JP6079291B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus.

In the field of conventional image forming apparatuses, the techniques described in Patent Documents 1 to 3 below are conventionally known as developing apparatuses that develop a latent image into a visible image.
Japanese Patent Application Laid-Open No. 2007-240619 as Patent Document 1 discloses a first developer carrier (3a) and a second developer carrier that are rotatable along the surface movement direction in the development region of the photosensitive drum (1). A configuration in which (3b) is arranged so as to face each other in the direction of rotation of the photosensitive drum (1) is described.
In the first developer carrier (3a) described in Patent Document 1, the development pole (S1) is disposed at a position shifted to the upstream side with respect to the rotation direction of the photosensitive drum (1). 2 On the developer carrying member (3b), a developing electrode (S1) having the same polarity as the developing electrode (S1) is disposed at the closest position to the photosensitive drum (1).

Japanese Patent Laid-Open No. 2012-053177 as Patent Document 2 discloses a second developer carrier (Gb) and a first developer carrier (Ga) in order from the upstream side with respect to the rotation direction of the photoconductor (PR). Is a developing device (G).
In Patent Document 2, the surface of the second developer carrying member (Gb) is in the second developing region (Q2b), which is a region facing the photosensitive member (PR), and the moving direction of the surface of the photosensitive member (PR). The rotation direction is set so as to move in the opposite direction. Further, in Patent Document 2, the surface of the second developer carrying member (Gb) corresponds to the second developing region (Q2b) that is a region facing the photosensitive member (PR), and the second developing magnetic pole (Q2b) S5) is arranged.
Further, in Patent Document 2, the first developer carrier (Ga) disposed corresponding to the second development magnetic pole (S5) of the second developer carrier (Gb) and the first development region (Q2a). ) Of the first developing magnetic pole (N4) is set to a reverse polarity.

Japanese Patent Application Laid-Open No. 2007-47639 as Patent Document 3 discloses a reverse rotation developing roll (1), a forward rotation developing roll (2), and a forward rotation developing in order from the upstream side in the rotation direction of the surface of the photoreceptor (101). A developing device (102) in which a roll (3) is arranged is described.
In the reverse rotation developing roll (1) described in Patent Document 3, a magnetic pole (S2) is disposed at a position closest to the photoreceptor (101), and the forward rotation developing roll (2) includes a photoreceptor. A magnetic pole (S3) having the same polarity as the magnetic pole (S2) is disposed at a position closest to (101).

JP 2007-240619 A (“0051”, “0114” to “0129”, “0136”, FIG. 3, FIG. 8, FIG. 13) JP 2012-053177 A (“0039”, “0041”, “0044”, “0045”, FIG. 3) JP 2007-47639 A (“0032”, “0037”, “0049”, FIG. 2, FIG. 4, FIG. 7)

  An object of the present invention is to reduce the occurrence of image defects in an area where development is performed.

In order to solve the technical problem, the developing device of the invention according to claim 1 comprises:
A first developing member disposed to face the rotating image carrier, and generates a magnetic force for attracting a magnetic developer, and the image carrier and the first developer member are opposed to each other. A first magnet member in which a first magnetic pole is disposed corresponding to the first magnet member, and a first rotating body that is rotatably supported around the first magnet member and rotates while holding a developer on the surface thereof. The first developing member comprising:
A second developing member disposed on the downstream side of the first developing member with respect to the rotation direction of the image holding member, which generates a magnetic force for adsorbing the developer, and the image holding member and the second developing member; A second magnetic member having a second magnetic pole having the same polarity as the first magnetic pole corresponding to a position facing the developing member, and being rotatably supported surrounding the second magnetic member. And a second rotating member that rotates with the developer held on the surface, and the second developing member,
With
The first magnetic pole is disposed at a position shifted to the downstream side in the rotation direction of the image carrier with respect to a virtual line segment connecting the rotation center of the image carrier and the rotation center of the first rotor. And
The second magnet member has a delivery magnetic pole arranged corresponding to the closest position with the first magnet member,
The first magnet member includes a first receiving magnetic pole disposed at a position shifted to the upstream side in the rotation direction of the first rotating body from a position closest to the second magnet member; A second receiving magnetic pole disposed at a position shifted to the downstream side in the rotation direction of the first rotating body,
The first and second receiving magnetic poles receive the developer more on the first receiving magnetic pole side upstream than the second receiving magnetic pole side with respect to the closest position. The magnetic pole has a polarity opposite to that of the magnetic pole and the same polarity as the second receiving magnetic pole,
The latent image formed on the surface of the image holding member is developed into a visible image with the developer of the first developing member and the second developing member.

The invention according to claim 2 is the developing device according to claim 1,
The first rotating body that rotates in a direction opposite to the rotation direction of the image holding body in a region facing the image holding body;
It is provided with.

The invention described in claim 3 is the developing device according to claim 1 or 2,
At a position shifted to the downstream side in the rotation direction of the image carrier so that the thickness of the developer layer at the position of the first magnetic pole is equal to or less than the distance between the image carrier and the first rotator. The first magnetic pole disposed;
It is provided with.

According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects,
The first developing member disposed on the upper side in the gravity direction of the second developing member;
It is provided with.

In order to solve the technical problem, an image forming apparatus according to claim 5 is provided.
A rotating image carrier;
A latent image forming apparatus for forming a latent image on the surface of the image carrier;
The developing device according to any one of claims 1 to 4, which develops a latent image on the surface of the image carrier into a visible image;
A transfer device for transferring a visible image of the surface of the image carrier to a medium;
A fixing device for fixing the visible image transferred to the medium;
It is provided with.

According to the first and fifth aspects of the present invention, it is possible to reduce the occurrence of image defects in a region where development is performed as compared with the case where the configuration of the present invention is not provided.
According to the second aspect of the present invention, development can be stabilized in a region where the relative speed between the image carrier and the first rotating body is large.
According to the third aspect of the present invention, it is possible to widen the developable region as compared with the case where the configuration of the present invention is not provided.
According to the fourth aspect of the present invention, it is possible to reduce the drop of the developer from the first developing member to the second developing member as compared with the case where the configuration of the present invention is not provided.

FIG. 1 is an explanatory diagram of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is an explanatory cross-sectional view of a main part of the developing device according to the first embodiment. FIG. 3 is an explanatory diagram of the developing device of Example 1, and is a cross-sectional view taken along the line III-III of FIG. FIG. 4 is an explanatory diagram of the magnetic field in the region where the developer is transferred, FIG. 4A is an explanatory diagram of the magnetic field in the conventional configuration, and FIG. 4B is an explanatory diagram of the magnetic field in the configuration of the first embodiment. FIG. 5 is an explanatory diagram of a magnetic field between the first developing member, the second developing member, and the image carrier, FIG. 5A is an explanatory diagram of a magnetic field in the configuration of the first embodiment, and FIG. 5B is a conventional configuration. It is explanatory drawing of a magnetic field.

