JP2008112197A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the horizontal dimension of a developing device and to achieve development of high image quality, in the developing device designed such that two-component developer is supplied to a developing roller along the longitudinal direction of the developing roller while stirred and conveyed in a circle. <P>SOLUTION: A scooping-up area (upper part) in which the developer is scooped up onto the developing roller, and a separating area (lower part) in which the developer is separated from the developing roller after development, are arranged around the developing roller 302. Forward and backward paths for the developer are formed by disposing screw type stirring-and-carrying members 304 (upper) and 305 (lower) near the corresponding areas. The stirring-and-carrying members are separated by a partition plate in the middle, that is, except parts corresponding to the longitudinal both ends of the developing roller. In areas near both ends of the partition plate, the forward path 11 and backward path 12 are connected by the scooping path 13 and falling path 14, thereby forming a circulation path for the developer. While supplied to the developing roller along the forward path 11, an agent is stirred and conveyed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device that is a means for visualizing an electrostatic latent image and an image forming apparatus such as a printer, a facsimile machine, and a copying machine using the developing device.

  2. Description of the Related Art As a means for visualizing an electrostatic latent image, a two-component developing type developing device using a two-component developer (hereinafter simply referred to as a developer) made of toner and a granular magnetic carrier is known. In such a developing device, a developer in which a carrier and toner are sufficiently mixed at a developer stirring portion is supplied to a cylindrical developer carrier (hereinafter referred to as a developing roller) as a rotating body, and the developer is developed by the developing roller. Is transferred to a region facing a cylindrical image carrier (hereinafter referred to as a photoconductor) as a rotating member, and toner is attached to the electrostatic latent image on the surface of the photoconductor for development.

  Various configurations of a developer agitating unit that stirs and mixes the developer and supplies the developer to the developing roller have been conventionally devised. However, as shown in FIG. In order to agitate and convey the developer 320 composed of toner and carrier in the horizontal direction or below the developing roller 501, two first screws 502 and two second screws 503 are arranged in the horizontal direction, and these members are covered with a casing 504. The configuration is mainstream.

  In the developing device 500 having such a configuration, the partition plate 504a is provided between the two screws, and the two screws convey the developer 320 in directions opposite to each other in the direction penetrating the paper surface. The developer 320 is circulated by delivering the developer at the opposite end portions.

  The first screw 502 disposed away from the developing roller 501 replenishes toner on the upstream side in the transport direction, transports the toner and the carrier while mixing them, and develops the developing roller 501 on the downstream side of the first screw 502. The developer is transferred to the second screw 503 arranged close to.

  The second screw 503 conveys the developer while supplying the developer to the developing roller 501 and collecting the developer from the developing roller 501, and delivers the developer to the first screw 502 on the downstream side.

  The developing roller 501 includes a magnet roller having a plurality of magnetic poles disposed therein, and a cylindrical sleeve rotates around the fixed magnet roller. In the portion facing the second screw 503, it is necessary to draw up the developer with respect to the developing roller 501 and to separate the developer that has been developed, and the magnet roller is provided with a magnetic pole to perform its function. ing.

  In the developing device having such a configuration, since the developing roller 501 and the first and second screws are arranged in the horizontal direction, the size in the vertical direction can be reduced, but it is difficult to reduce the size in the horizontal direction. .

  In recent years, image forming apparatuses using an electrophotographic method have been colorized, but in order to improve the productivity, there are four cylindrical photosensitivities for each color of yellow, magenta, cyan, and black. It is effective to adopt a tandem system that forms an image using a body.

  In the tandem system, four photoconductors are arranged in the horizontal direction, and an image forming device such as a charging device is provided for each photoconductor, and a developing device is also provided for each photoconductor. In order to reduce the size of the image forming apparatus, it is necessary to reduce the interval between the photoconductors. For this purpose, the developing apparatus also needs to be reduced in size in the horizontal direction (lateral direction). There is a limit to space saving in a developing device in which the screws are arranged in a horizontal direction.

  In Patent Document 1, two agitating and conveying screws are arranged side by side on the side of the developing roller, and the space can be saved in the lateral direction. After the development, the developer having a low toner density and the developer having a high toner density before the development are simultaneously pumped up to the developing roller, and the toner density of the developer on the developing roller is not uniform, so the image density is increased. Unevenness is likely to occur.

  Also, due to insufficiently charged toner, the graininess of the halftone image part deteriorates, the background stains where the toner adheres to the background, or the toner scattering due to the toner being released from the carrier. May occur.

  In addition, there is a high possibility that the developer stirred by the upper screw and the developer stirred by the lower screw will be changed in some places, and the developer is difficult to be stirred uniformly, so a uniform image can be obtained. It is difficult to cause the above problems.

JP-A-11-202627

  An object of the present invention is to provide a developing device and an image forming apparatus that can obtain high image quality while reducing the size in the horizontal direction, and that can reduce stress on the developer and provide stable performance. is there.

