JP6091087B2 - Developing device and process cartridge - Google Patents

Description

  The present invention relates to a developing device and a process cartridge used in, for example, an electrophotographic or electrostatic recording image forming apparatus.

  An image forming apparatus such as a printer using an electrophotographic process uniformly charges an electrophotographic photosensitive member (hereinafter also simply referred to as “photosensitive member”) as an image carrier. Next, an electrostatic image is formed on the photosensitive member by selectively exposing the charged photosensitive member. Next, the electrostatic image formed on the photosensitive member is visualized as a toner image by charging toner as a developer and attaching it to the electrostatic image by an electrostatic effect. The toner image formed on the photoconductor is transferred to a recording material such as recording paper or a plastic sheet, and the toner image is applied to the recording material by applying heat or pressure to the toner image transferred onto the recording material. Fix and record image.

  As a means for charging the toner, for example, a developing blade that charges the toner at the same time that the toner adhering to the developing roller is uniformly regulated to a predetermined thickness is provided in the developing device. In order to stabilize the toner amount and the toner charge amount on the developing roller, it is important to keep the pressing force of the developing blade against the developing roller stable. So far, various methods and apparatuses have been proposed as means for pressing the developing blade against the developing roller.

  For example, Patent Document 1 describes a developing device that supports a developing blade rotatably and presses the developing blade against the developing roller by applying a moment about a rotation fulcrum.

  Patent Document 2 describes a developing device that supports a developing blade in a rotatable manner, generates a potential difference between the developing roller and the developing blade, and presses the developing blade against the developing roller by electrostatic adsorption force. ing.

JP 10-239991 JP2009-31345A

  Incidentally, in a process cartridge used in an image forming apparatus, preventing toner leakage is important in improving image quality and usability. For the configuration of the developing blade that is rotatably supported as described above, a seal member that is disposed in contact with the developing blade in order to suppress toner leakage from between the developing device and the developing blade is generally used. Is necessary.

  However, when a repulsive force of the seal member is applied to the developing blade that is rotatably supported, the repulsive force of the seal member is converted into a regulating force of the developing blade as a moment of force around the rotation center of the developing blade. I will join. However, the seal member is generally composed of an elastic member, and after a long period of time, the repulsive force decreases due to creep (deformation by continuing to receive a constant force). As a result, there is a problem that the toner regulation of the developing blade is not stable for a long time. The present invention solves the above problems.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device and a process cartridge capable of stabilizing toner regulation on a developing roller by a developing blade over a long period of time.

A typical configuration of the present invention for solving the above problems is as follows.
In a developing device used in an image forming apparatus,
In order to develop the electrostatic latent image formed on the image carrier, a developer carrier that carries a developer, and the amount of developer that is in contact with the developer carrier and carried on the developer carrier A developer regulating member that is rotatably supported,
A frame forming a developer accommodating chamber;
A seal member that is compressed and disposed between the frame and the developer restricting member in order to restrict leakage of the developer accommodated in the developer containing chamber;
An urging unit that presses the developer regulating member against the developer carrying member by applying a moment to the developer regulating member;
Have
When the rotation center of the developer regulating member is projected from the direction perpendicular to the contact surface onto the contact surface of the developer regulating member that contacts the seal member, the projected rotation center overlaps with the seal member , The developer regulating member has a plate-like elastic member that contacts the developer carrier, and a support member that supports the elastic member,
The biasing means applies a force to the developer regulating member in a direction in which the elastic member extends from the support member toward the developer carrier .

  According to the present invention, it is possible to stably regulate the amount of toner carried on the developer carrying member by the developer regulating member over a long period of time.

1 is a schematic sectional view of a developing device according to the present invention. 1 is a schematic sectional view of an image forming apparatus main body according to the present invention. 1 is a schematic sectional view of a process cartridge according to the present invention. 1 is a schematic cross-sectional view of a developing device showing a force acting on a developing blade according to the present invention. Schematic explaining the setting position of the swing fulcrum shaft according to the present invention. Schematic explaining the shape of the tip of the developing blade according to the present invention. FIG. 3 is a schematic cross-sectional view of a developing device showing a force acting on a developing blade.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

[Electrophotographic image forming apparatus]
First, an image forming apparatus in which the process cartridge of this embodiment is detachably mounted will be described with reference to FIGS. FIG. 2 is a schematic cross-sectional view of the image forming apparatus 100 of the present embodiment, and FIG. 3 is a schematic cross-sectional view of the process cartridge 7 of the present embodiment. The image forming apparatus 100 of this embodiment is a full-color laser printer that employs an inline method and an intermediate transfer method. The image forming apparatus 100 can form a full-color image on the recording material 12 (for example, recording paper, plastic sheet, cloth, etc.) according to the image information. The image information is input to the image forming apparatus main body from an image reading apparatus connected to the image forming apparatus main body or a host device such as a personal computer connected to the image forming apparatus main body so as to be communicable.

  The image forming apparatus 100 includes, as a plurality of image forming units, first, second, and third images for forming yellow (Y), magenta (M), cyan (C), and black (K) images, respectively. And a fourth image forming unit. In the present embodiment, the first to fourth image forming units are arranged in a row in the direction intersecting the vertical direction as the first to fourth process cartridges 7Y, 7M, 7C, and 7K.

