JPH0138598Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] This invention applies to charging, exposure, development, transfer, and
The present invention relates to improvements in image forming apparatuses that obtain copied images using various devices such as cleaning devices.

[Technical background of the invention and its problems]

In the case of an electrophotographic device, an image forming device generally includes a photoreceptor drum and an image forming means provided around the photoreceptor drum, and the photoreceptor drum is charged, exposed, developed, transferred, peeled, neutralized, cleaned, etc. Copy images are obtained by repeating each step. In such an image forming apparatus, a cleaning blade, a fur brush, or even a magnetic brush has conventionally been used as a cleaning device for removing toner remaining on the photoreceptor drum and cleaning the photoreceptor drum after the transfer is completed. Among these devices, blade cleaning devices using a cleaning blade have been widely used in recent years as they can reduce the size and weight of the device and prevent wear on the photoreceptor drum. There is. However, in this blade cleaning device, the moment the cleaning blade made of urethane or the like separates from the photoreceptor drum after cleaning, the removed toner is electrostatically attracted to the contact portion of the photoreceptor drum with the cleaning blade. He gets attached. When the next copy starts, this adhered toner is removed by the contact of the cleaning blade with the photoreceptor drum and further by the rotation of the photoreceptor drum, and a portion of the adhered toner is removed from the cleaning blade on the downstream side of the rotation of the photoreceptor drum. It goes around the back side and follows the rotation of the photoreceptor drum.
When an image forming part having a surface potential of about 300V or more is passed through, it is electrostatically attracted to that part. This attracted toner appears as "black streaks" on the image forming area on the photoreceptor drum, causing "black streaks" in the copied image, which has the drawback of degrading the image quality. For this reason, we developed a device that first rotates the photoreceptor drum once with the transfer charger, peeling charger, and static elimination charger activated only during first copying, removes the "black streaks," and then starts the copying process. However, the problem is that the copying time is long and it is troublesome especially when obtaining a small number of copies.

[Purpose of invention]

This idea was made based on the above circumstances, and although it has a relatively simple configuration, it does not increase the first copy time and eliminates "black streaks" on copied images caused by residual toner that has gotten around to the back of the cleaning blade. It is an object of the present invention to provide an image forming apparatus that can prevent this phenomenon, prevent deterioration of image quality, and improve the reliability of the apparatus.

[Summary of the idea]

This idea uses a charge application device to apply a charge that is opposite in polarity to the toner and is sufficient for toner to adhere to the non-image forming portion of the photoreceptor drum before the cleaning blade, and this non-image forming portion is attached to the photoreceptor drum. By passing through the cleaning blade before the image forming area, the residual toner that has wrapped around the back of the cleaning blade is made to adhere to the non-image forming area, preventing the residual toner from adhering to the image forming area, and ultimately preventing the toner from forming on the copied image. The purpose is to prevent the occurrence of "black streaks" and improve image quality.

[Example of idea]

The first embodiment of this invention is shown below in Figures 1 and 2.
This will be explained with reference to the figures. Surrounding the photoreceptor drum 10 of an electrophotographic apparatus (not shown) are a charger 11, which is an image forming means and applies a surface potential of about 700 V to the photoreceptor drum 10, an exposure device 12,
A developing device 14 containing a toner 13 that is negatively charged by abrasion, a pre-transfer exposure device 15, a control device 16 that controls the timing of charge generation, and a transfer charger 17 that also serves as a charge imparting device, a peeling charger 18, A static elimination charger 20, a blade cleaning device 22 having a rotatable cleaning blade 21, and a static elimination lamp 23 are provided in this order. Note that 24 is a paper feeding section, and 25 is a sheet paper conveying device.

