JP2009086290A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of increasing the printing speed and reducing the size of the device without reducing the developer conveyance amount from the stirring supply member to the developing roller even when the developer interface in the developing tank is lowered. An image forming apparatus including the same is provided.
A stacking auxiliary member is a plate-shaped member, and its vertical tip is disposed below the position of the pumping magnetic pole N3 of the developing roller 3 in the vertical direction. The stacking auxiliary member 10 preferably has a back plate portion 15 and side wall portions 16 perpendicular to the back plate portion 15 at both longitudinal ends of the back plate portion 15, and the back plate portion 15 is fixed by a fixing member 19. Is provided so as to be in contact with the lower surface of the sink plate 9 in the vertical direction and the extending direction thereof is parallel to the axial direction of the developing roller 3.
[Selection] Figure 1

Description

  The present invention relates to a developing device and an image forming apparatus that use a two-component developer.

  An image forming apparatus (hereinafter simply referred to as an “image forming apparatus”) that forms an image using an electrophotographic method can form a high-quality image with a simple operation and is easy to maintain and manage. Widely used in printers, facsimiles, etc., and widely used. The image forming apparatus includes, for example, a photoconductor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a fixing unit. The photoreceptor is a drum-shaped member having a photosensitive layer on the surface thereof. The charging means charges the surface of the photoreceptor to a predetermined potential. The exposure means forms an electrostatic latent image on the charged photoreceptor surface. The developing means supplies toner to the electrostatic latent image on the surface of the photoreceptor to form a toner image. The transfer unit transfers the toner image on the surface of the photoreceptor to a recording medium. The fixing unit heat-fixes the toner image on the recording medium. As a result, an image is formed on the recording medium. In the image forming apparatus, as a developing unit using a two-component developer, a developing device including a developing tank, a developing roller, an agitation supply member, a regulating member, a flow plate, and the like is generally used. The developing tank rotatably supports the developing roller and the agitation supply member, and stores the developer therein. The developing roller carries a developer layer on its surface and rotates, and supplies toner to the electrostatic latent image on the surface of the photoreceptor to form a toner image. The agitation supply member uniformly agitates the developer in the developing tank and conveys the developer toward the developing roller. The regulating member regulates the layer thickness of the developer layer on the surface of the developing roller.

  With the rapid spread of image forming apparatuses to a wide range of fields, various performance enhancements are required for image forming apparatuses. For example, the printing speed is increased. The printing speed, which was 50 to 70 sheets / minute with A4 paper until several years ago, has recently reached 100 to 120 sheets / minute. Such speeding up is intended to advance into the field of light printing. In order to cope with an increase in printing speed, in the developing device, it is easiest to increase the diameter of the developing roller and increase the capacity of the developing tank. However, the image forming apparatus is required to increase the printing speed and downsize the apparatus. Therefore, the developing device itself is also required to be miniaturized, and even under such circumstances, it is required to appropriately develop the latent image on the photoreceptor and provide an image having a stable print quality.

  To perform high-speed printing with a miniaturized developing device, toner replenishment technology is important. Toner that is newly replenished in the developing tank and the developer in the developing tank are quickly mixed to shorten the toner. It is necessary to charge the design charge value over time. Therefore, the shape of the developing tank, the position of the toner replenishing port formed in the developing tank, the arrangement and shape of the developing roller, the stirring supply member, the regulating member, the sink plate, etc. in the developing tank, the number of stirring supply members, two components A study is made to find the optimum conditions for the type of developer. For example, when the height of the developing tank is reduced for miniaturization, the position of the toner supply port may be lower than the axial center height of the stirring supply member provided in the vicinity of the toner supply port in the developing tank. Usually, in order to mix the toner and the developer uniformly, a certain amount of toner dropping space is required, but the toner replenishment amount must be reduced at the position of the low toner replenishment port as described above. As a result, the amount of developer in the developing tank is reduced. In addition, the amount of developer in the developing tank is drastically reduced when a large amount of printing is performed at high speed. As a basic structure of the developing device, the developing roller is provided vertically above the stirring supply member (paddle roller) provided in the vicinity of the developing roller. Therefore, when the amount of developer in the developing tank decreases rapidly, This causes a problem that a sufficient amount of developer cannot be supplied.

  FIG. 5 is a schematic diagram showing a configuration of a conventional developing device 100. The developing device 100 includes a developing tank 101, a developing roller 102, a paddle roller 103 that is a stirring supply member, a regulating member 104, a flow plate 105, and positioning means (not shown), and further includes a two-component developer 106. Used to develop an electrostatic latent image on a photosensitive drum (not shown). The developing tank 101 rotatably supports the developing roller 102 and the paddle roller 103, and accommodates a two-component developer in its internal space (see, for example, Patent Document 1). The developing roller 102 includes a magnet roller 110 and a sleeve 111, and supplies toner to the electrostatic latent image on the photosensitive drum for development. The magnet roller 110 is a non-rotating roller-like member in which a plurality of N magnetic poles and S magnetic poles are alternately arranged in the circumferential direction. The sleeve 111 is a cylindrical member that is externally fitted to the magnet roller 110 and rotates while carrying a developer layer on the surface. The developer layer is an aggregate of magnetic brushes in which carrier particles having toner attached to the surface are combined in a brush shape. The paddle roller 103 agitates the two-component developer in the developing tank 101 and conveys it toward the developing roller 102. The regulating member 104 regulates the transport amount of the developer 106 by the developing roller 102 by regulating the layer thickness of the developer layer on the developing roller 102. The flow plate 105 guides the moving direction of the developer 106 to the vicinity of the paddle roller 103 when the developer 106 removed from the surface of the developing roller 102 by the regulating member 104 moves.

