JP5233855B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention provides a copying machine, a printer, a facsimile machine, or the like that forms an electrostatic latent image on an electrostatic latent image carrier by an electrophotographic method or an electrostatic recording method, and develops the toner image to develop a toner image. In particular, the present invention relates to an image forming apparatus such as a multifunction peripheral in which two or more of them are combined, and particularly relates to a developing device.

  An image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine combining two or more of these, which forms an electrostatic latent image on an electrostatic latent image carrier and develops it to form a toner image. Various types of developing devices are known, and the following are among them.

  A developer carrying rotator for applying toner to an electrostatic latent image corresponding to a target image formed on the electrostatic latent image carrier of the image forming apparatus, and facing the developer carrying rotator for development. A buffer unit that holds the developer, a first rotary transport body that is disposed in the buffer unit and that is rotationally driven to transport the developer in the direction of the rotation axis, and is disposed above the first rotary transport body, The developing device includes a second rotary transport body that transports the developer in the direction of the rotation axis when rotated and in the direction opposite to the first rotary transport body.

  In this type of developing device, the developer is allowed to move from the developer sending side end of the second rotating transport body to the developer feeding side end of the first rotating transport body and the developer sending of the first rotating transport body. The developer is stirred and circulated by the first and second rotary conveyance bodies while allowing the developer to move from the side end portion to the developer feeding side end portion of the second rotary conveyance body, and the developer from the first rotary conveyance body. The developer can be supplied to the carrying rotor side. Hereinafter, this type of developing device may be referred to as a “developer circulation type developing device”.

  In the developer circulation type developing device, a partition member is provided between the first rotating transport body and the second rotating transport body, and the developer of the first rotating transport body from the developer sending side end of the second rotating transport body. The developer movement to the feeding side end is performed through the first opening formed in the partition member, and the developer feeding side of the second rotating transport body from the developer sending side end of the first rotating transport body. In general, the developer moves to the end through a second opening formed in the partition member.

  A developer supplying rotator for supplying the developer to the developer carrying rotator may be disposed in the buffer unit.

  In developing devices that develop electrostatic latent image development to form a toner image, including the developer circulation type developing device, the amount of developer in the device decreases over time, so the amount of developer in the device is detected. A developing device is known in which toner can be replenished when the amount of developer decreases from a predetermined amount.

  For example, in the developing device described in Japanese Patent Application Laid-Open No. 2006-11226, the developer circulating type rotating device that supplies toner to the first rotating conveyance body, the electrostatic latent image bearing body, etc. A developer amount detection device is provided in the buffer unit in which is disposed.

  In addition, in a developing device such as a developer circulation type developing device, when the bulk fluctuation of the developer in the device occurs, the developer supply to the developer-carrying rotating body is not stabilized, resulting in a supply failure, and thus a development failure. Therefore, there is also known a developing device in which the developer is smoothly supplied even when the bulk of the developer in the device fluctuates.

  For example, the developing device described in Japanese Patent Application Laid-Open No. 11-288158 is provided with a developer reservoir for storing excess developer in preparation for when the developer fluctuates. In the developer circulation type developing device, the developer reservoir is continuously provided above a portion where the upper second rotary carrier is extended outward from the lower first rotary carrier. . The lower first rotating conveyance body for supplying the developer to the developer carrying rotating body is immersed in the developer.

JP 2006-11226 A Japanese Patent Laid-Open No. 11-288158

  However, according to the developing device described in Japanese Patent Application Laid-Open No. 2006-11226, the developer amount detection device includes an optical sensor that detects the developer amount through a light-transmitting developer detection window provided in the buffer unit, and the detection. It includes a cleaning device for cleaning the inner surface of the window, and the configuration of the portion including the detection device is complicated in combination with the portion where the detection device is provided, and further, the developer supply port to the development device is provided from the detection device. It is far away, and the response of the detection device to the developer replenishment tends to be shifted, and there is a risk that excessive developer will be replenished.

  In the developing device described in JP-A-11-288158, a developer reservoir is provided in order to stabilize the supply of developer to the developer-carrying rotating body. Since the first rotary transport body is located above the extending portion of the upper second rotary transport body that is separated from the first rotary transport body and is buried in the developer, the developer powder pressure in the vicinity of the first rotary transport body is high. Therefore, the developer amount regulating member or the like facing the developer carrying rotor may not function properly.

  The present invention relates to a developer circulation type developing device used for developing an electrostatic latent image in an image forming apparatus, in which the amount of developer in the developing device can be kept constant and toner is applied to the electrostatic latent image. It is a first object to provide a developing device that can stably supply the developer to the developer-carrying rotating member and that does not require a complicated structure.

