JPH02309376A - Pressure roller for fixing - Google Patents

Abstract

PURPOSE:To obtain a pressure roller having excellent permanent deformation characteristics and durability by using vulcanized silicone rubber possessing a prescribed compression permanent deformation and setting the hardness of the silicone rubber of an outer layer higher than that of an inner layer by a prescribed value. CONSTITUTION:A pressure roller is made of the vulcanized silicone rubber of the excellent compressive permanent deformation of<= 10% (according to a JIS K 6031 method: 180 deg.C X 22 hours). The hardness of the silicone rubber of the outer layer 2 is higher than that of the inner layer 1 by 20 deg. -50 deg. according to a penetrometer. The outer layer 2 is made of preferably separatable silicone rubber of 0.5 - 2mm in thickness. Under this constitution, the pressure roller of the excellent permanent deformation characteristics can be economically obtained, such defect is surely prevented that paper wrinkles in an electrostatic recording device, and the dulability of the pressure roller can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" This invention is applicable to electrophotographic copying machines, computers, OCs:
This invention relates to a fixing pressure roller in an electrostatic recording device such as a facsimile machine.

``Prior art and problems that the invention has not attempted to solve'' In general, in the fixing device of low-to-intermediate machines such as copying machines that use a heating roller and a pressure roller, the pressure roller used is separated from the core metal. Those coated with heat-curable or room-temperature-curable silicone rubber with good moldability, and those coated with silicone sponge rubber on a core metal and further coated with silicone rubber on the surface are used.

In a fixing device that uses a heating roller and a pressure roller to fix thermoplastic resin powder (toner) to paper, factors that affect fixing include the temperature of the heating roller, the duration of contact between the heating roller and the pressure roller, and the contact pressure. , the time it takes to pass between both rollers, etc. Among these methods, one method is to improve fixing by changing the contact pressure (so-called nip) during the contact between the heating roller and the pressure roller (so-called nip) without changing the time for the heating roller to pass through the pressure roller. need to be widened.

However, as the pressure increases, the rotational torque of the roller naturally increases, and the paper becomes more likely to wrinkle.

Therefore, in terms of -M, a method is used to lower the rubber hardness of the heating roller and widen the nip width without increasing the pressure.

In particular, since this method does not require increased pressure, it is effective in suppressing paper wrinkles (particularly in special paper such as envelopes).

However, there is a limit to reducing the hardness of this rubber.
Since no silicone rubber has been developed that is suitable as a fixing pressure roller material with a hardness of 15 degrees or less on the rSA hardness meter, it cannot be said that this method is completely effective for removing paper wrinkles from special paper.

Currently, sponge-type pressure rollers with a two-layer structure in which the core metal is coated with a silicone rubber sponge and the surface is further coated with silicone rubber that has good release properties, are more effective at removing wrinkles from paper with a lower hardness. has been developed and is used in some models.

The reason why this sponge-type pressure roller has a good effect on paper wrinkles is that it has a low hardness, but also because it has a two-layer structure with a difference in hardness between the inner and outer layers. This is one example.

This is considered to be because when pressure is applied to the pressure roller, the amount of deformation of the pressure roller due to the pressure is small considering the wide nip width (see FIG. 3).

However, the pressure roller of Bonsitive is also not perfect; the inner layer of sponge rubber has a poor compression set rate and lacks durability; the roller deforms when heated in the nip for a long time; However, there is a drawback that the bubbles break and the performance deteriorates.

"Means for Solving the Problems" In order to solve the above-mentioned conventional problems, the present invention uses silicone rubber with an excellent compression set rate (10% or less according to JIS K6031 method) as an inner layer instead of the conventional sponge rubber. The rubber hardness is higher than that of the inner layer ((JI
By coating it with silicone rubber with a thickness of 0.5 to 2 mm that has a hardness of 20 to 50 degrees on the S A hardness scale and good releasability, it is effective against paper wrinkles like a sponge type pressure roller. Moreover, the present invention proposes a durable pressure roller with excellent permanent distortion rate.

"Embodiments" Below, embodiments of the present invention shown in the drawings will be described.
A roller is made by coating a core metal with a diameter of 10 mm with a brimer, and then coating and molding an inner layer rubber 1 with a thickness of 4 mm made of liquid silicone rubber. A pressure roller for fixing with a diameter of 20 mm was obtained by covering and molding an outer rubber layer 2 made of silicone rubber and having a thickness of 20 to 50 degrees.

Silicone rubbers of various hardness (AS-1-AS-7:
)--manufactured by Resilicone) to create 12 types of pressure rollers, and when these were installed in an actual copying machine to check the occurrence of paper wrinkles, the results shown in Table 1 were obtained. Table 6-1 (Paper wrinkle actual machine test results) As can be seen from this table, it was found that creating a difference in rubber hardness between the inner and outer layers of 20 degrees or more was effective in solving the problem of paper wrinkles.

Next, we left the copier in a heated state with the power on and left it for one week, and compared the amount of outer diameter deformation (permanent distortion) between the present invention and a sponge type roller. The results are shown in Figure 2. It became.

And, for all the materials, the amount of deformation of the sponge roller is 3
It was less than one-fold.

In addition, when the inner layer rubber 1 was AS-1 and the outer layer rubber 2 was AS-6, the occurrence of paper wrinkles was investigated by changing the thickness of the outer layer rubber 2. When the thickness of the outer layer rubber 2 exceeded 2 man, the inner layer rubber The effect of 1 faded and became a problem.

On the other hand, if the rubber thickness is thinner than 0.5+nm, it is difficult to maintain uniformity in thickness, and unevenness in rubber thickness affects fixing performance, and it is likely to be expensive to manufacture while maintaining uniformity. ,
There are practical difficulties.

"Effects of the Invention" As described above, according to the present invention, in a pressure roller having a two-layer structure of silicone rubber, the outer layer of rubber is made higher by 20 or more on the JIS A hardness tester than the inner layer, and the thickness is 0.
Since it is set to 5 to 2 mto, it is possible to economically obtain a rubber pressure roller with excellent permanent deformation characteristics, and it is possible to reliably prevent problems caused by paper wrinkles in electrostatic recording devices, and to improve durability.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of the fixing pressure roller of the present invention;
FIG. 2 is a diagram showing the comparison results of a permanent deformation test between the pressure roller of the present invention and a conventional sponge type pressure roller;
FIG. 3 is a schematic diagram showing the state of pressure bonding between the fixing heating roller and the fixing pressure roller. 1. Inner layer rubber, 2. Outer layer rubber. Fig. 1...1 Amount dent 20- Fig. 3 Fig. 2/'' 11--One day after the alarm - Number of days elapsed after one week

Claims (1)

[Scope of Claims] 1) In a pressure roller for fixing in which a core metal is coated with two layers of silicone rubber, the compression set rate of the silicone rubber vulcanizate is 10% (according to JIS K6031 method: 18).
0°C x 22 hours) or less, and the hardness of the silicone rubber of the outer layer is 20 to 50 degrees higher than that of the silicone rubber of the inner layer on a JIS A hardness meter. Pressure roller for fixing. 2) The fixing pressure roller according to claim 1, wherein the outer layer of silicone rubber has a thickness of 0.5 to 2 mm.