JPH10228175A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently suppress the increase of the rotational torque of developer carrying members and further, to surely execute the operation of discharging a deteriorated developer, with a simple constitution, while meeting a demand for the miniaturization of a device. SOLUTION: In this device, a developer circulating path 6 having two-upper- and-lower-stage structure is formed on the rear side of the developer carrier 3 of a developing housing 2, the developer carrying members 7 and 8 are constituted so that the directions of carrying α developer are opposite to each other are arranged in the axial direction of the developer carrier 3, in the upper and lower paths of the developer circulating path 6, and a fresh developer supplying port 9 through which a fresh developer is supplied is formed at the arbitrary place of the developing housing 2 facing the developer circulating path 6. Further, a developer discharging port, 10 through which the developer is discharged is formed in the vicinity of the communicative port 5 of a partition member 4 in the developer housing 2 facing the developer circulating path 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine of an electrophotographic system or a printer, and more particularly to a developing device in which a two-component developer is carried on a developer carrier. The present invention relates to an improvement of a developing device of a type in which a developer circulation path having a two-stage configuration is formed on the back side of a developer carrying member, and a developer circulating while being stirred and conveyed in the developer circulation path is supplied to the developer carrying body. .

[0002]

2. Description of the Related Art In recent years, as an image forming apparatus for forming a full-color image, for example, as shown in FIG. 6, each color component (for example, black, yellow, magenta, cyan) is used.
A plurality of image forming units 100 (specifically, 100
K, 100Y, 100M, and 100C) are arranged in parallel, and each image forming unit 10 is provided with a latent image carrier 11 such as a photoconductor and an electrophotographic device provided around the latent image carrier 11 for example. Devices (for example, a charging device 12 for charging the latent image carrier 11, an exposure device 13 for writing an electrostatic latent image on the latent image carrier 11, a toner of a predetermined color for the electrostatic latent image on the latent image carrier 11) , A transfer device 15 for transferring the toner image on the latent image carrier 11 onto a transfer medium 17 such as paper, and a cleaning device 16) for removing residual toner on the latent image carrier 11). Then, the respective color component toner images formed by the respective image forming units 100 are sequentially transferred onto the transfer medium 17 in a superimposed manner.
There are already known ones in which a toner image of each color is fixed.

In such a color image forming apparatus,
For example, when focusing on a developing device, a two-component developer composed of a toner and a carrier is often used. In this type of developing device, a portion facing a latent image carrier such as a photoconductor is an opening for development. A developer carrying member (developing roll) for carrying a developer is disposed at a portion facing the developing opening, and a new replenishing member is provided on the back side of the developer carrying member. In general, a stirring and conveying member that conveys the developer or toner and the developer in the developing housing to the developer carrier while being stirred is provided.

From the viewpoint of avoiding an increase in the size of the developing device, for example, as shown in FIG. 6, a partition member 22 extending in the axial direction of the developer carrier 20 is provided on the rear side of the developer carrier 20. Communication ports (not shown) at both axial sides of the developer carrier 20 of the partition member 22
Are formed, and a developer circulating path 21 having a two-stage structure is formed in the upper and lower parts.
A developing device in which the developing device 4 is disposed along the axial direction of the developer carrier 20 has already been proposed.

[0005]

In the above-described developing device, the developer circulation path 2 is increased as the volume of the developer increases.
When the developer is sent from the lower stage to the upper stage, the rotation torque of the developer conveying member 23 on the lower stage side increases. In particular, a spiral conveying member is usually used as the developer conveying members 23 and 24. The spiral winding direction is determined so that the conveying direction is reversed near the lower part of the communication port, and the developer is accumulated. As described above, when the developer is sent from the lower communication port to the upper communication port along with the rotation of the lower developer conveyance member 23, the direction of the lower developer conveyance member 23 when pushing the developer to the communication port is increased. Due to the strong compression of the developer between the different spirals, its rotational torque increases.

In the uppermost path of the developer circulation path 21, at the most downstream portion of the area where the developer carrier 20 and the upper developer transport member 24 face each other, the developer amount regulating member 25 returns to the upper path. The developer and the developer transported by the upper developer transport member 24 are sent out. Therefore,
In the vicinity of the communication port for sending the developer from the upper path to the lower path of the developer circulation path 21, the development due to the increase in the volume of the developer compared to the position where the developer carrier 20 and the upper developer transport member 24 face each other. The increase in the height of the upper surface of the agent is large. For this reason, in some cases, it is difficult for the developer to pass through the communication port that sends the developer from the upper path to the lower path of the developer circulation path 21. Further, when the volume of the developer is extremely increased due to the replenishment of the new developer, the developer is filled near the communication port for sending the developer from the upper path to the lower path of the developer circulation path 21, The rotation torque of the developer conveying member 24 increases.

