JPS64295B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a copying machine, a printing machine, a recording machine, and other apparatuses (hereinafter referred to as copying machines) having a mechanism for conveying sheets (including those called copy paper, transfer paper, recording paper, etc.). This relates to a sheet guiding device for a machine (such as a machine). More specifically, a pair of pressure rollers used as a heat fuser in a copying machine, a pair of conveyor rollers for conveying a sheet in a printing machine, and a pair of pressure rollers used as a fuser in a laser beam printer. The present invention relates to a sheet guiding device for guiding a sheet.

Conventionally, when a sheet being conveyed in a copying machine or the like is guided to a nip between pressure rollers in a heat fixing device or the like, wrinkles occur on the sheet. There is a method that curls the sheet by slowing down the transport speed of the sheet transport section compared to other processing sections, and uses the stiffness of the sheet at that time to prevent wrinkles to some extent, but this method is not sufficiently effective. Moreover, if the curl is too large, there is a possibility that the curl may come into contact with the roller of the fixing device, which is not preferable.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, it is an object of the present invention to provide a sheet guiding device that can prevent wrinkles from forming on a sheet conveyed by a pair of rollers.

That is, the configuration of the present invention that can achieve the above object is as follows:
In a sheet guiding device such as a copying machine, in which a conveyed sheet is guided by a guiding member to a nip portion between a pair of rollers, the sheet guiding member guides a center portion of a leading edge of the sheet upwardly from the nip portion. The tip of the sheet guide member is provided to be inclined upward toward the pair of rollers, and the tip of the sheet guide member has a sheet edge guide portion that guides both ends of the tip of the sheet.
It is located upstream in the sheet conveyance direction from a sheet center guide portion that guides the center portion of the leading edge of the sheet, and is configured such that both ends of the leading edge of the sheet leave the sheet guiding member before the center portion and hang down near the nip portion. 1 is a sheet guiding device for a copying machine, characterized in that:

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing a fixing device of a copying machine to which the present invention is applied, and FIGS. 2 and 3 are plan views showing an embodiment of the sheet guiding device of the present invention. In the figure, the conveyed sheet passes over a sheet guide member, is advanced to the nip portion of pressurized fixing rollers 2 ₁ and 2 ₂ , is guided by other guide members 3 ₁ and 3 ₂ , and is discharged. be done. A cleaner 4 cleans the surface of the fixing roller ₂₁ that has been soiled by images on the sheet.

Next, the sheet guide member 1 will be explained.

As shown in FIG. 1, the sheet guide member 1 is provided to be inclined upward toward the fixing rollers 2 ₁ and 2 ₂ , and its tip is located above the common tangent of the fixing rollers 2 ₁ and 2 ₂ . Therefore, the leading edge of the sheet is guided upward from the nip portions of the fixing rollers 2 ₁ and 2 ₂ .
However, as shown in FIG. 2, the sheet guide member 1 has curves A and B formed at its tip, and is formed such that the sheet edge guide section is located upstream of the sheet center guide section in the sheet conveyance direction. ing. Therefore, both ends of the leading edge of the sheet move away from the guide member 1 first and hang down near the nip, and the center part is guided above the nip. Therefore, both ends of the sheet enter the nip section first, and the center section enters the nip section later. After the central portion of the sheet is delayed and enters the nip portion, the central portion of the leading edge of the sheet is held between the fixing rollers 2 ₁ and 2 ₂ while being deformed upstream in the conveying direction with respect to both ends. At this time, the sheet is subjected to stress that attempts to restore this deformation to its original state, that is, a force that attempts to relatively move the center of the leading edge of the sheet toward the downstream side in the conveyance direction and both ends toward the upstream side. arise. However, since the sheet is held between the fixing rollers 2 ₁ and 2 ₂ , it receives a frictional force from the fixing rollers 2 ₁ and 2 ₂ as a reaction against this stress. This frictional force acts on both ends of the sheet in the transport direction, and on the center part in the opposite direction to the transport direction. The deformation of the sheet is maintained by these frictional forces.

As described above, since the frictional force exerted on the sheet by the fixing rollers 2 ₁ and 2 ₂ is opposite in direction between the central portion and both ends, a rotational moment is generated in the sheet. This rotational moment tends to rotate the right half of the sheet located on the upstream side in the conveying direction with respect to the nip of the fixing rollers 2 ₁ and 2 ₂ to the right and the left half to the left. This opposite left-right moment acts as a force that spreads the sheet toward the rear, thereby preventing wrinkles.

