JP2021103264A - Developing device - Google Patents

Abstract

To provide a configuration capable of suppressing scattering of developer.SOLUTION: A magnet roller 44a having a plurality of magnetic poles is disposed inside a developing sleeve 44. A magnetic pole S1 is a magnetic pole disposed at a position closest to a photosensitive drum 1. A magnetic pole S2 is a magnetic pole for causing the developing sleeve 44 to support the developer in a developing container 41. A magnetic pole S3 has a same polarity as an adsorption magnetic pole S2. A magnetic pole N2 is, regarding a rotation direction of the developing sleeve 44, located at a downstream of a position Q where an opening end 41i downstream of the magnetic pole S1 of both ends of an opening unit 41h and the developing sleeve 44 oppose in a radial direction and at an upstream of a magnetic pole S3. A sealing sheet 48 is arranged so as to come into contact with the developer that is carried by the developing sleeve 44 in a range where an angle defined by the magnetic flux lines of the magnetic pole N2 and a tangent of the developing sleeve 44 is 30 degrees or larger and 150 degrees or less.SELECTED DRAWING: Figure 3

Description

The present invention relates to a developing apparatus using a developing agent containing toner and carriers.

An image forming apparatus using an electrophotographic method or an electrostatic recording method has a developing device that develops an electrostatic latent image formed on a photosensitive drum as an image carrier by a developer. The developing apparatus has a developing sleeve as a developing agent carrier that supports and rotates the developing agent, and supplies the developing agent supported on the developing sleeve to the photosensitive drum.

In the case of such a developing apparatus, there is a risk that the developing agent may scatter from the gap between the opening of the developing container in which the developing sleeve is arranged and the developing sleeve. For this reason, the elastically deformable plate-shaped member having one end fixed to the opening is placed on the surface of the developing sleeve where the normal component of the magnetic flux density of the magnetic poles of the magnets arranged in the developing sleeve is minimized. A configuration has been proposed in which the above-mentioned gaps are closed by being brought into contact with each other (Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-184042

In the case of the configuration described in Patent Document 1, a plate-shaped member (elastic member) is brought into contact with a portion where the normal component of the magnetic flux density of the magnetic pole is extremely small, that is, a portion where the developer supported on the developing sleeve is tilted. ing. Therefore, a gap is likely to occur between the elastic member and the developing agent on the developing sleeve due to the mounting accuracy of the elastic member, bending of the elastic member due to humidity, waviness, and the like. That is, there is a risk that the sealing performance of the elastic member may deteriorate depending on the mounting accuracy of the elastic member or a change due to the environment. As a result, the scattering of the developer may not be sufficiently suppressed.

An object of the present invention is to provide a configuration capable of suppressing scattering of a developer.

The present invention is a developing apparatus that develops an electrostatic latent image formed on an image carrier with a developing agent, wherein an opening is formed at a position facing the image carrier, and a developing agent containing toner and a carrier is formed. A developing container to be accommodated, a developing agent carrier which is arranged in the developing container so that a part of the opening is exposed, and which carries and rotates the developing agent in the developing container, and the developing agent carrier. A magnetic field generating means that is arranged non-rotatingly inside the developer, has a plurality of magnetic poles arranged in the direction of rotation of the developer-bearing body, and generates a magnetic field for carrying the developer on the developer-bearing body. A plurality of magnetic poles are arranged at a position where the developer carrier is in close contact with the image carrier, and the developer in the developing container is developed upstream of the first magnetic pole in the rotational direction. The magnetic field generating means including the second magnetic pole to be supported on the agent carrier and the third magnetic pole having the same pole as the second magnetic pole arranged adjacent to the upstream of the second magnetic pole in the rotational direction, and the development. A plate-shaped elastic member that is partially fixed to a container and arranged so as to extend toward the developing agent carrier, and among the plurality of magnetic poles, among both ends of the opening in the rotation direction. The magnetic flux line of a predetermined magnetic pole downstream from the position where the open end downstream of the first magnetic pole and the developer carrier are radially opposed to each other and upstream of the third magnetic pole is the developer. It is characterized by including the elastic member arranged so as to come into contact with the developing agent supported on the developing agent carrier in a range where the angle formed by the tangent line of the supporting body is 30 degrees or more and 150 degrees or less. ..

According to the present invention, scattering of the developer can be suppressed.

The schematic block sectional view of the image forming apparatus which concerns on 1st Embodiment. The schematic structural sectional view of the image forming part which concerns on 1st Embodiment. The schematic structural cross-sectional view of the developing apparatus which concerns on 1st Embodiment. The schematic structural vertical sectional view of the developing apparatus which concerns on 1st Embodiment. FIG. 6 is a schematic configuration sectional view of a replenishment device and a developing device according to the first embodiment. The schematic diagram which shows the relationship between the magnetic flux density on the developing sleeve and the magnetic spike angle. The schematic diagram explaining the behavior of the magnetic spike on the developing sleeve near the N2 pole. (A) When the sealing sheet is brought close to the N2 pole, and (b) When the sealing sheet is brought close to the N2 pole and the magnetic pole downstream of it, the magnetic spikes and sealing of the developing sleeve, respectively. The figure which shows the relationship of a sheet. A graph showing the relationship between the magnetic spike angle and the number of scattered toners. (A) When the sealing sheet is brought into contact with the developer at a position where the magnetic spike angle is larger than 90 degrees, (b) The sealing sheet is brought into contact with the developer at a position where the magnetic spike angle is less than 90 degrees. The figure which shows the relationship between the magnetic ear of a developing sleeve and a sealing sheet in each case. A table showing the relationship between the magnetic spike angle and the developer retention. FIG. 5 is a schematic configuration cross-sectional view of the developing apparatus according to the first embodiment, showing the relationship between the contact point of the sealing sheet and the distribution of the magnetic flux density. The schematic structural vertical sectional view of the developing apparatus which concerns on 2nd Embodiment. FIG. 6 is a schematic view showing a relationship between a sealing sheet near the boundary between a supported region A and a non-supported region B of a developing sleeve and a developing sleeve according to a comparative example. FIG. 6 is a schematic configuration cross-sectional view of the developing apparatus according to the second embodiment. The schematic diagram which shows the relationship between the sealing sheet near the boundary between the supported area A and the non-supported area B of a developing sleeve, and the developing sleeve which concerns on 2nd Embodiment.

<First Embodiment>
The first embodiment will be described with reference to FIGS. 1 to 12. First, the schematic configuration of the image forming apparatus of this embodiment will be described with reference to FIGS. 1 and 2.

[Image forming device]
The image forming apparatus 100 of the present embodiment is an electrophotographic tandem full-color printer including four image forming units PY, PM, PC, and PK each having a photosensitive drum 1 as an image carrier. The image forming apparatus 100 receives a toner image (image) according to an image signal from a document reading device (not shown) connected to the apparatus main body 100A or a host device such as a personal computer communicably connected to the apparatus main body 100A. ) Is formed on the recording material. Examples of the recording material include sheet materials such as paper, plastic film, and cloth. 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 100 have substantially the same configuration except that the developed colors are different. Therefore, the image forming unit PY will be described as a representative, and the description of other image forming units will be omitted.