  In the developing device 100, the developer 106 accommodated in the developing tank 101 is agitated by the paddle roller 103, and is conveyed to the developing roller 102 in a state where toner adheres to the carrier surface. Further, when the sleeve 111 of the developing roller 102 rotates in the direction opposite to the photosensitive drum, the developer 106 between the developing roller 102 and the flow plate 105 is conveyed toward the regulating member 104, and the developer 106 is conveyed. The amount is regulated. The developer 106 that has passed through the gap between the developing roller 102 and the regulating member 104 and whose layer thickness is regulated is transported to the electrostatic latent image, and excess developer 106 that is removed from the surface of the developing roller 102 by the regulating member 103 is regulated. It stays in a space formed by the member 104, the sink plate 105, and the developing tank wall on the upper side, the amount of stay increases, and the upper surface of the sink plate 105 flows away from the developing roller 102, and the paddle roller 103 Is refluxed upward.

  The developing device 100 has a general structure in which the developing roller 102 is disposed at a higher position than the paddle roller 103. In the developing device 100 having such a structure, the developer interface 106a (the upper surface of the developer layer) in the developing tank 101 is lowered due to a significant increase in the charge amount of the developer 106, the uneven distribution of the developer 106, and the like. Is likely to occur. FIG. 6 is a diagram for explaining a decrease in the developer interface 106a (upper surface of the developer layer) in the developing device 100 shown in FIG. When the developer interface 106a is lowered, the developer conveyance amount from the paddle roller 103 to the surface of the developing roller 102 is reduced, and the density of the magnetic brush on the surface of the developing roller 102 is reduced. As a result, the amount of developer carried by the developing roller 102 decreases, and image defects such as a decrease in image density and uneven image density occur. In the developing device 100, the developer interface 106a can be prevented from being lowered by adjusting the rotational speed of the paddle roller 103 and the positions of the regulating member 104 and the flow plate 105, but the effect is not sufficient. Therefore, it is very difficult to cope with the speeding up and downsizing of the image forming apparatus by using the developing device configured such that the developing roller is disposed at a higher position than the paddle roller.

  A developing roller including a magnet roller is disposed vertically above the agitation supply member, and is located at a position facing the developer transport magnetic pole (N1 pole) after development (toner supply to the electrostatic latent image) on the magnet roller. A two-component developing device provided with a stacking auxiliary member is proposed (see, for example, Patent Document 2). The developing device of Patent Document 2 efficiently collects the developer remaining on the sleeve surface after development, newly supplies a uniformly charged developer on the sleeve, and performs the next development, thereby reducing the image density. The purpose is to prevent image quality and improve image quality. However, in the developing device of Patent Document 2, since the developing roller is provided above the stirring supply member, it is possible to avoid a decrease in the amount of developer transported from the stirring supply member to the developing roller due to a decrease in the developer interface. Can not.

Japanese Unexamined Patent Publication No. 1-223777 JP 2001-337529 A

  An object of the present invention is to provide a developing device in which the developing roller is provided vertically above the stirring supply member, and even if the developer interface in the developing tank is lowered, the developer conveyance amount from the stirring supply member to the developing roller is small. It is an object of the present invention to provide a developing device and an image forming apparatus provided with the developing device that can cope with an increase in printing speed and a reduction in size of the apparatus without lowering.

The present invention includes a developing roller that includes a magnet roller, rotates on a surface carrying a two-component developer composed of toner and a carrier, and supplies toner to an electrostatic latent image on the surface of a photosensitive drum to develop it;
An agitation supply member for supplying a two-component developer to the developing roller;
An accumulation auxiliary member for accumulating two-component developer and assisting the supply of the two-component developer to the developing roller by the stirring supply member;
A regulating member that regulates the carrying amount of the two-component developer on the surface of the developing roller;
A sink plate that is provided in the vicinity of the developing roller and collects surplus two-component developer separated by the regulating member;
A stirring roller for mixing and stirring the recovered two-component developer and the replenished toner;
In a developing device having
The developing roller is provided vertically above the stirring supply member;
The stacking auxiliary member is a developing device characterized in that the lower end in the vertical direction is provided so as to be positioned vertically below the position where the magnetic poles are drawn up by the magnet roller.

In the invention, it is preferable that the accumulation assisting member is made of a nonmagnetic material.
In the invention, it is preferable that the accumulation assisting member is provided on a lower surface of the sink plate.

  In the invention, it is preferable that the stacking auxiliary member has a back plate portion and side wall portions perpendicular to the back plate portion at both ends in the longitudinal direction of the back plate portion, and the back plate portion is disposed on the lower surface of the sink plate. Further, the stretching direction is provided so as to be parallel to the axial direction of the developing roller.

