JP4764667B2 - Developing device, image forming apparatus, and process cartridge - Google Patents

Description

  The present invention relates to a developing device, a process cartridge using the same, and an image forming apparatus, and more particularly to a developing mechanism having a transfer residual toner collecting function.

  In an image forming apparatus such as a copying machine, a facsimile, a printer, or a printing machine, an electrostatic latent image corresponding to image information is formed on a latent image carrier such as a photoconductor uniformly charged by a charging device, The electrostatic latent image is subjected to a visible image processing with a developer such as toner, and the visible image is transferred to a recording medium such as a sheet and fixed to obtain a copy output.

As a configuration used for visible image processing of an electrostatic latent image, magnetic brush development using a two-component developer is well known.
In magnetic brush development, the developer is transported to the surface of the developer carrier, the developer is held in a brush shape (magnetic brush) and brought into contact with the image carrier, and an image carrier on which an electrostatic latent image is formed The toner is selectively attached to the latent image surface by an electric field between the sleeve to which an electrical bias is applied and development is performed.
The developer carrier is usually configured as a cylindrical sleeve (developing sleeve), and a magnet body (magnet roller) that forms a magnetic field so as to cause the developer to rise on the sleeve surface is provided inside the sleeve. ing.

  At the time of spike, the carrier is spiked on the sleeve so as to follow the lines of magnetic force generated by the magnet roller, and charged toner is attached to the carrier related to the spike.

The magnet roller has a plurality of magnetic poles, and the magnets forming the respective magnetic poles are formed in a rod shape or the like. In particular, the magnet roller has a developing main magnetic pole that raises the developer in the developing region portion of the sleeve surface.
When at least one of the sleeve and the magnet roller moves, the developer that has risen on the surface of the sleeve moves, and the developer conveyed to the developing area follows the magnetic field lines generated from the developing main magnetic pole. The developer chain spike comes into contact with the surface of the latent image carrier so as to bend, and the developer developer chain spike contacts the electrostatic latent image based on the relative linear velocity difference from the latent image carrier. Supply toner while rubbing each other. The developing area is a range in which the magnetic brush rises on the developer carrier and is in contact with the latent image carrier.

Usually, a cleaning device is provided to collect toner remaining on the image carrier after transfer to a recording material (transfer paper or the like). However, the cleaning device is eliminated to simplify and reduce the size of the device. The so-called cleaner-less process has been put into practical use.
When the cleaning device is eliminated, a developing sleeve provided in the developing device is used as a configuration for collecting the residual toner on the image carrier, so-called transfer residual toner, so that it can be reused. There is a configuration in which anti-fogging and toner collection are possible by setting a distance between the image forming member and a predetermined condition and applying a potential that enables the toner to move from the image carrier to the developing sleeve ( For example, Patent Document 1).

  As another configuration example, developing sleeves are arranged on the upstream side and the downstream side in the moving direction of the image carrier, and a low-frequency AC bias is provided between the upstream side and the image carrier. There is a configuration in which a developing bias having the same polarity as the surface potential of the image carrier is applied to the downstream developing sleeve (for example, Patent Document 2).

JP2003-307927 (paragraph "0003" column) JP 2001-296742 A (paragraph “0006” column)

  In the configuration disclosed in each patent document, although an effect relating to the recovery efficiency of the transfer residual toner on the image carrier can be obtained, no consideration is given to the handling of the recovered transfer residual toner. In other words, the collected toner is not taken into consideration until it is reused as it is in the developing device as the collection unit.

  Therefore, when the toner used for the two-component developer is consumed, it is necessary to replenish new toner, and as a result, a recycling environment cannot be provided.

  An object of the present invention is to provide a state in which the recovered toner can be reused as it is, not only for the recovery, in view of the problems in the above-described conventional developing device, particularly the developing device having the simultaneous development cleaning function. It is an object of the present invention to provide a developing device, a process cartridge, and an image forming apparatus having a configuration that can be used.

According to a first aspect of the present invention, there is provided a developing device capable of reversal development of an electrostatic latent image carried on a latent image carrier by toner in a magnetic brush using a two-component developer containing toner and a magnetic carrier. In addition, a magnetic field for attracting and holding the carrier in the two-component developer is provided inside, and a supply electric field for supplying the toner contained in the two-component developer can be formed and arranged in the vicinity. A developer supplying means for defining the carrying amount of the two-component developer by the layer thickness regulating member, and a latent image carrying that is arranged adjacent to the developer supplying means and carries an electrostatic latent image And a developer carrying means that can form a developing electric field for supplying toner to the latent image carrier, and the developer carrying means is positioned adjacent to the developer supply means. Formed on the developer carrying means side The toner is carried on the surface of the toner supplied by the supply electric field when supplied by the developing electric field, move in the same direction as the latent image bearing member at a position opposed to the aforementioned latent image supply means, the developer When collecting the toner remaining on the surface toward the position adjacent to the supply means , the toner moves in the direction opposite to the toner supply direction, and the toner remaining on the latent image carrier is adjacent to the developer supply means. When the toner is collected toward the position, the developing electric field reduces the electric field strength when supplying toner to the latent image carrier, and the supplied electric field moves to the adjacent position in accordance with the change of the developing electric field. It is characterized in that the electric field strength can be recovered.

