JP2013231914A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hopping-type developing device 1 capable of preventing the occurrence of toner scattering.SOLUTION: A developing device 1 develops an electrostatic latent image on a photoreceptor with a toner carrying roller 2 including a plurality of electrodes for hopping toner particles on the surface thereof. The developing device 1 is provided with an entrance opposing member 12 that is disposed at a casing entrance E that is a position where a hopping toner layer Lt on the surface of the toner carrying roller 2 is started to enter the inside of a casing 11 from the outside of the casing 11 in association with the rotation of the toner carrying roller 2, so as to oppose to the surface of the toner carrying roller 2 immediately after entering the inside of the casing 11 with a predetermined entrance gap therebetween, and is applied with a pressing voltage that is a voltage for electrostatically pressing the hopping toner layer Lt against the surface of the toner carrying roller 2.

Description

  The present invention relates to a developing device that develops a latent image by attaching toner particles hopped on the surface of a toner carrier to a latent image on the latent image carrier, and an image forming apparatus using the same.

  Conventionally, as this type of developing device, the one described in Patent Document 1 is known. This developing device has a cylindrical toner carrier having a plurality of electrodes arranged at a predetermined pitch in the circumferential direction. These electrodes are formed by repeatedly arranging electrode pairs composed of two adjacent electrodes. An alternating electric field is formed between the two electrodes in each electrode pair. As a result, after the toner particles levitated from one electrode in the electrode pair land on the other electrode, the toner particles levitated from the other electrode land on one electrode. Causes toner particle hopping.

  Most of the cylindrical toner carrier configured to be rotatable is accommodated in the casing of the developing device, but a partial area on the peripheral surface thereof is exposed to the outside through an opening provided in the casing, so that a latent image is formed. It directly faces the photoconductor as a carrier. The toner particles accommodated in the casing are supplied to the surface of the toner carrier by the toner supply roller, and then repeat hopping on the surface of the toner carrier. Then, after the toner carrying member is moved out of the casing as the toner carrying member rotates, the toner carrying member and the photosensitive member are conveyed to a developing region facing each other. In the developing region, the toner particles that have floated to the vicinity of the latent image on the photoreceptor are attracted to the electric field by the latent image and do not descend toward the electrode of the toner carrying member, and adhere to the latent image. As a result, the latent image on the photosensitive member is developed into a toner image.

  As described above, the method in which the toner particles hopped on the surface of the toner carrier contribute to the development is more sensitive than the method in which the toner particles adhered to the surface of the toner carrier or the magnetic carrier contribute to the development. The potential difference between the latent image on the body and the background portion can be reduced. For example, in the latter method (hereinafter referred to as an adhesion method), it is necessary to provide a potential difference of at least several hundred [V] between the latent image on the photoconductor and the surrounding background portion. On the other hand, in the former method (hereinafter referred to as hopping method), toner particles can be selectively attached to a latent image having a potential difference of only a few tens [V] from the surrounding background portion. is there.

  The toner particles that have not contributed to the development of the latent image in the development area pass through the development area as the toner carrier rotates, and then the gap between the inner wall of the casing opening and the toner carrier downstream from the development area. It returns to the inside of the casing via the casing inlet which is opposed thereto. In a conventional adhesion type developing device, in order to prevent toner scattering due to the backflow of toner from the inside of the casing to the outside of the casing via the casing inlet, it is common to provide an inlet seal that closes the gap at the casing inlet. It is. The inlet seal is supported in a cantilever manner by the casing, and the free end is brought into contact with the toner layer on the surface of the toner carrying member to close the gap. In the above-mentioned developing apparatus of the adhesion method, even if the free end of the inlet seal is brought into contact with the toner layer, the toner particles are adhered to the surface of the toner carrying member with a large adhesive force. The toner is not scraped off from the toner layer.

  However, in the hopping method, almost no adhesive force acts between the toner particles hopped on the surface of the toner carrier and the surface of the toner carrier. For this reason, if the free end of the inlet seal is brought into contact with the hopping toner layer on the surface of the toner carrier, the toner particles are blocked by the inlet seal, which promotes the occurrence of toner scattering. Therefore, in the developing device described in Patent Document 1, the entrance seal is not provided, or the free end of the entrance seal is separated from the surface of the toner carrier to suppress the occurrence of toner scattering.

  However, when the inlet seal is not provided, the toner particles in the casing are scattered outside the casing through the gap at the casing inlet, and thus toner scattering cannot be prevented. Further, even when the inlet seal is provided, the toner particles in the casing are scattered outside the casing through the gap between the free end of the inlet seal and the surface of the toner carrier, so that toner scattering can be prevented. It becomes impossible.

  The present invention has been made in view of the above background, and an object of the present invention is to provide a hopping developing device capable of preventing toner scattering and an image forming apparatus using the same. It is.

  To achieve the above object, the present invention provides a toner carrier comprising a plurality of electrodes for hopping toner particles in toner carried on its surface, and the toner carrier contained therein. A casing having an opening for exposing a portion of the endless moving surface in the endless moving direction to the outside so as to directly face the latent image carrier of the image forming apparatus, and on the surface of the toner carrier The toner image being hopped is transported to a developing region where the surface and the latent image carrier directly face each other as the surface moves endlessly, and adheres to the latent image of the latent image carrier. In the developing device for developing the surface, the surface after passing through the developing region with endless movement enters the casing in a state of facing the inner wall of the opening with a predetermined gap. In the vicinity of the casing inlet, at least immediately before entering the casing or immediately after entering the casing, the surface is disposed to face the surface with a predetermined gap. An inlet facing member to which a pressing voltage, which is a voltage for electrostatically pressing a hopping toner layer composed of a plurality of hopping toner particles, toward the surface is provided. is there.

  In the present invention, the toner particles carried toward the inlet of the casing by, for example, riding on the airflow in the casing, before leaving the casing, are separated from the gap between the inlet facing member and the toner carrier (hereinafter referred to as inlet gap). Need to pass through. In this entrance gap, a pressing electric field is formed on the surface of the entrance facing member by applying a pressing voltage to the entrance facing member. The pressing electric field is an electric field for pressing the hopping toner layer that moves together with the surface of the toner carrier toward the surface of the toner carrier. Further, by applying a hopping voltage to the plurality of electrodes of the toner carrier, a hopping electric field for hopping the toner is formed on the surface of the toner carrier. When the hopping toner layer formed on the surface of the toner carrier by the hopping electric field enters the entrance gap together with the surface of the toner carrier, the thickness is reduced more than usual by the action of the pressing electric field. A space in which no toner particles are present is formed between the hopping toner layer having a reduced thickness and the inlet facing member. Since this space exists in the vicinity of the surface of the inlet facing member to which the pressing voltage is applied, a pressing electric field acts strongly in the space. When toner particles carried from the casing to the entrance gap by air current enter the hopping toner layer that is thin due to the action of the pressing electric field, the toner particles are strongly restrained by the hopping electric field on the surface of the toner carrier. The hopping toner layer is formed together with other toner particles. In addition, when the toner particles carried to the entrance gap enter the space above the thin hopping toner layer instead of the thin hopping toner layer, the hopping toner layer is forcibly forced by the pressing electric field acting strongly in the space. Pressed. Then, it is taken into the hopping toner layer and constitutes a hopping toner layer together with other toner particles. The toner particles that form the hopping toner layer together with other toner particles follow the surface of the toner carrier and return to the inside of the casing. By this reversal, it is possible to prevent the toner particles from scattering from the inside of the casing through the casing inlet to the outside without providing an inlet seal. Alternatively, even if an inlet seal is provided, toner particles are prevented from scattering from the inside of the casing through the casing inlet without contacting the free end of the inlet seal with the hopping toner layer on the surface of the toner carrier. Is possible. For this reason, toner scattering due to damming up toner particles at the free end of the inlet seal does not occur. As described above, toner scattering is prevented by preventing toner scattering from inside the casing through the casing inlet and avoiding toner scattering by blocking toner particles at the free end of the inlet seal. can do.

