JP2014006287A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus capable of suppressing an image defect from generating after a change of a toner storage part.SOLUTION: An image formation apparatus 1 includes: an image formation part 30; a toner storage part; a toner quantity detection part 20 that detects the toner amount of the toner storage part; a first printing rate calculation part 92 that calculates an average area of a toner image formed at the image formation part 30 per prescribed area as a first average printing rate; a toner forcible consumption processing execution part 93 that executes toner forcible consumption processing if the first average printing rate is lower than a toner forcible consumption threshold value; a second printing rate calculation part 94 that calculates an average area of the toner image, per prescribed area, formed at the image formation part 30 until the toner amount detected at the toner quantity detection part 20 after the change of the toner storage part becomes lower than a preset toner amount as a second average printing rate; and a toner forcible consumption threshold value setting part 95 that sets toner forcible consumption threshold value according to the second average printing rate.

Description

  The present invention relates to an image forming apparatus provided with a developing unit for developing an electrostatic latent image formed by an electrophotographic method.

  In an image forming apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile machine, a photosensitive drum on which an electrostatic latent image is formed, a toner cartridge (toner storage unit) that stores toner, and a toner cartridge are supplied. A developing unit that stirs the toner and supplies the stirred toner to the photosensitive drum to develop (visualize) the electrostatic latent image; and a toner formed on the photosensitive drum by developing the electrostatic latent image Some include a transfer unit that transfers an image onto a sheet and forms a toner image on the sheet.

  In such an image forming apparatus, a toner image is formed on the surface of the photosensitive drum, so that the toner is consumed in the developing unit. Then, as the toner in the developing unit decreases, toner is supplied from the toner cartridge to the developing unit.

  However, when the development of the toner image having a low printing rate is continued in the developing unit, the toner remaining in the developing unit is not consumed and is repeatedly stirred. For this reason, the toner remaining in the developing portion deteriorates and the charge amount increases, and image defects such as a change in image density and background fog are likely to occur.

  In view of this, an image forming apparatus that performs forced toner consumption when the printing rate decreases during a normal printing operation or the like has been proposed (see Patent Document 1).

Japanese Patent No. 3029648

  In the above-described conventional image forming apparatus, the toner consumption is apt to increase because the toner is forcibly consumed so that the toner consumption is optimized so that the toner does not deteriorate. In recent years, it has been required to reduce the amount of toner consumption as much as possible in consideration of the environment and cost. For this reason, even in the forced toner consumption, the minimum necessary toner consumption is set so that the toner does not deteriorate.

  However, if the toner consumption amount in the forced toner consumption is set to be small, the charge amount of the toner remaining in the developing unit becomes high when the development of the toner image having a low printing rate is continued. In this state, when low-charge toner is supplied from the replaced toner cartridge, the difference between the charge amount of the toner remaining in the developing unit and the charge amount of the newly supplied toner increases. As a result, there has been a problem that image defects such as a change in image density and background fog are likely to occur in printing after replacement of the toner cartridge (toner storage unit).

  An object of the present invention is to provide an image forming apparatus capable of suppressing the occurrence of image defects after replacement of a toner container.

  The present invention provides an image forming unit that forms a toner image on a transfer material, an image carrier having an electrostatic latent image formed on a surface thereof, and supplying the toner to the image carrier to thereby form the electrostatic latent image. An image forming unit comprising: a developing unit that develops an image as a toner image; and a transfer unit that transfers the toner image developed on the surface of the image carrier to a transfer material to form a toner image on the transfer material; A toner storage unit configured to supply toner to the developing unit and replaceable with respect to the image forming unit; a toner amount detection unit configured to detect a toner amount stored in the toner storage unit; The first printing rate calculation unit that calculates an average area per predetermined area of the toner image formed on the transfer material in the image forming unit as the first average printing rate, and the first printing rate calculation unit. 1st average printing rate is strong toner If the toner consumption is less than the consumption threshold, the toner amount detected by the toner amount detection unit after the replacement of the toner forced consumption processing execution unit for executing the toner forced consumption processing and the toner storage unit is preset. A second printing rate calculating unit that calculates an average area per predetermined area of the toner image formed on the transfer material in the image forming unit as a second average printing rate until the amount becomes less than the amount; The present invention relates to an image forming apparatus including: a toner forced consumption threshold setting unit that sets the toner forced consumption threshold based on a second average printing rate calculated by a two printing rate calculation unit.

  According to the present invention, it is possible to provide an image forming apparatus capable of suppressing the occurrence of an image defect after replacement of the toner container.

1 is an explanatory diagram illustrating an overall configuration of a printer 1 according to an embodiment. 2 is a block diagram illustrating a functional configuration of the printer 1 according to the embodiment. FIG. 7 is a flowchart illustrating a processing procedure when toner forced consumption processing is executed in a control unit 90. 7 is a flowchart illustrating a processing procedure when a toner forced consumption threshold value Xth is set in the control unit 90. 6 is a graph showing experimental results when measuring the background fog after replacing the toner cartridge in the printer 1 of the embodiment.