According to a second aspect of the present invention, there is provided a developing device capable of reversal development of an electrostatic latent image carried on a latent image carrier by toner in a magnetic brush using a two-component developer containing toner and a magnetic carrier. A magnetic field for adsorbing and holding the carrier in the two-component developer is formed inside, and a supply electric field for supplying toner contained in the two-component developer can be formed, A developer carrying means for defining the carrying amount of the two-component developer by the arranged layer thickness regulating member, and a developing electric field for the latent image carrying body, which is arranged to face the latent image carrying body. A developer supply means that is capable of being disposed on the upstream side of the developer carrier in the moving direction of the latent image carrier, and the latent image carrier and the developer carrier. And the latent image carrying The moving direction at the position facing the body is opposite to the moving direction of the latent image carrier, and the transfer residual toner is collected from the latent image carrier .

According to a third aspect of the present invention, there is provided a developing device capable of reversal development of an electrostatic latent image carried on a latent image carrier by toner in a magnetic brush using a two-component developer containing toner and a magnetic carrier. In addition, a magnetic pole for attracting and holding the carrier in the two-component developer and a supply electric field for supplying toner contained in the two-component developer can be formed inside, and the magnetic field is disposed in the vicinity. A developer carrying means whose carrying amount of the two-component developer is regulated by the layer thickness regulating member, and the latent image carrying body arranged opposite to the latent image carrying body and a developing electric field for the latent image carrying body a formable developer supply means, said developer carrying means is disposed on the upper stream side than the developing agent supply means in the direction of movement of the latent image carrier the latent image bearing member and the developing opposed to both the carrier, the latent Movement direction at the position facing the carrying body is the moving direction and the opposite direction of the latent image bearing member is characterized by recovering the toner from the latent image carrier.

A fourth aspect of the invention is characterized in that the developing device according to one of the first to third aspects is used in an image forming apparatus.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect , the latent image carrier has a low surface energy.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth or fifth aspect , the toner contained in the two-component developer has a circularity of 90 to 97% and a content ratio exceeding 80%. It is characterized by being able to.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the fourth to sixth aspects, when the developing method of the latent image formed on the latent image carrier uses reversal development, a latent image is formed. As image formation conditions and bias application conditions to each means,
V _L <V _SL <V _B <V _D
However, the relationship is set such that V _L : latent image potential (exposure control potential), V _SL : supply bias, V _B : development bias, and V _D : charging potential.

According to an eighth aspect of the present invention, there is provided a process cartridge used in the image forming apparatus according to any one of the fourth to seventh aspects, the latent image carrier, a charging device for uniformly charging the latent image carrier, and the latent image carrier. A developing device that performs visible image processing on the electrostatic latent image formed on the image carrier is collectively disposed in the unit, and is detachably attached to the image forming apparatus main body.

According to the first aspect of the present invention , the movement direction of the developer carrying member can be switched between supplying and collecting the toner to the latent image carrying member, and at the time of collecting the transfer residual toner, the developer carrying means and the developer supply. Since the electric field intensity is set so that the toner used for reversal development can be collected in each of the means, the reversal-developed latent image carrier is collected on the developer carrying means and the transfer residual toner is supplied as the developer. The processing used for re-development becomes possible by taking in the means and performing re-stirring and re-charging on the developer supply means side.

  According to the second aspect of the present invention, the moving direction of the developer supply means that is a transfer residual toner collecting member is set with respect to the rotation direction of the latent image carrier, so that the transfer residual toner can be easily scraped off. The recovery efficiency of the toner to the magnetic brush can be improved.

According to the third aspect of the present invention, the developer carrying member facing the latent image carrying member and the transfer remaining toner collecting member can function, and the developer supplying means can function as the developer supplying member. .

According to the fourth aspect of the invention, it is possible not only to collect the transfer residual toner on the latent image carrier, but also to reuse the collected toner, thereby improving the energy saving effect.

According to the fifth aspect of the present invention, the surface energy of the latent image carrier is lowered, whereby the transfer residual toner can be easily peeled off from the latent image carrier, and scraping by means used for recovery is performed. The effect can be improved.

According to the sixth aspect of the present invention, when a toner having a circularity of 90 to 97% that is easy to roll is used, in other words, when a cleaning blade or the like is used, it is easy to slip through and is difficult to collect. Even in this case, it is possible to improve the recovery efficiency of the transfer residual toner.

According to the seventh aspect of the present invention, by setting the latent image forming condition and the bias condition for each means, it is possible to improve the transportability at the time of collecting the transfer residual toner and improve the collecting efficiency, and again. It becomes possible to make it easy to charge and to enable easy setting of reuse conditions.

According to the eighth aspect of the present invention, the unit containing the latent image carrier, the charging device, and the developing device is detachably attached to the main body of the apparatus. It is possible to prevent the size of the apparatus from being increased by reducing the space occupied by the recovery unit.

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

FIG. 1 is a schematic diagram for explaining 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 100 is a laser printer that performs writing with laser light, and includes a drum-shaped photosensitive member 1 as a latent image carrier.
Around the photoreceptor 1, a charging device 2, a writing device 3, a developing device 4, a transfer device 5, and a cleaning device 6 for performing image forming processing along the rotation direction of the photoreceptor 1 are disposed.

