JPS63249185A - Cleaning device for image forming device - Google Patents

Abstract

PURPOSE:To obtain a stable cleaning effect by reducing the variation of the resistance value of a conductive fur brush to limit the value of the current flowing to an image carrier. CONSTITUTION:A fur brush 71 is made of conductive cellulose fibers whose fiber specific resistance value for 20-80% variance of the ambient relative humidity is 10<6>OMEGAcm-10<8>OMEGAcm. Conductive fibers whose fiber specific resistance is hardly affected by the variance of humidity are used to limit the current flowing to an image carrier 40 from the conductive fur brush 71 and a recovery roller 72. Since the current flowing to the image carrier 40 is limited and stabilized even at high humidity, damage of a photosensitive layer due to discharge is prevented to extend the life of the image carrier and a stable cleaning effect is obtained at a low cost.

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to a cleaning device for an image forming apparatus that cleans residual toner on the surface of an image carrier by applying a bias voltage to a conductive bristle brush. [Prior Art] Image forming apparatuses such as transfer-type electrophotographic copying machines generally use an image carrier, which is a rotating drum-type photoreceptor having a photoconductive photosensitive layer on the outer peripheral surface, and rotate this image carrier. An electrostatic latent image is formed on the photosensitive layer while the photosensitive layer is being moved, and the electrostatic latent image is developed with toner, and the resulting toner image is transferred to recording paper. After 1g copying, the residual toner on the outer peripheral surface of the image carrier is removed and cleaned by a cleaning device, and an electrostatic latent image is formed again, and a new image is transferred. In recent years, as a method for removing residual toner adhering to the outer circumferential surface of an image carrier, a conductive bristle brush is charged to the opposite polarity to that of the residual toner and rubbed on the outer circumferential surface of the image carrier. Cleaning devices have come into use that remove residual toner using electric attraction and the scrubbing force of a brush. Regarding a cleaning device that removes residual toner by rubbing the surface of an image carrier with a bristle brush to which a bias voltage is applied, a basic method of applying a bias voltage to a bristle brush is disclosed in Japanese Patent Publication No. 42-16590. Ta. Next, in Japanese Patent Publication No. 49-20227, in order to collect the toner adsorbed to the bristle brush, a roller to which a bias voltage is applied is brought into contact with the bristle brush to collect the toner, and the toner adhering to the roller is removed by the blade. A method of scraping it off was disclosed. Japanese Patent Publication No. 58-40349 discloses a method in which the bristles of a brush are made of conductive fibers. Subsequently, the results of various studies were disclosed, including the material of the conductive fibers that make up the bristle brush, the planting density, the resistance value of the fibers, the voltage value applied to the conductive bristle brush, and its control method.

[Problems to be solved by the invention]