The present invention has the following configuration in order to achieve the above object.
(1). A developer carrying body that carries and rotates a developer containing a magnetic body and visualizes an electrostatic latent image formed on the image carrying body, and an agent pumping area that pumps the developer onto the developer carrying body A first developer agitating and conveying member that rotates around a center line parallel to the center line of the developer carrying member and conveys the developer while stirring the developer in the longitudinal direction; The first developer agitating / conveying member is disposed in the vicinity of a developer separation region that separates the developer from the developer carrier, and rotates about a center line parallel to the center line of the developer carrier. A second developer stirring and conveying member that conveys the developer in a direction opposite to the direction in which the developer is conveyed, and between the first developer agitating and conveying member and the second developer agitating and conveying member, In the central portion excluding both longitudinal ends of the developer carrier, the first current It was to have a partition plate for shielding the agitating and conveying member surrounding space and the second developer stirring and conveying member surrounding space (Claim 1).
(2). In the developing device according to (1), the agent scooping area is located above the agent separating area (claim 2).
(3). In the developing device according to (1) or (2), at the downstream end of the lower transport path of the developer formed in the longitudinal direction along the second developer agitation transport member, from the lower transport path to the upper side The developer is pumped up and transported to the upper transport path of the developer formed in the longitudinal direction along the first developer stirring and transporting member, and the first developer stirring at the downstream end is transported. A magnet member for pumping the agent is provided in the vicinity of the member.
(4). In the developing device according to (3), the magnet member is disposed around the first developer stirring and conveying member above the center line of the first developer stirring and conveying member.
(5). (1) to (4), in the developing device according to any one of (1) to (4), the developer is formed on the upstream end of the upper conveying path of the developer formed in the longitudinal direction along the first developer stirring and conveying member. A replenishing section was provided (claim 5).
(6). (1) thru | or (5) WHEREIN: The space | interval of the outer peripheral part of the said developer carrier and the said partition plate was set to the range of 0.2 mm-1 mm in (1) thru | or (5). .
(7). (6) In the developing device according to (6), the agent separation region is located in a lower portion around the developer carrier opposite to the image carrier with the developer carrier interposed therebetween, and the developer carrier is rotated. The agent pumping region is positioned adjacent to the downstream side of the agent separation region in the direction, and the developer adheres around the developer carrier between the agent separation region and the agent pumping region. The partition plate is provided at a position where the amount is the smallest so as to shield the space around the first developer agitating and conveying member and the space around the second developer agitating and conveying member, and the partition plate The end on the developer carrying body side is opposed to the developer carrying body (claim 7).
(8). In the developing device according to any one of (1) to (7), a developer transport amount per unit time by the first developer agitating / conveying member is a unit time per unit time by the second developer agitating / conveying member. The developer transport amount is set to be larger than the developer transport amount (claim 8).
(9). The uniformly charged image carrier is irradiated with light from the optical writing means to form an electrostatic latent image, and the electrostatic latent image is visualized by a developing device and transferred to a recording medium to obtain a recorded image. In the image forming apparatus, the developing device is the developing device according to any one of (1) to (8).

According to the first and second aspects of the invention, toner having a target charge amount is used for development, and high image quality can be obtained. In addition, since the deterioration of the toner can be suppressed, it is possible to stably maintain the performance of the developer for a long period of time, and it is possible to provide a developing device having a long life and high durability.
In the third and fourth aspects of the invention, the developer circulation is smooth. According to the fifth aspect of the present invention, the supplied toner is stirred and then subjected to development.
In the invention of claim 6, the degree of freedom of the partition plate setting position is increased.
In invention of Claim 7, the partition plate gap management at the time of partition plate setting can be eased.
In the invention according to claim 8, smooth circulation of the developer can be maintained. According to the ninth aspect of the present invention, it is possible to provide an image forming apparatus capable of miniaturizing high image quality.

[1] Outline of Image Formation FIG. 1 is an arrangement configuration diagram of each member showing an outline around the photoconductor 1 when the developing device 3 of the present invention is used in an image forming apparatus using the photoconductor 1. The photoreceptor 1 is rotated in the clockwise direction as indicated by an arrow. The charging device 2 is disposed at a position approximately 12 o'clock on the top of the photosensitive member 1 in terms of a clock face. In this example, the charging device 2 is composed of a rotating body that rotates at the same speed as that of the photosensitive member.

  The charging device 2 uniformly charges the surface of the photoconductor 1 in the dark, and then receives exposure light L from writing means (not shown) to form an electrostatic latent image. The electrostatic latent image moves downstream as the photosensitive member 1 rotates and reaches the developing device 3. The developing device 3 is disposed on the right side of the photoreceptor 1.

  The developing device 3 includes in the casing 301 a first developer agitating and conveying member 304 and a second developer agitating and conveying member 305 for agitating and conveying the developer 320, a rotating member such as a developing roller 302, and other members. . The developing roller 302 has a length in the longitudinal direction substantially the same as the length of the photoreceptor 1.

  The developing roller 302 is disposed in close proximity so as to form a developing nip region A by being opposed to the photosensitive member 1 at a position between 2 o'clock and 3 o'clock (position of 2:30). A portion of the casing 301 corresponding to the portion facing the photoconductor 1 is opened to expose the developing roller 302.

  The developer 320 in the casing 301 is conveyed to the development nip region A by the developing roller 302. The toner in the developer 320 adheres to the electrostatic latent image formed on the surface of the photoreceptor 1 in the development nip region A, and is visualized as a toner image.

  The toner image moves downstream as the photosensitive member 1 rotates and reaches the transfer device 5. The transfer device 5 is arranged at the bottom of the photoreceptor 1 at the 6 o'clock position. In this example, the transfer device 5 is composed of a rotating body, but is not limited to a rotating body, and may be a corona discharge type. A region where the photoreceptor 1 and the transfer device 5 face each other is referred to as a transfer region B.

  The toner image on the photoreceptor 1 is transferred to the transfer paper 8 in the transfer region B and becomes an image on the transfer paper 8. After the transfer, the photosensitive member 1 moves downstream as the photosensitive member 1 rotates and reaches the cleaning device 6.

  The cleaning device 6 is arranged at the 10 o'clock position. The cleaning device 6 uses a cleaning blade 601 to remove toner remaining on the surface of the photoreceptor 1 without being completely transferred onto the transfer paper. The surface of the photoreceptor 1 that has passed through the cleaning device 6 is then uniformly charged by the charging device 2 and the next image forming process is repeated.

[2] Developing device (related to claims 1 and 2)
The developing device 3 includes a developing roller 302, a first developer agitating / conveying member 304, a second developer agitating / conveying member 305, and a developer regulating member 303 inside the casing 301. The developer 320 is agitated and conveyed to circulate. I am letting.