1 is a schematic configuration diagram illustrating a schematic configuration of a copier according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating an intermediate transfer belt and an image forming unit provided in an image forming unit of the copier. FIG. 3 is an enlarged configuration diagram illustrating one of four image forming units in the image forming unit in an enlarged manner. FIG. 2 is an enlarged explanatory view showing a developing device of the image forming unit in an enlarged manner. FIG. 3 is a perspective view showing a toner carrying roller of the developing device. FIG. 3 is a partial cross-sectional view partially showing a cross-section of the toner carrying roller. FIG. 3 is a plan development view in which the electrode arrangement of the toner carrying roller is developed in a plane. 6 is a waveform diagram showing a first example of a waveform of a first voltage applied to a first electrode of the toner carrying roller and a second voltage applied to a second electrode. FIG. The wave form diagram which shows the 2nd example of the waveform of the 1st voltage and the 2nd voltage. The wave form diagram which shows the 3rd example of the waveform of the 1st voltage and the 2nd voltage. FIG. 3 is a partially enlarged configuration diagram illustrating a part of the vicinity of a casing inlet in the developing device in a partially enlarged manner. FIG. 6 is an enlarged configuration diagram showing a modification of the developing device. FIG. 3 is a partially enlarged configuration diagram illustrating a part of the vicinity of an entrance gap in the developing device of the copying machine according to the first embodiment, partially enlarged. FIG. 10 is a partially enlarged configuration diagram illustrating a part of the vicinity of an entrance gap in a developing device of a copying machine according to a second embodiment, partially enlarged. FIG. 10 is a partially enlarged configuration diagram illustrating a part of the vicinity of an entrance gap in a developing device of a copying machine according to a third embodiment, partially enlarged. FIG. 10 is a partially enlarged configuration diagram illustrating a portion of the vicinity of an entrance gap in a developing device of a copying machine according to a fourth embodiment, partially enlarged.

Hereinafter, an electrophotographic copying machine as an image forming apparatus to which the present invention is applied will be described.
FIG. 1 is a schematic configuration diagram showing a schematic configuration of the copying machine 100. FIG. 2 is a schematic configuration diagram showing the intermediate transfer belt 48 and the image forming unit provided in the image forming unit of the copying machine 100. In these drawings, the image forming unit of the copying machine 100 forms an endless intermediate transfer belt 48 and toner images of Y (yellow), M (magenta), C (cyan), and K (black). 4 image forming units. Each image forming unit includes a photoreceptor 49Y, M, C, K as a latent image carrier, a developing device 1Y, M, C, K that develops an electrostatic latent image formed on the surface of the photoreceptor, and a photoreceptor. There are charging devices 41Y, 41M, 41C, and 41K that uniformly charge the surface, and cleaning devices 44Y, 44M, 44C, and 44K that clean the surface of the photosensitive member. The subscripts Y, M, C, and K attached to the end of the reference numerals of the respective devices and members indicate the devices and members for Y, M, C, and K.

  The endless intermediate transfer belt 48 is tensioned by being stretched over a plurality of support rollers arranged inside the loop, and is rotated counterclockwise in the figure by the rotational drive of at least one of the support rollers. It can be moved endlessly in the direction.

  When the Y toner image is formed on the Y photoconductor 49Y, the surface of the Y photoconductor 49Y that is rotationally driven is first uniformly charged by the Y charging device 41Y. The surface portion of the Y photoconductor 49Y that has been charged is optically scanned in accordance with the Y image information by the optical writing unit 42 as a latent image forming unit. As a result, a Y electrostatic latent image is formed on the surface of the Y photoconductor 49Y. The electrostatic latent image formed on the surface of the Y photoconductor 49Y is developed into a Y toner image by supplying Y toner in a developing region facing the Y developing device 1Y. M, C, and K toner images are formed on the surfaces of the photoconductors 49M, C, and K for M, C, and K by a similar process.

  In this way, the Y, M, C, and K photoconductors 49Y, 49M, 49C, and 49K disposed below the intermediate transfer belt 48 are in contact with the front surface of the intermediate transfer belt 48. Primary transfer nips for Y, M, C, and K are formed. On the back side of the primary transfer nips for Y, M, C, and K, primary transfer rollers 43Y, M, C, and K disposed inside the belt loop use the intermediate transfer belt 48 for Y, M, C, and K, respectively. Are pressed toward the photoconductors 49Y, 49M, 49C, 49K. A primary transfer bias output from a power supply (not shown) is applied to the primary transfer rollers 43Y, 43M, 43C, and 43K. As a result, a primary transfer electric field is formed between the primary transfer rollers 43Y, M, C, and K and the photosensitive members 49Y, M, C, and K for electrostatically moving the toner from the photosensitive member side to the roller side. Yes.

  The Y, M, C, and K toner images formed on the photoreceptors 49Y, 49M, 49C, and 49K are affected by the primary transfer electric field and the nip pressure at the primary transfer nip for Y, M, C, and K. Thus, the intermediate transfer belt 48 is primary-transferred superimposed on the front surface. As a result, a four-color superimposed toner image is formed on the intermediate transfer belt 48. The Y, M, C, and K toners that are not primarily transferred to the intermediate transfer belt 48 and remain on the surface of the photoreceptors 49Y, 49M, 49C, and 49K are transferred to the photoreceptor surface by the cleaning devices 44Y, 44M, 44C, and 44K. Removed from.

  A secondary transfer counter roller is disposed on the right side of the intermediate transfer belt 48 in the figure. The secondary transfer counter roller is in contact with the front surface of the intermediate transfer belt 48 to form a secondary transfer nip. On the back side of the secondary transfer nip, the secondary transfer roller 45 disposed inside the belt loop presses the intermediate transfer belt 48 toward the secondary transfer counter roller. A secondary transfer bias output from a power source (not shown) is applied to the secondary transfer roller 45. As a result, a secondary transfer electric field for electrostatically moving the toner image on the belt from the secondary transfer roller 45 side to the secondary transfer counter roller side is formed between the secondary transfer roller 45 and the secondary transfer counter roller. Has been.

