JP5822087B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, or a multi-function machine thereof, and a developing device and a process cartridge installed therein, and particularly to a developer carrying member. A developing device in which a circulation path in the longitudinal direction of the developer is formed by the two conveying members arranged in the vertical direction and the conveying member arranged so as to face the conveying members, The present invention also relates to an image forming apparatus.

  Conventionally, in a developing device installed in an image forming apparatus such as a copying machine or a printer, a two-component developer composed of a toner and a carrier (including a case where an additive or the like is added) is accommodated, and three types are included. A technique for forming a circulation path while conveying a developer in a longitudinal direction by a conveying member (conveying screw) is known (for example, see Patent Documents 1 and 2).

  Specifically, the first conveying member (first conveying screw) is installed so as to face the developer carrying member (developing roller), and the developer is conveyed to the developer carrying member while conveying the developer in the longitudinal direction. Supply. The second transport member (second transport screw) is installed to face the developer carrier at a position below the first transport member, and transports the developer detached from the developer carrier in the longitudinal direction. To do. The third conveying member (third conveying screw) is installed so as to face the developer carrier via the first conveying member and the second conveying member, and is conveyed from the second conveying path by the second conveying member. The developed developer is conveyed obliquely upward toward the upstream side of the first conveyance path by the first conveyance member. Further, the developing device includes a first relay unit communicating with the downstream side of the second conveyance path by the second conveyance member and the upstream side of the third conveyance path by the third conveyance member, and the third conveyance by the third conveyance member. A second relay portion communicating with the downstream side of the path and the upstream side of the first transport path by the first transport member, the downstream side of the first transport path by the first transport member, and the second transport path of the second transport member A third relay portion communicating with the downstream side is provided, and the developing process is performed while the developer is circulated in the longitudinal direction.

  In this way, the developing device that forms the developer circulation path using three (or three or more) conveying members is compared with the developing device that forms the developer circulation path using two conveying members. Since a good developer circulation path can be formed even if the length in the longitudinal direction is increased or the amount of the developer is increased, the development installed in the image forming apparatus which is increased in speed and size It is often used as a device.

In the conventional developing device described above, air is discharged outside the apparatus along the rotation of the developer carrying member in the first conveying path, and the internal pressure is lowered, whereas in the second conveying path, air is discharged in the developer carrying member. The internal pressure was increased by being pulled into the device along with the rotation of. For this reason, in the second transport path, a problem may occur in which toner and developer are scattered (spouted) from a portion having a low sealing property due to the high internal pressure.
In particular, in a developing device that forms a developer circulation path using three or more transport members, the rotation speed of the developer carrier and the transport member is high, and the length of the developer carrier and the transport member in the longitudinal direction is also long. Further, since the amount of developer accommodated in the inside is large, the above-described problems cannot be ignored.

  The present invention has been made to solve the above-described problems, and has two conveying members arranged in the vertical direction so as to face the developer carrying member, and arranged so as to face the conveying members. Even when a developer circulation path in the longitudinal direction is formed with the provided conveyance member, the developing device is less likely to cause a problem that the internal pressure in the second conveyance path is increased and the toner and developer are scattered. Another object of the present invention is to provide a process cartridge and an image forming apparatus.

According to a first aspect of the present invention, there is provided a developing device for storing a developer having a carrier and a toner and developing a latent image formed on an image carrier, the image carrier. A plurality of conveying members that are opposed to the body and that carry a developer, and a plurality of conveying members that convey the developer contained in the apparatus in the longitudinal direction to form a circulation path. The member is opposed to the developer carrier, and is opposed to the developer carrier, a first conveyance member that supplies the developer to the developer carrier while conveying the developer in the longitudinal direction, and the member A second transport member that transports the developer separated from the developer carrying member in the longitudinal direction, and the developer transported by the second transport member is transported toward the upstream side of the transport path by the first transport member. A third conveying member; A wall portion that separates the first transport path by the first transport member, the second transport path by the second transport member, and the third transport path by the third transport member; 3 transport path, not buried and narrow part formed to the cross-sectional area of the conveying path is minimized in the third conveyance path, the developer at a position in the conveying direction downstream side with respect to the narrow part located And an opening communicating with the outside of the apparatus , wherein the wall communicates the downstream side in the transport direction of the second transport path and the upstream side in the transport direction of the third transport path. A first relay section to be communicated, a second relay section that communicates the downstream side in the transport direction of the third transport path and the upstream side in the transport direction of the first transport path, the downstream side in the transport direction of the first transport path, and the The third middle communicating with the downstream side in the transport direction of the second transport path The second transport path is disposed below the first transport path, and the third transport member obliquely injects the developer from the upstream side in the transport direction toward the downstream side in the transport direction. The narrow portion is disposed on the downstream side in the transport direction with respect to the first relay portion, and the opening portion is disposed on the upstream side in the transport direction with respect to the second relay portion, The third conveyance path is formed such that a cross-sectional area of the conveyance path from the position of the first relay portion to the position of the narrow portion gradually decreases, and is a portion adjacent to the narrow portion at a position downstream of the conveyance direction Is formed so that the cross-sectional area is maximized, and the opening is formed in the portion .

