JP2016184042A - Development device and image formation device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a situation that flying toner occurring inside a development vessel leaks to the outside.SOLUTION: A development device according to the present invention comprises: a developer holder 2 equipped with a development rotor 3 and a magnet member 4 in which a plurality of magnetic poles 5 are arrayed in the circumferential direction of the development rotor 3, and which includes at least an adjacent magnetic pole pair of opposite polarities and a magnetic pole 5a for development that is disposed in a portion facing an image holder 10; and a sealing member 6 provided downstream in the rotation direction of the developer holder 2 from a development area Pd where the magnetic pole 5 for development of the developer holder 2 is located, and configured with a plate-like member capable of elastic deformation which, with part of it fixed to a development vessel 1, extends toward the developer holder 2 side, the tip portion coming in contact with a developer in the developer holder 2, thereby sealing a clearance between the development vessel 1 and the developer holder 2. The sealing member 6 comes in contact with a developer G in the developer holder 2 at a position between the pair of magnetic poles of opposite polarities whose tips are adjacent that is closer to a minimum portion Pm than to a maximum portion Pp of the radial component Mr of magnetic flux density due to the magnetic pole 5 of the developer holder 2.SELECTED DRAWING: Figure 1

Description

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

Conventionally, as developing devices used in this type of image forming apparatus, those described in Patent Documents 1 and 2 are already known.
Japanese Patent Application Laid-Open No. 2004-228561 is intended to prevent or reduce scattering of toner and carriers caused by an abnormal blowing air flow generated from a downstream position of the developing device casing due to the interaction of the magnetic brush and the local developing device casing. Further, a developer casing having an opening formed so as to expose the developer carrier at a portion facing the latent image carrier and covering the developer carrier, and the developer carrier rather than the permanent magnet as the main pole A permanent magnet that is built in a fixed state in the developer carrying body at a position downstream of the opening of the developer casing and near the opening of the developer casing, and serves as an auxiliary pole, and faces the permanent magnet that serves as an auxiliary pole of the developer casing The portion to be pressed is recessed in the protruding direction of the magnetic brush formed by the magnetic field of the auxiliary pole so as to move away from the latent image carrier rather than the tip portion that forms the opening by approaching the latent image carrier. Developing apparatus is disclosed having a concave structure to form the can space.
Patent Document 2 discloses a developing sleeve that carries a developer and rotates in order to reduce the amount of toner cloud generated inside the developing device and reduce the amount of toner cloud leaking into the image forming apparatus. A development magnet having a first repulsion magnetic pole and a second repulsion magnetic pole of the same polarity, which are included in the development sleeve and are arranged adjacent to each other in order from the upstream side of the rotation direction of the development sleeve, and the first repulsion magnetic pole N of the development magnet A developing device is disclosed that includes a spike fall regulating member that regulates the fall of the developer sleeve on the upstream side in the rotational direction with respect to the spike of the developer formed on the developer sleeve.

Japanese Patent Laying-Open No. 2004-20772 (Embodiment of the Invention, FIG. 2) JP 2005-352077 A (Best Mode for Carrying Out the Invention, FIG. 2)

  A technical problem to be solved by the present invention is to prevent a situation in which flying toner generated in a developing container leaks outside.

  According to a first aspect of the present invention, there is provided a developing container that contains a developer containing toner and a carrier and that opens to face an image holding member capable of holding an electrostatic latent image, and is provided facing the opening of the developing container. A hollow developing rotator that rotates opposite to the image holding member, and a fixedly embedded in the developing rotator, and a plurality of magnetic poles are arranged in the circumferential direction of the developing rotator and The magnetic pole includes a magnet member including at least a pair of magnetic poles of different polarities adjacent to each other and a developing magnetic pole disposed in a portion facing the image carrier, and the magnetic pole of the magnet member is rotated by rotating the developing rotator. A developer holder that holds the developer on the developing rotator by the magnetic force of the developer, and a developing region on the downstream side in the rotation direction of the developer holder from the developing region where the developing magnetic pole of the developer holder is located. Part of the developer container provided The developer container and the developer holding body are configured by an elastically deformable plate-like member that is fixed and extends toward the developer holding body, and the tip portion contacts the developer on the developer holding body. A sealing member that seals the gap between the magnetic poles of the developer holder and the magnetic flux density in the radial direction. In the developing device, the developer contacts the developer on the developer holding member at a position closer to the minimum portion than the maximum portion of the component.

