JP2005309266A - 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 from occurring on an image to be formed or fading from occurring on the 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 formed on the image carrier by feeding toner (t) held on the surface of a toner carrier 11 to a developing area opposed to the image carrier, and an AC power source 15b applying at least rectangular AC voltage between the toner carrier and the image carrier. In the apparatus, the density of the image to be formed is changed by varying the inclination of voltage change shifting from peak potential Vp1 on a recovery side where the toner is restored to the toner carrier to peak potential Vp2 on a developing side where the toner is supplied to the image carrier in the rectangular AC voltage. <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 an AC power source that applies at least a rectangular AC voltage between the toner carrier and the image carrier. In the image forming apparatus, when adjusting the density of the 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 A developing bias voltage in which a DC voltage and a rectangular AC voltage are superimposed is applied from an AC power source 15b, and toner t is supplied to the portion of the electrostatic latent image formed on the image carrier 1 for development. To do.

  Further, when developing using such a developing device, the amount of toner t supplied to the image carrier 1 is adjusted to control the density of the formed image. The developing side that changes the DC voltage to be applied, changes the peak-to-peak value Vpp of the rectangular AC voltage applied from the AC power supply 15b, or supplies toner to the image carrier at the rectangular AC voltage The ratio (duty ratio) between the operation time of the toner and the recovery side operation time for returning the toner to the toner carrier is changed (for example, see 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. When image formation is performed using an image forming apparatus including a developing device that develops an electrostatic latent image and an AC power source that applies at least a rectangular AC voltage between the toner carrier and the image carrier. It is an object of the present invention to solve the above problems.

  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 development area facing the body, and at least a rectangular AC voltage is applied between the toner carrier and the image carrier. In the image forming apparatus including the alternating current power source, a voltage that shifts from the recovery-side peak potential at which the toner is returned to the toner carrier to the development-side peak potential that supplies the toner to the image carrier at the rectangular AC voltage described above. The gradient of the change is changed to change the density of the formed image.

  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 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 development area facing the body, and at least a rectangular AC voltage is applied between the toner carrier and the image carrier. In the image forming apparatus having the AC power source to be driven, a voltage that shifts from the peak potential on the development side that supplies toner to the image carrier to the peak potential on the recovery side that returns the toner to the toner carrier in the rectangular AC voltage described above. The gradient of the change is changed to change the density of the formed image.

  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 at least a rectangular alternating voltage to the toner, the recovery side peak potential at which the toner is returned to the toner carrier at the rectangular alternating voltage described above is used. When the slope of the voltage change that shifts to the developing-side peak potential for supplying toner to the image carrier is changed, the density of the image formed decreases as the slope increases.

  As a result, in the first image forming apparatus according to the present invention, the DC voltage applied between the toner carrier and the image carrier is changed, or the peak-to-peak value Vpp of the rectangular AC voltage is changed. Without changing the ratio (duty ratio) between the working time on the developing side for supplying the toner to the image carrier and the working time on the collecting side for returning the toner to the toner carrier (Duty ratio). By changing the slope of the voltage change from the recovery-side peak potential returned to the carrier to the development-side peak potential for supplying toner to the image carrier, the density of the formed image can be set appropriately. At the same time, the occurrence of image noise due to leakage in the formed image and the occurrence of blurring in the formed image are also 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. In developing the electrostatic latent image formed on the image carrier by applying at least a rectangular AC voltage, the peak potential on the developing side for supplying toner to the image carrier at the above-mentioned rectangular AC voltage is developed. If the slope of the voltage change that shifts the toner to the toner carrying member and changing to the peak potential on the collection side is changed, the density of the image formed increases as this slope increases.

  As a result, also in the second image forming apparatus according to the present invention, the DC voltage applied between the toner carrier and the image carrier is changed, or the peak-to-peak value Vpp of the rectangular AC voltage is changed. Without changing the ratio (duty ratio) between the working time on the developing side for supplying toner to the image carrier and the working time on the collecting side for returning the toner to the toner carrier (Duty ratio). By changing the slope of the voltage change from the development-side peak potential supplied to the carrier to the recovery-side peak potential for returning the toner to the toner carrier, the density of the formed image can be set appropriately. At the same time, the occurrence of image noise due to leakage in the formed image and the occurrence of blurring in the formed image are also suppressed.

