JP2015138080A - Development apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a development apparatus capable of more effectively reduce developer leakage to outside of a development container when a rib is provided with an agitation screw disposed in the development container.SOLUTION: With an agitation screw 205 provided in the agitation chamber 207 of a development container 200, the shaft diameter of a thin shaft part 205c where a rib 210 is provided in addition to a conveyance vane 205b is configured to be formed thinner than other parts where no rib 210 is formed. Thus, even when being reduced by the rib 210, the capacity in the agitation chamber 207 increases as much as the capacity obtained by thinning the shaft diameter of the thin shaft part 205c. Therefore, it is possible to effectively reduce developer leakage to outside of a development container in a development apparatus where the agitation screw 205 provided with the rib 210 is disposed in the development container.

Description

  The present invention relates to a developing device mounted on an image forming apparatus employing an electrophotographic system or an electrostatic recording system. In particular, the present invention relates to a technique for more effectively reducing developer leakage to the outside of a developing container in a developing device including a conveying screw provided with a rib in the developing container.

  2. Description of the Related Art Conventionally, developing devices that develop an electrostatic latent image formed on an image carrier into a toner image with a developer are known. In the developing device, the developer is not only transported through the developing container by the transport screw but also by the rotating developing sleeve. That is, a part of the developer in the developing container is supplied from the developing container to the developing sleeve, and is conveyed so as to be returned from the developing sleeve to the developing container.

  By the way, there is a case where a portion where there is almost no space for accommodating the developer is generated in the developing container due to the retention of the developer. In that case, most of the developer conveyed by the developing sleeve cannot be accommodated at the location, and the developer may leak out of the developing container without being returned to the developing container. In view of this, there has been proposed a developing device that improves the developer conveying force by providing ribs on the conveying screw (Patent Document 1). In this developing apparatus, a space where the developer can be stored is improved by improving the developer conveying force at the portion where the developer tends to stay, specifically, at both ends of the conveying screw, and reducing the amount of the developer staying at the portion. To prevent developer leakage.

JP-A-7-181787

  As described above, when ribs are provided at both ends of the conveying screw, the developer conveying force at the portions where the ribs are provided is improved, which contributes to securing a space that can accommodate the developer at the portions. However, since the volume in the developing container is reduced by the volume occupied by the rib at the location where the rib is provided, the amount of developer that can be accommodated at the location is reduced. If the amount of developer that can be stored is small, it becomes difficult to secure a space for storing the developer even if the developer conveying force is improved by the ribs, and eventually developer leakage occurs.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in the case where a rib is provided on a conveying screw disposed in a developing container, it is possible to more effectively reduce developer leakage outside the developing container. An object is to provide a developing device.

  The developing device according to the present invention includes a developer carrying member that carries a developer and develops an electrostatic latent image formed on the image carrying member, a developing container that contains the developer, and a rotation within the developing container. And a conveying means that is freely provided and conveys the developer in the developer container. The conveying means conveys the developer to a rotating shaft, and conveys the developer to a part of the rotating shaft. A rib member protruding in the radial direction in addition to the blade, and a shaft diameter of a part of the rotating shaft provided with the rib member is an axis of another portion of the rotating shaft not provided with the rib member It is characterized by being thinner than the diameter.

  According to the present invention, the conveying means provided in the developing container is configured such that the shaft diameter of a part of the rotating shaft provided with the rib member in addition to the conveying blade is the diameter of the other portion where the rib member is not provided. It is thinner than. If the shaft diameter of the rotating shaft at the portion where the rib is provided is thin, a space for accommodating the developer is secured in the developing container at the portion, and thus the leakage of the developer outside the developing container by the rib member is more effectively reduced. Can be realized.

