge injection member 39. The magnet roll 33 includes a plurality of magnetic poles 34 (34a to 34e) fixedly disposed therein, and a layer that regulates the developer layer thickness on the magnet roll 33 is provided on the surface side of the magnet roll 33 in the vicinity of the magnetic pole 34a. A developer that is provided with a thickness regulating member 48, and that has been spiked by the magnetic pole 34 a, is regulated by the layer thickness regulating member 48, so that development on the magnet roll 33 is regulated to a layer thickness approximately equivalent to one developer. The agent comes to be transported.

  In the present embodiment, an injection bias 43 for applying an electric field for charge injection to the developer is provided between the magnet roll 33 and the charge injection member 39. The charge injection member 39 and the development roll A moving bias 45 for applying a moving electric field for moving the toner from the charge injection member 39 toward the developing roll 32 is provided between the moving bias 45 and the toner. Further, a developing bias 44 is provided between the developing roll 32 and the photosensitive member 21.

The operation of the developing device 30 having such a configuration will be described.
The developer supplied to the magnet roll 33 from the supply auger 37 is regulated to substantially one developer by the layer thickness regulating member 48 in the state where the head is raised by the magnetic pole 34 a, and the layer thickness is regulated on the magnet roll 33. The developed developer is conveyed. When the developer whose layer thickness is regulated reaches the facing portion between the magnet roll 33 and the charge injection member 39, the charge is injected by the injection bias 43.
At the opposite portion, the developer sandwiched between the magnet roll 33 and the charge injection member 39 is appropriately rotated, and the toner in the developer appropriately contacts the charge injection member 39 so that the toner is desired. The toner in the developer is charged with a predetermined charge amount.
Further, in this opposite portion, the toner in the developer is attracted to the charge injection member 39 side by the mirror image force by the injection bias 43, while the carrier is attracted to the magnet roll 33 side by the magnetic pole 34c of the magnet roll 33. Only the toner is easily separated from the toner and moves to the charge injection member 39 side.
On the other hand, the carrier from which the toner is separated is peeled off from the magnet roll 33 and returned to the admixing auger 38.

  The toner that has moved to the charge injection member 39 is transported as the charge injection member 39 rotates, and reaches the opposite portion between the charge injection member 39 and the developing roll 33. Here, the toner on the charge injection member 39 is moved to the developing roll 32 by the moving bias 45, and is conveyed to the developing area which is the opposite portion of the developing roll 32 and the photosensitive member 21 as the developing roll 32 rotates. The latent image of the body 21 is developed.

Also in the present embodiment, the charge in the developer state is injected between the magnet roll 33 and the charge injection member 39, and charging with a narrow charge distribution is performed without applying excessive mechanical stress to the toner. Become so.
In the present embodiment, the charge injection member 39 is in the form of a roll. However, for example, it may be in the form of a belt. In this case, the portion facing the magnet roll 33 can be set longer. become.

Example 1
In this example, the developing device of the first embodiment is used, a voltage of 1000 V is applied between the charge injection member and the development sleeve, and the charge amount of the toner before and after passing through the charge injection member is evaluated. The toner was peeled off from the developer before passing through and the developer after passing through, respectively, and the charge amount of the toner was measured. In this embodiment, the charge injection member has an average thickness of 6 mm and a resistance of 5.2 × 10 ¹⁰ Ω, and the developer layer passing through the charge injection member has a thickness of 0.05 mm and a resistance of 4.8 ×. 10 ⁹ Ω, the developing sleeve (corresponding to the surface of the developer conveying member) was made of an aluminum alloy.
As a result, as shown in FIG. 7, the distribution of the charge amount is wide before passing through the charge injection member, the average charge amount is −14.7 μC / g, WST (Wrong Sign Toner: the original polarity of the toner) The amount of reverse polarity toner) was 1.8 wt%.
On the other hand, after passing through the charge injection member, as shown in FIG. 7B, the distribution of the charge amount was narrower than before the passage, the average charge amount was −12 μC / g, and the WST amount was 0.83 wt%. .
According to this, by using the charge injection member of the present application and performing charge injection in the developer state, the toner charge distribution is narrowed and WST is also greatly reduced.

