JP2007147915A - Developing device, imaging cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a developing device having constitution, capable of delaying deterioration of a developer and thereby maintaining the image quality with time passage, by preventing the formation of a staying part of the developer at the entrance part into a doctor gap and making the stress on the developer reduced. <P>SOLUTION: The developing device 4, using a two-component developer comprising toner and carrier and being capable of developing an electrostatic latent image formed on an image carrier 1 by the toner in the developer to visualize the image, includes a developer carrier 41 for carrying the developer and a developer quantity regulation member 47, arranged so as to be separated from the developer carrier 41 through a prescribed gap (doctor gap). The developer quantity regulation member 47 has a function of regulating the quantity of the developer pumped up from the image carrier 41 and an elastic member 52 is arranged at the entrance side of the developer with respect to a gap of a proximity part between the developer carrier 41 and the developer quantity regulation member 47. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus applied to a copying machine, a printer, a plotter, a facsimile machine, a printing machine, or a composite machine thereof, and more particularly to an image using a two-component developer composed of a toner and a carrier. The present invention relates to a developing device that visualizes an electrostatic latent image formed on a carrier as a toner image, an image forming cartridge using the developing device, and an image forming apparatus.

  2. Description of the Related Art A developing device used in an image forming apparatus such as a copying machine or a printer using an electrophotographic system often uses a two-component developer composed of a toner and a carrier. In an image forming apparatus using a two-component developer, only toner is consumed when a toner image is formed. Therefore, in order to continue to form a good image, it is necessary to replenish new toner as much as the consumed toner, and always keep the toner concentration of the developer contained in the developing device at an appropriate level. The developer is a developer amount regulating member while being agitated and mixed with the toner replenished from the toner cartridge by the agitating and conveying member such as a screw while being conveyed onto the developing roller as the developer carrying member and being held on the developing roller. After the developer amount and the layer thickness are regulated by a doctor blade or the like, the developer is conveyed to a development area facing the image carrier. The toner is brought into contact with and rubbed with the carrier by friction and agitation by mixing / mixing and the layer thickness regulation until it is conveyed to the development area, so that a predetermined charge amount is secured. Movement (development) to (for example, a photoreceptor) is possible.

  Developers are stressed by agitation / mixing / conveying, layer thickness regulation, etc., but if this stress is continued after long-term use, the charging ability and fluidity of the developer will change, resulting in deterioration of image quality and instability. become. In other words, when stress is applied to the developer, toner additive detachment, toner additive embedding, carrier coat layer film scraping, spent, etc. occur, the toner charge amount becomes unstable, and the developer durability is also improved. descend.

In an image forming apparatus that performs magnetic brush development using a two-component developer, inorganic fine particles such as silica and titanium oxide are added as external additives to the toner used. Such an external additive improves the fluidity of the toner, improves the dispersibility of the replenished toner and the charge rising property, and is effective in reducing toner scattering and maintaining good image quality.
As described above, inorganic fine particles such as silica and titanium oxide added to the toner in order to maintain good image quality are vulnerable to mechanical stress and thermal stress. For this reason, a phenomenon in which the external additive is embedded in the toner or detached from the toner surface is likely to occur due to stirring and mixing in the developing device. In order to maintain the stability and durability of the toner charge amount when such an external additive is used, it is desired to reduce the stress applied to the developer. Further, even when inorganic fine particles such as silica and titanium oxide are not used as external additives, the same phenomenon occurs to some extent, so that it is desired to reduce the stress applied to the developer.

Here, in the prior art described in Patent Document 1 (Japanese Patent Laid-Open No. 5-035067), immediately upstream of a regulating member (doctor blade) provided for regulating the layer thickness of the developer supplied to the developing region. In addition, a cylindrical developer conveying member that is constantly rotated while maintaining a constant distance from the developing sleeve is provided. This configuration eliminates the developer clogging in the developer regulating portion by the doctor blade or the developer staying in front of the doctor blade, thereby enabling stable image formation without density unevenness. .
However, in such a configuration, there is a region where the developer is clogged between the doctor blade and the developing roller as the developer carrying member, similarly to the known configuration in which two doctor blades are installed as a pre-doctor. ing. Therefore, the developer is clogged and stays between the doctor blade and the developing roller due to environmental fluctuations, change in developer fluidity over time, and the like. Therefore, in this configuration, the staying developer cannot be completely eliminated, and there is a problem that the configuration becomes complicated.