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus to which a developing device according to the present invention is applied. 1 is a schematic cross-sectional view illustrating an overall configuration of a developing device according to the present invention. It is a schematic sectional drawing for demonstrating one Example of a conveyance means. It is a schematic sectional drawing for demonstrating another Example of a conveying means.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The developing device according to the present invention is applied to an image forming apparatus described below, but is not limited thereto, and can be applied to other image forming apparatuses. That is, the image forming apparatus can be implemented without distinction between a tandem type / 1 drum type and an intermediate transfer type / direct transfer type. In this embodiment, only main parts related to toner image formation / transfer will be described. However, in the present invention, a printer, various printing machines, a copier, a FAX, It can be implemented in various applications such as a multifunction machine.

  The developing device according to the present invention will be described with reference to FIGS. First, a schematic configuration of an image forming apparatus to which a developing device according to the present invention is applied will be described with reference to FIG.

[Image forming apparatus]
The image forming apparatus shown in FIG. 1 forms a toner image on a photosensitive drum 100, and is a transfer material that is a recording material (sheet, sheet material such as an OHP sheet) that is carried by the transfer material conveyance belt 106 Transfer to paper 110. The transfer paper 110 onto which the toner image has been transferred is sent from the transfer material conveying belt 106 to the fixing device 105. The transfer paper 110 is heated / pressurized by the fixing device 105 to fix the toner image on the surface, and then is discharged to the outside of the machine body.

  As shown in FIG. 1, the image forming apparatus includes a primary charger 101, a developing device 102, a transfer roller 103, and a drum cleaning device 104 that surround a photosensitive drum 100 that is an image carrier. A photosensitive layer is formed on the outer peripheral surface of the photosensitive drum 100, and the photosensitive drum 100 rotates at a predetermined process speed in the direction of arrow R1 in the figure.

  The primary charger 101 irradiates charged particles accompanying corona discharge, for example, to charge the photosensitive drum 100 to a uniform negative dark potential. The surface of the charged photosensitive drum 100 is exposed to an image by a laser beam (indicated by an arrow L in FIG. 1) that is irradiated from a laser exposure device (not shown) and modulated based on an image signal. An image is formed. The developing device 102 supplies toner to the photosensitive drum 100 to develop the electrostatic latent image into a toner image. Since the developing device 102 will be described later, a description thereof is omitted here.

  The transfer roller 103 is pressed against the transfer material conveyance belt 106 to form a toner image transfer portion between the photosensitive drum 100 and the transfer material conveyance belt 106. By applying a DC voltage having a polarity opposite to the charging polarity of the toner to the transfer roller 103, the toner image carried on the photosensitive drum 100 is transferred to the transfer paper 110 on the transfer material conveyance belt 106. The so-called transfer residual toner remaining on the photosensitive drum 100 after the transfer is removed by the drum cleaning device 104.

  Here, the method of directly transferring the toner image from the photosensitive drum 100 to the transfer paper 110 conveyed to the transfer material conveyance belt 106 has been described, but the present invention is not limited to this. For example, an intermediate transfer member is provided in place of the transfer material conveyance belt 106, and after the toner image is primarily transferred from the photosensitive drum 100 to the intermediate transfer member, the toner image is secondarily transferred from the intermediate transfer member to the transfer paper 110. The present invention can also be applied to an image forming apparatus having a configuration.

[Developer]
The developing device 102 shown here uses an electrostatic latent image formed on the photosensitive drum 100 using a two-component developer containing a negatively charged toner (nonmagnetic) and a positively charged carrier (low magnetization high resistance). Develop the image into a toner image. Therefore, the two-component developer will be described.

  The toner is made of a binder resin such as styrene resin or polyester resin, a colorant such as carbon black, a dye, or a pigment, and, if necessary, other colored resin particles containing other additives and colloidal silica fine powder. And colored particles to which an additive is externally added. The volume average particle diameter of the toner is preferably 5 to 8 [μm]. As an example, a toner having a negative charge characteristic polyester-based resin and a volume average particle size of 7.0 [μm] may be used.