  As shown in FIG. 2, the developing roller 302 includes a magnet roller 302d in which a plurality of magnets MG (only one is indicated by a symbol for preventing complication of the drawing) in the circumferential direction. A cylindrical sleeve 302c is configured to rotate integrally with the rotating shaft 302e.

  The sleeve 302c is made of a nonmagnetic metal such as aluminum. The magnet roller 302d is fixed to an immovable member, for example, the casing 301, so that each magnet MG faces a predetermined direction, and a sleeve 302c rotates around the magnet roller MG to convey the developer 320 attracted by the magnet MG. To go.

  In FIG. 3 showing the structure of the developing roller 302, the developing roller 302 is mainly composed of a fixed shaft 302a fixed to the stationary member casing 301, a magnet roller 302d having a cylindrical shape integrated with the fixed shaft 302a, and a magnet roller 302d. It comprises a sleeve 302c covering the periphery with a gap and a rotating shaft 302e integrated with the sleeve 302c. The rotation shaft 302e is rotatable with respect to the fixed shaft 302a via a bearing 302f, and the rotation shaft 302e is driven to rotate by receiving power from a rotation driving means (not shown).

  A plurality of magnets MG are fixed to the outer periphery of the magnet roller 302d at a predetermined interval as shown in FIG. The sleeve 302c is rotated around these magnets MG.

  These magnets MG are for forming a magnetic field so that the developer can be spiked on the peripheral surface of the sleeve 302c, and can be cut off. Magnetic carriers are gathered to form a magnetic brush along the normal magnetic field lines emitted from these magnets MG.

  In this example, as shown in FIG. 2, five magnets MG are provided inside the sleeve 302c, and five magnetic poles (magnetic force distribution) are generated. The magnetic pole of the part (area corresponding to the development nip area A) facing on the line connecting the center O-1 of the developing roller 302 and the center O-2 of the photoreceptor is referred to as a P1 pole, and is shown in the following counterclockwise direction. The magnetic poles are referred to as P2, P3, P4, and P5 poles in the order of rotation of the roller 302.

  The polarities are from the P1 pole to the N, S, N, N, and S poles, but these poles may have opposite polarities. On the developing roller 302, each pole is located at the center, the P1 pole is approximately at 8 o'clock on the watch dial, the P2 pole is at 7 o'clock, the P3 pole is at 5 o'clock, and the P4 pole is approximately at 1 o'clock. ing.

  The developing roller 302 and the photosensitive member 1 are not in direct contact with each other in the developing nip region A but are opposed to each other while maintaining a developing gap GP1 at a constant interval suitable for development.

  On the developing roller 302, the developer 320 is caused to rise at the P1 pole, and the developer 320 is brought into contact with the photosensitive member 1, whereby toner is attached to the electrostatic latent image on the surface of the photosensitive member 1 to be visualized.

  In the developing device 3, as shown in FIG. 2, a grounded bias power source VP is connected to the fixed shaft 302a. The voltage of the power source VP connected to the fixed shaft 302a is applied to the sleeve 302c through the conductive bearing 111f and the conductive rotating shaft 302e shown in FIG. On the other hand, in FIG. 2, the lowermost conductive support 31 constituting the photoconductor 100 is grounded.

  Thus, an electric field for moving the toner separated from the carrier to the photosensitive member 1 side is formed in the developing nip region A, and the toner is generated by the potential difference between the sleeve 302c and the electrostatic latent image formed on the surface of the photosensitive member 1. Is moved toward the photosensitive member 1 side.

  Note that the developing apparatus of this example is combined with an image forming apparatus of a method of writing with exposure light L. The charging device 2 uniformly applies negative charges on the photosensitive member 1 and exposes the character portion with the exposure light L in order to reduce the writing amount. A so-called reversal development method is employed in which the latent image is developed with negative polarity toner. This is merely an example, and the polarity of the charged charge placed on the photoreceptor 1 is not a major problem in the developing method of the present invention.

  After the development, the P2 pole conveys the developed developer 320 carried on the developing roller 302 to the downstream side along with the rotation of the developing roller 302 and draws it into the casing 301. That is, there is a part of the casing 301 at a position corresponding to the P2 pole, and a part of the casing 301 has a curved shape close to the peripheral surface of the sleeve 302c. Plays.

  The P3 and P4 poles located on the downstream side of the P2 pole have the same polarity, and there is no magnetic force to rise between the P3 and P4 poles, so that the ears fall asleep and the developer 320 that has been drawn around the developing roller 302 until then. The action of “agent release” that separates the toner from the developing roller 302 works. The portion corresponding to the P3 to P4 poles on the developing roller where the ears are lying down (region where the peak of the magnetic distribution curve is extremely low compared to other regions) separates the developer 320 from the developing roller 302, the agent separating region ( In FIG. 1, it is indicated by reference numeral 9).

  The developer 320 having the toner adhered to the photosensitive member 1 has a lower toner concentration in the developer. Therefore, the developer having the lowered toner concentration is not separated from the developing roller 302 and again enters the developing nip region A. When transported and subjected to development, there is a problem that a target image density cannot be obtained.

  In order to prevent this, in this example, the developer is separated from the developing roller 302 in the agent separation region 9 after development. Thereafter, the developer separated from the developing roller 302 is sufficiently agitated and mixed in the casing 301 so that the target toner density and toner charge amount are obtained.

  Thus, the P4 pole pumps up the developer having the target toner density and charge amount to the developing roller 302, and the agent pumping area corresponding to the P4 pole on the developing roller (indicated by reference numeral 10 in FIG. 1). Thus, the developer is pumped up to the developing roller 302.

  The so-called pumped-up developer attracted to the developing roller 302 by the magnetic force of the P4 pole passes through the developer regulating member 303 located immediately downstream of the peak position of the P4 pole, and is adjusted to a predetermined thickness. Then, it is conveyed to the developing nip region A while forming a magnetic brush. The P5 pole located between the P4 pole and the P1 pole has a function of a transport pole for transporting the developer up to the P1 pole after passing through the developer regulating member 303.

