JPS62131283A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the surface of an image carrier from damage due to excess of local frictional force and an image from dot-like contamination due to filming caused by the damage by providing uniform frictional force over the longitudinal direction of a cleaning means. CONSTITUTION:At the time of rotation before a high voltage is impressed to an electrostatic charger 2 and the image carrier 1 is uniformly charged, an LED array 13 is turned off extremely instantaneously only for (t) sec and electrostatic charge is held on the image carrier only for (t) sec and visualized as a preceding toner image 20 by a developing unit 2. The preceding toner image 20 is carried to a cleaning device 8 as it is without being transferred and toner is fed to a cleaning roller 10 and a cleaning blade 9. Since new toner is uniformly and sufficiently applied to respective cleaning means before the formation of an image, uniform frictional force can be maintained over the longitudinal direction and the excess of locational frictional force can be removed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to image forming apparatuses such as copying machines and printers, and more particularly to a cleaning method for removing toner remaining on an image carrier. It is.

[Prior Art] FIG. 1 is a sectional view of a general electrophotographic copying machine having a cleaning device particularly related to the present invention. Electrostatic charge H14L formed on the image carrier 1 by the charger 2 and the image exposure 3
After il is visualized as a toner image by a developing device 4, it is transferred onto a transfer material by a transfer charger 6, and the transfer material is separated from the surface of the image carrier 1 by a series of separation steps 7a, b, and c. On the other hand, since the image bearing member 1 such as a photoreceptor is used repeatedly, toner remaining on the surface after transfer is removed by a cleaning device 8. In such a system in which an endless image carrier is used repeatedly, a cleaning device plays a very important role. Basically, the main role of this cleaning device is to remove the residual toner as described above, but in addition to the residual toner, there are also powders such as paper dust transferred from the transfer material on the image carrier. It is contaminated by foreign matter and discharge products such as Nox generated by each charger, and unless these are removed and cleaned from the image carrier, it will cause defective images such as image deletion. Therefore, conventionally, the cleaning device 8 is often provided with auxiliary cleaning means such as a cleaning roller 10 for cleaning the paper powder, NOx, etc., in addition to the cleaning blade 9 for removing residual toner. Most of this auxiliary means is the cleaning blade 9.
It is located on the upstream side of
Cleaning is performed by mechanically rubbing the surface of the image carrier while removing ox''4. However, the sliding force of the cleaning blade 9, cleaning roller 10, etc. is maintained by each cleaning means. It depends on the amount of toner, paper dust, etc.In most cases, the distribution of residual toner etc. in the longitudinal direction of each cleaning means is uneven, so the acid of toner etc. retained in each cleaning means is also uneven, and its As a result, the sliding force in the longitudinal direction of each cleaning means becomes non-uniform, resulting in uneven cleaning effects, resulting in partial image deletion, and local excessive sliding force causing damage to the surface of the image carrier. Filming caused by this causes harmful effects such as dotted contamination on the transfer material. Among these, this method is used as an auxiliary cleaning means to remove paper dust, NOx, etc. along with residual toner. The trend was great.

[Object of the Invention] The present invention has been made to solve the above-mentioned problems, and the purpose of the present invention is to provide a uniform sliding force in the longitudinal direction of the cleaning means, thereby preventing the image bearing member from being affected by local excessive sliding force. An object of the present invention is to provide an image forming apparatus that can prevent damage to the image forming apparatus and filming caused by the damage, and also prevent partial image deletion and obtain good images.

[Configuration for Solving the Problem] In order to achieve the above object, the present invention has the configuration shown below. That is, an image carrier that forms a toner image on its surface and moves endlessly, a developing device that forms a toner image on its surface, a transfer device that transfers this toner image onto a transfer material, and an image carrier that carries the image after the transfer. An image forming apparatus having a cleaning means for removing residual toner remaining on the surface of the body, and a toner image pattern forming means for forming a continuous toner image in the longitudinal direction of the cleaning means in front of an image forming area on the surface of an image carrier. It is.

[Embodiment] The cleaning blade 9 is taken as an example, and the cleaning roller 1O, which has a large sliding force against the image carrier, is taken as an example of the auxiliary cleaning means. Further, an LED array 13 is used as blank exposure means used to remove unnecessary charges outside the image forming area. Hereinafter, a description will be given along with FIG. 2 showing the sequence of the copying operation. After the user completes various mode settings such as the number of copies and magnification, the user presses a copy button (not shown) to start copying.
(copy ON), now to describe the case of continuous copying of two sheets, first, at the same time as the image carrier starts rotating, the LED array 13 for blank exposure lights up the entire surface to remove the static charge on the drum, including the lens. The period from when the optical system moves to a position corresponding to the set magnification until the transfer material enters a standby state in front of the image carrier 1 is the pre-rotation period. During this period, a high voltage is applied to the charger 2, and the image carrier l is uniformly charged. However, in the conventional example, the LED array 13 is lit continuously during the previous rotation, so that the image forming area is outside the image forming area. image carrier 1
Almost no charge remains on top. However, in the present invention, the LED array 13 is turned off very instantaneously for one second during the front rotation of the cylinder. Therefore, for this t seconds, on the image carrier l,
The electrostatic charge is retained, and this latent image portion is transferred to the third
This is visualized as a preceding toner image 20 as shown in the figure.