Therefore, in the prior art described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-302250), in an image forming apparatus that performs magnetic brush development, development with a developer carrier with respect to a developer layer thickness regulating member (doctor blade). In order to reduce the stress applied to the developer in the developer retention layer that occurs in the vicinity of the upstream side in the developer transport direction, and to improve the stability of the toner charge amount and the durability of the developer. By defining the range of the developer staying in front of the blade relative to the developing sleeve, the stress on the developer can be reduced, and as a result, the durability of the developer can be improved. Yes.
However, in the prior art described in Patent Document 1, the hardness of the member before the doctor blade is not defined. Therefore, when the member surface in front of the doctor blade is hard, the stress applied locally to the developer cannot be absorbed or released, and there is a problem that the stress reducing action is insufficient.

JP-A-5-035067 JP 2004-302250 A

If there is a space at a position where the developer enters a gap (called a doctor gap) where the developer carrier of the developing device and the developer amount regulating member (doctor blade) are close to each other, the developer stays there. There is a case. The developer staying in such a manner cannot contribute to the development, and accelerates the deterioration of the entire developer. As a countermeasure to this problem, there is a method of filling the space with a member so that the developer does not stay in the developer entrance portion of the doctor blade.
However, when the member is hard, it acts in a direction that suppresses the movement of the developer, and thus stress on the developer is often increased. When the developer is stressed in such a manner, developer deterioration such as liberation of additives and scraping of the coat layer of the carrier occurs, which adversely affects image quality.

  The present invention has been made in view of the above circumstances, and without causing a developer retaining portion at the entrance to the doctor gap, and simultaneously reducing the stress on the developer, thereby delaying the deterioration of the developer, Accordingly, it is an object of the present invention to provide a developing device having a configuration capable of maintaining image quality over time, an image forming cartridge using the developing device, and an image forming apparatus.

In order to achieve the above object, the present invention employs the following technical means.
The first means of the present invention uses a two-component developer comprising a toner and a carrier, and develops the electrostatic latent image formed on the image carrier with the developer toner to make a visible image. In the apparatus, the apparatus includes a developer carrying member that carries and conveys the developer, and a developer amount regulating member that is disposed with a predetermined gap (hereinafter referred to as a gap) from the developer carrying member, The developer amount regulating member has a function of regulating the amount of developer pumped up by the developer carrying member, and the developer amount regulating member has a function of the gap between adjacent portions of the developer carrying member and the developer amount regulating member. An elastic member is provided on the side where the developer enters (claim 1).

  According to a second means of the present invention, in the developing device of the first means, the developer carrying member includes a cylindrical developing sleeve constituting a surface layer and a plurality of magnetic poles fixedly arranged inside the developing sleeve. A developing roller comprising a magnet body or a plurality of magnets, wherein the developer amount regulating member is a doctor blade that regulates the amount of developer pumped up by the developing sleeve of the developing roller, The elastic member is provided on the side where the developer enters the gap between the sleeve and the vicinity of the doctor blade (claim 2).

A third means of the present invention is characterized in that, in the developing device of the first or second means, the elastic member has a shape having a dent (claim 3).
According to a fourth means of the present invention, in the developing device of the third means, the position of the recess of the elastic member is a plurality of magnetic poles or a plurality of magnets existing in the developing sleeve. It is made to correspond with the peak position of the magnetic force which adjoins to an elastic member.

  According to a fifth aspect of the present invention, there is provided an image forming cartridge mounted on the image forming apparatus, which includes at least an image carrier and a developing device of any one of the first to fourth means to form an image. It is provided detachably with respect to the apparatus main body (Claim 5).

