JP4752663B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device that performs development in an electrophotographic process and an image forming apparatus having the developing device.

  In electrophotographic image forming apparatuses, the amount of toner consumed has increased as a result of recent progress in colorization and speeding up, and as toner consumption increases, toner scattering and toner spillage that scatters outside the developing device. Has increased.

  As a countermeasure against this, Patent Document 1 proposes to provide a suction duct having a suction port facing each of a plurality of image forming stations to suck scattered toner.

  Patent Document 2 proposes that a developer regulating member is provided with a hollow portion, and an opening is provided in a wall forming the hollow portion, so that the developer is sucked into the hollow portion from the opening.

In Patent Document 3, a first space is provided on the downstream side of a position where the developing roller and the photosensitive member face each other, an air pressure in the first space is set low, and an opening communicating with the first space is provided. Accordingly, it has been proposed to suck the scattered toner into the first space.
Japanese Patent Laid-Open No. 7-20753 JP 2004-205999 A JP 2005-257739 A

  In a developing device that consumes a large amount of developer and is downsized, in addition to toner scattering, toner accumulates on the cover that covers the upper space of the developing device, and the deposited developer falls due to vibration or the like. The problem is toner spillage that adheres to the recording material and causes image smearing.

  The scattering prevention means of Patent Document 1 is effective in preventing scattered toner, but has almost no function for preventing the toner spillage.

  The toner scattering prevention means of Patent Documents 2 and 3 are effective in preventing toner scattering, but on the downstream side of the developer regulating member (downstream in the developer moving direction), the scattered toner is scattered on the side surface and cover of the regulating member. Is easy to accumulate and is not effective in preventing toner spillage.

  The present invention prevents toner spillage in which toner accumulates on a cover that covers the upper space of the developing roll and falls to cause image smearing, and an image that consumes a large amount of toner, such as a color image forming apparatus or a high-speed image forming apparatus. An object of the present invention is to provide a developing device capable of forming a high-quality image with very little deterioration in image quality due to toner spillage even when used in a forming device, and an image forming device having such a developing device.

The object is achieved by the following invention.
1.
A developer carrying member for transporting a developer to a development area and carrying the developer in the development area, the developer carrying body rotating, and a developer roll disposed in the development sleeve and having a magnet roll having a plurality of magnetic poles Carrier,
A regulating member for regulating the amount of developer on the developer carrying member;
Contains developer and opens upwards,
A casing for housing the developer, the developer carrier and the regulating member; and
In a developing device having a cover that covers at least a part of the developer carrier and the regulating member,
The developing device according to claim 1, wherein a portion of the cover covering the developer carrier and the regulating member is formed so as to satisfy the following condition.

a. Forming a gap having a uniform width between the cover and the developer carrying member; b. The tip of the cover close to the development region is disposed upstream of the transport pole disposed downstream of the developer transport direction with respect to the control pole of the plurality of magnetic poles facing the control member. C. In addition to forming an outlet through which air flows out between the developer carrier and the tip of the cover, an air inlet is formed in the cover, along the regulating member and the developer carrier, 1. Create a unidirectional air flow from the inlet to the outlet.
The magnet roll has a plurality of transport poles, and the tip of the cover is upstream of the position of the magnetic flux density peak of the transport pole on the most upstream side in the developer transport direction of the plurality of transport poles. 2. The developing device according to 1 above, wherein the developing device is located.
3.
3. The developing device according to 1 or 2 above, wherein the gap has a width such that the developer conveyed on the developer carrying member does not come into contact therewith.
4).
An image forming apparatus comprising: a photosensitive member; a latent image forming unit that forms an electrostatic latent image on the photosensitive member; and the developing device according to any one of the above items 1 to 3. An image forming apparatus having a duct for sucking flowing air.
5.
5. The image forming apparatus according to 4, wherein the duct is formed so that an interval between an inner surface of the duct and the developer carrying member is 2.5 mm or more.
6).
The image forming apparatus according to 4 or 5, wherein a part of the duct is formed by the cover.
7).
7. The image forming apparatus according to 6, wherein a portion of the cover that forms the duct has an inclination angle of 0 ° to 40 °.

  In the present invention, a cover that covers the upper side of the developer carrier is formed so that the tip is positioned upstream of the transport pole for transporting the developer in the developer transport direction downstream of the regulating member in the developer transport direction. Since a gap having a uniform width is formed between the agent carrier and the cover, and a flow of air in one direction is formed in the gap, the surface of the restriction member or the cover facing the restriction member or the cover Thus, toner is prevented from being deposited on the surface of the developer carrying member facing the developer carrying member, and toner spillage is well prevented.

