JP2008197289A - Developing device and image forming apparatus - Google Patents

Abstract

In a developing device in which a developing roller is provided vertically above a stirring member, even if the developer interface in the developing tank decreases, the amount of developer transport from the stirring member to the developing roller does not decrease, and printing is performed. This corresponds to higher speed and downsizing of the image forming apparatus.
In a developing device including a developing tank, a developing roller, a first agitating member, a second agitating member, a conveying member, a regulating member, and a sink plate, a sink is provided. A magnetic member 10 having a shape corresponding to the shape of the lower portion of the plate 9 in the vertical direction is provided so as to contact the lower surface of the flow plate 9 in the vertical direction, and the surface of the developing roller 3 and the magnetic member 10 on the side closest to the developing roller 3 The separation distance from the end is set to 0.1 mm to 10 mm.
[Selection] Figure 1

Description

  The present invention relates to a developing device and an image forming apparatus.

  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 roller-shaped member having a photosensitive layer on its surface. 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 the developing unit, a developing device including a developing tank, a developing roller, a stirring member, a regulating member, a sink plate, and the like is generally used. The developing tank rotatably supports the developing roller and the stirring 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 agitating 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. As the developer, a two-component developer containing toner and carrier is mainly used.

  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, it is easiest in the developing device 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. In particular, a downsized image forming apparatus with a short height from the floor that can be easily operated even when sitting in a wheelchair or the like is desired. 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.

  In order to perform high-speed printing with a miniaturized developing device, the newly replenished toner in the developing tank and the developer in the developing tank are quickly mixed, and the toner is charged to the designed charge value in a short time. is important. 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 member, the regulating member, the sink plate, etc. in the developing tank, the number of the stirring members, and the two-component developer Consideration is made to find the optimum condition for the type of the item. For example, when the height of the developing tank is reduced for miniaturization, the position of the toner replenishing port may be lower than the axial center height of the stirring member provided near the toner replenishing 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 amount of toner replenishment must be reduced at the position of the toner replenishing 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 even when a large amount of printing is performed at high speed. On the other hand, as the basic structure of the developing device, the developing roller is provided vertically above the stirring member (paddle roller) provided in the vicinity of the developing roller. Therefore, when the amount of developer in the developing tank decreases, This causes a problem that an amount of developer cannot be supplied.

  FIG. 10 is a cross-sectional view schematically showing a configuration of a conventional developing device 100. The developing device 100 includes a developing tank 101, a developing roller 102 including a magnet roller 110, a paddle roller 103 that is a stirring member, a regulating member 104, a flow plate 105, and positioning means (not shown), and further includes two components. An electrostatic latent image on a photosensitive drum (not shown) is developed using a developer 106. 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 an electrostatic latent image on a photosensitive drum (not shown) 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 fitted around the magnet roller 110 and rotates with 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 conveys the developer 106 removed from the surface of the developing roller 102 by the regulating member 104 toward the huddle roller 103. The positioning means is integrated with the bearing member of the magnet roller 110 and adjusts the arrangement of the regulating member 104 and the sink plate 105.

  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 conveyance amount of the developer 106 is increased. Is regulated. The developer 106 that has passed through the gap between the developing roller 102 and the regulating member 104 is conveyed to the electrostatic latent image, and the excess developer 106 that is removed from the surface of the developing roller 102 by the regulating member 103 includes the regulating member 104 and the flow plate 105. It stays in the space formed by the upper developing tank wall, the amount of stay increases, and the upper surface of the flow plate 105 flows away from the developing roller 102 and is returned to the upper side of the paddle roller 103. 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, as shown in FIG. 11, the developer interface 106a (development) in the developing tank 101 is caused by a significant increase in the charge amount of the developer 106, the uneven distribution of the developer 106, and the like. Lowering of the upper surface of the agent layer is likely to occur. FIG. 11 is a cross-sectional view 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 position of the regulating member 104 and the flow plate 105 is adjusted by the positioning means to prevent the developer interface 106a from being lowered, but the effect is not sufficient. Therefore, it is very difficult to cope with speeding up and downsizing of the image forming apparatus using a developing device in which the developing roller is disposed at a position higher than the paddle roller.

  Further, a developing roller having a magnet roller is disposed vertically above the stirring member, and is magnetically positioned 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 member is proposed (for example, see Patent Document 2). The technique of Patent Document 2 efficiently collects the developer remaining on the sleeve surface after development, and newly supplies a uniformly charged developer on the sleeve to perform the next development, thereby reducing the image density. The purpose is to prevent and improve image quality. However, in the developing device of Patent Document 2, since the developing roller is provided above the stirring member, it is inevitable that the developer conveyance amount from the stirring member to the developing roller is reduced due to the decrease in the developer interface.

