JP2013003415A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a printing quality and prolong a service life of an image forming part.SOLUTION: An image forming apparatus includes: an image forming part including an image carrier for forming an electrostatic latent image according to image data, a developer carrier which is applied with a developing voltage and develops the electrostatic latent image formed on a surface of the image carrier with developer, and a developer supply member applied with a supply voltage and supplying the developer to the developer carrier; and a control part for switching between a first image forming mode having an image forming condition to provide a high density image and a second image forming mode having the image forming condition to provide an image having a density lower than that of the first image forming mode. The control part makes the potential difference between the developing voltage and the supply voltage smaller than the potential difference between the developing voltage and the supply voltage in the second image forming mode when the first image forming mode is selected.

Description

  The present invention relates to an image forming apparatus and an image forming method for forming an image such as an electrophotographic printer or a copying machine.

  In the conventional image forming apparatus, the surface of the photosensitive drum uniformly charged by the charging unit is exposed by the exposing unit to form an electrostatic latent image, and the electrostatic latent image is developed by the image forming unit to develop the photosensitive drum. A method is employed in which after a toner image is formed on the toner image, the toner image is transferred to a sheet and fixed. For example, in a one-component contact development type image forming unit, toner is supplied from a toner cartridge, and the toner is charged by frictional charging between a supply roller and a development roller, and between a regulation blade and a development roller, A thin toner layer is uniformly formed on the developing roller by the regulating blade. The developing roller and the photosensitive drum are arranged in contact with each other, and an electric field is formed on the surface of the developing roller and the photosensitive drum to move the charged toner on the developing roller to the electrostatic latent image on the photosensitive drum. Subsequently, in the direct transfer method in which the toner on the photosensitive drum is directly transferred onto the sheet conveyed by the transfer belt, the toner moved to the transfer region by the rotation of the photosensitive drum is moved onto the sheet by the electric field.

  In such an image forming apparatus, the ambient conditions such as temperature and humidity, the usage frequency, the usage pattern such as the usage image pattern may be different, and the image density may fluctuate over time. In order to obtain a high-quality print output, for example, there is one that detects the density of a density detection pattern formed on the conveyance belt and corrects the density so as to be constant (see, for example, Patent Document 1). .

  In order to obtain a high-quality print output, it is necessary to increase the maximum density of the image, but in order to increase the image density (for example, printing a print pattern having a high image area ratio such as a solid image). In this case, it is necessary to increase the toner supply capability from the supply roller to the developing roller. To cope with this, the rotational speed of the supply roller is increased or the pressing force of the supply roller to the developing roller is increased.

JP 2004-341100 A (paragraph “0013” to paragraph “0016”, FIG. 1)

However, in the above-described conventional technology, the amount of wear of the supply roller of the image forming unit is large, the toner supply capability decreases with time, image blurring and afterimages occur, and the print quality deteriorates. There is a problem that the life of the part is shortened.
An object of the present invention is to solve such a problem, and it is an object to improve the print quality and prolong the life of an image forming unit.

  Therefore, the present invention provides an image carrier that forms an electrostatic latent image according to image data, and development that develops developer on the electrostatic latent image formed on the surface of the image carrier by applying a development voltage. A first image forming mode having an image forming section comprising a developer carrying member, a developer supplying member to which a supply voltage is applied and supplying the developer to the developer carrying member, and an image forming condition for obtaining a high density image And a control unit that switches between a second image forming mode having an image forming condition for obtaining an image having a density lower than that of the first image forming mode, wherein the control unit selects the first image forming mode. In this case, the potential difference between the development voltage and the supply voltage is made smaller than the potential difference between the development voltage and the supply voltage in the second image forming mode.

  According to the present invention, the print quality can be improved and the life of the image forming unit can be extended.

1 is a block diagram showing a control configuration of an image forming apparatus according to a first embodiment. 1 is a schematic side view illustrating a configuration of an image forming apparatus according to a first embodiment. The flowchart which shows the flow of the image formation process in 1st Example. Explanatory drawing which shows the relationship between the number of printed sheets and the afterimage level in the first embodiment. Schematic side view showing the configuration of the image forming apparatus in the second embodiment FIG. 3 is a block diagram illustrating a control configuration of an image forming apparatus according to a second embodiment. Flowchart showing the flow of toner disposal processing in the second embodiment 7 is a flowchart showing a flow of a modified example of toner disposal processing in the second embodiment. Flowchart showing the flow of toner end detection processing in the second embodiment.

  Hereinafter, embodiments of an image forming apparatus and an image forming method according to the present invention will be described with reference to the drawings.

FIG. 2 is a schematic side view showing the configuration of the image forming apparatus in the first embodiment.
In FIG. 2, an image forming apparatus 100 has four process cartridges 11 to 14 as image forming sections that respectively form black, yellow, magenta and cyan images, and these process cartridges 11 to 14 record. The image forming apparatus 100 is detachably disposed in order from the upstream side of the conveyance path 16 of the medium 15. In addition, LED (Light Emitting Diode) heads 17 to 20 as exposure means are disposed at positions facing each of the process cartridges 11 to 14.

  The internal structure of the process cartridges 11 to 14 as the image forming unit is common. For example, the black process cartridge 11 has a periphery of the photosensitive drum 21 as an image carrier that forms an electrostatic latent image according to image data. In addition, a charging roller 22 as a charging unit for supplying and charging the surface of the photosensitive drum 21 and an electrostatic latent image formed on the surface of the photosensitive drum 21 charged by exposure of the LED head 17, A developing roller 23 as a developer carrying member for developing toner (developer), a supply roller 24 as a developer supply member for supplying toner to the developing roller 23, and a toner on the developing roller 23 to make a thin layer The regulating blade 26 is disposed and integrated with each other.