  According to a second aspect of the present invention, there is provided a developing container that contains a developer containing toner and a carrier and opens to face an image holding member capable of holding an electrostatic latent image, and is provided facing the opening of the developing container. A hollow developing rotator that rotates opposite to the image holding member, and a fixedly embedded in the developing rotator, and a plurality of magnetic poles are arranged in the circumferential direction of the developing rotator and The magnetic pole includes a magnet member including at least a pair of magnetic poles of different polarities adjacent to each other and a developing magnetic pole disposed in a portion facing the image carrier, and the magnetic pole of the magnet member is rotated by rotating the developing rotator. A developer holder that holds the developer on the developing rotator by the magnetic force of the developer, and a developing region on the downstream side in the rotation direction of the developer holder from the developing region where the developing magnetic pole of the developer holder is located. Part of the developer container provided The developer container and the developer holding body are configured by an elastically deformable plate-like member that is fixed and extends toward the developer holding body, and the tip portion contacts the developer on the developer holding body. And a sealing member that seals between the developer and the developer on the developer holding member at a position between adjacent pairs of magnetic poles of different polarities. The radial direction component of the magnetic flux density at the intersection of the straight line passing through the tip of the sealing member and the center of the developer holder and the surface of the developing rotator is Bs, and the position closest to the intersection The developing device is characterized by satisfying a relationship of Bs / Bp ≦ 0.65, where Bp is a radial direction component of the magnetic flux density of the magnetic pole located at the center.

According to a third aspect of the present invention, in the developing device according to the first or second aspect, the developer holder has a peeling magnetic pole composed of a pair of magnetic poles of the same polarity adjacent to each other as the magnet member, The sealing member has a tip that contacts the developer on the developer holder positioned upstream of the peeling pole of the developer holder in the rotation direction of the developer holder. Is a developing device.
According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the front end of the sealing member is on the downstream side in the rotation direction of the developer holder relative to the developing magnetic pole. A developing device that contacts a developer on the developer holding member located further downstream than an adjacent magnetic pole.
According to a fifth aspect of the present invention, there is provided an image holding body capable of holding an electrostatic latent image and an image holding body facing the image holding body, and developing the electrostatic latent image on the image holding body with a developer. An image forming apparatus comprising the developing device according to any one of Items 1 to 4.

According to the first aspect of the invention, it is possible to prevent the flying toner generated in the developing container from leaking outside.
According to the second aspect of the present invention, the flying toner generated in the developing container can be obtained by selecting the contact position of the tip of the sealing member based on the radial component of the magnetic flux density on the surface of the developer holding member. A situation of leakage to the outside can be prevented.
According to the third aspect of the present invention, even if toner flying occurs around the separation magnetic pole of the developer holder, it is possible to prevent the flying toner generated in the developing container from leaking outside.
According to the invention of claim 4, the sealing position by the sealing member can be separated from the developing magnetic pole, and the behavior of the developer by the developing magnetic pole can be stabilized.
According to the fifth aspect of the present invention, it is possible to provide an image forming apparatus including a developing device capable of preventing a situation where the flying toner generated in the developing container leaks to the outside.

(A) is explanatory drawing which shows the outline | summary of embodiment of the image forming apparatus containing the developing device to which this invention was applied, (b) is explanatory drawing which shows the principal part of the developing device shown to (a). (A) is explanatory drawing which shows typically the surface magnetic flux distribution of a developer holding body and the behavior of a developer around the contact part of the sealing member of the developing device shown in FIG. 1, and (b) is a seal in this embodiment. Explanatory drawing which shows typically the contact state with the developer holding body of a stop member, (c) is explanatory drawing which shows typically the contact state with the developer holding body of the sealing member in a comparison form. . 1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment. FIG. 2 is an explanatory diagram showing a main part of a developing device used in Embodiment 1. (A) is explanatory drawing which shows the structure around the sealing film of the image development apparatus used in Embodiment 1, (b) is explanatory drawing which shows the contact position with the image development roll of a sealing film. 3 is an explanatory diagram showing a magnetic flux density distribution of a developing roll of a developing device used in Embodiment 1. FIG. It is a graph which shows the relationship between the length change of the sealing film in the image development apparatus which concerns on Example 1, and the magnetic flux density of the image development roll surface in the contact part of the said sealing film. In the developing device according to Example 1, it is a graph showing the relationship between the length of the sealing film (film length) and the toner adhesion amount indicating the sealing effect of the sealing film.

Outline of Embodiment FIG. 1A shows an outline of an embodiment of an image forming apparatus to which the present invention is applied.
In FIG. 1, an image forming apparatus is provided with an image holding body 10 capable of holding an electrostatic latent image, and opposed to the image holding body 10, and developing the electrostatic latent image on the image holding body 10 with a developer. And a developing device 11 for performing the above operation.
In this example, as shown in FIGS. 1A and 1B, the developing device 11 accommodates a developer G containing a toner and a carrier and faces an image holding body 10 that can hold an electrostatic latent image. The developing container 1 that opens, the hollow developing rotator 3 that faces the opening of the developing container 1 and rotates to face the image carrier 10, and the developing rotator 3 fixedly. A plurality of magnetic poles 5 (in this example, 5a to 5e) are arranged in the circumferential direction of the developing rotator 3, and at least adjacent to these magnetic poles 5 are magnetic pole pairs of different polarities (in this example, 5d-5e-). 5a-5b-5c) and a magnetic member 4 including a developing magnetic pole 5a disposed at a portion facing the image carrier 10, and by rotating the developing rotary member 3, the magnetic force generated by the magnetic pole 5 of the magnet member 4 is provided. The developer holding body 2 that holds the developer G on the developing rotator 3, and the development. Provided on the downstream side in the rotation direction of the developer holder 2 relative to the developing region Pd where the developing magnetic pole 5a of the holder 2 is located, a part of the developer holder 1 is fixed to the developer container 1 and extends toward the developer holder 2 side. A sealing member 6 that is formed of an elastically deformable plate-like member and seals the space between the developing container 1 and the developer holding body 2 by the tip portion coming into contact with the developer G on the developer holding body 2. The sealing member 6 has a radial component of the magnetic flux density due to the magnetic pole 5 of the developer holding body 2 among the magnetic pole pairs of different polarities (5b and 5c in this example) whose tip ends are adjacent to each other. On the developer holding member 2 at a position closer to the minimum part (corresponding to a part near the center of the magnetic poles 5b and 5c in this example) than the maximum part (corresponding to parts corresponding to the magnetic poles 5b and 5c in this example). In contact with the developer G.
In FIG. 1A, reference numeral 7 denotes a layer regulating member that regulates the layer thickness of the developer G held on the developer holding body 2 before reaching the developing region Pd, and reference numeral 8 denotes development in the developing container 1. An agitating and conveying member that agitates and conveys the developer G, and is held by the developer holder 2 after the developer G is charged.