  A pair of registration rollers is provided below the secondary transfer nip, and the secondary roller is synchronized with the four-color superimposed toner image on the intermediate transfer belt 48 by synchronizing the recording sheet supplied from the paper feed cassette. Send to the transfer nip. In the secondary transfer nip, the four-color superimposed toner image on the belt is secondarily transferred onto the surface of the recording sheet by the action of a secondary transfer electric field and nip pressure. Thereby, a full-color image is formed on the recording sheet.

  The recording sheet on which the full-color image is formed is discharged from the secondary transfer nip and then fed into the fixing device 46. Then, after the fixing process of the full-color image is performed in the fixing device 46, it is discharged out of the apparatus via a pair of discharge rollers.

  The copying machine according to the embodiment employs a tandem type configuration in which four image forming units are arranged and opposed to the intermediate transfer belt 48 along the moving direction, but the present invention is different from the tandem type. The present invention can also be applied to a type image forming apparatus. For example, a method of forming a color toner image on an intermediate transfer member by forming each color toner image in order on one latent image carrier and transferring the toner images on the intermediate transfer member in a superimposed manner. A method may be used in which toner images of respective colors are formed on a latent image carrier so as to overlap each other, and the superimposed toner images are directly transferred onto an intermediate transfer member or a recording material.

  Next, the configuration and operation of the developing devices 1Y, M, C, and K in the Y, M, C, and K image forming units will be described. Note that the image forming units for Y, M, C, and K and the various devices constituting the units have substantially the same configuration except that the color of the toner to be used is different. In the description, the subscripts Y, M, C, and K attached to the end of the code are omitted.

  FIG. 3 is an enlarged configuration diagram illustrating one of the four image forming units in an enlarged manner. FIG. 4 is an enlarged explanatory view showing the developing device 1 of the image forming unit in an enlarged manner. The toner used in the developing device 1 according to the embodiment is prepared by a polymerization method, has an average particle diameter of 5.2 [μm], a circularity of 0.98, and an angle of repose of 33. [°] and strontium titanate as an external additive.

  The drum-shaped photoreceptor 49 is rotationally driven in the clockwise direction (arrow A direction) in the figure by a driving unit (not shown). On the left side of the photoconductor 49 in the drawing, a developing device 1 having a toner carrying roller 2 as a toner carrying member is disposed. The developing device 1 has a toner accommodating portion 15 having a paddle screw 14 that is rotationally driven in a counterclockwise direction (in the direction of arrow C) in the figure inside a casing 11. The toner storage unit 15 stores negatively charged toner.

  The toner stored in the toner storage unit 15 is delivered to the toner supply roller 18 by the paddle screw 14 that is a stirring paddle. The toner supply roller 18 is rotationally driven in a counterclockwise direction (arrow D direction) in the figure in a state where a supply nip is formed by contacting the toner carrying roller 2 which is a toner carrier. In the supply nip, the surface of the toner supply roller 18 that is driven to rotate in the counterclockwise direction in the figure and the surface of the toner carrying roller 2 that is driven to rotate in the counterclockwise direction in the figure (the direction of arrow B in the figure) are mutually connected. Rub while moving in the counter direction. At the entrance of the supply nip, the toner on the surface of the toner carrying roller 2 is scraped off by the toner supply roller 18 and collected on the surface of the toner supply roller 18. Further, near the outlet of the supply nip, the toner on the surface of the toner supply roller 18 is supplied to the surface of the toner carrying roller 2. As described above, the toner supply roller 18 has a role of collecting the toner from the surface of the toner carrying roller 2 and a role of supplying the toner to the surface of the toner carrying roller 2. It may be done. In order to satisfactorily supply toner from the toner supply roller 18 to the toner carrying roller 2, a potential difference may be provided between the two rollers.

  The toner carrying roller 2 exposes a part of the outer peripheral surface from an opening (11 a in FIG. 4) provided in the casing 11 of the developing device 1. At the exposed portion, the surface of the toner carrying roller 2 is opposed to the photoreceptor 49 with a gap of several tens to several hundreds [μm]. In this way, the region where the toner carrying roller 2 and the photosensitive member 49 are opposed to each other is a developing region α in the image forming apparatus of the copying machine 100.

  When toner is supplied from the toner supply roller 18 to the toner carrying roller 2, the toner is charged by friction between the toner carrying roller 2 and the toner supply roller 18. The charged toner supplied on the surface of the toner carrying roller 2 is hopped on the surface of the toner carrying roller 2 for the reason described later, and is opposed to the regulating blade 23 as the toner carrying roller 2 rotates (for example, It is transported to the restricted area.

  Instead of the toner supply roller 18, an endless belt-like toner supply belt may be employed. In place of the toner carrying roller 2, an endless belt-like toner carrying belt may be employed.

  The regulating blade 23 is cantilevered on a casing 11 that is formed of a material such as phosphor bronze, SUS, or elastic rubber, and its free end is 10 [N] relative to the outer peripheral surface of the toner carrying roller 2. / M] and 100 [N / m] or less. For example, a roller-shaped layer thickness equalizing member may be used.

  The toner carried on the toner carrying roller 2 passes through the regulation region while being sandwiched between the outer peripheral surface of the toner carrying roller 2 and the regulation blade 23, so that the toner layer is uniformized to a desired layer thickness. , Electrification is promoted by friction.

When the charge amount and density of the toner immediately before entering the regulation region α while hopping on the surface of the toner carrying roller 2 are appropriate, the toner scattering and background contamination in the development region α can be reduced. The toner after the layer thickness is regulated by the regulating blade 23 is preferably in the range of 10 [μC / g] or more and 60 [μC / g] or less. The density is 0.3 [mg / cm ^2] or more, is preferably in the range of 1.0 [mg / cm ^2] or less.

  The toner that has passed through the regulation area as the toner carrying roller 2 is driven to rotate is conveyed to the developing area α as the toner carrying roller 2 rotates while hopping on the surface of the toner carrying roller 2. In the developing region α, the toner on the toner carrying roller 2 is statically exposed on the surface of the photoconductor 49 by the action of the developing electric field according to the potential difference between the average surface potential of the toner carrying roller 2 and the electrostatic latent image on the photoconductor 49. The electrostatic latent image is developed by transferring to the electrostatic latent image. The toner remaining on the toner carrying roller 2 without being transferred to the electrostatic latent image on the photosensitive member 49 in the developing region α is returned into the developing device 1 as the toner carrying roller 2 rotates.

  The toner that has passed through the development region α and returned to the developing device 1 is collected by the toner supply roller 18 that functions as a collection roller, and then returned to the toner storage unit 15. Since the toner on the toner carrying roller 2 is hopped, the toner carrying roller 2 exerts very little adhesion force and is easily collected by the toner supply roller 18. In the developing device 1, the toner is supplied from the toner container 15 to the toner carrying roller 2 via the toner supply roller 18 and then passes through the developing region α, and then the toner is supplied from the toner carrying roller 2 via the toner supply roller 18 to the toner. A series of processes of returning to the storage unit 15 is repeated. Thereby, in the developing device 1 in operation, a hopping toner layer is always formed on the toner carrying roller 2 by a plurality of hopping toner particles.