FIGS. 8A and 8B illustrate the charging state of the toner in a single layer state. FIG. 8 illustrates a state in which the toner starts to be charged and reaches a steady state. FIG. 8A is a schematic diagram, and FIG. (C) is an equation for calculating the charge amount of the toner.
As shown in (a), assuming that the injection bias is applied in a state where the toner is sandwiched between the resistor of the charge injection member and the conductor (approximate to the configuration including the carrier), as shown in (b) Approximate to equivalent circuit. Here, the capacitance C1 and the contact resistance R1 are related to the contact portion between the toner and the conductor, while the capacitance C2 and the contact resistance R2 are related to the contact portion between the toner and the resistor. Further, assuming that the resistance of the resistor is R3 and the partial pressure of each resistor at the boundary of the toner is V1, V2, and V3, the charge amount Q1 of the capacitance C1 at the boundary between the toner and the conductor is Q1 = C1V1, On the other hand, the charge amount of the capacitor C2 at the boundary between the toner and the resistor is Q2 = C2 (V2 + V3).
Here, the charge amount of the toner is Q1−Q2, and is obtained from the value of C1V1−C2 (V2 + V3). By transforming this equation, the polarity of the toner can be determined by the value of {C1R1-C2 (R2 + R3)}.
Accordingly, by sufficiently increasing R3 so that C1R1 <C2 (R2 + R3), the charge amount of the toner becomes negative. If R3 is small, the contact resistance is unstable, so that it is difficult to stably charge the toner.

Although FIG. 8 shows the steady state, the model shown in FIG. 9 can be considered when the charging time during charging is short and the steady state is not reached.
Even in such a case, if the resistance R3 of the resistor is sufficiently larger than the contact resistances R1 and R2 (R3 >>R2> R1), the toner can be charged to a desired polarity. In the example, negative charge is injected into the toner, and the charge amount of the toner becomes negative.

On the other hand, FIG. 10 illustrates the charging state of the toner when two toners are connected in the direction of the electric field, and shows the state when the toner starts to be charged and reaches a steady state. Schematic diagram, (b) shows (a) as an equivalent circuit, and (c) shows an equation for calculating the charge amount of toner.
Assuming that two toners are connected along the direction of the electric field as shown in (a), it is necessary to consider the factors of the capacitance C4 and the contact resistance R4 between the toners. In this case, as shown in (c), the charge polarity of the toner 1 on the conductor side is obtained from the value of (C1R1-C4R4), while the charge polarity of the toner 2 on the resistor side is {C4R4-C2 (R2 + R3)} Is determined by the value of.
Generally, R1 <R4 with respect to the charge amount of the toner 1 and tends to be negative. Further, the charge amount of the toner 2 becomes negative by setting R3 sufficiently large so that R4 <(R2 + R3). That is, in the steady state, the charge amount of any toner is negative.

  If the charging time during charging is short and does not reach a steady state, a model as shown in FIG. 11 is conceivable. In such a case, one may be a forward polarity toner (for example, toner 1) and the other may be a reverse polarity toner (for example, toner 2). When the two toners have different charges as described above, positive and negative charges are attracted to each other, and an attached pair is easily formed. When the negative charge is large due to the positive and negative charge balance of the toner in such a paired state, the toner is transferred to the developing roll, and is subjected to the development, and the pair is separated at the developing portion, so that the toner of reverse polarity is applied to the background portion. May adhere and cause fogging. Therefore, it is preferable that the toners are dispersed one by one before passing through the portion facing the charge injection member.

As the toner used for such charge injection, those utilizing electric field dependency are suitable, and known electric field dependent toners are used, and for example, those described in JP-A-2005-70677 are applied.
Also, the carrier generally has a tendency that its resistance depends on the electric field. If a carrier having a low resistance of about one digit is selected under one condition of the electric field to be used, the magnitude relationship of the resistance can be obtained. The concern of reversal is resolved.
The volume resistivity of such a toner or carrier is determined by, for example, placing a toner to be measured in a cylindrical container having a diameter of 10 mm and applying a load of 9.8 N / cm ² on the packed toner. An electrode is arranged on the bottom surface, and a current value when a voltage is applied so that an electric field of 1 kV / cm is generated between both electrodes is obtained. This measurement is performed under conditions of a temperature of 22 ± 2 ° C. and a humidity of 55 ± 10% RH.
The toner used in this example was 1.5 × 10 ¹⁰ Ω · cm, and the carrier was 5.3 × 10 ⁸ Ω · cm.

