JP2013097148A - Developing device and image forming device equipped with same, and process unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress toner scattering caused by weakly charged toner generated in a developing device using a flare developing system.SOLUTION: There is provided a developing device 5 which forms an electric field for hopping toner on the outer peripheral surface of a toner carrying roller by applying voltages different from each other to a first electrode 53 and a second electrode 54 provided on a toner carrying roller 16 and has a toner supply roller 61 disposed facing the outer peripheral surface of the toner carrying roller through a gap (supply gap) inside the developing device, wherein normally charged toner of toner held on the surface of the toner supply roller is moved to the outer peripheral surface of the toner carrying roller through the supply gap and the weakly charged toner forms a supply electric field which does not move the toner to the outer peripheral surface of the toner carrying roller through the supply gap in a toner supply region.

Description

  The present invention relates to a developing device that develops a latent image by transporting toner on a toner carrying member to a developing region and depositing the toner on the latent image carrying member, and a copier and printer including the developing device. The present invention relates to an image forming apparatus such as a facsimile and a process unit.

  Conventionally, this type of developing device does not use toner adsorbed on the surface of a toner carrier or a magnetic carrier for development, but uses a flare development system that uses toner hopped on the outer peripheral surface of the toner carrier for development. What was adopted is known. As a developing device adopting the flare developing method, for example, there is an apparatus having 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 electrodes adjacent to each other. An alternating electric field (hopping electric field) is formed between two electrodes in each electrode pair. As a result, the toner located on one electrode in the electrode pair floats and landes on the other electrode, or floats on the other electrode and landes on the one electrode. The hopping behavior is shown.

  Further, as a developing device adopting the flare developing method, for example, a toner in which one electrode is formed on the inner peripheral surface side of the toner carrier and the other comb-shaped electrode is formed thereon via an insulating layer. Those having a carrier are also known (Patent Document 1, Patent Document 2, etc.). Even with a toner carrier having such an electrode configuration, toner can be hopped on the outer peripheral surface thereof.

  While repeating such hopping, the toner on the toner carrier is transported to the development region by the surface movement accompanying the rotational driving of the toner carrier. In the developing region, the toner that has floated to the vicinity of the latent image on the latent image carrier is attracted to the electric field by the latent image and does not descend toward the electrode of the toner carrier, and adheres to the latent image. In such a configuration, toner that does not exert an attractive force by hopping is used for development instead of toner that is adsorbed on the surface of the toner carrier or a magnetic carrier. As a result, it is possible to realize low potential development that could not be realized by the conventional one-component development method or two-component development method. For example, toner can be selectively attached to an electrostatic latent image having a potential difference of only a few tens [V] with respect to surrounding non-image portions.

  In order to stably hop toner on the toner carrying member, it is important to carry the toner sufficiently charged to the normal charging polarity on the toner carrying member. However, in a conventional flare developing type developing device, toner that is not charged to the amount of charge necessary for stable hopping (hereinafter referred to as “weakly charged toner”) is usually contained in the toner carried on the toner carrying member. "). Such weakly charged toner tends to be released from the toner carrier for the following reasons.

FIGS. 9A and 9B are explanatory views for explaining a mechanism in which weakly charged toner is easily released from the toner carrier.
The normally charged toner on the toner carrier is subjected to the action of a hopping electric field and repeats hopping on the outer peripheral surface of the toner carrier as shown in FIG. On the other hand, the weakly charged toner on the toner carrier is not easily affected by the hopping electric field, and often remains attached to the outer peripheral surface of the toner carrier. The normally charged toner that hops on the toner carrier may collide with the weakly charged toner that remains on the outer peripheral surface of the toner carrier at the time of landing of the hopping. Due to this collision, the weakly charged toner is ejected from the outer peripheral surface of the toner carrier. The ejected weakly charged toner is less likely to be restrained by a hopping electric field formed outside the outer peripheral surface of the toner carrying member, and is thus easily released from the vicinity of the outer peripheral surface of the toner carrying member.

  As described above, since the weakly charged toner is easily released from the toner carrier, the weakly charged toner released in the region exposed from the case of the developing device or the weakly charged toner released in the developing device and flowing out of the developing device. Causes problems such as scattering outside the developing device and contaminating the inside of the image forming apparatus.

  In the developing device described in Patent Document 1, the weakly charged toner released from the toner carrier is collected downstream of the regulating member in the toner carrier rotation direction and upstream of the development region in the toner carrier rotation direction. Weakly charged toner collecting means is provided. In this developing device, the toner on the toner carrier is triboelectrically charged in the regulation region where the outer peripheral surface of the toner carrier and the regulation member abut before coming out of the development case and transported to the development region. The amount of charge increases. Further, the weakly charged toner having an insufficient charge amount even after passing through the regulation region is collected by the weakly charged toner collecting means, so that scattering of the toner by the weakly charged toner can be suppressed.

  However, at a location where the weakly charged toner collecting means is provided, that is, at a location downstream of the regulating member in the rotation direction of the toner carrier and upstream of the development region, the toner carrier rotates. The airflow in the direction of rotation of the toner carrier and the airflow in the direction of rotation of the latent image carrier generated by the rotation of the latent image carrier collide with each other. Therefore, in this location, turbulence is generated and the airflow is unstable. Since it is difficult to collect all of the weakly charged toner that is floated by such an unstable air current, the developing device described in Patent Document 1 does not have a sufficient effect of suppressing toner scattering by the weakly charged toner. There was a problem.

  Further, the developing device described in Patent Document 2 includes a toner supply member disposed so as to be in contact with the outer peripheral surface of the toner carrier, and the toner held on the surface of the toner supply member is transferred to the outer periphery of the toner carrier. Supply to the surface. In this configuration, in the supply region where the outer peripheral surface of the toner carrier and the surface of the toner supply member are in contact with each other, the toner is rubbed with the toner sandwiched therebetween. By this rubbing, the toner is triboelectrically charged, and the charge amount of the toner supplied onto the toner carrier is improved. Further, in this developing device, by applying a voltage to the toner supply member, the toner charged with a normal charging polarity is moved to the toner carrier outer peripheral surface side between the surface of the toner supply member and the outer peripheral surface of the toner carrier. A supply electric field is formed which acts to cause Therefore, in the supply region, the toner charged to the normal charging polarity on the toner supply member is supplied onto the toner carrier by the action of the supply electric field due to the potential difference between the outer peripheral surface of the toner carrier and the surface of the toner supply member. Is done.

  The developing device described in Patent Document 2 employs a configuration in which the outer peripheral surface of the toner carrier and the surface of the toner supply member are in contact with each other in order to frictionally charge the toner in the supply region. Therefore, in the supply region, not only the action of the supply electric field but also the mechanical adhesion force when sandwiched between the outer peripheral surface of the toner carrier and the surface of the toner supply member acts, and the toner on the toner supply member Is supplied onto the toner carrier. For this reason, in the supply region, the weakly charged toner that is hardly affected by the supply electric field also moves onto the toner carrier due to the mechanical adhesion force due to rubbing.

