JP2013254036A - Development device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device that enables a stable image formation with stable supply of developer from a developer supply member to a developer carrier.SOLUTION: The present invention relates to an image formation device forming an image on a medium by use of a development device. The development device comprises: a developer carrier that carries developer on its surface, adheres the carried developer to an electrostatic latent image carrier and develops the electrostatic latent image; a developer supply member that adheres the developer to the surface and supplies the developer adhered on the surface to the developer carrier; and a charging member that is for charging the developer supply member and has a plurality of electrodes facing the developer supply member provided at equal intervals. An electrode distance from a tip of each electrode composing the charging member to a surface of the developer supply member is configured to be equal to or more than an electrode interval among respective electrodes composing the charging member.

Description

    The present invention relates to a developing device and an image forming apparatus, and can be applied to, for example, an image forming apparatus such as a copying machine, a printer, and a fax machine using an electrophotographic system.

    In an electrophotographic printer, an image is formed by each process of charging, exposure, development, transfer, fixing, and cleaning.

  Among these, in the development process, a developing roller as a developer carrying member is brought into contact with the photosensitive drum, and a voltage is applied to the developing roller to convert the electrostatic latent image on the photosensitive drum into toner (for example, developer). A contact-type developing device (a developing device in which a photosensitive drum and a developing roller are in contact with each other) that develops with non-magnetic one-component toner) is often used because of the advantages of downsizing and cost reduction.

  In such a conventional developing device, a supply roller as a developer supply member is generally pressed against the development roller. For example, in order to increase the roller rotation speed, the roller is driven. It is important to reduce the torque and suppress the generation of heat. As a method for reducing the driving torque, there is a technique described in Patent Document 1. Patent Document 1 describes a developing device in which a developing roller and a supply roller having an uneven surface are arranged in a non-contact manner.

JP-A-2-101485

  However, in the developing device described in Patent Document 1, since the supply roller does not press the developing roller and the toner is not frictionally charged, it is precharged when high density printing is continuously performed. There is a problem in that the toner cannot be sufficiently supplied to the developing roller, resulting in a decrease in printing density and printing blurring.

  Therefore, there is a demand for a developing device and an image forming apparatus that can stably supply the developer from the developer supplying member to the developer carrying member and perform stable image formation.

  The developing device according to the first aspect of the present invention is (1) carrying a developer on the surface and attaching the carried developer to an electrostatic latent image carrier that carries an electrostatic latent image to form the electrostatic latent image. A developer carrying member to be developed; (2) a developer supplying member for attaching the developer to the surface and supplying the developer attached to the surface to the developer carrying member; and (3) the developer supplying member. A charging member having a plurality of electrodes opposed to the developer supply member formed at equal intervals, and (4) supplying the developer from the tip of each electrode constituting the charging member. The electrode distance to the surface of the member is greater than or equal to the electrode spacing between the electrodes constituting the charging member.

  The second aspect of the present invention is an image forming apparatus for forming an image on a medium using a developing device. (1) The developing device (1-1) carries a developer on the surface and carries an electrostatic latent image. A developer carrying member that develops the electrostatic latent image by attaching the carried developer to the electrostatic latent image carrier, and (1-2) development that adheres the developer to the surface and adheres to the surface. A developer supplying member for supplying the developer to the developer carrying member; and (1-3) charging the developer supplying member, wherein a plurality of electrodes facing the developer supplying member are formed at equal intervals. (1-4) The electrode distance from the tip of each electrode constituting the charging member to the surface of the developer supply member is between the electrodes constituting the charging member. It is characterized by being more than the electrode interval.

  According to the present invention, it is possible to provide an image forming apparatus capable of stably supplying a developer from a developer supply member to a developer carrying member and performing stable image formation.

1 is a schematic cross-sectional view of a developing device according to a first embodiment. It is a top view which expands and shows a part of sawtooth electrode which concerns on 1st Embodiment. 1 is a schematic sectional view of an image forming apparatus according to a first embodiment. It is explanatory drawing explaining the combination of the parameter regarding the shape of the electrode which comprises the sawtooth electrode which concerns on 1st Embodiment, and the evaluation result for every combination. It is a graph which shows distribution of the electric field strength which generate | occur | produces between a sawtooth electrode and a developer supply roller when the electrode width w of the sawtooth electrode which concerns on 1st Embodiment is changed. It is a graph which shows the experimental result regarding the printing quality at the time of printing by changing the electrode width w of the sawtooth electrode which concerns on 1st Embodiment. It is the graph which showed the setting possible range of angle theta of the electrode tip of the sawtooth electrode concerning a 1st embodiment. It is the graph 1 (angle (theta) = 10 degrees) which showed the electric field strength for every distance from an electrode at the time of changing the length l of the sawtooth electrode of 1st Embodiment. It is the graph 2 (angle (theta) = 5 degrees) which showed the electric field strength for every distance from an electrode at the time of changing the length l of the sawtooth electrode of 1st Embodiment. It is the graph 3 (angle (theta) = 15 degrees) which showed the electric field strength for every distance from an electrode at the time of changing the length l of the sawtooth electrode of 1st Embodiment. It is a graph which shows the result of having conducted the experiment regarding the print quality at the time of printing by changing the shape of the sawtooth electrode concerning a 1st embodiment. 6 is a graph (part 1) showing a distribution of electric field strength generated between the sawtooth electrode and the developer supply roller when the distance between the sawtooth electrode and the developer supply roller is changed according to the first embodiment. 6 is a graph (part 2) showing a distribution of electric field strength generated between the sawtooth electrode and the developer supply roller when the distance between the sawtooth electrode and the developer supply roller is changed according to the first embodiment. It is explanatory drawing shown about the conditions in the case of changing the distance of the sawtooth electrode which concerns on 1st Embodiment, and a developer supply roller. It is a graph which shows the result of having conducted the experiment regarding the printing quality at the time of printing by changing the distance d between the sawtooth electrode and developer supply roller concerning a 1st embodiment. It is a schematic sectional drawing of the image development apparatus concerning 2nd Embodiment. It is explanatory drawing shown about the waveform of the voltage output from the impulse power supply which concerns on 2nd Embodiment. It is a graph which shows the result of having conducted the experiment regarding the print quality at the time of printing by changing the amplitude of the impulse voltage applied to the sawtooth electrode concerning a 2nd embodiment. It is a graph which shows the result of having conducted the experiment regarding the printing quality at the time of printing by changing the amplitude of the impulse voltage to apply with the developing device concerning a 3rd embodiment.

(A) First Embodiment Hereinafter, a first embodiment of a developing device and an image forming apparatus according to the present invention will be described in detail with reference to the drawings.