In a printer having such a configuration, a writing device 3 that uses laser light modulated based on image information as writing light to the photosensitive member 1 uniformly charged by the charging device 2 in the axial direction of the photosensitive member. An electrostatic latent image is formed by scanning and writing processing. The formed electrostatic latent image is subjected to toner from the developing device 4 with respect to the photoreceptor 1 and the developing device 4 indicated by reference numeral A1 in FIG. Visible image processing is performed in the development region facing each other.
The toner image carried on the photosensitive member 1 by the visible image processing is transferred via the transfer device 5 to the transfer paper 20 which is fed from a paper supply device (not shown) with registration timing set by a registration roller 7. Electrostatic transfer. The transfer device 5 transfers the toner image by electrostatically transferring the toner toward the transfer paper 20 by applying a charge having a polarity opposite to that of the toner image on the photoreceptor 1. After transfer, the transfer paper 20 carrying the transferred toner image is fixed by a fixing device (not shown) to be an image output product.

  As shown in FIG. 2, a part of the above-described printer configuration apparatus is arranged in a unit that can be stored together, and a process cartridge constituted by this unit can be detachably provided to the printer main body. is there. As a device stored in the process cartridge, the photosensitive member 1, the charging device 2, and the developing device 4 are targeted.

The structure of the photoreceptor 1 used in the laser printer according to this embodiment is as follows.
The photosensitive member 1 is obtained by applying a photosensitive inorganic or organic photosensitive member to an element tube such as aluminum to form a photosensitive layer, and has a relatively thin polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). It is also possible to use a belt photoreceptor in which a photosensitive layer is formed on nickel or the like. In this embodiment, the negatively charged photosensitive member 1 is used. However, in consideration of the relationship with the charging polarity of the toner, a positively charged one is used as necessary. Also good. In this embodiment, the photosensitive member 1 has a diameter of 50 mm and is driven to rotate at a linear speed of 200 mm / sec.

  As for the photoreceptor 1, one having a reduced surface energy is used. That is, the photoconductor 1 in this embodiment has a surface friction coefficient within a predetermined range. Specifically, the maximum static friction coefficient μ of the surface is set within a range of 0.1 ≦ μ ≦ 0.4. As described above, by setting the maximum static friction coefficient μ on the surface of the photoreceptor 1 to the predetermined value, it becomes difficult for dirt toner, which is originally unnecessary to adhere to the photoreceptor 1, to adhere to the developing region, and the transfer residual toner. The removal efficiency can be increased.

In this embodiment, a lubricant is applied to the surface of the photoconductor 1 at a predetermined timing in order to maintain a friction coefficient range of 0.1 to 0.4 for reducing the surface energy of the photoconductor 1. It has become.
A conventionally known method can be employed as a method of applying the lubricant. For example, in Japanese Patent Laid-Open No. 4-372811, “When a toner having a volume average particle size of 4 to 10 μm is used, a substance that lowers the coefficient of friction of the photosensitive member is supplied onto the photosensitive member. Supply of lubricant is constant. It may be directly applied every other number, or a member carrying a lubricant may be brought into contact with the photosensitive member constantly or every certain number of times. Thus, by applying the lubricant to the surface of the photoreceptor, the maximum static friction coefficient μ on the surface of the photoreceptor 1 can be maintained in the range of 0.1 to 0.4. Instead of applying the lubricant to the surface of the photoreceptor 1, a lubricant may be added in advance to the photosensitive material itself constituting the surface portion of the photoreceptor 1.

  The maximum friction coefficient μ of the photoconductor 1 is measured using the measurement system shown in FIG.

  First, a paper sheet (TYPE 6200, A4 size, T mesh) manufactured by Ricoh Co., Ltd. is cut into 297 mm × 30 mm, and thread 101 is attached to both ends to create a measurement paper piece 100. Table 1 shows the characteristics of the measurement paper piece 100.

  Next, the measurement paper piece 100 is placed on the photosensitive member 1 set on the support member 103 on the table 102 so that the back surface is in contact with it, and 0.98 N (= 100 g) on one thread 101 of the measurement paper piece 100. A heavy weight 104 is attached, and the other thread 101 is connected to a digital force gauge (digital push-pull gauge) 105. Then, the measurement paper piece 100 is pulled with the weight 104, and the value of the gauge 105 when the measurement paper piece 100 starts to move is read. When the value at this time is F [N], the maximum static friction coefficient μ is obtained by the following equation (1).

μ = {ln (F / 0.98)} / (π / 2) (1)
The measured value of the maximum static friction coefficient μ of the photoconductor in the case where the surface of the photoconductor 1 is not treated with lubricant or the like is 0.5 to 0.6 and tends to increase with time. On the other hand, when the photoreceptor 1 coated with a lubricant was measured, the value μ was in the range of 0.1 to 0.4.

The configuration of the developing device 4 used for developing the electrostatic latent image formed on the photoreceptor 1 is shown in FIG.
In FIG. 4, a developing roller 402 as a toner carrier in a developer, a magnetic brush roller 403 as a toner supply member, and a stirring / conveying member 404 are arranged in the casing 401 of the developing device 4 from the photosensitive member 1 side. 405 are disposed.
A two-component developer (hereinafter referred to as “developer”) 12 containing the toner 10 and magnetic particles 11 in the casing 401 is agitated by the agitating / conveying members 404 and 405, and a part of the agitation is carried on the magnetic brush roller 403. It is carried on.
The developer 12 on the magnetic brush roller 403 comes into contact with the developing roller 402 in the toner supply region A2 after the layer thickness is regulated by a regulating blade 406 as a developer regulating member. In this toner supply area A2, only the toner 10 is separated from the developer 12 on the magnetic brush roller 403 and supplied to the developing roller 402.

