JP2009058894A - Developing device and image forming apparatus - Google Patents

Abstract

Provided is a developing device capable of preventing clogging of a filter even when toner having a small particle diameter is used and preventing toner from being scattered outside a developing tank over a long period of time.
A developing device 1 is provided in an upper partition wall of a developing tank 2, and an exhaust port 9 for discharging air in the developing device 1 and a flow of the exhausted air from a filter 11 provided in the exhaust port 9. An airflow diverting plate 10 that changes the direction of the airflow generated by the movement of the two-component developer removed from the surface of the developing roller 3 by the regulating member 7 above the developing roller 3 to the direction toward the filter 11; It has.
[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 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. By these processes, an image is formed on the recording medium.

  In such an image forming apparatus, 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 as a developing unit. 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 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 previously 50 to 70 sheets / minute with A4 paper, is now 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. In particular, there is a demand for a miniaturized image forming apparatus having a short height from the floor that can be easily operated even when sitting on a chair or the like. 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.

  Further, in order to meet the user's demand for high image quality, a toner having a small particle diameter of 5 to 7 μm is often used. Such a small particle size toner greatly improves dot reproducibility, and is effective for high image quality such as higher resolution and reduced graininess. However, when a two-component developer containing a small particle size toner is used in a high-speed image forming apparatus, there is a problem that the toner is scattered from the developing apparatus and the inside of the image forming apparatus becomes dirty.

Here, as a technique for preventing toner scattering from the developing device, for example, in Patent Document 1, a pressure release hole for reducing the pressure in the development device is provided, and a coarse filter is provided in the pressure release hole. There has been disclosed a developing device provided with two types of fine filters.
JP 62-244072 A (published Oct. 24, 2002)

  However, when a two-component developer containing a toner having a small particle diameter is used, the conventional developing apparatus can capture toner particles effectively, but has a problem that the filter is clogged immediately.

  Therefore, the present invention has been made in view of the above problems, and its purpose is to prevent the filter from being clogged even when toner having a small particle diameter is used, and to disperse the toner to the outside of the developing tank over a long period of time. It is an object of the present invention to provide a developing device and an image forming apparatus that can effectively prevent the occurrence of contamination and hardly cause dirt inside the image forming apparatus.

  In order to solve the above-described problems, the developing device of the present invention includes a developing tank that contains a two-component developer, a two-component developer that rotates on the surface, and the image carrier includes the two-component developer. A developing roller that supplies toner, a regulating member that regulates the amount of the two-component developer carried on the surface of the developing roller on the upper side of the developing roller, and an upstream of the regulating member in the rotation direction of the developing roller The two-component developer having one end close to the surface of the developing roller and the other end extending in a direction away from the developing roller and removed from the surface of the developing roller by the regulating member in a direction away from the developing roller. A developing plate provided with a sink plate to be transported, provided in a developing tank upper partition above the sink plate, an exhaust port for discharging air in the developing device, a filter provided in the exhaust port, Airflow direction that changes the direction of the airflow generated by the movement of the two-component developer removed from the surface of the developing roller by the restricting member to the direction toward the filter. And a board.

  Due to the rotation of the developing roller, the airflow flows upward on the flow plate in a state where the free toner of the developer is raised, toward the inlet of the exhaust port along the upper separation wall of the developing tank. Here, according to the said structure, the airflow which goes to the filter provided in the exhaust port among the airflow along a developing tank upper part separation wall can be diverted with an airflow direction change plate. The toner heavier than air goes straight in the direction along the separation wall at the upper part of the developing tank due to inertia, so that almost only air goes to the filter. Toner other than the toner traveling straight due to inertia adheres to the airflow diverting plate or hits the airflow diverting plate and falls. Even if it adheres to the airflow direction change plate, if it adheres to some extent, it falls naturally with its own weight.

  From the above, the number of toner particles carried on the airflow to the filter can be suppressed or reduced as compared with the conventional developing device. Therefore, the clogging of the filter by the toner can be suppressed or delayed from the conventional developing device. Therefore, in the developing device of the present invention, the life of the filter can be extended, the toner can be effectively prevented from scattering to the outside of the developing tank over a long period of time, and the developer contamination inside the image forming apparatus where the developing device is installed can be prevented. It can be made difficult to occur.

  In the developing device of the present invention, in addition to the above configuration, the airflow diverting plate has a direction of airflow generated by the movement of the two-component developer of 90 ° or more and less than 180 °, where the traveling direction is 0 °. The range may be changed.

