JP2009151084A - Developing device and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device sufficiently charging a developer on a developing roller and reducing degradation in the developer without causing deposition of an excessive developer on a developer supply roller. <P>SOLUTION: The developing device includes a pressing member pressing an elastic layer of a developer supply roller, wherein a rotation torque effecting on the developer supply roller by the contact of the pressing member to the developer supply roller is larger than a rotation torque effecting on the developer supply roller by the contact of the developing roller to the developer supply roller. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device that can be used in an image forming apparatus such as a laser printer, a copying machine, and a facsimile using an electrophotographic system or an electrostatic recording system.

  Conventionally, for example, in an image forming apparatus using an electrophotographic system, the surface of an electrophotographic photosensitive member (photosensitive member) that is an image carrier is charged by a charging unit, and then the surface of the photosensitive member is irradiated with light. An electrostatic image (latent image) is formed on the surface of the photoreceptor. This electrostatic image is developed as a toner image with toner which is a developer supplied from a developing device. This toner image is transferred from a photosensitive member to a transfer material (recording paper, OHP sheet, cloth, etc.) by a transfer unit, and then subjected to a fixing process by a fixing unit.

  As a developing method for converting an electrostatic image into a toner image, for example, a one-component developing method has been proposed and put into practical use. In the one-component development system, in many cases, a developer carrying member that carries a developer and rotates and conveys it to a photosensitive member in an image forming apparatus is pressed or brought into contact with the rotating photosensitive member with an appropriate relative speed difference. By doing so, the electrostatic image is developed.

  As the developer, a one-component developer consisting essentially of resin toner particles (toner) is used. In addition, an external additive (auxiliary particle) may be added to the toner particles in order to stabilize the chargeability of the toner or adjust the fluidity. The toner contains wax. This is to prevent glare of the recording medium (transfer material) such as recording paper due to the fixing oil when fixing the toner to the transfer material. In this way, the fixing oil and the transfer material can be released by including wax inside the toner instead of eliminating the fixing oil. In the developing method using a non-magnetic one-component developer, a magnetic material is not necessary for the developer, and it is not necessary to provide a magnet, so that the apparatus can be easily simplified and downsized. In addition, the development method using a non-magnetic one-component developer has many advantages such as easy application to a full-color image forming apparatus because of good color.

  FIG. 12 shows a schematic configuration of a conventional developing device.

  In FIG. 12, a developing roller 21 having elasticity and conductivity is used as the developer carrying member. That is, development is performed by pressing or contacting the image carrier, and particularly when the image carrier is a rigid body, the surface of the developing roller 21 is made of an elastic body in order to avoid damaging it. Further, a conductive layer may be provided on the surface of the developing roller 21 or in the vicinity of the surface, and a developing bias may be applied for use.

  Further, for the purpose of imparting charge to the toner and forming a uniform toner thin layer, the developing blade 22 is brought into contact with the developing roller as a developer regulating member. In this case, the developing blade 22 is supported by a blade support metal plate, and uses a rubber or elastic blade made of a metal thin plate having spring elasticity that comes into contact with the outer peripheral surface of the developing roller in the vicinity of the free end. Is possible. When the developing blade 22 is not installed in the opening of the developing container, it is provided on the downstream side in the developing container of the supply roller 23 described below.

  Then, inside the developing container, the supply roller 23 comes into contact with the developing roller 21 and is driven to rotate. The supply roller 23 is a sponge roller for supplying toner to the developing roller 21 and for removing toner remaining on the developing roller 21 without being developed.

In the developing device having the above-described configuration, a thin layer of nonmagnetic toner can be satisfactorily formed on the developing roller 21, and the electrostatic latent image on the photosensitive drum 24 can be satisfactorily developed. There is Patent Document 1 in which a regulating member is provided on the supply roller in order to sufficiently charge the toner without excessive toner adhering to the supply roller.
Japanese Patent Laid-Open No. 2004-4731

  In the conventional example, in order to obtain a high-quality image, a regulating member is provided on the supply roller to prevent excessive toner from adhering to the supply roller. Thereby, the toner can be sufficiently charged. As a result, the toner on the developing roller has a large charge amount, and a high-quality image can be obtained. However, since the amount of toner on the supply roller is regulated by the regulating member, the fluidity of the toner deteriorates due to long-term use. As a result, the toner conveyance amount of the supply roller is reduced, and when the toner conveyance amount is reduced, the density is reduced, and the image followability is deteriorated with respect to the required image. In addition, when the apparatus is continuously used, the toner deterioration occurs because the rubbing force and heat at the contact portion between the developing roller and the supply roller are generated in addition to the rubbing force and heat at the contact portion between the developing roller and the supply roller. Advances. Toner deterioration is so-called external additive adhering to the outer peripheral portion of the toner being embedded in the toner, or external additive being released from the toner. As a result, the amount of charged charge per unit weight of the toner decreases and the degree of aggregation increases, and image defects such as ghosts occur.

  In particular, in the case of a contact development method in which development is performed by bringing a developing roller, which is a developer carrying member, into contact with a photosensitive member, the developer is rubbed even in the development region, so that toner deterioration is more likely to occur.

  An object of the present invention is to provide a developing device in which excessive developer does not adhere to a supply roller.

  Another object of the present invention is to provide a developing device that can sufficiently charge the developer on the developer carrying member.

  Another object of the present invention is to provide a developing device that reduces the deterioration of the developer.

  Another object of the present invention is to provide a developing device that can appropriately carry the developer transport amount of the supply roller so that a stable image density can be maintained even when used for a long period of time.

  The present invention provides a developer carrier that is provided in contact with an image carrier and carries a developer for developing an electrostatic image formed on the image carrier with a developer, and the developer carrier. A developer supply roller provided in contact with the developer supply roller for supplying the developer to the developer carrying member, the developer supply roller having an elastic layer provided with a plurality of cell openings on the surface thereof. The apparatus includes a pressing member that presses against the elastic layer, and the rotational torque acting on the developer supply roller when the pressing member contacts the developer supply roller causes the developer carrier to supply the developer. The developing device is characterized in that it is larger than a rotational torque acting on the developer supply roller by contacting the roller.

  According to the present invention, the developer is forcibly absorbed into the cell opening of the supply roller, and the developer is stably conveyed to the developer carrying member. Can maintain sex. In addition, because the developer is forcibly included in the supply roller and the amount of developer supplied to the developer carrier is increased, the function of the supply roller is increased compared to the prior art, and the supply roller can be reduced in size. is there. Further, since the amount of intrusion between the developer carrying member and the supply roller can be suppressed as compared with the conventional case, the stress on the developer can be reduced, so that the deterioration of the developer can be suppressed.

