JP5789550B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic recording type image forming apparatus such as a fax machine and a copying machine, and more particularly to a developing device employed in these image forming apparatuses.

2. Description of the Related Art Conventionally, in an image forming apparatus, there is a method in which an electrostatic latent image formed on an electrostatic latent image carrier is developed with toner inside the developing device in a developing device to form a toner image.
(For example, refer to Patent Document 1).

JP-A-5-27567 (page 3, FIG. 1)

  However, in the conventional developing device using this type of system, there is a problem that the toner supply amount changes with time, resulting in a decrease in image density and blurring during printing.

The developing device according to the present invention comprises:
An electrostatic latent image carrier on which a latent image is formed; a developer carrier that develops the latent image formed on the electrostatic latent image carrier; and disposed vertically below the developer carrier, A developer supply body for supplying a developer to the developer carrying body, and a developer supply body that is disposed vertically below the developer supply body and forms a nip in contact with the developer supply body. A developer auxiliary supply body for supplying the developer to the developer , and a developer that forms an interface extending in the horizontal direction in a region vertically below the developer supply body and including the nip in the horizontal direction by the developer. And a constant current generating means for supplying a constant current to the developer auxiliary supply body, and a constant voltage generating means for applying a constant voltage to the developer supply body .

  According to the invention of the present application, it is possible to suppress a decrease in the supply amount of the developer supplied from the developer supply body to the developer carrying member over time, thereby suppressing a decrease in image density and occurrence of blurring during printing. it can.

FIG. 2 is a main part configuration diagram showing a main part configuration of the developing device according to the first embodiment of the present invention; FIG. 2 is a schematic configuration diagram schematically illustrating a main configuration of an image forming apparatus including a developing device. FIG. 2 is a schematic configuration diagram illustrating each part of a developing device and power supply wiring of a transfer roller in the first embodiment. 3 is a block diagram of a main control system of an image forming apparatus including a developing device in Embodiment 1. FIG. FIG. 4 is an explanatory diagram for explaining a positional relationship among a toner interface and a developing roller, a supply roller, an auxiliary supply roller, and a toner collection brush roller. It is a measurement explanatory drawing for demonstrating the measuring method of the resistance value of a developing roller, a supply roller, and an auxiliary supply roller, (a) is the schematic front view, (b) is the schematic side view. It is a schematic block diagram which shows the power supply wiring of a comparative example apparatus. It is a block diagram of the principal part control system in a comparative example apparatus. FIG. 4 is an equivalent circuit diagram showing an equivalent circuit of a current flowing from a supply roller to an auxiliary supply roller when a toner layer made of toner is supplied from the auxiliary supply roller to the supply roller. FIG. 6 is a graph showing evaluation results of a blur print evaluation test in the first embodiment. FIG. 10 is a main part configuration diagram illustrating a main part configuration of a developing device according to a modification of the first embodiment. FIG. 10 is a schematic configuration diagram illustrating each part of a developing device according to a modification of the first embodiment and power supply wiring of a transfer roller. It is a block diagram of the principal part control system of the image forming apparatus of Embodiment 2 by this invention. 6 is a flowchart of power supply control performed by an auxiliary supply roller constant current power supply in the second embodiment. In the case of using a constant current power supply as a DC power source of the auxiliary supply roller, which is a diagram of the relationship between the applied voltage V _out and output current I _out. In the second embodiment, in case of providing the limit voltage value _{V Out_limit} is an upper limit value of the applied voltage _{V out} to the auxiliary supplying roller constant current power supply, is a diagram of the relationship between the applied voltage _{V out} and output current _{I out} . It is the schematic which expressed Formula (13) roughly with the graph. FIG. 10 is a graph showing evaluation results of a blur print evaluation test in the second embodiment. FIG. 10 is a graph showing the evaluation results of a background print evaluation test in Embodiment 2. FIG. 10 is a schematic configuration diagram illustrating each part of a developing device according to a third embodiment and power supply wiring of a transfer roller. FIG. 10 is a block diagram of a main control system of an image forming apparatus including a developing device according to a third embodiment. FIG. 10 is a graph showing evaluation results of a blur print evaluation test in Embodiment 3. FIG. 10 is a graph showing the evaluation result of the color difference ΔE for fog evaluation in the third embodiment.

Embodiment 1 FIG.
FIG. 1 is a main part configuration diagram showing the main part configuration of the developing device according to the first embodiment of the present invention.

  In the figure, a photosensitive drum 1 as an electrostatic latent image carrier is composed of a conductive support and a photoconductive layer, and a charge is generated as a photoconductive layer on an aluminum metal pipe as a conductive support. An organic photoreceptor in which a layer and a charge transport layer are sequentially laminated. The charging roller 2 as a charging device is a metal shaft coated with a semiconductive epichlorohydrin rubber layer, and is rotatably disposed in contact with the photosensitive drum 1, as will be described later. To charge the surface. The LED head 3 serving as an exposure device is disposed to face the photosensitive drum 1 and exposes the surface of the photosensitive drum 1 to form an electrostatic latent image. The developing roller 4 as the developer carrying member is a metal shaft coated with an elastic layer made of semiconductive urethane rubber, and an electrostatic latent image formed on the surface of the photosensitive drum 1 by toner carried as will be described later. Develop.

  The supply roller 5 as a developer supply body is a metal shaft coated with a conductive urethane resin, and is rotatably disposed at a position separated from the development roller 4 by a predetermined distance. The auxiliary supply roller 6 as a developer auxiliary supply body is a metal shaft coated with a foamed semiconductive silicone rubber layer, and is rotatably disposed in pressure contact with the supply roller 5. The layer forming blade 7 as the first thin layer forming device is formed of a metal plate having a bent portion that contacts the surface of the developing roller 4 and is disposed so as to contact the developing roller 4 with a predetermined linear pressure. Yes.

  The toner collecting brush roller 8 serving as a first developer collecting device is formed by winding a cloth in which conductive fibers are woven around a metal shaft, and is rotatably disposed in contact with the developing roller 4. The toner recovery brush flicker 9 is a cleaning member for the toner recovery brush roller 8 and is made of metal. The toner 10 as a developer is composed of a binder resin, a charge control agent as an internal additive, a release agent, a colorant, and an external additive, and a toner cartridge as a developer container that accommodates the toner 10. 11 includes a shutter 13 that opens and closes when the toner 10 is replenished. The cleaning blade 12 as a second developer recovery device is made of urethane rubber, and is disposed so that the tip portion contacts the photosensitive drum 1 with a predetermined pressure.

