JPH02230277A - Fixing device - Google Patents

Abstract

PURPOSE:To maintain stable fixation performance for a long period by making a pressure roller longer than a fixing roller and forming areas which do not contact the fixing roller at both end parts and forming a communication hole which communicates with the outside between a tube and an elastic body layer. CONSTITUTION:A roller which is longer than the fixing roller 1 is used as the pressure roller 5 covered with the tube 53 made of a material with high peeling performance, the areas which do not contact the fixing roller 1 are provided at both end parts, and the heat of the fixing roller 1 is made hard to conduct to the areas 55, thereby securing the adhesive strength between the tube 53 and pressure roller 5. Further, the gas discharge hole 54 is formed between the tube 53 and the elastic body layer 52 of silicone rubber, etc., to discharge gas produced by the elastic body layer 52 to the outside, thereby preventing the tube 53 from expanding and peeling. Consequently, the stable fixation performance is maintained for along period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device that is installed in an electrostatic recording device such as a copying machine and fuses and fixes a toner image transferred onto a sheet of paper.

[Prior art]

In electrostatic recording devices such as electrophotographic copying machines, facsimile machines, and electrostatic printers, a toner image formed on a photoreceptor is transferred to a transfer paper, and recorded by being fixed. Conventionally, this fixing device has a fixing roller that has a built-in heat source and a pressure roller that is in pressure contact with the fixing roller and has an elastic layer on the outer periphery of a core metal, and a transfer paper that carries an unfixed toner image is passed through the pressure roller. A heated roller fixing device that fuses a toner image to a paper surface is widely used.

Conventionally, the material for the elastic layer of the pressure roller is HTV, R.
TV, liquid silicone rubber, etc. have been used, and are swollen with silicone oil to provide releasability to toner.

However, even with this type of roller, there are problems such as deterioration in peelability due to long-term use and deviation in roller dimensions due to wear.

Therefore, as a solution to the above-mentioned problem,
No. 3740 proposes a silicone rubber layer coated with a PFA (copolymer of polytetrafluoroethylene and perfluoroalkyl perfluorovinyl ether) tube.

[Problem to be solved by the invention]

PFA tubes have good toner releasability and silicone oil resistance, and are stronger and have better abrasion resistance than baked-on PFA.

However, in the structure where the rubber layer is covered with the PFA tube, there is no effective primer, so the rubber layer and the PFA tube cannot be brought into close contact with each other, and peeling often occurs between them, resulting in paper failure. There is a problem in that it becomes possible and leads to a reduction in lifespan.

The present invention has been made in view of such circumstances, and is based on the PF
It is an object of the present invention to provide a fixing device that can eliminate the above-mentioned drawbacks of a pressure roller covering a tube made of a highly releasable material such as A and can maintain stable fixing performance over a long period of time.

[Means for Solving the Problems] A fixing device according to the present invention includes a fixing roller having a built-in heat source, a tube made of a highly releasable material that is in pressure contact with the fixing roller, and a core material is attached via an elastic layer. In a fixing device that fixes a toner image by conveying a transfer material carrying an unfixed toner image under pressure between a covered pressure roller, the pressure roller is longer than the fixing roller. A non-contact area with the fixing roller is formed at both ends, and a communication hole with the outside is provided between the tube and the elastic layer.

[Effect]

The pressure roller is longer than the fixing roller and is in pressure contact with the fixing roller so that non-contact areas with the fixing roller are formed at both ends, and a communication hole with the outside is provided between the tube and the elastic layer. It will be done. This ensures long-term adhesion between the tube and the elastic layer in the non-contact region, and gases generated from the elastic layer are discharged to the outside.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 is a schematic diagram showing the internal structure of a heat roller fixing device according to the present invention. A fixing roller 1 having a built-in heater 2 is brought into pressure contact with a pressure roller 5 and is rotated in the direction of the arrow mark, respectively. The toner image is fused and fixed onto the paper by heating it at the nip and conveying it under pressure. A thermistor 3 is installed on the circumferential surface of the fixing roller 1 to detect the temperature in order to maintain the temperature at a predetermined temperature.
and a web cleaning roller 4 for cleaning the surface are arranged in contact with each other.

Further, the pressure roller 5 is also maintained at a predetermined temperature, and a heater 6 and a thermistor 7 for this purpose are provided similarly to the fixing roller. This is to increase the fixing strength and reduce heat curl to improve the reliability of the fixing, and is particularly important in high-speed machines.

In this embodiment, the temperature of the fixing roller 1 is adjusted to 190°C, and the temperature of the pressure roller 5 is adjusted to 140°C.

The paper that has passed through the nip between both rollers is separated from the fixing roller 1 or the pressure roller 5 by a separating claw 8 or 9 provided on the fixing roller 1 side or the pressure roller 5 side. ,
The fixed paper is cooled by the cooling roller 10 and discharged to the outside of the fixing device.

