JP2007058139A - Developer stirring controller in developing unit, and image forming apparatus provided with the developer stirring controller in the developing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower the deterioration speed of toner in a developing unit when continuously printing images small in image area ratio. <P>SOLUTION: The developer stirring controller in the developing unit D+C+D1+M1 is provided with: the developing unit D having a developing container V storing developer including the toner, developer stirring members R1 and R2 stirring the developer and a developing roll R0 conveying the developer to the surface of an image carrier PR; an image area ratio calculation and storage means C2 calculating and storing the image area ratio P of the image for one page on which the image is recorded; an image area ratio threshold setting and storing means C6 having a threshold reference value storage means C6a storing threshold reference values P1a and P2a; an image area ratio comparison and discrimination means C7 discriminating whether or not the calculated image area ratio P is smaller than image area ratio set thresholds P1 and P2; and a stirring member rotational speed setting and storing means C9 setting and storing the rotational speed of the developer stirring members R1 and R2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developer agitation control device in a developing device of a developing device used in an electrophotographic printer, a copying machine, a FAX (facsimile), a multifunction device, and the like, and an image including the developer agitation control device in the developer. In particular, when an image with a small image area ratio (that is, an image with a small amount of toner consumption) is printed continuously, unevenness in density due to toner replacement and less toner deterioration. The present invention relates to an in-developer developer agitation control device capable of preventing the occurrence of image quality defects such as the above and an image forming apparatus provided with the in-developer developer agitation control device.

  When images with a small image area ratio (images with low toner consumption) are continuously printed, the toner in the developing device is hardly replaced. An image quality defect occurs. As techniques for preventing the image quality defect, the following techniques (J01) to (J03) are conventionally known.

(J01) Technology described in Patent Document 1 (Japanese Patent Laid-Open No. 11-295976)
In the technique described in Patent Document 1, the operation time of the rotary developer is determined in advance, and when images with low image density are continuously processed during this operation time, the toner staying in the developer for a long time. In order to suppress the occurrence of density unevenness due to deterioration, the integrated image density during the predetermined operation time and the limit density predicted in advance are determined every predetermined time (1/2 of the operation time). Therefore, it is possible to quickly recognize toner deterioration. Further, when toner deterioration is recognized, the toner in the developing device is discharged and the same amount of toner as the discharged toner is replenished, so that subsequent density unevenness can be suppressed.

(J02) Technology described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-324842) In the technology described in Patent Document 2, measuring means 8 that measures the image density of an original by measuring image data as the number of dots, and measuring means 8 And a control means 9 for performing control to vary the exposure amount of the exposure unit 3 when the image density of the original measured by the above becomes a predetermined value or less.

(J03) Technology described in Patent Document 3 (Japanese Patent Laid-Open No. 2005-017631) In the technology described in Patent Document 3, the image forming apparatus forms a patch as a toner image for density measurement by the image forming means, and the density measuring means. The density control means for measuring the density of the patch and controlling the amount of toner supplied to the developing means so that the density becomes a predetermined target value at a predetermined timing; and other than the density control operation Patch correcting means for correcting the patch forming conditions based on an image forming operation. The patch correction unit corrects the patch formation condition so that the density of the patch is low when the image density during the image forming operation is higher than the reference value, and the image density during the image forming operation is the reference value. If lower, the patch formation conditions are corrected so that the density of the patch is increased.

Japanese Patent Laid-Open No. 11-295976 JP 2001-324842 A JP 2005-017631 A

(Problems of the techniques described in Patent Documents 1 to 3 of (J01) to (J03))
In the techniques described in Patent Documents 1 to 3, when an image with a small image area ratio (an image with a small amount of toner consumption and a small amount of toner in the developing device) is continuously printed, the developer stirring in the developing device is performed. Since the rotation speed of the member is not reduced, the toner deterioration speed cannot be reduced. In this case, since the deteriorated toner is eventually discharged and new toner is replenished, the toner consumption increases, which is uneconomical.

In view of the above circumstances, the present invention has the following description (O01) as a technical problem.
(O01) To reduce the deterioration rate of toner in the developing device when continuously printing images with a small image area ratio (images with low toner consumption and little toner replacement in the developing device).

Next, the present invention devised to solve the above problems will be described. In order to facilitate correspondence with the constituent elements of the embodiments described later, the constituent elements of the present invention are not described. Add the code enclosed in parentheses.
The reason why the present invention is described in correspondence with the reference numerals 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.

(First invention)
In order to solve the above-described problems, the developer stirring control device (D + C + D1 + M1) in the developing device according to the first aspect of the present invention includes the following structural requirements (A01) to (A05).
(A01) A developer container (V) containing a developer containing toner, developer agitating members (R1, R2) rotatably accommodated in the developer container (V) and agitating the developer, and the development A developing roll (R0) rotatably accommodated in a container (V) and transporting the stirred developer to the surface of an image carrier (PR) on which an electrostatic latent image is formed; A developing device (D) for developing the electrostatic latent image formed on the surface of the body (PR) into a toner image;
(A02) Image area ratio calculation storage means (C2) for calculating and storing the image area ratio P of an image for one page on which image recording is performed next,
(A03) Threshold value reference value storage means (C6a) for storing threshold value reference values (P1a, P2a) for determining whether or not the calculated image area ratio (calculated image area ratio) P is small. An image area ratio threshold value that sets the threshold values (P1, P2) based on the reference values (P1a, P2a) and stores the set threshold values (P1, P2) as image area ratio setting threshold values (P1, P2). Setting storage means (C6),
(A04) Image area ratio comparison determining means (C7) for determining whether or not the calculated image area ratio (P) is smaller than the image area ratio setting threshold values (P1, P2);
(A05) When the calculated image area ratio P is smaller than the image area ratio setting threshold value (P1, P2), the rotation speed of the developer stirring member (R1, R2) is set smaller than when it is larger. Stirring member rotation speed setting storing means (C9) for storing.

(Operation of the first invention)
In the developer agitation control device (D + C + D1 + M1) in the developing device according to the first aspect of the present invention having the structural requirements (A01) to (A05), the developer container (V) contains a developer containing toner. Developer agitating members (R1, R2) rotatably accommodated in the developer container (V) agitate the developer. A developing roll (R0) rotatably accommodated in the developing container (V) conveys the stirred developer to the surface of the image carrier (PR) on which an electrostatic latent image is formed. A developing device (D) having the developing roll (R0) develops the electrostatic latent image formed on the surface of the image carrier (PR) into a toner image.
The image area ratio calculation storage means (C2) calculates and stores the image area ratio P of an image for one page on which image recording is performed next.
The threshold reference value storage means (C6a) stores threshold reference values (P1a, P2a) for determining whether or not the calculated image area ratio (calculated image area ratio) P is small. The image area ratio threshold value setting storage means (C6) having the threshold value reference value storage means (C6a) sets the threshold values (P1, P2) based on the reference value, and the set threshold values (P1, P2). Are stored as image area ratio setting threshold values (P1, P2).
The image area ratio comparison / determination means (C7) determines whether or not the calculated image area ratio P is smaller than the image area ratio setting thresholds (P1, P2).
The agitation member rotation speed setting storage means (C9) is configured such that the developer agitation member (R1, R1) is larger than when the calculated image area ratio P is smaller than the image area ratio setting threshold (P1, P2). R2) is set to a small rotation speed and the set value is stored.
The rotation speed of the developer agitating members (R1, R2) during the image recording operation is controlled to be the set value.
Therefore, when the calculated image area ratio (P) is small (that is, when the toner consumption is small and the toner in the developing device (D) is little replaced), the rotation speed of the developer stirring members (R1, R2) Is reduced, the toner deterioration rate is reduced.

(First Embodiment 1)
The developer agitation control device (D + C + D1 + M1) in the developing device according to the first aspect of the present invention is characterized in that in the first invention, the following structural requirements (A06) and (A07) are provided.
(A06) The developing roll (R0) and the developer stirring member (R1, R2) rotating in conjunction with each other,
(A07) When the calculated image area ratio (P) is smaller than the image area ratio setting threshold values (P1, P2), the rotational speed N of the developing roll (R0) is set smaller than when it is larger. As a result, the stirring member rotation speed setting storage means (C9) for setting and storing the rotation speed of the developer stirring member (R1, R2) small.

(Operation of Form 1 of the First Invention)
In the developer agitation control device (D + C + D1 + M1) in the developing device according to the first aspect of the present invention having the structural requirements (A06) and (A07), the developing roll (R0) and the developer agitating members (R1, R2) Rotates in conjunction with each other. When the calculated image area ratio (P) is smaller than the image area ratio setting threshold values (P1, P2), the stirring member rotation speed setting storage means (C9) is more than the developing roll (R0). As a result, the rotation speed of the developer agitating member (R1, R2) is set to be small, and the set value is stored.
Therefore, when the calculated image area ratio (P) is small (that is, when the toner consumption is small and the toner in the developing device (D) is little replaced), the rotation speed of the developer stirring members (R1, R2) Is reduced, the toner deterioration rate is reduced.