  Further, each of the process cartridges 11 to 14 is detachably equipped with toner cartridges 27 to 30 and accommodates toner of each color. The internal configurations of the toner cartridges 27 to 30 are also common. For example, the black toner cartridge 27 contains black toner and is attached to the process cartridge 11 to open the toner supply port. 11 is replenished with toner. The toner cartridges 27 to 30 may be integrated with each of the process cartridges 11 to 14.

Under the image forming apparatus 100, a paper feed cassette 31 for storing the recording medium 15 and a hopping roller 32 for separating and feeding the recording media 15 stacked on the paper feeding cassette 31 one by one are arranged. It is installed.
The recording medium 15 accommodated in the paper feed cassette 31 is fed by the hopping roller 32, and then conveyed along the conveyance path 16 by the registration roller pairs 33 and 34 that correct skewing, and is further transferred by the transfer belt unit 35. The respective process cartridges 11 to 14 are sequentially conveyed.

  At a position facing the process cartridges 11 to 14 of the transfer belt unit 35, a transfer roller 37 to which a voltage for forming an electric field is applied to the photosensitive drum 21 via the transfer belt 36 is disposed. The toner images formed on the photosensitive drums 21 of the cartridges 11 to 14 are transferred to the recording medium 15.

  The fixing device 41 is disposed in contact with the heating roller and the backup roller, and the toner transferred onto the recording medium 15 is fixed to the recording medium 15 by pressurization and heating of the heating roller and the backup roller. The recording medium 15 discharged from the fixing device 41 is transported along the transport path 16 and is discharged to the stacker 43 by the discharge roller 42.

  Further, the image forming apparatus 100 includes a voltage supply circuit as a voltage control unit that applies a voltage to the charging roller 22, the developing roller 23, the supply roller 24, the transfer roller 37, and the like, a display unit such as a liquid crystal display, and a memory. A storage unit, and a control unit having a central processing unit (CPU) that controls the operation of the entire image forming apparatus 100 based on a control program (software) stored in the storage unit are provided.

  When the image forming apparatus 100 configured as described above receives the image data transmitted from the external host apparatus, the image forming apparatus 100 transmits the image data to the recording control unit via the image processing unit in the controller. While feeding paper, image data is transmitted to the LED heads 17-20, and the charging roller 22, the developing roller 23, the supply roller 24, and the transfer roller 37 are high when the recording medium 15 reaches the process cartridges 11-14. A voltage is applied, and the LED heads 17 to 20 are turned on according to the image data. Then, an electrostatic latent image is formed on the surface of the photosensitive drum 21, and the toner image developed by the developing roller 23 is transferred to the electrostatic latent image on the recording medium 15 by the transfer roller 37 to form an image. .

FIG. 1 is a block diagram illustrating a control configuration of the image forming apparatus according to the first embodiment. The control configuration of the image forming apparatus will be described with reference to FIGS. 1 and 2.
In FIG. 1, the control system of the image forming apparatus 100 includes a control unit 60 that controls the entire image forming apparatus 100, an I / F unit 61 that receives image data from a host device, and a charging that applies a voltage to the charging roller 22. A voltage control unit 66; a development voltage control unit 67 that applies a voltage to the development roller 23; a supply voltage control unit 68 that applies a voltage to the supply roller 24; an LED head control unit 70 that controls the LED head 17; The motor control unit 71 controls the motor group 51 that rotates the rollers, the display control unit 72 controls the display unit 52, and the operation unit 73.

The control unit 60 includes a CPU 62 and a storage unit 63 such as a memory, and controls each unit of the image forming apparatus 100 to perform image forming processing and the like.
The storage unit 63 stores in advance a program (software) to be executed by the control unit 60, and stores various data used for the program, processing results by the control unit 60, and the like.

The I / F unit 61 is connected to an external host device such as a computer (not shown) via a communication line, receives image data transmitted from the host device, and notifies the control unit 60 of the image data.
When the image data is notified from the I / F unit 61, the control unit 60 controls the operation of the motor group 51 that drives the photosensitive drum 21, the transfer belt 36, and the hopping roller 32 in accordance with the print timing generated by the CPU 62. The drive signal of each motor is output to the motor control unit 71.

  When a drive signal for each motor is output to the motor control unit 71, the recording medium 15 is fed out from the paper feed cassette 31 and paper feeding is started. At the same time, the control unit 60 controls the light emitting operation of the LED heads 17-20. Image data is output to the head control unit 70, and control signals are output to the charging voltage control unit 66, the development voltage control unit 67, and the supply voltage control unit 68 at the timing when the recording medium 15 reaches the process cartridges 11 to 14. A high voltage is applied to the charging roller 22, the developing roller 23 and the supply roller 24.

The LED heads 17 to 20 are turned on according to the image data, and after the electrostatic latent image is formed on the surface of each photosensitive drum 21 whose rotation is controlled by the motor control unit 71, the toner image attached to the electrostatic latent image. Is transferred onto the storage medium 15 by the transfer voltage applied to the transfer roller 37.
The display control unit 72 performs control to display various types of information such as toner remaining amount information on the display unit 52.

The operation unit 73 is arranged with the display unit 52 in the image forming apparatus 100 and includes an input key for selecting a menu displayed on the display unit 52 and changing setting contents.
In addition, the control unit 60 includes a control switching unit 64 that switches each image forming condition in accordance with the image forming mode.

  Here, the image forming mode is a first image forming mode (high density printing setting) in which high density printing is performed in order to improve printing quality, and a second mode in which low density printing is performed to extend the life of the process cartridge. In this embodiment, the operation unit 73 is operated to display a selection menu on the display unit 52, and the first image formation mode or the second image formation mode is selected. The set image forming mode is stored in the storage unit 63.

