JPH07323934A - Paper feeding device - Google Patents

Abstract

PURPOSE:To surely prevent the double feed of a paper sheet and to facilitate the stable carriage of the paper sheet only through the rotation of a paper feed roller by setting up the pressure contact force of a friction plate to the paper feed roller larger than the pressure contact force of a mounting base, and controlling the driving of the paper feed roller according to an output signal issued from a paper sheet detecting means. CONSTITUTION:A paper sheet mounted on 3 mounting base 34 is brought into pressure contact with a paper feed roller 35 under fixed pressure by the pressure contacting force of the mounting base 34. When the paper feed roller 35 rotates, the paper sheet is fed toward a friction plate 36 from the top paper sheet in order by frictional force between the paper sheet and the paper feed roller 35. The fed paper sheet passes through between the friction plate 36 and the paper feed roller 35, and is carried toward a paper sheet carrying member 37. In this case, if the paper sheet is led between the friction plate 36 and the paper feed roller 35 as two or more paper sheets are piled up, the piled up paper sheets are disposed by the pressure contact force of the friction plate 36 and the rotation of the paper feed roller 35, and carried from the paper sheet on an upper side in order by the rotation of the paper feed roller 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device for laser printers, copying machines, facsimiles and the like.

[0002]

2. Description of the Related Art As shown in FIGS. 9 and 10, a sheet feeding device in a conventional laser printer is attached to a tongue piece 1 in order to prevent double feeding of sheets at the time of sheet feeding. The elastic member 2 such as rubber is pressed against the paper feed roller 4 by using the spring member 3, and when the papers placed in the paper feed cassette 5 are sequentially fed by the rotation of the paper feed roller 4, a plurality of papers are generated. If the papers are fed at the same time, there is one that prevents unnecessary conveyance of the paper due to the frictional force between the paper and the elastic member 2. After the paper fed by the paper feed roller 4 is conveyed in the direction of the transfer position by the paper conveyance roller 6, the front end of the paper is detected by the paper detection switch 7, and the front end of the paper is held by the paper front end alignment roller 8. The paper leading edge aligning roller 8 is driven in synchronization with the optical system and the transfer timing, and the paper is conveyed to the transfer position to perform the transfer. Note that FIG.
Inside, 9 is an optical device, 10 is a developing device, 11 is a charging device,
Reference numeral 12 is a cleaning device, 13 is a photoconductor, 14 is a transfer roller, 15 is a fixing device, 16 is a paper conveying roller, and 17 is a paper discharging roller.

However, in this type of paper feeding device, since the double feeding of the paper is prevented only by the frictional force between the elastic member 2 pressed against the paper feeding roller 4 and the paper, for example, the elastic member 2 and the paper If the frictional force and the urging force of the spring member 3 are weak, double feeding of the paper occurs frequently, and conversely, if the paper is strong, the paper may slip due to the elastic member 2 and a paper jam may occur. Therefore, it is necessary to set the frictional force between the elastic member 2 and the paper and the biasing force of the spring member 3 so that such a problem does not occur. However, depending on the type of paper (plain paper, cardboard, postcard, etc.) Of the elastic member 2 and the elastic force of the elastic member 2 are different depending on the surface roughness of the sheet, and thus it is difficult to set the frictional force of the elastic member 2 and the urging force of the spring member 3. It was not possible to perform stable paper feeding for a long period of time.

In view of this, Japanese Patent Publication No. 53-42948 discloses that a paper pressing member having a concave curved surface is provided so as to be in contact with the outer peripheral surface of a sheet feeding roller for a required length in the circumferential direction. A sheet feeding device is described which, when a plurality of sheets are fed at the same time, prevents unnecessary conveyance of the sheets due to a frictional force between the concave curved surface and the sheets, that is, prevents double feeding of the sheets, and performs stable sheet feeding. .

Further, in Japanese Patent Publication No. 49-39698, a cut portion is formed in the center of the sheet mounting table, and slightly protrudes upward from the cut portion to contact the lowest sheet placed on the mounting table. The main roller and the sub roller are rotated in opposite directions, and a paper feed roller is provided in the front lower part of the cutout portion, and the rotation of the subroller feeds back the lowest placed sheet to bend it downward from the cutout portion. As the paper is drooped, the leading edge of the paper is dropped below the notch, and the main roller rotates to feed this paper forward and reach the paper feed roller, preventing double feeding of paper and ensuring stable paper feeding. The paper feeding device to be used is described.

