JPH07101572A - Feeding device and image forming device - Google Patents

Abstract

PURPOSE:To exert a constantly stable conveyance force on a paper sheet in spite of the size of the paper sheet. CONSTITUTION:A feeding device comprises feed rollers 5a and 5b to feed a paper sheet 9; feed auxiliary rollers 6a and 6b to assist feed; and a pressure plate 8 to bring the paper sheet 9 into pressure contact with the feed rollers 5a and 5b. The pressure plate 8 is prevented from making contact with the rollers 6a and 6b for assisting feed and even when bending by a pressure plate spring 1 occurs to the pressure plate 8, a stable conveyance force is exerted on the paper sheet 9 by the feed rollers 5a and 5b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feeding device for feeding a recording sheet applied in an image forming apparatus such as a copying machine, a facsimile or a printer.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus having a feeding device of this type, one shown in FIG. 10 is known.

In FIG. 10, a sheet 109 stacked on a pressure plate 108 includes feeding rollers 105a and 105b and feeding assisting rollers 106a and 106b having a substantially circular cross section which are coaxially fixed by a feeding roller shaft 107. , Separation nail 1
15 separates one by one. The separated sheet 109 ′ passes on the feeding guide 104 and is further fed to the lower portion of the print head 113 by the pair of conveying rollers 111. The print head 113 is attached to a head transport unit 112 that is movable in a direction perpendicular to the transport direction with respect to the sheet surface, and moves with the head transport unit 112 each time a sheet 109 ′ of one print width is transported. Ink droplets are ejected to print for one print width. Then sheet 1
09 'passes through the paper discharge roller pair 114 and passes through the image forming apparatus 10
3 is discharged to the outside.

Next, a portion of the feeding device for separating the sheets 109 one by one will be described. 10 and 11, the peripheral surfaces of the feeding rollers 105a and 105b are formed of rubber or the like having a high friction coefficient, and the pressure plate 108 on which a large number of sheets 109 can be stacked is the base 102 in the image forming apparatus.
It is pulled up by the force of the pressure plate spring 101 attached to and is pressed against it. When the feeding roller shaft 107 starts to rotate according to a command from the image forming apparatus 103, the sheet 109 is fed into the image forming apparatus 103 due to friction with the feeding rollers 105a and 105b, but the sheets 109 are separated one by one. A separating claw 115 is provided for this purpose.

When it is possible to feed sheets 109 of a plurality of sizes with the feeding device having the above-described structure, the feeding roller 1
The arrangement of 05a and 105b on the feeding roller shaft 107 is
Stable feeding should be possible even when the sheet 109 has the corresponding smallest size. In FIG. 11, the reference position 116 when the sheet 109 is loaded is the left end of the pressure plate 108, and when the sheet 109 has the corresponding minimum size, the two feeding rollers 105a and 105b are arranged so as to be positioned substantially evenly on the left and right sides of the sheet 109. Has been done. However, in this case, when the size of the sheet 109 is large, the feeding roller 10
Since the width pressed by the sheets 5a and 105b is not sufficiently larger than the width of the sheet 109, the feeding assisting rollers 106a and 106b are provided to compensate for this. The feeding assisting rollers 106a and 106b have the same cross-sectional shape as the feeding rollers 105a and 105b, and are made of the same material or slightly less frictional force.

[0006]

However, in the above-described conventional feeding device, as shown in FIG. 12, for example, the feeding rollers 105a and 105b and the feeding assisting roller 106 are provided.
When the pressure plate 108 pressed against the a and 106b by sandwiching the sheet 109 is slightly bent, the feeding assisting roller 106b and the pressure plate 108 come into contact with each other, so that the two feeding rollers 105a and 105b are different from each other. , A difference occurs in the contact state with the sheet 109. That is, the feeding roller 105
The pressing force between a and the pressure plate 108 is significantly different, and the feeding force of the feeding roller 105b is significantly inferior to that of the feeding roller 105a. Therefore, especially when the size of the sheet 109 is small and does not reach the feed assisting rollers 106a and 106b, the bias of the transport force easily causes a transport problem such as skewing.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to provide a sheet feeding device capable of constantly giving a stable feeding force to a sheet regardless of the sheet size. To provide.