Example 2
In this example, the development device of the first embodiment was used, and the change in the toner conveyance amount and the change in the background fog when the continuous printing was repeated were evaluated and confirmed.
There were two types of toner, the following charge injection type toner, toner A having a particle diameter of 6 μm and toner B having a particle diameter of 8 μm.
The running condition as a test condition is to print 1000 sheets per day with an output image with an image density of about 5%, at the start of the first run (RunStart), at the start of the day (DayStart), and at the end of the day At each time (DayEnd), a print sample was taken, and the toner transport amount at this time was measured (a method of sucking a fixed area and capturing it with a filter).
Furthermore, the environmental conditions of running were made into two conditions, high temperature high humidity conditions (28 degreeC85% RH) and low temperature low humidity conditions (10 degreeC30% RH).

  As for the toner transport amount, the weight per unit area of the toner layered on the developing roll was measured. Incidentally, as the reference amount, a toner transport amount of at least about 3 is required as a toner transport amount for supplying a toner amount necessary for the developing density including the speed ratio of the developing roll to the photosensitive member. Further, the background fog of the print sample was visually evaluated, and was evaluated at five stages.

As shown in FIG. 12A, the toner conveyance amount is not affected by the environmental conditions in any toner, and the toner A is constant at about 4.8 g / m ² and the toner B is about 3.8 g. It remained constant at / m ² . In other words, it has been found that the toner conveyance amount is not influenced by environmental conditions, and varies slightly depending on the type of toner.
Further, as shown in FIG. 12B, the background fog is at a level where there is no practical problem as long as it is 2 or less. It turns out that there is no problem.
For this reason, since no background fog was confirmed in both toner A and toner B, it was also confirmed that there was no problem with this toner conveyance amount.

Comparative Example Here, in order to confirm the effectiveness of the present application, a comparative evaluation was performed using a conventional developing device.
The developing devices used were device A shown in FIG. 13 and device B shown in FIG.
FIG. 13 shows the apparatus A, which is provided with a developing roll 102 that is spaced apart from the photoconductor 101 and rotates in different directions at the facing portion. Further, a toner supply roll 103 that supplies toner to the developing roll 102 is provided behind the developing roll 102, and the toner on the developing roll 102 is charged by being rubbed while being rubbed between the two. It will be a thing. Further, the layer thickness of the toner on the developing roll 102 is regulated by a layer thickness regulating member 105, and the toner layer having the regulated layer thickness on the developing roll 102 is a developing region where the developing roll 102 and the photosensitive member 101 are opposed to each other. It is conveyed to. Then, the developing bias 106 applied between the developing roll 102 and the photoconductor 101 causes the toner to visualize the latent image on the photoconductor 101. An agitator 104 is provided behind the toner supply roll 103, and the toner is supplied to the toner supply roll 103 side by the rotation of the agitator 104.

Here, the detailed conditions in this apparatus A are as follows.
Gap between the photoreceptor and the developing roll: 250 μm, speed of the photoreceptor: 200 mm / sec, speed of the developing roll: 1.5 times the speed of the photoreceptor, charging potential of the photoreceptor: about −500 V, exposure potential of the photoreceptor : About −150 V, development bias: Vpp = 1.9 kV, f = 3.2 kHz rectangular wave, V _DC = −410 V, linear pressure during layer regulation: 50 g / cm.

FIG. 14 shows the apparatus B, which is different from the apparatus A (see FIG. 13) in the rotation direction of the developing roll 102 and the layer thickness regulating member 107. The same components as those in the apparatus A are denoted by the same reference numerals, and detailed description thereof will be omitted.
In the same figure, the toner supply roll 103 and the developing roll 102 rotate in different directions at opposite portions, and the toner moves from the toner supply roll 103 to the developing roll 102. At this time, the toner is sufficiently charged, and the toner layer whose layer thickness is regulated by the layer thickness regulating member 107 reaches the development region. Then, the latent image on the photoconductor 101 is visualized with toner in a developing area where the photoconductor 101 and the developing roller 102 are rotated in the same direction at the opposite portions.
Further, detailed conditions in the device B are the same as those in the device A, and therefore will be omitted.

