JPH10273253A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device in which a sheet can be surely set along a conveyance reference face and an image with high precision can be formed. SOLUTION: A conveyance reference projection part 7a is arranged in a U-turn starting point for a sheet, while a conveyance reference projection part 7b is arranged in a U-turn ending point for a sheet, and the conveyance reference projection part 7a is positioned in the higher position as against the conveyance reference projection part 7b. A sheet side end parts are set along the conveying reference projection parts 7a, 7b, and the sheet is brought into contact with the lowermost downstream side point 7c of the conveying reference face, and as a result, a skew is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying section of an image forming apparatus such as a laser beam printer or a copying machine which employs an electrophotographic system or another recording system.

[0002]

2. Description of the Related Art Conventionally, in a sheet conveying section of an image forming apparatus of this type, when a sheet separated and fed from a sheet mounting table is conveyed to the image forming section, the sheet is straightened with respect to the image forming section. That is, it is important to convey the sheet so that the image is formed at an appropriate position on the sheet.

For this reason, generally, a skew feeding correcting means is provided in the conveying path immediately before the image forming section.

As the skew feeding correcting means, there is a case where a method is adopted in which a sheet is made to follow a conveyance reference plane so that a proper conveyance direction is set.

An example of such a transport section of the image forming apparatus will be described with reference to FIGS. 6 and 7. FIG.

In the image forming apparatus shown in FIG. 6, a sheet fed from a sheet mounting table 102 by a feed roller 103 is transported by a transport roller 106 and oblique feed rollers 104 and 105.
The sheet is conveyed to an image forming section, and after forming an image, the sheet is discharged through some processes.

Here, the skew correction is performed by bringing the side end of the sheet into contact with the conveyance reference plane 107.

FIG. 7 is a schematic explanatory view of sheet conveyance as viewed from the direction C in the figure.

The sheet conveying section nips the fed sheet with the conveying roller 106 and the oblique feeding roller 104 as shown in FIG. It is configured to convey in an appropriate direction to the image forming unit.

[0010]

However, in the case of the above-mentioned prior art, since the entire transport reference plane is a flat plane, securing a high flatness as a whole causes a decrease in productivity. Have difficulty. Even if only the transport reference plane immediately before the image forming unit (the most downstream side) is set to a high flatness, if the upstream transport reference plane is not completely flat, the transport on the most downstream side is not possible. Since the sheet may not come into contact with the reference surface, it is often impossible to convey the sheet to the image forming unit in an appropriate direction.

That is, since the unevenness is present on the transport reference surface, the leading end of the sheet faces in a direction away from the transport reference surface, and as a result, the sheet may enter the image forming section without following the most downstream transport reference surface. Was.

For this reason, an image cannot be formed at an appropriate position on a sheet, and a misaligned image is often recorded.

The first invention of the present application has been made to solve the above-mentioned problems of the prior art, and an object thereof is to achieve high-precision image formation by ensuring that a sheet is along a conveyance reference plane. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

Further, the sheet has skew feeding rollers 104, 10
5, a constant oblique feeding force is applied to the transport reference surface 107.
And between the transport rollers 106 (FIG. 7)
(B), the sheet-side end portion is deteriorated due to buckling or the like, so that not only cannot an appropriate image be formed, but also a jam may occur.

The second invention of the present application has been made to solve the above-mentioned problems of the prior art, and an object of the invention is to cause the sheet side end to come into contact with the conveyance reference surface and cause breakage or the like. It is an object of the present invention to provide an image forming apparatus which prevents the occurrence of a sheet and has high reliability in sheet conveyance.

[0016]

According to the first aspect of the present invention, in order to achieve the above object, the present invention is applied to a method of separating a sheet from a sheet mounting table.
In an image forming apparatus provided with skew correction means on a conveyance path that conveys a fed sheet to an image forming unit, the skew correction means includes: a conveyance reference plane parallel to an appropriate conveyance direction;
A skew feeding correcting means for correcting skew feeding by making a side edge of a sheet follow, wherein a feeding reference convex portion is provided on a feeding reference surface.

A plurality of transport reference convex portions are provided on the upstream side of the transport reference surface, and the height of the transport reference convex portion is set on the upstream side so that the sheet enters the downstreammost transport reference surface at a predetermined angle. From downstream to the downstream side.