  If the direction of the air flow generated by the movement of the two-component developer is changed within the range of 90 ° or more and less than 180 ° with the traveling direction as 0 °, only the air flow (air) that does not contain toner is efficiently conveyed in the filter direction. Can do.

  In the developing device of the present invention, in addition to the above-described configuration, a plurality of the airflow direction change plates may be provided, and the respective principal surfaces may be arranged in parallel to each other.

  According to the above configuration, since the principal surfaces of the plurality of airflow diverting plates are arranged in parallel to each other, a rectifying airflow is formed. That is, turbulent flow can be made difficult to occur. Even if the image forming apparatus in which the developing device is installed is a high-speed machine, turbulent flow can be hardly generated. Therefore, it is possible to suppress the clogging caused by the turbulent flow causing the toner particles to fly up around the exhaust port or around the exhaust port and be carried to the filter. Alternatively, the progress of filter clogging can be made slower than in conventional devices.

  In the developing device of the present invention, in addition to the above configuration, the main surface of the airflow direction change plate is 0 ° with respect to the vertical line, or is greater than 0 ° and 45 ° or less. You may incline to the upstream of the airflow produced by the movement of the said two-component developer.

  According to the above configuration, the airflow diverting plate has its main surface formed by movement of the two-component developer within a range of 0 ° with respect to the vertical line or greater than 0 ° and 45 ° or less. Installed by tilting upstream of the airflow. Therefore, even if the toner adhering to the airflow diverting plate accumulates, it naturally falls when it reaches a certain amount, so that it is possible to prevent the airflow from being blocked by the toner being clogged between the airflow diverting plates.

  In the developing device of the present invention, in addition to the above configuration, the airflow diverting plate may be made of a conductive material.

  According to the above configuration, since the airflow diverting plate is formed of a conductive material, the toner can be prevented from being adsorbed by an electrostatic force by being charged. The conductive material may be, for example, a metal plate or a resin containing a conductive material.

  In the developing device of the present invention, in addition to the above-described configuration, the inner wall of the exhaust port may be formed in parallel with the main surface of the airflow diverting plate.

  According to the above configuration, since the inner wall of the developing tank upper partition is formed in parallel with the main surface of the airflow diverting plate, the airflow can be more effectively diverted.

  In the developing device of the present invention, in addition to the above configuration, the volume average particle diameter of the toner contained in the developer may be 4 to 7 μm.

  Even when a developer having a toner having a volume average particle size of 4 to 7 μm is used, the toner can be prevented from entering in the direction of the filter, and the filter can be prevented from being clogged. Can be effectively prevented.

  In the developing device of the present invention, in addition to the above configuration, the filter may be formed of a fiber aggregate having a single fiber diameter of 1 to 10 μm.

  According to the above configuration, a filter having an excellent toner capturing effect and a low pressure loss can be obtained, so that the air flow in the developing device can be prevented from being ejected from other than the exhaust port provided with the filter. In addition, when the single fiber diameter is less than 1 μm, the pressure loss becomes large and the flow of the air current is hindered. On the other hand, when the single fiber diameter exceeds 10 μm, the effect of capturing the toner is lowered, and the performance as a filter is deteriorated.

  In the developing device of the present invention, in addition to the above configuration, the filter may include at least a polyester fiber or a polyamide fiber.

  Polyester fibers or polyamide fibers are easily charged. Therefore, according to the above configuration, when the toner comes into contact with the fiber of the filter, the toner is easily attached and held by electrostatic force, and even toner particles having a small particle diameter can be captured by the filter.

  In the developing device of the present invention, in addition to the above configuration, the filter may include two different types of fibers.

  By combining different types of fibers, the fibers are positively or negatively charged. Therefore, according to the above configuration, the ability of the filter to capture the charged toner particles due to electrostatic force can be enhanced, so that the scattering of the toner outside the developing tank can be further prevented. It is sufficient that two types of fibers of the filter are included, and of course, the fibers are not limited to only two types, and three or more types of fibers may be included.

  In order to solve the above-described problems, an image forming apparatus of the present invention includes any one of the developing devices described above.

  With the above configuration, it is possible to provide an image forming apparatus that does not cause toner contamination in the image forming apparatus for a long period of time, requires only a small replacement frequency of the filter of the developing device, and has excellent maintainability.

