JP3920845B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus, and more particularly to toner replenishment for a two-component developer.

In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine, an electrostatic latent image formed on a photosensitive member that is a latent image carrier is subjected to visible image processing with a developer.
As the developer, there are a two-component developer obtained by mixing a toner and a carrier, and a one-component developer containing no carrier.
As a configuration of a developing device using a two-component developer, there is a configuration using a magnetic brush in which the developer is raised by magnetic force. In this configuration, a rotatable developing sleeve having a plurality of fixed magnets disposed therein, an agitating and mixing and supplying member for supplying a frictionally charged developer to the developing sleeve, and a magnet carried on the developing sleeve A member for regulating the layer thickness of the brush is provided as a main component.

  When the developer is agitated and mixed and is supplied to the developing sleeve in a state where the frictionally charged toner and the carrier are adsorbed to each other, a magnetic brush is formed by the magnet in the developing sleeve to form a static brush on the photoreceptor. When contacting the electrostatic latent image, the toner is electrostatically attracted to the latent image side.

By the way, when the developer is consumed in the visible image processing of the electrostatic latent image, it is necessary to prevent the developer from being unable to maintain a uniform developer concentration. For this reason, conventionally, a configuration in which toner is replenished in the developer has been used, and the following configuration has been proposed as the configuration.
That is, a replenishing roller comprising a conductive roller coated with short fibers or a porous elastic body having a resistance value of 10 ⁸ to 10 ¹⁰ Ω / cm facing the developing sleeve in the toner replenishing means provided in the developing device. The replenishment toner is dispersed and adhered to the surface of the short fiber or the porous elastic body, and an electric field is formed between the replenishing roller and the developing sleeve so that the toner is electrostatically adsorbed to the developing sleeve side. It is a structure (for example, patent document 1).

On the other hand, if the charge amount of the toner is insufficient, the toner may be carelessly scattered and the background of the photoconductor may be soiled. Therefore, there is the following configuration as a configuration for sufficient frictional charging by stirring and mixing of the carrier and the toner.
Separately from the installation position of the developing sleeve, a magnet with a built-in magnet capable of transferring the developer between these stirring rollers is provided in an opening communicating with the first and second stirring rollers that are extended to the installation area of the developing sleeve. A conveyance roller is provided, and the developer transferred from one of the replenishing toner supplied to the conveyance roller and the agitation roller is transferred between the agitation rollers (for example, Patent Document 2).

JP-A-7-97249 (page 3, left column, lines 17 to 28) JP-A-10-149027 (paragraphs “0033” to “0038” columns)

  In the configuration disclosed in Patent Document 1, the toner is attracted to the magnetic brush by the bias effect, but the fact that the toner adheres to the developing sleeve side when the bias is applied is utilized. Therefore, if this state is continued, the toner deposited on the developing sleeve is fixed, so that a so-called toner filming state occurs, and as a result, it may be difficult to form the magnetic brush. In addition, since the short fibers or the hard elastic body constituting the replenishing roller come into contact with the magnetic brush on the developing sleeve, the carrier forming the magnetic brush on the developing sleeve is scraped off when the contact is made. As a result, the developer carrying amount on the developing sleeve decreases, and there is a possibility that the developer supply amount necessary for development cannot be secured. In addition, the developer on the developing sleeve, particularly the toner, is charged oppositely to that at the time of supply by contacting the electrostatic latent image after development. The toner is easily adsorbed by the toner, and there is a possibility that a necessary toner amount on the developing sleeve may not be maintained.

On the other hand, in the magnetic brush formed on the developing sleeve, the charge amount of the toner contained becomes a factor that affects the adhesion to the electrostatic latent image, in other words, development efficiency. Therefore, as disclosed in Patent Document 2, it is required to sufficiently perform stirring friction charging. However, in the configuration disclosed in Patent Document 2, since the toner replenishment position is a position other than the installation area of the developing sleeve (a position further outside the end portion in the axial direction of the stirring roller), the size of the apparatus cannot be increased. Absent.
In addition, in this configuration, since the toner replenishment position is a position where the developer is pumped up from the stirring roller by the conveyance roller, the magnetic brush contains a large amount of toner that is electrostatically attached to the carrier as well as the carrier. It is. For this reason, unlike the case where the mixing ratio of the toner to the carrier in the magnetic brush is low, the replenished toner is less likely to come into contact with the carrier, and as a result, the toner is not sufficiently charged. When such an insufficiently charged state occurs, there arises a problem that the chance of background contamination of the photoreceptor due to toner scattering increases.

  In view of the problems in the conventional developing device and the image forming apparatus using the same, it is an object of the present invention to prevent background contamination and inadvertent scattering by making it possible to sufficiently charge the replenished toner. Another object of the present invention is to provide a developing device and an image forming apparatus having such a configuration.

