JP2005309265A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus capable of restraining image noise caused by leak or fading from occurring on an image to be formed in controlling the density of the image to be formed by adjusting the amount of toner supplied to an image carrier. <P>SOLUTION: The image forming apparatus is equipped with the image carrier 1 on which an electrostatic latent image is formed, a developing device 10 developing the electrostatic latent image by feeding toner (t) held on the surface of a toner carrier 11 to a developing area opposed to the image carrier, and a DC power source 15a and an AC power source 15b applying DC voltage and AC voltage between the toner carrier and the image carrier. In the apparatus, the waveform of the AC voltage applied from the AC power source is made waveform obtained by changing rectangular waveform so that voltage change shifting from peak potential on a recovery side where the toner is restored to the toner carrier to peak potential on a developing side where the toner is supplied to the image carrier may be tilted, and the DC voltage applied from the DC power source is changed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer, and in particular, an image carrier on which an electrostatic latent image is formed, and a development region facing toner held on the surface of the toner carrier to the image carrier. A developing device that develops the electrostatic latent image formed on the image carrier, and a DC power source and an AC power source that apply a DC voltage and an AC voltage between the toner carrier and the image carrier. In the image forming apparatus having the above-described features, when adjusting the density of an image to be formed, image noise due to leakage and image blurring are suppressed.

  Conventionally, when an image is formed in an image forming apparatus such as a copying machine or a printer, toner is supplied from the developing device to the electrostatic latent image formed on the image carrier to develop the electrostatic latent image. I have to.

  A developing device as shown in FIG. 1 is known as one of the developing devices as described above.

  Here, in the developing device 10 shown in the figure, a toner carrier 11 is provided so as to face the image carrier 1 with a required distance d in the development region, and the toner carrier 11 and the image carrier 1 are provided. , And the toner t accommodated in the developing device 10 is fed to the rotating supply roller 13 in contact with the toner carrier 11 by the feed member 12, and the surface of the toner carrier 11 is fed from the supply roller 13. The toner t is supplied to the toner.

  Then, the regulating member 14 is brought into contact with the surface of the toner carrier 11 supplied with the toner t as described above, and the amount of the toner t supplied to the surface of the toner carrier 11 is regulated by the regulating member 14 and the toner. After charging t, the toner carrier 11 guides the toner t to a developing area facing the image carrier 1, and between the toner carrier 11 and the image carrier 1, a DC power source 15 a As shown in FIG. 2, a developing bias voltage in which a DC voltage Vdc and a continuous AC voltage having a rectangular shape are superimposed is applied from the AC power source 15 b to form the image carrier 1. Development is performed by supplying toner t to the portion of the electrostatic latent image.

  Further, when performing development using such a developing device 10, in controlling the density of the formed image by adjusting the amount of toner t supplied to the image carrier 1, the above-described DC power source 15 a is used. The DC voltage Vdc applied from the AC power source, the peak-to-peak value Vpp of the AC voltage applied from the AC power supply 15b, or the developing-side voltage for supplying the toner t to the image carrier 1 at the AC voltage. The ratio (duty ratio) between the working time ta of the toner and the working time tb of the voltage on the recovery side for returning the toner t to the toner carrier 11 has been changed (see, for example, Patent Document 1 and Patent Document 2). .)

However, when the amount of the toner t supplied to the image carrier 1 is adjusted as described above, leakage is likely to occur between the toner carrier 11 and the image carrier 1 and the toner is formed. There have been problems such as image noise due to leakage in the image, and blurring in the formed image.
JP-A-7-56424 JP 60-73647 A

  According to the present invention, an image carrier on which an electrostatic latent image is formed, and a toner having toner held on the surface of the toner carrier are transported to a development area facing the image carrier, and formed on the image carrier. An image forming apparatus having a developing device for developing an electrostatic latent image and a DC power source and an AC power source for applying a DC voltage and a rectangular AC voltage between the toner carrier and the image carrier are used. It is an object of the present invention to solve the above problems in image formation.

