JPH04352174A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the damage, filming, image flow, etc., of the surface of an image carrying member and to prevent the scraping off of toners by a sepn. assisting means and the wear of the sepn. assisting means. CONSTITUTION:This device has the image carrying member 1, a developing means 4, a transfer means 6, a cleaning means 8 for removing the residual toner on the surface of the image carrying member, the sepn. assisting means 14 for separating the transfer material from the image carrying member, and a toner image pattern forming means which forms the toner images in the longitudinal direction of the cleaning means exclusive of the contact part of the sepn. assisting means off the image forming region on the surface of the image carrying member.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image forming apparatuses such as copying machines and printers.

0002

2. Description of the Related Art A general electrophotographic copying machine having a conventional cleaning device has a structure as shown in FIG. 4, for example.

In FIG. 4, 1 is an image carrier, 2 is a charger, 3 is an image exposure device, and 4 is a developing device. That is, charger 2
The electrostatic latent image formed on the image carrier 1 by the image exposure 3 is visualized as a toner image by a developing device 4 and then transferred onto a transfer material by a transfer charger 6, and the transfer material is separated by a series of separation steps. Process (separation charger 7a, transfer material conveyance section 7b
) is separated from the surface of the image carrier 1.

On the other hand, since the image carrier 1 such as a photoreceptor is used repeatedly, a cleaning device 8 removes toner remaining on the surface after transfer.

[0005] As described above, in the system in which the endless image carrier 1 is used repeatedly, the cleaning device 8 plays a very important role. The main role of the cleaning device 8 is basically to remove the residual toner as described above, but in addition to the residual toner, there are also foreign particles such as paper dust transferred from the transfer material on the image carrier. The image bearing member is contaminated by discharge products such as nitrogen oxides generated by each charger, and unless these are removed and cleaned from the image bearing member, it will cause defective images such as image deletion.

Therefore, conventionally, the cleaning device 8 includes a cleaning blade 9 for removing residual toner, and a cleaning blade 9 for removing residual toner.
In order to clean the paper dust, nitrogen oxides, etc., an auxiliary cleaning means such as a cleaning roller 10 is often provided. Most of these auxiliary means are located upstream of the cleaning blade 9 and come into contact with the image carrier 1, and clean by mechanically rubbing the image carrier while removing residual toner paper dust, nitrogen oxides, etc. is being carried out.

However, these cleaning blades 9
The sliding force of the cleaning roller 10 and the like depends on the amount of toner, paper dust, etc. held by each cleaning means. In most cases, the distribution of residual toner etc. in the longitudinal direction of each cleaning means is uneven, so the amount of toner etc. retained in each cleaning means is also uneven, resulting in a sliding force in the longitudinal direction of each cleaning means. The cleaning effect may become uneven, resulting in partial image blurring, the surface of the image carrier may be damaged due to localized excessive rubbing force, and the resulting filming may cause dots on the transfer material. This may cause problems such as contamination. Among these, this tendency was particularly noticeable in auxiliary cleaning means whose purpose is to remove paper dust, nitrogen oxides, etc. along with residual toner.

[0008] Therefore, by providing a uniform sliding force in the longitudinal direction of the cleaning means, it is possible to prevent damage to the image carrier 1 due to local excessive sliding force and filming caused by this. Image forming apparatuses have been proposed that can prevent image deletion and obtain good images.

That is, an image carrier that forms a toner image on its surface and moves endlessly, a developing means that forms a toner image on its surface, a transfer means that transfers this toner image onto a transfer material, and a transfer means that forms a toner image on a transfer material. A cleaning device for removing residual toner remaining on the surface of the image carrier afterward, and a toner image pattern forming device for forming a continuous toner image in the longitudinal direction of the cleaning device in front of the image forming area on the surface of the image carrier. It is an image forming apparatus.

