JPH09226956A - Paper sheet supply device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a skew of a paper sheet caused by a non-uniform friction force or the like between a roller and the paper sheet when the paper sheet is supplied by a separation feeding means having a pair or rollers. SOLUTION: A sheet placed by a pickup roller 10 is carried to the spots of a feed roller 11 and a retard roller 12, then after its carrying by the pickup roller 10 is stopped, the sheet is carried to a skew correcting roller 13 pair by the feed roller 11 and the retard roller 12 and a detecting means 14 for detecting a sheet tip is provided between a sheet separation feeding means and the skew correcting roller pair. By detection of the sheet by the detecting means, the sheet is fed again from the pickup roller, the sheet tip is contacted to the skew correcting roller and a skew of the sheet is properly prevented.

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 provided in an image forming apparatus such as a printer or a copying machine, and an image forming apparatus equipped with such a sheet feeding device.

[0002]

2. Description of the Related Art Conventionally, a paper feeding device such as a printer or a copying machine is provided with a separating / feeding means consisting of a pair of rollers and a paper feeding means for feeding a paper to the separating / feeding means
A configuration has been proposed in which a sheet is conveyed from a separating / feeding unit to a printer, a copying machine, or the like via a plurality of rollers.

[0003]

However, the above-mentioned paper feeding means and paper separating / feeding means cause the paper to be skewed due to the way of setting the paper and the uneven frictional force between the rollers and the paper and the frictional force between the papers. In particular, when the conveyance distance from the sheet feeding position to the image forming apparatus is long, the sheet may be wrinkled or an image may not be obtained at an appropriate position.

[0004]

According to the present invention, a skew removing roller (13) is provided, and as means for increasing the sheet conveying force, the sheet feeding means (10) is used or the sheet separating and feeding means is selected depending on the sheet position. The present invention relates to a sheet feeding device having a mechanism for stabilizing the skew feeding effect by controlling (11, 12).

[0005]

According to the above construction, even if the conveying force of the sheet separating and feeding means (11, 12) set in the normal setting is reduced and the conveying speed of the sheet (S) is reduced, the sheet (S) is skewed. The conveyance force of the sheet (S) increases before reaching the roller, and it reliably abuts against the stopped skew feeding roller (13), and stable skew feeding can be suppressed.

The reference numerals in parentheses are for reference to the drawings and do not limit the structure in any way.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 5 shows an outline of a sheet supply device and an image forming apparatus. An image forming apparatus 1 is connected to the sheet feeding apparatus 2. Reference numeral 3 is a paper storage, and 4 is a paper stacking plate on which the paper S is stacked. Reference numeral 10 is a pickup roller which is a paper supply unit. Reference numeral 11 is a feed roller, and 12 is a retard roller, and this pair of rollers constitutes a separating and feeding means. Reference numeral 13 is a pair of skew feeding rollers, 14 is a paper detection sensor, and 15 is a paper guide.

FIG. 6 shows the paper feed mechanism. A pickup shaft 20 moves up and down by the movement of the pickup swing arm 17. The pickup swing arm 17 is in contact with the pickup cam 18. The feed roller 11 is rotationally driven by a feed roller drive shaft 21 and a feed gear 31. Reference numeral 16 denotes a torque limiter, which transmits the rotation of the retard drive shaft 22 and the retard gear 32 in the direction opposite to the paper conveyance direction to the retard roller 12 up to a set torque value.

In the separating and feeding section, the sheet is fed by the feed roller 11
When the sheet S is not provided between the pickup roller 10 and the retard roller 12, the torque limiter 16 causes the retard roller 12 to rotate in the sheet conveying direction, and when the sheet S is supplied, the retard roller 12 can be fed out in the forward direction. When one or more sheets S are supplied to the separating / feeding unit from the uppermost portion placed on the sheet stacking plate 4 and two or more sheets enter the nip portion of the roller pair, the retard roller 12 is set in the sheet feeding direction. Rotates in the opposite direction and returns the sheets other than the uppermost sheet to the upstream side to sequentially feed the uppermost sheets one by one.
The skew take-off roller 13 is driven after a preset time T has passed after the leading edge of the sheet S conveyed from the separating / feeding unit has passed the sheet detection sensor 14.