As shown in FIG. 2, a cylindrical photoconductor, that is, a photosensitive drum 1 is arranged as an image carrier in the image forming portion PY. The photosensitive drum 1 is rotationally driven in the direction of the arrow in the drawing. A charging roller 2 as a charging means, a developing device 4, a primary transfer roller 52 as a transfer means, and a cleaning device 7 as a cleaning means are arranged around the photosensitive drum 1. An exposure device (laser scanner in this embodiment) 3 as an exposure means is arranged below the photosensitive drum 1 in the drawing.

A transfer device 5 is arranged above FIG. 1 of each image forming unit. The transfer device 5 is configured such that an endless intermediate transfer belt 51 as an intermediate transfer body is stretched on a plurality of rollers and orbits (rotates) in the direction of an arrow. Then, the intermediate transfer belt 51 carries the toner image that has been primarily transferred to the intermediate transfer belt 51 by supporting it, as will be described later. A secondary transfer outer roller 54 as a secondary transfer means is arranged at a position facing the secondary transfer inner roller 53 and the intermediate transfer belt 51 among the rollers on which the intermediate transfer belt 51 is stretched. Then, the secondary transfer unit T2 that transfers the toner image on the intermediate transfer belt 51 to the recording material is configured. A fixing device 6 is arranged downstream of the secondary transfer unit T2 in the recording material transport direction.

A cassette 9 containing the recording material S is arranged below the image forming apparatus 100. The recording material S supplied from the cassette 9 is conveyed toward the registration roller 92 by the transfer roller 91. Then, the tip of the recording material S abuts against the registration roller 92 in the stopped state, and a loop is formed to correct the skew of the recording material S. After that, the registration roller 92 is started to rotate in synchronization with the toner image on the intermediate transfer belt 51, and the recording material 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 100 configured as described above will be described. First, when the image forming operation is started, the surface of the rotating photosensitive drum 1 is uniformly charged by the charging roller 2. Next, the photosensitive drum 1 is exposed by a laser beam corresponding to an image signal emitted from the exposure apparatus 3. As a result, an electrostatic latent image corresponding to the image signal is formed on the photosensitive drum 1. The electrostatic latent image on the photosensitive drum 1 is visualized by the toner as a developing agent contained in the developing device 4 and becomes a visible image.

The toner image formed on the photosensitive drum 1 is first-ordered on the intermediate transfer belt 51 by the primary transfer unit T1 (FIG. 2) formed between the toner image formed on the photosensitive drum 1 and the primary transfer roller 52 arranged so as to sandwich the intermediate transfer belt 51. Transferred. At this time, a primary transfer bias is applied to the primary transfer roller 52. The toner (transfer residual toner) remaining on the surface of the photosensitive drum 1 after the primary transfer is removed by the cleaning device 7.

Such an operation is sequentially performed in each of the image forming portions of yellow, magenta, cyan, and black, and the toner images of four colors are superimposed on the intermediate transfer belt 51. After that, the recording material S housed in the cassette 9 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 54, the four-color toner images on the intermediate transfer belt 51 are collectively secondary-transferred onto the recording material S. The toner that cannot be completely transferred by the secondary transfer unit T2 and remains on the intermediate transfer belt 51 is removed by the intermediate transfer belt cleaner 55.

Next, the recording material S is conveyed to the fixing device 6 as the fixing means. The fixing device 6 includes a fixing roller 61 and a pressure roller 62 having a heat source such as a halogen heater inside, and the fixing roller 61 and the pressure roller 62 form a fixing nip portion. The recording material S is heated and pressurized by passing the recording material S on which the toner image is transferred through the fixing nip portion of the fixing device 6. Then, the toner on the recording material S is melted and mixed, and fixed to the recording material S as a full-color image. After that, the recording material S is discharged to the discharge tray 102 by the discharge roller 101. This completes a series of image formation processes.

The image forming apparatus 100 of the present embodiment forms a monochromatic or multicolor 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 4 will be described with reference to FIGS. 3 and 4. The developing apparatus 4 has a developing container 41 that houses a developing agent containing a non-magnetic toner and a magnetic carrier, and a developing sleeve 44 as a developing agent carrier that rotates while supporting the developing agent in the developing container. In the developing container 41, transfer screws 43a and 43b are arranged as developer transporting members that circulate in the developing container while stirring and transporting the developer in the developing container. Further, inside the developing sleeve 44, a magnet roller 44a as a magnetic field generating means having a plurality of magnetic poles arranged in the rotation direction is arranged non-rotatingly. Further, a developing blade 42 as a regulating member for forming a thin layer of the developing agent is arranged on the surface of the developing sleeve 44.

The inside of the developing container 41 is divided horizontally into the developing chamber 41a and the stirring chamber 41b by a partition wall 41c whose substantially central portion extends in the direction perpendicular to the paper surface, and the developing agent is divided into the developing chamber 41a and the stirring chamber 41a. It is housed in 41b. Conveying screws 43a and 43b are arranged in the developing chamber 41a and the stirring chamber 41b, respectively. At both ends in the longitudinal direction of the partition wall 41c (both ends in the rotation axis direction of the developing sleeve 44, left and right sides in FIG. 4), a transfer portion 41d that allows the developing agent to pass between the developing chamber 41a and the stirring chamber 41b, 41e is provided.

The transport screws 43a and 43b are formed by providing spiral blades as transport portions around a shaft (rotary shaft), respectively. Further, in addition to the spiral blade, the transport screw 43b is provided with a stirring rib 43b1 that protrudes from the shaft in the radial direction and has a predetermined width in the transport direction of the developer. The stirring rib 43b1 stirs the developer as the shaft rotates.

The transport screw 43a is arranged at the bottom of the developing chamber 41a along the rotation axis direction of the developing sleeve 44, and the developer in the developing chamber 41a is moved along the axis direction by rotating the rotating shaft by a motor (not shown). The developer is supplied to the developing sleeve 44 while being conveyed. The developer supported on the developing sleeve 44 and whose toner is consumed in the developing step is collected in the developing chamber 41a.

Further, the transport screw 43b is arranged at the bottom of the stirring chamber 41b along the rotation axis direction of the developing sleeve 44, and transports the developer in the stirring chamber 41b along the axial direction opposite to the transport screw 43a. The developer is conveyed by the transfer screws 43a and 43b in this way, and circulates in the developing container 41 via the transfer portions 41d and 41e.

At the upstream end of the transfer screw 43b of the stirring chamber 41b in the transfer direction, a developer supply port 46 for replenishing the developer containing toner is provided in the developing container 41. The developer replenishment port 46 is connected to the replenishment transport unit 83 of the developer replenishment device 80 shown in FIG. 5, which will be described later. Therefore, the replenishing developer is supplied from the developer replenishing device 80 into the stirring chamber 41b via the replenishment transport unit 83 and the developer replenishment port 46. The transport screw 43b transports the developer replenished from the developer replenishment port 46 and the developer already in the stirring chamber 41b while stirring to make the toner concentration uniform.

Therefore, due to the conveying force of the conveying screws 43a and 43b, the developer in the developing chamber 41a whose toner is consumed in the developing step and the toner concentration is lowered is passed through one of the transfer portions 41d (left side in FIG. 4) to the stirring chamber. Move into 41b. Then, the developer that has moved into the stirring chamber 41b is conveyed while being stirred with the replenished developer, and moves to the developing chamber 41a via the other delivery section 41e (right side in FIG. 4).

