JP2010262080A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of reducing image unevenness by keeping a toner supply amount constant without increasing control loads, and to provide an image forming apparatus. <P>SOLUTION: The developing device includes: a developing container for storing the developer containing toner and carrier; a stirring means rotatably disposed in the developing container, for stirring and conveying the developer; a toner supply means for supplying the toner to the developing container. The developing device also includes: a toner concentration-detecting means for detecting the toner concentration inside the developing container; and a control unit configured to calculate the toner consumption according to the printed images, control the toner supply means so as to supply the toner equivalent to the quantity according to the toner consumption to the developing container, and when a difference between the toner concentration inside the developing container after the toner supply and a toner concentration reference value exceeds a predetermined threshold, correct the toner supply amount to be supplied according to the toner consumption. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus.

Patent Document 1 below discloses a toner replenishment control device capable of obtaining a desired image density by making toner replenishment based on the detection result of the toner density detecting means more appropriate.
In this toner replenishment control device, the toner concentration detection means has a storage device that detects the toner concentration in the developing device and stores sensitivity information, and the toner replenishment control means includes a toner replenishment amount and a correction value for the toner replenishment amount. Calculating means, and storage means for storing the calculated toner replenishment amount and the toner replenishment amount correction value. The toner replenishment amount is calculated based on the image area ratio, and the toner in the developing device before and after toner replenishment is calculated. Based on the detection result by the toner density detecting means and the sensitivity information in the storage device of the toner density detecting means, a toner replenishment amount correction value is calculated from a mathematical formula, and the toner replenishment amount correction value is recorded in the storage means. Thus, in the toner replenishment control device, the variation in toner replenishment amount can be known from the sensitivity of the toner density detecting means, and even if there is a difference in the replenishment control of the toner replenishment device, the variation in toner replenishment amount is corrected. Thus, stable toner replenishment amount control is possible.

JP 2007-304524 A

  By the way, in the above prior art, the toner replenishment amount is calculated based on the image area ratio, and based on the detection result by the toner density detection means in the developing device before and after the toner supply and the sensitivity information in the storage device of the toner density detection means. By calculating the toner replenishment amount correction value from the formula and controlling the toner replenishment amount based on the toner replenishment amount and the correction value, stable toner replenishment amount control without variations can be achieved. However, in the above prior art, since the correction value is calculated from the mathematical expression using the detection result and sensitivity information of the toner density detecting means as parameters, the correction is performed based on the mathematical formula every time the toner density detecting means detects the toner density. The value must be calculated. For this reason, in the above-described prior art, there is a concern that the control load is increased by repeating the calculation of the correction value based on the mathematical formula.

  The present invention has been made in view of the above-described circumstances, and provides a developing device and an image forming apparatus capable of reducing image unevenness by making the toner replenishment amount constant without increasing the control load. The purpose is to do.

  In order to achieve the above object, in the present invention, as a first solving means relating to a developing device, a developer container containing a developer containing toner and a carrier, a developer container rotatably provided in the developer container, and the developer A developing device comprising: agitating means for agitating and conveying the toner; and a toner replenishing means for replenishing toner to the developing container; a toner concentration detecting means for detecting a toner concentration inside the developing container; A toner consumption amount corresponding to the toner consumption amount is calculated, and the toner supply amount is supplied to the developer container by the toner supply means. Based on the detection result of the toner density detection means, And a controller for correcting a toner replenishment amount to be replenished according to a toner consumption amount when a difference between the internal toner concentration and the toner concentration reference value exceeds a predetermined threshold value. Adopted to.

  In the present invention, as the second solving means relating to the developing device, in the first solving means, means in which the toner density detecting means is a toner density sensor is employed.

  In the present invention, as a third solving means relating to the developing device, in the first or second solving means, the control unit employs a means for calculating a toner consumption amount based on a dot count in development.

  In the present invention, as a fourth solving means relating to the developing device, in any one of the first to third solving means, the toner replenishing means has a replenishing motor for replenishing toner by rotational movement, and the control unit Employs means for changing the replenishment speed table to change the toner replenishment speed by adjusting the rotational speed of the replenishment motor.

