JPH10319697A - Electrostatic latent image developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely circulate developer separated from a developer applying means on the downstream side of a developing area by providing a second developer stirring mechanism carrying the developer separated from the developer applying means and disposed in a developer returning chamber to a developer supplying chamber. SOLUTION: The developer mixed with toner fed backward by a first stirring carrying means 51 is carried upward along the bottom wall 12 and the rear wall 14 of a developing housing 10, namely, to a magnetic carrying means 53 while being stirred by the second stirring carrying means 52. Then, a paddle 512 constituting the second stirring carrying means 52 is inclined on a rear side in a rotating direction from the side of the front end wall 16 of the developing housing 10 to the side of the rear end wall 16 of that, so that the developer is supplied from the toner supplying port 160 provided at the front end wall 16 to the developer returning chamber 202. The toner carried with the developer to the side of the rear end wall 16 by the second stirring carrying means 52 is also fed to the side of the rear end wall 18 and is dispersed over an entire developer returning chamber 202 in a width direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image developing apparatus for developing an electrostatic latent image into a toner image in an image forming machine such as an electrostatic copying machine or a laser printer.

[0002]

2. Description of the Related Art As is well known, in order to develop an electrostatic latent image in an image generator, an electrostatic latent image developing apparatus using a developer comprising toner and carrier particles has been widely used. I have. The electrostatic latent image developing device includes a developing housing for containing a developer, a developer applying unit for applying the developer in the developing housing to the electrostatic latent image, and agitating the developer in the developing housing. And a developer stirring / conveying mechanism for supplying the developer to the developer applying means. The developer applying means usually includes a rotating sleeve member, holds the developer on the peripheral surface of the sleeve member, conveys the developer to a developing area, and selects a toner in the developer into an electrostatic latent image in the developing area. The electrostatic latent image is developed into a toner image. When the toner in the developer is consumed according to the development of the electrostatic latent image, the toner is supplied from the toner supply device into the development housing.

In the above-described electrostatic latent image developing apparatus, the developer is sufficiently stirred before being transported to the developing area by being held by the developer applying means, so that the toner and the carrier particles are uniformly mixed. It is important that they are charged and charged. On the downstream side of the developing area, the developer in which the toner is adhered to the electrostatic latent image and the ratio of the toner is reduced is effectively separated from the developer applying unit, and is stirred again in the developing housing. It is important to be circulated while being done.

[0004] A developer stirring and conveying device for conveying a developer while stirring it well is disclosed, for example, in Japanese Patent Application Laid-Open No. 7-175306. Japanese Patent Application Laid-Open No. 7-175306 discloses that a downstream transport path, a midstream transport path, and an upstream transport path are provided in a developing housing in parallel with a developer applying unit, and the developer is directed from a central portion to both ends in the downstream transport path. The downstream agitating and conveying member including the first spiral blade and the second spiral blade in which the spiral directions of the spirals to be transported are opposite to each other is transported from the both ends to the center toward the middle flow path. A middle-flow agitating / conveying member provided with a first spiral blade and a second spiral blade in which the winding directions of the spirals formed are opposite to each other, and transports the developer from the center to both ends to the upstream transport path. An upstream stirring and conveying member having a first spiral blade and a second spiral blade formed with spiral winding directions opposite to each other, respectively;
A developer stirring and conveying device configured to supply the developer conveyed to a downstream conveying path by the upstream stirring and conveying member and the middle flow stirring and conveying member and further conveyed by the downstream stirring and conveying unit to the developer applying unit is disclosed. Have been.

[0005]

Therefore, before the developer separated from the developer applying means on the downstream side of the developing area is conveyed to both ends by the downstream stirring and conveying member,
It may be pumped up again by the developer applying means and transported to the developing area to be subjected to a developing action. When the developer detached from the developer applying means on the downstream side of the development area, when a so-called solid black image is printed, the toner is attached to the electrostatic latent image and the ratio of the toner is reduced. Then, a spiral striped unevenness occurs.

The present invention has been made in view of the above-mentioned circumstances, and a main technical problem thereof is that a developer capable of reliably circulating the developer detached from the developer application means on the downstream side of the developing area. An object of the present invention is to provide an electrostatic latent image developing device provided with a stirring and conveying mechanism.