  Next, a specific configuration of the toner carrying roller 2 will be described. FIG. 5 is a perspective view showing the toner carrying roller 2. FIG. 6 is a partial cross-sectional view partially showing a cross-section of the toner carrying roller 2. FIG. 7 is a plan development view in which the electrode arrangement of the toner carrying roller 2 is developed in a plane.

  The toner carrying roller 2 has a plurality of electrode pairs arranged in the roller circumferential direction. The electrode pairs include a first electrode 3c extending in the roller axial direction and a second electrode 4c extending in the roller axial direction. It consists of and. The first electrode 3c and the second electrode 4c are alternately arranged in the circumferential direction with a predetermined interval therebetween. The plurality of first electrodes 3c are electrically connected to each other by being in contact with a disk-shaped first flange 3d disposed at one end in the roller axis direction. The plurality of second electrodes 4c are electrically connected to each other by being in contact with the disk-shaped second flange 4d disposed at the other end in the roller axis direction.

  The first electrode 3c and the second electrode 4c are formed on an insulating support substrate 7 formed in a cylindrical shape, and an organic or inorganic insulating material is formed on the support substrate 7 or these electrodes. A surface layer 6 made of a functional material is coated. In FIG. 6, lines extending from the respective electrodes (first electrode 3c and second electrode 4c) indicate conductive lines for applying a voltage to each electrode (first electrode 3c and second electrode 4c). In the example, each flange (the first flange 3d and the second flange 4d) plays the role of this conductive wire. A first power supply 25A is connected to the first flange 3d via a sliding contact (not shown). The second power source 25B is connected to the second flange 4d through a sliding contact (not shown). As a result, the plurality of first electrodes 3c are connected to the first power supply 25A via the first flange 3d and the sliding contact, respectively. The plurality of second electrodes 4c are in a state of being connected to the second power source 25B via the second flange 4d and the sliding contact, respectively.

As the support substrate 7 of the toner carrying roller 2, a substrate made of an insulating material such as a resin, or a substrate formed of an insulating film such as SiO _{2 on a} substrate made of a conductive material such as SUS is used. The 1st electrode 3c and the 2nd electrode 4c are 0.1-10 [micrometer] thickness which consists of electroconductive materials, such as Al, Cu, Ni-Cr, on the support substrate 7, Preferably it is 0.5-2. A film having a thickness of 0.0 [μm] is patterned into a predetermined electrode shape by a technique such as photolithography.

  The electrode width L and the electrode interval R on the toner carrying roller 2 greatly affect the hopping efficiency of the toner. The electrode pitch P is defined by P = R + L. The toner particles existing in the region between the first electrode 3c and the second electrode 4c in the entire area of the peripheral surface of the toner carrying roller 2 are substantially straight between the first electrode 3c and the second electrode 4c. Hopping along the lines of electric force to connect. On the other hand, the toner particles existing on the first electrode 3c or the second electrode 4c hop along an electric force line connecting the electrodes with a parabolic path. If the electrode width L is too wide, the intensity of the electric field formed in the vicinity of the center in the width direction of the electrode becomes insufficient and the toner remains attached to the electrode, so that the hopping efficiency is lowered.

  The electrode interval R is a factor that determines the electric field strength between the electrodes together with the voltage applied to the electrodes. If the voltage is constant, the electric field strength increases and the initial hopping speed increases as the electrode interval R decreases. On the other hand, the shorter the electrode interval R, the shorter the interelectrode movement time due to the hopping of the toner particles, so that the time during which the toner particles and the electrodes are attached to each other becomes longer. However, even when the electrode interval R is considerably narrowed, the above-described time can be shortened by increasing the frequency of the pulse voltage described later. Considering the above points, it is desirable to set an appropriate electrode interval R for efficiently hopping toner particles at a low voltage.

  The thickness of the surface layer 6 that is a surface protective layer covering the electrode surface also affects the strength of the electric field formed on the surface of the toner carrying roller 2. In particular, the electrostatic force in the normal direction in the electric field is greatly affected. Therefore, in order to efficiently hop toner particles at a low voltage, it is necessary to appropriately set the electrode width L, the electrode interval R, the thickness of the surface layer 6 and the like of the toner carrying roller 2. In the copying machine according to the embodiment, the electrode width L is set to 1 to 20 times the average toner particle size, and the electrode interval R is also set to 1 to 20 times the average toner particle size.

Examples of the material of the surface layer 6 include SiO ₂ , BaTiO ₂ , TiO ₂ , TiO ₄ , SiON, BN, TiN, Ta ₂ O _{5 and the} like. The thickness of the surface layer 6 is 0.5 to 30 [μm], preferably 0.5 to 3 [μm].

An uppermost layer made of an organic material such as polycarbonate may be coated on the surface layer 6 made of SiO ₂ or the like. It is also possible to select zirconia or a material generally used as a coating material for a carrier of a two-component developer, for example, a silicone resin. The material of the surface layer 6 is appropriately selected based on the insulating properties, durability, the production method of the toner carrying roller itself, and the charge train with the toner to be used.

  In recent years, when the demand for A4 size paper is increasing, it is necessary to use a toner carrying roller 2 having a length in the axial direction of at least the length of the A4 size in the short direction (210 mm). In the toner carrying roller 2 having such a size, it is necessary to form each electrode at a fine pitch.

A method for manufacturing the toner carrying roller 2 will be described with some examples.
The first manufacturing method is a method of obtaining the toner carrying roller 2 by using a substrate made of a flexible substrate as the support substrate 7 and winding an electrode pattern on the support substrate 7 around a drum-shaped support. A flexible substrate made of a polyimide film having a thickness of 20 to 100 [μm] is used as the support substrate 7, and a 0.1 to 0.3 [μm] thickness made of Cu, Al, Ni—Cr or the like is formed thereon. A conductive film is formed by a vapor deposition method or the like. A conductive film having a width of about 30 to 60 cm can be formed by a roll-to-roll apparatus, which greatly increases mass productivity.

  Specific examples of the above-described vapor deposition method include a sputtering method, an ion plating method, a CVD method, an ion beam method, and the like. For example, when a conductive film is formed by sputtering, a Cr film may be interposed in order to improve adhesion with polyimide, and adhesion can also be improved by plasma treatment or primer treatment. .

  An electrodeposition method can be exemplified as a method different from the vapor deposition method. When the electrodeposition method is used, a conductive film is first formed on the flexible support substrate 7 by electroless plating. A base electrode is formed by sequentially immersing in tin chloride, lead chloride, and nickel chloride, and then electroplating is performed in a nickel electrolyte to produce a conductive film with a thickness of 1 to 3 [μm] on a roll-to-roll basis. Is possible.