According to the first aspect of the present invention, in the developing device for processing the electrostatic latent image formed on the latent image carrier using a magnetic brush made of a two-component developer, the magnetic brush is conveyed. And a developer carrying member for bringing the magnetic brush close to or in contact with the latent image carrying member, a toner replenishing member for replenishing toner to the magnetic brush carried on the developer carrying member, A magnetic brush carried on the developer carrying member is provided separately from the developer detaching portion from which the magnetic carrying member is detached from the developer carrying member and the toner replenishing member, and supplies the two-component developer to the developer carrying member. A two-component developer supplying member, and charging means for precharging the toner replenished from the toner replenishing member, wherein the toner replenishing member has the two-component developer on the developer carrying member supported by the developer carrying member. To the body Is conveyed I, a position after passing through the developing area close to or in contact with the image bearing member, and to replenish the toner at a position before the position where the magnetic brush is disengaged by the disengagement portion The two-component developer supply member supplies the magnetic brush released at the developer detachment portion to the developer carrier, and the supplied two-component developer is again supplied to the development region by the developer carrier. It is transported .

  According to a second aspect of the present invention, in the developing device according to the first aspect, the replenishment position of the toner faces or is close to a magnetic pole built in the developer carrier in the moving direction of the developer carrier. It is characterized by being positioned.

According to a third aspect of the invention, in the developing device according to claim 1 or 2, the developer separated from the developer carrying member is performed with stirring and mixing step can be supplied to the developer carrying member It is a feature.

Invention of claim 4, wherein, in the developing device according to any one of claims 1 to 3, the toner to be replenished to the upper Symbol magnetic brush can be fed over a lengthwise end of the developer carrying member It is characterized by that.

According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the toner replenished to the magnetic brush is provided with an air flow conveying means provided with a discharge portion facing the tip of the magnetic brush. It is characterized by being supplied by.

The invention according to claim 6, wherein, in the developing device according to one of claims 1 to 4, the toner to be replenished to said magnetic brush, provided separately from the frictional charging and the developer carrying member The toner is supplied by a toner feeding means having a possible configuration.

According to a seventh aspect of the present invention, in the developing device according to any one of the first to sixth aspects, the toner replenished to the magnetic brush is provided close to the developer carrier. It is characterized by being supplied by a replenishing toner carrying means.

According to an eighth aspect of the present invention, in the developing device according to the fifth aspect , the discharge portion of the airflow means is constituted by a nozzle, and a charging electrode for the toner discharged together with the nozzle body is provided in the nozzle. It is characterized by being.

According to a ninth aspect of the present invention, in the developing device according to the fifth aspect , the replenishing toner carrying means includes a porous elastic body made of a dielectric, and a charging means disposed in the vicinity of the replenishing toner carrying means. It is characterized by having.

According to a tenth aspect of the present invention, in the developing device according to the eighth aspect , the nozzle is made of a material having a reverse polarity relationship with the replenished toner in a charging series.

According to an eleventh aspect of the present invention, in the developing device according to the fifth or eighth aspect , the replenished toner is pumped by a powder pump provided at an outlet of the replenishment toner storage portion. .

According to a twelfth aspect of the present invention, in the developing device according to any one of the fifth, eighth, and tenth aspects, a plurality of the nozzles are provided along a longitudinal direction of the developer carrier. .

A thirteenth aspect of the present invention is the developing device according to any one of the fifth, eighth, tenth and twelfth aspects, wherein the nozzle is a slit whose longitudinal direction is set along the longitudinal direction of the developer carrier. It is characterized by being composed.

According to a fourteenth aspect of the present invention, in the developing device according to any one of the fifth, eighth, tenth, twelfth and thirteenth aspects, the discharge amount from the nozzle can be changed in the longitudinal direction of the developer carrier. It is characterized by.

According to a fifteenth aspect of the present invention, in the developing device according to any one of the first to fourteenth aspects, the replenished toner has a toner coverage in a carrier contained in the two-component developer of 30 to 30. It is characterized by being replenished by setting the relationship to be 70%.

According to a sixteenth aspect of the present invention, in the developing device according to any one of the first to fourteenth aspects, the replenished toner has an average circularity of 96% or more.

According to a seventeenth aspect of the present invention, the developing device according to any one of the first to sixteenth aspects is used in an image forming apparatus.

According to an eighteenth aspect of the present invention, in the image forming apparatus according to the seventeenth aspect, the latent image carrier and the developing device used for visible image processing of the latent image carrier are provided in a process cartridge that is detachable from the image forming apparatus main body. It is characterized by being.

According to a nineteenth aspect of the present invention, in the image forming apparatus according to the seventeenth aspect , the latent image carrier, the developing device, and a process cartridge in which the cleaning device used for cleaning the latent image carrier is detachable from the image forming apparatus main body. It is characterized by being provided.

According to a twentieth aspect of the present invention, in the image forming apparatus according to the seventeenth aspect , a latent image carrier, a developing device, a cleaning device used for cleaning the latent image carrier, and a charging device for charging the latent image carrier. Is provided in a process cartridge that can be attached to and detached from the image forming apparatus main body.

