JPH09240863A - Paper feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease deformation of the tips of recording paper sheets, so as to provide stable conveyance of the recording paper sheets, by separating and bringing a frictional member from and in contact with the recording paper sheets by interlocking it with the printing operation. SOLUTION: Recording paper sheets 9 are overlapped and input into a paper feed cassette 4 and pressed up by a bottom plate 19 in the paper feed cassette 4. A paper feeding roller 17 and a friction plate 18 are arranged on an outlet side of the paper sheet cassette 4, and the uppermost surface of a bundle of the recording paper sheets 9 is pressed to the lower part of the paper feeding roller 17 by being energized by the bottom plate 19. The friction plate 18 is approached to or brought in contact with the paper feeding roller 17 side. An actuator 21 (a solenoid) capable of being controlled by a control part 22 is provided and driven, a lever 20, namely, a supporting member 30 is rotated by taking a pin 31 as a fulcrum, the friction plate 18 is turned, and force is prevented from acting on the recording paper sheets 9 after the friction plate is separated from the recording paper sheets 9. As a result, the deformation of the tips of the recording paper sheets 9 can be prevented, and stable conveyance of the recording paper sheets 9 can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus such as a copying machine or a printer, and more particularly to a paper feeding device with less paper jam.

[0002]

2. Description of the Related Art An electrophotographic apparatus such as an electrophotographic copying machine or an electrophotographic printer forms a toner image on a toner receiver such as a photosensitive drum or a transfer drum, and supplies the toner image from a recording paper cassette. After the transfer onto the recording paper to be paper, the recording paper is peeled from the toner receiver and fixed, which is repeated.

Conventionally, in Japanese Patent Laid-Open No. 7-196185, an angle of about 30 ° is formed in the conveying direction of the recording paper and a friction plate having a friction coefficient higher than that of the recording paper is brought into contact with the paper feed roller. A paper feeding device is disclosed in which the conveyance of the second and subsequent recording papers fed more than necessary is suppressed by the friction of the friction plate and double feeding is prevented.

However, in this state, since the second and subsequent recording sheets are still sandwiched between the paper feed roller 17 and the friction plate, if the paper cassette is pulled out as it is, the sandwiched recording sheet remains in the machine. Since it remains, a mechanism for releasing the bias of the friction plate to the paper feed roller is generally provided in association with the operation of pulling out the paper feed cassette, so that the above phenomenon does not occur.

[0005]

In the conventional paper feeding method,
As described above, since the second and subsequent recording sheets are still sandwiched between the paper feed roller and the friction plate, the leading edge of the recording sheet remains bent by the friction plate, and if left as it is,
The phenomenon that the leading edge of the recording paper is deformed occurs.

As a result, particularly in an electrophotographic apparatus of the type that forms a color image using the intermediate transfer drum, the bending or deformation of the leading edge of the recording paper causes the electrostatic attraction electric field of the recording paper to the intermediate transfer drum. It has been found that there are cases in which the recording paper is complicated and the peeling of the recording paper from the intermediate transfer drum is unstable.

In particular, in the case of a page-type color printer, since it is necessary to superimpose four color images of the area of one recording sheet, a large-diameter drum having a perimeter of one recording sheet is required in principle. Since the bending moment, which is the source of the peeling force of the recording paper at that time, is small, peeling of the recording paper is much more difficult than that of a monochrome printer.

It is an object of the present invention to provide a sheet feeding device of an electrophotographic apparatus which can reduce the deformation of the leading edge of the recording sheet and can stably convey the recording sheet even if the above-mentioned sheet feeding method is used. Especially.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a recording sheet supplied from a recording sheet stock section is provided in the vicinity of an exit of the recording sheet stock section, and is biased by the sheet feeding member. In the paper feeding device of the electrophotographic apparatus, which is sandwiched between the friction members that are in contact with each other, and conveys only one recording sheet at a time from the stock section to prevent double-fed printing of the recording sheets, The structure is such that the urging of the friction member to the paper feeding member can be released in conjunction with the printing operation.

With the above construction, the printing operation is monitored, and when unnecessary, the urging of the paper feed member of the friction member is released to minimize the deformation of the leading edge of the recording paper.
Stable peeling of the recording paper from the drum that carries the toner image.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, FIG. 2 shows a structural example of an electrophotographic color printer to which the present invention is applied. A photoconductor belt 1 and a yellow magenta for forming an electrostatic latent image on the photoconductor belt 1 for each color by an exposure device and visualizing the formed electrostatic latent image with toner to form a toner image.・ Cyan (3 primary colors) ・ Black 4 color developing devices 2Y ・ 2M ・ 2
C · 2K, an intermediate transfer drum 3 that sequentially transfers the toner images of each color developed on the photosensitive belt 1 to form a color toner image, and a paper feed cassette that is a stock unit that stocks recording paper. When the recording paper 9 fed from 4 arrives on the intermediate transfer drum 3, the recording paper 9 is rotated so as to contact the intermediate transfer drum 3, and the color toner image on the intermediate transfer drum 3 is recorded. Transfer roller 5 for retransfer onto 9
A sheet charge eliminator 15 for peeling off the recording paper 9 on the intermediate transfer drum 3, and a fixing device 16 for melting and fixing the color toner image on the recording paper 9 by heat or pressure. The present invention relates to a portion for feeding recording paper from the paper feed cassette 4, and its details will be described below.

