JP5960516B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using electrophotography, and a developing device for the same.

  2. Description of the Related Art Conventionally, a developing device used in an image forming apparatus is known in which toner accumulated in a lower portion of a developing device is pumped up by an application roller and a supply roller and supplied to the developing roller. In the developing device disclosed in Patent Document 1, the surfaces (outer peripheral surfaces) of the application roller and the supply roller are in contact with each other while moving in opposite directions, and the surfaces of the supply roller and the development roller are in contact with each other while moving in the opposite directions. . Thereby, the toner is frictionally charged at the contact portion between the rollers and moved to the developing roller.

JP-A-5-27567

  However, in the configuration in which the toner is moved while being frictionally charged as described above, the toner is easily damaged, which causes a decrease in chargeability and fluidity of the toner. For this reason, fogging and blurring are likely to occur, and there has been a problem that image quality deteriorates, for example, during continuous printing.

  SUMMARY An advantage of some aspects of the invention is that it provides a developing device and an image forming apparatus capable of preventing a reduction in image quality.

The developing device of the present invention is provided with a developer carrying member that develops an electrostatic latent image by attaching a developer to the electrostatic latent image carrying member, and a developer carrier that is provided below the developer carrying member. A first supply member that supplies the first supply member, a second supply member that is provided below the first supply member, and that supplies the developer to the first supply member, and is disposed so as to contact the first supply member And a conductive film that is applied with a voltage and assists charging of the developer carried on the first supply member . In the facing portion between the developer carrier and the first supply member, the surface of the developer carrier and the surface of the first supply member move in the same direction at substantially the same speed ,
In the facing portion between the first supply member and the second supply member, the surface of the first supply member and the surface of the second supply member move in the same direction at substantially the same speed .

An image forming apparatus of the present invention includes the above developing device. The image forming apparatus of the present invention also includes the above-described developing device and a detecting unit for detecting the upper surface level of the developer held in the developer holding unit.

  According to the present invention, it is possible to suppress the damage to the developer, thereby preventing the deterioration of the image quality.

1 is a cross-sectional view illustrating a configuration of a developing device according to a first embodiment of the present invention. FIG. 4 is a schematic diagram (A) showing a nip amount and a gap amount between rollers of the developing device in the first embodiment, and a schematic diagram (B) for explaining a nip amount between a blade and a roller. FIG. 3 is a schematic diagram illustrating a configuration of a drive transmission unit of the developing device according to the first embodiment. FIG. 6 is a perspective view illustrating a shape of an end portion of a toner remaining amount detection bar in the first embodiment. FIG. 3 is a diagram illustrating a configuration of a toner remaining amount detecting mechanism including a toner remaining amount detecting bar in the first embodiment. FIG. 6 is a diagram illustrating an operation of a toner remaining amount detection mechanism in the first embodiment. 1 is a diagram illustrating a basic configuration of an image forming apparatus according to a first embodiment. 2 is a block diagram illustrating a control system of the image forming apparatus according to the first embodiment. FIG. It is a figure which shows the cross-section of the developing roller in 1st Embodiment. It is the front view (A) and side view (B) for demonstrating the measuring method of the resistance value of the developing roller in 1st Embodiment. FIG. 3 is a diagram illustrating a cross-sectional structure of a toner collection roller according to the first embodiment. It is a schematic diagram for demonstrating the rotation direction of the developing roller in the 1st Embodiment, a supply roller, and an auxiliary supply roller. FIG. 6 is a schematic diagram illustrating a state where the toner level is higher than the vertex of the rotation locus of the remaining toner amount detection bar in the first embodiment. FIG. 6 is a schematic diagram illustrating a state where the toner level is lower than the rotation center of the remaining toner amount detection bar in the first embodiment. FIG. 6 is a schematic diagram illustrating a relationship between a toner level and a light reception time of reflected light by a light receiving element in the first embodiment. 6 is a flowchart illustrating toner level control according to the first embodiment. It is a figure which shows the structure of the image development apparatus of a comparative example. It is a figure which shows the fog evaluation result at the time of performing continuous printing using the image development apparatus of 1st Embodiment and a comparative example. It is a figure which shows the evaluation result of the blur at the time of performing continuous printing using the image development apparatus of 1st Embodiment and a comparative example. It is sectional drawing which shows the structure of the developing device in the 2nd Embodiment of this invention. It is a schematic diagram which shows the nip amount and gap amount between each roller of the developing device in 2nd Embodiment. FIG. 10 is a diagram illustrating a cross-sectional configuration of a toner supply roller according to a second embodiment. It is a figure which shows the fog evaluation result at the time of performing continuous printing using the image development apparatus of 1st Embodiment and 2nd Embodiment. It is a figure which shows the evaluation result of the blur at the time of performing continuous printing using the image development apparatus of 1st Embodiment and 2nd Embodiment. It is a figure which shows the fog evaluation result at the time of performing continuous printing in a low-temperature, low-humidity environment using the developing device of 1st Embodiment and 2nd Embodiment. It is a figure which shows the evaluation result of the blur at the time of performing continuous printing in a low-temperature, low-humidity environment using the developing device of 1st Embodiment and 2nd Embodiment. It is a figure which shows the evaluation result of the stain | pollution | contamination at the time of performing continuous printing in a low-temperature low-humidity environment using the image development apparatus of 1st Embodiment and 2nd Embodiment. It is a figure which shows 2by2 pattern used for evaluation of FIG.

First embodiment.
<Configuration of developing device>
First, the configuration of the developing device 100 according to the first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view illustrating a configuration of the developing device 100. A developing device (also referred to as a process unit) 100 includes a casing 101 as a casing and a toner replenishing unit 12 as a developer replenishing unit for supplying toner (developer) to the casing 101. In the casing 101, a photosensitive drum 3 as an electrostatic latent image carrier is provided.

  The developing device 100 has a “drum-integrated structure” in which the photosensitive drum 3 is built, but is not limited to such a structure. A portion that plays a role of developing the electrostatic latent image formed on the electrostatic latent image carrier (for example, the photosensitive drum 3) is referred to as a developing device. Further, the developing device 100 may have a form that does not include the toner replenishing unit 12.

  A charging roller 4 as a charging member for uniformly charging the surface of the photosensitive drum 3 so as to face the surface of the photosensitive drum 3 and the electrostatic latent image formed on the surface of the photosensitive drum 3 are developed. A developing roller 1 as a developer carrying member and a cleaning blade 9 as a cleaning member for scraping off toner remaining on the surface of the photosensitive drum 3 are disposed. The charging roller 4, the developing roller 1, and the cleaning blade 9 are arranged in this order along the rotation direction of the photosensitive drum 3 (counterclockwise direction in FIG. 1).

  Here, the charging roller 4 and the cleaning blade 9 are in contact with the surface of the photosensitive drum 3 from above. Further, the developing roller 1 is in contact with the surface of the photosensitive drum 3 from the obliquely lower side (left side in FIG. 1).

  The developing roller 1 rotates in a direction opposite to the photosensitive drum 3 (here, clockwise in the figure). That is, the developing roller 1 and the photosensitive drum 3 rotate so that the surfaces thereof move in the same direction at the opposing portions. The charging roller 4 also rotates in the opposite direction to the photosensitive drum 3 (here, clockwise in the figure).

  A developing blade 6 as a layer regulating member is disposed so as to face the developing roller 1. The developing blade 6 regulates the thickness of a thin toner layer (described later) formed on the surface of the developing roller 1.

  Further, a toner supply roller 2 as a first supply member is provided so as to face the developing roller 1 in a non-contact manner. The toner supply roller 2 is located below the developing roller 1 (here, obliquely below). In the rotation direction of the developing roller 1, the toner supply roller 2 is positioned upstream of the developing blade 6 and downstream of the photosensitive drum 3.

  The toner supply roller 2 rotates in a direction opposite to the developing roller 1 (here, counterclockwise in the figure). That is, the toner supply roller 2 and the developing roller 1 rotate so that the surfaces thereof move in the same direction at the mutually facing portions.

  An auxiliary supply roller 10 as a second supply member is provided so as to contact the toner supply roller 2. The auxiliary supply roller 10 is located below the toner supply roller 2. The auxiliary supply roller 10 rotates in the opposite direction to the toner supply roller 2 (here, clockwise in the figure). That is, the auxiliary supply roller 10 and the toner supply roller 2 rotate so that the surfaces thereof move in the same direction at the opposing portions.

  The auxiliary supply roller 10 is disposed at a lower portion of the casing 101, and toner as a developer supplied to the auxiliary supply roller 10 is accumulated at the lower portion of the casing 101. A lower portion of the casing 101 is referred to as a developer holding portion 102 that holds the toner (developer) 11.

  The toner replenishing portion 12 described above is for replenishing the toner 11 to the developer holding portion 102 in the casing 101, and is disposed on the upper portion of the casing 101. The toner replenishing unit 12 is a container (for example, a toner cartridge) that stores the toner 11 therein. A toner supply port 12b as a developer supply port for supplying the toner 11 into the casing 101 (developer holding unit 102) is formed below the toner supply unit 12, and the toner supply port 12b is opened and closed. A shutter 12a is provided for this purpose.

  Further, a toner as a developer collecting member that collects toner remaining on the surface of the developing roller 1 (toner that has not been used for developing the electrostatic latent image on the photosensitive drum 3) so as to face the developing roller 1. A collection roller 5 is arranged. In the rotation direction of the developing roller 1, the toner collection roller 5 is located upstream of the toner supply roller 2 and downstream of the photosensitive drum 3.