The developing chamber 41a of the developing container 41 has an opening 41h at a position corresponding to the facing region (development region) A facing the photosensitive drum 1, and the developing sleeve 44 is partially formed in the photosensitive drum 1 direction in the opening 41h. It is rotatably arranged so as to be exposed. On the other hand, the magnet roller 44a included in the developing sleeve 44 is fixed in a non-rotating manner. Such a developing sleeve 44 is rotated by a motor (not shown) so that the developing agent can be conveyed to the facing region A, and the developing agent is supplied to the photosensitive drum 1 in the facing region A. In the present embodiment, the developing sleeve 44 is formed in a cylindrical shape by, for example, aluminum or stainless steel as a non-magnetic material. Further, the developing sleeve 44 rotates in the facing region A from the lower side to the upper side in the direction of gravity, that is, in the counterclockwise direction of FIG.

A developing blade 42 as a regulating member that regulates the amount (layer thickness) of the developing agent supported on the developing sleeve 44 is fixed on the upstream side of the opening 41h in the rotational direction of the developing sleeve 44. In the present embodiment, since the developing sleeve 44 rotates from the lower side in the gravity direction to the upper side in the facing region A, the developing blade 42 is located below the facing region A in the gravity direction.

As shown in FIG. 3, the magnet roller 44a 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 44a generates a magnetic field for carrying the developer on the developing sleeve 44, and also generates a magnetic field for peeling the developer from the developing sleeve 44 in a peeling region described later. That is, the developer in the developing chamber 41a is supplied to the developing sleeve 44 by the transport screw 43a. Then, a predetermined amount of the developer supplied to the developing sleeve 44 is supported on the developing sleeve 44 (on the developing agent carrier) by the magnetic field generated by the suction magnetic pole S2 of the magnet roller 44a, and the developing agent pool is formed. Form. That is, the suction magnetic pole S2 corresponds to the second magnetic pole that supports the developer in the developing container on the developing sleeve 44.

The developer on the developing sleeve 44 passes through the developer pool as the developing sleeve 44 rotates, spikes on the regulating magnetic pole N1, and the layer thickness is regulated by the developing blade 42 facing the regulating magnetic pole N1. Will be done. Then, the developer whose layer thickness is regulated is conveyed to the facing region A facing the photosensitive drum 1, and spikes on the developing magnetic pole S1 to form magnetic spikes. The magnetic spikes come into contact with the photosensitive drum 1 that rotates in the same direction as the developing sleeve 44 in the facing region A, and the electrostatic latent image is developed as a toner image by the charged toner. That is, the developing magnetic pole S1 corresponds to the first magnetic pole arranged at a position where the developing sleeve 44 is in close contact with the photosensitive drum 1.

After that, the developer on the developing sleeve 44 is conveyed into the developing container 41 by the rotation of the developing sleeve 44 while maintaining the adsorption of the developer on the surface of the developing sleeve 44 by the transport magnetic pole N2. Then, the developer supported on the developing sleeve 44 is a peeling region formed by the peeling magnetic poles S3 and the suction magnetic poles S2 having the same poles arranged in order in the rotation direction of the developing sleeve 44, and is formed from the surface of the developing sleeve 44. It is peeled off. The peeled developer is collected in the developing chamber 41a of the developing container 41. That is, the peeling magnetic pole S3 corresponds to the third magnetic pole having the same pole as the suction magnetic pole S2 arranged adjacent to the upstream of the developing sleeve 44 of the suction magnetic pole S2 as the second magnetic pole in the rotation direction.

As shown in FIG. 4, the developing container 41 is provided with an inductance sensor 45 as a toner concentration sensor for detecting the toner concentration in the developing container 41. In the present embodiment, the inductance sensor 45 is provided on the downstream side of the stirring chamber 41b in the developer transport direction.

[Developer replenishment device]
Next, the developer replenishing device 80 will be described with reference to FIG. The developer replenishment device 80 includes a storage container 8 for accommodating a replenishing developer, a replenishment mechanism 81, and a replenishment transport unit 83. The storage container 8 has a structure in which a spiral groove is dug in the inner wall of the cylindrical container, and the storage container 8 itself rotates to generate a carrying force of the developer in the longitudinal direction (rotational axis direction). Let me. A replenishment mechanism 81 is connected to the downstream end of the storage container 8 in the developer transport direction. The replenishment mechanism 81 has a pump unit 81a that discharges the developer from the discharge port 82 to which the developer is conveyed from the storage container 8. The pump portion 81a is formed in a bellows shape, and when it is rotationally driven, the volume changes to generate air pressure, and the developer conveyed from the storage container 8 is discharged from the discharge port 82.

The upper end of the replenishment transport unit 83 is connected to the discharge port 82, and the lower end of the replenishment transport unit 83 is connected to the developer replenishment port 46 of the developing apparatus 4. That is, the replenishment transport unit 83 communicates the discharge port 82 with the developer replenishment port 46. Therefore, the developer discharged from the discharge port 82 by the pump unit 81a is replenished into the developing container 41 of the developing device 4 through the replenishment transport unit 83.

In the above-mentioned developing apparatus 4, the developing agent supply port 46 is located at the upstream end of the stirring chamber 41b in the developing agent transport direction and outside the developing agent circulation path formed by the developing chamber 41a and the stirring chamber 41b. Be prepared for. Specifically, the developer supply port 46 is provided on the upstream side of the stirring chamber 41b in the developer transport direction with respect to one of the delivery portions 41d. Therefore, in the vicinity of the developer replenishment port 46, there is almost no developer in the developer circulation path, and only the replenisher developer passes through.

Such replenishment by the developer replenishing device 80 is performed by automatic toner replenishment control (hereinafter, referred to as "ATR (Automatic Toner Replenisher) control"). This ATR control controls the operation of the developer replenishing device 80 according to the density detection result of the patch image by the image ratio at the time of image formation, the inductance sensor 45, and the density sensor 103 (FIG. 1) that detects the density of the toner image. Then, the developer is replenished to the developing apparatus 4.

As shown in FIG. 1, the density sensor 103 faces the surface of the intermediate transfer belt 51 in the rotation direction of the intermediate transfer belt 51, downstream of the most downstream image forming unit PK and upstream of the secondary transfer unit T2. Is arranged. In the control using the density sensor 103, for example, the toner image (patch image) for control is transferred onto the intermediate transfer belt 51 at the start of the image formation job or at the timing of each predetermined number of images to be formed, and the density sensor 103 is used. Detects the density of the patch image. Then, based on this detection result, the developer replenishment device 80 controls the replenishment of the developer.

The configuration for supplying the developing agent to the developing apparatus 4 is not limited to such a configuration, and a conventionally known configuration may be used.

[Scattering of developer]
Here, the scattering of the developer generated from the developing apparatus will be described. First, in the image forming apparatus, high speed and high image quality of the output image are required, and maintenance is required to be simplified. One of the simplifications of this maintenance is the reduction of contamination by the developer inside the image forming apparatus. If the inside of the image forming apparatus is contaminated with a developing agent, image defects such as stains on the output image may occur, or cleaning work may occur when replacing the developing apparatus or the photosensitive drum unit. Further, if the developing agent adheres to each drive system such as a gear, the drive system may slip or the like.

