JP2013020179A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that supplies developer to a developer carrier with uniform toner density to suppress variation in image density, and can reduce the size of the device.SOLUTION: After the supply of toner to a developer carrier, developer moves in circulation as follows: falling down into a recovery chamber 301b at a second communication part 311, being conveyed by a recovery chamber conveying member 305, and being brought up into a feed chamber 301a at a first communication part 307. When the pitch of blades of the recovery chamber conveying member 305 is L1, and the width in the longitudinal direction of the first communication part is L2, the relationship between L1 and L2 is set to satisfy 0.95×L2<L1<1.25×L2.

Description

  The present invention relates to a developing device that visualizes an electrostatic latent image on an image carrier with toner, a process cartridge having the developing device, a copying machine having the developing device or the process cartridge, a printer, a facsimile, a plotter, and the like. The present invention relates to an image forming apparatus such as a multifunction machine including at least one of the above.

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 “developer”) composed 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 in a developer stirring portion is supplied to a cylindrical developer carrier (hereinafter referred to as “developing sleeve”) as a rotating body, and developed by the developing sleeve. The agent is transported to a region (development region) opposite to the cylindrical image carrier (hereinafter referred to as “photoreceptor”) that is a rotating member, and the toner is attached to the electrostatic latent image on the surface of the photoreceptor for development. .
Various configurations of a developer stirring unit that stirs and mixes the developer and supplies the developer to the developing sleeve have been proposed. However, as illustrated in FIG. 11, the developing sleeve 501 disposed beside the photosensitive member 1. The first screw 502 and the second screw 503 are arranged in the horizontal direction in order to stir and convey the developer 320 composed of toner and carrier in the lateral direction or below, and these members are covered with a casing 504. 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 both ends where there is no developer.
The first screw 502 disposed away from the developing sleeve 501 replenishes toner on the upstream side in the transport direction, transports the toner and the carrier while mixing, and develops the sleeve 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 sleeve 501 and collecting the developer from the developing sleeve 501, and delivers the developer to the first screw 502 on the downstream side.

The developing sleeve 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 sleeve 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 sleeve 501 and the two first and second screws are arranged in the horizontal direction (horizontal direction), the vertical size can be reduced, but the horizontal size is It is difficult to make it smaller.
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 on 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. To that end, 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 books 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 sleeve to save space in the horizontal direction, but the developer is consumed due to adhesion to the electrostatic latent image during development. Therefore, the developer having a low toner density after development and the developer having a high toner density before development are simultaneously pumped to the developing sleeve, and the toner density of the developer on the developing sleeve is not uniform. Therefore, unevenness in image density 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.
Furthermore, there is a high possibility that the developer stirred by the upper screw and the developer stirred by the lower screw are interchanged in some places, and the developer is difficult to be stirred uniformly. It is difficult to obtain and it is considered that the above-mentioned problems are caused.

The developing device described in Patent Document 2 has a partition plate for dividing the chamber between a supply chamber and a recovery chamber arranged above and below, and the developer once collected in the recovery chamber by the partition plate is developed again. When it adheres to the sleeve, the developer on the developing sleeve is scraped off.
However, in this configuration, the developer between the developing sleeve and the partition member cannot be scraped off, and if the interval is narrowed, the developing sleeve and the partition member may come into contact and damage the developing sleeve. In this example, the distance between the developing sleeve and the partition plate is set to 0.2 to 1 mm, but if there is a gap of about 1 mm, there is not much effect of scraping off the developer.

In the developing device described in Patent Document 3, development on the developer carrying member is performed by bringing a developer peeling member fixed to a partition plate that partitions a supply chamber and a collecting chamber arranged above and below into contact with the developer carrying member. The agent is peeled off.
However, in this method, the surface of the developer carrying member is damaged. Further, the surface of the developer carrying member has a larger coefficient of friction for transporting the developer, but there is a concern that the coefficient of friction decreases due to contact with the developer peeling member and the developer transporting ability is decreased.

A configuration in which a rotatable scraping member is disposed between the developer carrier and the recovery chamber transport member is also conceivable.
However, in such a configuration, the scraping member requires a rotational drive mechanism, which increases the cost and hinders downsizing of the developing device.

  The present invention has been made in view of such a situation, and provides a developing device that can contribute to miniaturization by making the toner concentration of the developer supplied to the developer carrier uniform and suppressing fluctuations in image density. Is its main purpose.

