JPS6317473A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate the influence of a last image pattern by arranging plural plate electrostatic discharging devices which are provided with a dielectric electrode and a discharging electrode across a dielectric and applies an alternating voltage to between them and a constant voltage to between the discharging electrode and a photosensitive drum to charge the photosensitive drum electrostatically, and saturating an electrostatic charging potential at a constant value. CONSTITUTION:Two - three discharging members 21 are so arranged successively as to charge the photosensitive body 1 electrostatically. The alternating voltage is applied from an alternating voltage applying means 27 to between a dielectric electrode 22 and the discharging electrode 23. The photosensitive drum 1 which moves relatively to the discharging members 21 as shown by an arrow A is on OPC photosensitive body on a conductive base 26. A bias voltage is applied from a bias voltage applying means 28 to between the conductive base 26 and discharging electrode 23. Thus, the alternating voltage is applied to between the dielectric electrode 22 and discharging electrode 23 to cause electrostatic discharging from the periphery of the discharging electrode 23 and generate sufficient positive and negative ions, and positive or negative ions are extracted selectively in an electric field based on the bias voltage to charge the photoconductor surface of the photosensitive drum 1 to specific polarity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus such as an electrostatic recording apparatus or an electrophotographic apparatus.

Oka JLII Previously, color image copying devices using multicolor electrophotography were 2
Methods 3 to 3 have been devised and commercialized, and the method shown in FIG. 1 is also one of the typical methods.

In this method, each of the first to fourth image forming apparatuses Pa, Pb,
Dedicated photosensitive drums 1a, lb, lc, for each Pc and Pd,
ld, and around it are dedicated MIfR forming sections 2a, 2b, 2c, 2d, developing sections 3a, 3b, 3c, 3.
d, transfer section 4a.

4b, 4C14d, cleaning parts 5a, 5b.

5C15d is arranged. First, the image forming device 7Pa of FF51 forms a latent image of the yellow component color of the original image on the photosensitive drum la by a known method, and then a developer containing yellow toner is used in the developing section 3a. A visible image is formed, and the yellow toner is transferred to the transfer member 6 by the transfer section 4a.

On the other hand, while this yellow image is being transferred, a latent image of magenta component color is formed in the second image forming device Pb, and then a toner image of magenta toner is obtained in the developing section 3b. When the transfer member 6 whose transfer has been completed at Pa is carried into the transfer member 4b of the second image forming apparatus Pb, this magenta toner image is transferred to a predetermined position on the transfer member 6.

After image formation is completed in the same manner for cyan and black, the images are fixed in the fixing section 7.

A multicolor image is obtained on the transfer member 6. After the transfer, each photosensitive drum is cleaned by cleaning sections 5a, 5b, and 5c.
, 5d, the residual toner is removed to prepare for the next latent image formation to be performed subsequently.

However, in this type of apparatus, each unit is arranged in a separate image forming apparatus in correspondence with each color, and three to four units of the same structure are required as described above.

Among these units, the charging device uses a wire diameter of 0.1m.
Corona charging devices are widely used that perform corona discharge by applying a high voltage to a tungsten wire with a length of about m.

However, such a corona charging device has the disadvantage that the wire is thin and easily damaged, and furthermore, the wire becomes dirty and uneven discharge occurs, resulting in non-uniform charging of the charged object.

Furthermore, it is necessary to maintain a certain distance between the wire and the conductive shielding member surrounding the wire, which limits the miniaturization of the corona charging device.

On the other hand, in this type of multicolor copying apparatus, when the charging polarity of the charging process is negative, a problem arises in that, as described above, the number of charging devices is large, and the amount of ozone generated is considerable.

Particularly when using OPC photoreceptors, which have become mainstream in recent years, negative charging is common, and countermeasures must be taken to deal with this problem.

Furthermore, a scorotron charging device, in which a grid electrode is added to a corona charging device, has become common because of the stability of the charging potential. Therefore, it is inevitable that the charging current will be larger than that of the corona charging device, and the amount of ozone generated will also inevitably increase.

From the above, it is desirable to introduce a charging device that can be miniaturized and generates less ozone.For example, an AC voltage is applied between electrodes that sandwich a dielectric material, and one electrode is Some devices generate positive and negative ions at the junction between the end face of the dielectric and the dielectric, and extract ions of a desired polarity using an external electric field.