  Here, as described above, the “developer circulation type developing device” refers to a developer carrying rotator that imparts toner to an electrostatic latent image, and a buffer that holds the developer that faces the developer carrying rotator and is used for development. And a first rotary transport body that is disposed in the buffer section and is rotationally driven to transport the developer in the direction of the rotational axis, and is disposed on the upper side of the first rotational transport body and is rotationally driven. A second rotary transport body that transports the developer in a direction of the rotation axis and in a direction opposite to the first rotary transport body, wherein the first and second rotary transport bodies include the second rotary transport body. The developer is allowed to move from the developer delivery side end of the rotary carrier to the developer delivery side end of the first rotary carrier, and from the developer delivery side end of the first rotary carrier. The developer is stirred and circulated while allowing the developer to move to the developer feeding side end of the rotating carrier. A developing device capable of supplying the developer to said developer carrying rotor side from the first rotary transfer member.

  The present invention also provides an image forming apparatus for forming an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier and developing the electrostatic latent image with a developing device to form a toner image. In at least one developing device, the amount of developer in the developing device can be kept constant, and the developer can be stably supplied to the developer-carrying rotor for applying toner to the electrostatic latent image. A second problem is to provide an image forming apparatus that can perform such a good image.

In order to solve the above problems, the present invention provides the following developing device and image forming apparatus.
(1) Developing device A developing device used for developing an electrostatic latent image in an image forming apparatus capable of forming an electrostatic latent image on an electrostatic latent image carrier and developing the electrostatic latent image to form a toner image.
A developer carrying rotator for applying toner to the electrostatic latent image;
A buffer unit that holds the developer that faces the developer carrying rotor and is used for development;
A first rotary transport body that is disposed in the buffer unit and that is rotationally driven to transport the developer in the rotational axis direction;
A second rotary transport body that is disposed on the upper side of the first rotary transport body and is driven to rotate in the direction of the rotation axis and in the opposite direction to the first rotary transport body;
A developer reservoir,
The first and second rotary transport bodies allow the developer to move from the developer delivery side end of the second rotary transport body to the developer feed side end of the first rotary transport body and the first rotary transport body. The developer is stirred and circulated while allowing the developer to move from the developer delivery side end of the one-rotation conveyance body to the developer delivery-side end of the second rotation conveyance body, and the development from the first rotation conveyance body is performed. Can be supplied to the agent-carrying rotor
The first and second rotating transport bodies are at the developer sending side end of the first rotating transport body and the developer feeding side end of the second rotating transport body located above the end, Extending to the outside of the developer carrying rotator in the direction of the axis of rotation of the developer carrying rotator,
The developer reservoir is continuously provided above the extension of the second rotary transport body;
The developer conveying capability of the first rotating conveyance body is larger than the developer conveying capability of the second conveying rotation body.

(2) Image forming apparatus An image forming apparatus capable of forming an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier and developing the electrostatic latent image with a developing device to form a toner image. An image forming apparatus in which at least one developing device is a developing device according to the present invention.

  According to the developing device of the present invention, the developer reservoir is continuously provided above the developer feeding side end of the second rotary transport body in the developer transport direction of the upper second rotary transport body. In addition, a certain amount of developer required for the electrostatic latent image developing operation can be transported to the second rotary transport body, while a larger amount of developer can be retained in the developer reservoir. In other words, a certain amount of developer required for the electrostatic latent image developing operation can be transported to the second rotary transport body in a state where the developer is retained in the developer reservoir.

  Then, the lower first rotating transport body is equivalent to the amount of developer supplied from the developer sending side end of the upper second rotating transport body to the developer feeding side end of the first rotating transport body. The developer circulation is balanced when the developer is conveyed.

  At this time, since the developer transport capability of the first rotary transport body is greater than that of the second rotary transport body, the upper second rotary transport body transports the amount of developer required for the developing operation and the first rotational transport. And the first rotary transport body transports the developer in an amount equal to the amount of developer supplied from the second rotary transport body, so that a gap is formed above the first rotary transport body in the buffer unit. It is possible to adjust the amount of developer in the developing device so that By doing so, the developer amount required for the electrostatic latent image developing operation can be stably supplied to the developer-carrying rotating body in a state where the increase in the developer powder pressure is suppressed, and as a result, the electrostatic latent image can be satisfactorily improved. The image can be developed.

  When the developer is consumed by the developing operation, the developer upper surface in the buffer portion in which the first rotation conveyance body is disposed is lowered by the consumed amount, and the developer movement amount from the first rotation conveyance body to the second rotation conveyance body Is lowered, and the developer circulation amount is decreased to cause poor supply of the developer to the developer-carrying rotating body. However, the developer is located above the developer feeding side end of the second rotating transport body. Since there is a reservoir, the second rotary transport body supplies the developer amount necessary for development to the first rotary transport body side, so that the developer amount in the buffer section is maintained at the amount required for development, and as a result, the developer supply Generation of image noise due to defects is suppressed.

  In addition, by using the developer reservoir that is less affected by the presence of the first and second rotary conveyance bodies, the toner consumed for development can be easily replenished to the developer reservoir. The developer amount detecting device in the developing device can also be easily provided in the developer reservoir, and the developer replenishing portion and the developer amount detecting device are provided in the vicinity in this way, thereby the developer amount detecting device. As a result, the toner can be replenished in a state where the excess or deficiency is suppressed, and the amount of developer in the developing device can be made constant.

