JP5210792B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus such as a copying machine, a printer, or a facsimile machine.

  A developing device provided in an image forming apparatus such as a copying machine develops an image based on the electrostatic latent image on the image carrier by supplying a developer to the image carrier on which the electrostatic latent image is formed. To do. The developed image is transferred from an image carrier to a sheet or the like by a transfer device, and then heated and pressed by a fixing device to be fixed on the sheet.

Conventionally, the scattering of the developer has been a problem in the developing device. The scattered developer contaminates the image carrier disposed in the image forming apparatus, the optical system, the charger, and the like, and causes various image formation failures and operation failures.
As means for solving such a problem, for example, Japanese Patent Application Laid-Open No. H10-228561 discloses a device that includes a collection roller that collects the scattered developer and suppresses contamination in the image forming apparatus due to the scattered developer. According to Japanese Patent Laid-Open No. 2004-228561, the scattered developer is adsorbed and collected by applying a bias to the collecting roller and applying an electric adsorption force. Further, a bias corresponding to the formed image ratio or the like is applied to the collection roller by a control means for changing the bias to be applied.
JP-A-11-174792

By the way, the developer adsorbed and collected on the collection roller is usually scraped off from the collection roller by scraping means having a blade, a brush, etc., and then returned to the developing device and reused.
However, the developer may rub against the peripheral surface of the blade or the collection roller during the scraping, and may be triboelectrically charged, increasing the charge amount of the developer (charging up). The developer whose charge amount has increased due to frictional charging adheres (adsorbs) more strongly on the peripheral surface of the recovery roller, and remains on the peripheral surface of the recovery roller without being scraped off by the blade. . The developer remaining on the peripheral surface of the collecting roller reduces the attracting force of the collecting roller and affects the collecting ability of the scattered developer. In addition, if the developer whose charge amount has increased due to frictional charging is scraped off by the blade and returned to the developing device, it may affect the charging of the internal developer and cause image formation defects such as color unevenness, for example. There is.

  The present invention has been made in view of the above problems, and provides a developing device and an image forming apparatus capable of maintaining the ability to collect a developer scattered over a long period of time and suppressing image formation defects. With the goal.

In order to solve the above problems, the present invention provides a developer supply unit that supplies a developer to an image carrier, and at least a part of the developer that is applied with a bias and scattered during the supply. A developing device including a collecting roller that is electrically adsorbed and collected, wherein one of a nickel layer, a copper layer, a silver layer, and a chromium layer is provided on a peripheral surface of the collecting roller Is adopted.
By adopting such a configuration, in the present invention, an increase in charge amount due to friction of the adsorbed developer can be suppressed.

Further, in the present invention, the nickel layer, the copper layer, the silver layer, and the chromium layer are configured by plating.
By adopting such a configuration, in the present invention, each layer is formed on the circumferential surface of the collection roller by plating.

Moreover, in this invention, the said nickel layer employ | adopts the structure that it consists of electroless nickel plating formed by the electroless nickel process.
By adopting such a configuration, in the present invention, in addition to the property of suppressing the increase in the charge amount due to the friction of the adsorbed developer, it has corrosion resistance and friction resistance, and the collection roller is stable over a long period of time. The recovery capability can be maintained.

In the present invention, the developer includes toner and a magnetic carrier, and the developer supply unit includes a magnetic roller that rotates and forms a magnetic brush made of the developer on the peripheral surface. The collection roller is configured to be disposed at a position where the circumferential surface and the magnetic brush come into contact with each other.
By adopting such a configuration, in the present invention, the collected developer can be transferred from the peripheral surface of the collection roller to the magnetic roller side via the magnetic brush and contribute to development.

Further, in the present invention, a configuration is adopted in which the collection roller rotates by contacting with the magnetic brush.
By adopting such a configuration, in the present invention, there is no need to provide a drive source for rotationally driving the collection roller, which can contribute to a reduction in the number of parts and a reduction in cost.

  In the present invention, an image forming apparatus provided with the above developing device is obtained.