(A-1) Configuration of the First Embodiment FIG. 3 is a schematic cross-sectional view of the image forming apparatus 1 of the first embodiment.

  As shown in FIG. 3, the image forming apparatus 1 includes an image forming unit 40, a fixing device 9 (a heating roller 10, a heater 11, a pressure roller 12, and a thermistor 13), a drive roller 18a, a drive roller 18b, and a recording sheet. Travel guides 19a and 19b, a waste developer tank 21, a recording paper cassette 22, and a paper discharge tray 23 are arranged. The image forming unit 40 includes four image forming units 100 (100K, 100C, 100Y, and 100M), four LED heads 103 (103K, 103C, 103Y, and 103M), a transfer belt 16, transfer rollers 17a to 17d, and A transfer belt cleaning blade 20 is provided.

  The recording paper cassette 22 stores recording paper P as a medium on which the image forming apparatus 1 forms an image.

  The recording paper transport rollers 15a to 15v and the recording paper travel guides 19a and 19b feed recording paper P stored in the recording paper cassette 22 one by one and transport the recording paper P in the image forming apparatus 1. It constitutes.

  The four image forming units 100K, 100C, 100Y, and 100M develop print images using toner T (TK, TC, TY, TM) as developers of different colors. The four LED heads 103K, 103C, 103Y, and 103M are based on image signals supplied from control units (not shown) to the photosensitive drums (described later) of the corresponding image forming units 100K, 100C, 100Y, and 100M, respectively. It functions as a photosensitive means (exposure member) for irradiating light, and is disposed to face the photosensitive drum. In the image forming apparatus 1, another type of apparatus such as a laser may be applied as the photosensitive means (exposure member) instead of the LED head 103.

  In the present specification, “black” is also represented as “K”, “cyan” as “C”, “yellow” as “Y”, and “magenta” as “M”. For example, the image forming unit 100K performs development using a black toner color toner TK, and the image forming unit 100C performs development using a cyan toner color toner TC.

  The toner T (TK, TC, TY, TM) used in the first embodiment all uses a polyester resin as a binder resin, and a charge control agent, a release agent, a colorant, and an external additive as an internal additive. It is assumed that the resin particles have an average particle diameter of 5.8 (μm) obtained by the pulverization method.

  The transfer belt 16, the transfer rollers 17a to 17d, and the drive rollers 18a and 18b constitute transfer means for transferring the toner images developed by the image forming units 100K, 6C, 6Y, and 6M to the recording paper P. .

  The transfer belt cleaning blade 20 removes the toner T adhering to the transfer belt 16. The waste developer tank 21 is a storage for storing the toner T (waste developer) removed by the transfer belt cleaning blade 20.

  The fixing device 9 fixes the toner image transferred to the recording paper P by heat and pressure, and includes a heat roller 10, a heater 11, a pressure roller 12, and a thermistor 13.

  The heating roller 10 is a roller for heating the recording paper P. For example, a heat resistant elastic layer of silicone rubber is coated on a hollow cylindrical cored bar made of aluminum, and further, PFA (tetrafluoroethylene-par Fluoroalkyl vinyl ether copolymer) formed by coating the tube. A heater 11 is disposed inside the heat roller 10, and the heat roller 10 is overheated by the heater 11. For example, a heating member such as a halogen lamp can be applied to the heater 11.

  Further, a thermistor 13 as a temperature detecting means is disposed in the vicinity of the heat generating roller 10, and the heater 11 is controlled with an output corresponding to the temperature measured by the thermistor 13 by a control unit (not shown).

  When the recording paper P is nipped and conveyed between the pressure roller 12 and the heat generating roller 10, the pressure roller 12 presses the recording paper P toward the heat generating roller 10 at a pressure contact portion formed between the pressure roller 12 and the pressure roller 12. Is added. The pressure roller 12 can be configured, for example, by coating an aluminum cored bar with a heat-resistant elastic layer of silicone rubber and further covering a PFA tube thereon.

  The fixing device 9 of the first embodiment employs a roller system as shown in FIG. 3, but a belt system using a belt, a film system using a film, a flash system using light emission energy, and the like. May be applied. In the roller type or belt type fixing device, oil is supplied to the heating roller, belt toner, etc. by an oil supply fixing system equipped with an oil supply mechanism such as an oil supply roller, an oil supply sheet, and an oil tank. You may make it prevent offset reduction generate | occur | producing. The oil described above does not need to be a specific material, but it is generally desirable to use a silicone oil, mineral oil or the like having a relatively low viscosity. Further, in the roller type or belt type fixing device, it is possible to prevent the hot offset phenomenon from occurring by the oilless fixing method without replenishing the above-described oil.

  Next, the internal configuration of each image forming unit 100 (100K, 100C, 100Y, 100M) will be described. Each image forming unit 100 is different only in the color of the toner T used for development, and the other configurations are the same. Therefore, only the image forming unit 100K will be described below.

  FIG. 1 is a schematic cross-sectional view of the image forming unit 100K.

  As shown in FIG. 1, the image forming unit 100K is provided with a developing device 50, a photosensitive drum 101, a charging roller 102, and a cleaning blade 108. The developing device 50 includes a developing roller 104, a developer supply roller 105, a toner storage unit 106, a layer forming blade 107, and a sawtooth electrode 109. Note that the DC power sources 24, 25, 26, 27, 28, and 29 shown in FIG. 1 are disposed in the image forming unit 40 and apply a voltage to a predetermined portion of each image forming unit 100. . Details of each DC power supply will be described later.

  The photosensitive drum 101 functions as an electrostatic latent image carrier. For example, as shown in FIG. 1, the photosensitive drum 101 is configured by forming a photoconductive layer 101b on the surface of a conductive support 101a. May be. For example, an aluminum metal pipe can be applied as the conductive support 101a. As the photoconductive layer 101b, for example, an organic photoreceptor in which a charge generation layer and a charge transport layer are sequentially stacked can be applied. The photosensitive drum 101 is connected to a drive source (motor) (not shown) through a gear (not shown).

  The charging roller 102 functions as a charging member for charging the surface of the photosensitive drum 101. For example, as shown in FIG. 1, a semiconductive layer 102b is formed on the surface of the conductive support 102a. You may comprise by forming. For example, a metal shaft such as aluminum can be used as the conductive support 102a. As the semiconductive layer 102b, for example, semiconductive ebichlorohydrin rubber can be applied.

  The toner storage unit 106 stores (stores) the toner TK.

