JPH0695265B2 - Cleaning device in image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus such as a copying machine, and more particularly to a color type in which an image is formed on an image carrier by writing the image a plurality of times on the image carrier. The present invention relates to a cleaning device for an image forming apparatus.

[Background of the Invention]

Generally, in an image forming apparatus such as a transfer type electrophotographic copying machine, a rotating drum type image carrier having a photoconductive photosensitive layer on the outer peripheral surface is used, and the photosensitive layer is electrostatically charged while rotating the image carrier. A latent image is formed and developed with toner, and the obtained toner image is transferred to a recording sheet. On the outer peripheral surface of the image carrier after the transfer is completed, the residual toner adhering to the image carrier is peeled off and cleaned by the cleaning device to form an electrostatic latent image again, and a new image is transferred. In particular, in a color image forming apparatus for forming a color image by synthesizing a mono-color image, a plurality of developing devices loaded with toners of respective colors are arranged around the periphery of the image carrier, and the developing device is arranged for each rotation of the image carrier. A latent image corresponding to each color that is formed is developed in a non-contact manner, and a toner image is formed in multiple colors by rotating the image carrier a plurality of times.

After this toner image is transferred to a recording sheet as a transfer target, the residual toner is peeled and removed by the action of a cleaning device as in a general image forming apparatus, but the cleaning action is well known. Since it is carried out by the pressure contact (including contact) of the blade member or other cleaning member with respect to the image forming surface, it cannot be operated during the formation of the toner image or before the transfer, so that the image carrier is kept in the meantime. The blade member is kept in a position separated from it, and the pressure contact of the blade member is started immediately before the front end of the transferred toner image reaches the cleaning device, and the pressure contact is released immediately after the rear end of the toner image passes. The format is taken.

Although various cleaning devices have been proposed in the past, the blade cleaning device has a high cleaning efficiency in spite of its simplest structure and has a feature that it does not scatter and float the separated toner. It is used in electrophotographic devices.

On the other hand, however, the toner separated by the blade naturally falls along the surface of the image carrier drum and again accumulates and adheres to the residual toner on the image carrier, which only increases the cleaning load on the blade. However, it also has the drawback of hindering toner recovery. Further, there is a drawback that the dropped toner leaks out of the cleaning device and contaminates the outside.

As a means for eliminating such a defect in the blade cleaning device, a mylar blade for removing the toner falling on the surface of the image carrier by the cleaning blade upstream of the cleaning blade is used as the image carrier drum. A roller provided so as to be in sliding contact with the surface or a foaming roll made of foamed plastic or the like is provided upstream of the cleaning blade so as to be in sliding contact with the surface of the image carrier drum in the same manner as described above, and is rotated by being driven by the image carrier. In either case, the separated toner is pressed against the surface of the image carrier again to form a film of the toner, or toner is leaked to cause a device failure, or There are drawbacks such as damage and deterioration of the carrier. With the exception of the above-mentioned drawbacks, a device for collecting the toner separated by the cleaning blade has been proposed (Japanese Patent Publication No. 47-42340).

The toner collecting roller made of a conductive material is attached to the image carrier together with the cleaning blade rotatably upstream of the cleaning blade and slightly separated from the surface of the image carrier, and the peripheral speed of the toner collecting roller is set. And the moving direction in the gap are the same as the peripheral velocity and moving direction of the image carrier. A direct current high voltage power supply is connected to the toner collecting roller so as to apply a potential having a polarity opposite to that of the electric charge possessed by the toner and sufficient to attract the toner to the surface of the toner collecting roller.

According to this device, the residual toner on the image carrier is almost completely removed, and the surface of the image carrier is hardly damaged, toner spillage is prevented, and stable performance is maintained for a long time. It is possible.

[Problems to be solved by the invention]

However, in Japanese Patent Publication No. 47-42340, the mutual positional relationship between the cleaning blade and the toner collecting roller, the gap amount between the surface of the image carrier and the toner collecting roller, and the voltage applied to the toner collecting roller are described. There is no detailed description of relationships, lack of rigor,
In view of the fact that the performance could not be exhibited in practical use, an experiment was conducted in JP-A-60-262183 to clarify the above points, an optimum value was obtained, and a high voltage was determined by this value. It is possible to provide a cleaning device having an applied toner recovery roller and to almost completely remove the residual toner on the image bearing member without damaging the image bearing member. Due to the distortion and lack of accuracy due to the accumulated error of each member in the assembling of the cleaning device, the gap amount between the toner collecting roller and the image carrier cannot be made uniform, and the problems such as mutual short circuit may occur. It happened.

The present invention has been made to solve the above problems, and in a cleaning device for removing toner and the like remaining on an image carrier, a gap between a conductive toner collecting roller and the image carrier is provided. It is an object of the present invention to provide a device capable of forming a uniform electric field and almost completely removing the residual toner on the image carrier.