  In the developing device described in Patent Document 2, a voltage is applied to the toner supply member such that the potential difference between the surface of the toner supply member and the outer peripheral surface of the toner carrier is equal to or higher than the discharge start voltage. Thus, a discharge is generated in a minute gap adjacent to the downstream side in the rotation direction of the toner carrier. As a result of this discharge, a charge is imparted to the weakly charged toner supplied to the toner carrier, so that the amount of the weakly charged toner on the toner carrier can be reduced. However, it is difficult to raise the charge amount of all the weakly charged toners that have been supplied onto the toner carrying member to a normal charge amount by applying charges by this discharge. Therefore, even the developing device described in Patent Document 2 has a problem that the effect of suppressing toner scattering by weakly charged toner is not sufficient.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device having a high effect of suppressing toner scattering caused by weakly charged toner generated in a developing device adopting a flare developing system, and the same. An image forming apparatus and a process unit are provided.

  In order to achieve the above object, the present invention has a toner carrier having at least two types of electrode members to which different voltages are applied, and applies different voltages to the at least two types of electrode members. As a result, a hopping electric field for hopping the toner is formed on the outer peripheral surface of the toner carrier, and the hopped toner is sent to the development area opposite to the surface of the latent image carrier to bring the toner on the latent image carrier. In the developing device that develops the latent image by adhering to the latent image of the toner, the outer surface of the toner carrier or the surface of the toner holding member that holds the toner supplied to the toner carrier on the surface inside the developing device A toner supply member disposed on the surface of the toner carrier and holding the toner supplied to the outer peripheral surface of the toner carrier or the surface of the toner holding member. Among the toner held on the surface of the toner supply member, the toner charged to the normal charging polarity is moved to the outer peripheral surface of the toner carrier or the surface of the toner holding member via the gap. And a supply electric field forming means for forming a supply electric field in a supply region facing the toner carrier.

  In the present invention, since a gap is formed between the toner supply member and the toner carrier or toner holding member (hereinafter referred to as “toner carrier etc.”) in the supply region, the gap is held on the surface of the toner supply member. The toner is not pressed against the toner carrier or the like. Therefore, the toner on the toner supply member is not supplied to the outer peripheral surface of the toner carrier due to mechanical adhesion. As a result, as a factor affecting the movement (flying) of the toner from the toner supply member to the toner carrier, the action of the supply electric field formed by the supply electric field forming means is dominant.

  Since both the weakly charged toner and the normally charged toner are charged with the normal charging polarity, they are subjected to a force that moves from the toner supply member to the toner carrier by the action of the supply electric field. However, since the weakly charged toner has a smaller charge amount than the normal charged toner, it is not easily affected by the supply electric field, and the moving force from the toner supply member to the toner carrier is weaker than that of the normal charged toner. As a result, the weakly charged toner on the toner supply member has an electric field strength that does not reach the outer peripheral surface of the toner carrier while remaining on the surface of the toner supply member or while in the supply region. Thus, by appropriately setting the supply electric field, it is possible to selectively move only normally charged toner (toner having a sufficient charge amount for hopping under the action of the hopping electric field) to the toner carrier. It is. As a result, the amount of weakly charged toner contained in the toner carried on the outer peripheral surface of the toner carrier and conveyed to the development area is reduced, and the air flow generated at a location upstream of the development area in the rotation direction of the toner carrier. Even if the toner is unstable, the amount of weakly charged toner itself that is in the unstable air current is small, so that toner scattering is suppressed.

  According to the present invention, it is possible to obtain an excellent effect that the effect of suppressing toner scattering by the weakly charged toner generated in the developing device adopting the flare developing method is high.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment. 2 is a schematic configuration diagram illustrating a developing device in the image forming apparatus. FIG. FIG. 4 is a partial cross-sectional view schematically showing a cross section when the toner carrying roller of the developing device is cut along a plane orthogonal to the rotation axis thereof. 4 is a graph showing an example of a first voltage and a second voltage applied to a first electrode and a second electrode of the toner carrying roller, respectively. It is a graph which shows the other example of the 1st voltage applied to the 1st electrode and the 2nd electrode of the toner carrying roller, respectively, and the 2nd voltage. 6 is a graph showing a relationship between a voltage applied to a first electrode and a second electrode of the toner carrying roller and a voltage applied to a toner supply roller. It is a schematic block diagram which shows the developing device in a modification. 2 is a schematic configuration diagram showing a developing device in Comparative Example 1. FIG. (A) And (b) is explanatory drawing explaining the mechanism in which weakly charged toner is easy to release | separate from a toner carrier.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic copying machine as an image forming apparatus will be described.
First, the configuration and operation of the copier according to the present embodiment will be described.
FIG. 1 is a schematic configuration diagram showing a copying machine according to the present embodiment.
The copying machine accommodates a recording medium P such as a document conveying unit 32 that conveys a document to a document reading unit, a document reading unit (not shown) that reads image information of a document, a paper discharge tray 30 on which output images are stacked, and transfer paper. Sheet feeding unit 26, registration roller pair 28 for adjusting the conveyance timing of the recording medium P, and photosensitive drums 1Y and 1M as latent image carriers on which toner images of respective colors (yellow, magenta, cyan, and black) are formed. , 1C, 1BK, developing devices 5Y, 5M, 5C, 5BK for developing electrostatic latent images formed on the photosensitive drums 1Y, 1M, 1C, 1BK, and on the photosensitive drums 1Y, 1M, 1C, 1BK Are provided with transfer bias rollers 9Y, 9M, 9C, 9BK for transferring the toner images formed on the recording medium P in an overlapping manner. The copying machine also includes a paper conveying belt 8 that conveys the recording medium P, a fixing device 20 that fixes an unfixed image on the recording medium P, and each color toner that is supplied to the developing devices 5Y, 5M, 5C, and 5BK. A toner container 31 is also provided.

  The document is transported from the document table by the transport rollers of the document transport unit 32 and placed on the contact glass of a document reading unit (not shown). Then, the image information of the document placed on the contact glass is optically read by the document reading unit. Specifically, the document reading unit scans an image of the document on the contact glass while irradiating light emitted from an illumination lamp. Then, the light reflected from the original is imaged on the color sensor via the mirror group and the lens. The color image information of the original is read for each color separation light of RGB (red, green, blue) by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Image information of each color of yellow, magenta, cyan, and black is transmitted to a writing unit (not shown). The writing unit emits laser light based on the image information of each color toward the corresponding photosensitive drums 1Y, 1M, 1C, and 1BK. On the other hand, the four photosensitive drums 1Y, 1M, 1C, and 1BK are rotated counterclockwise in the drawing. The surfaces of the photosensitive drums 1Y, 1M, 1C, and 1BK are uniformly charged at a portion facing a charging unit (not shown) before the laser beam is irradiated from the writing unit. Thereafter, the surface portions of the charged photosensitive drums 1Y, 1M, 1C, and 1BK reach the irradiation positions of the respective laser beams, and the laser beams corresponding to the image signals from the four light sources in the writing unit correspond to the respective colors. Each is irradiated. Each laser beam passes through a different optical path for each color component of yellow, magenta, cyan, and black.