  As described above, the developing device according to the present invention is provided in the upper partition wall of the developing tank above the sink plate, the exhaust port for discharging the air in the developing device, the filter provided in the exhaust port, and the filter An airflow diverting plate that is provided upstream of the flow of the discharged air and changes the direction of the airflow generated by the movement of the two-component developer removed from the surface of the developing roller by the regulating member to the direction toward the filter. And.

  Due to the rotation of the developing roller, the airflow flows upward on the flow plate in a state where the free toner of the developer is raised, toward the inlet of the exhaust port along the upper separation wall of the developing tank. Here, according to the said structure, the airflow which goes to the filter provided in the exhaust port among the airflow along a developing tank upper part separation wall can be diverted with an airflow direction change plate. The toner heavier than air goes straight in the direction along the separation wall at the upper part of the developing tank due to inertia, so that almost only air goes to the filter. Toner other than the toner traveling straight due to inertia adheres to the airflow diverting plate or hits the airflow diverting plate and falls. Even if it adheres to the airflow direction change plate, if it adheres to some extent, it falls naturally with its own weight.

  From the above, the number of toner particles carried on the airflow to the filter can be suppressed or reduced as compared with the conventional developing device. Therefore, the clogging of the filter by the toner can be suppressed or delayed from the conventional developing device. Therefore, in the developing device of the present invention, the life of the filter can be extended, the toner can be effectively prevented from scattering to the outside of the developing tank over a long period of time, and the developer is contaminated inside the image forming apparatus where the developing device is installed. Can be difficult. According to the above configuration, the life of the filter can be extended, toner can be effectively prevented from scattering outside the developing tank over a long period of time, and developer contamination inside the image forming apparatus in which the developing apparatus is installed can be made difficult to occur. it can.

  First, the developing device according to this embodiment will be described. FIG. 1 is a cross-sectional view showing a configuration of a developing device 1 according to a first embodiment of the present invention. 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 sink plate 8, a toner concentration detection sensor 12, and the like. And an exhaust port 9. The exhaust port 9 is provided with an airflow diverting plate 10 and a filter 11 on the outside thereof.

  The developing tank 2 is a substantially prismatic container having an internal space. The developing tank 2 accommodates at least a part of the developing roller 3, the first stirring member 4, the second stirring member 5, and the conveying member 6 therein, and rotatably supports them. Further, the developing tank 2 accommodates therein a regulating member 7, a sink plate 8, and the like, and directly or indirectly supports them. The developing tank 2 contains a two-component developer. The two-component developer includes toner and a carrier that is magnetic powder. The toner has a volume average particle diameter of, for example, 4 to 7 μm, but is not limited thereto.

  In addition, when the developing device 1 is mounted on an electrophotographic image forming apparatus (not shown), an opening 2 a is formed in the developing tank 2 on the side facing the photosensitive drum 20 provided in the image forming apparatus. Further, a toner replenishing port 2 b is formed on the upper surface in the vertical direction of the developing tank 2. In addition, an upper partition wall (development tank upper partition wall) is provided above the developing tank 2 so that the toner does not scatter outside the developing device 1.

  A toner supply container (not shown) is provided above the toner supply port 2 b of the developing tank 2 in the vertical direction. The toner supply container is detachably provided on an image forming apparatus main body (not shown) to which the developing device 1 is attached. In the toner supply container, for example, a toner supply port that is an opening formed on the bottom surface in the vertical direction communicates with a toner supply port 2 b that is an opening formed on the top surface in the vertical direction of the developing tank 2 in the vertical direction. It is provided as follows. In the toner supply container, a toner supply roller (not shown) is provided above the toner supply port in the vertical direction. The toner supply roller is rotatably supported by a toner hopper (not shown) and is driven to rotate by a driving means (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, and at least a part of the developing roller 3 is rotatably supported by the developing tank 2 and is driven to rotate around an axis by a driving unit (not shown). Further, the developing roller 3 faces the photosensitive drum 20 provided in the image forming apparatus to which the developing device 1 is mounted 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. The closest portion between the developing roller 3 and the photosensitive drum 20 is a developing nip portion. In this developing nip portion, toner is supplied to the electrostatic latent image on the surface of the photosensitive drum 20 from a two-component 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 electrostatic latent image on the surface of the photosensitive drum 20 from the two-component developer layer on the surface of the developing roller 3. The toner transitions smoothly.

  The developing roller 3 includes a magnet roller 13 and a sleeve 14. Both ends of the magnet roller 13 in the longitudinal direction are supported by the side walls of the developing tank 2, and magnetic poles N1, N2, N3 and magnetic poles S1, which are a plurality of bar magnets having a rectangular cross section at the circumferential position of the developing roller 3, are provided. S2, S3 and S4 are multi-pole magnetized magnet rollers which 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).