  The stirring bars 14a to 14d are crank-shaped metal bars, which stir and convey the surrounding toner. The remaining toner amount detection bar 15 as the remaining toner amount detection unit is also a crank-shaped metal bar, and is configured such that the rotation state changes according to the remaining amount of toner in the toner storage unit 22 in the developing device. The supply layer regulating blade 16 as the second thin layer forming device is made of urethane rubber having conductivity, and is disposed so that the tip portion contacts the supply roller 5 with a predetermined pressure. The developing device 100 is configured by the above-described components 1 to 16.

  In FIG. 1, the direction of arrow A indicates a substantially vertical downward direction. Accordingly, here, the supply roller 5 is disposed below the developing roller 4 in the vertical direction, and the auxiliary supply roller 6 is disposed below the supply roller 5 in the vertical direction. These height positional relationships will be further described later.

  FIG. 2 is a schematic configuration diagram schematically illustrating a main configuration of the image forming apparatus 110 including the developing device 100 described above.

  In the figure, conveyance rollers 20a to 20e convey recording paper 17 as a printing medium placed in a stacked state in the lower part of the apparatus one by one along the conveyance path indicated by a dotted line in the figure. To do. The developing device 100 is disposed along the transport path, and the transfer roller 18 is disposed to face the photosensitive drum 1 of the developing device 100, and the recording sheet 17 transported along the transport path together with the photosensitive drum 1. As will be described later, the toner image formed on the photosensitive drum 1 is transferred to the recording paper 17, and the recording paper 17 is sent downstream. The transfer roller 18 is a metal shaft coated with a urethane sponge layer. The fixing device 19 as fixing means fuses and fixes the toner 10 transferred to the recording paper 17 by heating and pressurization, and the stacker unit 21 mounts the recording paper that is printed and discharged from the apparatus. Put.

  FIG. 3 is a schematic configuration diagram showing each part of the developing device 100 and the power supply wiring of the transfer roller 18.

  In the figure, a charging constant voltage power source 52 applies a constant voltage to the charging roller 2, a developing roller constant voltage power source 54 applies a constant voltage to the developing roller 4, and a layer forming blade constant voltage power source 57 applies to the layer forming blade 7. A constant voltage is applied, a supply roller constant voltage power supply 55 as a constant voltage generation means applies a voltage to the supply roller 5 and the supply layer regulating blade 16, and an auxiliary supply roller constant current power supply 56 as a constant current generation means is an auxiliary supply. The current flowing into the roller 6 is made constant, the toner recovery constant voltage power source 58 applies a constant voltage to the toner recovery brush roller 8, and the transfer constant voltage power source 68 applies a constant voltage to the transfer roller 18.

  FIG. 4 is a block diagram of a main control system of the image forming apparatus 110 including the developing device 100 described above.

  In the figure, the print control unit 30 includes a microprocessor, a ROM, a RAM, an input / output port, a timer, and the like. The print control unit 30 receives print data and a control command from the host device, performs sequence control on the entire image forming apparatus 110, and prints. Perform the action. The interface control unit 31 transmits printer information to the host device, analyzes a command input from the host device, and processes data received from the host device. The reception memory 32 temporarily stores print data input from the host device via the interface control unit 31, and the image data editing memory 33 receives the print data stored in the reception memory 32 and prints the print data. Image data formed by editing the data, that is, image data is stored.

  The operation unit 34 includes an LED for displaying the state of the image forming apparatus 110, a switch and a display unit for giving an instruction from the operator to the image forming apparatus 110, and the sensor group 35 is an operation of the image forming apparatus 110. It consists of various sensors for monitoring the state, such as a paper position detection sensor, a temperature / humidity sensor, a print density sensor, a toner remaining amount detection sensor, and the like.

  The high voltage power supply control unit 41 controls the voltage applied to each unit of the image forming apparatus 110 according to an instruction from the print control unit 30, and the shutter drive control unit 42 monitors the remaining toner amount detection bar 15 (FIG. 1). The opening / closing operation of the shutter 13 (see FIG. 1) disposed in the toner cartridge 11 is controlled by an instruction from the printing control unit 30 to determine the remaining amount of toner in the toner storage unit 22 (FIG. 1) inside the developing device 100. Accordingly, the toner 10 is replenished.

  The head drive control unit 43 sends the image data stored in the image data editing memory 33 to the LED head 3 (see FIG. 1) to drive the LED head 3 to emit light, and the fixing control unit 44 is transferred to the recording paper 17. In order to fix the toner image, a voltage is applied to the fixing device 19 (see FIG. 2). That is, the fixing device 19 includes a heater for melting the toner 10 constituting the toner image transferred onto the recording paper 17, a temperature sensor for detecting a fixing temperature, and the like, and the fixing control unit 44 is a sensor of the temperature sensor. The output is read, and the power supply to the heater is turned on / off based on the sensor output, so that the fixing temperature of the fixing device 19 is controlled to a desired value.

  The transport motor control unit 45 controls the paper transport motor 23 that drives the transport rollers 20a to 20e (FIG. 2), and transports or stops the recording paper 17 at a predetermined timing according to an instruction from the print control unit 30. At the time of printing, the recording paper 17 placed in a stacked state in the lower part of the image forming apparatus 110 (FIG. 2) is conveyed one by one in the direction of the arrow along a conveyance path indicated by a dotted line in the drawing.

  The drive control unit 46 drives and controls the drive motor 24 for rotationally driving the photosensitive drum 1, and the drive transmission unit 25 configured by a gear transmission mechanism or the like includes the photosensitive drum 1, the charging roller 2, and the development. The roller 4, the supply roller 5, the auxiliary supply roller 6, and the toner collection brush roller 8 are arranged between the rollers, and the rotation of the photosensitive drum 1 is transmitted to these parts. As shown in FIG. Is rotated at a predetermined speed in the direction of the arrow, and each part rotates at a predetermined speed in the direction of the arrow shown in FIG.

  The developing device 100 will be described in more detail.

