JP2020201307A - Developing device - Google Patents

Abstract

To obtain high stirring properties while maintaining conveyability even with a small amount of developer.SOLUTION: A developing device has a developer container having a developing chamber that supplies developer to a developing sleeve and a stirring chamber that forms a circulation path of the developer with the developing chamber, and a second conveying screw 65 that is disposed in the stirring chamber and conveys the developer in a forward direction F. The second conveying screw 65 has a first blade part 81 in a spiral shape, a second blade part 82 that has a spiral shape in the same direction as the first blade part 81, a third blade part 83 that is provided continuously between the first blade part 81 and the second blade part 82 and has a spiral shape with a narrower pitch in the same direction as the first blade part 81 and the second blade part 82, and a notch part 83b in a shape in which part of an outer peripheral part of the third blade part 83 is cut out. The third blade part 83 is arranged at a position opposite to part of an area from an end in a rearward direction R of a second communication port to an end in the forward direction F of a first communication port.SELECTED DRAWING: Figure 4

Description

The present invention relates to a developing apparatus applied to an image forming apparatus using an electrophotographic method or an electrostatic recording method.

Conventionally, electrophotographic and electrostatic recording image forming devices have been widely applied as copiers, printers, facsimiles, and multifunction devices having a plurality of these functions. In general, a developing device provided in an electrophotographic or electrostatic recording type image forming apparatus includes a one-component developer containing magnetic toner as a main component or a two-component developing agent containing non-magnetic toner and a magnetic carrier as main components. One of the agents is used. In particular, in an image forming apparatus that forms a full-color or multi-color image by an electrophotographic method, a two-component developer is used in most developing apparatus from the viewpoint of image tint and the like.

In a developing apparatus using such a two-component developer, a stirring member for sufficiently stirring the replenished toner and the carrier has been developed. For example, it is known that a transport screw that transports a developer in a developing container of a developing apparatus is provided with a stirring rib as a stirring member along the transport direction to improve stirring performance (see, for example, Patent Document 1). ..

Japanese Unexamined Patent Publication No. 2003-270947

By the way, in recent years, with the miniaturization of the image forming apparatus, the amount of the developing agent contained in the developing apparatus has decreased. Further, the speed of the image forming process in the image forming apparatus is also increasing, and the amount of replenished toner replenished per unit time is increasing accordingly. Therefore, it is necessary to quickly agitate the replenishing toner with respect to a small amount of the developer in the developing apparatus as compared with the conventional case.

However, in the developing apparatus described in Patent Document 1, since the transport screw is provided with a stirring rib along the transport direction, if the amount of toner to be transported is small, it easily passes through the region provided with the stirring rib, and the stirring property is poor. It was enough. Therefore, even if it is desired to quickly agitate the replenishing toner with respect to a small amount of the developer, the developing apparatus described in Patent Document 1 cannot sufficiently agitate the toner, and the image quality of the formed image deteriorates. There is a risk that it will end up.

An object of the present invention is to provide a developing apparatus capable of obtaining high agitation while maintaining transportability even when the amount of the developing agent is small.

In the developing apparatus of the present invention, a developing agent carrier that carries and rotates a developing agent, a first chamber that supplies the developing agent to the developing agent carrier, and the first chamber form a circulating path for the developing agent. A developing container having a second chamber, a first transport screw disposed in the first chamber and transporting the developer in the first direction, and a developing screw disposed in the second chamber and in the first direction. The developer is received from the second chamber to the first chamber by separating the first chamber and the second chamber inside the developing container and the second conveying screw that conveys the developer in the opposite second direction. A partition wall having a first communication port to be passed and a second communication port provided on the upstream side of the first communication port in the second direction and passing the developing agent from the first chamber to the second chamber. The developing apparatus includes a first blade portion having a spiral shape, a second blade portion having a spiral shape in the same direction as the first blade portion, the first blade portion, and the first blade portion. A third blade portion which is continuously provided between the two blade portions and has a spiral shape having a spiral shape having a pitch narrower than that of the first blade portion and the second blade portion in the same direction as the first blade portion and the second blade portion. And a notch portion having a shape in which a part of the outer peripheral portion of the third blade portion is cut out, and the third blade portion is an upstream end of the second communication port in the second direction. It is characterized in that it is arranged at a position facing a part of the region from the portion to the end on the downstream side in the second direction of the first communication port.

Further, in the developing apparatus of the present invention, a developing agent carrier that carries and rotates a developing agent, a first chamber that supplies the developing agent to the developing agent carrier, and a circulation path of the developing agent in the first chamber. A developing container having a second chamber forming the above, a first transport screw arranged in the first chamber and conveying the developer in the first direction, and a first conveying screw arranged in the second chamber. The developer is transferred from the second chamber to the first chamber by separating the first chamber and the second chamber inside the developing container and the second conveying screw that conveys the developer in the second direction opposite to the direction. A partition wall having a first communication port for delivering a developing agent and a second communication port provided on the upstream side in the second direction from the first communication port and delivering a developing agent from the first chamber to the second chamber. The second transport screw is a developing apparatus including, the first blade portion having a spiral shape, the second blade portion having a spiral shape in the same direction as the first blade portion, the first blade portion, and the first blade portion. A third blade portion that is continuously provided between the second blade portions and has a spiral shape in the direction opposite to the first blade portion and the second blade portion, and a part of the outer peripheral portion of the third blade portion. The third blade portion has a notch portion having a notched shape, and the third blade portion is from the upstream end portion of the second communication port in the second direction to the second direction of the first communication port. It is characterized in that it is arranged at a position facing a part of the region up to the end on the downstream side.

