JP2007328056A - Development device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize development property as well as to stably maintain a developer transport rate over a long period of time by regulating the thickness of a developer layer after development on a developer carrier on which a two-component developer is carried and transported. <P>SOLUTION: A development device is composed of: a developer carrier 2 having a rotatable development sleeve 3 capable of carrying a developer on a surface thereof and a magnet body 4 having a plurality of fixedly arranged magnetic poles including at least adjacent repelling magnetic poles m1, m2 of the same polarity within the development sleeve 3; a pre-development layer thickness regulating member 5 disposed apart from the developer carrier 2 on an upstream side of a development area in a developer transport direction of the developer carrier 2 and on a downstream side of a developer detachment portion from the developer carrier 2 by the repelling magnetic poles m1, m2 to regulate the thickness of a developer layer on the developer carrier 2 before development; and a post-development layer thickness regulating member 6 for regulating the thickness of a developer layer on the developer carrier 2 after development within a thickness smaller than the thickness of the developer layer regulated by the pre-development layer thickness regulating member 5 on a downstream side of the development area and on an upstream side of the detachment portion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, and more particularly to a developing device in which a two-component developer containing toner and a carrier is used and an image forming apparatus using the developing device.

  In general, in a developing system using a two-component developer (developer) including a toner and a carrier as a developing device used in an image forming apparatus such as an electrophotographic system, a developer carrier and an image carrier such as a photoconductor are opposed to each other. Before the development, which is provided with a predetermined gap from the developer carrier on the upstream side of the developer carrying direction on the developer carrier with a predetermined gap from the development region, which is a region, to regulate the layer thickness of the developer on the developer carrier Many layer thickness regulating members are used, and a device for maintaining a stable developer amount in the development region has been devised.

Further, when the developer is peeled off (pick-off) from the developer carrying member after the development is performed in this manner, those utilizing a repulsive magnetic pole are often used. Such a method using a repulsive magnetic pole has an advantage that it can be peeled while minimizing the deterioration of the developer as compared with the forced peeling method using a scraper or the like.
Furthermore, due to the recent demand for higher image quality, there has also been proposed a system that uses a spherical carrier instead of a conventional amorphous carrier such as a ferrite carrier as a developer carrier (see Patent Document 1). When a spherical carrier is used, stable layer thickness regulation on the developer carrying member is performed by the pre-development layer thickness regulating member, the development characteristics become stable, and the deterioration of the toner adhering to the carrier is suppressed. This also has the advantage that the life of the developer itself can be extended.

Japanese Patent Laid-Open No. 11-24406 (Example) Japanese Patent Laid-Open No. 11-7199 (Embodiment of the Invention, FIGS. 1 and 7)

However, when the repulsive magnetic pole is used, in the vicinity of the upstream magnetic pole (pick-off magnetic pole) of the repulsive magnetic pole, a force that prevents the developer conveyed by the developer carrying member from entering the repulsive magnetic field is applied. Therefore, stagnation of the developer is likely to occur due to the developer that is to be transported to the pick-off site and the developer that is to be returned by the force that prevents entry into the repulsive magnetic field before the pick-off site (the site to be picked off). This stagnation not only causes the developer peeling operation to become unstable, but also causes a slip phenomenon between the developer carrying member and the developer. Deterioration of the agent also occurs.
In particular, when a spherical carrier is used, the developer conveyance holding force by the developer carrying member is weakened, so that the force for conveying the developer to the pick-off site is reduced, and the above stagnation is more likely to occur. . Therefore, when a spherical carrier is used, it is necessary to further suppress stagnation on the upstream side of the pick-off site as compared with the case where a conventional ferrite carrier is used.

  On the other hand, a proposal of a method for improving developer peeling at a pick-off site is also known (see, for example, Patent Document 2). In Patent Document 2, a member having a guide surface and a guide surface for guiding and guiding the developer is arranged on the developer carrier before and after the pick-off magnetic pole, and the developer guided on the guide surface is picked off. A method is described in which good separation is achieved even with a developer having poor fluidity by being guided by a guide surface provided at a predetermined position after the magnetic pole.