  The present invention will be described below based on an embodiment of the present invention, but the present invention is not limited to the embodiment.

  FIG. 1 is a diagram showing an overall configuration of an image forming apparatus according to an embodiment of the present invention.

  This image forming apparatus is called a full-color image forming apparatus having a vertical tandem configuration, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, and an endless belt-shaped intermediate transfer body unit as an intermediate transfer body unit. 7, a paper feeding / conveying means 21 and a fixing device 24. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  An image forming unit 10Y that forms a yellow image includes a drum-shaped photoreceptor 1Y, a charging device 2Y, an exposure device 3Y, a developing device 4Y, and a primary transfer roller as a primary transfer unit disposed around the photoreceptor 1Y. 5Y and a cleaning device 6Y. The image forming unit 10M that forms a magenta image includes a drum-shaped photoconductor 1M, a charging device 2M disposed around the photoconductor 1M, an exposure device 3M, a developing device 4M, and a primary transfer roller as a primary transfer unit. 5M and a cleaning device 6M. An image forming unit 10C that forms a cyan image includes a drum-shaped photoreceptor 1C, a charging device 2C, an exposure device 3C, a developing device 4C, and a primary transfer roller as a primary transfer unit disposed around the photoreceptor 1C. 5C and a cleaning device 6C. An image forming unit 10K that forms a black image includes a drum-shaped photoconductor 1K, a charging device 2K arranged around the photoconductor 1K, an exposure device 3K, a developing device 4K, a primary transfer roller 5K as a primary transfer unit, It has a cleaning device 6K.

  An endless belt-like intermediate transfer body unit 7 as an intermediate transfer body unit is wound around a plurality of rollers and is rotatably supported, and is an endless belt-like intermediate transfer body 70 as a semiconductive endless belt-like intermediate transfer body. Have

  The images of the respective colors formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred and synthesized on the rotating endless belt-shaped intermediate transfer body 70 by the primary transfer rollers 5Y, 5M, 5C, and 5K. A color image is formed. A transfer material P such as a sheet as a recording medium accommodated in the sheet feeding cassette 20 is fed by a sheet feeding means 21, passes through a plurality of intermediate rollers 22 A, 22 B, 22 C, 22 D, and a registration roller 23, and is subjected to secondary transfer. The image is conveyed to a secondary transfer roller 5A as a means, and the color image is collectively transferred onto the transfer material P. The transfer material P onto which the color image has been transferred is subjected to fixing processing by the fixing device 24, is sandwiched between the paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the transfer material P by the secondary transfer roller 5A as the secondary transfer means, the residual toner is removed from the endless belt-shaped intermediate transfer body 70 from which the transfer material P is separated by the curvature by the cleaning device 6A. The

  During the image forming process, the primary transfer roller 5K is always in pressure contact with the photoreceptor 1K. The other primary transfer rollers 5Y, 5M, and 5C are pressed against the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5A is in pressure contact with the endless belt-shaped intermediate transfer body 70 only when the transfer material P passes through the secondary transfer roller 5A.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10K and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1K in the figure. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, 74, 76, and 77, primary transfer rollers 5Y, 5M, 5C, and 5K, and cleaning. Device 6A.

  The image forming units 10Y, 10M, 10C, and 10K and the endless belt-shaped intermediate transfer body unit 7 are integrally pulled out from the main body A by the drawer operation of the housing 8.

  An electrostatic latent image is formed on the photoreceptors 1Y, 1M, 1C, and 1K by a latent image forming unit including a charging device (2Y, 2M, 2C, and 2K) and an exposure device (3Y3M, 3C, and 3K), and a developing device ( 4Y, 4M, 4C, and 4K), a toner image is formed. The toner images of the respective colors are primarily transferred and superimposed on the endless belt-shaped intermediate transfer body 70, and then are collectively transferred to the transfer material P, and fixed and fixed by the fixing device 24 by pressing and heating. The photoreceptors 1Y, 1M, 1C, and 1K after transferring the toner image to the endless belt-shaped intermediate transfer body 70 are configured to remove residual toner left on the photoreceptors at the time of transfer by the cleaning devices 6Y, 6M, 6C, and 6K. After cleaning, the charging, exposure and development cycle described above is entered, and the next image formation is performed.

  FIG. 2 is a cross-sectional view of the developing device according to Embodiment 1 of the present invention. The developing device 4 in FIG. 2 shows the developing devices 4Y, 4M, 4C and 4K in FIG.

