JPH0455869A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a suspended matter from getting into a corona discharging device and sticking to a grid electrode by providing a ground or a conductive member on which a bias voltage having the same polarity as a polarity for electrostatically charging a photoconductor is impressed between the grid electrode stretched on the aperture of the corona discharging device being an electrostatic charging means and the insulating block at both ends of a shielding member. CONSTITUTION:The position that toner, etc., leaking from the end of the elastic rubber blade 72 of a cleaner 7 is sent to both ends of a primary electrostatic charger 2 along drum wind 62 and gets into a gap between a photosensitive drum 1 and the charger 2 is an outer side than the end of the discharging aperture 23. The blowoff of ion wind 27 is increased at the end of the aperture 23 because of the existence of the conductive member 52 installed at both ends of the charger 2. Thus, a discharge quantity at both ends of the discharging aperture is increased and the strong blow of outside air into a space in the shielding member is weakened, then a foreign matter is prevented from getting into the corona discharging device.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a printer, and particularly relates to the structure of a charging section.

(Prior Art) Fig. 7 and Fig. 8 show a general corona discharge device that is used by being incorporated into an image forming device such as an electrophotographic device, and is equipped with a clid electrode as a discharge current control member in a discharge opening. 7 is a cross-sectional view, and FIG. 8 is a longitudinal front view. In other words, the side facing the rotating photoconductive drum 101 as the object to be charged is opened as a discharge opening 123. A conductive shield member 122 (for example, made of stainless steel) having a simple U-shaped crosswise direction, and a corona discharge electrode wire 12 as a corona discharge electrode stretched between insulating blocks attached to both ends of each shield member 122.
It consists of 4.

Reference numeral 125 denotes an airflow (normal outside air) inflow opening formed along the length of the top plate on the side opposite to the discharge opening side of the shield member 122. There are some that do not have any particular openings. Furthermore, a lid electrode wire 126 as a discharge current control member is provided at the discharge opening.

A positive or negative high voltage is applied to the corona discharge wire 124 by a high voltage power supply (not shown), the shield plate is grounded, and a bias voltage of an appropriate potential and the same polarity as the corona discharge wire 124 is applied to the lid wire 126 from the bias power supply. As a result, the gas (air) around the corona discharge wire 124 becomes ionized. Then, the charged particles move toward the discharge opening 123, give kinetic energy to the gas molecules at that time, blow W toward the discharge opening, generate system ions J1127, and the ion wind 127 causes the rotating photoconductor 101 to The surface is charged.

The ion wind 127 is blown out at each longitudinal portion of the discharge opening 123 of the shield member 122, but the wind pressure distribution of the ion wind 127 along the length of the discharge opening 123 is weaker at both ends than at the longitudinal center of the discharge opening. This is because the insulating blocks 128 that support the corona discharge wires 124 are present on both ends of the shield member 122, so that the discharge in the portions closer to the insulating blocks 128 becomes weaker. On the other hand, as the ions [127 are blown out, the inside space of the shield member 122 becomes negative pressure, so that outside air enters the inside space of the shield member 122 from the shield member opening 123 to replace the ion wind 127. In this case, the inflow of the outside air into the space inside the shield member 122 is not carried out in a substantially uniformly distributed manner at each part along the length of the shield member opening 123, but because both ends of the shield member 122 are insulator blocks 128, each Insulator block 12
Ion wind 127 in the shield member opening portion 123 near 8
Because the blowing wind pressure is weak, the outside air actually flows into the interior of the shield member 122 only through the opening portions 123 near the insulator block 128 on both ends of the shield member 122, as shown by arrow 129.

As a result, foreign matter floating in the outside air and foreign matter on the photoconductor are carried into the inner space of the shield member 123 at a higher rate due to the sucked air flow, and the discharge electrode 124 and the shield member 1
The rate of contamination of the inner wall surface of 22 and the lid electrode 126 becomes faster. In the case of a copying machine, the above-mentioned suction air fii, 129 at both ends of the discharge device removes some of the floating dust and floating developer inside the machine, some of the paper fibers of the copying material P, and residual developer on the photoconductor 101. , paper fibers, etc. are forcibly sucked up and enter the shield member 122, and the discharge electrode wire 124, the inner wall surface of the shield member 122, and the lid electrode 126 become dirty at an early stage.

