JPH07122776B2 - Image carrier cleaning device - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a cleaning device for removing residual toner on an image carrier in an electrophotographic image forming apparatus.

BACKGROUND OF THE INVENTION

As a cleaning means in electrophotography, there are many cleaning means in which a blade member, which is said to have the highest cleaning efficiency, is arranged on the peripheral surface of the image bearing drum, although the structure is simple. In blade cleaning, the toner detached from the image carrier drum is behind the blade installation position (downstream side)
There is no re-adhesion in the area of, and the effect is extremely high even though the structure is simple. This gives good results for the next step of image formation,
Ultimately, it leads to the provision of an image forming apparatus such as a copying machine that can stably form a beautiful image. As toner collecting means associated with this blade cleaning, conventionally, a means provided by sliding an elastic member such as a Mylar blade made of a polyester plate on the surface of the image bearing drum and an elastic body such as a foamed plastic roll are used. Means and the like provided so as to rotate in sliding contact with the surface of the drum are adopted. In many cases, these toner collecting means are located below the blade cleaning member installation position (upstream side in the drum rotation direction).

[Problems to be Solved by the Invention]

Such a cleaning device, particularly the toner collecting means of the device, has the following drawbacks. (A) Since the cleaning blade, the Mylar blade, and the foamed plastic are all brought into sliding contact with and pressed against the surface of the image carrier drum, the toner film is formed on the surface of the drum for a long period of time. (B) Toner leakage or the like may occur and cause a device failure. (C) Foreign matter, and in some cases, carriers enter between the surface of the drum and each member slidingly contacting the surface, causing damage or deterioration of the surface of the drum. According to the description in Japanese Examined Patent Publication No. 47-42340 (patented by Xerox Co., Ltd.), a method excluding the above drawbacks has been proposed for the purpose of toner recycling. However, other drawbacks are pointed out as follows. (A) The applied voltage for collecting toner changes from 0.5 kV to several kV, which is a value too large as a use range, and there is a problem in safety as an apparatus. (B) Further, when the applied voltage is large in this way, the potential of the toner is changed, which is an unsuitable condition for the purpose of toner recycling. (C) The distance (gap) between the surface of the toner collecting roller and the surface of the image carrier drum is not specified at all, and dielectric breakdown (leakage), toner spill, carrier spill may occur depending on the matching with the set voltage value, and the device may malfunction. It also becomes a direct cause. (D) According to the device drawing shown, the blade and the toner collecting roller are arranged extremely above the horizontal plane including the shaft of the image carrier drum, and the distance between the blade and the toner collecting roller is too large. Therefore, the toner always remains on the surface of the image carrier existing between the blade and the roller, resulting in insufficient toner recovery and a heavy cleaning load on the blade.

[Means for solving problems]

(Object of the Invention) An object of the present invention is to increase the applied voltage value by clarifying an appropriate setting region (range) regarding the surface distance between the toner collecting roller and the image carrier drum and the applied voltage. Highly safe and almost complete collection and recovery of toner removed from the surface of the image carrier by the blade without damaging and degrading the surface of the image carrier without leaving the toner on the surface of the image carrier. It is to provide an efficient cleaning device. (Structure of the Invention) The object is to provide a cleaning means for mainly scraping and removing the toner from the surface of the image carrier drum of the electrophotographic image forming apparatus, and a surface slightly separated from the surface of the drum on the upstream side of the cleaning means. Are opposed to each other so as to be rotatable and to which a potential having a polarity different from that of the residual toner is applied, the applied voltage is V (unit: kV), and each surface of the conductive roller and the drum is When the distance (gap) between them is d (unit: mm), the applied voltage V is V _max.
= 4.0d−0.2 and V _min = 1.4d−0.1, and d is 0.1 <
d <0.5, and the conductive roller is located below the horizontal plane including the axis of the drum.