(Embodiment 1)
Hereinafter, the developing device according to the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a schematic sectional view of an image forming apparatus to which the present invention is applied, and FIG. 2 is a schematic sectional view of a developing device.

  First, an overall configuration and operation of an image forming apparatus 1 to which a developing device configured according to the present invention is applied will be described with reference to FIG.

  In this embodiment, the image forming apparatus 1 is a laser beam printer. The laser beam printer uses an electrophotographic method in accordance with an image information signal from a personal computer, a document reading device, or the like that is communicably connected to the apparatus main body of the image forming apparatus, and uses a transfer material (recording paper, OHP sheet, An image is formed on a cloth or the like and output. Further, the image forming apparatus 1 of this embodiment includes a developing device 4 that uses a non-magnetic one-component developer.

  In FIG. 1, a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum 2) as an image carrier rotates in the direction indicated by the arrow. The surface of the rotating photosensitive drum 2 is charged to a predetermined polarity (negative polarity in this embodiment) and potential by a charging roller 3 as a charging unit. Then, it exposes with the laser beam 5 from the laser optical apparatus 5a which is an exposure means, and an electrostatic image (latent image) is formed in the surface. A developer carrying member is pressed and brought into contact with the photosensitive drum 2 with a predetermined penetration amount, and the electrostatic latent image is visualized as a developer image (toner image). In FIG. 1, the photosensitive drum 2, the charging roller 3, and the developing device 4 are provided in a process cartridge that can be attached to and detached from the main body of the image forming apparatus 1. As a cartridge, the photosensitive drum 2 may not be provided, and only the developing device 4 may be used.

  The visualized toner image on the photosensitive drum 2 is transferred by a transfer roller 7 to a recording medium as a transfer material. The untransferred toner remaining on the photosensitive drum 2 without being transferred is scraped off by a cleaning blade 8 which is a cleaning member constituting a cleaning unit and stored in a waste toner container. The cleaned photosensitive drum 2 repeats the above operation to form an image.

  On the other hand, the recording medium onto which the toner image has been transferred is heated by the fixing device 9, and the toner image is melt-fixed on the recording medium. The fixed recording medium is discharged out of the apparatus.

  A developing device provided in the image forming apparatus will be described with reference to FIG.

  In FIG. 2, the developing device 4 is composed of a developing container composed of two parts: a developer accommodating chamber for accommodating a negatively chargeable non-magnetic one-component toner as a developer, and a developing chamber. The opening of the developing chamber extending in the longitudinal direction of the developing container is provided with a developing roller 11 as a developer carrying member disposed in contact with the photosensitive drum 2, and the developing roller 11 is an electrostatic latent image on the photosensitive drum 2. Develop and visualize.

As the developer, a non-magnetic one-component developer is used. Wax is contained inside the toner. This is to prevent glare of the recording medium (transfer material) such as recording paper due to the fixing oil when fixing the toner to the transfer material. Instead of eliminating the fixing oil, the fixing device 9 and the transfer material are released from each other by enclosing wax in the toner. In order to improve the image quality, silica is externally added as a fluidity imparting agent in order to improve transfer efficiency. By coating the toner surface with an external additive, negative charging performance is improved, and fluidity is improved by providing a minute gap between the toners. As the external additive used in the present embodiment, for example, the following are used. Metal oxide (aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide, etc.), nitride (silicon nitride, etc.), carbide (silicon carbide, etc.), metal salt (sulfuric acid) Calcium, barium sulfate, calcium carbonate and the like), fatty acid metal salts (such as zinc stearate and calcium stearate), carbon black and silica. These external additives are used in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the toner particles. These external additives may be used alone or in combination. Those subjected to hydrophobic treatment are more preferred. When the amount of the external additive is less than 0.01 parts by weight, the fluidity of the one-component developer is deteriorated, and the efficiency of transfer and development is lowered. So-called scattering occurs in which toner is scattered. On the other hand, when the amount of the external additive exceeds 10 parts by weight, excessive external additive adheres to the photosensitive drum 2 and the developing roller 11 to deteriorate the chargeability of the toner or disturb the image. . Further, in such a state of the outer shape of the toner, the value of the shape factor SF-1 representing the sphericity measured by the image analysis apparatus is preferably 100 to 160, and the value of the shape factor SF-2 is 100 to 160. 140 is preferred. Within these ranges, the toner has a spherical and smooth surface shape. In addition, in order to obtain the shape factors SF-1 and SF-2, 100 toner images enlarged at a magnification of 500 times using a FE-SEM (S-800) manufactured by Hitachi, Ltd. were randomly sampled. The image information is a value obtained based on the SF-1 and SF-2 expressions defined below after being introduced into the image analysis apparatus (Luxex 3) manufactured by Nicole via an interface and analyzed.
SF-1 = {(MXLNG) ² / AREA} × (π / 4) × 100
SF-2 = {(PERI) ² / AREA} × (1 / 4π) × 100
AREA: toner projected area, MXLNG: absolute maximum length, PERI: circumference

  The correspondence between the shape factor and the actual shape indicates that SF-1 indicates the degree of roundness of the toner particles, and corresponds to gradually changing from a spherical shape to an indefinite shape as the numerical value increases. SF-2 indicates the degree of unevenness of the toner particles, and similarly corresponds to the unevenness of the toner surface becoming more prominent as the numerical value increases. As a result, the toner has good rolling properties, and uniform charging is easily performed in the frictional charging. Therefore, it is easy to reduce the amount of uncharged or reversal toner that causes image fogging, which is advantageous. In addition, since the toner is uniformly charged, it is excellent in uniform followability with respect to the electric field, so that good development performance and transfer performance are exhibited. Therefore, it is advantageous even in the case where reproduction of a minute electrostatic latent image is required for high image quality, and the amount of residual toner can be reduced by good transfer performance.

  The developing roller 11 having elasticity protrudes from the developing container 10 at the right half of the circumference shown in FIG. The surface exposed from the developing container 10 faces the photosensitive drum 2 located on the left side of the developing device 4 so as to be pressed and brought into contact with the photosensitive drum 2 with a predetermined amount of penetration.