(First Embodiment 2)
The developer stirring control device (D + C + D1 + M1) in the developing device according to Embodiment 2 of the first invention is characterized in that in the first invention, the following constitutional requirements (A06) and (A07 ′) are provided.
(A06) The developing roll (R0) and the developer stirring member (R1, R2) rotating in conjunction with each other,
(A07 ′) When the calculated image area ratio (P) is smaller than the image area ratio setting thresholds (P1, P2), the peripheral speed of the developing roll (R0) is set smaller than when it is larger. As a result, the stirring member rotation speed setting storage means (C9) for setting and storing the rotation speed of the developer stirring member (R1, R2) small.

(Operation of the second aspect of the first invention)
In the developer agitation control device (D + C + D1 + M1) in the developing device according to the second aspect of the present invention having the structural requirements (A06) and (A07 ′), the development roll (R0) and the developer agitation members (R1, R2) ) Rotate in conjunction. When the calculated image area ratio (P) is smaller than the image area ratio setting threshold values (P1, P2), the stirring member rotation speed setting storage means (C9) is more than the developing roll (R0). ) Is set to be small, as a result, the rotation speed of the developer stirring member (R1, R2) is set to be small, and the set value is stored.
Therefore, when the calculated image area ratio (P) is small (that is, when the toner consumption is small and the toner in the developing device (D) is little replaced), the rotation speed of the developer stirring members (R1, R2) Is reduced, the toner deterioration rate is reduced.

(Embodiment 3 of the first invention)
The developer agitation control device (D + C + D1 + M1) in the developing device according to the third aspect of the first invention comprises the following constituent elements (A08) to (A010) in the first invention or the first or second aspect of the first invention. It is characterized by.
(A08) A continuous count that counts the number of times of continuous printing (n, n ₁ , n ₂ ) when the image area ratio P is smaller than the image area ratio setting threshold (P1, P2). Print counter (KT, KT '),
(A09) Continuous printing frequency threshold storage means (C8, C8 ′) for storing a threshold value (continuous printing frequency threshold, n0, n ₁ 0, n ₂ 0) of the continuous printing frequency (n, n ₁ , n ₂ )
(A010) Printing of an image in which the calculated image area ratio P is smaller than the image area ratio setting threshold value (P1, P2) continuously exceeds the continuous printing frequency threshold value (n0, n ₁ 0, n ₂ 0). The stirring member rotational speed setting storage means (C9) for setting and storing the rotational speed of the developer stirring member (R1, R2) small only when the developer stirring member (R9) is stored.

(Operation of the third aspect of the first invention)
In the developer agitation control device (D + C + D1 + M1) in the developing device according to the third aspect of the present invention having the structural requirements (A08) to (A010), the continuous printing number counter (KT, KT ′) is the calculated image area ratio. The number of continuous printing (n, n ₁ , n ₂ ) when the printing of images smaller than the image area ratio setting threshold (P1, P2) continues is counted.
The continuous printing frequency threshold storage means (C8, C8 ′) stores the threshold value of the continuous printing frequency (n, n ₁ , n ₂ ) (continuous printing frequency threshold, n0, n ₁ 0, n ₂ 0).
The stirring member rotation speed setting storage means (C9), the calculated image area ratio P is the image area ratio setting threshold compared to a small image printing (P1, P2) is the continuous printing count threshold (n0, n ₁ The rotation speed of the developer agitating member (R1, R2) is set to be small only when the value exceeds 0, n ₂ 0) and the set value is stored.

(First aspect 4)
The developer agitation control device (D + C + D1 + M1) in the developing device according to the fourth aspect of the first invention has the following structural requirements (A011) to (A013) in either the first invention or the first or third aspect of the first invention. It is characterized by having.
(A011) As threshold values for determining whether or not the calculated image area ratio (calculated image area ratio) P is small, two threshold values, a first threshold value P1 and a second threshold value P2 smaller than the first threshold value, are used. The image area ratio threshold value setting storage means (C6) for setting and storing the set first threshold value P1 and second threshold value P2 as the image area ratio first setting threshold value P1 and the image area ratio second setting threshold value P2,
(A012) The image area ratio comparison determination means (C7) for determining whether or not the calculated image area ratio P is smaller than the image area ratio first setting threshold value P1 and the image area ratio second setting threshold value P2.
(A013) When the calculated image area ratio P is smaller than the image area ratio second setting threshold value P2 (when P <P2), the calculated image area ratio P becomes the image area ratio first setting threshold value P1. The rotation of the stirring member for setting and storing the rotation speed of the developer stirring member (R1, R2) smaller than that when the image area ratio is smaller than the second setting threshold value P2 (when P1>P> P2). Speed setting storage means (C9).

(Operation of the fourth aspect of the first invention)
In the developer agitation control device (D + C + D1 + M1) in the developing device according to the fourth aspect of the first invention having the structural requirements (A011) to (A013), the image area ratio threshold value setting storage means (C6) is calculated as described above. Two threshold values, a first threshold value P1 and a second threshold value P2 smaller than the first threshold value, are set as threshold values for determining whether or not the image area ratio (calculated image area ratio) P is small. The first threshold value P1 and the second threshold value P2 are stored as the image area ratio first setting threshold value P1 and the image area ratio second setting threshold value P2.
The image area ratio comparison determining means (C7) determines whether or not the calculated image area ratio P is smaller than the image area ratio first setting threshold value P1 and the image area ratio second setting threshold value P2.
When the calculated image area ratio P is smaller than the image area ratio second setting threshold value P2 (when P <P2), the stirring member rotation speed setting storage means (C9) sets the calculated image area ratio P to The rotation speed of the developer stirring member (R1, R2) is smaller than the image area ratio first setting threshold value P1 and larger than the image area ratio second setting threshold value P2 (when P1>P> P2). Is set to a smaller value and the set value is stored.
In this case, when the calculated image area ratio P is small (when toner replacement is small), the rotation speed of the developer agitating member (R1, R2) is set to be small, so that the toner deterioration rate can be reduced. it can.

(First embodiment 5)
The developer agitation control device (D + C + D1 + M1) in the developing device according to the fifth aspect of the first invention is characterized in that, in the fourth aspect of the first invention, the following structural requirements (A014) to (A016) are provided.
(A014) A continuous printing number counter (KT) that counts the continuous printing number n when printing of an image in which the calculated image area ratio P is smaller than the image area ratio first setting threshold value P1 continues.
(A015) Continuous printing number threshold storage means (C8) for storing a threshold value (continuous printing number threshold value) n0 of the continuous printing number n
(A016) The developer stirring member (only when the calculated image area ratio P is smaller than the image area ratio first setting threshold value P1 and the printing of the image is continued beyond the continuous printing frequency threshold value n0) The stirring member rotational speed setting storage means (C9) for setting and storing the rotational speed of R1, R2) small.

(Operation of the fifth aspect of the first invention)
In the developer agitation control device (D + C + D1 + M1) in the developing device according to the fifth aspect of the first invention having the structural requirements (A014) to (A016), the continuous printing number counter (KT) indicates that the calculated image area ratio P is The number of consecutive printings n when the printing of images smaller than the image area ratio first setting threshold value P1 is continued is counted.
The continuous printing frequency threshold storage means (C8) stores a threshold value (continuous printing frequency threshold value) n0 of the continuous printing frequency n.
The stirring member rotation speed setting storage means (C9) continuously prints images whose calculated image area ratio P is smaller than the image area ratio first setting threshold value P1 exceeding the continuous printing frequency threshold value n0. Only when the developer stirring member (R1, R2) is set, the rotational speed of the developer agitating member (R1, R2) is set small, and the set value is stored.
When the calculated image area ratio P is small (when toner replacement is low), the toner hardly deteriorates when the number of continuous image printing is small. Therefore, in the fifth aspect of the first invention, the calculated image area ratio The rotation speed of the developer agitating member (R1, R2) is set small only when printing of an image with a small P exceeds the continuous printing frequency threshold value n0. Even if such a setting is performed, the toner deterioration rate can be reduced.

(First Embodiment 6)
The developer stirring control device (D + C + D1 + M1) in the developing device according to the sixth aspect of the present invention is characterized in that, in the fourth aspect of the first invention, the following structural requirements (A014 ′) to (A016 ′) are provided. .
(A014 ′) The number of times of continuous printing n ₁ when printing of images having a calculated image area ratio P smaller than the image area ratio first setting threshold value P1 is continued, and the image area ratio second setting threshold value P2 A continuous printing counter (KT ′) that counts the continuous printing number n ₂ when printing of small images is continued.
(A015 ') the continuous printing number _{n 1} and _{n 2} thresholds (continuous printing frequency threshold) continuous printing number threshold storage means for storing _{n 1} 0 and _{n 2} 0 (C8'),
(A016 ') When the calculated image area ratio P is smaller than the image area ratio first setting threshold value P1, printing of an image exceeds the continuous printing frequency threshold value n ₁₀ and the image area ratio The rotation speed of the developer agitating member (R1, R2) is set small and stored only when printing of an image smaller than the second setting threshold value P2 continues beyond the continuous printing frequency threshold value n _20. The stirring member rotation speed setting storage means (C9).