  The laser beam corresponding to the yellow component is applied to the surface of the first photosensitive drum 1Y from the lower side in the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 1Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 1Y after being charged by the charging unit. Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 1M from the bottom in the figure, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 1C from the bottom in the figure, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 1BK from the bottom in the figure, and an electrostatic latent image of the black component is formed.

  Thereafter, the surface portions of the photosensitive drums 1Y, 1M, 1C, and 1BK on which the electrostatic latent images of the respective colors are formed reach positions (developing regions) facing the developing devices 5Y, 5M, 5C, and 5BK, respectively. Then, the respective color toners are supplied from the developing devices 5Y, 5M, 5C, and 5BK onto the photosensitive drums 1Y, 1M, 1C, and 1BK, and the latent images on the photosensitive drums 1Y, 1M, 1C, and 1BK are formed. Developed.

  The surface portions of the photosensitive drums 1Y, 1M, 1C, and 1BK after development reach the facing portions (transfer areas) with respect to the paper transport belt 8, respectively. Here, transfer bias rollers 9Y, 9M, 9C, and 9BK are installed at the opposing portions so as to contact the inner peripheral surface of the paper transport belt 8. Then, on the photosensitive drums 1Y, 1M, 1C, and 1BK on the recording medium P that has been conveyed by the paper conveying belt 8 that runs in the clockwise direction in the drawing at the positions of the transfer bias rollers 9Y, 9M, 9C, and 9BK. The toner images of the respective colors formed in the above are sequentially transferred so as to overlap each other. The recording medium P transported to the facing portion (transfer region) between the photosensitive drums 1Y, 1M, 1C, and 1BK and the paper transport belt 8 is transported from the paper feed unit 26 via the registration roller pair 28 and the like. Specifically, the recording medium P fed from the paper feeding unit 26 that stores the recording medium P by the paper feeding roller 27 is transported toward the transfer region at the same timing after passing through the transport guide.

  The surfaces of the photosensitive drums 1Y, 1M, 1C, and 1BK after the transfer reach positions facing a cleaning unit (not shown). Then, the untransferred toner remaining on the photosensitive drums 1Y, 1M, 1C, and 1BK is collected by the cleaning unit. Thereafter, the surfaces of the photoconductive drums 1Y, 1M, 1C, and 1BK pass through a charge eliminating unit (not shown), and a series of image forming processes on the photoconductive drums 1Y, 1M, 1C, and 1BK is completed.

  On the other hand, the recording medium P on which the color image in which the color toner images overlap is transferred is guided to the fixing device 20. In the fixing device 20, the color image is fixed on the recording medium P at the nip between the fixing roller and the pressure roller. Then, the fixed recording medium P is discharged as an output image to the outside of the apparatus by a discharge roller and stacked on the discharge tray 30 to complete a series of image forming processes.

  In the copying machine of the present embodiment, at least the photosensitive drum and the developing device may be integrated to form a process cartridge that is detachable from the image forming apparatus main body. The process cartridge may be configured to be removable independently for each color. In addition to the photosensitive drum and the developing device, for example, a charging device or a cleaning device may be mounted on the process cartridge.

Next, the configuration and operation of the developing devices 5Y, 5M, 5C, and 5BK, which are features of the present invention, will be described.
The developing devices 5Y, 5M, 5C, and 5BK of the respective colors have the same basic configuration except that the colors of the toners to be used are different. Therefore, the color-coded symbols Y, M, C, and BK are hereinafter attached. Will be omitted.

FIG. 2 is a schematic configuration diagram showing the developing device 5 in the present embodiment.
The developing device 5 of the present embodiment includes a toner carrying roller 16 as a toner carrying member, and a toner supply roller 61 as a toner supply member that supplies toner to the toner carrying roller 16. The toner supply roller 61 is disposed inside the developing device 5 so as to face the outer peripheral surface of the toner carrying roller 16 with a gap. The toner carrying roller 16 carries the toner supplied from the toner supply roller 61 on the outer peripheral surface and is driven to rotate in the direction of the arrow in the figure, thereby conveying the toner to the developing region facing the surface of the photosensitive drum 1. .

  A toner container 66 formed inside the developing device stores a one-component toner made of a non-magnetic toner. The toner in the toner container 66 is circulated and conveyed by the two conveying screws 65, and a part of the circulated and conveyed toner moves to the supply screw 62 side. As the material of each conveying screw 65, for example, a material having soft elasticity such as polypropylene can be used, and the elastic screw is used to rotate in close contact with the inner wall of the toner accommodating portion 66 to reliably convey the toner. To do. The toner moved to the supply screw 62 side is rubbed with the surface of the toner supply roller 61 by the transfer of the supply screw 62 and frictionally charged, and is pumped up to the surface of the toner supply roller 61 by electrostatic force.

  The toner drawn up on the surface of the toner supply roller 61 is conveyed to a position (regulation position) facing the regulation blade 63 as a toner layer regulating member as the toner supply roller 61 rotates. At this restricting position, the restricting blade 63 receives an urging force of about 10 to 15 [N] and is in contact with the surface of the toner supply roller 61. When the toner on the toner supply roller 61 passes through between the regulation blade 63 and the toner supply roller 61 at this regulation position, the layer thickness is regulated, frictional charging is promoted, and the charge amount is increased.

The charge amount of the toner conveyed to the development area is preferably from −10 [μC / g] to −50 [μC / g], and more preferably from −15 [μC / g] to −45 [μC / g]. . In this embodiment, the toner conveyance amount per unit area conveyed to the development area is adjusted to be [30 mg / cm ² ].

  The toner that has passed through the regulation position reaches a supply region that faces the toner carrying roller 16 as the toner supply roller 61 rotates. In this supply region, the toner carrying roller 16 and the toner supply roller 61 are arranged to face each other via a gap (supply gap) having a minimum separation distance of about 300 [μm]. The toner supply roller 61 is connected to a toner supply power source 68 as a supply electric field forming unit, and a voltage is applied from the toner supply power source 68 to the toner supply roller 61. A supply electric field for electrostatically moving the toner on the toner supply roller 61 to the toner carrying roller 16 is formed in the supply region by the voltage applied to the toner supply roller 61. The toner charged to the normal charging polarity on the toner supply roller 61 is subjected to the action of the supply electric field, and flies to the toner carrying roller 16 and is carried on the outer peripheral surface of the toner carrying roller 16.