[0007]

According to the present invention, an electrostatic latent image formed on an image carrier which is moved through a developing area is solved by the present invention.
In an electrostatic latent image developing apparatus for developing a toner image by applying a developer comprising carrier particles and toner on the image carrier in the developing area, the electrostatic latent image developing apparatus is partitioned by a partition wall and formed above the partition wall. And a developer return chamber formed below the partition wall, and a front face of the developer housing facing the developer supply chamber and the developer return chamber. A developer applying means provided;
A first developer stirring / conveying mechanism disposed in the developer supply chamber for conveying the developer while stirring and supplying the developer to the developer application unit; and a developer application unit disposed in the developer return chamber. And a second developer stirring / transporting mechanism for transporting the developer removed from the developer supply chamber to the developer supply chamber.

It is preferable that the developing housing is provided with a toner supply port for supplying toner to the developer return chamber.

The first developer agitating and transporting mechanism includes a downstream transporting path and an upstream transporting path provided in parallel with the developer applying means, and is provided in the downstream transporting path to transport the developer in the axial direction. It comprises a downstream stirring / conveying member provided with a spiral blade and an upstream stirring / conveying member provided on the upstream conveying path and provided with a spiral blade for conveying the developer in the axial direction. The downstream agitating and conveying member includes a first spiral blade and a second spiral blade provided on the rotating shaft and having spirals formed to reverse the spirals for conveying the developer from the central portion toward both ends. The upstream stirring / conveying member is formed of a rotating shaft and a spiral provided on the rotating shaft and configured to convey the developer from both ends toward the center in a first direction. It preferably comprises a spiral blade and a second spiral blade.

[0010] The second developer stirring and conveying mechanism is provided in parallel with the developer application means and is rotatably mounted on a front end wall and a rear end wall constituting the developing housing. A stirring and conveying means provided with a plurality of paddles radially provided on a shaft, and a developer conveyed by the stirring and conveying means attracted to a peripheral surface by a magnetic force to be conveyed and peeled to face the developer supply chamber And a magnetic conveying means for feeding the developer to the developer supply chamber in the region. The front end wall constituting the developing housing is provided with a toner supply port for supplying toner to the developer return chamber, and the plurality of paddles constituting the stirring and conveying means are arranged from the front end wall side to the rear end wall side. It is desirable to be formed so as to be inclined rearward in the rotation direction.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an electrostatic latent image developing device constructed in accordance with the present invention will be described below in further detail with reference to the accompanying drawings.

FIG. 1 shows a preferred embodiment of an electrostatic latent image developing apparatus constructed according to the present invention, together with a part of a rotary drum 2 constituting an image carrier. The rotating drum 2 is provided with an appropriate electrostatic photoreceptor on its peripheral surface, and is rotated in a direction indicated by an arrow 4 in the figure by an appropriate driving means (not shown) so as to pass through the developing area 6. Have been. In the developing area 6, the electrostatic latent image formed on the peripheral surface of the rotary drum 2 is developed into a toner image by an electrostatic latent image developing device generally designated by the numeral 8 according to the present invention. The toner image developed by the electrostatic latent image developing device in this manner is transferred to a transfer member such as plain paper by a transfer unit (not shown) on the downstream side of the development area 6. Then, the toner image transferred to the transfer member is heated and fixed by a fixing unit (not shown).

Continuing the description with reference to FIGS. 1, 2 and 3, the electrostatic latent image developing device 8 includes a developing housing 10. The developing housing 10, which can be formed from a suitable synthetic resin, includes a front end wall 16 and a rear end wall 18 along with a bottom wall 12 and a rear wall 14 extending substantially vertically upward from the rear edge of the bottom wall 12. I have. The developing housing 10 is divided into a developer supply chamber 201 formed on the upper side by a horizontally provided partition wall 20 and a developer return chamber 202 formed on the lower side. A cover member 22 made of a synthetic resin that covers the upper surface of the developing housing 10 configured as described above is provided.