  In the present application, the “process cartridge” refers to a charging unit that charges the image carrier, a developing unit (developing device) that develops a latent image formed on the image carrier, and a cleaning on the image carrier. It is defined as a unit in which at least one of the cleaning units and the image carrier are integrated and installed detachably with respect to the image forming apparatus main body.

  The present invention provides a developer circulation path in the longitudinal direction by two conveying members arranged in the vertical direction so as to face the developer carrier and a conveying member arranged so as to face the conveying members. Even in the case of forming the second conveyance path, since the narrow portion is provided at the central portion in the conveyance direction in the third conveyance path and the opening portion communicating with the outside of the apparatus is provided at the downstream position of the narrow portion, the second conveyance It is possible to provide a developing device, a process cartridge, and an image forming apparatus that are less likely to cause a problem that toner and developer are scattered due to high internal pressure in the path.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a process cartridge installed in the image forming apparatus of FIG. 1. It is an enlarged view which shows a developing device. It is sectional drawing which looked at the circulation path in a developing device to the longitudinal direction. 5A is a schematic cross-sectional view showing a cross section of Y1-Y1 and FIG. 5B is a schematic cross-sectional view showing a cross section of Y2-Y2. FIG. 5A is a schematic cross-sectional view showing a narrow portion and a schematic cross-sectional view showing a wide portion in a third transport path. It is sectional drawing which looked at the circulation path in the developing device of another form in the longitudinal direction. It is a block diagram which shows the developing device of another form.

Embodiment.
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire image forming apparatus in the embodiment will be described with reference to FIG.
The writing units 2A to 2D are devices for writing an electrostatic latent image on the photosensitive drum 21 (image carrier) after the charging process based on image information. The writing units 2A to 2D are optical scanning devices using polygon mirrors 3A to 3D, optical elements 4A to 4D, and the like. An LED array can be used as the writing unit instead of the optical scanning device.
The paper feed unit 61 stores a transfer material P such as recording paper or OHP, and feeds the transfer material P toward the transfer belt 30 during image formation.

The transfer belt 30 is an endless belt for transferring the toner image formed on the photosensitive drum 21 onto the transfer material P by electrostatically attracting and transferring the transfer material P to the surface thereof. A suction roller 64 and a belt cleaner 65 are provided on the outer peripheral surface.
The transfer roller 24 that faces the photosensitive drum 21 via the transfer belt 30 includes a cored bar and a conductive elastic layer that covers the cored bar. The conductive elastic layer of the transfer roller 24 is prepared by blending and dispersing a conductive agent such as carbon black, zinc oxide or tin oxide in an elastic material such as polyurethane rubber or ethylene-propylene-diene polyethylene (EPDM). It is an elastic body whose (volume resistivity) is adjusted to medium resistance.

The fixing unit 66 includes a heating roller 68 and a pressure roller 67 and fixes the toner image on the transfer material P to the transfer material P by pressure and heat.
The four process cartridges 20Y, 20C, 20M, and 20BK arranged in the vertical direction along the transfer belt 30 are for forming toner images of yellow, cyan, magenta, and black, respectively.

On each process cartridge 20Y, 20C, 20M, 20BK, toner cartridges 28Y, 28C, 28M, 28BK for supplying toner (toner particles) of each color (yellow, cyan, magenta, black) to the developing device 23 are installed. Yes.
The process cartridges 20Y, 20C, 20M, and 20BK and the toner cartridges 28Y, 28C, 28M, and 28BK can be attached to and detached from the apparatus main body 1 by opening the transfer belt 30 around the rotation support shaft.

  The image forming apparatus according to the present embodiment is a composite image forming apparatus that functions as a copying machine and a printer. When functioning as a copying machine, the image information read from the scanner is subjected to various image processing such as A / D conversion, MTF correction, gradation processing, etc., and converted into writing data. In the case of functioning as a printer, image processing is performed on image information in a format such as a page description language or a bitmap transmitted from a computer or the like, and converted into write data.

  At the time of image formation, exposure light corresponding to the image information of black, magenta, cyan, and yellow is irradiated from the writing units 2A to 2D to the process cartridges 20BK, 20M, 20C, and 20Y, respectively. That is, exposure light (laser light) emitted from each light source passes through the polygon mirrors 3A to 3D, the optical elements 4A to 4D, and is irradiated onto each photosensitive drum 21. Thus, a toner image corresponding to the exposure light is formed on the photosensitive drum 21 (image carrier) of each process cartridge 20BK, 20M, 20C, 20Y. The toner image is transferred to the transfer material P.

  The material to be transferred P fed from the paper feeding unit 61 is conveyed to the position of the transfer belt 30 at the timing of the registration roller 63 and the timing. The suction roller 64 disposed at the feeding position of the transfer belt 30 causes the transfer belt 30 to suck the material to be transferred P fed by voltage application. As the transfer belt 30 travels in the direction of the arrow, the transfer material P moves sequentially through the positions of the process cartridges 20Y, 20C, 20M, and 20BK, and the toner images of the respective colors are superimposed and transferred.