  In the present invention, the height of the side wall portion closer to the developing roller in the side wall portion is higher than the height of the far side wall portion.

Further, in the present invention, the stirring supply member has a paddle shape having a plurality of blades,
The gap between the blades of the agitation supply member and the accumulation assisting member is wider than the distance between the developing roller and the accumulation assisting member.

The present invention also provides a photosensitive member on which an electrostatic latent image is formed, a charging unit that charges the surface of the photosensitive member, an exposure unit that forms an electrostatic latent image on the surface of the photosensitive member, and an electrostatic surface on the surface of the photosensitive member. Developing means for supplying toner to the latent image to form a toner image, transfer means for transferring the toner image on the surface of the photosensitive member to the recording medium, cleaning means for cleaning the surface of the photosensitive member, and the toner image on the recording medium In an image forming apparatus for forming an image using an electrophotographic method, including a fixing unit for fixing,
The developing means is an image forming apparatus characterized by being the above-described developing device.

  According to the present invention, a developing roller including a magnet roller rotates while carrying a two-component developer composed of toner and a carrier on the surface, and supplies the toner to the electrostatic latent image on the surface of the photosensitive drum for development. .

  The stirring supply member supplies the two-component developer to the developing roller. At this time, the accumulation auxiliary member accumulates the two-component developer and assists the supply of the two-component developer to the developing roller by the stirring supply member. ing.

  As for the developer supplied to the developing roller, the carrying amount of the developing roller surface is regulated by the regulating member, and the surplus binary developer separated by the regulating member is collected by the flow plate. The collected two-component developer is mixed and stirred with the toner replenished by the stirring roller.

  When the developing roller is provided vertically above the stirring supply member, there is a possibility that a decrease in the developer conveyance amount from the stirring supply member to the developing roller due to a decrease in the developer interface. Since the lower end in the vertical direction of the stacking auxiliary member is provided so as to be positioned vertically below the position where the magnet roller's pumping magnetic pole is disposed, the stacking auxiliary member is used as a developer even when the developer interface is lowered in the developing tank. Since the effect of pushing the developer under the magnetic pole that actually pumps up the toner is exhibited, a decrease in the amount of developer carried on the surface of the developing roller can be prevented, and the developer can be closely adhered to the developing roller. As a result, it is possible to stably supply the developer to the developing roller, and it is possible to prevent a decrease in image density and uneven image density.

  As described above, the present invention can supply a sufficient amount of developer to the developing roller even if the developer interface becomes low, thereby enabling an increase in printing speed and a shortening of the height of the developing tank, As a result, the entire apparatus can be reduced in size.

  According to the invention, it is preferable that the accumulation assisting member is made of a nonmagnetic material. By using a non-magnetic material, it is possible to prevent the generation of a magnetic field between the accumulation assisting member and the developer, stabilize the flow of the developer in the developing tank, and carry a sufficient amount of developer on the surface of the developing roller. it can.

  According to the invention, it is preferable that the stacking auxiliary member is attached to the lower surface of the sink plate. The sink plate is often resin-molded, and the sink plate can be reinforced by the stacking auxiliary member and is disposed immediately before the developer is carried on the developing roller. It can be exhibited more effectively.

  According to the invention, the stacking auxiliary member has a so-called U-shaped cross section having a back plate portion and side wall portions perpendicular to the back plate portion at both longitudinal ends of the back plate portion. In such a shape, the back plate portion is provided on the bottom surface of the flow plate so that the extending direction thereof is parallel to the axial direction of the developing roller.

  Compared with a simple plate shape, the flow plate can be reinforced more, so that it is possible to cope with a higher development speed.

  According to the present invention, the height of the side wall portion closer to the developing roller among the side wall portions at both ends is made higher than the height of the side wall portion on the far side, so that the axial direction of the developing roller in the developing tank is increased. Since the amount of the developer can be made uniform, the occurrence of uneven image density can be prevented.

  According to the invention, the distance between the blades of the stirring supply member and the stacking auxiliary member is made wider than the distance between the developing roller and the stacking auxiliary member.

  As a result, when a developer is carried on the developing roller, a constant amount of developer can be supplied at all times, so that it is possible to prevent the occurrence of image density reduction and image density unevenness.

  According to the invention, there is provided an image forming apparatus characterized in that development is performed by the developing device.

  As a result, it is possible to simultaneously cope with an increase in printing speed and a reduction in size. In particular, the height from the installation surface of the image forming apparatus can be reduced by shortening the height dimension of the developing tank in the developing apparatus. In addition, a high-quality image free from image defects such as a decrease in image density and uneven image density can be formed stably over a long period of time.

  FIG. 1 is a cross-sectional view showing a positional relationship between a developing device 1 according to an embodiment of the present invention and a photosensitive drum 20. FIG. 2 is a cross-sectional view showing the configuration of the developing device 1.

  The developing device 1 includes a developing tank 2, a developing roller 3, a stirring supply member 4, a stirring roller 5, a conveying member 6, a regulating member 7, a regulating member support 8, a sink plate 9, and an accumulation assist. A member 10, an accumulation assisting member support 11, and a toner concentration detection sensor 12 are included.