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

  An object of the present invention is to reduce the amount of developer transport from the stirring member to the developing roller even in the developing device in which the developing roller is provided vertically above the stirring member even if the developer interface in the developing tank is lowered. It is another object of the present invention to provide a developing device that can cope with an increase in printing speed and downsizing of an image forming apparatus.

The present invention
In a developing device mounted on an electrophotographic image forming apparatus including a photosensitive drum on which an electrostatic latent image is formed,
A developing roller that includes a magnet roller, carries a developer on its surface, rotates, supplies toner to the electrostatic latent image on the surface of the photosensitive drum, and develops the toner;
A stirring member for supplying developer to the developing roller;
A regulating member that regulates the amount of developer carried on the surface of the developing roller;
The surface of the developing roller and the developing roller in the vicinity of the developing roller from the position closest to the developing roller and the stirring member in the developing roller rotation direction to the upstream position in the developing roller rotating direction from the closest position of the developing roller to the regulating member And a magnetic member having a surface that comes into contact with the developer, and is provided so that a separation distance from an end portion closest to the edge is 0.1 mm to 10 mm (0.1 mm or more and 10 mm or less). The developing device.

The developing device of the present invention is
On the upstream side of the regulating member in the rotation direction of the developing roller, one end in the short side direction is close to the developing roller surface, the other end extends in a direction away from the developing roller, and is removed from the developing roller surface by the regulating member And a sink plate that conveys the toner in a direction away from the developing roller.

  Furthermore, the developing device of the present invention is characterized in that the sink plate is provided vertically above the magnetic member.

Furthermore, the developing device of the present invention provides:
It is characterized in that at least a part of the upper surface in the vertical direction of the magnetic member is provided so as to contact the lower surface in the vertical direction of the sink plate.

  Furthermore, the developing device of the present invention is characterized in that the magnetic member has a shape corresponding to the shape of the bottom surface of the sink plate in the vertical direction.

  Furthermore, the developing device of the present invention is characterized in that the surface of the magnetic member that contacts the developer is a flat surface or a convex surface.

Furthermore, the developing device of the present invention is characterized in that the magnetic member is a permanent magnet.
Furthermore, the developing device of the present invention is characterized in that the magnetic force of the permanent magnet is 50 mT to 500 mT (50 mT or more and 500 mT or less).

The present invention also provides
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,
The image forming apparatus is characterized in that the developing means is any one of the developing devices described above.

  The present invention includes a developing roller including a magnet roller, a stirring member, a regulating member, and a magnetic member, and is mounted on an electrophotographic image forming apparatus to increase the printing speed and reduce the size of the image forming apparatus. There is provided a developing device that can cope with the process. The developing device of the present invention is characterized by including a magnetic member, and the greatest feature is that the magnetic member is disposed at a specific position. In the developing device of the present invention, the magnetic member extends from the downstream side in the developing roller rotation direction from the closest position between the developing roller and the stirring member to the upstream side in the developing roller rotation direction from the closest position between the developing roller and the regulating member. In the vicinity of the developing roller, the separation distance between the surface of the developing roller and the end portion closest to the developing roller (hereinafter simply referred to as “the separation distance between the magnetic member and the developing roller” unless otherwise specified) is 0.1 mm to 10 mm. And has a surface in contact with the developer. By arranging the magnetic member as described above, even when the developer interface is lowered in the developer tank, the magnetic member exhibits the effect of lifting the developer interface by the magnetic force (that is, the effect of pumping up the developer) A decrease in developer density on the surface of the developing roller can be prevented, and the developer can be closely adhered to the developing roller. As a result, even when the interface of the developer is lowered, the developer can be stably supplied to the developing roller, and a decrease in image density and uneven image density can be prevented. Note that this effect cannot be obtained simply by providing a magnetic member, and it is important that the separation distance between the magnetic member and the developing roller be 0.1 mm to 10 mm. If it is less than 0.1 mm, it is difficult to carry a sufficient amount of developer on the surface of the developing roller, and if it exceeds 10 mm, the effect of lifting the developer interface by the magnetic member may be insufficient. As described above, in the developing device of the present invention, a sufficient amount of developer can be supplied to the developing roller even if the developer interface is low, so that the printing speed can be increased and the height of the developing tank can be shortened. It becomes possible.

  Moreover, according to this invention, the structure which contains a sink further is preferable. The flow plate extends upstream from the restricting member in the rotation direction of the developing roller, with one end in the short direction being close to the developing roller surface and the other end being away from the developing roller. The developer to be removed is conveyed in a direction away from the developing roller. Providing a flow plate prevents surplus developer removed from the surface of the developing roller by the regulating member from moving in the direction opposite to the developer transport direction (developing roller rotation direction) by the developing roller due to the magnetic force of the magnetic member. Then, it is conveyed along the sink plate in a direction away from the regulating member and the magnetic member. Therefore, the flow of the developer in the developing tank is stabilized, and a sufficient amount of developer can be carried on the surface of the developing roller.