  The material P to which the color toner image is transferred is separated from the transfer belt 30 and reaches the fixing unit 66. The toner image on the transfer material P is fixed on the transfer material P by being heated while being sandwiched between the heating roller 68 and the pressure roller 67. On the other hand, the surface of the transfer belt 30 after the transfer material P is separated reaches the position of the belt cleaner 65, and dirt such as toner adhering to the surface is cleaned.

Next, the process cartridge and the toner cartridge in the image forming apparatus will be described in detail.
The process cartridges 20Y, 20C, 20M, and 20BK have substantially the same structure, and the toner cartridges 28Y, 28C, 28M, and 28BK have substantially the same structure. The alphabet (Y, C, M, BK) is removed for illustration. In addition, the writing unit is illustrated by removing the alphabet (A to D).

  FIG. 2 is an enlarged view showing the process cartridge 20 and the toner cartridge 28 installed in the apparatus main body 1. FIG. 3 is an enlarged view showing the developing device 23 installed in the process cartridge 20. 4 is a cross-sectional view of the circulation path in the developing device 23 as viewed from the direction of the arrow X shown in FIG. 3 in the longitudinal direction. 5A is a schematic cross-sectional view showing a Y1-Y1 cross section of FIG. 4, and FIG. 5B is a schematic cross-sectional view showing a Y2-Y2 cross section of FIG. 6A is a schematic cross-sectional view of the developing device 23 showing the narrow portion B31 in the third transport path B3, and FIG. 5B is a diagram of the developing device 23 showing the wide portion B32 in the third transport path B3. It is a schematic sectional drawing.

As shown in FIG. 2, the process cartridge 20 is a unit in which a photosensitive drum 21 as an image carrier, a charging unit 22, a developing device 23 (developing unit), and a cleaning unit 25 are integrated.
The photosensitive drum 21 as an image carrier is a negatively charged organic photosensitive member, and is rotationally driven counterclockwise by a rotation driving mechanism (not shown).
The charging unit 22 is a charging roller having elasticity, in which a medium-resistance foamed urethane layer in which a urethane resin, carbon black as conductive particles, a sulfurizing agent, a foaming agent, and the like are formed in a roller shape on a core metal. The material of the middle resistance layer of the charging unit 22 is urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc. It is also possible to use a rubber material in which a conductive material such as the above is dispersed or a foamed material of these materials.
The cleaning unit 25 is provided with a cleaning brush (or cleaning blade) that is in sliding contact with the photosensitive drum 21, and mechanically removes and collects untransferred toner on the photosensitive drum 21.

  The developing device 23 is arranged such that a developing roller 23a as a developer carrying member is close to the photosensitive drum 21, and a developing region where the photosensitive drum 21 and the magnetic brush are in contact with each other is formed. Is done. In the developing device 23, a developer G (two-component developer) composed of toner T and carrier C is accommodated. The developing device 23 develops the electrostatic latent image formed on the photosensitive drum 21 (forms a toner image). The configuration and operation of the developing device 23 will be described in detail later.

Referring to FIG. 2, toner cartridge 28 accommodates new toner T to be supplied into developing device 23. Then, new toner T is appropriately supplied from the toner cartridge 28 to the developing device 23. Specifically, the shutter mechanism is based on the information of the toner density (the ratio of the toner T in the developer G) detected by the magnetic sensor 26 (see FIG. 4) installed in the developing device 23. 80 is opened and closed to appropriately supply the developer G from the toner cartridge 28 into the developing device 23.
The supply pipe 29 is for reliably guiding the toner T supplied from the toner cartridge 28 into the developing device 23. That is, the toner T discharged from the toner cartridge 28 is supplied into the developing device 23 via the supply pipe 29.

Next, an image forming process performed on the photosensitive drum 21 will be described.
Referring to FIG. 2, when the photosensitive drum 21 is driven to rotate counterclockwise, first, the surface of the photosensitive drum 21 is uniformly charged at the position of the charging unit 22. Thereafter, the surface of the charged photosensitive drum 21 reaches the irradiation position of the exposure light L, and an exposure process by the writing unit 2 is performed. That is, by selectively removing the charge on the photosensitive drum 21 in accordance with the image information by irradiation with the exposure light L, a difference (potential contrast) from the potential of the non-image portion that has not been irradiated is generated, and electrostatic latent Form an image. In this exposure step, the charge generation material receives light in the photosensitive layer of the photosensitive drum 21 to generate charges, and among these holes, the holes cancel out the charged charges on the surface of the photosensitive drum 21.

Thereafter, the surface of the photosensitive drum 21 on which the latent image is formed reaches a position facing the developing device 23. The electrostatic latent image on the photosensitive drum 21 is brought into contact with the magnetic brush on the developing roller 23a, and the negatively charged toner T in the magnetic brush is attached and visualized.
Specifically, the developer G pumped up by the magnetic force generated by the magnetic poles of the developing roller 23a is adjusted to an appropriate amount by a doctor blade 23c as a developer regulating member, and then developed in a developing region (developing roller) that faces the photosensitive drum 21. 23a and the photosensitive drum 21). The carrier C spiked in the development area rubs the photosensitive drum 21. At this time, the toner T mixed with the carrier C is negatively charged due to friction with the carrier C. On the other hand, the carrier C is positively charged. A predetermined developing bias is applied to the developing roller 23a from a power supply unit (not shown). As a result, an electric field is formed between the developing roller 23a and the photosensitive drum 21, and the negatively charged toner T is selectively attached only to the image portion on the photosensitive drum 21 by the electric field to form a toner image. To do.