  The developing tank 2 is a substantially prismatic container member having an internal space, and rotatably supports the developing roller 3, the stirring supply member 4, the stirring roller 5, and the conveying member 6, and directly supports the regulating member 7, the sink plate 9, and the like. To support the developer and contain the developer. The developer is a two-component developer containing toner and a carrier that is magnetic powder. Further, when the developing device 1 is mounted on an electrophotographic image forming apparatus (not shown), an opening 2a is formed in the developing tank 2 on the side surface facing the photosensitive drum 20 included in the image forming apparatus. A toner replenishing port 2 b is formed on the top surface of the developing tank 2 in the vertical direction.

  A toner cartridge and a toner hopper (not shown) are provided above the developing tank 2 in the vertical direction. More specifically, the toner cartridge, the toner hopper, and the developing tank 5 are provided in this order from the upper side to the lower side in the vertical direction. The toner cartridge is a cylindrical container member that accommodates toner in its internal space. The toner cartridge is detachably attached to an image forming apparatus main body (not shown) to which the developing device 1 is attached. Further, the toner cartridge is driven to rotate about the central axis of the cylinder by a driving unit (not shown) provided in the image forming apparatus. An elongated opening extending in the longitudinal direction is formed on the side surface in the longitudinal direction of the toner cartridge, and the toner falls from the elongated opening and is supplied to the toner hopper as the toner cartridge rotates. The toner hopper is provided, for example, such that a toner supply port, which is an opening formed in the bottom surface in the vertical direction, communicates with a toner supply port 2b, which is an opening formed in the top surface in the vertical direction of the developing tank 2, in the vertical direction. In the toner hopper, a toner replenishing roller is provided above the toner supply port in the vertical direction. The toner supply roller will be described later with reference to FIG.

  The toner replenishing roller is rotatably supported by a toner hopper and is rotationally driven by a driving unit (not shown). The rotation of the toner replenishing roller is controlled by a control means (not shown) provided in the image forming apparatus in accordance with the detection result of the toner concentration in the developing tank 2 by the toner concentration detection sensor 12. The toner is supplied into the developing tank 2 through the toner supply port and the toner supply port 2b by the rotation of the toner supply roller.

  The developing roller 3 is a roller-like member that is at least partially supported by the developing tank 2 so as to be rotatable, and is driven to rotate about an axis by a driving unit (not shown). Further, the developing roller 3 faces the photosensitive drum 20 through the opening 2 a of the developing tank 2. The developing roller 3 is provided so as to be separated from the photosensitive drum 20 with a gap, and the closest portion is a developing nip portion. In the developing nip portion, toner is supplied to the electrostatic latent image on the surface of the photosensitive drum 20 from a developer layer (not shown) on the surface of the developing roller 3. In the developing nip portion, a developing bias voltage is applied to the developing roller 3 from a power source (not shown) connected to the developing roller 3, and the developer layer on the surface of the developing roller 3 changes to the electrostatic latent image on the surface of the photosensitive drum 20. Toner transfer proceeds smoothly.

  The developing roller 3 includes a magnet roller 13 and a sleeve 14. FIG. 3 is a diagram showing the magnetic force distribution of each magnetic pole in the magnet roller 13. The magnet roller 13 is supported at both ends in the longitudinal direction by the developing tank wall of the developing tank 2, and as shown in the magnetic distribution diagram of FIG. The magnetic poles N1, N2, N3, and N4 and the magnetic poles S1, S2, and S3, which are magnets, are multipolar magnetized magnet rollers that are spaced apart from each other and arranged radially in the radial direction of the developing roller 3. The magnetic poles are provided in the order of the magnetic pole N1, the magnetic pole S1, the magnetic pole N2, the magnetic pole S2, the magnetic pole N3, the magnetic pole N4, and the magnetic pole S3 in the direction opposite to the rotation direction of the developing roller 3 (sleeve 14).

  In the magnet roller 13, the developer pumping magnetic pole N3 has an angle formed by a developer opening magnetic pole N4 positioned upstream in the rotation direction of the developing roller 3 (hereinafter simply referred to as “upstream” unless otherwise specified). It is preferable to arrange so as to be in an angle range. Here, the angle formed between the magnetic pole N3 and the magnetic pole N4 refers to the radius in the cross section of the developing roller 3 where the magnetic pole N4 is disposed (hereinafter referred to as “radius N4”) and the cross section of the developing roller 3 where the magnetic pole N3 is disposed. Is an angle formed by a radius (hereinafter referred to as “radius N3”). The angle range is preferably 75 ° or more, and in the present embodiment, the angle formed by the radius N4 and the radius N3 is 78 °. If the angle is less than 75 °, the developer cannot be released and pumped up and image defects such as uneven image density tend to occur.

  The sleeve 14 is a cylindrical member that is externally fitted to the magnet roller 13, is rotatably supported by the developing tank 2 and a support member (not shown), and is rotatably provided by a drive unit (not shown). The sleeve 14 is formed using a nonmagnetic material. In the present embodiment, the sleeve 14 rotates counterclockwise, and the photosensitive drum 20 rotates clockwise. Accordingly, the sleeve 14 and the photosensitive drum 20 rotate in the opposite directions at the developing nip portion.