According to the present invention, even if the amount of the developer is small, high stirring property can be obtained while maintaining transportability.

It is sectional drawing of the image forming apparatus which concerns on 1st Embodiment. It is sectional drawing of the developing apparatus which concerns on 1st Embodiment. It is a vertical sectional view of the developing apparatus which concerns on 1st Embodiment. It is a perspective view of the 3rd blade part of the 2nd transport screw which concerns on 1st Embodiment. It is a graph which shows the relationship between the blade angle and the outer peripheral length in the transfer screw which concerns on 1st Embodiment. It is a perspective view of the 3rd blade part of the 2nd transport screw which concerns on 2nd Embodiment.

<First Embodiment>
Hereinafter, the first embodiment of the present invention will be described in detail with reference to FIGS. 1 to 5. First, the schematic configuration of the image forming apparatus of this embodiment will be described with reference to FIG.

[Image forming device]
The image forming apparatus 1 of the present embodiment is an electrophotographic tandem full-color printer provided with four image forming units PY, PM, PC, and PK each having a photosensitive drum 3 as an image carrier. The image forming apparatus 1 records a toner image (image) according to an image signal from a host device such as a personal computer or the like, which is communicably connected to the document reading device 2 connected to the apparatus main body 10 or the apparatus main body 10. Form to. Examples of the recording material include sheet materials such as paper, plastic film, and cloth (hereinafter, abbreviated as sheets). Further, the image forming portions PY, PM, PC, and PK form toner images of yellow, magenta, cyan, and black, respectively.

The four image forming units PY, PM, PC, and PK included in the image forming apparatus 1 have substantially the same configuration except that the developed colors are different. Therefore, here, the image forming unit PY will be described as a representative, and the description of other image forming units will be omitted.

The image forming apparatus 1 includes a control unit 12. The control unit 12 is composed of a computer, and includes, for example, a CPU, a ROM that stores a program that controls each unit, a RAM that temporarily stores data, and an input / output circuit that inputs / outputs signals to and from the outside. The CPU is a microprocessor that controls the entire control of the image forming apparatus 1, and is the main body of the system controller. The CPU is connected to a sheet feeding unit, an image forming unit PY, PM, PC, PK, a sheet conveying unit, and the like via an input / output circuit, and exchanges signals with each unit and controls operations.

[Image forming part]
The image forming unit PY includes a photosensitive drum 3, a charging roller 4, an exposure device 5, a developing device 6, a primary transfer roller 7, and a cleaning blade 8. The photosensitive drum 3 and the charging roller 4 are rotatably supported by the drum container 51, and the charging roller 4 and the cleaning blade 8 are supported in a state of being pressed against the photosensitive drum 3. The photosensitive drum 3, the charging roller 4, the cleaning blade 8, and the drum container 51 form a drum cartridge 50, and are removable from the apparatus main body 10.

As the rotatable image carrier, the photosensitive drum 3 is a cylindrical (drum type) electrophotographic photosensitive member having a photosensitive layer which is an organic optical semiconductor having negative charging characteristics. The photosensitive drum 3 has a diameter of 30 mm and a length in the longitudinal direction of 360 mm, is driven and connected to a drive source (not shown) built in the apparatus main body 10, and has a process speed (peripheral speed) of 250 mm / sec. It rotates by the driving force. Since the charging roller 4 is pressed by the photosensitive drum 3, it rotates in accordance with the photosensitive drum 3. As the exposure apparatus 5, a laser beam scanner provided with a semiconductor laser that irradiates the photosensitive drum 3 charged by the charging roller 4 with laser light is applied.

A transfer device 20 is arranged above each image forming unit PY, PM, PC, and PK. The transfer device 20 is configured such that an endless intermediate transfer belt 21 is stretched on a plurality of rollers and orbits (rotates) in the direction of an arrow. Then, the intermediate transfer belt 21 carries and conveys the toner image that has been primarily transferred to the intermediate transfer belt 21. The secondary transfer outer roller 23 is arranged at a position where the secondary transfer inner roller 22 and the intermediate transfer belt 21 are opposed to each other among the rollers for tensioning the intermediate transfer belt 21, and the toner image on the intermediate transfer belt 21 is arranged. Consists of a secondary transfer unit T2 that transfers the sheet S to the sheet S. A fixing device 30 is arranged downstream of the secondary transfer unit T2 in the sheet transport direction. Above the transfer device 20, a storage container 9 for replenishing the developing device 6 with a developing agent for replenishment is arranged.

A cassette 40 containing the sheet S is arranged below the image forming apparatus 1. The sheet S fed from the cassette 40 is conveyed toward the registration roller 42 by the transfer roller 41. Then, the tip of the sheet S abuts against the registration roller 42 in the stopped state, and a loop is formed to correct the skew of the sheet S. After that, the registration roller 42 starts rotating in synchronization with the toner image on the intermediate transfer belt 21, and the sheet S is conveyed to the secondary transfer unit T2.

The process of forming, for example, a four-color full-color image by the image forming apparatus 1 configured as described above will be described. First, when the image forming operation is started, the surface of the rotating photosensitive drum 3 is uniformly charged by the charging roller 4. Next, the photosensitive drum 3 is exposed by a laser beam corresponding to the image signal emitted from the exposure apparatus 5, and an electrostatic image corresponding to the image signal is formed on the photosensitive drum 3. The electrostatic image on the photosensitive drum 3 is visualized by the toner as a developing agent contained in the developing device 6 and becomes a visible image.