Next, examples as specific examples of embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as the front side, the rear side, the right side, the left side, the upper side, the lower side, or the front side, the rear side, the right side, the left side, the upper side, and the lower side, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an explanatory diagram of an image forming apparatus according to a first embodiment of the present invention.
In FIG. 1, a copier U as an example of an image forming apparatus according to the first exemplary embodiment is an example of a recording unit, and includes a printer unit U1 as an example of an image recording apparatus. A scanner unit U2 as an example of a reading unit and an example of an image reading device is supported on the upper portion of the printer unit U1. An auto feeder U3 as an example of a document transport device is supported on the upper portion of the scanner unit U2. The scanner unit U2 of the first embodiment supports a user interface U0 as an example of an input unit. The user interface U0 can be operated by the operator by inputting the user interface U0.

  A document tray TG1 as an example of a medium container is disposed on the upper part of the auto feeder U3. A plurality of documents Gi to be copied can be stacked and stored in the document tray TG1. A document discharge tray TG2 as an example of a document discharge unit is formed below the document tray TG1. A document transport roll U3b is disposed along the document transport path U3a between the document tray TG1 and the document discharge tray TG.

A platen glass PG as an example of a transparent document table is disposed on the upper surface of the scanner unit U2. In the scanner unit U2 of the first embodiment, a reading optical system A is disposed below the platen glass PG. The optical system A for reading in Example 1 is supported so as to be movable in the left-right direction along the lower surface of the platen glass PG. The reading optical system A is normally stopped at the initial position shown in FIG.
On the left side of the optical system A for reading, an imaging element CCD as an example of an imaging member is disposed. An image processing unit GS is electrically connected to the image sensor CCD.
The image processing unit GS is electrically connected to the writing circuit DL of the printer unit U1. The writing circuit DL is electrically connected to an exposure machine ROS as an example of a latent image forming apparatus.

A photosensitive drum PR, which is an example of an image carrier, is disposed below the exposure machine ROS. The photosensitive drum PR rotates in the direction of the arrow Ya.
On the photosensitive drum PR, a charging roll CR, which is an example of a charger, is disposed opposite to the charging area Q0. A charging voltage is applied from the power supply circuit E to the charging roll CR. The power supply circuit E is controlled by a controller C as an example of a control unit. The controller C performs various controls by transmitting and receiving signals to and from the image processing unit GS and the writing circuit DL.
In the writing area Q1 set on the downstream side of the charging area Q0 with respect to the rotation direction of the photosensitive drum PR, a laser beam L as an example of writing light from the exposure device ROS is applied to the surface of the photosensitive drum PR. Is irradiated.
In the developing area Q2 set on the downstream side of the writing area Q1 with respect to the rotation direction of the photosensitive drum PR, the developing device G is disposed to face the surface of the photosensitive drum PR.
A transfer area Q3 is set on the downstream side of the development area Q2 with respect to the rotation direction of the photosensitive drum PR.

Under the printer unit U1, paper feed trays TR1 to TR4 as examples of a medium container are detachably supported. Sheets T as an example of a medium are accommodated in the sheet feed trays TR1 to TR4.
A pickup roll Rp as an example of a medium take-out member is disposed on the upper left side of the paper feed trays TR1 to TR4. On the left side of the pickup roll Rp, a separation roll Rs as an example of a spreading member is arranged.
On the left side of each of the paper feed trays TR1 to TR4, a medium transport path SH1 extending upward is formed. A plurality of transport rolls Ra as an example of a medium transport member are arranged in the transport path SH1. In the conveyance path SH1, a registration roll Rr as an example of a feeding member is disposed on the downstream side in the conveyance direction of the sheet S and on the upstream side of the transfer region Q3.

In the transfer area Q3, a transfer unit TU, which is an example of a transfer device and an example of a medium transport device, is disposed below the photosensitive drum PR. The transfer unit TU includes an endless transfer belt TB as an example of a medium transport member.
The transfer belt TB is rotatably supported by a driving roll Rd as an example of a driving member and a driven roll Rf as an example of a driven member.
Inside the transfer belt TB, a transfer roll TR as an example of a transfer device is supported. The transfer roll TR is disposed to face the photosensitive drum PR with the transfer belt TB interposed therebetween. Therefore, the transfer region Q3 is constituted by the region where the transfer roll TR and the photosensitive drum PR face each other. A transfer voltage is applied from the power supply circuit E to the transfer roll TR.

A peeling claw SC as an example of a medium peeling member is disposed at the right end of the transfer belt TB. Below the peeling claw SC, a belt cleaner CLb as an example of a cleaner of the transfer device is disposed to face the surface of the transfer belt TB.
Note that a drum cleaner CLp, which is an example of an image carrier cleaner, is disposed on the downstream side of the transfer region Q3 with respect to the rotation direction of the photosensitive drum PR so as to face the surface of the photosensitive drum PR. Yes.

A fixing device F is disposed on the right side of the transfer unit TU. The fixing device F includes a heating roll Fh as an example of a heating rotating member and a pressure roll Fp as an example of a pressing rotating member.
To the right of the fixing device F, a discharge path SH2 extending upward is connected as an example of a medium transport path.
In the discharge path SH2, as an example of a medium transport member, a transport roll Rb and a discharge roll Rh capable of transporting the medium and rotating in the forward and reverse directions are arranged.
A paper discharge tray TRh as an example of a medium discharge unit is formed on the upper surface of the printer unit U1.

A reversing path SH3, which is an example of a medium transport path, is formed below the discharge path SH2. The reversing path SH3 according to the first embodiment branches from the discharge path SH2 and extends downward, and joins the transport path SH1 on the upstream side in the sheet transport direction from the registration roll Rr.
A gate MG as an example of a transfer direction switching member is disposed at a branch portion between the discharge path SH2 and the reversal path SH3. The gate MG of the first embodiment is formed of an elastically deformable thin film shape, so-called film. When the sheet S conveyed from the fixing device F passes through the gate MG, the gate MG is pushed by the sheet S and is elastically deformed so that the sheet S can pass through the discharge path SH2. When the sheet S is conveyed from the discharge path SH2 to the reversing path SH3, the gate MG is held in an elastically restored state, preventing the sheet S from entering the fixing device F, and the reversing path SH3. It arrange | positions so that the sheet | seat S may be guided to the side.

(Description of image forming operation)
The plurality of documents Gi stored in the document tray TG1 sequentially passes through the document reading position on the platen glass PG and is discharged to the document discharge tray TG2.
When the automatic feeder U3 is used to automatically convey and copy a document, each document that sequentially passes through the reading position on the platen glass PG with the reading optical system A stopped at the initial position. Gi is exposed.
When the operator places the document Gi on the platen glass PG by hand, the optical system A for reading moves in the left-right direction, and the document on the platen glass PG is scanned while being exposed.
The reflected light from the document Gi passes through the optical system A and is collected on the image sensor CCD. The image pickup device CCD converts the reflected light of the original collected on the image pickup surface into an electric signal.

The image processing unit GS converts the read signal input from the image sensor CCD into a digital image signal and outputs the digital image signal to the writing circuit DL of the printer unit U1. The writing circuit DL outputs a control signal corresponding to the input image writing signal to the exposure device ROS.
The surface of the photosensitive drum PR is charged by the charging roll CR in the charging region Q0. At the latent image writing position Q1, the laser beam L output from the exposure device ROS forms an electrostatic latent image on the surface of the photosensitive drum PR. In the developing area Q2, the developing device G develops the electrostatic latent image on the photosensitive drum PR passing through the developing area Q2 into a toner image as an example of a visible image. When the developer is consumed in the developing device G, the developer is replenished to the developing device G from a developer container (not shown) according to the consumption amount.