[0006]

However, in the paper feeding device in Japanese Patent Publication No. 53-42948,
It is necessary to set the shape of the concave curved surface of the paper pressing body and the interval between the concave curved surface and the paper feed roller, etc. so that the paper will not be fed multiple times.
The design and layout of the paper presser were complicated.

Further, in the paper feeding device of Japanese Patent Publication No. 49-39698, it is necessary to form a cutout portion on the paper placing table, and a mechanism for rotating the main roller and the sub roller in opposite directions is required. Therefore, the structure is complicated and the manufacturing cost is high.

Further, in the conventional sheet feeding device such as a laser printer or a copying machine, it is difficult to stably convey the sheet from the sheet feeding roller to the transfer roller only by the conveying force of the sheet feeding roller. Therefore, on the paper transport path from the paper feed roller to the transfer roller, a paper transport roller that enhances the paper transport force and a paper leading edge alignment roller that has a clutch mechanism that aligns the leading edges of the paper are provided. There was a problem of upsizing and cost increase.

In view of the above, it is an object of the present invention to provide a paper feeding device capable of reliably preventing double feeding of paper and stably carrying the paper only by rotating the paper feeding roller.

[0010]

As shown in FIG. 1, the means for solving the problems according to the present invention is arranged on a sheet placing table 34 which is pressed against and separated from a sheet feeding roller 35, and on the downstream side of the placing table 34 in the sheet conveying direction. A sheet feed roller 35 and a friction plate 36 for preventing the double feed of the sheets which is pressed against and separated from the sheet feed roller 35, and the pressure contact force of the friction plate 36 with respect to the sheet feed roller 35 is set to be larger than the pressure contact force of the mounting table 34. Also, a paper conveyance member 37 is arranged on the outer periphery of the paper feed roller 35 on the downstream side in the paper conveyance direction, and paper detection means 23 for detecting a paper in the paper conveyance path 22 on the downstream side of the paper conveyance roller 35 in the paper conveyance direction. Is provided, and drive control means 45 for controlling the drive of the paper feed roller 35 in accordance with the output signal from the paper detection means 23 is provided.

[0011]

In the means for solving the above problems, the sheet placed on the table 34 is fed by the sheet feeding roller 3 by the pressure contact force of the table 34.
It is pressed against 5 at a predetermined pressure. When the paper feed roller 35 rotates, the paper is fed in the direction of the friction plate 36 in order from the uppermost paper due to the frictional force between the paper and the paper feed roller 35.

The fed sheet passes between the friction plate 36 and the sheet feeding roller 35 and is conveyed toward the sheet conveying member 37. At this time, when two or more sheets of paper are overlapped and guided between the friction plate 36 and the paper feed roller 35, the friction plate 36
The overlapped sheets are separated by the pressing force of the sheet and the rotation of the sheet feeding roller 35, and are conveyed by the rotation of the sheet feeding roller 35 in order from the upper side sheet.

The sheet conveyed in the direction of the sheet conveying member 37 is curved along the sheet feeding roller 35 between the sheet conveying member 37 and the sheet feeding roller 35, and the sheet feeding roller 35.
The sheet contacting area is increased and the sheet is conveyed with a large conveying force, and the sheet detecting unit 23 detects the leading edge of the sheet and the sheet is conveyed while being synchronized with the optical system and the timing of transfer.

[0014]

【Example】

(First Embodiment) A laser printer according to the first embodiment of the present invention will be described with reference to FIG. In FIG. 2, 20 is a printer main body, 21 is a paper feeding device, 22 is a paper conveyance path having a length shorter than paper, 23 is a paper detection switch which is a means for detecting the leading edge of the paper conveyed in the paper conveyance path 22, 24
Is an optical device, 25 is a developing device, 26 is a photoconductor, 27 is a charging device, 28 is a cleaning device, 29 is a transfer roller,
Reference numeral 30 is a fixing device, 31 is a paper conveying roller, and 32 is a paper discharging roller.