In this type of push-free floating method that uses electrical attraction, a bias voltage with a polarity that causes residual toner to be attracted by electrostatic attraction is exclusively applied to the conductive bristle brush to create a potential difference between it and the image carrier. ing. If this potential difference is too small, the electrostatic attraction to the residual toner will be weak, and some of the toner will slip through the conductive bristle brush and cannot be completely removed, resulting in poor cleaning. Also, if this potential difference is too large, toner band 1! A so-called reverse adhesion phenomenon occurs in which the polarity is reversed and the particles are adsorbed onto the surface of the image carrier, and the particles cannot be completely removed, resulting in poor cleaning. FIG. 8 is a diagram showing the relationship between the bias voltage value applied to the conductive bristle brush and the amount of toner remaining after cleaning on the surface of the image carrier. In the figure, the horizontal axis shows the bias voltage value applied to the conductive bristle brush, and the vertical axis shows the amount of toner remaining after cleaning on the surface of the image carrier. The dashed line is low temperature and low humidity (10℃, 30%), the solid line is room temperature (22℃, 50%), and the dotted line is high temperature (33℃, 80%).
%) are shown. The optimal applied bias voltage values corresponding to each of these three types of humidity environmental conditions take different values. Therefore, preferably, it is necessary to take measures such as switching the applied bias voltage value depending on the ambient humidity value. FIG. 7 shows the relationship between resistivity and relative humidity of a conventional conductive bristle brush. In the same figure, the horizontal axis shows relative humidity, and the vertical axis shows specific resistance. As the humidity increases, the specific resistance decreases significantly. The value J has decreased by a factor of 102. The bristles of conventional conductive bristle brushes are mainly composed of conductive regenerated cellulose fibers.6 Therefore, compared to synthetic fibers, they are more susceptible to moisture, and the resistance value of these conductive bristle brushes decreases under high humidity. will decline significantly. FIG. 9 is a diagram showing the relationship between the applied bias voltage value and the inflow current value. In the same figure, the t% horizontal axis shows the applied bias voltage value to the conductive bristle brush, and the vertical line shows the current value flowing into the image carrier. (22℃, 50%), the dotted line indicates high temperature (33℃, 80%)
) are shown for each characteristic curve. The current increases abnormally when the temperature is high and humidity is high. In this way, under high humidity, a large current flows through the conductive bristle brush to the image carrier, which may cause deterioration of the photosensitive layer on the surface of the image carrier and a reduction in cleaning performance. This is because the electrical conductivity of the conductive bristle brush becomes too high and discharge occurs from the bristle brush onto the surface of the image carrier, deteriorating the photosensitive layer. In addition, this large current applied to the image carrier cleans the residual toner on the surface of the image carrier, but at the same time, the surface of the image carrier is non-uniformly charged, and the toner once collected by the conductive bristle brush is removed by this non-uniform charge. This has the drawback that a so-called reverse adhesion phenomenon occurs, resulting in poor cleaning. The present invention has been made in view of the above-mentioned drawbacks of the prior art, and it reduces the fluctuation range of the resistance value of the conductive bristle brush, limits the current value flowing into the image carrier, and is suitable for use under high humidity. Another object of the present invention is to provide a cleaning device for an ill image forming apparatus in which the electric current flowing from a conductive bristle brush to an image carrier is set to an appropriate value to provide a stable cleaning effect.

[Means to solve the problem]

The above purpose is to apply a bias voltage to a bristle brush, rub the image carrier to remove toner remaining on the surface of the image carrier, and further apply a bias voltage to a conductive roller in contact with the bristle brush. , in a cleaning device for an image forming apparatus that collects toner from a bristle brush, the bristle brush is made of conductive cellulose fiber, and the fiber specific resistance corresponds to a change in ambient relative humidity of 20% to 80%. This is achieved by a cleaning device for an image forming apparatus characterized in that the value range is 10'ΩC- to 10'ΩCII.

