JP2011141371A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an increase in the manufacturing cost of an image forming apparatus by facilitating the control thereof, and to avoid degradation in quality of toner supplied to an image carrier. <P>SOLUTION: The image forming apparatus includes: a print information obtaining means 30 for obtaining the number of print pixels and a printing rate from a document; and a control means 13 for executing a staying-toner consumption process in which toner is moved to a non-printing area of an image carrier 14 when the printing rate obtained by the printing information obtaining means 30 is lower than a preset threshold. In the image forming apparatus, if the printing rate obtained by the print information obtaining means 30 is lower than a preset reference printing rate, an amount of toner for development, which is moved to the printing area of the image carrier 14 during printing is made larger than a regular amount. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, there has been known an image forming apparatus that acquires a printing rate of a document by a printing rate acquisition unit provided in the apparatus. Here, the printing rate represents the ratio of the number of printing pixels per unit rotation of the developing roller, and the case where all pixels are printed with the maximum printing width during the unit rotation of the developing roller is 100%. Depending on the level of the printing rate, the amount of developer supplied from the developing roller to the photosensitive drum varies, and the time for the developer to stay on the developing roller also varies. When printing of a document having a low printing rate continues and the developer stays on the developing roller for a long time, the developer is rubbed and the quality of the developer supplied to the image carrier is deteriorated.

  In the image forming apparatus disclosed in Patent Document 1, in order to solve the above problem, when the acquired printing rate is lower than a preset threshold value, development is performed in an area that is excluded from the area printed on the transfer material on the image carrier. Developing agent. After the development, the developer remaining on the image carrier without being transferred to the transfer material because it is removed from the area printed on the transfer material is removed by the cleaning member and discarded. In this way, by forcibly consuming the developer, the developer is prevented from staying on the developer carrying member for a long time so that the quality of the developer is prevented from deteriorating. However, as the developer is forcibly consumed, the storage space for the waste developer accommodating portion provided in the image forming apparatus is reduced, and the replacement interval of the waste developer accommodating portion is shortened. As a result, there arises another problem that the user is disadvantaged by an increase in labor for replacing the waste developer container and an increase in the cost of consumables for the replacement.

  In the image forming apparatus of Patent Document 2, in order not to cause all the above-described problems, a low print mode for forming an image with a low print rate on the image carrier, and an image with a high print rate on the image carrier. Is set, and the voltage applied to the developer carrier and the developer supply means is set for each print mode. In this way, by supplying a developer corresponding to each printing mode from the developer supply means to the developer carrying member, the developer is prevented from staying in the developer carrying member for a long time, and each printing mode is This makes it possible to cope with the consumption of the developer. However, in this image forming apparatus, since the developer supply means is controlled by the voltage in addition to the developer carrier, the control becomes complicated, and the manufacturing cost of the control apparatus increases accordingly. Has the problem.

JP 2001-75438 A JP 2006-84598 A

  It is an object of the present invention to provide an image forming apparatus that can easily control the apparatus, suppress an increase in manufacturing cost, and can avoid deterioration in quality of toner supplied to an image carrier.

  As means for solving the above-described problems, the image forming apparatus of the present invention is configured such that a print information acquisition unit that acquires the number of print pixels and a print rate from a document, and a print rate acquired by the print information acquisition unit are set in advance. A printing rate acquired by the print information acquisition unit is set in advance in an image forming apparatus having a control unit that executes a staying toner consumption process for moving toner to a non-printing area of the image carrier when the threshold is lower than the threshold value When the printing rate is lower than the standard printing rate, the toner development amount to be moved to the printing area of the image carrier during printing is increased more than usual.

  According to this configuration, when the printing rate acquired by the printing information acquisition unit is lower than a preset reference printing rate, the amount of toner consumption increases. Therefore, the amount of staying toner is reduced. This eliminates the need for complicated control, facilitates control of the apparatus, suppresses an increase in manufacturing cost, and avoids deterioration in the quality of toner supplied to the image carrier.

  Preferably, the control means increases the toner development amount by changing a developing bias of a developing roller with respect to the image carrier or a developing duty. According to this configuration, the toner development amount can be accurately adjusted by changing the development bias of the development roller or the development duty.