  When the amount of developer in the developer reservoir increases, the developer powder pressure increases and the amount of developer transported by the second rotating transport body increases, while the first rotating transport body moves from the second rotating transport body. The developer transfer amount tends to decrease. If this happens, a developer circulation failure and, in turn, a developer supply failure to the developer carrying rotor may occur.

  Therefore, in the developing device according to the present invention, the developer amount in the developer reservoir portion increases between the developer reservoir portion and the buffer portion (for example, increases due to the toner replenishment amount variation from the toner replenishing device). Regardless of variation, a developer conveying amount stabilizing member that stabilizes the developer conveying amount by the first and second rotary conveying members (prevents the backflow of the developer and conveys the developer to the developer conveying rotary member). A member that makes it possible to transport the developer in an amount corresponding to the capability may be provided for each of the first and second rotating transport bodies.

  In the developing device according to the present invention, the developer reservoir can be used to provide a detection window for detecting the developer amount and a toner supply port for supplying toner. Through this detection window, the developer amount detection device (for example, an optical sensor including a light emitting element and a light receiving element) can detect the developer amount (the upper surface position of the developer) in the developer reservoir, and the detection information indicates the inside of the developing device. Can know the amount of developer. Moreover, since the positions of the toner replenishment port and the detection window (and thus the detection sensor) are close to each other, the responsiveness to the toner replenishment of the developer amount detection device is improved, so that the toner is replenished in a state where the excess or deficiency is suppressed. As a result, the amount of developer in the developing device can be made constant.

  In order to improve the mixing and stirring of the toner replenished in the developer reservoir and the existing developer in the developing device, the developer is fed while the developer circulation is performed in the first and second rotating transport bodies. A mixing and stirring device for mixing and stirring may be allowed to face the developer reservoir. The mixing and stirring device may be configured using a part of at least one of the first and second rotating transport bodies.

  The developing device according to the present invention may be either one using a so-called one-component developer mainly composed of toner or one using a two-component developer mainly composed of toner and carrier.

  In the developing device according to the present invention, a partition member can be provided between the first rotary transport body and the second rotary transport body, and at least from the developer delivery side end of the second rotary transport body to the partition member. A first opening that allows the developer to move to the developer feed side end of the first rotary transport body; and a developer feed side of the second rotary transport pair from the developer feed end of the first rotary transport body A second opening that allows the developer to move to the end can be provided.

  In addition, a developer supplying rotator for supplying the developer to the developer carrying rotator can be disposed in the buffer portion according to the type of developer to be used. The developer supply rotator contacts and rotates with the developer carrying rotator, and scrapes the developer that is not consumed but returned to the buffer unit by being transported to the developer carrying rotator from the developer carrying rotator. At the same time, the developer may be supplied to the developer carrying rotor.

  The developing device according to the present invention includes a developer regulating member that regulates or further charges the amount of developer conveyed to the developing area where the electrostatic latent image is developed according to the type of developer used. Can do.

  The developing device according to the present invention may include a static eliminating device that eliminates charge from the developer that is not consumed and is returned to the buffer unit without being consumed, depending on the type of developer to be used. .

  Examples of the first and second rotary transport bodies in the developing device according to the present invention include a screw transport member having a spiral blade provided around the rotation shaft as a representative example, but is not limited thereto. As long as the developer can be conveyed, it may be in a paddle shape or other shapes.

  In the image forming apparatus according to the present invention, since at least one developing device is the developing device according to the present invention, in the developing device, the amount of developer in the apparatus can be maintained constant and the toner is transferred to the electrostatic latent image. It is possible to stably supply the developer to the developer-carrying rotating body for applying to the toner, and it is possible to form a good image accordingly.

  As described above, according to the present invention, a developer circulation type developing device used for developing an electrostatic latent image in an image forming apparatus, the developer amount in the developing device can be kept constant, and toner can be statically discharged. A developer can be stably supplied to the developer carrying rotator for applying to the electrostatic latent image, and a developing device that does not require a complicated structure can be provided.

  According to the present invention, there is also provided an image forming apparatus capable of forming an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier and developing the electrostatic latent image with a developing device to form a toner image. Thus, in at least one developing device, the amount of developer in the developing device can be kept constant, and the developer supply to the developer-carrying rotating body for applying toner to the electrostatic latent image can be stabilized. Therefore, it is possible to provide an image forming apparatus capable of forming a good image.

1 is a diagram schematically illustrating a configuration of an example of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating an outline of a cross-sectional structure of an example of a developing device according to the present invention in the image forming apparatus of FIG. 1. FIG. 3 is a diagram schematically showing the developing device shown in FIG. 2 as viewed from the right side in FIG. 2, but the developing roller and the supply roller are only indicated by their broken lines. 2A shows a state in which the amount of developer is substantially sufficient in the developing device shown in FIG. 2, and FIG. 2B shows a state in which the amount of developer is reduced due to consumption of the developer in the developing device shown in FIG. Is shown. FIG. 4 is a diagram showing an outline of a developing device provided with a cylindrical member which is a developer conveyance amount stabilizing member in the developing device shown in FIG. 3. The other example of a developer conveyance amount stabilization member is shown. FIG. (A) shows a perforated holding plate, and FIG. (B) shows a flexible plate with a cut hole held by the perforated holding plate. (C) shows a developer conveyance amount stabilizing member formed by attaching a flexible plate to a holding plate, and FIG. (D) shows a developing device equipped with the stabilizing member in the developing device of FIG. . FIG. 4 is a diagram illustrating a developing device provided with a developer mixing and stirring device in the developing device of FIG. 3.