  Hereinafter, an embodiment in which an image forming apparatus according to the present invention is applied to a printer will be described with reference to the drawings. First, the overall configuration of the printer 1 will be described. FIG. 1 is an explanatory diagram illustrating the overall configuration of the printer 1 according to the present embodiment.

  As shown in FIG. 1, the printer 1 according to the present embodiment includes a paper transport unit 10, an image forming unit 30, and a fixing unit 40 as main components.

  The paper transport unit 10 includes a first feed roller 11, a second feed roller 12, a registration roller pair 13, a first roller pair 14, a second roller pair 15, and a paper discharge unit 16. The conveyance path L through which the sheet K is conveyed includes a first conveyance path L1 from the first feeding roller 11 or the second feeding roller 12 to the image forming unit 30 (a transfer nip N described later), and the image forming unit 30 ( A second conveyance path L2 from a transfer nip N), which will be described later, to the fixing unit 40, a third conveyance path L3 from the fixing unit 40 to the paper discharge unit 16, and the sheet K discharged from the fixing unit 40 are registered with the registration roller pair 13. And a fourth transport path L4.

  The first feed roller 11 supplies the paper K (transfer material) stored in the paper feed cassette 17 to the first transport path L1. The second feed roller 12 supplies the paper K placed on the manual feed tray 18 to the first transport path L1. The registration roller pair 13 is formed on the photosensitive drum 31 by supplying the sheet K conveyed through the first conveyance path L <b> 1 to the transfer nip N formed between the photosensitive drum 31 and the transfer roller 38. In order to transfer the toner image onto the sheet K, the conveyance of the sheet K or the conveyance stop of the sheet K is performed.

  The registration roller pair 13 corrects skew (oblique paper feeding) of the paper K. The first roller pair 14 is provided in the third transport path L3, and transports the paper K discharged from the fixing unit 40 to the paper discharge unit 16 side. The second roller pair 15 carries the paper K transported to the paper discharge unit 16 side by the first roller pair 14 into the fourth transport path L4. The paper discharge unit 16 discharges the paper K on which the toner image is fixed to the outside of the printer 1. A paper discharge stacking unit 19 is formed outside the printer 1 in the paper discharge unit 16. In the paper discharge stacking unit 19, the paper K discharged from the paper discharge unit 16 is stacked.

  The image forming unit 30 is a device for forming a toner image on the paper K. The image forming unit 30 includes a photosensitive drum 31 as an image carrier, a charging unit 32, a laser scanner unit 33, a developing device 34 as a developing unit, a static eliminator 35, a cleaning unit 36, and a toner storage unit. A toner cartridge 37 and a transfer roller 38 as a transfer portion.

  In the present embodiment, the toner cartridge 37 constitutes a part of the image forming unit 30. The image forming unit 30 does not include a sensor that detects the amount of toner stored in the developing device 34 (developing unit). That is, the image forming unit 30 of the present embodiment is configured such that the amount of toner stored in the developing device 34 cannot be detected.

  The photosensitive drum 31 is supplied with toner from the toner layer of the developing roller 343 (toner carrier), whereby an image (toner image) along the electrostatic latent image formed on the surface is formed. Around the photosensitive drum 31, a charging unit 32, a laser scanner unit 33, a developing device 34, and a cleaning unit 36 are arranged in order from the upstream side to the downstream side along the rotation direction of the photosensitive drum 31.

  The charging unit 32 uniformly charges the surface of the photosensitive drum 31 negatively (minus polarity) or positively (plus polarity).

  The laser scanner unit 33 is disposed away from the surface of the photosensitive drum 31. The laser scanner unit 33 continuously or intermittently irradiates the surface of the photosensitive drum 31 with laser light based on image data (original image) transmitted by an external device (for example, a personal computer) arranged outside. (Exposure). By irradiating the photosensitive drum 31 with laser light from the laser scanner unit 33, the charge on the exposed portion is removed on the surface of the photosensitive drum 31, and an electrostatic latent image corresponding to the document image is formed. .

  The developing device 34 develops the electrostatic latent image as a toner image by attaching a single color (usually black) toner to the electrostatic latent image formed on the surface of the photosensitive drum 31. The developing device 34 includes a first stirring roller 341, a second stirring roller 342, and a developing roller 343. The first stirring roller 341, the second stirring roller 342, and the developing roller 343 are given a rotational force by a dedicated drive motor (not shown) connected to the respective roller shafts.

  The first stirring roller 341 and the second stirring roller 342 stir the toner supplied from the toner supply roller 371 (described later). The 1st stirring roller 341 and the 2nd stirring roller 342 are comprised by the member of a spiral screw shape, for example. The first agitation roller 341 and the second agitation roller 342 agitate the toner accommodated in the developing device 34 by rotating about the rotation axis. The toner stirred by the first stirring roller 341 and the second stirring roller 342 generates static electricity due to friction. As a result, the toner is charged.

  The developing roller 343 is configured by a developing sleeve made of a cylindrical nonmagnetic member. A plurality of magnetic members are disposed inside the developing roller 343. The developing roller 343 is driven so that the rotation direction of the developing sleeve is opposite to the rotation direction of the second stirring roller 342 at a position facing the surface of the photosensitive drum 31.

