JP2009098631A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-quality output image by changing a voltage applied to a developer regulating member for forming a developer thin layer on a developer carrier, in a non-image-forming period and making the difference between the voltage and a voltage applied to other members within a predetermined range, thereby efficiently discarding fogged toner and contaminated toner from a developing device. <P>SOLUTION: An image forming apparatus includes a latent image bearing body that bears a latent image, a charging member applied with a charging voltage and configured to charge a surface of the latent image bearing body, a developer bearing body applied with a developing voltage and configured to adhere a developer to the latent image bearing body, to form a developer image; a developer regulating member applied with a regulating-member-application voltage and configured to form the developer thin layer on the developer bearing body, and a voltage switching unit configured to switch the regulating-member-application voltage. In the non-image-forming period, the voltage switching unit switches the regulating-member-application voltage from a voltage set for an image forming period to a different voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  Conventionally, in image forming apparatuses such as electrophotographic printers, copiers, and facsimile machines, the surface of the photosensitive drum is uniformly charged by a charging device, and the charged surface of the photosensitive drum is exposed by an exposure device to be static. An electrostatic latent image is formed, and toner is attached to the electrostatic latent image by a developing device to form a toner image. The toner image is transferred to a recording medium such as printing paper and then fixed by a fixing device.

  In this case, in the developing device, toner as a developer is replenished from the toner cartridge, and the toner is charged by friction charging between the supply roller and the developing roller and between the developing blade and the developing roller. A thin toner layer is uniformly formed on the developing roller by the blade. In general, a non-magnetic one-component contact developing type image forming apparatus using a non-magnetic one-component toner and placing a developing roller and a photosensitive drum in contact with each other has a simplified structure and a small size. It is advantageous to make it more practical.

In such an image forming apparatus, the toner is moved from the developing roller to the electrostatic latent image on the photosensitive drum by giving a predetermined charge amount to the toner. However, due to deterioration of the toner or the like, an abnormally charged toner may be generated in which a predetermined charge amount is not given and the charge amount is significantly reduced or increased. Such abnormally charged toner easily moves from the developing roller to a non-exposed area on the photosensitive drum, and causes abnormal images such as fog printing and smudge printing. Therefore, a technique has been proposed in which a predetermined electrostatic latent image is formed on the surface of the charged photosensitive drum by an exposure device, and the deteriorated toner is discarded by supplying the deteriorated toner from the developing roller to the electrostatic latent image. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 2004-45481

  However, in the conventional image forming apparatus, the deteriorated toner present in the toner thin layer formed on the developing roller can be discarded, but the abnormally charged toner present in the developing apparatus can be discarded. As a result, the print quality is degraded. In addition to the deteriorated toner, normal toner that has not deteriorated moves onto the photosensitive drum in the same manner as normal development, and therefore even normal toner that has not deteriorated is discarded.

  The present invention solves the problems in the conventional image forming apparatus, changes the voltage applied to the developer regulating member for forming a developer thin layer on the developer carrying member during non-image formation, Provided is an image forming apparatus in which fog toner and dirt toner can be efficiently discarded from a developing device by obtaining a difference from a voltage applied to another member within a predetermined range, and a high-quality output image can be obtained. The purpose is to do.

  Therefore, in the image forming apparatus of the present invention, a latent image carrier that carries a latent image, a charging voltage is applied, a charging member that charges the surface of the latent image carrier, and a development voltage are applied, A developer carrying member that forms a developer image by attaching a developer to the latent image carrying member; a developer regulating member that is applied with a regulating member application voltage and forms a developer thin layer on the developer carrying member; A voltage switching unit that switches the voltage applied to the regulating member from a voltage at the time of image formation during non-image formation;

  According to the present invention, the image forming apparatus changes the voltage applied to the developer regulating member for forming the developer thin layer on the developer carrying member at the time of non-image formation and applies the voltage to other members. The difference is set within a predetermined range. Thereby, the fog toner and the dirt toner can be efficiently discarded from the developing device, and a high-quality output image can be obtained.

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

  FIG. 2 is a cross-sectional view showing the configuration of the image forming apparatus according to the first embodiment of the present invention, and FIG. 3 is a cross-sectional view showing the configuration of the main part of the image forming apparatus according to the first embodiment of the present invention. .

  In the figure, reference numeral 100 denotes an image forming apparatus according to the present embodiment. For example, a printer, a facsimile machine, a copying machine, a multifunction machine having various functions, and the like may be of any kind. Here, the image forming apparatus 100 will be described as an electrophotographic printer that forms an image by electrophotography. The image forming apparatus 100 may be a device that forms a color image, but for convenience of explanation, it is assumed that the image forming device 100 is a device that forms a monochrome image.

  In this case, the image forming unit 10 and the fixing device 4 are disposed inside the image forming apparatus 100 along the conveyance path of the recording medium 3 as a medium. The recording media 3 stacked and set in a paper cassette or the like are fed one by one by a paper feed roller 91 and conveyed in the direction indicated by arrow A in FIG. Is sent to. Subsequently, the recording medium 3 is sent out in a direction indicated by an arrow B by the registration roller 92 at a predetermined timing, and as a developer image formed by the image forming unit 10 while being conveyed along the conveyance path. The toner image is transferred.

  When the recording medium 3 is sent to the fixing device 4, a fixing process is performed by the fixing device 4, and the toner image is fixed on the recording medium 3 by heating and pressurizing the toner image. Subsequently, the recording medium 3 on which the toner image has been fixed is conveyed in the direction indicated by the arrow C, discharged in the direction indicated by the arrow D by the discharge roller 93, and stored in a stacker outside the image forming apparatus 100. .

  Here, the image forming unit 10 includes a photosensitive drum 1 as a latent image carrier, a charging roller 11 as a charging member for charging the photosensitive drum 1, and a photosensitive drum 1. The developing device 2 as a developing device for developing the electrostatic latent image, the cleaning device 16 and the like are accommodated.

  The developing device 2 accommodates toner as a developer replenished from a toner cartridge 94 as a developer accommodating device. The developing device 2 includes a developing roller 12 as a rotatable developer carrying member disposed to face the photosensitive drum 1, a toner supply roller 18 as a supply member that supplies toner to the developing roller 12, And a regulating blade 13 as a developer regulating member which is a toner layer thickness regulating blade for forming a thin layer of the toner supplied on the developing roller 11.

  Reference numeral 15 includes an LED (Light Emitting Diode) as a light emitting element, and an LED as an electrostatic latent image writing device that forms an electrostatic latent image by exposing the surface of the photosensitive drum 1 based on image data. Head. Further, reference numeral 14 denotes a transfer roller 14 as a transfer device disposed so as to face the photosensitive drum 1 across the conveyance path of the recording medium 3.

  Further, the cleaning device 16 is a device for cleaning the surface of the photosensitive drum 1 and scraping and storing the toner, and the stored toner is stored in an image forming unit by a spiral or the like in a waste toner collecting device (not shown). 10 is carried out.

  Note that the photosensitive drum 1, the developing roller 12, the toner supply roller 18, the charging roller 11, and the transfer roller 14 rotate in directions indicated by arrows. In this case, the photosensitive drum 1 is rotationally driven by an ID motor 17 described later. The developing roller 12 and the toner supply roller 18 are rotationally driven by gear transmission from the photosensitive drum 1. Further, the charging roller 11 is rotationally driven by friction transmission with the surface of the photosensitive drum 1.

  The photosensitive drum 1 is a member in which a photoconductive layer is formed on the surface of a drum-shaped conductor such as aluminum. The charging roller 11 is a device for uniformly charging the surface of the photosensitive drum 1, and for example, a conductor such as stainless steel is used as a shaft, and a conductive elastic body such as epichlorohydrin is coated around the shaft. Formed so as to be in contact with the photosensitive drum 1.

  Further, the LED head 15 is an exposure device for selectively exposing the surface of the uniformly charged photoreceptor drum 1 to form a latent image pattern, and includes an LED element, an LED driving element, and a lens array. The irradiation light from the LED element is disposed at a position where an image is formed on the surface of the photosensitive drum 1.

  The developing roller 12 is a member having, for example, a conductor such as stainless steel as a shaft, and a conductive elastic body such as urethane around the shaft. The toner supply roller 18 is a member having a shaft made of a conductor such as stainless steel and a foaming elastic body such as silicone coated around the shaft, and is disposed so as to be in contact with the developing roller 12. The Further, the regulating blade 13 is, for example, a stainless steel plate-like member, and is disposed so that the tip portion thereof is pressed against the developing roller 12. The developing device 2 is disposed so that the developing roller 12 is in contact with the surface of the photosensitive drum 1.

  The transfer roller 14 is a device for transferring the toner image formed on the photosensitive drum 1 to the recording medium 3. The transfer roller 14 is made of, for example, a conductive foaming elastic body and is in contact with the photosensitive drum 1. It is arranged like this.

  Further, the cleaning device 16 is a device for scraping and discarding the toner remaining on the photosensitive drum 1 due to untransferred or the like and the waste toner moved from the developing device 2 onto the photosensitive drum 1. For example, a rubber blade is provided, and the tip of the rubber blade is brought into contact with the surface of the photosensitive drum 1 so as to scrape off the toner on the photosensitive drum 1.

  Next, a control system of the image forming apparatus 100 will be described.

  FIG. 1 is a block diagram showing the configuration of the control system of the image forming apparatus according to the first embodiment of the present invention.

  As shown in the figure, a charging voltage is applied to the charging roller 11 by a charging voltage control unit 21, a developing voltage is applied to the developing roller 12 by a developing voltage control unit 22, and a regulating blade voltage control is applied to the regulating blade 13. The regulating blade voltage is applied by the unit 23.

  A voltage switching unit 31 is connected to the charging voltage control unit 21, the development voltage control unit 22, and the regulation blade voltage control unit 23. The voltage switching unit 31 includes a printing voltage setting unit 32 and a fog toner discard voltage setting unit 33, and in accordance with instructions from the recording control unit 30, the charging voltage control unit 21, the development voltage control unit 22, and the regulation blade voltage control unit 23. The voltage setting value to be notified is switched to the printing voltage held in the printing voltage setting unit 32 or the fog toner discarding voltage held in the fogging toner discard voltage setting unit 33. Then, the charging voltage control unit 21, the development voltage control unit 22, and the regulation blade control unit 23 output a voltage based on the voltage setting value notified from the voltage switching unit 31.