It is considered that such a technical problem can be solved by discharging the developer from the developing device. Heretofore, as disclosed in Japanese Patent Publication No. 2-15991, an apparatus for discharging a developer by providing a developer overflow portion at a predetermined height of a side wall of a developing housing, and Japanese Patent Application Laid-Open No. Sho 53-2274.
As disclosed in Japanese Patent Application Laid-Open No. 7, the device for controlling the discharge opening so as to replenish the developer and to carry and discharge the deteriorated developer every fixed number of sheets,
Alternatively, as disclosed in Japanese Patent Application Laid-Open No. 4-66984, a device that conveys and discharges a fixed amount of deteriorated developer, detects a change in the volume of the developer, and supplies carrier and toner based on the detection signal. Has already been proposed. Further, these apparatuses are intended to avoid image defects such as image quality deterioration and background fog due to a decrease in toner charging ability due to the deterioration of the developer, without performing a developer replacement operation.

However, as disclosed in Japanese Patent Publication No. Hei 2-21591, merely providing a developer discharge port at an arbitrary height of an arbitrary portion of a developing housing may cause a rapid increase in toner concentration, for example. If the volume of the developer increases abruptly, there is a possibility that the increase in the rotational torque of the developer conveying members 23 and 24 may not be able to cope with the increase. to do so,
There is a technical problem in that the motor capacity for driving the developer conveying members 23 and 24 must be increased, leading to an increase in the size of the apparatus itself and an increase in cost. Also, JP-A-53-2
In the case of Japanese Patent Application Laid-Open No. 2747 or Japanese Patent Application Laid-Open No. 4-66984, it is considered that the increase in the rotational torque of the developer conveying member can be suppressed and the deterioration of the developer can be avoided. Means for performing opening / closing control and means for detecting a change in the volume of the developer are indispensable, and accordingly, there is a technical problem that the cost of the apparatus itself becomes complicated and the cost increases unnecessarily. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and it is possible to efficiently increase the rotational torque of a developer conveying member with a simple configuration while satisfying a demand for downsizing of an apparatus. An object of the present invention is to provide a developing device capable of suppressing the deterioration of the developing agent and reliably performing the operation of discharging the deteriorated developer.

[0010]

That is, according to the present invention, as shown in FIGS. 1A and 1B, a portion facing a latent image carrier 1 on which an electrostatic latent image is formed is used as a developing opening. A developing housing 2 having an opening is provided. A two-component developer including a toner and a carrier is carried on a portion of the developing housing 2 facing the developing opening so that an electrostatic latent image on the latent image carrier 1 is developed. A developer carrier 3 is disposed on the rear side of the developer carrier 3 of the developing housing 2 and is vertically partitioned by a partition member 4 along the axial direction of the developer carrier 3 and the partition member Forming a developer circulation path 6 having a two-stage structure in which communication ports 5 are formed on both sides in the axial direction of the developer carrier 3;
A developing device in which developer conveying members 7 and 8 whose conveying directions of the developer are opposite to each other is disposed along the axial direction of the developer carrier 3 in the upper and lower stages of the developer circulation path 6. A new developer supply port 9 for supplying a new developer is provided at an arbitrary position of the development housing 2 facing the developer circulation path 6.
And a developer discharge port 10 for discharging the developer is formed in the vicinity of the communication port 5 of the partition member 4 in the development housing 2 facing the developer circulation path 6. is there.

In such technical means, the developer carrier 3 may be any as long as it can carry a two-component developer, and for example, a mode in which a magnetic field generating means 3b is provided inside a non-magnetic sleeve 3a. Usually used. In addition, as the developer circulation path 6, the developer carrier 3 is usually disposed facing the upper path, and the developer is circulated and transported from the lower path to the upper path, but is not limited thereto. Instead, for example, the developer carrier 3 may be provided facing the lower path, and the developer may be circulated and conveyed from the upper path to the lower path.