The toner image formed on the photosensitive drum 3 is formed on the intermediate transfer belt 21 by the primary transfer unit T1 (see FIG. 2) formed between the toner image and the primary transfer roller 7 arranged on the intermediate transfer belt 21. Primary transcription. At this time, a primary transfer bias is applied to the primary transfer roller 7. The transfer residual toner remaining on the surface of the photosensitive drum 3 after the primary transfer is removed by the cleaning blade 8.

Such an operation is sequentially performed by the yellow, magenta, cyan, and black image forming portions PY, PM, PC, and PK, and the toner images of four colors are superimposed on the intermediate transfer belt 21. After that, the sheet S housed in the cassette 40 is conveyed to the secondary transfer unit T2 at the timing of forming the toner image. Then, by applying the secondary transfer bias to the secondary transfer outer roller 23, the four-color toner images on the intermediate transfer belt 21 are collectively secondary-transferred onto the sheet S. The toner that cannot be completely transferred by the secondary transfer unit T2 and remains on the intermediate transfer belt 21 is removed by the intermediate transfer belt cleaner 24.

Next, the sheet S is conveyed to the fixing device 30. The fixing device 30 includes a fixing roller 31 and a pressure roller 32 having a heat source such as a halogen heater inside, and the fixing roller 31 and the pressure roller 32 form a fixing nip portion. The sheet S is heated and pressurized by passing the sheet S on which the toner image is transferred through the fixing nip portion of the fixing device 30. Then, the toner on the sheet S is melted and mixed, and fixed on the sheet S as a full-color image. After that, the sheet S is discharged to the discharge tray 11 by the discharge roller 43. This completes a series of image formation processes.

The image forming apparatus 1 of the present embodiment forms a monochromatic or multicolored image by using an image forming unit for some of desired monochromatic or four colors, such as a black monochromatic image. Is also possible.

[Developer]
Next, the detailed configuration of the developing apparatus 6 will be described with reference to FIGS. 2 and 3. In the present embodiment, the developing device 6 constitutes a developing cartridge in the form of a cartridge. The developing apparatus 6 includes a developing container 60 containing a developing agent containing a non-magnetic toner and a magnetic carrier, and a developing sleeve (development) which is a cylindrical rotating body that carries and rotates the developing agent in the developing container 60. Agent carrier) 70 and. The developing sleeve 70 is housed in the developing container 60 with a gap G between the photosensitive drum 3 and carries the developing agent contained in the developing container 60, and conveys the developing agent to the developing region Ar facing the photosensitive drum 3. It is possible to develop an electrostatic latent image.

As shown in FIG. 3, the developing sleeve 70 has a central axis 71 and is supported by a sleeve bearing 72 that rotatably supports the central axis 71 with respect to the developing container 60, in the direction of the arrow in FIGS. 2 and 3. It is driven to rotate. In the present specification, the rotation axis direction of the developing sleeve 70 is shown as the longitudinal direction (width direction) X, the front side of the apparatus main body 10 in the longitudinal direction X is shown as the front direction F, and the back side is shown as the rear direction R.

As shown in FIG. 2, inside the developing sleeve 70, a magnet roller 73 as a developing magnet having a plurality of magnetic poles arranged in the circumferential direction is arranged non-rotatingly with respect to the developing container 60 by a magnet support shaft 74. ing. The inside of the developing container 60 is horizontally left and right in the developing chamber (first chamber) 62 and the stirring chamber (second chamber) 63 by a partition wall 61 whose substantially central portion extends in the direction of the rotation axis of the developing sleeve 70. It is partitioned. As a result, the developer is housed in the developing chamber 62 and the stirring chamber 63 separated by the partition wall 61. The developing chamber 62 and the stirring chamber 63 form a circulation path for the developer. The first transfer screw 64 is arranged in the developing chamber 62, and the second transfer screw 65 is arranged in the stirring chamber 63. The first transfer screw 64 and the second transfer screw 65 as the stirring members are arranged substantially in parallel along the rotation axis direction of the developing sleeve 70, and the developing container 60 is agitated and conveyed while stirring and conveying the developer in the developing container 60. Circulate inside. At both ends (left side and right side in FIG. 3) of the partition wall 61 in the longitudinal direction X, a first communication port 61a and a second communication port that allow passage of the developer between the developing chamber 62 and the stirring chamber 63 are allowed to pass through. 61b is provided.

The first transfer screw 64 and the second transfer screw 65 are both screw-shaped members, and each has a spiral blade around a rotation axis. The first transfer screw 64 is arranged at the bottom of the developing chamber 62 along the longitudinal direction X of the developing sleeve 70, and the developer in the developing chamber 62 is rotated in the direction of the rotating axis by rotating the rotating shaft with a drive source. The developer is supplied to the developing sleeve 70 while being conveyed while stirring along the line. The developer supported on the developing sleeve 70 and whose toner is consumed in the developing step is collected in the developing chamber 62. The first transport screw 64 transports the developer in the rear direction R, which is the first direction.

The second transport screw 65 is arranged at the bottom of the stirring chamber 63 along the longitudinal direction X of the developing sleeve 70, and the developer in the stirring chamber 63 is directed in the direction of the rotation axis opposite to that of the first transport screw 64. Convey with stirring along the line to make the toner concentration uniform. The second transport screw 65 transports the developer in the front direction F, which is the second direction opposite to the rear direction R. Further, the partition wall 61 is provided on the first communication port 61a for passing the developer from the stirring chamber 63 to the developing room 62 and on the upstream side in the forward direction F from the first communication port 61a, and is provided from the developing room 62 to the developing room 63. It has a second communication port 61b for delivering the developing agent. The developer is conveyed by the first transfer screw 64 and the second transfer screw 65, passes through the first communication port 61a and the second communication port 61b, and circulates in the developing container 60.

