JPH03130789A - Transfer material separating device of image forming device - Google Patents

Abstract

PURPOSE:To perform excellent separating operation stably for a long period by making the hardness of a coating larger at and nearby a tip where a separation claw contributes to the separating operation than at the part of the separation claw where a transfer material slides. CONSTITUTION:The separation claw 2 which is fitted in a fixing device and has its pointed end part abutting on the surface 1a of a fixing roller is arranged on the side of a nip part N where the transfer material is discharged. When fixation is finished, the transfer material is separated by the claw 2 and separated forcibly from the roller 1a. The claw 2 is formed by coating an epoxy primer with PTFE. The part 3 which abuts on the roller 1a is coated with PFA enamel which has lower hardness than the PTFE to prevent the roller surface 1a from damaging. Then the separating operation is performed stably for a long period without flawing a photosensitive body.

Description

Detailed Description of the Invention (1) Purpose of the Invention ((Industrial Application Field) This 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 material separation device thereof. It is related to.

((Prior art and issues to be solved) A transferable toner image formed on the surface of an image carrier is electrostatically transferred to a transfer material such as paper, and the toner image electrostatically attached to the transfer material is removed. An image forming apparatus configured to fix and fix an image onto a transfer material through a fixing device is conventionally well known.

In such an image forming apparatus, a rotating cylindrical photoreceptor is used as an image carrier, and a pair of fixing rollers that are in pressure contact with each other are used as a fixing device, and the image forming apparatus uses a pair of fixing rollers that are placed in pressure contact with or close to the photoreceptor. A transfer site is formed with the provided transfer means, the transfer material is passed through this transfer site, and a transfer bias is applied to transfer the toner image to the transfer material. After the transfer, the transfer material carrying the toner image is fixed. Conventionally, a structure in which the toner is passed through a pressure nip between a pair of rollers and fixed by applying pressure and heating has been widely used.

In such an image forming apparatus, the transfer material tends to be electrostatically attracted to the photoconductor even after transfer, and at the fixing part, the transfer material tends to be fixed even after fixing due to the toner softened by the addition. The transfer material tends to stick to the roller,
There was a risk that the particles would travel along the periphery of the photoreceptor or the fixing roller and cause a jam.

In order to avoid such drawbacks, a conventional method has been proposed in which a separating claw is brought into contact with the fixing roller or photoconductor, and the incoming transfer material is stripped off from the fixing roller or photoconductor. What is happening is well known.

Looking at the fixing roller, the characteristics required for such a separating claw are: 1) the frictional resistance is as small as possible since the claw rubs against the fixing roller and the transfer material; 2) the fixing roller is In order to avoid damage, the hardness of the material making up the claws should not be too high; 3) toner adhesion, which can easily cause jams, should not occur easily; 4) this is necessary because it comes into contact with the fixing roller, which is heated to about 180 to 220 degrees Celsius. 5) It has high abrasion resistance because the tip of the transfer material comes into contact with it.

In order to meet these demands, nails made of heat-resistant resin such as polyamide-imide coated with Teflon have been developed.
(Japanese Unexamined Patent Publication No. 57-111569).

Furthermore, the conditions for the separation claw that comes into contact with the photoreceptor and peels off the transfer material after transfer are as follows: 1) Since it rubs against the photoreceptor and the transfer material, the coefficient of friction is small; 2) It does not damage the photoreceptor. 3) The volume resistance should be as small as possible so that the residual toner that remains on the photoreceptor does not adhere to the transfer material even after transfer and fall onto the transfer material. Nails made of a resin such as polyaridoimide coated with a layer of carbon dispersed therein are often used.

However, in recent years, this type of image forming apparatus has gradually become faster, and with this, when it comes to fixing devices, there is a trend toward faster and hotter fixing rollers.
It is becoming difficult to simultaneously meet the above-mentioned demands.

For example, in the case of separation claws for fixing, 2) above requires that the hardness not be high, but 5) requires higher hardness, which is a contradictory situation. I can't help but be invited.

As the photographing speed increases, the conditions required of the separation claws are becoming contradictory to each other.

The present invention has been made in view of the above situation, and the part of the separation claw that directly contributes to separation of the transfer material and the part on which the transfer material rubs after separation are made of different materials. It is an object of the present invention to provide a transfer material separation device which eliminates the above-mentioned drawbacks and exhibits a stable and good separation effect over a long period of time.

(2) Structure of the invention (technical means for solving the problem, its effect) In order to achieve the above-mentioned object, the present invention provides that when the transfer material tends to adhere to other members, the tip is inserted between the two. In a transfer material separation device of an image forming apparatus that is equipped with a separation claw that separates the two, the separation claw directly covers the leading edge and its vicinity that contributes to the separation of the transfer material, and after one separation, the transfer material rubs against the separation. The nail part is coated with a hardness higher than that of the latter part.