Hereinafter, an example of an image forming apparatus according to the present invention and a developing device used therein will be described with reference to the drawings.
FIG. 1 schematically shows the configuration of an example 100 of an image forming apparatus. The image forming apparatus 100 is a tandem type full color printer.

  The printer 100 includes an endless intermediate transfer belt 7 wound around a driving roller 71 and a roller 72 facing the driving roller 71. The transfer belt 7 is rotated in the counterclockwise direction (arrow direction in the figure) CCW by a driving roller 71 driven by a belt driving unit (not shown).

  A cleaning device 73 that cleans secondary transfer residual toner and the like on the transfer belt 7 faces the roller 72, and a secondary transfer roller 8 faces the drive roller 71. The toner or the like collected by the cleaning device 73 is sent to a waste container by a conveying means (not shown).

  The surface layer portion of the secondary transfer roller 8 is formed of an elastic material, and is pressed against a portion of the intermediate transfer belt 7 supported by the driving roller 71 by a pressing unit (not shown), so that a nip is formed between the secondary transfer roller 8 and the intermediate transfer belt 7. And can be rotated by being driven or driven by the movement of the recording medium S fed into the nip as will be described later. A secondary transfer bias can be applied to the secondary transfer roller 8 from a power supply (not shown).

  A fixing device 9 is disposed above the intermediate transfer belt 7 and the secondary transfer roller 8, a timing roller pair 11 is disposed below, and a recording medium S such as recording paper is accommodated below the fixing device 9. The recording medium storage cassette 10 is disposed.

The fixing device 9 includes a fixing heating roller having a heat source such as a halogen lamp heater and a pressure roller pressed against the fixing heating roller.
The recording medium S accommodated in the recording medium accommodating cassette 10 can be pulled out one by one by the medium supply roller 101 and supplied to the timing roller pair 11.

  Between the rollers 71 and 72 around which the intermediate transfer belt 7 is wound, the yellow image forming unit Y, the magenta image forming unit M, and the cyan image forming unit C are arranged along the transfer belt 7 from the roller 72 toward the roller 71. And the black image forming portion K are arranged in this order.

  Each of the image forming units Y, M, C, and K includes a drum-type photosensitive member 1 as an electrostatic latent image carrier, and a charger 2, an exposure device 3, a developing device 4 and the like around the photosensitive member. The cleaning devices 5 are arranged in this order.

  A primary transfer roller 6 is disposed opposite to the photoreceptor 1 of each image forming unit with a belt 7 therebetween. The primary transfer roller 6 is pressed in the direction of the photosensitive member 1 by a pressing unit (not shown), contacts the belt 7 and rotates in a driven manner, and can bring the belt 7 into contact with the photosensitive member 1.

  A primary transfer bias for primary transfer of the toner image formed on the photoreceptor 1 to the belt 7 can be applied to the primary transfer roller 6 from a power supply (not shown).

  The exposure device 3 can perform image exposure by dot (point) exposure on the photosensitive member 1 by blinking of a laser beam in accordance with image information provided from a personal computer (not shown), an image reading device, or the like.

  The photoconductor 1 in each image forming unit is a negatively chargeable photoconductor here, and can be driven to rotate clockwise in the drawing by a photoconductor drive motor (not shown).

  The charger 2 in each image forming unit is a scorotron charger in this example, and a charging voltage is applied from a power supply (not shown) at a predetermined timing. The charger 2 may be one using a charging roller.

  In this example, the developing device 4 in each image forming unit applies a developing bias to an electrostatic latent image formed on the photoreceptor 1 using a one-component developer mainly composed of toner from a power supply (not shown). The developer carrying rotating body (hereinafter referred to as “developing roller”) 41 (see FIG. 2) in the form of a roller can be used for reversal development. The developing device 4 will be further described later.

According to this printer, an image can be formed using one or more of Y, M, C, and K image forming units.
Taking a case where a full color image is formed using all of the image forming portions Y, M, C, and K as an example, first, a yellow toner image is formed in the yellow image forming portion Y, and this is formed on the transfer belt 7 as a primary. Transcript.

  That is, in the yellow image forming portion Y, the photosensitive member 1 is rotationally driven in the clockwise direction in the drawing, and the surface is uniformly charged to a predetermined potential by the charger 2, and the exposure device 3 corresponds to the yellow image in the charged area. Thus, an electrostatic latent image corresponding to the yellow image is formed on the photoreceptor 1. This electrostatic latent image is developed by a developing roller 41 to which a developing bias of the developing device 4 having yellow toner is applied, and becomes a visible yellow toner image. The yellow toner image is primarily transferred onto the transfer belt 7 by the primary transfer roller 6. At this time, a primary transfer bias is applied to the primary transfer roller 6 from a power supply (not shown).

