JPH10291663A - Paper feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize a space between continuously fed papers in the case of feeding the paper from whatever paper feed part, in the case of forming an image by continuously feeding paper from two or more paper feed parts having a different distance from a detection sensor of register sensor or the like detecting paper fed. SOLUTION: In the case of continuously feeding paper from a second paper feed part 23 with a distance lengthened from a detection sensor 15, when a rear end of paper fed is detected by a rear end detection sensor 26, based on this detection result, by a drive part, a second paper feed roller 24 is driven, a feed of the next paper can be performed. Accordingly, a space of paper continuously fed from the second paper feed part 23 can be shortened, even in the case of continuously feeding from the second paper feed part 23 with a long distance from the detection sensor 15, work efficiency forming an image can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeding device capable of selectively feeding paper from two or more paper feeding units.

[0002]

2. Description of the Related Art In recent years, in image forming apparatuses such as printers and copiers, two-
A paper feeding device having the above paper feeding unit is widely used.
Further, with the downsizing of the image forming apparatus, there is a type in which only one sheet feeding unit is provided as a standard and another sheet feeding unit is optionally provided.

When an image is formed by continuously feeding paper from a paper feeding unit, the detection of a first sheet of paper passing a predetermined position by a detection sensor such as a registration sensor is followed by the second sheet of paper. Feed paper.

Here, when two or more sheet feeding units are provided, it is difficult to make the distance from each sheet feeding unit to the registration sensor the same, and the distance from each sheet feeding unit to the registration sensor varies.

[0005]

A comparison between a case where continuous feeding is performed from a sheet feeding unit having a short distance from the registration sensor and a case where continuous feeding is performed from a sheet feeding unit having a long distance from the registration sensor is compared. The interval between the sheets to be printed is such that the length of the sheet continuously fed from the sheet feeding unit having a long distance from the registration sensor is long. Therefore, in the case where image formation is performed by continuously feeding paper from the paper feeding unit having a long distance from the registration sensor, compared with the case where image formation is performed by continuously feeding paper from the paper feeding unit whose distance from the registration sensor is short. The work efficiency of image formation is reduced. Such a decrease in work efficiency becomes remarkable when paper is fed from the lowermost sheet feeding unit in the sheet feeding units arranged in multiple stages.

In such a case, if the sheet feeding speed when feeding from a sheet feeding unit having a long distance from the registration sensor is increased, the operation efficiency of image formation is increased even if the interval between sheets is long. However, if the paper feeding speed is too high, the paper conveyance state becomes unstable, and the quality of an image formed on the paper is reduced. Therefore, it is desirable that the paper feed speed from each paper feed unit be the highest speed within a range that does not degrade image quality.

In view of the above, the present invention relates to a paper feeding method in which image formation is performed by continuously feeding paper from two or more paper feed units having different distances from a detection sensor such as a registration sensor for detecting that paper has been fed. When the paper is continuously fed from a paper feed unit that is long from the detection sensor, the work efficiency of the image forming operation can be increased even when the paper is continuously fed from the paper feed unit. It is an object to provide a paper device.

[0008]

According to a first aspect of the present invention, there is provided a paper feeder, comprising: a first paper feed unit having a first paper feed roller; and detecting that a fed paper has passed a predetermined position. A second paper feeding unit disposed at a position where the distance from the detection sensor is longer than the distance between the detection sensor and the first paper feeding unit; A second paper feed roller provided in a paper section, and a rear end located between the second paper feed section and the detection sensor for detecting the rear end of the paper fed from the second paper feed section A detection sensor;
And a driving unit that drives the second paper feed roller based on the detection result of the trailing edge detection sensor during continuous paper feeding from the paper feeding unit. Therefore, in the case where the sheet is continuously fed from the second sheet feeding unit having a long distance from the detection sensor, when the trailing edge detecting sensor detects the trailing edge of the fed sheet, the driving unit determines the position based on the detection result. The second paper feed roller is driven,
The next sheet is fed, and the interval between the continuously fed sheets is shortened.

According to a second aspect of the present invention, in the paper feeder of the first aspect, the detection of the sheet by the detection sensor is a trigger for starting the writing of the electrostatic latent image by the laser writing unit. Therefore, even in a sheet feeding apparatus that does not have a registration roller that adjusts the sheet feeding timing to the transfer position, the interval between sheets that are continuously fed from the second sheet feeding unit can be shortened.

According to a third aspect of the present invention, in the paper feeder of the first or second aspect, the distance between the first paper feed roller and the detection sensor and the distance between the second paper feed roller and the rear end detection sensor are different. The distance was almost the same. Therefore, in the case where an image is formed by continuous feeding from each sheet feeding unit, the interval between sheets continuously fed from each sheet feeding unit becomes the same.

[0011]

An embodiment of the present invention will be described with reference to the drawings. First, the schematic structure of the entire image forming apparatus employing the sheet feeding device of the present invention will be described with reference to FIG. An image reading device 2 for reading an image of a document is mounted on an upper part of a main body case 1 of the image forming apparatus, and a process cartridge 3 is detachably mounted inside the main body case 1.

