JP4883098B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile machine, or a combination machine combining two or more of these, and particularly relates to a developing device used in the image forming apparatus. is doing.

  In an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile machine, or a combination machine combining two or more of these, the surface of the electrostatic latent image carrier is charged by a charging device and exposed to the charged area. Image exposure can be performed from the apparatus to form an electrostatic latent image, and the electrostatic latent image can be developed by a developing device to form a toner image.

  Various types of developing devices are known for use in such image forming apparatuses. Among them, an image to be formed is formed on the electrostatic latent image carrier of the image forming apparatus. A developer carrying member that applies toner to the corresponding electrostatic latent image, a first carrying member that is arranged on the developer carrying member and that is driven to rotate and conveys the developer in the direction of the rotation axis, and is driven to rotate. Thus, there is a developing device including a second conveying member that conveys the developer in the direction of the rotation axis and in a direction opposite to the first conveying member.

  In this type of developing device, from the developer feeding side end (developer sending side end) of the first conveying member to the developer feeding side end (developer feeding side end) of the second conveying member Developer transport direction switching area, and developer transport direction in the developer transport direction switching area from the developer delivery side end of the second transport member to the developer feed side end of the first transport member The developer can be supplied to the developer carrying member from the first conveying member by stirring and circulating the developer with the first and second conveying members while allowing the switching.

Hereinafter, this type of developing device may be referred to as a “developer stirring circulation type developing device”.
A typical one of the first and second transport members is a screw transport member in which screw blades (spiral blades) are formed on the rotating shaft.

  On the other hand, as a developer to be used, a so-called one-component developer mainly composed of toner and a so-called two-component developer mainly composed of toner and carrier are known.

  A developing device using a two-component developer has advantages such as being able to stabilize the image quality over a long period of time compared to a developing device using a one-component developer, and is widely used.

  The two-component developer is a device in which the toner and the carrier are mixed and stirred to charge the toner and used for development. Therefore, the developer stirring and circulation type developing device is suitable when a two-component developer is used as the developer. . A developer agitation circulation type developing device is often used for a developing device using a two-component developer.

  In any case, in the developer agitation circulation type developing device, the rotation shaft portion of each conveying member extending to the outside of the developer circulation area is usually supported by the bearing portion. The bearing unit includes a bearing member that rotatably supports the rotation shaft of the conveying member, and also includes such a bearing member and developer sealing means. The developer seal means is for preventing the developer from entering the bearing member and preventing the bearing function from being exhibited (so-called bearing lock occurs).

  For example, in Japanese Patent Laid-Open No. 4-69691, in a developing device using a developer containing magnetic powder, a magnetic seal made of the magnetic powder is provided around the rotating shaft inside the rotating shaft bearing member of the developer conveying member. It is described to form.

  As the sealing means, in addition to such a magnetic seal, a developer seal member made of an elastic fluorine-based resin such as polytetrafluoroethylene and surrounding the conveying member rotating shaft may be employed.

  By the way, when the developing device is operated continuously for a long time, the developer used rises in temperature. This is due to frictional heat generation due to mutual contact between the developing device parts and the developer, heat generation due to friction between the developers, and heat generation due to friction between the rotating shaft of the developer conveying member and its bearing portion. is there.

  In the developer agitation circulation type developing device, the bearing portion (bearing member or bearing member and developer seal member, etc.) that supports the part of the conveying member rotating shaft extending outside the developer circulation area. Friction heat generation cannot be ignored. Particularly, in a developing device that requires high speed operation for high speed image formation, friction heat generation at the bearing portion is large and cannot be ignored.

  Such heat generation and high temperature of the bearing portion may cause the developer to become a high temperature, leading to deterioration of the developer and generation of developer agglomerates and the like, which may deteriorate the quality of the formed image. The developer (particularly toner) is melted and fixed due to heat between the rotating shaft of the toner and its bearing member and between the rotating shaft and the developer seal member surrounding the rotating shaft, making it difficult to rotate the developer conveying member. Can even become.

  To further explain the deterioration in image quality due to the occurrence of developer aggregates, the developer supplied to the developer carrier for applying toner to the electrostatic latent image is below the developer regulating member facing the developer carrier. The developer amount is regulated to a predetermined amount by passing through, but when developer aggregates are generated, this is stopped by the developer regulating member and developed in a streak form on the surface of the developer carrying member beyond that. An agent-deficient portion is generated, which causes a streak-like image defect.

  For this reason, measures for suppressing the increase in the temperature of the bearing have been proposed so far in order to suppress the increase in the temperature of the developer.