Thereafter, the surface of the photosensitive drum 21 on which the toner image is formed reaches a position facing the transfer belt 30 and the transfer roller 24. Then, the toner image on the photosensitive drum 21 is transferred onto the transfer material P conveyed to the opposite position in accordance with this timing. At this time, a predetermined voltage is applied to the transfer roller 24.
Thereafter, the transfer material P to which the toner image is transferred passes through the fixing unit 66 and is discharged from the discharge roller 69 to the outside of the apparatus.

On the other hand, the toner T (untransferred toner) remaining on the photosensitive drum 21 without being transferred to the transfer material P during the transfer process reaches a portion facing the cleaning unit 25 while remaining on the photosensitive drum 21. The untransferred toner on the photosensitive drum 21 is removed and collected by the cleaning unit 25. Thereafter, the surface of the photosensitive drum 21 passes through a static elimination unit (not shown), and a series of image forming processes on the photosensitive drum 21 is completed.
The untransferred toner collected by the cleaning unit 25 is collected as waste toner in a waste toner tank 100 (see FIG. 1) via a conveyance tube (not shown).

Hereinafter, the configuration and operation of the developing device 23 will be described in detail.
Referring to FIG. 3, the developing device 23 includes a developing roller 23a as a developer carrying member, conveying screws 23b1 to 23b3 (auger screws) as conveying members, a doctor blade 23c as a developer regulating member, and the like. ing. Further, in the developing device 23, three transport paths B1 to B3 (developer transport section) that transport the developer G to form a circulation path are formed.

The developing roller 23a (developer carrying member) is configured such that a sleeve formed of a nonmagnetic material such as aluminum, brass, stainless steel, or conductive resin in a cylindrical shape is rotated clockwise by a rotation driving mechanism (not shown). It is configured. In the sleeve of the developing roller 23a, a magnet for forming a magnetic field is fixed so as to cause the developer G to rise on the peripheral surface of the sleeve. The carrier C in the developer G rises in a chain shape on the sleeve so as to follow the normal magnetic field lines emitted from the magnet. The charged toner T is attached to the carrier C that is spiked in a chain shape to form a magnetic brush. The magnetic brush is transferred in the same direction (clockwise) as the sleeve by the rotation of the sleeve.
The doctor blade 23c (developer regulating member) is installed on the upstream side of the developing area, and regulates the developer on the developing roller 23a to an appropriate amount.

The three conveying screws 23b1 to 23b3 (conveying members) are formed with a screw portion spirally on the shaft portion, and the developer G accommodated in the developing device 23 is disposed in the longitudinal direction (the paper surface of FIG. 2). Stir and mix while circulating in the vertical direction.
The first conveying screw 23b1 as the first conveying member is disposed at a position facing the developing roller 23a in the first conveying path B1, and conveys the developer G in the horizontal direction (white arrow in FIG. 4). The developer G is supplied onto the developing roller 23a. In other words, the first transport path B1 by the first transport screw 23b1 faces the developing roller 23a and transports the developer G in the longitudinal direction (the rotation axis direction of the developing roller 23a) to the developing roller 23a. Developer G is supplied.

The 2nd conveyance screw 23b2 as a 2nd conveyance member is installed in 2nd conveyance path | route B2. The second transport screw 23b2 is disposed below the first transport screw 23b1 and at a position facing the developing roller 23a. Then, the developer G separated from the developing roller 23a (the developer G forcibly separated from the developing roller 23a by the agent separation pole after the developing step) is conveyed in the horizontal direction (indicated by the white arrow in FIG. 4). It is a left-hand conveyance.) In other words, the second transport path B2 by the second transport screw 23b2 is disposed at a position below the first transport path B1 and facing the developing roller 23a, and the developer G separated from the developing roller 23a. Is conveyed in the longitudinal direction.
The first transport screw 23b1 and the second transport screw 23b2 are arranged so that the rotation shaft is substantially horizontal, like the developing roller 23a and the photosensitive drum 21.

The 3rd conveyance screw 23b3 as a 3rd conveyance member is installed in 3rd conveyance path | route B3. The third transport screw 23b3 is arranged in the horizontal direction so as to linearly connect the downstream side of the second transport path B2 (downstream side in the transport direction) and the upstream side of the first transport path B1 (upstream side in the transport direction). They are arranged obliquely (see FIG. 4). In other words, the third transport screw 23b3 transports the developer G obliquely upward from the upstream side in the transport direction toward the downstream side in the transport direction.
The third transport screw 23b3 transports the developer G transported by the second transport screw 23b2 to the upstream side of the transport path B1 by the first transport member 23b1, and downstream of the transport path B1 by the first transport screw 23b1. The developer G circulated from the side through the third relay portion 23h (falling path) is transported to the upstream side of the transport path B1 by the first transport member 23b1 (conveyed obliquely upward to the right shown by the white arrow in FIG. 4) .) In other words, the third transport path B3 transports the developer G transported by the second transport path B2 to the upstream side of the first transport path B1, and also reaches the downstream side of the first transport path B1. Is transported upstream of the first transport path B1.