The image forming apparatus 1 is provided with a front loading type sheet cassette which is mounted from the front. Sheet S stored in the sheet cassette
Sheets 2 are separated one by one by the sheet separating and feeding means similar to the pickup roller 10, the feed roller 11 and the retard roller 12 and sent out. An image is formed on the sheet cassette and the sheet sent from the deck 2 by the image forming unit 101.

The image forming section 101 has a process cartridge 102 which is detachable from the main body of the image forming apparatus.
The process cartridge 102 has an electrophotographic photosensitive drum 103 as an image bearing member, a charging unit 104 for charging the surface of the photosensitive drum 103, a developing unit for forming a toner image on the photosensitive drum 103, and a residual member on the surface of the photosensitive drum 103. Cleaning means 1 for removing the formed toner image
06 and the like are provided. The photosensitive drum 103 is exposed by the image light emitted from the scanner unit 107 according to the image signal.

The image forming section 101 is also provided with a transfer roller 108 for transferring the toner image formed on the surface of the photosensitive drum 103 to a sheet. The transfer roller 108 presses the sheet sent from the sheet cassette or the deck 2 to the photosensitive drum 103, and by applying a voltage having a polarity opposite to that of the toner image to the transfer roller 108, a toner image on the surface of the photosensitive drum 103 is formed. By applying a voltage of opposite polarity, the toner image on the surface of the photosensitive drum 103 is transferred to the sheet.

A fixing unit 109 is provided downstream of the image forming unit 101 in the sheet flow direction. A fixing roller 110 is arranged in the fixing unit 109, and the toner image transferred onto the sheet in the image forming unit 101 is fixed by heat and pressure applied by the fixing roller 110. Then, the sheet on which the toner image is fixed is discharged onto the discharge tray 111.

The sheet feeding operation of the sheet feeding apparatus according to the first embodiment of the present invention is shown in FIGS. 1 shows a paper feed standby state, and FIG. 2 shows a paper feed state. When the pickup cam 18 rotates in response to a paper feed command, the pickup roller 10 comes into contact with the paper S and the paper S is fed. . FIG. 3 shows a state in which the sheet is separated, the pickup roller 10 returns to the standby position, and the sheet S is a sheet separating / feeding unit including a feed roller 11 and a retard roller 1.
The two roller pairs are separated and conveyed as described above. FIG. 4 shows the skewed state, and the leading edge of the sheet S is the sheet detection sensor 14.
Then, the pickup roller 10 comes into contact with the sheet S that is being conveyed again and abuts the sheet S against the skew feeding roller.

According to the above-described embodiment, by providing the skew feeding roller and feeding the sheet toward the roller by the pickup roller, abrasion between the separation feeding roller and the sheet, friction between the sheets, and a sheet type. It is possible to perform stable skew removal regardless of the situation.

<Second Embodiment> FIG. 7 shows a second embodiment according to the present invention. 41 is a retard spring, one of which is attached to the retard arm 40 which holds the retard roller shaft 22,
The other is attached to the retard spring attachment member 42 which is rotatable around the support portion 45. The retard spring mounting member 42 abuts on the stopper 43. Reference numeral 44 is a solenoid, which is connected to the retard spring mounting member.

The first embodiment from the paper feed command to before skew feeding
Therefore, the description is omitted. FIG. 8 shows the skewed state, and when the leading edge of the sheet S reaches the sheet detection sensor 14, the solenoid 44 is actuated, and the retard spring mounting member 42 connected to the solenoid 44 extends in the direction in which the retard spring 41 extends. The pulling force of the retard spring increases, and the nip pressure between the feed roller 11 and the retard roller 12 increases. The sheet S is abutted against the skew feeding roller 13 by the conveyance force thus increased. When the skew feeding roller 13 starts to rotate, the suction of the solenoid 44 is stopped and the normal retard spring pressure is restored.

