JPH04322266A - Curl elimination and cooling device for transfer paper - Google Patents

Abstract

PURPOSE:To offer the curl elimination and cooling device of a transfer paper which can eliminate a blocking phenomenon by eliminating the curl of a transfer paper by overcoming all the causes of the curl and simultaneously cooling the transfer paper. CONSTITUTION:The proper numbers of air holes 3b, which extend in a shaft direction on the outer circumferential surface of a hollow cylindrical tube 3a, are provided in a paper carrying path near the downstream side of a heat roller fixing part. On the outside thereof, an upper roller 3 covered with an elastic body 3c whose air permeability is excellent and a lower roller 4 which is made to press-contact with the upper roller 3 and whose surface hardness is higher than the upper roller 3 are provided. Besides, a ventilation means 7 is provided on the side of the upper roller 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer paper curl removal and cooling device applied to an image forming apparatus in which a toner image formed on a transfer paper by an electrophotographic process is heated and fixed by a heat roller fixing section. .

0002

2. Description of the Related Art FIG. 6 is a schematic diagram showing a curled state of a transfer sheet that has been heat-fixed by a heat roller fixing section. This is a pressure roller that presses and holds the transfer paper P. When the transfer paper P passes between the nip of the roller pair consisting of the fixing roller 1 and the pressure roller 2, the toner image on the transfer paper P is melted and fixed. By the way, the transfer paper P that has passed through the heat roller fixing section is affected by the shape of the nip between the fixing roller 1 and the pressure roller 2, the difference in thermal expansion coefficient between the front and back sides due to the fibers of the transfer paper P,
Due to the difference in moisture content between the front and back sides of the transfer paper P, it curls as shown in the figure.

[0003] When the transfer paper P curls, there are disadvantages such as causing a jam on the downstream side of the conveyance path and poor stacking properties at the paper discharge section. Further, the transfer paper P is heated by the heater inside the fixing roller 1, for example, about 8
Since the temperature reached approximately 0° C., there was a risk that the once-fixed toner would melt, causing a problem called blocking, in which the upper and lower transfer sheets P stacked on the paper ejection tray would stick together.

Various proposals have been made to overcome the above-mentioned drawbacks. For example, Utsukai Showa 62-186
Japanese Patent No. 160 discloses a technique of cooling the fixing surface side of a transfer paper after thermal fixing using a cooling fan. Also,
Japanese Unexamined Patent Publication No. 165877/1987 discloses a device that is composed of an insulating reflective baffle member that dissipates heat from the transfer paper, and a thermally conductive hollow cylinder provided with many through holes, and that the inside of the hollow cylinder is evacuated. A technique has been disclosed in which the transfer paper is attracted to the cylinder described above to absorb heat. Furthermore, Japanese Patent Application Laid-open No. 64-53976 discloses that curling of the transfer paper after heat fixing is corrected by passing the paper through a convex nip section composed of a large-diameter roller with low hardness and a small-diameter roller with high hardness. A technique for doing so has been disclosed.

[0005]

[Problems to be Solved by the Invention] However, in conventional techniques, cold air is applied to the transfer paper, heat is absorbed by the material and shape of the conveyance roller after fixing, and the transfer paper is forcibly bent in the opposite direction to the curl direction. The problem was that these measures were all isolated, passive or indirect, and therefore did not have sufficient effects.

The present invention has been made based on this background, and eliminates the drawbacks of the above-mentioned conventional techniques, overcomes all causes of curling of transfer paper, and removes curling.
It is an object of the present invention to provide a device for removing curls and cooling a transfer paper, which can simultaneously cool the transfer paper and eliminate the blocking phenomenon.

[0007]

[Means for Solving the Problems] The above object is to provide a heat roller fixing unit near the downstream side of a heat roller fixing unit consisting of a fixing roller having an internal heater and a pressure roller that presses and holds a transfer sheet between the fixing roller and the fixing roller. In the paper conveyance path, an appropriate number of air holes extending in the axial direction are provided on the outer peripheral surface of a hollow cylindrical tube, and an upper roller whose outside is covered with an elastic material with good air permeability is pressed against the upper roller. This is achieved by a first means that includes a lower roller having a surface hardness higher than that of the roller, and further includes a blowing means for blowing air into the tube of the upper roller at a position close to the upper roller. Further, in the first means, an arc-shaped guide cover is provided on the outside of the upper roller to guide air from the air blowing means before and after a nip portion formed by the upper roller and the lower roller. The second one loosely fitted
This is accomplished by the following means. Further, the above object is achieved by a third means in which the diameter of the lower roller is smaller than the diameter of the upper roller in the first means.

[0008]

[Operation] Curling (face curl) is removed by nipping the transfer paper between the upper roller whose surface is made of an elastic material and the lower roller whose surface hardness is higher than that of the upper roller. Furthermore, the surface of the transfer paper is cooled by air (which is cold and contains moisture) blown out from the outer peripheral surface of the upper roller. In addition, if a guide cover is provided outside the upper roller at a distance from the outer peripheral surface and air is sent to the front and back of the nip,
The transfer paper is cooled more efficiently. Furthermore, by making the diameter of the lower roller smaller than that of the upper roller, the curl removal effect becomes even higher.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 1 is a simplified configuration diagram of the vicinity of the heat roller fixing section.
is a fixing roller, 2 is a pressure roller, 3 is a large diameter upper roller,
4 is a small diameter lower roller, and 5 is a paper conveyance path.