[Examples and functions]

An embodiment of the present invention is shown in FIGS. First, the overall function of the color image forming apparatus incorporating the present invention will be described with reference to FIG. In FIG. 3, A is a reading unit, B is a writing unit, C is an image forming unit, and D is a paper feeding unit. In the reading unit A, 1 is a platen glass, and the original 2 is placed on the platen glass 1. The original 2 is illuminated by fluorescent lamps 5 and 6 provided on a carriage 4 that moves on a slide rail 3. The movable mirror unit 8 is provided with mirrors 9 and 9 ', moves on the slide rail 3, and in combination with the first mirror 7 provided on the carriage 4, the optical image of the original 2 on the platen glass 1 is read by a lens. Lead to unit 20. The carriage 4 and the movable unit 8 include pulleys 11 and 12 driven by a stepping motor 10 via a wire 15,
Driven in the same direction by the speeds of V and 1/2 V by 13 and 14, respectively. Standard white plates 16 and 17 are provided on the back side of both ends of the platen glass 1 before the start of scanning the original and / or
Alternatively, the standard white signal is obtained after the end of scanning. The lens reading unit 20 includes a lens 21, a prism 22, a first reading substrate 24, a red channel (hereinafter referred to as R-ch) CCD 25, a second reading substrate 26, and a cyan channel (hereinafter referred to as C-ch) CCD 27. The original light image transmitted by the first mirror 7, the mirror 9, and the mirror 9'is focused by the lens 21, and is provided on the R-ch CCD 25 provided on the first reading substrate 24 and the second reading substrate 26. An image is formed on each of the light receiving surfaces of the C-ch CCD 27. As the fluorescent lamps 5 and 6, commercially available warm white fluorescent lamps are used to prevent highlighting or attenuation of a specific color based on the light source when reading a color original, and 40 KHz to prevent flicker.
It is turned on by the high frequency power source and is kept warm by a heater using a posistor in order to maintain a constant temperature on the tube wall or to promote warm-up. The image signals output from the R-ch CCD25 and C-ch CCD27 are processed by a signal processing unit. In the signal processing unit, color signals that are color-separated according to the color of the toner, which will be described later, are output and input to the writing unit B. In the writing unit B, the laser beam generated by the semiconductor laser is rotationally scanned by the polygon mirror 32 rotated by the drive motor 30, passes through the Fθ lens 36, and is reflected by the reflecting mirror 37.
The optical path is bent by and is projected onto the surface of the image carrier drum 40 to form a bright line. When the scanning is started, the beam is detected by the index sensor, and the modulation of the beam by the first color signal is started. The modulated beam scans the image carrier drum 40, which is previously uniformly charged by the charger 41 as shown in FIG. By the main scanning by the laser beam and the sub-scanning by the rotation of the image carrier drum 40, a latent image corresponding to the first color is formed on the surface of the image carrier drum as shown in FIG. 5 (b). This latent image is developed by applying a bias as shown in FIG. 5 (c) by the developing device 43 loaded with red toner, and a red toner image is formed on the surface of the image carrier drum. The obtained toner image, while being held on the surface of the image carrier drum, passes under the cleaning device 46 which is separated and retracted from the surface of the image carrier drum, and enters the next copy cycle. Image carrier drum 40
Is uniformly charged by the charger 41 as in the previous cycle. Then, the second color signal output from the signal processing unit is input to the writing unit B, and writing is performed on the surface of the image carrier drum in the same manner as in the case of the first color signal to form a latent image. . The latent image is developed by a developing device 44 loaded with a second color toner, for example blue. This blue toner image is formed over the already formed red toner image on the surface of the image carrier drum. Reference numeral 45 denotes a developing device having black toner, which forms a black toner image on the surface of the image carrier drum based on a control signal generated by the signal processing unit. AC and DC biases are applied to the sleeves of the developing units 43, 44, and 45, jumping development is performed with a two-component developer, and development is performed in a non-contact manner with the grounded image carrier drum 40. There is. The toner image developed by the first color signal, the toner image developed by the second color signal, and the toner image developed by the black toner image are superimposed on each other. It is transferred onto the recording paper 61 which is a transfer body sent by the feeding belt 62 and the feeding roller 63. The recording paper on which the toner image has been transferred is separated from the surface of the image carrier drum by the separating electrode 52, and is further conveyed to the fixing device 53 to obtain a fixed color hard copy. Thus, the image bearing drum 40, which has been transferred, is actuated by the cleaning device 46 provided with the cleaning means according to the present invention shown in FIG. 1 to be negatively charged as shown in FIG. The unnecessary toner remaining on the surface is removed. As cleaning means in the cleaning device 46, a cleaning roller 49 and a blade 47 are arranged from the downstream side in the rotation direction of the image carrier drum 40 (shown by an arrow r).
Conductive metal roller 50 with insulating rollers 48 on both ends
The cleaning members are housed and arranged in the cleaning case 46a in a state of facing the peripheral surface of the image carrier drum 40. The blade 47 is made of urethane rubber in the form of a plate, is rotated clockwise by a blade holder 47a and is urged to press the peripheral surface of the image carrier drum 40, and the cleaning is performed. The roller 49 is made of abrasion-resistant urethane resin, and when the blade 47 is pressed and released, the driving device 49a acts to rotate the roller clockwise only for a predetermined time while pressing the peripheral surface of the image carrier drum. Is configured to. The conductive roller 50 arranged upstream of the blade 47 as a toner collecting roller has insulating rollers 48 slightly larger than the outer diameter of the roller at both ends thereof, and the roller 48 of the image carrier drum 40. Since it is brought into contact with the non-image portion, it maintains a very small gap with respect to the peripheral surface of the image carrier drum 40, which is a constant gap determined by the outer diameter of the insulating roller 48 and the outer diameter of the conductive roller 50. The counterclockwise rotation and a predetermined applied voltage can be applied at a certain position. Therefore, regarding the cleaning process by each of the cleaning members described above, the blade holder 47 before the tip of the toner image after transfer reaches the blade 47.