As shown in FIGS. 1 and 2, the paper feeding device 21 is provided with a paper feeding cassette 33 mounted in the side wall opening of the printer body 20 for storing paper and a plurality of papers arranged in the paper feeding cassette 33. A sheet placing table 34 to be placed, a sheet feeding roller 35 for feeding the sheet placed on the placing table 34, and a placing table 34
A friction plate 36 disposed on the downstream side of the sheet conveyance direction and capable of being pressed into contact with and separated from the sheet feeding roller 35;
A transport press-contact plate 37, which is a member for transporting a paper, is provided on the downstream side of the friction plate 36 so as to be press-contactable to and separated from the paper feed roller 35.

The loading table 34 is arranged so as to be slanted so that the loaded sheet is slid toward the sheet feeding roller 35, and one end thereof is supported by the tip of the sheet feeding cassette 33 so as to be swingable around a shaft 33a. The upper surface of the other end is arranged so that it can be pressed into contact with and separated from the paper feed roller 35. A mounting table spring 40 is interposed between the lower surface of the mounting table 34 and the bottom plate of the paper feed cassette 33,
The mounting table spring 40 urges the other end of the mounting table 34 toward the paper feed roller 35. Although not shown,
In the paper feed cassette 33, a member for controlling the height of the mounting table 34 urged by the mounting table spring 40 or the height of the uppermost sheet mounted on the mounting table 34 and the upper portion of the stacked sheets are placed. A member for restricting the end in the paper feed direction excluding the positioned paper is provided.

The paper feed roller 35 is made of a material such as EPDM, is rotatably supported in the printer body 20, and has a drive motor 41 via a gear, a belt or the like (not shown).
Is driven to rotate.

The friction plate 36 is formed of a material such as cork containing rubber, and is movably guided and supported by a side wall of the paper feed cassette 33, which is not shown. Then, the friction plate spring 4 is provided between the lower surface of the friction plate 36 and the bottom plate of the paper feed cassette 33.
2 is interposed, and the friction plate spring 42 is used for the friction plate 36.
Is urged toward the paper feed roller 35.

The transport press plate 37 is made of a material such as resin or metal on which the paper is slippery, and the end portions on the friction plate 36 side and the transport path 22 side are inclined downward to facilitate the passage of the paper. Although not shown, it is movably guided and supported by the side wall of the frame forming the paper transport path 22. And
A press contact plate spring 43 is interposed between the lower surface of the transfer press contact plate 37 and the bottom plate of the frame, and the transfer press contact plate 37 is urged toward the paper feed roller 35 by the press contact plate spring 43.

Further, the laser printer has a microcomputer 45 which is a drive control means for controlling the drive of the paper feed roller 35 in synchronization with the optical system and the transfer timing in accordance with the output signal from the paper detection switch 23. It is provided.

Next, the relationship between the urging force of the friction plate spring 42 and the urging force of the mounting table spring 40, which is set to prevent the double feeding of the sheets when the sheets are conveyed, as shown in FIG. Pressing force F1 of the friction plate 36 against the paper feed roller 35
And the pressure contact force F2 of the mounting table 34 will be described.

In FIG. 4, F3 is a force for feeding the first sheet on the mounting table 34 side, F4 is a force for feeding a second sheet overlapping the first sheet on the mounting table 34 side, and F5 is friction. The force of feeding the first sheet of paper on the plate 36 side, the force of F6 to feed the second sheet of paper overlapping the first sheet of the friction plate 36, and the brake of F7 on the paper passing on the friction plate 36. If you apply force,
Since the paper feed roller 35 is in direct contact with the first paper, the frictional force between the paper feed roller 1 and the first paper becomes larger than the frictional force between the first paper and the second paper. , F3> F
4, F5> F6.

When the pressure contact force F1 of the friction plate 36 is smaller than or equal to the pressure contact force F2 of the mounting table 34, the force of conveying the second sheet of paper is greater than the braking force of the friction plate 36. The larger one, F4 + F6 ≧ F7, and double feeding of paper occurs.