The sixth means of the present invention is an image forming apparatus comprising: an image carrier; and a developing device that develops the electrostatic latent image formed on the image carrier with a developer to visualize the image. The developing device includes a developing device of any one of first to fourth means (claim 6).
According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier; and a developing device that develops the electrostatic latent image formed on the image carrier with a developer to visualize the image. The image forming cartridge of the fifth means is provided (claim 7).

In the developing device of the present invention, the elastic member is the side where the developer enters the gap between the adjacent portions of the developer carrier (developing roller) and the developer amount regulating member (doctor blade), that is, the doctor blade. Since it is installed in the space portion existing in front, it is possible to prevent the developer that stays in the position in front of the doctor blade from being generated. Thereby, all the developers can contribute to the development.
In the developing device of the present invention, since the member installed in front of the doctor blade is an elastic material, it is possible to efficiently absorb or disperse locally generated pressure (stress) on the developer. Therefore, it is possible to reduce the stress applied to the developer, to reduce the deterioration of the developer such as the liberation of additives caused by the stress and the abrasion of the carrier coat layer, and to maintain good image quality over time. it can.

  Further, in the present invention, the elastic member has a shape having a recess, and the position of the recess is a magnetic force close to the elastic member among the magnetic forces of the plurality of magnetic poles or the plurality of magnets existing inside the developing sleeve. By matching with the peak position, it is possible to create a space where the developer is more susceptible to stress, where the developer is more susceptible to stress, and where the developer circulation is smoother, and it is possible to further prevent developer retention and stress. it can.

  The image forming cartridge of the present invention includes at least an image carrier and a developing device of any one of the first to fourth means, and is detachably attached to the image forming apparatus main body. And replacement at the time of failure can be facilitated, and workability can be greatly improved.

The image forming apparatus of the present invention can maintain good image quality over time by including the developing device of any one of the first to fourth means as the developing device.
In addition, the image forming apparatus of the present invention includes the image forming cartridge, so that good image quality can be maintained over time, and maintenance and replacement of the image forming unit are easy.

Hereinafter, the configuration, operation, and effects of the present invention will be described in detail with reference to the drawings.
First, FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus including a developing device according to the present invention, and only a configuration example of an image forming unit (printer unit) is shown. When the image forming apparatus 20 is a copying machine, a facsimile machine, a multifunction machine, or the like, a document reading device (scanner) that reads a document image is added to the upper part of the main body.

  In FIG. 1, reference numeral 1 denotes a drum-shaped photoconductor as an image carrier, and an electrostatic latent image is formed on the surface of the photoconductor 1 by charging by the charging device 2 and optical writing according to image information by the optical writing device 3. Is formed. The developing device 4 is a developing device using a two-component developer composed of a toner and a carrier. The developer is carried and conveyed by a developing roller 41 which is a developer carrying member, and an electrostatic latent image formed on the photoreceptor 1 is formed. The toner is developed with toner to form a visible image. In addition to the charging device 2 and the optical writing device 3, the image forming apparatus 20 includes a transfer device 5 that transfers a toner image on the photoreceptor 1 to a transfer material P such as recording paper, and a cleaning that cleans the surface of the photoreceptor after transfer. An apparatus 6; a charge eliminating device 7 for removing residual charges on the surface of the photoconductor; a fixing device 8 for fixing an image after transfer onto a transfer material P such as recording paper; and a paper discharge roller for discharging the transfer material P after fixing. 15 and a paper discharge tray 16 on which the discharged transfer material P is stocked. In addition, the image forming apparatus 20 transfers multi-stage sheet feeding cassettes 9-1 and 9-2 each containing a transfer material P such as recording paper, and one sheet at a time from each of the sheet feeding cassettes 9-1 and 9-2. The transfer material P selectively fed from one of the paper feed roller 10 and the separation roller pair 11 for feeding the material P and the multistage paper feed cassettes 9-1 and 9-2 is conveyed. Conveying rollers 12 and 13 and a registration roller 14 for feeding the transfer material P to a transfer portion between the photosensitive member 1 and the transfer device 5 in synchronization with image formation are provided.

