JP2006243512A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly control the amount of developer in a developing vessel with a simple configuration by controlling the discharge amount of the developer discharged from the developing vessel without providing a shutter operating mechanism. <P>SOLUTION: The developing device includes; a discharged developer storage chamber 21 wherein the developer discharged from a developer discharge port of a developing vessel V is stored and which is configured so that the stored developer closes the developer discharge port 7 to prevented the developer from being discharged from the developer discharge port 7 in the case that a large amount of the developer is stored in the discharged developer storage chamber; a stored developer carrying device (22a+R5) which carries the stored developer to a discharged developer recovery tank 23; a stored developer detection means which detects the stored developer in the discharged developer storage chamber 21; and a developer discharge control means which carries the stored developer in the discharge developer storage chamber 21 toward the discharged developer recovery tank 23 in response to an output signal of the stored developer detection means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a developing device for developing an electrostatic latent image formed on an image carrier of an image forming apparatus such as an electrophotographic copying machine or a laser printer into a toner image, and in particular, a two-component developer composed of toner and a carrier. The developer is replenished with new toner and carrier in accordance with the consumption of the toner by the developing operation, and the developer in the developing container that has deteriorated is always discharged on the developer container wall surface. The present invention relates to a trickle developing type developing device that overflows and discharges from an outlet and collects it in a developer collecting container.

In the trickle developing type developing device, a developing device that replenishes a high-concentration developer that is a two-component developer having a high toner concentration is conventionally known.
FIG. 20 is an example of a graph showing the relationship between the volume and weight of the two-component developer in the developing container of the trickle developing type developing device using a high-concentration developer as the replenishment developer, and the toner concentration and the carrier amount. .
In FIG. 20, for example, the amount of the two-component developer at the time of initializing (starting use) in the developing container is 600 cm ³ and the toner concentration is 11%. At this time, the carrier weight is 730 g. From this state (the state of the initial point P1), when the toner concentration increases along the isovolume line (with a constant amount of developer in the developing container), for example, 17% (a state of the point P2). The carrier weight is 550 g.

  That is, in the trickle developing type developing device having the characteristics shown in the graph of FIG. 20, when the toner concentration changes abruptly, for example, when the toner concentration rapidly rises, a high concentration developer is supplied. Therefore, the developer volume in the developing container increases. In this case, the increased developer (excess developer) overflows and is discharged from the developer discharge port, but if all the increased developer is discharged and the developer volume in the container is made constant, the state of P1 It moves from the state (carrier weight = 730 g) to the state P2 (carrier weight = 550 g). In this case, the amount of carrier in the container is reduced.

If the developing operation is performed without replenishing the high-density developer from the state of the point P2, the toner is consumed while the amount of carrier in the container is reduced (the carrier amount remains constant). From the state to the state of the point P3 (state where the toner concentration is 7.5%), the toner concentration rapidly decreases. If the state of point P3 is exceeded due to a rapid decrease in the toner concentration, the amount of developer in the developer container is reduced, resulting in poor developer layer formation.
Generally, when the toner concentration in the developer container in the developer container increases, the carrier amount in the container decreases, and when the developer concentration is drastically decreased in this state, the developer is discharged from the developer discharge port. The amount of carrier in the container is further reduced. At this time, as described above, the amount of the developer in the developing container is reduced, and a defective layer formation of the developer layer on the developing roll occurs, so that there is a problem that the image quality is deteriorated.

The following technique (J01) is known as a conventional technique for solving the above problems.
(J01) Technology described in Japanese Patent Application Laid-Open No. 7-199639 In this publication, in order to change the amount of developer discharged from the developing container depending on the toner concentration, the areas of the toner concentration detection means and the developer discharge port are made variable. A developing device provided with a shutter for this purpose is described.

JP-A-7-199639

(Problem of the above (J01))
However, in the technique (J01), it is necessary to provide a shutter operating device in order to change the developer discharge amount, and there is a problem that the configuration of the developing device becomes complicated.

The present invention takes the following description (O01) and (O02) as technical problems in view of the above-described examination results.
(O01) By controlling the amount of discharged developer discharged from the developing container without providing a shutter operating mechanism, the amount of developer in the developing container can be appropriately controlled with a simple configuration.
(O02) To prevent occurrence of poor layer thickness regulation due to excessive reduction of the developer amount in the developing container with a simple configuration.

  Next, the present invention that has solved the above problems will be described. In the description of the present invention, the reference numerals in parentheses added after the constituent elements of the present invention are constituent elements of the embodiments described later corresponding to the constituent elements of the present invention. It is a sign. The reason why the present invention is described in correspondence with the reference numerals of the constituent elements of the embodiments described later is to facilitate the understanding of the present invention, and not to limit the scope of the present invention to the embodiments.

(Invention)
In order to solve the above problems, the developing device of the present invention is characterized by comprising the following structural requirements (A01) to (A08).
(A01) A developer roll container (V0) that houses the developing roll (R0), and a developer that is stirred and conveyed while circulating a two-component developer composed of toner and carrier adjacent to the developer roll container (V0). Development that is agitated and conveyed in the circulation conveyance path (V1 + V2), the developer replenishment port (6) that replenishes the developer circulation conveyance path (V1 + V2), and the developer circulation conveyance path (V1 + V2). A developer container (V) having a developer discharge port (7) for discharging the developer and containing the developer;
(A02) The two-component developer that is rotatably accommodated in the developing roll accommodating portion (V0) and adhered to the rotating surface is opposed to the surface of the image carrier (PR) on which the electrostatic latent image is written and rotated. A developing roll (R0) that is transported to a developing area to develop the electrostatic latent image;
(A03) The developer circulation transport path (V1 + V2) has a rotating shaft and a stirring transport blade rotatably accommodated, and circulates the two-component developer while stirring and transporting at the time of rotation, and the developing roll storage section A stirring and conveying member (R1 + R2) for supplying the two-component developer to (V0);
(A04) A discharged developer storage chamber (21) in which the developer discharged from the developer discharge port (7) is stored, and when the stored developer in the discharged developer storage chamber (21) becomes large, The discharged developer storage chamber (21) configured such that the stored developer blocks the developer discharge port (7) and prevents the developer from being discharged from the developer discharge port (7);
(A05) A developer discharge path (22a) for transporting the stored developer to a discharged developer recovery tank (23) and a developer discharge path (22a) disposed to store the stored developer in the discharged developer storage A stored developer transport device (22a + R5) having a discharged developer transport member (R5) transported from the chamber (21) to the discharged developer recovery tank (23);
(A06) Stored developer detecting means (C8a) for detecting the stored developer in the discharged developer storing chamber (21),
(A07) A discharge driving device (D3 + M3) for driving the discharged developer conveying member (R5),
(A08) The operation of the discharge driving device (D3 + M3) is controlled in accordance with the output signal of the stored developer detecting means (C8a), and the stored developer in the discharged developer storage chamber (21) is used as the discharged developer. Developer discharge control means (C8) for transporting to the collection tank (23) side.

(Operation of the present invention)
In the developing device of the present invention having the structural requirements (A01) to (A08), the developing container (V) containing the developer includes the developing roll container (V0) that stores the developing roll (R0), and Adjacent to the developing roll container (V0), a developer circulation conveyance path (V1 + V2) in which a two-component developer composed of toner and carrier circulates while being circulated, and agitation conveyance in the developer circulation conveyance path (V1 + V2). A developer discharge port (7) for discharging the developer to be discharged. The developing roller (R0) rotatably accommodated in the developing roller accommodating portion (V0) is a two-component developer attached to the rotating surface, and an image carrier (PR) in which an electrostatic latent image is written and rotated. The electrostatic latent image is developed by being conveyed to a developing area facing the surface. An agitating / conveying member (R1 + R2) rotatably accommodated in the developer circulation conveying path (V1 + V2) has a rotating shaft and an agitating / conveying blade, and circulates the two-component developer while agitating and conveying at the time of rotation. The two-component developer is supplied to the roll container (V0).
In the discharged developer storage chamber in which the developer discharged from the developer discharge port (7) is stored, when the amount of stored developer in the discharged developer storage chamber becomes large, the stored developer is transferred to the developer discharge port (7 ) Is blocked to prevent the developer from being discharged from the developer discharge port (7). The stored developer transport device (22a + R5) is disposed in the developer discharge path (22a) and the developer discharge path (22a) for transporting the stored developer to the discharged developer recovery tank (23), and the stored developer. A discharged developer conveying member (R5) for conveying the discharged developer from the discharged developer storage chamber (21) to the discharged developer collecting tank (23). The discharge driving device (D3 + M3) drives the discharged developer transport member (R5). A stored developer detection means (C8a) detects the stored developer in the discharged developer storage chamber (21), and a developer discharge control means (C8) outputs an output signal of the stored developer detection means (C8a). Accordingly, the operation of the discharge driving device (D3 + M3) is controlled, and the stored developer in the discharged developer storage chamber (21) is conveyed to the discharged developer recovery tank (23) side.

(Embodiment 1 of the present invention)
The developing device according to Embodiment 1 of the present invention is characterized in that, in the present invention, the following structural requirements (A09) and (A010) are provided.
(A09) The stored developer detecting means (C8a) for detecting that the stored developer is in a state of closing the developer discharge port (7),
(A010) When the stored developer is in a state of blocking the developer discharge port (7), the stored developer in the discharged developer storage chamber (21) is conveyed to the discharged developer recovery tank (23) side. The developer discharge control means (C8).

(Operation of Form 1 of the Present Invention)
In the developing device according to the first embodiment of the present invention having the structural requirements (A09) and (A010), the stored developer detecting means (C8a) is in a state where the stored developer closes the developer discharge port (7). It detects that it became. When the stored developer enters the developer discharge port (7), the developer discharge control means (C8) controls the operation of the discharge drive device (D3 + M3) to discharge the discharge. The developer stored in the developer storage chamber (21) is conveyed to the discharged developer recovery tank (23).

(Embodiment 2 of the present invention)
The developing device according to the second embodiment of the present invention is characterized in that the developing device according to the first embodiment of the present invention has the following structural requirements (A011).
(A011) The developer discharge port (A011) is adjusted by adjusting the time from when the stored developer becomes blocked to the developer discharge port (7) until the discharge developer transport member (R5) starts to be driven. The developer discharge control means (C8) for adjusting the developer discharge speed from 7).

(Operation of Embodiment 2 of the present invention)
In the developing device according to the second embodiment of the present invention having the structural requirement (A011), the developer discharge control means (C8) is configured so that the stored developer is in a state of closing the developer discharge port (7). The developer discharge speed from the developer discharge port (7) is adjusted by adjusting the time until the discharge developer conveying member (R5) starts to be driven.

(Embodiment 3 of the present invention)
The developing device according to Embodiment 3 of the present invention is the developing device according to Embodiment 1 or 2 of the present invention, and is characterized by including the following structural requirement (A012).
(A012) By adjusting a driving time for driving the discharged developer conveying member (R5) in a state where the stored developer closes the developer discharge port (7), the discharged developer storage chamber ( 21) The developer discharge control means (C8) for adjusting the stored developer amount of 21) and consequently adjusting the developer discharge speed from the developer discharge port (7).

(Operation of Form 3 of the Present Invention)
In the developing device according to the third embodiment of the present invention having the structural requirement (A012), the developer discharge control means (C8) is in a state in which the stored developer closes the developer discharge port (7). The amount of stored developer in the discharged developer storage chamber (21) is adjusted by adjusting the driving time for driving the discharged developer conveying member (R5), and as a result, the developer discharge port (7) Adjust the developer discharge speed from.