That is, the control switching unit 64 includes a first image forming mode having an image forming condition for obtaining a high-density image, and a second image forming mode having an image forming condition for obtaining an image having a lower density than the first image forming mode. And switch.
This first image forming mode has a wide color reproduction range that can be expressed and can enhance the contrast of the image. Therefore, the first image forming mode is also suitable for uses such as DTP (Desk Top Publishing) and POP (Point Of Purchase). It is an image quality mode.

On the other hand, the second image forming mode is suitable for applications such as offices where a high density image is not strongly required because the frequency of printing a solid image is low or high contrast printing is not particularly required. This is a so-called long life mode that can extend the life of the battery.
It is assumed that the user of the image forming apparatus 100 selects and sets the first image forming mode or the second image forming mode as appropriate according to the purpose of use.

The operation of the above configuration will be described.
The image forming process performed by the control unit of the image forming apparatus will be described with reference to FIGS. 1 and 2 in accordance with the step represented by S in the flowchart showing the flow of the image forming process in the first embodiment of FIG. In the following description, the process cartridge 11 will be described, but the process cartridges 12 to 14 perform the same processing.

  S <b> 101: When image data is notified from the I / F unit 61, the control unit 60 of the image forming apparatus 100 starts image forming processing according to the print timing generated by the CPU 62, and the image stored in the storage unit 63. It is determined whether the formation mode is the first image formation mode or the second image formation mode. If the controller 60 determines that the image forming mode is the first image forming mode, the process proceeds to S102. If the controller 60 determines that the image forming mode is the second image forming mode, the process proceeds to S103.

  S102: When the control unit 60 determines that the image forming mode is the first image forming mode, the control switching unit 64 generates control signals for setting the developing voltage Vd1 and the supply voltage Vs1 that are setting conditions for forming a high density image, respectively. The output is output to the development voltage controller 67 and the supply voltage controller 68, and the process proceeds to S104.

  In this embodiment, when negatively charged toner is used and the resolution is 600 DPI (Dots Per Inch), the image density (solid image density) of a print pattern with a high image area ratio (hereinafter referred to as “solid image”) will be described. ) Is set to an OD (Optical Density) value of 1.5, the charging voltage is set to -1000 V so that the charging potential of the photosensitive drum 21 becomes -500 V, and the LED head 17 is exposed. It is assumed that the residual potential of the subsequent photosensitive drum 21 is -50V, the developing voltage Vd1 is -250V, and the supply voltage Vs1 is -350V. This is an example, and it is determined as appropriate depending on the toner charge amount.

  S103: When the control unit 60 determines that it is the second image forming mode, the control switching unit 64 generates control signals for setting the development voltage Vd2 and the supply voltage Vs2 that are setting conditions for forming a high density image, respectively. The output is output to the development voltage controller 67 and the supply voltage controller 68, and the process proceeds to S104.

  In this embodiment, when negatively chargeable toner is used and the resolution is 600 DPI (Dots Per Inch), the solid image density is set to an OD value 1.2 that is lower than the solid image density in the first image forming mode. Then, the charging voltage is set to −1000 V so that the charging potential of the photosensitive drum 21 becomes −500 V, and the residual potential of the photosensitive drum 21 after the exposure of the LED head 17 is set to −50 V, and the developing voltage Vd2 is applied. Is -150V, and the supply voltage Vs2 is -300V. This is an example, and it is determined as appropriate depending on the toner charge amount.

  S104: The control unit 60 that has set the development voltage Vd1 and the supply voltage Vs1, which are the setting conditions of the first image forming mode in S102, executes image formation according to the image forming conditions of the first image forming mode. That is, the control unit 60 sets the development contrast voltage, which is the potential difference between the development voltage and the photosensitive drum residual potential, to 200 V (= | (−250 V) − (− 50 V) |), and the development voltage and the photosensitive drum. The background portion contrast voltage, which is a potential difference from the non-latent image forming portion voltage, is 250 V (= | (−250 V) − (− 500 V) |), and the potential difference between the developing voltage and the supply voltage is 100 V (= | (−250 V). Image formation is performed with a setting of − (− 350V) |).

  On the other hand, the control unit 60 that has set the development voltage Vd2 and the supply voltage Vs2 that are the setting conditions of the second image forming mode in S103 executes the image formation according to the image forming conditions of the second image forming mode. That is, the control unit 60 sets the development contrast voltage, which is the potential difference between the development voltage and the photosensitive drum residual potential, to 100 V (= | (−150 V) − (− 50 V) |), and the development voltage and the photosensitive drum. The background portion contrast voltage, which is the potential difference from the non-latent image forming portion voltage, is 350 V (= | (−150 V) − (− 500 V) |), and the potential difference between the developing voltage and the supply voltage is 150 V (= | (−150 V). Image formation is performed with a setting of − (− 300 V) |).

As described above, when the first image forming mode is selected, the control unit 60 makes the potential difference between the developing voltage and the supply voltage smaller than the potential difference between the developing voltage and the supply voltage in the second image forming mode.
In the first image forming mode, the solid image density is set to an OD value of 1.5, the color reproduction range that can be expressed is wide, and the contrast of the image can be enhanced, so that it can be used for applications such as DTP and POP. It is a suitable high quality mode.

  In order to obtain a high image quality density, it is necessary to increase the toner adhesion amount of the toner image formed on the photosensitive drum 21. In order to increase the toner adhesion amount, the toner layer formed on the developing roller 23 has The material of the developing roller 23 is selected so as to increase the thickness, and the pressing force of the regulating blade 26 is set.