  A toner removing blade 8 as a developer removing member for scraping off the toner from the surface of the toner collecting roller 5 is disposed so as to face the toner collecting roller 5. The toner removing blade 8 is composed of, for example, an elastic body 8a such as urethane rubber and a fixing plate 8b made of, for example, metal that holds the elastic body 8a. The fixed plate 8b is fixed to the inner surface of the casing 101.

  In addition, a regulation film 7 is provided as a charging auxiliary member for thinning and charging the toner adhering to the surface of the toner supply roller 2 so as to face the toner supply roller 2. The restriction film 7 includes a conductive film 7a provided so as to be in contact with the surface of the toner supply roller 2, and a metal support frame 7b that holds the film 7a. The film 7 a has a long shape that is long in the axial direction of the toner supply roller 2, one end (fixed end) in the width direction is fixed to the support frame 7 b, and the other end (free end) is on the surface of the toner supply roller 2. It touches.

  The restriction film 7 is disposed on the upstream side of the facing portion between the toner supply roller 2 and the developing roller 1 in the rotation direction of the toner supply roller 2.

  Stirring members 13 a, 13 b, 13 c, and 13 d that stir and transport the toner 11 are provided in the lower portion of the casing 101 (that is, the developer holding unit 102). The stirring member is, for example, a metal bar having a crank shape, and a plurality (four in this case) of the stirring members 13 a, 13 b, 13 c, and 13 d have their axial directions parallel to the axial direction of the developing roller 1. It is arranged to be.

  Further, in order to detect the toner level (upper surface level of the toner 11) 11a in the developer holding unit 102 of the casing 101, a toner remaining amount detection bar 14 as a detection unit is provided. The toner remaining amount detection bar 14 is a metal bar having a crank shape, which will be described later in detail.

  FIG. 2A is a schematic diagram showing a nip amount and a gap amount between the rollers of the developing device 100. As shown in FIG. 2A, the developing roller 1 and the toner supply roller 2 are separated from each other, and the gap d1 is 0.25 mm. The toner supply roller 2 and the regulating film 7 are in contact with each other, and the nip amount d2 is 1.0 mm.

  Further, the developing roller 1 and the toner collecting roller 5 are in contact with each other, and the nip amount d3 is 0.5 mm. Further, the toner collecting roller 5 and the toner removing blade 8 are in contact with each other, and the nip amount d4 is 0.5 mm. The toner supply roller 2 and the auxiliary supply roller 10 are in contact with each other, and the nip amount d5 is 0.5 mm.

  The nip amount between the rollers is a value obtained by subtracting the distance between the centers of the rollers from the sum of the radii of the two rollers. Further, as schematically shown in FIG. 2B, the nip amount between the blade or film (indicated by symbol B) and the roller (indicated by symbol R) is such that the blade (or film) B contacts the roller R. This is a value e obtained by subtracting the distance d between the previous position (that is, before elastic deformation) and the center c of the roller from the radius r of the roller.

  As shown in FIG. 2A, the developing roller 1 and the toner supply roller 2 rotate so that the moving directions of the surfaces are the same direction (α direction) at the opposing portions. Further, the toner supply roller 2 and the auxiliary supply roller 10 rotate so that the moving direction of the surface is the same direction (β direction) in the nip portion. This is for suppressing damage to the toner 11 in the facing portion and the nip portion.

  FIG. 3 is a schematic diagram illustrating a configuration of the drive transmission unit 38 of the developing device 100. The photosensitive drum gear 3G, the developing roller gear 1G, the toner supply roller gear 2G, and the auxiliary supply roller gear are respectively provided on the shaft portions of the photosensitive drum 3, the developing roller 1, the toner supply roller 2, the auxiliary supply roller 10, and the toner collection roller 5. 10G and a collection roller gear 5G are attached.

  A motor gear 27G attached to the drive motor 27 (FIG. 8) meshes with the photosensitive drum gear 3G. The photosensitive drum gear 3G meshes with the developing roller gear 1G. The developing roller gear 1G meshes with the idle gears 38a and 38c. The idle gear 38a meshes with the idle gear 38b, and the idle gear 38b meshes with the toner supply roller gear 2G. The toner supply roller gear 2G meshes with the auxiliary supply roller gear 10G. Further, the idle gear 38c meshes with the idle gear 38d, and the idle gear 38d meshes with the collection roller gear 5G.

  With this configuration, the rotation of the drive motor 27 is transmitted to the photosensitive drum 3, the developing roller 1, the toner supply roller 2, the auxiliary supply roller 10, and the toner recovery roller 5, which are indicated by arrows, respectively. Rotate in the direction.

  Further, the agitating members 13a, 13b, 13c, and 13d shown in FIG. 1 are further transmitted with a driving force from the drive transmitting unit 38 via a gear train, and rotate, for example, clockwise as shown in FIG.

  FIG. 4 is a perspective view showing the shape of the end of the toner remaining amount detection bar 14 shown in FIG. FIG. 5 is a diagram showing the configuration of a toner remaining amount detecting mechanism (detecting means) 200 including the toner remaining amount detecting bar 14. The toner remaining amount detection bar 14 includes a shaft portion 14a positioned at an end portion in the rotation axis direction, a radius portion 14b bent from the shaft portion 14a and extending in the rotation radius direction, and rotation of the toner remaining amount detection bar 14. A central portion 14c located in the axial center and extending in the rotational axis direction.

  A shaft portion 14 a of the toner remaining amount detection bar 14 is fitted into a gear 28 that rotates the toner remaining amount detection bar 14. Note that the remaining toner amount detection bar 14 is free for the rotation of the gear 28.

  A contact portion 28 a that contacts the radius portion 14 b of the toner remaining amount detection bar 14 is attached to the gear 28. The contact portion 28 a has, for example, an L-shaped cross section, and has a predetermined length in the direction of the rotation axis of the toner remaining amount detection bar 14.

  In the gear 28, the driving force of the driving motor 27 (FIG. 8) is transmitted by the drive transmission unit 38 shown in FIG. 3 and a gear train (not shown). As a result, the gear 28 rotates at a constant speed in the direction indicated by the arrow in FIG. 4 along with the rotation of the photosensitive drum 3. When the gear 28 rotates, the contact portion 28 a urges the remaining toner amount detection bar 14 in the rotation direction, and the remaining toner amount detection bar 14 rotates in the same direction as the gear 28.

  The rotational speed of the gear 28 is set slower than the speed at which the toner remaining amount detection bar 14 rotates downward (drops) by its own weight from the top of the rotation locus.

  As shown in FIG. 5, of the shaft portions 14 a at both ends of the toner remaining amount detection bar 14, the shaft portion 14 a on the opposite side to the side on which the gear 28 is attached protrudes to the outside of the developing device 100. A reflection plate 29 as a member to be detected is fixed to the tip of the shaft portion 14a that protrudes outside the developing device 100. The reflecting plate 29 rotates with the rotation of the remaining toner amount detection bar 14.

  The reflecting plate 29 is preferably capable of reflecting laser light, and a mirror is used in the present embodiment. The main body of the image forming apparatus 300, which will be described later, includes a light emitting element 30 that emits laser light 30a and a light receiving element 31 that receives reflected light 31a emitted from the light emitting element 30 and reflected by the reflecting plate 29. Is provided.

  FIG. 6 is a view of the remaining toner amount detection mechanism (detection means) 200 shown in FIG. As shown in FIG. 6, the light emitting element 30 and the light receiving element 31 are only in a state where the reflecting plate 29 passes through the intermediate point 29M when the reflecting plate 29 moves from the top 29T of the rotation locus to the bottom 29B. It arrange | positions so that the light receiving element 31 can receive the reflected light 31a of the light 30a radiate | emitted from.

<Configuration of image forming apparatus>
Next, the image forming apparatus 300 including the developing device 100 according to the first embodiment will be described. FIG. 7 is a diagram illustrating a basic configuration of the image forming apparatus 300. Here, the image forming apparatus 300 is configured as an electrophotographic printer that forms a single-color (monochrome) image. The image forming apparatus 300 includes a medium accommodating unit 302 (for example, a tray) that accommodates a medium 18 such as printing paper at a lower portion of the main body 301.

  A conveyance roller 19a as a sheet feeding unit is disposed so as to be in contact with the surface of the medium stored in the medium storage unit 302. The transport roller 19a is rotationally driven by a transport motor 26 (FIG. 8) to be described later, and feeds the medium 18 stored in the medium storage unit 302 one by one.

  Adjacent to the conveyance roller 19a, a conveyance roller pair 19b is disposed as a conveyance unit that further conveys the medium 18 fed from the medium storage unit 302 by the conveyance roller 19a. Here, the conveyance roller pair 19b conveys the medium 18 fed out from the medium storage unit 302 obliquely upward (upper right direction in the figure).

  The developing device 100 described above is disposed on the downstream side of the conveyance roller pair 19b in the conveyance direction of the medium 18. A transfer roller 16 as a transfer member is disposed so as to face the photosensitive drum 3 of the developing device 100 with the medium 18 interposed therebetween. The transfer roller 16 transfers a toner image (developer image) formed on the surface of the photosensitive drum 3 to the medium 18.

  Further, an LED head 15 as an exposure device is disposed on the side opposite to the transfer roller 16 with respect to the photosensitive drum 3 of the developing device 100. The LED head 15 exposes the photosensitive layer on the surface of the photosensitive drum 3 according to image data to form an electrostatic latent image.

  A fixing device 17 as a fixing unit is disposed on the downstream side of the developing device 100 in the conveyance direction of the medium 18. The fixing device 17 fixes the toner image on the medium 18 by pressurizing and heating the medium 18 on which the toner image is transferred. The fixing device 17 detects a heat source (heater) and a temperature for melting the toner. Etc.