  The developing roller 343 forms a toner layer (not shown) on the surface by the toner supplied from the second stirring roller 342. Specifically, on the surface of the developing roller 343, only the toner whose layer thickness is regulated by a layer thickness regulating blade (not shown) of the second stirring roller 342 moves to form a toner layer. A developing bias (voltage) for developing is applied to the developing roller 343 by a developing bias applying unit (not shown).

  The static eliminator 35 irradiates the surface of the photosensitive member with light, thereby neutralizing the surface of the photosensitive drum 31 after the transfer is performed (removing the electric charge).

  The cleaning unit 36 removes the toner remaining on the surface of the photosensitive drum 31 after the surface of the photosensitive drum 31 is neutralized by the static eliminator 35.

  The toner cartridge 37 is a container for storing toner (magnetic one-component toner). A toner supply roller 371 is provided inside the toner cartridge 37. The toner supply roller 371 supplies the toner stored in the toner cartridge 37 to the developing device 34. The toner supply roller 371 is constituted by, for example, a spiral screw-shaped member. The toner supply roller 371 supplies toner to the developing device 34 by rotating about the rotation axis. The toner supply roller 371 and the developing device 34 are connected by a toner supply path (not shown).

  The toner cartridge 37 is detachably loaded in a toner cartridge mounting portion (not shown) provided adjacent to the developing device 34. That is, the toner cartridge 37 is configured to be replaceable with respect to the developing device 34. When the toner cartridge 37 is replaced, the toner cartridge mounting unit outputs a replacement detection signal to the control unit 90. As described above, the toner cartridge 37 (toner storage unit) is configured to be able to supply toner to the developing device 34 (developing unit) and replaceable with the image forming unit 30.

  A toner amount detection sensor 20 as a toner amount detection unit is provided in the vicinity of the toner cartridge 37. The toner amount detection sensor 20 detects the amount of toner stored in the toner cartridge 37. The toner amount detection sensor 20 detects the amount of toner contained in the toner cartridge 37 every predetermined time, and outputs a detection signal based on the detected toner amount to the control unit 90.

  The transfer roller 38 transfers the toner image formed on the surface of the photosensitive drum 31 onto the paper K by sandwiching the paper K between the photosensitive drum 31 and the transfer roller 38. A transfer bias (voltage) for transferring the toner image formed on the surface of the photosensitive drum 31 onto the paper K is applied to the transfer roller 38 by a transfer bias applying unit (not shown).

  The fixing unit 40 includes a heating rotator 41 and a pressure rotator 42. The heating rotator 41 and the pressure rotator 42 sandwich the paper K on which the toner image is transferred, melt and press the toner, and fix the toner to the paper K.

  Next, a functional configuration of the printer 1 according to the present embodiment will be described. FIG. 2 is a block diagram illustrating a functional configuration of the printer 1. In addition, about the structure demonstrated using FIG. 1, the description is abbreviate | omitted suitably.

  The printer 1 includes an operation unit 50, a display unit 60 as a notification unit, an interface unit 70, and a storage in addition to the above-described components (the paper transport unit 10, the image forming unit 30, the fixing unit 40, and the like). Unit 80 and a control unit 90.

  The operation unit 50 has a plurality of keys (not shown). These plurality of keys are operated, for example, when changing the setting of the printer 1 or resetting the job. The operation unit 50 transmits a signal corresponding to the operated key to the control unit 90 when any key is operated.

  The display unit 60 displays a setting mode, a paper size, the number of copies, an output destination, a message notifying that toner is being replenished, a message notifying that the paper K is not stored in the paper feeding cassette 17, and the like. To do. The display unit 60 also displays a message notifying that the toner remaining in the toner cartridge 37 is low (toner low) and a message notifying that the toner cartridge 37 has run out of toner (toner empty).

The interface unit 70 is connected to an external device installed outside the printer 1, for example, a personal computer or the like by wired (or wireless). The interface unit 70 has a function of acquiring image data of an electrostatic latent image formed on the surface of the photosensitive drum 31. The image data transmitted from the personal computer described above is received by the interface unit 70 and stored in the storage unit 80 (described later).

  The storage unit 80 includes a hard disk, a semiconductor memory, and the like. The storage unit 80 temporarily stores image data received from a personal computer. The storage unit 80 stores a control program used in the printer 1 and data used by the control program.

  The control unit 90 includes a CPU, a RAM, and a ROM. The RAM is a storage device having a function of temporarily storing various data and a function of a work area during calculation. The ROM is a storage device having a function as a flash memory for storing various programs. The CPU is an arithmetic device that reads and executes a program from a ROM. The CPU, RAM, and ROM perform data transmission / reception via a data bus (not shown). The CPU executes the program read from the ROM (or the storage unit 80), thereby executing processing corresponding to the content of the program.

  The control unit 90 controls the paper transport unit 10, the image forming unit 30, the fixing unit 40, and the display unit 60.