  At this time, when a so-called low duty image having a low area ratio of the image to be printed is continuously printed, the toner on the developing roller 23 is hardly consumed, and the toner that is not consumed continues to remain on the developing roller 23. As the number of times of triboelectric charging increases, the charge amount of the toner increases. If the toner charge amount becomes too high with a large amount of toner attached, the surface potential of the toner layer formed on the developing roller 23 exceeds the background contrast voltage in a minute region, and an electrostatic latent image is formed. So-called smear printing occurs in which the toner is developed up to a background portion that does not exist.

  In order to prevent this smear printing, the supply roller 24 made of a sponge material is pressed strongly against the developing roller 23 as a setting of the process cartridge 11, and the residual toner on the developing roller 23 is scraped off, so that the residual toner is formed on the developing roller 23. Is kept from staying.

  Further, in setting the supply voltage, if the potential difference between the development voltage and the supply voltage is increased, the toner supply performance to the development roller 23 is improved, so that the toner adhesion amount on the development roller 23 is increased. In order to perform high-density printing with high density and no blur, it is desirable to increase the supply voltage in order to ensure the amount of toner attached on the developing roller 23, but the amount of toner attached on the developing roller 23 increases. Even after this, smear printing occurs as described above, so the potential difference between the development voltage and the supply voltage is set to 100 V, which is in the region of the potential difference between the development voltage and the supply voltage that does not cause smear printing.

  By setting the process cartridge 11 in this way, it is possible to obtain a print output suitable for the high image quality mode. However, if the sponge material supply roller 24 is strongly pressed against the developing roller 23 as described above, the supply roller 24 When the supply roller 24 is worn out, the toner scraping ability is reduced and the toner supply performance to the developing roller 23 is also reduced. For example, when the solid image is printed, the rotation number of the supply roller 24 is reduced. As the toner increases, the toner supply amount decreases, and an afterimage is likely to occur due to a density step in the rotation period of the roller.

FIG. 4 is an explanatory diagram showing the relationship between the number of printed sheets and the afterimage level in the first embodiment.
FIG. 4 shows the afterimage level as an index of the print quality of bold characters when, for example, an image in which white bold characters are arranged on a background with high image density is printed. It can be seen that the afterimage level decreases, that is, the print quality decreases.
For this reason, in the first image forming mode indicated by the broken line, the life of the process cartridge 11 is the number of printed sheets Lf1 in which the afterimage level that decreases with the number of printed sheets does not fall below the allowable level with respect to the initial afterimage level.

  On the other hand, the second image forming mode is a setting in which the solid image density is set to an OD value of 1.2, and the high density is obtained because the frequency of printing a solid image is low or high-contrast printing is not particularly required. This is a long life mode that is suitable for applications such as offices where images are not strongly required, and can extend the life of the process cartridge 11.

  In this second image forming mode, since the image density is low, the toner adhesion amount of the toner image on the photosensitive drum 21 is small. Therefore, the thickness of the toner layer formed on the developing roller 23 forms a high image density. Even if the supply roller 24 is worn over time and the toner supply performance is lowered, the influence on the image is reduced.

  As shown by the solid line in FIG. 4, in the second image forming mode, the decrease in the afterimage level with respect to the number of printed sheets tends to be moderate as compared to the first image forming mode, and the afterimage level that decreases with the number of printed sheets Since the number of printed sheets Lf2 that does not fall below the permissible level with respect to the initial afterimage level is set as the lifetime of the process cartridge 11, the lifetime can be extended as compared with the first image forming mode.

  Further, when the process cartridge 11 is used for a long period of time, the external additive that has been released from the toner and charged with a polarity opposite to the toner charge passes through the regulating blade 26 and adheres to the surface of the photosensitive drum 21, and becomes solid. When an image is printed, so-called filming printing that appears as a white spot in a portion where an external additive is attached may occur, and the state may deteriorate.

In the second image forming mode, the potential difference between the developing voltage and the supply voltage is increased, and an electric field is formed so that the positively charged free external additive is strongly attracted to the supply roller 24 side. The free external additive is prevented from slipping through the regulating blade to cause filming printing.
By doing in this way, the tendency of the deterioration of the filming printing with respect to the number of printed sheets can be moderated, and the deterioration of the printing quality due to long-term use can be suppressed.

Further, in the second image forming mode, since the developing voltage is lowered as a low density setting, the background contrast voltage is set to be larger than that in the first image forming mode. For this reason, the potential difference between the developing voltage and the supply voltage becomes large, and it is possible to prevent smear printing from occurring even if the toner adhesion amount on the developing roller 23 increases.
Note that the setting values such as voltage values described in the present embodiment are merely examples, and are not limited thereto. If the toner charge amount changes due to the environment or the like, the setting values are appropriately changed to optimum values. Anyway.

  In this embodiment, the first image forming mode for increasing the image density and the second image forming mode for decreasing the image density can be selected, and the developing voltage is switched to switch the image density. However, for example, the image energy may be switched by changing the exposure energy of the LED head. At this time, the exposure energy may be increased in the first image forming mode, and the exposure energy may be decreased in the second image forming mode.

  Furthermore, the present invention can also be applied when the image forming apparatus performs density correction. For example, the target density for density correction is set to be high in the first image forming mode and low in the second image forming mode. At this time, the maximum image density is switched, but the halftone density is set to the same target density, so that it is possible to reduce the print quality of a photographic image or the like that uses a lot of halftone patterns even in the second image forming mode. Life can be extended.