However, the prior art described in Patent Document 2 has a technical problem to be solved that the developer having poor fluidity is difficult to peel from the developer carrier in the repulsive magnetic pole method. In addition, the guide surface and the guide surface merely assist the developer peeling action. For this reason, this technology does not solve the stagnation of the developer.For example, if the amount of the returned developer increases, there is a suspicion that the stagnation of the developer occurs between the developer carrier and the guide surface. There is a possibility that the problems associated with the problem cannot be solved completely.
Therefore, in the two-component development system, the amount of developer conveyed by the developer carrier after development and the influence of the repulsive magnetic field are taken into consideration, and the stagnation of the developer on the front side of the pick-off site is prevented to prevent the pick-off site. Ensuring good transportability of the developer to the surface is a major issue.

  The present invention is for solving such technical problems, and by regulating the developer layer thickness after development of the developer carrier on which the two-component developer is carried and conveyed, the developer conveyance amount The present invention provides a developing device and an image forming apparatus using the same, which stably maintain the toner for a long time and stabilize the developing characteristics.

  That is, according to the present invention, as shown in FIG. 1, a two-component developer (developer) including a toner and a carrier that is disposed opposite to the image carrier 1 is carried and conveyed. In the developing device that visualizes the image, a plurality of developing sleeves 3 that can carry a developer on the surface and that can rotate are provided, and at least a plurality of repulsive magnetic poles m1 and m2 of the same polarity adjacent to the inside of the developing sleeve 3 are included. Developer carrier 2 having a magnet body 4 with fixedly arranged magnetic poles, and a developer carrying body 2 upstream of the developer carrying direction of the developer carrier 2 with respect to the developing region of the opposite area between the developer carrier 2 and the image carrier 1. Further, on the downstream side of the developer peeling portion from the developer carrier 2 by the repelling magnetic poles m1 and m2, the developer layer thickness on the developer carrier 2 before development is set apart from the developer carrier 2 by being spaced apart from the developer carrier 2. From the pre-development layer thickness regulating member 5 to be regulated and the development area The developer layer thickness on the developer carrier 2 after development is regulated by a layer thickness smaller than the developer layer thickness regulated by the pre-development layer thickness regulating member 5 on the flow side and upstream from the peeling site. The post-development layer thickness regulating member 6 is provided. Here, FIG. 1 is a schematic view showing the present invention, and the present invention is not limited to the embodiment shown in FIG.

In such technical means, as the developing sleeve 3 of the developer carrier 2, a non-magnetic one is usually used from the viewpoint of effectively applying the magnetic action of the magnet body 4. Further, the rotation directions of the developer carrier 2 and the image carrier 1 may be the same direction (With direction) at the opposite portion or the opposite direction (Against direction).
The pre-development layer thickness regulating member 5 may be any member that is set with a predetermined gap with respect to the developer carrier 2 and can secure an appropriate amount of developer to the development region.
The post-development layer thickness regulating member 6 is not particularly limited in terms of rigidity, elasticity, and the like, but is preferably a flexible member having flexibility from the viewpoint of responding to changes in the developer amount after development.

The post-development layer thickness regulating member 6 in the present invention regulates the thickness of the developer layer on the developer carrier 2 after development, whereby the amount of developer conveyed to the developer peeling site (pick-off site). Can be suppressed to an appropriate amount, and it is possible to suppress the occurrence of developer stagnation that is likely to occur in the vicinity of the pick-off magnetic pole (the magnetic pole m1 upstream of the repulsive magnetic poles m1 and m2). The agent can be stably conveyed. If there is no restriction on the layer thickness of the developer after development, the developer is returned and transported by the action of returning the developer due to the repulsive magnetic field generated by the repulsive magnetic poles m1 and m2 in the vicinity of the pickoff magnetic pole m1. Stagnation occurs between the developing developer and the returned developer.
On the other hand, in the present invention, the developer amount that leads to the occurrence of stagnation is limited by the post-development layer thickness regulating member 6, so that the stagnation of the developer occurs in combination with the decrease in the amount of developer returned by the repulsive magnetic field. Can be reduced.
Therefore, the sliding of the developer with respect to the developer carrier 2 can be reduced, and stable development characteristics can be maintained over a long period. Further, since the developer layer thickness regulated by the post-development layer thickness regulating member 6 is made smaller than the layer thickness regulated by the pre-development layer thickness regulating member 5, the amount of developer on the developer carrier 2 changes. Even in this case, the developer can be stably conveyed to the pick-off site.

