JPH0666037B2 - Cleaning device for electrophotographic copying machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic apparatus using a one-component type or two-component type developer, and in particular, to a surface of a photosensitive member which is a recording medium after a toner image is transferred onto a transfer paper. The present invention relates to a cleaning device of an electrophotographic copying machine for effectively removing residual toner and paper dust of transfer paper.

2. Description of the Related Art Generally, in an electrophotographic copying machine in which an electrostatic latent image formed on a photoconductor, which is a recording medium, is developed with toner to make it a visible image, the photoconductor is developed even after the toner image is transferred onto a transfer paper. Since some untransferred toner still remains on the surface, a cleaning device is provided to remove it. A conventionally known cleaning device of this type is usually composed of a roll-shaped conductive brush arranged on the downstream side of the transfer unit, and an elastic cleaning blade arranged on the downstream side of the conductive brush. Has been done. Part of the untransferred toner remaining on the surface of the photoconductor is first removed by the conductive brush, and then the remainder is removed by the tip of the cleaning blade that contacts the surface of the photoconductor.

However, in such a cleaning apparatus, for example, when the area of the image portion with respect to the background portion of the original to be copied, that is, the ratio of the black background portion to the white background portion on the original is large, the toner remaining on the photoconductor after transfer is large. Is relatively large, and it is extremely difficult to sufficiently remove them with the conductive brush and the cleaning blade. Therefore, the residual toner that cannot be removed by the conductive brush is sent to the cleaning blade as it is, and a considerable amount of toner stays in the vicinity of the tip of the cleaning blade that contacts the surface of the photoconductor. However, there was a problem in that

In order to solve the above problems of the conventional apparatus, a pre-cleaning charger for charging the residual toner on the photoconductor with the same polarity as the charge polarity of the photoconductor is provided between the conductive brush and the transfer unit. It has been proposed to improve the cleaning ability of the conductive brush by grounding the conductive brush while providing the cleaning brush. However, the transfer conditions change sequentially according to the transfer conditions of the toner image on the photosensitive member, that is, the operation of the transfer unit including the pre-transfer lamp or the pre-transfer corona charger, so that the conductive brush and the cleaning blade are used to transfer the toner onto the photosensitive member. However, the residual toner cannot always be removed in a stable state, and as a result, a considerable amount of toner near the tip of the cleaning blade is retained, and the performance of the cleaning device cannot be fully exhibited. .

On the other hand, instead of grounding the conductive brush, it is also proposed to connect it to an appropriate bias power source and always apply a constant bias voltage to further improve the cleaning ability of the conductive brush. According to this proposal, not only a sufficiently high cleaning performance can be obtained even when the amount of toner remaining on the photoconductor is large, but the residual toner can be removed by the conductive brush even when the amount of toner remaining on the photoconductor is small. Since almost all of the toner is removed, the toner hardly stays near the tip of the cleaning blade that contacts the surface of the photoconductor. Therefore, it can be said that applying a constant bias voltage to the conductive brush in this way is extremely effective. However, the fact that almost no residual toner stays near the tip of the cleaning blade causes a new inconvenience. That is, the toner slightly staying in the vicinity of the tip of the cleaning blade has a function of effectively blocking the paper dust of the transfer paper, which easily adheres to the surface of the photoconductor after the transfer, and removing the dust. Therefore, not allowing any residual toner to stay near the tip of the cleaning blade suppresses the function of removing the paper dust of the transfer paper. In this respect, this method is not always satisfactory. I can not say.

The present invention was made to eliminate the above-mentioned drawbacks of the conventional cleaning device for an electrophotographic copying machine, and its purpose is to remove not only the residual toner on the photoconductor but also the paper dust of the transfer paper. Another object of the present invention is to provide a practical cleaning device for an electrophotographic copying machine, which has an extremely high cleaning property and can be removed at the same time.

Configuration An embodiment of the cleaning device according to the present invention will be described in detail below.

FIG. 1 is a schematic configuration diagram of an electrophotographic copying machine equipped with the cleaning device of the present invention, in which a drum-shaped photoconductor as a recording medium is used.
10 is formed of, for example, a selenium (Se) -based material, and is rotated in the arrow direction by a drive device (not shown). In the vicinity of the peripheral surface of the photoconductor 10, a charging charger 12 that uniformly charges the surface of the photoconductor and an image on the original 14 are provided on the photoconductor 10.
The exposure optical system 16 that forms an image on the
A developing unit 18 for developing the electrostatic latent image formed on the photosensitive drum 10 is sequentially arranged in the rotation direction of the photoconductor 10. The transfer unit 20 arranged on the downstream side of the developing unit 18 includes a pre-transfer charger 22 and a main transfer charger 24.
And a separation charger 26. Transfer sheets 30 are fed to the transfer unit 20 from a paper feed tray 28 one by one.

The cleaning device 32 according to the present invention disposed on the downstream side of the transfer unit 20 includes a precleaning charger 36 for cleaning pretreatment connected to a power source 34, a roll-shaped conductive brush 38, and an elastic body. It is composed of a cleaning blade 40 and a discharge lamp 42. Further, at the lower part of the housing 44 of the cleaning device 32, a means 46 for discharging the collected toner and the like is attached. In addition, the pre-cleaning charger 36 is a charging charger 12
The voltage of the same polarity as the charging polarity of the photoconductor 10 due to
Is uniformly charged, and the conductive brush 38 is electrically floated.