  In this embodiment, the supply voltage applied to the supply roller is controlled to increase the potential difference from the development voltage in the second image formation mode rather than the first image formation mode. The potential difference between the regulation voltage and the development voltage is switched between the first image formation mode and the second image formation mode, and in the second image formation mode, the positive externally charged free external additive is attracted to the regulation blade side. The electric field may be increased so that the external additive does not easily pass through the regulating blade.

  Furthermore, in this embodiment, the example in which the switching between the first image forming mode and the second image forming mode is performed by selecting the menu item displayed on the display unit has been described. A menu for switching between the first image forming mode and the second image forming mode is provided on a screen displayed by (software), and the printer driver switches between the first image forming mode and the second image forming mode. Anyway.

  As described above, in the first embodiment, the control switching unit switches the image between the first image forming mode for forming an image at a high density and the second image forming mode for forming an image at a low density. As a result of the formation, in the second image forming mode in which an image is formed at a low density, the deterioration of the quality of the image formed over time can be moderated, and the life of the process cartridge as the image forming unit can be reduced. As a result, it is possible to achieve an effect that it is possible to achieve both high quality of the image to be formed and long life of the process cartridge.

  FIG. 5 is a schematic side view showing the configuration of the image forming apparatus in the second embodiment, and FIG. 6 is a block diagram showing the control configuration of the image forming apparatus in the second embodiment. Note that parts similar to those of the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 5, the image forming apparatus 200 includes four process cartridges 211 to 214 as image forming units that respectively form black, yellow, magenta, and cyan images, and these process cartridges 211 to 214 perform recording. The image forming apparatus 200 is detachably disposed in order from the upstream side of the conveyance path 16 of the medium 15. In addition, LED heads 17 to 20 as exposure means are arranged at positions facing each of the process cartridges 211 to 214.

  The internal structure of the process cartridges 211 to 214 as image forming units is common. For example, the black process cartridge 211 has a periphery of the photosensitive drum 21 as an image carrier that forms an electrostatic latent image according to image data. In addition, a charging roller 22 as a charging unit for supplying and charging the surface of the photosensitive drum 21 and an electrostatic latent image formed on the surface of the photosensitive drum 21 charged by exposure of the LED head 17, Developing roller 23 as a developer carrying member for developing toner (developer), supply roller 24 as a developer supply member for supplying toner to developing roller 23, and toner on developing roller 23 to make the layer thin The regulating blade 26 is disposed and integrated with each other.

  Each of the process cartridges 211 to 214 is provided with toner cartridges 27 to 30 in an integrated manner, and each color toner is accommodated therein. The internal configurations of the toner cartridges 27 to 30 are also common. For example, the black toner cartridge 27 contains black toner and supplies the process cartridge 211 with toner.

Further, the process cartridges 211 to 214 are provided with a toner remaining amount detection mechanism 220 for detecting the remaining amount of toner.
The toner remaining amount detection mechanism 220 includes a gear that rotates at a constant speed, and an agitation shaft 220a that has a shaft that is substantially coaxial with the rotation axis of the gear and has a shaft that abuts against a protrusion formed on the gear. . At the tip of the stirring shaft 220a, a stirring portion for stirring the toner is provided, and the stirring portion rises from the bottom dead center to the top dead center by the rotation of the shaft that contacts the protrusion of the rotating gear. When the top dead center is reached, it is configured to rotate to the bottom dead center by its own weight and descend.

  If the remaining amount of toner in the process cartridge 211 is low when the agitating unit rotates to the top dead center, it immediately rotates to its bottom dead center until it is pushed by the rotating gear projection. On the other hand, if the remaining amount of toner is large, it takes time to rotate from the top dead center to the bottom dead center due to the resistance of the toner, and it is pushed by the rotating gear projection and rotates to the bottom dead center.

The stirrer located at the bottom dead center is detected by an optical sensor or the like of the toner remaining amount detector, and the time during which the stirrer is located at the bottom dead center is measured by a timer or the like, and based on the measured time. To detect the remaining amount of toner.
The toner remaining amount detecting unit notifies the control unit that it has been detected that the remaining amount of toner is low (toner low state) when the detected remaining amount of toner is equal to or less than a predetermined amount.

Next, the configuration of the control system of the image forming apparatus 200 will be described with reference to FIGS.
In FIG. 6, the control system of the image forming apparatus 200 includes a control unit 260 that controls the entire image forming apparatus 200, an I / F unit 61 that receives image data from the host apparatus, and a toner remaining amount detection mechanism 220. A toner remaining amount detecting unit 261 for detecting a remaining toner amount, a charging voltage control unit 66 for applying a voltage to the charging roller 22, a developing voltage control unit 67 for applying a voltage to the developing roller 23, and a supply roller 24. Supply voltage control unit 68 for applying voltage, LED head control unit 70 for controlling LED head 17, motor control unit 71 for controlling motor group 51 for rotating each roller, and display control unit for controlling display unit 52 72 and an operation unit 73.

  The toner remaining amount detecting unit 261 as a developer remaining amount detecting unit includes an optical sensor, a timer, and the like that detect the rotation period of the stirring shaft of the toner remaining amount detecting mechanism 220 in the process cartridge 211 and detects the remaining amount of toner. To do. When the toner remaining amount detection unit 261 detects that the rotation period of the stirring shaft of the toner remaining amount detection mechanism 220 is smaller than the threshold, that is, the time during which the stirring shaft is located at the bottom dead center is longer than the threshold. At this time, it is determined that the toner is in a low toner state, and a process for determining that the use of the process cartridge is stopped is executed as a toner end and the display unit 52 is displayed as a toner low state.

  As in the first embodiment, the control unit 260 includes a control switching unit 264 that switches each image forming condition according to the image forming mode, operates the operation unit 73 to display a selection menu on the display unit 52, and The first image forming mode or the second image forming mode is selected and set, and the set image forming mode is stored in the storage unit 63.