With this configuration, it becomes possible to perform stable and good separation over a long period of time, and it becomes possible to immediately respond to the increase in speed of the main image forming apparatus.

(Description of Embodiments) The attached drawing is a schematic side view showing an embodiment in which the present invention is applied to a fixing roller constituting a fixing device, in which a pair of rollers are in pressure contact with each other and rotate synchronously in the direction of arrow X in the figure. roller 1
A and 1b, a transfer material P carrying a toner image at an image forming area (not shown) located on the right side of the figure passes through the nip part N from the direction of arrow A. The toner image electrostatically adhered to the transfer material is fixed and fixed by being heated and pressurized by an appropriate heating means.

On the side of the nip N from which the transfer material is discharged, there is provided a separation claw 2 which is attached to a suitable position within the fixing device and whose sharp end is in contact with the surface of the fixing roller la. The transfer material that has been processed is forcibly separated from the fixing roller la by the separating claw and discharged.

It goes without saying that the pair of fixing rollers 1a and 1b is provided with a heat source for heating at least one of the rollers, a cleaner for removing toner adhering to the roller, etc., but these are not included in the present invention. It is omitted because it is not directly related.

In the illustrated embodiment, the separating claw 2 is generally made of an epoxy resin primer coated with PTFE, but this prevents toner from adhering to it and jams are less likely to occur. , P as primer
A mixture of I and PFA was used, and a PFA enamel coat with a hardness lower than that of PTFE was applied to the portion 3 including the tip that contacts the fixing roller La to prevent damage to the fixing roller.

In addition, a PFA coat containing mica was applied on the PFA enamel coat to improve the abrasion resistance in the area indicated by reference numeral 4 where the transfer material after separation rubs against each other.

Table 1 shows an experimental example of the separating claw device constructed in this way.

(Margins below) As can be seen from the table, in the known device, the coating wears down after passing around 10,000 sheets, exposing the epoxy resin part to which toner easily adheres, leading to frequent jams. but,
In the example device, even after passing 50,000 sheets, there was generally little wear, and in some cases the coating was slightly worn and the main body material was exposed, but a material to which toner does not easily adhere was used as a primer. Therefore, no jam occurred.

As explained above, the separation claw of the fixing part is made of different coating materials for the part that comes into contact with the fixing roller and separates the transfer material, and the part where the transfer material rubs against the separation claw after separation. The coating is relatively soft to prevent damage to the fixing roller, and by making the latter coating a hard material, stable fixing can be achieved over a long period of time while preventing jamming.

Next, the separation claws on the photoreceptor will be explained.

The material of the separation claw and the primer material are the same as above.
The part including the tip that comes into contact with the photoreceptor contains carbon molecules
A paper feeding experiment was conducted using one coated with PFA coating and one coated with PFA containing mica on the area where the transfer material rubs after separation, and the results are shown in Table 2.

In this case, the volume resistivity of the carbon-dispersed PFA coat is 10
2~lO6Ωcm, that of PFA coat with mica is 1
It was 0'4 Ωcm or more.

(Left below) It has been confirmed that damage to the photoconductor occurs when a part coated with mica-containing PFA comes into contact with the photoconductor. However, by using the above structure, it is possible to prevent damage to the photoconductor. , a separation claw with less toner falling can be obtained.

(3) As described in detail, the present invention provides a separation device that includes a pair of fixing rollers and a separation claw that presses against the photoreceptor, and separates the transfer material from the fixing roller and the photoreceptor after fixing and transfer. In this method, the parts that directly contribute to the separation of the transfer material and the parts where the transfer material rubs after separation are each coated with a suitable material, making it possible to perform stable separation over a long period of time. In particular, it greatly contributes to speeding up image forming apparatuses.

[Brief explanation of the drawing]

The accompanying drawing is a side view of a main part showing an embodiment in which the present invention is applied to a fixing roller. Coating on the tip side, coating on the rubbing side of the 4 transfer material.

Claims (3)

[Claims] (1) When the transfer material tends to adhere to other members, in a transfer material separation device of an image forming apparatus that is equipped with a separation claw that inserts the tip between the two and separates the two, the separation claw directly attaches to the transfer material. A transfer material separation device comprising: a coating on the tip and its vicinity that contributes to separation; and a coating on the separation claw portion where the transfer material rubs after separation, the former having a harder hardness than the latter. (2) The transfer material separation device according to claim 1, wherein the member to which the transfer material tends to adhere is a fixing roller. (3) The transfer material separation device according to claim 1, wherein the member to which the transfer material tends to adhere is a photoreceptor.