(Operation of the sixth aspect of the first invention)
In the developer agitation control device (D + C + D1 + M1) in the developing device according to the fifth aspect of the first invention having the structural requirements (A014 ′) to (A016 ′), the continuous printing number counter (KT ′) is the calculated image area ratio. When the printing of images with a smaller P is smaller than the image area ratio first setting threshold value P1, the number of continuous printings n ₁ and when the image is smaller than the image area ratio second setting threshold value P2 are continuously printed. to Kauto continuous printing number n ₂ in the case of.
The continuous printing frequency threshold storage means (C8 ′) stores the threshold values (continuous printing frequency thresholds) n ₁ 0 and n ₂ 0 of the continuous printing times n ₁ and n ₂ .
The stirring member rotation speed setting storage means (C9) continuously prints an image whose calculated image area ratio P is smaller than the image area ratio first setting threshold value P1 exceeding the continuous printing frequency threshold value n _10. And the developer agitating member (R1, R2) only when printing of images smaller than the image area ratio second setting threshold value P2 continues beyond the continuous printing frequency threshold value n _20. ) Set the rotation speed to a small value and store it.
Since the toner hardly deteriorates when the calculated image area ratio P is small (when the toner replacement is small) and the number of times of continuous printing (n ₁ , n ₂ ) is small, the toner is hardly deteriorated. Then, the rotation of the developer agitating member (R1, R2) is performed only when the printing of the image having the small calculated image area ratio P continues beyond the continuous printing frequency threshold (n ₁ 0, n ₂ 0). The speed is set small. Even if such a setting is performed, the toner deterioration rate can be reduced.

(First embodiment 7)
The developer agitation control device (D + C + D1 + M1) in the developing device according to the seventh aspect of the first invention is provided with the following constituent elements (A017) to (A020) in the first invention or the first to sixth aspects of the first invention. It is characterized by.
(A017) Photo ratio calculation storage means (C3) for calculating and storing a photo ratio Q, which is the ratio of the gradation display portion to the total display portion of the image for one page on which image recording is performed next,
(A018) Photo ratio threshold storage means (C4) for storing a threshold (photo ratio discrimination threshold, Q1 to Q3) for determining whether or not the calculated photo ratio (calculated photo ratio) Q is small;
(A019) Photo ratio comparison determination means (C5) for determining whether or not the calculated photo ratio Q is smaller than the photo ratio determination thresholds (Q1 to Q3);
(A020) The image area ratio setting thresholds (P1, P2) are set larger when the calculated photograph ratio Q is larger than the photograph ratio determination thresholds (Q1 to Q3) compared to a smaller case. Image area ratio threshold setting storage means (C6).

(Operation of the first aspect 7)
In the developer agitation control device (D + C + D1 + M1) in the developing device according to the seventh aspect of the first invention having the structural requirements (A017) to (A020), the photographic ratio calculation storage means (C3) next performs image recording 1 The photograph ratio Q, which is the ratio of the gradation display portion to the entire display portion of the image for the page, is calculated and stored.
The photo ratio threshold storage means (C4) stores a threshold (photo ratio discrimination threshold, Q1 to Q3) for determining whether or not the calculated photo ratio (calculated photo ratio) Q is small.
The photograph ratio comparison / determination means (C5) determines whether or not the calculated photograph ratio Q is smaller than the photograph ratio determination thresholds (Q1 to Q3).
The image area ratio threshold setting storage means (C6) is configured such that when the calculated photograph ratio Q is larger than the photograph ratio determination thresholds (Q1 to Q3), the image area ratio setting threshold is smaller than the smaller one. (P1, P2) is set large.
The larger the calculated photo ratio (P), the smaller the toner consumption and the less the toner replacement. In Embodiment 6 of the first aspect of the present invention, the image area ratio setting threshold (P1, P2) is set larger. The rotational speed of the developer stirring members (R1, R2) is reduced. By performing such settings, the toner deterioration rate can be appropriately reduced.

(Embodiment 8 of the first invention)
The developer stirring control device (D + C + D1 + M1) in the developing device according to the seventh aspect of the present invention comprises the following structural requirements (A021) to (A023) in the first invention or the first to sixth aspects of the present invention. It is characterized by.
(A021) The photograph ratio threshold value storage means (C4) for storing a plurality of threshold values (photo ratio determination threshold values, Q1 to Q3) for determining whether or not the calculated photograph ratio (calculated photograph ratio) Q is small. ,
(A022) Photo ratio comparison determination means (C5) for determining whether or not the calculated photo ratio Q is smaller than each of the plurality of photo ratio determination thresholds (Q1 to Q3),
(A023) When the calculated photo ratio Q is larger than each of the plurality of photo ratio determination thresholds (Q1 to Q3), the image area ratio setting threshold (P1, P2) is set larger than when the calculated photo ratio Q is small. The image area ratio threshold value setting storage means (C6) to be set.

(Operation of the eighth aspect of the first invention)
In the developer agitation control device (D + C + D1 + M1) in the developing device according to the eighth aspect of the first invention having the structural requirements (A021) to (A023), the photographic ratio threshold storage means (C4) is configured to calculate the calculated photographic ratio. (Calculated photo ratio) A plurality of threshold values (photo ratio determination threshold values, Q1 to Q3) for determining whether or not Q is small are stored.
The photograph ratio comparison / determination means (C5) determines whether or not the calculated photograph ratio Q is smaller than each of the plurality of photograph ratio determination thresholds (Q1 to Q3).
The image area ratio threshold setting storage means (C6) is configured such that when the calculated photograph ratio Q is larger than each of the plurality of photograph ratio determination thresholds (Q1 to Q3), the image area is smaller than the smaller one. The ratio setting threshold (P1, P2) is set large.
The larger the calculated photograph ratio, the smaller the toner consumption and the less the toner replacement. Therefore, in Embodiment 7 of the first invention, the larger the calculated photograph ratio, the larger the plurality of image area ratio setting threshold values (P1, P2), thereby rotating the developer stirring member (R1, R2). The speed is reduced. By setting a plurality of image area ratio setting thresholds (P1, P2) in this way, the toner deterioration rate can be more appropriately reduced.

(Second invention)
The image forming apparatus (U) according to the second aspect of the invention is characterized by comprising the following structural requirements (A024).
(A024) The developer stirring control device (D + C + D1 + M1) in the developing device according to any one of the first invention or the first to eighth embodiments.
(Operation of the second invention)
The image forming apparatus (U) according to the second aspect of the invention having the structural requirement (A024) includes the developer stirring control device (D + C + D1 + M1) in the developing device according to any one of the first aspect or the first aspect of the first aspect. Thus, the deterioration rate of the toner in the developing device (D) can be reduced.

The above-described developer agitation control device in the developing device and the image forming apparatus provided with the organ agitation developer agitation control device of the present invention have the following effect (E01).
(E01) It is possible to reduce the deterioration rate of the toner in the developing device when continuously printing images with a small image area ratio (images with low toner consumption and little toner replacement in the developing device). .

Next, specific 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.

FIG. 1 is a longitudinal sectional view of an image forming apparatus provided with a developer stirring control device in a developing device of the present invention.
In FIG. 1, an image forming apparatus U is detachably mounted on a digital copying machine body U1 as an image forming apparatus body having a platen glass (transparent document table) PG on an upper surface thereof, and the platen glass PG. And an automatic document feeder (auto document feeder, ADF) U2.
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 is sequentially discharged through the copy position on the platen glass PG to the document discharge tray TG2.

The copying machine main body U1 includes a UI (user interface), an IIT (image input terminal) as an image reading unit sequentially arranged below the platen glass PG, and an IOT (image output terminal) as an image recording operation unit. ) And an IPS (Image Processing System) provided in the IIT or IOT.
The IIT as a document reading device arranged below the transparent platen glass PG on the upper surface of the copying machine main body U1 has an exposure system registration sensor (platen registration sensor) Sp and an exposure optical system A arranged at a platen registration position. Yes.

The movement and stop of the exposure optical system A are controlled by the detection signal of the exposure system registration sensor Sp, and always stop at the home position.
In 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.
The exposed reflected light from the original document Gi passes through the exposure optical system A and is converged on a CCD (solid-state imaging device). The CCD converts the reflected document light converged on the imaging surface into an electric signal.

The 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 device DL of the IOT.
The laser drive signal output device DL outputs a laser drive signal corresponding to the input image data to a ROS (latent image writing scanning device). The operations of the IPS, the laser drive signal output device DL, the power supply circuit E, and the like are controlled by a controller C configured by a computer.
The image carrier PR disposed below the ROS rotates in the direction of the arrow Ya. The surface of the image carrier PR is charged to, for example, − (minus) 700 V by a charging roll (charger, charge roll) CR in the charging region Q0, and then the ROS (latent image writing device) at a latent image writing position Q1. ) To be exposed and scanned to form an electrostatic latent image of −300 V, for example. The latent image formation by the laser beam L on the image carrier PR is started after a predetermined time has elapsed since a sheet sensor (not shown) detects the leading edge of the sheet. The surface of the image carrier PR on which the electrostatic latent image is formed rotates and moves sequentially through the development area Q2 and the transfer area (image recording position) Q4.

A developing device (developing apparatus) D that develops the electrostatic latent image in the developing area Q2 conveys a developer including a negatively charged toner and a positively charged carrier to the developing area Q2 by the developing roller R0. Then, the electrostatic latent image on the image carrier PR passing through the development area Q2 is developed into a toner image Tn.
The transfer roll TR facing the image carrier PR in the transfer region (image recording position) Q4 is a member for transferring the toner image on the surface of the image carrier PR to the sheet S, and is used for developing used in the developing device D. A transfer voltage having a polarity opposite to the charging polarity of the toner is supplied from the power supply circuit E. A power supply having a charging bias applied to the charging roll CR, a developing bias applied to the developing roll R0, a bias such as a transfer bias applied to the transfer roll TR, and a heater power supply for heating a heater of a heating roll of the fixing device F described later The circuit E is controlled by the controller C.