  The toner 10 used in the present embodiment is a non-magnetic one-component negatively chargeable toner manufactured by a pulverization method and using a polyester resin as a binder, and has a volume average particle diameter of about 6 μm. The developing roller 4 is disposed so as to come into contact with the photosensitive drum 1, and here, urethane rubber is used as the material of the elastic layer. The toner recovery brush roller 8 is obtained by winding a cloth woven with conductive fibers adjusted to a desired resistance value around a conductive core bar in a spiral shape. A cylindrical toner collection brush flicker 9 abuts on the toner collection brush roller 8 in order to cause the toner 10 to be carried, that is, undeveloped toner collected from the development roller 4 to fly using the elasticity of the brush fibers. ing. The shape of the toner recovery brush flicker 9 is not limited to a cylinder, but may be a metal plate having a thickness of about 0.1 mm.

  In consideration of the toner flying property to the developing roller 4, the supply roller 5 has a structure in which a conductive urethane resin is coated on a metal shaft made of aluminum. In this embodiment, a gap of approximately 250 μm is provided between the supply roller 5 and the developing roller 4.

Although the supply roller 5 and the developing roller 4 can be brought into contact with each other, if control is performed so that a constant current flows through the auxiliary supply roller 6 in this contact state, a current flows into the developing roller 4. There is. In this case, since the applied voltage instructed by the high-voltage power source control unit 41 (FIG. 4) developing roller constant voltage power source 54 fluctuates, the supply roller 5 developing roller 4 is desirably separated. An example of contacting the supply roller 5 and the developing roller 4 will be described later as a modification of the present embodiment.

  The supply layer regulating blade 16 formed of conductive urethane rubber is installed so that the tip end portion is in contact with the supply roller 5 with a relatively weak force. Although it is possible to operate without providing the supply layer regulating blade 16, in order to stably supply the toner to the developing roller 4, the toner layer formed on the surface of the supply roller 5 is leveled. It is desirable to install the supply layer regulating blade 16 which has an effect.

The auxiliary supply roller 6 has a structure in which a silicone rubber sponge is provided on a conductive metal core, and comes into contact with the supply roller 5 and rotates in the opposite direction to the supply roller 5 as shown in FIG. In consideration of toner damage due to friction at the contact portion, the auxiliary supply roller 6 and the supply roller 5 are provided such that the surfaces of the auxiliary supply roller 6 and the supply roller 5 move in the same direction at substantially the same speed. The substantially constant speed here, the moving speed V ₆ of the surface of the auxiliary supplying roller 6 at the contact portion, the difference between the moving speed V ₅ of the surface of the supply roller 5 (V 6 _{-V 5),} the V6 Say within ± 10%.

  Note that the rotational driving of the supply roller 5 and the auxiliary supply roller 6 is not limited to this, and for example, the auxiliary supply roller 6 is set in the same direction as the supply roller 5 shown in FIG. By setting the direction (counterclockwise), charging shortage due to frictional charging of the toner 10 may be compensated, and by supplying the rotation direction of the supply roller 5 clockwise, the toner 10 is supplied to the developing roller 4. When the toner 10 is thinned by the layer forming blade 7, the toner 10 scraped off and dropped onto the supply roller 5 is supplied without passing through the contact portion between the supply roller 5 and the auxiliary supply roller 6. It is also possible to prevent the roller 5 from being supplied directly to the developing roller 4.

  FIG. 5 is an explanatory diagram for explaining the positional relationship among the interface of the toner 10, the developing roller 4, the supply roller 5, the auxiliary supply roller 6, and the toner collection brush roller 8. In addition, the arrow A direction in FIG. 5 has shown the perpendicular downward direction which is a gravity direction.

  The height of the vertical lowest point of the auxiliary supply roller 6 is defined as a reference position Pf, the height from the reference position Pf to the axial center of the auxiliary supply roller 6 is h1, and the interface of the toner 10 in the toner containing portion 22 is reached. Assuming that the height is ht, the auxiliary supply roller 6 picks up the toner 10, so the interface of the toner 10 needs to be above the reference position Pf.

Accordingly, the height ht of the interface of the toner 10 from the reference position Pf is
0 <ht
Toner 10 is supplied so as to satisfy.
In order to supply a more stable toner 10,
h1 <ht
Is effective. By doing so, the toner 10 supplied to the auxiliary supply roller 6 does not fall directly downward due to the influence of gravity, and the toner supply amount from the auxiliary supply roller 6 is stabilized.

  FIG. 6 is a measurement explanatory diagram for explaining a method of measuring the resistance values of the developing roller 4, the supply roller 5, and the auxiliary supply roller 6 (collectively referred to simply as the roller 60) in the present embodiment. FIG. 4A is a schematic front view thereof, and FIG. 4B is a schematic side view thereof. Hereinafter, a method for measuring the resistance value will be described.

  The resistance value of the roller 60 was measured using a high resistance meter (model number: 4339B) 601 manufactured by Hewlett-Packard Company. An SUS ball bearing 602 having a width of 2.0 mm and a diameter of 6.0 mm was brought into contact with the roller surface 62 of the roller 60 with a force of 20 gf, and the resistance value between the core metal 61 and the roller surface was measured.

There are six bearings 36 from P1 to P6. Measure while rotating the roller 60 at a speed of 50 rpm, measure 100 points for each circumference from P1 to P6, 600 points in total, and the average value is the resistance of the roller 60. Value. The applied voltage to the roller 60 at this time was 100V. In this embodiment,
The resistance value Rdv of the developing roller 4 is Rdv = 10 ⁷ [Ω],
The resistance value Rsp of the supply roller 5 is Rsp = 10 ⁵ [Ω],
The resistance value Rsub of the auxiliary supply roller 6 is Rsub = 10 ⁴ [Ω]
The thing of was used.

  With the above configuration, the operation of the image forming apparatus will be described in detail with reference to FIGS.

  For example, when a print command is input from a host device such as a personal computer, the print control unit 30 (FIG. 4) of the image forming apparatus 110 drives the drive motor 24 via the drive control unit 46 to drive the photosensitive drum 1. It rotates at a constant peripheral speed in the direction of the arrow shown in FIG. A drive transmission unit 25 configured by a gear transmission mechanism or the like transmits the rotation of the photosensitive drum 1 that is rotationally driven, and supplies the developing roller 4, the supply roller 5, the toner collection brush roller 8, and the auxiliary supply roller 6 to each other. It rotates in each direction shown in FIG. Further, the agitation bars 14a, 14b, 14c, 14d and the toner remaining amount detection bar 15 are rotated in the respective arrow directions shown in FIG.