  The photosensitive drum 2 as an image carrier is a rigid body in which an aluminum cylinder is used as a base and a photosensitive layer having a predetermined thickness is coated around the aluminum cylinder. Prior to the image process during image formation, the image is charged in the charging process. The surface of the charged photosensitive drum 2 is scanned and exposed in accordance with an image information signal by a laser scanner as an exposure unit (image writing unit). As a result, an electrostatic image is formed on the photosensitive drum 2. The electrostatic image formed on the photosensitive drum 2 is then visualized as a visible image, that is, a toner image, by supplying toner as a developer by the developing device 4.

  The developing roller 11 as a developer carrying member carries toner and transports it to the developing area of the photosensitive drum 2. The developing roller 11 is disposed in contact with the photosensitive drum 2 in the developing region, and rotates in the direction indicated by the arrow A.

  In this embodiment, the developing roller 11 has an outer diameter of 12 mm by laminating about 3 mm of an elastic layer on the outer periphery of a cylindrical metal rod (conductive core) having an outer diameter of 6 mm. As the elastic layer, general rubbers such as silicone rubber, urethane rubber, butyl rubber, epichlorohydrin rubber, nitrile butadiene rubber, and ethylene propylene diene rubber (EPDM) can be used. As the developing roller 11, the elastic layer itself may be the outermost layer, but the surface layer may be formed of a material different from that of the elastic layer in consideration of the charging property to the toner. When a negatively chargeable toner is used, urethane resin, polyamide resin, silicone resin, or the like can be used as the surface layer. When a positively charged toner is used, a fluorine resin or the like can be used as the surface layer.

In this embodiment, as the developing roller 11, an elastic layer made of silicone rubber is coated with 20 μm of urethane resin as a surface layer, the surface roughness is 10-point average roughness Rz (JIS B0601) 5 to 8 μm, and the electric resistance value. A roller having a size of 1.0 × 10 ^{3 to} 2.0 × 10 ⁷ Ω was used. In addition, the surface roughness tester “SE-30H” of Kosaka Laboratory was used for the measurement of the surface roughness. The electric resistance value of the developing roller 11 was measured as follows. That is, the electric current of the developing roller 11 is determined from the current value when a DC voltage of 100 V is applied between the core of the developing roller 11 and the stainless steel cylindrical member with the stainless steel cylindrical member having an outer diameter of 30 mm and the developing roller 11 in contact with each other. The resistance value was calculated.

  A developing bias applying means (power source) 15 is connected to the conductive core of the developing roller 11. During the developing operation, the toner on the developing roller 11 is supplied onto the photosensitive drum 2 in accordance with the electrostatic image by the action of the electric field generated by the developing bias applied from the developing bias applying unit to the developing roller 11. In this embodiment, toner charged to the same polarity (negative polarity in this embodiment) as the charging polarity of the photosensitive drum 2 is attached to a portion (bright portion) where the charged charge on the photosensitive drum 2 is attenuated by exposure.

  Above the developing roller 11, a developing blade 12 as an elastic regulating member is attached in order to regulate the layer thickness of the developer on the developing roller 11. The developing blade 12 is made of a metal thin plate such as stainless steel or phosphor bronze, or a resin such as polyamide elastomer (TPAE) having a stable regulation force and a stable (negative) charge imparting property to the toner. The metallic thin plate and the polyamide elastomer are supported by a support sheet metal and are provided so that the vicinity of the free end side is in contact with the outer peripheral surface of the developing roller 11 by surface contact. The contact pressure with respect to the developing roller 11 at this time is preferably about 10 to 45 g / cm. When the density is 10 g / cm or less, the toner cannot be appropriately charged, and “fogging” occurs where the toner adheres to the non-image area, thereby degrading the image quality. When it is 45 g / cm or more, the external additive mixed in the toner due to pressure or the like is easily peeled off from the toner surface, the toner is deteriorated, and the chargeability of the toner is lowered. The method of measuring the linear pressure is to halve the length of a stainless steel plate with a length of 100 mm × width 15 mm × thickness 30 μm as a drawing plate and a stainless steel plate with a length 180 mm × width 30 mm × thickness 30 μm as a sandwiching plate. I prepared something that was folded. Then, a drawing plate is inserted between the sandwiching plates, and the sandwiching plate is inserted between the developing roller 11 and the developing blade 12. In this state, the extraction pressure is withdrawn at a constant speed with only a spring or the like, and the value of the spring only at that time (unit: g) is read. The linear pressure is determined when the value of the spring is divided by 1.5 and the unit is g / cm. In this embodiment, a structure in which a polyamide elastomer (TPAE) is attached to a phosphor bronze plate surface capable of obtaining a stable pressure is used. However, the developing blade 12 is elastically conductive such as a metal thin plate having spring elasticity. A thin plate may be used. The contact direction is a counter direction in which the tip on the free end side with respect to the contact portion is located upstream in the rotation direction of the developing roller 11. The method of supporting the developing blade 12 on the support metal plate is not particularly limited, but is tightening with screws or welding. The developing blade 12 has an average surface roughness Ra of about 0.2 μm to 0.3 μm. In this embodiment, there is no potential difference between the developing roller 11 and the developing blade 12. However, in order to act in an advantageous direction on the solid black image density, a blade bias on the same polarity side as the normal charging polarity of the toner is applied to the developing blade 12 of a metallic thin plate such as phosphor bronze rather than the developing roller 11. You may apply.

  Below the developing roller 11, a supply roller 13 that supplies toner to the developing roller 11 is abutted, and is rotatably supported and rotationally driven in the same direction (arrow B) as the developing roller 11. The supply roller 13 is intended to supply toner to the developing roller 11 and to remove toner remaining on the developing roller 11 without being developed. The supply roller 13 is a foamed elastic material having a plurality of cell openings whose surfaces communicate with each other from the inside. The continuous bubble in which the respective foam cells are connected to each other as a hole is advantageous because a large amount of toner can be contained in the supply roller 13. In this example, open-cell urethane sponge was used. Further, as the foamed elastic member, foamed rubber obtained by foaming silicon rubber, ethylene propylene rubber (EPDM rubber), or the like may be used.

  The cell opening diameter of the supply roller 13 is preferably 10 μm to 1000 μm, and more preferably 200 μm to 600 μm. If the cell opening diameter is less than 10 μm, the sponge eyes are too small and toner does not easily enter the supply roller 13. Further, when the cell opening diameter is larger than 1000 μm, the chance of contact between the sponge partition and the surface of the developing roller 11 is reduced, so that the peeling action of the supply roller 13 is lowered.