  In the present embodiment, the configurations and operations of the first to fourth image forming units are substantially the same except that the colors of images to be formed are different. Therefore, in the following, unless there is a particular distinction, the subscripts Y, M, C, and K given to the reference numerals to indicate that they are elements provided for any color are omitted, and generally explain.

  In other words, in the present embodiment, the image forming apparatus 100 includes four drum-type electrophotographic photoreceptors, that is, the photoreceptor drums 1 arranged in parallel in a direction intersecting the vertical direction as a plurality of image carriers. . The photosensitive drum 1 is rotationally driven by a driving means (drive source) (not shown) in the direction indicated by an arrow A (clockwise). Around the photosensitive drum 1, a charging roller 2 as a charging unit that uniformly charges the surface of the photosensitive drum 1, a laser is irradiated based on image information, and an electrostatic image (electrostatic latent image) is formed on the photosensitive drum 1. A scanner unit (exposure device) 3 is disposed as exposure means for forming (image). Further, around the photosensitive drum 1, a developing unit (developing device) 4 as developing means for developing an electrostatic image as a toner image, toner remaining on the surface of the photosensitive drum 1 after transfer (transfer residual toner) A cleaning member 6 is disposed as a cleaning means for removing water. Further, an intermediate transfer belt 5 as an intermediate transfer body for transferring the toner image on the photosensitive drum 1 to the recording material 12 is disposed opposite to the four photosensitive drums 1. In the rotation direction of the photosensitive drum 1, the charging position by the charging roller 2, the exposure position by the scanner unit 3, the development position by the development unit 4, the transfer position of the toner image to the intermediate transfer belt 5, and the cleaning position by the cleaning member 6 are They are provided in this order.

  In the present embodiment, the developing unit 4 uses a non-magnetic one-component developer, that is, toner, as the developer. In this embodiment, the developing unit 4 performs reverse development by bringing a developing roller (described later) as a developer carrying member into contact with the photosensitive drum 1. That is, in the present embodiment, the developing unit 4 is a portion where the charge of the toner charged to the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in this embodiment) is attenuated by exposure on the photosensitive drum 1 ( It is attached to the image area and the exposure area. Thereby, the electrostatic image (electrostatic latent image) formed on the photosensitive drum 1 is developed.

  In the present embodiment, the photosensitive drum 1, the charging roller 2 as the process means acting on the photosensitive drum 1, the developing unit 4, and the cleaning member 6 are integrally formed into a cartridge to form a process cartridge 7. ing. The process cartridge 7 is attachable to and detachable from the apparatus main body 100A through mounting means such as a mounting guide and a positioning member provided in the apparatus main body 100A of the image forming apparatus 100. Here, the apparatus main body 100 </ b> A is a part obtained by removing the process cartridge 7 from the image forming apparatus 100.

  In this embodiment, the process cartridges 7 for the respective colors all have the same shape, and the process cartridges 7 for the respective colors have yellow (Y), magenta (M), cyan (C), and blank (K), respectively. ) Is stored.

  The intermediate transfer belt 5 formed of an endless belt as an intermediate transfer member is in contact with all the photosensitive drums 1 and circulates (rotates) in the direction of the arrow B (clockwise) in the figure. The intermediate transfer belt 5 is stretched around a driven roller 51, a secondary transfer counter roller 52, and a driving roller 53 as a plurality of support members.

  On the inner peripheral surface side of the intermediate transfer belt 5, four primary transfer rollers 8 as primary transfer means are arranged in parallel so as to face the respective photosensitive drums 1 with the intermediate transfer belt 5 interposed therebetween. Yes. The primary transfer roller 8 presses the intermediate transfer belt 5 toward the photosensitive drum 1 to form a primary transfer portion N1 where the intermediate transfer belt 5 and the photosensitive drum 1 abut. A bias having a polarity opposite to the normal charging polarity of the toner is applied to the primary transfer roller 8 from a primary transfer bias power source (high voltage power source) as a primary transfer bias applying unit (not shown). As a result, the toner image on the photosensitive drum 1 is transferred (primary transfer) onto the intermediate transfer belt 5.

  On the outer peripheral surface side of the intermediate transfer belt 5, a secondary transfer roller 9 as a secondary transfer unit is disposed at a position facing the secondary transfer counter roller 52 with the intermediate transfer belt 5 interposed therebetween. . The secondary transfer roller 9 is in pressure contact with the secondary transfer counter roller 52 via the intermediate transfer belt 5 to form a secondary transfer portion N2 where the intermediate transfer belt 5 and the secondary transfer roller 9 are in contact with each other. A bias having a polarity opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 9 from a secondary transfer bias power source (high voltage power source) as a secondary transfer bias applying unit (not shown). As a result, the toner image on the intermediate transfer belt 5 is transferred (secondary transfer) to the recording material 12. The primary transfer roller 8 and the secondary transfer roller 9 have the same configuration.

  At the time of image formation, first, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2. Next, the surface of the charged photosensitive drum 1 is scanned and exposed by laser light corresponding to the image information emitted from the scanner unit 3, and an electrostatic image according to the image information is formed on the photosensitive drum 1. Next, the electrostatic image formed on the photosensitive drum 1 is developed as a toner image by the developing unit 4. The toner image formed on the photosensitive drum 1 is transferred (primary transfer) onto the intermediate transfer belt 5 by the action of the primary transfer roller 8.