The image carrier drum 40 of the blade 47 by the action of a.
The residual toner is peeled off and dropped.
The conductive roller 50 having a constant gap from the image bearing drum 40 by the insulating roller 48 is extremely uniformly charged to the polarity for attracting toner according to the applied voltage based on the experimental results shown in FIG. Then, the blade 47 peels off and effectively absorbs the falling toner, conveys it counterclockwise, and scrapes it off by the scraper 50a, and the toner conveying path 4
It can be sent to 6b. Further, at the start of the cleaning action by the pressure contact of the blade 47 and at the time of ending the cleaning action and releasing the pressure contact, the rotation pressure contact of the cleaning roller 49 acts to cause a gap between the peripheral surface of the image carrier drum 40 and the blade 47. A small amount of toner left behind is removed to thoroughly clean the peripheral surface of the image carrier drum 40 to prepare for the next exposure. As described above, in the present invention, a conductive metal roller is used as a toner collecting roller on the upstream side of the cleaning unit that mainly scrapes and removes toner from the surface of the image carrier drum 40. The toner is disposed while maintaining a slight and constant gap from the surface, and the removed toner can be collected. Here, what size of the gap 2 was set and how the value of the applied voltage V of the conductive roller was determined.
The present invention will be described with reference to the experimental results of the applicant shown in FIG. Here, the angle G and the distance F representing the positions of the cleaning blade 47 and the conductive roller 50 in the arrangement of each member shown in FIG.
Were about 50 ° and about 10 mm, respectively. The image carrier is an OPC photosensitive drum having an outer diameter of 150 mm, the conductive roller is a stainless roller having an outer diameter of 8 mm to 12 mm, the toner has a particle diameter of about 15 μm, and the carrier has a particle diameter of about 40 μm. A magnetic carrier, which is substantially spherical particles coated with resin, and a cleaning blade made of urethane rubber were used, and the line speed was 70 mm / sec for both the drum and the roller. Then, due to the two-component jumping phenomenon, the toner adhesion amount
A 257 mm × 363 mm screen area was subjected to solid development at 0.86 to 1.02 mg / cm ² , and this was cleaned with a cleaning blade without transfer, and the recovery performance of the scraped off toner was confirmed by the recovery amount. Therefore, this experiment is a forced collection test with a very large amount of cleaning toner. In this state, the gap d and the applied voltage V are changed to find the limit of toner collection capacity.
And is represented by an empirical formula of V _min = 1.4d−0.1.
That is, it can be seen that the toner collecting ability decreases as the gap d increases and the applied voltage decreases in the region below the line I where the toner collecting ability decreases. However, it has been found that when the gap d is made too small or the applied voltage is made too high, dielectric breakdown (lightning strike) occurs between the drum and the rollers. Under ideal environmental conditions, Paschen's law states that voltage leakage does not occur in the arrangement of this embodiment, but in reality moisture, paper dust, dust, foreign matter, etc. occur between the drum and rollers. It turned out that a leak occurred. The insulation limit line becomes like the line II in Fig. 2, and V _max
= 0.1d-0.2. Further, if the gap d is made too large, it becomes difficult to prevent carrier spillage, which may possibly be mixed in suddenly. This limit line is represented by d = 0.5 on line III. As described above, the range of relation between the applied voltage V and the gap d may be the range of use surrounded by the line I, line II and line III shown in FIG. However, if d is 0.1 or less, it becomes difficult to adjust the accuracy, and it is preferable to avoid this. In view of this, in the present embodiment, the rigorous adjustment is not required at the time of assembly work or maintenance and the voltage applied to the conductive roller is not excessively increased. Good results were obtained with a voltage V of 0.5 kV. However, without being limited to this, all the adaptations in the use range of FIG. 2 were good. The cleaning blade was set below the horizontal plane including the drum shaft so that the scraped-off toner would not easily come back to the image bearing drum. The voltage applied to the conductive roller has a polarity different from that of the drum charging voltage and the residual toner as shown in FIG. 5 (e). The color image forming sequence in the color image forming apparatus of the present invention equipped with such a cleaning means will be described with reference to the time chart of FIG. 4. When starting the rotation, the image carrier drum in which the charging is started for some time in advance. Reference numeral 40 indicates the start of image exposure by the first color signal at the first rotation and the processing of development I delayed by time x from that, and then the second rotation by the start of image exposure by the second color signal and After receiving the development II processing delayed by the time y, the image exposure by the black signal is started at the third rotation and the development III processing is delayed by the time z to form a color toner image. Here, the times x, y, and z are the time required for a certain position of the image carrier drum 40 (the front end of the image in the figure) to reach the position where each development process is performed from the image exposure position, and the time is also within m. Is the time required to reach the transfer pole 51 from the image exposure position or less, and n is the time required to reach the cleaning device 46 from the image exposure position or less. Further, l is the time required for the entire image surface of the original to pass through a fixed point such as the image exposure or development processing position, and the operations such as image exposure, development processing, transfer, and cleaning are the time 1 as shown by the broken line. It is designed to be operated for some time before and after. That is, in the above-described embodiment, the blade 47 is operated for a time including a slight margin before and after the time l, and the cleaning roller 49 is operated approximately from the start of the operation of the blade 47 and the end of cleaning the entire image surface. Operated for 1 second. The timing of voltage application to the conductive roller 50 according to the present invention may be the same as the operation of the blade 47, or the voltage may be always applied.