  An ID motor control unit 27 is connected to the ID motor 17, a transfer voltage control unit 24 is connected to the transfer roller 14, and an LED head light emission control unit 25 is connected to the LED head 15. The ID motor control unit 27, the transfer voltage control unit 24, and the LED head light emission control unit 25 are respectively driven by the drive operation of the ID motor 17, the transfer voltage applied to the transfer roller 14, and the LED in accordance with instructions from the recording control unit 30. The light emission operation of the head 15 is controlled.

  Next, the operation of the image forming apparatus 100 having the above configuration will be described. First, the operation in the printing process will be described.

  In the printing process, first, a charging voltage is applied to the charging roller 11 to uniformly charge the surface of the photosensitive drum 1, and then the LED head 15 is caused to emit light in accordance with image data from the recording control unit 30. An electrostatic latent image pattern is formed on the surface of the drum 1. Then, a developing voltage is applied to the developing roller 12 having a thin toner layer formed on the surface, and the electrostatic latent image pattern on the photosensitive drum 1 is developed. Here, a regulation blade voltage is applied to the regulation blade 13 in order to set the charge amount of the toner in the toner thin layer on the developing roller 12 to a predetermined value.

  Next, a transfer voltage is applied to the transfer roller 14 to transfer the toner image on the photosensitive drum 1 onto the recording medium 3. Then, the toner image on the recording medium 3 is fixed on the recording medium 3 by the fixing device 4, and the printing operation is completed.

  Note that when the image forming apparatus 100 is operated in a normal temperature and humidity environment (20 to 25 [° C.] and 40 to 60 [%]) using negatively chargeable toner, the applied voltage setting is, for example, a charging voltage of − It is assumed that the developing voltage is 1000 [V], the developing voltage is −200 [V], and the regulation blade voltage is −300 [V]. The surface of the photosensitive drum 1 is charged when a charging voltage equal to or higher than a predetermined value is applied to the charging roller 11, and the surface voltage changes in proportion to the applied charging voltage. In the present embodiment, the surface voltage of the photosensitive drum 1 is −500 [V]. The latent image voltage of the latent image pattern formed by the light emission of the LED head 15 becomes −100 [V], and the toner is reversely developed from the developing roller 12 into the latent image pattern. The negatively chargeable toner is, for example, one obtained by externally adding silica or the like for imparting chargeability or fluidity to a polystyrene resin.

  The density of the image data is the density of the toner image formed by the image data, which means the density of the toner image area formed in the printable area with respect to the printable area. When formed (solid printing), the density is 100%.

  However, in the toner thin layer formed on the developing roller 12, only the toner corresponding to the latent image pattern is developed. Therefore, in the case of printing with low image data density, that is, in low density printing, undeveloped toner is present. There are many. Then, the undeveloped toner returns to the developing device 2 in a state of adhering to the developing roller 12, scraping by the toner supply roller 18, frictional charging between the developing roller 12 and the toner supply roller 18, After being frictionally charged between the developing roller 12 and the regulating blade 13, it is transported again to the developing unit with the photosensitive drum 1, or cannot pass through the regulating blade 13 and remains in the developing device 2. Things arise.

  Therefore, when low density printing is continued, the toner remaining on the developing roller 12 and the developing device 2 without being developed is damaged, and the external performance additive such as silica is separated or buried, etc. Reduction or reverse polarity charging may occur. Alternatively, the charge amount of the toner may be increased by repeating frictional charging while being scraped off by the toner supply roller 18 and attached to the surface of the developing roller 12.

  Next, the distribution of the charge amount of the thinned toner on the developing roller 12 will be described.

  FIG. 4 is a graph showing the charge amount distribution of the thinned toner on the developing roller in the first embodiment of the present invention.

  In the figure, the broken line A shows the distribution of the charge amount of the thinned toner on the developing roller 12 in the initial state, and the solid line B shows the thinned toner on the developing roller 12 after performing 20000 low-density printing. The charge amount distribution is shown.

  From the figure, it can be seen that after performing low density printing, the distribution range of the charge amount is widened and the frequency of the low charge toner and the high charge toner is increased as compared with the initial state. The toner charged to the opposite polarity is easily attracted and moved to the non-exposed area on the photosensitive drum 1 in the printing process, and the low-charged toner has a weak adhesion due to the mirror image force on the surface of the developing roller 12. Therefore, it is easy to move to the photosensitive drum 1, so that the so-called fog printing in which the toner adheres to the background portion of the image is likely to occur. In this way, with respect to the normally charged toner, the fog is caused by the toner adhering to the background portion of the image, that is, the non-image portion by the toner having a low charge amount or the toner charged to the opposite polarity. A toner having a low charge amount or a toner charged to a reverse polarity is used as a fog toner.

  Therefore, in the present embodiment, by switching the charging voltage, the developing voltage, and the regulating blade voltage from the printing voltage to the fogging toner discard voltage, the toner having a low charge amount and the toner charged to the reverse polarity in a period other than the printing time, That is, the fog toner can be selectively discarded. In other words, the fog toner can be efficiently discarded from the developing device 2 by changing the charging voltage, the developing voltage, and the regulating blade voltage from the voltage at the time of image formation to the preset voltage at the time of non-image formation. Like that.

  Here, the image formation means that a toner image is formed on the photosensitive drum 1 with normally charged toner, and printing that forms a toner image transferred to the recording medium 3 based on print data. It shows that a correction pattern such as an operation, color misregistration correction and density correction is formed. At this time, the charging voltage, the developing voltage, the regulating blade voltage, and the supply voltage are voltages at the time of image formation.

  Non-image formation is a process other than image formation. The fog toner discard mode is provided during non-image formation, and the fog toner discard mode is provided during at least a part of the period during non-image formation. The fog toner discard mode is a “voltage change period” in which the voltage is changed from the image forming voltage. That is, a “voltage change period” is provided as part of the non-image formation. It should be noted that the fog toner discard mode can be provided during the non-image formation and in the entire period during which the image forming apparatus 100 is driven.

  Next, the relationship among the photosensitive drum voltage, the developing voltage, and the regulating blade voltage when discarding the fog toner will be described.

  FIG. 5 is a graph showing the relationship among the photosensitive drum voltage, the developing voltage, and the regulating blade voltage when the fog toner is discarded in the first embodiment of the present invention.

  The figure is for simply explaining the order relationship of the photosensitive drum voltage, the developing voltage, and the regulating blade voltage when discarding the fog toner in non-image formation. An example of the fog toner discard voltage is shown in FIG. It is shown in comparison with the set voltage.

  In a normal printing process, that is, at the time of image formation, by forming an electric field so that the regulating blade 13 side has the same polarity as the toner charging with respect to the developing roller 12 in the relationship between the developing roller 12 and the regulating blade 13. In order to pass toner charged to a predetermined value (regularly charged toner), the regulation blade voltage Vbl-0 is set to have the same polarity as the developing voltage Vdv-0 and to have a large absolute value. Here, as described above, the regulated blade voltage Vbl-0 is set to -300 [V], the development voltage Vdv-0 is set to -200 [V], and the voltage difference between the regulated blade voltage Vbl-0 and the development voltage Vdv-0. Is −100 [V] (= (− 300 [V]) − (− 200 [V])).

  The charging voltage is set so that the toner on the developing roller 12 is reversely developed to the latent image pattern and is prevented from moving to the non-latent image pattern. In this case, −1000 [V] is applied as the charging voltage to charge the photosensitive drum voltage Vdr-0 as the surface voltage of the photosensitive drum 1 to −500 [V]. The latent image potential Vdv-e after the image is formed is set to -100 [V].

  As a result, the normally charged toner is obtained by setting the voltage difference between the photosensitive drum voltage Vdr-0 and the developing voltage Vdv-0 to -300 [V] (= (-500 [V])-(-200 [V])). And the voltage difference between the latent image voltage Vdv-e and the development voltage Vdv-0 is +100 [V] (= (− 100 [V]) − (− 200 [V])). Develop the pattern.

  On the other hand, when the fog toner is discarded during non-image formation, the absolute value of the regulation blade voltage is reduced as compared with the image formation. By reducing the absolute value of the regulation blade voltage, the voltage difference from the development voltage is reduced, the force attracted to the regulation blade 13 by the toner charged to the opposite polarity is weakened, and the probability that the fog toner passes through the regulation blade 13 Will increase. Desirably, the regulation blade voltage is set to have the same polarity as the development voltage and a low absolute value.

  As a result, an electric field having a polarity opposite to that of the normally charged toner is formed on the regulating roller 13 side with respect to the developing roller 12, so that the normally charged toner is attracted to the regulating blade 13 and the fog toner existing in the developing device 2. Is more likely to pass through the regulating blade 13. Here, when the fog toner is discarded, the regulation blade voltage Vbl-1 is set to −100 [V], the development voltage Vdv-1 is set to −300 [V], and the voltage between the regulation blade voltage Vbl-1 and the development voltage Vdv-1 is set. The difference is +200 [V] (= (− 100 [V]) − (− 300 [V])).

  Next, the distribution of the charge amount of the thinned toner on the developing roller 12 when the fog toner is discarded will be described.

  FIG. 6 is a graph showing the charge amount distribution of the thinned toner on the developing roller when the fog toner is discarded in the first embodiment of the present invention.

  The figure compares the charge amount distribution of the toner layer on the developing roller when the printing voltage is set during image formation and when the fog toner disposal voltage is set when discarding the toner during non-image formation. . The distribution of the charge amount at the time of discarding the fog toner indicated by the solid line D is shifted to a lower charge side as compared with the distribution of the charge amount at the time of printing indicated by the broken line C, and the frequency of the toner having a low charge amount is increased. I understand that. That is, the probability that the fog toner remaining in the developing device 2 passes through the regulating blade 13 and is discharged onto the developing roller 12 is increased.

  Next, the voltage difference between the photosensitive drum voltage Vdr-1 and the development voltage Vdv-1 is increased as compared with printing. Thereby, the probability that the fog toner discharged onto the developing roller 12 is electrically attracted to the photosensitive drum 1 and moves increases.

  In the present embodiment, the photosensitive drum voltage Vdr-1 is set to -700 [V], the developing voltage Vdv-1 is set to -300 [V], and the photosensitive drum voltage Vdr-1 and the developing voltage are set. The voltage difference from Vdv-1 is −400 [V] (= (− 700 [V]) − (− 300 [V])). In order to set the photosensitive drum voltage Vdr-1 to −700 [V], a charging voltage Vch−1 of −1200 [V] is applied to the charging roller 11.

  Next, the operation timing of each unit when the fog toner is discarded will be described.

  FIG. 7 is a time chart showing the operation timing when discarding the fog toner according to the first embodiment of the present invention.