  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. 2, 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, a DC voltage Vdc and a rectangular AC voltage Vac are supplied between the toner carrier 11 and the image carrier 1 from the DC power source 15a and the AC power source 15b. When the superimposed developing bias voltage is applied and the toner t is supplied to the portion of the electrostatic latent image formed on the image carrier 1, and the electrostatic latent image is developed, the rectangular power applied from the AC power supply 15b is used. The waveform of the AC voltage Vac having a shape is changed by a control device 20 such as a CPU, the amount of toner t supplied from the toner carrier 11 to the image carrier 1 is adjusted, and the density of the formed image is set appropriately. Like to do.

  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.

  In changing the waveform of the rectangular AC voltage Vac applied from the AC power supply 15b by the control device 20 as described above, without changing the peak-to-peak value Vpp or the duty ratio of the AC voltage Vac, As shown in FIG. 3, the slope of the voltage change 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 is appropriately changed. As shown in FIG. 4, the voltage change of the transition 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 performed. The inclination is changed appropriately.

  Here, as shown in FIG. 3 described above, the 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 is performed. When the slope is changed, the slope is gradually increased, and the times t1 and t2 of the peak potentials Vp1 and Vp2 on the collection side and the development side are shortened, the density of the formed image gradually decreases, and the image density is reduced. When it is desired to lower it, this inclination is set appropriately so that an appropriate image density can be obtained.

  On the other hand, as shown in FIG. 4 above, the slope of 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. When the time t1 and t2 of the peak potentials Vp1 and Vp2 on the development side and the collection side are shortened by gradually changing the slope and increasing the inclination, the density of the formed image gradually increases, and the image density is increased. If this is desired, this inclination is set appropriately so that an appropriate image density can be obtained.

  In addition, as described above, the inclination of the voltage change that shifts the toner t from the collection-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, and the toner t The density of the image to be formed is adjusted by changing the slope of the voltage change from the development-side peak potential Vp2 supplied to the image carrier 1 to the recovery-side peak potential Vp1 for returning the toner t to the toner carrier 11. In this case, the image due to leakage is changed as in the case of changing the DC voltage Vdc applied between the toner carrier 11 and the image carrier 1 or changing the peak-to-peak value Vpp or Duty ratio of the rectangular AC voltage. Generation of noise and blurring in the formed image are suppressed.

  Next, as shown in the above-described embodiment, the 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 is performed. It is formed by changing the inclination or the inclination of 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. It will be clarified based on experimental examples that the density of the image can be adjusted and the occurrence of leaks is suppressed.

  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 In the experimental example 1, as shown in FIG. 3, the developing side for supplying the toner t to the image carrier 1 from the collection-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 change that shifts to the peak potential Vp2 is changed. As shown in FIG. 4, the toner t is supplied from the development-side peak potential Vp2 that supplies the toner t to the image carrier 1. An image is printed by changing the slope of the voltage change that shifts to the recovery-side peak potential Vp1 returned to the toner carrier 11.

  Here, in Experimental Example 1, as shown in FIG. 3, 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 time t1 of the collection-side peak potential Vp1 to one cycle T [(t1 / T) × 100] and the ratio of the time t2 of the development-side peak potential Vp2 [(t2 / T ) × 100] uses six types of AC voltages Vac1 to Vac6 having 0%, 5%, 12.5%, 25%, 37.5%, and 50%, respectively, and the DC power supply 15a described above. The DC voltage Vdc to be applied is set to -320V, -370V and -420V, black solid images are printed, and the transmission density (TD) of each obtained image is measured by a transmission densitometer (Macbeth Co., Ltd.). : Measurement was performed using TD904), and the results are shown in Table 1 and FIG. In FIG. 5, the results when the DC voltage Vdc is −320V are indicated by ◯ and solid lines, the results when the DC voltage Vdc is −370V are indicated by □ and broken lines, and the results when the DC voltage Vdc is −420V. Δ and indicated by a dashed line.

  As a result, as shown in FIG. 3, the slope of the voltage change 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 is changed. In the case of changing, the ratio of the time t1 of the collection-side peak potential Vp1 to the period T and the ratio of the time t2 of the development-side peak potential Vp2 are reduced, and the collection-side peak potential for returning the toner t to the toner carrier 11 is reduced. The transmission density (TD) of the formed image decreased as the slope of the voltage change from 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. 4, the voltage that shifts from the development-side peak potential Vp <b> 2 that supplies the toner t to the image carrier 1 to the recovery-side peak potential Vp <b> 1 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 four types of AC voltages Vac6 to Vac9 having 50%, 37.5%, 25%, and 12.5%, respectively, and uses the DC voltage Vdc applied from the DC power supply 15a. A black solid image was printed at −220 V and −270 V, respectively, and the transmission density (TD) of each obtained image was measured. The results are shown in Table 2 and FIG. In FIG. 6, the results when the DC voltage Vdc is −220 V are indicated by ● and a solid line, and the results when the DC voltage Vdc is −270 V are indicated by ▲ and an alternate long and short dash line.

