JPH02282770A - Image forming device - Google Patents

Abstract

PURPOSE:To preclude toner fusion and filming on an image carrier by rotating a rotary body for transfer at different peripheral speeds when a transfer material is interposed between the image carrier and rotary body for transfer and not. CONSTITUTION:The peripheral speed of a transfer roll 5 as the rotary body for transfer is made different according to whether or not the transfer material 11 is interposed between a photo-sensitive body 1 as the image carrier and the transfer roll 5. Namely, a driving means 90 drives the transfer roll 5 to nearly the same peripheral speed as the peripheral speed of the photo-sensitive body 1 right before the transfer material 11 enters the contact part between the photosensitive body 1 and transfer roll 5. Further, the transfer roll 5 is rotated at the lower peripheral speed right after the transfer material 11 passes a transfer position. Consequently, the transfer material 1 is held strongly between the photosensitive body 1 and transfer roller while the transfer is carried out, but when the transfer is not performed, the transfer roll 5 slides on the photosensitive body 1 to preclude the toner fusion and filming by the sliding effect.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention involves forming a toner image on an image carrier, and transferring the toner image to the transfer material by bringing a rotating body to which a bias voltage is applied into contact with the transfer material. The present invention relates to an image forming apparatus that performs image transfer.

[Background technology] Conventionally, in an electrophotographic image forming apparatus, as is well known, an electrostatic latent image is formed, the latent image is visualized with toner, and the toner image is transferred to a transfer material. After fixing the upper toner image, the transfer material is discharged outside the machine as a print. On the other hand, the image bearing member after transfer is used repeatedly after cleaning the residual toner.

In image forming apparatuses such as those described above, a blade cleaning method is widely used as a cleaning means in which cleaning is performed by bringing an elastic blade into contact with an image carrier due to the advantages of performance, cost, and compactness. Although this blade cleaning method does have good cleaning performance, it is not perfect on its own and is simple, and when used, it may cause toner fusion to the image carrier, filming phenomenon, and contamination of the image carrier surface from paper particles. As a result, the image bearing member becomes resistive, which tends to cause image blurring or so-called image deletion.

Therefore, in recent years, as a cleaning aid, a method has been developed in which an elastic roller is brought into contact with the image carrier upstream of the cleaning blade and rotated at a different circumferential speed from the image carrier, thereby constantly refreshing the surface of the image carrier. was removed (Figure 2).

By adopting this method, the above-mentioned problems such as toner fusion, filming image blur, and image deletion have been almost completely solved.

However, in the above-mentioned conventional example, the cost increases due to the provision of the cleaning roller, and the cleaner itself also becomes larger, reducing the benefits of blade cleaning by half.

Particularly in recent years, process cartridges have become widely used in which the cleaner, image carrier, or even the developing unit are integrated and made disposable in order to achieve ease of handling and maintenance-free operation. Particularly in such process cartridges, incorporating the elastic roller into the cleaner not only increases the size of the cartridge, but also increases the cost of the cartridge, which in turn significantly increases running costs.

[Object of the Invention] The present invention has been made in view of the above points, and an object of the present invention is to provide an inexpensive and small-sized image forming apparatus that can properly clean an image carrier and obtain a good image. .

[Structure of the Invention] In order to achieve the above object, the present invention forms a toner image on an image carrier, brings a transfer rotating body into contact with a transfer material, and transfers the toner image on the image carrier onto the transfer material. In the image forming apparatus for transfer, the peripheral speed of the transfer rotor is made different between when a transfer material is interposed between the image carrier and the transfer rotor and when no transfer material is interposed. It is characterized by:

[Example] Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 shows an embodiment of an image forming apparatus of the present invention.

A photoreceptor l serving as an image carrier is uniformly charged by a charger 2 and then subjected to image exposure 3 to form an electrostatic latent image.

Next, the electrostatic latent image is developed with toner by the developing device 4. On the other hand, the transfer material 11, which is timed and sent to the leading edge of the toner image on the image carrier, enters between the photoreceptor 1 and the transfer roller 5 pressed against it. As a result, the toner image on the image carrier is transferred onto the transfer material 11 by a voltage having a polarity opposite to that of the toner applied to the transfer roller 5 by the power source 8.

Then, the toner image on the transfer material 11 is fixed by the fixing device 6 and then discharged to the outside of the machine.

On the other hand, after the photoreceptor 3 is cleaned of toner remaining during transfer, paper dust, etc. coming out of the transfer material with a cleaner 7, it proceeds to the next image forming cycle including charging again. Here, the cleaner does not use an auxiliary cleaning means such as a cleaning roller, and is composed only of a cleaning blade 71 mainly made of urethane rubber and a scoop sheet 72 for collecting toner scraped off by the cleaning blade 71.