[0008]

In order to achieve the above object, the present invention provides a feeding roller for feeding a sheet,
In a feeding device having a feeding assistance roller for assisting feeding and a pressure plate for pressing a sheet against the feeding roller, the pressure plate and the feeding assistance roller do not come into contact with each other. Is characterized by.

A recess or a hole may be provided on the pressure plate at a position facing the feeding assisting roller.

There is only one feeding assisting roller,
A step may be provided on the pressure plate at a position facing the feeding assisting roller.

An elastic member may be attached to the concave portion or the concave surface of the step provided on the pressure plate at a position facing the feeding assisting roller.

It is preferable that the feeding roller and the feeding assisting roller are coaxial with each other.

[0013]

In the feeder configured as described above, since the pressure plate and the feeding assistance roller do not contact each other, even if the pressure plate is bent, the feeding assistance roller is not pressed by the pressure plate. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments. (First Embodiment) FIGS. 1 to 3 show a first embodiment of the present invention. In the figure, the feeding rollers 5a and 5b and the feeding assisting rollers 6a and 6b are mounted coaxially with the feeding roller shaft 7, and their outer shapes are the same in the same phase, but the sheets are not sandwiched. Feed rollers 5a, 5b and pressure plate 8
When the rollers are pressed against each other, the feeding assisting rollers 6a and 6b are pressed against the pressure plate 8
So as not to come into contact with
A recess is provided in the portion facing 6b. Pressure plate 8
Is pushed up toward the feeding rollers 5a, 5b by the force of the pressure plate springs 1 attached to the left and right sides. Also, sheet 9
The reference position 16 for the loading of is the left end of the pressure plate 8.

As shown in FIG. 2, the feeding assisting roller 6 is provided.
When a small sheet 9 that does not cover the a and 6b is loaded, even if a slight bending occurs about the feeding roller 5b as a fulcrum on the pressure plate 8, the feeding assisting rollers 6a and 6b are It does not enter the depression and is not pressed by the pressure plate 8. Therefore, the feeding rollers 5a and 5b and the pressure plate 8 are
A substantially uniform pressing force is secured between the two, and stable paper feeding can be performed.

Next, when a larger sheet 9 is loaded on the feeding assisting roller 6a, the sheet 9 is placed on both edges of the feeding assisting roller 6a and the concave portion of the pressure plate 8 as shown in FIG. Since the sheet is sandwiched and there is tension of the sheet itself, the sheet feeding assist roller 6a also receives the conveying force. However, since its carrying force is smaller than that of the feeding rollers 5a and 5b,
The two feeding rollers 5a and 5b maintain a sufficient carrying force, and the feeding assisting roller 6a gives an auxiliary carrying force to the right side of the sheet 9, so that stable feeding can be performed.

Even when the sheet 9 is larger and extends up to the feeding assisting roller 6b, the same effect as above can be obtained.

(Other Embodiment) FIGS. 4 to 9 show another embodiment of the present invention. FIG. 4 shows an example in which the reference position when the sheet 9 is loaded is the center of the pressure plate 8 and the center line of the sheet 9 is aligned with the center of the pressure plate 8.
b is arranged on both outer sides of the feeding rollers 5a and 5b. How to provide the concave portion of the pressure plate 8 and the effect during use are the first
It is similar to the embodiment. FIG. 5 shows an example in which the feeding rollers 5a and 5b in the first embodiment are replaced by rollers 5 which are long in the axial direction. In addition, as shown in FIG.
In the case where the number is sufficient, the shape of the position of the pressure plate 8 facing the feeding assisting roller 6 is slightly inferior to that of forming the concave portion, but the same effect can be obtained even if a step is formed.