According to the first to third aspects of the present invention, toner is replenished to the magnetic brush after passing through the developing region, so that the toner in the magnetic brush where the toner has been consumed is opposite to the toner remaining on the carrier. By using the polar charge state, the replenished toner can be adsorbed. Thereby, the replenished toner can be charged in the magnetic brush. As a result, the equipment required for charging can be charged by using electrostatic adhesion to the carrier separately from frictional charging performed by stirring and mixing the developer supplied to the developer carrier. It is possible to save time.

  In particular, in the second aspect of the invention, the toner is replenished at a position facing or close to the magnetic pole built in the developer carrying member, so that contact with the magnetic brush is made according to the interval between the rising lines of magnetic lines of force by the magnetic pole. Opportunities can also be increased, which increases the chances of contact between toner and carrier. In the invention according to claim 3, the toner charged in advance with the carrier is further tribo-charged by shifting to a process in which the toner replenished in the magnetic brush is separated and stirred and mixed after the separation. Therefore, it becomes possible to obtain a charged state in which the shortage of the charge amount of the toner can be solved to prevent inadvertent scattering and background contamination.

According to the fourth aspect of the present invention, since the replenishment toner can be supplied over the entire longitudinal direction of the developer carrier, the distribution state can be made uniform in the longitudinal direction unlike local replenishment, and It is possible to increase the replenishment efficiency.

According to the fifth aspect of the present invention, toner replenishment is performed using the airflow conveying means having the discharge section, thereby promoting the entrance of the toner into the magnetic brush and supplying the toner to the carrier in the magnetic brush. Adhesion can be promoted.

According to the sixth aspect of the invention, since the toner to be supplied to the magnetic brush on the developer carrying member is in a charged state when supplied, the electrostatic adhesion with the carrier in the magnetic brush is promoted. It is possible to shorten the time required for frictional charging by stirring and mixing.

According to the seventh and ninth aspects of the invention, the toner is replenished in a charged state by the replenishment toner carrier provided in the vicinity of the developer carrier, so that it is uniform unlike the case where the toner falls by its own weight. It is possible to replenish in a state and promote electrostatic adhesion to the carrier in the magnetic brush.

According to the eighth and tenth aspects of the present invention, when the nozzle is provided in the ejection portion, the toner ejected by providing the nozzle with a charging electrode structure or using a charging system knob agent having a polarity opposite to that of the toner is provided. It can be in a charged state, and electrostatic adhesion to the carrier in the magnetic brush can be promoted.

According to the invention of claim 1 1, wherein, the powder pump is used for pneumatic conveying can be thereby enabling shortening of the transportation time of the toner facilitate the securing of the shortening and the replenishment amount of the replenishment time.

According to the present invention 2 and 1 3, wherein, since the discharge portion is configured to be replenished as target lengthwise end of the image bearing member, a magnetic unlike the case of a local supply position in the longitudinal direction Replenishment for the entire brush formation range is possible, so that the replenishment state to the magnetic brush formed in the longitudinal direction of the development carrier is not uneven, and one of the toner to be replenished It is possible to prevent the occurrence of a situation where the part is scattered or floated to contaminate the peripheral part.

According to the invention of claim 1 4, wherein, since the amount of discharge in the nozzle can be changed in the longitudinal direction of the developer carrying member, the consumption amount of the toner contained in the developer in the longitudinal direction of the developer carrying member Accordingly, it is possible to obtain a suitable replenishment form and to prevent excessive supply of toner used for replenishment.

According to claim 1 5 invention described, the supply amount of toner used in supplementation, because coverage with respect to the carrier are to have a relation of 30 to 70 percent, due to the occurrence of excess toner from the carrier It is possible to prevent contamination of the peripheral portion due to scattering and to prevent toner shortage with respect to a visible image.

According to the invention of claim 1 6, wherein it is possible to prevent the image omission of a character portion or a line portion which van der Waals force or image force being influenced by the degree of circularity is generated by the cause. That is, when the degree of circularity is low, the number of contact points with a smooth medium such as a latent image carrier increases, and electric charges are often concentrated on the tips of the protrusions that come into contact, resulting in an increase in van der Waals force and mirror image force. For this reason, when there are toner particles with low circularity that become irregular toner particles, the character portion and the line image portion are lost, but in the present invention, defective images are generated by defining such circularity. Can be prevented.

According to the invention described in claim 17, it is possible to prevent contamination of the peripheral portion including the background stain of the latent image carrier caused by scattering or floating due to insufficient charging of the toner.

According to the invention described in claims 18 to 20, since the apparatus used for the image forming process is provided in the process cartridge that can be attached to and detached from the main body, the maintenance work can be facilitated. It is possible to prevent contamination with toner inside.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram for explaining the configuration of an image forming apparatus to which a developing device according to an embodiment of the present invention is applied.
In FIG. 1, an image forming apparatus 1 includes a drum-shaped photosensitive member (hereinafter referred to as a photosensitive drum) 2 as a latent image carrier, and an image forming process is performed around the photosensitive drum 2 in a rotating process in the direction indicated by an arrow. Are provided with a charging device 3, a writing device 4, a developing device 5, a transfer device 6 and a cleaning device 7, respectively.