At the upstream end of the second transfer screw 65 of the stirring chamber 63 in the developer transfer direction, a developer supply port 66 for replenishing the developer containing toner is provided in the developing container 60. The developer supply port 66 is connected to the storage container 9 (see FIG. 1) via a developer supply device (not shown). Therefore, the replenishing developer is supplied from the storage container 9 into the stirring chamber 63 via the developing agent replenishing device and the developing agent replenishing port 66. The second transfer screw 65 conveys the developer supplied from the developer supply port 66 and the developer already in the stirring chamber 63 while stirring to make the toner concentration uniform.

Therefore, as shown in FIG. 3, the developing agent in the developing chamber 62 in which the toner is consumed in the developing step and the toner concentration is lowered due to the conveying force of the first conveying screw 64 and the second conveying screw 65 is moved in the rear direction R. It moves into the stirring chamber 63 through the first communication port 61a on the side. Then, the developer that has moved into the stirring chamber 63 is conveyed while being stirred with the replenished developer, and moves to the developing chamber 62 via the second communication port 61b on the front F side.

As shown in FIG. 2, in the developing chamber 62 of the developing container 60, there is an opening 60a at a position corresponding to the developing region Ar facing the photosensitive drum 3, and in this opening 60a, the developing sleeve 70 is formed on the photosensitive drum 3. It is rotatably arranged so as to be partially exposed in the direction. Such a developing sleeve 70 is rotationally driven by a drive source, can convey the developing agent to the developing region Ar, and supplies the developing agent to the photosensitive drum 3 in the developing region Ar. In the present embodiment, the developing sleeve 70 is formed in a cylindrical shape by, for example, aluminum or stainless steel as a non-magnetic material, has a diameter of 20 mm, a length in the longitudinal direction of 334 mm, and has a process speed (peripheral speed) of 250 mm / sec. Rotates during development operation.

A developing blade 67 that regulates the amount (layer thickness) of the developing agent supported on the developing sleeve 70 is fixed on the upstream side of the opening 60a in the rotational direction of the developing sleeve 70. The developing blade 67 forms a thin layer of the developing agent on the surface of the developing sleeve 70.

The magnet roller 73 has a total of five poles of a plurality of magnetic poles S1, S2, S3, N1 and N2 in the circumferential direction, and is formed in a roller shape. Such a magnet roller 73 generates a magnetic field for carrying the developer on the developing sleeve 70, and also generates a magnetic field for peeling the developer from the developing sleeve 70 in the peeling region.

The developer on the developing sleeve 70 forms magnetic spikes in the developing region Ar by rotating the developing sleeve 70. The magnetic spikes come into contact with the photosensitive drum 3 rotating in the same direction as the developing sleeve 70 in the developing region Ar, and the electrostatic image on the photosensitive drum 3 is developed as a toner image by the charged toner. Further, in order to improve the development efficiency, that is, the rate of applying toner to the latent image, a development bias voltage in which a DC voltage and an AC voltage are superimposed is usually applied to the development sleeve 70 from the development bias power supply. The developer on the developing sleeve 70 after the toner is supplied to the photosensitive drum 3 is recovered in the developing chamber 62 by further rotating the developing sleeve 70.

As shown in FIG. 3, the developing container 60 is provided with an inductance sensor (toner concentration detecting means) 68 that detects information regarding the toner concentration of the developer in the developing container 60. In the present embodiment, the inductance sensor 68 is provided on the downstream side of the stirring chamber 63 in the developer transport direction.

[Second transport screw]
Next, the detailed configuration of the second transport screw 65 will be described with reference to FIGS. 3 and 4. The second transport screw 65 has a shaft portion 80, and a first blade portion 81, a second blade portion 82, and a third blade portion 83, all of which have a spiral shape. In the present embodiment, the second transport screw 65 is made of, for example, plastic and is formed by injection molding. The second blade portion 82 has a spiral shape in the same direction as the first blade portion 81 and at the same pitch. In the present embodiment, the first blade portion 81 and the second blade portion 82 have, for example, one row, and have an outer diameter of 14 mm and a pitch of 20 mm. Therefore, the angle of the first blade portion 81 calculated from the outer peripheral length (43.98 mm) of the first blade portion 81 and the second blade portion 82 and the pitch (screw pitch) is 65.55 ° (FIG.). 5). Here, the first blade portion 81 and the second blade portion 82 have an outer diameter of 14 mm and a pitch of 20 mm, but the toner can be smoothly conveyed as long as the angle of one cycle is 80 ° or less. Therefore, the outer diameter and pitch are not limited to the above-mentioned dimensions. Further, in the present embodiment, the case where the number of rows of the first blade portion 81 and the second blade portion 82 is one is described, but the present invention is not limited to this, and the number of rows may be two or more.

The third blade portion 83 is continuously provided between the first blade portion 81 and the second blade portion 82, and the first blade portion 81 and the second blade portion 81 and the second blade portion 81 are provided in the same direction as the first blade portion 81 and the second blade portion 82. It has a spiral shape with a pitch narrower than that of the blade portion 82. With respect to the longitudinal direction X of the second transport screw 65, the total length of the third blade portion 83 is the length of one pitch of the first blade portion 81 and the second blade portion 82, that is, 20 mm. In the present embodiment, the total length of the third blade portion 83 is set to 20 mm for one pitch of the first blade portion 81 and the second blade portion 82, but the length is not limited to this and exceeds one pitch. The length may be less than one pitch of the pod.