Moreover, it is preferable that the ratio of the cell part opened with respect to the total surface area is 10 to 90%, and it is more preferable that it is 30 to 80%. When the ratio of the cells is equal to or lower than the lower limit value, sufficient toner cannot be contained in the supply roller 13. On the other hand, if the upper limit is exceeded, the cell walls are reduced, and the toner is clogged in the supply roller 13, whereby the sponge layer is not sufficiently compressed and recovered. One of the physical properties of the foamed elastic body is the amount of ventilation. This air flow rate indicates the degree of flow of air flowing inside the foamed elastic body, and JIS L 1096 is defined as the standard for the measurement method. In this embodiment, the air flow rate is desirably 10 to 60 cc / cm ² / sec. If the value of the air flow rate becomes larger than this, the toner can move quickly in the supply roller 13, but if the supply roller 13 contains too much toner, the supply roller 13 is cured and the toner deteriorates. As a result, a sufficient triboelectric charge cannot be obtained. As a result, both image density and image uniformity are deteriorated. On the contrary, if the value of the air flow amount becomes smaller than this, the movement of the toner in the supply roller 13 becomes small, and the toner supply amount from the supply roller 13 decreases, resulting in a decrease in density.

The resistance of the supply roller 13 is preferably a semiconductive sponge of 10 ⁴ Ω to 10 ⁸ Ω, and the resistance value of the supply roller 13 used in this example is about 10 ⁷ Ω. Supply roller 13 bias applying means is applied to the metal core which is the rotation shaft of the supply roller 13 so that the toner is supplied from the supply roller 13 toward the developing roller 11 when developing the electrostatic latent image on the photosensitive drum 2. A bias was applied by a power source of 14. In this embodiment, since a voltage of −300 V is applied to the core of the developing roller 11 and −500 V is applied to the core of the supply roller 13, the voltage is 200 V minus from the supply roller 13 with respect to the development roller 11. Applied. That is, the toner is applied to the normal charging polarity (minus) side of the toner with respect to the developing roller 11 rather than the supply roller 13.

  The hardness of the sponge layer of the supply roller 13 is preferably set under the following conditions. When the diameter of the metal core is 5 mm, the outer shape of the sponge layer is cylindrical, and the outer diameter is 16 mm, an aluminum cylinder 17 having the outer diameter of 12 mm and the length of 50 mm (the same as the outer shape of the developing roller 11) is supplied. The center axis of the core of the roller 13 and the longitudinal center line of the cylinder are brought into contact with the sponge layer of the supply roller 13 and compressed at 1.0 mm / sec by 1.0 mm (see FIG. 3). Under this condition, it is preferable to set the hardness of the sponge layer of the supply roller 13 such that the load applied in the vertical direction of the aluminum cylinder by the supply roller 13 is 0.5N to 4.0N, and more preferably, 1.0N to 2.0N. If it is less than this range, toner removal failure on the developing roller 11 that has not been used in development occurs, and image defects such as ghosts occur. If it is more than this range, the frictional force is increased at the contact portion of the supply roller 13 with the member, and the toner is markedly deteriorated to cause image defects. In this embodiment, the supply roller 13 has a hardness of 1.5N.

  A protrusion-shaped protruding member 16 as a pressing member is in pressure contact with the supply roller 13. The intrusion amount of the protruding member 16 with respect to the supply roller 13 is the rotational torque acting on the supply roller 13 when the protruding member 16 contacts the supply roller 13, and the supply roller 13 when the supply roller 13 contacts the developing roller 11. The value is larger than the working rotational torque. By doing so, a larger force than the supply roller 13 receives at the nip portion with the developing roller 11 is received at the nip portion with the protruding member 16, and the sponge is compressed. Further, the contact frictional force is increased by the protrusion member coming into contact with the supply roller 13, and the toner deterioration is advanced when the rotational torque acting on the supply roller 13 is increased. Therefore, it is desirable that the total rotational torque of the supply roller 13 in contact with the developing roller 11 and the protruding member 16 is smaller than the conventional configuration (0.015 N · m).

  In the present embodiment, a supply roller 13 having an outer diameter of 16 mm enters 250 μm into the developing roller 11 having an outer diameter of 12 mm, and a protrusion member 16 that contacts the supply roller 13 in the longitudinal direction enters 500 μm. As the protruding member 16, silicon rubber, which is a rectangular parallelepiped foamed elastic member having a thickness of 3 mm and a width of 3 mm, was used. In addition to this, foamed rubber obtained by foaming urethane sponge, ethylene propylene rubber (EPDM rubber) or the like may be used as the foamed elastic member. With this penetration amount, the rotational torque of the supply roller 13 was measured under the following conditions. That is, when the circumferential speed of the developing roller 11 is 250 mm / sec, the circumferential speed of the supply roller 13 is 220 mm / sec, and the rotational torque when the developing roller 11 and the supply roller 13 are not in contact is based on zero (the rotational torque shown below) Are all based on this). As a result, the rotational torque (FIG. 4) received by the supply roller 13 in contact with the developing roller 11 is 0.0015 N.m. m, the rotational torque (FIG. 5) received by the supply roller 13 upon contact with the protruding member 16 is 0.0065 N.m. m. The rotational torque of the supply roller 13 received by the protruding member 16 is set to be larger than the rotational torque of the supply roller 13 received by contact with the developing roller 11. Therefore, the total rotational torque applied to the supply roller 13 is 0.008 N.m. m, and in the case of the conventional configuration (when the amount of penetration of the supply roller 13 with respect to the developing roller 11 is 1.0 mm), the total rotational torque applied to the supply roller 13 is 0.015 N.m. It is a value smaller than m. Thereby, it is possible to suppress toner deterioration caused by contact friction by the supply roller 13 as compared with the conventional configuration. Here, the intrusion amount of the supply roller 13 with respect to the developing roller 11 is 250 μm. However, if the value is smaller than this value, the contact friction between the supply roller 13 and the developing roller 11 is too small, and the toner on the developing roller 11 that has not been used for development is not peeled off, resulting in image defects such as ghosts. On the other hand, when the intrusion amount of the supply roller 13 with respect to the developing roller 11 is larger than 500 μm, the rotational torque of the supply roller 13 received by contact with the protruding member 16 is the rotational torque received by contact with the developing roller 11. It will be a smaller value. As described above, the rotational torque of the supply roller 13 that is received by contact with the protruding member 16 becomes smaller than the rotational torque that is received by contact with the developing roller 11. In addition, the toner deteriorates and an image defect occurs, which is not desirable. Further, the amount of intrusion of the supply roller 13 with respect to the developing roller 11 is made larger than 500 μm, and the rotational torque of the supply roller 13 received by contacting the protruding member 16 is larger than the rotational torque applied by contacting the developing roller 11. Then, the total rotational torque acting on the supply roller 13 becomes larger than in the conventional configuration, the stress on the toner increases, the toner deteriorates, and an image defect occurs, which is not preferable.