  The control unit 90 includes a print control unit 91, a first print rate calculation unit 92, a forced toner consumption process execution unit 93, a second print rate calculation unit 94, and a forced toner consumption threshold setting unit 95. Including.

  The print control unit 91 controls each unit of the printer 1 when printing a document image. Here, an operation when the print control unit 91 causes the printer 1 to print a document image will be described. In the following description, a case where a toner image is formed on one side of the paper K is taken as an example.

  First, the print control unit 91 temporarily stores the image data received via the interface unit 70 in the storage unit 80. The print controller 91 controls the paper transport unit 10, the image forming unit 30, and the fixing unit 40 in order to form a toner image on the paper K based on the image data temporarily stored in the storage unit 80. That is, the print control unit 91 drives the first feed roller 11 or the second feed roller 12 to transport the paper K to the image forming unit 30.

  In addition, the print control unit 91 supplies data for forming a toner image generated based on the image data to the laser scanner unit 33, and is statically applied to the photosensitive drum 31 by the laser light emitted from the laser scanner unit 33. An electrostatic latent image is formed. The print controller 91 causes the developing device 34 to form a toner image on the photosensitive drum 31 and transfers the toner image onto the paper K by the transfer roller 38. The print control unit 91 controls the heating rotator 41 to be heated to a predetermined temperature so as to melt the toner of the toner image transferred to the paper K by the heating rotator 41 and press-contact the heating rotator 41 with the pressure. The toner is fixed to the paper K by the pressure rotating body 42 to be applied. Further, the print control unit 91 causes the paper transport unit 10 to discharge the paper K on which the toner image is fixed from the paper discharge unit 16.

  The print controller 91 determines that the toner amount in the toner cartridge 37 is less than a preset toner amount (toner low) in a second print rate calculator 94 (described later), and then in the image forming unit 30. When the cumulative value of the printing rate of the printed toner image exceeds the threshold value, it is determined that the toner amount of the toner cartridge 37 is in a toner empty state.

  Then, the print control unit 91 stops the operation of the printer 1 and causes the display unit 60 to display a message for prompting replacement of the toner cartridge 37. When the second print rate calculation unit 94 determines that the toner amount of the toner cartridge 37 is less than the preset toner amount (toner low), the print control unit 91 determines that the toner amount of the toner cartridge 37 is You may display the message which notifies that there are few on the display part 60. FIG.

  Next, the first printing rate calculation unit 92, the forced toner consumption processing execution unit 93, the second printing rate calculation unit 94, and the forced toner consumption threshold setting unit 95 will be described.

  The first printing rate calculation unit 92 calculates an average area per predetermined area of the toner image formed on the paper K in the image forming unit 30 as the first average printing rate X.

  The first printing rate calculation unit 92 cumulatively adds the toner amount used for printing (formation) of the toner image as the number of dots, and divides the cumulative addition value by the cumulative addition value of the number of printed sheets of paper K. A first average printing rate X is calculated. The cumulative addition value of the number of dots and the cumulative addition value of the number of printed sheets are counted by the counter function set in the storage unit 80, respectively. The first printing rate calculation unit 92 causes the cumulative addition value of the number of dots and the cumulative addition value of the number of printed sheets to be counted by the counter function of the storage unit 80 and is stored in the storage unit 80 after the toner forced consumption process is executed. Reset the count value that has been set.

  The first printing rate calculation unit 92 calculates the toner amount used for printing the toner image based on the image data (original image) acquired by the interface unit 70. Further, the first printing rate calculation unit 92 calculates the cumulative added value of the number of printed sheets based on the A4 size. For example, when one A4 size paper K is printed, the number of prints is set to “1”. When one A3 size paper K is printed, the coefficient (× 2) is multiplied by the number of prints. “2”. The first average print rate X is calculated every time one print job is completed while the printer 1 is operating.

  When the first average printing rate X calculated by the first printing rate calculation unit 92 is less than the forced toner consumption threshold Xth, the forced toner consumption processing execution unit 93 executes the forced toner consumption processing. The toner forced consumption threshold value Xth is a threshold value for determining whether or not to execute toner forced consumption processing (described later). The toner forced consumption threshold value Xth is stored in a predetermined storage area of the storage unit 80 so as to be rewritable.

  In the present embodiment, the toner forced consumption threshold value Xth is a toner forced consumption threshold setting unit from when the toner cartridge 37 is replaced until the toner amount of the toner cartridge 37 becomes less than a preset toner amount (toner low). 95 (described later) is set to 1%. Further, the toner forced consumption threshold value Xth is set to 1% or 1% by the toner forced consumption threshold setting unit 95 from the time when the toner amount of the toner cartridge 37 becomes less than the preset toner amount until the toner empty state is reached. One of 3% is set.

  Further, the toner forced consumption process execution unit 93 executes the toner forced consumption process as follows.