  On the downstream side of the fixing device 17 in the conveyance direction of the medium 18, a conveyance roller pair 19 c is disposed as a discharge unit that discharges the medium 18 on which the toner image is fixed to the outside of the apparatus. In addition, a stacker unit 19d on which the medium 18 discharged by the conveying roller pair 19c is placed is provided on the upper portion of the image forming apparatus 300.

<Control system>
FIG. 8 is a block diagram illustrating a control system of the image forming apparatus 300. The print control unit 20 as a control unit that controls the entire operation of the image forming apparatus 300 includes a microprocessor, a ROM, a RAM, an input / output port, a timer, and the like. The print control unit 20 executes the image forming process by controlling the sequence of the image forming apparatus 300 based on the print data and control commands sent from the host apparatus 50 such as a personal computer.

  The interface (I / F) control unit 21 includes an interface connector, an interface IC, and the like. The interface (I / F) control unit 21 receives print data and control commands sent from the host device 50 and transfers them to the print control unit 20.

  The reception memory 22 temporarily records print data input from the host device 50 via the interface control unit 21. The image data editing memory 23 receives the print data recorded in the reception memory 22 and records image data generated by editing the print data, that is, image data.

  The operation unit 24 includes a display unit (for example, an LED) for displaying the state of the image forming apparatus 300, and an input unit (for example, a switch, a display unit, etc.) for inputting an operator instruction to the image forming apparatus 300. ).

  The sensor group 25 includes various sensors for monitoring the operating state of the image forming apparatus 300, such as a medium position detection sensor, a temperature / humidity sensor, a print density sensor, a toner remaining amount detection sensor, and the like.

  The timer 32 is a timer that measures the time for the light receiving element 31 to detect the reflected light 31 a emitted from the light emitting element 30 and reflected by the reflecting plate 29.

  The charging roller power supply 4 a applies a predetermined charging voltage to the charging roller 4 in order to uniformly charge the surface of the photosensitive drum 3 based on an instruction from the printing control unit 20. The developing roller power source 1 a applies a predetermined developing voltage to the developing roller 1 and also applies a predetermined voltage to the developing blade 6 in order to develop the electrostatic latent image on the photosensitive drum 3.

  The toner supply roller power source 2 a applies a predetermined voltage to the toner supply roller 2 in order to supply the toner 11 to the developing roller 1. The auxiliary supply roller power supply 10 a applies a predetermined voltage to the auxiliary supply roller 10 in order to supply toner to the toner supply roller 2 and charge the toner 11.

  The toner recovery roller power supply 5 a applies a predetermined voltage to the toner recovery roller 5 in order to recover the toner 11 from the developing roller 1. The regulating film power source 7 c applies a predetermined voltage to the regulating film 7 in order to charge the toner 11. The transfer roller power supply 16 a applies a predetermined transfer voltage to the transfer roller 16 in order to transfer the toner image on the photosensitive drum 3 to the medium 18.

  The charging roller power supply 4a, the developing roller power supply 1a, the toner supply roller power supply 2a, the auxiliary supply roller power supply 10a, the toner recovery roller power supply 5a, the regulating film power supply 7c, and the transfer roller power supply 16a The voltage to be applied can be changed by an instruction from the unit 20.

  The shutter drive control unit (replenishment control unit) 12 c controls the opening / closing operation of the shutter 12 a of the toner replenishment unit 12. The shutter drive control unit 12c detects the toner level 11a (FIG. 1) in the casing 101 by the toner remaining amount detecting mechanism 200, and when the remaining amount of toner in the casing 101 becomes low, opens the shutter 12a and supplies toner. Control for replenishing toner from the section 12 into the casing 101 is performed.

  The head drive control unit 15 a sends the image data recorded in the image data editing memory 23 to the LED head 15 and drives the LED head 15.

  The fixing controller 17 a applies a voltage to the heater of the fixing device 17 in order to fix the toner image transferred to the medium 18 to the medium 18. Specifically, the fixing control unit 17a reads the sensor output of the temperature sensor provided in the fixing device 17, energizes the heater based on the sensor output, and controls the fixing device 17 to maintain a constant temperature. I do.

  The transport motor control unit 26 a controls the transport motor 26 for transporting the medium 18 based on an instruction from the print control unit 20. Thereby, the medium 18 stored in the medium storage unit 302 is fed one by one to the transport path by the transport roller 19a, passed through the developing device 100 by the transport roller pair 19b, and discharged outside the apparatus by the transport roller pair 19c.

  The drive control unit 27 a controls the drive motor 27 for rotating the photosensitive drum 3. When the drive motor 27 rotates, the above-described drive transmission unit 38 causes the photosensitive drum 3, the developing roller 1, the toner supply roller 2, the auxiliary supply roller 10, the toner recovery roller 5, the stirring members 13a, 13b, 13c, and 13d and the toner. The remaining amount detection bar 14 rotates.

<Preferred configuration example of developing device>
Next, a preferred configuration example of the developing device 100 in the first embodiment will be described. The configuration example described here is also a condition of a printing test (FIGS. 18 and 19) described later.

  First, the toner 11 will be described. The toner 11 used here is a non-magnetic one-component negatively chargeable toner manufactured by a pulverization method and using a polyester resin as a binder (binder resin). The volume average particle diameter of the toner 11 is 5.7 μm, the circularity is 0.92, and the blow-off charge amount is −36 μC / g.

  For the measurement of the volume average particle diameter, “Coulter Multisizer II” manufactured by Beckman Coulter Inc. was used. The circularity was measured using a “flow type particle image analyzer FPIA-3000” manufactured by Sysmex Corporation.

  The blow-off charge amount was measured using a “powder charge amount measuring device TYPE TB-203” manufactured by Kyocera Corporation. In the measurement, 0.5 g of toner and 9.5 g of ferrite carrier (F-60) manufactured by Powdertech Co., Ltd. were mixed, stirred for 30 minutes, and then subjected to conditions of a blow pressure of 7.0 kPa and a suction pressure of -4.5 kPa. The saturation charge amount was measured with

  Next, each roller and blade will be described. FIG. 9 is a diagram showing a cross-sectional structure of the developing roller 1. The developing roller 1 has a conductive shaft (core metal) 33, an elastic layer 34 formed on the surface of the shaft 33, and a semiconductive resin film 35 coated on the surface of the elastic layer 34. ing. The elastic layer 34 can be formed of a general rubber material such as silicone rubber or urethane rubber. Here, the elastic layer 34 is formed of silicone rubber. As the semiconductive resin film 35, in consideration of the charge imparting property to the toner 11, an acrylic resin in which carbon black or the like is dispersed is used.

  The rubber hardness of the elastic layer 34 is suitably about 50 to 80 ° in terms of Asker C hardness. Here, the Asker C hardness is 60 °.

  The developing blade 6 is made of stainless steel (SUS) and has a plate thickness of, for example, 0.08 mm. Further, the contact portion of the developing blade 6 with the developing roller 1 is bent. Here, the radius of curvature R of the bent portion was 0.18 mm, and the linear pressure against the developing roller 1 was 35 gf / cm.

  The surface roughness and resistance value of the developing roller 1 are factors that determine the thickness of the toner layer formed on the developing roller 1 and the toner charge amount together with the conditions of the developing blade 6. Here, the ten-point average roughness Rz (JIS B0601-1994) of the surface of the developing roller 1 was set to 2 to 8 μm. The surface roughness was measured with “Surf Coder SEF3500” manufactured by Kosaka Laboratory. The stylus radius of the measuring device was 2 μm, the stylus pressure was 0.7 mN, and the stylus feed speed was 0.1 mm / sec.

Further, the resistance value of the developing roller 1 is preferably in the range of 1 × 10 ⁶ to 1 × 10 ⁹ Ω as measured including the elastic layer 34 and the semiconductive resin film 35. FIG. 10 is a front view (A) and a side view (B) for explaining a method of measuring the resistance value of the developing roller 1. As the measuring device 36 for the resistance value of the developing roller 1, “High Resistance Meter (4339B)” manufactured by Hewlett-Packard Co., Ltd. was used.

  A ball bearing 37 made of stainless steel (SUS) having a width of 2.0 mm and a diameter of 6.0 mm is brought into contact with the surface (outer peripheral surface) of the developing roller 1 with a force of 20 gf, and the shaft 33 and the roller surface (semiconductive resin film 35) are contacted. ) Was measured by the measuring device 36. The bearings 37 were provided at six locations in the axial direction of the developing roller 1 (from P1 to P6 shown in FIG. 10A), and measurement was performed while rotating the developing roller 1 at a speed of 50 rpm. From P1 to P6, measurements were made at a total of 600 points for each round of 100 points, and the average value was taken as the roller resistance value. The applied voltage to the developing roller 1 at this time was 100V.

  As the toner supply roller 2, an aluminum roller having an outer diameter of 12.5 mm was used. By performing surface processing so that the surface roughness (ten-point average roughness) Rz of the toner supply roller 2 is 1 μm or less, the releasability of the toner from the surface of the toner supply roller 2 (that is, the toner to the developing roller 1) (Easy to move).

  The auxiliary supply roller 10 is provided with a foam, specifically a silicone rubber sponge, on the surface of a conductive shaft (core metal). The silicone rubber sponge is obtained by molding an unvulcanized silicone rubber compound by a method such as extrusion and vulcanizing and foaming by heating.

  The silicone rubber compound is obtained by adding a reinforcing silica filler, a vulcanizing agent necessary for vulcanization and a foaming agent, to various raw rubbers such as dimethyl silicone raw rubber and methylphenyl silicone raw rubber. As the foaming agent, an inorganic foaming agent such as sodium bicarbonate or an organic foaming agent such as ADCA is used. In addition, in order to impart semiconductivity, acetylene black, carbon black or the like is added.