  The agitation supply member 4 and the agitation roller 5 are both roller-like members that are rotatably supported by the developing tank 2 and that can be driven to rotate around an axis by a driving unit (not shown). In the present embodiment, the stirring supply member 4 rotates counterclockwise, and the stirring roller 4 rotates clockwise. The agitation supply member 4 is provided at a position facing the photosensitive drum 20 via the developing roller 3 and being vertically lower than the developing roller 3. The stirring roller 5 is provided at a position facing the developing roller 3 via the stirring supply member 4 and being vertically lower than the developing roller 3. The agitation supply member 4 and the agitation roller 5 agitate the developer stored in the developing tank 2 to give a uniform charge to the toner, and pump up the charged developer and send it around the development roller 3. To pay.

  The conveyance member 6 is a roller-like member that is rotatably supported by the developing tank 2 and is rotatably driven by a driving unit (not shown). The conveying member 6 faces the agitation supply member 4 through the agitation roller 5 and is provided below the toner supply port 2b in the vertical direction. The conveying member 6 conveys the toner replenished into the developing tank 2 through the toner replenishing port 2 b around the stirring roller 5.

  The regulating member 7 is a plate-like member extending parallel to the axial direction of the developing roller 3, and one end in the short direction is supported by the developing tank 2 and the regulating member support 8 above the developing roller 3 in the vertical direction. And the other end is provided so as to be separated from the surface of the developing roller 3 with a gap. In the present embodiment, the regulating member 7 is provided on an extension line of the radius of the developing roller 3, and an angle formed by the extension line and the radius N1 in the cross section of the developing roller 3 where the magnetic pole N1 is disposed is 90 °. It is provided as follows.

  The regulating member 7 is made of, for example, a nonmagnetic metal having elasticity such as stainless steel or aluminum, a synthetic resin, or the like. In the present embodiment, a thin plate-like stainless steel is used for the regulating member 7. The regulating member support 8 supports the regulating member 7 together with the developing tank 2. Specifically, one end of the regulating member 7 in the short direction and the vicinity thereof are supported so as to be sandwiched between the regulating member support 8 and the developing tank 2. The restricting member support 8 is formed of a material such as synthetic resin or metal. In this embodiment mode, the synthetic resin is used. The regulating member 7 adjusts the transport amount of the developer by removing excess developer from the developer layer carried on the surface of the developing roller 3 and regulating the thickness of the developer layer to be constant. Further, the regulating member 7 imparts electric charge to the developer that is insufficiently charged in the developer layer by rubbing between the other end in the short side direction and the developer layer, and the developer contained in the developer layer. Is sufficiently charged.

  The flow plate 9 is a plate-like member made of resin provided in the developing tank 2 upstream of the regulating member 7 in the rotation direction of the developing roller 3 and above the stirring supply member 4 and the stirring roller 5 in the vertical direction. It is. The sink plate 9 has one end in the short direction facing the surface of the developing roller 3 and is separated with a gap, and the other end extends in a direction away from the developing roller 3. In the present embodiment, the upper surface in the vertical direction of the flow plate 9 is parallel to the horizontal direction at the end portion on the developing roller 3 side in the short direction of the flow plate 9 and the vicinity thereof, and development is performed at other portions. It is provided so as to descend downward in the vertical direction as it is separated from the roller 3.

  The sink plate 9 is supported by a support member 9a that is inserted into a through-hole formed so as to penetrate the sink plate 9 in the longitudinal direction at the lower part in the vertical direction. By providing the flow plate 9, a smooth flow of the developer in the developing tank 2 is generated, and the occurrence of uneven charging of the toner, blocking of the toner and the like is prevented.

  Specifically, the developer removed (separated) from the surface of the developing roller 3 by the regulating member 7 temporarily stays in the space above the developing roller 3, but when the amount increases, the vertical upper surface of the sink plate 9 is moved over the developing roller 9. It starts to flow away from 3. The developer flows along the upper surface of the flow plate 9 and falls toward the stirring roller 5 from the end of the flow plate 9 opposite to the developing roller 3 side in the short direction. The dropped developer is uniformly mixed with the other developer and newly supplied toner by the agitation supply member 4 and the agitation roller 5, and is conveyed again toward the development roller 3.

  The accumulation assisting member 10 is provided in the vertical direction below the arrangement position of the pumping magnetic pole N3 of the developing roller 3 in the rotation direction of the developing roller 3. Specifically, the stacking auxiliary member 10 is a plate-shaped member, and the vertical tip of the stacking auxiliary member 10 is disposed below the arrangement position of the pumping magnetic pole N3 of the developing roller 3 in the vertical direction.

  In the present embodiment, the stacking auxiliary member 10 includes a back plate portion 15 and side wall portions 16 perpendicular to the back plate portion 15 at both longitudinal ends of the back plate portion 15. That is, the cross section perpendicular to the axial direction (the direction perpendicular to the paper surface) of the developing roller 3 is a U-shape, and the same cross section is continuous to the axial direction of the developing roller 3.

  The stacking auxiliary member 10 is provided by the fixing member 19 so that the back plate portion 15 is in contact with the lower surface in the vertical direction of the flow plate 9 and the extending direction thereof is parallel to the axial direction of the developing roller 3. The portion 16 is provided so as to extend vertically downward.