According to the second aspect of the present invention, a skew correcting means is provided in a conveying path for conveying the sheet separated and fed from the sheet mounting table to the image forming section. In the image forming apparatus, the skew correction unit is a skew correction unit that corrects skew by aligning a side edge of the sheet with respect to a conveyance reference plane parallel to an appropriate conveyance direction. A conveyance guide substantially parallel to the road is provided integrally with the conveyance reference plane.

On the other hand, it is also preferable that the transfer reference plane is provided integrally with the apparatus frame.

It is also preferable that the sheet mounting table is provided at an angle so that the sheet fed from the sheet mounting table is along the conveyance reference convex portion.

[0021]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, shape, relative arrangement, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

As an image forming apparatus according to an embodiment of the present invention, an electrophotographic laser beam printer that scans a photosensitive member with a laser beam for recording will be described with reference to FIGS.

FIG. 1 is a schematic configuration diagram of a laser beam printer, FIG. 2 is a perspective view of a transport section thereof, FIG. 3 is a view illustrating the movement of a sheet during transport, and FIG. 4 is a view illustrating a sheet stacking table of the present apparatus. FIG. 5 and FIG. 5 are diagrams for explaining the actual design of the present apparatus.

In the laser beam printer 1 shown in FIG. 1, 2 is a sheet mounting table, 3 is a feed roller, 4 and 5 are oblique feed rollers, 6 is a transport roller, 7 is a transport reference plane, 8 is a transfer roller, 9 Denotes a process cartridge, 9a denotes a photosensitive drum, 10 denotes a sheet conveyance path, 11 denotes a laser scanner, 12 denotes a return mirror, 13 denotes a fixing device, and 14 denotes a paper discharge roller.

The sheets stacked on the sheet mounting table 2 are separated and fed by a feeding roller 3, and are nipped by a conveying roller 6 and an oblique feeding roller 4. Thereafter, the sheet is conveyed along a substantially U-shaped conveyance path by receiving the oblique feeding force of the oblique feeding roller 4, and further nipped between the oblique feeding roller 5 and the conveying roller 6. Then, the sheet is nipped between the photosensitive drum 9 a and the transfer roller 8, which are image forming units.

Image information transmitted from the laser scanner 11 in advance is turned back by the turn-back mirror 12, exposed to the photosensitive drum 9a to form a latent image, and a toner image is formed by developing means (not shown).

This toner image is transferred onto a sheet by the transfer roller 8, and an image is formed on the surface.

The sheet on which the image is placed is conveyed to the fixing device 13 on the sheet conveying path 10 so as not to damage the image.

The sheet on which the image is fixed by the fixing device 13 is transported to a discharge roller 14 and discharged to a discharge tray.

Next, the operation of the sheet in the sheet conveying section will be described with reference to FIGS. 3A is a diagram viewed from the direction of arrow A in FIG. 1, and FIG. 3B is a diagram viewed from the direction of arrow B in FIG.

In FIG. 2, reference numeral 7 a denotes a transport reference convex portion provided at the U-turn start point of the sheet, 7 b denotes a transport reference convex portion provided at the U-turn end point of the sheet, and 7 c denotes the most downstream portion of the transport reference surface 7. Is the point.

Further, as shown in FIG.
Is provided so as to be higher than the transport reference convex portion 7b. Moreover, when the transport path is extended linearly, the extension line connecting those vertices is
It is designed to intersect the transport reference plane 7 at least upstream of 7c.

With this configuration, if only the heights of the vertices of the two transport reference convex portions of the transport reference surface are strictly controlled, the flatness near the most downstream point 7c is increased thereafter. The skew correction can be appropriately performed only by performing the above operation.

That is, as long as the processing accuracy of the apex of the convex portion is monitored as described above, the sheet side edge can be provided on the transport reference convex portion 7a without performing difficult processing such as improving the flatness of the entire transport reference surface 7. If the portion abuts, the transport reference surface downstream of the convex portion is lower than the transport reference convex portion 7a, so that the sheet leading end is always directed to the left side in the figure by the skew feeding roller, and the transport reference convex portion 7b , Always comes into contact with the most downstream point 7c of the transport reference surface 7, and can enter the image forming section in an appropriate direction.