  As means for solving the above-described problems, the image forming apparatus of the present invention is configured such that a print information acquisition unit that acquires the number of print pixels and a print rate from a document, and a print rate acquired by the print information acquisition unit are set in advance. And a control unit that executes a staying toner consumption process for moving the toner to the non-printing area of the image carrier when the threshold value is lower than the threshold value. Regardless of the printing rate, a first mode in which a predetermined toner development amount per unit area is moved to the printing area of the image carrier and printing is performed, or the printing rate acquired by the printing information acquisition unit is set in advance. When the printing rate is lower than the set reference printing rate, printing is performed by moving the toner development amount per unit area increased from the first mode to the printing area of the image carrier. And to perform any of the second mode.

  According to this configuration, the control unit executes printing in either the first mode or the second mode. By having two print modes with different toner development amounts per unit area, one can be set to a mode that prioritizes print quality and the other is a mode that prioritizes toner consumption.

  The first mode and the second mode are preferably selectable by a user. According to this configuration, the printing mode can be selected according to the user's preference.

  According to the present invention, when the printing rate acquired by the printing information acquisition unit is lower than a preset reference printing rate, the toner consumption is increased, so that the amount of staying toner is reduced. This eliminates the need for complicated control, facilitates control of the apparatus, suppresses an increase in manufacturing cost, and avoids deterioration in the quality of toner supplied to the image carrier.

1 is a schematic diagram showing the overall configuration of an image forming apparatus according to the present invention. FIG. 4 is a flowchart illustrating print control of the image forming apparatus. The figure which shows the experimental result about the quality of the image quality in each printing rate. The figure which shows the relationship between a printing rate and a toner usage-amount. FIG. 4 is a diagram illustrating an oscillating electric field formed between a photosensitive drum and a developing roller. FIG. 10 is a diagram illustrating an example of a toner development amount per unit area with respect to a printing rate set as a second mode. FIG. 10 is a diagram illustrating an example of a toner development amount per unit area with respect to a printing rate set as a second mode. FIG. 7 is a diagram illustrating a staying toner consumption amount when the image forming apparatus according to the present invention is controlled. FIG. 6 is a diagram illustrating a reduction rate of staying toner consumption when the image forming apparatus according to the present invention is controlled.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus 10 according to the present invention. The image forming apparatus 10 according to the present invention can be applied to both monochrome and color. The image forming apparatus 10 includes a printing unit 11, an image processing unit 12, and a device control unit (control unit) 13.

  The printing unit 11 includes a developing device 17 having a charging charger 15, a developing roller 16, and a cleaning member 18 around a photosensitive drum (image carrier) 14. The printing unit 11 includes an image exposure device 19, a paper feeding unit 21 containing recording paper 20, a transfer material conveyance path 22, a conveyance roller 23, a transfer roller 24, a fixing unit 25, a discharge roller 26, and a developing roller drive motor. 27 and a developing bias high-voltage power supply 28 are provided.

The image processing unit 12 is connected to a personal computer (external device) 29 and the image exposure device 19 of the printing unit 11. The image processing unit 12 develops the print language transmitted from the personal computer 29 into print data for exposure by the image exposure device 19 of the printing unit 11. The image processing unit 12 obtains the print pixel number D of the developed print data and the rotation number N of the developing roller 16 necessary for printing the developed print data, and the print pixel number D of the print data, and The printing information acquisition means 30 for calculating the printing rate P (= D / ( _{DU 100%} × N) per unit rotation speed of the developing roller 16 from the rotation speed N of the developing roller 16 and acquiring the value is provided. Here, _DU100% is the number of print pixels when all pixels are printed with the maximum print width during the unit rotation of the developing roller 16. In this embodiment, the print information acquisition means 30 is a microcomputer. The information acquisition unit 30 is configured to transmit data on the number D of print pixels and the print rate P to the apparatus control unit 13.

The apparatus control unit 13 is connected to the print information acquisition unit 30 of the image processing unit 12, the developing roller drive motor 27 of the printing unit 11, and the development bias high-voltage power supply 28 of the printing unit 11. In the present embodiment, the device control unit 13 is a microcomputer. The apparatus control unit 13 is provided with a developing roller integrated rotation speed acquisition unit 31 that acquires a value of the integrated rotation speed R of the developing roller 16 driven by the developing roller drive motor 27. In the present embodiment, the developing roller integrated rotation speed acquisition unit 31 is a microcomputer. In the apparatus control unit 13, the value of the print pixel number D received from the print information acquisition unit 30 is integrated. A value obtained by integrating the print pixel number D acquired for each print is defined as an integrated print pixel number D _TOTAL .