  For example, in Japanese Patent Application Laid-Open No. 2003-57927, in a developer agitation circulation type developing device, a bearing member that supports a rotating shaft portion at a developer delivery side end of a developer transport member and a developer circulation region side thereof. The space between the developer seal member (magnet) provided on the outside and the outside is communicated to the outside via a vent so that the space can be ventilated and cooled, thereby generating heat in the bearing member and the developer seal member. It is described that high temperature is suppressed.

JP-A-4-69691 JP 2003-57927 A

  However, when the space between the bearing member and the developer seal member is communicated to the outside through the vent as described in Japanese Patent Application Laid-Open No. 2003-57927, the space is supported by the bearing member and the developer seal member. If the size is large enough to obtain the cooling effect, the size of the developing device will be increased accordingly. Further, if a ventilation duct is provided to cool the space by ventilation, the configuration of the image forming apparatus is complicated accordingly. If the arrangement of the developing device in the image forming apparatus is devised in order to perform air cooling of the space without providing such a duct, the arrangement position of the developing device is restricted, and the developing apparatus itself or the image forming apparatus is restricted. The production becomes difficult. As a result, the price of the image forming apparatus increases.

  Therefore, the present invention is a developer agitation and circulation type developing device, and even if the temperature of the bearing portion of the developer conveying member rotating shaft rises, the temperature of the developer is increased, and as a result, the deterioration and aggregation of the developer are suppressed. The developer can be prevented from sticking between the rotating shaft and the bearing portion of the developer conveying member and causing a rotation failure of the developer conveying member. It is an object to provide a developing device that does not cause an increase in cost.

Here, as described above, the “developer stirring circulation developing device”
A developing device that develops an electrostatic latent image formed on an electrostatic latent image carrier in an electrophotographic image forming apparatus to form a toner image;
A developer carrier for applying toner to the electrostatic latent image;
A first conveying member that is erected on the developer carrier and conveys the developer in the rotation axis direction by being driven to rotate;
A second conveying member that conveys the developer in the direction of the rotation axis by being rotationally driven and in a direction opposite to the first conveying member;
The developer transport direction switching area from the developer delivery side end of the first transport member to the developer feed side end of the second transport member and the developer delivery side end of the second transport member The developer is stirred and circulated by the first and second transport members while allowing the developer transport direction to be switched in the developer transport direction switching area to the developer feeding side end of the first transport member. In the developing device, the developer can be supplied from the first conveying member to the developer carrying 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. The present invention provides an image forming apparatus capable of forming a good image in such a state that, in at least one developing device, the occurrence of poor rotation of the developer conveying member due to the high temperature of the developer or the fixing of the developer is suppressed. Let it be an issue.

According to the inventor's research,
(1) Due to the operation of the developing device, the bearing portion (bearing member or bearing member and developer seal member for the bearing member, etc.) of the conveyance member rotating shaft generates frictional heat, and at least this heat raises the temperature of the developer. May melt and stick,
(2) The developer (especially toner) melted and fixed between the rotation shaft of the conveying member and the bearing portion is more likely to occur when the developer agitation circulation is stopped by stopping the conveyance member than during the developer agitation circulation due to rotation of the conveyance member. This is because the developer that has stopped moving while being in contact with the bearing portion due to the stop of the conveying member is intensively heated by the bearing portion that has already generated heat.
(3) Looking at the developer powder pressure applied to the bearing portion of the developer conveying member during the developer agitation circulation, the bearing portion on the developer sending side of the conveying member is larger than the bearing portion on the developer feeding side. Due to the pressure, the developer is more likely to be pushed into the bearing portion on the developer delivery side, and the developer is more likely to come into contact.

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 that develops an electrostatic latent image formed on an electrostatic latent image carrier in an electrophotographic image forming apparatus to form a toner image,
A developer carrier for applying toner to the electrostatic latent image;
A first conveying member that is erected on the developer carrier and conveys the developer in the rotation axis direction by being driven to rotate;
A second conveying member that conveys the developer in the direction of the rotation axis by being rotationally driven and in a direction opposite to the first conveying member;
The developer transport direction switching area from the developer delivery side end of the first transport member to the developer feed side end of the second transport member and the developer delivery side end of the second transport member The developer is stirred and circulated by the first and second transport members while allowing the developer transport direction to be switched in the developer transport direction switching area to the developer feeding side end of the first transport member. A developing device capable of supplying a developer from a first conveying member to the developer carrier,
A developer push-back device is provided on at least one of the developer delivery side end of the first transport member and the developer delivery side end of the second transport member;
The developer push-back device is provided on the developer circulation area side from a bearing portion supporting a part of the conveying member rotating shaft extending to the outside of the developer circulation area at the developer delivery side end. During the developer agitation circulation by the rotation of the conveying member, the developer is retreated by the powder pressure of the developer conveyed to the end of the developer delivery side to provide a part of the developer circulation area, and when the conveying member is stopped, the elastic return is achieved. A developing device that pushes the developer back away from the bearing.