  Here, the diameter of the cell of the auxiliary supply roller 10 (fine holes generated by foaming) was 200 to 500 μm, and the Asker F hardness was in the range of 50 to 80 degrees. The hardness of the auxiliary supply roller 10 can be adjusted by the amount of vulcanizing agent added.

The resistance value of the auxiliary supply roller 10 is desirably in the range of 1 × 10 ⁷ to 1 × 10 ¹⁰ Ω with respect to the applied voltage of 100 V by the measurement method described with reference to FIG. Here, it was 1 × 10 ⁹ Ω. When the resistance value of the auxiliary supply roller 10 is lower than the above range, the current value between the auxiliary supply roller 10 and the toner supply roller 2 becomes large, and it becomes difficult to apply a desired voltage.

  As described with reference to FIG. 1, the auxiliary supply roller 10 contacts the toner supply roller 2 and rotates in the opposite direction to the toner supply roller 2, but the toner is damaged due to friction at the contact portion. The auxiliary supply roller 10 and the toner supply roller 2 rotate so that the surfaces thereof move in the same direction at substantially the same speed at the mutual contact portion.

  Here, “substantially the same speed” means the movement speed V10 of the surface of the auxiliary supply roller 10 and the movement speed V2 of the surface of the toner supply roller 2 at the contact portion between the auxiliary supply roller 10 and the toner supply roller 2. The absolute value of the difference (V10−V2) is within 10% of V10.

  Further, the damage of the toner 11 is, for example, peeling of the external additive from the toner base particles or embedding of the external additive in the toner base particles, and the like. This causes a decrease in sex.

  As shown in FIG. 2A, the regulating film 7 has one end (fixed end) of a conductive film 7a attached to a metal support frame 7b, and the other end (free end) of the film 7a is a toner. The surface of the supply roller 2 is brought into contact.

  In the rotation direction of the toner supply roller 2, the contact position between the toner supply roller 2 and the film 7a is downstream of the contact portion between the toner supply roller 2 and the auxiliary supply roller 10, and the toner supply roller 2 and the developing roller. 1 is upstream of the portion facing 1. As the film 7 a, for example, a film-shaped resin such as a urethane film, a PET film, or a PE film, in which a conductive material such as carbon black is kneaded, or urethane rubber that has been imparted with conductivity can be used.

  The film 7a has a function of leveling the surface of the toner 11 supplied from the auxiliary supply roller 10 onto the toner supply roller 2 and preventing the toner 11 from being conveyed to the supply unit to the developing roller 1 without being charged. . In order to minimize damage caused by friction on the toner 11, the charge amount and the layer thickness of the toner 11 are controlled by applying a voltage while lightly contacting the film 7 a with the surface of the toner supply roller 2.

  Here, “light contact” means that the drive load torque applied to the drive motor 27 when the film 7 a is not in contact with the toner supply roller 2 is Ta, and the drive motor when the film 7 a is in contact with the toner supply roller 2. 27, when the drive load torque applied to Tb is Tb, (Tb−Ta) is 5% or less of Ta. Within this range, damage to the toner 11 due to friction can be suppressed.

  Here, “New Light Film SCB” manufactured by Eiwa Co., Ltd. was used as the film 7a, and the thickness of the film 7a was 0.39 mm. The linear pressure at the contact portion between the toner supply roller 2 and the film 7a was about 30 gf / cm. In this case, (Tb-Ta) was about 4.8% of Ta (that is, light contact).

FIG. 11 is a diagram showing a cross-sectional structure of the toner collection roller 5. The toner collecting roller 5 includes a metal shaft (core metal) 5 s , a foam layer 5 b such as urethane rubber formed on the surface of the shaft 5 s , and a nitrile coated on the surface of the foam layer 5 b. And an elastic layer 5c made of rubber or the like. The surface of the elastic layer 5c has a predetermined surface roughness.

Here, the outer diameter of the shaft 5 s was 6 mm, the thickness of the foam layer 5 b was 2 mm, and the thickness of the elastic layer 5 c was 1 mm. The resistance value of the toner collecting roller 5 including the shaft 5s , the foam 5b, and the elastic layer 5c is 1 × 10 7 Ω · cm to 1 × 10 8 Ω · cm. The nip amount d3 (FIG. 2A) between the toner recovery roller 5 and the developing roller 1 was 0.5 mm.

The toner removing blade 8 is configured by fixing an elastic body 8a made of urethane rubber having a thickness of 2 mm and a resistance value of 1 × 10 ⁶ Ω · cm to 1 × 10 ⁸ Ω · cm to a metal fixing plate 8b. . The nip amount d4 between the toner collecting roller 5 and the toner removing blade 8 was 0.5 mm.

<Operation of Image Forming Apparatus>
Next, an image forming operation of the image forming apparatus 300 of the present embodiment will be described with reference to FIGS. 1 to 3 and FIGS.

  When a print command is input from a host device 50 such as a personal computer, the print control unit 20 of the image forming apparatus 300 controls the drive control unit 27a to drive the drive motor 27, and the photosensitive drum 3 is shown in FIG. It is rotated at a constant peripheral speed in the direction of the arrow shown. The driving force of the drive motor 27 is further transmitted by a drive transmission unit 38 (FIG. 3), and the developing roller 1, the toner supply roller 2, the toner collection roller 5, and the auxiliary supply roller 10 are rotated in the directions of arrows.

The rotation of the drive motor 27 via a gear train, not the drive transmission unit 38, and shown, 撹拌部material 13a, 13b, 13c, is transmitted to 13d and the toner remaining amount detection bar 14. Thus, 撹拌部material 13a, 13b, 13c, 13d and the toner remaining amount detection bar 14 is rotated in the arrow direction shown in FIG.

  The charging roller 4 is driven to rotate in a state where a charging voltage (direct current) is applied from the charging roller power source 4 a and is in pressure contact with the surface of the photosensitive drum 3. As a result, the surface of the photosensitive drum 3 is uniformly charged.

  Next, under the control of the head drive controller 15a, the LED head 15 emits light based on the image data, and the surface of the photosensitive drum 3 is exposed to form an electrostatic latent image.

  The electrostatic latent image formed on the surface of the photosensitive drum 3 is developed with toner by the developing roller 1, and a toner image (developer image) is formed on the surface of the photosensitive drum 3.

On the other hand, the medium 18 is conveyed one by one from the medium accommodating unit 302 of the image forming apparatus 300 by the conveying roller pair 19a and 19b, and reaches the transfer unit between the photosensitive drum 3 and the transfer roller 16 of the developing device 100. .

  The transfer roller 16 is applied with a transfer voltage by the transfer roller power supply 16 a, and the toner image formed on the surface of the photosensitive drum 3 is transferred to the medium 18.

  The medium 18 onto which the toner image has been transferred is conveyed to the fixing device 17. In the fixing device 17, heat and pressure are applied to the medium 18, and the toner 11 melts and penetrates between the fibers of the medium 18 to be fixed. The medium 18 on which the toner image is fixed is sent to the outside of the image forming apparatus 300 by the transport roller 19c and is stacked on the stacker unit 19d.

  In addition, a small amount of toner 11 may remain on the surface of the photosensitive drum 3 after the toner image is transferred. This residual toner 11 is written and removed by the cleaning blade 9. In this way, the photosensitive drum 3 is repeatedly used.

<Operation of developing device>
Next, the operation of the developing device 100 will be described in detail with reference to FIGS. 1 and 2. The toner 11 replenished from the toner replenishing unit 12 is accumulated in a lower portion (developer holding unit 102) of the casing 101 of the developing device 100. Further, when the photosensitive drum 3 rotates, as described above, the developing roller 1, the toner supplying roller 2, the toner recovery roller 5, the auxiliary supply roller 10, 撹拌部material 13a, 13b, 13c, 13d and the toner remaining amount detection bar 14 rotate in the direction of the arrow shown in FIG.

  At this time, the auxiliary supply roller 10 carries the toner on the sponge surface and in the cells, and rotates so as to pump up the toner in the lower part of the casing 101 (developer holding part 102). Transport to contact.

  To the toner supply roller 2, a DC bias voltage of −300 V is applied from the power supply 2 a for the toner supply roller, and an AC bias voltage of 600 V (peak to peak) is applied as a rectangular wave with a frequency of 2 kHz. That is, a bias voltage (AC + DC) from 0 V to −600 V is applied to the toner supply roller 2.

  The auxiliary supply roller 10 is biased by the auxiliary supply roller power supply 10a so that an effective value is −1 kV to −4 kV so that a constant current of about 10 μA flows from the toner supply roller 2 to the auxiliary supply roller 10. Applied.

  As described above, when a current (constant current) flows from the toner supply roller 2 to the auxiliary supply roller 10, the toner supply roller 10 passes through the toner supply roller 10 so as to pass the toner 11 positioned at the contact portion of both rollers. The negative charge moves toward 2.

  Therefore, the toner 11 is charged by the current flowing, and adheres to the surface of the toner supply roller 2 by the action of the electric field between the auxiliary supply roller 10 and the toner supply roller 2 and the image force. The charge amount (toner charge amount) held by the toner 11 at this time is about −4 to −7 μC / g.

  As the toner supply roller 2 rotates, the toner 11 attached to the surface of the toner supply roller 2 reaches a contact portion with the regulation film (charging auxiliary member) 7. Since the regulation film 7 is in light contact with the surface of the toner supply roller 2, a toner layer having a uniform thickness is formed on the surface of the toner supply roller 2.