  The image forming apparatus 10 has a first mode that is a normal mode and a second mode that is a waste toner storage unit save mode.

  The first mode is a mode in which printing is performed by moving a predetermined toner development amount per unit area to the printing area of the photosensitive drum 14 regardless of the printing rate acquired by the printing information acquisition unit 30.

  In the second mode, when the printing rate acquired by the printing information acquisition unit 30 is lower than a preset reference printing rate, the toner development amount per unit area increased from the first mode is set in the printing area of the photosensitive drum 14. It is a mode to move and print. In the second mode, when the printing rate acquired by the printing information acquisition unit 30 is equal to or higher than a preset reference printing rate, printing is performed with the same toner development amount as in the first mode. When the printing rate acquired by the printing information acquisition unit 30 is lower than a preset reference printing rate, the toner development amount to be moved to the printing area of the photosensitive drum 14 is increased from the first mode.

  The apparatus control unit 13 controls the image forming apparatus 10 according to any one of the first mode and the second mode selected by the user to perform printing.

  The image forming apparatus 10 starts a printing operation when the image processing unit 12 receives a print language (printing source data) corresponding to print data from the personal computer 29, and prints for exposure by the image exposure device 19 of the printing unit 11. Expand to data. The print information acquisition unit 30 of the image processing unit 12 acquires the number D of print pixels and the print rate P from the developed print data, and transmits them to the device control unit 13. The device control unit 13 controls the development bias high-voltage power supply 28 according to the received print data, sets the development bias of the development roller 16, and drives the printing unit 11. Then, the image forming apparatus 10 charges the photosensitive drum 14 with the charging charger 15, transmits the print data developed by the image processing unit 12 to the image exposure apparatus 19, and irradiates the laser light with the image exposure apparatus 19. An electrostatic latent image corresponding to the print data is formed on the photosensitive drum 14. The photosensitive drum 14 is visualized by supplying charged toner to the potential gap between the latent image potential and the developing bias voltage by the developing roller 16 controlled by the apparatus control unit 13 and driven by the developing roller driving motor 27. It becomes. The visualized toner image is transferred by the transfer roller 24 to the recording paper 20 transported by the transport roller 23 from the paper supply unit 21 on the transfer material transport path 22, and then fixed by the fixing unit 25, and the discharge roller 26 is discharged from the image forming apparatus 10 as an electrophotographic image. The toner remaining on the photosensitive drum 14 without being transferred from the photosensitive drum 14 to the recording paper 20 is scraped off by the cleaning member 18 pressed against the photosensitive drum 14.

  FIG. 2 shows a flowchart for printing control of the image forming apparatus 10.

When the developing device 17 is mounted on the image forming apparatus 10, the developing roller integrated rotation speed R is reset (step S201). Further, the total print pixel number D _TOTAL is reset (step S202).

The image processing unit 12 of the image forming apparatus 10 waits until the printing source data is received from the personal computer 29 (step S203: NO). When the printing source data is received (step S203: YES), the printing source data is developed into printing data, the number of print pixels D of the developed printing data and the developing roller 16 required for printing the developed printing data. , The printing pixel number D of the print data, and the printing rate P per unit rotation number of the developing roller 16 from the rotation number N of the developing roller 16 (= D / ( _{DU 100%} × N)) Obtain (step S204).

  The apparatus control unit 13 of the image forming apparatus 10 acquires information on the currently selected print mode.

If the currently selected print mode is the first mode, which is the normal mode (step S205: YES), the development condition is set to a development bias setting that provides a normal toner development amount per unit area (step S207). Then, the print pixel number D for printing is added to the integrated print pixel number D _TOTAL (step S208). Here, the normal toner development amount per unit area is about 5 g / m ² .

In the case of the second mode (waste toner storage unit save mode) that is not the normal mode (step S205: NO), the value of the printing rate P is compared with the value of the reference printing rate _PTH . The reference print rate _PTH is a reference value of the print rate per unit rotation of the developing roller. If the printing rate continues below this reference value, the toner consumption is too low and toner stays in the developing device 17, causing the toner to be unnecessarily charged and stressed by agitation, thereby degrading the image quality. End up.