【Example】

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings of FIGS. 1 to 6. First, with reference to FIG. 2, the general functions of the multicolor image forming apparatus equipped with the cleaning device of the present invention will be explained. In FIG. 2, A is a reading unit, B is a writing unit, C is an image forming section, and D is a paper feeding section. Reading unit) In A, 1 is the platen is lath,
Original 2 is placed on this platen plus 1. Hara 8I2
is illuminated by fluorescent lamps 5 and 6 provided on a carriage 4 moving on a slide rail 3. The movable mirror unit 8 is provided with mirrors 9a and 9b, which are moved on the slide rail 3, and which combination of the first mirror 7 provided on the carriage 4 and the optical image of the original M42 on the platen glass 1 are transferred to the lens reading unit. 20. The carriage 4 and the movable mirror unit 8 are driven by a stepping motor 10 via a wire 15.
They are driven in the same direction at a speed of 1/2V. Standard white plates 18 and 17 are provided on the back side of both ends of the platen plus 1, and are configured so that a standard white signal can be obtained before the start of document reading scan and/or after the end of scan. A patch for toner density control is provided near the starting position of the carriage 4, so that a toner density standard signal can be obtained prior to reading and scanning the original W4. The lens reading unit 20 includes a lens 21 and a prism 2.
2. No. 1 reading board 24, red channel (hereinafter referred to as R
-ch) CCD 25, a second reading board 26, and a cyan channel (hereinafter referred to as C-ah) CCD 27. The original light image transmitted by the first mirror 7, mirror 9m, and mirror 9b is focused by the lens 21,
R-chccD2 provided on the -th reading board 24
5, and C-ch provided on the second reading board 26
The images are respectively formed on the light receiving surface of ccD2. As the fluorescent lights 5 and 6, commercially available warm white fluorescent lights are used to prevent emphasis or attenuation of specific colors based on the light source when reading a multicolor document, and 40 KHz to prevent flickering.
The tube is powered by a high-frequency power source and kept warm by a heater using a POSISTOR to maintain the temperature of the tube wall and promote heating. The image signals output from the R-chccD 25 and C-ehccD 27 are subjected to signal processing in a signal processing section. In the signal processing section, a color signal separated according to the toner color, which will be described later, is output and input to the writing unit B. In the writing unit) B, a laser beam generated by a semiconductor laser is rotated by a drive motor 30, rotated and scanned by a polygon 32, passes through an Fθ lens 36, has an optical path bent by reflection @37, and is applied to an image carrier 40. The light is projected onto the surface of the photoreceptor drum to form a bright line. When scanning begins, the beam is detected by the index sensor and modulation of the beam by the first color signal begins. The modulated beam scans over the image carrier 40, which has been uniformly charged in advance by a charger 41. A latent image corresponding to the first color is formed on the surface of the image carrier through the main scanning by the laser beam and the sub-scanning by the rotation of the image carrier 40. This latent image is formed by, for example, a developer loaded with red toner. The red toner image is developed by the container 43 and a red toner image is formed on the surface of the image carrier. The obtained toner image, while being held on the surface of the image carrier, passes under the cleaning device 70, which is separated and retracted from the surface of the image carrier, and enters the next copy cycle. The image carrier 40 is uniformly charged by a charger 41. Next, the second color signal output from the signal processing section is input to the writing unit (H), and is written on the surface of the image carrier in the same manner as the first color signal, forming a latent image. be done. This latent image is developed by a developer 44 loaded with a second color, eg, blue toner. This blue toner image is formed to overlap the red toner image already formed on the surface of the image carrier. A developing device 45 has black toner, and forms a black toner image on the surface of the image carrier based on a control signal generated by a signal processing section. AC and DC bias voltages are applied to the sleeves of these developing devices 43, 44 and 45, and no-yamping development is performed using the two-component developer, and development is performed without contacting the grounded image carrier 40. . The superimposed image of the toner image based on the first color signal, the toner image based on the second color signal, and the toner image developed using the black toner image developed in this way is transferred to the paper feeding section by the transfer pole 50. The image is transferred onto a recording paper 61, which is a transfer body, which is fed by a feeding belt 62 and a feeding roller 63. A jam (paper jam 9) detecting means (not shown) including a plurality of detection sensors is provided in the middle of the recording paper feeding path from the vicinity of the paper feeding cassette in the paper feeding section to the transfer pole 50 to detect jams. The occurrence position is displayed on a panel (not shown), and the image forming operation is temporarily stopped. The recording paper onto which the toner image has been transferred is separated from the image carrier by the separation pole 51, and further conveyed to a fixing device 853 where it is fixed, thereby obtaining a multicolor hard copy. A cleaning device fi70 shown in FIG. f51 acts on the image carrier 40 which has completed the transfer in this way to remove unnecessary toner remaining on the circumferential surface. FIG. 1 is a sectional view of a cleaning device showing an embodiment of the present invention. The cleaning device 70 includes a cleaning means 80 in which a conductive bristle plan 71, a collection roller 72, a blade 73, and a toner suction means 74'4P are housed inside a frame 75;