  The sheets S of the respective trays TR1 to TR4 are taken out by the pickup roll Rp at a preset sheet feeding time. The sheets S picked up by the pickup roll Rp are separated one by one by the separating roll Rs when picked up in a state where a plurality of sheets S are overlapped. The sheet S that has passed the separating roll Rs is conveyed to the registration roll Rr by a plurality of conveyance rolls Ra.

The sheet S conveyed to the registration roll Rr is transferred from the sheet guide SG1 before transfer as an example of a guide member before transfer to the transfer area according to the timing when the toner image on the surface of the photosensitive drum PR moves to the transfer area Q3. It is transported toward Q3.
The sheet S conveyed from the registration roll Rr is supported on the surface of the transfer belt TB and passes through the transfer region Q3. A toner image on the surface of the photosensitive drum PR is transferred to the sheet S passing through the transfer region Q3 by a transfer voltage applied to the transfer roll TR.
The surface of the photosensitive drum PR after passing through the transfer region Q3 is cleaned by removing residual toner by the drum cleaner CLp. The surface of the photosensitive drum PR after cleaning is recharged by the charging roll CR.

The sheet S to which the toner image is transferred is peeled from the transfer belt TB by the peeling claw SC. From the transfer belt TB from which the sheet S has been peeled off, deposits such as developer and paper dust attached to the surface of the transfer belt TB are removed by the belt cleaner CLb. When the sheet S peeled from the transfer belt TB passes through the contact area between the heating roll Fh and the pressure roll Fp, the toner image is heated and pressed to be fixed.
The recording sheet S on which the toner image is fixed passes through the gate MG while being elastically deformed, and is conveyed to the discharge path SH2. The sheet S discharged to the paper discharge tray TRh is transported by the transport roll Rb and discharged to the paper discharge tray TRh by the discharge roll Rh.

  When duplex printing is performed, the trailing edge of the sheet S on which one side has been recorded is conveyed downstream by the conveyance roll Rb and the discharge roll Rh until it passes through the gate MG. When the trailing edge of the sheet S passes through the gate MG, the transport roll Rb and the discharge roll Rh rotate in the reverse direction and are transported from the discharge path SH2 toward the reversal path SH3. That is, the sheet S is so-called switched back with the conveyance direction reversed. The switched sheet S is guided by the gate MG and conveyed through the reversing path SH3. The sheet S conveyed on the reversing path SH3 joins the conveying path SH1, and is conveyed to the registration roll Rr with the front and back sides reversed. Then, an image is printed on the second surface of the sheet S in the transfer region Q3.

(Description of developing device)
FIG. 2 is an explanatory cross-sectional view of a main part of the developing device according to the first embodiment.
FIG. 3 is an explanatory diagram of the developing device of Example 1, and is a cross-sectional view taken along the line III-III of FIG.
1 and 2, the developing device G of Example 1 includes a container 1. The container 1 contains a developer. In Example 1, as a developer, a developer including a carrier as an example of magnetic powder and a toner as an example of powder for development, a so-called two-component developer is configured.
The container 1 has a container body 1a extending in the front-rear direction. A cylindrical portion 1b extending forward is supported at the front end of the main body 1a of the container. Moreover, the cylinder part 1c extended backward is supported by the rear-end part of the main body 1a of a container.

An admix chamber 2 as an example of a first storage chamber is formed on the left side of the container main body 1a and the cylindrical portion 1b. The admix chamber 2 extends in the front-rear direction. On the upper surface of the front end portion of the admix chamber 2, a supply port 2a as an example of a supply unit is formed. The replenishing port 2a is configured so that the developer can be replenished from a developer replenishing device (not shown). On the right side of the admix chamber 2, a supply chamber 3 as an example of a second storage chamber is formed. The supply chamber 3 extends in the front-rear direction in parallel with the admix chamber 2. A partition wall 4 as an example of a partition portion is formed between the admix chamber 2 and the supply chamber 3. The partition wall 4 is formed to be shorter in the front-rear direction than the admix chamber 2 and the supply chamber 3. Therefore, the admix chamber 2 and the supply chamber 3 are connected by the first inflow portion 6 at the front end and the second inflow portion 7 at the rear end. Therefore, the container 1 according to the first embodiment is configured such that the developer can move between the admix chamber 2 and the supply chamber 3 through the inflow portions 6 and 7.
The admix chamber 2 and the supply chamber 3 constitute circulation chambers 2 and 3 as an example of a circulation section.

A discharge chamber 8 as an example of a developer discharge unit is connected to the rear of the supply chamber 3. A developer discharge port 8 a is formed at the rear end of the discharge chamber 8. The developer discharge port 8a is connected to a collection container (not shown).
A first developing chamber 11 as an example of a housing portion for a first developing member is formed at the upper right end portion of the main body 1a of the container. In addition, a second developing chamber 12 as an example of a housing portion for a second developing member is formed at the upper right of the supply chamber 3 and below the first developing chamber 11.
A storage chamber 13 as an example of a storage unit is formed above the admix chamber 2 and the supply chamber 3. The bottom of the storage chamber 13 of the first embodiment is connected to the upper portion of the supply chamber 3. Therefore, the developer in the storage chamber 13 is configured to be able to flow into the supply chamber 3.

In the admix chamber 2, an admix auger 16 as an example of a first transport member is disposed. The admix auger 16 according to the first embodiment includes a first rotating shaft 16a as an example of a first shaft portion. A first transport blade 16b as an example of a first transport unit is supported on the outer periphery of the first rotating shaft 16a. The first conveying blade 16b is formed in a spiral shape with respect to the axial direction.
In the supply chamber 3, a supply auger 17 as an example of a second transport member is disposed. The supply auger 17 according to the first embodiment includes a second rotating shaft 17a as an example of a second shaft portion. A second conveying blade 17b as an example of a second conveying unit is supported on the outer periphery of the second rotating shaft 17a. The second conveying blade 17b is formed in a spiral shape with respect to the axial direction. Note that the second rotating shaft 17 a of the first embodiment extends to the rear end of the discharge chamber 8. The second rotating shaft 17a supports a discharge blade 17c as an example of a discharge transport unit in a range corresponding to the discharge chamber 8.
Each of the augers 16 and 17 has a rotational direction and a spiral direction of the conveying blades 16b and 17b so as to convey the developer in opposite directions when rotating.

A paddle 18 as an example of a third transport member is supported in the storage chamber 13. The paddle 18 has a third rotating shaft 18a as an example of a third shaft portion. A third transport blade 18b as an example of a third transport unit is supported on the third rotating shaft 18a. The third conveying blade 18b according to the first embodiment is formed in a plate shape extending in the radial direction from the third rotating shaft 18a.
A first developing roll 21 as an example of a first developing member is supported in the first developing chamber 11. The first developing roll 21 has a first magnet roll 21a as an example of a first magnet member. The first magnet roll 21 a is fixedly supported by the container 1. A first developing sleeve 21b, which is an example of a developer holding body and is an example of a first rotating body, is disposed on the outer periphery of the first magnet roll 21a. The first developing sleeve 21b is formed in a hollow cylindrical shape.