  First, a print job is started in accordance with a print job start signal from the recording control unit 30, the ID motor 17 is turned on (t1), and the photosensitive drum 1, the charging roller 11, the developing roller 12, and the toner supply roller 18 rotate. Driven. A charging voltage Vch-0 is applied to the charging roller 11 in synchronization with the start of rotational driving. By applying the printing charging voltage Vch-0, the surface of the photosensitive drum 1 is charged to the printing photosensitive drum voltage Vdr-0. At the same time, the development voltage Vdv-0 is applied to the developing roller 12 at the timing t1, and the regulation blade voltage Vbl-0 is applied to the regulation blade 13, and the printing period (L0) is reached.

  Subsequently, the light emission operation of the LED head 15 is performed according to the page signal and the image data. When the LED head 15 emits light, the photosensitive drum 1 becomes a latent image voltage Vdr-e, and the toner is developed to form a toner image corresponding to the image data. When the light emission operation of the LED head 15 for the transmitted pages is completed, the printing period (L0) ends (t2).

  At t2, the printed recording medium 3 is ejected and the voltage is changed. At t2, the charging voltage is switched to the fog toner discard charging voltage Vch-1 while the ID motor 17 is kept on. As the charging voltage is switched, the charging potential on the surface of the photosensitive drum 1 changes to the fog toner discarding photosensitive drum voltage Vdr-1. At the same time, at the timing t2, the developing voltage is switched to the fog toner discard developing voltage Vdv-1, the regulation blade voltage is switched to the fog toner discard regulation blade voltage Vdl-1, and the fog toner disposal period (L1) is reached.

  Here, an example in which the development voltage and the regulation blade voltage are switched at the same time as the charging voltage has been described. However, on the photosensitive drum 1, there is a delay corresponding to the rotational movement between the position of the charging roller 11 and the position of the developing roller 12. Therefore, the development voltage switching timing may be shifted in consideration of the delay. The fog toner discard period (L1) continues until t3, at which time the ID motor 17, the charging voltage, the developing voltage, the photosensitive drum voltage, and the regulating blade voltage are turned off, the printing job is completed, and the next job The off state is maintained until a signal is transmitted. During the fog toner discard period (L1), the light emission operation of the LED head 15 is in the off state for the entire period, and no latent image is formed on the photosensitive drum 1.

  As the fog toner discard period (L1) is longer, the fog toner discard amount increases. However, if the fog toner disposal period (L1) is too long, the life of the photosensitive drum 1 is shortened and the print throughput is reduced, so that the fog toner may be used depending on the application of the image forming apparatus 100 or the like. It is necessary to set the length of the discard period (L1) as appropriate. At least the fog toner present around the toner supply roller 18 needs to be discarded in addition to the circumference of the developing roller 12, preferably around the developing roller 12. Therefore, at least one fogging toner discard period (L1) longer than the time required for one rotation of the developing roller 12 may be provided. The time required for one rotation of the developing roller 12 and the time required for one rotation of the toner supply roller 18 It is more preferable that it is more than the total time.

  As described above, the voltage setting at the time of discarding the fog toner in the present embodiment has been described as an example in which all of the regulation blade voltage, the development voltage, and the charging voltage are switched with respect to printing.

  In the present embodiment, the entire printing period (L0) has been described as an image formation period. However, the present invention is not limited to this embodiment, and at least the photosensitive drum 1 is charged, exposed as necessary, and the developing roller 12 is charged. The step of supplying the toner and developing the toner image and transferring the toner image to a transfer medium such as the recording medium 3 or the transfer belt is included in the image forming period. In this embodiment, as an example, a voltage change period is provided when non-image formation is performed between print jobs. In this embodiment, the interval between the first page, the second page, the second page, and the third page, that is, the interval between sheets is also used as a printing process, but the interval between sheets is not an image. As this period, a voltage change period can be provided.

  In the example shown in FIG. 7, the charging voltage, the developing voltage, and the regulating blade voltage are switched at the same time. However, in consideration of the position movement due to the rotation of the photosensitive drum 1, there is a time difference in the change timing. Can also be provided.

  Next, a more preferable example of the operation timing of each unit when the fog toner is discarded will be described.

  FIG. 8 is a time chart showing another example of operation timing when discarding the fog toner according to the first embodiment of the present invention. FIG. 9 is a photoconductive drum when discarding the fog toner according to the first embodiment of the present invention. FIG. 6 is a schematic diagram illustrating operation timings of a developing roller and a charging roller.

  First, a print job is started in accordance with a print job start signal from the recording control unit 30, the ID motor 17 is turned on (t1), and the photosensitive drum 1, the charging roller 11, the developing roller 12, and the toner supply roller 18 rotate. Driven. A charging voltage Vch-0 is applied to the charging roller 11 in synchronization with the start of rotational driving. By applying the printing charging voltage Vch-0, the surface of the photosensitive drum 1 is charged to the printing photosensitive drum voltage Vdr-0. At the same time, the development voltage Vdv-0 is applied to the developing roller 12 at the timing t1, and the regulation blade voltage Vbl-0 is applied to the regulation blade 13, and the printing period (L0) is reached.

  Subsequently, the light emission operation of the LED head 15 is performed according to the page signal and the image data. When the LED head 15 emits light, the photosensitive drum 1 becomes a latent image voltage Vdr-e, and the toner is developed to form a toner image corresponding to the image data. When the light emission operation of the LED head 15 for the transmitted pages is completed, the printing period (L0) ends (t2).

  At t2, the photosensitive drum 1, the developing roller 12, and the charging roller 11 are in the state shown in FIG. If the position on the photosensitive drum 1 facing the charging roller 11 at time t2 is α, the charging voltage is Vch−1. Therefore, the position after the position α on the photosensitive drum 1 facing the charging roller 11 (arrow) In the direction indicated by γ), the surface potential of the photosensitive drum 1 is set to Vdr-1.

  At t2 ′, the photosensitive drum 1, the developing roller 12, and the charging roller 11 are in the state shown in FIG. 9B. That is, the position α becomes a position facing the developing roller 12 by the rotation. At this time, since the voltage of the developing roller 12 is set to Vdv−1, the fog toner adheres to the photosensitive drum 1 from the developing roller 12 when the region DR1 faces the developing roller 12 after t2 ′.

  At t3, the photosensitive drum 1, the developing roller 12, and the charging roller 11 are in the state shown in FIG. 9C. When the most downstream portion of the region DR1 is a position β, the charging voltage is turned off at a position where the position β faces the charging roller 11. When printing is performed continuously (for example, when the image forming apparatus 100 receives another print job), the charging voltage is set to Vch-0.

  Further, at t3 ′, the photosensitive drum 1, the developing roller 12, and the charging roller 11 are in the state shown in FIG. That is, the position β becomes a position facing the developing roller 12 by the rotation. At this time, the voltage of the developing roller 12 is turned off, and the disposal of the fog toner is completed. The timing at which the regulation blade voltage is switched is the same as the timing at which the development voltage is switched.

  However, as shown in FIG. 9E, the timing at which the regulation blade voltage is switched according to the distance DV1 between the facing portion of the developing roller 12 facing the photosensitive drum 1 and the facing portion of the regulation blade 13. The timing at which the development voltage is switched may be shifted. The ID motor 17 may be turned off after t3 'when the development voltage and the regulation blade voltage are turned off.

  Next, an experiment will be described in which fogging toner discarding is performed by switching the voltage of each unit with respect to the printing voltage.

  FIG. 10 is a table showing experimental results in the first embodiment of the present invention.

  In this experiment, the control blade voltage, the development voltage, and the charging voltage were switched with respect to the printing voltage, and the fog toner was discarded while changing the combination. In the figure, it was visually determined how much the fog level on the recording medium 3 printed after the fog toner discarding operation was improved as compared with the fog level on the recording medium 3 before the fog toner discarding operation was performed. The results are shown.

  The set values of the regulation blade voltage, the developing voltage, and the charging voltage after the switching were sequentially switched to the setting values as shown in FIG. The voltage settings during printing are a charging voltage of -1000 [V], a photosensitive drum voltage of -500 [V], a developing voltage of -200 [V], and a regulation blade voltage of -300 [V].

In the measurement of fog, the image forming apparatus 100 is stopped in the middle of printing at a density of 0 [%], and the toner on the photosensitive drum 1 after development and before transfer is removed with an adhesive tape (Scotch Mending Tape, manufactured by Sumitomo 3M Limited). ). I put it (covering tape) on pure white paper. For comparison, an adhesive tape (comparison tape) that was not attached to the photosensitive drum 1 was attached to a sheet on which the cover sampling tape was attached. Then, the hue difference between the fog collecting tape and the comparative tape was measured with a spectrocolorimeter (manufactured by Konica Minolta, CM-2600d, measurement diameter = φ8 [mm]). The hue difference (L * a * b color system chromaticity) was calculated by ΔE = (ΔL ² + Δa ² + Δb ² ) ^1/2 .

In addition, the standard of fogging evaluation was judged as follows.
0 ≦ ΔE <0.5 degree 5
0.5 ≦ ΔE <1.0 degree 4
1.0 ≦ ΔE <1.5 degree 3
1.5 ≦ ΔE <2.0 degree 2
ΔE ≧ 2.0 degree 1
(1) When the charging voltage was switched to -1200 [V] (the photosensitive drum voltage was -700 [V]), the fogging degree in the fogging evaluation result was low and was hardly improved. Since the purpose is to increase the voltage difference between the photosensitive drum voltage and the developing voltage, the developing voltage was not switched from -200 [V] here. The voltage difference between the photosensitive drum voltage and the development voltage is set to −500 [V] (= (− 700 [V]) − (− 200 [V])), which is larger than that at the time of printing. The attached fog toner was discarded efficiently. However, since the fog toner remaining in the developing device 2 is not discarded, a part of the fog toner remaining in the developing device 2 passes through the regulating blade 13 during printing after the disposal is finished, and the photosensitive member. It moves to the drum 1, and it is thought that this produced fogging.

  (2) When only the regulated blade voltage was switched to −100 [V], the fog degree in the medium fog evaluation result was obtained. The voltage difference between the regulation blade voltage and the development voltage is +100 [V] (= (− 100 [V]) − (− 200 [V])), and the polarity of the electric field on the regulation blade 13 side with respect to the developing roller 12 is reversed. As a result, the probability that the fog toner in the developing device 2 is discharged onto the developing roller 12 is increased, the amount of waste on the photosensitive drum 1 is increased, and the amount of fog toner in the developing device 2 is reduced. .

