JPH0317311Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a transfer device for a color copying machine with improved transfer efficiency to a transfer material.

[Conventional technology]

In the color copying method, as shown in FIG. 2, a photoreceptor 2 uniformly charged in advance by a charged corotron 1 is exposed to image light through a color separation filter 3, and a latent image is formed by a developing machine 5 containing toner of a predetermined color. The toner image is developed by a transfer corotron 9 and transferred to a transfer material 10 gripped by a transfer drum 8 which has a support sheet 7 made of an insulating mesh wound around a support drum frame 6. A color image is formed by repeating the process several times to overlap the colors on the transfer material. The transfer material 10 on the transfer drum 8 is charged to the opposite polarity to the toner image by a discharge current from the transfer corotron 9 while in contact with the photosensitive drum 2, and thereby the toner image is transferred to the transfer material. .

In the conventional transfer drum, the transfer material 10 was in almost line contact with the photosensitive drum 2 in the transfer area, as shown in a front sectional view in FIG. 3a and a side sectional view in FIG. 3b. That is, since the transfer drum 8 is fixed by wrapping an insulating support sheet 7 around the support drum frame 6 with tension applied in the width direction, the support sheet 7 has little degree of freedom, and the photosensitive drum 2 and the transfer drum The portion where the support sheet 7 (transfer material 10) was electrostatically attracted to the photoreceptor drum in the gap (approximately 0.3 mm) at the opposing position was in almost a line contact state.
For this reason, the unevenness of the support sheet 7 may cause transfer defects (if there are unevenness of 0.15 mm or more, transfer defects are likely to occur), or transfer defects may occur due to poor contact near both ends of the transfer material. or caused defects.

Furthermore, although a dielectric mesh has conventionally been used as a support sheet for the transfer material, the edges of the mesh have not been specially treated and are simply glued to the support drum frame 6. Particularly in the area around the transfer material gripper of the mesh, misgrips occur due to the unraveling of the mesh, and furthermore, due to the unraveling of the mesh at both ends, the distance between the photoreceptor drum and the transfer material cannot be maintained constant, which causes transfer. This caused image distortion and color shift during multiple color copying.

[Problem that the invention attempts to solve]

SUMMARY OF THE INVENTION An object of the present invention is to provide a transfer device for a color copying machine in which a transfer material on a transfer drum and a photoreceptor drum are in surface contact, and contact failure does not occur even at both ends.

Another object of the present invention is to provide a transfer device that does not cause poor contact between the transfer material and the photosensitive drum due to unraveling of the dielectric mesh wound around the support drum frame.

[Means and actions for solving problems]

The present invention provides a transfer device for a color copying machine that transfers a developed image multiple times to a transfer material on a transfer drum.
This transfer device is characterized in that the outer diameter of the dielectric support sheet wound around the support drum is larger at the center than at the flange of the support drum frame.

Further, the present invention is characterized in that the dielectric support sheet is made of a material whose edges (cut portions) are chemically or thermally melted and which does not unravel.

Hereinafter, the apparatus of the present invention will be explained based on the accompanying drawings.

FIG. 1a is a front sectional view of the transfer device of the present invention facing the photosensitive drum 2, and FIG. 1b is a side sectional view.

The support sheet 7 for the transfer material is configured so that there is a level difference between the supporting drum frame flange portions 6 at both ends and the other center portion, that is, the outer diameter of the center portion is larger than the outer diameter of the flange portion. There is. By increasing the outer diameter of the central portion in this manner, the contact width with the photoreceptor drum 2 becomes substantially longer, sufficient contact is made even at both ends, the degree of freedom of the support sheet 7 increases, and the transfer material 7 Since it can contact the photosensitive drum 2 in a surface state, the transfer efficiency is significantly improved.

The dielectric support sheet used in the present invention, which has a step between the flange portion and the center portion, can be manufactured as follows.

FIGS. 4a, 4b, and 4c are a perspective view, a front sectional view, and a side view of an aluminum mold 11 used for manufacturing the support sheet used in the present invention. This mold has a 0.3mm step between the flanges at both ends and the center.
The outer diameter of the central part is larger. Wrap a support sheet material (e.g. polyester, 70 mesh) around this aluminum pipe and fix it.
The sheet material is subjected to a melting process on the cut surface as described below. ) Then, when the whole is heated to 90℃ or higher, the support sheet material heat-shrinks along the shape of the aluminum pipe. Note that instead of the heat treatment, the support sheet material wound around the mold may be uniformly coated with a solvent (such as tetrahydrofuran) using an elastic roll containing a solvent, and then dried to shrink the material. In either case, the stiffness of the sheet after shrinkage (according to JISP8143, Clark method) is 129.8 (cm ³ /
100) is desirable. After shrinkage treatment,
The transfer drum of the present invention can be produced by peeling off the support sheet from the mold, wrapping it around a transfer support drum flange having the same diameter as the flange of the mold, and gluing both ends.

In the present invention, it is preferable to use a dielectric sheet whose cut surface has been melt-treated. For example, when cutting a sheet, the cut surface can be easily melted by using a heat cutter that covers a base material 12 with a Teflon tape 13 and has a nichrome wire 14 on it, as shown in FIG. can be done.
The cut surface can also be melted by chemical treatment, that is, treatment (infiltration or coating) and fixation with a chemical such as an adhesive. This melting process eliminates troubles caused by unraveling at the edges, and also facilitates the process of manufacturing a transfer drum support sheet by wrapping it around an aluminum mold as described above, as well as the work of wrapping it around a transfer drum frame. I can do it.

[Effect of idea]

The present invention provides a transfer device characterized in that the outer diameter of the dielectric support sheet wound around the transfer material support drum is larger at the center than at the flange of the support drum frame. Since contact with the body drum is made in a flat state and sufficiently near both ends of the drum, the transfer efficiency is significantly improved. Furthermore, by using a dielectric support sheet whose cut surface has been melt-treated, problems such as poor transfer due to unraveling of the sheet (mesh) are completely eliminated.

[Brief explanation of the drawing]

FIG. 1a is a front sectional view of the transfer device of the present invention with the photosensitive drums facing each other, FIG. 1b is a side sectional view of the same, and FIG. 2 is a schematic diagram of a color copying machine.
FIG. 3a is a front sectional view of a conventional transfer device, FIG. 3b is a side sectional view of the same, and FIGS. A perspective view, a front sectional view, a side view, and a sectional view of a thermal cutter used for cutting the support sheet. Codes in the figure: 1... Charging corotron, 2... Photosensitive drum, 3... Color separation filter, 4... Image exposure, 5... Developing machine, 6... Support drum frame, 7...
Dielectric support sheet, 8... Transfer drum, 9... Transfer corotron, 10... Transfer material, 11... Aluminum mold, 12... Base material, 13... Teflon tape, 14... Nichrome wire.

Claims (1)

[Scope of utility model registration request] In a color copying machine transfer device that transfers a developed image multiple times to a transfer material on a transfer drum, the outer diameter of the dielectric support sheet wrapped around the support drum is made larger at the center than at the flange of the support drum frame. Characteristic transcription device.