  That is, in the image forming apparatus according to the present invention, when adjusting the amount of toner supplied to the image carrier to control the density of the formed image, image noise due to leakage occurs in the formed image. An object of the present invention is to suppress the occurrence of blur in the formed image.

  In the first image forming apparatus of the present invention, in order to solve the above-described problems, an image carrier on which an electrostatic latent image is formed and a toner having toner held on the surface of the toner carrier are image-bearing. A developing device that develops the electrostatic latent image formed on the image carrier by being transported to a developing area facing the body, and a DC voltage and an AC voltage are applied between the toner carrier and the image carrier. In an image forming apparatus having a direct current power source and an alternating current power source, the development of supplying the toner to the image carrier from the recovery-side peak potential that returns the waveform of the alternating voltage applied from the alternating current power source to the toner carrier. The rectangular waveform is changed so that the voltage change to the peak potential on the side slopes, and the DC voltage applied from the DC power source is changed to change the density of the formed image. Because .

  Here, in the first image forming apparatus, as the AC voltage applied from the AC power source, the ratio of the action time of the recovery-side peak potential and the action time of the development-side peak potential with respect to one cycle T is 12 respectively. More preferably, the ratio of the action time of the peak potential on the recovery side and the action time of the peak potential on the development side with respect to one cycle T is 0%, and the AC voltage becomes 5% or less, and more preferably has a triangular shape. It is preferable to use an alternating voltage.

  In the second image forming apparatus of the present invention, in order to solve the above-described problems, an image carrier on which an electrostatic latent image is formed and a toner having toner held on the surface of the toner carrier are provided. A developing device that develops the electrostatic latent image formed on the image carrier by being transported to a developing area facing the image carrier, and a DC voltage and an AC voltage between the toner carrier and the image carrier. In an image forming apparatus having a DC power source and an AC power source for applying toner, the waveform of the AC voltage applied from the AC power source is changed from the peak potential on the developing side for supplying toner to the image carrier to the toner carrier. Change the density of the image to be formed by changing the rectangular waveform so that the voltage change to the recovery-side peak potential is inclined and changing the DC voltage applied from the DC power source. Made It is.

  Here, as in the first image forming apparatus according to the present invention, the toner held on the surface of the toner carrier is transported to a developing region facing the image carrier, and the toner carrier and the image carrier are interposed. When the electrostatic latent image formed on the image carrier is developed by applying a DC voltage and an AC voltage to the image carrier, the AC voltage waveform applied from the AC power source is used to return the toner to the toner carrier. In addition to changing the rectangular waveform so that the voltage change from the peak potential to the developing-side peak potential for supplying toner to the image carrier is inclined, the DC voltage applied from the DC power source is changed. Thus, when the density of the formed image is changed, it is possible to suppress the occurrence of image noise due to leakage in the formed image and the occurrence of blurring in the formed image.

  Further, in the first image forming apparatus according to the present invention, the ratio of the action time of the recovery-side peak potential and the action time of the development-side peak potential with respect to one cycle T is 12 as the AC voltage applied from the AC power source. When an AC voltage of less than 5% is applied, it is possible to further suppress the occurrence of image noise due to leakage in the formed image and the occurrence of blurring in the formed image. When the ratio of the action time of the peak potential on the recovery side and the action time of the peak potential on the development side with respect to the period T is 0%, and an alternating voltage having a triangular shape is used, generation of image noise due to leakage and image blurring Occurrence is further suppressed.

  Further, as in the second image forming apparatus according to the present invention, the toner held on the surface of the toner carrier is transported to a development area facing the image carrier, and between the toner carrier and the image carrier. When developing an electrostatic latent image formed on an image carrier by applying a DC voltage and an AC voltage, the development side for supplying toner to the image carrier using the waveform of the AC voltage applied from the AC power source described above. In addition to changing the rectangular waveform so that the voltage change from the peak potential to the recovery-side peak potential to return the toner to the toner carrier is inclined, the DC voltage applied from the DC power source is changed. As a result, even when the density of the formed image is changed, it is possible to suppress the occurrence of image noise due to leakage in the formed image and the occurrence of blurring in the formed image. .