According to the present invention, a developer supply unit that supplies a developer to the image carrier, and at least a part of the developer that is applied with a bias and scattered during the supply is electrically adsorbed and collected. A collecting roller, and a suction roller by adopting a configuration in which any one of a nickel layer, a copper layer, a silver layer, and a chromium layer is provided on the peripheral surface of the collecting roller. The increase in the charge amount due to the friction of the developed developer can be suppressed. Thus, the adsorbed developer can be easily scraped off from the collecting roller, and the remaining developer is prevented from affecting the collecting ability. Further, even if the adsorbed developer is reused, it is possible to prevent image formation failure.
Therefore, in the present invention, there is an effect that it is possible to provide a developing device capable of maintaining the ability to collect the developer scattered over a long period of time and suppressing image formation defects.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description, an example in which the developing device of the present invention is applied to an image forming apparatus will be described. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

First, the configuration of the image forming apparatus 1 in the present embodiment will be described with reference to FIG.
FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus 1 according to an embodiment of the present invention.
The image forming apparatus 1 is transferred to an image forming unit 2 that forms an image, a paper feed cassette 3 that stores paper, a secondary transfer unit 4 that transfers an image formed by the image forming unit 2 to paper. A fixing unit 5 that fixes the image on the sheet, and a conveyance path 6 that conveys the sheet in the order of the secondary transfer unit 4 and the fixing unit 5 while carrying the sheet out of the sheet feeding cassette 3.

The image forming unit 2 includes an intermediate transfer belt 21, a photoconductor (image carrier) 22, a charger 23, an exposure device 24, a developing device 100 (described later), a primary transfer roller 25, and a cleaning device 26. Have
The intermediate transfer belt 21 is stretched around a driving roller 27 and a driven roller 28, and is configured to endlessly rotate counterclockwise in FIG. The driving roller 27 is connected to a driving source such as a motor, and rotates while applying a gripping force to the intermediate transfer belt 21. The driven roller 28 is driven to rotate following the rotational drive of the drive roller 27.

The photosensitive member 22 is set in a cylindrical shape, and an electrostatic latent image and a toner image based on the electrostatic latent image are formed on the peripheral surface thereof. The charger 23 is disposed so as to face the photoconductor 22 and charges the peripheral surface of the photoconductor 22. The exposure device 24 scans the peripheral surface of the charged photosensitive member 22 with laser light emitted based on the print format image data. The developing device 100 develops an image based on the electrostatic latent image on the peripheral surface of the photoconductor 22 by supplying a developer to the peripheral surface of the photoconductor 22. The primary transfer roller 25 is disposed opposite to the photosensitive member 22 with the intermediate transfer belt 21 interposed therebetween, and primarily transfers an image developed on the photosensitive member 22 to the intermediate transfer belt 21. The cleaning device 26 removes toner remaining on the photosensitive member 22.
As an example, the electrostatic latent image is formed by irradiating the surface of the photosensitive member 22 to 200 to 800 V with the charger 23 and irradiating the semiconductor laser light or LED laser light with the exposure device 24. The post-exposure potential is 70 to 220 V if the photoreceptor 22 is an organic photoreceptor (OPC photoreceptor), and 10 to 50 V if the photoreceptor 22 is an amorphous silicon photoreceptor.
The photoconductor 22 in this embodiment is an amorphous silicon photoconductor and rotates clockwise in FIG. 1 with an outer diameter of 40 mm and a peripheral speed of 450 mm / sec. Further, as the photosensitive member 22, a photosensitive member having a surface potential of 310V and a post-exposure potential of 20V is adopted.

  The paper feed cassette 3 is freely drawable with respect to the apparatus main body and accommodates paper. The secondary transfer unit 4 performs secondary transfer of an image formed on the intermediate transfer belt 21 onto a sheet. The secondary transfer unit 4 drives the intermediate transfer belt 21 with the driving roller 27 and the intermediate transfer belt 21 interposed therebetween. A secondary transfer roller 41 disposed opposite to the roller 27 is provided. The fixing unit 5 includes a heating roller that fixes the image secondarily transferred onto the sheet by applying pressure and heating. The transport path 6 includes a plurality of rollers (not shown) for transporting paper, including a pickup roller for transporting paper from the paper feed cassette 3.