FIG. 3 shows the experimental results regarding the quality of image quality (background fogging) at each printing rate. At a printing rate of 1%, the image quality became unusable after printing 4000 sheets. At a printing rate of 2%, the image quality became unacceptable after printing 10,000 sheets. When the printing rate was 3% or more, the image quality did not become impossible even when 10,000 sheets were printed. Usually, it is desired that the image quality be maintained for about 10,000 prints. Therefore, based on this experimental result, the reference printing rate _PTH was set to 3%.

  FIG. 4 shows the relationship between the printing rate and the amount of toner used. The hatched portion indicates that unused toner is generated when printing is performed at a printing rate of less than 3% with respect to the amount of toner used at a printing rate of 3%. As described above, printing at a low printing rate that generates the unused toner causes a decrease in image quality. Therefore, in the present invention, the unused toner is reduced by the control described later.

When the value of the printing rate P is larger than the value of the reference printing rate _PTH (step S206: NO), the development condition is set to the development bias setting that is a normal toner development amount per unit area (step S207), and printing is performed. The number D of print pixels is added to the total number _DTOTAL of print pixels (step S208). Here, the normal toner development amount per unit area is about 5 g / m ² . The total number of print pixels D _TOTAL is expressed by the following equation (1).

  The developing bias setting is to change the potential of the oscillating electric field formed between the photosensitive drum 14 and the developing roller 16, that is, the magnitude of the force that moves the toner to the photosensitive drum 14.

FIG. 5 shows an oscillating electric field formed between the photosensitive drum 14 and the developing roller 16. The oscillating electric field skip-side potential is determined by an AC amplitude (voltage between peaks) V _{P of} the developing bias applied to the developing roller 16, a DC bias value V _D (potential of the developing roller 16) superimposed on the AC bias, and an AC rectangular wave bias. This can be changed by changing at least one of the toner blow-off voltage time ratio (hereinafter referred to as “development duty”). The potential difference between the potential V _B of the photosensitive drum 14 and the potential V _D of the developing roller 16 is G. The development duty D is expressed as the following equation (2).

By increasing the AC amplitude V _P of the developing bias, also by increasing the DC bias value V _D to the same polarity as the charge polarity side of the regular toner, and, by increasing the development duty D, the photosensitive drum 14 increases the force to move the toner. In order to increase the development duty D, in Formula (2), the value of H is decreased and the value of L is increased (for example, H = 60, L = 40 is changed to H = 52, L = 48). To change).

When the value of the printing rate P is smaller than the value of the reference printing rate _PTH (step S206: YES), the development condition is set to a development bias setting in which the toner development amount is M times the normal toner development amount per unit area. Setting is performed (step S209), and the number of printing pixels M times the number of printing pixels D to be printed is added to the total number of printing pixels D _TOTAL (step S210). The total number of print pixels D _TOTAL is expressed by the following equation (3).

FIG. 6 shows a case where the setting of the printing rate (%) and the toner development amount (g / m ² ) per unit area is set to the reference printing rate P _TH = 3% and the magnification M = 1.2. The magnification M is a constant from 1 to 2 or a numerical value from 1 to 2 obtained from a table in which the printing rate is input. As shown in FIG. 7, the toner development amount per unit area may be gradually changed when the printing rate is between about 2.5% and 3%.

Accumulated print pixel number D After the integration of the print pixel number D to _TOTAL (step S208 or step S210) is completed, a printing operation is performed (step S211).

After the printing is finished, the preset staying toner consumption control execution period R _CHECK is compared with the integrated rotation speed R of the developing roller 16 (step S212). The execution period R _CHECK of the staying toner consumption control set in advance is a developing roller integrated rotation speed for printing 100 sheets of normal A4 size. The execution cycle R _CHECK may be changed to any developing roller integrated rotation speed.

When the developing roller integrated rotation speed R is smaller than R _CHECK (step S212: NO), the image processing unit 12 of the image forming apparatus 10 waits until the printing source data is received from the personal computer 29 (step S203).

When the developing roller integrated rotation speed R is larger than R _CHECK (step S212: YES), the developing roller unit is calculated from the integrated printing pixel number D _TOTAL , the developing roller integrated rotation speed R, and the printing pixel number _{DU100% at} which the printing rate is 100%. An average printing rate D _TOTAL / ( _{DU 100%} × R) per number of revolutions is calculated, and the value is compared with the reference printing rate _PTH .