  The developing device 4 is a developing device that develops an electrostatic latent image using a two-component developer mainly composed of toner and a carrier, and a casing that houses the developer and various components described below, A cover that covers the upper opening of the casing is formed in a box shape having an opening in the developing region, and the four developing devices 4 are arranged so as to overlap each other, so that the height is compressed.

  The lower part of the box is composed of a casing 401, and the casing 401 opens upward. The upper part of the developing device is composed of covers 402 and 404 that cover the upper opening of the casing 401. An opening 420 as an air inlet having a length substantially equal to the developing width is formed in the cover 402, and the cover 402 covers the casing 401, the regulating member 410, and a part of the developing roll 405. A cover 404 is disposed with respect to the cover 402 with a gap 421 therebetween. The cover 404 covers the upper portion of the casing 401, forms a gap 421 through which air flows, and supports the regulating member 410.

  In the opening formed by the casing 401 and the cover 402, a developing roll 405 as a developer carrying member is disposed. The developing roll 405 includes a developing sleeve 406 that rotates counterclockwise as indicated by an arrow, and a magnet roll 407 disposed in the developing sleeve 406.

  As illustrated, the cover 402 covers a part of the developing roll 405, the regulating member 410 and the cover 404.

  The magnet roll 407 has magnetic poles M1 to M7.

  M1, M3, M4, and M6 are N poles, and M2, M5, and M7 are S poles.

  M1 is a developing pole for forming a magnetic brush for developing the electrostatic latent image on the photosensitive member P in the developing region G, M4 is a regulating pole, and M5 to M7 are configured to convey the developer by alternately arranging different magnetic poles. It is a transport pole.

  M3 and M4 have the same polarity, and a repulsive magnetic field is formed between the adjacent magnetic poles M3 and M4 having the same polarity, and the developer is separated from the developing sleeve 406 at this portion.

  Reference numeral 410 denotes a restricting member composed of a magnetic restricting member 410A and a nonmagnetic restricting member 410B. The lower end of the restricting member forms a predetermined narrow gap with respect to the surface of the developing sleeve 406, and the developer passing through the gap. The amount is regulated and a developer layer having a certain thickness is formed on the developing sleeve 406.

  As shown in the drawing, the magnetic restriction member 410A is disposed on the upstream side in the rotation direction of the developing sleeve 406, and the non-magnetic restriction member 410B is disposed on the downstream side, thereby suppressing toner scattering and restricting the restriction member 410 and the cover 402. Toner adhesion to the vicinity of the member is suppressed.

  Reference numerals 408 and 409 denote stirring / conveying members arranged in a room partitioned by a partition 401A formed in the casing 401, which are composed of screws, and stir / convey the developer by rotation.

  In the development, the developing sleeve 406 and the agitating / conveying member rotate, and the developer flow is changed to the agitating / conveying member 409 → the agitating / conveying member 408 → the upper side of the developing roll 406 → the lower side of the developing roll 405 → the agitating / conveying. Formed as a member 408 → stirring / conveying member 409, the developer circulates and the electrostatic latent image on the photoreceptor P is continuously developed.

  FIG. 3 shows the developer flow in the vicinity of the developing roll 405.

  The developer D is supplied to the regulation electrode M4 of the developing roll 405 by the stirring / conveying member 408, and is regulated by the regulation member 410 at the upstream portion of the regulation member 410. As a result, a massive developer D1 is formed. A developer layer D2 having a substantially uniform thickness is formed on the developing roll 405 in the downstream portion.

  The cover 402 covers the upper portion of the developing roll 405 with a gap 423 therebetween, covers the upper portion of the regulating member 410 with a gap 422, and covers the upper portion of the cover 404, thereby suppressing the scattering of toner above the developing roll 405. . The gap 423 formed between the developing roll 405 and the cover 402 is larger than the thickness of the developer layer formed on the developing roll 405, so that the developer D spiked by the transport pole M5 does not contact the lower surface of the cover 402. It is formed to have a width of The gap 423 is preferably formed with a uniform width from the vicinity of the downstream portion of the regulating member 410 to the tip 402A of the cover 402, and the widths of the gap 422 and the gap 423 are preferably substantially equal. If the width of the gap 423 is formed such that the developer layer formed on the developing roll 405 is in contact with the surface formed by the cover 402, the toner is likely to be scattered from the contact portion to the downstream side in the rotation direction of the developing roll. In particular, toner adheres to the downstream position near the contact portion, and toner spillage is likely to occur.

  The front end 402A, which is the downstream end in the developer transport direction of the cover 402, is positioned upstream of the most upstream magnetic pole of the transport poles M5 to M7, that is, the magnetic pole M5 closest to the regulating member 410. Is formed. Specifically, the cover 402 is formed such that the front end 402A is positioned upstream of the peak position of the magnetic flux density at the magnetic pole M5 in the developer transport direction.

