JPS6213663B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copying machine, and more specifically, it not only has functions such as normal charging, image formation, transfer, pre-cleaning, and erasing, but also has functions such as normal charging, image formation, transfer, pre-cleaning, and erasing. The present invention relates to a copying machine equipped with a developing and cleaning device capable of performing the following functions.

In a first embodiment, a photoconductor drum is used that is provided around its periphery with the required electrophotographic elements including a single developer-cleaner device. Second
In this embodiment, a photoconductor belt that can move back and forth is used. In any of the examples,
The cleaning cycle may be converted into a development cycle or may be activated following the formation of multiple images on the photoconductor surface. Conveniently, magnetic brush components are used to transport toner to the photoconductor surface during development and to remove residual toner from the photoconductor surface by contacting the photoconductor surface with developer during cleaning. constitute a contact surface for removing. A change in brush bias is provided during operation.

Representative prior art includes the following US patents.

USP.2484782, 2751616, 2752271, 2756676,
2815449, 2874063, 2911330, 2986442,
3108895, 3333572, 3357402, and 3424615.

Representative of the above is USP. 2874063, which describes magnetic functions for image development in electrostatic printing and describes the possible use of magnetic devices for cleaning purposes. Although it is suggested, no structure is shown to achieve the above objective.

USP. 2986442 describes an elongated electrosensitive belt that operates at one station to develop the image on the belt and a magnetic brush 24 that operates at a separate second station to remove residual developer from the belt.
An electrophotographic apparatus having the following is disclosed. However, this USP does not include a method for alternately energizing a common magnetic brush in contact with the photoconductive medium at a single station, and for developing or cleaning modes.
No means are suggested for applying the appropriate bias to the magnetic brush depending on which mode is required.

During the process of making a copy from an original document, with the important exception that according to the invention, a dual-purpose unit is provided for performing both developing and cleaning functions in a single station in a suitable temporal sequence. charging, imaging,
An electrophotographic device is provided with conventional functions for development, cleaning, transfer, precleaning and erasing. In the preferred embodiment shown herein, such a dual purpose unit is used to initiate the transfer of toner onto the photoconductor surface in the device during the development step and to remove residual toner from the photoconductor surface during the cleaning operation. The magnetic brush component includes a biasing means for setting a suitable bias to attract. As will be described in more detail, circuitry is provided for implementing a cyclic sequence that allows for the most efficient use of structures during multi-cycle operation.

A first embodiment includes a drum-shaped photoconductive structure, where the process of copying is associated with the rotation of a rotating drum and the movement of the drum past various stations during operation.

Instead, imaging is performed on the photoconductor drum during each cycle of drum rotation while making multiple copies of the original document, and up until the runout cycle or at other times, e.g. when an operator changes the original document. It is possible to postpone cleaning until such time as possible.

As previously mentioned, the second embodiment contemplates a photoconductor belt structure. Imaging may be a scanning method,
A lamp flash may be used to expose the entire imaged area at once. Operation with a belt photoconductor is similar to that described for a drum structure with alternate imaging and cleaning of the belt in successive cycles. Further, as with the drum embodiment, the belt may be imaged during each cycle of its travel, and cleaning may occur in cycles such as the runout cycle or at other convenient intervals. As detailed below, various combinations of biasing methods for magnetic brushes, toner particles, and developer mixtures may be provided in the apparatus for purposes of the present invention.

It is therefore an object of the present invention to provide an original document in which the various functions required in a process are carried out sequentially in time by connected integral parts of the apparatus which act as required during operation. To provide an electrophotographic device for making copies from.

Still other objects of the present invention include charging, imaging, developing,
It is an object of the present invention to provide an electrophotographic apparatus which requires cleaning, transfer, pre-cleaning and erasing of the image on the photoconductor surface, where at least the functions of development and cleaning are performed by common parts of the apparatus.

Another object of the present invention is to provide a magnetic brush developer and cleaner system for an electrophotographic machine that performs both functions in the machine as desired and when required.

Furthermore, the object of the present invention is to provide a magnetic brush component,
It is an object of the present invention to provide a development and cleaning device in an electrophotographic device having means for appropriately biasing a brush to perform either a development or cleaning function during operation of the device.