The image reading device 2 includes an image reading unit 4,
And a document tray 5 on which a document to be supplied to the image reading section 4 is placed. The document tray 5 is moved to a horizontal position indicated by a solid line and an upright position indicated by a two-dot chain line around a fulcrum shaft 6. It is supported so that it can rotate. The document tray 5 is configured to be stabilized between a horizontal position indicated by a solid line and an upright position indicated by a two-dot chain line by a stopper (not shown).

The process cartridge 3 includes a case 7
Inside, various process members and developer are stored.
The accommodated process members include a photosensitive drum 8, a charging roller 9 for uniformly charging the periphery of the photosensitive drum 8, and an electrostatic latent image on the photosensitive drum 8 developed with a developer to form a toner image. The developing roller 10 to be formed.

A laser writing unit 11 for writing an electrostatic latent image on the outer peripheral surface of the photosensitive drum 8 is provided around the process cartridge 3 in the main body case 1. A paper feed tray 12 serving as one paper feed unit, a first paper feed roller 13 for feeding paper loaded on the paper feed tray 12, and a toner image on the photosensitive drum 8 for the fed paper Roller 1 for transferring image
4. a registration sensor 15 which is located between the paper feed tray 12 and the transfer roller 14 and detects that the paper has passed, a fixing unit 16 for fixing the toner image transferred to the paper, and a fixing unit 16 A receiving plate 17 and the like on which the sheet passing through is discharged are provided. The registration sensor 15 is provided with a sensor claw 15 pressed by a conveyed sheet.
When a rotates to a position where the detection light is not blocked, the passage of the sheet is detected. The detection of the sheet by the registration sensor 15 triggers the start of writing of the electrostatic latent image by the laser writing unit 11.

Guides 18 and 19 for attaching and detaching the process cartridge 3 to and from the main body case 1 are formed on front and rear side plates in the main body case 1. On both front and rear sides of the main body case 1, two guide pins 20 and 21 for engaging with the guides 18 and 19 are formed. The mounting and dismounting of the process cartridge 3 is performed by the receiving plate 1.
This is performed from the side 7, and at the time of attachment / detachment, the receiving plate 17 is rotated to open the attachment / detachment side.

An optional cassette case 22 is detachably attached to a lower portion of the main body case 1. In the cassette case 22, a paper feed cassette 23 as a second paper feed unit for storing and holding paper is detachably mounted. Further, in the cassette case 22, a half-moon-shaped second sheet for feeding the sheets stored in the sheet cassette 23 is located above the sheet cassette 23.
A paper feed roller 24, a transport roller 25 that transports the paper fed by the second paper feed roller 24 toward a transfer position in the main body case 1, and a paper feed cassette 23 that is located near the transport roller 25. , A paper feed motor (not shown) for driving the second paper feed roller 24 and the transport roller 25, and a second paper feed roller 24 Is provided with a solenoid (not shown) which is a drive unit for intermitting a clutch (not shown) provided therein and intermitting transmission of a driving force from a sheet feeding motor. Note that the trailing edge detection sensor 26 detects the passage of the sheet by rotating the sensor claw 26a pressed by the sheet being conveyed to a position where the detection light is not blocked.

Here, the distance "a" between the first paper feed roller 13 and the registration sensor 15 and the distance "b" between the second paper feed roller 24 and the trailing edge detection sensor 26 are:
They are almost the same.

First, a description will be given of a case in which an image is formed by continuously feeding sheets placed on the sheet feed tray 12 in such a configuration. At the time of this continuous paper feeding, the first paper feed roller 13 stops rotating at a timing immediately after the leading end of the paper is transported to the transfer position, and the timing at which the rear end of the transported paper passes the registration sensor 15. Is set to restart rotation. Therefore, the paper fed continuously is made up of the registration sensor 15 and the first paper feed roller 1.
The paper is fed at a distance of “a” from the sheet No. 3. The writing of the electrostatic latent image by the laser writing unit 11 is started immediately after the leading edge of the fed sheet is detected by the registration sensor 15.

Next, a case in which a cassette case 22 is attached to the lower part of the main body case 1 and sheets in a sheet cassette 23 attached in the cassette case 22 are continuously fed to form an image is shown in FIG. This will be described with reference to the timing chart of FIG. During the image formation, the fixing heater, polygon motor, main motor, and the like provided in the main body case 1 are turned on. Further, the paper feed motor provided in the cassette case 22 is also turned on. Then, when the paper supply solenoid is turned on at a predetermined timing, the second paper supply roller 24 makes one rotation, and one sheet is supplied. The fed sheet is nipped by the transport rollers 25 and transported to the transfer position.

Here, when the fed sheet is being conveyed at the position of the trailing edge detecting sensor 26, the trailing edge detecting sensor 26 is turned on, and the trailing edge of the sheet is moved to the trailing edge detecting sensor 26.
, The rear end detection sensor 26 is turned off. When the trailing end detection sensor 26 is turned off, the sheet feeding solenoid is turned on, and the second sheet feeding roller 2 is turned on.
4 makes one rotation and the next sheet is fed.