  Furthermore, according to the present invention, by providing the sink plate vertically above the magnetic member, the above-described installation effect of the sink plate is more reliably exhibited.

  Further, according to the present invention, by providing the magnetic member so that at least a part of the vertical upper surface of the magnetic member is in contact with the vertical lower surface of the sink plate, the developing roller, magnetic The space in the developing tank surrounded by the member, the stirring member, etc. can be expanded. As a result, the flow of the developer in the developing tank is further stabilized, the developer is efficiently stirred and mixed, and the charge amount of the carrier and the toner becomes more uniform. Further, the developer can be prevented from staying in the space between the sink plate and the magnetic member.

  Further, according to the present invention, when the magnetic member has a shape corresponding to the shape of the bottom surface in the vertical direction of the sink plate, the development by the magnetic member is not performed without disturbing the flow of the developer in the developing tank due to the installation of the magnetic member. The effect of lifting the agent interface is fully exhibited.

  Furthermore, according to the present invention, when the surface of the magnetic member that contacts the developer is a flat surface or a convex surface, the developer flows unevenly (turbulent flow) due to the developer remaining on the surface, the developer It is possible to prevent the occurrence of non-uniform charging. When the surface includes a concave angle or a concave surface, the developer stays in that portion, and the above-described disadvantage occurs.

  Furthermore, according to the present invention, when a permanent magnet, which is a magnetic material having ferromagnetism or ferrimagnetism, is used as the magnetic member, a developer magnetic brush is always formed on the surface of the magnetic member. The lifting effect is further improved. Therefore, even if the amount of developer in the developing tank rapidly decreases due to mass printing at high speed, the amount of developer supplied to the developing roller can be kept substantially constant.

  Furthermore, according to the present invention, when a permanent magnet having a magnetic force of 50 mT to 500 mT is used, a sufficient amount of developer can be stably supplied to the developing roller even when the developer interface is extremely lowered. On the other hand, when the developer interface is less lowered and a sufficient amount of developer can be supplied to the developing roller without a magnetic member, the developer is pulled upward in the vertical direction by the magnetic force of the magnetic member. However, the developers are not bonded with a strong force, but the developers are individually floated by a magnetic force. Therefore, it returns to a fluid state easily by the shearing force generated by the rotation of the stirring member. Further, since the light is floated when the shearing force is applied, the shear stress applied to the developer is reduced, and a stress relaxation effect (buffer effect) on the developer is obtained. As a result, the service life of the developer can be extended. In addition, if it has this degree of magnetic force, it will be in contact with the developer in the developer tank, and there will be little decrease in magnetic force even if it is exposed to high temperatures, and it will be sufficient over the entire service life (life) set in the image forming apparatus. The effect of lifting the developer interface can be obtained.

  Further, according to the present invention, there is provided an electrophotographic image forming apparatus including a photoreceptor, a charging unit, an exposure unit, a developing device of the present invention, a transfer unit, a cleaning unit, and a fixing unit. . By including the developing device of the present invention, the image forming apparatus of the present invention can simultaneously cope with an increase in printing speed and a reduction in size. In particular, since 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 device, printing can be easily performed even when sitting in a wheelchair, for example. 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 schematically showing a configuration of a developing device 1 according to a first embodiment of the present invention. FIG. 2 is a sectional view showing the positional relationship between the developing device 1 and the photosensitive drum 20 shown in FIG. 3 and 4 are cross-sectional views showing the state of the developer interface in the developing device 1 shown in FIG. FIG. 5 is a diagram showing the magnetic force distribution of each magnetic pole in the magnet roller 13 included in the developing roller 3 which is one of the constituent members of the developing device 1 shown in FIG. The developing device 1 includes a developing tank 2, a developing roller 3, a first stirring member 4, a second stirring member 5, a conveying member 6, a regulating member 7, a regulating member support 8, and a sink plate 9. A magnetic member 10, a magnetic member support 11, and a toner concentration detection sensor 12.

  The developing tank 2 is a substantially prismatic container member having an internal space. The developing tank 2 rotatably supports the developing roller 3, the first stirring member 4, the second stirring member 5, and the conveying member 6, and includes a regulating member 7 and a sink plate 9. Etc. are directly or indirectly supported, and a developer is accommodated. 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 rotationally driven around the axis 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 in a vertical direction with a toner supply port 2 b that is an opening formed in the top surface in the vertical direction of the developing tank 2. In the toner hopper, a toner supply roller 19 is provided above the toner supply port in the vertical direction. The toner supply roller 19 is rotatably supported by a toner hopper and is driven to rotate by a driving means (not shown). The rotational driving of the toner replenishing roller 19 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 replenished into the developing tank 2 through the toner supply port and the toner supply port 2b by the rotational driving of the toner supply roller 19.