First, the structure of a conventional paper feeding unit will be described. FIG.
The configuration of the conventional paper feeding unit is shown in FIG.

As shown in the figure, recording sheets 9 are placed in the paper feed cassette 4 in an overlapping manner, and a bottom plate 19 in the paper cassette is placed.
Is pushed up by. At the outlet side of the paper cassette 4, a paper feed roller 17 as a paper feed member and a friction plate 1 as a friction member are provided.
8 is arranged, and the uppermost surface of the bundle of recording papers 9 is pressed against the lower part of the paper feed roller 17 by the urging of the bottom plate 19. The friction plate 18 is attached to a support member 31 having a lever 20, and the support member 31 is rotatably fixed to the electrophotographic apparatus main body side by a pin 30. When the paper feed cassette is mounted, the lever 20 of the support member 31 is pushed up by the end of the paper feed cassette and lifted, and the friction plate 1
8 is configured to be close to the paper feed roller 17.

When the paper feed roller 17 is rotated in this state, the recording paper 9 is rubbed by the frictional force between the surface of the paper feed roller and the surface of the recording paper.
Is transported. However, at this time, the frictional force also acts on the first and second sheets, the second and third sheets, and the subsequent sheets of the recording paper, so that the leading edge of the recording paper may be lost if the paper is not fed. There is a phenomenon in which a plurality of recording papers are deformed and overlapped and conveyed, which is called “double feeding” in some cases.

FIG. 4 is a schematic diagram showing the point at which the recording paper is peeled off from the intermediate transfer drum.

The intensity of the static elimination electric field due to the corona discharge reaching the paper peeling position from the static eliminator 15 has a distribution as shown in part A. However, AC corona discharge generally tends to have a stronger negative polarity discharge in the stable discharge voltage region, and therefore the facing dielectric material such as paper is subjected to static elimination and is also slightly charged. Therefore, in this case, the recording paper 9 conveyed facing the static eliminator 15 is charged with a potential tendency as shown in the portion B.

At this time, the intermediate transfer drum 3 located therebelow has a constant potential as shown in the portion C because of the electrophotographic process before that. The same applies when the intermediate transfer drum is a photosensitive drum.

The suction force between the intermediate transfer drum 3 and the recording paper 9 is generated by the Coulomb force generated from the electric field, that is, the potential difference existing between them. Generally, the potential relationship is adjusted so that the potential difference is minimized.

Further, a peeling force is also generated at the leading edge of the recording paper at this time due to a bending moment generated by the recording paper bending along the curvature of the drum.

At this time, if the leading edge of the recording paper 9 is deformed like 9 ', sufficient peeling force does not work on the leading edge of the paper at the position where the potential difference is minimized, and therefore the recording paper 9 moves again to a large potential difference area without peeling. The paper may remain wound around the intermediate transfer drum as it is, or may be peeled off at a position where there is a problem in paper transport.

According to the present invention, the paper feeding unit is constructed so that the above problems do not occur.

FIG. 1 is a block diagram of an embodiment of the sheet feeding section of the present invention, in which components equivalent to those of the conventional one are designated by the same reference numerals.

Recording papers 9 are placed in the paper feed cassette 4 in an overlapping manner and pushed up by a bottom plate 19 in the paper cassette. A paper feed roller 17 and a friction plate 18 are arranged on the exit side of the paper feed cassette 4, and the bottom plate 1 is provided below the paper feed roller 17.
The uppermost surface of the bundle of recording papers 9 is pressed by the bias of 9.

When the paper feed roller 17 is rotated in this state, the recording paper 9 is conveyed by the frictional force between the surface of the paper feed roller 17 and the surface of the recording paper 9. Here, 30 ° in the recording paper conveyance direction
By bringing the friction plate 18 having a friction coefficient higher than the friction coefficient between recording papers into contact with the paper feed roller 17 at a certain angle, it is possible to convey the second and subsequent recording papers fed more than necessary. As in the conventional device, the friction plate 18 has a function of suppressing the double feed by suppressing the friction.
However, when the lever 20 portion of the support member 30 that conventionally supports the friction plate is pushed by the end portion of the paper feed cassette when the paper feed cassette is set, the support member 30 rotates about the pin 31. In the invention, even when the paper feeding cassette is mounted, the supporting member 30 is not contacted.