  Further, the control unit 260 includes a toner disposal control unit 265 as a developer disposal unit that discards the toner (developer) remaining in the process cartridge when the image area ratio of the image data forming the image is smaller than the threshold value. The toner discard control unit 265 discards the toner remaining in the process cartridge on the transfer belt in accordance with the toner discard timing generated by the CPU 62. The discarded toner is collected by the cleaning unit and conveyed to a waste toner box provided in the image forming apparatus 200.

  The toner discard control unit 265 can control the amount of toner discarded based on the image pattern of the toner image formed on the photosensitive drum 21. The toner discard timing is, for example, the timing at which image data (print job) is received from the host device.

  The image forming apparatus 200 configured as described above can select and set a first image forming mode for setting high density printing and a second image forming mode for setting long life with low density. The toner discarding condition and the toner end display condition in the process cartridge are switched in the image forming mode and the second image forming mode.

  The operation of the above configuration will be described. In the following description, the process cartridge 211 will be described, but the process cartridges 212 to 214 perform the same processing. Further, the image forming process performed by the control unit of the image forming apparatus is the same as that in the first embodiment, so that the description thereof is omitted.

  The toner discarding process performed by the control unit of the image forming apparatus will be described with reference to FIGS. 5 and 6 according to the step represented by S in the flowchart showing the flow of the toner discarding process in the second embodiment of FIG.

  S201: The control unit 260 of the image forming apparatus 100 starts the toner discarding process according to the toner discarding timing generated by the CPU 62, and determines whether the image forming mode stored in the storage unit 63 is the first image forming mode. It is determined whether the image forming mode is the second image forming mode. If the controller 260 determines that the image forming mode is the first image forming mode, the process proceeds to S202. If the controller 260 determines that the image forming mode is the second image forming mode, the process proceeds to S203.

  S202: When determining that the image forming mode is the first image forming mode, the control unit 260 causes the control switching unit 264 to store (set) a threshold value TW1 for determining whether or not to discard the toner in the storage unit 63 to perform processing. The process proceeds to S204.

  The toner discarding process is a process for regularly discharging the toner remaining in the process cartridge without being developed in the image forming process to the outside of the process cartridge. When a low-duty image having a low print image density is continuously printed, the toner on the developing roller 23 is not used, and the toner is rubbed against the photosensitive drum 21, the supply roller 24, and the regulating blade 26. May be damaged due to repeated printing, and smear printing may occur due to an increase in the charge amount or an increase in the adhesion amount to the developing roller 23.

  The toner discard control unit 265 calculates the image duty of the image pattern printed before (for example, immediately before or until the present time), and discards a predetermined amount of toner when the image duty is lower than the threshold value. Prevents smudge printing due to damage received by the toner. The toner disposal control unit 265 forms a disposal image pattern stored in the storage unit 63 at the toner disposal timing on the photosensitive drum 21 as an electrostatic latent image, and develops the toner on the electrostatic latent image to thereby generate toner. Discard. The image duty is an image area ratio and is a ratio of pixels to be printed with respect to all printable pixels.

  In the first image forming mode, as described in the first embodiment, since the toner layer on the developing roller 23 is thick and smear printing due to toner damage is likely to occur, the toner is frequently discarded. Set. For example, the threshold value TW1 for determining whether to discard the toner is set to 5%.

  S203: On the other hand, when the control unit 260 determines that the second image forming mode is set in S201, the control switching unit 264 stores (sets) the threshold TW2 for determining whether or not to discard the toner in the storage unit 63. And the process proceeds to S204.

  In the second image forming mode, as described in the first embodiment, the background portion contrast voltage is increased, so that smear printing due to damage received by the toner hardly occurs and is less than in the first image forming mode. A setting for discarding toner at a frequency, that is, threshold TW2 <threshold TW1. For example, the threshold TW2 for determining whether to discard the toner is set to 2%.

  S204: The toner discard control unit 265 determines whether the image duty is equal to or less than the threshold using the threshold set in the storage unit 63. If it is determined that the image duty is equal to or less than the threshold, the process proceeds to S205. If it is determined that the image duty is larger than the threshold value, the process is terminated without discarding the toner, and the normal image forming process is started by the control unit 260.

  S205: When the toner discard control unit 265 determines that the image duty is equal to or less than the threshold, the toner discard control unit 265 executes toner discard. For example, if the image duty is 5% or less in the first image forming mode, the toner corresponding to the case of printing 5% with A4 size paper is discarded, and the image duty is 2% in the second image forming mode. In the following cases, the toner corresponding to the case of 2% printing corresponding to A4 size paper is discarded.

  As described above, the toner discard control unit 265 sets the threshold for determining whether or not to discard the toner in the first image forming mode and the toner discard amount when it is determined that the toner is to be discarded as compared with the second image forming mode. On the other hand, in the second image forming mode, the threshold for determining whether or not to discard the toner and the toner discarding amount when it is determined that the toner is to be discarded are smaller than those in the first image forming mode.

  As shown in FIG. 8, when the toner discarding control unit 265 determines in S301 that the image forming mode is the second image forming mode, the toner discarding process is immediately stopped (finished) so as to discard the toner. You may not perform.

  Next, in this embodiment, since the process cartridge is integrated with the toner cartridge, the remaining amount of toner to be accommodated before the process cartridge is stopped due to the service life due to the use amount exceeding the predetermined use amount. Even if there is no more, the life of the process cartridge is stopped and needs to be replaced.