When the pressure contact force F1 of the friction plate 36 is increased to prevent double feeding of the sheets, F6 <F7, and the braking force of the friction plate 36 increases. However, if the pressure contact force F1 is increased too much, F5 <F7 and paper is friction plate 36
Will slip and cause a paper jam.

Therefore, in order to prevent the double feeding of the sheets and to stably feed the sheets, F1> F2, F5>F7> F6.
Ideally, in this relationship, when the pressure contact force F1 of the friction plate 36 is not less than 5.1 times and not more than 7.0 times the pressure contact force F2 of the mounting table 34, it is possible to prevent double feeding during sheet conveyance. It was confirmed by experiment that the optimum value was.

Table 1 shows a paper feed roller 35 having a diameter of 33 mm, a width of 30 mm, a material of EPDM and a hardness of 35 ° (JIS-A).
And a cork containing rubber and a friction plate 36 having a hardness of 80 ° (JIS-A), the rotation speed of the paper feed roller 35 is 50
It is an experimental result of measuring the double feed rate of the paper and the variation of the leading edge of the paper according to the pressure contact force of the friction plate 36 and the mounting table 34 when mm / s, and the presence or absence of the transport pressure contact plate 37 and the weight of the paper ( It is also classified by g / m ² ).

[0027]

[Table 1]

FIG. 5 is a graph of the experimental results of Table 1. As is clear from Table 1 and FIG. 5, in the double feed rate, the ratio of the pressure contact force F1 and the pressure contact force F2 is large. As the pressure contact force F2 is constant (the pressure contact force F1 increases when the pressure contact force F2 is constant), the ratio between the pressure contact force F1 and the pressure contact force F2 is 5.1: 1 or more (for example, F1 = 180).
g, F2 = 35 g or F1 = 240 g, F2 = 35 g), the double feed is not generated, and the pressure contact force F1 and the pressure contact force F2
And the ratio is less than 5.1: 1 (for example, F1 = 130 g,
When F2 = 130 g), double feeding occurs.

In the variation in the tip, the friction plate 36 becomes a load in the sheet conveyance as the ratio of the pressure contact force F1 and the pressure contact force F2 increases (increases as the pressure contact force F1 increases when the pressure contact force F2 is constant). However, by providing the conveying press plate 37, the paper is fed by the paper feed roller 35.
Since the contact area of the sheet with the sheet feeding roller 35 is increased when the sheet is sandwiched between the sheet and the conveying pressure contact plate 37, the sheet can be conveyed more stably after the sorting process and the variation in the leading edge can be remarkably reduced.

On the other hand, when the ratio between the pressure contact force F1 and the pressure contact force F2 is extremely large (the pressure contact force F1 is greater than 7.0 times the pressure contact force F2), the pressure contact force F1 of the friction plate 36 is 290 g.
In the above-mentioned (misfeed area), the paper holding force of the friction plate 36 becomes too large, and even if the paper feed roller 35 rotates, the paper slips on the friction plate 36 and good paper conveyance cannot be performed. Such a problem occurs.

Therefore, in the present embodiment, in order to prevent the double feeding of the sheets from the above experimental results, the pressure contact force F1 is set to be not less than 5.1 times and not more than 7.0 times the pressure contact force F2. And the pressure contact force F2 are set respectively (for example, F1 = 18
0 g, F2 = 35 g), and a conveying press plate 37 is provided in order to suppress variations in the tip. In the above configuration, the optical device 24 takes out the required image information as a light beam based on the print information from the host computer connected by the interface or the like from the storage device such as the image memory, and forms an image on the photoconductor 26, An image is recorded on the fed and conveyed paper by being charged, developed, transferred and fixed by the electrophotographic process method.

The sheet on which the image is recorded is previously placed on the mounting table 34 and stored in the paper feeding cassette 33, and is fed by the pressure contact force of the mounting table 34 urged by the mounting table spring 40. It is pressed against the paper roller 35 with a predetermined pressure. When the paper feed roller 35 rotates, the paper is fed in the direction of the friction plate 36 in order from the uppermost paper due to the frictional force between the paper and the paper feed roller 35.

