JPH04144852A - Sheet conveyance device - Google Patents

Abstract

PURPOSE:To prevent the disorder in image transferring by forming the sheet carrying device in such a way that a sheet is carried at higher speed by a pair of rollers in the upper stream side than by a pair of rollers in the down stream side which are adjoining each other. CONSTITUTION:A sheet P is carried along a sheet guide 5 by a plurality pairs of rollers 3 and 4 arranged in series. The sheet P is carried at higher speed by a pair of the rollers 3 in the upper stream side than by a pair of the rollers 4 in the down stream side. The sheet P, therefore, is carried while forming loops between the rollers 3 and 4 adjoining each other.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a sheet conveyance device in an image forming apparatus such as a copying machine or a laser beam printer, and more particularly to a sheet conveyance regulating mechanism.

(B) Prior Art As shown in FIG. 4, a sheet conveying device of a conventional image forming apparatus has a drive roller b for conveying a sheet P in the direction of arrow A along guides a and a. , the driven rollers C are arranged obliquely to each other, and the driven rollers e are arranged obliquely in the same direction as the driven roller C to the downstream drive roller d. The conveyance speeds of rollers b and d were configured to be equal.

Thus, as shown in FIG. 5, the sheet P receives a conveying force FB perpendicular to the hollow rollers c and e by the driven rollers c and e, and is conveyed in the six directions of arrows by the driving rollers b and d. Since it receives the force FA, it receives the conveyance force FC that is the resultant force, and is conveyed along the guides a, a.

(c) Problems to be Solved by the Invention However, in the conventional example described above, since the conveying speeds of the rollers b and d were constant, there were the following drawbacks.

(2) Every time the rear end of the sheet P is removed from the upstream roller c, the load on the sheet P changes, causing image blurring at the image transfer section.

(2) When the distances between the rollers c, d, and e are small, the sheet clamping force of the rollers c, d, and e is strong, reducing the amount of skew feeding of each roller and reducing the skew feeding effect.

(2) Since the sheet P is laterally pressed against the guides a and C by the rollers c, d and e, there is a risk that the sides of the thin sheet P may be damaged by the guides a and a.

Accordingly, the present invention provides a structure in which the conveyance speed of the roller pair on the upstream side of the roller pairs adjacent to each other is faster than the conveyance speed of the roller pair on the downstream side. The object of the present invention is to provide a sheet conveyance device that can form images.

(d) Means for Solving the Problems The present invention has been made in view of the above-mentioned circumstances, and includes, for example, a pair of rollers (3, 4) for conveying a sheet (P), as shown in FIG. In a sheet conveying device (16) having a sheet guide (5) in which a plurality of pairs of rollers (3, 4) are disposed in series, a roller pair (3,
) is configured to be faster than the conveyance speed of the downstream roller pair (4).

Moreover, one roller pair (3b,
4b) are arranged inclined in the same direction with respect to the other pair of rollers (3a, 4a).

(E) Function Based on the above configuration, the sheet (P) is conveyed along the sheet guide (5) by a plurality of roller pairs (3, 4) arranged in series. At this time, the sheet (P) is transported faster by the upstream roller pair (3) than by the downstream roller pair (4). Therefore, the sheet (P) is attached to the adjacent roller pair (3, 4).
It is conveyed while forming a loop between the two.

Also, one oblique roller (
3b, 4b), the material is transported along guides (5, 5) arranged laterally in the transport direction.

It should be noted that the symbols in parentheses are for illustration purposes only, and do not limit the equivalent configurations of the present invention.

(f) Example The present invention will be described in detail below with reference to the drawings.

FIG. 3 shows a laser beam printer to which the present invention is applied.

A sheet P is fed from a cassette 1 containing a sheet by a half-moon-shaped feed roller 2, transported by a pair of transport rollers 3.4, and one side of the sheet P is guided by guides 5, 5. ing.