  First, the toner forced consumption processing execution unit 93 turns off the charging unit 32 and applies the developing bias to the developing roller 343 only for the time T required for the developing roller 343 to make one revolution. (Not shown). As a result, toner corresponding to one rotation of the developing roller 343 is developed on the photosensitive drum 31. In addition, the toner forced consumption processing execution unit 93 controls a transfer bias application unit (not shown) so that the transfer bias applied to the transfer roller 38 is a reverse bias. As a result, the toner does not move from the photosensitive drum 31. As a result, the toner developed on the photosensitive drum 31 moves to the cleaning unit 36 without being attached to the transfer roller 38 and is removed.

The amount of toner consumed in the forced toner consumption is calculated by the following equation (1) when the first average printing rate X calculated by the first printing rate calculation unit 92 is less than 1%. It is set based on the printing rate D.
Print rate D = (1−X) × cumulative addition value of the number of prints (1)

  The toner forced consumption processing execution unit 93 rotates the developing roller 343 as many times as necessary so that the amount of toner consumed in the forced toner consumption becomes an amount corresponding to the printing rate D calculated by the above formula.

  Here, an example in which the charging unit 32 is turned off when the toner is forcibly consumed has been described. However, the charging unit 32 is turned on as usual, and the developing roller 343 on the photosensitive drum 31 corresponds to one turn. An area corresponding to the above may be exposed by the laser scanner unit 33.

  The second printing rate calculation unit 94 is configured to be covered by the image forming unit 30 after the toner cartridge 37 is replaced and before the toner amount detected by the toner amount detection sensor 20 becomes less than a preset toner amount. The average area per predetermined area of the toner image formed on the transfer material is calculated as the second average printing rate A.

  The second printing rate calculation unit 94 can determine whether or not the toner cartridge 37 is replaced based on the replacement detection signal output from the toner cartridge mounting unit (not shown). Further, in the present embodiment, less than a preset toner amount (hereinafter also referred to as “toner low”) means that the toner amount has decreased to such an extent that the toner in the toner cartridge 37 cannot be detected by the toner amount detection sensor 20. This is the toner amount. The toner amount less than a preset toner amount may be a toner amount when the toner amount detected by the toner amount detection sensor 20 reaches an amount that can be regarded as the toner cartridge 37 being almost empty.

  Further, the second printing rate calculation unit 94 cumulatively adds the toner amount used for printing (formation) of the toner image as the number of dots, and divides the cumulative addition value by the cumulative addition value of the number of printed sheets of the paper K. Thus, the second average printing rate A is calculated.

  The second printing rate calculation unit 94 was used for printing the toner image after the toner cartridge 37 was replaced and before the toner amount of the toner cartridge 37 became less than the preset toner amount (toner low). The toner amount is calculated based on the image data (original image) acquired by the interface unit 70. Further, the second printing rate calculation unit 94 calculates the cumulative added value of the number of printed sheets on the basis of the A4 size. For example, when one A4 size paper K is printed, the number of prints is set to “1”. When one A3 size paper K is printed, the coefficient (× 2) is multiplied by the number of prints. “2”.

  The toner forced consumption threshold setting unit 95 sets the toner forced consumption threshold Xth stored in the predetermined storage area of the storage unit 80 based on the second average printing rate A calculated by the second printing rate calculation unit 94. . In the present embodiment, the toner forced consumption threshold setting unit 95, when the second average printing rate A calculated by the second printing rate calculation unit 94 is equal to or greater than an average printing rate determination value (described later), is a forced toner consumption threshold. Xth is set to 1% as the first threshold. The first threshold value is a standard threshold value set so that the toner consumption amount is the minimum necessary amount that does not deteriorate the toner during forced toner consumption. In addition, the toner forced consumption threshold setting unit 95 sets the toner forced consumption threshold Xth as the first threshold when the second average printing rate A calculated by the second printing rate calculation unit 94 is less than the average printing rate determination value. Is set to 3% as a higher second threshold. The second threshold value is a threshold value set so that the toner consumption amount is increased as much as possible in the forced toner consumption.

  If the second average printing rate A calculated by the second printing rate calculation unit 94 is 3% or more, the toner forced consumption threshold setting unit 95 does not need to increase the toner consumption amount in the toner forced consumption processing, in other words, Since it is not necessary to increase the toner forced consumption threshold value Xth, the toner forced consumption threshold value Xth is set to 1% (first threshold value). On the other hand, when the second average printing rate A calculated by the second printing rate calculation unit 94 is less than 3%, the toner forced consumption threshold setting unit 95 needs to increase the toner consumption amount in the toner forced consumption processing. . In other words, it is necessary to increase the toner forced consumption threshold value Xth. Therefore, the toner forced consumption threshold value Xth is set to 3% (second threshold value).