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

  Here, also in the image forming apparatus in this embodiment, as shown in FIG. 3, as in the conventional image forming apparatus shown in FIG. 1, it faces the image carrier 1 with a required distance d in the developing region. Thus, the toner carrier 11 is provided, the toner carrier 11 and the image carrier 1 are rotated, and the toner t accommodated in the developing device 10 is brought into contact with the toner carrier 11 by the feeding member 12. The toner is fed to the rotating supply roller 13, and the toner t is supplied from the supply roller 13 to the surface of the toner carrier 11.

  In addition, the regulating member 14 is brought into contact with the surface of the toner carrier 11 supplied with the toner t as described above, and the amount of the toner t supplied to the surface of the toner carrier 11 is regulated by the regulating member 14 and the toner. After charging t, the toner carrier 11 guides the toner t to a developing area facing the image carrier 1.

  In the image forming apparatus according to this embodiment, the DC voltage Vdc and the AC voltage Vac are superimposed between the toner carrier 11 and the image carrier 1 from the DC power source 15a and the AC power source 15b. In developing the electrostatic latent image by applying a developing bias voltage and supplying the toner t to the portion of the electrostatic latent image formed on the image carrier 1, the AC power source is controlled by the control device 20 such as a CPU. The waveform of the AC voltage Vac applied from 15b is changed to a waveform obtained by changing the rectangular waveform, and the DC voltage Vdc applied from the DC power supply 15a is changed and supplied from the toner carrier 11 to the image carrier 1. The amount of toner t to be formed is adjusted to appropriately set the density of the formed image.

  Here, in one cycle of the AC voltage Vac, the time for applying the development side voltage and the time for applying the recovery side voltage may be the same or different. In order to reduce the complexity when changing the slope of the voltage change, the time for applying the developing side voltage and the time for applying the collecting side voltage should be the same, that is, the duty ratio should be 50%. preferable.

  Further, when the waveform of the AC voltage Vac applied from the AC power supply 15b by the control device 20 as described above is changed to a rectangular waveform, the peak / peak value Vpp and Duty ratio of the AC voltage Vac are changed. As shown in FIG. 4, the change in voltage that shifts from the recovery-side peak potential Vp <b> 1 that returns the toner t to the toner carrier 11 to the development-side peak potential Vp <b> 2 that supplies the toner t to the image carrier 1. As shown in FIG. 5, the recovery side peak potential Vp <b> 1 for returning the toner t to the toner carrier 11 is changed from the development side peak potential Vp <b> 2 for supplying the toner t to the image carrier 1. The slope of the voltage change to be transferred is changed appropriately.

  Then, in the state where the waveform of the AC voltage Vac applied from the AC power supply 15b is changed to a waveform obtained by changing the rectangular waveform, the control device 20 applies the DC voltage Vdc applied from the DC power supply 15a. If the density of the image to be formed is changed by changing, the generation of image noise due to leakage or the scumming in the formed image is compared with the case where the peak-to-peak value Vpp and the duty ratio of the AC voltage are changed. As compared with the case where the DC voltage Vdc applied from the DC power supply 15a is changed by applying an AC voltage having a pulse-like continuous uneven shape as shown in FIG. The occurrence of image noise due to leakage and the occurrence of blur in the formed image are suppressed.

  Next, as shown in the above-described embodiment, a voltage change that shifts from the recovery-side peak potential Vp1 that returns the toner t to the toner carrier 11 to the development-side peak potential Vp2 that supplies the toner t to the image carrier 1 Then, an AC voltage Vac is applied so that the voltage change from the development-side peak potential Vp2 for supplying the toner t to the image carrier 1 to the recovery-side peak potential Vp1 for returning the toner t to the toner carrier 11 is inclined. In addition, when the DC voltage Vdc applied from the DC power supply 15a is changed, the density of the formed image can be adjusted appropriately, and the occurrence of leakage and the like can be suppressed. Reveal based on.