  Hereinafter, the arrangement configuration of each member will be described with reference to FIG. 4 showing the internal configuration of the developing device in an assembled state and FIG. 5 showing the disassembled state as necessary. As shown in FIGS. 1 and 2, the first developer agitating / conveying member 304 is disposed in the vicinity of the agent pumping region 10 at a position around the developing roller 302 and in the 2 o'clock direction of the developing roller 302. ing. This position is also on the upstream side of the developer regulating member 303. As shown in FIGS. 4 and 5, the first developer agitating and conveying member 304 has a screw shape with a spiral around the rotation axis, and a center line O-302a passing through the center O-302 of the developing roller 302 and The developer rotates in the clockwise direction indicated by the arrow about the parallel center line O-304a, and agitates the developer as indicated by the arrow 11 from the longitudinal back side toward the front side of the center line O-304a. Transport. That is, the first developer agitating and conveying member 304 conveys the developer from the axial direction, from the back side to the near side, by the rotation of the rotation shaft.

  The second developer agitating / conveying member 305 is disposed in the vicinity of the agent separation region 9 at a position around the developing roller 302 and in the 4 o'clock direction of the developing roller 302. As shown in FIG. 4, the second developer agitating / conveying member 305 has a screw shape with a spiral around the rotation axis, and is parallel to a center line O-302a passing through the center O-302 of the developing roller 302. It rotates in the counterclockwise direction indicated by an arrow about the center line O-305a, and conveys the developer while stirring the developer as indicated by the arrow 12 from the front side in the longitudinal direction of the center line O-305a toward the back side. To do. That is, the second developer agitating and conveying member 305 conveys the developer from the near side opposite to the conveying direction by the first developer agitating and conveying member 304 toward the back side by the rotation of the rotation shaft.

  The second developer agitating / conveying member 305 is positioned above the first developer agitating / conveying member 304, and the space around the first developer agitating / conveying member 304 and the second developer in the casing 301. It is adjacent to the space around the stirring and conveying member 305.

  The rear side ends of the first developer agitating / conveying member 304 and the second developer agitating / conveying member 305 are set so as to be located slightly behind the end on the back side of the developing roller 302, The supply of developer at the side end is ensured. Further, the front end portions of the first developer agitating / conveying member 304 and the second developer agitating / conveying member 305 are positioned in front of the front end portion of the developing roller 302 so as to supply toner, which will be described later. Space is secured. The developer regulating member 303 is installed according to the length of the developing roller 302.

  Between the first developer agitating / conveying member 304 and the second developer agitating / conveying member 305, in the central portion excluding both ends in the longitudinal direction of the developing roller 302, the space around the first developer agitating / conveying member 304 and the first developer agitating / conveying member 304 are arranged. (2) A partition plate 306 that shields the space around the developer agitating / conveying member 305 is formed in a cantilevered manner integrally with the inner wall of the casing 301 on the side away from the developing roller 302.

  The partition plate 306 is located at the center of the developing roller 302 except for both ends in the longitudinal direction, and is not located at the portion corresponding to both ends in the longitudinal direction of the developing roller 302. On the other hand, each longitudinal end of the first developer stirring and conveying member 304 and the second developer stirring and conveying member 305 extends to both ends in the longitudinal direction of the developing roller 302.

  The developer conveyed in the direction of arrow 12 by the second developer agitating / conveying member 305 is cut off along the side wall of the casing 301 at the end in the conveyance direction, and rises along the side wall. The developer agitating / conveying member 304 moves the upper conveying path along the first developer agitating / conveying member 304.

  Similarly, the developer conveyed in the direction of arrow 11 by the first developer agitating / conveying member 304 is lowered along the side wall in order to cut off the path at the side wall of the casing 301 at the end in the conveyance direction, and the arrow 14 Then, the second developer agitating and conveying member 305 moves to the lower conveying path by the second developer agitating and conveying member 305.

  The partition plate 306 is positioned at the center of the developing roller 302 except for both ends in the longitudinal direction, so that the developer flows in the direction of the arrows 13 and 14 at the ends in the longitudinal direction. In order to form a circulation conveyance path along the arrows 11, 14, 12, and 13 as a whole.

  In the illustrated example, the partition plate 306 is provided with an opening 307 in the vicinity of the end on the back side, and the developer is pumped up to the conveyance path that is raised from the lower conveyance path through the opening 307. Therefore, the partition plate 306 can be extended to the end in the longitudinal direction of the developing roller 302.

  Thus, the developing device 3 of the present invention carries the developer and rotates to visualize the electrostatic latent image formed on the photoconductor 100, and the agent to pump the developer to the developing roller 302. The developer rotates around a center line O-304a that is disposed in the vicinity of the region 10 and is parallel to the center line O-302a of the developing roller 302, and conveys the developer in the longitudinal direction of the center line O-304a while stirring. The first developer agitating / conveying member 304 is disposed in the vicinity of the agent separation region 9 that separates the developer from the developing roller 302, and rotates around a center line 305a parallel to the center line 302a of the developing roller 302. A first developer agitating and conveying member 305 that conveys the developer in a direction opposite to the direction in which the one developer agitating and conveying member 304 conveys the developer; a first developer agitating and conveying member 304; and a second developer It is between 拌搬 feed member 305.

  In such a configuration, the space around the first developer agitating / conveying member 304 and the space around the second developer agitating / conveying member 305 in the developing device 3, that is, in the central portion excluding both ends of the casing and the developing roller 302 in the longitudinal direction. And a partition plate 306 that shields the two developer agitating / conveying members 304 and 305 in 301 that constitute a circulation conveying path along the arrows 11, 14, 12, and 13, vertically above and below the developing roller 302. Since the two agitating / conveying members are arranged in the direction away from the developing roller (in the horizontal direction), the size of the developing device in the horizontal (horizontal direction) is smaller than that of the conventional technique shown in FIG. can do.