As the carrier, for example, metal such as surface-oxidized or unoxidized iron, nickel, cobalt, manganese, chromium, rare earth, alloys thereof, or oxide ferrite can be preferably used. The method for producing these magnetic particles is not particularly limited. The volume average particle diameter of the carrier is 20 to 50 [μm], preferably 30 to 40 [μm]. The resistivity of the carrier is 10 ⁵ [Ωm] or more, preferably 10 ⁶ [Ωm] or more. As an example, a magnetic carrier having a volume average particle size of 40 [μm], a resistivity of 5 × 10 ⁵ [Ωm], and a magnetization of 0.31 [Wb / m ² ] in a magnetic field of 100 [mT] is used. Good.

[Developer]
The developing device 102 according to the present invention will be described in detail with reference to FIG. A developing device 102 shown in FIG. 2 is a vertical stirring type developing device. The developing device 102 includes a developing container 200, a developing sleeve 201 as a developer carrying member, and a regulating blade 203 as a developer regulating member. The developing container 200 contains a two-component developer containing a nonmagnetic toner and a magnetic carrier as a developer. The inside of the developing container 200 is divided into a developing chamber 206 as a first chamber and an agitating chamber 207 as a second chamber by a partition wall 208 extending in a direction perpendicular to the paper surface at a substantially central portion. The upper developing chamber 206 and the lower agitating chamber 207 communicate with each other vertically at both ends to form a developer circulation path (see FIG. 3 described later).

  A developing screw 204 serving as a first transport unit is rotatably disposed in the developing chamber, and a stirring screw 205 serving as a second transport unit is rotatably disposed in the stirring chamber. Although details of the developing screw 204 and the agitating screw 205 will be described later, the developer is circulated and conveyed through the developing container while being agitated by the rotation of the screws 204 and 205. As the developer is stirred, the toner is negatively charged and the carrier is positively charged. Along with the circulating conveyance of the developer, a part of the developer in the developing chamber 206 is supplied to the rotating developing sleeve 201 by the magnetic force of the magnet roller 202. The supplied developer is carried on the developing sleeve 201 and conveyed from the developing chamber 206 to the stirring chamber 207. The rotation speed of each of the screws 204 and 205 at the time of stirring / conveying the developer is set to 400 [rpm], for example.

  The developing sleeve 201 is partly exposed from the opening of the developing container 200 disposed at a position facing the photosensitive drum 100 and is rotatably disposed in the developing container 200. For example, the diameter of the developing sleeve 201 is 24.5 [mm], the diameter of the photosensitive drum 100 is 80 [mm], and the interval between the locations where the developing sleeve 201 and the photosensitive drum 100 are closest is about 300 [μm]. It is good to set to. With these settings, the toner image can be developed with the developer carried and transported by the developing sleeve 201 in contact with the photosensitive drum 100. The developing sleeve 201 is formed in a cylindrical shape with a nonmagnetic material such as aluminum or stainless steel (SUS), and a magnet roller 202 as a magnetic field generating means is fixedly disposed therein.

  The magnet roller 202 has a magnetic pole S1 that is a developing pole and magnetic poles S2, N1, N2, and N3 for transporting the developer. Here, in the development area A, the magnetic pole S <b> 1 is disposed to face the photosensitive drum 100, and the magnetic pole S <b> 2 is disposed to face the regulating blade 203. A magnetic pole N1 is arranged between the magnetic poles S1 and S2, a magnetic pole N2 is arranged upstream of the magnetic pole S2 in the developing sleeve rotation direction (in the direction of arrow R2 in the figure), and a magnetic pole N3 is arranged downstream of the magnetic pole S1 in the developing sleeve rotation direction. doing.

  The developer is supplied from the developing chamber 206 to the developing sleeve 201 by the magnetic force of the magnet roller 202. The supplied developer is carried on the developing sleeve 201. At this time, magnetic spikes of the developer are formed on the surface of the developing sleeve. In accordance with the rotation of the developing sleeve 201, the magnetic spike is fed to the developing area A with the layer thickness regulated by the regulating blade 203. The regulating blade 203 is a plate-like member made of a nonmagnetic material such as aluminum, and is disposed along the longitudinal direction of the developing sleeve 201 on the upstream side in the developing sleeve rotation direction from the photosensitive drum 100. By adjusting the gap (gap) between the tip of the regulating blade 203 and the developing sleeve surface, the amount of magnetic spikes formed on the developing sleeve surface is regulated, and the amount of developer conveyed to the developing area A is reduced. Adjusted. The gap (gap) is set to 350 [μm], for example.

