JPH11314775A - Sheet feeder and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To feed sheets with substantially constant kinetic energy regardless of mass of a sheet so as to prevent multifeed of sheets by providing a speed changing means for changing the sheet feed speed in a feeder in which the sheets are fed to a separating means by a feeding rotor to be separated one by one. SOLUTION: A sheet feeder includes a pickup roller 22 as a feeding rotor for feeding sheets, and a separating means 23 for separating the fed sheets one by one. The separating means 23 comprises a feed roller 24, and a retard roller 25 rotated in the direction of returning the sheet. At this time, the rotary driving force is transmitted through a driving belt 26 and a solenoid clutch 27 to a feed roller shaft 28 and then transmitted to a pickup roller shaft 32 through plural timing belts 30, 43 and a one-way pulley 44. A solenoid clutch 40 is on-off controlled by a sheet mass input means to change the feed speed of the pickup roller 22 to two stages.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding apparatus for feeding a sheet to a separating means by a feeding rotary member, separating the sheet one by one and feeding the sheet, and an image processing apparatus using the same. It is about.

[0002]

2. Description of the Related Art An image processing apparatus such as a copying machine, a printer, a scanner, or the like sets a large number of sheets, and separates and feeds these sheets one by one to perform image formation or image reading. At this time, various mechanisms have been proposed as a mechanism for separating a large number of sheets one by one, but in recent years, a retard separation mechanism is often used.

[0003] As shown in FIG. 4, the retard separation mechanism includes a feed roller that rotates in a direction for feeding a sheet S.
50, and a retard roller 52 that rotates in a direction to return the sheet S by a torque within a predetermined range by a torque limiter 51. The sheet S stacked and set on a cassette or the like When the sheet S is fed to the nip (separation nip), the sheet S other than the top sheet is returned by the retard roller 52 so that only the top sheet S is fed.

[0004]

However, in the sheet feeding apparatus having the above structure, in the case of a sheet S having a large mass per sheet such as an OHP sheet, a sheet having a small mass such as plain paper is used. Since the sheet S sent by the pickup roller 53 has a greater kinetic energy when entering the separation nip than the sheet S, it is not possible to return the sheet S other than the top sheet by the retard roller 52 in time. Double feed may occur.

If the torque value of the torque limiter 51 is set to a large value in order to prevent the double feed, the load on the feed roller 50 becomes unnecessarily large, and the motor for driving the feed roller 50 becomes large. There is an inconvenience that the life of 50 is shortened.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object thereof is that when feeding sheets S having different masses, double feeding may occur even if the value of the torque limiter is not increased. And an image processing apparatus using the same.

[0007]

In order to achieve the above object, a typical configuration according to the present invention is to feed a sheet to a separating means by a feed rotating body, and to separate the sheets one by one by the separating means. In a sheet feeding apparatus for feeding a sheet, a speed changing unit capable of changing a sheet feeding speed by the feeding rotating body is provided.

In the above configuration, when a sheet having a small mass is fed, the feeding speed by the feeding rotating body is increased,
Conversely, when feeding a sheet with a large mass, the sheet can be fed to the separation means by a substantially constant kinetic energy regardless of the mass of the sheet by setting the feeding speed by the feeding rotating body to be slow. In addition, double feeding of sheets can be prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sheet feeding apparatus to which the present invention is applied and an image processing apparatus using the same will be described with reference to FIGS. 1 is an explanatory diagram of a drive transmission configuration of a sheet feeding device, FIG. 2 is an overall schematic explanatory diagram of a copying machine as an example of an image processing device, and FIG. 3 is an overall schematic explanatory diagram of a sheet feeding unit. is there.

Here, as the order of the description, first, the overall configuration of the copier as the image processing apparatus will be described, and then the sheet feeding apparatus will be described.

{Overall Configuration of Image Processing Apparatus} As shown in FIG. 2, an image processing apparatus according to the present embodiment has a feeding deck 2 in which a large number of sheets S are stacked and stored on one side of an image processing apparatus main body 1. And a plurality of feed cassettes 3 in which a predetermined amount of sheets S are stacked and stored in the lower portion of the image processing apparatus main body 1.
4 is provided.

A sheet feeding device 5 for feeding a sheet S, and a sheet feeding device 5, 6, 7 of a retard separation type are provided at a portion where the feeding cassettes 3, 4 are installed. Is provided. The feeding device will be described later in detail.