  Inside the casing 40 constituting the developing device 4, there are provided a developing roller 41 and conveying screws 44 and 45 having spiral fins as developer conveying members for conveying the developer in the device to the developing roller 41. The conveying screws 44 and 45 are respectively rotated in the directions of the arrows in the figure, and a developer containing a mixture of toner and carrier is contained in these portions. On the right side of the partition plate 46 in the drawing, the developer is transported, for example, from the back side to the front side in the drawing, and on the left side of the partition plate 46, the developer is transported from the near side to the back side. A portion without a central partition plate 46 is provided on the back side and the front side, and the developer is stirred and mixed while being circulated by the conveying screws 44 and 45.

  The developing roller 41 includes a developing sleeve 42 in which a nonmagnetic material is formed in a cylindrical shape and a magnet body (magnet roller) 43 (or a plurality of magnets) magnetized with a plurality of magnetic poles. A magnet roller 43 (or a plurality of magnets) is fixedly arranged. The developer that is stirred and mixed while being circulated by the conveying screws 44 and 45 is magnetically attracted by the magnetic force of the magnet roller 43 (or a plurality of magnets) in the developing roller 41 and is shown in the drawing of the developing sleeve 42. Along with the rotation in the direction of the arrow, it is carried and conveyed by unevenness (not shown) provided on the surface of the developing sleeve. The developer carried and transported by the developing sleeve 42 is transported to a developing region facing the photoreceptor 1 after the developer amount and the layer thickness are regulated by a doctor blade 47 which is a developer amount regulating member. The upper electrostatic latent image is developed with toner in the developer.

Here, only the toner adheres to the electrostatic latent image on the photosensitive member 1, and the toner that has not been developed and the carrier that has transported the toner are again agitated and conveyed in the developing device as the developing sleeve 42 rotates. It is carried to the department and released.
Further, in order to keep the amount of toner in the developer circulating in the developing device constant, the amount of toner used for development is replenished from the toner cartridge 49 by a toner replenishing device (not shown).

  Reference numeral 48 in the figure denotes a toner concentration sensor, which is a sensor that detects the toner concentration in the developer by measuring the magnetic permeability of the developer inside the developing device 4. A control unit (not shown) of the image forming apparatus detects the toner density based on the fluctuation of the detection output of the toner density sensor 48, and maintains a constant toner density in the developer inside the developing device 4. The toner is replenished by the toner replenishing device. However, since the magnetic permeability of the two-component developer fluctuates due to environmental changes, changes in the developer bulk density, and the like, the output target value of the toner concentration sensor 48 is corrected as appropriate. Specifically, a control unit (not shown) of the image forming apparatus converts the image density of a reference toner image formed on the photoreceptor 1 into an optical device composed of a light source (such as a light emitting diode) and a light receiving element (such as a photodiode). An image density sensor (not shown) of the equation is used for measurement, and the output target value of the toner density sensor 48 is corrected according to the output result of the image density sensor.

  The toner image developed on the photoreceptor 1 is selectively fed and transported from one of the multi-stage sheet cassettes 9-1 and 9-2, and is registered between the photoreceptor 1 and the transfer device 5 by the registration roller 14. The unfixed toner image on the transfer material P after the transfer is transferred onto the upper surface of the transfer material P sent to the transfer portion in between, and is fixed by the heating roller 8a, the pressure roller 8b, etc. of the fixing device 8. Then, the transfer material P after fixing is stocked on the paper discharge tray 16 by the paper discharge roller 15. Further, the residual toner on the surface of the photoconductor after the image transfer is removed by the cleaning device 6, and the residual charge on the surface of the photoconductor is removed by the static eliminator 7.

  The toner cartridge 49 contains toner, and the toner replenishing device operates only when a toner replenishment signal is received from the toner density sensor 48, and the toner in the toner cartridge 49 is placed on the developer in the casing 40 (conveying screw). 44 top).