At the forefront of the developing housing 10 (the leftmost part in FIG. 1 and the uppermost part in FIG. 2), a developer applying means 24 is disposed facing the developer supply chamber 201 and the developer return chamber 202. ing. The developer applying means 24 extends substantially horizontally in the developing region 6 in the width direction (the direction perpendicular to the paper surface in FIG. 1, the left-right direction in FIG. 2) and is arranged in parallel with the rotary drum 2. It comprises a member 26 and magnet means 28 disposed in the sleeve member 26. The sleeve member 26 is formed of a non-magnetic material such as aluminum, and is rotatably mounted on the developing housing 10. The magnet means 28 is constituted by a stationary permanent magnet, and is fixed at a predetermined position in the sleeve member 26. As shown in FIG. 1, an N-pole and an S-pole are alternately formed on the outer peripheral surface of the stationary permanent magnet constituting the magnet means 28, and the developer is not magnetized in the lower portion. An area 281 is formed. As shown in FIG. 2, the rotation shaft 30 to which the sleeve member 26 is fixed penetrates the rear end wall 18 of the developing housing 10 and protrudes rearward. An input gear (not shown) is fixed to the protruding end of the rotating shaft 30, and the input gear can be an electric motor via an appropriate transmission gear (not shown). Transmission). The sleeve member 26 of the first developer applying unit 24 thus configured moves in a direction indicated by an arrow 32 in FIG. 1, that is, in the developing area 6 in the same direction as the rotation of the rotary drum 2. Is driven to rotate.

On the inner surface of a cover member 22 formed of a synthetic resin that covers the upper surface of the developing housing 10, an ear-cutting plate 34 is mounted by fixing means such as screws. In the embodiment shown in the drawing, the cutting board 34 is made of non-magnetic stainless steel.
It is arranged along. The tip of the ear-cutting plate 34 thus configured is connected to the developer regulating area 28 of the developer applying unit 24.
2 is provided with a predetermined gap from the peripheral surface of the sleeve member 26.

Behind the developer applying means 24, there is provided a first developer stirring and transporting mechanism 40 which transports the developer while stirring it and supplies it to the developer applying means 24.
The first developer stirring and transporting mechanism 40 includes a downstream transport path 42 formed in the developer supply chamber 201 as the first developer transport path and an upstream transport path as a second developer transport path. 44. The downstream transport path 42 and the upstream transport path 44 are provided in parallel in the front-rear direction (the left-right direction in FIG. 1 and the up-down direction in FIG. 2).

A downstream stirring and conveying member 46 as a first stirring and conveying member is provided in the downstream conveying path 42.
As shown in FIG. 2, the downstream stirring and conveying member 46 has a rotating shaft 461 rotatably mounted between both end walls 16 and 18 of the developing housing 10. This rotation shaft 461
Is formed with a pair of spiral blades 462 and 463 at intervals in the axial direction, that is, in the width direction. Spiral blade 462
And the spiral blade 463 are formed so that the winding directions are opposite to each other. The outer diameter of the spiral blade 462 and the outer diameter of the spiral blade 463 are the same. Auxiliary spiral blades 464 and 465 are formed at both ends of the rotating shaft 461. The auxiliary spiral blades 464 and 465 have the same outer diameter as the outer diameters of the spiral blades 462 and 463, and are formed over an angle range of approximately 360 degrees. The winding directions of the auxiliary spiral blades 464 and 465 are opposite to the winding directions of the spiral blades 462 and 463 facing each other. The rotating shaft 461 constituting the downstream stirring and conveying member 46 is
An input gear (not shown) is fixed to the rear end of the rotating shaft 461 and penetrates through the rear end wall 18 of the developing housing 10. It is operatively connected to the drive mechanism of the application means 24. The downstream stirring / conveying member 46 thus configured is driven to rotate in a direction indicated by an arrow 460 in FIG. 1 and conveys the developer from the center toward both ends.

The upstream conveying path 44 is provided with an upstream stirring and conveying member 484 as a second stirring and conveying member. The upstream stirring and conveying member 48 is provided with the developing housing 10.
Has a rotating shaft 481 rotatably mounted between both end walls 16 and 18. A pair of spiral blades 482 and 483 are formed on the rotating shaft 481 at intervals in the axial direction, that is, in the width direction. Spiral blade 482 and spiral blade 4
The winding direction is opposite to that of 83. The outer diameter of the spiral blade 482 and the outer diameter of the spiral blade 483 are the same. The rotating shaft 481 constituting the upstream stirring and conveying member 48 is
Input gears (not shown) are fixed to the rear end wall of the rotating shaft 481, respectively. The input gears are fixed to the developer by penetrating the rear end wall 18 of the developing housing 10. It is operatively connected to the drive mechanism of the application means 24. The downstream stirring / conveying member 48 thus configured is driven to rotate in a direction indicated by an arrow 480 in FIG. 1, and conveys the developer from both ends toward the center.