  (3) When the regulated blade voltage is switched to −100 [V] and the development voltage is switched to −300 [V], the fog degree in the fog evaluation result is improved as compared with the case where only the regulated blade voltage is switched. did. By switching the developing voltage, the regulated blade voltage and the developing voltage are reversed, and the voltage difference becomes +200 [V] (= (− 100 [V]) − (− 300 [V])), This is probably because the probability that the fog toner in the developing device 2 is discharged onto the developing roller 12 is further increased.

  (4) When the regulated blade voltage is switched to -100 [V], the charging voltage is switched to -1200 [V] (the photosensitive drum voltage is -700 [V]), or the regulated blade voltage and the developing voltage are switched. The fogging degree was almost the same as the fogging evaluation result. The potential difference between the photosensitive drum voltage and the developing voltage in a state where the voltage difference between the regulated blade voltage and the developing voltage is inverted to +100 [V] (= (− 100 [V]) − (− 200 [V])) Is increased to −500 [V] (= (− 700 [V]) − (− 200 [V])), the fog toner discharged from the developing device 2 and adhering to the developing roller 12 is removed. This is considered to be because the probability of moving to the photosensitive drum 1 and being discarded becomes high.

  (5) When the regulation blade voltage is switched to -100 [V], the development voltage is switched to -300 [V], and the charging voltage is switched to -1200 [V] (the photosensitive drum voltage is -700 [V]). The fogging degree in the fogging evaluation result was further improved. The inverted potential difference between the regulated blade voltage and the developing voltage is increased to +200 [V] (= (− 100 [V]) − (− 300 [V])), and further, the potential difference between the photosensitive drum voltage and the developing voltage. Is set to −400 [V] (= (− 700 [V]) − (− 300 [V])), which is larger than that at the time of printing, so that the fog toner in the developing device 2 is discharged to the developing roller 12; This is probably because the probability that the fog toner moves from the developing roller 12 to the photosensitive drum 1 is increased.

  (6) The fogging degree was 1 when no voltage change period was provided. However, the fogging evaluation result was worse than the case (1).

  In the case of (1), only the charging voltage is changed. However, since the regulating blade voltage is not made lower than the developing voltage, the fog toner cannot pass through the regulating blade 13.

  In the case of (2), the regulation blade voltage is made equal to or lower than the development voltage, and the fog toner can pass through the regulation blade 13.

  Further, in the case (3), since the developing voltage is changed in addition to the regulated blade voltage, the regulated blade voltage is made lower than the developed voltage, and the potential difference is larger than in the case (2). More fog toner can pass through the regulating blade 13.

  Further, in the case of (4), since the charging voltage (photoreceptor drum voltage) is changed in addition to the regulation blade voltage, the regulation blade voltage is set to be equal to or lower than the development voltage, and the development voltage and the photoreceptor drum voltage are further reduced. Thus, the fog toner easily passes through the regulating blade 13 and further moves to the photosensitive drum 1 side.

  Further, in the case of (5), since the regulation blade voltage, the development voltage, and the charging voltage are changed, the regulation blade voltage is made equal to or lower than the development voltage, and the potential difference is large. Therefore, the fog toner easily passes through the regulating blade 13 and further moves to the photosensitive drum 1 side.

  In the present embodiment, the regulation blade voltage Vbl-1 is −100 [V], and the polarity of the voltage applied to the regulation blade 13 is the same as that of the toner with respect to the negatively chargeable toner. For this reason, fog toner that is negatively charged and has a low charge amount is also held by the developing roller 12 and is not attracted to the regulation blade 13 side when passing through the regulation blade 13 together with the fog toner charged to the opposite polarity. . That is, as the fog toner, the toner charged to the opposite polarity and the toner having a low charge amount pass through the regulation blade 13.

  The experimental results described above are merely examples of voltage setting combinations. Since the voltage difference between the regulated blade voltage and the development voltage, or the voltage difference between the photosensitive drum voltage and the development voltage is related to the degree of movement of the fog toner, the degree of the effect of improving the fog by changing the setting value of each voltage Will change. The above experimental results show that a certain degree of effect can be obtained only by switching the regulation blade voltage with respect to the effect of the fog improvement by discarding the fog toner, and further, a larger effect can be obtained by switching the developing voltage and the charging voltage. It is thought that it shows.

  Furthermore, it is preferable to change the supply voltage. At this time, a voltage having an absolute value higher than the developing voltage (for example, Vsp-0 = −300 [V]) is set during image formation, and a voltage having an absolute value lower than the developing voltage (for example, Vsp−1) during the voltage change period. = −100 [V]). In this case, since the fog toner can be moved from the toner supply roller 18 to the developing roller 12, the fog toner near the toner supply roller 18 can be discarded.

  Therefore, since the fog toner in the entire developing device 2 can be discarded by discarding the fog toner once, if the fog toner is discarded once, the interval until the next discard can be extended, and the voltage change period can be increased. The interval provided can be lengthened. In this example, the supply voltage is the same voltage as the regulated blade voltage. In this case, the power supply of the regulation blade voltage and the supply voltage can be made common. Furthermore, the present invention is not limited to this example, and may be different from the regulated blade voltage, for example, Vsp-0 = −350 [V], Vsp−1 = −50 [V].

  The description of this embodiment is merely an example, and the setting values of the voltages are not limited to this. Appropriately set the voltage value so that the fog toner is disposed of properly according to the charging conditions of the toner, the process conditions such as the physical properties of each roller, the usage conditions such as temperature and humidity, or the voltage output range of the power source used. Can be set.

  Further, the example in which the fog toner discarding timing is after the printing operation in the print job is finished has been described, but it may be before the printing operation in the print job is started. Alternatively, the toner discarding operation may be activated independently between print jobs. The operation of discarding toner for a short time may be activated for each print job. For example, the toner discarding operation may be activated at intervals of a predetermined number of printed sheets such as 500 sheets. Further, an activation button can be provided on the operation panel, and the toner discarding operation can be manually activated by a user operation.

  As described above, in the present embodiment, on the assumption that the regulation blade voltage is switched, the development voltage and the charging voltage are changed so that the voltage difference can discard the fog toner. Yes. Therefore, it is only necessary to provide a voltage difference, and the order may be main as follows.

  In this case, the regulation blade voltage is changed to Vbl-1. That is, the absolute value is made smaller than Vbl-0, and the absolute value is made smaller than the developing voltage Vdv-1. For example, even if the development voltage is not changed and Vdv-0 remains as it is, Vbl-1 only needs to have an absolute value smaller than Vdv-0. That is, as shown in FIG. 5, it is sufficient that the voltage difference between the changed regulated blade voltage and the development voltage is large and the absolute value of the regulated blade voltage is smaller than the absolute value of the development voltage. As the value increases, the fog toner moves to the developing roller 12 side.

  Further, the relationship between the photosensitive drum voltage and the development voltage may be any form as long as the absolute value of the development voltage is low. As shown in FIG. 5, not only the relationship between Vdv-1 and Vdr-1, but also the relationship between Vdr-0 and Vdv-1 in which the photoreceptor drum voltage is not changed, and the form in which the development voltage is not changed. Any of the relationship between Vdr-1 and Vdv-0, and the relationship between Vdr-0 and Vdv-0, in which the development voltage and the photosensitive drum voltage are not changed, may be used.

  However, in the relationship between the photosensitive drum voltage and the developing voltage, the fog toner moves to the photosensitive drum 1 side as the absolute value of the developing voltage is lower and the voltage difference is larger. Therefore, the relationship between the regulated blade voltage, the developing voltage, and the photosensitive drum voltage may be that the absolute value of the photosensitive drum voltage> the absolute value of the developing voltage ≧ the absolute value of the regulated blade voltage. The larger the voltage difference, the voltage difference between the photosensitive drum voltage and the developing voltage, is more preferable. The regulation blade voltage Vbl-1 may be 0 [V].

  Further, the regulation blade voltage may be equal to the development voltage. In this case, the potential difference between the developing voltage and the regulating blade voltage is 0, and the fog toner on the developing roller 12 is not attracted to the regulating blade 13, so that it passes through the regulating blade 13 while being carried on the developing roller 12. I will do it. Here, the photosensitive drum voltage is set to a desired voltage. For this purpose, the photosensitive drum voltage is changed by changing the charging voltage.

  As described above, in this embodiment, the voltage setting value is switched between printing and covering toner disposal, and the applied voltage at the disposal of covering toner is the low-charged toner and the reverse polarity charging remaining in the developing device 2. It is set so that the efficiency with which the toner is discharged to the developing roller 12 increases. Thereby, the deteriorated fog toner can be efficiently discarded from the developing device 2, and an output image of good quality without fog can be obtained.

  By the way, in the present embodiment, as described above, the regulation blade voltage is switched at the time of non-image formation and a low voltage is applied at the time of image formation, but this can be modified. Therefore, a modified example will be described below. In this modification, the developing voltage is changed so that the order of bias between the developing roller 12 and the regulating blade 13 satisfies the developing voltage> the regulating blade voltage. At that time, the photosensitive drum voltage is also changed so that the toner from the developing roller 12 is adhered.

  Specifically, the regulation blade voltage is not changed when the fog toner is discarded during non-image formation. At that time, the development voltage is set to have an absolute value larger than the regulation blade voltage. For example, when Vbl-0 is -300 [V], Vbl-1 is -300 [V] (= Vbl-0), Vdv-0 is -200 [V], but Vdv-1 is- 500 [V]. That is, | Vbl-1 | ≦ | Vdv-1 |.

  By the way, since Vdr-0 is -500 [V], it is preferable that | Vdr-1 |> | Vdv-1 |. Therefore, for example, the charging voltage may be set to -1400 [V] so that Vdr-1 becomes -900 [V].

  As described above, if | Vbl-1 | ≦ | Vdv-1 |, the fog toner is not attracted to the regulating blade 13. Further, if | Vdr-1 |> | Vdv-1 |, the fog toner that has passed through the regulating blade 13 can be discarded to the photosensitive drum 1 side. Therefore, if | Vdr-1 |> | Vdv-1 | ≧ | Vbl-1 |, the fog toner in the developing device 2 can be discarded. Therefore, the present embodiment and this modification are merely examples, and | Vdr-1 |> | Vdv-1 | ≧ | Vbl-1 |, so that the regulation blade voltage and the development voltage are set as necessary. The photosensitive drum voltage may be changed according to whether the image is formed or not.

  When Vbl-1 = Vdv-1, the potential difference between the development voltage and the regulation blade voltage is zero. Therefore, since the fog toner on the developing roller 12 is not attracted to the regulating blade 13, it passes through the regulating blade 13 while being carried on the developing roller 12. Therefore, if | Vbl-1 | ≦ | Vdv-1 |, the fog toner is not attracted to the regulating blade 13.

  Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operation and the same effect as those of the first embodiment is also omitted.

  FIG. 11 is a block diagram showing the configuration of the control system of the image forming apparatus according to the second embodiment of the present invention.

  In the first embodiment, the form in which the fog toner is discarded in response to the occurrence of the fog toner accompanying the toner deterioration has been described. By the way, in a low-humidity environment such as a humidity of 10 [%], charging may be excessive and stains may occur. Therefore, in the present embodiment, disposal of dirty toner will be described.

  In the present embodiment, a voltage switching unit 41 is connected to the charging voltage control unit 21, the development voltage control unit 22, and the regulation blade voltage control unit 23. The voltage switching unit 41 includes a printing voltage setting unit 42 and a dirty toner discard voltage setting unit 44, and in accordance with instructions from the recording control unit 30, the charging voltage control unit 21, the development voltage control unit 22, and the regulation blade voltage control unit 23. The voltage setting value to be notified is switched between the print voltage held in the print voltage setting unit 42 and the dirty toner discard voltage held in the dirty toner discard voltage setting unit 44. The charging voltage control unit 21, the development voltage control unit 22, and the regulation blade control unit 23 output a voltage based on the notified voltage setting value.

  Since the configuration of other points is the same as that of the first embodiment, description thereof is omitted.

  Next, the operation of the image forming apparatus 100 in the present embodiment will be described. The operation in the printing process is the same as that in the first embodiment, and a description thereof will be omitted.

  The distribution of the charge amount of the thinned toner on the developing roller 12 is the same as that in FIG. 4 described in the first embodiment. That is, after performing low density printing, the distribution range of the charge amount is widened compared to the initial state, and the frequency of the low charge toner and the high charge toner is increased.

  In the printing process, the toner having an extremely high charge amount is developed with a small voltage difference from the photosensitive drum voltage in the non-exposed area on the photosensitive drum 1. For this reason, when the charge distribution spreads in the high direction, so-called smear printing, in which toner adheres to the recording medium 3 regardless of the image pattern, is likely to occur. As described above, excessively charged toner causes contamination by a toner having a high charge amount, that is, so-called overcharged toner, which is attached to a background portion of an image, that is, a non-image portion. The charged toner is a dirty toner.

  Therefore, in the present embodiment, by switching the charging voltage, the developing voltage, and the regulating blade voltage from the printing voltage to the dirty toner disposal voltage, a toner with a high charge amount and a toner that is easily charged in a period other than during printing, that is, The dirty toner is selectively discarded. In other words, by changing the charging voltage, the developing voltage, and the regulating blade voltage from the voltage at the time of image formation to the preset voltage at the time of non-image formation, the dirty toner can be efficiently discarded from the developing device 2. Like that.

  Here, the image formation means that a toner image is formed on the photosensitive drum 1 by the normally charged toner as in the first embodiment, and the recording medium is based on the print data. 3 shows that a printing operation for forming a toner image to be transferred and a correction pattern such as color misregistration correction and density correction are formed. At this time, the charging voltage, the developing voltage, the regulating blade voltage, and the supply voltage are voltages at the time of image formation.

  Non-image formation is a process other than image formation. Note that a dirty toner discard mode is provided during non-image formation, and the dirty toner discard mode is provided during at least a part of the period during non-image formation. The dirty toner discard mode is a “voltage change period” in which the voltage is changed from the image forming voltage. That is, a “voltage change period” is provided as part of the non-image formation. It should be noted that the dirty toner discard mode can be provided during the non-image formation and in the entire period during which the image forming apparatus 100 is driven.

  Next, the relationship among the photosensitive drum voltage, the developing voltage, and the regulating blade voltage when discarding dirty toner will be described.

  FIG. 12 is a graph showing the relationship among the photosensitive drum voltage, the developing voltage, and the regulating blade voltage when the dirty toner is discarded in the second embodiment of the present invention.

  The figure is for simply explaining the order relationship among the photosensitive drum voltage, the developing voltage, and the regulation blade voltage when discarding dirty toner during non-image formation. It is shown in comparison with the set voltage.

  In a normal printing process, that is, when an image is formed, the control blade voltage Vbl-0 is set to -300 [V] and the development voltage Vdv-0 is set to -200 [V] as in the first embodiment. Thus, the voltage difference between the regulation blade voltage Vbl-0 and the development voltage Vdv-0 is set to −100 [V] (= (− 300 [V]) − (− 200 [V])). The photosensitive drum voltage Vdr-0 is set to -500 [V], and the voltage difference between the photosensitive drum voltage Vdr-0 and the developing voltage Vdv-0 is -300 [V] (= (-500 [ V]) − (− 200 [V])), and the voltage difference between the latent image voltage Vdv−e and the development voltage Vdv−0 is +100 [V] (= (− 100 [V]) − (− 200 [V ])), The latent image pattern is developed.

  On the other hand, at the time of discarding dirty toner during non-image formation, the voltage difference between the regulation blade voltage Vbl-2 and the development voltage Vdv-2 is increased as compared with printing. As a result, an electric field having the same polarity as that of the normally charged toner is formed on the regulating roller 13 side with respect to the developing roller 12, so that the toner charged to the opposite polarity is attracted to the regulating blade 13. Further, since the toner in a state that is easily charged is injected with the regulation blade voltage, the amount of charge is further increased by passing through the regulation blade 13. As a result, the probability that dirty toner present in the developing device 2 passes through the regulating blade 13 is improved.

  In this embodiment, when the dirty toner is discarded, the regulation blade voltage Vbl-2 is set to -500 [V], the development voltage Vdv-2 is set to -300 [V], and the regulation blade voltage Vbl-2 is set. And the development voltage Vdv-2 is −200 [V] (= (− 500 [V]) − (− 300 [V])).

  Next, the charge amount distribution of the thinned toner on the developing roller 12 when the dirty toner is discarded will be described.

  FIG. 13 is a graph showing the charge amount distribution of the thinned toner on the developing roller when the dirty toner is discarded in the second embodiment of the present invention.

  The figure compares the distribution of the charge amount of the toner layer on the developing roller when the print voltage is set during image formation and when the dirty toner discard voltage is set when discarding dirty toner during non-image formation. . The distribution of the charge amount at the time of discarding the dirty toner indicated by the solid line F shifts to the higher charge side as compared to the distribution of the charge amount at the time of printing indicated by the broken line E, and the frequency of the toner having a high charge amount increases. I understand that. That is, the probability that the dirty toner remaining in the developing device 2 passes through the regulating blade 13 and is discharged onto the developing roller 12 is increased.

  Next, the voltage difference between the photosensitive drum voltage Vdr-2 and the development voltage Vdv-2 is made smaller than that during printing. Thereby, the probability that the dirty toner discharged onto the developing roller 12 is electrically attracted to the photosensitive drum 1 and moves increases. Note that if the voltage difference between the photosensitive drum voltage Vdr-2 and the development voltage Vdv-2 is too small, even the normally charged toner is developed, and toner is consumed wastefully. It is desirable to set the voltage difference so as to develop.

  In the present embodiment, the photosensitive drum voltage Vdr-2 is set to -400 [V], the developing voltage Vdv-2 is set to -300 [V], and the photosensitive drum voltage Vdr-2 and the developing voltage are set. The voltage difference from Vdv-2 is set to −100 [V] (= (− 400 [V]) − (− 300 [V])). In order to set the photosensitive drum voltage Vdr-2 to −400 [V], a charging voltage Vch-2 of −900 [V] is applied to the charging roller 11.

  Next, the operation timing of each unit when discarding dirty toner will be described.

  FIG. 14 is a time chart showing the operation timing when the dirty toner is discarded in the second embodiment of the present invention.

  First, a print job is started in accordance with a print job start signal from the recording controller 30, the ID motor 17 is turned on (t4), and the photosensitive drum 1, the charging roller 11, the developing roller 12, and the toner supply roller 18 are rotated. Driven. A charging voltage Vch-0 is applied to the charging roller 11 in synchronization with the start of rotational driving. By applying the printing charging voltage Vch-0, the surface of the photosensitive drum 1 is charged to the printing photosensitive drum voltage Vdr-0. At the same time, at the timing of t4, the development voltage Vdv-0 is applied to the developing roller 12, and the regulation blade voltage Vbl-0 is applied to the regulation blade 13, and the printing period (L0) is reached.

  Subsequently, the light emission operation of the LED head 15 is performed according to the page signal and the image data. When the LED head 15 emits light, the photosensitive drum 1 becomes a latent image voltage Vdr-e, and the toner is developed to form a toner image corresponding to the image data. When the light emission operation of the LED head 15 for the transmitted pages is completed, the printing period (L0) ends (t5).

  At t5, the charging voltage is switched to the dirty toner disposal charging voltage Vch-2 while the ID motor 17 is kept on. As the charging voltage is switched, the charging potential on the surface of the photosensitive drum 1 changes to a dirty toner discarding photosensitive drum voltage Vdr-2. At the same time, at the timing of t5, the developing voltage is switched to the dirty toner discard developing voltage Vdv-2, the regulation blade voltage is switched to the dirty toner disposal regulation blade voltage Vbl-2, and the dirty toner disposal period (L2) is entered.

  Here, an example in which the development voltage and the regulation blade voltage are switched at the same time as the charging voltage has been described. However, on the photosensitive drum 1, there is a delay corresponding to the rotational movement between the position of the charging roller 11 and the position of the developing roller 12. Therefore, the development voltage switching timing may be shifted in consideration of the delay. The dirty toner disposal period (L2) continues until t6, at which time the ID motor 17, the charging voltage, the developing voltage, the photosensitive drum voltage, and the regulating blade voltage are turned off, the printing job is completed, and the next job The off state is maintained until a signal is transmitted. During the dirty toner disposal period (L2), the light emission operation of the LED head 15 is in the off state for the entire period, and no latent image is formed on the photosensitive drum 1.

  The longer the dirty toner discard period (L2), the greater the amount of dirty toner discarded. However, if the dirty toner discard period (L2) is too long, the life of the photosensitive drum 1 may be shortened and the print throughput may be reduced. Therefore, it is necessary to appropriately set the length of the dirty toner disposal period (L2) according to the use of the image forming apparatus 100 or the like. In order to discard at least the dirty toner existing around the developing roller 12 and the toner supply roller 18, it is desirable that the time is equal to or longer than the total time of one rotation of the developing roller 12 and one rotation of the toner supply roller 18. .

