JPH01257991A - Method and device for electrophotographic image formation - Google Patents

Abstract

PURPOSE:To clean a photosensitive body excellently by converting inverted toner in untransferred toner into its normal polarity and then sending the toner to a brush body. CONSTITUTION:Untransferred inverted toner on the side of the photosensitive body is attracted onto the surface of a dielectric member 11a with an electric field produced by the corona discharging of a transfer charger 11b and the toner on this dielectric is corrected into the normal polarity with the electric field produced by the corona discharging of a polarity correcting charger 11c. Further, the toner which is corrected into the normal polarity is repelled with the electric field produced by the transfer charge 11b and transferred reversely to the side of the photosensitive body, and the toner is sent to a brush cleaning device 9. Consequently, the removal of the untransfer toner by the brush cleaning device 9 is securely performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an electrophotographic image forming method and apparatus, and in particular, to cleaning the surface of the photoreceptor by removing untransferred toner remaining on the photoreceptor after transfer using a brush cleaning device. The present invention relates to an electrophotographic image forming method and apparatus.

(Prior art) In various image forming apparatuses that use electrophotography, such as copying machines, printers, and facsimiles, a toner image developed and formed on a photoreceptor is transferred onto a recording paper in a transfer section, and the toner image is transferred to a photosensitive member after transfer. Untransferred toner remaining on the photoreceptor is removed by a cleaning device, thereby cleaning and initializing the surface of the photoreceptor. As the above-mentioned cleaning device, a device equipped with a blade made of rubber or the like is widely adopted, but in full-color image forming apparatuses, high-speed image forming apparatuses, etc., the above-mentioned cleaning device is As such, brushes equipped with brush bodies such as magnetic brushes and fur brushes are often used.

In the above-mentioned brush cleaning device, untransferred toner is removed by the mechanical scraping force of the brush body, and the brush body is charged to the opposite polarity to the untransferred toner. The cleaning process is performed using electricity. Among these, the magnetic brush cleaning device utilizes the electrostatic force due to the [1-electrostatic charge of carrier particles chained in a brush shape, while the fur brush cleaning device utilizes the electrostatic force due to the triboelectric charge of the brush body made of resin bristles, etc. is being used.

However, in such a brush cleaning method and device, if toner with reversed polarity is generated in the untransferred toner to be removed, the brush cleaning device cannot electrostatically attract and clean the reversed toner, There is a problem in that the photoreceptor is not sufficiently cleaned. If the reversed toner that is not cleaned is left as it is, toner filming will occur on the surface of the photoreceptor, causing problems such as background stains and shortening the life of the photoreceptor. Therefore, in conventional devices, the surface of the photoreceptor is periodically wiped with a solvent, or the photoreceptor itself is replaced after a certain period of use. There is also a fur brush made of hard material that is used to scrape off adhered substances on the surface of the photoreceptor, but when this is done, the film around the photoreceptor is scraped away and becomes thinner, resulting in There are problems in that the charged potential of the body decreases and the photosensitivity deteriorates.

(Objective) Therefore, it is an object of the present invention to provide an electrophotographic image forming method and apparatus that can electrostatically attract even reversed toner in a brush cleaning device and can effectively clean a photoreceptor. With the goal.

(Structure) In order to achieve the above object, the invention stated in claim 1 electrostatically charges the untransferred toner remaining on the photoreceptor after transfer using a brush body charged to the opposite polarity to the untransferred toner. In an electrophotographic image forming method in which the surface of a photoconductor is cleaned by adsorption and removal, the reversed toner in the untransferred toner is converted to the normal polarity before cleaning the photoconductor with the brush body. It has a process in which it is sent to the brush body at the top.

In an electrophotographic image forming method including such a step, the brush cleaning step is executed after the polarity of the untransferred toner is corrected to the normal polarity by the above step, so that the removal action of the untransferred toner in the brush cleaning step is It will be done well.