(Embodiment 4)
The developing device according to Embodiment 4 of the present invention is characterized in that the developing device according to any one of Embodiments 1 to 3 of the present invention includes the following structural requirements (A013) and (A014).
(A013) In-container toner concentration sensor (SN1) for detecting the toner concentration of the two-component developer in the developing container (V);
(A014) The developer discharge control means (C8) for reducing the developer discharge speed when the toner density becomes higher than an upper limit set value.

(Operation of Form 4 of the Present Invention)
In the developing device according to the fourth embodiment of the present invention having the structural requirements (A013) and (A014), the toner concentration sensor (SN1) in the container is the toner concentration (Tc) of the two-component developer in the developing container (V). And the developer discharge control means (C8) reduces the developer discharge speed when the toner density (Tc) becomes higher than the upper limit set value.

(Embodiment 5)
The developing device according to Embodiment 5 of the present invention is characterized in that the developing device according to any one of Embodiments 1 to 3 of the present invention includes the following structural requirements (A013) and (A015).
(A013) In-container toner concentration sensor (SN1) for detecting the toner concentration (Tc) of the two-component developer in the developing container (V);
(A015) The developer discharge control means (C8) for increasing the developer discharge speed when the toner density (Tc) becomes lower than a lower limit set value (Tc1).

(Operation of Form 5 of the Present Invention)
In the developing device according to the fifth embodiment of the present invention having the structural requirements (A013) and (A015), the in-container toner concentration sensor (SN1) has the toner concentration (Tc) of the two-component developer in the developing container (V). ) Is detected, and the developer discharge speed is increased when the toner density (Tc) becomes lower than the lower limit set value (Tc1).

(Embodiment 6 of the present invention)
The developing device according to Embodiment 6 of the present invention is the developing device according to any one of Embodiments 1 to 5 of the present invention, and is characterized by including the following structural requirement (A016).
(A016) Developer replenishment for controlling the replenishment amount of the two-component developer into the developer container (V) from the developer replenishment port (6) according to the toner consumption amount in the developer container (V) Control means (C7),
(A017) Two-component developer replenishment amount integrated value storage means (C9) for accumulating and storing the replenishment amount of the two-component developer from the previous rotation to the current rotation of the discharged developer conveying member (R5);
(A018) Changes in the toner concentration (Tc) in the developer container (V) between the previous rotation and the current rotation of the discharged developer conveying member (R5), and until the previous rotation and the current rotation. The developer discharge control means (C8) for controlling the developer discharge speed from the developer discharge port (7) according to the integrated value (J1) of the two-component developer supply amount.

(Operation of Embodiment 6 of the present invention)
In the developing device according to the sixth aspect of the present invention having the structural requirement (A016), the developer replenishment control means (C7) has the developer replenishment port (C7) according to the toner consumption amount in the developer container (V). The replenishment amount of the two-component developer into the developing container (V) from 6) is controlled.
The two-component developer supply amount integrated value storage means (C9) integrates and stores the two-component developer supply amount (J1) from the previous rotation to the current rotation of the discharged developer transport member (R5). To do.
The developer discharge control means (C8) changes the toner concentration (Tc) in the developer container (V) between the previous rotation and the current rotation of the discharged developer conveying member (R5), The developer discharge speed from the developer discharge port (7) is controlled in accordance with the integrated value (J1) of the two-component developer supply amount until the rotation and the current rotation.

(Embodiment 7 of the present invention)
The developing device of Embodiment 7 of the present invention is the developing device of Embodiment 6 of the present invention, and is characterized by comprising the following structural requirements (A019) to (A023).
(A019) From the time when the discharge driving device (D3 + M3) is driven to transport the stored developer in the discharged developer storage chamber (21) to the discharged developer recovery tank (23), the discharge is then performed. A two-component developer replenishment amount integrated value storage means (C9) for accumulating and storing the replenishment amount of the two-component developer from the developer replenishment port (6) up to the time when the driving device (D3 + M3) is driven;
(A020) a driving time toner concentration detection storage means (C10a) for detecting and storing the toner concentration (Tc) in the developing container (V) at the time of driving the discharge driving device (D3 + M3);
(A021) This time based on the toner density (Tc4) at the previous driving time of the discharge driving device (D3 + M3) and the integrated value of the replenishment amount of the two-component developer from the previous driving time to the current driving time. Toner density theoretical value calculation means (C10) for calculating the theoretical value Tc5 of the toner density at the time of driving
(A022) Toner density change judging means (C11) for judging whether or not the detected toner density Tc at the current driving time point is Tc <Tc5 with respect to the theoretical value Tc5;
(A023) The developer discharge control means (C8) for lowering the developer discharge speed from the developer discharge port (7) when Tc <Tc5 than when Tc> Tc5.

(Operation of Embodiment 7 of the present invention)
In the developing device according to the seventh embodiment of the present invention having the structural requirements (A019) to (A023), the two-component developer replenishment amount integrated value storage means (C9) is stored in the discharged developer storage chamber (21). The developer from the time when the discharge driving device (D3 + M3) is driven to convey the developer to the discharged developer recovery tank (23) side until the next time when the discharge driving device (D3 + M3) is driven. The supply amount of the two-component developer from the supply port (6) is integrated and stored.
The driving time toner density detection storage means (C10a) detects and stores the toner density (Tc) in the developing container (V) at the time of driving the discharge driving device (D3 + M3).
The toner density theoretical value calculation means (C10) is configured to store the toner density (Tc4) at the previous driving time of the discharge driving device (D3 + M3) and the two-component developer from the previous driving time to the current driving time. Based on the integrated value (J1) of the replenishment amount, the theoretical value Tc5 of the toner density at the current driving time is calculated and stored.
The toner density change determining means (C11) determines whether or not the detected toner density Tc at the current driving time is Tc <Tc5 with respect to the theoretical value Tc5.
The developer discharge control means (C8) lowers the developer discharge speed from the developer discharge port (7) when Tc <Tc5 than when Tc> Tc5.
In the case of Tc <Tc5, it is highly possible that the amount of developer in the developer container (V) is less than the reference value. Therefore, the developer in the developer container (V) is reduced by reducing the developer discharge speed. The amount can be controlled more appropriately.

The above-described present invention has the following effects (E01) and (E02).
(E01) By controlling the amount of discharged developer discharged from the developing container without providing a shutter operation mechanism, the amount of developer in the developing container can be appropriately controlled with a simple configuration. .
(E02) With a simple configuration, it is possible to prevent the occurrence of poor layer thickness regulation due to an excessive decrease in the developer amount in the developing container.

Next, examples (examples) of the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as the front side, the rear side, the right side, the left side, the upper side, the lower side, or the front side, the rear side, the right side, the left side, the upper side, and the lower side, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.

Example 1
FIG. 1 is an overall explanatory view of an image forming apparatus including a developing device according to Embodiment 1 of the present invention.
In FIG. 1, an image forming apparatus U has a main body U1 and an automatic document feeder U2 placed on a platen glass PG on the upper surface of the main body U1. The automatic document feeder U2 has a document feed tray TG1 on which a plurality of documents Gi to be copied are stacked. Each of the plurality of documents Gi placed on the document feed tray TG1 sequentially passes through the copy position on the platen glass PG and is discharged to the document discharge tray TG2. The automatic document feeder U2 is rotatable with respect to the copying machine main body U1 by a hinge shaft (not shown) provided in the rear end portion (-X end portion) extending in the left-right direction. When a person puts it on the platen glass PG by hand, it is rotated upward.

The image forming apparatus main body U1 has a UI (user interface) through which a user inputs an operation command signal such as copy start.
An IIT (image input terminal) disposed below the transparent platen glass PG on the upper surface of the copying machine main body U1 has an exposure optical system A.
In the case of the ADF mode in which copying is performed using the automatic document feeder (auto document feeder) U2, the exposure optical system A is stopped at the home position, and sequentially passes through the copy position on the platen glass PG. The document Gi is exposed.
In the platen mode where the operator places the document Gi on the platen glass PG by hand, the exposure optical system A exposes and scans the document on the platen glass PG while moving. Reflected light from the original document Gi exposed by the lamp of the exposure optical system A passes through the exposure optical system A and is converged on a CCD (solid-state imaging device). The CCD outputs an electrical signal corresponding to the amount of original reflected light converged on the imaging surface.

The controller C controls the operation timing of an IPS (image processing system), a power supply circuit (power supply circuits such as a developing device, a transfer roll, and a fixing device) E, a laser drive circuit DL, and the like. The IPS converts the electrical signal input from the CCD into image data and temporarily stores it, and the image data is used as image data for forming a latent image at a predetermined timing as an IOT (image output terminal) laser. Output to the drive circuit DL.
The laser drive circuit DL outputs a laser drive signal to the ROS (latent image forming apparatus) according to the input image data.

The image carrier PR constituted by the photosensitive drum is rotated in the direction of the arrow Ya by the main motor M1 (see FIG. 6), and the surface thereof is uniformly charged by the charger CR in the charging region Q0. The latent image writing position Q1 is exposed and scanned by the laser beam L of the ROS to form an electrostatic latent image. The electrostatic latent image on the rotating image carrier PR is developed into a toner image by the developing device G in the developing region Q2.
The surface of the image carrier PR on which the toner image is formed moves to the transfer region Q3. Below the transfer area Q3, a slide frame Fs that is slidable back and forth (in a direction perpendicular to the paper surface) by a pair of left and right slide rails SR, SR is detachably supported from the image forming apparatus body U1. Yes. A transfer roll T, a transfer roll cleaner CLt, a roll support lever Lr, a post-transfer sheet guide SG2, and a sheet conveying belt BH are supported on the slide frame Fs.

The roll support lever Lr is a rotatable lever that supports the transfer roll T and the transfer roll cleaner CLt. The roll support lever Lr is rotated by a motor (not shown) to move the transfer roll T between a transfer position in contact with the image carrier PR and a jam processing position away from the image carrier PR.
The post-transfer sheet guide SG2 guides the recording sheet S that has passed through the transfer area Q3, which is a contact area of the transfer roll T and the image carrier PR, to the downstream sheet conveyance belt BH.

Below the slide frame Fs, a first paper feed tray TR1 for storing the recording sheet S, an intermediate tray TR0 used for duplex copying, a second paper feed tray TR2, and a third paper feed tray TR3 are detachable. It is stored in. The intermediate tray TR0 is a tray that is used when the recording sheet S that has been copied for the first time is reversed and retransmitted to the transfer area Q3 during duplex copying or the like.
A manual feed tray TRt is provided at an upper right position of the first paper feed tray TR1. Each recording sheet S sent out from the manual feed tray TRt or each of the paper feed trays TR0 to TR3 is transported to the transfer region Q3 through the first sheet transport path SH1.

The recording sheets S accommodated in the paper feed trays TR0 to TR3 are taken out by the pickup roll Rp at a predetermined timing, separated one by one by the separation roll Rs, conveyed by a plurality of conveying rolls Ra, and conveyed to the registration roll Rr. Is done. The recording sheet S conveyed to the registration roll Rr is conveyed from the pre-transfer sheet guide SG1 to the transfer area Q3 in time with the toner image on the image carrier PR moving to the transfer area Q3.
In the transfer area Q3, the transfer roll T transfers the toner image on the image carrier PR to the recording sheet S. Residual toner is removed from the surface of the image carrier PR after transfer by an image carrier cleaner CLp. The transfer roll T collects surface-adhered toner by a transfer roll cleaner CLt.