In a developer return chamber 202 formed in the developing housing 10, a second developer for transferring the developer released from the developer applying unit 24 to the developer supply chamber 201 is provided.
Is disposed. The second developer stirring and conveying mechanism 50 includes a first stirring and conveying unit 51, a second stirring and conveying unit 52, and a magnetic conveying unit 53.

The first stirring and conveying means 51 has a rotating shaft 511 rotatably mounted between both end walls 16 and 18 of the developing housing 10. The rotating shaft 511 is provided with a plurality of paddles 512 formed radially. The rotation shaft 511 penetrates the rear end wall 18 of the developing housing 10 and protrudes rearward. An input gear (not shown) is fixed to the rear end of the rotation shaft 511, and the input gear Is operatively connected to the drive mechanism of the developer applying unit 24. The first stirring / transporting means 51 thus configured is driven to rotate in the direction indicated by an arrow 510 in FIG. 1, and aft while stirring the developer in the developer return chamber 202, that is, the second stirring / transporting means 52. Conveyed toward. In the illustrated embodiment, the paddle 512 constituting the first stirring and conveying means 51 is formed to be inclined rearward in the rotation direction from the front end wall 16 side of the developing housing 10 to the rear end wall 18 side. Therefore, the developer is conveyed backward while being conveyed from the front end wall 16 side to the rear end wall 18 side.

The second stirring and conveying means 52 also has a rotating shaft 521 rotatably mounted between both end walls 16 and 18 of the developing housing 10. The rotary shaft 521 is provided with a plurality of paddles 522 formed radially. The rotation shaft 521 penetrates the rear end wall 18 of the developing housing 10 and protrudes rearward. An input gear (not shown) is fixed to the rear end of the rotation shaft 521, and the input gear Is operatively connected to the drive mechanism of the developer applying unit 24. The second stirring / transporting means 52 thus configured is driven to rotate in a direction indicated by an arrow 520 in FIG.
The developer conveyed by 1 is conveyed upward, that is, toward the magnetic conveying means 53 along the bottom wall 12 and the rear wall 14 of the developing housing 10 while stirring. In the illustrated embodiment, the paddle 522 constituting the second stirring / conveying means 52 is, like the paddle 512 of the first stirring / conveying means 51, from the front end wall 16 to the rear end wall 18 of the developing housing 10. Therefore, the developer is conveyed toward the magnetic conveying means 53 while being conveyed from the front end wall 16 side to the rear end wall 18 side.

The magnetic transport means 53 includes a developer peeling wall 204 formed upright at a rear end of the partition wall 20 provided on the developing housing 10 and a rear wall 1 of the developing housing 10.
4 is provided. The magnetic transport means 53 has the same configuration as the developer applying means 24, and
Above the agitating / conveying means 52 substantially horizontally in the width direction (FIG. 1).
, A sleeve member 531 extending in a direction perpendicular to the plane of the drawing and in the left-right direction in FIG. 2 and arranged in parallel with the second stirring and conveying means 52, and a magnet means 532 arranged in the sleeve member 531. It is composed of The sleeve member 531 is formed of a non-magnetic material such as aluminum, and is rotatably mounted on the developing housing 10.
The magnet means 532 is constituted by a stationary permanent magnet, and is fixed at a predetermined position in the sleeve member 531.
As shown in FIG. 1, N-poles and S-poles are alternately formed on the outer peripheral surface of the stationary permanent magnet constituting the magnet means 53, and are not magnetized from the upper part to the partition wall 20 side. A peeled area 533 is formed. As shown in FIG. 2, the rotation shaft 535 to which the sleeve member 26 is fixed penetrates the rear end wall 18 of the developing housing 10 and protrudes rearward. An input gear (not shown) is fixed to the protruding end of the rotary shaft 535, and the input gear is operatively connected to the drive mechanism of the developer applying unit 24. The magnetic transport means 53 thus configured is driven to rotate in the direction indicated by the arrow 530 in FIG.
The developer agitated by the stirring and conveying means 52 is attracted to the peripheral surface of the sleeve member 531 by the magnetic force of the magnet means 53, and is conveyed in the direction indicated by the arrow 530. And
The developer adsorbed and transported on the peripheral surface of the sleeve member 531 is separated by the developer peeling wall 204 in the peeling area 533 due to the reduction of the magnetic field, and is sent to the upstream transport path 44.