  As described above, when the second average printing rate A calculated by the second printing rate calculation unit 94 is equal to or greater than the average printing rate determination value, the developing device 34 has sufficiently consumed toner. Therefore, the toner forced consumption threshold setting unit 95 sets the toner forced consumption threshold Xth to 1% (first threshold) so that toner is not consumed more than necessary in the forced toner consumption. On the other hand, when the second average printing rate A calculated by the second printing rate calculation unit 94 is less than the average printing rate determination value, the toner is not sufficiently consumed in the developing device 34. In this case, since the toner in the developing device 34 has a high charge amount, a difference in the charge amount becomes large when toner with a low charge amount is supplied from the replaced toner cartridge 37 to the developing device 34. Image defects such as background fog are likely to occur. Therefore, when the second average printing rate A is less than the average printing rate determination value, the toner forced consumption threshold setting unit 95 sufficiently consumes the toner in the developing device 34 before the toner cartridge 37 is replaced. Therefore, the toner forced consumption threshold value Xth is set to 3% (second threshold value). As a result, even if toner with a low charge amount is supplied from the replaced toner cartridge 37 to the developing device 34, the difference in charge amount does not increase. Defects are less likely to occur.

  Next, the operation when the control unit 90 executes the forced toner consumption process will be described with reference to FIG. FIG. 3 is a flowchart showing a processing procedure when the controller 90 executes the forced toner consumption process. The processing of this flowchart is repeatedly executed during the operation of the printer 1.

  In step ST101 shown in FIG. 3, the control unit 90 (first print rate calculation unit 92) cumulatively adds the toner amount used for printing the toner image as the number of dots.

  In step ST102, the control unit 90 (first printing rate calculation unit 92) cumulatively adds the number of printed sheets of paper K.

  In step ST103, the control unit 90 (first printing rate calculation unit 92) determines whether or not printing has ended. In step ST103, when the control unit 90 (first printing rate calculation unit 92) determines that the printing is finished, the process proceeds to step ST104. In step ST103, when the control unit 90 (first printing rate calculation unit 92) determines that printing has not ended, the process returns to step ST101.

  In step ST104 (step ST103: YES), the control unit 90 (first printing rate calculation unit 92) calculates the first average printing rate X. The control unit 90 (first printing rate calculation unit 92) divides the cumulative addition value of the number of dots used for printing the toner image by the cumulative addition value of the number of prints of the paper K, thereby obtaining the first average printing rate. X is calculated. Thereby, in one print job, the average area per predetermined area of the toner image formed on the paper K in the image forming unit 30 is calculated as the first average print rate X.

  In step ST105, the control unit 90 (toner forced consumption processing execution unit 93) acquires the toner forced consumption threshold Xth stored in the storage unit 80 (see FIG. 2).

  In step ST106, the control unit 90 (toner forced consumption processing execution unit 93) determines whether or not the first average printing rate X calculated by the first printing rate calculation unit 92 is less than the toner forced consumption threshold Xth. If the control unit 90 (toner forced consumption processing execution unit 93) determines in step ST106 that the first average printing rate X is less than the toner forced consumption threshold Xth (YES), the process proceeds to step ST107. To do. If the control unit 90 (toner forced consumption processing execution unit 93) determines that the first average printing rate X is equal to or greater than the toner forced consumption threshold Xth (NO) in step ST106, the process proceeds to step ST108. Transition.

  In step ST107 (step ST106: YES), the control unit 90 (toner forced consumption process execution unit 93) executes the toner forced consumption process described above.

  In step ST108, the control unit 90 (first printing rate calculation unit 92) resets the cumulative added value of the number of dots counted by the counter function of the storage unit 80.

  In step ST109, the control unit 90 (first printing rate calculation unit 92) resets the cumulative added value of the number of printed sheets counted by the counter function of the storage unit 80.

  The control unit 90 ends the process of this flowchart when the process of step ST109 ends. According to the process of this flowchart, the first average printing rate X is calculated every time one print job is completed, and if the value is less than the toner forced consumption threshold value Xth, the process of forced toner consumption is executed.

  Next, the operation when the controller 90 sets the forced toner consumption threshold value Xth will be described with reference to FIG. FIG. 4 is a flowchart showing a processing procedure when the controller 90 sets the toner forced consumption threshold value Xth.

  In step ST201 shown in FIG. 4, the control unit 90 (first printing rate calculation unit 92) determines whether or not an exchange detection signal has been received from a toner cartridge mounting unit (not shown). In step ST201, when the control unit 90 (first printing rate calculation unit 92) determines that the replacement detection signal has been received (YES), the process proceeds to step ST202. In step ST201, when the control unit 90 (first printing rate calculation unit 92) determines that the replacement detection signal has not been received (NO), the process of step ST201 is repeated.

  In step ST202 (step ST201: YES), the control unit 90 (toner forced consumption threshold setting unit 95) sets the toner forced consumption threshold Xth stored in the predetermined storage area of the storage unit 80 to 3% (second threshold). It is determined whether or not there is. If the controller 90 (toner forced consumption threshold setting unit 95) determines that the toner forced consumption threshold Xth is 3% (YES) in step ST202, the process proceeds to step ST203. If the controller 90 (toner forced consumption threshold setting unit 95) determines in step ST202 that the toner forced consumption threshold Xth is not 3% (NO), the process proceeds to step ST204.

  In step ST203 (step ST202: YES), the control unit 90 (toner forced consumption threshold setting unit 95) sets the toner forced consumption threshold Xth stored in the predetermined storage area of the storage unit 80 to 1% (first threshold). Set. When the toner cartridge 37 is replaced, the control unit 90 (toner forced consumption threshold setting unit 95) sets the toner forced consumption threshold Xth to the minimum necessary toner consumption amount that does not deteriorate the toner in the forced toner consumption. The standard threshold value set as above is set to 1%.