In the first embodiment (FIG. 2), the tip of the sheet guide member 1 has a small-sized portion 5 formed with a radius of curvature for small-sized sheets from indicated point ₁₁ to indicated point ₁₂ , and a small-sized portion 5 for large-sized sheets. It consists of a large-sized portion 6 from the illustrated point 1 ₃ to the illustrated point 1 ₄ formed at a radius of curvature of 1.5 mm, and is separated by a step at the boundary. This embodiment is a sheet guiding member 1 for conveying a sheet based on one side of the illustrated point 1 ₁ , and preferably a small-sized sheet is guided between the illustrated point 1 ₁ and the illustrated point 1 ₂ .
For large size sheets, point 1 ₁ to point 1 ₄
You will be guided through the As a result, the sheet is conveyed under the influence of the guide section with the radius of curvature depending on the size of the sheet being used, so it is necessary to form the guide section with various radii of curvature depending on the size of the sheet being used. For example, one sheet guiding member can be used for sheets of multiple sizes.

In this case, part of width 7 of a small size sheet, for example A4 size, is also used as part of width 8 of a large size sheet, for example B4 size, so curve A section is suitable for both A4 and B4 size sheets. It is preferable that the radius of curvature of the curve B section is suitable for an A4 size sheet, and that the curve C section is a radius of curvature suitable for a B4 size sheet. In the embodiment, the boundary between the curve A section and the B section is located at the center of the width 7 of the B4 size sheet, but this may be at the center of the width 7 of the A4 size sheet or any other location. In addition, when one-sided separation is performed to separate sheets, the effect of the separation effect also occurs on the sheets on the sheet guide member 1 in front of the pressure rollers 2 ₁ and 2 ₂ , so the curve A section and the curve C section are It is better that the radius of curvature of is different. In the example of FIG. 2, curve A,
The radius of curvature of B and C is 1500 mm, 650 mm, and
By setting it to 3500mm, sheet size B4/A4
The sheet can enter the nip portion of the pressure rollers 2 ₁ and 2 ₂ in a more ideal shape for each size of the sheet. In particular, in a pressure fuser, there is an intersection angle between the two rollers, and the nip between the rollers is arranged at a slight angle with respect to the direction of sheet movement to prevent shocks caused by the sheet moving in and out. diagonally in one direction. Therefore, a slight margin (from point 1 ₂ to point 1 ₃ in the illustration) is provided in a portion corresponding to the edge of an A4 size sheet (point 1 ₂ in the illustration) to prevent the sheet from getting stuck.

Next, the embodiment shown in FIG. 3 will be explained.

This embodiment shows an example of the shape of the sheet guide member 9 when the sheet is conveyed based on the center, unlike the case shown in FIG. The curve D from the illustrated point 9 ₁ to the illustrated point 9 ₂ has a radius of curvature suitable for A4/B4 size sheets in the width 10 area of small size sheets, and the curve from the illustrated point 9 ₃ to the illustrated point 9 ₄ E is set to have a radius of curvature suitable for a B4 size sheet in an area of width 11 of a large size sheet. Further, as in the previous example, an allowance area (from point 9 ₂ to point 9 ₅ in the drawing) is provided on one side in case the sheet is slightly skewed.

Since the present invention has the above-described configuration, it is possible to prevent the occurrence of wrinkles in the sheet conveyed by the pair of rollers.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a fixing device of a copying machine or the like to which the present invention is applied, and FIGS. 2 and 3 are plan views of a sheet guide member of the present invention. 1 and 9 are sheet guide members, and 2 ₁ and 2 ₂ are pressure rollers.

Claims (1)

[Scope of Claims] 1. In a sheet guiding device such as a copying machine, in which a conveyed sheet is guided by a guiding member to a nip portion between a pair of rollers, the sheet guiding member guides the central portion of the leading edge of the sheet to the nip portion of a pair of rollers. The sheet guide member is provided so as to be inclined upwardly toward the pair of rollers so as to guide the sheet upwardly from the nip portion. It is configured to be located upstream in the sheet conveyance direction from a sheet center guide section that guides the center section, and so that both ends of the leading edge of the sheet separate from the sheet guide member and enter the nip section before the center section. A sheet guiding device for a copying machine, etc., characterized in that: 2. The sheet guiding device according to claim 1, wherein the sheet end guide portion of the sheet guiding member is formed at a plurality of locations depending on the sheet size. 3. The sheet guiding device according to claim 1 or 2, wherein the sheet end guide portion has a curved shape.