As shown in FIG. 1, a developer supply chamber 201 and a developer return chamber 202 formed in the developing housing 10 are provided.
Contains a developer 300 composed of toner and carrier particles. The developer stored in the developer return chamber 202 is sent to the developer supply chamber 201 by the first stirring / transporting means 51, the second stirring / transporting means 52, and the magnetic conveying means 53. The developer contained in the developer supply chamber 201 and the developer sent from the developer return chamber 202 are conveyed from both ends toward the center while being stirred by the upstream stirring conveyance member 48 in the upstream conveyance path 44. Then, the developer transported to the central portion of the upstream transport path 44 is
2 and is conveyed while being stirred by the downstream stirring and conveying member 46 from the center to both ends. The developer conveyed from the center to both ends of the downstream conveyance path 42 is supplied to the developer applying unit 24.

The front end wall 16 of the developing housing 10 is provided with a toner supply port 160 for introducing the toner conveyed by a toner supply device (not shown) into the developer return chamber 202. The partition wall 20 that divides the developing housing 10 into a developer supply chamber 201 and a developer return chamber 202 is formed with a hole 203 that opens at the center of the downstream transport path 42. In this hole 203, a detector 55 for detecting the toner concentration in the developer in the developer supply chamber 201 is provided. This detector 55
Detecting the toner concentration in the developer in the developer supply chamber 201 by detecting the magnetic permeability of the developer existing on the upper surface exposed in the downstream conveyance path 42 through the hole 203 is known per se. May be used. When the toner concentration in the developer detected by the detector 50 becomes equal to or lower than a predetermined value, a toner supply device (not shown) is operated by a control signal from a control device (not shown), and toner is supplied from the toner supply port 160 to the developer return chamber. 202. When the toner density detected by the detector 55 becomes equal to or higher than a predetermined value, the operation of the toner supply device is stopped by a control signal from the control device, and the supply of the toner to the developer return chamber 202 is stopped.

Next, the operation and effect of the electrostatic latent image developing apparatus as described above will be summarized and described as follows.
When the toner supply device (not shown) is operated, the toner supplied from the toner supply port 160 to the developer return chamber 202 is stirred by the first stirring and conveying means 51 together with the developer stored in the developer return chamber 202. While being transported toward the second stirring and transporting means 52. At this time, the paddle 512 constituting the first stirring and conveying means 51
Is formed to be inclined rearward in the rotation direction from the front end wall 16 side to the rear end wall 18 side of the developing housing 10,
The toner supplied to the developer return chamber 202 from the toner supply port 160 provided in the front end wall 16 is transported backward while being transported from the front end wall 16 side to the rear end wall 18 side together with the developer. The developer is dispersed in the width direction of the developer return chamber 202.

The developer mixed with the toner sent rearward by the first stirring / transporting means 51 is stirred by the second stirring / transporting means 52 while the developing housing 10
Along the bottom wall 12 and the rear wall 14 of FIG. At this time, the paddle 512 constituting the second stirring and conveying means 52 is connected to the developing housing 10.
Is formed to be inclined rearward in the rotational direction from the front end wall 16 side to the rear end wall 18 side, so that the toner is supplied from the toner supply port 160 provided in the front end wall 16 to the developer return chamber 202 and the second The toner conveyed toward the rear end wall 18 together with the developer by the stirring and conveying means 52 is further transferred to the rear end wall 18.
Side and is distributed over the entire width of the developer return chamber 202.