FIG. 2 is a sectional view showing the configuration of the pressure roller 5. As shown in FIG. The pressure roller 5 is applied to the outer peripheral surface of a cylindrical core material 51 made of metal such as aluminum. Rubber layer 52 bonded with
It further has a PFA tube 53 bonded to the outer peripheral surface of the rubber layer 52 with a primer.The suitable thickness of the PFA tube 53 is 30 to 150 μm, and thicker This increases the cost of the amplifier and makes it impossible to obtain the desired width.On the other hand, if the tube is too thin, the tube strength will be weakened and wrinkles will easily occur. Silicone rubber is used as the material for the rubber layer 52 in terms of heat resistance and cost.

Further, as the brimer between the rubber layer 52 and the PFA tube 53, a silicone-based brimer is suitable in consideration of the temperature during actual use, the base material, and the adherend.

Now, between the rubber N52 and PFA tube 53,
Gas vent holes 54,54 according to the present invention are provided at both ends of the roller in the axial direction to communicate with the outside.

The gas vent holes 54, 54 are formed by simply folding the PFA tube 53 into a flat plate and preventing the crease from being processed during the etching process on the inner surface, thereby forming a non-adhesive part that does not react with the primer. This is a gas vent hole. When the creases are utilized in this way, a gas vent hole that is easy to manufacture and has stable performance can be obtained.

FIG. 3 is a schematic diagram showing the length and arrangement relationship between the fixing roller 1 and the pressure roller 5.
, and is in pressure contact with the fixing roller 1 by protruding from both ends of the fixing roller 1 by a substantially equal length. In this embodiment, the portion of the pressure roller 5 protruding from both ends of the fixing roller 1, that is, the portion excluding the gas vent hole 54 in the non-contact area with the fixing roller 1, that is, the hunting portion is a rubber layer 52 made of a primer. Adhesion area 55 with PFA tube 53
．． 55.

Further, the fixing roller 1 is formed with rounded edges on both ends thereof, and is brought into pressure contact with the pressure roller 5 at an inner portion slightly away from the adhesive area 55, 55 of the pressure roller 5. By doing so, the load on the pressure roller 5 at the end of the fixing roller is reduced, and the durability of the PFA tube 53 is improved.

Next, the basis for configuring the apparatus of the present invention as described above will be specifically explained based on the background of experimental examples (1) to (6) shown below.

(1) First, as a general conventional device, both the fixing roller and the pressure roller have a length of 320 am, and the fixing roller has an aluminum core material coated with PF8 and has a baking diameter of 60 ln. The pressure roller has an outer diameter of 6 (hm) and a 70 μm PFA tube is coated on the outside of a 6-layer thick silicone rubber layer with a rubber hardness of JIS 1840°.
The following was used. Here, the inner surface of the PFA tube was etched with a mixture of sodium and naphthalenetetrahydride-furan, and the entire surface of the PFA tube was adhered to the surface of the rubber layer with a silicone rubber adhesive.

When the fixing roller and pressure roller as described above were set in the fixing device and intermittent running was performed at a paper conveyance speed of 380 dragons/sec, equivalent to 2,000 sheets per day, the PFA tube peeled off after 80,000 sheets had been passed. .

(2) When a fixing roller and a pressure roller having the same configuration as in Experimental Example +1) were continuously run for the equivalent of 20,000 sheets per day, no peeling occurred even after 800,000 sheets were passed.

The difference between Experimental Examples (1) and (2) is explained by the difference in thermal load applied to the pressure roller. In other words, in the running mode of Experimental Example fil, in which the roller was stationary a lot, the primer of the pressure roller directly received heat from the fixing roller, so that the adhesive force decreased more quickly than in (2).

(3) Therefore, based on the idea that peeling would not occur if only the ends of the pressure roller were adhered, the inventor set the length of the pressure roller to 330mm, and attached the pressure roller to the fixing roller. The pressure rollers are arranged so as to be longer by 5 lengths from each end, and by rounding both ends of the fixing roller, regions are provided at both ends of the pressure roller that do not come into contact with the fixing roller. When the same experiment as (1) was conducted, the PFA tube also peeled off after about 80,000 sheets. When the peeled tube was examined, it was confirmed that only both ends were adhered. In other words, it was found that although peeling occurred, adhesive strength could be ensured at both ends with the above-described configuration.

(4) Based on the results of Experimental Example (3), we assumed that the peeling was caused by the expansion of the tube due to the volatile components in the rubber layer material, and we fabricated a pressure roller with only the ends that did not come into contact with the fixing roller bonded. The tube expanded during the heating stage during production. The reason for the peeling in Experimental Example (3) is considered to be that the adhesion force was reduced due to heat, and gas was generated from the rubber layer material, causing the tube to expand and peeling off.