A first paper feed tray TR1 and a second second paper feed tray TR2 are arranged vertically below the copier body U1.
A take-out roll (pickup roll) Rp is disposed at the upper end of the right end of the first paper feed tray TR1 and the second paper feed tray TR2, and the sheets taken out by the take-out roll Rp are fed into the paper feed trays TR1, It is conveyed to the paper feed path SH1 on the right side of TR2.
A paper feed member Rs is disposed in the paper feed path SH1, and the paper feed member Rs has a paper feed roll Rs1 and a separation roll (separation member) Rs2 that form a nip portion by a portion that is pressed against each other. . The sheets conveyed to the nip portion are separated one by one by the sheet feeding member Rs and conveyed to the downstream side portion of the sheet conveying path SH1. A downstream portion of the sheet conveyance path SH1 extends vertically, and a conveyance roll (forward / reverse rotation conveyance roll) Rb that can rotate forward and reverse is disposed. The sheet S conveyed to the sheet conveyance path SH1 is conveyed to the upper upstream sheet conveyance path SH2 by a conveyance roll Rb that can rotate forward and backward.

The sheet S conveyed to the upstream sheet conveyance path SH2 is conveyed to the registration roll Rr by the conveyance roll Ra. The sheet S conveyed to the registration roll Rr is conveyed from the pre-transfer sheet guide SG1 to the transfer area Q4 in time with the toner image on the image carrier PR moving to the transfer area (image recording position) Q4. Is done.
The toner image Tn developed on the surface of the image carrier PR is transferred to the sheet S by the transfer roll TR in the transfer region Q4. After the transfer, the surface of the image carrier PR is cleaned by the photoreceptor cleaner CL1 to remove the residual toner, and then the charge is removed by the photoreceptor neutralizer JL and then recharged by the charging roll CR.
An image recording member G (PR + CR + ROS + D + TR + CL1 + JL) is constituted by the image carrier PR, charging roll CR, ROS (latent image writing device), developing unit D, transfer roll TR, photoconductor cleaner CL1, photoconductor static eliminator JL, and the like. Yes.

On the downstream side of the transfer area (image recording position) Q4 in the sheet conveyance direction, a downstream sheet conveyance path SH3 is provided for the recorded sheet S on which the toner image is recorded in the transfer area Q4. The sheet S on which the toner image is transferred by the transfer roll TR in the transfer region (image recording position) Q4 is peeled off from the surface of the image carrier PR, and is fed by the sheet guide SG2 and the sheet transport belt BH in the downstream sheet transport path SH3. It is conveyed to the fixing area Q5. When the sheet S passes through the fixing region Q5, the toner image is heated and fixed by the fixing device F, and then conveyed to the sheet discharge tray TRh through the sheet discharge path SH4.
A switching gate (sheet transport direction control member) GT is disposed on the downstream side of the fixing device F in the sheet discharge path SH4. The switching gate GT switches the conveyance direction of the sheet S that has passed through the fixing device F to either the sheet discharge tray TRh side or the sheet reverse connection path SH5. The sheet reversing connection path SH5 connects the upstream end of the sheet discharge path SH4 (the downstream portion of the fixing device F) and the sheet conveyance path SH1.

In the case of duplex copying, the one-side recorded sheet S on which the first-side toner image is recorded is fed from the sheet reversal connection path SH5 by the switching gate GT to the sheet feeding path by the forward / reverse rotation transport roll Rb at the upper end of the sheet feeding path SH1. After being conveyed below SH1, it is retransmitted to the upper upstream sheet conveying path SH2 in a state of being switched back and reversed.
The one-side recorded sheet S that has been reversed and retransmitted to the upstream sheet conveyance path SH2 is retransmitted to the transfer area (image recording position) Q4, and the toner image is transferred to the second side.

(Developer)
FIG. 2 is a block diagram of the developing device and its driving circuit.
In FIG. 2, a developing device D disposed opposite to the image carrier PR in the developing region Q2 has a developing container V that contains a two-component developer composed of a negatively chargeable toner and a positively chargeable magnetic carrier. is doing. Inside the developing container V, a developing roll storage chamber V0 for storing a developing roll (developer transport member) R0 and stirring member storage chambers V1, V2 for storing developer stirring members R1, R2 are provided. It has been. The developing roll R0 includes a magnet roll R0a and a rotatable developing sleeve (developer conveying sleeve) R0b disposed outside the magnet roll R0a. During the developing operation, the developing roll R0 and the developer stirring members R1 and R2 are rotationally driven by the rotational force of the developing device motor M1. The developing roll R0 and the developer agitating / conveying members R1 and R2 are rotated in conjunction with the developing device motor M1.
A partition wall Va is provided between the stirring member storage chambers V1 and V2 for storing the developer stirring members R1 and R2, respectively. The stirring member storage chambers V1 and V2 communicate with each other at both ends of the partition wall Va, and the developer in the developing container V is stirred while being circulated by the developer stirring members R1 and R2.

In FIG. 2, a developer replenishing port 1 is formed on the upper right side surface (Y side Z direction surface) of the developer container V. Further, a layer thickness regulating member 2 for regulating the layer thickness of the developer on the developing roll R0 is disposed in the developing container V. A developer supply tube 3 is connected to the developer container V above the developer supply port 1, and the inside of the developer supply tube 3 communicates with the developer supply port 1 of the developer container V.
Above the developer container V, a developer cartridge mounting case 4 is disposed. A developer cartridge 6 in which a two-component developer having a high toner concentration (high concentration developer) is stored is detachably mounted in the developer cartridge mounting case 4. A reserve tank 7 is provided below the developer cartridge mounting case 4. The two-component developer supplied from the developer cartridge 6 to the reserve tank 7 is agitated while circulating in the reserve tank 7 by the agitating and conveying members 8 a to 8 c in the tank and is conveyed to the developer supply cylinder 3.
The tank agitating and conveying members 8a to 8c are rotationally driven by a developer replenishing motor M2.
The replenishment of the two-component developer is a detection value of a toner image density sensor SN1 (see FIG. 3 described later) that detects the density of a density detection toner image (toner patch) formed on the image carrier PR during normal use. It is done by.

In FIG. 2, a discharge developer transport cylinder connecting portion 11 is disposed outside a developer discharge port (not shown) formed on the right side surface (Y side surface) of the developer container V.
A front end portion (X end portion) of the discharge developer transport tube 12 is connected to the discharge developer transport tube connection portion 11, and a rear end portion (−X end portion) of the discharge developer transport tube 12. ) Is connected to the discharged developer recovery tank 13.
Inside the discharge developer transport cylinder 12, a discharge developer transport member (not shown) is disposed. The excess developer discharged into the discharge developer transport cylinder 12 by the rotation of the discharge developer transport member is transported to the discharged developer recovery tank 13.
The developing device D, the controller C, the developing device motor drive circuit D1, and the developing device motor M1 constitute an in-developer developer stirring control device (D + C + D1 + M1).

FIG. 3 is a block diagram of the control unit of the image forming apparatus provided with the developer stirring control device in the developing device of the present invention.
FIG. 4 is a block diagram continued from the block diagram of the control unit of the image forming apparatus provided with the developer agitation control device in the developing unit shown in FIG.
3 and 4, the controller C includes 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) stored, RAM (random access memory) for temporarily storing necessary data, CPU (central processing unit) that performs processing according to the program stored in the ROM, and It is constituted by a computer having a clock oscillator and the like, and various functions can be realized by executing a program stored in the ROM.

(Signal input element connected to controller C)
The controller C receives signals from a UI (user interface), the toner image density sensor SN1, the toner density sensor SN2 in the developing container, and other signal input elements.
The UI includes a display UIa, a copy start key UIb, a copy number setting input key UIc, a numeric keypad UId, and the like.

(Control element connected to controller C)
The controller C is connected to the developing device motor drive circuit D1, the developer supply motor drive circuit D2, and other control elements, and outputs their operation control signals.
The developing device motor drive circuit D1 rotationally drives the developing roll R0, the developer stirring members R1, R2, and the like of the developing device D via the developing device motor M1.
The developer replenishing motor drive circuit D2 rotates and drives the agitation transport members 8a to 8c in the reserve tank 7 via the developer replenishing motor M2.

(Function of controller C)
The controller C has a function of executing processing according to an input signal from the signal output element and outputting a control signal to each control element.
That is, the controller C has the following functions.
C1: Developer replenishment control means The developer replenishment control means C1 has a developer replenishment amount setting means C1a and replenishes the developer replenishment amount set by the developer replenishment amount setting means C1a.
C1a: Developer replenishment amount setting means The developer replenishment amount setting means C1a is a developer replenishment amount (the rotational speed or the number of revolutions of the agitating and conveying members 8a to 8c in the tank) according to the toner image density detection value of the toner image density sensor SN1. ) Is set.