One of the causes of contamination by the developer inside the image forming apparatus is that the developer scatters from the inside of the developing apparatus. For example, in the case of a two-component developer, the toner and the carrier are usually triboelectrically charged inside the developing apparatus, so that the toner and the carrier are adhered by electrostatic force. However, there is a risk that this adhesion will be released by some kind of impact, and the developer released from the carrier will be discharged from the inside of the developing device together with the air flow.

As a typical path of toner scattering from the inside of the developing apparatus, the developing agent on the developing sleeve 44 is taken into the developing container 41 by the rotation of the developing sleeve 44 between the opening 41h of the developing container 41 and the developing sleeve 44. The intake port 47 can be mentioned (see FIG. 3). The intake port 47 is a gap between the development sleeve 44 and the opening end 41i downstream of the development region A at both ends of the opening 41h in the rotation direction of the development sleeve 44. On the other hand, on the side opposite to the intake port 47 (lower side in FIG. 3), the developing blade 42 is close to and facing the developing sleeve 44. Therefore, at this position, the layer thickness of the developer supported on the developing sleeve 44 is restricted by the developing blade 42, and air is unlikely to flow out from the gap between the developing sleeve 44 and the developing blade 42. Therefore, the toner scattering to the outside of the developing container mainly occurs at the intake port 47. In the present embodiment, as shown in FIG. 3, the toner scattering from the intake port 47 is suppressed by the sealing sheet 48. This point will be described later.

First, the outline of toner scattering from the intake port 47 will be described with reference to FIGS. 6 and 7. The toner scattering here means that the free toner generated in the developing container 41 due to the stirring / transporting of the developing agent and the replenishment of toner is discharged to the outside of the developing container 41 through the intake port 47 and cannot be completely collected in the developing container 41. It refers to things.

Toner release will be described. The toner and the carrier contained in the developing container 41 are triboelectrically charged in the stirring chamber 41b and the developing chamber 41a, and adhere to each other due to the electrostatic adhesive force generated by the triboelectric effect and the non-electrostatic adhesive force generated by the surface property. There is. When an impact or a shearing force is applied to the toner adhering to the carrier, the toner is peeled off from the carrier by inertial force or the like and released in the developing container 41. The impact and shear force at this time include the behavior of the developing agent when the developing agent is conveyed by the developing sleeve 44.

As shown in FIG. 6, the developing agent forms magnetic spikes having a chain-like structure along the magnetic field lines of the internal magnetic poles on the developing sleeve 44. That is, the developer forms magnetic spikes having a chain-like structure along the angle Φ of the magnetic flux density (magnetic flux line) B passing through each magnetic pole of the developing sleeve 44. The angle Φ of the magnetic flux line is determined by the size Br of the normal component of the magnetic flux density B and the size Bθ of the tangential component of the magnetic flux density B. The angle Φ of the magnetic flux density (magnetic flux line) is an angle formed by the magnetic flux density as a tangent to the developing sleeve 44.

Therefore, at the point Pa near the magnetic pole N2, the magnitude Bra of the magnetic flux density in the normal direction is large and the magnitude Bθa in the tangential direction is small, so that the angle Φa of the magnetic flux density (magnetic flux line) Ba is 90 degrees (normal direction). ) Approach. On the other hand, at the point Pb away from the magnetic pole N2, the magnitude Brb of the magnetic flux density in the normal direction is smaller and the magnitude Bθb in the tangential direction is larger than the point Pa, so that the magnetic flux density (magnetic flux line) Bb The angle Φb of the developing sleeve 44 with respect to the tangential direction becomes smaller. Therefore, as shown in FIG. 7, the magnetic flux density B created by the magnetic poles of the magnet roller 44a causes the magnetic spikes to rise before passing through the magnetic poles, and when they pass over the magnetic poles, the magnetic spikes collapse.

Here, the height h2 of the magnetic spike in the region where the angle Φ of the magnetic flux line is close to 90 degrees near the magnetic pole of the normal transport region of the developing sleeve 44 (from the downstream of the developing blade 42 to the upstream of the peeling magnetic pole S3) is set to 1. And. In this case, in general, the magnetic spike heights h0 and h4 in the region where the angles Φ of the magnetic flux lines are in the vicinity of 0 degrees and 180 degrees in the vicinity of the poles are about 1/2 to 1/4.

On the developing sleeve 44, the point P1 where the height h1 of the magnetic spike is the maximum 1/2 as the rising point of the magnetic spike, the point P2 where the height h2 of the magnetic spike is the maximum near the magnetic pole N2 for transportation, and the magnetic spike A point P3 in which the height h3 of the magnetic spike is halved to the maximum is defined as a point at which the magnetic spike falls. At these points, the angles Φ of the magnetic flux lines are 30 degrees, 90 degrees, and 150 degrees, respectively.

Further, the magnetic spike rises forward in the rotation direction immediately before the magnetic pole due to the rotation of the developing sleeve 44, and falls forward in the rotation direction when passing over the magnetic pole. At this time, the rotation direction of the magnetic spike is the same as the rotation direction of the developing sleeve 44. In particular, the toner is peeled off from the carrier due to the impact and inertial force when the magnetic spikes fall, which causes the toner to be released.

Further, the magnetic pole that contributes greatly to the release of toner when the developing agent is conveyed by the developing sleeve 44 is the peeling magnetic pole S3 that generates a repulsive magnetic field with the suction magnetic field S2. In the peeling magnetic pole S3, in order to peel the developer from the developing sleeve 44, a magnetic force is applied by the magnetic pole in the direction opposite to the rotation direction of the developing sleeve 44 to reduce the speed of the transported developer and allow the developer to stay. .. At this time, since the flow rate of the developer conveyed on the surface of the developing sleeve 44 is preserved, the length of the magnetic spike becomes longer along the magnetic flux line. When the magnetic spikes are long, the impact and inertial force when the magnetic spikes fall become large, and the amount of toner released tends to increase.

Further, when the developer is replenished to the developer replenishment port 46 from the developer replenisher device 80, the developer that is blown up before being sufficiently agitated is also a factor of free toner in the developing container 41. .. The toner supplied to the developer supply port 46 is conveyed while being stirred with the developer already in the stirring chamber 41b. At this time, in the mixed region of the supplementary developer and the existing developer, the mixing ratio of the toner to the developer is temporarily increased. When the mixing ratio of the toner to the developer is high, the toner and the carrier cannot sufficiently contact and rub, the amount of charge decreases, and the electrostatic adhesion between the toner and the carrier decreases. The toner that could not be completely mixed with the developer is released as it is or by the impact of stirring and transporting the developer by the transfer screws 43a and 43b, and the free toner flies up in the developing container 41.

Next, the airflow inside and near the developing device 4 will be described. It is the developing sleeve 44 and the photosensitive drum 1 that generate the airflow in the vicinity of the developing device 4. Each will be described here. First, due to the rotation of the developing sleeve 44 and the behavior of the magnetic spikes on the magnetic poles, an air flow is generated in a direction substantially the same as the rotation direction of the developing sleeve 44. The airflow generated in the direction substantially the same as the rotation direction of the developing sleeve 44 takes in air into the developing container 41 from the intake port 47 which is a communication port between the inside of the developing container 41 and the outside of the developing container 41. Air also flows into the developing container 41 by replenishing the developing agent.

Assuming that the developing container 41 is a substantially closed space, the continuity equation can be applied because air is a fluid. Assuming that the flow velocity of air is v and the density is ρ, the following equation (1) holds.