  Further, a bias voltage synchronized with the AC voltage of the toner supply roller 2 is applied to the restriction film 7 from the restriction film power supply 7c so that the potential difference with the toner supply roller 2 becomes −300V. Due to this potential difference, a current flows between the toner supply roller 2 and the regulating film 7, and the toner 11 is further charged by the effect of the current regardless of friction. After passing through the contact portion between the toner supply roller 2 and the regulating film 7, the charge amount of the toner 11 becomes about −7 to −13 μC / g.

  Further, as the toner supply roller 2 rotates, the toner 11 attached to the surface of the toner supply roller 2 reaches a portion facing the developing roller 1. A DC bias voltage of −200 V is applied to the developing roller 1 and the developing blade 6 by the developing roller power source 1a. Therefore, the electric field between the toner supply roller 2 and the developing roller 1 is an oscillating electric field from + 200v to −400V. Due to this oscillating electric field, the toner 11 on the surface of the toner supply roller 2 moves (flys) toward the developing roller 1.

  The toner adhering to the surface of the developing roller 1 is thinned by the developing blade 6 according to the rotation of the developing roller 1, and then adheres to the surface of the photosensitive drum 3 on which the electrostatic latent image is formed. Develop the latent image.

  On the other hand, among the toner thinned on the developing roller 1 by the developing blade 6, the toner 11 remaining on the developing roller 1 without being used for developing the electrostatic latent image is developed according to the rotation of the developing roller 1. It reaches the nip portion between the roller 1 and the toner recovery roller 5, that is, the toner recovery area (developer recovery area).

  A DC bias voltage of −100 V is applied to the toner collecting roller 5 by a toner collecting roller power source 5a. The toner 11 on the developing roller 1 moves to the surface of the toner collecting roller 5 and is collected by an electric field generated by a potential difference between the developing roller 1 and the toner collecting roller 5 when passing through the toner collecting region.

  The toner collecting roller 5 and the developing roller 1 rotate so that the surfaces thereof move in the same direction at substantially the same speed at the contact portions so as not to damage the toner 11. Here, “substantially the same speed” means that the absolute value of the difference (V5−V1) between the moving speed V5 of the surface of the toner collecting roller 5 at the contact portion and the moving speed V1 of the surface of the developing roller 1 is V5. Of 10% or less.

  The toner 11 held on the surface of the toner collection roller 5 comes into contact with the toner removal blade 8 and is scraped off from the surface of the toner collection roller 5. The toner 11 scraped off from the surface of the toner collecting roller 5 falls to the vicinity of the stirring member 13a by its own weight. Further, the agitating members 13a and 13b and the auxiliary supply roller 10 are rotated and agitated and conveyed for reuse.

<Operation of developing device>
Next, the rotation direction of the toner supply roller 2 will be described with reference to FIG. In the present embodiment, as described above, the developing roller 1 and the toner supply roller 2 rotate so that the moving directions of the surfaces are the same direction (α direction) at the opposing portions.

  The toner 11 scraped off from the surface of the developing roller 1 by the developing blade 6 enters the opposing portion of the toner supply roller 2 and the developing roller 1 (that is, the region where the toner 11 flies and adheres to the developing roller 1). Can be prevented.

  That is, if the toner 11 scraped off by the developing blade 6 enters the opposing portion between the toner supply roller 2 and the developing roller 1, there is a possibility that the flying of the toner 11 due to an electric field may be prevented, and the toner 11 attached to the developing roller 1. This causes unevenness in the amount of density and causes density unevenness and blurring on the printed image. On the other hand, in this embodiment, even if the toner 11 scraped off by the developing blade 6 falls on the surface of the toner supply roller 2, the toner 11 is opposed to the toner supply roller 2 and the developing roller 1. Therefore, the toner 11 is not hindered from flying.

  Further, as described above, the toner supply roller 2 and the auxiliary supply roller 10 rotate so that the movement direction of the surface is the same direction (β direction) in the nip portion. Therefore, the toner 11 on the upstream side in the β direction of the nip portion can be efficiently guided to the nip portion and charged. Further, since the moving speed of the surface is substantially the same (the speed difference is within ± 10%) at the nip portion between the toner supply roller 2 and the auxiliary supply roller 10, damage to the toner 11 can be suppressed.

  The toner replenishing position from the toner replenishing portion 12 (FIG. 1) described above is located on the downstream side in the α direction with respect to the facing portion between the developing roller 1 and the toner supply roller 2. Further, the toner collection roller 5 and the toner removal blade 8 described above are located on the upstream side in the α direction with respect to the facing portion between the developing roller 1 and the toner supply roller 2.

  With such an arrangement, the toner 11 replenished from the toner replenishing unit 12 is not directly supplied from the toner supply roller 2 to the developing roller 1, but the nip portion between the toner supply roller 2 and the auxiliary supply roller 10, and the toner The toner is supplied to the developing roller 1 through a contact portion between the supply roller 2 and the regulating film 7.

  Further, the toner replenishment position from the toner replenishing portion 12 (FIG. 1) is located upstream in the β direction with respect to the nip portion of the toner supply roller 2 and the auxiliary supply roller 10. Further, the toner collection roller 5 and the toner removal blade 8 described above are located on the downstream side in the β direction with respect to the nip portion of the toner supply roller 2 and the auxiliary supply roller 10.

  With such an arrangement, the toner 11 replenished from the toner replenishing portion 12 passes through the nip portion between the toner supply roller 2 and the auxiliary supply roller 10 (and is recovered from the developing roller 1 by the toner recovery roller 5). Since it is mixed with the collected toner, uneven charging can be suppressed.

  Further, the toner 11 supplied from the toner supply unit 12 can be smoothly guided to the nip portion between the toner supply roller 2 and the auxiliary supply roller 10 by the rotation of the auxiliary supply roller 10 (clockwise in FIG. 1). . For this reason, the toner 11 replenished from the toner replenishing portion 12 is less likely to move to the collection region (the region where the toner collection roller 5 is disposed) without passing through the nip portion between the toner supply roller 2 and the auxiliary supply roller 10. Become.

  Further, since the movement direction (β direction) of the surface of the toner supply roller 2 and the surface of the auxiliary supply roller 10 is the same, the toner 11 can be easily guided to the nip portion between the toner supply roller 2 and the auxiliary supply roller 10. Accordingly, it is possible to prevent the uncharged or insufficiently charged toner 11 from being supplied to the developing roller 1.

  Further, the toner 11 (collected toner) collected by the toner collecting roller 5 is mixed with the toner in the developer holding unit 102 (FIG. 1), and then adheres to the toner supply roller 2 and adheres to the developing roller 1. Since the collected toner is already charged, it may be overcharged when guided to the nip portion between the toner supply roller 2 and the auxiliary supply roller 10. However, the nip between the toner supply roller 2 and the auxiliary supply roller 10 may be overcharged. Since the toner collection roller 5 is downstream in the β direction with respect to the portion, the collected toner hardly reaches the nip portion. Thereby, excessive charging of the toner 11 can be prevented.

  Also, as shown in FIG. 12, the moving direction (α direction) of the surfaces of both rollers is the same in the facing portion between the developing roller 1 and the toner supply roller 2, and a layer is formed downstream of the facing portion in the α direction. A developing blade 6 is disposed as a regulating member. Thereby, the following effects are obtained.

  That is, since the developing blade 6 scrapes off the toner 11 having a small charge amount on the developing roller 1, the charged amount of the toner 11 that is scraped off is insufficient compared to the toner remaining on the developing roller 1. There are many. Therefore, the toner 11 that has been scraped off is attached to the surface of the toner supply roller 2 on the downstream side in the α direction with respect to the portion where the developing roller 1 and the toner supply roller 2 face each other. And the auxiliary supply roller 10 and the toner supply roller 2 and the regulating film 7 are sufficiently charged at the opposing portion, and can be conveyed to the developing roller 1. Thereby, the charge amount of the toner 11 supplied to the developing roller 1 can be made uniform.

  This effect is not only when the developing roller 1 and the toner supply roller 2 are arranged apart from each other, but also when the developing roller 1 and the toner supply roller 2 are arranged in contact with each other (second implementation described later). This is the same as the above.

  Further, as shown in FIG. 12, the contact position between the developing blade 6 and the developing roller 1 is downstream in the rotation direction of the toner supply roller 2 with respect to the vertical line A passing through the highest position of the toner supply roller 2 ( It is desirable to be in the direction indicated by arrow B).

<Toner level control>
Next, control of the toner level in the casing 101 of the developing device 100 (the upper surface level of the toner 11) will be described with reference to FIGS.

  As described above, in the developing device 100 according to the present embodiment, the current flowing through the toner 11 at the contact portion between the auxiliary supply roller 10 and the toner supply roller 2 and at the contact portion between the toner supply roller 2 and the regulating film 7. In order to charge the toner 11 efficiently and smoothly move the developing roller 1, the toner 11 deposited on the lower portion of the casing 101 (developer holding portion 102) is transferred to the developing roller 1, the toner supply roller 2, and the like. It is desirable that the auxiliary supply roller 10 is sufficiently immersed in the toner 11 and does not reach the contact portion of the control film 7 and the contact portion between the restriction film 7 and the toner supply roller 2.

  Therefore, in the present embodiment, the toner level 11a in the casing 101 is lower than the facing portion between the developing roller 1 and the toner supply roller 2 and the contact portion between the regulating film 7 and the toner supply roller 2, and Then, the auxiliary supply roller 10 is controlled to be equal to or greater than the rotation center. Therefore, the rotation center of the toner remaining amount detection bar 14 is provided within the range indicated by the symbol H in FIG.