  Here, in the experimental example, a commercially available printer (manufactured by Minolta-QMS: magiccolor 2300DL) using the negatively chargeable toner t is modified, and the toner carrier 11 is supplied from the AC power supply 15b as shown in the above embodiment. The waveform of the rectangular AC voltage Vac applied between the DC power source 15a and the image carrier 1 can be changed, and the DC voltage Vdc applied from the DC power source 15a can be changed. Note that the distance d between the image carrier 1 and the toner carrier 11 facing each other in the development region is 135 μm.

  As a basic rectangular AC voltage Vac applied between the toner carrier 11 and the image carrier 1 from the AC power source 15b, the peak-to-peak value Vpp is 1600 V, the duty ratio is 50%, and the frequency is As shown in FIG. 4 above, in Example 1, the developing side supplying toner t to the image carrier 1 from the recovery-side peak potential Vp1 for returning the toner t to the toner carrier 11 is used. In Example 2 of the experiment, the slope of the voltage transition to the peak potential Vp2 is changed, and as shown in FIG. 5, the toner t is supplied from the development-side peak potential Vp2 that supplies the toner t to the image carrier 1. The inclination of the voltage change that shifts to the recovery-side peak potential Vp1 returned to the toner carrier 11 is changed, and the DC voltage Vdc applied from the DC power supply 15a is changed to change the image. It was to be printed.

  Here, in Experimental Example 1, as shown in FIG. 4, the recovery-side peak potential Vp <b> 1 that returns the toner t to the toner carrier 11 shifts to the development-side peak potential Vp <b> 2 that supplies the toner t to the image carrier 1. In changing the slope of the voltage change, the ratio of the action time t1 of the recovery-side peak potential Vp1 to one cycle T [(t1 / T) × 100] and the ratio of the action time t2 of the development-side peak potential Vp2 [(t2 / T) × 100] uses five types of AC voltages Vac1 to Vac5 having 0%, 5%, 12.5%, 25%, and 37.5%, respectively, and the operation time t1, Using a basic rectangular AC voltage Vac6 in which the ratio of t2 is 50%, the DC voltage Vdc applied from the DC power supply 15a is changed in the range of −220 to −620 V, and a black solid image is pre-imaged. The transmission density (TD) of each obtained image was measured using a transmission densitometer (Macbeth: TD904), and the results are shown in Table 1 below.

  As a result, as shown in FIG. 4, the change in voltage is shifted from the recovery-side peak potential Vp1 for returning the toner t to the toner carrier 11 to the development-side peak potential Vp2 for supplying the toner t to the image carrier 1. Even when the applied DC voltage Vac1 to Vac5 is used to change the DC voltage Vdc applied from the DC power supply 15a, the transmission density (TD) of the image formed in accordance with the change in the DC voltage Vdc changes. Was.

  In addition, AC voltages Vac1 to Vac5 obtained by giving gradients to the voltage change that shifts from the recovery-side peak potential Vp1 for returning the toner t to the toner carrier 11 to the development-side peak potential Vp2 for supplying the toner t to the image carrier 1 are obtained. When used, the ratio of the working time t1 of the collection-side peak potential Vp1 to the period T and the ratio of the working time t2 of the development-side peak potential Vp2 become small, and the collecting side returns the toner t to the toner carrier 11. The transmission density (TD) of the image formed decreased as the slope of the voltage change from the peak potential Vp1 to the development-side peak potential Vp2 for supplying the toner t to the image carrier 1 increased.