Finally, by invading the photosensitive drum 9a in the process cartridge 9 in parallel with the rotation direction,
The image is transferred to the intended position on the sheet,
High image accuracy can be obtained.

Thus, it is possible to perform appropriate skew correction without impairing productivity, and it is possible to form images with high accuracy.

The transport reference surface 7 is provided integrally with a transport guide 7d (hatched portion) substantially parallel to the transport path. The conveyance guide 7 d prevents the side edge of the sheet from breaking along the conveyance reference surface 7 and falling into the inner diameter side of the conveyance roller 6 when the sheet comes into contact with the conveyance reference surface 7. . The conveyance guide 7d is provided on the inner side of the conveyance path where the sheet is properly conveyed and substantially parallel to the conveyance path so that the conveyance guide 6d does not contact the sheet and generate a conveyance load during conveyance by the conveyance roller 6. (Fig. 2
(B)).

Accordingly, it is possible to prevent the sheet from dropping due to the contact with the conveyance reference surface, to eliminate the buckling and deterioration of the sheet, and to reduce the jam.

Specifically, when a ridge-shaped conveyance guide having a height of about 0.5 mm is provided at a position about 0.2 to 0.5 mm away from the sheet conveyance path (outer peripheral surface of the conveyance roller 6). ,
The conveyance of the sheet was stable, and good results were obtained.

FIG. 4 is a diagram showing the positional relationship between the transport reference plane 7 and the sheet table 2 from the direction of arrow B in FIG.

The sheet mounting table 2 is provided at an angle so that the fed sheet is along the conveyance reference convex portion 7a (broken line portion in FIG. 7).

That is, as shown in the figure, the distance between the leading end of the placed sheet and the transport reference convex portion 7a in the direction perpendicular to the transport direction is α, and the rear end of the loaded sheet and the transport reference convex portion 7a are α. Part 7
If the distance from a is β, then α ≦ β.

With such an arrangement of the sheet mounting table 2,
The fed sheet is always directed to the transport reference surface 7 to further ensure the effect of the above-described transport reference convex portion.

In general, it is desirable that 0 <α <10 (mm).

Further, since the transfer reference surface 7 is formed integrally with the apparatus frame by casting with resin, the manufacturing process such as the mounting process can be shortened as compared with the conventional case where the transfer reference surface 7 is formed by a separate member. Performance can be improved.

(Embodiment) Here, the actual design process of the transport reference plane will be described with reference to FIG.

FIG. 5A is a side view of the transport reference plane 7, and FIG.
FIG. 4B is a diagram in which the convex shape of the conveyance reference surface 7 is represented by a curve (a recording material passing point is developed in a straight line).

These points are positions for controlling the dimensions of the transport reference plane when making a mold, and are provided at equal intervals along the sheet transport path.

The sheets conveyed at points p1 to p12 are p12, p11, p10, p9, p8, p7, p6
Make a U-turn in the order of p6, p5, p4, p3, p2
Go straight in the order of p1.

Specifically, the most downstream point 7 of the transport reference plane
The height (position in the sheet width direction) of each point is defined (unit: mm) as in the following A to C based on c (point p1). A: 0 <convex n−convex p1 ≦ 0.2 (where n = p2 to p5, p7 to p9, p11 to p1
2) B: 0.2 <convex p6−convex p1 ≦ 0.3 C: 0 <convex p10−convex p6 ≦ 0.8 By defining as above, the conveyance provided at the U-turn start point p10 of the sheet. The reference protrusion 7a is provided at the conveyance reference protrusion 7 provided at the U-turn end point p6 of the sheet.
b is more reliably convex than b, and is more reliably convex than the most downstream point 7c (point p1) of the transport reference plane.

In particular, it is desirable that 0 <convex p10-convex p6 <1.0, and convex p6-convex p1 <0.5 (unit: mm).

Further, the points p1 to p12 are smoothly connected so that the sheet is not caught.

The sheet transporting unit thus specifically configured operates as if the sheet is full.

Since the sheet mounting table 2 is arranged so that the sheet fed by the sheet feed roller 3 comes into contact with the conveyance reference convex portion 7a, the sheet passes through the point p10 without touching the points p12 and p11. At that time, the first
Since the skew feeding roller 4 applies a skew feeding force to the conveyance reference surface 7 side, the sheet passes while contacting the conveyance reference convex portion 7a.