Here, FIG. 3 is a developed view of the image carrier surface 1a showing the first embodiment of the preceding toner image 20 formed in front of the image forming area 21. As shown in FIG. At this point, the transfer material has not yet been supplied to the image carrier 1, so this visualized preceding toner image 20 is not transferred, and therefore reaches the cleaning device 8 as it is and the toner is deposited on the cleaning roller 10 and cleaning blade 9. It is replenished and a uniform toner coating is performed before image formation. Next, scanning of the optical system begins, and image exposure 3 is performed on the image carrier 1.
An electrostatic latent image is formed and developed as a toner image in the developing device 4. A transfer material is supplied to the image carrier 1 in synchronization with the movement of this toner image, and normal transfer and separation steps 7a, b, c
The toner image is transferred onto the transfer material and discharged through a fixing step (not shown). On the other hand, residual toner after transfer is
It reaches the cleaning device 8 and is cleaned. When the first image exposure is completed, there is a post-rotation period until the next image exposure. At this time, the LED array 13 for blank exposure is fully lit, but is turned off for only a second in the middle. Therefore, as in the previous rotation, a preceding toner image 20 as shown in FIG. 3 is formed on the image carrier l for this one second period, and it reaches the cleaning device 8 as an untransferred image and is deposited on the cleaning roller 10 and cleaning blade 9. When exposing a zero image to be coated, the same sequence as above is repeated, and after entering the post-rotation, high voltages such as the charger 2 and the developing bias are sequentially turned to O.
After that, the drive of the image carrier 1 and the LED array 13 for blank exposure are turned off at the same time to complete the series of copying operations. Similarly, when continuous copying of two or more sheets is used, a preceding toner image 20 as shown in FIG. 3 is always formed outside the image forming area during the post-rotation operation between each image exposure.

In addition, in the case of one-sheet copying, the effect on the cleaning operation under such a zero-order sequence in which the preceding toner image 20 is formed only during the pre-rotation will be described. As mentioned above, in the conventional sequence, the amount of toner supplied to the cleaning device 8 is small. There is considerable variation in the longitudinal direction of the cleaning device 8. Furthermore, since the residual toner remains after transfer, it has a low charging ability and is often unstable, and is particularly difficult to be attracted to the cleaning roller 10. Therefore, the toner coating on the cleaning blade 9 and the cleaning roller 10 is It is non-uniform over its longitudinal direction, and as a result, the sliding force becomes non-uniform, causing damage to the surface of the image carrier and partial image defects. In particular, when various external additives are used for charge control, such as in a primary developer, this tendency is significant because the ratio of toner and external additives in the longitudinal direction of the roller is non-uniform.

In contrast, in this embodiment using the present invention, a sufficient amount of toner is always uniformly supplied to the cleaning blade 9 and the cleaning roller 10 in the longitudinal direction before image exposure, so that a sufficient amount of toner is always supplied uniformly over each cleaning means. is already approximately evenly coated with fresh toner. If cleaning is performed in such a state, even if residual toner whose abrasiveness and composition are uneven in the longitudinal direction reaches each cleaning means, a sufficient amount of toner coated in advance on each cleaning means will eliminate the residual toner. Uniformity is almost canceled out. By maintaining a uniform sliding force in the longitudinal direction of each cleaning means, excessive local sliding force can be eliminated. Further, the cleaning roller 10 can effectively remove paper dust, NOx, etc. by mixing the toner with a sufficient amount of toner on the surface of the cleaning roller 10 . As a result, it is possible to prevent image defects due to image deletion, scratches, filming, etc. These effects have been confirmed in experiments. That is, in an electrophotographic copying machine whose main part is shown in FIG. 1, when the photosensitive drum 1 is rotated at a process speed of 170 mm/sec, the LED array 13 for blank exposure is =
By turning off only 0, ol), the above-mentioned remarkable effect was obtained.

This kind of effect is not limited to cleaning with a blade or roller; for example, in cleaning with a general fur brush, a small amount of toner may be unevenly distributed in the longitudinal direction of the cleaning means, and the toner may be unevenly distributed on the image carrier. It is well known that surface scratches and resulting filming can cause spot-like image contamination. It will be easily understood that it is effective to supply toner to the fur brush by using a magnetic roller.Furthermore, in FIG. When forming a carrier magnetic brush and using it to rub the image carrier L, the remaining toner after transfer is 1 m, so conventionally the toner supply to the magnetic roller could not keep up and the toner on the magnetic roller was transferred to the scraper 11. As the brush is dropped, the amount of the magnetic brush on the magnet roller decreases, and the rubbing force against the image carrier l weakens, which usually causes image deletion. However, by replenishing a sufficient amount of toner as in the present invention, a stable and uniform sliding force in the longitudinal direction can be obtained at all times, and as a result, the above-mentioned disadvantages can be avoided.

Further, in the above embodiment, the LED array 13 for blank exposure was used as the toner image pattern forming means for forming the preceding toner image, but the present invention is not limited to this.