Further, considering the steady state, since the internal pressure is constant and stable at a state higher than the atmospheric pressure, it can be considered that the density ρ does not change with time in each region in the developing container 41, and the equation (1) is expressed by the following equation (2). ) Can be described.

From this equation (2), the air flow rate ρv is preserved. In the cross section in the longitudinal direction (direction of the rotation axis of the developing sleeve 44) near the developing device 4, the balance of the flow rate ρv becomes 0, and the same amount as the air flow rate flowing in from the developing sleeve 44 and the replenishment is discharged to the outside of the developing device 4. It will be. Here, the air flow rate that flows into the developing container 41 as the developing sleeve 44 rotates through the intake port 47 composed of the upper wall 41k of the developing container 41 and the developing sleeve 44 is defined as Ia (sleeve inflow). Further, the air flow discharged from the intake port 47 passes through the upper wall 41k side so as to face the flow taken in from the intake port 47. The air flow rate discharged in this way is defined as Ib (sleeve discharge). In addition, assuming that the air flow discharged from the developing container 41 such as a gap or an edge is Ic (other leak), the relationship of the following equation (3) holds.
Ia (sleeve inflow) = Ib (sleeve discharge) + Ic (other leaks) ... (3)

The airflow taken in by the developing sleeve 44 and flowing along the developing sleeve 44 is folded back and discharged in the developing container 41. The above-mentioned free toner is involved in the flow of folding back in the developing apparatus, and the toner is scattered out of the developing apparatus.

[Toner scattering measures]
Next, measures against toner scattering in this embodiment will be described. In the present embodiment, in order to reduce toner scattering, the intake port 47 is sealed to reduce the above-mentioned Ia (sleeve inflow). First, a method of sealing the intake port 47 will be described. Normally, when the developer loading amount M / S per unit area on the developing sleeve 44 used is about 30 mg / cm ² , the height of the magnetic spikes on the developing sleeve 44 is approximately between the magnetic poles of the magnet roller 44a. It is 0.3 mm, and is about 1 mm in the spiked region near the magnetic pole. In the present embodiment, the sealing sheet 48 as a contact member is brought into contact with the magnetic spikes on the developing sleeve 44 to generate a nip of the developing agent and seal the intake port 47.

Specifically, the sealing sheet 48 is a plate-shaped elastic member having elasticity, and in the present embodiment, it is a resin sheet such as urethane or PET (polyethylene terephthalate). As shown in FIG. 3, the sealing sheet 48 as such a plate-shaped elastic member is arranged so as to be partially fixed to the developing container 41 and extend toward the developing sleeve 44. Further, the sealing sheet 48 is developed in a range where the magnetic flux density of the transport magnetic pole N2 as a predetermined magnetic pole is tangent to the developing sleeve 44, that is, the angle Φ of the magnetic flux line is 30 degrees or more and 150 degrees or less. It is arranged so as to come into contact with the developer carried on the sleeve 44.

The predetermined magnetic pole is the position Q in which the opening end 41i of the opening 41h of the developing container 41 and the developing sleeve 44 face each other in the radial direction with respect to the rotation direction of the developing sleeve 44 among the plurality of magnetic poles of the magnet roller 44a. The magnetic pole is located upstream of the peeling magnetic pole S3. The opening end 41i is an opening end downstream of the first magnetic pole at both ends of the opening 41h in the rotation direction of the developing sleeve 44. The first magnetic pole is a developing magnetic pole S1 arranged at a position where the developing sleeve 44 is in close contact with the photosensitive drum 1. Further, the position Q on the developing sleeve 44 is a position where the virtual line M lowered from the opening end 41i in the radial direction of the developing sleeve 44, that is, in the direction toward the rotation center of the developing sleeve 44, and the surface of the developing sleeve 44 intersect. Is.

In the present embodiment, as shown in FIG. 3, the magnet roller 44a has five magnetic poles in the rotation direction of the developing sleeve 44. Therefore, as described above, the predetermined magnetic poles are the developing magnetic poles as the first magnetic poles. The transport magnetic pole N2 adjacent to the downstream of S1 was used. However, the number of magnetic poles of the magnet roller 44a is not limited to this, and the number of magnetic poles may be larger than five. In this case, the predetermined magnetic pole does not have to be adjacent to the downstream of the first magnetic pole. For example, when there are a plurality of transport magnetic poles between the first magnetic pole and the third magnetic pole, a predetermined magnetic pole may not be adjacent to the downstream of the first magnetic pole. Even in this case, among the plurality of transport magnetic poles, the magnetic pole downstream of the position Q where the opening end 41i and the developing sleeve 44 face each other in the radial direction and upstream of the third magnetic pole is the predetermined magnetic pole. When there are a plurality of magnetic poles in this range, it is preferable that the magnetic pole closest to the opening end 41i is a predetermined magnetic pole.

Further, considering that the tip positions of the sealing sheet 48 have manufacturing tolerances, the sealing sheet 48 is arranged so that the sealing sheet 48 comes into contact with the surface of the developing sleeve 44 in a state where the developing sleeve 44 does not carry the developer. It is preferable to do so. However, as described above, the height of the magnetic spike is usually about 1 mm in the vicinity of the magnetic pole, so that the sealing sheet 48 may be located within a range of less than 1 mm from the surface of the developing sleeve 44. In any case, the sealing sheet 48 may be arranged so as to come into contact with the developing agent of the developing sleeve 44.

Further, the sealing sheet 48 may be arranged so that the portion between the fixed portion fixed to the developing container 41 and the tip portion extending from the fixed portion toward the developing sleeve 44 is closest to the developing sleeve 44. preferable. That is, it is preferable to arrange the sealing sheet 48 so that the intermediate portion rather than the tip portion of the sealing sheet 48 comes into contact with the developing agent on the developing sleeve 44. Hereinafter, the sealing sheet 48 of the present embodiment will be specifically described.

[Encapsulation sheet]
In the case of this embodiment, the sealing sheet 48 is a urethane sheet having a thickness of 100 μm and a hardness of 90 degrees (JIS K6253). Then, one end (fixed end) of the urethane sealing sheet 48 is fixed to the open end 41i of the developing container 41, and the other end (tip) is a free end. The sealing sheet 48 is arranged between the fixed end and the free end so as to abut the developing sleeve 44. One end of the sealing sheet 48 is fixed by being attached to, for example, the opening end 41i.

Here, the point where the sealing sheet 48 and the developing sleeve 44 are in contact with each other is defined as the contact point P. At this contact point P, the intake port 47 is sealed by forming a nip of a magnetic ear to be conveyed to the developing sleeve 44 between the sealing sheet 48 and the surface of the developing sleeve 44.

In an elastic sheet such as the sealing sheet 48 of the present embodiment, when one end is fixed, swelling due to moisture absorption causes wrinkling at the other end. When this waviness occurs, the gap between the surface of the sealing sheet 48 and the surface of the developing sleeve 44 becomes large. As shown in FIGS. 8A and 8B, the height of the magnetic spikes on the developing sleeve 44 is higher in the vicinity of the magnetic poles than in the vicinity of the magnetic poles. That is, as shown in FIG. 8A, since the magnetic spikes stand in the vicinity of the magnetic pole N2, the height d1 of the magnetic spikes from the developing sleeve 44 becomes high. On the other hand, as shown in FIG. 8B, since the magnetic spikes have fallen between the poles downstream of the magnetic pole N2 and between the adjacent magnetic poles (magnetic poles S3 in this embodiment), the developing sleeve 44 of the magnetic spikes 44. The height d2 from is lowered.