  The toner carried on the outer peripheral surface of the toner carrying roller 16 is conveyed to the developing region by the rotation of the toner carrying roller 16 in a state where it is hopped by the action of a hopping electric field described later. The toner conveyed to the development area is developed on the photosensitive drum 1 by a developing electric field between the toner carrying roller 16 and the image portion on the photosensitive drum 1. In this embodiment, when the surface moving speed of the toner carrying roller 16 is Vs and the surface moving speed of the photosensitive drum 1 is Vp, Vs / Vp is set to be in the range of 1.5 to 2.0. It is preferable to do this. The toner remaining on the toner carrying roller 16 without contributing to development in the developing region is further conveyed by the rotation of the toner carrying roller 16 and collected from the surface of the toner carrying roller 16 by a collecting unit (not shown). The collected toner is returned again to the toner container 66 and circulates in the developing device.

An example of the toner used in this embodiment will be described.
A low molecular weight polyester resin (100 parts by weight), carbon black (6 parts by weight), and a polymer charge control agent (1 part by weight) are kneaded by an ordinary screw kneader kneading method, followed by rolling and cooling to roughly pulverized toner. The toner was pulverized by a jet mill and finally passed through an airflow classifier to obtain a toner having a volume average particle diameter of 6.7 [μm] and a number average particle diameter of 6.1 [μm]. Similarly, for magenta, cyan and yellow, color toners were obtained by replacing the pigments. Next, 0.3 parts by weight of silica was added to 100 parts by weight of each of the obtained color toners, and mixed for 1 minute using a Henschel mixer. Subsequently, 0.3 part by weight of titania was added and mixed for 1 minute, and 1.0 part by weight of silica was further added and mixed for 1 minute.

Next, a specific configuration of the toner carrying roller 16 in the present embodiment will be described.
FIG. 3 is a partial cross-sectional view schematically showing a cross section when the toner carrying roller 16 according to the present embodiment is cut along a plane orthogonal to the rotation axis thereof.
The toner carrying roller 16 according to the present embodiment is configured by a hollow roller member, and includes a first electrode 53 serving as an inner peripheral side electrode member positioned on the innermost periphery thereof, and a first electrode 53 positioned on the outermost peripheral side. A comb-like second electrode 54 is provided as an outermost peripheral electrode member to which a voltage (second voltage) different from a voltage (first voltage) applied to one electrode 53 is applied. In addition, an insulating layer 55 is provided between the first electrode 53 and the second electrode 54 to insulate them. A surface layer 56 that covers the outer peripheral surface side of the second electrode 54 is also provided. That is, the toner carrying roller 16 of the present embodiment has a four-layer structure of the first electrode 53, the insulating layer 55, the second electrode 54, and the surface layer 56 in order from the inner peripheral side.

  The first electrode 53 also functions as a base of the toner carrying roller 16 and is a metal roller obtained by molding a conductive material such as SUS or aluminum into a cylindrical shape. In addition, as the configuration of the first electrode 53, there may be mentioned one in which a conductive layer made of a metal layer such as aluminum or copper is formed on the surface of a resin roller made of polyacetal (POM) or polycarbonate (PC). As a method of forming this conductive layer, a method of forming by metal plating, vapor deposition, or the like, a method of adhering a metal film to the roller surface, or the like can be considered.

  The outer peripheral surface side of the first electrode 53 is covered with an insulating layer 55. In the present embodiment, the insulating layer 55 is made of polycarbonate, alkyd melamine, or the like. In the present embodiment, the thickness of the insulating layer 55 is preferably in the range of 3 [μm] to 50 [μm]. If it is smaller than 3 [μm], the insulation between the first electrode 53 and the second electrode 54 cannot be sufficiently maintained, and a leak occurs between the first electrode 53 and the second electrode 54. The possibility increases. On the other hand, when it becomes larger than 50 [μm], the electric field generated between the first electrode 53 and the second electrode 54 is hardly formed outside the surface layer 56, and a strong hopping electric field is generated outside the surface layer 56. It becomes difficult to form. In the present embodiment, the thickness of the insulating layer 55 made of melamine resin is 20 [μm]. The insulating layer 55 can be formed with a uniform film thickness on the first electrode 53 by a spray method, a dip method or the like.

  A second electrode 54 is formed on the insulating layer 55. In the present embodiment, the second electrode 54 is formed of a metal such as aluminum, copper, or silver. Various methods can be considered as a method of forming the comb-shaped second electrode 54. For example, there is a method in which a metal film is formed on the insulating layer 55 by plating or vapor deposition, and a comb-like electrode is formed by photoresist etching. A method of forming a comb-like electrode by attaching a conductive paste on the insulating layer 55 by an ink jet method or screen printing is also conceivable.

  The outer peripheral surfaces of the second electrode 54 and the insulating layer 55 are covered with an insulating surface layer 56. When the hopping is repeated on the surface layer 56, the toner is charged by contact friction with the surface layer 56. In this embodiment, silicone, nylon (registered trademark), urethane, alkyd melamine, polycarbonate, or the like is used as the material of the surface layer 56 in order to give the toner a normal charging polarity (negative polarity in this embodiment). In this embodiment, polycarbonate is employed. Further, since the surface layer 56 also has a role of protecting the second electrode 54, the film thickness of the surface layer 56 is preferably in the range of 3 [μm] or more and 40 [μm] or less. If it is smaller than 3 [μm], the second electrode 54 is exposed due to film scraping or the like due to use over time, and leaks through the toner carried on the toner carrying roller 16 and other members contacting the toner carrying roller 16. There is a fear. On the other hand, if it is larger than 40 [μm], the electric field generated between the first electrode 53 and the second electrode 54 is difficult to be formed outside the surface layer 56, and a strong hopping electric field is generated outside the surface layer 56. It becomes difficult to form. In this embodiment, the film thickness of the surface layer is 20 [μm]. The surface layer 56 can be formed by a spray method, a dipping method, or the like, similarly to the insulating layer 55.

  In the present embodiment, the electric field created between the first electrode 53 and the second electrode 54, more specifically, the portion of the first electrode 53 that is not opposed to the second electrode 54 (the comb teeth of the second electrode 54). The electric field generated between the portion of the first electrode 53 positioned between the second electrode 54 and the comb-tooth portion of the second electrode 54 is formed outside the surface layer 56, thereby hopping the toner on the toner carrying roller 16. This makes the toner cloud. At this time, the toner on the toner carrying roller 16 flies between the surface layer portion facing the first electrode 53 via the insulating layer 55 and the surface layer portion facing the second electrode 54 adjacent thereto. While hopping so as to move back and forth.

  In order to stably form the toner in the cloud, it is important to form a hopping electric field having a corresponding magnitude. To form such a large hopping electric field, the first electrode 53 and the second electrode 54 are used. It is necessary to form a large potential difference between However, in order to stably form such a large potential difference, it is important to stably and effectively insulate between the first electrode 53 and the second electrode 54 to prevent leakage.