  In order to achieve the above object, the present invention comprises a developer carrier that carries a developer for forming a toner image on an image carrier, a supply chamber that supplies the developer to the developer carrier, and the developer chamber. A supply chamber transport member for transporting the developer in the supply chamber; a recovery chamber for recovering the developer on the developer carrying member that has passed through the development region; a recovery chamber transport member for transporting the developer in the recovery chamber; In a developing device having a first communication part where the developer moves from the recovery chamber to the supply chamber and a second communication part where the developer moves from the supply chamber to the recovery chamber, the blades of the recovery chamber transport member The pitch of is equal to the width in the longitudinal direction of the first series passage portion

  According to the present invention, the toner density of the developer supplied to the developer carrying member can be made uniform to suppress fluctuations in image density, which can contribute to downsizing of the developing device.

1 is a schematic sectional view of a developing device according to the present embodiment. It is a figure which shows magnetic flux density distribution formed in a developing agent carrier. 2 is a cross-sectional view of a developer carrier. FIG. FIG. 6 is a perspective view of a conveyance unit configuration of the developing device. It is a disassembled perspective view of the conveyance part structure of a developing device. It is sectional drawing in the position of the back | inner side of a developing device. It is a schematic diagram which shows the relationship between the width | variety in the longitudinal direction of a 1st communicating part, and the blade | wing pitch of a collection chamber conveyance member. It is a characteristic view which shows the relationship between the blade | wing pitch and rotation speed ratio of the collection chamber conveyance member in the specific opening width of a 1st communicating part. It is a schematic diagram which shows the blade | wing pitch of the collection chamber conveyance member in other embodiment. 1 is a schematic configuration diagram of an image forming apparatus. It is a schematic sectional drawing of the conventional image development apparatus.

Embodiments of the present invention will be described below with reference to the drawings.
First, a schematic configuration of image formation according to the present embodiment will be described. 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 the photosensitive member. However, the charging device 2 is not limited to the rotating member, and may be a corona discharge type.
The surface of the photosensitive member 1 is uniformly charged in the dark by the charging device 2, and then an electrostatic latent image is formed by irradiation with exposure light L from writing means (not shown). 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 a supply chamber conveyance member 304 and a collection chamber conveyance member 305 for agitating and conveying the developer 320 in the casing 301, and other members such as a developing roller 302 and other members.
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. It can also be applied to an intermediate transfer belt system in which the toner on the photoconductor is temporarily transferred to an intermediate transfer body (intermediate transfer belt, etc.), and then the multicolor toner is transferred to the transfer paper in a batch. In the region B, the toner on the photosensitive member is transferred to the intermediate transfer member (intermediate transfer belt).
After the transfer, the surface of the photoconductor 1 moves downstream as it 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.

The developing device 3 includes a developing roller 302, a supply chamber conveying member 304, a recovery chamber conveying member 305, and a developer regulating member 303 inside the casing 301, and the developer 320 is agitated and conveyed to circulate.
In this embodiment, the stirring member uses a spiral screw, and the screw blade has an outer diameter of 16 mm or less.
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.
In this embodiment, a developing roller having a diameter of 14 mm or less is used to reduce the size of the developing device.

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.
Since the developer on the developing roller is attracted by the magnet MG, the developing roller needs to have a certain degree of hardness. If the hardness is insufficient, the developing roller may be distorted.
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 a casing 301 as an immobile member, a magnet roller 302d having a cylindrical shape integrated with the fixed shaft 302a, and a magnet roller. A sleeve 302c covering the periphery of 302d via a gap, a rotating shaft 302e integrated with the sleeve 302c, and the like. 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).