According to the present embodiment, the skew feeding roller is provided and the nip pressure of the feed roller and the retard roller is increased toward the roller to feed the sheet, so that the abrasion between the separation feeding roller and the sheet is caused. In addition, stable skew feeding can be performed regardless of the friction between sheets and the type of paper.

<Embodiment 3> In the present embodiment, the feed gear 31 that rotationally drives the feed roller 12 is driven by a pulse motor whose rotation speed is variable. Since the process from the paper feed command to the separate feeding is the same as that of the first embodiment, the description is omitted.

FIG. 9 shows the sheet separation state, the pickup roller 10 returns to the standby position, and the sheet S is separated and fed by the roller pair of the sheet separating and feeding means, the feed roller 11 and the retard roller 12. At this time, the feed roller 11 is driven at the rotation speed v1. FIG. 10 shows the skew feeding state, and when the leading edge of the sheet S reaches the sheet detection sensor 14, the rotation speed variable motor 7 is rotated at a high speed to increase the speed of the feed roller 11 and the sheet S is projected onto the skew feeding roller. Hit When the skew feeding roller starts to rotate, the speed of the feed roller is returned to the initial speed. The ratio of the increasing speed required to hit the sheet S against the stopped skew feeding roller for a set time or longer is determined by setting the set feeding speed of the separating / feeding roller to v1 and determining the wear of the roller and the paper type. If the speed when the speed is decreased due to the difference is v2, it is v1 / v2 or higher.

As another embodiment, if the normal stop time of the skew feeding roller 13 is Tr1, the minimum guaranteed stop time is Tr2, and the distance Lr between the sheet detection sensor 14 and the skew feeding roller is set, the speed increases. The ratio of Lr / {Lr
* V2 / v1 + (Tr1-Tr2) * v2} or more can obtain the effect.

According to this embodiment, the skew feeding roller is provided and the rotation speed of the feed roller is increased toward the roller to feed the sheet, so that the sheet is fed without driving the pickup roller 10. However, stable skew feeding can be performed regardless of wear between the separating / feeding roller and the paper, friction between the paper, paper type, and the like.

As a modified example of each of the above-described embodiments, the elapsed time after the paper feed command by the paper feed command means (not shown) is measured without providing the detection sensor, the sheet is re-fed by the pickup roller after a predetermined set time, and then further. After a certain time, the skew feeding roller can be rotated to feed the sheet.

[0025]

As described above, according to the present invention,
An effect that stable skew removal can be achieved by providing a skew removal roller downstream of the sheet separating / feeding means and increasing the sheet transport force or the transport speed before starting the skew removal roller. There is.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a sheet feeding standby state of a sheet feeding device according to a first exemplary embodiment of the present invention.

FIG. 2 is an explanatory diagram of a sheet supply state of the sheet supply device according to the first exemplary embodiment of the present invention.

FIG. 3 is an explanatory diagram of a sheet separation state of the sheet supply device according to the first exemplary embodiment of the present invention.

FIG. 4 is an explanatory diagram of a skew feeding state of the sheet feeding device according to the first embodiment of the present invention.

FIG. 5 is a schematic view of a sheet supply device and an image forming apparatus of the present invention.

FIG. 6 is an explanatory view of a paper feeding mechanism of the present invention.

FIG. 7 is an explanatory diagram of a sheet feeding standby state of the sheet feeding device according to the second exemplary embodiment of the present invention.

FIG. 8 is an explanatory diagram of a skew feeding state of a sheet feeding device according to a second embodiment of the invention.

FIG. 9 is an explanatory diagram of a sheet feeding standby state of the sheet feeding device according to the third exemplary embodiment of the present invention.