  For example, when forming a full-color image, the above-described processes are sequentially performed in the first to fourth image forming units (process cartridges 7Y, 7M, 7C, and 7K), and toner images of each color are formed on the intermediate transfer belt 5. Next, the images are superimposed and primarily transferred.

  Thereafter, the recording material 12 is conveyed to the secondary transfer portion N2 in synchronization with the movement of the intermediate transfer belt 5, and the operation of the secondary transfer roller 9 that is in contact with the intermediate transfer belt 5 through the recording material 12 is performed. Thus, the four-color toner images on the intermediate transfer belt 5 are secondarily transferred onto the recording material 12 at once.

  The recording material 12 onto which the toner image has been transferred is conveyed to a fixing device 10 as a fixing unit. The toner image is fixed on the recording material 12 by applying heat and pressure to the recording material 12 in the fixing device 10.

Further, the primary transfer residual toner remaining on the photosensitive drum 1 after the primary transfer process is removed and collected by the cleaning member 6. The secondary transfer residual toner remaining on the intermediate transfer belt 5 after the secondary transfer process is cleaned by the intermediate transfer belt cleaning device 11.
Note that the image forming apparatus 100 can form a single-color or multi-color image using only a desired single or some (not all) image forming units.

[Process cartridge]
Next, the overall configuration of the process cartridge 7 attached to the apparatus main body 100A of the image forming apparatus 100 of the present embodiment will be described.

  In the present specification, terms indicating the direction of up, down, vertical, and horizontal in the configuration and operation of the developing unit (developing device) 4 or the process cartridge 7 are used in the normal manner unless otherwise specified. Indicates the direction when viewed in the state. The normal use state of the developing unit (developing apparatus) 4 or the process cartridge 7 is a state in which the developing unit (developing apparatus) 4 or the process cartridge 7 is properly attached to the apparatus body 100A of the image forming apparatus 100 that is properly arranged and can be used for image forming operations.

  FIG. 3 is a schematic cross-sectional view (main cross-sectional view) of the process cartridge 7 of this embodiment viewed along the longitudinal direction (rotational axis direction) of the photosensitive drum 1. In the present embodiment, the configuration and operation of the process cartridge 7 for each color are substantially the same except for the type (color) of the developer stored therein.

  The process cartridge 7 includes a photosensitive unit 13 including the photosensitive drum 1 and the like, and a developing unit 4 including a developing roller 17 and the like.

  The photoconductor unit 13 has a cleaning frame 14 as a frame that supports various elements in the photoconductor unit 13. The photosensitive drum 1 is rotatably attached to the cleaning frame 14 via a bearing (not shown). The photosensitive drum 1 is rotationally driven in the direction of the arrow A (counterclockwise) in accordance with the image forming operation by transmitting the driving force of the driving motor provided in the apparatus main body 100A to the photosensitive unit 13. . The photosensitive drum 1 which is the center of the image forming process is an organic photosensitive drum configured by coating a functional film on the outer peripheral surface of an aluminum cylinder. Here, the functional film refers to a film that imparts a function necessary for image formation to the photosensitive drum 1, and in this embodiment, the undercoat layer, the carrier generation layer, and the carrier transfer are arranged in the order from the aluminum cylinder. Has a layer. The rotational speed of the photosensitive drum 1 during image formation is 100 mm / sec.

  Further, the cleaning unit 6 and the charging roller 2 are disposed in the photosensitive unit 13 so as to come into contact with the peripheral surface of the photosensitive drum 1. The transfer residual toner removed from the surface of the photosensitive drum 1 by the cleaning member 6 falls and is stored in the cleaning frame 14.

  The charging roller 2 serving as charging means rotates by following the rotation of the photosensitive drum 1 by pressing and contacting the roller portion of the conductive rubber against the photosensitive drum 1. Here, as a charging step for charging the photosensitive drum 1, a DC voltage of −1100 V is applied to the core of the charging roller 2 as a charging process for charging the photosensitive drum 1. As a result, a uniform dark portion potential (Vd) of about −550 V is formed on the surface of the photosensitive drum 1.

  The spot pattern of the laser beam emitted from the scanner unit 3 corresponding to the image data exposes the photosensitive drum, and the exposed portion loses the surface charge due to the carrier generated from the carrier generation layer, and the potential is reduced. Decreases. As a result, the potential of the exposed portion is the bright portion potential Vl = −100 V, and the potential of the unexposed portion is the dark portion potential Vd = −550 V, so that an electrostatic latent image is formed on the photosensitive drum 1.

[Developing unit (developing device)]
Hereinafter, the developing unit (developing apparatus) used in this embodiment will be described.

  On the other hand, the developing unit 4 has a developing frame 18 as a frame that supports various elements in the developing unit 4. Further, the inside of the developing frame 18 becomes a toner storage chamber (developer storage chamber) that stores toner used in the development process.

  The developing unit 4 is provided with a developing roller 17 as a developer carrying member that contacts the photosensitive drum 1 and rotates in the illustrated arrow D direction (clockwise). In the present embodiment, the developing roller 17 and the photosensitive drum 1 rotate so that the surfaces of the developing roller 17 and the photosensitive drum 1 move in the same direction (in this embodiment, from the top to the bottom) in the opposite portion (contact portion). The rotation speed of the developing roller 17 is set to about 1.3 times the rotation speed of the photosensitive drum 1.