In the present embodiment, the developer holder 2 is developed as a magnet member 4 at least adjacent to the opposite polarity magnetic pole pairs (in this example, 5d-5e-5a-5b-5c), at a position facing the image carrier 10. It has a magnetic pole 5a.
Here, as a means for once separating the developer G from the developer holding body 2, a separation magnetic pole (pick-off magnetic pole) composed of a magnetic pole pair having the same polarity (5c-5d in FIG. 1A) is usually provided. For example, a scraping member may be additionally provided, and the developer on the developer holding member may be scraped once.
Further, since the sealing member 6 needs to allow the developer G on the developer holding body 2 to pass therethrough, a typical embodiment is a plate-like member (such as an elastic film) that can be elastically deformed. The sealing member 6 only needs to be partly fixed to the developing container 1 directly or via a bracket, and may fix one end of the plate-like member, or fix a part away from the one end. May be.

In this example, the magnetic brush BH by the developer G moves while changing the shape of the spike depending on the radial component Mr of the magnetic flux density by the magnetic pole 5 as shown in FIG. At this time, since the radial component Mr of the magnetic flux density becomes maximum at the magnetic pole position (for example, the magnetic poles 5b and 5c), the magnetic brush BH is in a state of rising, while the magnetic pole pair of different polarity (for example, the magnetic pole 5b) , 5c), the radial component Mr of the magnetic flux density is minimized near the center of the magnetic brush BH, so that the magnetic brush BH is in a state where the ears are laid down. For this reason, as the radial direction component Mr of the magnetic flux density decreases to the minimum portion Pm, the volume density of the spikes of the magnetic brush BH gradually increases.
In this example, as shown in FIG. 2 (b), it corresponds to the maximum portion Pp (for example, the magnetic poles 5b and 5c) of the radial component Mr of the magnetic flux density among the magnetic pole pairs of different polarities (for example, the magnetic poles 5b and 5c). The tip of the sealing member 6 is in contact with the minimum portion Pm (for example, the portion corresponding to the vicinity of the approximate center of the magnetic poles 5b and 5c) as compared with the minimum portion Pm. It is difficult to pass through the inside of the magnetic brush BH at the sealing position by the stop member 6 (corresponding to the contact portion Ps at the tip of the sealing member 6), and the flying toner is difficult to leak from the developing container 1.
On the other hand, as shown in FIG. 2C, for example, the tip of the sealing member 6 ′ is held by the developer at the maximum portion Pp of the radial component Mr of the magnetic flux density (for example, the portion corresponding to the magnetic poles 5b and 5c). Assuming that the developer on the body 2 is in contact with the developer, the magnetic brush BH by the developer G is in a raised state at that portion, so that the volume density of the magnetic brush BH is in a rough state, and the developing container 1 There is a concern that the toner flying inside easily leaks to the outside through the magnetic brush BH.

In this embodiment, the magnetic brush BH by the developer G behaves depending on the radial component Mr of the magnetic flux density by the magnetic pole 5 of the developer holder 2, but the sealing effect by the sealing member 6 is achieved. When obtaining the amount of the radial component Mr of the magnetic flux density that is in contact with the surface of the developer holder 2 at the tip of the sealing member 6 was examined, the following results were found. did.
That is, the sealing member 6 comes into contact with the developer on the developer holding body 2 at a position between the opposite polarity magnetic pole pairs (for example, the magnetic poles 5b and 5c) adjacent to each other. 1B, the radial component of the magnetic flux density at the intersection of the straight line passing through the tip of the sealing member 6 and the center of the developer holding body 2 and the surface of the developing rotator 3 is Bs. Assuming that Bp is the radial component of the magnetic flux density of the magnetic pole located in the position closest to (5b in this example), the smaller the Bs, the more the magnetic brush BH at that part lays the ears at a higher density. Become. At this time, when the amount of toner blown from the sealing portion of the sealing member 6 is measured under the condition that Bs is changed, if Bs / Bp ≦ 0.65, the amount of blown toner can be suppressed to an allowable level. It turned out to be.