Then, the sheet P is conveyed in synchronization with the photosensitive tram 6,
The toner image on the photosensitive drum 6 is transferred onto the sheet P by the transfer charger section 7, and after the toner image is fixed on the sheet P by the fixing device 8, the sheet P is guided by an upwardly facing guide 9 and is ejected. By the paper roller 10, the paper output tray 11
It is designed to be discharged.

On the other hand, an electronic latent image is formed on the photosensitive drum 6 by the laser beam scanner 12, and the latent image is turned into a toner image by the developing device 13. Note that 14 is a cleaner, and 15 is a charger that charges the photosensitive tram 6 uniformly.

Next, regarding the sheet conveying device 16 consisting of a pair of conveying rollers 3.4 and guides 5, 5, which constitutes the main point of the present invention, the first
This will be explained with reference to the drawings and FIG.

The drive roller 3a and the drive roller 4a are provided in series and in parallel, and the respective driven rollers 3b and 4b are disposed obliquely to the drive rollers 3a and 4a.
Guides 5, 5 are disposed on the left side of a to be perpendicular to the drive rollers 3a, 4a, and the sheet P is conveyed closer to the guides 5, 5.

The drive roller 3a is configured to rotate at a slightly faster speed than the drive roller 4a.

Next, the operation of the sheet conveying device 16 will be explained.

Since the driven rollers 3b and 4b are oblique to the conveyance direction of the sheet P, the sheet P is conveyed while receiving a component force in the direction of the guide 5.
These rollers 3a and 4 rotate a few percent faster than roller b.
The sheet P is conveyed while forming a loop between a.

Therefore, when the rear end of the sheet P comes off the upstream roller pair 3a, 3b, the downstream roller pair 4a.

Since the sheet P held between the sheets 4b is not subjected to the same fluctuating force, disturbances in image transfer do not occur.

Further, since the sheet P is conveyed by receiving a lateral force, or the sheet P has increased rigidity due to the loops, the side portions of the sheet P are not damaged.

Further, since the sheet P is pressed against the guides 5 as a stiff sheet, the pressing effect is enhanced and the conveyance of the sheet P is sufficiently regulated.

Note that the speed difference between the roller pairs 3a, 3b and 4a, 4b may be determined by making the drive rollers 3a, 4a have different diameters, or by adjusting the same diameter by adjusting the gear ratio from the drive source.

Further, the speed difference is determined by conditions such as the size of the sheet, the distance between the roller pairs, and the space for loop formation.

(G) Effects of the Invention According to the present invention, as described above, the conveyance speed of the upstream roller pair is higher than the conveyance speed of the downstream roller pair, so that the sheet forms a loop. Since the sheet is conveyed while being conveyed, when the rear end of the sheet is released from the roller pair on the upstream side, the sheet does not shake in the portion of the roller pair on the downstream side, so that disturbances in image transfer can be prevented.

In addition, by arranging one roller of each roller pair at an angle with respect to the other roller pair, the sheet is conveyed while always applying a lateral force to the sheet, and the sheet can be looped as described above. This increases the stiffness of the sheet and improves the conveyance regulation effect of the guide. Additionally, since the sheet is stiffer, damage to the sides of the sheet that is pressed against the guide can be reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a sheet conveying device that is an embodiment of the present invention, FIG. 2 is a plan view of FIG. 1, FIG. 3 is a longitudinal cross-sectional side view of a laser beam printer embodying the present invention, and FIG. FIG. 5 is a perspective view of a conventional sheet conveying device, and FIG. 5 is a plan view thereof. 3.4...Roller pair (driven roller) Roller (driving roller) 16...Sheet conveying device 3b, 4b...One opening 3a, 4a...Other 5...Sheet guide P... Sheet

Claims (1)

[Claims] 1. A plurality of pairs of rollers for conveying sheets are arranged in series,
What is claimed is: 1. A sheet conveying device having a sheet guide, characterized in that the conveying speed of the roller pair on the upstream side of the roller pairs adjacent to each other is configured to be faster than the conveying speed of the roller pair on the downstream side. 2. The sheet conveying device according to claim 1, wherein one roller of each roller pair is arranged inclined in the same direction with respect to the other roller.