(2) Image forming apparatus An image forming apparatus that forms an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier and develops 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 push-back device is provided on at least one of the developer delivery side end of the first transport member and the developer delivery side end of the second transport member. The developer push-back device is provided on the developer circulation area side from the bearing portion supporting the part of the conveying member rotating shaft that extends to the outside of the developer circulation area at the developer delivery side end. During the developer agitation circulation due to the rotation of the conveyance member, the developer is retreated by the powder pressure of the developer conveyed to the end of the developer delivery side to provide a part of the developer circulation area, and when the conveyance member is stopped, the elastic recovery is performed. The developer is pushed back so as to move away from the bearing portion.

  Therefore, even if the temperature of the bearing portion of the developer conveying member rotating shaft is increased due to the operation of the developing device, the developing is performed on at least one of the developer sending side ends of the first and second conveying members when the conveying member is stopped. The developer push-back device moves the developer away from the bearing portion facing the one side, thereby suppressing the temperature rise of the developer due to the heat of the bearing portion, and thus suppressing the deterioration and aggregation of the developer, thereby reducing the image quality. Reduction can be suppressed. Further, it is possible to prevent the developer from being melted and fixed between the rotation shaft of the transport member and the bearing portion to cause a rotation failure of the developer transport member.

  In addition, the developer push-back device that provides such an advantage communicates the space between the bearing portion and the developer seal member to the outside through the vent as described in JP-A-2003-57927. Compared to the case, the size of the developing device may be increased in order to provide the space, or a ventilation duct may be required for cooling the air in the space, or the arrangement of the developing device may be restricted. Therefore, it can be provided at a relatively low cost without an increase in cost that should be regarded as a problem in practice.

  In the image forming apparatus according to the present invention, the developing device according to the present invention is adopted as at least one developing device. Therefore, in at least one developing device, a developer conveying member due to high temperature of the developer or fixing of the developer. The occurrence of poor rotation is suppressed, and as a whole, a good image can be formed.

  The developer push-back device includes a developer push-back member that is movable in the direction of the transport member rotation axis at the developer delivery side end of the transport member provided with the push-back device, and a developer push-back force applied to the developer push-back member. The thing containing the elastic body which provides can be illustrated.

  The elastic body is elastically deformed so as to allow the developer push-back member to move backward due to the powder pressure of the developer conveyed to the developer delivery side end during the developer agitation circulation due to the rotation of the conveying member. When the conveying member is stopped, the developer pushing-back member is pushed by an elastic restoring force so that the developer pushes the developer away from the bearing portion.

  Examples of such an elastic body include a synthetic resin elastic body that can be compressed elastically such as a compression coil spring and elastic foamed urethane, and an elastic gel body that exhibits elasticity as a whole in which a gel-like resin is enclosed.

  The developer push-back member in the case of adopting such an elastic body is not limited thereto, but a plate-like member that can reciprocate along the transport member rotation axis can be exemplified.

  Further, examples of the developer push-back device include a plate-like flexible member disposed on the developer circulation area side from the bearing portion. The plate-like flexible member is deformed backward and bent so as to provide a part of the developer circulation area by the developer powder pressure during the developer agitation circulation by the rotation of the conveyance member, and is elastically restored when the conveyance member is stopped. Thus, the developer is pushed back away from the bearing portion.

  The bearing portion provided with the developer push-back device is not only a bearing member that rotatably supports the conveying member rotation shaft, but also development for suppressing such a bearing member and developer biting into the bearing member. It may also include an agent seal member (a seal member surrounding the conveying member rotation shaft).

  In the developing device according to the present invention, the developer push-back device can be provided on both the developer delivery side end of the first transport member and the developer delivery side end of the second transport member, but provided on either one. Just be fine.

  However, in the developer agitation circulation type developing device, the developer is supplied from the first conveying member to the developer carrying member while being conveyed by the first conveying member, while the replenishment toner is normally supplied to the developer carrying member. It is performed to the area where the second conveying member that does not face is arranged. This is because it is preferable that the developer containing the replenishment toner (new toner) is thoroughly stirred before being used for development.