Next, a typical aspect or a preferable aspect of the developing device according to the present embodiment will be described.
As an aspect in which the magnet member 4 of the developer holder 2 is provided with a peeling magnetic pole, the magnet member 4 has a peeling magnetic pole composed of at least a pair of adjacent magnetic pole pairs of the same polarity (5c-5d in this example). However, in this embodiment, the sealing member 6 has a tip portion on the developer holding body 2 positioned on the upstream side in the rotation direction of the developer holding body 2 with respect to the peeling magnetic pole of the developer holding body 2. A mode of contacting with the developer is preferable.
Since the repulsive magnetic field is generated in the peeling magnetic pole composed of the same polarity magnetic pole pair (5c-5d in this example), the toner is separated from the magnetic brush BH by the developer G and flies. Moreover, since the force in the center direction / conveyance direction due to the magnetic force is not applied on the downstream side in the rotation direction of the developer holder 2 in the peeling magnetic pole, the magnetic binding to the magnetic brush BH can be released. As a result, the magnetic brush BH is attracted to the upstream side in the rotation direction of the developer holding body 2, collides with the developer G being conveyed, and the toner detaches and flies. As described above, the toner easily flies around the peeling magnetic pole, and there is a high concern that the toner leaks from the developing container 1. For this reason, in this aspect, although the toner easily leaks from the developing container 1, the leakage of the toner can be effectively suppressed by devising the sealing member 6.

Further, as a preferable aspect of the layout of the sealing member 6, the tip portion thereof is further downstream than the magnetic pole (5 b in this example) adjacent to the developing magnetic pole 5 a on the downstream side in the rotation direction of the developer holder 2. The mode which contacts the developer on the said developer holding body 2 located in 1 is mentioned.
In this example, since there is a magnetic pole of different polarity (magnetic pole 5b in this example) between the sealing position by the sealing member 6 and the developing magnetic pole 5a, the behavior of the developer G by the developing magnetic pole 5a 6 is preferable in that the sealing operation according to 6 is hardly affected.

Embodiment 1
Hereinafter, the present invention will be described in more detail based on embodiments shown in the accompanying drawings.
<Overall configuration of image forming apparatus>
FIG. 3 is an explanatory view showing Embodiment 1 of the image forming apparatus to which the present invention is applied.
In the figure, an image forming apparatus 20 arranges image forming units 22 (specifically, 22a to 22d) of four colors (black, yellow, magenta, and cyan in this embodiment) in an apparatus casing 21 in the horizontal direction. A transfer module 23 including an intermediate transfer belt 230 that is circulated and conveyed along the arrangement direction of the image forming units 22 is disposed above the image forming unit 22. A recording material supply device 24 that accommodates the recording material is disposed, and a recording material conveyance path 25 from the recording material supply device 24 is disposed in a substantially vertical direction.

In the present embodiment, the image forming units 22 (22a to 22d) are, for example, for black, yellow, magenta, and cyan in order from the upstream side in the circulation direction of the intermediate transfer belt 230. (Not limited to) a toner image, a photoreceptor 31, a charging device (charging roll in this example) 32 that charges the photoreceptor 31 in advance, and each photoreceptor charged by the charging device 32. An exposure device 33 that writes an electrostatic latent image on 31 (in this example, a common exposure device is used for each image forming unit 22), and a corresponding color toner (this embodiment) that forms an electrostatic latent image formed on the photoreceptor 31. In this embodiment, a developing device 34 that develops with negative polarity, for example, and a cleaning device 35 that cleans the residue on the photoreceptor 31 are provided.
In the present embodiment, as shown in FIG. 3, each image forming unit 22 is configured as a process cartridge in which a photosensitive member 31, a charging device 32, a developing device 34, and a cleaning device 35 are integrated. 21 is detachably attached to an assembly receiving portion (not shown).
Here, the exposure apparatus 33 includes, for example, four semiconductor lasers (not shown), one polygon mirror 42, an imaging lens (not shown), and mirrors corresponding to the respective photoreceptors (see FIG. (Not shown), the light from the semiconductor laser of each color component is deflected and scanned by the polygon mirror 42, and the light image is guided to the exposure point on the corresponding photoreceptor 31 through the imaging lens and mirror. It is.
Reference numeral 36 (36a to 36d) denotes a toner cartridge for replenishing each developing device 34 with each color component toner.
Further, in the present embodiment, the transfer module 23 is, for example, a structure in which an intermediate transfer belt 230 is stretched between a pair of stretch rolls (one is a drive roll) 231 and 232, and the photoreceptor of each image forming unit 22. A primary transfer device (primary transfer roll 51 in this example) 51 is disposed on the back surface of the intermediate transfer belt 230 corresponding to 31, and a voltage having a polarity opposite to the charging polarity of the toner is applied to the primary transfer device 51, The toner image on the photoreceptor 31 is electrostatically transferred to the intermediate transfer belt 230 side.
Further, a secondary transfer device 52 is disposed at a portion corresponding to the tension roll 232 on the downstream side of the most downstream image forming unit 22d of the intermediate transfer belt 230, and a primary transfer image on the intermediate transfer belt 230 is recorded. Secondary transfer (collective transfer) is performed on the material.

