JP2011048041A - Two-component developing apparatus for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-component developing apparatus of the trickle developing type, effective in miniaturization that can set the length of the developing apparatus to substantially the same length as that of a roller body of a developing roller. <P>SOLUTION: The two-component developing apparatus includes: a first stirring carrier screw 14 provided in a first chamber 17 formed by a case 11, a barrier rib 12 and the developing roller 13; and second and third stirring carrier screws 15, 16 provided in second and third chambers 18, 19 formed by the case 11 and the barrier rib 12. The first, second and third stirring carrier screws 14, 15, 16 are arranged such that the center of each rotation axis forms the vertex of a triangle. A mixing port of new and old developers is formed between the second and third chambers 18, 19, and a supply port 21 of the new developer is formed in the third chamber 19, while a discharge port 22 of the old developer is formed in the second chamber 18. A supply port and a return port for circulation are formed in the first chamber 17. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a two-component developing device of an image forming apparatus that performs trickle development using a two-component developer.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses include a type using a one-component developer (toner) and a type using a two-component developer. Since the method using a single component developer is relatively easy to handle and control, a single component toner has been dominant as a developer.

  However, as demand for faster printing (hereinafter also referred to as printing) increases in recent years, a method using a two-component developer can better cope with faster printing processing. Various developing devices (or developing devices) using a developer have been proposed.

  Such a two-component developer is composed of a toner and a carrier. The carrier is mixed and agitated with the toner in the developing unit to give the toner a predetermined charge. The charged toner temporarily adheres to the surface of the carrier and coats the surface of the carrier.

  The carrier carries charged toner onto the photosensitive member, transfers the toner to the electrostatic latent image on the photosensitive member, and develops the toner image on the electrostatic latent image. The carrier that has released the toner on the surface remains on the developing roller, returns to the inside of the developing device, is mixed and stirred again with new toner, charges the toner, and transports the toner onto the photoreceptor. Is done.

  In the relationship between the carrier and the toner as described above, there is a problem of spending that the toner is fused to the carrier surface by frictional heat. In addition, the agitation in the developing device causes the resin coating layer on the carrier surface to be peeled off or dropped, resulting in a change in carrier resistance, resulting in insufficient image density or image fogging over time compared to the initial image. There is also a problem that the image is deteriorated.

  On the other hand, in recent years, there is a demand for extending the life of the developing device with respect to the carrier. In order to solve the above problems in response to such a request, the carrier is usually coated with a surface of a magnetic core on the surface of a silicon resin, an acrylic resin, or a fluorine resin. Processing is increasing.

  In addition to such measures for improving the surface coating process, the old carrier whose function has been reduced due to peeling or dropping off of the resin coating layer on the surface is replaced with a new carrier, and the toner adherence is regenerated. As a method for extending the life, there is a development method generally referred to as trickle development. An image forming apparatus provided with a developing device that performs such trickle development has been proposed (see, for example, Patent Documents 1, 2, and 3).

   In general, the developer circulation mechanism of a developing device using a two-component developer divides the inside of the developer hopper into two chambers as seen in Patent Documents 1, 2, and 3. Each of the two chambers is provided with one screw having a stirring function and a conveying function, and the developer is circulated in the developer hopper by these two screws and supplied to the developing roller. .

  In order to circulate the developer efficiently in accordance with the circulation path and to improve the stirring efficiency, such a screw is provided with a change in the fin shape of the portion corresponding to the circulation path connecting the two chambers. There is (for example, FIG. 2 of patent document 1).

  Such a change point of the fin shape has a great influence on the state of the developer on the developing roller. For this reason, a fin-shaped change point cannot be provided in the developing region of the developing roller of the developing roller side of the two screws.

  Therefore, it is necessary to configure the stirring / conveying mechanism serving as the fin shape changing point, that is, a part of the developer circulation path, at a position corresponding to the outside of the developing region of the developing roller, that is, the vicinity of one or both axial ends of the developing roller. There is.

  Further, in trickle development using a two-component developer, a method of discharging the old developer inside the developing device at the timing of supplying a new developer to the developing device and gradually reducing the ratio of deteriorated carriers circulating in the developing device. Have taken.