When the sheets S in the feeding deck 2 and the feeding cassettes 3 and 4 are fed by the respective sheet feeding devices 5, 6 and 7, first, they are sent to the registration roller pair 8 which is stopped rotating. Then, the skew state is corrected here.

Next, based on the information optically read by the reading means 21, a pair of registration rollers rotating at a timing with a latent image formed on the photosensitive drum 9 constituting an image forming unit as a processing means. 8, the photosensitive drum 9
, And the toner image on the photosensitive drum 9 is transferred here.

Thereafter, the sheet S is sent to the fixing device 12 by the conveyor belt 11, and is subjected to a fixing process for fixing the transferred toner image on the sheet surface.

The image processing apparatus is provided with a duplex copying mode for performing duplex copying on the sheet S and a multiplex copying mode for performing multiple copying. In the normal copying mode (single-sided copying mode), the sheet S after fixing is processed. Is discharged onto a discharge tray 15 outside the apparatus by an inner discharge roller pair 13 and an outer discharge roller 14.

In the case of the double-sided copy mode and the multiple copy mode, the pair of inner discharge rollers 13 or the pair of switchback rollers 16 temporarily place the sheet on the intermediate tray 19 via the re-feeding path 17 and the double-sided conveying path 18. It is loaded and stored.

Then, the sheet S stored on the intermediate tray 19 is again conveyed to the registration roller pair 8 for image formation by the re-feeding device 20, and thereafter discharged out of the apparatus through the same process as for one-sided copying. You.

{Sheet Feeding Apparatus} Next, the sheet feeding apparatuses 5, 6, and 7 will be described. Here, the configuration of the feeding device 5 will be described as an example, but it goes without saying that the other feeding devices 6 and 7 may have the same configuration as needed.

The sheet feeding device 5 sequentially separates and feeds the sheets one by one toward the above-mentioned image forming section. As shown in FIG. 3, a plurality of sheets S are stacked and stored. Roller serving as a feed rotator for feeding the uppermost sheet S one by one from the feed deck 2
22, separation means 23 for separating the sheets S fed from the feeding deck 2 by the pickup roller 22 one by one and feeding them into the image processing apparatus main body, and conveying the separated sheets S to the downstream side A registration roller pair 8 is provided.

The separating means 23 includes a feed roller 24, which is a rotating body that rotates in the direction of conveying the sheet, and a retard body, which is a rotating body that rotates in the direction of returning the sheet by contacting the feed roller 24 with a predetermined pressure. It is composed of rollers 25.

The pickup roller 22 and the separating means 23
Rotational drive from a drive source (not shown) installed in the image processing apparatus main body 1 is transmitted to the feed roller 24 and the retard roller 25 via a power transmission mechanism shown in FIG. That is, the rotational power of the drive source is transmitted to the roller shaft 28 of the feed roller 24 via the drive belt 26 and the electromagnetic clutch 27.

The rotational power transmitted to the roller shaft 28 of the feed roller 24 is transmitted 1: 1 to the pickup roller shaft 32 of the pickup roller 22 via the pulley 29, the timing belt 30, and the pulley 31. Further, the rotational power from the roller shaft 28 is supplied to the pulley 33, the timing belt 34, and the pulley 35.
And a torque limiter 37 that transmits only a torque within a certain range by a friction member and the like, and a roller shaft of the retard roller 25 through a coupling 38.
Has been communicated on 39.

When a voltage is applied to the electromagnetic clutch 27, the rotational power of the drive source is transmitted to the roller shaft 28,
Reference numeral 24 rotates in the direction in which the sheet is conveyed (the direction of arrow A).
Further, the pickup roller 22 also rotates via the timing belt 30 in the direction for transporting the sheet (the direction of arrow C). The rotation of the roller shaft 28 is transmitted to the relay shaft 36 via the timing belt 34. Accordingly, the retard roller 25 rotates in a direction (arrow B direction) to return the sheet S in synchronization with the rotation of the feed roller 24. But retard roller 25
When the torque greater than the set value is applied because the rotational power is transmitted through the torque limiter 37, the retard roller 25
Is idle, and is driven to rotate by the feed roller 24.