The recording sheet S to which the toner image has been transferred is conveyed to the fixing area Q4 by the post-transfer sheet guide SG2 and the sheet conveying belt BH, and is constituted by a heating roll Fh and a pressure roll Fp when passing through the fixing area Q4. Heat fixing is performed by a fixing device F having a pair of fixing rolls. The recording sheet S on which the toner image is fixed is conveyed to the sheet discharge path SH2 or the sheet reversal path SH3 by the conveyance path switching gate GT1. The recording sheet S conveyed to the sheet discharge path SH2 is discharged to the recording sheet discharge tray TRh by the conveyance roll Ra and the discharge roll Rh, and the recording sheet S conveyed to the sheet reversing path SH3 is reversed and then conveyed to the intermediate tray TR0. Is done.
A sheet conveying apparatus SH is constituted by the sheet conveying path SH1, the sheet discharging path SH2, the sheet reversing path SH3, and the elements indicated by the symbols Rp, Rs, Rr, SG1, SG2, BH, Ra and the like.

(Developer G)
FIG. 2 is an enlarged explanatory view of the developing device which is a main part of FIG.
FIG. 3 is a perspective view of a developing device as a main part of the developing device.
4 is an enlarged explanatory view of the developer replenishment port portion and the developer discharge port portion of the developing device shown in FIG. 3, and is a partial cross-sectional view seen from the arrow IV direction of FIG.
5 is an explanatory view of the developing device, FIG. 5A is a sectional view taken along the line VA-VA of FIG. 4, FIG. 5B is a sectional view taken along the line VB-VB of FIG. 4, and FIG. It is.
FIG. 6 is a block diagram of the developing device and its drive circuit.
2 to 5, a developing device G disposed opposite to the image carrier PR in the developing region Q2 includes a developing container that contains a two-component developer composed of a negatively chargeable toner and a positively chargeable magnetic carrier. V.
In FIG. 3, the developing container V includes a developing container main body 1 and a front connection member 2 connected to a front end (X end) and a rear end (−X end) of the developing container main body 1 (see FIGS. 3 and 5A). And a rear connection member 3. The front connection member 2 has a front upper connection member 2a and a front lower connection member 2b, and the rear connection member 3 has a rear upper connection member 3a and a rear lower connection member 3b.
In FIG. 3, a pair of supported portions 1 a and 1 a are provided on the upper portions of the front end and the rear end of the developing container main body 1, respectively, and the developing container V is mounted inside the image forming apparatus U. At this time, each supported portion 1a is supported by a frame (not shown) of the image forming apparatus U.

In FIG. 5, the developing container V formed by the developing container main body 1, the front connecting member 2 and the rear connecting member 3 (see FIG. 3) contains a developing roll (developer conveying member) R0 inside. Roll accommodating portion V0, upper developer circulation conveyance path V1 that accommodates upper stirring conveyance member R1, lower developer circulation conveyance path V2 that accommodates lower stirring conveyance member R2, and stirring member (residual developer stirring member) ) A stirring member accommodating portion V3 for accommodating R3. The upper developer circulation conveyance path V1 and the lower developer circulation conveyance path V2 are also formed inside the front connection member 2 and the rear connection member 3.
The developing roll R0 includes a magnet roll R0a and a rotatable developing sleeve (developer conveying sleeve) R0b that covers the outer surface of the magnet roll R0a.

A partition wall 4 (see FIG. 5) is provided between the stirring and conveying members R1 and R2. The upper developer circulation transport path V1 and the lower developer circulation transport path V2 are vertically partitioned by a partition wall 4. The upper developer circulation conveyance path V1 and the lower developer circulation conveyance path V2 constitute a developer circulation conveyance path (V1 + V2). Further, the upper stirring and conveying member R1 and the lower stirring and conveying member R2 constitute an agitating and conveying member (R1 + R2).
At the front end portion and the rear end portion of the partition wall 4, communication ports 4a and 4b (only 4a is shown in FIG. 4) for communicating the upper developer circulation conveyance path V1 and the lower developer circulation conveyance path V2 are formed. The developer in the developing container V is stirred while being circulated by the stirring and conveying members R1 and R2.

5A and 5B, a stirring member R3 (see FIG. 5B) is disposed between the stirring and conveying member R2 and the developing roll R0. The agitating member R3 is a member for agitating and conveying the developer staying between the agitating and conveying member R2 and the developing roll R0.
2 to 4, a developer replenishing port 6 is formed at the upper front end portion of the front upper connecting member 2a. 3, 4, and 5A, a developer discharge port 7 is formed on the side surface of the front upper connecting member 2a. The developer discharge port 7 is located upstream in the transport direction (rear side) from the position of the developer supply port 6 in order to reduce the rate at which new developer supplied from the developer supply port 6 is discharged immediately after supply. It is formed on the end side.
In FIG. 5B, a layer thickness regulating member 8 for regulating the layer thickness of the developer on the developing roll R0 is disposed in the developing container V.
Developing elements V (1 to 8) in this embodiment are constituted by the elements indicated by the reference numerals 1 to 8.

  3 and 5C, a gear G0 is attached to the rear end (-X end) of the shaft of the developing roll R0, and the rear ends of the shafts of the stirring and conveying members R1 and R2 and the stirring member R3 are provided. Gears G1, G2, and G3 are mounted. The gear G0 and the gear G1 are meshed with each other through an intermediate gear G4. The gears G1, G2, and G3 are meshed sequentially. During the developing operation, the rotational force of the main motor motor M1 (see FIG. 6) is sequentially transmitted to the gears G0, G4, G1, G2, G3, etc., and the developing sleeve R0b (see FIG. 5) of the developing roll R0 is stirred and conveyed. The members R1, R2 and the stirring member R3 are driven to rotate.

2 and 6, a developer supply cylinder support member 11 is disposed above the developer supply port 6 of the developer container V. A developer supply cylinder 12 is connected to the developer supply cylinder support member 11, and the inside of the developer supply cylinder 12 is connected to the developer supply port 6 of the developer container V via the developer supply cylinder support member 11. Communicate with.
Inside the developer supply cylinder 12, a supply developer transport member R4 is rotatably arranged. A gear G5 (see FIG. 2) is fixed to one end of the rotation shaft of the replenishment developer transport member R4, and the replenishment developer transport member R4 is rotationally driven by a developer replenishment motor M2 that meshes with the gear G5. It has become so.

A developer supply case 14 is disposed above the developing container V. The developer supply case 14 includes a developer storage container 16 in which a two-component developer having a high toner concentration (hereinafter referred to as “high concentration developer”) is stored, and a developer stirring container 17 provided below the developer storage container 16. ing. The high-concentration developer supplied from the developer storage container 16 to the developer stirring container 17 is stirred while circulating in the developer stirring container 17 and supplied to the developer supply cylinder 12 from the supply cylinder connection port 17a. .
A developer replenishing device (11-17 + G5) is constituted by the components indicated by the reference numerals 11-17, G5.
The high-concentration developer supplied from the developer storage container 16 into the developer supply cylinder 12 is transported by the replenishment developer transport member R4 that is driven to rotate, and is replenished into the developer container V from the developer supply port 6. It has become so.
The replenishment control of the high-density developer is performed based on the detection value of the toner image density sensor SN2 (see FIGS. 1 and 7) that detects the density of the density detection toner image Tn formed on the image carrier PR during normal use. Done accordingly.

3 and 5A, a developer storage chamber 21 for discharge is arranged outside the developer discharge port 7 of the developer container V.
A storage chamber developer sensor SNk is provided on the upper surface of the outer wall of the discharge developer storage chamber 21. The discharge developer storage chamber 21 is connected to a front end (X end) of a discharge developer transport cylinder 22, and a rear end (−X end) of the discharge developer transport cylinder 22. ) Is connected to a discharged developer recovery tank 23 (see FIG. 3). A developer discharge path 22a (see FIG. 5) is formed inside the discharge developer transport cylinder 22.
In FIG. 3, a discharged developer transport member R <b> 5 is disposed in the developer discharge path 22 a inside the discharge developer transport cylinder 22. The developer discharge path 22a and the discharged developer transport member R5 constitute a stored developer transport device (22a + R5).
The discharging of the developer is performed by the detection value of the toner concentration sensor SN1 (toner concentration detecting means) (see FIG. 4) in the developing container.

  3 and 5C, a gear G6 is attached to the rear end portion of the rotating shaft of the discharged developer conveying member R5, and the gear G6 is rotated by the developer discharging motor M3 shown in FIGS. Driven. When the gear G6 rotates, the discharged developer transport member R5 rotates. The excess developer discharged from the developer discharge port 7 into the discharge developer transfer cylinder 22 through the discharge developer storage chamber 21 by the rotation of the discharge developer transfer member R5 is collected in the discharge developer recovery. It is conveyed to the tank 23.

FIG. 7 is a block diagram of a control unit of the image forming apparatus including the developing device according to the first exemplary embodiment of the present invention.
In FIG. 7, the controller C stores an I / O (input / output interface) that performs input / output of signals to / from the outside and adjustment of input / output signal levels, programs and data for performing necessary processing, and the like. ROM (read-only memory), RAM (random access memory) for temporarily storing necessary data, CPU (central processing unit) that performs processing according to the program stored in the ROM, clock oscillator, etc. Various functions can be realized by executing a program stored in the ROM.

(Signal input element connected to the controller C)
The controller C is supplied with output signals such as the following signal output elements UI, SN1, SN2, and SNk.
UI: User Interface The user interface UI includes a display unit UI1, a copy start key UI2, a copy number input key UI3, a numeric keypad UI4, and the like.

SN1: toner density sensor in developing container (toner density detection means)
The toner density sensor SN1 in the developing container detects the toner density of the two-component developer in the developing container.
SN2: Toner Image Density Sensor The toner image density sensor SN2 detects the density of the toner patch Tn formed on the surface of the image carrier PR.
SNk: storage chamber developer sensor (stored developer detection means)
The storage chamber developer sensor SNk detects the stored developer in the discharged developer storage chamber 21.

(Controlled element connected to controller C)
The controller C outputs a control signal for the next controlled element.
IPS: Image Processing System The image processing system IPS converts the read image signal input from the CCD into a digital image write signal and outputs it to the laser drive signal output circuit DL.
DL: Laser driving circuit The laser driving circuit DL drives a laser diode LD of a ROS (latent image forming apparatus) to form an electrostatic latent image on the surface of the image carrier PR.
D1: Main motor driving circuit The main motor driving circuit D1 drives the main motor M1 to drive the developing roll R0, the image carrier PR, the charging roll CR, the transfer roll Rt, and the fixing of the developing device G through the gear G0 and the like. The heating roll Fh of the apparatus F is driven to rotate.

E: Power supply circuit The power supply circuit E has the following power supply circuit.
E1: Development bias power supply circuit The development bias power supply circuit E1 applies a development bias to the development sleeve R0b of the development roll R0 of the development device G.
E2: Charging power supply circuit The charging power supply circuit E2 applies a charging bias to the charging roll CR.
E3: Transfer Power Supply Circuit The transfer power supply circuit E3 applies a transfer bias to the transfer roll Rt.
E4: Power Supply Circuit for Fixing The power supply circuit for fixing E4 supplies heating power to the heating roll Fh.

D2: Developer replenishment motor drive circuit The developer replenishment motor drive circuit D2 drives the developer replenishment motor M2 to rotationally drive the replenishment developer transport member R4 of the developing device G via the gear G5. .
D3: Developer discharge motor drive circuit The developer discharge motor drive circuit D3 drives the developer discharge motor M3 to rotationally drive the discharged developer transport member R5 of the developing device G via the gear G6. The developer discharge motor drive circuit D3, the developer discharge motor M3, and the like constitute a discharge drive device (D3 + M3).