  Although such a circulation method can be executed by the configuration of the screw, if such a replenishing mechanism and a discharging mechanism are also in the developing region of the developing roller, the development does not function normally. Therefore, these mechanisms are also used as the replenishment port 82 and the recovery port 92 shown in FIG. 2 of Patent Document 1, the surplus developer discharge ports 20A and 20B shown in FIG. 1 of Patent Document 2, the replenishment opening 136, and Patent Document 3. As shown in FIGS. 1A and 1B, the developer replenishment port 7 and the excess developer discharge path 8 must be disposed at the end of the developing device outside the developing area of the developing roller.

  Further, when the screw is buried in the developer, the developer above the screw cannot be conveyed, and a defect occurs in the image. Therefore, as in Patent Documents 1, 2, and 3, the developer circulation path needs to be installed so that the upper part of the screw is exposed from the developer. For this reason, the two screws are arranged in parallel with each other along with the developing roller in a substantially horizontal direction.

  FIG. 4A of the present application is an external plan view of a conventional developing device designed based on the descriptions of Patent Documents 1, 2, and 3, and FIG. 4B is a cross-sectional view taken along the line AA ′. It is. As shown in FIG. 5A, the total length b of the developing device 1 is “a: b = 1: 1” with respect to the length a of the roller body 4 excluding both ends of the rotating shaft 3 of the developing roller 2. .30 ", that is, 1.3 times the length of the roller body 4.

  Further, as shown in FIG. 4B, the two screws 5 and 6 arranged in the developer circulation path partitioned into two chambers are arranged in parallel and horizontally with the developing roller 2 and have a width c. Is “a: c = 1: 0.27” with respect to the length a of the roller body 4 of the developing roller 2, that is, 27% of the length of the roller body 4.

JP 2001-194908 A JP 2006-308689 A Japanese Patent Laying-Open No. 2005-091914

  As described above, in the prior art of Patent Document 1, it is necessary to provide a fin shape change point, a replenishment mechanism, a discharge mechanism, and the like outside the developing area of the developing roller. Thus, the total length of the developing device becomes 1.3 times, and there is a problem that the developing device is increased in size, and consequently the image forming apparatus main body is increased in size.

  In addition, the width of the developing device is 27% compared to the length of the roller body of the developing roller, and it is necessary to arrange the developing device horizontally. There is a problem that the layout is limited to the arrangement of the developing system that develops on substantially the side surface of the photoreceptor, and there is no degree of freedom in design.

  In order to solve the above problems, a two-component developing device of the present invention is provided in a two-component developing device of an image forming apparatus that performs trickle development using a two-component developer, and a housing that covers the outside. The first agitating and conveying screw disposed in the first chamber formed by the partition wall and the peripheral surface of the developing roller, and the second and third chambers formed by the casing and the partition wall, respectively. Second and third agitating and conveying screws provided, and the first, second and third agitating and conveying screws are arranged such that the centers of their respective rotation axes form a vertex of a triangle. Configured as follows.

  In this two-component developing device, for example, the third chamber is a replenisher for replenishing the two-component developer from the outside at a position corresponding to the start end portion of the third agitating and conveying screw of the casing. The two-component developer is supplied to the first chamber at a position corresponding to a terminal end portion of the third agitating and conveying screw of the third agitating and conveying screw of the partition wall that forms a mouth and separates the first chamber. The first chamber has the supply port formed in the partition wall separating the third chamber as a starting end portion for stirring and conveying, and the partition wall separating the second chamber A return port for circulating the two-component developer is formed in the agitating and conveying terminal portion on the opposite end to the supply port, and the second chamber separates the first chamber from the partition wall. The return port formed in the above is used as the starting end of the agitation transport, and the third A mixing port for mixing the two-component developer being stirred and conveyed into the two-component developer in the third chamber is formed at a position corresponding to the middle in the longitudinal direction of the partition wall separating the chamber. A discharge port for discharging the remaining two-component developer mixed in the third chamber to the outside is formed at a position corresponding to the end opposite to the return port of the housing. Configured.

  In this case, for example, the first agitating and conveying screw supplies the two-component developer to the rotating circumferential surface of the developing roller while agitating and conveying the two-component developer from the supply port to the return port. The remaining two-component developer supplied to the developing roller is sent out from the return port to the second chamber, and the second stirring and conveying screw mixes the two-component developer fed from the return port into the second chamber. The two-component developer stirred and conveyed to the mouth is fed into the third chamber from the mixing port and mixed into the two-component developer in the third chamber. The two-component developer is conveyed to the discharge port, the conveyed two-component developer is discharged to the outside from the discharge port, and the third stirring and conveying screw is replenished from the supply port. The two-component developer is stirred and conveyed to the mixing port, and the two-component developer thus stirred and conveyed is stirred and conveyed to the supply port together with the two-component developer mixed from the mixing port. The two-component developer is supplied from the supply port to the first chamber.