  The developing roller 17 is rotatably supported by the developing frame 18 at both ends in the longitudinal direction (rotation axis direction) via a developing side plate (not shown). In the present embodiment, the developing roller 17 is disposed in contact with the photosensitive drum 1. However, the developing roller 17 is disposed adjacent to the photosensitive drum 1 at a predetermined interval. Also good.

  In the present embodiment, the toner charged negatively by frictional charging with respect to the DC bias applied to the developing roller 17 of −350 V in the developing unit that contacts the photosensitive drum 1, from the potential difference, the bright portion potential. The electrostatic latent image is visualized by transferring only to the part. The toner used is a non-magnetic one-component toner, and this embodiment is a reversal development system that transfers the toner to an exposed portion.

  The developing roller 17 is an elastic developing roller having an elastic layer on a mandrel. In the present embodiment, a first layer (base layer) made of solid rubber in which carbon is dispersed in silicone rubber is formed on a stainless steel core having a diameter of 6 mm. Further, as the second layer (surface layer), an acrylic / urethane rubber whose resistance is adjusted by a conductive agent is formed to a thickness of about 10 μm. The ASKER-C hardness of the developing roller 17 is 45 to 65 °, and the micro rubber hardness measured with MD-1 (Micro Rubber Hardness Meter (manufactured by Kobunshi Keiki Co., Ltd.)) is 35 to 50 °. The resistance (electrical resistance) of the developing roller 17 is 104 to 106Ω.

  Further, the surface of the developing roller 17 has moderate unevenness in order to enhance the friction with the toner and to carry the toner well, and the center line average roughness Ra is 0.6 to 2.8 μm. It is.

  The developing unit 4 is provided with a toner supply roller 20 as a developer supply member that rotates in the direction of the arrow E (clockwise) in the figure so as to come into contact with the peripheral surface of the developing roller 17. That is, in this embodiment, the toner supply roller 20 and the developing roller 17 rotate so that the surfaces of the toner supply roller 20 and the developing roller 17 move in opposite directions at the facing portion (contact portion). The peripheral speed of the surface of the toner supply roller 20 was 0.85 times the peripheral speed of the surface of the developing roller 17.

  The toner supply roller 20 supplies toner onto the developing roller 17 and also acts to peel off toner remaining on the developing roller 17 without being used for development from the developing roller 17. The developing unit 4 includes a developing blade 21 as a developer regulating member that regulates the layer thickness of the toner supplied onto the developing roller 17 by the toner supply roller 20 so as to be in contact with the peripheral surface of the developing roller 17. Is arranged.

  The toner supply roller 20 is formed by stacking a foam on the outer periphery of a conductive metal core. Hereinafter, the layer formed by the foam is referred to as a foam layer. The foam layer of the toner supply roller 20 has two functions of supplying toner to the developing roller 17 and peeling off the toner that has not contributed to development from the developing roller 17. Foamed cells formed in the firing layer of the supply roller 20 rub the edge portion of the foaming cell against the developing roller 17 to peel off the toner on the developing roller 17.

  In the present embodiment, the toner supply roller 20 has an outer diameter of the core metal of φ5 mm. Further, a polyurethane foam having a foamed skeleton structure and a relatively low hardness was laminated on the core bar as the above-mentioned foamed layer. The thickness of this firing layer is 5.5 mm, and a firing cell having a cell diameter of 300 to 450 μm is formed. That is, the toner supply roller 20 of this embodiment is an elastic sponge roller having an outer diameter of φ16 mm.

  By configuring the outer periphery of the toner supply roller 20 with a foam, the toner supply roller 20 contacts the developing roller 17 without applying excessive pressure. Then, the toner is supplied onto the developing roller 17 with moderate irregularities on the surface of the foam and the toner remaining without being consumed during development is peeled off from the developing roller.

  Note that the substance having the scraping property of the toner due to the foamed skeleton structure is not limited to the urethane foam. For example, the material of the foam (foaming layer) used for the toner supply roller 20 is NBR rubber, silicone rubber, acrylic rubber, hydrin rubber, ethylene propylene rubber (EPDM), chloroprene rubber, styrene butadiene rubber, isoprene rubber, acrylonitrile butadiene. Commonly used rubbers such as rubber and composite mixtures thereof can be used.

  Further, in order to adjust the resistance (electric resistance) of the foam layer, a known ionic conductive agent, inorganic fine particles, carbon black, or the like can be appropriately dispersed in the foam layer.

  Further, in order to assist the toner supply to the developing roller 17, a bias for biasing the toner from the toner supplying roller 20 side to the developing roller 17 side may be applied to the toner supply roller 20. By applying a bias for biasing the negatively charged toner to the developing roller 17 side, the amount of toner carried on the developing roller 17 before the developing blade 21 can be increased. Furthermore, the toner density on the developing roller 17 is likely to increase due to the bias, and even when the surface roughness of the developing roller 17 is low, a uniform toner density is easily obtained.

  The configuration of the image forming apparatus described so far is merely an example for explaining the embodiment of the present invention, and is not limited in view of the gist of the present invention.