Of the devices arranged around the photosensitive drum 2, all or a part of each device except the writing device 4 and the transfer device 6 is provided together with the photosensitive drum 2 in the process cartridge.
FIG. 2 shows the external appearance of a process cartridge (a member indicated by reference numeral PC in FIG. 1 for convenience) when the photosensitive drum 2 and the devices other than the writing device 4 and the transfer device 6 are combined. Note that the process cartridge PC is not limited to the structure accommodated together with the photosensitive drum 2, and for example, only the developing device 5 can be accommodated in the process cartridge.

  Although not shown, the photosensitive drum 2 is provided with a photosensitive layer using a photosensitive inorganic or organic photosensitive member on the outer peripheral surface of a conductive substrate using a grounded aluminum base tube or the like. The photosensitive layer is composed of a charge generation layer and a charge transport layer.

The photosensitive drum 2 is uniformly charged by the charging device 3, and when an electrostatic latent image using the writing device 4 is formed, the electrostatic latent image is subjected to visible image processing by supplying developer from the developing device 5. A process is performed in which the visible image is transferred via the transfer device 6 to a transfer sheet or the like fed from a registration roller R provided in the paper feeding device.
After the transfer, the photosensitive drum 2 is subjected to removal of residual toner and removal of residual charge by the cleaning device 7 and is used for the next image formation. Further, the transfer paper carrying the transferred visible image is image-fixed by a fixing device (not shown) to form a copy.

  The developing device 5 used for the visible image processing of the electrostatic latent image uses a two-component developer in which a toner and a carrier are mixed.

  In FIG. 1, the developing device 5 is configured by a developing sleeve 5A as a developer carrying member capable of forming a magnetic brush facing the photosensitive drum 2, and by stirring and mixing toner and a carrier with respect to the developing sleeve 5A. A supply roller 5B for supplying the two-component developer and a toner replenishing device 8. Although not shown in FIG. 1, as shown in FIG. 3, the developing sleeve 5A is provided with a doctor member 5E for defining the layer thickness of the two-component developer carried on the surface. Yes.

The developing sleeve 5A has a diameter of 18φ and is finished with the surface roughened to a range of 10 to 20 μm RZ by sandblasting. Instead of this surface treatment, a plurality of grooves having a depth of 0.1 to 1 mm may be formed.
In the developing sleeve 5A, as shown in FIG. 3, a developing main pole 5A1 for bringing a magnetic brush formed by raising a carrier in a two-component developer into contact with the photosensitive drum 2, and a magnetic brush Conveying magnetic poles 5A2 and 5A3 and repulsive magnetic poles 5A4 and 5A4 'having the same polarity are provided. The repelling magnetic poles 5A4 and 5A4' develop the magnetic brush carried on the developing sleeve 5A by repulsion of magnetic lines. It is used as a magnetic pole for peeling off from the peripheral surface of the sleeve 5A toward the supply roller 5B.

The toner replenishing device 8 is a replenishment disposed opposite to the position after the developing main pole 5A1 in the developing sleeve 5A and the photosensitive drum 2 have passed through the developing region in the clockwise rotation direction of the developing sleeve 5A. A tank 8A is provided.
Inside the replenishment tank 8A, a replenishment toner supply member 8B composed of a metal roller facing the position after the developing sleeve 5A has passed through the development area, and the replenishment toner supply member 8B are replenished by stirring. A regulating member composed of a stirring member 8C composed of a roller capable of frictionally charging the toner and supplying the toner to the supplementary toner supply member 8B and a blade defining the layer thickness of the supplementary toner carried on the supplementary toner supply member 8B 8D is provided.

  The replenishment toner supply member 8B is disposed to face the conveying magnetic pole 5A3 disposed at the position after the developing sleeve 5A has passed through the developing region among the magnetic poles disposed inside the developing sleeve 5A. The replenishment toner can be supplied to the magnetic brush carried on the developing sleeve 5A after passing through the developing region.

FIG. 4 is a view showing the positional relationship between the magnetic brush carried on the developing sleeve 5A after passing through the developing region and the replenishing toner supply member 8B. In FIG. 4, the developing sleeve after passing through the developing region is shown. The two-component developer carried on 5A consumes toner during the visible image processing of the electrostatic latent image on the photosensitive drum 2. For this reason, the amount of toner carried by the magnetic brush facing the conveying magnetic pole 5A3 before reaching the developing area is reduced.
When the replenishment toner is supplied from the replenishment toner supply member 8B of the toner replenishment device 8, a charged charge having a polarity opposite to that of the toner remains on the carrier in the magnetic brush. For this reason, when the supplied replenishing toner comes into contact with the carrier, it can adhere to the carrier by polarization.