The third blade portion 83 has, for example, one row, and has an outer diameter of 14 mm and a pitch of 5 mm. Therefore, the third blade portion 83 has a region of one pitch of the first blade portion 81 and the second blade portion 82 having spiral blades, that is, a region of 20 mm with a pitch of 5 mm and four turns. It is provided. In the present embodiment, the number of turns of the third blade portion 83 is set to four for the length of one pitch of the first blade portion 81 and the second blade portion 82, but this is limited to this. Absent. The third blade portion 83 may have a spiral shape having a narrow pitch in the same direction as the first blade portion 81 and the second blade portion 82. Therefore, the number of turns of the third blade portion 83 with respect to the length of one pitch of the first blade portion 81 and the second blade portion 82 may exceed one, and is particularly preferably 2 to 4 times. .. When the number of turns of the third blade portion 83 is three, the stirring property is lower than that of the case where the number of turns of the third blade portion 83 is four, but the transportability is higher. Similarly, when the number of turns of the third blade portion 83 is two, the stirring property is lower than the case where the number of turns of the third blade portion 83 is three times, but the transportability is higher. Therefore, it is most preferable that the number of turns of the third blade portion 83 is three from the viewpoint of the balance between transportability and agitation.

The third blade portion 83 has an outer diameter equivalent to the outer diameter of the first blade portion 81 and the second blade portion 82. However, the outer diameter of the third blade portion 83 is not limited to the same outer diameter as the outer diameters of the first blade portion 81 and the second blade portion 82, and for example, the outer diameters of the first blade portion 81 and the second blade portion 82. It may have an outer diameter equal to or less than the outer diameter. As a result, it is possible to prevent the outer peripheral edge of the third blade portion 83 from coming into contact with the inner peripheral surface of the stirring chamber 63.

The third blade portion 83 has a wall surface 83a facing the rearward R side of the transport wall, and a notch portion 83b having a shape in which a part of the outer peripheral portion of the transport wall is cut out. The notch 83b has a length of 4 mm in the circumferential direction and a depth of 4 mm in the radial direction. The radial depth of 4 mm is set to be about ½ of the height of the transport wall. Further, in the present embodiment, the case where the notch portion 83b has a length of 4 mm and a depth of 4 mm has been described, but the present invention is not limited to this, and other dimensions may be used. Alternatively, for example, the dimensions may be different for each notch 83b.

The notch 83b of the third blade portion 83 is provided at every 90 ° in the rotation direction R1 of the second transport screw 65. Therefore, in the longitudinal direction X, the phases of the adjacent notch portions 83b are in agreement with each other. Here, the state in which the phases of the notch portions 83b are matched in the present embodiment means that the positions of the notch portions 83b adjacent to each other in the longitudinal direction X are the same when the second transport screw 65 is viewed from the longitudinal direction X. It shall mean the state of the screw.

In the present embodiment, the cutout portion 83b is provided at every 90 ° in the rotation direction R1 of the second transport screw 65, but the present invention is not limited to this, and the notch portion 83b may be provided at an angle other than 90 °, for example, every 120 °. Good. Alternatively, 360 ° may be provided at an indivisible angle, for example, every 100 °. In this case, the notch 83b is arranged so that the position of the rotation direction R1 is different from that of the other notch 83b adjacent to the front direction F and the phases are shifted. Alternatively, for example, the angle between the notch 83b and the notch 83b adjacent to each other in the rotation direction R1 may be different for each notch 83b.

Here, regarding the third blade portion 83, the volume ratio of the transport wall per pitch when the notch portion 83b is not provided is set to 100%. In this case, the volume ratio of the third blade portion 83 is 86.2%, and the volume ratio of the space occupied by the notch portion 83b is 13.8%. In the present embodiment, the case where the third blade portion 83 has a volume ratio of 86.2% with respect to the case where the notch portion 83b is not provided has been described, but the present invention is not limited to this, and the notch portion 83b is not limited to this. By changing the dimensions and arrangement of, for example, it can be set to about 70 to 90%. When the volume ratio of the third blade portion 83 to the case where the notch portion 83b is not provided is set to exceed 90%, or when the notch portion 83b is not provided, the developer is used. This is not preferable because the stirring performance is significantly reduced. Further, if the volume ratio of the third blade portion 83 with respect to the case where the notch portion 83b is not provided is set to less than 70%, the transportability of the developer is significantly reduced, which is not preferable.

As shown in FIG. 3, the third blade portion 83 is arranged at a substantially central portion of the second transport screw 65. However, the arrangement position of the third blade portion 83 is not limited to this, and the arrangement position of the third blade portion 83 is in the region from the end on the rear R side of the second communication port 61b to the end on the front F side of the first communication port 61a. It may be a position facing a part. As a result, the third blade portion 83 is provided in the toner circulation path in the stirring chamber 63, so that the circulating toner can be effectively stirred.

In the present embodiment, since the inductance sensor 68 is arranged on the front F side of the stirring chamber 63, the third blade portion 83 is arranged in the substantially central portion of the second transport screw 65 so as to be in front of the inductance sensor 68. It is arranged on the upstream side of the direction F. As a result, even if toner may stay on the rear R side of the third blade portion 83 than on the front F side, it is possible to suppress the influence on the detection accuracy of the inductance sensor 68.