When there is only one sheet fed by the pickup roller 22 to the nip portion of the separating means 23 as described above, the retard roller 25 becomes idle and rotates following the feed roller 24 to rotate. Is transported downstream.
When a plurality of sheets fed by the pickup roller 22 enter, the retard roller 25 rotates in the direction of arrow B, so that the sheets other than the uppermost layer are returned to the retard roller 25 and Only the upper layer is separated and transported downstream.

{Speed Changing Means} The sheet feeding device 5 changes the rotation speed of the pickup roller 22 in accordance with the mass of the sheet S and the like, thereby changing the sheet feeding speed. Next, the configuration for that will be described.

As shown in FIG. 1, the pulley 31 is provided on an electromagnetic clutch 40. When the electromagnetic clutch 40 is turned on by applying a voltage, the driving force transmitted to the pulley 31 is transmitted to the pickup roller shaft 32. You. On the other hand, when the electromagnetic clutch 40 is in the off state, the pulley 31 idles, and the driving force is not transmitted to the pickup roller shaft 32. The electromagnetic clutch 40 is connected to a seat mass input unit 41.When the seat mass is input from the input unit 41, the electromagnetic clutch 40 is turned on when the mass is smaller than a predetermined range, and when the mass is larger than a predetermined range, the electromagnetic clutch 40 is turned on. It is configured to turn off.

Here, the pulleys 29 and 31 and the timing belt
30 constitutes a first rotation transmitting means, and the first rotation transmitting means and the electromagnetic clutch 40 constitute one of the transmission paths.

An output pulley 42 is fixed to the roller shaft 28 and can be rotated integrally therewith. A one-way clutch 44 is connected to the pickup roller shaft 32 via a timing belt 43.
The driving force can be transmitted to the one-way pulley 44 integrated with the a. The one-way pulley 44 is configured to run idle by the one-way clutch 44a when the pickup roller shaft 32 is faster than the rotation speed of the one-way pulley 44.

The pulleys 42, 44 and the timing belt 41 constitute a second rotation transmitting means, and the second rotation transmitting means and the electromagnetic clutch 44a constitute one transmission path.

Here, the pulley 29 and the pulley 31 driven and transmitted by the timing belt 30 have a 1: 1 ratio of the number of teeth, whereas the output pulley 42 and the one-way pulley 44 driven and transmitted by the timing belt 43 are The ratio of the number of teeth is 1:
It is set to 1.4. For this reason, the sheet feeding device 5 operates as follows.

For example, when a small sheet such as plain paper (about 3.8 g per sheet) is fed as the sheet S, the electromagnetic clutch 40 is fed by the sheet mass input means 41.
Turns on. Thus, the electromagnetic clutch 40 transmits the drive of the timing belt 30 to the pickup roller shaft 32. As described above, since the pulley 29 and the pulley 31 have the same number of teeth and the feed roller 24 and the pickup roller 22 have the same outer diameter, the sheet is fed at the same speed. At this time, the rotation speed of the one-way pulley 44 is 1 / 1.4, which is lower than the rotation speed of the pickup roller shaft 32.
44 idles and does not transmit drive to the pickup roller shaft 32.

Next, when feeding a large sheet such as an OHP sheet (about 7.6 g, which is twice the weight of plain paper per sheet), the electromagnetic clutch 40 is operated by the sheet mass input means 41. Turn off. As a result, the electromagnetic clutch 40 does not transmit the drive of the timing belt 30 to the pickup roller shaft 32. At this time, the one-way pulley 44
Is transmitted to the pickup roller shaft 32. Since the rotation speed ratio between the output pulley 42 and the one-way pulley 44 is 1.4: 1, the pickup roller 22
The HP sheet is fed at a rate of 1 / 1.4 times the speed of plain paper.

Here, the kinetic energy is proportional to the square of the velocity and is proportional to the mass. Therefore, when the OHP sheet is fed, the mass is twice as large as that of the plain paper, but the feeding speed is 1 / 1.4 times. Become. Therefore, the same torque limiter can be used to prevent double feed in the case of both plain paper and OHP sheets. Then, when feeding a sheet having a large mass, only the speed of the pickup roller 22 needs to be reduced, and there is no need to reduce the overall image forming speed.

In the above-described embodiment, there are two types of sheets to be fed: plain paper and OHP sheets, and the feeding speed of the pickup roller 22 can be changed in two stages in accordance with the two types. However, it is also possible to configure so as to be able to be changed to another stage, and further to be configured to be changed continuously according to the mass of the sheet S.