  Here, when two types of electrodes for forming a hopping electric field are each formed in a comb-teeth shape and arranged on concentric circles, and each comb-tooth portion is configured to enter between the other comb teeth, the comb If the formation quality of the tooth-like electrode is poor, the insulation between the two kinds of electrodes is remarkably lowered, and leakage is likely to occur. Specifically, for example, when an electrode is formed by etching, a part of the metal film to be removed remains, or when an electrode is formed by an ink jet method or a screen printing method, a conductive paste adheres between the electrodes. Can happen. When such a situation occurs, leakage easily occurs between the two types of electrodes, and an appropriate hopping electric field cannot be formed. In this configuration, even if the comb-like electrodes are formed with high quality on the resin surface of the roller, the outer peripheral surface side is covered with an insulating material after the two types of comb-like electrodes are formed. In order to obtain insulation between the electrodes by filling the insulating material, the interface between the resin surface of the roller and the insulating material is formed between the electrodes, and leakage through this interface is likely to occur, and a relatively large voltage is applied. The insulation between the electrodes is significantly reduced.

According to this embodiment, since the insulating layer 55 is provided on the first electrode 53 and the comb-like second electrode 54 is formed on the insulating layer, a leak may be caused between these electrodes. There is no interface to obtain. In addition, in the manufacturing stage of the toner carrying roller 16, the possibility that a conductive material that may cause a leak is interposed between the electrodes can be greatly reduced. Therefore, according to the present embodiment, the first electrode 53 and the second electrode 54 can be stably and effectively insulated, and leakage can be effectively prevented even when a relatively large voltage is applied. it can.
In the present embodiment, two types of electrodes for forming a hopping electric field are each formed in a comb-like shape and arranged concentrically so that each comb-tooth portion enters between the other comb-tooth. It can also be applied to examples.

  In the present embodiment, the electrode width of each second electrode 54 (the width of each comb tooth portion) is preferably 80 [μm] or more and 100 [μm] or less. If it is smaller than 80 [μm], the electrode may be too thin and the electrode may be broken in the middle. On the other hand, if it is larger than 100 [μm], the voltage at the location where the distance from the power-supplied portion of the second electrode 54 is low becomes low, and it becomes difficult to hop toner stably and effectively at that location. The power-supplied portions of the present embodiment are provided at both axial ends on the outer peripheral surface of the toner carrying roller 16. Therefore, in the present embodiment, when the electrode width of the second electrode 54 is larger than 100 [μm], the hopping electric field at the central portion in the axial direction of the toner carrying roller 16 is relatively lower than the hopping electric fields at both ends in the axial direction. Therefore, it becomes difficult to hop the toner carried on the central portion in the axial direction stably and effectively.

In the present embodiment, it is preferable that the electrode pitch of the second electrode 54 (the distance between the comb tooth portions) is the same as or wider than the electrode width. If it is smaller than the electrode width, most of the lines of electric force from the first electrode 53 converge on the second electrode 54 before coming out of the surface layer 56, and the hopping electric field formed outside the surface layer 56 is reduced. Because it becomes weak. On the other hand, when the electrode pitch is large, the hopping electric field at the center between the electrodes becomes weak. In the present embodiment, the electrode pitch is preferably in the range of not less than the electrode width and not more than three times the electrode width.
In this embodiment, the electrode width is set to 100 [μm], and the electrode pitch is set to 150 [μm].

  In the present embodiment, the electrode pitch of the second electrode 54 is set to be constant over the circumferential direction of the toner carrying roller 16. By making the electrode pitch constant, the hopping electric field created between the first electrode 53 and the second electrode 54 becomes substantially uniform over the circumferential direction on the toner carrying roller 16. Therefore, it is possible to achieve uniform toner hopping in the circumferential direction in the development region, and uniform development is possible.

Next, the voltage applied to the first electrode 53 and the second electrode 54 will be described.
A first voltage and a second voltage are applied to the first electrode 53 and the second electrode 54 on the toner carrying roller 16 from a pulse power source (not shown), respectively. A rectangular wave is most suitable for the first voltage and the second voltage applied by a pulse power supply (not shown). However, not limited to this, for example, a sine wave or a triangular wave may be used. In this embodiment, the electrodes for forming the hopping electrode have a two-phase configuration of the first electrode 53 and the second electrode 54, and voltages having a phase difference π are applied to the electrodes 53 and 54, respectively. Is done.

FIG. 4 is a graph showing an example of the first voltage and the second voltage applied to the first electrode 53 and the second electrode 54, respectively.
In the present embodiment, each voltage is a rectangular wave, and the first voltage and the second voltage applied to the first electrode 53 and the second electrode 54, respectively, have the same magnitude (peak-to-peak) whose phases are shifted from each other by π. Voltage Vpp). Therefore, there is always a potential difference of Vpp between the first electrode 53 and the second electrode 54. An electric field is generated between the electrodes due to this potential difference, and the toner hops on the surface layer 56 by a hopping electric field formed outside the surface layer 56 in the electric field. In the present embodiment, Vpp is preferably in the range of 100 [V] to 1000 [V]. When Vpp is smaller than 100 [V], a sufficient hopping electric field cannot be formed on the surface layer 56, and it becomes difficult to stably hop the toner. On the other hand, if Vpp is larger than 1000 [V], there is a high possibility that leakage will occur between the electrodes due to use over time.
In the present embodiment, the center value V0 of the first voltage and the second voltage is set between the image portion potential (the potential of the electrostatic latent image portion) and the non-image portion potential (the potential of the background portion), It varies depending on the development conditions.

  In the present embodiment, the frequency f of the first voltage and the second voltage is preferably 100 [Hz] or more and 1000 [Hz] or less. If the frequency is less than 100 [Hz], toner hopping may not catch up with the development speed. On the other hand, if the frequency is higher than 1000 [Hz], the movement of the toner cannot follow the switching of the electric field, and it becomes difficult to stably hop the toner.

FIG. 5 is a graph showing another example of the first voltage and the second voltage applied to the first electrode 53 and the second electrode 54.
In this example, a first voltage similar to that shown in FIG. 4 is applied to the first electrode 53, but a DC voltage is applied to the second electrode 54. In this case, the potential difference between the electrodes is Vpp / 2. Therefore, a suitable range of Vpp in this example is 200 [V] or more and 2000 [V] or less. According to this example, it is not necessary to consider the phase difference between the first electrode 53 and the second electrode 54, and the power supply cost is reduced.

Next, a specific configuration of the toner supply roller 61 in the present embodiment will be described.
The toner supply roller 61 has a surface formed of a metal such as aluminum or SUS, or a urea resin, a melamine resin, a urethane resin, a silicone resin, a fluorine resin, a phenol resin, a polyamide resin, an epoxy resin on these metal bases. Examples include those formed by coating a polyester resin or the like. Moreover, what formed the surface comprised with the conductive resin which disperse | distributed the electrically-conductive material to the melamine resin, the urethane resin, etc. may be used. As the conductive material, carbon black, copper powder, metal powder of aluminum powder, zirconium solid solution, solid solution containing F such as fluorite, and ionic conductor such as alkali metal salt such as aluminum can be used.