In addition, the invention described in claim 2 of the present application removes untransferred toner remaining on the photoreceptor after transfer by electrostatically adsorbing it with a brush body charged to the opposite polarity to that of the untransferred toner. In an electrophotographic image forming apparatus equipped with a brush cleaning device for cleaning the surface, reverse toner among untransferred toner is adsorbed to an area downstream of the brush cleaning device in the photoreceptor conveyance direction, and the adsorbed reverse toner is The structure includes an intermediate transfer body that converts the polarity to the proper polarity and then sends it to the brush cleaning device.

In an electrophotographic image forming apparatus having such a configuration, the untransferred toner is corrected to the correct polarity by the intermediate transfer member before being sent to the brush cleaning device, so that the toner removal action by the brush cleaning device is ensured. It will be done.

Furthermore, in the invention described in claim 3 of the present application, the intermediate transfer member includes an endless dielectric member arranged close to the surface of the photoreceptor and conveyed in a fixed direction, and a photoreceptor of the dielectric member. A transfer charger that forms an electric field that adsorbs the inverted toner on the photoreceptor to the surface of the dielectric member and reversely transfers the toner with corrected polarity to the photoreceptor in the vicinity of the photoreceptor; It has a configuration including a polarity correction charger that converts the reversed toner adsorbed onto the surface to the normal polarity.

In an electrophotographic image forming apparatus having such a configuration, the untransferred reversed toner on the photoreceptor is attracted onto the surface of the dielectric member by the electric field formed by the corona discharge of the transfer charger, and this dielectric The toner on the body is corrected to the normal polarity by the electric field formed by the corona discharge of the polarity correction charger, and the toner corrected to the normal polarity is further repelled by the electric field formed by the transfer charger and is exposed to light. The body is transferred back to the crocodile and sent to a brush cleaning device. As a result, the brush cleaning device can reliably remove untransferred toner.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a copying machine as an example of an image forming apparatus to which the present invention is applied. As shown in this figure, around the selenium photoreceptor drum 1, there is a charging charger 2 for uniformly charging the surface of the photoreceptor drum 1 along the conveyance direction of the photoreceptor drum 1, and a charged charger 2 for uniformly charging the surface of the photoreceptor drum 1. an exposure optical system 3 that irradiates and exposes the surface of the photoreceptor drum 1 with a light image to form an electrostatic latent image; a developing device 4 that supplies toner to the electrostatic latent image to develop it and visualize it; A transfer charger 6 that transfers the toner visible image onto a recording paper conveyed by a registration roller 5 or the like, a separation charger 7 and a separation claw 8 that separate the transferred recording paper from the photoreceptor drum 1, and a photoreceptor after transfer. A magnetic brush cleaning device 9 that removes untransferred toner remaining on the surface of the drum 1 and cleans the photoreceptor drum 1; and a static elimination lamp 10 that removes electric charges remaining on the surface of the photoreceptor drum 1 after transfer.
etc. are arranged.

To form an image using such a copying machine, first, the surface of the photoreceptor drum 1 is uniformly charged to a positive polarity by the corona discharge action of the charging charger 2, and then the surface of the photoreceptor drum 1 is charged. A light image is irradiated by the exposure optical system 3.
It is exposed to light to form a positive electrostatic latent image. Then, negatively charged toner is supplied from the developing device 4 to the formed electrostatic latent image to perform development, and the resulting toner visible image is transferred onto the recording paper by the corona discharge action of the transfer charger 6. transcribed. The transferred recording paper is separated from the photosensitive drum 1 by the separation charger 7 and the separation claw 8, and then sent to a fixing device (not shown) where the image is fixed, and then discharged outside. Further, the untransferred negative polarity toner remaining on the surface of the photoreceptor drum 1 without being transferred is removed by a magnetic brush cleaning device 9 in which positively charged carrier particles are raised in the form of a brush on a sleeve 9a. The particles are electrostatically attracted and removed, thereby cleaning the surface of the photoreceptor drum 1. In addition, the above-mentioned magnetic brush cleaning device 9
A positive bias voltage is applied to the magnetic brush supporting sleeve 9a, and the electric field formed by this bias voltage prevents toner from adhering to the photosensitive drum 1.