  In the present invention, a fin-shaped change point is not formed in the first agitating and conveying screw facing the developing roller, and a developer supply port is provided in the first chamber in which the first agitating and conveying screw is disposed. Since the discharge port is not formed, there is no problem even if the first chamber is set to the same length as the roller body of the developing roller. Therefore, the developer circulation path formed by three screws, that is, development The length of the apparatus can be set to be substantially the same as the length of the roller body of the developing roller, thereby contributing to the downsizing of the developing apparatus.

  In addition, since the same stirring, conveying and circulation are performed with three screws as with two screws, the load on each screw can be reduced, the diameter of each screw can be reduced, and these three screws can be reduced. Since the developer circulation path, that is, the developing device is configured in a shape in which the toner is bundled in a triangular shape, the arrangement angle with respect to the photosensitive member can be freely set in combination with the downsizing of the developing device, and there is an effect that the degree of freedom in design increases.

(a) is a top view of the two-component developing device concerning Example 1 of the present invention, and (b) is the BB 'arrow sectional view. It is a figure explaining the detail of a structure of each 1st, 2nd and 3rd chamber, and operation | movement of each 1st, 2nd and 3rd stirring conveyance screw, (a), (b), (c) Sectional view showing the orientation (or angle) of the two-component developing device changed, (d) is a sectional view taken along the line CC 'in (a), and (e) is a sectional view taken along the line DD' in (b). (F) is a cross-sectional view taken along the line EE ′ of (c). (a), (b), (c) is a figure which shows three examples among the arrangement | positioning forms with respect to the photoreceptor of the two-component developing apparatus which concerns on Example 1 of this invention. (a) is a plan view of a conventional developing device, and (b) is a sectional view taken along the line AA ′.

  Hereinafter, embodiments of the present invention will be described in detail. In this example, a two-component developer composed of a toner and a carrier is used, but in the following description, the two-component developer is simply referred to as a developer.

  FIG. 1A is a plan view of the two-component developing device according to the embodiment, and FIG. 1B is a cross-sectional view taken along the line BB ′. The image forming apparatus main body to which the two-component developing device is mounted is a two-component developing image forming apparatus that is normally used, and is not shown.

  As shown in FIGS. 1 (a) and 1 (b), the two-component developing device 10 of this example includes a housing 11 that covers the outside, a partition wall 12 provided inside, a developing roller 13, and first and first partitions. 2 and third stirring and conveying screws 14, 15 and 16.

  The first agitating and conveying screw 14 is disposed in a first chamber 17 formed by the casing 11, the partition wall 12, and the peripheral surface of the developing roller 13. The second agitating and conveying screw 15 is disposed in a second chamber 18 formed by the casing 11 and the partition wall 12. The third agitating and conveying screw is disposed in a third chamber 19 formed by the casing 11 and the partition wall 12.

  These first, second and third stirring and conveying screws 14, 15 and 16 are arranged such that the centers of their respective rotational axes form a triangular apex.

  Further, the two-component developing device 10 has an external developer hopper (not attached) in a portion corresponding to the third chamber 19 at one end of the partition wall 12 (the lower end in FIG. 1A). A developer supply port 21 to be supplied from the figure is formed.

  Similarly, at the other end of the partition wall 12 (the upper end in FIG. 1A), the internal developer is transferred to an external waste developer collection container (not shown) in a portion corresponding to the second chamber 18. ) Is formed.

  In the two-component developing device 10 of this example, the total length d of the device is “a: d = 1: 1.06” with respect to the length a of the roller body excluding both ends of the rotation shaft of the developing roller 13. That is, the length is 1.06 times the length of the roller body.

  Since the length a of the roller body of the developing roller 13 in the two-component developing device 10 of this example is the same as the length a of the conventional roller body shown in FIG. 4, the conventional developing device 1 shown in FIG. The length is shortened to “(1.06 / 1.30) × 100 = 81.5”, that is, a length of slightly less than 82%.

  Further, as shown in FIG. 1B, the width e of the two-component developing device 10 is “a: e = 1: 0.15” with respect to the length a of the roller body of the developing roller 13, that is, the roller. The width is 15% of the length of the main body.