The discharge electrode wire 124 and the inner wall surface of the shield member 122,
Foreign matter contamination on the lid electrode 126 is a major cause of uneven discharge, and in the case of a copying machine, it has a great negative effect on the image quality, so it is necessary to clean it frequently and keep it free from contamination6. For example, JP-A-57-188062 discloses a corona discharge device which is devised to suppress the external air suction phenomenon, thereby slowing down the rate of contamination and thus significantly reducing the frequency of cleaning. Further, as an improvement thereof, there is a method disclosed in Japanese Patent Application Laid-open No. 107359/1983.

These devices are installed on the top surface of the insulating block 128 at both ends of the discharge device, or a conductive member to which a bias voltage is applied is arranged to increase the amount of discharge at the end of the discharge device and to strengthen the ionic wind 127 at the end. This suppresses the inflow of outside air into the interior of the shield member 122 from both ends of the discharge opening, which is highly effective, and the image forming apparatus using such a corona discharge device operates well.

(Problems to be Solved by the Invention) The above-mentioned corona discharge device operates suitably, and an image forming apparatus using the corona discharge device similarly operates suitably, but the floating dust particles in one machine are It is not possible to completely prevent part of the material, part of the paper fibers of the copy material P, residual developer on the photoconductor, paper fibers, etc., from entering the shield member 122; If the amount of foreign matter is extremely large, uneven discharge will occur at an early stage due to foreign matter contamination of the discharge electrode wire 124, the inner wall surface of the shield member 122, and the lid electrode 126. FIG. 9 shows an example of an image forming apparatus using the above corona discharge device, and FIG. 10 is an enlarged view thereof. In such an image forming apparatus, the toner image formed on the rotating photoconductor 101 is transferred to the transfer means 1.
05, the toner remaining on the photoconductor drum 101 and some of the paper fibers of the copying material P adhering to the rotating drum are removed by a cleaning means 107.
The top of the photoconductor 101 is effectively cleaned by the cleaning method. However, it is difficult to completely seal both ends of the cleaning means 107, and some of the toner, paper fibers, etc. collected inside the cleaning means 107 leak out from the both ends. The photoconductor 101 is sent to the corona discharge device 102 along with a laminar airflow 162 called tram wind generated around the drum as the photoconductor 101 rotates. The amount of such toner and paper mix is larger than that normally floating in the image forming apparatus, and the amount of toner is particularly large, so even if the corona discharge device 102 is used, these toners and paper fibers can be In particular, since it is not possible to effectively prevent toner from entering the inside of the shield member 122, the discharge electrode wire 124, the inner wall surface of the shield member 122, and the lid electrode 126 become dirty more quickly, resulting in uneven discharge. A problem arose in that image quality deteriorated easily and cleaning had to be done more frequently.

Furthermore, in the case where the electrostatic latent image on the rotating drum is reversely developed after the toner is charged to the same polarity as the photoconductor 101, the surface potential of the photoconductor 101 after being charged is The toner whose absolute value potential is higher than the potential of the lid electrode 126 in the discharge device 102 and which is charged to the same polarity as the photoconductor 101 is transferred to the lid electrode 1 by the electric field created by the lid electrode 126 and the photoconductor 101.
26, the toner leaking from the end of the cleaning means 107 significantly adheres to the lid electrode 126. The toner adhering to the lid electrode 126 spreads inward from both ends of the corona charging device 102 and reaches the image forming area, and the lid electrode 126 in this area spreads inward from both ends of the corona charging device 102 and reaches the image forming area.
Since the photoconductor is covered with high-resistance toner, most of the corona discharge current that would normally flow into the lid electrode 126 flows toward the photoconductor 101, which increases the amount of charge in that area and reduces the density of the image. This phenomenon occurs very early. In addition, especially when using color toner as a developer, the color toner must have particularly excellent optical properties as well as good charging and fixing properties, but it is extremely difficult to achieve these properties at the same time. It is. Although the coloring material that imparts desired coloring to the toner has a very large influence on the charging properties of the toner, it is difficult to uniformly disperse the coloring material in the toner, and the charging properties of individual toners vary widely. Furthermore, it is extremely difficult to design a colorless and transparent charge control agent that does not impair the toner's natural color vision due to material limitations. It is extremely difficult to charge the toner uniformly, and it is necessary to sufficiently prevent the occurrence of toner with an inappropriate charge, such as toner with less than the appropriate charge, toner that is not charged, or toner that is charged to the opposite polarity. cannot be suppressed,
The behavior of uncharged toner or toner with less than the appropriate amount of charge is unstable, and most of it scatters or floats from the developing area and adheres to the discharge electrode 24, the inner wall surface of the shield, and the lid electrode 26. Furthermore, in the developing section, the toner charged to the opposite polarity is improperly developed and adhered to the electrostatic latent image forming area and the electrostatic latent image forming area on the photosensitive drum l, and many of these toners are It remains on the photoconductor 101 without being transferred to the transfer material P, and is removed from the photoconductor 101 by the cleaning means 107.