Further, the post-development layer thickness regulating member 6 of the present invention is flexibly provided in such a manner that the downstream side of the member 6 is narrower than the upstream side of the member 6 by being bent in the developer transport direction with respect to the developer carrier 2. In this case, even if the amount of developer on the developer carrier 2 changes, it is possible to maintain a uniform layer thickness regulating effect, which is stable over a long period of time. Development characteristics can be maintained.
Furthermore, from the viewpoint of maintaining a stable shape with respect to the developer carrier 2, the flexible member is supported at the upstream end by the developer housing 2 and the developer housing in which the developer is accommodated. It is preferable to be provided so as to project on the body 2 side in a convex shape. Further, it is preferable that the surface of the flexible member facing the developer carrying member 2 is subjected to a treatment for reducing the frictional force with the developer. Can be avoided, the deterioration of the developer can be suppressed, and the transportability of the developer can be kept good. In addition, as a process which reduces a frictional force, the aspect which provides a mold release process layer is mentioned, for example.

In the present invention, it is preferable to use a carrier having a shape factor SF-1 of 120 or less as the developer carrier. By using such a so-called spherical carrier, for example, by the pre-development layer thickness regulating member 5 The developer layer thickness on the developer carrier 2 can be easily stabilized, the development characteristics can be stabilized, and the life of the developer can be extended. At this time, the shape factor SF-1 is calculated as follows. When the maximum absolute length in the projected image of the carrier is ML and the projected image area of the carrier is A, SF-1 = (π / 4) × (ML ² / A) × 100.
And in order to produce such a carrier, it is preferable that the carrier has a configuration in which a magnetic material and a binder resin are dispersed and mixed. Thus, by using a carrier that is dispersed and mixed, The fluidity of the developer increases and the life of the developer can be improved. In addition, “having a configuration in which a magnetic substance and a binder resin are dispersed and mixed” means that the magnetic substance and the resin are dispersed and mixed, pulverized and classified, produced by a polymerization method, and a resin is applied to a porous magnetic substance. What was impregnated etc. are mentioned.
Further, the carrier preferably has a low magnetic force of 30 to 60 emu / g in a magnetic field of 1000 Oe, and has a strong magnetic force per carrier having a specific gravity of 3.0 to 4.0. When the thickness is small, the impact force of the developer on the surface of the developer carrier 2 can be reduced, and sliding wear due to the sliding of the developer can be further suppressed.

  The present invention is not limited to the above-described developing device, and is also intended for an image forming apparatus using these developing devices. In this case, an image carrier 1 on which an electrostatic latent image is formed and supported; What is necessary is just to provide the above-mentioned developing device.

According to the developing device of the present invention, a two-component developer including a toner and a carrier that is disposed opposite to the image carrier and carrying and conveying the latent image on the image carrier is visualized. A developer carrying body having a developing sleeve and a magnet body in which a plurality of magnetic poles including a repulsive magnetic pole of the same polarity adjacent to the inside of the developing sleeve are fixed; and upstream of the developing region and the repelling magnetic pole A developing layer thickness regulating member for regulating the thickness of the developer layer on the developer carrying body before development on the downstream side from the developer peeling site from the developer carrying body, and the downstream side of the development area and the peeling site A post-development layer thickness regulating member that regulates the developer layer thickness on the developer carrier after development at a layer thickness smaller than the developer layer thickness regulated by the pre-development layer thickness regulating member on the upstream side Development after development Developer on carrier is satisfactorily conveyed to the peeling site (pickoff site), it is possible to suppress the stagnation of occurrence of the developer. Therefore, sliding wear due to the developer on the developer carrying member is reduced, and deterioration of the developer is suppressed, and stable development characteristics can be maintained over a long period of time.
Further, by using such a developing device, it is possible to provide an image forming apparatus in which the developer transport amount is stable, the deterioration of the developer can be suppressed, and a stable image can be obtained over a long period of time. It becomes possible.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 2 shows an embodiment of an image forming apparatus including a developing device to which the present invention is applied. In the figure, reference numeral 21 denotes a photoconductor as an image carrier that rotates in the direction of the arrow and includes a photosensitive layer made of an organic photoconductive layer on the surface. The photoconductor 21 is charged by a charger 22 such as a charging roll. The electrostatic latent image is written by the exposure device 23 such as a laser writing device. The written electrostatic latent image is formed as a potential image based on the contrast with the high potential portion not exposed to light, because the surface potential of the exposed portion of the photoreceptor 21 is lowered.