In the above-described embodiment, the case where the sheet feeding device feeds the recording sheet of the copying machine has been described.
This sheet feeding apparatus can also be suitably used for an image reading apparatus or the like that separates and feeds a plurality of set originals one by one and reads the written information of the originals. Therefore, the image processing apparatus may be not only an image forming apparatus such as a copying machine or a printer but also an image reading apparatus such as a scanner.

[0037]

The present invention is constructed as described above.
When feeding a sheet with a small mass, the feeding speed by the feeding rotator is increased, and when feeding a sheet with a large mass, the feeding speed by the feeding rotator is set to be low. Irrespective of the mass of the sheet, the sheet can be fed to the separating means by a substantially constant kinetic energy, so that double feeding of the sheet can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a drive transmission configuration of a sheet feeding device.

FIG. 2 is an overall schematic diagram illustrating a copying machine as an example of an image processing apparatus.

FIG. 3 is an overall schematic diagram illustrating a sheet feeding unit.

FIG. 4 is an explanatory view of a retard separation mechanism.

[Explanation of symbols]

 S: Sheet 1: Image processing apparatus main body 2: Feeding deck 3, 4, Feeding cassette 5, 6, 7 ... Sheet feeding device 8: Registration roller pair 9: Photoconductor drum 10: Transfer charger 11: Conveying belt 12 ... fixing device 13 ... inner discharge roller pair 14 ... outer discharge roller 15 ... discharge tray 16 ... switchback roller pair 17 ... re-feed path 18 ... double-sided conveyance path 19 ... intermediate tray 20 ... re-feed device 21 ... reading means 22… Pickup roller 23… Separation means 24… Feed roller 25… Retard roller 26… Driving belt 27… Electromagnetic clutch 28… Roller shaft 29… Pulley 30… Timing belt 31… Pulley 32… Pickup roller shaft 33… Pulley 34… Timing belt 35 ... pulley 36 ... relay shaft 37 ... torque limiter 38 ... coupling 39 ... roller shaft 40 ... electromagnetic clutch 41 ... sheet mass input means 42 ... output pulley 43 ... Lee timing belt 44 ... the one-way pulley 44a ... one-way clutch

Claims (7)

[Claims] 1. A sheet feeding apparatus which feeds a sheet to a separating means by a feeding rotating body and separates and feeds the sheet one by one by the separating means, wherein the sheet feeding speed by the feeding rotating body is A sheet feeding device provided with a changeable speed changing means. 2. The sheet feeding device according to claim 1, wherein the speed changing unit changes the speed according to a mass of the sheet. 3. The speed change means comprises a drive transmission means for transmitting a drive from a drive shaft to the feed rotary body, comprising a plurality of transmission paths having different rotational speeds, and selectively using the transmission path. The sheet feeding apparatus according to claim 2, wherein the sheet feeding speed is changed by changing the sheet feeding speed. 4. A transmission path comprising a pair, a first transmission path for transmitting rotation from the drive shaft to the feed rotator and an electromagnetic clutch are disposed on one transmission path,
On the other transmission path, a second rotation transmission means for transmitting rotation from the drive shaft to the feed rotator and a one-way clutch are arranged, and when the electromagnetic clutch is turned on, the rotation from the first rotation transmission means is rotated. The rotation is transmitted from the second rotation transmission means when the electromagnetic clutch is turned off, and the rotation speed of the feed rotator when transmitted by the first rotation transmission means is changed by the second rotation transmission means. 4. The sheet feeding device according to claim 3, wherein the rotation speed of the feeding rotator when transmitted is higher. 5. The rotation transmitting means has a pair of pulleys and a timing belt wrapped around the pulleys, and varies the rotational speed transmitted in each transmission path according to the number of teeth of the pulleys. A sheet feeding device according to claim 4 or claim 5. 6. The apparatus according to claim 1, wherein said separating means comprises a feed roller rotating in a direction for feeding the sheet and a retard roller rotating in a direction for returning the sheet within a predetermined torque range. Sheet feeding device. 7. An image processing apparatus for performing image processing by feeding a sheet, wherein the sheet is fed by the sheet feeding apparatus according to claim 1 and the sheet feeding apparatus. An image processing apparatus, comprising: an image processing unit that performs image processing on a sheet.