Therefore, the total amount of toner removed by the cleaning means 107 increases significantly, so that the cleaning means 107
leaks from the vq ends of the discharge electrode 1 of the corona charger.
24, the inner wall surface of the shield member 122, and the lid electrode 126
The amount of toner that stains the surface of the printer also increases significantly. When color toner is used as described above, the discharge electrode 124
A problem has arisen in that the image quality deterioration caused by dirt on the inner wall surface of the shield member 122 and the lid electrode 126 cannot be addressed at all with the normally allowed cleaning frequency.

The present invention has been made to solve the problems of the prior art described above, and its purpose is to prevent floating objects such as toner and paper fibers from entering the corona discharge device and adhering to the lid electrode. It is an object of the present invention to provide an image forming apparatus that can prevent such problems from occurring.

(Means for Solving the Problems) The present invention provides a charging means for uniformly charging a photoconductor, an exposure means for exposing the charged photoconductor to form an electrostatic latent image, and an electrostatic latent image. A developing means for reversing the image with a color developer charged to the same polarity as the electrostatic latent image, a transfer means for transferring the developed image to a transfer material, and a transfer means for removing the developer remaining on the photoconductor after transfer. a cleaning means for removing the photoconductor, the length of which the charging means in a direction perpendicular to the traveling direction of the photoconductor effectively acts is longer than the length of which the cleaning means effectively acts. Furthermore, the charging means is a corona discharge device, and the lid electrode stretched over the corona discharge opening and the insulator blocks at both ends of the shield member are each connected to the ground or the photoconductor on the top side of the block. The gist of the present invention is an image forming apparatus characterized by providing a conductive member to which a bias voltage of the same polarity as that for charging a body is applied.

(Function) Due to the presence of a conductive member that is grounded or applied with a bias voltage at both ends of the corona discharge opening, the amount of discharge at both ends of the discharge opening increases, resulting in a strong flow of outside air from both ends of the discharge opening into the space inside the shield member. The blow-in of the corona discharge device is prevented or significantly weakened to prevent foreign matter from entering the corona discharge device, and furthermore, since the width of the cleaning means is longer than the opening width of the corona discharge device, It is possible to prevent leaked toner and paper fibers, especially a large amount of toner, from entering the corona discharge device, and it is possible to prevent image quality deterioration due to the toner adhering to the lid electrode.

(Example 1) Next, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

The present invention can be suitably implemented in digital color electrophotographic copying machines and printers. Therefore, in this embodiment, a digital color electrophotographic copying apparatus, particularly a multicolor electrophotographic copying apparatus, will be described, but the image forming apparatus of the present invention is not limited to this. A digital multicolor xerographic reproduction device is illustrated.

Briefly explained with reference to FIG. 3, the multicolor electrophotographic copying apparatus includes a photoconductor, that is, a photosensitive drum 1, which is rotatably supported on a shaft and rotates in the direction of the arrow, and an image forming means is arranged on the outer periphery of the photoconductor. Placed. In this example, a corona discharge device according to the present invention for uniformly charging the photosensitive drum 1, that is, a charger 2, and a photosensitive drum The photosensitive drum 1 includes an exposure means 3 consisting of a laser beam exposure device or the like that forms an electrostatic latent image thereon, and a rotary developing device 4 that turns the electrostatic latent image on the photosensitive drum 1 into a visible image.

The rotary developing device 4 transports desired developing devices for magenta, cyan, yellow, and black to a position facing the outer circumferential surface of the photosensitive drum l by rotating the casing, The electrostatic latent image is developed, and the casing rotates once, thereby making it possible to perform full-color development of so-called four colors.