  The reason why the toner level 11a is set to be higher than the rotation center of the auxiliary supply roller 10 is to make it easier for the auxiliary supply roller 10 to carry the toner 11 in the casing 101 by its own rotation.

  FIG. 13 is a schematic diagram illustrating a state in which the toner level 11a is higher than the vertex 14T of the rotation locus of the toner remaining amount detection bar 14. In this state, the entire rotation locus of the remaining toner amount detection bar 14 is stored in the toner 11. For this reason, the toner remaining amount detection bar 14 rotates when its radius portion 14 b is urged against the contact portion 28 a of the gear 28. That is, the toner remaining amount detection bar 14 rotates at the same rotational speed as the gear 28.

  FIG. 14 is a schematic diagram illustrating a state in which the toner level 11a is at a position lower than the rotation center of the toner remaining amount detection bar 14. In this state, the toner 11 does not exist in a certain region including the vertex 14T of the rotation locus of the toner remaining amount detection bar 14. Therefore, when the toner remaining amount detection bar 14 reaches the apex 14T of the rotation locus by the rotation of the gear 28, the toner remaining amount detection bar 14 falls by its own weight (away from the contact portion 28a of the gear 28), and the toner 11 has a height of the toner level 11a. Stops rotation in response to resistance from Then, the contact portion 28a of the gear 28 rotating at a constant speed catches up with and contacts the radius portion 14b of the toner remaining amount detection bar 14, so that the toner remaining amount detection bar 14 resumes rotating at the same rotational speed as the gear 28. To do.

  FIG. 15 shows the relationship between the toner level 11a and the light receiving time T of the reflected light 31a by the light receiving element 31 when the reflecting plate 29 passes through an intermediate point 29M (FIG. 6) between the vertex 29T and the bottom 29B of the rotation locus. . An intermediate point 29M between the vertex 29T and the bottom 29B of the rotation locus of the reflecting plate 29 is an intermediate point 14M (FIG. 14) between the vertex 14T and the bottom 14B of the rotation locus of the toner remaining amount detection bar 14, that is, the toner remaining amount. This corresponds to the rotation center of the detection bar 14.

  When the toner level 11a is higher than the intermediate point 29M in the rotation locus of the reflection plate 29, the speed at which the reflection plate 29 passes through the intermediate point 29M (toward the bottom 29B) coincides with the rotation speed of the gear 28. Yes. At this time, the time (light reception time) for the light receiving element 31 to receive the reflected light 31a is T1.

  On the other hand, when the toner level 11a is lower than the intermediate point 29M in the rotation locus of the reflecting plate 29, the speed at which the reflecting plate 29 passes through the intermediate point 29M is the speed at which the remaining toner amount detection bar 14 falls by its own weight. Therefore, the rotational speed of the gear 28 is faster. Therefore, if the light receiving time of the reflected light 31a by the light receiving element 31 at this time is T2, the relationship between T1 and T2 is T1> T2.

  Accordingly, by measuring the light reception time of the reflected light 31a by the light receiving element 31, it is determined whether or not the toner level 11a is higher than the intermediate point 29M in the rotation locus of the reflection plate 29 (that is, the rotation center of the toner remaining amount detection bar 14). Or higher).

  FIG. 16 is a flowchart showing toner level control. When the printing control unit 20 of the image forming apparatus 300 starts driving the developing device 100 in the image forming operation (printing operation) (step S1), the light receiving time T of the light receiving element 31 by the timer 32 is acquired (step S2). It is determined whether or not the light receiving time T is longer than T2 (step S3).

  If it is determined that the light receiving time T is longer than T2 (YES in step S3), the developing device 100 continues to be driven while the shutter 12a of the toner replenishing unit 12 is closed. In this case, the toner level 11 a is higher than the rotation center of the remaining toner amount detection bar 14, and a sufficient amount of toner 11 exists in the casing 101.

  On the other hand, when the light receiving time T of the light receiving element 31 is T2 or less (NO in step S3), it is determined that the remaining amount of the toner 11 in the casing 101 is small, and the shutter 12a of the toner replenishing unit 12 is opened to replenish the toner. The toner 11 is supplied from the portion 12 into the casing 101 (step S4).

  Further, the print control unit 20 acquires the light reception time T of the light receiving element 31 by the timer 32 (step S5), and determines whether or not the light reception time T is longer than the above T2 (step S6). If the light receiving time T of the light receiving element 31 is T2 or less (NO in step S6), the shutter 12a of the toner replenishing unit 12 is kept open and toner replenishment is continued. On the other hand, when the light receiving time T of the light receiving element 31 is longer than T2 (YES in step S6), the shutter 12a of the toner replenishing unit 12 is closed (step S7).

By such toner remaining amount detection and toner replenishment, the toner level 11 a in the developing device 100 is changed from the facing portion between the developing roller 1 and the toner supply roller 2 and the contact portion between the regulating film 7 and the toner supply roller 2. And is kept above the rotational center of the auxiliary supply roller 10.

<Printing test>
Next, a printing test by the image forming apparatus 300 using the developing device 100 configured as described above will be described.

  Here, a blank paper pattern was continuously printed on the medium 18 in an environment of a temperature of 23 ° C. and a relative humidity of 50%. In this way, the continuous printing test of the blank paper pattern was performed without moving the toner 11 to the photosensitive drum 3 side, without developing the developing roller 1, the toner supplying roller 2, the auxiliary supplying roller 10, the regulating film in the developing device 100. 7. This is because friction is continuously applied to the toner 11 by the toner collecting roller 5 and the like.

  Then, as a result of continuous printing, the toner 11 is continuously rubbed, and the external additive is peeled off from the toner base particles or the external additive is buried in the toner base particles (toner damage). The occurrence state of fogging and blurring caused by a decrease in toner supply ability due to a decrease in toner property and a decrease in fluidity as a powder was evaluated.

  The fog was evaluated as follows. That is, the operation of the image forming apparatus 300 is stopped in the middle of printing a blank paper pattern, and the position of the surface of the photosensitive drum 3 before development and before transfer (that is, the position facing the developing roller 1 and the position facing the transfer roller 16). The toner 11 was adhered to an adhesive tape (“Scotch Mending Tape” manufactured by Sumitomo 3M Limited). The adhesive tape was peeled off from the photosensitive drum 3 and attached to the printing paper.

  Separately, the same type of adhesive tape not attached to the photosensitive drum 3 was attached to the printing paper, and the color difference ΔE between the two adhesive tapes was measured with a spectrocolorimeter (CM2600d manufactured by Konica Minolta). The smaller the color difference ΔE, the smaller the fog.

  Scratch evaluation was performed by printing a black solid image (100% DUTY) after the continuous printing test of the above-mentioned blank paper pattern and observing the printed image.

  Specifically, the level 10 indicates that no blur is observed in the solid image, the level 9 indicates that the blur is less than 2% in the solid image, and the level 8 indicates that the solid image is less than 4%. It was. Similarly, the level in which the blur occupies the solid image is 4% or more and less than 6% is referred to as level 7, and the case where it is 6% or more and less than 8% is referred to as level 6. did.

  For comparison with the developing device 100 of the present embodiment, a developing device 400 of a comparative example shown in FIG. 17 was used.

  The developing device 400 of the comparative example shown in FIG. 17 is different from the developing device 100 of the present embodiment in the following three points. (1) The developing roller 401 and the toner supply roller 402 are in contact with each other. (2) The toner supply roller 402 and the charging blade 407 as a charging auxiliary member are in contact with each other for the purpose of frictional charging. (3) The rotation directions of the developing roller 401, the toner supply roller 402, and the auxiliary supply roller 410 are the same, and the moving directions of the surfaces at the respective contact portions are opposite to each other.

  In FIG. 18, the developing device 100 according to the present embodiment and the developing device 400 of the comparative example are mounted on the image forming apparatus 300, respectively, and up to 22,000 sheets (general developing device life) It is a figure which shows the evaluation result of fog when performing continuous printing 400 sheets at a time.

  Here, in continuous printing of 4,400 sheets per day, fog was measured when 2,200 printing was completed, and fog was measured again when 4,400 printing was completed. This was repeated for 5 days.

  In FIG. 19, the developing device 100 according to the present embodiment and the developing device 400 of the comparative example are mounted on the image forming apparatus 300, and continuous printing is performed in the same manner (up to 22,000 sheets, 4,400 sheets per day). It is a figure which shows the evaluation result of the blur when performed.

  Here, in continuous printing of 4,400 sheets per day, when 2,200 printing is completed, a solid pattern is printed and the blur is measured, and when 4,400 printing is completed, solid printing is performed again. The pattern was printed and the blur was measured. This was repeated for 5 days.

  Further, when the number of printed sheets per day (4,400 sheets) is reached, the image forming apparatus 300 is stopped and left for about 15 hours, and then the next (next day) continuous printing is started.

  From the results of FIGS. 18 and 19, it can be seen that when the developing device 100 according to the present embodiment is used, fogging and blurring are suppressed as compared with the case where the developing device 400 of the comparative example is used. That is, it can be seen that in the developing device 100 according to the present embodiment, a decrease in charging property and a decrease in supply property of the toner 11 due to toner damage are suppressed.

  The reason why such a result was obtained is considered as follows. That is, in the developing device 400 of the comparative example, the toner 11 is supplied to the developing roller 401 using the toner supply roller 402 that is in contact with the developing roller 401, and the toner 11 is positively charged by being frictionally charged. Therefore, toner damage is likely to increase.