C2: Image Area Ratio Calculation Storage Unit The image area ratio calculation storage unit C2 calculates and stores an image area ratio (calculated image area ratio) P% of an image for one page on which image recording is performed next.
C3: Photo Ratio Calculation Storage Unit The photo ratio calculation storage unit C3 calculates and stores a photo ratio Q% which is a ratio of the gradation display portion to the entire display portion of the image for one page on which image recording is performed next.

C4: Photo Ratio Threshold Storage Unit The photo ratio threshold storage unit C4 stores photo ratio determination thresholds Q1 to Q3 for determining whether or not the calculated photo ratio (calculated photo ratio) Q is small. In the embodiment, the photo ratio discrimination threshold Q1 is set to 25%, the photo ratio discrimination threshold Q2 is set to 50%, and the photo ratio discrimination threshold Q3 is set to 75%. .
C5: Photo ratio comparison / determination unit The photo ratio comparison / determination unit C5 determines whether the photo ratio Q is smaller than the photo ratio determination thresholds Q1 to Q3.
C6: Image Area Ratio Threshold Setting Storage Unit The image area ratio threshold setting storage unit C6 includes a threshold reference value storage unit C6a, a setting threshold value calculation correction coefficient storage unit C6b, and a set threshold value calculation storage unit C6c. When the photo ratio Q is larger than the photo ratio determination thresholds Q1 to Q3, the first set threshold (the image area ratio first set threshold, the image area ratio set threshold) is compared with the case where the photo ratio Q is small. ) P1 and the second setting threshold (image area ratio second setting threshold, image area ratio setting threshold) P2 are set large and stored.

C6a: Threshold reference value storage means The threshold reference value storage means C6a includes a first threshold reference value storage means C6a1 and a second threshold reference value storage means C6a2, and the image area ratio calculation storage. The threshold reference values P1a and P2a for determining whether or not the image area ratio (calculated image area ratio) P calculated by the means C2 is small are stored.
C6a1: First threshold reference value storage means The first threshold reference value storage means C6a1 stores a first threshold reference value P1a. In the embodiment, the first threshold reference value P1a is set to P1a = 6%.
C6a2: Second Threshold Reference Value Storage Unit The second threshold reference value storage unit C6a2 stores a second threshold reference value P2a. In the embodiment, the second threshold reference value P2a is set to P2a = 4%.

C6b: Correction coefficient storage means for setting threshold calculation The correction coefficient storage means C6b for setting threshold calculation calculates the value of the correction coefficient α according to the photo ratio (calculated photo ratio) Q% stored in the photo ratio calculation storage means C3. Is set (α = α0 to α3) and stored. In this embodiment, correction coefficients α0 = 1.0, α1 = 1.1, α2 = 1.2, and α3 = 1.3 are set.
When the photographic ratio Q is smaller than Q1 (25%) (Q <Q1), the correction coefficient α is set to α0 (= 1.0) and stored.
When the photographic ratio Q is equal to or higher than Q1 (25%) and smaller than Q2 (50%) (Q1 ≦ Q <Q2), the correction coefficient α is set to α1 (= 1.1) and stored.
When the photographic ratio Q is equal to or greater than Q2 (50%) and smaller than Q3 (75%) (Q2 ≦ Q <Q3), the correction coefficient α is set to α2 (= 1.2) and stored.
When the photographic ratio Q is Q3 (75%) or more (Q3 ≦ Q), the correction coefficient α is set to α3 (= 1.3) and stored.

C6c: Setting threshold value calculation storage means The setting threshold value calculation storage means C6c has a first setting threshold value P1% according to the value of the correction coefficient α (= α0 to α3) stored in the setting threshold value calculation correction coefficient storage means C6b. And the value of 2nd setting threshold value P2% is calculated and memorize | stored.
The first set threshold value P1 is obtained by the following equation based on the set correction coefficient α and the first threshold reference value P1a (= 6%) stored in the first threshold reference value storage means C6a1. be able to.
P1 (%) = P1a (6%) × α (α0 = 1.0) (1)
According to the equation (1), when the photo ratio Q <Q1 (25%), the first setting threshold value P1 is set to 6%.
The second set threshold value P2 is calculated based on the set correction coefficient α and the second threshold reference value P2a (= 4%) stored in the second threshold reference value storage means C6a2. Can be obtained.
P2 (%) = P2a (4%) × α (α0 = 1.0) (2)
According to the equation (2), when the photo ratio Q <Q1 (25%), the second setting threshold value P2 is set to 4%.
The setting threshold value calculation storage means C6c stores the set first setting threshold value P1 (= 6%) and second setting threshold value P2 (= 4%).

When the photographic ratio Q is equal to or greater than Q1 (25%) and smaller than Q2 (50%) (Q1 ≦ Q <Q2), the correction coefficient α in the equations (1) and (2) is set to α1 (= 1) .1), the first setting threshold value P1 (= 6.6%) and the second setting threshold value P2 (= 4.4%) are calculated and stored.
When the photographic ratio Q is equal to or greater than Q2 (50%) and smaller than Q3 (75%) (Q2 ≦ Q <Q3), the correction coefficient α in the equations (1) and (2) is set to α2 (= 1). .2), the first setting threshold value P1 (= 7.2%) and the second setting threshold value P2 (= 4.8%) are calculated and stored.
When the photographic ratio Q is Q3 (75%) or more (Q3 ≦ Q), the correction coefficient α in the equations (1) and (2) is set to α3 (= 1.3), and the first set threshold value is set. P1 (= 7.8%) and the second set threshold value P2 (= 5.2%) are calculated and stored.

C7: Image area ratio comparison / determination unit The image area ratio comparison / determination unit C7 sets the image area ratio P to the ratio first setting threshold value P1 and the second setting threshold value P2 set in the image area ratio threshold setting storage unit C6. It is determined whether or not it is small.
C8: Continuous printing frequency threshold storage unit The continuous printing frequency threshold storage unit C8 stores a continuous printing frequency threshold n0. In Example 1, the continuous printing frequency threshold value n0 is set to “10”.
KT: Continuous Print Count Counter The continuous print count counter KT counts the continuous print count n when the image area ratio P is continuously printed smaller than the first set threshold value P1.

C9: Stirring member rotation speed setting storage means The stirring member rotation speed setting storage means C9 is a reference value storage means C9a for developing device motor rotation speed, a correction coefficient storage means C9b for setting rotation speed calculation, and a setting motor rotation speed calculation storage. Means C9c, and printing of an image in which the image area ratio P is smaller than the first set threshold value P1 continues beyond the continuous printing frequency threshold value n0 (= 10). The rotational speed N of the developer motor M1 is set and stored so that the rotational speed of the developer agitating members R1 and R2 is small.
C9a: Developer motor rotation speed reference value storage means The developer motor rotation speed reference value storage means C9a is a reference value N0 of the rotation speed N of the developer motor M1 so that the developing roller R0 has a desired value. Memorize [rpm]. That is, since the developing roll R0 and the developer agitating members R1 and R2 rotate in conjunction with the rotation of the developing device motor M1, the rotation speed of the developer agitating members R1 and R2 is indirectly set. The

C9b: Correction coefficient storage means for setting rotational speed calculation The correction coefficient storage means C9b for setting rotational speed calculation corresponds to the set threshold values P1 and P2 of the image area ratio P (%) stored in the image area ratio calculation storage means C2. The rotational speed correction coefficient β (= β0 to β2) of the developing device motor M1 is set and stored according to the size. In the first embodiment, correction coefficients β0 = 1.0, β1 = 1.3 / 1.6, and β2 = 1 / 1.6 are set.
When the image area ratio P (%) is larger than the first set threshold value P1 (%) (P1 ≦ P), the correction coefficient β is set to β0 (= 1.0) and stored.
When the image area ratio P (%) is smaller than the first set threshold value P1 (%) and equal to or larger than the second set threshold value P2 (%) (P2 ≦ P <P1), the correction coefficient β is set to β1 (= 1). Set to 3 / 1.6) and store.
When the image area ratio P is smaller than the second set threshold value P2 (%) (P <P2), the correction coefficient β is set to β2 (= 1.0 / 1.6) and stored.

C9c: Set motor rotation speed calculation storage means The set motor rotation speed calculation storage means C9c is configured according to the value of the correction coefficient β (= β0 to β2) stored in the set rotation speed calculation correction coefficient storage means C9b. The rotational speed N (rpm) of the developing device motor M1 is calculated and stored. That is, when the image area ratio P (%) is equal to or larger than the first set threshold value P1 stored in the image area ratio threshold value setting storage means C6 (P1 ≦ P), the developing device motor is expressed by the following equation (3). The rotational speed N (rpm) of M1 can be calculated.
N (rpm) = N0 ......... Formula (3)
When the image area ratio P (%) is equal to or larger than the second setting threshold P2 stored in the image area ratio threshold setting storage unit C6 and smaller than the first setting threshold P1 (P2 ≦ P <P1), The rotational speed N (rpm) of the developing device motor M1 can be calculated by the equation (4).
N (rpm) = N0 × 1.3 / 1.6... Equation (4)
When the image area ratio P (%) is smaller than the second set threshold value P2 (P <P2), the rotation speed N (rpm) of the developing device motor M1 can be calculated by the following equation (5). .
N (rpm) = N0 × 1 / 1.6 ........ Formula (5)
The rotation speed N (rpm) of the developing device motor M1 calculated by the equations (3) to (5) is stored in the set motor rotation speed calculation storage means C9c.