(5) Therefore, when we made a pressure roller with the same configuration as in (3) from a rubber material with low molecular weight components that generate less gas and conducted the same experiment, we found that the PFA tube peeled off after about 80,000 sheets. occurred. From these results, it is considered that at the time when the adhesive strength decreased due to heat (80,000 sheets), gas that expanded the tube was already being generated.

(61 (When we conducted the same experiment as in (3) using the same pressure roller manufactured in step 51 and removing the heater inside the pressure roller, we found that even though 800,000 sheets were passed, the Pl'A tube No peeling occurred.

From the above results, it is thought that the temperature adjustment by the heater inside the pressure roller is related to the generation of gas as the rubber material deteriorates, and the core material. When we measured the temperature between the rubber layers, the maximum temperature was 2.
It was found that the temperature had reached 20℃.

Therefore, in order to prevent the rubber material from deteriorating, it may be possible to lower the adjustment temperature of the pressure roller, but it cannot be set extremely low because it is necessary to ensure reliability of paper feeding. Other possible methods for preventing deterioration include making the core material thicker or making the rubber layer thinner, but neither method has been able to provide sufficient effects.

Therefore, the inventor of the present invention provided a gas vent hole at the end of the pressure roller to allow the gas generated from the rubber material that promotes peeling to escape to the outside, and based on the fact found from Experimental Example (3), The pressure roller is made longer than the fixing roller, and non-contact areas with the fixing roller are provided at both ends of the pressure roller, so that the adhesive strength between the tube and the rubber layer can be ensured at the minimum in these areas.

As a specific example of such a pressure roller, Experimental Example (3)
When the length of the fixing roller is 320 mm as shown in , the length is set to 330 mm, and 5 lengths protrude from both ends of the fixing roller to be brought into pressure contact with the fixing roller. In addition, if the outer diameter of the pressure roller is 60 mm and two locations are provided as shown in Figure 2, the diameter of the gas vent hole should be 2 or less. This is undesirable as it may infiltrate and expand.

When the same experiment as in Experimental Example (3) was conducted using the pressure roller configured as described above, no peeling occurred in the PFA tube even after 800,000 sheets were passed, and good fixing performance was obtained.

In this example, the case where the tube made of I'FA is used is shown, but it is not limited to I'FA, and can be applied to any tube made of a material that provides high releasability to toner. It is possible.

Further, in this embodiment, the PFA dupe is configured to be bonded only at both ends forming the non-contact area M with the fixing roller, but it goes without saying that the same effect can be obtained even if the entire surface is bonded.

Furthermore, the arrangement position, number, and manufacturing method of the gas vent holes are not limited to those in this embodiment, and any holes may be used as long as the gas generated from the rubber layer can escape efficiently.

〔effect〕

As described above, in the fixing device according to the present invention, the pressure roller covered with a tube made of a highly releasable material such as PFA is longer than the fixing roller, and the fixing roller is attached to both ends of the pressure roller. By providing an area that does not come into contact with the fixing roller, it is difficult for the heat of the fixing roller to be transmitted to the area, and the adhesion force between the tube and the pressure roller can be ensured. Furthermore, gas is prevented between the tube and the elastic layer such as silicone rubber. By providing a vent hole, gas generated from the elastic layer can be discharged to the outside, and the tube can be prevented from expanding and peeling off.

As a result, even in a configuration in which the pressure roller is heated to a predetermined temperature in order to improve fixing strength and reliability of fixing, the tube does not separate from the pressure roller over a long period of time, resulting in stable fixing. The present invention has excellent effects such as being able to maintain performance.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the internal structure of the fixing device according to the present invention, FIG. 2 is a sectional view showing the configuration of the pressure roller, and FIG. 3 is a diagram showing the length and arrangement relationship between the fixing roller and the pressure roller. FIG. 1... Fixing roller 2, 6... Heater 5... Pressure opening-ra 5l... Core material 52... Rubber layer 53.
...PFA Tuff 54...Gas vent hole patent Applicant: Minolta Camera Co., Ltd. Agent Patent attorney: Noboru Kono ＼ Brother of memorial service? figure

Claims (1)

[Claims] 1. Between a fixing roller with a built-in heat source and a pressure roller that is in pressure contact with the fixing roller and whose core material is covered with a tube made of a highly releasable material via an elastic layer. , in a fixing device that fixes a toner image by conveying a transfer material carrying an unfixed toner image under pressure, the pressure roller is longer than the fixing roller, and the pressure roller has non-contact contact with the fixing roller at both ends. A fixing device characterized in that a region is formed, and a communication hole with the outside is provided between the tube and the elastic layer.