  Further, the contact position between the protruding member 16 and the supply roller 13 is preferably set as follows. That is, the displacement amount of the outer diameter of the supply roller 13 caused by the rotation of the supply roller 13 in contact with the developing roller 11 is at a position where the amount of change does not substantially change, and from the developer storage chamber 18 that stores toner to the development chamber 19. This is a position near the toner supply position (III in FIG. 6). When the developing roller 11 and the supply roller 13 rotate in the counter direction at the contact portion as shown in FIG. 6 and the developing roller 11 rotates rapidly with respect to the supply roller 13, the supply roller 13 is deformed as follows. That is, it has been observed that the sponge is deformed in the direction of depression in the region I (nip exit side) in FIG. 6, and the sponge is deformed in the direction of swelling in the region II (nip entrance side) in FIG. By disposing the sponge at this position, the supply roller 13 which is a sponge is compressed by the projecting member 16 and can actively absorb the toner around it when released. Further, the contact between the protruding member 16 and the supply roller 13 can open the eyes of the sponge immediately after passing through the contact portion, and forcibly absorb the toner into the sponge when the sponge recovers. Thereby, an electric field is formed in the direction in which the toner moves from the supply roller 13 containing a large amount of toner in the sponge to the developing roller 11, so that a large amount of toner can be supplied to the developing roller 11. Furthermore, since the supply amount is increased by forcibly including the toner in the supply roller 13, the supply roller 13 can be downsized, and the amount of the supply roller 13 entering the developing roller 11 can be reduced.

  That is, as in this embodiment, the surface is larger than the rotational torque acting on the supply roller 13 when the developing roller 11 comes into contact with the supply roller 13 made of a material having a plurality of cell openings that communicate with each other from the inside. The projecting member 16 is brought into contact with the supply roller 13 so as to have a rotational torque, the sponge of the supply roller 13 is forcibly compressed, and the sponge eye is opened to forcibly fill the toner in the supply roller 13. Can do. As a result, sufficient image density and followability can be maintained even after long-term use, and the supply roller 13 can be reduced in size and the amount of penetration of the supply roller 13 into the developing roller 11 can be reduced.

  An image output durability test was performed in the image forming apparatus 1 of the present embodiment. As described above, in the developing device 4 provided in the image forming apparatus 1 of the present embodiment, toner is forcibly included in the supply roller 13 even during continuous use of the device, and a large amount of toner is supplied to the developing roller 11 due to the effect of bias. Therefore, it is advantageous in increasing the image density and maintaining the image followability. Further, even if the amount of the supply roller 13 entering the developing roller 11 is reduced, sufficient toner can be supplied to the developing roller 11, so that the frictional force and heat at the contact portion between the developing roller 11 and the supply roller 13 are reduced. As a result, the toner can be stably supplied into the supply roller 13, thereby providing an apparatus capable of maintaining a high density and followability even after long-term use.

<< Examples and Comparative Examples >>
In order to clarify the advantageous effects of the present invention in the embodiment, examples and comparative examples of the present invention applied to the embodiment will be described below.

(Example 1-1)
The detailed form of the present embodiment is as described in the first embodiment. Briefly, again, the supply roller 13 enters the developing roller 11 by 250 μm, and the protrusion member 16 that contacts the supply roller 13 in the longitudinal direction enters 500 μm. With this penetration amount, when the peripheral speed of the developing roller 11 is 250 mm / sec, the peripheral speed of the supply roller 13 is 220 mm / sec, and the rotational torque when the developing roller 11 and the supply roller 13 are not in contact is zero reference, the supply roller The rotational torque of was measured. The rotational torque received by the supply roller 13 upon contact with the developing roller 11 is 0.0015N. m, the rotational torque that the supply roller 13 receives in contact with the protruding member 16 is 0.0065 N.m. m. The rotational torque of the supply roller 13 received by contact with the projecting member 16 is set to be larger than the rotational torque received by contact with the developing roller 11. Therefore, the total rotational torque applied to the supply roller 13 is 0.008 N.m. m.

(Comparative Example 1)
The amount of penetration of the supply roller 13 with respect to the developing roller 11 was changed from 1.0 mm to 0.6 mm using the image forming apparatus of the conventional developing device (FIG. 12). At this time, the rotational torque received by the supply roller 13 from the developing roller 11 is 0.008 N.m. m.

(Comparative Example 2)
The developing device of this comparative example basically conforms to the first embodiment, but differs in the following points.

  Specifically, the intrusion amount of the supply roller 13 with respect to the developing roller 11 was set to zero. At this time, the rotational torque received by the supply roller 13 in contact with the developing roller 11 is 0N. m.

(Comparative Example 3)
The developing device of this comparative example basically conforms to the first embodiment, but differs in the following points.

  The penetration amount of the supply roller 13 with respect to the developing roller 11 is set to 500 μm. In this case, the rotational torque received by the supply roller 13 in contact with the developing roller 11 is 0.007 N.m. Therefore, the rotational torque of the supply roller 13 received by contact with the protruding member 16 is smaller than the rotational torque received by contact with the developing roller 11.

(Example 1-2)
The penetration amount of the supply roller 13 with respect to the developing roller 11 was set to 500 μm or more. When the intrusion amount is 500 μm, the rotational torque received by the supply roller 13 in contact with the developing roller 11 is 0.007 N.m. m. In this case, in order to make the rotational torque of the supply roller 13 received by contacting the protruding member 16 larger than the rotational torque applied by contacting the developing roller 11, the intrusion amount of the protruding member 16 into the supply roller 13 is 600 μm. The above is necessary. When the penetration amount of the protruding member 16 into the supply roller 13 is 600 μm, the rotational torque is 0.008 N.m. m.