  On the other hand, in the developing device 100 according to the present embodiment, the toner 11 is supplied to the developing roller 1 using the toner supply roller 2 that is disposed so as to face the developing roller 1 in a non-contact manner. Since the toner 11 is charged not by friction charging but by causing the current to flow through the toner 11 at the opposite portions of both rollers, the toner 11 is charged by the same direction as the moving direction of the surface at the opposite portion of the toner supply roller 2. It is thought that we were able to suppress.

  As described above, according to the first embodiment of the present invention, the toner 11 is supplied to the developing roller 1 using the toner supply roller 2 arranged in non-contact with the developing roller 1, and the developing roller 1 and the toner supply roller 2 are opposed to each other in the same direction, so that toner damage can be suppressed and image quality deterioration (fogging, blurring, etc.) can be suppressed. As a result, it is possible to prevent deterioration in image quality during continuous printing.

Second embodiment.
<Configuration of developing device>
FIG. 20 is a cross-sectional view showing a developing device 500 according to the second embodiment. FIG. 21 is a schematic diagram for explaining the nip amount between the rollers of the developing device 500 according to the second embodiment. The developing device 500 of the second embodiment is different from the configuration of the developing device 100 of the first embodiment in the configuration and arrangement of the toner supply roller 502.

  FIG. 22 is a diagram illustrating a cross-sectional configuration of the toner supply roller 502 according to the second embodiment. In the toner supply roller 502 according to the second embodiment, for example, a foam layer 502b such as urethane rubber is formed on the surface of a metal shaft (core metal) 502a, and the surface of the foam layer 502b is further coated with nitrile rubber or the like. It coat | covers with the elastic layer 502c. Here, the outer diameter of the shaft 502a is 6 mm, the thickness of the foam layer 502b is 3 mm, and the thickness of the elastic layer 502c is 1 mm.

  Further, as shown in FIG. 21, the toner supply roller 502 is provided so as to contact the developing roller 1 with a predetermined nip amount d501. Here, the nip amount d501 is 0.5 mm.

The resistance value of the toner supply roller 502 including the shaft 502a, the foam layer 502b, and the elastic layer 502c is 1 × 10 ⁶ to 1 × 10 ^{9 with} respect to an applied voltage of 100 V by the measurement method described with reference to FIG. A range of Ω is desirable.

  The auxiliary supply roller 510 in the second embodiment has a smaller resistance value than the auxiliary supply roller 10 in the first embodiment. This is because the toner supply roller 502 in the second embodiment has a larger resistance than the toner supply roller 2 (for example, an aluminum roller) in the first embodiment.

Specifically, it is desirable that the resistance value of the auxiliary supply roller 510 has the same number of digits as the resistance value of the toner supply roller 502. More specifically, in the measurement method described with reference to FIG. 10, a range of 1 × 10 ⁶ to 1 × 10 ⁹ Ω with respect to an applied voltage of 100 V is desirable, and here it is 1 × 10 ⁸ Ω.

  The auxiliary supply roller 510 and the toner supply roller 502 are in contact with each other with a predetermined nip amount d505. Here, d505 = 0.5 mm.

  The surfaces of the toner supply roller 502 and the developing roller 1 are moved in the same direction at substantially the same speed at the contact portions. The “substantially the same speed” means that the absolute value of the difference (V502−V1) between the moving speed V502 of the surface of the toner supply roller 502 at the contact portion and the moving speed V1 of the surface of the developing roller 1 is V502. Say that it is 10% or less.

  The auxiliary supply roller 510 contacts the toner supply roller 502. In order to suppress toner damage, the surfaces of the auxiliary supply roller 510 and the toner supply roller 502 move in the same direction at substantially the same speed at the contact portions. . Note that the substantially same speed means that the absolute value of the difference (V502-V510) between the moving speed V502 of the surface of the toner supply roller 502 at the contact portion and the moving speed V510 of the surface of the auxiliary supply roller 510 is 10 of V502. Say that it is less than%.

  Other configurations of the developing device 500 and the image forming apparatus in the second embodiment are the same as those of the developing device and the image forming apparatus in the first embodiment.

<Operation of developing device>
Next, the operation of the developing device 500 will be described. The toner replenished from the toner replenishing unit 12 is accumulated in a lower portion (developer holding unit 102) of the casing 101 of the developing device 500. Further, when the photosensitive drum 3 is rotated by the drive transmission unit 38 described above, the developing roller 1, the toner supply roller 502, the toner recovery roller 5, the auxiliary supply roller 510, 撹拌部material 13a, 13b, 13c, 13d and the toner remaining The amount detection bar 14 rotates in the direction of the arrow shown in FIG.

  At this time, the auxiliary supply roller 510 carries toner on the sponge surface and in the cells, and rotates so as to pump up the toner in the lower part of the casing 101 (developer holding part 102). Transport to contact.

  A DC bias voltage of −600 V is applied to the toner supply roller 502 from the power supply 2a for the toner supply roller. A bias voltage (DC voltage) of −1 kV to −4 kV is applied to the auxiliary supply roller 510 so that a constant current of about 10 μA flows from the toner supply roller 502 toward the auxiliary supply roller 510 by the auxiliary supply roller power source 10a. Applied.

  Thus, since a current (constant current) flows from the toner supply roller 502 to the auxiliary supply roller 510, the auxiliary supply roller 510 transfers to the toner supply roller 502 so as to pass the toner 11 positioned at the contact portion of both rollers. Negative charge moves toward it. The toner 11 is charged by the current flowing, and adheres to the surface of the toner supply roller 502 by the action of the electric field between the auxiliary supply roller 510 and the toner supply roller 502 and the image force. The charge amount (toner charge amount) held by the toner 11 at this time is about −4 to −7 μc / g.

  As the toner supply roller 502 rotates, the toner 11 adhering to the surface of the toner supply roller 502 reaches a contact portion with the regulation film (charging auxiliary member) 7. Since the regulation film 7 is in light contact with the surface of the toner supply roller 502, a toner layer having a uniform thickness is formed on the surface of the toner supply roller 502.

  Further, a bias voltage is applied to the regulating film 7 from the regulating film power source 7c so that the potential difference from the toner supply roller 502 becomes −600V. Due to this potential difference, a current flows between the toner supply roller 502 and the regulating film 7, and the toner 11 is further charged by the effect of the current regardless of friction. After passing through the contact portion between the toner supply roller 502 and the regulating film 7, the charge amount of the toner 11 becomes about −7 to −13 μC / g.

  Further, as the toner supply roller 502 rotates, the toner 11 attached to the surface of the toner supply roller 502 reaches a contact portion (nip portion) with the developing roller 1. A DC bias voltage of −200 V is applied to the developing roller 1 and the developing blade 6 from the power supply 1 a for the developing roller, and an electric field of −400 V is formed between the toner supply roller 2 and the developing roller 1. As a result, the toner 11 on the surface of the toner supply roller 2 adheres to the developing roller 1.

  The toner 11 adhering to the surface of the developing roller 1 is thinned by the developing blade 6 as the developing roller 1 rotates, and then adheres to the surface of the photosensitive drum 3 on which the electrostatic latent image is formed. Develop the electrostatic latent image. The toner thinning by the developing blade 6 and the recovery of the toner on the surface of the developing roller 1 by the toner recovery roller 5 are as described in the first embodiment.

  In the second embodiment, the toner supply roller 502 and the developing roller 1 rotate so that the surfaces of the toner supply roller 502 and the developing roller 1 move in the same direction at substantially the same speed (speed difference is ± 10% or less). . Therefore, damage due to friction of the toner 11 can be suppressed at the contact portion between the developing roller 1 and the toner supply roller 502.

  Further, as described in the first embodiment, even when the toner 11 scraped off from the developing roller 1 by the developing blade 6 falls on the surface of the toner supply roller 502, the toner 11 remains in the toner supply roller 502. And the developing roller 1 move away from the contact portion, and do not enter the contact portion.

  Further, in the second embodiment, since the toner supply roller 502 is in contact with the developing roller 1, no unintended discharge occurs between the toner supply roller 502 and the developing roller 1.

<Printing test>
Next, a printing test by the image forming apparatus using the developing device 500 configured as described above will be described. The printing test and the image quality (fogging and blurring) evaluation method are as described in the first embodiment.

  23 and 24 show a case where the developing device 500 according to the second embodiment and the developing device 100 according to the first embodiment are mounted on the image forming apparatus 300 and 22,000 sheets are continuously printed. It is the figure which showed the evaluation result of fogging and blurring.

  The printing conditions are as described in the first embodiment. The number of continuous prints per day was 4,400. When the daily print number was reached, the image forming apparatus was stopped and left for about 15 hours, and then the next (next day) continuous printing was started.

  From the results shown in FIGS. 23 and 24, when the developing device 500 of the second embodiment is used, the fog evaluation result (FIG. 23) is slightly inferior to that of the first embodiment, but It can be seen that the evaluation result (FIG. 24) is almost the same as that of the first embodiment.

  Further, the same continuous printing test was conducted in a low temperature and low humidity environment (temperature 10 ° C., relative humidity 20%), and the change in fog and blur was evaluated in the same manner. Specifically, after storing the image forming apparatus in a low temperature and low humidity environment (temperature: 10 ° C., relative humidity: 20%) for 48 hours or more, 4,400 continuous printings per day were performed up to 22,000 sheets.

  25 and 26 are diagrams showing the evaluation results of fogging and blurring in a continuous printing test in a low temperature and low humidity environment. The evaluation results of fogging and blurring are as described above.