Further, the new developer supply port 9 may be basically provided at an arbitrary position of the developing housing 2 facing the developer circulation path 6. In consideration of the agitation property, it is preferable to provide the developer circulation path 6 at one end in the axial direction of the developer carrier 3 in the developer circulation path 6. The new developer supply port 9 may be configured to supply the new developer including the toner and the carrier from one place, or may be configured to supply the toner and the carrier separately.

Further, the form of the developer discharge port 10 may be such that it is simply opened at a predetermined height position of the lower path or the upper path of the developer circulation path 6 in consideration of the transport amount of the developer. However, the present invention is not limited to this, and another mode may be adopted as long as the amount of the developer in the developer circulation path 6 can be kept to a predetermined amount or less. For example, an opening is formed at an arbitrary height position of the lower path or the upper path, and A lid member made of a spring material may be provided in the opening, and when the pressure of the developer pressing the lid member exceeds a predetermined value, the lid member may be opened to discharge the developer.

The formation position of the developer discharge port 10 can be appropriately selected as long as it is basically in the vicinity of the communication port 5, but in order to increase the torque due to a change in the height or volume of the developer upper surface, the lower step is required. The vicinity of the communication port 5 for sending the developer from the developer transport member 7 to the upper developer transport member 8 is preferable because the sensitivity is higher and the discharge can be performed with good response. Further, in consideration of the compression of the developer and the like, it is more preferable to be near the communication port 5 for sending the developer from the lower developer conveying member 7 to the upper developer conveying member 8 and near the lower part of the communication port 5. Furthermore, for example, in a case where the new developer supply port 9 is provided at one axial end side of the developer carrier 3 in the developer circulation path 6, the discharge of the new developer immediately after the supply is effectively avoided. From the viewpoint, it is preferable to form the developer discharge port 10 at the other axial end of the developer carrier 3 in the developer circulation path 6. Further, the number of developer outlets 10 to be formed may be at least one, but may be provided at a plurality of places.

Next, the operation of the above technical means will be described. 1A and 1B, when a new developer is supplied from the new developer supply port 9, the new developer is supplied to the existing developer path 6 in the developer circulation path 6 as indicated by a black arrow in the figure. The developer circulating path 6 is conveyed while being stirred and mixed from the lower path to the upper path together with the developer, and supplied to the developer carrier 3 facing the upper path, for example. At this time, for example, the developer conveyed by the lower developer conveying member 7 is pressed against the left abutting portion (corresponding to the vicinity of the communication port 5) of the lower flow path of the developer circulation path 6, and the volume of the developer in that portion (or Pressure) will temporarily increase. In such a situation, when the amount of increase in the volume (or pressure) of the developer exceeds a predetermined value, surplus developer is discharged to the outside through the developer discharge port 10. Therefore, the amount of increase in the volume (or pressure) of the developer in the developer circulation path 6 does not increase extremely, and the rotational torque of the developer conveying members 7 and 8 increases accordingly. Absent.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. FIG. 2 is a perspective explanatory view showing one embodiment of a developing device to which the present invention is applied,
FIG. 3 is a sectional view taken along line III-III in FIG. 2, and FIG. 4 is a view as seen from the direction IV in FIG. 2 (FIG. 3). In these drawings, a developing device 40 according to the present embodiment includes a developing housing 4 in which a portion facing a latent image carrier 30 such as a photosensitive drum on which an electrostatic latent image is formed is opened as a developing opening 42.
The developing roller 43 is disposed at a portion of the developing housing 41 facing the developing opening 42.
Here, the developing roll 43 is a magnet roll 4 having a predetermined number of magnetic poles arranged in a rotatable non-magnetic developing sleeve 44.
5 is fixedly installed, carries a two-component developer composed of a toner and a carrier, and develops an electrostatic latent image on the latent image carrier 30 in a development area corresponding to the development opening 42. Has become. A developer amount regulating member 46 that regulates the amount of the developer on the peripheral surface of the developing roll 43 is provided in the periphery of the developing roll 43 before reaching the developing area.

The developing roll 4 of the developing housing 41
On the rear side of the developing roller 3, upper and lower two-stages are formed which are vertically partitioned by partition members 47 along the axial direction of the developing roll 43 and that communication ports 48 and 49 are formed on both axial sides of the developing roller 43 of the partition member 47. A developer circulation path 50 having a structure is formed. In the upper and lower stages of the developer circulation path 50, developer transport members 51 and 52 such as augers in which developer transport directions are opposite to each other are provided along the axial direction of the developing roll 43.