  The developer supply roller 105 functions as a developer supply member that attaches the toner TK stored in the toner storage unit 106 to the surface and supplies the attached toner TK to the development roller 104. As the material of the developer supply roller 105, for example, a metal such as aluminum or iron can be used. Note that a foamed elastic layer (for example, a urethane sponge layer) may be provided on the surface of the developer supply roller 105.

  The developing roller 104 functions as a developer carrying member for carrying the toner TK supplied from the developer supply roller 105 on its surface. For example, as shown in FIG. 1, the developing roller 104 is formed on the surface of the conductive support 104a. Alternatively, the semiconductive layer 4b may be formed. For example, a metal shaft such as aluminum can be used as the conductive support 104a. As the semiconductive layer 104b, for example, semiconductive urethane rubber can be applied. The developing roller 104 is connected to a driving source (motor) (not shown) through a gear (not shown).

  The layer forming blade 107 functions as a thin layer forming member that forms (thinns) the toner TK on the developing roller 104 into a thin layer having a uniform thickness. For the layer forming blade 107, for example, a metal such as iron or aluminum can be used.

  The cleaning blade 108 functions as a developer collecting member for removing and collecting the toner TK remaining after the transfer of the toner image onto the recording paper P by the photosensitive drum 101 from the photosensitive drum 101. As the cleaning blade 108, for example, a foamed elastic body such as urethane rubber can be used.

  The sawtooth electrode 109 functions as a charging member (charging auxiliary member) that assists the charging of the developer supply roller 105 in order to promote the movement of the toner TK from the developer supply roller 105 to the developing roller 104. In the first embodiment, a corona charger using a sawtooth electrode 109 is applied as the charging member (charging auxiliary member). In the first embodiment, the sawtooth electrode 109 is used as the charging member (charging auxiliary member). However, other corona charging electrodes (for example, corotron, scorotron, etc.) may be applied. .

  For example, as shown in FIG. 1, the transfer roller 17 a may be configured by forming a foamed elastic layer 17 a 2 on the surface of the conductive support 17 a 1. As the conductive support 17a1, for example, a metal shaft such as aluminum can be applied. As the foamed elastic layer 17a2, for example, urethane sponge can be applied. The other transfer rollers 17b to 17d have the same structure and will not be described.

  The DC power supply 24 is a DC power supply that applies a DC voltage to the charging roller 102. The DC power supply 25 is a DC power supply that applies a DC voltage to the transfer roller 17a. Further, the DC power source 26 is a DC power source that applies a DC voltage to the developing roller 104. Furthermore, the DC power source 27 is a DC power source that applies a DC voltage to the developer supply roller 105. The DC power supply 28 is a DC power supply that applies a DC voltage to the layer forming blade 107. Further, the DC power supply 29 is a DC power supply that applies a DC voltage to the sawtooth electrode 109.

  FIG. 2 is a schematic configuration diagram of the sawtooth electrode 109 used in the present invention.

  2 is an enlarged plan view showing a part of the sawtooth electrode 109 (a plan view showing an enlarged part when viewed from the direction of the arrow X in FIG. 1).

  As shown in FIGS. 1 and 2, the sawtooth electrode 109 is a plate-like electrode that is disposed so that one end thereof faces the outer peripheral surface of the developer supply roller 105, and is opposed to the outer peripheral surface of the developer supply roller 105. The same triangular tooth-shaped electrode 109a is formed at a uniform density (equal interval) at the end portion. In the sawtooth electrode 109, electrons based on the DC voltage supplied from the DC power supply 29 are emitted from the tip of each electrode 109 a (corona discharge), and the developer supply roller disposed at a position facing the tip of the sawtooth electrode 109. 105 will be charged.

  The sawtooth electrode 109 of the first embodiment uses a thin plate made of stainless steel having a thickness of 200 (μm). In the first embodiment, it is assumed that the longitudinal dimension of the sawtooth electrode 109 is the same as the width of the opposing developer supply roller 105. The longitudinal dimension of the sawtooth electrode 109 may be made wider than the width of the opposing developer supply roller 105. In the following, the length of the electrode 109a (triangular tooth) of the sawtooth electrode 109 (the dimension of the electrode 109a in the short direction of the sawtooth electrode 109) is “length l”, and the distance between the electrodes 109a (longitudinal length of the sawtooth electrode 109). The distance between the tip portions of the electrodes 109a in the direction) is “electrode width w”, the angle formed by the tip portions of the electrodes 109a is “angle θ”, and the distance from the tip of each electrode 109a to the developer supply roller 105 is “d”. Shall be called. In the first embodiment, it is assumed that the length l, the tip angle θ, and the distance d described above are the same in all the electrodes 109a constituting the sawtooth electrode 109. In the first embodiment, the intervals between adjacent electrodes 109a in the sawtooth electrode 109 are all w.

(A-2) Operation of the First Embodiment Next, the operation of the image forming apparatus 1 of the first embodiment having the above configuration will be described.

  First, the operation of the entire image forming apparatus 1 will be described with reference to FIG.

  The recording paper transport rollers 15a and 15b are rotated by driving means (not shown), whereby the recording paper P in the recording paper cassette 22 is selectively fed out. The fed recording paper P is transported onto the transfer belt 16 by the recording paper transport rollers 15c to 15f. The transfer belt 16 rotates in the direction of arrow f (or arrow r) in FIG. 2 as the drive rollers 18 a and 18 b rotate, and the recording paper P conveyed on the transfer belt 16 rotates the transfer belt 16. As a result, it moves in the same direction. Then, a toner image is transferred onto the recording paper P moving on the transfer belt 16 by the image forming units 100K, 100C, 100Y, and 100M and the transfer rollers 17a to 17d. Then, the toner of the toner image transferred to the recording paper P is fixed by the fixing device 9 disposed at the subsequent stage of the transfer belt 16. When the toner image is transferred and fixed by all the image forming units 100, the recording paper P is moved to the paper discharge tray 23 by the operations of the recording paper travel guide 19a and the recording paper transport rollers 15g to 15j. It is conveyed (discharged).

  Note that the image forming apparatus 1 according to the first embodiment is configured to be able to print on both sides of the recording paper P. When printing on both sides of the recording paper P, one of the recording papers P is used. After the toner image is transferred and fixed on the surface of the recording paper P, the recording paper P is turned over by the operation of the recording paper transport rollers 15k to 15v and 15c to 15f and the recording paper travel guides 19a and 19b (printing is performed). With the other side not facing up, the sheet is fed again onto the transfer belt 16.

  Next, the operation of each image forming unit 100 (100K, 100C, 100Y, 100M) will be described. Each image forming unit 100 is different only in the color of the toner T used for development, and the other configurations are the same. Therefore, only the image forming unit 100K will be described below.