  In the present invention, as a fifth solving means related to the developing device, in any one of the first to third solving means, the toner replenishing means has a replenishing motor for replenishing toner by a rotational motion, and the control unit Employs means for changing the replenishment speed table to change the toner replenishment speed by adjusting the ratio of the ON time and the OFF time of the replenishment motor.

  Further, in the present invention, as a first solving means relating to the image forming apparatus, means including a developing device that employs any one of the first to fifth solving means is employed.

  According to the present invention, the developing device contains a developer container containing a developer containing toner and a carrier, the developer container is rotatably provided, the stirring means for stirring and conveying the developer, and the developer container is replenished with toner. A developing device including a toner replenishing unit; a toner concentration detecting unit for detecting a toner concentration inside the developing container; and a toner consumption amount corresponding to the print image is calculated, and an amount corresponding to the toner consumption amount is calculated. The toner is supplied to the developing container by the toner replenishing means, and based on the detection result of the toner density detecting means, the difference between the toner density inside the developing container after the toner replenishment and the toner density reference value has a predetermined threshold value. A controller that corrects the amount of toner to be replenished according to the amount of toner consumption.

  Thus, in the developing device, the toner replenishment speed can be changed by changing the replenishment speed table, so that the control load for correcting the toner replenishment speed does not increase. Further, in the developing device, the toner density is changed by changing the replenishment speed table, and the toner is replenished at the toner replenishment speed, so that the inside of the developing container is brought to a toner density substantially equal to the toner density reference value. Variations in density can be reduced, thereby reducing image unevenness.

1 is a functional block diagram of a copying machine A according to an embodiment of the present invention. 1 is a perspective front view showing a schematic configuration of a copying machine A according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a schematic configuration of a developing device 44 of a copying machine A according to an embodiment of the present invention. 1 is a cross-sectional view taken along line XX of a developing device 44 of a copying machine A according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a toner supply table of a copying machine A according to an embodiment of the present invention. FIG. 3 is a diagram illustrating toner areas A1 to A32 of the copying machine A according to an embodiment of the present invention. It is a figure which shows the result of the toner density after the printing with the copying machine A which concerns on one Embodiment of this invention, and the conventional copying machine.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present embodiment relates to a copying machine which is one of the image forming apparatuses of the present invention.
First, the configuration of the copying machine A according to the present embodiment will be described with reference to FIGS. FIG. 1 is a functional block diagram of a copying machine A according to the present embodiment, and FIG. 2 is a perspective front view showing a schematic configuration of the copying machine A according to the present embodiment.

As shown in FIG. 1, the copier A of the present embodiment includes an image reading unit 1, an image data storage unit 2, an image processing unit 3, a paper transport / image forming unit 4, an operation display unit 5, and a control unit 6. ing.
The image reading unit 1 includes an ADF (automatic document feeder), a CCD (Charge Coupled Device) sensor, and the like. Under the control of the control unit 6, the image of the document sequentially fed by the ADF is read by the CCD sensor. Document image data based on the document image is output. The image reading unit 1 outputs the document image data to the control unit 6, while the control unit 6 stores the document image data in the image data storage unit 2.

The image data storage unit 2 includes an external storage device such as a hard disk and / or a semiconductor memory such as a flash memory, and stores document image data read by the image reading unit 1 under the control of the control unit 6.
The image processing unit 3 converts the document image data stored in the image data storage unit 2 into various types of image processing as necessary under the control of the control unit 6 to convert the image data into print format image data (print format image data). The print format image data is output.

  For example, when the image reading unit 1 reads a color document image, the document image data stored in the image data storage unit 2 is RGB (R: red, G: green, B: blue) image data. The image processing unit 3 converts the RGB image data into, for example, YMCK image data (image data with Y: yellow, M: magenta, C: cyan, K: black as reference colors), and the print format image data Output.