  In Experimental Example 2, as shown in FIG. 5, the voltage that shifts from the development-side peak potential Vp2 that supplies the toner t to the image carrier 1 to the recovery-side peak potential Vp1 that returns the toner t to the toner carrier 11. In changing the slope of the change, the ratio of the time t1 of the collection-side peak potential Vp1 to one period T [(t1 / T) × 100] and the ratio of the time t2 of the development-side peak potential Vp2 [(t2 / T) × 100] uses three types of AC voltages Vac7 to Vac9 having 37.5%, 25%, and 12.5%, respectively, and the DC voltage Vdc applied from the DC power supply 15a is −220 to − A basic pattern in which a solid black image is printed in a range of 420 V, the transmission density (TD) of each image obtained is measured, and the ratio of the above-described working times t1 and t2 is 50%. A rectangular shape The results are shown in Table 2 below together with the result of the AC voltage Vac6.

  As a result, as shown in FIG. 5, the change in voltage that shifts from the development-side peak potential Vp2 that supplies the toner t to the image carrier 1 to the recovery-side peak potential Vp1 that returns the toner t to the toner carrier 11 is inclined. Even when the applied DC voltages Vac7 to Vac9 are used to change the DC voltage Vdc applied from the DC power supply 15a, the transmission density (TD) of the formed image changes with the change of the DC voltage Vdc. Was.

  Further, AC voltages Vac7 to Vac9 obtained by giving an inclination to a change in voltage from the development-side peak potential Vp2 for supplying the toner t to the image carrier 1 to the recovery-side peak potential Vp1 for returning the toner t to the toner carrier 11 are provided. When used, the ratio of the working time t1 of the collection-side peak potential Vp1 to the period T and the ratio of the working time t2 of the development-side peak potential Vp2 become small, and the collecting side returns the toner t to the toner carrier 11. The transmission density (TD) of the image formed increased as the slope of the voltage change from the peak potential Vp1 of the toner to the development-side peak potential Vp2 for supplying the toner t to the image carrier 1 increased. By adjusting the absolute value of the applied DC voltage Vdc, it was possible to obtain a desired transmission density.

  When the image forming apparatus as described above is used, an image having a sufficient image density can be obtained, while a transmission density (TD) of the formed image is reduced in order to reduce toner consumption. .) Is preferably set in a range of 1.2 to 1.5.

  Further, as shown in FIG. 4, the slope of the voltage change that changes from the recovery-side peak potential Vp1 that returns the toner t to the toner carrier 11 to the development-side peak potential Vp2 that supplies the toner t to the image carrier 1 is changed. Using the above-mentioned five types of AC voltages Vac1 to Vac5 having the waveform and the basic rectangular AC voltage Vac6, an image having a transmission density (TD) of 1.5 can be obtained. The DC voltage Vdc applied from the DC power supply 15a is set to −485V, −470V, −435V, −405V, −355V and −300V as shown in Table 3 below, and a black solid image is printed. And changing the peak-to-peak value Vpp of each of the AC voltages Vac1 to Vac5 and the rectangular AC voltage Vac6, image noise due to leakage occurs in the image portion. Obtains a lower limit value of the raw peak-peak value Vpp, shown in Table 3 as a leakage occurs Vpp.

  In addition, under the same conditions as in the above case, the AC voltage Vac1 to Vac5 and the peak-to-peak value Vpp of the rectangular AC voltage Vac are changed so that an image pattern of 2 dots × 2 dots passes through an interval of 2 dots. The dot images arranged in a grid pattern are printed, and the upper limit value of the peak / peak value Vpp at which blurring occurs is obtained. The result is shown in Table 3 as the blurring occurrence Vpp.

  Further, the difference between the leak occurrence Vpp and the blur occurrence Vpp, that is, the width of Vpp at which neither image noise nor blur due to leak occurs is obtained, and this is shown in Table 3 as an allowable Vpp width.