  Also in this case, since the length a of the roller body of the developing roller 13 is the same as the length a of the conventional roller body shown in FIG. 4, it is compared with the width c of the conventional developing device 1 shown in FIG. Thus, “(0.15 / 0.27) × 100 = 55.6”, that is, the width is shortened to a little over 55%.

  2 (a) to 2 (f) show details of the configuration of the first, second, and third chambers 17, 18, and 19, and the first, second, and third stirring and conveying screws 14, It is a figure explaining operation | movement of 15 and 16.

  2A, 2B, and 2C are cross-sectional views showing the two-component developing device 10 in different directions (or angles), and FIG. 2D is a cross-sectional view taken along line C- in FIG. C 'arrow sectional view, FIG. 2 (e) is a DD' arrow sectional view of FIG. 2 (b), and FIG. 2 (f) is an EE 'arrow sectional view of FIG. 2 (c). .

  2 (d), (e), and (f) show a partition wall between two adjacent stirring and conveying screws shown in the front side of the figure (FIGS. 2 (a), (b), (c (See)) is omitted. 2 (a) and 2 (d) show the layout of the plan view of the external view shown in FIG. 1 (a) and the cross-sectional view taken along the line BB ′ shown in FIG. 1 (b). Shown in reverse drawing layout.

  The configuration of each chamber will be described below with reference to FIGS. 1 (a) and 1 (b) as well as FIGS. 2 (a) to 2 (f). First, the third chamber 19 shown in FIGS. 2 (a) and 2 (d) and FIGS. 2 (c) and 2 (f) is arranged along the rotary shaft 23 of the third agitating and conveying screw 16 disposed therein. As indicated by an arrow F, a developer flow path is formed from the upper side to the lower side of FIGS. 2 (d) and 2 (f).

  In the third chamber 19, the two-component developer is externally attached to the position corresponding to the start end of the housing 11 where the developer is stirred and conveyed (above FIG. 2D) as indicated by an arrow G. A replenishing port 21 is formed for replenishing (see FIG. 1 (a)).

  In addition, the third chamber 19 is located at a position corresponding to the terminal end of the agitating and conveying of the third agitating and conveying screw 16 of the partition wall 12 that separates the first chamber 17 (below in FIG. 2 (d)). A supply port 24 for supplying the two-component developer to the first chamber 17 as indicated by an arrow H is formed.

  Note that an arrow H shown in white in FIG. 4D indicates that the supply port 24 formed in the partition wall 12 between the two agitating and conveying screws (14, 16) adjacent to each other on the side facing the front of the figure is connected to the developer. Is passing through the first chamber 17 on the side facing away from the front of the figure.

  Also, the arrow H shown in black in FIG. (F) is not shown between the two agitating and conveying screws (14, 16) shown adjacent to each other on the front side of the figure because the orientation shown in the figure has changed. The direction in which the developer passes through the supply port 24 formed in the partition wall 12 (see FIG. 2C) to the first chamber 17 is shown.

  In the third chamber 19, the developer being circulated from the second chamber 18 to the partition wall 12 separating the second chamber 18 at a position between the supply port 21 and the supply port 24 is indicated by an arrow. As shown by I, a mixing port 25 to be mixed is formed.

  Note that an arrow I shown in black in FIG. 2 (d) indicates a partition wall 12 (not shown) between two agitating and conveying screws (15, 16) arranged so as to be adjacent to each other on the front side of the figure. 2 (a)), the direction in which the developer passes through the mixing port 25 formed in the third chamber 19 is shown.

  Next, the first chamber 17 shown in FIGS. 2 (b) and 2 (e) and FIGS. 2 (c) and 2 (f) is arranged along the rotation shaft 26 of the first agitating and conveying screw 14 disposed therein. 2 (e) and 2 (f), a developer flow path is formed from the bottom to the top.

  The first chamber 17 is configured with the supply port 24 formed in the partition wall 12 separating the third chamber 19 as a starting end portion of the developer agitating and conveying. In the first chamber 17, the two-component developer is indicated by an arrow K at the position of the stirring and conveying end portion that is the opposite end portion of the partition wall 12 that separates the second chamber 18 from the supply port 24. A return port 27 for circulation is formed.

  Note that an arrow K shown in black in FIG. 2 (e) indicates a partition wall 12 (not shown) between two adjacent stirring and conveying screws (14, 15) shown on the front side of the figure (FIG. 2 (b)). The direction in which the developer passes through the return port 27 formed in the reference) is shown in FIG.