  On the other hand, the magnetic brush carried on the developing sleeve 5A replenished with toner from the replenishing toner supply member 8B in the toner replenishing device 8 is developed along the magnetic lines of force generated by the repelling magnetic poles 5A4 and 5A4 'as the developing sleeve 5A rotates. By peeling off from 5A toward the supply roller 5B, the developing sleeve 5A is detached. This state corresponds to a state in which the magnetic brush facing the magnetic pole 5A4 'in FIG. 4 moves away from the developing sleeve 5A.

  The magnetic brush detached from the developing sleeve 5A is frictionally charged by stirring and mixing the carrier and toner contained therein by the supply roller 5B, and is supplied to the developing sleeve 5A with the charged charge applied to the toner. The

  In the embodiment as described above, the toner is supplied to the magnetic brush carried on the developing sleeve 5A after passing through the developing area, so that the toner is supplied to the magnetic brush before reaching the developing area. Unlike the case of replenishment, the toner can easily enter the magnetic brush. In other words, since the toner is consumed and the toner is replenished to the carrier in the magnetic brush in a state in which a so-called counter charge exists, the carrier in which the toner is consumed is based on the electrostatic adsorption relationship between the carrier and the toner. It will be actively adsorbed. As a result, the toner can also enter the deep part of the magnetic brush, and the toner adhering to the carrier is charged prior to frictional charging during stirring and mixing by the supply roller 5B.

  According to the above embodiment, since the toner replenished by electrostatic adhesion with the carrier contained in the magnetic brush after development can be charged, the equipment for charging the toner can be downsized. In addition, the charging time can be shortened. In particular, a large-scale facility such as a two-shaft stirring structure provided with a pair of screw augers capable of stirring and mixing while transporting the developer relatively in the axial direction of the developing sleeve 5A becomes unnecessary, and a single stirring member is used. It is only necessary to pump up the developer.

  As described above, in this embodiment in which the toner can be precharged, it is possible to prevent the toner from being insufficiently charged. As a result, the background of the photosensitive drum 2 that is generated when the insufficiently charged toner is scattered. It becomes possible to prevent dirt and adhesion contamination to the peripheral part.

  On the other hand, as in the case of the toner replenishing device 8 shown in FIG. 1, the toner to be replenished is in a state of being charged in advance by a stirring member 8C used as a friction charging member at a position different from the developing sleeve 5A. Since it is carried on the replenishing toner supply member 8B corresponding to the above and replenished to the developing sleeve 5A, the amount of charge can be increased in addition to the charge when entering the magnetic brush and adhering to the carrier. As a result, it is possible to easily secure the charge amount of the toner in the magnetic brush without strictly performing the friction charging process in the supply roller 5B.

  The replenishing toner supply member 8B in the toner replenishing device 8 shown in FIG. 1 is configured to be replenished over the entire area in the axial direction corresponding to the longitudinal direction of the developing sleeve 5A. Unlike this, the toner is uniformized quickly and appropriately.

Next, a modified example regarding the configuration of the toner replenishing device will be described.
The configuration shown in FIG. 5 is provided with a discharge portion facing the developing sleeve 5A instead of the supply roller 8A shown in FIG. 1 as a toner supply member used in a toner supply device (indicated by reference numeral 8 'for convenience). It is characterized by using the air current conveying means 100.

  5, similarly to the arrangement configuration of the replenishing toner supply member 8B shown in FIG. 1, a position opposite to the developing sleeve 5A after passing through the developing region is passed through a pipe 102 having a nozzle 101 at one end as a discharge portion. The air flow conveying means 100 is connected.

The airflow conveying means 100 includes a powder pump 104 communicating with the toner tank 103, and a schematic configuration of the powder pump 104 is shown in FIG.
In FIG. 6, the powder pump 104 uses the configuration described in the specification of Japanese Patent No. 3434085, which is the prior application of the present applicant, and specifically has a spiral groove 104 </ b> A communicating with the toner tank 103. The stator 104B, the rotor 104C that can rotate in the spiral groove 104A of the stator 104B, the outer periphery of the stator 104B, and the end of the pipe 101 that is connected between the stator 104B and the nozzle 101 are mounted. And an air passage 104F from an air pump connected to an air passage 104E formed by a gap provided between the casing 104D and the toner that is fed from the toner tank 103 by the rotation of the rotor 104C. The toner discharge section 10 in the casing 104D is supplied by the air supplied to the air passage 104E. So that the feed the toner to the pipe 102 to G side as negative trend.

  On the other hand, the nozzle 101 has a diameter of about 5 mm and a plurality of tube structures arranged at intervals of 10 mm along the axial direction of the developing sleeve 5A or slits whose longitudinal direction is set along the axial direction of the developing sleeve 5A. These nozzles are provided with charging portions for toner.