Since the developing device 4 in this embodiment uses the rigid drum-shaped photosensitive member 1 based on an aluminum tube, the developing roller 402 is made of a rubber material and has a hardness of 10 to 70 ° (JIS- The range of A) is good.
The diameter of the developing roller 402 is preferably 10 to 30 mm. In the present embodiment, the one having a diameter of 16 mm was used.
Further, the surface of the developing roller 402 was appropriately changed to have a roughness Rz (10-point average roughness) of 1 to 4 μm. The range of the surface roughness Rz is 13 to 80% with respect to the volume average particle diameter of the toner 10, and is a range in which the toner 10 is conveyed without being buried in the surface of the developing roller 402.

  Examples of materials that can be used as the rubber material for the developing roller 402 include silicon, butadiene, NBR, hydrin, and EPDM. Further, when a so-called belt photoconductor is used, it is not necessary to lower the hardness of the developing roller 402, so a metal roller or the like can also be used.

  The surface of the developing roller 402 is preferably coated with a coating material as appropriate in order to stabilize the quality with time. Further, the function of the developing roller 402 in this embodiment is only for carrying toner, and charging charge is applied to the toner 10 by frictional charging between the toner 10 and the developing roller 402 as in the conventional one-component developing device. Therefore, the developing roller 402 only needs to satisfy electric resistance, surface property, hardness, and dimensional accuracy, and the selection range of materials is remarkably increased.

The surface layer coating material of the developing roller 402 may have a polarity opposite to that of the toner 10 or may have the same polarity when the toner does not have a function of frictionally charging the toner to a desired polarity. Examples of the former surface layer coating material include materials containing a resin, such as silicon, acrylic, and polyurethane, and rubber. Examples of the latter surface layer coating material include a material containing fluorine. A so-called Teflon (registered trademark) material containing fluorine has a low surface energy and excellent releasability, and therefore toner filming with time is extremely difficult to occur.
Also, as general resin materials that can be used for the surface layer coating material, polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), tetrafluoroethylene / hexafluoropropylene polymer (FEP) , Polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), etc. Can be mentioned. In order to obtain conductivity, a conductive material such as carbon black is often contained in this. In order to coat the developing roller 402 more uniformly, another resin may be mixed. Regarding the electrical resistance, the volume resistivity of the bulk including the coat layer is set, and the resistance and adjustment of the base layer are performed so that it can be set to 10 ³ to 10 ⁸ Ω · cm. Since the volume resistivity of the base layer used in this example is 10 ³ to 10 ⁵ Ω · cm, the volume resistivity of the surface layer may be set slightly higher.

The volume resistivity of the surface portion of the developing roller 402 is measured by the method shown in FIGS. 5 (A) and 5 (B).
First, the developing roller 402 to be measured is set on a grounded conductive base plate 300, and F = 4.9 N (= 500 gf) is provided at both ends of a cored bar (rotating shaft) 402a of the developing roller 402, respectively. Apply a load, and apply a load of F = 9.8 N (1 kgf) as a whole. As a result, a nip W is formed between the base plate 300 and the base plate 300 as shown in FIG.
A DC power source 302 is connected to the core metal 402 a of the developing roller 402 via an ammeter 301. Then, a DC voltage V (= 1 V) is applied, and the current value I [A] at that time is read.
Using the measured values of the applied voltage value V [V] and current value I [A] and the measured values of various dimensions L1 [cm], L2 [cm], and W [cm], the developing roller 402 is expressed by the following equation. The volume resistivity ρv of the elastic layer 402b is obtained by the following equation (2).

ρv = (V / I) · (L1 × W) / L2 (2)
Further, the thickness of the coating layer of the developing roller 402 is preferably in the range of 5 to 50 μm, and there is a problem such as cracking when stress is generated when the hardness difference between the coat layer exceeding 50 μm and the hardness of the base layer is large. It tends to occur. On the other hand, if the surface wear is below 5 μm, the base layer is exposed and the toner tends to adhere.

On the other hand, the toner 10 constituting the developer 12 used in the developing device 4 is obtained by mixing a charge control agent (CCA) and a colorant in a resin such as polyester, polyol, styrene acryl, etc., and surrounding silica. The fluidity is enhanced by adding external additives such as titanium oxide.
The particle size of the additive is usually in the range of 0.1 to 1.5 μm. Examples of the colorant include carbon black, phthalocyanine blue, quinacridone, and carmine.
In some cases, the toner 10 may be a base toner in which a wax or the like is dispersed and mixed with an additive of the above type added to the base toner.

  The volume average particle diameter of the toner 10 is preferably in the range of 3 to 12 μm. The toner 10 used in this embodiment has a volume average particle diameter of 7 μm, and can sufficiently cope with a high resolution image of 1200 dpi or more. In the present embodiment, the toner 10 having a negative charge polarity is used, but a toner having a positive charge polarity may be used according to the charge polarity of the photoreceptor 1. Further, for the purpose of improving gradation, a toner having a circularity of 90 to 97 percent and a content ratio exceeding 80% is used.