  A charging roller 2 that is disposed in contact with or in pressure contact with the surface of the photosensitive drum 1 and to which a DC voltage is applied by a charging constant voltage power source 52 is driven by the photosensitive drum 1 to uniformly distribute the surface of the photosensitive drum 1. Charge uniformly. In the next exposure process, the LED head 3 emits light corresponding to the image data to the photosensitive drum 1, and an electrostatic latent image is formed on the surface of the photosensitive drum 1. In the next development process, the electrostatic latent image is developed with the toner 10 to form a toner image on the surface of the photosensitive drum 1 by an operation of the developing device 100 described later.

On the other hand, as shown in FIG. 2, the recording paper 17 is conveyed by the paper conveying rollers 20a, 20b, and 20c, and is sent to the transfer section where the photosensitive drum 1 and the transfer roller 18 face each other. Transfer roller 18 is the DC voltage applied transfer constant-voltage power supply 68 (FIG. 4) to transfer the toner image formed on the photosensitive drum 1 to the recording sheet 17. Thereafter, the recording paper 17 is further conveyed to the fixing device 19 where the toner 10 melted by heat and pressure penetrates between the fibers of the recording paper 17 and is fixed. The fixed recording paper 17 is sent to the stacker unit 21 outside the image forming apparatus by the transport rollers 20d and 20e. Further, a weak crown amount of toner 10 may remain on the photosensitive drum 1 after the transfer, but this residual toner 10 is removed by the cleaning blade 12 (FIG. 1). In this way, the photosensitive drum 1 is repeatedly used.

  The operation of the developing device 100 will be described in more detail with reference to FIG. 1, FIG. 3, and FIG.

  A drive transmission unit 25 (FIG. 4) configured by a gear transmission mechanism or the like transmits the rotation of the photosensitive drum 1 that is rotationally driven, and the developing roller 4, the supply roller 5, the toner collection brush roller 8, and the auxiliary supply roller. 6 are rotated in the respective directions shown in FIG. At this time, the auxiliary supply roller 6 rotates while carrying and pumping up the toner 10 on the sponge surface and in the cells, and eventually the carried toner 10 reaches the contact portion with the supply roller 5. At this time, a DC voltage of -1.0 kV is applied to the supply roller 5 by the supply roller constant voltage power supply 55, and the supply roller 5 is supplied to the auxiliary supply roller 6 by the auxiliary supply roller constant current power supply 56 (FIG. 4). Is supplied to the auxiliary supply roller 6 at a constant current of about 10 μA.

  Accordingly, negative charges move while passing the toner 10 from the auxiliary supply roller 6 toward the toner supply roller 5 at the contact portion between the auxiliary supply roller 6 and the supply roller 5. At this time, the toner 10 is charged, and the toner 10 adheres to the surface of the supply roller 5 by the action of the electric field between the auxiliary supply roller 6 and the supply roller 5. Since the adhered toner 10 is negatively charged, an adhesion force due to a self electric field is generated on the surface of the supply roller 5 and is held on the supply roller 5.

  The toner 10 held on the supply roller 5 reaches the contact portion with the supply layer regulating blade 16 to which the same voltage as that of the supply roller 5 is applied as the supply roller 5 rotates. Then, it reaches the part facing the developing roller 4. In the present embodiment, as shown in FIG. 3, there is no potential difference between the supply layer regulating blade 16 and the supply roller 5, but the toner 10 is charged when it is smoothed here. It is also possible to provide a potential difference.

  A DC voltage of −200 V is applied to the developing roller 4 by the developing roller constant voltage power source 54, and a DC voltage of −200 V is applied to the layer forming blade 7 from the layer forming blade constant voltage power source 57. Accordingly, since the potential difference between the developing roller 4 and the supply roller 5 is +800 V, the negatively charged toner 10 adhering to the surface of the supply roller 5 flies in the direction of the developing roller 4 to the surface of the developing roller 4. Supported. The developing roller 4 develops the electrostatic latent image formed on the photosensitive drum 1 with the toner 10 that has been thinned by the layer forming blade 7 as it rotates, and the toner 10 that has been further thinned.

  At this time, the toner 10 remaining on the surface of the developing roller 4 without developing the electrostatic latent image is in a nip portion between the developing roller 4 and the toner collecting brush roller 8, which is a toner collecting area according to the rotation of the developing roller 4. To reach. At this time, since the DC voltage −100 V is applied to the toner recovery brush roller 8 by the toner recovery constant voltage power source 58 (FIG. 4), the toner recovery brush roller having a potential difference of +100 V with respect to the developing roller 4 and the developing roller 4. An electric field is formed between 8 and 8. Accordingly, at the nip portion between the developing roller 4 and the toner collecting brush roller 8 in the toner collecting area, the action and electric field of scraping off the toner 10 remaining on the surface of the developing roller 4 while the brush thread of the toner collecting brush roller 8 is curved. As a result, the toner 10 remaining on the surface of the developing roller 4 moves to the toner collecting brush roller 8 and is collected.

  At the contact portion between the toner recovery brush roller 8 and the flicker 9, the brush thread is repelled as the toner recovery brush roller 8 rotates, and the toner held on the brush thread is repelled outside the toner recovery brush roller 8. And is reused as the toner 10 in the toner container 22 again.

  Here, as a comparative example, the configuration of a comparative example device that applies a constant voltage to the auxiliary supply roller 6 instead of a constant current will be described.

FIG. 7 is a schematic configuration diagram showing power supply wiring in the comparative apparatus, and FIG. 8 is a block diagram of a main control system in the comparative apparatus. As is apparent from FIGS. 7 and 8, in this comparative example device, a constant voltage is applied to the auxiliary supply roller 6 by the auxiliary supply roller constant voltage power source 556. Other configurations are the same as those of the image forming apparatus 110 of the present embodiment described above. Here, the auxiliary supply roller constant voltage power source 556 applies −1.8 kV to the auxiliary supply roller 6. Here, the applied voltage value is an applied voltage value that can supply an amount of current necessary for image formation as an initial state.

  Next, a method for calculating the current value of the current supplied from the auxiliary supply roller constant current power supply 56 to the auxiliary supply roller 6 in the present embodiment will be described with reference to the above-described comparative example.