  FIG. 7 is a diagram showing one configuration of the charging unit, in which the nozzle 101 of the tube structure is shown. In the figure, inside a nozzle 101, a rod-shaped charging electrode 101A is provided at the center of the flow path of the discharged toner, and the charging electrode 101A constitutes a counter electrode including the nozzle body. The charging electrode 101A shown in FIG. 7A is a needle-like electrode that has protrusions formed on the outer peripheral surface along the axial direction and can discharge charges in the radial direction. The charging electrode shown in FIG. The electrode 101A ′ is a needle-like electrode capable of tip discharge with an axial end portion having a thrust shape.

  As a configuration for efficiently charging the toner, a material having a charging series having a polarity opposite to that of the toner is used at least on the inner peripheral surface of the toner passage in the nozzle. For example, when the toner is a negative electrode The inner surface of the nozzle 101 is coated or coated with a charged material such as silicon, melamine or acrylic resin, or the material itself is used as the nozzle.

  As a configuration for charging the discharged toner, the configuration shown in FIG. 8 can be adopted. That is, the configuration shown in FIG. 8 is a supply of replenishment toner in the toner replenishing device 8 shown in FIGS. Instead of the member 8B, a charging roller 105 made of a porous elastic body such as sponge (for convenience, indicated by reference numeral 8B 'in FIG. 8) is used, and the charging device 105 capable of corona discharge with respect to the replenishing toner supply roller 8B'. Place. The toner is rubbed and carried on the replenishing toner supply roller 8B 'by using a paddle wheel 8B1' provided in the replenishing tank 8A.

  In the above configuration, the replenishment toner for the developing sleeve 5A is charged and supplied in advance before being discharged. For this reason, the carrier in the magnetic brush carried on the developing sleeve 5A after passing through the developing region is not attached only by the polarization action, but positively by setting the charging characteristic relationship of the reverse polarity. Adhesion to the toner can be promoted, and at the time of entering the magnetic brush carried on the developing sleeve 5A, the toner has already been charged to some extent. Accordingly, it is possible to prevent the toner from being insufficiently charged, thereby preventing the background contamination of the photosensitive drum due to the scattered toner and the toner contamination to the peripheral portion. In addition, labor and equipment required for charging the toner can be saved.

  Since the above-described nozzle has an opening at the discharge portion, the amount of toner replenishment may be adjusted by controlling the opening of the opening. That is, in this embodiment, the replenishment amount is set on condition that the toner to be replenished is set so that the coverage of the toner in the carrier contained in the two-component developer is set to 30 to 70%. It has been standardized. The reason for this is that if it is 30% or less, the electrostatic latent image cannot be developed, and if it is 70% or more, the toner is easily separated from the surface of the developing sleeve 5A in the development region, thereby preventing scattering. Because.

  Even when the replenishment amount described above is set, the toner consumption amount in the magnetic brush in the axial direction of the developing sleeve 5A may differ depending on the image density at the time of image formation. Therefore, it is also possible to set a replenishment amount corresponding to the image density, in other words, the amount of toner consumed on the developing sleeve 5A. This will be described below.

  Since both the tubular structure and the slit are arranged along the axial direction of the developing sleeve 5A, the opening degree of the opening can be adjusted according to the amount of toner consumed in the axial direction of the developing sleeve 5A. . As a configuration for this, although not shown, a shutter member capable of adjusting the opening degree is provided, and the density at the position along the axial direction of the developing sleeve at the time of image formation is detected, and high density output is performed. The opening degree of the shutter member corresponding to the position is increased, and conversely, if it is below the standard concentration, the opening degree of the shutter member is made smaller than the standard opening degree.

  Further, the toner replenishment amount can be adjusted not only in the case of the nozzle described above, but also in the case where the roller member shown in FIGS. 1, 3 and 8 is used as a replenishment toner supply member. In this case, the supply amount of the replenishment toner can be adjusted by dividing the replenishment toner supply members 8B and 8B 'along the axial direction of the developing sleeve 5A and controlling the rotation amount at each division position.

  In the adjustment of the toner replenishment amount for the nozzle or the replenishment toner supply member, when the toner corresponding to the replenishment amount at the corresponding axial position is replenished, the magnetic brush located in the vicinity of the corresponding axial position Since the toner can be electrostatically attracted to the carrier inside, even if it is replenished only to the corresponding position, the toner can be electrostatically attracted to the carrier of the magnetic brush in the vicinity. As a result, the toner can be uniformly dispersed in the axial direction.

Next, the developer used in this embodiment will be described.
The toner used in the developer used in this example is a mixture of a resin such as polyester, polyol, or styrene acrylic mixed with a charge control agent and a colorant, and an external additive such as silica or titanium oxide around it. Fluidity is enhanced by adding an agent. The particle size of the additive is usually in the range of 0.01 to 0.1 μm.

  Examples of the colorant include carbon black, phthalocyanine blue, quinacridone, and carmine. As the toner, toner obtained by externally adding the above-mentioned types of additives to a base toner in which wax or the like is dispersed and mixed can also be used.