Therefore, as compared with the case where the sealing sheet 48 is brought into contact with the magnetic poles as shown in FIG. 8B, the sealing sheet 48 is hit in the spike region near the magnetic poles as shown in FIG. 8A. The latitude of nip formation using magnetic ears can be increased when they are in contact with each other. Therefore, it is possible to make it easier to secure the sealing property against the waviness of the sealing sheet 48 by bringing the sealing sheet 48 into contact with the developing agent in the spike region near the magnetic pole.

Here, the spiked state of the magnetic spike can be represented by the angle Φ of the magnetic flux line described above, and as described with reference to FIG. 7, the magnetic flux line is between points P1 and P3 on the developing sleeve 44, that is, the magnetic flux line. A magnetic spike stands at an angle Φ of 30 to 150 degrees. In the present embodiment, the magnitude Br of the normal component of the magnetic flux density is determined by F.I. W. The measurement was performed using a magnetic field measuring instrument "MS-9902" (trade name) manufactured by BELL, with the distance between the probe, which is a member of the measuring instrument, and the surface of the developing sleeve set to about 100 μm. Further, the magnitude Bθ of the tangential component of the magnetic flux density can be obtained as follows.

_{First, the vector potential AZ} (r, θ) at the measurement position of the magnitude Br of the normal component of the magnetic flux density is calculated by the following equation (4) using the magnitude Br of the normal component of the measured magnetic flux density. ) Is required.

The boundary conditions and _A Z (r, _θ), obtaining the _A Z (r, theta) by solving the following equation (5).

Then, the magnitude Bθ of the tangential component of the magnetic flux density can be obtained by the following equation (6).

Further, the angle formed by the magnetic flux line between the tangent line of the developing sleeve 44, that is, the angle Φ of the magnetic flux line can be expressed as arctanBr / Bθ from the above-mentioned Br and Bθ. As described above, since the magnetic spikes on the developing sleeve 44 are formed along the magnetic flux lines, the angle of the magnetic spikes is the same as the angle Φ of the magnetic flux lines. Therefore, hereinafter, the angle Φ of the magnetic flux line is also referred to as a magnetic spike angle Φ.

[Toner scattering and magnetic spike angle Φ]
Next, an experiment in which the relationship between toner scattering and the magnetic spike angle Φ is investigated in a high-temperature and high-humidity environment (temperature 42 degrees, humidity 41%) in which waviness of the sealing sheet 48 is likely to occur will be described. In the experiment, the developing device 4 of Canon imageRUNNER ADVANCE C3530 and the driving unit thereof were cut out from the image forming device 100, and the developing device 4 was remodeled to change the magnetic spike angle Φ as described above for verification. .. Further, when the amount of the developing agent loaded on the developing sleeve 44 is the lower limit, the nip of the developing agent near the contact point P of the sealing sheet 48 becomes smaller and the sealing ability becomes the lower limit. Therefore, assuming the vicinity of the lower limit of the developer loading amount, the developer loading amount M / S per unit area on the developing sleeve 44 was set to ^{about 20 mg / cm 2.} Other various settings were in accordance with imageRUNNER ADVANCE C3530.

The outline of the method for measuring the amount of toner scattered used in the experiment will be described. The scattered toner of the developing device 4 passes through the intake port 47 and is scattered to the outside. Therefore, the line laser is irradiated to the substantially center of the air flow so as to be perpendicular to the developing sleeve 44. A line laser is a laser that is irradiated in a line shape having a constant line width to form a fan-shaped two-dimensional plane optical path. Scattered toner flying on the optical path of the line laser scatters the laser beam. Therefore, by observing with a high-speed camera or the like from a direction substantially perpendicular to the irradiation direction of the line laser, it is possible to measure the number and loci of the scattered toner existing in the area irradiated with the laser. As the line laser, a YAG laser manufactured by Nippon Laser Co., Ltd. was used as a light source, and a cylindrical lens was adjusted so that the line width was 0.5 mm and irradiated. For observation, a high-speed camera SA-3 manufactured by Photron is used, and the set values (frame rate and exposure time) and optical system (lens, etc.) of the high-speed camera are selected so that the scattered toner on the line laser can be observed. ing.

By the above method, the number of scattered toners from the center of the length (in the direction of the rotation axis) of the developing sleeve 44 was measured, and the number of scattered toners corresponding to one sheet of A4 paper was converted from the line width and the observation time. FIG. 9 shows the relationship between the number of scattered toners and the magnetic spike angle Φ at the contact point P of the sealing sheet 48.

As is clear from FIG. 9, the number of scattered toners was small and good when the magnetic spike angle Φ was in the range of 30 degrees to 150 degrees. On the other hand, when the magnetic spike angle Φ was outside this range of 15 degrees and 165 degrees, the number of scattered toners was large. This is because when the magnetic spike angle Φ is outside the range of 30 degrees to 150 degrees, the height of the magnetic spikes is low and the sealing is broken by the waviness of the sealing sheet 48. Generally, the developer loading amount M / S per unit area on the developing sleeve 44 is set to a value larger than the value of ^{about 20 mg / cm 2 used in the experiment, for example, 50 mg / cm 2} or less. Therefore, if the magnetic spike angle Φ at the contact point P of the sealing sheet 48, that is, the angle Φ of the magnetic flux density B is in the range of 30 degrees or more and 150 degrees or less, even if waviness occurs in the sealing sheet 48. Sealing performance can be ensured.

[Preferable contact point of sealing sheet]
Next, a preferable contact point P of the sealing sheet 48 will be described. In the present embodiment, in order to seal the intake port 47, the sealing sheet 48 is used to seal the intake port 47 in the vicinity of the magnetic pole closest to the intake port 47. As described above, since the magnetic spike in the vicinity of the magnetic pole becomes the toner scattering source, the toner scattering reducing function becomes more effective by arranging the magnetic pole as much as possible from the contact point P to the rotation downstream of the developing sleeve 44. Therefore, among the magnetic poles of the magnet roller 44a, the magnetic spikes formed by the magnetic poles (conveying magnetic pole N2 in the present embodiment) arranged adjacent to the developing sleeve 44 of the developing magnetic pole S1 in the rotational direction fall down. It is preferable to arrange the contact point P upstream. For example, it is preferable to arrange the contact point P upstream of the point P3 in FIG.

Further, as described above, although the sealing sheet 48 is an elastic member, it has a restrictive force on the developing agent like the developing blade 42 in order to form a nip by the magnetic spike. If the regulatory force is large, the developer cannot pass through the contact point P of the sealing sheet 48, and the developer stays there, causing the developer to overflow. Therefore, it is desirable to have a configuration in which the developer regulating force of the sealing sheet 48 is not unnecessarily increased.

In the present embodiment, as shown in FIG. 10A, the sealing sheet 48 is brought into contact with the developing sleeve 44 so as to be involved in the rotational direction of the developing sleeve 44 from the substantially tangential direction of the developing sleeve 44, and is deformed by the pressure of the developing agent passing therethrough. It is easy to make it. FIG. 10A shows the relationship between the magnetic spikes and the sealing sheet 48 when the sealing sheet 48 is brought into contact with the developer at a position where the magnetic spike angle Φ is larger than 90 degrees (point P2). .. On the other hand, FIG. 10B shows the relationship between the magnetic spike and the sealing sheet 48 when the sealing sheet 48 is brought into contact with the developer at a position where the magnetic spike angle Φ is less than 90 degrees.