  The developing sleeve 201 rotates in the same direction as the opposing photosensitive drum 100 (in the direction of arrow R2 in the figure) while carrying the developer whose layer thickness is regulated by the cutting of the magnetic ears by the regulating blade 203, and the carried development. The agent is conveyed to the development area A. In the development area A, the tips of the magnetic spikes rub against the photosensitive drum 100 and supply toner to the electrostatic latent image formed on the photosensitive drum 100 to develop the electrostatic latent image into a toner image. At this time, in order to improve the development efficiency, that is, the application rate of toner to the electrostatic latent image, a developing bias voltage in which an AC voltage is superimposed on a DC voltage is applied to the developing sleeve 201 from a power source (not shown). For example, an oscillating voltage obtained by superimposing a square-wave AC voltage having a peak-to-peak voltage of 1.5 [kV] and a waveform of 3 [kHz] on a predetermined DC voltage is applied. Of course, the AC voltage value and the waveform are not limited to these. When the AC voltage is superimposed, the development efficiency increases and the image becomes high quality, but conversely, a white background fog in which toner adheres to a white background easily occurs. In order to prevent this fogging, it is preferable to provide a potential difference between the DC voltage applied to the developing sleeve 201 and the charging potential of the photosensitive drum 100 (that is, the white background portion potential).

  When the electrostatic latent image formed on the photosensitive drum 100 is developed into a toner image, the toner contained in the developer is consumed. Therefore, a replenishment developer for replenishing the toner is automatically replenished into the stirring chamber 207 from the replenishing port 209 (see FIG. 3). That is, the replenishment developer is filled in a hopper (not shown) connected to the replenishing port 209, and is conveyed to the replenishing port 209 and replenished into the stirring chamber 207 according to the rotation of a screw provided in the hopper. The replenishment timing of the replenishment developer may be a predetermined timing such as when the weight ratio of the toner to the developer accommodated in the developer container is less than 8%, for example. The toner weight ratio may be calculated based on, for example, the average magnetic permeability of the developer detected by a magnetic permeability sensor (not shown) disposed in the developing container.

  In the magnet roller 202, the magnetic pole N2 and the magnetic pole N3 having the same polarity are arranged at adjacent positions. Therefore, a repulsive magnetic field is formed between these poles. The developer carried on the developing sleeve is separated from the surface of the developing sleeve by the repulsive magnetic field, and the separated developer is accommodated in the stirring chamber 207. That is, the developer is supplied to the developing sleeve 201 in the developing chamber 206 and is collected from the developing sleeve 201 in the stirring chamber 207.

<Example 1>
The developing screw 204 and the stirring screw 205 will be described with reference to FIG. As shown in FIG. 3, each of the developing screw 204 and the stirring screw 205 is formed with a series of conveying blades (204b, 205b) made of a nonmagnetic material in a spiral shape around the rotation shafts (204a, 205a, 205c). ing. The conveying blades (204b, 205b) are formed so that, for example, the outer radius is 10 [mm] and the screw pitch is 30 [mm].

  The developing screw 204 is disposed in the developing chamber 206 substantially in parallel along the rotation axis of the developing sleeve 201 (see FIG. 2). On the other hand, the stirring screw 205 is disposed in the stirring chamber 207 substantially in parallel with the developing screw 204. When the developing screw 204 rotates, the developer T in the developing chamber 206 is conveyed in one direction along the rotation axis of the developing screw 204 from left to right in FIG. On the other hand, when the agitating screw 205 rotates, the developer T in the agitating chamber 207 moves along the rotation axis of the agitating screw 205 in one direction from the right to the left in FIG. Are conveyed in the opposite direction. Thus, the developer T is transported in the direction indicated by the arrow R3 in the drawing according to the rotation of the developing screw 204 and the agitating screw 205, and through the openings 220 and 221 provided at both ends of the partition wall 208, the developing chamber 206 and the agitating chamber. Cycle between 207 and 207.