  Further, in this way, in the developing device 3 designed to be compact in the horizontal direction, the periphery of the first developer agitating / conveying member 304 and the second developer agitating are provided at the central portion excluding both ends in the longitudinal direction of the developing roller 302 by the partition plate 306. Since the space around the conveying member 305 is partitioned, only the developer 320 in which the toner and the carrier are sufficiently agitated and mixed is supplied to the developing roller 302 by the first developer agitating and conveying member 304. Since the developer whose toner density has decreased immediately after development is merely stirred and conveyed by the second developer agitating and conveying member 305, the developer is not immediately supplied to the developing roller 320. Only the toner having the toner is used for development, and high image quality can be obtained.

  Further, due to the function of the partition plate 306, the developer whose toner concentration is lowered by the second developer agitating and conveying member 305 does not pass through the gap between the developing roller 302 and the developer regulating member 303 and is agitated by a screw. Therefore, the stress applied to the carrier and toner can be suppressed and deterioration can be suppressed, so that the developer performance can be maintained over a long period of time, and a long-life and highly durable developing device can be provided. Such an advantage is not limited to the above-described example in which the developing device is disposed beside the photoconductor 1, but can be obtained by adopting a configuration in which the agent scooping area is located above the agent releasing area.

(Related to claims 6 and 7)
The partition plate 306 supports the developer 320 agitated and conveyed by the first developer agitating / conveying member 304 from below to form a developer conveying path, and at the upstream side of the separating member 306 in the agent separation region 9, the developing roller 302. The developer agitated and conveyed by the second developer agitating / conveying member 305 is again attracted to the developing roller 302 and prevented from moving to the space agitated by the first developer agitating / conveying member 304.

  In order to make this function more reliable, the gap between the outer peripheral portion of the developing roller 302 and the partition plate 306 and the partition plate gap GP2 are held in a gap of about 0.2 to 1 mm. If it is less than 0.2 mm, the partition plate 306 may collide with the developing roller due to eccentricity when the developing roller 302 rotates, and if it exceeds 1 mm, the trimming performance becomes incomplete. Thereby, a sufficient function can be obtained even when the setting position of the partition plate 306 is set to an arbitrary position in the agent separation region 9. That is, the degree of freedom of the partition plate setting position increases.

  Furthermore, it is possible to obtain a function as a partition plate even if the arrangement is shifted from the agent separation region 9. However, when the arrangement is shifted from the agent separation area 9, there is a possibility that the partition plate restricts a large amount of developer, which is not preferable because the stress received by the developer becomes large.

  Therefore, the agent separation region 9 is located in the lower part around the developing roller 302 on the opposite side of the photosensitive member 1 with the developing roller 302 in between, and the agent is pumped up adjacent to the downstream side of the upper agent separation region 9 in the rotation direction of the developing roller. The position of the first developer agitating and conveying member 304 is set at a position where the amount of developer adhering to the periphery of the developing roller 302 is the smallest between the agent separating area 9 and the agent pumping position 10. A configuration in which a partition plate 306 is provided so as to shield the space and the space around the second developer agitating / conveying member 305, and the end of the partition plate 306 on the developing roller 302 side is opposed to the developing roller 302. To do.

  According to this configuration, even if the partition plate gap GP2 is not set to 0.2 to 1 mm, the portion where the partition plate is provided is the position where the amount of developer adhering around the developing roller 302 is the smallest. Therefore, the function of the partition plate 306 can be exhibited, and the stress applied to the developer can be minimized by being regulated by the partition plate. That is, gap management at the time of setting the partition plate can be relaxed. However, if the configuration is further added with the condition that the partition plate gap GP2 is set to 0.2 to 1 mm, the stress applied to the developer can be further reduced.

  In this example, the closest position between the developing roller 302 and the partition plate 306 is the smallest amount of developer on the developing roller 302 between the first developer stirring and conveying member 304 and the second developer stirring and conveying member 305. The magnetic flux density on the surface of the developing roller is set in the agent separation region 9 of 10 mT or less between the regions, that is, the P3 and P4 poles.

(Related to claims 3 and 4)
As shown in FIGS. 4 and 5, the second developer agitating and conveying member 305 conveys the developer 320 separated from the developing roller 302 to the back side of the developing device in the direction of the arrow 12 while agitating. As shown in FIGS. 5 and 6, an opening 307 is provided in a part of the partition plate 306 at the downstream end of the second developer agitating / conveying member 305 in the developer conveying direction and at the back end of the developing device. 2 The developer 320 conveyed by the developer agitating / conveying member 305 moves in the direction of the arrow 307 to the upper conveying path along the first developer agitating / conveying member 304 positioned above.

  This upward movement is caused by the developer 320 conveyed by the second developer agitating / conveying member 305 colliding with the side wall of the casing 301 on the back side and collecting, and the portion that rises upward is the first developer agitating / conveying member 304. In this example, the development formed in the longitudinal direction along the second developer stirring and conveying member 305 is possible. The upper transport path of the developer formed in the longitudinal direction along the first developer agitation transport member 304 located on the upper side from the lower transport path at the downstream end (back end) of the lower transport path of the developer The developer is pumped up and conveyed to the developer, and a magnet member 309 for pumping up the agent is provided in the vicinity of the first developer stirring member 304 at the downstream end, and the magnetic member 309 contains a magnetic material. developing And pulled above the conveying path 320 from the lower conveying passage.

  As a result, the pumping of the developer between the upper and lower agitating and conveying members is promoted, so that the developer can be smoothly circulated as compared with the case where the developer is only relied upward.

  The magnet member 309 is disposed around the first developer stirring and conveying member 304 above the center line O-304a of the first developer stirring and conveying member 304. Specifically, the first developer agitating / conveying member 304 is provided so as to surround the upper portion of the axis (center O-304) of the first developer agitating / conveying member 304. Accordingly, a function of raising the developer 320 to a level at which the developer can be conveyed by the first developer agitating and conveying member 304 is obtained.