0010

[Problems to be Solved by the Invention] However, in the conventional technique shown in FIG. There is a problem in that the toner image pattern is scraped off by the separation auxiliary means, toner accumulates on the separation auxiliary means, and when the amount increases, it falls to the lower part and stains the transfer material. This was particularly noticeable when a one-component magnetic toner with a low charge amount was used.

Furthermore, due to the friction between the separation auxiliary means and the toner on the image carrier, especially when the toner contains a magnetic material, the amount of wear of the separation auxiliary means is large, and the performance of the separation auxiliary means is deteriorated. There was a problem that it decreased early.

The present invention is an attempt to solve the above-mentioned problems. That is, the present invention provides an image forming apparatus in which staining of the transfer material due to toner scraping by the separation assisting means for separating the transfer material is prevented, and the performance of the separation assisting means is maintained over a long period of time. The purpose is to provide

[0013]

[Means for Solving the Problems] In order to achieve the above object, an image forming apparatus of the present invention includes an image carrier that forms a toner image on the surface and moves endlessly, and a toner image on the surface of the image carrier. a developing device for forming an image; a transfer device for transferring the toner image onto a transfer material; a cleaning device for removing residual toner remaining on the surface of the image carrier after transfer; a separation auxiliary means for separating the transfer material from the carrier; and a toner image pattern for forming a toner image in the longitudinal direction of the cleaning means outside the image forming area on the surface of the image carrier except for the contact portion of the separation auxiliary means. and a forming means.

[0014]

[Operation] According to the present invention, a toner image is formed outside the image area along the longitudinal direction of the cleaning means on the surface of the image carrier, so damage to the surface of the image carrier, filming, image deletion, etc. can be prevented. Even if the separation auxiliary means is in contact with the image carrier, the abutment part of the separation auxiliary means
Since a toner image outside the image area is not formed, it is possible to prevent the separation auxiliary means from scraping off the toner on the surface of the image carrier and to prevent the separation auxiliary means from being worn out.

[0015]

[Embodiment] FIG. 1 shows an embodiment of the present invention. Similar to the one explained in FIG. 4, an electrophotographic copying machine is used as an example, and the same reference numerals as in FIG. It represents.

The cleaning device 8 is taken as an example of a cleaning blade 9, and the auxiliary cleaning means is taken as an example of a cleaning roller 10 having a large sliding force against the image carrier 1. In addition, as a blank exposure means used to remove unnecessary charges outside the image forming area, L
ED array 13 is used. Furthermore, a separation claw 14 made of polyamideimide is used as a separation aid.

Next, FIG. 2 shows the sequence of copying operation.
Explain along the lines.

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 the copy operation (copy ON).

Now, regarding the case of continuous copying of two sheets, first, at the same time as the image bearing member 1 starts rotating, the LED array 13 for blank exposure lights up completely to remove the static charge on the drum and close the lens. The period from when the included optical system moves to a position corresponding to a set magnification until the transfer material enters a standby state in front of the image carrier 1 is the pre-rotation period. During this time, high voltage is applied to the charger 2, and the image carrier 1 is uniformly charged.

During this pre-rotation, the LED array 13 lights up and almost no charge remains on the image carrier 1 outside the image forming area, but very momentarily during this pre-rotation, the L
The ED array 13 is partially turned off. Therefore, electrostatic charge is partially held on the image carrier 1 for this t seconds, and this latent image portion is visualized in the developing device 2 as a preceding toner image 20 as shown in FIG.

The portion 22 where the preceding toner image is not formed is a portion where the separation claws 14 of the separation assisting means are in contact with the image carrier 1, and in this embodiment, there are four separation claws 14 provided.

FIG. 3 is a developed view of the image carrier surface 1a showing an example 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 transferred to the cleaning roller 10 and cleaning blade 9. The toner is replenished to provide a uniform toner coating before image formation. Subsequently, the optical system starts scanning, and image exposure 3 is performed on the image carrier 1 to form an electrostatic latent image, which is 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 the toner image, and the toner image is transferred onto the transfer material through normal transfer and separation steps, and then discharged through a fixing step (not shown).