で表される。ここで、ρ_ｉは電気抵抗率、Ａ_ｉは断面積、そしてｄ_ｉは厚さである。ｉは各部材を表す添え字であり、以後、補助供給ローラ６はｓｕｂ、供給ローラ５はｓｐ、そしてトナー１０はｔで表す。 FIG. 9 is an equivalent circuit diagram showing the state of current flowing from the supply roller 5 to the auxiliary supply roller 6 as an equivalent circuit when the toner layer of the toner 10 is supplied from the auxiliary supply roller 6 to the supply roller 5. The supply roller 5 and the auxiliary supply roller 6 are connected in series via the toner layer, and a voltage is applied so that a current flows from the supply roller 5 to the auxiliary supply roller 6 as in the power supply wiring shown in FIG. .
The electrical resistance R _i of each member is
[Formula 1]

It is represented by Here, ρ _i is the electrical resistivity, A _i is the cross-sectional area, and d _i is the thickness. i is a subscript representing each member, hereinafter, the auxiliary supply roller 6 is represented by sub, the supply roller 5 is represented by sp, and the toner 10 is represented by t.

で表すことができる。更に、オームの法則
Ｖ＝ＲＩ （４）
と式（３）から
［式５］

となる。 Since the supply roller 5 and the auxiliary supply roller 6 are in contact with each other via the toner 10, the cross-sectional area at the contact portion is equal for the three elements. Therefore, A = A _sp = A _t = A _sub (2)
It is represented by Therefore, the combined resistance R of the three elements is
[Formula 3]

Can be expressed as Furthermore, Ohm's Law V = RI (4)
And Equation (3) [Equation 5]

It becomes.

となる。ここで、
［式７］

であり、供給ローラ５、補助供給ローラ６の厚さ、電気抵抗率は変化しないため、Ｂは定数である。 When formula (5) is transformed into formula for current I [Formula 6]

It becomes. here,
[Formula 7]

Since the thickness and electric resistivity of the supply roller 5 and auxiliary supply roller 6 do not change, B is a constant.

を式（６）に適用する。
距離ｄはトナー１０の厚さｄ_ｔと同等であり、式（６）と式（７）から
［式９］

が得られる。 Here, the discharge start voltage V _p (d) is considered.
Paschen's law depending on distance [Equation 8]

Is applied to equation (6).
The distance d is equivalent to the thickness _dt of the toner 10, and from the equations (6) and (7), [Equation 9]

Is obtained.

In the present embodiment, when the supply roller 5 and the developing roller 4 are separated from each other, and the separated distance is smaller than the thickness _{dt of the} toner 10, the contact is equivalent to the contact, so that the separation is performed. When the _gap is d _gap
d _gap > d _t (10)
Must also be met. Therefore, the toner 10 has a thickness d _t = 150 μm as an amount sufficient for image formation. At that time, the discharge start voltage V _p (d) is approximately 1.2 kV.

From the above conditions, the current value output from the auxiliary supply roller constant current power source 56 in the configuration of the present embodiment is I <12.6 μA (11)
Is obtained.

  The lower limit value of the applied current is the current when a constant voltage of −1.8 kV is applied to the auxiliary supply roller 6 in order to supply an amount of current necessary for image formation as an initial state as described in the comparative example device. Value. That is, a potential difference of 800 V is obtained from the constant voltage of −1.8 kV and the supply constant voltage of −1000 V applied to the supply roller 5, and when the obtained potential difference is substituted into Equation (6), the current required for image formation as an initial state is obtained. An amount of 8.4 μA is obtained.

From the above conditions, the current value I of the current supplied from the auxiliary supply roller constant current power source 56 to the auxiliary supply roller 6 is
8.4 μA <I <12.6 μA (12)
It is preferable to set in the range. In the present embodiment, based on the above calculation method, the current value output from the auxiliary supply roller constant current power supply 56 supplied to the auxiliary supply roller 6 is set to 10 μA. In addition, when setting the value of an applied current, it may determine by experiment etc. and is not the above-mentioned limit.

  Next, the results of a print evaluation test using the image forming apparatus of the present embodiment will be described in comparison with the same results obtained using the above-described comparative apparatus.

The test was conducted under the following test conditions.
-In an environment of a temperature of 23 ° C. and a relative humidity of 50%, a change in scum was confirmed as an index of print quality by toner supply performance.
In the test, an image forming apparatus 110 (hereinafter also referred to as an example apparatus) having an auxiliary supply roller constant current power source 56 (FIG. 3) and an auxiliary supply roller constant voltage power source 556 (FIG. 7) shown in FIG. ) Was used.
The printing speed (= linear speed of the photosensitive drum 1 = paper feeding speed) was set to 200 (mm / s).
A4 standard paper (for example, OKI excellent white paper), basis weight = 80 (g / m ² ) was used.
・ Printed with horizontal feed (printing two long sides as the leading and trailing edges), 100% duty (printing 100% of the area ratio when printing all over the printable area of one A4 sheet) .
-Continuous printing is performed 100 sheets each, and the blur evaluation is performed on the recording paper printed every 20 printed sheets.
・ When there was no scumming ratio, the level was 10; hereinafter, the scumming ratio was less than 2%, less than 4%,... Level 8 or higher is a good image range.

  FIG. 10 is a graph showing the evaluation results of the test. The level indicated by a dotted line indicates a pass / fail judgment level. When the level is less than the dotted line level, it is determined that the image is defective.

  As shown in the figure, in the comparative apparatus, the blur level decreases as the number of printed sheets increases, and when it exceeds 40, it is determined that the image is defective. Does not occur. Hereinafter, the cause of blurring in the case of the comparative apparatus will be considered.

  In each of the embodiment apparatus and the comparative apparatus, the toner 10 is supplied from the auxiliary supply roller 6 to the supply roller 5 and then supplied to the developing roller 4. All are not supplied to the developing roller 4. Therefore, the toner 10 that is not supplied to the developing roller 4 returns again to the contact area between the supply roller 5 and the auxiliary supply roller 6. Since the toner 10 once supplied from the auxiliary supply roller 6 to the supply roller 5 is already negatively charged, the toner 10 remaining on the supply roller 5 forms an electric field.

  Therefore, in the case of the comparative apparatus that applies a constant voltage to the auxiliary supply roller 6, the potential difference between the auxiliary supply roller 6 and the supply roller 5 becomes small, so that the Coulomb force that the charged toner 10 receives from the electric field becomes weak, and the auxiliary supply roller It becomes difficult for the toner to move from 6 to the supply roller 5. As a result, the supply amount of the toner 10 is reduced, and it is considered that blurring occurs.