Further, as shown in FIGS. 7 and 8, the feeding assisting roller 6 is used.
The relief plate 18 supported by an elastic body 17 as an elastic member or a weak spring 19 to such an extent that the can easily enter the recess.
When is attached to the pressure plate 8, a frictional force acts between the sheet 9 and the feeding assisting roller 6. If you adjust this friction force,
When the sheet 9 is large, an auxiliary carrying force is obtained without impairing the carrying force of the feeding rollers 5a and 5b, and the sheet can be fed.

Further, even if the shape of the position corresponding to the feeding assisting roller 6 on the pressure plate 8 is not a recess but a hole as shown in FIG. 9, the same auxiliary carrying force as in the first embodiment can be obtained.

In addition, although not shown, it is also possible to arrange the feeding roller and the feeding assisting roller not to be coaxial with each other, but to arrange them in front of and behind in the paper feeding direction, or to arrange them vertically.

[0022]

The present invention has the above-described structure and operation, and since the pressure plate and the feeding assisting roller do not come into contact with each other,
Even if the pressure plate bends, the feeding assist roller does not receive the pressing force from the pressure plate, and the pressing force between the feeding roller and the pressure plate does not fluctuate as in the past, and the feeding roller stabilizes on the sheet. The conveyance force is applied, and conveyance troubles such as skewing of the sheet are prevented.

Further, stable feeding of the sheet can be realized regardless of the size of the sheet.

[Brief description of drawings]

FIG. 1 is a schematic view showing a feeding device according to a first embodiment of the present invention.

FIG. 2 is a schematic view showing a feeding device which is a first embodiment of the present invention.

FIG. 3 is a schematic view showing a feeding device which is a first embodiment of the present invention.

FIG. 4 is a schematic view showing a feeding device according to another embodiment of the present invention.

FIG. 5 is a schematic view showing a feeding device according to another embodiment of the present invention.

FIG. 6 is a schematic view showing a feeding device according to another embodiment of the present invention.

FIG. 7 is a schematic view of a main part of a feeding device according to another embodiment of the present invention.

FIG. 8 is a schematic view of a main part of a feeding device according to another embodiment of the present invention.

FIG. 9 is a schematic view of a main part of a feeding device according to another embodiment of the present invention.

FIG. 10 is a schematic diagram of an image forming apparatus to which a conventional feeding device is applied.

FIG. 11 is a schematic view of a conventional feeding device.

FIG. 12 is a schematic view of a conventional feeding device.

[Explanation of reference numerals] 1,101 pressure plate spring 5,5a, 5b, 105a, 105b feeding roller 6,6a, 6b, 106a, 106b feeding assistance roller 8,108 pressure plate 9,109,109 'sheet 17 elastic body (Elastic member) 18 Escape plate 19 Spring (Elastic member)

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hitoshi Nakamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hideaki Kawakami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Hideki Yamaguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akira Kida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Akira Miyakawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takashi Nojima 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (6)

[Claims] 1. A feeding device having a feeding roller for feeding a sheet, a feeding auxiliary roller for assisting feeding, and a pressure plate for pressing a sheet against the feeding roller, A feeding device, wherein the pressure plate and the feeding assisting roller do not come into contact with each other. 2. The feeding device according to claim 1, wherein a concave portion or a hole is provided on the pressure plate at a position facing the feeding assisting roller. 3. The feeding device according to claim 1, wherein there is only one feeding assisting roller, and a step is provided on the pressure plate at a position facing the feeding assisting roller. . 4. An elastic member is attached to a position facing the feeding assisting roller on a concave portion or a concave surface of a step provided on the pressure plate.
Alternatively, the feeding device according to item 3. 5. The feeding device according to claim 1, wherein the feeding roller and the feeding assisting roller are coaxial with each other. 6. An image forming apparatus having the feeding device according to claim 1, 2, 3, 4 or 5.