The magnetic particles 11 for constituting the developer as a magnetic brush contain a magnetic material such as ferrite with a metal or resin as a core, and the surface layer is coated with a silicon resin or the like. The particle size of the magnetic particles 11 is preferably in the range of 20 to 50 μm. The resistance of the magnetic particles 11 is preferably in the range of 10 ⁴ to 10 ⁸ Ω in terms of dynamic resistance DR. Here, the measurement of the dynamic resistance DR of the magnetic particles 11 was performed as follows using the measuring apparatus shown in FIG.
First, a rotatable sleeve 201 having a diameter of φ20 mm with a fixed magnet built in a predetermined position is set above the grounded base 200. A counter electrode (doctor) 202 having a facing area with a width W = 65 mm and a length L = 0.5 to 1 mm is opposed to the surface of the sleeve 201 with a gap g = 0.9 mm. Next, the sleeve 201 starts to be rotationally driven at a rotational speed of 600 rpm (linear speed of 628 mm / sec). Then, a predetermined amount (14 g) of magnetic particles to be measured is supported on the rotating sleeve 201, and the magnetic particles are stirred for 10 minutes by the rotation of the sleeve 201. Next, the current I _II [A] flowing between the sleeve 201 and the counter electrode 202 is measured by the ammeter 203 without applying a voltage to the sleeve 201. Next, an applied voltage E [V] of a withstand voltage upper limit level (400 V for high-resistance silicon-coated carrier to several V for iron powder carrier) is applied to sleeve 201 from DC power supply 204 for 5 minutes. In this example, 200 V was applied. Then, the current I _RQ [A] flowing between the sleeve 201 and the counter electrode 202 with the voltage E applied is measured by the ammeter 203. From these results, the dynamic resistance DR [Ω] is calculated using the following equation (3).

_{DR = E / (I RQ -I} II) ··· (3)
In FIG. 4, the magnetic brush roller 403 includes a nonmagnetic rotatable sleeve 408 containing a magnet member 407 having a plurality of magnetic poles.
The magnet member 407 is fixedly arranged so that magnetic force acts when the developer 12 passes through a predetermined location on the sleeve 408. The sleeve 408 used in this example has a diameter of 18 mm and is sandblasted so that the surface roughness Rz (10-point average roughness) falls within the range of 10 to 20 μm.

  The magnet member 407 built in the magnetic brush roller 403 is arranged in the direction of rotation of the magnetic brush roller 403 from the restriction portion by the restriction blade 406 in the N pole (N1), S pole (S1), N pole (N2), and S pole (S2). ) And five magnetic poles of S pole (S3). The arrangement of the magnetic poles of the magnet member 407 is not limited to the configuration shown in FIG. 4, and other arrangements may be set according to the arrangement of the regulating blade 406 around the magnetic brush roller 403.

  Due to the magnetic force of the magnet member 407, the developer 13 composed of the toner 10 and the magnetic particles 11 is carried on the sleeve 408 in a brush shape. The toner 10 in the magnetic brush on the magnetic brush roller 403 is mixed with the magnetic particles 11 to obtain a specified charge amount. The charge amount of the toner on the magnetic brush roller 403 is preferably in the range of −10 to −40 [μC / g].

  The developing roller 402 is opposed to contact with the magnetic brush on the magnetic brush roller 4 in the toner supply area A2 adjacent to the magnetic pole N2 in the magnetic brush roller 403, and is opposed to the photoreceptor 1 in the developing area A1. It is arranged. Further, in this embodiment, the interval at the closest portion between the regulating blade 406 and the magnetic brush roller 403 is set to 500 μm, and the magnetic pole N1 of the magnet member 407 facing the regulating blade 406 is positioned at the position facing the regulating blade 406. Further, the magnetic brush roller 403 is inclined by several degrees on the upstream side in the rotation direction. Thereby, the circulation flow of the developer 12 in the casing 401 can be easily formed.

On the other hand, the regulating blade 406 contacts with the magnetic brush to regulate the amount of the developer 12 formed on the magnetic brush roller 4 03 in the opposing portion of the magnetic brush roller 403, a predetermined amount of the developer toner supply While being conveyed to the region, frictional charging between the toner 10 and the magnetic particles 11 in the developer 12 is promoted.

  Further, the developing roller 402 and the magnetic brush roller 403 are respectively driven to rotate in directions indicated by arrows b and c in FIG. 4 by a rotation driving device (not shown) so that the surfaces of both rollers move in opposite directions in the toner supply region A2. It has become. In this embodiment, the developing roller 402 is rotationally driven at a linear speed of 300 mm / s with respect to the linear speed of the photosensitive member 1 of 200 mm / s. Further, the gap between the developing roller 402 and the sleeve of the magnetic brush roller 403 in the toner supply area A2 is set to 0.6 mm.

Further, a power source 409 for applying a developing bias Vb for forming a developing electric field in the developing area A1 is connected to the shaft portion of the developing roller 402. Further, the sleeve 408 of the magnetic brush roller 403, the power source 410 for applying a toner supply bias V _S for forming a toner supplying electric field to the toner supply area A2 is connected.

In the developing device 4 having such a configuration, the developer 12 in which the toner 10 and the magnetic particles 11 are mixed is used, and both components in the developer 12 are mixed in the stirring / conveying members 404 and 405 and the magnetic brush roller 403. The toner 10 is agitated and mixed by the rotational force of the sleeve 408 and the magnetic force of the magnet member 407 to be frictionally charged and charge is applied to the toner 10.
On the other hand, the developer 12 carried on the magnetic brush roller 403 is regulated by the regulating blade 406, and a certain amount of the developer 12 is transferred to the developing roller 402 by an electric field formed by the toner supply bias, and the rest is left. Returned into the casing 401.
In the toner supply area A2, the toner in the magnetic brush is separated and transferred to the developing roller 402, and the thin-layer toner 10 is carried. The thin layered toner 10 carried on the developing roller 402 is conveyed to the developing area A 1 by the rotation of the roller 402. Then, the developing electric field formed by the developing bias selectively adheres to the electrostatic latent image on the photosensitive member 1, and the electrostatic latent image is developed.