In the second developing chamber 12, a second developing roll 22 as an example of a second developing member is supported. The second developing roll 22 is configured similarly to the first developing roll 21, and is an example of a second magnet roll 22a as an example of a second magnet member, and a developer holding body, And a second developing sleeve 22b as an example of a second rotating body.
In the first exemplary embodiment, the photosensitive drum PR and the developing rolls 21 and 22 are held with a predetermined interval therebetween. In addition, a first developing region Q2a is configured by a region where the first developing roll 21 and the photosensitive drum PR face each other. A second developing region Q2b is configured by a region where the second developing roll 22 and the photosensitive drum PR face each other.

Therefore, in the first embodiment, the first development region Q2a is disposed on the upstream side of the second development region Q2b with respect to the rotation direction of the photosensitive drum PR. The first development area Q2a and the second development area Q2b constitute the development area Q2 of Example 1.
Further, the first developing sleeve 21b according to the first exemplary embodiment rotates in the direction opposite to the rotation direction of the photosensitive drum PR in the first developing region Q2a. Further, the second developing sleeve 22b according to the first exemplary embodiment rotates in the direction along the rotation direction of the photosensitive drum PR in the second developing region Q2b. Accordingly, in the first embodiment, the first developing sleeve 21b rotates in the against direction and the second developing sleeve 22b rotates in the with direction with respect to the photosensitive drum PR.

In FIG. 2, a trimmer 31 as an example of a layer-thickness regulating member is supported at a position upstream of the second development region Q2b with respect to the rotation direction of the second development sleeve 22b. In Example 1, the thickness of the developer layer formed on the surface of the second developing sleeve 22b is added to the thickness of the developer layer formed on the surface of the first developing sleeve 21b. Accordingly, the trimmer 31 is disposed at a distance from the second developing sleeve 22b.
A chute 36 as an example of a developer guide member is disposed at a position downstream of the first developing region Q2a with respect to the rotation direction of the first developing sleeve 21b. The chute 36 of the first embodiment is disposed so that the tip is close to the surface of the first developing sleeve 21b. A proximal end portion of the chute 36 extends to the storage chamber 13. Therefore, the chute 36 guides the developer peeled from the first developing sleeve 21 b to the storage chamber 13.

(Description of magnetic pole)
In FIG. 2, the second magnet roll 22 a has a pickup magnetic pole N <b> 11 as an example of an attracting magnetic pole at a position corresponding to the supply auger 17.
A trimming magnetic pole S11 as an example of a regulation magnetic pole having a layer thickness is disposed downstream of the pickup magnetic pole N11 with respect to the rotation direction of the second developing sleeve 22b. The trimming magnetic pole S11 is arranged corresponding to the trimmer 31. The trimming magnetic pole S11 is composed of a magnetic pole having a polarity opposite to that of the pickup magnetic pole N11.
A transfer magnetic pole N12 as an example of one counter magnetic pole is disposed on the downstream side of the trimming magnetic pole S11 with respect to the rotation direction of the second developing sleeve 22b. The transfer magnetic pole N12 of the first embodiment is disposed corresponding to the closest position 41 of the developing sleeves 21b and 22b. The delivery magnetic pole N12 is composed of a magnetic pole having a polarity opposite to that of the trimming magnetic pole S11.

A second developing magnetic pole S12 as an example of a second magnetic pole is disposed downstream of the transfer magnetic pole N12 with respect to the rotation direction of the second developing sleeve 22b. The second developing magnetic pole S12 is disposed corresponding to the second developing region Q2b. The second developing magnetic pole S12 is composed of a magnetic pole having a polarity opposite to that of the transfer magnetic pole N12.
A pick-off magnetic pole N13 as an example of a separation magnetic pole is disposed downstream of the second development magnetic pole S12 with respect to the rotation direction of the second development sleeve 22b. The pick-off magnetic pole N13 is composed of a magnetic pole having the same polarity as the pickup magnetic pole N11 and a reverse polarity to the second developing magnetic pole S12. Further, the pick-off magnetic pole N13 is arranged so that the position where the magnetic force becomes minimum between the pick-off magnetic pole N13 and the pick-up magnetic pole N11 corresponds to the supply chamber 3.

  On the magnet roll 21 a of the first developing roll 21, receiving magnetic poles S <b> 21 and N <b> 21 as examples of the other opposing magnetic pole are arranged corresponding to the closest position 41. The receiving magnetic poles S21 and N21 of the first embodiment are configured by a pair of magnetic poles having different polarities. In the first embodiment, the receiving magnetic poles S21 and N21 are arranged at positions symmetrical with respect to the rotation direction of the first developing sleeve 21b with the closest position 41 interposed therebetween. Further, in the first embodiment, the first receiving magnetic pole S21 disposed on the upstream side with respect to the rotation direction of the first developing sleeve 21b is configured by a magnetic pole having a polarity opposite to the delivery magnetic pole N12. Therefore, the second receiving magnetic pole N21 arranged on the downstream side with respect to the rotation direction of the first developing sleeve 21b is composed of a magnetic pole having the same polarity as the delivery magnetic pole N12.

A first developing magnetic pole S22 as an example of the first magnetic pole is disposed on the downstream side of the second receiving magnetic pole N21 with respect to the rotation direction of the first developing sleeve 21b. The first developing magnetic pole S22 according to the first exemplary embodiment includes a magnetic pole having a polarity opposite to that of the second receiving magnetic pole N21. Therefore, a magnetic field for attracting the developer to the first developing sleeve 21b is generated between the first developing magnetic pole S22 and the second receiving magnetic pole N21 of the first embodiment.
Further, the first developing magnetic pole S22 of the first embodiment is disposed at a position corresponding to the first developing region Q2a. In the first embodiment, as shown in FIG. 2, the center of the first developing roll 21 with respect to the virtual line segment 51 that connects the center 21c of the first developing roll 21 and the rotation center PRa of the photosensitive drum PR. A first developing magnetic pole S22 is arranged at a position shifted by an inclination angle α on the upstream side in the rotation direction of the first developing sleeve 21b with 21c as a center. That is, the first embodiment of the first embodiment is located at a position shifted from the closest position between the first developing roll 21 and the photosensitive drum PR by an inclination angle α on the upstream side in the rotational direction of the first developing sleeve 21b. A developing magnetic pole S22 is arranged.

A first transport magnetic pole N22 is disposed downstream of the first developing magnetic pole S22 with respect to the rotation direction of the first developing sleeve 21b. The first transport magnetic pole N22 is composed of a magnetic pole having a polarity opposite to that of the first developing magnetic pole S22.
A second transport magnetic pole S23 is disposed on the downstream side of the first transport magnetic pole N22 with respect to the rotation direction of the first developing sleeve 21b. The second transport magnetic pole S23 is composed of a magnetic pole having a polarity opposite to that of the first transport magnetic pole N22.

A first pick-off magnetic pole N23 is disposed downstream of the second transport magnetic pole S23 with respect to the rotation direction of the first developing sleeve 21b. In addition, a second pick-off magnetic pole N24 is disposed downstream of the first pick-off magnetic pole N23 with respect to the rotation direction of the first developing sleeve 21b. In the first embodiment, the pick-off magnetic poles N23 and N24 are composed of magnetic poles having the same polarity and opposite to the second transport magnetic pole S23.
In the first embodiment, the pickoff magnetic poles N23 and N24 are arranged so that the position where the magnetic force between the first pickoff magnetic pole N23 and the second pickoff magnetic pole N24 is minimized corresponds to the tip of the chute 36. Has been.