[Toner regulating member]
The toner regulating member (developer regulating member) in this embodiment will be described. FIG. 1 is a schematic configuration diagram of the developing unit.

  The developing blade 21 as a toner regulating member is installed so as to contact the developing roller 17 on the downstream side of the toner supply roller 20 with respect to the rotation direction D of the developing roller 17. The developing blade 21 includes a thin plate elastic member 21a and a support metal plate 21b that supports the thin plate elastic member 21a. The free end of the thin plate elastic member 21a is directed from the downstream side to the upstream side in the rotation direction D of the developing roller 17. The cantilever is supported by the support metal plate 21b. The thin plate elastic member 21a is an elastic member (plate spring) made of a thin plate metal.

  On the other hand, the support metal plate 21 b is a metal plate thicker than the thin plate elastic member 21 a, is bent in an L shape, and is attached to the swing frame body 22. The support metal plate 21b is a support member that supports the thin plate elastic member 21a.

  The swing frame 22 is a frame having swing support shafts 23 at both ends in the longitudinal direction (the axial direction of the developing roller 17). The swing fulcrum shaft 23 is a shaft portion that enables the swing frame body 22 to be rotated, and is supported by the developing frame body 18. That is, the developing side plate provided on the developing frame 18 supports the swing fulcrum shaft 23 in addition to the developing roller 17 so that the swing fulcrum shaft 23 can rotate, so that the swing frame 22 rotates the axis z of the swing fulcrum shaft 23. It can rotate as a center. As a result, the developing blade 21 is also integrally supported with the swing frame 22 and is supported by the development frame 18 so as to be rotatable about the axis z of the swing fulcrum shaft 23. In this embodiment, the support sheet metal 21b is attached to the swinging frame body 22, but the developing blade 21 is rotated with respect to the developing frame body 18 by directly mounting the swinging fulcrum shaft 23 on the support sheet metal 21b. It is also possible to support it.

  A seal member 25 for preventing toner leakage is provided between the developing frame 18 and the developing blade 21 in the longitudinal direction of the developing blade 21 (the axial direction of the developing roller 17). The seal member 25 is attached to a seat surface (attachment surface) provided as a part of the developing device frame 18. Further, the seal member 25 is compressed by a certain amount by the developing blade 21, thereby preventing the toner from leaking from between the developing frame 18 and the developing blade 21 to the outside of the developing frame 18. In this embodiment, an EPDM (ethylene / propylene rubber) mixture foam was used as the seal member 25.

  Here, the pressing force of the developing blade 21 against the developing roller 17 will be described with reference to FIGS. 4 and 7. The developing frame 18 is provided with a pressure spring 24 that presses against the swinging frame 22, and applies a moment to the swinging frame 22 and the developing blade 21 around the swinging fulcrum shaft 23. ing. That is, the pressure spring 24 applies a force Fs by contacting the support sheet metal 21 b bent in an L shape, and thereby applies a counterclockwise moment to the developing blade 21 and the swing frame 22. As a result, the developing blade 21 is pressed against the developing roller 17.

  In this embodiment, as shown in the figure, the pressure spring 24 is a compression spring. However, there is no particular limitation on the method of pressing the developing blade 21, and a tension coil spring, a leaf spring or the like can be used instead of a compression spring. You may apply as a pressure method.

  By applying a moment about the swing fulcrum shaft 23, the developing blade 21 can be pressed against the developing roller 17. The pressing force of the developing blade 21 against the developing roller 17 is determined by the balance of the moment of force about the swing fulcrum shaft 23, and is obtained by the following equation (1).

Here, each code is defined as follows.
Fd: Pressure Ld generated on the developing roller 17 and the developing blade 21 Ld: Distance from the center (axis line z) of the swinging fulcrum shaft 23 to the contact portion between the developing roller 17 and the developing blade 21 θd: The swinging fulcrum shaft 23 Angle Fs formed by a straight line connecting the center (axis z) to the contact portion between the developing roller 17 and the developing blade 21 and the direction of Fd: Load Ls that the pressing spring 24 urges the swinging frame 22 Ls: swing Distance θs from the center of the fulcrum shaft 23 to the contact portion between the pressure spring 24 and the swinging frame body 22: a straight line connecting the contact point between the pressure spring 24 and the swinging frame body 22 from the center of the swinging fulcrum shaft 23 , Fs direction: Fsl: Load that the sealing member 25 urges the swinging frame body 22 Lsl: Distance θsl from the center of the swinging fulcrum shaft 23 to the contact portion between the sealing member 25 and the swinging frame body 22 : The seal member 25 and the swing frame from the center of the swing fulcrum shaft 23 Angle between a straight line connecting the contact point between 22, the direction of Fsl is

  As shown in FIG. 4, Fd is a load that the developing blade 21 receives from contact with the developing roller 17, and the magnitude thereof is equal to the magnitude of the force with which the developing blade 21 presses the developing roller 17. Fs is a force generated in a direction in which the pressurizing spring 24 extends, starting from a contact portion where the pressurizing spring 24 contacts the swing frame 22.

  In this embodiment, a seal member 25 that suppresses toner leakage is provided between the developing blade 21 and the developing frame 18, and this seal member 25 contacts the support metal plate 21b instead of the thin plate elastic member 21a. doing. This is to prevent the thin plate elastic member 21a from being deformed by the force of the repulsive force Fs1 generated by the seal member 25.

