JPH0123780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a charging device for charging a photoreceptor of an electrophotographic copying machine, for example.

(Prior Art) Conventionally, most electrophotographic copying machines have used a charger using a corona discharger.
Corona dischargers are dangerous because they use high pressure, pollute the atmosphere and equipment due to ozone generation, and are expensive. On the other hand, charging methods using rollers and brushes, which have been tried variously for a long time, do not damage the photoreceptor mechanically or electrically, and there is no method that can be applied to photoreceptors that are used repeatedly over several thousand times. Ta.

In recent years, a charging device that solves the above-mentioned drawbacks all at once has a resistance electrode with a flexible electrical resistor provided on the base, and a means for applying an electric field to this electrode. A charging device has been proposed which is characterized in that the above-mentioned contacts are brought into contact and charged. The charging device according to this proposal applies a DC voltage to an electrode placed on the back of a contact made of a brush-like material with a moderate electrical resistance, and at the same time applies an attenuated AC voltage. This is a completed charger. By using this charging device, very good results have been obtained in repeated charging over several thousand times.

Here, the resistance of the contact changes greatly depending on the external environment, especially humidity. Since this change in the resistance of the contact has a negative effect on the charging efficiency, it is necessary to maintain the resistance of the contact at a desired constant value. For this reason, in the charging device according to the above-mentioned proposal, the contact is constantly heated by a heater to prevent the contact from becoming damp, and the contact pressure of the contact that contacts the object to be charged is reduced by humidity. By installing a mechanism that allows the charging efficiency to change depending on the humidity, changes in charging efficiency due to the influence of humidity were prevented.

(Problems to be Solved by the Invention) However, with the above configuration, the charging device becomes a more complicated mechanism, and a constant supply of power is required for heating and humidity sensing, increasing running costs. There were some drawbacks.

Furthermore, if the resistance of the contactor decreases due to humidity, the current flowing into the photoreceptor increases, potentially shortening the life of the photoreceptor.

This invention was made in view of the above-mentioned circumstances, and its purpose is to enable charging without using a corona discharger, rollers, brushes, etc., and to prevent pollution of the atmosphere and equipment due to the generation of ozone. It is an object of the present invention to provide a charging device that can significantly extend the life of a photoreceptor, and that can uniformly charge a charged object by always bringing it into contact with a charged object under a constant pressure.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a contact that is formed flexibly and contacts a charged object, and a voltage is applied to the contact to touch the charged object. In the charging device, the contactor is swingably supported in a charging device including a charging application means for charging.

(Function) That is, by having the above-described structure, the present invention can be charged without using a corona discharger, roller, brush, etc., and can prevent atmospheric and equipment pollution due to ozone generation and photoreceptor damage. In addition to making it possible to significantly extend the lifespan,
The object to be charged can be uniformly charged by always contacting the object with a constant pressure.

(Embodiment) An embodiment of the charging device according to the present invention will be described in detail below with reference to FIGS. 1 to 7 of the accompanying drawings.