In addition, the conveyance path (1st conveyance path B1) by the 1st conveyance screw 23b1, the conveyance path (2nd conveyance path B2) by the 2nd conveyance screw 23b2, and the conveyance path (3rd conveyance path B3) by the 3rd conveyance screw 23b3 ) And are separated by walls.
4 and 5A, the wall portion is formed with a first relay portion 23f that communicates the downstream side of the second transport path B2 and the upstream side of the third transport path B3. Yes. In addition, the wall portion is formed with a third relay portion 23h that communicates the downstream side of the first transport path B1 and the downstream side of the second transport path B2. Further, referring to FIG. 4 and FIG. 5 (B), a second relay portion 23g that connects the downstream side of the third transport path B3 and the upstream side of the first transport path B1 is formed on the wall portion. Has been.
In the present embodiment, the third relay portion 23h is formed so as to communicate the downstream side of the first transport path B1 and the downstream side of the second transport path B2, and the downstream side of the first transport path B1. The developer G that has reached the side is configured to indirectly flow into the upstream side of the third transport path B3. In contrast, the third relay portion is formed so as to communicate the downstream side of the first transport path B1 and the upstream side of the third transport path B3, and reaches the downstream side of the first transport path B1. The developer G can also be configured to directly flow into the upstream side of the third transport path B3.

With such a configuration, a circulation path for circulating the developer G in the longitudinal direction in the developing device 23 is formed by the three conveyance paths B1 to B3 (conveyance screws 23b1 to 23b3). That is, when the developing device 23 is operated, the developer G accommodated in the device circulates (flows) as shown by the white arrow in FIG.
A magnetic sensor 26 as a toner concentration sensor is installed in the third transport path B3. Based on the toner density information detected by the magnetic sensor 26, the toner T is supplied from the toner cartridge 28 into the developing device 23 through the supply pipe 29. In the present embodiment, the toner concentration of the developer G in the developing device 23 is controlled to be 4 to 7% by weight.

Hereinafter, with reference to FIGS. 4 and 6, the configuration and operation of the developing device 23, which are characteristic in the present embodiment, will be described in detail.
4 and 6A, the third transport path B3 has the smallest cross-sectional area of the transport path in the third transport path B3 at the center in the transport direction (on the upstream side). A narrow portion B31 formed as described above is provided. 4 and 6B, the third transport path B3 is located downstream of the narrow portion B31 in the transport direction and is not buried in the developer G (third transport screw). 23b3), an opening 23r communicating with the outside of the developing device 23 is provided.

Specifically, the narrow portion B31 is disposed on the downstream side in the transport direction with respect to the first relay portion 23f. The narrow portion B31 has a cross-sectional shape of the rotation shaft of the third transport screw 23b3 so that a gap of about 0.5 to 2 mm is formed in the circumferential direction with respect to the outer diameter portion of the screw portion of the third transport screw 23b3. It is formed concentrically around the center.
The opening 23r is formed to open above the case (wall) of the developing device 23 on the upstream side in the transport direction with respect to the second relay portion 23g. The opening 23r is formed in a large portion B32 (a portion formed so that the cross-sectional area of the conveyance path is maximized in the third conveyance path B3) adjacent to the narrow part B31 at a downstream position. Has been. The wide part B32 in which the opening 23r is formed is formed so as to have a gap of about 0.5 to 2 mm with respect to the outer diameter part of the screw part of the third conveying screw 23b3 from the bottom part to the side part. A sufficient distance (at least a distance equal to or larger than the radius of the screw portion from the upper end of the screw portion) is formed upward from the third conveying screw 23b3 from the ceiling to the ceiling portion.
And the opening part 23r is formed in the ceiling part. Further, a filter 41 is installed (attached) so as to cover the opening 23r. The filter 41 has a large number of holes of 1 to 10 μm, and is used to collect the toner T (or carrier C) by discharging only air to the outside of the developing device 23.

With such a configuration, even if air is drawn into the developing device 23 (second transport path B2) along the rotation of the developing roller 23a in the second transport path B2, the first relay is likely to increase. Since the narrow part B31 of the third transport path B3 communicating with the second transport path B2 via the part 23f functions like a suction pump, an increase in internal pressure in the second transport path B2 can be reduced. This utilizes the property that the pressure tends to be constant between the communicating spaces. That is, the air drawn into the second transport path B2 along the rotation of the developing roller 23a is pumped by the narrow portion B31 toward the wide portion B32 that is always maintained at the same internal pressure as the external air pressure through the opening 23r. (This is an operation of sucking air from the upstream side to the downstream side by the pressure difference with the wide part B32 and the rotation of the third conveying screw 23b3), and the balance with the external air pressure is maintained at the wide part B32. (Air for increasing the internal pressure is discharged to the outside through the opening 23r).
In this way, the internal pressure of the second transport path B2 is maintained so as to be substantially equal to the external air pressure. Therefore, the toner T and the developer G from the portion where the internal pressure increases and the sealability is low in the second transport path B2. Will be prevented from scattering (spouting).