  The magnet member 309 is provided so as to be covered from the outside of the casing 301 using the casing 301. The length in the depth direction is provided over a range overlapping with the opening 307 provided in the partition plate 306. In other words, the downstream end of the magnet member 309 in the transport direction with respect to the first developer agitating / conveying member 304 has a first developer agitating / conveying member 304 having an opening 307 for pumping the developer from the lower conveying path to the upper conveying path. The first developer agitating / conveying member 304 is provided on the downstream side in the conveying direction with respect to the downstream end portion in the conveying direction. While the developer 320 is attracted upward by the magnet member 309, the developer 320 is sent to the near side by the first developer agitating / conveying member 304, and drops onto the partition plate 306 when the magnet member 309 disappears. While being supplied to the developing roller 302, the first developer agitating / conveying member 304 conveys it to the near side.

  The magnet member 309 is provided outside the casing 301 because, if the magnet member 309 is installed inside the developing device casing, the developer 320 adheres to the joint between the magnet member and the casing 301 or the magnet of the developer 320. This is because the adhesive force to the member 309 is strong, and the magnet member 309 remains attached and is wasted.

  In this example, as shown in FIG. 5 and FIG. 8 which shows a cross section on the back side in the developing device 3, a range corresponding to the opening 307 in the downstream direction of the developer conveyance direction by the second developer agitation conveyance member 305. Thus, the impeller 308 is configured in place of the screw portion.

  The impeller 308 has a configuration in which a plurality of blade-like members extending in a plate shape in the normal direction from the axial center (center line O-305a) is provided for the shaft portion 305J of the second developer agitating and conveying member 305. It has the function of jumping up the developer 320 upward with rotation.

  As shown in FIG. 6, the center O-304 of the first agitating and conveying member 304 and the center O-305 of the second agitating and conveying member 305 are on substantially the same vertical line, and the impeller 308 rotates in the counterclockwise direction. Then, the developer 320 jumps up along the inner wall of the casing 301. The opening 307 does not obstruct the path of the developer due to the jumping up, and the center O-304 and the center O-305 are prevented so that the developer jumped up does not fall into the second stirring / conveying member 305. Is formed so as to extend from a position slightly closer to the casing inner wall to a casing inner wall portion than a substantially vertical line connecting the two.

  That is, since the opening 307 is formed in a state in which a hole is formed in a part of the partition plate 306, the portion where the developer is pumped from the second developer agitating / conveying member 305 to the first developer agitating / conveying member 304 is formed. There is an opening 307 that connects the upper and lower spaces, and a partition plate is present at a position on the developing roller side corresponding to the opening 307 as in the central portion in the developing roller axial direction.

  By this remaining partition plate portion, the developer that has moved upward from the bottom through the opening 307 is attracted to the developing roller 302 without falling again and conveyed by the developing roller 302 to be developed, or The developer is conveyed by the first developer agitating and conveying member 304, so that efficient developer circulation can be performed.

  The rotation direction of the first developer agitating / conveying member 304 is a clockwise direction opposite to the developing roller 1 rotating in the counterclockwise direction. In general, since the screw has an action of moving the conveyed object in the axial direction and moving it in the rotational direction, the first developer stirring and conveying member 304 conveys the developer 320 while moving it toward the developing roller 302 in the upper conveying path. become. Accordingly, continuous developer supply to the developing roller 302 becomes possible.

  The second developer agitating / conveying member 305 is rotated in the same direction as the developing roller 302. In this example, it is counterclockwise. As a result, the second developer stirring and conveying member 305 conveys the developer 320 while moving the developer 320 away from the developing roller 302. Thereby, the developer once separated from the developing roller 302 by the magnetic force, the partition plate 306, or the like in the agent separating area 9 is prevented from adhering to the developing roller 302 again. Therefore, it is possible to prevent the developer having a lowered toner density after development from being transported to the region of the first developer stirring and transporting member 304.

(Related to claim 5)
Since the developer 320 in the developing device 3 consumes toner while repeating the developing operation, it is necessary to supply toner to the developer in the device from the outside of the developing device. In this example, the upstream end portion of the upper conveyance path by the second developer stirring and conveying member 305 disposed in the vicinity of the agent separation area 9 where the developer 320 is separated from the developing roller 302, that is, the front side of the developing device. The toner is replenished from the outside from a developer replenishing portion provided in the vicinity of the end. In the replenishment at this site, the replenished toner is not immediately used for development, but is agitated by the second developer agitating / conveying member 305 and is developed for a stable predetermined toner density.

  This replenishment part is comprised by the opening 310 for replenishment formed in the casing 301 above the edge part of the near side without the partition plate 306. FIG. The toner replenished from the replenishment opening 310 descends through the upstream end portion of the first developer agitating / conveying member 304 that is removed from the developing roller 302, and is conveyed by the second developer agitating / conveying member 305 in the lower conveyance. .

  In the lower conveyance path by the second developer agitating and conveying member 305, only the developer 320 separated from the developing roller 302 is collected, and the toner is not supplied to the developing roller 302. A developer having a non-uniform toner concentration that is not sufficiently stirred by the toner is not subjected to development.

  While the replenished toner is agitated and mixed in the developer 320 having a reduced toner concentration away from the developing roller 302, the toner concentration is normalized before being conveyed to the back side of the developing device 3, and the impeller 308, magnet It is pumped up to the upper conveyance path by the first developer agitating / conveying member 304 by the action of the member 309 and the like, supplied to the developing roller 302 while being conveyed to the near side by the first developer agitating / conveying member 304 and used for development. The

  The developer is deteriorated by receiving stirring in the developing device 3. The carrier is not able to exert its initial performance due to the coating film on the surface being scraped or the resin component of the toner adhering to the surface. Further, the performance of the toner decreases as the additive adhering to the periphery is buried.