  In step ST204, the control unit 90 (second print rate calculation unit 94) cumulatively adds the toner amount used for printing the toner image as the number of dots.

  In step ST205, the control unit 90 (second printing rate calculation unit 94) cumulatively adds the number of printed sheets of paper K.

  In step ST206, the control unit 90 (second print rate calculation unit 94) determines whether the toner amount of the toner cartridge 37 is toner low based on the detection signal output from the toner amount detection sensor 20. If the control unit 90 (second printing rate calculation unit 94) determines in step ST206 that the toner amount in the toner cartridge 37 is toner low (YES), the process proceeds to step ST207. If the control unit 90 (second printing rate calculation unit 94) determines that the toner amount in the toner cartridge 37 is not toner low (NO) in step ST206, the process returns to step ST204.

  Thus, in step ST206, the number of dots and the number of prints of the toner image printed on the paper K are cumulatively added until it is determined that the toner amount of the toner cartridge 37 is toner low (YES) (step ST206). Steps ST204 and ST205).

  In step ST207 (step ST206: YES), the control unit 90 (second printing rate calculation unit 94) calculates the second average printing rate A. The control unit 90 (second printing rate calculation unit 94) divides the cumulative addition value of the number of dots used for printing the toner image by the cumulative addition value of the number of prints of the paper K, thereby obtaining the second average printing rate. A is calculated. As a result, after the toner cartridge 37 is replaced and before the toner amount detected by the toner amount detection sensor 20 becomes toner low, the toner image formed on the paper K in the image forming unit 30 per predetermined area. The average area is calculated as the second average printing rate A.

  In step ST208, the control unit 90 (toner forced consumption threshold setting unit 95) determines whether or not the second average printing rate A calculated by the second printing rate calculation unit 94 is less than 3%, which is an average printing rate determination value. judge. When the control unit 90 (toner forced consumption threshold setting unit 95) determines in step ST208 that the second average printing rate A is less than 3% (YES), the process proceeds to step ST209. In step ST208, when the control unit 90 (toner forced consumption threshold setting unit 95) determines that the second average printing rate A is 3% or more (NO), the process proceeds to step ST210.

  In step ST209 (step ST208: YES), the control unit 90 (toner forced consumption threshold setting unit 95) sets the toner forced consumption threshold Xth to 3% (second threshold). If the second average printing rate A is 3% or more, the toner forced consumption threshold value Xth remains 1% that has already been set.

  In step ST210, the control unit 90 (printing control unit 91) determines whether or not the toner amount of the toner cartridge 37 is in a toner empty state. In step ST210, when the control unit 90 (printing control unit 91) determines that the toner empty state is set (YES), the process proceeds to step ST211. In step ST210, when the control unit 90 (printing control unit 91) determines that the toner is not empty (NO), the process in step ST210 is repeated.

  In step ST211 (step ST210: YES), the control unit 90 (printing control unit 91) stops the operation of the printer 1.

  In step ST212, the control unit 90 (printing control unit 91) causes the display unit 60 to display a message for prompting replacement of the toner cartridge 37. The control unit 90 ends the process of this flowchart when the process of step ST212 ends. According to the process of this flowchart, the second average printing rate A from when the toner cartridge is replaced until the toner low state is calculated, and if the value is less than the average printing rate determination value, the forced toner consumption The threshold value Xth is set to 3%.

  Next, a description will be given of an experimental result in which the printer 1 according to the present embodiment performs continuous printing at a predetermined average printing rate and measures the background fog after the toner cartridge is replaced when the toner becomes empty.

  FIG. 5 is a graph showing experimental results when measuring the background fog after the toner cartridge is replaced in the printer 1 of the present embodiment. In FIG. 5, the horizontal axis indicates the number of printed sheets (unit: sheet) after the toner cartridge 37 is replaced. In FIG. 5, the vertical axis indicates the background fog size for every 100 printed sheets.

  In this experiment, three patterns of 1%, 2%, and 3% were set as the average printing rate. The operation of printing a toner image at the average printing rate of each of the three patterns was continuously executed until the toner became empty. Then, after each became empty, the toner cartridge 37 was replaced, and this time, the operation of printing a toner image with an average printing rate of 3% was continuously executed until the number of printed sheets reached 800.

  As shown in FIG. 5, according to the printer 1 of the present embodiment, if printing is continuously performed at an average printing rate of 3%, the occurrence of background fogging is suppressed after the toner cartridge 37 is replaced, It was confirmed that the background fog was likely to occur after replacement of the toner cartridge 37 when printing was continuously performed at an average printing rate of 1%.