Using such apparatus A and apparatus B, the same evaluation confirmation as in Example 2 was performed.
The running environmental conditions were two conditions: a high temperature and high humidity condition (28 ° C., 85% RH) and a low temperature and low humidity condition (10 ° C., 30% RH).
FIG. 15 shows the result at high temperature and high humidity. As shown in FIG. 15A, the toner conveyance amount is different from the combination of the apparatus B and the toner A as shown in FIG. It became about 10 g / m ² by running. At this time, in other combinations, the toner conveyance amount was approximately 3 to 4 g / m ² .
Further, as shown in (b), the background fogging was poor from the beginning with the combination of the apparatus B and the toner A, and became worse as the toner conveyance amount increased. Further, in the combination of the apparatus B and the toner B, the background fog deteriorated in the RunEnd from the second day to the third day and the fourth day. In the combination of the apparatus B and the toner B, the toner conveyance amount tends to slightly increase in accordance with the deterioration time of the background fog. And there was no problem in particular about the combination with the apparatus A other than that.

  FIG. 16 shows the result at low temperature and low humidity. As with the result at high temperature and high humidity, the combination of the apparatus B and the toner A has a large amount of toner conveyance, and the background fog tends to deteriorate. confirmed. Further, in the combination of the apparatus B and the toner B, the toner conveyance amount is slightly larger than that at the time of high temperature and high humidity, and the background fog has been maintained at three levels. Note that no particular problem was found with other combinations with the device A.

  From the above, it has been confirmed that in the configuration of the conventional developing device, the influence on the toner is greatly different depending on the machine difference of the device itself rather than the type of toner. This is presumed that the toner transport amount and the background fog are affected differently by the difference in toner behavior between the developing roll and the toner supply roll.

Example 3
In this embodiment, running is performed in a high temperature and high humidity state in order to confirm the state of toner alteration in the developing device when a large amount of printing is performed. The running of 4000 sheets was performed using the combination of the apparatus of Embodiment 1 and toner A, and the change in transfer rate was evaluated and confirmed.
At this time, the combination of the apparatus A and the toner A was also evaluated for comparison.
As a result, as shown in FIG. 17, in this example, the transfer rate was maintained at about 86% even after running from about 91% to 4000 sheets in the initial stage. It was greatly reduced to about 77%.
It is estimated as follows that the transfer rate decreases due to running. In other words, if the printing is repeated, the inside of the developing device becomes in a high throughput state, the mechanical stress on the toner increases, and the toner external additive, for example, the transfer auxiliary external additive is embedded in the toner, and the transfer auxiliary effect is reduced. By doing.
Therefore, in the comparative example, the mechanical stress on the toner is large and the transfer rate is reduced, but in this example, since the decrease in the transfer rate is suppressed, the mechanical stress applied to the toner in the developing device is small. Is understood.

Example 4
Generally, it is sufficient that the toner transport amount at the time of charge injection satisfies the reference amount (reference transport amount). However, if the toner transport amount is too large, the toner is not sufficiently charged and WST increases. Easily fogging.
Therefore, in order to confirm what happens to the WST when the toner transport amount is too large, it is applied to a developing device that uses a charge injection type toner to inject charge into the toner, and the toner transport amount and the WST occurrence rate Confirmed the relationship.
As a result, as shown in FIG. 18, if the toner conveyance amount is close to the reference conveyance amount, the WST occurrence rate is less than 5%, but as the toner conveyance amount increases, the WST occurrence rate increases linearly. Was confirmed. In other words, by suppressing the toner conveyance amount to the reference conveyance amount, charging with a small WST and a narrow charge distribution is performed.
Furthermore, here, evaluation was also performed by changing the applied voltage. The difference in reference numerals in the figure shows an example in which the applied voltage at the time of charge injection is changed, and the magnitude of the applied voltage is in the order of ◯ <□ <Δ.
As a result, if the toner conveyance amount is close to the reference conveyance amount, the occurrence of WST is small, and it is not greatly affected by the applied voltage, but if the toner conveyance amount greatly exceeds the reference conveyance amount, the occurrence of WST increases, It was confirmed that the generation rate of WST also changes depending on the applied voltage.