The visible image on the photosensitive drum, that is, the toner image, is transferred to the copying material P that is conveyed to the transfer means 5. The transfer means is a transfer drum 5 rotatably supported. After the toner image on the photosensitive drum l has been transferred, the toner remaining on the photosensitive drum l is collected from the photosensitive drum by a releaning means 7. The cleaning means 7 is a cleaner in which an elastic rubber plate 72 is brought into contact with the photosensitive drum 1 in one counter direction, and foreign matter on the photosensitive drum l such as collected toner is temporarily stored inside the cleaning means 7. After being collected, the waste toner is transported to a waste toner collection container (not shown in the figure) at any time.

The image forming process by the multicolor electrophotographic copying apparatus having the above-mentioned configuration will be briefly explained as follows. First of all,
- The photosensitive drum 1 is uniformly charged by the charger 2. In this example, it is assumed that the battery is negatively charged.
It is not particularly driven by negative polarity. In this embodiment, the crid bias potential of the negative charger 2 is -300V.
~-800V is applied, and the surface potential of the photosensitive drum 1 is approximately -400V to -950V accordingly. Subsequently, by driving the image exposure means 3, a blue color-separated electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 1, and the electrostatic latent image is charged to the same negative polarity as the photosensitive drum 1. Reversal development is performed using yellow toner.

On the other hand, the copy material P fed to the transfer drum 5 comes into contact with the toner image formed on the outer peripheral surface of the photosensitive tram 1 as the transfer drum 5 rotates, and the toner image is transferred. The image is transferred onto the copying material P by the operation of the charger 5b.

Toner remaining on the photosensitive drum 1 and paper fibers adhering to the photosensitive drum 1 are removed by the cleaning means 7, and the photosensitive drum 1 is subjected to the next color or the next image forming process. The above image formation is also repeated for each color of magenta, cyan, yellow, and black.

When the overlapping transfer of the visible images of four colors onto the copy material P is completed, the copy material P is separated from the transfer drum 1 and discharged to the outside of the machine via the heat roller fixer 6.

1 and 2 show a corona discharge device equipped with a conductive member, which is used in this embodiment according to the present invention. The corona discharge device has a lid electrode 26 to which a grounded or bias voltage is applied for corona current control in the corona discharge opening 23 of the conductive shield member 22 having a U-shaped cross section.

The lid electrode 26 is made of a stainless steel wire with a diameter of approximately 50 to 150 mm, and is supported and fixed under a predetermined tension.

Further, the discharge electrode wire 24 is stretched between insulating blocks 28 provided at both ends of the shield member 122. A conductive member 5 is provided between the insulating block 28 and the lid electrode 26.
The conductive member 52 is made of a thin metal plate made of aluminum, stainless steel, etc. and is arranged in the shape of the book surface of the insulating block 28.
The block 28 is held between the block 28 and the lid electrode 26 by the tension. Note that the conductive member 52 may be directly fixed to the block 28, or may be supported and fixed to the lid electrode 26 using a conductive adhesive.

FIG. 5 shows the discharge opening 23 of the corona discharge device as the negative charger 2 and the cleaner 7 in this embodiment.
The elastic rubber blade 72 and the length of the image forming area width on one side with respect to the center of the image forming area are the lengths of the image forming area width in the main stitching direction of the photosensitive drum 1, respectively. 23 is 153 m5, the rubber blade 72 of the cleaner 7 is 161 mm, and the width of the image forming area is 149 mm. It is structured to be long.

By adopting the above configuration, as shown in FIG. 4, toner and the like leaking from the ends of the elastic rubber blade 72 of the cleaner 7 are sent along the drum wind 62 to both ends of the charger 2, Although it enters the gap between the photosensitive drum 1 and the negative charger 2, its position is outside the end of the discharge opening 23. A strong ionic wind 27 is generated at the end of the discharge opening 23 by the conductive member 52 disposed at both ends of the charger 2.
The balloons are the insulating blocks 2 at both ends of the charger.
When passing through the gap between the charger 8 and the photosensitive drum 1, there is a very strong blowout toward the outside of the charger 2.
Even though the amount of toner leaked from the end of the cleaner 7 is very large, it does not enter the charger 2 through the discharge opening 23, and as a result, the toner and the like leaked from the end of the cleaner 7. Even though the amount of foreign matter such as toner is significantly larger than that of toner and other foreign matter that normally exists floating inside a copying machine, their intrusion into the charger 2 is prevented and the charger 2 is It was confirmed that stable discharge characteristics were maintained over a long period of time with very little staining over time, and in particular, there was no deterioration in image quality due to the toner adhering to the lid 26 and spreading and reaching the image forming area.