  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. The magnet roller 13 is supported by the developing tank wall of the developing tank 2 at both ends in the longitudinal direction, and magnetic poles N1, N2, and N3 that are a plurality of bar magnets having a rectangular cross-sectional shape at the circumferential position of the developing roller 3. S1, S2, S3, and S4 are multi-pole 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 magnetic pole N3 is preferably provided in a specific angle range on the upstream side in the rotation direction of the developing roller 3 from the magnetic pole S2 (hereinafter, simply referred to as “upstream side” unless otherwise specified). Here, the angle range includes the radius in the cross section of the developing roller 3 where the magnetic pole S2 is disposed (hereinafter referred to as “radius S2”) and the radius in the cross section of the developing roller 3 where the magnetic pole N3 is disposed (hereinafter referred to as “ The radius N3 "). The angle range is 33 ° or more, and an angle formed by the radius S2 and a straight line connecting the axis of the developing roller 3 and the axis of the first stirring member 4 (hereinafter referred to as “installation of the first stirring member 4”). It is preferable that the angle is set to the following. If it is less than 33 °, image defects such as uneven image density tend to occur. If the installation angle of the first stirring member 4 is exceeded, the extension line of the radius N3 extends below the axis of the first stirring member 4 in the vertical direction. As a result, the ability of the first stirring member 4 to pump the developer to the developing roller 3 is reduced, and image defects such as a reduction in image density and uneven image density are likely to occur.

  The arrangement of the magnetic poles in the magnet roller is as follows in this embodiment. The magnetic pole N1 (peak value 105.8 mT) is provided on a straight line connecting the axis of the developing roller 3 and the axis of the photosensitive drum 20 at a position facing the photosensitive drum 20. The magnetic pole S1 (peak value = −87.0 mT) is provided at a position of 50.55 ° upstream from the magnetic pole N1. This angle is an angle formed by the radius S1 in the cross section of the developing roller 3 where the magnetic pole S1 is disposed and the radius N1 in the cross section of the developing roller 3 where the magnetic pole N1 is disposed. The same shall apply hereinafter. The magnetic pole N2 (peak value = 39.3 mT) is provided at a position 111.33 ° upstream from the magnetic pole N1. The magnetic pole S2 (peak value = −46.9 mT) is provided at a position 153.73 ° upstream from the magnetic pole N1. The magnetic pole N3 (peak value = 52.8 mT) is provided at a position 199.40 ° upstream from the magnetic pole N1 and 45.67 ° upstream from the magnetic pole S2. The magnetic pole N4 (peak value = 46.8 mT) is provided at a position 272.40 ° upstream from the magnetic pole N1. The magnetic pole S3 (peak value = −83.2 mT) is provided at a position 314.80 ° upstream from the magnetic pole N1. Each is arranged. FIG. 5 shows the magnetic force distribution of each magnetic pole in the magnet roller 13.

  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.

  Each of the first stirring member 4 and the second stirring member 5 is a roller-like member that is rotatably supported by the developing tank 2 and that can be driven to rotate about an axis by a driving unit (not shown). In the present embodiment, the first stirring member 4 rotates counterclockwise, and the second stirring member 4 rotates clockwise. The first stirring 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. In the present embodiment, the installation angle of the first stirring member 4 that is an angle formed by the radius S2 and a straight line connecting the axis of the developing roller 3 and the axis of the first stirring member 4 is 54 °. . The second stirring member 5 is provided at a position facing the developing roller 3 through the first stirring member 4 and being vertically lower than the developing roller 3. The first agitating member 4 and the second agitating member 5 agitate the developer stored in the developing tank 2 to give a uniform charge to the toner, and pump up the charged developer to Send to the surroundings.

  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 first stirring member 4 through the second stirring member 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 second stirring member 5.

  The regulating member 7 is a plate-like member extending in parallel with 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. 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 the radial direction of the developing roller 3 (extension line of the radius of the developing roller 3), and the radius N1 in the cross section of the developing roller 3 where the extension line and the magnetic pole N1 are disposed. The angle formed by and is set to be 90 °. 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, it is formed from a synthetic resin. 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 provided in the developing tank 2 upstream of the regulating member 7 in the rotation direction of the developing roller 3 and above the first stirring member 4 and the second stirring member 5. 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 formed so as to penetrate in the longitudinal direction of the sink plate 9 in the lower part in the vertical direction and is inserted into the through hole. 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 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 moves away from the developing roller 3. Begins to flow through. The developer flows along the upper surface of the sink plate 9, and falls toward the second stirring member 5 from the end of the sink 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 first stirring member 4 and the second stirring member 5, and is conveyed toward the developing roller 3.