As shown in FIG. 3, a plurality of magnets MG are fixed to the outer periphery of the magnet roller 302d at a predetermined interval. 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.
There are many configurations of the magnet roller. First, as shown in FIG. 2, a configuration of the magnet roller having five magnets MG inside the sleeve 302c and generating five magnetic poles (magnetic force distribution) will be described. 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 spiked 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 a conductive bearing and a conductive rotating shaft 302e not 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 image 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.
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 removal” 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 (denoted by reference numeral 10 in FIG. 1) is the portion corresponding to the P4 pole on the developing roller. 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 supply chamber conveying member 304 is disposed in the vicinity of the agent pumping region 10 at a position around the developing roller 302 and on the 2 o'clock direction of the developing roller 302. This position is also on the upstream side of the developer regulating member 303. As shown in FIGS. 4 and 5, the supply chamber conveying member 304 has a screw shape with a spiral around the rotation axis, and a center parallel to the center line O-302 a passing through the center O-302 of the developing roller 302. The developer rotates in the clockwise direction indicated by an arrow about the line O-304a, and the developer is conveyed while stirring as indicated by an arrow 11 from the longitudinal direction rear side to the front side of the center line O-304a. That is, the supply chamber conveying member 304 conveys the developer from the axial direction, from the back side to the near side, by the rotation of the rotating shaft.

The collection chamber 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 recovery chamber transport member 305 has a screw shape with a spiral around the rotation axis, and a center line O parallel to a center line O-302a passing through the center O-302 of the developing roller 302. The developer rotates in the counterclockwise direction indicated by an arrow about −305a and is conveyed while stirring the developer as indicated by an arrow 12 from the front side in the longitudinal direction of the center line O-305a toward the back side. That is, the recovery chamber transport member 305 transports the developer from the near side opposite to the transport direction by the supply chamber transport member 304 from the near side to the far side by the rotation of the rotation shaft.
The collection chamber transfer member 305 is positioned above the supply chamber transfer member 304, and the space around the supply chamber transfer member 304 (supply chamber) and the space around the recovery chamber transfer member 305 (in the casing 301 ( It is adjacent to the collection room.

The rear end portions of the supply chamber transport member 304 and the collection chamber transport member 305 are set to be located slightly behind the rear end portion of the developing roller 302, and the developer at the rear end portion of the developing roller 302 is set. Is secured. Further, the front end portions of the supply chamber transport member 304 and the collection chamber transport member 305 are positioned in front of the front end portion of the developing roller 302 to secure a space for toner replenishment described later. . The developer regulating member 303 is installed according to the length of the developing roller 302.
Between the supply chamber transfer member 304 and the collection chamber transfer member 305, a space around the supply chamber transfer member 304 and a space around the collection chamber transfer member 305 are formed in the central portion excluding both ends in the longitudinal direction of the developing roller 302. A shielding partition plate 306 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, the longitudinal ends of the supply chamber transport member 304 and the collection chamber transport member 305 extend to both longitudinal ends of the developing roller 302.

The developer transported in the direction of the arrow 12 by the recovery chamber transport member 305 is cut off along the side wall of the casing 301 at the end in the transport direction, and rises along the side wall, and feed chamber transport member 304 along the arrow 13. Thus, the upper transfer path (supply chamber) along the supply chamber transfer member 304 is moved.
Similarly, the developer conveyed in the direction of the arrow 11 by the supply chamber conveying member 304 is lowered along the side wall in order to cut off the path at the end of the conveying direction at the side wall of the casing 301, and along the arrow 14. The recovery chamber transfer member 305 moves to a lower transfer path (recovery chamber) along the recovery chamber transfer 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 as a first continuous portion in the vicinity of the end on the back side, and is developed from the lower conveyance path through the opening 307 to the conveyance path. Since the agent is lifted, the partition plate 306 may extend to the end in the longitudinal direction of the developing roller 302. However, the opening 307 partially covers the developing roller in order to reduce the size. ing.

  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. It is arranged in the vicinity of the region 10, rotates around a center line O-304a parallel to the center line O-302a of the developing roller 302, and conveys the developer while stirring the developer in the longitudinal direction of the center line O-304a. The supply chamber conveying member 304 and the developer separating area 9 that separates the developer from the developing roller 302 are arranged near the center line 305a parallel to the center line 302a of the developing roller 302, and the supply chamber is conveyed. A member 304 is disposed between the recovery chamber transport member 305 that transports the developer in a direction opposite to the direction in which the developer is transported, and between the supply chamber transport member 304 and the recovery chamber transport member 305, and In the central portion excluding both ends in the longitudinal direction of 302, a configuration having a partition plate 306 that shields the space around the supply chamber transfer member 304 and the space around the collection chamber transfer member 305, the arrows 11, 14, 12, 13 Since two developer agitating / conveying members 304 and 305 in 301 that constitute the circulation conveyance path along the vertical direction are arranged side by side on the side of the developing roller 302, two developer agitating / conveying members 304 and 305 are arranged in the direction away from the developing roller (in the horizontal direction). Compared to the prior art shown in FIG. 11 in which the agitating and conveying member is arranged, the horizontal (horizontal) size of the developing device can be reduced.