(Example 2) FIG. 6 shows another example of the corona discharge device used in the image forming apparatus according to the present invention. In this embodiment, the conductive member 52 is molded integrally with the lid electrode 26. The integrally molded member 72 of the conductive member 52 and the lid electrode 26 is made of stainless steel, for example, and is supported and fixed to the insulating blow 28 with a predetermined tension, and the portion corresponding to the discharge opening 23 is connected to the lid electrode 26. The unprocessed portions at both ends are etched to form a hole in an appropriate shape so as to function as a discharge opening 23.
It acts as a conductive member 52 to strengthen the blowout of the ion wind 27 at both ends. Grounding or a bias voltage having the same polarity as the photosensitive drum 1 is applied to the integrally molded member for corona current control.

The configuration of other parts of the image forming apparatus according to this example is the same as that of Example 1, and the same effects could be obtained.

(Embodiment 3) As another embodiment, as the cleaning means 7 of the image forming apparatus according to the present invention, for example, a structure in which a rotating fur brush is brought into contact with the photosensitive drum 1 or a structure in which an elastic blade 72 is used in combination is used. Also good.

(Embodiment 4) In each of the above embodiments, a digital multicolor electrophotographic copying machine has been described, but the image forming apparatus of the present invention is not limited to this; For example, similar effects can be obtained in image forming apparatuses such as monochrome electrophotographic copying machines, analog type copying machines, and electrophotographic printers.

(Effects of the Invention) As explained above, due to the presence of the conductive member that is grounded or applied with a bias voltage at both ends of the corona discharge opening, the amount of discharge at both ends of the discharge opening increases, and as a result, the shield member Strong blowing of outside air into the inner space is prevented or greatly weakened to prevent foreign matter from entering the corona discharge device, and furthermore, the width of the cleaning means is longer than the opening width of the corona discharge device. It is possible to prevent toner and paper fibers leaking from the end of the cleaning means, especially a large amount of toner, from entering the corona discharge device, and in particular, it is possible to prevent image quality deterioration due to the toner adhering to the lid electrode, In particular, it was possible to obtain an image forming apparatus that can maintain stable image quality over a long period of time even when color toner is used as a developer.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a corona discharge device according to an embodiment of the present invention, FIG. 2 is a diagram showing the discharge opening plane of FIG. 1, and FIG. 3 is a diagram showing an example of the image forming apparatus of the present invention. Figure 4 is an enlarged view of the primary charger and part of the cleaner in Figure 3, and Figure 5 shows the discharge opening of the corona discharge device as the primary charger in the embodiment of the present invention and the elastic rubber of the cleaner. FIG. 6 is a diagram showing the length of the blade and the width of the image forming area in the photosensitive drum generatrix direction. FIG. 6 is a diagram showing the discharge opening surface of a corona discharge device according to another embodiment of the present invention. FIG. A cross-sectional view of a conventional corona discharge device, FIG. 8, is a longitudinal sectional front view of FIG. 7. Explanation of symbols 1...Photosensitive drum (photoconductor) 2...-Charger 3...Laser beam exposure device 4...Rotary developing device P...Copying material 5...Transfer tram 72...Elastic rubber brake 7...Cleaner 21...Corona discharge device 26...Clid electrode 28...Insulating block 52...Conductive member door

Claims (2)

[Claims] (1) a charging means for uniformly charging a photoconductor; an exposure means for exposing the charged photoconductor to form an electrostatic latent image;
A developing means for reversing and developing the electrostatic latent image with a developer charged to the same polarity as the electrostatic latent image, a transfer means for transferring the developed image to a transfer material, and a developer remaining on the photoconductor after transfer. cleaning means for removing the agent, the length of the photoconductor in which the charging means effectively acts in a direction perpendicular to the traveling direction of the photoconductor is longer than the length of the cleaning means that acts effectively on the photoconductor; The charging means is a corona discharge device, and a lid electrode stretched over the corona discharge opening and an insulator block at both ends of the shield member are each connected to a ground or the photoconductor on the top side of the block. An image forming apparatus comprising: a conductive member to which a bias voltage of the same polarity as that for charging is applied. (2) The image forming apparatus according to claim 1, wherein a color developer is used as a developer for developing the electrostatic latent image.