  Under the control of the control unit 6, the paper transport / image forming unit 4 transfers the toner to the print paper transported from the paper tray based on the print format image data input from the image processing unit 3, and fixes the toner. By performing processing, an image is formed on the printing paper. As shown in FIG. 2, the image forming apparatus includes a photosensitive drum 41, a charging device 42, an exposure device 43, a developing device 44, a cleaning unit 45, a fixing device 46, and the like. It has a configuration. The photosensitive drum 41 is an image carrier in the present embodiment.

The photosensitive drum 41 is a cylindrical member on which an electrostatic latent image is formed. The photosensitive drum 41 extends in the depth direction of FIG. 2, and the electrostatic latent image and the electrostatic latent image are arranged on the peripheral surface. An image made of toner based on the above is formed.
The charging device 42 is disposed so as to face the photosensitive drum 41 and charges the peripheral surface of the photosensitive drum 41.
The exposure device 43 is disposed above the photosensitive drum 41, and forms an electrostatic latent image on the surface of the photosensitive drum 41 by scanning the peripheral surface of the photosensitive drum 41 with the irradiated laser light.

The developing device 44 develops an image based on the electrostatic latent image on the peripheral surface of the photosensitive drum 41 by supplying toner to the peripheral surface of the photosensitive drum 41, and is provided for the photosensitive drum 41. .
FIG. 3 is a cross-sectional view showing a schematic configuration of the developing device 44 of the copying machine A according to the present embodiment. FIG. 4 is along the line XX of the developing device 44 of the copying machine A according to the present embodiment. FIG. 3 and 4, the developing device 44 includes a developing container 441, a first screw 442, a second screw 443, a magnetic roller 444, a developing roller 445, a regulating blade 446, a toner concentration detection sensor 447, and a toner container 448. And a control unit 6. The toner container 448 is a toner replenishing unit in this embodiment. Further, the toner concentration detection sensor 447 is toner concentration detection means in the present embodiment.

The developer container 441 contains a developer composed of two components of toner and a magnetic carrier. As shown in FIG. 4, the first transport path 441a, the second transport path 441b, the supply path 441c, and the partition wall 441d.
The first transport path 441a accommodates a developer, and a first screw 442 is provided. The second transport path 441b accommodates a developer and is provided with a second screw 443. And the 1st conveyance path 441a and the 2nd conveyance path 441b are arranged in parallel via partition wall 441d, and are mutually connected in the both ends.
The replenishment path 441c is formed on one end side (left end side in FIG. 4) of the second transport path 441b so as to extend from the length of the first transport path 441a, and toner is replenished from the toner container 448 on the upper part. The supply port 441c-1 to be performed is formed.

  The first screw 442 conveys the developer in the first conveyance path 441a while stirring, and is provided over the length direction of the first conveyance path 441a and around a rotation axis extending in the length direction. It is supported so as to be freely rotatable, and is rotated by a rotational drive of a drive device (not shown) under the control of the control unit 6.

  The second screw 443 conveys the developer in the second conveyance path 441b while stirring, straddling the second conveyance path 441b and the replenishment path 441c, and the second conveyance path 441b and the replenishment path 441c. And is rotatably supported around a rotation axis extending in the length direction (conveying direction), and rotated by a driving device (not shown) under the control of the control unit 6. To do. The first screw 442 and the second screw 443 are transported in opposite directions by rotating in the opposite directions under the control of the control unit 6, and the developer is transported in the first transport path 441 a and the second transport. The passage 441b circulates while being stirred in the counterclockwise direction as shown in FIG.

The magnetic roller 444 is a roller composed of a magnetic body having a plurality of magnetic poles therein and a non-magnetic sleeve that encloses the magnetic body and is rotatable, and a magnetic brush composed of a magnetic carrier and toner is provided on the peripheral surface thereof. Then, the toner is supplied to the developing roller 445 using the magnetic brush.
The developing roller 445 supplies the toner supplied from the magnetic roller 444 to the photosensitive drum 41 by causing the toner to fly.

The regulating blade 446 is disposed to face the magnetic roller 444 and regulates the thickness of the magnetic brush formed on the peripheral surface of the magnetic roller 444. For example, the regulating blade 446 is made of SUS material or aluminum material.
As shown in FIG. 4, the toner concentration detection sensor 447 is electrically connected to the control unit 6 and detects the concentration (ratio) of the toner in the developer and the magnetic carrier in each region in the developing container 441. The detection result is output to the control unit 6.