  Here, in the present embodiment, as shown in FIG. 4, from the position of the first relay portion 23f in the third transport path B3, in order to more reliably and efficiently exhibit the pumping action of the narrow portion B31 described above. It is formed so that the cross-sectional area of the conveyance path to the position of the narrow portion B31 is gradually reduced. That is, in the third transport path B3, by forming the cross-sectional area of the transport path from the position of the first relay section 23f to the position of the narrow section B31, the air flowing from the first relay section 23f It will flow smoothly to the position of the narrow part B31 (it will be sucked).

Further, in the present embodiment, the first relay portion 23f is formed so as not to be buried in the developer G so that the air flow from the second transport path B2 to the third transport path B3 described above is surely generated. ing. Specifically, as shown in FIG. 5A, the upper end of the first relay portion 23f is sufficiently above the developer surface (height) of the developer G delivered by the first relay portion 23f. It is separated, and it is configured so that air flows reliably in the first relay portion 23f.
On the other hand, the second relay portion 23g is formed so as to be buried in the developer G. This is because, in the first transport path B1, air is discharged outside the developing device 23 along with the rotation of the developing roller 23a, so that the internal pressure of the first transport path B1 tends to be low. That is, by burying the second relay portion 23g with the developer G, it is difficult for air to be transferred between the first transport path B1 and the third transport path B3 via the second relay portion 23g. The internal pressure of the first transport path B1 can be maintained at a low level, and the effect of suppressing the problem that the toner T and the developer G are scattered in the first transport path B1 can be enhanced. Specifically, as shown in FIG. 5B, the upper end of the second relay portion 23g is substantially equal to the surface (height) of the developer G delivered by the second relay portion 23g. It is configured as follows.

Further, in order to more reliably and efficiently exhibit the above-described pumping action of the narrow portion B31, the narrow portion B31 has a length H2 in the longitudinal direction with respect to a length H1 in the longitudinal direction of the third transport path B3. It is preferable to form so that it may become 10% or more. In the present embodiment, the length H2 in the longitudinal direction of the narrow portion B31 is set to about 15% with respect to the length H1 in the longitudinal direction of the third transport path B3.
With such a configuration, since the screw pitch of the third transport screw 23b3 can be secured for at least one cycle in the narrow portion B31, the function of causing the air to flow from the upstream side to the downstream side by the rotation of the third transport screw 23b3 is ensured. Can be demonstrated.

  Further, in order to more reliably and efficiently exhibit the pumping action of the narrow portion B31 described above, the transport force of the third transport screw 23b3 (the force that transports the developer G in the longitudinal direction) is the first transport. It is preferable to form so as to be larger than the conveying force of the screw 23b1 or the conveying force of the second conveying screw 23b2. Specifically, the conveying force of the third conveying screw 23b3 is set by setting the screw pitch, screw diameter, and rotation speed of the third conveying screw 23b3 to be larger than those of the first conveying screw 23b1 and the second conveying screw 23b2. Can be increased.

The developing device 23 in the present embodiment is configured such that the opening 23r formed in the wide portion B32 of the third transport path B3 is covered with the filter 41, and the toner T is scattered from the opening 23r to the outside. Is preventing.
On the other hand, as shown in FIG. 7, the agent avoiding plate 42 (opening 23r so as to cover the opening 23r when viewed from below) is directly below the opening 23r formed in the wide part B32 of the third transport path B3. Even if the labyrinth structure is adopted by installing a plate-like member that is separated from the opening 23r by a small distance, it is possible to prevent the toner T from scattering from the opening 23r to the outside.

In the present embodiment, a suction unit that sucks the air in the developing device 13 through the opening 23r may be provided.
Specifically, referring to FIG. 8, a suction fan 110 as a suction means is installed above the opening 23r through a duct. In such a case, the internal pressure of the wide section B32 becomes lower than the external air pressure due to the suction from the suction fan 110. Accordingly, the internal pressure of the second transport path B2 is maintained at a low level, and the second transport path B2 Therefore, the problem that the toner T and the developer G are scattered is more reliably prevented.
In FIG. 8, the air sucked from the developing device 23 is configured to flow into the waste toner tank 100 through the tube 120. The air flowing into the waste toner tank 100 is discharged out of the tank through the opening in which the filter 101 is installed. In this way, by introducing the air sucked from the developing device 23 to a predetermined location away from the image forming unit, an air current is generated around the image forming unit, thereby preventing problems that affect the output image.

  As described above, in the present embodiment, the two conveying screws 23b1 and 23b2 (conveying members) disposed in the vertical direction so as to face the developing roller 23a (developer carrying member) and the conveying screws 23b1. , 23b2 and the third conveying screw 23b3 disposed so as to face the narrow portion B31 at the center in the conveying direction of the third conveying path B3. And an opening 23r communicating with the outside of the developing device 13 is provided at a position downstream of the narrow portion B32, so that the internal pressure in the second transport path B2 increases and the toner T and the developer G are scattered. It is possible to make it difficult to cause problems.