  When a conductive film is formed on the surface of the flexible support substrate 7, resist coating, photolithography, etching and the like are applied to the conductive film to pattern one conductive film into a plurality of electrode shapes. A conductive film having a thickness of about 1 to 3 [μm] can be patterned into a fine pitch electrode having a width of about 5 to 10 [μm] by photolithography or etching.

After the electrode pattern was _training, the SiO 2, BaTiO _2, made of a material such as TiO ₂ thickness 0.5 to 2 [[mu] m] about the surface layer 6 is formed by sputtering or the like. Alternatively, PI (polyimide) is applied with a thickness of about 2 to 5 [μm] by a roll coater or other coating apparatus, and then baked to obtain the surface layer 6. In the case where trouble is caused with PI, a surface film made of SiO ₂ or other inorganic material may be further formed with a thickness of about 0.1 to 0.5 [μm] by sputtering or the like. Further, an organic material such as polycarbonate may be coated on SiO ₂ or the like. It is also possible to select zirconia or a material generally used as a coating material for a carrier of a two-component developer, for example, a silicone resin.

  As described above, when a flexible circuit board having the flexible support substrate 7, the electrode pattern, and the surface layer 6 is obtained, it is affixed to a drum-shaped support to obtain the toner carrying roller 2.

  The second example of the production method is as follows. That is, as the support substrate 7, a flexible support substrate 7 is formed by baking polyimide with a thickness of 20 to 100 [μm] against a conductive film of 10 to 20 [μm] made of copper, stainless steel, or the like. Form. Thereafter, the conductive film is patterned into a plurality of electrodes by photolithography or etching. Then, a surface layer 6 is formed by coating polyimide on the solid surfaces of the electrodes and the support substrate 7. When unevenness of about 10 to 10 [μm] corresponding to the thickness of the electrode is formed on the surface of the surface layer 6, it is flattened. For example, the surface of the surface layer 6 is flattened by the surface tension of the material by spin-coating a polyimide-based material or a polyurethane-based material having a viscosity of 50 to 10,000 [cps], more preferably 100 to 300 [cps]. be able to.

A third production method example is as follows. That is, an insulating layer is formed by coating the surface of a metal substrate made of stainless steel or aluminum having a thickness of 20 to 30 [μm] with a roll coater to a thickness of about 5 [μm] polyimide. The insulating layer is then pre-baked at 150 ° C. for 30 minutes and post-baked at 350 ° C. for 60 minutes to obtain the support substrate 7. Then, after performing plasma treatment and primer treatment for improving adhesion, a conductive film having a thickness of 0.1 to 0.2 [μm] made of Ni—Cr is deposited, and photolithography or etching is performed on the conductive film. A plurality of electrodes are obtained by patterning by processing. Furthermore, _thereon by the SiO 2, BaTiO _2, the surface layer 6 of a thickness of about 0.5~1μm consisting TiO ₂ or the like formed by sputtering, to obtain a toner carrying roller 2. An organic material such as polycarbonate may be coated on SiO ₂ or the like. It is also possible to select zirconia or a material generally used as a coating material for a carrier of a two-component developer, for example, a silicone resin.

  As another manufacturing method example, a method of forming an electrode pattern on the surface of the support substrate 7 using screen printing using a conductive ink, ink jet printing, removing a non-electrode portion of a plated electrode by laser processing, or the like. May be used. As a method for creating the electrode pattern and the surface protective layer, a method different from those described so far may be employed.

  In order to stably hop the toner particles on the surface of the toner carrying roller 2, it is important to form a hopping electric field having a corresponding magnitude and strength on the surface. For this purpose, the first electrode 3c and the first electrode It is necessary to prevent discharge between the two electrodes 4c.

Next, the voltage applied to the first electrode 3c and the second electrode 4c will be described.
It is necessary to form an alternating electric field whose polarity is reversed at a predetermined cycle between the first electrode 3c and the second electrode 4c of the toner carrying roller 2 and to reciprocate the toner between both electrodes. Therefore, it is necessary to apply a pulse voltage that repeats rising and falling at a predetermined cycle to at least one of the first electrode 3c and the second electrode 4c. As this pulse voltage, those having various waveforms such as a sine wave, a rectangular wave, and a triangular wave can be used.

  FIG. 8 is a waveform diagram showing a first example of waveforms of the first voltage applied to the first electrode (3c) and the second voltage applied to the second electrode (4c). The first voltage is output from the first power source (25A). The second voltage is output from the second power source (25B). The first voltage and the second voltage are composed of rectangular waves that repeat rising and falling at the same frequency and amplitude, but the rising and falling phases are opposite to each other between the first voltage and the second voltage. It has become. The phases of each other are shifted by π. As a result, a potential difference having the same magnitude as the peak-to-peak voltage Vpp of the first voltage or the second voltage is always generated between the first electrode and the second electrode. Due to this potential difference, a hopping electric field is formed between the first electrode and the second electrode. The hopping electric field is an alternating electric field whose polarity is reversed at a time interval that is half of one cycle of the first voltage or the second voltage. Reciprocates between the two electrodes by this hopping electric field.

  The peak-to-peak voltage Vpp of the first voltage or the second voltage is preferably in the range of 100 [V] or more and 2000 [V] or less. When Vpp is less than 100 [V], a hopping electric field having a sufficient strength cannot be formed on the surface layer 6 and it becomes difficult to stably hop toner particles. On the other hand, if Vpp is larger than 2000 [V], there is a high possibility that leakage occurs between the electrodes due to use over time. In the copying machine according to the embodiment, the peak-to-peak voltage Vpp is set to 500 [V]. In the copying machine according to the embodiment, the center value V0 between the peaks of the first voltage and the second voltage is between the potential of the non-image portion (background portion) of the electrostatic latent image on the photoreceptor. Is set to a value. Therefore, in the developing region α, the hopping toner particles adhere to the electrostatic latent image on the photosensitive member and do not adhere to the non-image portion of the photosensitive member.

  As the toner particles, negatively charged ones are used, and the center value V0 is set to −300 [V]. Therefore, the first voltage and the second voltage are voltages that swing between a first peak of −50 [V] and a second peak of −550 [V]. Such first voltage and second voltage are pulse voltages having a peak-to-peak voltage Vpp of 500 [V] that swings between −250 [V] and +250 [V] around 0 [V]. On the other hand, it can be obtained by superimposing a DC voltage of −300 [V].

  About the frequency f in a 1st voltage or a 2nd voltage, it is preferable to set to 0.1 [kHz] or more and 10 [kHz] or less. If the frequency f is smaller than 0.1 [kHz], toner particle hopping may not be able to keep up with the development speed. On the other hand, if the frequency f is larger than 10 [kHz], the movement of the toner particles cannot follow the switching of the polarity of the electric field for hopping, and it becomes difficult to stably hop the toner particles. In the copying machine according to the embodiment, the frequency f is set to 500 [Hz] (0.5 [kHz]).