(Operation of Example 1)
In the copying machine U of the first embodiment having the above-described configuration, when the image forming operation is started, the developing rolls 21 and 22, the augers 16 and 17, and the paddle 18 of the developing device G start to rotate. As the augers 16 and 17 rotate, the developer contained in the admix chamber 2 and the supply chamber 3 is conveyed in the opposite directions while being agitated. The developer conveyed to the downstream portion of each chamber 2, 3 flows into the other chamber 2, 3 through the inflow portions 6, 7. Therefore, the developer circulates between the admix chamber 2 and the supply chamber 3. Part of the developer flowing from the admix chamber 2 into the supply chamber 3 is conveyed to the developer discharge port 8a. Therefore, the deteriorated developer is gradually discharged from the developer discharge port 8a.

The developer in the supply chamber 3 is attracted to the surface of the second developing sleeve 22b by the magnetic force of the pickup magnetic pole N11. The trimming magnetic pole S11 causes the developer to stand toward the trimmer 31, that is, a so-called spiked state. The trimmer 31 is in contact with the developer that has risen, and regulates the thickness of the developer layer on the surface of the second developing sleeve 22b.
The developer that has passed through the trimmer 31 is conveyed to a region between the transfer magnetic pole N12 and the reception magnetic poles S21 and N21 as the second developing sleeve 22b rotates.

  The developer on the surface of the second developing sleeve 22b receives the magnetic force of the magnetic field generated between the transfer magnetic pole N12 and the first receiving magnetic pole S21, and a part of the developer is on the first developing sleeve 21b side. Move to. At this time, each magnetic pole N12, so that half of the developer on the second developing sleeve 22b moves to the surface of the first developing sleeve 21b and the remaining developer remains on the second developing sleeve 22b. The magnetic force of S21 and N21 is set.

Along with the rotation of the photosensitive drum PR, the latent image on the surface of the photosensitive drum PR sequentially passes from the first developing area Q2a to the second developing area Q2b and is developed into a visible image. Accordingly, the latent image on the surface of the photosensitive drum PR is developed on the first developing sleeve 21b and then developed on the second developing sleeve 22b.
Therefore, with the development of the developing device G according to the first embodiment, the development failure is caused by two developments compared to the configuration in which the development failure may occur in one development due to the high speed rotation of the photosensitive drum PR. The occurrence of is reduced.

The developer that has not been consumed in the first developing region Q2a is transported to the downstream side while being held on the surface of the first developing sleeve 21b under the magnetic force of the first transport magnetic pole N22.
The developer leaves the first developing sleeve 21b at the position of the chute 36. The developer separated from the first developing sleeve 21 b is guided along the chute 36 and flows into the storage chamber 13. The paddle 18 returns the developer that has flowed into the storage chamber 13 to the supply chamber 3.
The developer that has not been consumed in the second developing region Q2b is attached to the surface of the second developing sleeve 22b, and the magnetic force between the pick-off magnetic pole N13 and the pick-up magnetic pole N11 is at a position where the second magnetic force is minimal. Detach from the developing sleeve 22b. The developer separated from the second developing sleeve 22b is returned to the supply chamber 3. The developer returned to the supply chamber 3 is conveyed while being stirred by the supply auger 17. The developer in the supply chamber 3 is adsorbed by the second developing roll 22 and reused, or conveyed to the admix chamber 2 and circulated.

FIG. 4 is an explanatory diagram of the magnetic field in the region where the developer is transferred, FIG. 4A is an explanatory diagram of the magnetic field in the conventional configuration, and FIG. 4B is an explanatory diagram of the magnetic field in the configuration of the first embodiment.
4A, in the configuration in which the developer is transferred from the second developing roll 01 to the first developing roll 02 in the conventional developing device, as in the configuration described in Patent Document 3, it faces the transfer magnetic pole 03. Thus, a receiving magnetic pole 04 having a polarity opposite to that of the delivery magnetic pole 03 is disposed. A trimmer 06 is disposed in the gap between the transfer magnetic pole 03 and the reception magnetic pole 04. In this configuration, the developer is distributed according to the balance of the magnetic force in the magnetic field between the transfer magnetic pole 03 and the reception magnetic pole 04 and the gap between the trimmer 06 and each of the rolls 01 and 02. Therefore, the developer that could not pass through the position of the trimmer 06 is held in the magnetic field between the transfer magnetic pole 03 and the reception magnetic pole 04, and tends to stay in the space between the transfer magnetic pole 03 and the reception magnetic pole 04. If the developer stays in the space between the transfer magnetic pole 03 and the reception magnetic pole 04, the developer is easily loaded and stressed, and the developer is likely to deteriorate. Further, when the developer is regulated by the trimmer 06, the developer is easily deteriorated due to stress. When the developer deteriorates, the fluidity and the charge amount are likely to fluctuate, and the toner density of the developer tends to fluctuate. If the fluidity or the like fluctuates, the amount of developer passing through the trimmer 06 may fluctuate, which may lead to poor development.
Further, in the configuration using the trimmer 06, there is a possibility that the amount of the developer may fluctuate due to a manufacturing error or an assembly error in the interval between the developing rolls 01 and 02 and the trimmer 06 and the accuracy of the positions of the magnetic poles 03 and 04.

On the other hand, in the developing device G of Example 1, as shown in FIG. 4B, in the region where the developer is transferred from the second developing roll 22 to the first developing roll 21, one transfer magnetic pole N12 and Two receiving magnetic poles S21 and N21 having different polarities are arranged. Accordingly, a magnetic field 42 attracted between the transfer pole N12 and the first reception pole S21 having opposite polarities is formed, and repulsion is generated between the transfer pole N12 and the second reception pole N21 having the same polarity. A magnetic field 43 is formed. Therefore, the delivery of the developer is promoted between the delivery magnetic pole N12 and the first reception magnetic pole S21, and the delivery of the developer is restricted between the delivery magnetic pole N12 and the second reception magnetic pole N21. .
The developer that has moved to the surface of the first developing roll 21 is held on the first developing roll 21 by a magnetic field 44 formed between the first receiving magnetic pole S21 and the second receiving magnetic pole N21. The That is, in the first developing roll 21 according to the first embodiment, the developer that can be held by the magnetic field between the receiving magnetic poles S <b> 21 and N <b> 21 is attracted to the first developing roll 21. Therefore, in the conventional configuration, there is a possibility that the width of the gap varies due to an installation error of the first developing roll 01 and the trimmer 06, and the amount of developer held on the surface of the first developing roll 01 varies. Although there is a fear, in the developing device G of Example 1, the amount of developer that can be held by a magnetic field is held by the first developing roll 21. Therefore, the amount of developer held on the surface of the first developing roll 21 is easily stabilized.

  In the developing device G of Example 1, not only the delivery of the developer is promoted but also the delivery of the developer to the region where the developer is delivered from the second development roll 22 to the first development roll 21. There is also a limited magnetic field. Therefore, in the region where the developer is delivered, the magnetic field whose delivery is restricted suppresses the holding of the developer, and the retention of the developer is suppressed. Therefore, compared with the conventional configuration, the stress accompanying the retention of the developer is reduced.