It is comprised of a contact/release means 81 that presses and releases the cleaning means 80 from the image carrier 40, and a drive means 82 that drives each cleaning member in the cleaning means 80. The cleaning means 80 is controlled by the contact/release means 81 to be in an operating state in which it is in pressure contact with the image carrier 40 and in an operating state in which it is out of contact with the image carrier 40. The conductive bristle brush 71 is a cylindrical brush in which conductive fibers 1178 are connected to a conductive pipe made of aluminum or the like together with a base fabric using a conductive adhesive. The conductive fibers 78 are woven into the base fabric in a so-called W weave 9 to increase the contact area with the conductive pipe. The planting density of the conductive fiber 4i78 in the pipe is 100
．． The conductive bristle brush of this embodiment has a length of 10 mm and a thickness of 5 mm.
~6 denier conductive fibers were used. FIG. 3 shows a method for measuring fiber resistivity. In Figure 3, 90 is a fiber resistivity measurement circuit, P and Q are electrodes, and 9
1 is a fiber to be measured, 92 is a 500V voltage power source, and 93 is an ammeter. The specific resistance of the fiber to be measured 91 is measured as follows. First, a filament-shaped fiber to be measured 9 is attached to W1 pole P and electrode Q.
The distance @1 between the 0 and 1 electrodes connecting 1 is 10cI11. A voltage of 500 V is applied between the electrodes P and Q by the voltage power source 92, and the current value I0 flowing at that time is read from the ammeter 93. The specific resistance ρ of the person to be measured J191 is calculated using the following formula. ρ=500/I. -S/1 Note that S is the total cross-sectional area of the fibers 91 to be measured, and is the product of the thickness and number of fibers. Conductive fiber Jli78 is conductive rayon rReeARJ
(manufactured by Unitika) was used. FIG. 6 is a characteristic diagram showing the relationship between relative humidity and fiber specific resistance. In the figure, the horizontal axis shows relative humidity, the vertical line shows fiber specific resistance, the solid line is the characteristic curve of the conductive fiber [RecARJ] of the example, and the dotted line is the characteristic dhM of the conventional conductive fiber. Conductive rayon “RecARJ” is suitable for use at room temperature and low humidity (22
The fiber specific resistance is 101 to 10'ΩC- at 20% at normal temperature and 106 to 10 at room temperature and high humidity (22°C and 80%).
7Ωe1m. The conductive bristle brush 71 is placed in pressure contact with the image carrier at a position spaced downstream from the pole 51 in the rotational direction of the image carrier. This press-contact state is a state in which the conductive bristle brush 71 and the image carrier 40 bite into each other by an overlapping amount of 21 in the radial direction. This conductive bristle blanket 71 is supplied with a direct current of 200 V by a first voltage power source 76.
A bias voltage of is applied. The collection roller 72 is a conductive metal roller. The collection roller 72 is placed in pressure contact with the brush at a position away from the pressure contact portion between the conductive bristle brush 71 and the image carrier 40 toward the downstream side in the direction of rotation of the brush. In this pressure-contact state, the collecting roller 72 and the conductive bristle brush 71
This is a state in which the two overlap in the radial direction by 2 to 41 points. A bias voltage of 400 to 600 V DC is applied to the collection roller 72 by a second bias voltage/piezo power source 7 . Play 1/73 is an elastic board made of hard urethane rubber with a thickness of 0.5 m. The blades 3 are in pressure contact with each other along the entire length of the collecting roller 72 in the direction of force, and scrape off the toner from the surface of the roller. The toner suction means 74 includes an electric suction 741 and a filter 742. This toner suction means 74
The suction 1m port has a conductive bristle brush 1 and a collection t1-27.
The brush 71 is provided so as to face the downstream portion of the brush 71 in the rotational direction near the pressure contact portion with the brush 71 . The conveyance screw 79 is provided near the bottom of the blade 73 and conveys the toner scraped off from the collection roller rough 2 to a toner collection tank (not shown). The cleaning means 80 is pressed against and released from the image carrier 40 by an eccentric cam 811 and a spring 812 fixed to the drive wheel 83. The eccentric cam 811 and the frame 75 of the cleaning means 80 are always urged by a spring 812 and are in pressure contact with each other, and as the eccentric cam 811 rotates, the conductive bristle brush 71 is pressed against the image carrier 40 and/or Or perform a deactivation action. The conductive bristle brush 71 and collection roller 72 in the cleaning hand #'i80 are rotated by a bell drive by a driving means 82 outside the frame 75. The cleaning device of the present invention has the above-described configuration, and its operation will be described below. While the cleaning means 80 is deactivated and retracted from the image carrier 40, the multicolor toner image completed after multiple exposures and development is transferred to the recording paper in the transfer process. be done. After the transfer process is completed, residual toner that has not been transferred and adheres to the outer peripheral surface of the image carrier 40 is
As the image carrier 40 rotates in the direction of the arrow, it reaches a position facing the conductive bristle brush 71. Immediately before this, the conductive bristle brush 71 is brought into pressure contact with the surface of the image carrier 40 by the action of the pressure contact/release means 81, and the residual toner that has reached the opposing position is rubbed and removed. At this time, the linear velocity of the outer peripheral surface of the image carrier 40 is 200