Therefore, the paper feed device of the present embodiment has the friction plate 1
A separation / contact means is provided in order to bring the sheet 8 close to or in contact with the sheet feed roller 17 side. The contact / detachment means is provided with an actuator 21 (solenoid) that can be controlled by the control unit 22, and drives the actuator 21 to rotate the lever 20, that is, the support member 30 with the pin 31 as a fulcrum to rotate the friction plate 18. The recording paper is configured so as to be separated from the recording paper and no force acts on the recording paper.

In one embodiment of the present invention, the urging release operation of the friction plate 18 is performed when printing is not possible, including during non-printing, that is, when the printer is not powered on and when the paper feed cassette 4 is pulled out. I decided to do it. In this embodiment, since the recording paper 9 is not stopped while being bent unnecessarily, the deformation of the recording paper 9 can be suppressed and stable recording paper conveyance can be obtained.

FIG. 5 is a graph showing the time during which the leading edge of the recording paper remains bent by the friction plate 18 and the voltage eliminator applied voltage margin at which the recording paper can be peeled off. The inside of the line in the graph is the area where the recording paper can be peeled off stably. The shorter the time that the leading edge of the recording paper remains bent by the friction plate 18, the wider the margin.

In another embodiment of the present invention, the friction plate 18 is used.
The bias release operation of is performed at all times except the paper feeding operation. In this embodiment, since the time when the recording paper 9 is stopped while being bent is extremely short, the deformation of the leading end of the recording paper 9 can be suppressed to an extremely small amount, and stable recording paper conveyance can be obtained. I can.

Further, in another embodiment of the present invention, the urging release operation of the friction plate 18 is carried out except during the substantially continuous printing operation. In the above-described embodiment, since the bias release operation is performed for each sheet of printing, the operation of the actuator 21 occurs every time,
The actuator 21 generates heat, wear, and operating noise.
In the present embodiment, attention is paid to the fact that, during the substantially continuous printing, the time during which the recording paper 9 is stopped while being bent is too short to be ignored, and frequent operation of the actuator 21 is omitted. While minimizing the problems in
It is possible to suppress the deformation of the leading end of the recording paper 9 to a small extent, and to obtain stable conveyance of the recording paper 9.

Further, in another embodiment of the present invention, the urging operation of the friction plate 18 is performed when there is no need for the next printing operation after a lapse of a fixed time after the end of the printing operation.
In order to deform the leading edge of the recording paper 9 until the conveyance failure occurs, it takes several minutes for the recording paper 9 to be stopped while bending the leading edge of the recording paper 9, so that the present embodiment is adopted. The effect of the embodiment can be further increased.

[0031]

INDUSTRIAL APPLICABILITY As described above, the present invention provides a sheet feeding device for an electrophotographic apparatus, which can prevent the leading edge of the recording sheet from being deformed and can stably convey the recording sheet.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a paper feeding unit according to an embodiment of the present invention.

FIG. 2 is a structural explanatory view of an electrophotographic color printer to which the present invention is applied.

FIG. 3 is an explanatory diagram of a configuration of a conventional paper feeding unit.

FIG. 4 is an explanatory view of the principle of the charged potential state of the paper peeling portion of the electrophotographic apparatus.

FIG. 5 is a graph showing a state of a margin for peeling paper according to the present invention.

[Explanation of symbols]

3 ... Intermediate transfer drum, 4 ... Paper feed cassette, 9 ... Recording paper,
17 ... Paper feed roller, 18 ... Friction plate, 21 ... Actuator, 22 ... Control section.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Wakamatsu 1-1-1, Higashitaga-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Electric Appliances Division, Taga Headquarters

Claims (7)

[Claims] 1. A stock unit for stocking recording paper, a paper feed member provided in the vicinity of the outlet of the stock unit, and a friction member for contacting the recording paper urged by the paper feed member, In a sheet feeding device of an electrophotographic apparatus, which sandwiches the recording sheet between the sheet feeding member and the friction member, and rotates the sheet feeding member to convey one sheet of the recording sheet at a time from the stock unit, A paper feeding device, characterized in that a separation / contact means for separating / contacting the friction member from the recording paper in association with a printing operation is provided. 2. The paper feeding device according to claim 1, wherein the separating / contacting means separates the friction member from the recording paper during non-printing so that no force acts on the recording paper. 3. The separation / contact means according to claim 1, wherein the friction member is separated from the recording paper except when a paper feeding operation is performed so that no force acts on the recording paper. Paper feeding device. 4. The separating / contacting device according to claim 1, wherein the friction member is separated from the recording paper except when a substantially continuous printing operation is performed so that no force acts on the recording paper. And a paper feeder. 5. The friction member separates from the recording sheet according to claim 1 or 2, when the separation / contact means does not need a next printing operation even after a lapse of a predetermined time after the end of the printing operation, A paper feeding device characterized in that no force acts on the recording paper. 6. The sheet feeding device according to claim 1, wherein the sheet feeding member is a rotating elastic roller. 7. The paper feeding device according to claim 1, wherein the friction member is a plate that generates a frictional force stronger than an adhesion force between recording sheets.