When the print button on the control panel (not shown) is turned on while the electrophotographic apparatus is in a standby state in which copying is possible, the tip of the cleaning blade 21 of the blade cleaning device 22 comes into contact with the photoreceptor drum 10 as shown in FIG. At the same time as the static elimination lamp 23 is turned on, the transfer charger 17 is turned on and the photosensitive drum 10 is turned on.
The non-image-forming portion of the device is charged to a high potential of 700V or more. Then, after 500 mS has elapsed, the control device 16 turns off the transfer charger 17, and then the photosensitive drum 10 is rotated in the direction of arrow X. Next, when the non-image forming portion of the photoreceptor drum 10 passes through the static elimination charger 20, the pre-transfer exposure device 15, the transfer charger 17, and the peeling charger 1
8. The static elimination charger 20 is turned on, and the image forming part of the photoreceptor drum 10 following the non-image forming part is also charged, but since the photoreceptor drum 10 is being rotated and the static elimination charger 20 has also passed, The surface potential of the imaged portion is lower than that of the non-imaged portion. When a non-image forming area with a surface potential of 700V or more passes through the blade cleaning device 22 in this state, the negatively charged toner 13 attached to the back surface of the cleaning blade 21 will cause "black streaks" to form on this non-image forming area. It is electrostatically attracted in a ``'' shape, conveyed, and removed before it reaches the image forming area. Thereafter, the non-image forming part is neutralized by the static eliminating lamp 23, while the image forming part is removed by the blade cleaning device 2.
2, but since the toner 13 on the back side of the cleaning blade 21 has already been removed at this time,
It does not adhere to the image forming area. Further, when the image forming portion reaches the charging charger 11, the charging charger 11, the exposure device 12, and the developing device 14 are also activated to start a copy cycle, and the non-image forming portion of the photoreceptor drum 10 also performs the duplication process after exposure. Then, the toner 13 is removed when the toner 13 passes through a blade cleaning device 22. When a predetermined number of copied images are obtained and the copy cycle is completed, the charging charger 11, the exposure device 12, the developing device 14, the pre-transfer exposure device 15, the transfer charger 17, the peeling charger 18, and the static elimination charger 2
After that, the photosensitive drum 10 is rotated once and then stopped, the cleaning blade 21 is separated from the photosensitive drum 10, the static elimination lamp 23 is turned off, and the standby state is returned.

With this configuration, when the toner 13 comes into contact with the photoreceptor drum 10, the toner 13 that has gone around and adhered to the back surface of the cleaning blade 21 is absorbed and conveyed to the non-image forming area of the photoreceptor drum 10 and is removed. This eliminates the problem of the toner 13 adhering in the form of "black streaks" and causing "black streaks" on the copied image and degrading the image quality. Furthermore, since the photoreceptor drum 10 is stationary when the non-image forming area is charged by the transfer charger 17, the non-image forming area receives a large amount of charge compared to the image forming area, and the output switching device etc. The non-image forming part can be charged to a higher potential than the image forming part without using the image forming part, and the toner 13 on the back surface of the cleaning blade 21 can be reliably removed by the non-image forming part.

Next, a second embodiment of this invention will be described with reference to FIG. It should be noted that the same parts as those in the first embodiment are given the same reference numerals and their explanations will be omitted. This embodiment uses a static elimination charger 20.
and the blade cleaning device 22, there is a charge applying device that generates a charge in a pulse form and charges the non-image forming position of the photoreceptor drum 10 to 700 V or more by a control device 26 that controls timing. 27.

When the print button on the control panel (not shown) is turned on while the electrophotographic apparatus is in a standby state, the cleaning blade 21 is brought into contact with the photoreceptor drum 10, the static elimination lamp 23 is turned on, and the photoreceptor drum 10 is turned on. is rotated in the direction of arrow X, and at the same time the auxiliary charger 2
7 is turned on for about 500 mS, and the non-image forming portion of the photosensitive drum 10 is charged to a high potential of 700 V or more.
Further, at this time, the transfer charger 17, the peeling charger 18, and the static elimination charger 20 are also turned on to sequentially apply charges to the image forming portion of the photoreceptor drum 10.
When the non-image forming area and the subsequent image forming area pass through the blade cleaning device 22 in this state, the toner 13 attached to the back surface of the cleaning blade 21 is electrostatically charged to the non-image forming area, as in the first embodiment. It is adsorbed, transported and removed. Thereafter, the photosensitive drum and each image forming means operate in the same manner as in the first embodiment to obtain a predetermined copy image, and then return to the standby state.

With this configuration, like the first embodiment,
The toner 13 adhering to the back surface of the cleaning blade 21 is adsorbed and conveyed to the non-image forming area of the photoreceptor drum 10, so that the toner adheres to the image forming area in the form of "black streaks" and causes "black streaks" to appear on the copied image. Nothing will happen.