  The separation distance between the vertical lower end of the side wall portion 16 and the surface of the developing roller 3 is 2 mm to 4 mm. When the separation distance is less than 2 mm, it becomes difficult to carry a sufficient amount of developer on the surface of the developing roller 3. On the other hand, if the separation distance exceeds 4 mm, the developer pushing effect by the stacking auxiliary member 10 may be insufficient. In the present embodiment, the separation distance is 3 mm.

  In the present embodiment, the vertically lower end of the side wall portion 16 is positioned 1.6 mm below the extension line of the radius N3 in the cross section of the developing roller 3 where the pumping magnetic pole N3 is disposed. Further, the accumulation assisting member 10 is preferably U-shaped including the reinforcement of the sink plate, but may be L-shaped including the back plate portion 15 and the side wall member 17.

  The accumulation assisting member 10 is not particularly limited as long as it includes a nonmagnetic material, but is preferably composed of nonmagnetic non-magnetic stainless steel such as SUS304 or SUS316, aluminum, or the like. In this embodiment, a 1.0 mm thick SUS316 plate was plastically deformed to obtain a U-shaped accumulation assisting member 10.

  By using such an accumulation assisting member 10, the developer can be pushed into the vicinity of the pumping magnetic pole N 3 of the developing roller 3, and as a result, the effect of raising the developer interface in the developing tank 2 can be obtained.

  The accumulation assisting member 10 plays an auxiliary role for the developing roller 3 to lift the developer. In the developing tank 2, when observed from the horizontal direction perpendicular to the longitudinal direction of the developing roller 3, The developer may be unevenly distributed. This is because there is an increase or decrease in the amount of developer conveyed due to the structure of the stirring roller 5 or the like.

  Therefore, the stacking auxiliary member 10 is provided so that the side wall member 16 is two plate-like members having different heights, and the side wall portion 17 having a higher height is close to the developing roller 3. Therefore, in the installed state, the vertically lower end portion 17a of the side wall portion 17 on the side close to the developing roller 3 is positioned lower than the vertical lower end portion 18a of the opposite side wall portion 18. Thereby, it is possible to make the amount of developer in the axial direction of the developing roller 3 uniform.

  The difference in height between the side wall portion 17 and the side wall portion 18 may be adjusted as appropriate by looking at the actual developed image.

  In addition to the positional relationship between the accumulation assisting member 10 and the pumping magnetic pole N3, the positional relationship between the accumulation assisting member 10 and the agitation supply member 4 is also important. That is, the distance between the tip of the paddle blade of the stirring supply member 4 and the tip of the side wall portion of the stacking auxiliary member 10 is made narrower than the distance between the developing roller 3 and the tip of the side wall portion of the stacking auxiliary member 10. It is possible to always supply a constant amount of the developer. If the distance between the developing roller 3 and the tip of the side wall portion of the stacking auxiliary member 10 is wide or the same, the developer push-in force will decrease, and the amount of developer that can actually be supplied below the pumping magnetic pole N3 will be insufficient. is there. In the present embodiment, the interval between the tip of the side wall portion of the stacking auxiliary member 10 and the paddle blade of the stirring supply member is 2.5 mm, whereas the interval between the tip of the side wall portion of the stacking auxiliary member 10 and the developing roller 3 is 3 mm.

  The dimensions of the agitation supply member 4, the agitation roller 5, the conveying member 6, the regulating member 7, the flow plate 9 and the stacking auxiliary member 10 are appropriately determined from an appropriate range according to the dimensions of the developing roller 3.

  FIG. 4 is a schematic diagram showing a configuration of an image forming apparatus 100 according to another embodiment of the present invention. The photosensitive drum 20 is a cylindrical member that is supported by a driving unit (not shown) so as to be rotatable about an axis, and has a photosensitive film on which an electrostatic latent image is formed and a toner image is formed after development. For the photosensitive drum 20, for example, a cylindrical member including a conductive substrate (not shown) and a photosensitive film (not shown) formed on the surface of the conductive substrate can be used. Examples of the photosensitive film include an organic photosensitive film and an inorganic photosensitive film. As an organic photosensitive film, a laminate of a charge generation layer, which is a resin layer containing a charge generation material, and a charge transport layer, which is a resin layer containing a charge transport material, a charge generation material and a charge transport material in one resin layer And a resin layer containing. Examples of the inorganic photosensitive film include films containing one or more selected from zinc oxide, selenium, amorphous silicon and the like. A base film may be interposed between the conductive substrate and the photosensitive film, and a surface film (protective film) for mainly protecting the photosensitive film may be provided on the surface of the photosensitive film.

  The charging unit 21 is a roller-like member provided so as to come into pressure contact with the photosensitive drum 20. A power source (not shown) is connected to the charging unit 21 to apply a voltage to the charging unit 21. The charging unit 21 receives a voltage from a power source and charges the surface of the photosensitive drum 20 to a predetermined polarity and potential. In the present embodiment, a roller-shaped charging unit is used, but the present invention is not limited to this, and charging brush type charger, charger type charger, sawtooth type charger, ion generator, contact type charger such as magnetic brush, etc. Can be used.