If towards the reference printing ratio _{P TH} is greater than the average printing ratio _{D TOTAL / (D U100% ×} R) ( step _{S213: YES), P TH -D} TOTAL / value and the developing roller integration of _{(D U100%} × R) The amount of staying toner to be consumed is calculated from the rotational speed R, and the calculated amount of toner is discharged (step S214). Specifically, the image data is transmitted from the apparatus control unit 13 to the image processing unit 12 so as to form print data having the number D of print pixels corresponding to the amount of staying toner. Next, the toner is moved to the non-printing area on the photosensitive drum 14 where the print data is formed, and a bias having a polarity opposite to the normal transfer bias is applied to the transfer roller 24 so that the toner is not transferred to the recording paper 20. To do. Then, the toner remaining on the photosensitive drum 14 is scraped off and discharged by the cleaning member 18. Thereafter, the developing roller integrated rotation speed R is reset (step S215). Further, the total print pixel number D _TOTAL is reset (step S216). Then, the image processing unit 12 of the image forming apparatus 10 stands by until the printing source data is received from the personal computer 29 (step S203).

If towards the reference printing ratio _{P TH} average printing ratio _{D TOTAL / (D U100% ×} R) is smaller than (Step S213: NO), reset the developing roller cumulative revolution speed R (step S215). Further, the total print pixel number D _TOTAL is reset (step S216). Then, the image processing unit 12 of the image forming apparatus 10 stands by until the printing source data is received from the personal computer 29 (step S203).

FIG. 8 shows the amount of staying toner consumed when the reference printing rate P _TH = 3% and the magnification M = 1.2. It can be seen that the amount of staying toner is reduced as compared with the conventional case where there is no control in the present invention.

  According to the present invention, when the printing rate acquired by the printing information acquisition unit 30 is lower than the preset reference printing rate value, the printing rate acquired by the printing information acquisition unit 30 is set in advance. A document is developed by printing with a toner development amount per unit area. Toner consumption by increasing the toner development amount per unit area by increasing the toner development amount per unit area and increasing the toner consumption when the printing rate is lower than a preset reference printing rate. To reduce stagnation. In this way, control of the apparatus can be facilitated, an increase in manufacturing cost can be suppressed, and deterioration in the quality of toner supplied to the image carrier 14 can be avoided.

  FIG. 9 shows the reduction rate of staying toner consumption. According to the present invention, the amount of staying toner can be reduced. As a result of changing the toner development amount per unit area depending on the printing rate, a slight change in image density appears. Therefore, the user selects one of the first mode in which the image density is stabilized and the print quality is prioritized and the second mode in which the toner consumption is prioritized as desired.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Printing part 12 Image processing part 13 Apparatus control part (control means)
14 Photosensitive drum (image carrier)
DESCRIPTION OF SYMBOLS 15 Charger charger 16 Developing roller 17 Developing device 18 Cleaning member 19 Image exposure device 20 Recording paper 21 Paper feed unit 22 Transfer material conveyance path 23 Conveyance roller 24 Transfer roller 25 Fixing unit 26 Discharge roller 27 Developing roller drive motor 28 High pressure for developing bias Power 29 PC (external device)
30 Print information acquisition means 31 Development roller rotation speed acquisition means

Claims (4)

Print information acquisition means for acquiring the number of print pixels and the print rate from the document;
And a control unit that executes a staying toner consumption process for moving the toner to the non-printing area of the image carrier when the printing rate acquired by the printing information acquisition unit is lower than a preset threshold value. ,
Image formation characterized in that when the printing rate acquired by the printing information acquisition means is lower than a preset reference printing rate, the toner development amount to be moved to the printing area of the image carrier during printing is increased more than usual. apparatus.   The image forming apparatus according to claim 1, wherein the control unit increases the toner development amount by changing a developing bias of a developing roller with respect to the image carrier or a developing duty. Print information acquisition means for acquiring the number of print pixels and the print rate from the document;
And a control unit that executes a staying toner consumption process for moving the toner to the non-printing area of the image carrier when the printing rate acquired by the printing information acquisition unit is lower than a preset threshold value. ,
The control means includes
A first mode in which printing is performed by moving a predetermined toner development amount per unit area to a print area of the image carrier regardless of the print rate acquired by the print information acquisition means, or the print information acquisition When the printing rate acquired by the means is lower than a preset reference printing rate, the toner development amount per unit area increased from the first mode is moved to the printing area of the image carrier to perform printing. One of the modes is executed.   The image forming apparatus according to claim 3, wherein the first mode and the second mode are selectable by a user.

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