FIG. 1 shows the basic configuration of an electronic copying machine, where 1 is the main body. A document mounting table 2 is provided on the upper surface of the main body 1, and is configured to reciprocate by a drive motor 3 provided within the main body 1. A photosensitive drum 4a that rotates in synchronization with the movement of the mounting table 2 is pivotally supported approximately at the center of the main body 1. The photoreceptor drum 4a has a cylindrical base and a photoreceptor layer 4, which is provided on the outer peripheral surface of the base and is made of a zinc oxide-resin dispersant and serves as a charged member. Photoreceptor layer 4 and document mounting table 2
An exposure system 7 consisting of a lamp 5, a converging light transmitter 6, etc. is provided between the lamp 5, a focusing light transmitter 6, and the like, which irradiates the original on the original platen 2 and guides the reflected light to the photoreceptor layer 4 to form an image of the original. It is becoming possible to form an image of A developing device 8, a transfer device 9, a cleaning device 10, and a charging device 11, which will be described later, are arranged in this order from this image forming position along the clockwise rotational direction of the photosensitive drum 4a. The developing device 8 visualizes the latent image of the document formed on the photoreceptor layer 4 by the exposure system 7. The transfer device 9 is for transferring the original toner image formed on the photoreceptor layer 4 onto the copy paper p, and the cleaning device 10 is for removing toner remaining on the surface of the photoreceptor layer 4. Further, at the bottom of the main body 1, there is provided a paper feeding device 14 consisting of a removable cassette 12 for storing copy paper p, and a paper feed roller 13 for feeding the copy paper p. Further, the transfer device 9 includes a transfer belt 17 having an insulating property such as Mylar (trade name), which is stretched between a transfer roller 15 and a plurality of guide rollers 16, 16. The transfer belt 17 is in contact with a part of the outer peripheral surface of the photoreceptor drum 4a, and the transfer belt 17
A transfer charging device 18, which basically has the same structure as the charging device 11, and a cleaning blade 19 are in contact with each other. Further, a fixing device 20 and a delivery roller 21 are provided on the delivery end side of the transfer belt 17, and the copy paper p onto which the image has been transferred by the transfer device 9 is fixed, and then delivered to the tray 22. ing. Note that 23 is a control device.

The motor 3 is a motor equipped with an exhaust fan, and is designed to exhaust heat generated in the exposure system 7 as the motor rotates to the outside of the main body 1. The photoreceptor drum 4a is made of a binder type zinc oxide-resin dispersant sensitized with a dye such as rose bengal on the outer peripheral surface of a thin aluminum drum as a base with a thickness of 0.8 mm and a diameter of about 80 mm. Photoreceptor layer 4
It is formed by coating. moreover,
The cleaning blade 19 described above is for cleaning the transfer belt 17 by scraping off toner and the like adhering to the transfer belt 17.

Next, the charging device 11 will be explained.
2 to 5 show a charging device 11 of the present invention.
30 is a guide frame provided on the upper part of the photoreceptor drum 4a along the axial direction, and this guide frame 30 has U-shaped guide grooves 31 facing each other, 31 are provided. The guide frame 30 is fixed to the free end of an elastic support 33 made of a plate spring fixed to the frame 32 of the main body 1, and the guide frame 30 is supported so as to be swingable in the vertical direction by the elastic action of the elastic support 33. has been done.
A charger 34 is removably attached to the guide frame 30. That is, this charger 3
The charger base 35 of No. 4 is made of a resin material such as acrylic or ABS and is molded into a prismatic shape, and the back side thereof has hooking collars 36, 36 that are slidably engaged with the guide grooves 31, 31 of the guide frame 30. are integrally protruded. Furthermore, on the front part of the charger base 35, that is, the part facing the outer circumferential surface of the photosensitive drum 4a, a contactor 38 is superposed in a layered manner with an electrode 37 interposed therebetween. The electrode 37 is divided into a main electrode 37a provided at the center in the width direction of the contactor 38 and auxiliary electrodes 37b, 37b provided at both sides, and these electrodes have a predetermined electrical resistance, for example, 10 ³ to 10 3 .
It is made of conductive rubber with a thickness of 1 to 10 mm and a resistance of 10 ¹² Ω·cm. The contact 38 has a thickness of 1 mm and has a predetermined electrical resistance, for example, 10 ⁷ Ω·cm.
It is formed from a sheet 39 made of conductive rubber and a hair body 40 that is implanted with adhesive on the surface of a sheet 39 made of conductive rubber. The hair body 40 is made of straight fibers mixed with carbon (REC-A product name), and has a thickness of 1
~10d (denier), length 0.1~5mm, flocking density 50~
70 pieces/mm ² , higher electrical resistance than the above electrode 37
It is maintained at 10 ¹⁰ to 10 ¹² Ω・cm. The bristles 40 formed in this way have flexibility and are in light contact with the photoreceptor layer 4.