  The toner can also be used as a magnetic toner by containing a magnetic material. Specific magnetic materials include iron oxides such as magnetite, hematite, and ferrite, metals such as cobalt and nickel, and these metals and aluminum, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, and calcium. , Alloys with metals such as manganese, selenium, titanium, tungsten, vanadium, and mixtures thereof. These magnetic materials desirably have an average particle size of about 0.1 to 2 μm, and the content of the magnetic material at this time is 20 to 200 parts by mass, particularly preferably a binder, with respect to 100 parts by mass of the binder resin. It is 40-150 mass parts with respect to 100 mass parts of resin.

As the additive, conventionally known ones can be used. Specifically, Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Examples thereof include oxides such as Cr, Mo, Cu, Ag, V, and Zr, composite oxides, and the like. In particular, silica, titania, and alumina, which are oxides of Si, Ti, and Al, are preferably used.
Moreover, it is preferable that the addition amount of the additive at this time is 0.5-3 mass parts with respect to 100 mass parts of base particles, Most preferably, it is 0.7-1.5 mass parts.

  When the additive amount is less than 0.5 parts by mass, the fluidity of the toner is lowered, so that sufficient chargeability cannot be obtained, transferability and heat-resistant storage stability are insufficient, and Also likely to cause dirt and toner scattering.

  On the other hand, if the amount of the additive added is more than 3 parts by mass, the fluidity is improved, but the photosensitive member cleaning failure such as chatter and blade turning, and the filling to the photosensitive drum 1 by the additive released from the toner are performed. As a result, the durability of the cleaning blade, the photosensitive drum, etc. is lowered and the fixing property is also deteriorated. In addition, toner in the thin line portion is liable to be generated, and in particular, in the case of a fine line output in a full color image, it is necessary to superimpose toner of at least two colors, and the amount of adhesion increases, and this tendency is particularly remarkable. It is. Furthermore, when used as a color toner, if a large amount of additives are contained, a projected image is generated when a toner image formed on a transparent sheet is projected by an overhead projector, and a clear projected image is obtained. It becomes difficult.

  Although there are various methods for measuring the content of the additive, it is generally determined by fluorescent X-ray analysis. That is, a calibration curve is prepared by fluorescent X-ray analysis for a toner whose content of the additive is known, and the content of the additive can be obtained using this calibration curve.

Furthermore, the additive used in the present embodiment is preferably subjected to a surface treatment for the purpose of hydrophobization, fluidity improvement, chargeability control, and the like, if necessary.
Here, the treatment agent used for the surface treatment is preferably an organic silane compound, for example, alkylchlorosilanes such as methyltrichlorosilane, octyltrichlorosilane, and dimethyldichlorosilane, and alkyl such as dimethyldimethoxysilane and octyltrimethoxysilane. Examples include methoxysilanes, hexamethyldisilazane, and silicone oil. In addition, as a treatment method, there are a method in which an additive is immersed in a solution containing an organosilane compound and drying, a method in which a solution containing an organosilane compound is sprayed and dried, and the like. In the method, any method can be suitably used.

  The volume average particle diameter of the toner is preferably in the range of 3 to 12 μm. The toner used in this embodiment has a volume average particle diameter of 6 μm, and can sufficiently cope with a high-resolution image of 1200 dpi or more. Further, in this embodiment, toner having a negative charge polarity is used, but a toner having a positive charge polarity according to the charge polarity of the photosensitive drum 1 may be used.

  For spherical toners, for example, toner charging becomes unstable when stirring using a screw auger, but when toner is replenished with this method, charging of the replenishing toner is stabilized. Further, by using a spherical toner having a circularity of 95% or more, the variation in surface area can be reduced as compared with an indeterminate type, so that uniform development is possible and image quality is improved. That is, when the degree of circularity is low, the number of contact points with a smooth medium such as a latent image carrier increases, and electric charges are often concentrated on the tips of the protrusions that come into contact, resulting in an increase in van der Waals force and mirror image force. For this reason, when there are toner particles with low circularity that become irregular toner particles, the character portion and the line image portion are lost, but in the present invention, defective images are generated by defining such circularity. Can be prevented.

  According to the embodiment as described above, even when the equipment required for charging the toner is downsized and the charging time is shortened, the amount of charge of the toner can be sufficient, and scattering due to insufficient charging of the toner is a cause. Thus, it is possible to reliably prevent contamination of the surface of the photosensitive drum and toner contamination on the peripheral portion.