Further, at the contact point P, when the magnetic spikes come into contact with the sealing sheet 48, the spikes tend to fall. This is because at the contact point P where the magnetic spikes come into contact with the sealing sheet 48, the state in which the magnetic spikes are directed toward the spikes (FIG. 10 (b)) is more likely to be toward the spikes (FIG. 10 (a)). This is because the carrying force given to the developer by the developing sleeve 44 is strong. In the present embodiment, this state is created by setting the contact point P of the sealing sheet 48 downstream of the point where the magnetic spike angle Φ becomes 90 degrees.

Further, the sticking surface of the fixed end of the sealing sheet 48 is set to be the same surface as the tangent line of the developing sleeve 44 at the contact point P so that the contact pressure of the sealing sheet 48 with respect to the developing sleeve 44 is substantially 0N. .. That is, it is preferable that the sealing sheet 48 is arranged substantially parallel to the tangent line of the developing sleeve 44. Further, in the present embodiment, the sealing sheet 48 has a thickness of 100 μm, a length from the fixed end to the contact point P of 11 mm, and a length from the contact point P to the free end of 3 mm.

[Magnetic spike angle and developer retention]
Next, FIG. 11 shows the results of an experiment investigating the relationship between the magnetic spike angle Φ at the contact point P between the sealing sheet 48 and the developer on the developing sleeve 44 and the retention of the developer on the developing sleeve 44. As described above, the developer retention refers to a state in which the developer cannot pass through the contact point P of the sealing sheet 48 and stays there. In the experiment, the developing sleeve was used when the developer loading amount M / S per unit area on the developing sleeve 44 was about 30 mg / cm ² for normal use and when the upper limit developer loading amount was about 55 mg / cm ^2. The retention of the developer on 44 was examined. Note that ◯ in FIG. 11 indicates that the retention of the developer could not be confirmed, triangle indicates that the retention of the developer could be confirmed, and X indicates that the developer overflowed from the developing apparatus due to the retention of the developer. Each case is shown.

When the M / S was 30 mg / cm ² , retention could not be confirmed when the magnetic spike angle Φ was 30 degrees or more. However, when the magnetic spike angle Φ was 15 degrees, a retention portion could be confirmed upstream of the contact point P. When the M / S was 55 mg / cm ² , retention could not be confirmed when the magnetic spike angle Φ was 90 degrees or more. However, when the magnetic spike angle Φ was 30 degrees, a retention portion could be confirmed upstream of the contact point P, and when the magnetic spike angle Φ was 15 degrees, the developer overflowed.

From the above, in the case of normal use, if the magnetic spike angle Φ at the contact point P is 30 degrees or more and 150 degrees or less, it is possible to reduce the occurrence of overflow of the developer. Further, in order to prevent retention up to the upper limit of the amount of the developing agent, it is preferable that the magnetic spike angle Φ at the contact point P is 90 degrees or more and 150 degrees or less.

Further, in the present embodiment, the magnitude of the magnetic flux density is set to S1> S3 in order to increase the latitude in the rotation direction of the contact point P of the sealing sheet 48. That is, among the plurality of magnetic poles of the magnet roller 44a, they are arranged adjacent to the upstream of the magnetic pole N2 in the rotational direction, rather than the magnetic flux density of the magnetic pole S3 arranged adjacent to the downstream of the magnetic pole N2 which is a predetermined magnetic pole. The magnetic flux density of the magnetic pole S1 is made larger. This is because the magnetic flux line of the magnetic pole N2 spreads to the magnetic pole S3 side on the downstream side where the magnetic flux density is small, so that the region where the magnetic spikes stand can be expanded downstream.

Based on the above, the configuration of this embodiment is as shown in FIG. That is, in the region where the angle Φ of the magnetic flux lines is 90 degrees or more and 150 degrees or less, the sealing sheet 48 is arranged so as to come into contact with the developing sleeve 44 in a state where the developing sleeve 44 does not carry the developer.

In the case of the present embodiment as described above, the sealing performance of the sealing sheet 48 can be ensured regardless of the waviness of the sealing sheet 48 due to the environment and the amount of the developer loaded on the developing sleeve 44. Therefore, the above-mentioned Ia (sleeve inflow) is reduced, and Ib (sleeve discharge) is sealed. The Ia (sleeve inflow) that has entered the developing device 4 is discharged to the outside of the developing device 4 as Ic (other leaks). As a result, it is possible to suppress the scattering of toner discharged from the intake port 47 from the developing device 4.

<Second embodiment>
The second embodiment will be described with reference to FIGS. 13 to 16. In the present embodiment, both ends of the sealing sheet 48 in the longitudinal direction are brought into contact with the non-supported region of the developing sleeve 44. Since other configurations and operations are the same as those of the first embodiment described above, the same reference numerals are given to the same configurations, and the description and illustration are omitted or simplified. The differences will be mainly explained.

Ia (sleeve inflow) that has entered the developing device 4A is discharged to the outside of the developing device 4A as Ic (other leaks). At this time, if toner is contained in Ic (other leaks), toner will be scattered from the developing apparatus 4A. In particular, in the non-supporting region in which the developer is not supported on the developing sleeve 44, toner tends to come from the supported region in which the developing agent is supported on the developing sleeve 44, so that there is a risk of toner scattering. Therefore, in the present embodiment, a configuration for suppressing toner scattering from the non-supporting region on the developing sleeve 44, which does not support the developer, will be described.

FIG. 13 shows the longitudinal range of the supported region A on which the developer is supported on the developing sleeve 44 and the non-supported region B that does not support the developer. That is, the developing sleeve 44 has a supporting region A that carries the developer and a non-supporting region that deviates from the supporting region in the longitudinal direction that intersects the rotational direction of the developing sleeve 44 (in the present embodiment, the rotation axis direction of the developing sleeve 44). It has a carrying region B.

The supporting region A is, for example, a range in which a recess for supporting the developer is provided on the surface of the developing sleeve 44. For example, the supported region A is a range in which irregularities are formed on the surface by blasting or a plurality of grooves are formed on the surface. Further, the magnet roller 44a (see FIG. 14) arranged in the developing sleeve 44 is generally arranged in the range of the supported region A. However, since the magnetic field is not stable at the longitudinal end of the magnet roller 44a and the developer cannot be sufficiently supported, generally, as shown in FIG. 14, the end of the magnet roller 44a is supported by the non-supporting region B. Is invading.

On the other hand, the non-supporting region B is a range in which a recess for supporting the above-mentioned developer is not formed, and the surface is usually a smooth cylindrical surface. The developer may accidentally adhere to the non-supporting region B for some reason, but even if the developer accidentally adheres in this way, the recess for supporting the above-mentioned developer is not formed. If it is a range, this range is the non-supported region B.