Furthermore, the main electrode 37a of the electrodes 37 is connected to an AC power source 42 of AC800V via a resistor 41, and is also connected to a DC power source 43 of DC700V. In addition, auxiliary electrodes 37b, 37b
are grounded to earth 45, 45 via capacitors 44, 44, respectively. Therefore, as shown in FIG. 4, the voltage applied to each electrode 37a, 37b, 37b can cut off the AC component from the main electrode 37a by the auxiliary electrodes 37b, 37b. With this configuration, as the photoreceptor drum 4a rotates, the bristles 40 on both sides of the contactor 38 that come into sliding contact with the photoreceptor drum 4a curl and become irregular as shown in FIG. 5 during charging. Even if a gap 46 is formed between the gap 46 and the photoreceptor layer 4, corona discharge will not occur in this portion, and damage to the photoreceptor layer 4 can be prevented. Note that even if the resistance value on both sides of the contactor 38 is made higher than the other parts, the AC component on both sides can be cut off as shown in FIG. 4 in the same way as described above, and corona discharge can be prevented. can.

Therefore, when copying a document onto the document table 2, by pressing the copy start button,
Each device can discharge the copy paper p on which the original copy image has been obtained to the tray 22 by a known operation. At this time, in the charging device 11, AC800V is applied to the electrode 37 as the photoreceptor drum 4a rotates.
DC700V is applied in a superimposed manner. Moreover, since the charger 34 is supported by the elastic support 33 so as to be able to swing elastically, the bristles of the bristles 40 of the contact 38 are applied uniformly and with a constant pressure to the surface of the photoreceptor layer 4. are in contact. Therefore, space charges generated on the photoreceptor layer 4 are prevented, and the photoreceptor layer 4 is uniformly charged. Furthermore, by supporting the charger 34 elastically and swingably by the elastic support 33 as described above, even if the photoreceptor drum 4a rotates eccentrically, the photoreceptor drum 4a follows and swings. This embodiment has the advantage that mounting accuracy of the body drum 4a and the charger 34 is not required.

6 and 7 show a second embodiment of the present invention, in which a guide frame 3 to which a charger 34 is attached is shown.
0 are provided with shafts 47, 47 protruding from both ends of the shaft 47, 47 having their axes centered at the center in the width direction, and these shafts 47, 4
7 are connected to elastic supports 48, 48 made of coil springs connected to the frame 32 of the main body 1, so that the charger 34 is suspended elastically and swingably. With this configuration, the charger 34 can swing freely not only in the vertical direction but also in the longitudinal direction and the width direction, so that the contactor 38 can uniformly contact the surface of the photoreceptor layer 4 with a constant pressure. Become.

〔Effect of the invention〕

As described above, the present invention can perform charging without using a corona discharger, roller, brush, etc., and can significantly prolong the life of the photoreceptor and avoid contaminating the atmosphere and equipment due to the generation of ozone. Moreover, the contactor can be brought into contact with the object to be charged uniformly and always with a constant pressure, uneven charging can be prevented, and mounting accuracy of the object to be charged and the charger is not required. Also, the contact
Since voltages of AC and DC components are applied and the AC component on at least one side of the contact is cut off to charge the object to be charged, the state of one side of the contact when charging is applied. Even if a gap is formed between the charged body and the charged body due to damage, corona discharge will not occur in this portion, and damage to the charged body can be prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram when the charging device of the present invention is adopted in an electronic copying machine, FIGS. 2 to 5 show a first embodiment of the present invention, and FIG. 2 is a front view. , FIG. 3 is a schematic configuration diagram showing the voltage applying means, FIG. 4 is a graph diagram showing voltage distribution, FIG. 5 is an explanatory diagram of the operation, and FIG. 6 is a front view showing a second embodiment of the present invention. , FIG. 7 is a side view as well. 4... Photoreceptor layer (charged body), 34... Charger,
37... Electrode, 38... Contact, 42, 43...
Power supply (applying means).

Claims (1)

[Claims] 1. A contact that is formed flexibly and is swingably supported by an elastic support and contacts a charged object, and a voltage of an AC component and a DC component is applied to this contact, and at least one side of the contact is A charging device comprising an application means for applying an AC component in a cut state to charge an object to be charged.