  Further, the position where the repulsive force Fsl of the seal member 25 is applied and the position of the swing fulcrum shaft 23 are set substantially opposite to each other with the support sheet metal 21b interposed therebetween. That is, as shown in FIG. 7, with respect to the surface (contact surface) 21b1 of the support metal plate 21b that contacts the seal member 25, the axis z of the swing fulcrum shaft 23 from the direction R perpendicular to the surface 21b1 (the rotation of the developing blade 21). When the center) is projected, the axis line z is located at the point z1. This point z <b> 1 is a position overlapping the seal member 25. In other words, the swing fulcrum shaft 23 is arranged so that a straight line passing through the center (axis line z) of the swing fulcrum shaft 23 and perpendicular to the surface 21b1 passes through the seal member 25 at the point z1.

  By arranging the swing fulcrum shaft 23 in this way, a straight line connecting the contact point (starting point of the force Fsl) between the seal member 25 and the swing frame 22 from the axis z of the swing fulcrum shaft 23, and the direction of Fsl The angle θsl formed by becomes smaller. Therefore, in the formula (1), the moment of force around the axis line z due to the repulsive force Fsl of the seal member 25 becomes very small. That is, the value of Fsl·Lsl · sin θsl in the equation (1) becomes small. It is possible to suppress the repulsive force Fsl of the seal member 25 from being applied as the pressing force Fd between the developing roller 17 and the developing blade 21.

  In this embodiment, an elastic EPDM foam is used as the seal member 25, and the seal member 25 is compressed by a certain amount between the seat surface provided on the developing frame 18 and the developing blade 21.

  Here, an elastic member such as a foam tends to reduce the repulsive force Fsl due to creep after a long period of time. However, in this embodiment, the repulsive force Fsl of the seal member 25 is suppressed from being applied as the pressing force Fd between the developing roller 17 and the developing blade 21. Therefore, even if the repulsive force Fsl of the seal member 25 decreases due to creep, the influence on the pressing force Fd generated between the developing roller 17 and the developing blade 21 is small. As a result, the toner regulation of the developing blade 21 can be stabilized over a long period of time.

Returning to the description of Expression (1), in this embodiment, the calculation can be performed by omitting the term of the moment of force by the seal member 25 for the reason described above.
That is, Fsl·Lsl · sinθsl = 0.

  Here, the left side of Equation (1) is a clockwise moment about the axis z of the swing fulcrum shaft 23 in FIG. 4, and the right side of Equation (1) is centered on the axis z of the swing fulcrum shaft 23. Counterclockwise moment. When the developing blade 21 is in contact with the developing roller 17, the expression (1) is established.

  The force Fd that the developing roller 17 applies to the developing blade 21 according to the expression (1) is obtained from Ld, θd, Fs, Ls, θs, and Fs. That is, by changing the configuration and arrangement of the pressure spring 24 and the swing frame 22, the force with which the developing blade 21 presses the developing roller 17 can be made suitable for image formation.

  In this embodiment, the pressure spring 24 is not attached to the thin plate elastic member 21a, but is attached to the support metal plate 21b. This is to prevent the thin plate elastic member 21a from being deformed when the pressure spring 24 applies a force Fs to the thin plate elastic member 21a.

  The support metal plate 21b to which the pressure spring 24 is attached is a metal that is thicker than the thin elastic member 21a, and has a higher strength because it is bent in an L shape, and when the force Fs is received from the pressure spring 24. However, it is difficult to deform. As a result, deformation of the thin plate elastic member 21a is also suppressed. As a result, the force with which the thin plate elastic member 21a presses the developing roller 17 can be kept constant.

  Further, when the support metal plate 21b is bent by about 90 °, the first surface 21b1 to which the thin plate elastic member 21a and the seal member 25 are attached and the second surface 21b2 that receives the urging force Fs from the pressure spring 24 intersect ( In this embodiment, it is substantially orthogonal). Therefore, even if the second surface 21b2 is deformed by the urging force Fs from the pressure spring 24, the influence of the second surface 21b2 on the first surface 21b1 is small. That is, the pressure spring 24 is suppressed from affecting the thin plate elastic member 21a and the seal member 25.

  As a result, the contact state between the thin elastic member 21a and the developing roller 17 and the change in the repulsive force Fsl of the seal member 25 are suppressed, and the pressing force Fd generated between the developing blade 21 and the developing roller 17 is kept constant.

  Next, a configuration for stabilizing the contact state between the developing blade 21 and the developing roller 17 by suppressing the rattling of the developing blade 21 with respect to the developing frame 18 will be described with reference to FIGS. 4 and 7. In this embodiment, there is a slight gap between the swing fulcrum shaft 23 and the bearing portion of the developing device frame 18 engaged with the swing fulcrum shaft 23 so that the swing fulcrum shaft 23 can rotate. Therefore, when the developing blade 21 receives a force from the developing roller 17 when the developing roller 17 rotates, the developing blade 21 moves (rattles) by this gap, and the thin plate elastic member 21a and the developing roller 17 are moved. May affect contact status.