(Explanation of flowchart of threshold setting process)
FIG. 5 is a flowchart of the threshold setting process of the present invention.
The processing of each ST (step) in the flowchart of FIG. 5 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 flowchart of the threshold setting process in FIG. 5 is started when the image forming apparatus U is turned on.

In ST1 of FIG. 5, it is determined whether or not the copy start key is turned on. If no (N), ST1 is repeated, and if yes (Y), the process proceeds to ST2.
In ST2, it is determined whether or not there is print image data. If no (N), the process returns to ST1, and if yes (Y), the process proceeds to ST3.
In ST3, the picture ratio Q (%) of the image for one page is calculated and stored. Then, the process proceeds to ST4.
In ST4, it is determined whether or not the photo ratio Q is smaller than Q1 (25%). If yes (Y), the process proceeds to ST5. If no (N), the process proceeds to ST6.
In ST5, the following processes (1) and (2) are executed, and the process returns to ST2.
(1) The first setting threshold value P1 is set to 6 [%].
(2) The second setting threshold value P2 is set to 4 [%].

In ST6, it is determined whether or not the photo ratio Q is smaller than Q2 (50%). If yes (Y), the process proceeds to ST7. If no (N), the process proceeds to ST8.
In ST7, the following processes (1) and (2) are executed, and the process returns to ST2.
(1) The first setting threshold value P1 is set to 6.6 [%].
(2) The second setting threshold value P2 is set to 4.4 [%].
In ST8, it is determined whether or not the photo ratio Q is smaller than Q3 (75%). If yes (Y), the process proceeds to ST9, and if no (N), the process proceeds to ST10.
In ST9, the following processes (1) and (2) are executed, and the process returns to ST2.
(1) The first setting threshold value P1 is set to 7.2 [%].
(2) The second setting threshold value P2 is set to 4.8 [%].
In ST10, the following processes (1) and (2) are executed, and the process returns to ST2.
(1) The first setting threshold value P1 is set to 7.8 [%].
(2) The second setting threshold value P2 is set to 5.2 [%].

FIG. 6 is a flowchart of the developing roll peripheral speed setting process.
Each ST (step) process in the flowchart of FIG. 6 is executed in parallel with other various processes of the image forming apparatus U, similarly to the threshold value setting process flowchart shown in FIG.
The flowchart of the developing roll peripheral speed setting process (that is, the developing device motor rotational speed setting process) shown in FIG. 6 is started when the image forming apparatus U is turned on.
In ST21 of FIG. 6, it is determined whether or not the copy start key is turned on. If no (N), ST21 is repeated, and if yes (Y), the process proceeds to ST22.
In ST22, it is determined whether there is image data for printing. If no (N), the process returns to ST21. If yes (Y), the process proceeds to ST23.
In ST23, the image area ratio P (%) of the image for one page is calculated and stored. Then, the process proceeds to ST24.

In ST24, it is determined whether or not the image area ratio P (%) is equal to or greater than the first set threshold value P1 set by the flowchart of the threshold value setting process shown in FIG. If yes (Y), the process proceeds to ST25, and, if no (N), the process proceeds to ST26.
In ST25, the following processes (1) and (2) are executed, and the process returns to ST22.
(1) The count value n of the continuous printing number counter KT is set to “n = 0”.
(2) The rotation speed N [rpm] of the developing device motor M1 is set to the reference value N0 of the developing device motor rotation speed.
In ST26, the count value n of the continuous printing number counter KT is set to “n = n + 1”. Then, the process proceeds to ST27.
In ST27, it is determined whether or not the count value n of the continuous printing number counter KT is 10 or more. If no (N), the process proceeds to ST28, and if yes (Y), the process proceeds to ST29.

In ST28, the rotation speed N [rpm] of the developer motor M1 is set to the reference value N0 of the developer motor rotation speed, and the process returns to ST22.
In ST29, it is determined whether or not the image area ratio P (%) is equal to or greater than the second set threshold value P2 set by the flowchart of the threshold value setting process shown in FIG. If yes (Y), the process proceeds to ST30, and, if no (N), the process proceeds to ST31.
In ST30, the rotation speed N [rpm] of the developing device motor M1 is set to N0 × 1.3 / 1.6 [rpm], and the process returns to ST22.
In ST31, the rotation speed N [rpm] of the developing device motor M1 is set to N0 × 1 / 1.6 [rpm], and the process returns to ST22.

FIG. 7 is a diagram showing the relationship between the image area ratio and the rotation speed of the developing device motor, and FIG. 7A is a diagram showing the relationship between the image area ratio and the developing device rotation speed when the photographic ratio is smaller than 25%. FIG. 7B is a diagram showing the relationship between the image area ratio and the rotation speed for the developing device when the photographic ratio is 75% or more.
In FIG. 7A, when the image area ratio P when the photographic ratio Q is smaller than Q1 (25%) is greater than or equal to the first set threshold value P1 (6%) (P1 ≦ P), the rotational speed N of the developing device motor M1. Is set to the reference value N0 [rpm] of the motor rotation speed for the developing device.
When the image area ratio P when the photo ratio Q is smaller than Q1 (25%) is smaller than the first setting threshold P1 (6%) and equal to or larger than the second setting threshold P2 (4%) (P2 ≦ P <P1) The rotation speed N of the developing device motor M1 is set to N0 × 1.3 / 1.6 [rpm].
When the image area ratio P when the photo ratio Q is smaller than Q1 (25%) is smaller than the second setting threshold P2 (4%) (P <P2), the rotational speed N of the developing device motor M1 is set to N0 × Set to 1 / 1.6 [rpm].

In FIG. 7B, when the image area ratio P when the photographic ratio Q is Q3 (75%) or more is equal to or more than the first set threshold value P1 (7.8%) (P1 ≦ P), the rotation speed of the developing device motor M1. N is set to a reference value N0 [rpm] of the developing motor rotation speed.
When the image area ratio P is smaller than the first setting threshold value P1 (7.8%) and the second setting threshold value P2 (5.2%) or more when the photo ratio Q is Q3 (75%) or more (P2 ≦ P <P1), the rotation speed N of the developing device motor M1 is set to N0 × 1.3 / 1.6 [rpm].
When the image area ratio P when the photo ratio Q is Q3 (75%) or more is smaller than the second set threshold value P2 (5.2%) (P <P2), the rotational speed N of the developing device motor M1 is set to N0. × Set to 1 / 1.6 [rpm].

(Operation of Example 1)
In the developer developing device agitation control device (D + C + D1 + M1) of Example 1 having the above-described configuration, the developing roll R0 and the developer agitating members R1 and R2 rotate in conjunction with the developing device motor M1. Therefore, when the rotation speed N of the developing device motor M1 is set so that the peripheral speed of the developing roll R0 becomes a desired value, the rotation speeds of the developer stirring members R1 and R2 are indirectly set. Become. For this reason, the rotation speed of the developer stirring members R1 and R2 can be reduced by lowering the set value of the rotation speed N of the developing device motor M1 when the toner in the developing container V is not changed. . In that case, toner deterioration due to excessive stirring of the developer stirring members R1 and R2 can be reduced.

When printing an image with a small image area ratio P (%) of an image for one page, the toner in the developing container V is not changed. For this reason, in the developer agitation control device (D + C + D1 + M1) of Example 1, the first setting threshold value P1 and the second setting threshold value P2 are provided, and the value of the image area ratio P (%) is set to the first value. The rotation speed N [rpm] of the developing device motor M1 is set as compared with the first setting threshold value P1 or the second setting threshold value P2.
That is, when the image area ratio P is equal to or greater than the first set threshold value P1 (P1 ≦ P), the rotation speed N of the developing device motor M1 is set to the reference value N0 [rpm] of the developing device motor rotation speed. When the image area ratio P is smaller than the first setting threshold value P1 and equal to or larger than the second setting threshold value P2 (P2 ≦ P <P1), the rotation speed N of the developing device motor M1 is set to N0 × 1.3 / 1.6 [ rpm]. When the image area ratio P is smaller than the second setting threshold value P2 (P <P2), the rotation speed N of the developing device motor M1 is set to N0 × 1 / 1.6 [rpm].
As described above, when the value of the image area ratio P (%) decreases, the rotation speed N of the developing device motor M1 is set to be low, so that toner deterioration due to the rotation of the developer stirring members R1 and R2 is reduced. be able to.

Further, when the photographic ratio Q (%), which is the ratio of the gradation display portion to the entire display portion of the image for one page, is large, the toner consumption is reduced. There is little replacement of toner in the developer container V. Therefore, the values of the first setting threshold value P1 (%) and the second setting threshold value P2 (%) are set according to the value of the photo ratio Q (%).
That is, when the photo ratio Q is smaller than Q1 (25%) (Q <Q1), the first setting threshold value P1 is set to 4%, and the second setting threshold value P2 is set to 6%. When the photo ratio Q is equal to or greater than Q1 (25%) and smaller than Q2 (50%) (Q1 ≦ Q <Q2), the first setting threshold P1 is set to 6.6%, and the second setting threshold P2 Is set to 4.4%. When the photo ratio Q is equal to or greater than Q2 (50%) and smaller than Q3 (75%) (Q2 ≦ Q <Q3), the first setting threshold P1 is set to 7.2%, and the second setting threshold P2 Is set to 4.8%. When the photo ratio Q is equal to or greater than Q3 (75%) (Q3 ≦ Q), the first setting threshold value P1 is set to 7.8% and the second setting threshold value P2 is set to 5.2%.
In this way, as the value of the photo ratio Q (%) increases, the values of the first setting threshold value P1 (%) and the second setting threshold value P2 (%) are set larger. Therefore, the developing device motor M1 The rotation speed is set small. In this case, the deterioration rate of the toner can be appropriately reduced.