  FIG. 9 is a waveform diagram showing a second example of waveforms of the first voltage and the second voltage. In the second example, the first voltage consists of the same pulse voltage as in the first example, whereas the second voltage consists of a constant DC voltage. The value of this DC voltage is the same value as the center value V0 in the first voltage. The potential difference between the first electrode and the second electrode is half the peak-to-peak voltage. Therefore, a suitable range of the peak-to-peak voltage Vpp in the second example is 200 [V] or more and 4000 [V] or less, which is twice that of the first example. According to this example, since it is not necessary to manage the phase difference between the first voltage and the second voltage, the cost of the power supply can be reduced.

  FIG. 10 is a waveform diagram showing a third example of waveforms of the first voltage and the second voltage. In the third example, contrary to the second example, the first voltage is a DC voltage, whereas the second voltage is a pulse voltage. The characteristics of the DC voltage and pulse voltage are the same as in the second example.

Next, a characteristic configuration of the copier according to the embodiment will be described.
In FIG. 4, a partial region of the peripheral surface of the toner carrying roller 2 is exposed to the outside of the casing 11 through the opening 11 a of the casing 11 and directly faces a photoconductor (not shown). Of the inner wall of the opening 11a, the casing inlet portion 11b constituting the inner wall facing downward in the vertical direction faces upward in the vertical direction on the peripheral surface of the toner carrying roller 2 disposed immediately below. It is opposed to the region with a predetermined gap. An inlet facing member 12 is fixed to a surface of the casing inlet portion 11b facing the toner carrying roller 2. The inlet facing member 12 is a region immediately after entering the casing inlet E where the casing inlet 11b and the toner carrying roller 2 face each other after passing through the developing region in the entire area in the circumferential direction of the toner carrying roller 2. Is opposed via a predetermined gap G. The entrance facing member 12 is for electrostatically pressing a hopping toner layer composed of a plurality of toner particles hopping on the surface of the toner carrying roller 2 at the casing entrance E toward the surface of the toner carrying roller 2. A pressing voltage, which is a voltage, is applied.

  FIG. 11 is a partially enlarged configuration diagram showing the vicinity of the casing inlet in the developing device 1 partially enlarged. A casing inlet in which the casing inlet 11 b of the casing 11 and the toner carrying roller 2 face each other is formed above the toner carrying roller 2 in the vertical direction. A casing outlet is formed below the toner carrying roller 2 in the vertical direction so that the inner wall of the opening 11a of the casing 11 and the toner carrying roller 2 face each other with a predetermined gap. Goes out of the casing 11 through the casing outlet and directly faces the photoconductor.

  At the casing outlet, the regulating blade 23 comes into contact with the toner layer on the peripheral surface of the toner carrying roller 2 and regulates the layer thickness, so that a gap for leaking the toner particles in the casing 11 to the outside is formed. It has not been. On the other hand, a gap is formed between the surface of the toner carrying roller 2 and the casing inlet 11b at the casing inlet, and the toner particles in the casing 11 may leak outside through the gap. .

  Therefore, in the copying machine according to the embodiment, as shown in the drawing, the inlet facing member 12 is fixed to the casing inlet portion 11b, and a pressing voltage is applied to the inlet facing member 12. The pressing voltage may be a DC voltage or a pulse voltage that repeats rising and falling at a predetermined cycle. In the case of a DC voltage, a voltage whose polarity is the same as the charging polarity of the toner and whose absolute value is larger than the absolute value of the central value V0 of the first voltage or the second voltage described above is adopted. Further, in the case of a pulse voltage, the one having the same characteristics as the above-described DC voltage is adopted for the center value between the peaks. On the surface of the inlet facing member 12 to which a pressing voltage composed of the DC voltage or pulse voltage is applied, the toner particles existing at the casing inlet are pressed from the inlet facing member 12 side toward the toner carrying roller 2 side. A pressing electric field is formed.

  On the other hand, on the peripheral surface of the toner carrying roller 2, the first voltage is applied to the first electrode (3c) and the second voltage is applied to the second electrode (4c), so that the toner on the peripheral surface of the roller A hopping electric field is formed to hop particles between the electrodes. The hopping toner layer Lt formed on the surface of the toner carrying roller 2 by the hopping electric field rotates and moves together with the surface of the toner carrying roller 2 so that the entrance facing member 12 and the surface of the toner carrying roller 2 pass through a gap. Enter the opposite entrance gap. In the entrance gap, as shown in the figure, the thickness is reduced more than usual by the action of the pressing electric field. A space S in which no toner particles are present is formed between the hopping toner layer Lt having a reduced thickness and the inlet facing member 12. Since this space S exists in the vicinity of the surface of the inlet facing member 12 to which the pressing voltage is applied, a pressing electric field acts strongly in the space S.

  It is assumed that the toner particles in the casing 11 are carried toward the casing inlet by riding on an air current as indicated by an arrow H in the drawing. In order for the toner particles to leak out of the casing 11, it is necessary to pass through the above-described inlet gap. In the inlet gap, as described above, a pressing electric field is formed on the surface of the inlet facing member 12. Has been. When the toner particles carried to the entrance gap enter the hopping toner layer Lt which is thin due to the action of the pressing electric field, the toner particles hop while being strongly restrained by the hopping electric field on the surface of the toner carrying roller 2. Thus, the hopping toner layer Lt is configured together with other toner particles. In addition, when the toner particles carried to the entrance gap enter the space S above the thin hopping toner layer Lt, the hopping toner layer Lt is strongly applied by the pressing electric field acting strongly in the space S. Forced to be pressed. Then, the toner is promptly taken into the hopping toner layer Lt to form the hopping toner layer Lt together with other toner particles. The toner particles that form the hopping toner layer Lt together with other toner particles follow the surface of the toner carrying roller 2 and return to the inside of the casing 11. By this reversal, it is possible to prevent the toner particles from scattering from the inside of the casing through the casing inlet to the outside without providing an inlet seal. For this reason, toner scattering due to damming up toner particles at the free end of the inlet seal does not occur. As described above, toner scattering is prevented by preventing toner scattering from inside the casing through the casing inlet and avoiding toner scattering by blocking toner particles at the free end of the inlet seal. can do.

  In addition, although the structure which does not provide an inlet seal was demonstrated, application of this invention is possible also to the structure which provided the inlet seal. In this case, the free end of the inlet seal is opposed to the surface of the toner carrying roller 2 with a predetermined gap. Then, the entrance facing member 12 is fixed to the free end of the entrance seal, and the entrance gap may be formed by facing the surface of the toner carrying roller 2 through a predetermined gap. In such a configuration, it is possible to prevent toner particles from scattering from the inside of the casing through the casing inlet without contacting the free end of the inlet seal with the hopping toner layer on the surface of the toner carrying roller 2.

  In addition, an example in which the inlet facing member 12 is fixed to the casing inlet portion 11b using a layered structure has been described. However, as shown in FIG. The surface of the carrier roller 2 may be opposed to the surface of the carrier roller 2 with a predetermined gap.