The toner container 448 stores toner to be replenished to the developing container 441, is provided for the developing device 44, and is disposed above the developing device 44. The toner container 448 is drivingly connected to a replenishing motor (not shown), and replenishes toner to the developing container 441 by rotating the replenishing motor under the control of the control unit 6. The toner container 448 adjusts the toner supply amount (toner supply speed) per unit time by changing the rotation speed of the supply motor. In the toner container 448, the higher the rotation speed of the supply motor, the higher the toner supply speed.
The control unit 6 controls not only the developing device 44 but also the overall operation of the copying machine A. Details of the control unit 6 will be described later.

The cleaning unit 45 includes a cleaning roller and a cleaning blade for removing toner remaining on the photosensitive drum 41 after an image is transferred from the photosensitive drum 41 to the printing paper. Yes.
The fixing device 46 fixes the toner transferred from the photosensitive drum 41 to the printing paper by applying heat and pressure to the printing paper, and is arranged in the printing paper conveyance path.

  The operation display unit 5 includes a start key, a stop / clear key, a power key, a numeric keypad (numerical value input key), a touch panel 9a, and other various operation keys, and outputs an operation instruction of each key to the control unit 6. At the same time, various screens are displayed on the touch panel under the control of the control unit 6.

  The control unit 6 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and the image reading unit 1, the image data storage unit 2, the image processing unit 3, the paper transport / The image forming unit 4 and the operation display unit 5 are each composed of an interface circuit for inputting / outputting signals, and the control program and toner supply table stored in the ROM and the operation instructions received by the operation display unit 5 are used. Based on this, the overall operation of the copying machine A is controlled.

  FIG. 5 is a schematic diagram showing the toner supply table. This toner replenishment table includes a replenishment speed registration table in which the replenishment speed of the toner container 448 for each toner consumption amount in development is registered, and different toner replenishment depending on the level of toner density inside the developing container 441 after toner replenishment. It consists of a plurality of replenishment speed tables in which speeds are registered. As shown in FIG. 5, in the toner replenishment table, the lower the toner replenishment speed is registered, the more the replenishment speed registration table having a high toner density inside the developing container 441. Further, the higher the toner supply speed is registered, the lower the toner density is in the supply speed registration table.

  In the toner consumption amount in the toner replenishment table, level 1 indicates the lowest toner consumption amount, and the toner consumption amount increases toward level 6. That is, level 6 indicates that the toner consumption is the highest. Further, the unit of the toner replenishment speed registered in each replenishment speed registration table of the toner replenishment table is “g / min” as shown in FIG.

Next, the operation of the copying machine A according to the present embodiment having the above configuration will be described.
First, a user who wants to copy a document with the copying machine A sets the document on the ADF of the image reading unit 1. Then, the user presses the start key of the operation display unit 5 to cause the copying machine A to start the copy process.

  When the operation display unit 5 receives a copy processing start instruction by pressing the start key, the control unit 6 rotates the first screw 442 and the second screw 443 to circulate the developer in the developing container 441. Part of the developer that reaches the first conveyance path 441a by the circulation is magnetically attached to the peripheral surface of the magnetic roller 444 to form a magnetic brush. The thickness of the magnetic brush is regulated by the regulating blade 446, and a desired amount of toner is supplied to the developing roller 445. The developing roller 445 develops an image based on the electrostatic latent image on the photosensitive drum 41 by supplying the toner received from the magnetic roller 444 to the opposing photosensitive drum 41 (developing operation). Along with the developing operation, the toner inside the developing container 441 decreases.