For example, this can be done by briefly switching the developing bias to the opposite polarity to the toner charge or to near Ov, or by changing part of the exposure optical system, such as by creating a solid black area at the tip of the platen glass. It is possible to use it.

Further, in the above embodiment, a configuration is adopted in which a preceding toner image is formed before image exposure is performed to form a latent image on the image carrier, but the gist of the present invention is to Even if this is done after image exposure, exactly the same effect can be obtained.

Next, a second embodiment using the present invention will be described.

In the first embodiment, a sequence for forming a uniform preceding toner image in the longitudinal direction was presented, but in consideration of the developing device, it is better to form a preceding toner image that varies in the longitudinal direction of the cleaning device. For example, a first hopper 32 having a developing sleeve 31 as shown in FIG.
In the one-component developing device 30, which has a first hopper and a second hopper 33 that replenishes toner from one side, the toner is supplied to the sleeve 31 while being conveyed from one side. changes in the longitudinal direction, and the toner base material and external additives such as silica are not sufficiently mixed, especially on the side near the replenishment port, i.e., on the right side in the figure, and the toner base material and external additives are separated. Developed in the same state. In general, external additives have a smaller particle size than toner and are difficult to transfer, so the ratio of external additives that reach the cleaner increases on the side closer to the replenishment port, and the ratio of toner base material gradually increases as you move away from it. . For this reason, cleaning means such as cleaning rollers may be damaged by relatively hard and fine external additives such as silica, resulting in image contamination due to filming or image contamination due to adhesion of paper dust, etc. There was a flow. Therefore, in this embodiment, a configuration is proposed in which the preceding toner image is made larger toward the near side closer to the replenishment port, thereby increasing the supply of toner to the cleaning means.

In FIG. 5, a non-reflective material 15a that forms a preceding toner image is pasted on the back surface of the document table gates 14. The optical system 17 performs a full scan from P to R, but the image forming area is from Q to R, and the area from P to Q is exposed outside the image forming area.6 Among the range from P to Q, the non-reflective material 15
The back surface of the tip indicator plate 16 is a reflective surface in the portion other than a, and outside the image forming area, a latent image is formed only in the portion corresponding to the non-reflective material 15a, forming a preceding toner image. The preceding toner image formed by this is the non-reflective material 1 in FIG.
The shape corresponds to 5a. In other words, since the width of the front side is wide and the amount of toner supplied is large, the toner coating is sufficient, and even if the residual toner after transfer, which has a relatively high proportion of external additives, comes, the surface of the cleaning roller 10 is Since it is mixed with the toner that has been sufficiently supplied in advance, the ratio of the external additive on the cleaning roller 10 is reduced as a result.
In the longitudinal direction, the toner component is approximately the same as that of other parts, and as in the first embodiment, problems such as point-like image contamination and image waviness due to filming do not occur.

In the second embodiment, the toner replenishment port is located on one side, but the toner replenishment port is not limited to this. In this case, it is easy to obtain the same effect as in each of the above embodiments by using a non-reflective material 15b having a shape as shown in FIG. 6 and increasing the amount of toner supplied near the center in the longitudinal direction. be understood.

Furthermore, although the above embodiments have been described using an electrophotographic copying machine as an example, the present invention is not limited to these embodiments, and can be applied generally to general image forming apparatuses using toner such as printers. can be applied.

Further, as the cleaning means, any device capable of rubbing and cleaning the surface of the image carrier, such as a fur brush or a magnetic roller forming a magnetic brush on the surface, can be used.

[Effects of the Invention] The present invention forms a continuous toner image in front of the image forming area of the image bearing member in the longitudinal direction of the cleaning means and supplies sufficient toner to the cleaning means in advance. A uniform sliding force can be maintained in the longitudinal direction, preventing damage to the surface of the image carrier due to excessive local sliding force and point-like image contamination due to filming, and improving the cleaning effect. It is possible to prevent partial image deletion due to unevenness and obtain a good image.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing an example of an image forming apparatus to which the present invention can be applied, FIG. 2 is a sequence diagram showing an example of the operation of an image forming apparatus using the present invention, and FIG. 3 is a front view of an image forming area. The original drawing formed in 1 is a correspondence diagram showing the non-reflective material and the exposure system with the document table, and FIG. 6 is a plan view of the document table on which another non-reflective material is arranged. l... Image carrier, 2... Charger, 4... Developer installation, 9... Cleaning blade, 10... Cleaning roller, 14... Original table, 15a, 15b...
Non-reflective material, 16... Reflective material, 20... Preceding toner image, 21... Image forming area. Male 21B Bamboo licking

Claims (1)

[Scope of Claims] An image carrier that forms a toner image on its surface and moves endlessly; a developing device that forms a toner image on the surface of the image carrier; and a transfer device that transfers the toner image onto a transfer material. a cleaning device for removing residual toner remaining on the surface of the image carrier after transfer; and a toner image pattern for forming a continuous toner image in the longitudinal direction of the cleaning device in front of an image forming area on the surface of the image carrier. An image forming apparatus comprising: a forming means.