Next, each example in which a more characteristic configuration is added to the copying machine according to the embodiment will be described. Unless otherwise specified, the configuration of the copying machine according to each example is the same as that of the embodiment.
[First embodiment]
FIG. 13 is a partially enlarged view showing a part of the vicinity of the entrance gap in the developing device 1 of the copying machine according to the first embodiment. In the copying machine according to the first modification, as illustrated, the entrance gap G formed between the surface of the toner carrying roller 2 and the entrance facing member 12 is reduced toward the downstream side of the roller surface movement direction. Yes. Thereby, the dimension GL1 on the most upstream side in the inlet gap G is significantly larger than the dimension GL2 on the most downstream side.

  Needless to say, the dimension GL1 on the most upstream side needs to be larger than the thickness of the hopping toner layer, but some of the toner particles existing on the surface of the toner carrying roller 2 are excessively charged than usual. Thus, not a few toner particles hop at a height greater than the average thickness of the hopping toner layer. When the size of the inlet gap G is uniformly set to a relatively large value so that the toner particles are surely taken into the inlet gap G, a pressing voltage is not applied to the inlet facing member 12 such as during transportation. In addition, the toner particles are easily scattered out of the casing 11. On the other hand, in the copying machine according to the first embodiment, the dimension GL1 on the most upstream side is set to a relatively large value so that the excessively charged toner particles can be reliably taken into the gap G. Thus, the dimension GL2 on the most downstream side is kept at a value that is small enough to pass through the hopping toner layer thinned by the pressing electric field. Accordingly, it is possible to suppress the occurrence of toner scattering when the pressing voltage is not applied to the inlet facing member 12 such as during transportation.

[Second Embodiment]
FIG. 14 is a partially enlarged view showing a part of the vicinity of the entrance gap in the developing device of the copying machine according to the second embodiment. In the copying machine according to the second modification, as shown in the figure, the entrance facing member 12 is covered at least on the surface of the electrode 12a facing the toner carrying roller 2 and the electrode 12a to which the pressing voltage is applied. An insulating layer 12b made of an insulating material is used. By providing the insulating layer 12b on the surface of the electrode 12a, direct contact between the electrode 12a and the toner particles is avoided. Thereby, it is possible to suppress the occurrence of charge injection from the electrode 12a to the toner particles due to the direct contact of the toner particles with the electrode 12a.

  The size of the entrance gap between the entrance facing member 12 and the toner carrying roller 2 is constant regardless of the position in the roller surface movement direction. By using toner having a relatively small charge amount distribution of toner particles, even if the entrance gap is uniformly set to a relatively small value, most toner particles can enter the entrance gap. .

  However, under the condition where the size of the entrance gap is relatively small, the toner particles are easily scattered from the hopping toner layer formed on the surface of the toner carrying roller 2 immediately before entering the entrance gap for the following reason. . That is, a pressing electric field formed on the surface of the inlet facing member 12 is abruptly applied to the hopping toner layer immediately after entering the entrance gap as the toner carrying roller 2 rotates. At this time, if the strength of the pressing electric field is relatively large, it becomes difficult to move the toner particles in the hopping toner layer by following the roller surface, and it is easy to be separated from the hopping toner layer and scattered around. It will end up. In order to suppress the occurrence of such toner scattering, if the intensity of the pressing electric field is set to be relatively small, the toner particles that have entered the space S of the entrance gap cannot be sufficiently pressed toward the hopping toner layer. There is a risk of leaking out of the casing 11 from the space S.

  Therefore, in the copying machine according to the second embodiment, as shown in the figure, the thickness of the insulating layer 12b is reduced toward the downstream side in the surface movement direction of the toner carrying roller 2. As a result, the intensity of the pressing electric field formed on the surface of the inlet facing member 12 is increased toward the downstream side in the movement direction of the roller surface, so that the toner is not scattered in the region on the most upstream side. The electric field strength is held down by keeping the value small. In the most downstream region, the strength of the pressing electric field is set to a relatively large value that can sufficiently press the toner particles that have entered the space S from the casing 11 against the hopping toner layer. Therefore, a very weak pressing electric field against the toner particles while preventing the occurrence of toner scattering due to abrupt action of the pressing electric field on the toner particles in the hopping toner layer immediately after entering the entrance gap. It is possible to avoid the occurrence of toner scattering due to the fact that it only acts.

  The insulating layer 12 b forms a surface facing the toner carrying roller 2 in the entrance facing member 12. The insulating layer 12b is made of a material that charges the toner particles to the normal charging polarity (minus polarity in this example) by friction with the toner particles. As a result, even if the toner particles that have entered the space S of the inlet gap from the inside of the casing 11 are weakly charged toner particles, they can be reliably prevented from being scattered by increasing the charge amount by contacting the insulating layer 12b. can do.

[Third embodiment]
FIG. 15 is a partially enlarged view of the vicinity of the entrance gap in the developing device of the copying machine according to the third embodiment. In the copying machine according to the third embodiment, an entrance-opposing member having an insulating base 12c, an electrode 12a, and an insulating layer 12b is used. A plurality of electrodes 12a are formed on the surface of the insulating substrate 12c so as to be aligned along the surface movement direction of the toner carrying roller 2. Different pressing voltages are applied to the plurality of electrodes 12a. When a DC voltage is used as the pressing voltage, the polarity of the DC voltage is made the same as the charging polarity of the toner, and the absolute value of the DC voltage becomes smaller as it goes from the upstream side to the downstream side in the roller surface movement direction. To do. Further, when a pressing voltage comprising a pulse voltage is used, the absolute value of the central value V0 of the pulse voltage is gradually increased from the upstream side to the downstream side in the roller surface movement direction in the same manner as the DC voltage described above. Make it smaller.

  Even in such a configuration, the electric field is suppressed to a relatively small value that does not cause toner scattering in the region on the most upstream side in the roller surface movement direction in the entrance gap due to the same operation as the copying machine according to the second embodiment. The strength of the. In the most downstream region, the strength of the pressing electric field is set to a relatively large value that can sufficiently press the toner particles that have entered the space S from the casing 11 against the hopping toner layer. Therefore, a very weak pressing electric field against the toner particles while preventing the occurrence of toner scattering due to abrupt action of the pressing electric field on the toner particles in the hopping toner layer immediately after entering the entrance gap. It is possible to avoid the occurrence of toner scattering due to the fact that it only acts.