Next, the operation when the second transport screw 65 is rotated to transport the toner in the forward direction F will be described in detail with reference to FIGS. 3 and 4. Here, in the present embodiment, since the third blade portion 83 has four turns, for the sake of explanation, the first winding portion 91 and the second winding portion 92 are directed from the rear direction R side to the front direction F side. It is assumed that the third winding portion 93 and the fourth winding portion 94 are provided. That is, the first winding portion 91 is for one winding on the rearmost R side, and the second winding portion 92 is for one winding adjacent to the front F side of the first winding portion 91. Further, the third winding portion 93 is one winding portion adjacent to the front direction F side of the second winding portion 92, and the fourth winding portion 94 is one winding portion adjacent to the front direction F side of the third winding portion 93. And. Further, the wall surface 83a has a wall surface 91a of the first winding portion 91, a wall surface 92a of the second winding portion 92, a wall surface 93a of the third winding portion 93, and a wall surface 94a of the fourth winding portion 94. Further, the notch portion 83b includes the notch portion 91b of the first winding portion 91, the notch portion 92b of the second winding portion 92, the notch portion 93b of the third winding portion 93, and the fourth winding portion 94. It has a notch portion 94b and a notch portion 94b.

As shown in FIG. 3, the developer flowing into the stirring chamber 63 from the second communication port 61b or the toner supplied from the developing agent supply port 66 moves forward in the stirring chamber 63 by the rotation of the second transport screw 65. It is transported to F. The developer that has been conveyed to the first blade portion 81 and has reached the third blade portion 83 has a reduced transfer speed due to the narrowing of the pitch, and the amount of the developer that cannot be conveyed by the third blade portion 83 is the first. It abuts on the wall surface 91a of the winding portion 91 and is dammed. The developer blocked by the wall surface 91a passes through the notch 91b of the first winding portion 91 in the front direction F, but abuts on the wall surface 92a adjacent to the front direction F side and is blocked. At the same time, due to the rotation of the second transport screw 65, the developer that is about to pass through the notch 91b is agitated so as to be sheared by the notch 91b in the circumferential direction. In this way, the developer that is about to pass through the notch 91b is hindered by the wall surface 92a adjacent to the front F side and stays there without being quickly conveyed, so that it is efficiently sheared in the circumferential direction. It is stirred as it is.

Similarly, the developer that is about to pass through the notch 92b is agitated so as to be blocked by the wall surface 93a adjacent to the front F side and sheared in the circumferential direction. Further, the developer that is about to pass through the notch 93b is agitated so as to be blocked by the wall surface 94a adjacent to the front F side and sheared in the circumferential direction. The developer that has passed through the notch portion 94b is conveyed in the forward direction F in the stirring chamber 63 by the rotation of the second blade portion 82, and reaches the inductance sensor 68. As a result, the agitation property can be significantly improved.

That is, the developer passes through the notch 83b of the third blade 83, so that the developer does not get over the third blade 83 and is further stirred by the notch 83b in the rotation direction of the second transport screw 65. Therefore, the stirring performance can be improved. Therefore, in order to solve the problem of efficiently stirring the replenishing toner with a small amount of the developer, the developer is retained in the third blade portion 83, and the developer is retained in the retained portion by the notch 83b provided in the third blade portion 83. The problem can be solved by stirring.

The pitch of the third blade portion 83 is narrower than that of the first blade portion 81 and the second blade portion 82, and the transport speed is lowered, so that the wall surface 83a temporarily blocks the developer. The transportability is lower than that of the 81 and the second blade portion 82. Therefore, in the stirring chamber 63, the height of the agent surface differs before and after the third blade portion 83. For example, in the second blade portion 82 on the front F side of the third blade portion 83, the agent surface is about the height of the shaft portion 80 of the second transport screw 65, whereas the agent surface is in the rear direction of the third blade portion 83. In the first blade portion 81 on the R side, the agent surface is higher than that of the shaft portion 80.

As described above, in the image forming apparatus 1 of the present embodiment, the third blade portion 83 of the second transport screw 65 has a spiral shape having a narrow pitch in the same direction as the first blade portion 81 and the second blade portion 82. , It has a notch 83b on the outer peripheral portion. Therefore, when the developer transported by the second transport screw 65 reaches the third blade portion 83 from the first blade portion 81, the transport speed decreases, and the developer comes into contact with the wall surface 83a and is blocked, so that the notch portion is formed. It is agitated to be sheared by 83b. Therefore, the stirring property can be improved as compared with the case where the developer is conveyed at the same transfer speed as the first blade portion 81 and the second blade portion 82 without being blocked by the third blade portion 83. Further, in the image forming apparatus 1 of the present embodiment, the third blade portion 83 is a region from the end on the rear R side of the second communication port 61b to the end on the front F side of the first communication port 61a. It is located at a position facing a part. Therefore, since the third blade portion 83 is provided in the toner circulation path in the stirring chamber 63, it is possible to effectively stir the toner that is circulated and conveyed. Therefore, according to the image forming apparatus 1 of the present embodiment, even if the amount of the developer is small, high agitation can be obtained while maintaining the transportability.

That is, according to the image forming apparatus 1 of the present embodiment, the second transfer screw 65 not only stirs uniformly in the entire transfer region, but also locally in the third blade portion 83 and in the entire transfer region. It becomes possible to stir more than uniform agitation. Further, in the third blade portion 83, not only the wall surface 83a locally blocks the flow of the developer in the transport direction, but also the notch portion 83b can significantly improve the stirring performance.

Further, according to the image forming apparatus 1 of the present embodiment, the notch portion 83b of the third blade portion 83 is provided every 90 ° in the rotation direction R1 of the second transport screw 65. For this reason, for example, the developer that is about to pass through the notch 83b is hindered by the wall surface 83a adjacent to the front F side and stays there without being promptly conveyed, so that the developer efficiently stays in the circumferential direction. Stir to be sheared. As a result, the agitation property can be significantly improved in the entire third blade portion 83.