  DESCRIPTION OF SYMBOLS 1 ... Image holding body, 2 ... Developing container, 2a ... Opening, 3 ... Agitation conveyance member, 4 ... Developer conveyance member, 5 ... Charge injection member, 6 ... Toner conveyance member, 7 ... Magnetic field generation means, 8 ... Layer thickness Restricting member, 9 ... Leveling member, D ... Developer, T ... Toner, C ... Carrier

Claims (13)

A developing container having an opening facing an image holding body in which a two-component developer containing toner and a carrier is contained and a latent image is held;
An agitating and conveying member that is provided in the developing container, charges the toner by mixing and agitating the two-component developer, and conveys the two-component developer; and
A developer conveying member that is provided in the developing container opposite to the agitating and conveying member and holds and conveys the two-component developer conveyed from the agitating and conveying member;
The toner of the two-component developer on the developer conveying member provided in the developing container opposite to the developer conveying member and by applying a predetermined electric field for charge injection between the developer conveying member and the developer conveying member. A charge injection member for injecting a charge having the same polarity as the charging characteristics of the toner,
Facing the opening of the developer container and facing the image carrier and the developer transport member, the developer transport is performed by applying a predetermined electric field for toner separation between the developer transport member and the developer transport member. A toner conveying member for separating toner injected by a charge injecting member from a two-component developer on the member, holding and conveying the separated toner, and developing a latent image on the image holding member When,
A developing device comprising: The developing device according to claim 1,
The developing device according to claim 1, wherein the charge injection member is disposed opposite to the developer conveying member with a space through which a single layer of developer can pass. The developing device according to claim 1 or 2,
The charge injection member is configured such that the side in contact with the developer has a resistance greater than the resistance of the developer layer on the developer transport member,
The developing device, wherein the developer conveying member is configured to have a resistance smaller than a resistance of the developer layer. In the aspect in which the carrier is a magnetic carrier in the developing device according to claim 1,
The developing device, wherein the developer conveying member includes a magnetic field generating unit that applies a magnetic field that attracts the carrier toward the developer conveying member corresponding to a portion facing the toner conveying member. The developing device according to any one of claims 1 to 4,
The developing device according to claim 1, wherein the charge injection member is provided on the upstream side of the developer conveying member in the developer conveying direction with respect to a portion where the developer conveying member and the toner conveying member are opposed to each other. The developing device according to claim 5, wherein
The developing device according to claim 1, wherein the charge injection member is provided with a curved shape along the outer periphery of the developer conveying member. The developing device according to claim 6.
The developing device according to claim 1, wherein the charge injection member also serves as a layer thickness regulating member that regulates the layer thickness of the developer on the developer conveying member to one layer. The developing device according to any one of claims 1 to 4,
The developing device according to claim 1, wherein at least a part of the toner conveying member also serves as a charge injection member, and the charge injection member is disposed opposite to the developer conveying member. The developing device according to claim 8, wherein
The toner conveying member includes an upstream toner conveying member that also serves as a charge injection member and faces the developer conveying member, and a downstream conveying member that faces a different side of the upstream toner conveying member from the developer conveying member. A developing device. The developing device according to claim 9, wherein
The developing device according to claim 1, wherein the rotation speed of the upstream toner conveyance member is set to be higher than the rotation speed of the downstream toner conveyance member. The developing device according to any one of claims 8 to 10,
A layer thickness that is provided on the upstream side of the developer conveying direction of the developer conveying member with respect to a portion where the toner conveying member and the developer conveying member are opposed to each other and restricts the layer thickness of the developer on the developer conveying member to one layer. A developing device comprising a regulating member. The developing device according to claim 11, wherein
A developing device comprising a leveling member for leveling a toner layer on the charge injection member at a position facing the charge injection member. An image carrier for holding a latent image;
The developing device according to any one of claims 1 to 12, provided to face the image carrier,
An image forming apparatus comprising:

Images