mm/sec. The linear velocity of the conductive bristle brush 71 and the image carrier 40 are equal, and the directions of rotation are opposite. Therefore, the residual toner on the image carrier 40 is rubbed by the conductive bristle brush 71 at a rubbing speed of 40 G-1/See. A bias voltage of 200 V DC is applied to the conductive bristle plan 71 by a first voltage source 76, and the conductive bristle plan 71 is charged with a polarity opposite to that of the residual toner. The conductive bristle brush 1 applies electrostatic attraction to the residual toner, causes the toner to be attracted to the conductive bristles, and removes the toner from the outer peripheral surface of the image carrier 40 . Conductive fibers 78 of this conductive bristle brush 71
The fiber specific resistance value under low humidity (20% relative humidity) is 1.
07ΩC-~101ΩC theory, and the fiber specific resistance value under high humidity (relative humidity 80%) is 106ΩC-~10'Ωe.
It is 1m. In other words, the fiber specific resistance value of the conductive fibers 78 does not show a large change even if the surrounding relative humidity increases or decreases 6 Therefore, even under high humidity, the fiber specific resistance value remains high and the image carrier It does not significantly increase the current flowing into the circuit. The toner adsorbed on the conductive bristle brush 71 is then transferred to the collection roller 7 which rotates while being pressed against the conductive bristle brush 71.
Recovered by 2. The conductive bristle brush 71 and the collection roller 2 have the same linear velocity in the vicinity of their outer circumferential surfaces, and their rotational directions are opposite. Therefore, the collection a-ra 72 slides the toner to be attracted by the conductive bristle brush 71 at a speed of 400 cm and 9 ec.
Rub with. The collection roller 72 is charged with a DC bias voltage of 400 V to 600 V by a second bias voltage power source 77 to have a polarity opposite to that of the toner. On the other hand, toner is collected by applying an electrostatic attraction force that is stronger than the attraction force of this brush. Then, the toner collected on the collection row 272 is scraped off from the surface of the roller by the blade 73 and falls onto the conveyance screw 79. On the other hand, a portion of the toner that has entered between the bristles of the conductive bristle brush 71 remains on the conductive bristle brush 71 without being collected by the collection row 272 . Conductive bristle brush 71 and collection row?
n minutes on the downstream side in the brush rotation direction near the contact portion with 72,
The conductive fibers 78 are released from the pressure of the collection roller 72,
The state of hair falling returns to the state of standing hair. The uncollected toner is separated from the conductive bristle brush 71 by the centrifugal force when returning to the raised state, and is scattered into the air. The scattered toner is collected by suction by a toner suction means 74, which has suction openings facing each other in the vicinity of the toner removal portion. FIG. 4 is a time chart of the sequence during multicolor image formation. In the first rotation, the image carrier 40, which has started to be charged some time before it starts rotating, starts image exposure using the first color signal and processes development I that is delayed by time X. receive. During the second rotation, the image carrier 40 undergoes the start of image exposure based on the color signal fjS2 and the development process (2) delayed by time y. Furthermore, 3
In the rotating eye, a multicolor toner image is formed through the development process (2) delayed by time 2 after the start of image exposure based on the black signal. Here, the times x, y, and Z are the time required for the position of the image carrier 40 (the leading edge of the image in the figure) to reach the position receiving each development process from the image exposure position, or the time within that time; Similarly, ``class'' is the time required to reach the transfer pole 50 from the image exposure position or the time less than that, and ``2'' is the time required to reach the cleaning device fi 70 from the image exposure position or the time less than that. Also, l is the time required for the entire image surface of the document to pass through a fixed point such as the image exposure or development processing position, and the actions of image exposure, development processing, transfer, cleaning, etc. It is designed to operate for a period of time with a little margin before and after. Next, the operation of the cleaning device during image formation will be described below. First, the image carrier 40 starts rotating, and the leading edge of the image ft'lJl area formed by the first color signal of the first original image reaches the opposite position of the cleaning device. The blower 71 is operating on the image carrier 40, and the image carrier 40 is cleaned. Unfinished! When the image area in which the untransferred toner image is formed passes through the opposite position of the cleaning device fi70, the conductive bristle brush 71 is deactivated from the image carrier 40, so that the untransferred toner image is removed. No disturbance. Immediately before the tip of the image area that has been transferred reaches a position facing the conductive bristle brush, the conductive bristle brush 71
starts operating the image carrier 40. Conductive bristle brush 71
The operation of the conductive bristle brush 7 is such that the rear end of the image area
It continues until it passes the opposite position of 1, and then it is canceled. Then, while the conductive bristle brush 71 is deactivated, multiple exposures and developments are performed to form the second image, and the cleaning process described above is repeated again to remove residual toner. FIG. 5 is a time chart of the sequence during monochrome image formation. Simultaneously with the rotation of the image carrier 40, the conductive bristle brush 71 starts rubbing and continues to clean the peripheral surface of the image carrier 40. During this period, monochrome image formation is performed one or more times, but the operation of the cleaning means 80 on the image carrier 40 is not released. They remain activated until they pass the position and are then deactivated.