Next, the configuration of the developing device 100 according to the present invention will be described in detail with reference to FIGS. 1 and 2.
FIG. 2 is an enlarged view of a main part of the developing device 100 according to the embodiment of the present invention.
The developing device 100 of the present embodiment is a so-called touch-down developing method (hybrid developing method combining a one-component developing method and a two-component developing method). The developing device 100 includes a developing container 110 that stores a two-component developer of toner and a magnetic carrier, a first screw 121 and a second screw 122 that stir and mix the developer stored in the developing container 110, A developer supply unit 130 that includes a magnetic roller 131 and a developing roller 132 and supplies the developer to the photosensitive member 22, and a recovery roller 140 that recovers the scattered developer.

The developing container 110 includes a first transport path 111A in which the first screw 121 is disposed, and a second transport path 111B in which the second screw 122 is disposed. 111 A of 1st conveyance paths and the 2nd conveyance path 111B are arranged in parallel via the partition wall 112, and become a structure which mutually communicates in both ends (both ends of a paper surface perpendicular direction).
The first screw 121 and the second screw 122 are configured to circulate the developer between the first conveyance path 111A and the second conveyance path 111B by being rotationally driven by a drive source such as a motor. The first screw 121 and the second screw 122 are configured to circulate the developer and stir the toner to frictionally charge the toner.

The toner preferably has a volume average particle size of 4.0 to 9.5 μm. When the volume average particle diameter is less than 4.0 μm, the influence of non-electrostatic adhesion is increased, and developability and recoverability are deteriorated. On the other hand, when the volume average particle diameter is larger than 9.5 μm, it is difficult to obtain a high-quality image. In this embodiment, the volume average particle diameter of the toner is 6.8 μm.
The toner charge amount is preferably 6 to 30 μC / g. When the charge amount is less than 6 μC / g, the toner is scattered from the magnetic roller 131 to contaminate the surroundings. If the charge amount is greater than 30 μC / g, the formation of a thin layer on the developing roller 132 is weakened. In the present embodiment, the charge amount of the toner is 20 μC / g.

As the magnetic carrier, a known carrier such as a resin core coated on the surface of a ferrite core can be used. As the resin coating, known materials such as silicone, fluorosilicone, polyamide, and polyamideimide can be used. The magnetic carrier preferably has a weight average particle diameter of 25 to 50 μm. When the weight average particle diameter is less than 25 μm, the holding force by the magnetic force (force for forming a magnetic brush) is weakened, so that the so-called carrier jump that the magnetic carrier moves from the magnetic roller 131 to the developing roller 132, the collecting roller 140, and the like. May occur. Further, if the weight average particle diameter is larger than 50 μm, the density of the magnetic brush may not be appropriate. For example, it affects the formation of a thin toner layer on the developing roller 132, and the specific surface area of the magnetic brush is reduced. As a result, the toner recoverability also decreases. In this embodiment, the weight average particle diameter of the magnetic carrier is 35 μm.
The magnetic carrier desirably has a saturation magnetization of 35 to 90 emu / g. When the saturation magnetization is less than 35 emu / g, the carrier jump occurs remarkably, and when the saturation magnetization is more than 90 emu / g, the magnetic brush becomes sparse and it is difficult to form a uniform thin layer of the developing roller 132.

The magnetic roller 131 is provided on the first conveyance path 111A side and faces the first screw 121, and conveys the developer in the first conveyance path 111A to the developing roller 132 by a magnetic action. The magnetic roller 131 has a plurality of magnetic members fixed inside and a cylindrical sleeve that rotates on the outer peripheral portion of the magnetic member, and a magnetic material composed of toner and a magnetic carrier on the peripheral surface of the sleeve. The brush is formed and the sleeve is rotated to convey the developer. Note that the magnetic brush can be conveyed more efficiently by performing blasting and groove processing on the peripheral surface of the magnetic roller 131.
The magnetic roller 131 is configured to be applied with a bias voltage obtained by superimposing an AC voltage on a DC voltage from an AC (AC) bias power supply and a DC (DC: Vdc1) bias power supply (both not shown). . The height of the magnetic brush is regulated to be constant by a regulation blade 100A1 provided in the housing 100A. The magnetic roller 131 in the present embodiment has a sleeve made of aluminum, and rotates counterclockwise in FIG. 2 at an outer diameter of 25 mm and a peripheral speed of 675 mm / sec.