(Function of the controller C)
The controller C has a program (function realization means) that realizes a function of executing a process according to an output signal from each signal output element and outputting a control signal to each control element. Next, a program (function realization means) for realizing various functions of the controller C will be described.
C1: Main motor rotation control means The main motor rotation control means C1 controls the operation of the main motor drive circuit D1, and the image carrier PR and the developing roll R0 of the developing device G control the rotation of the fixing device F and the like. .
C2: Power supply circuit control means The power supply circuit control means C2 includes the following means C2a to C2d, and controls the power supply circuit E to control the development bias, charging bias, transfer bias, and heater of the heating roll Fh. Control on-off etc.
C2a: Development Bias Control Unit The development bias control unit C2a applies a bias to the development roll R0 of the development unit G by controlling the operation of the development bias setting unit according to the toner density and the development bias power supply circuit E1.
C2a1: Development bias setting means according to toner density The development bias setting means C2a1 according to toner density is based on the developer density sensor detected value Tc detected by the toner density sensor SN1 in the development container. C2b for setting the developing bias to be applied to the G developing roll R0: charging bias control means The charging bias control means C2b controls the operation of the power supply circuit E2 for charging bias to control the charging bias applied to the charging roll CR. .

C2c: Transfer Bias Control Unit The transfer bias control unit C2c applies a transfer bias to be applied to the transfer roll Rt by controlling the operation of the transfer power supply circuit E3.
C2d: Fixing power supply control means The fixing power supply control means C2d controls the operation of the fixing power supply circuit E4 to turn on and off the heater of the heating roll Fh.

C3: Latent image formation control means The latent image formation control means C3 controls the operation of the laser drive circuit DL to drive the laser diode LD (see FIG. 1) of the ROS (latent image formation apparatus) to emit the laser beam L. The surface of the image carrier PR is irradiated to form an electrostatic latent image.
C4: Toner density discrimination means The toner density discrimination means C4 has a toner density upper limit value storage means C4a and a toner density lower limit value storage means C4b, and the toner in the developing device outputted from the toner density sensor SN1 in the developing container. It is determined whether the density sensor detection value Tc is within a set range (a range between the lower limit value and the upper limit value) or exceeds the upper limit value or the lower limit value.
C4a: Toner density upper limit storage means The toner density upper limit storage means C4a stores the toner density upper limit value Tc2 in the developing container.
C4b: Toner density lower limit value storage means The toner density upper limit value lower limit storage means C4b stores the toner density lower limit value Tc1 in the developing container.

C5: Toner patch density determination means The toner patch determination storage means C5 has a patch density upper limit value storage means C5a and a patch density lower limit value storage means C5b, and the density of the toner patch Tn output from the toner image density sensor SN2. It is determined from the detection signal whether the toner patch density Pc is within a set range or exceeds an upper limit value or a lower limit value.
C5a: Patch Density Upper Limit Value Storage Unit The patch density upper limit storage unit C5a stores a normal upper limit value Pc2 of the toner patch density Pc.
C5b: Patch Density Lower Limit Value Storage Unit The patch density lower limit value storage unit C5b stores a normal lower limit value Pc1 of the toner patch density Pc.
C6: Toner consumption detection means The toner consumption detection means C6 detects the toner consumption by counting the number of beam irradiation dots in the image data developed in the page memory PM in the IPS (image processing system).

C7: Developer replenishment control means The developer replenishment control means C7 has an additional developer replenishment amount storage means C7a and a developer replenishment amount calculation means C7b according to the toner consumption amount, and the developer replenishment motor M2 The developer replenishment amount is controlled by controlling this operation.
C7a: Additional developer replenishment amount storage means The additional developer replenishment amount storage means C7a detects the consumed amount when the toner patch density Pc detected by the toner image density sensor SN2 is lower than the toner patch density lower limit Pc1. The additional developer supply amount to be supplied in addition to the developer supply amount determined in accordance with is stored.
C7b: Developer replenishment amount calculation means according to toner consumption amount Developer replenishment amount calculation means C7b according to toner consumption amount calculates a developer replenishment amount according to the detection result of the toner consumption amount detection means C6.
C8: Developer Discharge Control Unit The developer discharge control unit C8 includes a stored developer detection unit C8a and a discharge conveyance member rotation time set value storage unit C8b, and controls the developer discharge motor drive circuit D3. And the discharged developer transport member R5 is driven to control the discharge speed of the stored developer in the discharged developer storage chamber 21.
C8a: Retained developer detecting means Retained developer detecting means C8a detects whether or not the developer to be discharged is stored in the discharged developer storage chamber 21 according to the detection signal of the storage chamber developer sensor SNk. To do.
C8b: discharge conveyance member rotation time set value storage means The discharge conveyance member rotation time set value storage means C8b stores the rotation time set value of the discharged developer conveyance member R5.

(Description of Flowchart of Embodiment 1)
(Developer supply control)
FIG. 8 is a flowchart of developer replenishment control according to the first embodiment of the present invention.
The processing of each ST (step) in the flowchart of FIG. 8 is performed according to a program stored in the ROM or hard disk of the controller C. This process is executed in a multitasking manner in parallel with other various processes of the image forming apparatus U. Note that the developer supply control process of FIG. 8 is common to the first embodiment and the second to fifth embodiments to be described later.
The flow of developer supply control shown in FIG. 8 is started when the image forming apparatus U is turned on.
In ST (step) 1 of FIG. 8, it is determined whether or not there is a job start instruction. If no (N), ST1 is repeatedly executed, and if yes (Y), the process proceeds to ST2.

In ST2, it is determined whether or not the toner patch (toner image for toner image density detection) Tn (see FIG. 1) formed on the image carrier PR has reached the density detection position. The toner patch Tn is created at the start of a job and every time a predetermined number (for example, four) of toner images are formed during job execution. In ST2, if no (N), ST2 is repeatedly executed, and if yes (Y), the process proceeds to ST3.
In ST3, the toner patch density Pc of the toner patch Tn is detected.
In ST4, it is determined whether or not the toner patch density Pc is lower than the toner patch density lower limit Pc1. For example, when the target density Pc0 of the toner patch density Pc is set to 50%, the toner patch density lower limit value Pc1 = 45% is set. If yes (Y), proceed to ST5.

Next, in ST5, a developer obtained by adding an additional developer supply amount to a developer supply amount corresponding to the toner consumption amount is supplied. That is, when the actually detected toner patch density Pc of the toner image created with the target toner patch density Pc0 = 50% is Pc <Pc1 (= 45%), the developer replenishment amount corresponding to the toner consumption amount is Replenish the amount of developer plus the additional developer replenishment amount.
In ST6, it is determined whether or not the next created toner patch Tn has reached the density detection position. If yes (Y), the process returns to ST3. If no (N), the process proceeds to ST7.
In ST7, it is determined whether or not the job is finished. If no (N), the process returns to ST5. If yes (Y), the process returns to ST1.
If no (N) in ST4, the process proceeds to ST8.

In ST8, it is determined whether or not the toner patch density Pc is Pc> Pc2 (= 55%) with respect to the toner patch density upper limit value Pc2 (for example, Pc2 = 55%). In the case of yes (Y), the detected toner patch density Pc is Pc> 55%, which is sufficiently higher than the target value Pc0 (= 50%), so there is no need to replenish toner. In this case, the process proceeds to ST9.
In ST9, it is determined whether or not the next created toner patch Tn has reached the density detection position. If yes (Y), return to ST3. If no (N), the process moves to ST10.
In ST10, it is determined whether or not the job is finished. If no (N), the process returns to ST9. If yes (Y), the process returns to ST1.

In the case of NO (N) in ST8, the detected toner patch density Pc is Pc1 (= 45%) ≦ Pc ≦ Pc2 (= 55%). In this case, it means that the detected toner patch density Pc is within a predetermined range (± 5% range) with respect to the target value. In this case, a developer corresponding to the toner consumption may be replenished. If no (N) in ST8, the process proceeds to ST11.
In ST11, a developer corresponding to the toner consumption is replenished.
In ST12, it is determined whether the next created toner patch Tn has reached the density detection position. If yes (Y), the process returns to ST3. If no (N), the process proceeds to ST13.
In ST13, it is determined whether or not the job is finished. If no (N), the process returns to ST11. If yes (Y), return to ST1.

(Development bias setting process)
FIG. 9 is a flowchart of the developing bias setting process.
The processing of each ST (step) in the flowchart of FIG. 9 is performed according to a program stored in the ROM or hard disk of the controller C. This process is executed in a multitasking manner in parallel with other various processes of the image forming apparatus U. The developing bias setting process in FIG. 9 is common to Examples 2 to 5 described later.
The development bias setting process shown in FIG. 9 is started when the image forming apparatus U is turned on.

In ST21, it is determined whether or not there is a job start instruction. If no (N), ST21 is repeatedly executed. If yes (Y), the process proceeds to ST22.
Whether or not the toner concentration sensor detection value Tc in the developing device detected by the toner concentration sensor SN1 in ST22 is Tc <Tc1 (= 6%) with respect to the toner concentration lower limit value Tc1 (= 6%) in the developing device. Judge. If no (N), the process moves to ST24, and if yes (Y), the process moves to ST23.
In ST23, the value of the developing bias Vd is set to the developing bias set value Vd1 (Vd1 = −550V). When Vd = Vd1 = −550V, the image portion potential Vb (= −300V) on the surface of the image carrier PR is Vb−Vd1 = −300 − (− 550) with respect to the development bias setting value Vd = Vd1−550V. = + 250V. If the answer is yes (Y) in ST22, the toner concentration Tc in the developing device is low, and the charging potential of the toner becomes high. In this case, only a small amount of toner having a high charging potential moves to the image portion on the surface of the image carrier PR, and the potential of the image portion and the surface of the developing roll becomes the same. Therefore, in ST23, the developing bias is increased, and the amount of toner that moves from the surface of the developing roll R0 to the image portion on the surface of the image carrier PR is reduced. As a result, the toner patch density Pc is temporarily lowered, and the developer replenishment control shown in FIG. 8 increases the developer replenishment, resulting in an operation of returning to Tc> Tc1. Next, the process proceeds to ST27.

In ST24, it is determined whether or not the toner density sensor detection value Tc in the developing unit is Tc> Tc2 (= 16%) with respect to the toner density upper limit value Tc2 (= 16%) in the developing unit. In the case of no (N), Tc1 ≦ Tc ≦ Tc2, and the process proceeds to ST26. If yes (Y), the process moves to ST25.
In ST25, the value of the developing bias Vd is set to the developing bias set value Vd2 (Vd2 = −450 V). When Vd = Vd2 = −450V, the image portion potential Vb (= −300V) on the surface of the image carrier PR is Vb−Vd2 = −300 − (− 450 with respect to the developing bias setting value Vd = Vd2 = −450V. ) = + 150V. In the case of YES (Y) in ST24, since the toner concentration Tc in the developing device is high, the charging potential of the toner is low. In this case, unless the toner having a low charging potential moves to the image portion on the surface of the image carrier PR, the potential on the image portion and the surface of the developing roll is not the same. Accordingly, in ST25, the developing bias is reduced and the amount of toner that moves from the surface of the developing roll R0 to the image portion on the surface of the image carrier PR is increased. As a result, the toner patch density Pc temporarily increases, and the developer replenishment control shown in FIG. 8 reduces the developer replenishment, resulting in an operation of returning to Tc <Tc2. Next, the process proceeds to ST27.