Further, according to the image forming apparatus 1 of the present embodiment, the third blade portion 83 is arranged on the rearward R side from the position facing the inductance sensor 68. Therefore, even when the toner stays on the rear side R side of the third blade portion 83 more than on the front direction F side, it is possible to suppress the influence on the detection accuracy of the inductance sensor 68.

<Second embodiment>
Next, a second embodiment of the present invention will be described in detail with reference to FIG. The third blade portion 83 differs from the first embodiment in that the third blade portion 83 has a spiral shape in the direction opposite to that of the first blade portion 81 and the second blade portion 82. However, since the other configurations are the same as those in the first embodiment, the same reference numerals are given and detailed description thereof will be omitted.

In the present embodiment, as shown in FIG. 6, the third blade portion 83 is continuously provided between the first blade portion 81 and the second blade portion 82, and the first blade portion 81 and the second blade portion 82 are provided. It has a spiral shape in the opposite direction to. The third blade portion 83 has, for example, one row, and has an outer diameter of 14 mm and a narrow pitch of 5 mm, which are equivalent to those of the first blade portion 81 and the second blade portion 82. Therefore, the third blade portion 83 has a region of one pitch of the first blade portion 81 and the second blade portion 82 having spiral blades, that is, a region of 20 mm with a pitch of 5 mm and four turns. It is provided.

In the present embodiment, the number of turns of the third blade portion 83 is set to four for the length of one pitch of the first blade portion 81 and the second blade portion 82, but this is limited to this. Absent. The pitch of the third blade portion 83 is not limited as long as it has a spiral shape in the direction opposite to that of the first blade portion 81 and the second blade portion 82. Therefore, the number of turns of the third blade portion 83 with respect to the length of one pitch of the first blade portion 81 and the second blade portion 82 can be appropriately set not only to exceed 1 but also to 1 or less. it can. However, the number of turns of the third blade portion 83 with respect to the length of one pitch of the first blade portion 81 and the second blade portion 82 is particularly preferably 2 to 4 times, and the transportability is preferably 3 times. And most preferable from the viewpoint of the balance of agitation.

The third blade portion 83 has a wall surface 83a facing the rearward R side of the transport wall, and a notch portion 83b having a shape in which a part of the outer peripheral portion of the transport wall is cut out. The notch 83b has a length of 4 mm in the circumferential direction and a depth of 4 mm in the radial direction. The radial depth of 4 mm is set to be about ½ of the height of the transport wall. The notch 83b of the third blade portion 83 is provided at every 90 ° in the rotation direction R1 of the second transport screw 65. Therefore, in the longitudinal direction X, the phases of the adjacent notch portions 83b are in agreement with each other.

Here, regarding the third blade portion 83, the volume ratio of the transport wall per pitch when the notch portion 83b is not provided is set to 100%. In this case, the volume ratio of the third blade portion 83 is 86.2%, and the volume ratio of the space occupied by the notch portion 83b is 13.8%. In the present embodiment, the case where the third blade portion 83 has a volume ratio of 86.2% with respect to the case where the notch portion 83b is not provided has been described, but the present invention is not limited to this, and the notch portion 83b is not limited to this. By changing the dimensions and arrangement of, for example, it can be set to about 60 to 90%. When the volume ratio of the third blade portion 83 to the case where the notch portion 83b is not provided is set to exceed 90%, or when the notch portion 83b is not provided, the developer is used. This is not preferable because the stirring performance is significantly reduced. Further, in this case, since the transportability of the third blade portion 83 in the rear direction R is increased, the transportability of the second transport screw 65 is also significantly reduced, which is not preferable. Further, when the volume ratio of the third blade portion 83 with respect to the case where the cutout portion 83b is not provided is set to less than 60%, the transportability of the developer is less likely to decrease, which is not preferable.

Next, the operation when the second transport screw 65 is rotated to transport the toner in the forward direction F will be described in detail. The developer that has been conveyed to the first blade portion 81 and has reached the third blade portion 83 is likely to be pushed back by the winding direction being opposite. However, since the third blade portion 83 is shorter than the first blade portion 81 and the first blade portion 81 has a larger conveying force, the developer is conveyed to the F side in the forward direction as a whole, but the conveying speed is lowered. .. Then, the developer that has reached the third blade portion 83 comes into contact with the wall surface 91a of the first winding portion 91 and is blocked. The developer blocked by the wall surface 91a passes through the notch 91b of the first winding portion 91 in the front direction F, but abuts on the wall surface 92a adjacent to the front direction F side and is blocked. At the same time, due to the rotation of the second transport screw 65, the developer that is about to pass through the notch 91b is agitated so as to be sheared by the notch 91b in the circumferential direction. In this way, the developer that is about to pass through the notch 91b is hindered by the wall surface 92a adjacent to the front F side and stays there without being quickly conveyed, so that it is efficiently sheared in the circumferential direction. It is stirred as it is.

Similarly, the developer that is about to pass through the notch 92b is agitated so as to be blocked by the wall surface 93a adjacent to the front F side and sheared in the circumferential direction. Further, the developer that is about to pass through the notch 93b is agitated so as to be blocked by the wall surface 94a adjacent to the front F side and sheared in the circumferential direction. Further, the developer that is about to pass through the notch 94b is stirred so as to be sheared in the circumferential direction. The developer that has passed through the notch portion 94b is conveyed in the forward direction F in the stirring chamber 63 by the rotation of the second blade portion 82, and reaches the inductance sensor 68.

While the developer passes through the third blade portion 83, a part of the developer passes through the notches 91b to 94b and moves to the F side in the forward direction, and a part of the developer moves to the F side in the forward direction, and a part of the developer passes through the wall surface due to the rotation of the third blade portion 83. It is conveyed to the rear R side along 91a to 94a. In this way, the developer is agitated so as to be sheared in the circumferential direction when passing through the notch portions 91b to 94b while being mixed in the front direction F side and the rear direction R side. It can be greatly improved.