  As a result, as shown in FIG. 4, the slope of the voltage change that shifts 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 obtained. In the case of changing, the ratio of the time t1 of the collection-side peak potential Vp1 to the period T and the ratio of the time t2 of the development-side peak potential Vp2 are reduced, and the collection-side peak potential for returning the toner t to the toner carrier 11 is reduced. The transmission density (TD) of the formed image increased as the slope of the voltage change from Vp1 to the developing-side peak potential Vp2 supplying the toner t to the image carrier 1 increased.

  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 1.6.

  Further, as shown in FIG. 3, 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. As described above, the ratio of the collection-side peak potential Vp1 to the time t1 and the development-side peak potential Vp2 to the time t2 are 0%, 5%, 12.5%, 25%, respectively. From the DC power supply 15a, the AC voltages Vac1 to Vac6 having 6 waveforms of 37.5% and 50% are used to obtain images having a transmission density (TD) of 1.5. The DC voltage Vdc to be applied is set to −485 V, −470 V, −435 V, −405 V, −355 V, and −300 V as shown in Table 3 below, and a solid black image is printed respectively. By changing the peak-to-peak value Vpp of the AC voltage Vac1～Vac6, we obtain a lower limit value of the peak-peak value Vpp of image noise due to leakage occurs in the image portion, shown in Table 3 as a leakage occurs Vpp.

  In addition, under the same conditions as in the above case, the peak-to-peak value Vpp of each of the AC voltages Vac1 to Vac6 is changed, so that 2 dots × 2 dots image patterns are arranged in a grid pattern with an interval of 2 dots Images were printed and the upper limit value of the peak / peak value Vpp at which blurring occurred was determined, and the result is shown in Table 3 as 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. 3, the slope of the voltage change 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 is changed. In the case of changing, the ratio of the time t1 of the collection-side peak potential Vp1 to the period T and the ratio of the time t2 of the development-side peak potential Vp2 are reduced, and the collection-side peak potential for returning the toner t to the toner carrier 11 is reduced. As the inclination of the voltage change from Vp1 to the developing-side peak potential Vp2 for supplying the toner t to the image carrier 1 increases, the allowable Vpp width that does not cause image noise or blur due to leakage increases, The generation of image noise and blur due to leaks is 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 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 changed the inclination of 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 changed the inclination of the voltage change which transfers to the peak potential of the side. In Experimental Example 1 using the image forming apparatus according to the above-described embodiment, the slope of the voltage change that shifts from the recovery-side peak potential for returning the toner to the toner carrier to the development-side peak potential for supplying the toner to the image carrier. 5 is a diagram showing a state in which the transmission density (TD) of the formed image changes as the value changes. In Experimental Example 2 using the image forming apparatus according to the above-described embodiment, the slope of the voltage change that shifts from the peak potential on the development side that supplies toner to the image carrier to the peak potential on the recovery side that returns the toner to the toner carrier 5 is a diagram showing a state in which the transmission density (TD) of the formed image changes as the value changes.

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 period t1 Peak on recovery side Potential time t2 Development side peak potential time Vdc DC voltage Vpp AC voltage peak / peak value Vp1 Recovery side peak potential Vp2 Development side peak potential

Claims (2)

An image carrier on which an electrostatic latent image is formed, and an electrostatic latent image formed on the image carrier by transporting toner having toner held on the surface of the toner carrier to a development area facing the image carrier. An image forming apparatus comprising: a developing device that develops a toner; and an AC power source that applies at least a rectangular AC voltage between the toner carrier and the image carrier. The density of an image to be formed is changed by changing a slope of a voltage change from a recovery-side peak potential returned to the toner carrier to a development-side peak potential for supplying toner to the image carrier. 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. An image forming apparatus comprising a developing device and an AC power source that applies at least a rectangular AC voltage between the toner carrier and the image carrier, and the image carrier is configured to carry toner at the rectangular AC voltage. Image formation characterized in that the density of the formed image is changed by changing the slope of the voltage change from the development-side peak potential supplied to the body to the recovery-side peak potential for returning the toner to the toner carrier. apparatus.

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