  Similarly, a magenta toner image is formed in the magenta image forming unit M and transferred to the transfer belt 7. A cyan toner image is formed in the cyan image forming unit C and transferred to the transfer belt 7. In the black image forming unit K. A black toner image is formed and transferred to the transfer belt 7.

Yellow, magenta, cyan, and black toner images are formed at a timing when these toner images are transferred onto the intermediate transfer belt 7 in an overlapping manner.
Thus, the multiple toner image formed on the transfer belt 7 moves toward the secondary transfer roller 8 by the rotation of the transfer belt 7.

  On the other hand, the recording medium S is pulled out from the recording medium accommodation cassette 10 by the medium supply roller 101 and is supplied to the timing roller pair 11 and is on standby.

  Thus, the recording medium S waiting at the timing roller pair 11 is supplied to the nip portion between the transfer belt 7 and the secondary transfer roller 8 in accordance with the multiple toner image sent by the intermediate transfer belt 7. . The multiple toner image is secondarily transferred onto the recording medium S by a secondary transfer roller 8 to which a secondary transfer bias is applied from a power supply (not shown).

  Thereafter, the recording medium S is passed through the fixing device 9 where the multiple toner images are fixed on the recording medium S under heat and pressure. The recording medium S is continuously discharged to the discharge tray 13 by the discharge roller pair 12.

  In the primary transfer of the toner image to the belt 7, transfer residual toner or the like remaining on the photoreceptor 1 is cleaned by the cleaning device 5, and secondary transfer residual toner or the like remaining on the belt 7 by the secondary transfer is cleaned by the cleaning device 73. It is cleaned with. Each of these cleaned and removed toners is sent to a waste container by a conveying means (not shown).

  Although the image is formed as described above, the developing device 4 will be further described. The developing device 4 is shown in FIGS. 2 to 4 and is an example of the developing device according to the present invention.

  FIG. 2 schematically shows a cross-sectional structure of the developing device 4. FIG. 3 schematically shows the developing device 4 as viewed from the right in FIG. 2, but the developing roller 41 and the supply roller 42 are only indicated by their positions with broken lines.

The developing device 4 includes a developing roller 41 and a supply roller 42 that supplies developer to the developing roller 41. The supply roller 42 is an example of a developer supply rotating body.
The developing roller 41 is provided with an elastic layer made of a thermoplastic elastomer or rubber on a conductive shutter, and a surface coat layer having a higher hardness than the elastic layer on the surface thereof.
The supply roller 42 has a conductive foamed material layer (for example, an elastic foamed polyurethane layer imparted with conductivity) having elasticity on the conductive shaft.

  The developing device 4 also includes a first rotary transport body 46 and a second rotary transport body 47 that supply the developer with stirring to the supply roller 42 side. Here, each of the first and second rotary transport bodies is a screw transport member in which screw blades (spiral blades) are provided around the rotation shaft.

  The developing roller 41, the supply roller 42, and the first and second screw conveying members 46 and 47 are accommodated in the developing device housing 40, and are rotatably supported by the housing. A part of the developing roller 41 protrudes outside the housing 40 so as to face the photoreceptor 1 when the developing device 4 is mounted on the image forming apparatus 100. The conveying members 46 and 47 are accommodated in the developing device housing 40.

  In the housing 40, there is formed a buffer portion 43 that holds a developer (toner T in this example) (see FIG. 4) for development and faces the supply roller 42 and the development roller 41.

  The first screw conveying member 46 is disposed in the buffer unit 43 above the supply roller 42 and at a position behind the roller 42. The second screw conveying member 47 is disposed above the first screw conveying member 46 and above the supply roller 42 with a plate-like partition member 48 therebetween.

  The first screw conveying member 46 is arranged in parallel with the developing roller 41, and the second screw conveying member 47 is arranged in parallel with the first screw conveying member 46 with the partition member 48 in between.

  The first screw conveying member 46 is rotationally driven by a rotation driving unit (not shown), so that the developer can be conveyed in the rotation axis direction from the right side to the left side in FIG. By being rotationally driven by a rotational drive unit (not shown), the developer can be conveyed in the direction of the rotational axis from the left side to the right side in FIG.

  As the first and second screw conveying members 46 and 47 are driven to rotate as described above, the developer is developed on the right side in FIG. The developer feeding side end (developer feeding side end) is conveyed to the left developer sending side end (developer sending side end), and the left side end of the partition member 48 from the developer sending side end. Through the opening (second opening) 482 of the second conveying member 47, the second conveying member 47 moves upward to the developer feeding side end, and is further conveyed by the second conveying member 47 toward the developer sending side end. From the delivery side end portion, the partition member 48 passes through the opening portion (first opening portion) 481 at the right end portion of the partition member 48 and drops and moves to the developer feeding side end portion of the first conveying member 46 while being assisted by gravity. . In this way, the developer is supplied to the supply roller 42 and, consequently, the developing roller 41 side from the first transport member 46 while being stirred and circulated by the first and second transport members 46 and 47.