  In this case, from the developer transport side end of the second transport member from the developer transport direction switching area from the developer transport side end of the first transport member to the developer transport side end of the second transport member. The developer amount tends to increase more in the developer conveyance direction switching area to the developer feeding side end of the first conveying member, and the developer is in contact between the conveying member rotating shaft and its bearing portion. Easy to be bitten.

  Further, as in a so-called vertical developing device in which the first conveying member is disposed on the upper side and the second conveying member is disposed on the lower side, the developer delivery side end of the second conveying member is the developer of the first conveying member. In the case of being arranged below the feeding side end, in the developer conveyance direction switching area where these conveyance member ends are arranged, the developer must move from below to above against gravity. Therefore, in such an area, the stress applied to the developer is large, and in particular, the developer tends to enter the bearing portion facing the developer delivery side end portion of the second conveying member located on the lower side.

  Therefore, a developer push-back device may be provided at least for the developer delivery side end of the second transport member among the developer delivery side ends of the first and second transport members.

  In this case, the sending side end of the second transport member may be disposed below the sending side end of the first transport member.

  Further, the developing device may be formed such that the replenishment toner is replenished to the second transport member.

  In any case, the developer may be a one-component developer mainly composed of toner, but a two-component developer mainly composed of toner and carrier can be exemplified as being suitable for the configuration of the developing device according to the present invention.

  As described above, according to the present invention, the developer agitating / circulating type developing device is provided, and even if the temperature of the bearing portion of the developer conveying member rotating shaft is increased, the temperature of the developer is increased accordingly. Deterioration and aggregation can be suppressed, and it is possible to suppress the developer from adhering between the rotation axis of the developer conveying member and the bearing portion, resulting in poor rotation of the developer conveying member. It is possible to provide a developing device that does not cause a significant increase in manufacturing cost of the developing device.

  According to the present invention, there is also provided an image forming apparatus that forms an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier and develops the electrostatic latent image with a developing device to form a toner image. An image forming apparatus capable of forming a good image in such a state that at least one developing device suppresses occurrence of rotation failure of the developer conveying member due to high temperature of the developer or fixing of the developer. Can

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 a developing device in the image forming apparatus of FIG. 1. FIG. 3 is a diagram schematically showing the developing device in the image forming apparatus of FIG. 1 as viewed from the left side in FIG. 2 with a part of the developing device housing removed. It is a figure which expands and shows roughly the internal structure of the housing by the side of the developer conveyance member drive of a developing device, and is a figure which shows the state during a developer circulation. FIG. 5 is a diagram showing a state in which the developer circulation is stopped in the developing device shown in FIG. 4. It is a figure which expands and shows roughly the internal structure of the housing of the conveyance member drive side of the other example of a developing device. It is a figure which expands and shows roughly the internal structure of the housing by the side of the conveyance member of further another example of a developing device, and is a figure which shows the state during a developer circulation. FIG. 8 is a diagram illustrating a state in which the developer circulation is stopped in the developing device illustrated in FIG. 7.

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 shows an outline of the configuration of an example PR of an image forming apparatus. The image forming apparatus PR is a tandem type full color printer.

  The printer PR includes an endless intermediate transfer belt 8 wound around a driving roller 81 and a roller 82 facing the driving roller 81. The transfer belt 8 is rotated counterclockwise (arrow direction in the figure) CCW in the figure by a driving roller 81 driven by a belt driving unit (not shown).

  A cleaning device 83 for cleaning the secondary transfer residual toner and the like on the transfer belt 8 faces the roller 82, and a secondary transfer roller 9 faces the drive roller 81. The toner or the like collected by the cleaning device 83 is sent to a waste container by a conveying means (not shown).

  The surface layer portion of the secondary transfer roller 9 is formed of an elastic material, and is pressed against a portion of the intermediate transfer belt 8 supported by the driving roller 81 by a pressing unit (not shown), and a nip is formed between the secondary transfer roller 9 and the intermediate transfer belt 8. And can be rotated following the rotation of the intermediate transfer belt 8 or following 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 9 from a power supply (not shown).

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

The fixing device FX includes a fixing heating roller incorporating 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 TR.

  Between the rollers 81 and 82 around which the intermediate transfer belt 8 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 8 from the roller 82 to the roller 81. 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 8 therebetween. The primary transfer roller 6 is pressed toward the photoconductor 1 by a pressing unit (not shown).

  A primary transfer bias for primary transfer of the toner image formed on the photoreceptor 1 to the belt 8 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.