  In the image forming unit 100K, the photosensitive drum 101 is rotated in the direction of arrow a via a driving gear (not shown). The charging roller 102 that comes into contact with the photosensitive drum 101 rotates in the direction of the arrow d by the frictional force with the photosensitive drum 101. A DC voltage is applied to the charging roller 102 by a DC power supply 24. Therefore, the charging roller 102 contacts the photoconductive drum 101 to charge the photoconductive drum 101.

  The LED head 103 irradiates the charged photosensitive drum 101 with light based on an image signal supplied from a control unit (not shown) to form an electrostatic latent image based on the image signal on the surface of the photosensitive drum 101. To do.

  On the other hand, the developer supply roller 105 rotates in the direction of arrow c via a driving gear (not shown). Further, a DC voltage is applied to the developer supply roller 105 by the power source 27, and further, auxiliary charging is performed by the sawtooth electrode 109. The developer supply roller 105 charged by the power source 27 and the sawtooth electrode 109 adheres the toner TK stored in the toner storage unit 106. When the developer supply roller 105 rotates in the direction of arrow c with the toner TK attached to the surface, the attached toner TK is supplied to the developing roller 104.

  The developing roller 104 rotates in the direction of arrow b via a driving gear (not shown) while being in contact with the photosensitive drum 101, and receives the supply of toner TK from the developer supply roller 105. When the toner TK supplied onto the surface of the developing roller 104 passes through the layer forming blade 107, the thickness of the layer is regulated and the toner TK is thinned. The developing roller 104 develops the toner image by attaching the supplied toner TK to the electrostatic latent image on the photosensitive drum 101.

  A DC voltage is applied to the transfer roller 17a disposed opposite to the photosensitive drum 101 of the image forming unit 100K by a DC power source 25. Then, the toner TK is transferred to the recording paper P by the potential difference between the transfer roller 17a and the electrostatic latent image on the photosensitive drum 101. On the other hand, the toner TK on the photosensitive drum 101 that has not been transferred to the recording paper P is removed from the photosensitive drum 101 by the cleaning blade 108.

  Next, the influence of the shape of the electrode 109a constituting the sawtooth electrode 109 (hereinafter also referred to as “shape S”) and the positional relationship with the developer supply roller 105 on the charging function of the sawtooth electrode 109 will be described.

  FIG. 4 is a list of the shapes S of the electrodes 109a used in the evaluation experiment described below and the evaluation results. As shown in FIG. 4, the shape S (S1-1 to S1-4, S2-0 to S2-5, S3-0 to S3-5, S4-0 to S4-5, S5-0 to S5-5, The combinations of parameters (electrode width w, length l, and angle θ) are different for each of S6-0 to S6-3).

  Each shape S shown in FIG. 4 is obtained by changing the electrode width in the range of 0.5 to 2.0 mm, the length l in the range of 0.3 mm to 3.5 mm, and the angle θ in the range of 5 ° to 20 °. It shows about the result of the evaluation experiment.

  Specifically, in the shapes S1-1 to S1-4, the angle θ of the tip of the electrode 109a is fixed to 10 °, the length l is fixed to 1.0 (mm), and the electrode width w is set to 0.5 mm to 2 mm. It is changed in the range of 0.0 mm. Further, in the shape S2-0 to the shape S2-5, the angle θ of the tip of the electrode 109a is fixed to 10 °, the electrode width w is fixed to 1.0 mm, and the length l changes in the range of 0.3 mm to 3.5 mm. I am letting. Furthermore, in the shape S3-0 to the shape S3-5, the angle θ of the tip of the electrode 109a is fixed to 5 °, the electrode width w is fixed to 1.0 mm, and the length l is changed in the range of 0.3 mm to 3.5 mm. I am letting. Furthermore, in the shape S4-0 to the shape S4-5, the angle θ of the tip of the electrode 109a is fixed to 15 °, the electrode width w is fixed to 1.0 mm, and the length l is in the range of 0.3 mm to 3.5 mm. It is changing. In the shape S5-0 to the shape S5-5, the angle θ of the tip of the electrode 109a is fixed to 3 °, the electrode width w is fixed to 1.0 mm, and the length l is changed in the range of 0.3 mm to 3.5 mm. I am letting. Further, in the shape S6-0 to the shape S6-3, the angle θ of the tip of the electrode 109a is fixed to 20 °, the electrode width w is fixed to 1.0 mm, and the length l changes in the range of 0.3 mm to 2.5 mm. I am letting.

  In the sawtooth electrode 109, the relationship between the angle θ, the length l, and the electrode width w of the tip of the electrode 109a needs to satisfy the following expression (1). This is because, when the following formula (1) is not satisfied, in the sawtooth electrode 109, the adjacent electrodes 109a interfere with each other in shape and do not form the sawtooth electrode. Note that all the shapes S (shape S1-1 to shape 6-3) shown in FIG. 4 described above satisfy the relationship of the following expression (1).

tan (θ / 2) ≦ w / 2l (1)
For example, when w = d = 1.0 mm in the above equation (1), the angle θ needs to satisfy the following equation (2).

θ ≦ 2 tan ⁻¹ (1 / 2l) (2)
The graph of FIG. 7 illustrates a curve of θ = 2 tan ⁻¹ (1 / 2l). In the graph of FIG. 7, the horizontal axis is length l and the vertical axis is θ. In FIG. 7, for example, the setting of the shape S6-3 (length l = 2.0 mm, angle θ = 20 °) satisfies the relationship of the above expression (2), but the setting of the shape S6-3 (angle θ = 20 °), when the length l is changed to 3 mm or more, the relationship of the above expression (2) is not satisfied.

  Next, the influence of the electrode width w of the electrode 109a on the performance of the auxiliary charging function will be described.

  FIG. 5 shows a straight line that passes through the bottom of the electrode 109a (the straight line Y in FIG. 2) with a width including the arbitrary three electrodes 109a (the width in the longitudinal direction of the sawtooth electrode 109) for each of the shapes S1-1 to S1-4. ) To the electric field strength (electric field strength) of each region on the plane passing through the straight line on the surface of the developer supply roller 105 (straight line parallel to the straight line Y). In FIG. 5, the lower end corresponds to a straight line portion on the surface of the developer supply roller 105, and the upper end corresponds to a straight line Y portion. FIG. 5 shows the result of numerical analysis (simulation) on the electric field strength from the tip of the electrode 109a toward the developer supply roller 105. In FIG. 5, the intensity of the electric field strength described above is indicated by the shading of the color of the area (spot density), and the darker the density (the higher the density of the stippling), the lower the electric field intensity. ing. In other words, FIG. 5 shows that the lower the density (the lower the density of stippling), the higher the electric field intensity.