  The electric resistance of the surface layer of the toner supply roller 61 is preferably 11 [LogΩ] or less. The surface roughness of the toner supply roller 61 is preferably in the range of 2 [μm] to 4 [μm] in terms of Rz. If the surface roughness Rz is too small, the amount of toner that can be held on the surface of the toner supply roller 61 decreases, and if the surface roughness Rz is too large, the uniformity of the toner layer held on the surface of the toner supply roller 61 is impaired. As a result, uneven toner supply to the toner carrying roller 16 occurs.

FIG. 6 is a graph showing the relationship between the voltage applied to the first electrode 53 and the second electrode 54 of the toner carrying roller 16 and the voltage applied to the toner supply roller 61.
A DC voltage VB2 is applied to the toner supply roller 61 in the present embodiment. In the present embodiment, among the toners held on the surface of the toner supply roller 61, normally charged toner having a sufficient charge amount to be hopped by the action of the hopping electric field on the toner carrying roller 16 is used as a gap ( For the weakly charged toner that is moved to the outer peripheral surface of the toner carrying roller 16 via the supply gap) but is insufficiently charged to hop under the action of the hopping electric field, the gap is supplied via the gap (supply gap). A supply electric field that does not move to the outer peripheral surface of the toner carrying roller 16 is formed. The set value of the DC voltage VB2 applied to the toner supply roller 61 is determined so that such a supply electric field is formed in the supply region where the toner supply roller 61 and the toner carrying roller 16 face each other.

In this embodiment, the settable range of the DC voltage VB2 applied to the toner supply roller 61 is mainly the center value VB1 (V0 in FIGS. 4 and 5) of the voltage applied to the toner carrying roller 16 and the peak-to-peak. It varies depending on the voltage VPP. For example, as in this embodiment, the DC voltage VB2 applied to the toner supply roller 61 has a negative polarity, the central value of the voltage applied to the toner carrying roller 16 is also a negative polarity, and the normal charging polarity of the toner is also a negative polarity. In this case, the DC voltage VB2 applied to the toner supply roller 61 can be set so that, for example, the following expression (1) is satisfied. In addition, VPA in the following formula (1) is a discharge start voltage, and varies depending on conditions such as a supply gap.
VB1>VB2> VB1 + VPP / 2-VPA (1)

Here, if the DC voltage VB2 applied to the toner supply roller 61 is equal to or higher than the central value VB1 of the voltage applied to the toner carrying roller 16 (VB2 is set equal to or lower than the VB2 lower limit value in FIG. 6). In the supply region, the supply electric field acts on the normal charge toner (toner charged sufficiently with negative polarity) on the toner carrying roller 16 so as to move to the toner supply roller 61 on the average. It will be. In this case, the normally charged toner on the toner carrying roller 16 has a higher hopping height in the supply area than outside the supply area. As a result, depending on the set value of the supply gap, there is a possibility of colliding with the toner held on the surface of the toner supply roller 61. As described above, when the normally charged toner hopping on the toner carrying roller 16 collides with the toner held on the surface of the toner supply roller 61, the electrostatic adhesion with the surface of the toner supply roller 61 is weak. A phenomenon that the charged toner is ejected from the toner supply roller 61 occurs. When this phenomenon occurs, the weakly charged toner floats in the vicinity of the supply region, and a part of the toner rides on the airflow generated by the rotation of the toner carrying roller 16 and leaks to the outside of the developing device, which may cause toner scattering. There is. Therefore, in this embodiment, the upper limit value of the DC voltage VB2 applied to the toner supply roller 61 is set as the center value VB1 of the voltage applied to the toner carrying roller 16.
The lower limit value of the DC voltage VB2 applied to the toner supply roller 61 is the difference between the voltage VB2 applied to the toner supply roller 61 and the maximum value of the voltage applied to the toner carrying roller 16 as shown in the above equation (1). The difference (maximum potential difference) is set not to exceed the discharge start voltage.

  As a specific example, when a supply gap is 300 [μm], and a voltage having a central value VB1 of −400 [V] and VPP of 500 [V] is applied to the toner carrying roller 16, it is applied to the toner supply roller 61. The settable range of the DC voltage VB2 to be set is a range larger than −400 [V] and smaller than −750 [V].

  In this embodiment, the DC voltage VB2 applied to the toner supply roller 61 has a negative polarity, the central value of the voltage applied to the toner carrying roller 16 is also a negative polarity, and the normal charging polarity of the toner is also a negative polarity. Although the case has been described, for a configuration in which some or all of these polarities are reversed, the settable range of the DC voltage VB2 applied to the toner supply roller 61 can be similarly determined from the above viewpoint.

  In this embodiment, a DC voltage is applied to the toner supply roller 61, but an AC voltage may be applied. However, when an AC voltage is applied, the toner once detached from the surface of the toner supply roller 61 is held on the surface of the toner supply roller 61 when the toner is pulled back to the toner supply roller 61 side due to a change in the voltage value. There is a possibility of colliding with weakly charged toner. When such a collision occurs, the above-described phenomenon of ejection occurs, which may cause toner scattering.

  In the present embodiment, the case where a gap is formed between the toner supply roller 61 and the toner carrying roller 16 and the above-described supply electric field is formed has been described. The same effect can be obtained by providing a supply roller, forming a gap between the second supply roller and the toner supply roller 61, and forming the above-described supply electric field. At this time, a gap may not be formed between the toner supply roller 61 and the toner carrying roller 16.

[Modification]
Next, a modification of the developing device of the above embodiment will be described.
The developing device in this modification is different from the developing device of the above-described embodiment in that a regulating roller is used instead of the regulating blade 63 as a toner layer regulating member. In the following description, description of matters common to the above embodiment is omitted.

FIG. 7 is a schematic configuration diagram illustrating a developing device according to this modification.
The regulating roller 80 uses a metal shaft for the support portion, and uses a conductive resin in which a conductive material is dispersed in a resin such as a fluororesin or a silicone resin having a low friction coefficient as a material of the surface layer portion. is there. As the conductive material, the same material as that described for the toner supply roller 61 in the above embodiment can be used. The electric resistance of the surface layer of the regulating roller 80 is preferably 11 [LogΩ] or less. If the surface roughness of the regulating roller 80 is too rough, unevenness occurs in the toner layer that has passed the regulating position. Therefore, it is preferable that Rz is 4 [μm] or less for a general image. For high definition (600 dpi or more) images, Rz is preferably 2 [μm] or less. Further, the hardness is a standard of JIS K6253, and is preferably selected within a range of 50 ° to 85 °.

  In this modified example, the regulating roller 80 is rotationally driven by a driving force from a driving source (not shown), and the linear speed ratio between the toner supply roller 61 and the regulating roller 80 is 1.5 or more and 2.0 or less. It is preferable to set the range. If the linear velocity ratio is less than 1.5, there is a risk that the frictional charging of the toner at the restriction position will be insufficient, and the amount of weakly charged toner may increase.