In particular, in the first exemplary embodiment, the first receiving magnetic pole S21 is disposed on the upstream side and the second receiving magnetic pole N21 is disposed on the downstream side with respect to the rotation direction of the first developing roll 21. Therefore, after the delivery of the developer is promoted on the upstream side, the delivery of the developer is limited on the downstream side. Therefore, on the downstream side in the rotation direction of the first developing roll 21, the magnetic field that restricts the delivery of the developer is developed between the developing rolls 21 and 22, similarly to the trimmer 06, without arranging the trimmer 06. Inhibits agent migration. Further, in the developing device G of the first embodiment, after the developer is moved by the attracting magnetic field on the upstream side, the developer is easily divided and distributed by the repelling magnetic field on the downstream side. Yes.
Therefore, the developer can be stably distributed in a state in which the stress applied to the developer is reduced as compared with the configuration in which the developer layer is physically distributed using the trimmer 06. Therefore, as compared with the conventional configuration, the deterioration of the developer can be suppressed and stable distribution is possible.

Further, in the developing device G of Example 1, two magnetic poles S21 and N21 are arranged on the first developing roll 21 that rotates in the against direction with respect to the photosensitive drum PR in the first developing region Q2a. . Here, in the first developing roll 21 rotating in the against direction, the relative speed with respect to the surface of the photosensitive drum PR is higher in the first developing region Q2a than in the second developing roll 22 rotating in the with direction. Get faster. Accordingly, in the first development region Q2a, the development conditions become more severe as the speed of the photosensitive drum PR and the first development roll 21 increases. Therefore, when the amount of developer held on the surface of the first developing roll 21 varies as compared with the second developing roll 22, the image quality is likely to be affected.
Here, in the region where the developer is transferred, two magnetic poles S21 and N21 are arranged on the side where the two magnetic poles S21 and N21 are arranged and on the side where the one magnetic pole N12 is arranged. On the side, the amount of developer is likely to be stabilized by the magnetic field between the two magnetic poles S21 and N21. In the developing device G of the first embodiment, the two magnetic poles S21 and N21 are arranged on the first developing roll 21 that rotates in the against direction, and the developer held on the surface of the first developing roll 21. It is easy to stabilize the amount, and it can cope with high-speed rotation and high image quality.

  In the developing device G according to the first embodiment, the first receiving magnetic pole S21 is disposed at a position shifted upstream from the closest position 41 between the first developing sleeve 21b and the second developing sleeve 22b. ing. Therefore, compared with the conventional configuration, the magnetic field 42 between the first receiving magnetic pole S21 and the passing magnetic pole N12 is less likely to reach the closest position 41. If the developing rolls 01 and 02 have eccentricity, curvature, and the like, the closest position 41 is likely to be affected by the gap becoming wider or narrower. Therefore, when the magnetic field delivered to the closest position 41 is generated as in the conventional configuration, the amount of developer delivered is likely to fluctuate. On the other hand, in the developing device G of the first embodiment, the magnetic field 42 approaching the closest position 41 is reduced and the influence of the curvature of the developing rolls 21 and 22 is reduced. Therefore, it is possible to stabilize the amount of developer delivered.

FIG. 5 is an explanatory diagram of the magnetic field between the first developing member, the second developing member, and the image carrier, FIG. 5A is an explanatory diagram of the magnetic field in the configuration of Example 1, and FIG. It is explanatory drawing of the magnetic field in a structure.
Further, in the configuration of the first embodiment, in FIG. 5A, in the first developing region Q2a, the developer in the first developing sleeve 21b conveyed to the position corresponding to the first developing magnetic pole S22 has magnetism. The carriers are aligned along the magnetic field lines formed by the first developing magnetic pole S22. A so-called career is launched. In addition, the rising carrier is charged with a positive polarity. Therefore, the negatively charged toner is adsorbed to the spiked carrier.
A developing voltage is applied to the first developing roll 21. On the surface of the photosensitive drum PR, as shown in FIG. 1, there are an exposed portion irradiated with the laser beam L and a non-exposed portion not irradiated with the laser beam L at the latent image writing position Q1. Is provided. The charged toner moves to the exposed portion on the surface of the photosensitive drum PR in accordance with the development voltage and the potential difference between the exposed portion and the non-exposed portion. Thus, the latent image is developed into a visible image.

As shown in FIG. 5B, in the first developing roll 021 having the conventional configuration, the conveying magnetic pole is not disposed at a position between the receiving magnetic pole N041 and the first developing region 012. Therefore, the first developing magnetic pole S022 is configured by a magnetic pole having a polarity opposite to that of the second developing magnetic pole N031 disposed on the second developing roll 022. Therefore, a magnetic field 031 is generated between the two poles of the first developing magnetic pole S022 and the second developing magnetic pole N031.
Here, when the developing device G is miniaturized with the miniaturization of the copying machine U, the distance between the developing rolls 021 and 022 becomes short according to the miniaturization of the developing device G. Therefore, the distance between the first developing magnetic pole S022 and the second developing magnetic pole N031 is shortened. As the distance between the first developing magnetic pole S022 and the second developing magnetic pole N031 becomes shorter, the magnetic force of the magnetic field 031 becomes stronger.

Further, with the rotation of the first developing sleeve 021b, the developer on the surface of the first developing sleeve 021b is conveyed to a position corresponding to the first developing magnetic pole S022.
On the surface of the first developing sleeve 021b, a developer spikes along a magnetic field line formed by the first developing magnetic pole S022 at a position corresponding to the first developing magnetic pole S022. In some cases, the surface of the photosensitive drum 011 may come into contact with a spiked developer. Therefore, part of the spiked developer may come into contact with the surface of the photosensitive drum 011 and the developer may not pass through the first development region 012.
The developer that could not pass is upstream of the first developing area 012 in the rotation direction of the first developing sleeve 021b, that is, the area 037 surrounded by the photosensitive drum 011 and the two developing rolls 021 and 022. It stays at. The developer staying in the region 037 may be held in the magnetic field 031 formed in the region 037. If the developer is held in the magnetic field 031, it becomes difficult for the developer to be conveyed to the first development area 012.

  Therefore, the developer tends to stay in the region 037 for a long time. When the developer stays, the charged charge is reduced by natural discharge or the like, and the developing ability is lowered. Therefore, when the developer whose developing ability is lowered is transported to the first developing area 012, the density of the image to be developed is lowered. Further, the surface of the photosensitive drum 011 passes through the area 037 after being developed in the first developing area 012. Therefore, if the developer held by the magnetic field 031 stays, the visible image may be scraped off by the staying developer. Therefore, there is a possibility that the density of the visible image on the surface of the photosensitive drum 011 may be reduced, or that the developed visible image may be defective.

On the other hand, as shown in FIG. 5A, in the first developing roll 21 of the first embodiment, the first developing magnetic pole S22 is the same as the second developing magnetic pole S12 disposed on the second developing roll 22. It is composed of polar magnetic poles. Therefore, a repulsive magnetic field 52 is formed between the first developing magnetic pole S22 and the second developing magnetic pole S12. Therefore, even if a developer that cannot pass through the first developing area Q2a is generated, the developer is not held in the magnetic field in the area 37 surrounded by the photosensitive drum PR and the developing rolls 21 and 22.
Therefore, compared with the configuration of the conventional developing device G in which the developer is held in the magnetic field 031 in the region 037, in the configuration of the developing device G of Example 1, the developer is not held in the magnetic field in the region 37, and the region 37 The developer is difficult to stay. Therefore, the developer is easily transported to the first development area Q2a before the development capability is deteriorated.
Therefore, compared to the configuration of the conventional developing device, the configuration of the developing device G of Example 1 reduces the density reduction of visible images and the occurrence of defects. Therefore, a decrease in image quality formed on the sheet S is reduced.