  In the developer agitation control device (D + C + D1 + M1) of Example 1, when the image area ratio P (%) is small (when toner replacement is small), when the number of continuous printing of the image is small, almost no toner is contained. Since deterioration does not occur, the rotation speed N of the developing device motor M1 is set small only when printing of an image with a small image area ratio P (%) exceeds the continuous printing frequency threshold value n0 (10). To do. In this way, the rotation speed N of the developing device motor M1 is set after the continuous printing number (count value of the continuous printing number counter KT) n becomes equal to or greater than the continuous printing number threshold value n0 (10). It is not necessary to control the output of the developing device motor M1 every time the image is printed.

FIG. 8 is a block diagram of the control unit of the image forming apparatus provided with the developer agitation control device in the developing device according to the second embodiment, and is a block diagram corresponding to FIG. 4 of the first embodiment.
In the description of the second embodiment shown in FIG. 8, the same reference numerals are given to the components corresponding to the components of the first embodiment, and the detailed description thereof is omitted.
The second embodiment is different from the first embodiment in the following points, but is configured in the same manner as the first embodiment in other points.
(Function of controller C)
The controller C of the second embodiment has the following functions.
C8 ′: Continuous Print Count Threshold Storage Unit The continuous print count threshold storage unit C8 ′ includes P <P1 continuous print count threshold storage unit C8a and P <P2 continuous print count threshold storage unit C8b.
C8a: P <P1 continuous printing number threshold storage unit P <P1 continuous printing number threshold storage unit C8a stores P <P1 continuous printing number threshold n ₂ 0. In Example 2, the P <P1 continuous printing frequency threshold n ₁ 0 is set to “10”.
The P <P2 continuous printing number threshold storage unit C8b stores P <P2 continuous printing number threshold n ₂ 0. In Example 2, the P <P2 continuous printing frequency threshold n ₂ 0 is set to “8”.
KT ′: Continuous Print Count Counter The continuous print count counter KT ′ has a P <P1 continuous print count counter KT1 and a P <P2 continuous print count counter KT2.
KT1: P <P1 continuous printing number counter P <P1 continuous printing number counter KT1 counts the continuous printing number n ₁ when images having an image area ratio P smaller than the first set threshold value P1 are continuously printed.
P <P2 continuous print counter KT2 is Kauto the continuous printing number n ₂ of when the image area ratio P is smaller image than the second set threshold value P2 printing is continuous.

FIG. 9 is a flowchart of developing roller peripheral speed setting processing, and corresponds to FIG. 6 of the first embodiment.
Each ST (step) process in the flowchart of FIG. 9 is executed in parallel with other various processes of the image forming apparatus U, similarly to the threshold value setting process flowchart shown in FIG.
In ST41 of FIG. 9, it is determined whether or not the copy start key is turned on. If no (N), ST41 is repeated, and if yes (Y), the process proceeds to ST42.
In ST42, it is determined whether there is print image data. If no (N), the process returns to ST41, and if yes (Y), the process proceeds to ST43.
In ST43, the image area ratio P (%) of the image for one page is calculated and stored. Then, the process proceeds to ST44.

In ST44, it is determined whether or not the image area ratio P (%) is smaller than the first set threshold value P1 set by the threshold value setting process flowchart shown in FIG. If no (N), the process proceeds to ST45, and if yes (Y), the process proceeds to ST46.
In ST45, the following processes (1) to (3) are executed, and the process returns to ST42.
(1) the rotational speed N of the developing dexterity motor M1 [rpm] is set to the reference value N0 of the developing dexterity motor rotation speed (2) P <P1, the count value _{n 1} of continuous printing number counter KT1 _"n 1 = 0" To.
(3) the count value _{n 2} of P <P2 continuous print counter KT2 to _"n 2 = 0".
In ST46, the count value _{n 1} of P <P1 continuous print counter KT1 to _"n 1 _{= n} 1 +1".
In ST47, it is determined whether or not the area ratio P (%) is smaller than the second set threshold value P2 set by the threshold value setting process flowchart shown in FIG. If yes (Y), the process proceeds to ST48, and, if no (N), the process proceeds to ST51.

In ST48, the count value n ₂ of P <P2 continuous printing number counter KT2 is set to “n ₂ = n ₂ +1”. Next, the process proceeds to ST49.
In ST 49, the count value _{n 2} of P <P2 continuous print counter KT2 it is determined whether or not P <P2 continuous printing frequency threshold _n 2 0 (= 8) or more. If yes (Y), the process proceeds to ST50, and, if no (N), the process proceeds to ST51.
In ST50, the rotation speed N [rpm] of the developing device motor M1 is set to N0 × 1 / 1.6 [rpm], and the process returns to ST42.
In ST51, it is determined whether or not the count value _{n 1} of P <P1 continuous print counter KT1 is P2 <P <P1 continuous printing frequency threshold _n 1 0 (= 10) or more. If yes (Y), the process proceeds to ST52, and, if no (N), the process proceeds to ST53.
In ST52, the rotation speed N [rpm] of the developing device motor M1 is set to N0 × 1.3 / 1.6 [rpm], and the process returns to ST42.
In ST53, the rotation speed N [rpm] of the developer motor M1 is set to the reference value N0 of the developer motor rotation speed, and the process returns to ST42.

(Operation of Example 2)
In the developer agitation control device (D + C + D1 + M1) in the developing device of Example 2 having the above-described configuration, P <P1 continuous printing number counter KT1 continuously prints images whose image area ratio P is smaller than the first set threshold value P1. the continuous printing number n ₁ in the case of that Kauto. Wherein if the continuous printing number _{n 1} is the P <P1 continuous printing frequency threshold _n 1 0 (= 10) described above, the rotational speed N [rpm] of N0 × 1.3 / 1.6 [rpm] of the developing dexterity motor M1 Set to.
P <P2 continuous print counter KT2 is Kauto the continuous printing number n ₂ of when the image area ratio P is smaller image than the second set threshold value P2 printing is continuous. Wherein if the continuous printing number _{n 2} of said P <P2 or continuous printing frequency threshold _n 2 0 (= 8), the set rotational speed N of the developing dexterity motor M1 to [rpm] to N0 × 1 / 1.6 [rpm] To do.
By performing such setting, when images with a small image area ratio P are continuous (P <P1 images are continuous n ₁ 0 (= 10) times or more, or P <P2 images are continuous n ₂ 0 (= 8). When the number of rotations of the developing device motor M1 is reduced), the toner deterioration rate can be reduced.
In addition, the operational effects of the in-developer developer agitation control device (D + C + D1 + M1) of Example 2 are the same as the in-developer developer agitation control device (D + C + D1 + M1) of Example 1.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to each said Example, A various change is made within the range of the summary of this invention described in the claim. Is possible. Modified examples (H01) to (H06) of the present invention are exemplified below.
(H01) In the first embodiment, two threshold values for the image area ratio P (%) are provided by the first setting threshold value (P1) and the second setting threshold value (P2). It is also possible to provide one or three or more.
(H02) In each of the above embodiments, the set values (n0 = 10, n ₁ 0 = 10, n ₂ 0 = 8) of the continuous printing frequency threshold (n0, n ₁ 0, n ₂ 0) are not limited to this. the continuous printing count threshold _{(n0, n 1 0, n} 2 0) to any set value (for _{example, n0 = 8, n 1 0} = 7, n 2 0 = 6) can be set to. When the continuous printing frequency threshold value n0 of the first embodiment is set to “0” or “1”, the setting of the rotation speed of the developer stirring members (R1, R2) is set for each page.

(H03) In the first embodiment, the reference value (P1a = 6%, P2a = 4%) of the image area ratio P (%) is not limited to this, and is an arbitrary value depending on the environment and the model of the image forming apparatus. (For example, P1a = 8%, P2a = 6%, etc.).
(H04) In the first embodiment, the value of the photo ratio discrimination threshold (Q1 = 25%, Q2 = 50%, Q3 = 75%) of the photo ratio Q (%) is not limited to this, and the environment and image formation It is possible to set an arbitrary value according to the model of the device (for example, Q1 = 20%, Q2 = 40%, Q3 = 60%, etc.).
(H05) In the first embodiment, the value of the correction coefficient α (α0 = 1.0, α1 = 1.1, α2 = 1.2, α3 = 1.3) is not limited to this, and the environment and image formation It is possible to set an arbitrary value according to the model of the apparatus (for example, α0 = 1.0, α1 = 1.2, α2 = 1.4, α3 = 1.6, etc.).
(H06) In the first embodiment, when the image area ratio P is P2 ≦ P <P1, the count value of the continuous printing number counter KT is set to n = n + 1, and when P <P2, n = n + 1.2. It is possible to reduce the rotational speed of the agitating / conveying members R1 and R2 when n = 10 or more. In the case of P <P2, n = n + 1.2, but the added value of 1.2 can be set to an arbitrary value (for example, 13, 14, 15).