  However, in this embodiment, since the direction of the force Fsl applied by the seal member 25 to the developing blade 21 and the direction of the force Fs applied by the pressure spring 24 to the developing blade 21 are crossed, the developing blade 21 is rattled. Suppressed.

  That is, the seal member 25 applies the force Fsl to the developing blade 21 in a direction orthogonal to the surface 21b1 (see FIG. 7) of the support metal plate 21b, thereby moving the developing blade 21 in the direction orthogonal to the surface 21b1. It is regulated. Further, since the force Fs applied to the developing blade 21 by the pressure spring 24 has a component parallel to the surface 21b1, the pressure spring 24 causes the developing blade 21 to move in a direction parallel to the surface 21b1 by this force Fs. Can be regulated. As described above, since the movement of the developing blade 21 is restricted in both the direction orthogonal to the surface 21b1 and the direction parallel to the surface 21b1, it is possible to prevent the developing blade 18 from rattling. The contact state with respect to the developing roller 17 is stabilized.

  In particular, in this embodiment, the force Fs of the pressure spring 24 of the seal member acts in a direction in which the tip of the thin plate elastic member 21 a is brought closer to the developing roller 17. That is, the force Fs is applied along the direction in which the thin elastic member 21 a extends from the support metal plate 21 b to the developing roller 17. Therefore, even if the thin plate elastic member 21 a receives a force from the developing roller 17, it is possible to suppress the tip of the thin plate elastic member 21 a from moving away from the developing roller 17. As a result, the contact state between the thin plate elastic member 21a and the developing roller 17 can be kept better.

Next, the position setting of the tip on the free end side of the thin plate elastic member 21a in the present embodiment will be described. The distance from the center (axis line z) of the swing fulcrum shaft 23 to the center of the developing roller 17 is r1, and the distance from the center (axis line z) of the swing fulcrum shaft 23 to the tip of the thin elastic member 21a is r2 (Ld Synonymous). At this time, in this embodiment, the position of the swing fulcrum shaft 23 is set so as to satisfy the following expression.
r1> r2 Formula (2)
As long as this equation is satisfied, the locus of the center of the swing fulcrum shaft 23 drawn by the tip of the thin plate elastic member 21a does not exceed the apex of the arc in the developing roller 17, and it is ensured from the tip edge of the thin plate elastic member 21a to the developing roller. 17 can begin to abut.

  By bringing the leading edge of the thin plate elastic member 21a into contact with the developing roller 17, it is possible to stabilize the toner intake shape formed at the contact portion between the developing roller 17 and the thin plate elastic member 21a. As a result, the toner regulation of the developing blade 21 can be stabilized.

  Here, the setting position of the swing fulcrum shaft 23 will be described with reference to FIG. FIG. 5 is a schematic sectional view of the developing unit, which is a section (plane) orthogonal to the axis of the developing roller 17. In the present invention, as the position of the oscillating fulcrum shaft 23 at which the repulsive force Fsl of the seal member 25 makes it difficult to apply a moment to the developing blade 21, positions of three patterns of 23a, 23b and 23c can be selected. With reference to the plane of the thin elastic member 21 a of the developing blade 21, 23 a is located on the opposite side of the center of the developing roller 17, and 23 c is located on the center side of the developing roller 17. Reference numeral 23b denotes an intermediate portion provided in the vicinity of the developing blade 21 (a position overlapping the supporting metal plate 21b of the developing blade 21). When the swing fulcrum shaft 23 is set at the position 23a or the position 23c, the swing fulcrum shaft 23 is provided on the swing frame 22 for attaching the support metal plate 21b. Further, when the swing fulcrum shaft 23 is set at the position 23b, the developing blade 21 is connected to the developing frame 18 without the swing frame 22 by providing the swing fulcrum shaft 23 directly on the support metal plate 21b. It is also possible to support it rotatably.

  FIG. 5 shows a swing locus at the tip of the developing blade 21 (thin plate elastic member 21a) when the center of the swing fulcrum shaft 23 is provided at each position 23a, 23b, 23c. Ta indicated by a one-dot chain line is a swing locus at the position 23a, Tb indicated by a dotted line is a swing locus at the position 23b, Tc indicated by a solid line is a swing locus at the position 23c, and the swing locus depends on the position of the swing support shaft 23. Is different.

  Here, since there is an elastic layer on the surface of the developing roller 17, when the thin elastic member 21a of the developing blade 21 contacts the developing roller 17, the developing roller 17 may bite into the developing roller 17 (see FIG. 6). That is, the tip of the thin plate elastic member 21 a approaches the developing roller 17 along any of the swing trajectories Ta, Tb, and Tc according to the position of the swing fulcrum shaft 23. At this time, the degree of change in the angle of the developing blade 21 with respect to the developing roller 17 varies depending on the swing trajectories Ta, Tb, and Tc.

  When the thin plate elastic member 21a bites into the elastic layer of the developing roller 17, the angle α (see FIG. 6) of the thin plate elastic member 21a with respect to the developing roller 17 increases. At this time, as can be seen from FIG. 5, the thin plate elastic member for the developing roller 17 is better when the swing fulcrum shaft 23 is provided at the position 23a than when the swing fulcrum shaft 23 is provided at the positions 23b and 23c. The angle α of 21a tends to increase.