  The exposure unit 22 receives image information of a document read by the scanner unit 29 or image information from an external device, and irradiates the charged surface of the photosensitive drum 20 with signal light corresponding to the image information. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 20. For the exposure means 22, a laser scanning unit including a light source is used. The laser scanning unit is a unit that combines, for example, a light source, a polygon mirror, an fθ lens, a reflection mirror, and the like. As the light source, for example, a semiconductor laser, an LED array, an electroluminescence (EL) element, or the like can be used.

The developing device 1 uses the developing device 1 shown in FIG.
The transfer unit 23 is a roller-like member that is rotatably supported by a support unit (not shown), is rotatably provided by a drive unit (not shown), and is brought into pressure contact with the photosensitive drum 20. For the transfer means 14, for example, a roller-shaped member including a metal core with a diameter of 8 to 10 mm and a conductive elastic layer formed on the surface of the metal core is used. As the metal forming the metal core, stainless steel, aluminum, or the like can be used. As the conductive elastic layer, a rubber material in which a conductive material such as carbon black is blended with a rubber material such as ethylene-propylene rubber (EPDM), foamed EPDM, or foamed urethane can be used. A pick-up roller and a registration roller (not shown) are fed from the paper feed tray 28 to the pressure contact portion (transfer nip portion) between the photosensitive drum 20 and the transfer means 23 in synchronization with the toner image being conveyed by the rotation of the photosensitive drum 20. The recording medium is supplied one by one through the. As the recording medium passes through the transfer nip portion, the toner image on the surface of the photosensitive drum 20 is transferred to the recording medium. A power source (not shown) is connected to the transfer means 23, and when transferring the toner image to the recording medium, a voltage having a polarity opposite to the charging polarity of the toner constituting the toner image is applied to the transfer means 23. As a result, the toner image is smoothly transferred to the recording medium. According to the transfer unit 23, the toner image on the surface of the photosensitive drum 20 is transferred to a recording medium.

  The cleaning unit 24 includes a cleaning blade (not shown) and a toner storage tank (not shown). The cleaning blade is a plate-like member that is provided so as to extend in parallel with the longitudinal direction of the photosensitive drum 20 and that one end in the short-side direction is in contact with the surface of the photosensitive drum 20. The cleaning blade removes toner, paper powder, and the like remaining on the surface of the photosensitive drum 20 from the surface of the photosensitive drum 20 after the toner image is transferred to the recording medium. The toner storage tank is a container-like member having an internal space, and temporarily stores the toner removed by the cleaning blade. The surface of the photosensitive drum 20 after the toner image is transferred is cleaned by the cleaning unit 24.

  The fixing unit 25 includes a fixing roller 26 and a pressure roller 27. The fixing roller 26 is a roller-like member that is rotatably supported by a support unit (not shown) and is rotatable about an axis by a drive unit (not shown). The fixing roller 26 has a heating means (not shown) inside, and heats and melts the toner constituting the unfixed toner image carried on the recording medium conveyed from the transfer nip portion to fix it on the recording medium. As the fixing roller 26, for example, a roller-shaped member including a cored bar and an elastic layer is used. The core metal is formed of a metal such as iron, stainless steel, or aluminum. The elastic layer is formed of an elastic material such as silicone rubber or fluorine rubber, for example. The heating means generates heat when a voltage is applied from a power source (not shown). A halogen lamp, an infrared lamp or the like can be used as the heating means.

  The pressure roller 27 is a roller-like member that is rotatably supported and is provided in pressure contact with the fixing roller 26 by a pressure unit (not shown). The pressure roller 27 rotates following the rotation of the fixing roller 26. A pressure contact portion between the fixing roller 26 and the pressure roller 27 is a fixing nip portion. The pressure roller 27 promotes fixing of the toner image to the recording medium by pressing the toner in a molten state against the recording medium when the fixing roller 26 heats and fixes the toner image to the recording medium. A roller-like member having the same configuration as that of the fixing roller 26 can be used for the pressure roller 27. A heating means may also be provided inside the pressure roller 27. As the heating means, the same heating means as in the fixing roller 26 can be used.

  According to the fixing unit 25, the toner image is fixed to the recording medium by passing the recording medium onto which the toner image has been transferred through the fixing nip, melting the toner constituting the toner image, and pressing the toner on the recording medium. Print the image. The recording medium on which the image is printed is discharged and stacked on a discharge tray 30 provided on a side surface in the vertical direction of the image forming apparatus 100 by a conveying unit (not shown).

  The paper feed tray 28 is a tray that stores recording media such as plain paper, coated paper, color copy paper, and OHP film. A plurality of paper feed trays 28 are provided, and recording media having different sizes are accommodated in the respective paper feed trays 28. The size of the recording medium includes A3, A4, B5, and B4. Further, a plurality of paper feed trays 28 may contain the same size recording medium. A recording medium is fed one by one in synchronization with the toner image on the surface of the photosensitive drum 20 being conveyed to the transfer nip portion by a pickup roller (not shown), a conveyance roller, and a registration roller.