【The invention's effect】

Since the electrophotographic image forming apparatus incorporating the cleaning device of the present invention performs good cleaning and toner recovery, toner filming does not occur on the surface of the image carrier drum, and lightning strikes do not occur. It was confirmed that the damage and deterioration of the body were eliminated and the life of the image bearing body was extended as compared with the conventional case. In addition, the long-run continuous test of 20,000 images confirmed that the toner was collected steadily and stably, and the pollution inside the device was also incomparably smaller than before, and the accident rate was also reduced. This has led to a significant reduction in the burden of services such as internal cleaning and inspection.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a cleaning device of the present invention. FIG. 2 is a Vd diagram showing a toner collecting force lowering region and a leak generating region of a conductive roller as a toner collecting roller. FIG. 3 is a schematic diagram of a color image forming apparatus. Figure 4 is a time chart. FIG. 5 is a potential pattern diagram of each process. 40: image carrier drum, 41: belt electrode 43,44,45 ... developing device, 46 ... cleaning device 46a ... housing, 46b ... toner transport path 47 ... cleaning blade 48 ... insulating roller , 50 …… conductive roller 50a …… scraper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Tamura 2970 Ishikawa-cho, Hachioji-shi, Tokyo Konishi Rokusha Makoto Co., Ltd. Satoko Hirai (56) Reference JP-A-55-40405

Claims (1)

[Claims] 1. A cleaning means for mainly scraping and removing toner from the surface of an image carrier drum of an electrophotographic image forming apparatus and a surface opposed to the upstream side of the cleaning means, slightly separated from the surface of the drum. A conductive roller that is rotatably arranged and to which a potential having a polarity different from that of the residual toner is applied, the applied voltage is V (unit: kV), and the distance between each surface of the conductive roller and the drum ( When the gap) is d (unit: mm), the applied voltage V is V _max
= 4.0d−0.2 and V _min = 1.4d−0.1, and d is 0.1 <
An apparatus for cleaning an image carrier, wherein d is in the range of d <0.5, and the conductive roller is located below a horizontal plane including the axis of the drum.