Further, in the present embodiment, a new developer supply port 61 for replenishing a new developer is provided on an upper wall portion of the developing housing 41 facing the developer circulation path 50 near one end of the upper path. Is formed. On the other hand, the developer circulation path 5
0 of the developer housing 41 facing the developer supply port 6
A developer discharge port 62 for discharging the developer is formed in the vicinity of the communication port 49 of the lower path away from 1. In the present embodiment, the developer discharge port 62 is formed at a position where the developer can be discharged when the height of the upper surface of the developer in the lower path exceeds an allowable level, in consideration of the transport amount of the developer. .

Furthermore, in the present embodiment, the lower developer transport member 51 and the upper developer transport member 52 basically include spiral blades 51a,
52 a, the end of the lower developer transport member 51 near the communication port 49 and the communication port 4 of the upper developer transport member 52.
8 (or a new developer supply port 61) has spiral blades 51b, 52b along the direction opposite to the direction in which the developer is circulated and conveyed.

In FIG. 2, reference numeral 71 denotes a driving gear for driving the developing roll 43, and 72 denotes a developer conveying member 51,
5 shows a drive gear train for driving the drive gear 52.

Next, the operation of the developing device according to the present embodiment will be described. In the configuration shown in FIG. 4, when the new developer including the toner and the carrier is supplied from the new developer supply port 61, the new developer is transported to the communication port 48 by the spiral blade 52 b of the upper developer transport member 52. Here, the developer circulation path 5
The developer is sent to the lower developer transport member 51 together with the existing developer in the area 0, and is transported while being mixed. In a region where the lower developer transport member 51 faces the developing roll 43, the transported developer and the developer passed through the image forming area by the developing roll 43 are transported while being mixed.

Next, the toner is sent from the lower path to the upper path at the communication port 49, and is conveyed by the upper developer conveying member 52 to a region facing the developing roll 43. here,
A part of the developer is supplied to the developing roll 43. And
The developer regulated by the developer amount regulating member 46 and not conveyed to the image forming area is returned to the upper developer conveying member 52. The returned developer and the developer not supplied to the developing roll 43 are mixed and agitated and transported to the communication port 48.

Here, the toner density of the developer changes due to a change in charging ability due to deterioration of the developer or a change in an environment in which the apparatus is used. For example, when the charging ability of the developer is improved, the developing property is reduced and the toner density is increased. Even if the developer has the same weight, the volume occupied increases as the toner concentration increases (the bulk density decreases). Therefore, when the toner concentration increases, the volume of the developer increases. As described above, the increase in the volume of the developer causes a problem such as an increase in the rotational torque of the developer transport member 51 (or 52) due to the increase in the volume particularly near the communication port 49 (or 48). . Therefore, if the volume of the developer near the communication port 49 (or 48) or the height of the upper surface of the developer is always smaller than a certain amount, an increase in the rotational torque due to an extremely large volume is prevented. In addition, since the developer in the developing device is discharged, when the developer is supplied from the new developer supply port 61, the deteriorated developer is discharged, so that the deterioration of the developer is suppressed. .

Such an operation is achieved by the communication port 49 (or 4).
This is realized by providing a developer discharge port 62 near 8). That is, the volume of the developer increases (the bulk density decreases)
When done, the lower (or upper) of the communication port 49 (or 48)
The height of the upper surface of the developer in the vicinity exceeds a predetermined amount, and the developer is discharged. The height of the upper surface of the predetermined developer is mainly determined by the position of the lower end of the developer outlet 62. For example, as shown by a solid line in FIG. 4, in the case where the developer discharge port 62 is provided in the vicinity of the lower part of the communication port 49, the spiral blades 5 in different directions of the lower developer transport member 51 do not pass through the communication port 49.
The amount of the developer accumulated between 1a and 51b can be limited. For this reason, the compression of the developer between the spiral blades 51a and 51b and when passing through the communication port can be effectively avoided.