  By using the roller-shaped regulating roller 80 as the toner layer regulating member as in this modification, toner adhesion to the toner layer regulating member is reduced as compared with the blade strip regulating blade 63 as in the above embodiment. can do. As a result, it is possible to increase the force for pressing the toner layer regulating member against the toner supply roller 61 at the regulation position, thereby increasing the frictional charging efficiency at the regulation position and reducing the amount of weakly charged toner.

In this modification, a toner removing member such as a scraper may be brought into contact with the surface of the regulating roller 80.
In the present modification, it is preferable that at least one of the toner supply roller 61, the supply screw 62, and the regulation roller 80 is grounded to release electric charges. When the toner supply roller 61, the supply screw 62, and the regulation roller 80 are all in an electrically floating state, when the toner is frictionally charged to a negative polarity, the toner supply roller 61, the supply screw 62, and the regulation roller 80 are A positive charge remains. Accumulation of the positive charge inhibits the frictional charging of the toner, the negative charge of the toner becomes insufficient, and the amount of reversely charged toner and weakly charged toner increases. If at least one of the toner supply roller 61, the supply screw 62, and the regulating roller 80 is grounded to release the charge, the positive charge accumulated by the frictional charge of the toner can be released.

  In this modification, the potential difference is eliminated between at least one pair of support portions selected from the support portion of the toner supply roller 61, the support portion of the supply screw 62, and the support portion of the regulating roller 80. It is good to comprise so that it may become. The toner is charged by friction with the toner supply roller 61, the supply screw 62, and the surface of the regulating roller 80. If these support portions have the same potential, the charge is unevenly distributed between them. Can be prevented. At this time, the electrical resistance between these support portions and the surface is preferably 11 [LogΩ] or less. When the electrical resistance increases, the electrical capacitance component increases. For example, charge accumulates between the surface of the toner supply roller 61 and the support portion of the toner supply roller 61, and the charge escapes without flowing to the ground. It will disappear. For this reason, there is a possibility that the amount of charge of the toner may be insufficient due to long-term use.

  The electrical resistance between the support portion and the surface of the toner supply roller 61, the supply screw 62, and the regulation roller 80 can be calculated as follows. That is, first, the measurement object, which is the toner supply roller 61, the supply screw 62, and the regulation roller 80, is placed on a horizontal metal flat plate, and 100 [g] is provided at both ends of the support portion (shaft portion). While applying a load, while applying a voltage of 100 [V] between the metal flat plate and the support portion of the measurement object, the current value is measured with an ammeter to calculate the electric resistance.

Next, an evaluation test performed for confirming the toner scattering suppression effect for the developing device of the embodiment and the developing device of the modification will be described.
In this evaluation test, ΔID is used as an evaluation index value representing the degree of toner scattering. As a method of measuring the evaluation index value ΔID, first, an image forming operation is performed without forming an electrostatic latent image on the photosensitive drum, and the developing device is operated. Thereafter, the toner adhering to the paper conveying belt 8 is collected using a printer. Next, the image density of the printer that collected the toner and the image density of a new printer that does not have toner attached are measured, and a difference value between them is calculated. The difference value obtained in this way is set as an evaluation index value ΔID. Here, if the evaluation index value ΔID is 0.01 or less, it is evaluated as “◯” because the toner scattering suppression effect is high, and if it is 0.02 or more and 0.04 or less, the toner scattering suppression effect is insufficient. Was evaluated as “Δ”, and if it was 0.05 or more, it was evaluated as “×” because the effect of suppressing the toner scattering was insufficient. In addition, X-Lite (made by AMTEC) was used for the measurement of image density.

  In this evaluation test, the amount of weakly charged toner among the toners carried on the toner carrying roller 16 was also evaluated. The amount of weakly charged toner on the toner carrying roller 16 was measured by using an E-Spart analyzer (manufactured by Hosokawa Micron) and capturing the charge amount of each toner as a distribution. Here, a toner whose charge amount is within a range of −2 [μC / g] or more and −3 [μC / g] is referred to as weakly charged toner, and the amount of the entire toner carried on the toner carrying roller 16 is determined. If it is 10% or more, it is evaluated as “large” because the amount of the weakly charged toner is large, and if it is 2% or less, it is evaluated as “small” because the amount of the weakly charged toner is small. In some cases, the amount of weakly charged toner was evaluated as “minimum” because the amount of toner was extremely small. The charge amount of the normally charged toner in the developing device is −25 [μC / g] or more and −30 [μC / g] or less.

The results of this evaluation test are as shown in Table 1 below.

Common parameters for this evaluation test are as follows.
Photoconductor drum linear velocity: 150 [mm / sec]
Toner carrying roller linear speed / photosensitive drum linear speed: 1.5
Toner carrying roller linear speed / toner supply roller linear speed: 1.5
Supply gap (in the case of non-contact): 0.3 [mm]
Development gap: 0.3 [mm]
Amount of toner per unit area conveyed to the development area: 30 [mg / cm ² ]
Diameter of toner supply roller and toner carrying roller: φ16 [mm]
Non-image area potential (charging potential): -700 [V]
Exposure part potential VL: -100 [V]
Center value of voltage applied to toner carrying roller VB1: -400 [V]
Peak-to-peak voltage VPP applied to the toner carrying roller: 500 [V]
Frequency of voltage applied to toner carrying roller: 700 [Hz]
DC voltage VB2 applied to the toner supply roller: -700 [V]

The developing device used in Example 1 of this evaluation test is the developing device of the above embodiment, and the urging force of the regulating blade 63 against the toner supply roller 61 is 15 [N].
The developing device used in Example 2 of this evaluation test is the developing device of the above modification, and the linear velocity of the regulating roller 80 / linear velocity (linear velocity ratio) of the toner supply roller 61 is 1.5.
The developing device used in Comparative Example 1 of this evaluation test is shown in FIG. 8, and the toner supply roller 61 is excluded from the developing device in Example 1 described above, and the toner supply to the toner carrying roller 16 is performed by the supply screw 62. It is the implemented configuration. Note that no voltage is applied to the supply screw 62.
The developing device used in Comparative Example 2 of this evaluation test is the same as the developing device in Example 1 described above. The supply gap with the roller 61 is narrowed.
The developing device used in Comparative Example 3 of this evaluation test is the same as the DC voltage VB2 applied to the toner supply roller 61 in the developing device of Example 1 described above, specifically, a voltage value outside the settable range described above. A voltage value equal to or higher than the central value VB1 of the voltage applied to the toner carrying roller 16 is used.

  As a result of this evaluation test, the toner supply roller 61 is opposed to the toner carrying roller 16 with a gap, and the voltage applied to the toner supply roller 61 is set within the settable range described above. It was confirmed that the amount of weakly charged toner carried on the carrying roller 16 is reduced and a high effect can be obtained with respect to the suppression of toner scattering.