In ST26, the value of the developing bias Vd is set to the developing bias set value Vd0 (Vd0 = −500V). In the first embodiment, the set value (target value) Va of the surface background potential of the image carrier PR (the potential of the portion not exposed by the laser beam) is Va = −700 V, and the surface image portion potential of the image carrier PR (with the laser beam). The set value (target value) Vb of the potential of the exposed portion is Vb = −300V. In this case, the image portion potential Vb (= −300 V) on the surface of the image carrier PR is Vb−Vd 0 = −300 − (− 500) = + 200 V with respect to the development bias setting value Vd = Vd 0 = −500 V. In this case, in the developing region Q2, the − (minus) charged toner adhering to the surface of the developing roll R0 moves to the image portion on the surface of the image carrier PR.
In ST27, it is determined whether or not the job is finished. If yes (Y), the process returns to ST21. If no (N), the process returns to ST22.

(Discharge control)
FIG. 10 is a flowchart of the discharge control according to the first embodiment.
In ST31 of FIG. 10, it is determined whether or not there is a job start instruction. If no (N), ST31 is repeatedly executed. If yes (Y), the process proceeds to ST32.
In ST32, the storage chamber developer sensor SNk determines whether or not the developer is detected. If no (N), ST32 is repeatedly executed. If yes (Y), the process proceeds to ST33.
In ST33, the discharged developer transport member R5 is rotated for a time Th (= 3 seconds), and the developer is discharged from the discharge developer storage chamber 21. The time Th is the time required to discharge all the developer in the storage chamber 21 from the storage chamber 21.
In ST34, it is determined whether or not the job is finished. If no (N), the process returns to ST32. If yes (Y), the process returns to ST31.

(Operation of Example 1)
In the developing device according to the first embodiment having the above-described configuration, the developer is replenished according to the toner consumption amount and the image density of the toner patch Tn, so that the developer replenishment control in the developing container V is simple. Further, since the developing bias Vd is set according to the toner density Tc in the developing container, the developing bias Vd can be easily controlled.
The developer discharge control is performed when the storage chamber 21 detects that a predetermined amount of developer has been stored in the storage chamber 21 in which the developer discharged from the developer discharge port 7 of the developer container is stored. Therefore, the developer discharge control is easy.
When the time until the predetermined amount of developer is stored in the storage chamber 21 is short, the amount of developer in the developing container V is small when the time is long. Therefore, when it is detected that a predetermined amount of developer has been stored in the storage chamber 21, the developer in the storage chamber 21 is discharged from the storage chamber 21 to thereby store the developer in the developer container V. When the amount of developer is large, the amount of developer discharged from the developer container V to the storage chamber 21 increases, so the developer discharge speed (discharge amount per unit time) is increased, and the developer in the developer container V is increased. When the amount is small, the amount of developer discharged from the developing container V through the storage chamber 21 decreases, so that the developer discharging speed decreases. Therefore, the discharge control of the developer in the developing container V is easy, and the amount of the developer in the developing container V can be appropriately maintained.

(Example 2)
The developer supply control and the development bias setting process of the second embodiment are the same as the developer supply control shown in FIG. 8 and the development bias setting process shown in FIG. 9 of the first embodiment. The developer discharge control of Embodiment 2 (see FIG. 12) is different from the developer discharge control of Embodiment 1 (see FIG. 10).
(Explanation of controller C function)
FIG. 11 is a block diagram of the control unit of the image forming apparatus including the developing device according to the second embodiment, and corresponds to FIG. 7 of the first embodiment.

In FIG. 11, the controller C of the second embodiment is added with the following functions (means) compared to the controller c of the first embodiment. Other functions, signal input elements, and control elements are the same as those in the first embodiment.
C4c: Threshold storage means The threshold storage means C4c stores a threshold value Tc3 for developer discharge prevention control for preventing discharge of the developer stored in the discharge developer storage chamber 21.
C8c: Developer discharge prevention time set value storage means Developer discharge prevention time set value storage means C8c is a developer discharge prevention time set value TM1a (for example, TM1a = 5 seconds) which is the operation time of the developer discharge prevention control. Remember.
TM1: Developer discharge prevention time measurement timer The developer discharge prevention time measurement timer TM1 measures the developer discharge prevention time set value TM1a (= 5 seconds) set by the controller C.

(Explanation of flowchart)
FIG. 12 is a flowchart of the discharge control of the second embodiment, and corresponds to the flowchart of FIG. 10 of the first embodiment.
In the flowchart of the second embodiment of FIG. 12, the processes of ST32a to ST32c are added between ST32 and ST33 of the flowchart of the first embodiment of FIG. Other processes in the second embodiment shown in FIG. 12 are the same as those in the first embodiment shown in FIG. In the description of the flowchart of FIG. 12, the description of the same ST (step) as that of the first embodiment is omitted.
If yes (Y) in ST32, the process proceeds to ST32a.
In ST32a, it is determined whether or not the toner concentration Tc in the developing container is equal to or higher than the developer discharge prevention control threshold Tc3. If no (N), the process moves to ST33. If yes (Y), the process proceeds to ST32b.
In ST32b, the developer discharge prevention time setting value TM1a is set in the developer discharge prevention time measurement timer TM1.
In ST32c, it is determined whether or not the developer discharge prevention time measurement timer TM1 has expired. If no (N), ST32c is repeatedly executed. If yes (Y), proceed to ST33.

(Operation of Example 2)
In the second embodiment, when the storage chamber developer sensor SNk detects the developer, and the toner concentration Tc in the developing container V is Tc <Tc3 (= 12%), the developer in the storage chamber 21 immediately. Execute the discharge.
However, when the toner concentration Tc in the developing container V is Tc ≧ Tc3 (= 12%), the discharged developer is conveyed after the time TM1a (for example, TM1a = 5 seconds) set in the timer TM1 has elapsed. The member R5 is rotated for a set time Th (= 3 seconds). Therefore, during the time TM1a (= 5 seconds) set in the timer TM1, the developer discharge port 7 is held closed by the developer stored in the developer storage chamber 21. Therefore, the developer is prevented from being discharged from the developer discharge port 7 during the time TM1a.
By such control, when the toner concentration Tc in the developing container V is high, it is possible to prevent the developer having a high concentration from being discharged unnecessarily as compared with the case where the toner concentration Tc is low. By performing such developer discharge control, the second embodiment can perform the developer discharge control for various developing devices more appropriately than the first embodiment.

(Example 3)
(Explanation of controller C function)
The developer replenishment control and the development bias setting process of the third embodiment are the same as the developer replenishment control shown in FIG. 8 and the development bias setting process of FIG. The developer discharge control of Embodiment 3 (see FIG. 14) is different from the developer discharge control of Embodiment 2 (see FIG. 12).
FIG. 13 is a block diagram of a control unit of an image forming apparatus including the developing device according to the third embodiment, and corresponds to FIG. 11 according to the second embodiment.
In FIG. 13, the controller C of the third embodiment is added with the following functions (means) compared to the controller c of the second embodiment. Other functions, signal input elements, and control elements are the same as those in the second embodiment.
C8d: Discharge / conveying member rotation time setting unit according to toner density The discharging / conveying member rotation time setting unit C8d according to toner density rotates the discharged developer conveying member R5 based on the detection signal of the toner concentration sensor SN1 in the developing container. Time, that is, the discharge time of the developer stored in the discharge developer storage chamber 21 is set.

(Explanation of flowchart)
FIG. 14 is a flowchart of the discharge control of the third embodiment, and corresponds to the flowchart of FIG. 12 of the second embodiment.
In the flowchart of the third embodiment shown in FIG. 14, processes of ST32d, ST32e, and ST33a to ST33c are provided instead of ST33 of the flowchart of the second embodiment shown in FIG. Other processes in the third embodiment shown in FIG. 14 are the same as those in the second embodiment shown in FIG. In the description of the flowchart in FIG. 14, the description of the same ST (step) as that of the second embodiment is omitted.
When ST32a in FIG. 14 is NO (N) (when the toner concentration Tc in the developing container is equal to or greater than the developer discharge prevention control threshold Tc3 (= 12%)) and when ST32c is YES (Y) (timer TM1 is timed) Move up to ST32d.

In ST32d, it is determined whether or not the toner density Tc in the developing container is lower than the normal toner density lower limit value Tc1 (= 6%). If yes (Y), the process proceeds to ST33a.
In ST33a, the discharged developer transport member R5 is rotated for a time Th1 (= 3 seconds). The time Th1 is set to the time (3 seconds) required to discharge all the developer in the storage chamber. Therefore, all the developer accumulated in the storage chamber 21 is discharged by the rotation of the time Th1. Next, the process proceeds to ST34.
If no (N) in ST32d, the process proceeds to ST32e.
In ST32e, it is determined whether or not the toner density Tc in the developing container is higher than the normal toner density upper limit value Tc2 (= 16%). If yes (Y), the process proceeds to ST33b.

In ST33b, the discharged developer conveying member R5 is rotated for a time Th2 (= 1 second). The time Th2 is set to (1/3) Th1, that is, 1 second. Accordingly, 1/3 of the developer accumulated in the storage chamber 21 by the rotation of the time Th2 is discharged. Next, the process proceeds to ST34.
If no (N) in ST32e, the process proceeds to ST33c.
In ST33c, the discharged developer transport member R5 is rotated by time Th0 = (2/3) Th1 = (2/3) × 3 seconds = 2 seconds. That is, the time Th0 is set to (2/3) Th1 = 2 seconds. Therefore, 2/3 of the developer accumulated in the storage chamber 21 is discharged by the rotation of the time Th0 (= 2 seconds). Next, the process proceeds to ST34.

(Operation of Example 3)
In the third embodiment, similarly to the second embodiment, when the toner concentration Tc in the developing container V is Tc ≧ Tc3 (= 12%), the time TM1a set in the timer TM1 (for example, TM1a = 5 seconds) ), The discharged developer conveying member R5 is rotated for a set time Th (= 3 seconds), so that the same effect as in the second embodiment is obtained.
In the third embodiment, when the toner concentration Tc in the developing container is Tc1 <Tc1 (= 6%), the discharged developer conveying member R5 is rotated only for the time Th1 (= 3 seconds), so that the inside of the storage chamber 21 All of the discharged toner is discharged from the storage chamber 21. Further, when the toner concentration Tc in the developing container is Tc1> Tc2 (= 16%), the discharged developer conveying member R5 is rotated only for the time Th2 (= 1 second), and 1/3 of the discharged toner in the storage chamber 21 is obtained. Is discharged from the storage chamber 21.
Further, when the toner concentration Tc in the developing container is Tc1 (= 6%) ≦ Tc ≦ Tc2 (= 16%), the discharged developer conveying member R5 is rotated for the time Th0 (= 2 seconds), and the inside of the storage chamber 21 is rotated. 2/3 of the discharged toner is discharged from the storage chamber 21.
Therefore, when the toner concentration Tc in the developing container V is high, the developer discharging speed can be reduced compared to when the developing container V is low, so that the developer having a high toner concentration can be prevented from being discharged wastefully.
By performing such developer discharge control, the third embodiment can more appropriately perform the developer discharge control for various developing devices as compared with the second embodiment.