The fed paper is guided between the paper feed roller 35 and the friction plate 36 pressed against the paper feed roller 35 by being biased by the friction plate spring 42, and abuts on the friction plate 36. By the rotation of the paper roller 35, the paper is conveyed in the direction of the conveying pressure plate 37.

At this time, when two sheets of paper fed from the paper feed cassette 33 are overlapped and guided between the friction plate 36 and the paper feed roller 35, the pressure contact force of the friction plate 36 and the paper feed roller 35 are increased.
The overlapped sheets are separated by the rotation of, and the sheets are conveyed in order from the upper side by the rotation of the sheet feeding roller 35. this is,
The upper sheet is in contact with the sheet feeding roller 35 and is conveyed by the conveying force of the sheet feeding roller 35, but the lower sheet does not contact the sheet feeding roller 35 because there is the upper sheet, and the friction plate 3
6, the braking force of the friction plate 36 is larger than the conveyance force of the paper feed roller 35, and conveyance is blocked, and the upper sheet passes between the friction plate 36 and the paper feed roller 35. After that, the lower sheet comes into contact with the sheet feeding roller 35 and is conveyed. Even if the number of fed sheets is two or more, if the conveyance of the bottom sheet is blocked, the second sheet from the bottom comes into contact with the friction plate 36 and the conveyance is similarly blocked. The top sheet is the friction plate 3
After passing between 6 and the paper feed roller 35, the paper is conveyed in order from the top.

The sheet conveyed in the direction of the conveying pressure contact plate 37 is sandwiched between the conveying pressure contact plate 37 and the sheet feed roller 35 and curved along the sheet supply roller 35, so that the sheet is conveyed to the sheet supply roller 35. When the contact area increases and the sheet is conveyed with a large conveying force and the leading edge of the sheet is detected by the sheet detection switch 23, the driving of the sheet feed roller 35 is temporarily stopped to stop the sheet conveyance. The paper feed roller 35 is driven again while synchronizing, and the paper is conveyed to the transfer position between the photoconductor 26 and the transfer roller 29, and the image is recorded on the paper and ejected as described above. When the leading edge of the sheet is detected by the sheet detection switch 23, the sheet may be conveyed while synchronizing with the optical system and the transfer timing by increasing or decreasing the rotation speed of the sheet feeding roller 35.

As described above, by setting the pressure contact force of the friction plate 36 which is in pressure contact with the paper feed roller 35 to be 5.1 times or more and 7.0 times or less of the pressure contact force of the mounting table 34, it is possible to transfer the paper with a simple structure. Double feeding can be prevented.

Further, the feeding pressure contact plate 37 is attached to the sheet feeding roller 35.
Since the paper is brought into contact with the paper feed roller 35 over a wide range, it is possible to enhance the carrying force of the paper after the sorting process by suppressing the variation of the leading end of the paper from the paper feed roller 35 to the transfer position. The paper can be stably transported.
Therefore, it is possible to eliminate the conventionally required sheet conveying roller from the sheet feeding roller to the transfer position.
Moreover, since the paper carrying roller is eliminated, the paper carrying path 22
Can be shortened and the device can be downsized.

Further, since the drive of the paper feed roller 35 is controlled by the output signal from the paper detection switch 23, the paper can be conveyed while being surely synchronized with the optical system and the transfer timing, which is conventionally required. It is possible to eliminate the sheet conveying roller between the sheet feeding roller and the transfer position, the drive controllable sheet leading edge aligning roller having the clutch mechanism, and the like, and it is possible to reduce the size and cost of the apparatus.

(Second Embodiment) In the laser printer of the second embodiment, as shown in FIG. 6, the feed pressure contact plate 37 is located downstream of the friction plate 36 in the paper feed direction, and the paper feed roller 3 is provided.
It is arranged at a position closer to the paper feed roller 35 than the tangent line between the friction plate 5 and the friction plate 36.

As a result, the paper feed roller 35 and the friction plate 36
The sheet that has passed between the sheet and the sheet comes into contact with the conveyance pressing plate 37 and bends toward the sheet feeding roller 35, and the contact area of the sheet with the sheet feeding roller 35 increases, so that the sheet is conveyed with a large conveying force.