(Hereinafter referred to as a plate charging device) FIG. 2 shows the basic configuration of this type of discharge member.
4, an induction electrode 22, and a radiation 71i'Ftli23.

Induction electrode 22 and radiation '21! An alternating voltage is applied between the electrodes 23 by an alternating voltage applying means 27, while the discharge member 2
The photosensitive drum l, which moves in the direction of arrow A relative to 1, is a photoconductor on a conductive base 26, and a bias voltage applying means 28 is provided between the conductive base 26 and the discharge electrode 23.
A bias voltage is applied by. By applying alternate voltages between the induction electrode 22 and the discharge chamber 8i23.

After causing a discharge from around the discharge electrode 23 and generating sufficient positive and negative ions, the discharge electrode 23 and the conductor base 26
The photosensitive drum 1 is charged by selectively extracting the positive or negative ions using an electric field caused by a bias voltage applied between the two.

Furthermore, the thickness of the dielectric 24 is changed (for example, the thickness is
00 end liter or less, preferably around 20 to 200 pg)
This allows for a lower applied voltage (e.g. approximately 1.5-2.5 KV peak-to-peak) compared to conventional corona charging devices.
A stable discharge can be obtained. Furthermore, the charging device can be made smaller than the conventional corona charging device.

In addition, this charging device is suitable for uniform charging because it is difficult to cause contamination of the discharge electrode, such as so-called wire contamination, which is caused by floating particles in the air adhering to the wire of a conventional corona charging device.

However, the present inventors installed such a plate charging device in an actual copying machine and formed an image. It was found that the phenomenon (referred to as a ghost phenomenon) tends to be relatively noticeable.

This ghost phenomenon can be removed by pre-charging exposure. However, as mentioned above, there is a strong demand for miniaturization in multicolor copying apparatuses in which three or four image forming apparatuses are arranged, and consideration must be given to reducing the number of component parts as much as possible.

Therefore, a charging device that does not require the use of pre-band fli exposure is desired.

Trowel! Another object of the present invention is to provide a discharge device that is simple and can suppress an increase in cost by simply improving existing components without installing a new mechanism such as pre-charging exposure.

11 1j According to the present invention, the present invention includes a photoreceptor, a charging means for charging the photoreceptor, and a means for image-wise electrifying the photoreceptor, and the charging means includes a dielectric material and a dielectric material sandwiched between the dielectric materials. Alternating voltage application means having a plurality of discharge members each having an induction electrode and a discharge electrode extending in the same direction, and further applying an alternate voltage between the induction electrode and the discharge electrode to generate ions in the vicinity of the discharge electrode; An image forming apparatus is provided, comprising an external electric field applying means that acts between the discharge electrode and the photoreceptor, extracts ions generated by the discharge, and charges the photoreceptor to a specific polarity. The generation of ghost images can be prevented.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. Although this embodiment has been described using a multicolor copying apparatus, it goes without saying that the present invention is not limited to these multicolor copying apparatuses, and can also be applied to monochrome copying apparatuses.

FIG. 3 is a sectional view showing an embodiment of the present invention. The apparatus of this embodiment has four sets of electrophotographic laser beam printer mechanisms built in as a plurality of image forming apparatuses. The main machine box of the apparatus, Pa, Pb, Pc, and Pd indicate four sets of image forming apparatuses arranged sequentially from right to left inside the main machine box 10.The conveyor belt drive roller 11 is rotationally driven by a drive source (not shown). and the conveyor belt 8 is suspended.

This conveyor belt 8 is composed of a Tetron ram mesh, and is moved by a driving roller 11 in the direction of the arrow shown in the figure. 13 is a paper feed mechanism located on the right side of the machine frame; 7
14 is an image fixing device disposed on the left end side, and 14 is an outlet for discharging the transfer member to the outside of the machine.

Each of the image forming apparatuses Pa, Pb, Pc, and Pd has substantially the same a structure itself. That is, these image forming apparatuses each have photoreceptor drums la, 8C, and 28d as image carriers that are rotationally driven in the directions of arrows around shafts 8a, 8b, and 8C28d.
1b, IC 11d, and chargers 15a, 15b, 15c, 1 sequentially arranged around the drum in the drum rotation direction.
5d, developing units 3a, 3b, 3c, 3d, transfer discharge g!
4a, 4b, 4C14d, cleaning device 5a, 5
b, 5c, and 5d, and laser beam scanners 16a, 16b, 16c, and lad arranged above the photoreceptor drum. The laser beam scanner has a semiconductor laser, a polygon mirror, an fO lens, etc., and receives an input of an electric digital pixel signal, and applies a laser beam modulated according to the signal to chargers 15a, 15b, 15c, and 15d for development. The drum surface is exposed by scanning in the drum generatrix direction between the drums 3a, 3b, and 3C13d.