  In addition to fog and blur, image quality was also evaluated for dirt. Specifically, a continuous printing test of 4,400 sheets per day is performed, and the printing operation is stopped at time points 0, 2,200, and 4,400, and a 25% DUTY called a blank image and 2by2 A halftone image was formed. Then, a blank paper image and a halftone image were observed, and it was confirmed whether or not stains occurred on the white background portion (portion other than the portion where the image is formed). FIG. 27 shows the result.

  As shown in FIG. 28, the 2by2 pattern forms four square dots formed by two vertical dots and two horizontal dots out of 16 square dots formed by four vertical dots and four horizontal dots. To do.

  “Dirt” is not fog (a phenomenon in which the toner 11 adheres faintly uniformly on the surface of the medium) but does not require the use of a color difference meter, and is a state where it is clear that the toner 11 is attached to a white background. Point to. This is because when the toner layer potential on the developing roller 1 becomes high, such as when a large amount of toner 11 is supplied onto the developing roller 1, the toner adheres to a portion that is not planned for development on the photosensitive drum 3. Arises.

  From FIG. 25, it can be seen that the same results are obtained for the fog in the first embodiment and the second embodiment. On the other hand, as shown in FIG. 26, with respect to the blur, the second embodiment is better than the first embodiment when 4,400 sheets (one day) have been printed. You can see that it is obtained.

  In addition, from FIG. 27, in the first embodiment, stains may occur when 4,400 sheets (one day) are printed, but in the second embodiment, stains are observed. Absent. That is, it can be seen that the second embodiment is superior in terms of image quality stability when continuous printing is performed in a low-temperature and low-humidity environment.

  Here, the evaluation results from FIG. 23 to FIG. 27 are considered. First, as shown in FIG. 23, with respect to the fog evaluation results in an environment of a temperature of 23 ° C. and a relative humidity of 50%, the second embodiment is slightly inferior to the first embodiment. This is considered as follows.

  That is, in the first embodiment, since the toner supply roller 2 and the developing roller 1 are not in contact with each other, the toner 11 attached to the developing roller 1 is only the toner 11 that is supplied by flying due to the action of an electric field. Accordingly, only those having a regular charge amount are obtained. That is, abnormally charged toner (toner having an irregular charge amount) that causes fogging does not adhere to the developing roller 1. On the other hand, in the second embodiment, since the toner supply roller 502 is in contact with the developing roller 1, the toner 11 adhering to the developing roller 1 includes a little abnormally charged toner, which is fogged. This is thought to be the cause of However, unlike the developing device of the comparative example (FIG. 17), the toner 11 is not configured to be damaged by friction, and thus the occurrence of fog does not increase with time.

  Next, the results of FIGS. 26 and 27 will be described. In a low-temperature and low-humidity environment (temperature: 10 ° C., relative humidity: 20%), the charged charge of the toner 11 that has been charged is difficult to escape due to natural discharge, so the charged toner 11 gradually accumulates in the developing device as continuous printing is performed. It will be done. Due to the influence of the toner 11, the toner 11 may cause electrostatic aggregation in the developing device, and the fluidity of the toner 11 may be reduced.

  In this case, in the first embodiment in which the toner 11 is supplied to the developing roller 1 in a non-contact manner, the ability to fly and supply the toner 11 is reduced as the fluidity of the toner 11 is reduced. It becomes easy to do. On the other hand, in the second embodiment, the toner 11 is supplied to the developing roller 1 by contact, and therefore, even if the fluidity of the toner 11 is reduced, the reduction in the supply capability of the toner 11 is suppressed. can do. For this reason, it is considered that blurring is less likely to occur.

  Further, when a lump of toner 11 that is electrostatically aggregated is supplied to the developing roller 1, the toner layer becomes thick locally and the potential of the toner layer becomes high, which causes a stain on the surface of the medium. In the second embodiment, when the toner 11 is supplied to the developing roller 1, the lump of the toner 11 is sandwiched between the toner supplying roller 502 and the developing roller 1 and broken, so that the occurrence of contamination is prevented. be able to. For these reasons, it is possible to obtain stable image quality particularly in continuous printing in a low temperature and low humidity environment.

  As described above, according to the second embodiment of the present invention, in addition to the effects described in the first embodiment, stable image quality can be obtained even in continuous printing in a low temperature and low humidity environment. The effect that it can be obtained.

  In each of the above-described embodiments, the image forming apparatus including one developing device as illustrated in FIGS. 1 and 20 has been described. However, the image forming apparatus may be applied to a color image forming apparatus including a plurality of developing devices. it can.

  In each of the embodiments, it has been described that the developing roller 1 and the toner supply roller 2 rotate so that the surfaces move in the same direction at the facing portions. However, the developing roller 1 and the toner supply roller 2 face each other. In this configuration, the surface of the developing roller 1 and the surface of the toner supply roller 2 may be moved in the same direction.

  Further, the present invention can be applied to image forming apparatuses such as a printer, an MFP (Multi-Function Peripheral), a facsimile machine, and a copying machine.

  DESCRIPTION OF SYMBOLS 1 Developing roller (developer carrier), 2 Toner supply roller (1st supply member), 3 Photosensitive drum (electrostatic latent image carrier), 4 Charging roller (charging member), 5 Toner collection roller (developer) Collecting member), 6 developing blade (layer regulating member), 7 regulating film (charging auxiliary member), 10 auxiliary feeding roller (second feeding member), 11 toner (developer), 11a toner level (upper surface level of developer) ), 12 toner replenishment section (developer storage section), 14 toner remaining amount detection bar (detection section), 16 transfer roller (transfer member), 17 fixing device (fixing means), 18 medium, 20 print control section (control means) ), 29 reflector (detected member), 30 light emitting element, 31 light receiving element, 100 developing device, 101 casing, 102 developer holding part, 200 toner Residual amount detecting mechanism (detecting means), 300 image forming apparatus, 500 a developing device, 502 toner supply roller (first supply member) 510 auxiliary supply roller (second supply member).

Claims (18)

A developer carrier for developing the electrostatic latent image by attaching a developer to the electrostatic latent image carrier;
A first supply member that is provided below the developer carrier and supplies the developer to the developer carrier;
A second supply member that is provided below the first supply member and supplies developer to the first supply member ;
A conductive film that is disposed in contact with the first supply member, is applied with a voltage, and assists charging of the developer carried on the first supply member ;
At the facing portion between the developer carrier and the first supply member, the surface of the developer carrier and the surface of the first supply member move in the same direction at substantially the same speed , and the first The surface of the first supply member and the surface of the second supply member move at substantially the same speed in the same direction at the facing portion between one supply member and the second supply member. Development device. The developer carrying member and the first supply member rotate so that the surface of the developer carrying member and the surface of the first supply member move in the same direction at substantially the same speed at the opposing portions. The developing device according to claim 1, wherein: In the first supply member and the second supply member, the surface of the first supply member and the surface of the second supply member are moved in the same direction at substantially the same speed at the opposing portions. The developing device according to claim 1, wherein the developing device rotates. A layer regulating member for regulating the thickness of the developer layer formed on the surface of the developer carrying member;
The layer regulating member, wherein the rotational direction of the developer carrying member, said claim, characterized in that it is arranged on the downstream side of the opposing portion between the developer carrying member a first feed member 2 or 3. The developing device according to 3 . A recovery member for recovering the developer remaining on the surface of the developer carrier;
The collecting member, in the rotating direction of said developer carrying member, claims 2 to 4, characterized in that arranged on the upstream side of the facing portion of said first supply member and the developer carrying member The developing device according to any one of the above. The recovery member is upstream of the facing portion in the moving direction of the surface of the developer carrying member and the surface of the first supply member at the facing portion between the developer carrying member and the first supply member. The developing device according to claim 5 , wherein the developing device is disposed in the middle. A developer holding unit for holding the developer supplied to the second supply member;
An apparatus according to any one of claims 1 to 6, characterized in that said a developer supply unit for supplying a developer to the developer holding section further. The developer replenishing section is configured so that the surface of the developer carrying body and the surface of the first supply member at the facing section between the developer carrying body and the first supply member are in the moving direction of the facing section. The developing device according to claim 7 , wherein the developing device is disposed on the downstream side. Wherein the first supply member, a developing device according to any one of claims 1 to 8, characterized in that disposed opposite a non-contact with the developer carrying member. Wherein the first supply member, a developing device according to any one of claims 1 to 8, characterized in that it is arranged so as to contact with the developer carrying member. The second supply member, a developing device according to any one of claims 1 to 10, characterized in that it is arranged to abut a first supply member. The second supply member, a developing device according to any one of claims 1 to 11, characterized in that a roller having a foam. The absolute value of the difference between the moving speed of the surface of the developer carrying body and the moving speed of the surface of the first supply member at the facing portion between the developer carrying body and the first supply member is the first value. The developing device according to claim 1, wherein the developing device is 10% or less of a moving speed of the surface of the supply member. The absolute value of the difference between the movement speed of the surface of the first supply member and the movement speed of the surface of the second supply member at the facing portion between the first supply member and the second supply member is The developing device according to claim 1, wherein the developing device is 10% or less of the moving speed of the surface of the second supply member. An image forming apparatus comprising the developing device according to claim 1 . A developing device according to claim 7;
Detecting means for detecting the upper surface level of the developer held in the developer holding section ;
Images forming apparatus characterized by comprising a. Wherein based on the detection result of the detecting means, the image forming apparatus according to claim 16, wherein the provided from the developer replenishing unit further a control means for performing control to supply the developer to the developer holding unit . The control means is configured so that the upper surface level of the developer held in the developer holding portion is lower than the facing portion between the first supply member and the developer carrier, and the conductive film The image forming apparatus according to claim 17, wherein the supply of the developer from the developer supply unit is controlled to be lower than a portion facing the first supply member.

Images