FIG. 2 is a partially cutaway perspective view of the main part of the curl removal and cooling device, in which the upper roller 3 appropriately opens air holes 3b extending in the axial direction on the outer peripheral surface of the hollow cylindrical tube 3a. A plurality of elastic bodies 3c are formed on the outside and covered with an elastic body 3c having good air permeability. Further, the lower roller 4 is made of a material harder than the elastic body 3c, and is pressed against the upper roller 3 by pressure springs 6 provided at both ends. 7 is the upper roller 3
A fan (
air blowing means). Note that the inner end of the tube 3a is formed into a wall surface so that all the air sent into the tube 3a by the fan 7 is blown out from the air hole 3b. Further, arrow A indicates the flow of air coming out through the air hole 3b and the elastic body 3c.

FIG. 3 is a longitudinal sectional front view of the entire decurling and cooling device, and FIG. 4 is a side view thereof. An arcuate guide cover 8 is loosely fitted outside the upper roller 3.
The air sent into the tube 3a by the fan 7 is blown directly from the elastic body 3a onto the transfer paper P at the nip, but is also guided by the inner peripheral surface of the guide cover 8 and is also blown from the front and back of the nip. It is sprayed onto the transfer paper P. In other words, all of the airflow A that blows out onto the outer peripheral surface of the upper roller 3 is guided by the guide cover 8 and is blown onto the front and rear of the nip portion of the transfer paper P, thereby efficiently cooling the transfer paper P. Ru. Furthermore, if the guide cover 8 is made of a heat insulating material, the heat of the fixing roller 1 will be cut off, so that the cooling effect will not be reduced. Note that 9 is a bush for fixing the upper roller 3.

FIG. 5 is a schematic diagram showing how the transfer paper P is decurled and cooled. As shown in FIG. By creating a reverse curl at the nip portion of the lower roller 4, the curl is removed as a result. Further, the transfer paper P is cooled by applying cold air to the transfer paper P at the nip portion and before and after the nip portion.

[0013]

Effects of the Invention As explained above, claims 1 and 4
According to the invention described, the curls on the transfer paper are removed at the nip between the upper and lower rollers, which have different surface hardnesses, and the transfer paper is cooled by the cold air blown onto the nip, thereby preventing curls and heat. Various troubles caused by this can be prevented. Further, according to the second aspect of the present invention, the guide cover guides all the airflow blown out from the upper roller to the front and back of the nip portion, so that the cooling effect of the transfer paper can be further enhanced. Further, according to the third aspect of the present invention, the curl removal effect can be further enhanced by making the lower roller, which has a higher surface hardness, smaller in diameter than the upper roller.

[Brief explanation of the drawing]

FIG. 1 is a simplified configuration diagram of a downstream side near a heat roller fixing section that employs a transfer paper curl removal and cooling device according to an embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view of a main part of a transfer paper curl removal and cooling device according to an embodiment of the present invention.

FIG. 3 is a vertical cross-sectional front view of the transfer paper curl removing and cooling device.

FIG. 4 is a vertical cross-sectional side view of the transfer paper decurling and cooling device.

FIG. 5 is a schematic diagram showing how the transfer paper is decurled and cooled.

FIG. 6 is a schematic diagram showing how the transfer paper curls in the heat roller fixing section.

[Explanation of symbols]

1 Fixing roller 2 Pressure roller 3 Upper roller 3a pipe 3b Air hole 3c Elastic body 4 Lower roller 5 Paper conveyance path 7 Juan 8 Guide cover A Air flow P Transfer paper

Claims (4)

[Claims] Claim 1: A fixing roller having a heater inside;
Air holes extending in the axial direction are provided on the outer peripheral surface of a hollow cylindrical tube in the paper conveyance path near the downstream side of the heat roller fixing section, which consists of a pressure roller that presses and holds the transfer paper between the fixing roller and the fixing roller. An appropriate number of upper rollers are provided, the outside of which is coated with an elastic material with good air permeability, and a lower roller that is in pressure contact with the upper roller and has a surface hardness higher than that of the upper roller. A device for removing curls and cooling transfer paper, characterized in that a blowing means for sending air into a tube of an upper roller is provided at a position. 2. An arc-shaped guide cover for guiding air from the air blowing means before and after a nip portion formed by the upper roller and the lower roller, on the outside of the upper roller. A decurling and cooling device for transfer paper, characterized in that it is loosely fitted. 3. The transfer paper curl removal and cooling device according to claim 1, wherein the diameter of the lower roller is smaller than the diameter of the upper roller. 4. The apparatus for removing curls and cooling transfer paper according to claim 1, wherein the blowing means comprises a fan provided on a side of the upper roller.