  The developer T in the developing chamber 206 falls from the opening 221 due to gravity and is transferred to the stirring chamber 207. On the other hand, the developer T in the stirring chamber 207 is pushed upward from the bottom against gravity in the opening 220 and is transferred to the developing chamber 206. The pushing-up of the developer T from the stirring chamber 207 to the developing chamber 206 is performed by applying pressure to the developer T staying on the downstream side of the stirring chamber 207 in the transport direction. This pressure is generated when the developer T is transported to the downstream side in the transport direction by the stirring screw 205 and the developer T staying on the downstream side in the transport direction is pushed into the side wall 200a side of the developing container 200.

  As described above, the developer T is delivered to the developing chamber 206 against the gravity on the downstream side of the stirring chamber 207 in the transport direction. Therefore, on the downstream side of the stirring chamber 207 in the transport direction, the ratio of the developer T in the stirring chamber 207 (hereinafter referred to as developer ratio) tends to be high. Further, since the developer T supplied from the developing chamber 206 to the developing sleeve 201 is collected in the stirring chamber 207 without being returned to the developing chamber 206, the developer ratio tends to be high throughout the stirring chamber 207. That is, in the vertical stirring type developing device, the developer staying in the stirring chamber 207 tends to be relatively larger than that in the developing chamber 206. In particular, a large amount of the developer T tends to stay at the position of the opening 220 that transfers the developer T from the stirring chamber 207 to the developing chamber 206 (see the thin shaft region B), that is, downstream in the transport direction of the stirring chamber 207. .

  By the way, if the transport efficiency of the developer T is insufficient on the downstream side of the stirring chamber 207 in the transport direction, a large amount of the developer T stays on the downstream side of the stirring chamber 207 in the transport direction, It is difficult to secure a space for accommodating T. In such a case, even if the developer T is transported by the developing sleeve 201, the developer T loses its place and is not stored (collected) in the stirring chamber 207 and leaks out from the lower portion of the developing sleeve 201 to the outside of the developing container. End up. The leaked developer T causes a failure of the apparatus.

  Therefore, in order to solve this problem, a rib member 210 (hereinafter simply referred to as a rib) is provided on the downstream side of the agitating screw 205 in the conveying direction so that the developer conveying force in the vertical direction at that location is higher than that at other locations. Improve. Therefore, the rib 210 is formed in a plate shape having, for example, an axial length (width) of 10 [mm], a radial length (height) of 5 [mm], and a thickness of 1 [mm]. Further, it is formed so as to protrude in a non-contact and radial direction with respect to the conveying blade (205b). Since the rib 210 positively pushes up the developer T and transfers it from the stirring chamber 207 to the developing chamber 206, the developer conveying force is improved.

  However, when the rib 210 is provided on the stirring screw 205, the volume of the stirring chamber 207 is reduced by the amount occupied by the rib at the position where the rib 210 is provided, and the amount of developer that can be accommodated in the stirring chamber 207 is reduced at that location. Less. If it does so, even if it improves the conveyance power of a developer by the rib 210, the space which can accommodate a developer cannot be ensured, but a developer leak may arise. That is, simply providing the rib 210 makes it difficult to greatly improve the leakage of the developer T conveyed by the developing sleeve 201 to the outside of the developing container. Therefore, in the present invention, the effect of improving the developer conveying force by the ribs 210 is further enhanced by making up for the volume of the stirring chamber 207 that is reduced by providing the ribs 210. Therefore, in the stirring screw 205, the rotation shaft (205c) at the place where the rib 210 is provided is thinner than the other places.