  The arrangement of the magnetic poles in the magnet roller 13 is as follows in the present 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 includes a radius S1 passing through the center of the magnetic pole S1 in the cross section of the developing roller 3 where the magnetic pole S1 is disposed and a radius N1 passing through the center of the magnetic pole N1 in the cross section of the developing roller 3 where the magnetic pole N1 is disposed. This is the angle of the angle formed. 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.

  The sleeve 14 is a cylindrical member, is fitted around 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 means (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.

  The first agitating member 4 and the second agitating member 5 are roller-like members, and both are rotatably supported by the developing tank 2 and are provided so as to be rotatable around an axis by driving means (not shown). In the present embodiment, the first stirring member 4 rotates counterclockwise, and the second stirring member 5 rotates clockwise. The first stirring member 4 is provided at a position that faces the photosensitive drum 20 via the developing roller 3 and is vertically lower than the developing roller 3. In the present embodiment, the radius S2 (the radius passing through the center of the magnetic pole S2 in the cross section of the developing roller 3 where the magnetic pole S2 is disposed) and the axis of the developing roller 3 and the axis of the first stirring member 4 are connected. The installation angle of the first stirring member 4, which is the angle formed by the straight line, is 54 °. The second agitating member 5 is provided at a position facing the developing roller 3 with the first agitating member 4 interposed therebetween and lower than the developing roller 3 in the vertical direction. The first stirring member 4 and the second stirring member 5 stir the two-component developer stored in the developing tank 2 to give a uniform charge to the toner, and pump the two-component developer in a charged state. Then, it is fed around the developing roller 3.

  The conveying member 6 is a roller-like member, is rotatably supported by the developing tank 2, and is rotatably provided 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 that extends parallel to the axial direction of the developing roller 3. The regulating member 7 is supported by the upper partition wall of the developing tank 2 at one end in the direction perpendicular to the longitudinal direction and thickness direction of the plate-like member (hereinafter referred to as the short direction) above the developing roller 3 in the vertical direction. And the other end is provided apart 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 7 is supported so that one end in the lateral direction and the vicinity thereof are sandwiched by the developing tank 2. The regulating member 7 removes excess two-component developer from the two-component developer layer carried on the surface of the developing roller 3, and regulates the layer thickness of the two-component developer layer so that the two-component developer is exposed to light. The conveyance amount to the body drum 20 is adjusted. Further, the regulating member 7 imparts a charge to the two-component developer that is insufficiently charged in the two-component developer layer by rubbing between the other end in the short-side direction and the two-component developer layer. The two-component developer contained in the developer layer is sufficiently charged.

  The sink plate 8 is a plate-like member, and is disposed upstream of the regulating member 7 in the rotation direction of the developing roller 3 in the developing tank 2, and is vertically above the first stirring member 4 and the second stirring member 5. Provided. The sink plate 8 has one end in the short direction facing the surface of the developing roller 3, spaced apart with a gap, and the other end extending in a direction away from the developing roller 3. In the present embodiment, the upper surface (upper surface) of the sink plate 8 in the vertical direction is parallel to the horizontal direction at the end portion on the developing roller 3 side in the short direction of the sink plate 8 and its vicinity. The other portions are provided so as to descend in the vertical direction as they are separated from the developing roller 3. The sink plate 8 is supported by a support member 9 a that is formed so as to penetrate in the longitudinal direction of the sink plate 8 and is inserted through the through hole at the lower portion in the vertical direction. By providing the flow plate 8, a smooth flow of the two-component 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 suppressed. Specifically, the two-component 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 the direction in which the upper surface of the sink plate 8 is separated from the developing roller 3 as the amount increases. Begins to flow through. The two-component developer flows along the upper surface of the flow plate 8 to form a flow of the two-component developer indicated by an arrow 8a, and the end of the flow plate 8 opposite to the developing roller 3 side in the short direction. To the second stirring member 5. The dropped two-component developer is uniformly mixed with the other two-component developer and the toner supplied from the toner supply port 2b by the first stirring member 4 and the second stirring member 5, and is conveyed toward the developing roller 3 again. Is done.