[Fourth embodiment]
FIG. 16 is a partially enlarged view showing a part of the vicinity of the entrance gap in the developing device of the copying machine according to the fourth embodiment. In the copying machine according to the fourth embodiment, an entrance facing member is used that includes an electrode 12a and an insulating layer 12b coated on the surface thereof. The insulating layer 12b is provided with a plurality of grooves 12b-1 arranged along the roller surface moving direction in a posture extending in the axial direction of the toner carrying roller 2. Even if a strong air flow is generated from the inside of the casing 11 toward the inlet gap due to some sudden factor, the air force is weakened by hitting the side walls of the plurality of grooves 12b-1. Even when a strong air current entrains many toner particles and enters the entrance gap, the force of the air current is weakened by the plurality of grooves 12b-1, so that the toner particles are surely taken into the hopping toner layer. Thus, toner scattering can be prevented. In addition, when there exists a possibility that the some groove | channel 12b-1 may generate | occur | produce a strong turbulent flow, it is possible to suppress generation | occurrence | production of a turbulent flow by making the depth of the groove | channel 12b-1 low to some extent.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
[Aspect A]
A toner carrier (for example, toner carrier roller 2) having a plurality of electrodes for hopping toner particles in the toner carried on its surface, and an endlessly moving surface of the toner carrier contained therein A casing (for example, casing 11) having an opening (for example, opening 11a) for exposing a part of the endless moving direction to the outside and directly facing a latent image carrier (for example, photoconductor 49) of the image forming apparatus; And the toner particles hopped on the surface of the toner carrier are transported to a developing region where the surface and the latent image carrier are directly opposed to each other as the surface moves endlessly. In the developing device (for example, the developing device 1) that develops the latent image by attaching the latent image to the latent image, the surface after passing through the developing region with endless movement is In the vicinity of the casing inlet (for example, the casing inlet 11b), which is a position to enter the casing in a state of facing the inner wall of the mouth with a predetermined gap, at least immediately before entering the casing or in the casing Immediately after entering, a hopping toner layer composed of a plurality of toner particles arranged on the surface so as to face the surface with a predetermined gap is electrostatically directed toward the surface. An inlet facing member (for example, the inlet facing member 12) to which a pressing voltage, which is a voltage for pressing on, is applied, is provided.

[Aspect B]
Aspect B is characterized in that in Aspect A, the gap formed between the surface of the toner carrying member and the inlet facing member is made smaller toward the downstream side in the movement direction of the surface. In this configuration, the distance between the surface of the toner carrier and the entrance facing member is relatively wide in the region upstream of the surface of the toner carrier in the gap, so that the distance between the surface of the toner carrier is relatively high. Even toner particles that have been hopped can be captured in the gap. In addition, in the region on the downstream side in the movement direction of the surface of the toner carrier in the gap, the distance between the surface of the toner carrier and the inlet facing member is made relatively small so that the backflow of toner particles from the casing to the gap is prevented. It can be effectively prevented.

[Aspect C]
Aspect C is characterized in that, in aspect A, the inlet facing member is composed of at least an electrode to which the pressing voltage is applied and an insulating layer or a high electrical resistance layer coated on the surface of the electrode. It is what. In such a configuration, it is possible to prevent charge injection from the electrode to the toner particles by preventing direct contact between the electrode of the inlet facing member and the toner particles.

[Aspect D]
Aspect D is characterized in that, in aspect C, the thickness of the insulating layer or the high electrical resistance layer is reduced as it goes to the downstream side in the moving direction of the surface of the toner carrier. In such a configuration, the intensity of the pressing electric field is relatively weakened in the upstream region in the direction of surface movement of the toner carrier in the gap between the surface of the toner carrier and the inlet facing member, so that the hopping toner in the upstream region. It is possible to prevent occurrence of toner scattering due to abrupt application of a pressing electric field to the layer. On the other hand, in the downstream region, the intensity of the pressing electric field is made relatively strong, so that it is possible to avoid the occurrence of toner scattering due to only a very weak pressing electric field acting on the toner particles. it can.

[Aspect E]
Aspect E is characterized in that, in aspect C or D, a plurality of the electrodes of the inlet facing member are arranged side by side along the moving direction of the surface of the toner carrier. In such a configuration, by applying a relatively low pressing voltage to the electrode disposed on the upstream side in the surface movement direction of the toner carrier among the plurality of electrodes in the inlet facing member, the pressing electric field is reduced. The strength can be made relatively weak. On the other hand, the strength of the pressing electric field can be made relatively strong by applying a relatively high pressing voltage to the electrode disposed on the downstream side.

[Aspect F]
Aspect F is characterized in that, in any one of Aspects A to E, a plurality of grooves arranged along the surface movement direction of the toner carrier are provided on the surface of the inlet facing member facing the toner carrier. To do. In this configuration, as already described, the backflow of toner from the inside to the outside due to a strong airflow can be more reliably suppressed.

[Aspect G]
Aspect G is characterized in that in any one of Aspects A to F, the surface of the inlet facing member that faces the toner carrier is made of a material that charges the toner to a normal charging polarity by friction with the toner. Is. In such a configuration, the weakly charged toner particles are triboelectrically charged to the normal charging polarity by rubbing against the surface of the entrance facing member, so that the backflow of the weakly charged toner particles can be prevented better.

1: Developing device 2: Toner carrying roller (toner carrying member)
11: casing 11a: opening 11b: casing inlet 12: inlet facing member 12a: electrode 12b: insulating layer 12b-1: groove 49: photoconductor (latent image carrier)

JP 2009-109863 A

Claims (8)

A toner carrier having a plurality of electrodes for hopping the toner particles in the toner carried on its surface, and a partial region in the endless movement direction on the endlessly moving surface of the toner carrier contained therein And a casing having an opening for directly facing the latent image carrier of the image forming apparatus, and the toner particles hopping on the surface of the toner carrier are moved endlessly on the surface. With the development device that develops the latent image by transporting the surface and the latent image carrier to a development region that directly faces and attaching the surface to the latent image of the latent image carrier,
At least in the vicinity of the casing inlet, which is a position where the surface after passing through the development area with endless movement enters the casing in a state of facing the inner wall of the opening with a predetermined gap, Immediately before entering the casing or immediately after entering the casing, the surface is arranged so as to face the surface with a predetermined gap, and includes a plurality of toner particles hopping on the surface. A developing device comprising an inlet facing member to which a pressing voltage, which is a voltage for electrostatically pressing the hopping toner layer toward the surface, is applied. The developing device according to claim 1.
2. A developing device according to claim 1, wherein a gap formed between the surface of the toner carrying member and the inlet facing member is reduced toward the downstream side in the moving direction of the surface. The developing device according to claim 1.
2. A developing apparatus according to claim 1, wherein said entrance-opposing member comprises at least an electrode to which said pressing voltage is applied, and an insulating layer or a high electrical resistance layer coated on the surface of said electrode. The developing device according to claim 3.
2. A developing device according to claim 1, wherein the thickness of the insulating layer or the high electrical resistance layer is reduced toward the downstream side in the moving direction of the surface of the toner carrier. The developing device according to claim 3 or 4,
A developing device, wherein a plurality of electrodes of the inlet facing member are arranged side by side along the moving direction of the surface of the toner carrier. The developing device according to any one of claims 1 to 5,
A developing device comprising a plurality of grooves arranged along a surface movement direction of the toner carrier on a surface of the inlet facing member facing the toner carrier. The developing device according to any one of claims 1 to 6,
2. A developing device according to claim 1, wherein a surface of the inlet facing member facing the toner carrier is made of a material that charges the toner to a normal charging polarity by friction with the toner. In an image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image carried on the latent image carrier.
As the developing means, the developing device according to any one of claims 1 to 7,
In addition, a power source is provided for outputting a voltage applied to a plurality of electrodes provided in the toner carrier and the pressing voltage in order to hop toner particles on the surface of the toner carrier. An image forming apparatus.

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