  This will be specifically described. The rotating shaft 204a of the developing screw 204 is formed to have the same diameter of, for example, 6 [mm] over the entire length. On the other hand, the rotating shaft 205a of the stirring screw 205 is not formed with the same diameter over the entire length, but a part thereof is formed with a different shaft diameter. More specifically, a part of a shaft portion 205c (hereinafter referred to as a thin shaft portion) of the rotating shaft 205a located within a predetermined range (thin shaft region B) from the end of the rotating shaft 205a, which is on the downstream side in the conveying direction of the stirring screw 205. Called) having a shaft diameter of 4 [mm]. The shaft portions other than the thin shaft portion 205c are formed to have the same shaft diameter of 6 [mm] as the rotation shaft 204a of the developing screw 204. That is, the stirring screw 205 has a series of rotating shafts (205a, 205c) in which the shaft diameter on the downstream side in the transport direction is narrower than the shaft diameter on the upstream side in the transport direction. The rib 210 described above is provided on the thin shaft portion 205c having a thin shaft diameter. In other words, a part of the rotation shaft 205a of the portion where the rib 210 is provided (thin shaft region B) is formed in the thin shaft portion 205c having a smaller shaft diameter than the shaft portion of the other portion.

  As described above, since the shaft diameter of the portion where the rib 210 is provided in the rotating shaft 205a of the stirring screw 205 is made smaller than the shaft diameter of other portions, the volume of the stirring chamber 207 is reduced by the rib 210. However, it is possible to make up for the volume corresponding to the reduced shaft diameter. That is, it is possible to secure a space for storing the developer in the stirring chamber 207 as compared with the conventional case. This improves the leakage of the developer T conveyed by the developing sleeve 201 to the outside of the developing container when the rib 210 is provided in the stirring screw 205 and the developer conveying force is improved. be able to. That is, the developer leakage can be more effectively reduced as compared with the case where the rib 210 is simply provided on the stirring screw 205.

  In general, in view of the fact that the thinner the rotating shaft, the weaker the strength, the stirring screw 205 having the thin shaft portion 205c can be said to be easily bent or twisted. If the agitating screw 205 is bent or twisted, the agitating screw 205 cannot efficiently transport the developer, and the possibility that the rotating shaft breaks increases. As described above, the thin shaft portion 205c is formed with a thin shaft diameter. If so, the above is also considered to apply to the thin shaft portion 205c. However, the thin shaft portion 205c is provided with ribs 210 along the axial direction. Therefore, the strength of the thin shaft portion 205c is secured by the rib 210, and the above-described stirring screw 205 is less likely to be bent or twisted.

<Example 2>
FIG. 4 is a schematic cross-sectional view for explaining another embodiment of the conveying means. The second embodiment is different from the first embodiment in the rib 210 provided on the thin shaft portion 205 c of the stirring screw 205. As shown in FIG. 4, the rib 210 is provided integrally with the conveying blade 205 b so as to connect adjacent conveying blades 205 b at the same circumferential position. That is, in this case, the rib 210 is formed to have an axial direction (longitudinal direction) length of 30 [mm] which is the same as the screw pitch. The length in the radial direction is 6 [mm] and the thickness is 1 [mm]. That is, compared with the case of Example 1, the rib 210 with the same thickness but larger area is provided. If the area of the rib 210 is large, the developer conveying force from the stirring chamber 207 to the developing chamber 206 is increased, which is advantageous from the viewpoint of improving the developer conveying force as compared with the first embodiment.

  On the other hand, if the rib 210 having a larger area is provided, the amount of developer that can be accommodated at the place where the rib 210 is provided is reduced, which is disadvantageous from that viewpoint. Therefore, in the second embodiment, in order to solve this point, the thin shaft portion 205c provided with the rib 210 is formed to have a thinner shaft diameter than the first embodiment. For example, in Embodiment 1, the thin shaft portion 205c is formed with a shaft diameter of 4.0 [mm], but in Embodiment 2, the thin shaft portion 205c is formed with a shaft diameter of 3.5 [mm]. As described above, in accordance with the provision of the rib 210 having a larger area compared to the first embodiment, the shaft diameter of the thin shaft portion 205c is made thinner, so that the volume occupied by the rib 210 is compensated. The volume in 207 is secured. Thereby, a space for accommodating the developer in the stirring chamber 207 is secured.