  The developing device 4 in each image forming unit does not show an electrostatic latent image formed on the photoreceptor 1 by using a so-called two-component developer mainly composed of a magnetic carrier and a negatively charged nonmagnetic toner. The developer carrying member (in other words, a developing sleeve or a developing roller) 41 in the form of a roller to which a developing bias is applied from a power source can be reversely developed. 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 8 as a primary. Transcript.

  That is, in the yellow image forming portion Y, the photosensitive member 1 is rotated in the clockwise direction in the drawing, and the surface is uniformly charged to a predetermined potential by the charger 2, and the yellow region for the yellow image is transferred from the exposure device 3 to the charged area. Image exposure is performed, and a yellow electrostatic latent 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 8 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 8. A cyan toner image is formed in the cyan image forming unit C and transferred to the transfer belt 8. In the black image forming unit K. A black toner image is formed and transferred to the transfer belt 8.

Yellow, magenta, cyan, and black toner images are formed at the timing when these toner images are transferred onto the intermediate transfer belt 8.
Thus, the multiple toner image formed on the transfer belt 8 moves toward the secondary transfer roller 9 by the rotation of the transfer belt 8.

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

  Thus, the recording medium S waiting at the timing roller pair TR is supplied to the nip portion between the transfer belt 8 and the secondary transfer roller 9 in accordance with the multiple toner image sent by the intermediate transfer belt 8. . The multiple toner image is secondarily transferred onto the recording medium S by a secondary transfer roller 9 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 FX, 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 DT by the discharge roller pair DR.

  In the primary transfer of the toner image to the belt 8, 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 8 by the secondary transfer is cleaned by the cleaning device 83. 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 using the two-component developer will be further described. The developing device 4 is shown in FIGS. 2 to 5 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 left side in FIG. 2 with a part of the developing device housing 40 removed. 4 and 5 are enlarged views of the internal structure of the housing on the developer conveying member driving side of the developing device 4.

  The developing device 4 has a developer carrier 41 and a magnet body 42 fixedly disposed therein. Here, the developer carrier 41 is a hollow roller-shaped sleeve formed of a nonmagnetic material and having a circular cross section. The developer carrier 41 is externally fitted to the magnet body 42 and is attached to the magnet body 42 via left and right bearings (not shown). It is rotatably supported and can be driven to rotate in the clockwise direction CW in FIG. 2 by driving means (not shown) from one of the left side and the right side. Here, the magnet body 42 is generally formed in a roller shape.

  The developing device 4 further includes a first conveying member 43 and a second conveying member 44 that supply the developer to the developing sleeve 41 while stirring. Here, the first conveying member 43 is a screw conveying member in which a screw blade (spiral blade) 432 is provided around the rotating shaft 431, and the second conveying member 44 is also provided with a screw blade (spiral blade) 442 around the rotating shaft 441. It is a screw conveying member.

The developing sleeve 41 and the conveying members 43 and 44 are all housed in the developing device housing 40 and are rotatably supported by the housing. A part of the developing sleeve 41 protrudes to the outside of the housing 40 so as to face the photoreceptor 1 when the developing device 4 is installed in the image forming apparatus PR. The conveying members 43 and 44 are accommodated in the developing device housing 40.

The first conveying member 43 faces the developing sleeve 41 and is arranged in parallel with the developing sleeve. The second conveying member 44 is parallel to the first conveying member 43 with the partition wall 45 therebetween and below the conveying member 43. Has been placed.
As shown in FIG. 3, a developer flow path h1 is formed on the left side of the partition wall 45, and a developer flow path h2 is formed on the right side.

  One end portion (left end portion in FIG. 3) of the rotation shaft 431 of the first transport member 43 rotates to a portion 43a corresponding to a bearing member that also serves as a part of the developing device housing 40, as shown in FIGS. It is supported so that it protrudes out of the housing. On the inner side (developer circulation area A side) of the bearing member 43a, the developing seal member 43s slidably contacts the rotating shaft 431 and surrounds the shaft. As shown in FIG. 3, the other end portion of the rotation shaft 431 (the right end portion in FIG. 3) is rotatably supported by a bearing portion 43 b on the opposite side that also serves as a part of the housing 40.

  One end portion (left end portion in FIG. 3) of the rotation shaft 441 of the second transport member 44 also rotates to a portion 44a corresponding to a bearing member that also serves as a part of the developing device housing 40, as shown in FIGS. It is supported and supported so as to protrude out of the housing. On the inner side (developer circulation area A side) of the bearing member 44a, the developing seal member 44s slidably contacts the rotating shaft 441 and surrounds the shaft. As shown in FIG. 3, the other end portion of the rotation shaft 441 (the right end portion in FIG. 3) is rotatably supported by a bearing portion 44 b on the opposite side that also serves as a part of the housing 40.