  Fig.5 (a)-FIG.5 (d) have each shown distribution of the electric field strength generate | occur | produced when shape S1-1-S1-4 are used.

  In FIG. 5, it is assumed that a DC voltage of −2250 V is applied from the DC power supply 29 to the sawtooth electrode 109 in all shapes S. In addition, a DC voltage of −1000 V is applied to the developer supply roller 105 from the DC power supply 27. That is, in this case, the potential difference generated between the sawtooth electrode 109 and the developer supply roller 105 is −1250V.

  As shown in FIG. 5, while the electrode width w of the electrode 109a is less than or equal to the distance d (that is, the shape S1-1 and the shape S1-2), the surface of the developer supply roller 105 that is the counter electrode of the sawtooth electrode 109 is In other words, the electric field strength at (the lower end portion of each graph in FIG. 5) becomes substantially uniform. However, when the distance d is shorter than the electrode width w of the electrode 109a (shape S1-3, shape S1-4), in the longitudinal direction on the surface of the developer supply roller 105 (lateral direction of the graph of FIG. 5). On the other hand, it can be seen that the electric field strength is uneven.

  Next, an experiment relating to print quality when printing is performed by changing the shape of the electrode 109a of the sawtooth electrode 109 to the shape S1-1 to the shape S1-4 (the electrode width w is changed between 0.5 mm and 2 mm). The result of having performed is demonstrated using FIG.

  In the experiment shown in FIG. 6, the printing speed (= rotational speed of the photosensitive drum 101 = paper passing speed) is set to 0.20 (m / s), and A4 standard paper (for example, OKI excellent white paper, basis weight = 80 (g / m2)) 3 sheets were printed in a longitudinal direction continuously (a direction in which two short sides out of the four sides become the leading and trailing edges) and a 100% duty image was printed (hereinafter referred to as “through”). Called “paper test”). The “100% duty image” described above is an image in which 100% density pixels are arranged on the entire printable range of one recording sheet (A4 sheet) to be printed. Then, as an evaluation method of the print quality for each shape of the electrode 109a, the density at the 10 lower ends in the longitudinal direction of the printable range of the printing paper printed last in the paper passing test is measured, and the measured density The difference between the maximum value and the minimum value (hereinafter referred to as “density difference”) was confirmed.

  The print density of the printing surface subjected to the paper passing test was measured using a spectral densitometer “X-Rite 528” (manufactured by X-Rite, C light source, viewing angle 2 ° C., response E mode). Normally, when the above-described paper passing test is performed on an image forming apparatus, if a density difference of 0.3 or more occurs on the same printing surface, the image forming apparatus cannot withstand practical use because the image quality deteriorates. Means that.

  FIG. 4 shows the print quality evaluation results for each shape S based on the graph of FIG. In FIG. 4, “good” is displayed when the density difference is less than 0.15, “good” is displayed when the density difference is 0.15 or more and less than 0.3, and “impossible” is displayed when the density difference is 0.3 or more. doing. When the evaluation result is “impossible”, it indicates that the print quality is unpractical due to deterioration of image quality.

  In the experimental results shown in FIG. 6, as the electrode width w increases, the density difference increases (that is, the printing density unevenness increases, similarly to the occurrence of the electric field intensity unevenness shown in FIG. 5 described above. There was a tendency for print quality to deteriorate. Therefore, in order to maintain the printing quality of the image forming apparatus 1 to a level that can withstand practical use, for example, the relationship between the electrode width w and the distance d between the electrodes may be such that w <2d. Recognize.

  Next, the influence of the length l of the electrode 109a on the performance of the auxiliary charging function will be described.

  FIG. 8 shows the shape of the electrode 109a of the sawtooth electrode 109 from the electrode 109a when the shape is changed to the shape S2-1 to the shape S2-4 (the length l is changed between 0.5 mm to 3.5 mm). It is the graph which showed the electric field strength (result of numerical analysis) for every distance. The graph of FIG. 8 shows the result of a numerical analysis assuming that a DC voltage of −2250 V is applied to the sawtooth electrode 109 and a DC voltage of −1000 V is applied to the developer supply roller 105.

  FIG. 9 shows the electrode 109a when the shape of the electrode 109a of the sawtooth electrode 109 is changed to the shape S3-1 to the shape S3-4 (the length l is changed between 0.5 mm to 3.5 mm). It is the graph which showed the electric field strength for every distance from. Further, FIG. 10 shows the electrode 109a when the shape of the electrode 109a of the sawtooth electrode 109 is changed to the shape S4-1 to the shape S4-4 (the length l is changed between 0.5 mm and 3.5 mm). It is the graph which showed the electric field strength for every distance from. In the graphs of FIGS. 9 and 10, the conditions other than the shape of the electrode 109a are the same as those in FIG.

  As shown in FIGS. 8 to 10 described above, regardless of the electrode width w and the angle θ, the longer the length l of the electrode 109a tends to increase the electric field strength near the tip of the electrode 109a. Recognize.

  Next, the influence of the length l and the angle θ of the electrode 109a on the performance of the auxiliary charging function will be described.

  11 shows the shape S of the electrode 109a of the sawtooth electrode 109 (S1-1 to S1-4, S2-0 to S2-5, S3-0 to S3-5, S4-0 to S4-5, S5-0. For each of S5-5 and S6-0 to S6-3), the result of measuring the density difference when the paper passing test similar to that of FIG. 6 is performed is shown. In S1-1 to S6-3, since the electrode width w is common with 1.0, the only variable parameters are the length l and the angle θ. In FIG. 11, the horizontal axis represents the length l and the vertical axis represents the density difference.

  In FIG. 4 described above, the evaluation results of the print quality for each shape S are shown based on the graphs of FIGS. 6 and 11 described above. In FIG. 4, “good” is displayed when the density difference is less than 0.15, “good” is displayed when the density difference is 0.15 or more and less than 0.3, and “impossible” is displayed when the density difference is 0.3 or more. doing. When the evaluation result is “impossible”, it indicates that the print quality is unpractical due to deterioration of image quality.

  In the result of FIG. 11, the concentration difference increases as the length l of the electrode 109a is increased. In particular, as can be seen from the results of FIG. 11, when the length l exceeds 3.00 mm, depending on the angle θ, the density difference exceeds 0.15, and the evaluation result often becomes “OK”. Therefore, it can be seen that the upper limit of the length l of the electrode 109a is preferably about 3.00 mm. In addition, when the angle θ of the electrode 109a is 20 °, if the length l exceeds 3.00 mm, the above formulas (1) and (2) cannot be satisfied. In order to facilitate design and manufacture, the length l is preferably 3.00 mm or less.