After the developing operation, the control unit 6 calculates the toner consumption amount of each of the toner regions A1 to A32 of the toner in the developing container 441 shown in FIG. 6 from the dot count in the development, and an amount of toner corresponding to the toner consumption amount Is supplied to the toner container 448 to the developing container 441. FIG. 6 is a view showing toner areas A1 to A32 of the copying machine A according to the present embodiment. The toner areas A1 to A32 indicate toner areas. Therefore, as the toner circulates in the developing container 441, the toner areas A1 to A32 also circulate with the toner.
The toner concentration detection sensor 447 detects the toner and magnetic carrier concentrations in the toner regions A1 to A32 of the replenished toner that circulates in the developing container 441, and outputs the detection result to the control unit 6.

  Based on the detection result of the toner concentration detection sensor 447, the control unit 6 determines the toner concentration of each of the toner regions A1 to A32 of the toner circulating in the developing container 441, and the toner concentration and the toner concentration reference value “12%”. It is determined whether or not there are 10 consecutive toner areas in which the difference between the values exceeds “0.2%” or “0.4%”.

  In the above determination, the control unit 6 determines that 10 toner regions in which the difference from the toner concentration reference value “12%” is less than “0.2%” and equal to or less than “11.8%” are 10 regions. In this case, the replenishment speed registration table used for calculating the toner replenishment speed is changed from the “normal” replenishment speed registration table toner density to the “slightly lower” replenishment speed registration table, and the toner is based on the “slightly lower” replenishment speed registration table. By changing the supply speed and adjusting the rotation speed of the supply motor, the toner container 448 is supplied at the changed toner supply speed.

  In addition, in the above determination, the control unit 6 determines that ten consecutive toner areas having a toner density “12.2%” or more that exceeds “0.2%” as the difference from the toner density reference value “12%” have continued. When the determination is made, the replenishment speed registration table used for calculating the toner replenishment speed is changed from the “normal” replenishment speed registration table toner density to the “slightly higher” replenishment speed registration table, and based on the “slightly higher” replenishment speed registration table. The toner supply speed is changed, and the rotation speed of the supply motor is adjusted, so that the toner container 448 is supplied at the changed toner supply speed.

  In addition, in the above determination, the control unit 6 determines that 10 toner regions having a toner density “11.6%” or less that exceeds the “0.4%” difference from the toner density reference value “12%” continue 10 regions. When the determination is made, the replenishment speed registration table used for calculating the toner replenishment speed is changed from the “normal” replenishment speed registration table to the “low” replenishment speed registration table, and the toner is changed based on the “low” replenishment speed registration table. By changing the supply speed and adjusting the rotation speed of the supply motor, the toner container 448 is supplied at the changed toner supply speed.

In addition, in the above determination, the control unit 6 determines that ten consecutive toner areas having a toner density “12.4%” or more that exceeds “0.4%” as the difference from the toner density reference value “12%” continue. When the determination is made, the replenishment speed registration table used for calculating the toner replenishment speed is changed from the “normal” replenishment speed registration table toner density to the “high” replenishment speed registration table, and the toner is based on the “high” replenishment speed registration table. By changing the supply speed and adjusting the rotation speed of the supply motor, the toner container 448 is supplied at the changed toner supply speed.
In addition, in the above determination, the control unit 6 registers “normal” replenishment speed when there are not 10 consecutive toner regions where the difference from the toner density reference value “12%” exceeds “0.2%”. The toner is supplied to the toner container 448 without changing the table.

FIG. 7 is a diagram showing the results of toner density after printing by the copying machine A according to the present embodiment and a conventional copying machine. In FIG. 7, the density setting of the copying conditions of the copying machine A and the conventional copying machine is set to “dark”, “normal”, and “light”, and the original is set with the density setting in which each setting value is set. Each toner region A1 after printing a total of 100 sheets in the order of 20 sheets with a printing rate of 5%, 20 sheets with a document printing ratio of 10%, 20 sheets with a document printing ratio of 20%, and 20 sheets with a document printing ratio of 25%. -A32 shows the toner density.
As shown in FIG. 7, the copying machine A has a smaller standard deviation than the conventional copying machine, and the average value of the areas A1 to A32 is closer to the toner density reference value “12%” than the conventional copying machine. Yes. That is, the copying machine A has less variation in toner density in the areas A1 to A3 than the conventional copying machine, and the toner density in each of the areas A1 to A3 is also set to the toner density reference value “12%” than the conventional copying machine. It is close.