In order to suppress toner scattering from the non-supporting region B that does not support the developer of FIG. 13, the sealing sheet 48 may be brought into contact with the non-supporting region B as well. However, as shown in FIG. 14, at the interface between the supported region A and the non-supported region B, the sealing sheet 48 cannot fully abut on the developing sleeve 44 and floats due to the influence of the space of the developing agent. That is, on the developing sleeve 44, the developer 49 is present in the supported region A, but the developer 49 is not present in the non-supported region B. Therefore, the sealing sheet 48 is formed at the interface between the supported region A and the non-supported region B. Will not come into contact with the developing sleeve 44, resulting in a floating region. Then, toner may be scattered from this region.

Therefore, in the present embodiment, as shown in FIGS. 15 and 16, the contact assisting member 50 that brings the sealing sheet 48 into contact with the non-supported region B is provided. The contact auxiliary member 50 presses the surface of the sealing sheet 48 opposite to the developing sleeve 44 toward the developing sleeve 44 on the non-supporting region side of the boundary line between the supported region A and the non-supported region B. It is an arranged member having elasticity.

Specifically, the contact auxiliary member 50 is arranged in an elastically deformed state between the developing container 41 facing the non-supported region B and the sealing sheet 48 facing the non-supported region B. Then, the elastic restoring force of the contact assisting member 50 presses the end portion of the sealing sheet 48 in the longitudinal direction toward the non-supporting region B of the developing sleeve 44.

Further, the contact auxiliary member 50 is preferably an elastic member, and more preferably a soft member such as a sponge. In the case of this embodiment, foamable polyurethane was used as the contact auxiliary member 50. Further, the shape of the contact auxiliary member 50 is preferably a shape in which the sealing sheet 48 is evenly pressed over the entire range of the non-supported region B, and in the present embodiment, it is a substantially rectangular parallelepiped.

As shown in FIG. 16, by arranging the contact auxiliary member 50 as described above, the floating of the sealing sheet 48 can be suppressed at the boundary surface α between the supported region A and the non-supported region B. That is, by arranging the contact auxiliary member 50, the contact property of the sealing sheet 48 with the developing sleeve 44 can be improved. As a result, toner scattering from the non-supported region B can be suppressed.

In order to suppress the floating of the sealing sheet 48 in the vicinity of the boundary surface α, it is preferable that the inner end portion of the contact auxiliary member 50 in the longitudinal direction is as close as possible to the boundary surface α. For example, it is preferable to dispose the inner end portion of the contact auxiliary member 50 in the longitudinal direction at a position separated by the thickness of the sealing sheet 48 from the boundary surface α. Further, the contact auxiliary member 50 does not have to be arranged in the entire non-supported region B as long as it can suppress the floating of the sealing sheet 48 on the boundary surface α. However, in order to more reliably suppress the scattering of toner from the non-supported region B, the contact auxiliary member 50 is arranged so that the sealing sheet 48 is brought into contact with the surface of the developing sleeve 44 over the entire non-supported region B. Is preferable.

<Other Embodiments>
In each of the above-described embodiments, the case where a printer is used as the image forming apparatus has been described, but the present invention can be applied to an image forming apparatus such as a copying machine, a facsimile, and a multifunction device in addition to the printer.

Further, in each of the above-described embodiments, as a developing device, a configuration in which a developing agent is supplied from the developing chamber to the developing sleeve and the developing agent peeled from the developing sleeve is collected in the developing chamber has been described. However, the present invention can also be applied to a so-called function-separated configuration in which a developing chamber for supplying the developing agent to the developing sleeve and a collecting chamber for collecting the developing agent from the developing sleeve are separated.

1 ... Photosensitive drum (image carrier) / 4, 4A ... Development device / 41 ... Development container / 41h ... Opening / 41i ... Open end / 42 ... Development blade (regulation) Member) / 44 ... Development sleeve (developer carrier) / 44a ... Magnet roller (magnetic field generating means) / 47 ... Intake port / 48 ... Sealing sheet (elastic member) / 50 ...・ Contact auxiliary member / S1 ・ ・ ・ Development magnetic pole (1st magnetic pole) / S2 ・ ・ ・ Adsorption magnetic pole (2nd magnetic pole) / S3 ・ ・ ・ Peeling magnetic pole (3rd magnetic pole)

Claims (7)

A developing device that develops an electrostatic latent image formed on an image carrier with a developing agent.
A developing container in which an opening is formed at a position facing the image carrier and contains a developing agent containing toner and a carrier, and a developing container.
A developer carrier that is arranged in the developing container so that a part of the opening is exposed and rotates while carrying the developing agent in the developing container.
A magnetic field generating means that is arranged non-rotatingly inside the developer carrier, has a plurality of magnetic poles arranged in the rotation direction of the developer carrier, and generates a magnetic field that causes the developer carrier to support the developer. The plurality of magnetic poles are the first magnetic pole arranged at a position where the developer carrier is in close contact with the image carrier, and the first magnetic pole in the developing container upstream of the first magnetic pole in the rotational direction. The magnetic field generation including a second magnetic pole for supporting the developer on the developer carrier and a third magnetic pole having the same pole as the second magnetic pole arranged adjacent to the upstream of the second magnetic pole in the rotational direction. Means and
A plate-shaped elastic member that is partially fixed to the developing container and arranged so as to extend toward the developing agent carrier, and has both ends of the opening in the rotational direction among the plurality of magnetic poles. The magnetic flux lines of a predetermined magnetic pole downstream of the position where the open end downstream of the first magnetic pole and the developer carrier are radially opposed to each other and upstream of the third magnetic pole are described above. The elastic member is arranged so as to come into contact with the developer carried on the developer carrier in a range where the angle formed by the tangent line of the developer carrier is 30 degrees or more and 150 degrees or less.
A developing device characterized by this. The predetermined magnetic pole is a magnetic pole arranged adjacent to the downstream of the first magnetic pole in the rotational direction.
The developing apparatus according to claim 1, wherein the developing apparatus is characterized in that. The elastic member is developed supported on the developer carrier in a range in which the angle between the normal component and the tangential component of the magnetic flux line of the predetermined magnetic pole on the developer carrier is 90 degrees or more and 150 degrees or less. Arranged to contact the agent,
The developing apparatus according to claim 1 or 2, wherein the developing apparatus is characterized in that. The elastic member is arranged so that the portion between the fixed portion fixed to the developing container and the tip portion extending from the fixed portion toward the developing agent carrier is closest to the developing agent carrier. Yes,
The developing apparatus according to any one of claims 1 to 3, wherein the developing apparatus is characterized in that. Of the plurality of magnetic poles, the magnetic poles arranged adjacent to the upstream of the predetermined magnetic pole in the rotational direction rather than the magnetic flux density of the magnetic poles arranged adjacent to the downstream of the predetermined magnetic pole in the rotational direction. The magnetic flux density is higher,
The developing apparatus according to any one of claims 1 to 4, wherein the developing apparatus is characterized in that. The developer-supported body has a supported region that supports the developer and a non-supported region that is out of the supported region with respect to the direction of the rotation axis of the developer-supported body.
A contact auxiliary member for bringing the elastic member into contact with the non-supported region is provided.
The developing apparatus according to any one of claims 1 to 5, wherein the developing apparatus is characterized in that. The contact assisting member faces the developer-supported body on the non-supported region side of the boundary between the supported region and the non-supported region, and the surface of the elastic member opposite to the developer-supported body. An elastic member arranged to be pressed against the surface.
The developing apparatus according to claim 6, wherein the developing apparatus is characterized in that.

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