In the present embodiment, the secondary transfer device 52 includes a secondary transfer roll 521 arranged in pressure contact with the toner image holding surface side of the intermediate transfer belt 230, and a secondary transfer roll disposed on the back side of the intermediate transfer belt 230. A backup roll (in this example, also serving as a stretching roll 232) is provided.
For example, the secondary transfer roll 521 is grounded, and a bias having the same polarity as the charging polarity of the toner is applied to the backup roll (stretching roll 232).
Furthermore, a belt cleaning device 53 is disposed on the upstream side of the most upstream image forming portion 22a of the intermediate transfer belt 230 so as to remove residual toner on the intermediate transfer belt 230.

Further, the recording material supply device 24 is provided with a supply roll 61 for supplying a recording material. A transport roll 62 for transporting the recording material is disposed immediately after the supply roll 61 and immediately before the secondary transfer site. A positioning roll (registration roll) 63 for supplying the recording material to the secondary transfer portion at a predetermined timing is disposed in the recording material conveyance path 25 positioned at the position.
On the other hand, a fixing device 66 is provided in the recording material conveyance path 25 located on the downstream side of the secondary transfer site. As shown in FIG. 3, the fixing device 66 is a heat fixing in which a heater (not shown) is incorporated. A roll 66a and a pressure fixing roll 66b that is arranged in pressure contact with the roll 66 and rotates following the roll 66a are provided. A recording material discharge device 67 is provided on the downstream side of the fixing device 66. The recording material discharge device 67 includes paired discharge rollers 67 a and 67 b for discharging the recording material in the apparatus housing 21. The recording material is sandwiched and conveyed to be discharged, and is formed on the upper portion of the apparatus housing 21. A recording material is accommodated in the material accommodating receptacle 68.
Further, in the present embodiment, a manual feed device (MSI) 71 is provided on the side of the apparatus housing 21, and the recording material on the manual feed device 71 is supplied by the supply roll 72 to the recording material conveyance path 25. It is to be supplied towards.
Furthermore, a double-sided recording module 73 is attached to the apparatus housing 21. The double-sided recording module 73 reverses the recording material discharging device 67 when selecting the double-sided mode in which image recording is performed on both sides of the recording material, and Then, the recording material on which one-side recording is performed is taken into the inside by the guide roll 74 before the entrance, the recording material is conveyed along the internal recording material return conveyance path 76 by an appropriate number of conveyance rolls 77, and the positioning roll 63 side again. To supply.

<Developing device>
As shown in FIG. 4, the developing device 34 has a developing container 120 that opens toward the photosensitive member 31 and contains a two-component developer containing toner and carrier, and faces the opening of the developing container 120. A developing roll 121 that holds and conveys the developer is disposed at the site, and a pair of agitating and conveying members 122 and 123 that agitate and convey the developer are disposed on the back side of the developing roll 121 in the developing container 120. Furthermore, a layer regulating member 124 for regulating the layer thickness of the developer held on the developing roll 121 is provided on the upstream side of the developing portion of the developing roll 121 in the rotation direction.
Furthermore, in this example, a position adjusting tracking roll (not shown) slightly larger than the diameter of the developing roll 121 is provided at both ends of the developing roll 121, and the tracking roll is brought into contact with the surface of the photoreceptor 31. The gap between the developing roll 121 and the photoconductor 31 is adjusted to a predetermined amount.

-Development roll-
As shown in FIG. 4, the developing roll 121 is provided with a cylindrical developing sleeve 131 made of aluminum, for example, and a fixed inside of the developing sleeve 131, and a plurality of (in this example, five) magnetic poles are arranged around it. The magnet roll 132 is provided.
In this example, the magnetic pole 133 of the magnet roll 132 includes a developing magnetic pole (S1) for developing the electrostatic latent image on the photosensitive member 31 provided in the developing region Pd facing the photosensitive member 31, and a developing region Pd. On the other hand, the conveying magnetic poles (N1, S2, N2) provided on the downstream side in the rotation direction of the developing sleeve 131 and further provided on the downstream side in the rotating direction of the developing sleeve 131 and corresponding to the layer regulating member 124. In addition, an adsorption / layer regulating magnetic pole (N 3) that adsorbs the developer onto the surface of the developing sleeve 131 and regulates the layer thickness of the developer between the layer regulating member 124 is provided.
In this example, adjacent magnetic poles are magnetized with different polarities between the magnetic pole for adsorption / layer regulation (N3), the magnetic pole for development (S1), and the magnetic pole for conveyance (N1, S2, N2). Since the adjacent magnetic poles of the magnetic pole (N2) and the adsorption / layer regulating magnetic pole (N3) have the same polarity, the developer held on the developing sleeve 131 is peeled off once by generating a repulsive magnetic field. It functions as a magnetic pole.
A developing voltage (not shown) is applied to the developing sleeve 131 so that a predetermined developing electric field is formed between the photosensitive member 31 and the developing sleeve 131.