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 carrying member such as a toner carrying roller 16 having at least two types of electrode members such as a first electrode 53 and a second electrode 54 to which different voltages are applied, and the at least two types of electrode members By applying different voltages to each other, a hopping electric field for hopping the toner is formed on the outer peripheral surface of the toner carrier, and the hopped toner faces the surface of the latent image carrier such as the photosensitive drum 1. In the developing device 5 for developing the latent image by feeding it to the developing area and attaching it to the latent image on the latent image carrier, the toner is supplied to the outer peripheral surface of the toner carrier or the toner carrier inside the developing device. The toner holding member that holds the toner on the surface thereof is opposed to the surface of the toner holding member via a gap (supply gap), and the outer peripheral surface of the toner carrier or the surface of the toner holding member A toner supply member such as a toner supply roller 61 for holding the toner to be supplied to the surface, and a toner charged to a normal charge polarity among the toners held on the surface of the toner supply member through the gap Supply electric field forming means such as a toner supply power source 68 for forming a supply electric field in a supply region where the toner supply member and the toner carrier face each other so as to move to the outer peripheral surface of the toner supply surface or the surface of the toner holding member. It is characterized by having.
According to this, as described above, the amount of the weakly charged toner carried on the toner carrying member can be reduced, and a high effect can be obtained with respect to the suppression of toner scattering.

(Aspect B)
In the above aspect A, the supply electric field forming unit is configured such that, among the toners held on the surface of the toner supply member, a normally charged toner having a charge amount sufficient to hop under the action of the hopping electric field is The weakly charged toner, which is moved to the outer peripheral surface of the toner carrier through the gap but is insufficiently charged for hopping under the action of the hopping electric field, passes through the gap of the toner carrier. The supply electric field is formed so as to have an electric field strength that does not move to the outer peripheral surface.
According to this, as described above, the amount of the weakly charged toner carried on the toner carrier can be suppressed to a small level, and a high effect can be stably obtained with respect to suppression of toner scattering.

(Aspect C)
In the aspect A or B, the toner supply member is a rotating body such as a toner supply roller 61, and the toner held on the surface of the toner supply member is upstream of the supply region in the rotation direction of the toner supply member. It has a toner layer regulating member such as a regulating blade 63 and a regulating roller 80 arranged so as to be sandwiched between the surface of the toner supply member.
According to this, the toner held on the toner supply member is frictionally charged by being rubbed at the restriction position where the toner layer restriction member and the toner supply member face each other before being conveyed to the supply region. As a result, the charge amount increases. As a result, the amount of weakly charged toner contained in the toner held on the toner supply member and conveyed to the supply region can be reduced. Therefore, the effect of suppressing toner scattering by the weakly charged toner is further enhanced.

(Aspect D)
In the aspect C, the toner layer regulating member is a rotating body such as a regulating roller 80 that is rotationally driven so as to generate a speed difference with the surface moving speed of the toner supply member at a position facing the surface of the toner supply member. It is characterized by that.
According to this, frictional charging of the toner at the regulation position is promoted, and the amount of weakly charged toner contained in the toner held on the toner supply member and conveyed to the supply region can be effectively reduced. The effect of suppressing toner scattering by charged toner is high.

(Aspect E)
In the image forming apparatus for developing the latent image by attaching toner to the latent image of the latent image carrier, and finally transferring the resulting toner image to a recording material to form an image, the latent image The developing device according to any one of the above aspects A to D is used as a means for developing the latent image on the carrier.
According to this, since the toner scattering suppression effect is high, contamination in the image forming apparatus due to toner scattering can be suppressed, and ground contamination due to toner scattering can also be suppressed.

(Aspect F)
The latent image carrier and the developing device that develops the latent image formed on the latent image carrier with toner are held as a single unit on a common holder and integrated with the image forming apparatus main body. In the detachable process unit, the developing device according to any one of the above aspects A to D is used as means for developing the latent image on the latent image carrier.
According to this, since the toner scattering suppression effect is high, contamination in the image forming apparatus due to toner scattering can be suppressed, and ground contamination due to toner scattering can also be suppressed.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 5 Developing apparatus 16 Toner carrying roller 53 1st electrode 54 2nd electrode 55 Insulating layer 56 Surface layer 61 Toner supply roller 62 Supply screw 63 Control blade 65 Conveying screw 66 Toner accommodating part 68 Toner supply power supply 80 Control roller

JP 2011-154098 A JP 2010-191208 A

Claims (6)

A toner carrier having at least two types of electrode members to which different voltages are applied, and a hopping electric field for hopping the toner by applying different voltages to the at least two types of electrode members. The latent image is formed on the outer peripheral surface of the toner carrying member by sending the hopped toner to a developing area facing the surface of the latent image carrying member and attaching the toner to the latent image on the latent image carrying member. In the developing device for developing,
Inside the developing device, the outer peripheral surface of the toner carrier is disposed opposite to the outer peripheral surface of the toner carrier or the surface of the toner holding member that holds the toner supplied to the toner carrier on the surface, and the outer peripheral surface of the toner carrier. Or a toner supply member that holds the toner supplied to the surface of the toner holding member on the surface;
Of the toner held on the surface of the toner supply member, the toner supply member is arranged so that the toner charged with a normal charge polarity moves to the outer peripheral surface of the toner carrier or the surface of the toner holding member through the gap. And a supply electric field forming means for forming a supply electric field in a supply region where the toner carrier and the toner carrier face each other. The developing device according to claim 1.
The supply electric field forming means is configured such that, among the toners held on the surface of the toner supply member, a normally charged toner having a sufficient charge amount for hopping under the action of the hopping electric field passes through the gap. Although the toner is moved to the outer peripheral surface of the toner carrier, weakly charged toner that is insufficiently charged to hop under the action of the hopping electric field is not moved to the outer peripheral surface of the toner carrier through the gap. A developing apparatus, wherein the supply electric field is formed so as to have electric field strength. The developing device according to claim 1 or 2,
The toner supply member is a rotating body,
A toner layer regulating member arranged to sandwich the toner held on the surface of the toner supply member with the surface of the toner supply member upstream of the supply region in the rotation direction of the toner supply member; A developing device. The developing device according to claim 3.
The developing device according to claim 1, wherein the toner layer regulating member is a rotating body that is rotationally driven so as to generate a speed difference with a surface moving speed of the toner supply member at a position facing the surface of the toner supply member. In the image forming apparatus for developing the latent image by attaching toner to the latent image on the latent image carrier, and finally transferring the resulting toner image to a recording material to form an image.
An image forming apparatus using the developing device according to claim 1 as a means for developing a latent image on the latent image carrier. The latent image carrier and the developing device that develops the latent image formed on the latent image carrier with toner are held as a single unit on a common holder and integrated with the image forming apparatus main body. In process units configured to be detachable,
A process unit using the developing device according to claim 1 as the developing device.

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