[Means for solving problems]

In the cleaning device for removing the toner and the like remaining on the image carrier of the image forming apparatus, a cleaning unit that mainly scrapes and removes the toner from the surface of the image carrier, and an upstream of the cleaning unit. Side, a conductive metal roller rotatably arranged at a slight distance from the surface of the image carrier, and an insulating material provided at both ends of the conductive metal roller and having an outer diameter slightly larger than the outer diameter of the roller. A roller of resin is provided, and a gap of 0.5 mm or less is formed by bringing the roller of the insulating resin into contact with the non-image portion of the image carrier, and a DC bias is applied to the conductive metal roller to apply toner. Is charged to the polarity that allows
In addition, a cleaning device in an image forming apparatus is characterized in that a uniform electric field is formed in a gap between the conductive metal roller and the image carrier.

[Work]

The present invention makes it possible to rotate a metallic conductive roller on the upstream side of a blade member that mainly scrapes and removes toner as viewed in the running direction of the image carrier, at a slight distance from the surface of the image carrier. Insulating rollers having an outer diameter slightly larger than the outer diameter of the electrically conductive roller are provided at both ends of the electrically conductive roller, and the insulating roller is brought into contact with the non-image portion of the image carrier. Therefore, a uniform gap defined by the outer diameter of the insulating roller and the outer diameter of the conductive roller is formed between the conductive roller and the image carrier, and a voltage is applied. Further, a uniform electric field is formed between the conductive roller and the image carrier. Other means for mainly scraping off the toner include a brush, a magnetic brush, a roller and the like.

〔Example〕

An embodiment of the present invention is shown in FIGS. First, the overall function of the color image forming apparatus of 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 mirror unit 8 are pulleys driven by a stepping motor 10 via wires 15.
11, 12, 13, and 14 are driven in the same direction at speeds of V and 1/2 V, respectively. Standard white plates 16 and 17 are provided on the back surfaces of both ends of the platen glass 1 so that the standard white signal can be obtained before the start of scanning the original and / or after the end of the 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 the light receiving surface of each C-ch CCD 27.

As the fluorescent lamps 5 and 6, commercially available warm white fluorescent lamps are used to prevent coordination and attenuation of specific colors based on the light source when reading color originals, 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 CCD 25 and the C-ch CCD 27 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, the optical path is bent by the reflecting mirror 37 through the Fθ lens 36, and the photosensitive drum 40 serving as an image carrier. Are projected onto the surface of the to form bright lines.

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 40 that has been uniformly charged in advance by the charger 41. A latent image corresponding to the first color is formed on the surface of the image carrier by the main scanning by the laser beam and the sub-scanning by the rotation of the image carrier 40. This latent image is, for example, a developing device 43 loaded with red toner.
To develop a red toner image 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 46 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 the charger 41.

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 to form a latent image in the same manner as in the case of the first color signal. . The latent image is developed by a developing device 44 loaded with a second color toner, for example blue. The blue toner image is formed on the already formed red toner image on the surface of the image carrier.

Reference numeral 45 denotes a developing device having a black toner, which forms a black toner image on the surface of the image carrier based on the control signal generated by the signal processing section. AC and DC biases are applied to the sleeves of the developing devices 43, 44, and 45, jumping development is performed by a two-component developer, and development is performed in a non-contact manner on the grounded image carrier 40. .

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 transfer paper on which the toner image has been transferred is separated from the image carrier by the separating electrode 52, and is further conveyed to the fixing device 53 to be fixed and a color hard copy is obtained.

Thus, the image bearing member 40 which has completed the transfer is acted on by the cleaning device 46 having the cleaning means according to the present invention shown in FIG. 1 to remove the unnecessary toner remaining on the peripheral surface.

As cleaning means in the cleaning device 46, a cleaning roller 49 and a blade 47 are arranged from the downstream side of 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. Examples of the material of the insulating roller 48 include an insulating resin such as polyacetal resin and polycarbonate.

The blade 47 is made of a plate-shaped urethane rubber and is urged in a clockwise direction by a blade holder 47a so as to press the peripheral surface of the image carrier drum 40, and the cleaning roller 49 is resistant. It is made of abradable urethane resin and is configured to press the peripheral surface of the photosensitive drum while rotating clockwise only for a predetermined time by the action of the drive device 49a when the blade 47 is pressed and released. ing.

The conductive roller 50 arranged upstream of the blade 47 as a toner receiving roller has an insulating roller 48 at both ends which is slightly larger than the outer diameter of the roller (here, 8 mmφ).
(Here, it is 8.4 mm) and the roller 48 is brought into contact with the non-image portion of the image carrier 40.
Rotation in a counterclockwise direction and application of a predetermined applied voltage at a position maintaining a constant gap determined by the outer diameter of the insulating roller 48 and the outer diameter of the conductive roller 50, which is extremely small with respect to the peripheral surface of It is configured so that The roller is then DC biased. In this embodiment, a gap of half the outer diameter difference of 0.2 mm was used, and a good effect was obtained. However, this gap may be 0.5 mm or less if the roller 50 and the image carrier 40 are not in contact with each other. FIG. 2 is a perspective view showing only this main part.