FIG. 10 is an explanatory diagram of a skew feeding state of a sheet feeding device according to a third embodiment of the invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming device 2 ... Paper supply device 10 ... Pickup roller 11 ... Feed roller 12 ... Retard roller 13 ... Skew removing roller 14 ... Paper detection sensor 15 ... Paper guide 16 ... Torque limiter 17 ... Pickup swing arm 18 ... Pickup Cam 40 ... retard arm 41 ... retard spring 42 ... retard spring mounting member 44 ... solenoid

Claims (7)

[Claims] 1. A sheet stacked by a first roller is sent to a retard type sheet separating / feeding means composed of second and third rollers, the sending of the first roller is stopped, and the sheet separating / feeding means is stopped. In the sheet feeding device, the sheet is fed to the next pair of skew removing rollers while being separated by, and the skew removing roller pair starts to rotate after a predetermined time after the sheet reaches the roller pair. A sheet characterized in that a detecting means for detecting the leading edge of the sheet is provided between the separating / feeding means and the skew feeding roller pair, and the sheet is fed again by the first roller when the sheet is detected by the detecting means. Supply device. 2. A sheet stacked by a first roller is sent out to a retard type sheet separating and feeding means composed of second and third rollers, and the sending out of the first roller is stopped to stop the sheet separating and feeding means. The sheet feeding device is configured to feed the sheet to the next pair of the skew feeding rollers while separating the sheet by the sheet feeding device, and the skew feeding roller pair starts to rotate after a certain time after the sheet reaches the roller pair. Measure the elapsed time after the command by the paper feeding command means other than the means, after a predetermined set time, re-feed the sheet by the first roller,
After that, the sheet feeding device is characterized in that the skew feeding roller is rotated after a predetermined time. 3. A sheet feeding mechanism that conveys to a next conveying roller pair by a separating and feeding means that also serves as a separating means and a conveying means, and the conveying roller pair starts to rotate after a lapse of a certain time after the sheet arrives. In a sheet feeding device which is a take-up roller, a detecting means for detecting the leading edge of the sheet is provided between the retard separating roller pair and the skew-feeding roller pair, and when the detecting means detects the sheet, the separating feeding means conveys the sheet. A paper feeding device characterized by increasing power. 4. A sheet feeding mechanism for conveying a sheet to a next conveying roller pair by a retard type separating and feeding means which also serves as a separating means and a conveying means, and the conveying roller pair has a predetermined time after the sheet arrives. In the sheet feeding device that is the skew feeding roller that starts to rotate later, the elapsed time after the instruction by the sheet feeding instruction means other than the sheet detection means is measured, and the conveyance force of the separation feeding means is increased after a predetermined set time, After that, the sheet feeding device is characterized in that the skew feeding roller is rotated after a predetermined time. 5. A sheet feeding mechanism that conveys a sheet to a next conveying roller pair by a retard type separating and feeding means that also serves as a separating means and a conveying means, and the conveying roller pair has a predetermined time after the sheet arrives. In a sheet feeding device which is a skew take-off roller which starts to rotate later, a detecting means for detecting the sheet front end is provided between the separation feeding means and the skew take-up roller pair, and when the sheet front end is detected by the detecting means. A sheet feeding device, characterized in that the conveyance speed of the separation feeding means is increased. 6. A sheet feeding mechanism for conveying a sheet to a next conveying roller pair by a retard type separating and feeding means which also serves as a separating means and a conveying means, and the conveying roller pair has a predetermined time after the sheet arrives. In a sheet feeding device which is a skew feeding roller that starts to rotate later, the elapsed time after the instruction by the sheet feeding instruction means other than the sheet detection means is measured, and after a predetermined set time, the conveyance speed of the separation feeding means is increased, and thereafter, A sheet feeding device characterized in that the skew feeding roller is rotated after a predetermined time. 7. An image forming apparatus, comprising: the sheet feeding device according to claim 1; and an image forming unit that forms an image on a sheet fed by the sheet feeding device.