【Effect of the invention】

In the cleaning device for an image forming apparatus of the present invention, a conductive fiber whose fiber resistivity is not easily affected by changes in humidity is used to limit the current flowing into the image carrier from the conductive bristle brush and collection roller. Therefore, it is possible to limit and stabilize the current flowing into the image carrier even under high humidity, thereby preventing damage to the photosensitive layer due to discharge, extending the life of the image carrier, and reducing the cost. Therefore, it is possible to provide a cleaning device for an image forming apparatus that has a stable cleaning effect at a low cost.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a cleaning device showing a -t+ embodiment of the present invention, FIG. 2 is a configuration diagram of a multicolor image forming apparatus, FIG. 3 is a circuit diagram showing a method for measuring fiber resistivity, and FIG. FIG. 5 is a sequence time chart when forming a multicolor image, FIG. 5 is a sequence time chart when forming a monochrome image, and FIG. 6 is a characteristic diagram showing the relationship between relative humidity and fiber resistivity.
Figure 7 is a characteristic diagram showing the relationship between relative humidity and specific resistance, Figure 8 is a characteristic diagram showing the relationship between brush applied bias and the amount of toner remaining after cleaning, and Pt59 diagram is a characteristic diagram showing the relationship between brush applied bias and current flowing into the image carrier. It is a characteristic diagram showing a relationship. 40... Image carrier 50... Transfer pole 51... Separation pole 70... Cleaning device 71... Conductive bristle brush 72. ...Recovery roller 73...Blade 74...Toner suction means 75...Frame 76...Constant current power supply means 78...・・Conductivity fiJl 79・・・・
- Conveyance screw 80...Cleaning means 81...Press/release means 82...Drive means A...Reading unit B...Writing unit C: Image forming department D: Paper feeding department Applicant: Konishi Roku Photo Industry Co., Ltd. Figure 3 Four electric nine needles Figure 6 Thick j=f Warm, 6 pull.

Claims (1)

[Claims] A bias voltage is applied to the bristle brush to rub the image carrier to remove the toner remaining on the surface of the image carrier, and a bias voltage is applied to the conductive roller in contact with the bristle brush to remove the toner from the bristle brush. In a cleaning device for an image forming apparatus that collects toner, the bristle brush is made of conductive cellulose fiber, and the fiber specific resistance value range corresponding to a change in ambient relative humidity of 20% to 80% is 10^.
A cleaning device for an image forming apparatus, characterized in that the resistance is 6Ωcm to 10^8Ωcm.