The developing roller 132 receives toner from a magnetic brush formed on the magnetic roller 131 and supplies the received toner to the photosensitive member 22, and is provided between the magnetic roller 131 and the photosensitive member 22. The developing roller 132 includes a magnetic member having a magnetic pole different from that of the magnetic member of the magnetic roller 131 and has a cylindrical sleeve that rotates the outer peripheral portion of the magnetic member, and adsorbs toner to the peripheral surface of the sleeve. A thin layer is formed and the sleeve is rotated to convey the developer.
The developing roller 132 is configured to be applied with a bias voltage obtained by superimposing an AC voltage on a DC voltage from an AC (AC) bias power supply and a DC (DC: Vdc2) bias power supply (both not shown). . The magnetic roller 131 in the present embodiment has a sleeve made of aluminum, and rotates counterclockwise in FIG. 2 with an outer diameter of 20 mm and a peripheral speed of 700 mm / sec.

  As for the bias conditions during development, it is desirable to apply a DC voltage of 300 to 500 V to the magnetic roller 131 and a DC voltage of 100 V to the developing roller 132. As the potential difference between the two for forming a thin layer on the developing roller 132, 150 to 400V is appropriate. Further, the AC condition is that the developing roller 132 is Vp-p (peak AC bias) = 1.0 to 2.0 kV, the frequency is 2 to 6 kHz, the DUTY ratio is 20 to 40%, and the magnetic roller 131 is the developing roller. It is desirable that the same frequency as 132, Vp-p = 0.1 to 2.0 kV, frequency 2 to 6 kHz, and DUTY ratio = 60 to 80%. In this embodiment, the applied voltage of the developing roller 132 is Vdc2 = 100V, Vp-p = 1.6 kV, the frequency f = 2.7 kHz, the DUTY ratio = 45%, the applied voltage of the magnetic roller 131 is Vdc1 = 300V, and the developing In the same period as the roller 132, Vp-p = 1.3 kV, frequency f = 4.5 kHz, and DUTY ratio = 70%.

  The gap between the magnetic roller 131 and the developing roller 132 is preferably 200 to 600 μm. More preferably, it is 200-400 micrometers. If the gap is less than 200 μm, the magnetic brush disturbs the thin layer of the developing roller 132. On the other hand, if the gap is larger than 600 μm, the efficiency of transporting toner from the magnetic roller 131 to the developing roller 132 is lowered, causing a thin layer formation failure, and there is a possibility of causing a problem of image formation failure such as so-called development ghost. In the present embodiment, the gap between the magnetic roller 131 and the developing roller 132 is 350 μm.

  The collection roller 140 collects the scattered toner and returns the collected toner to the developing container 110. The collection roller 140 is disposed below the magnetic roller 131 and closes the gap between the magnetic roller 131 and the housing 100A. Is done. The collection roller 140 is disposed downstream of the developing roller 132 in the rotation direction of the magnetic roller 131 and so as to face the magnetic roller 131. By disposing in this way, the image forming apparatus via the toner scattered in the vicinity of the developing roller 132 and the magnetic roller 131 and the gap between the magnetic roller 131 and the housing 100A from the first conveyance path 111A. The toner scattered in 1 can be adsorbed on the peripheral surface of the collection roller 140.

  The collection roller 140 has a sleeve (base material) such as stainless steel or aluminum, and a nickel layer 141 is provided on the peripheral surface of the sleeve. In the present embodiment, the sleeve is made of aluminum, and the nickel layer 141 is formed by electroless nickel treatment on the surface of the sleeve and covers the peripheral surface of the sleeve. The nickel layer 141 has conductivity and corrosion resistance and friction resistance. On the peripheral surface of the collection roller 140, a tip portion of a scraping blade 100A2 provided in the housing 100A is disposed. The scraping blade 100A2 is arranged in contact with the peripheral surface of the collection roller 140 or in a non-contact manner with a small distance. In the case of contact, the tip of the scraping blade 100A2 and the peripheral surface of the collection roller 140 are brought into pressure contact with each other, so that the adsorbed toner is more reliably scraped off. In the case of non-contact, the toner collecting ability is kept constant by regulating the thickness of the toner formed on the peripheral surface of the collecting roller 140 to a certain value or less.