-Stirring conveying member-
In this example, the developer accommodating chamber 134 of the developing container 120 is divided into two chambers 134a and 134b via a partition wall 135, and the developing roll 121 and one agitating and conveying member 122 are accommodated in one developer accommodating chamber 134a. Then, the other agitation transport member 123 is accommodated in the other developer accommodating chamber 134b. Passing ports (not shown) are opened near both ends in the longitudinal direction of the partition wall 135, and the developer conveying chambers 122 and 123 rotate in the two chambers of the developer accommodating chamber 134 so that the developer accommodating chamber is rotated. The developer in 134 is divided into two chambers and is circulated and conveyed through the passage port.
In this example, the agitating / conveying members 122 and 123 are both in a form in which a spiral blade 137 is attached around the rotation shaft 136, and one agitating / conveying member 122 is disposed substantially immediately below the developing roll 121. Since the developer stirred and conveyed by the agitating / conveying member 122 is supplied toward the developing roll 121, it functions as a developer supply member to the developing roll 121.

-Layer regulating member-
In this example, the layer regulating member 124 is configured by a plate-like member, and is fixed to a mounting portion 140 formed in advance in the developing container 120, and a developer layer is provided between the developing container 120 and the developing roll 121. A gap for regulating the thickness is secured. In this example, a plate-like member is used as the layer regulating member 124. However, the present invention is not limited to this, and for example, a roll-like member may be used.

-Sealing film-
In the present embodiment, a sealing film 150 that seals between the developing container 120 and the developing roll 121 is provided at the upper edge of the opening of the developing container 120 that is located downstream of the developing area Pd in the rotation direction of the developing roll 121. Is provided.
In this example, the sealing film 150 is made of an elastic thin film material such as polyethylene or polypropylene and is formed of a long thin plate extending in the axial direction of the developing roll 121, as shown in FIGS. 4 and 5A. As described above, one end side in the short direction (width direction) of the thin plate is fixed to the upper edge of the opening of the developing container 120 with an adhesive or a stopper, and the tip end that is the other end side in the width direction of the thin plate is fixed on the developing roll 121 The upper developer is brought into elastic contact with the developer.
In particular, in the present embodiment, the leading end of the sealing film 150 is in contact with the developer on the developing roll 121 within a predetermined range between the magnetic poles N1 and S2 having different polarities. It has become.

More specifically, in this example, a predetermined magnetic flux density distribution by the magnetic pole 133 is generated on the surface of the developing roll 121 as shown in FIG.
In the drawing, the solid line indicates the radial direction component Mr of the magnetic flux density, and the alternate long and short dash line indicates the circumferential direction component Mc of the magnetic flux density, and the radial direction component Mr of the magnetic flux density indicates each magnetic pole 133 (S1 to S3, N1, N2). ) Shows a local maximum value, and shows a local minimum value in the vicinity of the approximate center of each magnetic pole 133. In addition, the circumferential direction component Mc of the magnetic flux density shows a local minimum value at a portion corresponding to each magnetic pole 133 (S1 to S3, N1, N2), contrary to the radial direction component Mr of the magnetic flux density. The maximum value is shown near the center.
With respect to the developing roller 121 having such a magnetic flux density distribution, as the contact site Ps at the tip of the sealing film 150, as shown by the solid line in FIG. 5B, the minimum site Pm of the radial component Mr of the magnetic flux density. The magnetic poles N1 and S2 are preferably disposed in the vicinity of the center of the magnetic poles N1 and S2. However, the present invention is not limited to this, and as shown by the dotted line in FIG. In the region R closer to the minimum part Pm than the maximum part Pp due to or as shown by a two-dot chain line in FIG. 5B, for example, the minimum part compared to the maximum part Pp due to the magnetic pole S2 for transport What is necessary is just to arrange | position in the area | region R near Pm.

Further, in the present embodiment, if the value of the radial component Mr of the magnetic flux density due to the magnetic pole 133 at the contact portion Ps at the tip of the sealing film 150 is smaller than the maximum value, the sealing by the sealing film 150 is performed. An experiment was conducted to verify whether the performance was secured, and the following results were obtained.
Now, as shown in FIG. 5B and FIG. 6, the radial component Mr of the magnetic flux density at the intersection of the straight line passing through the front end of the sealing film 150 and the center of the developing roll 121 and the surface of the developing sleeve 131. Bs, the contact of the tip of the sealing film 150 with the condition that the radial component Mr of the magnetic flux density of the magnetic pole 133 (in this example, the magnetic pole N1 for conveyance) located closest to the intersection is Bp and Bs is changed. As a result of measuring the amount of toner blown from the site (corresponding to the sealed site) Ps, it was found that if Bs / Bp ≦ 0.65, the amount of blown toner can be suppressed to a preselected tolerance level. .
Here, the permissible level can be selected as appropriate. For example, if the permissible level of the toner blowing amount is selected more strictly, the threshold value of Bs / Bp is selected to be smaller than 0.65, and vice versa. In addition, if the allowable level of the toner blowing amount is selected gently, the threshold value of Bs / Bp is selected to be larger than 0.65. In this embodiment, the sealing effect of the sealing film 150 is selected. A threshold value of 0.65 is selected.
In addition, this experiment is explained in full detail in the Example mentioned later.