  The above is an example of the configuration and operation of the developing device 4 according to the present invention and the image forming apparatus 20 including the developing device 4. In the image forming apparatus according to the present invention, at least a photoconductor that is an image carrier. 1 and an image forming cartridge (also referred to as a process cartridge) 30 incorporating the developing device 4 are used. For example, in the example of FIG. 1, the photosensitive member 1, the charging device 2, the developing device 4, the cleaning device 6, and the charge eliminating device 7 are built in one image forming cartridge 30, and the image forming cartridge 30 is formed on the image forming apparatus main body 20. The image unit is detachably provided. As described above, the constituent members of the image forming unit are built in the image forming cartridge 30 and are detachably attached to the image forming unit of the image forming apparatus main body 20, thereby facilitating maintenance and replacement in the event of a failure. Can greatly improve the performance. In other words, when a failure or failure occurs in the constituent members of the image forming unit, it is often difficult for a service person to repair on site, and the image forming apparatus cannot be used. However, by using the image forming cartridge 30 described above, when a failure or malfunction occurs, it is only necessary to replace the image forming cartridge with a new image forming cartridge, and the image forming apparatus can be used immediately. Also, by storing a spare image forming cartridge, the user can easily perform the replacement work without calling a service person. In addition, the used image forming cartridge can be reused by returning it to the factory for maintenance, and is excellent in recyclability.

As described above, the present invention relates to an electrophotographic image forming apparatus using the two-component developing type developing device 4. However, the developing device 4 has the following problems.
FIG. 2 shows a schematic view of a part of the developing device. A developing sleeve 42 of a developing roller 41, which is a developer carrying member, is disposed with a suitable gap with respect to the photosensitive member 1, which is an image carrier that carries an electrostatic latent image. Inside the developing sleeve 42, a magnet body (magnet roller) having a plurality of magnetic poles or a plurality of magnets are fixedly arranged, and the developer 50, which is a mixture of toner and carrier, is applied to the developing sleeve by the magnetic force. 42 is adsorbed on the surface. The developing sleeve 42 rotates in the direction of the broken line arrow shown in FIG. 2, and the developer 50 is conveyed to the developing gap formed by the gap between the photosensitive member 1 and the developing sleeve 42, and development is performed. In the conveyance process by the developing sleeve 42, the developer 50 is regulated to an appropriate amount by the doctor blade 47 which is a developer amount regulating member, and is conveyed to the development gap.

  In the developing device 4 having such a configuration, the developer 50 stays in front of the doctor blade 47, and a part thereof passes through the gap (doctor gap) between the developing sleeve 42 and the doctor blade 47. For this reason, there is a problem that the developer 51 that stays as shown by the dashed ellipse in FIG. 2 is inevitably generated. As a result, the developer 51 staying in this way cannot contribute to the development and loses its function.

  Therefore, in the present invention, the developing device having the above-described configuration is improved, and the developer is deteriorated by reducing the stress on the developer at the same time without creating the developer retaining portion at the entrance portion to the doctor gap. In order to maintain the image quality over time. Hereinafter, specific examples of the developing device according to the present invention will be described.

FIG. 3 is a schematic view of a main part of a developing device showing an embodiment of the present invention. In the present embodiment, as shown in FIG. 3, the space where the developer 50 enters the developing sleeve 42 of the developing roller 41 and the doctor gap in the vicinity of the doctor blade 47, that is, the space in front of the doctor blade 47. The elastic member 52 was installed in the part. More specifically, the elastic member 52 is fixed to the doctor blade 47 by adhesion or the like so as to fill a space where the developer in front of the doctor blade 47 is likely to stay.
Thereby, all the developers 50 can be contributed to development, without producing the stagnant developer 51 as shown in FIG. Further, the elastic member 52 is used as the member to be installed in the space portion, so that the stress applied to the developer 50 can be reduced, and the developer such as liberation of the additive generated by the stress and scraping of the carrier coat layer can be reduced. Deterioration can be reduced.