  In the range of the experimental results shown in FIG. 11, the concentration difference tends to decrease as the length l of the electrode 109a is shortened. However, if the length l is less than 0.5 mm, the manufacturing cost increases, It becomes difficult to control the electric field intensity on the surface of the developer supply roller 105. For example, if the sawtooth electrode 109 is damaged (deformed or scratched) or dust adheres while the image forming unit 100K is in use, the damaged portion or attached portion is not the tip of the electrode 109a. May cause discharge. As described above, in the sawtooth electrode 109, the possibility of discharge from an unintended portion increases as the length of the electrode 109a decreases. In view of the above reasons, the length l of the electrode 109a is desirably 0.5 mm or more.

  As described above, in the image forming unit 100K, the length l of the electrode 109a is desirably set in the range of 0.5 mm to 3.0 mm.

  In the results of FIG. 11, the concentration difference tends to increase as the angle θ of the electrode 109a increases. In particular, as can be seen from the results of FIG. 11, when the angle θ exceeds 15 °, depending on the length l, the density difference exceeds 0.15 and the evaluation result often becomes “OK”. Therefore, it can be seen that the upper limit of the angle θ of the electrode 109a is preferably about 15 ° mm. In addition, when the angle θ of the electrode 109a is 20 °, if the length l exceeds 3.00 mm, the above formulas (1) and (2) cannot be satisfied. In order to facilitate design and manufacture, the angle θ is desirably 15 ° or less.

  In the range of the experimental results in FIG. 11, the concentration difference tends to decrease as the angle θ of the electrode 109a is decreased. However, in reality, when the angle θ is less than 5 °, the manufacturing cost increases and the durability increases. The electric field intensity on the surface of the developer supply roller 105 becomes difficult to control due to a decrease (becomes easy to deform). For example, when the sawtooth electrode 109 is replaced with a parallel plate electrode (a square plate without triangular teeth), discharge may occur depending on the state of the electrode surface (effect of scratches or deposits). The length up to the tip portion (the length corresponding to the length l of the sawtooth electrode 109) cannot be specified. In the image forming apparatus 1, in order to make the discharge position from the electrode toward the developer supply roller 105 constant, it is necessary to intentionally generate an unequal electric field. Therefore, the image forming apparatus 1 includes the sawtooth electrode 109 in which the triangular-tooth-shaped electrode 109a is formed, generates an unequal electric field, and makes the discharge position constant. In other words, the parallel plate electrode can be said to have a shape in which the angle θ of the tip of the electrode 109a in the sawtooth electrode 109 is 180 °. That is, as the angle θ of the tip of the electrode 109a is reduced, it becomes possible to create a biased unequal electric field in which the periphery of the tip of the electrode 109a has a strong electric field strength. However, if the angle θ of the electrode 109a is too small, the electric field strength around the tip of the electrode 109a becomes uneven, and conversely, it becomes difficult to uniformly control the electric field strength on the surface of the developer supply roller 105. In view of the above reasons, the angle θ of the electrode 109a is desirably 5 ° or more.

  As described above, in the image forming unit 100K, the angle θ of the electrode 109a is desirably set in the range of 5 ° to 15 °.

  Next, the influence of the distance d between the tip of the electrode 109a and the developer supply roller 105 on the performance of the auxiliary charging function of the sawtooth electrode 109 will be described.

  12 and 13 show the case where the distance d is changed (changed between 0.2 mm and 4.0 mm) according to each condition C (condition C1 to condition C9) shown in FIG. Similarly, the electric field strength (electric field strength) of each region on a plane passing from a straight line passing through the bottom of the electrode 109a (straight line Y in FIG. 2) to a straight line on the surface of the developer supply roller 105 (straight line parallel to the straight line Y). It shows about the result of numerical analysis. In all of the conditions C1 to C9, the interval w = 1.0 mm, the length l = 2.0 mm, and the angle θ = 10 °.

  When the electric field strength generated between the electrodes is E, the potential difference between the electrodes is V, and the distance between the electrodes is d, the relationship of E = V / d is generally satisfied. Therefore, in each condition C (conditions C1 to C9) shown in FIG. 14, even if the distance d changes, the average electric field strength generated on the surface of the developer supply roller 105 is approximately the same. The potential difference between the electrodes (potential difference between the tip of the electrode 109a and the developer supply roller 105) is also changed in accordance with the change. In any of the conditions C, the DC voltage applied to the developer supply roller 105 side is −1000V.

  12A to 12D show conditions C1 (d = 0.2 mm), C3 (d = 0.6 mm), C4 (d = 0.8 mm), C5 (d = 1. The distribution of the electric field intensity generated at 0 mm) is shown. FIGS. 13A to 13D show conditions C5 (d = 1.0 mm), C7 (d = 2.0 mm), C8 (d = 3.0 mm), C9 (d = 4. The distribution of the electric field intensity generated at 0 mm) is shown.

  Between conditions C1 to C4 (distance d is between 0.2 mm and 0.8 mm), distance d is less than electrode width w. As shown in FIG. 12, when the distance d is longer while the distance d is less than the electrode width w (between conditions C1 to C4), the electric field strength in the vicinity of the sawtooth electrode 109 is increased on the surface of the developer supply roller 105. The distribution gradually increases. That is, as shown in FIG. 12, when the distance d is less than the electrode width w (between conditions C1 to C4), the electric field strength on the surface of the developer supply roller 105 is uneven.

  As shown in FIG. 13, the electric field strength on the surface of the developer supply roller 105 is uniform (unevenness) between the conditions C5 to C9 (that is, when the distance d is greater than or equal to the electrode width w). No).

  Next, the results of experiments regarding print quality when printing is performed under the conditions C (conditions C1 to C8) illustrated in FIG. 14 will be described with reference to FIG. FIG. 15 shows a case where a paper passing test similar to that of FIG. 6 is performed under each condition C (condition C1 to condition C8, that is, when the distance d is changed between 0.2 mm and 3.00 mm). It shows about the result of having measured the density difference.

  As shown in FIG. 14, when the distance d is less than the electrode width w (less than 1.00 mm), the concentration difference decreases as the distance d increases, and the distance d becomes equal to or greater than the electrode width w (1.00 mm or more). The decrease in density difference stops and converges at a constant value (about 0.1). This tends to coincide with the occurrence of unevenness on the surface of the developer supply roller 105 in FIGS. That is, when the unevenness on the surface of the developer supply roller 105 is reduced, the print quality is improved (the density difference in the paper passing test is reduced).