1 is a schematic diagram of an image forming apparatus in which a developing measure according to the present embodiment is used. 1 is an external view of a process cartridge including a developing device according to an embodiment. It is a schematic diagram for demonstrating the principal part structure of the image development apparatus by a present Example. It is a schematic diagram for demonstrating the effect | action in the image development apparatus shown in FIG. It is a schematic diagram for demonstrating another example of the principal part structure of a present Example. It is a figure for demonstrating the structure of the powder pump used for the principal part structure shown in FIG. It is a figure which shows the structure of the nozzle used for the principal part structure shown in FIG. It is a schematic diagram for demonstrating the partial modification of the principal part structure shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum 5 Developing device 5A Developing sleeve 5A1 Developing main pole 5A3 Conveying magnetic pole 5A4 Repulsive magnetic pole 8,8 'Toner replenishing device 8B, 8B' Replenishing toner supplying member 100 Means 101 Nozzle 104 Powder pump

Claims (20)

In a developing device that processes an electrostatic latent image formed on a latent image carrier using a magnetic brush made of a two-component developer,
A developer carrying body for transporting the magnetic brush and bringing the magnetic brush close to or in contact with the latent image carrying body;
A toner replenishing member for replenishing toner to the magnetic brush carried on the developer carrying member;
A developer detachment portion from which the magnetic brush carried on the developer carrier is detached from the developer carrier;
And it provided separately from the aforementioned toner supply member, and the two-component developer supplying member for supplying the two-component developer to the developer carrying member,
Charging means for precharging toner supplied from the toner supply member,
The toner replenishment member is a position after the two-component developer on the developer carrying member has been transported by the developer carrying member and has passed through a developing region in proximity to or in contact with the latent image carrying member, and The toner is replenished at a position before the position at which the magnetic brush is detached at the separation part ,
The two-component developer supply member supplies the magnetic brush released at the developer detachment portion to the developer carrier, and the supplied two-component developer is conveyed again to the development area by the developer carrier. developing device characterized in that it is. The developing device according to claim 1,
The developing device according to claim 1, wherein the toner replenishing position is a position facing or close to a magnetic pole built in the developer carrier in the moving direction of the developer carrier. The developing device according to claim 1 or 2,
A developing device characterized in that the developer separated from the developer carrying member can be supplied to the developer carrying member by performing a stirring and mixing process . 4. The developing device according to claim 1, wherein the toner replenished to the magnetic brush can be supplied over the entire longitudinal direction of the developer carrier . 5. In the developing device according to any one of claims 1 to 4,
2. A developing device according to claim 1, wherein the toner supplied to the magnetic brush is supplied by an air flow conveying means having a discharge portion facing the tip of the magnetic brush . The developing device according to one of claims 1 to 4,
2. A developing device according to claim 1, wherein the toner supplied to the magnetic brush is supplied by toner feeding means provided separately from the developer carrying member and capable of triboelectric charging . The developing device according to any one of claims 1 to 6,
2. A developing device according to claim 1, wherein the toner supplied to the magnetic brush is supplied by a replenishing toner carrying means provided close to the developer carrying member . The developing device according to claim 5 , wherein
2. A developing apparatus according to claim 1, wherein the discharge section of the airflow conveying means is constituted by a nozzle, and a charging electrode for the toner discharged together with the nozzle body is provided in the nozzle . The developing device according to claim 7 .
2. A developing apparatus according to claim 1, wherein said replenishing toner carrying means comprises a porous elastic body made of a dielectric and a charging means arranged in proximity to said replenishing toner carrying means . The developing device according to claim 8 , wherein
The developing device , wherein the nozzle is made of a material having a reverse polarity relationship with the toner to be replenished in a charging series . The developing device according to claim 5 or 8 ,
The developing device according to claim 1, wherein the toner to be replenished is pumped by a powder pump provided at an outlet of the replenishing toner container . In the developing device according to any one of claims 5, 8 , and 10,
A developing device, wherein a plurality of the nozzles are provided along a longitudinal direction of the developer carrier . The developing device according to any one of claims 5, 8, 10 , and 12,
The developing device according to claim 1, wherein the nozzle includes a slit whose longitudinal direction is set along the longitudinal direction of the developer carrier . The developing device according to any one of claims 5, 8, 10, 12, and 13 ,
A developing device characterized in that the discharge amount from the nozzle can be changed in the longitudinal direction of the developer carrier . The developing device according to claim 1 ,
The developing device according to claim 1, wherein the toner to be replenished is set so as to have a toner coverage ratio of 30 to 70% in a carrier contained in the two-component developer. The developing device according to claim 1 ,
The developing device according to claim 1, wherein the replenished toner has an average circularity of 96% or more . An image forming apparatus using the developing device according to claim 1. The image forming apparatus according to claim 17 ,
An image forming apparatus, wherein the latent image carrier and a developing device used for visible image processing of the latent image carrier are provided in a process cartridge that is detachable from a main body of the image forming apparatus . The image forming apparatus according to claim 17 .
An image forming apparatus comprising: a latent image carrier, a developing device, and a cleaning device used for cleaning the latent image carrier provided in a process cartridge that is detachable from the main body of the image forming apparatus . The image forming apparatus according to claim 17 .
A latent image carrier, a developing device, a cleaning device used for cleaning the latent image carrier, and a charging device for charging the latent image carrier are provided in a process cartridge that can be attached to and detached from the image forming apparatus main body. image forming apparatus characterized by.

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