Example 4
The developer replenishment control and the development bias setting process of the fourth embodiment are the same as the developer replenishment control shown in FIG. 8 and the development bias setting process shown in FIG. 9 of the first embodiment. The developer discharge control of Embodiment 2 (see FIG. 12) is different from the developer discharge control of Embodiment 1 (see FIG. 10).
(Explanation of controller C function)
The developer supply control and the development bias setting process of the fourth embodiment are the same as the developer supply control shown in FIG. 8 and the development bias setting process shown in FIG. The developer discharge control of Embodiment 4 (see FIG. 16) is different from the developer discharge control of Embodiment 2 (see FIG. 12).
FIG. 15 is a block diagram of a control unit of an image forming apparatus including the developing device according to the fourth embodiment, and corresponds to FIG. 11 according to the second embodiment.
In FIG. 15, the controller C of the fourth embodiment has the following functions (means) added to the controller c of the second embodiment. Other functions, signal input elements, and control elements are the same as those in the second embodiment.
TM2: Discharge member stop time measurement timer The discharge member stop time measurement timer TM2 measures a discharge member stop time set value TM2a (for example, TM2a = 3 seconds).
n: Discharge member rotation frequency counter The discharge member rotation frequency counter n counts the number of discharge developer transport operations performed by the discharge developer transport member R5.

(Explanation of flowchart)
FIG. 16 is a flowchart of the discharge control of the fourth embodiment, and corresponds to the flowchart of FIG. 12 of the second embodiment.
In the flowchart of Embodiment 4 in FIG. 16, ST33 'is provided instead of ST33 in the flowchart of Embodiment 2 in FIG. 12, and ST41 to ST47 are added. The processing of ST41 to ST46 is executed when no (N) in ST32, and the processing of ST47 is executed after ST34. Other processes in the third embodiment shown in FIG. 16 are the same as those in the second embodiment shown in FIG. In the description of the flowchart of FIG. 16, the description of the same ST (step) as that of the second embodiment is omitted.
In ST32c of FIG. 16, if yes (Y), the process moves to ST33 '.
In ST33 ′, the following processing is executed.
(1) The discharged developer conveying member R5 is rotated for a time Th2.
(2) Set the discharge member rotation frequency counter n = 1.
(3) TM2a (= 3 seconds) is set in the discharge member stop time measurement timer TM2.
Next, the process proceeds to ST34.

If no (N) in ST32, the process proceeds to ST41.
In ST41, it is determined whether or not the discharge member rotation frequency counter n = 0. If yes (Y), the process returns to ST32. If no (N), the process moves to ST42.
In ST42, it is determined whether or not the discharge member stop time measurement timer TM2 has expired. If no (N), the process returns to ST32. If yes (Y), the process transfers to ST43.
In ST43, the following processing is executed.
(1) The discharged developer conveying member R5 is rotated for a time Th2 (= 1 second).
(2) The discharge member rotation frequency counter n = n + 1.
In ST44, it is determined whether or not the discharge member rotation frequency counter n = 3. If no (N), the process moves to ST45, and if yes (Y), the process moves to ST46.
In ST45, TM2a (3 seconds) is set in the discharging member stop time measuring timer TM2.
In ST46, the discharge member rotation frequency counter n = 0, that is, the rotation frequency is once reset.
After ST45 and ST46, it is determined in ST34 whether the job has been completed. If no (N), the process returns to ST32. If yes (Y), the process moves to ST47.
In ST47, the timer TM2 is stopped.
Next, the process returns to ST31.

(Operation of Example 4)
In the fourth embodiment, similarly to the second embodiment, when the toner concentration Tc in the developing container V is Tc ≧ Tc3 (= 12%), the time TM1a set in the timer TM1 (for example, TM1a = 5 seconds) ), The discharged developer transport member R5 is rotated, so that the same effect as in the second embodiment is obtained.
In the fourth embodiment, the discharged developer conveying member R5 is rotated by Th2 (= 1 second) in ST33 ', the count value n of the discharged member rotation frequency counter is set to n = 1, and the timer TM2 is set. Time TM2a (= 3 seconds) is set (first set).

After that, if the timer TM2 expires in ST42 before the storage chamber developer sensor SNk detects the developer in ST32, the discharged developer transport member R5 rotates by Th2 (= 1 second) in ST43. The count value n of the discharge member rotation frequency counter is set to n = n + 1 = 1 + 1 = 2. Next, when n is not n = 3 in ST44, time TM2a (= 3 seconds) is set (second set) in timer TM2 in ST45.
After that, if the timer TM2 expires in ST42 before the storage chamber developer sensor SNk detects the developer in ST32, the discharged developer transport member R5 rotates Th2 (= 1 second) in ST43 ( And the count value n of the discharge member rotation frequency counter is set to n = n + 1 = 2 + 1 = 3. Next, in ST44, when n is n = 3, n = 0 is set.

  In the fourth embodiment, when the storage chamber developer sensor SNk detects the developer in ST32, the developer in the storage chamber 21 is not discharged in one rotation as in the second embodiment, but the discharged developer. After the transport member R5 is rotated for 1 second and then stopped for a time TM2a (= 3 seconds), the developer in the storage chamber 21 is divided into three times and discharged. Therefore, it is possible to precisely control the developer discharge speed as compared with the second embodiment.

(Example 5)
The developer supply control and the development bias setting process of the fifth embodiment are the same as the developer supply control shown in FIG. 8 and the development bias setting process shown in FIG. 9 which are common to the first to fifth embodiments. . The developer discharge control of Embodiment 5 (see FIG. 18) is different from the developer discharge control of Embodiment 2 (see FIG. 12).
(Explanation of controller C function)
FIG. 17 is a block diagram of the control unit of the image forming apparatus including the developing device according to the fifth embodiment, and corresponds to FIG. 11 of the second embodiment.
In FIG. 17, the controller C of the fifth embodiment is added with the following functions (means) compared to the controller C of the second embodiment. Other functions, signal input elements, and control elements are the same as those in the second embodiment.

C8d: Discharge / conveying member rotation time setting unit according to toner density The discharging / conveying member rotation time setting unit C8d according to toner density rotates the discharged developer conveying member R5 based on the detection signal of the toner concentration sensor SN1 in the developing container. The time, that is, the discharge time Th of the developer stored in the discharge developer storage chamber 21 is set.
C9: Two-component developer replenishment weight integrated value storage means The two-component developer replenishment weight integrated value storage means C9 is for conveying the stored developer in the discharged developer storage chamber 21 to the discharged developer collection tank 23 side. The replenishment amount of the two-component developer from the developer replenishment port 7 from the time when the discharge driving device D3 + M3 is driven to the time when the discharge drive device D3 + M3 is driven next is accumulated and stored.
C10: Toner density theoretical value calculation means The toner density theoretical value calculation means C10 has a driving time toner density detection storage means C10a, and the toner density at the previous driving time of the discharge driving device D3 + M3 and the previous toner density. Based on the integrated value J1 of the replenishment amount of the two-component developer from the driving time point to the current driving time point, the toner concentration Tc4 at the previous driving time, and the reference value J0 of the developer amount in the developing container V, the current driving time point. The theoretical value Tc5 of the toner density is calculated.

C10a: Driving time toner density detection storage means The driving time toner density detection storage means C10a detects and stores the toner density at the time of driving the discharge driving device D3 + M3.
C11: Toner density change determining means The toner density change determining means C11 determines whether or not the detected toner density Tc at the current driving time is Tc <Tc5 with respect to the theoretical value Tc5.

(Explanation of flowchart)
FIG. 18 is a flowchart of the discharge control according to the fifth embodiment, and is a flowchart corresponding to FIG. 12 of the second embodiment.
The flowchart of Embodiment 5 in FIG. 18 differs from the flowchart of Embodiment 2 in FIG. 12 in the following points.
(1) ST51 to ST55 are provided between ST32 and ST32a in FIG.
(2) ST33 ″ is provided instead of ST33 in FIG.
Other processes in the fifth embodiment shown in FIG. 18 are the same as those in the second embodiment shown in FIG. In the description of each ST (step) in the flowchart of FIG. 18, detailed description of the same ST (step) as the ST (step) of FIG.

If yes (Y) in ST32 of FIG. 18, the process proceeds to ST51, and if no (N), ST32 is repeatedly executed.
In ST51, it is determined whether or not the developer detection by the SNk (storage chamber developer sensor) in ST32 is the first detection from the job start time. If yes (Y), the process proceeds to ST32a, and, if no (N), the process proceeds to ST52.
In ST52, the following processing is executed.
(1) Store the integrated value J1 of developer replenishment weight.
(2) The current toner density theoretical value Tc5 of the toner density Tc in the developing container is calculated from the integrated value J1 and the value of the toner density Tc4 at the previous discharge. A method for calculating Tc5 will be described later.

Next, the process proceeds to ST53.
In ST53, it is determined whether or not the toner density Tc in the developing container is Tc ≦ Tc5 with respect to the current toner density theoretical value Tc5. In the case of yes (Y), it means that the actual developer amount J in the developing container V is J ≦ J0 compared to the reference value J0. This will be described later.
In the case of YES (Y) in ST53, that is, when the developer amount J in the developer container V is small compared to the reference value J0 (when J ≦ J0), in order to set the developer discharge speed low, Move on to ST54.
In ST54, the discharge conveyance member rotation time set value Th is set to Th = Th2 (= 1 second). Next, the process proceeds to ST32a.

If the determination result in ST53 is NO (N), it means that the developer amount J in the developing container V is J> J0 compared to the reference value J0. This will be described later.
In the case of No (N) in ST53, that is, when the actual developer amount J in the developer container V is larger than the reference value J0 (when J> J0), the developer discharge speed is set high. Then, move to ST55.
In ST55, the discharge conveyance member rotation time set value Th is set to Th = Th1 (= 3 seconds). Next, the process proceeds to ST32a.

If no (N) in ST32a or yes (Y) in ST32c, the process proceeds to ST33 ″.
In ST33 ″, the following processing is executed.
(1) The discharged developer conveying member R5 is rotated for a time Th (Th = Th1 or Th2).
(2) The value of the toner concentration Tc in the developing container is stored as the previous discharge toner concentration Tc4.
(3) Start integration after setting the developer replenishment weight integrated value J1 to 0.
Next, the process proceeds to ST34.
In ST34, it is determined whether or not the job is finished. If no (N), return to ST32; if yes (Y), return to ST31

(Operation of Example 5)
In the fifth embodiment, similarly to the second embodiment, when the toner concentration Tc in the developing container V is Tc ≧ Tc3 (= 12%), the time TM1a set in the timer TM1 (for example, TM1a = 5 seconds) ), The discharged developer conveying member R5 is rotated for the set time Th, and thus the same operation as in the second embodiment is achieved.
In the fifth embodiment, the detected value Tc4 of the toner concentration in the developing container V at the previous rotation of the discharged developer conveying member R5, and the detected value Tc of the toner density in the developing container V at the current rotation. Depending on the integrated value J1 of the developer replenishment weight from the previous time to the current time and the developer weight reference value J0 in the developer container V, the set time Th is set to Th = Th1 (= 3 seconds) or Th = Th2 ( = 1 second).

The following explanations of (1) and (2) are shown below.
(1) A method of calculating the current toner density theoretical value Tc5 of the toner density Tc in the developing container based on the integrated value J1 and the previous discharge toner density Tc4 in ST52.
(2) When it is determined in ST53 that Tc ≦ Tc5, if yes (Y), the actual developer amount J in the developing container V is J ≦ J0 compared to the reference value J0. This means that, in the case of No (N), the developer amount J in the developer container V means that J> J0 compared to the reference value J0.
In ST33 ″, the amount of toner consumed is detected after the previous discharge toner concentration Tc4 is stored (see ST33 ″) and then in ST32 until SNk (storage chamber developer sensor) detects the developer. The high-density two-component developer is replenished according to the detected toner consumption, and the developer replenishment amount J1 at that time is integrated. As a method for detecting the amount of consumed toner, various conventionally known methods (such as a method for counting the number of printed dots) can be employed.