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.
By the action of a, the blade 47 is pressed against the image carrier 40, and the peeling / falling of the residual toner begins. The electrically conductive roller 50 having a constant gap from the image carrier 40 by the insulating roller 48 is extremely uniformly charged with a polarity for attracting toner by an applied voltage, and the blade 47.
The toner that separates and falls is effectively adsorbed and conveyed in the counterclockwise direction, scraped off by the scraper 50a, and the toner conveyance path 4
It can be sent to 6b. In addition,
The 48 may be rotatable so as to follow the image carrier 40.

Further, when the cleaning action by the pressure contact of the blade 47 is started and when the pressure action is released after finishing the cleaning action, the rotation pressure contact of the cleaning roller 49 acts and remains between the peripheral surface of the drum 40 and the blade 47. A small amount of toner is removed to thoroughly clean the peripheral surface of the photosensitive drum 40, which is an image carrier, to prepare for the next exposure.

As described above, in the present invention, a conductive metal roller is used as a toner receiving roller on the upstream side of the cleaning unit that mainly scrapes and removes the toner from the surface of the image carrier 40, and is slightly separated from the peripheral surface of the image carrier 40. In addition, the toner is disposed while maintaining a constant gap, and the removed toner can be collected.

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. Body 40
Starts the image exposure by the first color signal at the first rotation and the development I processing delayed by time x from that, and then enters the second rotation by starting the image exposure by the second color signal and After 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 40 (the leading edge 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 before and after the time 1 with a slight margin, and the cleaning roller 49 is operated approximately from the start of the operation of the blade 47 and the end of cleaning of all image surfaces. 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.

Further, in the embodiment, the process of developing with three colors of red, blue and black has been described, but it can be used with other colors or with four or more colors. In this case, the sequence of the third rotation shown in FIG. 4 may be performed at the final rotation.

〔The invention's effect〕

As is clear from the above description, the cleaning device in the image forming apparatus of the present invention includes a cleaning unit that mainly scrapes and removes toner from the surface of the image carrier, and an upstream side with respect to the rotation direction of the image carrier. , A chargeable conductive metal roller rotatably arranged at a slight distance from the surface of the image carrier, and an insulating member provided at both ends of the conductive metal roller and having an outer diameter slightly larger than the outer diameter of the roller. And a conductive resin roller, and the insulating resin roller is brought into contact with the non-image portion of the image carrier. As a result, the surface of the image carrier and the conductive metal roller are even. Since the gap is maintained and therefore the electric field generated between them can take an ideal value, the residual toner scraped off from the surface of the image carrier by the cleaning means can be collected very efficiently, and each part can be recovered. Since it is possible to prevent a non-uniform gap between the conductive metal roller and the image carrier caused by a distortion due to the cumulative error of the error and a lack of accuracy, the recovery function is reduced and the mutual function is reduced when the gap between them becomes large. In order to prevent the dielectric breakdown caused by the short circuit between them and the influence of the nonuniformity of the gap, lightning development caused by the dielectric breakdown when the voltage is raised too much does not cause the deterioration or damage of the image carrier, and the image quality is generally improved. Therefore, a cleaning device in an image forming apparatus which can obtain a good and accurate copy has been provided.

[Brief description of drawings]

1 and 2 are a sectional view and a perspective view of a main part of a cleaning device in an image forming apparatus of the present invention. FIG. 3 is a block diagram of an image forming apparatus equipped with the cleaning device, and FIG.
The figure is a time chart of its operation. 40 …… image carrier, 46 …… cleaning device 47 …… cleaning blade 48 …… insulating resin roller, 49 …… cleaning roller 50 …… conductive metal roller

Claims (1)

[Claims] 1. A cleaning device for removing toner and the like remaining on an image carrier of an image forming apparatus, a cleaning device for mainly scraping and removing the toner from the surface of the image carrier, and an upstream of the cleaning device. Side, a conductive metal roller rotatably arranged slightly apart from the surface of the image carrier, and an insulating material provided at both ends of the conductive metal roller and having an outer diameter slightly larger than the outer diameter of the roller. A resin roller is provided, a gap of 0.5 mm or less is formed by bringing the insulating resin roller into contact with the non-image portion of the image carrier, and a DC bias is applied to the conductive metal roller to apply toner. The image forming apparatus is characterized in that it is charged to a polarity for adsorbing a magnetic field and a uniform electric field is formed in the gap between the conductive metal roller and the image carrier. Burning device.