Further, the developing device 3a of the first image forming apparatus Pa is filled with yellow toner, and the second developing device 3a is filled with magenta toner.
The third container contains cyan toner and the fourth container contains black toner. The laser beam scanner 16a of the first image forming bag Pa receives a pixel signal corresponding to the yellow component image of the color image, the second image forming device Pb receives a signal corresponding to the magenta component image, and the third image forming bag receives a pixel signal corresponding to the yellow component image of the color image. A signal corresponding to the cyan component image is input to the device PC, and a signal corresponding to the black component image number B is input to the fourth device Pd.

A cut sheet-like transfer paper 6 is transferred to a paper feeder a1 as a transfer member.
When the paper is inserted onto the feed guide 51 of No. 3, its leading edge is detected by the sensor 52, and this start signal causes the photosensitive drums la, l of each of the image forming apparatuses Pa, Pb, Pc, and Pd to be inserted.
b, lc, and ld start rotating. The drive roller 11 is also driven at the same time, and the conveyor belt 8 also begins to run in the direction of the arrow. The transfer paper 6 passes through a paper feed guide 57 and is fed onto the conveyor belt 8 . Thereupon, the transfer paper 6 receives corona discharge from the attraction charger 59 and is reliably attracted to the conveyor belt 8.

Furthermore, the leading edge of the transfer paper 6 is attached to each sensor Boa, 60b, 60.
When c and Sod are shut off, the signals sequentially start image formation on the pre-rotating photoreceptor drums la, lb, lc, and ld of each image forming apparatus Pa, Pb, Pc, and Pd. That is, the photosensitive drum la of the first image forming apparatus Pa carries a yellow image, the second apparatus Pb carries a magenta image, the third apparatus NPC carries a cyan image, and the fourth apparatus 21Pd carries a black image. are divided and formed.

The image forming principle in each image forming apparatus is already well known as the Carlson process, so its explanation will be omitted. Then, the transfer paper 6 is moved toward the fixing device 7 by the rotation of the conveyor belt 8 to the first to fourth image forming apparatuses i! tPa, Pb,
The transfer paper 6 is conveyed sequentially through the lower parts of Pc and Pd, and is transferred to the transfer paper 6 by the transfer dischargers 4a, 4b, 4c, and 4d of each device.
Each color is sequentially superimposed and transferred onto the surface of the image plane to synthesize a color image. When the transfer paper 6 passes through the fourth image forming device Pd, the charge is removed by a static eliminator 61 to which an AC voltage is applied, and the transfer paper 6 is separated from the conveyor belt 8.Next, the transfer paper 6 enters the fixing device 7 where one image is formed. The paper is then discharged from the machine through the outlet 14, and one print cycle is completed.

In this embodiment, the charging device includes two to three plate charging devices (discharging members) arranged so as to sequentially charge the photoreceptor, as shown in FIG. For ease of explanation, these charging devices and the power supply applied thereto are extracted and shown in FIG.

Three discharge members 21 are arranged with respect to the photoreceptor drum 1,
A dielectric material 24 and an induction electrode 22 . It has a discharge electrode 23. The discharge electrode 23 is linear and arranged substantially parallel to the center line of the induction electrode 22 in the width direction.

Alternate voltages are applied between the induction electrode 22 and the discharge electrode 23 by an alternate voltage application means 27.

On the other hand, the photosensitive drum 1, which moves in the direction of arrow A relative to the discharge member 21, is an OPC photosensitive member on a conductive base 26. A bias voltage is applied between the conductor base 26 and the discharge electrode 23 by a bias voltage applying means 28. At this time, the application of bias voltage is not limited to the discharge electrode 23,
The induction electrode 22 may also be used.

As a charging method, by applying alternate voltages between the induction electrode 22 and the discharge electrode 23, a discharge is caused from around the discharge electrode 23, sufficient positive and negative ions are generated, and the discharge electrode 23 and the conductor are An electric field caused by a bias voltage applied between the substrates 26 selectively extracts the positive or negative ions and charges the photoconductor surface of the photosensitive drum 1 to a specific polarity and a desired value.