The scanner unit 29 includes a document set tray (not shown), an automatic document feeder (RADF,
Reversing Automatic Document Feeder) and the like, and document reading means (not shown) are also provided. The automatic document feeder conveys a document placed on a document set tray to a document placing table of a document reading unit. The document reading means includes a document placement table, a document scanning unit, reflection means, a photoelectric conversion device (Charge Coupled Device, hereinafter referred to as “CCD”) licensor, and the like, and image information of a document placed on the document placement table. Are read every plural lines, for example every 10 lines. The document placing table is a glass plate-like member for placing a document for reading image information. The document scanning unit includes a light source (not shown) and a first reflecting mirror, and reciprocates at a constant speed V in parallel along the lower surface in the vertical direction of the document mounting table, so that the image forming surface of the document placed on the document mounting table Irradiate light. A reflected light image is obtained by light irradiation. The light source is a light source for irradiating a document placed on the document table. The first reflecting mirror reflects the reflected light image toward the reflecting means. The reflection means includes a second reflection mirror, a third reflection mirror, and an optical lens (not shown), and forms a reflected light image obtained by the document scanning unit on the photoelectric conversion element licensor. The reflecting means reciprocates at a speed of V / 2 following the reciprocating movement of the document scanning unit. The second and third reflection mirrors reflect the reflected light image so that the reflected light image faces the optical lens. The optical lens forms a reflected light image on the photoelectric conversion element licensor. The CCD licensor includes a CCD circuit (not shown) that photoelectrically converts a reflected light image formed by the optical lens into an electric signal, and outputs an electric signal as image information to an image processing unit in the control means. The image processing unit converts image information input from an external device such as a document reading unit or a personal computer into an electrical signal and outputs the electrical signal to the exposure unit 22.

  According to the image forming apparatus 100, since the developing device 1 that can reduce the height dimension in the vertical direction and can always stably supply the developer is used, the printing speed can be increased and the apparatus main body can be reduced in size. Is easy.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

2 is a cross-sectional view showing a positional relationship between the developing device 1 according to an embodiment of the present invention and a photosensitive drum 20. FIG. 2 is a cross-sectional view illustrating a configuration of the developing device 1. FIG. FIG. 6 is a diagram showing a magnetic force distribution of each magnetic pole in the magnet roller 13. It is the schematic which shows the structure of the image forming apparatus 100 which is other embodiment of this invention. FIG. 6 is a schematic diagram illustrating a configuration of a conventional developing device 100. It is a figure for demonstrating the fall of the developer interface 106a (upper surface of a developer layer).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing device 2 Developing tank 3 Developing roller 4 Stirring supply member 5 Stirring roller 6 Conveying member 7 Restricting member 8 Restricting member support 9 Drift plate 10 Accumulation assisting member 11 Accumulation assisting member support 12 Toner density detection sensor 13 Magnet roller 14 Sleeve DESCRIPTION OF SYMBOLS 19 Toner replenishing roller 20 Photosensitive drum 21 Charging means 22 Exposure means 23 Transfer means 24 Cleaning means 25 Fixing means 28 Paper feed tray 29 Scanner part 30 Paper discharge tray 100 Image forming apparatus

Claims (7)

A developing roller that includes a magnet roller, carries a two-component developer composed of toner and carrier on its surface, rotates, supplies toner to the electrostatic latent image on the surface of the photosensitive drum, and develops it;
An agitation supply member for supplying a two-component developer to the developing roller;
An accumulation auxiliary member for accumulating two-component developer and assisting the supply of the two-component developer to the developing roller by the stirring supply member;
A regulating member that regulates the carrying amount of the two-component developer on the surface of the developing roller;
A sink plate that is provided in the vicinity of the developing roller and collects surplus two-component developer separated by the regulating member;
A stirring roller for mixing and stirring the recovered two-component developer and the replenished toner;
In a developing device having
The developing roller is provided vertically above the stirring supply member;
The developing device according to claim 1, wherein the stacking auxiliary member is provided such that a lower end in the vertical direction is positioned below the arrangement position of the pumping magnetic poles of the magnet roller in the vertical direction.   The developing device according to claim 1, wherein the accumulation assisting member is made of a nonmagnetic material.   The developing device according to claim 2, wherein the stacking auxiliary member is provided on a lower surface of the sink plate.   The stacking auxiliary member has a back plate portion and side wall portions perpendicular to the back plate portion at both ends in the longitudinal direction of the back plate portion, and the back plate portion is formed on the lower surface of the sink plate in the extending direction. The developing device according to claim 3, wherein the developing device is provided so as to be parallel to an axial direction of the developing roller.   5. The developing device according to claim 4, wherein, of the side wall portions, the height of the side wall portion closer to the developing roller is made higher than the height of the far side wall portion. The stirring supply member has a paddle shape having a plurality of blades,
The developing device according to claim 2, wherein a distance between the blade of the stirring supply member and the stacking auxiliary member is wider than a distance between the developing roller and the stacking auxiliary member. A photosensitive member on which an electrostatic latent image is formed, a charging unit for charging the surface of the photosensitive member, an exposure unit for forming an electrostatic latent image on the surface of the photosensitive member, and a toner on the electrostatic latent image on the surface of the photosensitive member. Developing means for supplying and forming a toner image; transfer means for transferring the toner image on the surface of the photoreceptor to the recording medium; cleaning means for cleaning the surface of the photoreceptor; and fixing means for fixing the toner image to the recording medium; In an image forming apparatus for forming an image using an electrophotographic method,
An image forming apparatus, wherein the developing unit is the developing device according to claim 1.

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