  In this way, in the developing device 3 that is compact in the horizontal direction, the partition plate 306 partitions the space around the supply chamber conveyance member 304 and the collection chamber conveyance member 305 at the central portion excluding both ends in the longitudinal direction of the development roller 302. Therefore, 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 supply chamber conveying member 304. Since the toner is simply agitated and conveyed by the collection chamber conveying member 305 and is not immediately supplied to the developing roller 320, only the toner having a target charge amount is used for the developing roller 320. Image quality can be obtained.

As shown in FIGS. 4 and 5, the collection chamber 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 stirring. As shown in FIGS. 5 and 6, an opening 307 is provided in a part of the partition plate 306 at the downstream end in the developer transport direction of the collection chamber transport member 305 and at the back end of the developing device. The developer 320 conveyed by 305 moves in the direction of the arrow 307 to the upper conveyance path along the supply chamber conveyance member 304 located above.
This upward movement is caused by the developer 320 transported by the recovery chamber transport member 305 colliding with the side wall of the casing 301 on the back side and collecting and scraping the raised portion with the screw of the supply chamber transport member 304. This is performed on the conveyance path of the supply chamber conveyance member 304.
As a result, the lifting 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 only the swell is relied on the developer.

In this example, as shown in FIG. 5 and FIG. 6 which shows a cross section on the back side in the developing device 3, the screw is moved in the range corresponding to the opening 307 in the downstream portion in the developer transport direction by the collection chamber transport member 305. The impeller 308 is configured instead of the section.
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 axis (center line O-305a) is provided on the shaft portion 305J of the recovery chamber transport member 305, and with the rotation thereof. And has a function of jumping up the developer 320 upward.
Although the developer lifting portion uses an impeller, the developer can be lifted even when the screw blades are extended, and the present invention can also be applied.

As shown in FIG. 6, the center O-304 of the supply chamber transfer member 304 and the center O-305 of the recovery chamber transfer member 305 are on substantially the same vertical line, and the impeller 308 rotates counterclockwise. The developer 320 is flipped up along the inner wall of the casing 301. The opening 307 does not disturb the course of the developer due to the jumping up, and the center O-304 and the center O-305 are arranged so that the developer that has jumped up does not fall into the collection chamber transport member 305. Are formed so as to extend from a position slightly closer to the casing inner wall to a casing inner wall portion (upstream side in the 304 rotation direction) 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, an opening that connects the upper and lower spaces to the portion where the developer is lifted from the collection chamber transfer member 305 to the supply chamber transfer member 304. 307, but there is a partition plate at the developing roller side portion 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 transported to the collection chamber transport member 305 by the developing roller 302. Alternatively, since the toner is conveyed by the supply chamber conveying member 304, efficient developer circulation can be performed.

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, in the upstream end of the upper transport path by the collection chamber transport 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, in the vicinity of the front end of the developing device. Toner is replenished from the outside from the provided developer replenishment section.
In the replenishment at this portion, the replenished toner is not immediately used for development, but is agitated by the collection chamber transport member 305 and used for development at 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 of the supply chamber conveyance member 304 that is separated from the developing roller 302, and is conveyed in the lower conveyance by the collection chamber conveyance member 305.

In the lower conveyance path by the collection chamber conveyance 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. Thus, a developer having a non-agitated toner concentration is not provided for development.
The replenished toner is agitated and mixed in the developer 320 having a reduced toner concentration away from the developing roller 302, and the toner concentration is normalized before being conveyed to the back side of the developing device 3, so that the operation of the impeller 308, etc. Thus, it is lifted up to the upper conveyance path by the supply chamber conveyance member 304 and is supplied to the developing roller 302 while being conveyed to the near side by the supply chamber conveyance member 304 and used for development.