  Next, FIG. 4 is a schematic view of the essential portions of a developing apparatus showing another embodiment of the present invention. In the present embodiment, the elastic member 52 shown in FIG. 3 is improved, and the elastic member 52 installed in the above-described space is provided with a dent as shown in FIG. The position of this indentation coincides with the peak position of the magnetic force close to the elastic member 52 among the magnetic forces of the plurality of magnetic poles or the plurality of magnets existing inside the developing sleeve 42. Thus, by matching the position of the indentation with the peak position of the magnetic force close to the elastic member, a space where the magnetic force is stronger and the developer 50 is subject to stress is created, and the developer 50 is smoothly circulated. It is possible to prevent stagnation and stress of the developer 50.

With the above configuration, the developer 50 is transported to the developing region without generating a developer that stays in front of the doctor blade 47 while the developer 50 is being transported by the developing sleeve 42 and without increasing stress. Therefore, the stress applied to the developer 50 can be reduced, the deterioration of the developer such as the liberation of additives caused by the stress and the abrasion of the carrier coat layer can be reduced, and good image quality can be maintained over time. be able to.
In the image forming apparatus of the present invention, since the developing device having the configuration shown in FIG. 3 or 4 is provided as the developing device, good image quality can be maintained over time.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus including a developing device according to the present invention. It is a principal part schematic diagram for demonstrating the subject of the image development apparatus concerning this invention. 1 is a schematic view of a main part of a developing device showing an embodiment of the present invention. It is a principal part schematic of the image development apparatus which shows another Example of this invention.

Explanation of symbols

1: Photoconductor (image carrier)
2: Charging device 3: Optical writing device 4: Developing device 5: Transfer device 6: Cleaning device 7: Static eliminating device 8: Fixing device 9-1, 9-2: Paper feed cassette 10: Paper feed roller 11: Separating roller pair 12, 13: Conveyance roller 14: Registration roller 15: Paper discharge roller 16: Paper discharge tray 20: Image forming apparatus 30: Image forming cartridge (process cartridge)
40: casing 41: developing roller (developer carrier)
42: Developing sleeve 43: Magnet roller 44, 45: Conveying screw 46: Partition plate 47: Doctor blade (developer amount regulating member)
48: toner density sensor 49: toner cartridge 50: developer 51: stagnant developer 52: elastic member

Claims (7)

In a developing device that uses a two-component developer composed of a toner and a carrier and develops the electrostatic latent image formed on the image carrier with the toner of the developer to make a visible image,
A developer carrying member that carries and conveys the developer, and a developer amount regulating member that is installed with a predetermined gap (hereinafter referred to as a gap) from the developer carrying member;
The developer amount regulating member has a function of regulating the amount of developer pumped up by the developer carrier.
A developing device, wherein an elastic member is provided on a side where the developer enters a gap between adjacent portions of the developer carrying member and the developer amount regulating member. The developing device according to claim 1,
The developer carrying member is a developing roller comprising a cylindrical developing sleeve constituting a surface layer, and a magnet body having a plurality of magnetic poles fixedly arranged inside the developing sleeve or a plurality of magnets,
The developer amount regulating member is a doctor blade that regulates the amount of developer pumped up by the developing sleeve of the developing roller,
2. A developing apparatus according to claim 1, wherein said elastic member is disposed on a side where developer enters a gap between adjacent portions of said developing sleeve and said doctor blade. The developing device according to claim 1 or 2,
The developing device according to claim 1, wherein the elastic member has a concave shape. The developing device according to claim 3.
The developing device according to claim 1, wherein a position of the recess of the elastic member is made to coincide with a peak position of a magnetic force close to the elastic member among magnetic forces of a plurality of magnetic poles or a plurality of magnets existing inside the developing sleeve. An image forming cartridge attached to the image forming apparatus,
An image forming cartridge comprising at least an image carrier and the developing device according to claim 1, wherein the image forming cartridge is provided detachably with respect to a main body of the image forming apparatus. In an image forming apparatus comprising: an image carrier; and a developing device that develops the electrostatic latent image formed on the image carrier with a developer to visualize the image.
An image forming apparatus comprising the developing device according to claim 1 as the developing device. In an image forming apparatus comprising: an image carrier; and a developing device that develops the electrostatic latent image formed on the image carrier with a developer to visualize the image.
An image forming apparatus comprising the image forming cartridge according to claim 5.

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