  The magnetic member 10 is provided downstream of the closest position between the developing roller 3 and the first stirring member 4 and upstream from the closest position between the developing roller 3 and the regulating member 7 in the rotation direction of the developing roller 3. It is done. The installation position of the magnetic member 10 is preferably a space between the sink plate 9 and the first stirring member 4 in the vertical direction, more preferably in the vicinity of the lower surface of the sink plate 9 in the vertical direction, and particularly preferably the sink plate 9. It is the position which touches the vertical direction lower surface. In the present embodiment, the magnetic member 10 extends in the axial direction (longitudinal direction) of the developing roller 3, is provided so as to be in contact with the vertical lower surface of the sink plate 9, and has a shape corresponding to the lower shape of the sink plate 9. It is a shaped member. The magnetic member 10 has a shape in which a cross section in a direction perpendicular to the longitudinal direction is L-shaped. In the magnetic member 10, one end of a portion corresponding to the long side of the L shape (hereinafter referred to as “L-shaped long side portion”) faces the developing roller 3, and the other end is separated from the developing roller 3 in a substantially horizontal direction. It is provided to extend. The separation distance between the one end of the L-shaped long side portion and the closest portion between the surface of the developing roller 3 is 0.1 mm to 10 mm. When the separation distance is less than 0.1 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 10 mm, the effect of lifting the developer interface by the magnetic member 10 may be insufficient. In the present embodiment, the separation distance is 2.0 mm. Further, a portion corresponding to the short side of the L shape (hereinafter referred to as “L-shaped short side portion”) is provided so as to extend in the substantially vertical direction from the other end of the L-shaped long side portion. In the present embodiment, the L-shaped long side portion has an angle of 178 ° between the radius N1 and the magnetic member arrangement line in the cross section of the developing roller 3 where the magnetic pole N1 is arranged, and the radius S2 and the magnetic member arrangement line. The angle formed by and is set to be 25 °. Here, the magnetic member arrangement straight line means a straight line connecting the center point in the vertical direction at the end portion on the developing roller 3 side and the axial center of the developing roller 3 in the cross section shown in FIG. . Further, the magnetic member 10 contacts the developer on the lower surface in the vertical direction.

  Although it will not restrict | limit especially if the magnetic member 10 contains a magnetic material, The thing containing stainless steel which has magnetism, such as SUS430 and SUS410, is preferable. By using the magnetic member 10 containing these magnetic materials, the magnetic force (magnetic flux density) around the magnetic member 10 is increased, and the effect of raising the developer interface in the developing tank 2 can be obtained. The magnetic member 10 can be a permanent magnet. The permanent magnet is a magnetic material having ferromagnetism or ferrimagnetism. By using a permanent magnet, a strong magnetic force (magnetic flux density) can be generated regardless of the magnetic force of the magnet roller 13, so that the effect of raising the developer interface can be further improved. The magnetic force of the permanent magnet is not particularly limited, but is preferably 50 mT to 500 mT. When a permanent magnet having a magnetic force of 50 mT to 500 mT is used as the magnetic member 10, a sufficient amount of developer can always be stably supplied to the developing roller 3 regardless of the position of the developer interface in the developing tank 2. If the magnetic force is less than 50 mT, the effect of lifting the developer interface may be insufficient. If the magnetic force exceeds 500 mT, the fluidity of the developer in the developing tank 2 may be significantly reduced.

  The magnetic member 10 exhibits the effect of lifting the developer. As shown in FIG. 3, in the developing tank 2, the developer interface L1 is locally present in the developing tank 2 due to a significant increase in charge amount, uneven distribution of the developer, and rapid consumption of the developer due to mass printing. Or it may go down overall. Even in such a case, the developer reaches the first stirring member 4 in the vertical direction by the clockwise rotation by the second stirring member 5 and the counterclockwise rotation by the first stirring member 4. Since the magnetic force of the magnetic member 10 extends above the first stirring member 4 in the vertical direction, the effect of lifting the developer interface by the magnetic member 10 (developing effect of the developer) is sufficiently exerted. Therefore, even if the developer interface L1 falls, the developer interface L1 rises at least in the vicinity of the developing roller 3 to prevent the developer density from being lowered, and it is possible to maintain a dense pressure contact of the developer to the developing roller 3. As a result, the amount of developer conveyed by the developing roller 3 can be stabilized.