  Further, the developing device 30 disposed facing the photoconductor 21 accommodates a toner that is colored particles and a two-component developer (developer) including a carrier that carries and transports the toner in a developing housing 31. A developer is carried on a developing roll 32 as a developer carrying member, and a developing bias from a bias power source (not shown) is applied to the developing roll 32, so that the developing roll 32 side is set as a high potential portion of an electrostatic latent image. The image portion of the electrostatic latent image on the photosensitive member 21 is developed with the charged toner in the developer while being held at an intermediate potential with respect to the low potential portion.

Further, a transfer device 24 is provided around the photoconductor 21, and this transfer device 24 is constituted by, for example, a transfer roll arranged in pressure contact with the photoconductor 21, and the toner on the photoconductor 21 by a bias power source (not shown). The toner image developed on the photoreceptor 21 is transferred to the recording material 26 by applying a transfer bias in a direction that attracts the image to the recording material 26 side. Furthermore, the toner remaining on the photosensitive member 21 after the transfer is removed by, for example, a doctor blade type cleaner 25.
In this embodiment, the recording material 26 onto which the toner image on the photosensitive member 21 is transferred is conveyed to a fixing device 50, and the toner image on the recording material 26 is fixed by the fixing device 50. As the fixing device 50, for example, a heat roll method is adopted, which includes a heating roll 51 and a pressure roll 52, and a toner image is obtained by passing the recording material 26 between the heating roll 51 and the pressure roll 52. Is fixed to the recording material 26.

As shown in FIG. 3, the developing device 30 in the present embodiment has a developing housing 31 that opens toward the photosensitive member 21, and a developing roll 32 is disposed facing the opening of the developing housing 31. A trimmer 33 is provided as a pre-development layer thickness regulating member that regulates the layer thickness of the developer on the development roll 32 before development at a position above the development roll 32 and close to the development roll 32.
Further, behind the developing roll 32 in the developing housing 31, the auger 34 (34a, 34b) as an agitating member that charges the developer while agitating and conveying the developer and supplies the developer to the developing roll 32 side. Is provided. In the auger 34 according to the present embodiment, a supply auger 34a that mainly supplies developer to the developing roll 32 is disposed on the developing roll 32 side, and the supply auger 34a includes a part of the developing housing 31 behind the supply auger 34a. An admixing auger 34b that mainly mixes and agitates the developer is provided through the partition wall 31a (performed through the passages of the partition walls 31a provided near both ends of the auger). .

  The developing roll 32 according to the present embodiment is rotatably provided with a nonmagnetic developing sleeve 32a that is blasted so that the surface thereof has a predetermined uneven surface that allows the developer to be conveyed, and the inside of the developing sleeve 32a. A magnet roll 32b is provided as a magnet body in which five magnetic poles are fixedly arranged. Further, the magnetic pole in the magnet roll 32b is provided with an S1 magnetic pole as a developing magnetic pole at a position facing the photoconductor 21, the N1 magnetic pole as a conveying magnetic pole downstream from the S1 magnetic pole, and the repulsive magnetic pole downstream from the N1 magnetic pole. An S2 magnetic pole (S2 magnetic pole acts as a pick-off magnetic pole) and an S3 magnetic pole (S3 magnetic pole acts as a pick-up magnetic pole) are provided, and an N2 magnetic pole as a trimmer magnetic pole is disposed at a position substantially opposite to the trimmer 33. ing. Note that the magnetic pole arrangement is not limited to this, and may be appropriately selected as long as it has a repulsive magnetic pole.

