JPH03212671A - Transfer device for image forming device - Google Patents

Abstract

PURPOSE:To prevent toner from being welded and stuck and to excellently secure transfer performance by changing a transfer speed according to whether or not a transfer paper exists at a transfer part and allowing a transfer means to have a function for scraping the toner. CONSTITUTION:At a paper passing time when a transfer material exists between a photosensitive body 1 and a transfer roller 2, the transfer speed is made equal to the processing speed. At the time of allowing the paper not to pass, the transfer speed is made 5% lower than the processing speed. By performing such an operation, a force in a direction shown by an arrow B works between the photosensitive body 1 and the transfer roller 2 and it is in an opposite direction to the growth direction of the welded toner on the surface of the photosensitive body, so that an action that the welded toner is scraped and the growth thereof is prevented is accomplished.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrostatic copying machine or a printer, and particularly to a transfer apparatus thereof. be.

((Prior art and issues to be solved) In an image forming apparatus that includes a step of transferring a transferable toner image formed on the surface of an image carrier to a transfer material such as paper, a transfer device that presses against the image carrier is used as a transfer means. Transfer methods using contact type transfer means such as rollers have already been proposed and are well known.

A device equipped with such a contact type transfer means,
Compared to devices using corona dischargers that have been widely used in the past, it does not require a high-voltage power supply, so it is simpler in construction and can be made smaller, which is advantageous in cost. It has many advantages, such as there is no risk of image quality deterioration due to image transfer (and there is little generation of ozone or nitrides, etc.), and it also prevents transfer misalignment because the transfer material is firmly held in a predetermined position during transfer. However, on the other hand, the following problems could not be avoided.

To explain this, in the case of an image forming apparatus configured with a transfer roller in pressure contact with an image carrier, image accuracy (expansion/contraction)
, blurring, skewing, etc., it is desirable to apply a driving force to the transfer roller 2 using a gear, a belt, or the like.

In order to reliably transport the transfer material at the process speed and prevent transfer misalignment, the peripheral speed of the transfer roller at the transfer site where the transfer roller is in pressure contact with the photoreceptor (hereinafter referred to as transfer speed) must be adjusted to the photoreceptor. Circumferential velocity of the relevant part of the body (
It is common practice to match the processing speed).

However, in this case, a problem arises in that the toner adheres to the surface of the photoreceptor.

Toner fusion is formed from scratches on the surface of the photoconductor, adhesion of foreign matter, etc., and grows downstream when viewed in the direction of travel of the photoconductor. When the photoreceptor and the transfer roller run in perfect synchronization as described above, at the transfer site, the transfer material or the transfer roller only presses down the fused toner on the surface of the photoreceptor. Therefore, rather, it promotes fusion and promotes its growth.

Also, OHP sheets, cardboard (about 90gr/m2 or more)
In order to deal with the problem of hollow characters during transfer, which often occurs in
Although it has been attempted to deal with this problem by setting the toner to a higher value, such a method is not preferable from the viewpoint of toner fusing.

In other words, when the photoconductor and transfer roller are in pressure contact and the transfer material is passing between them, the speed of the transfer roller is high, so the toner is rubbed against the surface of the photoconductor through the transfer material. This tends to promote the fusion of toner.

In order to avoid this situation, it is possible to increase the pressure of the cleaner's cleaning blade on the surface of the photoconductor, but if this force is too large, it may cause damage to the photoconductor or cause damage to subsequent images. In the case of forming, there is a risk that blade marks will appear, leading to deterioration of image quality, and it is difficult to solve toner fusion by using the pressure force of the blade.

In addition, it is preferable to keep the temperature inside the image forming apparatus and the temperature near the cleaning blade low from the viewpoint of toner fusing, but it is uncertain and practical to prevent toner fusing only by temperature factors. Alternatively, it may be possible to further increase the melting point of the toner, but this is not preferable since it would lead to deterioration of fixing properties.

The present invention has been made to deal with the above-mentioned situation.In an image forming apparatus equipped with an image bearing member and a transfer means such as a transfer roller that comes into pressure contact with the image bearing member, a transfer material exists at a transfer site. By changing the transfer speed depending on whether or not to transfer the toner, the transfer means has a function of scraping off the toner on the surface of the image carrier, thereby preventing toner from fusing and ensuring good transfer performance. The purpose is to provide a device.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention comprises an image bearing member and a transfer means that presses against the image carrier, and transfers images to the pressure contact portion of both. The image forming apparatus is characterized in that the speed of the transfer means is configured to be different depending on when the paper is passing through the paper and when the paper is not passing through the image forming apparatus.

With this configuration, it is possible to effectively prevent the toner from adhering to the image carrier and the growth of the fused toner.

(Description of Embodiments) FIG. 1 is a schematic side view schematically showing the configuration of an image forming apparatus suitable for applying the present invention, which has an axis perpendicular to the plane of the paper and rotates in the direction of arrow X. A charging roller 3 is applied to the surface of a cylindrical image carrier (referred to as a photoreceptor) 1 by a power source 4.
A bias voltage is applied across the surface to uniformly charge the surface.

An image signal 5 such as an image-modulated laser beam is applied to this charged surface to form an electrostatic latent image.