  As shown in FIG. 4, when the developer interface L2 in the developing tank 2 is high and a sufficient amount of developer can be supplied to the developing roller 3, it is above the first stirring member 4 in the vertical direction. The developer is in a state of being pulled upward in the vertical direction by the lifting action of the magnetic member 10. However, the magnetic force of the magnetic member 10 is not so strong as to prevent the developer from adhering to the developing roller 3 and easily returns to the fluid state by the shearing force applied by the rotation of the first stirring member 4. Supply to the developing roller 3 is performed smoothly. On the other hand, when the developer is pulled upward in the vertical direction, the shearing force applied to the developer is relaxed, the stress applied to the developer, particularly the carrier, is reduced, and the service life of the carrier can be extended.

  The magnetic member support 11 supports the magnetic member 10 by fixing the magnetic member 10 to the sink plate 9. The magnetic member 10 is formed with a plurality of through holes (not shown) penetrating in the thickness direction in the longitudinal direction. In addition, a hole which is a recess for fixing the magnetic member support 11 is formed on the surface of the sink plate 9 in contact with the magnetic member 10 at a position corresponding to the through hole formed in the magnetic member 10. The magnetic member 10 is fixed to the sink plate 9 by inserting the magnetic member support 11 through the through holes and fixing holes formed in the sink plate 9 and fixing the magnetic member support 11.

  The dimensions of the first agitating member 4, the second agitating member 5, the conveying member 6, the regulating member 7, the flow plate 9 and the magnetic member 10 are appropriately determined from an appropriate range according to the dimensions of the developing roller 3. .

  For example, the toner concentration detection sensor 12 is mounted on the bottom surface of the developing tank 2 below the second stirring member 5 in the vertical direction, and is provided so that the sensor surface is exposed to the inside of the developing tank 2. The toner density detection means is electrically connected to control means (not shown). The control means controls to rotate the toner cartridge according to the detection result by the toner density detection means and replenish the toner into the developing tank 2 through the toner hopper. That is, when it is determined that the detection result by the toner density detecting means is lower than the toner density setting value, a control signal is sent to the driving means for driving the toner cartridge to rotate, and the toner cartridge is driven to rotate. As the toner concentration detection means, a general toner concentration detection sensor can be used, and examples thereof include a transmitted light detection sensor, a reflected light detection sensor, and a magnetic permeability detection sensor. Among these, a magnetic permeability detection sensor is preferable. A power supply (not shown) is connected to the magnetic permeability detection sensor. The power supply applies a drive voltage for driving the magnetic permeability detection sensor and a control voltage for outputting the detection result of the toner density to the control means. Application of a voltage to the magnetic permeability detection sensor by the power source is controlled by the control means. The permeability detection sensor is a type of sensor that receives the control voltage and outputs the toner density detection result as an output voltage value. Basically, the sensitivity near the median value of the output voltage is good. It is used by applying a control voltage to obtain a voltage. Such a type of magnetic permeability detection sensor is commercially available, and examples thereof include TS-L, TS-A, and TS-K (all are trade names, manufactured by TDK Corporation).

  The control unit may be provided exclusively for the developing device 1 or may also be a control unit provided in an image forming apparatus to which the developing device 1 is attached. The control means includes, for example, a storage unit, a calculation unit, and a control unit. Detection results, setting values, image information, table data, programs, and the like by various sensors are written in the storage unit. As the storage unit, those commonly used in this field can be used, and examples thereof include a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). The arithmetic unit takes out various data (print command, detection result, image information, etc.) input to the storage unit and a program for executing various controls, and performs various detections and / or determinations. A control part sends a control signal to an applicable apparatus according to the determination result in a calculating part, and performs operation control. A control part and a calculating part are processing circuits implement | achieved by the microcomputer provided with a central processing unit (CPU, Central Processing Unit), a microprocessor, etc., for example. The control means includes a main power supply together with the storage unit, the calculation unit, and the control unit.

  According to the developing device 1, the developer stored in the developing tank 2 is conveyed upward in the vertical direction of the first stirring member 4 by the rotation of the first stirring member 4 and the second stirring member 5. It is lifted and supplied to the surface of the developing roller 3. The developing roller 3 carries a developer layer on its surface, rotates, undergoes layer thickness regulation of the developer layer by the regulating member 7 and charging of the developer, and then, on the photosensitive drum 20 at the development nip portion. The toner is supplied to the electrostatic latent image and developed. After the development is completed, the developing roller 3 further rotates and receives the developer again. On the other hand, the developer removed from the surface of the developing roller 3 by the regulating member 7 flows in the direction away from the developing roller 3 on the upper surface in the vertical direction of the flow plate 9, and between the second stirring member 5 and the conveying member 6. Then, it is mixed again with another developer and conveyed toward the developing roller 3. In the developing tank 2, the developer circulation as described above occurs. Further, the transport member 6 transports the toner replenished into the developing tank 2 around the second stirring member 5 according to the detection result by the toner concentration detection sensor 12.