  On the other hand, in the case of the embodiment device that supplies a constant current to the auxiliary supply roller 6, the current flows even when the charged toner 10 returns to the contact area of the auxiliary supply roller 6 and the supply roller 5. To increase. Accordingly, a sufficient potential difference is generated even when the charged toner 10 is present, so that the toner 10 does not easily move to the supply roller 5 side as in the comparative apparatus.

  FIG. 11 is a main part configuration diagram showing the main part configuration of a developing device according to a modification of the present embodiment, and FIG. 12 is a schematic configuration diagram showing the power wiring of each part and the transfer roller 18.

  In the developing device 100 of the present embodiment shown in FIG. 1, the supply roller 5 is spaced from the developing roller 4. In this modification, the supply roller 5 is in contact with the developing roller 4. It is different in that it is arranged in a state. Other configurations are exactly the same.

11 and 12, when the supply roller 5 and the developing roller 4 are installed in contact with each other, the current flowing between the developing roller 4 that directly affects the image quality and the contact member in contact with the developing roller 4 Therefore, it is necessary to consider so that the set voltage of the developing roller 4 does not change. Therefore, the relationship between the resistance value R _dv [Ω] of the developing roller 4, the resistance value R _sp [Ω] of the supply roller 5, and the resistance value R _bl [Ω] of the layer forming blade 7 is
R _dv > R _sp × 10 ³ and R _dv > R _bl × 10 ³
Therefore, the developing roller 4 can be regarded as an insulator from other members in contact with each other, and the influence of the current flowing into the developing roller 4 can be reduced, and voltage fluctuation can be suppressed. it can. Note that R _dv > R _bl × 10 ³ is the same in the developing device 100 of Embodiment 1 shown in FIG. 1 as well as the modified example.

Since the photosensitive drum 1 is covered with an insulating layer, the influence on the developing roller 4 due to the contact with the insulating layer can be ignored. Further, for the resistance value R _sub [Ω] of the auxiliary supply roller 6,
It is preferable to satisfy R _sp > R _sub .
As a result, the current is less likely to flow between the supply roller 5 and the developing roller 4.

  As described above, according to the image forming apparatus of the present embodiment, since a predetermined constant current is passed through the auxiliary supply roller 6, the toner is stably supplied from the auxiliary supply roller 6 to the supply roller 5 regardless of time. And the blurring phenomenon at the time of printing due to insufficient toner supply can be suppressed.

Embodiment 2. FIG.
FIG. 13 is a block diagram of a main control system of the image forming apparatus according to the second embodiment of the present invention.

  The image forming apparatus of the present embodiment that employs this control system is mainly different from the image forming apparatus of the first embodiment shown in FIG. 4 described above in that a constant current by an auxiliary supply roller constant current power supply 256 in the control system. It is a control method. Therefore, in the image forming apparatus of the present embodiment, the same reference numerals are given to the parts common to the image forming apparatus 110 (FIG. 1) of the first embodiment, or the description is omitted by omitting the drawing. , Explain different points with emphasis. The main part configuration of the image forming apparatus according to the present embodiment is the same as that of the main part of the image forming apparatus 110 according to the first embodiment shown in FIG. 1 except for the control system described above. Please refer to FIG.

  In the image forming apparatus of the present embodiment, an upper limit is applied to the voltage applied to the auxiliary supply roller 6 by the auxiliary supply roller constant current power supply 256. The contents will be described below.

FIG. 14 is a flowchart of power control performed by the auxiliary supply roller constant current power source 256. After first control start, when receiving an instruction of the current supply from the high voltage power supply control unit 41, the auxiliary supply roller constant current power supply 256 to output the output current _{I out} of the set current value _{I sub} (step S101 and S102). At this time, the applied voltage _Vout applied to the auxiliary supply roller 6 is measured (step S103), and the measured applied voltage _Vout is compared with a preset limit voltage value _{Vout_limit} (step S104).

Here, when the applied voltage _Vout is _{equal to} or lower than the limit voltage value _{Vout_limit} (step S104, No), the process directly reaches step S106, and when the applied voltage _Vout is larger than the limit voltage _{Vout_limit} (step S104, Yes), A new output current that is 0.1 μA less than the current output current _Io is output (step S105, step S102). Then, Step S102 to Step S105 are repeated until the applied voltage _Vout becomes equal to or lower than the limit voltage value _{Vout_limit,} and then Step S106 is reached.

In step S106, determines the output current _{I out} is whether less than the set current value _{I sub} at this time, if the output current _{I out} is less than the set current value _{I sub} (step S104, Yes), the output current at this time A new output current _out obtained by adding 0.1 μA to I _out is returned to step S102 and output. If the output current I _out is equal to or greater than the set current value I _sub (step S104, No), the process returns to step S102 and output as it is. To do.

This flow is performed in real time at least during the printing operation, and the auxiliary supply roller constant current power supply 256 operating according to this flow normally outputs a constant current of the set current value I _sub as a constant current source. When the applied voltage _Vout applied to the auxiliary supply roller 6 reaches the limit voltage value _{Vout_limit} as the upper limit in accordance with the fluctuation of the constant voltage drive, constant voltage driving is performed so that the applied voltage _Vout does not increase any more.

FIG. 15 is an explanatory diagram showing the relationship between the applied voltage V _out and the output current I _out when a constant current power source is used as the DC power source of the auxiliary supply roller 6. _Iout is an output current supplied to the auxiliary supply roller 6, and _Vout is an applied voltage applied to the auxiliary supply roller 6 at this time. Since the output current I _out maintains a constant set current value I _sub , the voltage increases indefinitely depending on the load condition and reaches the discharge start voltage.

On the other hand, FIG. 16 shows the applied voltage Vout when the limited voltage value Vout_limit, which is the upper limit value of the applied voltage Vout, is provided in the constant current power supply according to the flow of FIG. 14 like the auxiliary supply roller constant current power supply 256. It is explanatory drawing showing the relationship of the output electric current Iout. The auxiliary supply roller constant current power supply 256 according to the present embodiment has an applied voltage Vout and an output current along the thick line L shown in the figure in accordance with the state of the auxiliary supply roller 6 as a load and members related thereto. Iout fluctuates.

Here, the setting conditions of the limit voltage value _{Vout_limit} will be described. First, an expression representing the possible thickness of the toner layer under the conditions of FIGS. 15 and 16 is derived.