  The deterioration of the developer is more easily promoted when the developer is stirred at a low toner concentration than when the developer is stirred at a high toner concentration. In terms of which part of the developing device is subjected to stress that promotes deterioration, it is most stressed when passing through a narrow space between the developing roller and the agent regulating part developer, and the stress in the screw part is Almost no.

  In this example, the developer whose toner concentration has decreased after development is separated from the developing roller 302 in the agent separation region 9 and then conveyed while being stirred only with the screw of the second developer stirring and conveying member. After being mixed with the replenished developer, the developer is supplied to the developing roller 302.

  Further, since the partition plate 306 is provided, the developer in a state where the toner density is lowered does not pass through the gap between the developing roller 302 and the developer regulating member 303, so that the deterioration of the developer is not promoted. Since deterioration of the developer is suppressed, stable image quality can be maintained over a long period of time.

(Related to Claim 8)
In the developing device 3 according to this example, the developer 320 conveyed by the first developer agitating and conveying member 304 is pumped up to the developing roller 302 while being conveyed toward the front side. The developer 320 pumped up by the developing roller 302 is brought into contact with the photosensitive member 1 through the magnetic brush and used for development, and is then separated from the developing roller 302 in the agent separating area 9 in the developing device 3, and the second The developer agitating and conveying member 305 is conveyed toward the back side.

  Such a developer circulation path is as described with reference to arrows 11, 14, 12 and 13 in FIGS. 4 and 5, etc., but before the developer is conveyed to the near side by the first developer agitating and conveying member 304, development is performed. Therefore, more developer is returned to the back side by the second developer stirring and conveying member 305, and the developer 320 tends to accumulate on the back side. If this is left unattended, smooth circulation of the agent may be hindered.

  Therefore, the developer conveyance amount per unit time by the first developer agitating / conveying member 304 is set larger than the developer conveyance amount per unit time by the second developer agitating / conveying member 305.

  By making the developer conveying capability of the first developer agitating / conveying member 304 greater than that of the second developer agitating / conveying member 305, it is possible to balance the developer conveyance in the depth direction. Thereby, smooth circulation of the developer can be maintained over a long period of time.

  In this example, the developer conveying capability of the second developer agitating / conveying member 305 is increased by increasing the outer diameter of the screw of the first developer agitating / conveying member 304 relative to the second developer agitating / conveying member 305. Yes. The spiral pitch of the screw of the first developer stirring and conveying member 304 is increased. Increase the number of revolutions. Further, the same advantage can be obtained by increasing the space of the developer transport path by the first developer stirring and transporting member 304.

[3] Image forming apparatus (related to claim 9)
According to FIG. 7, an electrostatic latent image is formed by irradiating the uniformly charged image carrier with light from the optical writing means, and the electrostatic latent image is visualized by the developing device according to the present invention. An example of a color image forming apparatus will be described as an example of an image forming apparatus that obtains a recorded image by transferring it to a recording medium.

  In this color image forming apparatus, a plurality of image forming units 17K, 17M, 17Y, and 17C are arranged in order from the upstream side in the moving direction (conveying direction) of the conveying belt along the conveying belt 15 that conveys the transfer paper 8. The so-called tandem type.

  Each of these image forming units is formed of a combination of a plurality of members and forms an image. It is not necessarily configured as a unit. The image forming unit 17K forms black, the image forming unit 17M forms magenta, the image forming unit 17Y forms yellow, and the image forming unit 17C forms cyan. The image forming units have different colors. However, the internal configuration is the same for each image forming unit. Therefore, in the following description, the outline of the image forming unit 17K will be described. For the other image forming units, K added to the end of the reference numeral of each member in the image forming unit 17K, M for the image forming unit 17M, and the image The forming unit 17Y is replaced with Y, and the image forming unit 17C is replaced with C, and the description thereof is omitted.

  The conveyor belt 15 is composed of a driving roller, one of which is driven to rotate, and an endless belt that is rotatably supported by the conveying rollers 18, 19 that are driven rollers, the other of which is driven to rotate. , Can be rotated in the direction of the arrow. Below the transport belt 15, paper feed trays 20, 21, and 22 that store the transfer paper 8 are provided.

  For example, the transfer paper 8 at the uppermost position among the transfer papers 8 stored in the paper feed tray 20 is sent out at the time of image formation and is temporarily kept on standby by the registration roller 23, and the image formation and timing in the image forming unit 17K are set. They are fed together and attracted to the conveyor belt 15 by electrostatic attraction. In this way, the transfer paper 8 adsorbed to the conveyance belt 15 is conveyed to the first image forming unit 17K, where a black image is transferred.

  The image forming unit 17K includes a member having the same configuration function as the member described with reference to FIG. The members having the same configuration functions are denoted by the same reference numerals as those in FIG. 1 with K added to the end of the photosensitive member 1K, the charging device 2K, the developing device 3K, and the like. Although the conveyance belt 15 is omitted in FIG. 1, actually, as shown in FIG. 7, a transfer device 5K is disposed on the back side of the upper stretched portion of the conveyance belt 15, and the photosensitive member is also provided. Writing means 16 is provided as means for forming an electrostatic latent image by irradiating exposure light L to 1.

  When forming a color image, in the image forming unit 17K, the peripheral surface of the photoreceptor 1K is uniformly charged by the charging device 256K in the dark, and then the exposure light corresponding to the black image from the optical scanning device 1K. L is exposed to form an electrostatic latent image. This electrostatic latent image is visualized with black toner in the developing device 3K, and a black toner image is formed on the photoreceptor 1K.

  This toner image is transferred onto the transfer paper 8 by the action of the transfer device 5K in alignment with the transfer paper 8 at a position where the photosensitive member 1K and the transfer paper 8 on the transport belt 15 come into contact, that is, a so-called transfer position. A monochromatic (black) image is formed on top. After the transfer, the photosensitive member 1K is freed of unnecessary toner remaining on the peripheral surface of the photosensitive member 1K by the cleaning device 6K, and is prepared for the next image formation.