  The developing roller 41 and the supply roller 42 are driven to rotate counterclockwise in FIG. 2 by a rotation driving unit (not shown). Accordingly, at the nip portion where the rollers 41 and 42 face each other, both roller surfaces move in opposite directions. As a result, the supply roller 42 scrapes off the developer that returns to the developing device housing 40 without being consumed by the development from the development roller 41 and supplies the developer to the development roller 41 anew.

  When the developer thus supplied passes through the blade-shaped developer regulating member 44 that is in contact with the developing roller 41, the amount of the developer is properly regulated and charged, and the developer faces the photoreceptor 1. It is used for developing the electrostatic latent image on the photoreceptor 1 in the developing area (toner is applied to the electrostatic latent image). The developer that has not been consumed by the development returns to the case 40 as the developing roller 41 rotates. At this time, the developer is neutralized by a neutralization member 45 to which a neutralization bias is applied from a neutralization power supply (not shown) in order to facilitate scraping of the development roller 41 by the supply roller 42.

As a noteworthy point of the developing device 4,
(1) The developer conveying capability of the first screw conveying member 46 is larger than that of the second screw conveying member 47, and
(2) The first and second screw conveying members 46 and 47 rotate the developing roller 41 at the developer feeding side end of the conveying member 46 and the developer feeding side end of the conveying member 47 located above the first and second screw conveying members 46 and 47. It can be mentioned that it extends to the outside of the developing roller 41 in the axial direction, and a developer reservoir 49 is provided above the extended portion of the second conveying member 47.

  Although not limited thereto, in this example, the first screw conveying member 46 has a rotating shaft diameter of 3.5 mm, an outer diameter of 8 mm, and a screw lead of 15 mm. The second screw conveying member 47 has a rotating shaft diameter of 3.5 mm, an outer diameter of 8 mm, and a screw lead of 8 mm. Both conveying members are rotated at 200 revolutions per minute by a driving unit (not shown). The conveyance member 46 has a conveyance capacity about twice that of the conveyance member 47.

  Although not limited thereto, in this example, in the longitudinal direction of the developing device 4 in FIG. 3, the development reservoir 49 is about 50 mm, the portion between the developer reservoir 49 and the buffer 43 is about 40 mm, and the buffer 43 Is approximately 280 mm to 290 mm, and the length of the developing roller 41 in the longitudinal direction is approximately 220 mm to 230 mm.

In FIG. 3, for example, a transparent resin (for example, polystyrene) for detecting the amount of developer (here, the upper surface position of the developer in the reservoir) on each of the front and back walls facing each other of the developer reservoir 49. ), And a developer amount detection device TS is provided for these windows.
When the developer reservoir 49 is formed of a transparent material such as transparent polystyrene resin, a part of the developer reservoir 49 can be used as a detection window.

  The developer amount detection device TS includes an optical sensor having a light emitting element s1 and a light receiving element s2 (not shown) in this example. The light emitting element s1 faces one detection window dw from the outside, and the light receiving element s2 faces the other detection window dw from the outside. When the light receiving element s2 receives a predetermined amount of light from the light emitting element s1, it is determined that the amount of developer in the developing device 4 is insufficient, and the light from the light emitting element s1 is blocked by the developer, so that the light receiving element s2 has a predetermined amount. If the light is not received, it is determined that the developer amount is sufficient. The developer reservoir 49 is provided with a toner supply port 490 to which the toner bottle portion of the toner supply unit TB including the toner bottle can be detachably mounted. When the detecting device TS detects that the developer amount is insufficient, the toner can be supplied from the toner supply unit TB.

  Thus, in the developing device 4, the developer reservoir 49 is continuously provided above the developer feeding side end of the transport member in the developer transport direction of the upper second screw transport member 47. While the fixed amount of developer T required for the developing operation of the electrostatic latent image on the photoreceptor 1 is conveyed to the second conveying member 47, the developer of a larger amount is retained in the developer reservoir 49. I can keep it. In other words, a certain amount of developer T required for the electrostatic latent image developing operation can be transported to the second transport member 47 in a state where the developer T is retained in the developer reservoir 49.

  Then, the lower first conveying member 46 supplies an amount of developer equivalent to the amount of developer supplied from the developer delivery side end of the upper second conveying member 47 through the first opening 481 of the partition member 48. A balance of developer circulation can be achieved at the time of conveyance.

  At this time, since the developer transport capability of the first transport member 46 is greater than that of the second transport member 47, the upper second transport member 47 transports the developer amount required for the electrostatic latent image developing operation. The first transport member 47 transports the developer in an amount equal to the amount of developer supplied from the second transport member 47 and the first transport member 47 transports the first transport member 46 to the first transport member 46. It is possible to adjust the amount of developer in the developing device so that a gap is formed above the member 46. Here, the amount of the developer T in the device 4 is adjusted in this way (FIG. 4A). reference). Thus, the developer amount required for the electrostatic latent image developing operation can be stably supplied to the developing roller 41 in a state where the increase in the developer powder pressure is suppressed, and the electrostatic latent image can be developed as well.