Another object of the present invention is to establish a temporal sequence of electrophotographic steps, thereby allowing alternate imaging and cleaning of the photoconductor surface, with cleaning immediately following development in successive cycles. The purpose of this invention is to provide a device with functions that enable various sequences.

In addition, it is an object of the present invention to make multiple copies during an uninterrupted imaging sequence, following this imaging sequence at a time typically used for copying operations, such as run-at time or other available time. It is an object of the present invention to provide an apparatus of the type described above having means for performing a cleaning operation of the entire imaging area on the photoconductor surface during periods when the photoconductor surface is not occupied.

Referring to FIG. 1, a typical electrophotographic reproduction apparatus is shown in connection with an embodiment of the present invention. A cylindrical drum 21 is rotatably mounted on a shaft 22,
The outer periphery 23 has a photoconductive insulating layer containing an organic or inorganic photoconductive material. Drum 21 is rotated to deliver photoconductive layers to various stations associated with the electrophotographic process. Various photoconductive materials are suitable for use, such as selenium, selenium-tellurium, anthracene, zinc oxide, etc. in resin binders.

The pre-exposure corona device 35 is maintained in the dark to deposit a charge on the photoconductive material. A document 27 is placed in position on transparent plate 29 and an image of the document is projected onto the surface of photoconductive insulating layer 23 by an illuminated scanning station 31 and optical system 33. The photoconductor is discharged at the portion 37 illuminated by the light to form a charged image corresponding to the document 27.
The image is then developed in a combined development and cleaning station 38 which serves to contact the charged image on the surface of photoconductor layer 23 with finely divided toner particles. In accordance with the apparatus of the present invention, this station 38 is a magnetic brush developer unit that serves as both a developer and a cleaner in the apparatus. At station 38a, a two-component developer composition is moved across the surface of the photoconductor layer. The developer composition consists of relatively large carrier particles and relatively small colored particles of heat fixable toner. The toner particles are attracted to and adhere to the charged areas of the photoconductive layer.

The rotating photoconductor surface is contacted by a cylindrical magnetic brush 49 (the length of which approximately corresponds to the width of the photoconductor layer on the drum) which is driven to rotate in the opposite direction.

At station 39, the toner image on the surface of the photoconductor layer is transferred to a sheet or web 41 of plain paper using a toner transfer corona unit 43. The paper is then separated from the photoconductor layer and passed through heating device 45 which fuses the toner image to the paper. If the transfer step is not 100% effective, toner particles will be left on the drum. The adhesion of residual toner particles to the photoconductor surface is reduced by the discharge of the precleaning corona device 47.

When used in the cleaning mode, brush 49 is rotated to brush the developer mixture against the photoconductor surface, which effectively removes any residual toner remaining on the drum surface.

FIG. 2 shows one form of cycle control for the drum-type device of FIG. The drum cycle unit 1 includes a charging circuit 2, an imaging circuit 3,
It provides outputs for gating the various circuits necessary for the copying process, including development circuit 4, cleaning circuit 5, transfer circuit 6, and optionally preclean and erase circuit 7. Operation is obtained via OR circuits 8 and 9. That is, cycles 1 and 3 sequentially charge, image, and
It can be seen that a control signal is provided through OR circuit 8 to gate development and transfer. Instead, cycles 2 and 4 only gate the cleaning circuit 5 and the preclean and erase circuit 7 during these cycles via the OR circuit 9. The set sequence includes imaging and development in cycle 1, cleaning in cycle 2, imaging and development in cycle 3, cleaning in cycle 4, and so on.

Bias on the magnetic brush also aids in its cleaning efficiency. Controlling the magnitude of the brush bias voltage during cleaning is a critical method of controlling the efficiency of the techniques presented herein. Means is provided for applying a bias voltage onto brush 49 that can vary depending on whether brush 49 is being used for development or cleaning. As an example, using a dark charge level of 650 volts and a light charge level of 150 volts, 200 volts is appropriate for development. The bias voltage needs to be increased even higher for cleaning.