  A gear g1 is provided at a portion of the rotating shaft 431 protruding out of the housing, and a gear g2 is provided at a portion of the rotating shaft 441 protruding out of the housing, and the gears g1 and g2 are engaged with each other. In the developing device 4, the side on which the gears g1 and g2 are provided is the conveying member driving side. When the gear g2 is rotationally driven by a drive device (not shown), the gear g1 is also driven in the opposite direction.

  As shown by the arrow in FIG. 3, the first and second transport members 43 and 44 are driven to rotate so that the developer in the housing 40 is moved by the first transport member 43. In FIG. 3, the developer is transported from the left developer feed side end (developer feed side end) to the right developer feed end (developer feed side end), and from the developer feed side end The developer flows through the developer flow path h2 and falls to the developer feeding side end of the second transport member 44 while being aided by gravity, and is further transported toward the developer delivery side end by the second transport member 44. , And moves upward from the delivery side end portion to the developer feeding side end portion of the first conveying member 43 through the developer flow path h1, and thus the first and second conveying members 43, 44, Developer formed by the partition wall 45, the developer flow paths h1 and h2, and the housing portion around them. With stirring circulated in the ring zone, it is supplied to the developing sleeve 41 from the first conveying member 43.

  In FIG. 3, the developer feeding side end of the first conveying member 43 and the developer feeding side end of the second conveying member 44 at the right end of the developing device 4 are bearing portions of the conveying member rotating shafts 431 and 441. Screw blades 432 and 442 extend to the vicinity of 43b and 44b, and a range A surrounded by a dotted line in FIG. 3 is a developer circulation region.

  The developing sleeve 41 holds the developer brush (magnetic brush made of developer) on the peripheral surface by the action of the internal magnet body 42 and conveys it toward the developing area facing the photoreceptor 1, and in the middle of the developer regulating member At 400, the developer amount is regulated and used for developing the electrostatic latent image. Of the developer used for development, the developer that has not been consumed is returned to the first conveying member 43 as the developing sleeve 41 rotates.

  Although not shown in FIG. 1, toner can be supplied from the toner supply device T indicated by a broken line in FIG. 2 to the lower second conveying member 44.

  It should be noted about the developing device 4 that, as shown in FIGS. 3, 4, and 5, the developer pushing-back device 46 is provided at the developer delivery side end of the second conveying member 44 on the conveying member driving side. It is a point provided.

  Here, the developer push-back device 46 includes a developer push-back member 461 that can move in the direction of the conveying member rotation shaft 441, and an elastic body 462 that applies a developer push-back force to the member 461.

  In this example, the push-back member 461 is a plate-like body that is externally fitted and supported on the shaft so as to be movable along the rotation shaft 441. In this example, the elastic body 462 is a compression coil spring that is disposed between the bearing portion (here, the bearing member equivalent portion 44 a and the seal member 44 s therein) and the plate-like body 461, and is externally fitted to the rotary shaft 441. . One end of the spring 462 is connected to the plate-like body 461, and the other end is supported by a spring support 462 s on the shaft 441.

  According to the developing device 4, during the operation of the developing device 4, that is, when the developer circulates by rotation of the conveying members 43 and 44, as shown in FIG. The plate-like body 461 is retracted against the spring 462 to the bearing member 43a and the seal member 43a side by the powder pressure due to the developer conveyance toward the developer delivery side end, so that one part of the developer circulation region is obtained. Part (the part of the circulation zone at the end of the developer delivery side) is provided, and stirring and circulation of the developer is not hindered.

  However, when the operation of the developing device is stopped and the developer circulation is stopped by the stop of the conveying members 43 and 44, the plate-like body 461 is released from the developer powder pressure to the spring 462 as shown in FIG. Is pushed back to the developer circulation area side. At this time, the developer is pushed back in the same direction by the plate-like body 461, and is moved away from the bearing member 43a and the seal member 43s.

  Therefore, even if the bearing member 43a and the seal member 43s constituting the bearing portion in this example are heated and heated due to friction with the rotating shaft 441 during the developer operation, The developer is moved away from the bearing portion including the bearing member 43a and the seal member 43s by the developer push-back device 46, and the temperature rise of the developer due to the heat of the bearing member 43a and the seal member 43s is suppressed accordingly, and the developer is deteriorated accordingly. And agglomeration can be suppressed to prevent degradation of image quality. Further, it is also possible to prevent the developer from being melted and fixed between the transport member rotating shaft 441 and the bearing member 43a or the seal member 43s to cause a rotation failure of the developer transport member 441.

