JPS6332575A - Fixing device for copying machine - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a fixing device for a copying machine, and more particularly to a heat fixing device that combines a heating roller and a pressure roller.

(Prior Art) Generally, in copying, an unfixed image transferred onto a transfer material in a transfer section is melted and fixed on the transfer material in a heat fixing section.

For this reason, in the fixing section, for example, a roller heating fixing device is used, which includes a heating roller with a built-in heat source and a pressure roller that comes into contact with the heating roller and works together with the heating roller to grip and convey the transfer material. It is being

Incidentally, in such a heat fixing device, a coating layer is often provided on the surface VC of the heating roller and pressure roller to prevent offset. The coating layer is made of a material with relatively high volume resistivity, such as fluorocarbon resin or silicone rubber.

Therefore, when a pair of rollers having such a structure is rotated, for reasons that are not clear, the roller surface is charged, and in particular, the axial center of the roller is non-uniformly charged, with the potential of band 7IL peaking. Occur.

Due to this phenomenon, the transfer material cannot be peeled off uniformly from the roller in the axial direction of the roller after fixing, and it becomes necessary to provide a special separation mechanism to solve this problem. Alternatively, a portion of the roller surface VC= or dust may easily adhere to the roller surface in the axial direction of the roller, and the roller surface may be damaged by this dust or dust.
Further, problems such as damage to images have arisen.

(Objective) In view of the problems of conventional heat fixing devices, an object of the present invention is to provide a heat fixing device that can simplify the separation mechanism in the fixing device and prevent damage to the roller surface and images in the fixing device. is to obtain.

(Purchase) In order to achieve the above object, the present invention is characterized in that the electrical charge generated in the axial direction of the roller in the heat fixing device is controlled.

Hereinafter, detailed explanations of embodiments of the present invention will be given with reference to FIGS. 1 to 7.

FIG. 1 shows a heating roller 1 and a pressure roller 2 separated.
FIG. 2 is an explanatory diagram showing changes in surface potential of each roller when conductors such as metals are arranged with an interval e at degrees Celsius for the heating roller 1. FIG.

In the embodiment shown in Figure 1, a coating layer of Teflon (trade name) is formed on the surface of the heating roller, while a coating layer of silicone rubber is formed on the surface of the pressure roller 2.

A conductive filter, such as a coiled metal wire, whose longitudinal direction is set in the axial direction of the roller, is arranged opposite to the heating roller 1 with an interval g.

This conductor 5 is, of course, grounded, and the local part of the coil is opposed to the heating roller 1, and the opposing distance is changed by 1'l by a mechanism not shown.

Now, in the conventional device in which the conductor 6 is not opposed to the heating roller 1Vc, uneven charging occurs on the heating roller 1 in the axial direction of the roller, as shown by the solid line in the figure. However, charging unevenness with opposite polarity occurs due to the influence of the band percentage of the heating roller.

On the other hand, the conductor 3 is placed opposite the heating roller 1Vc and g
= less than 5 m/m, l = 5-10 m/m,
1 = 10 to 15 m/m, the charges at both ends of the heating roller 1 in the axial direction discharge against the conductor 3Vc, approach 0 potential and become saturated, and the center of the axial direction The potential difference between the two parts becomes smaller.

On the other hand, along with this, the potential difference in the axial direction becomes smaller on the pressure row 22 side as well due to the change in the potential level on the surface of the heating roller, and as a result, uneven charging in the axial direction is eliminated.

Generally, when removing static electricity, it is considered to bring the static eliminating member into contact with the surface of the roller that holds the charge. There is a risk of damage to the surface. However, in the case of this embodiment, such a preface is eliminated, and the charging unevenness that occurs in the axial direction of the roller is eliminated. In addition, in this case, what is meant by eliminating charging unevenness?
This does not mean lowering the entire charging potential in the axial direction of the roller, but rather reducing the potential difference between the peak value and the minimum value of the charging potential.

Next, in Figure 2, an example will be explained in which the difference between the peak value of the charged potential in the axial direction of the roller and the lowest value of the same potential is reduced by charging the roller in the opposite way to the embodiment shown in Figure 1. do.

That is, in Figure 2, the surface of the heating roller 1 is coated with Teflon (trade name) K, and the axial center of the roller 1 is coated with silicone rubber or the like that has the same polarity triboelectric properties as Teflon. Friction member 4 with high volume resistivity
are in contact.

Therefore, the heating roller 1 when the friction member 4 is not in contact with the
When the charging characteristic of is in the state shown by the solid line in the figure, when the friction member 4 is brought into contact with the heating roller 1Vc,
The heating roller 1 is charged with the same polarity as the charging polarity of the heating roller 1 at the center in the axial direction.

In this embodiment, the charging potential at the axial center of the heating roller 1 increases and approaches the peak value of the charging potential at both axial ends, thereby reducing the potential difference in the axial direction and reducing charging unevenness. Eliminate.

Further, in order to eliminate such charging unevenness in the axial direction of the roller, it is also possible to take measures to eliminate charging unevenness on the pressure roller 2VC, instead of taking measures only for the heating roller 1VC.

Examples of this case are shown in FIGS. 16 and 4.