It is further contemplated that a large number of copies, for example 200, can be imaged, developed, transferred, etc. from the original document in succession without intermediate cleaning of the image area. After the first copy is made, each subsequent copy is made by reimaging the remaining untransferred toner on the photoconductive material by means of precisely registering the image information. The first copy in such a process is slightly less dense than subsequent copies, but all copies are of good quality. After such a multiple copy process, there is a large amount of toner residue that must be removed from the photoconductor surface to avoid ghost images in the next process using another document. In such cases, a single runout cleaning cycle is required to remove all residue from the photoconductor surface and to prepare the machine for making subsequent copies from another document. The need for a runout cycle is determined when the required number of copies has been made, when the same or another original document is repositioned within the device by changing the exact alignment of the images, or similar conditions. can be determined by a suitable sensing device.

Some parameters considered to be useful in practice are shown below. The photoconductor surface was conditioned with a dark charge of 650 volts and a bright charge of 150 volts. For such charging, the magnetic brush was biased to 200 volts. Doctor Rod (doctor)
Various structures such as rod engagement, magnetic brush engagement, and fiber orientation were set at levels found to be optimal for development and cleaning. The carrier used in some cases is the Dupont 850.
It was approximately 450μ steel ball with a 3μ top coat of DuPont 852-201 Teflon enamel coated with a 2μ main coat of -201 Teflon. The toner used was polystyrene/n-butyl methacrylate 62.0 parts, maleic anhydride-polyhydric alcohol/rosin modified resin (Amberol 800,
Rohm & Haas) 28.5 parts, vinyl polystearate 1.5 parts, and carbon black 8.0 parts. Median value of toner particle size per weight % is 13.0μ
It was hot. Note that the developer material acts as an effective cleaning means even though it contains sufficient toner concentration to form dark, thick copies. Various other toner and carrier compositions may also prove equally effective.

With the apparatus arranged as shown, after the last copy of a given document process has been copied,
If a runout cycle with an on magnetic brush is used, acceptable copies can be obtained in multiple copy mode without a runout cycle between each copy.

Regarding cleaning after a process of multiple copies, the cleaning operation may be performed, e.g. once every 5 copies, rather than after the entire process of multiple copies has been performed.
The device can be configured to be used frequently depending on the timing and condition. However, as mentioned above, in order to obtain the best copy and avoid ghost images, it is always necessary to restore the photoconductor to its initial state for retaining image information each time an original document is loaded. be.

FIG. 3 shows another embodiment of the invention in which an electrophotographic device can be moved in a temporal relationship within the device to perform all of the various process steps in a manner comparable to that described above. Equipped with a photoconductor belt. As shown, the apparatus of FIG. 3 includes a developing and cleaning device 17 which performs a function comparable to that in the drum-type apparatus of FIGS. 1 and 2.

The reproduction apparatus includes a photoconductor belt 12 and has a main frame that supports various components that produce multiple copies of an original document at high speed. The original document is placed,
It is illuminated by a flash lamp in temporal relation to the movement of the belt 12. An optical system (not shown) including a mirror 13 and a lens projects an image of the original document onto an image plane 12a on the belt 12.

The apparatus in FIG. 3 includes various electrophotographic functions for making copies. These are a charging corona station 18, an imaging surface 12a, a developing and cleaning station 17, a transfer station 19, and a pre-cleaning corona station 20. Belt 12 is drum drive component 14
and 16 for rotation as shown by arrow 15. Paper supply 11 contains a number of sheets of paper that are fed by various devices, including belt 10, in temporal relation to the movement of belt 12 to transfer station 19 for image transfer. Following transfer, the images are fused by a fuser (not shown) and sent to a final station.

The sequence of development and cleaning station 17 in the belt version of FIG. 3 can be compared to the sequence in the drum version of FIG.

[Brief explanation of the drawing]

1 and 3 are diagrams of a copying machine using the combined developing and cleaning device of the present invention, and FIG. 2 is a diagram showing the cycle relationship regarding the photoconductor drum structure of FIG. 1.

Claims (1)

[Claims] 1. In an electrophotographic apparatus having means for charging, imaging and transferring a photoconductor, the electrophotographic apparatus is arranged to couple with said photoconductor only in a single station and in a first mode a developing and cleaning device comprising a magnetic brush and means for applying a bias to the magnetic brush for developing the image and cleaning the photoconductor in a second mode; and means for charging the photoconductor during the second mode; An electrophotographic apparatus comprising: a control device for applying a bias potential different from that in the first mode to the developing/cleaning device so as to inhibit the operation of the developing/cleaning device and perform a cleaning action.