In the present embodiment, the present invention is applied to the developing device 23 in which three conveying screws 23b1 to 23b3 are installed. However, the present invention is also applied to a developing device in which four or more conveying screws are installed. Can be applied. Even in that case, the same effect as the present embodiment can be obtained.
In the present embodiment, the third transport screw 23b3 is disposed obliquely with respect to the horizontal direction. However, the third transport screw 23b3 can be disposed horizontally.

  In this embodiment, the toner T is supplied from the toner cartridge 28 serving as the supply unit toward the developing device 23, but new developer G (toner T and carrier C) is supplied from the supply unit to the developing device 23. Can also be supplied. In that case, the developing device 23 to which the new developer G is supplied is provided with a discharging means for discharging the surplus developer G (carrier C). Even in such a case, the same effect as in the present embodiment can be obtained.

Further, in the present embodiment, the present invention is applied to an image forming apparatus in which a part of the image forming unit is configured by the process cartridge 20. However, the application of the present invention is not limited to this, and the present invention can naturally be applied to an image forming apparatus in which the image forming unit is not formed into a process cartridge. Specifically, the present invention can naturally be applied even when the developing device 23 is configured as a unit that is detachably attached to the image forming apparatus main body.
Furthermore, in the present embodiment, the present invention is applied to the developing device 23 in which one developing roller 23a is installed, but the present invention is naturally applied to a developing device in which two or more developing rollers are installed. Can be applied. Even in that case, the same effect as the present embodiment can be obtained.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1 image forming apparatus body (apparatus body),
20, 20Y, 20C, 20M, 20BK Process cartridge,
21 Photosensitive drum (image carrier),
23 Developing device (developing part),
23a Development roller (developer carrier),
23b1 first conveying screw (first conveying member),
23b2 second conveying screw (second conveying member),
23b3 third conveying screw (third conveying member),
23c Doctor blade (developer regulating member),
23f 1st relay part,
23g 2nd relay part,
23h 3rd relay part,
23r opening,
41 filter,
42 Agent avoidance plate,
110 Suction fan (suction means),
B1 1st conveyance path, B2 2nd conveyance path, B3 3rd conveyance path,
B31 narrow part, B32 wide part,
G developer (two-component developer), T toner, C carrier.

JP 2007-316495 A JP 2001-249545 A

Claims (16)