The developer transported by the second stirring and transporting means 52 toward the magnetic transporting means 53 along the bottom wall 12 and the rear wall 14 of the developing housing 10 is transferred to the magnetic transporting means 5.
The sleeve member 5 is formed by the magnetic force of the magnet 53 constituting the sleeve member 5.
31 and is transported in the direction indicated by arrow 530. The developer adsorbed and transported on the peripheral surface of the sleeve member 531 is separated by the developer peeling wall 204 in the peeling area 533 due to the reduction of the magnetic field, and is upstream of the developer supply chamber 201. It is sent to 44.

The upstream conveying path 44 of the developer supply chamber 201
Is transported from both sides in the axial direction toward the center in the axial direction while being stirred by the action of the pair of spiral blades 482 and 483 of the upstream stirring and conveying member 48. Then, it is introduced into the downstream transport path 42 at the center of the upstream transport path 42. The developing material introduced into the downstream transport path 42 is transported while being agitated by the downstream agitating transport member 46 from the center to both ends. The developer transported to both ends of the upstream transport path 44 by the downstream stirring transport member 46 is returned to the upstream transport path 44 again, and transported toward the axial center by the upstream stirring transport member 48.

Continuing the description with reference to FIG. 1, on the downstream side (left side in FIG. 1) of the downstream transport path 42, the sleeve member 26 of the developer applying means 24 is rotated in the direction indicated by the arrow 32. In the developer pumping area indicated by reference numeral 283 in FIG. 1, a part of the developer conveyed from the axial center portion to both axial side portions while being agitated by the downstream agitating and conveying member 46 is transferred to the stationary permanent magnet member 28. The magnetic field is pumped to the peripheral surface of the sleeve member 26 due to the formed magnetic field. The developer pumped to the peripheral surface of the sleeve member 26 is accompanied by the rotation of the sleeve member 26 by an arrow 32.
Are transported in the direction shown by the arrow and transported to the developing zone 6. At this time, the excess developer is removed from the peripheral surface of the sleeve member 26 by the action of the cutting board 34 attached to the inner surface of the cover 22 of the developing housing 10. In the developing area 6, as described above, the toner in the developer is selectively adhered to the electrostatic latent image formed on the peripheral surface of the rotating drum 4, and the electrostatic latent image is developed into a toner image. Is done. Developing area 6
The developer is separated from the peripheral surface of the sleeve member 26 in the developer peeling region 281 located downstream of the sleeve member 26 due to the magnetic field formed by the permanent magnet member 28 being reduced. The toner released from the peripheral surface of the sleeve member 26 in this manner has a reduced toner concentration because the toner has been consumed in the developing area 6. The developer released from the peripheral surface of the sleeve member 26 is dropped into the developer return chamber 202, and is returned to the developer return chamber 202.
The first stirring and conveying means 51 and the second stirring and conveying means 52 and the magnetic conveying means 5
3, the developer is supplied to the developer supply chamber 201. In this manner, the developer in which the toner is consumed and the toner concentration is reduced in the developing area 6 is circulated from the developer return chamber 202 to the developer supply chamber 201 and is again subjected to the developing operation.

As described above, in the electrostatic latent image developing device in the illustrated embodiment, the developer in which the toner is consumed and the toner density is reduced in the developing area 6 is:
The developer is returned to the developer return chamber 202 and circulated from the developer return chamber 202 to the developer supply chamber 201 to be subjected to the developing operation again. Therefore, the toner is consumed in the development area 6 and the toner concentration is reduced. Since the developing agent is not immediately subjected to the developing action, when a so-called solid black image is printed, no unevenness of the spiral stripe pattern occurs.

Further, in the illustrated embodiment, since the new toner is supplied from the toner supply port 160 to the developer return chamber 202, the first stirring and conveying means 51 provided in the developer return chamber 202 and the Since the stirring is carried out sufficiently by the second stirring and conveying means 52, the mixing with the developer is performed well and the toner is sufficiently charged by friction.

Furthermore, in the illustrated embodiment, the downstream stirring and conveying member 46 and the upstream stirring and conveying member 48 disposed in the developer supply chamber 201 are configured to convey the developer in the axial direction while stirring. There is no scattering of the developer. Further, the first stirring and conveying means 51 provided in the developer return chamber 202
Further, since the second stirring and conveying means 52 is constituted by a plurality of paddles provided radially, the developer can be sufficiently stirred.