After passing through the transport reference convex portion 7a, the sheet passes through a point p6. At this time, since the skew feeding force is applied to the conveyance reference surface 7 side by the second skew feeding roller 5, the sheet passes while abutting on the conveyance reference projection 7b.

Then, at the most downstream point 7c (point p1) of the sheet on the conveyance reference plane, the oblique feeding force of the first and second oblique feeding rollers 4 and 5 is continued even after the leading edge of one edge contacts. , After passing point p1, the transport reference plane 7
Follow along.

The sheet along the transport reference surface 7 designed as described above is properly transported to the nip between the photosensitive drum 9a and the transfer roller 8 in the process cartridge 9 to form a highly accurate image. It is.

[0058]

According to the present invention, since the transport reference projection is provided on the transport reference surface, a high-precision image formation is achieved by ensuring that the sheet is along the transport reference surface without lowering the productivity of the apparatus. An image forming apparatus that can be provided.

A plurality of transport reference convex portions are provided on the upstream side of the transport reference surface, and the height of the transport reference convex portion is set on the upstream side so that the sheet enters at a predetermined angle with respect to the most downstream transport reference surface. , It becomes lower toward the downstream side, so that the skew of the sheet can be corrected more reliably.

Further, since a conveyance guide substantially parallel to the conveyance path is provided integrally with the conveyance reference plane, the reliability of sheet conveyance can be improved.

On the other hand, since the transfer reference plane is provided integrally with the apparatus frame, productivity can be improved.

Since the sheet mounting table is provided at an angle so that the sheet fed from the sheet mounting table is along the conveyance reference convex portion, it is possible to more surely control the skew of the sheet. it can.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laser beam printer according to an embodiment of the present invention. .

FIG. 2 is a perspective view showing a transport unit of the laser beam printer according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a sheet operation in a transport unit of the laser beam printer according to the embodiment of the present invention.

FIG. 4 is a diagram showing a sheet mounting table of the laser beam printer according to the embodiment of the present invention.

FIG. 5 is a diagram showing a method of designing a transport reference plane of the laser beam printer according to the embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a conventional image forming apparatus.

FIG. 7 is a diagram illustrating a sheet operation in a transport unit of a conventional image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser beam printer main body 2 sheet mounting table 3 feed roller 4, 5 skew feed roller 6 transfer roller 7 transfer reference surface 7 a, 7 b transfer reference convex portion 7 c lowest point of transfer reference surface 7 d transfer guide 8 transfer roller 9 process cartridge 9a photosensitive drum 10 transport path 11 laser scanner 12 folding mirror 13 fixing device 14 paper discharge roller

Claims (5)

[Claims] 1. An image forming apparatus in which a skew feeding correcting means is provided in a feeding path for feeding a sheet separated and fed from a sheet mounting table to an image forming unit, wherein the skew feeding correcting means is configured to set a proper feeding direction. Skew correction means for correcting skew by aligning the side edge of the sheet with a conveyance reference plane parallel to the conveyance reference plane, wherein a conveyance reference projection is provided on the conveyance reference plane. Image forming device. 2. The transport reference convex portion is provided in a plurality on the upstream side of the transport reference surface, and the height of the transport reference convex portion is set so that the sheet enters at a predetermined angle with respect to the most downstream transport reference surface. The image forming apparatus according to claim 1, wherein the image forming apparatus is lower from the side toward the downstream side. 3. An image forming apparatus in which a skew feeding correcting means is provided in a feeding path for feeding a sheet separated and fed from a sheet mounting table to an image forming unit, wherein the skew feeding correcting means has a proper feeding direction. Skew correction means for correcting skew by aligning the side edge of the sheet with a conveyance reference plane parallel to the conveyance reference plane, wherein a conveyance guide substantially parallel to the conveyance path is provided integrally with the conveyance reference plane. An image forming apparatus characterized in that: 4. The image forming apparatus according to claim 1, wherein said transport reference surface is provided integrally with an apparatus frame. 5. The sheet mounting table according to claim 1, wherein the sheet fed from the sheet mounting table is provided at an angle so as to be along the conveyance reference plane. 5. The image forming apparatus according to 4.