After the accumulation of the developer replenishment amount is started at ST33 ″, when the SNk (storage chamber developer sensor) detects the developer at ST32, the developer replenishment weight integrated value J1 is stored at ST52. When the toner concentration (weight concentration) of the developer is a, the replenishment toner weight and carrier weight included in the developer replenishment weight integrated value J1 can be expressed by the following equations.
Replenishment toner weight = a × J1
Replenishment carrier weight = (1-a) × J1
When it is assumed that the amount of developer accommodated in the developer container V is the developer weight reference value J0 when the developer was discharged last time, the developer weight reference value J0 in the developer container V at that time is included. The toner weight is expressed by the following formula.
Toner weight within developer weight reference value J0 = Tc4 × J0

When the reference developer amount at the previous developer discharge is J0 and the replenishment developer amount integrated value is J1, the total developer weight (the developer weight at the current developer discharge) is (J0 + J1). The toner weight in the developer amount (J0 + J1) is (Tc4 × J0 + a × J1). However, there is toner weight consumed between the previous developer discharge and the current developer discharge. Assuming that the consumed toner weight and the replenished toner weight are equal, the developer weight and toner weight in the developer container V when the developer is discharged this time can be expressed by the following equations.
Developer amount = J0 + J1-aJ1 = J0 + (1-a) J1
Toner weight = Tc4 × J0
Therefore, assuming that the developer weight in the developer container V at the previous developer discharge was the reference developer amount J0, the toner concentration Tc5 in the developer container V at the current developer discharge can be expressed by the following equation (1). .
Tc5 = (Tc4 × J0) / {J0 + (1-a) J1} (1)

If the actual amount of developer in the developer container V when the developer was discharged last time is J, the developer weight and toner weight in the developer container V when the developer is discharged this time can be expressed by the following equations.
Developer amount = J + J1-aJ1 = J + (1-a) J1
Toner weight = Tc4 × J
In this case, the toner concentration Tc in the developing container when the developer is discharged this time can be expressed by the following equation.
Tc = (Tc4 × J) / {J + (1-a) J1} (2)

From the above equations (1) and (2), the following equation is obtained.
Tc-Tc5
= [(Tc4 × J) / {J + (1-a) J1}]
− [(Tc4 × J0) / {J0 + (1-a) J1}]
= (1-a) Tc4J1 (J-J0) / {J + (1-a) J1} {J0 + (1-a) J1}
In this formula:
K = (1-a) Tc4J1 / {J + (1-a) J1} {J0 + (1-a) J1}
Then, K> 0, and the following equation is established.
Tc-Tc5 = K (J-J0) (3)

If the expression (3) is negative, the answer is yes (Y) in ST53. In that case, J ≦ J0 from the equation (3). That is, the actual developer weight J in the developing container V is smaller than the reference developer amount J0. In this case, the rotation time Th of R5 (discharged developer conveying member) is set to Th = Th2 (= 1 second) in ST54.
That is, when the actual developer weight J in the developer container V is smaller than the reference developer amount J0, the developer discharge speed is decreased.

When the formula (3) is positive, it becomes no (N) in ST53. In that case, J> J0 from equation (3). That is, the actual developer weight J in the developer container V is larger than the reference developer amount J0. In this case, in ST55, the rotation time Th of R5 (discharged developer conveying member) is set to Th = Th1 (= 3 seconds).
That is, when the actual developer weight J in the developer container V is larger than the reference developer amount J0, the developer discharge speed is increased.

  From the above description, in the fifth embodiment, when the actual developer amount J in the developer container V is smaller than the reference developer amount J0, the developer discharge speed is lowered, and when the actual developer amount J is large, the developer discharge speed is decreased. Therefore, appropriate developer discharge control can be performed according to the amount of developer in the developer container V.

(Example 6)
FIG. 19 is an explanatory diagram of an image forming apparatus provided with a developing device according to Embodiment 6 of the present invention.
In FIG. 19, an image forming apparatus (digital copying machine) U according to the first embodiment includes a printer (image forming apparatus main body) U1, an image scanner U2, and an automatic document feeder U3.
The automatic document feeder U3 is supported on a platen glass PG on the upper surface of the image scanner U2.

The automatic document feeder U3 has a document feed tray TG1 on which a plurality of documents Gi to be copied are stacked. Each of the plurality of documents Gi placed on the document feed tray TG1 sequentially passes through the copy position on the platen glass PG (the press contact position of the platen roll GR1) and is discharged from the document discharge roll GR2 to the document discharge tray TG2. It is comprised so that.
The automatic document feeder U3 is rotatable with respect to the upper surface of the platen glass PG by a hinge shaft (not shown) extending in the left-right direction provided at the rear end portion (the rear side portion of the paper surface of FIG. 1). When the operator places the document Gi on the platen glass PG by hand, the document Gi is rotated upward.

The image scanner U2 has a UI (user interface) (see FIGS. 1 and 5) through which a user inputs an operation command signal such as a copy start.
An exposure optical system A for reading a document image is disposed below the transparent platen glass PG.
Reflected light from a document which is transported to the upper surface of the platen glass PG by the automatic document feeder U3 and passes through the copy position or a document (not shown) manually placed on the platen glass PG is reflected by the exposure optical system A. Then, it is converted into an electrical signal by a CCD (solid-state imaging device).
The IPS (image processing system) converts R, G, B (red, green, blue) electrical signals input from the CCD into Y, M, C, K (yellow, magenta, cyan, black) image data (digital). Data) and temporarily stored, and the image data is output to the laser drive circuit DL as image data for forming a latent image at a predetermined timing.
The laser drive circuit DL outputs a laser drive signal to a laser diode (not shown) of a ROS (latent image forming apparatus) according to the input image data. A bias voltage is applied to the UI (user interface), the IPS and the laser driving circuit DL, and development rollers R0, transfer rolls Ty to Tk, T2 secondary transfer rolls (sheet transfer members) T2b of colors Y to K described later. The operation of the power supply circuit E and the like is controlled by the controller C.

  The laser drive circuit DL to which the four-color image data (laser drive data) of YMCK output from the IPS is input, the laser drive signal of each color corresponding to the input image data of each color at a predetermined timing for each color. ROSy to ROSk (latent image forming apparatus).

  Each image carrier (photosensitive body) Py, Pm, Pc, Pk is uniformly charged by each charging roll (charging member) CRy to CRk, and then output from each color ROSy to ROSK (latent image forming apparatus). An electrostatic latent image is formed on the surface of the light beam. The electrostatic latent images on the surfaces of the image carriers Py, Pm, Pc, and Pk are developed into toner images of the respective colors YMCK in the developing areas that face the developing units Gy, Gm, Gc, and Gk, respectively. Each of the developing units Gy, Gm, Gc, and Gk includes a developing container that stores toner of each color, an electrostatic image on the surface of the image carrier Py, Pm, Pc, and Pk that is rotatably supported by the developing container. A developing roll R0 is provided for conveying toner to the latent image and developing the toner image. The developing containers Gy, Gm, Gc, and Gk of the respective colors are configured to be supplied with toner of each color from the toner cartridges TY to TK.

The developed toner image of each color YMCK is conveyed to a primary transfer region Q3 where each of the image carriers Py, Pm, Pc, Pk and an endless intermediate transfer belt (image carrier) B are in contact. The primary transfer roll T1 disposed on the back side of the intermediate transfer belt B in each primary transfer region Q3 has a polarity opposite to the developer charging polarity at a predetermined timing from the power supply circuit E controlled by the controller C. A primary transfer voltage is applied. The toner images on the image carriers Py to Pk are primary-transferred on the intermediate transfer belt B in a primary transfer region Q3 facing the primary transfer rolls T1. Residual toner on the surface of the image carrier Py, Pm, Pc, Pk after the primary transfer is removed by the image carrier cleaner CLp of each color Y to K.
Above the intermediate transfer belt B, a toner image density sensor SN2 for detecting the toner patch density is provided.

  Each color toner that forms a toner image of each color on each image carrier Py-Pk by each image carrier Py-Pk, each color ROSy-ROSK (latent image forming device), and each color developer Gy-Gk An image forming apparatus UY (Py + ROSy + Gy), UM (Pm + ROSm + Gm), UC (Pc + ROSc + Gc), and UK (Pk + ROSK + Gk) are configured.

Below the image carriers Py, Pm, Pc, Pk of the respective colors, a slide frame F1 is slidable in the front-rear direction (direction perpendicular to the paper surface, that is, the X-axis direction) by a pair of left and right slide rails SR, SR. It is supported. The slide frame F1 includes an operating position where the belt frame F2 of the belt module BM is raised (position where it contacts the image carriers Py to Pk) and a maintenance position where the belt frame BM is moved downward (position away from the image carriers Py to Pk). It is supported so that it can move up and down. In a state where the belt module BM is lowered to the belt maintenance position, the slide frame F1 and the belt module BM supported by the slide frame F1 are brought into contact with the image carrier Py to Pk without being brought into frictional contact with the image forming apparatus body U1. It is comprised so that it can be made to go in / out.
The configuration for moving the slide frame F1 back and forth and the configuration for moving the belt module BM up and down are conventionally known (see, for example, JP-A-8-171248), and various conventionally known configurations can be employed. .

  The belt module BM includes a belt support roll (Rd, Rt, Rw) including the intermediate transfer belt B, a belt drive roll Rd, a tension roll Rt, a walking roll Rw, a plurality of idler rolls (free rolls) Rf, and a backup roll T2a. , Rf, T2a) and the four primary transfer rolls T1. The intermediate transfer belt B is supported by the belt support rolls (Rd, Rt, Rw, Rf, T2a) so as to be rotatable in the arrow Ya direction.

A secondary transfer roll (sheet transfer member) T2b is disposed opposite to the surface of the intermediate transfer belt B in contact with the backup roll T2a. A transfer region (sheet transfer region) Q4 is formed. A secondary transfer voltage having a polarity opposite to the charging polarity of the developer is applied to the secondary transfer roll T2b from the power supply circuit E controlled by the controller C at a predetermined timing. The backup roll T2a disposed opposite to the secondary transfer roll T2b is grounded, and when a secondary transfer voltage is applied to the secondary transfer roll T2b, the secondary transfer roll T2b and A secondary transfer electric field is formed between the backup rolls T2a. The backup roll T2a and the secondary transfer roll T2b constitute a secondary transfer device T2.
By the belt module BM including the four primary transfer rolls Ty to Tk and the intermediate transfer belt B, the secondary transfer unit T2, and the like, the image carrier Py to the toner image forming device (UY, UM, UC, UK). A transfer device (BM + T2) is configured to transfer the toner image formed on the Pk surface to the recording sheet S.

Under the printer (image forming apparatus main body) U1, cassette trays (sheet feeding trays T) R1 to TR3 for storing sheets S and a sheet feeding path SH1 are provided. The sheet feeding path SH1 is configured to be fed from a manual feed tray (sheet feeding tray) TR4. The sheets S accommodated in the cassette trays (sheet feeding trays) TR1 to TR3 are taken out by the pick-up roll Rp at a predetermined timing, separated one by one by the separating roll Rs, and transferred to the registration roll Rr by a plurality of transport rolls Ra. Be transported. Further, the sheet fed from the manual feed tray (paper feed tray) TR4 is transported to the registration roll Rr by the transport roll Ra. The recording sheet S conveyed to the registration roll Rr has a secondary transfer area in time with the multiple toner image or single color toner image that has been primarily transferred to the intermediate transfer belt B moved to the secondary transfer area Q4. It is conveyed to Q4.
When the recording sheet S passes through the secondary transfer region Q4, the secondary transfer voltage is applied to the secondary transfer roll T2b, so that the color toner image primarily transferred over the intermediate transfer belt B is Secondary transfer is performed onto the recording sheet S at once in the secondary transfer region Q4.
The residual toner is removed from the intermediate transfer belt B after the secondary transfer by the belt cleaner CLb.