  By rotation of the sleeve 406 indicated by the arrow, an air flow in one direction indicated by an arrow is formed as the opening 420 → the gap 421 → the gap 422 → the gap 423. In the gap 423, the regulating member 410 moves to the tip 402A of the cover 402. A unidirectional air flow is formed.

  Next, the accumulation of scattered toner will be described with reference to the conventional example shown in FIG.

  In the conventional example, the cover 402 is formed so that the tip end portion 402B on the downstream side in the developer transport direction covers the transport poles M5 and M6.

  For this reason, the developer poles are formed on the developing sleeve 406 by the transport poles M5 and M6, the toner is scattered at the positions of the transport poles M5 and M6 where the developer spikes are formed, and the scattered toner is covered by the cover 402. Adheres to and deposits on the lower surface.

  As the developing device operates for a long time, scattered toner, particularly toner scattered at the positions of the transport poles M5 and M6, accumulates on the lower surface of the cover 402. The accumulated toner is peeled off by the developer or vibration that comes in contact, and the blocky toner is transported and dropped by the developing sleeve 406, adheres to the photoreceptor P, is transferred to the recording material, and causes image smearing.

  In the conventional example shown in FIG. 4, not only the scattered toner is likely to be deposited due to the positional relationship between the transport poles M5 and M6 and the cover 402, but also the scattered toner is likely to be deposited due to the air flow described below.

  The rotation of the developing sleeve 460 in the configuration of FIG. 4 generates an air flow in the gap between the cover 402 and the developing sleeve 406, but since there is no air inlet on the regulating member 410 side, the opening of the front end portion 402B of the cover 402 Air enters the air and flows out from the front end 402B. As a result, air does not flow on the upper surface of the regulating member 410 or the lower surface of the cover 402 near the regulating member, and scattered toner adheres and accumulates, causing toner spillage. In the present invention, the cover 402 is formed so that the front end 402A of the cover 402 is positioned upstream of the transport pole in the developer transport direction, thereby eliminating such accumulation of scattered toner agent and preventing image smearing. ing.

  Further, in order to prevent the developer from adhering to and / volume on the lower surface of the cover 402, the gap 423 has a uniform width (the distance between the lower surface of the cover 402 and the outer peripheral surface of the developing sleeve 406, hereinafter the same). It is formed.

  Further, the unidirectional air flow described above is formed to prevent toner scattering accumulation.

  Regarding the air flow generated by the developer flow, the above-described opening 420 → gap 421 → gap 422 → gap 423 is one example, and can be formed by other methods. For example, it is possible to adopt a method of introducing air into the gap 423 by introducing air from the side of the developing device without providing the gap 420.

  FIG. 5 shows another example of forming a one-way air flow, and is a perspective view of a state in which the cover 402 in FIG. 2 is removed while leaving its side wall 402D.

  Openings 402E as air inlets are formed in both side walls 402D of the cover 402.

  The rotation of the developing sleeve 406 (see FIG. 2) forms a one-way air flow as indicated by an arrow AIR, and prevents scattered toner from accumulating.

  The width of the gap 423 is formed wider than the thickness of the developer layer formed on the developing sleeve 406. As a result, the developer flow and air flow conveyed by the developing sleeve 406 become smooth, and the volume of scattered toner on the lower surface of the cover 402 is prevented.

  FIG. 6 is a diagram showing a main part of another example of the image forming apparatus according to the embodiment of the present invention.

  In the present embodiment, a duct 430 is formed by the duct forming member 431 and the cover 402, and the fan 432 sucks scattered toner from the duct 430.

  The duct 430 prevents the toner from scattering from the developing device, and can prevent image stains and in-machine stains due to toner spills from which the scattered toner falls.

  The gap between the duct 430 and the developing roll 5, that is, the gap between the duct forming member 431 and the developing sleeve 6, is preferably 2.5 mm or more, and more preferably 3 mm or more. When the gap is smaller than 2.5 mm, toner spillage tends to occur.

  Further, the cover 402 forms a part of the duct 430, and air rises along the inclined cover upper surface 402C. However, if the inclination angle θ of the cover upper surface 402C is too large, the toner falls from the duct 430 and the toner Spills may occur. In the color image forming apparatus shown in FIG. 1, a plurality of developing devices are arranged vertically. However, in such an arrangement, the height is limited, so that the cover 402 is formed as a part of the duct 430. Yes. As a result, the scattered toner easily accumulates on the upper surface 402C of the cover 402. For this reason, the inclination angle θ of the cover upper surface 402CB is preferably 0 to 40 °, particularly preferably 0 to 31 °.