  When the developer is consumed by the developing operation, the upper surface of the developer T in the buffer 43 having the first transport member 46 is lowered by the consumed amount (FIG. 4B). 2 The amount of developer movement to the conveying member 47 is reduced, thereby reducing the amount of developer circulation and causing a failure in supplying the developer to the developing roller 41, but the developer conveying side of the second conveying member 47 There is a developer reservoir 49 above the end, and the second conveying member 47 supplies the developer amount necessary for development to the first conveying member 46, so that the amount of developer in the buffer 43 is required for development. The amount of image noise that would occur if there was a poor supply of developer to the developing roller 41 is suppressed.

  Further, by using the developer reservoir 49 that is less affected by the presence of the first and second transport members 46 and 47, the toner consumed for development can be easily replenished and the developer in the developing device can be supplied. The amount detection device TS can also be easily provided in the developer reservoir 49, and by providing the toner replenishment site and the developer amount detection device TS in this manner, the developer amount detection device TS of the developer amount detection device TS can be provided. Responsiveness to toner replenishment is improved, and accordingly, toner can be replenished in a state where excess or deficiency is suppressed, and the amount of developer in the developing device 4 can be made constant.

  By the way, when the amount of developer in the developer reservoir 49 increases, the developer powder pressure increases, and the amount of developer transported by the second transport member 47 increases, while the second transport from the first transport member 46 increases. There is a tendency for the amount of developer movement to the member 47 to decrease, which may result in poor developer circulation, and hence poor developer supply to the developing roller 41.

  Therefore, as shown in FIG. 5, between the developer reservoir 49 and the buffer 43, an increase in the developer amount in the developer reservoir 49 (for example, an increase fluctuation due to a change in the toner supply amount from the toner supply portion TB). ), The developer transport amount stabilizing members 51 and 52 for stabilizing the developer transport amount by the first and second screw transport members 46 and 47 may be provided.

  The developer conveying amount stabilizing members 51 and 52 shown in FIG. 5 are both cylindrical members, and the member 51 is externally fitted to the first conveying member 46 with a slight gap, and the member 52 is the second member. The transfer member 47 is externally fitted with a slight gap. In this example, each of the members 51 and 52 has an inner diameter that is 1 mm larger than the outer diameter of the screw conveying member into which it is fitted, and is fixed to the case 40 or the like. The length in the longitudinal direction is about 40 mm.

  By providing the cylindrical members 51 and 52, it is possible to prevent the developer from flowing backward, and to cause the conveying members 46 and 47 to carry the developer in an amount corresponding to the developer conveying ability, The developer conveyance amount by the conveyance members 46 and 47 can be stabilized.

  The developer transport amount stabilizing members 51 and 52 are cylindrical members, but the stabilizing member is not limited to this, and for example, the stabilizing members 61 and 62 shown in FIG. . The developer transport amount stabilizing members 61 and 62 are adhered to the holding plate 601 illustrated in FIG. 6A by attaching a flexible film 602 that is radially cut as shown in FIG. 6B. C). As shown in FIG. 6D, the flexible film 602 may be externally fitted to each of the conveying members 46 and 47 between the developer reservoir 49 and the buffer 43 while being bent. In FIGS. 6A to 6C, the outer contours of the holding plate 601 and the film 602 are shown as squares, but these contours are actually formed on the case 40, the partition member 48, and the like. In accordance with this, the shape can be equipped.

  Further, as shown in FIG. 7, the developing device 4 includes a first and a first in order to improve the mixing and stirring of the toner supplied to the developer reservoir 49 and the existing developer T in the developing device 4. A mixing and stirring device 480 may be provided for mixing and stirring the developer while circulating the developer in the two screw conveying members 46 and 47. The mixing and stirring device 480 shown in FIG. 7 faces the developer reservoir 49. Although not shown in FIG. 7, the mixing and stirring device may be provided together with the developer transport amount stabilizing member.

  The mixing and stirring device 480 divides the second opening 482 of the partition member 48 into openings 482a and 482b by a small partition member 483 disposed in the opening, and further, the developer conveying side of the first conveying member 46 The direction of the spiral blade 460 at the end is the direction in which the developer is fed from the left side to the right side in FIG. 7 and the direction of the spiral blade 470 at the developer feeding side end of the second transport member 47 is developed from the right side to the left side in FIG. It is configured to send the agent.

  In FIG. 7, the developer sent by the first transport member 46 (sent from the right side to the left side) moves upward from the opening 482 a to the second transport member 47, and the original transport of the second transport member 47. The developer is conveyed in the direction (left to right) and circulates so as to move from the partition member opening 481 to the first conveyance member 46, but a part of the developer that has moved upward from the opening 482 a is conveyed to the left by the spiral blade 470. Then, it moves downward from the opening 482b, moves toward the opening 482a by the lower spiral blade 460, and mixes with the developer sent from the right to the left in FIG. While moving upward from the opening 482a. In this way, the developer is stirred.