As the photoreceptor 1 rotates, when this latent image arrives at a developing area where the photoreceptor 1 and the developing device 6 face each other, charged toner with a predetermined polarity is supplied from the developing device to the latent image to form a toner. An image is formed.

Next, when this toner image reaches the transfer site formed by pressure contact between the photoreceptor 1 and the transfer roller 2, the transfer material P is supplied from the conveyance path 7 at the same timing, and at the same time, the transfer material P is supplied to the transfer roller 2. A transfer bias is applied by a power source 4, and the toner image on the photoreceptor side is transferred to the transfer material by the action of the electric field formed.

Thereafter, the transfer material carrying the toner image is separated from the photoconductor 1 and conveyed to a fixing site (not shown), and some of the toner that was not transferred to the transfer material during transfer is removed by the cleaner 10, and the toner image is transferred to the photoconductor 1. 1 is ready to enter the next image forming process.

In the above apparatus, although not shown, the transfer row 22 is actively driven by a suitable drive means such as a gear from a photoreceptor or a separate motor, and is driven as necessary. The speed can be changed accordingly.

In such a configuration, in the first embodiment, the transfer speed is set to be equal to the process speed when a transfer material is present between the photoreceptor 1 and the transfer roller 2, and the transfer speed is set to the same speed as the process speed when the paper is not passed. is 5% slower than the process speed.

FIG. 2 shows the sequence in this case.

By performing such an operation, as shown in FIG. 3, which shows only the photoreceptor 1, transfer roller 2, and transfer material P in the vicinity of the transfer site, there is a gap between the photoreceptor 1 and the transfer roller 2 as shown in the figure. A force acts in the direction indicated by arrow B, which is opposite to the direction in which the fused toner grows on the surface of the photoreceptor, and therefore has the effect of scraping off the fused toner and inhibiting its growth.

The evaluation when implementing such an embodiment is 32.5.
℃, 85% RH environment, without implementing the present invention, one sheet was intermittently tested for durability.100
'O~ When printing 2000 sheets, dotted toner fusion occurred on the surface of the photoreceptor, and white spots occurred in the image.

When implementing the present invention, similar experiments were conducted, and
Even when printing 4,000 sheets, no toner fusion occurred and no deterioration in image quality was observed.

Similar results were also obtained when the transfer speed was made faster than the process speed.

FIG. 4 is a sequence showing another embodiment of the present invention, in which a device similar to that shown in FIG. It is 3% slower than

By operating in this manner, a force in the direction of arrow B in FIG. 3 is applied even when paper is passing, so that the effect of preventing the generation and growth of fused toner is activated.Furthermore, when paper is not passing, in the case of the above embodiment, Similarly, since it has a toner scraping effect, the effect of preventing toner fusion is greater.

The experimental results in this case are shown in Table 2.

Table 2 and FIG. 5 show still another embodiment of the present invention.

In this apparatus, a transfer belt is used as a transfer means, and other parts corresponding to those of the apparatus shown in the first figure are designated by the same reference numerals.

Even in such an apparatus, it is possible to use either the sequence shown in FIG. 2 or FIG. 4 described above.

As explained above, the transfer speed is close to a constant speed within 5% of the process speed when paper is passing, without affecting the image, and when the paper is not passing, the transfer speed is 3 to 10% of the process speed. By slowing down or speeding up the transfer process within a range of 1.5%, the transfer means can perform a toner scraping action, and it is possible to prevent the generation and growth of fused toner.

(3) As described in detail of the invention, according to the present invention, in an image forming apparatus equipped with an image bearing member and a contact type transfer means that comes into contact with the image bearing member, the number of transfer means is small (in other words, when the paper is not passing, the image forming apparatus is Since it acts to scrape off toner from the carrier, it prevents toner from adhering to the image carrier, eliminates the need to increase the pressing force of the cleaning blade, and also takes special measures against temperature rises and changes to toner characteristics. The present invention has a simple configuration, maintains good transferability, and greatly contributes to stably obtaining good images over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of an image forming apparatus suitable for applying the present invention, FIG. 2 is an operation sequence of the same as above, and FIG. FIG. 4 is a sequence showing another embodiment, and FIG. 5 is a schematic side view of another image forming apparatus suitable for applying the present invention. 1... Image carrier (photoreceptor), 2... Transfer roller, 3
...Charging roller, 4...Power source, 5...Image signal,
6...Developer, 9...Transfer belt. 1st Illustration Singing Iil Beni-Misaki-Ranshi 11 Rotation Diagram A 0 Death Susujin 0- Do and Upper Hi Diagram 5

Claims (3)

[Claims] (1) In an image forming apparatus that is equipped with an image carrier and a transfer means that is in pressure contact with the image carrier, and is configured such that the transfer material passes through the pressure contact portion between the two, the speed of the transfer means is determined when paper passes and when the paper does not pass. A transcription device configured differently depending on the time. (2) The transfer device according to claim 1, wherein the transfer speed when paper is not passed is different from the process speed by 3 to 10%. (3) Claim 1 in which the transfer speed during paper passing is slower than the process speed by within 5%.
2. The transfer device according to claim 1 or 2.