The recording sheet S on which the toner image is secondarily transferred is conveyed to the fixing device F by the post-transfer sheet guide SG and the sheet conveying belt HB. The fixing device F has a pair of pressure rolls Fh and pressure rolls Fp (see FIG. 2) that are in pressure contact with each other, and a fixing area Q5 is formed by the pressure contact areas of the heat roll Fh and pressure roll Fp. The toner image on the recording sheet S is heat-fixed when passing through the fixing region Q5. The recording sheet S on which the toner image is fixed is conveyed to the discharge sheet conveyance path SH2 or the duplex recording sheet conveyance path SH3. The sheet conveyed to the discharge sheet conveying path SH2 is discharged to the paper discharge tray TRh, and the sheet conveyed to the double-sided recording sheet conveying path SH3 is reversed and then retransmitted to the registration roll Rr.
A sheet conveying device SH is constituted by the elements indicated by the symbols Rp, Rs, Ra, Rr, SG, HB, SH1, SH2, SH3 and the like.
A sheet conveying path (SH1 to SH3) is configured by the elements indicated by the symbols SH1, SH2, and SH3. Further, a sheet conveying member (Rp, Rs, Ra, Rr, HB) is constituted by the elements indicated by the symbols Rp, Rs, Ra, Rr, HB and the like.

The developing devices Gy to Gk of the image forming apparatus of the sixth embodiment are configured in the same way as the developing device G of the first embodiment, and the developer discharge port 7, the discharged developer storage chamber 21 of the first embodiment, A discharged developer transport member R5, a discharged developer recovery tank 23, and the like are provided, and the discharged developer transport member R5 is rotationally controlled as in the first embodiment.
Accordingly, the developing devices Gy to Gk of the image forming apparatus according to the sixth embodiment have the same operation as that of the first embodiment.

(Example of change)
Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. Is possible. Examples of modifications of the present invention are illustrated below.
(H01) The number of rotations of the discharged developer conveying member R5 can be set arbitrarily.
(H02) The set times TM1a and TM2a of the timers TM1 and TM2 can be set according to the developing device.
(H03) The rotation control of the discharged developer conveying member R5 in the sixth embodiment can be controlled in the same manner as in the second to fifth embodiments.
(H04) A plurality of storage chamber developer sensors can be provided to detect the storage amount of the developer. The operation of the discharged developer conveying member can be controlled in accordance with detection signals from a plurality of stored developer sensors.

FIG. 1 is an overall explanatory view of an image forming apparatus including a developing device according to Embodiment 1 of the present invention. FIG. 2 is an enlarged explanatory view of the developing device which is the main part of FIG. FIG. 3 is a perspective view of a developing device which is a main part of the developing device. 4 is an enlarged explanatory view of a developer supply port portion and a developer discharge port portion of the developing device shown in FIG. 3, and is a partial cross-sectional view seen from the direction of arrow IV in FIG. 5 is an explanatory view of the developing device, FIG. 5A is a sectional view taken along the line VA-VA of FIG. 4, FIG. 5B is a sectional view taken along the line VB-VB of FIG. 4, and FIG. It is. FIG. 6 is a block diagram of the developing device and its drive circuit. FIG. 7 is a block diagram of a control unit of the image forming apparatus including the developing device according to the first exemplary embodiment of the present invention. FIG. 8 is a flowchart of developer replenishment control according to the first embodiment of the present invention. FIG. 9 is a flowchart of the developing bias setting process. FIG. 10 is a flowchart of the discharge control according to the first embodiment. FIG. 11 is a block diagram of the control unit of the image forming apparatus including the developing device according to the second embodiment, and corresponds to FIG. 7 of the first embodiment. FIG. 12 is a flowchart of the discharge control of the second embodiment, and corresponds to the flowchart of FIG. 10 of the first embodiment. FIG. 13 is a block diagram of the control unit of the image forming apparatus including the developing device according to the second embodiment, and corresponds to FIG. 7 of the first embodiment. FIG. 14 is a flowchart of the discharge control of the third embodiment, and corresponds to the flowchart of FIG. 10 of the first embodiment. FIG. 15 is a block diagram of the control unit of the image forming apparatus including the developing device according to the fourth embodiment, and corresponds to FIG. 7 of the first embodiment. FIG. 16 is a flowchart of the discharge control of the fourth embodiment, and corresponds to the flowchart of FIG. 10 of the first embodiment. FIG. 17 is a block diagram of a control unit of an image forming apparatus including the developing device according to the fourth embodiment, and corresponds to FIG. 7 of the first embodiment. FIG. 18 is a flowchart of the discharge control of the fifth embodiment, and corresponds to the flowchart of FIG. 10 of the first embodiment. FIG. 19 is an explanatory diagram of an image forming apparatus provided with a developing device according to Embodiment 6 of the present invention. FIG. 20 is an example of a graph showing the relationship between the volume and weight of the two-component developer in the developing container of the trickle developing type developing device using a high-concentration developer as the replenishment developer, and the toner concentration and the carrier amount. .

Explanation of symbols

C7: developer replenishment control means,
C8 ... developer discharge control means,
C8a: stored developer detection means,
C9 ... Two-component developer supply amount integrated value storage means,
C10: Toner density theoretical value calculation means,
C10a: toner concentration detection storage means at driving time point,
C11: toner density change determining means,
J1 ... Two-component developer supply amount integrated value,
PR: Image carrier,
R0: Developing roll,
R5 ... discharged developer conveying member,
SN1 ... toner density sensor in the container,
Tc: toner density,
Tc1 ... lower limit set value,
Tc4: previous toner density,
Tc5: The theoretical value of the toner density at the time of this driving,
V0: developing roll container,
V: Developer container
6 ... Developer supply port,
7 ... Developer outlet,
21 ... discharged developer storage chamber,
22a ... Developer discharge path,
23 ... discharged developer recovery tank,
(22a + R5)... Stored developer transport device,
(D3 + M3) ... drive device for discharge,
(R1 + R2) ... agitating and conveying member,
(V1 + V2)... Developer circulation conveyance path.

Claims (8)

A developing device comprising the following structural requirements (A01) to (A08):
(A01) A developing roll accommodating portion that accommodates a developing roll, a developer circulation conveying path that adjoins the developing roll accommodating portion and that is stirred and conveyed while circulating a two-component developer composed of toner and a carrier, and the developer circulation A developer replenishing port for replenishing the two-component developer in the conveying path and a developer discharging port for discharging the developer stirred and conveyed in the developer circulation conveying path;
(A02) The two-component developer that is rotatably accommodated in the developing roll accommodating portion and adhered to the rotating surface is conveyed to a developing region facing the surface of the image carrier on which the electrostatic latent image is written and rotated. A developing roll for developing the electrostatic latent image;
(A03) It has a rotating shaft and agitating / conveying blade rotatably accommodated in the developer circulation conveying path, and circulates the two-component developer while agitating and conveying at the time of rotation, and the developer roll accommodating portion is provided with the 2 An agitating and conveying member for supplying a component developer;
(A04) A discharged developer storage chamber in which the developer discharged from the developer discharge port is stored, and when the amount of stored developer in the discharged developer storage chamber becomes large, the stored developer becomes the developer discharge port. The discharged developer storage chamber configured to block the developer from being discharged from the developer discharge port,
(A05) A developer discharge path for transporting the stored developer to a discharged developer recovery tank and a developer discharge path disposed in the developer discharge path to transfer the stored developer from the discharged developer storage chamber to the discharged developer recovery tank. A stored developer conveying device having a discharged developer conveying member for conveying;
(A06) Stored developer detecting means for detecting the stored developer in the discharged developer storing chamber;
(A07) A discharge driving device for driving the discharged developer conveying member,
(A08) Developer discharge for controlling the operation of the discharge driving device in accordance with the output signal of the stored developer detection means and transporting the stored developer in the discharged developer storage chamber to the discharged developer recovery tank side. Control means. The developing device according to claim 1, comprising the following structural requirements (A09) and (A010):
(A09) The stored developer detecting means for detecting that the stored developer is in a state of closing the developer discharge port;
(A010) The developer discharge control means for transporting the stored developer in the discharged developer storage chamber to the discharged developer collection tank side when the stored developer is in a state of closing the developer discharge port. The developing device according to claim 2, comprising the following constituent elements (A011):
(A011) The developer discharge speed from the developer discharge port is adjusted by adjusting the time from when the stored developer is in a state of closing the developer discharge port until the discharge developer transport member starts to be driven. The developer discharge control means for adjusting. The developing device according to claim 2, comprising the following configuration requirement (A012):
(A012) The amount of stored developer in the discharged developer storage chamber is adjusted by adjusting the driving time for driving the discharged developer conveying member in a state where the stored developer is in a state of closing the developer discharge port. As a result, the developer discharge control means for adjusting the developer discharge speed from the developer discharge port. 5. The developing device according to claim 2, comprising the following constituent elements (A013) and (A014):
(A013) In-container toner concentration sensor for detecting the toner concentration of the two-component developer in the developer container;
(A014) The developer discharge control means for reducing the developer discharge speed when the toner density becomes higher than an upper limit set value.
5. The developing device according to claim 2, comprising the following constituent elements (A013) and (A015):
(A013) In-container toner concentration sensor for detecting the toner concentration of the two-component developer in the developer container;
(A015) The developer discharge control means for increasing the developer discharge speed when the toner density becomes lower than a lower limit set value. The developing device according to any one of claims 2 to 6, comprising the following constituent elements (A016) to (A018):
(A016) Developer replenishment control means for controlling the replenishment amount of the two-component developer into the developer container from the developer replenishment port according to the toner consumption amount in the developer container;
(A017) Two-component developer replenishment amount integrated value storage means for accumulating and storing the replenishment amount of the two-component developer from the previous rotation to the current rotation of the discharged developer conveying member;
(A018) Integration of the toner density change in the developer container between the previous rotation and the current rotation of the discharged developer conveying member and the two-component developer supply amount between the previous rotation and the current rotation The developer discharge control means for controlling the developer discharge speed from the developer discharge port according to the value. The developing device according to claim 7, comprising the following structural requirements (A019) to (A023):
(A019) From the time when the discharge driving device is driven to convey the stored developer in the discharged developer storage chamber to the discharged developer recovery tank side, until the next time when the discharge driving device is driven. A two-component developer replenishment amount integrated value storage means for accumulating and storing a replenishment amount of the two-component developer from the developer replenishment port;
(A020) a driving time toner concentration detection storage means for detecting and storing the toner concentration in the developing container at the time of driving the discharge driving device;
(A021) The toner concentration at the current driving time based on the toner concentration at the previous driving time of the discharge driving device and the integrated value of the replenishment amount of the two-component developer from the previous driving time to the current driving time. Toner density theoretical value calculating means for calculating the theoretical value Tc5 of
(A022) Toner concentration change determining means for determining whether or not the detected toner concentration Tc at the current driving time point is Tc <Tc5 with respect to the theoretical value Tc5;
(A023) The developer discharge control means for lowering the developer discharge speed from the developer discharge port when Tc <Tc5 than when Tc> Tc5.

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