  As described above, the voltage setting at the time of discarding the dirty toner in the present embodiment has been described as an example in which all of the regulation blade voltage, the development voltage, and the charging voltage are switched with respect to the printing.

  Next, a more preferable example of the operation timing of each part when discarding dirty toner will be described.

  FIG. 15 is a time chart showing another example of the operation timing when discarding dirty toner according to the second embodiment of the present invention. FIG. 16 is a photoconductive drum when discarding dirty toner according to the second embodiment of the present invention. FIG. 6 is a schematic diagram illustrating operation timings of a developing roller and a charging roller.

  First, a print job is started in accordance with a print job start signal from the recording controller 30, the ID motor 17 is turned on (t4), and the photosensitive drum 1, the charging roller 11, the developing roller 12, and the toner supply roller 18 are rotated. Driven. A charging voltage Vch-0 is applied to the charging roller 11 in synchronization with the start of rotational driving. By applying the printing charging voltage Vch-0, the surface of the photosensitive drum 1 is charged to the printing photosensitive drum voltage Vdr-0. At the same time, the development voltage Vdv-0 at the time of printing is applied to the developing roller 12 at the timing t4, the regulation blade voltage Vbl-0 at the time of printing is applied to the regulation blade 13, and the printing period (L0) is reached.

  Subsequently, the light emission operation of the LED head 15 is performed according to the page signal and the image data. When the LED head 15 emits light, the photosensitive drum 1 becomes a latent image voltage Vdr-e, and the toner is developed to form a toner image corresponding to the image data. When the light emission operation of the LED head 15 for the transmitted pages is completed, the printing period (L0) ends (t5).

  At t5, the photosensitive drum 1, the developing roller 12, and the charging roller 11 are in the state shown in FIG. If the position on the photosensitive drum 1 that faces the charging roller 11 at t5 is α, the charging voltage is Vch-2, and therefore the position α on and after the position on the photosensitive drum 1 that faces the charging roller 11 (arrow) In the direction indicated by γ), the surface potential of the photosensitive drum 1 is set to Vdr-2.

  At t5 ′, the photosensitive drum 1, the developing roller 12, and the charging roller 11 are in the state shown in FIG. That is, the position α becomes a position facing the developing roller 12 by the rotation. At this time, since the voltage of the developing roller 12 is set to Vdv-2, after t5 ′, when the region DR1 faces the developing roller 12, the dirty toner adheres to the photosensitive drum 1 from the developing roller 12.

  At t6, the photosensitive drum 1, the developing roller 12, and the charging roller 11 are in the state shown in FIG. When the most downstream portion of the region DR1 is a position β, the charging voltage is turned off at a position where the position β faces the charging roller 11. When printing is performed continuously (for example, when the image forming apparatus 100 receives another print job), the charging voltage is set to Vch-0.

  Further, at t6 ′, the photosensitive drum 1, the developing roller 12, and the charging roller 11 are in the state shown in FIG. That is, the position β becomes a position facing the developing roller 12 by the rotation. At this time, the voltage of the developing roller 12 is turned off, and the disposal of the dirty toner is completed. The timing at which the regulation blade voltage is switched is the same as the timing at which the development voltage is switched.

  However, as shown in FIG. 16E, the timing at which the regulation blade voltage is switched according to the distance DV1 between the facing portion of the developing roller 12 facing the photosensitive drum 1 and the facing portion of the regulation blade 13. The timing at which the development voltage is switched may be shifted. The ID motor 17 may be turned off after t6 'when the development voltage and the regulation blade voltage are turned off.

  Next, an experiment for discarding dirty toner by switching the voltage of each unit with respect to the printing voltage will be described.

  FIG. 17 is a table showing experimental results in the second embodiment of the present invention.

  In this experiment, the regulation blade voltage, the development voltage, and the charging voltage are switched with respect to the printing voltage, and the dirty toner is discarded while changing the combination. In the figure, it was visually determined how much the degree of dirt on the recording medium 3 printed after the dirt toner discarding operation was improved compared to the degree of dirt on the recording medium 3 before the dirt toner discarding operation was performed. The results are shown.

  The set values of the regulation blade voltage, the development voltage, and the charging voltage after switching were sequentially switched to the set values as shown in FIG. The voltage settings during printing are a charging voltage of -1000 [V], a photosensitive drum voltage of -500 [V], a developing voltage of -200 [V], and a regulation blade voltage of -300 [V].

For the measurement of the stain, the image forming apparatus 100 is stopped in the middle of printing at a density of 0 [%], and the toner on the photosensitive drum 1 after the development and before transfer is removed with an adhesive tape (Scotch Mending Tape, manufactured by Sumitomo 3M Limited). ). It (stain collecting tape) was pasted on white paper. For comparison, an adhesive tape (comparison tape) that was not attached to the photosensitive drum 1 was attached to a sheet on which the dirt collection tape was attached. Then, the hue difference between the dirt collecting tape and the comparative tape was measured with a spectrocolorimeter (manufactured by Konica Minolta, CM-2600d, measurement diameter = φ8 [mm]). The hue difference (L * a * b color system chromaticity) was calculated by ΔE = (ΔL ² + Δa ² + Δb ² ) ^1/2 .

In addition, the standard of dirt evaluation was judged as follows.
0 ≦ ΔE <0.5 degree 5
0.5 ≦ ΔE <1.0 degree 4
1.0 ≦ ΔE <1.5 degree 3
1.5 ≦ ΔE <2.0 degree 2
ΔE ≧ 2.0 degree 1
(1) When the charging voltage is switched to -900 [V] (the photosensitive drum voltage is -400 [V]) and the developing voltage is switched to -300 [V], the degree of dirt in the dirt evaluation result is low and hardly improved. It was. The voltage difference between the photosensitive drum voltage and the developing voltage is −100 [V] (= (− 400 [V]) − (− 300 [V])), which is smaller than that at the time of printing. The dirty toner is discarded. However, since the dirty toner remaining in the developing device 2 is not discharged onto the developing roller 12, the amount of dirty toner discarded is extremely small, and the residual image remaining in the developing device 2 at the time of printing after the disposal is completed. It is considered that a part of the toner passes through the regulating blade 13 and moves to the photosensitive drum 1, thereby causing dirt.

  (2) When only the regulated blade voltage was switched to -500 [V], the contamination was slightly improved. The voltage difference between the regulation blade voltage and the development voltage is −300 [V] (= (− 500 [V]) − (− 200 [V])), and the electric field on the regulation blade 13 side with respect to the developing roller 12 is normally charged with toner. , The probability that the dirty toner in the developing device 2 passes through the regulating blade 13 and is discharged onto the developing roller 12 is increased, and the dirty toner is moved to the photosensitive drum 1 and discarded. The amount is thought to have increased.

  (3) When the regulated blade voltage is switched to -500 [V] and the development voltage is switched to -300 [V], the degree of dirt in the dirt evaluation result is improved as compared with the case where only the regulated blade voltage is switched. The voltage difference between the regulated blade voltage and the developing voltage is -200 [V] (-(-500 [V])-(-300 [V])), which is larger than that at the time of printing. The probability that the toner passes through the regulating blade 13 and is discharged onto the developing roller 12 increases, and the voltage difference between the photosensitive drum voltage and the developing voltage is −400 [V] (= (− 700 [V]). This is considered to be due to an increase in the amount of dirt toner adhering to the developing roller 12 moved to the photosensitive drum 1 and discarded due to the reduction of − (− 300 [V])).

  (4) When the regulation blade voltage is switched to -500 [V] and the charging voltage is switched to -900 [V] (the photosensitive drum voltage is -400 [V]), when the regulation blade voltage and the development voltage are switched, The soiling degree was almost the same as the soiling evaluation result. The voltage between the photosensitive drum voltage and the developing voltage in a state where the voltage difference between the regulation blade voltage and the developing voltage is increased to −300 [V] (= (− 500 [V]) − (− 200 [V])). By reducing the difference to −200 [V] (= (− 400 [V]) − (− 200 [V])), the dirty toner discharged from the developing device 2 and adhering to the developing roller 12 This is considered to be because the probability of being moved to the photosensitive drum 1 and being discarded increases.

  (5) When the regulation blade voltage is changed to -500 [V], the developing voltage is set to -300 [V], and the charging voltage is changed to -900 [V] (the photosensitive drum voltage is -700 [V]), the dirt is generated. The degree of contamination in the evaluation results was further improved. The voltage difference between the regulated blade voltage and the developing voltage is increased to −200 [V] (= (− 500 [V]) − (− 300 [V])), and the voltage between the photosensitive drum voltage and the developing voltage is increased. By reducing the difference to −100 [V] (= (− 400 [V]) − (− 300 [V])), the probability of discharging the dirty toner in the developing device 2 to the developing roller 12, and the development This is probably because the probability that the dirty toner moves from the roller 12 to the photosensitive drum 1 is increased.

  (6) When the voltage change period was not provided, the degree of contamination was 1. However, the dirt evaluation result was worse than that in the case (1).

  In the case of (1), the development voltage and the charging voltage are changed. However, since the potential difference between the regulation blade voltage and the development voltage is not increased, the dirty toner passes through the regulation blade 13. I can't.

  In the case (2), the potential difference between the regulation blade voltage and the development voltage is increased, so that the dirty toner easily passes through the regulation blade 13.

  Further, in the case of (3), since the development voltage is changed in addition to the regulation blade voltage, the potential difference between the development voltage and the regulation blade voltage is larger than that during image formation, and the development voltage and the photosensitive drum Since the potential difference from the voltage is reduced, the dirty toner easily passes through the regulating blade 13, and the dirty toner adheres more selectively to the photosensitive drum 1 (the voltage difference between the developing voltage and the photosensitive drum voltage). Is large, it becomes difficult for the dirt toner to move to the photosensitive drum 1 side).

  Further, in the case (4), since the charging voltage (photosensitive drum voltage) is changed in addition to the regulation blade voltage, the potential difference between the developing voltage and the photosensitive idle drum voltage is compared with the case (2). And the dirty toner adheres to the photosensitive drum 1 more selectively (if the voltage difference between the development voltage and the photosensitive drum voltage is large, the dirty toner is difficult to move to the photosensitive drum 1 side).

  Further, in the case of (5), since the regulation blade voltage, the development voltage, and the charging voltage are changed, the dirty toner easily passes through the regulation blade 13, and the dirty toner is more selectively exposed. It adheres to the photosensitive drum 1 (if the voltage difference between the developing voltage and the photosensitive drum voltage is large, the dirty toner is difficult to move to the photosensitive drum 1 side).