  In particular, in the present embodiment, a layer thickness regulating member 35 that regulates the layer thickness of the developer on the developing roll 32 is provided in the vicinity of the S2 magnetic pole of the pickoff magnetic pole. The layer thickness regulating member 35 is made of, for example, a flexible non-magnetic stainless thin plate, one end side of which is fixed to the developing housing 31 and is provided in a state of being bent convexly with respect to the developing roll 32. In the vicinity of the S2 magnetic pole, the developer roll 32 is contacted with no developer. For this reason, the developer layer thickness regulated on the developing roll 32 is smaller than the developer layer thickness regulated by the trimmer gap (the gap between the trimmer 33 and the developing roll 32). The layer thickness regulating member 35 is preferably a non-magnetic material from the viewpoint of effectively regulating the developer layer thickness, and may be a metal material such as stainless steel. A rubber sheet such as a sheet may be used. Furthermore, it is also possible to use a resin-based sheet such as a polyester sheet.

Further, as the developer in the present embodiment, for example, a polymerization carrier is used as a carrier, and a spherical carrier having a shape factor SF-1 of 115 is used. Here, the shape factor is calculated by the above-described SF-1 = (π / 4) × (ML ² / A) × 100. The absolute maximum length ML of the carrier and the projected image area A of the carrier are optical values. A carrier image magnified by a magnification of 500 times is photographed using a microscope, and the obtained image information can be obtained from an image analysis result introduced into, for example, an image analysis apparatus (LUZEXIII) manufactured by Nireco Corporation via an interface. . The shape factor SF-1 is preferably an average value obtained by measuring 1000 randomly sampled carriers.
The magnetization intensity of the used carrier is 60 emu / g (2.4π × 10 ⁻⁵ Wb · m / kg) at a magnetic field of 1000 Oe {10 ⁶ / (4π) (A / m)}. )Met.

Next, the operation of the developing device 30 will be described. In FIG. 3, the developer charged by the auger 34 is supplied onto the developing roll 32 by the action of the supply auger 34a and the action of the pickup magnetic pole (S3 magnetic pole) of the developing roll 32. The developer supplied to the developing roll 32 (specifically, the developing sleeve 32a) moved with the rotation of the developing roll 32, and spiked by the action of the N2 magnetic pole of the magnet roll 32b at the position of the trimmer 33. The magnetic brush is regulated to a predetermined layer thickness by a trimmer gap. The developer restricted to the predetermined layer thickness is developed by the action of a developing bias (not shown) in the developing region, which is a region where the developing roll 32 and the photosensitive member 21 are opposed to each other. The electrostatic latent image on the photoconductor 21 is visualized. The developer whose toner has been reduced after the development is moved on the developing roll 32 as the developing roll 32 is rotated, is transported toward the S2 magnetic pole beyond the N1 magnetic pole, and the S2 magnetic pole and the S3 magnetic pole are repelled. The magnetic field is picked off from the developing roll 32.
Then, the developer picked off from the developing roll 32 is mixed and stirred by the auger 34, adjusted to a predetermined toner concentration and charge amount, and again used for development.

In such a developer flow on the developing roll 32, the pick-off is performed on the upstream side of the pick-off portion (located between the S2 magnetic pole and the S3 magnetic pole) due to the influence of the magnetic field lines due to the repulsive magnetic pole (S2 magnetic pole, S3 magnetic pole). A force that prevents the developer from entering the region acts.
FIG. 4A shows a situation in which the stagnation of the developer in the vicinity of the S2 magnetic pole occurs when the layer thickness regulating member 35 is not provided as in the present embodiment. The developing roll 32 is affected by the lines of magnetic force. The developer transportability due to the toner is impaired, and the developer stagnation is likely to occur. In particular, when a spherical carrier is used as the developer carrier, the developer conveying force due to the unevenness on the surface of the developing roll 32 is smaller than when a normal ferrite carrier is used, and the magnetization strength per carrier is also increased. If it is small, the force in the direction of pressing the developer against the developing roll becomes small, so that the developer conveying force is further reduced. For this reason, the amount of developer conveyed to the pick-off site is small, while the amount of developer to be returned by the repulsive magnetic field relatively increases, and the developer stagnation tends to occur more easily.