(1) Example 1
Photoconductor drum-like OPC photoconductor Linear speed: 300, 200, 150 mm / sec (not a range, but a single point value, the same applies hereinafter)
-Charging potential (unexposed portion potential): -600V
・ Exposure part potential: -100V
・ Developing device ・ Developing sleeve linear speed: 540, 360, 270 mm / sec
・ Magnet roll, cover, stirring. As shown in FIG. 1, the configuration of the conveying member, etc. (stirring. The rotating speed of the conveying member ... / sec)
Development bias: DC bias: -450 V, AC bias: 1.0 kVp-p, 5 kHz
Developer: Two-component developer mainly composed of polymerized toner and resin-coated carrier 50,000 sheets were developed under the above apparatus conditions.

  Table 1 shows the state of occurrence of toner spillage where unnecessary toner adheres to the recording material.

As shown in Table 1, in the example in which the cover was disposed only on the upstream side of the conveyance pole of the magnet roll, toner spillage did not occur. In the example in which the front end 402A of the cover 402 and the peak position of the transport pole coincide with each other, toner spillage is slightly visible but acceptable. In the comparative example in which the front end of the cover was extended to the downstream side of the conveying electrode, obvious toner spillage occurred.
(2) Example 2
In addition to the conditions of Example 1, 50,000 sheets were developed in the same manner as in Example 1 using a developing device with a duct added as shown in FIG.

  The occurrence status of toner spill is as shown in Tables 2 and 3.

  As shown in Table 2, clear toner spillage occurred when the gap between the duct 430 and the developing roll 405 was 2 mm. In the example of 2.5 mm, slight toner spillage was observed, but this was an acceptable level. In the example of 3 mm, toner spillage did not occur.

  Further, as shown in Table 3, obvious toner spillage occurred in the comparative example in which the inclination angle of the upper surface of the cover was 41 °. In the example in which the inclination angle was 30 °, slight toner spillage occurred, but it was at an acceptable level. In the example in which the angle was 25 °, toner spillage did not occur.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing of the developing device which concerns on Embodiment 1 of this invention. FIG. 4 is a diagram illustrating a developer flow in the vicinity of a developing roll 405. It is sectional drawing of the conventional image development apparatus. It is a figure which shows the other example which forms the flow of the air of one direction. It is a figure which shows the principal part of the other example of the image forming apparatus which concerns on embodiment of this invention.

Explanation of symbols

401 Casing 402, 40 Cover 405 Developing roll 406 Developing sleeve 407, Magnet roll 420-423 Gap 430 Duct

Claims (7)

A developer carrying member for transporting a developer to a development area and carrying the developer in the development area, the developer carrying body rotating, and a developer roll disposed in the development sleeve and having a magnet roll having a plurality of magnetic poles Carrier,
A regulating member for regulating the amount of developer on the developer carrying member;
Contains developer and opens upwards,
A casing for housing the developer, the developer carrier and the regulating member; and
In a developing device having a cover that covers at least a part of the developer carrier and the regulating member,
The developing device according to claim 1, wherein a portion of the cover covering the developer carrier and the regulating member is formed so as to satisfy the following condition.
a. Forming a gap having a uniform width between the cover and the developer carrying member; b. The tip of the cover close to the development region is disposed upstream of the transport pole disposed downstream of the developer transport direction with respect to the control pole of the plurality of magnetic poles facing the control member. C. In addition to forming an outlet through which air flows out between the developer carrier and the tip of the cover, an air inlet is formed in the cover, along the regulating member and the developer carrier, Create a one-way air flow from the inlet to the outlet The magnet roll has a plurality of transport poles, and the tip of the cover is upstream of the position of the magnetic flux density peak of the transport pole on the most upstream side in the developer transport direction of the plurality of transport poles. The developing device according to claim 1, wherein the developing device is located. The developing device according to claim 1, wherein the gap has a width such that a developer conveyed on the developer carrying member does not come into contact therewith. An image forming apparatus comprising: a photosensitive member; a latent image forming unit that forms an electrostatic latent image on the photosensitive member; and the developing device according to claim 1. An image forming apparatus having a duct for sucking air flowing through the apparatus. The image forming apparatus according to claim 4, wherein the duct is formed so that an interval between an inner surface of the duct and the developer carrying member is 2.5 mm or more. 6. The image forming apparatus according to claim 4, wherein a part of the duct is formed by the cover. The image forming apparatus according to claim 6, wherein a portion of the cover forming the duct has an inclination angle of 0 ° to 40 °.

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