The circumferential surface of the collection roller 140 and the circumferential surface of the magnetic roller 131 rotate in the same direction at positions facing each other. In other words, the rotation direction of the magnetic roller 131 is counterclockwise in FIG. 2, whereas the rotation direction of the collection roller 140 is clockwise in FIG. Note that the outer diameter of the collection roller 140 of this embodiment is 10 mm.
The circumferential speed of the collection roller 140 is desirably 10 to 100 mm / sec. More preferably, it is 20 to 70 mm / sec. If the circumferential speed of the collection roller 140 is less than 10 mm / sec, the number of rotations is small and the scattered toner cannot be collected. Further, when the peripheral speed of the collecting roller 140 is larger than 100 mm / sec, the rotation speed increases, and on the contrary, the collecting ability of the scattered toner is lowered and the toner is scattered again when the collected toner is peeled off by the magnetic brush. There is a risk that. In this embodiment, the circumferential speed of the collection roller 140 is 30 mm / sec.

The collection roller 140 is configured to apply a bias voltage obtained by superimposing an AC voltage on a DC voltage from an AC (AC) bias power supply and a DC (DC: Vdc3) bias power supply (both not shown). The AC bias power source and the DC bias power source are configured such that the bias applied to the collection roller 140 is adjusted by a control device (not shown). The control device includes a computer system having a CPU, a memory, and the like. In the present embodiment, the control device is configured to adjust the bias according to the printing rate for printing on paper.
In the present embodiment, when the printing rate is less than 5%, the applied voltage of the collection roller 140 is Vdc3 = −100 V, Vp−p = 0.3 kV having the same period and opposite phase as the magnetic roller 131, and the frequency f = 4.5 kHz. , DUTY ratio = 30%. When the printing rate is 5 to 15%, the applied voltage of the recovery roller 140 is Vdc3 = 0V, the same period as the magnetic roller 131 and the reverse phase Vp-p = 0.3 kV, frequency f = 2.7 kHz, DUTY ratio = 30%. When the printing rate is greater than 15%, the applied voltage of the recovery roller 140 is Vdc3 = 300 V, the same period as the magnetic roller 131 and Vp-p = 0.3 kV in the opposite phase, frequency f = 4.5 kHz, DUTY ratio = 30%.

The gap between the magnetic roller 131 and the collection roller 140 is such an interval that the magnetic brush of the magnetic roller 131 contacts (contacts) the circumferential surface of the collection roller 140. It is desirable to make it smaller than the gap. By making the gap between the magnetic roller 131 and the collecting roller 140 smaller than the gap between the magnetic roller 131 and the developing roller 132, the toner scattered from the magnetic roller 131 is not on the developing roller 132 side but on the collecting roller 140 side. Can be absorbed.
The gap between the magnetic roller 131 and the collection roller 140 is preferably 150 to 500 μm. More preferably, it is 200-300 micrometers. If the gap is less than 150 μm, a leak may occur. On the other hand, if the gap is larger than 500 μm, the scattered toner cannot be collected and the toner may be scattered on the developing roller 132 side. In the present embodiment, the gap between the magnetic roller 131 and the collection roller 140 is 250 μm. Further, the gap between the developing roller 132 and the collection roller 140 is set to 1000 μm.

Next, the operation of the developing device 100 configured as described above will be described.
The developing device 100 rotates and drives the first screw 121 and the second screw 122 to circulate the toner and the magnetic carrier in the developing container 110 and to frictionally charge them.
A magnetic brush is formed on the circumferential surface of the magnetic roller 131 by a magnetic field generated by the magnetic member inside the magnetic roller 131 and the magnetic member inside the developing roller 132. The magnetic brush is composed of a magnetic carrier that is magnetically constrained to the peripheral surface of the magnetic roller 131 to form a plurality of spikes, and toner that is charged and held on the surface of the magnetic carrier. The height of the magnetic brush is regulated to be constant by the counterclockwise rotation of the magnetic roller 131 and the regulating blade 100 </ b> A <b> 1, and the magnetic brush is conveyed toward the developing roller 132.

  A developing bias voltage obtained by superimposing an alternating voltage (AC) on a direct current voltage (DC: Vdc1) is applied to the magnetic roller 131, and an alternating voltage (AC) is superimposed on the direct current voltage (DC: Vdc2) on the developing roller 132. A developing bias voltage is applied. The magnetic brush is regulated in height by the regulating blade 100A1 and then conveyed toward the developing roller 132, and the toner charged in the magnetic brush by the potential difference between the magnetic roller 131 and the developing roller 132. Only the magnetic roller 131 moves from the developing roller 132 to the developing roller 132 and forms a thin layer of toner on the peripheral surface of the developing roller 132. The toner on the developing roller 132 develops the electrostatic latent image on the photoreceptor 22. Further, the magnetic brush electrically transfers the toner to the developing roller 132 side, and at the same time, scrapes the residual toner on the developing roller 132 that has not contributed to development by a mechanical action.