  As described above, in the image forming apparatus 1, the design of the shape of the electrode 109a is facilitated if w ≦ d is satisfied.

(A-3) Effects of First Embodiment According to the first embodiment, the following effects can be achieved.

  In the image forming apparatus 1, by satisfying w ≦ d, the developer supply roller 105 can be stably charged by the sawtooth electrode 109. As a result, the image forming apparatus 1 can stably form a good print image free from blurring and unevenness, and the design and manufacture of the electrode 109a can be facilitated.

  Further, in the image forming apparatus 1, by setting the length l of the electrode 109a within the range of 0.5 mm to 3.0 mm, the design and manufacture of the electrode 109a can be facilitated and the durability can be enhanced. Furthermore, in the image forming apparatus 1, by setting the angle θ of the electrode 109a within the range of 5 ° to 15 °, the design and manufacture of the electrode 109a can be facilitated and the durability can be enhanced.

(B) Second Embodiment Next, an image forming unit and an image forming apparatus according to a second embodiment of the present invention will be described in detail with reference to the drawings.

  In the image forming apparatus 1 of the first embodiment, a DC power source is used as the power source 29 applied to the sawtooth electrode 109. However, in the image forming apparatus 1, when the potential difference generated between the sawtooth electrode 109 and the developer supply roller 105 becomes large, spark discharge may occur and the image may deteriorate.

  The sawtooth electrode 109 performs corona discharge from the tip of the triangular-tooth-shaped electrode 109a. This corona discharge forms a streamer that is in a discharged state. When the formed streamer reaches the opposing electrode (developer supply roller 105), spark discharge may occur. Thus, temporal changes occur in the process of forming a streamer in corona discharge and reaching the counter electrode.

  Therefore, in each image forming unit 100 (100K, 100C, 100Y, 100M) constituting the image forming apparatus 1 of the second embodiment, the voltage applied to the sawtooth electrode 109 is set as an impulse voltage to prevent the occurrence of spark discharge.

  FIG. 15 is a schematic cross-sectional view of an image forming unit 100K according to the second embodiment. Each image forming unit 100 is different only in the color of the toner T used for development, and the other configurations are the same. Therefore, only the image forming unit 100K will be described below.

  As shown in FIG. 15, the image forming unit 100 </ b> K according to the second embodiment is different in that the power source applied to the sawtooth electrode 109 is replaced from the DC power source 29 to the impulse power source 30.

  FIG. 17 is a timing chart showing the waveform of the impulse voltage output from the impulse power supply 30. As shown in FIG. 17, the impulse power supply 30 outputs an impulse voltage having an amplitude A and a period T (1 / f). As shown in FIG. 17, it is assumed that the minimum voltage of the impulse voltage output from the impulse power supply 30 is -A [V] and the maximum voltage is 0 [V].

  Next, the results of an evaluation experiment relating to print quality when printing is performed in the image forming unit 100K of the second embodiment will be described with reference to FIG. In the evaluation experiment of FIG. 18, in the first embodiment and the second embodiment, a density difference was measured when a paper passing test similar to that of FIG. 6 described above was performed for each voltage (DC voltage, amplitude A). The results are shown. The measurement results in FIG. 18 are obtained when the distance d = 1.0 mm, the interval w = 1.5 mm, the length l = 1.0 mm, and the angle θ = 10 °.

  In the evaluation experiment of the image forming unit 100K of the second embodiment shown in FIG. 18, the amplitude A is 0 to 4 kV with the frequency f (1 / T) of the waveform output from the impulse power supply 30 fixed at 1.0 kHz. The density difference of the paper passing test when changing between the two is shown. Further, in the evaluation experiment of the image forming unit 100K of the first embodiment shown in FIG. 18, the density difference of the paper passing test when the voltage of the DC voltage output from the DC power supply 29 is changed between 0 and −4 kV. Is shown. In practice, the amplitude A according to the second embodiment and the positive / negative of the DC voltage according to the first embodiment are opposite, but in the graph of FIG. 18, the same horizontal axis is used for ease of explanation. It is illustrated using.

  As shown in FIG. 18, in the image forming unit 100K of the first embodiment, there is no change in density difference (about 1.3) when the DC voltage is between 0 V and −1.5 kV, but the DC voltage is −2 kV. At the following times, the density difference suddenly decreases (about 0.2). This is because in the image forming unit 100K of the first embodiment, when a DC voltage of −2 kV or less is applied to the sawtooth electrode 109, corona discharge is started from the sawtooth electrode 109. In the image forming unit 100K according to the first embodiment, the density difference is drastically reduced from −2 kV to −2.5 kV, and the density difference is rapidly increased when the density is −3 kV or less. This is because, in the image forming unit 100K of the first embodiment, when a DC voltage of −3 kV or less is applied to the sawtooth electrode 109, a spark discharge is generated on the developer supply roller 105. On the other hand, in the image forming unit 100K of the second embodiment, there is no change in density difference between the amplitude A from 0 V to 1.5 kV (about 1.3), but when the amplitude A is set to 2 kV or more, Corona discharge starts as in the second embodiment, and the concentration difference suddenly decreases (about 0.2). In the image forming unit 100K of the second embodiment, when the amplitude A decreases from 2 kV to 3.5 kV and the amplitude A becomes 4 kV or more, a spark discharge is generated on the developer supply roller 105. The density difference is increasing rapidly.

  Therefore, from the evaluation experiment of FIG. 18, in the first embodiment (when the DC power supply 29 is used), the voltage width from the corona discharge start voltage to the spark discharge start voltage is only about 500V. However, in the second embodiment (when the DC power supply 30 is used), it is possible to cope with a good voltage (amplitude A) width of about 1500V.

  As a result, in the second embodiment, by applying an impulse voltage to the sawtooth electrode 109, it is possible to suppress spark discharge at the time of corona generation, the voltage applied to the sawtooth electrode 109 can be set high, and the developer supply The charging efficiency of the toner 6 on the roller 105 is increased. Therefore, in the second embodiment, the toner supply from the developer supply roller 105 to the development roller 2 is stable, and a good image without unevenness and blurring can be formed.

(C) Third Embodiment Next, an image forming unit and an image forming apparatus according to a third embodiment of the present invention will be described in detail with reference to the drawings.

  In the third embodiment, a conductive external additive is added to the toner T (TK, TC, TY, TM) used in each image forming unit 100 (100K, 100C, 100Y, 100M). This is different from the second embodiment.