  In addition, the developer push-back device 46 that provides such advantages can be provided at a relatively low cost without an increase in cost that should be regarded as a practical problem.

  Since the image forming apparatus PR employs such a developing device 4 as a developing device, the high temperature of the developer is suppressed in each developing device, and a good image can be formed as the whole image forming device.

FIG. 6 schematically shows an enlarged housing internal structure on the conveying member driving side of another example of the developing device according to the present invention.
This developing device 4A employs a developer pushing back device 46A in place of the developer pushing back device 46 in the developing device 4. The other points are the same as those of the developing device 4, and the same reference numerals are assigned to the same parts and parts as the developing device 4.

  The developer push-back device 46A employs the same plate-like body 461 as the plate-like body in the push-back device 46 as a developer push-back member, and a synthetic resin that can be compressed elastically such as elastic foamed urethane as an elastic body that pushes the developer. An elastic body 463 is employed. One end portion of the elastic body 463 is connected to the plate-like member 461, and the other end portion is supported by a support portion 463 s on the rotating shaft 441.

  According to the push-back device 46A, when the developer circulates due to the rotation of the transport members 43 and 44, the powder pressure due to the transport of the developer toward the developer delivery side end by the second transport member 44. As a result, the plate-like body 461 is retracted toward the bearing member 43a and the seal member 43a against the elastic force of the elastic body 463, thereby providing a part of the developer circulation area and hindering the developer circulation. Absent.

  However, when the developer circulation is stopped by stopping the conveying members 43 and 44, the plate-like body 461 is released from the developer powder pressure applied thereto, and is pushed back to the developer circulation area side by the elastic body 463. At this time, the developer is pushed back in the same direction by the plate-like body 461, and is moved away from the bearing member 43a and the seal member 43s.

Thus, similarly to the push-back device 46, the push-back device 46A can suppress the increase in the temperature of the developer, and the bearing lock of the rotation shaft of the conveying member can be suppressed.
In place of the elastic body 463, for example, an elastic gel body that exhibits elasticity as a whole in which a gel-like resin is enclosed may be employed.

7 and 8 schematically show an enlarged housing internal structure on the conveying member driving side of still another example of the developing device according to the present invention.
The developing device 4B employs a developer pushing-back device 46B in place of the developer pushing-back device 46 in the developing device 4. The other points are the same as those of the developing device 4, and the same reference numerals are assigned to the same parts and parts as the developing device 4.

The developer push-back device 46B is composed of a plate-like flexible member 464 disposed on the developer circulation area A side from the bearing portion including the bearing member 43a and the seal member 43s.
Examples of the plate-like flexible member 464 include those made of a synthetic resin such as polyester, polyethylene, polyurethane, polypropylene, and polyamide.

  One end portion of the plate-like flexible member 464 rises to a portion of the developing device housing 40 on the bearing portion side and abuts against it, and the opposite end portion is slightly below the second conveying member 44. It contacts the developing device housing 40 so as to enter. And it is slidably fitted in the axial direction of the conveying member rotation shaft 441 through a through hole (not shown) provided in the one end side portion.

  According to the push-back device 46B, when the developer circulates due to the rotation of the transport members 43 and 44, as shown in FIG. 7, the second transport member 44 moves toward the developer delivery side end. The plate-like flexible member 464 is pushed and bent toward the bearing portion against its elasticity by the powder pressure due to the developer conveyance of the developer, thereby providing a part of the developer circulation area, I can't interfere.

  However, when the developer circulation is stopped by stopping the conveying members 43 and 44, as shown in FIG. 8, the plate-like flexible member 464 is released from the developer powder pressure thereon, and developed by the elastic restoring force. It returns to its original form while pushing the developer back to the developer circulation area. Thus, the developer is moved away from the bearing member 43a and the seal member 43s.

  In this manner, the push-back device 46B can suppress the increase in the temperature of the developer similarly to the push-back device 46, and can suppress the bearing lock of the transport member rotation shaft.

In the developing devices 4, 4 </ b> A, and 4 </ b> B described above, the developer push-back device is provided only at the developer delivery side end on the driving side of the second transport member 44, but the developer delivery side end of the first transport member 43. A similar developer push-back device may be provided.
The present invention can also be applied to a developing device in which both conveying members are arranged at the same height or substantially the same height. In this case, at least one developer delivery end on the drive side and the opposite side is also provided. A similar developer push-back device can also be provided.