Therefore, when paper is continuously fed from the paper feed cassette 23, the trailing edge of the preceding paper is
Before passing through the position 5, the feeding of the next sheet is started.
Then, the continuously fed paper is fed with a distance “b” between the trailing edge detection sensor 26 and the second paper feed roller 24. The interval “b” between the continuously fed papers is substantially the same as the interval “a” between the continuously fed papers from the paper feed tray 12, and is different from the case where the paper is continuously fed from the paper feed tray 12. In the case where the paper is continuously fed from the paper cassette 23, the interval between the papers is substantially the same. For this reason, in the case where the sheet is continuously fed from the sheet feeding tray 12 and the case where the sheet is continuously fed from the sheet feeding cassette 23, even if the sheet feeding speed is the same, the operation efficiency of image formation can be made the same. By setting the paper speed to an optimum speed, stable paper feeding can be performed, and the quality of an image formed on the paper is improved.

In this embodiment, the case where one sheet cassette 23 is mounted in the cassette case 22 has been described as an example. However, two or more sheet cassettes are It may be mounted in a stacked state. In this case, a paper feed roller and a rear end detection sensor are provided corresponding to each paper feed cassette, and the distance between the paper feed roller and the rear end detection sensor corresponding to each paper feed cassette is "b".

[0023]

According to the paper feeding apparatus of the first aspect, the first paper feeding section having the first paper feeding roller and the detection for detecting that the fed paper has passed the predetermined position. A sensor, a second paper supply unit disposed at a position where a distance from the detection sensor is longer than a distance between the detection sensor and the first paper supply unit, and a second paper supply unit provided in the second paper supply unit. A second paper feed roller, a rear end detection sensor positioned between the second paper supply unit and the detection sensor to detect a rear end of the paper fed from the second paper supply unit; A driving unit that drives the second paper feed roller based on the detection result of the trailing edge detection sensor during continuous paper feeding from the paper feeding unit, so that the distance from the detection sensor becomes longer. In continuous paper feeding, when the trailing edge detection sensor detects the trailing edge of Second by the drive unit on the basis of the results
The paper feed roller can be driven to feed the next paper, so that the interval between the papers continuously fed from the second paper feed unit can be shortened, whereby the work of the image forming work can be performed. Efficiency can be improved.

According to the second aspect of the present invention, in the paper feeding apparatus according to the first aspect, the detection of the sheet by the detection sensor is a trigger for starting the writing of the electrostatic latent image by the laser writing unit. Because there is no registration roller that adjusts the timing of feeding paper to the transfer position, the timing for feeding paper to the transfer position is adjusted by the registration roller, and the paper is fed continuously from each paper feed unit. Even in a paper feeder in which the adjustment of the same paper interval cannot be performed, it is possible to shorten the space between the papers continuously fed from the second paper supply unit, thereby improving the work efficiency of the image forming operation. it can.

According to a third aspect of the present invention, in the paper feeder according to the first or second aspect, the distance between the first paper feed roller and the detection sensor, and the distance between the second paper feed roller and the rear end detection sensor. Is approximately the same as above, and when forming an image by continuously feeding from each sheet feeding unit, the interval between sheets continuously fed from each sheet feeding unit can be made the same. The paper feeding speed of the paper continuously fed from each paper feeding unit can be made the same, and by setting the paper feeding speed to the optimum value, more stable paper feeding can be performed and the paper is formed on the paper Image quality can be improved.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing a schematic structure of an entire image forming apparatus.

FIG. 2 is a timing chart for explaining sheet feeding timing when continuously feeding sheets from a sheet cassette.

[Explanation of symbols]

 12 First paper feed unit 13 First paper feed roller 15 Detection sensor 23 Second paper feed unit 24 Second paper feed roller 26 Rear end detection sensor

Claims (3)

[Claims] A first paper feed unit having a first paper feed roller;
A detection sensor for detecting that the fed paper has passed a predetermined position, and at least one of a detection sensor disposed at a position where a distance from the detection sensor is longer than a distance between the detection sensor and the first paper supply unit. At least one second paper supply unit, a second paper supply roller provided in the second paper supply unit, and a second paper supply unit located between the second paper supply unit and the detection sensor. The second paper feed roller is driven based on a detection result of the rear edge detection sensor for detecting a rear edge of the paper fed from the second paper feeding unit and a continuous paper feed from the second paper feeding unit. A sheet feeding device comprising: a driving unit. 2. The sheet feeding device according to claim 1, wherein the detection of the sheet by the detection sensor triggers the start of writing of the electrostatic latent image by the laser writing unit. 3. The feeding device according to claim 1, wherein a distance between the first sheet feeding roller and the detection sensor is substantially equal to a distance between the second sheet feeding roller and the rear end detection sensor. Paper equipment.