Further, as shown by a virtual line in FIG. 4, in the case where the developer outlet 62 is provided near the upper portion of the communication port 49, the amount of the developer passing through the communication port 49 can be limited. In addition, since the excess amount of the developer existing in the vicinity of the communication port 49 is discharged, it is possible to suppress the torque of the upper developer transport member 52 when the developer passes through the communication port and to prevent the poor passage of the developer. Further, as shown by a virtual line in FIG. 4, in the case of a mode in which a developer discharge port 62 is provided near the upper part of the communication port 48 that sends the developer from the upper developer transport member 52 to the lower developer transport member 51, In addition, it is possible to avoid an increase in the torque of the upper developer transport member 52 and a poor passage of the developer when the volume of the developer is rapidly increased such as when the developer is supplied. Note that, basically, a mode in which the developer discharge port 62 is provided near the lower portion of the communication port 48 that sends the developer from the upper developer transport member 52 to the lower developer transport member 51 is also possible. From the viewpoint of avoiding the concern that the new developer immediately after replenishment from 61 is discharged, it is preferable to exclude the developer.

In any of the above positions, if the height or volume of the developer upper surface in the developer circulation path 50 exceeds a predetermined amount, the developer is discharged. When this occurs, substantially the same effect can be obtained. However, in order to increase the torque due to a change in the height or volume of the upper surface of the developer, the lower developer transport member 51 is moved from the upper developer transport member 5 to the upper developer transport member 5.
The sensitivity is higher near the communication port 49 for sending the developer to the developer outlet 2, and the discharge can be performed with good response. Further, in consideration of the compression of the developer and the like, it is preferable to be near the communication port 49 for sending the developer from the lower developer transport member 51 to the upper developer transport member 52 and near the lower part of the communication port 49. The performance in the present embodiment as described above is supported by the following examples.

[0027]

【Example】

Example 1 The performance was confirmed using the developing device 40 described in the embodiment. The main configuration of the developing device 40 is as described below. Developing roll 43: outer diameter 30 mm: developing sleeve 44 rotation speed 390 mm / sec Auger (developer conveying member) 51, 52: outer diameter 23.5 mm (both upper and lower stages): rotation speed 400 rpm (both upper and lower stages) A developer comprising a ferrite carrier having a diameter of 35 μm and a toner having an average particle diameter of 7 μm was used. The amount of the developer in the developing device was 900 g at a toner concentration of 6.0 wt%. Here, a toner image is formed on the photosensitive drum (latent image carrier) 30 at an area ratio of 10%, and a new development is performed so that a substantially constant amount (5.0 g / m ² ) of the toner is transferred onto the paper. The toner was supplied from the agent supply port 61.

The developing conditions used in this embodiment are as follows. Distance between the photosensitive drum 30 and the developing sleeve 44 at the closest position: 0.4 mm Rotation speed of the photosensitive drum 30: 260 mm / sec Toner image forming section potential: -300 V Background section potential: -700 V Development bias (DC):- 550V developing bias (AC, peak to peak):
1.5 kV Developing bias (AC, Duty): 0.5 Developing bias (AC, frequency): 4.0 kHz The developer discharge port 62 is positioned as shown by the solid line in FIG. 4, that is, from the lower auger 51 to the upper auger 52. In the vicinity of the lower part of the communication port 49 for sending the developer, the lower auger 51
Near the end of the. The lower end of the developer outlet 62 was set at the lowest position where the developer was not discharged when the developer was charged.
The size of the opening was 3 mm in the horizontal direction and 4 mm in the vertical direction.

As the toner image formation and toner replenishment are continued, the charging performance of the developer gradually increases as shown in FIGS. 5A and 5B, and the toner density increases to 10.8%. did. As shown in Table 1 below, when the torque required to rotate the upper and lower augers 51 and 52 at this time was measured by a torque gauge, it was about 3.0 kgf · cm at the maximum. The weight of the developer in the developer circulation path 50 was about 740 g. Thereafter, the developer deteriorated and the charging performance of the developer tended to decrease, and the toner concentration decreased. As described above, even in the case of the high toner concentration, which is considered to be the largest in volume, the increase in torque can be effectively suppressed by discharging the developer.

Comparative Example A running test was performed in the same manner as in the embodiment except that the developer outlet 40 was not provided in the developing device 40 according to the embodiment. Rose. When the amount of the developer and the rotational torque of the augers 51 and 52 were measured when the toner concentration became the highest, as shown in Table 1 below, the amount of the developer was approximately 950 g, and the rotational torque was approximately 4.2 kgf · cm. Auger 5
In some cases, rotation of motors (not shown) for driving the developing sleeves 1 and 52 and the developing sleeve 44 is stopped. In this example, since there is no developer discharge port 62, the rotational torque is about 1.4 times that of the first embodiment.