Therefore, although the paper feeding force is smaller than that in the first embodiment, the paper can be stably fed from the paper feed roller 35 to the transfer position, and the paper can be moved depending on the position of the feeding press plate 37. The conveyance direction of can be set freely, increasing the degree of freedom in the design of the device. Other configurations,
The operation and effect are similar to those of the first embodiment, and the members having the same functions as those of the first embodiment are designated by the same reference numerals.

The present invention is not limited to the above embodiment, and it goes without saying that many modifications and changes can be made to the above embodiment within the scope of the present invention.

For example, an optical sensor such as a photo interrupter may be used as the paper detecting means, and the transport pressure contact plate 3 may be used.
The pressure contact plate spring 43 for urging 7 may be omitted, and the paper feed cassette 33 may be used as a manual paper feed tray. Further, instead of the transport pressure contact plate 37, a driven roller 50 for transporting the sheet as shown in FIG. 7 or 8 may be provided. In FIG. 7, the driven roller 50 is arranged in pressure contact with the paper feed roller 35 in the same manner as in the first embodiment, and the paper conveying force can be increased. In FIG. 8, the driven roller 50 is arranged at a position closer to the paper feed roller 35 than the tangent line between the paper feed roller 35 and the friction plate 36 in the same manner as in the second embodiment to enhance the paper carrying force and the paper. The conveyance direction of can be set freely. In FIG. 8, reference numeral 51 is a guide plate for guiding the paper to the driven roller 50.

[0044]

As is apparent from the above description, according to the present invention, by making the pressure contact force of the friction plate which is in pressure contact with the sheet feeding roller larger than the pressure contact force of the mounting table, the weight of the sheet is simple and simple. It can be prevented from being sent.

Further, by providing a sheet conveying member on the outer circumference of the sheet feeding roller, the sheet conveying force after the sorting process can be increased, and stable sheet conveying can be performed. Therefore, it is possible to eliminate the conventionally required paper transport roller on the paper transport path.

Further, since the drive of the paper feed roller is controlled by the output signal from the paper detecting means, the paper can be conveyed while being surely synchronized with the optical system and the timing of transfer, which has been conventionally required. Further, it is possible to eliminate the paper transport roller on the paper transport path, the drive controllable paper leading edge aligning roller provided with the clutch mechanism, etc., and it is possible to realize the downsizing and cost reduction of the apparatus.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a sheet feeding device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a laser printer.

FIG. 3 is a diagram showing a pressure contact force between a friction plate and a mounting table.

FIG. 4 is a diagram showing a force applied to the first and second sheets.

FIG. 5 is a diagram showing a relationship between a pressure contact force of a friction plate and a mounting table, a multi-feed rate of sheets, and variations in leading edges of sheets.

FIG. 6 is a configuration diagram of a sheet feeding device according to a second embodiment.

FIG. 7 is a configuration diagram of a sheet feeding device when a follower roller for conveyance is applied.

FIG. 8 is a configuration diagram of another sheet feeding device when a follower roller for conveyance is applied.

FIG. 9 is a configuration diagram of a conventional laser printer.

FIG. 10 is a configuration diagram of main parts of a conventional paper feeding device.

[Description of Reference Signs] 22 Paper Conveying Path 23 Paper Detecting Means 34 Paper Placing Table 35 Paper Feeding Rollers 36 Friction Plates 37 Paper Conveying Members 45 Drive Control Means

Claims (3)

[Claims] 1. A sheet mounting table that comes into pressure contact with and separates from a sheet feeding roller, and a friction plate for preventing double feed of sheets that is disposed downstream of the table in the sheet conveying direction and that comes into pressure contact with and separates from the sheet feeding roller. A sheet feeding device, wherein a pressure contact force of the friction plate with respect to the sheet feed roller is set to be larger than a pressure contact force of the mounting table. 2. The paper feeding device according to claim 1, wherein a paper feeding member is arranged on the outer periphery of the paper feeding roller downstream of the friction plate in the paper feeding direction. 3. A paper detection means for detecting a paper is provided on a paper conveyance path downstream of the paper feed roller in the paper conveyance direction, and the paper feed roller is driven according to an output signal from the paper detection means. The sheet feeding device according to claim 2, further comprising drive control means for controlling.