  From the above, the same effects as in the first embodiment can be obtained in the second embodiment. In other words, since the developer can be efficiently transferred from the stirring chamber 207 to the developing chamber 206 without impairing the volume of the stirring chamber 207, the developer leakage can be reduced more effectively than in the prior art. .

  In the second embodiment, since the thin shaft portion 205c is formed to be thinner than the first embodiment, it can be said that the thin shaft portion 205c is more likely to bend or twist compared to the first embodiment. However, the strength of the thin shaft portion 205c is ensured by integrally providing the rib 210 and the conveying blade 205b on the thin shaft portion 205c. Therefore, although the thin shaft portion 205c has a thinner shaft diameter than the first embodiment, the stirring screw 205 is less likely to be bent or twisted.

  In the above-described embodiments, the developing screw 204 and the agitation screw 205 are illustrated as having the conveying blades (204b, 205b) formed in a spiral around the rotation shafts (204a, 205a, 205c). Absent. For example, the developing screw 204 and the agitation screw 205 may have a plurality of elliptical plates that are attached to the rotation shafts (204a, 205a, and 205c) at a constant inclination angle.

  In the above-described embodiment, the developing device 102 provided with only one developing sleeve 201 has been described as an example, but a plurality of developing sleeves may be provided. For example, the present invention can be applied to a developing device having a configuration in which two developing sleeves are arranged in the upper and lower stages.

DESCRIPTION OF SYMBOLS 100 ... Photosensitive drum, 102 ... Developing apparatus, 200 ... Developing container, 201 ... Developing sleeve 204 ... Developing screw, 205 ... Stir screw, 204a, 205a ... Rotating shaft 204b, 205b ... Conveying blade, 205c ... Thin shaft part, 206 ... Development chamber, 207 ... Stirring chamber 210 ... Rib, A ... Development area, B ... Fine axis area, T ... Developer

Claims (7)

A developer carrying member that carries the developer and develops the electrostatic latent image formed on the image carrying member;
A developer container containing the developer;
A conveying means that is rotatably provided in the developing container and conveys the developer in the developing container,
The conveying means is provided with a conveying blade for conveying the developer to the rotating shaft, and a rib member protruding in the radial direction in addition to the conveying blade on a part of the rotating shaft. A developing device characterized in that a part of the rotation shaft has a diameter smaller than that of other portions of the rotation shaft where the rib member is not provided.   The developing device according to claim 1, wherein the rib member is formed integrally with the conveying blade.   The developing device according to claim 1, wherein the transport blade is formed in a spiral shape on the rotation shaft. A developer carrying member that carries the developer and develops the electrostatic latent image formed on the image carrying member;
A first chamber for supplying a developer to the developer carrier;
A second chamber that communicates with the first chamber to form a developer circulation path, delivers the developer to and from the first chamber, and collects the developer carried on the developer carrier;
A first conveying means provided in the first chamber for conveying the developer in the first chamber in one direction;
A second conveying means provided in the second chamber for conveying the developer in the second chamber in a direction opposite to the first chamber;
The second conveying means includes a conveying blade for conveying the developer to the rotating shaft, and the conveying blade on a part of the rotating shaft on the downstream side in the conveying direction where the developer is transferred between the first chamber. And a rib member projecting in the radial direction is provided, and the shaft diameter of a part of the rotation shaft provided with the rib member is equal to the shaft diameter of another part of the rotation shaft not provided with the rib member. A developing device characterized by being thinner.   The developing device according to claim 4, wherein the rib member is formed integrally with the conveying blade.   The developing device according to claim 4, wherein the conveying blade is formed in a spiral shape on the rotating shaft.   The developing device according to claim 4, wherein the first chamber is disposed in an upper stage, and the second chamber is disposed in a lower stage.

Images