  FIG. 6 is a cross-sectional view schematically showing the configuration of the developing device 15 according to the second embodiment of the present invention. The developing device 15 is similar to the developing device 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. The developing device 15 has the same configuration as the developing device 1 except that the developing device 15 includes a magnetic member 10 a instead of the magnetic member 10. The magnetic member 10 a is a plate-like member having a shape corresponding to the lower shape of the sink plate 9, provided so as to be in contact with the lower surface in the vertical direction of the sink plate 9, and extending in the axial direction of the developing roller 3. Further, the cross section of the magnetic member 10 a in the direction perpendicular to the axial direction of the developing roller 3 is L-shaped like the magnetic member 10. The difference from the magnetic member 10 is that the end portion facing the developing roller 3 of the L-shaped long side portion, the surface on the lower side in the vertical direction at the connecting portion of the L-shaped long side portion and the L-shaped short side portion, and the L-shaped short side That is, the end portion on the lower side in the vertical direction of the portion is configured by a surface having a radius of curvature. That is, these portions have no corners as compared with the corresponding portions in the magnetic member 10, and are configured by curved surfaces. Thereby, the flow of the developer in the vicinity of the magnetic member 10 becomes smoother, and the stable supply of the developer to the developing roller 3 can be more reliably performed. Further, the developer is prevented from adhering to the magnetic member 10 and causing the developer to stay. In particular, when the magnetic member 10a is a permanent magnet, it is preferable to use a member having a shape like that of the magnetic member 10a because the developer easily adheres to the corner if there is a corner. As the magnetic member 10a, a material made of the same magnetic material or permanent magnet as the magnetic member 10 can be used. The magnetic member 10 a is fixed to the sink plate 9 by the magnetic member support 11 in the same manner as the magnetic member 10.

  FIG. 7 is a cross-sectional view schematically showing the configuration of the developing device 16 according to the third embodiment of the present invention. The developing device 16 is similar to the developing device 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. The developing device 16 has the same configuration as the developing device 1 except that the developing device 16 includes a magnetic member 10b instead of the magnetic member 10. The magnetic member 10 b is a plate-like member that has a shape corresponding to the lower shape of the sink plate 9, is provided so as to be in contact with the lower surface in the vertical direction of the sink plate 9, and extends in the axial direction of the developing roller 3. The cross section of the magnetic member 10b in the direction perpendicular to the axial direction of the developing roller 3 is substantially trapezoidal. The magnetic member 10b is formed such that its vertical lower surface 10x is a slope that becomes higher in the vertical direction as it approaches the developing roller 3, and the slope itself becomes a flat surface. Since the lower surface 10x of the magnetic member 10b is in contact with the developer, it is possible to prevent the developer from adhering to the lower surface 10x by making the lower surface 10x a flat surface and an inclined surface that becomes higher in the vertical direction as it approaches the developing roller 3. When the developer adheres to the lower surface 10x, the amount of adhesion gradually increases and the developer stays, so that the fluidity of the developer is deteriorated and the developer is unevenly flowed (turbulent flow). In order to prevent this, as described above, it is preferable that the lower surface 10x in contact with the developer has a planar shape. Such a configuration is particularly effective when the magnetic member 10b is a permanent magnet. Similarly to the magnetic member 10, the magnetic member 10 b is also fixed to the sink plate 9 by the magnetic member support 11.

  FIG. 8 is a cross-sectional view schematically showing the configuration of the developing device 17 according to the fourth embodiment of the present invention. The developing device 17 is similar to the developing device 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. The developing device 17 has the same configuration as the developing device 1 except that the developing device 17 includes a magnetic member 10 c instead of the magnetic member 10. The magnetic member 10 c is a plate-like member that has a shape corresponding to the lower shape of the sink plate 9, is provided so as to be in contact with the lower surface in the vertical direction of the sink plate 9, and extends in the axial direction of the developing roller 3. Further, the magnetic member 10c is configured as a convex surface whose vertical lower surface 10y has a radius of curvature and protrudes vertically downward. By constituting the lower surface 10y, it is possible to prevent the developer from adhering to the lower surface 10y, and hence the flowability of the developer from being lowered, the uneven flow (turbulent flow) of the developer, and the like. Such a configuration is particularly effective when the magnetic member 10c is a permanent magnet. Similarly to the magnetic member 10, the magnetic member 10 c is also fixed to the sink plate 9 by the magnetic member support 11.