となる。ここで、
［式１４］

である。 When the above equation (5) is transformed into an equation for the thickness _dt of the toner 10,
[Formula 13]

It becomes. here,
[Formula 14]

It is.

FIG. 17 is a schematic diagram schematically representing Expression (13) by a graph. From this graph, in the present embodiment, in a case of changing the output current _{I out} supplied to the auxiliary supply roller 6 also, by providing the limit voltage value _{V Out_limit} which is the upper limit on the applied voltage _{V out,} the toner layer It can be seen that the thickness d _t of the _slab can be prevented from increasing beyond a certain upper limit value d _limit .
Here, the thickness _dt of the toner 10 substantially indicates the layer thickness of the toner layer formed on the surface of the supply roller 5.

Based on the above points, a method for setting the limit voltage value _{Vout_limit} that is the upper limit value of the applied voltage of the auxiliary supply roller constant current power supply 256 in the present embodiment will be described.

When the current value supplied to the auxiliary supply roller 6 is 10 μA (the direction is shown in FIG. 3), the voltage at which the thickness _dt of the toner 10 reaches the separation distance 250 μm between the supply roller 5 and the developing roller 4 is expressed by the equation ( 13) to −1.6 kV is applied to the toner 10 layer. In this embodiment, since the voltage applied to the supply roller 5 is −1.0 kV, the layer thickness of the toner 10 is in direct contact with the developing roller 4 when −2.6 kV is applied to the auxiliary supply roller 6. Become thick. In order to avoid this, the limit voltage value _{Vout_limit} , which is the upper limit value of the applied voltage of the auxiliary supply roller constant current power supply 256, is set to _-2.5 kV.

When the thickness _{dt of the} toner layer formed on the surface of the supply roller 5 increases and comes into contact with the developing roller 4, excessive toner is supplied to the developing roller 4, causing a background stain during printing. It is thought that it becomes. As described above, the image forming apparatus according to the present embodiment provides an appropriate upper limit value for the applied voltage of the auxiliary supply roller constant current power supply 256 to eliminate these disadvantages. A printing test conducted to confirm this effect will be described below.

Results of performing a print evaluation test on _blurring and scumming using the image forming apparatus according to the present embodiment employing the auxiliary supply roller constant current power supply 256 (FIG. 13) in which the limit voltage value Vout_limit is set to _−2.5 kV. Will be described in comparison with the same results obtained using the image forming apparatus of the first embodiment that employs the auxiliary supply roller constant current power source 56 (FIG. 4) in which no limit voltage value is set. Since the test was performed under exactly the same test conditions as the print evaluation test performed in the first embodiment, the description of the test conditions here is omitted.

  For evaluation of background stain, 100 sheets were continuously printed at 0% duty and recording paper printed every 20 printed sheets was set to level 10 when there was no background stain. As the occupying ratio of background stains was less than 0.5%, less than 1.0%, and so on, it was judged as level 9, level 8, and so on. Level 8 or higher is a good image range.

  FIG. 18 is a graph showing the evaluation result of the blur, and FIG. 19 is a graph showing the evaluation result of the background stain. Note that the level indicated by a dotted line in FIGS. 18 and 19 indicates a pass / fail judgment level.

  As shown in FIG. 18, in the blur evaluation, the image forming apparatus of the present application, as in the case of the image forming apparatus of the first embodiment, obtained a good result in which no blur occurred in the experimental range. On the other hand, as shown in FIG. 19, in the scumming evaluation, the image forming apparatus according to the first embodiment has scumming from around 40 sheets, whereas the image forming of the present embodiment is performed. In the apparatus, a good result was obtained that no scumming occurred in the range of the experiment.

  Here, as illustrated in FIG. 1 of the first embodiment, the description has been made assuming a developing device in which the developing roller 4 and the supply roller 5 are separated from each other. However, a modification of the first embodiment is described. As shown in FIG. 11, the same evaluation result can be obtained even in the developing device arranged with the developing roller 4 and the supply roller 5 in contact with each other.

  As described above, according to the image forming apparatus of the present embodiment, as with the apparatus of the first embodiment, it is possible to suppress the blurring phenomenon during printing due to insufficient toner supply regardless of time, It is possible to prevent scumming during printing due to excessive toner supply.

Embodiment 3 FIG.
20 is a schematic configuration diagram showing each part of the developing device according to the third embodiment and the power supply wiring of the transfer roller 18 according to the present invention, and FIG. 21 is a main part of an image forming apparatus including the developing device according to the third embodiment. It is a block diagram of a control system.

  The image forming apparatus according to the present embodiment that employs this developing device is mainly different from the image forming apparatus according to the second embodiment described above in that supply as an AC voltage generating unit that applies an AC constant voltage to the supply roller 5 is performed. The roller constant voltage AC power source 355 is provided. Therefore, in the image forming apparatus according to the present embodiment, the same reference numerals are given to portions common to the image forming apparatus 110 (FIG. 1) of the first embodiment and the image forming apparatus of the second embodiment. Alternatively, the drawings are omitted and the description is omitted, and different points are mainly described. The main part configuration of the image forming apparatus according to the present embodiment is the same as that of the main part of the image forming apparatus 110 according to the first embodiment shown in FIG. 1 except for the control system described above. refer.

  The supply roller constant voltage AC power source 355 applies a rectangular wave AC voltage changing at a frequency of 2 kHz between the two voltages of −300 ± 300 V to the supply roller 5, and the auxiliary supply roller constant current power source 256 is configured as described above. As described in the second embodiment, after setting −2.5 kV as the upper limit value of the applied voltage, a predetermined constant current (direction shown in FIG. 20) is supplied to the auxiliary supply roller 6.

  When the voltage applied to the supply roller 5 is a DC voltage, there are many charged toners on the supply roller 5, and therefore when the toner 10 is aggregated, the uncharged toner 10 is also supplied to the developing roller 4. May end up. Therefore, when an AC voltage is applied to the supply roller 5, the toner 10 supplied between the developing roller 4 and the supply roller 5 is reciprocated, and the aggregation state of the toner aggregated during this time is released, and the supply roller 5 is released. The uncharged toner 10 aggregated above can be prevented from moving to the developing roller 4.

  When toner that is not properly charged is generated on the developing roller 4, the toner adheres to the surface of the photosensitive drum 1 other than the region where the electrostatic latent image is formed and the toner is to be adhered. A so-called “fogging” phenomenon occurs, and an image defect may occur during printing. As described above, the image forming apparatus according to the present embodiment suppresses the toner charged to the opposite polarity from moving to the developing roller 4 to eliminate these disadvantages. A printing test conducted to confirm this effect will be described below.