Evaluation Method for Each Example and Comparative Example Hereinafter, image evaluation for examining the difference between the present invention and the comparative example will be described.

a) Solid black image density evaluation at the initial stage of printing Image evaluation was performed by continuously outputting 10 solid black images, and the output of the 10th solid black image has three points on the left, right, and center of the output, 9 points in total. The average of the point concentrations was measured using a spectrodensitometer 500 manufactured by X-Rite. The solid black image density difference was evaluated after printing 100 sheets in an evaluation environment of 23 ° C. and 50% Rh. The printing test was performed by continuously passing a horizontal line of recorded images having an image ratio of 5%.

Here, image evaluation was performed according to the following criteria.
×: Solid black image / density is less than 1.0 Δ: Solid black image / density is 1.0 or more and less than 1.3 ○: Solid black image / density is 1.3 or more

b) Solid black image density difference evaluation at the initial stage of printing Image evaluation is performed by continuously outputting 10 solid black images, and evaluation is performed based on the density difference between the output leading edge and the trailing edge of the 10th solid black image using a spectrodensitometer 500 manufactured by X-Rite. Used. The solid black image density difference evaluation at the initial printing was performed after printing 100 sheets in an evaluation environment of 23 ° C. and 50% Rh. The printing test was performed by continuously passing a horizontal line of recorded images having an image ratio of 5%.

Here, image evaluation was performed according to the following criteria.
×: Solid black image / density difference between leading edge and trailing edge is 0.3 or more △: Solid black image / density difference between leading edge and trailing edge is 0.2 or more and less than 0.3 ○: Solid black image / leading edge And back end density difference is less than 0.2

c) Solid black image density difference evaluation after endurance Image evaluation is performed by continuously outputting 10 solid black images, and evaluating the density difference between the leading edge and the trailing edge of the 10th solid black image using a spectrodensitometer 500 manufactured by X-Rite. Used. The evaluation of the solid black image density difference after endurance was performed after printing 20,000 sheets in an evaluation environment of 23 ° C. and 50% Rh. The printing test was performed by continuously passing a horizontal line of recorded images having an image ratio of 5%.

Here, image evaluation was performed according to the following criteria.
×: Solid black image / density difference between leading edge and trailing edge is 0.3 or more △: Solid black image / density difference between leading edge and trailing edge is 0.2 or more and less than 0.3 ○: Solid black image / leading edge And back end density difference is less than 0.2

d) Ghost evaluation at the initial stage of printing A ghost image appearing in the developing roller cycle was evaluated. Specifically, a ghost is determined to be an image defect due to a ghost when a density difference appearing on the first round of the developing roller cycle in a halftone image can be visually recognized after printing a solid black patch image of 25 mm × 25 mm square at the leading edge of the paper. did. Ghost evaluation at the initial stage of printing was performed after printing 100 sheets in an evaluation environment of 23 ° C. and 50% Rh. The printing test was performed by continuously passing a horizontal line of recorded images having an image ratio of 5%.

Here, image evaluation was performed according to the following criteria.
X: A ghost image can be recognized.
○: A ghost image cannot be recognized.

e) Ghost evaluation after endurance A ghost image appearing in the developing roller cycle was evaluated. Specifically, a ghost is determined to be an image defect due to a ghost when a density difference appearing in the first round of the developing roller cycle in a halftone image can be visually recognized after printing a solid black patch image of 25 mm × 25 mm square at the leading edge of the paper. did. The ghost evaluation after durability was performed after printing 20,000 sheets in an evaluation environment of 23 ° C. and 50% Rh. The printing test was performed by continuously passing a horizontal line of recorded images having an image ratio of 5%.

Here, image evaluation was performed according to the following criteria.
X: A ghost image can be recognized.
○: A ghost image cannot be recognized.

Advantages over the prior art The advantages of the present invention will be described by comparing the prior art with Example 1-1 (Table 1). In the developing device 20 having the conventional configuration, toner deterioration progresses due to the rubbing force and heat at the contact portion between the developing roller 11 and the supply roller 13 in the second half of the endurance. As a result, in the second half of the endurance, the charged charge amount decreased and the degree of aggregation increased, resulting in image defects such as ghosts, and a tracking failure that caused a density difference between the leading and trailing edges of a solid black image. On the other hand, Example 1-1 which is the present invention remarkably suppresses the occurrence of ghost and follow-up failure in the latter half of the durability, and the number of durable sheets without image defects is 1.2 to 1. Increased 5 times.

Superiority with respect to the comparative technique The superiority of the present invention will be described by comparing Example 1-1 with Comparative Examples 1 to 3 and Example 1-2 (Table 1).

  The comparative example 1 has a smaller amount of penetration of the supply roller 13 with respect to the developing roller 11 than the configuration of the conventional example. As a result, the amount of compression of the sponge portion of the supply roller 13 is reduced, the amount of toner released from the supply roller 13 is reduced, and the supply amount is reduced. As a result, the solid black image density was low from the beginning, and an image follow-up failure was caused in which there was a density difference between the output front end and the rear end of the solid black image.

  In Comparative Example 2, the intrusion amount of the supply roller 13 with respect to the developing roller 11 is zero with respect to Example 1-1. The protruding member 16 contacts the supply roller 13 in the same manner as in Example 1-1, and the toner is forcibly conveyed into the supply roller 13. As a result, if the bias in the direction in which the toner is pushed out to the developing roller 11 acts on the supply roller 13, the initial density is slightly higher than that in the comparative example 1. However, the contact frictional force does not act between the supply roller 13 and the developing roller 11, and the toner on the developing roller 11 that has not been used in the development cannot be peeled off, resulting in image defects such as ghosts from the beginning.

  In Comparative Example 3, the intrusion amount of the supply roller 13 with respect to the developing roller 11 is larger than that of Example 1-1. As a result, the compression amount of the sponge portion of the supply roller 13 increases, the amount of toner released from the supply roller 13 increases, and the supply amount increases. As a result, the initial solid black image density was higher than that in Example 1-1. However, the rotational torque received by contact with the developing roller 11 is larger than the rotational torque of the supply roller 13 received by contact with the protruding member 16. Accordingly, the contact friction between the supply roller 13 and the developing roller 11 is large, toner deterioration progresses with durability at this contact portion, and image defects such as ghost and follow-up failure occur in the second half of the durability.