Based on the above configuration, a configuration that is a feature of the present embodiment will be described below.
This embodiment is characterized in that a cleaning device that has been conventionally used as a device for removing the transfer residual toner on the photosensitive member 1 is unnecessary, and the toner collected from the photosensitive member 1 is reused. That is, the transfer residual toner is collected in the developing device 4 by the cleaning device, and the collected toner is restored to a reusable state.

FIG. 7 shows a configuration when the developing device 4 having the configuration shown in FIG. 4 is targeted. In FIG. 7 and subsequent figures, the constituent members shown in FIG. 4 are simplified, those having the same function are indicated by the same reference numerals, and the toner used is negatively charged.
In the drawing, the developing roller 402 that is a toner carrier is in contact with the photosensitive member 1, and the magnetic brush roller 403 that is a toner supply unit is not in contact with the developing roller 402 . In other words, the toner can be transferred to and from the developing roller 402.
In this embodiment, the developing roller 402 is selected from a state in which toner is supplied to the photosensitive member 1 and a state in which the transfer residual toner is collected from the photosensitive member 1.
That is, the developing roller 402 is provided so as to be able to rotate in the forward and reverse directions, and rotates in the same direction at the position facing the photoconductor 1 when supplying toner (the direction indicated by symbol b in FIGS. 4 and 7). The rotation direction is set so that when the transfer residual toner is collected, the rotation direction is opposite to the direction when the toner is supplied (the direction indicated by symbol d in FIG. 7).

As described above, the developing roller 402 is set to 300 mm / sec, which is 1.5 times the linear velocity of the photosensitive member 1 as the linear velocity in the toner supply state, as described above. The linear velocity when rotating and in the toner collecting state is set to 150 mm / sec.
On the other hand, the bias applied to the developing roller 402 and the magnetic brush roller 403 is switched between when the toner is supplied and when the toner is recovered. In this embodiment, the developing roller 402 side is used as the applied bias when the toner is recovered. The voltage is switched from −300 V used at the time of supply to 0 V, and is set to +200 V on the magnetic brush roller 403 side in accordance with the bias change on the developing roller 402 side. As a result, when the transfer residual toner on the photoconductor 1 side is transferred to the developing roller 402, it can be attached to the magnetic particles constituting the magnetic brush formed on the magnetic brush roller 403. As a result, the toner density temporarily increases due to the increase of the toner moved to the magnetic brush roller 403, but it is recharged by being brought to the positions of the agitating / conveying members 404 and 405 and corrected to a charged state of a predetermined potential. Will be. For this reason, the transfer residual toner collected from the photoreceptor 1 is collected and then recharged and can be used for development.

Next, another embodiment of the present invention will be described.
In the embodiment shown in FIGS. 8 and 9, the developing roller 402 and the magnetic brush roller 403 are opposed to the photoreceptor 1 in the same relationship, while the developing roller 402 and the magnetic brush roller 403 are in the moving direction of the photoreceptor 1. It is characterized by the fact that the arrangement position of is different.

In FIG. 8, a magnetic brush roller 403 is disposed on the upstream side of the developing sleeve 403 with respect to the rotational direction that is the moving direction of the photosensitive member 1, and the magnetic brush roller 403 includes both the photosensitive member 2 and the developing roller 402. It is considered to be a relationship that can be opposed to. Further, the developing roller 402 is moved in the same direction at the position facing the photoconductor 1 with respect to the rotation direction of the photoconductor 1, and the magnetic brush roller 403 is in the opposite direction at the position facing the photoconductor 1. The direction of rotation is set. This configuration corresponds to an embodiment of the invention described in claim 4.
In this configuration, the transfer residual toner on the photoreceptor 1 is collected by the magnetic brush roller 403.
The collected toner is transferred by the magnetic brush roller 403 toward the agitating / conveying members 404 and 405 for recharging, and the toner in the magnetic brush is supplied from the magnetic brush roller 403 toward the developing roller 402. . In this configuration, the moving direction of the magnetic brush roller 403, which is a transfer residual toner recovery member, is set with respect to the rotation direction of the photosensitive member 1, thereby facilitating scraping of the transfer residual toner and recovery of the toner onto the magnetic brush. Efficiency can be improved.
In particular, the transfer residual toner is negatively charged due to the bias characteristic, and the magnetic particles in the magnetic brush, which is in contact with the transfer residual toner, so-called carrier, is in contact with the toner because the amount of toner is reduced due to toner consumption. Therefore, the transfer residual toner on the photoreceptor 1 is easily transferred to the magnetic brush and collected.

As a charging condition for improving the toner recovery efficiency in such a charged state, in this embodiment, when reversal development is assumed, the charging potential (V _D ) of the photoreceptor 1 is V _D = −500. ˜−60 (V), latent image portion potential (V _L ) is V _L = −50 to −100 (V), development bias (V _B ) is V _B = −200 to −450 (V), FIG. A supply bias (V _SL ) used to form a toner supply electric field in the toner supply region indicated by the odor symbol A2 is set to V _SL = −250 to −500 (V), respectively. The relationship is V _L <V _SL <V _B <V _D.