  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 concentration detection sensor 12 is electrically connected to control means (not shown). The control means controls the toner supply container to rotate and supply toner into the developing tank 2 via the toner hopper according to the detection result of the toner concentration detection sensor 12. That is, when it is determined that the detection result by the toner concentration detection sensor 12 is lower than the toner concentration setting value, a control signal is sent to the driving means for driving the toner supply container to rotate, thereby rotating the toner supply container. As the toner concentration detection sensor 12, 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 a detection result of the toner concentration 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 two-component developer stored in the developing tank 2 is conveyed vertically above the first stirring member 4 by the rotation of the first stirring member 4 and the second stirring member 5, and the developing roller 3. Supplied to the surface. The developing roller 3 carries a two-component developer layer on its surface and rotates. After the two-component developer layer is regulated by the regulating member 7 and charged to the two-component developer, the developing roller 3 The electrostatic latent image on the photosensitive drum 20 is supplied with toner and developed. After the development is completed, the developing roller 3 further rotates and receives the supply of the two-component developer again. On the other hand, the two-component 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 vertical upper surface of the flow plate 8, and the second stirring member 5 and the conveying member 6 Returned in between. Therefore, it is mixed again with the other two-component developer and conveyed toward the developing roller 3. In the developing tank 2, the two-component developer is circulated as described above. 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.

  The exhaust port 9 is provided in the upper partition wall of the developing tank 2 and discharges air inside the developing tank 2. The exhaust port 9 is provided at a position where the two-component developer accommodated in the developing tank 2 is not blocked even if the bulk of the developer increases. The shape of the exhaust port 9 is rectangular when viewed from above the developing tank 2, and the length of the exhaust port 9 in the longitudinal direction is substantially the same as the length of the sleeve 14 in the longitudinal direction. The exhaust port 9 is provided with an airflow diverting plate 10 on the upstream side of the exhausted airflow and a filter 11 on the downstream side thereof. In this embodiment, the exhaust port 9 is provided so as to protrude from the upper partition wall (ceiling) of the developing tank 2, but the upper surface (outer wall surface) of the upper partition wall and the upper surface of the filter 11 are provided so as to form substantially the same plane. (See the developing device 1a of the second embodiment described later shown in FIG. 3).

  The airflow diverting plate 10 is a plate-like member, and the main surface of the airflow diverting plate 10 is an airflow (arrow Fa + Fb in FIG. 2) generated by the movement of the two-component developer above the sink plate 8 described below with respect to the vertical line. It is inclined 45 ° on the upstream side. In other words, when the wall surface (ceiling) of the upper partition wall of the developing tank 2 is set to 0 °, the wall is disposed with an inclination of 45 ° on the upstream side of the air flow generated by the movement of the two-component developer. A plurality of the airflow direction change plates 10 are arranged in parallel to each other at the exhaust port 9. As schematically shown by the broken-line arrow Fa in FIG. 1, the airflow diverting plate 10 is directed to the direction of the airflow generated by the movement of the two-component developer removed from the surface of the developing roller 3 by the regulating member 7, here, the developing tank. The direction of the airflow flowing along the wall of the upper partition wall in the upper space 2 is changed to 135 ° with the traveling direction being 0 °, and the airflow is guided to the filter 11.

  The air flow schematically represented by the broken-line arrow Fa is generated by the rotation of the developing roller 3 (sleeve 14) carrying the two-component developer. In other words, the air current indicated by the arrow Fa flows into the developing tank 2 from the opening 2a, flows around the developing roller 3, and flows in the upper space of the developing tank 2 along the upper partition. Actually, a complicated air flow is generated with the movement of the two-component developer, such as the air flow indicated by the broken arrow Fb schematically. In the space formed between the sink plate 8 and the upper partition wall of the developing tank 2, an airflow in the direction indicated by the arrows Fa and Fb is generated. In particular, when the image forming apparatus provided with the developing device 1 is a high-speed machine, the rotation of the developing roller 3 is fast, so that the moving speed of the two-component developer is fast, and the flow of the airflow is accordingly fastened. Under such circumstances, the toner contained in the two-component developer is easily released and moves together with air as an aerosol. If the exhaust port 9 is closed, the airflow that has lost its escape is discharged to the outside through the gap between the regulating member 7 and the developing roller 3, so that the toner in the developing tank 2 is stored in the image forming apparatus or the image forming apparatus. It will fly out of the device.