  In Example 1-2, the intrusion amount of the supply roller 13 with respect to the developing roller 11 was set to 500 μm or more with respect to Example 1-1 (the torque at the time of 500 μm intrusion is described in Table 1). Further, the rotational torque of the supply roller 13 received by contacting the protruding member 16 is set to be larger than the rotational torque applied by contacting the developing roller 11. As a result, when the toner is conveyed from the developer storage chamber 18 to the development chamber 19, a larger amount of toner is forced into the supply roller 13 immediately after passing the contact portion between the supply roller 13 and the protruding member 16 than in Example 1-1. to go into. A large amount of toner is supplied from the supply roller 13 to the developing roller 11 by compression of the sponge at the nip portion between the supply roller 13 and the developing roller 11. As a result, the image density of solid black became deep from the beginning. However, if the total rotational torque received by the supply roller 13 is the same as or higher than that of the conventional example (0.015 N.m), the toner deteriorates with the endurance, and ghost and follow-up failure occur in the end of the endurance. The image defect occurred to the same extent as the conventional example or more.

(Embodiment 2)
Next, a developing device according to another embodiment of the present invention will be described with reference to FIG. The basic configurations and operations of the developing device and the image forming apparatus of the present embodiment are almost the same as those of the first embodiment. Therefore, elements having substantially the same or corresponding functions and configurations as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In the present embodiment, the shape of the protruding member 16 that is a pressing member that press-contacts the supply roller 13 is a triangular shape as shown in FIG. 7, and the protruding member 16 and the supply roller 13 are more in line contact than in the first embodiment. Like that.

  In this embodiment, high-impact polystyrene (HIPS), which is the same material as the developing container 10, is used for the protruding member 16. However, a general-purpose resin such as polyethylene (PE), polypropylene (PP), or polystyrene (PS) may be used as long as the protruding member 16 is not greatly deformed by contact between the supply roller 13 and the protruding member 16. Good.

  As in the first embodiment, the protruding amount of the protruding member 16 is supplied by the rotation torque acting on the supply roller 13 when the protruding member 16 contacts the supply roller 13 and when the supply roller 13 contacts the developing roller 11. The value is set to be larger than the rotational torque acting on the roller 13. By doing so, a larger sponge compression force is received at the nip portion with the protruding member 16 than the supply roller 13 receives at the nip portion with the developing roller 11. Further, as in the first embodiment, when the contact friction force is increased and the total rotational torque acting on the supply roller 13 is increased, the toner deterioration is advanced. Accordingly, it is desirable that the total rotational torque of the supply roller 13 that contacts the developing roller 11 and the protruding member 16 is smaller than that of the conventional configuration (0.015 N · m).

  In the second embodiment, a supply roller 13 having an outer diameter of 16 mm enters 250 μm into the developing roller 11 having an outer diameter of 12 mm, and a protrusion member 16 which contacts the supply roller 13 in the longitudinal direction enters 500 μm.

  According to the present example, in addition to the effect of the first embodiment, the following new effect occurs. By making the shape of the protruding member 16 triangular, and making the apex of the triangle line contact with the supply roller 13, the nip width between the protruding member 16 and the supply roller 13 becomes narrower than that of the first embodiment. Therefore, as in the first embodiment, even if the protruding member 16 enters the supply roller 13 by 500 μm, the rotational torque received by the contact between the protruding member 16 and the supply roller 13 is smaller than that in the first embodiment. When the peripheral speed of the developing roller 11 is 250 mm / sec, the peripheral speed of the supply roller 13 is 220 mm / sec, and the rotational torque when the developing roller 11 and the supply roller 13 are not in contact with each other is zero reference, the supply roller 13 is the development roller 11. The rotational torque received in contact with the m, the rotational torque received by the supply roller 13 upon contact with the protruding member 16 is 0.0050 N.m. m. Therefore, the total rotational torque applied to the supply roller 13 is 0.0065 N.m. m (Example 2 of Table 1).

  As a result, by forming the protruding member 16 in a triangular shape at the contact portion between the supply roller 13 and the protruding member 16, the supply roller 13 receives the contact with the protruding member 16 even with the same amount of sponge compression as in the first embodiment. The rotational torque is reduced, which is advantageous for durability deterioration. Further, the triangular apex of the protruding member 16 squeezes the sponge surface layer portion of the supply roller 13, opens the eyes of the sponge surface layer portion of the supply roller 13, and puts toner into the supply roller 13.

  An image output durability test was performed in the image forming apparatus 1 of the present embodiment. As described above, in the developing device 4, even when the device is continuously used, the toner is forcibly included in the supply roller 13 while the rotational torque is smaller than that in the first embodiment, and the bias in the sponge surface layer portion is included. A lot of toner is supplied to the developing roller 11. Therefore, it is advantageous for increasing the concentration and maintaining the followability from the initial durability to the latter half of the durability. As a result, as compared with the conventional developing device 20, the number of durable sheets that maintain a high density and do not cause a follow-up failure increased 1.3 to 1.6 times.

  As described above, the toner can be forcibly included in the supply roller 13 stably without applying a load to the supply roller 13 as compared with the first embodiment. It was possible to provide an apparatus capable of maintaining higher concentration and followability than 1.

(Embodiment 3)
Next, a developing device according to another embodiment of the present invention will be described with reference to FIG. The basic configurations and operations of the developing device and the image forming apparatus of the present embodiment are almost the same as those of the first embodiment. Therefore, elements having substantially the same or corresponding functions and configurations as those of the first and second embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the protruding member 16 that is a pressing member that presses and contacts the supply roller 13 is integrated with the developing container frame. That is, the protruding member 16 is a part of the frame of the developing container. The material of the projecting portion may be the same as that of the developing container frame, but the surface of the projecting member 16 is polished to increase the frictional force with the supply roller 13, and the contact between the projecting member 16 and the supply roller 13 causes a sponge eye. May be made easier to open, and toner may be forcibly absorbed into the sponge (FIG. 9).

  The shape of the protruding portion may be triangular as shown in the second embodiment, and the protruding member 16 portion may be integrated with the developing container frame. As in the first embodiment, the intrusion amount of the protruding portion into the supply roller 13 is the rotation torque that acts on the supply roller 13 by contacting the projection member 16 and the rotation torque that acts on the supply roller 13 by contacting the developing roller 11. The value is larger than the torque. Further, since the toner deterioration progresses when the total rotational torque acting on the supply roller 13 increases, the total rotational torque of the supply roller 13 that contacts the developing roller 11 and the protruding member 16 is made smaller than that of the conventional configuration (0.015 N.m). It is desirable.