There is a toner density sensor at the bottom of the unit in FIG. This sensor is a sensor for measuring magnetic permeability, and can detect the carrier concentration (= 100−toner concentration) of the developer. Further, it is determined from the detected carrier concentration whether the toner concentration on the sensor is appropriate or insufficient, and the amount of toner to be replenished is determined.
This toner density sensor is disposed downstream of the collection chamber transport member 305 in the transport direction and upstream of the developer lifting portion.
As described with reference to arrows 11, 14, 12, and 13 in FIGS. 4, 5, etc., the recovery chamber transport member 305 is used for development before being transported to the near side by the supply chamber transport member 304. As a result, the amount of the developer returned to the back side increases, and the developer 320 tends to accumulate on the back side. Therefore, by disposing the toner concentration sensor on the downstream side of the collection chamber transport member 305, the developer is always filled above the sensor, and stable carrier concentration detection is possible.
In addition, the developer below the opening 307 is equipped with a large number of screws or paddles in order to change the compression force applied by the recovery chamber transport member 305 into a moving force efficiently, so that accurate carrier concentration is measured. Difficult to do. Therefore, the toner concentration detection sensor is disposed on the downstream side of the collection chamber transport member and upstream of the opening.
By adopting such a configuration, it is possible to produce a developing device that realizes space saving at low cost.

Next, features of the present invention will be described.
FIG. 7 is a longitudinal sectional view of the developing device according to the present embodiment. With the partition plate 306 as a boundary, the upper part is a supply chamber (supply conveyance path) 301a, and the lower part is a collection chamber (collection conveyance path) 301b. As described above, the opening 307 serves as a first communication portion, and the portion where the partition plate 306 is interrupted on the front side is the second communication portion 311. A supply opening 310 is located above the second communication portion 311.
The width in the longitudinal direction of the opening 307 as the first communication portion is L2, and the pitch of the blades of the collection chamber transport member 305 (distance between adjacent blades) is L1.

FIG. 8 shows the experimental results regarding the conveyance efficiency when L2 is 20 mm.
According to the result, the most efficient is when L1 is equal to or slightly wider than the length of L2, and it may not be too long or too short. From this experimental result, the pitch L1 is preferably 0.95 × L2 ≦ L1 ≦ 1.25 × L2. The reason will be described below.

As described above, in this embodiment, the part for supplying the developer to the developer carrying member and the part for collecting the developer are separated by the partition plate 306. This is because the developer supplied to the developer carrier is always supplied from the supply unit, and the developer once passed through the development area is collected in the recovery chamber, stirred after replenishing the toner, and again until it is carried to the supply unit. This mechanism is not supplied to the developer carrying member.
With such a configuration, the developer supplied to the developer carrying member can always have the same toner density, so that the image density can always be kept constant in the longitudinal direction of the developing sleeve.
With such a configuration, the recovery chamber conveys the recovery agent from the developing sleeve to the first series passage. In the meantime, the developer in the recovery chamber may fly by the stirring force of the screw (recovery chamber transport member 305), or the simply accumulated developer may adhere to the developer carrier again. In this case, the toner density of the developer on the developer carrying member cannot always be kept appropriate.
In addition, the developer pool can be eliminated by increasing the rotation speed of the conveying member (increasing the conveying capacity), but if the developer speed is increased and the rotation speed increases too much, the bearing supporting the conveying member The load on increases.

Generally, a rubber seal member is mounted so that the developer does not enter the bearing. However, wear of the seal member is accelerated, and the life is affected.
In addition, the increase in the number of rotations increases the temperature rise and increases the damage to the developer.
SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device capable of solving the above problems and creating a uniform image without density unevenness without increasing the number of rotations of a conveying member.

As shown in FIG. 8, the experiment was conducted on the transfer efficiency when the longitudinal width L2 of the opening 307 was 20 mm and the screw pitch L1 of the collection chamber transfer member 305 was swung. As described above, the conveyance efficiency is represented by the rotation speed ratio at which the developer does not adhere again.
The developer can be efficiently moved by making the pitch of the collection chamber conveying member 305 the same as or wider than the width L2 in the longitudinal direction of the first series passage portion, and the range of L2 ≦ L1 ≦ 1.2 × L2 is the best. I understand that.
Actually, there is no problem with the increase in rotational load within the range of about 5% of the rotational speed ratio. If it is defined within this range, the screw pitch L1 is 19 to 25 mm, and converted to L2, 0.95 × L2 ≦ L1 ≦ 1.25 × L2 is a desirable range.
When set in this way, the number of rotations of the conveying member is not increased more than necessary, so the load on the bearing and the seal member can be reduced and the life can be extended.
It is possible to prevent solidification and aggregation of the developer due to an increase in temperature, and it is possible to prevent abnormal images.
Since the toner density of the developer on the developer carrying member can always be kept appropriate, a uniform image without density unevenness can be created, and a long-life developing device free from abnormal images can be provided.