FIG. 1 is a longitudinal sectional view of an image forming apparatus provided with a developer stirring control device in a developing device of the present invention. FIG. 2 is a block diagram of the developing device and its driving circuit. FIG. 3 is a block diagram of the control unit of the image forming apparatus provided with the developer stirring control device in the developing device of the present invention. FIG. 4 is a block diagram continued from the block diagram of the control unit of the image forming apparatus provided with the developer stirring control device in the developing unit shown in FIG. FIG. 5 is a flowchart of the threshold setting process of the present invention. FIG. 6 is a flowchart of the developing roll peripheral speed setting process. 7 is a diagram showing a control relationship between the image area ratio and the developing roll rotation speed, and FIG. 7A is a diagram showing a control relationship between the image area ratio and the developing roll rotation speed when the photographic ratio is smaller than 25%. FIG. 5 is a diagram showing a control relationship between an image area ratio and a developing roll rotation speed when the photographic ratio is 75% or more. FIG. 8 is a block diagram of the control unit of the image forming apparatus provided with the developer agitation control device in the developing device according to the second embodiment, and is a block diagram corresponding to FIG. 4 of the first embodiment. FIG. 9 is a flowchart of developing roller peripheral speed setting processing, and corresponds to FIG. 6 of the first embodiment.

Explanation of symbols

C2: Image area ratio calculation storage means,
C3: Photo ratio calculation storage means,
C4: Photo ratio threshold value storage means,
C5: Photo ratio comparison / discrimination means,
C6: Image area ratio threshold value setting storage means,
C6a: threshold value reference value storage means,
C7: Image area ratio comparison determination means,
C8: Continuous printing frequency threshold value storage means,
C9: Stirring member rotation speed setting storage means,
D ... Developer,
D + C + D1 + M1 ... Developer developer agitation control device,
KT: Continuous printing counter
n, n ₁ , n ₂ ... continuous printing times,
_{n0, n 1 0, n 2} 0 ... continuous printing number of times threshold,
P: Calculated image area ratio,
P1, P2 ... Image area ratio setting threshold,
P1a, P2a ... threshold value reference values,
PR: Image carrier,
Q1-Q3 ... Threshold for determining the photo ratio,
R0: Developing roll,
R1, R2 ... stirring members,
U: Image forming apparatus,
V: Developer container.

Claims (10)

A developer agitation control device in the developing device having the following constituent elements (A01) to (A05):
(A01) A developer container containing a developer containing toner, a developer agitating member rotatably accommodated in the developer container and agitating the developer, and rotatably accommodated in the developer container and the agitated A developing roller for transporting the developer to the surface of the image carrier on which the electrostatic latent image is formed, and developing the electrostatic latent image formed on the surface of the image carrier to a toner image;
(A02) Image area ratio calculation storage means for calculating and storing the image area ratio P of an image for one page on which image recording is performed next;
(A03) a threshold reference value storage unit that stores a threshold reference value for determining whether or not the calculated image area ratio (calculated image area ratio) P is small, and based on the reference value An image area ratio threshold setting storage means for setting a threshold and storing the set threshold as an image area ratio setting threshold;
(A04) Image area ratio comparison and determination means for determining whether or not the calculated image area ratio P is smaller than the image area ratio setting threshold;
(A05) Stirring member rotation speed setting storage means for setting and storing the rotation speed of the developer agitating member smaller when the calculated image area ratio P is smaller than the image area ratio setting threshold. The developer agitation control device in a developer unit according to claim 1, comprising the following constituent elements (A06) and (A07):
(A06) The developing roll and the developer stirring member that rotate in conjunction with each other;
(A07) When the calculated image area ratio is smaller than the image area ratio setting threshold, the rotation speed N of the developing roll is set smaller than when the calculated image area ratio is larger, resulting in the rotation of the developer stirring member. The agitating member rotation speed setting storage means for setting and storing the speed small. The developer agitation control device in a developer unit according to claim 1, comprising the following constituent elements (A06) and (A07 '):
(A06) The developing roll and the developer stirring member that rotate in conjunction with each other;
(A07 ′) When the calculated image area ratio P is smaller than the image area ratio setting threshold, the peripheral speed of the developing roll is set to be smaller than when the calculated image area ratio P is large. The stirring member rotation speed setting storage means for setting the rotation speed to be small and storing it. The developer agitation control device in a developer unit according to any one of claims 1 to 3, comprising the following constituent elements (A08) to (A010):
(A08) A continuous printing number counter that counts the number n of continuous printings when printing of an image in which the calculated image area ratio P is smaller than the image area ratio setting threshold is continued;
(A09) Continuous printing frequency threshold storage means for storing the threshold value (continuous printing frequency threshold) n0 of the continuous printing frequency n (A010) Printing an image in which the calculated image area ratio P is smaller than the image area ratio setting threshold value The stirring member rotation speed setting storage means for setting the rotation speed of the developer stirring member to be small and storing it only when the continuous printing frequency threshold value n0 is continued. The developer agitation control device in a developer unit according to any one of claims 1 to 3, comprising the following constituent elements (A011) to (A013):
(A011) As threshold values for determining whether or not the calculated image area ratio (calculated image area ratio) P is small, two threshold values, a first threshold value P1 and a second threshold value P2 smaller than the first threshold value, are used. The image area ratio threshold setting storage means for setting and storing the set first threshold value P1 and second threshold value P2 as the image area ratio first setting threshold value P1 and the image area ratio second setting threshold value P2,
(A012) The image area ratio comparison and determination means for determining whether or not the calculated image area ratio P is smaller than the image area ratio first setting threshold value P1 and the image area ratio second setting threshold value P2.
(A013) When the calculated image area ratio P is smaller than the image area ratio second setting threshold value P2 (when P <P2), the calculated image area ratio P becomes the image area ratio first setting threshold value P1. The agitation member rotation speed setting storage means for setting and storing the rotation speed of the developer agitation member to be smaller than when the image area ratio is smaller than the second setting threshold value P2 (when P1>P> P2). The developer agitation control device in a developer unit according to claim 5, comprising the following constituent elements (A014) to (A016):
(A014) A continuous printing number counter that counts the number of continuous printings n when printing of an image in which the calculated image area ratio P is smaller than the image area ratio first setting threshold value P1 continues.
(A015) Continuous printing frequency threshold storage means for storing the threshold value (continuous printing frequency threshold) n0 of the continuous printing frequency n (A016) The calculated image area ratio P is smaller than the image area ratio first setting threshold value P1. The stirring member rotation speed setting storage unit that sets and stores a low rotation speed of the developer stirring member only when image printing continues beyond the continuous printing frequency threshold value n0. The developer agitation control device in the developer unit according to claim 5, comprising the following constituent elements (A014 ') to (A016'):
(A014 ′) The number of times of continuous printing n ₁ when printing of images having a calculated image area ratio P smaller than the image area ratio first setting threshold value P1 is continued, and the image area ratio second setting threshold value P2 continuous printing number counter for Kauto continuous printing number n ₂ when compared to a small image printing is continuous,
(A015 ') the continuous printing number _{n 1} and _{n 2} thresholds (continuous printing frequency threshold) _{n 1} 0 and continuous printing number threshold storage means for storing _{n 2} 0 (A016') the calculated image area ratio P is the image Printing of an image smaller than the area ratio first setting threshold value P1 and printing smaller than the continuous printing frequency threshold value n _{10 and} printing of an image smaller than the image area ratio second setting threshold value P2 The stirring member rotation speed setting storage means for setting the rotation speed of the developer agitating member to be small and storing only when the continuous printing frequency threshold value n ₂ 0 is continued. The developer agitation control device in a developer unit according to any one of claims 1 to 7, comprising the following constituent elements (A017) to (A020):
(A017) Photo ratio calculation storage means for calculating and storing a photo ratio Q, which is the ratio of the gradation display portion to the total display portion of the image for one page on which image recording is performed next,
(A018) Photo ratio threshold value storage means for storing a threshold value (photo ratio determination threshold value) for determining whether or not the calculated photo ratio (calculated photo ratio) Q is small;
(A019) Photo ratio comparison determination means for determining whether or not the calculated photo ratio Q is smaller than the photo ratio determination threshold;
(A020) The image area ratio threshold setting storage means for setting the image area ratio setting threshold larger when the calculated photograph ratio Q is larger than the photograph ratio determination threshold. The in-developer developer agitation control device according to any one of claims 1 to 7, comprising the following constituent elements (A021) to (A023):
(A021) The photograph ratio threshold value storage means for storing a plurality of threshold values (photo ratio determination threshold values) for determining whether or not the calculated photograph ratio (calculated photograph ratio) Q is small;
(A022) Photo ratio comparison determination means for determining whether or not the calculated photo ratio Q is smaller than each of the plurality of photo ratio determination thresholds;
(A023) The image area ratio threshold setting storage means for setting the image area ratio setting threshold larger when the calculated photograph ratio Q is larger than the plurality of photograph ratio determination thresholds. . An image forming apparatus having the following configuration requirements (A024);
(A024) The developer stirring control device in a developing unit according to any one of claims 1 to 9.

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