A developing device that contains a developer having a carrier and toner and that develops a latent image formed on an image carrier,
A developer carrying body facing the image carrying body and carrying a developer;
A plurality of transport members that transport the developer contained in the apparatus in the longitudinal direction to form a circulation path;
With
The plurality of conveying members are:
A first conveying member facing the developer carrying member and supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction;
A second conveying member that faces the developer carrying member and conveys the developer released from the developer carrying member in the longitudinal direction;
A third transport member that transports the developer transported by the second transport member toward the upstream side of the transport path by the first transport member;
Comprising
A wall portion separating the first conveyance path by the first conveyance member, the second conveyance path by the second conveyance member, and the third conveyance path by the third conveyance member;
The third transport path is
A narrow part formed to the cross-sectional area of the conveying path is minimized in the third conveyance path,
An opening that is disposed at a position downstream of the narrow portion in the transport direction and not buried in the developer, and communicates with the outside of the apparatus;
Equipped with,
The wall is
A first relay unit that communicates the downstream side in the transport direction of the second transport path and the upstream side in the transport direction of the third transport path;
A second relay unit that communicates the downstream side in the transport direction of the third transport path and the upstream side in the transport direction of the first transport path;
A third relay unit that communicates the downstream side in the transport direction of the first transport path and the downstream side in the transport direction of the second transport path;
Comprising
The second transport path is disposed below the first transport path,
The third transport member transports the developer obliquely upward from the upstream side in the transport direction toward the downstream side in the transport direction,
The narrow portion is disposed downstream in the transport direction with respect to the first relay portion,
The opening is disposed upstream in the transport direction with respect to the second relay unit,
The third transport path is
Formed so that the cross-sectional area of the conveyance path from the position of the first relay portion to the position of the narrow portion gradually decreases,
2. A developing device according to claim 1, wherein said narrow portion is formed such that a cross-sectional area of a portion adjacent to the narrow portion at a downstream side in the conveying direction is maximized, and said opening is formed in said portion . The first relay portion is formed so as not to be buried in the developer,
The developing device according to claim 1, wherein the second relay portion is formed so as to be buried in a developer. A developing device that contains a developer having a carrier and toner and that develops a latent image formed on an image carrier,
A developer carrying body facing the image carrying body and carrying a developer;
A plurality of transport members that transport the developer contained in the apparatus in the longitudinal direction to form a circulation path;
With
The plurality of conveying members are:
A first conveying member facing the developer carrying member and supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction;
A second conveying member that faces the developer carrying member and conveys the developer released from the developer carrying member in the longitudinal direction;
A third transport member that transports the developer transported by the second transport member toward the upstream side of the transport path by the first transport member;
Comprising
A wall portion separating the first conveyance path by the first conveyance member, the second conveyance path by the second conveyance member, and the third conveyance path by the third conveyance member;
The third transport path is
A narrow portion formed so that the cross-sectional area of the transport path is minimized in the third transport path;
An opening that is disposed at a position downstream of the narrow portion in the transport direction and not buried in the developer, and communicates with the outside of the apparatus;
Comprising
The wall is
A first relay unit that communicates the downstream side in the transport direction of the second transport path and the upstream side in the transport direction of the third transport path;
A second relay unit that communicates the downstream side in the transport direction of the third transport path and the upstream side in the transport direction of the first transport path;
A third relay unit that communicates the downstream side in the transport direction of the first transport path and the downstream side in the transport direction of the second transport path;
Comprising
The second transport path is disposed below the first transport path,
The third transport member transports the developer obliquely upward from the upstream side in the transport direction toward the downstream side in the transport direction,
The first relay portion is formed so as not to be buried in the developer,
The developing device, wherein the second relay portion is formed so as to be buried in a developer. The narrow portion is disposed downstream in the transport direction with respect to the first relay portion,
The developing device according to claim 3, wherein the opening is disposed upstream in the transport direction with respect to the second relay unit. The narrow portion is formed so that a length in a longitudinal direction thereof is 10% or more with respect to a length in a longitudinal direction of the third transport path. The developing device according to any one of the above. The third conveying member has a larger conveying force for conveying the developer than the conveying force for conveying the developer in the first conveying member, and compared with the conveying force for conveying the developer in the second conveying member. 6. The developing device according to claim 1, wherein the developing device is formed to be large. A developing device that contains a developer having a carrier and toner and that develops a latent image formed on an image carrier,
A developer carrying body facing the image carrying body and carrying a developer;
A plurality of transport members that transport the developer contained in the apparatus in the longitudinal direction to form a circulation path;
With
The plurality of conveying members are:
A first conveying member facing the developer carrying member and supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction;
A second conveying member that faces the developer carrying member and conveys the developer released from the developer carrying member in the longitudinal direction;
A third transport member that transports the developer transported by the second transport member toward the upstream side of the transport path by the first transport member;
Comprising
A wall portion separating the first conveyance path by the first conveyance member, the second conveyance path by the second conveyance member, and the third conveyance path by the third conveyance member;
The third transport path is
A narrow portion formed so that the cross-sectional area of the transport path is minimized in the third transport path;
An opening that is disposed at a position downstream of the narrow portion in the transport direction and not buried in the developer, and communicates with the outside of the apparatus;
Comprising
The developing device according to claim 1, wherein the narrow portion is formed so that a length in a longitudinal direction thereof is 10% or more with respect to a length in a longitudinal direction of the third transport path. The third conveying member has a larger conveying force for conveying the developer than the conveying force for conveying the developer in the first conveying member, and compared with the conveying force for conveying the developer in the second conveying member. The developing device according to claim 7, wherein the developing device is formed to be large. A developing device that contains a developer having a carrier and toner and that develops a latent image formed on an image carrier,
A developer carrying body facing the image carrying body and carrying a developer;
A plurality of transport members that transport the developer contained in the apparatus in the longitudinal direction to form a circulation path;
With
The plurality of conveying members are:
A first conveying member facing the developer carrying member and supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction;
A second conveying member that faces the developer carrying member and conveys the developer released from the developer carrying member in the longitudinal direction;
A third transport member that transports the developer transported by the second transport member toward the upstream side of the transport path by the first transport member;
Comprising
A wall portion separating the first conveyance path by the first conveyance member, the second conveyance path by the second conveyance member, and the third conveyance path by the third conveyance member;
The third transport path is
A narrow portion formed so that the cross-sectional area of the transport path is minimized in the third transport path;
An opening that is disposed at a position downstream of the narrow portion in the transport direction and not buried in the developer, and communicates with the outside of the apparatus;
Comprising
The third conveying member has a larger conveying force for conveying the developer than the conveying force for conveying the developer in the first conveying member, and compared with the conveying force for conveying the developer in the second conveying member. A developing device formed to be large. The wall is
A first relay unit that communicates the downstream side in the transport direction of the second transport path and the upstream side in the transport direction of the third transport path;
A second relay unit that communicates the downstream side in the transport direction of the third transport path and the upstream side in the transport direction of the first transport path;
A third relay unit that communicates the downstream side in the transport direction of the first transport path and the downstream side in the transport direction of the second transport path;
Comprising
The second transport path is disposed below the first transport path,
The developing device according to claim 7, wherein the third transport member transports the developer obliquely upward from the upstream side in the transport direction toward the downstream side in the transport direction. The narrow portion is disposed downstream in the transport direction with respect to the first relay portion,
The developing device according to claim 10, wherein the opening is disposed on the upstream side in the transport direction with respect to the second relay unit. The developing device according to claim 1, wherein the third transport path is disposed at a central portion in the transport direction. The developing device according to claim 1, further comprising a filter that covers the opening and is configured to collect the toner. The developing device according to claim 1, further comprising suction means for sucking air in the apparatus through the opening. A process cartridge that is detachably installed on the main body of the image forming apparatus,
15. A process cartridge in which the developing device according to claim 1 and the image carrier are integrated. An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

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