For this phenomenon, in this embodiment, as shown in FIG. 4B, a layer thickness regulating member 35 for regulating the developer layer thickness on the developer carrier after development is arranged. Therefore, by regulating the thickness of the developer layer at this portion, the developer is surely transported, and the amount of developer to be returned by the repulsive magnetic pole (S2 magnetic pole and S3 magnetic pole) is also reduced. As a result, the occurrence of stagnation can be suppressed.
Further, by controlling with the layer thickness regulating member 35, a force to be pressed against the developing roll 32 side acts on the developer. As a result, a sufficient transport force for transporting in the direction of the pick-off site is ensured, and stable developer transportability can be maintained. Then, the developer conveyed by the developing roll 32 is picked off from the developing roll 32 at the pick-off site, and is collected by the auger 34, so that the developer on the developing roll 32 can be exchanged satisfactorily. become.

  Further, by using the layer thickness regulating member 35, for example, even if the developer characteristics change due to environmental changes or changes with time, and the amount of developer on the developing roll 32 changes, the developer by the layer thickness regulating member 35 changes to the developer. The effect of regulating the layer thickness is stably exhibited. In particular, by using a flexible member as the layer thickness regulating member 35, the layer thickness regulating member 35 itself can follow the change in the developer amount and can perform stable layer thickness regulation. .

  In such a system using a repulsive magnetic pole, the location where the developer is likely to stagnate slightly changes depending on the magnetic pole arrangement of the repulsive magnetic pole and the strength of the magnetic pole. For this reason, the layer thickness regulating member 35 may be provided at a stagnation place near the S2 magnetic pole. In order to cause the developer to reach the layer thickness regulating member 35 smoothly and to have an effective layer thickness regulating effect, the gap between the upstream end of the layer thickness regulating member 35 and the developing roll 32 is separated from the trimmer 33 and the development. The gap is preferably wider than the gap with the roll 32, and the gap is not particularly limited as long as the conveyance of the developer is not impaired.

  In the present embodiment, the layer thickness regulating member 35 is configured such that no processing is performed on the member surface. For example, as shown in FIG. 5, at least the surface of the layer thickness regulating member 35 on the developing roll 32 side has a fluorine resin or the like. The coating layer 35a may be applied. In this case, the friction force between the layer thickness regulating member 35 and the developer is reduced by the coating layer 35a, and the layer thickness regulating member 35 against the developer on the developing roll 32 is reduced. This prevents the developer transportability from being reduced by the frictional force. In addition, the developer can be prevented from being deteriorated due to the friction between the layer thickness regulating member 35 and the developer. If the frictional force between the layer thickness regulating member 35 and the developer is large, the frictional force acts in a direction that impairs the developer conveying force by the developing roll 32, and the developer stagnation is likely to occur at this portion. There is a risk that the deterioration of the developer or the developer may progress. Needless to say, the layer thickness regulating member 35 itself may be made of a material having a small frictional resistance with the developer without providing the coating layer 35a.

Although the layer thickness regulating member 35 of the present embodiment is a flexible member, it may be configured as shown in FIG. 6, for example.
In the drawing, the layer thickness regulating member 35 is made of a rigid member formed in a slightly arc shape, for example, and has a fulcrum 36 on a surface different from the developing roll 32 side. This fulcrum 36 may be constituted by, for example, the developing housing 31 or may be made by another method. In addition, a spring 37 having one end fixed to the developing housing 31 is brought into contact with, for example, the vicinity of the end of the surface of the layer thickness regulating member 35 on the developing roll 32 side. The thickness regulating member 35 is pressed against the developing roll 32 side.
According to such a configuration, an effective layer thickness regulating effect can be applied to the developer on the developing roll 32, and the layer thickness regulating member can be applied to changes in the developer amount on the developing roll 32. The function as 35 can be effectively functioned. Note that other elastic means may be used instead of the spring 37, and any method may be used as long as the layer thickness regulating member 35 is biased toward the developing roll 32.

As a developer suitable for this embodiment, if the shape factor SF-1 is 120 or less, an effective action by the layer thickness regulating member 35 functions. The specific gravity of the carrier is 3.0 to 4.0, and the magnetization intensity is 30 to 60 emu / g (1.2π) in a magnetic field of 1000 oe {10 ⁶ / 4π (A / m)}. If it is -2.4 (pi) * 10 < ^-5 > Wb * m / kg), it will show the same effect | action.
If the shape factor SF-1 is too large, the flow of the developer by the layer thickness regulating member 35 may be impaired, or the developer may be easily deteriorated. On the other hand, if the magnetization strength per carrier is too large, the impact force that the developer gives to the surface of the developing roll 32 becomes strong, and the developing roll 32 is easily damaged. The transportability of the is deteriorated.