  Therefore, the toner end detection process performed by the control unit of the image forming apparatus is referred to FIG. 5 and FIG. 6 according to the step represented by S in the flowchart showing the flow of the toner end detection process in the second embodiment of FIG. While explaining.

  S401: When the printing operation using the image data received by the image forming apparatus 200 is completed, the toner remaining amount detecting unit 261 starts a toner end detection process according to an instruction from the control unit 260, and detects the toner remaining amount in the process cartridge 211. If the toner remaining amount is equal to or greater than the toner low threshold, the toner end detection process is terminated as not being in the toner low state, and if the toner remaining amount is equal to or less than the toner low threshold, the process proceeds to S402.

  S402: The control unit 260 determines whether the image forming mode stored in the storage unit 63 is the first image forming mode or the second image forming mode. If the controller 260 determines that the image forming mode is the first image forming mode, the process proceeds to S403. If the controller 260 determines that the image forming mode is the second image forming mode, the process proceeds to S404.

  S403: When the control unit 260 determines that the image forming mode is the first image forming mode, the control switching unit 264 stores the toner end threshold value TE1 as the developer remaining amount determination amount for determining the toner end in the storage unit 63. (Set), and the process proceeds to S405.

  If the remaining amount of toner in the process cartridge 211 becomes too low, faint printing will occur, and if the image forming process is continued with a small amount of toner remaining, the toner will be easily damaged and smeared printing will occur due to increased charge etc. There is a case. Therefore, in order to maintain the quality of image output until the lifetime of the process cartridge 211, the toner end threshold value TE1 is set so that a predetermined amount of toner remains in the process cartridge 211 in the first image forming mode.

  S <b> 404: When the control unit 260 determines that the image forming mode is the second image forming mode, the control switching unit 264 stores the toner end threshold value TE <b> 2 as the developer remaining amount determination amount for determining the toner end in the storage unit 63. (Set), and the process proceeds to S405.

  In the second image forming mode, since the background contrast voltage is increased as described above, the setting is such that smear printing due to damage received by the toner hardly occurs. Therefore, the toner end threshold value TE2 for the toner end determination is set as a threshold value with a smaller amount of toner remaining in the process cartridge 211 than the toner end threshold value TE1 for the toner end determination in the first image forming mode. The threshold value TE1 is set as a threshold value in which the amount of toner remaining in the process cartridge 211 is larger than the toner end threshold value TE2 of the toner end determination in the second image forming mode.

  S405: The control unit 260 determines whether or not the toner usage amount after the toner low is detected using the toner end threshold set in the storage unit 63 exceeds the threshold, and the toner usage exceeds the toner end threshold. If it is determined that the toner usage amount has not reached the toner end threshold value, the process proceeds to S407.

  That is, in the first image forming mode, the control unit 260 determines whether or not the toner usage amount after detecting toner low using the toner end threshold value TE1 set in the storage unit 63 exceeds the toner end threshold value TE1. If it is determined that the toner usage amount exceeds the toner end threshold TE1, the process proceeds to S406. If it is determined that the toner usage amount does not reach the toner end threshold TE1, the process proceeds to S407.

  Further, in the second image forming mode, the control unit 260 determines whether or not the amount of toner used after the toner low is detected using the toner end threshold value TE2 set in the storage unit 63 exceeds the toner end threshold value TE2. If it is determined that the toner usage amount exceeds the toner end threshold value TE2, the process proceeds to S406. If it is determined that the toner usage amount does not reach the toner end threshold value TE2, the process proceeds to S407.

S406: When the control unit 260 determines that the toner usage amount exceeds the toner end threshold value, the control unit 260 displays that the toner end state is displayed on the display unit 52, informs that the process cartridge needs to be replaced, and ends the process. To do.
S407: If the control unit 260 determines that the toner usage amount has not reached the toner end threshold value, the control unit 260 displays that the toner low state is displayed on the display unit 52, and ends the process.

  As described above, in the second embodiment, in addition to the effects of the first embodiment, the first image forming mode for forming an image at a high density and the second image forming mode for forming an image at a low density. Is switched by the control switching unit and the damaged toner in the process cartridge is discarded, so that an effect of improving the quality of an image formed even in the first image forming mode can be obtained. .

In the second image forming mode in which the toner in the process cartridge is hardly damaged, the amount of toner used can be increased by setting the threshold for detecting the toner end low. Is obtained.
In the second embodiment, the example of the image forming apparatus provided with the process cartridge having a configuration in which the toner cartridge is integrated has been described. However, as in the first embodiment, a process cartridge to which the toner cartridge can be attached and detached is described. The image forming apparatus may be provided.

11 to 14, 211 to 214 Process cartridge 16 Transport path 17 to 20 LED head 21 Photosensitive drum 22 Charging roller 23 Developing roller 24 Supply roller 26 Regulating blade 31 Paper feed cassette 35 Transfer belt unit 36 Transfer belt 41 Fixing device 52 Display unit 60, 260 Control unit 62 CPU
63 Storage unit 64, 264 Control switching unit 66 Charging voltage control unit 67 Development voltage control unit 68 Supply voltage control unit 70 LED head control unit 71 Motor control unit 72 Display control unit 73 Operation unit 100, 200 Image forming apparatus 261 Toner remaining amount Detection unit 265 Toner disposal control unit

Claims (15)