  The image forming apparatus described with reference to FIG. 1 is a tandem type full-color printer PR, but 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. In an image forming apparatus including a plurality of developing devices, only a number of developing devices smaller than the total number of the developing devices may be the developing devices according to the present invention.

  The present invention relates to a developing device capable of forming a good image by suppressing the temperature rise of the developer and the fixing of the developer at the bearing portion of the rotation shaft of the conveying member, and an image capable of forming an image as well by mounting the developing device. It can be used to provide a forming apparatus.

PR Printer Y Yellow image forming unit M Magenta image forming unit C Cyan image forming unit K Black image forming unit 1 Photoconductor 2 Charging device 3 Image exposing device 4, 4A, 4B Developing device 40 Developing device housing 41 Developer carrier (development) sleeve)
42 Fixed magnet body 43 First transport member 431 Rotating shaft 432 Screw blades 43a, 43b Bearing member 43s Developer seal member 44 Second transport member 441 Rotating shaft 442 Screw blades 44a, 44b Bearing portion 44s Developer seal member 45 Partition h1, h2 Developer distribution opening 400 Developer regulating member A Developer circulation zone A1 Driving-side developer transport direction switching zone 46, 46A, 46B Developer push-back device 461 Plate (example of developer push-back member)
462 Compression coil spring (example of elastic body)
463 Synthetic resin elastic body 464 Plate-like flexible plate member T Toner replenishing device 5 Cleaning device 6 Primary transfer roller 8 Intermediate transfer belt 81 Driving roller 82 Opposing roller 83 Cleaning device 9 Secondary transfer roller 10 Recording medium supply cassette 101 Recording medium supply roller TR Timing roller pair FX Fixing device DR Recording medium discharge roller pair DT Recording medium discharge tray S Recording medium

Claims (8)

A developing device that develops an electrostatic latent image formed on an electrostatic latent image carrier in an electrophotographic image forming apparatus to form a toner image;
A developer carrier for applying toner to the electrostatic latent image;
A first conveying member that is erected on the developer carrier and conveys the developer in the rotation axis direction by being driven to rotate;
A second conveying member that conveys the developer in the direction of the rotation axis by being rotationally driven and in a direction opposite to the first conveying member;
The developer transport direction switching area from the developer delivery side end of the first transport member to the developer feed side end of the second transport member and the developer delivery side end of the second transport member The developer is stirred and circulated by the first and second transport members while allowing the developer transport direction to be switched in the developer transport direction switching area to the developer feeding side end of the first transport member. A developing device capable of supplying a developer from a first conveying member to the developer carrier,
A developer push-back device is provided on at least one of the developer delivery side end of the first transport member and the developer delivery side end of the second transport member;
The developer push-back device is provided on the developer circulation area side from a bearing portion supporting a part of the conveying member rotating shaft extending to the outside of the developer circulation area at the developer delivery side end. During the developer agitation circulation by the rotation of the conveying member, the developer is retreated by the powder pressure of the developer conveyed to the end of the developer delivery side to provide a part of the developer circulation area, and when the conveying member is stopped, the elastic return is achieved. And a developer that pushes the developer back away from the bearing.   The developer push-back device includes a developer push-back member that is movable in the direction of the transport member rotation axis at the developer delivery side end of the transport member provided with the push-back device, and a developer push-back force applied to the developer push-back member. An elastic body to be applied, and the elastic push-back member retracts due to the powder pressure of the developer conveyed to the developer delivery side end during the developer agitation circulation by the rotation of the conveying member. The developing device according to claim 1, wherein the developer pushing back member is elastically deformed so as to allow it to be pushed, and the developer pushing back member is pushed back by an elastic restoring force when the conveying member is stopped so that the developer moves away from the bearing portion.   The developer push-back device includes a plate-like flexible member disposed on the developer circulation area side from the bearing portion, and the plate-like flexible member is in the developer agitation circulation by the rotation of the conveying member. 2. The developing device according to claim 1, wherein the developer powder is deformed backward and bent so as to provide a part of the developer circulation region by the developer powder pressure, and when the conveying member is stopped, the developer is pushed back away from the bearing portion by elastic restoration. .   4. The developing device according to claim 1, wherein the bearing portion includes a bearing member that rotatably supports a conveying member rotating shaft and a developer seal member that surrounds the conveying member rotating shaft and that supports the bearing member.   5. The developing device according to claim 1, wherein the developer pushing-back device is provided at least at a developer delivery side end of the second conveying member.   The developing device according to claim 5, wherein a developer feeding side end of the second conveying member is disposed below a developer feeding side end of the first conveying member.   The developing device according to claim 5, wherein replenishment toner is replenished to the second conveying member.   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