Furthermore, an intermediate transfer member 11 is installed in an upstream region of the magnetic brush cleaning device 9 in the direction of conveyance of the photoreceptor, which adsorbs toner particles whose polarity has been reversed to positive in the untransferred toner. This intermediate transfer body 11 adsorbs the positive polarity inverted toner to the intermediate transfer body 11 and converts the toner to the regular negative polarity, and then transfers the toner corrected to the regular negative polarity to the magnetic brush cleaning device 9. It is equipped with a function to send data to That is, as shown in FIG. 2, the intermediate transfer body 11 includes a dielectric member 11a disposed close to the surface of the photosensitive drum 1.
is provided. This FAN body member 11a is formed by forming a sheet material such as polyester film or polyvinylidene fluoride into a hollow endless drum shape, and is transported in a fixed direction indicated by an arrow by a drive device (not shown). It has become. Further, the dielectric member 11
A transfer charger 11b is installed in the inner area of a so as to face the photosensitive drum 1 with the dielectric member 11a interposed therebetween. This transfer charger 11b is connected to the photosensitive drum 1.
Corona discharge is performed to form an electric field that transfers and attracts the untransferred toner whose polarity has been reversed to positive on the surface of the dielectric member 11a. Further, in the dielectric member 11a, a polarity correction charger 11C is provided in a region opposite to the transfer/adsorption region of the positive polarity reversal toner, which is located opposite to the outer surface of the dielectric member 11a. is located. This polarity correction charger 11C performs corona discharge so as to form an electric field that converts the inverted positive polarity toner adsorbed onto the surface of the dielectric member 11a to the regular negative polarity. Furthermore, the polarity correction charger 1 is provided on the inner side of the dielectric member 11a.
A ground electrode 11d is arranged to face 1c.

In the apparatus of this embodiment, the following cleaning process for untransferred toner is performed.

First, untransferred toner remaining on the surface of the photoreceptor drum 1 after the transfer by the transfer charger 6 is
In addition to the regular negative polarity toner, a small number of positive polarity reversal toner particles are present. The positive polarity reversal toner particles are sent to the opposing portion of the intermediate transfer member 11 by the conveyance force of the photoreceptor drum 1, and there, due to the corona discharge action of the transfer charger 11b, the surface of the drum-shaped dielectric member 11a of the intermediate transfer member 11 is It is transferred and adsorbed onto the surface. The positive polarity reversal toner particles transferred and adsorbed onto the surface of the dielectric member 11a are
The polarity correction charger 1 is
1G, where the polarity correction charger 1
By the corona discharge action of 1c, it is charged to the normal negative polarity and corrected. Further, as shown in FIG. 3, the toner particles whose polarity has been corrected are transferred again to the opposite portion of the transfer charger 11b by the conveying force of the dielectric member 11a, and there, the corona of the transfer charger 11C It receives a repulsive action based on the negative electric field formed by the discharge action. Then, the toner particles after the above correction are reversely transferred to the photosensitive drum 1 by this repulsive force. That is, in the installation portion of the transfer charger 11b, toner particles are mutually transferred between the photosensitive drum 1 and the dielectric member 11a.

Through this polarity correction step of the positive polarity reversal toner particles, all the untransferred toner particles on the photoreceptor drum 1 are unified to the normal negative polarity, and in this state, they are directed toward the magnetic brush cleaning device 9. sent.

Therefore, the magnetic brush cleaning device 9 can reliably remove untransferred toner, and as a result, the cleaning process of the photosensitive drum 1 can be performed satisfactorily.

Note that it is also possible to use an AC power source as the power source for the polarity correction charger 11G. In this case, not only the reversed toner particles but also the regular toner particles are transferred to the dielectric member 11a.

If this is done, it is equivalent to removing AC static electricity from the dielectric member 11a, and the dielectric member 11a will not be charged more strongly than necessary. Therefore, dielectric member 1
It is possible to weaken the discharge output of the polarity correction charger 11c that charges the surface of the photosensitive drum 1a, and even when the gap precision between the photosensitive drum 1 and the dielectric member 11a is poor, uniform transfer and reverse transfer can be performed. You can get the advantage of being able to

Further, in the above embodiment, a cleaning device equipped with a magnetic brush is employed, but the present invention can be similarly applied to cleaning devices equipped with a fur brush or other cleaning devices.