  In this embodiment, the regulation blade voltage Vbl-2 is −500 [V], the photosensitive drum voltage Vdr-2 is −400 [V], and the photosensitive drum voltage is higher than the absolute value of the regulation blade voltage. The absolute value is made smaller. For this reason, charge is injected into the toner having a low charge amount and the reversely charged toner held by the regulating blade 13, and among the toners that pass through the regulating blade 13 and are held by the developing roller 12, the photosensitive drum The normally charged toner held on the developing roller 12 without moving to 1 is not excessively charged because the charge injection from the photosensitive drum 1 is not performed.

  Even if there is a dirt toner between the regulating blade 13 and the photosensitive drum 1 that is separated from the developing roller 12 on the upstream side of the facing portion between the developing roller 12 and the photosensitive drum 1, the regulating blade 13 side Instead, it is attracted to the photosensitive drum 1 side.

  Further, the toner that passes through the regulating blade 13 and is held by the developing roller 12 has a smaller photosensitive drum voltage absolute value than the regulating blade voltage even if it passes through the regulating blade 13. It moves relative to the drum 1. Therefore, it becomes easy for the dirty toner to pass through the regulating blade 13 and move to the photosensitive drum 1.

  The experimental results described above are merely examples of voltage setting combinations. The voltage difference between the regulated blade voltage and the development voltage, or the voltage difference between the photosensitive drum voltage and the development voltage is related to the degree of movement of the dirty toner. However, the above experimental results show that the effect of improving dirt by discarding dirty toner can be achieved by switching the regulation blade voltage to some extent, and by switching the development voltage and charging voltage, It is thought that it shows that an effect is acquired.

  Furthermore, it is preferable to change the supply voltage. At that time, a voltage having an absolute value higher than the developing voltage (for example, Vsp-0 = −300 [V]) is formed during image formation, and a voltage having an absolute value higher than the developing voltage and a large voltage difference (for example, Vsp−0 = −300 [V]). Vsp-2 = −500 [V]). In this case, since the dirty toner can be moved from the toner supply roller 18 to the developing roller 12, the dirty toner near the toner supply roller 18 can be discarded.

  Therefore, since the dirty toner of the entire developing device 2 can be discarded by discarding the dirty toner once, if the dirty toner is discarded once, the interval until the next disposal can be extended, and a voltage change period is provided. The interval can be increased. In this example, the supply voltage is the same voltage as the regulated blade voltage. In this case, the power supply of the regulation blade voltage and the supply voltage can be made common. Furthermore, the present invention is not limited to this example, and may be different from the regulated blade voltage, for example, Vsp-0 = −350 [V], Vsp−2 = −550 [V].

  The description of this embodiment is merely an example, and the setting values of the voltages are not limited to this. Appropriately set the voltage value so that dirty toner is disposed of properly according to the toner charging characteristics, process conditions such as physical properties of each roller, usage conditions such as temperature and humidity, or the voltage output range of the power supply used. Can be set.

  Further, although an example in which the dirty toner disposal timing is after the printing operation in the print job is finished has been described, it may be before the printing operation in the print job is started. Alternatively, the toner discarding operation may be activated independently between print jobs. The operation of discarding toner for a short time may be activated for each print job. For example, the toner discarding operation may be activated at intervals of a predetermined number of printed sheets such as 500 sheets. Further, an activation button can be provided on the operation panel, and the toner discarding operation can be manually activated by a user operation.

  As described above, in the present embodiment, on the premise that the regulation blade voltage is switched, the development voltage and the charging voltage are changed so that the toner with a voltage difference can be discarded. Yes. Therefore, it is only necessary to provide a voltage difference, and the order may be main as follows.

  When the dirty toner is discarded, the absolute value of the regulation blade voltage is larger than the absolute value of the developing voltage and larger than the potential difference during image formation. Therefore, the dirty toner moves to the developing roller 12 as compared with the time of image formation.

  Further, in the relationship between the development voltage and the photosensitive drum voltage, the absolute value of the photosensitive drum voltage is larger and smaller than the potential difference during image formation. Therefore, while the normally charged toner is held on the developing roller 12, the overcharged dirty toner is selectively moved, and since the potential difference is smaller than that at the time of image formation, In addition, the overcharged toner can be easily moved to the photosensitive drum 1 side.

  Therefore, the relationship between the regulated blade voltage, the developing voltage, and the photosensitive drum voltage is as follows: the absolute value of the photosensitive drum voltage> the absolute value of the developing voltage, and the absolute value of the regulated blade voltage> the developing voltage. It is sufficient if the potential difference between the regulation blade voltage and the development voltage is large. Further, it is more preferable that the potential difference between the photosensitive drum voltage and the developing voltage is smaller than that at the time of image formation. Here, the photosensitive drum voltage is set to a desired voltage. For this purpose, the photosensitive drum voltage is changed by changing the charging voltage.

  As described above, in this embodiment, the voltage setting value is switched between printing and dirty toner disposal, and the applied voltage at the time of disposal of dirty toner remains in the developing device 2 and is easily charged. It is set so that the efficiency with which the toner is discharged to the developing roller 12 increases. As a result, the deteriorated dirty toner can be efficiently discarded from the developing device 2, and an output image of good quality free from the stain can be obtained.

  By the way, in this embodiment, as described above, the regulation blade voltage is switched at the time of non-image formation and a high voltage is applied at the time of image formation, but this can be modified. Therefore, a modified example will be described below. In this modification, the developing voltage is changed so that the order of bias between the developing roller 12 and the regulating blade 13 satisfies the developing voltage <the regulating blade voltage. At that time, the photosensitive drum voltage is also changed so that the toner from the developing roller 12 is adhered.

  Specifically, the regulation blade voltage is not changed when dirty toner is discarded during non-image formation. At this time, the potential difference between the regulation blade voltage and the development voltage is increased. For example, when Vbl-0 is -300 [V], Vbl-2 is -300 [V] (= Vbl-0), Vdv-0 is -200 [V], but Vdv-2 is- 100 [V]. That is, | Vbl-2 |> | Vdv-2 |.

  By the way, since Vdr-0 is −500 [V], it is preferable that the potential difference between the developing voltage and the photosensitive drum voltage is smaller than the potential difference during image formation. Therefore, for example, the charging voltage may be set to -700 [V] so that Vdr-2 becomes -200 [V].

  As described above, if | Vbl-2 |> | Vdv-2 | and the potential difference is larger than that during image formation, the dirty toner is not attracted to the regulating blade 13. Further, if | Vdr-2 |> | Vdv-2 | and the potential difference is smaller than that at the time of image formation, the dirty toner that has passed through the regulating blade 13 can be discarded to the photosensitive drum 1 side. Therefore, if | Vbl-2 |> | Vdv-2 | and | Vdr-2 |> | Vdv-2 |, the dirty toner in the developing device 2 can be discarded. Therefore, this embodiment and this modification are merely examples, and are necessary to satisfy | Vbl-2 |> | Vdv-2 | and | Vdr-2 |> | Vdv-2 |. Accordingly, the regulation blade voltage, the development voltage, and the photosensitive drum voltage may be changed according to the time of image formation and the time of non-image formation.

  Next, a third embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st and 2nd embodiment, the description is abbreviate | omitted by providing the same code | symbol. Also, the description of the same operations and effects as those of the first and second embodiments is omitted.

  FIG. 18 is a block diagram showing the configuration of the control system of the image forming apparatus according to the third embodiment of the present invention.

  In the present embodiment, a voltage switching unit 51 is connected to the charging voltage control unit 21, the development voltage control unit 22, and the regulation blade voltage control unit 23. The voltage switching unit 51 includes a print voltage setting unit 52, a fog toner discard voltage setting unit 53, and a dirty toner discard voltage setting unit 54, and in accordance with instructions from the recording control unit 30, the charging voltage control unit 21, the development The voltage setting values notified to the voltage control unit 22 and the regulation blade voltage control unit 23 are the print voltage held in the print voltage setting unit 52 and the fog toner discard voltage held in the fog toner discard voltage setting unit 53. The dirty toner discard voltage setting unit 54 switches to the dirty toner discard voltage. The charging voltage control unit 21, the development voltage control unit 22, and the regulation blade control unit 23 output a voltage based on the notified voltage setting value.

  Since the configuration of other points is the same as that of the first embodiment, description thereof is omitted.

  Next, the operation of the image forming apparatus 100 in the present embodiment will be described. The operation in the printing process is the same as in the first and second embodiments, and a description thereof is omitted.

  In this embodiment, by switching the charging voltage, the developing voltage, and the regulating blade voltage from the printing voltage to the fog toner discard voltage and the dirt toner discard voltage, both the fog toner and the dirt toner are selected in a period other than printing. To be discarded.

  The order relationship among the photosensitive drum voltage, the developing voltage, and the regulating blade voltage when discarding the fog toner is the same as that of the first embodiment, and the photosensitive drum voltage, developing voltage, and regulating blade voltage when discarding the dirty toner is the same. Are the same as those in the second embodiment, and the description of the set voltage is omitted.

  Next, the operation timing of each unit when the fog toner and the dirty toner are discarded will be described.

  FIG. 19 is a time chart showing the operation timing when discarding the fog toner and the dirty toner in the third embodiment of the present invention.

  First, a print job is started in accordance with a print job start signal from the recording control unit 30, the ID motor 17 is turned on (t7), and the photosensitive drum 1, the charging roller 11, the developing roller 12, and the toner supply roller 18 rotate. Driven. A charging voltage Vch-0 is applied to the charging roller 11 in synchronization with the start of rotational driving. By applying the printing charging voltage Vch-0, the surface of the photosensitive drum 1 is charged to the printing photosensitive drum voltage Vdr-0. At the same time, at the timing of t7, the development voltage Vdv-0 at the time of printing is applied to the developing roller 12, the regulation blade voltage Vbl-0 at the time of printing is applied to the regulation blade 13, and the printing period (L0) is reached.

  Subsequently, the light emission operation of the LED head 15 is performed according to the page signal and the image data. When the LED head 15 emits light, the photosensitive drum 1 becomes a latent image voltage Vdr-e, and the toner is developed to form a toner image corresponding to the image data. When the light emission operation of the LED head 15 for the transmitted pages is completed, the printing period (L0) ends (t8).

  At t8, with the ID motor 17 kept on, the charging voltage is switched to the fog toner discard charging voltage Vch-1. As the charging voltage is switched, the charging potential on the surface of the photosensitive drum 1 changes to the fog toner discarding photosensitive drum voltage Vdr-1. At the same time, at the timing of t8, the developing voltage is switched to the fog toner discard development voltage Vdv-1, the regulation blade voltage is switched to the fog toner disposal regulation blade voltage Vbl-1, and the fog toner disposal period (L1) is entered. The fog toner discard period (L1) continues until t9. During the fog toner disposal period (L1), the light emission operation of the LED head 15 is an off bear for the entire period, and no latent image is formed on the photosensitive drum 1.