Further, in the configuration of the first embodiment, as shown in FIG. 5A, the first developing roller 21a has a first developing sleeve with respect to the closest position between the first developing roller 21 and the photosensitive drum PR. A first developing magnetic pole S22 is disposed at a position shifted by an inclination angle α on the upstream side in the rotational direction of 21b.
Accordingly, the magnetic lines of force of the first developing magnetic pole S22 are located at a position shifted from the closest position between the first developing roll 21 and the photosensitive drum PR by an inclination angle α on the upstream side in the rotation direction of the first developing sleeve 21b. Along with, the developer is sprinkled.

In the conventional configuration, as shown in FIG. 5B, the first developing magnetic pole S022 is provided on the first developing roll 021 at a position corresponding to the closest position between the first developing roll 021 and the photosensitive drum 011. Has been placed. Therefore, the center of the first developing roll 021 and the center of the photosensitive drum 011 are arranged on the surface of the first magnetic sleeve 021b at a position corresponding to the closest position between the first developing roll 021 and the photosensitive drum 011. The developer is spiked along the magnetic line 051 connecting the rotation center 011a.
That is, in the conventional configuration, the developer spikes at the closest position where the gap is the narrowest in the region between the surface of the first developing sleeve 021b and the surface of the photosensitive drum 011. Further, the developer layer thickness locally increases. Therefore, when the developer that has risen in contact with the surface of the photosensitive drum 011, the contact pressure at the time of contact may be excessive. Then, when the contact pressure of the spiked developer is excessive, the spiked developer may scrape off the visible image on the surface of the photosensitive drum 011.

On the other hand, in the configuration of the first embodiment, the position shifted by the inclination angle α to the upstream side in the rotation direction of the first developing sleeve 21b with respect to the closest position between the first developing roll 21 and the photosensitive drum PR. Then the developer comes up.
Accordingly, at the closest position of the surface of the photosensitive drum PR to the first developing sleeve 21b, the developer is slightly tilted along the lines of magnetic force. Therefore, it is possible to reduce an excessive contact pressure when the developer that comes up on the surface of the photosensitive drum PR contacts.
Therefore, compared to the conventional configuration in which the first developing magnetic pole S022 is disposed at the closest position, in the configuration of the first embodiment, the spiked developer may scrape the visible image on the surface of the photosensitive drum PR. Is reduced. Therefore, in the configuration of the first embodiment, visible image defects are reduced as compared with the conventional configuration.

  In the conventional configuration, the developer is spiked at the closest position on the surface of the photosensitive drum 011 with respect to the first developing sleeve 021b. Therefore, the area where the latent image on the surface of the photosensitive drum 011 can be developed is only in the vicinity of the closest position. Therefore, if the rotational speed of the photosensitive drum 011 or the first developing sleeve 021b is increased, there is a possibility that development failure may occur. In particular, in the configuration in which the rotation direction of the developing sleeve 021b and the photosensitive drum 011 is “gainst”, the first developing sleeve 021b and the photosensitive member in the closest position are compared with the configuration in which the rotating direction of the developing sleeve 021b and the photosensitive drum 011 is “with”. The relative speed with the body drum 011 is large. Therefore, development defects are more likely to occur.

On the other hand, in the configuration of the first embodiment, the developer spike stands on the downstream side in the rotation direction of the photosensitive drum PR with respect to the closest position between the first developing sleeve 21b and the photosensitive drum PR. It becomes the state. Therefore, development is possible not only at the closest position but also at the downstream side in the rotation direction of the photosensitive drum PR. That is, in the configuration of the first exemplary embodiment, the developable area is widened from the closest position toward the downstream side in the rotation direction of the photosensitive drum PR.
Therefore, compared with the conventional configuration in which the first developing magnetic pole S022 is disposed at the closest position, the configuration of the first embodiment has a wider width of the region where the latent image on the surface of the photosensitive drum PR can be developed. . Therefore, compared with the conventional configuration, the configuration of the first embodiment can reduce the development failure of the latent image, and can reduce the deterioration of the image quality formed on the sheet S.

In particular, in the first exemplary embodiment, the distance between the surface of the photosensitive drum PR and the surface of the developing sleeve 21b is greater than the set value of the height that rises in the normal direction at the position corresponding to the first developing magnetic pole S22. It is preferable to set. When the setting value of the height of the heading coincides with the distance between the surface of the photosensitive drum PR and the surface of the developing sleeve 21b, the first position that is downstream in the rotation direction of the photosensitive drum PR from the closest position. At the position of the developing magnetic pole S22, the tip of the developer spike contacts the surface of the photosensitive drum PR, and the contact pressure hardly acts on the surface of the photosensitive drum PR.
Further, in this case, at the closest position, the tip of the developer comes into contact with the surface of the photosensitive drum PR with the developer rising slightly tilted. Therefore, development is possible at the closest position as well as at the position corresponding to the first current magnetic pole S22. Therefore, as described above, it is possible to expand the width of the developable region while suppressing an excessive contact pressure at the closest position.

Further, in the conventional configuration that rises at the closest position, when the visible image on the surface of the photosensitive drum 011 is scraped off by the developer that is raised at the closest position, the visible image that has been scraped off is removed. The part is difficult to be developed again. Therefore, there is a risk that a defect occurs in the visible image on the surface of the photosensitive drum 011.
On the other hand, in the configuration of the first embodiment, even if the visible image on the surface of the photosensitive drum PR is scraped in the vicinity of the closest position, the developable region has a width. Development is possible on the downstream side in the rotation direction of the photosensitive drum PR from the contact position. Therefore, in the developing device G of Example 1, the portion where the visible image has been scraped is easily developed again.

Therefore, compared with the conventional configuration, in the configuration of the first embodiment, it is possible to reduce the occurrence of defects in the visible image on the surface of the photosensitive drum PR. Therefore, it is possible to reduce deterioration in image quality formed on the sheet S.
In the configuration of Embodiment 1, it is desirable that the inclination angle α is larger than + 8 ° in order to reduce the risk of the developer that spikes the visible image on the surface of the photosensitive drum PR scraping off. Further, the inclination angle α is set to + 20 ° in order to reduce the possibility of developing defects due to excessive rising of the developer at the closest position between the first developing sleeve 21b and the photosensitive drum PR. Small is desirable.

  Further, in the conventional configuration, the developer may be densely packed and pressed against each other at the closest position. Therefore, the pushed developer may fall off the surface of the first developing sleeve 021b and fall downward. When the developer falls from the first developing sleeve 021b, the developer may fall on the surface of the second developing sleeve 22b disposed below. Therefore, the amount of developer on the surface of the second developing roll 021b may change, and development failure may occur.