  FIG. 9 is a cross-sectional view schematically showing a configuration of an image forming apparatus 100 according to another embodiment of the present invention. The image forming apparatus 100 has a copy mode and a print mode. In the copy mode, a copy of the original is printed according to image information of the original read by the scanner unit 29 described later. This is a digital copying machine that prints an image corresponding to image information from an external device connected via the printer. The image forming apparatus 100 includes a photosensitive drum 20, a charging unit 21, an exposure unit 22, a developing device 1, a transfer unit 23, a fixing unit 25, a cleaning unit 24, a paper feed tray 28, and a scanner unit. 29 and a paper discharge tray 30.

  The photosensitive drum 20 is a roller-like member having a photosensitive film on which a latent electrostatic image and, consequently, a toner image is formed. For the photosensitive drum 11, for example, a roller-shaped member including a conductive base (not shown) and a photosensitive film (not shown) formed on the surface of the conductive base can be used. As the conductive substrate, a conductive substrate having a cylindrical shape, a columnar shape, a sheet shape or the like can be used, and among them, the cylindrical conductive substrate is preferable. 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 is the developing device 1 of the present invention 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 extends in parallel with the longitudinal direction of the photosensitive drum 20 and is provided so that one end in the short direction abuts 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 reflecting 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.

1 is a cross-sectional view schematically showing a configuration of a developing device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a positional relationship between a developing device and a photosensitive drum shown in FIG. 1. FIG. 2 is a cross-sectional view illustrating a state of a developer interface in the developing device illustrated in FIG. 1. FIG. 2 is a cross-sectional view illustrating a state of a developer interface in the developing device illustrated in FIG. 1. It is drawing which shows magnetic force distribution of each magnetic pole in the magnet roller contained in the developing roller which comprises the developing device shown in FIG. It is sectional drawing which shows typically the structure of the image development apparatus which is 2nd Embodiment of this invention. It is sectional drawing which shows typically the structure of the developing device which is 3rd Embodiment of this invention. It is sectional drawing which shows typically the structure of the developing device which is 4th Embodiment of this invention. It is sectional drawing which shows typically the structure of the image forming apparatus which is another form of implementation of this invention. It is sectional drawing which shows the structure of the conventional image development apparatus typically. It is sectional drawing explaining the fall of the developer interface in the image development apparatus shown in FIG.

Explanation of symbols

1, 15, 16, 17 Developing device 2 Developing tank 3 Developing roller 4 First agitating member 5 Second agitating member 6 Conveying member 7 Restricting member 8 Restricting member support 9 Sink plate 10, 10a, 10b, 10c Magnetic member 11 Magnetic Member support 12 Toner density detection sensor 13 Magnet roller 14 Sleeve 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 section 30 Paper discharge tray 100 Image formation apparatus

Claims (9)

In a developing device mounted on an electrophotographic image forming apparatus including a photosensitive drum on which an electrostatic latent image is formed,
A developing roller that includes a magnet roller, carries a developer on its surface, rotates, supplies toner to the electrostatic latent image on the surface of the photosensitive drum, and develops the toner;
A stirring member for supplying developer to the developing roller;
A regulating member that regulates the amount of developer carried on the surface of the developing roller;
The surface of the developing roller and the developing roller in the vicinity of the developing roller from the position closest to the developing roller and the stirring member in the developing roller rotation direction to the upstream position in the developing roller rotating direction from the closest position of the developing roller to the regulating member And a magnetic member having a surface that comes into contact with the developer and is provided so that a separation distance from an end portion closest to the surface is 0.1 mm to 10 mm.   On the upstream side of the regulating member in the rotation direction of the developing roller, one end in the short side direction is close to the developing roller surface, the other end extends in a direction away from the developing roller, and is removed from the developing roller surface by the regulating member The developing device according to claim 1, further comprising a sink plate that conveys the toner in a direction away from the developing roller. The sink is
The developing device according to claim 2, wherein the developing device is provided vertically above the magnetic member. Magnetic member
4. The developing device according to claim 3, wherein at least part of the upper surface in the vertical direction is provided so as to contact the lower surface in the vertical direction of the sink plate. Magnetic member
The developing device according to claim 4, wherein the developing device has a shape corresponding to a shape of a lower surface of the sink plate in a vertical direction. Magnetic member
The developing device according to claim 1, wherein the surface in contact with the developer is a flat surface or a convex surface.   The developing device according to claim 1, wherein the magnetic member is a permanent magnet.   The developing device according to claim 7, wherein the permanent magnet has a magnetic force of 50 mT to 500 mT. 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,
The image forming apparatus according to claim 1, wherein the developing unit is any one of the developing devices according to claim 1.

Images