  Specifically, as toner T used in the third embodiment, binder resin (polyester resin, number average molecular weight Mn = 3700, glass transition temperature Tg = 62 ° C.) is 100 parts by weight, and carna as a release agent. 5 parts by weight of UPA wax (Kato Yoko, Carnaupa wax No. 1 powder), 1 part by weight of Pigment Blue 15.3 “ECB-301” (manufactured by Dainichi Chemical Co., Ltd.) as a colorant, and negatively charged 4 parts by weight of a salicylic acid complex “Bontron E-84” (manufactured by Orient Chemical Co., Ltd.) as a charge control agent for the resin, mixed with a Henschel mixer, melt-kneaded with a twin-screw extruder, cooled, and diameter 2 After coarsely pulverizing with a cutter mill having a (mm) screen, pulverization is performed using a collision-type pulverizer “Dispersion Separator” (manufactured by Nippon Pneumatic Industry Co., Ltd.). , Further followed by classification using an air classifier to obtain a powder comprising a base particle. Next, as an external addition step, 2.5 parts by weight of hydrophobic silica R972 (manufactured by Nippon Aerosil Co., Ltd., average primary particle size 16 nm) is added to 100 parts by weight of the obtained powder of the mother particles, and hydrophobic titanium oxide (Titanium Industry). 0.5 parts by weight (average primary particle shape 20 nm, manufactured by the company) was added, stirred for 5 minutes with a 100 liter Henschel mixer at a rotational speed of 3200 (rotations / minute), cooled as it was, and further Henschel mixer The toner T (TK) used in the third embodiment is repeatedly stirred for 5 minutes at a rotational speed of 3200 (rotation / minute) and cooled 5 times (total stirring time during rotation is 25 minutes). , TC, TY, TM).

  Hereinafter, the toner T (TK, TC, TY, TM) to which the external additive having conductivity used in the third embodiment is added is also referred to as “conductive addition toner”.

  Next, the results of an evaluation experiment regarding print quality when printing is performed in the image forming unit 100K according to the third embodiment will be described with reference to FIG. The evaluation experiment of FIG. 19 shows the result of measuring the density difference when the same paper passing test as in FIG. 18 is performed for each applied voltage in the second embodiment and the third embodiment. In FIG. 19, in the evaluation experiment of the third embodiment, an impulse voltage is applied using an impulse power source 30 as a power source for the saw-tooth electrode 109 as in the second embodiment. However, in the third embodiment, the power source for the sawtooth electrode 109 may be replaced with a DC power source. Note that the measurement results in FIG. 19 are the same as in the case of FIG. 18 described above when the distance d = 1.0 mm, the interval w = 1.5 mm, the length l = 1.0 mm, and the angle θ = 10 °. Is.

  As shown in FIG. 19, compared to the second embodiment (when no conductive external additive is added to the toner T), the third embodiment (when a conductive additive toner is used for the toner T). ) With a smaller amplitude of about 500 V, the concentration difference decreases more rapidly (corona discharge starts). Furthermore, as shown in FIG. 19, even in the same amplitude, the third embodiment shows a tendency that the measured density difference is smaller than that of the second embodiment.

  Therefore, in the image forming apparatus 1 according to the third embodiment, the toner T has conductivity, so that a region where the density difference of the printed image can be reduced (allowable width of the impulse voltage amplitude) can be widened. it can.

  As described above, the image forming apparatus 1 according to the third embodiment can stably form a good print image without blurring or unevenness as compared with the second embodiment. Etc. becomes easy to design and manufacture.

(D) Other Embodiments The present invention is not limited to the above-described embodiments, and may include modified embodiments as exemplified below.

(D-1) In each of the above embodiments, the example in which the image forming apparatus provided with the developing device of the present invention is used as a printer has been described. However, the application of the image forming apparatus of the present invention is not limited, and the printing machine The present invention may be applied to other types of image forming apparatuses such as copying machines, multifunction machines, and facsimiles.

(D-2) In each of the embodiments described above, four image forming units (developing devices) included in the image forming apparatus correspond to color image formation. However, one image forming unit (developing device) is used. It is also possible to provide only one and correspond to image formation of a monochrome image.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 100, 100K, 100C, 100Y, 100M ... Image forming unit, 101 ... Photosensitive drum, 102 ... Charging roller, 103 ... LED head, 104 ... Developing roller, 105 ... Developer supply roller, 106 ... Toner container 107: Layer forming blade 108 ... Cleaning blade 109 109 Sawtooth electrode 109a Electrode 109a 9 Fixing device 10 Heating roller 11 Heating heater 12 Pressure roller 13 Thermistor 15a to 15v ... recording paper transport roller, 16 ... transfer belt, 17a to 17d ... transfer roller, 18a, 18b ... drive roller, 19a, 19b ... recording paper travel guide, 20 ... transfer belt cleaning blade, 21 ... waste developer tank , 22 ... recording paper cassette, 22 ... discharge tray, P ... recording paper, T, TK TC, TY, TM ... toner, 24-29 ... DC power supply, 30 ... impulse power, 40 ... imaging unit, 50 ... developing device.

Claims (6)

A developer carrying member for carrying the developer on the surface and developing the electrostatic latent image by attaching the carried developer to the electrostatic latent image carrying member carrying the electrostatic latent image;
A developer supply member for attaching a developer to the surface and supplying the developer attached to the surface to the developer carrier;
A charging member for charging the developer supply member, wherein a plurality of electrodes facing the developer supply member are formed at equal intervals;
The developing is characterized in that the electrode distance from the tip of each electrode constituting the charging member to the surface of the developer supply member is equal to or greater than the electrode interval between the electrodes constituting the charging member. apparatus.   The developing device according to claim 1, wherein an electrode tip angle formed by tips of the respective electrodes constituting the charging member is 5 ° to 15 °.   The developing device according to claim 1, wherein a length of each electrode constituting the charging member in a direction toward the developer supply member is 0.5 mm to 3 mm.   The developing device according to claim 1, wherein the developer used for development in the developing device has conductivity. In an image forming apparatus that forms an image on a medium using a developing device,
The developing device includes:
A developer carrying member for carrying the developer on the surface and developing the electrostatic latent image by attaching the carried developer to the electrostatic latent image carrying member carrying the electrostatic latent image;
A developer supply member for attaching a developer to the surface and supplying the developer attached to the surface to the developer carrier;
A charging member for charging the developer supply member, wherein a plurality of electrodes facing the developer supply member are formed at equal intervals;
An image in which an electrode distance from a tip of each electrode constituting the charging member to a surface of the developer supply member is equal to or more than an electrode interval between the electrodes constituting the charging member. Forming equipment.   The image forming apparatus according to claim 5, wherein an impulse voltage is applied to the charging member.

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