On the other hand, the residual toner after the transfer 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 partially turned off for t seconds in the middle.

Therefore, as in the previous rotation, a preceding toner image 20 as shown in FIG. 3 is formed on the image bearing member 1 for t seconds, which also reaches the cleaning device 8 as an untransferred image, and is transferred to the cleaning roller 10. and is coated on the cleaning blade 9. During image exposure, 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 off, and then,
LED array 13 for driving the image carrier 1 and blank exposure
are turned off at the same time, and the series of copying operations ends.

Similarly, when two or more sheets are continuously copied, 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. Furthermore, in the case of one-sheet copying, the preceding toner image 20 is formed only during the previous rotation.

Note that in the electrophotographic copying machine shown in FIG.
When the image carrier 1 is rotated at a process speed of 170 mm per second, the LED array 13 for blank exposure
．． By turning off for 0.01 seconds (the above t is 0.01),
Problems such as image deletion, scratches, filming, staining of the transfer material due to toner falling, and abrasion of the separation claw 14 can be prevented. A second embodiment of the present invention is as follows.

In the above embodiment, the position of the separation claw 14 as a separation assisting means in the longitudinal direction of the image carrier 1 is fixed, but the longitudinal position of the separation claw 14 is changed for each copy (for one or more copies). ) or according to the number of rotations of the image bearing member, etc., and the formation area of the toner image in the longitudinal direction outside the image area is changed accordingly.

In this way, it is possible to prevent a toner image from being formed outside the image area only at a specific position in the longitudinal direction of the cleaning means, and to prevent damage to the surface of the image carrier corresponding to the position of the separation assisting means. , filming, and image deletion do not occur.

In this case, the moving distance of the separation assisting means in the longitudinal direction must be equal to or greater than the width of one element of the LED array.

A third embodiment of the present invention is as follows.

A mechanism is provided to control the contact and separation of the separation claw 14 with respect to the image carrier 1, and when the toner image outside the image area passes through the contact position of the separation auxiliary means, the separation auxiliary means is brought into contact with the image carrier 1. The toner image is continuously formed over the entire length of the cleaning means. In this case too,
The same effects as in the second embodiment can be obtained.

A fourth embodiment of the present invention is as follows. As described above, in order to prevent the toner image outside the image area from being supplied to the portion corresponding to the separation auxiliary means, a mechanism for moving the separation auxiliary means or the like is required. Therefore, in low-speed copying machines and the like where the durability of the separation auxiliary means is not required, it is sufficient to simply make the width of the toner image outside the image area narrower in the part corresponding to the position of the separation auxiliary means than in other parts. .

[0033]

[Effects of the Invention] As explained above, according to the present invention,
Since the toner image is formed outside the image area in the longitudinal direction of the cleaning means on the surface of the image carrier, excluding the position corresponding to the separation assisting means, damage to the surface of the image carrier, filming, and In addition to preventing image deletion, it is also possible to prevent toner from being scraped off by the separation auxiliary means and wear of the separation auxiliary means.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing part of the operation of the image forming apparatus shown in FIG. 1;

3 is a developed view of the surface of an image carrier showing an example of a preceding toner image formed in front of an image forming area of the image forming apparatus of FIG. 1; FIG.

FIG. 4 is a sectional view showing an example of a conventional technique.

[Explanation of symbols]

1: Image carrier
2: Charger 3: Image exposure
4: Developing device 9: Cleaning blade 10: Cleaning roller 13: LED array 14
: Separation claw (separation auxiliary means) 20: Preceding toner image 21
: Image forming area 22: Portion where no preceding toner image is formed (separation assisting means contact portion)

Claims (1)

[Claims] 1. 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 separation assisting device that comes into contact with the surface of the image carrier and separates the transfer material from the image carrier;
and a toner image pattern forming means for forming a toner image outside the image forming area on the surface of the image carrier in the longitudinal direction of the cleaning means except for the contact portion of the separation assisting means. .