On the other hand, in the configuration shown in FIG. 9, the developing roller 402 is disposed upstream of the magnetic brush roller 403 with respect to the rotation direction of the photosensitive member 1, and unlike the case shown in FIG. While collecting the transfer residual toner, the magnetic brush roller 403 functions as a developing member. The developing roller 402 is set in the same rotational direction as the magnetic brush roller 403 shown in FIG. 8 with respect to the rotational direction of the photosensitive member 1, as indicated by an arrow in FIG. In the configuration shown in FIG. 9, the magnetic brush roller 403 has a developer carried on the surface thereof whose layer thickness is regulated by a regulating blade 406 having a configuration similar to that shown in FIG. It is like that. In this configuration, when the developing sleeve 402 collects the transfer residual toner, based on the same principle as in the example shown in FIG. 4, the developing electrolytic strength that allows the toner used for reversal development to transfer to the developing sleeve. It becomes possible by setting.

In such a configuration, the transfer residual toner on the photosensitive member 1 captured by the magnetic particles (carrier) in the magnetic brush formed on the magnetic brush roller 403 is returned to the stirring region and again stirred and transported. By being provided, it is recharged and pumped up by the magnetic brush roller 403.
When the magnetic brush roller 403 collects the transfer residual toner on the developing sleeve 402, the charging condition based on the reverse development used in FIG. On the other hand, the toner carried on the magnetic brush roller 403 is transferred and repelled against the developing sleeve 402, so that the toner is conveyed to the stirring region without being transferred. That is, the above-described charging conditions are the charging bias (V _D ), latent image portion potential (V _L ), developing bias (V _B ) of the photosensitive member 1 and the supply bias (V _B ) used for forming the toner supply electric field. in the case of the _SL), a relationship that a _{V L <V SL <V B} <V D.

The present inventor has determined whether the transfer residual toner is collected using the developing device according to the present embodiment and the transfer residual toner is collected using the cleaning device using the conventional cleaning blade. As a result, the results shown in FIG. 10 were obtained.
As is clear from the results shown in FIG. 10, the background stain is eliminated in the transfer residual toner collecting configuration according to this embodiment as compared with the case where the conventional cleaning device is used.

The results shown in FIG. 10 are obtained by copying the surface of the photosensitive member 1 onto a transparent adhesive tape and affixing the surface to a transfer paper to compare the optical density difference (ΔID).
The reason why the results shown in FIG. 10 are obtained is that the surface of the photoreceptor is damaged by the blade when a conventional cleaning device is used, and if toner adheres to the scratched part, it remains unremoved. It is considered that the body surface is soiled. On the other hand, in the transfer residual toner collecting configuration according to the present embodiment, the above-described problems hardly occur because there is no sliding member on the surface of the photoreceptor 1.

In this embodiment, attention is also paid to the relationship between the particle size and charge distribution of the toner used in the developing device 4 and the image quality. In other words, the influence on the background stain and the influence on the image quality due to the relationship between the toner particle size and the collection efficiency are clarified through experiments.
For measurement of toner particle size and charge amount distribution, E-SPART ANALYZER (Analyzer manufactured by Hosokawa Micron Co., Ltd., hereinafter referred to as “E-SPART analyzer”) was used. This E-SPART analyzer employs a method using a dual beam frequency shift laser Doppler velocimeter and an elastic wave that perturbs the movement of particles in an electrostatic field, and applies air to the toner on the developing roller 402. It is possible to obtain data on the particle size and the charge amount of each toner by spraying and capturing the movement in the electric field. In this confirmation experiment, 3000 toners were sampled to see the difference in distribution.
Here, if the charge is uniformly present throughout the toner in each toner, the toner charge amount is proportional to the third power of the toner particle diameter, but is actually proportional to the toner particle diameter itself. Thus, since the toner charge amount and the toner particle size are in a proportional relationship, in this confirmation experiment, the value obtained by dividing the toner charge amount q by the particle size d, that is, the influence of the toner particle size is eliminated (q / The toner number distribution was measured for the value of d).

FIG. 11 shows a comparative measurement result of the toner charge amount distribution on the developing roller 402 measured by the E-SPART analyzer and in the region where the collected toner is supplied.
As is apparent from FIG. 11, in this embodiment, the charge amount distribution profile of the toner carried on the developing roller 402 is 6.1% compared with the reverse charge amount rate of 21.4% immediately after collection. As a result, the conditions for re-supplying the collected toner are adjusted, and there is no problem with respect to the background dirt, and a high-quality image can be obtained.

FIG. 12 is a diagram showing the result of comparative evaluation of the amount of residual toner collected by using spherical toner and conventional pulverized toner. This evaluation is based on the measurement of the optical density difference (ΔID) due to background contamination of the photoreceptor 1. It is the obtained result.
As is apparent from FIG. 12, it can be seen that the spherical toner method has high recovery efficiency.