  In this way, the transfer paper 8 on which the single color (black) is transferred by the image forming unit 17K is transported to the next image forming unit 17M by the transport belt 15. In the image forming unit 17M, the magenta toner image formed on the photoconductor 1M by the same process as in the image forming unit 17K is superimposed and transferred onto the black toner image on the transfer paper 8.

  The transfer paper 8 is further conveyed to the next image forming unit 17Y, and the yellow toner image formed on the photoconductor 1Y in the same manner is overlaid on the black and magenta toner images already formed on the transfer paper 8. Is done. Similarly, in the next image forming unit 17C, a cyan toner image is transferred and overlapped to obtain a full color image.

  The transfer paper 8 on which the full-color superimposed image is formed in this way passes through the image forming unit 17C, is peeled off from the conveyance belt 15, and then fixed by the fixing unit 24 while passing between the pair of fixing rollers. The paper is discharged to the paper discharge tray 25.

  As shown in this example, for each color of yellow, magenta, cyan, and black, a photoconductor is arranged in the horizontal direction, and a charging device, a developing device, etc. are provided on each photoconductor to form an electrostatic latent image for visualization. In a tandem type color image forming apparatus that sequentially transfers to a transfer sheet and obtains a full color image, developing devices 3K, 3M, 3Y, and 3C are provided for the photoconductors 1K, 1M, 1Y, and 1C arranged in the horizontal direction, respectively. Therefore, in order to reduce the size of the image forming apparatus, it is necessary to narrow the interval between the photosensitive members. .

  By using each developing device having the structure of the present invention, the horizontal dimension of each developing device can be made smaller than that of the conventional one shown in FIG. 8, so that the image forming apparatus can be miniaturized. In addition, as described above, these developing devices 3K, 3M, 3Y, and 3C include the agent separation region, the agent pumping region, the first developer agitating and conveying member, the second developer agitating and conveying member, and the partition plate. Therefore, toner having a target charge amount is used for development, and high image quality can be obtained. In addition, since the deterioration of the toner can be suppressed, it is possible to stably maintain the performance of the developer for a long period of time, and it is possible to provide a developing device having a long life and high durability. Such a benefit is not unique to the tandem full-color image forming apparatus, but can be obtained in a single-color image forming apparatus.

It is a schematic block diagram around a photoconductor. It is a figure showing magnetic flux density distribution etc. which are formed in a development roller. It is sectional drawing of a developing roller. It is a principal part perspective view of a developing device. It is a principal part disassembled perspective view of a developing device. It is sectional drawing of the back | inner side of a developing device. 1 is a schematic configuration diagram of a tandem type full-color image forming apparatus. It is a figure explaining the conventional developing device.

Explanation of symbols

9 Agent separation area 10 Agent pumping area 304 First developer stirring and conveying member 305 Second developer stirring and conveying member 306 Partition plate

Claims (9)

  A developer carrying body that carries and rotates a developer containing a magnetic body and visualizes an electrostatic latent image formed on the image carrying body, and an agent pumping area that pumps the developer onto the developer carrying body A first developer agitating and conveying member that rotates around a center line parallel to the center line of the developer carrying member and conveys the developer while stirring the developer in the longitudinal direction; The first developer agitating / conveying member is disposed in the vicinity of a developer separation region that separates the developer from the developer carrier, and rotates about a center line parallel to the center line of the developer carrier. A second developer stirring and conveying member that conveys the developer in a direction opposite to the direction in which the developer is conveyed, and between the first developer agitating and conveying member and the second developer agitating and conveying member, In the central portion excluding both longitudinal ends of the developer carrier, the first current Developing apparatus is characterized in that it has a partition plate for shielding the agitating and conveying member around the space and the second developer stirring and conveying member surrounding space.   The developing device according to claim 1, wherein the agent scooping area is located above the agent separating area.   3. The developing device according to claim 1, wherein the downstream end of the lower transport path of the developer formed in the longitudinal direction along the second developer stirring transport member is positioned above the lower transport path. In the vicinity of the first developer agitating member at the downstream end, the developer is pumped up and conveyed to the upper conveying path of the developer formed in the longitudinal direction along the first developer agitating and conveying member. A developing device characterized in that a magnet member for pumping up the agent is provided on the surface.   4. The developing device according to claim 3, wherein the magnet member is disposed around the first developer agitating and conveying member above the center line of the first developer agitating and conveying member. .   5. The developer supply unit according to claim 1, wherein a developer replenishing portion is provided at an upstream end of an upper transport path of the developer formed in a longitudinal direction along the first developer agitating and transporting member. And a developing device.   6. The developing device according to claim 1, wherein an interval between an outer peripheral portion of the developer carrying member and the partition plate is set in a range of 0.2 mm to 1 mm. .   7. The developing device according to claim 1, wherein the agent separation region is located in a lower portion around the developer carrier opposite to the image carrier with the developer carrier interposed therebetween. The developer pumping region is positioned adjacent to the downstream side of the agent separation region in the rotation direction of the developer carrier, and the developer carrier between the agent separation region and the agent pumping region. The partition plate is shielded so that the space around the first developer agitating and conveying member and the space around the second developer agitating and conveying member are shielded at a position where the amount of developer adhering to the periphery is the smallest. And a developing device in which an end of the partition plate on the developer carrier side is opposed to the developer carrier.   8. The developing device according to claim 1, wherein the developer transport amount per unit time by the first developer agitation transport member is equal to the development per unit time by the second developer agitation transport member. A developing device characterized in that it is larger than the agent transport amount.   The uniformly charged image carrier is irradiated with light from the optical writing means to form an electrostatic latent image, and the electrostatic latent image is visualized by a developing device and transferred to a recording medium to obtain a recorded image. 9. An image forming apparatus according to claim 1, wherein the developing device is the developing device according to claim 1.

Images