  The collection roller 140 sucks and collects the toner scattered by the above operation. Specifically, the recovery roller 140 is applied with a recovery bias voltage obtained by superimposing an alternating voltage (AC) on a direct current voltage (DC: Vdc3), and electrically attracts scattered scattered toner. to recover. The collection roller 140 is scattered in the vicinity of the developing roller 132 and the magnetic roller 131 and the toner floating in the image forming apparatus 1 through the gap between the magnetic roller 131 and the housing 100A from the first conveyance path 111A. The toner to be absorbed is attracted to the peripheral surface of the collection roller 140.

Further, since the circumferential surface of the collection roller 140 is disposed at a position where it comes into contact with the magnetic brush, the attracted toner is scraped off by the magnetic brush and returns to the magnetic roller 131 side. The toner still remaining on the peripheral surface of the collection roller 140 by the magnetic brush is scraped off by the scraping blade 100A2 and returns into the developing container 110.
During the above scraping or scraping, the toner may be frictionally charged by rubbing against the peripheral surface of the recovery roller 140 or the scraping blade 100A2, and the toner charge amount may increase. Since a nickel layer 141 is formed on the peripheral surface of the toner and has corrosion resistance and friction resistance, it is strong against friction and because it has conductivity, a predetermined amount of charge of the toner can be released, so that it is caused by friction of the adsorbed toner. An increase in charge amount can be suppressed. Therefore, toner does not remain on the peripheral surface of the collecting roller 140, and even if the scraped toner is returned into the developing container 110, it is possible to prevent charging of the internal developer. .

Furthermore, the effect of the collection roller 140 in the present embodiment will be described based on the following two experimental results. The following experiment is an experimental example in which a conventional collecting roller (only stainless steel) is compared with the collecting roller 140 (aluminum + electroless nickel) of the present embodiment.
[Experiment 1] It was confirmed whether or not toner scattering occurred outside the developing device 100 when the number of printed sheets was 1000, 10000, and 20000.
[Experiment 2] When the number of printed sheets was 1000, 5000, and 10,000, the charge amount of the toner on the collecting roller was measured. The charge amount of the toner was measured with a QM meter (manufactured by TREK, MODEL210HS).

  In Experiment 1, when the number of printed sheets was 1000, toner scattering to the outside of the developing device 100 was not confirmed in both the conventional and the present embodiments. However, in the case of 10,000 sheets and 20,000 sheets, it was confirmed that the toner scattered in the jaw portion 100B was adhered to the developing device 100 equipped with the stainless steel collection roller. On the other hand, in the developing device 100 equipped with the recovery roller 140 of this embodiment in which electroless nickel plating is applied to aluminum, toner scattering to the outside was not confirmed.

  Next, the experimental results of Experiment 2 are shown in Table 1 below.

  As shown in Table 1, it was confirmed that the charge amount of the toner on the stainless steel collecting roller increased in proportion to the increase in the number of printed sheets. On the other hand, it was confirmed that the charge amount of the toner on the collection roller 140 of the present embodiment in which electroless nickel plating is applied to aluminum is slightly increased but not increased.

Therefore, according to the present embodiment, the developer supply unit 130 that supplies the developer to the photosensitive member 22 and at least a part of the developer that is applied with the bias and scattered during the supply are electrically connected. The developing device 100 includes a collecting roller 140 that sucks and collects, and a configuration in which a nickel layer 141 is provided on the peripheral surface of the collecting roller 140 makes it possible to charge the toner by the friction of the adsorbed toner. Can be suppressed. Therefore, the adsorbed toner can be easily scraped off from the collecting roller 140, and the remaining toner is prevented from affecting the collecting ability of the collecting roller 140. Further, even if the adsorbed toner is returned to the developing container 110 and reused, it is possible to prevent image formation defects from being caused.
Therefore, in the present embodiment, there is an effect that it is possible to provide the developing device 100 that can maintain the ability to collect the developer scattered over a long period of time and can suppress image formation defects.