[0033]

The electrostatic latent image developing device according to the present invention is configured as described above, and the developer whose toner has been consumed in the developing area separates from the developer applying means and falls into the developer return chamber. Then, the toner is conveyed from the developer return chamber to the developer supply chamber by the second developer stirring / conveying mechanism and is again subjected to the developing operation, so that the toner is consumed in the development area and the toner concentration is reduced. Since the developer is not immediately subjected to the developing action, when a so-called solid black image is printed, no unevenness of the spiral stripe pattern occurs.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a preferred embodiment of an electrostatic latent image developing device configured according to the present invention.

FIG. 2 is a plan view of the electrostatic latent image developing device shown in FIG. 1 with a cover member that covers an upper surface of a developing housing omitted.

FIG. 3 is a cross-sectional view of the electrostatic latent image developing device shown in FIG.

[Explanation of symbols]

 2: Rotary drum 6: Developing area 10: Developing housing 20: Partition wall 22: Cover member 24: Developer applying means 26: Sleeve member 28: Magnet means 30: Rotating shaft of sleeve member 34: Rotating plate 40: First Developer stirring and conveying mechanism 42: downstream conveying path 44: upstream conveying path 46: downstream stirring and conveying member 48: upstream stirring and conveying member 49: toner concentration detector 50: second developer stirring and conveying mechanism 51: first stirring Conveying means 52: Second stirring and conveying means 53: Magnetic conveying means 160: Toner supply port 201: Developer supply chamber 202: Developer return chamber

Claims (6)

[Claims] An electrostatic latent image formed on an image carrier that is moved through a developing area is formed by applying a developer comprising carrier particles and toner on the image carrier in the developing area. An electrostatic latent image developing device for developing an image, comprising: a developer supply chamber partitioned by a partition wall and formed above the partition wall; and a developer return chamber formed below the partition wall. A developing housing; a developer applying means disposed in front of the developing housing so as to face the developer supply chamber and the developer return chamber; and agitating the developer disposed in the developer supply chamber. A first developer stirring / transporting mechanism that transports the developer while supplying the developer to the developer application unit; and transports the developer disposed in the developer return chamber and separated from the developer application unit to the developer supply chamber. And a second developer stirring / conveying mechanism. Electrostatic latent image developing device according to claim. 2. The electrostatic latent image developing device according to claim 1, wherein the developing housing is provided with a toner supply port for supplying toner to the developer return chamber. 3. The first developer stirring / transporting mechanism includes a downstream transport path and an upstream transport path provided in parallel with the developer application unit, and a developer disposed in the downstream transport path and moving the developer in an axial direction. 2. The downstream stirring / conveying member provided with a spiral blade for conveying, and an upstream stirring / conveying member provided on the upstream conveying path and provided with a spiral blade for conveying the developer in an axial direction. An electrostatic latent image developing device. 4. A first spiral blade provided with the downstream agitating and conveying member, the first spiral blade being provided on the rotary shaft and configured to reverse the winding directions of spirals for conveying the developer from a central portion toward both ends. And a second spiral blade, wherein the upstream stirring and conveying member is formed with a rotating shaft and spirals provided on the rotating shaft and configured to convey the developer from both ends toward the center, in opposite directions. The electrostatic latent image developing device according to claim 3, further comprising a first spiral blade and a second spiral blade. 5. A second developer stirring and conveying mechanism, comprising: a rotating shaft disposed in parallel with the developer applying means and rotatably mounted on a front end wall and a rear end wall constituting the developing housing; A stirring and conveying means having a plurality of paddles radially provided on a rotating shaft; and a developer conveyed by the stirring and conveying means being attracted to a peripheral surface by a magnetic force to be conveyed and opposed to the developer supply chamber. 2. The electrostatic latent image developing device according to claim 1, further comprising: a magnetic transport unit that sends the developer to the developer supply chamber in a separation area. 6. A toner supply port for supplying toner to the developer return chamber is provided at the front end wall constituting the developing housing, and a plurality of paddles constituting the stirring and conveying means are provided at the front end wall. The electrostatic latent image developing device according to claim 5, wherein the electrostatic latent image developing device is formed so as to be inclined rearward in the rotation direction from the side toward the rear end wall.