  On the other hand, in the configuration of the first embodiment, the position shifted by the inclination angle α downward, which is the upstream side in the rotation direction of the first developing sleeve 21b, with respect to the closest position to the photosensitive drum PR, A first developing magnetic pole S22 is disposed. In the first embodiment, the pressure at the closest position is suppressed. However, even if the developer is about to fall downward due to the influence of gravity, the developer that stands out at the position corresponding to the first developing magnetic pole S22 is changed. In the meantime, the developer is easily captured. Therefore, in the configuration of the first embodiment, the amount of the developer that falls from the first developing sleeve 21b to the second developing roll 22 is reduced as compared with the conventional configuration in which the developer grows at the closest position. Is expected, and the occurrence of defective development is reduced.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is made in the range of the summary of this invention described in the claim. Is possible. Modification examples (H01) to (H011) of the present invention are exemplified below.
(H01) In each of the above embodiments, the copying machine U is illustrated as an example of the image forming apparatus, but the present invention is not limited to this. For example, the present invention can be applied to a printer as an example of an image forming apparatus, a FAX, or a multifunction machine having a plurality of these functions. Further, the present invention is not limited to a single color image forming apparatus, and can be applied to a multicolor image forming apparatus.

(H02) In the above-described embodiment, the configuration in which two developing members are used is illustrated, but the present invention is not limited to this. For example, a configuration having three or more developing members is also possible. At this time, if at least the developing magnetic poles of a pair of adjacent developing members are configured with the same polarity, no magnetic field is generated between the adjacent developing magnetic poles with the same polarity. Therefore, as compared with the conventional developing device in which the developing magnetic poles of the adjacent developing members are all opposite in polarity, it is possible to reduce the place where the developer stays in the developing device G as a whole.
(H03) In the above-described embodiment, it is desirable to arrange the two receiving magnetic poles S21 and N21 with respect to one passing magnetic pole N12. However, with respect to the passing magnetic pole N12, only the receiving pole S21 having the opposite polarity is arranged. Is also possible.
(H04) In the embodiment, it is desirable to arrange one magnetic pole N12 on the developing roller 22 on the side and two magnetic poles S21 and N21 on the developing roller 21 on the gainst side in the transfer area. The reverse is also possible.

(H05) Of the receiving magnetic poles S21 and N21 in the above embodiment, it is desirable that the magnetic pole S21 having the opposite polarity to the delivery magnetic pole N12 is disposed on the upstream side, and the magnetic pole N21 having the same polarity is disposed on the downstream side. It is also possible to arrange the magnetic pole S21 of the same polarity on the downstream side and arrange the magnetic pole N21 of the same polarity on the upstream side.
(H06) In the above-described embodiment, the drum-shaped photosensitive drum PR is exemplified as an example of the image carrier. However, the present invention is not limited to this, and for example, a belt-shaped image carrier may be configured.
(H07) In the above embodiment, the configurations of the admix chamber 2, the supply chamber 3, the storage chamber 13, the augers 16, 17 and the paddle 18 are not limited to the configurations illustrated in the embodiments. For example, arbitrary changes are possible, such as a configuration in which the developer flows from the storage chamber 13 into the admix chamber 2 or a configuration similar to the augers 16 and 17 of the paddle 18.

(H08) In the above-described embodiment, it is desirable that the same trimmer as in the prior art is not disposed. However, a trimmer as an example of a sorting auxiliary member is installed as an auxiliary member to the present invention. It is also possible to do.
(H09) In the above-described embodiments, the polarities such as N and S and the positions and numbers of the magnetic poles are not limited to the configurations exemplified in the embodiments. It can be changed arbitrarily according to the design and specifications.
(H010) In the above-described embodiment, a configuration in which the first developing roll 21 is disposed above the second developing roll 22 is desirable, but the present invention is not limited to this. For example, a configuration in which the first developing roll 21 and the second developing roll 22 are arranged in the horizontal direction at the same height in the vertical direction is also possible.

(H011) In the above embodiment, in the second developing region Q2b, the first developing sleeve 21b rotates in the Against direction and the second developing sleeve 22b rotates in the with direction with respect to the photosensitive drum PR. However, the present invention is not limited to this. For example, the configuration in which the rotation direction of the first developing sleeve 21b and the rotation direction of the second developing sleeve 22b are reversed, or the developing sleeves 21b and 22b are both in the against direction or with the photosensitive drum PR. A configuration rotating in the direction is also possible.

21: First developing member,
21a ... 1st magnet member,
21b ... 1st rotation member,
21c ... rotation center 22 ... second developing member,
51 ... Virtual line segment,
F: Fixing device,
G: Developing device,
N22: Magnetic pole,
PR: Image carrier,
PRa: Center of rotation
Q2a: first development area,
Q2b ... second development area,
S ... medium,
S12 ... second magnetic pole,
S22 ... 1st magnetic pole,
TR ... Transcription device,
U: Image forming apparatus.

Claims (5)

A first developing member disposed to face the rotating image carrier, and generates a magnetic force for attracting a magnetic developer, and the image carrier and the first developer member are opposed to each other. A first magnet member in which a first magnetic pole is disposed corresponding to the first magnet member, and a first rotating body that is rotatably supported around the first magnet member and rotates while holding a developer on the surface thereof. The first developing member comprising:
A second developing member disposed on the downstream side of the first developing member with respect to the rotation direction of the image holding member, which generates a magnetic force for adsorbing the developer, and the image holding member and the second developing member; A second magnetic member having a second magnetic pole having the same polarity as the first magnetic pole corresponding to a position facing the developing member, and being rotatably supported surrounding the second magnetic member. And a second rotating member that rotates with the developer held on the surface, and the second developing member,
With
The first magnetic pole is disposed at a position shifted to the downstream side in the rotation direction of the image carrier with respect to a virtual line segment connecting the rotation center of the image carrier and the rotation center of the first rotor. And
The second magnet member has a delivery magnetic pole arranged corresponding to the closest position with the first magnet member,
The first magnet member includes a first receiving magnetic pole disposed at a position shifted to the upstream side in the rotation direction of the first rotating body from a position closest to the second magnet member; A second receiving magnetic pole disposed at a position shifted to the downstream side in the rotation direction of the first rotating body,
The first and second receiving magnetic poles receive the developer more on the first receiving magnetic pole side upstream than the second receiving magnetic pole side with respect to the closest position. The magnetic pole has a polarity opposite to that of the magnetic pole and the same polarity as the second receiving magnetic pole,
A developing device that develops the latent image formed on the surface of the image holding member into a visible image with the developer of the first developing member and the second developing member. The first rotating body that rotates in a direction opposite to the rotation direction of the image holding body in a region facing the image holding body;
The developing device according to claim 1, further comprising: At a position shifted to the downstream side in the rotation direction of the image carrier so that the thickness of the developer layer at the position of the first magnetic pole is equal to or less than the distance between the image carrier and the first rotator. The first magnetic pole disposed;
The developing device according to claim 1, further comprising: The first developing member disposed on the upper side in the gravity direction of the second developing member;
The developing device according to claim 1, further comprising: A rotating image carrier;
A latent image forming apparatus for forming a latent image on the surface of the image carrier;
The developing device according to any one of claims 1 to 4, which develops a latent image on the surface of the image carrier into a visible image;
A transfer device for transferring a visible image of the surface of the image carrier to a medium;
A fixing device for fixing the visible image transferred to the medium;
An image forming apparatus comprising:

Images