  By the way, as the thin plate elastic member 21a of the developing blade 21, a die-cutting plate (a plate formed by a punching process) that can be stably produced is used. In the die-cutting plate, as shown in FIG. 21a2 and burr 21a1 (protrusion formed on the fracture surface 21a) are present. Therefore, when the angle α increases, the fracture surface of the thin plate elastic member 21a tends to approach the surface of the developing roller 17. The fracture surface and the burr portion of the thin elastic member 21a have a low surface accuracy (the surface is rough), and the toner regulation on the developing roller 17 is affected. Further, when the angle α increases, the tip of the thin elastic member 21 a is easily turned by the rotation of the developing roller 17.

  From the above, it is preferable that the angle α does not increase even if the thin plate elastic member 21 a bites into the developing roller 17.

  However, in the case where the swing fulcrum shaft 23 is provided at the position 23a shown in FIG. 5 and the tip of the thin elastic member 21a has the swing locus Ta, the balance between the inclination of the swing locus and the curvature of the developing roller 17 The fracture surface of the elastic member 21a is likely to approach the surface of the developing roller 17. In other words, when the swing fulcrum shaft 23 is set at the position 23a, the angle of the developing blade 21 is set to be small with respect to the developing roller 17 in advance so that no vertical stripe is generated in the toner on the developing roller 17. There is a need.

  Therefore, it is desirable that the setting position of the swing fulcrum shaft 23 is located near the developing blade 21 as in the case of 23b and 23c or closer to the developing roller 17 than the developing blade 21 (thin plate elastic member 21a). In this embodiment, the swing fulcrum shaft 23 is set at the position 23c, and the toner regulation on the developing roller 17 can be stabilized even when the setting angle of the developing blade 21 is large.

  When the swing fulcrum shaft 23 is provided at the position 23b, the swing fulcrum shaft 23 can be provided directly on the support metal plate 21b, so that the swing frame body 22 used in this embodiment is not necessary. Therefore, the developing unit (developing device) can be reduced in size by the space occupied by the swing frame 22.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 4 Developing unit 7 Process cartridge 17 Developing roller 21 Developing blade 21a Thin plate elastic member 21b Support sheet metal 23 Oscillating fulcrum shaft 24 Pressure spring 25 Seal member 100 Image forming apparatus

Claims (8)

In a developing device used in an image forming apparatus,
In order to develop the electrostatic latent image formed on the image carrier, a developer carrier that carries a developer, and the amount of developer that is in contact with the developer carrier and carried on the developer carrier A developer regulating member that is rotatably supported,
A frame forming a developer accommodating chamber;
A seal member that is compressed and disposed between the frame and the developer restricting member in order to restrict leakage of the developer accommodated in the developer containing chamber;
An urging unit that presses the developer regulating member against the developer carrying member by applying a moment to the developer regulating member;
Have
When the rotation center of the developer regulating member is projected from the direction perpendicular to the contact surface onto the contact surface of the developer regulating member that contacts the seal member, the projected rotation center overlaps with the seal member,
The developer regulating member has a plate-like elastic member that contacts the developer carrier, and a support member that supports the elastic member,
The developing device according to claim 1, wherein the biasing means applies a force to the developer regulating member in a direction in which the elastic member extends from the support member toward the developer carrying member.   The distance from the rotation center of the developer regulating member to the center of the developer carrying member is set longer than the distance from the rotation center of the developer regulating member to the tip of the developer regulating member. The developing device according to claim 1.   3. The developing device according to claim 1, wherein a direction in which the seal member applies a force to the developer regulating member intersects a direction in which the biasing unit applies a force to the developer regulating member.   The support member is bent and has a first surface and a second surface intersecting the first surface, the first surface is in contact with the seal member, and the second surface is The developing device according to claim 1, wherein the developing device receives a force from the urging unit. The elastic member is an elastic member whose tip is directed upstream with respect to the rotation direction of the developer carrier, and the tip is in contact with the developer carrier.
5. The developing device according to claim 1, wherein the rotation center of the developer regulating member and the developer carrying member are on the same side with respect to the elastic member. In a developing device used in an image forming apparatus,
In order to develop the electrostatic latent image formed on the image carrier, a developer carrier that carries a developer, and the amount of developer that is in contact with the developer carrier and carried on the developer carrier A developer regulating member that is rotatably supported,
A frame forming a developer accommodating chamber;
A seal member that is compressed and disposed between the frame and the developer restricting member in order to restrict leakage of the developer accommodated in the developer containing chamber;
An urging unit that presses the developer regulating member against the developer carrying member by applying a moment to the developer regulating member;
Have
When the rotation center of the developer regulating member is projected from the direction perpendicular to the contact surface onto the contact surface of the developer regulating member that contacts the seal member, the projected rotation center overlaps with the seal member,
The developer regulating member has a plate-like elastic member whose tip is directed upstream with respect to the rotation direction of the developer carrier, and a support that supports the elastic member. Having a member,
The developing device according to claim 1, wherein a rotation center of the developer regulating member is located at a position overlapping the support member on a plane perpendicular to the axis of the developer carrying member. The developing device developing device according to any one of claims 1 to 6, characterized in that detachable from the apparatus main body of the image forming apparatus. An image carrier;
A developing device according to any one of claims 1 to 6 ,
A process cartridge that is detachable from an apparatus main body of an image forming apparatus.

Images