  Also, the arrow K shown in white in FIG. 2 (f) indicates the partition wall 12 between the two agitating and conveying screws (14, 15) shown adjacent to each other on the side facing the front of the figure because the orientation shown in the figure has changed. It is shown that the developer passes through the return port 27 formed in (2) to the second chamber 18 on the side facing away from the front of the figure.

  The length of the developer flow path in the first chamber 17 from the supply port 24, which is the starting end of the developer stirring and conveying, to the return port 26, which is the end of the developer stirring and conveying, is shown in FIG. As shown in FIG. 5, the image forming area corresponds to the developing area 28 of the developing roller 13 as it is.

  As a result, as shown in FIG. 1A, the total length d of the two-component developing device 10 of this example is 1.06 times the length a of the roller body of the developing roller 13, that is, 6%. The length of the two-component developing device 10 of this example can be greatly reduced even if a developing roller having the same length as that of the conventional one is used.

  Subsequently, the second chamber 18 shown in FIGS. 2 (a) and 2 (d) and FIGS. 2 (b) and 2 (e) has a second stirring and conveying screw 15 (15a, 15b, 15c) disposed therein. 2), a developer flow path is formed from the top to the bottom in FIGS. 2 (d) and 2 (e).

  In the second chamber 18, the return port 27 serving as the starting end of the developer agitation and conveyance is formed in the partition wall 12 with the first chamber 17, and the mixing port 25 is provided in the middle of the developer flow path. Is formed in the partition wall 12 with the third chamber 19.

  Further, the remaining developer mixed in the third chamber 19 is placed in the second chamber 18 at the position opposite to the return port 27 of the housing 11 as indicated by an arrow M. A discharge port 22 (see also FIG. 1 (a)) is formed for discharge to

  In the configuration of the first to third chambers described above, the operation of the first to third agitating and conveying screws 14 to 16 and the operation of the developer will be described below.

  First, the first agitating / conveying screw 14 supplies the developer to the developing region 28 on the circumferential surface of the developing roller 13 while agitating and conveying the developer from the supply port 24 to the return port 27. At the same time, the first agitating and conveying screw 14 sends the remaining developer supplied to the developing roller 13 from the return port 27 to the second chamber 15.

  The second agitating / conveying screw 15 is composed of screws 15a and 15c for conveying the developer in the direction of the flow path and screws 15b for conveying the developer in the direction opposite to the flow path. The screws 15 a and 15 c are arranged in a state of being divided into two at the mixing port 25, and the screw 15 c is arranged at a predetermined length on the downstream side of the flow channel of the mixing port 25.

  A part of the old developer circulating in the developing device is sent to the third chamber 19 by the screw 15a that conveys the developer in the flow path direction and the screw 15b that conveys the developer in the direction opposite to the flow path. A part of the old developer is mixed in the new developer supplied to the third chamber 19.

  That is, the second stirring and conveying screw 15 forms a fin-shaped change point at the position of the mixing port 25. The remaining developer mixed in the third chamber 19 from the mixing port 25 is transported from the mixing port 25 to the discharge port 22 at the downstream of the change point, and the transported developer is discharged from the discharge port 22 to the outside. Discharge.

  The third agitating and conveying screw 16 agitates and conveys the developer replenished from the replenishing port 21 to the mixing port 25, and agitates the agitated and conveyed developer together with the developer mixed from the mixing port 25 to the supply port 24. Transport.

  That is, the third agitating and conveying screw 16 conveys the replenished developer from the replenishing port 21 and the mixed developer from the mixing port 25 to the supply port 24 while stirring and mixing them on an average basis. The developer mixed on the average is supplied from the supply port 24 to the first chamber 17.

  Since the supply port 24 is not a replenishment port for a new developer, it is not a change point of the developer, and is not a mixing point and is not a change point of the fin shape. Therefore, the developer supplied from the supply port 24 to the first chamber 17 is mixed in the old and new averages and is developed as a uniform developer while being conveyed through the first chamber 17 from the beginning to the end of the flow path. Adsorbed to the roller 13.

  Further, since the return port 27 is not a discharge port for the old developer, it is not a change point of the fluidity of the developer, nor is it a change point of the fin shape because it is not a mixing port. Therefore, the fluidity of the developer conveyed through the first chamber 17 does not vary at the end of the flow path.

  Thus, the replenishment port 21 and the discharge port 22 are not formed in the first chamber 17, and the old and new mixing of the developer is not performed in the first chamber 17. The developer in a uniform state is only conveyed.