  In the third embodiment, a supply roller 13 having an outer diameter of 16 mm enters 250 μm into the developing roller 11 having an outer diameter of 12 mm, and a protrusion member 16 which contacts the supply roller 13 in the longitudinal direction enters 500 μm.

  When the peripheral speed of the developing roller 11 is 250 mm / sec, the peripheral speed of the supply roller 13 is 220 mm / sec, and the rotational torque when the developing roller 11 and the supply roller 13 are not in contact is zero reference, the supply roller 13 is the development roller 11. The rotational torque received in contact with the m, the rotational torque received by the supply roller 13 in contact with the protruding member 16 is 0.007 N.m. m. Therefore, the total rotational torque applied to the supply roller 13 is 0.0085 N.m. m (Example 3 of Table 1).

  As described above, by integrating the protruding member 16 that contacts the supply roller 13 with the developing container frame, in addition to the effects shown in the first and second embodiments, the protruding member 16 is newly bonded in the developing container. The process is gone. Furthermore, since the member of the protruding portion may be the same as the developing container frame, the manufacturing cost can be suppressed.

(Embodiment 4)
Next, a developing device according to another embodiment of the present invention will be described based on. The basic configurations and operations of the developing device and the image forming apparatus of this embodiment are almost the same as those of the first, second, and third embodiments. Therefore, detailed description is abbreviate | omitted using drawing of Embodiment 1,2,3.

In this embodiment, carbon black or a metal oxide is added in order to give a resistance of about 10 ⁴ Ω to 10 ⁸ Ω to the developer supply roller 13 having at least a surface layer made of a semi-independent foamed elastic body. An electronically conductive material made by dispersion was used. The use of an electronic conductive material has the following advantages compared to the case of using an ionic conductive material (a material added with a quaternary ammonium salt or an aliphatic alcohol sulfate salt). That is, there is almost no difference between the resistance value under low temperature and low humidity of 15 ° C. and 10% and the resistance value of the supply roller 13 under high temperature and high humidity of 30 ° C. and 80%.

  In the fourth embodiment, a supply roller 13 having an outer diameter of 16 mm enters 250 μm into the developing roller 11 having an outer diameter of 12 mm, and a protrusion member 16 which contacts the supply roller 13 in the longitudinal direction enters 500 μm. When the peripheral speed of the developing roller 11 is 250 mm / sec, the peripheral speed of the supply roller 13 is 220 mm / sec, and the rotational torque when the developing roller 11 and the supply roller 13 are not in contact with each other is zero reference, the supply roller 13 is the development roller 11. The rotational torque received in contact with the m, the rotational torque received by the supply roller 13 in contact with the protruding member 16 is 0.007 N.m. m. Therefore, the total rotational torque applied to the supply roller 13 is 0.009 N.m. ms (Example 4 in Table 1).

  As described above, according to this example, in addition to the effects of the first, second, and third embodiments, the following new effects are produced. By making the supply roller 13 electronically conductive, the resistance value does not vary under any environment, and a desired potential difference can be stably applied between the developing roller 11 and the supply roller 13. Therefore, the toner forcibly contained in the supply roller 13 can be stably supplied to the developing roller 11, so that high density and followability can be maintained even when used for a long time in any environment. We were able to provide a device that can be used.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention. It is a schematic block diagram which shows an example of the image development apparatus concerning this invention. It is a figure explaining the method to measure the hardness of a sponge layer. The graph which shows the rotational torque which acts on the supply roller which concerns on this invention. The graph which shows the rotational torque which acts on the supply roller which concerns on this invention. It is a schematic block diagram which shows the optimal position of the projection member which concerns on this invention. It is a schematic block diagram which shows an example of the developing device which concerns on this invention. It is a schematic block diagram which shows an example of the developing device which concerns on this invention. It is a schematic block diagram which shows an example of the protrusion member which concerns on this invention. It is a schematic block diagram which shows an example of the process cartridge which concerns on this invention. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention. It is a schematic block diagram which shows an example of the conventional developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum (image carrier)
DESCRIPTION OF SYMBOLS 3 Charging means 4 Developing device 10 Developing container 11 Developing roller (developer carrier)
12 Development blade (developer regulating member)
DESCRIPTION OF SYMBOLS 13 Supply roller 14 Supply roller bias application means 15 Development bias application means 16 Projection member 17 Aluminum cylinder 18 Developer storage chamber 19 Development chamber 20 Conventional developing device 30 Process cartridge

Claims (13)

Provided in contact with the image carrier, provided in contact with the developer carrier, and a developer carrier that carries the developer to develop the electrostatic image formed on the image carrier with the developer. A developer supply roller for supplying a developer to the developer carrying member, the developer supply roller having an elastic layer provided with a plurality of cell openings on a surface thereof;
There is a pressing member that presses against the elastic layer, and when the pressing member contacts the developer supply roller, the rotational torque acting on the developer supply roller is such that the developer carrier contacts the developer supply roller. Thus, the developing device is larger in rotational torque acting on the developer supply roller.   The developing device according to claim 1, wherein the developer carrying member has elasticity.   The developing device according to claim 1, wherein the pressing member has a protruding shape.   4. The developing device according to claim 1, wherein a load applied when the elastic layer is compressed by 1.0 mm is 0.5 N to 4.0 N.   A voltage is applied to the developer supply roller so that an electric field is formed between the developer carrier and the developer supply roller in a direction in which the developer is directed from the developer supply roller to the developer carrier. The developing device according to claim 1, wherein the developing device is applied.   The developing device according to claim 1, wherein the pressing member is a foamed elastic member.   The developing device according to claim 1, wherein the pressing member is a part of a frame of a developing container that contains a developer. The developing device according to claim 1, wherein a resistance value of the developer supply roller is 10 ⁴ to 10 ⁸ Ω.   The developing device according to claim 8, wherein the elastic layer has an electronic conductivity in which carbon is dispersed.   The developing device according to any one of claims 1 to 9, wherein the developer has a shape factor SF-1 of 100 to 160 and a shape factor SF-2 of 100 to 140.   The total rotational torque acting on the developer supply roller is 0.015 N.m. The developing device according to claim 1, wherein the developing device is smaller than m.   12. The developing device according to claim 1, wherein the developer carrying member is provided in contact with the image carrying member.   A process cartridge, which is detachable from a main body of an image forming apparatus, and includes the image carrier and the developing device according to claim 1.

Images