The operation of the electrophotographic copying machine equipped with the cleaning device of the present invention as described above will be described below. First, the photoconductor
10 is charged by a charging charger 12 to a voltage of a predetermined polarity, for example (+) 800V in this embodiment, and then an exposure optical system 16 forms an electrostatic latent image corresponding to the image of the original 14 on the surface thereof. It This electrostatic latent image is developed by the developing unit 18 and visualized as a toner image. Incidentally, the toner of the two-component developer which is usually used retains an electric charge of about (−) 10 to 20 μC / g after being charged.

Next, the pre-transfer charger 22 charges the surface of the photoconductor and the toner image to make their potentials uniform, and then the main transfer charger 24 effectively transfers the toner image to the transfer paper 30. The transfer paper 30 onto which the toner image has been transferred is separated from the surface of the photoconductor 10 by the action of the separation charger 26, and sent to a fixing unit (not shown) for fixing processing.

On the other hand, a photoconductor that has untransferred residual toner on its surface
10 rotates and moves to the cleaning device 32 according to the invention. In the cleaning device 32, first, the pre-cleaning charger 36 uniformly charges the toner with a predetermined polarity (in this embodiment, the polarity is (+)), and then the conductive brush 38 in the floating state removes a large amount of residual toner. The part is removed. Other residual toner that is not removed by the conductive brush 38 and still adheres to the surface of the photoconductor is
It is scraped off by the tip of the cleaning blade 40 made of an elastic material arranged downstream thereof. It should be noted that the surface of the photoconductor 10 after cleaning is further neutralized by a static elimination lamp so as to have a uniform and low potential, and is prepared for the next copying cycle.

Now, in the cleaning device 32 of the present invention as described above, what is particularly noteworthy is that the conductive brush 38 is electrically floated, and the surface of the photoconductor 10 is caused by the pre-cleaning charger 36. That is, the conductive brush 38 is charged with the same polarity (in this embodiment, the polarity of (+)), and therefore the conductive brush 38 is applied with a voltage of the same polarity (+) as this conductive polarity. Since the induced voltage is induced, the cleaning ability of the conductive brush 38 is significantly improved, and the load on the cleaning blade 40 is significantly reduced. The voltage induced in the conductive brush 38 changes in accordance with the ratio of the image portion to the background portion of the document 14, that is, the black background portion to the white background portion, as shown in FIG. More specifically, when the ratio of the black background portion of the document 14 is large and the amount of residual toner is large, the voltage induced in the conductive brush 38 is high, and therefore the cleaning ability thereof is significantly improved. On the contrary, when the ratio of the black portion is small and the amount of residual toner is small,
The voltage induced in the conductive brush 38 is low. Therefore, some residual toner is sent to the cleaning blade 40, and is scraped off by the tip end portion thereof that abuts on the surface of the photoconductor. At that time, since a small amount of residual toner that is not too much remains stays near the tip of the cleaning blade 40, the paper dust of the transfer paper that tends to occur when transferring an image with a lot of white background is It is prevented from being blocked by the staying toner and being caught between the surface of the photoreceptor and the tip of the blade.

FIG. 2 shows the relationship between the ratio of the black portion on the original and the voltage induced in the conductive brush 38. This is especially true when the pre-cleaning charger 36 has a width of 45 cm and the drum current to ground is small. It shows the case where (+) is 100 μA. Therefore, the ratio of the black area is It is represented by. In this embodiment, as shown in the figure, when the ratio of the black portion is large and the induced voltage is 300 V or more, the cleaning property of the conductive brush 38 is significantly improved, and the load on the cleaning blade 40 is significantly reduced. It Further, when the ratio of the black background is small and the induced voltage is reduced to about (+) 100V, the cleaning property of the conductive brush 38 is slightly deteriorated, but this causes some residual toner to be sent to the cleaning blade 40. However, since it stays in the vicinity of the leading end, the paper dust of the transfer paper is effectively removed here.

As described above, according to the present invention, when the ratio of the black background portion on the original is large, a high voltage is induced in the conductive brush 38, so that the cleaning property is greatly improved and the residual toner is effectively removed. Can be removed. Further, when the ratio of the white background portion on the original is large and therefore paper dust of the transfer paper is likely to be generated, a low potential is induced in the conductive brush 38, so that some residual toner is sent to the cleaning blade. Since it stays at the tip, the paper dust can be effectively removed here.

As described above, according to the cleaning device of the electrophotographic copying machine of the present invention, in addition to the untransferred toner remaining on the photoconductor as a recording medium, it is not likely to occur when copying an original having many white background portions. It is possible to effectively remove the paper dust of the transfer paper as well.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic copying machine equipped with a cleaning device according to the present invention, and FIG. 2 is a background portion (white background portion) of a document to be copied.
FIG. 5 is a diagram showing a relationship between a ratio of an image portion (black background portion) with respect to and a voltage induced in the conductive brush at that time. Explanation of the symbols of the main parts 10 …… Photoconductor 12 …… Charging charger 16 …… Exposure optical system 18 …… Developing unit 20 …… Transfer unit 32 …… Cleaning device 36 …… Pre-cleaning charger 38 …… Conductive brush 40 ... Cleaning blade

Claims (1)

[Claims] 1. A cleaning device for removing untransferred toner and paper dust of transfer paper remaining on the surface of a recording medium of an electrophotographic device using a one-component or two-component developer, the cleaning device comprising: A pre-cleaning charger for charging the surface of the recording medium after transfer with a predetermined polarity to perform a cleaning pretreatment, and a voltage of a predetermined polarity from the surface of the recording medium charged by the pre-cleaning charger. A conductive brush that is induced and is electrically floated to remove untransferred toner remaining on the surface of the recording medium; and a conductive brush that is located downstream of the conductive brush in the moving direction of the recording medium. And a cleaning blade for removing untransferred toner on the surface of the recording medium.