  As a result, as shown in FIG. 4, the change in voltage is shifted from the recovery-side peak potential Vp1 for returning the toner t to the toner carrier 11 to the development-side peak potential Vp2 for supplying the toner t to the image carrier 1. When the applied AC voltages Vac1 to Vac5 are used, the allowable Vpp width in which image noise is not generated due to leakage and no blur is generated as compared with the case where the rectangular AC voltage Vac is used. The ratio of the time t1 of the recovery-side peak potential Vp1 to the time T and the ratio of the time t2 of the development-side peak potential Vp2 to 12.5% or less, and the recovery-side peak potential Vp1 for returning the toner t to the toner carrier 11 As the slope of the voltage change that shifts from the toner t to the developing-side peak potential Vp2 for supplying the toner t to the image carrier 1 becomes larger, the generation of image noise due to leakage also becomes more distorted. Raw also allowable Vpp width further increases does not occur, occurrence of image noise and blurring due to leakage was also easily suppressed.

In the conventional image forming apparatus, it is the schematic explanatory drawing which showed the state which develops the electrostatic latent image formed in the image carrier with the image development apparatus. In the conventional image forming apparatus, it is the figure which showed the waveform of the rectangular AC voltage which became the continuous uneven | corrugated shape applied from AC power supply. In the image forming apparatus according to the embodiment of the present invention, it is a schematic explanatory view showing a state where an electrostatic latent image formed on an image carrier is developed by a developing device. In the image forming apparatus according to the above-described embodiment, when changing the waveform of the rectangular AC voltage applied from the AC power supply, the development that supplies the toner to the image carrier from the recovery-side peak potential that returns the toner to the toner carrier. It is the figure which showed the waveform of the alternating voltage which provided the inclination to the voltage change which transfers to the peak potential of the side. In the image forming apparatus according to the above-described embodiment, when changing the waveform of the rectangular AC voltage applied from the AC power source, the toner is returned to the toner carrier from the development-side peak potential that supplies the toner to the image carrier. It is the figure which showed the waveform of the alternating voltage which provided the inclination to the voltage change which transfers to the peak potential of the side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 10 Developing device 11 Toner carrier 12 Feed member 13 Supply roller 14 Restriction member 15a DC power source 15b AC power source 20 Controller d Space between toner carrier and image carrier t toner T 1 cycle t1 recovery side Action time of peak potential of t2 Action time of peak potential on development side Vdc DC voltage Vpp Peak / peak value of AC voltage Vp1 Peak potential on recovery side Vp2 Peak potential on development side

Claims (4)

The electrostatic latent image formed on the image carrier is developed by transporting the image carrier on which the electrostatic latent image is formed and the toner held on the surface of the toner carrier to a development area facing the image carrier. In an image forming apparatus comprising a developing device and a DC power source and an AC power source for applying a DC voltage and an AC voltage between the toner carrier and the image carrier, an AC applied from the AC power source The waveform of the voltage is a waveform obtained by changing the rectangular waveform so that the voltage change from the peak potential on the collecting side for returning the toner to the toner carrier to the peak potential on the developing side for supplying the toner to the image carrier is inclined. An image forming apparatus, wherein the density of an image to be formed is changed by changing a DC voltage applied from the DC power source. 2. The image forming apparatus according to claim 1, wherein the AC voltage has a ratio of an action time of the peak potential on the recovery side and an action time of the peak potential on the development side to one cycle T is 12.5% or less, respectively. An image forming apparatus. 3. The image forming apparatus according to claim 2, wherein the AC voltage has a triangular shape in which the ratio of the action time of the peak potential on the recovery side and the action time of the peak potential on the development side with respect to one cycle T is 0%. An image forming apparatus. The electrostatic latent image formed on the image carrier is developed by transporting the image carrier on which the electrostatic latent image is formed and the toner held on the surface of the toner carrier to a development area facing the image carrier. In an image forming apparatus comprising a developing device and a DC power source and an AC power source for applying a DC voltage and an AC voltage between the toner carrier and the image carrier, an AC applied from the AC power source The waveform of the voltage is a waveform obtained by changing the rectangular waveform so that the voltage change from the peak potential on the developing side for supplying toner to the image carrier to the peak potential on the collecting side for returning the toner to the toner carrier is inclined. An image forming apparatus, wherein the density of an image to be formed is changed by changing a DC voltage applied from the DC power source.

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