FIG. 2 is a conceptual diagram showing the behavior of the toner when the direction of the airflow (aerosol) containing the released toner is changed by the airflow diverting plate 10. As for the airflow flowing in the vicinity of the upper partition wall of the developing tank 2, two types of airflows indicated by arrows Fa and Fb overlap (Fa + Fb in FIG. 2). Among the airflows that have reached the airflow diverting plate 10 (inlet of the exhaust port 9), a part of the airflow goes to the exhaust port 9, but in order to go to the exhaust port 9, the direction going straight to the exhaust port 9 is 0. The angle is changed by 135 °. Toner having a specific gravity heavier than air (approximately 1.1 g / cm ² ) travels straight (in the direction of Fa + Fb in FIG. ² ) due to inertia, and only air (airflow) that does not contain toner travels to the exhaust port 9. Note that the toner other than the straight traveling due to inertia adheres to the airflow diverting plate 10 or falls on the airflow diverting plate 10 and falls. Even if it adheres to the airflow diverting plate 10, if it adheres to some extent, it naturally falls with its own weight.

  When turbulent flow is generated around the airflow diverting plate 10, the inertia force of the toner is reduced and the toner is sucked into the exhaust port 9. Therefore, a plurality of airflow diverting plates 10 are provided to prevent the turbulent flow. The faces are preferably arranged parallel to each other. Further, the inner wall of the exhaust port 9 is preferably formed into a streamline shape, and is preferably formed in parallel with the main surface of the airflow diverting plate 10.

  In the present embodiment, the installation angle of the airflow diverting plate 10 is 45 ° as described above, but the direction of the airflow generated by the movement of the two-component developer above the sink plate 8 is changed with respect to the vertical line. In particular, the installation angle is not limited as long as the direction of travel of the airflow is 0 ° and the angle is changed within a range of 90 ° to less than 180 °. However, if the toner adhering to the airflow diverting plate 10 is accumulated, the flow of the airflow is hindered. Therefore, the installation angle of the airflow diverting plate 10 is set so that the main surface of the airflow diverting plate 10 is 0 with respect to the vertical line. It is preferable that the angle is at an angle, or is inclined upstream of the airflow generated by the movement of the two-component developer in the range of greater than 0 ° and less than or equal to 45 °. In other words, the horizontal is 0 °, the vertical direction is 90 °, and the wall surface (ceiling) of the upper partition wall is made to coincide with the horizontal direction. It is preferable to incline to the upstream side of the generated airflow (Fa + Fb). If the airflow diverting plate 10 is installed at this angle, if the toner adheres to the airflow diverting plate 10 to some extent, it naturally falls by its own weight, so that the toner does not clog the exhaust port 9. Therefore, the flow of the airflow at the exhaust port 9 is not hindered by the toner. In addition, the airflow diverting plate 10 is preferably formed of a resin including a metal plate or a conductive material so that the toner can be prevented from being adsorbed by electrostatic force when charged.

  The filter 11 captures toner particles from the air discharged from the developing tank 2. The type of the filter 11 is not particularly limited, but a fiber aggregate having a single fiber diameter of 1 to 10 μm is preferable in that a filter having an excellent toner capturing effect and a low pressure loss can be obtained and a large amount of adhered toner can be retained. . If the single fiber diameter is less than 1 μm, the pressure loss becomes large and the flow of airflow is hindered. If the single fiber diameter exceeds 10 μm, the effect of capturing the toner is reduced and the performance as a filter is inferior. Although the thickness of the filter 11 is not specifically limited, 1-20 mm is preferable. The fiber material is preferably polyester fiber or polyamide fiber. Polyester fibers or polyamide fibers are easily charged, and the toner is attached and held by electrostatic force when the fibers come into contact with the fibers. Therefore, even toner particles having a small particle diameter are captured by the filter 11. Further, it is more preferable to use two types of fibers of different types, and by combining different types of fibers, the fibers are charged positively or negatively, so that the ability to capture charged toner particles due to electrostatic force is enhanced. .

  3 to 5 show modifications of the developing device 1. In the developing device shown in FIGS. 3 to 5, the same components as those of the developing device 1 are denoted by the same reference numerals and description thereof is omitted.