That is, in the embodiment shown in FIG. 6, a sheet metal member 5 having a comb-shaped tip is placed close to and opposed to the axial center of a pressure roller 2 made of silicone rubber.

In this implementation filJ Vc, similarly to the case where the conductor 6 is closely opposed to the heating roller 1 shown in 3-1,
Electric discharge occurs between the axial center of the pressure roller 2 and the tip of the sheet metal member 5, lowering the potential at the center and reducing the potential difference between the axial ends and the charging unevenness. .

Therefore, when the charging unevenness in the axial direction is eliminated in the pressure roller 2VC, as explained in Figure 1,
This also affects the charging unevenness on the surface of the heating roller that is in contact with the roller 2, and as a result, the M charging unevenness on the heating roller is also eliminated.

In the embodiment shown in FIG. 4, a conductive curved plate 6 having a curvature is opposed to the axial center of the pressure roller 2 so that a portion having a small area is close to the pressure roller 2.

Even in the case of this embodiment, the charging unevenness in the axial direction of the pressure roller 2 is eliminated, as shown in FIG.
Even in the axial direction of the heating roller 1, charging unevenness is eliminated compared to the conventional structure shown by the solid line in the figure.

The embodiments described above are all specific examples in which measures are taken to eliminate uneven charging on the heating roller or pressure roller, but in the present invention, one of these rollers is It is not limited to taking measures to eliminate charging unevenness.

That is, FIGS. 5 and 6 show an example in which measures are taken to eliminate charging unevenness for both heating and pressure rollers.

In the embodiment shown in FIG. 5, the area VC of the heating roller 1 excluding the central part in the axial direction is made to face the conductive static eliminating brush 7, while the axially central part of the pressure roller 2 is also provided with a conductive neutralizing brush 7. The static elimination bra/8 is placed opposite to the other.

The static elimination brush 7 on the side of the heating roller 1 adjusts the distance g1 between the axial end of the roller 1° and the curved surface of the heating roller 1 to
The neutralization brush 8 on the pressure roller 2 side has a distance e3 between the axial center of the roller 2 and the circumferential surface of the pressure roller 2 that is the same. The distance between both sides of the central portion and the surface of the roller 2 is set to be narrower than the distance 4.

Therefore, in this embodiment, the same effect as the embodiment shown in Fig. 4 can be obtained on the pressure roller 2 side, and the same (enviable effect) as the embodiment shown in Fig. 1 on the heating roller 1 side. As a result, uneven charging on the pressure roller 2 side is eliminated compared to the conventional method shown by the solid line in the figure.

In addition, by arranging the static eliminating brush in this manner, it is possible to obtain the same condition as if static electricity is being completely removed over the entire axial direction of the roller, so that the level of the charged potential can also be reduced over the entire axial direction. It becomes possible.

In addition, instead of changing the distance between the static eliminating brush 9 and the surface of each roller in the axial direction as shown in Figure 3-5, as shown in Figure 6, the static eliminating brush 9.10
It is also possible to set the density between the brushes, and even in this case, as in the embodiment shown in Fig. 5, it is possible to reduce the charging level in the axial direction of the roller and eliminate charging unevenness. Let it go.

On the other hand, it is also possible to apply the static elimination brush of the embodiment shown in Figure 6 to a heating roller with improved charging characteristics.

That is, the heating roller in this case is constructed by, for example, v) dispersing carbon in a Teflon (trade name) coating j. According to the TA structure of this heating roller, some charging unevenness has been eliminated as shown by the broken line, compared to the charging properties of the heating roller consisting of only Teflon coating layer shown by the solid line in Figure 7. be done.

When applying the static eliminator 5 brush shown in O66 to such a heating roller, the static electricity removal brush 5 shown in Fig. 7 is
The M electric unevenness in the axial direction of the roller was eliminated, and the charging potential also reached approximately 0VVc, resulting in the roller's life being shortened.

(Effects) As is clear from the above description, according to the present invention, by arranging the neutralizing member or the charging member to face the central portion or both ends of at least one of the heating roller and the pressure roller in the axial direction, 'VIt in the axial direction of the same roller
Since the potential is controlled and uneven charging in the axial direction can be eliminated, the transfer material can be evenly peeled off from the roller. Therefore, it is possible to eliminate the need for a special transfer material separation mechanism, and it is also possible to eliminate the occurrence of portions on the Oka roller where dust and dirt tend to adhere.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the structure and operation of a roller according to an embodiment of the present invention, and FIGS. FIG. 7 is a diagram showing the operation of another embodiment of the present invention. 1... Heating roller, 2... Pressure roller, 3... Electric conductor. 4... Friction member, 5... Sheet metal member, 6... Curved plate,
7-10... Static elimination brush. Figure 7

Claims (1)

[Claims] In a fixing device equipped with a heating roller and a pressure roller that are in contact with each other, have a coating layer with a high volume resistivity such as fluoride resin or silicone rubber on their surfaces, and are rotatable in relative directions, at least one of the rollers. 1. A fixing device for a copying machine, characterized in that a neutralizing member or a charging member is arranged to face the roller at its center or both ends thereof in the axial direction of the roller to control the charging potential in the axial direction of the roller.