FIG. 2 is a schematic diagram for explaining a configuration of an image forming apparatus using a developing device according to an embodiment of the present invention. FIG. 2 is an external view of a process cartridge used in the image forming apparatus illustrated in FIG. 1. It is a figure for demonstrating the experimental apparatus regarding a friction coefficient among the surface characteristics of the photoreceptor used for the image forming apparatus shown in FIG. It is a schematic diagram for demonstrating the structure of the developing device by the Example of this invention. FIG. 5 is a schematic diagram for explaining a configuration used for measurement related to a volume resistivity of a developing roller surface portion used in the developing device shown in FIG. 4. FIG. 5 is a schematic diagram for explaining a configuration for measuring dynamic resistance of magnetic particles corresponding to carriers in a developer used in the developing device shown in FIG. 4. It is a schematic diagram for demonstrating the principal part structure of the image development apparatus by the Example of this invention. It is a schematic diagram for demonstrating the principal part structure of the image development apparatus by another Example of this invention. It is a schematic diagram for demonstrating the principal part structure of the image development apparatus by another Example of this invention. It is a figure which shows the result of having compared the toner collection rate using the image development apparatus by the Example of this invention, and the toner collection rate using the conventional cleaning blade by the optical density difference of background dirt. It is a figure which shows the result of having experimented on the relationship between the particle size and charge distribution of the toner used for the image development apparatus by the Example of this invention, and image quality. It is a figure which shows the experimental result of the influence of the collection | recovery residual toner amount by a spherical toner and the conventional grinding | pulverization toner.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Developing apparatus 402 Developing roller 403 Magnetic brush roller 409,410 Bias power supply 50 Process cartridge

Claims (8)

A developing device capable of reversal development of an electrostatic latent image carried on a latent image carrier by toner in a magnetic brush using a two-component developer containing toner and a magnetic carrier,
A layer that is provided with a magnetic pole for attracting and holding the carrier in the two-component developer inside, can form a supply electric field for supplying toner contained in the two-component developer, and is disposed in the vicinity Developer supply means for regulating the amount of the two-component developer carried by the thickness regulating member;
Development that is disposed adjacent to the developer supply means and is opposed to a latent image carrier that carries an electrostatic latent image and that can form a developing electric field for supplying toner to the latent image carrier. Agent carrying means,
It said developer carrying means, when supplying the toner by the developing electric field carries the toner supplied by the supply electric field formed developer carrying means side in adjacent position between the developing agent supply means to the surface to, at the time of collecting the toner to move in the same direction as the latent image bearing member at a position opposed to the aforementioned latent image supply means, remaining on the surface toward the adjacent position between the developing agent supply means, of the toner Move in the opposite direction to the supply direction,
When the toner remaining on the latent image carrier is collected toward the position adjacent to the developer supply means, the development electric field reduces the electric field strength when supplying toner to the latent image carrier, and The developing device, wherein the supply electric field is changed to an electric field intensity capable of collecting the toner moved to the adjacent position in accordance with the change of the developing electric field. A developing device capable of reversal development of an electrostatic latent image carried on a latent image carrier by toner in a magnetic brush using a two-component developer containing toner and a magnetic carrier,
A magnetic pole for attracting and holding the carrier in the two-component developer is provided inside, and a supply electric field for supplying the toner contained in the two-component developer can be formed, and is arranged in the vicinity. A developer supply means for defining the carrying amount of the two-component developer by the layer thickness regulating member;
A developer carrying means disposed opposite to the latent image carrier and capable of forming a developing electric field for supplying toner to the latent image carrier;
The developer supply means is disposed upstream of the developer carrier in the moving direction of the latent image carrier, and faces both the latent image carrier and the developer carrier, so that the latent image A developing device characterized in that a moving direction at a position facing the carrier is opposite to a direction of movement of the latent image carrier, and the transfer residual toner is collected from the latent image carrier . A developing device capable of reversal development of an electrostatic latent image carried on a latent image carrier by toner in a magnetic brush using a two-component developer containing toner and a magnetic carrier,
A magnetic pole for attracting and holding the carrier in the two-component developer and a supply electric field for supplying the toner contained in the two-component developer can be formed inside, and the layer thickness is arranged in the vicinity. Developer supply means in which the carrying amount of the two-component developer is defined by the member;
A developer carrying means that is disposed opposite to the latent image carrier and capable of forming a developing electric field for the latent image carrier;
It said developer carrying means is disposed on the upper stream side than the developing agent supply means in the direction of movement of the latent image bearing member opposed to both the said latent image bearing member and said developer carrying member, the latent A developing device characterized in that a moving direction at a position facing the image carrier is opposite to a moving direction of the latent image carrier, and the toner is collected from the latent image carrier .   An image forming apparatus using the developing device according to claim 1. The image forming apparatus according to claim 4.
An image forming apparatus, wherein the latent image carrier has a low surface energy. The image forming apparatus according to claim 4 or 5, wherein:
An image forming apparatus, wherein the toner contained in the two-component developer is one having a circularity of 90 to 97% and a content ratio exceeding 80%. The image forming apparatus according to claim 4, wherein:
When the development method of the latent image formed on the latent image carrier uses reversal development, the latent image formation conditions and bias application conditions to each means are as follows:
V _L <V _SL <V _B <V _D
However, the image forming apparatus is characterized in that the relationship of V _L : latent image potential (exposure control potential), V _SL : supply bias, V _B : development bias, and V _D : charging potential is set. A process cartridge for use in the image forming apparatus according to claim 4,
The latent image carrier, a charging device for uniformly charging the latent image carrier, and a developing device for processing a visible image of the electrostatic latent image formed on the latent image carrier are collectively arranged in a unit, and the image forming apparatus main body A process cartridge, wherein the process cartridge is detachable from the process cartridge.

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