Example 2 A similar running test was performed with the same configuration as in Example 1 and a developer having a toner concentration of about 75 wt% was supplied.
As shown in FIGS. 5A and 5B, the charging performance is slightly more gradually improved than in the first embodiment, and thereafter, the charging performance and the toner density are reduced, and the higher charging performance is maintained as compared with the first embodiment. Was completed. For this reason, the deterioration of the image quality was small compared to the first embodiment. At the point where the toner concentration is highest, it is almost the same as in the case of Embodiment 1, and as shown in Table 1 below, the toner concentration is 11.0 wt%, and the augers 51 and 52
The rotational torque of was measured by a torque gauge,
It was about 3.0 kgf · cm at the maximum. As described above, even when the developer is supplied, the rotation torque of the augers 51 and 52 can be suppressed from increasing as in the case where the toner is supplied.

In each of the embodiments, the rectangular developer outlet 62 is used, but it is not always necessary that the developer outlet 62 be rectangular. Further, the position of the developer discharge port 62 may be sufficient if the developer can be sufficiently discharged in the vicinity of the communication port.

[0033]

[Table 1]

[0034]

As described above, according to the present invention,
In a developing device using a two-component developer, an upper and lower two-staged developer circulation path is formed on the back side of the developer carrier in the development housing, and any part of the development housing facing the developer circulation path A new developer supply port and a developer discharge port near the upper and lower communication paths of the developer circulation path. Excess developer can be discharged from a portion where the developer tends to increase. For this reason, it is possible to efficiently suppress the increase in the rotational torque of the developer conveying member and to reliably perform the operation of discharging the deteriorated developer with a simple configuration while satisfying the demand for the downsizing of the apparatus.

[Brief description of the drawings]

FIG. 1A is a schematic diagram illustrating a configuration of a developing device according to the present invention, and FIG. 1B is a schematic cross-sectional diagram corresponding to line BB in FIG. 1A.

FIG. 2 is a perspective explanatory view illustrating an outline of a developing device according to the embodiment.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a view as viewed from an arrow IV in FIG. 2;

FIG. 5A is a graph showing the charging performance of a developer in Examples 1 and 2, and FIG. 5B is a graph showing a change in toner density in Examples 1 and 2.

FIG. 6 is an explanatory diagram illustrating a configuration example of a color image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Latent image carrier, 2 ... Developing housing, 3 ... Developer carrier, 4 ... Partition member, 5 ... Communication port, 6 ... Developer circulation path, 7, 8 ... Developer conveying member, 9 ... New developer Supply port, 1
0: developer outlet, 30: photosensitive drum (latent image carrier), 40: developing device, 41: developing housing, 43 ...
Developing roll, 44: developing sleeve, 45: magnet roll,
47: partition member, 48, 49: communication port, 50: developer circulation path, 51, 52: auger (developer conveying member),
61: new developer supply port, 62: developer discharge port

Claims (4)

[Claims] A latent image carrier on which an electrostatic latent image is formed (1)
Has a developing housing (2) opening as a developing opening, and a part facing the developing opening of the developing housing (2) carries a two-component developer composed of toner and carrier. A developer carrier (3) on which the electrostatic latent image on the latent image carrier (1) is developed is provided, and the developing housing (2) is provided with a developing agent on the back side of the developer carrier (3). The partition member (4) is vertically partitioned by a partition member (4) along the axial direction of the developer carrier (3), and communication ports (5) are formed at both axial sides of the developer carrier (3) of the partition member (4). A developer circulating path (6) having a two-stage structure is formed. ) Is disposed along the axial direction of the developer carrying member (3), the developer circulating path ( A new developer supply port (9) for supplying new developer is formed at an arbitrary position of the developing housing (2) facing the developer housing (6), and the developing housing (2) facing the developer circulation path (6). And a developer discharge port (10) for discharging the developer is formed near the communication port (5) of the partition member (4). 2. The developing device according to claim 1, wherein the developer discharge port is formed near a communication port in the developer circulation path from the lower path to the upper path. A developing device. 3. The developing device according to claim 1, wherein the developer discharge port is located near a communication port in the developer circulation path from which the developer flows from the lower path to the upper path. A developing device formed so as to face a lower path. 4. The developing device according to claim 1, wherein the new developer supply port is formed at one axial end of the developer carrier in the developer circulation path. The developing device, wherein the developer discharge port (10) is formed at the other axial end of the developer carrier (3) in the developer circulation path (6).