  FIG. 3 is a cross-sectional view showing a configuration of the developing device 1a according to the second embodiment of the present invention. In the developing device 1a, the wall surface (ceiling) of the upper separating wall of the developing tank 2 is inclined from the upper side of the developing roller 3 toward the inlet of the exhaust port 9 toward the inside of the developing tank 2 by 45 ° from the horizontal direction. A plurality of airflow diverting plates 10 are arranged at the exhaust port 9 so as to form 0 ° with respect to the vertical line (in the vertical direction), and their main surfaces are parallel to each other. Yes. The air flow proceeds along the inclined surface (45 °) which is the wall surface of the upper separation wall of the developing tank 2 from the upper side of the developing roller 3 toward the entrance of the exhaust port 9 above the flow plate 8, and is changed by the air flow diverting plate 10. Be directed. When the traveling direction of the air flow along the inclined surface is 0 °, the air flow along the inner surface of the upper partition wall of the developing tank 2 is 45 ° + 90 = 135 by the air flow diverting plate 10 installed in the vertical direction. ° Turned.

  In the developing device 1a, the upper surface of the upper partition wall (ceiling) of the developing tank 2 and the upper surface of the filter 11 are provided so as to form substantially the same plane. However, it may be provided so as to protrude from the upper partition wall (ceiling) of the developing tank 2, and the shape is not limited.

  FIG. 4 is a cross-sectional view showing a configuration of a developing device 1b according to the third embodiment of the present invention. In the developing device 1b, the wall surface (ceiling) of the upper separation wall of the developing tank 2 is inclined from the upper side of the developing roller 3 toward the inlet of the exhaust port 9 toward the inside of the developing tank 2 from the horizontal direction. A plurality of airflow diverting plates 10 are arranged at the exhaust port 9 so as to form 0 ° with respect to the vertical line (in the vertical direction), and their main surfaces are parallel to each other. Yes. The air flow proceeds along the inclined surface (30 °) which is the wall surface of the upper separation wall of the developing tank 2 from the upper side of the developing roller 3 toward the entrance of the exhaust port 9 above the sink plate 8 and is changed by the air flow diverting plate 10. Be directed. When the traveling direction of the air flow along the inclined surface is 0 °, the air flow along the wall surface of the upper partition wall of the developing tank 2 is changed by 30 ° + 90 = 120 ° by the air flow diverting plate 10 installed in the vertical direction. Be directed.

  In the developing device 1b, the exhaust port 9 is provided so as to protrude from the upper partition wall (ceiling) of the developing tank 2, but the shape is not limited thereto.

  FIG. 5 is a cross-sectional view showing a configuration of a developing device 1c according to the fourth embodiment of the present invention. In the developing device 1 c, the inner surface (ceiling) of the upper separation wall of the developing tank 2 is provided horizontally as in the developing device 1. A plurality of airflow diverting plates 10 are arranged at the exhaust port 9 so as to form 0 ° with respect to the vertical line (in the vertical direction), and their main surfaces are parallel to each other. Yes. The airflow travels along the wall surface of the upper separation wall of the developing tank 2 from the upper side of the developing roller 3 toward the entrance of the exhaust port 9 above the sink plate 8 and is redirected by the airflow diverting plate 10. Assuming that the angle of the air flow along the inner surface of the upper separation wall increases to 0 ° and initially upward in the vertical direction, the air flow along the inner surface of the upper partition wall of the developing tank 2 is installed in the vertical direction. The airflow diverting plate 10 is turned 90 °.

  Next, an image forming apparatus 100 that is another embodiment of the present invention provided with the developing device 1 (or any one of the developing devices 1a to 1c) will be described. FIG. 6 is a cross-sectional view schematically showing the configuration of the image forming apparatus 100. The image forming apparatus 100 is an electrophotographic color image forming apparatus, for example, based on image data transmitted from the outside via a network or image data read by an image reading apparatus (not shown). A multicolor or single color image is formed on the (transfer medium).

  The image forming apparatus 100 is a digital copying machine and has a copy mode and a print mode. In the copy mode, a copy of the original is printed according to the image information of the original read by the scanner unit 29 described later. In the print mode, according to the image information from the external device connected to the image forming apparatus 100 via the network. The corresponding image is printed. The image forming apparatus 100 includes a photosensitive drum 20, a charging unit 21, an exposure unit 22, a developing unit 1, a transfer unit 23, a fixing unit 25, a cleaning unit 24, a paper feed cassette 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 20, for example, a member including a conductive substrate (not shown) and a photosensitive film (not shown) formed on the surface of the conductive substrate 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 this embodiment, a roller-shaped charging unit is used, but the present invention is not limited to this, and a contact such as a charging brush type charger, a non-contact type corotron or a scorotron charger, a sawtooth type charger, an ion generator, a magnetic brush, etc. System chargers 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 according 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 according to the present invention described with reference to FIG.