  Further, since the mixing and stirring device 480 is positioned below the toner supply port 490, the toner supplied from the supply port is efficiently mixed and stirred with the existing developer circulating in the device, and sufficiently mixed and stirred. The developed developer can be supplied to the buffer unit.

  Since the printer 100 employs the developing device 4 described above as the developing device, each developing device 4 can maintain a constant amount of developer in the apparatus and also applies toner to the electrostatic latent image. Thus, the developer can be stably supplied to the developing roller 41, and a good image can be formed accordingly.

  The image forming apparatus described with reference to FIG. 1 is a tandem type full-color printer 100. However, the present invention can also be applied to a monochrome image forming apparatus, and also to other types of multicolor image forming apparatuses. it can. Further, in an image forming apparatus provided with a plurality of developing devices, the present invention may be applied only to a smaller number of developing devices than the total number of the developing devices.

  According to the present invention, the amount of developer in the developing device can be maintained constant, and the developer can be stably supplied to the developer-carrying rotor for applying toner to the electrostatic latent image. Therefore, the present invention can be used to provide a developing device that does not require a complicated structure, and to provide an image forming apparatus that can form a good image by providing such a developing device.

DESCRIPTION OF SYMBOLS 100 Printer Y Yellow image formation part M Magenta image formation part C Cyan image formation part K Black image formation part 1 Photoconductor 2 Charger 3 Image exposure apparatus 4 Developing apparatus 40 Developing apparatus housing 41 Developing roller 42 Developer supply roller 43 Buffer part 44 Developer regulating member 45 Neutralizing member 46 First screw conveying member 47 Second screw conveying member 48 Partition member 481, 482 Developer flow opening 49 of partition member Developer reservoir 490 Toner replenishment port TS Developer amount detection device s1 Light emitting element s2 Light receiving element dw Detection window TB Toner replenishing device 5 Cleaning device 6 Primary transfer roller 7 Intermediate transfer belt 71 Driving roller 72 Opposing roller 73 Cleaning device 8 Secondary transfer roller 9 Fixing device 10 Recording medium supply cassette 101 Recording medium Supply roller 11 Timing roller Pair 12 Recording medium discharge roller pair 13 Recording medium discharge tray S Recording medium 51, 52 Developer transport amount stabilizing member 601 Film holding member 602 Flexible film 61, 62 Developer transport amount stabilizing member 480 Developer mixing and stirring device 483 Small partition members 482a, 482b Openings 460, 470 formed in a split manner Spiral blade T Developer

Claims (5)

A developing device used for electrostatic latent image development in an image forming apparatus capable of forming an electrostatic latent image on an electrostatic latent image carrier and developing the electrostatic latent image to form a toner image;
A developer carrying rotator for applying toner to the electrostatic latent image;
A buffer unit that holds the developer that faces the developer carrying rotor and is used for development;
A first rotary transport body that is disposed in the buffer unit and that is rotationally driven to transport the developer in the rotational axis direction;
A second rotary transport body that is disposed on the upper side of the first rotary transport body and is driven to rotate so as to transport the developer in the direction of the rotation axis and in a direction opposite to the first rotary transport body;
A developer reservoir,
The first and second rotary transport bodies allow the developer to move from the developer delivery side end of the second rotary transport body to the developer feed side end of the first rotary transport body and the first rotary transport body. The developer is stirred and circulated while allowing the developer to move from the developer delivery side end of the one-rotation conveyance body to the developer delivery-side end of the second rotation conveyance body, and the development from the first rotation conveyance body is performed. Can be supplied to the agent-carrying rotor
The first and second rotating transport bodies are at the developer sending side end of the first rotating transport body and the developer feeding side end of the second rotating transport body located above the end, Extending to the outside of the developer carrying rotator in the direction of the axis of rotation of the developer carrying rotator,
The developer reservoir is continuously provided above the extension of the second rotary transport body;
2. A developing device according to claim 1, wherein the developer conveying capability of the first rotating carrier is greater than the developer conveying capability of the second rotating carrier.   A developer that stabilizes the developer transport amount by the first and second rotary transport bodies between the developer reservoir portion and the buffer portion, regardless of an increase in the developer amount in the developer reservoir portion. The developing device according to claim 1, wherein a conveyance amount stabilizing member is provided for each of the first and second rotary conveyance bodies. The developing device according to claim 1, wherein a detection window for detecting a developer amount and a toner supply port for supplying toner are provided in the developer reservoir.   4. The developing device according to claim 1, wherein a mixing and stirring device that mixes and stirs the developer while circulating the developer in the first and second rotary transport members faces the developer reservoir. 5.   An image forming apparatus capable of forming an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier and developing the electrostatic latent image with a developing device to form a toner image, at least one developing device An image forming apparatus comprising the developing device according to claim 1.

Images