As described above, in the image forming apparatus 1 of the present embodiment, the third blade portion 83 of the second transport screw 65 has a spiral shape having a narrow pitch in the direction opposite to the first blade portion 81 and the second blade portion 82. , It has a notch 83b on the outer peripheral portion. Therefore, when the developer transported by the second transport screw 65 reaches the third blade portion 83 from the first blade portion 81, a pushing force acts to abut against the wall surface 83a and is blocked and cut. It is stirred so as to be sheared by the notch 83b. Therefore, the stirring property can be improved as compared with the case where the developer is conveyed at the same transfer speed as the first blade portion 81 and the second blade portion 82 without being blocked by the third blade portion 83. Further, in the image forming apparatus 1 of the present embodiment, the third blade portion 83 is a region from the end on the rear R side of the second communication port 61b to the end on the front F side of the first communication port 61a. It is located at a position facing a part. Therefore, since the third blade portion 83 is provided in the toner circulation path in the stirring chamber 63, it is possible to effectively stir the toner that is circulated and conveyed. Therefore, according to the image forming apparatus 1 of the present embodiment, even if the amount of the developer is small, high agitation can be obtained while maintaining the transportability.

6 ... developing device, 60 ... developing container, 61 ... partition wall, 61a ... first communication port, 61b ... second communication port, 62 ... developing room (first room), 63 ... stirring room (second room), 64 ... 1st transfer screw, 65 ... 2nd transfer screw, 68 ... Inductance sensor (toner concentration detecting means), 70 ... Development sleeve (developer carrier), 81 ... 1st blade, 82 ... 2nd blade, 83 ... 3rd blade part, 83b ... notch part, 91 ... 1st winding part, 91b ... notch part, 92 ... 2nd winding part, 92b ... notch part, 93 ... 3rd winding part, 93b ... notch part, 94 ... 4th winding portion, 94b ... Notch portion, F ... Front direction (second direction), R ... Rear direction (first direction).

Claims (8)

A developer carrier that carries and rotates a developer, and
A developing container having a first chamber for supplying the developer to the developer carrier and a second chamber for forming a circulation path for the developer in the first chamber.
A first transport screw, which is arranged in the first chamber and transports the developer in the first direction,
A second transport screw, which is arranged in the second chamber and transports the developer in the second direction opposite to the first direction,
A first communication port that separates the first chamber and the second chamber inside the developing container and delivers the developer from the second chamber to the first chamber, and the second communication port from the first communication port. A developing apparatus including a partition wall provided on the upstream side of the above and having a second communication port for delivering a developing agent from the first chamber to the second chamber.
The second transport screw is continuous between the first blade portion having a spiral shape, the second blade portion having a spiral shape in the same direction as the first blade portion, and the first blade portion and the second blade portion. A third blade portion having a spiral shape with a pitch narrower than that of the first blade portion and the second blade portion in the same direction as the first blade portion and the second blade portion, and the third blade portion. It has a notch in the shape of a part of the outer periphery of the
The position of the third blade portion faces a part of the region from the upstream end of the second communication port in the second direction to the downstream end of the first communication port in the second direction. Placed in,
A developing device characterized by this. A developer carrier that carries and rotates a developer, and
A developing container having a first chamber for supplying the developer to the developer carrier and a second chamber for forming a circulation path for the developer in the first chamber.
A first transport screw, which is arranged in the first chamber and transports the developer in the first direction,
A second transport screw, which is arranged in the second chamber and transports the developer in the second direction opposite to the first direction,
A first communication port that separates the first chamber and the second chamber inside the developing container and delivers the developer from the second chamber to the first chamber, and the second communication port from the first communication port. A developing apparatus including a partition wall provided on the upstream side of the above and having a second communication port for delivering a developing agent from the first chamber to the second chamber.
The second transport screw is continuous between the first blade portion having a spiral shape, the second blade portion having a spiral shape in the same direction as the first blade portion, and the first blade portion and the second blade portion. A third blade portion having a spiral shape in the direction opposite to that of the first blade portion and the second blade portion, and a notch portion having a shape in which a part of the outer peripheral portion of the third blade portion is cut out. And have
The position of the third blade portion faces a part of the region from the upstream end of the second communication port in the second direction to the downstream end of the first communication port in the second direction. Placed in,
A developing device characterized by this. The notch portion is positioned differently from the other notch portions adjacent to the second direction in the circumferential direction about the rotation axis of the second transport screw.
The developing apparatus according to claim 1 or 2. The second chamber is provided with a toner concentration detecting means for detecting information on the toner concentration of the developer in the developing container.
The third blade portion is arranged on the upstream side in the second direction from a position facing the toner concentration detecting means.
The developing apparatus according to any one of claims 1 to 3, wherein the developing apparatus is characterized by this. With respect to the rotation axis direction of the second transport screw, the total length of the third blade portion is the length of one pitch of the first blade portion and the second blade portion.
The developing apparatus according to any one of claims 1 to 4, wherein the developing apparatus is characterized by this. The number of turns of the third blade portion is two.
The developing apparatus according to any one of claims 1 to 5, wherein the developing apparatus is characterized by this. The number of turns of the third blade portion is three.
The developing apparatus according to any one of claims 1 to 5, wherein the developing apparatus is characterized by this. The number of turns of the third blade portion is four.
The developing apparatus according to any one of claims 1 to 5, wherein the developing apparatus is characterized by this.

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