-Operation of the developing device-
Next, the operation of the developing device according to the present embodiment will be described.
Assuming that an image forming process is being performed by the image forming apparatus now, attention is paid to the operation of the developing apparatus at that time as follows.
When an electrostatic latent image is formed on the photoreceptor 31 of each image forming unit 22, the developing device 34 rotates the developing roll 121 and the agitating / conveying members 122 and 123 in a predetermined direction to charge the developer and develop it. After attracting the developer by the attracting magnetic pole S3 of the roll 121 and regulating the layer thickness of the developer by the layer regulating member 124, the electrostatic latent image on the photoconductor 31 is developed in the development region Pd.
As the developing roller 121 rotates, the developer after development passes through the sealing portion by the sealing film 150 and then returns to the developing container 120, and the developer is peeled by the repulsive magnetic field of the peeling magnetic poles N2 and N3. Is done.
At this time, when the developer is peeled off from the peeling magnetic poles N2 and N3, a phenomenon that the toner flies along with this is seen. The toner flying in this way becomes a cloud shape in the developing container 120, and when the internal pressure by the toner cloud increases, there is an increased risk of leakage from the opening of the developing container 120.

In such a situation, in this example, the front end portion of the sealing film 150 is located near the minimum portion Pm of the radial component Mr of the magnetic flux density due to the magnetic pole 133 between the magnetic poles N1 and S2 for conveyance. Since the developer 121 is in contact with the developer 121, the leakage of the toner cloud is sealed for the following reason.
That is, in this example, the radial direction component Mr of the magnetic flux density shows a change that continuously decreases from the maximum portion Pp toward the minimum portion Pm. Therefore, the contact portion Ps at the tip portion of the sealing film 150 is the maximum. If it is arranged closer to the minimum part Pm than the part Pp, the radial component Mr of the magnetic flux density at the contact part Ps can be suppressed smaller than the case where it is arranged closer to the maximum part Pp.
In this way, when the tip of the sealing film 150 comes into contact with a portion where the radial component Mr of the magnetic flux density on the surface of the developing roll 121 is small and seals the portion, the magnetic brush BH by the developer at the sealing portion. Since the ears are in a state where they are laid down, the developer is filled with a high density, and the ventilation resistance of the magnetic brush BH portion is increased. For this reason, it is difficult for the toner cloud in the developing container 120 to pass through the magnetic brush BH at the sealing portion of the sealing film 150, and the blowing out of the toner cloud is suppressed.
In particular, in this embodiment, since the sealing condition of the sealing film 150 is selected so as to satisfy Bs / Bp ≦ 0.65, it is possible to suppress the toner blowing amount to a predetermined allowable level. It is.

Example 1
In this example, the developing device according to the first embodiment is embodied, and an experiment for evaluating the sealing performance by the sealing film is performed.
Now, the radial component Mr of the magnetic flux density on the surface of the developing roll used in this embodiment is set to the origin 0 as the center position of the developing region Pd, and the radial component Mr of the magnetic flux density changes along the clockwise direction of the developing roll. A plot of is shown in FIG.
In the figure, the horizontal axis indicates the angular position from the origin of the developing roll, and the vertical axis indicates the value of the radial component Mr of the magnetic flux density on the surface of the developing roll.
Furthermore, as the length (length in the width direction) from the base end of the sealing film to the front end extending to the developing roll side, samples of 6 mm, 8 mm, 10 mm, and 12 mm were prepared and each sealing film was equipped. When the position of the front surface of the sealing film in contact with the surface of the developing roll was examined, as shown in FIGS. 7a to 7d, the sample a had a diameter of magnetic flux density corresponding to the transport magnetic pole N1. The sample d is transferred to the local maximum portion Pp (see FIG. 5) of the directional component Mr, the sample d is transferred to the local maximum portion Pp (see FIG. 5) of the radial direction component Mr of the magnetic flux density corresponding to the magnetic pole S2 for transfer. It was confirmed that the magnetic poles N1 and S2 are arranged in the region R (see FIG. 5) near the minimal portion Pm of the radial component Mr of the magnetic flux density.
In addition, when the sample whose length of a sealing film is 9 mm was created, it was confirmed that the front-end | tip part of the said sealing film is an aspect which contacts the minimum site | part Pm of the radial direction component Mr of magnetic flux density.

Using each sample of such a sealing film, a test paper was placed in a part facing the opening of the developing container of the developing device according to Example 1, and the developing device was operated for a predetermined time of 3 minutes Below, when the toner adhesion amount on the paper as the toner blows out from the developing container was measured, the result shown in FIG. 8 was obtained.
In the figure, the horizontal axis indicates the length of the sealing film (film length), and the vertical axis indicates the toner adhesion amount (mg).
According to the figure, it is understood that the toner adhesion amount increases and decreases with the change in the length of the sealing film. At this time, the smaller the toner adhesion amount, the smaller the leakage of the toner cloud. Therefore, in order for the toner adhesion amount to be within a predetermined allowable value (allowable level), in this example, in the sealing film, It has been found that the length may be 8 to 10.4 mm. The circumferential angle range of the developing roll was 86 to 110 °.
Based on such experimental results, in FIG. 7, the radial component Bs of the magnetic flux density at the surface of the developing roll at the contact portion Ps at the tip of the sealing film and the surface of the developing roll at the transport magnetic pole N1 When the ratio of the magnetic flux density to the maximum value Bp, which is the radial direction component Mr, was examined, it was found that Bs / Bp ≦ 0.65.
In this experiment, the sample with the sealing film length of 9 mm is the minimal portion Pm of the radial component Mr of the magnetic flux density on the surface of the developing roll, and the sample a with the sealing film length of 6 mm and 12 mm is used. , D are the maximum portions Pp of the radial component Mr of the magnetic flux density on the surface of the developing roll, so that in each of the samples b and c, the contact portion Ps at the tip of the sealing film is the magnetic flux density on the surface of the developing roll. The aspect which is near the minimum site | part Pm of radial direction component Mr of is shown.