  Therefore, as shown in FIGS. 1 (a) and 2 (e), the first chamber 17 in which the first stirring and conveying screw 14 is arranged is placed in the arrangement position of the supply port 21 and the discharge port 22 of the housing 11. Even if it is disposed opposite to the developing roller 13 in the entire length including the length of the developer, there is no possibility of adversely affecting the state of the developer on the developing roller 13.

  Further, the arrangement structure of the three agitating and conveying screws of the two-component developing device 10 of the above-described example has almost no gap between the inner wall of each chamber and the fin of the screw, and the chamber is in a sealed state. No matter what angle the two-component developing device 10 is tilted, there is no risk of the developer leaking out and no problem with stirring.

  FIGS. 3A, 3B, and 3C are views showing three examples of various arrangements of the two-component developing device 10 of this example with respect to the photosensitive member. 3A shows a state in which the developing roller 13 of the two-component developing device 10 is in contact with the upper surface of the photoconductor 30, and FIG. 3B shows that the developing roller 13 is in contact with the lower surface of the photoconductor 30. FIG. 3C shows a state in which the developing roller 13 is in contact with the side surface of the photoconductor 30. The arrangement of the two-component developing device 10 with respect to the photoconductor is not limited to these three examples.

  The present invention can be used in a two-component developing device of an image forming apparatus that performs trickle development using a two-component developer.

DESCRIPTION OF SYMBOLS 1 Developing device 2 Developing roller 3 Rotating shaft 4 Roller body 5, 6 Screw 10 Two-component developing device 11 Housing 12 Partition 13 Developing roller 14 First stirring and conveying screw 15 Second stirring and conveying screw 16 Third stirring and conveying screw 17 First chamber 18 Second chamber 19 Third chamber 21 Supply port 22 Discharge port 23 Rotating shaft 24 Supply port 25 Mixing port 26 Rotating shaft 27 Return port 28 Development area 29 Rotating shaft 30 Photoconductor

Claims (3)

In a two-component developing device of an image forming apparatus that performs trickle development using a two-component developer,
A first stirring and conveying screw disposed in a first chamber formed by a casing covering the outside, a partition wall provided inside, and a peripheral surface of the developing roller;
Second and third agitating and conveying screws respectively disposed in second and third chambers formed by the casing and the partition;
With
The first, second and third agitating and conveying screws are arranged such that the centers of their respective rotation axes form a triangular apex,
A two-component developing device. The third chamber is
A replenishing port for replenishing the two-component developer from the outside is formed at a position corresponding to the start end portion of the third agitating and conveying screw of the casing.
A supply port for supplying the two-component developer to the first chamber is formed at a position corresponding to a terminal end portion of the third agitating and conveying screw of the third agitating and conveying screw that separates the first chamber. ,
The first chamber is
The supply port formed in the partition that separates the third chamber is the starting end of stirring and conveying,
A return port for circulating the two-component developer is formed at the agitating and conveying terminal portion at the end opposite to the supply port of the partition wall separating the second chamber;
The second chamber is
The return port formed in the partition that separates the first chamber is the starting end of stirring and conveying,
A mixing port for mixing the two-component developer being stirred and conveyed into the two-component developer in the third chamber at a position corresponding to the middle in the chamber longitudinal direction of the partition wall separating the third chamber. Formed,
A discharge port for discharging the remaining two-component developer mixed in the third chamber to the outside is formed at a position corresponding to the end opposite to the return port of the housing.
The two-component developing device according to claim 1. The first stirring and conveying screw is
While supplying the two-component developer from the supply port to the return port while stirring and conveying the two-component developer to the peripheral surface of the developing roller rotating,
The remaining two-component developer supplied to the developing roller is sent out from the return port to the second chamber,
The second stirring and conveying screw is
The two-component developer fed from the return port is agitated and conveyed to the mixing port, and the two-component developer that has been agitated and conveyed is fed from the mixing port to the third chamber to be fed into the third chamber. Mixed into the two-component developer,
The mixed residual two-component developer is conveyed to the discharge port, and the conveyed two-component developer is discharged from the discharge port to the outside.
The third stirring and conveying screw is
The two-component developer replenished from the replenishing port is stirred and conveyed to the mixing port, and the two-component developer that has been stirred and conveyed is supplied to the supply port together with the two-component developer mixed from the mixing port. Agitating and conveying, and supplying the two-component developer from the replenishing port and the mixed component from the mixing port to the first chamber from the supply port;
The two-component developing device according to claim 2.