An image carrier that forms an electrostatic latent image according to image data, a developer carrier that develops developer on the electrostatic latent image formed on the surface of the image carrier by applying a development voltage, and supply An image forming unit comprising a developer supply member to which a voltage is applied and supplies the developer to the developer carrying member;
A control unit that switches between a first image forming mode having an image forming condition for obtaining a high density image and a second image forming mode having an image forming condition for obtaining an image having a lower density than the first image forming mode; Prepared,
When the first image forming mode is selected, the control unit makes a potential difference between the developing voltage and the supply voltage smaller than a potential difference between the developing voltage and the supply voltage in the second image forming mode. An image forming apparatus. An image carrier that forms an electrostatic latent image according to image data, a developer carrier that develops a developer on the electrostatic latent image formed on the surface of the image carrier, and development to the developer carrier An image forming unit comprising a developer supply member for supplying the agent;
A developer discarding unit for discarding the developer remaining in the image forming unit when the image area ratio of the image data is smaller than a threshold;
A control unit that switches between a first image forming mode having an image forming condition for obtaining a high density image and a second image forming mode having an image forming condition for obtaining an image having a lower density than the first image forming mode; Prepared,
The control unit, when selecting the first image forming mode, causes the developer discarding amount by the developer discarding unit to be larger than the developer discarding amount in the second image forming mode. Forming equipment. An image carrier that forms an electrostatic latent image according to image data, a developer carrier that develops a developer on the electrostatic latent image formed on the surface of the image carrier, and development to the developer carrier An image forming unit comprising a developer supply member for supplying the agent;
A developer remaining amount detecting means for notifying that the developer is insufficient when it is detected that the remaining amount of developer in the image forming unit is less than a developer remaining amount determination amount;
A control unit that switches between a first image forming mode having an image forming condition for obtaining a high density image and a second image forming mode having an image forming condition for obtaining an image having a lower density than the first image forming mode; Prepared,
When the first image forming mode is selected, the control unit makes the remaining developer amount determination amount larger than the remaining developer amount determination amount in the second image forming mode. . The image forming apparatus according to claim 1.
When the image area ratio of the image data is smaller than a threshold, the developer disposal means for discarding the developer remaining in the image forming unit,
The control unit, when selecting the first image forming mode, causes the developer discarding amount by the developer discarding unit to be larger than the developer discarding amount in the second image forming mode. Forming equipment. The image forming apparatus according to claim 4.
The control unit does not discard the developer by the developer discarding unit when the second image forming mode is selected. The image forming apparatus according to any one of claims 1, 4, and 5,
When it is detected that the remaining amount of developer in the image forming unit is less than the developer remaining amount determination amount, the developer remaining amount detecting means for notifying that the developer is insufficient,
When the first image forming mode is selected, the control unit makes the remaining developer amount determination amount larger than the remaining developer amount determination amount in the second image forming mode. . The image forming apparatus according to claim 1, wherein:
The image forming apparatus, wherein the image forming unit is a process cartridge that is detachable from the image forming apparatus. The image forming apparatus according to claim 7.
The image forming apparatus, wherein the process cartridge is configured to be detachable from a toner cartridge for containing a developer. The image forming apparatus according to claim 7.
An image forming apparatus, wherein the process cartridge is integrally formed with a toner cartridge for containing a developer. A step of forming an electrostatic latent image on the image carrier according to the image data, and a developing voltage is applied to the developer carrier to develop the developer on the electrostatic latent image formed on the surface of the image carrier. An image forming method comprising: a step of applying a supply voltage to the developer supply member and supplying the developer to the developer carrying member;
The control unit switches between a first image forming mode having an image forming condition for obtaining a high-density image and a second image forming mode having an image forming condition for obtaining an image having a lower density than the first image forming mode. Steps,
When the control unit selects the first image forming mode, the potential difference between the developing voltage and the supply voltage is made smaller than the potential difference between the developing voltage and the supply voltage in the second image forming mode. And an image forming method. Forming an electrostatic latent image on the image carrier according to image data; developing a developer on the electrostatic latent image formed on the surface of the image carrier; and developing the developer onto the developer carrier An image forming method comprising:
When the image area ratio of the image data is smaller than the threshold, the developer discarding unit discards the developer remaining in the image forming unit;
The control unit switches between a first image forming mode having an image forming condition for obtaining a high-density image and a second image forming mode having an image forming condition for obtaining an image having a lower density than the first image forming mode. Steps,
And a step of causing the developer discarding amount by the developer discarding unit to be larger than the developer discarding amount in the second image forming mode when the control unit selects the first image forming mode. An image forming method. Forming an electrostatic latent image on the image carrier according to image data; developing a developer on the electrostatic latent image formed on the surface of the image carrier; and developing the developer onto the developer carrier An image forming method comprising:
A step of notifying that the developer is insufficient when the developer remaining amount detecting unit detects that the remaining amount of developer in the image forming unit is less than the remaining amount of developer;
The control unit switches between a first image forming mode having an image forming condition for obtaining a high-density image and a second image forming mode having an image forming condition for obtaining an image having a lower density than the first image forming mode. Steps,
And a step of making the remaining amount of developer determination amount larger than the remaining amount of developer determination amount in the second image forming mode when the control unit selects the first image forming mode. Image forming method. The image forming method according to claim 10.
When the image area ratio of the image data is smaller than the threshold, the developer discarding unit discards the developer remaining in the image forming unit;
And a step of causing the developer discarding amount by the developer discarding unit to be larger than the developer discarding amount in the second image forming mode when the control unit selects the first image forming mode. An image forming method. The image forming method according to claim 13.
An image forming method comprising: a step of canceling developer discarding by the developer discarding unit when the control unit selects the second image forming mode. 15. The image forming method according to claim 10, 13 or 14,
A step of notifying that the developer is insufficient when the developer remaining amount detecting unit detects that the remaining amount of developer in the image forming unit is less than the remaining amount of developer;
And a step of making the remaining amount of developer determination amount larger than the remaining amount of developer determination amount in the second image forming mode when the control unit selects the first image forming mode. Image forming method.

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