  Further, at the timing of t9, the charging voltage is switched to the dirty toner disposal charging voltage Vch-2 while the ID motor 17 is kept on. As the charging voltage is switched, the charging potential on the surface of the photosensitive drum 1 changes to a dirty toner discarding photosensitive drum voltage Vdr-2. At the same time, at the timing of t9, the developing voltage is switched to the dirty toner discard developing voltage Vdv-2, the regulation blade voltage is switched to the dirty toner disposal regulation blade voltage Vbl-2, and the dirty toner disposal period (L2) is entered. The dirty toner disposal period (L2) continues until t10, and at t10, the ID motor 17, the charging voltage, the developing voltage, and the regulating blade voltage are turned off, and the printing job is completed and turned off until the next job signal is transmitted. Maintain state. During the dirty toner disposal period (L2), the light emitting operation of the LED head 15 is off for the entire period, and no latent image is formed on the photosensitive drum 1.

  Here, an example in which the development voltage and the regulation blade voltage are switched at the same time as the charging voltage at t8 and t9 has been described. However, on the photosensitive drum 1, rotational movement is performed between the position of the charging roller 11 and the position of the developing roller 12. Therefore, the development voltage switching timing may be shifted in consideration of the delay.

  The longer the fog toner discard period (L1) and the dirty toner discard period (L2), the more the fog toner and dirty toner discard amount increases, but if the fog toner discard period (L1) and the dirty toner discard period (L2) are too long. Shortening of the service life and reduction of printing throughput occur due to an increase in the rotational speed of the photosensitive drum 1. Therefore, it is necessary to appropriately set the length of the fog toner discard period (L1) and the dirty toner discard period (L2) according to the use of the image forming apparatus 100 and the like. In order to discard at least the fog toner and the dirty toner existing around the developing roller 12 and the toner supply roller 18, the development is performed in each of the fog toner discard period (L1) and the dirty toner discard period (L2). It is desirable that the time is equal to or longer than the total time of one rotation of the roller 12 and one rotation of the toner supply roller 18.

  The description of the present embodiment is merely an example, and each voltage setting value is not limited to this. A voltage that allows the waste toner and dirt toner to be disposed of satisfactorily according to the charging conditions of the toner, the process conditions such as the physical properties of each roller, the usage conditions such as temperature and humidity, or the voltage output range of the power supply used. The value can be set as appropriate.

  Further, although the example in which the fog toner and dirty toner disposal timing is after the printing operation in the print job is completed has been described, it may be before the printing operation in the print job is started. Alternatively, the toner discarding operation may be activated independently between print jobs. The operation of discarding toner for a short time may be activated for each print job. For example, the toner discarding operation may be activated at intervals of a predetermined number of printed sheets such as 500 sheets. Further, an activation button can be provided on the operation panel, and the toner discarding operation can be manually activated by a user operation. Further, the example in which the fog toner discard and the dirty toner discard are continuously performed has been described. For example, the fog toner discard is performed before the printing operation in the print job is started, and the dirty discard is performed after the printing operation is completed. For example, the waste toner discard and the dirty toner discard may be separated and executed at different timings.

  As described above, in this embodiment, the voltage setting value is switched between printing, covering toner discarding, and dirty toner discarding, and the applied voltage at the time of discarding the fog toner remains in the developing device 2. The efficiency is set so that the low-charged toner and the reverse-polarity charged toner are discharged to the developing roller 12 and the applied voltage at the time of discarding the dirty toner is set to the high-charged toner remaining in the developing device 2 and charged. It is set so that the efficiency with which easy toner is discharged to the developing roller 12 is increased. As a result, both the deteriorated fog toner and the dirty toner can be efficiently selected from the developing device 2 and discarded, and an output image of good quality free from the fog or dirt can be obtained.

  In the first to third embodiments, examples in which the present invention is applied to a printer have been described. However, the present invention can also be applied to an MFP (Multi Function Printer), a facsimile machine, a copying machine, and the like.

  Further, the present invention can be applied not only to a monochrome printer using one developing device but also to a tandem type color printer that performs transfer in one cycle using four developing devices. The present invention can also be used in a four-cycle color printer that forms a color image by sequentially repeating transfer four times using an intermediate transfer belt.

  Furthermore, although the example applied to the one-component contact development type printer has been described, it can also be applied to the one-component non-contact development method and the two-component development method.

  In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

1 is a block diagram illustrating a configuration of a control system for an image forming apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view illustrating a configuration of a main part of an image forming apparatus according to a first embodiment of the present invention. 6 is a graph showing a charge amount distribution of a thinned toner on the developing roller according to the first embodiment of the present invention. 6 is a graph showing the relationship among the photosensitive drum voltage, the developing voltage, and the regulating blade voltage when discarding the fog toner according to the first embodiment of the present invention. 6 is a graph showing the distribution of charge amount of the thinned toner on the developing roller when the fog toner is discarded in the first embodiment of the present invention. 3 is a time chart showing the operation timing when discarding the fog toner according to the first embodiment of the present invention. 6 is a time chart showing another example of the operation timing when discarding the fog toner according to the first embodiment of the present invention. FIG. 6 is a schematic diagram illustrating operation timings of the photosensitive drum, the developing roller, and the charging roller when discarding the fog toner according to the first embodiment of the present invention. It is a table | surface which shows the experimental result in the 1st Embodiment of this invention. FIG. 6 is a block diagram illustrating a configuration of a control system for an image forming apparatus according to a second embodiment of the present invention. 6 is a graph showing the relationship between the photosensitive drum voltage, the developing voltage, and the regulating blade voltage when discarding dirty toner according to the second embodiment of the present invention. 7 is a graph showing a distribution of charge amount of a thinned toner on a developing roller when dirty toner is discarded in a second embodiment of the present invention. 10 is a time chart showing the operation timing when dirty toner is discarded in the second embodiment of the present invention. It is a time chart which shows the other example of the operation timing at the time of dirty toner disposal in the 2nd Embodiment of this invention. FIG. 10 is a schematic diagram illustrating operation timings of the photosensitive drum, the developing roller, and the charging roller when discarding dirty toner according to the second embodiment of the present invention. It is a table | surface which shows the experimental result in the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the control system of the image forming apparatus in the 3rd Embodiment of this invention. 10 is a time chart illustrating operation timings when discarding fog toner and dirty toner according to the third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 11 Charging roller 12 Developing roller 13 Regulation blade 31,41,51 Voltage switching part 100 Image forming apparatus

Claims (17)

(A) a latent image carrier that carries a latent image;
(B) a charging member to which a charging voltage is applied to charge the surface of the latent image carrier;
(C) a developer carrying body to which a developing voltage is applied and a developer is attached to the latent image carrying body to form a developer image;
(D) a developer regulating member to which a regulating member applied voltage is applied and forms a developer thin layer on the developer carrying member;
(E) An image forming apparatus comprising: a voltage switching unit that switches the voltage applied to the regulating member from a voltage during image formation during non-image formation. The image forming apparatus according to claim 1, wherein the voltage switching unit switches the regulating member applied voltage from a voltage at the time of image formation during a predetermined voltage change period at the time of the non-image formation. The image forming apparatus according to claim 2, wherein the voltage switching unit switches at least one of the charging voltage and the developing voltage during the voltage change period. The image forming apparatus according to claim 2, wherein a developer that causes fogging is discarded during the voltage change period. The image forming apparatus according to claim 2, wherein a developer that causes contamination is discarded during the voltage change period. (A) a latent image carrier that carries a latent image;
(B) a charging member to which a charging voltage is applied to charge the surface of the latent image carrier;
(C) a developer carrying body to which a developing voltage is applied and a developer is attached to the latent image carrying body to form a developer image;
(D) having a developer regulating member to which a regulating member application voltage is applied and forming a developer thin layer on the developer carrying member;
(E) An image forming apparatus, wherein an absolute value of the regulating member applied voltage is set to be equal to or less than an absolute value of the developing voltage during non-image formation. The image forming apparatus according to claim 6, wherein the polarity of the regulating member applied voltage and the polarity of the developing voltage are set to the same polarity during the non-image formation. The image forming apparatus according to claim 6, wherein an absolute value of the regulating member applied voltage is set to be equal to or less than an absolute value of the developing voltage during a predetermined voltage change period during the non-image formation. The image forming apparatus according to claim 8, further comprising a voltage switching unit that switches at least one of the charging voltage and the developing voltage during the voltage change period. 10. The image forming apparatus according to claim 8, wherein an absolute value of a surface voltage of the latent image carrier is set to be larger than an absolute value of the development voltage during the voltage change period. The image forming apparatus according to claim 9, wherein the voltage switching unit switches the charging voltage. (A) a latent image carrier that carries a latent image;
(B) a charging member to which a charging voltage is applied to charge the surface of the latent image carrier;
(C) a developer carrying body to which a developing voltage is applied and a developer is attached to the latent image carrying body to form a developer image;
(D) having a developer regulating member to which a regulating member application voltage is applied and forming a developer thin layer on the developer carrying member;
(E) During non-image formation, the absolute value of the regulating member applied voltage is made larger than the absolute value of the developing voltage, and the difference between the regulating member applied voltage and the developing voltage is made larger than during image formation. An image forming apparatus. The image forming apparatus according to claim 12, wherein an absolute value of the voltage applied to the regulating member is larger than an absolute value of a surface voltage of the latent image carrier during the non-image formation. In a predetermined voltage change period during the non-image formation, the absolute value of the regulating member applied voltage is made larger than the absolute value of the developing voltage, and the difference between the regulating member applied voltage and the developing voltage is greater than that during image formation. The image forming apparatus according to claim 12 or 13, wherein the image forming apparatus is enlarged. The image forming apparatus according to claim 14, further comprising a voltage switching unit that switches at least one of the charging voltage and the developing voltage during the voltage change period. During the voltage change period, the absolute value of the surface voltage of the latent image carrier is made larger than the absolute value of the development voltage, and the difference between the surface voltage of the latent image carrier and the development voltage is made smaller than that during image formation. The image forming apparatus according to claim 14 or 15. 17. The image forming apparatus according to claim 14, wherein an absolute value of the voltage applied to the regulating member is larger than an absolute value of a surface voltage of the latent image carrier during the voltage change period.

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