FIG. 9 shows another embodiment. In addition, the same part as the said embodiment is shown with the same code | symbol, and unless it was especially required, the description on the structure and function which were already demonstrated is abbreviate | omitted, and only the principal part is demonstrated.
In the present embodiment, the first series-passing portion facing portion satisfies the condition of 0.95 × L2 ≦ L1 ≦ 1.25 × L2, and the collection chamber transport member 305 in the upstream toner replenishing facing portion (the replenishing opening 310 facing portion). The pitch L3 is wider than L1 (L1 <L3).
An object of the present embodiment is to change the pitch of other portions without changing the efficiency of developer movement in the first series passage.
By increasing the pitch other than at least the portion facing the first series passage, the agitation with respect to the replenishing toner is improved.
This is because the larger the pitch of the replenishing toner, the smaller the blades lie than when the pitch is short, so that the straightness of the developer is reduced, the developer is agitated radially, and the toner is more dispersed (mixed well) with respect to the developer.
Although not shown, the screw shape of the conveying member may be a non-tapered shape without a taper. In this way, since the blades stand in the transport direction, the transport efficiency can be increased.

As shown in FIG. 10, 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. The order of colors is not limited to this. For example, it is possible to arrange black at the most downstream side and form an image in the order of MCYK.
In each image forming unit 17, at least the photosensitive member 1 and the developing device 3 may be integrally held to constitute a process cartridge, which may be provided detachably with respect to the image forming apparatus main body.

Each of these image forming units is composed of a combination of a plurality of members, and performs image formation. 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 photoreceptor 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. In order to reduce the size of the image forming apparatus, it is necessary to reduce the interval between the photoconductors. For this purpose, it is necessary to reduce the size of each developing device in the horizontal direction (lateral direction). is there.

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 are configured to include the agent separation region, the agent pumping region, the supply chamber conveyance member, the collection chamber conveyance member, the partition plate, and the like. Toner having a 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.

DESCRIPTION OF SYMBOLS 1 Photosensitive body as an image carrier 301a Supply chamber 301b Recovery chamber 302 Developer carrier 304 Supply chamber conveyance member 305 Collection chamber conveyance member 307 Opening as a first continuous portion 311 Second communication portion 320 Developer

JP-A-11-202627 JP 2003-263012 A Japanese Patent No. 4093677

Claims (8)

A developer carrier that carries a developer for forming a toner image on the image carrier, a supply chamber that supplies the developer to the developer carrier, and a supply chamber conveyance member that conveys the developer in the supply chamber A recovery chamber that recovers the developer on the developer carrying member that has passed through the development region, a recovery chamber transport member that transports the developer in the recovery chamber, and the developer moves from the recovery chamber to the supply chamber In the developing device having a first communication portion and a second communication portion where the developer moves from the supply chamber to the recovery chamber,
2. A developing apparatus according to claim 1, wherein a pitch of the blades of the collection chamber conveying member is equal to a width in a longitudinal direction of the first continuous passage portion. The developing device according to claim 1,
When the pitch of the blades of the collection chamber conveying member is L1, and the width in the longitudinal direction of the first continuous portion is L2,
0.95 × L2 <L1 <1.25 × L2
A developing device characterized by the above. The developing device according to claim 1 or 2,
The developing device according to claim 1, wherein at least a portion of the collection chamber conveying member facing the first series passage is shorter than a width in a longitudinal direction of the first series passage. In the developing device according to any one of claims 1 to 3,
The developing device, wherein the collection chamber transport member is a screw. In the developing device according to any one of claims 1 to 4,
The developing device, wherein the recovery chamber transport member is a non-taper screw.   A process cartridge comprising the developing device according to claim 1.   An image forming apparatus comprising the developing device according to claim 1 or the process cartridge according to claim 5. The image forming apparatus according to claim 7.
An image forming apparatus comprising a plurality of the developing devices or process cartridges and capable of forming a color image.

Images