According to the printer 1 of the present embodiment described above, for example, the following effects are achieved.
In the printer 1 of the present embodiment, the toner forced consumption threshold setting unit 95 sets the toner forced consumption threshold Xth based on the second average printing rate A calculated by the second printing rate calculation unit 94. The toner forced consumption threshold setting unit 95 of the present embodiment sets the toner forced consumption threshold Xth to the first when the second average printing rate A calculated by the second printing rate calculation unit 94 is equal to or greater than the average printing rate determination value. When the second average printing rate A calculated by the second printing rate calculation unit 94 is set to a threshold (1%) and is less than the average printing rate determination value, the toner forced consumption threshold Xth is higher than the first threshold. Set to the second threshold (3%).

  According to this, when the second average printing rate A is less than the average printing rate determination value, the toner is forcibly consumed so that the toner is sufficiently consumed in the developing device 34 before the toner cartridge 37 is replaced. The threshold value Xth is set to the second threshold value (3%). Thus, even when toner with a low charge amount is supplied from the replaced toner cartridge 37 to the developing device 34, the difference in charge amount does not increase. Therefore, in the printer 1 of this embodiment, image defects such as background fog are less likely to occur during printing after the toner cartridge 37 is replaced.

  When the second average printing rate A is equal to or higher than the average printing rate determination value, the toner forced consumption threshold value Xth is set to the first threshold value (1%). Therefore, in the printer 1 of the present embodiment, it is possible to suppress the toner consumption more than necessary in the forced toner consumption.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It can implement with a various form.

  For example, in the present embodiment, an example in which the toner forced consumption threshold setting unit 95 sets the first threshold (1%) or the second threshold (3%) as the toner forced consumption threshold Xth has been described. The numerical values of these threshold values are not limited to the example of the present embodiment, and can be changed as appropriate according to the performance of the image forming unit 30 and the like. Further, the toner forced consumption threshold value Xth is set more finely according to the second average printing rate A, such as the first threshold value (1%), the second threshold value (2%), and the third threshold value (3%). May be.

  In the present embodiment, the example in which the first average print rate X is calculated every time one print job is completed has been described. However, the present invention is not limited to this, and the first average printing rate X in the printing for the predetermined number of sheets may be calculated when the printing for the predetermined number of sheets is completed. As described above, the forced toner consumption process may be executed not only at the time when one print job is completed but also at any timing.

  The printer 1 described in the present embodiment is a monochrome printer. However, the present invention is not limited to this form, and may be a color printer.

  In addition, the printer 1 described in the present embodiment is configured to directly transfer the toner image formed on the photosensitive drum 31 onto the paper K (direct transfer method). However, the present invention is not limited to this form, and may be a form (indirect transfer system) in which a toner image is transferred onto a sheet via an intermediate transfer belt.

  The embodiment of the image forming apparatus according to the present invention is not limited to the printer 1 described above. That is, the image forming apparatus according to the present invention can be applied not only to a copying machine and a facsimile machine but also to a multifunction machine having functions of a copying machine, a facsimile machine, and a printer.

  DESCRIPTION OF SYMBOLS 1 ... Printer (image formation apparatus), 20 ... Toner amount detection sensor (toner amount detection part), 30 ... Image formation part, 31 ... Photosensitive drum (image carrier), 34 ... Development apparatus (development part), 37 ... Toner cartridge (toner storage unit), 38 ... transfer roller (transfer unit), 90 ... control unit, 91 ... print control unit, 92 ... first print rate calculation unit, 93 ... toner forced consumption processing execution unit, 94 ... second Print rate calculation unit, 95 ... toner forced consumption threshold setting unit

Claims (4)

An image forming unit that forms a toner image on a transfer material,
An image carrier on which an electrostatic latent image is formed on the surface;
A developing unit that develops the electrostatic latent image as a toner image by supplying toner to the image carrier;
An image forming unit comprising: a transfer unit that transfers a toner image developed on the surface of the image carrier to a transfer material to form a toner image on the transfer material;
A toner storage unit configured to supply toner to the developing unit and to be replaceable with respect to the image forming unit;
A toner amount detection unit for detecting a toner amount stored in the toner storage unit;
A first printing rate calculation unit that calculates an average area per predetermined area of the toner image formed on the transfer material in the image forming unit as a first average printing rate;
A toner forced consumption processing execution unit that executes a forced toner consumption process when the first average printing rate calculated by the first printing rate calculation unit is less than a toner forced consumption threshold;
The toner image formed on the transfer material in the image forming unit after the toner storage unit is replaced and before the toner amount detected by the toner amount detection unit becomes less than a preset toner amount. A second printing rate calculation unit that calculates an average area per predetermined area as a second average printing rate;
A toner forced consumption threshold setting unit that sets the toner forced consumption threshold based on the second average printing rate calculated by the second printing rate calculation unit;
An image forming apparatus comprising: The toner forced consumption threshold setting unit sets the toner forced consumption threshold to the first threshold when the second average printing rate calculated by the second printing rate calculation unit is equal to or greater than an average printing rate determination value, When the second average printing rate calculated by the second printing rate calculation unit is less than the average printing rate determination value, the toner forced consumption threshold is set to a second threshold higher than the first threshold;
The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the toner is a magnetic one-component toner. The image forming unit is configured such that the amount of toner contained in the developing unit cannot be detected.
The image forming apparatus according to claim 1.

Images