Note that this invention is not limited to the above-mentioned embodiments, and can be modified in various ways. For example, in the first embodiment, the photosensitive drum may be rotated when charging the non-image forming portion; As in the first modification shown in FIG. 4, the high voltage transformer 28b is controlled by the control device 28 via the set value switching device 28a that switches the applied voltage, so that the applied voltage in the non-image forming portion is higher than that in the image forming portion. Then, the surface potential of the non-image forming area is higher than that of the image forming area, and the toner can be reliably attracted electrostatically. In addition, in the second embodiment, the operating time and timing of the auxiliary charger are arbitrary, and it is not only activated at the start of copying, but also operates between an image forming part and the next image forming part in continuous copy mode. Charges may be generated in a pulsed manner in the non-image forming area. In this way, during continuous copying, it is possible to remove the toner that has gradually leaked onto the back of the cleaning blade, and to maintain stable contact between the cleaning blade and the photoreceptor drum at all times, improving the cleaning effect and ultimately improving the image quality of the device. reliability is further improved. Furthermore, the surface potential of the non-image forming area can be set arbitrarily as long as it can sufficiently electrostatically attract toner, and in particular, if it is set higher than the subsequent image forming area, the electrostatic adsorption force of the image forming area will be higher than that of the non-image forming area. Since it is lower than the image forming area, even if some toner remains after passing through the non-image forming area, there is no risk that the toner will adhere to the image forming area. It is also possible to use the charge applying device as a stripping charger or a static elimination charger. For example, as in the second modification shown in FIG. is A.
C. High voltage power supply 33 and D. C. It is connected to one of the high-voltage power supplies 34, and when copying starts, a DC high voltage of opposite polarity to the toner 13 is applied in a pulsed manner to the static elimination charger 32 to charge the non-image forming portion of the photoreceptor 10 to a high voltage. You can do it like this.

[Effect of idea]

As explained above, according to this invention, the non-image forming part of the photoreceptor, which is charged to a high voltage by the charge applying device, reaches the blade cleaning device before the image forming part and wraps around the back of the cleaning blade. By removing toner,
This prevents toner from adhering to the image forming area and improves the image quality without causing "black streaks" on the copied image.Moreover, the first copy time is not increased, preventing deterioration in operability. Along with
The contact between the cleaning blade and the photoreceptor can be maintained stably, and the cleaning effect can also be improved. In addition, since the non-image forming area undergoes the same copying process as the image forming area after toner adsorption, cleaning and cleaning are performed as the photoreceptor rotates.
After the static electricity is removed, it can be used as an image forming part. Furthermore, if the transfer charger, peeling charger, etc. are used also as a device for applying charges to non-image forming areas, there is no need to provide a new auxiliary charger near the photoreceptor, space can be saved, and the device can be made more compact. In particular, in the case of a transfer charger, when charging a non-image forming area, the non-image forming area can be charged to a higher potential than the image forming area by simply keeping the photoreceptor stationary, and an output switching device or the like is not required.

[Brief explanation of the drawing]

Figures 1 and 2 show a first embodiment of this invention, Figure 1 is a schematic sectional view thereof, Figure 2 is a timing chart showing its operation, and Figure 3 is a second embodiment of this invention. 4 is a schematic sectional view showing a first modification of this invention, and FIG. 5 is a schematic sectional view showing a second modification of this invention. 10... Photosensitive drum, 11... Charger, 12... Exposure device, 13... Toner, 14...
...Developing device, 15... Pre-transfer exposure device, 16...
Control device, 17... Transfer charger, 18... Peeling charger, 20... Static elimination charger, 21...
... Cleaning blade, 22 ... Blade cleaning device, 23 ... Static elimination lamp, 26 ... Control device, 27 ... Auxiliary charger.

Claims (1)

[Scope of utility model registration request] A photoreceptor having a non-image forming portion preceding the image forming portion, a blade cleaning device for cleaning the photoreceptor, and the non-image forming portion being attached to the blade cleaning device when passing through the blade cleaning device. An image forming apparatus comprising: a charge applying device that applies a charge having a polarity opposite to that of the toner to the non-image forming portion so as to electrostatically attract the toner.