  In this embodiment, the nickel layer 141 has a characteristic that suppresses an increase in charge amount due to friction of the adsorbed toner by adopting a configuration in which the nickel layer 141 is made of electroless nickel plating formed by electroless nickel treatment. In addition, it has corrosion resistance and friction resistance, and the recovery roller 140 can maintain a stable recovery capability over a long period of time.

  In this embodiment, the developer is composed of toner and a magnetic carrier, and the developer supply unit 130 includes a magnetic roller 131 that rotates and forms a magnetic brush made of the developer on the peripheral surface. By adopting a configuration in which the collecting roller 140 is disposed at a position where the peripheral surface and the magnetic brush come into contact with each other, the attracted toner is transferred from the peripheral surface of the collecting roller 140 to the magnetic roller side via the magnetic brush. Can contribute to development.

  Further, in the present embodiment, the image forming apparatus 1 provided with the developing device 100 is obtained, and scattered toner is efficiently collected and toner adhesion on the peripheral surface of the collection roller 140 is reduced. It is possible to always perform stable toner collection and good image formation.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  For example, in the present embodiment, it has been described that the nickel layer 141 is made of electroless nickel plating formed by electroless nickel treatment, but the present invention is not limited to the above configuration. For example, the nickel layer 141 may be formed by using a normal non-electroless plating process, vapor deposition, sputtering, or the like. However, if the electroless nickel process is used, in addition to the above-described effects. The nickel layer can be easily formed and the cost is reduced.

In addition, for example, in the present invention, the collection roller 140 may be configured to rotate by contacting the magnetic brush of the magnetic roller 131.
By adopting such a configuration, it is not necessary to provide a drive source for rotationally driving the collection roller 140, which can contribute to a reduction in the number of parts and a reduction in cost.

Further, for example, in the present embodiment, the nickel layer 141 is provided on the peripheral surface of the collecting roller 140 in order to suppress the frictional charging of the developer (toner), but instead of the copper layer, the silver layer, and the chromium layer. Even if it is the structure which uses either, the effect | action and effect similar to this embodiment mentioned above are acquired. There are various methods for forming each of these layers, but it is desirable from the viewpoint of cost to form them by plating.
As an example, when the number of printed sheets is 1000, the charge amount of the toner is 9.17 μC / g if the recovery roller has copper plating on the peripheral surface. Further, in the case of a collecting roller having a silver plating formed on the peripheral surface, the toner charge amount is 6.4 μC / g. Further, it was confirmed by experiments that the charge amount is 7.1 μC / g in the case of a collecting roller having a chrome plating on the peripheral surface. That is, the charge amount of the toner on each collection roller is smaller than the charge amount of the toner on the conventional stainless steel collection roller, and each of the collection rollers acts to suppress an increase in the charge amount due to the friction of the toner. It can be confirmed that there is an effect.

  For example, in the present embodiment, the developing device is described as a so-called touch-down developing method, but the present invention is a developing device of another developing method (for example, a one-component developing method, a two-component developing method, etc.). Even can be applied.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part of the developing device in the embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 22 ... Photoconductor (image carrier), 100 ... Developing device, 130 ... Developer supply part, 131 ... Magnetic roller, 140 ... Collection roller, 141 ... Nickel layer

Claims (5)

A developer supply unit configured to supply a developer to the image carrier; and a collection roller that applies a bias and electrically attracts and collects at least a part of the developer scattered during the supply. A developing device,
The developer comprises a toner and a magnetic carrier,
The developer supply unit includes a magnetic roller that is rotationally driven and forms a magnetic brush made of the developer on a peripheral surface,
The collection roller has a peripheral surface on which any one of a nickel layer, a copper layer, a silver layer, and a chromium layer is provided, and is disposed at a position where the peripheral surface and the magnetic brush come into contact with each other. A developing device.   The developing device according to claim 1, wherein each of the nickel layer, the copper layer, the silver layer, and the chromium layer is made of plating.   The developing device according to claim 2, wherein the nickel layer is made of electroless nickel plating formed by electroless nickel treatment. The developing device according to claim 1 , wherein the collection roller rotates by contacting the magnetic brush. An image forming apparatus comprising the developing device according to claim 1 .

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