  Furthermore, by arranging such a layer thickness regulating member 35, the strength of the pick-off magnetic pole can be made weaker than usual. This is because the effect that the developer is pressed against the developing roll 32 by the layer thickness regulating member 35 also acts, so that the developer easily reaches the pick-off portion, and even if the pick-off magnetic pole is reduced, the developer is sufficiently moved to the pick-off portion. This is because of the arrival of. For this reason, the occurrence of stagnation of the developer is further reduced.

Furthermore, in the present embodiment, the configuration in which the trimmer 33 in the developing device 30 is disposed above the developing roll 32 and the developer conveying direction on the developing roll 32 is counterclockwise is shown. The developing device 30 may be configured such that 33 is disposed below the developing roll 32 and the developer transport path on the developing roll 32 is configured to be clockwise.
In the present embodiment, a monochromatic image forming apparatus is shown. However, a plurality of developing devices 30 according to the present embodiment may be provided, for example, a full color image forming apparatus.

It is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention. 1 is an explanatory diagram showing an embodiment of an image forming apparatus to which the present invention is applied. It is explanatory drawing which shows the developing device of embodiment. (A) (b) is explanatory drawing which shows the effect | action of a layer thickness control member, (a) shows the case where a layer thickness control member is provided, (b) shows the case where a layer thickness control member is provided. It is explanatory drawing which shows the modification of a layer thickness control member. It is explanatory drawing which shows the modification of the attachment method of a layer thickness control member.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Developer carrier, 3 ... Developing sleeve, 4 ... Magnet body, 5 ... Pre-development layer thickness regulation member, 6 ... Post-development layer thickness regulation member, m1, m2 ... Repulsive magnetic pole

Claims (8)

In a developing device arranged to face an image carrier and carrying and transporting a two-component developer including a toner and a carrier to visualize an electrostatic latent image on the image carrier,
A developer carrying device having a developing sleeve capable of carrying a developer on its surface and a rotatable developing sleeve, and a magnet body in which a plurality of magnetic poles including repulsive magnetic poles of the same polarity adjacent to each other are fixedly arranged inside the developing sleeve. Body,
The developer on the upstream side of the developer carrying direction of the developer carrying body from the developing area of the opposed area between the developer carrying body and the image carrying body and on the downstream side of the developer peeling site from the developer carrying body by the repulsive magnetic pole. A pre-development layer thickness regulating member that is spaced apart from the carrier and regulates the developer layer thickness on the developer carrier before development;
The developer layer thickness on the developer carrier after development at a layer thickness smaller than the developer layer thickness regulated by the pre-development layer thickness regulating member on the downstream side from the development region and the upstream side from the peeling site. And a post-development layer thickness restricting member for restricting the development. The developing device according to claim 1,
The post-development layer thickness regulating member is formed of a flexible member that is bent in the developer transport direction with respect to the developer carrying member so that the downstream side is narrower than the upstream side of the member. A developing device. The developing device according to claim 2, wherein
The developing device is characterized in that the flexible member is provided so that a developer housing and a developing housing in which the developer is accommodated are supported at one end on the upstream side so as to project in a convex manner toward the developer bearing member. The developing device according to claim 2, wherein
A developing device characterized in that a surface of the flexible member facing the developer carrying member is subjected to a treatment for reducing a frictional force with the developer. The developing device according to claim 1,
The developing device according to claim 1, wherein the carrier has a shape factor SF-1 of 120 or less. The developing device according to claim 1,
The developing device according to claim 1, wherein the carrier has a configuration in which a magnetic material and a binder resin are dispersed and mixed. The developing device according to claim 5, wherein
2. A developing apparatus according to claim 1, wherein the carrier has a low magnetic force of 30 to 60 emu / g in magnetization at a magnetic field of 1000 Oe. An image carrier on which an electrostatic latent image is formed and carried;
An image forming apparatus comprising: the developing device according to claim 1.

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