Next, the transfer device will be explained in detail.

The transfer roller 5, which is a rotating body for transfer, is made by dispersing carbon or metal powder on a core metal 51.
A urethane sponge having a large number of bubbles having a conductivity of 0 Ω·Cm, a NBR sponge, a soft urethane rubber, or a silicone rubber layer 52 is used. A bias having a polarity opposite to that of the toner is applied to the core metal 51 of the transfer roller 5 by the high-voltage power supply 8 . This bias shall be appropriately determined in the range of 500 to 5 kV.

Further, the transfer roller 5 is driven by a drive means 9, and the control means 10 controls the drive means 9, so that the transfer roller 5 is driven at two different speeds. The speed is such that the first speed is 30 to 80 relative to the circumferential speed of the photoreceptor.
．． The second speed is a suitable circumferential speed between 130 and 180%, and the second speed allows the photoreceptor to rotate at approximately the same circumferential speed.

Next, the operation will be explained.

First, when an operator manually inputs an image forming start signal using a button (not shown), an image forming operation is started, and the photoreceptor starts rotating in order to uniformly charge the surface potential of the photoreceptor. At this time, the peripheral speed of the transfer roller is approximately 60% of the peripheral speed of the photoreceptor. Next, just before the transfer material enters the contact area between the photoreceptor and the transfer roller, that is, the transfer site, in synchronization with the image on the photoreceptor, the driving means 9 adjusts the circumferential speed of the transfer roller 5 to the photoreceptor. The circumferential speed is driven at approximately the same speed. Immediately after the transfer material 11 passes through the transfer site, the transfer roller 5 is rotated again at a peripheral speed of 60%. By doing this, during transfer, the transfer material is firmly held between the photoreceptor and the transfer roller, so when the transfer material enters the fixing device or from the register roller before the transfer material enters the transfer area. This eliminates the blurring that would easily occur when the printer is separated from the photoreceptor, and the transfer roller 5 rubs the photoreceptor during non-transfer, so the rubbing effect allows toner fusion and filming to be achieved without adding any auxiliary means to the cleaner. This prevents the cleaning from occurring and makes it possible to always obtain good images without image blurring or image deletion.

In the above embodiment, the transfer roller 5 was driven at approximately the same circumferential speed as the photoreceptor when paper was present, but in this case, the transfer roller 5 was rotated in a driven manner relative to the photoreceptor. The mechanism can be simplified while maintaining its effectiveness.

Further, when a transfer material is interposed between the photoreceptor 1 and the transfer roller 5, the circumferential speeds of the photoreceptor 1 and the transfer roller 5 are approximately the same, and otherwise the circumferential speeds are different, as in the previous embodiment. When there is paper in the contact area between the photoreceptor 1 and the transfer roller 5, that is, during transfer, a bias with the opposite polarity to the toner is applied to the transfer roller 5, but at other times when the transfer is not being performed, for example, during pre-rotation or post-rotation. A bias having the same polarity as the toner is applied to the transfer roller 5 during rotation and also to part or all of the paper gap (the non-image area of the photoreceptor between the transfer materials when continuous image formation is performed). . As a result, the toner accumulated on the surface of the transfer roller 5 is cleaned, and a good rubbing effect can always be obtained.

In the above embodiments, a roller-shaped transfer body is used, but it is of course possible to use a belt-shaped transfer body.

[Effects of the Invention] As explained above, according to the present invention, when a transfer material is interposed between the image bearing member and the transfer rotary member, and when the transfer material is not interposed, the transfer rotary member can be By making the circumferential speeds of the rollers different, it is possible to prevent toner from adhering to the image carrier and filming, and to obtain good images without image blurring or image deletion, without having to provide an auxiliary means such as a cleaning roller to the cleaner. Therefore, it was possible to provide an inexpensive and small-sized image forming apparatus.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention, and FIG. 2 is a sectional view showing a part of a conventional image forming apparatus. 1, the photoreceptor 5 is a transfer roller.

Claims (1)

[Claims] 1. In an image forming apparatus that forms a toner image on an image carrier and transfers the toner image on the image carrier to the transfer material by bringing a transfer rotor into contact with a transfer material, the image carrier and the transfer rotor are used. An image forming apparatus characterized in that the circumferential speed of the transfer rotary body is set to be different when a transfer material is interposed between the image forming apparatus and the image forming apparatus.