  DESCRIPTION OF SYMBOLS 1 ... Development container, 2 ... Developer holding body, 3 ... Development rotary body, 4 ... Magnetic member, 5 (5a-5e) ... Magnetic pole, 6 ... Sealing member, 7 ... Layer control member, 8 ... Agitating conveyance member, DESCRIPTION OF SYMBOLS 10 ... Image holding body, 11 ... Developing apparatus, G ... Developer, Pp ... Maximum part of radial component of magnetic flux density, Bp ... Maximum value of radial component of magnetic flux density, Pm ... Minimal of radial component of magnetic flux density Part, Bm ... Minimum value of radial component of magnetic flux density, Ps ... Contact part between tip of sealing member and surface of developer holding member, Bs ... Tip of sealing member and surface of developer holding member Component of magnetic flux density in the contact area

Claims (5)

A developer container containing a developer containing toner and a carrier and opening to face an image holding body capable of holding an electrostatic latent image;
A hollow developing rotator which is provided facing the opening of the developing container and rotates to face the image carrier, and is fixedly included in the developing rotator, and is provided in a circumferential direction of the developing rotator. A plurality of magnetic poles are arranged, and each of the magnetic poles includes a magnet member including at least a pair of magnetic poles of different polarities adjacent to each other and a magnetic pole for development arranged at a portion facing the image carrier, and the development rotating body A developer holding body that holds the developer on the development rotating body by the magnetic force of the magnetic poles of the magnet member by rotating
Provided on the downstream side in the rotation direction of the developer holder relative to the developing region where the developing magnetic pole of the developer holder is located, and a part of the developer holder is fixed to the developer container and extends toward the developer holder. A sealing member that is configured by an elastically deformable plate-like member, and that seals between the developer container and the developer holding body by having the tip end portion in contact with the developer on the developer holding body; With
The developing member is located at a position closer to the minimum portion than the maximum portion of the radial component of the magnetic flux density due to the magnetic poles of the developer holding member, between the pair of magnetic poles of different polarities adjacent to each other at the tip. A developing device which is in contact with the developer on the agent holder. A developer container containing a developer containing toner and a carrier and opening to face an image holding body capable of holding an electrostatic latent image;
A hollow developing rotator which is provided facing the opening of the developing container and rotates to face the image carrier, and is fixedly included in the developing rotator, and is provided in a circumferential direction of the developing rotator. A plurality of magnetic poles are arranged, and each of the magnetic poles includes a magnet member including at least a pair of magnetic poles of different polarities adjacent to each other and a magnetic pole for development arranged at a portion facing the image carrier, and the development rotating body A developer holding body that holds the developer on the development rotating body by the magnetic force of the magnetic poles of the magnet member by rotating
Provided on the downstream side in the rotation direction of the developer holder relative to the developing region where the developing magnetic pole of the developer holder is located, and a part of the developer holder is fixed to the developer container and extends toward the developer holder. A sealing member that is configured by an elastically deformable plate-like member, and that seals between the developer container and the developer holding body by having the tip end portion in contact with the developer on the developer holding body; With
The sealing member is in contact with the developer on the developer holding body at a position between adjacent magnetic pole pairs of different polarities at the front ends thereof,
The radial component of the magnetic flux density at the intersection of the straight line passing through the tip of the sealing member and the center of the developer holding member and the surface of the developing rotator is Bs, and the magnetic pole located closest to the intersection If the radial component of the magnetic flux density is Bp,
A developing device satisfying a relationship of Bs / Bp ≦ 0.65. The developing device according to claim 1 or 2,
The developer holding body has a peeling magnetic pole composed of at least a pair of magnetic poles of the same polarity adjacent to each other as the magnet member,
The sealing member has a tip that contacts the developer on the developer holder positioned upstream of the peeling pole of the developer holder in the rotation direction of the developer holder. A developing device. In the developing device according to any one of claims 1 to 3,
The sealing member is in contact with the developer on the developer holder whose tip is located further downstream than the magnetic pole adjacent to the developing magnetic pole on the downstream side in the rotation direction of the developer holder. A developing device characterized by that. An image carrier capable of holding an electrostatic latent image;
The developing device according to any one of claims 1 to 4, wherein the developing device is provided to face the image carrier and develops an electrostatic latent image on the image carrier with a developer.
An image forming apparatus comprising:

Images