(Effects) As described above, the invention in claim 1 provides a method for cleaning the brush body so that the brush cleaning step is performed after the untransferred toner remaining on the photoreceptor after transfer is corrected to the normal polarity. Before the photoreceptor cleaning process, the reversed toner in the untransferred toner is converted to the normal polarity before being sent to the brush body. Therefore, the reversed toner is also statically removed in the brush cleaning device. The toner can be electrostatically attracted, and the photoreceptor can be cleaned well and toner filming can be prevented from occurring.

In addition, the invention as set forth in claim 2 provides an inversion of the untransferred toner in an area downstream of the photoreceptor conveyance direction of the brush cleaning device, so that the untransferred toner is corrected to the normal polarity before being sent to the brush cleaning device. Since an intermediate transfer body is installed which adsorbs toner and converts the adsorbed reversed toner into the normal polarity before sending it to the brush cleaning device, the reversed toner can also be electrostatically attracted by the brush cleaning device. This makes it possible to effectively clean the photoreceptor and prevent toner filming from occurring.

Furthermore, the invention according to claim 3 provides an endless dielectric member disposed close to the surface of the photoreceptor so as to correct the polarity of the toner particles after the reverse toner is once attracted to the intermediate transfer member. On the other hand, a transfer charger that forms an electric field that attracts the reversed toner to the surface of the dielectric member, and a polarity correction charger that converts the reversed toner adsorbed onto the surface of the dielectric member to the normal polarity are installed. Therefore, while correcting the polarity of the reversed toner, the corrected normal polarity toner can be reversely transferred and returned to the photoreceptor again. Therefore, the reversed toner can also be electrostatically attracted by the brush cleaning device, and the photoreceptor can be cleaned well and toner filming can be prevented from occurring.

[Brief explanation of the drawing]

FIG. 1 is an explanatory side view showing a copying machine as an example of an image forming apparatus to which the present invention is applied, FIG. 2 is an enlarged explanatory view of the installation part of the intermediate transfer body, and FIG. FIG. 7 is an enlarged explanatory diagram showing a corrected toner reverse transfer operation. 1... Photosensitive drum, 6... Transfer charger, 9
...Magnetic brush cleaning device, 11...Intermediate transfer body, 11a...Dielectric member, 11b...Transfer charger, 11c...Polarity correction charger. (% l)

Claims (1)

[Claims] 1. After transfer, untransferred toner remaining on the photoreceptor is electrostatically attracted and removed by a brush body charged with the opposite polarity to the untransferred toner, thereby cleaning the surface of the photoreceptor. The electrophotographic image forming method as described above may further include a step of converting the reversed toner in the untransferred toner to a normal polarity and sending it to the brush body before cleaning the photoreceptor with the brush body. Characteristic electrophotographic image forming method. 2. Equipped with a brush cleaning device that electrostatically adsorbs and removes untransferred toner remaining on the photoreceptor after transfer with a brush body charged to the opposite polarity to the untransferred toner, thereby cleaning the surface of the photoreceptor. In an electrophotographic image forming apparatus, reversed toner among non-transferred toners is attracted to an area upstream of the photoconductor conveyance direction of the brush cleaning device, and the reversed toner that has been attracted is converted to a normal polarity before being removed by a brush. An electrophotographic image forming apparatus comprising an intermediate transfer body that is sent to a cleaning device. 3. The intermediate transfer body includes an endless dielectric member arranged close to the surface of the photoconductor and conveyed in a fixed direction, and a portion of the dielectric member close to the photoconductor that transfers the reversed toner on the photoconductor. a transfer charger that forms an electric field to reversely transfer the toner that has been attracted to the surface of the dielectric member and whose polarity has been corrected to the normal polarity onto the photoconductor; 3. The electrophotographic image forming apparatus according to claim 2, further comprising a polarity correction charger for converting the polarity to a normal polarity.