  As a result of performing a print evaluation test on blur and fog using the image forming apparatus of the present embodiment employing the above-described supply roller constant voltage AC power source 355, a DC supply roller constant voltage power source 55 (FIG. 4) is provided. This will be described in comparison with the results obtained using the image forming apparatus of the first embodiment. Since the test was performed under exactly the same test conditions as the print evaluation test performed in the first embodiment, the description of the test conditions here is omitted.

As the evaluation of fogging, print the white paper of A4 standard paper, paper every 20 sheets the number of printed sheets off the power supply of the image forming apparatus while passing through the photosensitive drum 1 is stopped forcibly device. In this state, the toner 10 remaining on the photosensitive drum 1 is peeled off by “Scotch tape” (manufactured by Sumitomo 3M), and the scotch tape to which the toner is attached and the unused scotch tape are pasted on the same paper and pasted The color difference ΔE * ab in the L * a * b * color system was measured using a spectrocolorimeter “CM-2600d” (manufactured by Konica Minolta) with the scotch tape. This evaluation was repeated 5 times to print 100 sheets. The evaluation criterion is that the color difference ΔE is 0.6 or less in a range where the print quality is good.

  FIG. 22 is a graph showing the evaluation result of blur, and FIG. 23 is the result of the color difference ΔE of fog evaluation. The level indicated by the dotted line in FIGS. 22 and 23 indicates the pass / fail judgment level. In the case of the blur evaluation in FIG. 22, the color difference is less than the dotted line level, and in the case of the fog evaluation in FIG. When ΔE is larger than 0.6, it is determined that the image is defective.

  As shown in FIG. 22, in the blur evaluation, the image forming apparatus according to the present application, as in the case of the image forming apparatus according to the first embodiment, obtained a good result in which no blur occurred in the experimental range. On the other hand, as shown in FIG. 23, in the fog evaluation, the image forming apparatus of the present embodiment adopting the supply roller constant voltage AC power source 355 is provided with a DC supply roller constant voltage power source 55 (FIG. 4). It was proved that better results were obtained than the image forming apparatus of Form 1.

  As described above, according to the image forming apparatus of the present embodiment, as with the apparatus of the first embodiment, it is possible to suppress the blurring phenomenon during printing due to insufficient toner supply regardless of time, Image defects during printing due to fogging can be suppressed.

  In each of the above-described embodiments, the image forming apparatus has been described by taking a monochrome printer having one developing device as an example. However, the present invention is not limited to this, and a color image forming apparatus having a plurality of developing devices. It is also applicable to. It can also be used for an MFP (Multi Function Printer), a facsimile, a copying machine, and the like.

  DESCRIPTION OF SYMBOLS 1 Photosensitive drum, 2 Charging roller, 3 LED head, 4 Developing roller, 5 Supply roller, 6 Auxiliary supply roller, 7 Layer formation blade, 8 Toner collection brush roller, 9 Toner collection brush flicker, 10 Toner, 11 Toner cartridge , 12 Cleaning blade, 13 Shutter, 14 Stirring bar, 15 Toner remaining amount detection bar, 16 Supply layer regulating blade, 17 Recording paper, 18 Transfer roller, 19 Fixing device, 20a-20e Conveying roller, 21 Stacker unit, 22 Toner storage Section, 23 paper transport motor, 24 drive motor, 25 drive transmission section, 30 print control section, 31 interface control section, 32 reception memory, 33 image data editing memory, 34 operation section, 35 sensor group, 41 high power Power supply control unit, 42 shutter drive control unit, 43 head drive control unit, 44 fixing control unit, 45 transport motor control unit, 46 drive control unit, 52 charging constant voltage power source, 54 developing roller constant voltage power source, 55 supply roller constant voltage Power supply, 56 Auxiliary supply roller constant current power supply, 57 Layer forming blade constant voltage power supply, 58 Toner recovery constant voltage power supply, 60 Roller, 68 Transfer constant voltage power supply, 100 Developing device, 110 Image forming device, 256 Auxiliary supply roller constant current power supply 355 Supply roller constant voltage AC power supply.

Claims (12)

An electrostatic latent image carrier on which a latent image is formed;
A developer carrier for developing the latent image formed on the electrostatic latent image carrier;
A developer supply body that is disposed vertically below the developer carrier and supplies the developer to the developer carrier;
A developer auxiliary supply body that is disposed vertically below the developer supply body, and that forms a nip in contact with the developer supply body to supply the developer to the developer supply body;
A developer container that forms an interface extending in the horizontal direction with the developer in a region vertically below the developer supply body and including the nip in the horizontal direction;
Constant current generating means for supplying a constant current to the developer auxiliary supply body ;
And a constant voltage generating means for applying a constant voltage to the developer supply body . It said developer carrying member and the developing agent supplying body is characterized in that spaced claim 1 Symbol mounting of the developing device. The developer carrier and the developer according to claim 1 Symbol mounting of the developing device and the supply body, characterized in that it abuts. It said constant current generating means includes a developing device according to any one of claims 1 to 3, characterized in that the upper limit of the applied voltage applied to the developer auxiliary supply member is defined. The developing device according to claim 4 , wherein the upper limit value of the applied voltage is set so that a developer layer formed on the developer supply body does not contact the developer carrier. The relationship between the resistance value Rdv [Ω] of the developer carrying member and the resistance value Rsp [Ω] of the developer supply member is Rdv> Rsp × 10 ³
The developing device according to claim 3, wherein: The relationship between the resistance value Rsp [Ω] of the developer supply body and the resistance value Rsub [Ω] of the developer auxiliary supply body is Rsp> Rsub
The developing device according to claim 6, wherein: The latent electrostatic image bearing member, a developing device according to any one of claims 1 to 7, characterized in that a photosensitive drum. The developer carrier, the developer supply member, and a developing device according to any one of claims 1 to 8 wherein the developer auxiliary supply body is characterized by a roller.   The developing device according to claim 9, wherein the developer auxiliary supply body rotates in a direction opposite to the developer supply body. 11. The difference (V6-V5) between the peripheral speed V5 of the developer supply body and the peripheral speed V6 of the developer auxiliary supply body is within ± 10% of the peripheral speed V6. Development device. An image forming apparatus comprising the developing device according to claim 1 .

Images