  The transfer means 23 is a roller-like member that is rotatably supported by a support means (not shown), is rotatably provided by a drive means (not shown), and is provided in pressure contact with the photosensitive drum 20. For the transfer means 23, for example, a roller-shaped member including a metal core having 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 cassette 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 supply (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. One end of the plate-like member in the direction perpendicular to the longitudinal direction and the thickness direction is provided so as to contact 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 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 so as to come into 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. In that case, the heating means similar to the heating means inside the fixing roller 26 can be used.

  According to the fixing unit 25, the recording medium on which the toner image is transferred is passed through the fixing nip portion, and the toner constituting the toner image is melted and pressed against the recording medium, thereby fixing the toner image 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 cassette 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 cassettes 28 are provided, and recording media of different sizes are accommodated in each paper feed cassette 28. Examples of the size of the recording medium include A3, A4, B5, and B4. In addition, a plurality of paper feed cassettes 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 is provided with a document set tray (not shown), an automatic document feeder (RADF), and the like, and a document reading unit (not shown). 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 unit includes a document placing table, a document scanning unit, a reflecting unit, a photoelectric conversion device (Charge Coupled Device, hereinafter referred to as “CCD”) licensor, and the like. The document reading means reads the image information of the document placed on the document placing table every plural lines, for example, every ten 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 (speed V) 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.

  The image forming apparatus 100 is excellent in maintainability because toner contamination does not occur inside the image forming apparatus 100 for a long period of time and the replacement frequency of the filter 11 can be reduced.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  The present invention can be used in a developing device used in an electrophotographic image forming apparatus.

It is sectional drawing which shows the structure of the image development apparatus which is 1st Embodiment of this invention. FIG. 6 is a conceptual diagram illustrating the behavior of toner when the direction of airflow is changed by an airflow diverting plate. It is sectional drawing which shows the structure of the image development apparatus which is 2nd Embodiment of this invention. It is sectional drawing which shows the structure of the developing device which is 3rd Embodiment of this invention. It is sectional drawing which shows 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.

Explanation of symbols

1, 1a, 1b, 1c Developing device 2 Developing tank 3 Developing roller 4 First stirring member 5 Second stirring member 6 Conveying member 7 Restricting member 8 Sink plate 9 Exhaust port 10 Airflow diverting plate 11 Filter 12 Toner concentration 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 unit 30 Paper discharge tray 100 Image forming apparatus

Claims (11)

A developing tank containing a two-component developer;
A developing roller that carries a two-component developer on its surface, rotates, and supplies toner contained in the two-component developer to the image carrier;
A regulating member that regulates the carrying amount of the two-component developer on the surface of the developing roller on the upper side of the developing roller;
Arranged upstream of the regulating member in the rotational direction of the developing roller, one end is close to the developing roller surface, the other end extends away from the developing roller, and is removed from the developing roller surface by the regulating member. In a developing device comprising a two-component developer and a sink plate that conveys the two-component developer in a direction away from the developing roller,
An exhaust port provided in the upper partition wall of the developing tank above the sink plate and for discharging the air in the developing device;
A filter provided at the exhaust port;
An airflow change that changes the direction of the airflow generated by the movement of the two-component developer removed from the surface of the developing roller by the restriction member to the direction toward the filter. And a developing plate.   2. The airflow direction change plate according to claim 1, wherein the airflow direction change plate changes the direction of the airflow generated by the movement of the two-component developer within a range of 90 ° or more and less than 180 °, where the traveling direction is 0 °. Development device.   3. The developing device according to claim 1, wherein a plurality of the airflow diverting plates are provided, and main surfaces thereof are arranged in parallel to each other.   The main surface of the airflow diverting plate is at 0 ° with respect to the vertical line, or on the upstream side of the airflow generated by the movement of the two-component developer in the range of more than 0 ° and 45 ° or less. The developing device according to claim 1, wherein the developing device is inclined.   The developing device according to claim 1, wherein the airflow diverting plate is made of a conductive material.   6. The developing device according to claim 1, wherein an inner wall of the exhaust port is formed in parallel with a main surface of the airflow diverting plate.   The developing device according to claim 1, wherein a volume average particle diameter of toner contained in the developer is 4 to 7 μm.   The developing device according to claim 1, wherein the filter is formed of a fiber aggregate having a single fiber diameter of 1 to 10 μm.   The developing device according to claim 1, wherein the filter includes at least a polyester fiber or a polyamide fiber.   The developing device according to claim 1, wherein the filter includes two different types of fibers.   An image forming apparatus comprising the developing device according to claim 1.

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