In this embodiment, the bias voltage is -560■, and the alternating voltage AC1
, 4KV frequency 24KHz was applied.

FIG. 5 shows the charging characteristics in this case in comparison with the charging characteristics when one plate charging device is used.

The curve 48 is for this example, and the curve 42 is for the plate charging system.

As is clear from this figure, the surface potential of the photoreceptor drum approaches the saturated state widely while passing through the charging width 43.

It has been confirmed that by using such a plate charging device, the occurrence of the ghost phenomenon described in the explanation of the prior art can be prevented.

This is considered to be due to the following reasons.

As is clear from FIG. 5, in the charging device of the present invention, the charging width is 4
Between 3 and 3, the surface potential of the photoreceptor has already stabilized to a constant value. On the other hand, the surface potential of the photoreceptor after the cleaning process is different between the exposed area and the non-exposed area as shown in FIG. Since it is used after being saturated to a certain value, even if there is the above-mentioned potential difference, this potential difference is equalized while passing through the charging width, and as shown in FIG. I can't pick up the influence of.

On the other hand, in the case of one charging device, the surface potential of the photoreceptor is not saturated during charging @43, so this potential difference remains as it is. In other words, from the charging characteristics 42 in FIG. 5, in a single plate charging device, the respective potentials are added up, resulting in a charging potential as shown at 47 in FIG. 6, and an image pattern called a ghost occurs after development. According to the present invention, this can be prevented.

FIG. 7 shows another embodiment of the invention.

In this embodiment, the dielectric material 34 is made of an organic polymer material such as polyimide or tetrafluoroethylene, and is made into a single piece of wood to match the shape of the photosensitive drum to form a curved surface as shown.

Furthermore, the induction electrode 32 is integrated into a common electrode.

With this configuration, 1) Reduction in man-hours during manufacturing (v
The following advantages are brought about: 2) simplification of the charging device mounting method, and 3) simplification of maintenance. Furthermore, it was confirmed that charging characteristics similar to those of the previous embodiments can be obtained even with the configuration shown in the figure.

As described above, according to the present invention, an induction electrode and a discharge electrode are provided with a dielectric material sandwiched between them, and voltages are applied alternately between them, and a constant voltage is applied between the discharge electrode and the photoreceptor drum. Since a plurality of plate charging devices are arranged to charge the photoreceptor drum and the potential of the band '1 is saturated to a constant value before being used in the image forming apparatus, the photoreceptor potential corresponding to the previous image pattern is set before charging. There is no need to set up a new exposure or erase the image.
The influence of these previous image patterns can be prevented.

Furthermore, compared to a scorotron charging device, both the applied voltage and current are lower, and therefore the amount of ozone generated can be kept low. Particularly, the advantages of a multicolor copying apparatus having three or four image forming apparatuses as described in the embodiments of the present invention are significant, and the overall effect of the copying apparatus such as miniaturization of the power supply and reduction of the amount of ozone generation is achieved. You can expect it.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view illustrating a typical configuration of a multicolor copying apparatus. FIG. 2 is a diagram explaining the basic configuration of a plate charging device. FIG. 3 is a longitudinal sectional view illustrating the detailed configuration of an example of a multicolor copying apparatus in which the present invention is effectively used. FIG. 4 is a diagram illustrating the detailed configuration of the plate charging device according to the present invention. FIG. 5 is a diagram showing the charging characteristics of the plate charging device according to the present invention. FIG. 6 is a diagram showing the surface potential of the photosensitive drum when a charging device is used. FIG. 7 is a diagram illustrating another embodiment of the present invention. l... Photosensitive drum 22... Induction electrode 23... Discharge electrode 24... Dielectric 27... Alternating voltage power supply 28... Bias voltage power supply Fig. 1 Fig. 3 Fig. 5

Claims (1)

[Scope of Claims] A photoreceptor, a charging means for charging the photoreceptor, and a means for image-wise irradiating the photoreceptor, the charging means extending between a dielectric and the dielectric. comprising a plurality of discharge members each having an induction electrode and a discharge electrode, and further comprising an alternating voltage applying means for applying an alternate voltage between the induction electrode and the discharge electrode to generate ions in the vicinity of the discharge electrode; An image forming apparatus comprising an external electric field applying means that acts between an electrode and the photoreceptor, extracts ions generated by the discharge, and charges the photoreceptor to a specific polarity.