  As described above, in the copying machine A according to the present embodiment, the control unit 6 calculates the toner consumption amount from the dot count in the development, and supplies the toner according to the toner consumption amount to the developing container 441 as a toner toner container. The difference between the toner density in the toner area and the toner density reference value “12%” exceeds “0.2%” or “0.4%” based on the detection result of the toner density detection sensor 447. When it is determined that the toner area is 10 consecutive, the supply speed registration table used for calculating the toner supply speed is changed, and the toner supply speed is changed based on the supply speed table.

  As described above, in the copying machine A, the toner replenishment speed can be changed by changing the replenishment speed table. Therefore, the control load for correcting the toner replenishment speed necessary for adjusting the toner density in the developing container 441 is increased. It will not be high. Further, in the copying machine A, the toner density is changed by changing the replenishment speed table, and the toner is replenished at the toner replenishment speed, thereby approaching the toner density reference value “12%” as shown in FIG. Since the toner density is set, it is possible to reduce the variation in toner density, thereby reducing image unevenness.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, For example, the following modifications can be considered.

(1) In the above embodiment, the control unit 6 changes the replenishment speed table based on the detection result of the toner density detection sensor 447, but the present invention is not limited to this.
For example, the copier A is equipped with an image sensor that reads an image on a printing paper. Then, the control unit 6 may determine the toner density of the toner regions A1 to A32 from the image unevenness from the image read by the image sensor.

(2) In the above-described embodiment, the controller 6 replenishes the toner container 448 at the changed toner replenishment speed by adjusting the rotation speed of the replenishment motor. However, the present invention is not limited to this.
For example, the control unit 6 may cause the toner container 448 to replenish toner at the changed toner replenishment speed by adjusting the ratio of the ON time and the OFF time of the auxiliary motor.

DESCRIPTION OF SYMBOLS A ... Copy machine, 1 ... Image reading part, 2 ... Image data storage part, 3 ... Image processing part, 4 ... Paper conveyance / image formation part, 5 ... Operation display part, 6 ... Control part, 41 ... Photosensitive drum, 42 ... Charging device, 43 ... Exposure device, 44 ... Developing device, 441 ... Developing container, 441a ... First transport path, 441b ... Second transport path, 441c ... Supply path, 441c-1 ... Supply port, 441d ... Partition wall, 442 ... first screw, 443 ... second screw, 444 ... magnetic roller, 445 ... developing roller, 446 ... regulator blade, 447 ... toner density detection sensor, 448 ... toner container, 45 ... cleaning unit, 46 ... fixing device

Claims (6)

A developer container containing a developer including toner and carrier;
Agitating means rotatably provided in the developing container and agitating and conveying the developer;
A developing device comprising toner supply means for supplying toner to the developer container,
Toner concentration detecting means for detecting the toner concentration inside the developing container;
A toner consumption amount corresponding to the print image is calculated, and an amount of toner corresponding to the toner consumption amount is supplied to the developer container by the toner supply unit, and the toner after the toner supply is supplied based on the detection result of the toner density detection unit. A controller for correcting a toner replenishment amount to be replenished according to a toner consumption amount when a difference between a toner concentration inside the developing container and a toner concentration reference value exceeds a predetermined threshold value;
A developing device comprising: a developing device;   The developing device according to claim 1, wherein the toner density detection unit is a toner density sensor.   The developing device according to claim 1, wherein the control unit calculates a toner consumption amount based on a dot count in development. The toner replenishing means has a replenishment motor for replenishing toner by a rotational motion,
The developing device according to claim 1, wherein when the replenishment speed table is changed, the control unit changes the toner replenishment speed by adjusting a rotation speed of the replenishment motor. The toner replenishing means has a replenishment motor for replenishing toner by a rotational motion,
The said control part changes a toner replenishment speed by adjusting the ratio of the ON time of the said replenishment motor, and OFF time, if a replenishment speed table is changed, The any one of Claims 1-3 characterized by the above-mentioned. Development device. An image forming apparatus comprising the developing device according to claim 1.

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